ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (103)
  • Data
  • 36.40  (59)
  • Immunocytochemistry  (44)
  • Springer  (103)
  • Annual Reviews
  • PANGAEA
  • 1990-1994  (103)
  • 1980-1984
  • 1991  (103)
Collection
  • Articles  (103)
  • Data
Publisher
Years
  • 1990-1994  (103)
  • 1980-1984
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 84-89 
    ISSN: 1432-0649
    Keywords: 36.40 ; 42.65 ; 47.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Coherent Stokes and anti-Stokes Raman scattering CSRS and CARS have been employed to study the spectroscopy of nitrogen molecules and clusters in the expansion of a supersonic jet. In the vibrational spectrum, at strong stagnation conditions, an intense redshifted peak is observed which can be assigned to the intramolecular vibrations in large N2 clusters having adopted the β-phase structure. Another weak feature is assigned to nitrogen clusters in the α-phase. In the rotational region of the spectrum only monomer features have been observed. The failing to observe librational motions is consistent with the finding that the nitrogen clusters are predominantly in the orientationally unordered β-phase. The low rotational temperature suggests supercooling of the β-phase.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 353-361 
    ISSN: 1432-0649
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We are investigating the thermodynamic conditions under which condensation occurs in laser ablated copper plasma plumes. The plasma is created by XeCl excimer laser ablation (308 nm, 300 mJ/pulse) at power densities from 500–1000 MW/cm2 into backing pressures of helium in the range 0–50 torr. We use laser-induced fluorescence (LIF) to probe velocity and relative density of both atomic copper and the copper dimer molecule, Cu2, which is formed during condensation onset. At low pressure (10 mtorr), the atomic Cu velocity peaks at approximately 2×106 cm/s. Copper dimer time-of-flight data suggest that condensation onset occurs after the Cu atoms have slowed very significantly. Excitation scans of the Cu2A-X (0,0) and (1,1) bands yield a rotational and vibrational temperature in the neighborhood of 300 K for all conditions studied. Such low temperatures support the theory that Cu2 is formed under thermally and translationally cold conditions. Direct laser beam absorption is used to determine the number density of atomic copper. Typical densities attained with 5 torr of helium backing gas are 6–8×1013 cm−3. Rayleigh scattering from particulate is easily observable under conditions favorable to particulate production.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 213-217 
    ISSN: 1432-0630
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Mass spectroscopic studies of the neutral particles sputtered by Ar+ ions at 8 keV from polycrystaline samples have been performed, using non-resonant laser ionization and subsequent time-of-flight mass spectroscopy. Besides sputtered atoms, also dimer and trimer contributions in the order of 10−1 to 10−2 and 10−3 to 10−4, respectively, are found in the sputtered flux. The data obtained here together with previously published data by other groups for different bombarding energies provide strong support for the validity of the recombination model.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 445-447 
    ISSN: 1432-0630
    Keywords: 82.65 ; 36.40 ; 73.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Desorption of K atoms by laser-excitation of surface plasmons in small K particles is reported. The desorption rate has been measured for different laser wavelengths and particle sizes. Time-of-flight measurements reveal a kinetic energy of the desorbed atoms of Ekin=0.13(3) eV. From the experimental data it is concluded that the desorption mechanism is non-thermal in nature. Comparison of the results reported here with our earlier work on Na desorption is made.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 169 (1991), S. 39-50 
    ISSN: 1432-1351
    Keywords: Photoreception ; Retinally degenerate ; Mouse ; Circadian ; Rods ; Cones ; 11-cis retinaldehyde ; Immunocytochemistry ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We have examined the effects of light on circadian locomotor rhythms in retinally degenerate mice (C57BL/6J mice homozygous for the rd allele: rd/rd). The sensitivity of circadian photoreception in these mice was determined by varying the irradiance of a 15 min light pulse (515 nm) given at circadian time 16 and meauring the magnitude of the phase shift of the locomotor rhythm. Experiments were performed on animals 80 days of age. Despite the loss of visual photoreceptors in the rd/rd retina, animals showed circadian responses to light that were indistinguishable from mice with normal retinas (rd/+ and +/+). While no photoreceptor outersegments were identified in the retina of rd/rd animals (80–100 days of age), we did identify a small number of perikarya that were immunoreactive for cone opsins, and even fewer cells that contained rod opsin. Using HPLC, we demonstrated the presence and photoisomerization of the rhodopsin chromophore 11-cis retinaldehyde. The rd/rd retinas contained about 2% of 11-cis retinaldehyde found in +/+ retinas. We have yet to determine whether the opsin immunoreactive perikarya or some other unidentified cell type mediate circadian light detection in the rd/rd retina.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-1351
    Keywords: Aplysia ; Motoneurons ; Immunocytochemistry ; Small cardioactive peptides ; Facilitation ; Depression ; Buccal ; Feeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We used physiological recordings, intracellular dye injections and immunocytochemistry to further identify and characterize neurons in the buccal ganglia of Aplysia calif ornica expressing Small Cardioactive Peptide-like immunoreactivity (SCP-LI). Neurons were identified based upon soma size and position, input from premotor cells B4 and B5, axonal projections, muscle innervation patterns, and neuromuscular synaptic properties. SCP-LI was observed in several large ventral neurons including B6, B7, B9, B10, and B11, groups of s1 and s2 cluster cells, at least one cell located at a branch point of buccal nerve n2, and the previously characterized neurons B1, B2 and B15. B6, B7, B9, B10 and B11 are motoneurons to intrinsic muscles of the buccal mass, each displaying a unique innervation pattern and neuromuscular plasticity. Combined, these motoneurons innervate all major intrinsic buccal muscles (I1/I3, I2, I4, I5, I6). Correspondingly, SCP-LI processes were observed on all of these muscles. Innervation of multiple nonhomologous buccal muscles by individual motoneurons having extremely plastic neuromuscular synapses, represents a unique form of neuromuscular organization which is prevalent in this system. Our results show numerous SCPergic buccal motoneurons with widespread ganglionic processes and buccal muscle innervation, and support extensive use of SCPs in the control of feeding musculature.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 263 (1991), S. 207-215 
    ISSN: 1432-0878
    Keywords: Somatolactin (SL) ; Pituitary gland, pars intermedia ; PAS-positive cells ; Immunocytochemistry ; Gadus morhua, Oncorhynchus mykiss, Poecillia latipinna (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We report here on the cellular localization in the fish pituitary of somatolactin (SL), a putative new pituitary hormone related to growth hormone and prolactin, which has been recently identified in the piscine pituitary gland. Immunocytochemical staining, using anti-cod SL serum, revealed that in the cod pituitary gland, SL is produced by cells in the intermediate lobe, bordering the neural tissue. These cells, staining weakly with periodic-acid-Schiff (PAS), are distinct from the melanocyte stimulating hormone (MSH) cells which, as in all teleosts, are PAS-negative. SL-immunoreactivity was observed in the same location in all other teleost species examined: flounder, rainbow trout, killifish, molly, catfish and eel. In most fish the SL-immunoreactive cells are either strongly or weakly PAS-positive but in rainbow trout are chromophobic, indicating that the SL protein can probably exist in glycosylated and non-glycosylated forms. Thus, in demonstrating the cellular localization of SL, this study provides the first identification of the enigmatic, second cell-type of the fish pars intermedia.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-0878
    Keywords: Neurofilaments ; Phosphorylation ; Axon ; Immunocytochemistry ; Golden syrian hamster, Mesocricetus auratus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of phosphorylated and nonphosphorylated neurofilament epitopes was determined immunocytochemically in adjacent 2 μm-thick sections of sciatic nerve, ventral root and spinal cord. Staining was scored as either intense, moderate or absent and the proportion of labeled axons was calculated for each category. Nearly all sciatic nerve and ventral root axons were immunoreactive with both antibodies against phosphorylated and non-phosphorylated neurofilaments and there were no significant differences in the number of intensely- or moderately-labeled axons. Within the spinal cord however, while the majority of large caliber axons was stained with both antibodies, there was a significant number of small caliber axons which stained only with antibodies against phosphorylated neurofilaments. These results show that phosphorylated and nonphosphorylated neurofilaments are extensively codistributed in CNS and PNS axons, and that in the CNS, staining intensity for non-phosphorylated epitopes is less in the smaller axons.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 263 (1991), S. 271-284 
    ISSN: 1432-0878
    Keywords: Serotonin ; Immunocytochemistry ; Avian brain ; Hypothalamus ; Japanese quail, Coturnix coturnix japonica (Aves)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The presence and topographical localization of the serotoninergic system in the brain of the Japanese quail (Coturnix coturnix japonica) have been studied by means of peroxidase-anti-peroxidase immunocytochemistry. The perimeter, diameter, area, and shape factor of immunoreactive cells have been recorded and analyzed morphometrically for intra- and interspecies comparison. The data reported here confirm and extend results previously obtained in the brain of other avian species. Serotonin-immunoreactive neurons of the quail are mainly located in the hypothalamic paraventricular organ and adjacent areas, and in the brainstem where they form three separate groups. The first of these groups consists of small-sized neurons located in the ventro-rostral mesencephalon. The second group is composed of medium-sized neurons located in the dorsal mesencephalo-pontine region. The third group is also formed by medium-sized neurons, and is located ventrally in the ponto-medullary region. In the quail brain, serotoninergic neurons are not restricted to nuclei located in the vicinity of the midsagittal plane, but show some lateralization, especially in the brainstem. The organization of the different groups of immunoreactive neurons based on this topographical distribution and morphometric analysis has been compared with descriptions of the serotoninergic system in other birds. Serotonin-immunoreactive nerve fibers are widely distributed throughout the brain, but appear to be particularly abundant in regions involved in the control of reproductive activities, such as the septal region, the medial preoptic nucleus, the nucleus intercollicularis, and the external zone of the median eminence. The data reported here have allowed the drawing of a map of serotoninimmunoreactive structure.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-0878
    Keywords: Met-enkephalin-Arg6-Gly7-Leu8 ; Immunocytochemistry ; Neuropeptides ; Allatostatins ; Neurosecretory cells ; Corpus cardiacum/corpus allatum complex ; Diploptera punctata, Calliphora vomitoria (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neuronal circuits in the brain and retrocerebral complex of the cockroach Diploptera punctata have been mapped immunocytochemically with antisera directed against the extended enkephalin, Met-enkephalin-Arg6-Gly7-Leu8 (Met-8). The pathways link median and lateral neurosecretory cells with the corpus cardiacum/corpus allatum complex. In females, nerve fibres penetrate the corpora allata and varicosities or terminals, immunoreactive to Met-8, surround the glandular cells. Males differ in having almost no Met-8 immunoreactivity in the corpora allata. The corpora cardiaca of both males and females are richly supplied with Met-8 immunoreactive material, in particular in the ‘cap’ regions immediately adjacent to the corpora allata. A similarity in the amino-acid sequences of Met-8 and the C-terminus of the recently characterised allatostatins of D. punctata suggests that the pathways identified with the Met-8 antisera may be the same as those by which the allatostatins are transported from the brain to the corpus allatum. In comparative studies on the blowfly Calliphora vomitoria, similar neuronal pathways have been identified except that no sexual dimophism with respect to amounts of immunoreactive material within the corpus allatum has been observed. These results suggest a possible homology in the neuropeptide regulation of the gland.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    ISSN: 1432-0878
    Keywords: Vitamin D-1,25(OH)2D3-like immunoreactivity ; 1,25(OH)2D3 receptor-like immunoreactivity ; Immunocytochemistry ; Calcium ions ; Orchestia cavimana (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary For the first time, immunoreactivity to 1,25(OH)2D3-like molecules and their receptors has been investigated in a calcium transporting epithelium of a crustacean, Orchestia, using vertebrate antisera on ultrathin cryosections of posterior caeca previously fixed in glutaraldehyde, then postfixed in osmium tetroxide. Both immunoreactivities were located mainly in the nuclei of epithelial cells. Quantitative differences in 1,25(OH)2D3-like immunoreactivity were noticed from one stage of the molt cycle to another. These results, together with other data, contribute to evidence that immunoreactive 1,25(OH)2D3-like molecules may be involved in the regulatory processes of calcium metabolism in this terrestrial crustacean and suggest an involvement of these substances in the regulation of calcium movements in the posterior caeca.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 264 (1991), S. 23-32 
    ISSN: 1432-0878
    Keywords: Male urethra ; Urethral epithelium ; Immunocytochemistry ; Ultrastructure ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distal segment of the human male urethra, in particular the fossa navicularis, was studied with light- and electron microscopy as well as by means of histochemical and immunocytochemical methods. The fossa navicularis of the urethra contains a circumscribed zone of extremely thick, non-keratinized stratified squamous epithelium composed of cells containing a large amount of glycogen. These cells lack acid phosphatase activity and lysozyme-like immunoreactivity, both of which can be demonstrated to varying extents in the other zones of the distal male urethra. These glycogen-rich cells are considered to be the substrate for an endogenous flora of lactobacteria, whereas the acid-phosphatase activity and the lysozyme-like immunoreactivity indicate the presence of macrophages and the secretion of bactericidal agents at the epithelial surface. These observations suggest that the different zones with heterogeneous properties in the distal male urethra probably represent a defense system against the invasion of pathogenic microorganisms. Moreover, the glycogen-rich zone, which resembles the glycogen-rich epithelium of the vagina, is estrogen-dependent. This is demonstrated in cases of sex reversal in which after long-lasting estrogen treatment the glycogen-rich zone becomes extremely extended by displacement of the neighbouring epithelium.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 1432-0878
    Keywords: Enkephalins ; Tegmentum mesencephali ; Tectum opticum ; Immunocytochemistry ; Retrograde labeling ; Cobalt-lysine ; Salmo gairdneri, Salmo salar (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Immunocytochemistry using antibodies against Met-enkephalin and Leu-enkephalin has demonstrated a group of large enkephalin-immunoreactive neurons in the nucleus of the rostral mesencephalic tegmentum (mRMT) of two teleost fish, Salmo gairdneri and Salmo salar. Injections of cobalt-lysine in the medial optic tectum retrogradely labeled the above group of tegmental neurons. Tegmental neurons were labeled only ipsilaterally to the injection site. This indicates that enkephalinergic neurons in the nRMT project to the optic tectum, and that at least some of the enkephalinergic axons observed in the optic tectum belong to a tegmento-tectal pathway. Comparable enkephalinergic pathways have been described in reptiles and birds, where pretectal-mesencephalic nuclei contribute to the enkephalin-containing fibers that project to the optic tectum.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    ISSN: 1432-0878
    Keywords: Pancreas, endocrine ; Larval development ; Serial thin/semithin sections ; Immunocytochemistry ; Rana temporaria (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pancreatic endocrine component was studied at different stages of development in the tadpoles of Rana temporaria. The material was embedded in Epon, and serial semithin and thin sections were made in order to correlate ultrastructural features and tinctorial traits of the endocrine cells. Serial semithin sections were also stained with the peroxidase-antiperoxidase immunocytochemical method and with silver impregnations for argyrophilia and argentaffinity. In early larvae (legless tadpoles), A and B cells are present. Both can be found within ducts and exocrine tissue or, more frequently, in cellular clusters among the ducts and acini. These primitive islets are solid structures, surrounded but not penetrated by capillaries. Mitoses were observed in A and B cells. In the following phase (tadpoles with hindlegs), D and pancreatic polypeptide-immunoreactive cells are also present, as well as numerous endocrine cells scattered among exocrine tissue. There is also a change in the vascular-insular pattern: capillaries not only surround but also penetrate the endocrine group. The structure of the endocrine pancreas in older tadpoles is similar. Tinctorial traits and ultrastructural features of endocrine cells are described, and the origin of primitive islets is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 1432-0878
    Keywords: Immunocytochemistry ; Neuropeptide Y ; Gonadotropin-releasing hormone ; Reproductive function ; Domestic chicken, Gallus domesticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Nerve fibers and perikarya containing gonadotropin-releasing hormone (GnRH-like) immunoreactivity were investigated in the brain of the three-week-old chick, Gallus domesticus using the technique of immunocytochemistry. Six major groups of perikarya were found to include the olfactory bulb, olfactory tubercle/lobus parolfactorius, nucleus accumbens, septal preoptic hypothalamic region (three sub-nuclei), lateral anterior thalamic nucleus and in and about the oculomotor complex. The immunostaining was unusual in the latter group, suggesting that the neurons may contain a GnRH-II like material. Immunoreactive fibers for GnRH were found throughout the entire brain extending from the olfactory bulbs to the caudal brainstem. Two anatomical areas, not emphasized in the past literature, which had distinct GnRH-like immunoreactivity, included the lateral anterior thalamic nucleus and the preoptic recess. The former included a group of GnRH perikarya that is also known to be a retino-recipient area while the latter contained neuronal terminals some of which appeared to be contacting the cerebrospinal fluid of the preoptic recess. An attempt was made to list all anatomical structures that contained or were juxta-positioned to sites that displayed immunoreactive perikarya and fibers including circumventricular organs.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 1432-0878
    Keywords: Rhabdomeres ; Cytoskeleton ; Actin ; Immunocytochemistry ; Membrane shedding ; Leptotarsus spp. (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rhabdomeres of tipulid flies lose membrane during turnover from a ‘shedding zone’ composed of microvillar tips. These distal domains lack intramicrovillar cytoskeletons and appear to be empty sacs of membrane. Recent concerns about the role of ninaC mechano-enzymes in the architecture of dipteran rhabodomeral microvilli and the dynamic role that they may play in the creation of shedding zones demand an examination of the distribution of actin in tipulid rhabdomeres. We compared rhabdomeres from tipulid retinae incubated before fixation for immunocytochemistry in a buffer without additives and a stabilising buffer that contained a cocktail of cysteine protease inhibitors; both were challenged by an anti-actin antibody for immunogold labelling after embedding in LR White Resin. Shedding zones thus processed collapse to structureless detritus. Stabilised and unstabilised shedding zones were immunonegative to anti-actin. To ensure that the negative results were not consequent upon conformational changes generated by the processing protocol, we examined microvilli of degenerating rhabdomeres of the Drosophila light-dependent retinal degeneration mutant rdgB KS222 (which separate and collapse without creating a shedding zone) and found the detritus they generate to be immunopositive to anti-actin. Stabilised and unstabilised regions of basal regions of tipulid rhabdomeres were equally immunopositive. We infer that (a) actin is absent from shedding zones; (b) actin is not degraded by microvillar cysteine proteases. The implications of these conclusions are discussed in relation to some functional models of arthropod photoreceptor microvilli.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 265 (1991), S. 485-492 
    ISSN: 1432-0878
    Keywords: ACTH ; Brain ; Hypothalamus ; Hypophysectomy ; Cortisol ; Metopirone ; Immunocytochemistry ; Pituitary ; Corticotropin-releasing factor ; Anguilla anguilla (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ACTH-like peptidergic system was demonstrated in the brain of three teleost species by immunocytochemistry. In order to investigate the origin of brain ACTH and factors modulating its synthesis, similar techniques were applied to the brain of eels (1) submitted to hypothysectomy in order to suppress pituitary ACTH and plasma cortisol, (2) injected with cortisol to inhibit pituitary ACTH synthesis and release, and (3) injected with metopirone to block cortisol synthesis and stimulate ACTH synthesis and release. Hypophysectomized eels showed a normal distribution of immunoreactive perikarya in the ventral hypothalamus and fibers in the brain, suggesting that brain ACTH does not arise from the pituitary. In cortisol-treated eels immunostaining was markedly reduced in brain perikarya and pituitary corticotropes, suggesting a reduced synthesis. In metopirone-injected eels, one third of the animals showed an increased immunostaining in perikarya and a dense network of immunoreactive fibers, suggesting that ACTH synthesis was increased. Brain ACTH was not affected in other animals. Pituitary corticotropes were rapidly degranulated. Responses of ACTH in the brain and pituitary occur independently when cortisol synthesis is inhibited. These responses are compared to those of the corticotropin-releasing factor system in the same eels.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 265 (1991), S. 527-534 
    ISSN: 1432-0878
    Keywords: Autonomic nervous system ganglia ; Enteric nervous system ; Intestine, large ; Tissue culture ; Immunocytochemistry ; Peptides ; Guinea-pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ganglia of the myenteric plexus from the newborn guinea-pig, isolated by microdissection, were dissociated by a combination of enzymatic and mechanical methods. The neurones and glial cells in the resulting cell suspension were cultured for up to 21 days in vitro. The growth of the enteric ganglion cells in serum-free, hormone-supplemented (N1) medium and in serum-supplemented medium containing a mitotic inhibitor was compared over a period of 14 days in vitro. Enteric neurones were outnumbered by glia in both culture media, although glial cell proliferation was inhibited in both media compared with that in serum-supplemented medium without mitotic inhibitors. Glial cell numbers appeared to decline in serum-free medium after the first week in vitro. Neurites tended to be more varicose in the serum-free medium, and the morphology of the enteric glial cells also differed markedly in the two media. This is the first report of the dissociation and subsequent culture of myenteric ganglia that had previously been completely isolated from the remainder of the gut wall.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 265 (1991), S. 517-525 
    ISSN: 1432-0878
    Keywords: Spermiogenesis ; Spermatids ; DNA ; Immunocytochemistry ; Electron microscopy ; Bovine ; Mouse ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary DNA distribution in mouse, rabbit and bull spermatids was analyzed by electron microscopy, after using a Feulgen-like HCl-osmium ammine procedure, and after immunocytochemistry with anti-DNA antibodies. In addition, nucleic acids were visualized with the intercalating dye ethidium bromide and phosphotungstic acid. The parts of DNA displaying a beta helix configuration (possibly A-T rich parts) were identified by epifluorescence microscopy after staining with Hoechst 33258. In all 3 species, young spermatid nuclei were seen to have large areas poor in DNA, as well as DNA-rich areas, which were mostly concentrated into a peripheral layer close to the acrosome and into one or several masses, displaying species-specific locations. These DNA-rich areas were stained with Hoechst 33258. Elongating spermatid nuclei contained homogeneously distributed DNA, and this was evident following both immunocytochemistry and nucleic acid histochemistry in all 3 species. However, the distribution appeared more heterogeneous after the Feulgen-like procedure, and was accompanied by a disappearance of Hoechst-fluorescence. In fully elongated spermatids, all nuclear areas stained with Hoechst 33258, while the 3 other techniques labeled either all or species-specific parts of the condensed chromatin. The reasons for these variable reactions are discussed in terms of technique specificities, DNA configuration and nucleoprotein moiety replacements.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    ISSN: 1432-0878
    Keywords: Retina ; Melatonin ; Rhythmic biosynthesis ; Immunocytochemistry ; Pike, Esox lucius (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The levels of melatonin and the activities of two enzymes of the melatonin biosynthetic pathway, serotonin N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT), were measured throughout the light-dark cycle in the retina of a teleost fish, the pike. HIOMT activity did not display significant variations, whereas NAT activity and melatonin content showed a daily rhythm, high levels occurring during the night. The profiles of the latter two rhythms did not closely match one another and differed from those previously described in the pineal organ of the same species. These results are discussed with respect to a possible paracrine role of retinal melatonin. Melatonin-like immunoreactivity was found in the photoreceptor cell layer and in the Müller cells of the inner nuclear layer. The intensity of the melatonin-like immunoreactivity varied throughout the 24 h light-dark cycle, in good correlation with the variations in the melatonin level as measured by radioimmunoassay.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 265 (1991), S. 611-614 
    ISSN: 1432-0878
    Keywords: Immunocytochemistry ; Met-enkephalin ; Merkel cells ; Dense-core granules ; Mouse (ICR)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The electron-microscopic immunogold method was applied to Merkel cells of adult mice to demonstrate the subcellular localization of met-enkephalin-like immunoreactivity. Post-embedding incubation with metenkephalin antisera showed that the gold particles were associated with the dense-core granules of the Merkel cells. The majority, but not all, of the dense-core granules were strongly labelled. Osmication caused a significant reduction in the number of gold particles on these granules. The nerve terminal associated with the Merkel cell did not show met-enkephalin-like immunoreactivity. To the best of our knowledge, this is the first report of the ultrastructural localization of a positive met-enkephalin immunoreactivity in the dense-core granules of Merkel cells in mice.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 266 (1991), S. 247-258 
    ISSN: 1432-0878
    Keywords: Monoclonal antibodies ; Immunocytochemistry ; Olfactory epithelium ; Respiratory epithelium ; Antigens ; (Rat Wistar) ; (Mouse BALB/c)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two panels of monoclonal antibodies have been generated, each panel having a distinct specificity for antigens located in the ciliary zone of either the olfactory or respiratory epithelium of rats. Tissue specificity was confirmed in enzyme-linked immunosorbent assays on membrane fractions from various tissues. During ontogeny, the expression of olfactory-specific antigens preceeds that of respiratory-specific antigens; this observation correlates with differences in the genesis of the respective cilia type and confirms that different molecular entities are recognized. A spatial segregation of immunoreactivity in the chemosensory epithelium was observed for one of the olfactory-specific monoclonal antibodies; negative zones were located in the dorsal recess of the nasal cavity and on the tips of the turbinates. Olfactory-specific antibodies reacted with distinct polypeptide bands on Western blots from olfactory ciliary preparations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 266 (1991), S. 359-364 
    ISSN: 1432-0878
    Keywords: Immunocytochemistry ; Neuropeptide ; Diuretic hormone ; Neurosecretion ; Manduca sexta, Eurema nicippe (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Separate antisera were raised to the N- and C-terminal half of the diuretic hormone from Manduca sexta. Antisera against the two halves of this peptide recognized the same cells in M. sexta, and preabsorption of the antisera with the peptides used as antigens abolished the immunoreactivity, confirming their specificity. The antisera reacted with two median neurosecretory cells on each side of the protocerebral groove in larvae, and with a group of about 80 small median neurosecretory cells in the adult, as well as their axons to, and their axon terminals in, the corpora cardiaca. During the early pupal stages, small cells, which are possibly derived from a common neuroblast, differentiate into immunoreactive neurosecretory cells, which explains the large increase in cell numbers in the adult. In the sleepy sulphur butterfly, Eurema nicippe, homologous median neurosecretory cells in the adult were immunoreactive with both antisera.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    ISSN: 1432-0878
    Keywords: Pigment-dispersing hormone ; Orthopteroid insects ; Immunocytochemistry ; Insect brain ; Periplaneta americana, Schistocerca gregaria, Teleogryllus commodus (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a comparative study, the anatomy of neurons immunoreactive with an antiserum against the crustacean β-pigment-dispersing hormone was investigated in the brain of several orthopteroid insects including locusts, crickets, a cockroach, and a phasmid. In all species studied, three groups of neurons with somata in the optic lobes show pigment-dispersing hormone-like immunoreactivity. Additionally, in most species, the tritocerebrum exhibits weak immunoreactive staining originating from ascending fibers, tritocerebral cells, or neurons in the inferior protocerebrum. Two of the three cell groups in the optic lobe have somata at the dorsal and ventral posterior edge of the lamina. These neurons have dense ramifications in the lamina with processes extending into the first optic chiasma and into distal layers of the medulla. Pigment-dispersing hormone-immunoreactive neurons of the third group have somata near the anterior proximal margin of the medulla. These neurons were reconstructed in Schistocerca gregaria, Locusta migratoria, Teleogryllus commodus, Periplaneta americana, and Extatosoma tiaratum. The neurons have wide and divergent arborizations in the medulla, in the lamina, and in several regions of the midbrain, including the superior and inferior lateral protocerebrum and areas between the pedunculi and α-lobes of the mushroom bodies. Species-specific differences were found in this third cell group with regard to the number of immunoreactive cells, midbrain arborizations, and contralateral projections, which are especially prominent in the cockroach and virtually absent in crickets. The unusual branching patterns and the special neurochemical phenotype suggest a particular physiological role of these neurons. Their possible function as circadian pacemakers is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 266 (1991), S. 385-389 
    ISSN: 1432-0878
    Keywords: Amniotic epithelium ; Cytoskeleton ; Filaments ; α-Actinin ; Ezrin ; Immunocytochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The amniotic epithelium constitutes a diffusion barrier controlling the passage of solutes and water between the aminotic cavity and maternal circulation. With the present immunocytochemical approach, we have shown that several major components of the cytoskeleton, i.e., actin, α-actinin, spectrin and ezrin, are preferentially associated with the apical and lateral cell surfaces of the human amniotic epithelium. Keratins are distributed throughout the entire cytoplasm, whereas vimentin mainly forms a perinuclear scaffold. These findings indicate a role of the various components of the cytoskeleton in the structural integrity and modulation of cell shape and junctional permeability.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    ISSN: 1432-0878
    Keywords: Proventriculus ; Endocrine secretory cells ; Secretory granules ; Peptide hormones ; Colocalization ; Immunocytochemistry ; Colloidal gold ; Chicken
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The endocrine cells of the chicken proventriculus were investigated immunocytochemically, using the peroxidase-antiperoxidase technique on paraffin and semithin sections for light microscopy, and immunogold staining in osmium-fixed material for electron microscopy. The fixation procedure also allowed a detailed ultrastructural investigation. Twenty-three antisera were tested and 7 immunoreactive cell-types were identified: D-cells containing somatostatin-like peptide; EG-cells immunoreactive to anti-glucagon, anti-GLP1 and antineurotensin; NT-cells labelled only with anti-neurotensin; BN-cells containing bombesin-like material; ENK-cells showing met-enkephalin immunoreactivity; EC-cells reactive to anti-serotonin; and APP-cells positive to anti-avian pancreatic polypeptide. In addition, enterochromaffin-like (ECL) cells, were also detected by electron microscopy. The presence of ENK-cells and the ultrastructure of these and NT-cells are described for the first time in chicken proventriculus, and glucagon, GLP1 and neurotensin are shown to be colocalized in the EG-cells.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    ISSN: 1432-0878
    Keywords: Neuroendocrine cells ; Intestine ; Chromogranin ; Serotonin ; Regulatory peptides ; Immunocytochemistry ; Podarcis hispanica (Reptilia, Lacertilia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Numerous endocrine cells can be observed in the gut of the lizard Podarcis hispanica after application of the Grimelius silver nitrate technique. The argyrophilic endocrine cells are usually tall and thin in the small intestine but short, basal, and round in the large intestine. Eleven types of immunoreactive endocrine cells have been identified by immunocytochemical methods. Numerous serotonin-, caerulein/gastrin/cholecystokinin octapeptide-and peptide tyrosine-tyrosine-immunoreactive cells; a moderate number of pancreatic polypeptide-, neurotensin-, somatostatin-, glucagon-like peptide-1-and glucagon-immunoreactive cells, and few cholecystokinin N-terminal-and bombesin-immunoreactive cells were found in the epithelium of the small intestine. Coexistence of glucagon with GLP-1 or PP/PYY has been observed in some cells. In the large intestine a small number of serotonin-, peptide tyrosine-tyrosine-, pancreatic polypeptide-, neurotensin-, somatostatin-and glucagon-like peptide-1-immunoreactive cells were detected. Vasoactive intestinal peptide immunoreactivity was found in nerve fibers of the muscular layer. Substance P-immunoreactive nerve fibers were detected in lamina propria, submucosa and muscular layer. Chromogranin A-immunoreactive cells were observed throughout the intestine, although in lower numbers than argyrophilic cells.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    ISSN: 1432-0878
    Keywords: Gliobastoma multiforme ; Cell culture ; Glial fibrillary acidic protein ; Immunocytochemistry ; Cytogenetics ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two human cell lines (GL15 and GL22) derived from glioblastoma multiforme were established and characterized by immunohistochemical and cytogenetic techniques. The expression of glial fibrillary acidic proteins and the karyotype were analyzed at different passages for both cell lines. The course of marker-pattern differed in the two cell lines. The main findings were a cell-density-dependent expression of glial fibrillary acidic protein in the cell line GL15 at all passages and a decreased expression of this protein over time in the cell line GL22. Both cell lines had hyperdiploid karyotypes and exhibited glioma-specific chromosomal abnormalities (gain of chromosome 7 and loss of chromosome 10). In the GL15 cell line no relevant chromosomal changes were produced during culturing, whereas in the GL22 cell line a hypodiploid clone appeared at the 42nd passage. The immunohistochemical and cytogenetic data resulting from this study confirm that the two cell lines established in our laboratory originated from astrocytic tumor cells.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    ISSN: 1432-0878
    Keywords: Pituitary adenylate cyclase-activating peptide (PACAP) ; Vasoactive intestinal peptide (VIP) ; Immunocytochemistry ; Respiratory tract ; Autonomic innervation ; Mammals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pituitary adenylate cyclase-activating peptide (PACAP) is a vasoactive intestinal peptide (VIP)-like peptide recently isolated from ovine hypothalami. Nerve fibers displaying PACAP immunoreactivity were found in the respiratory tract of rats, guinea pigs, ferrets, pigs, sheep and squirrel monkeys. A moderate supply of PACAP-immunoreactive fibers was seen in the nasal mucosa of guinea pigs. Few to moderate numbers of PACAP-containing fibers occurred in the tracheo-bronchial wall of rats, guinea pigs, ferrets, pigs, sheep and squirrel monkeys. The fibers were distributed beneath the epithelium, around blood vessels and seromucous glands, and among bundles of smooth muscle. In the lungs, the immunoreactive fibers were observed close to small bronchioli. A few PACAP-immunoreactive nerve cell bodies were seen in the sphenopalatine and otic ganglia of guinea pigs. Simultaneous double immunostaining of the respiratory tract of sheep and ferrets revealed that all PACAP-containing nerve fibers stored VIP. We suggest that neuronal PACAP may take part in the regulation of smooth muscle tone and glandular secretion.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    ISSN: 1432-0878
    Keywords: Brain, vertebrate ; Phenylethanolamine-N-methyltransferase ; Adrenaline ; Immunocytochemistry ; HPLC ; Rat (Wistar, Sprague-Dawley, Long Evans, Zucker)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Immunocytochemistry was used to compare the immunoreactivity of adrenergic neurons to a well characterized specific immunoserum to phenylethanolamine-N-methyltransferase (PNMT) in different strains of rats commonly used in research studies. In adult animals, marked differences were found in the PNMT-immunoreactivity of neurons between Wistar rats and other strains, resulting in a lower PNMT-immunostaining intensity (i) within neuronal perikarya of the medulla oblongata, and (ii) more strikingly, within nerve fibers and terminals located in various brain regions. This low PNMT-immunoreactivity of nerve fibers was detected both in 14- and 35-day-old Wistar rats. On the other hand, the HPLC measurement of catecholamines, in particular of adrenaline in the hypothalamus and the medulla oblongata, did not show any difference between adult Wistar and Sprague-Dawley rats. These data suggest that the low PNMT-immunoreactivity observed in central adrenergic neurons of the Wistar rats is related to the poor recognition of the antigen by the PNMT-antibody used. Possibly, these nerve cells mainly display an isoform of the enzyme that is immunologically different from the PNMT contained within the adrenergic neurons of other rat strains.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    ISSN: 1432-0878
    Keywords: Pituitary gland ; Rathke's pouch ; Intermediate filaments ; Cytokeratins ; Development, ontogenetic ; Immunocytochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An immunohistochemical study of the production of the intermediate filaments [vimentin, cytokeratin, and glial filament acidic protein (GFAP)] during development of the pituitary gland was made by use of fetal and adult human pituitary tissue. Among these intermediate filament proteins in the anterior and intermediate lobes of the pituitary, cytokeratin is the first to appear, followed by GFAP and vimentin. However, only cytokeratin is seen during the period of morphogenesis of the pituitary gland, with the type-II subfamily cytokeratin 8 being the earliest to appear. Among the simple-epithelial-type cytokeratins, cytokeratins 8 and 19 were observed within the pituitary primordium during morphogenesis. Cells immunoreactive for cytokeratins 8 and 19 showed a heterogeneous three-dimensional distribution pattern in Rathke's pouch. Both cytokeratins 8 and 19 tended to be strongly positive at sites in the pituitary primordium where cells had become more loosely arranged (i.e., areas far from the diencephalon) but were only weakly positive in areas in which the epithelial cells were densely packed (i.e., areas closely associated with the diencephalon). It is concluded that, during the period of morphogenesis, Rathke's pouch has the intermediate filaments characteristic of simple epithelium and shows different immunoreactivity for simple-epithelial-type cytokeratins from place to place according to the extent of cellular differentiation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    ISSN: 1432-0878
    Keywords: Clotting factors ; Antimicrobial substances ; Hemocytes ; Immunocytochemistry ; Tachypleus tridentatus (Chelicerata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure of hemocytes in the normal state and during blood coagulation, and the intracellular localization of three clotting factors and two antimicrobial factors were examined in the Japanese horseshoe crabTachypleus tridentatus. Two types of hemocytes were found in the circulating blood: non-granular and granular hemocytes. The latter contained numerous dense granules classed into two major types: L- and D-granules. The L-granules were larger (up to 1.5 μm in diameter) and less electron-dense than the D-granules (less than 0.6 μm in diameter). The L-granules contained three clotting factors and one antimicrobial factor, whereas the D-granules exclusively contained the other antimicrobial factor. After treatment with endotoxin, the L-granules were released more rapidly than the D-granules, although almost all granules were finally exocytosed. The granular hemocyte possessed a single Golgi complex; possible precursor granules of L-granules and D-granules contained tubular and condensed dense material, respectively. These data are discussed in relation to the self-defense mechanisms of the horseshoe crab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    ISSN: 1432-0878
    Keywords: Gonadotropin ; Gonadotropin subunits ; Gonadotropes ; In situ hybridization ; Immunocytochemistry ; Pituitary gland, pars distalis ; Oogenesis ; Oncorhynchus mykiss (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Biosynthesis of salmon gonadotropins, GTH I and GTH II, during ovarian development, were examined by means of in situ hybridization histochemistry and indirect immunocytochemistry. In rainbow trout pituitary glands, expression of GTH Iβ- and IIβ-subunit genes appeared separately in distinct cells (GTH I- and GTH II-cells), whereas the GTH α-subunit gene was expressed in both cell-types. In the GTH I-cells, coordinated increases in GTh, α and Iβ messenger ribonucleic acids (mRNAs) occurred coincident with the onset of vitellogenesis, indicating active synthesis of GTH I during vitellogenesis. In contrast, in the GTH II-cells, both GTH α-and IIβ-mRNA signals markedly increased from a later stage of vitellogenesis and persisted throughout oocyte maturation and ovulation, supporting the idea that GTH II is actively synthesized as a maturational GTH. GTH α-mRNA levels in the GTH I-cells selectively decreased prior to final oocyte maturation, although Iβ-mRNA levels remained elevated, thus suggesting a decline of biosynthesis of GTH I after vitellogenesis. These findings clarify how the synthesis of GTH I and GTH II are coordinated in the piscine pituitary, and indicate that the expression of GTH subunit genes during gametogenesis is regulated differentially in a cell-specific manner, both temporally and spatially.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    ISSN: 1432-0878
    Keywords: Visual system ; Neuropeptides ; Serotonin ; Pigment-dispersing hormone ; Immunocytochemistry ; Neuromodulators ; Phormia terraenovae (Insecta) ; Leucophaea maderae (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pigment-dispersing hormone (PDH) family of neuropeptides comprises a series of closely related octadecapeptides, isolated from different species of crustaceans and insects, which can be demonstrated immunocytochemically in neurons in the central nervous system and optic lobes of some representatives of these groups (Rao and Riehm 1989). In this investigation we have extended these immunocytochemical studies to include the blowfly Phormia terraenovae and the cockroach Leucophaea maderae. In the former species tissue extracts were also tested in a bioassay: extracts of blowfly brains exhibited PDH-like biological activity, causing melanophore pigment dispersion in destalked (eyestalkless) specimens of the fiddler crab Uca pugilator. Using standard immunocytochemical techniques, we could demonstrate a small number of pigment-dispersing hormone-immunoreactive (PDH-IR) neurons innervating optic lobe neuropil in the blowfly and the cockroach. In the blowfly the cell bodies of these neurons are located at the anterior base of the medulla. At least eight PDH-IR cell bodies of two size classes can be distinguished: 4 larger and 4 smaller. Branching immunoreactive fibers invade three layers in the medulla neuropil, and one stratum distal and one proximal to the lamina synaptic layer. A few fibers can also be seen invading the basal lobula and the lobula plate. The fibers distal to the lamina appear to be derived from two of the large PDH-IR cell bodies which also send processes into the medulla. These neurons share many features in their laminamedulla morphology with the serotonin immunoreactive neurons LBO-5HT described earlier (see Nässel 1988). It could be demonstrated by immunocytochemical double labeling that the serotonin and PDH immunoreactivities are located in two separate sets of neurons. In the cockroach optic lobe PDH-IR processes were found to invade the lamina synaptic region and form a diffuse distribution in the medulla. The numerous cell bodies of the lamina-medulla cells in the cockroach are located basal to the lamina in two clusters. Additional PDH-IR cell bodies could be found at the anterior base of the medulla. The distribution and morphology of serotonin-immunoreactive neurons in the cockroach lamina was found to be very similar to the PDH-IR ones. It is hence tempting to speculate that in both species the PDH-and serotonin-immunoreactive neurons are functionally coupled with common follower neurons. These neurons may be candidates for regulating large numbers of units in the visual system. In the flies photoreceptor properties may be regulated by action of the two set of neurons at sites peripheral to the lamina synaptic layer, possibly by paracrine release of messengers.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    ISSN: 1432-0878
    Keywords: Corticotropin-releasing factor (CRF) ; Immunocytochemistry ; Arginine vasotocin (AVT) ; Mesotocin (MST) ; Co-localization ; Natrix maura (Serpentes)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The anatomical distribution of neurons and nerve fibers containing corticotropin-releasing factor (CRF) has been studied in the brain of the snake, Natrix maura, by means of immunocytochemistry using an antiserum against rat CRF. To test the possible coexistence of CRF with the neurohypophysial peptides arginine vasotocin (AVT) and mesotocin (MST) adjacent sections were stained with antisera against the two latter peptides. CRF-immunoreactive (CRF-IR) neurons exist in the paraventricular nucleus (PVN). In some neurons of the PVN, coexistence of CRF with MST or of CRF with AVT has been shown. Numerous CRF-IR fibers run along the hypothalamo-hypophysial tract and end in the outer layer of the median eminence. In addition, some fibers reach the neural lobe of the hypophysis. CRF-IR perikarya have also been identified in the following locations: dorsal cortex, nucleus accumbens, amygdala, subfornical organ, lamina terminalis, nucleus of the paraventricular organ, nucleus of the oculomotor nerve, nucleus of the trigeminal nerve, and reticular formation. In addition to all these locations CRF-IR fibers were also observed in the lateral septum, supraoptic nucleus, habenula, lateral forebrain bundle, paraventricular organ, hypothalamic ventromedial nucleus, raphe and interpeduncular nuclei.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 1432-0878
    Keywords: Subcommissural organ ; Secretory pathway ; C1B8A8 monoclonal antibody ; Immunocytochemistry ; Immunoaffinity chromatography ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The secretory pathway of the complex-type glycoprotein specific to the subcommissural organ (SCO) was examined using the monoclonal antibody (Mab) C1B8A8. Immunoreactive material was revealed in various compartments of the secretory ependymocyte, i.e., the endoplasmic reticulum, the Golgi area and the secretory vacuoles. In addition, immunoreactive material was also observed in the ventricular cavity. Evidence of a release both at the apical lining and at the basal process of the SCO ependymocytes suggests that the same protein could be secreted into the cerebrospinal fluid and the perivascular spaces. After immunoaffinity chromatography of soluble extracts of the SCO on Mab C1B8A8 immunoadsorbent columns, three glycopeptides were identified on Western blots; they were concanavalin A (Con A)-positive (88, 54 and 34 kDa) and wheat-germ agglutinin (WGA)-positive (54 and 34 kDa). The Con A-positive glycopeptide (88 kDa) is probably related to the high-mannose-type glycoprotein, the precursor form of the secreted compound, whereas the 54 kDa-glycopeptide that is both Con A- and WGA-positive could represent an intermediate form. The 34 kDa-glycopeptide that is strongly WGA-positive could be related to the monomeric form of the secreted compound. These three glycopeptides were not revealed in eluted fractions of soluble extracts of the ependyma that served as control.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 263 (1991), S. 71-79 
    ISSN: 1432-0878
    Keywords: Aromatase ; Immunocytochemistry ; Brain aromatase ; Preoptic area ; Hypothalamus ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of aromatase-immunoreactive cells was studied by immunocytochemistry in the mouse forebrain using a purified polyclonal antibody raised against human placental aromatase. Labeled perikarya were found in the dorso-lateral parts of the medial and tuberal hypothalamus. Positive cells filled an area extending between the subincertal nucleus in the dorsal part, the ventromedial hypothalamic nucleus in the ventral part, and the internal capsule and the magnocellular nucleus of the lateral hypothalamus in the lateral part. The same distribution was seen in the two strains of mice that were studied (Jackson and Swiss), and the number of immunoreactive perikarya did not seem to be affected by castration or testosterone treatment. No immunoreactivity could be detected in the medial regions of the preoptic area and hypothalamus; these were expected to contain the enzyme based on assays of aromatase activity performed in rats and on indirect autoradiographic evidence in mice. Our data raise questions concerning the distribution of aromatase in the brain and the mode of action of the centrally produced estrogens.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 263 (1991), S. 195-198 
    ISSN: 1432-0878
    Keywords: Pancreas, endocrine ; Islets of Langerhans ; Immunocytochemistry ; Endocrine cells four types ; Electron microscopy ; Sminthopsis crassicaudata (Marsupialia)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The endocrine pancreas of the Australian fattailed dunnart, Sminthopsis crassicaudata, was investigated by means of electron-microscopic immunocytochemistry using the protein A-gold technique on London resin (LR) white-embedded tissue. The primary antibodies used were raised against insulin, glucagon, somatostatin and pancreatic polypeptide. The morphology of the secretory granules differed in the four cell types. The insulin cells are pleomorphic, and the secretory granules composed of an electron-dense core surrounded by an electron-lucen halo. The glucago cells possess granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells have large, less dense secretory granules. The pancreatic polypeptide cells show small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by immunocytochemical data at the light-or preferably electron-microscopic level. Recent developments in immuno-electron-microscopic techniques have contributed to a better knowledge of cells responsible for the secretion of a wide variety of hormones, as in this study.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    ISSN: 1432-0878
    Keywords: Pineal organ ; Epithalamus ; Pinealocytes ; Hydroxyindole O-methyltransferase (HIOMT) ; Immunocytochemistry ; HIOMT-mRNA ; In-situ hybridization ; Bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hydroxyindole O-methyltransferase (HIOMT)-immunoreactive cells and melatonin synthesis were demonstrated in bovine epithalamus (including the pineal gland) with monoclonal antibodies and cRNA probes to HIOMT. The HIOMT-immunoreactive product was present in the cytoplasm of pinealocytes. All identifiable pinealocytes were clearly labeled in the pineal gland. The expression of the HIOMT gene was first identified in pinealocyte cytoplasm by in-situ hybridization (ISH). The distribution of the hybridization-positive cells in the pineal gland was compatible with that revealed by immunocytochemistry using the monoclonal antibody to HIOMT. In addition, HIOMT transcripts were found in the medial habenular nucleus, and the habenular and posterior commissure; they may correspond to S-antigen-immunoreactive cells demonstrated in the same regions of the hamster and the mouse. In these regions, the hybridization-positive cells did not exhibit HIOMT-immunoreactivity; thus, cells devoid of immunoreactivity may synthesize but rapidly transport the newly synthesized proteins. These results indicate (1) that the conversion of N-acetylserotonin into melatonin takes place in the cytoplasm of pinealocytes, (2) that some epithalamic cells in the habenular area may synthesize melatonin, and (3) that melatonin may act as a chemical messenger in centrally directed processes, as shown by using S-antigen immunocytochemistry.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 264 (1991), S. 321-328 
    ISSN: 1432-0878
    Keywords: Tooth pulp ; NGF receptor ; Calcitonin gene-related peptide ; Substance P ; Neuropeptide Y ; Immunocytochemistry ; Electron microscopy ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of nerve growth factor receptor (NGF receptor)-like immunoreactivity in pulps of developing primary and mature permanent cat canine teeth was examined, by use of a monoclonal antibody against NGF receptor detected by fluorescence immunohistochemistry and pre-embedding immunocytochemical light- and electron microscopy. Both primary and permanent pulps contained a vast number of NGF receptor-like immunoreactive nerves. Immunolabelling appeared to be localized both to axons and Schwann cells. In addition, many blood vessel walls in immature primary tooth pulps showed NGF receptor-like immunoreactivity, in contrast to permanent pulps where blood vessels rarely were NGF receptor-immunoreactive. Double-labelling immunofluorescence experiments revealed that in the permanent pulp a majority of the NGF receptor-positive nerves also showed calcitonin gene-related peptide (CGRP)-like immunoreactivity, and many showed substance P-like immunoreactivity. However, nerve fibers with neuropeptide Y-like immunoreactivity lacked NGF receptor-like immunoreactivity. In developing primary tooth pulps fewer NGF receptor-positive nerves were CGRP-like immunoreactive or substance P-like immunoreactive, as compared to the permanent pulp. Neuropeptide Y-like immunoreactive nerve fibers were not detected in the primary tooth pulp. The results suggest a role for nerve growth factor in both developing and mature sensory nerves of the tooth pulp.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    ISSN: 1432-0878
    Keywords: Serotonin ; Immunocytochemistry ; Olfactory interneurons ; Macrobrachium rosenbergii, Munida sarsi, Pacifastacus leniusculus (Crustacea)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An antiserum raised against serotonin (5HT) was applied to the brains of representatives of four different infraorders of decapod crustaceans, and revealed two morphological classes of olfactory interneurons. They were classified by the position and size of their cell bodies, and by their connection pattern. One class consisted of giant olfactory interneurons and the other of globuli cells. They were regarded as input and intrinsic interneurons, respectively, because of their morphology. The two classes displayed a similar pattern in two of the infraorders, whereas only one class appeared in the other two infraorders.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    ISSN: 1432-0878
    Keywords: Inhibin ; LH ; FSH ; Pituitary gland, pars anterior ; Immunocytochemistry ; Maccaca fascicularis, Macaca mulatta (Primates)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Inhibin-like immunoreactivity was detected by immunocytochemistry in the pituitaries of untreated male crab-eating macaques (cynomolgus monkey) and rhesus monkeys, in rhesus monkeys actively immunized against FSH, and in one orchidectomized crab-cating macaque. Localizations were performed by the immunogold-silver staining with 5-nm colloidal gold-conjugated second or third antibodies and by the alkaline phosphatase-anti-alkaline-phosphatase technique. Two different inhibin-specific antisera, raised against the α-subunit or the entire inhibin molecule, provided identical staining patterns. Positive label was confined to the pars distalis of the pituitary and occurred exclusively in the cytoplasm of morphologically different cell types throughout the pars distalis in all pituitaries. Staining was most prominent in clusters of chromophobic cells. The presence of inhibin-like activity in the pituitary of an orchidectomized monkey with undetectable serum inhibin levels suggests that inhibin is produced within the pituitary gland. Co-localization studies for the β-subunits of the gonadotropic hormones revealed that on average 82% of the gonadotropes were bihormonal. Using the same protocol, co-localization of inhibin-like activity with gonadotropin-like immunoreactivity revealed only a small degree of common distribution (〈15%). Inhibinpositive cells were frequently in close proximity to gonadotropic cells and, thus, paracrine effects of inhibin on gonadotropin-synthesizing cells are conceivable.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 1432-0878
    Keywords: Neuropeptide Y (NPY) ; Immunocytochemistry ; Avian brain ; Japanese quail, Coturnix coturnix japonica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the present study, we have demonstrated, by means of the biotin-avidin method, the widespread distribution of neuropeptide Y (NPY)-immunoreactive structures throughout the whole brain of the Japanese quail (Coturnix coturnix japonica). The prosencephalic region contained the highest concentration of both NPY-containing fibres and perikarya. Immunoreactive fibres were observed throughout, particularly within the paraolfactory lobe, the lateral septum, the nucleus taeniae, the preoptic area, the periventricular hypothalamic regions, the tuberal complex, and the ventrolateral thalamus. NPY-immunoreactive cells were represented by: a) small scattered perikarya in the telencephalic portion (i.e. archistriatal, neostriatal and hyperstriatal regions, hippocampus, piriform cortex); b) medium-sized cell bodies located around the nucleus rotundus, ventrolateral, and lateral anterior thalamic nuclei; c) small clustered cells within the periventricular and medial preoptic nuclei. The brainstem showed a less diffuse innervation, although a dense network of immunopositive fibres was observed within the optic tectum, the periaqueductal region, and the Edinger-Westphal, linearis caudalis and raphes nuclei. Two populations of large NPY-containing perikarya were detected: one located in the isthmic region, the other at the boundaries of the pons with the medulla. The wide distribution of NPY-immunoreactive structures within regions that have been demonstrated to play a role in the control of vegetative, endocrine and sensory activities suggests that, in birds, this neuropeptide is involved in the regulation of several aspects of cerebral functions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    ISSN: 1432-0878
    Keywords: FMRFamide ; Brain, vertebrate ; Hypothalamus ; Pituitary gland, pars intermedia ; Nervus terminalis ; Immunocytochemistry ; Scyliorhinus torazame (Elasmobranchii)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of the molluscan cardioexcitatory tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2) in the brain of the cloudy dogfish, Scyliorhinus torazame, was examined by immunocytochemistry. FMRFamide-like immunoreactivity was demonstrated to occur extensively in various regions of the dogfish brain, except for the corpus cerebelli. Immunoreactive neuronal perikarya were located in the ganglion of the nervus terminalis, the preoptic area, and the hypothalamic periventricular gray matter consisting of the nucleus medius hypothalamicus, the nucleus lateralis tuberis, and the nucleus lobi lateralis. some of the immunoreactive cells in the hypothalamus were identified as cerebrospinal fluid-contacting neurons. The bulk of the immunostained fibers in the nervus terminalis penetrated into the midventral portion of the telencephalon and ran dorsocaudally toward the basal telencephalon and hypothalamus, showing radial projections or ramifications. The labeled fibers were abundant in the midbasal part of the telencephalon and in the hypothalamus, where some fibers were found in loose networks around the cell bodies of the nucleus septi and hypothalamic periventricular nuclei. The fibers demonstrated in the hypothalamus terminated around the vascular wall of the primary capillary plexus of the median eminence or penetrated deeply into the pars intermedia of the hypophysis. These results suggest that, in the dogfish, an FMRFamide-like substance participates in the regulation of adenohypophysial function. This molecule may have a role as a neurotransmitter and/or neuromodulator in the central nervous system.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 163 (1991), S. 199-202 
    ISSN: 1615-6102
    Keywords: Actin ; Freeze substitution ; Fungi ; Hyphal tip ; Immunocytochemistry ; Magnaporthe grisea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have successfully localized fungal actin for the first time using immuno-electron microscopy and hyphal tips of the rice blast pathogenMagnaporthe grisea. Following ultrarapid freezing, samples were processed in a novel substitution fluid of 10% acrolein in anhydrous ethanol and embedded in LR White resin. A monoclonal anti-actin antibody, previously shown to recognizeM. grisea actin, bound specifically to filasomes concentrated in the peripheral cytoplasm of subapical regions, and to the core-region of the Spitzenkörper.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    ISSN: 1615-6102
    Keywords: Chlamydomonas ; Cryofixation ; Freeze-substitution ; Immunocytochemistry ; Nuclear proteins ; Nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We describe the preparation of monoclonal antibodies to nuclear antigens in the green alga,Chlamydomonas reinhardtii, and their localization at the light and electron microscope level. Supernatants from hybridomas were screened by the ELISA method and the four antibodies giving the strongest signal were subjected to further analysis. At the LM level immunogold silver staining was used on semi-thick resinless sections. We have examined at the EM level the distribution of these antigens by post-embedding immunocytochemical techniques on sections of conventionally fixed specimens compared to cryofixed and freeze-substituted ones. Enhanced ultrastructural preservation was observed in cells which were cryofixed, freeze-substituted and embedded at −35°C in Lowicryl K4M. Different preparative procedures involving cryofixation and substitution are described. Of the four antibodies three were localized under light and electron microscopy. All three were distributed in the interchromatin space. One of these antigens (QUL4D2, 54 kDa) is also found in the dense fibrillar component and fibrillar centers of the nucleolus.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    ISSN: 1615-6102
    Keywords: Polygalacturonan ; Pectin ; Methyl esterification ; Extracellular matrix ; Frankia ; Ceanothus ; Root nodule ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During early stages of nodule development inCeanothus spp., theFrankia infection pathway is characterized by a distinctive host-derived extracellular matrix. In the present study, a major component of the host interface is shown to consist of pectic polysaccharides. The distribution of these pectic polysaccharides in developing nodules has been delineated in root and nodule tissue. The levels of polygalacturonic acid detected were extremely high in the root mucilage and in the intercellular infection matrix in the root cortex, as detected by indirect immunogold localization with an antibody, and with fluorescein-conjugated alginate and pectate probes. Polygalacturonans in the intercellular matrix and in nodule tissue were predominantly esterified. The non-esterified polygalacturonans were located in cell junctions. Within the infected nodule cortical cells, (poly)galacturonate content of the interfacial encapsulation surrounding theFrankia endosymbiont was very high, while the cell walls were not labeled above background, suggesting that the encapsulation is a specialized wall layer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 162 (1991), S. 38-45 
    ISSN: 1615-6102
    Keywords: Green algae ; Immunocytochemistry ; Pyrenoid ; RuBisCo ; RuBisCo activase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary RuBisCo activase catalyzes the activation and maintains the activated state of the photosynthetic enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCo, EC 4.1.1.39). We employed antisera prepared against the RuBisCo holoenzyme purified from tobacco and RuBisCo activase isolated from spinach to determine the localization of these proteins in leaves of C3-type higher plants and green algae. In leaves ofVicia faba, both RuBisCo activase and RuBisCo are distributed throughout the chloroplast stroma. In contrast, RuBisCo activase and RuBisCo are predominantly localized to the pyrenoid in the green algaeChlamydomonas reinhardtii andColeochaete scutata. The co-immunolocalization of RuBisCo activase and RuBisCo to the pyrenoid in these two green algal species suggests that pyrenoid-localized RuBisCo is catalytically competent. We conclude that the pyrenoid functions as a unique metabolic compartment of the chloroplast in which the reactions of the photosynthetic carbon reduction pathway are initiated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 203-206 
    ISSN: 1434-6079
    Keywords: 36.40 ; 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Direct production of cations and anions of metal clusters of Sb and Bi by laser evaporation in a vacuum has been studied. Bulk sample substrates are irradiated by 1064, 532 and 355 nm beams at variable intensity, and the ions produced are accelerated and identified by time-of-flight mass spectrometry. At 1064 nm, the cation distributions show that Sb 3 + and Bi 3 + are the most abundant species, while the monomer and dimer cations are almost non-existent. The anion spectra indicate very low yields of Sb− and Bi− with dominant dimer anion species. These patterns persist with laser power variation within the stable operation domain. With lower incident laser wavelength, the mass distributions are modified, favouring the production of the light cluster ions. In no circumstances were Sb and Bi ions withn〉5 observed. Many of the observed phenomena can be explained if one assumes that for these elements, clusters withn〈6 are formed on the substrate surface. Cluster ions are produced via a prompt desorption process, and are subjected to photon induced reactions due to the same incident laser beam. However, more detailed investigation of the desorption properties will be necessary to confirm such a desorption mechanism.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 333-335 
    ISSN: 1434-6079
    Keywords: 36.40 ; 61.16.D ; 82.65.F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Gold particles deposited on graphite in vacuum have been studied by STM observation in air. Liquid-like coalescence between small gold-particles has been observed near room temperature. Preparation of small particles in vacuum is discussed. Small particles are formed in nucleation process if the degree of coalescence of particles is reduced. Over 400 Au particles of 5 nm in diameters with a narrow size-distribution with FWHM 2 nm and a high density of 3×1012/cm2 is prepared by evaporating gold in a vacuum of about 2×10−5 Torr and at the substrate (HOPG) temperature of 20°C.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 347-351 
    ISSN: 1434-6079
    Keywords: 82.65.Jv ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Palladium clusters with a low size dispersion and a single crystallographic shape have been obtained by epitaxial growth on (100) MgO. The isothermal adsorption — desorption kinetics of CO is obtained by a molecular beam method allowing the direct determination of the global adsorption probability and of the mean life time of CO molecules on the clusters. Three main results are deduced from these measurements: — an increase of the adsorption rate of CO on the clusters by the capture of CO molecules physisorbed on the substrate, — a faster desorption rate from (100) than from (111) facets at high coverage, — an increase of the adsorption energy for clusters smaller than 3 nm.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 423-425 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structural stability and energetics of carbon, silicon, and germanium microclusters containing 3−7 atoms have been investigated by using a recently developed empirical many-body potential energy function (PEF), which comprises two- and three-body atomic interactions. The PEF satisfies both bulk cohesive energy per atom and bulk stability exactly. It has been found that the most stable C3−4 microclusters are linear withD ∞h symmetry but C5−7 microclusters are planar withD nh symmetry. Silicon and germanium microclusters show similar structural stability. TheX n (X=Si, Ge;n=3−7) microclusters are found to be most stable in the following forms:X 3 is triangular withD 3h symmetry,X 4 is tetragonal withT d symmetry,X 5 is square pyramidal withD 4h symmetry,X 6 is bipyramidal square withO h symmetry, and finallyX 7 is square pyramidal having two atoms underneath withD 2h symmetry.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 431-433 
    ISSN: 1434-6079
    Keywords: 35.20 ; 36.40 ; 82.30Q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent theoretical studies proved some of the small carbon clusters C n (n≈1−10) are represented by several isomeric structures. Evaluation of the isomer relative stabilities is necessary for comparison of theoretical data with observation, this being exemplified by the C4 and C6 cases. For the former cluster a new energy estimation has been suggested based on the isomerism reasoning. Relative-stability evaluation for clusters of different dimensions is discussed on the C60/C70 system, pointing out a strong pressure-dependency of the picture. The scheme is matched to the recent observations of Bethune and Meijer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 21 (1991), S. 271-279 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Hückel model is used to study the electronic structure of monovalent metal clusters. In an fcc cluster the Hückel model gives an estimate to the electronic structure of a free electron cluster. It is shown that the surface faceting of the fcc cluster can destroy the electronic shell structure already when the cluster has about 100 electrons. In the Hückel model the icosahedral structure has smaller total energy than the fcc structures, from which the Wulff construction has the smallest energy already when the cluster has 600 atoms.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 21 (1991), S. 285-288 
    ISSN: 1434-6079
    Keywords: 36.40 ; 35.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Metal clusters have been produced using a laser evaporation source. A Nd-YAG laser beam focused onto a solid silver rod was used to evaporate the material, which was then cooled to form clusters with the help of a pulsed high pressure He beam. TOF mass spectra of these clusters reveal a strong occurrence of small and medium sized clusters (n〈100). Clusters were also deposited onto grid supported thin layers of carbon-films which were investigated by transmission electron microscopy. Very high resolution pictures of these grids were used to analyze the size distribution and the structure of the deposited clusters. The diffraction pattern caused by crystalline structure of the clusters reveals 3-and 5-fold symmetries as well asfcc bulk structure. This can be explained in terms of icosahedron and cuboctahedron type clusters deposited on the surface of the carbon layer. There is strong evidence that part of these cluster geometries had already been formed before the depostion process. The non-linear dependence of the cluster size and the cluster density on the generating conditions is discussed. Therefore the samples were observed in HREM in the stable DEEKO 100 microscope of the Fritz-Haber-Institut operating at 100 KV with the spherical aberrationc S =0.5 mm. The quality of the pictures was improved by using the conditions of minimum phase contrast hollow cone illumination. This procedure led to a minimum of phase contrast artefacts. Among the well-crystallized particles were a great amount of five- and three-fold symmetries, icosahedra and cuboctahedra respectively. The largest clusters with five- and three-fold symmetries have been found with diameters of 7 nm; the smallest particles displaying the same undistorted symmetries were of about 2 mm. Even smaller ones with strong distortions could be observed although their classification is difficult. The quality of the images was improved by applying Fourier filtering techniques.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 199-201 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Neutral lead cluster beams with ultra-narrow size distribution were produced by neutralization of mass-selected lead cluster ions, Pb n + withn≤12, in sodium vapor under near-resonant conditions. Absolute charge exchange cross sections were measured as a function of cluster size and are on the order of 40 Å2 forn≥4. Possible fragmentation of the clusters associated with charge transfer was examined by translational spectroscopy. No indication of fragmentation was found.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 409-412 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Large even-numbered carbon clusters in the size range from 100 to 600 atoms (giant fullerenes) were generated by laser vaporization and directly injected as positive ions via a supersonic beam into the magnetic trap of an ion cyclotron resonance apparatus. Intense laser excitation of the magnetically levitated fullerenes at 4.0 eV was found to result in production of multiply charged fragments in the trap. Details of the time scale and size dependence of this process suggest it is due to thermionic emission from the superheated gas phase clusters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 435-438 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic spectrum of C60 is calculated using quantum mechanical methods. The first allowed transition in C60 is calculated at an energy of 3.5 eV and with an oscillator strength of 0.09. Several transitions are found at higher energies with comparatively strong oscillator strengths, the strongest one being at 5.78 eV (λ=214 nm). The calculated energy level diagram of C60 is also used to predict wavelengths for transitions in C 60 + and C 60 − . A comparison is made with some recently observed diffuse interstellar bands at 1180 nm and 1320 nm, which have been speculated to originate from C 60 + .
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 18 (1991), S. 181-188 
    ISSN: 1434-6079
    Keywords: 36.40 ; 82.50.F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The infrared photodissociation spectra of C2H4 and CH3OH dimers are measured for different internal excitation energies ΔE. The dimers are size-selected in a scattering process with He and the internal energy is varied by using (1) different collision energies, (2) different scattering angles and (3) by measuring the complete energy loss spectra with and without laser radiation by time-of-flight analysis of the scattered clusters. For (CH3OH)2 the width Γ of the spectrum increases strongly with ΔE, while the cross section at the maximum is constant, a normal behaviour for an inhomogeneously broadened system. For (C2H4)2 Γ is nearly constant after a sort of threshold and the cross section increases with increasing ΔE. These results are explained by hot band excitation and the coupling to the darkv 10-mode.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 18 (1991), S. 257-265 
    ISSN: 1434-6079
    Keywords: 33.20 ; 35.20 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Rotationally cold Na3-molecules are formed during the adiabatic expansion of an argon beam, seeded with 5% sodium vapor. With a single mode tunable dyelaser crossing the molecular beam perpendicularly within the ion source of a mass spectrometer the Na3-molecules are excited into levels of the2 A 2-state which are then ionized by acw argon-laser. Rotational lines of the electronic2 A 2 ←X 2 B 2 transition and their hyperfine structure could be resolved using an OODR-technique. A preliminary analysis of the measured spectra is discussed and a comparison of the experimental results with ab initio calculations is presented.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 18 (1991), S. 267-280 
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.80E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Analysis of free metal clusters studied with photoionization mass spectrometry or photoelectron spectroscopy requires theoretical predictions of the photoionization cross sections to gain a deeper physical understanding. Calculated energy-dependent photoionization cross sections of Na2–8 and K2–8 clusters are presented in this study. The ground state electronic structure of the clusters are calculated using the Local Spin Density method (LSD) which is also the starting point for the cross section calculation with the continuum multiple scattering method. A basic analysis of the photoionization process is given within the independent electron picture. Strong resonances are predicted in the UV cross sections (5–10 eV) of K3–8 but not for Na3–8, interpreted as shape resonances, i.e. quasibound states in which electrons are trapped by a potential barrier. Unfortunately experimental data are only known close to the ionization threshold and a comparison between our values and experimental data in a broad energy range is not possible.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 31-36 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A brief survey is presented of recent simulations of small clusters, made with both ab-initio and classical approaches, with particular emphasis on the application of the Car-Parrinello method. The discussion mainly focusses on the structural properties of a variety of materials and on the effects of temperature.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    ISSN: 1434-6079
    Keywords: 36.40 ; 35.20.Wg ; 03.65.-w
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the mass abundance spectra of sodium clusters containing up to 600 atoms are presented. The clusters are produced in a seeded supersonic expansion of Ar or Kr gas, and the spectra are obtained by a time-of-flight technique. The sawtooth features in the spectra are interpreted as evidence of a regular spherical shell structure with magic numbers,N 0, scaling approximately with the cube root of the number of sodium atoms. Altogether twelve shell closings are observed,N 0=2, 8, 20, 40, 58, 92, 138, 196, 260, 344, 440 and 558. There is also a pronounced odd-even staggering all the way up toN=70. The experimentally observed intensity changes for the clusters around the magic numbers are discussed in terms of the electronic free energy,F(N), calculated at finite temperature, and the second differences of the free energy Δ2 F(N)=F(N−1)−2F(N)+F(N+1). The processes behind the non-uniform abundance distributions, and the thermodynamics of finite electron systems with non-uniform level spacings are discussed on this basis.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    ISSN: 1434-6079
    Keywords: 36.40 ; 31.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analytic expression for the total energy of metallic clusters composed ofN identical atoms of valencev and with net chargeQ is obtained by means of a variational solution of the Thomas-Fermi-Weizsäcker energy density functional within the spherical jellium model. The minimum energy is given as an expansion in decreasing powers of the cluster radiusR=r s Z 1/3, withZ=vN andr s the radius per electron of the bulk metal. The coefficients are obtained as functions ofr s . Terms of volume (R 3), surface (R 2), curvature (R), constant (R 0), (1/R) and (1/R 2) are clearly separated in the formula, as well as the different contributions (kinetic, coulombic and exchange-correlation) to each of them. The asymptotic values (R→∞) for the work functions,W(r s ), and surface energies σ(r s ), are compared to analogous semiclassical and Kohn-Sham calculations of jellium-like surfaces and to the experimental values. The size dependent behaviour of chemical potentials, μ(R), electron affinities,AF(R), and ionization potentials,IP(R), are easily obtained for any kind of metallic clusters. In particular we discuss the Coulomb and quantum corrections to the coefficients β, δ in the asymptotic formulae:IP≃W+β/R andAF≃W+δ/R.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 77-79 
    ISSN: 1434-6079
    Keywords: 34.80G ; 36.40 ; 35.20V
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The previously measured relative cross section function for electron impact ionization (EII) of neutral Ag2 has now been calibrated quantitatively by combining the electron impact ionization with in situ non resonant two photon ionization (NR2PI). By comparing the NR2PI saturation intensities measured for Ag 2 + and Ag+ with the corresponding EII intensities, the ratio between the electron impact ionization cross sections (EIICS) of neutral Ag2 and Ag was determined to be σAg2/σAg=1.53 for an electron energy of 46 eV. This result agrees well with the geometricn 2/3-rule $$(\sigma X_n \sim n^{2/3} )$$ commonly proposed for the dependence of the EIICS of clustersX n on the cluster sizen.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 85-87 
    ISSN: 1434-6079
    Keywords: 36.40 ; 78.40-q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The optical absorption spectrum around the surface plasmon peak is presented for K 21 + . Hot, charged potassium clusters are produced by an adapted liquid metal ion source. The plasmon is found to be slightly red shifted from and distinctly broader than the one reported in an experiment on colder clusters by Bréchignac et al. [3]. Mechanisms responsible for the temperature dependence of the width and position of the surface plasmon in small metal clusters are discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 93-96 
    ISSN: 1434-6079
    Keywords: 36.40 ; 71.45.G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The usual spherical jellium model of alkaline clusters is generalized to allow for a finite surface thickness in the positive background distribution. Static (relative stability, ionization potentials) and response properties have been calculated and the results show a better agreement with experiments.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 97-99 
    ISSN: 1434-6079
    Keywords: 34.80.B ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The following calculations are based on the local density approximation potential (LDA) of W. Ekardt for the spherical jellium-background model (SJBM). Taking into account the smooth shape of the potential, the WKB approximation was used to calculate the energy and angular dependence of the electron scattering cross-sections fo rsmall Na clusters. The number of phase shifts needed to describe the scattering in the range of energies 〈4.5 eV increases with the size of cluster. The calculated elastic electron scattering cross-sections for the Na clusters, corresponding to the shell closings (8, 20, 40), are exhibiting a pronounced peak structure, correlated with resonance states. The computed peaks of the angular dependences of the cross-sections on energy are shifted to small angles with increasing the cluster size. The absence of fragmentation at these small electron energies presents a challenge for the experimentalists.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 129-131 
    ISSN: 1434-6079
    Keywords: 36.40 ; 79.70 ; 35.20X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Cluster ions of alloys (Li-Na, Li-Mg) have been produced by a liquid metal ion source (LMIS), and analyzed by mass spectrometry. For the Li-Na system, bimetallic clusters with various compositions were formed, and dominant bimetallic species were Na2Li+, NaLi+, NaLi 2 + and NaLi 8 + with this sequence of ion intensity. These clusters are systems containing 2 or 8 valence electrons except for NaLi+. For the Li-Mg, observed bimetallic clusters were limited to only three species (MgLi+, MgLi 2 + and Mg2Li+), but unexpectedly small multiply charged homonuclear clusters, Mg 2 2+ and Mg 3 2+ , were observed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 181-184 
    ISSN: 1434-6079
    Keywords: 05.70 ; 07.75 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The vapor over sodium-tellurium alloys was investigated using Knudsen effusion mass spectrometry. The stoichiometries of the molecules in the gas phase are compared with the stoichiometries of those appearing in liquid ammonia. Enthalpies of formation for the gaseous molecules are obtained using van't Hoff plots and third law evaluations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 189-190 
    ISSN: 1434-6079
    Keywords: 36.40 ; 35.20X ; 79.20X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Manganese cluster ions Mn k + (k≲60) have been produced by 7 keV Xe ion bombardment and analyzed by a double-focusing mass spectrometer. Discontinuous variations of intensity are found atk=5, 14, 16, 29, 34, 45 and 54. Most of these magic numbers coincide with or differ by only one from those observed in Ar k + . The similarity in magic numbers between Mn k + and Ar k + indicates that the bonding nature in the charged Mn clusters is similar to that in the charged Ar clusters; The polarization force between a positive ion in the center of a cluster and surrounding neutral atoms is dominant binding force.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Photodetachment spectra of negative carbon clusters are reported in the size range from 5 through 20 atoms. The clusters were prepared in a supersonic beam by laser vaporization and 2nd (2.3 eV) and 3rd (3.5 eV) harmonics of Nd-YAG laser were used for photodetachment. The resultant data indicate that carbon negative cluster ions in the 10–20 range take the forms of both linear chain and cyclic ring under a certain condition.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 447-449 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The hydrogen uptake for small carbon clusters C4 to C22 has been studied at high hydrogen pressure. This study indicate that both chain and ring structures exist in parallel.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 19 (1991), S. 443-446 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Structural properties of 3d carbon clusters were calculated employing recently developed model potential energy functions for carbon. Primarily, spherical shell structures were included in the present investigation. Configurations corresponding to local energy minima were calculated for various shells of an icosahedron containing different number of C atoms. For C60, the two low-lying isomers, the buckminsterfullerene and truncated dodecahedron, were found to be almost isoenergetic. It was also found that fully relaxed structures of C90 and C120 have energies very comparable to that of C60. Furthermore, a systematic analysis carried out in this study for carbon clusters with varying dimensionalities, revealed an interesting relationship between the bond lengths and the distribution of bond angles. In all cases, shorter bond distances were found to be associated with larger bond angles.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 35-38 
    ISSN: 1434-6079
    Keywords: 36.40 ; 34.80 ; 71.35
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method to measure electron energy loss spectra (EELS) of clusters with a high resolution (30 meV) has been developed and has been applied to some van der Waals clusters (Ar n , Kr n ). Structures have been found which relate to the excitation of atoms on the surface and inside the cluster. An influence of the cluster size on the spectra has been observed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 39-42 
    ISSN: 1434-6079
    Keywords: 36.40 ; 71.90 ; 78.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Absorption spectra of Ar clusters containing between 10 and 106 atoms are dominated by strong transitions into bulk and surface states. The intensity variation of bulk and surface excitations is analyzed within a model, which divides the cluster into a surface layer and into an interior part. The thickness of the surface layer is determined by the intensity ratio of bulk and surface excitations. For then=2, 2′ excitons a reasonable value ranging between the radius of then=2 exciton and the nearest neighbour distance is obtained. In case of then=1 excitons the thickness of the surface layer is much smaller than the nearest-neighbour distance indicating that then=1 surface excitons might be interpreted as excitations of atoms on the cluster surface.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 53-55 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An exact theory for excess electrons in clusters of rare gas atoms is limited to small sizes,n 〈 20, because of many body polarization interactions which make it necessary to solve a large system of linear equations. We present a simple dielectric screening approximation, which avoids this difficulty and which is in very good agreement with the exact calculation. This approximation can be used to examine the excitation energies of excess electrons and exciton energies in large clusters. A new atomic structure is proposed for a cluster of 12 Xe atoms, resulting in an increased binding energy for the excess electron, which is larger than the electron affinity of a cluster of 13 atoms. This might explain the relatively large abundance of Xe 12 − observed in the experiment.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 111-113 
    ISSN: 1434-6079
    Keywords: 36.40 ; 61.25
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Qualitative similarities and differences between metal cluster and nuclear fission are discussed in terms of the liquid drop model. Points covered include the dependence onz 2/n of the relative fission rate, the critical size, and the competition between fission and evaporation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 115-118 
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.80 ; 82.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract One of the major problems in cluster beam experiments with uncharged clusters is to relate the detected distribution of cluster ions to the original distribution of the neutrals. Fragmentation of the clusters, differences in ionization efficiencies, and desorption of ligands for chemically reacted clusters distort the initial distribution. In this contribution the abundances of the neutral and the ionized particles will be related by rate equations in terms of phenomenological rate constants. Two approaches are chosen. In the more simple one the ionization and decay processes are fast and take place during the excitation pulse. In the second approach delayed processes are also allowed. In both cases recursion formulas are derived as analytical solutions of the coupled rate equations for the time evolution of the neutral and ionized cluster intensities. The general solutions contain a considerable number of parameters which have to be reduced by experimental conditions and observations. Applications are discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 153-155 
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.80 ; 33.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The absolute cross section for photodissociation of Ar2N 2 + was measured as a function of wavelength in the 470–550 nm range. A structureless broad band was observed; the cross section has a maximum of ∼ 210 × 10−18 cm2 at ∼ 500 nm. The measurement of the photofragment time-of-flight spectrum shows that(1) N 2 + , Ar+ and Ar 2 + are produced in the photodissociation of Ar2N 2 + in the wavelength range studied, and that(2) the observed visible absorption band is ascribable to a parallel-type transition of Ar2N 2 + , which possibly retains a linear geometry.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 147-151 
    ISSN: 1434-6079
    Keywords: 36.40 ; 71.10 ; 77.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For Ar2–29 and Ar 2–29 + clusters at 20 K in the polarization model presented here the electrodynamical dipole-dipole many-body problem is solved selfconsistently with the Monte-Carlo method (MC) at 20 K, i.e. the instantaneous dipole-dipole interaction is solved to infinite perturbation order and in cluster expansion to the order of the cluster size. The long range many-body dipole-dipole interaction is coupled to exchange interaction by a modified effective dipole polarizability. This model will be compared to the dimer model and classical MC simulation of Ar n . The resulting different magic numbers in the binding energies are discussed in this connection with different experimental techniques of cluster ionization. By the mean square cluster diameter a shape parameter is introduced and it is found that with this parameter structural form transition in cluster growth can be resolved, and surprisingly do not correlate with the magic numbers.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 163-166 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Extensive molecular dynamics simulations have been done to study the evaporation of a 13-atom Lennard-Jones cluster. The survival probability and the evaporative lifetime are calculated as a function of the cluster total energy from a classical trajectory analysis. The results are interpreted in terms of the RRK theory of unimolecular dissociation. The calculation of the binding energy of the evaporated species from the evaporation rate and the average kinetic energy release is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    ISSN: 1434-6079
    Keywords: 36.40 ; 82.50.F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Infrared photodissociation spectra of (CH3NH2) n clusters were measured fromn=2 ton=6 near the monomer absorption of the C-N stretching mode at 1044 cm−1 using a cw-CO2 laser. The clusters were size-selected by scattering from a helium beam. The spectrum of cold dimers shows a red (1038 cm−1) and a blue (1048 cm−1) shifted peak which is attributed to the non-equivalent position of the C-N in the open dimer structure. The larger clusters exhibit only one peak between 1045.4 cm−1 and 1046.0 cm−1 caused by the equivalent position of the C-N in the cyclic structures of the larger clusters. Structure calculations confirm these results. Secondly, the mixed complexes C2H4-CH3COCH3 and C2H4-(CH3COCH3)2 were investigated. The dimer spectrum, measured around the monomer frequency of the out-of-plane bending mode of C2H4 at 949 cm−1, shows two peaks at 946.2 cm−1 and 961.3 cm−1. This splitting is attributed to two different isomers that are found in configuration calculations. A similar behaviour is found for the trimer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    ISSN: 1434-6079
    Keywords: 36.40 ; 34.80.G
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The hydrogen-bonded (N2H4) n clusters and the van der Waals (OCS) n clusters are size selected in a scattering experiment with a He beam up to the cluster sizen=6. By measuring the angular distributions of the scattered clusters the complete fragmentation pattern of electron impact ionization is obtained. For Hydrazine the two main fragment masses are the protonated species (N2H4) n−1H+ and with somewhat weaker intensities also the nominal ion mass (N2H4) n + . The largest intensity is observed for the monomer ion N2H 4 + to which clusters up ton=5 fragment. For carbonylsulfide, completely different results are obtained. Aside from the fragments of the OCS monomer and the van der Waals cluster fragments (OCS) 2 + and (OCS) 3 + signals at mass S 2 + , S 3 + and S2OCS+ are detected. This indicates a fast chemical reaction in the cluster according to: S + OCS → CO + S2 which occurs for clusters of sizen ≥ 2. Peaks at S 3 + and S2OCS+ are seen for the first time forn ≥ 5 according to a further reaction of S2 in the cluster.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 185-187 
    ISSN: 1434-6079
    Keywords: 33.65 ; 33.80E ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The internal energy exchanges inside an inhomogeneous van der Waals cluster are investigated by means of molecular dynamic calculations. The very long time scales for relaxation of the high frequency degrees of freedom are examined within the framework of Nekhoroshev's theorem.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stoichiometric and non-stoichiometric, positive and negative oxygen cluster ions (n up to 70) have been produced in a crossed neutral beam/electron beam ion source. The abundance and stability of the ions formed have been analyzed with a double focussing sector field mass spectrometer in a series of experiments. Positive and negative ion mass spectra observed exhibit distinct abundance anomalies, however, at different cluster sizes. Abundance maxima and minima correlate with correspondingly small and large metastable fractions of (O2) n + and (O2) n − ions, respectively. (O2) n + ions may also lose up top=(n−1) monomers by collision induced dissociation with monotonously decreasing probability with increasingp. Metastable fractions determined for (O2) n − ions produced with appr. zero eV electrons are in general larger than those for ions produced with appr. 7 eV electrons. (O2) n − ions are also observed to decay via autodetachment, with lifetimes increasing with increasing cluster size. Finally, here we were able to prove that an apparent loss of the monomer fragment O (and higher homologues) observed in the metastable time regime is due to ordinary metastable monomer evaporation in the acceleration region. Moreover, we will also present here some new data and interpretation concerning the electron attachment cross section function for O2 clusters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 89-91 
    ISSN: 1434-6079
    Keywords: 36.40 ; 34.80 ; 33.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The laser ablation of solid targets made of mixtures of simple components yields cluster ions of various composition. In this paper, positive cluster ions formed by laser ablation of metal oxide and graphite systems are reported. The formation of Me m C n + cluster ions indicate a chemical reaction in the surrounding area hit by the laser beam.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Production and stability of Ar n +* ions (withn up to 420) formed by electron impact ionization of a supersonic Ar cluster beam were investigated with a double focussing sector field mass spectrometer. The present study confirms previous magic number determinations up to the 4th icosahedral shell. A systematic study of metastable dissociations (monomer evaporation, magic number evaporation) for singly charged cluster ions as a function of cluster size, internal excitation energy and time elapsed since ion formation gives new insight into the ionization process and subsequent reactions of the ions formed. At a well-defined threshold energy ofca. 28 eV, the magic number loss mechanism occurs simultaneously with the well known single monomer evaporation process which proceeds at all energies. The new mechanism is the first known example of cluster ion metastability showing an exponential dependence on time, providing further evidence that the precursor parent cluster ion is produced in a specific energy state.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 235-238 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The transition from solid-like to liquid-like behavior in Au n ,n=6, 7, 13, clusters is studied using molecular dynamics simulations. A Gupta-type potential with all-neighbour interactions is employed to incorporaten-body effects. The melting-like transition is described in terms of short-time averages of the kinetic energy per particle, root-mean-square bond length fluctuations and mean square displacements. A comparison between melting temperatures of Au n and Ni n clusters is presented.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 239-242 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of molecular dynamics simulation studies of structural and dynamical properties of 12-, 13-, and 14-atom transition metal clusters are presented. The calculations are carried out using a Gupta-like potential expressed in reduced units. The transformation to absolute units involves two size-dependent parameters which effectively convert the potential into a size-dependent one. The minimum energy geometries of the clusters are obtained through the technique of simulated thermal quenching. A melting-like transition is observed as the energy of the clusters is increased. A novel element of the transition is that it may involve a premelting state.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 251-253 
    ISSN: 1434-6079
    Keywords: 36.40 ; 61.14F ; 64.70K
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structure of SF6 clusters produced in a free jet expansion is studied by electron diffraction methods. A solid phase transition is known to occur when clusters are warmed up by changing several experimental conditions in the expansion of a Ne + SF6 mixture. In the present study, the total stagnation pressure and the SF6 mole fraction are varied in order to understand how these parameters influence the structural state of the clusters and further to observe the phase transition for different cluster sizes. When the stagnation pressurep 0 is larger than about 10 bar, a given mole fraction results in clusters with identical structure and probably identical temperature. Whenp 0 is decreased below 10 bar, identical structures are found for lower and lower mole fractions. This structural behaviour suggests that for small clusters, containing less than about 500 molecules, the transition steps occur at temperatures lower than those observed for larger clusters. The possibility of detecting a temperature variation in the diffraction patterns of small cubic clusters is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 255-257 
    ISSN: 1434-6079
    Keywords: 36.40 ; 61.14.F ; 64.60.Q ; 82.20.M
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method has been devised to study the kinetics of phase changes in an unfamiliar regime of extreme undercooling and rate of transformation. We show how electron diffraction can monitor the time evolution of phase changes in molecular clusters condensed from the vapor in supersonic flow. Transitions taking place in microseconds are readily followed. Examples include solid state transformations as well as the freezing of liquid clusters. Aspects of the experiment making it possible to observe familiar transitions under highly unusual conditions will be discussed along with some advantages of the new technique.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 259-261 
    ISSN: 1434-6079
    Keywords: 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stabilities and structural fluctuations of both neutral and charged Au55 clusters are examined and discussed in relation to recent experimental observations of small gold particles with an electron microscope. Transition probabilities between the icosahedral and cuboctahedral structures are calculated according to the transition state theory using a model potential consisting of attractive many-body, repulsive pairwise and Coulomb parts. It is shown that for a neutral cluster the cuboctahedral structure has too short life time to be observed around room temperature and that, on the other hand, for more than 6-fold multiply charged clusters, both structures have life times of the order of 0.1 s around room temperature and, therefore, the transition between them can be observed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 297-300 
    ISSN: 1434-6079
    Keywords: 33.20.K ; 36.40 ; 42.20 ; 78.40 ; 82.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Au55 cluster compounds are investigated by optical spectroscopy and TEM. The optical spectra appear to be rather structureless, neither showing a collective excitation resonance nor exhibiting distinct absorption bands known from lower nuclearity clusters. We discuss changes of the electronic properties compared to larger Au clusters affecting both, 6sp electrons and5d-6sp interband transitions, the cluster-ligand-interaction being considered as a charge transfer process. We additionally report on a low temperature instability of the cluster compound, which results in changed optical extinction spectra. A characteristic absorption feature at λ=400 nm is attributed to small, ligand-free Au cluster fragments.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.60 ; 33.80.E
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The photodetachment spectra of (H2O) n =2−69/− and (NH3) n =41−1100/− have been recorded, and vertical detachment energies (VDEs) were obtained from the spectra. For both systems, the cluster anion VDEs increase smoothly with increasing sizes and most species plot linearly withn −1/3, extrapolating to a VDE (n=∞) value which is very close to the photoelectric threshold energy for the corresponding condensed phase solvated electron system. The linear extrapolation of this data to the analogous condensed phase property suggests that these cluster anions are gas phase counterparts to solvated electrons, i.e. they are embryonic forms of hydrated and ammoniated electrons which mature with increasing cluster size toward condensed phase solvated electrons.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 377-379 
    ISSN: 1434-6079
    Keywords: 79.60 ; 71.20 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We measured XPS and UPS spectra of gold clusters with 55 atoms, embedded in an electrically isolating phosphine matrix, and of gold-phosphine, from which the clusters were chemically derived. Compared to the spectra of bulk gold the valence band spectrum and the core level spectra of the clusters showed shifts of the peaks and the fermi level to higher binding energies. The shift of the peaks could qualitatively be interpreted by a final state effect. We succeeded in a separation of bulk and surface contributions to the core level spectra and in a reasonable quantitative analysis of the valence band spectrum of the clusters. The Au 4f core level spectrum of gold-phosphine showed two peaks at 1.5 eV higher binding energies than the corresponding peaks of the clusters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 387-390 
    ISSN: 1434-6079
    Keywords: 79.20 ; 73.20 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic structure of small chromium clusters deposited by evaporation onto clean polycrystalline graphite has been studied by means of Auger, X-ray Photoemission (XPS) and Electron Energy Loss (EELS) spectroscopies. The XPS results show an increase in the binding energy of both core levels and valence band reducing the cluster size. The EELS measurements show a variation of the intensity ratio of L3-to-L2 ionization core edges. We interpret this change as due to different redistribution, within the clusterd-band, of the empty states above the Fermi level. As a consequence the XPS results may also be attributed to sizeable change of the electronic structure of the small clusters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 391-394 
    ISSN: 1434-6079
    Keywords: 79.60 ; 36.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Silver and chromium particles in the size range 10 nm to 25 nm formed by deposition in ultra-high vacuum on graphite have been studied using synchrotron radiation. We have determined the island size by measuring the spectral dependence of the reflectivity of each sample using light in the photon energy range 35 eV to 190 eV. Comparing this measurement to a calculation of the reflectivity modified by the size-dependent extinction, determined using Mie theory, gives the average particle radius. Using this sizing technique we find that, for the growth of silver at room temperature, the average radius increases linearly with the cube root of evaporation time. Deposition with the substrate at elevated temperatures produces, for similar coverages, an increase in the average size for temperatures between 200°C and 225°C followed by a rapid decrease above 225°C. Chromium shows size effects in the photoemission spectra from the 3s and 3p core levels and the 3d valence band. With decreasing radius a decrease in the multiplet splitting of the 3s core level and a large change in the relative intensity among the 3p multiplets occurs indicating increased electron correlation as the system becomes smaller. A narrowing of the valence band also occurs which we attribute to a structural change at the surface of the particles.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    ISSN: 1434-6079
    Keywords: 36.40 ; 33.40. Hp ; 32.30. Bv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Microwave spectroscopy in highly excited Rydberg states is proposed for structure determination of small metal cluster ions. An experimental setup for microwave optical triple resonance is developed and tested for Yb atom. Many microwave transitions are measured with the line width less than 1 MHz (HWHM).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 20 (1991), S. 425-428 
    ISSN: 1434-6079
    Keywords: 36.40 ; 61.50.C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The first successful experiments to generate continuum silver cluster beams from nozzle expansions are described. A mixture Ar/Ag expands out of a conical nozzle (0.35 mm dia., 10° cone angle, length 17 mm). At 2150 K, total pressure 300 kPa, silver partial pressure 8 kPa the silver intensity measured with a rate meter 479mm away from the source is 1.8 nm/s, or 0.02 g m−2s−1. The data for the onset of clustering confirm the predictions of the scaling laws developed to compare condensation in nozzle expansions of metal vapors with that of rare gases.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...