878 research outputs found
Letter from J. A. Wofford to Gen. W. S. Featherston. 23 January 1869
Letter sent from Washington; regarding case of Mississippi before the Reconstruction Committee, amendment on elections, constitution, Republican Party. Envelope.https://egrove.olemiss.edu/ciwar_corresp/1262/thumbnail.jp
Molecular Dynamics in Hydrogenâbonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field for HCNâââHF
Observation of the 2ν1 overtone band in the hydrogenâbonded complex HCNâââHF permits evaluation of the anharmonicity constant X 1 1=â116.9(1) cmâ 1 and determination of the anharmonicity corrected fundamental frequency Ď1. This information, and available data from previous rovibrational analyses in the common and perdeuterated isotopic species of HCNâââHF, offer an opportunity for calculation of an approximate stretching harmonic force field. With the assumptions f 1 2=f 2 4=0.0, the remaining force constants (in mdyn/Ă
) are evaluated as: f 1 1=8.600(20), f 2 2=6.228(9), f 3 3=19.115(40), f 4 4=0.2413(39), f 1 3=0.000(13), f 1 4=0.0343(2), f 2 3=â0.211(6), f 3 4=0.000(2). These compare to f 1 1=9.658(2) in the HF monomer and f 1 1=6.244(3) and f 3 3=18.707(16) in the HCN monomer. These results provide the information necessary to quantitatively assess the applicability of the Cummings and Wood approximation in this hydrogenâbonded complex and also give an estimate of D e j , the equilibrium distortion constant in the harmonic limit. Comparisons of these experimentally determined parameters with the predictions of a b i n i t i o molecular orbital calculations at several levels of approximation are presented
The Spectroscopy and Molecular Dynamics of the High Frequency ν1 6 Intermolecular Vibrations in HCNâââHF and DCNâââDF
Gas phase rovibrational analysis of the high frequency intermolecular hydrogen bonded bending overtone 2ν0 6 [ν0=1132.4783(2) cmâ 1] in HCNâââHF and its corresponding perdeuterated fundamental ν1 6 [ν0=409.1660(2) cmâ 1] are reported. Evaluated rovibrational parameters provide the basis for quantitative modeling of the molecular dynamics associated with this vibration. A quantum mechanical calculation permits determination of the quadratic and quartic force constants K 6 6=537(17) and K 6 6 6 6=4.98(12) cmâ 1 which in turn are used to estimate the pertinent cubic band stretching interaction constants K 4 6 6=â149.3(50) cmâ 1 and account for the unexpected behavior in the rotational constantB 1 6. Second order expansion of the vibrational term energies, give X 4 6=â21.61(2), X 6 7=â7.694(1), X 6 6=â14.84(90), g 6 6=â31.04(90) cmâ 1, neglecting corrections for Fermi resonance. The common isotopic species equilibrium rotational constantB e is evaluated to be 3681.1(11) MHz
Erratum: Determination of Dissociation Energies and Thermal Functions of Hydrogen Bond Formation Using High Resolution FTIR Spectroscopy [J. Chem. Phys. 8 7, 5674 (1987)]
Erratu
Determination of Dissociation Energies and Thermal Functions of Hydrogenâbond Formation using High Resolution FTIR Spectroscopy
A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bonddissociation energiesD 0 and D e . Results for HCNââHF give a D 0=20.77(22) and D e =28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and a b i n i t i o molecular orbital calculations. Rovibrational band information available for HCNââHF also permits evaluation of thermal functions of dimer formation in kJ/mol: ÎU â 298.2 =20.1(2), ÎH â 298.2 =22.6(2), ÎG â 298.2 =59.4(2), ÎS â 298.2 =â0.1235
A Comprehensive Comparative Test of Seven Widely-Used Spectral Synthesis Models Against Multi-Band Photometry of Young Massive Star Clusters
We test the predictions of spectral synthesis models based on seven different
massive-star prescriptions against Legacy ExtraGalactic UV Survey (LEGUS)
observations of eight young massive clusters in two local galaxies, NGC 1566
and NGC 5253, chosen because predictions of all seven models are available at
the published galactic metallicities. The high angular resolution, extensive
cluster inventory and full near-ultraviolet to near-infrared photometric
coverage make the LEGUS dataset excellent for this study. We account for both
stellar and nebular emission in the models and try two different prescriptions
for attenuation by dust. From Bayesian fits of model libraries to the
observations, we find remarkably low dispersion in the median E(B-V) (~0.03
mag), stellar masses (~10^4 M_\odot) and ages (~1 Myr) derived for individual
clusters using different models, although maximum discrepancies in these
quantities can reach 0.09 mag and factors of 2.8 and 2.5, respectively. This is
for ranges in median properties of 0.05-0.54 mag, 1.8-10x10^4 M_\odot and
1.6-40 Myr spanned by the clusters in our sample. In terms of best fit, the
observations are slightly better reproduced by models with interacting binaries
and least well reproduced by models with single rotating stars. Our study
provides a first quantitative estimate of the accuracies and uncertainties of
the most recent spectral synthesis models of young stellar populations,
demonstrates the good progress of models in fitting high-quality observations,
and highlights the needs for a larger cluster sample and more extensive tests
of the model parameter space.Comment: Accepted for publication in MNRAS (14 Jan. 2016). 30 pages, 16
figures, 9 table
Sampling Local Fungal Diversity in an Undergraduate Laboratory using DNA Barcoding
Traditional methods for fungal species identification require diagnostic morphological characters and are often limited by the availability of fresh fruiting bodies and local identification resources. DNA barcoding offers an additional method of species identification and is rapidly developing as a critical tool in fungal taxonomy. As an exercise in an undergraduate biology course, we identified 9 specimens collected from the Hendrix College campus in Conway, Arkansas, USA to the genus or species level using morphology. We report that DNA barcoding targeting the internal transcribed spacer (ITS) region supported several of our taxonomic determinations and we were able to contribute 5 ITS sequences to GenBank that were supported by vouchered collection information. We suggest that small-scale barcoding projects are possible and that they have value for documenting fungal diversity
LEGUS and Halpha-LEGUS Observations of Star Clusters in NGC 4449: Improved Ages and the Fraction of Light in Clusters as a Function of Age
We present a new catalog and results for the cluster system of the starburst
galaxy NGC 4449 based on multi-band imaging observations taken as part of the
LEGUS and Halpha-LEGUS surveys. We improve the spectral energy fitting method
used to estimate cluster ages and find that the results, particularly for older
clusters, are in better agreement with those from spectroscopy. The inclusion
of Halpha measurements, the role of stochasticity for low mass clusters, the
assumptions about reddening, and the choices of SSP model and metallicity all
have important impacts on the age-dating of clusters. A comparison with ages
derived from stellar color-magnitude diagrams for partially resolved clusters
shows reasonable agreement, but large scatter in some cases. The fraction of
light found in clusters relative to the total light (i.e., T_L) in the U, B,
and V filters in 25 different ~kpc-size regions throughout NGC 4449 correlates
with both the specific Region Luminosity, R_L, and the dominant age of the
underlying stellar population in each region. The observed cluster age
distribution is found to decline over time as dN/dt ~ t^g, with g=-0.85+/-0.15,
independent of cluster mass, and is consistent with strong, early cluster
disruption. The mass functions of the clusters can be described by a power law
with dN/dM ~ M^b and b=-1.86+/-0.2, independent of cluster age. The mass and
age distributions are quite resilient to differences in age-dating methods.
There is tentative evidence for a factor of 2-3 enhancement in both the star
and cluster formation rate ~100 - 300 Myr ago, indicating that cluster
formation tracks star formation generally. The enhancement is probably
associated with an earlier interaction event
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