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Background: Current selection methods for neurosurgical residents lack objective measurements of psychomotor performance. This pilot study was designed to answer three questions: 1) What are the differences in bimanual psychomotor performance among neurosurgical residency applicants using the NeuroVR (formerly NeuroTouch) neurosurgical simulator? 2) Are there exceptionally skilled medical student applicants? 3) Does previous surgical exposure influence surgical performance? Methods: Medical students attending neurosurgery residency interviews at McGill University were asked to participate. Participants were instructed to remove 3 simulated brain tumors. Validated tier 1, tier 2, and advanced tier 2 metrics were utilized to assess bimanual psychomotor performance. Demographic data included weeks of neurosurgical elective and prior operative exposure. Results: Sixteen of 17 neurosurgical applicants (94%) participated. Performances clustered in definable top, middle, and bottom groups with significant differences for all metrics. Increased time spent playing music, increase applicant self-evaluated technical skills, high self-ratings of confidence and increased skin closures statistically influenced performance on univariate analysis. A trend for both self-rated increased operating room confidence and increased weeks of neurosurgical exposure to increase blood loss was seen in multivariate analysis. Conclusions: Simulation technology identifies neurosurgical residency applicants at the extremes of technical ability and extrinsic and intrinsic applicant factors appear to influence performance.
Background: Virtual reality simulators allow development of novel methods to analyze neurosurgical performance. Force pyramids provide visual and spatial analysis of 3 dimensional force application by any instrument used during simulated tumor resection. This study was designed to answer three questions: 1) Do study groups have distinct force pyramids? 2) Do handedness and ergonomics influence force pyramid structure? 3) Are force pyramids dependent on visual and haptic characteristics of simulated tumors? Methods: NeuroVR (formerly NeuroTouch), a virtual reality simulator, continually assessed simulated ultrasonic aspirator force application of neurosurgeon, resident and medical student groups during resection of 18 simulated brain tumors with different visual and haptic characteristics. Results: Sixteen neurosurgeons, 15 residents and 84 medical students participated. Neurosurgeon, resident and medical students groups displayed easily distinguishable 3 dimensional ‘force pyramid fingerprints’. Neurosurgeons had the lowest force pyramids, indicating application of the lowest forces, followed by resident and medical student groups. Handedness, ergonomics, visual and haptic tumor characteristics resulted in distinct well-defined 3 dimensional force pyramid patterns. Conclusions: ‘Force pyramid fingerprints’ provide 3 dimensional spatial assessment displays of instrument force application during simulated tumor resections. Neurosurgeon force utilization and ergonomics data form a basis for understanding and modulating resident force application and improving patient safety during tumor resection.
We report on the identifications of 15 new X-ray selected Active Galactic Nuclei (AGN). The AGN have been discovered during an ongoing program to identify and study the optical counterparts of X-ray sources detected by the HEAO-1 satellite. The new AGN add to our existing data base of 26 making a sample of 41 objects which are the subject of a multiwavelength study including radio, infrared, optical, UV and X-ray observations. As part of this study 8.4 GHz flux measurements have been made at Parkes. Radio-optical-X-ray continuum spectral index comparisons are presented.
Plutonium metal is a very unusual element, exhibiting six allotropes at ambient pressure, between room temperature and its melting point, a complicated phase diagram, and a complex electronic structure. Many phases of plutonium metal are unstable with changes in temperature, pressure, chemical additions, or time. This strongly affects structure and properties, and becomes of high importance, particularly when considering effects on structural integrity over long periods of time . This paper presents a time-dependent neutron total scattering study of the local and average structure of naturally aging δ-phase 239Pu-Ga alloys, together with preliminary results on neutron tomography characterization.
We assessed if there has been a decline in the median number of reported lifetime sexual partners in Kenya following the AIDS epidemic. The Wilcoxon rank-sum test was used to compare the median and interquartile range (IQR) of the number of lifetime sexual partners for men aged 20–54 years in the 1993 and 2008 Kenyan Demographic Health Surveys. The median number of sexual partners in 1993 increased rapidly to 10 partners reported at age 30 years then plateaued at this level. In 2008, the median number of sexual partners plateaued at around half the value of the 1993 plateau. The median number of lifetime sexual partners for men aged 20–54 years declined from 10 (IQR 4-20) in 1993 to 3 (IQR 2-7) in 2008 (P < 0·001). This decline could be due to a combination of the effects of AIDS mortality and a misreporting bias.
The measurement of precise submicron displacements is essential in several MEMS applications. For instance, the measurement of the mechanical parameters of biological cells requires repeatable measurement of displacements in the nanometer regime. This paper presents a method to make displacement measurements in an aqueous MEMS environment with a ± 10 nm accuracy by using the blue channel of RGB pictures in combination with a FFT phase shift analysis.
Plutonium and Pu-Ga alloys have been observed to have anomalous hydrogen solubility behavior, including a significant concentration dependence of hydrogen diffusivity in the dilute regime, a sharp drop off in the hydrogen solubility constant in the dilute regime, and a near complete absence of change in the Sieverts’ constant as the alloys are heated across phase transformation boundaries. We are investigating the possibility that a vacancy mechanism is responsible for this behavior. X-ray diffraction measurements show a 0.14% lattice contraction in Pu-2 at. % Ga alloys when they are charged with ~2 at. % hydrogen. The lattice re-expands when the hydrogen is removed. Density functional calculations show that increasing the number of hydrogen atoms associated with a vacant lattice site in Pu lowers the energy of the hydrogen-vacancy complex. These observations support the idea that vacancies are stabilized by hydrogen in the Pu lattice well beyond their thermal equilibrium concentration and could be responsible for the anomalous hydrogen response of Pu.
Elemental bismuth nanoparticles and nanotubes were obtained via microwave hydrothermal synthesis starting from bismuth oxide (Bi2O3) in the range of temperatures 200-220oC for 10-45 min. The formed nanostructures were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Relationship between reaction parameters and shape of the formed nanostructures is discussed.
Thin films of SnO2 were prepared via wet chemical method and deposited by dip-coating on glass substrate. The annealing temperatures of the samples were 300, 400, 500 and 600o C, respectively. Water vapor sensor responses were measured and the experimental results are tested using the Freundlich model. The better water vapor sensitivities were obtained for annealing temperatures of 500 and 600oC, respectively. The samples were characterized morphological and structurally by SEM, XRD, Mössbauer spectroscopy and Raman spectroscopy. The fringes features in the ultraviolet-visible region indicate films thickness around 370 nm. The results are discussed in terms of the fine grain size of the samples.
Rahm Emanuel, White House Chief of Staff, to President Barack Obama, 21 November 2008
The notion – which now approaches the status of conventional wisdom – that policy breakthroughs can be achieved in times of crisis, finds an academic echo in the common-sense idea that something particularly useful can be learned about a significant socio-economic phenomenon, such as government procurement, by studying its performance in times of crisis. Indeed, that insight drives both this chapter and the previous one. This chapter proceeds by examining and comparing the lessons that emerge – or which are believed to emerge – from three recent episodes of political or economic crisis in the US, each of which had significant consequences for the procurement system of the US national (‘federal’) government. The three episodes examined are: (i) the procurement response to Hurricane Katrina, which struck the Gulf Coast of the US in the summer of 2005; (ii) the procurement issues that emerged in response to the attacks of 11 September 2001 and the ensuing US military engagements in Iraq and in Afghanistan; and (iii) the procurement aspects of the federal government's stimulus response to the current ‘Great Recession’.
This contribution is not offered as a piece of primary empirical research but as a vehicle for meta-analysis. There are several reasons for choosing this approach. First, with respect to some of these crisis episodes, the primary work has already been done elsewhere.
This study investigated the role of verbal working memory on bilingual lexical disambiguation. Spanish–English bilinguals read sentences that ended in either a cognate or noncognate homonym or a control word. Participants decided whether follow-up target words were related in meaning to the sentences. On critical trials, sentences biased the subordinate meaning of a homonym and were followed by targets related to the dominant meaning. Bilinguals with high span were faster at rejecting unrelated targets when the sentences ended in a homonym, whereas bilinguals with low span were slower. Furthermore, error rates for bilinguals with low span showed cognate inhibition, while bilinguals with high span showed no effects of cross-language activation. Results demonstrated that bilinguals with high span benefit from shared lexical codes whether these converge on to a single semantic representation (cognates) or not (homonyms). Conversely, bilinguals with low span showed inhibition from the competing lexical codes, even when they converge onto a single semantic representation.
A 60-year-old patient with a clinical diagnosis of schizophrenia underwent a magnetic resonance imaging (MRI) scan related to the evaluation of isolated seizures that emerged while medicated with clozapine. Unexpectedly, the MRI scan revealed evidence of asymmetric and enlarged cerebral ventricles that were interpreted as congenital in origin. The presence of both congenital lateral ventricular asymmetry and ventriculomegaly may interact to increase risk of schizophrenia. The history and clinical features, including cognitive testing, of the illustrative patient are presented.
We describe a novel, facile method for the alignment of multi-walled carbon nanotubes (MWNTs) in a magnetic field facilitated by the decoration of the MWNTs with monodisperse γ-Fe2O3 magnetic (maghemite) nanoparticles. The tethering of the nanoparticles was achieved by the attachment of γ-Fe2O3 nanoparticles that were synthesized using a modified sol-gel process, onto the carboxylate-activated MWNTs. Sodium dodecylbenzene sulfonate (NaDDBS) was used to prevent the formation of an iron oxide 3D network. Various characterization methods were employed to confirm the formation of homogeneously-distributed and nearly-monodispersed iron oxide nanoparticles, and show that they were indeed tethered to the walls of the MWNTs. The γ-Fe2O3 nanoparticles imparted magnetic characteristics to the MWNTs, which in turn, were oriented parallel to the direction of an externally-applied magnetic field. This facile alignment of MWNT could promote the enhancement of various properties, e.g. mechanical and electrical properties, of the resulting composites. Moreover, this facile alignment at low magnetic fields, made possible by the magnetization of the carbon nanotubes through the tethering of maghemite nanoparticles, may be applied to a variety of other useful nanofillers, such a glass fibers, clay nanoparticles and cellulose nanowhiskers.
We examined how linguistic context influences the nature of bilingual lexical activation. We hypothesized that in single-word context, form-related words would receive the strongest activation while, in sentence context, semantically related words would receive the strongest activation. Spanish–English bilinguals performed a semantic verification task on English target words preceded by a prime. On critical trials, the prime and target words were paired based either on a form-mediated relationship through the native language (L1), [e.g., bark (barco): BOAT] (Experiment 1) or on a semantically-mediated relationship [e.g., boat (barco): BARK] (Experiment 2). The prime word was presented either in isolation or after a sentence context. In Experiment 1 interference was observed in the single word condition only. In Experiment 2 interference was observed in both single-word and sentence contexts. The findings demonstrate that the context in which words are embedded has an impact on the type of lexical competitors that become active.
Williams syndrome is a neurodevelopmental disorder that results from the deletion of ~25-30 genes spanning about 1.5 megabases in the q11.23 region of chromosome 7. Patients with this syndrome present with a combination of a distinctive elfin-like facial appearance; growth retardation; mild mental retardation; an inconsistent cognitive profile that includes visuospatial impairments with good facial discrimination and relatively preserved expressive language skills; and cardiovascular abnormalities. In addition, a striking behavioral feature of the syndrome is the high sociability and empathy that these patients show for others. The study of patients with “partial” deletions of the chromosome band 7q11.23, mutated genes in this region and knockout mice with deletions of specific genes in the homologous G1–G2 region of mouse chromosome 5 are clarifying some genotype/phenotype relationships. Futhermore, genes located in this region that are prominently expressed have been implicated in brain development and function.The neuropsychological profile of patients with Williams syndrome is heterogeneous, highlights important dissociations between cognitive functions and suggests that the behavioral dimensions of sociability, empathy, engageability, and talkativeness may be independent of, or not easily explained by, the cognitive deficits. Williams syndrome has enormous heuristic value because its pathological feature of heightened “sociability” can be a “deficit” symptom of major complex neuropsychiatrie disorders, such as schizophrenia and autism. Data consistent with a core inability of patients with Williams syndrome to inhibit social approach suggest that this disorder may afford an opportunity to study the biological basis of the “drive” toward socialization. From a research perspective, the syndrome lends itself to neurobiological studies of sociability as a dimension that varies independently of cognition (or at least many separable cognitive processes). Importantly, from a clinical perspective, the syndrome challenges us to administer strategic psychosocial interventions that take advantage of the opportunities that “pathological” sociability provide, while avoiding its threats. An illustrative example of an effective strategically planned psychosocial intervention for a patient with Williams syndrome is briefly presented.
Hydrogen peroxide formed by radiolysis of carbonate –bicarbonate media was followed by 13C NMR using dissolved [233UO2(13CO3)3]4- as the alpha source (Dα=12.1 Gy/hr). It is shown that the speciation of the peroxide carbonates (or other species) that are formed in the pH region 5.9 and 11.6 by titration with hydrogen peroxide are common to those formed by hydrogen peroxide generated by radiolysis. Radiolytic generation of hydrogen peroxide was followed by observing the formation of a uranyl peroxide carbonate complex. Complex formation was observed to accelerate for about 1200 hours and to terminate between 1×10-4 and 5×10-4 M. It is assumed that either a steady state H2O2 production rate was established in solution or that some limiting feature of the experiment was responsible for slowing the yield of product.
We have used the new approach to fatigue phenomenon for analysis of the switching current and C-V characteristic evolution during cycling in PZT thin films. It was shown that in accordance with theoretical predictions the rejuvenation stage precedes the fatigue one. We have demonstrated that fatigue behavior corresponds to the spreading of the internal bias field distribution function during ac switching.