5,816 research outputs found
Analysis of ring laser gyroscopes including laser dynamics
Inertial sensors stimulate very large interest, not only for their
application but also for fundamental physics tests. Ring laser gyros, which
measure angular rotation rate, are certainly among the most sensitive inertial
sensors, with excellent dynamic range and bandwidth. Large area ring laser
gyros are routinely able to measure fractions of prad/s, with high duty cycle
and bandwidth, providing fast, direct and local measurement of relevant
geodetic and geophysical signals. Improvements of a factor would open
the windows for general relativity tests, as the GINGER project, an Earth based
experiment aiming at the Lense-Thirring test at level. However, it is
well known that the dynamics of the laser induces non-linearities, and those
effects are more evident in small scale instruments. Sensitivity and accuracy
improvements are always worthwhile, and in general there is demand for high
sensitivity environmental study and development of inertial platforms, where
small scale transportable instruments should be used. We discuss a novel
technique to analyse the data, aiming at studying and removing those
non-linearity. The analysis is applied to the two ring laser prototypes GP2 and
GINGERINO, and angular rotation rate evaluated with the new and standard
methods are compared. The improvement is evident, it shows that the
back-scatter problem of the ring laser gyros is negligible with a proper
analysis of the data, improving the performances of large scale ring laser
gyros, but also indicating that small scale instruments with sensitivity of
nrad/s are feasible.Comment: 9 pages and 7 figure
Molecular systematics, phylogeny and biogeography of roaches (Rutilus, Teleostei, Cyprinidae)
The aims of the present study are: (1) to produce a phylogenetic
hypothesis for the genus Rutilus by using sequence variation of the
entire mitochondrial (mt) cytochrome b (cyt-b) gene. To accomplish
this we had sampled a total of 22 populations from the Eastern
peri-Mediterranean area and Central Europe. These include 12
species (five of which with multiple populations; Fig. 1 and Table
1) out of the 14 reported in FishBase; (2) to test whether molecular
data support the current systematics of the genus; and (3) to
produce a biogeographic hypothesis for its diversification based
on estimates of divergence times. Results will be discussed in light of the two contrasting biogeographic scenarios available for Southern
European primary freshwater fishes
Particle yield fluctuations and chemical non-equilibrium at RHIC
We study charge fluctuations within the statistical hadronization model.
Considering both the particle yield ratios and the charge fluctuations we show
that it is possible to differentiate between chemical equilibrium and
non-equilibrium freeze-out conditions. As an example of the procedure we show
quantitatively how the relative yield ratio together with the
normalized net charge fluctuation v(Q)=\ave{\Delta Q^2}/\ave{\Nch} constrain
the chemical conditions at freeze-out. We also discuss the influence of the
limited detector acceptance on fluctuation measurements, and show how this can
be accounted for within a quantitative analysis.Comment: Accepted for publication by Physical Review
Calibration of White Dwarf cooling sequences: theoretical uncertainty
White Dwarf luminosities are powerful age indicators, whose calibration
should be based on reliable models. We discuss the uncertainty of some chemical
and physical parameters and their influence on the age estimated by means of
white dwarf cooling sequences. Models at the beginning of the white dwarf
sequence have been obtained on the base of progenitor evolutionary tracks
computed starting from the zero age horizontal branch and for a typical halo
chemical composition (Z=0.0001, Y=0.23). The uncertainties due to nuclear
reaction rates, convection, mass loss and initial chemical composition are
discussed. Then, various cooling sequences for a typical white dwarf mass
(M=0.6 Mo) have been calculated under different assumptions on some input
physics, namely: conductive opacity, contribution of the ion-electron
interaction to the free energy and microscopic diffusion. Finally we present
the evolution of white dwarfs having mass ranging between 0.5 and 0.9 Mo. Much
effort has been spent to extend the equation of state down to the low
temperature and high density regime. An analysis of the latest improvement in
the physics of white dwarf interiors is presented. We conclude that at the
faint end of the cooling sequence (log L/Lo=-5.5) the present overall
uncertainty on the age is of the order of 20%, which correspond to about 3 Gyr.
We suggest that this uncertainty could be substantially reduced by improving
our knowledge of the conductive opacity (especially in the partially degenerate
regime) and by fixing the internal stratification of C and O.Comment: 14 figures, accepted by Ap
Mindfulness as a protective factor for dissatisfaction in HCWS: The moderating role of mindful attention between climate stress and job satisfaction
With the aim of investigating the possible moderating effect of job control and dispositional mindfulness between different sources of organizational stress and job satisfaction, a correlational study was designed involving health care workers (HCWs). The following questionnaires were administered and completed by 237 HCWs: (1) Occupational Stress Indicator (OSI), to measure the sources of stress at work (managerial role, climate power, climate structure, internal relationships), and job satisfaction; (2) Mindfulness Attention Awareness Scale (MAAS) to assess the individual's level of attention to what is taking place in the present; (3) Job Control Scale (JCS) to assess the perceived control at work. Hierarchical regression analyses were used to test the hypothesized relationships between variables; the results showed that, between the different sources of stress, the organizational climate dimension was negatively associated with job satisfaction; moreover, mindfulness attention moderated the relationship between climate stress and job satisfaction; unexpectedly, the interaction between job control and the organizational climate dimension was not significant in affecting job satisfaction. This study can provide useful information for Human Resources Management (HRM) practices regarding job and mental control interventions and empowerment, and possibly offer a new interpretation of the role of attention to what is happening in the present moment and autonomy between climate stressors and occupational satisfaction
Real-Time Wavelet-transform spectrum analyzer for the investigation of 1/f^\alpha noise
A wavelet transform spectrum analyzer operating in real time within the
frequency range 3X10^(-5) - 1.3X10^5 Hz has been implemented on a low-cost
Digital Signal Processing board operating at 150MHz. The wavelet decomposition
of the signal allows to efficiently process non-stationary signals dominated by
large amplitude events fairly well localized in time, thus providing the
natural tool to analyze processes characterized by 1/f^alpha power spectrum.
The parallel architecture of the DSP allows the real-time processing of the
wavelet transform of the signal sampled at 0.3MHz. The bandwidth is about
220dB, almost ten decades. The power spectrum of the scattered intensity is
processed in real time from the mean square value of the wavelet coefficients
within each frequency band. The performances of the spectrum analyzer have been
investigated by performing Dynamic Light Scattering experiments on colloidal
suspensions and by comparing the measured spectra with the correlation
functions data obtained with a traditional multi tau correlator. In order to
asses the potentialities of the spectrum analyzer in the investigation of
processes involving a wide range of timescales, we have performed measurements
on a model system where fluctuations in the scattered intensities are generated
by the number fluctuations in a dilute colloidal suspension illuminated by a
wide beam. This system is characterized by a power-law spectrum with exponent
-3/2 in the scattered intensity fluctuations. The spectrum analyzer allows to
recover the power spectrum with a dynamic range spanning about 8 decades. The
advantages of wavelet analysis versus correlation analysis in the investigation
of processes characterized by a wide distribution of time scales and
non-stationary processes are briefly discussed.Comment: 12 pages, 6 figure
Multifractal properties of return time statistics
Fluctuations in the return time statistics of a dynamical system can be
described by a new spectrum of dimensions. Comparison with the usual
multifractal analysis of measures is presented, and difference between the two
corresponding sets of dimensions is established. Theoretical analysis and
numerical examples of dynamical systems in the class of Iterated Functions are
presented.Comment: 4 pages, 3 figure
The mean field theory of spin glasses: the heuristic replica approach and recent rigorous results
The mathematically correct computation of the spin glasses free energy in the
infinite range limit crowns 25 years of mathematic efforts in solving this
model. The exact solution of the model was found many years ago by using a
heuristic approach; the results coming from the heuristic approach were crucial
in deriving the mathematical results. The mathematical tools used in the
rigorous approach are quite different from those of the heuristic approach. In
this note we will review the heuristic approach to spin glasses in the light of
the rigorous results; we will also discuss some conjectures that may be useful
to derive the solution of the model in an alternative way.Comment: 12 pages, 1 figure; lecture at the Flato Colloquia Day, Thursday 27
November, 200
Of detectability and camouflage: evaluating Pollard Walk rules using a common, cryptic butterfly
Abstract Estimating distribution and abundance of species depends on the probability at which individuals are detected. Butterflies are of conservation interest worldwide, but data collected with Pollard walksâthe standard for national monitoring schemesâare often analyzed assuming that changes in detectability are negligible within recommended sampling criteria. The implications of this practice remain poorly understood. Here, we evaluated the effects of sampling conditions on butterfly counts from Pollard walks using the Arctic fritillary, a common but cryptic butterfly in boreal forests of Alberta, Canada. We used an open population binomial Nâmixture model to disentangle the effects of habitat suitability and phenology on abundance of Arctic fritillaries, and its detectability by sampling different conditions of temperature, wind, cloud cover, and hour of the day. Detectability varied by one order of magnitude within the criteria recommended for Pollard walks (P varying between 0.04 and 0.45), and simulations show how sampling in suboptimal conditions increases substantially the risk of falseâabsence records (e.g., falseâabsences are twice as likely than trueâpresences when sampling 10 Arctic fritillaries at P = 0.04). Our results suggest that the risk of falseâabsences is highest for species that are poorly detectable, low in abundance, and with short flight periods. Analysis with open population binomial Nâmixture models could improve estimates of abundance and distribution for rare species of conservation interest, while providing a powerful method for assessing butterfly phenology, abundance, and behavior using counts from Pollard walks, but require more intensive sampling than conventional monitoring schemes
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