Addendum: One‐Speed Neutron Transport in Two Adjacent Half‐Spaces

The interface current for the problem of two half‐spaces with a constant source in one half‐space is obtained in closed form.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70010/2/JMAPAQ-5-12-1804-1.pd

One‐Speed Neutron Transport in Two Adjacent Half‐Spaces

Using Case's method for solving the one‐speed transport equation with isotropic scattering, the Milne problem solution, the solution for a constant source in one half‐space, and the Green's function solution are obtained for two adjacent half‐spaces. These problems have been solved previously by other methods. Here the derivations are greatly simplified by using Case's method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71048/2/JMAPAQ-5-5-668-1.pd

Differences in Spectral Sensitivity Within and Among Species of Darters (genus Etheostoma)

We examined variation in the visual system both within and among seven species of darters, colorful freshwater fishes of the genus Etheostoma. Using microspectrophotometry, we found that darters possess rod photoreceptor cells, single cone photoreceptor cells containing middle wavelength sensitive (MWS) visual pigments, and twin photoreceptor cells containing (LWS) visual pigments. No variation in peak sensitivity was detected among species or individuals in the rod class. In the MWS class, significant variation was detected among species and a strong statistical trend suggests differences among individuals. By contrast, all differences in the LWS class could be attributed to variation among individuals. Patterns of variation detected among species, among individuals, and among cone classes suggest that complex patterns of selection may be shaping the visual system of these fishes. Further, differences among individuals may have important consequences for visually based behaviors

Opportunities for system level improvement in antibiotic use across the surgical pathway

Optimizing antibiotic prescribing across the surgical pathway (before, during, and after surgery) is a key aspect of tackling important drivers of antimicrobial resistance and simultaneously decreasing the burden of infection at the global level. In the UK alone, 10 million patients undergo surgery every year, which is equivalent to 60% of the annual hospital admissions having a surgical intervention. The overwhelming majority of surgical procedures require effectively limited delivery of antibiotic prophylaxis to prevent infections. Evidence from around the world indicates that antibiotics for surgical prophylaxis are administered ineffectively, or are extended for an inappropriate duration of time postoperatively. Ineffective antibiotic prophylaxis can contribute to the development of surgical site infections (SSIs), which represent a significant global burden of disease. The World Health Organization estimates SSI rates of up to 50% in postoperative surgical patients (depending on the type of surgery), with a particular problem in low- and middle-income countries, where SSIs are the most frequently reported healthcare-associated infections. Across European hospitals, SSIs alone comprise 19.6% of all healthcare-acquired infections. Much of the scientific research in infection management in surgery is related to infection prevention and control in the operating room, surgical prophylaxis, and the management of SSIs, with many studies focusing on infection within the 30-day postoperative period. However it is important to note that SSIs represent only one of the many types of infection that can occur postoperatively. This article provides an overview of the surgical pathway and considers infection management and antibiotic prescribing at each step of the pathway. The aim was to identify the implications for research and opportunities for system improvement

Twirling Elastica: Kinks, Viscous Drag, and Torsional Stress

Biological filaments such as DNA or bacterial flagella are typically curved in their natural states. To elucidate the interplay of viscous drag, twisting, and bending in the overdamped dynamics of such filaments, we compute the steady-state torsional stress and shape of a rotating rod with a kink. Drag deforms the rod, ultimately extending or folding it depending on the kink angle. For certain kink angles and kink locations, both states are possible at high rotation rates. The agreement between our macroscopic experiments and the theory is good, with no adjustable parameters.Comment: 4 pages, 4 figure

Molecular elasticity and the geometric phase

We present a method for solving the Worm Like Chain (WLC) model for twisting semiflexible polymers to any desired accuracy. We show that the WLC free energy is a periodic function of the applied twist with period 4 pi. We develop an analogy between WLC elasticity and the geometric phase of a spin half system. These analogies are used to predict elastic properties of twist-storing polymers. We graphically display the elastic response of a single molecule to an applied torque. This study is relevant to mechanical properties of biopolymers like DNA.Comment: five pages, one figure, revtex, revised in the light of referee's comments, to appear in PR

The Viscous Nonlinear Dynamics of Twist and Writhe

Exploiting the "natural" frame of space curves, we formulate an intrinsic dynamics of twisted elastic filaments in viscous fluids. A pair of coupled nonlinear equations describing the temporal evolution of the filament's complex curvature and twist density embodies the dynamic interplay of twist and writhe. These are used to illustrate a novel nonlinear phenomenon: ``geometric untwisting" of open filaments, whereby twisting strains relax through a transient writhing instability without performing axial rotation. This may explain certain experimentally observed motions of fibers of the bacterium B. subtilis [N.H. Mendelson, et al., J. Bacteriol. 177, 7060 (1995)].Comment: 9 pages, 4 figure

Rapidly progressive post-transplant lymphoproliferative disease following withdrawal of sirolimus

Sirolimus, a potent inhibitor of B- and T-cell activation, is a commonly used immunosuppressant after renal transplantation. Withdrawal of sirolimus from the immunosuppression regimen may reduce B-cell surveillance. We present a case of rapidly progressive central nervous system (CNS) polymorphic Epstein-Barr virus (EBV)-related post-transplant lymphoproliferative disorder following the withdrawal of sirolimus

A Paraconsistent Higher Order Logic

Classical logic predicts that everything (thus nothing useful at all) follows from inconsistency. A paraconsistent logic is a logic where an inconsistency does not lead to such an explosion, and since in practice consistency is difficult to achieve there are many potential applications of paraconsistent logics in knowledge-based systems, logical semantics of natural language, etc. Higher order logics have the advantages of being expressive and with several automated theorem provers available. Also the type system can be helpful. We present a concise description of a paraconsistent higher order logic with countable infinite indeterminacy, where each basic formula can get its own indeterminate truth value (or as we prefer: truth code). The meaning of the logical operators is new and rather different from traditional many-valued logics as well as from logics based on bilattices. The adequacy of the logic is examined by a case study in the domain of medicine. Thus we try to build a bridge between the HOL and MVL communities. A sequent calculus is proposed based on recent work by Muskens.Comment: Originally in the proceedings of PCL 2002, editors Hendrik Decker, Joergen Villadsen, Toshiharu Waragai (http://floc02.diku.dk/PCL/). Correcte

Semiflexible chains in confined spaces

We develop an analytical method for studying the properties of a noninteracting wormlike chain (WLC) in confined geometries. The mean-field-like theory replaces the rigid constraints of confinement with average constraints, thus allowing us to develop a tractable method for treating a WLC wrapped on the surface of a sphere, and fully encapsulated within it. The efficacy of the theory is established by reproducing the exact correlation functions for a WLC confined to the surface of a sphere. In addition, the coefficients in the free energy are exactly calculated. We also describe the behavior of a surface-confined chain under external tension that is relevant for single molecule experiments on histone-DNA complexes. The force-extension curves display spatial oscillations, and the extension of the chain, whose maximum value is bounded by the sphere diameter, scales as f−1 at large forces, in contrast to the unconfined chain that approaches the contour length as f−1∕2. A WLC encapsulated in a sphere, that is relevant for the study of the viral encapsulation of DNA, can also be treated using the mean-field approach. The predictions of the theory for various correlation functions are in excellent agreement with Langevin simulations. We find that strongly confined chains are highly structured by examining the correlations using a local winding axis. The predicted pressure of the system is in excellent agreement with simulations but, as is known, is significantly lower than the pressures seen for DNA packaged in viral capsids