Solar tracking system

A solar tracker for a solar collector is described in detail. The collector is angularly oriented by a motor wherein the outputs of two side-by-side photodetectors are discriminated as to three ranges: a first corresponding to a low light or darkness condition; a second corresponding to light intensity lying in an intermediate range; and a third corresponding to light above an intermediate range, direct sunlight. The first output drives the motor to a selected maximum easterly angular position; the second enables the motor to be driven westerly at the Earth rotational rate; and the third output, the separate outputs of the two photodetectors, differentially controls the direction of rotation of the motor to effect actual tracking of the Sun

Solar tracking control system Sun Chaser

The solar tracking control system, Sun Chaser, a method of tracking the Sun in all types of weather conditions is described. The Sun Chaser follows the Sun from east to west in clear or cloudy weather, and resets itself to the east position after sundown in readiness for the next sunrise

Cold dark matter models with high baryon content

Recent results have suggested that the density of baryons in the Universe, OmegaB, is much more uncertain than previously thought, and may be significantly higher. We demonstrate that a higher OmegaB increases the viability of critical-density cold dark matter (CDM) models. High baryon fraction offers the twin benefits of boosting the first peak in the microwave anisotropy power spectrum and of suppressing short-scale power in the matter power spectrum. These enable viable CDM models to have a larger Hubble constant than otherwise possible. We carry out a general exploration of high OmegaB CDM models, varying the Hubble constant h and the spectral index n. We confront a variety of observational constraints and discuss specific predictions. Although some observational evidence may favour baryon fractions as high as 20 per cent, we find that values around 10 to 15 per cent provide a reasonable fit to a wide range of data. We suggest that models with OmegaB in this range, with h about 0.5 and n about 0.8, are currently the best critical-density CDM models.Comment: 14 pages, LaTeX, with 9 included figures, to appear in MNRAS. Revised version includes updated references, some changes to section 4. Conclusions unchange

Using piloted simulation to measure pilot workload of landing a helicopter on a small ship

When conducting landings to a ship's deck in strong winds, helicopter pilot workload is often dominated by the turbulence within the ship's airwake. Previous studies have shown that larger ships create more aggressive airwakes and simulated flight trials had shown that it can be easier to land to a smaller ship than a large one. However, there are helicopter-enabled ships that are less than 100m in length and these will have significantly greater ship motion in rough seas than a large ship. The study reported in this paper has used a motion-base flight simulator to evaluate the pilot workload when landing to three geometrically similar ships of lengths 100m, 150m and 200m. Ship motion software has been used to create realistic deck displacements for sea states 4, 5 and 6, which are consistent with the increasing wind speed over the deck. It has been shown that the 100m ship was the most difficult to land to, with deck motion being the limiting factor. The next most difficult ship to land to was the 200m ship, with airwake turbulence being the limiting factor. The 150m ship generated the lowest pilot workload. The study has demonstrated that when ship motion is excessive, as it will be with small ships in rough seas, pilot workload will be dominated by deck motion during a landing task, but as the ship gets larger and more stable, airwake disturbances will dominate. It is clear from this study that realistic ship motion is essential when using piloted flight simulation to conduct simulated ship-helicopter operations

Evolution of X-ray cluster scaling relations in simulations with radiative cooling and non-gravitational heating

We investigate the redshift dependence of X-ray cluster scaling relations drawn from three hydrodynamic simulations of the LCDM cosmology: a Radiative model that incorporates radiative cooling of the gas, a Preheating model that additionally heats the gas uniformly at high redshift, and a Feedback model that self-consistently heats cold gas in proportion to its local star-formation rate. While all three models are capable of reproducing the observed local Lx-Tx relation, they predict substantially different results at high redshift (to z=1.5), with the Radiative, Preheating and Feedback models predicting strongly positive, mildly positive and mildly negative evolution, respectively. The physical explanation for these differences lies in the structure of the intracluster medium. All three models predict significant temperature fluctuations at any given radius due to the presence of cool subclumps and, in the case of the Feedback simulation, reheated gas. The mean gas temperature lies above the dynamical temperature of the halo for all models at z=0, but differs between models at higher redshift with the Radiative model having the lowest mean gas temperature at z=1.5. We have not attempted to model the scaling relations in a manner that mimics the observational selection effects, nor has a consistent observational picture yet emerged. Nevertheless, evolution of the scaling relations promises to be a powerful probe of the physics of entropy generation in clusters. First indications are that early, widespread heating is favored over an extended period of heating that is associated with galaxy formation.Comment: Accepted for publication in ApJ. Minor changes following referee's comment

Modelling and Simulation at The University of Liverpool in Support of UK Naval Aviation

Along with the restricted landing area and the rolling, pitching and heaving of the ship's deck, the pilot also needs to contend with the turbulent wake produced by the air flow over the ship's superstructure. There has been significant research in the past decade or more to better understand the flying environment around the ship and how it impacts the helicopter’s handling qualities and pilot workload. Central to this research has been the use of modelling and simulation, with a particular emphasis on understanding the unsteady airflow over the ship and how this is affected by the superstructure geometry. In the UK, this flight simulation research has been led by the Flight Science and Technology Research Group at the University of Liverpool. This paper reviews the research that has been carried out at Liverpool, and how this has led to simulated flight trials to establish a simulated Ship-Helicopter Operating Limits envelope and how modelling and simulation is being used to assess the aerodynamic characteristics of the ship while it is still in the design phase, and to inform at-sea first of class flight trials

When supercomputers go over to the dark side

Despite oodles of data and plenty of theories, we still don't know what dark matter is. Martin White and Pat Scott describe how a new software tool called GAMBIT – run on supercomputers such as Prometheus – will test how novel theories stack up when confronted with real data

Regulation of the RNA and DNA nuclease activities required for Pyrococcus furiosus Type III-B CRISPR-Cas immunity

Funding: National Institutes of Health (NIH) [R35GM118160 to M.P.T., R01GM097330 to S.B. and 1F31GM125365 toK.F.]; Biotechnology and Biological Sciences Research Council [REF: BB/S000313/1 to M.F.W.]. Funding for open access charge: NIH grant.Type III CRISPR-Cas prokaryotic immune systems provide anti-viral and anti-plasmid immunity via a dual mechanism of RNA and DNA destruction. Upon target RNA interaction, Type III crRNP effector complexes become activated to cleave both target RNA (via Cas7) and target DNA (via Cas10). Moreover, trans-acting endoribonucleases, Csx1 or Csm6, can promote the Type III immune response by destroying both invader and host RNAs. Here, we characterize how the RNase and DNase activities associated with Type III-B immunity in Pyrococcus furiosus (Pfu) are regulated by target RNA features and second messenger signaling events. In vivo mutational analyses reveal that either the DNase activity of Cas10 or the RNase activity of Csx1 can effectively direct successful anti-plasmid immunity. Biochemical analyses confirmed that the Cas10 Palm domains convert ATP into cyclic oligoadenylate (cOA) compounds that activate the ribonuclease activity of Pfu Csx1. Furthermore, we show that the HEPN domain of the adenosine-specific endoribonuclease, Pfu Csx1, degrades cOA signaling molecules to provide an auto-inhibitory off-switch of Csx1 activation. Activation of both the DNase and cOA generation activities require target RNA binding and recognition of distinct target RNA 3' protospacer flanking sequences. Our results highlight the complex regulatory mechanisms controlling Type III CRISPR immunity.Publisher PDFPeer reviewe

Effect of Two Week L-Arginine Supplementation on Variables Related to Endurance and Strength Performance in Collegiate Football Players

Background: It has been shown that a month-long supplementation period of L-arginine, coupled with exercise training, increases exercise performance more than either supplementation or exercise alone (Hambrecht et al., 2000). Purpose: The purpose of this study was to examine the effects of a shorter 2 wk L-arginine supplementation period on factors related to endurance and strength performance. Methods: Twelve collegiate football players volunteered to participate in this study. The control group (n = 6) and treatment group (n = 6) both participated in the same off-season training program that consisted of strength training 3 d/wk and agility training 2 d/wk. In addition, the treatment group received 1g of L-arginine twice daily, whereas the control group received a placebo twice daily. At the beginning of the study, participants performed a baseline bench press maximum repetitions test at 70% of their most recently recorded bench press 1 RM (MMR). The participants also performed a graded exercise test (GXT) on a cycle ergometer to volitional exhaustion. Following baseline testing, participants immediately began the supplementation period, and were retested in the MMR and the GXT after 2 wk of supplementation. The effect of supplementation on each dependent variable was determined using ANCOVA with pretests serving as the covariates. Results: ANCOVA did not reveal significant effects of L-arginine supplementation on MMR (F(1,9) = 1.71, p = 0.22), VO2max (F(1,9) = 1.08, p = 0.33), time to exhaustion in the GXT (F(1,9) = 0.19, p = 0.67) , or HRmax during the GXT (F(1,9) = 4.79, p = 0.06). Conclusion: A 2 wk supplementation period coupled with training may not be of sufficient length to improve factors related to endurance and strength performance in trained college-aged men