1,144 research outputs found
Round-the-clock photocatalytic memory systems: Phenomenon and applications
No full textSemiconductor (SC) photocatalysis based on solar energy are progressively paving their ways toward the advancement of energy and environmental technologies and applications. Nonetheless, to expand their potential, studies have also been focused to make the activation of such catalytic reactions independent of photons and upgrade their activity not only under light irradiation but also in the dark. Thereby, it essentially enables the catalytic reactions round-the-clock from day to night. The construction of such catalytic materials requires an SC and a supporting material to accept/store the electrons during the light irradiation and supply them back in dark. Such phenomenon is essentially known as the “catalytic memory, " where the portion of photoinduced electrons, which stored in the material under illumination, reacts with adsorbed oxygen or water molecules and degrades pollutants under dark conditions at ambient temperature and pressure. This capacity of round-the-clock photocatalytic (PC) activity is significant toward the degradation of pollutants in wastewater or air, where it can be expanded toward designing the materials at low cost with low energy consumption. As a matter of fact, the exploitation of such PC memory systems has emerged as a promising field as a step forward toward producing more efficient PC materials for the degradation of various toxic organic pollutants, detoxification of heavy metal ions, bacterial disinfection, and hydrogen generation
Introduction to Photocatalytic Hydrogen Production
No full textNowadays, one of the major academic and technological challenges we face is the search for a sustainable source of clean energy. The need to convert solar energy into a form suitable for everyday use has triggered intense research in this field. The conversion of solar energy into chemical energy with the formation of renewable fuels through green processes has significant advantages over traditional methods. In this scenario, the photocatalytic production of H2 from pure water or from aqueous solutions containing suitable sacrificial agents represents one of the most attractive methods since it can be carried out in mild conditions (ambient pressure and temperature). In this chapter, we describe the principles of photocatalytic H2 production, the most used sacrificial agents, and photocatalytic systems together with techniques for improving photocatalyst efficiency. Even if there are numerous strategies to obtain a better efficiency of the photocatalyst, and consequently of the whole process, most of them have the purpose of decreasing the recombination of the photo-produced electrons and holes, thus increasing the number of those available on the photocatalyst surface for the reactive steps
Geophysical applicability of atomic clocks: direct continental geoid mapping
No full textThe geoid is the true physical figure of the Earth, a particular equipotential surface of the Earth's gravity field that accounts for the effect of all subsurface density variations. Its shape approximates best (in the sense of least squares) the mean level of oceans, but the geoid is more difficult to determine over continents. Satellite missions carry out distance measurements and derive the gravity field to provide geoid maps over the entire globe. However, they require calibration and extensive computations including integration, which is a non-unique operation. Here we propose a direct method and a new tool that directly measures geopotential differences on continents using atomic clocks. General relativity theory predicts constant clock rate at sea level, and faster (slower) clock rate above (below) sea level. The technology of atomic clocks is on the doorstep of reaching an accuracy level in clock rate (frequency ratio inaccuracy of 10-18), which is equivalent to 1 cm in determining equipotential surface (including geoid) height. We discuss the value and future applicability of such measurements including direct geoid mapping on continents, and joint gravity-geopotential surveying to invert for subsurface density anomalies. Our synthetic calculations show that the geoid perturbation caused by a 1.5 km radius sphere with 20 per cent density anomaly buried at 2 km depth in the Earth's crust is already detectable by atomic clocks of achievable accuracy. Therefore atomic clock geopotential surveys, used together with relative gravity data to benefit from their different depth sensitivities, can become a useful tool in mapping density anomalies within the Earth
Effectiveness of vaginal tablets containing lactobacilli versus pH tablets on vaginal health and inflammatory cytokines: A randomized, double-blind study
No full textThe purpose of this study was to evaluate the effectiveness of lactobacilli on vaginal health and proinflammatory cytokines. Sixty-seven patients with bacterial vaginosis (BV), 50 with intermediate flora and 42 with normal vaginal flora were enrolled in this double-blind study. The subjects were randomized to receive probiotic lactobacilli vaginal tablets (L. brevis CD2, L. salivarius subsp. salicinius, L. plantarum) or the vaginal pH tablet (active comparator). Cervico-vaginal lavage was collected to measure the concentrations of IL-1β, TNFα and IL-6 by ELISA. Neutral sphingomyelinase activity was also quantified in both arms before and after treatment. The probiotic vaginal tablet was well tolerated and no side effects were reported. The study demonstrated a cure rate of nearly 80 %; i.e., 32 % of the women could restore normal vaginal flora and 47 % had improved Nugent score, whereas 20 % of the subjects did not clear BV in the first follow-up (after 8 days treatment). The pH tablet containing pH lowering compounds induced resolution of BV and restoration of normal vaginal flora in 74 % and 26 %, respectively. The lactobacilli tablet was found to be better than the pH tablet in preventing BV in healthy subjects. A significant reduction in IL-1β and IL-6 vaginal cytokines was observed after treatment with lactobacilli, while the active comparator did not have any effect on local proinflammatory cytokines. Vaginal neutral sphingomyelinase activity was not modified in either group. Vaginal tablets containing lactobacilli can cure BV and reduce vaginal inflammatory response. © 2012 Springer-Verlag
Evaluation of vaginal pH for detection of bacterial vaginosis
No full textBackground & objectives: Bacterial vaginosis (BV) is highly prevalent among women in reproductive age group. Little information exists on routine vaginal pH measurement in women with BV. We undertook this study to assess the utility of vaginal pH determination for initial evaluation of bacterial vaginosis. Methods: In this cross-sectional study vaginal swabs were collected from women with complaints of white discharge, back ache and pain abdomen attending a government hospital and a community health clinic, and subjected to vaginal pH determination, Gram stain, wet mount and whiff test. Nugent score and Amsel criteria were used for BV confirmation. Results: Of the 270 women included in the analysis, 154 had BV based on Nugents' score. The mean vaginal pH in women with BV measured by pH strips and pH glove was 5 and 4.9, respectively. The vaginal pH was significantly higher in women with BV. Vaginal discharge was prevalent in 84.8 per cent women, however, only 56.8 per cent of these actually had BV by Nugent score (NS). Presence of clue cells and positive whiff test were significant for BV. Vaginal pH >4.5 by pH strips and pH Glove had a sensitivity of 72 and 79 per cent and specificity of 60 and 53 per cent, respectively to detect BV. Among the combination criteria, clue cells and glove pH >4.5 had highest sensitivity and specificity to detect BV. Interpretation & conclusions: Vaginal pH determination is relatively sensitive, but less specific in detecting women with BV. Inclusion of whiff test along with pH test reduced the sensitivity, but improved specificity. Both, the pH strip and pH glove are equally suitable for screening women with BV on outpatient basis
Delayed Default Dependency and Default Contagion
No full textDelayed, hence non-simultaneous, dependent defaults are discussed in a reduced form model. The model is a generalization of a multi-factor model based on simultaneous defaults to incorporate delayed defaults. It provides a natural smoothening of discontinuities in the joint probability densities in models with simultaneous defaults. It is a dynamic model that exhibits default contagion in a multi-factor setting. It admits an efficient Monte Carlo simulation algorithm that can handle heterogeneous collections of credit names. It can be calibrated to provide exact fits to CDX.NA.IG and iTraxx Europe CDOs just as its version with simultaneous defaults.Default Risk; Default Correlation; Default Contagion; Delayed Default; CDO; Monte Carlo
Numerical simulations of oscillating soliton stars: Excited states in spherical symmetry and ground state evolutions in 3D
No full textExcited state soliton stars are studied numerically for the first time. The stability of spherically symmetric S-branch excited state oscillatons under radial perturbations is investigated using a 1D code. We find that these stars are inherently unstable either migrating to the ground state or collapsing to black holes. Higher excited state configurations are observed to cascade through intermediate excited states during their migration to the ground state. This is similar to excited state boson stars [J. Balakrishna, E. Seidel, and W.-M. Suen, Phys. Rev. D 58, 104004 (1998).]. Ground state oscillatons are then studied in full 3D numerical relativity. Finding the appropriate gauge condition for the dynamic oscillatons is much more challenging than in the case of boson stars. Different slicing conditions are explored, and a customized gauge condition that approximates polar slicing in spherical symmetry is implemented. Comparisons with 1D results and convergence tests are performed. The behavior of these stars under small axisymmetric perturbations is studied and gravitational waveforms are extracted. We find that the gravitational waves damp out on a short time scale, enabling us to obtain the complete waveform. This work is a starting point for the evolution of real scalar field systems with arbitrary symmetries
Transition metal chemistry of phosphorus based ligands. Ruthenium(II) chemistry of bis(phosphino)amines, X2PN(R)PX2 (R = H or Ph, X = Ph; R = Ph, X-2 = O2C6H4)
No full textReactions of CpRuCl(PPh3)(2) with bis(phosphino)amines, X2PN(R)PX2 (1 R = H, X = Ph; 2 R = X = Ph; 3 R = Ph, X-2 = O2C6H4) give neutral or cationic mononuclear complexes depending on the reaction conditions. Reaction of 1 with CpRuCl(PPh3)(2) gives one neutral complex, [CpRu(Cl)(eta(2)-Ph2PN(H)PPh2)] (4) and two cationic complexes, [CpRu(eta(2)-Ph2PN(H)PPh2)(eta(1)-Ph2PN(H)PPh2)]Cl (5) and [CpRu(PPh3)(eta(2)-Ph2PN(H)PPh2)]Cl (6), whereas the reaction of 2 with CpRuCl(PPh3)(2) leads only to the isolation of cationic complex, [CpRu(PPh3)(eta(2)-Ph2PN(Ph)PPh2)]Cl (7). The catechol derivative 3, in a similar reaction, affords an interesting mononuclear complex [CpRu(PPh3){eta(1)-(C4H4O2)PN(Ph)P(O2H4C6)}(2)]Cl (8) containing two monodentate bis(phosphino)amine ligands. The structural elucidation of the complexes was carried out by elemental analyses, IR and NMR spectroscopic data. (C) 1998 Elsevier Science S.A.
Umbrella Review of Systematic Reviews and Meta-analyses on Consumption of Different Food Groups and Risk of All-cause Mortality
No full textConsumption of different food groups is linked to a range of health outcomes. It is essential to integrate the most reliable evidence regarding intake of different food groups and risk of mortality to optimize dietary guidance. Our aim is to systematically and comprehensively assess the associations between the consumption of various food groups and all-cause mortality. The food groups under consideration include edible grains (refined and whole grains), fruits, vegetables, nuts, legumes, fish and fish products, eggs, dairy products/milk, meat and meat products (including processed meat, unprocessed red and white meat), sugar-sweetened beverages, and added sugars. We present these associations with high compared with low consumption and per serving comparisons. We comprehensively and systematically reviewed a search in Medline, Embase, Web of Science, and Epistemonikos (PROSPERO: CRD42024498035), identifying 41 meta-analyses involving over a million participants, many of which showed significant heterogeneity. Of the 41 studies, 18 were rated high quality, 8 moderate quality, 5 low quality, and 10 critically low quality according to AMSTAR-2 assessments. Our findings revealed that higher consumption of nuts, whole grains, fruits, vegetables, and fish was associated with lower mortality rates, both in high compared with low comparisons and per serving analyses. Similarly, we observed favorable outcomes for legumes and white meat in high compared with low comparisons. Conversely, high intakes of red and processed meats, as well as sugar-sweetened beverages, were linked to higher all-cause mortality. Dairy products and refined grains did not show clear associations with mortality, whereas there was a tendency in all-cause mortality for high intakes of added sugars and eggs
H 0 Reconstruction with Type Ia Supernovae, Baryon Acoustic Oscillation and Gravitational Lensing Time Delay
No full textThere is a persistent H 0-tension, now at more than gsim4σ level, between the local distance ladder value and the Planck cosmic microwave background measurement, in the context of flat Lambda-cold-dark-matter (ΛCDM) model. We reconstruct H(z) in a cosmological-model-independent way using three low-redshift distance probes including the latest data from baryon acoustic oscillation, supernova Ia (SN Ia) and gravitational lensing time-delay (GLTD) observations. We adopt general parametric models of H(z) and assume a Gaussian sound horizon at drag epoch, , from Planck measurement. The reconstructed Hubble constant H 0,rec using Pantheon SN Ia and Baryon Acoustic Oscillations (BAO) data are consistent with the Planck flat ΛCDM value. When including the GLTD data, H 0,rec increases mildly, yet remains discrepant with the local measurement at ~2.2σ level. With our reconstructions being blind to the dark sectors at low redshift, we reaffirm the earlier claims that the Hubble tension is not likely to be solved by modifying the energy budget of the low-redshift universe. We further forecast the constraining ability of future realistic mock BAO data from Dark Energy Spectroscopic Instrument and GLTD data from Large Synoptic Survey Telescope, combining which, we anticipate that the uncertainty of H 0,rec would be improved by ~27%, reaching uncertainty level
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