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1.
J Infect Dis ; 2024 Jul 16.
Article in English | MEDLINE | ID: mdl-39013016

ABSTRACT

BACKGROUND: Pneumococcal carriage in children has been extensively studied, but carriage in healthy adults and its relationship to invasive pneumococcal disease (IPD) is less understood. METHODS: Nasal wash samples from adults without close contact with young children (Liverpool, UK), 2011-2019, were cultured, and culture-negative samples tested by PCR. Pneumococcal carriage in adults 18-44 years was compared with carriage among PCV-vaccinated children 13-48 months (nasopharyngeal swabs, Thames Valley, UK) and IPD data for England for the same ages for 2014-2019. Age-group specific serotype invasiveness was calculated and used with national IPD data to estimate carriage serotype distributions for adults aged 65+ years. RESULTS: In total 98 isolates (97 carriers) were identified from 1,631 adults aged 18+ years (age and sex standardized carriage prevalence 6.4%), with only three identified solely by PCR. Despite different carriage and IPD serotype distributions between adults and children, serotype invasiveness was highly correlated (R=0.9). Serotypes 3, 37 and 8 represented a higher proportion of adult carriage than expected from direct low-level transmission from children to adults. The predicted carriage serotype distributions for 65+ years aligned more closely with the carriage serotype distribution for young adults than young children. CONCLUSIONS: The nasal wash technique is highly sensitive; additional benefit of PCR is limited. Comparison of carriage serotype distributions suggests some serotypes may be circulating preferentially within these specific young adults. Our data suggest that for some serotypes carried by adults 65+ years, other adults may be an important reservoir for transmission. Age groups such as older children should also be considered.

2.
Int J Food Microbiol ; 413: 110584, 2024 Mar 02.
Article in English | MEDLINE | ID: mdl-38295484

ABSTRACT

The stomach's acidic pH is a crucial barrier against foodborne pathogens such as Salmonella enterica. This study investigated the survival of S. enterica under simulated oral and gastric conditions (SGC; pH 2 for 120 min) as a function of intrinsic pathogen characteristics and food matrix. Fifty-seven S. enterica strains isolated from food and human infections (previously characterized by serotype, virulotype, multi-drug resistance, isolation source, and isolation season) were subjected to SGC using water as a vehicle. Population reduction among the 57 isolates ranged from 2.7 to 4.7 log CFU, revealing that human isolates were inactivated less than food isolates (p = 0.0008). Among food strains, strains isolated during the cold season (food sampled from December to February) displayed the highest reduction (p = 0.00002). Six representatives of the 57 S. enterica strains were selected according to their virulotype and antimicrobial profile. They were further used to evaluate their survival under SGC in four food matrices (water, mango, tomato, and chicken), measuring S. enterica at 30 min intervals. The strains in chicken showed the lowest reduction and inactivation rate (1.42 ± 0.35 log CFU; 0.03 ± 0.005 min-1), followed by tomato (3.75 ± 0.57 log CFU; 0.15 ± 0.02 min-1), water (4.23 ± 0.27 log CFU; 0.17 ± 0.02 min-1), and mango (4.49 ± 0.39 log CFU; 0.17 ± 0.03 min-1). These data suggest that not all S. enterica strains have the same ability to survive under SGC, influencing the probability of arriving into the small intestine.


Subject(s)
Salmonella enterica , Humans , Food Microbiology , Colony Count, Microbial , Food Contamination/analysis , Water/pharmacology
3.
ISME J ; 17(11): 2035-2046, 2023 11.
Article in English | MEDLINE | ID: mdl-37709939

ABSTRACT

Seasonal cycles within the marginal ice zones in polar regions include large shifts in temperature and salinity that strongly influence microbial abundance and physiology. However, the combined effects of concurrent temperature and salinity change on microbial community structure and biochemical composition during transitions between seawater and sea ice are not well understood. Coastal marine communities along the western Antarctic Peninsula were sampled and surface seawater was incubated at combinations of temperature and salinity mimicking the formation (cold, salty) and melting (warm, fresh) of sea ice to evaluate how these factors may shape community composition and particulate metabolite pools during seasonal transitions. Bacterial and algal community structures were tightly coupled to each other and distinct across sea-ice, seawater, and sea-ice-meltwater field samples, with unique metabolite profiles in each habitat. During short-term (approximately 10-day) incubations of seawater microbial communities under different temperature and salinity conditions, community compositions changed minimally while metabolite pools shifted greatly, strongly accumulating compatible solutes like proline and glycine betaine under cold and salty conditions. Lower salinities reduced total metabolite concentrations in particulate matter, which may indicate a release of metabolites into the labile dissolved organic matter pool. Low salinity also increased acylcarnitine concentrations in particulate matter, suggesting a potential for fatty acid degradation and reduced nutritional value at the base of the food web during freshening. Our findings have consequences for food web dynamics, microbial interactions, and carbon cycling as polar regions undergo rapid climate change.


Subject(s)
Ecosystem , Salinity , Temperature , Antarctic Regions , Seawater/microbiology , Particulate Matter , Ice Cover/microbiology
4.
Biointerphases ; 18(2): 021001, 2023 03 10.
Article in English | MEDLINE | ID: mdl-36898958

ABSTRACT

Tumor invasion is likely driven by the product of intrinsic and extrinsic stresses, reduced intercellular adhesion, and reciprocal interactions between the cancer cells and the extracellular matrix (ECM). The ECM is a dynamic material system that is continuously evolving with the tumor microenvironment. Although it is widely reported that cancer cells degrade the ECM to create paths for migration using membrane-bound and soluble enzymes, other nonenzymatic mechanisms of invasion are less studied and not clearly understood. To explore tumor invasion that is independent of enzymatic degradation, we have created an open three-dimensional (3D) microchannel network using a novel bioconjugated liquid-like solid (LLS) medium to mimic both the tortuosity and the permeability of a loose capillary-like network. The LLS is made from an ensemble of soft granular microgels, which provides an accessible platform to investigate the 3D invasion of glioblastoma (GBM) tumor spheroids using in situ scanning confocal microscopy. The surface conjugation of the LLS microgels with type 1 collagen (COL1-LLS) enables cell adhesion and migration. In this model, invasive fronts of the GBM microtumor protruded into the proximal interstitial space and may have locally reorganized the surrounding COL1-LLS. Characterization of the invasive paths revealed a super-diffusive behavior of these fronts. Numerical simulations suggest that the interstitial space guided tumor invasion by restricting available paths, and this physical restriction is responsible for the super-diffusive behavior. This study also presents evidence that cancer cells utilize anchorage-dependent migration to explore their surroundings, and geometrical cues guide 3D tumor invasion along the accessible paths independent of proteolytic ability.


Subject(s)
Microgels , Humans , Cell Movement , Neoplasm Invasiveness/pathology , Extracellular Matrix/metabolism , Collagen Type I , Cell Line, Tumor , Tumor Microenvironment
5.
Mar Pollut Bull ; 182: 113957, 2022 Sep.
Article in English | MEDLINE | ID: mdl-35872476

ABSTRACT

Finfish aquaculture is a fast-growing primary industry and is increasingly common in coastal ecosystems. Bacterioplankton is ubiquitous in marine environment and respond rapidly to environmental changes. Changes in bacterioplankton community are not well understood in semi-enclosed stratified embayments. This study aims to examine aquaculture effects in the composition and functional profiles of the bacterioplankton community using amplicon sequencing along a distance gradient from two finfish leases in a marine embayment. Results revealed natural stratification in bacterioplankton associated to NOx, conductivity, salinity, temperature and PO4. Among the differentially abundant bacteria in leases, we found members associated with nutrient enrichment and aquaculture activities. Abundant predicted functions near leases were assigned to organic matter degradation, fermentation, and antibiotic resistance. This study provides a first effort to describe changes in the bacterioplankton community composition and function due to finfish aquaculture in a semi-enclosed and highly stratified embayment with a significant freshwater input.


Subject(s)
Ecosystem , Plankton , Animals , Aquaculture , Aquatic Organisms , Fishes , Plankton/microbiology , RNA, Ribosomal, 16S
6.
Phys Rev Lett ; 125(13): 131803, 2020 Sep 25.
Article in English | MEDLINE | ID: mdl-33034491

ABSTRACT

We report the first precision measurement of the parity-violating asymmetry in the direction of proton momentum with respect to the neutron spin, in the reaction ^{3}He(n,p)^{3}H, using the capture of polarized cold neutrons in an unpolarized active ^{3}He target. The asymmetry is a result of the weak interaction between nucleons, which remains one of the least well-understood aspects of electroweak theory. The measurement provides an important benchmark for modern effective field theory and potential model calculations. Measurements like this are necessary to determine the spin-isospin structure of the hadronic weak interaction. Our asymmetry result is A_{PV}=[1.55±0.97(stat)±0.24(sys)]×10^{-8}, which has the smallest uncertainty of any hadronic parity-violating asymmetry measurement so far.

7.
Proc Biol Sci ; 287(1920): 20192497, 2020 02 12.
Article in English | MEDLINE | ID: mdl-32019443

ABSTRACT

Urbanization and associated environmental changes are causing global declines in vertebrate populations. In general, population declines of the magnitudes now detected should lead to reduced effective population sizes for animals living in proximity to humans and disturbed lands. This is a cause for concern because effective population sizes set the rate of genetic diversity loss due to genetic drift, the rate of increase in inbreeding and the efficiency with which selection can act on beneficial alleles. We predicted that the effects of urbanization should decrease effective population size and genetic diversity, and increase population-level genetic differentiation. To test for such patterns, we repurposed and reanalysed publicly archived genetic datasets for North American birds and mammals. After filtering, we had usable raw genotype data from 85 studies and 41 023 individuals, sampled from 1008 locations spanning 41 mammal and 25 bird species. We used census-based urban-rural designations, human population density and the Human Footprint Index as measures of urbanization and habitat disturbance. As predicted, mammals sampled in more disturbed environments had lower effective population sizes and genetic diversity, and were more genetically differentiated from those in more natural environments. There were no consistent relationships detectable for birds. This suggests that, in general, mammal populations living near humans may have less capacity to respond adaptively to further environmental changes, and be more likely to suffer from effects of inbreeding.


Subject(s)
Birds/genetics , Genetic Variation , Mammals/genetics , Urbanization/trends , Animals , Biodiversity , Ecosystem , Genetics, Population
8.
J Expo Sci Environ Epidemiol ; 29(6): 860, 2019 Oct.
Article in English | MEDLINE | ID: mdl-30899068

ABSTRACT

Corrigendum: This work was also funded by the European Commission grant 603794 (GERoNiMO project).

9.
Vaccine ; 37(2): 333-342, 2019 01 07.
Article in English | MEDLINE | ID: mdl-30522906

ABSTRACT

A human cytomegalovirus (HCMV) vaccine to prevent infection and/or reduce disease associated with congenital infection or visceral disease in transplant recipients is a high priority, but has remained elusive. We created a disabled infectious single cycle rhesus CMV (RhCMV) deleted for glycoprotein L (gL) and the MHC class I immune evasion genes Rh178 and Rh182-189, and restored its epithelial cell tropism by inserting the Rh128-131A genes. The resulting virus, RhCMVRΔgL/178/182-189, was used to vaccinate rhesus monkeys intramuscularly and was compared with vaccination of animals with soluble RhCMV glycoprotein B (gB) in alum/monophosphoryl lipid A or with PBS as a control. At 4 weeks after the second vaccination, an increased frequency of RhCMV-specific CD8 T cells was detected in animals vaccinated with the RhCMVRΔgL/178/182-189 vaccine compared to animals vaccinated with soluble gB. In contrast, monkeys vaccinated with soluble gB had 20-fold higher gB antibody titers than animals vaccinated with RhCMVRΔgL/178/182-189. Titers of neutralizing antibody to RhCMV infection of fibroblasts were higher in animals vaccinated with gB compared with RhCMVRΔgL/178/182-189. Following vaccination, monkeys were challenged subcutaneously with RhCMV UCD59, a low passage virus propagated in monkey kidney epithelial cells. All animals became infected after challenge; however, the frequency of RhCMV detection in the blood was reduced in monkeys vaccinated with soluble gB compared with those vaccinated with RhCMVRΔgL/178/182-189. The frequency of challenge virus shedding in the urine and saliva and the RhCMV copy number shed at these sites was not different in animals vaccinated with RhCMVRΔgL/178/182-189 or soluble gB compared with those that received PBS before challenge. Although the RhCMVRΔgL/178/182-189 vaccine was superior in inducing cellular immunity to RhCMV, it induced lower titers of neutralizing antibody and antibody to gB than the soluble gB vaccine; after challenge, animals vaccinated with soluble gB had a lower frequency of virus detection in the blood than those vaccinated with RhCMVRΔgL/178/182-189.


Subject(s)
Cytomegalovirus Infections/prevention & control , Cytomegalovirus/immunology , Defective Viruses/immunology , Gene Deletion , Genes, MHC Class I , Immune Evasion/genetics , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Cytomegalovirus/physiology , Cytomegalovirus Infections/immunology , DNA, Viral/blood , Defective Viruses/genetics , Macaca mulatta , Vaccination/methods , Viral Envelope Proteins/genetics , Virus Replication
10.
Phys Chem Chem Phys ; 20(45): 28425-28434, 2018 Nov 21.
Article in English | MEDLINE | ID: mdl-30406236

ABSTRACT

We report a six-dimensional (6D) potential energy surface (PES) for the CS-H2 system computed using high-level electronic structure theory and fitted using a hybrid invariant polynomial method. Full-dimensional quantum close-coupling scattering calculations have been carried out using this potential for rotational and, for the first time, vibrational quenching transitions of CS induced by H2. State-to-state cross sections and rate coefficients for rotational transitions in CS from rotational levels j1 = 0-5 in the ground vibrational state are compared with previous theoretical results obtained using a rigid-rotor approximation. For vibrational quenching, state-to-state and total cross sections and rate coefficients were calculated for the vibrational transitions in CS(v1 = 1,j1) + H2(v2 = 0,j2) → CS(v1' = 0,j1') + H2(v2' = 0,j2') collisions, for j1 = 0-5. Cross sections for collision energies in the range 1 to 3000 cm-1 and rate coefficients in the temperature range of 5 to 600 K are obtained for both para-H2 (j2 = 0) and ortho-H2 (j2 = 1) collision partners. Application of the computed results in astrophysics is also discussed.

11.
Anesth Prog ; 65(2): 89-93, 2018.
Article in English | MEDLINE | ID: mdl-29952648

ABSTRACT

The purpose of this article was to determine if pediatric dental treatment under general anesthesia utilizing orotracheal intubation takes longer than using nasotracheal intubation techniques. Twenty-six American Society of Anesthesiologists Physical Status Classification I and II pediatric dental patients, ages 2-8 years treated under general anesthesia, were assigned to 1 of 2 groups: (a) nasotracheal intubation (control, n = 13), (b) orotracheal intubation (experimental, n = 13). Times for intubation, radiographic imaging, and dental procedures, as well as total case time were quantified. Data were collected on airway difficulty, numbers of providers needed for intubation, intubation attempts, and intubation trauma. There was a significant difference in mean intubation time (oral = 2.1 minutes versus nasal = 6.3 minutes; p < .01). There was no difference in mean radiograph time (oral = 4.2 minutes versus nasal = 3.4 minutes; p = .144), and overall radiograph image quality was not affected. There was no difference in dental procedure time ( p = .603) or total case time ( p = .695). Additional providers were needed for intubation and more attempts were required for nasotracheal intubation versus orotracheal intubation (6 additional providers/22 attempts vs 0 additional providers/15 attempts, p < .01 and p < .05, respectively). Nine of 13 nasotracheal intubations were rated as traumatic (69%) versus 0 of 13 for orotracheal intubations (0%) ( p < .01). In 7/9 orotracheal intubation cases (78%), the tube was not moved during treatment ( p < .01). Orotracheal intubation does not increase case time, does not interfere with radiographic imaging, and is less traumatic for the patient when performed by physician anesthesiologists, emergency and pediatric medicine physician residents, certified registered nurse anesthetists, and student nurse anesthetists, all with variable nasotracheal intubation experience.


Subject(s)
Anesthesia, Dental/methods , Anesthesia, General/methods , Anesthesiologists , Internship and Residency , Intubation, Intratracheal/methods , Nurse Anesthetists , Oral Surgical Procedures , Students, Nursing , Anesthesia, Dental/adverse effects , Anesthesia, General/adverse effects , Child , Child, Preschool , Clinical Competence , Female , Humans , Intubation, Intratracheal/adverse effects , Male , Operative Time , Oral Surgical Procedures/adverse effects , Pilot Projects , Time Factors
12.
J Appl Microbiol ; 125(4): 952-963, 2018 Oct.
Article in English | MEDLINE | ID: mdl-29799652

ABSTRACT

AIMS: Factors such as seasonal temperature and diet components, for example, fishmeal (FM) inclusion, can influence the composition of the gut microbiota of fish. In this study, we examined changes in the gut bacterial populations, in particular lactic acid bacteria (LAB), of farmed Tasmanian Atlantic salmon in response to different diets, during periods of higher water temperature. METHODS AND RESULTS: Between December 2011 and March 2012 hindgut faecal samples were collected from Atlantic salmon from a commercial fish farm in south of Hobart, Tasmania, fed with one of four trial diets containing either high or low FM inclusion levels with or without prebiotics. Overall there was little difference in the cultivatable bacterial populations in response to varying levels of FM and prebiotic supplementation, with LAB counts decreasing in response to increased water temperatures. However, it was observed that the high FM diet supported the presence of LAB in January, when these were not detected in the low FM diets. CONCLUSIONS: Our study indicates that the inclusion of higher amounts of FM rather than the addition of prebiotics has a greater effect on LAB colonization of the gut in Atlantic salmon. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the importance of the new fish feeds for promoting salmon health in aquaculture industry.


Subject(s)
Animal Feed/analysis , Feces/microbiology , Gastrointestinal Microbiome , Prebiotics/analysis , Salmo salar/metabolism , Animals , Aquaculture/methods , Bacteria/classification , Bacteria/genetics , Bacteria/isolation & purification , Diet/veterinary , Salmo salar/growth & development , Salmo salar/microbiology , Tasmania
13.
Science ; 360(6385): 212-215, 2018 04 13.
Article in English | MEDLINE | ID: mdl-29519919

ABSTRACT

In temperate and boreal ecosystems, seasonal cycles of growth and dormancy allow perennial plants to adapt to winter conditions. We show, in hybrid aspen trees, that photoperiodic regulation of dormancy is mechanistically distinct from autumnal growth cessation. Dormancy sets in when symplastic intercellular communication through plasmodesmata is blocked by a process dependent on the phytohormone abscisic acid. The communication blockage prevents growth-promoting signals from accessing the meristem. Thus, precocious growth is disallowed during dormancy. The dormant period, which supports robust survival of the aspen tree in winter, is due to loss of access to growth-promoting signals.


Subject(s)
Abscisic Acid/physiology , Cell Communication/physiology , Photoperiod , Plant Dormancy/physiology , Plant Growth Regulators/physiology , Populus/growth & development , Trees/growth & development , Circadian Rhythm , Meristem/cytology , Meristem/growth & development , Populus/cytology , Populus/genetics , Seasons , Trees/cytology , Trees/genetics
14.
J Phys Chem A ; 122(6): 1511-1520, 2018 Feb 15.
Article in English | MEDLINE | ID: mdl-29365271

ABSTRACT

We report the first full-dimensional potential energy surface (PES) and quantum mechanical close-coupling calculations for scattering of SiO due to H2. The full-dimensional interaction potential surface was computed using the explicitly correlated coupled-cluster (CCSD(T)-F12b) method and fitted using an invariant polynomial approach. Pure rotational quenching cross sections from initial states v1 = 0, j1 = 1-5 of SiO in collision with H2 are calculated for collision energies between 1.0 and 5000 cm-1. State-to-state rotational rate coefficients are calculated at temperatures between 5 and 1000 K. The rotational rate coefficients of SiO with para-H2 (p-H2) are compared with previous approximate results which were obtained using SiO-He PESs or scaled from SiO-He rate coefficients. Rovibrational state-to-state and total quenching cross sections and rate coefficients for initially excited SiO (v1 = 1, j1 = 0 and 1) in collisions with p-H2 (v2 = 0, j2 = 0) and ortho-H2 (o-H2) (v2 = 0, j2 = 1) are also obtained. The application of the current collisional rate coefficients to astrophysics is briefly discussed.

15.
Sci Rep ; 8(1): 1676, 2018 01 26.
Article in English | MEDLINE | ID: mdl-29374211

ABSTRACT

Type III solar radio bursts are the Sun's most intense and frequent nonthermal radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III bursts imaged by the Murchison Widefield Array and detected by the Learmonth radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5-10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III radio bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III bursts; thus different special conditions exist for electrons leaving reconnection regions to produce observable radio, EUV, UV, and X-ray bursts.

16.
Phys Rev Lett ; 121(24): 242002, 2018 Dec 14.
Article in English | MEDLINE | ID: mdl-30608729

ABSTRACT

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.

17.
Br Dent J ; 223(4): 239, 2017 08 25.
Article in English | MEDLINE | ID: mdl-28840899
18.
J Laryngol Otol ; 131(S1): S57-S61, 2017 Jan.
Article in English | MEDLINE | ID: mdl-27762178

ABSTRACT

BACKGROUND: The skull base is a highly complex anatomical region that provides passage for important nerves and vessels as they course into and out of the cranial cavity. Key to the management of pathology in this region is a thorough understanding of the anatomy, with its variations, and the relationship of various neurovascular structures to the pathology in question. Targeted high-resolution magnetic resonance imaging on high field strength magnets can enable the skull base surgeon to understand this intricate relationship and deal with the pathology from a position of relative advantage. OBJECTIVE: With the help of case studies, this paper illustrates the application of specialised magnetic resonance techniques to study pathology of the orbital apex in particular. CONCLUSION: The fine anatomical detail provided gives surgeons the ability to design an endonasal endoscopic procedure appropriate to the anatomy of the pathology.


Subject(s)
Graves Ophthalmopathy/diagnostic imaging , Meningeal Neoplasms/diagnostic imaging , Meningioma/diagnostic imaging , Nerve Compression Syndromes/diagnostic imaging , Optic Nerve Diseases/diagnostic imaging , Skull Base/diagnostic imaging , Adult , Decompression, Surgical , Female , Graves Ophthalmopathy/complications , Humans , Magnetic Resonance Imaging , Meningeal Neoplasms/complications , Meningeal Neoplasms/surgery , Meningioma/complications , Meningioma/surgery , Neoplasm, Residual , Nerve Compression Syndromes/etiology , Nerve Compression Syndromes/surgery , Optic Nerve Diseases/etiology , Optic Nerve Diseases/surgery
19.
J Chem Phys ; 145(22): 224307, 2016 Dec 14.
Article in English | MEDLINE | ID: mdl-27984886

ABSTRACT

We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm-1. Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

20.
J Chem Phys ; 145(3): 034308, 2016 Jul 21.
Article in English | MEDLINE | ID: mdl-27448888

ABSTRACT

Inelastic scattering computations are presented for collisions of vibrationally and rotationally excited CO with H2 in full dimension. The computations utilize a newly developed six-dimensional potential energy surface (PES) and the previously reported four-dimensional V12 PES [P. Jankowski et al., J. Chem. Phys. 138, 084307 (2013)] and incorporate full angular-momentum coupling. At low collision energies, pure rotational excitation cross sections of CO by para-, ortho-, and normal-H2 are calculated and convolved to compare with recent measurements. Good agreement with the measured data is shown except for j1 = 0 → 1 excitation of CO for very low-energy para-H2 collisions. Rovibrational quenching results are presented for initially excited CO(v1j1) levels with v1 = 1, j1 = 1-5 and v1 = 2, j1 = 0 for collisions with para-H2 (v2 = 0, j2 = 0) and ortho-H2 (v2 = 0, j2 = 1) over the kinetic energy range 0.1-1000 cm(-1). The total quenching cross sections are found to have similar magnitudes, but increase (decrease) with j1 for collision energies above ∼300 cm(-1) (below ∼10 cm(-1)). Only minor differences are found between para- and ortho-H2 colliders for rovibrational and pure rotational transitions, except at very low collision energies. Likewise, pure rotational deexcitation of CO yields similar cross sections for the v1 = 0 and v1 = 1 vibrational levels, while rovibrational quenching from v1 = 2, j1 = 0 is a factor of ∼5 larger than that from v1 = 1, j1 = 0. Details on the PES, computed at the CCSD(T)/aug-cc-pV5Z level, and fitted with an invariant polynomial method, are also presented.

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