The colored Hanbury Brown--Twiss effect

The Hanbury Brown--Twiss effect is one of the celebrated phenomenologies of modern physics that accommodates equally well classical (interferences of waves) and quantum (correlations between indistinguishable particles) interpretations. The effect was discovered in the late thirties with a basic observation of Hanbury Brown that radio-pulses from two distinct antennas generate signals on the oscilloscope that wiggle similarly to the naked eye. When Hanbury Brown and his mathematician colleague Twiss took the obvious step to propose bringing the effect in the optical range, they met with considerable opposition as single-photon interferences were deemed impossible. The Hanbury Brown--Twiss effect is nowadays universally accepted and, being so fundamental, embodies many subtleties of our understanding of the wave/particle dual nature of light. Thanks to a novel experimental technique, we report here a generalized version of the Hanbury Brown--Twiss effect to include the frequency of the detected light, or, from the particle point of view, the energy of the detected photons. In addition to the known tendencies of indistinguishable photons to arrive together on the detector, we find that photons of different colors present the opposite characteristic of avoiding each others. We postulate that fermions can be similarly brought to exhibit positive (boson-like) correlations by frequency filtering.Comment: 18 pages, includes supplementary material of the derivation

Optimizing Phase Settings of High-Frequency Voltage Regulators for Power Delivery Applications

Every new computer server introduced to the market aims at delivering the best tradeoff between performance and power consumption. This goal is crucial in the case of servers for cloud computing hardware infrastructure. In this context, power delivery (PD) experts are adopting higher frequency switching voltage regulators (VR) to reduce platform’s cost as well as total cost of ownership (TCO). Because of this fact, the real estate of components, such as voltage regulators and output inductors, is shrinking as VR frequency increases. As a consequence, achieving the best performance of the VR implies looking into phase shedding schemes, as well as EM coupled inductor design, among other techniques, to mitigate power losses. This paper focuses on the study of the best angle arrangement possible for high frequency VR applications, by exploring angle settings under light load scenarios, aiming to minimize VR’s power loss and output’s voltage ripple

Variation of growth performance of the striped venus clam Chamelea gallina (Mollusca: Bivalvia) (Linnaeus, 1758) in relation to environmental variables along the southern part of its geographic range

This study reports relative growth, shell length-age keys and growth performance indices (overall growth performance (OGP) and phi prime) for the striped venus Chamelea gallina from the Huelva coast in southwest (SW) Spain. The morphometric relationship shell height (SH)/shell length (SL) presented isometric growth whereas SL/shell width (SW) and SL/weight (W) displayed negative allometric growth. Shell length at age was estimated through length-frequency distribution (LF) and internal shell growth bands by acetate peel method (AP). C. gallina population consists mainly of three age classes with shell lengths around 13-15 mm for the first year, 25 mm for the second year and 30 mm for the third year. The OGP and phi prime values obtained in the present study are within the range of values for other C. gallina populations from the Gulf of Cádiz. Nevertheless, marked differences in growth performance were observed between populations from the Black Sea (lower growth performance) and from other locations along the southern distribution area of this species, which may be related to the low levels of temperature (SST), salinity (SSS) and chlorophyll-a (chl-a) concentration that exhibit large intra-annual fluctuations.En prensa0,371

PtRu nanoparticles supported on noble carbons for ethanol electrooxidation

In this work, three cytosine derived nitrogen doped carbonaceous materials (noble carbons, NCs) with different atomic C/N ratios and porous networks have been synthesized and used as supports for PtRu electrocatalysts in the ethanol oxidation reaction (EOR) for clean hydrogen production. Both, the metal phase and the carbon support play critical roles in the electrocatalysts final performance. Lower NPs size distribution was obtained over supports with low atomic C/N ratios (i.e., 4 and 6) and defined porosity (i.e., 1701 m2 g−1 for PtRu/CNZ and 1834 m2 g−1 for PtRu/CLZ, respectively). In contrast, a lower C/N ratio and poor porous network (i.e., 65 m2 g−1, PtRu/CLK) led to the largest particle size and fostered an increase of the alloying degree between Pt and Ru NPs (i.e., 3 for C/N ~ 6 and 28 for C/N ~ 3). Electrochemical active surface area was found to increase with decreasing NPs size and the alloy extent, due to a higher availability of Pt active sites. Accelerated degradation tests showed that PtRu/NCs outperform similar to PtRu NPs on commercial carbon pointing at the stabilizing effect of NCs. PtRu/CNZ exhibited the best electrochemical performance (i.e., 69.1 mA mgPt−1), outperforming PtRu/CLZ and PtRu/CLK by 3- and 9-fold, respectively, due to a suitable compromise between particle sizes, degree of alloy, textural properties and elemental composition. Best anodes were scaled-up to a proton exchange membrane cell and PtRu/CNZ was proved to provide the best electrocatalytic activity (262 mA cm−2 and low energy requirements), matching the values obtained by the state of the art of EOR electrocatalysts

Alteraciones en la tasa de respiración de Daphnia magna bajo concentraciones subletales de anatoxina-a

Anatoxina-a es una potente neurotoxina producida por cianobacterias dulceacuícolas que puede representar un riesgo, por sus efectos agudos, para diferentes formas de vida, incluyendo los seres humanos. Aunque se conocen los efectos agudos y crónicos de esta toxina, pocos estudios aportan datos de medidas de efectos subletales sobre la respiración del zooplancton. En este trabajo se cuantifican cambios en la respiración de Daphnia magna bajo una concentración subletal de anatoxina-a, en condiciones experimentales, por medio de un sistema automatizado de medida en continuo de consumo de Oxígeno. Los resultados indican que la presencia de anatoxina-a en dosis subletales reduce significativamente la actividad respiratoria en esta especie, con efectos, dependientes de la edad del organismo.Anatoxin-a is a potent neurotoxin produced by some freshwater cyanobacteria which, because of its acute toxic effects, may represent a hazard to aquatic organisms, and even to human beings. Both the acute and chronic effects of this toxin are rather well known, but few studies provided information about its sublethal effect on the zooplankton respiration. In this paper we have quantified respiration changes in Daphnia magna under sublethal anatoxin-a concentrations in experimental conditions, using an automatic open-flow system of continuous measurement of oxygen consumption. Our results show that the presence of anatoxin-a at sublethal doses reduces significantly the respiratory activity of the animals, being the effects greatly dependent on the individual age

Size determination and quantification of engineered cerium oxide nanoparticles by flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry

Facing the lack of studies on characterization and quantification of cerium oxide nanoparticles (CeO2 NPs), whose consumption and release is greatly increasing, this work proposes a method for their sizing and quantification by Flow Field-flow Fractionation (FFFF) coupled to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two modalities of FFFF (Asymmetric Flow- and Hollow Fiber-Flow Field Flow Fractionation, AF4 and HF5, respectively) are compared, and their advantages and limitations discussed. Experimental conditions (carrier composition, pH, ionic strength, crossflow and carrier flow rates) are studied in detail in terms of NP separation, recovery, and repeatability. Size characterization of CeO2 NPs was addressed by different approaches. In the absence of feasible size standards of CeO2 NPs, suspensions of Ag, Au, and SiO2 NPs of known size were investigated. Ag and Au NPs failed to show a comparable behavior to that of the CeO2 NPs, whereas the use of SiO2 NPs provided size estimations in agreement to those predicted by the theory. The latter approach was thus used for characterizing the size of CeO2 NPs in a commercial suspension. Results were in adequate concordance with those achieved by transmission electron microscopy, X-ray diffraction and dynamic light scattering. The quantification of CeO2 NPs in the commercial suspension by AF4-ICP-MS required the use of a CeO2 NPs standards, since the use of ionic cerium resulted in low recoveries (99 ± 9% vs. 73 ± 7%, respectively). A limit of detection of 0.9 µg L-1 CeO2 corresponding to a number concentration of 1.8 × 1012 L-1 for NPs of 5 nm was achieved for an injection volume of 100 µL

The Sunyaev-Zel'dovich effects from a cosmological hydrodynamical simulation: large-scale properties and correlation with the soft X-ray signal

Using the results of a cosmological hydrodynamical simulation of the concordance LambdaCDM model, we study the global properties of the Sunyaev-Zel'dovich (SZ) effects, both considering the thermal (tSZ) and the kinetic (kSZ) component. The simulation follows gravitation and gas dynamics and includes also several physical processes that affect the baryonic component, like a simple reionization scenario, radiative cooling, star formation and supernova feedback. Starting from the outputs of the simulation we create mock maps of the SZ signals due to the large structures of the Universe integrated in the range 0 < z < 6. We predict that the Compton y-parameter has an average value of (1.19 +/- 0.32) 10^-6 and is lognormally distributed in the sky; half of the whole signal comes from z < 1 and about 10 per cent from z > 2. The Doppler b-parameter shows approximately a normal distribution with vanishing mean value and a standard deviation of 1.6 10^-6, with a significant contribution from high-redshift (z > 3) gas. We find that the tSZ effect is expected to dominate the primary CMB anisotropies for l >~ 3000 in the Rayleigh-Jeans limit, while interestingly the kSZ effect dominates at all frequencies at very high multipoles (l >~ 7 10^4). We also analyse the cross-correlation between the two SZ effects and the soft (0.5-2 keV) X-ray emission from the intergalactic medium and we obtain a strong correlation between the three signals, especially between X-ray emission and tSZ effect (r_l ~ 0.8-0.9) at all angular scales.Comment: 12 pages, 15 figures. Accepted for publication in MNRAS. Minor changes, added reference

Improving the Efficiency of the Bowden Cable Terminal Injection Process for the Automotive Industry

Control cables transfer force between two separate locations by a flexible mean, and hence, they are important in the automotive industry and many others; their terminals interact with both moving and moved mechanisms, so they must be strong. Cable terminals are commonly made of ZAMAK and are created by injection molding. However, such a production method requires leaving extra material to allow the correct molding, also known as sprues, which are removed later in the process. In this case, the sprues were separating from the terminals in an uncontrolled way. In this work, the cause of sprues separating prematurely from the terminals in a production line is addressed. The whole process was analyzed, and each possible solution was evaluated using process improvement techniques and the Finite Element Method, leading to the best solutions. Molds, mold structures, and auxiliary equipment were improved, resulting in a minimally invasive intervention and remaining compatible with other equipment. Cost analyses were done, indicating an investment return in less than a year. The modification led to a reduction of 62.6% in the sprue mass, while porosity was reduced by 10.2% and 55.9%, corresponding to two terminal models. In conclusion, the interventions fulfilled the requirements and improved the operation of the line.info:eu-repo/semantics/publishedVersio

Integrated K-band spectra of old and intermediate-age globular clusters in the Large Magellanic Cloud

Current stellar population models have arguably the largest uncertainties in the near-IR wavelength range, partly due to a lack of large and well calibrated empirical spectral libraries. In this paper we present a project, which aim it is to provide the first library of luminosity weighted integrated near-IR spectra of globular clusters to be used to test the current stellar population models and serve as calibrators for the future ones. Our pilot study presents spatially integrated K-band spectra of three old (>10 Gyr) and metal poor ([Fe/H]~-1.4), and three intermediate age (1-2 Gyr) and more metal rich ([Fe/H]~-0.4) globular clusters in the LMC. We measured the line strengths of the Na I, Ca I and 12CO(2-0) absorption features. The Na I index decreases with the increasing age and decreasing metallicity of the clusters. The Dco index, used to measure the 12CO(2-0) line strength, is significantly reduced by the presence of carbon-rich TP-AGB stars in the globular clusters with age ~1 Gyr. This is in contradiction with the predictions of the stellar population models of Maraston (2005). We find that this disagreement is due to the different CO absorption strength of carbon-rich Milky Way TP-AGB stars used in the models and the LMC carbon stars in our sample. For globular clusters with age >2 Gyr we find Dco index measurements consistent with the model predictions.Comment: 15 pages, 11 figures, accepted for publication in A&