Prologue to Perfectly Parsing Proxy Patterns

As libraries spend an increasing percentage of precious collection funds on electronic resources, important questions arise to drive collection management decisions: What is being used? How much? and finally, Who is using our resources? Vendor-supplied statistics can help answer the first two questions, but we have encountered specific questions about our users at Mercer University. To help answer this question, we turned to our proxy server logs and began a pilot study in the spring semester 2017. This presentation will explain the methodology we used in mining data from our proxy server logs in combination with our existing user database. It will describe the demographic information we were able to glean from this combination of information resources. We uncovered valuable insights to our database usage including: usage pattern over time, database popularity by program, database usage by enrollment status, usage by faculty/ employee group, and usage by campus group

Enzyme activity below the dynamical transition at 220 K

Enzyme activity requires the activation of anharmonic motions, such as jumps between potential energy wells. However, in general, the forms and time scales of the functionally important anharmonic dynamics coupled to motion along the reaction coordinate remain to be determined. In particular, the question arises whether the temperature-dependent dynamical transition from harmonic to anharmonic motion in proteins, which has been observed experimentally and using molecular dynamics simulation, involves the activation of motions required for enzyme function. Here we present parallel measurements of the activity and dynamics of a cryosolution of glutamate dehydrogenase as a function of temperature. The dynamical atomic fluctuations faster than ~100 ps were determined using neutron scattering. The results show that the enzyme remains active below the dynamical transition observed at ~220 K, i.e., at temperatures where no anharmonic motion is detected. Furthermore, the activity shows no significant deviation from Arrhenius behavior down to 190 K. The results indicate that the observed transition in the enzyme's dynamics is decoupled from the rate-limiting step along the reaction coordinate

The Effects of Very Light Jet Air Taxi Operations on Commercial Air Traffic

This study investigates the potential effects of Very Light Jet (VLJ) air taxi operations adding to delays experienced by commercial passenger air transportation in the year 2025. The affordable cost relative to existing business jets and ability to use many of the existing small, minimally equipped, but conveniently located airports is projected to stimulate a large demand for the aircraft. The resulting increase in air traffic operations will mainly be at smaller airports, but this study indicates that VLJs have the potential to increase further the pressure of demand at some medium and large airports, some of which are already operating at or near capacity at peak times. The additional delays to commercial passenger air transportation due to VLJ air taxi operations are obtained from simulation results using the Airspace Concepts Evaluation System (ACES) simulator. The direct increase in operating cost due to additional delays is estimated. VLJs will also cause an increase in traffic density, and this study shows increased potential for conflicts due to VLJ operations

Direct determination of vibrational density of states change on ligand binding to a protein

The change in the vibrational density of states of a protein (dihydrofolate reductase) on binding a ligand (methotrexate) is determined using inelastic neutron scattering. The vibrations of the complex soften significantly relative to the unbound protein. The resulting free-energy change, which is directly determined by the density of states change, is found to contribute significantly to the binding equilibrium

Mega-phylogeny approach for comparative biology: an alternative to supertree and supermatrix approaches

Abstract Background Biology has increasingly recognized the necessity to build and utilize larger phylogenies to address broad evolutionary questions. Large phylogenies have facilitated the discovery of differential rates of molecular evolution between trees and herbs. They have helped us understand the diversification patterns of mammals as well as the patterns of seed evolution. In addition to these broad evolutionary questions there is increasing awareness of the importance of large phylogenies for addressing conservation issues such as biodiversity hotspots and response to global change. Two major classes of methods have been employed to accomplish the large tree-building task: supertrees and supermatrices. Although these methods are continually being developed, they have yet to be made fully accessible to comparative biologists making extremely large trees rare. Results Here we describe and demonstrate a modified supermatrix method termed mega-phylogeny that uses databased sequences as well as taxonomic hierarchies to make extremely large trees with denser matrices than supermatrices. The two major challenges facing large-scale supermatrix phylogenetics are assembling large data matrices from databases and reconstructing trees from those datasets. The mega-phylogeny approach addresses the former as the latter is accomplished by employing recently developed methods that have greatly reduced the run time of large phylogeny construction. We present an algorithm that requires relatively little human intervention. The implemented algorithm is demonstrated with a dataset and phylogeny for Asterales (within Campanulidae) containing 4954 species and 12,033 sites and an rbcL matrix for green plants (Viridiplantae) with 13,533 species and 1,401 sites. Conclusion By examining much larger phylogenies, patterns emerge that were otherwise unseen. The phylogeny of Viridiplantae successfully reconstructs major relationships of vascular plants that previously required many more genes. These demonstrations underscore the importance of using large phylogenies to uncover important evolutionary patterns and we present a fast and simple method for constructing these phylogenies.</p

Cis/trans energetics in epoxide, thiirane, aziridine and phosphirane containing cyclopentanols: Effects of intramolecular OH···O,S,N and P contacts

c 2019 by the authors A recent computational analysis of the stabilizing intramolecular OH···O contact in 1,2-dialkyl-2,3-epoxycyclopentanol diastereomers has been extended to thiiriane, aziridine and phosphirane analogues. Density functional theory (DFT), second-order Møller-Plesset perturbation theory (MP2) and CCSD(T) coupled-cluster computations with simple methyl and ethyl substituents indicate that electronic energies of the cis isomers are lowered by roughly 3 to 4 kcal mol−1 when the OH group of these cyclopentanol systems forms an intramolecular contact with the O, S, N or P atom on the adjacent carbon. The results also suggest that S and P can participate in these stabilizing intramolecular interactions as effectively as O and N in constrained molecular environments. The stabilizing intramolecular OH···O, OH···S, OH···N and OH···P contacts also increase the covalent OH bond length and significantly decrease the OH stretching vibrational frequency in every system with shifts typically on the order of −41 cm−

A Dense Gas Trigger for OH Megamasers

HCN and CO line diagnostics provide new insight into the OH megamaser (OHM) phenomenon, suggesting a dense gas trigger for OHMs. We identify three physical properties that differentiate OHM hosts from other starburst galaxies: (1) OHMs have the highest mean molecular gas densities among starburst galaxies; nearly all OHM hosts have = 10^3-10^4 cm^-3 (OH line-emitting clouds likely have n(H2) > 10^4 cm^-3). (2) OHM hosts are a distinct population in the nonlinear part of the IR-CO relation. (3) OHM hosts have exceptionally high dense molecular gas fractions, L(HCN)/L(CO)>0.07, and comprise roughly half of this unusual population. OH absorbers and kilomasers generally follow the linear IR-CO relation and are uniformly distributed in dense gas fraction and L(HCN), demonstrating that OHMs are independent of OH abundance. The fraction of non-OHMs with high mean densities and high dense gas fractions constrains beaming to be a minor effect: OHM emission solid angle must exceed 2 pi steradians. Contrary to conventional wisdom, IR luminosity does not dictate OHM formation; both star formation and OHM activity are consequences of tidal density enhancements accompanying galaxy interactions. The OHM fraction in starbursts is likely due to the fraction of mergers experiencing a temporal spike in tidally driven density enhancement. OHMs are thus signposts marking the most intense, compact, and unusual modes of star formation in the local universe. Future high redshift OHM surveys can now be interpreted in a star formation and galaxy evolution context, indicating both the merging rate of galaxies and the burst contribution to star formation.Comment: 5 pages, 3 figures, 1 table, accepted by ApJ Letter

Isotopic Carbon Abundances in M71

High resolution echelle spectra of the 8005 Angstroms CN bands are presented for five bright giants in the globular cluster M71 (C1951 +186, NGC 6838). An analysis of the (13) CN feature included in this region confirms the results of \cite{briley94a}; that the M71 red giants evince low (12}C/({13)) C ratios and that these ratios are correlated with CN band strengths (CN-strong stars having lower (12}C/({13)) C ratios). This finding is consistent with the theory that the star-to-star CN band strength variations, as well as the oxygen and possibly sodium differences observed in M71, are related to the CN(O)-cycle of hydrogen burning. (One asymptotic giant branch candidate is also included in the present sample, which exhibits both weak-CN band strength and a low (12}C/({13)) C ratio.) Examination of published data on CN band strengths and (12}C/({13)) C ratios among the more metal-poor clusters implies a metallicity dependence in the efficiency of the underlying mechanism responsible for the low (12}C/({13)) C ratios. A likely candidate appears to be the mixing of CN(O)-processed material into the stellar atmospheres, although a primordial source of CN-processing cannot be ruled out