1,196 research outputs found
Basic obstacle for electrical spin-injection from a ferromagnetic metal into a diffusive semiconductor
We have calculated the spin-polarization effects of a current in a two
dimensional electron gas which is contacted by two ferromagnetic metals. In the
purely diffusive regime, the current may indeed be spin-polarized. However, for
a typical device geometry the degree of spin-polarization of the current is
limited to less than 0.1%, only. The change in device resistance for parallel
and antiparallel magnetization of the contacts is up to quadratically smaller,
and will thus be difficult to detect.Comment: Revtex, 4 pages, 3 figures (eps), Definition of spin pilarization
changed to standard definition in GMR, some straight forward algebra removed.
To appear as PRB Rap. Comm. August 15t
Co-ordination between Rashba spin-orbital interaction and space charge effect and enhanced spin injection into semiconductors
We consider the effect of the Rashba spin-orbital interaction and space
charge in a ferromagnet-insulator/semiconductor/insulator-ferromagnet junction
where the spin current is severely affected by the doping, band structure and
charge screening in the semiconductor. In diffusion region, if the the
resistance of the tunneling barriers is comparable to the semiconductor
resistance, the magnetoresistance of this junction can be greatly enhanced
under appropriate doping by the co-ordination between the Rashba effect and
screened Coulomb interaction in the nonequilibrium transport processes within
Hartree approximation.Comment: 4 pages, 3 figure
Agricultural intensification can help protect the Amazon Forest and reduce global warming / Protecting the Amazon forest and reducing global warming via agricultural intensification
The Amazon basin includes 550 M ha covered with rainforests, with 60% of this area being in Brazil. Conversion of rainforest for soybean production raises concerns about the degree to which Brazil can reconcile production and environmental goals. Here we investigated the degree to which intensification could help Brazil produce more soybean without further encroachment of the Amazon Forest. Our analysis shows that continuation of current trends in soybean yield and area would lead to conversion of additional 5.7 M ha of forests and savannas during the next 15 years, with an associated 2550 Mt of CO2eq released into the atmosphere. In contrast, acceleration of yield improvement, coupled with expansion of soybean area only in areas currently used for livestock production, would allow Brazil to achieve similar economic benefits without deforestation and with substantially lower global climate warming
Spin injection and spin accumulation in all-metal mesoscopic spin valves
We study the electrical injection and detection of spin accumulation in
lateral ferromagnetic metal-nonmagnetic metal-ferromagnetic metal (F/N/F) spin
valve devices with transparent interfaces. Different ferromagnetic metals,
permalloy (Py), cobalt (Co) and nickel (Ni), are used as electrical spin
injectors and detectors. For the nonmagnetic metal both aluminium (Al) and
copper (Cu) are used. Our multi-terminal geometry allows us to experimentally
separate the spin valve effect from other magneto resistance signals such as
the anomalous magneto resistance (AMR) and Hall effects. We find that the AMR
contribution of the ferromagnetic contacts can dominate the amplitude of the
spin valve effect, making it impossible to observe the spin valve effect in a
'conventional' measurement geometry. In a 'non local' spin valve measurement we
are able to completely isolate the spin valve signal and observe clear spin
accumulation signals at T=4.2 K as well as at room temperature (RT). For
aluminum we obtain spin relaxation lengths (lambda_{sf}) of 1.2 mu m and 600 nm
at T=4.2 K and RT respectively, whereas for copper we obtain 1.0 mu m and 350
nm. The spin relaxation times tau_{sf} in Al and Cu are compared with theory
and results obtained from giant magneto resistance (GMR), conduction electron
spin resonance (CESR), anti-weak localization and superconducting tunneling
experiments. The spin valve signals generated by the Py electrodes (alpha_F
lambda_F=0.5 [1.2] nm at RT [T=4.2 K]) are larger than the Co electrodes
(alpha_F lambda_F=0.3 [0.7] nm at RT [T=4.2 K]), whereas for Ni (alpha_F
lambda_F<0.3 nm at RT and T=4.2 K) no spin signal is observed. These values are
compared to the results obtained from GMR experiments.Comment: 16 pages, 12 figures, submitted to PR
Molecular Biomarkers for the Evaluation of Colorectal Cancer
Objectives: To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens
Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline From the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology
OBJECTIVES: - To develop evidence-based guideline recommendations through a systematic review of the literature to establish standard molecular biomarker testing of colorectal cancer (CRC) tissues to guide epidermal growth factor receptor (EGFR) therapies and conventional chemotherapy regimens.
METHODS: - The American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology convened an expert panel to develop an evidence-based guideline to establish standard molecular biomarker testing and guide therapies for patients with CRC. A comprehensive literature search that included more than 4,000 articles was conducted.
RESULTS: - Twenty-one guideline statements were established.
CONCLUSIONS: - Evidence supports mutational testing for EGFR signaling pathway genes, since they provide clinically actionable information as negative predictors of benefit to anti-EGFR monoclonal antibody therapies for targeted therapy of CRC. Mutations in several of the biomarkers have clear prognostic value. Laboratory approaches to operationalize CRC molecular testing are presented
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
Attenuation of lung inflammation and fibrosis in CD69-deficient mice after intratracheal bleomycin
<p>Abstract</p> <p>Background</p> <p>Cluster of differentiation 69 (CD69), an early activation marker antigen on T and B cells, is also expressed on activated macrophages and neutrophils, suggesting that CD69 may play a role in inflammatory diseases. To determine the effect of CD69 deficiency on bleomycin(BLM)-induced lung injury, we evaluated the inflammatory response following intratracheal BLM administration and the subsequent fibrotic changes in wild type (WT) and CD69-deficient (CD69<sup>-/-</sup>) mice.</p> <p>Methods</p> <p>The mice received a single dose of 3 mg/kg body weight of BLM and were sacrificed at 7 or 14 days post-instillation (dpi). Lung inflammation in the acute phase (7 dpi) was investigated by differential cell counts and cytokine array analyses of bronchoalveolar lavage fluid. In addition, lung fibrotic changes were evaluated at 14 dpi by histopathology and collagen assays. We also used reverse transcription polymerase chain reaction to measure the mRNA expression level of transforming growth factor β1 (TGF-β1) in the lungs of BLM-treated mice.</p> <p>Results</p> <p>CD69<sup>-/- </sup>mice exhibited less lung damage than WT mice, as shown by reductions in the following indices: (1) loss of body weight, (2) wet/dry ratio of lung, (3) cytokine levels in BALF, (4) histological evidence of lung injury, (5) lung collagen deposition, and (6) TGF-β1 mRNA expression in the lung.</p> <p>Conclusion</p> <p>The present study clearly demonstrates that CD69 plays an important role in the progression of lung injury induced by BLM.</p
Effective Rheology of Bubbles Moving in a Capillary Tube
We calculate the average volumetric flux versus pressure drop of bubbles
moving in a single capillary tube with varying diameter, finding a square-root
relation from mapping the flow equations onto that of a driven overdamped
pendulum. The calculation is based on a derivation of the equation of motion of
a bubble train from considering the capillary forces and the entropy production
associated with the viscous flow. We also calculate the configurational
probability of the positions of the bubbles.Comment: 4 pages, 1 figur
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