Berechnung von Bauteilwöhlerlinien unter Berücksichtigung der statistischen und spannungsmechanischen Stützziffer

Estimation of S-N Curves under Consideration of Geometrical and Statistical Size Effects In this paper a concept for the estimation of fatigue limit in [11] will be extended to the calculation of S-N curves. The statistical size effect is taken into account with the well known weakest link theory. The geometrical size effect is considered according to the cyclic plastic deformation in the notch root. This model gives good correlation with test results. According to the present model the slope of the S-N curve depends on the specimen size and strength of materials, but does not depend on the stress concentration factor. The S-N curve becomes flatter with larger notch size and higher material strength.     

Lack of type 2 T cell-independent B cell responses and defect in isotype switching in TNF-lymphotoxin alpha-deficient mice

TNF is implicated in in vitro Ig production, but its role in vivo is not clearly defined. Our previous studies had shown that TNF-LT alpha double-deficient mice have defective IgM and IgG primary Ab responses to the T cell-dependent (TD) Ag SRBC. We now extend these studies to secondary responses and to T cell-independent (TI) B cell responses. Injections of the TD Ag SRBC did not induce germinal center formation in the spleen of TNF-LT alpha-deficient mice. Associated with the morphologic defect, there was a defective IgG Ab response and a secondary hyper-IgM response to the TD Ag in TNF-LT alpha-deficient mice. The response to the TI Ag type 2 DNP-alanyl-glycyl-glycyl-Ficoll was essentially absent in TNF-LT alpha-deficient mice, while that to the TI Ag type 1 TNP-LPS was significantly reduced only for IgG2b isotype. Transplantation of bone marrow cells from wild-type mice into irradiated TNF-LT alpha-deficient mice restored the formation of splenic germinal centers and corrected the IgM and IgG responses to both TD and TI Ags. These data suggest that TNF and/or LT alpha signaling are critically required for germinal center formation and for the IgM and IgG responses to both TD and TI type 2 Ags.     

Efficient gene transfer in primitive CD34+/CD38lo human bone marrow cells reselected after long-term exposure to GALV-pseudotyped retroviral vector

Successful retroviral gene transfer into human hematopoietic stem cells was demonstrated in preliminary clinical trials at low efficiency. We have shown previously that gene transfer into committed hematopoietic progenitor cells is more efficient using a gibbon ape leukemia virus (GALV)-pseudotyped retroviral vector instead of an amphotropic retroviral vector. Here, we have conducted a systematic study of human hematopoietic progenitor cells after extended transduction with a GALV-pseudotyped retroviral vector. CD34+/CD38lo Cells were transduced for 5 days and reselected according to phenotype after culture and analyzed for cell cycle status, long-term culture-initiating cell (LTC-IC) activity, and gene transfer. Reselection of rare, very primitive progenitor cells was successful. Equal to fresh CD34+/CD38lo cells, >90% of reselected CD34+/CD38lo cells were in G0/G1. CD34+/CD38lo reselection enriched for LTC-IC (10-fold), as compared to freshly isolated CD34+/CD38lo cells with excellent specificity (82.7% of total LTC-IC were recovered in the reselected CD34+/CD38lo population) and recovery (62% of initial LTC-IC number in CD34+/CD38lo cells were recovered in the reselected fraction after transduction). Gene transfer into primitive progenitor cells was efficient with 50.5% G418-resistant LTC-IC colonies and more than 40 copies of vector provirus detectable per 100 nuclei of CD34+/CD38lo cells. To our knowledge, this is the first systematic analysis of phenotype, function, and cell cycle demonstrating retroviral gene transfer into rare, very primitive human hematopoietic progenitor cells. The chosen strategy should be of considerable value for analyzing and improving gene therapy of the hematopoietic system.     

An implantable piezoelectric hearing aid transducer for inner ear deafness. II: Clinical implant]

A miniature, hermetically sealed implant was development and manufactured in several clinical and technical iteration steps based on the prototype of an implantable piezo-electric hearing-aid transducer described in Part 1 of the work presented here. The transducer is made of pure titanium (medical grade 2, ASTM F67) and designed to be implanted into the mastoid cavity. Transfer of mechanical oscillations to an ossicle in the middle ear is effected by a fixed directly coupling rod of pure titanium or via suitable coupling elements. The transducer is highly tuned with a resonance frequency in the range of 7-10 kHz, depending on the dynamic mass load. Below this resonance and down to low frequencies, the frequency response of elongation is smooth with a very small ripple of less than +/- 1 dB. Unlike the prototype, an increase in vibration amplitude of around 10 dB was achieved for a comparable power consumption. Vibration amplitude at low and middle frequencies is about 60 nm with a transducer voltage of 1 V, corresponding to an equivalent sound-pressure level of around 100 dB SPL at up to 1 kHz. At higher frequencies of up to 10 kHz, the output level increases to beyond 130 dB SPL. Nonlinear distortions at maximum volume (1 V) are extremely small (THD < 0.1%) throughout the whole transfer range. Due to an extremely short attack time (50 microseconds) and short release time (approximately 2 ms), the dynamic properties of the transducer allow good transmission of audio signals with fast changes in the time domain, i.e., plosives in speech signals. Electric power consumption at full volume and broadband signals is in the region of 1 microW. Unlike electromagnetic transducers described in the literature, the low power consumption of this piezoelectric transducer allows the realization of fully implantable hearing aids for rehabilitation of moderate to severe sensorineural hearing loss.     

Neuropsychological aspects of the rehabilitation of patients with paralysis from a spinal injury who also have a brain injury

In order to examine the rehabilitation process of patients suffering from a severe spinal cord injury and who also have a cerebral injury, 322 patients with paralysis from a spinal injury were subjected to neuro-psychiatric and neuro-psychological examinations. On average 20.2% of these patients showed an associated cerebral lesion. The psychological results of such cerebral lesions are summarized under the concept of the co-called organic psychic syndrome (OPS). In 27.7% of these patients no organic psychic syndrome resulted, and in these patients a conventional paralysis rehabilitation could be carried out. 41.6% showed very minor to moderate injuries, with 30.7% being severely disabled from the cerebral injury. Rehabilitation for these patients was modified, using new therapeutic approaches, and also traditional therapeutic methods adapted to the abilities and needs of this patient group. In 25.5% of the patients there was no substantial improvement during the treatment period of initial rehabilitation (x = 12.5 weeks for the treatment of cerebral injury); but in 36.2% of the patients there was substantial improvement and in 38.3% full remission of organic psychic disorders occurred. Improvements in this sphere have a direct bearing on the rehabilitation capacity of this patient group.     

Interventional therapy of inferior vena cava thrombosis in pregnancy--use of a new kind of temporary vena cava filter

The most common suicide theories share a widely recognized set of social factors that contribute to suicide and suicide attempts. This paper discusses additional suicide risk factors that affect the gay and lesbian community such as: discrimination, gay adolescence, coming out, establishment of a gay identity, HIV/AIDS, intrapersonal stressors, drugs and alcohol, racial/ethnic factors and limited support structures. Poor awareness of these additional risks, both within mainstream society and within the gay and lesbian community, is also discussed. A review of the literature is conducted that examines the impact of these risk factors and the implications of these issues to mental health nursing.     

Isolation, purification, and cross-linking profiles of elastin from lung and aorta

Elastin from anatomically defined regions of young calf lung and dog aorta was isolated and purified by a procedure which sequentially removed lipids, collagen, structural glycoproteins, and the microfibrillar proteins without apparent damage to the cross-linking residues, which have been shown to be sensitive to autoclaving and hot alkali treatment. One of the methods described was effective in obtaining pure elastin from lung parenchyma. Visceral pleura was found to be the richest source (25% dry weight) of elastin in the lung tissues examined. The amino acid compositions of the elastins purified by different methods were compared for purity and for the detection of possible damage to cross-linking compounds. Cross-linking profiles were obtained by column chromatography either after reduction with 3[H]NaBH4 or after reaction with 14[C]NaCN and NH3. The 3[H]NaBH4 method, under carefully controlled conditions, proved not to be quantitatively reproducible. The reaction of elastin with 14[C]NaCN and NH3 appeared preferable due to its reproducibility; this procedure required one type of hydrolysis for the analysis of all the cross-linking compounds. Examination of the cross-linking profiles of the elastins from various tissue regions revealed differences in the type, distribution, and quality of cross-links.