Ratios Of Br Research Articles

Mechanism of Tunable Band Gap of Halide Cubic Perovskite CsPbBr3−xIx

Perovskites are organic-inorganic compounds with a crystal structure that revolutionize many optoelectronic applications, especially solar cells. The CsPbBr3−xIx, a perovskite, has garnered significant attention due to its tunable band gap and excellent photovoltaic properties. In this theoretical study, the structural, electronic, and optical properties of CsPbBr3−xIx are investigated through density functional theory calculations. The calculations reveal that the substitution of Br with I leads to a significant reduction in the band gap of CsPbBr3−xIx, resulting in improved light absorption properties. The obtained data show that the coexistence of Br and I ions in the structure creates an energy level similar to the shallow energy levels caused by doping at the R symmetry point in the band structure.

COMBINED FORCED AND NATURAL CONVECTION FROM A SINGLE TRIANGULAR CYLINDER

Unsteady laminar confined and unconfined fluid flow and mixed (forced and free) convection heat transfer around equilateral triangular cylinders are investigated numerically. The computation model is a two-dimensional domain with blockage ratios of BR=0.5, 0.25, 0.2, 0.1, 0.05, and 0.0333, with the Reynolds numbers ranging from 100 to 200. The working fluid is water (Pr = 7). The effects of aiding and opposing thermal buoyancy are incorporated into the Navier-Stokes equations using the Boussinesq approximation. The Richardson number, which is a relative measure of free convection, is varied in the range -2 ≤ Ri ≤ 2. The governing equations are solved by using the Finite Volume Method with a second-order upwind scheme used for differencing of the convection terms, and the SIMPLE algorithm is used for the velocity-pressure coupling. A discussion of the effect of the blockage ratio on the mean drag, mean rms lift coefficients, the Strouhal number, and the mean Nusselt number is also presented. The iso-vorticity contours and dimensionless temperature field are generated to interpret and understand the underlying physical mechanisms. The results reveal that, in addition to the Richardson and Reynolds numbers, the blockage rate is effective in the vortex distribution in the channel. It has been determined that the vortices formed behind the cylinder spread to the channel with a decreasing blockage rate. Especially at high Reynolds numbers, both the drag coefficient and the mean Nusselt number are significantly affected by the blockage ratio. For Ri=0, the drag coefficients for BR=0.25 in comparison to the BR=0.05 case are about 9% and 29% larger for Re= 100 and 200, respectively. For BR

Sex Differences in Treatment Response to Nucleos(t)ide Therapy in Chronic Hepatitis B: A Multicenter Longitudinal Study

It is unclear if there may be sex differences in response to nucleos(t)ide analogs including virologic response (VR), biochemical response (BR), complete response (CR), and hepatocellular carcinoma (HCC) incidence among hepatitis B patients. We compared nucleos(t)ide analog treatment outcomes by sex. We performed a retrospective cohort study of 3388 treatment-naïve adult hepatitis B patients (1250 female, 2138 male) from the Real-World Evidence from the Global Alliance for the Study of Hepatitis B Virus consortium who initiated therapy with either entecavir or tenofovir from 22 sites (Argentina, Korea, Japan, Taiwan, and the United States). We used propensity-score matching to balance background characteristics of the male and female groups and competing-risks analysis to estimate the incidence and subdistribution hazard ratios (SHRs) of VR, BR, CR, and HCC. Females (vs males) were older (52.0 vs 48.6 y); less likely to be overweight/obese (49.3% vs 65.7%), diabetic (9.9% vs 13.1%), or cirrhotic (27.9% vs 33.0%); and had a lower HBV DNA level (5.9 vs 6.0 log10 IU/mL) and alanine aminotransferase level (91 vs 102 IU/L) (all P < .01). However, after propensity-score matching, relevant background characteristics were balanced between the 2 groups. Females (vs males) had similar 5-year cumulative VR (91.3% vs 90.3%; P= .40) and HCC incidence rates (5.1% vs 4.4%; P= .64), but lower BR (84.0% vs 90.9%; P < .001) and CR (78.8% vs 83.4%; P= .016). Males were more likely to achieve BR (SHR, 1.31; 95% CI, 1.17-1.46; P < .001) and CR (SHR, 1.16; 95% CI, 1.03-1.31; P= .016), but VR and HCC risks were similar. Sex differences exist for treatment outcomes among hepatitis B patients. Male sex was associated with a 16% higher likelihood of clinical remission and a 31% higher likelihood of biochemical response than females, while virologic response and HCC incidence were similar between the 2 groups.

A Way to Reach 10% Efficiency with Carbon‐Based Electrodeposited Mixed Perovskite Solar Cells

Electrodeposition is investigated in this work as an alternative method to develop a large‐area perovskite active layer for solar device application. In addition to the single perovskite MAPbI3, the deposition of mixed perovskites MAPbI x Cl1−x and MA1−y FA y PbI3−x Br x is studied. This study is unique since these mixed perovskites have never been developed by electrodeposition before. It is noticed that depending on the ratios of FA, Br, and Cl infiltrated into the perovskite lattice, different microstructures and optical and chemical properties are obtained, having an impact on the photovoltaic performance of the perovskite layer. In fact, increasing the percentages of FA, Br, and Cl in the mixed perovskite improves the photovoltaic performance. Thanks to a maturation step carried out under vacuum at 40 °C for 500 h, the performances can be significantly improved, at best by 60%, to reach record efficiencies of 10%. An improvement of the stability under air at 40 °C is also observed. All the results obtained are compared with recent results in the literature, which makes it possible to appreciate the originality and innovation of the study proposed in this article. In summary, this work illustrates the importance of electrodeposition and its flexibility to develop different types of perovskites.

Strengthened photocatalytic removal of bisphenol A under visible light by magnetic ternary heterojunctions Bi4O5Br2/Bi4O5I2/Fe3O4

Magnetic ternary composites Bi 4 O 5 Br 2 /Bi 4 O 5 I 2 /Fe 3 O 4 (BBF) were constructed by the combination of exotic Fe 3 O 4 nanoparticles and Bi 4 O 5 Br 2 /Bi 4 O 5 I 2 with controllable molar ratios of Br to I through a facile one-pot route. Microstructural, morphological, and optical features of achieved composites were thoroughly characterized by a succession of analytical techniques. It was realized that three expected components were coexisted to form efficient heterojunction structures. These magnetic composites showed reinforced photocatalytic removal of bisphenol A (BPA) under visible light illumination. Particularly, the best candidate BBF(3:7) possessed the largest apparent reaction rate constant of 0.041 min −1 that was respectively about 1.95, 372.73, 4.71, 39.42, and 3.72 times those of Bi 4 O 5 I 2 /Fe 3 O 4 , Bi 4 O 5 Br 2 /Fe 3 O 4 , Bi 4 O 5 I 2 , Bi 4 O 5 Br 2 , and BB(3:7), mainly attributed to the strengthened visible-light absorption by the shrinkage of band gaps, the harmony of various morphologies, the suitable phase composition, and the promoted segregation of charge carriers by ternary heterojunctions with proper band structures. In addition, a possible photocatalysis mechanism was proposed by entrapping experiments and band structures estimation. The sufficient reusability by recycling experiments together with enhanced photocatalytic outcome ensured these magnetic composites as potential and applicable candidates in fields of environmental protection and energy reservation. • Magnetic composites Bi 4 O 5 Br 2 /Bi 4 O 5 I 2 /Fe 3 O 4 were prepared in a facile manner. • Ternary heterojunction structures were formed in these composites. • These magnetic composites showed enhanced photocatalytic removal of BPA. • A plausible photocatalysis mechanism was conjectured.

Theoretical study on η′ → π+π−π+(0)π−(0)

The η′ meson is associated with the U(1) anomaly. In this paper, a successful effective chiral theory of mesons has been applied to study the anomalous decays of η′→π+π−π+(0)π−(0). Contribution of triangle and box diagrams is calculated, which indicates that the box anomaly has a significant contribution to the decay amplitudes. We predict branching ratios of Br(η′→π+π−π+π−)=12Br(η′→π+π−π0π0)=(8.3±1.2)×10−5, which is in good agreement with BESIII measurement.

Experimental Investigation of Sweeping Jet Film Cooling in a Transonic Turbine Cascade

Abstract The sweeping jet (SJ) film cooling hole has shown promising cooling performance compared to the standard shaped hole in low-speed conditions. The present work demonstrates the first attempt of SJ film cooling at an engine relevant Mach number. An experimental investigation was conducted to study the SJ film cooling on a nozzle guide vane suction surface. A well-established additive manufacturing technique commonly known as stereolithography (SLA) was utilized to design a transonic, engine representative vane geometry in which a row of SJ holes was used on the vane suction surface. Experiments were performed in a linear transonic cascade at an exit Mach number of 0.8 and blowing ratios of BR = 0.25–2.23. The measurement of heat transfer was conducted with the transient IR method, and the convective heat transfer coefficient (HTC) and adiabatic film cooling effectiveness were estimated using a dual linear regression technique (DLRT). Aerodynamic loss measurements were also performed with a total pressure Kiel probe at 0.25Cax downstream of the exit plane of the vane cascade. Experiments were also conducted for a baseline-shaped hole (777-hole) for a direct comparison. Results showed that the SJ hole has a wider coolant spreading in the lateral direction near the hole exit due to its sweeping motion that improves the overall cooling performance particularly at high blowing ratios (BR &amp;gt; 1). Aerodynamic loss measurement suggested that the SJ hole has a comparable total pressure loss to the 777-shaped hole.

Hydrogeochemical Evolution and Heavy Metal Contamination in Groundwater of a Reclaimed Land on Zhoushan Island

The need for valuable land has encouraged reclamation in coastal areas worldwide in the past decades. Land reclamation can alter the groundwater quality in coastal aquifers. The purpose of this study is to identify the effect of land reclamation on groundwater chemistry, especially the major ions, and heavy metals on Zhoushan Island, China. The subsurface media on the island is composed of two layers, i.e., an upper infill layer and an underlain clay layer. The upper layer is previously ocean and filled with various materials. The clay layer is the original marine sediment. The dominated Na and Cl ions in groundwater illustrate high salinity sources of groundwater in the subsurface of the reclaimed land. A mixing trend between seawater and river water of the groundwater in infill layer is also detected based on the ratios of Cl and Br. Though the heavy metal concentrations (Cd, Cr, Zn and Hg) are high in marine sediments, no significant releasing trends in the groundwater are detected in a short-term after reclamation (based on standard GB18668). Meanwhile, Fe-III concentrations in the aquifer have a strong correlation with precipitation events. Column desorption experiments and simulations indicate the Cd and Cr release from the sediment would pose a health risk when the groundwater in the infill layer being gradually flushed by fresh water. These results provide a foundation for the prediction of groundwater quality and are helpful for the future water management in a newly reclaimed land.

Ultrastability and color-tunability of CsPb(Br/I)3 nanocrystals in P-Si-Zn glass for white LEDs.

A series of CsPbBrxI3-x NC glasses, showing tunable emission (523-693 nm) controlled by different ratios of Br- and I-, were successfully prepared. The CsPbBrxI3-x NC glasses exhibited excellent optical properties and outstanding stability towards ambient conditions, water and heat.

Bromide and chloride distribution across the snow‐sea ice‐ocean interface: A comparative study between an Arctic coastal marine site and an experimental sea ice mesocosm

AbstractDuring springtime in the Arctic, bromine explosion events occur when high concentrations of reactive bromine species are observed in the boundary layer with the concurrence of ozone depletion events and mercury depletion events. While a variety of substrates including snow, sea ice, frost flowers, and aerosols have been proposed to be the substrate and/or source of bromine activation in the Arctic, recent studies have highlighted the role of snow. Here we report concentration profiles of halides (Br− and Cl−), Na+, and mercury across the snow‐sea ice‐seawater interface at a coastal marine site in the Canadian Arctic Archipelago in March and June 2014, as well as in an experimental sea ice mesocosm in Winnipeg in January and February 2014. The occurrence of bromine activation at the Arctic site in March was indicated by the high mercury concentrations in snowpack. At both the Arctic and mesocosm sites, the molar ratios of Br−/Na+ were nearly constant throughout the sea ice depth, but highly variable in the upper layer of the overlying snowpack, revealing that bromine activation takes place in the sunlit snow instead of sea ice. This is supported by calculations showing that the loss of Br– from the upper layer of the snowpack is large enough to produce the observed concentrations of reactive bromine in the atmospheric boundary layer. However, the upper layer of the Arctic snowpack tends to be generally enriched in Br– due to the net addition of Br–‐containing gases and nonsea‐salt aerosols.

Investigation of processes controlling summertime gaseous elemental mercury oxidation at midlatitudinal marine, coastal, and inland sites

Abstract. A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate the oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (AI; marine), Thompson Farm (TF; coastal, rural), and Pack Monadnock (PM; inland, rural, elevated). The chemical mechanism in this box model included the most up-to-date Hg and halogen chemistry. As a result, the box model was able to simulate reasonably the observed diurnal cycles of gaseous oxidized mercury (GOM) and chemical speciation bearing distinct differences between the three sites. In agreement with observations, simulated GOM diurnal cycles at AI and TF showed significant daytime peaks in the afternoon and nighttime minimums compared to flat GOM diurnal cycles at PM. Moreover, significant differences in the magnitude of GOM diurnal amplitude (AI &gt; TF &gt; PM) were captured in modeled results. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80–99 % of total GOM production during daytime. H2O2-initiated GEM oxidation was significant (∼ 33 % of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL) atmosphere, Br and BrO became dominant GEM oxidants, with mixing ratios reaching 0.1 and 1 pptv, respectively, and contributing ∼ 70 % of the total GOM production during midday, while O3 dominated GEM oxidation (50–90 % of GOM production) over the remaining day when Br and BrO mixing ratios were diminished. The majority of HgBr produced from GEM+Br was oxidized by NO2 and HO2 to form brominated GOM species. Relative humidity and products of the CH3O2+BrO reaction possibly significantly affected the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas–particle partitioning could potentially be important in the production of GOM as well as Br and BrO at the marine site.

Dosimetric evaluation of hybrid brass/stainless-steel apertures for proton therapy

In passive scattering proton therapy, patient specific collimators (apertures) are used to laterally shape the proton beam, and compensators are employed to distally conform proton dose to the target. Brass is a commonly used material for apertures and recently a hybrid brass/stainless-steel (BR/SST) aperture design has been introduced to reduce treatment cost without clinical flow change. We measured stopping power and leakage dose for apertures made of stainless steel and brass in the Proton Therapy system. The linear stopping power ratios for stainless steel (type 304) and brass to water were calculated to be 5.46 and 5.51, respectively. Measured stopping power ratios of SST and BR were 5.51 ± 0.04 and 5.56 ± 0.08, respectively, which agrees with the calculated values within 1%. Leakage dose on the downstream surface of two slabs of Ø18 cm stainless steel apertures (total thickness of 6.5 cm) for the maximum available proton energy (235 MeV) was 1.283% ± 0.004% of the prescription dose, and was smaller compared to the 1.358% ± 0.005% leakage dose measured for existing brass apertures of identical physical dimensions. Therefore, the existing beam range limits for brass aperture slabs used at our institution with safety margin allowances for material composition and delivered beam range uncertainties can be safely applied for the new BR/SST aperture design. Potential range differences in the brass and stainless steel interface regions of the hybrid design were further investigated using EBT3 GafChromic film. Film dosimetry revealed no discernible range variations across the brass and stainless steel interface regions. Neutron dose to the patient from brass and stainless steel apertures was simulated using the Monte Carlo method. The results indicate that stainless steel produces similar patient neutron dose compared to brass. Material activation dose rates of stainless steel were measured over a period of 7 d after irradiation. The measurements showed that the proton induced SST activity is initially lower and also decays at a faster rate than that induced in brass, therefore requires no changes in radiation protection requirements on material disposals. The Monte Carlo simulation confirmed higher initial activity of brass than stainless steel shortly after irradiation. The hybrid BR/SST aperture design is suitable for clinical use to replace the current brass apertures for all clinically used proton ranges. The existing aperture disposal procedures also satisfy radiation protection requirements for the new hybrid type apertures.

Sensitivity of tropospheric chemical composition to halogen-radical chemistry using a fully coupled size-resolved multiphase chemistry–global climate system: halogen distributions, aerosol composition, and sensitivity of climate-relevant gases

Abstract. Observations and model calculations indicate that highly non-linear multiphase atmospheric processes involving inorganic Cl and Br significantly impact tropospheric chemistry and composition, aerosol evolution, and radiative transfer. The sensitivity of global atmospheric chemistry to the production of marine aerosol and the associated activation and cycling of inorganic Cl and Br was investigated using a size-resolved multiphase coupled chemistry–global climate model (National Center for Atmospheric Research's Community Atmosphere Model (CAM) v3.6.33). Simulated results revealed strong meridional and vertical gradients in Cl and Br species. They also point to possible physicochemical mechanisms that may account for several previously unexplained phenomena, including the enrichment of Br- in submicron aerosol and the presence of a BrO maximum in the polar free troposphere. However, simulated total volatile inorganic Br mixing ratios in the troposphere were generally higher than observed, due in part to the overly efficient net production of BrCl. In addition, the emission scheme for marine aerosol and associated Br−, which is the only source for Br in the model, overestimates emission fluxes from the high-latitude Southern Ocean. Br in the stratosphere was lower than observed due to the lack of long-lived precursor organobromine species in the simulation. Comparing simulations using chemical mechanisms with and without reactive Cl and Br species demonstrates a significant temporal and spatial sensitivity of primary atmospheric oxidants (O3, HOx, NOx), CH4, non-methane hydrocarbons (NMHCs), and dimethyl sulfide (DMS) to halogen cycling. Globally, halogen chemistry had relatively less impact on SO2 and non-sea-salt (nss) SO42− although significant regional differences were evident. Although variable geographically, much of this sensitivity is attributable to either over-vigorous activation of Br (primarily BrCl) via the chemical mechanism or overproduction of sea-salt aerosol simulated under higher-wind regimes. In regions where simulated mixing ratios of reactive Br and Cl fell within observed ranges, though, halogen chemistry drove large changes in oxidant fields and associated chemical processes relative to simulations with no halogens. However, the overall simulated impacts of Br chemistry globally are overestimated and thus caution is warranted in their interpretation.

Search for resonances decaying toηcπ+π−in two-photon interactions

We report a study of the process gamma gamma -> X -> eta_c pi+ pi-, where X stands for one of the resonances chi_{c2}(1P), eta_c(2S), X(3872), X(3915), or chi_{c2}(2P). The analysis is performed with a data sample of 473.9 fb^{-1} collected with the BaBar detector at the PEP-II asymmetric-energy electron-positron collider. We do not observe a significant signal for any channel, and calculate 90% confidence-level upper limits on the products of branching fractions and two-photon widths Gamma(X -> gamma gamma)BR(X -> eta_c pi+ pi-): 15.7 eV for chi_{c2}(1P), 133 eV for eta_c(2S), 11.1 eV for X(3872) (assuming it to be a spin-2 state), 16 eV for X(3915) (assuming it to be a spin-2 state), and 19 eV for chi_{c2}(2P). We also report upper limits on the ratios of branching fractions BR(eta_c(2S) -> eta_c pi+ pi-)/BR(eta_c(2S)-> K_S^0 K+ pi-) < 10.0 and BR(chi_{c2}(1P) -> eta_c pi+ pi-)/BR(chi_{c2}(1P)-> K_S^0 K+ pi-) <32.9 at the 90% confidence level.

GAC removal of organic nitrogen and other DBP precursors

The increased mutagenicity of disinfection by‐products (DBPs) containing bromide (Br−) and nitrogen requires a renewed evaluation of best available treatment technologies for DBP control. The aim of this article is to document the removal of organic nitrogen during granular activated carbon (GAC) treatment and to illustrate how GAC treatment alters DBP speciation. Rapid small‐scale column tests (RSSCTs) with GAC were conducted on pretreated surface water sources to evaluate the simultaneous removal of carbonaceous and nitrogenous DBP precursors: dissolved organic nitrogen (DON), dissolved organic carbon (DOC), organics absorbed by ultraviolet light at 254 nm (UV254), and Br−. Simulated distribution system tests were conducted with RSSCT effluent samples throughout natural organic matter breakthrough, and free chlorine was used to evaluate the formation of halogenated carbonaceous and nitrogenous DBPs. GAC preferentially removed UV254‐absorbing material over DOC, which was removed more effectively than DON. Br− was not removed. Consequently, effluent ratios of Br− to DOC and Br− to DON changed during GAC treatment, and the ratio of brominated DBPs to chlorinated DBPs shifted during the GAC breakthrough cycle; brominated DBPs dominated earlier in the breakthrough of DOC. Neither DON nor nitrogenous DBP precursors were removed efficiently during GAC treatment.

Showerhead Film Cooling Performance of a Turbine Vane at High Freestream Turbulence in a Transonic Cascade

This paper experimentally investigates the effect of blowing ratio and exit Reynolds number/Mach number on the film cooling performance of a showerhead film cooled first stage turbine vane. The vane midspan was instrumented with single-sided platinum thin film gauges to experimentally characterize the Nusselt number and film cooling effectiveness distributions over the surface. The vane was arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Three different exit Mach numbers of Mex = 0.57, 0.76 and 1.0—corresponding to exit Reynolds numbers based on vane chord of 9.7 × 105, 1.1 × 106 and 1.5 × 106, respectively—were tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx/P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0, 1.5, 2.0, and 2.5 and a density ratio of DR = 1.3. Nusselt number and adiabatic film cooling effectiveness distributions were presented on the vane surface over a range of s/C = −0.58 on the pressure side to s/C = 0.72 on the suction side of the vane. The primary effects of coolant injection were to augment the Nusselt number and reduce the adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at all exit Mach number conditions. In general, an increase in blowing ratio (BR = 1.5 to 2.5) showed noticeable Nusselt number augmentation on pressure surface as compared to suction surface at exit Mach 0.57 and 0.75; however, the Nusselt number augmentation for these blowing ratios was found to be negligible on the vane surface for exit Mach 1.0 case. At exit Mach 1.0, an increase in blowing ratio (BR = 1.5 to 2.5) was observed to have an adverse effect on the adiabatic effectiveness on the pressure surface but had negligible effect on suction surface. The effectiveness trend on the suction surface was also found to be influenced by a favorable pressure gradient due to Mach number and boundary layer transition in the region s/C = 0.28 to s/C = 0.45 at all blowing ratio and exit Mach number conditions. An increase in Reynolds number from exit Mach 0.76 to 1.0 increased heat transfer levels on the vane surface at all blowing ratio conditions. A large increase in Reynolds number adversely affected adiabatic effectiveness on the pressure surface at all blowing ratio conditions. On the suction surface, a large increase in Reynolds number also affected adiabatic effectiveness in the favorable pressure gradient and boundary layer transition region.

Specific features of the ecological functioning of urban soils in Moscow and Moscow oblast

Urban soils (constructozems) were studied in Moscow and several cities (Dubna, Pushchino, and Serebryanye Prudy) of Moscow oblast. The soil sampling from the upper 10-cm-thick layer was performed in the industrial, residential, and recreational functional zones of these cities. The biological (the carbon of the microbial biomass carbon, Cmic and the microbial (basal) respiration, BR) and chemical (pHwater and the contents of Corg, heavy metals, and NPK) indices were determined in the samples. The ratios of BR to Cmic (the microbial respiration quotient, qCO2) and of Cmic to Corg were calculated. The Cmic varied from 120 to 738 μg C/g soil; the BR, from 0.39 to 1.94 μg CO2-C/g soil per hour; the Corg, from 2.52 to 5.67%; the qCO2, from 1.24 to 5.28 μg CO2-C/mg Cmic/g soil per h; and the Cmic/Corg, from 0.40 to 1.55%. Reliable positive correlations were found between the Cmic and BR, the Cmic and Cmic/Corg, and the Cmic and Corg values (r = 0.75, 0.95, and 0.61, respectively), as well as between the BR and Cmic/Corg values (r = 0.68). The correlation between the Cmic/Corg and qCO2 values was negative (r = −0.70). The values of Cmic, BR, Corg, and Cmic/Corg were found to correlate with the ammonium nitrogen content. No correlative relationships were revealed between the determined indices and the climatic characteristics. The principal component analysis described 86% of the variances for all the experimental data and clearly subdivided the locations of the studied soil objects. The ANOVA showed that the variances of Cmic, Corg, and BR are controlled by the site location factor by 66, 63, and 35%, respectively. The specificity of the functioning of the anthropogenic soils as compared with their natural analogues was clearly demonstrated. As shown in this study, measurable biological indices might be applied to characterize the ecological, environmental-regulating, and productive functions of soils, including urban soils.

Temperature-Dependent Mechanical Properties and Model of Magnetorheological Elastomers

Magnetorheological elastomers (MREs) are composed of magnetizable particles (iron particles) and a soft rubberlike matrix. Their mechanical properties, including modulus and damping capability, depend on both an external magnetic field and an environmental temperature. To systematically investigate thetemperature-dependent mechanical properties, six different kinds of MREs samples based on a mixed rubber matrices (cis-polybutadiene rubber and natural rubber) and their mass ratios of BR and NR were 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100, were fabricated in this study. The steady-state and dynamic mechanical properties of the samples were measured under different conditions by using a rheometer. The results revealed that storage modulus (G′) and loss modulus (G′′) of samples, which contained only cis-polybutadiene rubber (BR), decreased linearly with the temperature increment. However, the modulus of sample which contained much natural rubber (NR) showed different characteristic, and the relationships between stress and strain also exhibited different characteristics with different rubber matrix. An improved constitutive equation was developed to model these properties under different magnetic fields and temperatures. The comparison between modeling predicting results with experimental data demonstrated that the model can well-predict the modulus of MRE in different conditions.

Factors influencing the formation of chlorination brominated trihalomethanes in drinking water

The formation of brominated trihalomethanes (THMs-Br) which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities. This study was performed to assess the effects of water quality parameters (bromide concentration, pH value and ammonia concentration), chlorination conditions (chlorine dose, reaction time) and ratios of Br − /DOC and Br − /Cl2 consumption on the formation and distribution of THMs-Br in chlorination. The results showed good correlation between the bromine incorporation factor (BIF) n(Br) and Br − /Cl2 consumption ratio. The formation of total THM (TTHM) was found to decrease with increasing ammonia concentration but to increase with bromide concentration and pH value. The n(Br) trends were significantly affected by the presence of bromide concentration. The effects on the molar yields of THMs were more strongly influenced by bromide concentration and dissolved organic carbon (DOC) concentration than pH value and natural organic matter (NOM) source. High Br − /DOC and Br − /Cl2 favor the formation of THMs-Br over chlorinated THMs (THMs-Cl). The experimental data including the main parameters such as bromide, DOC, ammonia, pH and reaction time were used for developing the predictive model for THMs-Br.

Photodissociation of dibromoethanes at 248 nm: An ignored channel of Br2 elimination

Br(2) molecular elimination is probed in the photodissociation of 1,1- and 1,2-C(2)H(4)Br(2) isomeric forms at 248 nm by using cavity ring-down absorption spectroscopy. Their photodissociation processes differ markedly from each other. The quantum yield of the Br(2) fragment in 1,2-dibromoethane is 0.36+/-0.18, in contrast to a value of 0.05+/-0.03 in 1,1-dibromoethane. The vibrational population ratios of Br(2)(v=1)/Br(2)(v=0) are 0.8+/-0.1 and 0.5+/-0.2 for 1,2- and 1,1-dibromoethanes, respectively. The Br(2) yield densities are found to increase by a factor of 35% and 190% for 1,2- and 1,1-dibromoethanes within the same temperature increment. In the ab initio potential energy calculations, the transition state (TS) along the adiabatic ground state surface may correlate to the Br(2) products. The TS energy for 1,2-dibromoethane is well below the excitation energy at 483 kJ/mol, whereas that for 1,1-dibromoethane is slightly above. Such a small TS energy barrier impedes the photodissociation of the ground state 1,1-dibromoethane such that the production yield of Br(2) may become relatively low, but rise rapidly with the temperature. The TS structure shows a larger bond distance of Br-Br in 1,2-dibromoethane than that in 1,1-dibromoethane. That explains why the former isomer may result in hotter vibrational population of the Br(2) fragments.