A family of memristor‐based reactance‐less oscillators

In this paper, we present for the first time a family of memristor‐based reactance‐less oscillators (MRLOs). The proposed oscillators require no reactive components, that is, inductors or capacitors, rather, the ‘resistance storage’ property of memristor is exploited to generate the oscillation. Different types of MRLO family are presented, and for each type, closed form expressions are derived for the oscillation condition, oscillation frequency, and range of oscillation. Derived equations are further verified using transient circuit simulations. A comparison between different MRLO types is also discussed. In addition, detailed fabrication steps of a memristor device and experimental results for the first MRLO physical realization are presented. Copyright © 2013 John Wiley & Sons, Ltd.     

Predictive modelling of angiotensin converting enzyme inhibitory dipeptides

The ability of docking to predict angiotensin converting enzyme (ACE) inhibitory dipeptide sequences was assessed using AutoDock Vina. All potential dipeptides and phospho-dipeptides were docked and scored. Peptide intestinal stability was assessed using a prediction amino acid clustering model. Selected dipeptides, having AutoDock Vina scores ? −8.1 and predicted to be ‘stable’ intestinally, were characterised, using LIGPLOT and for ACE-inhibitory potency. Two newly identified ACE-inhibitory dipeptides, Asp-Trp and Trp-Pro, having Vina scores of −8.3 and −8.6 gave IC₅₀ values of 258 ± 4.23 and 217 ± 15.7 μM, respectively. LIGPLOT analysis indicated no zinc interaction for these dipeptides. Phospho-dipeptides were predicted to have a good affinity for ACE. However, the experimentally determined IC₅₀ results did not correlate since, for example, Trp-pThr and Pro-pTyr, having Vina scores of −8.5 and −8.1, respectively, displayed IC₅₀ values of >500 μM. While docking allowed identification of new ACE inhibitory dipeptides, it may not be a fully reliable predictive tool in all cases.     

Selectivity,Kinetics, and Efficiency of Reversible Anion Exchange with TcO4− in a Supertetrahedral Cationic Framework

[ThB₅O₆(OH)₆][BO(OH)₂]·2.5H₂O (Notre Dame Thorium Borate‐1, NDTB‐1) is an inorganic supertetrahedral cationic framework material that is derived from boric acid flux reactions. NDTB‐1 exhibits facile single crystal to single crystal anion exchange with a variety of common anions such as Cl^?, Br^?, NO₃^?, IO₃^?, ClO₄^?, MnO₄^?, and CrO₄^2?. More importantly, NDTB‐1 is selective for the removal of TcO₄^? from nuclear waste streams even though there are large excesses of competing anions such as Cl^?, NO₃^?, and NO₂^?. Competing anion exchange experiments and magic‐angle spinning (MAS)‐NMR spectroscopy of anion‐exchanged NDTB‐1 demonstrate that this unprecedented selectivity originates from the ability of NDTB‐1 to trap TcO₄^? within cavities, whereas others remain mobile within channels in the material. The exchange kinetics of TcO₄^? in NDTB‐1 are second‐order with the rate constant k₂ of 0.059 s^?1 M^?1. The anion exchange capacity of NDTB‐1 for TcO₄^? is 162.2 mg g^?1 (0.5421 mol mol^?1) with a maximum distribution coefficient K_d of 1.0534 × 10⁴ mL g^?1. Finally, it is demonstrated that the exchange for TcO₄^? in NDTB‐1 is reversible. TcO₄^? trapped in NDTB‐1 can be exchanged out using higher‐charged anions with a similar size such as PO₄^3? and SeO₄^2?, and therefore the material can be easily recycled and reused.     

Determination of fluoroquinolones in aquaculture products by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)

An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of fluoroquinolones–ciprofloxacin (CIPRO), danofloxacin (DANO), enrofloxacin (ENRO) and sarafloxacin (SARA)–in aquaculture products, specifically salmon, shrimp and tilapia. After initial sample extraction with an acidic acetonitrile solution, the extract was diluted with dichloromethane and centrifuged, then an aliquot was concentrated and applied to a C18 solid-phase extraction cartridge and concentrated for a second time. The resultant residue was dissolved in acetonitrile, diluted with water, and then further defatted with hexane. The fluoroquinolone residues were determined by UPLC with an HSS T3 C18 reverse-phase column using an ammonium hydroxide-formic acid buffer in an acetonitrile gradient with MS/MS detection using multiple reaction monitoring. Average recoveries for salmon tissue ranged from 73% for DANO to 95% for SARA, for shrimp from 71% for DANO to 109% for SARA, and from 62% for DANO to 111% for SARA in tilapia, fortified at the 1.0 ng g^?1 level. Standard curves were linear between 0.002 and 0.5 ng injected for all compounds. Detection limits of 0.2 ng g^?1 for CIPRO, DANO, ENRO, and SARA were easily obtainable. The operational errors, interferences, and recoveries for fortified samples demonstrate that this described method is suitable for routine use in a regulatory programme. The recommended method is simple, rapid, specific and reliable for the routine monitoring of fluoroquinolone residues in aquatic species such as salmon, tilapia and shrimp.     

Targeting of Glycosaminoglycans in Genetic and Inflammatory Airway Disease

In the lung, glycosaminoglycans (GAGs) are dispersed in the extracellular matrix (ECM) occupying the interstitial space between the capillary endothelium and the alveolar epithelium, in the sub-epithelial tissue and in airway secretions. In addition to playing key structural roles, GAGs contribute to a number of physiologic processes ranging from cell differentiation, cell adhesion and wound healing. Cytokine and chemokine–GAG interactions are also involved in presentation of inflammatory molecules to respective receptors leading to immune cell migration and airway infiltration. More recently, pathophysiological roles of GAGs have been described. This review aims to discuss the biological roles and molecular interactions of GAGs, and their impact in the pathology of chronic airway diseases, such as cystic fibrosis and chronic obstructive pulmonary disease. Moreover, the role of GAGs in respiratory disease has been heightened by the current COVID-19 pandemic. This review underlines the essential need for continued research aimed at exploring the contribution of GAGs in the development of inflammation, to provide a better understanding of their biological impact, as well as leads in the development of new therapeutic agents.     

超低温双螺旋速冻对猪背最长肌加工品质的影响

为研究超低温双螺旋速冻（Ultra-low Temperature Double Spiral Quick Freezing，UTDSQF）对原料猪肉加工品质的影响，该研究以宰后24 h且pH值在正常范围内的猪背最长肌为研究对象，分别采用常规空气冻结（Air-blast Freezing，AF）和超低温双螺旋速冻两种方式对猪背最长肌进行冻结，随后在-20 ℃冷库中冻藏90 d后于4 ℃解冻，加工制成乳化香肠，测定两种冻结方式对其理化、质构和感官品质的影响。研究表明：原料肉不同冻结方式对乳化肠pH值没有显著影响（P>0.05）；与AF组相比，UTDSQF组的TBARS值和蒸煮损失分别降低26.67%、31.25%（P<0.05）；L*值和a*值显著升高（P<0.05），但b*值显著降低（P<0.05）；UTDSQF组的硬度、咀嚼性、回复性和内聚性显著升高（P<0.05），而弹性没有显著性差异（P>0.05）；同时，UTDSQF处理原料肉显著提升了乳化肠的感官评分（P<0.05）。因此超低温双螺旋速冻处理能够整体提升原料肉的加工品质。     

High Fructose Corn Syrup. A Case History of Innovation

High fructose corn syrup, or isomerized corn syrup as it is sometimes called, qualifies as a major innovation because this new product is having a revolutionary effect on the important sweetener business. The history of high fructose corn syrup is particularly interesting because of the varied research lessons it teaches. This article traces and analyzes the sequence of events in the development of high fructose corn syrup from the time of the basic discovery and conception of product to the time of commerciallization.