5,051 research outputs found
Molecular characterization of novel ADP-ribosyl cyclases from the sea urchin
Calcium signalling is ubiquitous and regulates diverse cellular processes. Cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) are second messengers that are involved in calcium release from the intracellular organelles. These molecules are structurally and mechanistically distinct but synthesised by a common enzyme, ADP-ribosyl cyclase (ARC). The sea urchin has long been a model system for both calcium signalling and embryogenesis. In fact, cADPR and NAADP were both discovered in the sea urchin. However, molecular details of ARCs and their roles during development are limited. Recently three ARC isoforms: SpARC1, SpARC2 and SpARC3 were identified from the sea urchin. In this study, additional novel isoforms including SpARC4 were cloned from S.purpuratus, highlighting the further expansion of ARCs in basal deuterostomes. SpARC2, SpARC3 and SpARC4 were found to be glycoproteins tethered to the plasma membrane via a GPI-anchor. SpARC2 and SpARC4 were multi-functional and able to produce both cADPR and NAADP over a wide pH range. SpARC2 was a preferential base-exchanger and SpARC4 a preferential cyclase. A unique non-canonical active site tyrosine residue regulated the cyclisation: base-exchange activity ratio of SpARC4. Both SpARC2 and SpARC4 were poor hydrolases and unable to cyclise NGD, a NAD surrogate. A single non-conserved glycine residue in the “TLEDTL domain” of SpARC2 was responsible for its poor hydrolase activity. All SpARC isoforms were detectable in S.purpuratus egg and the majority of ARC activity was GPI-anchored. During the course of early development, SpARC isoforms were differentially expressed and the endogenous ARC activity also varied. Over-expression and knock-down of SpARC4 during embryo development interfered with gastrulation. These findings provide new insights into the molecular mechanisms of multifunctionality of this remarkable family of enzymes and suggest that the expression and activities of ARCs could be fine-tuned for production of specific calcium messengers during embryogenesis of S.purpuratus
A comparison of the structureborne and airborne paths for propfan interior noise
A comparison is made between the relative levels of aircraft interior noise related to structureborne and airborne paths for the same propeller source. A simple, but physically meaningful, model of the structure treats the fuselage interior as a rectangular cavity with five rigid walls. The sixth wall, the fuselage sidewall, is a stiffened panel. The wing is modeled as a simple beam carried into the fuselage by a large discrete stiffener representing the carry-through structure. The fuselage interior is represented by analytically-derived acoustic cavity modes and the entire structure is represented by structural modes derived from a finite element model. The noise source for structureborne noise is the unsteady lift generation on the wing due to the rotating trailing vortex system of the propeller. The airborne noise source is the acoustic field created by a propeller model consistent with the vortex representation. Comparisons are made on the basis of interior noise over a range of propeller rotational frequencies at a fixed thrust
Providing a Meaningful Opportunity for Release: A Proposal for Improving Washington\u27s Miller-Fix
Miller v. Alabama1 set forth new constitutional requirements that necessitated changes in Washington State’s sentencing law for children. In response, the Washington legislature passed RCW 9.94A.730: a parole statute that presumptively releases children who committed crimes after they have served twenty years. Unless the parole board finds they are more likely than not to commit a future crime if released, the Miller-fix statute requires that eligible petitioners are released. The parole board has wide discretion in determining whether someone is more likely than not to commit a future crime because the statute provides no guidance about how to make this prediction. It is nearly impossible to determine what someone will do in the future, and justifications for continuing to incarcerate an individual convicted of a crime as a child after they have served a twenty-year sentence are limited. Therefore, this Comment argues that the Washington legislature should instead require that sentences for children are twenty years or shorter
Isozyme Studies on some Selected Camellia Clones
Polyphenoloxidase and peroxidase enzymes were extracted and the isozyme banding pattern was studied in
twelve south Indian tea clones of Camellia species conserved an ex situ gene bank. Banding pattern exhibited
variations at inter specific and clonal level. A maximum of 6 isozymes were observed for polyphenol oxidase
in UPASI 2 clone and a minimum of 3 in the clone BSS 1. Peroxidase isozyme exhibited two bands in all the
clones with variation in its mobility (Rf). Isozyme profile of polyphenol oxidase and peroxidise in few clones
have shown unique pattern not detected in others. The isozyme profile of PPO indicates that the clones of the
respective Camellia species are more similar than those of the other species. In the present study, isozyme
banding pattern was compared among the Camellia species to understand the existing inter and intra clonal
relationship
A Pathwise Ergodic Theorem for Quantum Trajectories
If the time evolution of an open quantum system approaches equilibrium in the
time mean, then on any single trajectory of any of its unravelings the time
averaged state approaches the same equilibrium state with probability 1. In the
case of multiple equilibrium states the quantum trajectory converges in the
mean to a random choice from these states.Comment: 8 page
Effect of Ni-doping on magnetism and superconductivity in Eu0.5K0.5Fe2As2
The effect of Ni-doping on the magnetism and superconductivity in
Eu0.5K0.5Fe2As2 has been studied through a systematic investigation of magnetic
and superconducting properties of Eu0.5K0.5(Fe1-xNix)2As2 (x = 0, 0.03, 0.05,
0.08 and 0.12) compounds by means of dc and ac magnetic susceptibilities,
electrical resistivity and specific heat measurements. Eu0.5K0.5Fe2As2 is known
to exhibit superconductivity with superconducting transition temperature Tc as
high as 33 K. The Ni-doping leads to a rapid decrease in Tc; Tc is reduced to
23 K with 3% Ni-doping, and 8% Ni-doping suppresses the superconductivity to
below 1.8 K. In 3% Ni-doped sample Eu0.5K0.5(Fe0.97Ni0.03)2As2
superconductivity coexists with short range ordering of Eu2+ magnetic moments
at Tm ~ 6 K. The suppression of superconductivity with Ni-doping is accompanied
with the emergence of a long range antiferromagnetic ordering with TN = 8.5 K
and 7 K for Eu0.5K0.5(Fe0.92Ni0.08)2As2 and Eu0.5K0.5(Fe0.88Ni0.12)2As2,
respectively. The temperature and field dependent magnetic measurements for x =
0.08 and 0.12 samples reflect the possibility of a helical magnetic ordering of
Eu2 moments. We suspect that the helimagnetism of Eu spins could be responsible
for the destruction of superconductivity as has been observed in Co-doped
EuFe2As2. The most striking feature seen in the resistivity data for x = 0.08
is the reappearance of the anomaly presumably due to spin density wave
transition at around 60 K. This could be attributed to the compensation of
holes (K-doping at Eu-site) by the electrons (Ni-doping at Fe site). The
anomaly associated with spin density wave further shifts to 200 K for x = 0.12
for which the electron doping has almost compensated the holes in the system.Comment: 9 pages, 10 figure
Modeling and Analysis of Interactions in Virtual Enterprises
Advances in computer networking technology and open system standards are making the creation and management of virtual enterprises feasible. A virtual enterprise is a temporary consortium of autonomous, diverse, and possibly geographically dispersed organizations that pool their resources to meet short-term objectives and exploit fastchanging market trends. For a virtual enterprise to succeed, its business processes must be automated, and its startup costs must be minimized. In this paper we describe a formal framework for modeling and reasoning about interactions in a virtual enterprise. Such a framework will form the basis for tools that provide automated support for creation and operation of virtual enterprises. 1
Ginzburg-Landau Like Theory for High Temperature Superconductivity in the Cuprates: Emergent d-wave Order
High temperature superconductivity in the cuprates remains one of the most
widely investigated, constantly surprising, and poorly understood phenomena in
physics. Here, we describe briefly a new phenomenological theory inspired by
the celebrated description of superconductivity due to Ginzburg and Landau and
believed to describe its essence. This posits a free energy functional for the
superconductor in terms of a complex order parameter characterizing it. We
propose, for superconducting cuprates, a similar functional of the complex, in
plane, nearest neighbor spin singlet bond (or Cooper) pair amplitude psi_ij. A
crucial part of it is a (short range) positive interaction between nearest
neighbor bond pairs, of strength J'. Such an interaction leads to nonzero long
wavelength phase stiffness or superconductive long range order, with the
observed d-wave symmetry, below a temperature T_c\simzJ' where z is the number
of nearest neighbours; it is thus an emergent, collective consequence. Using
the functional, we calculate a large range of properties, e.g. the pseudogap
transition temperature T* as a function of hole doping x, the transition curve
T_c(x), the superfluid stiffness rho_s(x,T), the specific heat (without and
with a magnetic field) due to the fluctuating pair degrees of freedom, and the
zero temperature vortex structure. We find remarkable agreement with
experiment. We also calculate the self energy of electrons hopping on the
square cuprate lattice and coupled to electrons of nearly opposite momenta via
inevitable long wavelength Cooper pair fluctuations formed of these electrons.
The ensuing results for electron spectral density are successfully compared
with recent ARPES experiments, and comprehensively explain strange features
such as temperature dependent Fermi arcs above T_c and the 'bending' of the
superconducting gap below T_c .Comment: 22 pages, 14 figures, to appear in Int J Mod Phys
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