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1.
J Am Chem Soc ; 146(31): 21308-21319, 2024 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-39073403

RESUMEN

Wavelength and pressure dependent quantum yields (ϕ, QYs) of propanal photolysis have been measured for photolysis wavelengths, λ = 300-330 nm, and buffer gases of 3-10 Torr propanal and 0-757 Torr N2. Following laser photolysis, three photochemical pathways were established, using Fourier transform infrared spectroscopy of the stable end-products. Photolysis is dominated by the Norrish Type 1 reaction, which has been reported previously, but with inconsistent quantum yields. The propanal α-hydrogen leads to a 4-center elimination of H2, as observed in CH3CHO, here leading to methylketene. The presence of hydrogen attached to the ß-carbon allows a new photochemical pathway: concerted triple fragmentation into CO + H2 + C2H4 via a 5-center transition state. Neither of these channels has been reported previously. No evidence for the previously reported C2H6 + CO, C2H4 + H2CO or CH3 + CH2CHO channels, nor for phototautomerization to 1-propenol (CH3CH═CHOH) was found. Modeling of the wavelength, pressure and collision partner dependence of the QYs allows us to reconcile the previous NT1a results and make recommendations for the quantum yields of all three channels under tropospheric conditions. The general impact of ß-hydrogen atoms in the photochemistry of aldehydes is to open up new pathways from cyclic transition states and to reduce the importance of other photolysis or isomerization channels.

2.
Int J Lang Commun Disord ; 59(1): 84-93, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-37340952

RESUMEN

BACKGROUND: This study reports on new contexts in which formulaic language has been used in the years since 2013 when the last synthesis was carried out. The background presents an old but still useful definition and lists themes under which research was arranged in 2013 and which continue to be used. AIMS: This study has a particular emphasis on the relevance of formulaic language to people living with dementia. METHODS: Section 3, identifying new directions, reviews new 'third waves' of research priorities in several fields in which formulaic sequences play a major role, including sociolinguistic variation, corpus-based and corpus-driven analyses, pragmatics, human-computer interaction, and psycholinguistics, all of which are relevant to speech-language therapists. Section 4, outreach and expansions, illustrates new contributions from cognitively impaired person-to-person exchanges in online environments, recent examinations of infant- and pet-directed speech incorporating formulaic language, and online graphic explorations such as emojis. Section 5 focuses on growth of research in theoretical and clinical applications by Van Lancker Sidtis, as illustrated by references to her recent work. MAIN CONTRIBUTION: The paper's main contribution is to summarize the work on formulaic language over the last 10 years, to indicate its continued importance and relevance in ordinary conversation, and especially in allowing people living with dementia to continue to interact with others. CONCLUSION: The paper concludes by suggesting that more focus be placed on the analysis of formulaic language with an emphasis on its relevance for speech-language therapists and other clinicians. WHAT THIS PAPER ADDS: What is already known on the subject Research has been growing since the late 1970s and early 1980s on non-propositional language (as opposed at that time to the Chomskyan paradigm) and especially on lexical bundles, idioms, second language acquisition and multiword expressions. Studies beginning with Hughlings Jackson (1874) have been annotated through early 2012 (Wray, 2013). What this study adds This study examines 'third waves' in pragmatics, sociolinguistics and areas of neurology and speech perception contributing to what Van Lancker Sidtis (2021) calls the third wave of acceptance of the range and depth of formulaic sequences in ordinary or familiar language. What are the clinical implications of this work? Conversations with pet robots or web-based composition with emojis are but two of the developing areas built on formulaic sequences currently being used for communication interventions with persons living with dementia or other major neurocognitive disorder. Overviews of major contributions in theory and social contexts by Wray (2020, 2021) and theoretical and cognitive applications by Van Lancker Sidtis (2021) detail new areas for the study of formulaic sequences and their contributions to a range of neurocognitive disorders.


Asunto(s)
Demencia , Lenguaje , Femenino , Humanos , Comunicación , Habla , Psicolingüística , Demencia/terapia
3.
Issues Ment Health Nurs ; 44(9): 809-815, 2023 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-37669558

RESUMEN

In Appalachia, rates of depression and suicidality are higher than national averages. Additional disparities of age, geographic isolation, economic distress, and mental healthcare provider shortages contribute to mental health challenges among rural Appalachian older adults (RAOAs). Based on ethnonursing research in East Tennessee, this article expands on findings about how RAOA faith beliefs and practices enhance mental health. Faith was found to decrease worry, improve coping, facilitate a sense of peace, and deepen thankfulness and joy. Implications for nursing practice and education indicate the importance of providing spiritual care to promote mental health and well-being for this vulnerable population.

4.
J Psychosoc Nurs Ment Health Serv ; 61(5): 45-52, 2023 May.
Artículo en Inglés | MEDLINE | ID: mdl-36322869

RESUMEN

Appalachia leads the country in mortality related to chronic comorbidities, such as heart disease, cancer, depression, and suicide. Appalachian older adults experience disproportionate risks for poor health outcomes. Spirituality is integral to Appalachian culture, and many older adults use spiritual engagement (SE) to cope with health challenges. Despite these connections, there is limited evidence about SE and well-being in this population. Therefore, the current systematic review addresses the literature gap of how SE influences health of Appalachian older adults. Using thematic synthesis, we analyzed 11 qualitative and three mixed methods studies. Major findings indicate that SE positively impacts holistic health through adaptive coping, guided partnerships with God, decreased loneliness, and enhanced sense of purpose. Future studies could examine SE practices among diverse populations, SE virtual experiences, and SE nursing assessments. Understanding how SE influences health of Appalachian older adults could prepare nurses to reduce disparities and improve health outcomes for this vulnerable population. [Journal of Psychosocial Nursing and Mental Health Services, 61(5), 45-52.].


Asunto(s)
Adaptación Psicológica , Servicios de Salud Mental , Humanos , Anciano , Región de los Apalaches , Espiritualidad
5.
J Community Health Nurs ; 38(4): 232-243, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34787041

RESUMEN

Purpose: Despite numerous established benefits of exercise, many older adults do not get enough. The purpose of this study was to identify facilitators and barriers to physical activity/exercise; gain greater understanding of older adults' physical activity self-efficacy; and increase understanding of how to reduce sedentary behavior.Design: Cross-sectional descriptiveMethods: Quantitative with convenience sample of 66 older adultsFindings: Nearly one third of participants reported engaging in regular physical activity. They tended to have rather strong physical activity self-efficacy and limited barriers to being active.Conclusions: The sample had limited involvement in physical activity or exercise, despite feeling confident in their ability to be active. There could be additional barriers or motivating factors that are preventing them from being more active.Clinical Evidence: Honest and directed conversation about older adults' understanding and attitudes towards exercise, paired with an individualized plan tailored to their interests and lifestyle could help increase physical activity/exercise.


Asunto(s)
Ejercicio Físico , Estilo de Vida , Anciano , Actitud , Estudios Transversales , Humanos
6.
J Gerontol Nurs ; 47(10): 23-29, 2021 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-34590978

RESUMEN

Generally considered an epidemic among young people, substance misuse has been a growing issue among older Americans for the past 40 years. Legal substances, such as alcohol, tobacco, and prescription drugs, including opioids and marijuana, are of primary concern when it comes to aging Baby Boomers. By 2050, 22% of Americans will be aged ≥65 years. Currently, eHealth interventions are receiving attention in treating substance misuse among younger Americans. The current study has two aims: to evaluate the effectiveness of eHealth interventions for older adults treated for substance misuse problems, as well as to investigate behavioral outcomes in reducing substance misuse. A comprehensive search of databases yielded 35,041 articles that examined reductions in substance misuse and problem behaviors as a primary outcome with eHealth interventions delivered to older adults. Once duplicate and irrelevant articles were removed, seven were left to be analyzed. Findings suggest use of technology to assess and intervene with older adults using various substances shows promise and, as a whole, older adults are receptive to online learning, screening and assessment, and interventions. [Journal of Gerontological Nursing, 47(10), 23-29.].


Asunto(s)
Medicamentos bajo Prescripción , Trastornos Relacionados con Sustancias , Telemedicina , Adolescente , Anciano , Envejecimiento , Humanos , Trastornos Relacionados con Sustancias/prevención & control , Tecnología
7.
Geriatr Nurs ; 41(6): 846-851, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32571586

RESUMEN

Many older adults eat poorly balanced diets and are physically inactive, posing a risk to their cardiovascular and mental health. The benefits of healthful living extend beyond cardiovascular health and disease risk reduction such that physical activity has been shown to positively affect mood state. This was a cross-sectional investigation completed at three senior lunch program sites in Charlotte, NC to assess the status and relationship of nutrition, physical activity patterns, and mood state in older adults, prior to the center offering a new nutritional and physical activity intervention. Some significant relationships between cardiovascular indicators and mood were found.


Asunto(s)
Ejercicio Físico , Estado Nutricional , Afecto , Anciano , Estudios Transversales , Humanos , Conducta Sedentaria
8.
Phys Chem Chem Phys ; 21(26): 14284-14295, 2019 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-30629059

RESUMEN

The first experimental observation of the primary photochemical channel of acetaldehyde leading to the formation of ketene (CH2CO) and hydrogen (H2) molecular products is reported. Acetaldehyde (CH3CHO) was photolysed in a molecular beam at 305.6 nm and the resulting H2 product characterized using velocity-map ion (VMI) imaging. Resonance-enhanced multiphoton ionization (REMPI), via two-photon excitation to the double-well EF 1Σ state, was used to state-selectively ionize the H2 and determine angular momentum distributions for H2 (ν = 0) and H2 (ν = 1). Velocity-map ion images were obtained for H2 (ν = 0 and 1, J = 5), allowing the total translational energy release of the photodissociation process to be determined. Following photolysis of CH3CHO in a gas cell, the CH2CO co-fragment was identified, using Fourier transform infrared spectroscopy, by its characteristic infrared absorption at 2150 cm-1. The measured quantum yield of the CH2CO + H2 product channel at 305.0 nm is φ = 0.0075 ± 0.0025 for both 15 Torr of neat CH3CHO and a mixture with 745 Torr of N2. Although small, this result has implications for the atmospheric photochemistry of carbonyls and this reaction represents a new tropospheric source of H2. Quasi-classical trajectory (QCT) simulations on a zero-point energy corrected reaction-path potential are also performed. The experimental REMPI and VMI image distributions are not consistent with the QCT simulations, indicating a non reaction-path mechanism should be considered.

9.
J Phys Chem A ; 123(48): 10381-10396, 2019 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-31675237

RESUMEN

Norrish Type I (NTI) α-bond cleavage is the dominant photolysis mechanism in small carbonyls and is an important source of radicals in the troposphere. In nonsymmetric species two cleavages are possible, NTIa and NTIb, forming larger and smaller alkyl radicals, respectively. For a data set of 20 small, atmospherically relevant carbonyls we predict NTIa and NTIb thresholds on the S0, S1, and T1 electronic states. The calculated NTIa T1 thresholds give a mean absolute deviation (MAD) of 5.8 kJ/mol with respect to the available experimental thresholds of five carbonyls. In addition, the intrinsic barrier heights to dissociation on the S0, S1, and T1 electronic states are predicted. We find RI-B2GP-PLYP/def2-TZVP calculations on S0 and unrestricted RI-B2GP-PLYP/def2-TZVP calculations on T1 give MADs of 6.1 kJ/mol for S0 asymptotic energies and 6.3 kJ/mol for S0 → T1 0-0 excitation energies, with respect to available experimental data. A composite method is used to determine S1 thresholds, with bt-STEOM-CCSD/cc-pVQZ calculation of vertical excitation energies and TD-RI-B3LYP/def2-TZVP calculations on S1, which achieves a MAD of 7.2 kJ/mol, with respect to experimental 0-0 excitation energies. Our calculations suggest, with the exception of bifunctional carbonyls and enones, NTI reactions on S1 are unlikely to be important at tropospherically relevant photolysis energies (<400 kJ/mol). In contrast, at these energies almost all possible NTI channels on T1 are open, and all barrierless S0 NTI dissociations are accessible. Our calculations allow a number of structural effects on both 0-0 excitation energies and intrinsic reaction barriers, on a given electronic state, to be elucidated and rationalized.

10.
J Chem Phys ; 148(7): 074106, 2018 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-29471661

RESUMEN

Quantum thermodynamic parameters can be determined using path integral Monte Carlo (PIMC) simulations. These simulations, however, become computationally demanding as the quantum nature of the system increases, although their efficiency can be improved by using higher order approximations to the thermal density matrix, specifically the action. Here we compare the standard, primitive approximation to the action (PA) and three higher order approximations, the Takahashi-Imada action (TIA), the Suzuki-Chin action (SCA) and the Chin action (CA). The resulting PIMC methods are applied to two realistic potential energy surfaces, for H2O and HCN-HNC, both of which are spectroscopically accurate and contain three-body interactions. We further numerically optimise, for each potential, the SCA parameter and the two free parameters in the CA, obtaining more significant improvements in efficiency than seen previously in the literature. For both H2O and HCN-HNC, accounting for all required potential and force evaluations, the optimised CA formalism is approximately twice as efficient as the TIA formalism and approximately an order of magnitude more efficient than the PA. The optimised SCA formalism shows similar efficiency gains to the CA for HCN-HNC but has similar efficiency to the TIA for H2O at low temperature. In H2O and HCN-HNC systems, the optimal value of the a1 CA parameter is approximately 13, corresponding to an equal weighting of all force terms in the thermal density matrix, and similar to previous studies, the optimal α parameter in the SCA was ∼0.31. Importantly, poor choice of parameter significantly degrades the performance of the SCA and CA methods. In particular, for the CA, setting a1 = 0 is not efficient: the reduction in convergence efficiency is not offset by the lower number of force evaluations. We also find that the harmonic approximation to the CA parameters, whilst providing a fourth order approximation to the action, is not optimal for these realistic potentials: numerical optimisation leads to better approximate cancellation of the fifth order terms, with deviation between the harmonic and numerically optimised parameters more marked in the more quantum H2O system. This suggests that numerically optimising the CA or SCA parameters, which can be done at high temperature, will be important in fully realising the efficiency gains of these formalisms for realistic potentials.

11.
J Chem Phys ; 148(19): 194113, 2018 May 21.
Artículo en Inglés | MEDLINE | ID: mdl-30307216

RESUMEN

A new approach for preventing zero-point energy (ZPE) violation in quasi-classical trajectory (QCT) simulations is presented and applied to H2CO "roaming" reactions. Zero-point energy may be problematic in roaming reactions because they occur at or near bond dissociation thresholds and these channels may be incorrectly open or closed depending on if, or how, ZPE has been treated. Here we run QCT simulations on a "ZPE-corrected" potential energy surface defined as the sum of the molecular potential energy surface (PES) and the global harmonic ZPE surface. Five different harmonic ZPE estimates are examined with four, on average, giving values within 4 kJ/mol-chemical accuracy-for H2CO. The local harmonic ZPE, at arbitrary molecular configurations, is subsequently defined in terms of "projected" Cartesian coordinates and a global ZPE "surface" is constructed using Shepard interpolation. This, combined with a second-order modified Shepard interpolated PES, V, allows us to construct a proof-of-concept ZPE-corrected PES for H2CO, V eff, at no additional computational cost to the PES itself. Both V and V eff are used to model product state distributions from the H + HCO → H2 + CO abstraction reaction, which are shown to reproduce the literature roaming product state distributions. Our ZPE-corrected PES allows all trajectories to be analysed, whereas, in previous simulations, a significant proportion was discarded because of ZPE violation. We find ZPE has little effect on product rotational distributions, validating previous QCT simulations. Running trajectories on V, however, shifts the product kinetic energy release to higher energy than on V eff and classical simulations of kinetic energy release should therefore be viewed with caution.

12.
J Phys Chem A ; 121(19): 3679-3688, 2017 May 18.
Artículo en Inglés | MEDLINE | ID: mdl-28436675

RESUMEN

Fourier transform infrared spectra of isolated 1-propenol and 2-propenol in the gas-phase have been collected in the range of 900-3800 cm-1, and the absolute infrared absorption cross sections reported for the first time. Both cis and trans isomers of 1-propenol were observed with the trans isomer in greater abundance. Syn and anti conformers of both 1- and 2-propenol were also observed, with abundance consistent with thermal population. The FTIR spectrum of the smaller ethenol (vinyl alcohol) was used as a benchmark for our computational results. As a consequence, its spectrum has been partially reassigned resulting in the first report of the anti-ethenol conformer. Electronic structure calculations were used to support our experimental results and assign vibrational modes for the most abundant isomers, syn-trans-1-propenol and syn-2-propenol.

13.
J Chem Phys ; 147(1): 013935, 2017 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-28688440

RESUMEN

The dynamics of CO production from photolysis of H2CO have been explored over a 8000 cm-1 energy range (345 nm-266 nm). Two-dimensional ion imaging, which simultaneously measures the speed and angular momentum distribution of a photofragment, was used to characterise the distribution of rotational and translational energy and to quantify the branching fraction of roaming, transition state (TS), and triple fragmentation (3F) pathways. The rotational distribution for the TS channel broadens significantly with increasing energy, while the distribution is relatively constant for the roaming channel. The branching fraction from roaming is also relatively constant at 20% of the observed CO. Above the 3F threshold, roaming decreases in favour of triple fragmentation. Combining the present data with our previous study on the H-atom branching fractions and published quantum yields for radical and molecular channels, absolute quantum yields were determined for all five dissociation channels for the entire S1←S0 absorption band, covering almost 8000 cm-1 of excitation energy. The S0 radical and TS molecular channels are the most important over this energy range. The absolute quantum yield of roaming is fairly constant ∼5% at all energies. The T1 radical channel is important (20%-40%) between 1500 and 4000 cm-1 above the H + HCO threshold, but becomes unimportant at higher energy. Triple fragmentation increases rapidly above its threshold reaching a maximum of 5% of the total product yield at the highest energy.

14.
Pain Med ; 17(2): 278-94, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26814305

RESUMEN

OBJECTIVE: To compare the outcomes of a new group assessment format with conventional individual assessment. DESIGN: A randomized controlled trial. SETTING: An Australian tertiary hospital multidisciplinary pain service. PATIENTS: Adults referred with chronic non-cancer pain. METHODS: Following attendance at an education and orientation group, 211 participants were randomized to either a group assessment format (focused on supported self-assessment) or individual assessment. Follow-up occurred 3 months post-assessment and prior to subsequent pain service intervention. Outcome measures were pain intensity, pain interference, self-efficacy, psychological distress, health care utilization beyond the pain service, waiting time, participant satisfaction, and implementation of self-management strategies. RESULTS: Seventy-two participants undertook group assessment and 90 were assessed individually. Follow-up data were collected on 57 group and 72 individual assessment participants. Results revealed no significant differences between the two assessment formats in outcome with the exception of wait-times. Median wait-time to the first offer of assessment was 47 days for the group format and 144 days for individual. CONCLUSIONS: Group assessment provides a viable alternative to conventional individual assessment. The group assessment reduced wait-times while delivering otherwise comparable outcomes.


Asunto(s)
Dolor Crónico/psicología , Dolor Crónico/terapia , Dimensión del Dolor/métodos , Dimensión del Dolor/psicología , Psicoterapia de Grupo/métodos , Centros de Atención Terciaria , Adulto , Australia/epidemiología , Dolor Crónico/epidemiología , Femenino , Estudios de Seguimiento , Humanos , Masculino , Nueva Gales del Sur/epidemiología , Clínicas de Dolor/normas , Dimensión del Dolor/enfermería , Dimensión del Dolor/normas , Psicoterapia de Grupo/normas , Autoeficacia , Centros de Atención Terciaria/normas
15.
J Phys Chem A ; 119(50): 12166-81, 2015 Dec 17.
Artículo en Inglés | MEDLINE | ID: mdl-26322374

RESUMEN

A general method is presented for constructing, from ab initio quantum chemistry calculations, the potential energy surface (PES) for H2 absorbed in a porous crystalline material. The method is illustrated for the metal-organic framework material MOF-5. Rigid body quantum diffusion Monte Carlo simulations are used in the construction of the PES and to evaluate the quantum ground state of H2 in MOF-5, the zero-point energy, and the enthalpy of adsorption at 0 K.

16.
J Chem Phys ; 143(4): 044114, 2015 Jul 28.
Artículo en Inglés | MEDLINE | ID: mdl-26233114

RESUMEN

We have developed a multi-agent quantum Monte Carlo model to describe the spatial dynamics of multiple majority charge carriers during conduction of electric current in the channel of organic field-effect transistors. The charge carriers are treated by a neglect of diatomic differential overlap Hamiltonian using a lattice of hydrogen-like basis functions. The local ionization energy and local electron affinity defined previously map the bulk structure of the transistor channel to external potentials for the simulations of electron- and hole-conduction, respectively. The model is designed without a specific charge-transport mechanism like hopping- or band-transport in mind and does not arbitrarily localize charge. An electrode model allows dynamic injection and depletion of charge carriers according to source-drain voltage. The field-effect is modeled by using the source-gate voltage in a Metropolis-like acceptance criterion. Although the current cannot be calculated because the simulations have no time axis, using the number of Monte Carlo moves as pseudo-time gives results that resemble experimental I/V curves.

17.
J Chem Phys ; 143(7): 074311, 2015 Aug 21.
Artículo en Inglés | MEDLINE | ID: mdl-26298138

RESUMEN

Quantum and anharmonic effects are investigated in (H2)2-Li(+)-benzene, a model for hydrogen adsorption in metal-organic frameworks and carbon-based materials, using rigid-body diffusion Monte Carlo (RBDMC) simulations. The potential-energy surface (PES) is calculated as a modified Shepard interpolation of M05-2X/6-311+G(2df,p) electronic structure data. The RBDMC simulations yield zero-point energies (ZPE) and probability density histograms that describe the ground-state nuclear wavefunction. Binding a second H2 molecule to the H2-Li(+)-benzene complex increases the ZPE of the system by 5.6 kJ mol(-1) to 17.6 kJ mol(-1). This ZPE is 42% of the total electronic binding energy of (H2)2-Li(+)-benzene and cannot be neglected. Our best estimate of the 0 K binding enthalpy of the second H2 to H2-Li(+)-benzene is 7.7 kJ mol(-1), compared to 12.4 kJ mol(-1) for the first H2 molecule. Anharmonicity is found to be even more important when a second (and subsequent) H2 molecule is adsorbed; use of harmonic ZPEs results in significant error in the 0 K binding enthalpy. Probability density histograms reveal that the two H2 molecules are found at larger distance from the Li(+) ion and are more confined in the θ coordinate than in H2-Li(+)-benzene. They also show that both H2 molecules are delocalized in the azimuthal coordinate, ϕ. That is, adding a second H2 molecule is insufficient to localize the wavefunction in ϕ. Two fragment-based (H2)2-Li(+)-benzene PESs are developed. These use a modified Shepard interpolation for the Li(+)-benzene and H2-Li(+)-benzene fragments, and either modified Shepard interpolation or a cubic spline to model the H2-H2 interaction. Because of the neglect of three-body H2, H2, Li(+) terms, both fragment PESs lead to overbinding of the second H2 molecule by 1.5 kJ mol(-1). Probability density histograms, however, indicate that the wavefunctions for the two H2 molecules are effectively identical on the "full" and fragment PESs. This suggests that the 1.5 kJ mol(-1) error is systematic over the regions of configuration space explored by our simulations. Notwithstanding this, modified Shepard interpolation of the weak H2-H2 interaction is problematic and we obtain more accurate results, at considerably lower computational cost, using a cubic spline interpolation. Indeed, the ZPE of the fragment-with-spline PES is identical, within error, to the ZPE of the full PES. This fragmentation scheme therefore provides an accurate and inexpensive method to study higher hydrogen loading in this and similar systems.

18.
J Chem Phys ; 143(19): 194302, 2015 Nov 21.
Artículo en Inglés | MEDLINE | ID: mdl-26590532

RESUMEN

Finite temperature quantum and anharmonic effects are studied in H2-Li(+)-benzene, a model hydrogen storage material, using path integral Monte Carlo (PIMC) simulations on an interpolated potential energy surface refined over the eight intermolecular degrees of freedom based upon M05-2X/6-311+G(2df,p) density functional theory calculations. Rigid-body PIMC simulations are performed at temperatures ranging from 77 K to 150 K, producing both quantum and classical probability density histograms describing the adsorbed H2. Quantum effects broaden the histograms with respect to their classical analogues and increase the expectation values of the radial and angular polar coordinates describing the location of the center-of-mass of the H2 molecule. The rigid-body PIMC simulations also provide estimates of the change in internal energy, ΔUads, and enthalpy, ΔHads, for H2 adsorption onto Li(+)-benzene, as a function of temperature. These estimates indicate that quantum effects are important even at room temperature and classical results should be interpreted with caution. Our results also show that anharmonicity is more important in the calculation of U and H than coupling-coupling between the intermolecular degrees of freedom becomes less important as temperature increases whereas anharmonicity becomes more important. The most anharmonic motions in H2-Li(+)-benzene are the "helicopter" and "ferris wheel" H2 rotations. Treating these motions as one-dimensional free and hindered rotors, respectively, provides simple corrections to standard harmonic oscillator, rigid rotor thermochemical expressions for internal energy and enthalpy that encapsulate the majority of the anharmonicity. At 150 K, our best rigid-body PIMC estimates for ΔUads and ΔHads are -13.3 ± 0.1 and -14.5 ± 0.1 kJ mol(-1), respectively.

20.
Environ Manage ; 55(6): 1217-26, 2015 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-25822888

RESUMEN

Influenced by natural climatic, geological, and evolutionary changes, landscapes and the ecosystems within are continuously changing. In addition to these natural pressures, anthropogenic drivers have increasingly influenced ecosystems. Whether affected by natural or anthropogenic processes, ecosystems, ecological communities, and ecosystem functioning are dynamic and can lead to "novel" or "emerging" ecosystems. Current literature identifies several definitions of these ecosystems but lacks an unambiguous definition and framework for categorizing what constitutes a novel ecosystem and for informing decisions around best management practices. Here we explore the various definitions used for novel ecosystems, present an unambiguous definition, and propose a framework for identifying the most appropriate management option. We identify and discuss three approaches for managing novel ecosystems: managing against, tolerating, and managing for these systems, and we provide real-world examples of each approach. We suggest that this framework will allow managers to make thoughtful decisions about which strategy is most appropriate for each unique situation, to determine whether the strategy is working, and to facilitate decision-making when it is time to modify the management approach.


Asunto(s)
Evolución Biológica , Cambio Climático , Conservación de los Recursos Naturales/métodos , Ecosistema , Animales , Humanos
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