262 research outputs found
MC4.3 - Optically Coupled Mode-Locked Laser Array for Spectroscopy in InP Generic Integration
We propose a two-element mode-locked laser
array operating at 1.56 µm. Optical pulses with 14.5-ps width,
spectral bandwidth exceeding 7 nm, and RF line width of 260
kHz at 12.448 GHz are experimentally reported
External optical self-injection stabilization of an InP generic foundry platform based passively mode-locked ring laser
Timing stabilization of a photonic integrated circuit extended cavity passively mode-locked semiconductor ring laser with four gain sections and two saturable absorbers in a symmetric ring geometry by optical self-injection is presented. The laser has been fabricated using an InP generic integration technology platform. Repetition rate tuning up to 5.5MHz and a timing jitter reduction by optical self-injection from 99 fs (solitary laser operation) to 20 fs is demonstrated. The experimental results are in excellent agreement with results obtained by a stochastic time domain model which yet had been solely applied to edge-emitting straight waveguide semiconductor lasers
Electronic structure and spectroscopy of the quaternary Heusler alloy CoCrFeAl
Quaternary Heusler alloys CoCrFeAl with varying Cr to Fe
ratio were investigated experimentally and theoretically. The electronic
structure and spectroscopic properties were calculated using the full
relativistic Korringa-Kohn-Rostocker method with coherent potential
approximation to account for the random distribution of Cr and Fe atoms as well
as random disorder. Magnetic effects are included by the use of spin dependent
potentials in the local spin density approximation.
Magnetic circular dichroism in X-ray absorption was measured at the
edges of Co, Fe, and Cr of the pure compounds and the alloy in order to
determine element specific magnetic moments. Calculations and measurements show
an increase of the magnetic moments with increasing iron content. Resonant
(560eV - 800eV) soft X-ray as well as high resolution - high energy (keV) hard X-ray photo emission was used to probe the density of the
occupied states in CoCrFeAl.Comment: J.Phys.D_Appl.Phys. accepte
Design of magnetic materials: CoCrFeAl
Doped Heusler compounds CoCrFeAl with varying Cr to Fe
ratio were investigated experimentally and theoretically. The electronic
structure of the ordered, doped Heusler compound CoCrFeAl
( was calculated using different types of band structure
calculations. The ordered compounds turned out to be ferromagnetic with small
Al magnetic moment being aligned anti-parallel to the 3d transition metal
moments. All compounds show a gap around the Fermi-energy in the minority
bands. The pure compounds exhibit an indirect minority gap, whereas the
ordered, doped compounds exhibit a direct gap. Magnetic circular dichroism
(MCD) in X-ray absorption spectra was measured at the edges of Co,
Fe, and Cr of the pure compounds and the alloy in order to determine
element specific magnetic moments. Calculations and measurements show an
increase of the magnetic moments with increasing iron content. The
experimentally observed reduction of the magnetic moment of Cr can be explained
by Co-Cr site-disorder. The presence of the gap in the minority bands of
CoCrAl can be attributed to the occurrence of pure Co and mixed CrAl
(001)-planes in the structure. It is retained in structures with
different order of the CrAl planes but vanishes in the -structure with
alternating CoCr and CoAl planes.Comment: corrected author lis
Extended Classical Over-Barrier Model for Collisions of Highly Charged Ions with Conducting and Insulating Surfaces
We have extended the classical over-barrier model to simulate the
neutralization dynamics of highly charged ions interacting under grazing
incidence with conducting and insulating surfaces. Our calculations are based
on simple model rates for resonant and Auger transitions. We include effects
caused by the dielectric response of the target and, for insulators, localized
surface charges. Characteristic deviations regarding the charge transfer
processes from conducting and insulating targets to the ion are discussed. We
find good agreement with previously published experimental data for the image
energy gain of a variety of highly charged ions impinging on Au, Al, LiF and KI
crystals.Comment: 32 pages http://pikp28.uni-muenster.de/~ducree
Effect of transport-induced charge inhomogeneity on point-contact Andreev reflection spectra at ferromagnet-superconductor interfaces
We investigate the transport properties of a ferromagnet-superconductor
interface within the framework of a modified three-dimensional
Blonder-Tinkham-Klapwijk formalism. In particular, we propose that charge
inhomogeneity forms via two unique transport mechanisms, namely, evanescent
Andreev reflection and evanescent quasiparticle transmission. Furthermore, we
take into account the influence of charge inhomogeneity on the interfacial
barrier potential and calculate the conductance as a function of bias voltage.
Point-contact Andreev reflection (PCAR) spectra often show dip structures,
large zero-bias conductance enhancement, and additional zero-bias conductance
peak. Our results indicate that transport-induced charge inhomogeneity could be
a source of all these anomalous characteristics of the PCAR spectra.Comment: 9 pages, 6 figure
Bending elasticity of a curved amphiphilic film decorated anchored copolymers: a small angle neutron scattering study
Microemulsion droplets (oil in water stabilized by a surfactant film) are
progressively decorated with increasing amounts of poly ethylene- oxide (PEO)
chains anchored in the film by the short aliphatic chain grafted at one end of
the PEO chain . The evolution of the bending elasticity of the surfactant film
with increasing decoration is deduced from the evolution in size and
polydispersity of the droplets as reflected by small angle neutron scattering.
The optimum curvature radius decreases while the bending rigidity modulus
remains practically constant. The experimental results compare well with the
predictions of a model developed for the bending properties of a curved film
decorated by non-adsorbing polymer chains, which takes into account, the finite
curvature of the film and the free diffusion of the chains on the film.Comment: 30 June 200
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State of the California current 2012-13: No such thing as an “average” year
This report reviews the state of the California Current System (CCS) between winter 2012 and spring 2013, and includes observations from Washington State to Baja California. During 2012, large-scale climate modes indicated the CCS remained in a cool, productive phase present since 2007. The upwelling season was delayed north of 42°N, but regions to the south, especially 33° to 36°N, experienced average to above average upwelling that persisted throughout the summer. Contrary to the indication of high production suggested by the climate indices, chlorophyll observed from surveys and remote sensing was below average along much of the coast. As well, some members of the forage assemblages along the coast experienced low abundances in 2012 surveys. Specifically, the concentrations of all lifestages observed directly or from egg densities of Pacific sardine, Sardinops sagax, and northern anchovy, Engraulis mordax, were less than previous years’ survey estimates. However, 2013 surveys and observations indicate an increase in abundance of northern anchovy. During winter 2011/2012, the increased presence of northern copepod species off northern California was consistent with stronger southward transport. Krill and small-fraction zooplankton abundances, where examined, were generally above average. North of 42°N, salps returned to typical abundances in 2012 after greater observed concentrations in 2010 and 2011. In contrast, salp abundance off central and southern California increased after a period of southward transport during winter 2011/2012. Reproductive success of piscivorous Brandt’s cormorant, Phalacrocorax penicillatus, was reduced while planktivorous Cassin’s auklet, Ptychoramphus aleuticus was elevated. Differences between the productivity of these two seabirds may be related to the available forage assemblage observed in the surveys. California sea lion pups from San Miguel Island were undernourished resulting in a pup mortality event perhaps in response to changes in forage availability. Limited biological data were available for spring 2013, but strong winter upwelling coastwide indicated an early spring transition, with the strong upwelling persisting into early summer
Deficiency in origin licensing proteins impairs cilia formation: implications for the aetiology of meier-gorlin syndrome
Mutations in ORC1, ORC4, ORC6, CDT1, and CDC6, which encode proteins required for DNA replication origin licensing, cause Meier-Gorlin syndrome (MGS), a disorder conferring microcephaly, primordial dwarfism, underdeveloped ears, and skeletal abnormalities. Mutations in ATR, which also functions during replication, can cause Seckel syndrome, a clinically related disorder. These findings suggest that impaired DNA replication could underlie the developmental defects characteristic of these disorders. Here, we show that although origin licensing capacity is impaired in all patient cells with mutations in origin licensing component proteins, this does not correlate with the rate of progression through S phase. Thus, the replicative capacity in MGS patient cells does not correlate with clinical manifestation. However, ORC1-deficient cells from MGS patients and siRNA-mediated depletion of origin licensing proteins also have impaired centrosome and centriole copy number. As a novel and unexpected finding, we show that they also display a striking defect in the rate of formation of primary cilia. We demonstrate that this impacts sonic hedgehog signalling in ORC1-deficient primary fibroblasts. Additionally, reduced growth factor-dependent signaling via primary cilia affects the kinetics of cell cycle progression following cell cycle exit and re-entry, highlighting an unexpected mechanism whereby origin licensing components can influence cell cycle progression. Finally, using a cell-based model, we show that defects in cilia function impair chondroinduction. Our findings raise the possibility that a reduced efficiency in forming cilia could contribute to the clinical features of MGS, particularly the bone development abnormalities, and could provide a new dimension for considering developmental impacts of licensing deficiency
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Recent pre-recruit Pacific hake (Merluccius productus) occurrences in the Northern California Current suggest a northward expansion of their spawning area
Coastal Pacific hake (Merluccius productus) are known
to spawn in the southern California Bight from January
to March, migrate north during late spring and summer
to feed off Oregon, Washington, and British Columbia,
and then move back to southern California in the fall.
Juvenile Pacific hake nursery areas have been found to
occur along the coastal shelf and slope of California, and
occasionally into southern Oregon during strong El Niño
events. In this paper, we combine information from several
studies that captured larval and high abundances of
young-of-the-year (YOY) Pacific hake in the northern
California Current from 2003–06. These preliminary
results suggest that spawning and recruitment of Pacific
hake have expanded northward and this will likely have
major economic and ecological consequences in the
northern California Current (NCC).Previously published in California Cooperative Oceanic Fisheries Investigations, Progress Report, 2007, Vol. 48; access courtesy of publisher and authors.Keywords: Northern California Current, Pacific hakeKeywords: Northern California Current, Pacific hak
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