1,768 research outputs found
Single-shot compressed ultrafast photography: a review
Compressed ultrafast photography (CUP) is a burgeoning single-shot computational imaging technique that provides an imaging speed as high as 10 trillion frames per second and a sequence depth of up to a few hundred frames. This technique synergizes compressed sensing and the streak camera technique to capture nonrepeatable ultrafast transient events with a single shot. With recent unprecedented technical developments and extensions of this methodology, it has been widely used in ultrafast optical imaging and metrology, ultrafast electron diffraction and microscopy, and information security protection. We review the basic principles of CUP, its recent advances in data acquisition and image reconstruction, its fusions with other modalities, and its unique applications in multiple research fields
Learning and Recognition of a Non-conscious Sequence of Events in Human Primary Visual Cortex
Published Online: March 03, 2016Human primary visual cortex (V1) has long been
associated with learning simple low-level visual discriminations
[1] and is classically considered outside
of neural systems that support high-level cognitive
behavior in contexts that differ from the original
conditions of learning, such as recognition memory
[2, 3]. Here, we used a novel fMRI-based dichoptic
masking protocol—designed to induce activity in
V1, without modulation from visual awareness—to
test whether human V1 is implicated in human observers
rapidly learning and then later (15–20 min)
recognizing a non-conscious and complex (secondorder)
visuospatial sequence. Learning was associated
with a change in V1 activity, as part of a
temporo-occipital and basal ganglia network, which
is at variance with the cortico-cerebellar network
identified in prior studies of ‘‘implicit’’ sequence
learning that involved motor responses and visible
stimuli (e.g., [4]). Recognition memory was associated
with V1 activity, as part of a temporo-occipital
network involving the hippocampus, under conditions
that were not imputable to mechanisms associated
with conscious retrieval. Notably, the V1 responses
during learning and recognition separately
predicted non-conscious recognition memory, and
functional coupling between V1 and the hippocampus
was enhanced for old retrieval cues. The results
provide a basis for novel hypotheses about the
signals that can drive recognition memory, because
these data (1) identify human V1 with a memory
network that can code complex associative serial
visuospatial information and support later nonconscious
recognition memory-guided behavior (cf.
[5]) and (2) align with mouse models of experiencedependent
V1 plasticity in learning and memory [6].This work was supported by the Wellcome Trust (WT073735MA;
C.R.R. and C.K.; http://www.wellcome.ac.uk/), the Medical Research Council
(UK, 89631; D.S.; http://www.mrc.ac.uk/), the National Institute for Health
Research (NIHR) Oxford Biomedical Research Centre based at Oxford University
Hospitals NHS Trust and University of Oxford (C.R.R., C.A.A., and C.K.;
http://oxfordbrc.nihr.ac.uk/), and the Dementias and Neurodegenerative Diseases
Research Network (C.A.A.; https://www.crn.nihr.ac.uk/dementia)
Correlated Pseudorandomness from the Hardness of Quasi-Abelian Decoding
Secure computation often benefits from the use of correlated randomness to
achieve fast, non-cryptographic online protocols. A recent paradigm put forth
by Boyle (CCS 2018, Crypto 2019) showed how pseudorandom
correlation generators (PCG) can be used to generate large amounts of useful
forms of correlated (pseudo)randomness, using minimal interactions followed
solely by local computations, yielding silent secure two-party computation
protocols (protocols where the preprocessing phase requires almost no
communication). An additional property called programmability allows to extend
this to build N-party protocols. However, known constructions for programmable
PCG's can only produce OLE's over large fields, and use rather new splittable
Ring-LPN assumption.
In this work, we overcome both limitations. To this end, we introduce the
quasi-abelian syndrome decoding problem (QA-SD), a family of assumptions which
generalises the well-established quasi-cyclic syndrome decoding assumption.
Building upon QA-SD, we construct new programmable PCG's for OLE's over any
field with . Our analysis also sheds light on the security
of the ring-LPN assumption used in Boyle (Crypto 2020). Using
our new PCG's, we obtain the first efficient N-party silent secure computation
protocols for computing general arithmetic circuit over for any
.Comment: This is a long version of a paper accepted at CRYPTO'2
Dispersion-shifted all-solid high index-contrast microstructured optical fiber for nonlinear applications at 1.55µm
We report the fabrication of an all-solid highly nonlinear microstructured optical fiber. The structured preform was made by glass extrusion using two types of commercial lead silicate glasses that provide high index-contrast. Effectively single-moded guidance was observed in the fiber at 1.55µm. The effective nonlinearity and the propagation loss at this wavelength were measured to be 120W/km respectively at 1.55µm. These predictions are consistent with the experimentally determined dispersion of +12.5ps/nm/km at 1.55µm. Tunable and efficient four-wave-mixing based wavelength conversion was demonstrated at wavelengths around 1.55µm using a 1.5m length of the fiber
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