FLUORESCENCE SPECTRA IN LUNG WITH PORPHYRIN INJECTION

The fluorescence emission spectra from human bronchial mucosa and tumors, before and after injection of dihematoporphyrin ether/ester, have been measured with an optical multichannel analyzer from 500 to 750 nm. Fluorescence was excited with a violet krypton ion laser (average wavelength 410 nm). The autofluorescence spectra decrease monotonically with increasing wavelength except for a small broad peak near 600 nm. The spectra from tumor sites, after injection of the fluorescent porphyrin, exhibit the characteristic fluorescence emission at 630 and 690 nm, added to the autofluorescence spectrum. The spectra from control or nontumor sites are similar but the magnitude of the component due to the injected porphyrin is smaller than at a tumor site. The magnitude ratio of tumor to control site fluorescence depends on concentration of the porphyrin, tumor thickness, and time after injection. Autofluorescence degrades contrast and thus makes very thin tumors difficult to image. Subtraction of the autofluorescence background is desirable.     

On the Computational Complexity of a Rigidity Problem

Consider a structure of flexible joints connected by rigid bars.These bars will constrain the possible motions of the jointsof this structure. By "pinning down" some of the joints so thatthey cannot move further constraints will be added. In thisway the entire structure can be made rigid. A problem consideredby Bolker & Crapo (1977) and others, is that of findingthe minimum number of joints that must be pinned in order tomake a given two- or three-dimensional structure rigid. We considerthe computational complexity of this problem. Lovasz (1980)gives a somewhat complicated but polynomial time procedure forthis problem in the two-dimensional case. In this paper we showthat in three or more dimensions the problem is NP-complete,and so is unlikely to have a polynomial time algorithm.     

AN INDIVIDUAL‐BASED MODEL FOR FERAL HOGS IN GREAT SMOKY MOUNTAINS NATIONAL PARK

The expansion of feral hog (Sus scrofa) populations in the United States has resulted in increased efforts to develop and implement control strategies designed to minimize the impacts done by this invasive species. We describe an individual‐based model for feral hogs in Great Smoky Mountains National Park (GSMNP). The objectives of the model are to provide an understanding of the population dynamics of this feral hog population and to determine the efficacy of the annual harvest as a population control method. Results suggest that the dynamics of the population are driven by fall hard mast production and the GSMNP harvests currently limit growth of the population, but these control efforts have not reduced the population.     

The thymine radicals and their respective anions: molecular structures and electron affinities

The adiabatic electron affinities (AEA), vertical electron affinities (VEA) and vertical detachment energies (VDE) are predicted for six different radicals derived from thymine by the removal of one hydrogen atom. Geometry optimizations were carried out utilizing the DFT functionals B3LYP, BLYP and BP86 with double-c quality basis sets plus polarization and diffuse functions (DZP++). These methods have been carefully calibrated for the prediction of electron affinities [RIENSTRA-KIRACOFE, J. C., TSCHUMPER, G. S., SCHAEFER, H. F., NANDI, S., and ELLISON, G. B., 2002, Chem. Rev., 102, 231]. All optimized structures were confirmed to be minima via vibrational frequency analyses. Both the neutrals and the anion radicals were observed to possess C_s, symmetry, conserving the parent molecule's qualitative conformation. The electron affinities ranged between 1.04 and 3.74eV for the different radicals, contrasting to the small electron affinities associated with the closed-shell thymine species. The radicals with a hydrogen atom removed from one of the nitrogens present the largest electron affinities of all six radicals investigated (3.22eV for NI and 3.74eV for N3).     

Report On ‘Planning And Implementing Curriculum Change in Chemistry: A Case Study in Creating a Blended General/Organic Course Sequence’

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).     

Advection-diffusion in reversing and oscillating flows: 2. Flows with multiple reversals

The dispersion of a passive tracer from a continuous point sourcein an estuary is modelled by a two-dimensional advection-diffusionequation with a time-varying, unidirectional velocity. Asymptoticsolutions obtained by Kay (1990, IMA J. Appl. Math., 45, 115–37)for a constant-acceleration flow are generalized to take accountof arbitrary velocity variations, and a new solution is presentedfor the case of rapidly varying acceleration around a time offlow reversal. A procedure for building up the total concentrationdistribution by linear superposition of the various types ofsolution is described. This is applied to the case of an estuarineflow, considered to consist of a constant river flow superimposedon tidal oscillations. Depending on the relative size of thesetwo components, the concentration distribution may include prominentpeaks, with concentrations which are many times higher thanthose in nearby waters. The effect of allowing the diffusioncoefficient to vary proportionally to the flow speed is shownto be small except close to the tracer source.     

Rotational statistics and thermodynamic functions of hydrogen peroxide

Partition functions for both the rotational modes (hindered internal rotation and overall rotation) of the hydrogen peroxide (H₂O₂) molecule in the ground electronic state are studied using quantum and classical Gibbsian statistical mechanics. The partition functions are used to calculate rotational thermodynamic functions (internal energy, enthalpy, Helmholtz free energy, Gibbs free energy and entropy) of a hydrogen peroxide gas of weakly interacting molecules at temperatures above 300 K.     

An ab initio study of vibrational corrections to the electrical properties of the fluoromethanes: CH3F,CH2F2, CHF3 and CF4

Accurate SCF and MP2 quartic property hypersurfaces have been computed for the energy, dipole moments, quadrupole moments and polarizability tensors of the fluorinated methanes CF₄, CHF₃, CH₂F₂ and CH₃F, to establish accurate values of zero-point vibrational corrections to the properties. Using a consistent set of r_e geometries from density functional theory, these ZPVCs are coupled with accurate electrical properties computed using a range of correlated methods, especially BD and BD(T), and a number of purpose-built polarized basis sets, to obtain near definitive estimates of these properties that incorporate the effects of vibrational averaging. Careful attention has been paid to a critical comparison between these theoretical estimates and experimental measurements, and agreement between the two is shown to be exceptionally good. In particular, it is clear that in many instances more precise experimental results would be required in order to discriminate between different correlated results, or between the present results and those which may be obtained with larger basis sets. The work highlights the necessity to allow for the effects of zero-point vibrational averaging when comparing theory with experiment, or even when comparing different theoretical results with one another using experiment as a benchmark. It also points to the need for further precise experimental measurements of some of these properties.     

Laser-induced condensation in colloid—polymer mixtures

We study a mixture of hard sphere colloidal particles and non-adsorbing polymers exposed to a plane wave external potential which represents a three-dimensional standing laser field. With computer simulations and density functional theory we investigate the structure and phase behaviour using the simple Asakura-Oosawa model. For varying laser wavelength λ we monitor the emergence of structure in response to the external field, as measured by the amplitude of the oscillations in the one-body density distribution. Between the ideal gas limit for small λ and the bulk limit of large λ there is a non-monotonic crossover that is governed by commensurability of λ and the colloid diameter. The theoretical curves are in good agreement with simulation results. Furthermore, the effect of the periodic field on the liquid-vapour transition is studied, a situation that we refer to as laser-induced condensation. Above a threshold value for λ the theoretical phase diagram indicates the stability of a ‘stacked’ fluid phase, which is a periodic succession (in the beam direction) of liquid and vapour slabs. This partially condensed phase causes a splitting of the liquid-vapour binodal leading to two critical and a triple point. All our predictions should be experimentally observable for colloid-polymer mixtures in an optical resonator.