16,372 research outputs found
Ultracold neutron depolarization in magnetic bottles
We analyze the depolarization of ultracold neutrons confined in a magnetic
field configuration similar to those used in existing or proposed
magneto-gravitational storage experiments aiming at a precise measurement of
the neutron lifetime. We use an extension of the semi-classical Majorana
approach as well as an approximate quantum mechanical analysis, both pioneered
by Walstrom et al. [Nucl. Instr. Meth. Phys. Res. A 599, 82 (2009)]. In
contrast with this previous work we do not restrict the analysis to purely
vertical modes of neutron motion. The lateral motion is shown to cause the
predominant depolarization loss in a magnetic storage trap. The system studied
also allowed us to estimate the depolarization loss suffered by ultracold
neutrons totally reflected on a non-magnetic mirror immersed in a magnetic
field. This problem is of preeminent importance in polarized neutron decay
studies such as the measurement of the asymmetry parameter A using ultracold
neutrons, and it may limit the efficiency of ultracold neutron polarizers based
on passage through a high magnetic field.Comment: 18 pages, 6 figure
A MEMS electrostatic particle transportation system
We demonstrate here an electrostatic MEMS system
capable of transporting particles 5-10μm in diameter in
air. This system consists of 3-phase electrode arrays
covered by insulators (Figs. 1, 2). Extensive testing of
this system has been done using a variety of insulation
materials (silicon nitride, photoresist, and Teflon),
thickness (0- 12μm), particle sizes (1-10μm), particle
materials (metal, glass, polystyrene, spores, etc),
waveforms, frequencies, and voltages. Although
previous literature [1-2] claimed it impractical to
electrostatically transport particles with sizes 5-10μm
due to complex surface forces, this effort actually
shows it feasible (as high as 90% efficiency) with the
optimal combination of insulation thickness, electrode
geometry, and insulation material. Moreover, we suggest a qualitative theory for our particle transportation system which is consistent with our data and finite-element electrostatic simulations
Spin flip loss in magnetic storage of ultracold neutrons
We analyze the depolarization of ultracold neutrons confined in a magnetic
field configuration similar to those used in existing or proposed
magneto-gravitational storage experiments aiming at a precise measurement of
the neutron lifetime. We use an approximate quantum mechanical analysis such as
pioneered by Walstrom \emph{et al} [Nucl. Instrum. Methods Phys. Res. A 599, 82
(2009)]. Our analysis is not restricted to purely vertical modes of neutron
motion. The lateral motion is shown to cause the predominant depolarization
loss in a magnetic storage trap.Comment: 12 pages, 3 figures, for Proceedings of Neutron Lifetime Worksho
Nanofiller Fibre-Reinforced Polymer Nanocomposites
In this work, the technology of nano and micro-scale particle reinforcement
concerning various polymeric fibre-reinforced systems including polyamides (PA),
polyesters, polyurethanes, polypropylenes and high performance/temperature
engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK),
polyarylacetylene (PAA) and poly p-phenylene benzobisoxazole (PBO) is reviewed.
When the diameters of polymer fibre materials are shrunk from micrometers to
submicrons or nanometers, there appear several unique characteristics such as
very large surface area to volume ratio (this ratio for a nanofibre can be as
large as 103 times of that of a microfibre), flexibility in surface
functionalities and superior mechanical performance (such as stiffness and
tensile strength) compared with any other known form of the material. However,
nanoparticle reinforcement of fibre reinforced composites has been shown to be a
possibility, but much work remains to be performed in order to understand how
nanoreinforcement results in dramatic changes in material properties. The
understanding of these phenomena will facilitate their extension to the
reinforcement of more complicated anisotropic structures and advanced polymeric
composite systems
Calculation of geometric phases in electric dipole searches with trapped spin-1/2 particles based on direct solution of the Schr\"odinger equation
Pendlebury [Phys. Rev. A , 032102 (2004)] were
the first to investigate the role of geometric phases in searches for an
electric dipole moment (EDM) of elementary particles based on Ramsey-separated
oscillatory field magnetic resonance with trapped ultracold neutrons and
comagnetometer atoms. Their work was based on the Bloch equation and later work
using the density matrix corroborated the results and extended the scope to
describe the dynamics of spins in general fields and in bounded geometries. We
solve the Schr\"odinger equation directly for cylindrical trap geometry and
obtain a full description of EDM-relevant spin behavior in general fields,
including the short-time transients and vertical spin oscillation in the entire
range of particle velocities. We apply this method to general macroscopic
fields and to the field of a microscopic magnetic dipole.Comment: 11 pages, 4 figure
Two-twenty Kev Spectrum of X-rays from the Crab Nebula and the Diffuse Background near Galactic Anticenter
X ray spectroscopy of Crab nebula and diffuse background by sounding balloons and rocket
Immunotherapy-based combinations in metastatic NSCLC.
Immuno-oncology has revolutionized the treatment of metastatic non-small cell lung cancer (mNSCLC) since the approval of immunotherapy by the U.S. FDA in 2015. Despite the advancements, outcomes for patients have room for further improvement. Combination therapies have shown promise in overcoming resistance and improving outcomes. This review focuses on current immunotherapy-based combination approaches, reported and ongoing trials, as well as novel combination strategies, challenges, and future directions for mNSCLC treatment. We summarize approaches in combination with chemotherapy, novel immune checkpoints, tyrosine kinase inhibitors and other strategies including vaccines, and radiation therapy. The promise of biomarker-driven studies to understand resistance and design multi-arm platform trials that evaluate novel therapies is becoming of increasing relevance with the ultimate goal of administering precision immunotherapy by identifying the right dose of the right combination for the right patient at the right time
Diffuse gamma-ray background and cosmic-ray positrons from annihilating dark matter
We study the annihilating dark matter contribution to the extra-galactic
diffuse gamma-ray background spectrum, motivated by the recent observations of
cosmic-ray positron/electron anomalies. The observed diffuse gamma-ray flux
provides stringent constraint on dark matter models and we present upper bounds
on the annihilation cross section of the dark matter. It is found that for the
case of cored dark matter halo profile, the diffuse gamma-rays give more
stringent bound compared with gamma-rays from the Galactic center. The Fermi
satellite will make the bound stronger.Comment: 20 pages, 11 figures; references added; to appear in PR
Attitudes to self-sampling for HPV among Indian, Pakistani, African-Caribbean and white British women in Manchester, UK
Objective: To examine attitudes to self-sampling for human papillomavirus (HPV) testing among women from contrasting ethnic groups.Setting: Manchester, UK.Methods: Two hundred women of Indian, Pakistani, African-Caribbean and white British origin were recruited from social and community groups to participate in a questionnaire survey. The questionnaire included items on attitudes to self-sampling and intention to use the test.Results: Willingness to try to use the test was high, and women did not foresee religious or cultural barriers to self-sampling; however, a large proportion of women were concerned about doing the test properly. This concern was greatest in the Indian and African-Caribbean groups.Conclusions: Although women's willingness to try self-sampling for HPV is encouraging, worries about carrying out the procedure correctly must be addressed if women are to feel confident about the results of self-sampling methods and reassured by a negative result
- …