On the Volta potential measured by SKPFM – fundamental and practical aspects with relevance to corrosion science

ABSTRACT

The Volta potential is an electron-sensitive parameter and describes the thermodynamic propensity of a metal to take part in electrochemical reactions. It has found widespread acceptance among corrosion researchers due to its connection to the corrosion potential and its easy measurability in local scale, being often used to study localised corrosion phenomena and micro-galvanic activities. The principle object of this paper is to provide a comprehensive, fundamental insight into the meaning of the Volta potential and to define a polarity convention of measured potentials by the scanning Kelvin probe force microscopy (SKPFM) in order to assess local nobilities in microstructures. Conditions to relate the Volta potential with the mixed-potential theory are discussed and a possible connection to corrosion phenomena explained. The limitations of the Volta potential as well as the SKPFM technique are also aimed to be explained, with some practical information to maximise the output of high quality data.     

Crosstalk between Sodium–Glucose Cotransporter Inhibitors and Sodium–Hydrogen Exchanger 1 and 3 in Cardiometabolic Diseases

Abnormality in glucose homeostasis due to hyperglycemia or insulin resistance is the hallmark of type 2 diabetes mellitus (T2DM). These metabolic abnormalities in T2DM lead to cellular dysfunction and the development of diabetic cardiomyopathy leading to heart failure. New antihyperglycemic agents including glucagon-like peptide-1 receptor agonists and the sodium–glucose cotransporter-2 inhibitors (SGLT2i) have been shown to attenuate endothelial dysfunction at the cellular level. In addition, they improved cardiovascular safety by exhibiting cardioprotective effects. The mechanism by which these drugs exert their cardioprotective effects is unknown, although recent studies have shown that cardiovascular homeostasis occurs through the interplay of the sodium–hydrogen exchangers (NHE), specifically NHE1 and NHE3, with SGLT2i. Another theoretical explanation for the cardioprotective effects of SGLT2i is through natriuresis by the kidney. This theory highlights the possible involvement of renal NHE transporters in the management of heart failure. This review outlines the possible mechanisms responsible for causing diabetic cardiomyopathy and discusses the interaction between NHE and SGLT2i in cardiovascular diseases.     

The influence of gallium on the magnetocaloric properties of Gd5Si2Ge2

Gd₅Si₂Ge₂ was alloyed with varying amounts of Ga to study its influence on the giant magnetocaloric effect. Investigations on Gd₅(Si_2−xGe_2−x)Ga_2x with 2x = 0.03, 0.05 and 0.13 were carried out using X-ray powder diffraction, temperature and magnetic field dependent magnetization measurements, and differential scanning calorimetry. We observe that as the Ga content increases, the temperature stability range of the monoclinic phase narrows, and the orthorhombic structure gains stability. This is expected to be related to the decrease in the (Si/Ge)(Si/Ge) bond distance in the monoclinic phase. The maximum entropy change for the parent compound at 270 K was found to be 9.8 J kg⁻¹ K⁻¹ in an applied field of 5 T. For 2x = 0.03, this value reduces to 8.5 J kg⁻¹ K⁻¹, and the temperature corresponding to the maximum entropy change shifts marginally to 278 K. For other 2x values, the maximum entropy change further decreases.     

Molecular origins of toughening mechanism in uniaxially stretched nylon 6 films with clay nanoparticles

Introduction of nanoplatelets into the nylon matrix preorients the polymer chains in the film plane during melt casting leading to uniplanar (001) texture in nylon 6 crystalline as well as clay phase. This behavior enhances the uniformity of films during cold deformation well above the glass transition temperature by suppressing the localized necking behavior. The clay platelets reduce the polymer interchain hydrogen bonding and entanglements leading to decrease of long range “connectivity”. As a result, a delay in strain hardening during deformation occurs allowing much larger deformations to be attained without fracture. This in turn leads to increase in toughness.     

Application of Solid‐Phase Micro‐Extraction (SPME) for Determining Residues of Chlorpyrifos and Chlorpyrifos‐Methyl in Wine with Gas Chromatography (GC)

The incorrect use of insecticides in many countries' vineyards may result in some toxicological risks for the consumers by their presence on the grapes. In this research, a rapid gas chromatographic method was used for the determination of the residue levels of two organophosphorus pesticides (chlorpyrifos and chlorpyrifos‐methyl) in wine. Pesticides are described and compared with each other. Ten red wines from two different regions of Turkey were analyzed for their chlorpyrifos and chlorpyrifos‐methyl content. The samples were diluted with water and extracted by solid‐phase micro extraction. Nitrogen‐Phosphorus Detection (NDP) and Electron‐Capture Detection (ECD) were used to identify and quantify the pesticides, the findings being confirmed using Mass Spectrometric Detection. Individual detection limits were in the range of (chlorpyrifos) 0.02‐(chlor‐pyrifos‐methyl) 0.1 ng. Limits of quantification varied from (chlorpyrifos) 0.01‐(chlorpyrifos‐methyl) 0.05 mg kg^?1. The maximum residues limits of the two pesticides in the Turkish wines examined were much lower than the Turkish and European Union limits.     

Efficient solution techniques for the integrated coverage, sink location and routing problem in wireless sensor networks

Sensors are tiny electronic devices having limited battery energy and capability for sensing, data processing and communicating. They can collectively behave to provide an effective wireless network that monitors a region and transmits the collected information to gateway nodes called sinks. Most of the applications require the operation of the network for long periods of times, which makes the efficient management of the available energy resources an important concern. There are three major issues in the design of sensor networks: sensor deployment or the coverage of the sensing area, sink location, and data routing. In this work, we consider these three design problems within a unified framework and develop two mixed-integer linear programming formulations. They are difficult to solve exactly. However, it is possible to compute good feasible solutions of the sink location and routing problems easily, when the sensors are deployed and their locations in the sensor field become known. Therefore, we propose a tabu search heuristic that tries to identify the best sensor locations satisfying the coverage requirements. The objective value corresponding to each set of sensor locations is calculated by solving the sink location and routing problem. Computational tests carried out on randomly generated test instances indicate that the proposed hybrid approach is both accurate and efficient.     

Contribution of Capillary Zone Electrophoresis Hyphenated with Drift Tube Ion Mobility Mass Spectrometry as a Complementary Tool to Microfluidic Reversed Phase Liquid Chromatography for Antigen Discovery

The discovery of new antigens specific to multiple myeloma that could be targeted by novel immunotherapeutic approaches is currently of great interest. To this end, it is important to increase the number of proteins identified in the sample by combining different separation strategies. A capillary zone electrophoresis (CZE) method, coupled with drift tube ion mobility (DTIMS) and quadrupole time-of-flight mass spectrometry (QTOF), was developed for antigen discovery using the human myeloma cell line LP-1. This method was first optimized to obtain a maximum number of identifications. Then, its performance in terms of uniqueness of identifications was compared to data acquired by a microfluidic reverse phase liquid chromatography (RPLC) method. The orthogonality of these two approaches and the physicochemical properties of the entities identified by CZE and RPLC were evaluated. In addition, the contribution of DTIMS to CZE was investigated in terms of orthogonality as well as the ability to provide unique information. In conclusion, we believe that the combination of CZE-DTIMS-QTOF and microfluidic RPLC provides unique information in the context of antigen discovery.     

International facilities location: A heuristic procedure for the dynamic uncapacitated problem

It is now well known that most major companies no longer operate in a single market. To penetrate global markets and obtain their benefits, companies are under tremendous pressure to reduce the price of their products, and thus their production and material costs. When a foreign location is used, the components of a product are produced there and final assembly takes place either at the foreign location or at the parent domestic plant. This paper first presents the issues related to international facilities location (IFL) problems, and provides the framework required to deal with such problems. It then presents a heuristic algorithm for solving the IFL problem. Extensive computational experience was gained by solving a variety of IFL problems of different sizes.