Optimization of a Third-Order Gradiometer for Operation in Unshielded Environments

The optimum geometry of a third-order gradiometer for operation in unshielded environments is discussed. The optimization result depends on the specific signal and noise conditions. The fetal heart is considered as an example of the signal source. We optimized the gradiometer such that the signal-to-noise ratio is maximized in an averaged sense for all relevant environmental noise conditions and distances to the signal source. The resulting design consists of two second-order gradiometers that can be combined to form a third-order gradiometer in noisy environments, whereas a single second-order gradiometer can be used in low-noise environments. The gradiometer can provide the signal-to-noise ratio that allows detection of fetal heart signals in all relevant environmental noise conditions

Evidence for RNA recombination between distinct isolates of Pepino mosaic virus.

Genetic recombination plays an important role in the evolution of virus genomes. In this study we analyzed publicly available genomic sequences of Pepino mosaic virus (PepMV) for recombination events using several bioinformatics tools. The genome-wide analyses not only confirm the presence of previously found recombination events in PepMV but also provide the first evidence for double recombinant origin of the US2 isolate

Multiple functions of the 32K and 60K proteins in cowpea mosaic virus RNA replication

Cowpea mosaic virus (CPMV) is the type member of the comoviridae , a group of 14 different plant viruses that have a divided genome consisting of two plus-strand RNAs. These RNAs, designated B-RNA and M-RNA, have a small protein, VPg, attached to the 5'-end and a poly(A) tail at the 3'-end and are separately packaged into icosahedral particles of 28 nm in diameter. Nucleotide sequence analysis has revealed that each RNA contains one large open reading frame. Upon infection the RNAs are translated into large polyproteins that are subsequently processed into several stable intermediate and final cleavage products.The B-RNA and its encoded enzyme activities constitute an autonomous RNA replicon, since the B- RNA can replicate independently of M-RNA in isolated plant cells. However, B-RNA is dependent on M-RNA for cell-to-cell movement in intact plants. The development of full-length cDNA clones, of B- and M-RNA from which infectious RNA transcripts can be derived, has made it possible to study the mechanism of viral gene expression in more detail. By introducing specific mutations in B cDNA clones, several functional domains in the B-polyprotein were identified, but the understanding of the activity of each individual B-RNA encoded protein in the replicative machinery is still incomplete. At the start of the research described in this thesis the B-RNA encoded 110K, which consists of the 24K protein and the 97K core polymerase protein, has been shown to represent the viral RNA-dependent RNA-polymerase. The 60K protein has been proposed to function as a precursor for VPg, that probably has a role as a primer in the initiation of viral RNA replication. Furthermore, the 60K protein is thought to function in anchoring the viral RNA replication complex to membranes, known to be the site of viral RNA replication. Processing of the B-polyprotein is accomplished by the B-RNA encoded 24K proteinase, cleaving the viral proteins at specific Gln/Gly, Gln/Ser and Gln/Met sites. However, for efficient trans processing of the Gin/Met site in the M-polyprotein also the B-RNA encoded 32K protein is required.The studies described in this thesis were concentrated on elucidating the role of the 32K and 60K proteins in the viral replication process. The work presented in chapter 2 of this thesis was directed towards the role of the 32K protein in the polyprotein processing. By employing an in vitro transcription/translation system, to express specifically modified cDNA clones, it was shown that the 32K protein regulates both M- and B-polyprotein processing, by interacting with the 58K domain of the 170K and 84K precursors of the 24K proteinase, thereby modulating the cleavage activity and specificity of the 24K proteinase. In chapters 3 and 4 processing of several VPg precursors has been examined. This study showed that in vitro processing of the 170K protein can occur via three alternative pathways to generate 112K, 84K and 60K putative VPg precursor proteins. The 60K protein was found to be stable in this in vitro system, whereas the 112K and 84K proteins were processed and might function as a VPg precursor. Using a transient expression system, the 112K protein was evidently shown to function as a direct VPg precursor in cowpea protoplasts (chapter 4).A study on the biochemical properties of the B-RNA encoded 60K and 84K proteins is described in chapters 5 and 6 of this thesis. A covalent affinity labelling assay was exploited and the 60K and 84K protein were shown to specifically bind ATP, possibly at a ribonucleoside triphosphate binding motif (NTBM) located in the 58K domain of these proteins (chapter 5). In chapter 6 the effect of mutations that were introduced in the coding region of the NTBM is described. With this study an essential role in viral RNA replication could be attributed to the NTBM

Approximating the inspiral of test bodies into Kerr black holes

We present a new approximate method for constructing gravitational radiation driven inspirals of test-bodies orbiting Kerr black holes. Such orbits can be fully described by a semi-latus rectum $p$, an eccentricity $e$, and an inclination angle $\iota$; or, by an energy $E$, an angular momentum component $L_z$, and a third constant $Q$. Our scheme uses expressions that are exact (within an adiabatic approximation) for the rates of change ($\dot{p}$, $\dot{e}$, $\dot{\iota}$) as linear combinations of the fluxes ($\dot{E}$, $\dot{L_z}$, $\dot{Q}$), but uses quadrupole-order formulae for these fluxes. This scheme thus encodes the exact orbital dynamics, augmenting it with approximate radiation reaction. Comparing inspiral trajectories, we find that this approximation agrees well with numerical results for the special cases of eccentric equatorial and circular inclined orbits, far more accurate than corresponding weak-field formulae for ($\dot{p}$, $\dot{e}$, $\dot{\iota}$). We use this technique to study the inspiral of a test-body in inclined, eccentric Kerr orbits. Our results should be useful tools for constructing approximate waveforms that can be used to study data analysis problems for the future LISA gravitational-wave observatory, in lieu of waveforms from more rigorous techniques that are currently under development.Comment: 15 pages, 5 figures, submitted to PR

Complete genome sequence and taxonomic position of anguillid herpesvirus 1

Eel herpesvirus or anguillid herpesvirus 1 (AngHV1) frequently causes disease in freshwater eels. The complete genome sequence of AngHV1 and its taxonomic position within the family Alloherpesviridae were determined. Shotgun sequencing revealed a 249 kbp genome including an 11 kbp terminal direct repeat that contains 7 of the 136 predicted protein-coding open reading frames. Twelve of these genes are conserved among other members of the family Alloherpesviridae and another 28 genes have clear homologues in cyprinid herpesvirus 3. Phylogenetic analyses based on amino acid sequences of five conserved genes, including the ATPase subunit of the terminase, confirm the position of AngHV1 within the family Alloherpesviridae, where it is most closely related to the cyprinid herpesviruses. Our analyses support a recent proposal to subdivide the family Alloherpesviridae into two sister clades, one containing AngHV1 and the cyprinid herpesviruses and the other containing Ictalurid herpesvirus 1 and the ranid herpesviruses

Prediction formulae for lung function parameters in females of south eastern Nigeria.

This study was carried out to obtain normal lung function values for women in south eastern Nigeria with a view to establishing prediction equations for forced vital capacity (FVC), forced expiratory volume at the first second (FEV1) and peak expiratory flow rate (PEFR). Lung function values were measured in 600 apparently healthy Nigerian women aged between 18 and 57 years. FVC and FEV1 were significantly related to height (

Gravitational signals emitted by a point mass orbiting a neutron star: effects of stellar structure

The effects that the structure of a neutron star would have on the gravitational emission of a binary system are studied in a perturbative regime, and in the frequency domain. Assuming that a neutron star is perturbed by a point mass moving on a close, circular orbit, we solve the equations of stellar perturbations in general relativity to evaluate the energy lost by the system in gravitational waves. We compare the energy output obtained for different stellar models with that found by assuming that the perturbed object is a black hole with the same mass, and we discuss the role played by the excitation of the stellar modes. Ouresults indicate that the stellar structure begins to affect the emitted power when the orbital velocity is v >0.2c (about 185 Hz for a binary system composed of two canonical neutron stars). We show that the differences between different stellar models and a black hole are due mainly to the excitation of the quasinormal modes of the star. Finally, we discuss to what extent and up to which distance the perturbative approach can be used to describe the interaction of a star and a pointlike massive body.Comment: 22 pages, 6 figures, to appear in Phys. Rev. D. Revised version, added one table and extended discussio

Aspects of meson properties in dense nuclear matter

We investigate the modification of meson spectral densities in dense nuclear matter at zero temperature. These effects are studied in a fully relativistic mean field model which goes beyond the linear density approximation and also includes baryon resonances. In particular, the role of N*(1520) and N*(1720) on the rho meson spectral density is highlighted. Even though the nucleon-nucleon loop and the nucleon-resonance loop contribute with the opposite sign, an overall reduction of rho meson mass is still observed at high density. Importantly, it is shown that the resonances cause substantial broadening of the rho meson spectral density in matter and also induces non-trivial momentum dependence. The spectral density of the a0 meson is also shown. We study the dispersion relations and collective oscillations induced by the rho meson propagation in nuclear matter together with the influence of the mixing of rho with the a0 meson. The relevant expression for the plasma frequency is also recovered analytically in the appropriate limit.Comment: 19 pages, 17 figure

Gravitational waveforms from a point particle orbiting a Schwarzschild black hole

We numerically solve the inhomogeneous Zerilli-Moncrief and Regge-Wheeler equations in the time domain. We obtain the gravitational waveforms produced by a point-particle of mass $\mu$ traveling around a Schwarzschild black hole of mass M on arbitrary bound and unbound orbits. Fluxes of energy and angular momentum at infinity and the event horizon are also calculated. Results for circular orbits, selected cases of eccentric orbits, and parabolic orbits are presented. The numerical results from the time-domain code indicate that, for all three types of orbital motion, black hole absorption contributes less than 1% of the total flux, so long as the orbital radius r_p(t) satisfies r_p(t)> 5M at all times.Comment: revtex4, 24 pages, 23 figures, 3 tables, submitted to PR