1,037 research outputs found
Weak antilocalization in quasi-two-dimensional electronic states of epitaxial LuSb thin films
Observation of large non-saturating magnetoresistance in rare-earth
monopnictides has raised enormous interest in understanding the role of its
electronic structure. Here, by a combination of molecular-beam epitaxy,
low-temperature transport, angle-resolved photoemssion spectroscopy, and hybrid
density functional theory we have unveiled the bandstructure of LuSb, where
electron-hole compensation is identified as a mechanism responsible for large
magnetoresistance in this topologically trivial compound. In contrast to bulk
single crystal analogues, quasi-two-dimensional behavior is observed in our
thin films for both electron and holelike carriers, indicative of dimensional
confinement of the electronic states. Introduction of defects through growth
parameter tuning results in the appearance of quantum interference effects at
low temperatures, which has allowed us to identify the dominant inelastic
scattering processes and elucidate the role of spin-orbit coupling. Our
findings open up new possibilities of band structure engineering and control of
transport properties in rare-earth monopnictides via epitaxial synthesis.Comment: 20 pages, 12 figures; includes supplementary informatio
Performance of GEDI space-borne LiDAR for quantifying structural variation in the temperate forests of South-Eastern Australia
Monitoring forest structural properties is critical for a range of applications because structure is key to understanding and quantifying forest biophysical functioning, including stand dynamics, evapotranspiration, habitat, and recovery from disturbances. Monitoring of forest structural properties at desirable frequencies and cost globally is enabled by space-borne LiDAR missions such as the global ecosystem dynamics investigation (GEDI) mission. This study assessed the accuracy of GEDI estimates for canopy height, total plant area index (PAI), and vertical profile of plant area volume density (PAVD) and elevation over a gradient of canopy height and terrain slope, compared to estimates derived from airborne laser scanning (ALS) across two forest age-classes in the Central Highlands region of south-eastern Australia. ALS was used as a reference dataset for validation of GEDI (Version 2) dataset. Canopy height and total PAI analyses were carried out at the landscape level to understand the influence of beam-type, height of the canopy, and terrain slope. An assessment of GEDIâs terrain elevation accuracy was also carried out at the landscape level. The PAVD profile evaluation was carried out using footprints grouped into two forest age-classes, based on the areas of mountain ash (Eucalyptus regnans) forest burnt in the Central Highlands during the 1939 and 2009 wildfires. The results indicate that although GEDI is found to significantly under-estimate the total PAI and slightly over-estimate the canopy height, the GEDI estimates of canopy height and the vertical PAVD profile (above 25 m) show a good level of accuracy. Both beam-types had comparable accuracies, with increasing slope having a slightly detrimental effect on accuracy. The elevation accuracy of GEDI found the RMSE to be 10.58 m and bias to be 1.28 m, with an R2 of 1.00. The results showed GEDI is suitable for canopy densities and height in complex forests of south-eastern Australia
Retrospective unbiased plasma lipidomic of progressive multiple sclerosis patients-identifies lipids discriminating those with faster clinical deterioration.
The disease course of patients with a confirmed diagnosis of primary progressive multiple sclerosis (PPMS) is uncertain. In an attempt to identify potential signaling pathways involved in the evolution of the disease, we conducted an exploratory unbiased lipidomic analysis of plasma from nonâdiseased controls (n = 8) and patients with primary progressive MS (PPMS, n = 19) and either a rapid (PPMSâP, n = 9) or slow (PPMSâNP, n = 10) disease course based on worsening disability and/or MRIâvisible appearance of new T2 lesions over a oneâyearâassessment. Partial least squaresâdiscriminant analysis of the MS/MSALL lipidomic dataset, identified lipids driving the clustering of the groups. Among these lipids, sphingomyelinâd18:1/14:0 and monoâhexosylceramideâd18:1/20:0 were differentially abundant in the plasma of ppMS patients compared to controls and their levels correlated with MRI signs of disease progression. Lysoâphosphatidic acidâ18:2 (LPAâ18:2) was the only lipid with significantly lower abundance in PPMS patients with a rapidly deteriorating disease course, and its levels inversely correlated with the severity of the neurological deficit. Decreased levels of LPAâ18:2 were detected in patients with more rapid disease progression, regardless of therapy and these findings were validated in an independent cohort of secondary progressive (SPMS) patients, but not in a third cohorts of relapsingâremitting (RRMS) patients. Collectively, our analysis suggests that sphingomyelinâd18:1/14:0, monoâhexosylceramideâd18:1/20:0, and LPAâ18:2 may represent important targets for future studies aimed at understanding disease progression in MS
Magneto-Mechanical Transmitters for Ultra-Low Frequency Near-field Communication
Electromagnetic signals in the ultra-low frequency (ULF) range below 3 kHz
are well suited for underwater and underground wireless communication thanks to
low signal attenuation and high penetration depth. However, it is challenging
to design ULF transmitters that are simultaneously compact and energy efficient
using traditional approaches, e.g., using coils or dipole antennas. Recent
works have considered magneto-mechanical alternatives, in which ULF magnetic
fields are generated using the motion of permanent magnets, since they enable
extremely compact ULF transmitters that can operate with low energy consumption
and are suitable for human-portable applications. Here we explore the design
and operating principles of resonant magneto-mechanical transmitters (MMT) that
operate over frequencies spanning a few 10's of Hz up to 1 kHz. We
experimentally demonstrate two types of MMT designs using both single-rotor and
multi-rotor architectures. We study the nonlinear electro-mechanical dynamics
of MMTs using point dipole approximation and magneto-static simulations. We
further experimentally explore techniques to control the operation frequency
and demonstrate amplitude modulation up to 10 bits-per-second.Comment: 10 pages, 9 figure
The rise and fall of aspirin in the primary prevention of cardiovascular disease
Aspirin is one of the most frequently used drugs worldwide and is generally considered effective for the secondary prevention of cardiovascular disease. By contrast, the role of aspirin in primary prevention of cardiovascular disease is controversial. Early trials evaluating aspirin for primary prevention, done before the turn of the millennium, suggested reductions in myocardial infarction and stroke (although not mortality), and an increased risk of bleeding. In an effort to balance the risks and benefits of aspirin, international guidelines on primary prevention of cardiovascular disease have typically recommended aspirin only when a substantial 10-year risk of cardiovascular events exists. However, in 2018, three large randomised clinical trials of aspirin for the primary prevention of cardiovascular disease showed little or no benefit and have even suggested net harm. In this narrative Review, we reappraise the role of aspirin in primary prevention of cardiovascular disease, contextualising data from historical and contemporary trials
Effects of pressure on diffusion and vacancy formation in MgO from non-empirical free-energy integrations
The free energies of vacancy pair formation and migration in MgO were
computed via molecular dynamics using free-energy integrations and a
non-empirical ionic model with no adjustable parameters. The intrinsic
diffusion constant for MgO was obtained at pressures from 0 to 140 GPa and
temperatures from 1000 to 5000 K. Excellent agreement was found with the zero
pressure diffusion data within experimental error. The homologous temperature
model which relates diffusion to the melting curve describes well our high
pressure results within our theoretical framework.Comment: 4 pages, latex, 1 figure, revtex, submitted to PR
Sustained Immune Tolerance Induction in Enzyme Replacement Therapy-Treated CRIM-Negative Patients with Infantile Pompe Disease
BACKGROUND: Cross-reactive immunological material-negative (CRIM-negative) infantile Pompe disease (IPD) patients develop an immune response against enzyme replacement therapy (ERT) with alglucosidase alfa that nullifies ERT efficacy. Prophylactic immune tolerance induction (ITI) with rituximab, methotrexate, and IVIG successfully prevents development of deleterious rhGAA IgG antibodies; however, safety, likelihood of success, and long-term efficacy of ITI in a larger cohort remain unknown. METHODS: Clinical data were analyzed for 19 CRIM-negative IPD patients who received ITI with rituximab, methotrexate, and IVIG in the ERT-naive setting (ERT+ITI) and compared to a historical cohort of 10 CRIM-negative IPD patients on ERT monotherapy. RESULTS: ITI was safely tolerated, although infections were reported in 4 patients. Fourteen (74%) ERT+ITI patients were alive, with a median age of 44.2 months at their final assessment. The eldest survivor was 103.9 months old, with 100.2 months of follow-up after initiation of ERT+ITI. Death (n = 5) occurred at a median age of 29.2 months and was unrelated to the administration of ITI. Fifteen patients either did not seroconvert (n = 8) or maintained low titers (n = 7; defined as titers of /=51,200 at or beyond 6 months on ERT). Left ventricular mass index (LVMI) decreased from a median of 248.5 g/m2 at baseline to 76.8 g/m2 at a median time from ERT+ITI initiation to 59 weeks. ERT+ITI significantly improved overall survival (P = 0.001), eliminated/reduced antibodies at values o
The Energetics of Li Off-Centering in KLiTaO; First Principles Calculations
KLiTaO (KLT) solid solutions exhibit a variety of
interesting physical phenomena related to large displacements of Li-ions from
ideal perovskite A-site positions. First-principles calculations for KLT
supercells were used to investigate these phenomena. Lattice dynamics
calculations for KLT exhibit a Li off-centering instability. The energetics of
Li-displacements for isolated Li-ions and for Li-Li pairs up to 4th neighbors
were calculated. Interactions between nearest neighbor Li-ions, in a Li-Li
pair, strongly favor ferroelectric alignment along the pair axis. Such Li-Li
pairs can be considered "seeds" for polar nanoclusters in KLT.
Electrostriction, local oxygen relaxation, coupling to the KT soft-mode, and
interactions with neighboring Li-ions all enhance the polarization from Li
off-centering. Calculated hopping barriers for isolated Li-ions and for nearest
neighbor Li-Li pairs are in good agreement with Arrhenius fits to experimental
dielectric data.Comment: 14 pages including 10 figures. To Physical Review B. Replaced after
corrections due to referees' remark
Growth and characterization of -Sn thin films on In- and Sb-rich reconstructions of InSb(001)
-Sn thin films can exhibit a variety of topologically non-trivial
phases. Both studying the transitions between these phases and making use of
these phases in eventual applications requires good control over the electronic
and structural quality of -Sn thin films. -Sn growth on InSb
often results in out-diffusion of indium, a p-type dopant. By growing
-Sn via molecular beam epitaxy on the Sb-rich c(44) surface
reconstruction of InSb(001) rather than the In-rich c(82), we
demonstrate a route to substantially decrease and minimize this indium
incorporation. The reduction in indium concentration allows for the study of
the surface and bulk Dirac nodes in -Sn via angle-resolved
photoelectron spectroscopy without the common approaches of bulk doping or
surface dosing, simplifying topological phase identification. The lack of
indium incorporation is verified in angle-resolved and -integrated ultraviolet
photoelectron spectroscopy as well as in clear changes in the Hall response
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