610 research outputs found

    Homeostatic Plasticity and STDP: Keeping a Neuron's Cool in a Fluctuating World

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    Spike-timing-dependent plasticity (STDP) offers a powerful means of forming and modifying neural circuits. Experimental and theoretical studies have demonstrated its potential usefulness for functions as varied as cortical map development, sharpening of sensory receptive fields, working memory, and associative learning. Even so, it is unlikely that STDP works alone. Unless changes in synaptic strength are coordinated across multiple synapses and with other neuronal properties, it is difficult to maintain the stability and functionality of neural circuits. Moreover, there are certain features of early postnatal development (e.g., rapid changes in sensory input) that threaten neural circuit stability in ways that STDP may not be well placed to counter. These considerations have led researchers to investigate additional types of plasticity, complementary to STDP, that may serve to constrain synaptic weights and/or neuronal firing. These are collectively known as “homeostatic plasticity” and include schemes that control the total synaptic strength of a neuron, that modulate its intrinsic excitability as a function of average activity, or that make the ability of synapses to undergo Hebbian modification depend upon their history of use. In this article, we will review the experimental evidence for homeostatic forms of plasticity and consider how they might interact with STDP during development, and learning and memory

    Identification of Ajnala skeletal remains using multiple forensic anthropological methods and techniques: a bioarchaeological report.

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    Fragmented and badly damaged commingled human remains present a tough challenge for their identification pursuits in forensic anthropology. Thousands of unknown human remains along with items of contextual identity, reportedly belonging to 282 Indian sepoys killed in 1857, were exhumed non-scientifically from a disused ancient well at Ajnala (Amritsar, India). In this manuscript, the non-scientific excavation of unknown human remains from the abandoned well, their forensic anthropological strategies for identification purposes, challenges being faced and future possibilities of their biological profiling have been discussed. Multiple methods and techniques like anthropological examinations, odontological profiling, radiological analyses, stable isotope and mitochondrial DNA (mtDNA) analyses were applied to few bones and teeth collected from the Ajnala skeletal assemblage. Though majority of studied bones and teeth were found belonging to adult males, very few of them had morphological, osteological and molecular features questioning the authenticity and validity of the written records. Due to certain ambiguous findings or gaps observed between the anthropological analyses of the Ajnala skeletal remains and the reported versions about their affiliations; certain advanced radiological, chemical and molecular techniques were applied to estimate their probable age, sex and populational affinity. The obtained radiological, isotopic and molecular signatures of the remains were compared with the available databases to estimate their affinity with the individuals of geographic area to whom the remains reportedly belonged to. The maternally inherited mtDNA haplogroup assignments, and stable isotope analysis of carbon and oxygen suggested that the studied human remains belonged to the individuals from West Bengal, Bihar, Odisha, Awadh (presently in Uttar Pradesh) and parts of Meghalaya and Manipur as potential regions of their geographic identity and thus, attributing the victims to be non-local to the site. However, merely on the basis of forensic anthropological examinations of very few bones and teeth (collected out of a huge collection of thousands of bones and teeth); it would be just an unqualified and sweeping conclusion to claim their identity as adult or non-adult, male or female, local or non-local, victims of 1857 mass killings or to the victims of ceremonial sacrifices or criminal activities committed in the past. A sufficient number of bones and teeth along with items of personal identity needs to be examined with multiple scientific techniques to arrive at some valid conclusions about their biological identity

    A NOVEL APPROACH TOWARDS DEVELOPMENT OF QUINAZOLINE DERIVATIVES IN PAIN MANAGEMENT

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    ABSTRACT-   Objective: To synthesis evaluation of the analgesic and anti-inflammatory activities of pyrazoline bearing 4(3H)-quinazolinone derivatives. Methods: Synthesis of Chalcone (3a-3j) involves the Claisen-Schmidt condensation of equimolar quantities of substituted acetophenone with aromatic aldehyde in the presence of aqueous alkali (10%). Comp. (3a-3j) undergoes cyloaddition reaction with semicarbazide HCl in the presence of suitable solvent to yield comp. (4a-4j). It undergoes addition cyclization reaction with anthranillic acid to yield final comp. (6a-6j). Acute toxicity study of synthesized compound was found according to OECD guidelines 423. The test compound do not showed any toxicity up to 200mg/kg dose. Mortality was not observed during the course of study. The analgesic and anti-inflammatory activity of all synthesized compounds were carried by using hot plate method and Carrageenan induced Rat Paw Edema Method respectively. Results: All compounds synthesized are obtained in crystalline form with good practical yield. The purity and homogeneity of compounds synthesized were determined by sharp melting points and TLC method. The chemical structures were confirmed by FTIR, 1HNMR, and Mass spectrum. Conclusion: The synthesized compound 6b, 6d, 6e, 6i and 6j showed good analgesic and anti-inflammatory activities whereas others showed significant activities. Keywords: Quinazoline, pyrazole, analgesic and anti-inflammatory activity

    Spatially Resolved Galaxy Star Formation and its Environmental Dependence I

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    We use the photometric information contained in individual pixels of 44,964 (0.019<z<0.125 and -23.5<M_r<-20.5) galaxies in the Fourth Data Release (DR4) of the Sloan Digital Sky Survey to investigate the effects of environment on galaxy star formation (SF). We use the pixel-z technique, which combines stellar population synthesis models with photometric redshift template fitting on the scale of individual pixels in galaxy images. Spectral energy distributions are constructed, sampling a wide range of properties such as age, star formation rate (SFR), dust obscuration and metallicity. By summing the SFRs in the pixels, we demonstrate that the distribution of total galaxy SFR shifts to lower values as the local density of surrounding galaxies increases, as found in other studies. The effect is most prominent in the galaxies with the highest star formation, and we see the break in the SFR-density relation at a local galaxy density of 0.05\approx 0.05 (Mpc/h)3^{-3}. Since our method allows us to spatially resolve the SF distribution within galaxies, we can calculate the mean SFR of each galaxy as a function of radius. We find that on average the mean SFR is dominated by SF in the central regions of galaxies, and that the trend for suppression of SFR in high density environments is driven by a reduction in this nuclear SF. We also find that the mean SFR in the outskirts is largely independent of environmental effects. This trend in the mean SFR is shared by galaxies which are highly star forming, while those which are weakly star forming show no statistically significant correlation between their environment and the mean SFR at any radius.Comment: 37 pages, 11 figures. Referee's comments included and matches version accepted for publication in the Astrophysical Journal. For high resolution figures, see http://www.phyast.pitt.edu/~welikala/pixelz/paper1

    Constraint-based Wavevector- and Frequency-dependent Exchange-Correlation Kernel of the Uniform Electron Gas

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    According to time-dependent density functional theory, the exact exchange-correlation kernel fxc_{xc}(n, q, ω\omega) determines not only the ground-state energy but also the excited-state energies/lifetimes and time-dependent linear density response of an electron gas of uniform density n == 3/(4π\pirs3^3_s). Here we propose a parametrization of this function based upon the satisfaction of exact constraints. For the static (ω\omega = 0) limit, we modify the model of Constantin and Pitarke at small wavevector q to recover the known second-order gradient expansion, plus other changes. For all frequencies ω\omega at q == 0, we use the model of Gross, Kohn, and Iwamoto. A Cauchy integral extends this model to complex ω\omega and implies the standard Kramers-Kronig relations. A scaling relation permits closed forms for not only the imaginary but also the real part of fxc_{xc} for real ω\omega. We then combine these ingredients by damping out the ω\omega dependence at large q in the same way that the q dependence is damped. Away from q == 0 and ω\omega == 0, the correlation contribution to the kernel becomes dominant over exchange, even at rs_s == 4, the valence electron density of metallic sodium. The resulting correlation energy from integration over imaginary ω\omega is essentially exact. The plasmon pole of the density response function is found by analytic continuation of fxc_{xc} to ω\omega just below the real axis, and the resulting plasmon lifetime first decreases from infinity and then increases as q grows from 0 toward the electron-hole continuum. A static charge-density wave is found for rs_s >> 69, and shown to be associated with softening of the plasmon mode. The exchange-only version of our static kernel confirms Overhauser's 1968 prediction that correlation enhances the charge-density wave.Comment: 20 pages including 11 figure

    Pixel-z: Studying Substructure and Stellar Populations in Galaxies out to z~3 using Pixel Colors I. Systematics

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    We perform a pixel-by-pixel analysis of 467 galaxies in the GOODS-VIMOS survey to study systematic effects in extracting properties of stellar populations (age, dust, metallicity and SFR) from pixel colors using the pixel-z method. The systematics studied include the effect of the input stellar population synthesis model, passband limitations and differences between individual SED fits to pixels and global SED-fitting to a galaxy's colors. We find that with optical-only colors, the systematic errors due to differences among the models are well constrained. The largest impact on the age and SFR e-folding time estimates in the pixels arises from differences between the Maraston models and the Bruzual&Charlot models, when optical colors are used. This results in systematic differences larger than the 2{\sigma} uncertainties in over 10 percent of all pixels in the galaxy sample. The effect of restricting the available passbands is more severe. In 26 percent of pixels in the full sample, passband limitations result in systematic biases in the age estimates which are larger than the 2{\sigma} uncertainties. Systematic effects from model differences are reexamined using Near-IR colors for a subsample of 46 galaxies in the GOODS-NICMOS survey. For z > 1, the observed optical/NIR colors span the rest frame UV-optical SED, and the use of different models does not significantly bias the estimates of the stellar population parameters compared to using optical-only colors. We then illustrate how pixel-z can be applied robustly to make detailed studies of substructure in high redshift galaxies such as (a) radial gradients of age, SFR, sSFR and dust and (b) the distribution of these properties within subcomponents such as spiral arms and clumps. Finally, we show preliminary results from the CANDELS survey illustrating how the new HST/WFC3 data can be exploited to probe substructure in z~1-3 galaxies.Comment: 37 pages, 21 figures, submitted to Ap

    Evolutionary fine-tuning of conformational ensembles in FimH during host-pathogen interactions

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    Positive selection in the two-domain type 1 pilus adhesin FimH enhances Escherichia coli fitness in urinary tract infection (UTI). We report a comprehensive atomic-level view of FimH in two-state conformational ensembles in solution, composed of one low-affinity tense (T) and multiple high-affinity relaxed (R) conformations. Positively selected residues allosterically modulate the equilibrium between these two conformational states, each of which engages mannose through distinct binding orientations. A FimH variant that only adopts the R state is severely attenuated early in a mouse model of uncomplicated UTI but is proficient at colonizing catheterized bladders in vivo or bladder transitional-like epithelial cells in vitro. Thus, the bladder habitat has barrier(s) to R state–mediated colonization possibly conferred by the terminally differentiated bladder epithelium and/or decoy receptors in urine. Together, our studies reveal the conformational landscape in solution, binding mechanisms, and adhesive strength of an allosteric two-domain adhesin that evolved “moderate” affinity to optimize persistence in the bladder during UTI
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