| 1. |
- Da, Silva A.F., et al.
(författare)
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Asymmetric nonlinear amplitude in patterns of porous silicon
- 2000
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Ingår i: Physica A. - 0378-4371 .- 1873-2119. ; 283:1, s. 223-227
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Tidskriftsartikel (refereegranskat)abstract
- A gradient pattern analysis is used to report a phenomenogical evidence of asymmetric nonlinear spatial distribution of porous silicon structures. We used a canonical sample set obtained from scanning force microscopy. Due to the high sensitivity of the gradient field operator, it is possible to correlate the photoluminescence performance of porous silicon with different degree of asymmetries and spatial nonlinearity. A generalization of this new approach to quantify nonlinear amplitude fragmentation in complex lattices is proposed.
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| 2. |
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| 3. |
- Ferreira, Da Silva A., et al.
(författare)
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Characterization of asymmetric fragmentation patterns in SFM images of porous silicon
- 2000
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Ingår i: Solid State Communications. - 0038-1098 .- 1879-2766. ; 113:12, s. 703-708
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Tidskriftsartikel (refereegranskat)abstract
- Due to possible technological applications in opto-electronic devices, the interest in characterizing porous silicon structure patterns has recently increased. From scanning force microscopy (SFM) we have obtained images of different samples of porous silicon and applied pattern characterization operators on these matrices. In this paper, asymmetric spatial fragmentation in amplitude envelopes of porous silicon samples are characterized by means of a parameter that quantifies the amount of spatial asymmetry in the gradient field. The results show that this method is well suited to characterize silicon porosity quantitatively.
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| 4. |
- Gerdts, E., et al.
(författare)
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Impact of age on left ventricular hypertrophy regression during antihypertensive treatment with losartan or atenolol (the LIFE study)
- 2004
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Ingår i: J Hum Hypertens. - 0950-9240. ; 18:6, s. 417-22
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Tidskriftsartikel (refereegranskat)abstract
- To assess the influence of age on changes in left ventricular (LV) mass and geometry during antihypertensive treatment, we related age to clinical and echocardiographic findings before and after 4 years of antihypertensive treatment in a subset of 560 hypertensive patients without known concurrent disease in the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study, which randomized patients to blinded losartan- or atenolol-based treatment. Patients >/=65 years (older group) included more women and patients with isolated systolic hypertension or albuminuria (all P<0.05). Compared to patients <65 years, older patients had higher pulse pressure, LV mass, and prevalence of concentric hypertrophy at baseline (78 vs 69 mmHg, 234 vs 224 g, and 28 vs 16%, respectively, all P<0.01), while the mean blood pressure did not differ. Over 4 years, reductions in LV mass and the mean blood pressure were similar in both groups, but older patients more often had residual hypertrophy (31 vs 15%, P<0.001) with a preponderance of eccentric geometry. In multivariate analysis of 4-year change in LV mass controlling for baseline mass, larger hypertrophy reduction was associated with losartan treatment, while age, gender, body mass index, and 4-year change in pulse pressure and albuminuria did not enter (Multiple R (2)=0.40, P<0.001). Thus, in up-to-80-year-old hypertensive patients with left ventricular hypertrophy, age did not significantly attenuate hypertrophy reduction during antihypertensive treatment, although residual hypertrophy was more prevalent in older patients as a consequence of higher initial LV mass.
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| 5. |
- Il'in, K.S., et al.
(författare)
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Picosecond hot-electron energy relaxation in NbN superconducting photodetectors
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:19, s. 2752-2754
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved characterization of superconducting NbN hot-electron photodetectors using an electro-optic sampling method. Our samples were patterned into micron-size microbridges from 3.5-nm-thick NbN films deposited on sapphire substrates. The devices were illuminated with 100 fs optical pulses, and the photoresponse was measured in the ambient temperature range between 2.15 and 10.6 K (superconducting temperature transition TC). The experimental data agreed very well with the nonequilibrium hot-electron, two-temperature model. The quasiparticle thermalization time was ambient temperature independent and was measured to be 6.5 ps. The inelastic electron–phonon scattering time τe–ph tended to decrease with the temperature increase, although its change remained within the experimental error, while the phonon escape time τes decreased almost by a factor of two when the sample was put in direct contact with superfluid helium. Specifically, τe–ph and τes, fitted by the two-temperature model, were equal to 11.6 and 21 ps at 2.15 K, and 10(±2) and 38 ps at 10.5 K, respectively. The obtained value of τe–ph shows that the maximum intermediate frequency bandwidth of NbN hot-electron phonon-cooled mixers operating at TC can reach 16(+4/−3) GHz if one eliminates the bolometric phonon-heating effect.
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| 6. |
- Koehler, M., et al.
(författare)
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Modeling bilayer polymer/fullerene photovoltaic devices
- 2004
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 96:1, s. 40-43
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Tidskriftsartikel (refereegranskat)abstract
- The electrical transport and charge generation of polymer/fullerene photovoltaic devices were investigated. The polymer/fullerene photodiodes were formed by a heterojunction of fullerene and a semiconducting polymer poly (3,4-ethylenedioxythiophene). The current-voltage characteristic of the devices were measured with variable thickness of the C60 layer, under monochromatic light of different wavelengths. The results show that the values of the electrical photoconductivity are related to the optical absorption coefficient of the fullerene, and thus implying a large contribution of the C60 films to the diode photocurrent.
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| 7. |
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| 8. |
- Palmieri, V., et al.
(författare)
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Usefulness of the assessment of the appropriateness of left ventricular mass to detect left ventricular systolic and diastolic abnormalities in absence of echocardiographic left ventricular hypertrophy: the LIFE study
- 2004
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Ingår i: J Hum Hypertens. - 0950-9240. ; 18:6, s. 423-30
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Tidskriftsartikel (refereegranskat)abstract
- Conventional definitions of left ventricular (LV) hypertrophy do not account for interindividual differences in loading conditions. We may define LV mass as inappropriately high when exceeding 128% of theoretical values predicted by gender, height(2.7), and stroke work, which explain up to 82% of the variability of LV mass in normal reference subjects. In 652 participants in the Losartan Intervention For Endpoint reduction in hypertension study without clinically overt cardiovascular disease or diabetes, we investigated whether inappropriately high LV mass is associated with relevant LV abnormalities independent of traditional definition of LV hypertrophy (ie, LV mass index >116 g/m(2) in men and >104 g/m(2) in women). The study sample was divided into three groups: patients with inappropriately high LV mass but without LV hypertrophy were compared to patients with LV hypertrophy and to patients with appropriate LV mass and without LV hypertrophy. Patients with inappropriately high but nonhypertrophic LV mass had higher body mass index and relative wall thickness, and lower LV myocardial systolic function, than patients with appropriate LV mass or patients with LV hypertrophy. In multivariate analyses, inappropriately high LV mass was independently associated with lower myocardial systolic function independent of LV hypertrophy and other covariates. Inappropriately high LV mass was also associated with prolonged isovolumic relaxation time and lower mitral E/A ratio independent of covariates. In conclusion, inappropriately high LV mass was associated with relevant, often preclinical, manifestations of cardiac disease in the absence of traditionally defined echocardiographic LV hypertrophy and concentric geometry.
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| 9. |
- Ploj, Karolina, et al.
(författare)
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Effects of melanocortin receptor ligands on ethanol intake and opioid peptide levels in alcohol-preferring AA rats
- 2002
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Ingår i: Brain Research Bulletin. - 0361-9230 .- 1873-2747. ; 59:2, s. 97-104
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Tidskriftsartikel (refereegranskat)abstract
- Melanocortin (MC) peptides are suggested to play a role in opiate dependence, where they antagonise the addictive properties of opiates. To further study the involvement of the MCs in drug dependence, we analysed the effects of the MC(4)-receptor antagonist HS014 (1 nmol/rat), and the non-selective MC-receptor agonist MTII (1 nmol/rat), using i.c.v. administration, on ethanol intake in alcohol-preferring AA rats. The rats had access to ethanol during 40 days, resulting in a mean ethanol intake of 6.6 g/kg/day, before treatment. One group received only artificial cerebrospinal fluid solution. MTII caused a reduction in ethanol intake and ethanol preference, whereas HS014 was without effect. No effect on water intake was observed. A decrease in food intake was detected after MTII, whereas HS014 induced an increase in food intake. Analysis of dynorphin B and Met-enkephalin-Arg(6)Phe(7) immunoreactive levels revealed that MTII and HS014 altered opioid peptide levels in several brain areas and the pituitary gland of the rats with an established ethanol intake. This is the first report showing that manipulation of the MC-receptor system changes ethanol intake in chronically ethanol-drinking AA rats. In addition, manipulation of the MC system modulates ethanol-induced changes in opioid peptide levels.
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| 10. |
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