344 research outputs found
Robust Ferroelectric State in Multiferroic MnZnWO
We report the remarkably robust ferroelectric state in the multiferroic
compound MnZnWO. The substitution of the magnetic Mn
with nonmagnetic Zn reduces the magnetic exchange and provides control
of the various magnetic and multiferroic states of MnWO. Only 5 % of Zn
substitution results in a complete suppression of the frustrated collinear
(paraelectric) low temperature phase. The helical magnetic and ferroelectric
phase develops as the ground state. The multiferroic state is stable up to a
high level of substitution of more than 50 %. The magnetic, thermodynamic, and
dielectric properties as well as the ferroelectric polarization of single
crystals of MnZnWO are studied for different substitutions up
to x=0.5. The magnetic phases have been identified in single crystal neutron
scattering experiments. The ferroelectric polarization scales with the neutron
intensity of the incommensurate peak of the helical phase.Comment: 6 pages, 8 figure
Rapid Determination of Macrolide and Lincosamide Resistance in Group B Streptococcus Isolated from Vaginal-Rectal Swabs
Objective. Our objective was to assess the ability of real-time PCR to predict in vitro resistance in isolates of
group B streptococcus (GBS). Methods. The first real-time PCR assays for the genes known to confer resistance to erythromycin and clindamycin in GBS were developed. Three hundred and forty clinical GBS isolates were assessed with these assays and compared with conventional disk diffusion. Results. The presence of an erythromycin ribosome methylation gene (ermB or ermTR variant A) predicted in vitro constitutive or inducible resistance to clindamycin with a sensitivity of 93% (95% CI 86%–97%), specificity of 90% (95% CI 85%–93%), positive predictive value of 76% (95% CI 67%–84%), and negative predictive
value of 97% (95% CI 94%–99%).
Conclusion. This rapid and simple assay can predict in vitro susceptibility to clindamycin within two hours of isolation as
opposed to 18–24 hours via disk diffusion. The assay might also be used to screen large numbers of batched isolates to establish the prevalence of resistance in a given area
Evaluation of the Xpert Carba-R Nxg Assay for Detection of Carbapenemase Genes in a Global Challenge Set of \u3cem\u3ePseudomonas aeruginosa \u3c/em\u3e Isolates
The growing prevalence and diversity of carbapenemase producers among carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates warrants an expansion of detection capabilities. The purpose of this study was to evaluate the performance of the commercially available Xpert Carba-R (Carba-R) and the research-use-only Xpert Carba-R NxG (Carba-R NxG) in a global collection of P. aeruginosa. The challenge set included 123 P. aeruginosa clinical isolates from 12 countries. Isolates were previously categorized via PCR or whole-genome sequencing. Carbapenemase classes tested include VIM, IMP, NDM, SPM, KPC, and GES. Non-carbapenemase (non-CP)-harboring isolates were also tested (negative control). Isolates were tested using the Carba-R NxG and the Carba-R tests per the manufacturer’s instructions. Carba-R NxG testing was completed by Cepheid (Sunnyvale, CA), blinded to genotype. Both assays gave negative results for all non-CP isolates and positive results for all VIM, NDM, and KPC isolates. An improvement in IMP detection among isolates was observed (100% detection by Carba-R NxG versus 58% by Carba-R). All SPM and GES isolates, targets not present in commercially available Carba-R, were positive by Carba-R NxG. Two isolates harbored both VIM and GES, while a third isolate contained VIM and NDM. The Carba-R NxG identified both targets in all 3 isolates, while the Carba-R was negative for both GES-containing isolates. Overall, the Carba-R NxG successfully categorized 100% of isolates tested compared with 68% for its predecessor. The Carba-R NxG will expand the detection spectrum of the current Carba-R assay to include SPM, GES, and expanded IMP variants, increasing the global utility of the test
Freshwater microcrustaceans (Cladocera: Anomopoda and Ctenopoda, Copepoda: Cyclopoida and Calanoida) in the highly urbanized Metropolitan Manila area (Luzon, Philippines)
Despite the increasing interest in studying Cladocera and Copepoda in Philippine freshwaters, there is a need to update our knowledge on its taxonomy and distribution in highly urbanized areas, such as Metropolitan Manila. This paper presents an updated listing of freshwater microcrustaceans and their distribution in Metropolitan Manila, considering the continued deterioration of water quality and increased urbanization in many areas since the last comprehensive study on these taxa in 1950s. We collected water samples from 33 freshwater sites in Metropolitan Manila and 23 of which were found to contain microcrustacean zooplankton. A total of 13 species were identified including two new locality records for C. cornuta and D. dubium in Pasig River. All 8 cladocerans, we identified have already recorded in previous studies while 3 cyclopoid copepods are new records for Metropolitan Manila. Furthermore, 16% of all known freshwater microcrustacean zooplankton species in the Philippines are found in Metropolitan Manila, including the Luzon-endemic Filipinodiaptomus insulanus collected from man-made reservoirs in less-disturbed habitats (an urban wildlife park, golf course and eco-park). Other identified species such as Thermocyclops taihokuensis may serve as indicator for high levels of nutrient. These results point to the importance of monitoring urban aquatic biodiversity for their potential in determining aquatic ecosystem health and of maintaining urban aquatic sanctuaries which may serve as alternative habitat for flora and fauna in rapidly developing urban centers such as Metropolitan Manila
Spin-orbit coupling controlled ground states in the double perovskite iridates A2BIrO6 (A = Ba, Sr; B = Lu, Sc)
Iridates with the 5 electronic configuration have attracted recent
interest due to reports of magnetically-ordered ground states despite
longstanding expectations that their strong spin-orbit coupling would generate
a electronic ground state for each Ir ion. The major focus of
prior research has been on the double perovskite iridates BaYIrO and
SrYIrO, where the nature of the ground states (i.e. ordered vs
non-magnetic) is still controversial. Here we present neutron powder
diffraction, high energy resolution fluorescence detected x-ray absorption
spectroscopy (HERFD-XAS), resonant inelastic x-ray scattering (RIXS), magnetic
susceptibility, and muon spin relaxation data on the related double perovskite
iridates BaLuIrO, SrLuIrO, BaScIrO, and SrScIrO
that enable us to gain a general understanding of the electronic and magnetic
properties for this family of materials. Our HERFD-XAS and RIXS measurements
establish electronic ground states for the Ir ions in all cases,
with similar values for Hund's coupling and the spin-orbit coupling
constant . Our bulk susceptibility and muon spin relaxation
data find no evidence for long-range magnetic order or spin freezing, but they
do reveal weak magnetic signals that are consistent with extrinsic local
moments. Our results indicate that the large is the key
driving force behind the electronic and magnetic ground states realized in the
5 double perovskite iridates, which agrees well with conventional wisdom.Comment: 13 pages, 7 figures, accepted for publication by PR
Helical magnetic order and Fermi surface nesting in non-centrosymmetric ScFeGe
An investigation of the structural, magnetic, thermodynamic, and charge
transport properties of non-centrosymmetric hexagonal ScFeGe reveals it to be
an anisotropic metal with a transition to a weak itinerant incommensurate
helimagnetic state below K. Neutron diffraction measurements
discovered a temperature and field independent helical wavevector
\textbf{\textit{k}} = (0 0 0.193) with magnetic moments of 0.53 per
formula unit confined to the {\it ab}-plane. Density functional theory
calculations are consistent with these measurements and find several bands that
cross the Fermi level along the {\it c}-axis with a nearly degenerate set of
flat bands just above the Fermi energy. The anisotropy found in the electrical
transport is reflected in the calculated Fermi surface, which consists of
several warped flat sheets along the -axis with two regions of significant
nesting, one of which has a wavevector that closely matches that found in the
neutron diffraction. The electronic structure calculations, along with a strong
anomaly in the {\it c}-axis conductivity at , signal a Fermi surface
driven magnetic transition, similar to that found in spin density wave
materials. Magnetic fields applied in the {\it ab}-plane result in a
metamagnetic transition with a threshold field of 6.7 T along with a
sharp, strongly temperature dependent, discontinuity and a change in sign of
the magnetoresistance for in-plane currents. Thus, ScFeGe is an ideal system to
investigate the effect of in-plane magnetic fields on an easy-plane magnetic
system, where the relative strength of the magnetic interactions and
anisotropies determine the topology and magnetic structure.Comment: 15 pages, 13 figure
Microscopic mechanisms of spin-dependent electric polarization in 3d oxides
We present a short critical overview of different microscopic models for
nonrelativistic and relativistic magnetoelectric coupling including the
so-called "spin current scenario", ab-initio calculations, and several recent
microscopic approaches to a spin-dependent electric polarization in 3d oxides.Comment: 8 pages, 3 figure
Focusing and Compression of Ultrashort Pulses through Scattering Media
Light scattering in inhomogeneous media induces wavefront distortions which
pose an inherent limitation in many optical applications. Examples range from
microscopy and nanosurgery to astronomy. In recent years, ongoing efforts have
made the correction of spatial distortions possible by wavefront shaping
techniques. However, when ultrashort pulses are employed scattering induces
temporal distortions which hinder their use in nonlinear processes such as in
multiphoton microscopy and quantum control experiments. Here we show that
correction of both spatial and temporal distortions can be attained by
manipulating only the spatial degrees of freedom of the incident wavefront.
Moreover, by optimizing a nonlinear signal the refocused pulse can be shorter
than the input pulse. We demonstrate focusing of 100fs pulses through a 1mm
thick brain tissue, and 1000-fold enhancement of a localized two-photon
fluorescence signal. Our results open up new possibilities for optical
manipulation and nonlinear imaging in scattering media
A Quantitative Ethnobotanical Study of Plants Used by the Locals in Camiguin Island, Calayan, Cagayan, Philippines
Traditional knowledge concerning plant utilization in the Philippines is common but is largely underappreciated. Assessment of plant resources by groups of people helps promote valorization of cultural heritage. However, particularly in the Camiguin Is-landof the North, Cagayan (not to be confused with the island province of Camiguin in Mindanao), the use of terrestrial plants remains unknown. As a response, this study aims to identify island terrestrial plants withethnobotanical importance through semi-structured interviews. The data collected were then analyzed using quantitative ethnobotanical methods. A total of 70 species belonging to 65 genera and 44 families were surveyed from the 33 informants. The statistical analysis showed a significant difference between male and female informants in ethnobotan-ical knowledge. Lamiaceae was the most represented plant family with five species recorded. Leaves were the most used plant part (51%), congruent to previous ethno-botanical studies in the Philippines. Most medicinal preparations were done through decoctions (41.03%). Much of the medicinal plants surveyed were administered through topical medication (54.90%), and this is because the occupation of the peo-ple of Camiguin island mostly involves heavy physical activities. Thus, the proba-bility of being wounded in the area is very high. It was found that Vitex negundowas the most used plant in Camiguin island with the used value of 0.15.Furthermore, five ailment/disease categories obtained a 100% fidelity level. This result indicates that the plants used for that disease category are considered the most preferred spe-cies. Respiratory diseases obtained the highest FIC value of 0.40, indicating species within that category are the best candidates to search for bioactive compounds. This documentation provides the first checklist of useful plants in Camiguin island and will serve as a basis for future ethnobotanical studies in the Philippines
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