1,131 research outputs found
Large Coercivity in Nanostructured Rare-earth-free MnxGa Films
The magnetic hysteresis of MnxGa films exhibit remarkably large coercive
fields as high as 2.5 T when fabricated with nanoscale particles of a suitable
size and orientation. This coercivity is an order of magnitude larger than in
well-ordered epitaxial film counterparts and bulk materials. The enhanced
coercivity is attributed to the combination of large magnetocrystalline
anisotropy and ~ 50 nm size nanoparticles. The large coercivity is also
replicated in the electrical properties through the anomalous Hall effect. The
magnitude of the coercivity approaches that found in rare-earth magnets, making
them attractive for rare-earth-free magnet applications
Prediction of Ferromagnetic Ground State of NaCl-type FeN
Ab-initio results for structural and electronic properties of NaCl-type FeN
are presented in a framework of plane-wave and ultrasoft pseudopotentials.
Competition among different magnetic ordering is examined. We find the
ferromagnetic phase stable overall. Stabilization over the unpolarized phase is
obtained by splitting one flat t_2g-type band crossing the Fermi energy. A
comparison with CrN is considered. We find large differences in the properties
of the two systems that can be addressed to the smaller ionicity and
magnetization of FeN.Comment: 5 pages, 4 figures, twocolumn latex style Sentence changed in Section
III line 1
How context can impact clinical trials : a multi-country qualitative case study comparison of diagnostic biomarker test interventions
Background
Context matters for the successful implementation of medical interventions, but its role remains surprisingly understudied. Against the backdrop of antimicrobial resistance, a global health priority, we investigated the introduction of a rapid diagnostic biomarker test (C-reactive protein, or CRP) to guide antibiotic prescriptions in outpatient settings and asked, “Which factors account for cross-country variations in the effectiveness of CRP biomarker test interventions?”
Methods
We conducted a cross-case comparison of CRP point-of-care test trials across Yangon (Myanmar), Chiang Rai (Thailand), and Hanoi (Vietnam). Cross-sectional qualitative data were originally collected as part of each clinical trial to broaden their evidence base and help explain their respective results. We synthesised these data and developed a large qualitative data set comprising 130 interview and focus group participants (healthcare workers and patients) and nearly one million words worth of transcripts and interview notes. Inductive thematic analysis was used to identify contextual factors and compare them across the three case studies. As clinical trial outcomes, we considered patients’ and healthcare workers’ adherence to the biomarker test results, and patient exclusion to gauge the potential “impact” of CRP point-of-care testing on the population level.
Results
We identified three principal domains of contextual influences on intervention effectiveness. First, perceived risks from infectious diseases influenced the adherence of the clinical users (nurses, doctors). Second, the health system context related to all three intervention outcomes (via the health policy and antibiotic policy environment, and via health system structures and the ensuing utilisation patterns). Third, the demand-side context influenced the patient adherence to CRP point-of-care tests and exclusion from the intervention through variations in local healthcare-seeking behaviours, popular conceptions of illness and medicine, and the resulting utilisation of the health system.
Conclusions
Our study underscored the importance of contextual variation for the interpretation of clinical trial findings. Further research should investigate the range and magnitude of contextual effects on trial outcomes through meta-analyses of large sets of clinical trials. For this to be possible, clinical trials should collect qualitative and quantitative contextual information for instance on their disease, health system, and demand-side environment.
Trial registration: ClinicalTrials.gov Identifiers NCT02758821 and NCT01918579
Phenotype of Transgenic Mice Carrying a Very Low Copy Number of the Mutant Human G93A Superoxide Dismutase-1 Gene Associated with Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of the motor neuron. While most cases of ALS are sporadic, 10% are familial (FALS) with 20% of FALS caused by a mutation in the gene that codes for the enzyme Cu/Zn superoxide dismutase (SOD1). There is variability in sporadic ALS as well as FALS where even within the same family some siblings with the same mutation do not manifest disease. A transgenic (Tg) mouse model of FALS containing 25 copies of the mutant human SOD1 gene demonstrates motor neuron pathology and progressive weakness similar to ALS patients, leading to death at approximately 130 days. The onset of symptoms and survival of these transgenic mice are directly related to the number of copies of the mutant gene. We report the phenotype of a very low expressing (VLE) G93A SOD1 Tg carrying only 4 copies of the mutant G93ASOD1 gene. While weakness can start at 9 months, only 74% of mice 18 months or older demonstrate disease. The VLE mice show decreased motor neurons compared to wild-type mice as well as increased cytoplasmic translocation of TDP-43. In contrast to the standard G93A SOD1 Tg mouse which always develops motor weakness leading to death, not all VLE animals manifested clinical disease or shortened life span. In fact, approximately 20% of mice older than 24 months had no motor symptoms and only 18% of VLE mice older than 22 months reached end stage. Given the variable penetrance of clinical phenotype, prolonged survival, and protracted loss of motor neurons the VLE mouse provides a new tool that closely mimics human ALS. This tool will allow the study of pathologic events over time as well as the study of genetic and environmental modifiers that may not be causative, but can exacerbate or accelerate motor neuron disease
Magnetic Interactions and Transport in (Ga,Cr)As
The magnetic, transport, and structural properties of (Ga,Cr)As are reported.
Zincblende GaCrAs was grown by low-temperature molecular beam
epitaxy (MBE). At low concentrations, x0.1, the materials exhibit unusual
magnetic properties associated with the random magnetism of the alloy. At low
temperatures the magnetization M(B) increases rapidly with increasing field due
to the alignment of ferromagnetic units (polarons or clusters) having large
dipole moments of order 10-10. A standard model of
superparamagnetism is inadequate for describing both the field and temperature
dependence of the magnetization M(B,T). In order to explain M(B) at low
temperatures we employ a distributed magnetic moment (DMM) model in which
polarons or clusters of ions have a distribution of moments. It is also found
that the magnetic susceptibility increases for decreasing temperature but
saturates below T=4 K. The inverse susceptibility follows a linear-T
Curie-Weiss law and extrapolates to a magnetic transition temperature
=10 K. In magnetotransport measurements, a room temperature resistivity
of =0.1 cm and a hole concentration of cm
are found, indicating that Cr can also act as a acceptor similar to Mn. The
resistivity increases rapidly for decreasing temperature below room
temperature, and becomes strongly insulating at low temperatures. The
conductivity follows exp[-(T/T)] over a large range of
conductivity, possible evidence of tunneling between polarons or clusters.Comment: To appear in PRB 15 Mar 200
Determining Magnetic Nanoparticle Size Distributions from Thermomagnetic Measurements
Thermomagnetic measurements are used to obtain the size distribution and
anisotropy of magnetic nanoparticles. An analytical transformation method is
described which utilizes temperature-dependent zero-field cooling (ZFC)
magnetization data to provide a quantitative measurement of the average
diameter and relative abundance of superparamagnetic nanoparticles. Applying
this method to self-assembled MnAs nanoparticles in MnAs-GaAs composite films
reveals a log-normal size distribution and reduced anisotropy for nanoparticles
compared to bulk materials. This analytical technique holds promise for rapid
assessment of the size distribution of an ensemble of superparamagnetic
nanoparticles.Comment: Correction Appl. Phys. Lett. 98, 216103 (2011
Investigating Antifungal Susceptibility in Candida Species With MALDI-TOF MS-Based Assays
Half of invasive fungal infections lead to death. Amongst pathogenic fungi, the most widespread species belong to the Candida genus and vary in their susceptibility to antifungal drugs. The emergence of antifungal resistance has become a major clinical problem. Therefore, the definition of susceptibility patterns is crucial for the survival of patients and the monitoring of resistance epidemiology. Although, most routinely used methods of AntiFungal Susceptibility Testing (AFST) have reached their limits, the rediscovery of Matrix Associated Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) in the field of mycology provides a promising alternative for the study of antifungal resistance. MALDI-TOF MS is already used in mycology for fungal identification, which permits to highlight inherent antifungal resistance. However, the main concern of clinicians is the rise of acquired antifungal resistance and the time needed for their detection. For this purpose, MALDI-TOF MS has been shown to be an accurate tool for AFST, presenting numerous advantages in comparison to commonly used techniques. Finally, MALDI-TOF MS could be used directly to detect resistance mechanisms through typing. Consequently, MALDI-TOF MS offers new perspectives in the context of healthcare associated outbreaks of emerging multi-drug resistant fungi, such as C. auris. As a proof of concept, we will illustrate the current and future benefits in using and adapting MALDI-TOF MS-based assays to define the susceptibility pattern of C. auris, by species identification, AFST, and typing
Evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in EuGdO
Raman scattering studies as functions of temperature, magnetic field, and
Gd-substitution are used to investigate the evolution of magnetic polarons and
spin-carrier interactions through the metal-insulator transition in
EuGdO. These studies reveal a greater richness of phase behavior
than have been previously observed using transport measurements: a
spin-fluctuation-dominated paramagnetic (PM) phase regime for T T
T, a two-phase regime for T T in which magnetic polarons
develop and coexist with a remnant of the PM phase, and an inhomogeneous
ferromagnetic phase regime for T T
Point-of-care C-reactive protein testing to reduce inappropriate use of antibiotics for non-severe acute respiratory infections in Vietnamese primary health care: a randomised controlled trial
Background Inappropriate antibiotic use for acute respiratory tract infections is common in primary health care, but
distinguishing serious from self-limiting infections is diffi cult, particularly in low-resource settings. We assessed
whether C-reactive protein point-of-care testing can safely reduce antibiotic use in patients with non-severe acute
respiratory tract infections in Vietnam.
Method We did a multicentre open-label randomised controlled trial in ten primary health-care centres in northern
Vietnam. Patients aged 1–65 years with at least one focal and one systemic symptom of acute respiratory tract infection
were assigned 1:1 to receive either C-reactive protein point-of-care testing or routine care, following which antibiotic
prescribing decisions were made. Patients with severe acute respiratory tract infection were excluded. Enrolled
patients were reassessed on day 3, 4, or 5, and on day 14 a structured telephone interview was done blind to the
intervention. Randomised assignments were concealed from prescribers and patients but not masked as the test
result was used to assist treatment decisions. The primary outcome was antibiotic use within 14 days of follow-up. All
analyses were prespecifi ed in the protocol and the statistical analysis plan. All analyses were done on the intention-totreat
population and the analysis of the primary endpoint was repeated in the per-protocol population. This trial is
registered under number NCT01918579.
Findings Between March 17, 2014, and July 3, 2015, 2037 patients (1028 children and 1009 adults) were enrolled and
randomised. One adult patient withdrew immediately after randomisation. 1017 patients were assigned to receive
C-reactive protein point-of-care testing, and 1019 patients were assigned to receive routine care. 115 patients in the
C-reactive protein point-of-care group and 72 patients in the routine care group were excluded in the intention-to-treat
analysis due to missing primary endpoint. The number of patients who used antibiotics within 14 days was 581 (64%)
of 902 patients in the C-reactive protein group versus 738 (78%) of 947 patients in the control group (odds ratio
[OR] 0·49, 95% CI 0·40–0·61; p<0·0001). Highly signifi cant diff erences were seen in both children and adults, with
substantial heterogeneity of the intervention eff ect across the 10 sites (I²=84%, 95% CI 66–96). 140 patients in the
C-reactive protein group and 137 patients in the routine care group missed the urine test on day 3, 4, or 5. Antibiotic
activity in urine on day 3, 4, or 5 was found in 267 (30%) of 877 patients in the C-reactive protein group versus
314 (36%) of 882 patients in the routine treatment group (OR 0·78, 95% CI 0·63–0·95; p=0·015). Time to resolution
of symptoms was similar in both groups. Adverse events were rare, with no deaths and a total of 14 hospital admissions
(six in the C-reactive protein group and eight in the control group).
Interpretation C-reactive protein point-of-care testing reduced antibiotic use for non-severe acute respiratory tract
infection without compromising patients’ recovery in primary health care in Vietnam. Health-care providers might
have become familiar with the clinical picture of low C-reactive protein, leading to reduction in antibiotic prescribing
in both groups, but this would have led to a reduction in observed eff ect, rather than overestimation. Qualitative
analysis is needed to address diff erences in context in order to implement this strategy to improve rational antibiotic
use for patients with acute respiratory infection in low-income and middle-income countries
Theory of anyon excitons: Relation to excitons of nu=1/3 and nu=2/3 incompressible liquids
Elementary excitations of incompressible quantum liquids (IQL's) are anyons,
i.e., quasiparticles carrying fractional charges and obeying fractional
statistics. To find out how the properties of these quasiparticles manifest
themselves in the optical spectra, we have developed the anyon exciton model
(AEM) and compared the results with the finite-size data for excitons of nu=1/3
and nu=2/3 IQL's. The model considers an exciton as a neutral composite
consisting of three quasielectrons and a single hole. The AEM works well when
the separation between electron and hole confinement planes, h, is larger than
the magnetic length l. In the framework of the AEM an exciton possesses
momentum k and two internal quantum numbers, one of which can be chosen as the
angular momentum, L, of the k=0 state. Existence of the internal degrees of
freedom results in the multiple branch energy spectrum, crater-like electron
density shape and 120 degrees density correlations for k=0 excitons, and the
splitting of the electron shell into bunches for non-zero k excitons. For h
larger than 2l the bottom states obey the superselection rule L=3m (m are
integers starting from 2), all of them are hard core states. For h nearly 2l
there is one-to-one correspondence between the low-energy spectra found for the
AEM and the many- electron exciton spectra of the nu=2/3 IQL, whereas some
states are absent from the many-electron spectra of the nu=1/3 IQL. We argue
that this striking difference in the spectra originates from the different
populational statistics of the quasielectrons of charge conjugate IQL's and
show that the proper account of the statistical requirements eliminates
excessive states from the spectrum. Apparently, this phenomenon is the first
manifestation of the exclusion statistics in the anyon bound states.Comment: 26 pages with 9 figures, typos correcte
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