Deviations from Poisson statistics in the spectra of free rectangular thin plates.

The counterintuitive fact that wave chaos appears in the bending spectrum of free rectangular thin plates is presented. After extensive numerical simulations, varying the ratio between the length of its sides, it is shown that (i) frequency levels belonging to different symmetry classes cross each other and (ii) for levels within the same symmetry sector, only avoided crossings appear. The consequence of anticrossings is studied by calculating the distribution of the ratio of consecutive level spacings for each symmetry class. The resulting ratio distributions disagree with the expected Poissonian result. They are then compared with some well-known transition distributions between Poisson and the Gaussian orthogonal random matrix ensemble. It is found that the distribution of the ratio of consecutive level spacings agrees with the prediction of the Rosenzweig-Porter model. Also, the normal-mode vibration amplitudes are found experimentally on aluminum plates, before and after an avoided crossing for symmetrical-symmetrical, symmetrical-antisymmetrical, and antisymmetrical-symmetrical classes. The measured modes show an excellent agreement with our numerical predictions. The expected Poissonian distribution is recovered for the simply supported rectangular plate.

Emulating tightly bound electrons in crystalline solids using mechanical waves.

Solid state physics deals with systems composed of atoms with strongly bound electrons. The tunneling probability of each electron is determined by interactions that typically extend to neighboring sites, as their corresponding wave amplitudes decay rapidly away from an isolated atomic core. This kind of description is essential in condensed-matter physics, and it rules the electronic transport properties of metals, insulators and many other solid-state systems. The corresponding phenomenology is well captured by tight-binding models, where the electronic band structure emerges from atomic orbitals of isolated atoms plus their coupling to neighboring sites in a crystal. In this work, a mechanical system that emulates dynamically a quantum tightly bound electron is built. This is done by connecting mechanical resonators via locally periodic aluminum bars acting as couplers. When the frequency of a particular resonator lies within the frequency gap of a coupler, the vibrational wave amplitude imitates a bound electron orbital. The localization of the wave at the resonator site and its exponential decay along the coupler are experimentally verified. The quantum dynamical tight-binding model and frequency measurements in mechanical structures show an excellent agreement. Some applications in atomic and condensed matter physics are suggested.

Experimental Evidence of Rainbow Trapping and Bloch Oscillations of Torsional Waves in Chirped Metallic Beams.

The Bloch oscillations (BO) and the rainbow trapping (RT) are two apparently unrelated phenomena, the former arising in solid state physics and the latter in metamaterials. A Bloch oscillation, on the one hand, is a counter-intuitive effect in which electrons start to oscillate in a crystalline structure when a static electric field is applied. This effect has been observed not only in solid state physics but also in optical and acoustical structured systems since a static electric field can be mimicked by a chirped structure. The RT, on the other hand, is a phenomenon in which the speed of a wave packet is slowed down in a dielectric structure; different colors then arrive to different depths within the structure thus separating the colors also in time. Here we show experimentally the emergence of both phenomena studying the propagation of torsional waves in chirped metallic beams. Experiments are performed in three aluminum beams in which different structures were machined: one periodic and two chirped. For the smaller value of the chirping parameter the wave packets, with different central frequencies, are back-scattered at different positions inside the corrugated beam; the packets with higher central frequencies being the ones with larger penetration depths. This behavior represents the mechanical analogue of the rainbow trapping effect. This phenomenon is the precursor of the mechanical Bloch oscillations, which are here demonstrated for a larger value of the chirping parameter. It is observed that the oscillatory behavior observed at small values of the chirp parameter is rectified according to the penetration length of the wave packet.

Experimental evidence of coherent transport.

Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations.

Diffuse reflectance optical topography: location of inclusions in 3D and detectability limits.

In the present contribution we investigate the images of CW diffusely reflected light for a point-like source, registered by a CCD camera imaging a turbid medium containing an absorbing lesion. We show that detection of µa variations (absorption anomalies) is achieved if images are normalized to background intensity. A theoretical analysis based on the diffusion approximation is presented to investigate the sensitivity and the limitations of our proposal and a novel procedure to find the location of the inclusions in 3D is given and tested. An analysis of the noise and its influence on the detection capabilities of our proposal is provided. Experimental results on phantoms are also given, supporting the proposed approach.

Physiological and practical effects of progesterone on reproduction in dairy cattle.

The discovery of progesterone (P4) and elucidation of the mechanisms of P4 action have an important place in the history of endocrinology and reproduction. Circulating P4 concentration is determined by a balance between P4 production, primarily by the corpus luteum (CL), and P4 metabolism, primarily by the liver. The volume of luteal tissue and number and function of large luteal cells are primary factors determining P4 production. Rate of P4 metabolism is generally determined by liver blood flow and can be of critical importance in determining circulating P4 concentrations, particularly in dairy cattle. During timed artificial insemination (AI) protocols, elevations in P4 are achieved by increasing number of CL by creating accessory CL or by supplementation with exogenous P4. Dietary manipulations can also alter circulating P4, although practical methods to apply these techniques have not yet been reported. Elevating P4 before the timed AI generally decreases double ovulation and increases fertility to the timed AI. Near the time of AI, slight elevations in circulating P4, possibly due to inadequate luteal regression, can dramatically reduce fertility. After AI, circulating P4 is critical for embryo growth and establishment and maintenance of pregnancy. Many studies have attempted to improve fertility by elevating P4 after timed AI. Our recent meta-analysis and manipulative study indicated small fertility benefits (3% to 3.5%) mostly in primiparous cows. Thus, previous research has provided substantial insight into mechanisms regulating circulating P4 concentrations and actions. Understanding this prior research can focus future research on P4 manipulation to improve reproductive success.

Maximum force levels in different positions of shoulder and elbow.

The number of occupational diseases in Mexico is alarming and clearly it is important to do studies with the purpose of improving the design of workstations. The objective of this research is to determine the maximum force levels in different positions of shoulder and elbow. An experiment was conducted with 16 subjects between 18 and 28 years old: 8 male and 8 female. We considered 16 different positions, working with the right and left arm to perform the tasks of pull and push. The tasks consisted of pushing or pulling a dynamometer for a period of 3 seconds as hard as possible. The results were presented in tables. The tables show the mean, standard deviation and range of force levels in different positions.

Use of color lights for the detection of anomalies in quality systems.

The importance of eye care in the industry is a first level topic, due to most of the assembly and manufacturing aimed companies of various products that require direct health care of their employees, specially eye care. The lighting system, the lamp features and job tasks are factors that impact over the visual performance of the worker. Each of these factors, either by themselves or in conjunction, influences the visual performance of the employee, and therefore its safety and efficacy. Some of the reported symptoms are: problem of visual fixation, eye redness, tearing, headache, blurred vision, eyelids heaviness and dry eyes, [7]. The research was developed with 48 people, 27 male and 21 female, in the range of ages of 17 to 58 years old. In the experiment were used illumination system base on Diode Emitting lights (LED's) of five different colors (White, Blue, Green, Red and Yellow), the reason of use of LED's it is because are source of monochromatic light, also it is also saving power light and low heating dissipation.

Intravenous gammaglobulin-associated renal impairment reported to the FDA: 2004 - 2009.

Since the 1999 US Food and Drug Administration (FDA) warning of renal failure/dysfunction associated with intravenous gammaglobulin (IVIg), there has been a movement towards developing safer, more convenient formulations. Until now, the scope of renal failure associated with IVIg, has not been well described. The FDA Adverse Event Reporting System (AERS) from 2004 through 2009 was examined for renal impairment reactions due to IVIg and associated demographic features, comorbidities and indications. Anaphylaxis cases associated with IVIg administration were used as a comparison group. There were 90 renal impairment cases associated with IVIg administration. Neuromuscular disorders (33/37%) and hematologic disorders (32/36%) were the predominant treatment indications. When reported anaphylaxis versus renal impairment due to IVIg was examined as a binary outcome in logistic regression modeling, renal impairment was predicted by sucrose presence, increasing age and non-hypogammaglobulinemic indications. Of the 34 hemodialysis cases, the excipient was known in 28 and all but 1 consisted of sucrose. IVIg containing sucrose was used in 33 of 48 nonhemodialysis cases. More hemodialysis cases also had diabetes mellitus. When the interval between renal impairment and the first IVIg infusion was determined, the renal impairment was reported by the second day in 43.3% of cases, and between 3 and 5 days in 41.7% of cases. Despite an evolution in clinical usage and formulations, renal impairment after IVIg administration continues to be reported. Sucrose as the excipient in IVIg plays a major role, but other factors are also important. These findings have implications in the management of patients treated with IVIg.

Absorption strength in absorbing chaotic cavities.

We derive an exact formula to calculate the absorption strength in absorbing chaotic systems such as microwave cavities or acoustic resonators. The formula allows us to estimate the absorption strength as a function of the averaged reflection coefficient and the real coupling parameter. We also define the weak and strong absorption regimes in terms of the coupling parameter and the absorption strength.

Comparative study of the effectiveness of thyroxine and steroids on reduction of neonatal morbidity: outcome at 20 months follow-up

This study analyzes health, growth and neurodevelopmental outcome of infants who received prenatal corticosteroids with or without thyroxine for fetal lung maturation. During a 12 month period infants from a prospective double blind study who received either steroids or steroids combined with thyroxine for pulmonary maturation and who had reached 18 months of age were recalled for evaluation of health status, growth parameters and neurodevelopmental outcome using the Bayley Scales 2nd edition (BSID-II). Mental developmental index (MDI), psychomotor developmental index (PDI), language developmental age (LDA), cognitive developmental age (CDA), and behavioral rating scales (BRS) were compared for the two treatment groups. The Hollingshead Socioeconomic Status Index was determined for each infant. Of a total of 134 patients enrolled during the study period, 66 patients return for follow up. Data from 60 patients was included in the final analysis. Of these, 32 had received the combination regimen and 28 had solely received only steroids. Demographics and neonatal morbidity were similar in both groups. No statistical differences in growth parameters, hospital admissions, respiratory problems, surgical procedures or frequency of infections were found. Neurodevelopmental parameters (MDI, PDI) were similar in both treatment groups, although, below normal in both groups. Language delay was more common in infants who received prenatal corticosteroids. There were no difference in the incidence of neurologic abnormalities. The addition of thyroxine to steroids did not affect growth or neuro-developmental outcome of the infants at 18 to 22 postnatal age.

Fluctuation-dissipation theorem for metastable systems.

We show that an appropriately defined fluctuation-dissipation theorem, connecting generalized susceptibilities and time correlation functions, is valid for times shorter than the nucleation time of the metastable state of Markovian systems satisfying detailed balance. This is done by assuming that such systems can be described by a superposition of the ground and first excited states of the master equation. We corroborate our results numerically for the metastable states of a two-dimensional Ising model.