Degradation of Ta2O5 / SiO2 dielectric cavity mirrors in ultra-high vacuum.

In order for optical cavities to enable strong light-matter interactions for quantum metrology, networking, and scalability in quantum computing systems, their mirrors must have minimal losses. However, high-finesse dielectric cavity mirrors can degrade in ultra-high vacuum (UHV), increasing the challenges of upgrading to cavity-coupled quantum systems. We observe the optical degradation of high-finesse dielectric optical cavity mirrors after high-temperature UHV bake in the form of a substantial increase in surface roughness. We provide an explanation of the degradation through atomic force microscopy (AFM), X-ray fluorescence (XRF), selective wet etching, and optical measurements. We find the degradation is explained by oxygen reduction in Ta2O5 followed by growth of tantalum sub-oxide defects with height to width aspect ratios near ten. We discuss the dependence of mirror loss on surface roughness and finally give recommendations to avoid degradation to allow for quick adoption of cavity-coupled systems.

On-site growth of perovskite nanocrystal arrays for integrated nanodevices.

Despite remarkable progress in the development of halide perovskite materials and devices, their integration into nanoscale optoelectronics has been hindered by a lack of control over nanoscale patterning. Owing to their tendency to degrade rapidly, perovskites suffer from chemical incompatibility with conventional lithographic processes. Here, we present an alternative, bottom-up approach for precise and scalable formation of perovskite nanocrystal arrays with deterministic control over size, number, and position. In our approach, localized growth and positioning is guided using topographical templates of controlled surface wettability through which nanoscale forces are engineered to achieve sub-lithographic resolutions. With this technique, we demonstrate deterministic arrays of CsPbBr3 nanocrystals with tunable dimensions down to <50 nm and positional accuracy <50 nm. Versatile, scalable, and compatible with device integration processes, we then use our technique to demonstrate arrays of nanoscale light-emitting diodes, highlighting the new opportunities that this platform offers for perovskites' integration into on-chip nanodevices.

Nanoparticle contact printing with interfacial engineering for deterministic integration into functional structures.

Deterministic, pristine, and scalable integration of individual nanoparticles onto arbitrary surfaces is an ongoing challenge, yet essential for harnessing their unique properties for functional nanoscale devices. To address this challenge, we present a versatile technique where spatially arranged nanoparticles assembled in a topographical template are printed onto diverse surfaces, through a single contact-and-release step, with >95% transfer yield and <50-nanometer placement accuracy. Through engineering of interfacial interactions, our approach uniquely promotes high-yield transfer of individual particles without needing solvents, surface treatments, and polymer sacrificial layers, which are conventionally inevitable. By avoiding these mediation steps, surfaces can remain damage and contamination free and accessible to integrate into functional structures. We demonstrate this in a particle-on-mirror model system, where >2000 precisely defined nanocavities display a consistent plasmonic response with minimized interstructure variability. Through fabricating arrays of emitter-coupled nanocavities, we further highlight the integration opportunities offered by our contact printing.

HEPATOCELLULAR TOXICITY OF THE METABOLITE EMODIN PRODUCED BY THE COMMON BUCKTHORN (RHAMNUS CATHARTICA) IN GREEN FROG (LITHOBATES CLAMITANS) TADPOLES.

The secondary metabolite emodin, produced by the widely distributed invasive shrub known as the common buckthorn (Rhamnus cathartica), has been shown to produce deformities and mortality in invertebrates, fish, and amphibian larvae. Here, we describe the effects on the liver of green frog (Lithobates clamitans) tadpoles after 21 d of exposure to high concentrations of emodin in a controlled environment. Histopathologic analysis showed fibrosis, bile duct proliferation, hepatocellular swelling, and accumulations of flocculent material consistent with emodin within the gall bladder and bile ducts of exposed individuals. The extensive fibrosis produced probably impeded the blood flow within the portal triads, limiting the detoxification function of the liver and resulting in hepatocellular necrosis and premature death for the individuals exposed. Exposure to emodin in the environment could represent a significant threat to developing amphibian larvae and contribute to local declines of populations.

Acetonitrile based single step slot-die compatible perovskite ink for flexible photovoltaics.

The demonstration of photovoltaic devices with high power conversion efficiencies using low cost perovskite materials hints at the possibility of dramatically lowering the cost of solar energy. Key to further exploiting the potential of these materials is developing rapid processing techniques that can be used to deliver lower cost high throughput manufacture. This work details the development of low viscosity rapid drying perovskite formulations designed to give high quality solar films when slot-die coated on flexible roll-to-roll compatible substrates. A single step slot-die compatible perovskite ink based on an acetonitrile/methylamine solvent system utilizing a chloride additive is developed, resulting in large area perovskite films from slot-die coating under ambient conditions. The drying conditions for the perovskite film are optimized and fast (<10 min), low temperature (<120 °C) drying of slot-die coated films on flexible substrates are demonstrated and result in high performance devices.

The Impact of Atmosphere on the Local Luminescence Properties of Metal Halide Perovskite Grains.

Metal halide perovskites are exceptional candidates for inexpensive yet high-performing optoelectronic devices. Nevertheless, polycrystalline perovskite films are still limited by nonradiative losses due to charge carrier trap states that can be affected by illumination. Here, in situ microphotoluminescence measurements are used to elucidate the impact of light-soaking individual methylammonium lead iodide grains in high-quality polycrystalline films while immersing them with different atmospheric environments. It is shown that emission from each grain depends sensitively on both the environment and the nature of the specific grain, i.e., whether it shows good (bright grain) or poor (dark grain) luminescence properties. It is found that the dark grains show substantial rises in emission, while the bright grain emission is steady when illuminated in the presence of oxygen and/or water molecules. The results are explained using density functional theory calculations, which reveal strong adsorption energies of the molecules to the perovskite surfaces. It is also found that oxygen molecules bind particularly strongly to surface iodide vacancies which, in the presence of photoexcited electrons, lead to efficient passivation of the carrier trap states that arise from these vacancies. The work reveals a unique insight into the nature of nonradiative decay and the impact of atmospheric passivation on the microscale properties of perovskite films.

Stable Light-Emitting Diodes Using Phase-Pure Ruddlesden-Popper Layered Perovskites.

State-of-the-art light-emitting diodes (LEDs) are made from high-purity alloys of III-V semiconductors, but high fabrication cost has limited their widespread use for large area solid-state lighting. Here, efficient and stable LEDs processed from solution with tunable color enabled by using phase-pure 2D Ruddlesden-Popper (RP) halide perovskites with a formula (CH3 (CH2 )3 NH3 )2 (CH3 NH3 )n-1 Pbn I3n+1 are reported. By using vertically oriented thin films that facilitate efficient charge injection and transport, efficient electroluminescence with a radiance of 35 W Sr-1 cm-2 at 744 nm with an ultralow turn-on voltage of 1 V is obtained. Finally, operational stability tests suggest that phase purity is strongly correlated to stability. Phase-pure 2D perovskites exhibit >14 h of stable operation at peak operating conditions with no droop at current densities of several Amperes cm-2 in comparison to mixtures of 2D/3D or 3D perovskites, which degrade within minutes.

Probing buried recombination pathways in perovskite structures using 3D photoluminescence tomography.

Perovskite solar cells and light-emission devices are yet to achieve their full potential owing in part to microscale inhomogeneities and defects that act as non-radiative loss pathways. These sites have been revealed using local photoluminescence mapping techniques but the short absorption depth of photons with energies above the bandgap means that conventional one-photon excitation primarily probes the surface recombination. Here, we use two-photon time-resolved confocal photoluminescence microscopy to explore the surface and bulk recombination properties of methylammonium lead halide perovskite structures. By acquiring 2D maps at different depths, we form 3D photoluminescence tomography images to visualise the charge carrier recombination kinetics. The technique unveils buried recombination pathways in both thin film and micro-crystal structures that aren't captured in conventional one-photon mapping experiments. Specifically, we reveal that light-induced passivation approaches are primarily surface-sensitive and that nominal single crystals still contain heterogeneous defects that impact charge-carrier recombination. Our work opens a new route to sensitively probe defects and associated non-radiative processes in perovskites, highlighting additional loss pathways in these materials that will need to be addressed through improved sample processing or passivation treatments.

Disassembly of a tadpole community by a multi-host fungal pathogen with limited evidence of recovery.

Emerging infectious diseases can cause host community disassembly, but the mechanisms driving the order of species declines and extirpations following a disease outbreak are unclear. We documented the community disassembly of a Neotropical tadpole community during a chytridiomycosis outbreak, triggered by the generalist fungal pathogen, Batrachochytrium dendrobatidis (Bd). Within the first 11 months of Bd arrival, tadpole density and occupancy rapidly declined. Species rarity, in terms of tadpole occupancy and adult relative abundance, did not predict the odds of tadpole occupancy declines. But species losses were taxonomically selective, with glassfrogs (Family: Centrolenidae) disappearing the fastest and tree frogs (Family: Hylidae) and dart-poison frogs (Family: Dendrobatidae) remaining the longest. We detected biotic homogenization of tadpole communities, with post-decline communities resembling one another more strongly than pre-decline communities. The entire tadpole community was extirpated within 22 months following Bd arrival, and we found limited signs of recovery within 10 years post-outbreak. Because of imperfect species detection inherent to sampling species-rich tropical communities and the difficulty of devising a single study design protocol to sample physically complex tropical habitats, we used simulations to provide recommendations for future surveys to adequately sample diverse Neotropical communities. Our unique data set on tadpole community composition before and after Bd arrival is a valuable baseline for assessing amphibian recovery. Our results are of direct relevance to conservation managers and community ecologists interested in understanding the timing, magnitude, and consequences of disease outbreaks as emerging infectious diseases spread globally.

The Impact of Phase Retention on the Structural and Optoelectronic Properties of Metal Halide Perovskites.

The extent to which the soft structural properties of metal halide perovskites affect their optoelectronic properties is unclear. X-ray diffraction and micro-photoluminescence measurements are used to show that there is a coexistence of both tetragonal and orthorhombic phases through the low-temperature phase transition, and that cycling through this transition can lead to structural changes and enhanced optoelectronic properties.

Water Temperature Affects Susceptibility to Ranavirus.

The occurrence of emerging infectious diseases in wildlife populations is increasing, and changes in environmental conditions have been hypothesized as a potential driver. For example, warmer ambient temperatures might favor pathogens by providing more ideal conditions for propagation or by stressing hosts. Our objective was to determine if water temperature played a role in the pathogenicity of an emerging pathogen (ranavirus) that infects ectothermic vertebrate species. We exposed larvae of four amphibian species to a Frog Virus 3 (FV3)-like ranavirus at two temperatures (10 and 25°C). We found that FV3 copies in tissues and mortality due to ranaviral disease were greater at 25°C than at 10°C for all species. In a second experiment with wood frogs (Lithobates sylvaticus), we found that a 2°C change (10 vs. 12°C) affected ranaviral disease outcomes, with greater infection and mortality at 12°C. There was evidence that 10°C stressed Cope's gray tree frog (Hyla chrysoscelis) larvae, which is a species that breeds during summer-all individuals died at this temperature, but only 10% tested positive for FV3 infection. The greater pathogenicity of FV3 at 25°C might be related to faster viral replication, which in vitro studies have reported previously. Colder temperatures also may decrease systemic infection by reducing blood circulation and the proportion of phagocytes, which are known to disseminate FV3 through the body. Collectively, our results indicate that water temperature during larval development may play a role in the emergence of ranaviruses.

Susceptibility of fish and turtles to three ranaviruses isolated from different ectothermic vertebrate classes.

Ranaviruses have been associated with mortality of lower vertebrates around the world. Frog virus 3 (FV3)-like ranaviruses have been isolated from different ectothermic vertebrate classes; however, few studies have demonstrated whether this pathogen can be transmitted among classes. Using FV3-like ranaviruses isolated from the American bullfrog Lithobates catesbeianus, eastern box turtle Terrapene carolina carolina, and Pallid Sturgeon Scaphirhynchus albus, we tested for the occurrence of interclass transmission (i.e., infection) and host susceptibility (i.e., percent mortality) for five juvenile fish and three juvenile turtle species exposed to each of these isolates. Exposure was administered via water bath (10(3) PFU/mL) for 3 d and survival was monitored for 28 d. Florida softshell turtles Apalone ferox experienced no mortality, but 10% and 20% of individuals became infected by the turtle and fish isolate, respectively. Similarly, 5% of Mississippi map turtles Graptemys pseudogeographica kohni were subclinically infected with the turtle isolate at the end of the experiment. Channel Catfish Ictalurus punctatus experienced 5% mortality when exposed to the turtle isolate, while Western Mosquitofish Gambusia affinis experienced 10% mortality when exposed to the turtle and amphibian isolates and 5% mortality when exposed to the fish isolate. Our results demonstrated that interclass transmission of FV3-like ranaviruses is possible. Although substantial mortality did not occur in our experiments, the occurrence of low mortality and subclinical infections suggest that fish and aquatic turtles may function as reservoirs for FV3-like ranaviruses. Additionally, our study is the first to report transmission of FV3-like ranaviruses between fish and chelonians.

Transmission of ranavirus between ectothermic vertebrate hosts.

Transmission is an essential process that contributes to the survival of pathogens. Ranaviruses are known to infect different classes of lower vertebrates including amphibians, fishes and reptiles. Differences in the likelihood of infection among ectothermic vertebrate hosts could explain the successful yearlong persistence of ranaviruses in aquatic environments. The goal of this study was to determine if transmission of a Frog Virus 3 (FV3)-like ranavirus was possible among three species from different ectothermic vertebrate classes: Cope's gray treefrog (Hyla chrysoscelis) larvae, mosquito fish (Gambusia affinis), and red-eared slider (Trachemys scripta elegans). We housed individuals previously exposed to the FV3-like ranavirus with naïve (unexposed) individuals in containers divided by plastic mesh screen to permit water flow between subjects. Our results showed that infected gray treefrog larvae were capable of transmitting ranavirus to naïve larval conspecifics and turtles (60% and 30% infection, respectively), but not to fish. Also, infected turtles and fish transmitted ranavirus to 50% and 10% of the naïve gray treefrog larvae, respectively. Nearly all infected amphibians experienced mortality, whereas infected turtles and fish did not die. Our results demonstrate that ranavirus can be transmitted through water among ectothermic vertebrate classes, which has not been reported previously. Moreover, fish and reptiles might serve as reservoirs for ranavirus given their ability to live with subclinical infections. Subclinical infections of ranavirus in fish and aquatic turtles could contribute to the pathogen's persistence, especially when highly susceptible hosts like amphibians are absent as a result of seasonal fluctuations in relative abundance.

Lumbalgia mecánica en el ámbito laboral, Costa Rica / Lower back pain of mechanical causes at the work place, Costa Rica

Objetivo: Comparar las diferentes modalidades terapéuticas para una lumbalgia mecánica post esfuerzo ofrecida por el dispensario del Instituto Nacional de Salud de la localidad de San Antonio de Belén. Materiales y Método: Estudio descriptivo. Muestra a conveniencia de todos los pacientes vistos en el dispensario del Instituto de Seguros de San Antonio de Belén, durante abril 2008 -octubre del 2010. Se valoraron tres modalidades diclofenaco sódico, ibuprofeno/indometacina y complejo B. El indicador utilizado para determinar adecuada respuesta fueron días de incapacidad. Resultados: Del total de 145 pacientes valorados 55 presentaron incapacidad superior a los 10 días. Seis paciente presentaron incapacidades superiores a los 20 días y un paciente presentó incapacidad superior a los 30 días. Discusión: Los pacientes tratados diclofenaco sódico y complejo B, presentaron un cantidad menor de días de incapacidad, una cantidad menor de reaperturas y por ende una mayor respuesta.

Objective: To compare the different therapeutic modalities for mechanical low back post effort clinic offered by the National Institute of Health in the town of San Antonio de Belén. Materials and Methods: Descriptive study. Convenience samples all patients seen at the clinic from the Insurance Institute of SanAntonio de Belén, duringApril 2008 -October 2010. We evaluated three methods diclofenac sodium, ibuprofen / indomethacin complex B. The indicator used to determine adequate response were days of disability. Results: A total of 145 patients evaluated 55 had failure of more than 10 days. Six patients had disabilities over 20 days and one patient had failure of more than 30 days. Discussion: Patients receiving diclofenac sodium and B complex, presented a smaller number of days of disability, a smaller number of reopening and there fore more responsive.

Placental mesenchymal and cord blood stem cell therapy for dilated cardiomyopathy.

Regenerative treatment of dilated, non-ischaemic cardiomyopathy represents a significant unmet clinical need. Intracoronary administration of autologous bone marrow stem cells has demonstrated positive results in treatment of post-infarct and chronic ischaemic patients. Limitations of this procedure include: invasiveness of bone marrow extraction and cardiac catheterization, and dependence on stem cell populations that are aged and possibly senescent. Here, the use of intravenously administered allogeneic placental matrix derived mesenchymal stem cells for treatment of dilated cardiomyopathy is discussed. Safety of this cell population has already been established in completed Phase I and II trials; however, to date, clinical implementation for dilated cardiomyopathy has not been reported. Preclinical studies have demonstrated that mesenchymal stem cells: (i) inhibit myocardial inflammation; (ii) inhibit cardiomyocyte apoptosis; (iii) stimulate angiogenesis; and (iv) display therapeutic activity in models of dilated cardiomyopathy. Clinical studies have demonstrated the ability of mesenchymal stem cells to inhibit post-infarct remodelling, as well as potently block inflammatory processes in graft versus host and Crohn disease. Presented here is case report of a patient with dilated cardiomyopathy treated with intravenous allogeneic mesenchymal stem cells and expanded umbilical cord blood CD34 cells who underwent a profound clinical improvement.

Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community.

Pathogens rarely cause extinctions of host species, and there are few examples of a pathogen changing species richness and diversity of an ecological community by causing local extinctions across a wide range of species. We report the link between the rapid appearance of a pathogenic chytrid fungus Batrachochytrium dendrobatidis in an amphibian community at El Copé, Panama, and subsequent mass mortality and loss of amphibian biodiversity across eight families of frogs and salamanders. We describe an outbreak of chytridiomycosis in Panama and argue that this infectious disease has played an important role in amphibian population declines. The high virulence and large number of potential hosts of this emerging infectious disease threaten global amphibian diversity.

Evaluación de dos métodos para establecer el contenido de polifenoles en frijol crudo y cocido, y efecto que éstos provocan en la digestibilidad de la proteína / Evaluation of two methods for establish the polyphenol content of raw and cooked beans and the effect of these on protein digestibility

Se cuantificaron los polifenoles de frijol común de color blanco, negro y colorado, crudos, cocidos y secados, con y si caldo, por el método de Folin-Denis que mide polifenoles totales, y por el procedimiento de precipitación de proteína de Hagerman-Butler, que mide su actividad biológica. La evaluación consistió en determinar polifenoles en las mismas muestras durante 20 días consecutivos, utilizando tres volúmenes de extracto de una misma muestra. Los resultados obtenidos con el método de Folin-Denis, analizados estadísticamente, indicaron que la variabilidad fue diferente en los tres volúmenes de extracto de cada uno de los colores de frijol. Sin embargo, una prueba no paramétrica señaló que los promedios en los tres niveles de concentración para todos los frijoles, eran iguales. La variabilidad y los promedios en los tres niveles de extracto de frijoles negros y colorados-determinados por el método de Hagerman-Butler-fueron iguales, no siendo así con los frijoles blancos. El coeficiente de variación fue más bajo para el nivel de mayor volumen de extracto. Se encontró una correlación significativa ...

Efectos del tratamiento de la pulpa de cafe, fresca o ensilado, con hidroxido de cálcio, sobre su valor nutritivo / Effects of the treatment of coffee pulp, fresh or ensilaged, with calcium hydroxide, on its nutritive value

El presente estudio se efectuó para determinar los efectos de la adición de hidróxido de calcio sobre la composición química y valor nutritivo de la pulpa de café, fresca o ensilada. Se mezcló pulpa fresca o ensilada con 1,2 y 3% de hidróxido de calcio. El proceso se llevó a cabo en dos períodos de tiempo, 0 y 16 horas, respectivamente, después de los cuales las pulpas se dejaron secar al sol durante 36 horas, hasta alcanzar 12% de humedad. Estas muestras se analizaron para determinar su composición química proximal y de algunos minerales (Ca, P, Na, K), así como por su contenido de cafeína, taninos y ácidos clorogénico y cafeíco. Con los materiales ya analizados, se elaboraron raciones con 15% de proteína y 15 ó 30% de pulpa de café fresca o ensilada, las que se ofrecieron a ratas recién destetadas durante seis semanas. Se recoletó la información requerida, y los materiales necesarios para determinar ganancia de peso, eficiencia de alimentación, digestibilidad aparente y toxicidad de las raciones. Los resultados del análisis químico mostraron que los principales cambios ocurridos en las pulpas a causa del efecto del hidróxido de calcio, fueron los siguientes: disminución del extracto etéreo (de 4.0 a 2.5), de la fibra cruda (de 18.3 a 11.9), y de la proteína (de 12.3 a 8.6), en una relación inversa al porcentaje de hidróxido de calcio utilizando ambas pulpas. La cantidad de ceniza se incrementó, fluctuando los valores entre 5.5 y 14.4% como consecuencia del Ca(OH)2 agregado, lo que influyó al calcular la relación calcio: fósforo en las dieta. Se encontró una relación promedio de 7.2:1 en las pulpas control (0% de Ca(OH)2 y de 59.0:1 en las pulpas que contenían el mayor porcentaje de Ca(OH)2 (3%). Con respecto al contenido de cafeína, taninos y ácidos cloregénico y cafeico, se encontró que los tratamientos alcalinos sólo fueron efectivos en reducir ls taninos de la pulpa, más en la fresca que en la ensilada...

The chemical composition and protein quality of amaranth grain germ plasm in Guatemala

El presente trabajo se llevó a cabo con el propósito de recolectar parte del germoplasma de grano de amaranto de Guatemala y evaluarlo en términos de rendimiento, composición química y valor nutritivo. Junto con una selección de México (A. Cruentus) y siete de Cusco, Perú (A. Caudatus), se sembraron 27 selecciones de Guatemala en junio de 1982, en lotes experimentales de 7.5 m2, en cuatro repeticiones. Las semillas cosechadas se utilizaron para análisis químico de proteína, grasa, fibra, cruda, taninos e inhibidodres de tripsina, así como NPR. Con base en su contenido proteínico, se formaron cinco grupos para análisis de aminoácidos y 10 selecciones se evaluaron en un segundo ensayo, para determinar calidad proteínica, por medio del método de NPR y digestibilidad proteínica. Se informa, asimismo, sobre un ensayo de suplementación con aminoácidos en semilla cruda. Las selecciones difirieron significativamente en cuanto a rendimiento de grano. Se encontró una relación negativa entre la altura de la planta y rendimiento de materia seca vegetativa. El contenido proteínico del grano varió entre 12.8 y 17.4% con un promedió de 15%. Se encotró que las semillas con mayor contenido de protína acusaban mayor contenido de aminoácidos por peso, pero al expresarse por gramo de nitrógeno, los contenidos fueron muy parecidos. De acuerdo al patrón de FAO/OMS, la proteína es deficiente en aminoácidos azufrados, lo que se demostró por medio de un ensayo de PER. La calidad proteínica de un grupo seleccionado fue variable. Las muestras del Perú dieron una NPR de 2.30, la de México de 2.36, y una de Guatemala de 2.04. La digestibilidad proteínica aparente fue de 80,82 y 74% para las muestras del Perú, México y Guatemala, respectivamente. Los datos indican diferencias en rendimiento, composición química y valor nutritivo, y un rendimiento favorable de grano

Composición quimica y evaluación de la calidad de la proteina del frijol en humanos adultos por el método de balance nitrogenado de corto tiempo / Chemical composition and evaluation of the quality of proteins in human adults by the short-term nitrogen balance method

Se analizaron químicamente tres variedades de frijol común, evaluándose la calidad de su proteína en 12 sujetos adultos por el método de balance de nitrógeno de corto plazo. Los análisis químicos se llevaron a cabo en el grano crudo y cocido, observándose una reducción, por cocción, de 28 a 73% de los inhibidores de tripsina, 100% de hemaglutininas, 9 a 72% de los taninos expresados como equivalentes de ácido tánico, 55-75% expresados como equivalentes de catequinas, y 65% de reducción en el contenido de nitrógeno soluble en álcali. Los frijoles negro y rojo acusaron un mayor contenido de inhibidores de tripsina residuales y taninos, mientras que la mayor cantidad de nitrógeno soluble en álcali se encontró en los frijoles blancos. Aun cuando los frijoles coloreados presentaron un mayor contenido de los factores antinutricionales que afectan la digestibilidad de la proteína, el valor nutritivo de ésta (BN, NPU, NBI) fue semejante a la de los blancos. Ello podría deberse a que la composición y/o balance aminoacídico del nitrógeno absorbido procedente de los frijoles rojos y negros es superior a la de los blancos, por lo que la interrelación entre todos los factores sería la que determine el valor nutritivo final. Además, en cada una de las variedades se constató un mayor contenido de por lo menos un depresor de la calidad proteínica. Se encontraron diferencias significativas (P>0.05) entre los sujetos y los períodos de estudio de balance nitrogenado, mientras que no se comprobaron diferencias por efecto del tratamiento (variedad de frijol) y efecto residual (días de adaptación). El nivel de 0.65 g de proteína de frijol/kg/día no fue suficiente para mantener en balance nitrogenado a los sujetos alimentados a base de una dieta en que la única fuente de proteína era el frijol. Por cálculo, se determinó que 0.9 a 1.0 g de proteína de frijol/kg/día son necesarios para que los individuos estén en balance, y para una población se recomendaría una ingestión de 1.2 a 1.3 g de proteína de las variedades de frijol estudiadas