The Synthesis of [{n-Bu2Sn(S2N2)}2] and its use in the preparation of Organometallic Iridium Sulfur Nitrogen Complexes

The addition of [n-Bu2SnCl2] to a solution of [S4N3][Cl] in liquid ammonia gave after extraction of the dry reaction mixture the new tin disulfur dinitrido compound [{n-Bu2Sn(S2N2)}(2)] (1). Reaction of [{n-Bu2Sn(S2N2)}(2)] (1) with the pentamethylcyclopentadienyl (Cp*) iridium derivatives [{IrCl(mu-Cl)(eta(5)-C5Me5)}(2)] or [(eta(5)-C5Me5)IrCl2(PPh3)] gave different products, which were dependent on the reactant ratios. A 1:1 reaction between 1 and [{IrCl(mu-Cl)(eta(5)-C5Me5)}(2)] gave only [(eta(5)-C5Me5)Ir(S2N2)] (2) in moderate yield; the same product in higher yield was obtained from a 2:1 reaction between 1 and [(eta(5)-C5Me5)IrCl2(PPh3)]. Reaction of 1 and [(eta(5)-C5Me5)(2)IrCl2(PPh3)] (1:1 molar ratio) in the presence of NH4[PF6] gave the unusual bimetallic species [(eta(5)-C5Me5)IrCl(PPh3)(S2N2)Ir(eta(5)-C5Me5)][PF6] (3). The X-ray crystal structures of 1, 2, and 3 are reported.PostprintPeer reviewe

Long-term disturbance dynamics and resilience of tropical peat swamp forests

Summary 1.The coastal peat swamp forests of Sarawak, Malaysian Borneo, are undergoing rapid conversion, predominantly into oil palm plantations. This wetland ecosystem is assumed to have experienced insignificant disturbance in the past, persisting under a single ecologically-stable regime. However, there is limited knowledge of the past disturbance regime, long-term functioning and fundamentally the resilience of this ecosystem to changing natural and anthropogenic perturbations through time. 2. In this study, long-term ecological data sets from three degraded peatlands in Sarawak were collected to shed light on peat swamp forest dynamics. Fossil pollen and charcoal were counted in each sedimentary sequence to reconstruct vegetation and investigate responses to past environmental disturbance, both natural and anthropogenic. 3. Results demonstrate that peat swamp forest taxa have dominated these vegetation profiles throughout the last c. 2000-year period despite the presence of various drivers of disturbance. Evidence for episodes of climatic variability, predominantly linked to ENSO events, and wildfires is present throughout. However, in the last c. 500 years, burning and indicators of human disturbance have elevated beyond past levels at these sites, concurrent with a reduction in peat swamp forest pollen. 4. Two key insights have been gained through this palaeoecological analysis: (i) peat swamp forest vegetation has demonstrated resilience to disturbance caused by burning and climatic variability in Sarawak in the late Holocene, however (ii) coincident with increased fire combined with human impact c. 500 years ago, these communities started to decline. 5. Synthesis. Sarawak's coastal peat swamps have demonstrated resilience to past natural disturbances, with forest vegetation persisting through episodes of fire and climatic variability. However, palaeoecological data presented here suggest that recent, anthropogenic disturbances are of a greater magnitude, causing the observed decline in the peat swamp forest communities in the last c. 500 years and challenging the ecosystem's persistence. This study greatly extends our knowledge of the ecological functioning of these understudied ecosystems, providing baseline information on the past vegetation and its response to disturbance. This understanding is central to developing management strategies that foster resilience in the remaining peat swamp forests and ensure continued provision of services, namely carbon storage, from this globally important ecosystem.</p

Search for dark mesons decaying to top and bottom quarks in proton-proton collisions at √s = 13 TeV with the ATLAS detector

A search for dark mesons originating from strongly-coupled, SU(2) dark favor symmetry conserving models and decaying gaugephobically to pure Standard Model final states containing top and bottom quarks is presented. The search targets fully hadronic final states and final states with exactly one electron or muon and multiple jets. The analyzed data sample corresponds to an integrated luminosity of 140 fb−1 of proton-proton collisions collected at √s = 13 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess over the Standard Model background expectation is observed and the results are used to set the first direct constraints on this type of model. The two-dimensional signal space of dark pion masses mπD and dark rho-meson masses mρD is scanned. For mπD /mρD = 0.45, dark pions with masses mπD < 940 GeV are excluded at the 95% CL, while for mπD /mρD = 0.25 masses mπD < 740 GeV are excluded

Combination of searches for Higgs boson decays into a photon and a massless dark photon using pp collisions at √s = 13 TeV with the ATLAS detector

A combination of searches for Higgs boson decays into a visible photon and a massless dark photon (H → γγd) is presented using 139 fb−1 of proton-proton collision data at a centre-of-mass energy of √s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The observed (expected) 95% confidence level upper limit on the Standard Model Higgs boson decay branching ratio is determined to be B(H → γγd) < 1.3% (1.5)%. The search is also sensitive to higher-mass Higgs bosons decaying into the same final state. The observed (expected) 95% confidence level limit on the cross-section times branching ratio ranges from 16 fb (20 fb) for mH = 400 GeV to 1.0 fb (1.5 fb) for mH = 3 TeV. Results are also interpreted in the context of a minimal simplified model

Growth and application of WSe

Tungsten di-selenide (WSe2) belonging to the family of layered transition metal di-chalcogenides (TMDCs) is at present widely used in optoelectronic devices due to their adequate energy band gap suitable for photosensing applications. In the present investigation, WSe2 single crystals are grown by direct vapor transport (DVT) technique in a dual zone horizontal furnace maintaining a temperature difference of 50 K between source zone (SZ) and growth zone (GZ). The crystals thus obtained were thin, shiny and with an average thickness of 30 mm. The surface topography of crystals studied by optical microscope revealed hexagonal spirals on the crystal surface which seemed to arise due to screw dislocation defect. The structural properties of the as grown crystals studied by powder X-ray diffraction (XRD) elucidated good crystallinity, hexagonal structure and confirmed the orientation of crystals along crystallographic c-axis. P-type semiconductor nature of the crystals was affirmed by thermoelectric power (TEP) measurement. Optical and vibrational properties of the grown crystals were studied by UV–Visible, photoluminescence (PL) and Raman spectroscopy. An optical direct band gap of 1.41 eV was determined for the crystals which were micromechanically exfoliated upto few layers. The excitonic mechanism of the grown WSe2 crystal was explained by PL spectroscopy. The results of Raman spectroscopy disclosed A1g and E2g vibrational modes present in the crystals. The current–voltage characteristics of nSnSe/pWSe2 hetero-structure studied using Keithley 2400 SMU showed rectification behavior at low bias voltage in dark and illuminated conditions. The diode parameters like ideality factor and barrier potential were determined to be 2.54 and 0.4 eV, respectively, by following conventional lnI–V method. The photodetection properties of the fabricated device were studied using a Laser source (670 nm) having an intensity of 3 mWcm−2at different bias voltage ranging from 0.3 V to 3 V. Parameters such as responsivity, detectivity and external quantum efficiency (EQE) were calculated to substantiate the excellent detection properties shown by the prepared photodetector using time resolved pulsed photoresponse. Value of responsivity and EQE increased from 42.22 mA W−1 to 533.77 mA W−1 and 7% to 95%, respectively, with increase in bias voltage from 0.3 V to 3 V. Also, detectivity values were found to be of the order of 107 Jones

Sex Differences in Quality of Life in Patients With Systemic Lupus Erythematosus

Objective. Systemic lupus erythematosus (SLE) predominantly affects women. Clinical phenotype and outcomes in SLE may vary by sex and are further complicated by unique concerns that are dependent upon sex-defined roles. We aimed to describe sex differences in disease-specific quality of life (QoL) assessment scores using the Lupus Patient-Reported Outcome (LupusPRO) tool in a large international study. Methods. Cross-sectional data from 1,803 patients with SLE on demographics, self-identified sex status, LupusPRO, and disease activity were analyzed. The LupusPRO tool has 2 constructs: health-related QoL (HRQoL) and non-HRQoL. Disease activity and damage were evaluated using the Safety of Estrogens in Lupus Erythematosus National Assessment version of the Systemic Lupus Erythematosus Disease Activity Index and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index, respectively. Nonparametric tests were used to compare QoL and disease activity by sex. Results. A total of 122 men and 1,681 women with SLE participated. The mean age was similar by sex, but the damage scores were greater among men. Men fared worse on the non-HRQoL social support domain than women (P = 0.02). When comparing disease and QoL among men and women ages 6445 years, men were found to have greater damage and worse social support than women. However, women fared significantly worse on lupus symptoms, cognition, and procreation domains with trends for worse functioning on physical health and pain-vitality domains. Conclusion. In the largest study of a diverse group of SLE patients, utilizing a disease-specific QoL tool, sex differences in QoL were observed on both HRQoL and non-HRQoL constructs. Although men performed worse in the social support domain, women (especially those in the reproductive age group) fared worse in other domains. These observations may assist physicians in appropriately addressing QoL issues in a sex-focused manner

Optimization of a Permanent Step Mold Design for Mg Alloy Castings

The design of a permanent Step mold for the evaluation of the mechanical properties of light alloys has been reviewed. An optimized Step die with a different runner and gating systems is proposed to minimize the amount of casting defects. Numerical simulations have been performed to study the filling and solidification behavior of an AM60B alloy to predict the turbulence of the melt and the microshrinkage formation. The results reveal how a correct design of the trap in the runners prevents the backwave of molten metal, which could eventually reverse out and enter the die cavity. The tapered runner in the optimized die configuration gently leads the molten metal to the ingate, avoiding turbulence and producing a balanced die cavity filling. The connection between the runner system and the die cavity by means of a fan ingate produces a laminar filling in contrast with a finger-type ingate. Solidification defects such as shrinkage induced microporosity, numerically predicted through a dimensionless version of the Niyama criterion, are considerably reduced in the optimized permanent Step mold