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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
A Study Of The Spawning Ecology And Early Life History Survival Of Bonneville Cutthroat Trout, Phaedra E. Budy, Sarah Wood, Brett B. Roper
A Study Of The Spawning Ecology And Early Life History Survival Of Bonneville Cutthroat Trout, Phaedra E. Budy, Sarah Wood, Brett B. Roper
Watershed Sciences Faculty Publications
We completed a large-scale field experiment in four tributaries of the Logan River, Utah, where the largest metapopulation of imperiled Bonneville cutthroat trout Oncorhynchus clarkii utah persists. We documented the spatial and temporal distributions of spawners, quantified substrate use versus substrate availability, and evaluated differences in hatch and emergence fry success between and among sites in relation to habitat characteristics. We observed considerable variability in the timing, magnitude, and duration of spawning among study areas (streams), in part as a function of a variable, multipeaked hydrograph. Nevertheless, across study areas, >70% of redds were constructed on the final descending limb …
Two New Species Of Trigonotylus (Hemiptera: Heteroptera: Miridae: Stenodemini) From Western Canada And Northwestern United States, G G.E. Scudder, Michael D. Schwartz
Two New Species Of Trigonotylus (Hemiptera: Heteroptera: Miridae: Stenodemini) From Western Canada And Northwestern United States, G G.E. Scudder, Michael D. Schwartz
Green Canyon Environmental Research Area, Logan Utah
No abstract provided.
Effects Of Carbon Chain Substituent On The P∙∙∙N Noncovalent Bond, U. Adhikari, Steve Scheiner
Effects Of Carbon Chain Substituent On The P∙∙∙N Noncovalent Bond, U. Adhikari, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The effects of carbon chains placed on the electron-accepting P atom of a P⋯N bond are examined via ab initio calculations. Saturated alkyl groups have a mild weakening effect, regardless of chain length. In contrast, incorporation of double bonds into the chain strengthens the interaction, Ctriple bond; length of mdashC triple bonds even more so. These effects are only slightly enhanced by additional conjugated double bonds or an aromatic ring. Placing F atoms onto the carbon chains strengthens the P⋯N bond, but only by a small amount, which wanes as the F atom is displaced further from the P along …
Contributions Of Various Noncovalent Bonds To The Interaction Between An Amide And S-Containing Molecules, U. Adhikari, Steve Scheiner
Contributions Of Various Noncovalent Bonds To The Interaction Between An Amide And S-Containing Molecules, U. Adhikari, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
N-Methylacetamide, a model of the peptide unit in proteins, is allowed to interact with CH3SH, CH3SCH3, and CH3SSCH3 as models of S-containing amino acid residues. All of the minima are located on the ab initio potential energy surface of each heterodimer. Analysis of the forces holding each complex together identifies a variety of different attractive forces, including SH⋅⋅⋅O, NH⋅⋅⋅S, CH⋅⋅⋅O, CH⋅⋅⋅S, SH⋅⋅⋅π, and CH⋅⋅⋅π H-bonds. Other contributing noncovalent bonds involve charge transfer into σ* and π* antibonds. Whereas some of the H-bonds are strong enough that they represent the sole attractive force in several dimers, albeit not usually in the …
Sensitivity Of Noncovalent Bonds To Intermolecular Separation: Hydrogen, Halogen, Chalcogen, And Pnicogen Bonds, Steve Scheiner
Sensitivity Of Noncovalent Bonds To Intermolecular Separation: Hydrogen, Halogen, Chalcogen, And Pnicogen Bonds, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
It is well known that noncovalent bonds are weakened when stretched from their equilibrium intermolecular separation. Quantum chemical calculations are used to examine and compare the sensitivity to stretches of hydrogen, halogen, chalcogen, and pnicogen bonds. NH3 was taken as the universal electron donor, paired with HOH and FH in H-bonds, as well as with FPH2, FSH, and FCl. Even though the binding energies span a wide range, stretching the intermolecular separation by 1 Å cuts this quantity by the same proportion, roughly in half, for each system. Taking the sum of van der Waals radii as an arbitrary cutoff, …
Preferred Configurations Of Peptide-Peptide Interactions, U. Adhikari, Steve Scheiner
Preferred Configurations Of Peptide-Peptide Interactions, U. Adhikari, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The natural and fundamental proclivities of interaction between a pair of peptide units are examined using high-level ab initio calculations. The NH···O H-bonded structure is found to be the most stable configuration of the N-methylacetamide (NMA) model dimer, but only slightly more so than a stacked arrangement. The H-bonded geometry is destabilized by only a small amount if the NH group is lifted out of the plane of the proton-accepting amide. This out-of-plane motion is facilitated by a stabilizing charge transfer from the CO π bond to the NH σ* antibonding orbital. The parallel and antiparallel stacked dimers are nearly …
Evaluation Of Dft Methods To Study Reactions Of Benzene With Oh Radical, Steve Scheiner
Evaluation Of Dft Methods To Study Reactions Of Benzene With Oh Radical, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
Several density functional theory” (DFT) methods are applied to two different reaction channels involving OH• + C6H6, and the results compared with high-level ab initio calculations. The OH• adds directly to one C atom in the first channel, first forming an encounter complex with the OH• poised above the aromatic plane. B3LYP, BH&HLYP, and MPW1K compute an accurate estimate of the overall exothermicity, whereas M05-2X, PBE0, and PBEPBE overestimate this quantity to some degree. With the exceptions of PBEPBE and PBE0, the other methods produce an acceptable barrier to addition. All approaches except BH&HLYP correctly predict an exothermic H• abstraction, …
First Steps In Growth Of A Polypeptide Toward Β-Sheet Structure, U. Adhikari, Steve Scheiner
First Steps In Growth Of A Polypeptide Toward Β-Sheet Structure, U. Adhikari, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The full conformational energy surface is examined for a molecule in which a dipeptide is attached to the same spacer group as another peptide chain, so as to model the seminal steps of β-sheet formation. This surface is compared with the geometrical preferences of the isolated dipeptide to extract the perturbations induced by interactions with the second peptide strand. These interpeptide interactions remove any tendency of the dipeptide to form a C5 ring structure, one of its two normally stable geometries. A C7 structure, the preferred conformation of the isolated dipeptide, remains as the global minimum in the full molecule. …
Extrapolation To The Complete Basis Set Limit For Binding Energies Of Noncovalent Interactions, Steve Scheiner
Extrapolation To The Complete Basis Set Limit For Binding Energies Of Noncovalent Interactions, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
A means of extrapolating from double and triple-valence basis sets to a complete basis set is examined in the context of the pnicogen bonds in the BH2P⋯NH3 complexes, with B = CH3, H, NH2, CF3, OH, Cl, F, and NO2. Binding energies converge smoothly, and the trends for the various substituents B are unaffected by the basis set size, extrapolation, or level of inclusion of electron correlation, including MP2 and CCSD(T). The approach appears to be successful also for H-bonded systems, in particular the water dimer. In the event that full extrapolation within the context of CCSD(T) is not feasible, …
Livestock Foraging Behavior In Response To Sequence And Interactions Among Alkaloids, Tannins, And Saponins, Tiffany L. Jensen
Livestock Foraging Behavior In Response To Sequence And Interactions Among Alkaloids, Tannins, And Saponins, Tiffany L. Jensen
Green Canyon Environmental Research Area, Logan Utah
No abstract provided.
The Role Of Fine-Scale Habitat Associations In Structuring Spider Assemblages: Determinants Of Spatial Patterns In Community Compostion, Stephanie M. Cobbold
The Role Of Fine-Scale Habitat Associations In Structuring Spider Assemblages: Determinants Of Spatial Patterns In Community Compostion, Stephanie M. Cobbold
Green Canyon Environmental Research Area, Logan Utah
No abstract provided.
Detailed Comparison Of The Pnicogen Bond With Chalcogen, Halogen And Hydrogen Bonds, Steve Scheiner
Detailed Comparison Of The Pnicogen Bond With Chalcogen, Halogen And Hydrogen Bonds, Steve Scheiner
Chemistry and Biochemistry Faculty Publications
The characteristics of the pnicogen bond are explored using a variety of quantum chemical techniques. In particular, this interaction is compared with its halogen and chalcogen bond cousins, as well as with the more common H-bond. In general, these bonds are all of comparable strength. More specifically, they are strengthened by the presence of an electronegative substituent on the electron-acceptor atom, and each gains strength as one moves down the appropriate column of the periodic table, for example, from N to P to As. These noncovalent bonds owe their stability to a mixture in nearly equal parts of electrostatic attraction …