Exchange Liquid Research Articles

Financial Risks and Financial Performance of Commercial Banks in Kenya

Due to their erratic financial performance and failure to honour shareholder promises, the Kenyan central bank has formally placed a few commercial banks under receivership. Although commercial banks constantly use thorough risk management procedures, the banking industry nonetheless suffers losses. This results from the banking industry's exposure to risks related to liquidity, credit, interest rates, and foreign exchange rates. The purpose of this research was, thus, to assess the impact of credit, interest rate, and foreign currency rate risks on the return on equity of Kenyan commercial banks. The research study examined how financial risks affect Kenya's commercial banks' profits. The study was founded on agency theory and reinforced by international Fischer's affect theory, liquidity preference theory, and interest rate parity. This study employed a causal analysis approach. The participants in this study comprised all of the 39 commercial banks operating in Kenya between 2017 and 2021. The data collecting sheet was used to compile the secondary data. STATA was used to analyse the data using a panel regression model at a 95% level of significance. Tests for multicollinearity, heteroscedasticity, and normalcy as well as the Hausman test were established. Descriptive statistics such as mean, standard deviation and both the minimum and maximum were used to present the data. The study established that while credit risk had a significant negative impact on commercial banks' performance, liquidity risk had a significant positive benefit. Furthermore, exchange risk improved commercial banks' bottom lines, however, this benefit was not statistically significant. Finally, interest rate risk impacted commercial banks' bottom lines negatively but not statistically significantly. According to the study's findings, commercial bank management should be cautious when lending money to new clients and should evaluate existing customers' credit histories before extending credit. To support failing banks, the report suggested that the government and the Central Bank of Kenya increase the minimum liquidity ratio required by law. The government bank should keep a close eye on commercial banks' liquidity ratios to alert any that are having trouble meeting the minimum statutory requirement. Keywords: Financial Risks, credit risk, liquidity risk, exchange rate risk, interest rate risk, financial performance

A general framework for jointly modelling thermal and hydric constraints on developing eggs

Abstract Eggs are a vulnerable stage because they are sensitive to thermal and hydric conditions and yet cannot behaviourally avoid stressful environments. A general mechanistic model of egg development in natural nests requires microclimatic predictions of temperature, humidity, radiation (if above ground) and water potential (if buried in soil) to be integrated with models of heat and water exchange of the egg and the metabolism of the developmental process. Although all the required pieces for such a model now exist, they have not been integrated into a general modelling framework. We developed such an integration using NicheMapR package for mechanistic niche modelling. Specifically, we took an existing general model of egg water exchange and connected it with the microclimate model in NicheMapR to simulate nest thermal and hydric environments, including the effects of soil water potential on liquid and vapour exchange and moisture‐mediated soil thermal conductivity on heat exchange. We then used the Dynamic Energy Budget model within the ectotherm model of NicheMapR as the mechanistic engine for the developmental process, allowing the explicit computation of the dynamics of metabolic heat production and all aspects of mass exchange. We illustrate the modelling framework using existing laboratory and field data on reptiles, insects, and birds. We show that it can capture laboratory observations of water exchange and metabolic heat production and how it can be used to map potential development and water uptake under natural conditions at the continental scale. The modelling framework can be used to interpret laboratory experiments and allows strong inferences to be made about the abiotic constraints on egg development in natural nests under past, present, and future environmental change.

Superhydrophobic Pt@SBA-15 catalyst for tritium separation in liquid phase catalytic exchange

Through the modification of mesoporous silica (SBA-15), a hydrophobic microscopic reaction environment was constructed, which was beneficial to improve the catalytic activity of the LPCE reaction. The Pt@SBA-15-tetramethyldisilazane catalyst is prepared by the modification of the SBA-15 carrier and the loading of metal Pt, with a water contact angle of 158°. This superhydrophobic structure can enhance the catalytic performance and can prevent the deactivation of the catalyst. By measuring the actual catalytic performance of tritium water under different conditions, we found that it has good catalytic activity, and the catalyst can still maintain a high catalytic activity after 30 days in tritium water environment.

Fe2+–Mg partitioning between olivine and liquid at low oxygen fugacity: an experimental and thermodynamic framework

A set of 1-atm gas-mixing experiments (n = 31) was run using Re wire loops at low-oxygen fugacity (ƒO2, within one half-log unit of the Fe–FeO buffer) and temperatures of 1175–1400 °C to explore the compositional dependence of the Fe2+–Mg olivine–liquid exchange coefficient, {mathrm{K}}_{mathrm{D},{mathrm{Fe}}^{2+}-mathrm{Mg}}^{mathrm{ol}/mathrm{liq}}, under conditions where corrections for liquid Fe3+ are small. The bulk compositions used for these experiments include a picrite, a high-alumina basalt, and a suite of three MORB compositions with variable Fe/Mg. The {mathrm{K}}_{mathrm{D},{mathrm{Fe}}^{2+}-mathrm{Mg}}^{mathrm{ol}/mathrm{liq}} values from the n = 14 experiments run on pre-saturated Re wire loops were fit to a regular solution model that relates {mathrm{K}}_{mathrm{D},{mathrm{Fe}}^{2+}-mathrm{Mg}}^{mathrm{ol}/mathrm{liq}} to temperature, melt composition, and olivine composition. Fe2+–Mg exchange in the experiments is well-described using two parameters: the SiO2 content of the liquid and the coexisting olivine composition. Combining our experiments with a literature compilation of low-pressure, low-ƒO2 experiments (largely on non-terrestrial bulk compositions) produced a combined data set spanning a broad region of composition space (e.g., liquid TiO2 and Na2O + K2O contents up to 18.4 wt% and 8.4 wt%, respectively). Fitting this expanded experimental database required two additional liquid compositional terms: Ti, and a Si-(Na + K) cross-term. Because the Fe3+ content of all of the experimental liquids is low, the compositional variation seen in {mathrm{K}}_{mathrm{D},{mathrm{Fe}}^{2+}-mathrm{Mg}}^{mathrm{ol}/mathrm{liq}} is effectively independent of the compositional effects on liquid Fe3+/Fe2+ ratios. Given olivine–liquid Mg or Fe2+ partition coefficient information, it is possible to eliminate the explicit dependence of {mathrm{K}}_{mathrm{D},{mathrm{Fe}}^{2+}-mathrm{Mg}}^{mathrm{ol}/mathrm{liq}} on olivine composition, enabling a simple iterative approach for calculating the composition of coexisting olivine given only the bulk composition (and Fe3+/Fe2+ ratio) of an olivine-saturated liquid.

Optimization of the Adaptability of the Fuel Cell Vehicle Waste Heat Utilization Subsystem to Extreme Cold Environments

In extremely cold environments, the fuel cell vehicle (FCV) waste heat utilization subsystem can only exchange a small amount of proton exchange membrane fuel cell (PEMFC) waste heat into the warm air circuit for cab heating, which has poor adaptability to extremely cold environments. The first step in this study was to build a test bench for the waste heat utilization subsystem of fuel cell vehicles. Secondly, the PEMFC heating capacity and liquid–liquid exchanger heat transfer capacity were analyzed using experimental data to assess the ability of FCV waste heat utilization subsystems with different rated powers to adapt to extremely cold environments. Then, the optimization mathematical model of the liquid–liquid exchanger was established, and the heat transfer performance of the liquid–liquid exchanger was orthogonally optimized based on the Taguchi method. Finally, the optimized liquid–liquid exchanger was installed in the waste heat utilization subsystem for experimental tests. The results show that when the ambient temperature is −20 °C, −25 °C or −30 °C, in the optimized waste heat utilization subsystem, the inlet and outlet temperatures of the PEMFC are reduced, and the power consumption of the positive temperature coefficient (PTC) is reduced by 57.6% and 48% and 34.3%, respectively, improving the utilization rate of PEMFC waste heat, and thereby improving the adaptability of FCV in extremely cold environments.

Refrigeration system development with limited charge of flammable Refrigerant, R-290

Recently, natural refrigerants have gained a significant attention as a future alternative because of their performance and environmentally friendly characteristics; No Ozone Depleting Potential and near zero Global Warming Potential. The present paper reports an experimental study performed with refrigeration systems developed using one of natural refrigerants, R-290 (Propane & GWP = 3), particularly with the limited charge amount to meet the most stringent regulatory requirement, IATA - Dangerous Goods Regulation. Under IATA regulation, refrigerating machines and components containing flammable gas are forbidden for international air freight unless the flammable charge shall be less than 100 g. Two types of standalone system were developed, so called Liquid Circulating Chiller and Air-Air Cooler. Both were with air-cooled condensers. Liquid Circulating Chiller consisted of a liquid cooled evaporator (liquid to liquid heat exchanger) while Air-Air Cooler came with an air-cooled evaporator (air to liquid heat exchanger). All component selections were made to achieve the minimum refrigerant charge and as a result, the total system charge was kept around 100 g or less. During the system development, several combinations of the components were considered (e.g., compressors and heat exchangers), and system developed was tested under various test conditions as a part of the system optimization. From the study, the maximum cooling capacity achieved was around 3 kW with less than 100 g of R-290 refrigerant charge.

The Python Package open-crypto: A Cryptocurrency Data Collector

This paper introduces the package open-crypto for free-of-charge and systematic cryptocurrency data collecting. The package supports several methods to request (1) static data, (2) real-time data and (3) historical data. It allows to retrieve data from over 100 of the most popular and liquid exchanges world-wide. New exchanges can easily be added with the help of provided templates or updated with build-in functions from the project repository. The package is available on GitHub and the Python package index (PyPi). The data is stored in a relational SQL database and therefore accessible from many different programming languages. We provide a hands-on and illustrations for each data type, explanations on the received data and also demonstrate the usability from R and Matlab. Academic research heavily relies on costly or confidential data, however, open data projects are becoming increasingly important. This project is mainly motivated to contribute to openly accessible software and free data in the cryptocurrency markets to improve transparency and reproducibility in research and any other disciplines.

Effect of heat treatment on the antioxidant activities of camel milk alpha, beta and total caseins

This study aimed to evaluate the effect of various heating temperatures on the antioxidant activities of camel milk caseins. The samples were processed with three different heat treatments: Pasteurization at low and high temperatures and boiling. Fresh camel milk (unheated) was used as a control. Camel milk caseins were separated by fast ion exchange liquid chromatography (FPLC) and identified by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS page). The antioxidant activities of caseins were measu- red by three different in vitro methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2, 2'-azino-bis (3-ethylbenzthiazoline-6-sulfonate) (ABTS) radical scavenging activity and ferric reducing power assay (FRAP). The antioxidant activity evaluated by the DPPH assay decreased significantly (p<0.05) with the increase in heat treatment of caseins. However, there was no significant difference in ABTS radical scavenging activity and Ferric Reducing Antioxidant Power assay (FRAP) of heat-treated camel caseins compared to unheated onesStill, a decrease was observed in those activities by the increase of temperature in the different casein concentrations. Besides, whatever the concentration tested and the methods applied, the antioxidant activity of beta-casein (β-CN) was more pronounced than the alpha-casein (α-CN). Therefore, camel milk casein could be used as a natural source of antioxidants which may have a potential application in the food and nutraceutical industries. Throughout the different heat treatments applied, pasteurization at low temperature could be the most suitable alternative to preserve the antioxidant properties of camel milk.

Hydrogen/deuterium exchange in 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide-based solutions

Here, hydrogen/deuterium (H/D) exchange in hydrophobic ionic liquid (IL)-propanol solutions were investigated by Raman spectroscopy. The ILs were 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Cnmim][TFSI] (n = 2–6). Fully deuterated methanol (MeOD-d4), acetone‑d6, and 2-propanol (2-PrOD-d8) were used. H/D exchange was not observed in [C2mim][TFSI]-based mixtures. The constant fraction of D over the entire concentration range of 2-PrOD-d8 studied was observed in [C3mim][TFSI]-based mixtures. The distinct H/D exchange in [C4mim][TFSI]-based mixtures was dependent on the 2-PrOD-d8 concentration. The H/D exchange had no cationic alkyl chain length dependencies. Kinetic H/D exchange depended on the types of additives.

Seeking sigma: Time-of-the-day effects on the Bitcoin network

This research investigates and tests for the presence of time-of-the-day effects on the Bitcoin network. Results indicate that NYSE trading sessions lead Bitcoin trading activity, both on the blockchain and centralised exchanges. Effects are found to have strengthened over time, however, simultaneously diminished at the weekend indicating significant exchange interactions, and that Bitcoin has developed somewhat outside its intended design parameters and is influenced by other forces such as those originating from NYSE trading. While proponents consider Bitcoin trading to be ‘24/7’, our findings suggest that both transaction and on-chain network activity are best described to be, at best, ‘12/5’, presenting significant implications for traders, with regards to centralised exchange liquidity and the speed of their transaction inclusion on the blockchain. Finally, the role and influence of both algorithm and volatility traders cannot be eliminated.

Degradation and in-use stability study of five marketed therapeutic monoclonal antibodies by generic weak cation exchange liquid chromatographic method ((WCX)HPLC/DAD)

Therapeutic monoclonal antibodies (mAbs) represent a very important class of the current biopharmaceutics. The great complexity of their structure made necessary the use of different analytical approaches for assessing different physico-chemical properties. In this work, weak cation exchange (WCX) high performance liquid chromatography with diode array detection ((WCX)HPLC/DAD) is used to assess the charge variant profile. The method here developed combined the effect of ionic strength and controlled pH gradient and allows for the charge variants analysis of the five mAbs studied, namely bevacizumab (BVZ), cetuximab (CTX) infliximab (INF), rituximab (RTX) and trastuzumab (TTZ), which are among the most used mAbs worldwide. The differences in the charge variants in the natural isoforms of the mAbs promoted characteristic WCX chromatograms for each of mAbs that can be also useful for identification purposes. These chromatograms have provided to be suitable for tracking changes in the charge variants of each mAb analyzed both in controlled degraded and in stabilities study along time of in-use samples solutions at 2 mg/mL in 0.9% NaCl stored refrigerated (at 4 °C) and frozen (−20 °C) for two months. The results obtained indicated different stabilities of these mAbs, all IgG1, against degradation by different stressed environmental conditions and in-use stability along two months.

Fabrication of biomimetic networks using viscous fingering in flexographic printing

Mammalian tissue comprises a plethora of hierarchically organized channel networks that serve as routes for the exchange of liquids, nutrients, bio-chemical cues or electrical signals, such as blood vessels, nerve fibers, or lymphatic conduits. Despite differences in function and size, the networks exhibit a similar, highly branched morphology with dendritic extensions. Mimicking such hierarchical networks represents a milestone in the biofabrication of tissues and organs. Work to date has focused primarily on the replication of the vasculature. Despite initial progress, reproducing such structures across scales and increasing biofabrication efficiency remain a challenge. In this work, we present a new biofabrication method that takes advantage of the viscous fingering phenomenon. Using flexographic printing, highly branched, inter-connective channel structures with stochastic, biomimetic distribution and dendritic extensions can be fabricated with unprecedented efficiency. Using gelatin (5%–35%) as resolvable sacrificial material, the feasability of the proposed method is demonstrated on the example of a vascular network. By selectively adjusting the printing velocity (0.2–1.5 m s−1), the anilox roller dip volume (4.5–24 ml m−2) as well as the shear viscosity of the printing material used (10–900 mPas), the width of the structures produced (30–400 µm) as well as their distance (200–600 µm) can be specifically determined. In addition to the flexible morphology, the high scalability (2500–25 000 mm2) and speed (1.5 m s−1) of the biofabrication process represents an important unique selling point. Printing parameters and hydrogel formulations are investigated and tuned towards a process window for controlled fabrication of channels that mimic the morphology of small blood vessels and capillaries. Subsequently, the resolvable structures were casted in a hydrogel matrix enabling bulk environments with integrated channels. The perfusability of the branched, inter-connective structures was successfully demonstrated. The fabricated networks hold great potential to enable nutrient supply in thick vascularized tissues or perfused organ-on-a-chip systems. In the future, the concept can be further optimized and expanded towards large-scale and cost-efficient biofabrication of vascular, lymphatic or neural networks for tissue engineering and regenerative medicine.

Investigation of a Macromolecular Additive on the Decrease of the Aluminum Horizontal Etching Rate in the Wet Etching Process

The effect of a macromolecular additive on the etching rate of aluminum (Al) horizontal etching in the wet process was investigated in this work. The horizontal etching in the Al wet etching process became more evident as the film Al becomes thicker. The proposed macromolecule additive, including polyethylene-polypropylene glycol, was added into the Al etchant solution to reduce the Al horizontal etching rate (ER). The undercut problem during metal patterning can then be improved. By using this method, the Al horizontal ER was reduced from 2.0 to 0.9 μm per minute and the selection ratio between the horizontal and vertical ER was effectively improved from 3 to 1.3 times. As well, a hypothesis of physical mechanism for the improvement was proposed. The dispersed particles from the additive emulsion inhibited the transport and exchange of liquid in a horizontal direction. This work provides an alternative reference to improve the selection ratio performance in the metal wet etching process compared with that when using traditional method.

Experimental Investigation of Using Liquid Suction Heat Exchanger with Condensed Cold-Water on the Performance of Air Conditioning System

This paper reports experimental investigation of using liquid suction heat exchanger (LSHX) with condensed cold-water (LSHX-CW) on the performance of a split type room air conditioning. To this end, we used a large room of a residential house of 64 m3 equipped with a 2-tons conventional commercial split-type air conditioner fitted with R22. The coaxial design of LSHX-CW allows to exchange heat between the vapor and liquid refrigerants in the center part and condensed water and the warm liquid refrigerant on the outer part. LSHX-CW was well insulated on the outside to reduce heat transfer with ambient. The air conditioning was tested several times for three scenarios namely, conventional system, system with LSHX alone and LSHX with condensed water LSHX-CW. Experimental results showed that the use of LSHX-CW improved the performance of air conditioning noticeably when compared to the use of LSHX alone. The maximum LSHX-CW effectiveness was 7.67%. The pressure discharge line and electricity consumed decreased by 8.23% and 9.40% respectively.

Analytical and experimental evaluation of a household refrigerator operating under a diffusion-absorption refrigeration cycle

The diffusion-absorption refrigeration (DAR) cycle has characteristics as the use of three working fluids and a low COP. In this work, an analytical and experimental investigation of a household refrigerator operating under a H20-NH3-H2DAR cycle is performed. A thermodynamic model of the DAR cycle was developed and adjusted based on models available in the literature. An experimental investigation was performed aiming to validate the developed DAR model using operating data collected in a real refrigerator. Subsequently the role of refrigerant rectification in the cycle was investigated and it was found that the temperature at the outlet of the rectifier should not exceed 70 °C. In addition, the importance of the production of liquid refrigerant in the condenser was investigated. It was observed that the COP decreases with the increase in the temperature of the inert gas entering the liquid heat exchanger (LHE). Finally, it was demonstrated that by increasing the amount of inert gas in the evaporator, there is a drop in evaporation temperature and consequently in the system COP.The model proved to be robust in the operational conditions tested experimentally.

Automated and Dynamic Control of Chemical Content in Droplets for Scalable Screens of Small Animals (Small 17/2022)

Small Animal Screening In article number 2200319, Hang Lu and co-workers develop a droplet-based microfluidic platform for the screening of dynamic phenotypes in small animals. The microfluidic liquid exchanger unit illustrated here allows switching of the chemical environment of an animal encapsulated in a droplet. This method represents an efficient way of altering the chemical or biological environment of an animal (here C. elegans) and monitoring its dynamic response. Integrated with an encapsulation unit and chemical dispensers, this system leads to a powerful technology that will help bridge the gap between the environment, genotype, and phenotype.

Automated and Dynamic Control of Chemical Content in Droplets for Scalable Screens of Small Animals.

Screening functional phenotypes in small animals is important for genetics and drug discovery. Multiphase microfluidics has great potential for enhancing throughput but has been hampered by inefficient animal encapsulation and limited control over the animal's environment in droplets. Here, a highly efficient single-animal encapsulation unit, a liquid exchanger system for controlling the droplet chemical environment dynamically, and an automation scheme for the programming and robust execution of complex protocols are demonstrated. By careful use of interfacial forces, the liquid exchanger unit allows for adding and removing chemicals from a droplet and, therefore, generating chemical gradients inaccessible in previous multiphase systems. Using Caenorhabditis elegans as an example, it is demonstrated that these advances can serve to analyze dynamic phenotyping, such as behavior and neuronal activity, perform forward genetic screen, and are scalable to manipulate animals of different sizes. This platform paves the way for large-scale screens of complex dynamic phenotypes in small animals.

Slow Kinetics of Iron Binding to Marine Ligands in Seawater Measured by Isotope Exchange Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry.

Current understanding of dissolved iron (Fe) speciation in the ocean is based on two fundamentally different approaches: electrochemical methods that measure bulk properties of a heterogeneous ligand pool and liquid chromatography mass spectrometry methods that characterize ligands at a molecular level. Here, we describe a method for simultaneously determining Fe-ligand dissociation rate constants (kd) of suites of naturally occurring ligands in seawater by monitoring the exchange of ligand-bound 56Fe with 57Fe using liquid chromatography-inductively coupled mass spectrometry. Values of kd were determined for solutions of ferrichrome and ferrioxamine E. In seawater, the dissociation rate constant of ferrichrome (kd = 10 × 10-8 s-1) was greater than that of ferrioxamine E (kd = 3.6 × 10-8 s-1). The rates for both compounds were over twice as fast in seawater compared with pure water, suggesting that seawater salts accelerate dissociation. Isotope exchange experiments on organic extracts of natural seawater indicated that ligand-binding sites associated with chromatographically unresolved dissolved organic matter exchanged Fe more quickly (kd = 1.8 × 10-5 s-1) than amphibactin siderophores (kd = 2.15 × 10-6 s-1) and an unidentified siderophore with m/z 709 (kd = 9.6 × 10-6 s-1). These findings demonstrate that our approach can bridge molecular-level ligand identification with kinetic and thermodynamic metal-binding properties.

Pharmacological characterization of a primary nicotinic receptor from the neuromuscular junction

Nicotinic receptors at the neuromuscular junction are important targets in the study of autoimmune disorders such as myasthenia gravis. Historic efforts targeting nAChR drug discovery focused on fluorescence based calcium flux assays along with low throughput manual patch clamp techniques due to its dependence on complete liquid exchange. With the advent of next generation automated patch champ instruments with integrated solution control and rapid solution change, extensive pharmacological characterization of the neuromuscular nAChR ((α1)2β1γδ) is now possible.

Air-Liquid Exchange by Free Hand and One Needle for Unhealed Macular Hole.

Aim To report the treatment of 7 cases of unsealed hole after macular hole surgery with air-fluid exchange. Methods Retrospective case series. We collected 7 eyes of 7 patients with unsealed hole an unsealed hole about 2 weeks after macular hole surgery (23G vitrectomy with internal limiting membrane peeling with sterilizing air tamponade) in our hospital from February 2018 to December 2018. All patients underwent “air-liquid exchange by free hand and one needle.” The prone position was taken one week after operation. The macular holes before and after operation were examined by frequency-domain optical coherence tomography (SD-OCT). Results The size of the macular hole before vitrectomy was 481 ± 156 μm (range: 281–609 μm). Two weeks after vitrectomy (before air and liquid exchange), the size of the macular hole was 295 ± 92 μm (range: 210–421 μm). All macular holes were closed within 7–14 days after air-liquid exchange. There was no complaint of discomfort among these patients. Conclusion From this preliminary study, air-liquid exchange by free hand and one needle seems to be safe and effective in the treatment for patients with unsealed and tiny macular hole after vitrectomy as the lack of long effective gas in China. However, the exact efficacy and safety need further large case studies.