741 research outputs found
Phonon anomalies and charge dynamics in Fe_{1-x}Cu_{x}Cr_{2}S_{4} single crystals
A detailed investigation of phonon excitations and charge carrier dynamics in
single crystals of Fe_{1-x}Cu_{x}Cr_{2}S_{4} (x = 0, 0.2, 0.4, 0.5) has been
performed by using infrared spectroscopy. In FeCr_{2}S_{4} the phonon
eigenmodes are strongly affected by the onset of magnetic order. Despite
enhanced screening effects, a continuous evolution of the phonon excitations
can be observed in the doped compounds with x = 0.2 (metallic) and x = 0.4, 0.5
(bad metals), but the effect of magnetic ordering on the phonons is strongly
reduced compared to x = 0. The Drude-like charge-carrier contribution to the
optical conductivity in the doped samples indicates that the colossal
magneto-resistance effect results from the suppression of spin-disorder
scattering.Comment: 8 pages, 6 figure
Transport, magnetic, thermodynamic and optical properties in Ti-doped Sr_2RuO_4
We report on electrical resistivity, magnetic susceptibility and
magnetization, on heat capacity and optical experiments in single crystals of
Sr_2Ru_(1-x)Ti_xO_4. Samples with x=0.1 and 0.2 reveal purely semiconducting
resistivity behavior along c and the charge transport is close to localization
within the ab-plane. A strong anisotropy in the magnetic susceptibility appears
at temperatures below 100 K. Moreover magnetic ordering in c-direction with a
moment of order 0.01 mu_B/f.u. occurs at low temperatures. On doping the
low-temperature linear term of the heat capacity becomes reduced significantly
and probably is dominated by spin fluctuations. Finally, the optical
conductivity reveals the anisotropic character of the dc resistance, with the
in-plane conductance roughly following a Drude-type behavior and an insulating
response along c
Assessing the energy implications of replacing car trips with bicycle trips in Sheffield, UK
A wide range of evidence supports policies which encourage people to cycle more and drive less, for health and environmental reasons. However, the likely energy implications of such a modal shift have remained relatively unexplored. In this paper we generate scenarios for increasing the cycling rate in Sheffield between 2010 and 2020. This is done through the novel application of a simple model, borrowed from population ecology. The analysis suggests that pro-cycling interventions result in energy savings through reduced consumption of fuel and cars, and energy costs through increased demand for food. The cumulative impact is a net reduction in primary energy consumption, the magnitude of which depends on a number of variables which are subject to uncertainty. Based on the evidence presented and analysed in this paper, we conclude that transport policy has a number of important energy implications, some of which remain unexplored. We therefore advocate the formation of closer links between energy policy and transport policy in academia and in practice; our approach provides a simple yet flexible framework for pursuing this aim in the context of modal shift
Definitive chemoradiotherapy versus neoadjuvant chemoradiotherapy followed by radical surgery for locally advanced oesophageal squamous cell carcinoma:meta-analysis
Background: The literature lacks robust evidence comparing definitive chemoradiotherapy (dCRT) with neoadjuvant chemoradiotherapy and surgery (nCRS) for oesophageal squamous cell carcinoma (ESCC). This study aimed to compare long-term survival of these approaches in patients with ESCC.Methods: A systematic review performed according to PRISMA guidelines included studies identified from PubMed, Scopus, and Cochrane CENTRAL databases up to July 2021 comparing outcomes between dCRT and nCRS for ESCC. The main outcome measure was overall survival (OS), secondary outcome was disease-free survival (DFS). A meta-analysis was conducted using random-effects modelling to determine pooled adjusted multivariable hazard ratios (HRs).Results: Ten studies including 14 092 patients were included, of which 30 per cent received nCRS. Three studies were randomized clinical trials (RCTs) and the remainder were retrospective cohort studies. dCRT and nCRS regimens were reported in six studies and surgical quality control was reported in two studies. Outcomes for OS and DFS were reported in eight and three studies respectively. Following meta-analysis, nCRS demonstrated significantly longer OS (HR 0.68, 95 per cent c.i. 0.54 to 0.87, P < 0.001) and DFS (HR 0.50, 95 per cent c.i. 0.36 to 0.70, P < 0.001) compared with dCRT.Conclusion: Neoadjuvant chemoradiotherapy followed by oesophagectomy correlated with improved survival compared with definitive chemoradiation in the treatment of ESCC; however, there is a lack of literature on RCTs
Electronic and optical properties of LiBC
LiBC, a semiconducting ternary borocarbide constituted of the lightest
elements only, has been synthesized and characterized by x-ray powder
diffraction, dielectric spectroscopy, and conductivity measurements. Utilizing
an infrared microscope the phonon spectrum has been investigated in single
crystals. The in-plane B-C stretching mode has been detected at 150 meV,
noticeably higher than in AlB2, a non-superconducting isostructural analog of
MgB2. It is this stretching mode, which reveals a strong electron-phonon
coupling in MgB2, driving it into a superconducting state below 40 K, and is
believed to mediate predicted high-temperature superconductivity in hole-doped
LiBC [H. Rosner, A. Kitaigorodsky, and W. E. Pickett, Phys. Rev. Lett. 88,
127001 (2002)].Comment: 4 pages, 4 figure
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Exploring gendered cycling behaviours within a large-scale behavioural data-set
Analysing over 10 million journeys made by members of London’s Cycle Hire Scheme, we find that female customers’ usage characteristics are demonstrably different from those of male customers. Usage at weekends and within London’s parks characterises women’s journeys, whereas for men, a commuting function is more clearly identified. Some of this variation is explained by geodemographic differences and by an atypical period of usage during the first 3 months after the scheme’s launch. Controlling for each of these variables brings some convergence between men and women. However, many differences are preserved. Studying the spatio-temporal context under which journeys are made, we find that women’s journeys are highly spatially structured. Even when making utilitarian cycle trips, routes that involve large, multi-lane roads are comparatively rare, and instead female cyclists preferentially select areas of the city associated with slower traffic streets and with cycle routes slightly offset from major roads
Phonon anomalies and electron-phonon interaction in RuSr_2GdCu_2O_8 ferromagnetic superconductor: Evidence from infrared conductivity
Critical behavior of the infrared reflectivity of RuSr_2GdCu_2O_8 ceramics is
observed near the superconducting T_{SC} = 45 K and magnetic T_M = 133 K
transition temperatures. The optical conductivity reveals the typical features
of the c-axis optical conductivity of strongly underdoped multilayer
superconducting cuprates. The transformation of the Cu-O bending mode at 288
cm^{-1} to a broad absorption peak at the temperatures between T^* = 90 K and
T_{SC} is clearly observed, and is accompanied by the suppression of spectral
weight at low frequencies. The correlated shifts to lower frequencies of the
Ru-related phonon mode at 190 cm^{-1} and the mid-IR band at 4800 cm^{-1} on
decreasing temperature below T_M are observed. It provides experimental
evidence in favor of strong electron-phonon coupling of the charge carriers in
the Ru-O layers which critically depends on the Ru core spin alignment. The
underdoped character of the superconductor is explained by strong hole
depletion of the CuO_2 planes caused by the charge carrier self-trapping at the
Ru moments.Comment: 11 pages incl. 5 figures, submitted to PR
Neighbourhood, Route and Workplace-Related Environmental Characteristics Predict Adults' Mode of Travel to Work
Commuting provides opportunities for regular physical activity which can reduce the risk of chronic disease. Commuters' mode of travel may be shaped by their environment, but understanding of which specific environmental characteristics are most important and might form targets for intervention is limited. This study investigated associations between mode choice and a range of objectively assessed environmental characteristics.Participants in the Commuting and Health in Cambridge study reported where they lived and worked, their usual mode of travel to work and a variety of socio-demographic characteristics. Using geographic information system (GIS) software, 30 exposure variables were produced capturing characteristics of areas around participants' homes and workplaces and their shortest modelled routes to work. Associations between usual mode of travel to work and personal and environmental characteristics were investigated using multinomial logistic regression.Of the 1124 respondents, 50% reported cycling or walking as their usual mode of travel to work. In adjusted analyses, home-work distance was strongly associated with mode choice, particularly for walking. Lower odds of walking or cycling rather than driving were associated with a less frequent bus service (highest versus lowest tertile: walking OR 0.61 [95% CI 0.20–1.85]; cycling OR 0.43 [95% CI 0.23–0.83]), low street connectivity (OR 0.22, [0.07–0.67]; OR 0.48 [0.26–0.90]) and free car parking at work (OR 0.24 [0.10–0.59]; OR 0.55 [0.32–0.95]). Participants were less likely to cycle if they had access to fewer destinations (leisure facilities, shops and schools) close to work (OR 0.36 [0.21–0.62]) and a railway station further from home (OR 0.53 [0.30–0.93]). Covariates strongly predicted travel mode (pseudo r-squared 0.74).Potentially modifiable environmental characteristics, including workplace car parking, street connectivity and access to public transport, are associated with travel mode choice, and could be addressed as part of transport policy and infrastructural interventions to promote active commuting
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