456 research outputs found
Suppression of spin relaxation in an InAs nanowire double quantum dot
We investigate the triplet-singlet relaxation in a double quantum dot defined
by top-gates in an InAs nanowire. In the Pauli spin blockade regime, the
leakage current can be mainly attributed to spin relaxation. While at weak and
strong inter-dot coupling relaxation is dominated by two individual mechanisms,
the relaxation is strongly reduced at intermediate coupling and finite magnetic
field. In addition we observe a charateristic bistability of the spin-non
conserving current as a function of magnetic field. We propose a model where
these features are explained by the polarization of nuclear spins enabled by
the interplay between hyperfine and spin-orbit mediated relaxation.Comment: 5 pages, 4 figure
More is Better: A Meta-Analysis of Dose and Efficacy in Face-to-Face Psychological Treatments for Gambling Disorder
More is Better: A Meta-Analysis of Dose and Efficacy in Face-to-Face Psychological Treatments for Gambling Disorde
Self-aligned charge read-out for InAs nanowire quantum dots
A highly sensitive charge detector is realized for a quantum dot in an InAs
nanowire. We have developed a self-aligned etching process to fabricate in a
single step a quantum point contact in a two-dimensional electron gas and a
quantum dot in an InAs nanowire. The quantum dot is strongly coupled to the
underlying point contact which is used as a charge detector. The addition of
one electron to the quantum dot leads to a change of the conductance of the
charge detector by typically 20%. The charge sensitivity of the detector is
used to measure Coulomb diamonds as well as charging events outside the dot.
Charge stability diagrams measured by transport through the quantum dot and
charge detection merge perfectly.Comment: 11 pages, 3 figure
Relative Impact of Key Rendering Parameters on Perceived Quality of VR Imagery Captured by the Facebook Surround 360 Camera
High quality, 360 capture for Cinematic VR is a relatively new and rapidly evolving technology. The field demands very high quality, distortion- free 360 capture which is not possible with cameras that depend on fish- eye lenses for capturing a 360 field of view. The Facebook Surround 360 Camera, one of the few āplayersā in this space, is an open-source license design that Facebook has released for anyone that chooses to build it from oļ¬-the-shelf components and generate 8K stereo output using open-source licensed rendering software. However, the components are expensive and the system itself is extremely demanding in terms of computer hardware and software. Because of this, there have been very few implementations of this design and virtually no real deployment in the field. We have implemented the system, based on Facebookās design, and have been testing and deploying it in various situations; even generating short video clips. We have discovered in our recent experience that high quality, 360 capture comes with its own set of new challenges. As an example, even the most fundamental tools of photography like āexposureā become diļ¬cult because one is always faced with ultra-high dynamic range scenes (one camera is pointing directly at the sun and the others may be pointing to a dark shadow). The conventional imaging pipeline is further complicated by the fact that the stitching software has diļ¬erent eļ¬ects on various as- pects of the calibration or pipeline optimization. Most of our focus to date has been on optimizing the imaging pipeline and improving the qual- ity of the output for viewing in an Oculus Rift headset. We designed a controlled experiment to study 5 key parameters in the rendering pipelineā black level, neutral balance, color correction matrix (CCM), geometric calibration and vignetting. By varying all of these parameters in a combinatorial manner, we were able to assess the relative impact of these parameters on the perceived image quality of the output.
Our results thus far indicate that the output image quality is greatly influenced by the black level of the individual cameras (the Facebook cam- era comprised of 17 cameras whose output need to be stitched to obtain a 360 view). Neutral balance is least sensitive. We are most confused about the results we obtain from accurately calculating and applying the CCM for each individual camera. We obtained improved results by using the average of the matrices for all cameras. Future work includes evaluating the eļ¬ects of geometric calibration and vignetting on quality
Zinc(II) Complexes with Triplet Charge-Transfer Excited States Enabling Energy-Transfer Catalysis, Photoinduced Electron Transfer, and Upconversion
Many CuI complexes have luminescent triplet charge-transfer excited states with diverse applications in photophysics and photochemistry, but for isoelectronic ZnII compounds, this behavior is much less common, and they typically only show ligand-based fluorescence from singlet ĻāĻ* states. We report two closely related tetrahedral ZnII compounds, in which intersystem crossing occurs with appreciable quantum yields and leads to the population of triplet excited states with intraligand charge-transfer (ILCT) character. In addition to showing fluorescence from their initially excited 1ILCT states, these new compounds therefore undergo tripletātriplet energy transfer (TTET) from their 3ILCT states and consequently can act as sensitizers for photo-isomerization reactions and tripletātriplet annihilation upconversion from the blue to the ultraviolet spectral range. The photoactive 3ILCT state furthermore facilitates photoinduced electron transfer. Collectively, our findings demonstrate that mononuclear ZnII compounds with photophysical and photochemical properties reminiscent of well-known CuI complexes are accessible with suitable ligands and that they are potentially amenable to many different applications. Our insights seem relevant in the greater context of obtaining photoactive compounds based on abundant transition metals, complementing well-known precious-metal-based luminophores and photosensitizers
Dynamics of coupled spins in quantum dots with strong spin-orbit interaction
We investigated the time dependence of two-electron spin states in a double
quantum dot fabricated in an InAs nanowire. In this system, spin-orbit
interaction has substantial influence on the spin states of confined electrons.
Pumping single electrons through a Pauli spin-blockade configuration allowed to
probe the dynamics of the two coupled spins via their influence on the pumped
current. We observed spin-relaxation with a magnetic field dependence different
from GaAs dots, which can be explained by spin-orbit interaction. Oscillations
were detected for times shorter than the relaxation time, which we attribute to
coherent evolution of the spin states.Comment: 5 pages, 4 figure
Geometrical enhancement of the proximity effect in quantum wires with extended superconducting tunnel contacts
We study Andreev reflection in a ballistic one-dimensional channel coupled in
parallel to a superconductor via a tunnel barrier of finite length . The
dependence of the low-energy Andreev reflection probability on
reveals the existence of a characteristic length scale beyond which
is enhanced up to unity despite the low interfacial transparency. The
Andreev reflection enhancement is due to the strong mixing of particle and hole
states that builds up in contacts exceeding the coherence length ,
leading to a small energy gap (minigap) in the density of states of the normal
system. The role of the geometry of such hybrid contacts is discussed in the
context of the experimental observation of zero-bias Andreev anomalies in the
resistance of extended carbon nanotube/superconductor junctions in field effect
transistor setups.Comment: 11 pages, 8 figures; minor revisions including added Ref. 7 and inset
to Fig. 3b; version as accepted for publication to Phys. Rev.
Postoperative outcome of ambulatory dogs with intervertebral disc extrusion causing incontinence and/or tail dysfunction:18 cases (2010-2020)
OBJECTIVES: To assess the recovery of urinary continence, faecal continence and tail function in ambulatory dogs with caudal lumbar intervertebral disc extrusion and to explore clinical factors that may be associated with recovery. MATERIALS AND METHODS: Medical records from January 2010 to December 2020 were searched to identify ambulatory dogs undergoing surgical treatment for a caudal lumbar intervertebral disc extrusion causing urinary incontinence, faecal incontinence and/or tail dysfunction. Signalment, history, presenting clinical signs, neurological examination findings, diagnostic test results, treatment and outcome were recorded for all dogs. RESULTS: Eighteen dogs with caudal lumbar intervertebral disc extrusion causing tail dysfunction, urinary and/or faecal incontinence were included. Urinary continence was recovered in 12 (86%) of 14 affected dogs, faecal continence recovered in nine (90%) of 10 affected dogs and tail function recovered in 13 (87%) of 15 affected dogs. Loss of tail nociception was recorded in three dogs on presentation; two made a full recovery and one showed mild persistent tail paresis. CLINICAL SIGNIFICANCE: The prognosis for functional recovery of urinary continence, faecal continence and tail function in ambulatory dogs with caudal lumbar intervertebral disc extrusion following surgical treatment is good. Larger studies are needed to identify prognostic factors associated with failure of recovery
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