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One-step synthesis of hydrophilic functionalized and cytocompatible superparamagnetic iron oxide nanoparticles (SPIONs) based aqueous ferrofluids for biomedical applications
No full textThis work systematically describes one-step synthesis of hydrophilic functionalized superparamagnetic iron oxide nanoparticies (SPIONs) via thermolysis in presence of polyamines such as diethylene triamine (DETA), triethylene tetraamine (TETA), tetraethylene pentamine (TTEPA), or pentaethylene hexamine (PEHA) or mixture of a polyamine (TETA) and polyols such as diethylene glycol (DEG), triethylene glycol (TEG) or tetraethylene glycol (TTEG) while varying the polyamine: polyol (v/v) ratio, reaction temperature and reaction time, The saturation magnetization (Ms) values of the as-prepared polyamine (DETA/TETA/TTEPA/PEHA) coated SPIONs are determined in the range of 31.8-48.5 emu/g, which is altered in the range of 40.2-57.8 emu/g by the addition of a polyol (DEG/TEG/TTEG) to the polyamine (TETA) at different ratios. Moreover, the Ms. values are further improved to 64.6 and 66.8 emu/g at the optimized TETA:TEG (1:1) ratio by prolonging the reaction time up-to 2 h and the reaction temperature to 270 degrees C, respectively. In addition, the TETA-TEG coated SPIONs have displayed their average particle sizes, hydrodynamic sizes, and zeta potential (zeta) values in the range of 7-11 nm, 99-120 nm and +45 to +57 mV, respectively (indicating high water solubility). Finally, the TETA-TEG coated SPIONs with the highest Ms. and zeta values (i.e. 66.8 emu/g and +57 my) are selected for the biological studies, where they have revealed excellent (i) cytocompatibility, and (ii) intracellular uptake in the cancer (HepG2 liver & MCF-7 breast) cells for the incubation periods of 24/48 h. Thus, the TETA-TEG coated SPIONs based aqueous ferrofluids have a great potential to be used in biomedical applications. (C) 2018 Elsevier B.V. All rights reserved
Partially-disordered to frozen-state crossover induced magnetocaloric properties of the antiferromagnetic one-dimensional spin-chain Sr(3)ColrO(6)
No full textLow-dimensional and geometrically frustrated spin-chain Sr-3(Co/Ni)IrO6 compounds exhibit interesting physical phenomena due to the exotic anisotropy associated with the spin-orbit entangled Ir4+ state. Temperature dependent magnetic susceptibility of polycrystalline Sr3CoIrO6 characterizes the partially-disordered antiferromagnetic with T-N1 similar to 90 K and the frozen state of this antiferromagnetic order below T-N2 similar to 30 K. The fitting of chi T versus T (K) data to the Ising model reveal that the intra-chain exchange interactions are ferromagnetic, whereas the inter-chain exchange correlations are antiferromagnetic. Field-induced alteration of the partially-disordered antiferromagnetic state in the temperature regime of T-N1 <= T <= T-N2 is responsible for the anomalous magnetic hysteresis loop. Further, a large value of isothermal magnetic-entropy change (Delta S-M similar to 22 J kg(-1)K(-1) for 7 T), absence of thermal hysteresis in magnetization and highly insulating nature consents Sr3CoIrO6 to be classified as a good magnetocaloric material for the low-temperature refrigeration
Enhanced sensor life using UV treatment of sulphur poisoned Pt-PtOx
No full textIn this work,we report a novel method for recovery of sulphur poisoned platinum/platinum oxide (Pt-PtOx) core shell nanowire sensor using UV irradiation. The optimum core to shell thickness ratio and the operating conditions are the key factors to achieve a high-performance H2S sensor,described in this report. The fabricated core shell nanowire sensor demonstrated response of 6.4% at 1 ppm H2S with detection limit of 10 ppb at 150 degrees C operating temperature. The sensor undergoes prominent time-dependent poisoning at H2S exposure of 3 ppm when operated at 150 degrees C due to sensor surface contamination by sulphur,later confirmed by XPS analysis. Ultraviolet light at two wavelengths, 365 nm, and 248 nm is investigated to recover the poisoned Pt-PtOx surface. UV irradiation at 248 nm for 5 min results in sensor recovery, confirmed by further H2S sensing characterization and XPS studies on the recovered sensor. To the best of our knowledge, this is one of the first reports on UV irradiation for recovery of sulphur poisoned metal-oxide surfaces
A Systematic Approach to Incremental Redundancy With Application to Erasure Channels
No full textThis paper focuses on the design and evaluation of pragmatic schemes for delay-sensitive communication. Specifically, this contribution studies the operation of data links that employ incremental redundancy as a means to shield information bits from the degradation associated with unreliable channels. While this inquiry puts forth a general methodology, exposition centers around erasure channels because they are well suited for analysis. Nevertheless, the goal is to identify both structural properties and design guidelines that are broadly applicable. Conceptually, this paper leverages a methodology, termed sequential differential optimization, aimed at identifying near-optimal block sizes for hybrid ARQ. This technique is applied to erasure channels and it is extended to scenarios where throughput is maximized subject to a constraint on the feedback rate. The analysis shows that the impact of the coding strategy adopted and the propensity of the channel to erase symbols naturally decouple when maximizing throughput. Ultimately, block size selection is informed by approximate distributions on the probability of decoding success at every stage of the incremental transmission process. This novel perspective, which rigorously bridges hybrid automatic repeat request and coding, offers a computationally efficient framework to select code rates and blocklengths for incremental redundancy. These findings are supported through numerical results
Low-loss 7-bit S-band CMOS passive phase shifter with digital control
No full textThis paper presents the design and implementation of a 7-bit S-band digital passive phase shifter using Complementary Metal-Oxide-Semiconductor (CMOS) 65-nm technology in 2.6- to 3.2-GHz frequency band. New switched delay network topology has been used for 5.625 degrees and 2.8 degrees, and modified switched filter topology has been used for implementation of other phase bits to achieve 7-bit performance with low insertion loss and better isolation. The measured results of the fabricated chip show 7-bit performance with an average insertion loss of 11 dB, average root mean square (RMS) phase error of less than 2.0 degrees, average RMS amplitude error of less than 0.6 dB, input matching (S-11) better than -7.5 dB, and output matching (S-22) better than -14.5 dB across the target frequency band at 50 omega input/output impedance
Tuning the Stability of DNA Nanotubes with Salt
No full textWe report the enhancement of the structural stability of a DNA nanotube (DNT) by changing the salt concentrations for three different salt species, namely, NaCl, KCl, and MgCl2. Using fully atomistic molecular dynamics simulations, we find that, with the gradual increment in the NaCl salt concentration, the DNT becomes compact and rigid. The significant reduction in the average root-mean-square deviation, root-mean-square fluctuation, and effective radius of the DNT with an increase in the NaCl concentration quantifies our observation. We explain how the DNT-ion interactions play a vital role in the conformational fluctuation of the DNT. To understand the salt dependence of the mechanical properties of the DNTs, we have calculated the stretch modulus (gamma) and persistence length (L-P) as a function of salt concentration. The calculated stretch moduli of the DNTs change from 8.3 to 13 nN, and the persistence length of the DNT varies from 6 to 10 mu m when the NaCl salt concentration is varied from 0 to 1 M. Both the stretch modulus and the persistence length calculations reaffirm the structural stability of the DNT at higher salt concentrations. We find similar trends for another monovalent salt (KCl). However, for a divalent salt (MgCl2), we find minimal variation in the structural properties with an increase in the salt concentration
Risk sensitive control of pure jump processes on a general state space
No full textWe study stochastic control problem for pure jump processes on a general state space with risk sensitive discounted and ergodic cost criteria. For the discounted cost criterion we prove the existence and Hamilton-Jacobi-Bellman characterization of optimal a-discounted control for bounded cost function. For the ergodic cost criterion we assume a Lyapunov type stability assumption and a small cost condition. Under these assumptions we show the existence of the optimal risk-sensitive ergodic control
Protein model discrimination attempts using mutational sensitivity, predicted secondary structure, and model quality information
No full textStructure prediction methods often generate a large number of models for a target sequence. Even if the correct fold for the target sequence is sampled in this dataset, it is difficult to distinguish it from other decoy structures. An attempt to solve this problem using experimental mutational sensitivity data for the CcdB protein was described previously by exploiting the correlation of residue depth with mutational sensitivity (r similar to 0.6). We now show that such a correlation extends to four other proteins with localized active sites, and for which saturation mutagenesis datasets exist. We also examine whether incorporation of predicted secondary structure information and the DOPE model quality assessment score, in addition to mutational sensitivity, improves the accuracy of model discrimination using a decoy dataset of 163 targets from CASP. Although most CASP models would have been subjected to model quality assessment prior to submission, we find that the DOPE score makes a substantial contribution to the observed improvement. We therefore also applied the approach to CcdB and four other proteins for which reliable experimental mutational data exist and observe that inclusion of experimental mutational data results in a small qualitative improvement in model discrimination relative to that seen with just the DOPE score. This is largely because of our limited ability to quantitatively predict effects of point mutations on in vivo protein activity. Further improvements in the methodology are required to facilitate improved utilization of single mutant data
Disparate forms of heterogeneities and interactions among them drive channel decorrelation in the dentate gyrus: Degeneracy and dominance
No full textThe ability of a neuronal population to effectuate channel decorrelation, which is one form of response decorrelation, has been identified as an essential prelude to efficient neural encoding. To what extent are diverse forms of local and afferent heterogeneities essential in accomplishing channel decorrelation in the dentate gyrus (DG)? Here, we incrementally incorporated four distinct forms of biological heterogeneities into conductance-based network models of the DG and systematically delineate their relative contributions to channel decorrelation. First, to effectively incorporate intrinsic heterogeneities, we built physiologically validated heterogeneous populations of granule (GC) and basket cells (BC) through independent stochastic search algorithms spanning exhaustive parametric spaces. These stochastic search algorithms, which were independently constrained by experimentally determined ion channels and by neurophysiological signatures, revealed cellular-scale degeneracy in the DG. Specifically, in GC and BC populations, disparate parametric combinations yielded similar physiological signatures, with underlying parameters exhibiting significant variability and weak pair-wise correlations. Second, we introduced synaptic heterogeneities through randomization of local synaptic strengths. Third, in including adult neurogenesis, we subjected the valid model populations to randomized structural plasticity and matched neuronal excitability to electrophysiological data. We assessed networks comprising different combinations of these three local heterogeneities with identical or heterogeneous afferent inputs from the entorhinal cortex. We found that the three forms of local heterogeneities were independently and synergistically capable of mediating significant channel decorrelation when the network was driven by identical afferent inputs. However, when we incorporated afferent heterogeneities into the network to account for the divergence in DG afferent connectivity, the impact of all three forms of local heterogeneities was significantly suppressed by the dominant role of afferent heterogeneities in mediating channel decorrelation. Our results unveil a unique convergence of cellular- and network-scale degeneracy in the emergence of channel decorrelation in the DG, whereby disparate forms of local and afferent heterogeneities could synergistically drive input discriminability
Late Reverberation Cancellation Using Bayesian Estimation of Multi-Channel Linear Predictors and Student's t-Source Prior
No full textMulti-channel linear prediction (MCLP) can model the late reverberation in the short-time Fourier transform domain using a delayed linear predictor and the prediction residual is taken as the desired early reflection component. Traditionally, a Gaussian source model with time-dependent precision (inverse of variance) is considered for the desired signal. In this paper, we propose a Student's t-distribution model for the desired signal, which is realized as a Gaussian source with a Gamma distributed precision. Further, since the choice of a proper MCLP order is critical, we also incorporate a Gaussian distribution prior for the prediction coefficients and a higher order. We consider a batch estimation scenario and develop variational Bayes expectation maximization (VBEM) algorithm for joint posterior inference and hyper-parameter estimation. This has lead to more accurate and robust estimation of the late reverb component and hence its cancellation, benefitting the desired residual signal estimation. Along with these stochastic models, we formulate single channel output (MISO) and multi channel output (MIMO) schemes using shared priors for the desired signal precision and the estimated MCLP coefficients at each microphone. Experiments using real room impulse responses show improved late reverberation suppression with the proposed VBEM approach over the traditional methods, for different room conditions. Additionally, we achieve a sparse coefficient vector for the MCLP avoiding the criticality of manually choosing the model order. The MIMO formulation is easily extended to include spatial filtering of the enhanced signals, which further improves the estimation of the desired signal