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.

Effective absorption coefficient and effective thickness in attenuated total reflection spectroscopy.

Since the introduction of attenuated total reflection (ATR) spectroscopy for the characterization of materials, attempts have been made to relate the measured reflectivity (R) to the absorption coefficient (α) of the absorbing material of interest. The common approach is limited to the low absorption case under the assumption R∼exp(-αde), where de is an effective thickness, which is evaluated for the lossless case. In this Letter, a more detailed derivation leads to R=exp(-ßdp/2), enabling the definition of an ATR-effective absorption coefficient ß and the penetration depth dp of the electric field in the absorbing material. It is found that ß∼4πε2/λ, where ε2 is the imaginary part of the complex dielectric function of the absorbing material, and λ is the wavelength. An alternative formulation is R=exp(-αdef), where def is a generalized effective thickness for arbitrary strength of absorption which reduces to de in the low absorption limit. The experimental data for water, the biopolymer chitosan, and soda-lime glass prove the reliability of the ATR-effective absorption coefficient in the infrared range.

Diagnostic agreement between video capsule endoscopy and single and double balloon enteroscopy for small bowel bleeding at a tertiary care hospital in Bogota, Colombia. / Concordancia diagnóstica entre la videocápsula endoscópica y enteroscopia mono y de doble balón en la hemorragia de intestino delgado en un hospital de alta complejidad en Bogotá, Colombia.

INTRODUCTION: Video capsule endoscopy and balloon-assisted enteroscopy are complementary diagnostic methods in the study of small bowel bleeding, and different factors can affect their diagnostic yield. AIMS: To define the level of agreement between video capsule endoscopy and enteroscopy in small bowel bleeding, according to the type of lesion, in a cohort of patients at a tertiary care referral center. MATERIALS AND METHODS: A retrospective study was conducted that included 428 capsule endoscopies performed within the time frame of 2011 and 2019 at our healthcare institution. Seventy-four video capsule endoscopies, followed by enteroscopy, in 71 patients suspected of presenting with small bowel bleeding, were analyzed. RESULTS: Mean patient age was 63.9 ± 13.5 years and 42 patients were women. The two diagnostic procedures were performed. Overall diagnostic yield of positive findings between video capsule endoscopy and enteroscopy was 86.5% vs. 58.1%, respectively (p = 0.0527). Agreement between video capsule endoscopy and enteroscopy for positive pathologic findings was weak (Ik = 0.17, 95% CI: -0.0097-0.3543), but according to lesion type, it was good for inflammatory lesions (Ik = 0.71, 95% CI: 0.5182-0.9119) and moderate for angiectasias (Ik = 0.45, 95% CI: 0.2469-0.6538) and tumors (Ik = 0.40, 95% CI: 0.1217-0.6794). The results between the two methods differed in 38 patients (51.3%). There was complete intestinal capsule retention in one patient (1.4%) and active bleeding in 13 (17.6%). CONCLUSIONS: The present study showed that the two techniques had a similar overall detection rate for small bowel lesions, but the type of lesion was the main factor that could modify diagnostic agreement.

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.

Combined antibacterial/tissue regeneration response in thermal burns promoted by functional chitosan/silver nanocomposites.

We report the combined antibacterial/tissue regeneration responses to thermal burns promoted by functional chitosan/silver nanocomposites (CS/nAg) with ultralow silver content (0.018wt.%, 7-30nm). Our approach allows one to produce CS/nAg nanocomposites without silver nanoparticles (nAg) agglomeration, with bactericide potency higher than 1wt.% of nAg (ca. 10nm) content and, promoting the healing process in controlled thermal burns. CS/nAg films exhibit high antibacterial activity against S. aureus and P. aeruginosa after 1.5h of incubation, demonstrating the bacterial penetration into hydrated films and their interaction with nAg. Additionally, exceptional healing of induced thermal burns was obtained by increasing myofibroblasts, collagen remodeling, and blood vessel neoformation. These factors are associated with epiderma regeneration after 7days of treatment with no nAg release. Our results corroborate the controlled synthesis of nAg embedded in CS matrix with combined antibacterial/biocompatibility properties aiming to produce functional nanocomposites with potential use in wound dressing and health care applications.

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.

Functional diversity of phytochrome family in the control of light and gibberellin-mediated germination in Arabidopsis.

In several species, seed germination is regulated by light in a way that restricts seedling emergence to the environmental conditions that are likely to be favourable for the success of the new individual, and therefore, this behaviour is recognized to have adaptive value. The phytochromes are one of the most relevant photoreceptors involved in light perception by plants. We explored the redundancy and diversity functions of the phytochrome family in the control of seed responsiveness to light and gibberellins (GA) by using a set of phytochrome mutants of Arabidopsis. Our data show that, in addition to the well-known role of phyB in the promotion of germination in response to high red to far-red ratios (R/FR), phyE and phyD stimulate germination at very low R/FR ratios, probably by promoting the action of phyA. Further, we show that phyC regulates negatively the seed responsiveness to light, unravelling unexpected functions for phyC in seed germination. Finally, we find that seed responsiveness to GA is mainly controlled by phyB, with phyC, phyD and phyE having relevant roles when acting in a phyB-deficient background. Our results indicate that phytochromes have multiple and complex roles during germination depending on the active photoreceptor background.

Emergence of acoustic and optical bands in elastic systems.

Two elastic systems are considered in this work: A special linear chain of harmonic oscillators and a quasi one-dimensional vibrating rod. Starting in both cases with a locally periodic system formed by unit cells with a single element, these cells are converted into binary cells. The acoustic and optical bands then appear. For the vibrating rod experimental values are compared with theoretical results; in particular, the normal-mode amplitudes are obtained and the agreement is excellent.

Wave systems with direct processes and localized losses or gains: the nonunitary Poisson kernel.

We study the scattering of waves in systems with losses or gains simulated by imaginary potentials. This is done for a complex delta potential that corresponds to a spatially localized absorption or amplification. In the Argand plane the scattering matrix moves on a circle C centered on the real axis, but not at the origin, that is tangent to the unit circle. From the numerical simulations it is concluded that the distribution of the scattering matrix, when measured from the center of the circle C, agrees with the nonunitary Poisson kernel. This result is also obtained analytically by extending the analyticity condition, of unitary scattering matrices, to the no-unitary ones. We use this nonunitary Poisson kernel to obtain the distribution of nonunitary scattering matrices when measured from the origin of the Argand plane. The obtained marginal distributions have excellent agreement with the numerical results.

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.

Colesterol-IDL y parámetros lipídicos en diabéticos tipo 2 / IDL-cholesterol and lipidic parameters in diabetic patients type 2

La diabetes mellitus ocupa el sexto lugar de las defunciones por causas definidas en la provincia de Misiones. Nos propusimos establecer si existen diferencias significativas para Colesterol Total (CT), Triglicéridos (TG), Colesterol-HDL(CHDL), Colesterol-LDL(CLDL), Colesterol-IDL(CIDL), Colesterol no-HDL y los índices CT/CHDL y TG/CHDL entre diabéticos tipo 2 y un grupo control y comparar los valores de CIDL entre ambos grupos según fenotipo de dislipidemia. Se estudiaron 70 diabéticos tipo 2 (DM 2) y 57 controles. CT, TG, CHDL y CLDL se determinaron por métodos enzimáticos colorimétricos y CIDL por método de Wikinski. Los resultados obtenidos en DM 2 vs. controles fueron: CT 214±49 vs. 205±34 mg/dl (p=0.488); TG 194±119 vs. 128±65 mg/dl (p<0.001); CHDL 43±11 vs. 50±13 mg/dl (p=0.001); CLDL 135±43 vs. 132±32 mg/dl (p=0.934); CIDL 13.8±8.7 vs. 7.2±3.5 mg/dl (p<0.001); CT/CHDL 5.26±1.54 vs. 4.40±1.33 (p=0.001); TG/CHDL 5.01±3.95 vs. 2.97±2.24 (p<0.001) y Col no-HDL 172±48 vs. 155±35 mg/dl (p=0.07); a igual patrón electroforético tanto normolipémico (p=0.043), fenotipo II (p=0.006) o fenotipo IV (p=0.001) el CIDL fue más elevado en el primer grupo. La cuantificación del CIDL mejora la valoración del riesgo aterogénico en DM 2 principalmente en los normolipémicos.

Diabetes Mellitus is in the sixth death cause in the province of Misiones. Majority of patients die in relation with atherosclerosis, being dislipidemias one of the mechanism that explain this increased risk. We aimed to establish if there are significant differences for total cholesterol (TC), triglyceride (TG), HDL-cholesterol (HDLC), LDL-Cholesterol (LDLC), IDL-Cholesterol (IDLC), no-HDL Cholesterol and the index TC/HDLC and TG/HDLC between diabetic patients type 2 and a control group, as well as comparing the IDLC amount between both groups according to the dislipidemia phenotype. We studied 70 diabetic patients type 2 and 57 controls, with similar distribution in age, sex and body mass index. TC, TG, HDLC and LDLC were tested by enzymatic colorimetric methods with internal and external quality controls and the IDLC by Wikinski method. The results obtained in diabetic patients vs controls were (table N°1): TC 214 ±49 vs 205± 34 mg/dl (p=0.488); TG 194±119 vs 128±65 mg/dl (p<0.001); HDLC 43±11 vs 50±13 mg/dl(p=0.001); LDLC 135±43 vs 132± 32 mg/dl (p=0.934); IDLC 13.8± 8.7 vs 7.2±3.5 mg/dl (p<0.001) (figure N°1); TC/HDLC 5.26 ±1.54 vs 4.40± 1.33 (p=0.001); TG/HDLC 5.01±3.95 vs 2.97±2.24 (p<0.001) y no-HDL cholesterol 172±48 vs 155±35 mg/dl (p=0.07); at a same electrophoretic pattern ( normolipemic (p=0.043), phenotype II (p=0.006) or phenotype IV (p=0.001)),the IDLC was higher in the first group (figure N°2). The diabetic patients show a more atherogenic lipoprotein profile than the control group. The quantification of IDLC improvement the assessment of atherogenic risk in type 2 diabetic patients, specially normolipemics.

Wannier-stark ladders in one-dimensional elastic systems.

The optical analogues of Bloch oscillations and their associated Wannier-Stark ladders have been recently analyzed. In this Letter we propose an elastic realization of these ladders, employing for this purpose the torsional vibrations of specially designed one-dimensional elastic systems. We have measured, for the first time, the ladder wave amplitudes, which are not directly accessible either in the quantum-mechanical or optical cases. The wave amplitudes are spatially localized and coincide rather well with theoretically predicted amplitudes. The rods we analyze can be used to localize different frequencies in different parts of the elastic systems and vice versa.

Locally periodic Timoshenko rod: experiment and theory.

The flexural vibrations of a locally periodic rod, which consists of N unit cells, are discussed both from the experimental and theoretical points of view. Timoshenko's beam theory and the transfer matrix method are used to calculate the normal-mode frequencies and amplitudes. The theoretical values are then compared with the experimental ones, which are obtained using an electromagnetic acoustic transducer (EMAT). Good agreement between the numerical results and the experimental measurements is obtained. It is shown that as N grows, a band spectrum emerges.

Direct processes in chaotic microwave cavities in the presence of absorption.

We quantify the presence of direct processes in the S matrix of chaotic microwave cavities with absorption in the one-channel case. To this end the full distribution P(S)(S) of the S matrix, i.e., S=sqrt[R]e(itheta), is studied in cavities with time-reversal symmetry for different antenna coupling strengths T(a) or direct processes. The experimental results are compared with random-matrix calculations and with numerical simulations including absorption. The theoretical result is a generalization of the Poisson kernel. The experimental and the numerical distributions are in excellent agreement with theoretical predictions for all cases.

Distribution of reflection coefficients in absorbing chaotic microwave cavities.

The distribution of reflection coefficients P(R) for chaotic microwave cavities with time-reversal symmetry is investigated in different absorption and antenna coupling regimes. For all regimes the agreement between experimental distributions and random-matrix theory predictions is very good, provided both the antenna coupling T(a) and the wall absorption strength T(w) are taken into account in an appropriate way. These parameters are determined by independent experimental quantities.

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.

Compressional and torsional wave amplitudes in rods with periodic structures.

To measure and detect elastic waves in metallic rods a low-frequency electromagnetic-acoustic transducer has been developed. Frequencies range from a few hertz up to hundreds of kilohertz. With appropriate configuration of the transducer, compressional or torsional waves can be selectively excited or detected. Although the transducer can be used in many different situations, it has been tested and applied to a locally periodic rod, which consists of a finite number of unit cells. The measured wave amplitudes are compared with theoretical ones, obtained with the one-dimensional transfer matrix method, and excellent agreement is obtained.

Higher urinary albumin excretion is associated with abnormal erythrocyte Na(+)/Li(+) countertransport (SLC) in non-modulating essential hypertensives and offspring of hypertensive parents.

Non-modulating is a highly reproducible type of sodium-sensitive hypertension. The aim of this study was to evaluate in non-modulating individuals the erythrocyte sodium-lithium countertransport (SLC) abnormalities, which have been mentioned as a marker of non-modulation, and the association with increased microalbuminuria, as a marker of an early kidney impairment. We measured erythrocyte SLC in 10 normotensives (NT, 28 +/- 4 years), 20 offspring of hypertensive parents being 10 modulating (MHO, 25 +/- 6 years) and 10 non-modulating (NMHO, 26 +/- 5 years), and 23 essential hypertensives being 12 modulating (MHT, 34 +/- 5 years) and 11 non-modulating (NMHT, 32 +/- 4 years). In all the subjects studied, microalbuminuria was determined by duplicate 24-h urine collection by radioimmunoassay. In non-modulating offspring of hypertensive parents and essential hypertensives. SLC was significantly elevated when compared either with normotensives without family history of hypertension, modulating offspring of hypertensive parents or essential hypertensives (P < 0.025). Likewise, 24-h urinary albumin excretion was found higher in non-modulating individuals (essential hypertensives and offspring of hypertensive parents) than in modulating individuals (P < 0.01). In conclusion, non-modulators with higher SLC countertransport sodium transport abnormalities showed higher elimination of microalbuminuria suggesting that non-modulators may have an increased risk for developing cardiovascular morbidity and kidney impairment even in normotensive subjects with familiarity history of hypertension.