15,852 research outputs found
Can Capital Mobility be Destabilizing?
In a standard two-sector neoclassical model with distortions, capital mobility can render the steady state indeterminate, in the sense that there exist infinitely many convergent paths. In the closed economy with no international capital mobility, the utility function must be linear or close to it for indeterminacy to occur, while in the open economy the shape of the utility function makes no difference. The reason is that in the no mobility case changes in aggregate investment must be matched by changes in aggregate consumption, while in the case of full capital mobility they can simply be financed by borrowing abroad. The paper provides some solid theoretical underpinnings to the concerns that de-regulating the capital account may be destabilizing.
Insights from using a subject specific Facebook group for student engagement and learning
Although discussion boards have been available in the Learning Management System (LMS) for several years, they have not served well as a means of extending student engagement outside class time. The social media site Facebook was incorporated into an Engineering Mechanics class with the aim of increasing subject specific student engagement. This paper reports a small preliminary study exploring the effect of the introduction of the Facebook group. These students found the Facebook group increased the frequency of their engagement with the subject material compared to other subjects, and they considered it valuable because almost all students and the instructor were involved. However, students emphasised that the Facebook group was a supplement to, and not a substitute for, the face-to-face lecture and tutorial sessions. This study confirmed the value of undertaking focus groups with students to assist interpretation of data collected by more objective methods such as social network analysis
Chiral bands for quasi-proton and quasi-neutron coupling with a triaxial rotor
A particle rotor model (PRM) with a quasi-proton and a quasi-neutron coupled
with a triaxial rotor is developed and applied to study chiral doublet bands
with configurations of a proton and a quasi-neutron. With
pairing treated by the BCS approximation, the present quasi-particle PRM is
aimed at simulating one proton and many neutron holes coupled with a triaxial
rotor. After a detailed analysis of the angular momentum orientations, energy
separation between the partner bands, and behavior of electromagnetic
transitions, for the first time we find aplanar rotation or equivalently chiral
geometry beyond the usual one proton and one neutron hole coupled with a
triaxial rotor.Comment: 25 pages, 10 figures, accepted for publication in Physical Review
Supersymmetric Modified Korteweg-de Vries Equation: Bilinear Approach
A proper bilinear form is proposed for the N=1 supersymmetric modified
Korteweg-de Vries equation. The bilinear B\"{a}cklund transformation of this
system is constructed. As applications, some solutions are presented for it.Comment: 8 pages, LaTeX using packages amsmath and amssymb, some corrections
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The effects of ocular and lens parameters on the postlens tear thickness.
PURPOSE:To assess the effects of soft contact lens base curve radius (BCR), sex, ethnicity, central corneal curvatures, and vertical palpebral aperture size (PAS) on the postlens tear thickness (PLTT). METHODS:The PLTT was measured using optical pachometry on 114 experienced lens wearers who were fitted with lathe-cut soft lenses (Alden 47, polymacon, 35.5% H2O, -2.00 diopter, and 14.0 mm). Each subject was randomly allocated to one lens group receiving a BCR of 7.9, 8.3, or 8.7 mm. Pachometry measurements were taken at 30 min after lens insertion. Vertical PAS and keratometry readings were measured for 94 of the 114 subjects. RESULTS:The mean (95% confidence interval) PLTT was 15.7 microm (13.2-18.0 microm), 12.8 microm (10.9-14.7 microm), and 12.1 microm (10.2-14.0 microm) for the 7.9-mm, 8.3-mm, and 8.7-mm BCR groups, respectively. The differences in PLTT among the three BCR groups was significant (analysis of variance F-test; P=0.039). Post hoc testing using the Tukey honestly significant difference statistic showed that only the two extreme BCR groups (7.9 mm and 8.7 mm) were significantly different. Sex had no effect on the PLTT; however, the PLTT was significantly thinner for the Asian compared with non-Asian eyes (P=0.0001). The Asian PLTT did not vary with different soft lens BCRs. The non-Asian PLTT was thicker with lenses of the steep BCR compared with the flat BCR. CONCLUSION:These results show that the base curve radius of a soft contact lens and several ocular characteristics can affect the thickness of the postlens tear film
Composite Polarons in Ferromagnetic Narrow-band Metallic Manganese Oxides
A new mechanism is proposed to explain the colossal magnetoresistance and
related phenomena. Moving electrons accompanied by Jahn-Teller phonon and
spin-wave clouds may form composite polarons in ferromagnetic narrow-band
manganites. The ground-state and finite-temperature properties of such
composite polarons are studied in the present paper. By using a variational
method, it is shown that the energy of the system at zero temperature decreases
with the formation of composite polaron; the energy spectrum and effective mass
of the composite polaron at finite temperature is found to be strongly
renormalized by the temperature and the magnetic field. It is suggested that
the composite polaron contribute significantly to the transport and the
thermodynamic properties in ferromagnetic narrow-band metallic manganese
oxides.Comment: Latex, no figur
Aberrant posterior cingulate connectivity classify first-episode schizophrenia from controls: A machine learning study
Background Posterior cingulate cortex (PCC) is a key aspect of the default mode network (DMN). Aberrant PCC functional connectivity (FC) is implicated in schizophrenia, but the potential for PCC related changes as biological classifier of schizophrenia has not yet been evaluated. Methods We conducted a data-driven approach using resting-state functional MRI data to explore differences in PCC-based region- and voxel-wise FC patterns, to distinguish between patients with first-episode schizophrenia (FES) and demographically matched healthy controls (HC). Discriminative PCC FCs were selected via false discovery rate estimation. A gradient boosting classifier was trained and validated based on 100 FES vs. 93 HC. Subsequently, classification models were tested in an independent dataset of 87 FES patients and 80 HC using resting-state data acquired on a different MRI scanner. Results Patients with FES had reduced connectivity between PCC and frontal areas, left parahippocampal regions, left anterior cingulate cortex, and right inferior parietal lobule, but hyperconnectivity with left lateral temporal regions. Predictive voxel-wise clusters were similar to region-wise selected brain areas functionally connected with PCC in relation to discriminating FES from HC subject categories. Region-wise analysis of FCs yielded a relatively high predictive level for schizophrenia, with an average accuracy of 72.28% in the independent samples, while selected voxel-wise connectivity yielded an accuracy of 68.72%. Conclusion FES exhibited a pattern of both increased and decreased PCC-based connectivity, but was related to predominant hypoconnectivity between PCC and brain areas associated with DMN, that may be a useful differential feature revealing underpinnings of neuropathophysiology for schizophrenia
Real-time analysis of gene regulation by glucocorticoid hormones
There is increasing evidence that temporal factors are important in allowing
cells to gain additional information from external factors, such as hormones and
cytokines. We sought to discover how cell responses to glucocorticoids develop
over time, and how the response kinetics vary according to ligand structure and
concentration, and hence have developed a continuous gene transcription
measurement system, based on an interleukin-6 (IL-6) luciferase reporter gene.
We measured the time to maximal response, maximal response and integrated
response, and have compared these results with a conventional, end point
glucocorticoid bioassay. We studied natural glucocorticoids (corticosterone and
cortisol), synthetic glucocorticoids (dexamethasone) and glucocorticoid
precursors with weak, or absent bioactivity. We found a close correlation
between half maximal effective concentration (EC50) for maximal response, and
for integrated response, but with consistently higher EC50 for the latter. There
was no relation between the concentration of ligand and the time to maximal
response. A comparison between conventional end point assays and real-time
measurement showed similar effects for dexamethasone and hydrocortisone, with a
less effective inhibition of IL-6 seen with corticosterone. We profiled the
activity of precursor steroids, and found pregnenolone, progesterone,
21-hydroxyprogesterone and 17-hydroxyprogesterone all to be ineffective in the
real-time assay, but in contrast, progesterone and 21-hydroxyprogesterone showed
an IL-6 inhibitory activity in the end point assay. Taken together, our data
show how ligand concentration can alter the amplitude of glucocorticoid
response, and also that a comparison between real-time and end point assays
reveals an unexpected diversity of the function of glucocorticoid precursor
steroids, with implications for human disorders associated with their
overproduction
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