Anomalous behavior of the spin gap of a spin-1/2 two-leg antiferromagnetic ladder with Ising-like rung interactions

Using mainly numerical methods, we investigate the width of the spin gap of a spin-1/2 two-leg ladder described by \cH= J_\rl \sum_{j=1}^{N/2} [ \vS_{j,a} \cdot \vS_{j+1,a} + \vS_{j,b} \cdot \vS_{j+1,b} ] + J_\rr \sum_{j=1}^{N/2} [\lambda (S^x_{j,a} S^x_{j,b} + S^y_{j,a} S^y_{j,b}) + S^z_{j,a} S^z_{j,b}] , where $S^\alpha_{j,a(b)}$ denotes the $\alpha$-component of the spin-1/2 operator at the $j$-th site of the $a (b)$ chain. We mainly focus on the J_\rr \gg J_\rl > 0 and $|\lambda| \ll 1$ case. The width of the spin gap as a function of $\lambda$ anomalously increases near $\lambda = 0$; for instance, for $-0.1 < \lambda < 0.1$ when $J_{\rm l}/J_{\rm r} = 0.1$. The gap formation mechanism is thought to be different for the $\lambda 0$ cases. Since, in usual cases, the width of the gap becomes zero or small at the point where the gap formation mechanism changes, the above gap-increasing phenomenon in the present case is anomalous. We explain the origin of this anomalous phenomenon by use of the degenerate perturbation theory. We also draw the ground-state phase diagram.Comment: 4 pages, 11 figures; Proc. "The International Conference on Quantum Criticality and Novel Phases" (2012), to be published in Phys. Stat. Solidi

Kernel Choice Matters for Boundary Inference using Local Polynomial Density: With Application to Manipulation Testing

Local polynomial density (LPD) estimation has become an essential tool for boundary inference, including manipulation tests for regression discontinuity. It is common sense that kernel choice is not critical for LPD estimation, in analogy to standard kernel smoothing estimation. This paper, however, points out that kernel choice has a severe impact on the performance of LPD, based on both asymptotic and non-asymptotic theoretical investigations. In particular, we show that the estimation accuracy can be extremely poor with commonly used kernels with compact support, such as the triangular and uniform kernels. Importantly, this negative result implies that the LPD-based manipulation test loses its power if a compactly supported kernel is used. As a simple but powerful solution to this problem, we propose using a specific kernel function with unbounded support. We illustrate the empirical relevance of our results with numerous empirical applications and simulations, which show large improvements

Hydrodynamics in bridging and aggregation of two colloidal particles in a near-critical binary mixture

We investigate bridging and aggregation of two colloidal particles in a near-critical binary mixture when the fluid far from the particles is outside the coexistence (CX) curve and is rich in the component disfavored by the colloid surfaces. In such situations, the adsorption-induced interaction is enhanced, leading to bridging and aggregation of the particles. We realize bridging firstly by changing the temperature with a fixed interparticle separation and secondly by letting the two particles aggregate. The interparticle attractive force dramatically increases upon bridging. The dynamics is governed by hydrodynamic flow around the colloid surfaces. In aggregation, the adsorption layers move with the particles and squeezing occurs at narrow separation. We take into account the renormalization effect due to the critical fluctuations using the recent local functional theory [J. Chem. Phys. 136, 114704 (2012)].Comment: 10 Pages, 11 figures, accepted in Softmatte

Somatosensory and Visual Deprivation Each Decrease the Density of Parvalbumin Neurons and Their Synapse Terminals in the Prefrontal Cortex and Hippocampus of Mice

In the phenomenon known as cross-modal plasticity, the loss of one sensory system is followed by improved functioning of other intact sensory systems. MRI and functional MRI studies suggested a role of the prefrontal cortex and the temporal lobe in cross-modal plasticity. We used a mouse model to examine the effects of sensory deprivation achieved by whisker trimming and visual deprivation achieved by dark rearing in neonatal mice on the appearance of parvalbumin (PV) neurons and the formation of glutamic acid decarboxylase 67 (GAD67)-positive puncta around pyramidal neurons in the prefrontal cortex and hippocampus. Whisker trimming, but not dark rearing, decreased the density of PV neurons in the hippocampus at postnatal day 28 (P28). In the prefrontal cortex, whisker trimming and dark rearing decreased the density of PV neurons in layer 5/6 (L5/6) at P28 and in L2/3 at P56, respectively, whereas dark rearing increased the density of PV neurons in L5/6 at P56. Whisker trimming decreased the density of GAD67-positive puncta in CA1 of the hippocampus at both P28 and P56 and in L5/6 of the prefrontal cortex at P28. Dark rearing decreased the density of GAD67-positive puncta in CA1 of the hippocampus and in both L2/3 and L5/6 of the prefrontal cortex at P28, and in L2/3 of the prefrontal cortex at P56. These results demonstrate that somatosensory or visual deprivation causes changes in the PV-interneuronal network in the mouse prefrontal cortex and hippocampus. The results also suggest that the alteration of the PV-interneuronal network, especially in the prefrontal cortex, may contribute to cross-modal plasticity

Real-time cheat-free gaming on the basis of time-stamp service

A cheat-proof protocol for real-time gaming is proposed under the assumption that time-stamp servers issue serially numbered time stamps honestly and are available near every player, i.e., they exist everywhere in the Internet. With this protocol, each player sends its action to the other player and also sends its hash to the nearest time-stamp server. The time-stamp server sends the signed hash with the time and a serial number back to the player. The actions are checked to verify that they are compatible with the hashes, and the signed hashes are checked to verify that they have the correct time and the serial numbers are contiguous. The only latency in this protocol is the travel time of the packet from one player to another. In comparison with other existing protocols, we confirm that the proposed protocol is as fast as and more secure than the fair synchronization protocol, the fastest existing protoco

Transient Occlusion of Bilateral Internal Iliac Arteries Facilitates Bloodless Operative Field in Subcapsular Prostatectomy

Transurethral resection of the prostate is the gold standard of surgical treatment for benign prostatic hyperplasia (BPH). Nevertheless, open subcapsular prostatectomy is still performed for large BPH. While enucleation of prostatic adenoma is being performed, unneglectable bleeding can occur and surgeons need to rush to remove adenomas, often using fingers and in a blinded fashion. The blood supply to the prostatic capsule and adenoma can be reduced to a marked extent in subcapsular prostatectomy if the bilateral internal iliac arteries are transiently occluded. Thus, a bloodless operative field is reasonably acquired during enucleation of adenoma, which would, otherwise, be a cause for concern to surgeons due to bleeding. It is not always applicable, but it could be an option if the estimated volume of BPH is more than 100 mL. In two cases, bilateral internal iliac arteries were occluded with Bulldog clamps, and then adenomas of 159 and 97 g were enucleated

Efficacy and Safety of Ramucirumab/nab-paclitaxel for Previously Treated Advanced Gastric Cancer in Community Hospitals

As the nanoparticle albumin-bound paclitaxel (nab-PTX) is free of ethanol and premedication, the duration of administration is shorter and patients can drive themselves to and from the hospital. In the 2018 Japanese gastric cancer treatment guidelines, ramucirumab (RAM) plus weekly nab-PTX is conditionally recommended for previously treated patients with advanced gastric cancer. Here, we retrospectively analysed the efficacy and safety of RAM+nab-PTX for such patients in community hospitals. From January 2018 to December 2019, 43 patients with metastatic and recurrent gastric cancer received RAM+nab-PTX treatment. Six patients (13.9%) were older than 80 years and 9 patients (20.9%) showed ECOG-PS 2. Progression-free survival (PFS), overall survival (OS), overall response rate (ORR), disease control rate (DCR), and adverse events (AEs) were reviewed retrospectively. Median PFS was 114 days (95% confidence interval [CI]: 84-190) and median OS was 297 days (95% CI: 180-398). ORR and DCR were 32.4% and 72.2%, respectively. The incidence rates of ≥grade 3 neutropenia and febrile neutropenia were 53.5% and 2.3%, respectively. No treatment-related deaths occurred. RAM plus nab-PTX combination therapy demonstrated manageable toxicity even patients who were elderly or had an ECOG-PS 2. This treatment is useful in community hospital settings