Ruggedized gamma radiation detector Final report

Design, fabrication and performance testing of gamma radiation detector capable of operating in vicinity of nuclear powered rocket engine

SafeguaRDP: an Architecture for Mediated Control of Desktop Applications by Untrusted Crowd Workers

The future of crowdsourcing depends on improving usability for the requesters who post jobs. Allowing workers to perform tasks directly on a requester’s computer could help, by obviating the need to adapt data into formats that a crowdsourcing platform can handle. However, granting remote access to a requester’s desktop would also pose the risk the workers might steal information or take malicious actions. This thesis presents SafeguaRDP, an architecture designed to enable future services in which a mediated and redacted desktop is shown to a remote worker. The redaction of the desktop does not modify any files on the desktop; it only changes what is shown to the worker. This thesis contributes the rationale behind the architecture as well as a threat analysis based on accepted software security principles. To place the SafeguaRDP architecture in context, a set of eight vignettes illustrate potential applications that would be possible with future services based on the SafeguaRDP architecture. With these applications, the transfer of digital labor may someday become as simple as the transfer of data today, all while preserving the privacy of the hiring party

Combining DLC, Shot blasting, chemical dip and nano fullerene surface treatments to reduce wear and friction when used with bio-lubricants in automotive contacts

The interaction of three bio-lubricant base oil candidates with seventeen combinations of surface treatment was studied, comparing wear scar volumes and coefficient of friction results. Substrates were initially ground, then a combination of superfinished, Dymon-iC™ DLC, an impact technique of ultra-fine shot blasting method doped with Tin and Molybdenum Disulfide, a calcium based chemical dip containing calcium sulfate and nano fullerene, were used.DLC is well reported to reduce friction. Some reports suggest wear in coated contacts is independent of the type of lubricant used, whilst others report that bio-lubricants offer reduced friction and wear in combination with DLC. Shot blasting can also reduce wear and friction, due to the surface dimples acting as lubricant reservoirs, making hydrodynamic lubrication more likely. Previous work has also explored the performance of surface texturing in combination with coatings, some reporting higher friction when surface texturing and DLC is used. As a surface coating, fullerene has been shown to have significantly lower wear and friction than DLC coatings. The calcium based chemical treatment used has no published data.A ball on flat reciprocating wear tester was used with bio-lubricant base oil candidates, jojoba and soybean oil, with a mineral base oil used for comparison. Wear scars were analysed using a scanning electron microscope.Coefficient of friction results from testing with bio-lubricant base oil candidates’ soybean and jojoba oil were lower than tests with mineral base oil. A hybridized coating combination of superfinish, diamond like carbon and chemical dip gave the highest wear protection for tests with the mineral base oil and bio-lubricant base oil candidate soybean oil. A hybridized coating combination of superfinish, impact technique and chemical dip gave highest wear protection when tested with bio-lubricant base oil candidate jojoba oil. Results showed no overall improvement in wear protection when substrates were processed with the impact technique. Superfinishing substrates improved the performance of both the chemical dip and DLC

Hamster oocyte membrane potential and ion permeability vary with preantral cumulus cell attachment and developmental stage

BACKGROUND: In vitro maturation of mammalian oocytes is an area of great interest due to its potential application in the treatment of infertility. The morphological and physiological changes that occur during oocyte development are poorly understood, and further studies are needed investigating the physiological changes associated with oocyte maturation. In this study we evaluated the membrane potential and the sodium/potassium permeability ratio of oocytes acutely isolated, and cumulus-oocyte complexes in metaphase II and preantral follicle stages. RESULTS: Intracellular electrical recordings revealed that cumulus-enclosed oocytes have a membrane potential significantly more negative at the preantral follicle stage than at metaphase II stage (-38.4 versus -19.7 mV, p < 0.0005). The membrane potential of the cumulus-free oocytes was not different between the preantral and metaphase II stages. The membrane potential of the cumulus cells forming preantral stage follicles was shown to be significantly different from that of the oocyte within the follicle (-28.6 versus -38.4 mV, p < 0.05). The sodium/potassium permeability measured in cumulus-enclosed oocytes at the preantral stage equaled a mean value of 0.33. The ratio was significantly lower when measured in oocytes denuded of cumulus cells or cumulus-enclosed metaphase II oocytes, 0.76, 0.79, 0.77 respectively (p < 0.001). CONCLUSIONS: These data show a change in the membrane potential and Na(+)/K(+) permeability ratio during ooycte development from the preantral stage oocyte to the metaphase II stage. We have also demonstrated a change in the preantral oocyte membrane potential when surrounding cumulus cells are removed; either due to membrane changes or loss of cumulus cells

Residues and World-Sheet Instantons

We reconsider the question of which Calabi-Yau compactifications of the heterotic string are stable under world-sheet instanton corrections to the effective space-time superpotential. For instance, compactifications described by (0,2) linear sigma models are believed to be stable, suggesting a remarkable cancellation among the instanton effects in these theories. Here, we show that this cancellation follows directly from a residue theorem, whose proof relies only upon the right-moving world-sheet supersymmetries and suitable compactness properties of the (0,2) linear sigma model. Our residue theorem also extends to a new class of "half-linear" sigma models. Using these half-linear models, we show that heterotic compactifications on the quintic hypersurface in CP^4 for which the gauge bundle pulls back from a bundle on CP^4 are stable. Finally, we apply similar ideas to compute the superpotential contributions from families of membrane instantons in M-theory compactifications on manifolds of G_2 holonomy.Comment: 47 page

Identification of polymorphisms and balancing selection in the male infertility candidate gene, ornithine decarboxylase antizyme 3

Abstract Background The antizyme family is a group of small proteins that play a role in cell growth and division by regulating the biosynthesis of polyamines (putrescine, spermidine, spermine). Antizymes regulate polyamine levels primarily through binding ornithine decarboxylase (ODC), an enzyme key to polyamine production, and targeting ODC for destruction by the 26S proteosome. Ornithine decarboxylase antizyme 3 (OAZ3) is a testis-specific antizyme paralog and the only antizyme expressed in the mid to late stages of spermatogenesis. Methods To see if mutations in the OAZ3 gene are responsible for some cases of male infertility, we sequenced and evaluated the genomic DNA of 192 infertile men, 48 men of known paternity, and 34 African aborigines from the Mbuti tribe in the Democratic Republic of the Congo. The coding sequence of OAZ3 was further screened for polymorphisms by SSCP analysis in the infertile group and an additional 250 general population controls. Identified polymorphisms in the OAZ3 gene were further subjected to a haplotype analysis using PHASE 2.02 and Arlequin 2.0 software programs. Results A total of 23 polymorphisms were identified in the promoter, exons or intronic regions of OAZ3. The majority of these fell within a region of less than two kilobases. Two of the polymorphisms, -239 A/G in the promoter and 4280 C/T, a missense polymorphism in exon 5, may show evidence of association with male infertility. Haplotype analysis identified 15 different haplotypes, which can be separated into two divergent clusters. Conclusion Mutations in the OAZ3 gene are not a common cause of male infertility. However, the presence of the two divergent haplotypes at high frequencies in all three of our subsamples (infertile, control, African) suggests that they have been maintained in the genome by balancing selection, which was supported by a test of Tajima's D statistic. Evidence for natural selection in this region implies that these haplotypes may be associated with a trait other than infertility. This trait may be related to another function of OAZ3 or a region in tight linkage disequilibrium to the gene.</p

Degenerate flag varieties: moment graphs and Schr\"oder numbers

We study geometric and combinatorial properties of the degenerate flag varieties of type A. These varieties are acted upon by the automorphism group of a certain representation of a type A quiver, containing a maximal torus T. Using the group action, we describe the moment graphs, encoding the zero- and one-dimensional T-orbits. We also study the smooth and singular loci of the degenerate flag varieties. We show that the Euler characteristic of the smooth locus is equal to the large Schr\"oder number and the Poincar\'e polynomial is given by a natural statistics counting the number of diagonal steps in a Schr\"oder path. As an application we obtain a new combinatorial description of the large and small Schr\"oder numbers and their q-analogues.Comment: 25 page

Crystal structures of native and thrombin-complexed heparin cofactor II reveal a multistep allosteric mechanism

The serine proteases sequentially activated to form a fibrin clot are inhibited primarily by members of the serpin family, which use a unique β-sheet expansion mechanism to trap and destroy their targets. Since the discovery that serpins were a family of serine protease inhibitors there has been controversy as to the role of conformational change in their mechanism. It now is clear that protease inhibition depends entirely on rapid serpin β-sheet expansion after proteolytic attack. The regulatory advantage afforded by the conformational mobility of serpins is demonstrated here by the structures of native and S195A thrombin-complexed heparin cofactor II (HCII). HCII inhibits thrombin, the final protease of the coagulation cascade, in a glycosaminoglycan-dependent manner that involves the release of a sequestered hirudin-like N-terminal tail for interaction with thrombin. The native structure of HCII resembles that of native antithrombin and suggests an alternative mechanism of allosteric activation, whereas the structure of the S195A thrombin–HCII complex defines the molecular basis of allostery. Together, these structures reveal a multistep allosteric mechanism that relies on sequential contraction and expansion of the central β-sheet of HCII