343 research outputs found
In-Vacuum Photogrammetry of a 10-Meter Solar Sail
In July 2004, a 10-meter solar sail structure developed by L Garde, Inc. was tested in vacuum at the NASA Glenn 30-meter Plum Brook Space Power Facility in Sandusky, Ohio. The three main objections of the test were to demonstrate unattended deployment from a stowed configuration, to measure the deployed shape of the sail at both ambient and cryogenic room temperatures, and to measure the deployed structural dynamic characteristics (vibration modes). This paper summarizes the work conducted to fulfill the second test objective. The deployed shape was measured photogrammetrically in vacuum conditions with four 2-megapixel digital video cameras contained in custom made pressurized canisters. The canisters included high-intensity LED ring lights to illuminate a grid of retroreflective targets distributed on the solar sail. The test results closely matched pre-test photogrammetry numerical simulations and compare well with ABAQUS finite-element model predictions
Assessing cognitive dysfunction in Parkinsonâs: An online tool to detect visuo-perceptual deficits
BACKGROUND: People with Parkinsonâs disease
(PD) who develop visuo-perceptual deficits are at higher
risk of dementia, but we lack tests that detect subtle visuoperceptual
deficits and can be performed by untrained personnel.
Hallucinations are associated with cognitive impairment
and typically involve perception of complex objects.
Changes in object perception may therefore be a sensitive
marker of visuo-perceptual deficits in PD.
Objective: We developed an online platform to test
visuo-perceptual function. We hypothesised that (1)
visuo-perceptual deficits in PD could be detected using
online tests, (2) object perception would be preferentially
affected, and (3) these deficits would be caused
by changes in perception rather than response bias.
METHODS: We assessed 91 people with PD and 275 controls.
Performance was compared using classical frequentist
statistics. We then fitted a hierarchical Bayesian signal
detection theory model to a subset of tasks.
RESULTS: People with PD were worse than controls at
object recognition, showing no deficits in other visuoperceptual
tests. Specifically, they were worse at identifying
skewed images (P <.0001); at detecting hidden
objects (P 5.0039); at identifying objects in peripheral
vision (P <.0001); and at detecting biological motion
(P 5.0065). In contrast, people with PD were not worse
at mental rotation or subjective size perception. Using
signal detection modelling, we found this effect was
driven by change in perceptual sensitivity rather than
response bias.
CONCLUSIONS: Online tests can detect visuo-perceptual defi-
cits in people with PD, with object recognition particularly
affected. Ultimately, visuo-perceptual tests may be developed
to identify at-risk patients for clinical trials to slow PD dementia
Assessment of health care needs and utilization in a mixed public-private system: the case of the Athens area
BACKGROUND: Given the public-private mix of the Greek health system, the purpose of this study was to assess whether variations in the utilisation of health services, both primary and inpatient care, were associated with underlying health care needs and/or various socio-economic factors. METHODS: Data was obtained from a representative sample (N = 1426) residing in the broader Athens area (response rate 70.6%). Perceived health-related quality of life (HRQOL), as measured by the physical and mental summary component scores of the SF-36 Health Survey, was used as a proxy of health care need. Health care utilization was measured by a) last-month visits to public sector physicians, b) last-month visits to private sector physicians, c) last-year visits to hospital emergency departments and d) last-year hospital admissions. Statistical analysis involved the implementation of logistic regression models. RESULTS: Health care need was the factor most strongly associated with all measures of health care utilization, except for visits to public physicians. Women, elderly, less wealthy and individuals of lower physical health status visited physicians contracted to their insurance fund (public sector). Women, well educated and those once again of lower physical health status were more likely to visit private providers. Visits to hospital emergency departments and hospital admissions were related to need and no socio-economic factor was related to the use of those types of care. CONCLUSION: This study has demonstrated a positive relationship between health care need and utilisation of health services within a mixed public-private health care system. Concurrently, interesting differences are evident in the utilization of various types of services. The results have potential implications in health policy-making and particularly in the proper allocation of scarce health resources
Cosmological Evolution of a Brane Universe in a Type 0 String Background
We study the cosmological evolution of a D3-brane Universe in a type 0 string
background. We follow the brane-universe along the radial coordinate of the
background and we calculate the energy density which is induced on the brane
because of its motion in the bulk. We find that for some typical values of the
parameters and for a particular range of values of the scale factor of the
brane-universe, the effective energy density is dominated by a term
proportional to indicating a slow varying inflationary
phase. For larger values of the scale factor the effective energy density takes
a constant value and the brane-universe enters its usual inflationary period.Comment: 25 pages,1 figure,LaTex file,final version to appear in Phys. Rev.
OdreÄivanje donepezil hidroklorida u humanoj plazmi i ljekovitim oblicima pomoÄu HPLC s detekcijom fluorescencije
A sensitive, isocratic reversed-phase high performance liquid chromatographic method involving fluorescence detection was developed for the determination of donepezil hydrochloride in tablets and in human plasma. Pindolol was successfully used as an internal standard. Good chromatographic separation was achieved by using analytical column C18. The system operated at room temperature using a mobile phase consisting of methanol, phosphate buffer (0.02 mol L1) and triethyl amine (pH 3.5) (55: 45: 0.5 V/V/V) at a flow rate 0.9 mL min1. The analyte and internal standard were extracted from human plasma via liquid-liquid extraction. The proposed method was validated for selectivity, linearity, accuracy and precision. The calibration curve was linear over the range of 5-2000 ng mL1 of donepezil with detection limit of 1.5 ng mL1. Intra- and inter-day relative standard deviations were less than 2.5 %. The method was found to be suitable for the quality control of donepezil hydrochloride in bulk drug as well as in human plasma.Ovaj rad opisuje HPLC metodu odreÄivanja donepezil hidroklorida (DP) u tabletama i u ljudskoj plazmi u nano podruÄju. Postavljena je osjetljiva metoda izokratiÄne HPLC s fluorescencijskom detekcijom. Kao unutarnji standard upotrebljen je pindolol. Dobro kromatografsko odjeljivanje postignuto je primjenom analitiÄke kolone C18. Radna temperatura bila je sobna, a kao mobilna faza upotrebljena je smjesa metanola, fosfatnog pufera (0,02 mol L1) i trietilamina (pH 3,5) (55:45:0.5 V/V/V). Analit i unutarnji standard su ekstrahirani iz ljudske plazme ekstrakcijom tekuÄe-tekuÄe. PredloĆŸena metoda je validirana s obzirom na selektivnost, podruÄje linearnosti, ispravnost i preciznost. Kalibracijska funkcija bila je linearna u podruÄju od 5-2000 ng mL1 donepezila, a granica detekcije iznosila je 2 ng mL1. Relativna standardna devijacija za repetabilnost i intermedijarnu preciznost bila je manja od 2,5 %. Metoda je primjenljliva u kontroli kvalitete ljekovitih formulacija s DP-om i u praÄenju DP-a u ljudskoj plazmi
Mammography screening: views from women and primary care physicians in Crete
Background: Breast cancer is the most commonly diagnosed cancer among women and a leading cause of death from cancer in women in Europe. Although breast cancer incidence is on the rise worldwide, breast cancer mortality over the past 25 years has been stable or decreasing in some countries and a fall in breast cancer mortality rates in most European countries in the 1990s was reported by several studies, in contrast, in Greece have not reported these favourable trends. In Greece, the age-standardised incidence and mortality rate for breast cancer per 100.000 in 2006 was 81,8 and 21,7 and although it is lower than most other countries in Europe, the fall in breast cancer mortality that observed has not been as great as in other European countries. There is no national strategy for screening in this country. This study reports on the use of mammography among middleaged women in rural Crete and investigates barriers to mammography screening encountered by women and their primary care physicians.
Methods: Design: Semi-structured individual interviews. Setting and participants: Thirty women between 45â65
years of age, with a mean age of 54,6 years, and standard deviation 6,8 from rural areas of Crete and 28 qualified
primary care physicians, with a mean age of 44,7 years and standard deviation 7,0 serving this rural population.
Main outcome measure: Qualitative thematic analysis.
Results: Most women identified several reasons for not using mammography. These included poor knowledge
of the benefits and indications for mammography screening, fear of pain during the procedure, fear of a serious
diagnosis, embarrassment, stress while anticipating the results, cost and lack of physician recommendation.
Physicians identified difficulties in scheduling an appointment as one reason women did not use mammography
and both women and physicians identified distance from the screening site, transportation problems and the
absence of symptoms as reasons for non-use.
Conclusion: Women are inhibited from participating in mammography screening in rural Crete. The provision
of more accessible screening services may improve this. However physician recommendation is important in
overcoming women's inhibitions. Primary care physicians serving rural areas need to be aware of barriers
preventing women from attending mammography screening and provide women with information and advice in a sensitive way so women can make informed decisions regarding breast caner screening
A Quintessentially Geometric Model
We consider string inspired cosmology on a solitary -brane moving in the
background of a ring of branes located on a circle of radius . The motion of
the -brane transverse to the plane of the ring gives rise to a radion field
which can be mapped to a massive non-BPS Born-Infeld type field with a cosh
potential. For certain bounds of the brane tension we find an inflationary
phase is possible, with the string scale relatively close to the Planck scale.
The relevant perturbations and spectral indices are all well within the
expected observational bounds. The evolution of the universe eventually comes
to be dominated by dark energy, which we show is a late time attractor of the
model. However we also find that the equation of state is time dependent, and
will lead to late time Quintessence.Comment: 11 pages, 3 figures. References and comments adde
Evaluation of the psychometric properties of the SF-36 health survey for use among Turkish and Moroccan ethnic minority populations in the Netherlands
Purpose: To evaluate the psychometrics of the SF-36 Health Survey among Turkish and Moroccan ethnic minority populations in the Netherlands and to compare the results to those based on the indigenous Dutch population. Methods: Data were derived from the Second Dutch National Survey of General Practice. In total, SF-36 data were available for 409 Turkish, 377 Moroccan, and 9,628 Dutch respondents. Language subgroup analyses were performed for the Turkish (n = 162) and Moroccan-Arabic (n = 52) versions of the SF-36. Psychometric properties were evaluated by descriptive statistics, factor analysis, internal consistency estimates, known-group comparisons, and differential item function (DIF) analysis. Results Low levels of missing SF-36 data were observed across all groups. Confirmatory factor analysis supported the hypothesized SF-36 scale structure for the Dutch and Turkish group, but high correlations between the MH and VT factors were observed in the Moroccan group. All Cronbachâs alpha coefficients were above 0.70, except for
the Vitality scale in the Moroccan group and the Vitality and Social Functioning scales in the Moroccan-Arabic language subgroup. Known-groups validity was found across samples using age, sex, education, and comorbidity as grouping variables, but not marital status. Some evidence for DIF was found in both ethnic group samples. Conclusions: The results generally support the use of the SF-36 for general population research among Turkish and Moroccan ethnic minorities in the Netherlands. Additional studies are needed to confirm the psychometrics of the questionnaire when used among these populations in other Western European countries. (aut. ref.
Experimental plug&play quantum coin flipping
Performing complex cryptographic tasks will be an essential element in future
quantum communication networks. These tasks are based on a handful of
fundamental primitives, such as coin flipping, where two distrustful parties
wish to agree on a randomly generated bit. Although it is known that quantum
versions of these primitives can offer information-theoretic security
advantages with respect to classical protocols, a demonstration of such an
advantage in a practical communication scenario has remained elusive. Here, we
experimentally implement a quantum coin flipping protocol that performs
strictly better than classically possible over a distance suitable for
communication over metropolitan area optical networks. The implementation is
based on a practical plug&play system, designed for quantum key distribution.
We also show how to combine our protocol with coin flipping protocols that are
almost perfectly secure against bounded adversaries, hence enhancing them with
a level of information-theoretic security. Our results offer a powerful toolbox
for future secure quantum communications.Comment: Version 2, 19 pages including detailed security analysi
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