The series connections of converter cells are interesting for high voltage applications, while parallel connections are for high current applications. The series/parallel is interesting for medium ...voltage and current applications because they present semiconductor devices with a lower rating in both voltage and current, thus, reducing the cost and size of the converters. This article investigates the configuration of a single-phase multilevel DC-AC converter based on series and parallel connections of H-bridges using floating capacitors to reduce the number of independent DC sources. The use of the floating capacitor has the limitation of working in certain operating regions. This article investigates which regions can work with floating capacitors and presents the mathematical model, general control strategy, pulse width modulation (PWM) strategies, and loss comparison with conventional series or parallel systems. Simulations and experimental results are presented to validate the control and PWM strategies used.
Energy security and environmental concerns, related to the increasing carbon emissions, have prompted in the last years the search for renewable and sustainable fuels. Biodiesel, a mixture of fatty ...acids alkyl esters shows properties, which make it a feasible substitute for fossil diesel. Biodiesel can be produced using different processes and different raw materials. The most common, first generation, biodiesel is produced by methanolysis of vegetable oils using basic or acid homogeneous catalysts. The use of vegetable oils for biodiesel production raises serious questions about biodiesel sustainability. Used cooking oils and animal fats can replace the vegetable oils in biodiesel production thus allowing to produce a more sustainable biofuel. Moreover, methanol can be replaced by ethanol being totally renewable since it can be produced by biomass fermentation. The substitution of homogeneous catalyzed processes, nowadays used in the biodiesel industry, by heterogeneous ones can contribute to improve the biodiesel sustainability with simultaneous cost reduction. From the existing literature on biodiesel production, it stands out that several strategies can be adopted to improve the sustainability of biodiesel. A literature review is presented to underline the strategies allowing to improve the biodiesel sustainability.
Organic Farming (OF) is a response to challenges caused by conventional or intensive agriculture. Successful organic production depends on farmers choosing to grow organic products. The main goal of ...this study is to analyze and identify factors affecting farmers' willingness to implement OF in southwest Iran. For this, we borrowed the health belief model (HBM) from the health psychology domain. The study, a questionnaire-based cross-sectional survey in Behbahan County, Khuzestan province, in southwest Iran, comprises 320 farmers who were selected through a multistage random sampling technique. The structural equations modeling reveals that four variables - cue to action, perceived barriers, general beliefs, and perceived benefits - account for 54% of the variance in farmers' willingness toward OF. Furthermore, cue to action is the most important factor determining farmer willingness towards implementing OF. The results reveal that HBM has appropriate explanatory power and is an effective tool for investigating farmer willingness toward OF. It is suggested that government agencies use socio-psychological frameworks to develop organic agriculture. Additionally, as government agencies develop policies that increase OF, the consideration of how farmers perceive the benefits and barriers of implementing OF is critical, along with understanding their general beliefs and concerns about the use of chemical fertilizers and pesticides in conventional agriculture. Offering extension services is also key.
Renal cell carcinoma (RCC) displays a glycolytic phenotype (Warburg effect). Increased lactate production, impacting on tumor biology and microenvironment modulation, has been implicated in ...epigenetic mechanisms' regulation, leading to histone deacetylases inhibition. Thus, in-depth knowledge of lactate's impact on epigenome regulation of highly glycolytic tumors might allow for new therapeutic strategies. Herein, we investigated how extracellular lactate affected sirtuin 1 activity, a class III histone deacetylase (sirtuins, SIRTs) in RCC.
In vitro and in vivo interactions between lactate and SIRT1 in RCC were investigated in normal kidney and RCC cell lines. Finally, SIRT1 and N-cadherin immunoexpression was assessed in human RCC and normal renal tissues.
Lactate inhibited SIRT1 expression in normal kidney and RCC cells, increasing global H3 and H3K9 acetylation. Cells exposed to lactate showed increased cell migration and invasion entailing a mesenchymal phenotype. Treatment with a SIRT1 inhibitor, nicotinamide (NAM), paralleled lactate effects, promoting cell aggressiveness. In contrast, alpha-cyano-4-hydroxycinnamate (CHC), a lactate transporter inhibitor, reversed them by blocking lactate transport. In vivo (chick chorioallantoic membrane (CAM) assay), lactate and NAM exposure were associated with increased tumor size and blood vessel recruitment, whereas CHC displayed the opposite effect. Moreover, primary RCC revealed N-cadherin upregulation whereas SIRT1 expression levels were downregulated compared to normal tissues.
In RCC, lactate enhanced aggressiveness and modulated normal kidney cell phenotype, in part through downregulation of SIRT1, unveiling tumor metabolism as a promising therapeutic target.
Hornification remains a great challenge to the large‐scale use of oven‐dried microfibrillated cellulose (MFC) in industrial processes due to the difficulty to redisperse the oven‐dried MFC, ...especially in non‐polar polymer matrices. Therefore, an MFC coverage treatment with a low molecular weight copolymer is proposed here as a method to overcome hornification. MFC‐copolymer is produced by mechanical stirring and then oven‐dried. A poly(lactic acid) (PLA)/poly(ε‐caprolactone) (PCL)/MFC‐copolymer blend is prepared by melt extrusion to assess the dispersiveness of the treated MFC into the polymer matrix. Fourier Transform Infrared (FTIR) results suggest that the copolymer terminal hydroxyls can interact with the reactive hydroxyls present on the MFC surface, decreasing MFC hydrophilicity. Scanning Electron Microscopy (SEM) confirms that the copolymer covers parts of the MFC surface, which enables the microfibrils' redispersion. The solvent‐free, eco‐friendly, and low‐cost MFC‐copolymer treatment facilitates MFC redispersion by melting extrusion process in a low polarity polymeric matrix.
Remains of parasites in vertebrates are rare from the Mesozoic and Paleozoic. Once most parasites that live in - or pass through - the gastrointestinal tract of vertebrates, fossil feces (coprolites) ...or even intestinal contents (enterolites) can eventually preserve their remains. Here we announce the discovery of a spiral shark coprolite from the Paleozoic bearing a cluster of 93 small oval-elliptical smooth-shelled structures, interpreted as eggs of a tapeworm.The eggs were found in a thin section of an elasmobranch coprolite. Most of the eggs are filled by pyrite and some have a special polar swelling (operculum), suggesting they are non-erupted eggs. One of the eggs contains a probable developing larva. The eggs are approximately 145-155 µm in length and 88-100 µm in width and vary little in size within the cluster. The depositional and morphological features of the eggs closely resemble those of cestodes. Not only do the individual eggs have features of extant tapeworms, but their deposition all together in an elongate segment is typical to modern tapeworm eggs deposited in mature segments (proglottids). This is the earliest fossil record of tapeworm parasitism of vertebrates and establishes a timeline for the evolution of cestodes. This discovery shows that the fossil record of vertebrate intestinal parasites is much older than was hitherto known and that the interaction between tapeworms and vertebrates occurred at least since the Middle-Late Permian.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Hybridization and polyploidy are key evolutionary forces in plant diversification, and their co-occurrence in the context of allopolyploid speciation is often associated with increased ...ability to colonize new environments and invasiveness. In the genus Ulex (Fabaceae), the European gorse (Ulex europaeus subsp. europaeus) is the only invasive and the only polyploid that has recently spread in different eco-geographical regions across the world. Understanding what confers such ecological advantages to this species, compared to its diploid and polyploid congeners, first requires clarification of the ecogeographical and evolutionary context of its formation. To achieve this, the geographical distributions of all Ulex spp. were estimated from species occurrence records, and phylogenetic analyses including all Ulex spp. were performed based on four nuclear (ITS and ETS nrDNA) and plastid (rps12 intron and trnK-matK) regions. The resulting trees were dated using a secondary calibration. Patterns of DNA sequence variation and dated phylogenetic trees were then interpreted in light of previous knowledge of chromosome numbers in Ulex to infer past events of polyploid speciation in the genus. We show that: (1) most current Ulex spp. radiated in the Iberian Peninsula during the past 1–2 Myr; (2) the history of Ulex was punctuated by multiple whole-genome duplication events; and (3) U. europaeus subsp. europaeus is the only gorse taxon that was formed by hybridization of two well-differentiated lineages (which separated c. 5 Mya) with wide climatic ranges (currently represented by Ulex minor and Ulex europaeus subsp. latebracteatus), possibly contributing to the invasive nature and wider climatic range of U. europaeus subsp. europaeus. These findings provide a much-needed evolutionary framework in which to explore the adaptive consequences of genome mergers and duplication in Ulex.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Photoelectrochemical water splitting represents an attractive method of capturing and storing the immense energy of sunlight in the form of hydrogen, a clean chemical fuel. Given the large energetic ...demand of water electrolysis, and the defined spectrum of photons available from incident sunlight, a two absorber tandem device is required to achieve high efficiencies. The two absorbers should be of different and complementary bandgaps, connected in series to achieve the necessary voltage, and arranged in an optical stack configuration to maximize the utilization of sunlight. This latter requirement demands a top device that is responsive to high‐energy photons but also transparent to lower‐energy photons, which pass through to illuminate the bottom absorber. Here, cuprous oxide (Cu2O) is employed as a top absorber component, and the factors influencing the balance between transparency and efficiency toward operation in a tandem configuration are studied. Photocathodes based on Cu2O electrodeposited onto conducting glass substrates treated with thin, discontinuous layers of gold achieve reasonable sub‐bandgap transmittance while retaining performances comparable to their opaque counterparts. This new high‐performance transparent photocathode is demonstrated in tandem with a hybrid perovskite photovoltaic cell, resulting in a full device capable of standalone sunlight‐driven water splitting.
Transparent gold substrates enable photocathodes based on electrodeposited cuprous oxide, which drive efficient photoelectrochemical hydrogen evolution while also exhibiting semitransparency to sub‐bandgap photons. This enables construction of an optical tandem, demonstrated here by coupling the photocathode above a perovskite photovoltaic, capable of performing complete sunlight‐driven water splitting.
The aim of this study was to identify the main characteristics of school-based drug prevention programs in Brazil and verify whether these interventions apply the prevention principles suggested hy ...the National Institute on Drug Abuse (NIDA). A cross-sectional study was conducted using a random national sample of 1,151 public and private school managers. The data were collected using an online questionnaire. Poisson regression was used to identify factors associated with the application of a greater number of prevention principles in the programs. The findings showed that programs were generally sporadic, had an average duration of one semester, incorporated different program models, and primarily directed at students. The most active organization in the delivery of programs was the Military Police. Private schools were shown to be 14% more likely to apply more good practice principles than public schools. Furthermore, programs delivered by school staff, health institutions, or departments of education were more likely to apply more prevention principles. Efforts are needed to improve drug prevention practice in Brazilian schools. Our findings show that, overall, school-based drug prevention programs do not apply the NIDA prevention principles.
Objective:
To investigate the validity and test–retest reliability of mHealth devices (Google Fit, Health, STEPZ, Pacer, and Fitbit Ultra) to estimate the number of steps in individuals after chronic ...stroke and to compare whether the measurement of the number of steps is affected by their location on the body (paretic and non-paretic side).
Design:
Observational study with repeated measures.
Setting:
University laboratory.
Subjects:
Fifty-five community-dwelling individuals with chronic stroke.
Intervention:
Not applicable.
Main measures:
The number of steps was measured using mHealth devices (Google Fit, Health, STEPZ, Pacer, and Fitbit Ultra), and compared against criterion-standard measure during the Two-Minute Walk Test using habitual speed.
Results:
Our sample was 54.5% men, mean age of 62.5 years (SD 14.9) with a chronicity after stroke of 66.8 months (SD 55.9). There was a statistically significant association between the actual number of steps and those estimated by the Google Fit, STEPZ Iphone and Android applications, Pacer iphone and Android, and Fitbit Ultra (0.30 ⩽ r ⩾ 0.80). The Pacer iphone application demonstrated the highest reliability coefficient (ICC(2,1) = 0.80; P < 0.001). There were no statistically significant differences in device measurements that depended on body location.
Conclusions:
mHealth devices (Pacer–iphone, Fitbit Ultra, Google Fit, and Pacer–Android) are valid and reliable for step counting in chronic stroke survivors. Body location (paretic or non-paretic side) does not affect validity or reliability of the step count metric.
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