Giant current fluctuations in an overheated single electron transistor

Interplay of cotunneling and single-electron tunneling in a thermally isolated single-electron transistor (SET) leads to peculiar overheating effects. In particular, there is an interesting crossover interval where the competition between cotunneling and single-electron tunneling changes to the dominance of the latter. In this interval, the current exhibits anomalous sensitivity to the effective electron temperature of the transistor island and its fluctuations. We present a detailed study of the current and temperature fluctuations at this interesting point. The methods implemented allow for a complete characterization of the distribution of the fluctuating quantities, well beyond the Gaussian approximation. We reveal and explore the parameter range where, for sufficiently small transistor islands, the current fluctuations become gigantic. In this regime, the optimal value of the current, its expectation value, and its standard deviation differ from each other by parametrically large factors. This situation is unique for transport in nanostructures and for electron transport in general. The origin of this spectacular effect is the exponential sensitivity of the current to the fluctuating effective temperature.Comment: 10 pages, 11 figure

Waterfalls as sources of small charged aerosol particles

In this study, we measured the mobility distributions of cluster and intermediate ions with an ion spectrometer near a waterfall. We observed that the concentration of negative 1.5–10 nm ions was one-hundred fold higher than a reference point 100 m away from the waterfall. Also, the concentration of positive intermediate ions was found to be higher than that at the reference point by a factor of ten. This difference was observed only at the smallest sizes; above 10 nm the difference was insignificant

Left ventricular dysfunction with reduced functional cardiac reserve in diabetic and non-diabetic LDL-receptor deficient apolipoprotein B100-only mice

BACKGROUND: Lack of suitable mouse models has hindered the studying of diabetic macrovascular complications. We examined the effects of type 2 diabetes on coronary artery disease and cardiac function in hypercholesterolemic low-density lipoprotein receptor-deficient apolipoprotein B100-only mice (LDLR(-/-)ApoB(100/100)). METHODS AND RESULTS: 18-month-old LDLR(-/-)ApoB(100/100 )(n = 12), diabetic LDLR(-/-)ApoB(100/100 )mice overexpressing insulin-like growth factor-II (IGF-II) in pancreatic beta cells (IGF-II/LDLR(-/-)ApoB(100/100), n = 14) and age-matched C57Bl/6 mice (n = 15) were studied after three months of high-fat Western diet. Compared to LDLR(-/-)ApoB(100/100 )mice, diabetic IGF-II/LDLR(-/-)ApoB(100/100 )mice demonstrated more calcified atherosclerotic lesions in aorta. However, compensatory vascular enlargement was similar in both diabetic and non-diabetic mice with equal atherosclerosis (cross-sectional lesion area ~60%) and consequently the lumen area was preserved. In coronary arteries, both hypercholesterolemic models showed significant stenosis (~80%) despite positive remodeling. Echocardiography revealed severe left ventricular systolic dysfunction and anteroapical akinesia in both LDLR(-/-)ApoB(100/100 )and IGF-II/LDLR(-/-)ApoB(100/100 )mice. Myocardial scarring was not detected, cardiac reserve after dobutamine challenge was preserved and ultrasructural changes revealed ischemic yet viable myocardium, which together with coronary artery stenosis and slightly impaired myocardial perfusion suggest myocardial hibernation resulting from chronic hypoperfusion. CONCLUSIONS: LDLR(-/-)ApoB(100/100 )mice develop significant coronary atherosclerosis, severe left ventricular dysfunction with preserved but diminished cardiac reserve and signs of chronic myocardial hibernation. However, the cardiac outcome is not worsened by type 2 diabetes, despite more advanced aortic atherosclerosis in diabetic animals

Initial steps of aerosol growth

International audienceThe formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent ? mainly condensational ? growth. This work focuses on the initial steps of growth, meaning the growth right after nucleation, where the interplay of curvature effects and thermodynamics has a significant role on the growth kinetics. More specifically, we investigate how ion clusters and aerosol particles grow from 1.5 nm to 20 nm (diameter) in atmospheric conditions using experimental data obtained by air ion and aerosol spectrometers. The measurements have been performed at a boreal forest site in Finland. The observed trend that the growth rate seems to increase as a function of size can be used to investigate possible growth mechanisms. Such a growth rate is consistent with a recently suggested nano-Köhler mechanism, in which growth is activated at a certain size with respect to condensation of organic vapors. The results also imply that charge-enhanced growth associated with ion-mediated nucleation plays only a minor role in the initial steps of growth, since it would imply a clear decrease of the growth rate with size. Finally, further evidence was obtained on the earlier suggestion that atmospheric nucleation and the subsequent growth of fresh nuclei are likely to be uncoupled phenomena via different participating vapors

Ion production rate in a boreal forest based on ion, particle and radiation measurements

International audienceIn this study the ion production rates in a boreal forest were studied based on two different methods: 1) cluster ion and particle concentration measurements, 2) external radiation and radon concentration measurements. Both methods produced reasonable estimates for ion production rates. The average ion production rate calculated from aerosol particle size distribution and air ion mobility distribution measurements was 2.6 ion pairs cm-3s-1, and based on external radiation and radon measurements, 4.5 ion pairs cm-3s-1. The first method based on ion and particle measurements gave lower values for the ion production rates especially during the day. A possible reason for this is that particle measurements started only from 3nm, so the sink of small ions during the nucleation events was underestimated. It may also be possible that the hygroscopic growth factors of aerosol particles were underestimated. Another reason for the discrepancy is the nucleation mechanism itself. If the ions are somehow present in the nucleation process, there could have been an additional ion sink during the nucleation days

Basic characteristics of atmospheric particles, trace gases and meteorology in a relatively clean Southern African Savannah environment

We have analyzed one year (July 2006–July 2007) of measurement data from a relatively clean background site located in dry savannah in South Africa. The annual-median trace gas concentrations were equal to 0.7 ppb for SO<sub>2</sub>, 1.4 ppb for NO<sub>x</sub>, 36 ppb for O<sub>3</sub> and 105 ppb for CO. The corresponding PM<sub>1</sub>, PM<sub>2.5</sub> and PM<sub>10</sub> concentrations were 9.0, 10.5 and 18.8 μg m<sup>−3</sup>, and the annual median total particle number concentration in the size range 10–840 nm was 2340 cm<sup>−3</sup>. During Easterly winds, influence of industrial sources approximately 150 km away from the measurement site was clearly visible, especially in SO<sub>2</sub> and NO<sub>x</sub> concentrations. Of gases, NO<sub>x</sub> and CO had a clear annual, and SO<sub>2</sub>, NO<sub>x</sub> and O<sub>3</sub> clear diurnal cycle. Atmospheric new-particle formation was observed to take place in more than 90% of the analyzed days. The days with no new particle formation were cloudy or rainy days. The formation rate of 10 nm particles varied in the range of 0.1–28 cm<sup>−3</sup> s<sup>−1</sup> (median 1.9 cm<sup>−3</sup> s<sup>−1</sup>) and nucleation mode particle growth rates were in the range 3–21 nm h<sup>−1</sup> (median 8.5 nm h<sup>−1</sup>). Due to high formation and growth rates, observed new particle formation gives a significant contribute to the number of cloud condensation nuclei budget, having a potential to affect the regional climate forcing patterns

Alien Registration- Laakso, Isak E. (Livermore, Androscoggin County)

https://digitalmaine.com/alien_docs/26901/thumbnail.jp

Stability of Terrestrial Planets in the Habitable Zone of Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208

We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.Comment: 14 pages, 18 figures submitted to A&