Review of a frugal cooling mattress to induce therapeutic hypothermia for treatment of hypoxic-ischaemic encephalopathy in the UK NHS

Hypoxic ischaemic encephalopathy (HIE) is a major cause of neonatal mortality and disability in the United Kingdom (UK) and has significant human and financial costs. Therapeutic hypothermia (TH), which consists of cooling down the newborn’s body temperature, is the current standard of treatment for moderate or severe cases of HIE. Timely initiation of treatment is critical to reduce risk of mortality and disability associated with HIE. Very expensive servo-controlled devices are currently used in high-income settings to induce TH, whereas low-income settings rely on the use of low-tech devices such as water bottles, ice packs or fans. Cooling mattresses made with phase change materials (PCMs) were recently developed as a safe, efficient, and affordable alternative to induce TH in low-income settings. This frugal innovation has the potential to become a reverse innovation for the National Health Service (NHS) by providing a simple, efficient, and cost-saving solution to initiate TH in geographically remote areas of the UK where cooling equipment might not be readily available, ensuring timely initiation of treatment while waiting for neonatal transport to the nearest cooling centre. The adoption of PCM cooling mattresses by the NHS may reduce geographical disparity in the availability of treatment for HIE in the UK, and it could benefit from improvements in coordination across all levels of neonatal care given challenges currently experienced by the NHS in terms of constraints on funding and shortage of staff. Trials evaluating the effectiveness and safety of PCM cooling mattresses in the NHS context are needed in support of the adoption of this frugal innovation. These findings may be relevant to other high-income settings that experience challenges with the provision of TH in geographically remote areas. The use of promising frugal innovations such as PCM cooling mattresses in high-income settings may also contribute to challenge the dominant narrative that often favours innovation from North America and Western Europe, and consequently fight bias against research and development from low-income settings, promoting a more equitable global innovation landscape

Coherent ultrafast spin-dynamics probed in three dimensional topological insulators

Topological insulators are candidates to open up a novel route in spin based electronics. Different to traditional ferromagnetic materials, where the carrier spin-polarization and magnetization are based on the exchange interaction, the spin properties in topological insulators are based on the coupling of spin- and orbit interaction connected to its momentum. Specific ways to control the spin-polarization with light have been demonstrated: the energy momentum landscape of the Dirac cone provides spin-momentum locking of the charge current and its spin. The directionality of spin and momentum, as well as control with light has been demonstrated. Here we demonstrate a coherent femtosecond control of spin-polarization for states in the valence band at around the Dirac cone.Comment: 14 pages, 4 figure

Valence and magnetic ordering in intermediate valence compounds : TmSe versus SmB6

The intermediate valent systems TmSe and SmB6 have been investigated up to 16 and 18 GPa by ac microcalorimetry with a pressure (p) tuning realized in situ at low temperature. For TmSe, the transition from an antiferromagnetic insulator for p<3 GPa to an antiferromagnetic metal at higher pressure has been confirmed. A drastic change in the p variation of the Neel temperature (Tn) is observed at 3 GPa. In the metallic phase (p>3 GPa), Tn is found to increase linearly with p. A similar linear p increase of Tn is observed for the quasitrivalent compound TmS which is at ambiant pressure equivalent to TmSe at p=7 GPa. In the case of SmB6 long range magnetism has been detected above p=8 GPa, i.e. at a pressure slightly higher than the pressure of the insulator to metal transition. However a homogeneous magnetic phase occurs only above 10 GPa. The magnetic and electronic properties are related to the renormalization of the 4f wavefunction either to the divalent or the trivalent configurations. As observed in SmS, long range magnetism in SmB6 occurs already far below the pressure where a trivalent Sm3+ state will be reached. It seems possible, to describe roughly the physical properties of the intermediate valence equilibrium by assuming formulas for the Kondo lattice temperature depending on the valence configuration. Comparison is also made with the appearance of long range magnetism in cerium and ytterbium heavy fermion compounds.Comment: 22 pages including figure

Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics

Uranium and plutonium's 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (eg. the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization, for which a quantitative measure is lacking. By employing resonant x-ray emission spectroscopy (RXES) and x-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu, and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework for understanding the strongly-correlated behavior of actinide materials.Comment: 30 pages, concatenated article and supporting information, 10 figure

Ultrafast carrier dynamics in tetrahedral amorphous carbon: carrier trapping versus electron–hole recombination

We report the investigation of the ultrafast carrier dynamics in thin tetrahedral amorphous carbon films by means of femtosecond time-resolved reflectivity. We estimated the electronphonon relaxation time of a few hundred femtoseconds and we observed that under low optical excitation photo-generated carriers decay according to two distinct mechanisms attributed to trapping by defect states and direct electronhole recombination. With high excitation, when photo-carrier and trap densities are comparable, a unique temporal evolution develops, as the time dependence of the trapping process becomes degenerate with the electronhole recombination. This experimental evidence highlights the role of defects in the ultrafast electronic dynamics and is not specific to this particular form of carbon, but has general validity for amorphous and disordered semiconductors. peerReviewe

Strain induced phase separation in La0.7Sr0.3MnO3 thin films.

La0.7Sr0.3MnO3 thin films having different thicknesses were grown by pulsed laser deposition with in situ reflection high energy electron diffraction diagnostics on LaAlO3 substrates. The mismatch between film and substrate gives rise to an in-plane compressive biaxial strain, which partially relaxes in films thicker than 30 unit cells. Accordingly, the ratio between the out-of-plane and the in-plane lattice parameter c/a varies between 1.06 fully strained and 1.03 partially relaxed. In-plane compressive strain favors the stabilization of the 3z2−r2 orbitals chain-type antiferromagnetic phase, thus giving rise to a sizeable x-ray absorption linear dichroism signal. The shape of the linear dichroism depends weakly on the c/a ratio, while its intensity strongly increases with c/a. At the same time, the metal-insulator transition temperature shifts from about 360 K towards lower temperatures with decreasing thickness, eventually reaching an insulating state for the 30 unit cells film. Low-temperature nuclear magnetic resonance spectra show a decrease of the MnDE doubleexchange metallic contribution with decreasing the thickness, which becomes negligible in the 30 unit cells thick film. The experimental results demonstrate a strain driven competition between two stable phases: the orbital ordered chain-type insulating antiferromagnetic and the orbital disordered metallic ferromagnetic. For intermediate values of the epitaxial strain the local minimum state of the system lies in a gap region between the two stable phases. Such a region has glassy characteristics with coexisting clusters of the two phases. The strain is used as a driving force to span the glassy region

Evidence for suppressed metallicity on the surface of La2-xSrxCuO4 and Nd2-xCexCuO4

Hard X-ray Photoemission spectroscopy (PES) of copper core electronic states, with a probing depth of $\sim$60 \AA, is used to show that the Zhang-Rice singlet feature is present in La$_2$CuO$_4$ but is absent in Nd$_2$CuO$_4$. Hole- and electron doping in La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) and Nd$_{2-x}$Ce$_x$CuO$_4$ (NCCO) result in new well-screened features which are missing in soft X-ray PES. Impurity Anderson model calculations establish metallic screening as its origin, which is strongly suppressed within 15 $\text{\AA}$ of the surface. Complemented with X-ray absorption spectroscopy, the small chemical-potential shift in core levels ($\sim0.2$ eV) are shown to be consistent with modifications of valence and conduction band states spanning the band gap ($\sim1$ eV) upon hole- and electron-doping in LSCO and NCCO.Comment: 4 pages, 4 figure

A determination of the pairing interaction in the high Tc cuprate superconductor Tl2Ba2CaCu2O8 (Tl2212)

We have measured the near-normal reflectance of Tl2Ba2CaCu2O8 (Tl2212) for energies from 0.1 to 4.0 eV at room temperature and used a Kramers-Kronig analysis to find the complex, frequency dependent dielectric function, from which the optical conductivity was determined. Using Thermal-Difference-Reflectance (TDR) Spectroscopy the reflectance of the sample in the normal state just above the superconducting transition, and in the superconducting state were then obtained. From these data we determined the ratio of the superconducting- to normal-state optical conductivities. Mattis and Bardeen had calculated this function within the BCS theory, where the gap is a fixed energy-independent quantity. Taking into account the retarded nature of the electron-phonon coupling results in a complex, energy dependent gap causing deviations from the Mattis-Bardeen plot at energies where the phonon coupling function is large. We find a typical deviation near the phonon energies in Tl2212, and in addition, at 1.2 and 1.7eV. The phonon, and these electronic terms can each be described by a coupling constant. None of which by itself gives rise to a high transition temperature, but the combination does. Using Resonant Inelastic X-Ray Scattering (RIXS) we find that the d-to-d excitations of the cuprate ion in Tl2212 fall at the same energies as the dips in the Mattis-Bardeen plot. We conclude that the high superconducting transition temperature of the cuprates is due to the sum of the phonon interaction, and interactions with the Cu-ion d-shell.Comment: Preprint submitted to Physica C. Paper presented at M2S-HTSC-VIII, Dresden, Germany, July 9-14,200