Ferromagnetism in annealed Ce0.95Co0.05O2 and Ce0.95Ni0.05O2 nanoparticles.

This paper reports an investigation on the role of transition-metal ions in producing ferromagnetism in CeO2 nanoparticles by electron paramagnetic resonance (EPR). Several samples of CeO2 nanoparticles annealed at 200, 300, 400, and 500 degrees C, doped with 5% Ni and 5% Co ions, characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry analysis (TGA) and mass spectroscopy (MS), were investigated by X-band EPR at 4, 10 and 300 K, and by magnetometry at 300 K. Magnetic properties and EPR/FMR (Ferromagnetic Resonance) spectra of these nanoparticle samples were found to depend strongly on the annealing temperature (T(A)), oxygen stoichiometry, and dopant-ion species. Different behavior of saturation magnetization in the samples with the dopants, Co and Ni, is found to be due to different-inward and outward-surface diffusion of these impurity ions, respectively, during annealing. A detailed simulation of EPR/FMR spectra of isolated Co and Ni ions carried out here provides in-depth details on the role of the doped ions and oxygen (O-) defects played in the observed magnetic properties.

Inverse expression states of the BRN2 and MITF transcription factors in melanoma spheres and tumour xenografts regulate the NOTCH pathway.

The use of adherent monolayer cultures have produced many insights into melanoma cell growth and differentiation, but often novel therapeutics demonstrated to act on these cells are not active in vivo. It is imperative that new methods of growing melanoma cells that reflect growth in vivo are investigated. To this end, a range of human melanoma cell lines passaged as adherent cultures or induced to form melanoma spheres (melanospheres) in stem cell media have been studied to compare cellular characteristics and protein expression. Melanoma spheres and tumours grown from cell lines as mouse xenografts had increased heterogeneity when compared with adherent cells and 3D-spheroids in agar (aggregates). Furthermore, cells within the melanoma spheres and mouse xenografts each displayed a high level of reciprocal BRN2 or MITF expression, which matched more closely the pattern seen in human melanoma tumours in situ, rather than the propensity for co-expression of these important melanocytic transcription factors seen in adherent cells and 3D-spheroids. Notably, when the levels of the BRN2 and MITF proteins were each independently repressed using siRNA treatment of adherent melanoma cells, members of the NOTCH pathway responded by decreasing or increasing expression, respectively. This links BRN2 as an activator, and conversely, MITF as a repressor of the NOTCH pathway in melanoma cells. Loss of the BRN2-MITF axis in antisense-ablated cell lines decreased the melanoma sphere-forming capability, cell adhesion during 3D-spheroid formation and invasion through a collagen matrix. Combined, this evidence suggests that the melanoma sphere-culture system induces subpopulations of cells that may more accurately portray the in vivo disease, than the growth as adherent melanoma cells.

Benthic changes at McMurdo Station, Antarctica following local sewage treatment and regional iceberg-mediated productivity decline.

McMurdo Station, the largest research station in Antarctica, ceased on-site garbage dumping in 1988 and initiated sewage treatment in 2003. In 2003-2004 its sea-ice regime was altered by the massive B-15A and C-19 iceberg groundings in the Ross Sea, approximately 100km distant. Here we follow macrofaunal response to these changes relative to a baseline sampled since 1988. In the submarine garbage dump, surface contaminants levels have declined but associated macrofaunal recolonization is not yet evident. Although sewage-associated macrofauna were still abundant around the outfall nearly 2yr after initiation of treatment, small changes downcurrent as far as 434m from the outfall suggest some community recovery. Widespread community changes in 2003-2004, not seen in the decade previously, suggests that the benthos collectively responded to major changes in sea-ice regime and phytoplankton production caused by the iceberg groundings.

Decreasing supply of family physicians and general practitioners. Serious implications for the future.

OBJECTIVE: To document a decrease in the supply of family physicians (FPs) and general practitioners among Canadian graduates of medical schools since rotating internships ceased to serve as a route to national licensure. DESIGN: Review of data from the Association of Canadian Medical Colleges, the Canadian Post-M.D. Education Registry, and the Canadian Institute for Health Information to track final training fields and eventual types of practice of graduates of Canadian faculties of medicine from 1987 to 1997. SETTING: Canadian faculties of medicine and residency training programs. MAIN OUTCOME MEASURES: Number of Canadian medical graduates entering family medicine training programs from 1991 to 1998, number of Canadian graduate physicians exiting from these training programs, and proportion of each graduating class (1987 to 1994) practising as FPs or GPs in Canada in 1997. RESULTS: In 1993, 890 physicians (51% of graduates) were trained as FPs or GPs. By 1994, although the proportion remained at 40%, the number of Canadian graduates entering family medicine had dropped to 646, and by 1998, to 619. CONCLUSIONS: A deficit of FPs is already noticeable in the practice environment. For the way in which medical care is delivered in Canada, with FPs serving as first contact for patients, the authors conclude that the number of graduating FPs in Canada will not be sufficient to provide the primary care services Canadians need.

Spinal cord dose is higher than expected in head and neck radiation.

Myelopathy is a feared consequence of radiation therapy. Risk factors are multifocal; therefore, total dose calculation is crucial. We evaluated the contribution of scatter radiation to obtain an accurate cumulative spinal cord dose. Twenty patients undergoing three field head and neck radiation by Cobalt or 6 MV Linac had a total cord dose calculated from direct and scatter radiation. The cord was removed from the radiation field at tumor doses no higher than 4,400 cGy. Total tumor dose ranged from 5,400-7,400 cGy (mean 6060). All patients achieved the prescribed dose and none were lost to follow up (mean 36 months). It was found that scatter radiation can contribute as much as 20% extra dose to the spinal cord. Mean extra dose was 9% (range 1%-20%). This additional dose ranged from 52-810 cGy (mean 339 cGy). No apparent difference was seen with Cobalt or Linac source. Our conclusion was that significant additional dose is delivered to the spinal cord by scatter radiation and that scatter may contribute more to the development of myelopathy than previously believed.

The Class of 1989 and physician supply in Canada.

BACKGROUND: "The Class of 1989" is a study of 1722 people who were awarded an MD degree by a Canadian university in 1989. This paper reports on migration, specialty choices and patterns of post-MD training in order to assess the contribution of the graduating cohort to the physician workforce of Canada. METHODS: A longitudinal study was conducted over 7 years after graduation to trace the current location, the post-MD training history and the professional activity of the graduating cohort. Several medical professional and educational associations in Canada and the United States provided year-by-year information on field and location of post-MD training, certification achieved, whether in practice and location of practice through to spring 1996. Information from all sources was linked to a list of 1989 medical school graduates. RESULTS: From entry to medical school through to 7 years after graduation the cohort was diminished by about 16%. The main reason for loss was migration to other countries: 193 graduates (11.2%) were outside Canada in 1995-96. Internal migration was extensive also; for example, by 1995-96 relatively few of the graduates were located in Newfoundland or Saskatchewan. Of the 1516 graduates active in Canada in 1995-96, 878 (57.9%) were in general practice/family medicine, and only 638 (42.1%) were practising or training in a specialty. INTERPRETATION: The "yield" of the Class of 1989 for Canada's physician workforce is insufficient to meet annual physician inflows from Canadian sources to serve population growth and to replace retiring or emigrating physicians. As output from Canada's medical schools drops even further, the gap between requirements and supply will grow even wider.

The Class of 1989 and post-MD training.

BACKGROUND: "The Class of 1989" is a longitudinal study of 1722 people who were awarded an MD degree by a Canadian university in 1989. This paper reports on the details of their post-MD training up to spring 1996. METHODS: Several medical professional and educational associations in Canada and the United States provided year-by-year information on field and location of post-MD training, certification achieved, whether in practice and location of practice through to spring 1996. Information from all sources was linked to a list of 1989 medical school graduates. RESULTS: Of the 1722 graduates 57 (3.3%) never entered post-MD training in Canada; 147 (8.5%) did 1 or more years of training in the United States. A total of 222 graduates (12.9%) took a break of at least 1 year from training, and 301 (17.5%) changed their choice of field or specialty after starting training. Substantial numbers took 1 or more years longer to complete training than would be expected based on the prescribed length of the training program chosen. The field or specialty choices of the cohort produced a generalist:specialist ratio of 58:42. The final numbers in several fields depended heavily on trainees changing their initial career choice. INTERPRETATION: The data point out widely differing and often very long lead times from start to completion of training. Since 1993, changes to licensure requirements have reduced opportunities for recent graduating cohorts to delay final career choices, take a break in training, prolong training or change initial career choices. Rigidities in the post-1993 training environment point to the emergence of a number of serious problems, such as dissatisfaction and high anxiety levels among residents, licensing authorities being faced with people who have not completed a training program to certification, and insufficient provision of positions for post-MD training because of underestimates of the time needed to complete training programs. The insights gained from this study lead to the recognition that planning the specialty distribution of the physician workforce is highly complex and difficult.

Interactions between toluene and alcohol.

Weanling male Fischer-344 rats were exposed by inhalation to air or 2000 ppm toluene for 8 hours each day for 2 weeks. Subgroups had access to water or 6% alcohol as their only fluid sources, respectively. Rats exposed to both toluene and alcohol subsequently showed a marked preference for 6% alcohol in two-bottle choice tests that persisted for up to 20 days for some rats. Rats exposed to toluene without access to alcohol and control rats (exposed to air and water) showed a marked aversion to the alcohol solution, and only 2 of 12 rats forced to drink alcohol without exposure to toluene preferred alcohol in the preference tests. Exposure to both toluene and alcohol also caused greater inhibition of weight gain than exposure to either substance alone, accompanied by greater signs of organ toxicity as indicated by clinical blood chemistries. Exposure to toluene caused marked hearing loss as assessed by a behavioral technique (conditioned avoidance), and there was a trend toward enhancement of this ototoxic effect by forced consumption of alcohol.

Problem-solving strategies and manifest brain asymmetry.

The dichhaptic stimulation procedures developed by Witelson (1974) for the study of brain lateralization in children were modified and extended for use with adults. Consistent with findings in children, an overall left hand advantage was found under conditions of simultaneous or dichhaptic stimulation, although it was not found under conditions of monohaptic stimulation. The major purpose of the study was to determine whether in adults hand differences (assumed to reflect hemisphere utilization) could be influenced by the use of differential problem-solving strategies. Half the Ss were instructed to approach the haptic learning and recognition problems in a "sequential" or "analytic" manner, and half to approach them in a "holistic" or "Gestalt" manner. The results indicated that the degree of left hand superiority was indeed influenced by this manipulation, although it is to be noted that the actual basis of the effect is unclear. The results were consistent with the idea that brain lateralization must be defined, not strictly by tasks, but by strategies used by subjects to perform the tasks used to detect and study that lateralization. It is suggested that this immensely complicates the issue of interpreting the origin and basis of individual and group differences in laterality effects.