1,032 research outputs found
The self-assembly and evolution of homomeric protein complexes
We introduce a simple "patchy particle" model to study the thermodynamics and
dynamics of self-assembly of homomeric protein complexes. Our calculations
allow us to rationalize recent results for dihedral complexes. Namely, why
evolution of such complexes naturally takes the system into a region of
interaction space where (i) the evolutionarily newer interactions are weaker,
(ii) subcomplexes involving the stronger interactions are observed to be
thermodynamically stable on destabilization of the protein-protein interactions
and (iii) the self-assembly dynamics are hierarchical with these same
subcomplexes acting as kinetic intermediates.Comment: 4 pages, 4 figure
All-Optical Quantum Random Bit Generation from Intrinsically Binary Phase of Parametric Oscillators
True random number generators (RNGs) are desirable for applications ranging
from cryptogra- phy to computer simulations. Quantum phenomena prove to be
attractive for physical RNGs due to their fundamental randomness and immunity
to attack [1]- [5]. Optical parametric down conversion is an essential element
in most quantum optical experiments including optical squeezing [9], and
generation of entangled photons [10]. In an optical parametric oscillator
(OPO), photons generated through spontaneous down conversion of the pump
initiate the oscillation in the absence of other inputs [11, 12]. This quantum
process is the dominant effect during the oscillation build-up, leading to
selection of one of the two possible phase states above threshold in a
degenerate OPO [13]. Building on this, we demonstrate a novel all-optical
quantum RNG in which the photodetection is not a part of the random process,
and no post processing is required for the generated bit sequence. We implement
a synchronously pumped twin degenerate OPO, which comprises two identical
independent OPOs in a single cavity, and measure the relative phase states of
the OPO outputs above threshold as a bit value. We show that the outcome is
statistically random with 99% confidence. With the use of micro- and nanoscale
OPO resonators, this technique offers a promise for simple, robust, and
high-speed on-chip all-optical quantum random number generators
(Il)Legitimisation of the role of the nation state: Understanding of and reactions to Internet censorship in Turkey
This study aims to explore Turkish citizen-consumers' understanding of and reactions to censorship of websites in Turkey by using in-depth interviews and online ethnography. In an environment where sites such as YouTube and others are increasingly being banned, the citizen-consumers' macro-level understanding is that such censorship is part of a wider ideological plan and their micro-level understanding is that their relationship with the wider global network is reduced, in the sense that they have trouble accessing full information on products, services and experiences. The study revealed that citizen-consumers engage in two types of resistance strategies against such domination by the state: using irony as passive resistance, and using the very same technology used by the state to resist its domination
Auxiliary "massless" spin-2 field in de Sitter universe
For the tensor field of rank-2 there are two unitary irreducible
representation (UIR) in de Sitter (dS) space denoted by and
[1]. In the flat limit only the coincides
to the UIR of Poincar\'e group, the second one becomes important in the study
of conformal gravity. In the pervious work, Dirac's six-cone formalism has been
utilized to obtain conformally invariant (CI) field equation for the "massless"
spin-2 field in dS space [2]. This equation results in a field which
transformed according to , we name this field the auxiliary
field. In this paper this auxiliary field is considered and also related
two-point function is calculated as a product of a polarization tensor and
"massless" conformally coupled scalar field. This two-point function is de
Sitter invariant.Comment: 16 page
Incident Diabetes Complications among Women with type 1 diabetes based on Parity
Objectives
To assess risk factors and incidence of diabetes complications in women with type 1 diabetes (T1D) based on parity.
Research design/methods
Data were collected from women (16–40 years old) in the T1D Exchange completing pregnancy/childbirth questionnaires during 2011–2013 and 2016–2018. Incidence of risk factors and diabetes complications were compared between women with a first pregnancy at/within 1-year of enrollment (n = 28) and never pregnant women by year 5 (n = 469).
Results
There was a trend for lower HbA1c (adjusted p = .14) and higher rates of overweight/obesity, triglyceride/HDL > 2, log (triglyercide/HDL), and hypertension among parous women compared with nulliparous women. There were no significant differences in rates of advanced nephropathy, albuminuria or cardiovascular disease.
Conclusions
Four-5 years after delivery, parous women with T1D tended to have lower HbA1c levels despite higher body mass indices and more frequent adverse lipid profiles and hypertension compared with nulliparous women. Further studies based on these trends are warranted
A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in
neutral B meson decays collected with the BABAR detector at the PEP-II
asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data
sample consists of 29.7 recorded at the
resonance and 3.9 off-resonance. One of the neutral B mesons,
which are produced in pairs at the , is fully reconstructed in
the CP decay modes , , , () and , or in flavor-eigenstate
modes involving and (). The flavor of the other neutral B meson is tagged at the time of
its decay, mainly with the charge of identified leptons and kaons. The proper
time elapsed between the decays is determined by measuring the distance between
the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample
finds . The value of the asymmetry amplitude is determined from
a simultaneous maximum-likelihood fit to the time-difference distribution of
the flavor-eigenstate sample and about 642 tagged decays in the
CP-eigenstate modes. We find , demonstrating that CP violation exists in the neutral B meson
system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
Measurement of the Branching Fraction for B- --> D0 K*-
We present a measurement of the branching fraction for the decay B- --> D0
K*- using a sample of approximately 86 million BBbar pairs collected by the
BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is
detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the
K*- through its decay to K0S pi-. We measure the branching fraction to be
B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid
Communications
Evidence for the Rare Decay B -> K*ll and Measurement of the B -> Kll Branching Fraction
We present evidence for the flavor-changing neutral current decay and a measurement of the branching fraction for the related
process , where is either an or
pair. These decays are highly suppressed in the Standard Model,
and they are sensitive to contributions from new particles in the intermediate
state. The data sample comprises
decays collected with the Babar detector at the PEP-II storage ring.
Averaging over isospin and lepton flavor, we obtain the branching
fractions and , where the
uncertainties are statistical and systematic, respectively. The significance of
the signal is over , while for it is .Comment: 7 pages, 2 postscript figues, submitted to Phys. Rev. Let
Measurement of the branching fraction and CP content for the decay B(0) -> D(*+)D(*-)
This is the pre-print version of the Article. The official published version can be accessed from the links below. Copyright @ 2002 APS.We report a measurement of the branching fraction of the decay B0→D*+D*- and of the CP-odd component of its final state using the BABAR detector. With data corresponding to an integrated luminosity of 20.4 fb-1 collected at the Υ(4S) resonance during 1999–2000, we have reconstructed 38 candidate signal events in the mode B0→D*+D*- with an estimated background of 6.2±0.5 events. From these events, we determine the branching fraction to be B(B0→D*+D*-)=[8.3±1.6(stat)±1.2(syst)]×10-4. The measured CP-odd fraction of the final state is 0.22±0.18(stat)±0.03(syst).This work is supported by DOE and NSF (USA), NSERC (Canada), IHEP (China), CEA and CNRS-IN2P3 (France), BMBF (Germany), INFN (Italy), NFR (Norway), MIST (Russia), and PPARC (United Kingdom). Individuals have received support from the A.P. Sloan Foundation, Research Corporation, and Alexander von Humboldt Foundation
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