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  • 1
    ISSN: 1572-8838
    Keywords: Chalcopyrite ; Bioleaching ; Thermophilic bacteria ; Sulfolobus ; Silver catalysis ; Potentiodynamic polarization ; Cyclic voltammetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The electrochemical behaviour of massive chalcopyrite electrodes has been studied in an acid medium (pH1.5) containing silver ions (0.02gdm−3Ag+) and thermophilic bacteria (68°C). Preliminary tests on particulate electrodes made from graphite, elemental sulfur and Ag2S were included to determine the electrochemical response of reactants (Ag+) and products (S° and Ag2S) associated with the dissolution of chalcopyrite in the presence of silver. Massive chalcopyrite electrodes under potential scan showed a dependence on the dissolution of the Ag2S film with both the time of contact with the silver solution and [Ag+]. As well as Ag2S, metallic silver was detected on the chalcopyrite surface. It has been demonstrated that Fe3+ and bacteria play an important role in the regeneration of the Ag2S film. The breakdown of this film is a requirement for the further dissolution of chalcopyrite. The bioleaching of chalcopyrite with thermophilic microorganisms in the presence of silver decreased the decomposition potential of the electrode and favoured its electrodissolution. Bioleaching treatment in the presence of silver ions for periods of time longer than two weeks did not improve the surface reactivity. However, in the initial stages of the process, the lower reactivity of the bioleached electrodes was probably related to a toxic effect of silver on the microorganisms.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 256 (1997), S. 403-410 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the parametric decays of an electromagnetic wave propagating along an external magnetic field in an electron-positron plasma. We include weakly relativistic effects on the particle motions in the wave field, and the nonlinear ponderomotive force. We find resonant and nonresonant wave couplings. These include, ordinary decay instabilities, in which the pump wave decays into an electro-acoustic mode and a sideband wave. There are also nonresonant couplings involving two sideband waves, and a nonresonant modulational instability in which the pump wave decays into two sideband modes. Depending on the parameters involved, there is a resonant modulational instability involving a forward propagating electro-acoustic mode and a sideband daughter wave.
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  • 3
    ISSN: 1432-0827
    Keywords: Key words: Hyperthyroidism — Bone mineral density — Dual X-ray absorptiometry — Bone turnover markers — Osteoporosis prediction.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Active hyperthyroidism is associated with reduced bone mass. Nevertheless, not all patients show the same risk for developing osteoporosis. Our aim was to analyze some clinical and biochemical potential predictors of low bone mass in hyperthyroid patients. We studied 127 consecutive hyperthyroid patients (110 females, 17 males; aged 42 ± 16 years). Bone mineral density (BMD) was measured by dual X-ray absorptiometry (DXA) at lumbar spine (LS; L2–L4) and femoral neck (FN). Data were expressed as g/cm2 and T-score. Patients were placed into two groups based on recent WHO criteria: Group A, no osteoporosis (n = 98); and group B, lumbar or femoral osteoporosis (n = 29). Study protocol included evaluation of osteoporosis risk factors, anthropometrical variables, thyroid function, and bone turnover markers. Receiver-operating characteristic (ROC) plots for the precision of bone markers and multivariate analysis for the prediction of BMD and osteoporosis were performed. Group B showed greater age and proportion of menopausal females; lower weight, height, and calcium intake; longer duration of menopause; and greater levels of total and bone alkaline phosphatase and of urine hydroxyproline. No differences in thyroid function, osteocalcin, tartrate-resistant acid phosphatase, and type I collagen C-telopeptide (ICTP) were found. The best predictive model accounted for 46% and 62% of the variability of lumbar and femoral BMD respectively and correctly classified 89% of the osteoporotic hyperthyroid patients. No significant difference in ROC plots was observed. It is concluded that hyperthyroid patients with lumbar or femoral osteoporosis show a typical clinical and biochemical profile illustrating that the relationship between BMD and bone markers is better in high turnover states. Classical bone turnover markers show high performance in the evaluation of hyperthyroid bone disease.
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  • 4
    ISSN: 1436-5073
    Keywords: bentonite-modified carbon paste electrode ; differential pulse voltammetry ; 2-nitrophenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A bentonite-modified carbon paste electrode has been applied to the determination of 2-nitrophenol by differential pulse voltammmetry. The electrochemical reduction of 2-nitrophenol at −0.8 V is carried out in an artificial sea water-formic acid/sodium formate medium at pH 4. The peak height was found to be dependent on the pH over the range 2–11; the presence of a secondary process was observed in the pH range 8–11. The peak potential showed a dependence on pH, with two linear regions with different slopes. A linear relationship between peak intensity and concentration was obtained in the range 0.07–10 mgl−1, with a detection limit of 0.03 mg 1−1 and a coefficient of variation of 1.3% at 5 mg 1−1. The effects of organic and inorganic species on the 2-nitrophenol determination were studied with a view to testing the resolution of the voltammetric technique. The proposed method has been applied to sea water samples with good results.
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  • 5
    ISSN: 1432-041X
    Keywords: Key words Planarian ; Homeobox ; Paired-like ; Polyclonal antibodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The genome of the planarian (Platyhelminthes; Turbellaria; Tricladida) Dugesia (Girardia) tigrina includes a paired-like type of homeobox gene. The Dtprd-1 gene encodes a protein of 382 amino acids. The open reading frame of Dtprd-1 is interrupted by two short introns of 65 and 56 bp, and one long intron of 4.8 kb. The intron positions are not located in the homeobox and are not shared with any other known paired-like gene. The Dtprd-1 homeodomain conserves most of the residues characteristic of the paired-like class. Similarity with other members of this class is low, except with the rat, mouse and Caenorhabditis elegans proteins PHD1, Uncx-4.1 and unc-4, with 86–83% of similarity in the homeodomain, plus several peptides in the flanking regions. Such proteins share specific residues in their homeodomains that can be used to define a new family in the paired-like class of genes. The spatial distribution of gene transcript and product in adult tissues, as revealed by RT-PCR, northern blots and polyclonal antibody, demonstrates that Dtprd-1 is highly expressed in cyanophilic gland cells located in the ventral parenchyma close to the nervous system. No expression is observed during the early stages of regeneration (0–3 days). This suggests a possible role for this homeobox gene within these secretory gland cells, but not in the pattern formation mechanisms known to occur at the early stages of regeneration.
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  • 6
    ISSN: 1432-0827
    Keywords: Key Words: Cirrhosis — Osteoporosis — Hypoparathyroidism — Hypogonadism.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of this study was to determine the prevalence of osteoporosis, to estimate the bone turnover and hormonal status, and to identify the factors associated with bone disease in patients with end-stage liver disease who were referred for orthotopic liver transplantation. A prospective study was performed on 58 cirrhotic patients (6 with primary biliary cirrhosis, 14 with alcoholic cirrhosis, and 38 with posthepatitic cirrhosis), who were referred for orthotopic liver transplantation. Patients, excluding those with primary biliary cirrhosis, were classified in Child-Pugh groups according to the severity of liver disease (class B [28 patients], class C [24 patients]). Biochemical parameters of bone mineral metabolism and standard liver function tests were measured in all patients. Additionally, serum osteocalcin, urinary hydroxyproline/creatinine ratio, serum intact parathyroid hormone, serum 25-hydroxyvitamin D, serum 1,25-dihydroxyvitamin D, folliclestimulating hormone, and luteinizing hormone levels were determined in patients and controls within the same age range. Plasma testosterone, sex hormone-binding globulin levels, and free testosterone index were obtained for all men included in the study. Bone mass of the lumbar spine and femur were measured by dual X-ray absorptiometry (DPX-L), and were expressed as a standard deviation of mean values (Z-score) from a sex and age-matched control group. Spinal X-rays were obtained to assess vertebral fractures. Osteoporosis was considered as a factor in spinal bone mineral density with a Z-score below 2 or at least one vertebral fracture. Twenty-five patients (43%) had osteoporosis, with lower bone mass measurements in the lumbar spine than in the femoral neck (P 〈 0.005). Alcoholic and Child-Pugh C patients showed the lowest femoral bone mineral density values. Cirrhotic patients showed lower osteocalcin levels than controls (14.3 ± 5.9 vs. 18.2 ± 8.1 ng/ml; P 〈 0.05) and showed increased urinary hydroxyproline (125.1 ± 51.5 vs. 107.9 ± 26.6 nM/mg creatinine; P 〈 0.05). Serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and parathyroid hormone levels were significantly lower in cirrhotic patients than in controls (10.3 ± 9.1 vs. 23.1 ± 26.6 ng/ml; P= 0.000), (12.9 ± 9.1 vs. 48.3 ± 11.5 pg/ml; P= 0.000), (16.6 ± 9.2 vs. 27.9 ± 8.2 pg/ml; P= 0.000), with no differences between Child-Pugh groups. Alcoholic Child-Pugh C patients showed the lowest 25-hydroxyvitamin D serum values (4.5 ± 2.2 ng/ml; P 〈 0.05). Male patients had lower testosterone levels than controls (302.5 ± 229.4 vs. 556.7 ± 146.5 ng/dl; P= 0.000), with increased sex hormone-binding globulin values. Levels of testosterone and gonadotropin were related to Child-Pugh classification. No correlation was found between bone mass and hormonal values. A significant decrease in bone mass, particularly in the lumbar spine, is seen in end-stage cirrhotic patients. Reduced bone formation and significant disorders of bone mineral metabolism, such as vitamin D deficiency, reduced parathyroid hormone levels, and hypogonadism are involved. Moreover, severity and etiology of the liver disease are the main risk factors for developing bone loss and mineral metabolism disorders in patients referred for orthotopic liver transplantation.
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  • 7
    ISSN: 1432-0827
    Keywords: Key words: Bone remodeling — Progressive diaphyseal dysplasia.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Moderate increases in ``classical'' biochemical markers of bone turnover have been described only in some patients with Camurati–Engelmann disease. However, the determination of the following ``new'' markers has not been previously performed: serum osteocalcin (BGP), bone alkaline phosphatase (BAP), carboxyterminal propeptide of type I procollagen (PICP), aminoterminal propeptide of type I procollagen (PINP), tartrate-resistant acid phosphatase (TRAP), telopeptide carboxyterminal of type I collagen (ICTP), urinary pyridinoline (PYR), crosslinked N-telopeptides of type I collagen (NTX), and Crosslaps (CL). Such a determination may improve the evaluation of the disease activity. To evaluate the usefulness of biochemical markers of bone turnover reflecting Camurati–Engelmann disease activity we measured the levels of all these markers in four affected patients. The results were compared with bone scintigraphic indices of disease activity. Except for PICP and TRAP, bone formation and resorption markers were abnormal in all patients and were related to bone scan indices of disease activity. Among the markers of bone formation PINP, BAP, and BGP showed the highest values, whereas NTX and CL were the most sensitive markers of bone resorption. These results suggest that the determination of NTX or CL, and PINP or either BAP and BGP, associated with bone scan evaluation, provides the best assessment of Camurati–Engelmann disease activity.
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  • 8
    ISSN: 1432-0827
    Keywords: Key words: Bone mineral density — Smokers — Healthy men — Mineral metabolism — Sex steroids.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Smoking is related to a decreased bone mass and increased risk of osteoporotic fractures. Nevertheless, the effect of smoking in males is poorly understood. The purpose of this study was to assess the repercussion of smoking on bone mass in otherwise healthy male smokers and its relationship with markers of mineral metabolism and hormone profile. We measured bone mineral density (BMD) in 57 healthy males (26 nonsmokers, 31 smokers; aged 20–45 years) by dual X-ray absorptiometry (DXA, Hologic QDR1000) in the lumbar spine and proximal femur. In a subset we measured biochemical markers of bone metabolism and hormonal profile. We found significant differences in BMD between heavy smokers (more than 20 cigarettes/day) and nonsmokers in all skeletal sites. Serum levels of dehydroepiandrosterone sulfate (S-DHEAS) were lower in smokers and correlated with femoral BMD measurements. No significant differences in bone turnover markers were found. Our findings show that smoking by healthy young males is associated with decreased bone mass.
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  • 9
    ISSN: 1432-0983
    Keywords: Key words Hydrophobins ; Heterologous hybridization ; Sporulation genes ; Spore proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA clone encoding a spore-related hydrophobin, SRHI, was isolated from a cDNA bank prepared from mRNA induced in sporulating cultures of Trichoderma harzianum by heterologous hybridization using the hfb2 gene encoding a spore-bound hydrophobin of Trichoderma reesei as a probe. Based on sequence similarity the predicted protein was identified as a new member of the class-II hydrophobin family. Including the signal sequences, SRHI has 65% and 56% amino-acid similarity with the T. reesei hydrophobins HFBII and HFBI, respectively, being less similar with other hydrophobins. srh1 is present as one copy in the T. harzianum genome. It is highly expressed under sporulating conditions, both in submerged as well as in aerial cultures. Moreover, nutrient limitation induces srh1 expression.
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  • 10
    ISSN: 1432-1327
    Keywords: Key words Metallothionein ; N-Ethylmaleimide ; Alkylation ; Kinetics and mechanism ; 111Cd-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  The model alkylating agent N-ethylmaleimide (NEM) reacts reversibly at the metal-bound thiolates of Zn7MT and Cd7MT. An unprecedented feature of this reaction is that it approaches equilibrium and requires a large excess of NEM (〉1 mM for 3 μM protein) to drive it to completion. The complex kinetics of the reaction can be followed by monitoring the release of bound metal ions using the metallochromic dyes Zincon (ZI) for Zn7MT and pyridylazoresorcinol for Cd7MT. An initial lag phase is followed by more rapid release of zinc ions. The observed pseudo-first-order rate constants for the two phases are independent of the ZI and Zn7MT concentrations. The complex NEM concentration dependence of each phase, k f, obs=k f 1+k f 2 [NEM] and k s, obs=k s 1+k s 2 [NEM], demonstrates that the forward reactions are second order and the reverse reactions are first order. The alkylation can be reversed using 2-mercaptoethanol to compete for the protein-bound NEM and regenerate the Zn-binding capability of alkylated MT. An explanation of these observations, based on the reversibility of cysteine alkylation by NEM, was developed and tested. The reactions of Cd7MT are less complete than those of Zn7MT and occur more slowly. 111Cd-NMR studies of the partially alkylated 111Cd7MT reveal that reaction with only four equivalents of NEM completely alters the cluster structure and eliminates the spectral signatures of the α and β clusters, although very little cadmium has been removed from the protein. This finding substantiates the proposed kinetic intermediate, a partially alkylated MT with complete or nearly complete retention of the metal ions, and rules out the possibility of cooperative reactions at either cluster.
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