Reactivity Rate Research Articles

Achieving superior ignition and combustion performance of Al/I2O5 biocidal nanoenergetic materials by CuO addition

It was found that all iodine-containing biocidal energetic materials has a relatively long ignition delay upon combustion. A shorter ignition time (from the thermal trigger to the peak pressure) for Al/iodine oxides might further boost their combustion performance due to their high reactivity and high gas release rate. To achieve this goal, a secondary oxidizer, CuO, is incorporated into Al/I2O5 at different mass content keeping the overall thermite stoichiometry constant. The ternary Al/I2O5/CuO thermites were characterized in ignition using a T-jump ignition temperature set up, and in combustion in a constant volume combustion cell. Consequently, all ternary thermites outperform traditional Al/I2O5 counterpart with an optimum for 80/20 wt% of I2O5/CuO. This later composition ignites in 0.01 ms (30 times shorter than Al/I2O5) and produces peak pressure and pressurization rate of ∼4 and 26 times greater than those produced by Al/I2O5. A series of additional characterizations using Fourier-transform infrared spectroscopy, Differential Scanning Calorimetry, Electrical/Thermal conductivity measurement, etc., permitted to unravel the cause of such improvement and to propose a reaction mechanism for this ternary Al/I2O5/CuO system. From an applications point of view, this study proposes a facile, inexpensive and efficient way to enhance the combustion performance of Al/I2O5 biocidal nanoenergetic materials.

High rates of high on-aspirin platelet reactivity in patients after transcatheter aortic valve implantation

Abstract Background Guidelines recommend aspirin monotherapy in patients after transcatheter aortic valve replacement (TAVR) without an indication for oral anticoagulation. The prevalence of high on-aspirin platelet reactivity (HAPR) varies from 1% to 34% and may be associated with long-term ischemic risk or subclinical valve thrombosis which occurs in 17-40% of the patients after TAVR. Purpose To determine the prevalence of HAPR and its association with subclinical valve thrombosis in patients undergoing TAVR using methods that directly indicate the degree of platelet cyclooxygenase inhibition. Methods Data were collected in a prospective, single-center, observational cohort study between October 2020 and June 2022. Patients were enrolled after TAVR, and platelet function was assessed during the hospital stay with light-transmittance platelet aggregation (LTA) and thrombelastography (TEG) platelet mapping. Platelet aggregation was induced with arachidonic acid (AA)-induced LTA (final concentration [fc] 1.64 mM) and TEG (fc 1.0mM). The maximum percent aggregation (%aggr) was recorded. According to the literature, HAPR was defined as >20% aggregation by LTA or >50% aggregation by TEG, respectively. All patients were under maintenance of 100 mg aspirin or received a loading dose of 300-600mg aspirin before measurement. 47 of 75 patients underwent computed tomography (CT) to detect valve thrombosis (VT) 6 months after TAVR. Results Data from 75 patients under maintenance of aspirin were analyzed. The median age was 82 years (interquartile range, IQR 79-85), and 52% were male. 12 patients (16%) had a history of stroke or TIA, and 7 (9%) had suffered a previous myocardial infarction. TEG and LTA were performed during the hospital stay between days 0 and 17 post-TAVR. Median AA-induced maximum aggregation by LTA was 17 % (interquartile range, IQR 13-38) and by TEG was 29 % (IQR 5-64). When determining platelet function using LTA, 33 patients (44%) had residual platelet function (i.e., %aggrLTA >20%) despite aspirin treatment. According to the TEG results, 27 patients (36 %) were identified as HAPR (i.e., %aggrTEG >50%). The agreement (Kappa=0.06) and correlation (r=0.32, Figure 1) between the two tests were low to moderate. 13 patients had HAPR in both methods. 19 of 47 patients (40%) had VT on CT 6 months after TAVI. 12 of these 19 patients (63%) with VT responded well to aspirin in the TEG and LTA, while 7 (37%) had HAPR in both tests. HAPR was not significantly associated with HALT when measured with TEG or LTA (OR 0.90 [95% CI 0.27.2.76], p=0.86 and 0.58 [95% CI 0.17-2.04], p=0.37, respectively; Table 1). Conclusion HAPR assessed by LTA and TEG is frequent in patients undergoing TAVR. In this exploratory study, HAPR was not significantly associated with the occurrence of HALT. Further studies are required to evaluate the long-term risk of leaflet thrombosis or thromboembolic events in patients with HAPR.

Low molarity geopolymer concrete: Effects on compressive strength, elastic modulus, sorptivity and chloride migration

The present study explores the application of low molarity geopolymer concrete for structural applications. In this context, 35 compositions with 4 M and 6 M NaOH concentrations have been developed to yield compressive strength ranging from 10 to 40 MPa. The flow values at low water to binder (w/b) ratio are shown to be influenced by molarity of NaOH while it remains range bound at higher w/b ratio. The effect of curing conditions reveals low reactivity rate under ambient conditions with significant enhancements at elevated curing conditions. Three compositions with compressive strength of 30 ± 2 MPa have been further investigated for tensile strength, elastic modulus, plastic strain, sorptivity and chloride migration. The results reveal that despite similar compressive strength, the mix compositions have significant impact on the fresh and hardened properties indicating possibility of multiparameter optimization. The development of low molarity geopolymer concrete with possibility to optimize other structural/durability parameters in addition to compressive strength would enhance sustainability, economy and structural performance of geopolymer concrete.

Physico-Mechanical and Durability Characterization of Eco-Ternary Cementitious Binder Containing Calcined Clay/Rice Husk Ash and Recycled Glass Powder.

The objective of this study is to determine the influence of recycled glass powder (GP) on the physico-mechanical behavior and durability of a ternary cementitious binder containing calcined clay_metakaolin (MK) or rice husk ash (RHA). Different mortars were produced and characterized in fresh and hardened states. Reference mortars were produced using 100% cement CEM II/B-L 42.5R and 70% CEM + 30% MK or RHA. Test mortars were produced with the substitution of the MK or RHA with the GP and keeping the rate of the substitution at 30%; i.e., in ratios of 20:10, 15:15, and 20:10 of MK/RHA:GP. The water/binder weight ratio was maintained at 0.5, and the consistency of all mortars was adjusted using an admixture (superplasticizer/binder weight ratio of 0.75%). The substitution of MK and RHA with GP reduces the water demand to achieve the normal consistency of pastes and therefore increases the workability of mortars containing both binders CEM+MK+GP and CEM+RHA+GP. The substitution of MK and RHA with GP slightly reduces the compressive strength for both binders. The water-accessible porosity slightly increases for the substitution of MK and reduces for the substitution of RHA with GP. The mass losses after acid attack slightly increase with the substitution with GP, lower for the MK than the RHA up to 15% GP, but it remained far below that of 100% CEM. The results show that the substitution of MK and RHA with GP can improve the physical properties and durability of the mortars compared with that of 100% CEM, but it slightly decreases the mechanical properties due to the low rate of the pozzolanic reactivity of the GP. Further studies should seek to understand the reactivity behavior of the GP at the microstructure scale and therefore improve the mechanical performance of GP based mortar.

Investigating sensitization activity of azobenzene disperse dyes via the Direct Peptide Reactivity Assay (DPRA)

Azobenzene disperse dyes are the fastest-growing category of commercial dyestuffs and have been found in indoor house dust and in children’s polyester apparel. Azobenzene disperse dyes are implicated as potentially allergenic; however, little experimental data is available on allergenicity of these dyes. Here, we examine the binding of azobenzene disperse dyes to nucleophilic peptide residues as a proxy for their potential reactivity as electrophilic allergenic sensitizers. The Direct Peptide Reactivity Assay (DPRA) was utilized via both a spectrophotometric method and a high-performance liquid chromatography (HPLC) method. We tested dyes purified from commercial dyestuffs as well as several known transformation products. All dyes were found to react with nucleophilic peptides in a dose-dependent manner with pseudo-first order kinetics (rate constants as high as 0.04 h−1). Rates of binding reactivity were also found to correlate to electrophilic properties of dyes as measured by Hammett constants and electrophilicity indices. Reactivities of polyester shirt extracts were also tested for DPRA activity and the shirt extracts with high measured abundances of azobenzene disperse dyes were observed to induce greater peptide reactivity. Results suggest that azobenzene disperse dyes may function as immune sensitizers, and that clothing containing these dyes may pose risks for skin sensitization.

Moisture content effects on self-heating in stored biomass: An experimental study

Biomass is essential for modern bioenergy applications, but long-term storage of large volumes of it can pose challenges to plant safety due to the intrinsic self-heating characteristics of biomass piles. In recent years, serious fire accidents have occurred because of self-heating. However, little research has been conducted on this concern. The effects of different initial moisture contents (range of 20–95 %) on the self-heating characteristics of rice and wheat straw, which are two different agricultural biomass residues, are investigated in this study. Biomass samples with different initial moisture contents are stored in a well-insulated container, and the temperature and oxygen levels within the stored biomass samples are monitored. Based on the tests, the heat production rate, oxygen consumption rate and microorganism growth rate are derived, and the impacts of the initial moisture contents on the self-heating characteristics of the stored biomass samples are analysed. The highest temperatures in the stored rice straw and wheat straw are attained under initial moisture contents of 50 % and 20 %, respectively, while the largest heat production rates for both straw types are attained under an initial moisture content of 95 %. An increase in the initial moisture content greatly enhances the overall biological reactivity and oxygen consumption rate. The heat production and oxygen consumption levels exhibit a clear positive correlation. Under identical storage conditions, wheat straw is more susceptible to self-heating than rice straw, as shown by its higher heat generation, faster oxygen consumption, and shorter temperature peaking time. This study contributes to a quantitative understanding of the underlying processes and provides valuable experimental data for model development to guide safe biomass storage systems.

Effects of yard weaning and human contact compared to paddock weaning on the liveweight gain and stress reactivity of beef cattle

ABSTRACT In New Zealand beef herds, calves undergo ‘paddock weaning’ by separating calves and cows into different paddocks. Anecdotal evidence indicates ‘yard weaning’ whereby calves are yarded and receive regular human contact during weaning may improve long-term stress reactivity and growth rates. Calves were allocated to one of three treatments for seven days post-separation from dams: paddock weaned with minimal human interaction (PN), paddock weaned with daily human interaction (PV), yard weaned with daily human interaction (YV). Calf liveweight, behavioural and physiological measures of stress reactivity and faecal corticosterone concentration were measured. Until day seven, YV calves lost less liveweight than PV or PN calves (0.5 kg vs. 3.5 and 4.8 kg P < 0.05). On day seven, PN calves had a 23% greater heart rate compared to YV calves and a greater faecal corticosterone concentration than PV and YV calves (in cohort 2 only) (P < 0.05). This indicates, regular non-aversive human contact during weaning may reduce stress associated with the weaning process itself and reduced stress reactivity to subsequent handling and restraint. However, this effect was transient with no consistent longer-term benefits over traditional paddock weaning, in terms of growth or stress reactivity to human handling.

Evaluating Physiological MRI Parameters in Patients with Brain Metastases Undergoing Stereotactic Radiosurgery-A Preliminary Analysis and Case Report.

Brain metastases occur in ten to thirty percent of the adult cancer population. Treatment consists of different (palliative) options, including stereotactic radiosurgery (SRS). Sensitive MRI biomarkers are needed to better understand radiotherapy-related effects on cerebral physiology and the subsequent effects on neurocognitive functioning. In the current study, we used physiological imaging techniques to assess cerebral blood flow (CBF), oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen (CMRO2) and cerebrovascular reactivity (CVR) before and three months after SRS in nine patients with brain metastases. The results showed improvement in OEF, CBF and CMRO2 within brain tissue that recovered from edema (all p ≤ 0.04), while CVR remained impacted. We observed a global post-radiotherapy increase in CBF in healthy-appearing brain tissue (p = 0.02). A repeated measures correlation analysis showed larger reductions within regions exposed to higher radiotherapy doses in CBF (rrm = -0.286, p < 0.001), CMRO2 (rrm = -0.254, p < 0.001), and CVR (rrm = -0.346, p < 0.001), but not in OEF (rrm = -0.004, p = 0.954). Case analyses illustrated the impact of brain metastases progression on the post-radiotherapy changes in both physiological MRI measures and cognitive performance. Our preliminary findings suggest no radiotherapy effects on physiological parameters occurred in healthy-appearing brain tissue within 3-months post-radiotherapy. Nevertheless, as radiotherapy can have late side effects, larger patient samples allowing meaningful grouping of patients and longer follow-ups are needed.

Physalis Mottle Virus-Like Nanocarriers with Expanded Internal Loading Capacity.

An ongoing challenge in precision medicine is the efficient delivery of therapeutics to tissues/organs of interest. Nanoparticle delivery systems have the potential to overcome traditional limitations of drug and gene delivery through improved pharmacokinetics, tissue targeting, and stability of encapsulated cargo. Physalis mottle virus (PhMV)-like nanoparticles are a promising nanocarrier platform which can be chemically targeted on the exterior and interior surfaces through reactive amino acids. Cargo-loading to the internal cavity is achieved with thiol-reactive small molecules. However, the internal loading capacity of these nanoparticles is limited by the presence of a single reactive cysteine (C75) per coat protein with low inherent reactivity. Here, we use structure-based design to engineer cysteine-added mutants of PhMV VLPs that display increased reactivity toward thiol-reactive small molecules. Specifically, the A31C and S137C mutants show a greater than 10-fold increased rate of reactivity towards thiol-reactive small molecules, and PhMV Cys1 (A31C), PhMV Cys2 (S137C), and PhMV Cys1+2 (double mutant) VLPs display up to three-fold increased internal loading of the small molecule chemotherapeutics aldoxorubicin and vcMMAE and up to four-fold increased internal loading of the MRI imaging reagent DOTA(Gd). These results further improve upon a promising plant virus-based nanocarrier system for use in targeted delivery of small-molecule drugs and imaging reagents in vivo.

Effect of CaO doping on the properties and crystallization behavior of Y2O3–Al2O3–SiO2 glass

Nowadays, Y2O3–Al2O3–SiO2 (YAS) glass joining is considered to be a promising scheme for nuclear-grade continuous silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC). CaO has great potential for nuclear applications since it has low reactivity and low decay rate under nuclear irradiation. In this paper, the effect of CaO doping on the structure, thermophysical properties, and crystallization behavior of YAS glass was systematically studied. As the CaO doping content increased, the number of bridge oxygens and the viscosity at high temperatures reduced gradually. After heat treatment at 1400 °C, the main phases in YAS glass were β-Y2Si2O7, mullite, and SiO2 (coexistence of crystalline and glass phases), while that with 3.0% CaO doping turned into a single glassy phase under the same treatment conditions. Moreover, a structural model and the modification mechanism were proposed, which provided a theoretical basis for the subsequent component design and optimization.

Advanced Photo-Oxidation Process for Treatment of River Water Pollutants and Pathogens

Water is a fundamental resource for human civilisation, yet there is a critical water shortage happening all across the world in the twenty-first century. In some areas of underdeveloped nations, people drink water that has been extensively polluted and comes from rivers that are home to deadly diseases. Microbial infections in drinking water can cause illness and increase the prevalence of disease. There are several treatment methods available to remove microorganisms from drinking water. This study suggests employing two techniques, photocatalytic semiconductor and photo Fenton, as an enhanced oxidation process to get rid of diverse water impurities and offer a reliable water treatment approach. A test on samples of river water was undertaken, and the analysis of a number of parameters was used to determine how well the test had removed contaminants and pathogens. The physiochemical criteria were used to evaluate the reaction and determine the properties of safe water using both approaches. The two techniques effectively eliminated between 80 and 100 percent of the contaminants that were detected in the river sampled. Variations in Titanium Dioxide concentration correlated with changes in reactivity and degradation rates. Results showed that light absorption was reduced dramatically as titanium dioxide concentration rose to saturation. Besides, the rate of degradation was directly correlated with light intensity.

Evaluation of Ortho VITROS and Roche Elecsys S and NC Immunoassays for SARS-CoV-2 Serosurveillance Applications.

SARS-CoV-2 seroprevalence studies are instrumental in monitoring epidemic activity and require well-characterized, high-throughput assays, and appropriate testing algorithms. The U.S. Nationwide Blood Donor Seroprevalence Study performed monthly cross-sectional serological testing from July 2020 to December 2021, implementing evolving testing algorithms in response to changes in pandemic activity. With high vaccine uptake, anti-Spike (S) reactivity rates reached >80% by May 2021, and the study pivoted from reflex Roche anti-nucleocapsid (NC) testing of Ortho S-reactive specimens to parallel Ortho S/NC testing. We evaluated the performance of the Ortho NC assay as a replacement for the Roche NC assay and compared performance of parallel S/NC testing on both platforms. Qualitative and quantitative agreement of Ortho NC with Roche NC assays was evaluated on preselected S/NC concordant and discordant specimens. All 190 Ortho S+/Roche NC+ specimens were reactive on the Ortho NC assay; 34% of 367 Ortho S+/Roche NC- specimens collected prior to vaccine availability and 43% of 37 Ortho S-/Roche NC+ specimens were reactive on the Ortho NC assay. Performance of parallel S/NC testing using Ortho and Roche platforms was evaluated on 200 specimens collected in 2019 and 3,903 study specimens collected in 2021. All 200 pre-COVID-19 specimens tested negative on the four assays. Cross-platform agreement between Roche and Ortho platforms was 96.4% (3,769/3,903); most discordant results had reactivity close to the cutoffs on the alternate assays. These findings, and higher efficiency and throughput, support the use of parallel S/NC testing on either Roche or Ortho platforms for large serosurveillance studies. IMPORTANCE Seroprevalence studies like the U.S. Nationwide Blood Donor Seroprevalence Study (NBDS) have been critical in monitoring SARS-CoV-2 epidemic activity. These studies rely on serological assays to detect antibodies indicating prior infection. It is critical that the assays and testing algorithms used in seroprevalence studies have adequate performance (high sensitivity, high specificity, ability to discriminate vaccine-induced and infection-induced antibodies, etc.), as well as appropriate characteristics to support large-scale studies, such as high throughput and low cost. In this study we evaluated the performance of Ortho's anti-nucleocapsid assay as a replacement for the Roche anti-nucleocapsid assay and compared performance of parallel anti-spike and anti-nucleocapsid testing on both platforms. These data demonstrate similar performance of the Ortho and Roche anti-nucleocapsid assays and that parallel anti-spike and anti-nucleocapsid testing on either platform could be used for serosurveillance applications.

Reactivity and Mechanisms of Methane, Ethane, and Benzene C–H Amination with an Iodine(III) Bistriflimide Complex

The iodine(III) bistriflamide complex (C6F5)IIII(NTf2)2 in HNTf2 (bistriflimide acid; (CF3SO2)2NH) selectively aminates methane and ethane. At a 100 °C reaction with methane after 3 h, it resulted in the exclusive formation of MeNTf2 with a yield of approximately 40%. For ethane, at 100 °C in 2 h, a > 80% yield was found for a combination of monofunctionalized and difunctionalized amination products. In contrast to alkanes giving functionalized products, the reaction of (C6F5)IIII(NTf2)2 with benzene resulted in being stalled at (C6F5)IIII(Ph)(NTf2) with a <5% conversion to PhNTf2 even at 120 °C. PWPB95-D3(BJ) density functional theory calculations indicate that C–H activation is the lowest energy pathway to break the hydrocarbon bonds and is lower in energy than radical, electron-transfer, proton-coupled electron-transfer, or hydride substitution pathways. For methane, from the (C6F5)IIII(CH3)(NTf2) intermediate, there is a one-step amine functionalization mechanism that avoids a carbocation intermediate. For ethane, from the (C6F5)IIII(Et)(NTf2) intermediate, dynamics simulations suggest the possibility of a competitive two-step functionalization pathway that involves a short-lived carbocation intermediate. A reaction coordinate strain analysis provides a straightforward model for understanding the relative reactivity rates for alkyl versus aryl functionalization.

Effects of ammonia on combustion of coal in stoichiometric premixed methane–air flames

NH3 has long been considered a promising alternative fuel·NH3 from renewables can be used for energy storage·NH3 is a zero-carbon molecule and can be burned directly and used as a hydrogen carrier. Compared with hydrocarbon fuels, NH3 has several drawbacks, such as an inferior flammability limit, flame temperature, and flame burning velocity, resulting in a lower reactivity rate and the production of pollutants.Therefore, cofiring coal with NH3 is an approach that has been growing in popularity. This study investigated the combustion of coal cofired with NH3 and conducted two-color pyrometry to measure the temperature profiles of coal particles in hybrid flames, that is, methane–coal–air and methane–NH3–coal–air premixed flames. The axial temperature distribution at the center of the flame was measured using two-color pyrometry and a thermocouple. The temperature values obtained were not identical but exhibited similar trends. The results indicated that the temperature at the origin significantly decreased upon ammonia addition, but as the measuring height increased, the final temperatures approached similarity.In addition, the emissions of pollutants such as CO and NOx were also measured. The results indicate that the addition of coal particles without ammonia gas leads to an increase in CO concentration due to the pyrolysis of the pulverized coal. However, there was no significant impact on NOx emissions.In contrast, the addition of coal particles under CH4 − NH3 gas combustion conditions results in a significant decrease in both CO and NOx concentrations. Specifically, under the 80 %CH4 + 20 %NH3 condition and with a coal particle feeding rate increasing from 0 to 0.24 g/min, there was a reduction of approximately 34% in CO concentration and 35% in NOx concentration.In order to confirm the coal consumption rate, coal particles were captured before and after flame sheet using a metal grid, and the particle projected area was determined based on scanning electron microscopy (SEM) images. These results provided evidence that the addition of NH3 to the CH4 − air flame enhances coal combustion, as indicated by a decrease in the particle shrinkage rate and sampling density.

Alexithymic vs. non-alexithymic participants: The effect of slow breathing intervention on emotional reactivity, blood pressure and heart rate

Alexithymic vs. non-alexithymic participants: The effect of slow breathing intervention on emotional reactivity, blood pressure and heart rate

Retrospective Investigation of Viral Hepatitis Seroprevalence in Patients Admitted at the Outpatient Clinics of Internal Medicine

ABSTRACT&#x0D; Aim: Viral hepatitis agents include Hepatitis B and Hepatitis C virus, which cause an important public health problem due to serious complications. Patients examined at the outpatient clinics of internal medicine are among main risk groups, as they have concomitant diseases and undergo various procedures. We aimed to investigate retrospectively the seroprevalence of viral hepatitis in outpatients in internal medicine in our region.&#x0D; Material and Methods: HBsAg and Anti-HCV parameters, and demographic data such as age and gender of patients admitted at the outpatient clinics of internal medicine at our hospital between January 2017 and July 2022 were retrospectively evaluated, with HBV-DNA and HCV-RNA levels of those who showed reactivity.&#x0D; Results: HBsAg test results of 2618 patients and Anti-HCV test results of 2943 patients were obtained in this study. The mean age of patients with HBsAg tests was 34.2±15.7, and mean age of patients with Anti-HCV test was 34.3±15.7 years. HBsAg reactivity rate was 0.9%; and the mean age of patients showing reactivity was 47.7±14.4 years. Anti-HCV reactivity rate was %0.1, with a mean age of 52.6±21.3 years. Both HBsAg and Anti-HCV reactivity was not present at the same patient in our study.&#x0D; Conclusion: Early diagnosis of Hepatitis B and Hepatitis C viruses decrease the risk of developing complications, easing treatment processes and decreasing the risk of contagion. Thus, increasing use of screening tests as part of preventive medicine is very important.

Improved Performance of the QuantiFERON-SARS-CoV-2 Assay with the Extended Set.

Multiple assays have been developed for the characterization of the functional activation of SARS-CoV-2 specific T-cells. This study was conducted to assess the post-vaccination and post-infection T cell response, as detected by the QuantiFERON-SARS-CoV-2 assay using the combination of three SARS-CoV-2 specific antigens (Ag1, Ag2 and Ag3). An amount of 75 participants with different infection and vaccination backgrounds were recruited for the evaluation of humoral and cellular immune responses. An elevated IFN-γ response in at least one Ag tube was observed in 69.2% of convalescent subjects and 63.9% of vaccinated ones. Interestingly, in a healthy unvaccinated case and three convalescents with negative IgG-RBD, we detected a positive QuantiFERON test after stimulation with Ag3. The majority of the T cell responders reacted simultaneously to the three SARS-CoV-2 specific antigens, and Ag3 demonstrated the highest rate of reactivity. At univariable analysis, the only factor that was associated with an absence of a cellular response was time from blood collection, being less than 30 days (OR:3.5, CI95% [1.15-10.50], p = 0.028). Overall, the inclusion of Ag3 improved the performance of the QuantiFERON-SARS-CoV-2 and showed a particular interest among subjects who fail to achieve a measurable antibody response after infection or vaccination.

Distribution and dissolution kinetics of biogenic silica in sediments of the northern South China Sea

The dissolution efficiency of sedssimentary biogenic silica (bSiO2) dramatically affects the regeneration of dissolved silicic acid (dSi) at the sediment-water interface, which is a crucial pathway to maintain Si balance and silicic productivity growth in marine environments. We conducted wet alkaline leach and flow-through experiments to explore the dissolution behaviors of sedimentary bSiO2 in the northern South China Sea (NSCS), one of the largest marginal sea continental shelves. The bSiO2 contents of surface sediments were 0.64 - 2.06%, with an average of 1.04 ± 0.35%, varying with isobath water depth. The solubility of bSiO2 in surface sediments ranged from 227 μmol L-1 to 519 μmol L-1, and the dissolution rate constants varied from 0.67 to 1.53 yr-1 under specific conditions in lab incubation. The correlation between the biogenic materials (bSiO2, OC, and TN) revealed a different preservation pattern of bSiO2 in finer (Φ &amp;gt; ~ 5.5) and coarser (Φ&amp;lt; ~ 5.5) sediments. The high concentration of Al in sea water and “Al – detrital – bSiO2” interactions in sediments significantly interfered with the apparent solubility and dissolution dynamics of bSiO2. We combined the regional characteristics (primary production, bottom current, and resuspension-deposition) and the reconstructed dissolution kinetics of bSiO2 explained the mismatch between the surface (diatom biomass)/(total phytoplankton biomass) ratio and the sedimentary bSiO2/OC ratio, and the mismatch between the surface bSiO2 primary productivity and the bSiO2 sediment records in the NSCS. The resuspension-deposition, the higher reconstructed rate constants (0.94 ± 0.13 yr-1), and the dissolution rate (0.20 ± 0.01 yr-1) were responsible for the lower bSiO2/OC ratio (0.45 ± 0.28) at the inner shelf, and the winnowing process at the outer shelf with the lower reconstructed reactivity (0.30 yr-1) and dissolution rate (0.001 yr-1) led to the good preservation of bSiO2 in the upper slope. Furthermore, through the comparison with other sea areas, the relatively lower reactivity (1.12 ± 0.3 yr-1) of bSiO2 in sediments supported the notion that the NSCS sediments may serve as an important silica sink in the world ocean silica cycle.

Depressive symptoms, anxiety and social stress are associated with diminished cardiovascular reactivity in a psychological treatment-naive population

BackgroundThere is now an increasing appreciation of how psychological health can contribute to cardiovascular disease, called the mind-heart connection. A blunted cardiovascular reactivity to depression and anxiety may be responsible for the potential mechanism, however, with inconsistent results. Anti-psychological drugs have an effect on the cardiovascular system and, thus, may disturb their relationship. However, in treatment-naive individuals with psychological symptoms, no research has specifically evaluated the relationship between psychological state and cardiovascular reactivity. MethodsWe included 883 treatment-naive individuals who came from a longitudinal cohort study of Midlife in the United States. Symptoms of depression, anxiety, and stress were assessed by the Center for Epidemiologic Studies Depression Scale (CES-D), Spielberger Trait Anxiety Inventory (STAI), the Liebowitz Social Anxiety scale (LSAS) and the Perceived Stress Scale (PSS), respectively. Cardiovascular reactivity was measured using standardized, laboratory-based stressful tasks. ResultsTreatment-naive individuals with depressive symptoms (CES-D ≥ 16), anxiety symptoms (STAI ≥ 54), and higher stress levels (PSS ≥ 27) had lower cardiovascular reactivity as assessed by systolic blood pressure (SBP) reactivity, diastolic blood pressure (DBP) reactivity and heart rate (HR) reactivity (P < 0.05). Pearson analyses showed that psychological symptoms were correlated with lower SBP reactivity, DBP reactivity, and heart rate reactivity (P < 0.05). Multivariate linear regression showed that depression and anxiety were negatively related to lower cardiovascular reactivity (SBP, DBP and HR reactivity) after full adjustments (P < 0.05). Stress was associated with reduced SBP and DBP reactivity but with a nonsignificant association with HR reactivity (P = 0.056). ConclusionDepression, anxiety, and stress symptoms are associated with blunted cardiovascular reactivity in treatment-naive adult Americans. These findings suggest that blunted cardiovascular reactivity is an underlying mechanism linking psychological health and cardiovascular diseases.

Testing the Limits of Imbalanced CPET Reactivity: Mechanistic Crossover in H-Atom Abstraction by Co(III)-Oxo Complexes.

Transition metal-oxo complexes are key intermediates in a variety of oxidative transformations, notably C-H bond activation. The relative rate of C-H bond activation mediated by transition metal-oxo complexes is typically predicated on substrate bond dissociation free energy in cases with a concerted proton-electron transfer (CPET). However, recent work has demonstrated that alternative stepwise thermodynamic contributions such as acidity/basicity or redox potentials of the substrate/metal-oxo may dominate in some cases. In this context, we have found basicity-governed concerted activation of C-H bonds with the terminal CoIII-oxo complex PhB(tBuIm)3CoIIIO. We have been interested in testing the limits of such basicity-dependent reactivity and have synthesized an analogous, more basic complex, PhB(AdIm)3CoIIIO, and studied its reactivity with H-atom donors. This complex displays a higher degree of imbalanced CPET reactivity than PhB(tBuIm)3CoIIIO with C-H substrates, and O-H activation of phenol substrates displays mechanistic crossover to stepwise proton transfer-electron transfer (PTET) reactivity. Analysis of the thermodynamics of proton transfer (PT) and electron transfer (ET) reveals a distinct thermodynamic crossing point between concerted and stepwise reactivity. Furthermore, the relative rates of stepwise and concerted reactivity suggest that maximally imbalanced systems provide the fastest CPET rates up to the point of mechanistic crossover, which results in slower product formation.