RESUMEN
We present a joint experimental-theoretical study on the effect of the carrier-envelope phase (CEP) of a few-cycle pulse on the atomic excitation process. We focus on the excitation rates of argon at intensities in the transition between the multiphoton and tunneling regimes. Through numerical simulations, we show that the resulting bound-state population is highly sensitive to both the intensity and the CEP. The experimental data clearly agree with the theoretical prediction, and the results encourage the use of precisely tailored laser fields to coherently control the strong-field excitation process. We find a markedly different behavior for the CEP-dependent bound-state population at low and high intensities with a clear boundary, which we attribute to the transition from the multiphoton to the tunneling regime.
RESUMEN
AIMS: Existing methods for the identification of the subspecies of Xylella fastidiosa are time-consuming which can lead to delays in diagnosis and the associated plant health response to outbreaks and interceptions. METHODS AND RESULTS: Diagnostic markers were identified using a comparative genomics approach to allow fine differentiation of the very closely related subspecies. Five qPCR assays were designed to allow specific detection of X. fastidiosa subsp. fastidiosa, X. fastidiosa subsp. multiplex, X. fastidiosa subsp. pauca, X. fastidiosa subsp. morus and X. fastidiosa subsp. sandyi. All assays were validated according to the European and Mediterranean Plant Protection Organisation (EPPO) standard PM7/98(2). CONCLUSIONS: All of the assays were shown to be specific to the target subspecies and all the assays could be used to detect femtogram quantities of X. fastidiosa DNA. SIGNIFICANCE AND IMPACT OF THE STUDY: At present, diagnosing the subspecies of X. fastidiosa requires multiple conventional PCR assays (although only available for three of the five subspecies) or multi-locus sequence typing which takes several days. By comparison, the new assays provide a substantial reduction in the turnaround time for direct identification to the subspecies level in as little as 75 min.
Asunto(s)
Genómica , Enfermedades de las Plantas , Reacción en Cadena en Tiempo Real de la Polimerasa , Xylella/clasificación , ADN Bacteriano/genética , Tipificación de Secuencias Multilocus , Enfermedades de las Plantas/microbiologíaRESUMEN
We present a detailed experimental and theoretical study on the relativistic nondipole effects in strong-field atomic ionization by near-infrared linearly polarized few-cycle laser pulses in the intensity range of 10^{14}-10^{15} W/cm^{2}. We record high-resolution photoelectron momentum distributions of argon using a reaction microscope and compare our measurements with a truly ab initio fully relativistic 3D model based on the time-dependent Dirac equation. We observe counterintuitive peak shifts of the transverse electron momentum distribution in the direction opposite to that of laser propagation as a function of laser intensity and demonstrate an excellent agreement between the experimental results and theoretical predictions.
RESUMEN
We demonstrate the generation of metastable krypton in the long-lived 1s^{5} state using laser excitation. The atoms are excited through a two-photon absorption process into the 2p^{6} state using a pulsed optical parametric oscillator laser operating near 215 nm, after which the atoms decay quickly into the metastable state with a branching ratio of 75%. The interaction dynamics are modeled using density matrix formalism and, by combining this with experimental observations, we are able to calculate photoionization and two-photon absorption cross sections. When compared to traditional approaches to metastable production, this approach shows great potential for high-density metastable krypton production with minimal heating of the sample. Here, we show metastable production efficiencies of up to 2% per pulse. The new experimental results gained here, when combined with the density matrix model we have developed, suggest that fractional efficiencies up to 30% are possible under optimal conditions.
RESUMEN
This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrödinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and measure the ionisation rate as the a function of different steady-state populations in the fine structure of the target state which shows significant ionisation rate dependence on populations of spin-polarised states. The physical mechanism for this effect is unknown.
RESUMEN
A 38-year-old HIV-positive Nigerian woman presented with a three-week history of cervical lymphadenopathy, night sweats, weight loss and fever. Provisional diagnoses of tuberculosis and lymphoma were considered; however, a histological diagnosis of Kikuchi-Fujimoto Disease was reached. This rare benign disease has presenting features that mimic more serious conditions commonly occurring in HIV-positive patients. This case report emphasises the importance of Kikuchi-Fujimoto Disease in the differential diagnosis of cervical lymphadenopathy in HIV-positive patients.
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Infecciones por VIH/complicaciones , Linfadenitis Necrotizante Histiocítica/complicaciones , Linfadenitis Necrotizante Histiocítica/diagnóstico , Ganglios Linfáticos/patología , Adulto , Analgesia/métodos , Población Negra , Diagnóstico Diferencial , Femenino , Fiebre/etiología , Linfadenitis Necrotizante Histiocítica/terapia , Humanos , Nigeria , Resultado del TratamientoRESUMEN
The complete nucleotide sequences of RNA 1 and RNA 2 of the nepovirus potato black ringspot virus (PBRSV) from two different isolates were determined, as well as partial sequences from two additional isolates. RNA1 is 7,579-7,598 nucleotides long and contains one single open reading frame (ORF), which is translated into a large polyprotein with 2,325 amino acids and a molecular weight of 257 kDa. The complete sequence of RNA2 ranges from 3857 to 3918 nt between the different isolates. It encodes a polyprotein of 1079-1082 amino acids with a molecular weight of 120 kDa. Sequence comparison using the Pro-Pol region and CP showed that all four isolates formed two distinct groups, corresponding to potato and arracacha, that were closely related to each other and also to tobacco ringspot virus (TRSV). Comparing our data to those obtained with other nepoviruses, our results confirm that PBRSV belongs to a distinct species and is a member of subgroup A in the genus Nepovirus based on its RNA2 size, genome organization, and nucleotide sequence.
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Genoma Viral , Nepovirus/clasificación , Nepovirus/genética , ARN Viral/genética , Análisis de Secuencia de ADN , Análisis por Conglomerados , Datos de Secuencia Molecular , Peso Molecular , Nepovirus/aislamiento & purificación , Sistemas de Lectura Abierta , Filogenia , Homología de Secuencia , Solanum tuberosum/virología , Proteínas Virales/química , Proteínas Virales/genéticaRESUMEN
This study reports the first complete genome sequence of Piper yellow mottle virus (PYMoV, KC808712) identified in black pepper. The genome is 7,622 nucleotides long, possessing four open reading frames (ORFs). ORF1, ORF2 and ORF4 of PYMoV are reported as hypothetical proteins of unknown function with a predicted molecular mass of 15.7, 17.1 and 17.9 kDa, respectively. ORF3 of PYMoV encodes a polyprotein of 218.6 kDa and consists of a viral movement protein (MP), trimeric dUTPase, zinc finger, retropepsin, RT-LTR, and RNAse H. Detailed PYMoV genome analysis confirmed that it is a member of the family Caulimoviridae, genus Badnavirus. Fragments of two additional novel sequences resembling those found in members of the family Caulimoviridae were also identified in the black pepper sample, and the viruses from which they were derived were tentatively named Piper DNA virus 1 and 2.
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Badnavirus/genética , ADN Viral/química , ADN Viral/genética , Genoma Viral , Badnavirus/aislamiento & purificación , Datos de Secuencia Molecular , Peso Molecular , Sistemas de Lectura Abierta , Piper nigrum/virología , Análisis de Secuencia de ADN , Proteínas Virales/química , Proteínas Virales/genéticaRESUMEN
The complete genome sequences of RNA1 and RNA2 of the oca strain of the potato virus arracacha virus B were determined using next-generation sequencing. The RNA1 molecule is predicted to encode a 259-kDa polyprotein with homology to proteins of the cheraviruses apple latent spherical virus (ALSV) and cherry rasp leaf virus (CRLV). The RNA2 molecule is predicted to encode a 102-kDa polyprotein which also has homology to the corresponding protein of ALSV and, to a lesser degree, CRLV (30 % for RNA1, 24 % for RNA2). Detailed analysis of the genome sequence confirms that AVB is a distinct member of the genus Cheravirus.
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Genoma Viral , Virus de Plantas/genética , Virus ARN/genética , Secuencia de Aminoácidos , Secuencia de Bases , Regulación Viral de la Expresión Génica/fisiología , Datos de Secuencia Molecular , Filogenia , Virus de Plantas/clasificación , Poliproteínas/genética , Poliproteínas/metabolismo , Virus ARN/clasificación , ARN Viral/genética , ARN Viral/metabolismo , Proteínas Virales/genética , Proteínas Virales/metabolismoRESUMEN
Canna yellow streak virus (Potyvirus, Potyviridae) was sequenced using the novel method of next-generation pyrosequencing. The complete genome was found to be 9,502 nucleotides excluding the poly-A tail with a predicted genome organisation typical for a member of the genus Potyvirus. As with other potyviruses that infect monocotyledons, some of the predicted cleavage sites of the polyprotein genome were unusual, such as a glutamic acid/threonine (E/T) between the CI and 6K2 proteins and a glutamic acid/aspartic acid (E/D) between the NIa and NIb proteins. Evidence of the presence of endogenous pararetroviruses in the canna genome was found from the large number of sequences obtained with this method.
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Genoma Viral , Potyvirus/genética , Secuencia de Bases , Cannabaceae/virología , Datos de Secuencia Molecular , Filogenia , Enfermedades de las Plantas/virología , Potyvirus/clasificación , Potyvirus/aislamiento & purificaciónRESUMEN
We investigate the nonlinear optical phenomenon of self-focusing in air with phase-stabilized few-cycle light pulses. This investigation looks at the role of the carrier-envelope phase by observing a filament in air, a nonlinear phenomenon that can be utilized for few-cycle pulse compression [Appl. Phys. B79, 673 (2004)]. We were able to measure the critical power for self-focusing in air to be 18+/-1 GW for a 6.3 fs pulse centered at 800 nm. Using this value and a basic first-order theory, we predicted that the self-focusing distance should deviate by 790 mum as the carrier-envelope phase is shifted from 0 to pi/2 rad. In contrast, the experimental results showed no deviation in the focus distance with a 3sigma upper limit of 180 mum. These counterintuitive results show the need for further study of self-focusing dynamics in the few-cycle regime.
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The complete genome sequence for an isolate of the Ugandan and Tanzanian strain types of Cassava brown streak virus have been determined using the novel approach of non-directed next generation sequencing. Comparison of the genome sequences revealed that CBSV is highly heterogeneous at the isolate level as well as the strain level. The isolate of the Ugandan strain was found to have a genome 9,070 nucleotides long coding for a polypeptide with 2,902 amino acid residues. The isolate of the Tanzanian strain was 9,008 nucleotides long and coded for a polypeptide with 2,916 amino acid residues. Nucleotide identity between the isolates across the genome was 76%, with protein encoding regions 57-77% and individual proteins had 65-91% amino acid similarity. In addition between the two strains four protein products (PIPO, CI, NIa-Vpg and coat protein) varied in size and an unusual HAM1-like protein, whilst of identical nucleotide length, was found to have the lowest homology. The implication of diversity of CBSV is discussed in the context of speciation, evolution, development of diagnostics, and breeding for resistance.
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Enfermedades de las Plantas/virología , Potyviridae/genética , ARN Viral/genética , Análisis de Secuencia de ADN , Manihot/virología , Datos de Secuencia Molecular , Polimorfismo Genético , Potyviridae/aislamiento & purificación , Homología de Secuencia de Aminoácido , Homología de Secuencia de Ácido Nucleico , Sintenía , Tanzanía , UgandaRESUMEN
Identification of the juveniles of economically important thrips species on imports by morphology alone can be challenging and culturing is usually required. In the case of EU quarantine species such as Thrips palmi, rapid and accurate identification is essential. DNA barcoding using the Cytochrome oxidase I (COI) gene has become a popular technique for species identification; however, in some invertebrate genera COI has been shown to provide insufficient variability for species discrimination. This study presents a comparison of five different loci to investigate their ability to discriminate a small number of Thrips species. All five loci discriminated the species by neighbour-joining tree and varying degrees of discrimination were determined upon further investigation of the intraspecific and interspecific distances. Two distinct COI clades were observed for T. Palmi and judged to be COI haplotypes when data from the other four additional loci and geographical collection data were taken into consideration. COI was shown to provide sufficient variation to be used in future DNA barcoding efforts within the genus Thrips.
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We present a new technique to measure absolute total collision cross sections from metastable neon atoms. The technique is based on the observation of the decay rate of trapped atoms as they collide with room temperature atoms. We present the first measurement of this kind using trapped neon atoms in the (3)P(2) metastable state colliding with thermal ground state argon. The measured cross section has a value of 556+/-26 A(2).
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Técnicas Químicas Combinatorias/instrumentación , Gases/química , Magnetismo/instrumentación , Ensayo de Materiales/instrumentación , Óptica y Fotónica/instrumentación , Radiometría/instrumentación , Espectrofotometría Atómica/instrumentación , Técnicas Químicas Combinatorias/métodos , Ensayo de Materiales/métodos , Radiometría/métodos , Espectrofotometría Atómica/métodosAsunto(s)
Tuberculosis Bovina/historia , Tuberculosis/historia , Animales , Bovinos , Historia del Siglo XIX , Historia del Siglo XX , Enfermedades de los Caballos/historia , Caballos , Humanos , Paratuberculosis/historia , Paratuberculosis/microbiología , Prueba de Tuberculina/historia , Tuberculosis/diagnóstico , Tuberculosis/prevención & control , Tuberculosis Bovina/prevención & control , Tuberculosis Bovina/transmisiónRESUMEN
The quenching of the Y(D)(.) tyrosyl radical in photosystem II by nitric oxide was reported to result from the formation of a weak tyrosyl radical-nitric oxide complex (Petrouleas, V., and Diner, B. A. (1990) Biochim. Biophys. Acta 1015, 131-140). This radical/radical reaction is expected to generate an electron spin resonance (ESR)-silent 3-nitrosocyclohexadienone species that can reversibly regenerate the tyrosyl radical and nitric oxide or undergo rearrangement to form 3-nitrosotyrosine. It has been proposed that 3-nitrosotyrosine can be oxidized by one electron to form the tyrosine iminoxyl radical (>C=N-O*). This proposal was put forth as a result of ESR detection of the iminoxyl radical intermediate when photosystem II was exposed to nitric oxide (Sanakis, Y., Goussias, C., Mason, R. P., and Petrouleas, V. (1997) Biochemistry 36, 1411-1417). A similar iminoxyl radical was detected in prostaglandin H synthase-2 (Gunther, M. R., Hsi, L. C., Curtis, J. F., Gierse, J. K., Marnett, L. J., Eling, T. E., and Mason, R. P. (1997) J. Biol. Chem., 272, 17086-17090). Although the iminoxyl radicals detected in the photosystem II and prostaglandin H synthase-2 systems strongly suggest a mechanism involving 3-nitrosotyrosine, the iminoxyl radical ESR spectrum was not unequivocally identified as originating from tyrosine. We report here the detection of the non-protein L-tyrosine iminoxyl radical generated by two methods: 1) peroxidase oxidation of synthetic 3-nitroso-N-acetyl-L-tyrosine and 2) peroxidase oxidation of free L-tyrosine in the presence of nitric oxide. A newly developed ESR technique that uses immobilized enzyme was used to perform the ESR experiments. Analysis of the high resolution ESR spectrum of the tyrosine iminoxyl radical generated from free tyrosine and nitric oxide reveals a 28.4-G isotropic nitrogen hyperfine coupling and a 2.2-G proton hyperfine coupling assigned to the proton originally ortho to the phenoxyl oxygen.
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Radicales Libres , Óxido Nítrico/química , Compuestos Nitrosos/química , Tirosina/química , Antioxidantes/química , Ácido Ascórbico/química , Espectroscopía de Resonancia por Spin del Electrón , Iminas/química , Oxidación-Reducción , Tirosina/análogos & derivadosRESUMEN
The occurrence and characterization of yeasts isolated from sorghum beer produced in Ghana and Burkina Faso, West Africa, were investigated. The yeasts involved in the fermentations were found to consist of Saccharomyces spp. almost exclusively. Of the isolates investigated, 45% were identified as Saccharomyces cerevisiae, whereas more than half of the isolates (53%) had physiological properties atypical of S. cerevisiae or any other member of the complex sensu strictu, as they were able to assimilate only glucose, maltose and ethanol as carbon sources. Both ITS-PCR RFLP and PFGE strongly indicated that these isolates were related to S. cerevisiae, regardless of their phenotypic characteristics. Sequencing of the D1/D2 domain of the 26S rDNA confirmed the close relatedness to S. cerevisiae with 0.5% nucleotide differences. The MAL1 and MAL3 loci were found for all isolates as the only recognized MAL loci. Besides, for 40% of the isolates the MAL61 probe hybridized to a position of about 950 kbp, which has not formerly been described as a MAL locus. The results showed that the spontaneous fermentation of West African sorghum beer is dominated by a variety of strains of S.cerevisiae not previously described, among which starter cultures should be selected.
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Cerveza/microbiología , Proteínas de Transporte de Monosacáridos , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/clasificación , Saccharomyces cerevisiae/fisiología , Simportadores , Secuencia de Bases , Burkina Faso , Proteínas Portadoras/genética , Cromosomas Fúngicos/genética , ADN de Hongos/genética , ADN Ribosómico/genética , Electroforesis en Gel de Campo Pulsado , Fermentación , Proteínas Fúngicas/genética , Genes Fúngicos , Genotipo , Ghana , Maltosa/metabolismo , Datos de Secuencia Molecular , Fenotipo , Poaceae , Reacción en Cadena de la Polimerasa , Polimorfismo Genético , Polimorfismo de Longitud del Fragmento de Restricción , ARN Ribosómico/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/aislamiento & purificación , Análisis de Secuencia de ADNRESUMEN
The Emergency Medical Treatment and Labor Act imposes a number of requirements on hospital outpatient treatment departments, including the assurance of patient access to hospital care for providers participating in the Medicare program. The author describes the key provisions of the legislation, including hospital staffing and policy requirements.
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Servicios Médicos de Urgencia/legislación & jurisprudencia , Adhesión a Directriz , Servicio Ambulatorio en Hospital/legislación & jurisprudencia , Transferencia de Pacientes/legislación & jurisprudencia , Servicios Médicos de Urgencia/normas , Tratamiento de Urgencia/normas , Accesibilidad a los Servicios de Salud/legislación & jurisprudencia , Humanos , Medicare/legislación & jurisprudencia , Servicio Ambulatorio en Hospital/normas , Admisión y Programación de Personal/legislación & jurisprudencia , Estados UnidosRESUMEN
Electron paramagnetic resonance (EPR) spectroscopy was used to study the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on endotoxin (lipopolysaccharide)-induced nitric oxide (NO) production in Fischer rats. We found that rats treated with 50 microg/kg TCDD had increased sensitivity to endotoxin, resulting in an approximately 2-fold increase in the level of NO production detected as nitrosylhemoglobin (HbNO) in venous blood. At lower concentrations (< or = 5 microg/kg), TCDD did not affect the endotoxin-induced NO production. The TNF-alpha serum concentration was found to parallel that of NO. TCDD alone did not induce the production of detectable HbNO or TNF-alpha. We found that TCDD induced a dose-dependent increase in the EPR signal intensity of (Fe(3+)) low-spin methemoprotein complexes found in the liver and kidney. These species with EPR resonance at g = 2.43, 2.26, and 1.92 are attributed to low-spin Fe(3+) in cytochromes P450 and P420. Our data confirm previous studies that have shown that TCDD induces a dose-dependent increase in the production of some cytochrome P450 enzymes. However, in rats that were subsequently challenged with endotoxin, a smaller increase in the EPR intensity of these species was observed. The decrease in the low-spin Fe(3+) cytochrome P450 EPR signal in endotoxin-challenged rats could be due to one or more of the following occurring: (1) cytochrome destruction, (2) reduction of the ferric to the ESR-silent ferrous oxidation state of cytochromes by nitric oxide, and/or (3) formation of ferrous nitrosyl cytochrome complexes that contribute, in part, to the characteristic five-coordinate nitrosyl hemoprotein triplet also observed in these tissues. Since low concentrations of endotoxin can leak from the gut lumen into the systemic circulation, this investigation explores the possibility that endotoxin interaction with TCDD may be, in part, responsible for the effects of TCDD observed in these tissues.