170 research outputs found
Sources Of Student Engagement In Introductory Physics For Life Sciences
We explore the sources of student engagement with curricular content in an Introductory Physics for Life Science (IPLS) course at Swarthmore College. Do IPLS students find some life-science contexts more interesting than others, and, if so, what are the sources of these differences? We draw on three sources of student data to answer this question: (1) quantitative survey data illustrating how interested students were in particular contexts from the curriculum, (2) qualitative survey data in which students describe the source of their interest in these particular contexts, and (3) interview data in which students reflect on the contexts that were and were not of interest to them. We find that examples that make interdisciplinary connections with studentsâ other coursework in biology and chemistry, and examples that make connections to what students perceive to be the âreal world,â are particularly effective at fostering interest. More generally, students describe being deeply engaged with contexts that foster a sense of coherence or have personal meaning to them. We identify various âengagement pathwaysâ by which different life-science students engage with IPLS content, and suggest that a curriculum needs to be flexible enough to facilitate these different pathways
Negative Energy: Why Interdisciplinary Physics Requires Multiple Ontologies
Much recent work in physics education research has focused on ontological
metaphors for energy, particularly the substance ontology and its pedagogical
affordances. The concept of negative energy problematizes the substance
ontology for energy, but in many instructional settings, the specific
difficulties around negative energy are outweighed by the general advantages of
the substance ontology. However, we claim that our interdisciplinary setting (a
physics class that builds deep connections to biology and chemistry) leads to a
different set of considerations and conclusions. In a course designed to draw
interdisciplinary connections, the centrality of chemical bond energy in
biology necessitates foregrounding negative energy from the beginning. We argue
that the emphasis on negative energy requires a combination of substance and
location ontologies. The location ontology enables energies both "above" and
"below" zero. We present preliminary student data that illustrate difficulties
in reasoning about negative energy, and the affordances of the location
metaphor.Comment: 4 pages, submitted to PERC 2013 Proceeding
Ontological metaphors for negative energy in an interdisciplinary context
Teaching about energy in interdisciplinary settings that emphasize coherence
among physics, chemistry, and biology leads to a more central role for chemical
bond energy. We argue that an interdisciplinary approach to chemical energy
leads to modeling chemical bonds in terms of negative energy. While recent work
on ontological metaphors for energy has emphasized the affordances of the
substance ontology, this ontology is problematic in the context of negative
energy. Instead, we apply a dynamic ontologies perspective to argue that
blending the substance and location ontologies for energy can be effective in
reasoning about negative energy in the context of reasoning about chemical
bonds. We present data from an introductory physics for the life sciences
(IPLS) course in which both experts and students successfully use this blended
ontology. Blending these ontologies is most successful when the substance and
location ontologies are combined such that each is strategically utilized in
reasoning about particular aspects of energetic processes.Comment: 11 pages, 4 figure
Kinematic Effects of Tidal Interaction on Galaxy Rotation Curves
We use self-consistent N-body models, in conjunction with models of test
particles moving in galaxy potentials, to explore the initial effects of
interactions on the rotation curves of spiral galaxies. Using nearly
self-consistent disk/bulge/halo galaxy models (Kuijken & Dubinski 1995), we
simulate the first pass of galaxies on nearly parabolic orbits; we vary orbit
inclinations, galaxy halo masses and impact parameters. For each simulation, we
mimic observed rotation curves of the model galaxies. Transient
interaction-induced features of the curves include distinctly rising or falling
profiles at large radii and pronounced bumps in the central regions. Remarkably
similar features occur in our statistical sample of optical emission-line
rotation curves of spiral galaxies in tight pairs and n-tuples.Comment: 9 pages, 2 figures, accepted for publication in ApJ Letter
Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities
The disruption of binary stars by the tidal field of the black hole in the
Galactic Center can produce the hypervelocity stars observed in the halo. We
use numerical models to simulate the full spectrum of observable velocities of
stars ejected into the halo by this binary disruption process. Our model
includes a range of parameters for binaries with 3-4 M_Solar primaries,
consideration of radial orbits of the ejected stars through an approximate mass
distribution for the Galaxy, and the impact of stellar lifetimes. We calculate
the spectrum of ejection velocities and reproduce previous results for the mean
ejection velocity at the Galactic center. The model predicts that the full
population of ejected stars includes both the hypervelocity stars with
velocities large enough to escape from the Galaxy and a comparable number of
ejected, but bound, stars of the same stellar type. The predicted median speeds
of the population of ejected stars as a function of distance in the halo are
consistent with current observations. Combining the model with the data also
shows that interesting constraints on the properties of binaries in the
Galactic Center and on the mass distribution in the Galaxy can be obtained even
with modest samples of ejected stars.Comment: 26 pages, including 6 figures, accepted for publication in the
Astrophysical Journa
Leucine-rich alpha-2-glycoprotein-1 is upregulated in sera and tumors of ovarian cancer patients
<p>Abstract</p> <p>Background</p> <p>New biomarkers that replace or are used in conjunction with the current ovarian cancer diagnostic antigen, CA125, are needed for detection of ovarian cancer in the presurgical setting, as well as for detection of disease recurrence. We previously demonstrated the upregulation of leucine-rich alpha-2-glycoprotein-1 (LRG1) in the sera of ovarian cancer patients compared to healthy women using quantitative mass spectrometry.</p> <p>Methods</p> <p>LRG1 was quantified by ELISA in serum from two relatively large cohorts of women with ovarian cancer and benign gynecological disease. The expression of LRG1 in ovarian cancer tissues and cell lines was examined by gene microarray, reverse-transcriptase polymerase chain reaction (RT-PCR), Western blot, immunocytochemistry and mass spectrometry.</p> <p>Results</p> <p>Mean serum LRG1 was higher in 58 ovarian cancer patients than in 56 healthy women (89.33 ± 77.90 vs. 42.99 ± 9.88 ug/ml; p = 0.0008) and was highest among stage III/IV patients. In a separate set of 193 pre-surgical samples, LRG1 was higher in patients with serous or clear cell ovarian cancer (145.82 ± 65.99 ug/ml) compared to patients with benign gynecological diseases (82.53 ± 76.67 ug/ml, p < 0.0001). CA125 and LRG1 levels were moderately correlated (r = 0.47, p < 0.0001). <it>LRG1 </it>mRNA levels were higher in ovarian cancer tissues and cell lines compared to their normal counterparts when analyzed by gene microarray and RT-PCR. LRG1 protein was detected in ovarian cancer tissue samples and cell lines by immunocytochemistry and Western blotting. Multiple iosforms of LRG1 were observed by Western blot and were shown to represent different glycosylation states by digestion with glycosidase. LRG1 protein was also detected in the conditioned media of ovarian cancer cell culture by ELISA, Western blotting, and mass spectrometry.</p> <p>Conclusions</p> <p>Serum LRG1 was significantly elevated in women with ovarian cancer compared to healthy women and women with benign gynecological disease, and was only moderately correlated with CA125. Ovarian cancer cells secrete LRG1 and may contribute directly to the elevated levels of LRG1 observed in the serum of ovarian cancer patients. Future studies will determine whether LRG1 may serve as a biomarker for presurgical diagnosis, disease recurrence, and/or as a target for therapy.</p
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