In-patient characteristics of peripheral artery disease in Germany.

Background: Peripheral artery disease (PAD) frequently leads to hospital admission. Sex related differences in in-patient care are a current matter of debate. Patients and methods: Data were provided from the German national in-patient sample provided by the Federal Bureau of Statistics (DESTATIS). Trends on risk profiles, therapeutic procedures, and outcomes were evaluated from 2014 until 2019 stratified by sex and PAD severity. Results: Two-thirds of an annual >191,000 PAD in-patient cases applied to male sex. Chronic limb-threatening ischemia (CLTI) was recorded in 49.6% of male and 55.2% of female cases (2019). CLTI was as a major risk factor of in-hospital amputation (OR 229) and death (OR 10.5), whereas endovascular revascularisation (EVR) with drug-coated devices were associated with decreased risk of in-hospital amputation (OR 0.52; all p<0.001). EVR applied in 47% of CLTI cases compared to 71% in intermittent claudication (IC) irrespective of sex. In-hospital mortality was 4.3% in male vs. 4.8% in female CLTI cases, minor amputations 18.4% vs. 10.9%, and major amputation 7.5% vs. 6.0%, respectively (data 2019; all p<0.001). After adjustment, female sex was associated with lower risk of amputation (OR 0.63) and death (OR 0.96) during in-patient stay. Conclusions: Male PAD patients were twice as likely to be admitted for in-patient treatment despite equal PAD prevalence in the general population. Among in-patient cases, supply with invasive therapy did not relevantly differ by sex, however is strongly reduced in CLTI. CLTI is a major risk factor of adverse short-term outcomes, whereas female sex was associated with lower risk of in-patient amputation and/or death.

Ultrafast Umklapp-assisted electron-phonon cooling in magic-angle twisted bilayer graphene.

Understanding electron-phonon interactions is fundamentally important and has crucial implications for device applications. However, in twisted bilayer graphene near the magic angle, this understanding is currently lacking. Here, we study electron-phonon coupling using time- and frequency-resolved photovoltage measurements as direct and complementary probes of phonon-mediated hot-electron cooling. We find a remarkable speedup in cooling of twisted bilayer graphene near the magic angle: The cooling time is a few picoseconds from room temperature down to 5 kelvin, whereas in pristine bilayer graphene, cooling to phonons becomes much slower for lower temperatures. Our experimental and theoretical analysis indicates that this ultrafast cooling is a combined effect of superlattice formation with low-energy moiré phonons, spatially compressed electronic Wannier orbitals, and a reduced superlattice Brillouin zone. This enables efficient electron-phonon Umklapp scattering that overcomes electron-phonon momentum mismatch. These results establish twist angle as an effective way to control energy relaxation and electronic heat flow.

A pre-time-zero spatiotemporal microscopy technique for the ultrasensitive determination of the thermal diffusivity of thin films.

Diffusion is one of the most ubiquitous transport phenomena in nature. Experimentally, it can be tracked by following point spreading in space and time. Here, we introduce a spatiotemporal pump-probe microscopy technique that exploits the residual spatial temperature profile obtained through the transient reflectivity when probe pulses arrive before pump pulses. This corresponds to an effective pump-probe time delay of 13 ns, determined by the repetition rate of our laser system (76 MHz). This pre-time-zero technique enables probing the diffusion of long-lived excitations created by previous pump pulses with nanometer accuracy and is particularly powerful for following in-plane heat diffusion in thin films. The particular advantage of this technique is that it enables quantifying thermal transport without requiring any material input parameters or strong heating. We demonstrate the direct determination of the thermal diffusivities of films with a thickness of around 15 nm, consisting of the layered materials MoSe2 (0.18 cm2/s), WSe2 (0.20 cm2/s), MoS2 (0.35 cm2/s), and WS2 (0.59 cm2/s). This technique paves the way for observing nanoscale thermal transport phenomena and tracking diffusion of a broad range of species.

Unraveling Heat Transport and Dissipation in Suspended MoSe2 from Bulk to Monolayer.

Understanding heat flow in layered transition metal dichalcogenide (TMD) crystals is crucial for applications exploiting these materials. Despite significant efforts, several basic thermal transport properties of TMDs are currently not well understood, in particular how transport is affected by material thickness and the material's environment. This combined experimental-theoretical study establishes a unifying physical picture of the intrinsic lattice thermal conductivity of the representative TMD MoSe2 . Thermal conductivity measurements using Raman thermometry on a large set of clean, crystalline, suspended crystals with systematically varied thickness are combined with ab initio simulations with phonons at finite temperature. The results show that phonon dispersions and lifetimes change strongly with thickness, yet the thinnest TMD films exhibit an in-plane thermal conductivity that is only marginally smaller than that of bulk crystals. This is the result of compensating phonon contributions, in particular heat-carrying modes around ≈0.1 THz in (sub)nanometer thin films, with a surprisingly long mean free path of several micrometers. This behavior arises directly from the layered nature of the material. Furthermore, out-of-plane heat dissipation to air molecules is remarkably efficient, in particular for the thinnest crystals, increasing the apparent thermal conductivity of monolayer MoSe2 by an order of magnitude. These results are crucial for the design of (flexible) TMD-based (opto-)electronic applications.

Milliwatt terahertz harmonic generation from topological insulator metamaterials.

Achieving efficient, high-power harmonic generation in the terahertz spectral domain has technological applications, for example, in sixth generation (6G) communication networks. Massless Dirac fermions possess extremely large terahertz nonlinear susceptibilities and harmonic conversion efficiencies. However, the observed maximum generated harmonic power is limited, because of saturation effects at increasing incident powers, as shown recently for graphene. Here, we demonstrate room-temperature terahertz harmonic generation in a Bi2Se3 topological insulator and topological-insulator-grating metamaterial structures with surface-selective terahertz field enhancement. We obtain a third-harmonic power approaching the milliwatt range for an incident power of 75 mW-an improvement by two orders of magnitude compared to a benchmarked graphene sample. We establish a framework in which this exceptional performance is the result of thermodynamic harmonic generation by the massless topological surface states, benefiting from ultrafast dissipation of electronic heat via surface-bulk Coulomb interactions. These results are an important step towards on-chip terahertz (opto)electronic applications.

Observation of giant and tunable thermal diffusivity of a Dirac fluid at room temperature.

Conducting materials typically exhibit either diffusive or ballistic charge transport. When electron-electron interactions dominate, a hydrodynamic regime with viscous charge flow emerges1-13. More stringent conditions eventually yield a quantum-critical Dirac-fluid regime, where electronic heat can flow more efficiently than charge14-22. However, observing and controlling the flow of electronic heat in the hydrodynamic regime at room temperature has so far remained elusive. Here we observe heat transport in graphene in the diffusive and hydrodynamic regimes, and report a controllable transition to the Dirac-fluid regime at room temperature, using carrier temperature and carrier density as control knobs. We introduce the technique of spatiotemporal thermoelectric microscopy with femtosecond temporal and nanometre spatial resolution, which allows for tracking electronic heat spreading. In the diffusive regime, we find a thermal diffusivity of roughly 2,000 cm2 s-1, consistent with charge transport. Moreover, within the hydrodynamic time window before momentum relaxation, we observe heat spreading corresponding to a giant diffusivity up to 70,000 cm2 s-1, indicative of a Dirac fluid. Our results offer the possibility of further exploration of these interesting physical phenomena and their potential applications in nanoscale thermal management.

Hot-Carrier Cooling in High-Quality Graphene Is Intrinsically Limited by Optical Phonons.

Many promising optoelectronic devices, such as broadband photodetectors, nonlinear frequency converters, and building blocks for data communication systems, exploit photoexcited charge carriers in graphene. For these systems, it is essential to understand the relaxation dynamics after photoexcitation. These dynamics contain a sub-100 fs thermalization phase, which occurs through carrier-carrier scattering and leads to a carrier distribution with an elevated temperature. This is followed by a picosecond cooling phase, where different phonon systems play a role: graphene acoustic and optical phonons, and substrate phonons. Here, we address the cooling pathway of two technologically relevant systems, both consisting of high-quality graphene with a mobility >10 000 cm2 V-1 s-1 and environments that do not efficiently take up electronic heat from graphene: WSe2-encapsulated graphene and suspended graphene. We study the cooling dynamics using ultrafast pump-probe spectroscopy at room temperature. Cooling via disorder-assisted acoustic phonon scattering and out-of-plane heat transfer to substrate phonons is relatively inefficient in these systems, suggesting a cooling time of tens of picoseconds. However, we observe much faster cooling, on a time scale of a few picoseconds. We attribute this to an intrinsic cooling mechanism, where carriers in the high-energy tail of the hot-carrier distribution emit optical phonons. This creates a permanent heat sink, as carriers efficiently rethermalize. We develop a macroscopic model that explains the observed dynamics, where cooling is eventually limited by optical-to-acoustic phonon coupling. These fundamental insights will guide the development of graphene-based optoelectronic devices.

Out-of-plan pharmacy use: insights into patient behavior.

OBJECTIVES: The purpose of this study was to identify and describe patient rationales for filling prescriptions at an out-of-plan pharmacy (OOPP). STUDY DESIGN: A cross-sectional survey conducted in February 2013 among a random sample of 1000 patients. METHODS: Adult Kaiser Permanente Colorado (KPCO) patients who had a prescription electronically issued to an OOPP in November 2012 were surveyed. The study questionnaire was developed using items obtained from the literature and prepared de novo, as needed. The questionnaire included items regarding whether the electronic prescription issued to an OOPP was filled; if filled, which OOPP was used; factors that may have influenced the use of an OOPP; and the patient's ability to afford medications. Responses to the survey were tabulated and reported as percentages. RESULTS: The survey response rate was 38%. Respondents (N=382) had a mean age of 61 years, 35% were males, and anti-hypertensives were their most common OOPP prescription. Overall, 330 (86%) respondents reported that they had their prescription filled at an OOPP. The most commonly reported OOPPs utilized were supermarket pharmacies (42%). Factors that influenced the decision to use an OOPP included the prescription being less expensive (58%), the OOPP had a discount generic prescription program (57%), and the OOPP's location was convenient (44%). Thirty-nine percent of respondents reported that using an OOPP helped them afford their prescriptions. CONCLUSIONS: Prescription cost and pharmacy convenience were identified as the most significant drivers of OOPP use. Future research should be conducted to assess the health-related consequences of OOPP use.