Spin dynamics for the Lebwohl-Lasher model

A spin dynamics algorithm, combining checkerboard updating and a rotation algorithm based on the local second-rank ordering field, is developed for the Lebwohl-Lasher model of liquid crystals. The method is shown to conserve energy well and to generate simulation averages that are consistent with those obtained by Monte Carlo simulation. However, care must be taken to avoid the undesirable effects of director rotation, and a method for doing this is proposed

THE IMPACT OF MARKETING INFORMATION SUPPLY ON PRODUCT MANAGERS: AN ORGANIZATIONAL INFORMATION PROCESSING PERSPECTIVE

This paper examines the impact of information supply and distribution on managerial information processing using a model derived from the organizational information processing (OIP) framework developed by Daft and Weick (1984). The model suggests that more supply and distribution of information wiltlead to greater information use and the acquisition of more knowledge, given the organization\u27s information processing capabilities match its requirements. The model was extended to include the influence of social factors (i. e., culture and power) and the level of knowledge in the organization. Product managers in two consumer goods organizations providing different levels of information technology support were studied to compare the effect of different approaches to supplying and distributing information. The focused comparison case research method (George and McKeown 1985) was used, in which sites are selected differing only on the dimensions of interest, namely information supply and distribution. The cases provided evidence to support the model. The company which had more data and analytic tools available for its product managers used more information and knew more about the factors that influenced the marketing of its products. In addition, organizational culture and the level of knowledge at the companies affected their approach to information supply, information use, and knowledge acquisition. The results suggest that the effective use of information technology requires a combination of managing the organization culture and fitting the characteristics of information supply and distribution mechanisms to information requirements

Sumoylation silences the plasma membrane leak K+ channel K2P1.

Reversible, covalent modification with small ubiquitin-related modifier proteins (SUMOs) is known to mediate nuclear import/export and activity of transcription factors. Here, the SUMO pathway is shown to operate at the plasma membrane to control ion channel function. SUMO-conjugating enzyme is seen to be resident in plasma membrane, to assemble with K2P1, and to modify K2P1 lysine 274. K2P1 had not previously shown function despite mRNA expression in heart, brain, and kidney and sequence features like other two-P loop K+ leak (K2P) pores that control activity of excitable cells. Removal of the peptide adduct by SUMO protease reveals K2P1 to be a K+-selective, pH-sensitive, openly rectifying channel regulated by reversible peptide linkage

Coefficient of Restitution as a Fluctuating Quantity

The coefficient of restitution of a spherical particle in contact with a flat plate is investigated as a function of the impact velocity. As an experimental observation we notice non-trivial (non-Gaussian) fluctuations of the measured values. For a fixed impact velocity, the probability density of the coefficient of restitution, $p(\epsilon)$, is formed by two exponential functions (one increasing, one decreasing) of different slope. This behavior may be explained by a certain roughness of the particle which leads to energy transfer between the linear and rotational degrees of freedom.Comment: 4 pages, 4 figure

Collective chemotactic dynamics in the presence of self-generated fluid flows

In micro-swimmer suspensions locomotion necessarily generates fluid motion, and it is known that such flows can lead to collective behavior from unbiased swimming. We examine the complementary problem of how chemotaxis is affected by self-generated flows. A kinetic theory coupling run-and-tumble chemotaxis to the flows of collective swimming shows separate branches of chemotactic and hydrodynamic instabilities for isotropic suspensions, the first driving aggregation, the second producing increased orientational order in suspensions of "pushers" and maximal disorder in suspensions of "pullers". Nonlinear simulations show that hydrodynamic interactions can limit and modify chemotactically-driven aggregation dynamics. In puller suspensions the dynamics form aggregates that are mutually-repelling due to the non-trivial flows. In pusher suspensions chemotactic aggregation can lead to destabilizing flows that fragment the regions of aggregation.Comment: 4 page

A BPS Interpretation of Shape Invariance

We show that shape invariance appears when a quantum mechanical model is invariant under a centrally extended superalgebra endowed with an additional symmetry generator, which we dub the shift operator. The familiar mathematical and physical results of shape invariance then arise from the BPS structure associated with this shift operator. The shift operator also ensures that there is a one-to-one correspondence between the energy levels of such a model and the energies of the BPS-saturating states. These findings thus provide a more comprehensive algebraic setting for understanding shape invariance.Comment: 15 pages, 2 figures, LaTe

A noninvasive method for in situ determination of mating success in female American lobsters (Homarus americanus)

Despite being one of the most productive fisheries in the Northwest Atlantic, much remains unknown about the natural reproductive dynamics of American lobsters. Recent work in exploited crustacean populations (crabs and lobsters) suggests that there are circumstances where mature females are unable to achieve their full reproductive potential due to sperm limitation. To examine this possibility in different regions of the American lobster fishery, a reliable and noninvasive method was developed for sampling large numbers of female lobsters at sea. This method involves inserting a blunt-tipped needle into the female's seminal receptacle to determine the presence or absence of a sperm plug and to withdraw a sample that can be examined for the presence of sperm. A series of control studies were conducted at the dock and in the laboratory to test the reliability of this technique. These efforts entailed sampling 294 female lobsters to confirm that the presence of a sperm plug was a reliable indicator of sperm within the receptacle and thus, mating. This paper details the methodology and the results obtained from a subset of the total females sampled. Of the 230 female lobsters sampled from George's Bank and Cape Ann, MA (size range = 71-145 mm in carapace length), 90.3% were positive for sperm. Potential explanations for the absence of sperm in some females include: immaturity (lack of physiological maturity), breakdown of the sperm plug after being used to fertilize a clutch of eggs, and lack of mating activity. The surveys indicate that this technique for examining the mating success of female lobsters is a reliable proxy that can be used in the field to document reproductive activity in natural populations

Expressions for forces and torques in molecular simulations using rigid bodies

Expressions for intermolecular forces and torques, derived from pair potentials between rigid non-spherical units, are presented. The aim is to give compact and clear expressions, which are easily generalised, and which minimise the risk of error in writing molecular dynamics simulation programs. It is anticipated that these expressions will be useful in the simulation of liquid crystalline systems, and in coarse-grained modelling of macromolecules

Radiative Transfer Theory Verified by Controlled Laboratory Experiments

We report the results of high-accuracy controlled laboratory measurements of the Stokes reflection matrix for suspensions of submicrometer-sized latex particles in water and compare them with the results of a numerically exact computer solution of the vector radiative transfer equation (VRTE). The quantitative performance of the VRTE is monitored by increasing the volume packing density of the latex particles from 2 to 10. Our results indicate that the VRTE can be applied safely to random particulate media with packing densities up to 2. VRTE results for packing densities of the order of 5 should be taken with caution, whereas the polarized bidirectional reflectivity of suspensions with larger packing densities cannot be accurately predicted. We demonstrate that a simple modification of the phase matrix entering the VRTE based on the so-called static structure factor can be a promising remedy that deserves further examination

A Rare Case of Idiopathic Pyometra in a Premenopausal Patient.

Pyometra is a very uncommon disease principally occurring in postmenopausal women. It is characterized by the accumulation of purulent material within the uterine cavity. This paper presents the clinical history of a 35-year-old premenopausal woman with otherwise normal menstruation who developed heavy menstruation and was diagnosed with a benign pyometra of indeterminate etiology in March 2017. The patient underwent repeated ultrasound-guided drainage, dilation and curettage, and antibiotic therapy. Biopsies of the pelvic sidewall revealed endometriosis in June 2017. The heavy menstruation and suppurative fluid in the uterus of the patient persisted in which intramuscular leuprolide acetate was prescribed to address the endometriosis and heavy menstrual bleeding. Ultimately, the leuprolide acetate effectively resolved the patient\u27s bleeding and pyometra. The medication was concluded after 12 months of supervision and the patient is currently symptom free. Pyometra is an unusual condition rarely identified in premenopausal women. Drainage and antibiotic therapy are routinely employed; however, one may consider gonadotropin-releasing hormone agonist medication to potentially confer a beneficial patient outcome in rare cases where endometriosis and bleeding are intractable