Biaxial spin-nematic phase of two dimensional disordered rotor models and spin-one bosons in optical lattices

We show that the ground state of disordered rotor models with quadrupolar interactions can exhibit biaxial nematic ordering in the disorder-averaged sense. We present a mean-field analysis of the model and demonstrate that the biaxial phase is stable against small quantum fluctuations. We point out the possibility of experimental realization of such rotor models using ultracold spin-one Bose atoms in a spin-dependent and disordered optical lattice in the limit of a large number of atoms per site and also suggest an imaging experiment to detect the biaxial nematicity in such systems.Comment: revtex file 7 pages, 2 figures, version published in PR

Sociodemographic Correlates of Sexlessness Among American Adults and Associations with Self-Reported Happiness Levels: Evidence from the U.S. General Social Survey

Although sexual activity is commonly believed to be a key component of emotional well-being, little is known about the factors associated with the absence of sexual activity or its associations with self-reported happiness. Using the U.S. General Social Survey–National Death Index 2008 dataset, a series of nationally representative surveys (1988–2002), this study analyzed the sociodemographic and lifestyle factors associated with past-year sexlessness and self-reported happiness among American adults (n = 17,744). After adjustment for marital status, there were no significant time trends evident in the proportion of American adults reporting past-year sexlessness. Among participants (age = 18–89 years), 15.2% of males and 26.7% of females reported past-year sexlessness while 8.7% of males and 17.5% of females reported no sex for 5 years or more. For both genders, past-year sexlessness was most strongly associated with older age and being currently non-married in the multivariable models. Among males, the multivariable analysis also showed that sexlessness was associated with providing less than 20% of the house-hold income (OR 2.27). In female participants, sexlessness was associated with very low income, poor health, lower financial satisfaction, absence of children, and having conservative sexual attitudes (OR 1.46–3.60). For both genders, Black race was associated with a much lower likelihood of sexlessness among currently non-married adults. The purported detrimental impact of sexlessness on self-reported happiness levels was not evident in this large, nationally representative study after adjusting for sociodemographic factors. Sexless Americans reported very similar happiness levels as their sexually active counterparts

High-pressure study of X-ray diffuse scattering in ferroelectric perovskites

We present a high-pressure x-ray diffuse scattering study of the ABO$_3$ ferroelectric perovskites BaTiO_3 and KNbO_3. The well-known diffuse lines are observed in all the phases studied. In KNbO_3, we show that the lines are present up to 21.8 GPa, with constant width and a slightly decreasing intensity. At variance, the intensity of the diffuse lines observed in the cubic phase of BaTiO_3 linearly decreases to zero at $\sim 11$ GPa. These results are discussed with respect to x-ray absorption measurements, which leads to the conclusion that the diffuse lines are only observed when the B atom is off the center of the oxygen tetrahedron. The role of such disorder on the ferroelectric instability of perovskites is discussed.Comment: 4 pages, Accepted in PR

The cohesin ring concatenates sister DNA molecules

Sister chromatid cohesion, which is essential for mitosis, is mediated by a multi-subunit protein complex called cohesin whose Scc1, Smc1, and Smc3 subunits form a tripartite ring structure. It has been proposed that cohesin holds sister DNAs together by trapping them inside its ring. To test this, we used site-specific cross-linking to create chemical connections at the three interfaces between the ring’s three constituent polypeptides, thereby creating covalently closed cohesin rings. As predicted by the ring entrapment model, this procedure produces dimeric DNA/cohesin structures that are resistant to protein denaturation. We conclude that cohesin rings concatenate individual sister minichromosome DNAs

Endovascular foreign body retrieval

ObjectiveThe number of endovascular procedures performed is increasing exponentially as technology improves. A serious complication of endovascular therapy is loss of a foreign body in the vasculature. We reviewed our experience and evaluated the cause, management, and outcomes of intravascular foreign body (IVFB) misplacement.MethodsWe completed a retrospective review of patients who underwent endovascular retrieval of IVFBs between 2005 and 2010. Patients were identified by current procedural terminology code or by our hospital's risk management team. Patients undergoing routine endovascular retrieval of temporary vena cava filters were excluded.ResultsTwenty-seven IVFBs were identified in 26 patients. Twenty patients were asymptomatic (76.9%). Six patients were symptomatic (22.2%) with either pain (n = 4) or abnormal physical findings (n = 2). There were 13 (48.1%) catheter fragments, six (22.2%) guidewires, five (18.5%) inferior vena cava (IVC) filter (embolisms), two (7.4%) stents, and one (3.7%) sheath fragment. There were five (15.6%) embolizations of an IVFB into the right heart, three (9.4%) into a pulmonary artery, eight (25%) into the vena cava, eight (25%) into peripheral veins, five (15.6%) into peripheral arteries, one (3.1%) into a coronary artery, one (3.1%) into a hepatic vein, and one (3.1%) into adjacent soft tissue. The mechanism of endovascular loss was device fracture in 16 (59.3%) cases, loss of control in six cases (22.2%), migration in four (14.8%) cases, and incorrect device deployment in one case (3.7%). The probable cause of foreign body loss was technical error in eight (29.6%) cases. In three cases, IVFB retrieval was not attempted. The misplacement and retrieval were completed during the same procedure in 13 (48%) cases. Twenty-four endovascular retrievals were performed. Fifteen (62.5%) procedures used a snare to remove the IVFB and two (8.2%) used balloon catheters. Three IVFBs could not be removed and two cases were converted to open procedures. Technical success was achieved in 19/24 cases (79.2%). There were no immediate complications related to the retrieval of the IVFB; however, there was a single late complication of pulmonary embolism after failed endovascular retrieval (1/24, 4.2%). Thirty-day survival was 100%.ConclusionsIntravascular foreign bodies are a serious complication of endovascular therapy that can be minimized with proper device selection and deployment. When an intravascular foreign body is identified, endovascular retrieval should be attempted due to its high success rate and minimal morbidity

Procedure-based assessment for laparoscopic cholecystectomy can replace global rating scales

Introduction Global rating scales (GRSs) such as the Objective Structured Assessment of Technical Skills (OSATS) and Global Operative Assessment of Laparoscopic Surgery (GOALS) are assessment methods for surgical procedures. The aim of this study was to establish construct validity of Procedure-Based Assessment (PBA) and to compare PBA with GRSs for laparoscopic cholecystectomy. Material and methods OSATS and GOALS GRSs were compared with PBA in their ability to discriminate between levels of performance between trainees who can perform the procedure independently and those who cannot. Three groups were formed based on the number of procedures performed by the trainee: novice (1-10), intermediate (11-20) and experienced (>20). Differences between groups were assessed using the Kruskal-Wallis and Mann-Whitney U tests. Results Increasing experience correlated significantly with higher GRSs and PBA scores (all p < .001). Scores of novice and intermediate groups overlapped substantially on the OSATS (p = .1) and GOALS (p = .1), while the PBA discriminated between these groups (p = .03). The median score in the experienced group was higher with less dispersion for PBA (97.2[85.3-100]) compared to OSATS (82.1[60.7-100]) and GOALS (80[60-100]). Conclusion For assessing skill level or the capability of performing a laparoscopic cholecystectomy independently, PBA has a higher discriminative ability compared to the GRSs

Organization of Block Copolymers using NanoImprint Lithography: Comparison of Theory and Experiments

We present NanoImprint lithography experiments and modeling of thin films of block copolymers (BCP). The NanoImprint lithography is used to align perpendicularly lamellar phases, over distances much larger than the natural lamellar periodicity. The modeling relies on self-consistent field calculations done in two- and three-dimensions. We get a good agreement with the NanoImprint lithography setups. We find that, at thermodynamical equilibrium, the ordered BCP lamellae are much better aligned than when the films are deposited on uniform planar surfaces

Graph products of spheres, associative graded algebras and Hilbert series

Given a finite, simple, vertex-weighted graph, we construct a graded associative (non-commutative) algebra, whose generators correspond to vertices and whose ideal of relations has generators that are graded commutators corresponding to edges. We show that the Hilbert series of this algebra is the inverse of the clique polynomial of the graph. Using this result it easy to recognize if the ideal is inert, from which strong results on the algebra follow. Non-commutative Grobner bases play an important role in our proof. There is an interesting application to toric topology. This algebra arises naturally from a partial product of spheres, which is a special case of a generalized moment-angle complex. We apply our result to the loop-space homology of this space.Comment: 19 pages, v3: elaborated on connections to related work, added more citations, to appear in Mathematische Zeitschrif