293 research outputs found
In-cell NMR reveals potential precursor of toxic species from SOD1 fALS mutants
Mutations in the superoxide dismutase 1 (SOD1) gene are related to familial cases of
amyotrophic lateral sclerosis (fALS). Here we exploit in-cell NMR to characterize the protein
folding and maturation of a series of fALS-linked SOD1 mutants in human cells and to obtain
insight into their behaviour in the cellular context, at the molecular level. The effect of various
mutations on SOD1 maturation are investigated by changing the availability of metal ions in
the cells, and by coexpressing the copper chaperone for SOD1, hCCS. We observe for most of
the mutants the occurrence of an unstructured SOD1 species, unable to bind zinc.
This species may be a common precursor of potentially toxic oligomeric species, that are
associated with fALS. Coexpression of hCCS in the presence of copper restores the correct
maturation of the SOD1 mutants and prevents the formation of the unstructured species,
confirming that hCCS also acts as a molecular chaperone
Optimal quantum cloning of orbital angular momentum photon qubits via Hong-Ou-Mandel coalescence
The orbital angular momentum (OAM) of light, associated with a helical
structure of the wavefunction, has a great potential for quantum photonics, as
it allows attaching a higher dimensional quantum space to each photon.
Hitherto, however, the use of OAM has been hindered by its difficult
manipulation. Here, exploiting the recently demonstrated spin-OAM information
transfer tools, we report the first observation of the Hong-Ou-Mandel
coalescence of two incoming photons having nonzero OAM into the same outgoing
mode of a beam-splitter. The coalescence can be switched on and off by varying
the input OAM state of the photons. Such effect has been then exploited to
carry out the 1 \rightarrow 2 universal optimal quantum cloning of OAM-encoded
qubits, using the symmetrization technique already developed for polarization.
These results are finally shown to be scalable to quantum spaces of arbitrary
dimension, even combining different degrees of freedom of the photons.Comment: 5 pages, 3 figure
Experimental demonstration of a hyper-entangled ten-qubit Schr\"odinger cat state
Coherent manipulation of an increasing number of qubits for the generation of
entangled states has been an important goal and benchmark in the emerging field
of quantum information science. The multiparticle entangled states serve as
physical resources for measurement-based quantum computing and high-precision
quantum metrology. However, their experimental preparation has proved extremely
challenging. To date, entangled states up to six, eight atoms, or six photonic
qubits have been demonstrated. Here, by exploiting both the photons'
polarization and momentum degrees of freedom, we report the creation of
hyper-entangled six-, eight-, and ten-qubit Schr\"odinger cat states. We
characterize the cat states by evaluating their fidelities and detecting the
presence of genuine multi-partite entanglement. Small modifications of the
experimental setup will allow the generation of various graph states up to ten
qubits. Our method provides a shortcut to expand the effective Hilbert space,
opening up interesting applications such as quantum-enhanced super-resolving
phase measurement, graph-state generation for anyonic simulation and
topological error correction, and novel tests of nonlocality with
hyper-entanglement.Comment: 11 pages, 5 figures, comments welcom
Observation of eight-photon entanglement
Using ultra-bright sources of pure-state entangled photons from parametric
down conversion, an eight-photon interferometer and post-selection detection,
we demonstrate the ability to experimentally manipulate eight individual
photons and report the creation of an eight-photon Schr\"odinger cat state with
an observed fidelity of .Comment: 6 pages, 4 figure
Beating the channel capacity limit for linear photonic superdense coding
Dense coding is arguably the protocol that launched the field of quantum
communication. Today, however, more than a decade after its initial
experimental realization, the channel capacity remains fundamentally limited as
conceived for photons using linear elements. Bob can only send to Alice three
of four potential messages owing to the impossibility of carrying out the
deterministic discrimination of all four Bell states with linear optics,
reducing the attainable channel capacity from 2 to log_2 3 \approx 1.585 bits.
However, entanglement in an extra degree of freedom enables the complete and
deterministic discrimination of all Bell states. Using pairs of photons
simultaneously entangled in spin and orbital angular momentum, we demonstrate
the quantum advantage of the ancillary entanglement. In particular, we describe
a dense-coding experiment with the largest reported channel capacity and, to
our knowledge, the first to break the conventional linear-optics threshold. Our
encoding is suited for quantum communication without alignment and satellite
communication.Comment: Letter: 6 pages, 4 figures. Supplementary Information: 4 pages, 1
figur
A Light Stop with Flavor in Natural SUSY
The discovery of a SM-like Higgs boson near 125 GeV and the flavor texture of
the Standard Model motivate the investigation of supersymmetric quiver-like BSM
extensions. We study the properties of such a minimal class of models which
deals naturally with the SM parameters. Considering experimental bounds as well
as constraints from flavor physics and Electro-Weak Precision Data, we find the
following. In a self-contained minimal model - including the full dynamics of
the Higgs sector - top squarks below a TeV are in tension with b->s{\gamma}
constraints. Relaxing the assumption concerning the mass generation of the
heavy Higgses, we find that a stop not far from half a TeV is allowed. The
models have some unique properties, e.g. an enhancement of the h->
b\bar{b},\tau\bar{{\tau}} decays relative to the h->\gamma{\gamma} one, a
gluino about 3 times heavier than the stop, an inverted hierarchy of about 3-20
between the squarks of the first two generations and the stop, relatively light
Higgsino neutralino or stau NLSP, as well as heavy Higgses and a W' which may
be within reach of the LHC.Comment: LaTeX, 22 pages, 4 figures; V2: references adde
Gluino Decay as a Probe of High Scale Supersymmetry Breaking
A supersymmetric standard model with heavier scalar supersymmetric particles
has many attractive features. If the scalar mass scale is O(10 - 10^4) TeV, the
standard model like Higgs boson with mass around 125 GeV, which is strongly
favored by the LHC experiment, can be realized. However, in this scenario the
scalar particles are too heavy to be produced at the LHC. In addition, if the
scalar mass is much less than O(10^4) TeV, the lifetime of the gluino is too
short to be measured. Therefore, it is hard to probe the scalar particles at a
collider. However, a detailed study of the gluino decay reveals that two body
decay of the gluino carries important information on the scalar scale. In this
paper, we propose a test of this scenario by measuring the decay pattern of the
gluino at the LHC.Comment: 29 pages, 9 figures; version published in JHE
Effect of Prenatal Exposure to Airborne Polycyclic Aromatic Hydrocarbons on Neurodevelopment in the First 3 Years of Life among Inner-City Children
Our prospective cohort study of nonsmoking African-American and Dominican mothers and children in New York City is evaluating the role of prenatal exposure to urban pollutants, including polycyclic aromatic hydrocarbons (PAHs), environmental tobacco smoke (ETS), and pesticides, in the pathogenesis of neurobehavioral disorders. We used the Bayley Scales of Infant Development to evaluate the effects on child mental and psychomotor development of prenatal exposure to airborne PAHs monitored during pregnancy by personal air sampling. Behavioral development was assessed by the Child Behavior Checklist. We adjusted for potential confounders including sociodemographic factors and prenatal exposure to ETS and chlorpyrifos. Prenatal exposure to PAHs was not associated with psychomotor development index or behavioral problems. However, high prenatal exposure to PAHs (upper quartile) was associated with lower mental development index at age 3 [ÎČ= â5.69; 95% confidence interval (CI), â9.05 to â2.33; p < 0.01]. The odds of cognitive developmental delay were also significantly greater for children with high prenatal exposure (odds ratio = 2.89; 95% CI, 1.33 to 6.25; p = 0.01). General estimated equation analysis showed a significant age Ă PAH effect on mental development (p = 0.01), confirming the age-specific regression findings. Further adjustment for lead did not alter the relationships. There were no differences in effect sizes by ethnicity. The results require confirmation but suggest that environmental PAHs at levels recently encountered in New York City air may adversely affect childrenâs cognitive development at 3 years of age, with implications for school performance
Revealing the footprints of squark gluino production through Higgs search experiments at the Large Hadron Collider at 7 TeV and 14 TeV
The invariant mass distribution of the di-photons from the decay of the
lighter scalar Higgs boson(h) to be carefully measured by dedicated h search
experiments at the LHC may be distorted by the di-photons associated with the
squark-gluino events with much larger cross sections in Gauge Mediated
Supersymmetry Breaking (GMSB) models. This distortion if observed by the
experiments at the Large Hadron Collider at 7 TeV or 14 TeV, would disfavour
not only the standard model but various two Higgs doublet models with
comparable h - masses and couplings but without a sector consisting of new
heavy particles decaying into photons. The minimal GMSB (mGMSB) model
constrained by the mass bound on h from LEP and that on the lightest neutralino
from the Tevatron, produce negligible effects. But in the currently popular
general GMSB(GGMSB) models the tail of the above distribution may show
statistically significant excess of events even in the early stages of the LHC
experiments with integrated luminosity insufficient for the discovery of h. We
illustrate the above points by introducing several benchmark points in various
GMSB models - minimal as well as non-minimal. The same conclusion follows from
a detailed parameter scan in a simplified GGMSB model recently employed by the
CMS collaboration to interpret their searches in the di-photon + \etslash
channel. Other observables like the effective mass distribution of the
di-photon + X events may also reveal the presence of new heavy particles beyond
the Higgs sector. The contamination of the h mass peak and simple remedies are
also discussed.Comment: 23 pages, 7 figures, title and organization of the paper is changed,
detailed parameter scan in a simplified GGMSB model is added, conclusions and
old numerical results remain unchange
Higgs decay with monophoton + MET signature from low scale supersymmetry breaking
We study the decay of a standard model-like Higgs boson into a gravitino and
a neutralino, which subsequently decays promptly into another gravitino and a
photon. Such a decay can be important in scenarios where the supersymmetry
breaking scale is of the order of a few TeV, and in the region of low
transverse momenta of the photon, it may provide the dominant contribution to
the final state with a photon and two gravitinos. We estimate the relevant
standard model backgrounds and the prospects for discovering this Higgs decay
through a photon and missing transverse energy signal at the LHC in terms of a
simplified model. We also give an explicit model with manifest, but
spontaneously broken, supersymmetry in which the usual MSSM soft terms are
promoted to supersymmetric operators involving a dynamical goldstino
supermultiplet. This model can give rise to a SM-like CP-even neutral Higgs
particle with a mass of 125 GeV, without requiring substantial radiative
corrections, and with couplings sufficiently large for a signal discovery
through the above mentioned Higgs decay channel with the upcoming data from the
LHC.Comment: 28 pages, 5 figures, 4 tables; v2: updated to JHEP version,
references adde
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