33,586 research outputs found
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Expanding the use of real-time electromagnetic tracking in radiation oncology.
In the past 10 years, techniques to improve radiotherapy delivery, such as intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT) for both inter- and intrafraction tumor localization, and hypofractionated delivery techniques such as stereotactic body radiation therapy (SBRT), have evolved tremendously. This review article focuses on only one part of that evolution, electromagnetic tracking in radiation therapy. Electromagnetic tracking is still a growing technology in radiation oncology and, as such, the clinical applications are limited, the expense is high, and the reimbursement is insufficient to cover these costs. At the same time, current experience with electromagnetic tracking applied to various clinical tumor sites indicates that the potential benefits of electromagnetic tracking could be significant for patients receiving radiation therapy. Daily use of these tracking systems is minimally invasive and delivers no additional ionizing radiation to the patient, and these systems can provide explicit tumor motion data. Although there are a number of technical and fiscal issues that need to be addressed, electromagnetic tracking systems are expected to play a continued role in improving the precision of radiation delivery
Two mini-band model for self-sustained oscillations of the current through resonant tunneling semiconductor superlattices
A two miniband model for electron transport in semiconductor superlattices
that includes scattering and interminiband tunnelling is proposed. The model is
formulated in terms of Wigner functions in a basis spanned by Pauli matrices,
includes electron-electron scattering in the Hartree approximation and modified
Bhatnagar-Gross-Krook collision tems. For strong applied fields, balance
equations for the electric field and the miniband populations are derived using
a Chapman-Enskog perturbation technique. These equations are then solved
numerically for a dc voltage biased superlattice. Results include
self-sustained current oscillations due to repeated nucleation of electric
field pulses at the injecting contact region and their motion towards the
collector. Numerical reconstruction of the Wigner functions shows that the
miniband with higher energy is empty during most of the oscillation period: it
becomes populated only when the local electric field (corresponding to the
passing pulse) is sufficiently large to trigger resonant tunneling.Comment: 26 pages, 3 figures, to appear in Phys. Rev.
Phylogenomic and comparative genomic studies robustly demarcate two distinct clades of Pseudomonas aeruginosa strains: proposal to transfer the strains from an outlier clade to a novel species Pseudomonas paraeruginosa sp. nov
The strains of Pseudomonas aeruginosa exhibit considerable differences in their genotypic and pathogenic properties. To clarify their evolutionary/taxonomic relationships, comprehensive phylogenomic and comparative genomic studies were conducted on the genome sequences of 212 P. aeruginosa strains covering their genetic diversity. In a phylogenomic tree based on 118 conserved proteins, the analysed strains formed two distinct clades. One of these clades, Clade- 1, encompassing >70 % of the strains including the type strain DSM 50071T, represents the species P. aeruginosa sensu stricto. Clade- 2, referred to in earlier work as the outlier group, with NCTC 13628T as its type strain, constitutes a novel species level lineage. The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values between the strains from Clade- 1 and Clade- 2 are in the range of 93.4–93.7, 95.1–95.3 and 52–53 %, respectively. The 16S rRNA gene of P. aeruginosa DSM 50071T also shows 98.3 % similarity to that of NCTC13628T. These values are lower than the suggested cut- off values for species distinction, indicating that the Clade- 2 strains (NCTC 13628T) constitute a new species. We also report the identification of 12 conserved signature indels in different proteins and 24 conserved signature proteins that are exclusively found in either Clade- 1 or Clade- 2, providing a reliable means for distinguishing these clades. Additionally, in contrast to swimming motility, twitching motility is only present in Clade- 1 strains. Based on earlier work, the strains from these two clades also differ in their pathogenic mechanisms (presence/absence of Type III secretion system), production of biosurfactants, phenazines and siderophores, and several other genomic characteristics. Based on the evidence from different studies, we propose that the Clade- 2 strains constitute a novel species for which the name Pseudomonas paraeruginosa is proposed. The type strain is NCTC 13628T (=PA7T=ATCC 9027T). The description of Pseudomonas aeruginosa is also emended to include information for different molecular markers specific for this species
Micropatterned Electrostatic Traps for Indirect Excitons in Coupled GaAs Quantum Wells
We demonstrate an electrostatic trap for indirect excitons in a field-effect
structure based on coupled GaAs quantum wells. Within the plane of a double
quantum well indirect excitons are trapped at the perimeter of a SiO2 area
sandwiched between the surface of the GaAs heterostructure and a
semitransparent metallic top gate. The trapping mechanism is well explained by
a combination of the quantum confined Stark effect and local field enhancement.
We find the one-dimensional trapping potentials in the quantum well plane to be
nearly harmonic with high spring constants exceeding 10 keV/cm^2.Comment: 21 pages, 6 figures, submitted to Phys. Rev.
Microscopic derivation of multi-channel Hubbard models for ultracold nonreactive molecules in an optical lattice
Recent experimental advances in the cooling and manipulation of bialkali
dimer molecules have enabled the production of gases of ultracold molecules
that are not chemically reactive. It has been presumed in the literature that
in the absence of an electric field the low-energy scattering of such
nonreactive molecules (NRMs) will be similar to atoms, in which a single
-wave scattering length governs the collisional physics. However, in Ref.
[1], it was argued that the short-range collisional physics of NRMs is much
more complex than for atoms, and that this leads to a many-body description in
terms of a multi-channel Hubbard model. In this work, we show that this
multi-channel Hubbard model description of NRMs in an optical lattice is robust
against the approximations employed in Ref. [1] to estimate its parameters. We
do so via an exact, albeit formal, derivation of a multi-channel resonance
model for two NRMs from an ab initio description of the molecules in terms of
their constituent atoms. We discuss the regularization of this two-body
multi-channel resonance model in the presence of a harmonic trap, and how its
solutions form the basis for the many-body model of Ref. [1]. We also
generalize the derivation of the effective lattice model to include multiple
internal states (e.g., rotational or hyperfine). We end with an outlook to
future research.Comment: 19 pages, 4 figure
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Healthy shopper? Blood pressure testing in a shopping centre Pop-Up in England
Background: Improving detection of elevated blood pressure (BP) remains a public health need. We present results from a Pop-Up health check stationed in shopping centres in England. We hypothesise the rate of case detection is related to measurable ‘unhealthiness’ of the shopping centres.
Methods: A Pop-Up health check was sited in four and three shopping centres sampled from the top ten unhealthiest and top 15 healthiest shopping regions respectively, following a report ranking towns/cities based on their unhealthy and healthy retail outlets. On one day in each shopping centre, people were approached and consented to BP testing. Outcome measure was people flagged with BP ≥ 140/90 mmHg (cases).
Results: We detected 45 (22.6%) and 20 (13.1%) cases from testing 199 and 152 adults in the unhealthy and healthy locations respectively (relative risk 1.72; 95% confidence interval: 1.06 to 2.78). A measure of unhealthy retail outlets (e.g. fast-food outlets) within each shopping centre was associated with detection rate (R2 = 0.61; p = 0.04).
Conclusion: An association exists between cases of suspect hypertension found in a health check Pop-Up and measured ‘unhealthiness’ of the shopping centre site. Results hint at strategies for public testing of BP, potentially in the context of reducing health inequalities
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Feeling the pressure: a cross-sectional study exploring feasibility of a healthcare Pop-Up for intraocular pressure measurements in shopping centres in England
OBJECTIVES: To test the hypothesis that a shopping centre Pop-Up health check combining an intraocular pressure (IOP) check with a general health check (blood pressure (BP)) is more readily accepted by the general public than an IOP check only. We investigate public awareness of IOP compared with BP and the feasibility of measuring IOP in large numbers in a Pop-Up. DESIGN: A cross-sectional study using a tailor-made healthcare Pop-Up. SETTING: The 'Feeling the Pressure' Pop-Up was sited in eight regionally-different shopping centres in England. PARTICIPANTS: Adult members of the public in shopping centres. METHODS: On one day we measured IOP only and on another measured BP and IOP. IOP was measured by Icare IC100 tonometer (Helsinki, Finland). Potential participants were asked about their awareness of IOP and BP and when they last visited their optometrist. RESULTS: More people attended the combined BP + IOP days (461; 60%; 95% CI 56% to 64%) than IOP-only days (307; 40%, 95% CI 37% to 43%) over 16 days of testing. We recorded IOP in 652 participants (median (IQR) age and IOP of 54 (42 to 68) years and 13 (11 to 15) mm Hg, respectively). Fewer people reported awareness about IOP (19%, 95% CI 16% to 23%) compared with BP (71%, 95% CI 66% to 75%). Of 768 participants, 60 (8%) reported no previous optometric eye examination and 185 (24%) reported >2 years since their most recent examination. CONCLUSIONS: Measuring IOP in large numbers of the public via a shopping centre Pop-Up is feasible. Public engagement was greater when a BP check was offered alongside an IOP check, suggesting unfamiliar health checks can be promoted by aligning them with a more familiar check. Our findings hint at strategies for public health schemes that engage the public with their eye health
Effects of Effluents of Industrial Waste on Soil Properties (A Case Study of Nandesari Area, Vadodara)
Around Vadodara City (Gujarat) number of chemical industries dispose of water, air and oil based pollutant everyday. The pollution process in soil due to the industrial effluent discharge on to the land and its effect on the geotechnical properties of soil arc discussed in the present case study. Uncontrolled exploitation of the natural resources have resulted in an unanticipated soil behaviour due to environmental degradation. This resulted in an increased interest in the study of environmental geotechnics which is a means of forecasting soil behaviour to the changing environment
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