Hard body amphiphiles at a hard wall

We investigate the structure of amphiphilic molecules exposed to a substrate that is modelled by a hard wall. Our simple model amphiphiles consist of a hard sphere head group to which a vanishingly thin needle tail is radially attached, resulting in a lollipop shape. Such particles act as amphiphiles when added to a binary fluid of hard spheres and needles. Focusing on the pure amphiphile system we compare the results for the positional and orientational order profiles obtained from a recent density functional approximation to those of our computer simulations and find good agreement. For low densities the structure is ruled by the loss of orientational free volume near the wall, while for higher densities packing of the spherical heads dominates. Furthermore, we test the wall sum rule explicitly for this model fluid and find rich structure of the contact distribution which can be interpreted in terms of typical particle configurations.     

The structure and energetics of carbon-nitrogen clusters

The structures and energies of clusters of carbon and nitrogen with up to 12 atoms have been investigated by density functional theory using the hybrid B3LYP functional and the cc-pVTZ basis set. This is the first systematic study of these clusters. Geometries are reported for the lowest energy states at this level of theory. Linear structures tend to be the global minima for clusters containing one or two nitrogen atoms, and patterns in the electronic structure of these clusters are reported. More complex branched structures lie close in energy to the linear conformations and, for clusters greater than six atoms and containing three or more nitrogen atoms, these branched structures are the minimum energy conformers. Comparisons are made with pure carbon and silicon-carbon clusters.     

PRIMARY PHOTOCHEMISTRY OF PHOTOSYNTHESIS Report on a Conference held at Argonne National Laboratory, November 1971

In conclusion, the conference was judged to be extremely useful for the 230 persons who attended, and all departed with an optimistic enthusiasm about the certainty of progress in this field over the next 5 to 10 years. A statistic that perhaps represents a new record and should be shared to underscore the significance of the meeting to researchers in this area of photosynthesis is that out of 59 scheduled speakers all were in attendance and only one had to be replaced because of a commitment to take part in ceremonies for the 150th anniversary of a famous university in the East. From our experience with the form of the meeting, we feel that the open attendance but limited subject concept is a highly desirable meeting form and should be used for most scientific meetings.     

Report On ‘Water Chemistry: Using Field and Laboratory Experiences to Teach Scientific-Thinking Skills’

A new curriculum involving a blended general and organic chemistry course is being introduced at San Jose State University this fall by Stephen Branz and Maureen Scharberg. They shared their experiences in creating this new curriculum and described how they overcame resistance to this change from the university community to the workshop participants. The participants of the workshop then had the opportunity to examine the new curriculum and consider how they would approach problems in both the planning and implementation phase of such a project. The workshop participants created a final list of pros and cons for the planning stage (content, pedagogy, and transportability) and a list of possible strategies for the implementation stage (marketing, resources, and logistics).     

PHOTOREACTIONS ASSOCIATED WITH IN VITRO HEMOLYSIS IN ERYTHROPOIETIC PROTOPORPHYRIA*

Abstract— –Photohemolysis of erythrocytes. from patients with erythropoietic protoporphyria results from damage to the cell membrane following photoexcitation of the protoporphyrin molecule by 400 nm radiation. Photochemical reactions were assessed for their roles in initiating cell destruction in an in vitro model in which erythrocytes from patients with erythropoietic protoporphyria were irradiated. Electron transfer properties were demonstrated using 2,3,6-trichloroindophenol as an electron acceptor. Photohemolysis of these abnormal cells is due to cell membrane damage initiating colloid osmotic hemolysis. Additional data are offered demonstrating that this type of photohemolysis is oxygen-dependent, associated with peroxide formation, and preceded by increased osmotic fragility. An hypothesis explaining the interrelationship of the photochemistry of protoporphyrin with the photobiologic observation of hemolysis is offered.     

A personal recollection of Ernest Roy Davidson's contributions to organic chemistry

Ernest Davidson's contributions of potential energy surfaces for thermal reactions of organic compounds form an important body of scientific work. His pursuit, with Borden, of the methylenecyclopropane degenerate rearrangement involving the trimethylenemethane singlet biradical with planar and orthogonal species is a classic example that also touches on the Davidson-Borden characterization of open shell, pi conjugated biradicals as either disjoint or non-disjoint systems. In a related effort with vinylmethylenecyclopropane he not only calculated all reasonable stationary points for both the singlet and triplet species, but demonstrated the preference for a conrotatory-bevel closure of a cross-conjugated 1,5 singlet biradical. Further, he pursued the classic hydrocarbon 1,3 biradicals trimethylene and vinyltrimethylene, showing in the latter case that there are no intermediates on the potential energy surface. Thus the reaction appears to proceed from saddle point to saddle point by traversing coordinates perpendicular to the reaction coordinates. He became embroiled in the Cope rearrangement energy surface that pushed the limits of approximations to the solution of the Schroedinger equation. He provided evidence that the conservation of orbital symmetry ‘forbidden’ suprafacial-inversion 1.5 shift of carbon in the circumambulatory degenerate rearrangement of norcaradiene is comparable in energy with the ‘allowed’ suprafacial-retention pathway. And he provided important insights into the captodative effects of monoradicals. Ernest understands more organic chemistry than most organic chemists.     

A METAPOPULATION MODEL FOR FERAL HOGS IN GREAT SMOKY MOUNTAINS NATIONAL PARK

Feral Hogs (Sus scrofa) are an invasive species that have occupied the Great Smoky Mountains National Park since the early 1900s. Recent studies on vegetation, mast, and harvest history were important for our work. Using these data, a model with discrete time and space was formulated to represent the feral hog dynamics in the Park. Management strategies and key characteristics of the population were investigated. The model uses observed mast variation to help govern population dynamics and results indicate that Park control efforts have limited the growth of the population.     

A Symmetric Adaptive Model of Combat

Analytical models are used to examine theories of military combat, a violent conflict between two groups. Typically these models focus on combat power (manpower and technology) and ignore intrinsic sociological factors, both in terms of the interaction between forces, and each force's organizational structure and internal dynamics, such as social climate, morale, and leadership. This paper describes a symmetric adaptive model of combat, in which the use of feedback allows opposing forces to attempt to regulate the intensity of the fight, or even abandon the fight, depending on battlefield losses. Furthermore, parameters are introduced to provide a framework for incorporating the sociological structure and dynamics of the two forces. A preliminary analysis of the model is presented.     

A direct proof of a generalized harish-chandra isomorphism

A direct proof of a Harish-Chandra isomorphism recently established by Khoroshkin, Nazarov and Vinberg [10] involving Zhelobenko operators, is given. A key point is the computation of certain determinants analogous to those of Parthasarathy, Ranga Rao, Varadaragan [14]. This analysis avoids the passage to graded objects and the subsequent geometric arguments.