1,136 research outputs found
The impacts of surface conditions on the vapor-liquid-solid growth of germanium nanowires on Si (100) substrate
The impacts of surface conditions on the growth of Ge nanowires on a Si (100) substrate are discussed in detail. On SiO2-terminated Si substrates, high-density Ge nanowires can be easily grown. However, on H-terminated Si substrates, growing Ge nanowires is more complex. The silicon migration and the formation of a native SiO2 overlayer on a catalyst surface retard the growth of Ge nanowires. After removing this overlayer in the HF solution, high-density and well-ordered Ge nanowires are grown. Ge nanowires cross vertically and form two sets of parallel nanowires. It is found that nanowires grew along ?110? direction
Nanometre-scale nuclear-spin device for quantum information processing
We have developed semiconductor point contact devices in which nuclear spins
in a nanoscale region are coherently controlled by all-electrical methods.
Different from the standard nuclear-magnetic resonance technique, the
longitudinal magnetization of nuclear spins is directly detected by measuring
resistance, resulting in ultra-sensitive detection of the microscopic quantity
of nuclear spins. All possible coherent oscillations have been successfully
demonstrated between two levels from four nuclear spin states of I = 3/2
nuclei. Quantum information processing is discussed based on two fictitious
qubits of an I = 3/2 system and methods are described for performing arbitrary
logical gates both on one and two qubits. A scheme for quantum state tomography
based on Mz-detection is also proposed. As the starting point of quantum
manipulations, we have experimentally prepared the effective pure states for
the I = 3/2 nuclear spin system.Comment: 16 pages, 5 figure
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Rice consumption and risk of cardiovascular disease: results from a pooled analysis of 3 U.S. cohorts1234
Background: Health concerns have been raised about rice consumption, which may significantly contribute to arsenic exposure. However, little is known regarding whether habitual rice consumption is associated with cardiovascular disease (CVD) risk. Objective: We examined prospectively the association of white rice and brown rice consumption with CVD risk. Design: We followed a total of 207,556 women and men [73,228 women from the Nurses’ Health Study (1984–2010), 92,158 women from the Nurses’ Health Study II (1991–2011), and 42,170 men from the Health Professionals Follow-Up Study (1986–2010)] who were free of CVD and cancer at baseline. Validated semiquantitative food-frequency questionnaires were used to assess consumption of white rice, brown rice, and other food items. Fatal and nonfatal CVD (coronary artery disease and stroke) was confirmed by medical records or self-reports. Results: During 4,393,130 person-years of follow-up, 12,391 cases of CVD were identified. After adjustment for major CVD risk factors, including demographics, lifestyle, and other dietary intakes, rice consumption was not associated with CVD risk. The multivariable-adjuted HR of developing CVD comparing ≥5 servings/wk with <1 serving/wk was 0.98 (95% CI: 0.84, 1.14) for white rice, 1.01 (0.79, 1.28) for brown rice, and 0.99 (0.90, 1.08) for total rice. To minimize the potential impact of racial difference in rice consumption, we restricted the analyses to whites only and obtained similar results: the HRs of CVD for ≥5 servings/wk compared with <1 serving/wk were 1.04 (95% CI: 0.88, 1.22) for white rice and 1.01 (0.78, 1.31) for brown rice. Conclusions: Greater habitual consumption of white rice or brown rice is not associated with CVD risk. These findings suggest that rice consumption may not pose a significant CVD risk among the U.S. population when consumed at current amounts. More prospective studies are needed to explore these associations in other populations
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Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies
Objective: To determine whether individual fruits are differentially associated with risk of type 2 diabetes. Design: Prospective longitudinal cohort study. Setting: Health professionals in the United States. Participants: 66 105 women from the Nurses’ Health Study (1984-2008), 85 104 women from the Nurses’ Health Study II (1991-2009), and 36 173 men from the Health Professionals Follow-up Study (1986-2008) who were free of major chronic diseases at baseline in these studies. Main outcome measure Incident cases of type 2 diabetes, identified through self report and confirmed by supplementary questionnaires. Results: During 3 464 641 person years of follow-up, 12 198 participants developed type 2 diabetes. After adjustment for personal, lifestyle, and dietary risk factors of diabetes, the pooled hazard ratio of type 2 diabetes for every three servings/week of total whole fruit consumption was 0.98 (95% confidence interval 0.96 to 0.99). With mutual adjustment of individual fruits, the pooled hazard ratios of type 2 diabetes for every three servings/week were 0.74 (0.66 to 0.83) for blueberries, 0.88 (0.83 to 0.93) for grapes and raisins, 0.89 (0.79 to 1.01) for prunes, 0.93 (0.90 to 0.96) for apples and pears, 0.95 (0.91 to 0.98) for bananas, 0.95 (0.91 to 0.99) for grapefruit, 0.97 (0.92 to 1.02) for peaches, plums, and apricots, 0.99 (0.95 to 1.03) for oranges, 1.03 (0.96 to 1.10) for strawberries, and 1.10 (1.02 to 1.18) for cantaloupe. The pooled hazard ratio for the same increment in fruit juice consumption was 1.08 (1.05 to 1.11). The associations with risk of type 2 diabetes differed significantly among individual fruits (P<0.001 in all cohorts). Conclusion: Our findings suggest the presence of heterogeneity in the associations between individual fruit consumption and risk of type 2 diabetes. Greater consumption of specific whole fruits, particularly blueberries, grapes, and apples, is significantly associated with a lower risk of type 2 diabetes, whereas greater consumption of fruit juice is associated with a higher risk
Local implicit modeling of blood vessels for interactive simulation
International audienceIn the context of computer-based simulation, contact management requires an accurate, smooth, but still efficient surface model for the blood vessels. A new implicit model is proposed, consisting of a tree of local implicit surfaces generated by skeletons ({\em blobby models}). The surface is reconstructed from data points by minimizing an energy, alternating with an original blob selection and subdivision scheme. The reconstructed models are very efficient for simulation and were shown to provide a sub-voxel approximation of the vessel surface on 5 patients
Dissociation of vertical semiconductor diatomic artificial molecules
We investigate the dissociation of few-electron circular vertical
semiconductor double quantum dot artificial molecules at 0 T as a function of
interdot distance. Slight mismatch introduced in the fabrication of the
artificial molecules from nominally identical constituent quantum wells induces
localization by offsetting the energy levels in the quantum dots by up to 2
meV, and this plays a crucial role in the appearance of the addition energy
spectra as a function of coupling strength particularly in the weak coupling
limit.Comment: Accepted for publication in Phys. Rev. Let
Older adults with chronic musculoskeletal pain are at increased risk of recurrent falls and the brief pain inventory could help identify those most at risk
Aim:
Chronic musculoskeletal pain (CMP) and falls are common among community-dwelling older adults. The study aims were: (i) to investigate the relationship between CMP and any falls (≥1), single falls and recurrent falls (≥2) in community-dwelling older adults; and (ii) to determine the discriminative validity of the Brief Pain Inventory (BPI) to differentiate between non-fallers and (a) any and (b) recurrent fallers.
Methods:
A cross-sectional study involving 295 community-dwelling participants (mean age 77.5 ± 8.1 years, 66.4% female) was carried out. CMP was assessed and classified as none (comparison group), single and multisite (≥2). The BPI severity and interference subscales were used, and falls were recorded over 12 months. Data were analyzed with logistic regression and receiver operating characteristic curves (ROC).
Results:
Over half of the participants (154/295, 52.2%) had CMP (41.6% single and 58.4% multisite pain). Participants with CMP were at increased risk of recurrent falls (OR 2.25, 95% CI 1.03–4.88), and this risk was highest in those with multisite CMP (OR 3.43, CI 1.34–8.65). The BPI severity subscale showed good discriminative ability to differentiate between recurrent and non-fallers with an area under the curve (AUC) of 0.731 (95% CI 0.635–0.826); a mean score of 5.1 had a sensitivity of 93.3% and specificity of 56.7%. The AUC for the BPI interference subscale was 0.724 (95% CI 0.630–0.818), and a cut-off score of 4.6 had a sensitivity of 84.4% and specificity of 57.8%
Conclusion:
Older adults with multisite CMP are at greatest risk of recurrent falls. In clinical settings, the BPI could prove useful to discriminate between recurrent and non-fallers
Solar Neutron Events of October-November 2003
During the period when the Sun was intensely active on October-November 2003,
two remarkable solar neutron events were observed by the ground-based neutron
monitors. On October 28, 2003, in association with an X17.2 large flare, solar
neutrons were detected with high statistical significance (6.4 sigma) by the
neutron monitor at Tsumeb, Namibia. On November 4, 2003, in association with an
X28 class flare, relativistic solar neutrons were observed by the neutron
monitors at Haleakala in Hawaii and Mexico City, and by the solar neutron
telescope at Mauna Kea in Hawaii simultaneously. Clear excesses were observed
at the same time by these detectors, with the significance calculated as 7.5
sigma for Haleakala, and 5.2 sigma for Mexico City. The detector onboard the
INTEGRAL satellite observed a high flux of hard X-rays and gamma-rays at the
same time in these events. By using the time profiles of the gamma-ray lines,
we can explain the time profile of the neutron monitor. It appears that
neutrons were produced at the same time as the gamma-ray emission.Comment: 35 pages, 21 figures, accepted for publication in Ap
Collapse of ringlike structures in 2DEGs under tilted magnetic fields
In the quantum Hall regime, the longitudinal resistivity plotted
as a density--magnetic-field () diagram displays ringlike structures
due to the crossings of two sets of spin split Landau levels from different
subbands [e.g., Zhang \textit{et al.}, Phys. Rev. Lett. \textbf{95}, 216801
(2005)]. For tilted magnetic fields, some of these ringlike structures "shrink"
as the tilt angle is increased and fully collapse at . Here we theoretically investigate the topology of these structures
via a non-interacting model for the 2DEG. We account for the inter Landau-level
coupling induced by the tilted magnetic field via perturbation theory. This
coupling results in anti-crossings of Landau levels with parallel spins. With
the new energy spectrum, we calculate the corresponding diagram of
the density of states (DOS) near the Fermi level. We argue that the DOS
displays the same topology as in the diagram. For the
ring with filling factor , we find that the anti-crossings make it
shrink for increasing tilt angles and collapse at a large enough angle. Using
effective parameters to fit the data, we find a collapsing
angle . Despite this factor-of-two discrepancy with
the experimental data, our model captures the essential mechanism underlying
the ring collapse.Comment: 3 pages, 2 figures; Proceedings of the PASPS V Conference Held in
August 2008 in Foz do Igua\c{c}u, Brazi
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