Comparison And Optimization Of Three Types Of Refrigeration System Under Different Operating Conditions

As well known, the performance of the compressor is concerned with the corresponding refrigeration system. In this paper, by comparing three types of refrigeration cycle, an optimized range of the intermediate pressure for gaining better coefficient of performance (COP) is proposed. Additionally, the effect of the cycle on the construction of the compressor and performances under different refrigerants are discussed. The simulation result indicates that the coefficient of intermediate pressure under freezing condition and refrigeration condition ranges from 0.81 to 0.91 and 0.93 to 0.97, respectively. The results obtained here may provide some guides for the optimal design and operation of practical refrigeration system

General Trinajstić Index

In memory of the outstanding theoretical chemist Nenad Trinajstić, Furtula introduced a new distance-based molecular structure descriptor "Trinajstić index" in chemical graph theory. In this paper, we propose the general Trinajstić index, and give the calculation formula of the general Trinajstić index for double-star graphs, double brooms, Kragujevac trees, firefly graphs and wheel graphs. As an application, we calculate the general Trinajstić index for some hydrocarbons

Enhancing grain boundary ionic conductivity in mixed ionic electronic conductors

The emergent properties arising from the interactions of phases including interfacial contributions and phase evolution at the mesoscale present new opportunities, as well as challenges, for materials performance and functionality. Mixed ionic-electronic conductors are widely used in devices for energy conversion and storage. Grain boundaries in these materials have nanoscale spatial dimensions, which can generate substantial resistance to ionic transport due to dopant segregation. Here, we report a concept of targeted phase formation in a Ce0.8Gd0.2O2-δ-CoFe2O4 (CGO-CFO) composite that serves to enhance the grain boundary ionic conductivity. Using spatially resolved electron microscopy, we probed the grain boundary charge distribution and chemical environments altered by the phase reaction between the two constituents. The formation of an emergent phase successfully avoided segregation of the Gd dopant and depletion of oxygen vacancies at the Ce0.8Gd0.2O2-δ-Ce0.8Gd0.2O2-δ grain boundary. This resulted in superior grain boundary ionic conductivity as demonstrated by the enhanced oxygen permeation flux. This work illustrates the control of mesoscale level transport properties in mixed ionic-electronic conductor composites through processing induced modifications of the grain boundary defect distribution. Implications for controlling grain boundary composition in diverse applications of ceramic-ceramic composites such as nuclear waste immobilization will be discussed

Alterations in the surface properties of sea spray aerosols introduced by the presence of sterols

SSCI-VIDE+CARE+CGOInternational audiencehe mixed stearic acid (SA)/sterol systems were used as sea spray aerosol mimics to get more insights into the al-terations in surface properties of aerosols induced by sterols. By means of surface pressure (π)–area(A) isotherms and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS), the effect ofcholesterol (chol), stigmasterol (stig) and ergosterol (erg) on the lateral packing and chain conformation of SAmonolayer was explored. The fact that the excess areas of mixing of the mixed monolayers exhibit significant devi-ations from ideally mixedfilm proves that, the sterols are miscible withSA throughout all the monolayer composi-tions and surface pressures examined. The lift-off areas inπ–A isotherms were found to increase with increasingmole fraction of sterols, indicating that expulsive interactions exist between SA and sterols, which are more pro-nounced when the mole fraction of sterols is 0.7. In addition, the peak intensities ofνa(CH2)andνs(CH2)inIRRASspectra decrease with increasing sterols levels, which is consistent with ourfindings in theπ–A isotherms, thatthe addition of sterols leads to a looser chain packing in SA monolayer. The proportion ofgauchedefects in SA mono-layer induced by the sterols follows the order cholesterol stigmast ergosterol at a certain sterol level, as reflected by the decreasing peak intensities fνa(CH2)andνs(CH2). Consequently, the sterols generally give riseto considerable expanding effects on SA monolayer, which are particularly pronounced for stigmasterol and ergos-terol, suggesting that the additional alkyl side chains and double bonds of thesterols play a role on disordering SAmonolayer. The present study is likely to shed light on many boundary processes take place at the interface ofSSAs, in particular, transport processes of water and trace gases across the interfac

Evaluation of the antioxidant activity of Coreopsis tinctoria Nuff. and optimisation of isolation by response surface methodology

The aim of the present study was to determine the antioxidant activity of Coreopsis tinctoria flowering tops (CTFT). Studies were conducted to obtain suitable extraction conditions for chlorogenic acid, quercetin, luteolin, apigenin and kaempferol, which were identified and quantified by HPLC. Response surface methodology was employed to optimise the ultrasound-assisted extraction conditions, including extraction time, ethanol concentration and liquid-solid ratio. The antioxidant activity of the extracts was analysed using various antioxidant models, such as DPPH, ABTS and hydroxyl radical scavenging assay. CTFT extracted for 15.0 min with ethanol at a concentration of 60.4 % and with liquid-solid ratio 27.5:1 possessed a considerable amounts of total flavonoids and polyphenols (18.9 %). This extract showed higher scavenging activity of ABTS and hydroxyl radical activity than rutin, however not in the DPPH test. We may assume that CTFT possess antioxidant and free radical scavenging potentials

Estrogen and progesterone-related gene variants and colorectal cancer risk in women

<p>Abstract</p> <p>Background</p> <p>Observational studies and randomized trials have suggested that estrogens and/or progesterone may lower the risk for colorectal cancer. Inherited variation in the sex-hormone genes may be one mechanism by which sex hormones affect colorectal cancer, although data are limited.</p> <p>Method</p> <p>We conducted a comprehensive evaluation of single nucleotide polymorphisms (SNPs) in genes encoding 3 hormone receptors (<it>ESR1, ESR2, PGR</it>) and 5 hormone synthesizers (<it>CYP19A1 and CYP17A1, HSD17B1, HSD17B2, HSD17B4</it>) among 427 women with incident colorectal cancer and 871 matched controls who were Caucasians of European ancestry from 93676 postmenopausal women enrolled in the Women's Health Initiative Observational cohort. A total of 242 haplotype-tagging and functional SNPs in the 8 genes were included for analysis. Unconditional logistic regression with adjustment for age and hysterectomy status was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).</p> <p>Results</p> <p>We observed a weak association between the <it>CYP17A1 </it>rs17724534 SNP and colorectal cancer risk (OR per risk allele (A) = 1.39, 95% CI = 1.09-1.78, corrected p-value = 0.07). In addition, a suggestive interaction between rs17724534 and rs10883782 in 2 discrete LD blocks of <it>CYP17A1 </it>was observed in relation to colorectal cancer (empirical p value = 0.04). Moreover, one haplotype block of <it>CYP19A1 </it>was associated with colorectal cancer (corrected global p value = 0.02), which likely reflected the association with the tagging SNP, rs1902584, in the block.</p> <p>Conclusion</p> <p>Our findings offer some support for a suggestive association of <it>CYP17A1 </it>and <it>CYP19A1 </it>variants with colorectal cancer risk.</p

ATP Released by Astrocytes Mediates Glutamatergic Activity-Dependent Heterosynaptic Suppression

AbstractExtracellular ATP released from axons is known to assist activity-dependent signaling between neurons and Schwann cells in the peripheral nervous system. Here we report that ATP released from astrocytes as a result of neuronal activity can also modulate central synaptic transmission. In cultures of hippocampal neurons, endogenously released ATP tonically suppresses glutamatergic synapses via presynaptic P2Y receptors, an effect that depends on the presence of cocultured astrocytes. Glutamate release accompanying neuronal activity also activates non-NMDA receptors of nearby astrocytes and triggers ATP release from these cells, which in turn causes homo- and heterosynaptic suppression. In CA1 pyramidal neurons of hippocampal slices, a similar synaptic suppression was also produced by adenosine, an immediate degradation product of ATP released by glial cells. Thus, neuron-glia crosstalk may participate in activity-dependent synaptic modulation

The Aromatase Gene (CYP19A1) Variants and Circulating Hepatocyte Growth Factor in Postmenopausal Women

Background: Estrogen and androgen have been linked to the regulation of circulating hepatocyte growth factor (HGF), an adipose tissue-derived cytokine. It is possible that the CYP19A1 gene which alters sex hormones production may influence HGF levels. We examined the association between the CYP19A1 gene variants and plasma HGF concentrations. Design We evaluated 45 common and putative functional variants of CYP19A1 and circulating levels of HGF among 260 postmenopausal women who later developed colorectal cancer from the Women's Health Initiative Observational Cohort. As the distribution of HGF levels was highly skewed, we transformed HGF concentrations for all women into a log-, ranked-, or normal score-scale value. Multiple linear regression with adjustment for age was used to evaluate the associations. Results: We observed an association between the rs7172156, rs1008805, rs6493494, rs749292, and rs11636639 variants and HGF levels in ranked and normal score scales (corrected p values ≤0.02), although the association of these 5 SNPs with log-scale HGF was not significant (corrected p values ≥0.16). The associations remained unchanged after additional adjustment for hormone therapy use and estradiol levels. These 5 SNPs, which were in linkage disequilibrium (pairwise D′≥97%, r2≥56%), constituted a block with 2 common haplotypes accounting for 82% frequency. The most common haplotype, TCCCA, was associated with lower ranked- or normal score-transformed HGF levels (corrected p values ≤0.001), whereas the second most common haplotype, CTTCA, was associated with higher ranked- or normal score-transformed HGF levels (corrected p values ≤0.02). Conclusion: Our findings of a potential association between the CYP19A1 variants and circulating HGF levels warrant confirmation in studies with larger sample size

Study of an unusually high level of N-glycolylneuraminic acid (NGNA) sialylation on a monoclonal antibody expressed in Chinese hamster ovary cells

Sialic or neuraminic acids of recombinant therapeutic glycoproteins produced in mammalian cells, including monoclonal antibodies, have significant impact on the half-life, stability, and biological activity of these proteins (Hossler et al., 2009; Ghaderi et al., 2012). The predominant sialic acid N-acetylneuraminic acid (NANA or Neu5Ac) is added from precursor CMP-NANA to galactose residues of N-linked glycoproteins by sialytransferases. In most mammals CMP-NANA can also be modified to its hydroxylated derivative CMP-NGNA by CMP-N-acetylneuraminic acid hydroxylase (CMAH). NGNA can then be added from CMP-NGNA to galactose residues of the N-linked glycoproteins, also by sialytransferases. However, humans cannot make functional CMAH due to an inactivating exon deletion mutation in CMAH gene (Okerblom and Varki, 2017), and therefore cannot convert CMP-NANA to CMP-NGNA. Consequently, when injected into human patients, NGNA sialic acid containing mAbs or other recombinant glycoproteins may induce immune responses, which could negatively impact pharmacokinetics or efficacy. Therefore high levels of NGNA on therapeutic mAbs or other recombinant glycoproteins are an undesirable product quality attribute. The level of total sialic acids of recombinant glycoproteins produced in Chinese hamster ovary (CHO) cells is dictated largely by the selected cell lines, upstream process, and to a lesser degree, downstream process. NGNA sialylation is generally rare in CHO cells (Könitzer et al., 2015). Hence, therapeutic glycoproteins manufactured in these cells are considered safe for human use. However, during a first-in-human (FIH) upstream process development for a novel mAb, an initially selected desirable cell line (A) was found to produce the mAb with an unexpectedly high level of the NGNA sialic acid (\u3e30%). To the best of our knowledge such high level of NGNA sialylation on a mAb produced by CHO cells has not been reported. To mitigate potential risks associated with high NGNA in human patients, a new cell line (B) that produces the mAb with very low NGNA was selected as the manufacturing cell line for this project. In order to understand the molecular mechanism causing the high NGNA content in cell line A, we initiated comprehensive genetic gap analyses using next-generation sequencing technologies and determined the differences in genomic, transcriptomic, and miRnomic profiles of the two cell lines. The results indicate spontaneous upregulation of CMAH mRNA expression, at least 10 fold higher in cell line A compared to cell line B. In this talk we will summarize the results of our studies of this unusual sialylation behavior in CHO cells