9,135 research outputs found
The photoelectric effect without photons
Mathematical model of photoelectric effect without photon
Build-up of laser oscillations from quantum noise
Laser oscillation build up from quantum nois
A non-destructive analytic tool for nanostructured materials : Raman and photoluminescence spectroscopy
Modern materials science requires efficient processing and characterization
techniques for low dimensional systems. Raman spectroscopy is an important
non-destructive tool, which provides enormous information on these materials.
This understanding is not only interesting in its own right from a physicist's
point of view, but can also be of considerable importance in optoelectronics
and device applications of these materials in nanotechnology. The commercial
Raman spectrometers are quite expensive. In this article, we have presented a
relatively less expensive set-up with home-built collection optics attachment.
The details of the instrumentation have been described. Studies on four classes
of nanostructures - Ge nanoparticles, porous silicon (nanowire), carbon
nanotubes and 2D InGaAs quantum layers, demonstrate that this unit can be of
use in teaching and research on nanomaterials.Comment: 32 pages, 13 figure
Formation of Box Canyon, Idaho, by megaflood: implications for seepage erosion on Earth and Mars
Amphitheater- headed canyons have been used as diagnostic indicators of erosion by groundwater seepage, which has important implications for landscape evolution on Earth and astrobiology on Mars. Of perhaps any canyon studied, Box Canyon, Idaho, most strongly meets the proposed morphologic criteria for groundwater sapping because it is incised into a basaltic plain with no drainage network upstream, and approximately 10 cubic meters per second of seepage emanates from its vertical headwall. However, sediment transport constraints, ^4He and ^14C dates, plunge pools, and scoured rock indicate that a megaflood (greater than 220 cubic meters per second) carved the canyon about 45,000 years ago. These results add to a growing recognition of Quaternary catastrophic flooding in the American northwest, and may imply that similar features on Mars also formed by floods rather than seepage erosion
The development of parental preferences in the first two years of life
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45603/1/11199_2004_Article_BF00287413.pd
Does a monetary incentive improve the response to a postal questionnaire in a randomised controlled trial? : the MINT incentive study
Background: Sending a monetary incentive with postal questionnaires has been found to improve
the proportion of responders, in research in non-healthcare settings. However, there is little
research on use of incentives to improve follow-up rates in clinical trials, and existing studies are
inconclusive. We conducted a randomised trial among participants in the Managing Injuries of the
Neck Trial (MINT) to investigate the effects on the proportion of questionnaires returned and
overall non-response of sending a £5 gift voucher with a follow-up questionnaire.
Methods: Participants in MINT were randomised to receive either: (a) a £5 gift voucher (incentive
group) or (b) no gift voucher (no incentive group), with their 4 month or 8 month follow-up
questionnaire. We recorded, for each group, the number of questionnaires returned, the number
returned without any chasing from the study office, the overall number of non-responders (after
all chasing efforts by the study office), and the costs of following up each group.
Results: 2144 participants were randomised, 1070 to the incentive group and 1074 to the no
incentive group. The proportion of questionnaires returned (RR 1.10 (95% CI 1.05, 1.16)) and the
proportion returned without chasing (RR 1.14 (95% CI 1.05, 1.24) were higher in the incentive
group, and the overall non-response rate was lower (RR 0.68 (95% CI 0.53, 0.87)). Adjustment for
injury severity and hospital of recruitment to MINT made no difference to these results, and there
were no differences in results between the 4-month and 8-month follow up questionnaires.
Analysis of costs suggested a cost of £67.29 per additional questionnaire returned.
Conclusion: Monetary incentives may be an effective way to increase the proportion of postal
questionnaires returned and minimise loss to follow-up in clinical trials
Confined Quantum Time of Arrival for Vanishing Potential
We give full account of our recent report in [E.A. Galapon, R. Caballar, R.
Bahague {\it Phys. Rev. Let.} {\bf 93} 180406 (2004)] where it is shown that
formulating the free quantum time of arrival problem in a segment of the real
line suggests rephrasing the quantum time of arrival problem to finding a
complete set of states that evolve to unitarily arrive at a given point at a
definite time. For a spatially confined particle, here it is shown explicitly
that the problem admits a solution in the form of an eigenvalue problem of a
class of compact and self-adjoint time of arrival operators derived by a
quantization of the classical time of arrival. The eigenfunctions of these
operators are numerically demonstrated to unitarilly arrive at the origin at
their respective eigenvalues.Comment: accepted for publication in Phys. Rev.
Treatment compliance and effectiveness of a cognitive behavioural intervention for low back pain : a complier average causal effect approach to the BeST data set
Background:
Group cognitive behavioural intervention (CBI) is effective in reducing low-back pain and disability in comparison to advice in primary care. The aim of this analysis was to investigate the impact of compliance on estimates of treatment effect and to identify factors associated with compliance.
Methods:
In this multicentre trial, 701 adults with troublesome sub-acute or chronic low-back pain were recruited from 56 general practices. Participants were randomised to advice (control n = 233) or advice plus CBI (n = 468). Compliance was specified a priori as attending a minimum of three group sessions and the individual assessment. We estimated the complier average causal effect (CACE) of treatment.
Results:
Comparison of the CACE estimate of the mean treatment difference to the intention-to-treat (ITT) estimate at 12 months showed a greater benefit of CBI amongst participants compliant with treatment on the Roland Morris Questionnaire (CACE: 1.6 points, 95% CI 0.51 to 2.74; ITT: 1.3 points, 95% CI 0.55 to 2.07), the Modified Von Korff disability score (CACE: 12.1 points, 95% CI 6.07 to 18.17; ITT: 8.6 points, 95% CI 4.58 to 12.64) and the Modified von Korff pain score (CACE: 10.4 points, 95% CI 4.64 to 16.10; ITT: 7.0 points, 95% CI 3.26 to 10.74). People who were non-compliant were younger and had higher pain scores at randomisation.
Conclusions:
Treatment compliance is important in the effectiveness of group CBI. Younger people and those with more pain are at greater risk of non-compliance
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