Graphene, a monolayer of graphite sheet consisting of sp2 hybridized carbon atoms covalently bonded to three other atoms (discovered in 2004), has recently attracted the attention of chemical sensor ...researchers owing to its unprecedented structural, mechanical and electrical properties. Excellent mechanical strength (Young modulus ∼0.05TPa), potentiality of ultrafast electron transport (highest mobility ∼200,000cm2/Vs) along with the best surface to volume ratio has opened up the opportunity to use the material for future gas and vapor sensors with ultra fast speed and long-term durability. Since it is a two dimensional material, every atom of graphene may be considered a surface atom and as a result every atom site may be involved in the gas interactions. This feature of graphene can eventually be responsible for its ultra sensitive sensor response with the lowest detection capability approaching even a single molecule. Further, the ease of functionalization of the material either by chemical means (absorption of many molecules like oxygen or hydrogen) or by application of voltage or pressure, facilitates bandgap-engineering which in turn may lead to a possible solution to the selectivity issues, the perennial problems of chemical sensors. In this review, the latest advancement and new perspectives of graphene based gas and vapor sensors have been discussed critically.
A digital assay is one in which the sample is partitioned into many small containers such that each partition contains a discrete number of biological entities (0, 1, 2, 3, …). A powerful technique ...in the biologist’s toolkit, digital assays bring a new level of precision in quantifying nucleic acids, measuring proteins and their enzymatic activity, and probing single-cell genotypes and phenotypes. Part I of this review begins with the benefits and Poisson statistics of partitioning, including sources of error. The remainder focuses on digital PCR (dPCR) for quantification of nucleic acids. We discuss five commercial instruments that partition samples into physically isolated chambers (cdPCR) or droplet emulsions (ddPCR). We compare the strengths of dPCR (absolute quantitation, precision, and ability to detect rare or mutant targets) with those of its predecessor, quantitative real-time PCR (dynamic range, larger sample volumes, and throughput). Lastly, we describe several promising applications of dPCR, including copy number variation, quantitation of circulating tumor DNA and viral load, RNA/miRNA quantitation with reverse transcription dPCR, and library preparation for next-generation sequencing. This review is intended to give a broad perspective to scientists interested in adopting digital assays into their workflows. Part II focuses on digital protein and cell assays.
デジタルアッセイとはサンプルを多数の微細なコンテナに分配し、各パーティションに個々の数（0、1、2、3…）の生物学的実体が含まれるようにする方法である。生物学者用ツールキットの有力な手段であるデジタルアッセイは、核酸の定量、種々のタンパク質とそれらの酵素活性の測定、および単細胞由来の遺伝子型と表現型の探索の精度を新たなレベルに引き上げる。本レビューのパート1では始めに、パーティショニングのベネフィットおよびエラーの発生源を含めたPoisson分布の統計処理について述べる。次に核酸を定量するデジタルPCR（dPCR）に注目する。サンプルを物理的に隔離されたチャンバー（cdPCR）またはエマルジョン化したドロップレット（ddPCR）内に分配する5種類の市販ツールについて述べる。dPCRの長所（絶対定量、高精度、希少ターゲットまたは変異ターゲットの検出力）を、従来のPCR、すなわちリアルタイム定量PCRの長所（ダイナミックレンジ、多サンプル量、およびハイスループット）と比較する。最後に、将来有望ないくつかのdPCRの応用について述べる、例えば、コピー数多型の解析、循環腫瘍DNAおよびウイルス負荷の定量、逆転写反応dPCRによるRNA/miRNAの定量、および次世代シーケンシングのためのライブラリの作成などである。本レビューの目的は、デジタルアッセイを自身のワークフローに採用することに関心のある科学者に、幅広い展望を示すことである。パート2ではタンパク質と細胞のデジタルアッセイに注目する。
数字测定表示将样本分别装入众多小容器中，以便每个分区包含不同数量的生物实体（0、1、2、3……）。作为生物学家工具包中一项功能出色的技术，数字测定可以全面提升核酸定量、蛋白质及其酶活性测量以及单细胞基因型和显性检测的精度。本文第一部分将介绍分区的优势和泊松统计，包括误差源。第二部分将关注用于定量核酸的数字PCR（dPCR）。我们将讨论5种用于将样本分割为物理隔离室（cdPCR）或滴乳液（ddPCR）的仪器，并就dPCR（绝对定量、精度、能够探测罕见或突变目标）与之前采用的实时定量PCR（动态范围、更大的采样量和更高的效率）的优劣进行比较。最后，我们将介绍dPCR的数种潜在应用，包括拷贝数变异、定量循环肿瘤DNA和病毒量、应用逆转录dPCR的RNA/miRNA定量以及制备库以用于新一代排序。本文旨在为有意引入数字测定的科学家提供全面的介绍。第二部分关注数字蛋白质和细胞测定。
数字测定表示将样本分别装入众多小容器中，以便每个分区包含不同数量的生物实体（0、1、2、3……）。作为生物学家工具包中一项功能出色的技术，数字测定可以全面提升核酸定量、蛋白质及其酶活性测量以及单细胞基因型和显性检测的精度。本文第一部分将介绍分区的优势和泊松统计，包括误差源。第二部分将关注用于定量核酸的数字PCR（dPCR）。我们将讨论5种用于将样本分割为物理隔离室（cdPCR）或滴乳液（ddPCR）的仪器，并就dPCR（绝对定量、精度、能够探测罕见或突变目标）与之前采用的实时定量PCR（动态范围、更大的采样量和更高的效率）的优劣进行比较。最后，我们将介绍dPCR的数种潜在应用，包括拷贝数变异、定量循环肿瘤DNA和病毒量、应用逆转录dPCR的RNA/miRNA定量以及制备库以用于新一代排序。本文旨在为有意引入数字测定的科学家提供全面的介绍。第二部分关注数字蛋白质和细胞测定。
Emerging assays in droplet microfluidics require the measurement of parameters such as drop size, velocity, trajectory, shape deformation, fluorescence intensity, and others. While micro particle ...image velocimetry (μPIV) and related techniques are suitable for measuring flow using tracer particles, no tool exists for tracking droplets at the granularity of a single entity. This paper presents droplet morphometry and velocimetry (DMV), a digital video processing software for time-resolved droplet analysis. Droplets are identified through a series of image processing steps which operate on transparent, translucent, fluorescent, or opaque droplets. The steps include background image generation, background subtraction, edge detection, small object removal, morphological close and fill, and shape discrimination. A frame correlation step then links droplets spanning multiple frames via a nearest neighbor search with user-defined matching criteria. Each step can be individually tuned for maximum compatibility. For each droplet found, DMV provides a time-history of 20 different parameters, including trajectory, velocity, area, dimensions, shape deformation, orientation, nearest neighbour spacing, and pixel statistics. The data can be reported via scatter plots, histograms, and tables at the granularity of individual droplets or by statistics accrued over the population. We present several case studies from industry and academic labs, including the measurement of 1) size distributions and flow perturbations in a drop generator, 2) size distributions and mixing rates in drop splitting/merging devices, 3) efficiency of single cell encapsulation devices, 4) position tracking in electrowetting operations, 5) chemical concentrations in a serial drop dilutor, 6) drop sorting efficiency of a tensiophoresis device, 7) plug length and orientation of nonspherical plugs in a serpentine channel, and 8) high throughput tracking of >250 drops in a reinjection system. Performance metrics show that highest accuracy and precision is obtained when the video resolution is >300 pixels per drop. Analysis time increases proportionally with video resolution. The current version of the software provides throughputs of 2-30 fps, suggesting the potential for real time analysis.
Neonatal sepsis: the gut connection Basu, S.
European journal of clinical microbiology & infectious diseases,
02/2015, Volume:
34, Issue:
2
Journal Article
Peer reviewed
Colonization of the neonatal gut takes place immediately after birth. Bacteria that get colonized are considered to be “normal” flora derived principally from the mother and the immediate ...environment. However, for some neonates, the colonization of the gut, particularly with potential pathogens, may lead to subsequent infections or sepsis. The immune system and the gut barrier in neonates is vulnerable, with decreased acid secretion, low levels of protective mucous, and decreased motility, particularly in those who are premature and of low birth weight. This makes the neonatal gut especially prone to colonization with aerobic Gram-negative bacilli (GNB). And these GNB may later, under circumstances favorable to them, cause disease in the neonates. In developing countries, it is the GNB that cause the majority of the infections. In addition, the use of antibiotics in the neonatal intensive care unit also triggers colonization with antibiotic-resistant bacteria. This review discusses various aspects of neonatal gut colonization, neonatal sepsis, and tries to gather support to understand the connection between the gut and subsequent sepsis in neonates.
Computational model of a proton exchange membrane (PEM) water electrolyzer is developed to enable investigation of the effect of operating conditions and electrolyzer components on its performance by ...expending less time and effort than experimental investigations. The work presents a dynamic model of a PEM electrolyzer system based on MATLAB/Simulink software. The model consists mainly of four blocks – anode, cathode, membrane and voltage. Mole balances on the anode and cathode blocks form the basis of the model along with Nernst and Butler–Volmer equations. The model calculates the cell voltage by taking into account the open circuit voltage and various over-potentials. The model developed predicted well the experimental data on PEM water electrolyzer available in the literature. The dynamic behavior of the electrolyzer system is analyzed and the effects of varying electrolyzer temperature and pressure on electrolyzer performance and over-potentials are presented.
► PEM water electrolyzer (PEMWE) modelled in Matlab/Simulink to capture the dynamic behaviour to some extent. ► Model predicts experimental data well on performance of PEMWE at different temperatures. ► Model results show operating temperature and pressure have opposite effects on performance. ► Operating temperature, pressure and performance of PEMWE have to be optimized for pressure require to store hydrogen. ► Ohmic overvoltage increases sharply with current density indicating improvement in performance possible by using low resistance electrolyte.
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•A comprehensive review of various direct ethanol fuel cells has been provided.•Bio-ethanol sources and production processes have been discussed in detail.•Fuel cells operating on ...bio-ethanol fuel offer economic and environmental advantages.•Materials, operating regimes, performance and life time issues are discussed.•The technology status and market applications have been detailed.
Fuel cells are one of the most efficient means of converting chemical energy into electrical energy. The major deterrents to the commercialisation of fuel cell technologies, especially for the transport sector, are the hydrogen storage and almost non-existence of hydrogen transportation and distribution infrastructure. The utilisation of bio-fuels such as methanol and ethanol instead of hydrogen as a fuel in fuel cells, not only reduces issues with fuel transportation and storage, but can also provide a CO2 neutral power generation technology and lead to a reduction in CO2 and other pollutants. In particular bioethanol is attractive as it is non-toxic, inexpensive, renewable and readily available. Currently around 90billionlitres per annum of ethanol is produced globally. It can be produced from a range of feedstock which includes sugar-cane, wheat, corn and low grade biomass such as woodchips, bagasse, waste from agro-industries, organic fractions from municipal waste or forestry residue. These factors make ethanol, especially when used with a low emission technology such as fuel cells, attractive from both an economic and environmental perspective. This has lead to a considerable interest in developing fuel cell systems operating directly on bioethanol. In this paper various types of direct ethanol fuel cells currently under development have been reviewed with emphasis on ethanol sources and production methods, cell construction materials, operating regime, cell and stack fabrication, performance and life time issues, technology status and market applications.
We perform axisymmetric resistive MHD calculations that demonstrate that centrifugal disks can indeed form around Class 0 objects despite magnetic braking. We follow the evolution of a prestellar ...core all the way to near-stellar densities and stellar radii. Under flux-freezing, the core is braked and disk formation is inhibited, while Ohmic dissipation renders magnetic braking ineffective within the first core. In agreement with observations that do not show evidence for large disks around Class 0 objects, the resultant disk forms in close proximity to the second core and has a radius of only ≈ 10 $R_{\odot}$ early on. Disk formation does not require enhanced resistivity. We speculate that the disks can grow to the sizes observed around Class II stars over time under the influence of both Ohmic dissipation and ambipolar diffusion, as well as internal angular momentum redistribution.
Currently, breast cancer is one of the most frequently diagnosed and the second leading cause of cancer related deaths in women worldwide. Our present study aimed to investigate the major mechanistic ...effects of micelles (TSD-30-F, TSD-34-F) on breast cancer cells as well as their antitumor efficacy in in vivo DL bearing BALB/c mice.
Apoptotic death by micelles was investigated by mitochondrial aggregation, membrane potential and DNA fragmentation assay in MCF-7 and MDA-MB-231 cells. Molecular mode of action of micelles were determined by RT-PCR and western blot analysis, drug-ligand interaction was analyzed by in silico methods, while, in vivo antitumor activity was investigated by Kaplen-Meier survival curve, T/C value, body weight and belly size of BALB/c mice.
TSD-30-F and TSD-34-F micelles displayed significant apoptotic induction. At molecular level, TSD-30 and TSD-34 micelles showed up-regulation of p53, Bax, Bak, Caspase-3 and down-regulation of Bcl-2 genes as well as proteins in tested breast cancer cells. In silico analysis revealed that TSD-30 and TSD-34 showed efficient binding affinity with p53, Caspase-3, Bax and Bcl-2 proteins. Significant in vivo antitumor efficacy was exhibited by the micelles formulations by increasing life span with reduced bodyweight and belly size growth pattern in BALB/c mice compared to DTX-F micelles.
Our results suggest that triphenyltin (IV) micelles could be a very promising therapeutic candidate for treatment of breast cancer patients and occupy a new place in targeted breast cancer therapeutic.
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•Triphenyltin (IV) micelles induced mitochondrial mediated apoptosis in breast cancer.•Micelles induced apoptosis by p53 upregulation, and down regulation of Bcl-2.•Micelles enhanced antitumor efficacy in DL bearing BALB/c mice than DTX-F micelles.
Context. The Kepler space mission has made it possible to measure the rotational splittings of mixed modes in red giants, thereby providing an unprecedented opportunity to probe the internal rotation ...of these stars. Aims. Asymmetries have been detected in the rotational multiplets of several red giants. This is unexpected since all the red giants whose rotation profiles have been measured thus far are found to rotate slowly, and low rotation, in principle, produces symmetrical multiplets. Our aim here is to explain these asymmetries and find a way of exploiting them to probe the internal rotation of red giants. Methods. We show that in the cases where asymmetrical multiplets were detected, near-degeneracy effects are expected to occur, because of the combined effects of rotation and mode mixing. Such effects have not been taken into account so far. By using both perturbative and non-perturbative approaches, we show that near-degeneracy effects produce multiplet asymmetries that are very similar to the observations. We then propose and validate a method based on the perturbative approach to probe the internal rotation of red giants using multiplet asymmetries. Results. We successfully apply our method to the asymmetrical l = 2 multiplets of the Kepler young red giant KIC 7341231 and obtain precise estimates of its mean rotation in the core and the envelope. The observed asymmetries are reproduced with a good statistical agreement, which confirms that near-degeneracy effects are very likely the cause of the detected multiplet asymmetries. Conclusions. We expect near-degeneracy effects to be important for l = 2 mixed modes all along the red giant branch (RGB). For l = 1 modes, these effects can be neglected only at the base of the RGB. They must therefore be taken into account when interpreting rotational splittings and as shown here, they can bring valuable information about the internal rotation of red giants.
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