2,433 research outputs found
Propagation of Rarefaction Pulses in Discrete Materials with Strain-Softening Behavior
Discrete materials composed of masses connected by strongly nonlinear links
with anomalous behavior (reduction of elastic modulus with strain) have very
interesting wave dynamics. Such links may be composed of materials exhibiting
repeatable softening behavior under loading and unloading. These discrete
materials will not support strongly nonlinear compression pulses due to
nonlinear dispersion but may support stationary rarefaction pulses or
rarefaction shock-like waves. Here we investigate rarefaction waves in
nonlinear periodic systems with a general power-law relationship between force
and displacement , where . An exact solution
of the long-wave approximation is found for the special case of ,
which agrees well with numerical results for the discrete chain. Theoretical
and numerical analysis of stationary solutions are discussed for different
values of in the interval . The leading solitary rarefaction
wave followed by a dispersive tail was generated by impact in numerical
calculations.Comment: 15 pages, 4 figure
A method validation for simultaneous determination of phthalates and bisphenol A released from plastic water containers
Phthalates (or phthalate esters, PAEs) and bisphenol A (BPA) are widely used in various industries, particularly in the fields of cosmetics and packaging, and they increase the malleability and workability of materials. As a result of their use, some international health organizations have begun to study them. In this study, the authors developed a methodology for the simultaneous determination of dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP); dibutyl phthalate (DBP), bis(2-ethylhexyl) phthalate (DEHP); di-n-octyl-phthalate (DnOP) and bisphenol A (BPA) from drinking and non-potable waters. The extraction of PAEs and BPA was performed using a solvent-based dispersive liquid-liquid microextraction (SB-DLLME) method. The analytical determination was performed using a gas chromatography-ion trap mass spectrometry (GC-IT/MS) analysis. The entire procedure was validated as recoveries were studied according to the volume and the extraction solvent used, pH, and ionic strength. Dynamic linearity ranges and linear equations of all the compounds were experimentally determined as well as the limit of detection (LOD) (1-8 ng mL-1) and the limit of quantification (LOQ) (5-14 ng mL-1), reproducibility, and sensitivity. The method was applied to 15 water samples (mineral water and tap water) for determining PAEs and BPA released from the plastic container. After the release simulation, four PAEs (i.e., DiBP, DBP, DHEP, and DnOP) were determined at very low concentrations (below 1.2 ng mL-1) in two water samples from (sport) bottles
Increasing future gravitational-wave detectors sensitivity by means of amplitude filter cavities and quantum entanglement
The future laser interferometric gravitational-wave detectors sensitivity can
be improved using squeezed light. In particular, recently a scheme which uses
the optical field with frequency dependent squeeze factor, prepared by means of
a relatively short (~30 m) amplitude filter cavity, was proposed
\cite{Corbitt2004-3}. Here we consider an improved version of this scheme,
which allows to further reduce the quantum noise by exploiting the quantum
entanglement between the optical fields at the filter cavity two ports.Comment: 10 pages, 7 figure
A survey on energy efficiency in information systems
Concerns about energy and sustainability are growing everyday involving a wide range
of fields. Even Information Systems (ISs) are being influenced by the issue of reducing
pollution and energy consumption and new fields are rising dealing with this topic. One
of these fields is Green Information Technology (IT), which deals with energy efficiency
with a focus on IT. Researchers have faced this problem according to several points of
view. The purpose of this paper is to understand the trends and the future development
of Green IT by analyzing the state-of-the-art and classifying existing approaches to
understand which are the components that have an impact on energy efficiency in ISs
and how this impact can be reduced. At first, we explore some guidelines that can help
to understand the efficiency level of an organization and of an IS. Then, we discuss
measurement and estimation of energy efficiency and identify which are the components
that mainly contribute to energy waste and how it is possible to improve energy efficiency,
both at the hardware and at the software level
Who brings home the bacon? The influence of context on partners' contributions to the household income
Background: Female-breadwinner families represent a relatively new phenomenon in Europe. Little is known about the determinants of this couple type, which sensibly diverts from the traditional economic superiority of men within the household.Objective: This paper studies the contextual correlates of partners’ contribution to the household income, distinguishing between female-breadwinner, male-breadwinner, and equal-income couples. In particular, it focuses on the role of male unemployment rate and the prevalence of gender-egalitarian attitudes as possible explanations for the emergence of female-breadwinner and equal-income couples across European regions and countries.Methods: Using data from the fifth round (2010/2011) of the European Social Survey, integrated with data from the Eurostat database, we model the categorical variable identifying the couple type (male-breadwinner, female-breadwinner, or equal-income couple) by using a multilevel multinomial logistic regression model where individuals are nested within regions and countries.Results: The prevalence of female-breadwinner, male-breadwinner, and equal-income couples varies considerably across European countries as well as within countries. The prevalence of female-breadwinner couples is positively associated with male unemployment, while it is not influenced by the diffusion of gender-egalitarian attitudes. However, the diffusion of gender-egalitarian attitudes matters for explaining the variation in the prevalence of equal-income couples across Europe.Contribution: We add to the literature on partners’ contributions to household income by analysing the spatial distribution and the contextual correlates of female-breadwinner, male-breadwinner, and equal-income couples across European countries and regions.<br/
Self-cooling of a movable mirror to the ground state using radiation pressure
We show that one can cool a micro-mechanical oscillator to its quantum ground
state using radiation pressure in an appropriately detuned cavity
(self-cooling). From a simple theory based on Heisenberg-Langevin equations we
find that optimal self-cooling occurs in the good cavity regime, when the
cavity bandwidth is smaller than the mechanical frequency, but still larger
than the effective mechanical damping. In this case the intracavity field and
the vibrational mechanical mode coherently exchange their fluctuations. We also
present dynamical calculations which show how to access the mirror final
temperature from the fluctuations of the field reflected by the cavity.Comment: 4 pages, 3 figure
Quantum-limited force measurement with an optomechanical device
We study the detection of weak coherent forces by means of an optomechanical
device formed by a highly reflecting isolated mirror shined by an intense and
highly monochromatic laser field. Radiation pressure excites a vibrational mode
of the mirror, inducing sidebands of the incident field, which are then
measured by heterodyne detection. We determine the sensitivity of such a scheme
and show that the use of an entangled input state of the two sideband modes
improves the detection, even in the presence of damping and noise acting on the
mechanical mode.Comment: 8 pages, 4 figure
Comment on: Evidence and Stability Field of fcc Superionic Water Ice Using Static Compression
Weck et al. (1) report on the existence and stability fields of two
superionic (SI) phases of H2O ice at high P-T (P-T) conditions, which has been
a topic of static and dynamic experiments and theoretical calculations (see
Ref. (2) and references therein). They confirm Ref. (2) in that there are two
SI phases with bcc and fcc oxygen sublattices with the stability at low- and
high-P. However, they report on an extended stability field of fcc-SI ice
toward lower T but no sign of it below 57 GPa. Here we argue that the reported
phase boundaries of fcc-SI phase are not well experimentally justified due to
difficulties to perform adequate X-ray diffraction (XRD) and radiometric
measurements.Comment: 2 pages, 2 figures, 2 reference
Computer vision approach for the determination of microbial concentration and growth kinetics using a low cost sensor system
The measurement of microbial contamination is of primary importance in different fields, from environmental monitoring to food safety and clinical analysis. Today, almost all microbiology laboratories make microbial concentration measurements using the standard Plate Count Technique (PCT), a manual method that must be performed by trained personnel. Since manual PCT analysis can result in eye fatigue and errors, in particular when hundreds of samples are processed every day, automatic colony counters have been built and are commercially available. While quick and reliable, these instruments are generally expensive, thus, portable colony counters based on smartphones have been developed and are of low cost but also not accurate as the commercial benchtop instruments. In this paper, a novel computer vision sensor system is presented that can measure the microbial concentration of a sample under test and also estimate the microbial growth kinetics by monitoring the colonies grown on a Petri dish at regular time intervals. The proposed method has been in-house validated by performing PCT analysis in parallel under the same conditions and using these results as a reference. All the measurements have been carried out in a laboratory using benchtop instruments, however, such a system can also be realized as an embedded sensor system to be deployed for microbial analysis outside a laboratory environment
High-Pressure Synthesis of a Pentazolate Salt
The pentazolates, the last all-nitrogen members of the azole series, have
been notoriously elusive for the last hundred years despite enormous efforts to
make these compounds in either gas or condensed phases. Here we report a
successful synthesis of a solid state compound consisting of isolated
pentazolate anions N5-, which is achieved by compressing and laser heating
cesium azide (CsN3) mixed with N2 cryogenic liquid in a diamond anvil cell. The
experiment was guided by theory, which predicted the transformation of the
mixture at high pressures to a new compound, cesium pentazolate salt (CsN5).
Electron transfer from Cs atoms to N5 rings enables both aromaticity in the
pentazolates as well as ionic bonding in the CsN5 crystal. This work provides a
critical insight into the role of extreme conditions in exploring unusual
bonding routes that ultimately lead to the formation of novel high nitrogen
content species
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