7,641 research outputs found
Water hexamer: Self-consistent phonons versus reversible scaling versus replica exchange molecular dynamics
Classical free energies for the cage and prism isomers of water hexamer
computed by the self- consistent phonons (SCP) method and reversible scaling
(RS) method are presented for several flexible water potentials. Both methods
have been augmented with a rotational correction for improved accuracy when
working with clusters. Comparison of the SCP results with the RS results
suggests a fairly broad temperature range over which the SCP approximation can
be expected to give accurate results for systems of water clusters, and
complements a previously reported assessment of SCP. Discrepancies between the
SCP and RS results presented here, and recently published replica exchange
molecular dynamics (REMD) results bring into question the convergence of the
REMD and accompanying replica exchange path integral molecular dynamics
results. In addition to the ever-present specter of unconverged results,
several possible sources for the discrepancy are explored based on inherent
characteristics of the methods used.Comment: Submitted to Journal Chemical Physic
Anomalous quantum and isotope effects in water clusters: Physical phenomenon, model artifact, or bad approximation?
Free energy differences are computed for
several isomers of water hexamer relative to the "prism" isomer using the
self-consistent phonons method. % We consider the
isotope effect defined by the quantity , and the quantum effect, , and evaluate them using different flexible
water models. While both and are found
to be rather small for all of the potentials, they are especially small for two
of the empirical models, q-TIP4P/F and TTM3-F, compared to q-SPC/Fw and the two
{\it abinitio}-based models, WHBB and HBB2-pol. This qualitative difference in
the properties of different water models cannot be explained by one being "more
accurate" than the other. We speculate as to whether the observed anomalies are
caused by the special properties of water systems, or are an artifact of either
the potential energy surface form/parametrization or the numerical
approximation used.Comment: Submitted to Journal of Chemical Physic
Assessing the Performance of the Diffusion Monte Carlo Method as Applied to the Water Monomer, Dimer, and Hexamer
The Diffusion Monte Carlo (DMC) method is applied to the water monomer,
dimer, and hexamer, using q-TIP4P/F, one of the most simple, empirical water
models with flexible monomers. The bias in the time step () and
population size () is investigated. For the binding energies, the bias in
cancels nearly completely, while a noticeable bias in still
remains. However, for the isotope shift, (e.g, in the dimer binding energies
between (HO) and (DO)) the systematic errors in do
cancel. Consequently, very accurate results for the latter (within
kcal/mol) are obtained with relatively moderate numerical effort (). For the water hexamer and its (DO) isotopomer the DMC results
as a function of are examined for the cage and prism isomers. For a given
isomer, the issue of the walker population leaking out of the corresponding
basin of attraction is addressed by using appropriate geometric constraints.
The population size bias for the hexamer is more severe, and in order to
maintain accuracy similar to that of the dimer, the population size must
be increased by about two orders of magnitude. Fortunately, when the energy
difference between cage and prism is taken, the biases cancel, thereby reducing
the systematic errors to within kcal/mol when using a population of
walkers. Consequently, a very accurate result for the
isotope shift is also obtained. Notably, both the quantum and the isotope
effects for the prism-cage energy difference are small.Comment: 11 pages, 5 figures, 36 references. Submitted to the Journal of
Physical Chemistr
Sandra Brown to Dear Mr. Meredith (Undated)
https://egrove.olemiss.edu/mercorr_pro/1785/thumbnail.jp
Administration of galacto-oligosaccharide prebiotics in the Flinders Sensitive Line animal model of depression
INTRODUCTION: Major depressive disorder is the leading source of disability globally and current pharmacological treatments are less than adequate. Animal models such as the Flinders Sensitive Line (FSL) rats are used to mimic aspects of the phenotype in the human disorder and to characterise candidate antidepressant agents. Communication between the gut microbiome and the brain may play an important role in psychiatric disorders such as depression. Interventions targeting the gut microbiota may serve as potential treatments for depression, and this drives increasing research into the effect of probiotics and prebiotics in neuropsychiatric disorders. Prebiotics, galacto-oligosaccharides and fructooligosaccharides that stimulate the activity of gut bacteria have been reported to have a positive impact, reducing anxiety and depressive-like phenotypes and stress-related physiology in mice and rats, as well as in humans. Bimuno, the commercially available beta-galacto-oligosaccharide, has been shown to increase gut microbiota diversity. AIM: Here, we aim to investigate the effect of Bimuno on rat anxiety-like and depressive-like behaviour and gut microbiota composition in the FSL model, a genetic model of depression, in comparison to their control, the Flinders Resistant Line (FRL) rats. METHODS: Sixty-four male rats aged 5–7 weeks, 32 FSL and 32 FRL rats, will be randomised to receive Bimuno or control (4 g/kg) daily for 4 weeks. Animals will be tested by an experimenter unaware of group allocation on the forced swim test to assessed depressive-like behaviour, the elevated plus maze to assess anxiety-like behaviour and the open field test to assess locomotion. Animals will be weighed and food and water intake, per kilogram of bodyweight, will be recorded. Faeces will be collected from each animal prior to the start of the experiment and on the final day to assess the bacterial diversity and relative abundance of bacterial genera in the gut. All outcomes and statistical analysis will be carried out blinded to group allocation, group assignments will be revealed after raw data have been uploaded to Open Science Framework. Two-way analysis of variance will be carried out to investigate the effect of treatment (control or prebiotic) and strain (FSL or FRL) on depressive-like and anxiety-like behaviours
Development of Environmental Education Field Trip Guides for Elementary School Teachers in Cache Valley, Utah
The purpose of this study was two-fold. The first was the development of environmental education field trip guides to areas in Cache Valley for teachers in grades three through six that would provide learning activities that cannot be structured in the classroom. Six field trip guides to areas of Cache Valley with accompanying activities and discussion questions were constructed. The guides were tested in the field by three groups of teachers and students and teachers not participating in the field test evaluated the guides for difficulties they would encounter in using the guides.
The second study purpose was to determine constraints faced by Cache Valley elementary teachers in using such guides and conducting environmental education programs. This was accomplished by the use of a questionnaire which was given to elementary teachers in Logan City . Although a lack of environmental education guides and materials was apparent, major constraints listed were a lack of transportation and funds and inadequate student supervision
Exploring Part-Time Teacher Professional Development and Best Practices on Adult Learners\u27 Outcomes
The issue of limited part-time teacher professional development and its effect on adult learners\u27 success at an adult education center in the northeast United States was addressed in this study. At the research site, almost 50% of the teaching staff are adjuncts. Professional development opportunities have been limited, with only 1 opportunity recorded during the 2014-2015 school year. When teachers are provided appropriate and relevant support for the curriculum and student needs, they realize their own craft growth, with measureable student achievement as a result. Knowles\u27s adult learning theory served as the conceptual framework and provided structure for exploring and understanding nontraditional students. Using a qualitative exploratory case study design, the research questions focused on part-time teachers\u27 perception of professional development on their teaching and instructional practice. Purposeful sampling was used to select 8 adjuncts to participate in semistructured interviews. Data analysis involved an inductive study of coded data retrieved and explored 5 themes: barriers to delivering an excellent teaching plan, teacher knowledge of student needs, administrative concerns, sense of community, and professional development needs. Themes were examined to develop a 3-day adult education training program. Implications for positive social change at the local level include information for educational administrators to design and promote appropriate and relevant professional development opportunities for adjuncts. This advancement of ongoing professional development could improve teaching and learning for adjuncts that may result in their craft improvement, positively impacting their nontraditional students
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