1,252 research outputs found
Cluster Model for Near-barrier Fusion Induced by Weakly Bound and Halo Nuclei
The influence on the fusion process of coupling transfer/breakup channels is
investigated for the medium weight Li+Co systems in the vicinity
of the Coulomb barrier. Coupling effects are discussed within a comparison of
predictions of the Continuum Discretized Coupled-Channels model. Applications
to He+Co induced by the borromean halo nucleus He are also
proposed.Comment: 5 pages, 3 figures, FINUSTAR2 Conference, Aghios Nikolaus, Crete,
Greece. 10-14 September 200
Pulse sequences for measuring exchange rates between proton species: From unlocalised NMR spectroscopy to chemical exchange saturation transfer imaging
Within the field of NMR spectroscopy, the study of chemical exchange processes through saturation transfer techniques has a long history. In the context of MRI, chemical exchange techniques have been adapted to increase the sensitivity of imaging to small fractions of exchangeable protons, including the labile protons of amines, amides and hydroxyls. The MR contrast is generated by frequency-selective irradiation of the labile protons, which results in a reduction of the water signal associated with transfer of the labile protons’ saturated magnetization to the protons of the surrounding free water. The signal intensity depends on the rate of chemical exchange and the concentration of labile protons as well as on the properties of the irradiation field. This methodology is referred to as CEST (chemical exchange saturation transfer) imaging. Applications of CEST include imaging of molecules with short transverse relaxation times and mapping of physiological parameters such as pH, temperature, buffer concentration and chemical composition due to the dependency of this chemical exchange effect on all these parameters. This article aims to describe these effects both theoretically and experimentally. In depth analysis and mathematical modelling are provided for all pulse sequences designed to date to measure the chemical exchange rate. Importantly, it has become clear that the background signal from semi-solid protons and the presence of the Nuclear Overhauser Effect (NOE), either through direct dipole-dipole mechanisms or through exchange-relayed signals, complicates the analysis of CEST effects. Therefore, advanced methods to suppress these confounding factors have been developed, and these are also reviewed. Finally, the experimental work conducted both in vitro and in vivo is discussed and the progress of CEST imaging towards clinical practice is presented
Premitotic Labeling and Inflammation in the Gingiva of Rhesus Monkeys
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141674/1/jper0606.pd
Open, sesame! Introducing access control to voice services
Personal voice assistants (VAs) are shown to be vulnerable against record–and–replay, and other acoustic attacks which allow an adversary to gain unauthorized control of connected devices within a smart home. Existing defenses either lack detection and management capabilities or are too coarse-grained to enable flexible policies on par with other computing interfaces. In this work, we present Sesame, a lightweight framework for edge devices which is the first to enable fine-grained access control of smart-home voice commands. Sesame combines three components: Automatic SpeechRecognition, Natural Language Understanding (NLU) and a Policymodule. We implemented Sesame on Android devices and demonstrate that our system can enforce security policies for both Alexa and Google Home in real-time (362ms end-to-end inference time), with a lightweight (<25MB) NLU model which exhibits minimal accuracy loss compared to its non-compact equivalent
Dynamical and quasistatic structural relaxation paths in Pd_(40)Ni_(40)P_(20) glass
By sequential heat treatment of a Pd_(40)Ni_(40)P_(20) metallic glass at temperatures and durations for which
α-relaxation is not possible, dynamic, and quasistatic relaxation paths below the glass transition are
identified via ex situ ultrasonic measurements following each heat treatment. The dynamic
relaxation paths are associated with hopping between nonequilibrium potential energy states of the
glass, while the quasistatic relaxation path is associated with reversible β-relaxation events toward
quasiequilibrium states. These quasiequilibrium states are identified with secondary potential energy
minima that exist within the inherent energy minimum of the glass, thereby supporting the concept
of the sub-basin/metabasin organization of the potential-energy landscape
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