1,014 research outputs found
Charge and Current Compensation of Intense Charged Beams in Future Accelerators
Proposals for future high-energy accelerators are characterized by demands for increasingly intense and energetic beams. The classical operation of high-current accelerators is severely constrained by collective electrodynamic phenomena, such as problems related to space-charge, to high-current flow, to beamstrahlung and pair production. These detrimental electrodynamic effects dominate the dynamic s and the collision interactions of high-intensity beams. With the introduction of soft space-charge and current compensation techniques utilizing low- to medium-energy lepton beams with charge polari ty opposite to that of the beams to be neutralized, all electromagnetic high-intensity limitations may be removed. The application of beam compensation is proposed for various sections of different ty pes of classical accelerator systems, such as for ion sources and the low-energy beam transport sections of ion linacs, for the crossing points of circular and linear colliders and for the final focii of ion beam fusion drivers. The design and the operation of partially compensated accelerators becomes much more comfortable and design goals can be reached more easily without any significant electro magnetic perturbation. The ingredients of neutralization technology low-energy electron and positron beams are state-of-the-art and, as such, applicable today. Several methods of smooth beam compe nsation can be identified and must be studied and selected for each specific case. Practical experience has to be gained in dedicated pilot experiments
Neutralization principles for the Extraction and Transport of Ion Beams
The strict application of conventional extraction techniques of ion beams from a plasma source is characterized by a natural intensity limit determined by space charge.The extracted current may be enhanced far beyond this limit by neutralizing the space charge of the extracted ions in the first extraction gap of the source with electrons injected from the opposite side. The transverse and longitudinal emittances of a neutralized ion beam, hence its brightness, are preserved. Results of beam compensation experiments, which have been carried out with a laser ion source, are resumed for proposing a general scheme of neutralizing ion sources and their adjacent low-energy beam transport channels with electron beams. Many technical applications of high-mass ion beam neutralization technology may be identified: the enhancement of ion source output for injection into high-intensity, low-and high-energy accelerators, or ion thrusters in space technology, for the neutral beams needed for plasma heating of magnetic confinement fusion devices, and for future accelerator-driven systems for fusion, fission and nuclear waste incineration
Biomolecular imaging and electronic damage using X-ray free-electron lasers
Proposals to determine biomolecular structures from diffraction experiments
using femtosecond X-ray free-electron laser (XFEL) pulses involve a conflict
between the incident brightness required to achieve diffraction-limited atomic
resolution and the electronic and structural damage induced by the
illumination. Here we show that previous estimates of the conditions under
which biomolecular structures may be obtained in this manner are unduly
restrictive, because they are based on a coherent diffraction model that is not
appropriate to the proposed interaction conditions. A more detailed imaging
model derived from optical coherence theory and quantum electrodynamics is
shown to be far more tolerant of electronic damage. The nuclear density is
employed as the principal descriptor of molecular structure. The foundations of
the approach may also be used to characterize electrodynamical processes by
performing scattering experiments on complex molecules of known structure.Comment: 16 pages, 2 figure
Sykepleierens erfaringer som pÄrÞrende : Hvilke personlige erfaringer har sykepleiere som er pÄrÞrende til et nÊrt familiemedlem?
Bakgrunn:
Litteraturen skiller mellom ulike typer av roller, og viser at det kan vÊre et dilemma Ä inneha flere roller samtidig. Disse dilemmaene kan fÞre til rollekonflikter. Det er relativt lite kunnskap pÄ feltet om det Ä ha rollen som bÄde profesjonell helsearbeider og nÊr pÄrÞrende. Den manglende kunnskapen pÄ feltet og egen opplevd erfaring som pÄrÞrende og sykepleier er derfor bakgrunnen for arbeidet med denne tematikken.
FormÄl:
FormÄl med studien er Ä undersÞke hvilke erfaringer sykepleiere har i rollen som pÄrÞrende.
Metode:
Oppgaven er en kvalitativ studie. Det er utfÞrt kvalitative forskningsintervju med 7 sykepleiere som har pÄrÞrendeerfaring til et nÊrt familiemedlem. Det empiriske materialet er analysert ved hjelp av meningsfortetting innenfor en fortolkende tradisjon.
Teoretisk perspektiv:
Den teoretiske referanserammen er hentet fra bÄde sosiologien og sykepleiefaget. Sosiologien er opptatt av Ä analysere samhandlingen mellom mennesker innenfor ulike sosiale systemer. Hvordan relasjonene er mellom mennesker og hvilke forventninger man har til rollene avgjÞr hvordan mennesker hÄndterer Ä ha flere roller samtidig. For Ä belyse pÄrÞrendeperspektivet er tema som hvem den pÄrÞrende er, pÄrÞrendes erfaringer og opplevelsen av avmakt sett nÊrmere pÄ. For Ä belyse sykepleierperspektivet er omsorg, skjÞnnet, sykepleiefokus og sykepleiernes erfaringer lÞftet frem. Det benyttes ogsÄ forskningsartikler for Ä belyse sykepleieres erfaringer som pÄrÞrende og sykepleier.
Resultater:
Sykepleiere med pÄrÞrendeerfaring er ofte kritiske pÄrÞrende og ikke alltid enige i behandlingen av pasienten. De sier samtidig at de har opplevd mye god pleie av pasienten, men savner initiativ fra personalet i forhold til informasjon og tiltak. Flere informanter opplevde situasjoner hvor de stilte spÞrsmÄlstegn ved fagkunnskapen til personalet, og hvordan de tilegnet seg ny kunnskap. Hvis noe ikke er bra sier de fra pÄ en forsiktig mÄte, med faglige argument. Om forholdet til sÞsken hadde informantene ulike erfaringer, noen opplevde det som problematisk, andre ikke. Alle la vekt pÄ viktigheten av stÞtte fra sÞsken.
Konklusjon:
Sykepleiere med pÄrÞrendeerfaring greier ikke Ä vÊre enten 100 % pÄrÞrende eller 100 % sykepleier, de er i en spenning mellom rollene. Det er vanskelig Ä vÊre profesjonell, de har en dobbeltrolle som gir konsekvenser for hver av rollene. De opplever en rollekonflikt. De bruker egne erfaringer til beste for pasienten, bÄde i rollen som pÄrÞrende og i rollen som sykepleier, og legger vekt pÄ Ä ta bÄde pasient og pÄrÞrende pÄ alvor.
NÞkkelord: Sykepleier, sykepleie, pÄrÞrende, omsorg, rolle, rolleteori, rollekonflikt, dobbeltrolle, pÄrÞrenderolle, sykepleierrolle, nurse, nursing, nursing role, caregivers, double duty caregivers, relatives
Ion Beam Neutralization with Ferroelectrically Generated Electron Beams
A technique for ion beam space-charge neutralization with pulsed electron beams is described. The intensity of multiply-charged ions produced with a laser ion source can be enhanced or decreased separately with electron beam trains of MHz repetition rate. These are generated with ferroelectric cathodes, which are pulsed in synchronization with the laser ion source. The pulsed electron beams guide the ion beam in a similar way to the alternating gradient focusing of charged particle beams in circular accelerators such as synchrotrons. This new neutralization technology overcomes the Langmuir Child space-charge limit and may in future allow ion beam currents to be transported with intensities by orders of magnitude higher than those which can be accelerated today in a single vacuum tube
GeschÀftsanalyse im Kontext der Unternehmensarchitektur
Zusammenfassung: Die WandlungsfĂ€higkeit von Organisationen ist ein wesentlicher Erfolgsfaktor, zu dem die Unternehmensarchitektur einen wichtigen Beitrag leisten kann. GeschĂ€ftsanalysen liefern die Voraussetzungen fĂŒr das VerstĂ€ndnis und die transparente Weiterentwicklung des GeschĂ€ftsmodells und die dafĂŒr notwendige Ausrichtung der Informationstechnologie. Vor diesem Hintergrund wird am Beispiel eines Schweizerischen Versicherungsunternehmens gezeigt, wie durch GeschĂ€ftsanalyse einerseits das VerstĂ€ndnis des GeschĂ€ftsmodells gefördert und andererseits die Abstimmung zwischen GeschĂ€fts- und IT-Architektur unterstĂŒtzt wird. Ferner wird ein Ansatz vorgestellt, der verschiedene Ziele und Typen der GeschĂ€ftsanalyse im Kontext von Unternehmensarchitekturen zusammenfĂŒhr
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