232 research outputs found
Linux Based Ethernet Communication for Xilinx FPGAs
This article presents the implementation of an Ethernet communication platform for use on Xilinx FPGAs. The proposed solution relies on a synthesized embedded system to provide network data transfer and control capabilities, for use with synthesizable electronic devices. Most TCP/IP stack services and protocols were implemented and the design is flexible to allow adaptation and/or expansion for different application scenarios. Currently this platform is being used on the development of a FPGA based JTAG controller, with remote access. The embedded system hardware requires a MicroBlaze softcore microprocessor running a Petalinux operating system.info:eu-repo/semantics/publishedVersio
Evidence of resonant surface wave excitation in the relativistic regime through measurements of proton acceleration from grating targets
The interaction of laser pulses with thin grating targets, having a periodic
groove at the irradiated surface, has been experimentally investigated.
Ultrahigh contrast () pulses allowed to demonstrate an enhanced
laser-target coupling for the first time in the relativistic regime of
ultra-high intensity >10^{19} \mbox{W/cm}^{2}. A maximum increase by a factor
of 2.5 of the cut-off energy of protons produced by Target Normal Sheath
Acceleration has been observed with respect to plane targets, around the
incidence angle expected for resonant excitation of surface waves. A
significant enhancement is also observed for small angles of incidence, out of
resonance.Comment: 5 pages, 5 figures, 2nd version implements final correction
Selective Deuterium Ion Acceleration Using the Vulcan PW Laser
We report on the successful demonstration of selective acceleration of
deuterium ions by target-normal sheath acceleration (TNSA) with a high-energy
petawatt laser. TNSA typically produces a multi-species ion beam that
originates from the intrinsic hydrocarbon and water vapor contaminants on the
target surface. Using the method first developed by Morrison, et al., an
ion beam with 99 deuterium ions and peak energy 14 MeV/nucleon is
produced with a 200 J, 700 fs, laser pulse by cryogenically
freezing heavy water (DO) vapor onto the rear surface of the target prior
to the shot. Within the range of our detectors (0-8.5), we find
laser-to-deuterium-ion energy conversion efficiency of 4.3 above 0.7
MeV/nucleon while a conservative estimate of the total beam gives a conversion
efficiency of 9.4.Comment: 5 pages, 5 figure
Signatures of the Self-Similar Regime of Strongly Coupled Stimulated Brillouin Scattering for Efficient Short Laser Pulse Amplification
Plasma-based laser amplification is considered as a possible way to overcome the technological limits of
present day laser systems and achieve exawatt laser pulses. Efficient amplification of a picosecond laser
pulse by stimulated Brillouin scattering (SBS) of a pump pulse in a plasma requires to reach the self-similar
regime of the strongly coupled (SC) SBS. In this Letter, we report on the first observation of the signatures
of the transition from linear to self-similar regimes of SC-SBS, so far only predicted by theory and
simulations. With a new fully head-on collision geometry, subpicosecond pulses are amplified by a factor
of 5 with energy transfers of few tens of mJ. We observe pulse shortening, frequency spectrum broadening,
and down-shifting for increasing gain, signatures of SC-SBS amplification entering the self-similar regime.
This is also confirmed by the power law dependence of the gain on the amplification length: doubling the
interaction length increases the gain by a factor 1.4. Pump backward Raman scattering (BRS) on SC-SBS
amplification has been measured for the first time, showing a strong decrease of the BRS amplitude and
frequency bandwidth when SBS seed amplification occurs
Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers
A novel method for characterising the full spectrum of deuteron ions emitted
by laser driven multi-species ion sources is discussed. The procedure is based
on using differential filtering over the detector of a Thompson parabola ion
spectrometer, which enables discrimination of deuterium ions from heavier ion
species with the same charge-to-mass ratio (such as C6+, O8+, etc.). Commonly
used Fuji Image plates were used as detectors in the spectrometer, whose
absolute response to deuterium ions over a wide range of energies was
calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium
ion spectrum diagnosed in a recent experimental campaign is presented.Comment: 7 pages, 7 figure
Rapid Tooling Method for Soft Customized Removable Oral Appliances
Traditionally oral appliances i.e. removable orthodontic appliances, bite splints and snoring / sleep apnea appliances are made with alginate impressions and wax registrations. Our aim was to describe the process of manufacturing customized oral appliances with a new technique i.e. rapid tooling method. The appliance should ideally be custom made to match the teeth. An orthodontic patient, scheduled for conventional orthodontic treatment, served as a study subject. After a precise clinical and radiographic examination, the approach was to digitize the patient’s dental arches and then to correct them virtually by computer. Additive manufacturing was then used to fabricate a mould for a soft customized appliance. The mould was manufactured using stereolithography from Somos ProtoGen O-XT 18420 material. Casting material for the mould to obtain the final appliance was silicone. As a result we managed to create a customized soft orthodontic appliance. Also, the accuracy of the method was found to be adequate. Two versions of the described device were manufactured: one with small and one with moderate orthodontic force. The study person also gave information on the subjective patient adaptation aspects of the oral appliance
Inference of Co-Evolving Site Pairs: an Excellent Predictor of Contact Residue Pairs in Protein 3D structures
Residue-residue interactions that fold a protein into a unique
three-dimensional structure and make it play a specific function impose
structural and functional constraints on each residue site. Selective
constraints on residue sites are recorded in amino acid orders in homologous
sequences and also in the evolutionary trace of amino acid substitutions. A
challenge is to extract direct dependences between residue sites by removing
indirect dependences through other residues within a protein or even through
other molecules. Recent attempts of disentangling direct from indirect
dependences of amino acid types between residue positions in multiple sequence
alignments have revealed that the strength of inferred residue pair couplings
is an excellent predictor of residue-residue proximity in folded structures.
Here, we report an alternative attempt of inferring co-evolving site pairs from
concurrent and compensatory substitutions between sites in each branch of a
phylogenetic tree. First, branch lengths of a phylogenetic tree inferred by the
neighbor-joining method are optimized as well as other parameters by maximizing
a likelihood of the tree in a mechanistic codon substitution model. Mean
changes of quantities, which are characteristic of concurrent and compensatory
substitutions, accompanied by substitutions at each site in each branch of the
tree are estimated with the likelihood of each substitution. Partial
correlation coefficients of the characteristic changes along branches between
sites are calculated and used to rank co-evolving site pairs. Accuracy of
contact prediction based on the present co-evolution score is comparable to
that achieved by a maximum entropy model of protein sequences for 15 protein
families taken from the Pfam release 26.0. Besides, this excellent accuracy
indicates that compensatory substitutions are significant in protein evolution.Comment: 17 pages, 4 figures, and 4 tables with supplementary information of 5
figure
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