Research efforts to control highly pathogenic arenaviruses: a summary of the progress and gaps.

Significant progress has been made in the past 10 years in unraveling the molecular biology of highly pathogenic arenaviruses that are endemic in several West African countries (Lassa fever virus) and in some regions of South America (Argentine and Bolivian hemorrhagic fever viruses). While this has resulted in proof-of-concept studies of novel vaccine candidates in non-human primates and in the discovery of several novel antiviral small molecule drug candidates, none of them has been tested in the clinic to date. The recent Ebola outbreak in West Africa has demonstrated very clearly that there is an urgent need to develop the prophylactic and therapeutic armamentarium against viral hemorrhagic fever viruses as part of a global preparedness for future epidemics. As it pertains to this goal, the present article summarizes the current knowledge of highly pathogenic arenaviruses and identifies opportunities for translational research.

Differential and integral cross sections in OH(X) + Xe collisions.

Differential cross sections (DCSs) for inelastic collisions of OH(X) with Xe have been measured at a collision energy of 483 cm(-1). The hydroxyl (OH) radicals were initially prepared in the X(2)Π3/2 (v = 0, j = 1.5, f) level using the hexapole electric field selection method. Products were detected state-selectively by [2 + 1] resonance-enhanced multiphoton ionization of OH, combined with velocity-map imaging. Integral cross sections in OH(X) + Xe at a collision energy of 490 cm(-1) were also measured by laser-induced fluorescence. The results are compared with exact close-coupling quantum mechanical scattering calculations on the only available ab initio potential energy surface (PES). The agreement between experimental and theoretical results is generally very satisfactory. This highlights the ability of such measurements to test the available PES for such a benchmark open-shell system. The agreement between experiment and theory for DCSs is less satisfactory at low scattering angles, and possible reasons for this disagreement are discussed. Finally, theoretical calculations of OH(X) + He DCSs have been obtained at various collision energies and are compared with those of OH(X) + Xe. The role of the reduced mass in the DCSs and partial cross sections is also examined.

Inelastic scattering of hydroxyl radicals with helium and argon by velocity-map imaging.

The hydroxyl radical (OH) is one of the most interesting molecules in molecular dynamics. In particular, inelastic collisions of free radicals such as OH are profoundly important in environments ranging from combustion to astrochemistry. However, measuring the velocities of OH molecules in specific internal quantum states has proven to be very difficult. A method that can provide this important information is velocity-map imaging. Although this technique is very widely applicable in principle, it does require a sensitive and selective laser-ionization scheme. Here we show that, under the right conditions, velocity-map imaging can be applied to the study of the inelastic scattering of OH using crossed-molecular-beam methods. We measure fully quantum-state-specified product angular distributions for OH collisions with helium and argon. The agreement between exact close-coupling quantum scattering calculations on ab initio potential energy surfaces and experimental data is generally very satisfactory, except for scattering in the most forward directions.

State-to-state differential and relative integral cross sections for rotationally inelastic scattering of H2O by hydrogen.

State-to-state differential cross sections (DCSs) for rotationally inelastic scattering of H(2)O by H(2) have been measured at 71.2 meV (574 cm(-1)) and 44.8 meV (361 cm(-1)) collision energy using crossed molecular beams combined with velocity map imaging. A molecular beam containing variable compositions of the (J = 0, 1, 2) rotational states of hydrogen collides with a molecular beam of argon seeded with water vapor that is cooled by supersonic expansion to its lowest para or ortho rotational levels (J(KaKc) = 0(00) and 1(01), respectively). Angular speed distributions of fully specified rotationally excited final states are obtained using velocity map imaging. Relative integral cross sections are obtained by integrating the DCSs taken with the same experimental conditions. Experimental state-specific DCSs are compared with predictions from fully quantum scattering calculations on the most complete H(2)O-H(2) potential energy surface. Comparison of relative total cross sections and state-specific DCSs show excellent agreement with theory in almost all details.

Communication: Mapping water collisions for interstellar space conditions.

We report a joint experimental and theoretical study that directly tests the quality of the potential energy surfaces used to calculate energy changing cross sections of water in collision with helium and molecular hydrogen, at conditions relevant for astrophysics. Fully state-to-state differential cross sections are measured for H(2)O-He and H(2)O-H(2) collisions at 429 and 575 cm(-1) collision energy, respectively. We compare these differential cross sections with theoretical ones for H(2)O+H(2) derived from state-of-the-art potential energy surfaces [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)] and quantum scattering calculations. This detailed comparison forms a stringent test of the validity of astrophysics calculations for energy changing rates in water. The agreement between theory and experiment is striking for most of the state-to-state differential cross sections measured.

Imaging the inelastic scattering of water with helium. Comparison of experiment and theory.

State-to-state differential cross sections for rotationally inelastic He-H(2)O scattering have been measured at 53.3 meV (429 cm(-1)) collision energy, using the crossed molecular beam technique. The inelastic events are detected by velocity map imaging of nascent H(2)O(+) ions, which are formed by state-selective (2 + 1) resonance enhanced multiphoton ionization (REMPI) of the scattered H(2)O molecules. Raw density images are converted to flux images and the extracted differential cross sections are compared with full close-coupling calculations of state-to-state cross sections for rotational excitation based on a previously published ab initio potential. A hard-shell ellipsoid model is also employed to yield a more physical insight useful in interpreting the results. The excellent agreement of fully quantum theory and experiment found here for water collisions with helium at a collision energy relevant to that of the interstellar media place the theoretically determined potential energy surface and the collision cross sections extracted using this surface on a firmer basis.

REMPI spectroscopy and predissociation of the C(1)B(1)(v = 0) rotational levels of H(2)O, HOD and D(2)O.

Rotational analysis of the (2 + 1) resonance enhanced multiphoton ionization (REMPI) spectrum of the C(1)B(1) Rydberg state of the water isotopomers H(2)O, HOD and D(2)O is reported. Spectroscopic parameters for the v = 0 vibrational level of the C(1)B(1) state of the mixed isotopomer HOD are derived and its spectra are accurately simulated for the first time using the PGOPHER program. Simulation of two photon spectra of the C(1)B(1)-X(1)A(1) transition of HOD requires two transition moments, and the ratio of these is determined and explained by a simple geometrical model. Optimal transitions for state-selective detection of low energy rotational states are identified for all three molecules. Analysis of the linewidths in the present work, combined with previous work [H. H. Kuge and K. Kleinermanns, J. Chem. Phys., 1989, 90, 46-52; K. J. Yuan et al., Proc. Natl. Acad. Sci. U. S. A., 2008, 105, 19148-19153; M. N. R. Ashfold et al., Chem. Phys., 1984, 84, 35-50; G. Meijer et al., J. Chem. Phys., 1986, 85, 6914-6922.], suggests that while a simple ⟨J(a)'(2)〉-dependent model for heterogeneous predissociation of the C(1)B(1) Rydberg state accounts for much of the quantum number dependence, it is not sufficient for describing the predissociation in any of the three isotopomers. The component of the linewidth due to the homogeneous predissociation attributed to predissociation of the C(1)B(1) by the Ã(1)B(1) state was found to be significantly narrower than in previous work, indicating a longer lifetime of the C(1)B(1) Rydberg state. The current work provides the basis for on-going studies of rotational energy transfer in the mixed isotopomers of water using the velocity map imaging technique.

Molybdenum interlayers for nucleation enhancement in diamond CVD growth.

The use of a 50-nm thick Mo interlayer on silicon substrates for the nucleation enhancement of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films synthesized by hot filament chemical vapour deposition was studied. The MCD and NCD films were deposited using methane concentrations of 1% and 2%, respectively. The presence of a Mo nucleation layer enabled the formation of more uniform NCD films with reduced surface roughness (rms roughness approximately 40 nm for a 750-nm thick layer) and with significantly less interfacial voids due to the superior nucleation densities and surface coverage in the early stages of NCD film formation. During the initial stages of MCD film growth, the nucleation density increased by one order of magnitude as compared to uncoated silicon. As a result, much thinner MCD films with smaller surface grain sizes and, thus, reduced surface roughness could be produced as well. The presence of a Mo nucleation layer not only leads to a structural optimization of NCD and MCD films but also allows fast nucleation and film growth kinetics at relatively low substrate temperatures (approximately 575 degrees C), relevant for the coating of substrate materials that do not withstand high substrate temperatures.

Predissociation of the A2Sigma+ (v' = 3) state of the OH radical.

Predissociation of electronically excited OH A(2)Sigma(+) (v' = 3) is studied using velocity-map imaging of the atomic oxygen photofragments. Fine structure yields, angular distributions and alignment parameters are obtained for the O((3)P(J)), J = 2,1,0 products. Angular distributions for the O(3)P(0) (J = 0) fragment, which has no angular momentum polarization, agree well with predictions from the angular distribution simulation computer routine by Kim et al. [J. Chem. Phys., 2006, 125, 133316] which calculates the anisotropy of photofragment recoil as a function of dissociation lifetime, excitation frequency, rotational level, and rotational constant. When angular momentum polarization (i.e. non-equilibrium population distributions of the magnetic sublevels) of the atomic fragments is present, the polarization sensitivity of the O((3)P(J)) (2 + 1) resonance enhanced multiphoton ionization (REMPI) detection scheme used to detect the O((3)P(2,1)) products affects the measured angular distribution. Strong polarization effects are observed for the O((3)P(2,1)) products and accounted for in a simple sudden limit model for the photodissociation. In agreement with the sudden limit predictions for pre-dissociation of OH A(2)Sigma(+) (v' = 3) through the (4)Sigma(-) state, strongly aligned O((3)P(2)) is found to be the major product.

Laser-induced fluorescence of NCN in low and atmospheric pressure flames.

The cyanonitrene radical, NCN, is detected by laser-induced fluorescence in laminar, adiabatic, flat phi=1.3 methane-air flames at 200 hPa and atmospheric pressure. Laser excitation of the A approximately 3Piu(020)-X approximately 3Sigmag-(000) band at 317 nm allows off-resonant fluorescence to be detected at 326 nm. Excitation and dispersed fluorescence spectra are presented, as well as profiles of NCN and CH versus height above burner.

State-to-state inelastic scattering of OH by HI: a comparison with OH-HCl and OH-HBr.

Relative state-to-state cross sections and steric asymmetries have been measured for the scattering process: OH (X (2)Pi(32),v=0,J=32,M(J)=32,f)+HI ((1)Sigma,v=0,J<4)-->OH (X (2)Pi,v=0,Omega=12,J=12-52 and Omega=32,J=32-92,ef)+HI, at 690 cm(-1) collision energy. Comparison with the previously studied systems OH-HCl and OH-HBr reveals relevant features of the potential energy surfaces of these molecular systems. Some measured differences concerning the internal energy distribution after collision and the propensities for the impact with one or the other side of the OH molecule in scattering by HCl, HBr, and HI molecules are discussed.

Genetic identification of Kodoko virus, a novel arenavirus of the African pigmy mouse (Mus Nannomys minutoides) in West Africa.

Genetic evidence of a novel arenavirus species related to but distinct from lymphocytic choriomeningitis virus (LCMV) was obtained from a rodent belonging to an endemic African subgenus of Mus (Nannomys). The phylogenetic position among Old World arenaviruses of this new arenavirus, named Kodoko virus, was reconstructed based on L and NP genes sequences. The finding of an Old World arenavirus related to LCMV outside the known geographical range of LCMV in a novel rodent species reveals new insights about the evolutionary history of arenaviruses.

Monitoring neurotransmitter release using surface-enhanced Raman spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) is a promising tool to monitor neurotransmitter release at the single-cell level: it is a sensitive technique that provides structural information of the released compounds and spatial information about their release sites. In this study we demonstrate that depolarization-evoked catecholamine secretion by rat phaeochromocytoma (PC12) cells can be spatially resolved by SERS using silver colloids. A suitable SERS substrate was created by adding silver colloids to the cell culture medium. Nomarski-DIC microscopy combined with reflection confocal laser scanning microscopy showed that the colloids were primarily present on top of the cell membrane. The SERS spectra were successfully corrected for the contribution of cell constituents. Dopamine and noradrenaline were localized by examining the correlation coefficient between spectra and reference catecholamine spectra. Potential improvements of the temporal resolution of the technique are discussed.

Rotationally inelastic scattering of OH (2Pi 3/2, v=0, J=3/2, f) by HBr (1Sigma, v=0, J<4).

Relative state-to-state cross sections of OH molecules in the (2)Pi(32), v=0, J=32, M(J)=32, f state have been determined for transitions up to (2)Pi(32), v=0, J=112, f and (2)Pi(12), v=0, J=72, e states by collisions with HBr molecules ((1)Sigma, v=0, J<4) at 750 cm(-1) collision energy. In order to investigate features of the anisotropy of the OH-HBr potential energy surface, the steric asymmetries, which account for the effect of the OH orientation with respect to the collision partner, have been measured. A comparison with other systems previously studied shows strong similarities with the OH-HCl system.

[Detection of anti-Lassa antibodies in the Western Forest area of the Ivory Coast]. / Detection des anticorps anti-virus de Lassa dans l'ouest forestier de la Côte d'Ivoire.

Lassa fever is an African viral hemorrhagic fever (VHF) known to be endemic in a number of West African countries including Nigeria, Sierra Leone, Liberia and Guinea. Despite having common borders with Liberia and Guinea, Côte d'Ivoire has never reported any cases of Lassa fever. In March 2000, as part of a research project on VHF--mainly yellow fever, Lassa fever and Ebola fever--in Guinea and Cote d'Ivoire, an exploratory survey was conducted to assess knowledge about VHF and immunological status against Lassa virus among forest workers in the Duekoue and Guiglo regions. One hundred and sixty-three male forest workers were interviewed using a questionnaire designed to assess risk factors for VHF exposure and personal medical history over the last 12 months. Detection of IgG antibodies against Lassa virus was performed by immunofluorescence assay with Lassa virus antigens from the Josiah and Las/AV strains. The overall prevalence of IgG antibodies was 26% (42/161). Among the Lassa IgG positive subjects, 38.5% were loggers including 20% that were positive at a serum dilution of 1/40 and 46.7% were national park workers or forest rangers including 69% that were positive at a dilution of 1/40 and more. Forty-one percent of subjects had heard of VHF including 14% who attributed it to animals and 2% who attributed it to plants. Contact with rodents was frequent and more than 50% of subjects had either eaten or skinned rodents. Although the prevalence of anti-Lassa IgG antibodies seemed high in the study population, no conclusion can be about level of exposure to Lassa virus.

Detection des anticorps anti-virus de Lassa dans l'ouest forestier de la Cote d'Ivoire

La fievre de Lassa est une fievre hemorragique virale (FHV) africaine endemique en Afrique de l'Ouest; notamment au Nigeria; en Sierra Leone; au Liberia et en Guinee. La Cote d'ivoire qui part age des frontieres avec le Liberia et la Guinee n'a jamais notifie de cas de fievre de Lassa. Dans le cadre d'un projet de recherche sur les fievres hemorragiques virales principalement la fievre jaune; la fievre de Lassa et la fievre Ebola en Guinee et en Cote d'Ivoire; une enquete a ete realisee en mars 2000 chez des travailleurs forestiers des prefectures de Guiglo et Duekoue; dans le but de determiner le niveau de connaissance sur les fievres hemorra-giques virales et le statut immunitaire vis a vis du virus de Lassa. Cent soixante-trois sujets de sexe masculin professionnels de la foret ont ete interroges a l'aide d'un questionnaire sur les facteurs de risque d'exposition aux FHV et leurs antecedents medicaux des 12 dern i e rs mois. Les anticorps seriques de type IgG anti-virus de Lassa ont ete detectes par technique d'immunofluorescence utilisant les antigenes Lassa des souches Josuah et LAS/AV. La prevalence globale en IgG obtenue etait de 26(42/161). Pa rmi les sujets positifs; 38;5etaient des bucherons dont 20positifs au 1/40; 46;7des agents du parc national ou gardes forestieres dont 69positifs au 1/40 et plus. De plus; 41des sujets avaient entendu parler des FHV; 14ont attribue leur origine a des animaux et 2a des plantes. Les contacts avec les rongeurs etaient frequents et plus de 50des personnes ont deja consomme ou depece des rongeurs. La proportion de sujets porteurs d'anticorps IgG anti-virus de Lassa dans cette population semblait elevee. Cependant cette prevalence ne permet pas de conclure a une exposition particuliere au virus de Lassa

Steric effects in state-to-state scattering of OH (2pi(3/2),J=3/2,f) by HCl.

In this paper we address stereo-dynamical issues in the inelastic encounters between OH (chi2pi) radicals and HCl (chi1sigma+). The experiments were performed in a crossed molecular-beam machine at the nominal collision energy of 920 cm(-1). Prior to the collisions, the OH molecules were selected using a hexapole in a well-defined rotational state v=0, omega=32, J=32, M(J)=32, f, and subsequently oriented in a homogeneous electrical field. We have measured rotationally resolved relative cross sections for collisions in which OH is oriented with either the O side or the H side towards HCl, from which we have calculated the corresponding steric asymmetry factors S. The results are presented in comparison with data previously obtained by our group for the inelastic scattering of OH by CO (E(coll)=985 cm(-1)) and N2 (E(coll)=985 cm(-1)) studied under similar experimental conditions. The dissimilarity in the behavior of the OH+HCl system revealed by this comparison is explained on the basis of the difference in the anisotropy of the interaction potential governing the collisions. The interpretation of the data takes into account the specific features of both nonreactive and reactive parts of the potential-energy surface. The results indicate that the scattering dynamics at this collision energy may be influenced by the HO-HCl van der Waals well and by reorientation effects determined by the long-range electrostatic forces and, furthermore, may involve reactive collisions.

Inelastic state-to-state scattering of OH (2Pi3/2, J=3/2,f) by HCl.

Parity resolved state-to-state cross sections for inelastic scattering of OH (X2Pi) by HCl were measured in a crossed molecular beam experiment at the collision energy of 920 cm(-1). The OH (X2Pi) radicals were prepared in a single quantum state, Omega=3/2, J=3/2, MJ=3/2, f, by means of electrostatic state selection in a hexapole field. The rotational distribution of the scattered OH radicals by HCl was probed by saturated LIF spectroscopy of the 0-0 band of the A 2Sigma+ - X 2Pi transition. Relative state-to-state cross sections were measured for rotational excitations up to J=9/2 within the Omega=3/2 spin-orbit manifold and up to J=7/2 within the Omega=1/2 spin-orbit manifold. A propensity for spin-orbit conserving transitions was found, but no propensity for excitation into a particular Lambda-doublet component of the same rotational state was evident. The data are presented and discussed in comparison with results previously obtained for collisions of OH with CO (Ecoll=450 cm(-1)) and N2 (Ecoll=410 cm(-1)) and with new data we have measured for the OH+CO system at a comparable collision energy (Ecoll=985 cm(-1)). This comparison suggests that the potential energy surface (PES) governing the interaction between OH and HCl is more anisotropic than the PES's governing the intermolecular interaction of OH with CO and N2.

Quantitative spectrally resolved imaging through a spectrograph.

A grating spectrograph can be used for spectrally selective two-dimensional imaging if it is operated with a broad entrance slit. The resulting intensity distribution in its exit plane is a one-dimensional convolution of the spatial and spectral distributions of incident light. We present a dedicated deconvolution filter to reconstruct the spatial image from the spectrograph output. The algorithm is illustrated on Raman imaging of an underexpanded dry air jet. Recorded Raman images correspond to density maps convolved with the Raman spectrum of air; the latter essentially acts as a blurring function for the density map. The deconvolution filter combines the individual images recorded in the O2 and N2 Raman bands into a single image of relative air density.