38 research outputs found
Spin interactions and switching in vertically tunnel-coupled quantum dots
We determine the spin exchange coupling J between two electrons located in
two vertically tunnel-coupled quantum dots, and its variation when magnetic (B)
and electric (E) fields (both in-plane and perpendicular) are applied. We
predict a strong decrease of J as the in-plane B field is increased, mainly due
to orbital compression. Combined with the Zeeman splitting, this leads to a
singlet-triplet crossing, which can be observed as a pronounced jump in the
magnetization at in-plane fields of a few Tesla, and perpendicular fields of
the order of 10 Tesla for typical self-assembled dots. We use harmonic
potentials to model the confining of electrons, and calculate the exchange J
using the Heitler-London and Hund-Mulliken technique, including the long-range
Coulomb interaction. With our results we provide experimental criteria for the
distinction of singlet and triplet states and therefore for microscopic spin
measurements. In the case where dots of different sizes are coupled, we present
a simple method to switch on and off the spin coupling with exponential
sensitivity using an in-plane electric field. Switching the spin coupling is
essential for quantum computation using electronic spins as qubits.Comment: 13 pages, 9 figure
Increased circulating ANG II and TNF-α represents important risk factors in obese Saudi adults with hypertension irrespective of diabetic status and BMI
Central adiposity is a significant determinant of obesity-related hypertension risk, which may arise due to the pathogenic inflammatory nature of the abdominal fat depot. However, the influence of pro-inflammatory adipokines on blood pressure in the obese hypertensive phenotype has not been well established in Saudi subjects. As such, our study investigated whether inflammatory factors may represent useful biomarkers to delineate hypertension risk in a Saudi cohort with and without hypertension and/or diabetes mellitus type 2 (DMT2). Subjects were subdivided into four groups: healthy lean controls (age: 47.9±5.1 yr; BMI: 22.9±2.1 Kg/m2), non-hypertensive obese (age: 46.1±5.0 yr; BMI: 33.7±4.2 Kg/m2), hypertensive obese (age: 48.6±6.1 yr; BMI: 36.5±7.7 Kg/m2) and hypertensive obese with DMT2 (age: 50.8±6.0 yr; BMI: 35.3±6.7 Kg/m2). Anthropometric data were collected from all subjects and fasting blood samples were utilized for biochemical analysis. Serum angiotensin II (ANG II) levels were elevated in hypertensive obese (p<0.05) and hypertensive obese with DMT2 (p<0.001) compared with normotensive controls. Systolic blood pressure was positively associated with BMI (p<0.001), glucose (p<0.001), insulin (p<0.05), HOMA-IR (p<0.001), leptin (p<0.01), TNF-α (p<0.001) and ANG II (p<0.05). Associations between ANG II and TNF-α with systolic blood pressure remained significant after controlling for BMI. Additionally CRP (p<0.05), leptin (p<0.001) and leptin/adiponectin ratio (p<0.001) were also significantly associated with the hypertension phenotype. In conclusion our data suggests that circulating pro-inflammatory adipokines, particularly ANG II and, TNF-α, represent important factors associated with a hypertension phenotype and may directly contribute to predicting and exacerbating hypertension risk