1,092 research outputs found
Acceleration Of Protons To Above 6 MeV Using H2O >Snow> Nanowire Targets
A scheme is presented for using H2O >snow> nanowire targets for the generation of fast protons. This novel method may relax the requirements for very high laser intensities, thus reducing the size and cost of laser based ion acceleration system.Physic
Spatially and genetically distinct African trypanosome virulence variants defined by host interferon-g response
We describe 2 spatially distinct foci of human African trypansomiasis in eastern Uganda. The Tororo and Soroti foci of <i>Trypanosoma brucei rhodesiense</i> infection were genetically distinct as characterized by 6 microsatellite and 1 minisatellite polymorphic markers and were characterized by differences in disease progression and host-immune response. In particular, infections with the Tororo genotype exhibited an increased frequency of progression to and severity of the meningoencephalitic stage and higher plasma interferon (IFN)âÎł concentration, compared with those with the Soroti genotype. We propose that the magnitude of the systemic IFN-Îł response determines the time at which infected individuals develop central nervous system infection and that this is consistent with the recently described role of IFN-Îł in facilitating blood-brain barrier transmigration of trypanosomes in an experimental model of infection. The identification of trypanosome isolates with differing disease progression phenotypes provides the first field-based genetic evidence for virulence variants in T. <i>brucei rhodesiense</i>
5.5-7.5 MeV Proton generation by a moderate intensity ultra-short laser interaction with H2O nano-wire targets
We report on the first generation of 5.5-7.5 MeV protons by a moderate
intensity short-pulse laser (4.5 \times 1017 W/cm^2, 50 fsec) interacting with
H2O nano-wires (snow) deposited on a Sapphire substrate. In this setup, the
laser intensity is locally enhanced by the tip of the snow nano-wire, leading
to high spatial gradients. Accordingly, the plasma near the tip is subject to
enhanced ponderomotive potential, and confined charge separation is obtained.
Electrostatic fields of extremely high intensities are produced over the short
scale length, and protons are accelerated to MeV-level energies.Comment: submitted to PRL, under press embargo. 6 figure
RARITAN FORMATION (UPPER CRETACEOUS), LONG ISLAND, NEW YORK: SEDIMENTOLOGICAL AND GEOCHEMICAL ASSESSMENT
The lithology of the Upper Cretaceous Raritan Formation (RF) consists of two members: an upper clay member (Raritan clay) and a lower unit, the Lloyd Sand Member. RF is unconformably overlain by upper Pleistocene glacial deposits. The RF consists of stratified white, light- to dark-gray, and red beds and lenses of clay, silt, and sand; lignite and pyrite are common. Variegated, thin to thickly-bedded Lloyd sandstone (LS) is considered to be one of the extensive regional aquifers in Long Island and interpreted to be nearshore, fluvio-deltaic deposit. Proximity to fluvial axes and active deltaic lobes plays an important role in sequence thickness and maintaining an overall architecture of deltaic sandbodies. Presumably large amounts of deltaically derived sand are reworked by wave action and redistributed by longshore currents. LS is generally identified as containing clayey lenses, pyrite and hematitic, highly micaceous reddish silty sandstone. Its upper surface lies about 400 feet below sea level in northwest Huntington and at Orient, and over 1,500 feet below sea level at western Fire Island. The exposed unit is about 30 m thick in Caumsett State Park, Long Island. Preliminary geochemical investigations using ICP-MS (Inductively coupled plasma mass spectrometry), Ultra Trace Aqua Regia ICP-MS, and routine petrography on selected samples (both outcrop and subsurface) revealed a distinctive geochemical signature associated with RF units (Raritan Clay and Lloyd Sandstone). Clay unit known as Raritan Clay contains 60-42% silica, 27-15% alumina, 7% iron-oxide, and 3% K2O, whereas LS is found to be dominantly silica rich (97%) and remarkably poor in alumina, iron-oxide, and K2O. RF clayey unit also showed LOI to be 7-40%. Field exposure of RF clay resembles a kaolinitic-illitic type of high plasticity. Selected trace elements were identified and include Zr, Cu, Ti, Rb, La, Ba, Sr, Ce, Cr, Y, and Zn. Clayey units in RF were found to contain significantly higher proportion of Cu (80-30 ppm), Rb (35-15 ppm), Ba (80-40 ppm), Ce (105 ppm), Cr (60-20 ppm), Y (30 ppm) and Zn (200-40 ppm), compared to LS. Distinctive geochemical variations between the RF clay and LS point to variable provenance, diagenetic pathways, and depositional environments. Further investigations will proceed to differentiate subunits within the LS and RF clayey unit
Evolution of the electric fields induced in high intensity laser-matter interactions
Multi MeV protons \cite{snavely2000intense} and heavier ions are emitted by
thin foils irradiated by high-intensity lasers, due to the huge accelerating
fields, up to several teraelectronvolt per meter, at sub-picosecond timescale
\cite{dubois2014target}. The evolution of these huge fields is not well
understood till today. Here we report, for the first time, direct and
temporally resolved measurements of the electric fields produced by the
interaction of a short-pulse high-intensity laser with solid targets. The
results, obtained with a sub- fs temporal diagnostics, show that such
fields build-up in few hundreds of femtoseconds and lasts after several
picoseconds
Recent studies on single-shot diagnostics for plasma accelerators at SPARC_LAB
Plasma wakefield acceleration is the most promising acceleration technique
for compact and cheap accelerators, thanks to the high accelerating gradients
achievable. Nevertheless, this approach still suffers of shot-to-shot
instabilities, mostly related to experimental parameters fluctuations.
Therefore, the use of single shot diagnostics is needed to properly understand
the acceleration mechanism. In this work, we present two diagnostics to probe
electron beams from laser-plasma interactions, one relying on Electro Optical
Sampling (EOS) for laser-solid matter interactions, the other one based on
Optical Transition Radiation (OTR) for single shot measurements of the
transverse emittance of plasma accelerated electron beams, both developed at
the SPARC_LAB Test Facility
Hasbara 2.0: Israelâs Public Diplomacy in the Digital Age
The Internet has been a counter-public space for Palestinian liberation politics for over a decade, and digital technologies have become an increasingly important tool for solidarity groups across the world. However, the Israeli state and Zionist supporters worldwide are harnessing the same technologies and platforms to mobilize technology primarily to increase pro-Israel sentiments. The aims of this article are to examine hasbara [Israeli public diplomacy] through an exploration of similar diplomacy programmes; to illustrate how social media have affected the basic algorithms of hasbara; and to probe the assertions of hasbara in the light of pro-Palestinian solidarity. Through a study of public diplomacy, this article critically analyzes hasbara as a site of contestation and a method that is hampered by contradictions. On the one hand, there has been a massive growth in hasbara in recent yearsâindicated by the increase in funding for it and by its professionalized and centralized character; and on the other hand, hasbara has attracted sharp critiques in Israel for its reputed failures. To understand this contradiction, hasbara must be placed within the context of Israelâs settler-colonialism, which sets the state apart from other âpost-conflictâ states. This article reviews the methods utilized in hasbara, as well as their readjustment in the context of recent wars. Events in 2014 illustrate that hasbara actually destabilizes Israelâs diplomacy. Online journalism and the suppression of solidarity for Palestine together stimulate more criticism and, in turn, help to shift public opinion. Paradoxically, therefore, adjustments (âhasbara 2.0â) have underlined the image of Israel as a colonial power engaged in violent occupation
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