10,644 research outputs found
Varying the effective refractive index to measure optical transport in random media
We introduce a new approach for measuring both the effective medium and the
transport properties of light propagation in heterogeneous media. Our method
utilizes the conceptual equivalence of frequency variation with a change in the
effective index of refraction. Experimentally, we measure intensity
correlations via spectrally resolved refractive index tuning, controlling the
latter via changes in the ambient pressure. Our experimental results perfectly
match a generalized transport theory that incorporates the effective medium and
predicts a precise value for the diffusion constant. Thus, we directly confirm
the applicability of the effective medium concept in strongly scattering
materials.Comment: 5 pages, 5 figure
Control of light transmission through opaque scattering media in space and time
We report the first experimental demonstration of combined spatial and
temporal control of light trajectories through opaque media. This control is
achieved by solely manipulating spatial degrees of freedom of the incident
wavefront. As an application, we demonstrate that the present approach is
capable to form bandwidth-limited ultrashort pulses from the otherwise randomly
transmitted light with a controllable interaction time of the pulses with the
medium. Our approach provides a new tool for fundamental studies of light
propagation in complex media and has potential for applications for coherent
control, sensing and imaging in nano- and biophotonics
Compound poisson approximation via information functionals
An information-theoretic development is given for the problem of compound Poisson approximation, which parallels earlier treatments for Gaussian and Poisson approximation. Nonasymptotic bounds are derived for the distance between the distribution of a sum of independent integer-valued random variables and an appropriately chosen compound Poisson law. In the case where all summands have the same conditional distribution given that they are non-zero, a bound on the relative entropy distance between their sum and the compound Poisson distribution is derived, based on the data-processing property of relative entropy and earlier Poisson approximation results. When the summands have arbitrary distributions, corresponding bounds are derived in terms of the total variation distance. The main technical ingredient is the introduction of two "information functionals,'' and the analysis of their properties. These information functionals play a role analogous to that of the classical Fisher information in normal approximation. Detailed comparisons are made between the resulting inequalities and related bounds
Single institution implementation of permanent 131Cs interstitial brachytherapy for previously irradiated patients with resectable recurrent head and neck carcinoma
Purpose: Permanent interstitial brachytherapy is an appealing treatment modality for patients with locoregional recurrent, resectable head and neck carcinoma (HNC), having previously received radiation. Cesium-131 (131Cs) is a permanent implant brachytherapy isotope, with a low average photon energy of 30 keV and a short half-life of 9.7 days. Exposure to medical staff and family members is low; patient isolation and patient room shielding are not required. This work presents a single institution’s implementation process of utilizing an intraoperative, permanent 131Cs implant for patients with completely resected recurrent HNC.
Materials & Methods: Fifteen patients receiving 131Cs permanent seed brachytherapy were included in this analysis. The process of pre-planning, selecting the dose prescription, seed ordering, intraoperative procedures, post-implant planning, and radiation safety protocols are described.
Results: Tumor volumes were contoured on the available preoperative PET/CT scans and a pre-implant treatment plan was created using uniform source strength and uniform 1 cm seed spacing. Implants were performed intraoperatively, following tumor resection. In five of the fifteen cases, intraoperative findings necessitated a change from the planned number of seeds and recalculation of the pre-implant plan. The average prescription dose was 56.1 ±6.6 Gy (range, 40-60 Gy). The average seed strength used was 2.2 ±0.2 U (3.5 ±0.3 mCi). Patients returned to a recovery room on a standard surgical floor and remained inpatients, without radiation safety restrictions, based on standard surgical recovery protocols. A post-implant treatment plan was generated based on immediate post-operative CT imaging to verify the seed distribution and confirm delivery of the prescription dose. Patients were provided educational information regarding radiation safety recommendations.
Conclusions: Cesium-131 interstitial brachytherapy is feasible and does not pose major radiation safety concerns; it should be considered as a treatment option for previously irradiated patients with recurrent, resectable HNC
A standardised protocol for the assessment of lower limb muscle contractile properties in football players using Tensiomyography
Tensiomyography is used to measure skeletal muscle contractile properties, most notably muscle displacement (Dm) and contraction time (Tc). Professional football medical departments are currently using the equipment to profile the muscle function of their squad and subsequently evaluate change due to injury or intervention. However, at present there are no published standardised operating procedures for identifying probe position for muscle assessment. In this technical report we propose standardised operating procedures for the identification of precise probe position as part of an on-going study in male professional footballers
A systematic review of treating recurrent head and neck cancer: a reintroduction of brachytherapy with or without surgery.
Purpose: To review brachytherapy use in recurrent head and neck carcinoma (RHNC) with focus on its efficacy and complication rates.
Material and methods: A literature search of PubMed, Ovid, Google Scholar, and Scopus was conducted from 1990 to 2017. Publications describing treatment of RHNC with brachytherapy with or without surgery were included. The focus of this review is on oncologic outcomes and the safety of brachytherapy in the recurrent setting.
Results: Thirty studies involving RHNC treatment with brachytherapy were reviewed. Brachytherapy as adjunctive treatment to surgical resection appears to be associated with an improved local regional control and overall survival, when compared with the published rates for re-irradiation utilizing external beam radiotherapy (RT) or brachytherapy alone. Safety data remains variable with different isotopes and dose rates with implantable brachytherapy demonstrating a tolerable side effect profile.
Conclusions: Although surgery remains a mainstay treatment for RHNC, intraoperative interstitial brachytherapy delivery as adjunctive therapy may improve the treatment outcome and may be associated with fewer complication rates as compared to reirradiation using external beam radiotherapy. Further investigations are required to elucidate the role of brachytherapy for RHNC
Stripe Fluctuations, Carriers, Spectroscopies, Transport, and BCS-BEC Crossover in the High-T_c Cuprates
The quasiparticles of the high-T_c cuprates are found to consist of:
polaron-like "stripons" carrying charge, and associated primarily with large-U
orbitals in stripe-like inhomogeneities; "quasielectrons" carrying charge and
spin, and associated with hybridized small-U and large-U orbitals; and
"svivons" carrying spin and lattice distortion. It is shown that this
electronic structure leads to the systematic behavior of spectroscopic and
transport properties of the cuprates. High-T_c pairing results from transitions
between pair states of stripons and quasielectrons through the exchange of
svivons. The cuprates fall in the regime of crossover between BCS and
preformed-pairs Bose-Einstein condensation behaviors.Comment: Latex file, 8 pages (new version including a figure
Experimental observation of second-harmonic generation and diffusion inside random media
We have experimentally measured the distribution of the second-harmonic
intensity that is generated inside a highly-scattering slab of porous gallium
phosphide. Two complementary techniques for determining the distribution are
used. First, the spatial distribution of second-harmonic light intensity at the
side of a cleaved slab has been recorded. Second, the total second-harmonic
radiation at each side of the slab has been measured for several samples at
various wavelengths. By combining these measurements with a diffusion model for
second-harmonic generation that incorporates extrapolated boundary conditions,
we present a consistent picture of the distribution of the second-harmonic
intensity inside the slab. We find that the ratio of the
mean free path at the second-harmonic frequency to the coherence length, which
was suggested by some earlier calculations, cannot describe the second-harmonic
yield in our samples. For describing the total second-harmonic yield, our
experiments show that the scattering parameter at the fundamental frequency
\k_{1\omega}\ell_{1\omega} is the most relevant parameter in our type of
samples.Comment: 10 pages, 7 figure
The BaSICS (Baby Skin Integrity Comparison Survey) study : a prospective experimental study using maternal observations to report the effect of baby wipes on the incidence of irritant diaper dermatitis in infants, from birth to eight weeks of age
Background
Baby wipes have been shown to be safe and effective in maintaining skin
integrity when compared to the use of water alone. However, no previous study
has compared different formulations of wipe. The aim of the BaSICS study was to
identify any differences in incidence of irritant diaper dermatitis (IDD) in infants
assigned to three different brands of wipe, all marketed as suitable for neonates,
but which contained varying numbers of ingredients.
Methods
Women were recruited during the prenatal period. Participants were randomly
assigned to receive one of three brands of wipe for use during the first eight
weeks following childbirth. All participants received the same nappies.
Participants reported their infant’s skin integrity on a scale of 1 to 5 daily using a
bespoke smartphone application. Analysis of effect of brand on clinically
significant IDD (score 3 or more) incidence was conducted using a negative
binomial generalised linear model, controlling for possible confounders at
baseline. Analysts were blind to brand of wipe.
Results
Of 737 women enrolled, 15 were excluded (admitted to neonatal intensive care,
premature or other infant health issues). Of the 722 eligible babies, 698 (97%)
remained in the study for the full 8-week duration, 24.6% of whom had IDD at
some point during the study. Mothers using the brand with the fewest
ingredients reported fewer days of clinically significant nappy rash (score≥3)
than participants using the two other brands (p=0.002 and p<0.001). Severe IDD
(grades 4 and 5) was rare (2.4%).
Conclusions
Rarity of severe IDD suggested that sensitive formula baby wipes are safe when
used in cleansing babies from birth to eight weeks during nappy changes. The
brand with fewest ingredients had significantly fewer days of clinically
significant IDD. Daily observations recorded on a smartphone application proved
to be a highly acceptable method of obtaining real-time data on IDD
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