36,053 research outputs found
Supplemental material for Sustained reactive oxygen species generation from percarbamide nanomedicine via a mechanism of X-Ray-initiated free radical chain reactions
No full textSupplemental Material for Sustained reactive oxygen species generation from percarbamide nanomedicine via a mechanism of X-Ray-initiated free radical chain reactions by Yongping Huang, Yiran Shao and Yingchun Zhu in Journal of Biomaterials Applications</p
High energy and high intensity electron and X-ray beams by pyroelectric effect
No full textThe production of x-rays has been a useful technique in many areas of
science, medicine and various industries for over 100 years. Over this
time various new methods of generating x-rays have been produced,
allowing improved performance in existing applications as well as
the application of x-rays in new areas. In this project a novel method
of electron beam production, with the potential for development
into a novel method of x-ray production is presented, using both
pyroelectric and ferroelectric materials.
The pyroelectric e ect, i.e. the generation of a charge due to a
change in temperature is an e ect exhibited by certain dielectric
materials. This e ect has previously been used in x-ray generation,
and has been su ently successful that a commercial device has been
produced: the Amptek Cool-X. While the Cool-X has only a limited
electron / x-ray energy, high energy applications of this technology
are present in the literature. This shows that these materials are
capable of high voltages. However, the technique is not suitable
for high beam intensity applications, limiting the potential use of
pyroelectric x-ray devices.
Ferroelectric electron emission is a technique used to generate elec-
tron beams by applying a high voltage pulse to a specially prepared
cathode. This technique has shown great potential for very high
intensity pulsed electron beam generation. The major drawback of
this technique is that while the cathodes are relitivly cheap and
easy to produce, the other required equipment (such as high vacuum
systems and high voltage pulse generators) is typically large and
expensive. This project combines these two technologies to create
an electron beam generation system that exhibits many of the ad-
vantages of each technology, while minimizing the drawbacks. The
result is a device using pyroelectric materials as voltage generatingelements for electron acceleration and high voltage pulse production,
while a ferroelectric cathode is employed as the electron generating
element. This system has been shown to, depending on con guation,
be capable of accelerating voltages above 5 kV, and generating total
collected charges of more than -40 nC per pulse
[Letter from Alex Bradford to Lieutenant and Mrs. Ray Starner - November 4, 1940]
No full textLetter from Alex Bradford to Lieutenant and Mrs. Ray Starner describing the the current state of affairs that the author was experiencing, including: the London blitz, the moral of the troops on the ground, and the collective company of men opposing the Nazi regime
The student's guide to completing an author study
No full textThe 'Student's guide to completing an author study' emerged during the early development of the school library resource center program at Glen Stewart Elementary School in Stratford Canada on Prince Edward Island. This research process centered on an author study, with direct teaching and clear assignment. The resulting model has been adapted to various grade levels and subject areas in different schools.Source type: Electronic(1)http://proquest.umi.com/pqdweb?did=49237063&Fmt=7&clientId=65345&RQT=309&VName=PQ
Active X-ray optics for the next generation of X-ray space telescopes
No full textDescribed within is the design, manufacture, metrology and X-ray testing of an active X-ray
prototype intended for the next generation of X-ray telescopes. One of the challenges faced by
the X-ray telescope community is how to combine high resolution and high sensitivity into one
system, as weight limitations place constraints on the optics that can be launched. Therefore the
mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics
to be nested and to deliver high angular resolution through the active control of the optic’s form.
Piezoelectric unimorph actuators provide the active component: it is intended that they will correct
for figure errors within the optic and therefore increase the angular resolution capability.
The prototype’s design is based upon an ellipsoidal segment which provides point-to-point
focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic
where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production
of the prototype that is the core of the presented research. Metrology of the actuators’ influence
functions is presented and highlight the prototype’s ability to deform its optic surface by microns.
In addition, the measured influence functions are compared against finite element models and a
distinct similarity between the functions is observed.
The prototype was tested at an X-ray beamline facility in November 2008 and the results
showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from
0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties
in the manufacture of the prototype and X-ray testing shall be presented alongside future work in
conclusion to this thesis
Ray Huang – China: A Macro History [1997, new edition]
No full textSignalement d’une référence pour comprendre la situation chinoise sur la longue durée. Réf. : Ray Huang, China: A Macro History, Turn of the century ed., Armonk, N.Y., M.E. Sharpe, “An East gate book” 1997. Lien Google Books : https://books.google.fr/books?id=c7PbzIoSc-0
Author, Geraldine Brooks at the National Library of Australia for the 2009 Ray Mathew Lecture, Canberra, 23 October 2009 [picture] /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author, Geraldine Brooks during her visit to the National Library of Australia for the 2009 Ray Mathew Lecture, Canberra, 23 October 2009.; Acquired in digital format; access copy available online.; Mode of access: Internet via World Wide Web.; Photographed by a staff member of the National Library of Australia
Characterization of Aptamer-Protein Complexes by X-ray Crystallography and Alternative Approaches
No full textAptamers are oligonucleotide ligands, either RNA or ssDNA, selected for high-affinity binding to molecular targets, such as small organic molecules, proteins or whole microorganisms. While reports of new aptamers are numerous, characterization of their specific interaction is often restricted to the affinity of binding (KD). Over the years, crystal structures of aptamer-protein complexes have only scarcely become available. Here we describe some relevant technical issues about the process of crystallizing aptamer-protein complexes and highlight some biochemical details on the molecular basis of selected aptamer-protein interactions. In addition, alternative experimental and computational approaches are discussed to study aptamer-protein interactions.
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Site Occupancies, VUV-UV-vis Photoluminescence, and X-ray Radioluminescence of Eu<sup>2+</sup>-Doped RbBaPO<sub>4</sub>
No full textRbBaPO4:Eu2+ phosphors have been prepared by a high-temperature solid-state reaction method, and the structure was determined by Rietveld refinement based on powder X-ray diffraction (P-XRD) data. Their VUV-UV-vis photoluminescence properties are systematically investigated with three objectives: (1) based on low-temperature spectra, we clarify the site occupancies of Eu2+, and demonstrate that the doublet emission bands at ∼406 and ∼431 nm originate from Eu2+ in Ba2+ [Eu2+(I)] and Rb+ [Eu2+(II)] sites, respectively; (2) an electron-vibrational interaction (EVI) analysis is conducted to estimate the Huang-Rhys factors, the zero-phonon lines (ZPLs) and the Stokes shifts of Eu2+ in Rb+ and Ba2+ sites; (3) the studies on luminescence decay of Eu2+(I) reveal that dipole-dipole interaction is mainly responsible for the energy transfer from Eu2+(I) to Eu2+(II), and the energy migration between Eu2+(I) is weak. Finally, the X-ray excited luminescence (XEL) spectrum indicates that the light yield of the sample RbBa0.995Eu0.005PO4 is ∼17700 ph/MeV, showing its potential application in X-ray detecting. Accepted Author ManuscriptRST/Luminescence Material
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