35 research outputs found
Higher-point conformal blocks and entanglement entropy in heavy states
We consider conformal blocks of two heavy operators and an arbitrary number
of light operators in a (1+1)-d CFT with large central charge. Using the
monodromy method, these higher-point conformal blocks are shown to factorize
into products of 4-point conformal blocks in the heavy-light limit for a class
of OPE channels. This result is reproduced by considering suitable worldline
configurations in the bulk conical defect geometry. We apply the CFT results to
calculate the entanglement entropy of an arbitrary number of disjoint intervals
for heavy states. The corresponding holographic entanglement entropy calculated
via the minimal area prescription precisely matches these results from CFT.
Along the way, we briefly illustrate the relation of these conformal blocks to
Riemann surfaces and their associated moduli space.Comment: 41 pages, 10 figures. (Published version; typos corrected and
references added.
Radio frequency spectroscopy of the attractive Hubbard model in a trap
Attractive interaction between fermions can lead to pairing and superfluidity
in an optical lattice. In contrast to the `continuum', on a lattice the trap
induced density variation can generate a non monotonic profile of the pairing
amplitude, and completely modify the spectral signatures of any possible
pseudogap phase. Using a tool that fully captures the inhomogeneity and strong
thermal fluctuations, we demonstrate how the crucial radio frequency signatures
of pairing are `inverted' in a trapped attractive fermion lattice compared to
the traditional continuum case. These features would be central in interpreting
any spectroscopic hint of fermion pairing and superfluidity.Comment: this article supersedes arXiv:1104.491
AIM2 activates the inflammasome and cell death in response to cytoplasmic DNA.
Host- and pathogen-associated cytoplasmic double-stranded DNA triggers the activation of a NALP3 (also known as cryopyrin and NLRP3)-independent inflammasome, which activates caspase-1 leading to maturation of pro-interleukin-1beta and inflammation. The nature of the cytoplasmic-DNA-sensing inflammasome is currently unknown. Here we show that AIM2 (absent in melanoma 2), an interferon-inducible HIN-200 family member that contains an amino-terminal pyrin domain and a carboxy-terminal oligonucleotide/oligosaccharide-binding domain, senses cytoplasmic DNA by means of its oligonucleotide/oligosaccharide-binding domain and interacts with ASC (apoptosis-associated speck-like protein containing a CARD) through its pyrin domain to activate caspase-1. The interaction of AIM2 with ASC also leads to the formation of the ASC pyroptosome, which induces pyroptotic cell death in cells containing caspase-1. Knockdown of AIM2 by short interfering RNA reduced inflammasome/pyroptosome activation by cytoplasmic DNA in human and mouse macrophages, whereas stable expression of AIM2 in the non-responsive human embryonic kidney 293T cell line conferred responsiveness to cytoplasmic DNA. Our results show that cytoplasmic DNA triggers formation of the AIM2 inflammasome by inducing AIM2 oligomerization. This study identifies AIM2 as an important inflammasome component that senses potentially dangerous cytoplasmic DNA, leading to activation of the ASC pyroptosome and caspase-1
The AIM2 inflammasome is critical for innate immunity to Francisella tularensis.
Francisella tularensis, the causative agent of tularemia, infects host macrophages, which triggers production of the proinflammatory cytokines interleukin 1beta (IL-1beta) and IL-18. We elucidate here how host macrophages recognize F. tularensis and elicit this proinflammatory response. Using mice deficient in the DNA-sensing inflammasome component AIM2, we demonstrate here that AIM2 is required for sensing F. tularensis. AIM2-deficient mice were extremely susceptible to F. tularensis infection, with greater mortality and bacterial burden than that of wild-type mice. Caspase-1 activation, IL-1beta secretion and cell death were absent in Aim2(-/-) macrophages in response to F. tularensis infection or the presence of cytoplasmic DNA. Our study identifies AIM2 as a crucial sensor of F. tularensis infection and provides genetic proof of its critical role in host innate immunity to intracellular pathogens
Developing Tailor-Made Microbial Consortium for Effluent Remediation
The work describes a biofilm-based soluble sulphate reduction system, which can treat up to 1600 ppm of soluble sulphate within 3.5 hours of incubation to discharge level under ambient condition using a well-characterized sulphate-reducing bacterial (SRB) consortium. This system ensures the treatment of 1509 litres of sulphate solution in 24 hours using a 220-litre bioreactor. Performance of the system during series operation was compromised, indicating the presence of inhibitor in solution at a toxic level. A single unit bioreactor would be the ideal configuration for this consortium. Modified designs of bioreactors were tested for optimization of the process using response surface methodology (RSM), where the system could function optimally at an initial sulphate concentration of 1250 ppm with a flow rate of 1.8 litre/hour. The time course of sulphate reduction yielded a parabolic profile (with coefficient of determination r
2 = 0.99 and p value < 0.05). The rate of sulphate reduction was found to be independent of seasonal variation as well as the specific design characteristic
The C-terminal tail of presenilin regulates Omi/HtrA2 protease activity
Presenilin mutations are responsible for most cases of autosomal dominant inherited forms of early onset Alzheimer disease. Presenilins play an important role in amyloid beta-precursor processing, NOTCH receptor signaling, and apoptosis. However, the molecular mechanisms by which presenilins regulate apoptosis are not fully understood. Here, we report that presenilin-1 (PS1) regulates the proteolytic activity of the serine protease Omi/HtrA2 through direct interaction with its regulatory PDZ domain. We show that a peptide corresponding to the cytoplasmic C-terminal tail of PS1 dramatically increases the proteolytic activity of Omi/HtrA2 toward the inhibitor of apoptosis proteins and beta-casein and induces cell death in an Omi/HtrA2-dependent manner. Consistent with these results, ectopic expression of full-length PS1, but not PS1 lacking the C-terminal PDZ binding motif, potentiated Omi/HtrA2-induced cell death. Our results suggest that the C terminus of PS1 is an activation peptide ligand for the PDZ domain of Omi/HtrA2 and may regulate the protease activity of Omi/HtrA2 after its release from the mitochondria during apoptosis. This mechanism of Omi/HtrA2 activation is similar to the mechanism of activation of the related bacterial DegS protease by the outer-membrane porins
A numerical solution to enzyme emulsion liquid membrane reactor model for sequential bienzymatic reaction
307-313Dynamic mathematical models of liquid
membrane-immobilized multienzyme reaction systems involve a large number of algebraic,
ordinary and nonlinear partial differential equations with different types of boundary
conditions. Solutions of such model equations are often difficult and stand in
the way of realistic modeling efforts in this field. In the present study, attempt
has been made to numerically solve such model equations for a liquid
membrane-immobilized sequential bienzymatic reaction system through development
of a software (MEMBSOL). In the solution process, partial differential
equations have been converted into ordinary differential equations by using a finite
difference technique in which the spatial derivatives have been discretized
while leaving the temporal derivatives unconverted. Through mathematical
manipulations, use of fictitious points at the boundaries has been eliminated thereby
making the solution-approach a general-purpose one.
To integrate the differential equations,
Runge-Kutta-Fehlberg method has been applied. An automatic step-size adjustment
mechanism has been incorporated in the integration process to produce results with
a reasonably desired level of accuracy. In the present computations, numerical solutions
with 0.1 percent relative error have been obtained
Studies on extraction of chromium(VI) from acidic solution by emulsion liquid membrane
713-718High molecular
weight amines, quaternary salts etc. have the potential of removing heavy metal
ions including the toxic ones at low concentrations. In the present work an
attempt has been made to extract Cr(VI) through emulsion liquid surfactant
membrane (or, emulsion liquid membrane-ELM) from it’s acidic solution using alamine-336
and caustic soda as extractant and striping reagents respectively. Around 97%
extraction of Cr(VI) from aqueous solutions of potassium dichromate through
batch experimentations have been achieved. Being crucial to the overall success
of the ELM processes, experiments on emulsion stability have also been
performed to arrive at a reasonably stable emulsion composition. Effect of
various process parameters such as initial solute concentration, concentration
of internal phase etc. as also that of pH on extraction of chromium have been
investigated.</i