Aharonov–Bohm phase shifts induced by laser pulses

An experimentally accessible scalar Aharonov–Bohm (AB)-effect is proposed using a ponderomotive potential induced by a pulsed laser. This ponderomotive AB (PAB)-effect is unique in that the time-averaged description is classified as type-I, whereas the underlying time-dependent theory is classified as type-II. Not only is the PAB-effect of fundamental interest, it may also be used to characterize ultrashort electron pulses (<100 fs), using low power femtosecond lasers, which is important for ultrafast electron diffraction and microscopy

Overview of the ANITA project

Journal ArticleThe ANITA project is designed to investigate ultra-high energy (>1017 eV) cosmic ray interactions throughout the universe by detecting the neutrinos created in those interactions. These high energy neutrinos are detectable through their interactions within the Antarctic ice sheet, which ANITA will use as a detector target that effectively converts the neutrino interactions to radio pulses. This paper will give an overview of the project including scientific objectives, detection description and mission design

Antarctic impulsive transient antenna (ANITA) instrumentation

Journal ArticleWe will report on the details of the ANITA instrument. This instrument is fundamentally a broadband antenna, which is arrayed and constructed in such a way as to be optimized for the detection and characterization of high-energy neutrino cascades [1]. The requirement to maximize the detector view of the Antarctic ice fields implies low gain antennas yet the need for maximum sensitivity dictates using the highest gain possible. Since the Cherenkov signal increases quadratically at higher frequencies suggesting that the optimal selection is an antenna with constant gain as a function of frequency. The baseline design will be a linearly polarized log-periodic zigzag (LPZZ) antenna

An experiment to measure the energy spectrum of cosmic ray antiprotons from 100 to 1000 MeV

Production models were developed and the confirmation of each one had significant astrophysical impact. These include radical modifications of propagation models, cosmic ray antiprotons injection from neighboring domains of antimatter, p production by evaporating primordial black holes, and cosmic ray p's as annihilation products of supersymmetry particles that might make up the dark dynamical mass of the Galaxy. It is that p's originating from supersymmetric parents might have distinct spectral features that would survive solar modulation; in one model, higgsino annihilation proceeds through the bb quark-antiquark channel, producing a spectral bump at approx. 0.3 GeV in the p spectrum

Complete Boolean algebras are Bousfield lattices

Given a complete Heyting algebra we construct an algebraic tensor triangulated category whose Bousfield lattice is the Booleanization of the given Heyting algebra. As a consequence we deduce that any complete Boolean algebra is the Bousfield lattice of some tensor triangulated category. Using the same ideas we then give two further examples illustrating some interesting behaviour of the Bousfield lattice.Comment: 10 pages, update to clarify the products occurring in the main constructio

4D visualization of embryonic, structural crystallization by single-pulse microscopy

In many physical and biological systems the transition from an amorphous to ordered native structure involves complex energy landscapes, and understanding such transformations requires not only their thermodynamics but also the structural dynamics during the process. Here, we extend our 4D visualization method with electron imaging to include the study of irreversible processes with a single pulse in the same ultrafast electron microscope (UEM) as used before in the single-electron mode for the study of reversible processes. With this augmentation, we report on the transformation of amorphous to crystalline structure with silicon as an example. A single heating pulse was used to initiate crystallization from the amorphous phase while a single packet of electrons imaged selectively in space the transformation as the structure continuously changes with time. From the evolution of crystallinity in real time and the changes in morphology, for nanosecond and femtosecond pulse heating, we describe two types of processes, one that occurs at early time and involves a nondiffusive motion and another that takes place on a longer time scale. Similar mechanisms of two distinct time scales may perhaps be important in biomolecular folding

IceCube's In-Ice Radio Extension: Status and Results

In 2006-2010, several Radio Frequency (RF) detectors and calibration equipment were deployed as part of the IceCube array at depths between 5 to 1400 meters in preparation for a future large scale GZK neutrino detector. IceCube's deep holes and well-established data handling system provide a unique opportunity for deep-ice RF detection studies at the South-Pole. We will present verification and calibration results as well as a status-review of ongoing analyses such as ice-properties, RF noise and reconstruction algorithms.Comment: 4 pages, 6 figures, to appear in the proceedings of the Acoustic and Radio EeV Neutrino detection Activities (ARENA) 2010 conferenc

Design and implementation of a fs-resolved transmission electron microscope based on thermionic gun technology [post-print]

In this paper, the design and implementation of a femtosecond-resolved ultrafast transmission electron microscope is presented, based on a thermionic gun geometry. Utilizing an additional magnetic lens between the electron acceleration and the nominal condenser lens system, a larger percentage of the electrons created at the cathode are delivered to the specimen without degrading temporal, spatial and energy resolution significantly, while at the same time maintaining the femtosecond temporal resolution. Using the photon-induced near field electron microscopy effect (PINEM) on silver nanowires the cross-correlation between the light and electron pulses was measured, showing the impact of the gun settings and initiating laser pulse duration on the electron bunch properties. Tuneable electron pulses between 300 fs and several ps can be obtained, and an overall energy resolution around 1 eV was achieved

From attosecond to zeptosecond coherent control of free-electron wave functions using semi-infinite light fields

Light-electron interaction in empty space is the seminal ingredient for free-electron lasers and also for controlling electron beams to dynamically investigate materials and molecules. Pushing the coherent control of free electrons by light to unexplored timescales, below the attosecond, would enable unprecedented applications in light-assisted electron quantum circuits and diagnostics at extremely small timescales, such as those governing intramolecular electronic motion and nuclear phenomena. We experimentally demonstrate attosecond coherent manipulation of the electron wave function in a transmission electron microscope, and show that it can be pushed down to the zeptosecond regime with existing technology. We make a relativistic pulsed electron beam interact in free space with an appropriately synthesized semi-infinite light field generated by two femtosecond laser pulses reflected at the surface of a mirror and delayed by fractions of the optical cycle. The amplitude and phase of the resulting coherent oscillations of the electron states in energymomentum space are mapped via momentum-resolved ultrafast electron energy-loss spectroscopy. The experimental results are in full agreement with our theoretical framework for light-electron interaction, which predicts access to the zeptosecond timescale by combining semi-infinite X-ray fields with free electrons.Comment: 22 pages, 6 figure

Health Researchers' Use of Social Media: Scoping Review.

BackgroundHealth researchers are increasingly using social media in a professional capacity, and the applications of social media for health researchers are vast. However, there is currently no published evidence synthesis of the ways in which health researchers use social media professionally, and uncertainty remains as to how best to harness its potential.ObjectiveThis scoping review aimed to explore how social media is used by health researchers professionally, as reported in the literature.MethodsThe scoping review methodology guided by Arksey and O'Malley and Levac et al was used. Comprehensive searches based on the concepts of health research and social media were conducted in MEDLINE, EMBASE, CINAHL, PsycINFO, ERIC, and Web of Science databases, with no limitations applied. Articles were screened at the title and abstract level and at full text by two reviewers. One reviewer extracted data that were analyzed descriptively to map the available evidence.ResultsA total of 8359 articles were screened at the title and abstract level, of which 719 were also assessed at full text for eligibility. The 414 articles identified for inclusion were published in 278 different journals. Studies originated from 31 different countries, with the most prevalent being the United States (52.7% [218/414]). The health discipline of the first authors varied, with medicine (33.3% [138/414]) being the most common. A third of the articles covered health generally, with 61 health-specific topics. Papers used a range of social media platforms (mean 1.33 [SD 0.7]). A quarter of the articles screened reported on social media use for participant recruitment (25.1% [104/414]), followed by practical ways to use social media (15.5% [64/414]), and use of social media for content analysis research (13.3% [55/414]). Articles were categorized as celebratory (ie, opportunities for engagement, 72.2% [299/414]), contingent (ie, opportunities and possible limitations, 22.7% [94/414]) and concerned (ie, potentially harmful, 5.1% [21/414]).ConclusionsHealth researchers are increasingly publishing on their use of social media for a range of professional purposes. Although most of the sentiment around the use of social media in health research was celebratory, the uses of social media varied widely. Future research is needed to support health researchers to optimize their social media use