1,543 research outputs found
Tunable X-ray source by Thomson scattering during laser-wakefield acceleration
We report results on all-optical Thomson scattering intercepting the
acceleration process in a laser wakefield accelerator. We show that the pulse
collision position can be detected using transverse shadowgraphy which also
facilitates alignment. As the electron beam energy is evolving inside the
accelerator, the emitted spectrum changes with the scattering position. Such a
configuration could be employed as accelerator diagnostic as well as reliable
setup to generate x-rays with tunable energy
Timing attacks and local timing attacks against Barrett’s modular multiplication algorithm
Montgomery’s and Barrett’s modular multiplication algorithms are widely used in modular exponentiation algorithms, e.g. to compute RSA or ECC operations. While Montgomery’s multiplication algorithm has been studied extensively in the literature and many side-channel attacks have been detected, to our best knowledge no thorough analysis exists for Barrett’s multiplication algorithm. This article closes this gap. For both Montgomery’s and Barrett’s multiplication algorithm, differences of the execution times are caused by conditional integer subtractions, so-called extra reductions. Barrett’s multiplication algorithm allows even two extra reductions, and this feature increases the mathematical difficulties significantly.
We formulate and analyse a two-dimensional Markov process, from which we deduce relevant stochastic properties of Barrett’s multiplication algorithm within modular exponentiation algorithms. This allows to transfer the timing attacks and local timing attacks (where a second side-channel attack exhibits the execution times of the particular modular squarings and multiplications) on Montgomery’s multiplication algorithm to attacks on Barrett’s algorithm. However, there are also differences. Barrett’s multiplication algorithm requires additional attack substeps, and the attack efficiency is much more sensitive to variations of the parameters. We treat timing attacks on RSA with CRT, on RSA without CRT, and on Diffie-Hellman, as well as local timing attacks against these algorithms in the presence of basis blinding. Experiments confirm our theoretical results
Anisotropic electrical and thermal magnetotransport in the magnetic semimetal GdPtBi
The half-Heusler rare-earth intermetallic GdPtBi has recently gained
attention due to peculiar magnetotransport phenomena that have been associated
with the possible existence of Weyl fermions, thought to arise from the
crossings of spin-split conduction and valence bands. On the other hand,
similar magnetotransport phenomena observed in other rare-earth intermetallics
have often been attributed to the interaction of itinerant carriers with
localized magnetic moments stemming from the -shell of the rare-earth
element. In order to address the origin of the magnetotransport phenomena in
GdPtBi, we performed a comprehensive study of the magnetization, electrical and
thermal magnetoresistivity on two single-crystalline GdPtBi samples. In
addition, we performed an analysis of the Fermi surface via Shubnikov-de Haas
oscillations in one of the samples and compared the results to \emph{ab initio}
band structure calculations. Our findings indicate that the electrical and
thermal magnetotransport in GdPtBi cannot be solely explained by Weyl physics
and is strongly influenced by the interaction of both itinerant charge carriers
and phonons with localized magnetic Gd-ions and possibly also paramagnetic
impurities.Comment: 11 figure
Assessing periodicity of periodic leg movements during sleep
Periodic leg movements (PLM) during sleep consist of involuntary periodic movements of the lower extremities. The debated functional relevance of PLM during sleep is based on correlation of clinical parameters with the PLM index (PLMI). However, periodicity in movements may not be reflected best by the PLMI. Here, an approach novel to the field of sleep research is used to reveal intrinsic periodicity in inter movement intervals (IMI) in patients with PLM
Strong anisotropy of electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations
In this study, we report on the observation of de Haas-van Alphen-type
quantum oscillations (QO) in the ultrasound velocity of NbP as well as `giant
QO' in the ultrasound attenuation in pulsed magnetic fields. The difference of
the QO amplitude for different acoustic modes reveals a strong anisotropy of
the effective deformation potential, which we estimate to be as high as
for certain parts of the Fermi surface. Furthermore, the
natural filtering of QO frequencies and the tracing of the individual Landau
levels to the quantum limit allows for a more detailed investigation of the
Fermi surface of NbP as was previously achieved by means of analyzing QO
observed in magnetization or electrical resistivity.Comment: 5 figure
Biophotonic sensors with integrated SiN-organic hybrid (SiNOH) lasers for point-of-care diagnostics
Early and efficient disease diagnosis with low-cost point-of-care devices is gaining importance for personalized medicine and public health protection. Within this context, waveguide-(WG)-based optical biosensors on the silicon-nitride (SiN) platform represent a particularly promising option, offering highly sensitive detection of indicative biomarkers in multiplexed sensor arrays operated by light in the visible-wavelength range. However, while passive Si3N4-based photonic circuits lend themselves to highly scalable mass production, the integration of low-cost light sources remains a challenge. In this paper, we demonstrate optical biosensors that combine Si3N4 sensor circuits with hybrid on-chip organic lasers. These Si3N4-organic hybrid (SiNOH) lasers rely on a dye-doped cladding material that are deposited on top of a passive WG and that are optically pumped by an external light source. Fabrication of the devices is simple: The underlying Si3N4 WGs are structured in a single lithography step, and the organic gain medium is subsequently applied by dispensing, spin-coating, or ink-jet printing processes. A highly parallel read-out of the optical sensor signals is accomplished with a simple camera. In our proof-of-concept experiment, we demonstrate the viability of the approach by detecting different concentrations of fibrinogen in phosphate-buffered saline solutions with a sensor-length (L-)-related sensitivity of S/L = 0.16 rad nM−1 mm−1. To our knowledge, this is the first demonstration of an integrated optical circuit driven by a co-integrated low-cost organic light source. We expect that the versatility of the device concept, the simple operation principle, and the compatibility with cost-efficient mass production will make the concept a highly attractive option for applications in biophotonics and point-of-care diagnostics
Detecting adverse childhood experiences with a little help from tablet computers
Adverse childhood experiences, ranging from abuse to emotional neglect, damage the mental and physical health and may impede the treatment of mental disorders. However, validated instruments that assess childhood adversity including the full range of childhood maltreatment are lacking. The adverse childhood experiences index (ACE; Dube et al., 2003; Felitti et al., 1998) retrospectively assessed different forms of abuse, neglect, and household dysfunctioning during the first 18 years of life, and quantified the ‘‘breadth of the experienced adversities’’, by means of the ACE score. Thus, this instrument allows quantifying the magnitude or ‘‘dose’’ of toxic childhood experiences. A recent modification of the ACE index, by Teicher and colleagues (2011, MACE Scale), gathers in even greater detailed and in more comprehensive ways information about the various types of maltreatment: self experienced abuse or neglect, as well as peer victimization and witnessing domestic violence are all explored in detail. Supplementary information gained about emotional reactions to the events, and temporal anchoring of the experienced, are highly valuable for psychotherapeutic and research purpose. We present short versions of the MACE and a pediatric version (Isele et al., in prep.), adjusted to the cognitive and emotional development status of minors. These new versions fill the need for structured clinical interviews, mapping abuse, and neglect in this sample. Their application in clinical research and therapeutic contexts is shown including an electronic tablet-computer supported assessment
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