Laboratory study of rotationally inelastic collisions of CO2 at low temperatures.

The rotational relaxation of CO2 by inelastic collisions has been studied in three supersonic jets. The jets were probed by means of Raman spectroscopy with high spectral and spatial resolutions, measuring the rotational populations and the total number density. The time evolution of the rotational populations was analyzed by means of a kinetic master equation, with the help of the energy-corrected sudden power law to relate the numerous state-to-state rate (STS rates) coefficients. In the thermal range investigated, 60-260 K, the STS rates decrease with increasing temperature and with increasing change in the rotational quantum number. Other quantities of interest for fluid dynamics, such as the rotational collision number, the relaxation cross section, and the bulk viscosity, have been derived from the STS rates.

Inelastic Collisions of O2 with He at Low Temperatures.

Rotationally inelastic collisions of O2 with He in the 10-34 K thermal range are investigated by means of an experimental procedure based on supersonic gas jets probed by Raman spectroscopy. The procedure employs a kinetic master equation (MEQ) that describes the time evolution of the rotational populations of O2 along supersonic jets of O2 and He mixtures. The MEQ is expressed in terms of experimental quantities (number density and rotational populations) measured here, and state-to-state rate coefficients for the O2:He inelastic collisions calculated here, plus those for O2:O2 collisions from the literature. An agreement with the experiments is accomplished for temperatures between 10 and 34 K. Within this thermal range, the role of the fine structure due to electron spin in the collision dynamics of O2 is discussed.

Insecticide susceptibility status in Mexican populations of Stegomyia aegypti (= Aedes aegypti): a nationwide assessment.

In Mexico, mosquito vector-borne diseases are of public health concern as a result of their impact on human morbidity and mortality. The use of insecticides against adult mosquitoes is one of the most common ways of controlling mosquito population densities. However, the use of these compounds has resulted in the development of insecticide resistance. The aim of this study was to estimate susceptibility to six pyrethroids, two carbamates and two organophosphates in Mexican populations of Stegomyia aegypti (Linnaeus, 1762) (= Aedes aegypti) (Diptera: Culicidae) mosquitoes. Bottle insecticide susceptibility tests, with 1 h exposure, were performed on adult mosquitoes from 75 localities across 28 states. At 30 min of exposure, the proportion of fallen mosquitoes was recorded. After 60 min of exposure, mosquitoes were recovered in non-treated containers and mortality was determined at 24 h after the set-up of the experiment. In general, the carbamate insecticides represented the most effective group in terms of the proportion of mosquitoes fallen at 30 min (72-100%) and 24-h mortality (97-100%). High and widespread resistance to pyrethroids Types I and II and, to a lesser extent, to organophosphates was observed. Insecticide susceptibility among and within states was highly variable.

First report of Stegomyia aegypti (= Aedes aegypti) in Mexico City, Mexico.

Stegomyia aegypti (= Aedes aegypti) (Diptera: Culicidae) is a species of mosquito that is currently widespread in Mexico. Historically, the mosquito has been distributed across most tropical and subtropical areas lower than 1700 m a.s.l. Currently, populations that are found at higher altitudes in regions with cold and dry climates suggest that these conditions do not limit the colonization and population growth of S. aegypti. During a survey of mosquitoes in September 2015, larvae of S. aegypti mosquitoes were found in two different localities in Mexico City, which is located at about 2250 m a.s.l. Mexico City is the most populous city in Mexico and has inefficient drainage and water supply systems. These factors may result in the provision of numerous larval breeding sites. Mosquito monitoring and surveillance are now priorities for the city.

Development of a neuroprotective peptide that preserves survival pathways by preventing Kidins220/ARMS calpain processing induced by excitotoxicity.

Kinase D-interacting substrate of 220 kDa (Kidins220), also known as ankyrin repeat-rich membrane spanning (ARMS), has a central role in the coordination of receptor crosstalk and the integration of signaling pathways essential for neuronal differentiation, survival and function. This protein is a shared downstream effector for neurotrophin- and ephrin-receptors signaling that also interacts with the N-methyl-d-aspartate type of glutamate receptors (NMDARs). Failures in neurotrophic support and glutamate signaling are involved in pathologies related to excitotoxicity and/or neurodegeneration, where different components of these dynamic protein complexes result altered by a combination of mechanisms. In the case of Kidins220/ARMS, overactivation of NMDARs in excitotoxicity and cerebral ischemia triggers its downregulation, which contributes to neuronal death. This key role in neuronal life/death decisions encouraged us to investigate Kidins220/ARMS as a novel therapeutic target for neuroprotection. As the main mechanism of Kidins220/ARMS downregulation in excitotoxicity is proteolysis by calpain, we decided to develop cell-penetrating peptides (CPPs) that could result in neuroprotection by interference of this processing. To this aim, we first analyzed in detail Kidins220/ARMS cleavage produced in vitro and in vivo, identifying a major calpain processing site in its C-terminal region (between amino acids 1669 and 1670) within a sequence motif highly conserved in vertebrates. Then, we designed a 25-amino acids CPP (Tat-K) containing a short Kidins220/ARMS sequence enclosing the identified calpain site (amino acids 1668-1681) fused to the HIV-1 Tat protein basic domain, able to confer membrane permeability to attached cargoes. Transduction of cortical neurons with Tat-K reduced Kidins220/ARMS calpain processing in a dose- and time-dependent manner upon excitotoxic damage and allowed preservation of the activity of pERK1/2 and pCREB, signaling molecules central to neuronal survival and functioning. Importantly, these effects were associated to a significant increase in neuronal viability. This Kidins220/ARMS-derived peptide merits further research to develop novel neuroprotective therapies for excitotoxicity-associated pathologies.

Mixing effects in the crystallization of supercooled quantum binary liquids.

By means of Raman spectroscopy of liquid microjets, we have investigated the crystallization process of supercooled quantum liquid mixtures composed of parahydrogen (pH2) or orthodeuterium (oD2) diluted with small amounts of neon. We show that the introduction of the Ne impurities affects the crystallization kinetics in terms of a significant reduction of the measured pH2 and oD2 crystal growth rates, similarly to what found in our previous work on supercooled pH2-oD2 liquid mixtures [Kühnel et al., Phys. Rev. B 89, 180201(R) (2014)]. Our experimental results, in combination with path-integral simulations of the supercooled liquid mixtures, suggest in particular a correlation between the measured growth rates and the ratio of the effective particle sizes originating from quantum delocalization effects. We further show that the crystalline structure of the mixtures is also affected to a large extent by the presence of the Ne impurities, which likely initiate the freezing process through the formation of Ne-rich crystallites.

Inelastic collisions in molecular oxygen at low temperature (4 ≤ T ≤ 34 K). Close-coupling calculations versus experiment.

Close-coupling calculations and experiment are combined in this work, which is aimed at establishing a set of state-to-state rate coefficients for elementary processes ij → lm in O(2):O(2) collisions at low temperature involving the rotational states i, j, l, m of the vibrational ground state of (16)O(2)((3)Σ(g)(-)). First, a set of cross sections for inelastic collisions is calculated as a function of the collision energy at the converged close-coupled level via the MOLSCAT code, using a recent ab-initio potential energy surface for O(2)-O(2) [M. Bartolomei et al., J. Chem. Phys. 133, 124311 (2010)]. Then, the corresponding rates for the temperature range 4 ≤ T ≤ 34 K are derived from the cross sections. The link between theory and experiment is a Master Equation which accounts for the time evolution of rotational populations in a reference volume of gas in terms of the collision rates. This Master Equation provides a linear function of the rates for each rotational state and temperature. In the experiment, the evolution of rotational populations is measured by Raman spectroscopy in a tiny reference volume (≈2 × 10(-4) mm(3)) of O(2) travelling along the axis of a supersonic jet at a velocity of ≈700 m/s. The accuracy of the calculated rates is assessed experimentally for 10 ≤ T ≤ 34 K by means of the Master Equation. The rates, jointly with their confidence interval estimated by Monte Carlo simulation, account to within the experimental uncertainty for the evolution of the populations of the N = 1, 3, 5, 7 rotational triads along the supersonic jet. Confidence intervals range from ≈6% for the dominant rates at 34 K, up to ≈17% at 10 K. These results provide an experimental validation of state-to-state rates for O(2):O(2) inelastic collisions calculated in the close-coupling approach and, indirectly, of the anisotropy of the O(2)-O(2) intermolecular potential employed in the calculation for energies up to 300 cm(-1).

Effects of voluntary physical exercise on adult hippocampal neurogenesis and behavior of Ts65Dn mice, a model of Down syndrome.

The Ts65Dn (TS) mouse is the most widely used model of Down syndrome (DS). This mouse shares many phenotypic characteristics with the human condition including cognitive and neuromorphological alterations. In this study the effects of physical exercise on hippocampal neurogenesis and behavior in TS mice were assessed. 10-12 month-old male TS and control (CO) mice were submitted to voluntary physical exercise for 7 weeks and the effects of this protocol on hippocampal morphology, neurogenesis and apoptosis were evaluated. Physical exercise improved performance in the acquisition sessions of the Morris water maze in TS but not in CO mice. Conversely, it did not have any effect on anxiety or depressive behavior in TS mice but it did reduce the cognitive components of anxiety in CO mice. TS mice presented a reduced dentate gyrus (DG) volume, subgranular zone area and number of granule neurons. Hippocampal neurogenesis was reduced in TS mice as shown by the reduced number of 5-bromo-2-deoxyuridine (BrdU) positive cells. Voluntary physical exercise did not rescue these alterations in TS mice but it did increase the number of doublecortin (DCX)-and phospho histone 3 (PH3)-positive neurons in CO mice. It is concluded that physical exercise produced a modest anxiolytic effect in CO mice and that this was accompanied by an increased number of immature cells in the hippocampal DG. On the other hand, voluntary physical exercise exerted a positive effect on TS mice learning of the platform position in the Morris water maze that seems to be mediated by a neurogenesis-independent mechanism.

The onset of molecular condensation: hydrogen.

The very first steps of condensation as studied experimentally in the simplest molecular system (para-H(2)) are reported. The fast time-space evolution of the nascent clusters have been measured using state-of-the-art Raman spectroscopy implemented on cryogenic supersonic jets. The time-dependent onset of condensation is presented in a non-equilibrium pressure-temperature phase diagram. Dimer and trimer formation are found to obey three-body processes whose rates have been determined.

Nonequilibrium processes in supersonic jets of N2, H2, and N2 + H2 mixtures: (II) shock waves.

We report an experimental study of the shock wave system of three continuous axisymmetric jets of pure N(2) and H(2), and of the N(2) + 2H(2) mixture, generated at p(0) = 1 bar and T(0) = 295 K through a D = 310 microm cylindrical nozzle against a background pressure p(b) = 6.1 mbar. Number density and rotational populations have been measured by Raman spectroscopy with high spatial resolution (approximately 15 microm) across the normal shock wave located at z/D approximately 8, and across the barrel shock wave at the plane z/D = 5.2. Significant differences in position, widths, and gradients of the shock waves are observed among the three jets. Such differences are qualitatively interpreted in terms of disparity in mass, inelastic cross sections, and collision numbers. Non-Boltzmann distributions of the rotational populations of N(2) are observed within the shock waves at regions where the local Knudsen number is higher than 0.05. In the N(2) + 2H(2) mixture the different behavior of the two species leads to a localized enrichment of the light component up to 20%, which might provide the basis for an efficient separation device. Measurements on the invasion of the shock wave system by the background molecules are also reported, proving such invasion to be more efficient for the lighter species H(2) than for the heavier N(2).

Nonequilibrium processes in supersonic jets of N2, H2, and N2 + H2 mixtures: (I) Zone of silence.

Number density and rotational temperature in the zone of silence of supersonic jets of N(2), H(2), and their mixtures N(2) + 2H(2) and 2N(2) + H(2), at p(0) = 1 bar and T(0) = 295 K, have been measured by Raman spectroscopy. Translational temperature in the jets has been derived from the experimental data assuming isentropic flow. The density along the jet axis decays at a rate depending on the composition of the expanded gas, which can be explained by the variation of its effective heat capacity ratio. Measurements across the jet axis do not support numerical off-axis density modeling from the literature. A strong nonequilibrium between the rotational degrees of freedom of both species is observed, even between the two spin species ortho-H(2) and para-H(2). From the corresponding rotational temperature data, a relationship between rotational cross sections for the inelastic collisions of the different species is established. In the expansions of the mixtures, an enrichment of N(2) is measured on the axis, which is compared with the predictions from the theory of diffusive separation in jets.

Low-temperature inelastic collisions between hydrogen molecules and helium atoms.

Inelastic H(2):He collisions are studied from the experimental and theoretical points of view between 22 and 180 K. State-to-state cross sections and rates are calculated at the converged close-coupling level employing recent potential energy surfaces (PES): The MR-PES [J. Chem. Phys. 100, 4336 (1994)], and the MMR-PES and BMP-PESs [J. Chem. Phys. 119, 3187 (2003)]. The fundamental rates k(2-->0) and k(3-->1) for H(2):He collisions are assessed experimentally on the basis of a master equation describing the time evolution of rotational populations of H(2) in the vibrational ground state. These populations are measured in the paraxial region of supersonic jets of H(2)+He mixtures by means of high-sensitivity and high spatial resolution Raman spectroscopy. Good agreement between theory and experiment is found for the k(2-->0) rate derived from the MR-PES, but not for the BMP-PES. For the k(3-->1) rate, which is about one-third to one-half of k(2-->0), the result is less conclusive. The experimental k(3-->1) rate is compatible within experimental error with the values calculated from both PESs. In spite of this uncertainty, the global consistence of experiment and theory in the framework of Boltzmann equation supports the MR-PES and MMR-PESs, and the set of gas-dynamic equations employed to describe the paraxial region of the jet at a molecular level.

Inelastic collisions in molecular nitrogen at low temperature (2 < or = T < or = 50 K).

Theory and experiment are combined in a novel approach aimed at establishing a set of two-body state-to-state rates for elementary processes ij --> lm in low temperature N(2):N(2) collisions involving the rotational states i,j,l,m. First, a set of 148 collision cross sections is calculated as a function of the collision energy at the converged close-coupled level via the MOLSCAT code, using a recent potential energy surface for N(2)-N(2). Then, the corresponding rates for the range of 2 < or = T < or = 50 K are derived from the cross sections. The link between theory and experiment, aimed at assessing the calculated rates, is a master equation which accounts for the time evolution of rotational populations in a reference volume of gas in terms of the collision rates. In the experiment, the evolution of rotational populations is measured by Raman spectroscopy in a tiny reference volume (approximately 2 x 10(-3) mm(3)) of N(2) traveling along the axis of a supersonic jet. The calculated collisional rates are assessed experimentally in the range of 4 < or = T < or = 35 K by means of the master equation, and then are scaled by averaging over a large set of experimental data. The scaled rates account accurately for the evolution of the rotational populations measured in a wide range of conditions. Accuracy of 10% is estimated for the main scaled rates.

Rotranslational state-to-state rates and spectral representation of inelastic collisions in low-temperature molecular hydrogen.

Inelastic collisions in natural H2 are studied from the experimental and theoretical points of view between 10 and 140 K. Rotational populations and number densities measured by Raman spectroscopy along supersonic expansions of H2 provide the link between experimental and theoretical rotranslational state-to-state rate coefficients of H2 in the vibrational ground state. These rates are calculated in the close-scattering approach with the MOLSCAT code employing a recent ab initio H2-H2 potential. The calculated rates are assessed by means of a master equation describing the time evolution of the experimental rotational populations. The feasibility for obtaining the rates on the sole basis of the experiment is discussed. The dominant processes j(1)j(2)-->j'(1)j'(2) in the investigated thermal range are found to be 21-->01 >30-->12 >31-->11, proving the importance of double processes such as 30-->12. Good agreement is found between theory and experiment, as well as with earlier ultrasonic measurements of relaxation times. A spectral representation is proposed in order to visualize quantitatively the collisional contributions in any nonequilibrium time evolving process.

Inelastic collisions in para-H2: translation-rotation state-to-state rate coefficients and cross sections at low temperature and energy.

We report an experimental determination of the k(00-->02) rate coefficient for inelastic H(2):H(2) collisions in the temperature range from 2 to 110 K based on Raman spectroscopy data in supersonic expansions of para-H(2). For this purpose a more accurate method for inverting the master equation of rotational populations is presented. The procedure permits us to reduce the measured k(00-->02) rate coefficient to the corresponding sigma(00-->02) cross section in the range of precollisional energy from 360 to 600 cm(-1). Numerical calculations of sigma(00-->02) carried out in the frame of the coupled channel method are also reported for different intermolecular potentials of H(2). A good agreement is found between the experimental cross section and the numerical one derived from Diep and Johnson's potential [J. Chem. Phys. 112, 4465 (2000)].

Raman spectroscopy of small para-H2 clusters formed in cryogenic free jets.

Small para-H2 clusters (pH2)N with N=2,...,8 have been identified by Raman spectroscopy in cryogenic free jets of the pure gas, near the Q(0) Raman line of the H2 monomer. The high resolution in space, time, and number size makes it possible to follow their growth kinetics with distance from the orifice. At lower source temperatures liquid clusters appear early in the expansion and then undergo a gradual phase transition to the solid state. The technique is very promising for exploring superfluidity in pure (pH2)N clusters.

Cutaneous leishmaniasis caused by members of Leishmania braziliensis complex in Nayarit, State of Mexico.

An epidemiological study was carried out in the northern Mexican state, Nayarit. Fourteen patients with possible cutaneous leishmaniasis skin lesions gave positive Montenegro skin tests. Biopsies were taken from the skin ulcer and analyzed by polymerase chain reaction (PCR) with specific primers for the Leishmania mexicana complex; however all biopsies were not amplified. PCR carried out with specific primers for the L. braziliensis complex resulted in the amplification of all patient DNA. DNA from 12 out of 14 biopsies gave positive amplification with primers species specific for L. (Viannia) braziliensis and hybridized with a species specific L. (V.) braziliensis probe. These results demonstrate the presence in Nayarit of at least two members of the L. braziliensis complex. Most of the cutaneous lesions were caused by L. (V.) braziliensis and two by another species belonging to the L. braziliensis complex. As far as we are aware, this is the first report of L. (V.) braziliensis in Nayarit. The main risk factor associated with the contraction of this disease in Nayarit is attributed to working on coffee plantations.

Raman spectroscopy of hypersonic shock waves

Raman spectroscopy is shown to be an efficient diagnostic methodology for the study of hypersonic shock waves. As a test, absolute density and rotational population profiles have been measured across five representative normal shock waves of N2 generated in a free jet, spanning the Mach number range 7.7

Visceral leishmaniosis caused by Leishmania (L.) mexicana in a Mexican patient with human immunodeficiency virus infection.

A 36 year old male was admitted in December 1997 to hospital with afternoon fever, malaise and hepatosplenomegaly. He also had a dry cough, dyspnoea and anaemia. Pneumonia caused by Pneumocystis carinii and human immunodeficiency virus (HIV) infection were documented. The HIV infection was confirmed in 1997 with 290,000 virus copies. The patient had been in the Mexican State of Chiapas which is known to be endemic for visceral leishmaniosis (VL) and localized cutaneous leishmaniosis (LCL). The visceral symptoms were diagnosed as VL and the causal agent was identified as Leishmania (L. ) mexicana. Identification of Leishmania was carried out by the analysis of amplified DNA with specific primers belonging to the Leishmania subgenus and by dot blot positive hybridisation of these polymerase chain reaction derived products with kDNA from the L. (L. ) mexicana MC strain used as probe. This is the first case in Mexico of VL caused by a species of Leishmania that typically produces a cutaneous disease form.

Ro-vibrational Raman Cross Sections of Water Vapor in the OH Stretching Region.

The Raman spectrum of H2O, in the gas phase at 26 mbar and 295 K, has been recorded from 3400 to 4130 cm-1 using an improved spectrometer of very high sensitivity. This spectrum is analyzed in terms of the wavefunctions and energy levels of Flaud and Camy-Peyret [J. Mol. Spectrosc. 51, 142 (1974)], and of the polarizability derivatives with respect to the dimensionless normal coordinates q1 and q3. It is shown that the anharmonic coupling between the vibrational states nu1 and nu3 has to be considered for a correct simulation of the observed spectrum. Tables with scattering strengths and energies of ro-vibrational transitions are provided in order to simulate the Raman spectrum of water vapor over a broad range of temperatures, from few Kelvin, under supersonic expansions, to high temperature, in combustion processes. Copyright 1999 Academic Press.