We report the coherent study of structural, transport, and ultrafast dynamic properties of V1−xNbxO2 thin films. Films of a solid solution of V1−xNbxO2(0≤x≤1) are prepared on (0001) sapphire ...substrates using reactive target bias ion beam deposition. We found that, at room temperature, the low-temperature lattice symmetry of pure VO2 (monoclinic, P21/c) and NbO2 (tetragonal, I41/a) is only maintained at low substituting levels (x<0.1 and x>0.9) and regular rutile lattices are adopted by films with higher substituting levels (0.1<x<0.9). We characterized the dc transport properties and the photoinduced ultrafast dynamics at the terahertz frequency range, both of which demonstrate strong dependence on the film composition. At x∼0.5, both the dc conductivity and ultrafast response diminish, which corresponds to a strong localization of free charge carriers in the system. The strong composition dependence of film transport, ultrafast dynamic, and insulator-metal transition properties promises approaches to improve the performance of devices based on transition metal oxides.
The strong electron-lattice interactions in correlated electron systems provide unique opportunities for altering the material properties with relative ease and flexibility. In this Rapid ...Communication, we use localized strain control via a focused-ion-beam patterning of TiO2 substrates to demonstrate that one can selectively engineer the insulator-to-metal transition temperature, the fractional component of the insulating and metallic phases, and the degree of optical anisotropy down to the length scales of the intrinsic phase separation in VO2 thin films without altering the quality of the films. The effects of localized strain control on the strongly correlated electron system are directly visualized by state-of-the-art IR near-field imaging and spectroscopy techniques and x-ray microdiffraction measurements.
We investigated the formation of nanoribbon hydrogels in a mixed system of zinc ions, bis(ligand)s, and triblock peptide copolymers. Using a combination of experimental techniques: dynamic light ...scattering, cryo-transmission electron microscopy, small-angle X-ray scattering and circular dichroism, we arrived at a model for the formation of nanoribbon hydrogels in which well-defined nanoribbons are formed out of multiple supramolecular interactions: (1) metal coordination that yields supramolecular polyelectrolytes; (2) electrostatic complexation between the supramolecular polyelectrolytes and the oppositely charged blocks of the peptide copolymers; (3) hydrogen bond and (4) hydrophobic interactions that support the secondary and ternary structure of the ribbons; (5) van der Waals interactions that enable bundling of the ribbons.
RASopathies account for nearly 20% of cases of childhood hypertrophic cardiomyopathy (HCM). Sudden cardiac death (SCD) occurs in patients with RASopathy-associated HCM, but the risk factors for SCD ...have not been systematically evaluated.
To validate the HCM Risk-Kids SCD risk prediction model in children with RASopathy-associated HCM and investigate potential specific SCD predictors in this population.
Validation of HCM Risk-Kids was performed in a retrospective cohort of 169 patients with a RASopathy-associated HCM from 15 international paediatric cardiology centres. Multiple imputation by chained equations was used for missing values related to the HCM Risk-Kids parameters.
Eleven patients (6.5%) experienced a SCD or equivalent event at a median age of 12.5 months (IQR 7.7–28.64). The calculated SCD/equivalent event incidence was 0.78 (95% CI 0.43–1.41) per 100 patient years. Six patients (54.54%) with an event were in the low-risk category according to the HCM Risk-Kids model. Harrell's C index was 0.60, with a sensitivity of 9.09%, specificity of 63.92%, positive predictive value of 1.72%, and negative predictive value of 91%; with a poor distinction between the different risk groups. Unexplained syncope (HR 42.17, 95% CI 10.49–169.56, p < 0.001) and non-sustained ventricular tachycardia (HR 5.48, 95% CI 1.58–19.03, p < 0.007) were predictors of SCD on univariate analysis.
Unexplained syncope and the presence of NSVT emerge as predictors for SCD in children with RASopathy-associated HCM. The HCM Risk-Kids model may not be appropriate to use in this population, but larger multicentre collaborative studies are required to investigate this further.
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•Children with RASopathy associated hypertrophic cardiomyopathy (HCM) have a high risk for sudden cardiac death (SCD)•The HCM Risk-Kids risk prediction model used for children with non-syndromic HCM appears unsuitable for use in this cohort•Non-sustained ventricular tachycardia and unexplained syncope emerge as predictors of SCD•Larger collaborations are needed to validate these results and identify specific risk factors for SCD in this population
Superconducting State Kresin, Vladimir Z; Morawitz, Hans; Wolf, Stuart A
2013, 2013-12-12, 2014, Volume:
161
eBook
This book provides a very detailed theoretical treatment of the key mechanisms of superconductivity. including the current state of the art (phonons, magnons, plasmons). It also includes a very ...complete description of the electron–phonon mechanism responsible for superconductivity in the majority of superconducting systems and the history of its development, and a detailed description of the key experimental techniques used to study the superconducting state and determine the mechanisms. In addition, the chapters describe the discovery and properties of the key superconducting compounds that are of the most interest for science and applications, including a special chapter on the cuprate superconductors. Also included are detailed treatments of some very novel aspects of superconductivity, including multiple bands (gaps), the “pseudogap” state, novel isotope effects beyond BCS, and induced superconductivity.
SPIN TRansport electrONICS or SPINTRONICS, in which the spin degree of freedom of the electron will play an important role in addition to or in place of the charge degree of freedom in mainstream ...electronics will be important as we start the new millennium. The prospects for this new electronics in nonvolatile radiation hard magnetic memory for the Department of Defense (DoD) is described.
Doped cuprates are inhomogeneous superconductors. The concept of an intrinsic critical temperature,
, whose value greatly exceeds that for the resistive
, is supported by a number of experimental ...studies, including those performed recently. These data are discussed in this review. The anomalous diamagnetism observed at
is a manifestation of the presence of superconducting clusters embedded into a normal metallic matrix. The value of intrinsic critical temperature in some cuprates reaches a value which is close to room temperature. The a.c. properties of such inhomogeneous systems are discussed.
Spintronics—A retrospective and perspective Wolf, S A; Chtchelkanova, A Y; Treger, D M
IBM journal of research and development,
1/2006, Volume:
50, Issue:
1
Journal Article
Peer reviewed
Spintronics is a rapidly emerging field of science and technology that will most likely have a significant impact on the future of all aspects of electronics as we continue to move into the 21st ...century. Conventional electronics are based on the charge of the electron. Attempts to use the other fundamental property of an electron, its spin, have given rise to a new, rapidly evolving field, known as spintronics, an acronym for spin transport electronics that was first introduced in 1996 to designate a program of the U.S. Defense Advanced Research Projects Agency (DARPA). Initially, the spintronics program involved overseeing the development of advanced magnetic memory and sensors based on spin transport electronics. It was then expanded to included Spins IN Semiconductors (SPINS), in the hope of developing a new paradigm in semiconductor electronics based on the spin degree of freedom of the electron. Studies of spin-polarized transport in bulk and low-dimensional semiconductor structures show promise for the creation of a hybrid device that would combine magnetic storage with gain-in effect, a spin memory transistor. This paper reviews some of the major developments in this field and provides a perspective of what we think will be the future of this exciting field. It is not meant to be a comprehensive review of the whole field but reflects a bias on the part of the authors toward areas that they believe will lead to significant future technologies. PUBLICATION ABSTRACT
Vanadium dioxide exhibits a thermally induced metalinsulator transition near room temperature. Metallic puddles nucleate and coarsen, embedded in the insulating matrix. The coexistence of these two ...phases spans distinct length scales as their relative domain sizes change. On page 30, using far‐field optical probing at very different frequencies, R. A. Lukaszew and co‐workers are able to follow the dynamic evolution of these phases across the transition.
Genetically engineered protein polymers (GEPP) are a class of multifunctional materials with precisely controlled molecular structure and property profile. Representing a promising alternative for ...currently used materials in biomedical applications, GEPP offer multiple benefits over natural and chemically synthesized polymers. However, producing them in sufficient quantities for preclinical research remains challenging. Here, we present results from an in vitro cellular response study of a recombinant protein polymer that is soluble at low pH but self-organizes into supramolecular fibers and physical hydrogels at neutral pH. It has a triblock structure denoted as C2S(H)48C2, which consists of hydrophilic collagen-inspired and histidine-rich silk-inspired blocks. The protein was successfully produced by the yeast Pichia pastoris in laboratory-scale bioreactors, and it was purified by selective precipitation. This efficient and inexpensive production method provided material of sufficient quantities, purity and sterility for cell culture study. Rheology and erosion studies showed that it forms hydrogels exhibiting long-term stability, self-healing behavior and tunable mechanical properties. Primary rat bone marrow cells cultured in direct contact with these hydrogels remained fully viable; however, proliferation and mineralization were relatively low compared to collagen hydrogel controls, probably because of the absence of cell-adhesive motifs. As biofunctional factors can be readily incorporated to improve material performance, our approach provides a promising route towards biomedical applications.
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