Geosynchronous inclined orbits for high-latitude communications

We present and discuss a solution to the growing demand for satellite telecommunication coverage in the high-latitude geographical regions (beyond 55◦N), where the signal from geostationary satellites is limited or unavailable. We focus on the dynamical issues associated to the design, the coverage, the maintenance and the disposal of a set of orbits selected for the purpose. Specifically, we identify a group of highly inclined, moderately eccentric geosynchronous orbits derived from the Tundra orbit (geosynchronous, eccentric and critically inclined). Continuous coverage can be guaranteed by a constellation of three satellites in equally spaced planes and suitably phased. By means of a highprecision model of the terrestrial gravity field and the relevant environmental perturbations, we study the evolution of these orbits. The effects of the different perturbations on the ground track (which is more important for coverage than the orbital elements themselves) are isolated and analyzed. The physical model and the numerical setup are optimized with respect to computing time and accuracy. We show that, in order to maintain the ground track unchanged, the key parameters are the orbital period and the argument of perigee. Furthermore, corrections to the right ascension of the ascending node are needed in order to preserve the relative orientation of the orbital planes. A station-keeping strategy that minimizes propellant consumption is then devised, and comparisons are made between the cost of a solution based on impulsive maneuvers and one with continuous thrust. Finally, the issue of end-of-life disposal is discussed

Analysis of Cases inWhich a Biopsy Specimen Is Positive and an Excised Lesion Is Negative for Nonmelanoma Skin Cancer

Nonmelanoma skin cancers (NMSCs), including squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), are the most common types of cancer with the fastest-growing treatment costs in the United States.1 Standard treatment requires biopsy for histologic confirmation, followed by excision. Oftentimes, no residual carcinoma is detected, implying spontaneous clearance at rates reported to vary from 24% to 76%.2- 5 These types of lesions have been investigated by others2- 5 and are not fully understood. Our study aims to determine the lesion and patient characteristics that would most strongly predict a histologically negative result for an excised lesion after a biopsy specimen had positive margins

An implicit unsteady hydraulic solver for suspended cuttings transport in managed pressure wells

We present a simulation tool for transient events in complex hydraulic networks. The code includes modelling of the transport of suspended cuttings in near-vertical wells. An unstructured finite volume formulation with implicit time integration has been chosen. The unconditional stability of the integrator makes the method suitable for the simulation of transient events over a wide range of characteristic timescales. It handles both very fast transients (e.g. fluid hammer events) and the long-term evolution of the well (e.g. hole cleaning operations). The software has been developed to address the need of the oil industry for a robust and efficient predictive tool allowing effective well control in managed pressure drilling operations. The physical modelling follows the standard practices accepted by the industry (e.g. mud rheology computations). The mathematical foundation of the algorithm is described followed by validation cases that illustrate its capabilities and accuracy. Finally, a practical industrial application example is provided to demonstrate the real-world performance of the software.Peer ReviewedPostprint (author's final draft

Cyanoflan: A cyanobacterial sulfated carbohydrate polymer with emulsifying properties

Abstract The extracellular polysaccharides produced by cyanobacteria have distinctive characteristics that make them promising for applications ranging from bioremediation to biomedicine. In this study, a sulfated polysaccharide produced by a marine cyanobacterial strain and named cyanoflan was characterized in terms of morphology, chemical composition, and rheological and emulsifying properties. Cyanoflan has a 71% carbohydrate content, with 11% of sulfated residues, while the protein account for 4% of dry weight. The glycosidic-substitution analysis revealed a highly branched complex chemical structure with a large number of sugar residues. The cyanoflan high molecular mass fractions (above 1 MDa) and entangled structure is consistent with its high apparent viscosity in aqueous solutions and high emulsifying activity. It showed to be a typical non-Newtonian fluid with pseudoplastic behavior. Altogether, these results confirm that cyanoflan is a versatile carbohydrate polymer that can be used in different biotechnological applications, such as emulsifying/thickening agent in food or cosmetic industries

Dynamical Casimir-Polder interaction between an atom and surface plasmons

We investigate the time-dependent Casimir-Polder potential of a polarizable two-level atom placed near a surface of arbitrary material, after a sudden change in the parameters of the system. Different initial conditions are taken into account. For an initially bare ground-state atom, the time-dependent Casimir-Polder energy reveals how the atom is "being dressed" by virtual, matter-assisted photons. We also study the transient behavior of the Casimir-Polder interaction between the atom and the surface starting from a partially dressed state, after an externally induced change in the atomic level structure or transition dipoles. The Heisenberg equations are solved through an iterative technique for both atomic and field operators in the medium-assisted electromagnetic field quantization scheme. We analyze in particular how the time evolution of the interaction energy depends on the optical properties of the surface, in particular on the dispersion relationof surface plasmon polaritons. The physical significance and the limits of validity of the obtained results are discussed in detail.Comment: 12 pages, 8 figure

Effects of N2 Plasma Pretreatment on the SiN Passivation of AlGaN/GaN HEMT

The impact of in situ low-power plasma pretreatment, prior to silicon-nitride (SiN) deposition, was investigated in AlGaN/GaN high-electron mobility transistors (HEMTs). These studies reveal that the use of plasma in HEMT passivation reduces current-collapse and gate-lag effects. Such treatment is also beneficial to improve gate leakage, and from RF measurements, no degradation of was observed. These beneficial effects of the plasma pretreatment seem to be due to a significant reduction in interface charge density, as shown in this letter using GaN MIS devices, where a decrease of 60% was observed

Učinak praha avokada, suncokretova ulja te različitih omjera voluminozne i koncentrirane krme u obroku na unos hrane, probavljivost hrane i proizvodnost mladih ovnova

The objective of this study was to evaluate the inclusion of avocado flour and sunflower oil as energy sources in different proportions, as well as different forage:concentrate ratios on the productive performance and feed intake of male rams, and the in vitro dry matter digestibility, organic matter digestibility and gas production. The intake was measured in diets containing avocado flour or sunflower oil with 60% forage: 40% concentrate, and in diets with different forage:concentrate ratios and 10% inclusion of avocado flour or sunflower oil. The daily weight gain was registered for 84 days, the in vitro dry matter digestibility was determined at 48 h, and the in vitro gas production was evaluated at 72 h. The partial production of gas at 24 hours, raw protein, raw fat, and ash were used to estimate the metabolizable energy and organic matter digestibility. Low levels of avocado flour and sunflower oil in the diet showed the highest intake, in vitro dry matter digestibility and in vitro gas production. Daily weight gains were 0.28 kg in avocado flour and 0.30 kg in sunflower oil diets, both at 10% inclusion and 40% forage: 60% concentrate. The inclusion of high levels of avocado flour or forage in the diet decreased the feed intake of male sheep. The best avocado flour level was 10% with 40% forage: 60% concentrate.Cilj rada bio je istražiti utjecaj različitih omjera između praha avokada i suncokretova ulja kao izvora energije, te različitih omjera između voluminozne i koncentrirane krme u obroku na unos hrane i proizvodnost mladih ovnova. Osim toga, in vitro istražena je probavljivost suhe tvari, probavljivost organske tvari i proizvodnja plina. Unos hrane mjeren je u obrocima koji su sadržavali prah avokada ili suncokretovo ulje uz omjer između voluminozne i koncentrirane krme od 60:40% ili u obrocima sa različitim omjerom voluminozne i koncentrirane krme uz dodatak 10% praha avokada ili suncokretova ulja. Dnevni prirast bilježen je tijekom 84 dana. Probavljivost suhe tvari in vitro određivana je 48 h, a proizvodnja plina in vitro 72 h od uzimanja uzoraka. Za određivanje metaboličke energije i probavljivosti organske tvari korišteni su parcijalna proizvodnja plina 24-ti sat, sirovi protein, sirova mast i pepeo. Niske razine praha avokada i suncokretova ulja u obroku rezultirale su najvišim unosom hrane te najvišom in vitro probavljivošću suhe tvari i in vitro proizvodnjom plina. Dnevni prirast bio je 0,28 kg u životinja kojima je davano 10% praha avokada, 0,30 kg u životinja kojima je davano 10% suncokretova ulja, pri čemu je omjer voluminozne i koncentrirane krme iznosio 40:60%. Dodavanje visokih razina praha avokada ili voluminozne krme u obrok dovelo je do nižeg unosa hrane kod mladih ovnova pa je zaključeno da je najpovoljnija razina dodanog praha avokada 10% uz omjer voluminozne i koncentrirane krme 40:60%

Stimulated Raman Scattering for All Optical Switches

We theoretically and experimentally investigate an all optical switch based on stimulated Raman scattering in optical fibers. The experimental setup consists of a Raman circuit of two stages connected in series through a bandpass filter. In the first stage, we have a saturated amplifier, in this stage the pump pulses are saturated when pump and signal are launched to the input or the pump pulses remain without saturation when pump only is launched at the input. The second stage works as the Raman amplifier; for this stage amplification is directly dependent on the pump power entering from the first stage. For the case when pump pulse only is launched at the input pass to the second stage without saturation and amplifies the signal entering in the second stage, very intense signal pulses appear at the output of this stage. For the case when both pump and signal pulses are launched to the input, the pump pulse is saturated in the first stage and the filter rejected the amplified signal, so that only low power pump enters the second stage and consequently no signal pulses appear at the output. We show that the contrast can be improved when using fibers with normal and anomalous dispersion connected in series in the first stage. The best contrast (the ratio of energies) obtained was 15 dB at 6 W pump peak power

The role of the muscarinic system in regulating estradiol secretion varies during the estrous cycle: the hemiovariectomized rat model

There is evidence that one gonad has functional predominance. The present study analyzed the acute effects of unilateral ovariectomy (ULO) and blocking the cholinergic system, by injecting atropine sulfate (ATR), on estradiol (E(2)) serum concentrations during the estrous cycle. The results indicate that ULO effects on E(2 )concentrations are asymmetric, vary during the estrous cycle, and partially depend on the cholinergic innervation. Perforation of the left peritoneum resulted in lower E(2 )serum concentrations in the three stages of the estrous cycle. At proestrus, unilateral or bilateral perforation of the peritoneum resulted in lower E(2 )serum concentrations. ULO of the right ovary (left ovary in situ) resulted in significantly higher E(2 )concentrations than animals with ULO of the left ovary (right ovary in situ). ATR treatment to ULO rats on D1 resulted in a significant drop of E(2 )serum concentrations. ULO rats treated with ATR on D2 or P, resulted in an asymmetrical E(2) secretion response; when the right ovary remained in situ an increase in E(2) was observed, and a decrease when the left ovary remained in situ. The results obtained in the present study suggest that each ovary's ability to compensate the secretion of E(2 )from the missing ovary is different and varies during the estrous cycle. The results also suggest that the cholinergic system participates in regulating ovarian E(2 )secretion. Such participation varies according to the ovary remaining in situ and the stage of the estrous cycle of the animal. The results agree with previously stated hypothesis of a neural pathway arising from the peritoneum that participates in regulating E(2 )secretion, and also supports the idea of cross-talk between the ovaries, via a neural communication, that modulates E(2 )secretion