75 research outputs found
Topology by Design in Magnetic nano-Materials: Artificial Spin Ice
Artificial Spin Ices are two dimensional arrays of magnetic, interacting
nano-structures whose geometry can be chosen at will, and whose elementary
degrees of freedom can be characterized directly. They were introduced at first
to study frustration in a controllable setting, to mimic the behavior of spin
ice rare earth pyrochlores, but at more useful temperature and field ranges and
with direct characterization, and to provide practical implementation to
celebrated, exactly solvable models of statistical mechanics previously devised
to gain an understanding of degenerate ensembles with residual entropy. With
the evolution of nano--fabrication and of experimental protocols it is now
possible to characterize the material in real-time, real-space, and to realize
virtually any geometry, for direct control over the collective dynamics. This
has recently opened a path toward the deliberate design of novel, exotic
states, not found in natural materials, and often characterized by topological
properties. Without any pretense of exhaustiveness, we will provide an
introduction to the material, the early works, and then, by reporting on more
recent results, we will proceed to describe the new direction, which includes
the design of desired topological states and their implications to kinetics.Comment: 29 pages, 13 figures, 116 references, Book Chapte
Predictors of Medication Adherence and Blood Pressure Control among Saudi Hypertensive Patients Attending Primary Care Clinics: A Cross-Sectional Study
Purpose To assess the level of medication adherence and to investigate predictors of medication adherence and blood pressure control among hypertensive patients attending primary healthcare clinics in Makkah, Saudi Arabia. Patients and methods Hypertensive patients meeting the eligibility criteria were recruited from eight primary care clinics between January and May 2016 for this study. The patients completed Arabic version of Morisky Medication Adherence Scale (MMAS-8), an eight-item validated, self-reported measure to assess medication adherence. A structured data collection form was used to record patients’ sociodemographic, medical and medication data. Results Two hundred and four patients, of which 71.6% were females, participated in the study. Patients’ mean age was 59.1 (SD 12.2). The mean number of medication used by patients was 4.4 (SD 1.89). More than half (110; 54%) of the patients were non-adherent to their medications (MMAS score 65 years (OR 2.0 [95% CI: 1.0–4.2; P = 0.04]), and being diabetic (OR 0.25 [95% CI: 0.1–0.6; P = 0.04]) were found to be independent predictors of medication adherence. Conclusion Medication adherence is alarmingly low among hypertensive patients attending primary care clinics in Saudi Arabia which may partly explain observed poor blood pressure control. There is a clear need to educate patients about the importance of medication adherence and its impact on improving clinical outcomes. Future research should identify barriers to medication adherence among Saudi hypertensive patients
Azimuthal anisotropy and correlations at large transverse momenta in and Au+Au collisions at = 200 GeV
Results on high transverse momentum charged particle emission with respect to
the reaction plane are presented for Au+Au collisions at =
200 GeV. Two- and four-particle correlations results are presented as well as a
comparison of azimuthal correlations in Au+Au collisions to those in at
the same energy. Elliptic anisotropy, , is found to reach its maximum at
GeV/c, then decrease slowly and remain significant up to
-- 10 GeV/c. Stronger suppression is found in the back-to-back
high- particle correlations for particles emitted out-of-plane compared to
those emitted in-plane. The centrality dependence of at intermediate
is compared to simple models based on jet quenching.Comment: 4 figures. Published version as PRL 93, 252301 (2004
Azimuthal anisotropy in Au+Au collisions at sqrtsNN = 200 GeV
The results from the STAR Collaboration on directed flow (v_1), elliptic flow
(v_2), and the fourth harmonic (v_4) in the anisotropic azimuthal distribution
of particles from Au+Au collisions at sqrtsNN = 200 GeV are summarized and
compared with results from other experiments and theoretical models. Results
for identified particles are presented and fit with a Blast Wave model.
Different anisotropic flow analysis methods are compared and nonflow effects
are extracted from the data. For v_2, scaling with the number of constituent
quarks and parton coalescence is discussed. For v_4, scaling with v_2^2 and
quark coalescence is discussed.Comment: 26 pages. As accepted by Phys. Rev. C. Text rearranged, figures
modified, but data the same. However, in Fig. 35 the hydro calculations are
corrected in this version. The data tables are available at
http://www.star.bnl.gov/central/publications/ by searching for "flow" and
then this pape
Rapidity and Centrality Dependence of Proton and Anti-proton Production from Au+Au Collisions at sqrt(sNN) = 130GeV
We report on the rapidity and centrality dependence of proton and anti-proton
transverse mass distributions from Au+Au collisions at sqrt(sNN) = 130GeV as
measured by the STAR experiment at RHIC. Our results are from the rapidity and
transverse momentum range of |y|<0.5 and 0.35 <p_t<1.00GeV/c. For both protons
and anti-protons, transverse mass distributions become more convex from
peripheral to central collisions demonstrating characteristics of collective
expansion. The measured rapidity distributions and the mean transverse momenta
versus rapidity are flat within |y|<0.5. Comparisons of our data with results
from model calculations indicate that in order to obtain a consistent picture
of the proton(anti-proton) yields and transverse mass distributions the
possibility of pre-hadronic collective expansion may have to be taken into
account.Comment: 4 pages, 3 figures, 1 table, submitted to PR
Creation and annihilation of topological meron pairs in in-plane magnetized films
Merons which are topologically equivalent to one-half of skyrmions can exist only in pairs or groups in two-dimensional (2D) ferromagnetic (FM) systems. The recent discovery of meron lattice in chiral magnet Co8Zn9Mn3 raises the immediate challenging question that whether a single meron pair, which is the most fundamental topological structure in any 2D meron systems, can be created and stabilized in a continuous FM film? Utilizing winding number conservation, we develop a new method to create and stabilize a single pair of merons in a continuous Py film by local vortex imprinting from a Co disk. By observing the created meron pair directly within a magnetic field, we determine its topological structure unambiguously and explore the topological effect in its creation and annihilation processes. Our work opens a pathway towards developing and controlling topological structures in general magnetic systems without the restriction of perpendicular anisotropy and Dzyaloshinskii-Moriya interaction
Nonlinearity and Topology
The interplay of nonlinearity and topology results in many novel and emergent
properties across a number of physical systems such as chiral magnets, nematic
liquid crystals, Bose-Einstein condensates, photonics, high energy physics,
etc. It also results in a wide variety of topological defects such as solitons,
vortices, skyrmions, merons, hopfions, monopoles to name just a few.
Interaction among and collision of these nontrivial defects itself is a topic
of great interest. Curvature and underlying geometry also affect the shape,
interaction and behavior of these defects. Such properties can be studied using
techniques such as, e.g. the Bogomolnyi decomposition. Some applications of
this interplay, e.g. in nonreciprocal photonics as well as topological
materials such as Dirac and Weyl semimetals, are also elucidated
Myocardial tagging by Cardiovascular Magnetic Resonance: evolution of techniques--pulse sequences, analysis algorithms, and applications
Cardiovascular magnetic resonance (CMR) tagging has been established as an essential technique for measuring regional myocardial function. It allows quantification of local intramyocardial motion measures, e.g. strain and strain rate. The invention of CMR tagging came in the late eighties, where the technique allowed for the first time for visualizing transmural myocardial movement without having to implant physical markers. This new idea opened the door for a series of developments and improvements that continue up to the present time. Different tagging techniques are currently available that are more extensive, improved, and sophisticated than they were twenty years ago. Each of these techniques has different versions for improved resolution, signal-to-noise ratio (SNR), scan time, anatomical coverage, three-dimensional capability, and image quality. The tagging techniques covered in this article can be broadly divided into two main categories: 1) Basic techniques, which include magnetization saturation, spatial modulation of magnetization (SPAMM), delay alternating with nutations for tailored excitation (DANTE), and complementary SPAMM (CSPAMM); and 2) Advanced techniques, which include harmonic phase (HARP), displacement encoding with stimulated echoes (DENSE), and strain encoding (SENC). Although most of these techniques were developed by separate groups and evolved from different backgrounds, they are in fact closely related to each other, and they can be interpreted from more than one perspective. Some of these techniques even followed parallel paths of developments, as illustrated in the article. As each technique has its own advantages, some efforts have been made to combine different techniques together for improved image quality or composite information acquisition. In this review, different developments in pulse sequences and related image processing techniques are described along with the necessities that led to their invention, which makes this article easy to read and the covered techniques easy to follow. Major studies that applied CMR tagging for studying myocardial mechanics are also summarized. Finally, the current article includes a plethora of ideas and techniques with over 300 references that motivate the reader to think about the future of CMR tagging
Modeling of Human Prokineticin Receptors: Interactions with Novel Small-Molecule Binders and Potential Off-Target Drugs
The Prokineticin receptor (PKR) 1 and 2 subtypes are novel members of family A GPCRs, which exhibit an unusually high degree of sequence similarity. Prokineticins (PKs), their cognate ligands, are small secreted proteins of ∼80 amino acids; however, non-peptidic low-molecular weight antagonists have also been identified. PKs and their receptors play important roles under various physiological conditions such as maintaining circadian rhythm and pain perception, as well as regulating angiogenesis and modulating immunity. Identifying binding sites for known antagonists and for additional potential binders will facilitate studying and regulating these novel receptors. Blocking PKRs may serve as a therapeutic tool for various diseases, including acute pain, inflammation and cancer.Ligand-based pharmacophore models were derived from known antagonists, and virtual screening performed on the DrugBank dataset identified potential human PKR (hPKR) ligands with novel scaffolds. Interestingly, these included several HIV protease inhibitors for which endothelial cell dysfunction is a documented side effect. Our results suggest that the side effects might be due to inhibition of the PKR signaling pathway. Docking of known binders to a 3D homology model of hPKR1 is in agreement with the well-established canonical TM-bundle binding site of family A GPCRs. Furthermore, the docking results highlight residues that may form specific contacts with the ligands. These contacts provide structural explanation for the importance of several chemical features that were obtained from the structure-activity analysis of known binders. With the exception of a single loop residue that might be perused in the future for obtaining subtype-specific regulation, the results suggest an identical TM-bundle binding site for hPKR1 and hPKR2. In addition, analysis of the intracellular regions highlights variable regions that may provide subtype specificity
Evidence from d+Au measurements for final-state suppression of high-p(T) hadrons in Au plus Au collisions at RHIC
We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high p(T)) in minimum bias and central d+Au collisions at roots(NN)=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high p(T) previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions
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