3,274 research outputs found
Compact set of invariants characterizing graph states of up to eight qubits
The set of entanglement measures proposed by Hein, Eisert, and Briegel for
n-qubit graph states [Phys. Rev. A 69, 062311 (2004)] fails to distinguish
between inequivalent classes under local Clifford operations if n > 6. On the
other hand, the set of invariants proposed by van den Nest, Dehaene, and De
Moor (VDD) [Phys. Rev. A 72, 014307 (2005)] distinguishes between inequivalent
classes, but contains too many invariants (more than 2 10^{36} for n=7) to be
practical. Here we solve the problem of deciding which entanglement class a
graph state of n < 9 qubits belongs to by calculating some of the state's
intrinsic properties. We show that four invariants related to those proposed by
VDD are enough for distinguishing between all inequivalent classes with n < 9
qubits.Comment: REVTeX4, 9 pages, 1 figur
Evidence for a change in the nuclear mass surface with the discovery of the most neutron-rich nuclei with 17<Z <25
The results of measurements of the production of neutron-rich nuclei by the
fragmentation of a 76-Ge beam are presented. The cross sections were measured
for a large range of nuclei including fifteen new isotopes that are the most
neutron-rich nuclides of the elements chlorine to manganese (50-Cl, 53-Ar,
55,56-K, 57,58-Ca, 59,60,61-Sc, 62,63-Ti, 65,66-V, 68-Cr, 70-Mn). The enhanced
cross sections of several new nuclei relative to a simple thermal evaporation
framework, previously shown to describe similar production cross sections,
indicates that nuclei in the region around 62-Ti might be more stable than
predicted by current mass models and could be an indication of a new island of
inversion similar to that centered on 31-Na.Comment: 4 pages, 3 figures, to be published in Physical Review Letters, 200
Production cross sections from 82Se fragmentation as indications of shell effects in neutron-rich isotopes close to the drip-line
Production cross sections for neutron-rich nuclei from the fragmentation of a
82Se beam at 139 MeV/u were measured. The longitudinal momentum distributions
of 126 neutron-rich isotopes of elements 11 <= Z <= 32 were scanned using an
experimental approach of varying the target thickness. Production cross
sections with beryllium and tungsten targets were determined for a large number
of nuclei including several isotopes first observed in this work. These are the
most neutron-rich nuclides of the elements 22 <= Z <= 25 (64Ti, 67V, 69Cr,
72Mn). One event was registered consistent with 70Cr, and another one with
75Fe. The production cross sections are correlated with Qg systematics to
reveal trends in the data. The results presented here confirm our previous
result from a similar measurement using a 76Ge beam, and can be explained with
a shell model that predicts a subshell closure at N = 34 around Z = 20. This is
demonstrated by systematic trends and calculations with the Abrasion-Ablation
model that are sensitive to separation energies.Comment: 13 pages, 11 figures, accepted to Phys.Rev.
The Role of Chiggers as Human Pathogens
Trombiculid mites (Acari: Trombiculidae) are distributed worldwide ectoparasites of a wide range of vertebrates. More than 50 species are known to bite humans, and about 20 have medical importance. The larval stages (chiggers) of the genus Leptotrombidium are vectors of Orientia tsutsugamushi, causative agent of scrub typhus. This life-threatening disease is widely endemic in Asian Pacific regions where more than one billion people are at risk of acquiring the infection and around one million new cases are estimated to occur annually. In addition, although underreported and often misdiagnosed, trombiculiasis, defined as a dermatitis caused by the salivary secretion of biting chiggers, is present in America and Europe
TOF-Brho Mass Measurements of Very Exotic Nuclides for Astrophysical Calculations at the NSCL
Atomic masses play a crucial role in many nuclear astrophysics calculations.
The lack of experimental values for relevant exotic nuclides triggered a rapid
development of new mass measurement devices around the world. The
Time-of-Flight (TOF) mass measurements offer a complementary technique to the
most precise one, Penning trap measurements, the latter being limited by the
rate and half-lives of the ions of interest. The NSCL facility provides a
well-suited infrastructure for TOF mass measurements of very exotic nuclei. At
this facility, we have recently implemented a TOF-Brho technique and performed
mass measurements of neutron-rich nuclides in the Fe region, important for
r-process calculations and for calculations of processes occurring in the crust
of accreting neutron stars.Comment: 8 pages, 4 figures, submitted to Journal of Physics G, proceedings of
Nuclear Physics in Astrophysics II
Zooplankton biomass and indices of feeding and metabolism in relation to an upwelling filament off northwest Africa
Zooplankton biomass and indices of grazing (gut fluorescence), respiration (electron transfer system activity, ETS) and growth (aspartate transcarbamylase, ATC) were studied in relation to an upwelling filament off northwest Africa during August 1993. The filament extended 150 km offshore into the oligotrophic waters. It was generated by a trapped, quasi-permanent cyclonic eddy located between the Canary Islands and the African shelf. High biomass, specific gut fluorescence and electron transfer system activity in zooplankton were observed along the filament structure. In contrast, low values of biomass, gut fluorescence, ETS and ATC specific activities were found in the center of the trapped cyclonic eddy. Assuming a 50% of pigment destruction, the calculated grazing impact of zooplankton on primary production varied between 16 and 97%, a high range compared to other oceanic systems. Ingestion, estimated from indices of metabolism and growth, accounted for 47–296% of the primary production (assuming an herbivorous feeding). Mesozooplankton transported offshore into the oligotrophic area fulfilled their metabolic demands with nonpigmented food as observed from the increase of omnivory from the coastal waters to the open ocean. The progressive decay of grazing and metabolic indices along the filament suggests that advection, rather than local enrichment processes, is mostly responsible for the high biomass values in this physical structure
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