4,782 research outputs found
Sampling and handling of desert soils
Sampling and handling of desert soils - area site, transportation, processing, and storag
Hysteresis phenomenon in deterministic traffic flows
We study phase transitions of a system of particles on the one-dimensional
integer lattice moving with constant acceleration, with a collision law
respecting slower particles. This simple deterministic ``particle-hopping''
traffic flow model being a straightforward generalization to the well known
Nagel-Schreckenberg model covers also a more recent slow-to-start model as a
special case. The model has two distinct ergodic (unmixed) phases with two
critical values. When traffic density is below the lowest critical value, the
steady state of the model corresponds to the ``free-flowing'' (or ``gaseous'')
phase. When the density exceeds the second critical value the model produces
large, persistent, well-defined traffic jams, which correspond to the
``jammed'' (or ``liquid'') phase. Between the two critical values each of these
phases may take place, which can be interpreted as an ``overcooled gas'' phase
when a small perturbation can change drastically gas into liquid. Mathematical
analysis is accomplished in part by the exact derivation of the life-time of
individual traffic jams for a given configuration of particles.Comment: 22 pages, 6 figures, corrected and improved version, to appear in the
Journal of Statistical Physic
A hydrogen energy carrier. Volume 1: Summary
The production, technology, transportation, and implementation of hydrogen into the energy system are discussed along with the fossil fuel cycle, hydrogen fuel cycle, and the demands for energy. The cost of hydrogen production by coal gasification; electrolysis by nuclear energy, and solar energy are presented. The legal aspects of a hydrogen economy are also discussed
Primary radiotherapy in progressive optic nerve sheath meningiomas: a long-term follow-up study
Background/aims: To report the outcome of primary radiotherapy in patients with progressive optic nerve sheath meningioma (ONSM). Methods: The clinical records of all patients were reviewed in a retrospective, observational, multicentre study. Results: Thirty-four consecutive patients were included. Twenty-six women and eight men received conventional or stereotactic fractionated radiotherapy, and were followed for a median 58 (range 51–156) months. Fourteen eyes (41%) showed improved visual acuity of at least two lines on the Snellen chart. In 17 (50%) eyes, the vision stabilised, while deterioration was noted in three eyes (9%). The visual outcome was not associated with age at the time of radiotherapy (p=0.83), sex (p=0.43), visual acuity at the time of presentation (p=0.22) or type of radiotherapy (p=0.35). Optic disc swelling was associated with improved visual acuity (p<0.01) and 4/11 patients with optic atrophy also showed improvement. Long-term complications were dry eyes in five patients, cataracts in three, and mild radiation retinopathy in four. Conclusion: Primary radiotherapy for patients with ONSM is associated with long-term improvement of visual acuity and few adverse effects.Peerooz Saeed, Leo Blank, Dinesh Selva, John G. Wolbers, Peter J.C.M. Nowak, Ronald B. Geskus, Ezekiel Weis, Maarten P. Mourits, Jack Rootma
Rare events, escape rates and quasistationarity: some exact formulae
We present a common framework to study decay and exchanges rates in a wide
class of dynamical systems. Several applications, ranging form the metric
theory of continuons fractions and the Shannon capacity of contrained systems
to the decay rate of metastable states, are given
Chaotic Cascades with Kolmogorov 1941 Scaling
We define a (chaotic) deterministic variant of random multiplicative cascade
models of turbulence. It preserves the hierarchical tree structure, thanks to
the addition of infinitesimal noise. The zero-noise limit can be handled by
Perron-Frobenius theory, just as the zero-diffusivity limit for the fast dynamo
problem. Random multiplicative models do not possess Kolmogorov 1941 (K41)
scaling because of a large-deviations effect. Our numerical studies indicate
that deterministic multiplicative models can be chaotic and still have exact
K41 scaling. A mechanism is suggested for avoiding large deviations, which is
present in maps with a neutrally unstable fixed point.Comment: 14 pages, plain LaTex, 6 figures available upon request as hard copy
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Three ways to decouple electric-utility revenues from sales
Utility energy efficiency programs hurt shareholders because these programs reduce electricity use, and this reduction lowers revenues by more than costs are cut. Utilities and their regulators have adopted various methods to deal with these net lost revenues. The two most widely used methods include explicit calculations of the revenues lost because of the energy and demand reductions caused by the utility`s programs, and decoupling of electric revenues from sales. Decoupling first breaks the link between utility revenues and kWh sales. It then recouples revenues to something else, such as growth in the number of customers, the determinants of changes in fixed costs, or the determinants of changes in electricity use. This paper explains and compares three forms of decoupling:revenue-per- customer (RPC) decoupling, RPC decoupling with a factor that allows for changes in electricity use per customer, and statistical recoupling. We used data from five utilities to see how the three methods perform in terms of electicity-price volatility and ease of implementation. We discuss the strengths and limitations of each approach, emphasizing the tradeoff between simplicity and price stability
Asymmetry and rotation of the in-plane magnetic easy axis in La0.67Sr0.33MnO3 thin films grown on NdGaO3 (112)
High-precision measurement of the half-life of Ga
The beta-decay half-life of 62Ga has been studied with high precision using
on-line mass separated samples. The decay of 62Ga which is dominated by a 0+ to
0+ transition to the ground state of 62Zn yields a half-life of T_{1/2} =
116.19(4) ms. This result is more precise than any previous measurement by
about a factor of four or more. The present value is in agreement with older
literature values, but slightly disagrees with a recent measurement. We
determine an error weighted average value of all experimental half-lives of
116.18(4) ms.Comment: 9 pages, 5 figures, accepted for publication in PR
Impact of frequent apheresis blood donation on bone density: A prospective,longitudinal, randomized, controlled trial
Background
Blood for transfusion is lifesaving and essential to many elements of modern medical practice. The global blood supply relies on volunteer blood donors. Apheresis is increasingly used to collect blood and requires anticoagulant to prevent extracorporeal coagulation. Citrate, the standard apheresis anticoagulant, chelates ionized calcium with consequent perturbations of serum calcium, parathyroid hormone, vitamin D, and markers of bone remodeling in donors. Cross-sectional studies of bone mineral density (BMD) among apheresis donors exhibit conflicting results. Methods
The longitudinal, randomized, controlled ALTRUYST trial (NCT02655055) was undertaken to determine whether BMD declined following high frequency apheresis blood donation over 1 year. The study was powered at 80% to detect the primary outcome of a 3% decline in BMD. Subjects new to apheresis agreed to make ≥20 apheresis donations in a one-year period and were randomized to treatment (high frequency apheresis) or control (no apheresis). Dual-energy x-ray absorptiometry was performed before and after participation. Two-sided t-test and multivariable logistic regression were used to assess outcomes. Findings
Mean lumbar spine BMD did not change during the study among control donors (−0.002 g/cm2, 95%CI [−0.020, 0.016], p = 0.78), or among donors in the apheresis arm (mean change = 0.007 g/cm2, 95%CI [−0.005, 0.018], p = 0.24). Mean total hip BMD did not change for control donors (mean change = 0.002 g/cm2, 95%CI [−0.006, 0.009], p = 0.63) or apheresis donors (−0.004 g/cm2, 95%CI [−0.10, 0.002], p = 0.16). Tests for differences in proportions of donors with change in BMD exceeding the least significant change at the lumbar spine in either a positive [8 apheresis (31%), 4 control (27%), p = 0.78] or negative direction [4 apheresis (15%), 5 control (33%)] were statistically non-significant (p = 0.18). Proportional increases [0 apheresis (0%), 1 control (7%), p = 0.18] and decreases [3 apheresis (12%), 1 control (14%)] were also not significantly different at the total hip (p = 0.61). Interpretation
ALTRUYST is the first longitudinal trial to demonstrate that apheresis blood collection guidelines in the United States adequately protect the skeletal health of male volunteer blood donors
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