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  • 1
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermally stable, low-resistance PdGe-based ohmic contacts to high–low doped n-GaAs have been developed. The lowest contact resistance obtained is two times lower than that of previously reported PdGe ohmic contacts. The contacts are thermally stable even after isothermal annealing for 5 h at 400 °C under atmosphere ambient. X-ray diffraction results and Auger depth profiles show that the good PdGe-based ohmic contact is due to the formation of both AuGa and TiO compounds. The AuGa compound enhances the creation of more Ga vacancies, followed by the incorporation of Ge into Ga vacancies, and the TiO compound suppresses As outdiffusion from the GaAs substrate, respectively. © 1995 American Institute of Physics.
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interfacial microstructures of Pd/Ge/Ti/Au ohmic contact to n-type GaAs have been investigated using cross-sectional transmission electron microscopy, and the results are used to interpret the electrical properties. Annealing at 300 °C yields a contact resistance of 0.62 Ω mm and the layer structure is changed to GaAs/PdGe/Au4Ti/TiO. The ohmic contact is formed through a solid phase regrowth of GaAs heavily doped with Ge below the PdGe layer. At 380 °C, the lowest contact resistance of 0.43 Ω mm is obtained. The layer structure is changed to GaAs/(Ge–Ti)/PdGe/TiO. Spikes composed of Au and AuGa are found at the grain boundaries of the PdGe compound. The formation of AuGa at 380 °C reduces the contact resistance through the creation of more Ga vacancies at the interface of GaAs/PdGe, and the incorporation of elemental Ge. © 1996 American Institute of Physics.
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  • 3
    ISSN: 1432-0738
    Keywords: Key words Cysteine S-conjugates  ;  Damage to the S3 region of proximal tubules by halogenated xenobiotics  ;  Intranephron distribution of cysteine S-conjugate β-lyase  ;  β-Lyase activity staining with S-(1 ; 2-dichlorovinyl)-l-cysteine  ;  Nephrotoxicity of hexachloro-1 ; 3-butadiene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The intranephron distribution of two major cysteine S-conjugate β-lyases was determined in order to clarify the role of these enzymes in promoting the nephrotoxicity associated with certain halogenated xenobiotics. Various nephron segments [i.e., glomerulus, early, middle, and terminal portions of the proximal tubule (S1, S2, and S3 respectively), the thick ascending limb, the distal tubule, and the collecting tubule] were isolated by microdissection from collagenase-treated rat kidneys. Each segment was dissected in Hanks' solution, solubilized with Triton X-100, and applied to a micropolyacrylamide gel constructed with a continuous gradient. The gels were subjected to electrophoresis and then incubated in the dark in a solution containing S-(1,2 dichlorovinyl)-l-cysteine (DCVC), sodium α-keto-γ-methiolbutyrate, phenazine methosulfate, and nitroblue tetrazolium. The position of cysteine S-conjugate β-lyase- and l-amino acid oxidase activities in the gels was revealed by the presence of blue formazen dye bands. The relative intensities of the bands were determined by optical scanning with a microdensitometer. Three bands were detected: band I (Mr ˜ 330 000) corresponds to a recently described high Mr cysteine S-conjugate β-lyase whereas band III (Mr ˜ 90 000) corresponds to a lower Mr cysteine S-conjugate β-lyase (identical to cytosolic glutamine transaminase K). Band II (Mr ˜ 240 000) corresponds to l-amino acid oxidase (a unique activity of the B isoform of rat kidney l-hydroxy acid oxidase). β-Lyase activity with DCVC as substrate was detected in the S1, S2, and S3 segments of the nephron but not in other regions of the kidney. The activity was in the order: S2 = S3 〉 S1. In another series of experiments, rats were killed 24 h after treatment with hexachloro- 1,3-butadiene (HCBD). In whole kidney homogenates the relative intensity of band III (per 22.2 μg tissue wet weight) after a 30 min incubation was induced significantly (by 50%), but the relative intensities of the other two bands were unchanged. On the other hand, in proximal tubules isolated from HCBD-treated rats the relative intensities (per 5 mm of nephron) of peak I of S2, peak II of S3, and peak III of S3 were significantly reduced by 28, 33, and 72%, respectively. These findings suggest that the low Mrβ-lyase is induced by HCBD and that impaired cell function in the segments (especially S3) results in proteins leaking out of the target cells. To examine the relationship between the nephrotoxic effect of HCBD and cysteine S-conjugate β-lyase activity, the intracellular ATP:protein ratio was quantitated in each nephron segment and in whole kidney homogenates. In HCBD-treated rats the ATP:protein ratio of the S1, S2, and S3 segments was unchanged, decreased by ˜50%, and increased by ˜30%, respectively. In the kidney homogenates of HCBD-treated rats the ATP content was decreased by 32%. However, the loss of ATP was significantly less when the rats were pretreated with aminooxyacetate (a general inhibitor of pyridoxal 5′-phosphate-dependent enzymes, including β-lyase) 1 h before HCBD administration. The results strongly suggest that HCBD is converted to toxic metabolites within the kidney and that this process leads to metabolic derangement and reduction of ATP in susceptible kidney cells.
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The eukaryotic genome contains a putative ATPase gene family that encodes proteins with one or two highly conserved domain(s) of approximately 230 amino acids. These proteins have diverse cellular functions and mutation in at least one member of the family has been associated with human disease, while mutations in other family members are known to cause cell cycle defects in yeast. Therefore it is of interest to map more family members and so we have localized PSMC5 (the thyroid hormone receptor-interacting protein, TRIP1) and PSMC3 (the Tat-binding protein, TBP1) to chromosomes 17q24– q25 and 11p12–p13, respectively. We also present the map position of a probable PSMC3 processed pseudogene locus on chromosome 9p.
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  • 5
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The autosomal β1 integrin knockout mouse mutation was selected as a model to experimentally determine preimplantation diagnosis test reliability for autosomal gene deletions and duplications. In experiment 1, which analyzed 198 individually disaggregated single blastomeres, the observed test frequencies matched the mathematically predicted frequencies calculated from the independently derived values of 90% normal allele amplification, 92% mutant allele amplification, 4% alternate allele contamination, and 4% failure to transfer amplifiable target DNA into the PCR reaction mix. This experiment correctly predicted a normal embryonic phenotype in 143 (99.3%) of the 144 phenotypically normal autosomal recessive results. Experiment 2 compared single biopsied blastomere test results to test results on the remaining embryonic cells cultured 1 week until trophoblast outgrowth. Single biopsied blastomere analysis correctly predicted a normal autosomal recessive phenotype in 87 (98%) of the 89 embryos that would have been selected for implantation. Experiment 3 compared the PCR results of two biopsied blastomeres tested independently to the PCR result from the remaining cultured blastomeres to improve test reliability. Given that embryos would have been implanted only when two normal results were obtained, 17 of 17 phenotypically normal embryos would have been implanted from among the 44 embryos tested. These experiment 3 results are consistent with the mathematical prediction that about 99.9% of embryos implanted with two unaffected biopsied blastomere results would have had a phenotypically normal genotype.
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  • 6
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Dual blastomere biopsy and independent blastomere analysis dramatically improved preimplantation diagnostic reliability as confirmed by testing the remaining biopsied eight-cell mouse embryo. The autosomal dominant trembler mouse point mutation was selected as a model for human preimplantation diagnosis because: (1) single cell assay failure is predicted to be the highest when testing autosomal dominant mutations; (2) point mutations represent the most common of all mutation categories and the most demanding mutation to assay reliably; and (3) the trembler mouse point mutation in peripheral myelin protein 22 (Pmp22) is a model of human Charcot-Marie-Tooth type 1A disease. Mathematical models predict our experimental results assuming amplification of 80% of each target allele as well as trembler sperm DNA contamination in 1 of 44 normal biopsied single blastomeres. Single blastomere analysis correctly predicted the genotype in only 84% of embryos that would have been implanted as normal. In contrast, when independent tests of both biopsied blastomeres agreed, test results were confirmed in 20 of 21 (95.2%) of the remaining six-cell biopsied embryos designated as normal. Thus, biopsied six-cell embryo confirmation demonstrated that dual biopsied blastomere analysis improved test reliability remarkably.
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  • 7
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The factor IX gene (F9) is an advantageous system for analyzing recent spontaneous germline mutation in humans. Herein, the male:female ratio of mutation ("r") in F9 have been estimated by Bayesian analysis from 59 germline origin families. The overall "r" in F9 was estimated at 3.75. The "r"s varied with the type of mutation. The "r"s ranged from 6.65 and 6.10 for transitions at CpG and A:T to G:C transitions at non-CpG dinucleotides, respectively, to 0.57 and 0.42 for microdeletions/microinsertions and large deletions (〉1 kb), respectively. The "r" for the two subtypes of non-CpG transitions differed (6.10 for A:T to G:C vs 0.80 for G:C to A:T). Somatic mosaicism was detected in 11% of the 45 origin individuals for whom the causative mutation was visualized directly by genomic sequencing of leukocyte DNA (estimated sensitivity of approximately one part in 20). Four of the five defined somatic mosaics had G:C to A:T transitions at non-CpG dinucleotides, hinting that this mutation subtype may occur commonly early in embryogenesis. The age at conception was analyzed for 41 US Caucasian families in which the age of the origin parent and the year of conception for the first carrier/hemophiliac were available. No evidence for a paternal age effect was seen. However, an advanced maternal age effect was observed (P=0.03) and was particularly prominent for transversions (average of the 79th percentile when maternal age was normalized for the year of conception). This suggests that an increased maternal age results in a higher rate of transmitted mutation, whereas the increased number of mitotic replications associated with advanced paternal age has little, if any, effect on the rate of transmitted mutation.
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  • 8
    ISSN: 1432-1084
    Keywords: Key words: Lung infection ; Lung abnormalities ; Pneumocystis carinii ; Radiation therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The radiographic findings of Pneumocystis carinii pneumonia (PCP) are various. The typical findings are diffuse, bilateral, symmetric, finely granular, or reticular infiltrates. In patients taking aerosol pentamidine, atypical findings may be the first manifestation. One interesting radiologic finding of PCP is that the pneumonia may spare the irradiated lung. We report PCP developed in a patient undergoing irradiation for lung cancer. High-resolution CT revealed diffuse, bilateral, and symmetric ground-glass opacities with septal thickening in both lungs; however, the radiation port was spared and appeared as the “photographic negative of post-radiation pneumonia.” The distribution of the pneumonic infiltrates was altered by radiotherapy.
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  • 9
    ISSN: 1433-7347
    Keywords: Anterior cruciate ligament ; Knee joint ; Biomechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Sports Science
    Notes: Abstract This study was conducted to evaluate the effect of applied load on the magnitude, direction, and point of tibial intersection of the in situ forces of the anteromedial (AM) and posterolateral (PL) bands of the human anterior cruciate ligament (ACL) at 30° and 90° of knee flexion. An Instron was used to apply a 100 N anterior shear force to 11 human cadaver knees, 6 at 30° of knee flexion and 5 at 90° of knee flexion. A Universal Force Sensor (UFS) recorded the resultant 6 degree-of freedom (DOF) forces/moments. Each specimen then underwent serial removal of the AM and PL bands. With the knee limited to 1 DOF (anteroposterior), tests were performed before and after each structure was removed. Because the path was identical in each test, the principle of superposition was applied. Thus, the difference between the resultant forces could be attributed to the force carried by the structure just removed. The magnitudes of force in the ACL at 30° and 90° of knee flexion were 114.1±7.4 N and 90.8±8.3 N, respectively (P〈0.05). At 30°, the AM and PL bundles carried 95% and 4% of the total ACL force, respectively. At 90°, the AM and PL bands carried 85% and 13%, respectively (P〈0.05). The direction of the in situ force in the whole ACL as well as its two bands correlated with the anatomic orientation of the ligament. The resultant total ACL force intersected the tibial plateau at the posterolateral aspect of the AM band's insertion at 30° of knee flexion, while at 90°, the force intersection moved posteriorly to the AM/PL border. This research provides new insight into the fundamental force relationships of the ACL and its bundles. In response to an anterior tibial shear force, the AM band of the ACL was the predominant load carrier at both 30° and 90° of knee flexion. However, contrary to carlier reports, the in situ force carried in the PL band increased as knee flexion increased. Further, the tibial intersection of the resultant ACL force moved laterally with knee flexion. These findings confirm the dynamic structure of the ACL that in itself has no isometricity and may also indicate that there is no ideal location in which to position a replacement graft. The use of this methodology with more physiologically unconstrained motion should lead to more definitive clinical conclusions.
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  • 10
    ISSN: 1432-5195
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé. Les dommages osseux importants dans les fractures ouvertes du Tibia sont généralement traités par une greffe osseuse conventionelle: on utilise soit une greffe de péroné vascularisée, soit la technique du fixateur (type llizarov). Une greffe de péroné vascularisée peut être meilleure qu’une greffe osseuse conventionnelle, mais c’est une greffe qui est techniquement, difficile et parfois impossible à réaliser. Dans ce cas, le transfert du péroné avec l’utilisation du fixateur externe (type Ilizarov) est une méthode alternative. Cette opération peut être accomplie en transférant la partie ostéotomisée du péroné sur le Tibia au moyen de cables «olives». Récemment, un jeune homme de 20 ans a présenté une fracture ouverte du Tibia de type Gustilo IIIb. Les dommages causés aux tissues étaient sévères. Seule l’artère tibiale postérieure était perméable et l’artère péronéale était partiellement endommagée. Un recouvrement par lambeau de grand dorsal fût réalisé afin de couvrir les tissues endommagés. Le seule artère tibiale postérieure étant déjà utilisé pour le recouvrement, il était difficile de réaliser une greffe de péroné vascularisée. De plus il était techniquement difficile d’accomplir un déplacement graduel en utilisant la fixateur externe (type Ilizarov) car la partie distale du Tiba était perdue. Ainsi, un transfert de péroné fût immédiatement réalisé avoir appliqué le fixateur externe. Une bonne fusion osseuse, ainsi qu’une hypertrophie du péronée ont été obtenues, bien que ces 2 opérations aient été effectuées simultanément.
    Notes: Abstract. Massive segmental bony defects in open tibial fractures are generally treated with conventional bone grafting, a free vascularised fibular graft or the ring fixator technique. A vascularised fibular graft may be superior to a conventional bone graft, but it is technically difficult and occasionally impossible. In such circumstances, fibular transfer in conjunction with a ring fixator is an alternative method. This procedure can be accomplished by transferring the osteotomised part of the fibula to the tibia by means of olive wires. The authors have treated a 20-year-old male who presented with a Gustilo type IIIB open tibial fracture. The soft tissue defect was severe, only the tibialis posterior artery was patent and the peroneal artery was partially damaged. A latissimus dorsi flap was performed to cover the soft tissue defect. Since the patent tibialis posterior artery had already been used for the flap, it was difficult to perform a vascularised fibular graft. Moreover, it was technically difficult to accomplish a gradual transport using a ring fixator because the distal tibia was lost. For this reason, the fibular transfer was performed immediately after the ring fixator was applied. Good bony union and fibular hypertrophy were obtained even though these two procedures were undertaken simultaneously.
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