Current-induced reversal in magnetic nanopillars passivated by silicon

We demonstrate that magnetic multilayer nanopillars can be efficiently protected from oxidation by coating with silicon. Both the protected and the oxidized nanopillars exhibit an increase of reversal current at cryogenic temperatures. However the magnetic excitation onset current increases only in the oxidized samples. We show that oxidized nanopillars exhibit anomalous switching statistics at low temperature, providing a simple test for the quality of magnetic nanodevices.Comment: 3 pages, 4 figure

Spins in Thin Films and Nanodevices

The central theme of this work is the engineering of devices and materials that exhibit spin dependent phenomena. In particular, the spin orientation of charge carriers can play a central role in transport, especially in magnetic or other spin correlated media. Propagation of charge carriers with net spin results in a transfer of angular momentum that can excite static and dynamical states in active device elements. To utilize such phenomena in practical devices, new mew means of device characterization and optimization must be developed. To that end, we have performed experiments which elucidate some of the mechanisms underlying spin dependent transport phenomena.;We report the observation of hysteretic synchronization of point contact spin torque nano-oscillators (STNOs) by a microwave magnetic field. The hysteresis was asymmetric with respect to the frequency detuning of the driving signal, and appeared in the region of a strong dependence of the oscillation frequency on the bias current. Theoretical analysis showed that hysteretic synchronization occurred when the width of the synchronization range, enhanced by the oscillator\u27s nonlinearity, became comparable to the dissipation rate, while the observed asymmetry was a consequence of the nonlinear dependence of frequency on the bias current.;Another emergent phenomenon was a series of fractional synchronization regimes in a STNO driven by a microwave field. These regimes are characterized by rational relations between the driving frequency and the frequency of the oscillation. Analysis based on the phase model of auto-oscillator indicates that fractional synchronization becomes possible when the driving signal breaks the symmetry of the oscillation, while the synchronization ranges are determined by the geometry of the oscillation orbit. Measurements of fractional synchronization were utilized to obtain information about the oscillation characteristics in nanoscale systems not accessible to direct imaging techniques.;Oxidation in magnetic nanosystems can result in changes of the magnetic ordering of active layers in devices, resulting in degraded device performance. We demonstrate that magnetic multilayer nanopillars can be efficiently protected from oxidation by coating with silicon. Both the protected and the oxidized nanopillars exhibited an increase of reversal current at cryogenic temperatures. However the magnetic excitation onset current increased only in the oxidized samples. We show that oxidized nanopillars exhibit anomalous switching statistics at low temperature, providing a simple test for the quality of magnetic nanodevices.;We studied exchange bias in magnetic multilayers incorporating antiferromagnet CoO doped with up to 35 atomic percent of Pt. The exchange bias increased with doping in epitaxial films, but did not significantly change in polycrystalline films at the lowest measured temperature of 5 K, and decreased at higher temperatures. We explain our results by the increased granularity of the doped antiferromagnetic films, resulting in simultaneous enhancement of the uncompensated spin density and reduction of the magnetic stability of antiferromagnetic grains.;Finally, we demonstrate the growth of Bi2Se3, a material known as a topological insulator (TI). The structural and electronic properties of Bi2Se3 films grown on Al2O 3 (110) by molecular beam epitaxy were investigated. The epitaxial films grew in the Frank-van der Merwe mode and were c-axis oriented. They exhibited the highest crystallinity, the lowest carrier concentration, and optimal stoichiometry at a substrate temperature of 200 .C determined by the balance between surface kinetics and desorption of selenium. The crystallinity of the films improved with increasing selenium/bismuth flux ratio

Fractional Synchronization of Spin-Torque Nano-Oscillators

We experimentally demonstrate a series of fractional synchronization regimes (Devil\u27s staircase) in a spin-torque nano-oscillator driven by a microwave field. These regimes are characterized by rational relations between the driving frequency and the frequency of the oscillation. An analysis based on the phase model of auto-oscillator indicates that fractional synchronization becomes possible when the driving signal breaks the symmetry of the oscillation, while the synchronization ranges are determined by the geometry of the oscillation orbit. Measurements of fractional synchronization can be utilized to obtain information about the oscillation characteristics in nanoscale systems not accessible to direct imaging techniques

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Home and Online Management and Evaluation of Blood Pressure (HOME BP) using a digital intervention in poorly controlled hypertension: randomised controlled trial

Objective: The HOME BP (Home and Online Management and Evaluation of Blood Pressure) trial aimed to test a digital intervention for hypertension management in primary care by combining self-monitoring of blood pressure with guided self-management. Design: Unmasked randomised controlled trial with automated ascertainment of primary endpoint. Setting: 76 general practices in the United Kingdom. Participants: 622 people with treated but poorly controlled hypertension (>140/90 mm Hg) and access to the internet. Interventions: Participants were randomised by using a minimisation algorithm to self-monitoring of blood pressure with a digital intervention (305 participants) or usual care (routine hypertension care, with appointments and drug changes made at the discretion of the general practitioner; 317 participants). The digital intervention provided feedback of blood pressure results to patients and professionals with optional lifestyle advice and motivational support. Target blood pressure for hypertension, diabetes, and people aged 80 or older followed UK national guidelines. Main outcome measures: The primary outcome was the difference in systolic blood pressure (mean of second and third readings) after one year, adjusted for baseline blood pressure, blood pressure target, age, and practice, with multiple imputation for missing values. Results: After one year, data were available from 552 participants (88.6%) with imputation for the remaining 70 participants (11.4%). Mean blood pressure dropped from 151.7/86.4 to 138.4/80.2 mm Hg in the intervention group and from 151.6/85.3 to 141.8/79.8 mm Hg in the usual care group, giving a mean difference in systolic blood pressure of −3.4 mm Hg (95% confidence interval −6.1 to −0.8 mm Hg) and a mean difference in diastolic blood pressure of −0.5 mm Hg (−1.9 to 0.9 mm Hg). Results were comparable in the complete case analysis and adverse effects were similar between groups. Within trial costs showed an incremental cost effectiveness ratio of £11 ($15, €12; 95% confidence interval £6 to £29) per mm Hg reduction. Conclusions: The HOME BP digital intervention for the management of hypertension by using self-monitored blood pressure led to better control of systolic blood pressure after one year than usual care, with low incremental costs. Implementation in primary care will require integration into clinical workflows and consideration of people who are digitally excluded. Trial registration: ISRCTN13790648

Design and synthesis of ferrocene probe molecules for detection by electrochemical methods

A series of ferrocenyl conjugates to fatty acids have been designed and synthesized to establish the key properties required for use in biomolecular binding studies. Amperometric detection of the ferrocene conjugates was sought in the region of 0.3 V (vs Ag/AgCl) for use in protein/blood solutions. Different linkers and solubilizing moieties were incorporated to produce a conjugate with optimal electrochemical properties. In electrochemical studies, the linker directly attached to the ferrocene was found to affect significantly the E 1/2 value and the stability of the ferrocenium cation. Ester-linked ferrocene conjugates had E 1/2 ranging from +400 to +410 mV, while amide-linked compounds ranged from +350 to +370 mV and the amines +260 to +270 mV. Folding of long-chain substituents around the ferrocene, also significantly affected by the choice of linker, was inferred as a secondary effect that increased E 1/2. The stability of the ferrocenium cation decreased systematically as E 1/2 increased. Disubstituted ferrocene ester and amide conjugates, with oxidation potentials of +640 and +570 mV, respectively, showed only a barely discernible reduction wave in cyclic voltammetry at 50 mV/s. Electrochemical measurements identified two lead compounds with the common structural characteristics of an amide and carbamate linker (compounds 17 and 21) with a C 11 fatty acid chain attached. It is envisaged that such molecules can be used to mimic and study the biomolecular binding interaction between fatty acids and molecules such as human serum albumin

Evaluation of MALDI-TOF mass spectroscopy methods for determination of Escherichia coli pathotypes

It is rapidly becoming apparent that many E. coli pathotypes cause a considerable burden of human disease. Surveillance of these organisms is difficult because there are few or no simple, rapid methods for detecting and differentiating the different pathotypes. MALDI-TOF mass spectroscopy has recently been rapidly and enthusiastically adopted by many clinical laboratories as a diagnostic method because of its high throughput, relatively low cost, and adaptability to the laboratory workflow. To determine whether the method could be adapted for E. coli pathotype differentiation the Bruker Biotyper methodology and a second methodology adapted from the scientific literature were tested on isolates representing eight distinct pathotypes and two other groups of E. coli. A total of 136 isolates was used for this study. Results confirmed that the Bruker Biotyper methodology that included extraction of proteins from bacterial cells was capable of identifying E. coli isolates from all pathotypes to the species level and, furthermore, that the Bruker extraction and MALDI-TOF MS with the evaluation criteria developed in this work was effective for differentiating most pathotypes