Para States Research Articles

Rotational-Energy Transfer in H2 Ortho-Para Conversion on a Metal Surface: Interplay between Electron and Phonon Systems.

Clarifying energy transfer processes in molecular adsorption on solid surfaces is essential to understand the gas-surface interaction. Unlike the vibrational-energy transfer processes, which are thought to be well understood in detail, the rotational-energy transfer process still remains unclear. Considering the interconversion between ortho and para states of H2 is accompanied by the nuclear spin flip and the rotational-energy transfer, the surface-temperature dependence of the ortho-to-para conversion of molecularly chemisorbed H2 on Pd(210) is studied. The conversion rate is accelerated with an increase in surface temperature. Based on the conversion model proposed for metal surfaces, we analyze the temperature dependence of the conversion rate, taking into account both electron and phonon systems of the substrate. The rotational-energy transfer is most likely mediated by surface electrons with the assistance of the substrate phonons.

Adiabatic Trajectory Approximation: A New General Method in the Toolbox of Mixed Quantum/Classical Theory for Collisional Energy Transfer

A new version of the MQCT program is presented, which includes an important addition, adiabatic trajectory approximation (AT-MQCT), in which the equations of motion for the classical and quantum parts of the system are decoupled. This method is much faster, which permits calculations for larger molecular systems and at higher collision energies than was possible before. AT-MQCT is general and can be applied to any molecule + molecule inelastic scattering problem. A benchmark study is presented for H2O + H2O rotational energy transfer, an important asymmetric-top rotor + asymmetric-top rotor collision process, a very difficult problem unamenable to the treatment by other codes that exist in the community. Our results indicate that AT-MQCT represents a reliable computational tool for prediction of collisional energy transfer between the individual rotational states of two molecules, and this is valid for all combinations of state symmetries (such as para and ortho states of each collision partner).

Оптическое возбуждение спин-триплетных состояний двухэлектронных доноров в кремнии

In this paper, we propose a method for resonant optical excitation of ortho states of two-electron donors in silicon, direct transitions to which from the ground state are extremely suppressed in case of a weak spin-orbit coupling. Excitation is proposed to be carried out using the points of anti-crossing of ortho and para states under conditions of uniaxial stress of the crystal. In these points the states cannot be unambiguously assigned to any group of states with a certain spin, as a result of which the optical transition becomes allowed. The structure of the energy levels of two-electron impurities is such that the excitation of such state almost unambiguously leads to the population of the underlying ortho-type state, which is expected to be very long-lived in the case of weak spin-orbit coupling. In the present work, theoretical estimates of the cross sections for optical transitions in the vicinity of the level anticrossing point as a function of strain for strong and weak spin-orbit coupling are made.

Abstract- Poster

Background:- ”Catatonia” is characterized by alterations in motor, behavioral, and vocal signs occurring in the context of medical, neurologic, & psychiatric disorders. While considering medical etiology, renal failure has been described as one of the factors. It may result in seizures & catatonia. Furthermore, renal failure even though rare has also been implicated in the causation.Aim:- We aim to report a rare case describing multiple etiologies (Renal failure, Seizure, Covid-19) & treatment in a patient with catatonia.Result/Case report:- The patient had Covid-19 infection with concomitant renal insufficiency with uremia. He developed an episode of seizure on 3rd day of admission and subsequently developed catatonic symptoms in the post-ictal phase. He did not respond to anticonvulsive treatment but did so with Lorazepam.Discussion:- A variety of conditions can produce catatonia. It is less widely recognized that this state may be caused by seizures; which in turn can also be due to renal failure. Catatonia occurring in the wake of seizures generally responds to the anticonvulsive medication. Even though rare and anecdotal, catatonia has been reported in a few cases reports in patients suffering from Covid-19 infection & it can occur in both the para & post-infectious states.Conclusion:- We also want to highlight that lorazepam proved to be an effective and safe choice for the treatment of catatonic symptoms & eventually led to the improvement in the symptomatology of Covid-19. Therefore, we also propose further studies for the treatment of such patients.

Lamb-dip cavity ring-down spectroscopy of acetylene at 1.4 μm

Doppler-free saturated-absorption Lamb dips are observed for weak vibration-rotation transitions of C2H2 between 7167 and 7217 cm−1, using a frequency-comb assisted cavity ring-down spectrometer based on the use of a pair of phase-locked diode lasers. We measured the absolute center frequency of sixteen lines belonging to the 2 band, targeting ortho and para states of the molecule. Line pairs of the P and Q branches were selected so as to form a ‘V’-scheme, sharing the lower energy level. Such a choice made it possible to determine the rotational energy separations of the excited vibrational state for J-values from 11 to 20. Line-center frequencies are determined with an overall uncertainty between 3 and 13 kHz. This is over three orders of magnitude more accurate than previous experimental studies in the spectral region around the wavelength of 1.4 μm. The retrieved energy separations provide a stringent test of the so-called MARVEL method recently applied to acetylene.

Bioinformatics on the Road: Taking Training to Students and Researchers Beyond State Capitals

In Brazil, training capable bioinformaticians is done, mostly, in graduate programs, sometimes with experiences during the undergraduate period. However, this formation tends to be inefficient in attracting students to the area and mainly in attracting professionals to support research projects in research groups. To solve these issues, participation in short courses is important for training students and professionals in the usage of tools for specific areas that use bioinformatics, as well as in ways to develop solutions tailored to the local needs of academic institutions or research groups. In this aim, the project “Bioinformática na Estrada” (Bioinformatics on the Road) proposed improving bioinformaticians’ skills in undergraduate and graduate courses, primarily in the countryside of the State of Pará, in the Amazon region of Brazil. The project scope is practical courses focused on the areas of interest of the place where the courses are occurring to train and encourage students and researchers to work in this field, reducing the existing gap due to the lack of qualified bioinformatics professionals. Theoretical and practical workshops took place, such as Introduction to Bioinformatics, Computer Science Basics, Applications of Computational Intelligence applied to Bioinformatics and Biotechnology, Computational Tools for Bioinformatics, Soil Genomics and Research Perspectives and Horizons in the Amazon Region. In the end, 444 undergraduate and graduate students from higher education institutions in the state of Pará and other Brazilian states attended the events of the Bioinformatics on the Road project.

Optical properties of two-dimensional two-electron quantum dot in parabolic confinement

Abstract The Hamiltonian and wavefunctions of two-dimensional two-electron quantum dots (2D2eQD) in parabolic confinement are determined. The ground and excited state energies are calculated solving the Schrödinger equation analytically and numerically. To determine the energy eigen-value of the system variational method is employed due to the large coupling constant λ ≈ 1.1 \lambda \approx 1.1 . The trial wavefunctions are developed for both ground and excited states. The ground state wave function is a para state and the excited state wavefunctions belong to both para and ortho states based on the symmetry and antisymmetry of spatial wavefunctions. Using the obtained energy eigen-values at the two states, the first- and third-order nonlinear absorption coefficient and refractive index are analytically obtained with the help of density matrix formalism and iterative procedure.

Rapid Ortho-to-para Nuclear Spin Conversion of H2 on a Silicate Dust Surface

Abstract The H2 molecule has two nuclear spin isomers, the so-called ortho and para isomers. Nuclear spin conversion (NSC) between these states is forbidden in the gas phase. The energy difference between the lowest ortho and para states is as large as 14.7 meV, corresponding to ∼170 K. Therefore, each state of H2 differently affects not only the chemistry but also the macroscopic gas dynamics in space; thus, the ortho-to-para abundance ratio (OPR) of H2 has significant impacts on various astronomical phenomena. For a long time, the OPR of nascent H2 upon formation on dust grains has been assumed to have a statistical value of 3 and to gradually equilibrate in the gas phase at the temperature of the circumstances. Recently, the NSC of H2 was experimentally revealed to occur on water ice at very low temperatures and thus incorporated into gas–dust chemical models. However, H2 molecules should form well before dust grains are coated by water ice. Information about how the OPR of H2 behaves on bare silicate dust before ice-mantle formation is lacking. Knowing the influence of the OPR of H2 is desirable, if the OPR changes even on a bare silicate surface within an astronomically meaningful timescale. We report the first laboratory measurements of the NSC of H2 physisorbed on amorphous silicate (Mg2SiO4) at temperatures up to 18 K. The conversion was found to occur very rapidly.

Water ortho–para conversion by microwave background radiation in space

ABSTRACT A theoretical model of water ortho–para conversion induced by blackbody radiation in space is developed. The model is based on two main ingredients: the mixing of water ortho and para states by a hyperfine spin-rotation interaction in the molecule and the interruption of this mixing by surrounding blackbody radiation. The model predicts the lifetime of water spin isomers τ = 2.7 Myr for radiation with a temperature of 100 K and τ = 1.3 Gyr for microwave background radiation. The time dependence of the ortho-to-para ratio (OPR) of water molecules interacting with microwave background radiation is determined. The temperature dependence of the stationary OPR predicted by the model is found to be different from the usually accepted OPR for water spin isomers.

Core collection of Hevea brasiliensis from the 1995 RRIM Hevea germplasm for effective utilisation in the rubber breeding programme

The rubber tree (Hevea brasiliensis) is the world’s major source of natural rubber. An expedition to the Amazonas and Para states by the Rubber Research Institute of Malaysia (RRIM) in 1995 led to the successful collection of more than 50,000 genotypes from different locations of the states to broaden the existing gene pool. Realising the severe limitations faced with large germplasm, a core collection consisting of a reduced number of genotypes derived from a base collection of 505 selected genotypes was developed. The genotypes were first sorted based on their relative contributions to the total variability by principal component scores of a set of 11 quantitative traits. Then, the cumulative proportion of their contributions to the total variance was computed. The size of the core set was decided by a cut-off value when the rate of increase in cumulative contributions reached a maximum value and began to decline. Entries with a high degree of similarity in the selected core collection were eliminated using Gower metric coefficient. Shannon–Weaver diversity index of 14 morphological qualitative descriptors was used to verify the size and choice of entries in the final collection. As a result, 25.35% of the base collection or a total of 128 genotypes (73 from Manaus, 17 Manicore, 13 Atalaia do Norte, 11 Borba, 8 Benjamin Constant, 3 Tapajoz, 2 Belem, and 1 Iranduba) were selected to be included in the final core collection. Establishment of the core collection of this germplasm will enable a more rapid and effective utilisation of these genetic materials in the rubber breeding programme.

Two New Species of the Armored Catfish Genus Baryancistrus Rapp Py-Daniel, 1989 (Siluriformes: Loricariidae) from Jari River, Amazon Basin, Brazil

Two new species of the suckermouth armored catfish genus Baryancistrus are described from the Jari River basin, at the border of Para and Amapa states, Brazil. The new species are the first representatives of the genus described from rivers draining the Guiana shield, and can be distinguished from their congeners by color pattern and a combination of nonexclusive characters. Baryancistrus micropunctatus, new species, has a color pattern similar to B. longipinnis from the Tocantins River, whereas Baryancistrus hadrostomus, new species, has a color pattern that is unique for the genus, with a gray to black body covered by small and widely spaced white points. The first exemplars of the two new species were collected in the late 1980s by INPA ichthyological staff, and in 2007 additional materials were collected by the Museu de Zoologia da Universidade de Sao Paulo (MZUSP), providing a foundation for this description of the new species.

Highly accurate experimentally determined energy levels of H3.

A sub-Doppler rovibrational spectroscopic survey of H3 + has been conducted which included 36 transitions in the ν2 ← 0 fundamental band, 15 transitions in the 2ν2 2←ν2 hot band, and 7 transitions in the 2ν2 2←0 overtone band, improving the uncertainties of most transitions by more than an order of magnitude to ∼4 MHz. Combination differences were used to determine relative energy levels and forbidden rotational transitions up to J = 6. A fit of the ground state to an effective Hamiltonian was used to connect ortho and para states, and to determine the absolute energy levels relative to the forbidden (0, 0) state. Ultimately, 62 rovibrational energy levels in the ground, ν2, and 2ν2 2 states were determined with ∼10 MHz uncertainty. Comparing the experimentally determined energy levels with ab initio calculations revealed an unexpected dependence of the residuals on the quantum number G.

Conversion of nuclear spin isomers of water molecules under ultracold conditions of space

The conversion rate of nuclear spin isomers of water molecules in space is calculated using the model of quantum relaxation in the absence of particle collisions. The model is based on the intramolecular mixing of the ortho and para states of H2O by the spin-rotation interaction and on the interruption of the mixing by radiative transitions of a molecule in a thermal radiation field. The lifetime of water isomers at a thermal radiation temperature T = 50 K is ∼2 × 107 years, and at a temperature T = 100 K it is 3 × 106 years. The lifetimes of the spin isomers of water molecules are found to be large, but still smaller, for example, than the age of the Solar System. The proposed process of conversion of the spin isomers of water molecules is important for areas of space with low (n < 1 cm−3) particle concentrations.

Nonlinear absorption coefficient and refractive index changes of two-dimensional two-electron quantum dot in rigid confinement

The Hamiltonian and wavefunctions describing two-dimensional (2D) two-electron ZnO quantum dot in rigid confinement are developed. Then the Schrödinger equation is solved analytically and numerically for determining the ground and excited state energies. The ground state energy of 2D two-electron ZnO quantum dot (QD) in rigid confinement is studied using perturbation and variational methods. The obtained result show that our trial wavefunction is good enough to describe the 2D two-electron QD in rigid confinement. The wavefunction describing the ground state is the combination of symmetric spatial wavefunction and antisymmetric spin wavefunction which is a para-state. The ground state energy eigenvalue obtained by variational technique is a little above that of a perturbation technique. Based on this; the trial wavefunction for the excited state is developed. The excited state energy of 2D two-electron ZnO QD in rigid confinement is studied computationally using variational method. The wavefunction describing the excited state is the combination of symmetric spatial wavefunction with antisymmetric spin wavefunction (para-state) or vice versa (ortho-state). The para and ortho-state energies of the first excited state are calculated and their difference is twice of the exchange energy. Based on the obtained energy eigenvalues of the ground and the first excited state at the value of the coupling constant [Formula: see text] [Formula: see text] 1, the third-order nonlinear absorption coefficient and refractive index changes are investigated. The optical transition is only considered between the two lowest para states.

Fourier Transform Microwave Spectra of the Nitrogen Molecule-Ethylene Sulfide and Nitrogen Molecule-Dimethyl Sulfide Complexes.

We recorded the rotational spectra of N2-ethylene sulfide (ES) and N2-dimethyl sulfide (DMS) including the 15N2 and 15N14N isotopomers in the frequency range of 5-25 GHz by using a Fourier transform microwave spectrometer. The b-type transitions for the ortho and para states of 14N2-ES and 15N2-ES and c-type transitions of 14N2-DMS and 15N2-DMS were observed. The 15N14N-ES and 15N14N-DMS species were found to exist in two isomeric forms: inner (14N15N-ES and 14N15N-DMS) and outer (15N14N-ES and 15N14N-DMS). Neither the -ES nor -DMS complexes showed weak accompanying spectra, which had been observed for N2-ethylene oxide (EO). This is because the potential barriers to internal rotation of ES and DMS are higher than that of EO. The spectra were analyzed by an A-reduced asymmetric-top rotational program with less than 4 kHz standard deviation, except for the 15N14N-DMS and 14N15N-DMS complexes. Rotational, centrifugal distortion, and nuclear electric quadrupole coupling constants were determined by the spectral analysis. The V3 potential barrier to internal rotation of the two equivalent methyl groups of DMS in the ortho and para states of the 15N2-DMS complex was determined to be about 740 cm-1. We performed ab initio calculations in order to complement the information on the intracomplex motions obtained from the experimental spectra.

Biomassa e sazonalidade das raízes finas em savanas da Amazônia Oriental

Este trabalho objetivou comparar a biomassa de raízes finas em diferentes fisionomias e avaliar a influência da sazonalidade sobre a massa de raízes finas em savanas amazônicas localizadas no Amapá e Pará. Amostras de solos foram coletadas em cinco profundidades, de 10 em 10 cm, em três pontos no Cerrado sensu stricto, quatro no Campo Cerrado e dois no Campo Limpo, com 4 repetições em cada posição. A influência da sazonalidade foi verificada apenas no Campo Cerrado, em abril (pico das chuvas), julho (final das chuvas) e outubro (pico da seca) de 2010 e em janeiro de 2011 (inicio das chuvas). As fisionomias foram diferenciadas pela massa de raízes, quando analisadas nas diferentes classes diamétricas de raízes e nas diferentes profundidades. A maior massa de raízes finas ocorreu no pico da estação seca. Esses resultados sugerem estratégias diferentes das fisionomias na alocação das raízes mais finas em diferentes profundidas do solo e na dinâmica das raízes para aumentar o potencial de absorção durante a seca.

Detection of Microwave Transitions between Ortho and Para States in a Free Isolated Molecule.

Microwave transitions between the ortho and para states of the S_{2}Cl_{2} molecule in a free isolated condition are observed for the first time. In the theoretical treatment, we derive eigenfunctions of an effective Hamiltonian including the ortho-para interaction to calculate the intensities and frequencies of forbidden ortho-para transitions in the cm-wave region and pick up some promising candidates for the spectroscopic detection. In the experiment, transitions of the S_{2}Cl_{2} molecule under a supersonic jet condition are observed with a Fourier transform microwave spectrometer. Seven hyperfine resolved rotational transitions including the lowest rotational level are detected as the ortho-para transitions at the predicted frequencies within the experimental errors. The observed intensities are about 10^{-3} times the allowed transitions, which are consistent with the predictions based on the intensity-borrowing model. This result suggests that the ortho-para conversion of this molecule occurs in a few thousand years through spontaneous emission even in a circumstance where molecular collisions occur rarely like in interstellar space.

Crescimento diamétrico e tempo de passagem de Minquartia guianensis após manejo na Floresta Nacional do Tapajós

Minquartia guianensis Aubl. (acariquara) ocorre nos estados do Acre, Amazonas, Roraima, Pará e Amapá, com grande procura de mercado e utilidade na região Amazônica. Seu principal uso é na construção civil, por apresentar alta durabilidade e reentrâncias em seu tronco, que a tornam de beleza singular e muito valorizada. A maioria das árvores utilizadas apresenta pequenos diâmetros, sendo este um fator crítico para seu manejo e comercialização. Portanto, objetivou-se avaliar o crescimento diamétrico e o ciclo de corte de M. guianensis, por meio da análise do tempo de passagem entre como classes diamétricas, no período de 31 anos, após uma exploração florestal, na Floresta Nacional do Tapajós, estado do Pará. Foram estabelecidos cinco tratamentos, e em cada um foram instaladas 12 parcelas permanentes de 0,25 ha, nas quais foram medidas todas as árvores com diâmetro a 1,30 m do solo (DAP) ≥ 5 cm, de 1981 a 2012. Como árvores com DAP ≤ 50 cm tem potencial para ser manejadas, em razão da diminuição do crescimento diamétrico a partir do DAP ≥ 50 cm. Esses resultados máfia de base para subsidiarhadas silviculturais sem manejo sustentável da espécie.

MARVEL analysis of the measured high-resolution rovibrational spectra of C2H2

Rotation-vibration energy levels are determined for the electronic ground state of the acetylene molecule, 12C2H2, using the Measured Active Rotational-Vibrational Energy Levels (Marvel) technique. 37,813 measured transitions from 61 publications are considered. The distinct components of the spectroscopic network linking ortho and para states of the molecule are considered separately. The 20,717 ortho and 17,096 para transitions measured experimentally are used to determine 6013 ortho and 5200 para energy levels. The Marvel results are compared with alternative compilations based on the use of effective Hamiltonians.

The covalent interaction between dihydrogen and gold: A rotational spectroscopic study of H2-AuCl.

The pure rotational transitions of H2-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both 35Cl and 37Cl isotopologues have been measured for both ortho and para states of H2. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms Daa, Dbb, and Dcc for H2 were required to fit the ortho state of hydrogen, as well as a nuclear-spin rotation constant Caa. The values of the nuclear quadrupole coupling constant of gold are χaa=-817.9929(35) MHz, χbb=504.0(27) MHz, and χcc=314.0(27). This is large compared to the eQq of AuCl, 9.63 312(13) MHz, which indicates a strong, covalent interaction between gold and dihydrogen.