1,802 research outputs found
Some Tests for Checking the Efficiency of a High School Curriculum
A thesis submitted to the department of Education and the faculty of the Graduate School of the University of Kansas in partial fulfillment for the degree of Master of Arts
Optical matrix elements in tight-binding models with overlap
We investigate the effect of orbital overlap on optical matrix elements in
empirical tight-binding models. Empirical tight-binding models assume an
orthogonal basis of (atomiclike) states and a diagonal coordinate operator
which neglects the intra-atomic part. It is shown that, starting with an atomic
basis which is not orthogonal, the orthogonalization process induces
intra-atomic matrix elements of the coordinate operator and extends the range
of the effective Hamiltonian. We analyze simple tight-binding models and show
that non-orthogonality plays an important role in optical matrix elements. In
addition, the procedure gives formal justification to the nearest-neighbor
spin-orbit interaction introduced by Boykin [Phys. Rev \textbf{B} 57, 1620
(1998)] in order to describe the Dresselahaus term which is neglected in
empirical tight-binding models.Comment: 16 pages 6 figures, to appear in Phys. Rev.
Electronic and optical properties of beryllium chalcogenides/silicon heterostructures
We have calculated electronic and optical properties of
Si/BeSeTe heterostructures by a semiempirical
tight-binding method. Tight-binding parameters and band bowing of
BeSeTe are considered through a recent model for highly
mismatched semiconductor alloys. The band bowing and the measurements of
conduction band offset lead to a type II heterostucture for
Si/BeSeTe with conduction band minimum in the Si layer and
valence band maximum in the BeSeTe layer. The electronic
structure and optical properties of various (Si/(BeSeTe [001] superlattices have been considered. Two
bands of interface states were found within the bandgap of bulk Si. Our
calculations indicate that the optical edges are below the fundamental bandgap
of bulk Si and the transitions are optically allowed.Comment: 16 pager, 7 figure
Omega-3 Fatty Acids Improve Recovery, whereas Omega-6 Fatty Acids Worsen Outcome, after Spinal Cord Injury in the Adult Rat
Spinal cord injury (SCI) is a cause of major neurological disability, and no satisfactory treatment is currently available. Evidence suggests that polyunsaturated fatty acids (PUFAs) could target some of the pathological mechanisms that underlie damage after SCI. We examined the effects of treatment with PUFAs after lateral spinal cord hemisection in the rat. The ω-3 PUFAs α-linolenic acid and docosahexaenoic acid (DHA) injected 30 min after injury induced significantly improved locomotor performance and neuroprotection, including decreased lesion size and apoptosis and increased neuronal and oligodendrocyte survival. Evidence showing a decrease in RNA/DNA oxidation suggests that the neuroprotective effect of ω-3 PUFAs involved a significant antioxidant function. In contrast, animals treated with arachidonic acid, an ω-6 PUFA, had a significantly worse outcome than controls. We confirmed the neuroprotective effect of ω-3 PUFAs by examining the effects of DHA treatment after spinal cord compression injury. Results indicated that DHA administered 30 min after spinal cord compression not only greatly increased survival of neurons but also resulted in significantly better locomotor performance for up to 6 weeks after injury.
This report shows a striking difference in efficacy between the effects of treatment with ω-3 and ω-6 PUFAs on the outcome of SCI, with ω-3 PUFAs being neuroprotective and ω-6 PUFAs having a damaging effect. Given the proven clinical safety of ω-3 PUFAs, our observations show that these PUFAs have significant therapeutic potential in SCI. In contrast, the use of preparations enriched in ω-6 PUFAs after injury could worsen outcome after SCI
Spin tunneling through an indirect barrier
Spin-dependent tunneling through an indirect bandgap barrier like the
GaAs/AlAs/GaAs heterostructure along [001] direction is studied by the
tight-binding method. The tunneling is characterized by the proportionality of
the Dresselhaus Hamiltonians at and points in the barrier and by
Fano resonances. The present results suggest that large spin polarization can
be obtained for energy windows that exceed significantly the spin splitting. We
also formulate two conditions that are necessary for the existence of energy
windows with large polarization.Comment: 19 pages, 7 figure
Prevalence and Factors Associated With Hazardous Alcohol Consumption Among Motorcycle Taxi Riders in Kinondoni District, Dar-Es-Salaam, Tanzania: A Cross-Sectional Study
Background: Hazardous alcohol consumption is a significant public health problem contributing to road traffic accidents in nearly all countries. Despite the fact that motorcycles are involved in more than half of all road traffic accidents in Tanzania, little has been reported about hazardous alcohol consumption among motorcyclists. This study investigated the prevalence and factors associated with hazardous alcohol consumption among motorcycle taxi riders in Kinondoni District, Dar es Salaam.
Methods: A cross-sectional survey was conducted in Kinondoni District in August 2018 among motorcycle taxi riders. Multistage sampling was applied to select the study participants. Data were collected using structured self-administered questionnaires incorporating the Alcohol Use Disorders Identification Test. Analysis was done using IBM SPSS version 20.
Results: A total of 210 individuals participated in the study. Within the study sample, the prevalence of hazardous alcohol consumption was 61.5% (n=128). Hazardous alcohol consumption was positively associated with a positive family history of alcohol consumption (odds ratio [OR] 11.74; 95% confidence interval [CI], 5.14 to 26.79; P<.001). Protective factors were younger age (OR 0.09; 95% CI, 0.02 to 0.40; P<.001), having a secondary level of education (OR 0.21; 95% CI, 0.04 to 0.99; P=.034), having a primary level of education (OR 0.06; 95% CI, 0.01 to 0.26; P<.001), and being employed (OR 11.74; 95% CI, 5.14 to 26.79; P<.001).
Conclusion: A high prevalence of hazardous alcohol consumption among motorcycle taxi riders was reported along with several associated factors. Interventions to mitigate hazardous alcohol consumption among commercial motor vehicle drivers must be developed and implemented
One-nucleon transfer reactions and the optical potential
We provide a summary of new developments in the area of direct reaction
theory with a particular focus on one-nucleon transfer reactions. We provide a
status of the methods available for describing (d,p) reactions. We discuss the
effects of nonlocality in the optical potential in transfer reactions. The
results of a purely phenomenological potential and the optical potential
obtained from the dispersive optical model are compared; both point toward the
importance of including nonlocality in transfer reactions explicitly. Given the
large ambiguities associated with optical potentials, we discuss some new
developments toward the quantification of this uncertainty. We conclude with
some general comments and a brief account of new advances that are in the
pipeline.Comment: 7 pages, 5 figures, proceedings for the 14th International Conference
on Nuclear Reaction Mechanisms, Varenna, June 201
HST and Palomar Imaging of GRB 990123: Implications for the Nature of Gamma-Ray Bursts and their Hosts
We report on HST and Palomar optical images of the field of GRB 990123,
obtained on 8 and 9 February 1999. We find that the optical transient (OT)
associated with GRB 990123 is located on an irregular galaxy, with magnitude
V=24.20 +/- 0.15. The strong metal absorption lines seen in the spectrum of the
OT, along with the low probability of a chance superposition, lead us to
conclude that this galaxy is the host of the GRB. The OT is projected within
the ~1'' visible stellar field of the host, nearer the edge than the center. We
cannot, on this basis, rule out the galactic nucleus as the site of the GRB,
since the unusual morphology of the host may be the result of an ongoing
galactic merger, but our demonstration that this host galaxy has extremely blue
optical to infrared colors more strongly supports an association between GRBs
and star formation. We find that the OT magnitude on 1999 Feb 9.05, V = 25.45
+/- 0.15, is about 1.5 mag fainter than expected from extrapolation of the
decay rate found in earlier observations. A detailed analysis of the OT light
curve suggests that its fading has gone through three distinct phases: an early
rapid decline (f_{nu} \propto t^{-1.6} for t < 0.1 days), a slower intermediate
decline power-law decay (f_{nu} \propto t^{-1.1} for 0.1 < t < 2 days), and
then a more rapid decay (at least as steep as (f_{\nu} \propto t^{-1.8} for t >
2 days). The break to steeper slope at late times may provide evidence that the
optical emission from this GRB was highly beamed.Comment: Accepted for publication in Astrophysical Journal (Letters). Fourteen
pages. Three encapsulated figure
Menstrual and reproductive factors in relation to ovarian cancer risk
We assessed menstrual and reproductive factors in relation to ovarian cancer risk in a large, population-based, case–control study. 563 cases in Massachusetts and New Hampshire were ascertained from hospitals and statewide tumour registries; control women (n= 523) were selected through random digit dialing and matched to case women by age and telephone sampling unit. We used multivariate logistic regression to evaluate factors in relation to risk of ovarian cancer and the major tumour histologic subtypes. Ovarian cancer risk was reduced among parous women, relative to nulliparous women (OR = 0.4; 95% CI = 0.3−0.6). Among parous women, higher parity (P= 0.0006), increased age at first (P= 0.03) or last (P= 0.05) birth, and time since last birth (P= 0.04) were associated with reduced risk. Early pregnancy losses, abortions, and stillbirths were unrelated to risk, but preterm, term, and twin births were protective. Risk was lower among women who had breast-fed, relative to those who had not (OR = 0.7; 95% CI = 0.5–1.0), but the average duration of breast-feeding per child was unrelated to risk (P for trend = 0.21). Age at menarche and age at menopause were unrelated to risk overall, although increasing menarcheal age was protective among premenopausal women (P= 0.02). Menstrual cycle characteristics and symptoms were generally unrelated to risk, although cycle-related insomnia was associated with decreased risk (OR = 0.5; 95% CI = 0.3–0.8). We found no association between the type of sanitary product used during menstruation and ovarian cancer risk. In analyses by histologic subtype, reproductive and menstrual factors had most effect on risk of endometrioid/clear cell tumours, and least influential with regard to risk of mucinous tumours. Overall, our findings offer some support to current hypotheses of ovarian pathogenesis, and show aetiologic differences among the tumour subtypes. © 2001 Cancer Research Campaign http://www.bjcancer.co
Categorizing Health Outcomes and Efficacy of mHealth Apps for Persons With Cognitive Impairment: A Systematic Review
Background
Use of mobile health (mHealth) apps is growing at an exponential rate in the United States and around the world. Mild cognitive impairment (MCI), Alzheimer disease, and related dementias are a global health problem. Numerous mHealth interventions exist for this population, yet the effect of these interventions on health has not been systematically described.
Objective
The aim of this study is to catalog the types of health outcomes used to measure effectiveness of mHealth interventions and assess which mHealth interventions have been shown to improve the health of persons with MCI, Alzheimer disease, and dementia.
Methods
We searched 13 databases, including Ovid MEDLINE, PubMed, EMBASE, the full Cochrane Library, CINAHL, PsycINFO, Ei Compendex, IEEE Xplore, Applied Science & Technology Source, Scopus, Web of Science, ClinicalTrials.gov, and Google Scholar from inception through May 2017 for mHealth studies involving persons with cognitive impairment that were evaluated using at least one quantitative health outcome. Proceedings of the Annual ACM Conferences on Human Factors in Computing Systems, the ACM User Interface Software and Technology Symposium, and the IEEE International Symposium on Wearable Computers were searched in the ACM Digital Library from 2012 to 2016. A hand search of JMIR Publications journals was also completed in July 2017.
Results
After removal of duplicates, our initial search returned 3955 records. Of these articles, 24 met final inclusion criteria as studies involving mHealth interventions that measured at least one quantitative health outcome for persons with MCI, Alzheimer disease, and dementia. Common quantitative health outcomes included cognition, function, mood, and quality of life. We found that 21.2% (101/476) of the fully reviewed articles were excluded because of a lack of health outcomes. The health outcomes selected were observed to be inconsistent between studies. For those studies with quantitative health outcomes, more than half (58%) reported postintervention improvements in outcomes.
Conclusions
Results showed that many mHealth app interventions targeting those with cognitive impairment lack quantitative health outcomes as a part of their evaluation process and that there is a lack of consensus as to which outcomes to use. The majority of mHealth app interventions that incorporated health outcomes into their evaluation noted improvements in the health of persons with MCI, Alzheimer disease, and dementia. However, these studies were of low quality, leading to a grade C level of evidence. Clarification of the benefits of mHealth interventions for people with cognitive impairment requires more randomized controlled trials, larger numbers of participants, and trial designs that minimize bias.
Trial Registration
PROSPERO Registration: PROSPERO 2016:CRD42016033846; http://www.crd.york.ac.uk/PROSPERO/ display_record.asp?ID=CRD42016033846 (Archived by WebCite at http://www.webcitation.org/6sjjwnv1M
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