Impact of MoS2 Monolayers on the Thermoelastic Response of Silicon Heterostructures.

Understanding the thermoelastic response of a nanostructure is crucial for the choice of materials and interfaces in electronic devices with improved and tailored transport properties at the nanoscale. Here, we show how the deposition of a MoS2 monolayer can strongly modify the nanoscale thermoelastic dynamics of silicon substrates close to their interface. We demonstrate this by creating a transient grating with extreme ultraviolet light, using ultrashort free-electron laser pulses, whose ≈84 nm period is comparable to the size of elements typically used in nanodevices, such as electric contacts and nanowires. The thermoelastic response, featuring coherent acoustic waves and incoherent relaxation, is tangibly modified by the presence of monolayer MoS2. Namely, we observed a major reduction of the amplitude of the surface mode, which is almost suppressed, while the longitudinal mode is basically unperturbed, aside from a faster decay of the acoustic modulations. We interpret this behavior as a selective modification of the surface elasticity, and we discuss the conditions to observe such effect, which may be of immediate relevance for the design of Si-based nanoscale devices.

Reducing cardiometabolic risk with semaglutide in type 1 diabetes (RESET1): Study protocol of a phase 2 double-blinded randomised placebo-controlled trial.

BACKGROUND: Premature cardiovascular disease is the leading cause of death in people living with type 1 diabetes. Therapies are urgently needed to address cardiovascular risk in this group. Semaglutide, a long-acting glucagon-like peptide-1 receptor agonist, has been shown to reduce cardiovascular events and improve weight and glycaemia in type 2 diabetes. Semaglutide may offer cardioprotective and metabolic benefits in type 1 diabetes. METHODS: We will study 60 adults aged 25-70 years with type 1 diabetes of duration at least 2 years, body mass index ≥25 kg/m2, HbA1c ≥7% and at least one cardiovascular risk factor (microalbuminuria, hypertension or anti-hypertensive treatment, hyperlipidemia or lipid lowering therapy, current smoking). Participants will receive semaglutide up to 1.0 mg weekly or matched placebo for 26 weeks. The primary outcome is carotid femoral pulse wave velocity, a measure of arterial stiffness, as a surrogate marker of cardiovascular risk. Potential mechanisms for metabolic changes will be explored including change in insulin sensitivity determined by hyperinsulinaemic-euglycaemic clamp; and incretin and pancreatic hormone action measured during mixed meal tolerance test. CONCLUSION: The REducing cardiometabolic risk with SEmaglutide in Type 1 diabetes study will investigate whether semaglutide, a long acting glucagon-like peptide receptor agonist, can improve markers of cardiometabolic health in T1D. Underlying mechanisms predicting response, including insulin resistance and incretin hormone status, will also be explored.

A 72-h sedated porcine model of traumatic spinal cord injury.

Introduction: There is an increasing focus on the prevention of secondary injuries following traumatic spinal cord injury (TSCI), especially through improvement of spinal cord perfusion and immunological modulation. Such therapeutic strategies require translational and controlled animal models of disease progression of the acute phases of human TSCI. Research question: Is it possible to establish a 72-h sedated porcine model of incomplete thoracic TSCI, enabling controlled use of continuous, invasive, and non-invasive modalities during the entire sub-acute phase of TSCI? Material and methods: A sham-controlled trial was conducted to establish the model, and 10 animals were assigned to either sham or TSCI. All animals underwent a laminectomy, and animals in the TSCI group were subjected to a weight-drop injury. Animals were then kept sedated for 72 h. The amount of injury was assessed by ex-vivo measures MRI-based fiber tractography, histology and immunohistochemistry. Results: In all animals, we were successful in maintaining sedation for 72 h without comprising vital physiological parameters. The MRI-based fiber tractography showed that all TSCI animals revealed a break in the integrity of spinal neurons, whereas histology demonstrated no transversal sections of the spine with complete injury. Notably, some animals displayed signs of secondary ischemic tissue in the cranial and caudal sections. Discussion and conclusions: This study succeeded in producing a porcine model of incomplete TSCI, which was physiologically stable up to 72 h. We believe that this TSCI model will constitute a potential translational model to study the pathophysiology secondary to TSCI in humans.

Spin-Polarized Charge Separation at Two-Dimensional Semiconductor/Molecule Interfaces.

Spin-polarized electrons can improve the efficiency and selectivity of photo- and electro-catalytic reactions, as demonstrated in the past with magnetic or magnetized catalysts. Here, we present a scheme in which spin-polarized charge separation occurs at the interfaces of nonmagnetic semiconductors and molecular films in the absence of a magnetic field. We take advantage of the spin-valley-locked band structure and valley-dependent optical selection rule in group VI transition metal dichalcogenide (TMDC) monolayers to generate spin-polarized electron-hole pairs. Photoinduced electron transfer from WS2 to fullerene (C60) and hole transfer from MoSe2 to phthalocyanine (H2Pc) are found to result in spin polarization lifetimes that are 1 order of magnitude longer than those in the TMDC monolayers alone. Our findings connect valleytronic properties of TMDC monolayers to spin-polarized interfacial charge transfer and suggest a viable route toward spin-selective photocatalysis.

Spontaneous exciton dissociation in transition metal dichalcogenide monolayers.

Since the seminal work on MoS2, photoexcitation in atomically thin transition metal dichalcogenides (TMDCs) has been assumed to result in excitons, with binding energies order of magnitude larger than thermal energy at room temperature. Here, we reexamine this foundational assumption and show that photoexcitation of TMDC monolayers can result in a substantial population of free charges. Performing ultrafast terahertz spectroscopy on large-area, single-crystal TMDC monolayers, we find that up to ~10% of excitons spontaneously dissociate into charge carriers with lifetimes exceeding 0.2 ns. Scanning tunneling microscopy reveals that photocarrier generation is intimately related to mid-gap defects, likely via trap-mediated Auger scattering. Only in state-of-the-art quality monolayers, with mid-gap trap densities as low as 109 cm-2, does intrinsic exciton physics start to dominate the terahertz response. Our findings reveal the necessity of knowing the defect density in understanding photophysics of TMDCs.

Feasibility of telehealth counselling pilot for people experiencing homelessness and/or complex needs: During COVID-19 and beyond.

ISSUES ADDRESSED: People experiencing homelessness and/or complex needs often require targeted health services to address unique vulnerabilities. COVID-19 restrictions acted as a barrier for this group accessing health and alcohol and other drug (AOD) treatment services. The Haymarket Foundation, an accommodation and health facility in Australia, transitioned from in-person AOD-counselling services to online consultations. Clients accessing these services were tracked, from March 2019 to November 2020, to assess the impact of the switch to telehealth on client retention. METHODS: Qualitative analysis of Haymarket clients' service experience surveys and quantitative descriptives of "no-show" (nonattended sessions) rates and survival analysis of client treatment separations were completed to assess the impact of transitioning to telehealth on client retention. RESULTS: Although the initial transition to telehealth in March 2020 minimally impacted client no-show rates, reinstated government restrictions in June/July 2020 coincided with increasing no-shows and a substantial increase in treatment exits without notice, especially amongst males. Qualitative analysis showed clients had mixed feelings towards telehealth: some attributed their dissatisfaction to the inability to build rapport with their counsellor online, or with COVID-19 in general. Others appreciated the availability and genuine care of their counsellors through either setting. CONCLUSIONS: Telehealth may be a feasible replacement for face-to-face AOD counselling for people experiencing homelessness, however further investigation needs to be conducted to understand factors associated with improved client retention. SO WHAT?: This pilot demonstrates telehealth may be a feasible ongoing feature of health promotion for vulnerable high-needs populations, including people experiencing homelessness who use substances.

Direct View of Phonon Dynamics in Atomically Thin MoS2.

Transition-metal dichalcogenide monolayers and heterostructures are highly tunable material systems that provide excellent models for physical phenomena at the two-dimensional (2D) limit. While most studies to date have focused on electrons and electron-hole pairs, phonons also play essential roles. Here, we apply ultrafast electron diffraction and diffuse scattering to directly quantify, with time and momentum resolution, electron-phonon coupling (EPC) in monolayer molybdenum disulfide and phonon transport from the monolayer to a silicon nitride substrate. Optically generated hot carriers result in a profoundly anisotropic distribution of phonons in the monolayer within ∼5 ps. A quantitative comparison with ab initio ultrafast dynamics simulations reveals the essential role of dielectric screening in weakening EPC. Thermal transport from the monolayer to the substrate occurs with the phonon system far from equilibrium. While screening in 2D is known to strongly affect equilibrium properties, our findings extend this understanding to the dynamic regime.