Successful Strategies for Integrating High School Students into a Graduate Research Group

A series of pedagogical approaches are presented that have proven effective in integrating seven high school students over a period of six years into an active graduate research program. Students working independently on their own research projects have successfully explored a wide range of topics including hemoproteins, bioconjugation chemistry, drug delivery, perfusion chromatography, cyclic voltammetry, electronic absorption spectroscopy, and resonance Raman spectroscopy. Their original research contributions have been presented at regional and national American Chemical Society conferences and have been published as peer-reviewed technical papers. All student participants to date have been graduated from high school and have matriculated on scholarship at area colleges and universities where they continue to be successful academically and where the majority has selected science-related majors.     

T1rho dispersion of rat tissues in vitro.

The purpose of this study was to demonstrate T1rho dispersion in different rat tissues (liver, brain, spleen, kidney, heart, and skeletal muscle), and to compare the 1/T1rho data to previous 1/T1 data and magnetization transfer of rat tissues at low (0.1 T) B0 field. The 1/T1rho dispersion showed a fairly similar pattern in all tissues. The highest 1/T1rho relaxation rates were seen in liver and muscle followed by heart, whereas the values for spleen, kidney, and brain were quite similar. Compared to 1/T2 relaxation rate, the greatest difference was seen in liver and muscle. The rank order 1/T1rho value at each locking field B1 was the same as the transfer rate of magnetization from the water to the macromolecular pool (Rwm) for liver, muscle, heart, and brain. The potential value T1rho imaging is to combine high T1 contrast of low field imaging with the high signal to noise ratio of high static field imaging. When the T1rho value for a given tissue is known, the contrast between different tissues can be optimized by adjusting the locking time TL. Further studies are encouraged to fully exploit this. Targets for more detailed research include brain infarct, brain and liver tumors.     

The Complexity of Gene Placement

We focus on algorithmic problems related to deriving gene locations on DNA sequences of closely related species by using comparative mapping data. Conventional genetic mapping generates intervals on the DNA sequence of given species for potential gene positions. The simultaneous analysis of gene intervals in related species, e.g., human and mouse, may eliminate some of the ambiguities and lead to better estimates of gene locations. We address the problem of eliminating the ambiguities in gene orders by means of minimizing the number of conserved regions among the species. This is equivalent to the problem of choosing gene coordinates (gene placement) that satisfy the genetic mapping constraints and minimize the breakpoint distance between genomes. We first show that the gene ordering problem is hard: there is no polynomial-time approximation scheme unless P = NP, even under the restrictions that: (1) the order of genes in one of species is known, or (2) at most two intervals overlap at any location on the map of any of the species. Then we provide two polynomial-time algorithms under restriction (1) above; the first approximates the problem within a factor of 3, and the second exactly solves the problem under the additional restriction that (3) no more than O((log n)/(log log n)) intervals overlap at a location on the map of any of the species. We also prove the tractability of the general problem when there is a single conserved region (i.e., when there exists a gene placement resulting in identical gene orders).     

Cytotoxicity and photocytotoxicity of a dendritic C(60) mono-adduct and a malonic acid C(60) tris-adduct on Jurkat cells

The cytotoxic and photocytotoxic effects of two water-soluble fullerene derivatives, a dendritic C(60) mono-adduct and the malonic acid C(60) tris-adduct were tested on Jurkat cells. Cell growth and vitality were determined by a cell counting and staining technique. After 2 weeks cultivation in the presence of the fullerene derivatives, it was found that only the dendritic mono-adduct inhibits cell growth (within 2 weeks the cell number decreased to 19%), whereas the tris-malonic acid adduct has little effect. The growth inhibition is reversible; cultivating the same cells further in the absence of fullerene, the cell number increased to 106.4%. Other experiments showed that these fullerene derivatives become toxic when irradiated with UVA or UVB light. The cell death is mainly caused by membrane damage and it is UV dose-dependent. Tris-malonic acid fullerene was found to be more phototoxic than the dendritic derivative. This result is in contrast to the singlet oxygen quantum yields determined for the two compounds. We propose that the two fullerene derivatives may interact with the cell membrane in different ways thus causing the observed effects. Further experiments will be done to determine the location and concentration of the two compounds in and on the cells.     

Dual-acquisition phase-sensitive fat-water separation using balanced steady-state free precession

Balanced steady-state free precession (SSFP) sequences use fully re-focussed gradient waveforms to achieve a high signal and useful image contrast in short scan times. Despite these strengths, the clinical feasibility of balanced SSFP is still limited both by bright fat signal and by the signal voids that result from off-resonance effects such as field or susceptibility variations. A new method, dual-acquisition phase-sensitive SSFP, combines the signals from two standard balanced SSFP acquisitions to separate fat and water while simultaneously reducing the signal voids. The acquisitions are added in quadrature and then phase corrected using a simple algorithm before fat and water can be identified simply by the sign of the signal. This method is especially useful for applications at high field, where the RF power deposition, spatial resolution requirements and gradient strength limit the minimum repetition times. Finally, dual-acquisition phase-sensitive SSFP can be combined with other magnetization preparation schemes to produce specific image contrast in addition to separating fat and water signals.     

Luminescence dating: laboratory procedures and protocols

In the last 30 years, from 1967 to 1997, the use of luminescence signals from naturally occurring minerals has gone though a major metamorphosis, from thermoluminescence (TL) dating of pottery to optically stimulated luminescence (OSL) dating of sediments. Laboratory procedures for dating sediments have been adapted from those for pottery and new procedures have been developed as the need arises.

The majority of sediment dating applications are carried out on quartz and potassium-rich feldspars and the general characteristics of the TL and OSL signals from these minerals are reviewed. For sediments some new problems were encountered, with some grains perhaps not being completely bleached at deposition. For OSL signals there is no simple procedure for the selection of a thermally stable signal, as there had been in the case of pottery.

Many different laboratory protocols have been developed as our understanding of the fundamental behaviour of luminescence signals from quartz and feldspar has improved. These protocols are explained and discussed, giving the advantages and disadvantages of each procedure as applied to different types of sediment.

This review is presented as a guide to the selection of the most appropriate procedure for a particular dating application.     

Operator analysis of proton decay in an SU(7) gut

An SU(7) model, with a surviving low-energy SU(4) × SU(3) × U(1) gauge symmetry, may reduce the number of low-energy effective four-fermion baryon number violating interactions from six to two. A simple argument, applicable to general SU(N), shows that the terms allowed by SU(4) × SU(3) × U(1) are the same as those allowed by SU(7).     

The exterior algebra for Wiemann manifolds

We discuss the theory of infinite-dimensional manifolds from the point of view of establishing a widely applicable framework for generalization of the finite-dimensional Hodge theory. The principal result is the development of an exterior algebra based on a weakened definition of differentiation, so that “C^∞” partitions of unity are available for paracompact manifolds modelled on arbitrary real separable Banach spaces. We prove a Poincaré lemma for our new notion of exterior differentiation, and go on to discuss the relationship of the exterior derivative with current research efforts toward the definition of an infinite-dimensional Laplace-Beltrami operator.     

The synthesis and X-Ray crystallographic analysis of a stable norbornadienone: 17-Oxo-7,16-methano-7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene

The reaction of 4,5-didehydroacenaphthene with phencyclone yields the title compound, a stable dibenzo-fused norbornadienone (8). The X-ray structure of8 is presented and compared with the structure predicted from a MM3, PM3, and a MMX calculation. Thermal decomposition of 8 produces, 7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (9), a hydrocarbon that is computed to have a significantly twisted polycyclic aromatic skeleton with 19 kcal/mole of strain energy.     

Structure determination of lavendamycin- a new antitumor antibiotic from streptomyces lavendulae

The structure elucidation of lavendamycin (1a), a new antitumor antibiotic related to streptonigrin (2) is described. The NMR spectra of 1a and several model compounds 3,4 < and 5a-b are also discussed.