4,422 research outputs found
The Social Construction of Chinese Models of Teaching
Five principal relationships, derived from long-standing Confucian values, are described as the cultural and social foundation for Chinese models of teaching. Three related models of teaching will be described during the presentation: Teacher as master; teacher as virtuoso; and teacher as coach
The Recent Star Formation in Sextans A
We investigate the relationship between the spatial distributions of stellar populations and of neutral and ionized gas in the Local Group dwarf irregular galaxy Sextans A. This galaxy is currently experiencing a burst of localized star formation, the trigger of which is unknown. We have resolved various populations of stars via deep UBV(RI)_C imaging over an area with diameter ~5farcm3. We have compared our photometry with theoretical isochrones appropriate for Sextans A, in order to determine the ages of these populations. We have mapped out the history of star formation, most accurately for times ≾ 100 Myr. We find that star formation in Sextans A is correlated both in time and space, especially for the most recent (≾ 12 Myr) times. The youngest stars in the galaxy are forming primarily along the inner edge of the large H I shell. Somewhat older populations, ≾ 50 Myr, are found inward of the youngest stars. Progressively older star formation, from ~50–100 Myr, appears to have some spatially coherent structure and is more centrally concentrated. The oldest stars we can accurately sample appear to have approximately a uniform spatial distribution, which extends beyond a surface brightness of μ_B ≃ 25.9 mag arcsec^(-2) (or, a radius r ≃ 2farcm3). Although other processes are also possible, our data provide support for a mechanism of supernova-driven expansion of the neutral gas, resulting in cold-gas pileup and compression along the H I shell and sequential star formation in recent times
Comparison of total body water estimates from O-18 and bioelectrical response prediction equations
Identification of an indirect, rapid means to measure total body water (TBW) during space flight may aid in quantifying hydration status and assist in countermeasure development. Bioelectrical response testing and hydrostatic weighing were performed on 27 subjects who ingested O-18, a naturally occurring isotope of oxygen, to measure true TBW. TBW estimates from three bioelectrical response prediction equations and fat-free mass (FFM) were compared to TBW measured from O-18. A repeated measures MANOVA with post-hoc Dunnett's Test indicated a significant (p less than 0.05) difference between TBW estimates from two of the three bioelectrical response prediction equations and O-18. TBW estimates from FFM and the Kushner & Schoeller (1986) equation yielded results that were similar to those given by O-18. Strong correlations existed between each prediction method and O-18; however, standard errors, identified through regression analyses, were higher for the bioelectrical response prediction equations compared to those derived from FFM. These findings suggest (1) the Kushner & Schoeller (1986) equation may provide a valid measure of TBW, (2) other TBW prediction equations need to be identified that have variability similar to that of FFM, and (3) bioelectrical estimates of TBW may prove valuable in quantifying hydration status during space flight
Laparoscopic insertion of pelvic tissue expander to prevent radiation enteritis prior to radiotherapy for prostate cancer
Radiation enteritis is a significant complication of external beam radiotherapy (EBRT) to the pelvis, particularly in patients having high dose radiotherapy (>80 Gy) and in those with a low pelvic peritoneal reflection allowing loops of small bowel to enter the radiation field. Laparoscopic insertion and subsequent removal of a pelvic tissue expander before and after external beam radiotherapy is a relatively convenient, safe and effective method for displacing loops of bowel out of the pelvis. We report on a patient with prostate cancer who ordinarily would not have been a candidate for EBRT due to loops of bowel low in the pelvis. With laparoscopic insertion and subsequent removal of a tissue expander, he was able to have radiotherapy to the prostate without developing radiation enteritis
Lineage dynamics of murine pancreatic development at single-cell resolution.
Organogenesis requires the complex interactions of multiple cell lineages that coordinate their expansion, differentiation, and maturation over time. Here, we profile the cell types within the epithelial and mesenchymal compartments of the murine pancreas across developmental time using a combination of single-cell RNA sequencing, immunofluorescence, in situ hybridization, and genetic lineage tracing. We identify previously underappreciated cellular heterogeneity of the developing mesenchyme and reconstruct potential lineage relationships among the pancreatic mesothelium and mesenchymal cell types. Within the epithelium, we find a previously undescribed endocrine progenitor population, as well as an analogous population in both human fetal tissue and human embryonic stem cells differentiating toward a pancreatic beta cell fate. Further, we identify candidate transcriptional regulators along the differentiation trajectory of this population toward the alpha or beta cell lineages. This work establishes a roadmap of pancreatic development and demonstrates the broad utility of this approach for understanding lineage dynamics in developing organs
The influence of mortality and socioeconomic status on risk and delayed rewards: a replication with British participants
Here, we report three attempts to replicate a finding from an influential psychological study (Griskevicius et al., 2011b). The original study found interactions between childhood SES and experimental mortality-priming condition in predicting risk acceptance and delay discounting outcomes. The original study used US student samples. We used British university students (replication 1) and British online samples (replications 2 and 3) with a modified version of the original priming material, which was tailored to make it more credible to a British audience. We did not replicate the interaction between childhood SES and mortality-priming condition in any of our three experiments. The only consistent trend of note was an interaction between sex and priming condition for delay discounting. We note that psychological priming effects are considered fragile and often fail to replicate. Our failure to replicate the original finding could be due to demographic differences in study participants, alterations made to the prime, or other study limitations. However, it is also possible that the previously reported interaction is not a robust or generalizable finding
Nonlinear Meissner effect in a high-temperature superconductor: Local versus nonlocal electrodynamics
Measured intermodulation distortion (IMD) power at 1.5 GHz in a series of YBa[subscript 2]Y[subscript 3]O[subscript 7−δ] stripline resonators of varying strip widths is compared to the predictions of two qualitatively distinct theories of the nonlinear Meissner effect. The stripline resonators are patterned from a single wafer to ensure uniformity of the material properties. According to the first theory [T. Dahm and D. J. Scalapino, Phys. Rev. B 60, 13125 (1999)], the IMD power is dominated by contributions from the strip edges, while according to the second theory [D. Agassi and D. E. Oates, Phys. Rev. B 72, 014538 (2005)] it is dominated by contributions from the body of the strip. The parameter-free comparison of the measured data with the theoretical predictions clearly favors the latter theory. We conclude that the nonlinear component of the penetration depth must be treated with nonlocal electrodynamics. The origins of this outcome are discussed briefly in the framework of a Green’s-function approach
Demonstrating Photon Ring Existence with Single-Baseline Polarimetry
Images of supermassive black hole accretion flows contain features of both
curved spacetime and plasma structure. Inferring properties of the spacetime
from images requires modeling the plasma properties, and vice versa. The Event
Horizon Telescope Collaboration has imaged near-horizon millimeter emission
from both Messier 87* (M87*) and Sagittarius A* (Sgr A*) with
very-long-baseline interferometry (VLBI) and has found a preference for
magnetically arrested disk (MAD) accretion in each case. MAD accretion enables
spacetime measurements through future observations of the photon ring, the
image feature composed of near-orbiting photons. The ordered fields and
relatively weak Faraday rotation of MADs yield rotationally symmetric
polarization when viewed at modest inclination. In this letter, we utilize this
symmetry along with parallel transport symmetries to construct a gain-robust
interferometric quantity that detects the transition between the weakly lensed
accretion flow image and the strongly lensed photon ring. We predict a shift in
polarimetric phases on long baselines and demonstrate that the photon rings in
M87* and Sgr A* can be unambiguously detected {with sensitive, long-baseline
measurements. For M87* we find that photon ring detection in snapshot
observations requires mJy sensitivity on G baselines at
230 GHz and above, which could be achieved with space-VLBI or higher-frequency
ground-based VLBI. For Sgr A*, we find that interstellar scattering inhibits
photon ring detectability at 230 GHz, but mJy sensitivity on
G baselines at 345 GHz is sufficient, which is accessible from the
ground. For both sources, these sensitivity requirements may be relaxed by
repeated observations and averaging.Comment: 14 pages, 7 figures, Accepted to ApJ
Macrostate Data Clustering
We develop an effective nonhierarchical data clustering method using an
analogy to the dynamic coarse graining of a stochastic system. Analyzing the
eigensystem of an interitem transition matrix identifies fuzzy clusters
corresponding to the metastable macroscopic states (macrostates) of a diffusive
system. A "minimum uncertainty criterion" determines the linear transformation
from eigenvectors to cluster-defining window functions. Eigenspectrum gap and
cluster certainty conditions identify the proper number of clusters. The
physically motivated fuzzy representation and associated uncertainty analysis
distinguishes macrostate clustering from spectral partitioning methods.
Macrostate data clustering solves a variety of test cases that challenge other
methods.Comment: keywords: cluster analysis, clustering, pattern recognition, spectral
graph theory, dynamic eigenvectors, machine learning, macrostates,
classificatio
Pancreatectomy for metastatic real cell carcinoma : twenty years of experience at a tertiary centre
Renal Cell Carcinoma (RCC) accounts for approximately 90% of primary renal malignancies, of which the clear cell subtype is most common. While metastatic disease is common at the time of diagnosis and generally confers a poor prognosis, metastatic RCC may demonstrate relatively indolent behaviour and present many years after resection of the primary tumour, including to the pancreas. The available literature suggested that surgical resection was appropriate for select patients, including those with a solitary pancreatic metastasis, minimal comorbidities and uncomplicated progress from initial treatment of their primary renal malignancy. A retrospective case series of patients presenting with RCC metastases to the pancreas, managed via surgical resection at a tertiary teaching hospital was reviewed. Analysis of patient demographics, investigations, management and outcomes were performed, with a focus on post-operative morbidity and overall survival. Between 2000 and 2020, 7 patients underwent pancreatic resection of RCC metastases at our tertiary teaching hospital with curative intent. Median age at time of resection was 66 years. No post-operative mortality or major morbidity was experienced by the 7 patients, although 4 patients developed some degree of pancreatic insufficiency. Four patients experienced recurrent metastatic RCC, with median time to recurrence of 3.5 years. This was the largest local study to describe an Australian experience of the surgical management of RCC pancreatic metastases. These patients are frequently afforded prolonged survival following pancreatic resection, but often develop other distant sites of disease and second renal tumours
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