Search results for " magnitude"
showing 10 items of 407 documents
Search for Coherent Elastic Scattering of Solar B8 Neutrinos in the XENON1T Dark Matter Experiment
2021
We report on a search for nuclear recoil signals from solar $^8$B neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold from 2.6 keV to 1.6 keV. We develop a variety of novel techniques to limit the resulting increase in backgrounds near the threshold. No significant $^8$B neutrino-like excess is found in an exposure of 0.6 t $\times$ y. For the first time, we use the non-detection of solar neutrinos to constrain the light yield from 1-2 keV nuclear recoils in liquid xenon, as well as non-standard neutrino-quark interactions. Finally, we improve upon world-leading constraints on dark matter-nucleus interactions for dark matter masses between 3 GeV/…
Measurement of ultra-low heating rates of a single antiproton in a cryogenic Penning trap
2019
Physical review letters 122(4), 043201 (2019). doi:10.1103/PhysRevLett.122.043201
Modelling of silver adhesion on MgO(100) surface with defects
1999
We show how surface defects (especially Fs 0 and Vs 0 centres) can play a major role in the adhesion of Ag (at 1:4 and 1:1 coverages) on the MgO(100) surface. Our calculations use a periodic (slab) model and an ab initio Hartree-Fock approach with a posteriori electron correlation corrections. We are able to analyse the interatomic bond populations, effective charges and multipole moments of ions, in combination with the interface binding energy and the equilibrium distances. Both surface defects cause strong redistributions of the electron density which increase the binding energy of metal atoms by more than an order of magnitude. This implies radiation-induced strengthening of metal adhes…
Increased conductivity of a hole transport layer due to oxidation by a molecular nanomagnet
2008
Thin film transistors based on polyarylamine poly?N,N?-diphenyl-N,N ?bis?4-hexylphenyl?- ?1,1?biphenyl?-4,4?-diamine ?pTPD? were fabricated using spin coating in order to measure the mobility of pTPD upon oxidation. Partially oxidized pTPD with a molecular magnetic cluster showed an increase in mobility of over two orders of magnitude. A transition in the mobility of pTPD upon doping could also be observed by the presence of a maximum obtained for a given oxidant ratio and subsequent decrease for a higher ratio. Such result agrees well with a previously reported model based on the combined effect of dipolar broadening of the density of states and transport manifold filling. Peer Reviewed
Protocols for UV camera volcanic SO2 measurements
2010
Abstract Ultraviolet camera technology offers considerable promise for enabling 1 Hz timescale acquisitions of volcanic degassing phenomena, providing two orders of magnitude improvements on sampling frequencies from conventionally applied scanning spectrometer systems. This could, for instance enable unprecedented insights into rapid processes, such as strombolian explosions, and non-aliased corroboration with volcano geophysical data. The uptake of this technology has involved disparate methodological approaches, hitherto. As a means of expediting the further proliferation of such systems, we here study these diverse protocols, with the aim of suggesting those we consider optimal. In part…
Denoising Autoencoders for Fast Combinatorial Black Box Optimization
2015
Estimation of Distribution Algorithms (EDAs) require flexible probability models that can be efficiently learned and sampled. Autoencoders (AE) are generative stochastic networks with these desired properties. We integrate a special type of AE, the Denoising Autoencoder (DAE), into an EDA and evaluate the performance of DAE-EDA on several combinatorial optimization problems with a single objective. We asses the number of fitness evaluations as well as the required CPU times. We compare the results to the performance to the Bayesian Optimization Algorithm (BOA) and RBM-EDA, another EDA which is based on a generative neural network which has proven competitive with BOA. For the considered pro…
A Convolutional Neural Network based Cascade Reconstruction for the IceCube Neutrino Observatory
2021
Continued improvements on existing reconstruction methods are vital to the success of high-energy physics experiments, such as the IceCube Neutrino Observatory. In IceCube, further challenges arise as the detector is situated at the geographic South Pole where computational resources are limited. However, to perform real-time analyses and to issue alerts to telescopes around the world, powerful and fast reconstruction methods are desired. Deep neural networks can be extremely powerful, and their usage is computationally inexpensive once the networks are trained. These characteristics make a deep learning-based approach an excellent candidate for the application in IceCube. A reconstruction …
Chalcogenide thin films for direct resistors fabrication and trimming
2004
Abstract The fabrication of thin film resistors based on Ge–Sb–Te chalcogenide alloys is proposed. By exploiting the phase change properties of the deposited film, a laser beam is used for inducing a transition from high to low resistivity along selected paths. Conductivity changes as high as four orders of magnitude can be routinely achieved. This candidates the technique for maskless fabrication of compact precision resistors for a variety of applications.
Liquid-phase alkali-doping of individual carbon nanotube field-effect transistors observed in real-time
2011
The carbon nanotube (CNT) is known to be very sensitive to changes in its surrounding environment. Our study is on the effects of mild, liquid-phase alkali-doping on electronic transport in individual CNTs. We find clear and consistent reversal from p- to n-type behavior, with all seven investigated CNT field-effect transistors (FETs) retaining a similar ON/OFF ratio and subthreshold slope. We have also measured the realtime electronic response during liquid-phase doping, and demonstrate detection of alkali cations with a signal response that ranges over more than three orders of magnitude. The doping is fully reversible upon exposure to oxygen, and the doping cycle is repeatable. We also c…
Enhancing single-parameter quantum charge pumping in carbon-based devices
2011
We present a theoretical study of quantum charge pumping with a single ac gate applied to graphene nanoribbons and carbon nanotubes operating with low resistance contacts. By combining Floquet theory with Green's function formalism, we show that the pumped current can be tuned and enhanced by up to two orders of magnitude by an appropriate choice of device length, gate voltage intensity and driving frequency and amplitude. These results offer a promising alternative for enhancing the pumped currents in these carbon-based devices.