On the thermodynamics of hydrogen adsorption over Pt(111) in 0.05M NaOH

The reasons for the sluggish kinetics of the hydrogen adsorption reaction in alkaline media remain a question still to be solved. This information is important to achieve a complete understanding of the mechanistic details that could lead to the production of key catalytic materials necessary for the development of a future hydrogen economy. For a better understanding of this reaction, it is important to acquire information about the thermodynamic parameters characteristic of the different steps in the reaction. Among these, the hydrogen adsorption is a key step in the process of hydrogen evolution. Although some debate still remains about the difference between adsorbed hydrogen in the underpotential deposition (UPD) region and at the overpotential deposition region, there is no doubt that understanding the former can help in the understanding of the latter. Making use of charge density measurements, we report on this paper a thermodynamic study of the hydrogen UPD process on Pt(111) in 0.05M NaOH over the range of temperatures from 283 ≤ T/K ≤ 313. The coulometric features corresponding to H_UPD allow for the calculation of the hydrogen coverage and a fit to a Generalized Frumkin isotherm. From these values, different thermodynamic functions for the UPD reaction have been calculated: ΔG_ads, ΔS_ads, ΔH_ads, and the Pt-H bond energy. From extrapolation, a value of ΔS_ads ^◦=-7.5±4Jmol^-1K^-1 was found, which is very close to 0, much lower than previously reported measurements both in acid and in alkaline solutions. Such value has an effect on the enthalpy and bond energy calculations, the latter having a decreasing tendency with pH and coverage. This tendency is completely different from the acidic systems and implies that the change in the thermodynamic functions due to the formation of the double layer and the reorganization of interfacial water has a strong influence on the process in high pH solutions.

Clinical characteristics and natural history of PRKAG2 syndrome

Purpose

Mutations in the PRKAG2 gene cause a syndrome characterized by hypertrophic cardiomyopathy, conduction disease and ventricular preexcitation. Only a small number of cases have been reported, and the natural history of the disease is poorly understood. The aim of this study is to describe phenotype and natural history of PRKAG2 mutation in a large multicenter international cohort.

Methods

We retrospectively studied clinical, electrocardiographic and echocardiographic data from 90 individuals with PRKAG2 mutations (53% males, 33±21 years) from 27 centers.

Results

At baseline evaluation, 93% of patients were in NYHA functional class I-II. Maximum left ventricular (LV) wall thickness was 18±8 mm and LV hypertrophy (LVH) was present in 60 (67%) subjects at baseline. LV ejection fraction was 61±12%. Seventeen pactients (19%) had a pacemaker (mean age at implantation 37±15and 16 (18%) had atrial fibrillation (AF) (mean age 41±23 years) and 33% had ventricular preexcitation or had undergone an accessory pathway ablation. After a median follow-up of 6 years (IQR:2.3–13.9), 71% of individuals had LVH, 29% had AF, 21% a de novo pacemaker (mean age at implantation 38±18 years), 14% required admission for heart failure (HF), 8% experienced sudden cardiac death or equivalent, 4% required a heart transplant and 13% died.

Conclusions

PRKAG2 syndrome is a severe, progressive cardiomyopathy characterized by high rates of AF, conduction disease, advanced HF and life-threatening arrhythmias. Outcome is not clearly related to the classical features of preexcitation and severe LVH, which are not always present.

Natural history of PRKAG2 syndrome

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Instituto de Salud Carlos III (ISCIII)

Imaging the optical properties of turbid media with single-pixel detection based on the Kubelka-Munk model

We present a diffuse optical imaging system with structured illumination and integrated detection based on the Kubelka-Munk light propagation model for the spatial characterization of scattering and absorption properties of turbid media. The proposed system is based on the application of single-pixel imaging techniques. Our strategy allows us to retrieve images of the absorption and scattering properties of a turbid media slab by using integrating spheres with photodiodes as bucket detectors. We validate our idea by imaging the absorption and scattering coefficients of a spatially heterogeneous phantom.

5163Predictors of adverse cardiovascular events in patients with truncating variants in the filamin c (flnc) gene

Background

Truncating variants in Filamin C (FLNCtv) are associated with arrhythmogenic (AC) and dilated cardiomyopathies (DCM). Affected patients are reported to demonstrate a high incidence of arrhythmic and heart-failure related cardiovascular events. The aim of this study was to determine factors that predict adverse events in mutation carriers.

Methods

The study cohort comprised 168 FLNCtv carriers followed at 19 European centres. Baseline and longitudinal follow-up clinical data were collected. The primary endpoint was a composite of sudden cardiac death (SCD), aborted SCD, appropriate implantable cardioverter-defibrillator (ICD) shock, cardiac transplantation (HTx) and mortality from end-stage heart failure (ESHF).

Results

47 different pathogenic or likely-pathogenic FLNCtv were identified in 60 unrelated probands. In those with baseline and longitudinal data (160 patients; 57 probands), 114 (71.3%) patients exhibited evidence of cardiac disease at initial evaluation. Gene penetrance was 85% by the age of 40 years. During a median follow-up of 1.5 years (IQR 4.1), 24 individuals (15%) reached the primary endpoint – 16 arrhythmic (SCD/aborted SCD/ICD shock) and 8 heart failure (ESHF/HTx) related-events. Univariable predictors at baseline evaluation of the composite primary endpoint included proband status (HR 4.0, 95% CI: 1.5–10.9, p=0.01), symptoms of dyspnoea (HR 2.8, 95% CI: 1.2–6.4, p=0.02), LV systolic dysfunction (LVSD) (HR 12.4, 95% CI: 2.9–53.2, p=0.001), frequent ventricular ectopy (VE>500) on 24-hour Holter (HR 9.3, 95% CI: 1.2–74.7, p=0.04) and the presence of late gadolinium enhancement on CMR (HR 8.9, 95% CI: 1.2–68.5, p=0.04).

Multivariable analysis identified LVSD (LVEF <50%) at baseline as an independent predictor of the primary endpoint with a hazard ratio of 8.6 (95% CI: 1.8–41.5, p=0.007). ROC analysis using LV systolic dysfunction to predict the primary endpoint demonstrated an area under the curve of 0.84 (95% CI: 0.76–0.91, p<0.001) and identified an optimal LVEF “cut-off” of 47% for predicting adverse events with a Youden's index of 0.61 (sensitivity 0.91; specificity 0.70).

Kaplan-Meier plot to demonstrate freedom

Conclusions

LVSD is associated with an over 8-fold increase in the hazard of a primary endpoint event in FLNCtv gene carriers indicating that these patients should be considered for implantable cardioverter-defibrillator (ICD) implantation, optimal heart failure medical therapy and close clinical follow-up.

Acknowledgement/Funding

NIHR Biomedical Research Centre; Instituto de Salud Carlos III; DETECTIN-HF project; Wellcome Trust;CIBERCV; EU Regional Development Fund; FEDER.

Efficacy of Ranolazine in Patients With Symptomatic Hypertrophic Cardiomyopathy: The RESTYLE-HCM Randomized, Double-Blind, Placebo-Controlled Study

BACKGROUND

The late sodium current inhibitor ranolazine reverses the main electrophysiological and mechanical abnormalities of human hypertrophic cardiomyopathy (HCM) cardiomyocytes in vitro, suggesting potential clinical benefit. We aimed to assess the effect of ranolazine on functional capacity, symptomatic status, diastolic function, and arrhythmias in HCM.

METHODS AND RESULTS

In this multicenter, double-blind, phase 2 study, 80 adult patients with nonobstructive HCM (age 53±14 years, 34 women) were randomly assigned to placebo (n=40) or ranolazine 1000 mg bid (n=40) for 5 months. The primary end point was change in peak VO₂ compared with baseline using cardiopulmonary exercise test. Echocardiographic lateral and septal E/E' ratio, prohormone brain natriuretic peptide levels, 24-hour Holter arrhythmic profile, and quality of life were assessed. Ranolazine was safe and well tolerated. Overall, there was no significant difference in VO₂ peak change at 5 months in the ranolazine versus placebo group (delta 0.15±3.96 versus -0.02±4.25 mL/kg per minute; P=0.832). Ranolazine treatment was associated with a reduction in 24-hour burden of premature ventricular complexes compared with placebo (>50% reduction versus baseline in 61% versus 31%, respectively; P=0.042). However, changes in prohormone brain natriuretic peptide levels did not differ in the ranolazine compared with the placebo group (geometric mean median [interquartile range], -3 pg/mL [-107, 142 pg/mL] versus 78 pg/mL [-71, 242 pg/mL]; P=0.251). Furthermore, E/E' ratio and quality of life scores showed no significant difference.

CONCLUSIONS

In patients with nonobstructive HCM, ranolazine showed no overall effect on exercise performance, plasma prohormone brain natriuretic peptide levels, diastolic function, or quality of life. The drug showed an excellent safety profile and was associated with reduced premature ventricular complex burden. Late sodium current inhibition does not seem to improve functional capacity in HCM.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrialsregister.eu. Unique identifier: 2011-004507-20.

Single-pixel digital holography with phase-encoded illumination

We demonstrate imaging of complex amplitude objects through digital holography with phase-structured illumination and bucket detection. The object is sampled with a set of micro-structured phase patterns implemented onto a liquid-crystal spatial light modulator while a bucket detector sequentially records the irradiance fluctuations corresponding to the interference between object and reference beams. Our reconstruction algorithm retrieves the unknown phase information from the full set of photocurrent measurements. Interestingly, the sampling functions can be codified onto the reference beam, so they can be nonlocal with respect to the object. Finally, we show that the system is well-fitted for transmission of the object information through scattering media.

Involvement of the -420C>G RETN polymorphism in myocardial fibrosis in patients with hypertrophic cardiomyopathy

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and fibrosis. HCM is an autosomal-dominant disease caused by more than 400 mutations in sarcomeric genes. Changes in nonsarcomeric genes contribute to its phenotypic heterogeneity. Cardiac fibrosis can be studied using late gadolinium enhancement (LGE) cardiac magnetic resonance imaging. We evaluated the potential role of two polymorphisms in nonsarcomeric genes on interstitial fibrosis in HCM.

MATERIALS AND METHODS

Two polymorphisms in nonsarcomeric genes [ACE (deletion of 287 bp in the 16th intron) and RETN (-420C>G)] were analysed in 146 HCM patients. Cardiac fibrosis was assessed using LGE to determine the number of affected segments.

RESULTS

Allelic frequencies in ACE and RETN polymorphisms were consistent with the Hardy-Weinberg equilibrium (both P > 0.05). We found that the presence of the polymorphic allele in the -420C>G RETN polymorphism was independently associated with the number of affected segments of LGE (P = 0.038). Increased circulating resistin concentration, measured by enzyme-linked immunosorbent assay, was associated with a higher degree of cardiac fibrosis. Myocardial fibrosis, assessed by Masson's trichrome staining, was associated with the -420C>G RETN polymorphism in 46 tissue samples obtained by septal myectomy (P = 0.044).

CONCLUSIONS

The -420C>G RETN polymorphism was independently associated with the degree of cardiac fibrosis, assessed by LGE, in patients with HCM. In addition, there was an association between the polymorphism and the circulating resistin levels as well as with myocardial fibrosis in tissues obtained by myectomy. Investigating the physiological implication of the RETN polymorphism in HCM in combination with the use of imaging technologies might help to establish the severity of disease in patients with HCM.

Prognostic value of two polymorphisms in non-sarcomeric genes for the development of atrial fibrillation in patients with hypertrophic cardiomyopathy

BACKGROUND

Several non-sarcomeric genes have been postulated to act as modifiers in the phenotypic manifestations of hypertrophic cardiomyopathy (HCM). The development of atrial fibrillation (AF) in HCM has adverse prognostic implications with increased thromboembolism and functional class impairment.

AIM

We tested the hypothesis that 2 non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] are associated with the development of AF.

DESIGN

Prospective study.

METHODS

Two polymorphisms in non-sarcomeric genes [CYP11B2 (-344T>C) and COL1A1 (2046G>T)] were analysed in 159 HCM patients (49.3 ± 14.9 years, 70.6% male) and 136 controls. All subjects were clinically stable and in sinus rhythm at entry in the study, without ischemic heart disease or other significant co-morbidities that could mask the effect of the analysed polymorphisms (i.e. previous AF). Thirty-nine patients (24.4%) developed AF during a median follow-up of 49.5 months.

RESULTS

Patients with the -344T>C polymorphism in CYP11B2 gene had a higher risk for AF development [HR: 3.31 (95% CI 1.29-8.50); P = 0.008]. In a multivariate analysis, the presence of the C allele in CYP11B2 gene [HR: 3.02 (1.01-8.99); P = 0.047], previous AF [HR: 2.81 (1.09-7.23); P = 0.033] and a left atrial diameter of ≥42 mm [HR: 2.69 (1.01-7.18); P = 0.048] were independent predictors of AF development. The presence of the polymorphic allele was associated with higher aldosterone serum levels.

CONCLUSION

We have shown for the first time that the CYP11B2 polymorphism is an independent predictor for AF development in HCM patients. This highlights the importance of non-sarcomeric genes in the phenotypic heterogeneity of HCM. The association with higher aldosterone serum levels could relate to greater fibrosis and cardiac remodelling.

Compressive holography with a single-pixel detector

This Letter develops a framework for digital holography at optical wavelengths by merging phase-shifting interferometry with single-pixel optical imaging based on compressive sensing. The field diffracted by an input object is sampled by Hadamard patterns with a liquid crystal spatial light modulator. The concept of a single-pixel camera is then adapted to perform interferometric imaging of the sampled diffraction pattern by using a Mach-Zehnder interferometer. Phase-shifting techniques together with the application of a backward light propagation algorithm allow the complex amplitude of the object under scrutiny to be resolved. A proof-of-concept experiment evaluating the phase distribution of an ophthalmic lens with compressive phase-shifting holography is provided.

Wavelength tuning of femtosecond pulses generated in nonlinear crystals by using diffractive lenses

We demonstrate that diffractive lenses (DLs) can be used as a simple method to tune the central wavelength of femtosecond pulses generated from second-order nonlinear optical processes in birefringent crystals. The wavelength tunability is achieved by changing the relative distance between the nonlinear crystal and the DL, which acts in a focusing configuration. Besides the many practical applications of the so-generated pulses, the proposed method might be extended to other wavelength ranges by demonstrated similar effects on other nonlinear processes, such as high-order harmonic generation.

Spatio-temporal characterization of ultrashort pulses diffracted by circularly symmetric hard-edge apertures: theory and experiment

We carry out a complete spatio-temporal characterization of the electric field of an ultrashort laser pulse after passing through a diffractive optical element composed of several binary amplitude concentric rings. Analytical expressions for the total diffraction field in the time and spectral domain are provided, using the Rayleigh-Sommerfeld formulation of the diffraction. These expressions are experimentally validated. The spatio-temporal amplitude and phase structure of the pulse are measured at different planes beyond the diffractive optical element using spatially-resolved spectral interferometry assisted by an optical fiber coupler (STARFISH). Our results allow corroborating theoretical predictions on the presence of multiple pulses or complex spectral distributions due to the diffraction-induced effects by the hard-edge ring apertures.

Reconfigurable Shack-Hartmann sensor without moving elements

We demonstrate wavefront sensing with variable measurement sensitivity and dynamic range by means of a programmable microlens array implemented onto an off-the-shelf twisted nematic liquid crystal display operating as a phase-only spatial light modulator. Electronic control of the optical power of a liquid lens inserted at the aperture stop of a telecentric relay system allows sensing reconfigurability without moving components. Results of laboratory experiments show the ability of the setup to detect both smooth and highly aberrated wavefronts with adequate sensitivity.

Diffractive pulse shaper for arbitrary waveform generation

We propose an all-diffractive pulse shaper for arbitrary waveform generation in the femtosecond regime. This optical device improves in several aspects the performance of our previous quasi-direct pulse shaper reported in Mínguez-Vega et al. [Opt. Express16, 16993 (2008)]. In the present implementation, by using grayscale masks we can achieve arbitrary temporal waveforms. Additionally, the holographic reconstruction of the above masks by means of phase holograms allows for a high-efficiency shaping process. The behavior of the pulse shaper is tested by numerical simulations.

Left atrial remodelling in hypertrophic cardiomyopathy: relation with exercise capacity and biochemical markers of tissue strain and remodelling

BACKGROUND

Left atrial remodelling, assessed as left atrial volume (LAV), has been proposed as a good marker of left ventricular diastolic dysfunction. The aim of this study was to analyse the influence of LAV on exercise performance in hypertrophic cardiomyopathy (HCM), and in a subset of subjects, assess the relation of LAV and exercise performance to four biomarkers of disease pathophysiology: matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) (as indices of tissue remodelling), N-terminal portion of pro B-type natriuretic peptide (NT-pro-BNP) (associated with ventricular dysfunction) and C-reactive protein (CRP, an index of inflammation).

METHODS

We studied 75 consecutive HCM patients (aged 46 +/- 14 years, 56 men) where LAV was calculated assuming the ellipsoid model with two orthogonal planes. LAV was indexed to body surface area. Exercise capacity was evaluated by treadmill exercise test (symptom limited) and assessed with metabolic equivalent units (MET). Basal NT-pro-BNP and CRP levels were measured in 70 patients, whereas MMP-2 and TIMP-1 in 43 patients.

RESULTS

Enlarged LAV was observed in those patients with previous atrial fibrillation (p = 0.016). Mean LAV was greater in patients with impaired functional New York Heart Association (NYHA) class (p < 0.001). LAV correlated with age (Spearman, r: 0.28), higher maximal left ventricular wall thickness (r: 0.32) and raised E/A ratio (r: 0.37) (all p < 0.01). LAV was significantly correlated with NT-pro-BNP values (r: 0.34; p = 0.04), MMP-2 (r: 0.32; p = 0.034), CRP (r: 0.33; p = 0.005) and correlated inversely with MET units (r: -0.39; p < 0.01). In multivariate analysis, MET units were only associated with NT-pro-BNP (p = 0.002) and LAV (p = 0.010).

CONCLUSIONS

Enlarged LAV is associated with impaired functional NYHA class and inversely with treadmill exercise capacity. Enlarged LAV is also associated with NT-pro-BNP, MMP-2 and CRP, perhaps as markers of disease severity and tissue remodelling. Age, LAV and NT-pro-BNP are independent predictors of exercise performance.

Single-shot digital holography by use of the fractional Talbot effect

We present a method for recording in-line single-shot digital holograms based on the fractional Talbot effect. In our system, an image sensor records the interference between the light field scattered by the object and a properly codified parallel reference beam. A simple binary two-dimensional periodic grating is used to codify the reference beam generating a periodic three-step phase distribution over the sensor plane by fractional Talbot effect. This provides a method to perform single-shot phase-shifting interferometry at frame rates only limited by the sensor capabilities. Our technique is well adapted for dynamic wavefront sensing applications. Images of the object are digitally reconstructed from the digital hologram. Both computer simulations and experimental results are presented.

Fractal generalized zone plates

The construction of fractal generalized zone plates from a set of periodic diffractive optical elements with circular symmetry is proposed. This allows us, for instance, to increase the number of foci of a conventional fractal zone plate while keeping the self-similarity property within the axial irradiance. The focusing properties of these fractal diffractive optical elements for points not only along but also in the close vicinity of the optical axis are investigated. In both cases analytical expressions for the irradiance are derived. Numerical simulations of the energetic efficiency of fractal generalized zone plates under plane wave illumination are carried out. In addition, some effects on the axial irradiance caused by variations in the area of their transparent rings are shown.

Optical filters with fractal transmission spectra based on diffractive optics

The duality between the axial irradiance distribution originated by any circularly symmetric diffracting aperture under monochromatic illumination and its diffracted spectral intensity at a fixed on-axis point under broadband illumination is highlighted and experimentally investigated. Two applications are derived from this basic result. On the one hand, we suggest the use of a broadband source and a spectrometer for a single-shot measurement of the axial response of pupil filters. Second, we implement a spectral filter having a transmission spectrum with a fractal structure of frequencies. Experimental results and potential applications in synthetic spectra designs are provided.

Spectral analysis of femtosecond pulse diffraction through binary diffractive optical elements: theory and experiment

We report on the changes in the spectrum of a femtosecond pulse originated by diffraction of the ultrashort waveform through a circularly symmetric binary diffractive optical element. The analysis is performed in the framework of the Rayleigh-Sommerfeld formulation of the diffraction, where an analytical expression for the monochromatic amplitude distribution close to the optical axis is obtained. To corroborate our results, we experimentally measure the variations of the pulse spectrum within the collecting area of a spectrometer located at the output plane. Multiple splitting of the pulse spectrum in the vicinity of a focal position and a phase singularity are shown.

Use of polar decomposition of Mueller matrices for optimizing the phase response of a liquid-crystal-on-silicon display

We provide experimental measurement of the Mueller matrices corresponding to an on-state liquid-crystal-on-silicon display as a function of the addressed voltage. The polar decomposition of the Mueller matrices determines the polarization properties of the device in terms of a diattenuation, a retardance and a depolarization effect. Although the diattenuation effect is shown to be negligible for the display, the behavior of the degree of polarization as a function of the input polarization state shows a maximum coupling of linearly polarized light into unpolarized light of about 10%. Concerning the retardation effect, we find that the display behaves as a retarder with a fast-axis orientation and a retardance angle that are voltage-dependent. The above decomposition provides a convenient framework to optimize the optical response of the display for achieving a phase-mostly modulation regime. To this end, the display is sandwiched between a polarization state generator and a polarization state analyzer. Laboratory results for a commercial panel show a phase modulation depth of 360 masculine at 633 nm with a residual intensity variation lower than 6 %.

Measurement and compensation of optical aberrations using a single spatial light modulator

We describe a compact adaptive optical system using a spatial light modulator (SLM) as a single element to both measure and compensate optical aberrations. We used a low-cost, off-the-shelf twisted nematic liquid-crystal display (TNLCD) optimally configured to achieve maximum phase modulation with near constant transmittance. The TNLCD acts both as the microlens array of a Hartmann-Shack wavefront sensor and as the aberration compensation element. This adaptive setup is easy to implement and offers great versatility.

Focusing and spectral characteristics of periodic diffractive optical elements with circular symmetry under femtosecond pulsed illumination

The analytical solution is derived, within the Rayleigh-Sommerfeld formulation of diffraction, for the on-axis spectral irradiance of a broadband source after diffracting through a circular symmetric hard aperture. By using this solution, and within the paraxial approximation, we investigate several diffraction-induced effects originated by binary diffractive optical elements made up of a set of annular apertures with equal areas and periodic in the squared radial coordinate. In particular, the ability to focus femtosecond pulses is investigated. In addition, the analysis of the spectral modifier function associated with these elements allows us to simulate spectral shifts at focus positions. Finally, we introduce a relatively simple and low-cost technique to slice the spectrum of a broadband source in order to generate narrow bands or wavelength channels.

On-axis diffraction of an ultrashort light pulse by circularly symmetric hard apertures

The analytical solution of the Rayleigh-Sommerfeld on-axis diffraction integral for an ultrashort light pulse diffracted by circularly symmetric hard apertures is derived. The particular case of a circular aperture is treated in detail. The time changes of the instantaneous intensity along the axial direction are predicted. An analysis of the standard deviation width shows a pulse broadening about the axial positions where the instantaneous intensity reaches a zero value. We show that the temporal shape of the instantaneous intensity depends on the number of oscillation cycles at the central frequency of the real electric field.

Dispersion-compensated beam-splitting of femtosecond light pulses: Wave optics analysis

Recently, using parageometrical optics concepts, a hybrid, diffractive-refractive, lens triplet has been suggested to significantly improve the spatiotemporal resolution of light spots in multifocal processing with femtosecond laser pulses. Here, we carry out a rigorous wave-optics analysis, including the spatiotemporal nature of the wave equation, to elucidate both the spatial extent of the diffractive spots and the temporal duration of the pulse at the output plane. Specifically, we show nearly transform-limited behavior of diffraction maxima. Moreover, the temporal broadening of the pulse is related to the group velocity dispersion, which can be pre-compensated for in practical applications. Finally, some numerical simulations of the spatiotemporal wave field at the output plane in a realistic case are provided.

Efficient compensation of Zernike modes and eye aberration patterns using low-cost spatial light modulators

Off-the-shelf spatial light modulators (SLMs) like those commonly included in video projection devices have been seldom used for the compensation of eye aberrations, mainly due to the relatively low dynamic range of the phase retardation that can be introduced at each pixel. They present, however, some interesting features, such as high spatial resolution, easy handling, wide availability, and low cost. We describe an efficient four-level phase encoding scheme that allows us to use conventional SLMs for compensating optical aberrations as those typically found in human eyes. Experimental results are obtained with artificial eyes aberrated by refractive phase plates introducing either single Zernike terms or complex eye aberration patterns. This proof-of-concept is a step toward the use of low-cost, general purpose SLMs for the compensation of eye aberrations.

Effect of Deposited Bismuth on the Potential of Maximum Entropy of Pt(111) Single-Crystal Electrodes

The effect of bismuth adsorption on the entropy of formation of the double layer on Pt(111) electrodes has been studied with the laser-induced temperature jump method. The coulostatic response to the temperature change induced by pulsed laser illumination allows the estimation of the sign and magnitude of the thermal coefficient of the potential drop at the interphase. This is related to the entropy of formation of the double layer, and the particular potential where this thermal coefficient becomes zero can be identified with the potential of maximum entropy of double-layer formation (pme). The effect of bismuth adsorption on the pme depends on the adatom coverage. At high coverages, a marked decrease of the pme is observed. This trend follows the change of the potential of zero charge expected from work function measurements, and it is likely due to the change in the orientation of solvent molecules induced by surface dipoles originated between the adatom and the substrate. At low coverage, the pme increases with the bismuth coverage. The disruption of the water structure due to the presence of the bismuth adatoms is tentatively proposed as the most likely explanation for this behavior.

A new floating sensor array to detect electric near fields of beating heart preparations

A new flexible sensor for in vitro experiments was developed to measure the surface potential, Phi, and its gradient, E (electric near field), at given sites of the heart. During depolarisation, E describes a vector loop from which direction and magnitude of local conduction velocity theta can be computed. Four recording silver electrodes (14 microm x 14 microm) separated by 50 microm, conducting leads, and solderable pads were patterned on a 50 microm thick polyimide film. The conductive structures, except the electrodes, were isolated with polyimide, and electrodes were chlorided. Spacer pillars mounted on the tip fulfil two functions: they keep the electrodes 70 microm from the tissue allowing non-contact recording of Phi and prevent lateral slipping. The low mass (9.1 mg) and flexibility (6.33 N/m) of the sensor let it easily follow the movement of the beating heart without notable displacement. We examined the electrodes on criteria like rms-noise of Phi, signal-to-noise ratio of Phi and E, maximum peak-slope recording dPhi/dt, and deviation of local activation time (LAT) from a common signal and obtained values of 24-28 microV, 46 and 41 dB, 497-561 V/s and no differences, respectively. With appropriate data acquisition (sampling rate 100 kHz, 24-bit), we were able to record Phi and to monitor E and theta on-line from beat-to-beat even at heart rates of 600 beats/min. Moreover, this technique can discriminate between uncoupled cardiac activations (as occur in fibrotic tissue) separated by less than 1 mm and 1 ms.

Taurine and cholestasis associated to TPN. Experimental study in rabbit model

Taurine seems to be essential in the newborn for bile acid (BA) tauroconjugation, and its deficiency has been implicated in total parenteral nutrition-associated cholestasis (TPN-AC). Our purpose was to study the relationship between taurine (Ta) and TPN-AC in rabbits, which have a similar biliary metabolism to that of humans. We used 40 young rabbits, fed for 10 days according to the following four groups: GA [10] given TPN, with amino acid solution (AA) but without taurine (Ta) or its AA-precursors (methionine, cysteine, and serine); GB [10] the same but only without taurine; GC [10] the same but with taurine and its precursors; and GD [10] the control group with oral nutrition and saline infusion. Complete blood and bile analytical data were obtained and analyzed, including plasma AA and BA. Liver samples were studied under optical and electron microscopy. Serum: In GC there was a 20% increase in the AA-precursors, but paradoxically it was greater in GA. Bile: In GC there was 30% more excretion of total and free BA compared with less than 20% in GA and GB. Regarding toxic BA, there was a 15% decline in GLC3S excretion, but more than 20% in LCA excretion, than in GA and GB. Moreover, in GC the glyco-/tauro-conjugate ratio was worse than in the other groups. Histomorphology: While in GA and GB liver steatosis was diffuse (microsteatohepatitis type), in GC there was macrosteatosis with mitochondria-surrounded lipid droplets. In GA and GB, the canaliculi appeared dilated, with abundant bile plugs and loss of microvilli. There are signs that taurine may protect against TPN-AC. The mechanism does not seem to be BA tauroconjugation, but probably taurine's antioxidant, membrane stabilization (with Ca2+ and HCO3-), and/or osmotic effects.

Sinus node revisited in the era of electroanatomical mapping and catheter ablation

OBJECTIVE

To study the architecture of the human sinus node to facilitate understanding of mapping and ablative procedures in its vicinity.

METHODS

The sinoatrial region was examined in 47 randomly selected adult human hearts by histological analysis and scanning electron microscopy.

RESULTS

The sinus node, crescent-like in shape, and 13.5 (2.5) mm long, was not insulated by a sheath of fibrous tissue. Its margins were irregular, with multiple radiations interdigitating with ordinary atrial myocardium. The distances from the node to endocardium and epicardium were variable. In 72% of the hearts, the whole nodal body was subepicardial and in 13 specimens (28%) the inner aspect of the nodal body was subendocardial. The nodal body cranial to the sinus nodal artery was more subendocardial than the remaining nodal portion, which was separated from the endocardium by the terminal crest. In 50% of hearts, the most caudal boundaries of the body of the node were at least 3.5 mm from the endocardium. When the terminal crest was > 7 mm thick (13 hearts, 28%), the tail was subepicardial or intramyocardial and at least 3 mm from the endocardium.

CONCLUSIONS

The length of the node, the absence of an insulating sheath, the presence of nodal radiations, and caudal fragments offer a potential for multiple breakthroughs of the nodal wavefront. The very extensive location of the nodal tissue, the cooling effect of the nodal artery, and the interposing thick terminal crest caudal to this artery have implications for nodal ablation or modification with endocardial catheter techniques.

Chromatic compensation of broadband light diffraction: ABCD-matrix approach

Compensation of chromatic dispersion for the optical implementation of mathematical transformations has proved to be an important tool in the design of new optical methods for full-color signal processing. A novel approach for designing dispersion-compensated, broadband optical transformers, both Fourier and Fresnel, based on the collimated Fresnel number is introduced. In a second stage, the above framework is fully exploited to achieve the optical implementation of the fractional Fourier transform (FRT) of any diffracting screen with broadband illumination. Moreover, we demonstrate that the amount of shift variance of the dispersion-compensated FRT can be tuned continuously from the spatial domain, which is totally space variant, to the spectral domain, which is totally space invariant, with the chromatic correction remaining unaltered.

High-contrast white-light Lau fringes

We present a new optical assembly with which to achieve Lau fringes with totally incoherent illumination. Gratinglike codification of the spatially incoherent source combined with an achromatic Fresnel diffraction setup allows us to achieve Lau fringe-pattern visibility of almost 100% with broadband light. The white-light character to our proposed setup is in stark contrast to previous monochromatic implementations. Potential implications of this fact are identified.

Broadband space-variant Fresnel processor

We present a radically new class of optical setup working with white-light illumination, namely, a chromatically compensated processor operating in the Fresnel domain. The optical configuration is a hybrid (diffractive-refractive) three-lens system that exhibits an intermediate achromatic Fresnel plane and an output image plane without chromatic distortion. As a first application of this optical arrangement we develop a parallel space-variant color pattern-recognition experiment with white light.

The terminal crest: morphological features relevant to electrophysiology

OBJECTIVE

To investigate the detailed anatomy of the terminal crest (crista terminalis) and its junctional regions with the pectinate muscles and intercaval area to provide the yardstick for structural normality.

DESIGN

97 human necropsy hearts were studied from patients who were not known to have medical histories of atrial arrhythmias. The dimensions of the terminal crest were measured in width and thickness from epicardium to endocardium, at the four points known to be chosen as sites of ablation.

RESULTS

The pectinate muscles originating from the crest and extending along the wall of the appendage towards the vestibule of the tricuspid valve had a non-uniform trabecular pattern in 80% of hearts. Fine structure of the terminal crest studied using light and scanning electron microscopy consisted of much thicker and more numerous fibrous sheaths of endomysium with increasing age of the patient. 36 specimens of 45 (80%) specimens studied by electron microscopy had a predominantly uniform longitudinal arrangement of myocardial fibres within the terminal crest. In contrast, in all specimens, the junctional areas of the terminal crest with the pectinate muscles and with the intercaval area had crossing and non-uniform architecture of myofibres.

CONCLUSIONS

The normal anatomy of the muscle fibres and connective tissue in the junctional area of the terminal crest/pectinate muscles and terminal crest/intercaval bundle favours non-uniform anisotropic properties.

Wavelength-compensated Fourier and Fresnel transformers: a unified approach

We recognize that one can adapt any dispersion-compensated broadband optical Fourier transformer to achieve wavelength compensation in the Fresnel diffraction region just by inserting a diffractive lens at the input plane and vice versa. This unification procedure is employed in a second stage in the design of a novel hybrid (diffractive-refractive) optical setup that provides, in a sequential way, nearly wavelength-independent Fresnel diffraction patterns in the irradiance of the object transmittance.

Scale-tunable optical correlation with natural light

We describe two different scale-tunable optical correlators working under totally incoherent light. They behave as spatially incoherent wavelength-independent imaging systems with an achromatic point-spread function (PSF). In both cases it is possible to adapt the scale of the achromatic PSF, i.e., to modify the scaling factor of the PSF and preserve the chromatic compensation, by one's shifting the input along the optical axis. The remarkable properties of these systems allow us to carry out a scale-tunable color pattern-recognition experiment with natural light.

[A case of Carney syndrome]

The Carney complex is an autosomal dominant syndrome characterised by multiple neoplasies, including myxomas at various sites (cardiac, cutaneous, mammary), spotty pigmentation, endocrine overactivity (Cushing's syndrome, acromegalia), testicular tumours and schwannomas. This report describes the case of a 43-year-old woman with an acute inferior myocardial infarction, probably due to coronary embolization from a large left atrial myxoma and who presented this association. A brief review of the Carney complex is provided after discussion of this rare case that required an screening of family members.