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- Nguyen, Quang Ngoc, 1976-
(författare)
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Understanding and managing cardiovascular disease risk factors in Vietnam : integrating clinical and public health perspectives
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Vietnam, like other low-income countries, is facing an epidemic burden of cardiovascular disease risk factors (CVDRFs). The magnitude and directions of CVDRF progression are matters of uncertainty. Objectives: To describe the epidemiological progression of CVDRFs and the preventive effects of community lifestyle interventions, with reference to the differences in progression of CVDRF patterns between men and women. Methods: The study was conducted during 2001-2009 in nationally representative samples and in a local setting of rural areas of Ba-Vi district, Ha-Tay province. Both epidemiological and interventional approaches were applied: (i) a population-based cross-sectional survey of 2,130 people aged ≥25 years in Thai-Binh and Hanoi; (ii) an individual participant-level meta analysis of 23,563 people aged 24-74 years from multiple similar surveys in 9 provinces around Vietnam; (iii) a 17-month cohort study of 497 patients in a hypertension management programme; (iv) a quasi-experimental trial on community lifestyle promotion integrated with a hypertension management programme, evaluated by surveys of 4,645 people in both intervention and reference communes before and after a 3-year intervention. Main findings: (i) in the general adult population ≥25 years, CVDRFs were common, often clustered within individuals, and increased with age; (ii) the Vietnamese population is facing a growing epidemic of CVDRFs, which are generally not well managed; (iii) it is possible to launch a community intervention in low-resource settings within the scope of a commune-based patient-targeted programme on hypertension management; (iv) community health intervention with comprehensive healthy lifestyle promotion improves blood pressure and some behavioural CVDRFs. Conclusion: Alarming increases in CVDRFs in the general population need comprehensive multi-level prevention strategies, which combine both individual high-risk and population health approaches. The commune-based hypertension-centred management programmes integrated with community health promotion are the initial but essential steps towards comprehensive and effective management of CVDRFs and should be part of an integrated and co-ordinated national program on the prevention and control of chronic diseases in low-resource settings like Vietnam.
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| 2. |
- Chung, Sunjae, et al.
(författare)
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Magnetic droplet solitons in all-perpendicular nano-contact spin torque oscillators
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Annan publikation (populärvet., debatt m.m.)abstract
- Spin-torque-generated magnetic droplets are nontopological solitons that have both dynamic and static characteristics. Although theoretical studies of these droplets originally dealt with an all-perpendicular magnetic system, all experimental demonstrations have so far relied on orthogonal spin valve structures that require a rather strong magnetic field to nucleate the droplet. Here, for the first time, we show the nucleation and sustained operation of magnetic droplets under a low magnetic field using nanocontact spin-torque oscillators (NC-STO), both the free Co/Ni and fixed Co/Pd multilayers of which have strong perpendicular magnetic anisotropy. Droplet nucleation is observed as a change in the NC-STO resistance and the appearance of significant broadband microwave signal generation below 1 GHz. We also observe another important phenomenon in which the nucleated magnetic droplet can transform into a skyrmionic nanobubble in the low-field regime. Both magnetic droplet solitons and skyrmionic nanobubbles have been studied in detail using micromagnetic simulation.
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| 3. |
- Le, Quang Tuan, 1976-, et al.
(författare)
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Bias dependence of parallel spin torque in all-perpendicular magnetic tunnel junction nanodevices
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Annan publikation (populärvet., debatt m.m.)abstract
- We performed spin-torque ferromagnetic resonance measurements on spin-torque oscillators based on CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs), with both free and fixed layers having perpendicular magnetic anisotropy, under the application of an in-plane field. A dc current between near-zero and -250 $\mu{A}$ was introduced to investigate the influence of spin-transfer torque effects on the asymmetric and symmetric components of the output voltage. Both components showed a minimum at a misalignment of about 30$^\circ$ between the magnetization of the two CoFeB layers, indicating a strong electric-field effect. We also found that the bias dependence of the spin-torque terms is in contrast to that of in-plane anisotropy CoFeB MTJs.
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| 4. |
- Le, Quang Tuan, 1976-, et al.
(författare)
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Ultra-high frequency tunability in low-current and low-field spin-torque oscillators based on perpendicular magnetic tunnel junctions
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Annan publikation (populärvet., debatt m.m.)abstract
- We demonstrate ultra-high frequency tunability of up to 4.4 GHz/mA, and low threshold currents of about -21 $\mu$A, in spin-torque oscillators based on CoFeB/MgO/CoFeB magnetic tunnel junctions, in which both free and fixed layers have perpendicular magnetic anisotropy (PMA). By using different thicknesses of the two CoFeB layers, their individual PMA strengths can be tailored to achieve significant relative misalignment of their respective magnetizations in moderate in-plane fields. We observe a broad maximum in both the device resistance and the generated microwave power around maximum misalignment. Maximum frequency tunability is observed at low-to-moderate fields and decrease rapidly after maximum misalignment.
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