On the geometric structure of fMRI searchlight-based information maps

Information mapping is a popular application of Multivoxel Pattern Analysis (MVPA) to fMRI. Information maps are constructed using the so called searchlight method, where the spherical multivoxel neighborhood of every voxel (i.e., a searchlight) in the brain is evaluated for the presence of task-relevant response patterns. Despite their widespread use, information maps present several challenges for interpretation. One such challenge has to do with inferring the size and shape of a multivoxel pattern from its signature on the information map. To address this issue, we formally examined the geometric basis of this mapping relationship. Based on geometric considerations, we show how and why small patterns (i.e., having smaller spatial extents) can produce a larger signature on the information map as compared to large patterns, independent of the size of the searchlight radius. Furthermore, we show that the number of informative searchlights over the brain increase as a function of searchlight radius, even in the complete absence of any multivariate response patterns. These properties are unrelated to the statistical capabilities of the pattern-analysis algorithms used but are obligatory geometric properties arising from using the searchlight procedure.Comment: 15 pages, 7 figure

Information entropy of classical versus explosive percolation

We study the Shannon entropy of the cluster size distribution in classical as well as explosive percolation, in order to estimate the uncertainty in the sizes of randomly chosen clusters. At the critical point the cluster size distribution is a power-law, i.e. there are clusters of all sizes, so one expects the information entropy to attain a maximum. As expected, our results show that the entropy attains a maximum at this point for classical percolation. Surprisingly, for explosive percolation the maximum entropy does not match the critical point. Moreover, we show that it is possible determine the critical point without using the conventional order parameter, just analysing the entropy's derivatives.Comment: 6 pages, 6 figure

EPIDEMIOLOGICAL STUDIES ON VARYING EXTENDED-SPECTRUM β-LACTAMASES PRODUCING UROPATHOGENIC BACTERIA

Objective: Urinary tract infection (UTI) is the most common serious infection during infancy, adult male and female, as well as at the time of pregnancy. UTI is also the most common nosocomial infection in many hospitals and accounts for approximately 35% of all hospital acquired infections. Hence the present study was aimed to screen the presence of multi-drug resistant bacterial pathogens among the urine samples collected from in and out patients of multi-speciality hospital. Methods: Standard microbiological laboratory protocols were followed and about 152 samples were processed and screened. Among them, 49 reported positive for the presence of urinary bacterial pathogens. Results: Among 49 isolates, Escherichia coli registered its prevalence in about 44 samples followed by Klebsiella spp. (4) and Pseudomones spp. (1). The gender wise distribution was found to be more among female patients (42%) than male patients (24%). The age wise distribution of infection among male and female patients was also noticed. Further, the multi-drug resistance of the isolates was done by using 8 antibiotics. Conclusion: All the isolates exhibited the multiple antibiotic resistance and the isolates showed 27 different antibiotic resistance patterns. This confirms the prevalence of ESBL producers among the urinary pathogens

INCIDENCES OF STAPHYLOCOCCUS SPECIES IN SURGICAL SITE INFECTIONS-PROSPECTIVE STUDY FROM TERTIARY CARE CENTER, COIMBATORE, TAMILNADU

Objective: Surgical site infection (SSIs) is of great importance to regulatory agencies and public because of their clinical implication and occurrence. Human skin is populated with normal bacterial flora, which also gains access during immunocompromised state causing infection. This present study focuses on surveillance of SSIs with emphases over Staphylococcus species infection among patients from tertiary care centers of Coimbatore, TamilNadu, India.Methods: Clinical samples were collected and plated on mannitol salt agar (MSA) medium for isolation of Staphylococcus species. Furthermore, other conventional methods like Gram staining, catalase reaction were also performed in strict aseptic conditions with standard microbiological procedures for sample processing.Results: A total of 221 samples were collected and processed which resulted in 42.08% positivity with 59.13% Gram positive strains. Staphylococcus species were more prevalent in the Gram positive isolates, where other Gram negative microorganisms such as E. coli, P. aeruginosa, K. pneumoniae, M. morganii, E. faecalis, Enterobacter species, A. baumanii, S. marcescens and P. mirabilis were also isolated. The antibiogram pattern of the Staphylococcus species revealed resistance to antibiotics.Conclusion: This study has shown the prevalence of Staphylococcus species among SSIs, implicating the importance of further extended surveillance for better understanding of the prevalence rate and antimicrobial resistance pattern.Â

Synthesis and characteristics of polyarylene ether sulfones

A method utilizing potassium carbonate/dimethyl acetamide, as base and solvent respectively, was used for the synthesis of several homopolymers and copolymers derived from various bisphenols. It is demonstrated that this method deviates from simple second order kinetics; this deviation being due to the heterogeneous nature of the reaction. Also, it is shown that a liquid induced crystallization process can improve the solvent resistance of these polymers. Finally, a Monte Carlo simulation of the triad distribution of monomers in nonequilibrium copolycondensation is discussed

Spin-Hall effect and circular birefringence of a uniaxial crystal plate

The linear birefringence of uniaxial crystal plates is known since the 17th century, and it is widely used in numerous optical setups and devices. Here we demonstrate, both theoretically and experimentally, a fine lateral circular birefringence of such crystal plates. This effect is a novel example of the spin-Hall effect of light, i.e., a transverse spin-dependent shift of the paraxial light beam transmitted through the plate. The well-known linear birefringence and the new circular birefringence form an interesting analogy with the Goos-H\"anchen and Imbert-Fedorov beam shifts that appear in the light reflection at a dielectric interface. We report the experimental observation of the effect in a remarkably simple system of a tilted half-wave plate and polarizers using polarimetric and quantum-weak-measurement techniques for the beam-shift measurements. In view of great recent interest in spin-orbit interaction phenomena, our results could find applications in modern polarization optics and nano-photonics.Comment: 16 pages, 8 figures, to appear in Optic

Concurrent Chemoradiation for Vaginal Cancer

Background: It is not known whether the addition of chemotherapy to radiation therapy improves outcomes in primary vaginal cancer. Here, we review clinical outcomes in patients with primary vaginal cancer treated with radiation therapy (RT) or concurrent chemoradiation therapy (CRT). Methods: Seventy-one patients with primary vaginal cancer treated with definitive RT with or without concurrent chemotherapy at a single institution were identified and their records reviewed. A total of 51 patients were treated with RT alone; 20 patients were treated with CRT. Recurrences were analyzed. Overall survival (OS) and disease-free survival (DFS) rates were estimated using the Kaplan-Meier method. Cox regression analysis was performed. Results: The median age at diagnosis was 61 years (range, 18–92 years) and the median follow-up time among survivors was 3.0 years. Kaplan-Meier estimates for OS and DFS differed significantly between the RT and CRT groups (3-yr OS = 56% vs. 79%, log-rank p = 0.037; 3-yr DFS = 43% vs. 73%, log-rank p = 0.011). Twenty-three patients (45%) in the RT group had a relapse at any site compared to 3 (15%) in the CRT group (p = 0.027). With regard to the sites of first relapse, 10 patients (14%) had local only, 4 (6%) had local and regional, 9 (13%) had regional only, 1 (1%) had regional and distant, and 2 (3%) had distant only relapse. On univariate analysis, the use of concurrent chemotherapy, FIGO stage, tumor size, and date of diagnosis were significant predictors of DFS. On multivariate analysis, the use of concurrent chemotherapy remained a significant predictor of DFS (hazard ratio 0.31 (95% CI, 0.10–0.97; p = 0.04)). Conclusions: Vaginal cancer results in poor outcomes. Adequate radiation dose is essential to ensure curative management. Concurrent chemotherapy should be considered for vaginal cancer patients