ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
Filter
  • Polymer and Materials Science  (65)
  • Inorganic Chemistry  (23)
  • 72.20.-i
  • 78.20.-e
  • 1990-1994  (74)
  • 1980-1984  (16)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of arsenic vapour species on electrical and optical properties of GaAs grown by molecular beam epitaxy (1982)
    Springer
    Applied physics 28 (1982), S. 167-173 
    Details
    ISSN: 1432-0630
    Keywords: 68.55.+ b ; 71.55.-i ; 72.20.-i ; 78.55.-m
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hall effect, DLTS and low-temperature photoluminescence measurements were used to study the effect of dimeric (As2) vs tetrameric (As4) vapour species on the electrical and optical properties of nominally undoped and of Ge-doped GaAs layers grown by molecular beam epitaxy (MBE). The arsenic molecular beam was generated from separate As2 and As4 sources, respectively, and from a single source providing an adjustable As2/As4 flux ratio. The occurence of the previously described defect related bound exciton lines in the luminescence spectra at 1.504–1.511 eV was found to be directly correlated with the presence of three deep states (M1, M3, M4) which are characteristic of MBE grown GaAs. The intensity of the extra luminescence lines and simultaneously the concentration of the deep electron traps can be reduced substantially simply by decreasing the As4/As2 flux ratio. The incorporation of defect related centers as well as of amphoteric dopants like Ge strongly depends on the surface chemistry involved. Therefore, a considerably lower autocompensation ratio in Ge-dopedn-GaAs is obtained with As2 molecular beam species which provide a higher steady-state arsenic surface population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617982
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Photoluminescence of Al x Ga1−x As/GaAs quantum well heterostructures grown by molecular beam epitaxy (1984)
    Springer
    Applied physics 33 (1984), S. 9-17 
    Details
    ISSN: 1432-0630
    Keywords: 81.15.-z ; 78.55.-m ; 78.20.-e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Nominally undoped AlxGa1−xAs grown by molecular beam epitaxy from As4 species at elevated substrate temperatures of 670°C exhibits well-resolved excitonic fine structure in the low-temperature photoluminescence spectra, if the effective As-to-(Al+Ga) flux ratio on the growth surface is kept within a rather narrow range of clearly As-stabilized conditions. In contrast to previous results on AlxGa1−xAs of composition 0.15〈x〈0.25, the prominent carbon-related recombination at ∼23 meV below the bound exciton line was foundnot to shift in energy by changing the excitation intensity. This implies a simple freeelectron carbon-acceptor recombination mechanism for the line without any participation of a donor. In AlxGa1−xAs of composition close to the direct-to-indirect cross-over point, two distinct LO-phonons separated by 34 and 48 meV from the (D 0,C 0) peak position at x=0.43 were observed which were before only detectable by Raman scattering experiments. The intensity of the carbon-impurity related luminescence lines in bulk-type AlxGa1−xAs and GaAs layers was found to be strongly reduced, as compared to the excitonic recombination lines, if the respective active layer was covered by a very thin confinement layer of either GaAs on top of AlxGa1−xAs or vice versa grown in the same growth cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01197079
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Preparation and uranyl ion adsorptivity of macroreticular chelating resins containing phosphono groups (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 197 (1992), S. 117-129 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Makroretikulare Copolymerperlen wurden durch Suspensionspolymerisation von Styrol, Bis(2-chlorethyl)vinylphosphonat (CEVP) und Divinylbenzol (DVB) in Gegenwart von Toluol als Verdünnungsmittel hergestellt. Die auf der Perlenoberfläche vorhandenen 2-Chlorethylphosphonat-Gruppen wurden durch Hydrolyse mit verdünnter Salpetersäure in Phosphon-Gruppen transformiert. Für die Einführung zusätzlicher Phosphon-Gruppen wurden die Copolymeren in Gegenwart von Aluminiumchlorid-Katalysator mit Phosphortrichlorid phosphoryliert, und die dabei entstandenen Dichlorphosphingruppen wurden mit verdünnter Salpetersäure verseift und oxidiert. Die Untersuchungen zur Chelatbildung der Copolymeren mit Metallionen zeigten, daß sie ein hohes Adsorptionsvermögen für Uranylionen und gute Stabilität gegen Chemikalien wie Säuren und Alkalien aufweisen. Es wurde auch gefunden, daß die Phosphongruppen enthaltenden Copolymeren recht effektive Adsorbentien für eine Vielzahl von Schwermetalionen wie Pb2+, Hg2+, Cd2+ und Cu2+ sind.
    Notes: Macroreticular copolymer beads were prepared by suspension polymerization of styrene, bis(2-chloroethyl) vinyl phosphonate (CEVP) and divinylbenzene (DVB) in the presence of toluene as diluent. The bis(2-chloroethyl) phosphonate groups on the bead surface were converted into phosphono groups by hydrolysis with dilute nitric acid. For the additional enrichment of phosphono groups, the copolymers were phosphorylated at the phenyl rings with phosphorus trichloride in the presence of aluminum chloride and hydrolyzed and oxidized with dilute nitrics acid. The investigations on metal ion chelation characteristics of the bead-type copolymers revealed that they have very high adsorptivity toward uranyl ions and good chemical resistance under acidic and alkaline media. It was also found that the phosphono group-containing copolymer beads are effective adsorbents for other heavy metal ions such as Pb2+, Hg2+, Cd2+, and Cu2+.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051970110
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Circular dichroism and conformational analysis of the membrane-modifying peptide -N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu-(OBzl)-Gln-OMe with respect to alamethicin (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 203-214 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of the CD spectrum is reported for the synthetic and membrane-modifying nonadecapeptide analog of alamethicin N-t-Boc-(Aib-L-Ala)5-Gly-Ala-Aib-Pro-Ala-Aib-Aib-Glu(OBzl)- Gln-OMe. The CD data are evaluated according to three different methods and are discussed with respect to those obtained from natural alamethicin and suitable models such as N-t-Boc-(Aib-L-Ala)7-OPOE, fragments of the synthetic nonadecapeptide, and the hexadecapeptide N-t-Boc-(Aib-L-Ala)5-Pro-Ala-Aib-Aib-Glu(OBzl)-Gln-OMe. The synthetic nonadecapeptide with the longer helical region exhibits membrane activities comparable to those of alamethicin, whereas the hexadecapeptide with the shorter helix is inactive.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190114
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Stabilizing effects of 2-methylalanine residues on β-turns and α-helices (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 241-246 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C-, 1H-nmr, CD, and x-ray crystallography revealed β-turns of type III for Boc-Gly-L-Ala-Aib-OMe, Boc-L-Ala-Aib-L-Ala-OMe; the 310-helix for Boc-Aib-L-Ala-Aib-L-Ala-Aib-OMe; and antiparallel arranged α-helices for Boc-L-Ala-Aib-Ala-Aib-Ala-Glu(OBzl)-Ala-Aib-Ala-Aib-Ala-OMe. An N-terminal rigid α-helical segment is found in the polypeptide antibiotics alamethicin, suzukacillin, and trichotoxin. The α-helix dipole is essential for their voltage-dependent pore formation in lipid bilayer membranes, which is explained by a flip-flop gating mechanism based on dipole-dipole interactions of parallel and antiparallel arranged α-helices within oligomeric structures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220133
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    α-Helical small molecular size analogues of neuropeptide Y: Structure-activity relationships (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 613-619 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: C-terminal analogues of neuropeptide Y (NPY) of small molecular size have been synthesized. The influence of chain length, single or multiple amino acid substitution, and segment substitutions on receptor binding, pre- and postsynaptic biological activity, and conformational properties have been investigated. Receptor binding and in vivo assays revealed biological activity for NPY Ac-25-36 that increased with increasing α-helicity. In attempts to stabilize the α-helical content, three independent types of modified NPY Ac-25-36 analogues were synthesized. Strong agonistic activities could be detected in a series of discontinuous analogues, which are constructs of N-terminal parts linked via different spacer molecules to C-terminal segments. One of the most active molecules was NPY 1-4-Aca-25-36 (Aca, ε-aminocaproic acid). For the first time conformational properties of a series of small NPY analogues have been investigated by CD, and correlated with biological activity and receptor binding. A C-terminal dodecapeptide segment of NPY with an amount of 50% substitution to the native C-terminal sequence of NPY was found to exhibit significant receptor binding.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310605
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The solution structure of the lantibiotic gallidermin (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 803-811 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 21-peptide amide antibiotic gallidermin is a potential therapeutic against acne disease. It belongs to the class of polycyclic lanthionine and α,β-clidehydroamino acids containing polypeptides, which were named “lantibiotics.” The structural gene of the recently elucidated lantibiotic gallidermin encodes a precursor peptide containing Ser, Thr, and Cys residues in the Oterminal prolantibiotic part, and an unusually hydrophilic leader peptide. The ribosomally synthesized pregallidermin is posttranslationally modified and processed to a complex peptide antibiotic with four/sulfide rings and two unsaturated residues.The complete solution structure of gallidermin was determined in triffuoroethanol : water (95 : 5) and dimethylsulfoxide by two-dimensional 1H-nmr at 500 MHz, using a combination of double quantum filtered correlated spectroscopy, homonuclear Hartman-Hahn, and nuclear Overhauser enhancement spectroscopy experiments. Using a total number of 152 distance constraints from NOEs and 14 torsional constraints, derived from coupling constants, we obtained a screwlike solution structure of gallidermin. Restrained molecular dynamics simulations yielded a set of five converging structures with an atomic rms difference of 1.7 Å for the backbone atoms, not dependent on the starting structure. The spatial structure model is in excellent agreement with the amphiphilic and channel-forming properties of gallidermin on membranes and its tryptic cleavage at the exposed site between residues 13 and 14.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310626
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Stacking interactions of ApA analogues with modified backbones (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1351-1363 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD spectra have been measured as a function of temperature for a number of ApA analogues with modified backbones. Oligonucleotides with these modified backbones are being used as antisense agents having potential as viral therapeutics. Results of these studies show that when a carbonyl is substituted for the phosphate to produce an uncharged backbone, the analogues that have either sugar or morpholino substitution do not stack. In contrast, when a morpholino group is substituted for the sugar and the phosphate is modified so as to be uncharged, there is strong base stacking. Stacking interactions in the phosphorus-linked morpholino analogues are at least as strong as those found in d (ApA). The stacking interactions in ApA are weak by comparison. Singular value decomposition demonstrates that the stacking is two state, and Taylor series decomposition yields a coefficient that measures base stacking interactions. The van't Hoff equation is applied to the base stacking coefficient from the Taylor series fitting to give thermodynamic parameters. © 1992 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360321009
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Investigation of the Enantiomerization Barrier of Homofuran by Computer Simulation of Interconversion Profiles Obtained by Complexation Gas Chromatography (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1301-1303 
    Details
    ISSN: 0009-2940
    Keywords: Enantiomerization ; Dynamic complexation gas chromatography ; Homofuran ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By computer simulation of experimental interconversion profiles, obtained by complexation gas chromatography, rate constants of enantiomerization have been determined for homofuran between 95 and 130°C. Since enantiomerization proceeds at similar rates in the mobile and stationary phase, the rate constants obtained by an Arrhenius plot are in excellent agreement with values determined independently by polarimetry between 60 and 90°C. We thus demonstrate that dynamic chromatography can be an easy means for the rapid determination of enantiomerization (or isomerization) barriers of ca. 70-120 kJ mol-1 requiring only minute amounts of racemic sample.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250543
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Acetylendicarbonyldichlorid (1982)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 804-807 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetylenedicarbonyl DichlorideIn situ prepared carbonyl chloride 2 can be used as „activated acetylenedicarboxylic acid“ in Diels-Alder syntheses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19821150244
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...