Ultranarrow conducting channels defined in GaAs-AlGaAs by low-energy ion damage

We have laterally patterned the narrowest conducting wires of two-dimensional electron gas (2DEG) material reported to date. The depletion induced by low-energy ion etching of GaAs-AlGaAs 2DEG structures was used to define narrow conducting channels. We employed high voltage electron beam lithography to create a range of channel geometries with widths as small as 75 nm. Using ion beam assisted etching by Cl2 gas and Ar ions with energies as low as 150 eV, conducting channels were defined by etching only through the thin GaAs cap layer. This slight etching is sufficient to entirely deplete the underlying material without necessitating exposure of the sidewalls that results in long lateral depletion lengths. At 4.2 K, without illumination, our narrowest wires retain a carrier density and mobility at least as high as that of the bulk 2DEG and exhibit quantized Hall effects. Aharonov–Bohm oscillations are seen in rings defined by this controlled etch-damage patterning. This patterning technique holds promise for creating one-dimensional conducting wires of even smaller sizes

The epidemiology of malignant giant cell tumors of bone: an analysis of data from the Surveillance, Epidemiology and End Results Program (1975–2004)

Malignant giant cell tumor (GCT) of bone is a rare tumor with debilitating consequences. Patients with GCT of bone typically present with mechanical difficulty and pain as a result of bone destruction and are at an increased risk for fracture. Because of its unusual occurrence, little is known about the epidemiology of malignant GCT of bone. This report offers the first reliable population-based estimates of incidence, patient demographics, treatment course and survival for malignancy in GCT of bone in the United States. Using data from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) program, we estimated the overall incidence and determinants of survival among patients diagnosed with malignant GCT of bone from 1975–2004. Cox proportional hazards regression was used to evaluate demographic and clinical determinants of survival among malignant GCT cases. Based on analyses of 117 malignant GCT cases, the estimated annual incidence in the United States was 1.6 per 10,000,000 persons per year. Incidence was highest among adults aged 20 to 44 years (2.4 per 10,000,000 per year) and most patients were diagnosed with localized (31.6%) or regional (29.9%) disease compared to distant disease (16.2%). Approximately 85% of patients survived at least 5 years, with survival poorest among older patients and those with evidence of distant metastases at time of diagnosis. The current study represents the largest systematic investigation examining the occurrence and distribution of malignancy in GCT of bone in the general U.S. population. We confirm its rare occurrence and suggest that age and stage at diagnosis are strongly associated with long-term survival

Rare germline mutations in African American men diagnosed with earlyâ onset prostate cancer

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142420/1/pros23464_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142420/2/pros23464.pd

Assessing binary mixture effects from genotoxic and endocrine disrupting environmental contaminants using infrared spectroscopy

Benzo[a]pyrene (B[a]P), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent contaminants and concern has arisen over co-exposure of organisms when the chemicals exist in mixtures. Herein, attenuated total reflection Fouriertransform infrared (ATR-FTIR) spectroscopy was used to identify biochemical alterations induced in cells by single and binary mixtures of these environmental chemicals. It was also investigated as a method to identify if interactions are occurring in mixtures and as a possible tool to predict mixture effects. Mallard fibroblasts were treated with single and binary mixtures of B[a]P, PCB126, PCB153, BDE47 and BDE209. Comparison of observed spectra from cells treated with binary mixtures with expected additive spectra, which were created from individual exposure spectra, indicated that in many areas of the spectrum, less-than-additive binary mixture effects may occur. However, possible greater-than-additive alterations were identified in the 1650-1750 cm-1 lipid region and may demonstrate a common mechanism of B[a]P and PCBs or PBDEs, which can enhance toxicity in mixtures

Development of an improved porcine embryo culture medium for cloning, transgenesis and embryonic stem cell isolation

Work in our laboratory for more than two decades has focussed on the production of genetically modified pigs for xeno transplantion research. More recent work has focussed on the isolation of porcine embryonic stem cells to facilitate this as well as and other research applications. Central to this research has been the production of in vitro Produced (IVP) embryos. These embryos are produced using a twostep culture system based on NCSU23. This culture system which was developed by modifying energy substrate availability and concentrations and by adding non-essential and essential amino acids in a sequential manner. As a result of this work we have developed a culture system that better suits the changing metabolic needs of the pig embryo and produces embryos with relatively high developmental competence compared to the original formulation. These embryos can be used for a range of research applications including the isolation of embryonic stem cells.Luke FS Beebe, Stephen M McIlfatrick, Ivan M Vassiliev and Mark B Nottl

Interaction of eddies and mean zonal flow on Jupiter as inferred from Voyager 1 and 2 images

Voyager 1 and 2 narrow-angle frames were used to obtain displacements of features at resolutions of 130 km over time intervals of 1 Jovian rotation. The zonal velocity ū was constant to 1.5% during the 4 months between the Voyager 1 and 2 encounters. The latitudes of the zonal jet maxima (extrema of ū) are the same as inferred from earth-based observations extending over the past 80 years. The curvature of the velocity profile d²ū/dy² varies with latitudinal coordinate y in the range from −3β to +2β, where β is the planetary vorticity gradient. The barotropic stability criterion is violated at about 10 latitudes between ±60°. The eddy momentum flux variation with latitude (u'ν')(overbar) is positively correlated with dū/dy for both Voyager 1 and 2 data. The rate of conversion {K'K(overbar)} of eddy kinetic energy into zonal mean kinetic energy is in the range 1.5–3.0 Wm^(−2), for a layer 2.5 bar deep. The time constant for resupply of zonal mean kinetic energy by eddies is in the range 2–4 months, less than the interval between Voyager encounters. The rate of energy conversion is more than 10% of the total infrared heat flux for Jupiter, in contrast with earth where it is only 0.1% of the infrared heat flux. This hundred-fold difference suggests that the thermomechanical energy cycles are very different on the two planets