Probabilistic Fracture Mechanics and Optimum Fracture Control Analytical Procedures for a Reusable Solid Rocket Motor Case

A methodology for the reliability analysis of a reusable solid rocket motor case is discussed. The analysis is based on probabilistic fracture mechanics and probability distribution for initial flaw sizes. The developed reliability analysis is used to select the structural design variables of the solid rocket motor case on the basis of minimum expected cost and specified reliability bounds during the projected design life of the case. Effects of failure prevention plans such as nondestructive inspection and the material erosion between missions are also considered in the developed procedure for selection of design variables. The reliability-based procedure can be modified to consider other similar structures of reusable space vehicle systems with different failure prevention plans

Probabilistic fracture mechanics and optimum fracture control of the solid rocket motor case of the shuttle

Development of a procedure for the reliability analysis of the solid rocket motor case of the space shuttle is described. The analysis is based on probabilistic fracture mechanics and consideration of a probability distribution for the initial flaw sizes. The reliability analysis can be used to select design variables, such as the thickness of the SRM case, projected design life and proof factor, on the basis of minimum expected cost and specified reliability bounds. Effects of fracture control plans such as the non-destructive inspections and the material erosion between missions can also be considered in the developed methodology for selection of design variables. The reliability-based procedure can be easily modified to consider other similar structures and different fracture control plans

Growth Kinetics and Production of Glucose Oxidase Using Aspergillus niger NRRL 326

In this paper, we demonstrate the substrate inhibition phenomena for growth kinetics of Aspergillus niger NRRL 326 grown on sucrose during glucose oxidase production. The initial set of experiments were carried out using three different substrates, viz., glucose, sucrose and raffinose of which it was observed that sucrose serves better for higher production of glucose oxidase. Experiments involving sensitivity studies conveyed that substrate inhibition became predominant when sucrose mass concentration was above γ = 30 g L-1 in the cultivation medium. The later part of the work was dovetailed towards validation of substrate inhibited growth kinetics with established models such as Haldane, Andrews, Luong, Han-Levenspiel and Aiba. Finally, it was observed that none of the classical models explains the kinetics well

Growth Kinetics and Production of Glucose Oxidase Using Aspergillus niger NRRL 326

In this paper, we demonstrate the substrate inhibition phenomena for growth kinetics of Aspergillus niger NRRL 326 grown on sucrose during glucose oxidase production. The initial set of experiments were carried out using three different substrates, viz., glucose, sucrose and raffinose of which it was observed that sucrose serves better for higher production of glucose oxidase. Experiments involving sensitivity studies conveyed that substrate inhibition became predominant when sucrose mass concentration was above γ = 30 g L-1 in the cultivation medium. The later part of the work was dovetailed towards validation of substrate inhibited growth kinetics with established models such as Haldane, Andrews, Luong, Han-Levenspiel and Aiba. Finally, it was observed that none of the classical models explains the kinetics well

Periodic and Quasiperiodic Motion of an Elongated Microswimmer in Poiseuille Flow

We study the dynamics of a prolate spheroidal microswimmer in Poiseuille flow for different flow geometries. When moving between two parallel plates or in a cylindrical microchannel, the swimmer performs either periodic swinging or periodic tumbling motion. Although the trajectories of spherical and elongated swimmers are qualitatively similar, the swinging and tumbling frequency strongly depends on the aspect ratio of the swimmer. In channels with reduced symmetry the swimmers perform quasiperiodic motion which we demonstrate explicitely for swimming in a channel with elliptical cross section

Testing the theory of immune selection in cancers that break the rules of transplantation

Modification of cancer cells likely to reduce their immunogenicity, including loss or down-regulation of MHC molecules, is now well documented and has become the main support for the concept of immune surveillance. The evidence that these modifications, in fact, result from selection by the immune system is less clear, since the possibility that they may result from reorganized metabolism associated with proliferation or from cell de-differentiation remains. Here, we (a) survey old and new transplantation experiments that test the possibility of selection and (b) survey how transmissible tumours of dogs and Tasmanian devils provide naturally evolved tests of immune surveillance

Distribution of immune cells in head and neck cancer: CD8+ T-cells and CD20+ B-cells in metastatic lymph nodes are associated with favourable outcome in patients with oro- and hypopharyngeal carcinoma

<p>Abstract</p> <p>Background</p> <p>Tumour infiltrating lymphocytes (TIL) are generally considered to represent a host immune response directed against tumour antigens. TIL are also increasingly recognised as possible prognostic parameters. However, the effects observed are variable indicating that results cannot be extrapolated from type of tumour to another. Moreover, it has been suggested that primary solid tumours may be ignored by the immune system and that a meaningful immune response is only mounted in regional lymph nodes.</p> <p>Methods</p> <p>We have examined the local distribution of immune cells in tumour-related compartments in head and neck squamous cell carcinomas (HNSCC). In a second step, the prognostic impact of these cells on disease-free survival (DFS) was analysed. A total of 198 tissue cores from 33 patients were evaluated using tissue mircroarray technique and immunohistochemistry. Tumour-infiltrating immune cells were identified using antibodies specific for CD3, CD8, GranzymeB, FoxP3, CD20 and CD68 and quantified using an image analysis system.</p> <p>Results</p> <p>We demonstrate a relative expansion of FoxP3⁺regulatory T-cells (Treg) and of cytotoxic T-cells among tumour infitrating T-cells. We also show that intratumoural CD20⁺B-cells are significantly more frequent in metastatic deposits than in primary tumours. Furthermore, we observed a reduced number of peritumoural CD8⁺T-cells in metastatic lymph nodes as compared to univolved regional nodes suggesting a local down-modulation of cellular immunity. All other immune cells did not show significant alterations in distribution. We did not observe an association of tumour infiltrating immune cells at the primary site with outcome. However, increased numbers of intraepithelial CD8⁺TIL in metastatic tumours as well as large numbers of peritumoural B-cells in lymph node metastases were associated with favourable outcome. Unexpectedly, no effect on patient outcome was observed for Treg in any compartment.</p> <p>Conclusion</p> <p>Our results suggest that alterations in lymphocyte distribution in regional lymph nodes rather than at the primary tumour site may be relevant for patient prognosis. Moreover, we demonstrate that in addition to cellular immunity humoral immune responses may be clinically relevant in anti-tumour immunity.</p

Prolonged Graft Survival in Older Recipient Mice Is Determined by Impaired Effector T-Cell but Intact Regulatory T-Cell Responses

Elderly organ transplant recipients represent a fast growing segment of patients on the waiting list. We examined age-dependent CD4+ T-cell functions in a wild-type (WT) and a transgenic mouse transplant model and analyzed the suppressive function of old regulatory T-cells. We found that splenocytes of naïve old B6 mice contained significantly higher frequencies of T-cells with an effector/memory phenotype (CD4+CD44highCD62Llow). However, in-vitro proliferation (MLR) and IFNγ-production (ELISPOT) were markedly reduced with increasing age. Likewise, skin graft rejection was significantly delayed in older recipients and fewer graft infiltrating CD4+T-cells were observed. Old CD4+ T-cells demonstrated a significant impaired responsiveness as indicated by diminished proliferation and activation. In contrast, old alloantigen-specific CD4+CD25+FoxP3+ T-cells demonstrated a dose-dependent well-preserved suppressor function. Next, we examined characteristics of 18-month old alloreactive T-cells in a transgenic adoptive transfer model. Adoptively transferred old T-cells proliferated significantly less in response to antigen. Skin graft rejection was significantly delayed in older recipients, and graft infiltrating cells were reduced. In summary, advanced recipient age was associated with delayed acute rejection and impaired CD4+ T-cell function and proliferation while CD4+CD25+FoxP3+ T-cells (Tregs) showed a well-preserved function

A Quantitative 3D Motility Analysis of Trypanosoma brucei by Use of Digital In-line Holographic Microscopy

We present a quantitative 3D analysis of the motility of the blood parasite Trypanosoma brucei. Digital in-line holographic microscopy has been used to track single cells with high temporal and spatial accuracy to obtain quantitative data on their behavior. Comparing bloodstream form and insect form trypanosomes as well as mutant and wildtype cells under varying external conditions we were able to derive a general two-state-run-and-tumble-model for trypanosome motility. Differences in the motility of distinct strains indicate that adaption of the trypanosomes to their natural environments involves a change in their mode of swimming