761 research outputs found
Simple computer method provides contours for radiological images
Computer is provided with information concerning boundaries in total image. Gradient of each point in digitized image is calculated with aid of threshold technique; then there is invoked set of algorithms designed to reduce number of gradient elements and to retain only major ones for definition of contour
Teaching and understanding of quantum interpretations in modern physics courses
Just as expert physicists vary in their personal stances on interpretation in
quantum mechanics, instructors vary on whether and how to teach interpretations
of quantum phenomena in introductory modern physics courses. In this paper, we
document variations in instructional approaches with respect to interpretation
in two similar modern physics courses recently taught at the University of
Colorado, and examine associated impacts on student perspectives regarding
quantum physics. We find students are more likely to prefer realist
interpretations of quantum-mechanical systems when instructors are less
explicit in addressing student ontologies. We also observe contextual
variations in student beliefs about quantum systems, indicating that
instructors who choose to address questions of ontology in quantum mechanics
should do so explicitly across a range of topics.Comment: 18 pages, references, plus 2 pages supplemental materials. 8 figures.
PACS: 01.40.Fk, 03.65.-
Development and Uses of Upper-division Conceptual Assessment
The use of validated conceptual assessments alongside more standard course
exams has become standard practice for the introductory courses in many physics
departments. These assessments provide a more standard measure of certain
learning goals, allowing for comparisons of student learning across
instructors, semesters, and institutions. Researchers at the University of
Colorado Boulder have developed several similar assessments designed to target
the more advanced physics content of upper-division classical mechanics,
electrostatics, quantum mechanics, and electrodynamics. Here, we synthesize the
existing research on our upper-division assessments and discuss some of the
barriers and challenges associated with developing, validating, and
implementing these assessments as well as some of the strategies we have used
to overcome these barriers.Comment: 12 pages, 5 figures, submitted to the Phys. Rev. ST - PER Focused
collection on Upper-division PE
Development of quantum perspectives in modern physics
Introductory undergraduate courses in classical physics stress a perspective
that can be characterized as realist; from this perspective, all physical
properties of a classical system can be simultaneously specified and thus
determined at all future times. Such a perspective can be problematic for
introductory quantum physics students, who must develop new perspectives in
order to properly interpret what it means to have knowledge of quantum systems.
We document this evolution in student thinking in part through pre- and
post-instruction evaluations using the Colorado Learning Attitudes about
Science Survey. We further characterize variations in student epistemic and
ontological commitments by examining responses to two essay questions, coupled
with responses to supplemental quantum attitude statements. We find that, after
instruction in modern physics, many students are still exhibiting a realist
perspective in contexts where a quantum-mechanical perspective is needed. We
further find that this effect can be significantly influenced by instruction,
where we observe variations for courses with differing learning goals. We also
note that students generally do not employ either a realist or a quantum
perspective in a consistent manner.Comment: 18 pages, plus references; 3 figures; 9 tables. PACS: 01.40.Fk,
03.65._
Tuberculosis prevalence survey in Kashmir valley
A tuberculosis prevalence survey was conducted in about 18,000 persons in
Kashmir valley situated about 1650 m above the mean sea level. All persons
were tested with 3 IU of PPD-S and 10 units of PPD-B. Persons aged 5 yr
and above were X-rayed (70 mm X-ray), and from such persons whose photofluorograms
were interpreted as abnormal two specimens of sputum were
collected and bacteriologically examined. In addition, a large X-ray of the
chest was taken for children aged 0-4 yr who had reactions of 10 mm or more
to PPD-S. They were then clinically examined by a paediatrician, taking into
account all available data, for evaluation for any evidence of tuberculosis.
The results of the survey showed that the prevalence of non-specific sensitivity
(59%) in the Kashmir valley is significant. The prevalence of tuberculous infection
was 38 per cent. The prevalence of culture positive tuberculous patients
(3 per 1000) and that of abacillary X-ray positive patients (14 per 1000) were
found to be similar in the two sexes contrary to the usual experience of a
higher prevalence among males. Results from studies of phage typing, susceptibility
to thiophen-2-carbonic acid hydrazide (TCH) and virulence in the
guineapig of strains obtained from patients diagnosed in the survey showed
that most of these strains belonged to phage type A, were resistant to TCH
and were not of low virulence. Regional variations in the prevalence rates
were seen, the- problem of tuberculosis appeared to he more in the Baramulla
district as compared to Srinagar and Anantnag districts. A comparison of results
obtained from the present survey with those obtained from the BCG trial
in Chingleput (Tamil Nadu) revealed that the tuberculosis situation in the
two areas was quite different
Pregnancy after complex myomectomy: neither age of patient nor size, number or location of fibroids should be a barrier
Giant magnetothermopower of magnon-assisted transport in ferromagnetic tunnel junctions
We present a theoretical description of the thermopower due to
magnon-assisted tunneling in a mesoscopic tunnel junction between two
ferromagnetic metals. The thermopower is generated in the course of thermal
equilibration between two baths of magnons, mediated by electrons. For a
junction between two ferromagnets with antiparallel polarizations, the ability
of magnon-assisted tunneling to create thermopower depends on the
difference between the size of the majority and
minority band Fermi surfaces and it is proportional to a temperature dependent
factor where is the magnon Debye
energy. The latter factor reflects the fractional change in the net
magnetization of the reservoirs due to thermal magnons at temperature
(Bloch's law). In contrast, the contribution of magnon-assisted
tunneling to the thermopower of a junction with parallel polarizations is
negligible. As the relative polarizations of ferromagnetic layers can be
manipulated by an external magnetic field, a large difference results in a magnetothermopower effect. This
magnetothermopower effect becomes giant in the extreme case of a junction
between two half-metallic ferromagnets, .Comment: 9 pages, 4 eps figure
Special values of canonical Green's functions
We give a precise formula for the value of the canonical Green's function at
a pair of Weierstrass points on a hyperelliptic Riemann surface. Further we
express the 'energy' of the Weierstrass points in terms of a spectral invariant
recently introduced by N. Kawazumi and S. Zhang. It follows that the energy is
strictly larger than log 2. Our results generalize known formulas for elliptic
curves.Comment: 10 page
A hybrid radiation detector for simultaneous spatial and temporal dosimetry
In this feasibility study an organic plastic scintillator is calibrated against ionisation chamber measurements and then embedded in a polymer gel dosimeter to obtain a quasi-4D experimental measurement of a radiation field. This hybrid dosimeter was irradiated with a linear accelerator, with temporal measurements of the dose rate being acquired by the scintillator and spatial measurements acquired with the gel dosimeter. The detectors employed in this work are radiologically equivalent; and we show that neither detector perturbs the intensity of the radiation field of the other. By employing these detectors in concert, spatial and temporal variations in the radiation intensity can now be detected and gel dosimeters can be calibrated for absolute dose from a single irradiation
Anti-cancer effects and mechanism of actions of aspirin analogues in the treatment of glioma cancer
INTRODUCTION: In the past 25 years only modest advancements in glioma treatment have been made, with patient prognosis and median survival time following diagnosis only increasing from 3 to 7 months. A substantial body of clinical and preclinical evidence has suggested a role for aspirin in the treatment of cancer with multiple mechanisms of action proposed including COX 2 inhibition, down regulation of EGFR expression, and NF-ÎșB signaling affecting Bcl-2 expression. However, with serious side effects such as stroke and gastrointestinal bleeding, aspirin analogues with improved potency and side effect profiles are being developed. METHOD: Effects on cell viability following 24 hr incubation of four aspirin derivatives (PN508, 517, 526 and 529) were compared to cisplatin, aspirin and di-aspirin in four glioma cell lines (U87 MG, SVG P12, GOS â 3, and 1321N1), using the PrestoBlue assay, establishing IC50 and examining the time course of drug effects. RESULTS: All compounds were found to decrease cell viability in a concentration and time dependant manner. Significantly, the analogue PN517 (IC50 2mM) showed approximately a twofold increase in potency when compared to aspirin (3.7mM) and cisplatin (4.3mM) in U87 cells, with similar increased potency in SVG P12 cells. Other analogues demonstrated similar potency to aspirin and cisplatin. CONCLUSION: These results support the further development and characterization of novel NSAID derivatives for the treatment of glioma
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