Radial Quasiballistic Transport in Time-Domain Thermoreflectance Studied Using Monte Carlo Simulations

Recently, a pump beam size dependence of thermal conductivity was observed in Si at cryogenic temperatures using time-domain thermal reflectance (TDTR). These observations were attributed to quasiballistic phonon transport, but the interpretation of the measurements has been semi-empirical. Here, we present a numerical study of the heat conduction that occurs in the full 3D geometry of a TDTR experiment, including an interface, using the Boltzmann transport equation. We identify the radial suppression function that describes the suppression in heat flux, compared to Fourier's law, that occurs due to quasiballistic transport and demonstrate good agreement with experimental data. We also discuss unresolved discrepancies that are important topics for future study

Active Thermal Extraction and Temperature Sensing of Near-field Thermal Radiation

Recently, we proposed an active thermal extraction (ATX) scheme that enables thermally populated surface phonon polaritons to escape into the far-field. The concept is based on a fluorescence upconversion process that also occurs in laser cooling of solids (LCS). Here, we present a generalized analysis of our scheme using the theoretical framework for LCS. We show that both LCS and ATX can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ATX. Using this framework, we compare the ideal efficiency and power extracted for the two schemes and examine the parasitic loss mechanisms. This work advances the application of ATX to manipulate near-field thermal radiation for applications such as temperature sensing and active radiative cooling

Active Thermal Extraction of Near-field Thermal Radiation

Radiative heat transport between materials supporting surface-phonon polaritons is greatly enhanced when the materials are placed at subwavelength separation as a result of the contribution of near-field surface modes. However, the enhancement is limited to small separations due to the evanescent decay of the surface waves. In this work, we propose and numerically demonstrate an active scheme to extract these modes to the far field. Our approach exploits the monochromatic nature of near-field thermal radiation to drive a transition in a laser gain medium, which, when coupled with external optical pumping, allows the resonant surface mode to be emitted into the far field. Our study demonstrates an approach to manipulate thermal radiation that could find applications in thermal management

Active Thermal Extraction and Temperature Sensing of Near-field Thermal Radiation

Recently, we proposed an active thermal extraction (ATX) scheme that enables thermally populated surface phonon polaritons to escape into the far-field. The concept is based on a fluorescence upconversion process that also occurs in laser cooling of solids (LCS). Here, we present a generalized analysis of our scheme using the theoretical framework for LCS. We show that both LCS and ATX can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ATX. Using this framework, we compare the ideal efficiency and power extracted for the two schemes and examine the parasitic loss mechanisms. This work advances the application of ATX to manipulate near-field thermal radiation for applications such as temperature sensing and active radiative cooling

Nonlinear Photoelasticity to Explicate Acoustic Dephasing Dynamics

Detection and controlling of acoustic (AC) phonon phase have been strenuous tasks although such capability is crucial for further manipulating thermal properties. Here, we present a versatile formalism for tracing AC nanowaves with arbitrary strain compositions by incorporating the nonlinear photoelasticity (PE) into ultrafast acoustics where broad AC spectrum encompassing thermally important THz frequency range should be collected far beyond Brillouin frequency. The initial AC phase upon displacive carrier generation could be inherently varied depending on the bipolar AC compositions by implementing externally biased piezoelectric diodes. The importance of adopting nonlinear PE is then manifested from the transient phase shift either abrupt at the point of diffuse surface scattering or gradual during phonon-phonon or phonon-electron scattering events based on which the ratio of nonlinear to linear PE coefficient is experimentally extracted as a function of the detection probe energy, reaching 0.98 slightly below the bandgap. As the probing energy is rather set away from the bandgap, AC phase is completely invariant with any scattering events, exhibiting the conventional trend at Brillouin frequency in linear regime. Under potent influence of nonlinear PE, the AC dephasing time during the propagation are quantified as a function of AC wavepacket size and further correlated with intrinsic and extrinsic AC scattering mechanisms in electron reservoir

'Treatment of the Sportsman's groin': British Hernia Society's 2014 position statement based on the Manchester Consensus Conference

<b>Introduction</b> The aim was to produce a multidisciplinary consensus to determine the current position on the nomenclature, definition, diagnosis, imaging modalities and management of Sportsman's groin (SG).<p></p> <b>Methods</b> Experts in the diagnosis and management of SG were invited to participate in a consensus conference held by the British Hernia Society in Manchester, UK on 11–12 October 2012. Experts included a physiotherapist, a musculoskeletal radiologist and surgeons with a proven track record of expertise in this field. Presentations detailing scientific as well as outcome data from their own experiences were given. Records were made of the presentations with specific areas debated openly.<p></p> <b>Results</b> The term ‘inguinal disruption’ (ID) was agreed as the preferred nomenclature with the term ‘Sportsman's hernia’ or ‘groin’ rejected, as no true hernia exists. There was an overwhelming agreement of opinion that there was abnormal tension in the groin, particularly around the inguinal ligament attachment. Other common findings included the possibility of external oblique disruption with consequent small tears noted as well as some oedema of the tissues. A multidisciplinary approach with tailored physiotherapy as the initial treatment was recommended with any surgery involving releasing the tension in the inguinal canal by various techniques and reinforcing it with a mesh or suture repair. A national registry should be developed for all athletes undergoing surgery.<p></p> <b>Conclusions</b> ID is a common condition where no true hernia exists. It should be managed through a multidisciplinary approach to ensure consistent standards and outcomes are achieved