Development of electrical test procedures for qualification of spacecraft against EID. Volume 2: Review and specification of test procedures

A combined experimental and analytical program to develop system electrical test procedures for the qualification of spacecraft against damage produced by space-electron-induced discharges (EID) occurring on spacecraft dielectric outer surfaces is described. A review and critical evaluation of possible approaches to qualify spacecraft against space electron-induced discharges (EID) is presented. A variety of possible schemes to simulate EID electromagnetic effects produced in spacecraft was studied. These techniques form the principal element of a provisional, recommended set of test procedures for the EID qualification spacecraft. Significant gaps in our knowledge about EID which impact the final specification of an electrical test to qualify spacecraft against EID are also identified

Acute aortic dissection in a young healthy athlete with androgenic anabolic steroid use: A case report

Background: Acute aortic dissection can occur at the time of intense physical exertion in strength-trained athletes like weight lifters, bodybuilders, throwers, and wrestlers. Rapid rise in blood pressure and history of hypertension are the most common causes of aortic dissection in athletes. It is a very tragic event because of its high mortality rate of about 32% in young patients. We report a case of aortic dissection in a young weightlifter with a history of anabolic steroid usage with an extensive intimal tear of the aorta at Sino tubular junction and arch. All athletes must be assessed for predisposing factors for aortic dissection, and all patients should be encouraged to undergo appropriate diagnostic studies, like echocardiography and blood pressure monitoring while weightlifting to recognize possible predisposing factors for aortic dissection. Athletes who do have a problem should be encouraged to avoid or limit their exercise or activity by their cardiologist. It is vital that this disastrous event be prevented in young people. In conclusion, although a rare occurrence, AD should be considered in symptomatic patients with any family history of early cardiac deaths, a history suggestive of a connective tissue disorder (that is, multiple joint surgeries) or who practice weightlifting

Two RNA-binding motifs in the double-stranded RNA-activated protein kinase, DAI

The protein kinase DAI, the double-stranded RNA-activated inhibitor of translation, is an essential component of the interferon-induced cellular antiviral response. The enzyme is regulated by the binding of activator and inhibitor RNAs. We synthesized DAI in vitro and located its RNA-binding domain within the amino-terminal 171 residues. This domain contains two copies of an RNA-binding motif characterized by a high density of basic amino acids, by the presence of conserved residues, and by a probable alpha-helical structure. Deletion of either of the two motifs prevents the binding of dsRNA, but their relative positions can be exchanged, suggesting that they cooperate to interact with dsRNA. Clustered point mutations within the RNA-binding motifs and duplications of the individual motifs indicate that the first copy of the motif plays the more important role. Mutations that impair binding have similar effects on the binding of double-stranded RNAs of various lengths and of adenovirus VA RNAI, implying that discrimination between activator and inhibitory RNAs takes place subsequent to RNA binding

Model Independent Primordial Power Spectrum from Maxima, Boomerang, and DASI Data

A model-independent determination of the primordial power spectrum of matter density fluctuations could uniquely probe physics of the very early universe, and provide powerful constraints on inflationary models. We parametrize the primordial power spectrum $A_s^2(k)$ as an arbitrary function, and deduce its binned amplitude from the cosmic microwave background radiation anisotropy (CMB) measurements of Maxima, Boomerang, and DASI. We find that for a flat universe with $A_s^2(k)=1$ (scale-invariant) for scales $k<0.001$h/Mpc, the primordial power spectrum is marginally consistent with a scale-invariant Harrison-Zeldovich spectrum. However, we deduce a rise in power compared to a scale-invariant power spectrum for 0.001 h/{Mpc} \la k \la 0.01 h/{Mpc}. Our results are consistent with large-scale structure data, and seem to suggest that the current observational data allow for the possibility of unusual physics in the very early universe.Comment: substantially revised and final version, accepted by Ap

Structural features of adenovirus 2 virus-associated RNA required for binding to the protein kinase DAI

The double-stranded RNA activated protein kinase DAI contains an RNA binding domain consisting of two copies of a double-stranded RNA binding motif. We have investigated the role of RNA structure in the interaction between DAI and the structured single-stranded RNA, adenovirus VA RNAI, which inhibits DAI activation. Mutations in the apical stem, terminal stem, and central domain of the RNA were tested to assess the contribution of these elements to DAI binding in vitro. The data demonstrate that over half a turn of intact apical stem is required for the interaction and that there is a correlation between the binding of apical stem mutants and their ability to function both in vivo and in vitro. There was also evidence of preference for GC-rich sequence in the proximal region of the apical stem. In the central domain the correlation between binding and function of mutant RNAs was poor, suggesting that at least some of this region plays no direct role in binding to DAI, despite its functional importance. Exceptionally, central domain mutations that encroached on the phylogenetically conserved stem 4 of VA RNA disrupted binding, and complementary mutations in this sequence partially restored binding. Measurement of the binding of wild-type VA RNAI to DAI and p20, a truncated form of the protein containing the RNA binding domains alone, under various ionic conditions imply that the major interactions are electrostatic and occur via the protein's RNA binding domain. However, differences between full-length DAI and p20 in their binding to mutants in the conserved stem suggest that regions outside the RNA binding domain also participate in the binding. The additional interactions are likely to be non-ionic, and may be important for preventing DAI activation during virus infection

Revised Relativistic Hydrodynamical Model for Neutron-Star Binaries

We report on numerical results from a revised hydrodynamic simulation of binary neutron-star orbits near merger. We find that the correction recently identified by Flanagan significantly reduces but does not eliminate the neutron-star compression effect. Although results of the revised simulations show that the compression is reduced for a given total orbital angular momentum, the inner most stable circular orbit moves to closer separation distances. At these closer orbits significant compression and even collapse is still possible prior to merger for a sufficiently soft EOS. The reduced compression in the corrected simulation is consistent with other recent studies of rigid irrotational binaries in quasiequilibrium in which the compression effect is observed to be small. Another significant effect of this correction is that the derived binary orbital frequencies are now in closer agreement with post-Newtonian expectations.Comment: Submitted to Phys. Rev.

Synergy between HIV-1 Tat and adenovirus E1A is principally due to stabilization of transcriptional elongation

We studied the combined effects of Tat and general trans-activators, such as E1A and phorbol esters, on human immunodeficiency virus-1 (HIV-1) gene expression. Interaction between these two types of trans-activators may be involved in the transition from transcriptional quiesence during viral latency to active gene expression during productive infection. E1A cooperated with Tat to produce a fourfold greater increase in accumulation of full-length, cytoplasmic HIV-1-directed RNA than is expected if they were acting additively to increase RNA accumulation. Similarly, phorbol 12-myristate 13-acetate (PMA) also cooperated with Tat to elevate HIV RNA levels synergistically. Analysis of transcription rates across the HIV-1-directed transcription unit indicated, unexpectedly, that synergy between Tat and E1A could not be accounted for by increased promoter proximal transcription rates that were merely additive. However, Tat and E1A produced a greater than additive increase in transcription rates in the 3' end of the gene. These findings imply that synergy between Tat and E1A (or other general transcriptional activators) is due principally to stabilization of transcriptional elongation. Furthermore, the observation that Tat elicits only a small increase in promoter proximal transcription in the presence of E1A suggests that the magnitude of the effect of Tat on initiation is decreased when the basal level of transcription is increased. These findings underscore the importance of the ability of Tat to stabilize elongation, as well as to stimulate initiation, in an HIV-1-directed transcription unit

Analytic calculation of energies and wave functions of the quartic and pure quartic oscillators

Ground state energies and wave functions of quartic and pure quartic oscillators are calculated by first casting the Schr\"{o}dinger equation into a nonlinear Riccati form and then solving that nonlinear equation analytically in the first iteration of the quasilinearization method (QLM). In the QLM the nonlinear differential equation is solved by approximating the nonlinear terms by a sequence of linear expressions. The QLM is iterative but not perturbative and gives stable solutions to nonlinear problems without depending on the existence of a smallness parameter. Our explicit analytic results are then compared with exact numerical and also with WKB solutions and it is found that our ground state wave functions, using a range of small to large coupling constants, yield a precision of between 0.1 and 1 percent and are more accurate than WKB solutions by two to three orders of magnitude. In addition, our QLM wave functions are devoid of unphysical turning point singularities and thus allow one to make analytical estimates of how variation of the oscillator parameters affects physical systems that can be described by the quartic and pure quartic oscillators.Comment: 8 pages, 12 figures, 1 tabl

Eigen modes for the problem of anomalous light transmission through subwavelength holes

We show that the wide-spread concept of optical eigen modes in lossless waveguide structures, which assumes the separation on propagating and evanescent modes, fails in the case of metal-dielectric structures, including photonic crystals. In addition to these modes, there is a sequence of new eigen-states with complex values of the propagation constant and non-vanishing circulating energy flow. The whole eigen-problem ceases to be hermitian because of changing sign of the optical dielectric constant. The new anomalous modes are shown to be of prime importance for the description of the anomalous light transmission through subwavelength holes.Comment: 5 pages, 4 figure