Improved performance low-cost incremental conductance PV MPPT technique

Variable-step incremental conductance (Inc.Cond.) technique, for photovoltaic (PV) maximum power point tracking, has merits of good tracking accuracy and fast convergence speed. Yet, it lacks simplicity in its implementation due to the mathematical division computations involved in its algorithm structure. Furthermore, the conventional variable step-size, based on the division of the PV module power change by the PV voltage change, encounters steadystate power oscillations and dynamic problems especially under sudden environmental changes. In this study, an enhancement is introduced to Inc.Cond. algorithm in order to entirely eliminate the division calculations involved in its structure. Hence, algorithm implementation complexity is minimised enabling the utilisation of low-cost microcontrollers to cut down system cost. Moreover, the required real processing time is reduced, thus sampling rate can be improved to fasten system response during sudden changes. Regarding the applied step-size, a modified variable-step size, which depends solely on PV power, is proposed. The latter achieves enhanced transient performance with minimal steady-state power oscillations around the MPP even under partial shading. For proposed technique's validation, simulation work is carried out and an experimental set up is implemented in which ARDUINO Uno board, based on low-cost Atmega328 microcontroller, is employed

Assessment Of The Global Fallout Of Plutonium Isotopes In The Topsoil Of Qatar: Establishing A Baseline Concentrations Of 238pu, 239pu, And 240pu

A radio-analytical technique for determination of plutonium (Pu) isotopes in soil samples is tested against NIST and IAEA standard reference materials to determine its accuracy and precision for reliable results. The technique is then used in the investigation of 132 topsoil samples, collected from the natural environment of Qatar, to assess the effect of global fallout accumulation of these radionuclides in the region. Plutonium was sequentially leached form 1000 g of each soil sample using nitric and hydrochloric acids. The residual fine particles were separated by filtration and centrifuge. The solution was reduced to 1 ml by evaporation in dry oven and measured directly by CRC-ICP-MS/MS without prior chemical separation of Pu. The concentrations of 238Pu in the collected soil samples vary from < 0.026 - 0.058 fg/g (< 0.0160 - 0.0266 Bq/kg) with a mean value of 0.034 fg/g (0.0195 Bq/kg) and a median value of 0.032 fg/g (0.0195 Bq/kg). The concentrations of 239Pu fall in the range 5.67 - 166.09 fg/g (0.014 - 0.381 Bq/kg) with a mean value of 67.33 fg/g (0.154 Bq/kg) and a median value of 63.21 fg/g (0.145 Bq/kg). The concentrations of 240Pu fall in the range 1.48 - 28.21 fg/g (0.013 - 0.240 Bq/kg) with a mean value of 11.46 fg/g (0.098 Bq/kg) and a median value of 10.835 fg/g (0.093 Bq/kg). The isotopic and activity concentrations ratios of 238Pu/239Pu, 240Pu/239Pu, and 238Pu/239+240Pu can be used to identify the source. The main isotope ratios of 238Pu/239Pu in Qatari soils is (3.33 ± 1.02) x 10-4. A reported global and Chernobyl fallouts isotope ratio of 238Pu/239Pu are 1.77 x 10-4 and 4.3 x 10-3, respectively. The main isotope ratio of 240Pu/239Pu in Qatari soils is 0.1749 ± 0.0211. A reported global and Chernobyl fallouts isotope ratios of 240Pu/239Pu are 0.18-0.19 and 0.34-0.57, respectively. The average isotopic and activity ratios of 238Pu/239,240Pu in Qatari soils are (2.856 ± 0.881) x 10-4 and 0.0505 ± 0.0032, respectively. The activity ratio 238Pu/239+240Pu in releases from nuclear fuel reprocessing plants, nuclear tests, weapons grade, and Chernobyl fallout are about 0.25, 0.026, 0.014 and 0.47, respectively. Accordingly, it is difficult to identify the source, but it may be due to the contribution of more than one source. The most probable sources are both Chernobyl fallout of Pu isotopes and several decades of fallout Pu accumulation due to nuclear weapons testing. Novel Aspect New data base was established for the concentration and isotope ratios of Pu isotopes (238Pu, 239Pu, and 240Pu) in Qatar topsoil.qscienc

Optimization, Purification and Physicochemical Characterization of Curdlan Produced by Paenibacillus sp. Strain NBR-10

In recent years, significant progress has been done to discover a novel microbial exopolysaccharides that possess novel and highly functional properties. During our screening program for curdlan producing bacteria, 35 bacterial strains were isolated from 15 sandy soils collected from Rafha governorate, Northern Border region, Saudi Arabia. Among them isolate, NBR-10 was selected for its promising ability for curdlan production. The selected isolate was identified based on methods or results mentioned in this paper as Paenibacillus sp. For enhancing the curdlan yield produced by Paenibacillus sp. NBR-10, different culture conditions and medium compositions were optimized. It was found that, the maximum yield was obtained at 35 °C, initial pH 7 after 48 h of incubation. Also different carbon and nitrogen sources were used to improve the curdlan yield, it was indicated that sucrose and yeast extract were the best carbon and nitrogen sources respectively. Generally, optimization of the different parameters was approximately duplicated the curdlan yield from 2.34 g/l to 4.82 g/l. The precipitated curdlan dissolved in 2M NaOH exhibited high affinity to gel formation. Analysis of FT-IR, 1 H NMR and 13 C NMR spectra proved that the produced polymer by Paenibacillus sp. NBR-10 has β β β β β-(1-3)-D-glucan (curdlan) structure

Synthesis and biological evaluation of novel cYY analogues targeting Mycobacterium tuberculosis CYP121A1

The rise in multidrug resistant (MDR) cases of tuberculosis (TB) has led to the need for the development of TB drugs with different mechanisms of action. The genome sequence of Mycobacterium tuberculosis (Mtb) revealed twenty different genes coding for cytochrome P450s. CYP121A1 catalyzes a C-C crosslinking reaction of dicyclotyrosine (cYY) producing mycocyclosin and current research suggests that either mycocyclosin is essential or the overproduction of cYY is toxic to Mtb. A series of 1,4-dibenzyl-2-imidazol-1-yl-methylpiperazine derivatives were designed and synthesised as cYY mimics. The derivatives substituted in the 4-position of the phenyl rings with halides or alkyl group showed promising antimycobacterial activity (MIC 6.25 μg/mL), with the more lipophilic branched alkyl derivatives displaying optimal binding affinity with CYP121A1 (iPr KD = 1.6 μM; tBu KD = 1.2 μM). Computational studies revealed two possible binding modes within the CYP121A1 active site both of which would effectively block cYY from binding

THE POWER OF INTEGRATION TOWARDS SUSTAINABLE PERFORMANCE: A MODEL TO MINIMIZE TECHNOSTRESS AMONG FRONTLINE RESTAURANT EMPLOYEES BY COMBINING JOB AND EMPLOYEE RESOURCES

To develop a model that integrates restaurant and employee resources to overcome technostress and achieve sustainable performance. This qualitative study is based on twenty-two semi-structured interviews with restaurant managers and frontline employees (FLEs) to comprehensively understand how restaurant resources and personnel can be employed to combat technostress and achieve sustainable performance. Restaurant FLEs experience technostress from multiple sources, including unclear work-life boundaries, complex new systems, job insecurity, and the frequent use of new technologies. In addition, restaurant managers and FLEs concur that integrating restaurant and FLE resources is an effective model for reducing technostress and achieving FLEs' sustainable performance. The study expands the JD-R model to address the challenges faced by FLEs in managing technology-induced job demands, offering a comprehensive solution that benefits restaurants and employees. This approach considers the role of both employers and employees in managing technostress, leading to a supportive work environment and improved sustainable performance

LOCUS OF CONTROL THEORY IN TREATING TOURIST BEHAVIOR: THE THEORY ROOTS AND RESEARCH DIRECTION IN DESTINATION BRANDING FIELD

We aim to shed light on this issue by reviewing the roots and development of the locus of control theory. Moreover, we will introduce how we can use this development, in theory, to provide a new research direction in the tourism service field. A theory-based review was conducted to investigate the locus of control theory roots and its potential implications in the tourism industry using the Australian Business Deans Council (ABDC) list to explore the current literature. We followed the PRISMA methodology to collect the data from the Scopus database as well as Google Scholar and ResearchGate. The study found that the locus of control theory has its roots in social psychology and has been developed over the years to explain individual differences in behavior and decision-making. In the tourism service field, we found that understanding the locus of control can help service providers tailor their services to meet the needs and expectations of different types of tourists. This will contribute to attribution literature in psychological aspects and tourism literature with a deep understanding of how tourists behave and interpret differently

Alterations in the transcriptome and antibiotic susceptibility of Staphylococcus aureus grown in the presence of diclofenac

<p>Abstract</p> <p>Background</p> <p>Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) which has been shown to increase the susceptibility of various bacteria to antimicrobials and demonstrated to have broad antimicrobial activity. This study describes transcriptome alterations in <it>S. aureus </it>strain COL grown with diclofenac and characterizes the effects of this NSAID on antibiotic susceptibility in laboratory, clinical and diclofenac reduced-susceptibility (Dc^RS) <it>S. aureus </it>strains.</p> <p>Methods</p> <p>Transcriptional alterations in response to growth with diclofenac were measured using <it>S. aureus </it>gene expression microarrays and quantitative real-time PCR. Antimicrobial susceptibility was determined by agar diffusion MICs and gradient plate analysis. Ciprofloxacin accumulation was measured by fluorescence spectrophotometry.</p> <p>Results</p> <p>Growth of <it>S. aureus </it>strain COL with 80 μg/ml (0.2 × MIC) of diclofenac resulted in the significant alteration by ≥2-fold of 458 genes. These represented genes encoding proteins for transport and binding, protein and DNA synthesis, and the cell envelope. Notable alterations included the strong down-regulation of antimicrobial efflux pumps including <it>mepRAB </it>and a putative <it>emrAB/qacA</it>-family pump. Diclofenac up-regulated <it>sigB </it>(σ^B), encoding an alternative sigma factor which has been shown to be important for antimicrobial resistance. <it>Staphylococcus aureus </it>microarray metadatabase (SAMMD) analysis further revealed that 46% of genes differentially-expressed with diclofenac are also σ^B-regulated. Diclofenac altered <it>S. aureus </it>susceptibility to multiple antibiotics in a strain-dependent manner. Susceptibility increased for ciprofloxacin, ofloxacin and norfloxacin, decreased for oxacillin and vancomycin, and did not change for tetracycline or chloramphenicol. Mutation to Dc^RSdid not affect susceptibility to the above antibiotics. Reduced ciprofloxacin MICs with diclofenac in strain BB255, were not associated with increased drug accumulation.</p> <p>Conclusions</p> <p>The results of this study suggest that diclofenac influences antibiotic susceptibility in <it>S. aureus</it>, in part, by altering the expression of regulatory and structural genes associated with cell wall biosynthesis/turnover and transport.</p

Alterations In the Transciptome and Antibiotic Susceptibility of \u3ci\u3eStaphylococcus aureus\u3c/i\u3e Grown In the Presence of Diclofenac

Background Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) which has been shown to increase the susceptibility of various bacteria to antimicrobials and demonstrated to have broad antimicrobial activity. This study describes transcriptome alterations in S. aureus strain COL grown with diclofenac and characterizes the effects of this NSAID on antibiotic susceptibility in laboratory, clinical and diclofenac reduced-susceptibility (DcRS) S. aureus strains. Methods Transcriptional alterations in response to growth with diclofenac were measured using S. aureus gene expression microarrays and quantitative real-time PCR. Antimicrobial susceptibility was determined by agar diffusion MICs and gradient plate analysis. Ciprofloxacin accumulation was measured by fluorescence spectrophotometry. Results Growth of S. aureus strain COL with 80 μg/ml (0.2 × MIC) of diclofenac resulted in the significant alteration by ≥2-fold of 458 genes. These represented genes encoding proteins for transport and binding, protein and DNA synthesis, and the cell envelope. Notable alterations included the strong down-regulation of antimicrobial efflux pumps including mepRAB and a putative emrAB/qacA-family pump. Diclofenac up-regulated sigB (σB), encoding an alternative sigma factor which has been shown to be important for antimicrobial resistance. Staphylococcus aureus microarray metadatabase (SAMMD) analysis further revealed that 46% of genes differentially-expressed with diclofenac are also σB-regulated. Diclofenac altered S. aureus susceptibility to multiple antibiotics in a strain-dependent manner. Susceptibility increased for ciprofloxacin, ofloxacin and norfloxacin, decreased for oxacillin and vancomycin, and did not change for tetracycline or chloramphenicol. Mutation to DcRS did not affect susceptibility to the above antibiotics. Reduced ciprofloxacin MICs with diclofenac in strain BB255, were not associated with increased drug accumulation. Conclusions The results of this study suggest that diclofenac influences antibiotic susceptibility in S. aureus, in part, by altering the expression of regulatory and structural genes associated with cell wall biosynthesis/turnover and transport

Microfluidic-Based Formulation of Essential Oils-Loaded Chitosan Coated PLGA Particles Enhances Their Bioavailability and Nematocidal Activity

In this study, poly (lactic-co-glycolic) acid (PLGA) particles were synthesized and coated with chitosan. Three essential oil (EO) components (eugenol, linalool, and geraniol) were entrapped inside these PLGA particles by using the continuous flow-focusing microfluidic method and a partially water-miscible solvent mixture (dichloromethane: acetone mixture (1:10)). Encapsulation of EO components in PLGA particles was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction, with encapsulation efficiencies 95.14%, 79.68%, and 71.34% and loading capacities 8.88%, 8.38%, and 5.65% in particles entrapped with eugenol, linalool, and geraniol, respectively. The EO components’ dissociation from the loaded particles exhibited an initial burst release in the first 8 h followed by a sustained release phase at significantly slower rates from the coated particles, extending beyond 5 days. The EO components encapsulated in chitosan coated particles up to 5 μg/mL were not cytotoxic to bovine gut cell line (FFKD-1-R) and had no adverse effect on cell growth and membrane integrity compared with free EO components or uncoated particles. Chitosan coated PLGA particles loaded with combined EO components (10 µg/mL) significantly inhibited the motility of the larval stage of Haemonchus contortus and Trichostrongylus axei by 76.9%, and completely inhibited the motility of adult worms (p < 0.05). This nematocidal effect was accompanied by considerable cuticular damage in the treated worms, reflecting a synergistic effect of the combined EO components and an additive effect of chitosan. These results show that encapsulation of EO components, with a potent anthelmintic activity, in chitosan coated PLGA particles improve the bioavailability and efficacy of EO components against ovine gastrointestinal nematodes

Exosomal miR-940 maintains SRC-mediated oncogenic activity in cancer cells: a possible role for exosomal disposal of tumor suppressor miRNAs

Exosomes have emerged as important mediators of diverse biological functions including tumor suppression, tumor progression, invasion, immune escape and cell-to-cell communication, through the release of molecules such as mRNAs, miRNAs, and proteins. Here, we identified differentially expressed exosomal miRNAs between normal epithelial ovarian cell line and both resistant and sensitive ovarian cancer (OC) cell lines. We found miR-940 as abundant in exosomes from SKOV3-IP1, HeyA8, and HeyA8-MDR cells. The high expression of miR-940 is associated with better survival in patients with ovarian serous cystadenocarcinoma. Ectopic expression of miR-940 inhibited proliferation, colony formation, invasion, and migration and triggered G0/G1 cell cycle arrest and apoptosis in OC cells. Overexpression of miR-940 also inhibited tumor cell growth in vivo. We showed that proto-oncogene tyrosine-protein kinase (SRC) is directly targeted by miR-940 and that miR-940 inhibited SRC expression at mRNA and protein levels. Following this inhibition, the expression of proteins downstream of SRC, such as FAK, paxillin and Akt was also reduced. Collectively, our results suggest that OC cells secrete the tumor-suppressive miR-940 into the extracellular environment via exosomes, to maintain their invasiveness and tumorigenic phenotype