Reduced susceptibility to quinolones among Salmonella serotypes isolated from poultry at slaughter in Venezuela

Today there are recognized global "hot spots" that are areas in which nontyphoid Salmonella serotypes have been reported to have a high prevalence of quinolone resistance. There is concern that resistant strains can be disseminated from these localized geographical areas by travelers or via commercial food products. The objective of this article is to report a high frequency of reduced susceptibility to first- and second-generation quinolones among nontyphoid Salmonella isolates from poultry at slaughter in two processing plants belonging to the largest poultry integration companies in Zulia State, Venezuela. Nearly all (74 of 77; 96.1%) of the isolated strains were resistant to nalidixic acid, and 3.7% were resistant to ciprofloxacin; most (45 of 77; 58%) exhibited reduced susceptibility to ciprofloxacin and norfloxacin (15 of 77; 19.5%). In contrast, all of the isolates were susceptible to beta-lactamic antimicrobial drugs. Ninety-three percent (72 of 77) of the isolates were either Salmonella Parathyphi B or Salmonella Heidelberg, which have been reported as invasive Salmonella. The predominant serotypes in each slaughter plant showed different antimicrobial susceptibilities, only having in common their high resistance to nalidixic acid, suggesting that different clones disseminated in each commercial integration. The detection of high frequency of reduced susceptibility to first- and second-generation quinolones among nontyphoid Salmonella isolates from fresh poultry during processing is noteworthy. Resistance to quinolone drugs will not only make antimicrobial therapy more complicated if foodborne disease results, but also these quinolone-resistant strains can disseminate from this local hot spot to other geographical areas, spreading the resistance against this important antimicrobial drug.     

Relationships between volatile composition and sensory evaluation in eight varieties of netted muskmelon (Cucumis melo L var reticulatus Naud)

The quality parameter of muskmelon (Cucumis melo L var reticulatus Naud) is often identified with the sugar content, particularly sucrose. However, high soluble solids concentration at harvest does not always correspond with high overall fruit quality and should be used in conjunction with the evaluation of aroma. In order to find quality indices, correlations were checked between aroma compounds detected on the melon pulp by headspace gas chromatography and sensory evaluation. Eight cultivars of muskmelon were analysed for their aroma content and other quality parameters. Aroma compounds were mainly esters, while (Z)‐6‐nonenal and (E)‐6‐nonenol, characteristic of melon, were not detected with the technique used. The data were subjected to statistical analyses in order to find significant correlations. High values of correlation were not found between chromatographic and sensory data, but a high correlation was found between total aromas and ethyl esters, both data of analytical source. This fact means that ethyl esters could be very important compounds for melon flavour and could be considered as markers of a good‐quality aroma. © 2002 Society of Chemical Industry     

微通道内液滴/气泡破裂动力学分析

微化学工程与技术是现代化学工程学科的前沿领域。微通道内液滴及气泡破裂动力学是决定多相过程并行微通道数目放大的基础与难点。破裂流型转换条件、界面动力学和尺寸调控等三方面是微通道内液滴与气泡破裂动力学的主要研究对象。讨论了对称微通道、非对称微通道、多级微通道、旁路微通道、含有障碍物的微通道内气泡和液滴破裂行为及影响因素,指出了目前微尺度下气泡与液滴破裂行为相关研究工作存在的不足,并对该领域未来的发展进行了展望。     

Synthesis of Four Steroidal Carbamates with Antitumor Activity against Mouse Colon Carcinoma CT26WT Cells: In Vitro and In Silico Evidence

Colorectal cancer (CRC) is one of the most lethal cancers worldwide. If detected on time, surgery can expand life expectations of patients up to five more years. However, if metastasis has grown deliberately, the use of chemotherapy can play a crucial role in CRC control. Moreover, the lack of selectivity of current anticancer drugs, plus mutations that occur in cancerous cells, demands the development of new chemotherapeutic agents. Several steroids have shown their potentiality as anticancer agents, while some other compounds, such as Taxol and its derivatives bearing a carbamate functionality, have reached the market. In this article, the synthesis, characterization, and antiproliferative activity of four steroidal carbamates on mouse colon carcinoma CT26WT cells are described. Carbamate synthesis occurred via direct reaction between diosgenin, its B-ring modified derivative, and testosterone with phenyl isocyanate under a Brønsted acid catalysis. All obtained compounds were characterized by ¹H and ¹³C Nuclear Magnetic Resonance (NMR), High Resolution Mass Spectroscopy (HRMS); their melting points are also reported. Results obtained from antiproliferative activity assays indicated that carbamates compounds have inhibitory effects on the growth of this colon cancer cell line. A molecular docking study carried out on Human Prostaglandin E Receptor (EP4) showed a high affinity between carbamates and protein, thus providing a valuable theoretical explanation of the in vitro results.     

Brain Proteome and Behavioural Analysis in Wild Type,BDNF+/− and BDNF−/− Adult Zebrafish (Danio rerio) Exposed to Two Different Temperatures

Experimental evidence suggests that environmental stress conditions can alter the expression of BDNF and that the expression of this neurotrophin influences behavioural responses in mammalian models. It has been recently demonstrated that exposure to 34 °C for 21 days alters the brain proteome and behaviour in zebrafish. The aim of this work was to investigate the role of BDNF in the nervous system of adult zebrafish under control and heat treatment conditions. For this purpose, zebrafish from three different genotypes (wild type, heterozygous BDNF^+/− and knock out BDNF^−/−) were kept for 21 days at 26 °C or 34 °C and then euthanized for brain molecular analyses or subjected to behavioural tests (Y-maze test, novel tank test, light and dark test, social preference test, mirror biting test) for assessing behavioural aspects such as boldness, anxiety, social preference, aggressive behaviour, interest for the novel environment and exploration. qRT-PCR analysis showed the reduction of gene expression of BDNF and its receptors after heat treatment in wild type zebrafish. Moreover, proteomic analysis and behavioural tests showed genotype- and temperature-dependent effects on brain proteome and behavioural responding. Overall, the absent expression of BDNF in KO alters (1) the brain proteome by reducing the expression of proteins involved in synapse functioning and neurotransmitter-mediated transduction; (2) the behaviour, which can be interpreted as bolder and less anxious and (3) the cellular and behavioural response to thermal treatment.     

Study of validity of the single-diode model for solar cells by I–V curves parameters extraction using a simple numerical method

The I–V measurement of solar cells is one of the most employed electrical characterization techniques in the photovoltaics research field due to the valuable information one can obtain from such a curve. Parameters like Voc, Isc and the maximum power can be easily observed at a glance. Furthermore, additional information can be extracted by a more exhaustive analysis involving the equivalent electrical circuit of a solar cell which is based on ideal electrical components with a well-defined behavior. This equivalent circuit is typically assumed to be formed by a current source in parallel with a single diode and a shunt resistor, connected to a series resistor. However, this model does not take into account the separate contributions of the different carrier transport mechanisms in solar cells; for example, carrier diffusion and recombination-generation in the depletion region. Therefore, the single diode model may not be suitable in many practical cases. In this work, a simple numerical method was developed to extract the parameters for both single diode and double diode models from experimental I–V curves of solar cells. The developed numerical algorithm was applied to extract the parameters for a published benchmark solar cell which has been used for testing this kind of algorithms. The extracted parameters using our simple method are comparable with other more sophisticated and computer power demanding algorithms. Thereafter, we applied the developed algorithm to extract the single-diode parameters from simulated “experimental” I–V curves, where two carrier transport mechanisms are present, trying to understand under what conditions the single diode approximation would provide meaningful parameters for such experimental curves. It is shown that the extracted parameters can vary strongly, particularly for the dark saturation current and ideality factor, without much variation of the root mean square error between the experimental data and the model, causing these values to be unreliable and its physical interpretation misleading. We show that the same algorithm can be applied to a double diode (two exponentials) model providing physically meaningful parameters without much computing power requirements. In summary, there is no further justification for using a single diode model to interpret the experimental I–V curves of real solar cells.     

A sequential augmentation method to eliminate multicollinearity

This article presents a new augmentation method to eliminate multicollinearity in observational datasets that contain several correlated variables. The purpose is to eliminate the correlations to facilitate the application of the least squares regression method. The procedure is based on the addition of new observations to the point in which an appropriate linear regression model can be constructed. Original data can be observational but the new information is obtained through designed experiments. The proposed method uses the R3 algorithm to perform the augmentations and the VIF statistic to determine the point in which the correlations have been significantly reduced.