550 research outputs found
Evidence for Direct Involvement of the Capsid Protein in HIV Infection of Nondividing Cells
HIV and other lentiviruses can productively infect nondividing cells, whereas most other retroviruses, such as murine leukemia virus, require cell division for efficient infection. However, the determinants for this phenotype have been controversial. Here, we show that HIV-1 capsid (CA) is involved in facilitating HIV infection of nondividing cells because amino acid changes on CA severely disrupt the cell-cycle independence of HIV. One mutant in the N-terminal domain of CA in particular has lost the cell-cycle independence in all cells tested, including primary macrophages. The defect in this mutant appears to be at a stage past nuclear entry. We also find that the loss of cell-cycle independence can be cell-type specific, which suggests that a cellular factor affects the ability of HIV to infect nondividing cells. Our data suggest that CA is directly involved at some step in the viral life cycle that is important for infection of nondividing cells
Multiphoton Discrete Fractional Fourier Dynamics in Waveguide Beam Splitters
We demonstrate that when a waveguide beam splitter (BS) is excited by N
indistinguishable photons, the arising multiphoton states evolve in a way as if
they were coupled to each other with coupling strengths that are identical to
the ones exhibited by a discrete fractional Fourier system. Based on the
properties of the discrete fractional Fourier transform, we then derive a
multiphoton suppression law for 50/50 BSs, thereby generalizing the
Hong-Ou-Mandel effect. Furthermore, we examine the possibility of performing
simultaneous multiphoton quantum random walks by using a single waveguide BS in
combination with photon number resolving detectors. We anticipate that the
multiphoton lattice-like structures unveiled in this work will be useful to
identify new effects and applications of high-dimensional multiphoton states.Comment: Accepted for publication in JOSA B on June 26, 201
Assessment of the toll-like receptor 4 Asp299Gly, Thr399Ile and interleukin-8 -251 polymorphisms in the risk for the development of distal gastric cancer
<p>Abstract</p> <p>Background</p> <p>The intensity of the inflammation induced by <it>Helicobacter pylori </it>colonization is associated with the development of distal gastric cancer (GC). The host response to <it>H</it>. <it>pylori </it>has been related to genetic polymorphisms that influence both innate and adaptive immune responses.</p> <p>Our aim was to investigate whether the presence of the <it>TLR4 Asp299Gly</it>, <it>TLR4 Thr399Ile </it>and <it>IL-8-251 </it>A/T polymorphisms had any influence in the development of distal GC in a Mexican population.</p> <p>Methods</p> <p>We studied 337 patients that were divided in two groups: 78 patients with histologically confirmed distal GC and 259 non-cancer controls. The presence of <it>H. pylori </it>in the control population was defined by positive results of at least two of four diagnostic tests: serology, histology, rapid urease test and culture. Human DNA was purified and genotyped for <it>TLR4 Asp299Gly </it>polymorphism by pyrosequencing, for <it>TLR4 Thr399Ile </it>by PCR-RFLP and for <it>IL8-251 </it>by the amplification refractory mutation system (ARMS)-PCR.</p> <p>Results</p> <p>The non-cancer control group was found to be in Hardy-Weinberg equilibrium at the polymorphic loci studied (chi-square <sub>H-W </sub>= 0.58 for <it>IL8-251</it>, 0.42 for <it>TLR4 Asp299Gly </it>and 0.17 for <it>TLR4 Thr399Ile</it>). The frequencies of mutated alleles (homozygous plus heterozygous) were compared between cases and controls. We found no significant difference for <it>TLR4- Asp299Gly </it>[the 7.7% of distal GC patients and 7.7 % non-cancer controls (p = 0.82)] and for <it>TLR4 Thr399Ile </it>[the 1.3% of GC patients and the 5% of the control population (p = 0.2)]. In contrast, for <it>IL-8-251 </it>A/T, 80.77% of the GC patients and 66.4% in the control group age and gender matched had at least one copy of mutated allele (OR = 2.12, 95% CI = 1.1–4.2) (p = 0.023).</p> <p>Conclusion</p> <p>This study showed that the <it>IL8-251*A </it>allele could be related to the development of distal gastric cancer in this Mexican population.</p
Identification of Light Sources using Machine Learning
The identification of light sources represents a task of utmost importance
for the development of multiple photonic technologies. Over the last decades,
the identification of light sources as diverse as sunlight, laser radiation and
molecule fluorescence has relied on the collection of photon statistics or the
implementation of quantum state tomography. In general, this task requires an
extensive number of measurements to unveil the characteristic statistical
fluctuations and correlation properties of light, particularly in the
low-photon flux regime. In this article, we exploit the self-learning features
of artificial neural networks and naive Bayes classifier to dramatically reduce
the number of measurements required to discriminate thermal light from coherent
light at the single-photon level. We demonstrate robust light identification
with tens of measurements at mean photon numbers below one. Our work
demonstrates an improvement in terms of the number of measurements of several
orders of magnitude with respect to conventional schemes for characterization
of light sources. Our work has important implications for multiple photonic
technologies such as LIDAR and microscopy.Comment: 8 pages, 10 figure
Exceptional points of any order in a single, lossy waveguide beam splitter by photon-number-resolved detection
Exceptional points (EPs) are degeneracies of non-Hermitian operators where, in addition to the eigenvalues, the corresponding eigenmodes become degenerate. Classical and quantum photonic systems with EPs have attracted tremendous attention due to their unusual properties, topological features, and an enhanced sensitivity that depends on the order of the EP, i.e., the number of degenerate eigenmodes. Yet, experimentally engineering higher-order EPs in classical or quantum domains remain an open challenge due to the stringent symmetry constraints that are required for the coalescence of multiple eigenmodes. Here, we analytically show that the number-resolved dynamics of a single, lossy waveguide beam splitter, excited by indistinguishable photons and post-selected to the -photon subspace, will exhibit an EP of order +1. By using the well-established mapping between a beam splitter Hamiltonian and the perfect state transfer model in the photon-number space, we analytically obtain the time evolution of a general -photon state and numerically simulate the system’s evolution in the post-selected manifold. Our results pave the way toward realizing robust, arbitrary-order EPs on demand in a single device
Multiphoton Quantum-State Engineering using Conditional Measurements
The quantum theory of electromagnetic radiation predicts characteristic
statistical fluctuations for light sources as diverse as sunlight, laser
radiation and molecule fluorescence. Indeed, these underlying statistical
fluctuations of light are associated with the fundamental physical processes
behind their generation. In this contribution, we demonstrate that the
manipulation of the quantum electromagnetic fluctuations of a pair of vacuum
states leads to a novel family of quantum-correlated multiphoton states with
tunable mean photon numbers and degree of correlation. Our technique relies on
the use of conditional measurements to engineer the excitation mode of the
field through the simultaneous subtraction of photons from two-mode squeezed
vacuum states. The experimental generation of multiphoton states with quantum
correlations by means of photon subtraction unveils novel mechanisms to control
fundamental properties of light. As a remarkable example, we demonstrate the
engineering of a quantum correlated state of light, with nearly Poissonian
photon statistics, that constitutes the first step towards the generation of
entangled lasers. Our technique enables a robust protocol to prepare quantum
states with multiple photons in high-dimensional spaces and, as such, it
constitutes a novel platform for exploring quantum phenomena in mesoscopic
systems
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