Calor de sorbición y cambio en energía libre en pulpa de piña liofilizada

Two thermodynamic properties, the heat of sorption (Qs) and the Gibbs free energy change (∆G) were evaluated at several temperatures (5, 25, 30, 35 and 55°C) on freeze-dried pineapple pulp. It was found that 1) the heat of sorption follows the Clauslus-Clapeyron relationship; 2) the shape of the heat of sorption vs. the equilibrium moisture content curve was sigmoid; 3) the heat of sorption from adsorption data gave higher values than those from desorption data; and 4) the free energy change (∆G) is linearly related to the equilibrium moisture content. These two parameters are very important in dealing with food stability because it is possible to predict the water activity at any given temperature of either of these values is known.Dos propiedades termodinámicas, el calor de sorción (Qs) y el cambio en energía libre de Gibbs (∆G) fueron evaluadas a diferentes temperaturas (5, 25, 30, 35 y 55°C) en pulpa de piña liofilizada. Se encontró que: 1) el calor de sorbición sigue la relación de Clausius-Clapeyron; 2) la forma de la curva que representa la relación de calor contra humedad es sigmoide; 3) los calores de sorbición obtenidos de los datos de adsorción son más altos que los obtenidos de los datos de desorción; 4) los cambios en energía libre están linealmente relacionados con el contenido de humedad en equilibrio. Estos dos parámetros son muy importantes cuando se estudia la estabilidad de un alimento, ya que conociendo el valor de cualquiera de ellos es posible predecir la actividad de agua a cualquier temperatura

Rodajas de piña preservadas por métodos combinados

Pineapple slices were treated by two combined methods, packaged and stored at room temperature. The first preservation method consisted of blanching pineapple slices at 100° C for two minutes followed by a cooling period of 1.5 minutes at room temperature. The slices were then immersed in a 50% sucrose solution with 1,000 ppm of potassium sorbate and 150 ppm of sodium bisulfite. The osmotic treatment was done at room temperature (28.5 ± 1.5° C) for 24 hours. The treated slices were removed from the osmotic solution, the excess syrup from the slices was removed, and the product was later packaged in sealed plastic bags. The final water activity values ranged between 0.95 and 0.97 for the packaged product. For the second preservation method, the pineapple slices were blanched in saturated steam for 12 minutes and stored at 12° C until processing by combined methods. Sucrose solutions (55 and 60° Brix) with four different concentrations of potassium sorbate (100, 200, 300, or 500 ppm) were used as osmotic solutions. The water activity was 0.91 after the osmotic process and 0.88 after hot air drying. A shelf life of at least 30 days was observed for product prepared with both preservation techniques, and the sensory characteristics noted were similar to those in a commercially canned product (Del Monte canned slices). The inhibitory effect of potassium sorbate on yeast and mold growth was significant for concentrations above 300 ppm.Se trataron rebanadas de pina con dos métodos combinados y se almacenaron a temperatura ambiente para evaluar su vida útil. El primer método de preservación consistió en escaldar la fruta a 100° C por dos minutos y luego enfriarla a temperatura ambiente (28.5 ± 1.5° C) por 1.5 minutos. Tras el enfriamiento se procedió a colocar las rodajas en almíbar al 50% de sacarosa con 1,000 ppm de sorbato de potasio y 150 ppm de bisulfito de sodio. El tratamiento osmótico se hizo a temperatura ambiente por 24 horas. Las rodajas se sacaron del almíbar y se empacaron en bolsas plásticas luego de escurrir la mayor parte del almíbar. La actividad de agua del producto empacado fluctuó entre 0.95 y 0.97. En el segundo método de preservación, las rebanadas de piña se escaldaron en vapor saturado por 12 minutos y se almacenaron en refrigeración (12° C) hasta su tratamiento por métodos combinados. Se usaron soluciones de sacarosa de 66 y 60° Brix con cuatro niveles de sorbato de potasio (100, 200, 300, 500 ppm) para la deshidratación osmótica de las rebanadas. Una vez en equilibrio, se removieron las rebanadas de la solución de sacarosa y se secaron parcialmente con aire caliente por una hora. El valor de actividad de agua fuego del tratamiento osmótico fue de 0.91 y bajó a 0.88 luego del secado parcial con aire caliente. Para ambos métodos de preservación se observó un período no menor a 30 días durante el cual las características sensoriales del producto compararon favorablemente con las de productos comerciales de piña enlatada (Del Monte). El efecto inhibidor de sorbato de potasio sobre los hongos y las levaduras fue evidente a concentraciones mayores de 300 ppm

Single-ion and exchange anisotropy effects and multiferroic behavior in high-symmetry tetramer single molecule magnets

We study single-ion and exchange anisotropy effects in equal-spin $s_1$ tetramer single molecule magnets exhibiting $T_d$, $D_{4h}$, $D_{2d}$, $C_{4h}$, $C_{4v}$, or $S_4$ ionic point group symmetry. We first write the group-invariant quadratic single-ion and symmetric anisotropic exchange Hamiltonians in the appropriate local coordinates. We then rewrite these local Hamiltonians in the molecular or laboratory representation, along with the Dzyaloshinskii-Moriay (DM) and isotropic Heisenberg, biquadratic, and three-center quartic Hamiltonians. Using our exact, compact forms for the single-ion spin matrix elements, we evaluate the eigenstate energies analytically to first order in the microscopic anisotropy interactions, corresponding to the strong exchange limit, and provide tables of simple formulas for the energies of the lowest four eigenstate manifolds of ferromagnetic (FM) and anitiferromagnetic (AFM) tetramers with arbitrary $s_1$. For AFM tetramers, we illustrate the first-order level-crossing inductions for $s_1=1/2,1,3/2$, and obtain a preliminary estimate of the microscopic parameters in a Ni$_4$ from a fit to magnetization data. Accurate analytic expressions for the thermodynamics, electron paramagnetic resonance absorption and inelastic neutron scattering cross-section are given, allowing for a determination of three of the microscopic anisotropy interactions from the second excited state manifold of FM tetramers. We also predict that tetramers with symmetries $S_4$ and $D_{2d}$ should exhibit both DM interactions and multiferroic states, and illustrate our predictions for $s_1=1/2, 1$.Comment: 30 pages, 14 figures, submitted to Phys. Rev.

Gestión clínica de la consulta: previsibilidad y contenido clínico (estudio SyN-PC)

ObjetivoDescribir la actividad asistencial en función de la naturaleza de la consulta (previsibilidad) y las necesidades de los pacientes (contenido clínico). Analizar la relación con las características de la consulta, del paciente y del centroDiseñoEstudio observacional descriptivo multicéntricoEmplazamientoAtención primaria. Área 17 de la Conselleria de Sanidad de la Comunidad Valenciana. Población de 197.316 habitantes. Trece centros de saludParticipantesRecogida de información en tiempo real por un observador externo. Muestreo aleatorio estratificado de 2.051 pacientes que ocasionaron 3.008 motivos de consulta médicaMediciones principalesConsulta previsible (Pr): se puede prever su contenido (revisiones, recogida de resultados). Consulta imprevisible (Ip): no podemos prever su contenido (problemas agudos) y surgen inesperadamente. Engloba la consulta urgente. Consulta administrativa (Ad): tareas burocráticas (recetas, partes de confirmación, certificados). Consulta asistencial (As): prevenir, diagnosticar y tratar la enfermedad, o realizar seguimiento de ésta. Variables del paciente, el centro y la consultaResultadosEl 60% (n=1.809; IC del 95%, 58,69–61,59%) de los motivos fueron previsibles y el 40% (n=1.199; IC del 95%, 36,6–43,12%), imprevisibles. El 50% (n=1.509; IC del 95%, 47,26–53,06%) fueron consultas asistenciales y el 50% (n=1.499; IC del 95%, 46,34–53,39%), administrativas. El 40% (n=1.189; IC del 95%, 37,78–41,28%) fueron previsibles-administrativas y tan sólo un 21% (n=620; IC del 95%, 19,16– 22,06%) resultaron de carácter previsible-asistencial. El 30% (n=889; IC del 95%, 27,92–31,18%) fueron de carácter imprevisible–asistencial y el 10% (n=310; IC del 95%, 9,22– 11,4%), imprevisibles-administrativas. En los pacientes con un único motivo, el 48% (n=577; IC del 95%, 44,25–52,05%) fueron consultas previsibles-administrativas. Los centros docentes o informatizados tienen menos carga de consultas previsibles-administrativas. Éstas aumentan con la edad del paciente y con la presión asistencialConclusionesCasi un 40% de los motivos de consulta son previsibles-administrativos, lo que implica una gestión clínica inadecuada. Sería necesaria una intervención que permitiera liberar tiempo médico consumido en asuntos burocráticos para dedicarlo a la tarea asistencial propiamente dichaObjectivesTo describe care activity as a function of the nature of the consultation (predictability) and the needs of the patients (clinical content). To analyse the relationship of these with the characteristics of the consultation, of the patient and of the centreDesignMulti-centre, descriptive, observational study.SettingPrimary care. Area 17 of the Health Department of the Community of Valencia, with 197 316 inhabitants and 12 health centresParticipantsInformation gathering in real time by outside observer. Stratified randomised sampling of 2051 patients who gave rise to 3008 reasons for medical consultationMain measurementsPredictable consultations (Pr): their content can be foreseen (check-ups, picking up results). Unpredictable consultations (Unp): we cannot predict their content (acute problems may arise unexpectedly). These include urgent consultations. Administrative consultations (Ad): bureaucratic tasks (prescriptions, repeat sick-notes, sick certificates). Care consultations (Car): prevention, diagnosis and treatment of the illness, or monitoring of it. Variables here are the patient, the doctor and the consultationResults60% (1809) (95% CI, 58.69%–61.59%) of the reasons were Pr and 40% (1199) (95% CI, 36.6%–43.12%) were Unp. 50% (1509) (95% CI, 47.26%–53.06%) were Car, and 50% Ad (1499) (95% CI, 46.34%–53.39%). 40% (1189) (95% CI, 37.78%–41.28%) were Pr-Ad and only 21% (620) (95% CI, 19.16%–22.06%) were Pr-Car. 30% (889) (95% CI, 27.92%–31.18%) were Unp–Car, and 10% (310) (95% CI, 9.22%– 11.4%) Unp-Ad. 48% of patients with a single reason for attendance were Pr-Ad (577) (95% CI, 44.25%–52.05). Teaching centres and computerised ones had less Pr-Ad load. Pr-Ad consultations increased with patient´s age and with case-load.ConclusionsAlmost 40% of the reasons for consultation are Pr-Ad, which implies inadequate clinical management. An intervention is needed to free up medical time consumed by bureaucratic questions, so that this time can be devoted fully to health-care task

Power-dependent effective reflection of fiber Bragg grating as output coupler of Ytterbium-doped fiber laser

In this paper, we discuss the effective reflection of a fiber Bragg grating and its dependence on laser power when it is used as an output coupler of an ytterbium-doped fiber laser (here the effective reflection is considered to be a part of intracavity laser power reflected by the grating back to the laser cavity). We propose and discuss an experimental technique based on spectral and power analysis and derive simple formulae that permits one to obtain the intra-cavity power and the grating effective reflection. We show that, due to spectral broadening, the effective reflection dramatically decreases with increasing laser power, the effect precisely fitted using the derived formulae describing this quantity. The experimental part of the present study is based on an analysis of the operational regime of a long-wavelength ytterbium-doped fiber laser

Study of strawberry flavored milk under pulsed electric field processing

Few studies exist on flavored milk processed by pulsed electric fields (PEF). The main concern is product stability. This study aimed to analyze the degradation of coloring agent Allura Red in strawberry milk under PEF. Four systems were tested containing Allura Red: two commercial milks and two model systems. PEF conditions were 40 kV/cm, 48 pulses (2.5 μs), and 55 °C; coloring agent was quantified via RP-HPLC. After processing, only minor changes were observed in color, Allura Red concentration, and pH. During storage (32 d) at refrigerated conditions (4 °C) commercial samples maintained pH above 6. Model systems dropped below pH 6 after 10 days of storage. Color of samples showed important decrease in a⁎; hue angle and chroma changed during storage. HPLC analysis reported a bi-phasic effect in Allura Red concentrations versus time. Concentration changed, reaching a maximum value during the middle of storage, possibly attributed to microbial growth, pH reduction, or interaction of proteins. However, PEF affected the stability of Allura Red in milk when additional ingredients were not added to the product

Study of strawberry flavored milk under pulsed electric field processing

Few studies exist on flavored milk processed by pulsed electric fields (PEF). The main concern is product stability. This study aimed to analyze the degradation of coloring agent Allura Red in strawberry milk under PEF. Four systems were tested containing Allura Red: two commercial milks and two model systems. PEF conditions were 40 kV/cm, 48 pulses (2.5 μs), and 55 °C; coloring agent was quantified via RP-HPLC. After processing, only minor changes were observed in color, Allura Red concentration, and pH. During storage (32 d) at refrigerated conditions (4 °C) commercial samples maintained pH above 6. Model systems dropped below pH 6 after 10 days of storage. Color of samples showed important decrease in a⁎; hue angle and chroma changed during storage. HPLC analysis reported a bi-phasic effect in Allura Red concentrations versus time. Concentration changed, reaching a maximum value during the middle of storage, possibly attributed to microbial growth, pH reduction, or interaction of proteins. However, PEF affected the stability of Allura Red in milk when additional ingredients were not added to the product

Associations between feed efficiency and aspects of lactation curves in primiparous Holstein dairy cattle.

Genetic selection for improved feed efficiency in dairy cattle has received renewed attention over the last decade to address the needs of a growing global population. As milk yield is a critical component of feed efficiency metrics in dairy animals, our objective was to evaluate the associations between feed efficiency in primiparous Holstein cattle and parameters of a mathematical model describing individual lactation curves. The Dijkstra lactation curve model was fit to individual lactation records from 34 Holstein heifers with previously estimated measures of feed efficiency. We found that the optimal fit of the Dijkstra model was achieved using daily milk yield records up to 21 d in milk to capture the rise to peak milk yield and using monthly dairy herd improvement records for the remainder of lactation to accurately characterize lactation persistency. In the period of lactation before peak milk yield, improved feed efficiency was associated with a faster increase in daily milk yield over a shorter period of time at the expense of increased mobilization of body reserves; this serves to reinforce the concept that dairy cattle are primarily capital breeders versus income breeders. Feed efficiency in the period following peak lactation, as measured by gross feed efficiency, return over feed costs, and net energy efficiency of lactation, was positively associated with higher peak milk yield. The findings in early lactation suggest that estimates of feed efficiency could be improved by evaluating feed efficiency relative to conception, rather than parturition and lactation, to better account for the energy stored and released from body reserves in capital breeding

Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission

We report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime’s coherence time dramatically shortens, from few ns to tens ps, with increasing laser power