Static-Electric-Field-Induced Polarization Effects in Harmonic Generation

Two static-electric-field-induced effects on harmonic generation are demonstrated analytically and numerically: elliptic dichroism (in which the harmonic yield is different for right and left elliptically polarized laser fields) and elliptical polarization of harmonics produced by linearly polarized driving laser fields. Both effects stem from interference of real and imaginary parts of the nonlinear atomic susceptibilities. Possibilities for experimentally measuring these effects are discussed

Identification of a novel virulence determinant within the E2 structural glycoprotein of classical swine fever virus

AbstractClassical swine fever virus (CSFV) E2 glycoprotein contains a discrete epitope (TAVSPTTLR, residues 829–837 of CSFV polyprotein) recognized by monoclonal antibody (mAb) WH303, used to differentiate CSFV from related ruminant pestiviruses, Bovine Viral Diarrhea Virus (BVDV) and Border Disease Virus (BDV), that infect swine without causing disease. Progressive mutations were introduced into mAb WH303 epitope in CSFV virulent strain Brescia (BICv) to obtain the homologous amino acid sequence of BVDV strain NADL E2 (TSFNMDTLA). In vitro growth of mutants T1v (TSFSPTTLR), T2v (TSFNPTTLR), T3v (TSFNMTTLR) was similar to parental BICv, while mutants T4v (TSFNMDTLR) and T5v (TSFNMDTLA) exhibited a 10-fold decrease in virus yield and reduced plaque size. In vivo, T1v, T2v or T3v induced lethal disease, T4v induced mild and transient disease and T5v induced mild clinical signs. Protection against BICv challenge was observed at 3 and 21 days post-T5v infection. These results indicate that E2 residues TAVSPTTLR play a significant role in CSFV virulence

Effect of specific amino acid substitutions in the putative fusion peptide of structural glycoprotein E2 on Classical Swine Fever Virus replication

AbstractE2, along with Erns and E1, is an envelope glycoprotein of Classical Swine Fever Virus (CSFV). E2 is involved in several virus functions: cell attachment, host range susceptibility and virulence in natural hosts. Here we evaluate the role of a specific E2 region, 818CPIGWTGVIEC828, containing a putative fusion peptide (FP) sequence. Reverse genetics utilizing a full-length infectious clone of the highly virulent CSFV strain Brescia (BICv) was used to evaluate how individual amino acid substitutions within this region of E2 may affect replication of BICv. A synthetic peptide representing the complete E2 FP amino acid sequence adopted a β-type extended conformation in membrane mimetics, penetrated into model membranes, and perturbed lipid bilayer integrity in vitro. Similar peptides harboring amino acid substitutions adopted comparable conformations but exhibited different membrane activities. Therefore, a preliminary characterization of the putative FP 818CPIGWTGVIEC828 indicates a membrane fusion activity and a critical role in virus replication

Treatment with interferon-alpha delays disease in swine infected with a highly virulent CSFV strain

AbstractInterferon-alpha (IFNα) can effectively inhibit or abort a viral infection within the host. It has been reported that IFN induction and production is hindered during classical swine fever virus (CSFV) infection. Most of those studies have been performed in vitro, making it difficult to elucidate the actual role of IFNs during CSFV infection in swine. Here, we report the effect of IFNα treatment (delivered by a replication defective recombinant human adenovirus type 5, Ad5) in swine experimentally infected with highly virulent CSFV strain Brescia. Treatment with two different subtypes of IFNα delayed the appearance of CSF-related clinical signs and virus replication although it did not prevent lethal disease. This is the first report describing the effect of IFNα treatment during CSFV infection in swine

Origin and Properties of the Gap in the Half-Ferromagnetic Heusler Alloys

We study the origin of the gap and the role of chemical composition in the half-ferromagnetic Heusler alloys using the full-potential screened KKR method. In the paramagnetic phase the C1_b compounds, like NiMnSb, present a gap. Systems with 18 valence electrons, Z_t, per unit cell, like CoTiSb, are semiconductors, but when Z_t > 18 antibonding states are also populated, thus the paramagnetic phase becomes unstable and the half-ferromagnetic one is stabilized. The minority occupied bands accommodate a total of nine electrons and the total magnetic moment per unit cell in mu_B is just the difference between Z_t and $2 \times 9$. While the substitution of the transition metal atoms may preserve the half-ferromagnetic character, substituting the $sp$ atom results in a practically rigid shift of the bands and the loss of half-metallicity. Finally we show that expanding or contracting the lattice parameter by 2% preserves the minority-spin gap.Comment: 11 pages, 7 figures New figures, revised tex

Nonquasiparticle states in half-metallic ferromagnets

Anomalous magnetic and electronic properties of the half-metallic ferromagnets (HMF) have been discussed. The general conception of the HMF electronic structure which take into account the most important correlation effects from electron-magnon interactions, in particular, the spin-polaron effects, is presented. Special attention is paid to the so called non-quasiparticle (NQP) or incoherent states which are present in the gap near the Fermi level and can give considerable contributions to thermodynamic and transport properties. Prospects of experimental observation of the NQP states in core-level spectroscopy is discussed. Special features of transport properties of the HMF which are connected with the absence of one-magnon spin-flip scattering processes are investigated. The temperature and magnetic field dependences of resistivity in various regimes are calculated. It is shown that the NQP states can give a dominate contribution to the temperature dependence of the impurity-induced resistivity and in the tunnel junction conductivity. First principle calculations of the NQP-states for the prototype half-metallic material NiMnSb within the local-density approximation plus dynamical mean field theory (LDA+DMFT) are presented.Comment: 27 pages, 9 figures, Proceedings of Berlin/Wandlitz workshop 2004; Local-Moment Ferromagnets. Unique Properties for Moder Applications, ed. M. Donath, W.Nolting, Springer, Berlin, 200

Threshold-Related Enhancement of the High-Energy Plateau in Above-Threshold Detachment

We present nonperturbative theoretical results showing a resonant-like enhancement of above-threshold detachment spectra in the region of the high-energy plateau as the laser intensity sweeps across channel thresholds. This enhancement has a pure quantum origin stemming from well-known threshold phenomena in multichannel problems whose features are clearly demonstrated in our numerical results. Similar well-known anomalies at neutral atom thresholds are expected to explain experimentally observed resonant-like enhancements of above-threshold ionization spectra

Threshold Effects on Angular Distributions for Multiphoton Detachment by Intense Elliptically Polarized Light

Unusual threshold effects are found theoretically in the frequency and intensity dependence of angular distributions produced by an elliptically polarized laser as well as in the elliptic dichroism parameter, which measures the asymmetry of the angular distribution

Mutations in the carboxyl terminal region of E2 glycoprotein of classical swine fever virus are responsible for viral attenuation in swine

AbstractWe have previously reported [Risatti, G.R., Borca, M.V., Kutish, G.F., Lu, Z., Holinka, L.G., French, R.A., Tulman, E.R., Rock, D.L. 2005a. The E2 glycoprotein of classical swine fever virus is a virulence determinant in swine. J. Virol. 79, 3787–3796] that chimeric virus 319.1v containing the E2 glycoprotein gene from Classical Swine Fever Virus (CSFV) vaccine strain CS with the genetic background of highly virulent CSFV strain Brescia (BICv) was markedly attenuated in pigs. To identify the amino acids mediating 319.1v attenuation a series of chimeric viruses containing CS E2 residues in the context of the Brescia strain were constructed. Chimera 357v, containing CS E2 residues 691 to 881 of CSFV polyprotein was virulent, while chimera 358v, containing CS E2 residues 882 to 1064, differing in thirteen amino acids from BICv, was attenuated in swine. Single or double substitutions of those amino acids in BICv E2 to CS E2 residues did not affect virulence. Groups of amino acids were then substituted in BICv E2 to CS E2 residues. Mutant 32v, with six substitutions between residues 975 and 1059, and mutant 33v, with six substitutions between 955 and 994, induced disease indistinguishable from BICv. Mutant 31v, with seven substitutions between residues 882 and 958, induced a delayed onset of lethal disease. Amino acids abrogating BICv virulence were then determined by progressively introducing six CS residues into 31v. Mutant 39v, containing nine residue substitutions, was virulent. Mutant 40v, containing ten residue substitutions, induced mild disease. Mutant 42v, containing twelve substitutions, and mutant 43v, with an amino acid composition identical to 358v, were attenuated in swine indicating that all substitutions were necessary for attenuation of the highly virulent strain Brescia. Importantly, 358v protected swine from challenge with virulent BICv at 3 and 28 days post-infection