ResearchPad - Condensed Matter Physics https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[The effect of Mn2Sb2 and Mn2Sb secondary phases on magnetism in (GaMn)Sb thin films]]> https://www.researchpad.co/product?articleinfo=N94466bcc-ad77-4d3b-8f3f-3aceb39bbed5

In this work, a detailed study of structural, electrical and magnetic characterization of (GaMn)Sb diluted magnetic semiconductors (DMS) is presented. (GaMn)Sb thin films were grown by DC magnetron co-sputtering method as an innovative procedure to fabricate III-V DMS. The presence of unusual Mn2Sb2 and Mn2Sb secondary phases, induced by substrate temperature and deposition time, were revealed through XRD measurements. Magnetization measurements allow determining crossover between a paramagnetic-like to a ferromagnetic-like behavior controlled by secondary phases. It was found that both, the magnetic remanence and magnetic coercivity, increases with substrate temperature. Interestingly, the magnetic response is paramagnetic at lower deposition times and substrate temperatures, and XRD measurements suggest the absence of Mn2Sb and Mn2Sb2 in secondary phases. For longer deposition times or higher substrate temperature, XRD shows the presence of Mn2Sb2 and Mn2Sb phases and ferromagnetic-like behavior. The DC resistivity of our samples was characterized and the carrier density was determined by Hall measurements and, in contrast with the reported in other studies, found them to be a p-type semiconductor with carrier densities as big as one order of magnitude larger than reported values. From the ferromagnetic-like samples, evidence of an anomalous Hall-effect in the sample was found, with higher magnetic saturation and a anomalous Hall conductivity of 2380 S/cm. All the results point to a contribution of the secondary phases to the overall magnetic response of the samples used, and suggest the importance of studying the formation of secondary phases in the growth of DMS, especially, for the case of (GaMn)Sb where Mn ion can have multiple oxidation states.

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<![CDATA[High-frequency rectification via chiral Bloch electrons]]> https://www.researchpad.co/product?articleinfo=Ne2b629de-c87a-465c-9632-724022c3d4df

Engineering quantum crystals realizes high-frequency rectifiers by rational material design.

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<![CDATA[Four-wave mixing of topological edge plasmons in graphene metasurfaces]]> https://www.researchpad.co/product?articleinfo=N3e5b3352-8705-493d-9b5e-bb322490e321

It is demonstrated that net optical gain can be achieved via topologically protected four-wave mixing in a graphene metasurface.

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<![CDATA[Scaling, rotation, and channeling behavior of helical and skyrmion spin textures in thin films of Te-doped Cu2OSeO3]]> https://www.researchpad.co/product?articleinfo=N0ecd204c-15d0-4098-ad5b-56fd27cdab92

We report on scaling, rotation, and channeling behavior of helical and skyrmion spin textures in thin films of Te-doped Cu2OSeO3.

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<![CDATA[Chiral superconductivity in the alternate stacking compound 4Hb-TaS2]]> https://www.researchpad.co/product?articleinfo=N734210af-0ecf-4171-948b-fc8335194069

Chiral superconductivity in 4Hb-TaS2 was discovered using muon spin rotation.

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<![CDATA[Nonreciprocal transport in gate-induced polar superconductor SrTiO3]]> https://www.researchpad.co/product?articleinfo=N13bebcd3-3e09-488b-9c02-4611e11cf398

Characteristics of gate-induced 2D superconductor SrTiO3, a possible Rashba superconductor, are studied via nonlinear transport.

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<![CDATA[Surface-state Coulomb repulsion accelerates a metal-insulator transition in topological semimetal nanofilms]]> https://www.researchpad.co/product?articleinfo=N0a4ade9e-7b60-44fc-88b4-e5bfe548c8eb

Increased Coulomb repulsion from surface states substantially modulates quantum confinement in topological semimetal nanofilms.

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<![CDATA[Microscopic pathways for stress relaxation in repulsive colloidal glasses]]> https://www.researchpad.co/product?articleinfo=Na082c33b-f870-4886-b656-a338eb2fabeb

How residual stresses in colloids generate directional and heterogeneous motions down to fundamental length scales.

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<![CDATA[The electronic thickness of graphene]]> https://www.researchpad.co/product?articleinfo=N34d390e3-f4c7-426b-8396-a65465411992

The electronic thickness of graphene is measured by two capacitively coupled, atomically close graphene layers.

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<![CDATA[Local Berry curvature signatures in dichroic angle-resolved photoelectron spectroscopy from two-dimensional materials]]> https://www.researchpad.co/product?articleinfo=Nccbefd34-f6f7-490a-bc40-1902bd0fa9c1

Orbital polarization and Berry curvature signatures are mapped out by circular dichroism in angle-resolved photoemission.

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<![CDATA[Scalable Majorana vortex modes in iron-based superconductors]]> https://www.researchpad.co/product?articleinfo=Nbc0fabdd-ba1e-4042-ad64-e47058f382f2

A simulation study with experimental data analysis shows the presence of multiple Majorana modes in iron-based superconductors.

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<![CDATA[Generalized Anderson’s theorem for superconductors derived from topological insulators]]> https://www.researchpad.co/product?articleinfo=N1c88d9d5-a670-4596-9732-cfd177ee2307

Cooper pairs in unconventional superconductors having extra internal degrees of freedom are protected in an unexpected way.

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<![CDATA[Automated structure discovery in atomic force microscopy]]> https://www.researchpad.co/product?articleinfo=Nbac1a396-0a61-42e9-8558-9c2080e4396f

We develop a deep learning method that predicts atomic structure directly from experimental atomic force microscopy images.

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<![CDATA[Crystal structures of Triosephosphate Isomerases from Taenia solium and Schistosoma mansoni provide insights for vaccine rationale and drug design against helminth parasites]]> https://www.researchpad.co/product?articleinfo=N340e3046-cb91-4c84-8d1b-fb2a65cf4cdb

Triosephosphate isomerases (TPIs) from Taenia solium (TsTPI) and Schistosoma mansoni (SmTPI) are potential vaccine and drug targets against cysticercosis and schistosomiasis, respectively. This is due to the dependence of parasitic helminths on glycolysis and because those proteins elicit an immune response, presumably due to their surface localization. Here we report the crystal structures of TsTPI and SmTPI in complex with 2-phosphoglyceric acid (2-PGA). Both TPIs fold into a dimeric (β-α)8 barrel in which the dimer interface consists of α-helices 2, 3, and 4, and swapping of loop 3. TPIs from parasitic helminths harbor a region of three amino acids knows as the SXD/E insert (S155 to E157 and S157 to D159 in TsTPI and SmTPI, respectively). This insert is located between α5 and β6 and is proposed to be the main TPI epitope. This region is part of a solvent-exposed 310–helix that folds into a hook-like structure. The crystal structures of TsTPI and SmTPI predicted conformational epitopes that could be used for vaccine design. Surprisingly, the epitopes corresponding to the SXD/E inserts are not the ones with the greatest immunological potential. SmTPI, but not TsTPI, habors a sole solvent exposed cysteine (SmTPI-S230) and alterations in this residue decrease catalysis. The latter suggests that thiol-conjugating agents could be used to target SmTPI. In sum, the crystal structures of SmTPI and TsTPI are a blueprint for targeted schistosomiasis and cysticercosis drug and vaccine development.

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<![CDATA[Giant optical nonlinearity interferences in quantum structures]]> https://www.researchpad.co/product?articleinfo=N8f18f394-87d1-4f8f-a101-b6b33803e492

We bring to light the complex interplay of optical nonlinearities in quantum structures.

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<![CDATA[Topological charge transport by mobile dielectric-ferroelectric domain walls]]> https://www.researchpad.co/product?articleinfo=Ncb65dbeb-c828-4c37-a782-4f176b458da8

Resistivity and NMR measurements demonstrate an electrical conduction mechanism by topological domain walls and solitons.

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<![CDATA[Exploring magnetohydrodynamic voltage distributions in the human body: Preliminary results]]> https://www.researchpad.co/product?articleinfo=5c89777ed5eed0c4847d2e42

Background

The aim of this study was to noninvasively measure regional contributions of vasculature in the human body using magnetohydrodynamic voltages (VMHD) obtained from electrocardiogram (ECG) recordings performed inside MRI’s static magnetic field (B0). Integrating the regional VMHD over the Swave-Twave segment of the cardiac cycle (Vsegment) provides a non-invasive method for measuring regional blood volumes, which can be rapidly obtained during MRI without incurring additional cost.

Methods

VMHD was extracted from 12-lead ECG traces acquired during gradual introduction into a 3T MRI. Regional contributions were computed utilizing weights based on B0’s strength at specified distances from isocenter. Vsegment mapping was performed in six subjects and validated against MR angiograms (MRA).

Results

Fluctuations in Vsegment, which presented as positive trace deflections, were found to be associated with aortic-arch flow in the thoracic cavity, the main branches of the abdominal aorta, and the bifurcation of the common iliac artery. The largest fluctuation corresponded to the location where the aortic arch was approximately orthogonal to B0. The smallest fluctuations corresponded to areas of vasculature that were parallel to B0. Significant correlations (specifically, Spearman’s ranked correlation coefficients of 0.96 and 0.97 for abdominal and thoracic cavities, respectively) were found between the MRA and Vsegment maps (p < 0.001).

Conclusions

A novel non-invasive method to extract regional blood volumes from ECGs was developed and shown to be a rapid means to quantify peripheral and abdominal blood volumes.

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<![CDATA[Detailed characterization of the solution kinetics and thermodynamics of biotin, biocytin and HABA binding to avidin and streptavidin]]> https://www.researchpad.co/product?articleinfo=5c818e96d5eed0c484cc260a

The high affinity (KD ~ 10−15 M) of biotin for avidin and streptavidin is the essential component in a multitude of bioassays with many experiments using biotin modifications to invoke coupling. Equilibration times suggested for these assays assume that the association rate constant (kon) is approximately diffusion limited (109 M-1s-1) but recent single molecule and surface binding studies indicate that they are slower than expected (105 to 107 M-1s-1). In this study, we asked whether these reactions in solution are diffusion controlled, which reaction model and thermodynamic cycle describes the complex formation, and if there are any functional differences between avidin and streptavidin. We have studied the biotin association by two stopped-flow methodologies using labeled and unlabeled probes: I) fluorescent probes attached to biotin and biocytin; and II) unlabeled biotin and HABA, 2-(4’-hydroxyazobenzene)-benzoic acid. Both native avidin and streptavidin are homo-tetrameric and the association data show no cooperativity between the binding sites. The kon values of streptavidin are faster than avidin but slower than expected for a diffusion limited reaction in both complexes. Moreover, the Arrhenius plots of the kon values revealed strong temperature dependence with large activation energies (6–15 kcal/mol) that do not correspond to a diffusion limited process (3–4 kcal/mol). Accordingly, we propose a simple reaction model with a single transition state for non-immobilized reactants whose forward thermodynamic parameters complete the thermodynamic cycle, in agreement with previously reported studies. Our new understanding and description of the kinetics, thermodynamics, and spectroscopic parameters for these complexes will help to improve purification efficiencies, molecule detection, and drug screening assays or find new applications.

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<![CDATA[Molecular features of steroid-binding antidins and their use for assaying serum progesterone]]> https://www.researchpad.co/product?articleinfo=5c76fe5fd5eed0c484e5b998

Chicken avidin (Avd) and streptavidin from Streptomyces avidinii are extensively used in bionanotechnology due to their extremely tight binding to biotin (Kd ~ 10−15 M for chicken Avd). We previously reported engineered Avds known as antidins, which have micro- to nanomolar affinities for steroids, non-natural ligands of Avd. Here, we report the 2.8 Å X-ray structure of the sbAvd-2 (I117Y) antidin co-crystallized with progesterone. We describe the creation of new synthetic phage display libraries and report the experimental as well as computational binding analysis of progesterone-binding antidins. We introduce a next-generation antidin with 5 nM binding affinity for progesterone, and demonstrate the use of antidins for measuring progesterone in serum samples. Our data give insights on how to engineer and alter the binding preferences of Avds and to develop better molecular tools for modern bionanotechnological applications.

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<![CDATA[Combination of colonoscopy and magnetic resonance enterography is more useful for clinical decision making than colonoscopy alone in patients with complicated Crohn's disease]]> https://www.researchpad.co/product?articleinfo=5c76fe3fd5eed0c484e5b78a

Background/aims

The small bowel is affected in more than half of patients with Crohn’s disease (CD) at the time of diagnosis, and small bowel involvement has a negative impact on the long-term outcome. Many patients reportedly have active lesions in the small intestine even in patients in clinical remission. This study was performed to compare findings of magnetic resonance enterography (MRE) and ileocolonoscopy.

Methods

A single-center retrospective study was conducted in 50 patients (60 imaging series) with CD, for whom MRE was additionally performed during the bowel preparation for subsequent ileocolonoscopy. Endoscopic remission was defined as a Simple Endoscopic Score for CD (SES-CD) of <5. MRE remission was defined as a Magnetic Resonance Index of Activity (MaRIA) score of <50. The time to treatment escalation was assessed by the log-rank test.

Results

Importantly, 7 of 29 patients (24.1%) with endoscopic remission had a MaRIA score of ≥50. Both SES-CD and MaRIA correlated with the need for treatment escalation (P = 0.025, P = 0.009, respectively). MRE predicted the need for treatment escalation even in patients with endoscopic remission. Although no correlation was present between SES-CD and MaRIA score in patients with structuring/penetrating disease, or insufficient ileal insertion (<10cm), a high MaRIA score still correlated with the need for treatment escalation in stricturing or penetrating disease (P = 0.0306).

Conclusions

The MaRIA score predicts the need for treatment escalation even in patients with endoscopic remission, indicating that addition of MRE to conventional ileocolonoscopy alone can be a useful, noninvasive tool for monitoring CD especially in stricturing or penetrating disease.

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