1,140 research outputs found
Intrinsic mitigation of the after-gate attack in quantum key distribution through fast-gated delayed detection
The information theoretic security promised by quantum key distribution (QKD) holds as long as the assumptions in the theoretical model match the parameters in the physical implementation. The superlinear behaviour of sensitive single-photon detectors represents one such mismatch and can pave the way to powerful attacks hindering the security of QKD systems, a prominent example being the after-gate attack. A longstanding tenet is that trapped carriers causing delayed detection can help
mitigate this attack, but despite intensive scrutiny, it remains largely unproven. Here we approach this problem from a physical perspective and find new evidence to support a detector's secure response. We experimentally investigate two different carrier trapping mechanisms causing delayed detection in fast-gated semiconductor avalanche photodiodes, one arising from the multiplication layer, the other from the heterojunction interface between absorption and charge layers. The release of trapped carriers increases the quantum bit error rate measured under the after-gate attack above the typical QKD security threshold, thus favouring the detector's inherent security. This represents a significant step to avert quantum hacking of QKD systems
Genetic changes that increase 5-hydroxymethyl furfural resistance in ethanol-producing Escherichia coli LY180
The ability of a biocatalyst to tolerate furan inhibitors present in hemicellulose hydrolysates is important for the production of renewable chemicals. This study shows EMFR9, a furfural-tolerant mutant of ethanologenic E. coli LY180, has also acquired tolerance to 5-hydroxymethyl furfural (5-HMF). The mechanism of action of 5-HMF and furfural appear similar. Furan tolerance results primarily from lower expression of yqhD and dkgA, two furan reductases with a low Km for NADPH. Furan tolerance was also increased by adding plasmids encoding a NADPH/NADH transhydrogenase (pntAB). Together, these results support the hypothesis that the NADPH-dependent reduction of furans by YqhD and DkgA inhibits growth by competing with biosynthesis for this limiting cofactor
HLA-Associated Immune Pressure on Gag Protein in CRF01_AE-Infected Individuals and Its Association with Plasma Viral Load
BACKGROUND: The human leukocyte antigen (HLA)-restricted cytotoxic T-lymphocyte (CTL) immune response is one of the major factors determining the genetic diversity of human immunodeficiency virus (HIV). There are few population-based analyses of the amino acid variations associated with the host HLA type and their clinical relevance for the Asian population. Here, we identified HLA-associated polymorphisms in the HIV-1 CRF01_AE Gag protein in infected married couples, and examined the consequences of these HLA-selected mutations after transmission to HLA-unmatched recipients. METHODOLOGY/PRINCIPAL FINDINGS: One hundred sixteen HIV-1-infected couples were recruited at a government hospital in northern Thailand. The 1.7-kb gag gene was amplified and directly sequenced. We identified 56 associations between amino acid variations in Gag and HLA alleles. Of those amino acid variations, 35 (62.5%) were located within or adjacent to regions reported to be HIV-specific CTL epitopes restricted by the relevant HLA. Interestingly, a significant number of HLA-associated amino acid variations appear to be unique to the CRF01_AE-infected Thai population. Variations in the capsid protein (p24) had the strongest associations with the viral load and CD4 cell count. The mutation and reversion rates after transmission to a host with a different HLA environment varied considerably. The p24 T242N variant escape from B57/58 CTL had a significant impact on the HIV-1 viral load of CRF01_AE-infected patients. CONCLUSIONS/SIGNIFICANCE: HLA-associated amino acid mutations and the CTL selection pressures on the p24 antigen appear to have the most significant impact on HIV replication in a CRF01_AE-infected Asian population. HLA-associated mutations with a low reversion rate accumulated as a footprint in this Thai population. The novel HLA-associated mutations identified in this study encourage us to acquire more extensive information about the viral dynamics of HLA-associated amino acid polymorphisms in a given population as effective CTL vaccine targets
Increased S-nitrosylation and proteasomal degradation of caspase-3 during infection contribute to the persistence of adherent invasive escherichia coli (AIEC) in immune cells
Adherent invasive Escherichia coli (AIEC) have been implicated as a causative agent of Crohn's disease (CD) due to their isolation from the intestines of CD sufferers and their ability to persist in macrophages inducing granulomas. The rapid intracellular multiplication of AIEC sets it apart from other enteric pathogens such as Salmonella Typhimurium which after limited replication induce programmed cell death (PCD). Understanding the response of infected cells to the increased AIEC bacterial load and associated metabolic stress may offer insights into AIEC pathogenesis and its association with CD. Here we show that AIEC persistence within macrophages and dendritic cells is facilitated by increased proteasomal degradation of caspase-3. In addition S-nitrosylation of pro- and active forms of caspase-3, which can inhibit the enzymes activity, is increased in AIEC infected macrophages. This S-nitrosylated caspase-3 was seen to accumulate upon inhibition of the proteasome indicating an additional role for S-nitrosylation in inducing caspase-3 degradation in a manner independent of ubiquitination. In addition to the autophagic genetic defects that are linked to CD, this delay in apoptosis mediated in AIEC infected cells through increased degradation of caspase-3, may be an essential factor in its prolonged persistence in CD patients
Progression to AIDS in South Africa Is Associated with both Reverting and Compensatory Viral Mutations
We lack the understanding of why HIV-infected individuals in South Africa
progress to AIDS. We hypothesised that in end-stage disease there is a shifting
dynamic between T cell imposed immunity and viral immune escape, which, through
both compensatory and reverting viral mutations, results in increased viral
fitness, elevated plasma viral loads and disease progression. We explored how T
cell responses, viral adaptation and viral fitness inter-relate in South African
cohorts recruited from Bloemfontein, the Free State
(nâ=â278) and Durban, KwaZulu-Natal
(nâ=â775). Immune responses were measured by
Îł-interferon ELISPOT assays. HLA-associated viral polymorphisms were
determined using phylogenetically corrected techniques, and viral replication
capacity (VRC) was measured by comparing the growth rate of gag-protease
recombinant viruses against recombinant NL4-3 viruses. We report that in
advanced disease (CD4 counts <100 cells/Âľl), T cell responses narrow,
with a relative decline in Gag-directed responses (p<0.0001). This is
associated with preserved selection pressure at specific viral amino acids
(e.g., the T242N polymorphism within the HLA-B*57/5801 restricted TW10
epitope), but with reversion at other sites (e.g., the T186S polymorphism within
the HLA-B*8101 restricted TL9 epitope), most notably in Gag and suggestive
of âimmune relaxationâ. The median VRC from patients with CD4 counts
<100 cells/Âľl was higher than from patients with CD4 counts âĽ500
cells/Âľl (91.15% versus 85.19%,
pâ=â0.0004), potentially explaining the rise in viral load
associated with disease progression. Mutations at HIV Gag T186S and T242N
reduced VRC, however, in advanced disease only the T242N mutants demonstrated
increasing VRC, and were associated with compensatory mutations
(pâ=â0.013). These data provide novel insights into the
mechanisms of HIV disease progression in South Africa. Restoration of fitness
correlates with loss of viral control in late disease, with evidence for both
preserved and relaxed selection pressure across the HIV genome. Interventions
that maintain viral fitness costs could potentially slow progression
Quinoline Group Modified Carbon Nanotubes for the Detection of Zinc Ions
Carbon nanotubes (CNTs) were covalently modified by fluorescence ligand (glycine-N-8-quinolylamide) and formed a hybrid material which could be used as a selective probe for metal ions detection. The anchoring to the surface of the CNTs was carried out by the reaction between the precursor and the carboxyl groups available on the surface of the support. Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA) unambiguously proved the existence of covalent bonds between CNTs and functional ligands. Fluorescence characterization shows that the obtained organicâinorganic hybrid composite is highly selective and sensitive (0.2 ÎźM) to Zn(II) detection
Observation of associated near-side and away-side long-range correlations in âsNN=5.02ââTeV proton-lead collisions with the ATLAS detector
Two-particle correlations in relative azimuthal angle (ÎĎ) and pseudorapidity (ÎΡ) are measured in âsNN=5.02ââTeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1ââÎźb-1 of data as a function of transverse momentum (pT) and the transverse energy (ÎŁETPb) summed over 3.1<Ρ<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|ÎΡ|<5) ânear-sideâ (ÎĎâź0) correlation that grows rapidly with increasing ÎŁETPb. A long-range âaway-sideâ (ÎĎâźĎ) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ÎŁETPb, is found to match the near-side correlation in magnitude, shape (in ÎΡ and ÎĎ) and ÎŁETPb dependence. The resultant ÎĎ correlation is approximately symmetric about Ď/2, and is consistent with a dominant cosâĄ2ÎĎ modulation for all ÎŁETPb ranges and particle pT
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
Quantifying the impact of human immunodeficiency virus-1 escape from cytotoxic T-lymphocytes.
Published versio
Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV
The performance of muon reconstruction, identification, and triggering in CMS
has been studied using 40 inverse picobarns of data collected in pp collisions
at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection
criteria covering a wide range of physics analysis needs have been examined.
For all considered selections, the efficiency to reconstruct and identify a
muon with a transverse momentum pT larger than a few GeV is above 95% over the
whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4,
while the probability to misidentify a hadron as a muon is well below 1%. The
efficiency to trigger on single muons with pT above a few GeV is higher than
90% over the full eta range, and typically substantially better. The overall
momentum scale is measured to a precision of 0.2% with muons from Z decays. The
transverse momentum resolution varies from 1% to 6% depending on pseudorapidity
for muons with pT below 100 GeV and, using cosmic rays, it is shown to be
better than 10% in the central region up to pT = 1 TeV. Observed distributions
of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO
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