Para States Research Articles

Observation of nuclear spin species conversion inside the 1593 cm −1 structure of H 2O trapped in argon matrices: Nitrogen impurities and the H 2O:N 2 complex

We have investigated, at high resolution (0.03 cm −1), the 1593 cm −1 structure observed in the IR absorption spectrum of water trapped in solid argon doped with nitrogen. It exhibits a doublet at 1592.59 ± 0.05 and 1593.08 ± 0.05 cm −1 and a line centered at 1592.93 ± 0.05 cm −1. The central component, which increases irreversibly upon annealing and when the concentration is increased, is due to the proton acceptor submolecule of the H 2O dimer, as mentioned in the literature. The doublet is assigned to the H 2O:N 2 complex. After a fast cooling of the sample from 20 to 4 K, the low frequency line of the doublet decreases with time and the high frequency one increases, the total integrated absorption increasing slightly. The ratio of the integrated intensities between the low frequency component and the high frequency one reaches a constant limit of 0.5 ± 0.1 at infinite time. This time behavior, perfectly exponential with a time constant τ of about 680 min, is reproducible. As the nitrogen molecule cannot rotate in an argon substitutional site, and as the H 2O submolecule seems to preserve somewhat its identity, this is interpreted as nuclear spin species conversion between ortho and para states of the H 2O submolecule within the complex. The order of magnitude of the energy difference between the ortho and para lowest levels, about 5 cm −1, is too weak to imply any, even very hindered, rotational motion of H 2O, but it could be the energy range of a tunneling effect. When the temperature is increased, the two components coalesce at 25 K into a single symmetrical line pointing at 1593.3 cm −1 and the conversion time shortens dramatically. An Arrhenius plot leads to a weak activation energy of the conversion process (about 30 cm −1). A possible geometry of the complex in solid argon, different from the gas phase one, is proposed.

Spectroscopy and potential energy surface of the H2–CO2van der Waals complex: experimental and theoretical studies

A 4-D ab initio potential energy surface is calculated for the intermolecular interaction of hydrogen and carbon dioxide, using the CCSD(T) method with a large basis set. The surface has a global minimum with a well depth of 212 cm(-1) and an intermolecular distance of 2.98 A for a planar configuration with both the O-C-O and H-H axes perpendicular to the intermolecular axis. Bound state calculations are performed for the H(2)-CO(2) van der Waals complex with H(2) in both the para and ortho spin states, and the binding energy of paraH(2)-CO(2)(50.4 cm(-1)) is found to be significantly less than that of orthoH(2)-CO(2)(71.7 cm(-1)). The surface supports 7 bound intermolecular vibrational states for paraH(2)-CO(2) and 19 for orthoH(2)-CO(2), and the lower rotational levels with J< or = 4 follow an asymmetric rotor pattern. The calculated infrared spectrum of paraH(2)-CO(2) agrees well with experiment. For orthoH(2)-CO(2), the ground state rotational levels allowed by symmetry are found to have (K(a), K(c))=(even, odd) or (odd, even). This somewhat unexpected fact enables the previously observed experimental spectrum to be assigned for the first time, in good agreement with theory, and indicates that the orientation of hydrogen is perpendicular to the intermolecular axis in the ground state of the orthoH(2)-CO(2) complex.

Human Hantavirus Infection, Brazilian Amazon

Human Hantavirus Infection, Brazilian Amazon

Validity of &lt;I&gt;Homalodisca&lt;/I&gt; and of &lt;I&gt;H. vitripennis&lt;/I&gt; as the Name for Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae: Cicadellinae)

Abstract A male of Tettigonia vitripennis Germar—deposited in the recently rediscovered Germar Hemiptera collection, in the Ivan Franko National University (Ukraine)—is designated as the lectotype and assumed to be erroneously labeled as from Brazil. Homalodisca vitripennis is considered a senior synonym of Tettigonia coagulata syn. nov. and therefore should be used as the scientific name for the glassy-winged sharpshooter, a major vector of the bacterial Pierce’s disease of grapes, phony peach disease, plum leaf scald, and oleander leaf scorch in southern United States and northern Mexico. The previously designated type species of Homalodisca Stal, Cicada triquetra F., was found to be mistaken by Stal for C. triangularis F., which is herein fixed as the new type species of this economically important genus. Propetes triquetra comb. nov., previously known only from an unknown locality in South America, is newly recorded from Brazil (Mato Grosso and Para states).

Produção de metabólitos bioativos pelo líquen Cladonia substellata Vainio

Objetivando comparar a atividade antimicrobiana de extratos brutos de Cladonia substellata, proveniente dos Estados de Minas Gerais e Pará, Brasil, utilizou-se o método de difusão em meio sólido. Extratos etéreo, clorofórmico e acetônico foram testados contra patógenos humanos e fitopatógenos na concentração de 1,0 mg/mL, 0,1 mg/mL e 0,01 mg/mL. Os extratos foram submetidos à cromatografia em camada delgada, e o princípio ativo atribuído através de biocromatografia. Os resultados demonstraram que as sete espécies de fungos testadas foram resistentes aos extratos de C. substellata procedente do Pará, porém, quatro destas espécies mostraram-se sensíveis aos extratos etéreo e clorofórmico da amostra de Minas Gerais. Todos os extratos foram ativos contra as mesmas espécies de bactérias, entretanto os extratos da amostra procedente de Minas Gerais demonstraram melhor atividade. Das bactérias inibidas, Staphylococcus aureus mostrou-se a menos sensível, ao contrário das fitopatógenas que apresentaram grande sensibilidade. Os testes cromatográficos revelaram a presença de ácido úsnico em todos os extratos, porém, em maior quantidade na amostra do Pará. O biocromatograma revelou este ácido como princípio ativo da espécie, além de sua ação sinérgica com o ácido norestíctico, na amostra de Minas Gerais, justificando sua maior atividade.

Produção de soros policlonais com alta afinidade contra o biotipo 'C' e o biotipo 'S' de Crinipellis perniciosa

A obtenção de soros policlonais contra fitopatógenos tem por finalidade a elaboração de imunoensaios que permitam identificar e caracterizar os mesmos com rapidez e a custos baixos. Soros policlonais foram produzidos contra extratos das hifas de isolados de Crinipellis perniciosa, agente causal da vassoura-de-bruxa, coletados de cacaueiro (Theobroma cacao) nos estados do Pará e Bahia para identificação e caracterização de isolados de diversas regiões e hospedeiros. O soro denominado de 1 foi produzido a partir do isolado ESJOH-1 (originário do Pará), e o soro 2 foi produzido com o isolado CP-85 (originário da Bahia). Não houve reação cruzada dos soros contra extratos protéicos das espécies Alternaria solani, Marasmius sp., Oudemansiella canarii e Verticillium fungicola. Os soros apresentaram reação cruzada de alta afinidade com extratos de Moniliophthora roreri e de baixa a média afinidade com Marasmius cladophyllus. A caracterização dos isolados foi feita com amostras do biotipo-C coletados no Amazonas, Bahia, Mato Grosso, Rondônia e Pará. As reações sorológicas dos dois soros não permitiram diferenciar os isolados do Pará e da Bahia, contra os quais foram produzidos, e também não reagiram diferencialmente com isolados de outros estados. O reconhecimento dos antígenos entre os soros foi variável, pois o soro 1 e soro 2 apresentaram reação sorológica diferenciada para alguns isolados. Os soros produzidos apresentaram alta afinidade contra isolados dos biotipos-C e S, independente de sua origem geográfica, podendo ser usados para identificação.

The hydrogen ortho-to-para ratio in the stratospheres of the giant planets

Observations of the H 2 S(0) and S(1) quadrupole lines in the four giant planets by the short-wavelength spectrometer of the Infrared Space Observatory are analyzed. These lines probe pressure levels located between 10 and 1 mbar and allow us to determine the stratospheric hydrogen para fraction for the first time. In Jupiter and Saturn, the stratospheric para fraction is close to its tropopause value. In the stratosphere of these planets as well as in Neptune’s, the para fraction presents a significant departure from thermodynamic equilibrium. This situation results from a lagged conversion between the ortho and the para states as molecular hydrogen is transported upward under the influence of turbulent eddy diffusion. In contrast, the uranian stratosphere lies close to thermodynamic equilibrium. The magnitude of the departure from thermodynamic equilibrium appears to be anti-correlated with the amount of stratospheric aerosols. To validate this assumption, we estimate the hydrogen equilibration time with a one-dimensional diffusion model for different conversion processes in the gas phase or on aerosols. The comparison between our results and the tropospheric estimates from Conrath et al. (1998, Icarus, 135, 501–517) shows that paramagnetic conversion on aerosols matches the estimated tropospheric and stratospheric relaxation times in the four giant planets. In contrast, paramagnetic conversion in the gas phase can only explain the relaxation times measured in Jupiter and Saturn atmospheres. This situation provides quantitative evidence for an equilibration mechanism dominated by conversion on aerosols.

Spin-selective adsorption of water vapor

The spin-selective adsorption of water vapor on an aluminum-oxide surface was discovered about a decade ago (see, e.g., [1]). As was shown in [2], this effect can be used to separate the spin isomers of water by frontal chromatography. When hydrogen spins in a water molecule are parallel and antiparallel to each other, the molecule is in the ortho and para states, respectively. The ratio of the statistical weights of the ortho and para states is equal to three; therefore, in an equilibrium water vapor under normal conditions, the ratio of orthoto-para isomer content is equal to three. Since transitions between molecular ortho and para states are forbidden, water vapor is essentially a mixture of independent ortho and para fractions. In this paper, we describe a laboratory experiment in which the equilibrium orthoto-para ratio 3 : 1 in water vapor was changed by at least a factor of 3 by spin-selective adsorption. This phenomenon is qualitatively explained. It is shown that the change in the ortho-to-para ratio in the real atmosphere can be responsible for marked variations in its radiative characteristics.

Ortho and paraO−H2complexes in silicon

Interstitial ${\mathrm{H}}_{2}$ becomes bound to interstitial O in silicon, forming an ${\mathrm{O}\ensuremath{-}\mathrm{H}}_{2}$ complex. Infrared absorption experiments performed for the O-HD complex in Si reveal HD vibrational lines that appear at elevated temperature $(T&gt;10\mathrm{K}).$ These lines and their properties lead to the conclusion that the ${\mathrm{H}}_{2}$ molecule in the ${\mathrm{O}\ensuremath{-}\mathrm{H}}_{2}$ complex is a nearly free rotor. Two near-lying lines seen for the oxygen mode of the ${\mathrm{O}\ensuremath{-}\mathrm{H}}_{2}$ complex are attributed to the ortho and para ${\mathrm{O}\ensuremath{-}\mathrm{H}}_{2}$ complexes. The ortho and para states of the ${\mathrm{O}\ensuremath{-}\mathrm{H}}_{2}$ complex also give rise to ${\mathrm{H}}_{2}$ vibrational lines with distinct properties. These results may be understood in terms of a hindered-rotor model for the hydrogen molecule.

Relação da circunferência escrotal e parâmetros da qualidade do sêmen em touros da raça Nelore, PO

Em 960 touros da raça Nelore, PO, de 11,4 a 135 meses de idade, pertencentes a fazendas localizadas nos Estados de São Paulo, Goiás e Pará, estudou-se a possível associação entre o tamanho da circunferência escrotal (CE) e os parâmetros da qualidade do sêmen, motilidade progressiva (MOT) e patologias espermáticas: defeitos maiores (DEFMAI), menores (DEFMEN) e totais (DEFTOT). Os touros foram divididos por faixas etárias em: menores que 18, de 18 a 24, de 24 a 30, de 30 a 36 e maiores que 36 meses de idade. Este estudo foi realizado com a finalidade de obter tamanhos de CE que possam indicar o estatus funcional dos testículos, ou seja, a qualidade do sêmen, a serem utilizados para predizer o potencial reprodutivo dos animais destinados à seleção de reprodutores. Da correlação da CE com a MOT, por faixa etária, resultou uma associação (R=0,60; P&lt;0,0001) destes parâmetros nos touros até 18 meses de idade, em que CEs acima de 26 cm indicaram sêmen de alta MOT (60 a 80%). As correlações entre CE e patologias espermáticas foram baixas e a maioria, negativa. Foi concluído, neste estudo, que nos touros jovens o tamanho da CE indica a qualidade do sêmen, portanto pode ser utilizado como um dos critérios na seleção de animais de alto potencial reprodutivo.

Nuclear spin conversion in formaldehyde

A theoretical model of the nuclear spin conversion in formaldehyde (H2CO) has been developed. The conversion is governed by the intramolecular spin–rotation mixing of molecular ortho and para states. The rate of conversion has been found to be γ/P=1.4×10−4s−1/Torr. The temperature dependence of the spin conversion is predicted to be weak in the temperature range T=200–900K.

Positive and Negative Mixtures in Relativistic Schrödinger Theory

The general formalism of relativistic Schrodinger theory (RST) is specialized to a scalar two-particle system with electromagnetic interactions (scalar helium atom). The set of dynamically allowed field configurations splits up into positive and negative mixtures and pure states. The static and spherically symmetric solutions are constructed by means of first-order perturbation theory for the case of an attractive Coulomb potential. The corresponding energy levels for the positive and negative mixtures resemble the emergence of ortho and para states in the conventional quantum theory. The associated energy eigenvalues predicted by the RST seem to undergo a certain kind of mixture degeneracy as the RST analog of the conventional exchange degeneracy. The charge densities of the positive mixtures assimilate, whereas the densities of the negative mixtures recede from one another. Thus, positive (negative) mixtures strongly resemble the bosonic (fermionic) matter of the conventional theory when the Pauli principle is applied.

The Mechanism of Magnetically Tuned Singlet–Triplet Avoided Crossings in the Ã1A2–[formula omitted]1A1 410 Band of Thioformaldehyde H2CS

Magnetically tuned singlet–triplet perturbations in the 41Ã1A2–2131ã3A2 system of thioformaldehyde, found in ortho-rotational states (I = 1, the two hydrogen spins parallel) have been identified as being caused by vibronic spin–orbit coupling. This perturbation mechanism has been confirmed in several avoided crossings observed in this work for para states (I = 0, hydrogen spins antiparallel) which are much stronger. Parametrization of the theory has led to a quantitative understanding of the experimental frequency-field relations, and to an accurate prediction of the rovibrational energies of the triplet state. This in turn permitted the detection of about 100 Doppler-limited 2131ã3A2–00X̃1A1 rovibronic transitions which led into fine structure states. The combined data was then used to determine a set of rotational, fine, and hyperfine triplet-state parameters, the term value T0(2131ã3A2) = (16 685.385 ± 0.002) cm−1, and the spin–orbit vibronic singlet–triplet coupling constant, WST = (0.0691 ± 0.0016) cm−1. A large number of frequency perturbations observed in the crossings, ranging from 2 to 300 MHz, can be explained with this single parameter.

Ortho-para conversion in CH3F: Self-consistent theoretical model

A complete theoretical model of the nuclear spin conversion in13CH3F induced by intramolecular ortho-para state mixing is proposed. The model contains parameters determined from the levelcrossing spectra of the13CH3F spin conversion. This set of parameters includes the ortho-para decoherence rate, the magnitude of the spin-spin interaction between the molecular nuclei and the energy gap between the mixed ortho and para states. These parameters are found to be in good agreement with their theoretical estimates.

Hyperfine spectra of CH3F nuclear spin conversion

A theoretical model of hyperfine spectra of nuclear spin conversion of molecular isomers has been developed. The model takes into account the nuclear spin-spin and spin-rotation interactions, as well as the saturation of intramolecular mixing of molecular ortho and para states. The model has been applied to hyperfine spectra of nuclear spin conversion in 13CH3F molecules subjected to an external electric field. Conditions under which the hyperfine structure in the spectra can be resolved have been determined.

Nuclear spin conversion in CH F induced by an alternating electric field

The nuclear spin conversion in CH3F molecules subjected to an alternating electric field was investigated experimentally. The conversion rate was found to be almost unaffected by low electric fields ( V/cm) but sharply increased tenfold when the electric field amplitude exceeds the values ( V/cm) sufficiently high to produce crossings of the ortho and para states of the molecule. A theoretical model for the molecular conversion in alternating electric field was developed. The results of the experiment were found to be in a good agreement with the theory.

Avaliação taxonômica e ecológica das diatomáceas (Chrysophyta - Bacillariophyceae) marinhas e estuarinas nos estados de Pernambuco, Paraíba, Rio Grande do Norte, Ceará, Piauí, Maranhão, Pará e Amapá, Brasil.

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Rotationally inelastic scattering of jet cooled H2O with Ar: State-to-state cross sections and rotational alignment effects

State-to-state rotationally inelastic scattering cross sections of H2O with Ar are measured under single-collision conditions in crossed supersonic jets at a collision energy of 480(90) cm−1. The H2O is initially prepared in its lowest ortho (101) and para (000) rotational levels by supersonic cooling in a Ne expansion, and then excited in the intersection region by single collisions with a second pulsed jet of Ar atoms. Column-integrated densities of H2O in both initial and final scattering states are monitored via direct absorption of narrow bandwidth (Δν≈0.0001 cm−1) infrared light from a continuous wave (cw) F-center laser. Absolute inelastic cross sections for state-to-state collisional energy transfer out of para and ortho initial states are determined from the dependence of infrared absorption signals on collider gas densities. Overall, the results can be approximately characterized by an exponential decrease in cross section with the magnitude of rotational energy transferred, i.e., as suggested by exponential energy gap models. However, at the state-to-state level, a highly structured, nonmonotonic dependence on energy is observed, which indicates a propensity for rotational excitation around the A (in-plane, perpendicular to C2) and C (out-of-plane) principal axes. This preferential state-to-state scattering dynamics reflects an intramolecular alignment of J in the body-fixed frame and is in good qualitative agreement with theoretical classical trajectory predictions. A rigorous comparison is made via full quantum close-coupling scattering calculations on empirical and ab initio Ar-H2O potential energy surfaces, which successfully reproduce all the state-to-state trends observed, but at the more quantitative level appear to overestimate the intramolecular alignment effects experimentally observed.

Fungal endophytes ofSpondias mombin leaves in Brazil

Endophytic fungi were isolated from symptomless leaf blades and the rachis of Spondias mombin (Anacardiaceae) collected in Para and Rio de Janeiro states of Brazil. A total of 822 and 690 isolates were obtained from leaves and rachises, respectively. Of the 13 taxa isolated from the two sites examined, only three, Colletotrichum gloeosporioides, Guignardia sp., and Phomopsis sp., were recovered from the rachis. An unidentified Guignardia species was the dominant species with high overall frequency of isolation in leaf blades and rachis at both sites. An unidentified Phomopsis species was the second mostly common isolated species, significantly showing preference in colonizing the rachis tissues.

Violation of nuclear-spin symmetry in collisions of symmetric tops

Evidence of nuclear-spin symmetry violation in molecular collisions is presented. Measurements of the ortho-para conversion rates in 12 CH 3F embedded in an gaseous oxygen or nitrogen shows that oxygen speeds up the nuclear spin conversion by 2×10 −4 s −1/Torr contrary to nitrogen which slows down the conversion by 1×10 −4 s −1/Torr. The difference is attributed to direct collisional transitions between the ortho and para states in CH 3F due to the large oxygen magnetic moment, which is much smaller in the case of nitrogen.