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Amorphous Fe75Nb10B15 and (Fe70Co30)75Nb10B15 alloys were prepared by mechanical alloying from the elemental constituents and hot compacted at different temperatures within the supercooled liquid region. After compaction, the microstructure studied by X-ray diffraction shows an increase in the crystalline fraction for both compositions. Magnetic properties and magnetic entropy change of compacted samples of the Co-free alloy were enhanced with respect to the powder sample, meanwhile, a deterioration in these properties was observed for the Co containing alloy after compaction. Both changes could be ascribed to an enrichment in boron in the amorphous phase.

Since the discovery of the giant magnetocaloric effect (MCE) close to room temperature in FeRh and particularly in Gd5Si2Ge2 compounds, the study of this phenomenon has experienced an exponential growth. Among the different techniques used to produce magnetocaloric materials, ball milling has been shown as a very versatile one and presents several advantages over other preparation techniques (e.g., easy scale-up to industrial production). Although a general decrease of the peak value of the magnetic entropy change is observed for milled samples, it can be compensated by the large broadening of the MCE peak, leading to an increase of the refrigeration capacity. In this short review, several aspects inherent to powder samples affecting MCE will be discussed, such as the relevant effect of the demagnetizing field, the possible multiphase character, and the presence of Curie temperature distributions. In mechanically alloyed samples, the two latter factors are typically affected by the degree of integration of the different starting constituents.

Gas-atomized MnAl particles constituted nominally of only ε- and γ-phases, i.e. no content of the ferromagnetic L1-type τ-phase, have been used to study the evolution of phases during short time of high-energy milling and subsequent annealing. Milling for 3 min is sufficient to begin formation of the τ-MnAl phase. A large coercivity of 4.9 kOe has been obtained in milled powder after annealing at 355 °C for 10 min. The large increase in coercivity, by comparison with the lower value of 1.8 kOe obtained for the starting material after the same annealing conditions, is attributed to the combined formation of the τ-MnAl and β-Mn phases and the creation of a very fine microstructure with grain sizes on the order of 20 nm. Correlation between morphology, microstructure and magnetic properties of the rapidly milled MnAl powders constitutes a technological advance to prepare highly coercive MnAl powders., The gas-atomized powders were provided by Prof. Ian Baker, Dartmouth College where they were produced via a grant from the U.S. Department of Energy, Advanced Research Projects Agency – Energy (ARPA-E) through REACT program contract no. DE-AR0000188. This research has been funded by MINECO (Spanish Ministry of Science and Innovation): ENMA-National project (MAT2014-56955-R) and Northeastern University, MINECO through M-era.Net Programme: NEXMAG project (PCIN-2015-126) and Regional Government (Comunidad de Madrid): NANOFRONTMAG (Ref. S2013/MIT-2850), MINECO (project MAT2013-45165-P) and the PAI of the Regional Government of Andalucía. N. López acknowledges MINECO for the “Promoción de Empleo Joven” (PEJ-2014) in the frame of Sistema Nacional de Garantía Juvenil and funding by FSE and IEJ.

The magnetocaloric effect of La(Fe,Si) samples deteriorates with the presence of secondary phases. However, it is highly challenging to produce single phase samples by conventional procedures and purification requires long annealing time. We propose grinding and particle size selection of non-optimal starting samples as procedure to enhance the magnetocaloric response. In this study a starting multiphase LaFeSi ingot was grinded and sieved to select three different particle size ranges. X-ray diffraction and Mössbauer spectrometry reveal that all samples mainly contain fcc-La(Fe,Si) and bcc-Fe(Si) phases. Microstructural and magnetic results show that the fcc-La(Fe,Si) phase fraction increases for samples with the smallest average particle size, increasing their magnetocaloric response in a factor larger than three with respect to that of the bulk sample., This work was supported by the Spanish MINECO and EU FEDER (projects MAT2013-45165-P and MAT2016-77265-R) and the PAI of the Regional Government of Andalucía. L.M. Moreno-Ramírez acknowledges a FPU fellowship from the Spanish MECD.

The structural relaxation of multicomponent Fe(Co)SiAlGaPCB amorphous alloys was investigated calorimetrically for annealed samples over a wide temperature range below the glass transition temperature. Upon heating, the annealed samples exhibit an endothermic reaction (enthalpy relaxation) starting around the annealing temperature and continuing over a temperature range of about 50-140 K, that it is followed by a broad exothermic reaction. Changes in the heat flow curves with annealing temperature and time were analyzed. Experimental values of the overall enthalpy change, ΔH, the peak temperature of the difference in heat flow between the annealed and the as-quenched samples, Tp, and Curie temperature, TC, were fitted by exponential functions including two relaxation times. Values of the two relaxation times are the same for different annealing temperatures regardless the considered property. Saturation values of these magnitudes show a linear dependence with the inverse of the annealing temperature. Tiny domains (2-3 nm in diameter) in the matrix observed by spherical aberration corrected high-resolution transmission electron microscopy could be attributed to some medium-range order in the atomic structure of these quenched alloys. Ministerio de Ciencia e Innovación MAT 2010-20537 European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER) MAT 2010-20537 Junta de Andalucía P10-FQM-6462 ESTEEM 312483 - ESTEEM2

The CentriMag (Levitronix LLC, Waltham, MA, USA) ventricular assist device is a centrifugal pump designed for short-term support in patients with cardiogenic shock. In patients with restrictive physiology, there is some concern about the use of these devices due a very small ventricular cavity. We review the evolution of a 32-year-old woman with restrictive cardiomyopathy, moderate pulmonary hypertension, and severe biventricular systo-diastolic dysfunction in whom a biventricular Centrimag device was implanted due to a progressive clinical worsening.

Since the discovery of the giant magnetocaloric effect (MCE) close to room temperature in FeRh and particularly in Gd5Si2Ge2 compounds, the study of this phenomenon has experienced an exponential growth. Among the different techniques used to produce magnetocaloric materials, ball milling has been shown as a very versatile one and presents several advantages over other preparation techniques (e.g., easy scale-up to industrial production). Although a general decrease of the peak value of the magnetic entropy change is observed for milled samples, it can be compensated by the large broadening of the MCE peak, leading to an increase of the refrigeration capacity. In this short review, several aspects inherent to powder samples affecting MCE will be discussed, such as the relevant effect of the demagnetizing field, the possible multiphase character, and the presence of Curie temperature distributions. In mechanically alloyed samples, the two latter factors are typically affected by the degree of integration of the different starting constituents.

The influence of the Co content on the microstructure and magnetic behaviour of a series of amorphous and nanocrystalline (FeCo)79Mo8Cu1B12 alloys is reported. Changes in the magnetic properties provoked by the microstructural evolution upon different thermal treatments of as-cast samples are analyzed as well. Kinetics of nanocrystallization process can be described by an isokinetic approach. As the Co content in the alloy increases, the Curie temperature of the amorphous as-cast samples increases while the crystallization onset temperature decreases. The crystalline volume fraction as well as the mean grain size of the nanocrystals at the end of the nanocrystallization process are slightly higher for the lowest Co content alloy but smaller than in similar Hitperm Mo-free alloys. The average magnetic field and the average isomer shift of the as-cast samples show a linear increase with two slopes with the Co content of the alloy. The same tendency is found for the saturation magnetization. Combined TEM, XRD, and MS data indicate the presence of Mo atoms in the nanocrystals. At the end of the nanocrystallization process the softest magnetic behaviour corresponds to the lowest Co content alloy. The second crystallization process provokes a magnetic hardening of these alloys.

X-ray diffraction, Mössbauer spectrometry and magnetic properties have been performed on FeGa arc-melted binary alloys in order to study the compositional dependence of the structural ordering and magnetic properties of these alloys. The average magnetic hyperfine field at 300 K decreases with increasing Ga content as does the average magnetic moment per Fe atom and a linear dependence between both quantities is found for Ga content up to 20 at. %. The substitution of Fe by Ga atoms increases the lattice parameter and causes a change in the order of the crystal structure that has been modelled using a binomial distribution method. The effect of Ga atoms as near neighbours of Fe on the average magnetic hyperfine field is evaluated

Resumen Las valoraciones periciales realizadas en pacientes con lesiones vertebrales es de por si sumamente dificil, exigiendo completos conocimientos de anatomia, funcional y patologica, y sus diferentes posibilidades diagnosticas. A pesar de que la principal causa del peritaje es el dolor, resulta coincidente con la causa primaria de derivacion a fisioterapia por lesiones de columna vertebral traumaticas. Este trabajo pretende analizar la repercusion de la participacion del fisioterapeuta tras la valoracion pericial, bien en primera instancia, o bien como continuacion de un primer ciclo iniciado antes de la peritacion.

Resumen La utilizacion de sistemas de medicion y valoracion de la discapacidad requieren la validacion por los sistemas psicometricos mas habituales. El presente estudio analiza la fiabilidad del denominado Cuestionario del Dolor Lumbar de Oswestry, instrumento de medicion del grado de discapacidad de la lesion referida, utilizando una muestra de 26 pacientes, y analizando la consistencia interna de los items de los cuestionarios aplicados mediante el coeficiente α de Cronbach (Teoria Clasica de los Tests). Los resultados revelan la aproximacion a los estudios ya publicados y ponen de manifiesto las posibilidades expresas de nuevas validaciones en muestras superiores, incluso por medio de otras teorias psicometricas.

A Microwave Photoconductivity Decay (M-PCD) technique which senses changes insample conductivity as carriers recombine following excitation by a laser pulse, has been used to determine the minority carrier recombination lifetime from the decay rate of carriers in 4H-SiC epitaxial layers. Decay times varying from 60 ns to 500 ns have been measured, with the decay increasing with thickness. Device simulations show that I-V characteristics of pin diodes fabricated with these epitaxial layers are compatible with the observed decay times.

The short-range order of (Fe x Co y B z C u ) 80 Si 3 Al 5 Ga 2 P 10 with x = 5 – 70 , y = 0 – 63 , z = 5 – 12 and u = 0 – 5 amorphous alloys has been investigated by X-ray absorption spectroscopy. The existence of some chemical preferences leading the B atoms to locate near Fe atoms and Si atoms near Co atoms can be concluded which allows to explain the small increase of the short-range order previously found for these alloys in the Co-rich side by Mossbauer spectrometry. Co and Fe neighbourhood in the amorphous was found to be similar to that of the crystalline phases formed during the primary crystallization.

A Mossbauer spectrometry and magnetic study have been performed on FeCoSiAlGaPCB amorphous alloys in order to get information about the variations in the atomic short range order with the substitution of Fe by Co. The decrease of the Curie temperature with decreasing Fe content was analyzed in the framework of the molecular field theory. The average hyperfine magnetic field at 77 K decreases linearly with increasing Co content as does the average magnetic moment per transition metal atom and a linear dependence between both quantities is found. The standard deviation of the hyperfine magnetic field distribution at 77 K does not change with Fe substitution and the average isomer shift increases linearly with the Co content of the alloy. The hyperfine magnetic field distributions show a bimodal character that evidences the presence of two types of Fe environments in the as-cast alloys.

Radio-frequency (RF) photoreflectance measurements and one-dimensional device simulations have been used to evaluate bulk and surface recombination parameters in doubly capped, 0.50–0.59-eV, p-type InGaAsSb epitaxial materials. The InGaAsSb lifetime structures with variable active-layer thicknesses are used to extract the surface recombination velocity (SRV), while samples with different active-layer doping concentrations have been used to determine the Auger and radiative recombination coefficients. The RF photoreflectance measurements and analysis are compatible with a radiative recombination coefficient (B) of approximately 3×10−11 cm3/s, Auger coefficient (C) of 1×10−28 cm6/s, and SRV of ∼103 cm/s or lower for 0.50–0.59 eV, doubly capped, p-type InGaAsSb epitaxial layers.

The kinetics of the glass transition and the crystallization process of Co62−xFexNb6Zr2B30 (x=0,16) amorphous alloys with large supercooled liquid region was investigated by differential scanning calorimetry. The dependence of the glass transition on the heating rate was analyzed in terms of the Vogel–Fulcher–Tamman equation. The glass-forming ability of these alloys is discussed with respect to the width of the supercooled liquid region, the reduced glass transition temperature, and the fragility parameter. The studied alloys are found to be rather strong glass formers. The crystalline phases formed after the devitrification are identified by means of x-ray diffraction and thermomagnetic measurements. The complicated crystallization process requiring long-range atomic rearrangements seems to contribute to the high stability of the supercooled liquid against crystallization.

Fe75Nb10B15 alloys were prepared by mechanical alloying using different boron powders (crystalline B, commercial amorphous B, optimized amorphous B and intermetallic FeB) in the initial mixture in order to study the boron incorporation into the Fe matrix and its influence on the amorphization of the alloys. Another composition with the same Fe/Nb ratio but without boron was prepared in order to differentiate between the influence of B and Nb in the evolution of microstructure and magnetic properties. Amorphization of samples was followed by X-ray diffraction and Mössbauer spectroscopy, concluding that only B-containing alloys develop an amorphous phase, while for the B-free alloy a supersaturated solid solution was observed as the final microstructure. Nb is rapidly incorporated into the matrix whereas remaining B inclusions are found at the end of the explored milling range for all B-containing samples. The amount of dissolved boron into the amorphous matrix was estimated from magnetic measurements, being the alloy prepared using FeB powder the one that most effectively dissolves this element. © 2014 Elsevier Ltd. All rights reserved.

Amorphous samples of nominal composition Co62Nb 6Zr2B30 have been prepared using mechanical alloying (MA) and rapid quenching (RQ) techniques. Differences appear in Curie temperature and the phases developed after crystallization. Refrigerant capacity is enhanced 20% in the MA-sample with respect to that of RQ-sample. Neglecting the demagnetizing factor of powder samples significantly affects the exponent n characterizing the field dependence of the maximum magnetic entropy change. © 2014 AIP Publishing LLC.

Fe 73.5− x Co x Si 13.5 B 9 Cu 1 Nb 3 ( x =13.5 and 60 at.%) materials with different volumetric fractions of nanometer-sized (Fe, Co)Si crystallites produced by controlled crystallization of the amorphous alloy, were studied by combining 57 Fe Mossbauer spectrometry (MS) and X-ray diffraction (XRD). The crystalline fractions were first estimated and the compositions of both the amorphous residual phase and the nanocrystalline phase were modelled. The composition of the (Fe, Co)Si nanosized crystals does not change with the crystalline fraction but depends on the amorphous composition. Lattice parameters, hyperfine fields and Curie temperatures data are consistent with the proposed composition.

New composite soft magnetic alloys in the compositional series Fe73.5−xAlxSi13.5B9Cu1Mo3 were recently obtained by partial thermal devitrification of amorphous ribbons. We report the results of Mossbauer and X-ray diffraction (XRD) investigations of nanocrystalline alloys containing 0, 2, 4, 6 and 8 at.% Al, following annealing at 560°C for 1 h. The results indicate that most of the Si and Al are located in the cubic-DO3Fe(Si,Al) crystallites, after the primary crystallization is achieved.

Structural relaxation in FeSiB-Cu(NbX) alloys is evidenced by enthalpy release exothermic DSC maxima and by changes in the Curie temperature of the amorphous phase upon annealing. A monotonic increase in T C with annealing temperature and time is found and the equilibrium T C values show a linear dependence with the inverse of the annealing temperature. An uniformly linear log (time) kinetics results and the relaxation time decreases exponentially as the annealing temperature increases.

Transient radio frequency photoreflectance measurements were performed on 0.53 eV p-type InGaAsSb double heterostructures, grown by organometallic vapor phase epitaxy on lattice matched GaSb substrates, for determining excess carrier lifetime. Direct evidence of photon recycling was observed by changing the GaSb backsurface reflectivity and observing the change in excess carrier lifetime. Consistent with theory developed for this type of structure, effective lifetimes increased by 30%–40% when the backsurface was changed from an absorbing to a reflecting surface. The theory develops a closed-form expression for the total radiative recombination rate, starting with continuity equations for both excess minority carriers and the photon density. Lifetime measurements in these p-InGaAsSb structures with different doping concentrations and epitaxial layer thicknesses allow the extraction of minority carrier recombination parameters. Measurements indicate a value for the radiative recombination coefficient of B=...

This report presents an assessment of the efficiency and power density limitations of thermophotovoltaic (TPV) energy conversion systems for both ideal (radiative limited) and practical (defect-limited) systems. Thermodynamics is integrated into the unique physics of TPV conversion, and used to define the intrinsic tradeoff between power density and efficiency. The results of the analysis reveal that the selection of diode band gap sets a limit on achievable efficiency well below the traditional Carnot level. In addition it is shown that filter performance dominates diode performance in any practical TPV system and determines the optimum band gap for a given radiator temperature. It is demonstrated that for a given radiator temperature, lower band-gap diodes enable both higher efficiency and power density when spectral control limitations are included. The goal of this work is to provide a better understanding of the basic system limitations that will enable successful long-term development of TPV energy conversion technology.

Introduccion y objetivos La muerte cerebral es capaz de provocar disfuncion contractil del miocardio e hipotiroidismo. Dicha disfuncion miocardica es un factor limitante al considerar el corazon del donante para trasplante. Se ha demostrado que el dano miocardico es el mecanismo a traves del cual se establece la disfuncion contractil en los donantes. Por otro lado, se ha invocado al hipotiroidismo como un factor causal primordial en las alteraciones cardiovasculares que acontecen en los sujetos en muerte cerebral. No se conoce si existe alguna relacion entre este hipotiroidismo y el dano miocardico que aparecen en la muerte cerebral. En este estudio cuantificamos el dano miocardico y el estado hormonal tiroideo en un grupo de donantes y analizamos si existe una relacion entre hipotiroidismo y el dano del musculo cardiaco. Pacientes y metodo En el suero de 45 donantes se cuantificaron troponinas T e I como marcadores de dano miocardico, asi como hormonas tiroideas. Se analizo la correlacion entre las troponinas y el estado tiroideo. Resultados Una o ambas troponinas estaban elevadas en 19 donantes (42,2%). El hipotiroidismo fue muy frecuente, ya que estuvo presente en 39 donantes (86,7%). No hubo correlacion alguna entre ninguna de las troponinas y las concentraciones de triyodotironina. Conclusiones El hipotiroidismo y el dano miocardico son frecuentes en los donantes en muerte cerebral, sin que exista asociacion alguna entre ambas alteraciones.

Mossbauer experiments were performed at room temperature using different experimental configurations on several series of nanocrystalline FeSiBCuNbX alloys (X = Zr, Nb, Mo and V) obtained after annealing treatments of melt-spun ribbons. The refinement of Mossbauer spectra allows the kinetics and the local structural rearrangement mechanisms associated with the nanocrystallization process to be compared. The hyperfine field distributions of the intergranular phase show the emergence of a bimodal behaviour that becomes significantly more pronounced from volumetric crystalline fractions estimated at ~20-25%, regardless of the nature of the substituting element. The hyperfine field distribution can be described by means of two Gaussian components, consistent with of a two-cluster-like model. Such a behaviour can be attributed to the presence of iron-rich and iron-poor zones within the intergranular phase, resulting from the diffusion process. These mechanisms are found to be independent of the nature of X. In addition, strong in-plane magnetic structures are evidenced for Nb-, Mo-, and V-based systems while the magnetic domains tend to be randomly distributed in Zr-based nanocrystalline alloys.

We propose a method to describe accurately Mossbauer spectra recorded on nanocrystalline FINEMET-type alloys by means of two independent components. The validity of the fitting procedure is controlled by comparing hyperfine characteristics of spectra recorded under different experimental configurations. In addition, the reliability of the fitting model is discussed from spectra obtained on nanocrystalline alloys resulting from different annealing treatments, i.e., with different crystalline contents. Such a method allows us to estimate more accurately the crystalline fraction and to refine the values of hyperfine parameters, both their annealing temperature and time dependencies, the hyperfine field distribution characteristic of the intergranular component and the magnetic texture. Finally, their changes versus crystalline fraction provide relevant information to describe the nanocrystallization process occurring during the transformation from the amorphous into the nanocrystalline state in the case of FINEMET alloys.

Recombination processes in antimonide-based materials for thermophotovoltaic (TPV) devices have been investigated using a radio-frequency (rf) photoreflectance technique, in which a Nd–YAG pulsed laser is used to excite excess carriers, and the short-pulse response and photoconductivity decay are monitored with an inductively coupled noncontacting rf probe. Both lattice-matched AlGaAsSb and GaSb have been used to double cap InGaAsSb active layers to evaluate bulk lifetime and surface recombination velocity with different active layer thicknesses. With an active layer doping of 2×1017 cm−3, effective bulk lifetimes of 95 ns and surface recombination velocities of 1900 cm/s have been obtained. As the laser intensity is increased the lifetime decreases, which is attributed to radiative recombination under these high-level injection conditions. Similar measurements have been taken on both TPV device structures and starting substrate materials for comparison purposes.

The hotside operating temperatures for many projected thermophotovoltaic (TPV) conversion system applications are approximately 1000 °C, which sets an upper limit on the TPV diode band gap of 0.6 eV from efficiency and power density considerations. This band gap requirement has necessitated the development of new diode material systems never previously considered for energy generation. To date, InGaAsSb quaternary diodes grown lattice matched on GaSb substrates have achieved the highest performance. In this article we relate observed diode performance to electro-optical properties such as minority carrier lifetime, diffusion length, and mobility and provide initial links to microstructural properties. This analysis has bounded potential diode performance improvements. For the 0.53 eV InGaAsSb diodes used in this analysis (active layer doping is 2×1017 cm−3) the dark current density measured is 2×10−5 A/cm2 versus a potential Auger and/or a radiative limit of 2×10−6 A/cm2 (no photon recycling), and an abso...

Thermophotovoltaic (TPV) devices have been fabricated using ternary and quaternary layers grown by metalorganic vapor phase epitaxy (MOVPE) on GaSb substrates. GaInSb ternary devices were grown with buffer layers to accommodate the lattice mismatch, and GaInAsSb quaternary devices were grown with lattice-matched compositions. Improved devices are obtained when optical absorption occurs in the p-layer due to the longer minority carrier diffusion length. Thick emitter p/n devices are limited by surface recombination, with highest quantum efficiency and lowest dark current being achieved with epitaxially grown surface passivation layers on lattice-matched MOVPE quaternaries. Thin emitter/thick base, n/p devices are very promising since surface passivation is less critical than for p-emitter devices.

The nanocrystallization process in (Fe73.5-x Crx)Si13.5B9Cu1Nb3 (x = 0,3 and 5) amorphous alloys has been studied by in-situ X-ray diffraction, using a synchrotron radiation source. The nanocrystalline volume fraction and the mean grain size of the (Fe, Si) crystallites were estimated from an intensity profile analysis of the main diffraction maximum. Cr alloying lowers the crystalline fraction for the same annealing conditions. The mean size of the crystallites initially increases with increasing annealing time but the growth rate slows down and a saturation value of about 12 nm is reached. The Si content of the (Fe, Si) phase initially correlates with the concentration in the as-cast glassy alloy but a final value of about 21 at.% Si is reached. The transformation kinetics are described by an Avrami exponent below unity, as usually found for Finemet alloys.

Introduction. Emergency heart transplantation remains an important controversy due to the shortage of donors and the previously demonstrated results inferior to other patients. These recipients display a worse clinical status and their donors are more often considered suboptimal. Nevertheless, it is the only therapeutic option for patients with advanced cardiomyopathy and acute decompensation with no response to other therapies. We compared results among the emergency indication with those of elective transplants. Methods. We analyzed the 213 patients who underwent cardiac transplantation in our center up to December 2004 to compare emergency with elective heart transplantations for preoperative and surgical variables as well as outcomes. Results. A higher percentage of emergency patients were New York Heart Association class IV, displayed renal dysfunction, and were women. Regarding donors, a higher percentage were over 40 years of age. No differences were observed in the early and first-year mortality or morbidity rates, although we noted a greater 5-year mortality rate among emergency cases. Conclusions. In our center emergency heart transplantation was associated with only slightly worse results compared with elective transplantations. Both donors and recipients should be carefully selected to improve results.

Infections are one of the main complications that cause morbidity and mortality in cardiac transplant recipients. We sought to establish the incidence of infections, identify the predisposing factors and determine their consequences.A prospective study of 30 patients who received cardiac transplantations in our hospital from July 2003 to May 2005.Of the 30 transplant recipients, 93.3% were men (average age, 48 years); the average age of the women was 53 years. The incidence of infection was 70%: 21 episodes of infection. The main clinical symptoms were bacteriemia (28%), pneumonia (19%), and surgical wound infections (14%). The etiology of the infection, as established in 12 cases (57%), was bacterial (66%), viral (25%), or fungal (9%). The most common microorganisms were cytomegalovirus and coagulase-negative staphylococcus. None of the donors had a history of infection. There was a higher frequency of serious complications, such as renal failure (12.9%), respiratory insufficiency (9.6%), and multiorgan failure (9.6%) among patients with versus without infections (P.05). The 1-year survival rate of patients with infections was similar to that of patients with no infections (83% vs 88%, P = NS).The incidence of infections was 70%. Bacteremia, pneumonia, and surgical wound infections occurred most frequently. Cytomegalovirus and coagulase-negative staphylococcus were the most frequent microorganisms. Patients with infections had the most serious complications, but their survival rate was similar to that of patients free of this complication.

We used modulation spectroscopy to characterize InP and GaAs photovoltaic solar cells. The clear-cut Franz-Keldysh oscillations displayed by solar cell modulation spectra make it possible to directly measure the electric field at the p-n junction of typical devices. Byperforming this measurement under different bias conditions, the impurity concentration in the base of the solar cells was obtained. Measurements were made both using electrical modulation and electrical bias and, alternatively, using contactless optical modulation and optical bias.

The administration of protamine to neutralize the circulating heparin is common practice in cardiovascular surgery. The use of this drug is some-times associated with hemodynamic alterations of varying degree and intensity (systemic hypotension, pulmonary hypertension and even cardiogenic shock). An intrinsic action of protamine has been suggested to be the cause of these vascular reactions. This action is blocked when protamine forms a complex with heparin, although in other cases it appears that the heparin-protamine complex is the factor responsible for these hemodynamic alterations. The aim of this experimental study was to characterize the vasodilatory action of protamine on the systemic circulation, determining whether or not it is dose-dependent; to analyze the role of endothelium; and to evaluate whether this vasodilatory effect is modified by the presence of heparin. Materials and methods. The abdominal aorta was dissected from eight New Zealand rabbits and then sectioned into vascular rings for study in an organ chamber. Mechanical disruption of endothelium was performed on some rings (n = 14). Once submaximal contraction was reached (ClK 80 mM), protamine sulfate with a final concentration in the organ chamber of 80–400 μg/ml was added to one of the groups (n = 12). In the second group (n = 12), equal con-centrations of protamine were tested in the presence of heparin at a final concentration of 100 U/ml. Results. The mean vasodilatation reached in the group of rings exposed only to protamine was 95.4±1.5% with respect to the submaximal contraction induced with ClK. In the second study group, the rings were exposed to protamine at equally increasing concentrations (80–400 μg/ml) but with the presence of heparin in the organ chamber. The mean vasodilatation in this group was 90±1.5. No statistically significant differences in vasodilatation were found between this group and the protamine without heparin group. On the other hand, in the endothelium-denuded rings (n = 14) exposed to isolated protamine and to protamine-heparin, no vasodilatory response was observed. Conclusion. Our results show that the administration in vitro of protamine induces endothelium-dependent vasodilatation of the systemic circulation. Likewise, this relaxing effect mediated through endothelium is not blocked when protamine forms a complex with heparin in comparable concentrations of both drugs. Based on these preliminary findings, we believe that in highrisk patients the prevention of systemic vasodilatation and cardiovascular collapse produced by protamine should move towards the use of other substances that can neutralize the anticoagulant effect of heparin or towards pre-medication guidelines that prevent these secondary effects in the case of protamine administration.