Use Of Resistance Research Articles

An experimental study of I beam-RHS column demountable joints with welded studs

This paper presents the results of an extensive experimental investigation on the behaviour of a new type of joint between open structural steel beam and rectangular hollow section (RHS) column. The proposed joint is demountable: threaded studs are welded to the front face of the hollow section column and angle cleat legs are then bolted to the column by means of the welded studs and to the beam flanges by ordinary bolts. Twenty-one full-scale single side or double side bolted beam-column joints combining different sections have been tested under monotonic and cyclic loads. The test results confirm that these joints behave as semi rigid and partial strength ones which possess sufficient stiffness and moment resistance for use in the construction of low to medium-rise steel buildings as an alternative to other traditional solutions. The proposed joints also exhibit a moderate energy dissipation capacity under cyclic loads, suitable for construction in moderate seismic regions. This research work demonstrates that the proposed joint is easy to execute on site without specialized manpower or expensive facilities.

Effect of Different Reinforced Metal-Matrix Composites on Mechanical and Fracture Behaviour of Aluminium Piston Alloy

Al-Si10Cu2Fe and Al-Si12Cu aluminium alloy composites were fabricated by using various weight percentage of SiC and TiB2 reinforcement particles in a two-step stir-casting process to improve their corrosion resistance for use in transport, aerospace and marine industries. Morphological and microstructural analysis of the composites were carried out using field-emission scanning electron microscopy and energy dispersive X-ray spectrometry, respectively. The results indicated a homogeneous distribution of the SiC and TiB2 particles in the matrix, resulting in enhanced materials with better mechanical properties. The improvement of the tensile strength and elastic modulus for Al-Si12Cu–7%TiB2 was 73% and 15.3%, respectively, as compared with the Al-Si10Cu2Fe matrix alloy. The uniform incorporation of SiC and TiB2 microparticles increases the bonding strength with the matrix and improves the hardness. These properties are useful to improve the tribological behaviour.

Establishment of a Rolling-Sliding Test Bench to Analyze Abrasive Wear Propagation of Different Bearing Materials for Knee Implants

Currently, new materials for knee implants need to be extensively tested but such tests are expensive in a knee wear simulator in a realized design. However, using a rolling-sliding test bench, these materials can be examined under the same test conditions, but with simplified geometries. In the present study, the test bench was optimized, and forces were adapted to the physiological contact pressure in the knee joint using the available geometric parameters. Various polymers made of polyethylene and polyurethane, articulating against test wheels made of cobalt-chromium and aluminum titanate, were tested in the test bench using adapted forces based on ISO 14243–1. Polyurethane materials showed distinctly higher wear rates than polyethylene materials and showed inadequate wear resistance for use as knee implant material. Thus, the rolling-sliding test bench is an adaptable test setup to evaluate newly developed bearing materials for knee implants. It combines the advantages of screening and simulator tests and allows for the testing of various bearing materials under physiological load and tribological conditions of the human knee joint. The wear behavior of different material compositions and the influence of surface geometry and quality can be initially investigated without the need to produce complex implant prototypes of total knee endoprosthesis or interpositional spacers.

Silicate Spray-Coated Nickel-Plated Titanium Alloy for Space Applications: Corrosion Resistance and Thermo-optical Properties

An inorganic silicate black spray coating (BSC) is employed on the blackened electroless nickel (ENB)-plated Ti-6Al-4V to enhance thermo-optical properties as well as corrosion resistance for use in spacecraft thermal control applications. The composite coating (BSC-coated ENB) is characterized with respect to impedance spectroscopy and potentiodynamic polarization to evaluate corrosion resistance. The results indicated that the corrosion resistance of the ENB specimen could be improved by post-spray coating due to reduction in porosity rate from 8.4 to 1.7. Further to ascertain the space worthiness of the composite coating, thermo-optical properties before and after the environmental tests (humidity, thermo-vacuum and thermal cycling tests) were measured. The composite coating showed a marked enhancement in solar absorptance (αs≥ 0.94) and infrared emittance (eIR≥0.84) values as compared to ENB specimen. Hence, the proposed composite coating demonstrated greater potential to be used in advanced thermal control applications in spacecraft where enhanced corrosion resistance and thermo-optical properties are essential.

Epoxy Nanocomposites with Increased Hydroabrasive Wear Resistance for Use in Vehicles

Epoxy Nanocomposites with Increased Hydroabrasive Wear Resistance for Use in Vehicles

Paclitaxel exposure downregulates miR-522 expression and its downregulation induces paclitaxel resistance in ovarian cancer cells

Paclitaxel resistance is a critical challenge in ovarian cancer treatment. This study aimed to identify microRNAs (miRNAs) that modulate paclitaxel resistance for use as potential therapeutic targets in such settings. Paclitaxel-resistant cell lines were established using two ovarian cancer cell lines: SKOV3ip1 and HeyA8. The evaluation of miRNA polymerase chain reaction (PCR) arrays indicated that the expression of miR-522-3p was downregulated in paclitaxel-resistant cells. The restoration of miR-522-3p sensitized the resistant cells to paclitaxel, and its downregulation desensitized the parental cells. Using PCR arrays, we focused on E2F2, with the luciferase reporter assay revealing that it was a direct target for miR-522-3p. The paclitaxel-resistant cells showed stronger E2F2 expression than the parental cells, while E2F2 inhibition sensitized the resistant cells to paclitaxel. Forced E2F2 expression in the parental cells led to the acquisition of paclitaxel resistance, while miR-522-3p inhibited E2F2 expression and was associated with retinoblastoma protein phosphorylation attenuation, which resulted in G0/G1 arrest. The effects of miR-522-3p and E2F2 in ovarian cancer were examined using public databases, revealing that low miR-522-3p expression and high E2F2 expression were associated with significantly poorer overall survival. In conclusion, miR-522-3p attenuated the degree of paclitaxel resistance in vitro through the downregulation of E2F2; miR-522-3p supplementation may be a therapeutic target for paclitaxel-resistant ovarian cancer.

In Vivo Activity of QPX7728, an Ultrabroad-Spectrum Beta-Lactamase Inhibitor, in Combination with Beta-Lactams against Carbapenem-Resistant Klebsiella pneumoniae.

Resistance to beta-lactams has created a major clinical issue. QPX7728 is a novel ultrabroad-spectrum cyclic boronic acid beta-lactamase inhibitor with activity against both serine and metallo-beta-lactamases developed to address this resistance for use in combination with beta-lactam antibiotics. The objective of these studies was to evaluate the activity of QPX7728 in combination with multiple beta-lactams against carbapenem-resistant Klebsiella pneumoniae isolates in a neutropenic mouse thigh infection model. Neutropenic mice were infected with strains with potentiated beta-lactam MICs of ≤2 mg/liter in the presence of 8 mg/liter QPX7728. Two strains of carbapenem-resistant K. pneumoniae were tested with aztreonam, biapenem, cefepime, ceftazidime, ceftolozane, and meropenem alone or in combination with 12.5, 25, or 50 mg/kg of body weight of QPX7728 every 2 hours for 24 hours. Treatment with all beta-lactams alone either was bacteriostatic or allowed for bacterial growth. The combination of QPX7728 plus each of these beta-lactams produced bacterial killing at all QPX7728 doses tested. Overall, these data suggest that QPX7728 administered in combination with different partner beta-lactam antibiotics may have utility in the treatment of bacterial infections due to carbapenem-resistant K. pneumoniae.

Hydrothermal corrosion of 2nd generation FeCrAl alloys for accident tolerant fuel cladding

As part of an effort to develop advanced fuel cladding for use in light water reactors, several FeCrAl alloys have been developed at Oak Ridge National Laboratory. A second generation of these alloys bearing additional alloying elements over the previously tested model alloys were tested in boiling water reactor (BWR) conditions to determine their resistance to hydrothermal corrosion. Coupons with alloy compositions Fe–10Cr–6Al–2Mo, Fe–13Cr–5Al–2Mo, Fe–13Cr–6Al–2Mo, Fe–13Cr–7Al–2Mo, and Fe–13Cr–5Al–2Mo–1Nb were tested in normal water chemistry (NWC) and hydrogen water chemistry (HWC) for 9 months in continuously refreshing autoclaves. Commercial FeCrAl alloy APMT and Zircaloy-2 were also tested for comparison. Among samples exposed to HWC, Fe–13Cr–7Al–2Mo performed worst with an average mass loss of 1.3 mg/cm2 over 9 months. This mass loss represents an estimated thickness loss of approximately 60 μm over 6 years. Samples exposed to NWC had very small mass losses of less than 0.15 mg/cm2 or mass gains up to 0.05 mg/cm2. Based on the results of this testing, the 2nd generation FeCrAl alloys tested exhibit low wall thickness loss and are suitable in terms of corrosion resistance for use as LWR cladding in BWR-HWC and BWR-NWC under normal operating conditions.

Characterization of a bean rugose mosaic virus isolate and search for virus resistance in a germplasm bank of Phaseolus vulgaris

Common bean is an economically important crop grown in several areas in the world. Among the constraints for this crop development, bean rugose mosaic virus (BRMV) infections can potentially lead to serious yield reduction. Genetic resistance is the most effective control method, and the search for sources of resistance is an essential step. The objective of this study was to biologically characterize the BRMVGO isolate and search for virus resistance in germplasm accessions of Phaseolus vulgaris L. To biologically characterize the isolate, 15 plants, selected from a list of indicators, were inoculated, among them soybean (Glycine max L) and pea (Pisum sativum L). The host range demonstrated that the virus can infect different plant species, reinforcing the need for resistance sources. In order to screen for resistance, 172 P. vulgaris accessions were inoculated with the isolate and scored for disease symptoms at 5, 21 and 30 days after inoculation. Among the evaluated accessions, four exhibited hypersensitive reactions (HR) while the remaining showed typical susceptible reactions. The virus seemed to be restricted and could not be retrieved from the common bean accessions showing HR and they are likely interesting sources of resistance for use in breeding programs.

Perspectives of metal-diamond composites additive manufacturing using SLM-SPS and other techniques for increased wear-impact resistance

In this paper, a new route is introduced to fabricate parts with increased wear and impact resistance for use in tunneling and mining applications. A combination of selective laser melting (SLM) and spark plasma sintering (SPS) to 3D print functionally graded lattices (FGL) that are later filled with metal-diamond composites was used. It was demonstrated that a cellular lattice plays an important role in the consolidation of diamond particles. Impact-abrasive laboratory experiments with tribological device, developed in-house, were carried out to characterize the fabricated samples. The results show that the balance of nickel, molybdenum, and chromium significantly affects the performance of the fabricated specimens. The addition of a higher content of MoCr, Ni and coated diamond particles guarantees higher impact-abrasive resistance of the composite. Our experimental results show that the FGL structure allows a more accurate distribution of diamond particles (variable metal/refractory material content) across the structure and our finite element simulations showed increased ductility and impact absorption ability due to a more uniform distribution of stresses throughout the volume.

Exploring resistance factors on the usage of hospital information systems from the perspective of the Markus’s Model and the Technology Acceptance Model

Although information systems provide many benefits to the organization, many organizations are experiencing difficulties with the process of change. Resistance to change is one of the most considerable challenges in this phase. This study aimed to investigate the causes of resistance by healthcare personnel to IT in Adana Numune Hastanesi, which is a state-run hospital located in Adana, Turkey. The Technology Acceptance Model (TAM) was expanded by adding factors such as affective commitment, gender, and age. Logistic regression analysis was carried out on the research model through 291 collected survey data using SPSS (version 21). The overall percentage accuracy prediction was 55.3% for parameters of the initial model and 80.8% for the stepwise model after the third step. According to the results, while the factors “perceived usefulness of IT,” “perceived ease of use of IT,” and “affective commitment” were found to have an influence on the resistance of use of IT, demographic factors such as age, gender, position, and tenure were not related. Managers should create an environment for increasing staff commitment by including them in decision-making and process changing. Thus, not only could the manager use the organizations’ resources productively, but also future change projects could be carried out effectively, roughly, and timely. Therefore, through its committed personnel, the hospital could sustainably compete with its competitors in the market and make more profit.

Исследование диодов Шоттки на стойкость для применения в радиоэлектронной аппаратуре

The article presents the method of evaluation and results of research Schottky diodes resistance for use in electronic equipment. Studies were carried out to determine the structural and technological reserves for durability. Also in the article the schemes of inclusion of Schottky diodes for measurement of direct reverse current and direct excitation of the diode applied at researches are considered.

Intrinsically Stretchable and Shape Memory Conducting Nanofiber for Programmable Flexible Electronic Films.

Recently, flexible and stretchable electronic films have been drawing increasing attention but are limited by the nature of elastomeric materials and the embedded structure; thus, these films cannot achieve long-term and stable electrical performance at certain deformation states in practical applications. Here, we report intrinsically stretchable and shape memory polycaprolactone/polyethylene glycol/silver nanowires films (PPAFs) based on a dual-layer network structure of nanofibers that can achieve both shape-fixable and deformation-reversible conductivity in the elongation range. We also demonstrate the resistance characteristic of PPAFs at the same/different deformation rates, which shows the unique memorable resistance and the variable conversion of a "conductive-insulation-conductive" state. Importantly, the change in sheet resistance of the PPAFs fixed at any rate of deformation could sustainably recover the initial sheet resistance even after cyclic thermal responses. Furthermore, we successfully develop the programmable conductivity of PPAFs as a monitoring, switching, and alarming device for shape memory cycles through the ingenious design of a microcircuit and simulation analysis using Proteus software. PPAFs show great potential for changeable characteristics in both shape and resistance for use in flexible electronic films.

SCREENING OF THE CUCUMBER COLLECTION FOR RESISTANCE TO DOWNY MILDEW IN THE LOWER VOLGA REGION

Background. Currently, the most widespread and harmful disease of cucumber is downy mildew. In this regard, a vitally important trend in cucumber breeding is the development of new cultivars, more resistant to downy mildew, for cultivation in different regions. Solution to this problem requires searching for donors of resistance for use in breeding practice.Materials and methods. The studies were conducted at Volgograd Experiment Station of VIR using conventional methods. The material for the screening was the collection of cucumber genetic resources held by VIR.Results and conclusions. During 32 years of work, 2873 cucumber accessions from VIR’s holdings were screened. As a result, 57 accessions with resistance or relative resistance to downy mildew were identified, i. e. 2.0% of the total number studied. Immune accessions were not found. Among the selected accessions, those with the highest yield are noteworthy: landraces from Azerbaijan (temp. k-3999 and temp. k-4004) as well as the cultivars from China ‘Zungsungerum-oi’ (temp. k-3701), ‘Tianin mini cucumber’ (k-4490), ‘Tian Uzin Yao No. 5’ (temp. k-3840) and ‘Tian Uzin Yang No. 6’ (temp. k-3841). Of the resistant and relatively resistant accessions, 76% were from Southeast Asia. During the years of study, 23 accessions, previously resistant to downy mildew, lost their resistance and suffered severe damage from the disease. Hence, it seems obvious that resistant accessions should be periodically retested for susceptibility to downy mildew. Twenty accessions were selected to form a group of tolerant ones. Of these, ‘Yeo leam sam chuk oi’ (k-4545), ‘Crispy Top F1’ (temp. k-3549) and ‘Pchelka F1’ (temp. k-3981) had the highest average yield.

Structural and electrochemical study of resorbable Ca32Mg12Zn38Yb18-xBx (x=1, 2, 3) metallic glasses in Ringer's solution

A new class of CaZn-based bulk glassy alloys with minor addition of boron and enhanced corrosion resistance for use in bioresorbable materials is introduced. The CaMgZnYbB alloys represent a new family of biomaterials with potential applications in orthopedic implants with controlled degradation rates and corrosion in the human body. The effect of substituting Yb for B in the structure on the corrosion and mechanical properties of quinternary Ca32Mg12Zn38Yb18-xBx (x = 1,2,3 at.%) alloys was investigated using X-ray diffraction, high-resolution transmission electron microscopy, differential scanning calorimetry, immersion and electrochemical polarization, compressive tests, and hardness measurements. The corrosion behavior was also evaluated using electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Microstructural investigations showed that the Ca32Mg12Zn38Yb16B2 alloy was mainly amorphous, while small reflections from nanocrystals were observed in Ca32Mg12Zn38Yb17B1 and Ca32Mg12Zn38Yb15B3. Electrochemical polarization and immersion tests in Ringer's solution at 37 °C revealed that the CaMgZnYbB alloys had significantly higher corrosion resistance than CaMgZn alloys. Electrochemical impedance spectroscopy of alloys showed only single capacitive loops. The corrosion products were identified as CaO, MgO, Mg(OH)2, and CaCO3. The compressive strengths of the alloys from 220 MPa to 283 MPa were suitable for implant applications.

Distinct immune response profile during rhipicephalus (boophilus) microplus infestations of guzerat dairy herd according to the maternal lineage ancestry (mitochondrial DNA)

Rhipicephalus (Boophilus) microplus ticks cause major constraints to public and livestock health, and serious economic losses. It is well known that the immune response to infestations with cattle ticks is influenced by the host genetic background leading to distinct immunological profiles between bovine hosts genetically susceptible and resistant. The influence of Bos indicus (Bi) and Bos taurus (Bt) maternal lineage ancestry of mitochondrial DNA in the profile of the immune response of Zebu cattle to ticks remains unknown. The present work evaluated the hematological parameters and the immune response profile in the peripheral blood of a Guzerat dairy herd, further categorized into two maternal lineage ancestry subgroups (Bi-mtDNA and Bt-mtDNA) after experimental infestation with larvae of R. microplus. Our data demonstrated that although hematological and erythrogram analysis showed a similar profile throughout, some cell populations present a distinct profile between the groups. Especially MON, CD335+ and CD8+ T-cells are predominant in Bi-mtDNA. Moreover, an overall picture of R. microplus infestation demonstrated that Bi-mtDNA presented a more efficient and earlier innate immune response. Bi-mtDNA showed a greater number of connections with R. microplus counts and also with the CD25+ activation marker of the immune response. Bi-mtDNA showed greater number of connections, with an important participation of the innate immune while Bt-mtDNA showed a delay in the immune response. Elucidating the mechanisms by which resistant animals prevent heavy tick infestation is a crucial step in the development of predictive biomarkers for tick resistance for use in selective breeding programs, and is also potentially useful for the development of anti-tick vaccines.

Microbial Contamination and Antimicrobial Resistance in Use of Ophthalmic Solutions at the Department of Ophthalmology, Jimma University Specialized Hospital, Southwest Ethiopia.

Background Eye drops are most frequently used medications in ophthalmology. The carriage of pathogenic organisms to eyes through the agency of eye drops has presented a serious problem for several decades. The objective of this study was to determine the magnitude of contamination and pattern of antimicrobial resistance of in-use ophthalmic solutions. Method A cross-sectional study was conducted at the Department of Ophthalmology, Jimma University Specialized Hospital (JUSH), Southwest Ethiopia, from June to December 2015. Samples from all ophthalmic solutions from outpatient department, operation theaters, and wards after an average duration of use of two weeks were taken. Samples were cultured and organisms were identified; antimicrobial susceptibility testing was performed using standard microbial identification techniques. The data were analyzed using SPSS software. Chi-square test was done and associations were taken as significant if P < 0.05. Result The rate of contamination of eye drops in the study setup was found to be 51/70 (72.8%). Frequency of contamination of eye drops found was to be statistically associated with the duration of use of eye drops. Contaminations of eye drops were high among patients who self-administer the medications and those individuals who apply the medication less frequently. Tips of the bottles were more often contaminated than the content of the eye drop. Majority of both Gram-positive and Gram-negative organisms were sensitive for most of the broad-spectrum antibiotics; however, there were a significant number of Gram-negative organisms resistant to almost all antibiotics used. Conclusion There is high rate of contamination of eye drops in the setup (72.8%). Duration of use of eye drops is a significant factor associated with contamination. Knowing duration time of each container and patient education on eye drop administration technique are mandatory.

Progress breeding for resistance to eastern filbert blight in the eastern United States

Eastern filbert blight (EFB) is a hazelnut disease caused by Anisogramma anomala, a fungus endemic to North America where it can be found associated with the wild hazelnut Corylus americana. While C. americana is resistant to EFB, the commercial hazelnut C. avellana is highly susceptible and typically dies within 5 years from exposure. A hazelnut breeding program was initiated in 1996 at Rutgers University in New Brunswick, New Jersey. The early objective was to identify sources of resistance to EFB for use in breeding regionally adapted, EFB-resistant plants to support the establishment of a hazelnut industry in eastern USA. By working with Oregon State University (OSU) and international colleagues, germplasm collections were made in Russia, Ukraine, Poland, Georgia, Latvia, Lithuania, Estonia, Italy, and Turkey. Over 5,000 seedlings were grown and evaluated for response to EFB. While most plants succumbed to EFB, about three percent were found to be resistant. Interestingly, the resistant plants spanned nearly all collection locations and molecular markers have shown them to be highly diverse. Today, we have access to over 100 EFB-resistant accessions selected from more than 60 locations, which represents a significant pool of germplasm to support breeding. Recent studies have shown that most resistance seems to be controlled by only one or a few major genes; R-gene mapping projects are underway at Rutgers as well as Oregon State University. We continue to study new sources of resistance for use in a focused cultivar improvement program.

Porosity formation and fatigue properties of AlSiCu cast alloy

The need for aluminium alloys having a good toughness, high strength, adequate damage tolerance capability, good fatigue resistance and good corrosion resistance for use in the industries applications of aerospace, automotive and even commercial products led to study of the properties and structure of the AlSi9Cu3 cast alloy. The most important metallurgical parameters affecting the aluminium alloy’s resistance to fatigue load are the amount, types and size of casting defects. Therefore quantitative analysis was used for determination of casting defects size by optical microscopy on metallographic sections and an analysis of the size distribution by extreme value statistics. The software NIS Elements was used for quantitative analysis of casting defects and results show that porosity have a great influence on to the fatigue properties of AlSi9Cu3 cast alloy.

Development of Self-Assembled Titania Nanopore Arrays for Orthopedic Applications

Self-assembled TiO2 nanopore arrays (TNPA) were developed by electrochemical anodization. Microscopic studies revealed the presence of nanoporous surface with pore diameter and length of about 84 and 100 nm, respectively. Growth of apatite (HAp) on TNPA after immersion in Hank’s solution for different durations such as 3, 5, and 7 days was confirmed by various spectroscopic studies. Polarization study exhibited that the specimens after immersion in Hank’s solution showed high corrosion resistance which is attributed to the HAp growth on TNPA surface. Hence, TNPA is a viable material with required biocompatibility and corrosion resistance for use as orthopedic implants.