Effects of Porosity on Piezoelectric Characteristics of Polyvinylidene Fluoride Films for Biomedical Applications

Objective:The objective of this work is to study the effects of porosity on mechanical and piezoelectric properties of polyvinylidene fluoride(PVDF)films for biomedical applications.Impact Statement:By investigating the piezoelectric properties of PVDF and the porosity effect on its electromechanical performance,there is potential for further development of PVDF as a hemodynamic sensor that can lead to further technological advancements in the biomedical field,benefiting patients and physicians alike.Introduction:PVDF thin films have shown potential in the application of hemodynamic flow sensing and monitoring the effects on blood flow caused by prosthetic valve implantation via the transcatheter aortic valve replacement operation.The piezoelectric performance of PVDF films can be influenced by the porosity of the material.Methods:In this study,strain tracking was performed on thin film PVDF specimens with various levels of porosity and pore sizes to determine the mechanical properties of the specimens.The mechanical properties were used to model the PVDF material in COMSOL multiphysics software,in which compression test simulations were performed to determine the piezoelectric coefficient d33 of the PVDF.Results:A decline in the elastic modulus was found to be highly inversely correlated with porosity of the specimens and the simulation results show that elastic modulus had a much greater effect on the piezoelectric properties than Poisson’s ratio.Conclusion:A combination of experimental and computational techniques was able to characterize and correlate the mechanical properties of PVDF films of varying porosities to their piezoelectric properties.

Graphene-based electrodes and catalysts for electroreduction of CO_(2)to low-carbon alcohols

The electrochemical reduction of CO_(2)(CO_(2)ER)into the renewable and sustainable green fuels,such as low-carbon alcohols,is one of several workable strategies.CO_(2)ER can be combined with renewable electricity to transform intermittent energy sources(such as wind,hydro,and solar)into a fuel that can be stored until it is ready to be used.The intrinsic characteristics of the employed catalyst have a significant and substantial effect on the efficiency of CO_(2)ER and the ensuing economic viability.The paradigmatic multicarbon alcohol catalysts should increase the concentration of*CO in the reaction environment,stabilize the key intermediate products during the reaction,and facilitate the C-C coupling interaction.Since graphene has a large surface area and exceptional conductivity,it has been used as a support for active phases(nanoparticles or nanosheets).It is possible for graphene to enhance charge transport and accelerate CO_(2)conversion through its electronic and structural coupling effects.At the interface,a synergy can be produced that improves CO_(2)ER by increasing*CO adsorption,intermediate binding,and stability.This article focuses on recent advancements in graphene-based catalysts that promote CO_(2)ER to alcohols.Likewise,this paper also describes and discusses the key role graphene plays in catalyzing CO_(2)ER into alcohols.Finally,we hope to provide future ideas for the design of graphene-based electrocatalysts.

美国明尼苏达大学偏微分方程基础课程的教学特点及其启示

偏微分方程基础是许多理工科本科专业开设的重要专业基础课程。本文研究了美国明尼苏达大学偏微分方程基础课程的教学特点,以期对国内偏微分方程基础课程以及其他理工类专业的课程教学改革和课程建设提供一点启示和借鉴作用。

A systematic review of active video games on rehabilitative outcomes among older patients

Background: Although current research supports the use of active video games(AVGs) in rehabilitation, the evidence has yet to be systematically reviewed or synthesized. The current project systematically reviewed literature, summarized findings, and evaluated the effectiveness of AVGs as a therapeutic tool in improving physical, psychological, and cognitive rehabilitative outcomes among older adults with chronic diseases.Methods: Seven databases(Academic Search Complete, Communication & Mass Media Complete, ERIC, Psyc INFO, Pub Med, SPORTDiscus,and Medline) were searched for studies that evaluated the effectiveness of AVG-based rehabilitation among older patients. The initial search yielded 946 articles; after evaluating against inclusion criteria and removing duplicates, 19 studies of AVG-based rehabilitation remained.Results: Most studies were quasi-experimental in design, with physical functioning the primary outcome investigated with regard to the use of AVGs in rehabilitation. Overall, 9 studies found significant improvements for all study outcomes, whereas 9 studies were mixed, with significant improvements on several study outcomes but no effects observed on other outcomes after AVG-based treatments. One study failed to find any benefits of AVG-based rehabilitation.Conclusion: Findings indicate AVGs have potential in rehabilitation for older patients, with several randomized clinical trials reporting positive effects on rehabilitative outcomes. However, existing evidence is insufficient to support the advantages of AVGs over standard therapy. Given the limited number of studies and concerns with study design quality, more research is warranted to make more definitive conclusions regarding the ability of AVGs to improve rehabilitative outcomes in older patients.

Thiolsulfonate functionalized polystyrene resin:Preparation and application in the isolation and identification of electrophilic mutagens

A new approach for isolation and identification of elecrtophilic mutagens from complex matrix was developed. Thiosulforfic anion was immobilized onto polystyrene beads and used as separation media. Potassium polystyryl-thiosulfonate, prepared from polystyryl- sulfonyl chloride and KHS, was observed to selectively react with model electrophilic mutagens such as alkyl halides, ct-chloroketones and α-chloroesters to produce polystyryl-thiosulfonlc esters. After separation from other nonreactive organic compounds, the beads then reacted with ethanethiol to produce unsymmetrical ethyl disulfides which are easily detected by GC/MS. For one mutagenic compound, only one unsymmetrical disulfide was found to contain its structure part. Thus, the structure of the parent mutagens could be deduced from that of the unsymmetrical disulfides. The degree of functionalization of the potassium polystyryl-thiosulfonate resin was 1.11 mmol/g. Its reactivity was discussed and its recycling method was reported here.

Synergistic effect between Er-doped MoS_(2)nanosheets and interfacial Mo-N coupling phases for enhanced electrocatalytic hydrogen evolution

Hydrogen production via electrochemical water splitting is a promising and green technology.As one of the most representative transition metal sulfides layered materials,Molybdenum disulfide(MoS_(2))has immense potential for the hydrogen evolution reaction(HER).We successfully prepared a nitrogen-doped carbon(NC)in situ-grown erbium-doped MoS_(2)polyhedral structure(Er-MoS_(2)/NC)that incorporates an interfacial Mo-N coupling phase.

Experimental studies on the Danxia landscape morphogenesis in Mt. Danxiashan, South China

The formation of Danxia landscapes is too slow to be observed in our life time and the paleoclimates in which Danxia landscapes developed are significantly different from the present. Thus, this study adopted experimental approaches to examine the lithological and paleoclimatic control on the formation of various landscape morphologies in the Mt. Danxiashan, South China. A total of 122 rock samples were collected from a range of Danxia landscape morphologies such as white spots, small and large through caves, honeycomb caves, horizontal grooves, natural bridges, stone pillars, and squama stones. Analyses of the collected samples were conducted in different kinds of experiments, including uniaxial mechanical strength testing; rock resistance against sulfuric acid erosion, freezing, and thawing; X-ray fluorescence spectrometry（XRF） analysis; inductively coupled plasma mass spectrometry（ICP-MS） analysis; and identification analysis under a polarizing microscope. The results indicated that the formation of the various Danxia landscape morphologies could result from one or more of the following processes： differential erosion due to lithological difference, chemical dissolution and recrystallization, freezing and thawing actions, acid corrosion, weathering, lateral erosion of river flows, and tectonic uplifts. Water erosion in humid monsoon climate and the alternations of intensive freezing and thawing actions in the Quaternary glacial stages and the interglacial stages could have had great influences on the formation of Danxia landscape topographies.

DNA-PKcs promotes alcohol-related liver disease by activating Drp1-related mitochondrial fission and repressing FUNDC1-required mitophagy

DNA-dependent protein kinase catalytic subunit(DNA-PKcs)is a novel housekeeper of hepatic mitochondrial homeostasis outside the DNA repair process.In this study,DNA-PKcs was upregulated in the livers of mice that were exposed to alcohol;the expression of DNA-PKcs positively correlated with hepatic steatosis,fibrosis,apoptosis,and mitochondrial damage.Functional studies revealed that liver-specific DNA-PKcs knockout(DNA-PKcsLKO)mice were protected from chronic ethanol-induced liver injury and mitochondrial damage.Mechanistic investigations established that DNA-PKcs promoted p53 activation,which elevated dynamin-related protein 1(Drp1)-related mitochondrial fission but repressed FUN14 domain containing 1(FUNDC1)-required mitophagy.Excessive fission and defective mitophagy triggered mtDNA damage,mitochondrial respiratory inhibition,mROS overproduction,cardiolipin oxidation,redox imbalance,calcium overload,and hepatic mitochondrial apoptosis.In contrast,the deletion of DNA-PKcs rescued these phenotypic alterations,which alleviated the susceptibility of hepatocytes to alcohol-induced cytotoxicity.Additionally,we also showed that orphan nuclear receptor subfamily 4 group A member 1(NR4A1)was the upstream signal for DNA-PKcs activation and that the genetic ablation of NR4A1 ameliorated the progression of alcohol-related liver disease(ARLD);these results were similar to those obtained in DNA-PKcs knockout mice.Collectively,our results identified the NR4A1/DNA-PKcs/p53 axis as a novel signaling pathway responsible for ARLD pathogenesis that acts by activating Drp1-related mitochondrial fission and restricting FUNDC1-required mitophagy.The findings have potential implications for new approaches for ARLD therapy.