501 research outputs found
A Mach-Zehnder Interferometer for a Two-Photon Wave Packet
We propose an experiment that permits observation of the de Broglie
two-photon wave packet behavior for a pair of photons, using a Mach-Zehnder
interferometer. It is based on the use of pulsed lasers to generate pairs of
photons via spontaneous parametric down-conversion and the post-selection of
events. It differs from previous realizations by the use of a third
time-correlated photon to engineer the state of the photons. The same technique
can give us which-path information via an ``interaction-free'' experiment and
can be used in other experiments on the foundations of quantum mechanics
related to wave-particle duality and to nonlocality.Comment: Submmited for publication in Physical Review
Motional effects of single trapped atomic/ionic qubit
We investigate theoretical decoherence effects of the motional degrees of
freedom of a single trapped atomic/ionic electronically coded qubit. For single
bit rotations from a resonant running wave laser field excitation, we found the
achievable fidelity to be determined by a single parameter characterized by the
motional states. Our quantitative results provide a useful realistic view for
current experimental efforts in quantum information and computing.Comment: 3 fig
Magneto-thermal evidence of a partial gap at the Fermi surface of UPt_2Si_2
Motivated by the observation of a giant Nernst effect in URu_2Si_2, the
thermoelectric response of the related system UPt_2Si_2 was investigated using
thermal and electric transport properties such as the Nernst and Seebeck
effects, thermal conductivity, Hall effect and electrical resitivity. Unlike
URu_2Si_2, UPt_2Si_2 is neither superconducting nor exhibits a ``hidden-order''
state. Nevertheless a pronounced Nernst effect anomaly is found to coincide
with the onset of the antiferromagnetic order in UPt_2Si_2. Although the
absolute values are substantially lower, its appearance and characteristics can
favorably be compared to the giant Nernst effect in URu_2Si_2 indicating the
common feature of a partial Fermi surface gap.Comment: 4 pages, 4 figure
Irreversible Effects of Ivermectin on Adult Parasites in Onchocerciasis Patients in the Onchocerciasis Control Programme in West Africa
Ivermectin is an effective drug for the treatment of human onchocerciasis, a disease caused by the parasitic filarial nematode Onchocerca volvulus. When humans are treated, the microfilariae normally found in the skin are rapidly and very nearly completely eliminated. Nonetheless, after a delay, microfilariae gradually reappear in the skin. This study is concerned with the causes of this delay. Hypotheses are tested by comparing the results of model calculations with skin microfilaria counts collected from 114 patients during a trial of five annual treatments in the focus area of Asubende, Ghana. The results obtained strongly suggest that annual treatment with ivermectin causes an irreversible decline in microfilariae production of ∼30%/treatment. This result has important implications for public health strategies designed to eliminate onchocerciasis as a significant health hazar
Observation of three-photon Greenberger-Horne-Zeilinger entanglement
We present the experimental observation of polarization entanglement for
three spatially separated photons. Such states of more than two entangled
particles, known as GHZ states, play a crucial role in fundamental tests of
quantum mechanics versus local realism and in many quantum information and
quantum computation schemes. Our experimental arrangement is such that we start
with two pairs of entangled photons and register one photon in a way that any
information as to which pair it belongs to is erased. The registered events at
the detectors for the remaining three photons then exhibit the desired GHZ
correlations.Comment: Revtex, 4 pages, uses floats, epsfi
Testing for cattle allergy: modified diagnostic cutoff levels improve sensitivity in symptomatic claw trimmers
Frequency of Peripheral CD8+ T Cells Expressing Chemo-Attractant Receptors CCR1, 4 and 5 Increases in NPC Patients with EBV Clearance upon Radiotherapy
Radiotherapy (RT) is the standard-of-care for Epstein–Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC), where the post-RT clearance of plasma EBV DNA is prognostic. Currently, it is not known whether the post-RT clearance of plasma EBV DNA is related to the presence of circulating T-cell subsets. Blood samples from NPC patients were used to assess the frequency of T-cell subsets relating to differentiation, co-signaling and chemotaxis. Patients with undetectable versus detectable plasma EBV DNA levels post-RT were categorized as clearers vs. non-clearers. Clearers had a lower frequency of PD1+CD8+ T cells as well as CXCR3+CD8+ T cells during RT compared to non-clearers. Clearers exclusively showed a temporal increase in chemo-attractant receptors CCR1, 4 and/or 5, expressing CD8+ T cells upon RT. The increase in CCR-expressing CD8+ T cells was accompanied by a drop in naïve CD8+ T cells and an increase in OX40+CD8+ T cells. Upon stratifying these patients based on clinical outcome, the dynamics of CCR-expressing CD8+ T cells were in concordance with the non-recurrence of NPC. In a second cohort, non-recurrence associated with higher quantities of circulating CCL14 and CCL15. Collectively, our findings relate plasma EBV DNA clearance post-RT to T-cell chemotaxis, which requires validation in larger cohorts.</p
Notch signaling during human T cell development
Notch signaling is critical during multiple stages of T cell development in both mouse and human. Evidence has emerged in recent years that this pathway might regulate T-lineage differentiation differently between both species. Here, we review our current understanding of how Notch signaling is activated and used during human T cell development. First, we set the stage by describing the developmental steps that make up human T cell development before describing the expression profiles of Notch receptors, ligands, and target genes during this process. To delineate stage-specific roles for Notch signaling during human T cell development, we subsequently try to interpret the functional Notch studies that have been performed in light of these expression profiles and compare this to its suggested role in the mouse
Breakfast partly restores the anti-inflammatory function of high-density lipoproteins from patients with type 2 diabetes mellitus
BACKGROUND AND AIMS: High-density lipoproteins (HDL) of patients with type 2 diabetes mellitus (T2DM) have impaired anti-inflammatory activities. The anti-inflammatory activity of HDL has been determined ex vivo after isolation by different methods from blood mostly obtained after overnight fasting. We first determined the effect of the HDL isolation method, and subsequently the effect of food intake on the anti-inflammatory function of HDL from T2DM patients. METHODS: Blood was collected from healthy controls and T2DM patients after an overnight fast, and from T2DM patients 3 h after breakfast (n = 17 each). HDL was isolated by a two-step density gradient ultracentrifugation in iodixanol (HDL(DGUC2)), by sequential salt density flotation (HDL(SEQ)) or by PEG precipitation (HDL(PEG)). The anti-inflammatory function of HDL was determined by the reduction of the TNFα-induced expression of VCAM-1 in human coronary artery endothelial cells (HCAEC) and retinal endothelial cells (REC). RESULTS: HDL isolated by the three different methods from healthy controls inhibited TNFα-induced VCAM-1 expression in HCAEC. With apoA-I at 0.7 μM, HDL(DGUC2) and HDL(SEQ) were similarly effective (16% versus 14% reduction; n = 3; p > 0.05) but less effective than HDL(PEG) (28%, p < 0.05). Since ultracentrifugation removes most of the unbound plasma proteins, we used HDL(DGUC2) for further experiments. With apoA-I at 3.2 μM, HDL from fasting healthy controls and T2DM patients reduced TNFα-induced VCAM-1 expression in HCAEC by 58 ± 13% and 51 ± 20%, respectively (p = 0.35), and in REC by 42 ± 13% and 25 ± 18%, respectively (p < 0.05). Compared to preprandial HDL, postprandial HDL from T2DM patients reduced VCAM-1 expression by 56 ± 16% (paired test: p < 0.001) in HCAEC and by 34 ± 13% (paired test: p < 0.05) in REC. CONCLUSIONS: The ex vivo anti-inflammatory activity of HDL is affected by the HDL isolation method. Two-step ultracentrifugation in an iodixanol gradient is a suitable method for HDL isolation when testing HDL anti-inflammatory function. The anti-inflammatory activity of HDL from overnight fasted T2DM patients is significantly impaired in REC but not in HCAEC. The anti-inflammatory function of HDL is partly restored by food intake
- …