The Role of Sp1 Family Genes in Wnt Mediated Neural Plate Patterning

Wnt signaling has a conserved role in anterior-posterior (A-P) patterning of the remarkably complex vertebrate brain from a very basic primordium, the neural plate, by differentially regulating downstream target genes to induce distinct neural fates. Wnt proteins originate from the blastoderm margin and diffuse anteriorly to re-pattern the default state of the anterior neural tissue to more posterior fates. How this graded Wnt ligand in the neural plate is translated by responding cells to establish specific cell fate zones along the A-P axis is not well established. In order to understand neural patterning by Wnt better, we need to identify the downstream components of this pathway, for instance, the transcriptional targets of Wnt signaling and their subsequent roles. Two well known but less studied targets of Wnt/β-catenin signaling in Zebrafish, the sp5a and sp5-like (sp5l) genes, are good models to study induction of transcription factors and gene regulatory network that drives neural posteriorization downstream of Wnt signaling because these paralogous genes potentially play an important role in mediating Wnt-dependent posterior neural plate patterning. Results from our recent RNA sequencing analysis identifies another gene, sp8b, along with the sp5a and sp5l genes, that may also play a role in Wnt dependent patterning in the nervous system. These Wnt target genes encode zinc finger transcription factors (TFs) belonging to the Sp1 gene family and transcriptional regulation of sp5 orthologs by Wnt signaling is known to be conserved in vertebrates. In spite of the compelling evidence of a significant and evolutionarily conserved relation between the sp5 genes and Wnt signaling in vertebrates, the function of these genes and how they are regulated by the Wnt pathway to pattern the vertebrate brain is not understood properly. This thesis is aimed at understanding the in-vivo function of the sp5 an sp8b genes by generating zebrafish genetic mutants

The Role of Sp1 Family Genes in Wnt Mediated Neural Plate Patterning

Wnt signaling has a conserved role in anterior-posterior (A-P) patterning of the remarkably complex vertebrate brain from a very basic primordium, the neural plate, by differentially regulating downstream target genes to induce distinct neural fates. Wnt proteins originate from the blastoderm margin and diffuse anteriorly to re-pattern the default state of the anterior neural tissue to more posterior fates. How this graded Wnt ligand in the neural plate is translated by responding cells to establish specific cell fate zones along the A-P axis is not well established. In order to understand neural patterning by Wnt better, we need to identify the downstream components of this pathway, for instance, the transcriptional targets of Wnt signaling and their subsequent roles. Two well known but less studied targets of Wnt/β-catenin signaling in Zebrafish, the sp5a and sp5-like (sp5l) genes, are good models to study induction of transcription factors and gene regulatory network that drives neural posteriorization downstream of Wnt signaling because these paralogous genes potentially play an important role in mediating Wnt-dependent posterior neural plate patterning. Results from our recent RNA sequencing analysis identifies another gene, sp8b, along with the sp5a and sp5l genes, that may also play a role in Wnt dependent patterning in the nervous system. These Wnt target genes encode zinc finger transcription factors (TFs) belonging to the Sp1 gene family and transcriptional regulation of sp5 orthologs by Wnt signaling is known to be conserved in vertebrates. In spite of the compelling evidence of a significant and evolutionarily conserved relation between the sp5 genes and Wnt signaling in vertebrates, the function of these genes and how they are regulated by the Wnt pathway to pattern the vertebrate brain is not understood properly. This thesis is aimed at understanding the in-vivo function of the sp5 an sp8b genes by generating zebrafish genetic mutants

Plasma rich in growth factors (PRGF) in non-surgical periodontal therapy: a randomized clinical trial

Abstract The aim of this split mouth, double blinded, randomized clinical trial was to evaluate the clinical efficacy of use of Plasma rich in growth factors (PRGF) as an adjunct to scaling and root planing (SRP) in the treatment of periodontal pockets. Twenty six patients (15 males, 11 females) diagnosed with generalized periodontitis with Pocket Depth > 5mm and plaque index score 4mm necessitating further treatment after 6-month follow-up were significantly lesser for SRP+PRGF group. The use of PRGF technology in non-surgical periodontal therapy, by single intra-pocket application in to periodontal pockets as an adjunct to SRP, in chronic periodontitis patients, was found to be effective in reduction of pocket depth and gain in clinical attachment level

Improvement in hot corrosion resistance of dissimilar alloy 825 and AISI 321 CO2-laser weldment by HVOF coating in aggressive salt environment at 900°C

This study investigated the hot corrosion performance of a dissimilar weldment of Ni-based superalloy and stainless steel joined by CO2-laser welding and improved by high-velocity oxy-fuel (HVOF) coating in a Na2SO4-60wt%V2O5 environment at 900°C. A dissimilar butt joint of AISI 321 and alloy 825 was fabricated by CO2-laser welding with low heat input after obtaining the optimum welding parameters by bead-on-plate trials. The metallurgical and mechanical properties of the laser weldment were evaluated. The tensile test results indicated the occurrence of fracture in the base metal AISI 321 side. The HVOF process was employed to coat Ni-20wt%Cr on the weldment. To evaluate the surface morphology of the corrosion products formed on the uncoated and Ni-20wt%Cr-coated weldments, scanning electron microscopy (SEM) analysis was performed. Energy-dispersive spectroscopy (EDS) was used to determine the different elements present on the surface scales. The existence of oxide phases on the weldments was determined by X-ray diffraction (XRD). The cross sections of the weldments were characterized by SEM with EDS line mapping analysis. The results indicated that the Ni-20wt%Cr-coated weldment exhibited superior hot corrosion resistance due to the development of Cr2O3 and NiCr2O4 protective oxide scales

The Effects of Close Companions (and Rotation) on the Magnetic Activity of M Dwarfs

We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf -- main sequence binaries from Rebassa et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space to construct a sample of 1756 WD+dM high-quality pairs from the SDSS DR8 spectroscopic database. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the H{\alpha} emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types \leqM7. Our results show that early-type M dwarfs (\leqM4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just past the onset of full convection in M dwarfs), the activity fraction and lifetimes of WD+dM binary systems becomes more comparable to that of the field M dwarfs. One of the implications of having a close binary companion is presumed to be increased stellar rotation through disk-disruption, tidal effects, or angular momentum exchange. Thus, we interpret the similarity in activity behavior between late-type dMs in WD+dM pairs and late-type field dMs to be due to a decrease in sensitivity in close binary companions (or stellar rotation), which has implications for the nature of magnetic activity in fully-convective stars. (Abridged)Comment: 21 pages, 19 figures, emulateapj style, accepted to Astronomical Journal June 28, 201

Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. IV. Discovery of an M9 + L6 BInary Separated by Over 100 AU

We report the discovery of a faint L6 \pm 1 companion to the previously known M9 dwarf, 2MASS J01303563-4445411, based on our near-infrared imaging and spectroscopic observations with the 3m Infrared Telescope Facility SpeX imager/spectrometer. The visual binary is separated by 3. 28 \pm 0. 05 on the sky at a spectrophotometric distance of 40 \pm 14 pc. The projected physical separation is 130 \pm 50 AU, making it one of the widest VLM field multiples containing a brown dwarf companion. 2MASS J0130-4445 is only one of ten wide VLM pairs and only one of six in the field. The secondary is considerably fainter ({\Delta}K ~ 2.35 mag) and redder ({\Delta} (J - Ks) ~ 0.81 dex), consistent with component near-infrared types of M9.0 \pm 0.5 and L6 \pm 1 based on our resolved spectroscopy. The component types suggest a secondary mass well within the hydrogen-burning limit and an age-dependent mass ratio of 0.6-0.9. The system's space motion and spectroscopic indicators suggest an age of 2-4 Gyr while the model-dependent masses and binding energies suggest that this system is unlikely to have formed via dynamical ejection. The age, composition, and separation of the 2MASS J01303563-4445411 system make it useful for tests of VLM formation theories and of condensate cloud formation in L dwarfs.Comment: Accepted by the AJ (8 pages, emulateapj format

Refined Metallicity Indices for M Dwarfs Using the SLoWPoKES Catalog of Wide, Low-mass Binaries

We report the results from spectroscopic observations of 113 ultra-wide, low-mass binary systems, composed largely of M0--M3 dwarfs, from the SLoWPoKES catalog of common proper motion pairs identified in the Sloan Digital Sky Survey. Radial velocities of each binary member were used to confirm that they are co-moving and, consequently, to further validate the high fidelity of the SLoWPoKES catalog. Ten stars appear to be spectroscopic binaries based on broad or split spectral features, supporting previous findings that wide binaries are likely to be hierarchical systems. We measured the H{\alpha} equivalent width of the stars in our sample and found that components of 81% of the observed pairs has similar H{\alpha} levels. The difference in H{\alpha} equivalent width amongst components with similar masses was smaller than the range of H{\alpha} variability for individual objects. We confirm that the Lepine et al. {\zeta}(CaH2+CaH3, TiO5) index traces iso-metallicity loci for most of our sample of M dwarfs. However, we find a small systematic bias in {\zeta}, especially in the early-type M dwarfs. We use our sample to recalibrate the definition of {\zeta}. While representing a small change in the definition, the new {\zeta} is a significantly better predictor of iso-metallicity for the higher mass M dwarfs.Comment: Accepted for publication in AJ, 10 page

Discovery of a Very Low Mass Triple with Late-M and T Dwarf Components: LP 704-48/SDSS J0006-0852AB

We report the identification of the M9 dwarf SDSS J000649.16-085246.3 as a spectral binary and radial velocity variable with components straddling the hydrogen burning mass limit. Low-resolution near-infrared spectroscopy reveals spectral features indicative of a T dwarf companion, and spectral template fitting yields component types of M8.5\pm0.5 and T5\pm1. High-resolution near-infrared spectroscopy with Keck/NIRSPEC reveals pronounced radial velocity variations with a semi-amplitude of 8.2\pm0.4 km/s. From these we determine an orbital period of 147.6\pm1.5 days and eccentricity of 0.10\pm0.07, making SDSS J0006-0852AB the third tightest very low mass binary known. This system is also found to have a common proper motion companion, the inactive M7 dwarf LP 704-48, at a projected separation of 820\pm120 AU. The lack of H-alpha emission in both M dwarf components indicates that this system is relatively old, as confirmed by evolutionary model analysis of the tight binary. LP 704-48/SDSS J0006-0852AB is the lowest-mass confirmed triple identified to date, and one of only seven candidate and confirmed triples with total masses below 0.3 Msun currently known. We show that current star and brown dwarf formation models cannot produce triple systems like LP 704-48/SDSS J0006-0852AB, and we rule out Kozai-Lidov perturbations and tidal circularization as a viable mechanism to shrink the inner orbit. The similarities between this system and the recently uncovered low-mass eclipsing triples NLTT 41135AB/41136 and LHS 6343ABC suggest that substellar tertiaries may be common in wide M dwarf pairs.Comment: 19 pages, 20 figures, accepted to Ap

Melioidosis of the Head and Neck: A Case Series from Eastern India

Melioidosis is an emerging entity in India. Though it is a potentially fatal disease, prognosis is excellent with early detection and appropriate management, especially of localized infections like abscesses of the head and neck area. We report nine cases of focal abscesses in the head and neck region due to Burkholderia pseudomallei, the causative agent of melioidosis, presenting to our hospital within a span of two-and-half years. Since melioidotic abscesses in the cervicofacial and head and neck region are likely to be confused with cold abscesses caused by Mycobacterium tuberculosis in a tuberculosis-endemic country like India, increased vigilance is necessary because of the widely divergent treatment modalities of the two disease entities