925 research outputs found
Foraging areas of king penguins (Aptenodytes patagonicus) breeding at Possession Island in the Southern Indian Ocean
Between January and March 1994 and between January and June 1995 we used Global Location Sensors(GLS) to determine the feeding areas of King Penguins Aptenodytes patagonicus breeding at Possession Island, Crozet Archipalago. In both years, the preferred feeding area during summer was located about 300 km south of the island, being slightly more distant in 1995. Mean foraging trip duration was 5.7±1.1 days (n = 6) during summer 1994 and 8.9±3.7 days (n = 9) during summer 1995, respectively. During summer the travelling speed of the King Penguins studied was highest at the first and last days of the foraging trip (c. 8 km/h). During the middle days of foraging trips travelling speeds were much lower (< 5 km/h). In early winter, between late April and mid-June 1995, two King Penguins equipped with GLSs executed foraging trips with durations of 53 and 59 days, respectively. Both birds travelled beyond 60°S with maximum distances to the colony of 1600 and 1800 km, respectively, and total distances covered of about 5000 km. The winter trips were characterized by alternating periods of higher and lower distances covered, indicating a highly variable feeding success at different localities. The relationships between foraging trip duration (days) and maximum distance to the colony (km) and total distance covered (km) were calculated to be maximum distance = 210 + 27 d and total distance = 340 + 85 d
Two-photon double ionization of neon using an intense attosecond pulse train
We present the first demonstration of two-photon double ionization of neon
using an intense extreme ultraviolet (XUV) attosecond pulse train (APT) in a
photon energy regime where both direct and sequential mechanisms are allowed.
For an APT generated through high-order harmonic generation (HHG) in argon we
achieve a total pulse energy close to 1 J, a central energy of 35 eV and a
total bandwidth of eV. The APT is focused by broadband optics in a
neon gas target to an intensity of Wcm. By tuning
the photon energy across the threshold for the sequential process the double
ionization signal can be turned on and off, indicating that the two-photon
double ionization predominantly occurs through a sequential process. The
demonstrated performance opens up possibilities for future XUV-XUV pump-probe
experiments with attosecond temporal resolution in a photon energy range where
it is possible to unravel the dynamics behind direct vs. sequential double
ionization and the associated electron correlation effects
Production/maintenance cooperative scheduling using multi-agents and fuzzy logic
Within companies, production is directly concerned with the manufacturing schedule, but other services like sales, maintenance, purchasing or workforce management should also have an influence on this schedule. These services often have together a hierarchical relationship, i.e. the leading function (most of the time sales or production) generates constraints defining the framework within which the other functions have to satisfy their own objectives. We show how the multi-agent paradigm, often used in scheduling for its ability to distribute decision-making, can also provide a framework for making several functions cooperate in the schedule performance. Production and maintenance have been chosen as an example: having common resources (the machines), their activities are actually often conflicting. We show how to use a fuzzy logic in order to model the temporal degrees of freedom of the two functions, and show that this approach may allow one to obtain a schedule that provides a better compromise between the satisfaction of the respective objectives of the two functions
Spatio-temporal coupling of attosecond pulses
The shortest light pulses produced to date are of the order of a few tens of
attoseconds, with central frequencies in the extreme ultraviolet range and
bandwidths exceeding tens of eV. They are often produced as a train of pulses
separated by half the driving laser period, leading in the frequency domain to
a spectrum of high, odd-order harmonics. As light pulses become shorter and
more spectrally wide, the widely-used approximation consisting in writing the
optical waveform as a product of temporal and spatial amplitudes does not apply
anymore. Here, we investigate the interplay of temporal and spatial properties
of attosecond pulses. We show that the divergence and focus position of the
generated harmonics often strongly depend on their frequency, leading to strong
chromatic aberrations of the broadband attosecond pulses. Our argumentation
uses a simple analytical model based on Gaussian optics, numerical propagation
calculations and experimental harmonic divergence measurements. This effect
needs to be considered for future applications requiring high quality focusing
while retaining the broadband/ultrashort characteristics of the radiation
UniPathway: a resource for the exploration and annotation of metabolic pathways
UniPathway (http://www.unipathway.org) is a fully manually curated resource for the representation and annotation of metabolic pathways. UniPathway provides explicit representations of enzyme-catalyzed and spontaneous chemical reactions, as well as a hierarchical representation of metabolic pathways. This hierarchy uses linear subpathways as the basic building block for the assembly of larger and more complex pathways, including species-specific pathway variants. All of the pathway data in UniPathway has been extensively cross-linked to existing pathway resources such as KEGG and MetaCyc, as well as sequence resources such as the UniProt KnowledgeBase (UniProtKB), for which UniPathway provides a controlled vocabulary for pathway annotation. We introduce here the basic concepts underlying the UniPathway resource, with the aim of allowing users to fully exploit the information provided by UniPathwa
Spinocerebellar ataxia types 1, 2, 3, and 6: disease severity and nonataxia symptoms.
OBJECTIVE: To identify factors that determine disease severity and clinical
phenotype of the most common spinocerebellar ataxias (SCAs), we studied 526
patients with SCA1, SCA2, SCA3. or SCA6.
METHODS: To measure the severity of ataxia we used the Scale for the Assessment
and Rating of Ataxia (SARA). In addition, nonataxia symptoms were assessed with
the Inventory of Non-Ataxia Symptoms (INAS). The INAS count denotes the number of
nonataxia symptoms in each patient.
RESULTS: An analysis of covariance with SARA score as dependent variable and
repeat lengths of the expanded and normal allele, age at onset, and disease
duration as independent variables led to multivariate models that explained 60.4%
of the SARA score variance in SCA1, 45.4% in SCA2, 46.8% in SCA3, and 33.7% in
SCA6. In SCA1, SCA2, and SCA3, SARA was mainly determined by repeat length of the
expanded allele, age at onset, and disease duration. The only factors determining
the SARA score in SCA6 were age at onset and disease duration. The INAS count was
5.0 +/- 2.3 in SCA1, 4.6 +/- 2.2 in SCA2, 5.2 +/- 2.5 in SCA3, and 2.0 +/- 1.7 in
SCA6. In SCA1, SCA2, and SCA3, SARA score and disease duration were the strongest
predictors of the INAS count. In SCA6, only age at onset and disease duration had
an effect on the INAS count.
CONCLUSIONS: Our study suggests that spinocerebellar ataxia (SCA) 1, SCA2, and
SCA3 share a number of common biologic properties, whereas SCA6 is distinct in
that its phenotype is more determined by age than by disease-related factors
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