Coalescence of rigid droplets in a stirred dispersion-II. Band-limited force fluctuations

The coalescence of nearly rigid liquid droplets in a turbulent flow field is viewed as the drainage of a thin film of liquid under the action of a stochastic force representing the effect of turbulence. The force squeezing the drop pair is modelled as a correlated random function of time. The drops are assumed to coalesce once the film thickness becomes smaller than a critical thickness while they are regarded as separated if their distance of separation is larger than a prescribed distance. A semi-analytical solution is derived to determine the coalescence efficiency. The veracity of the solution procedure is established via a Monte-Carlo solution scheme. The model predicts a reversing trend of the dependence of the coalescence efficiency on the drop radii, the film liquid viscosity and the turbulence energy dissipation per unit mass, as the relative fluctuation increases. However, the dependence on physical parameters is weak (especially at high relative fluctuation) so that for the smallest droplets (which are nearly rigid) the coalescence efficiency may be treated as an empirical constant. The predictions of this model are compared with those of a white-noise force model. The results of this paper and those in Muralidhar and Ramkrishna (1986, Ind. Engng Chem. Fundam. 25, 554-56) suggest that dynamic drop deformation is the key factor that influences the coalescence efficiency.

Solubilities of solids in supercritical fluids using dimensionally consistent modified solvate complex models

New dimensionally consistent modified solvate complex models are derived to correlate solubilities of solids in supercritical fluids both in the presence and absence of entrainers (cosolvents). These models are compared against the standard solvate complex models [J.Chrastil, J. Phys. Chem. 86 (1982) 3016-3021; J.C. Gonzalez, M.R.Vieytes, A.M. Botana, J.M. Vieites, L.M. Botana, J. Chromatogr. A 910 (2001) 119-125; Y. Adachi, B.C.Y. Lu, Fluid Phase Equilb. 14 (1983) 47-156; J.M. del Valle, J.M. Aguilera, Ind. Eng. Chem. Res. 27 (1988) 1551-1553] by correlating the solubilities of 13 binary and 12 ternary systems. Though the newly derived models are not significantly better than the standard models in predicting the solubilities, they are dimensionally consistent. (C) 2009 Elsevier B.V. All rights reserved.

Specificity of protein - Nucleic acid interaction and the biochemical evolution

The water soluble carbodiimide mediated condensation of dipeptides of the general form Gly-X was carried out in the presence of mono- and poly-nucleotides. The observed yield of the tetrapeptide was found to be higher for peptide-nucleotide system of higher interaction specificity following mainly the anticodon-amino acid relationship (Basu, H.S. & Podder, S.K., 1981, Ind. J. Biochem. Biophys.,19, 251-253). The yield of the condensation product of L-peptide was more because of its higher interaction specificity. The extent of the racemization during the condensation of Gly-L-Phe, Gly-L-Tyr and Gly-D-Phe was found to be dependent on the specificity of the interaction -the higher the specificity, the lesser the racemization. The product formed was shown to have a catalytic effect on the condensation reaction. These data thus provide a mechanism showing how the specific interaction between amino acids/dipeptides and nucleic acids could lead to the formation of the lsquoprimitiversquo translation machinery.

Baron de Hirsch Fund records undated, 1870-1991.

Contains Deed of Trust, By-Laws, Annual Reports, Corporation Minutes (1909, 1913-1919, 1923-1924, 1926-1933), Minutes of the Board of Trustees (1893, 1899, 1907, 1910, 1915-1916, 1918, 1923, 1926-1927, 1930-1933), and the minutes, correspondence, and reports of the various national and local committees. Financial materials include income and expenditure records (1891-1933), audits (1919-1923, 1926-1928), the records of agricultural loans and mortgages, bond and real estate holdings, and bequests. Includes also correspondence and other materials regarding the establishment of the Fund, correspondence of and other papers concerning the Baron and Baroness de Hirsch, and several histories of the Fund. Included in the wide range of activities are material on the work of the Agriculture Bureau and the Jewish Agriculture Society, Housing, English Classes, Immigration (including monthly reports for several ports of entry 1885-1916) and Immigrant Aid, German Refugee Aid in the early years of the Holocaust, Kings Park, N.Y. Test Farm, the Laundry Project, Peekskill Farm, Public Baths, Student Loans, the Baron de Hirsch Trade School, and the Woodbine Colony and Baron De Hirsch Agricultural & Industrial School. Contains also materials on the Colonization attempts made in Colorado, Connecticut, Florida, Louisiana, Michigan, Minnesota, North Dakota, New Jersey, New York, Pennsylvania, South Dakota, Galveston, Texas, The Southwest, Washington, Canada, and Mexico.

Invertebrate predation and trophic cascades in a pelagic food web : The multiple roles of Chaoborus flavicans (Meigen) in a clay-turbid lake

In lake ecosystems, both fish and invertebrate predators have dramatic effects on their prey communities. Fish predation selects large cladocerans while invertebrate predators prefer prey of smaller size. Since invertebrate predators are the preferred food items for fish, their occurrence at high densities is often connected with the absence or low number of fish. It is generally believed that invertebrate predators can play a significant role only if the density of planktivorous fish is low. However, in eutrophic clay-turbid Lake Hiidenvesi (southern Finland), a dense population of predatory Chaoborus flavicans larvae coexists with an abundant fish population. The population covers the stratifying area of the lake and attains a maximum population density of 23000 ind. m-2. This thesis aims to clarify the effects of Chaoborus flavicans on the zooplankton community and the environmental factors facilitating the coexistence of fish and invertebrate predators. In the stratifying area of Lake Hiidenvesi, the seasonal succession of cladocerans was exceptional. The spring biomass peak of cladocerans was missing and the highest biomass occurred in midsummer. In early summer, the consumption rate by chaoborids clearly exceeded the production rate of cladocerans and each year the biomass peak of cladocerans coincided with the minimum chaoborid density. In contrast, consumption by fish was very low and each study year cladocerans attained maximum biomass simultaneously with the highest consumption by smelt (Osmerus eperlanus). The results indicated that Chaoborus flavicans was the main predator of cladocerans in the stratifying area of Lake Hiidenvesi. The clay turbidity strongly contributed to the coexistence of chaoborids and smelt at high densities. Turbidity exceeding 30 NTU combined with light intensity below 0.1 μE m-2 s-1provides an efficient daytime refuge for chaoborids, but turbidity alone is not an adequate refuge unless combined with low light intensity. In the non-stratifying shallow basins of Lake Hiidenvesi, light intensity exceeds this level during summer days at the bottom of the lake, preventing Chaoborus forming a dense population in the shallow parts of the lake. Chaoborus can be successful particularly in deep, clay-turbid lakes where they can remain high in the water column close to their epilimnetic prey. Suspended clay alters the trophic interactions by weakening the link between fish and Chaoborus, which in turn strengthens the effect of Chaoborus predation on crustacean zooplankton. Since food web management largely relies on manipulations of fish stocks and the cascading effects of such actions, the validity of the method in deep clay-turbid lakes may be questioned.

A Combinatorial Construct for Keyless Message Dispersal (Work in Progress)

We propose a keyless and lightweight message transformation scheme based on the combinatorial design theory for the confidentiality of a message transmitted in multiple parts through a network with multiple independent paths, or for data stored in multiple parts by a set of independent storage services such as the cloud providers. Our combinatorial scheme disperses a message into v output parts so that (k-1) or less parts do not reveal any information about any message part, and the message can only be recovered by the party who possesses all v output parts. Combinatorial scheme generates an xor transformation structure to disperse the message into v output parts. Inversion is done by applying the same xor transformation structure on output parts. The structure is generated using generalized quadrangles from design theory which represents symmetric point and line incidence relations in a projective plane. We randomize our solution by adding a random salt value and dispersing it together with the message. We show that a passive adversary with capability of accessing (k-1) communication links or storage services has no advantage so that the scheme is indistinguishable under adaptive chosen ciphertext attack (IND-CCA2).

Nafion and modified-Nafion membranes for polymer electrolyte fuel cells: An overview

Polymer electrolyte fuel cells (PEFCs) employ membrane electrolytes for proton transport during the cell reaction. The membrane forms a key component of the PEFC and its performance is controlled by several physical parameters, viz. water up-take, ion-exchange capacity, proton conductivity and humidity. The article presents an overview on Nafion membranes highlighting their merits and demerits with efforts on modified-Nafion membranes.

Steady laminar flow with suction or injection and heat transfer through porous pipe

Following the method due to Bhatnagar (P. L.) [Jour. Ind. Inst. Sic., 1968, 1, 50, 1], we have discussed in this paper the problem of suction and injection and that of heat transfer for a viscous, incompressible fluid through a porous pipe of uniform circular cross-section, the wall of the pipe being maintained at constant temperature. The method utilises some important properties of differential equations and some transformations that enable the solution of the two-point boundary value and eigenvalue problems without using trial and error method. In fact, each integration provides us with a solution for a suction parameter and a Reynolds number without imposing the conditions of smallness on them. Investigations on non-Newtonian fluids and on other bounding geometries will be published elsewhere.

Polarization Caging in Diffusion-Controlled Electron Transfer Reactions in Solution

In some bimolecular diffusion-controlled electron transfer (ET) reactions such as ion recombination (IR), both solvent polarization relaxation and the mutual diffusion of the reacting ion pair may determine the rate and even the yield of the reaction. However, a full treatment with these two reaction coordinates is a challenging task and has been left mostly unsolved. In this work, we address this problem by developing a dynamic theory by combining the ideas from ET reaction literature and barrierless chemical reactions. Two-dimensional coupled Smoluchowski equations are employed to compute the time evolution of joint probability distribution for the reactant (P-(1)(X,R,t)) and the product (p((2))(X,R,t)), where X, as is usual in ET reactions, describes the solvent polarization coordinate and R is the distance between the reacting ion pair. The reaction is described by a reaction line (sink) which is a function of X and R obtained by imposing a condition of equal energy on the initial and final states of a reacting ion pair. The resulting two-dimensional coupled equations of motion have been solved numerically using an alternate direction implicit (ADI) scheme (Peaceman and Rachford, J. Soc. Ind. Appl. Math. 1955, 3, 28). The results reveal interesting interplay between polarization relaxation and translational dynamics. The following new results have been obtained. (i) For solvents with slow longitudinal polarization relaxation, the escape probability decreases drastically as the polarization relaxation time increases. We attribute this to caging by polarization of the surrounding solvent, As expected, for the solvents having fast polarization relaxation, the escape probability is independent of the polarization relaxation time. (ii) In the slow relaxation limit, there is a significant dependence of escape probability and average rate on the initial solvent polarization, again displaying the effects of polarization caging. Escape probability increases, and the average rate decreases on increasing the initial polarization. Again, in the fast polarization relaxation limit, there is no effect of initial polarization on the escape probability and the average rate of IR. (iii) For normal and barrierless regions the dependence of escape probability and the rate of IR on initial polarization is stronger than in the inverted region. (iv) Because of the involvement of dynamics along R coordinate, the asymmetrical parabolic (that is, non-Marcus) energy gap dependence of the rate is observed.

Monoclonal antibodies in the study of architecture of plant viruses

Monoclonal antibodies have been used as probes to study the architecture of several plant viruses over the past decade. These studies complement the information obtained through X-ray crystallography and help in delineating epitopes on the surface of the virus. The monoclonal antibodies that recognize distinct epitopes also aid in unravelling the mechanisms of assembly/disassembly of virus particles. Group-specific and strain-specific monoclonal antibodies are widely used in the classification of viruses. The significant developments made in this emerging area are reviewed here with specific examples.

Instrumento metodológico de evaluación de la efectividad de manejo de la reserva de bíosfera Bosawas por los pueblos índigenas Mayangnas y Miskitus

La Facultad de Recursos Naturales y del Ambiente (FARENA) de la Universidad Nacional Agraria (UNA) en conjunto con la Secretaria Técnica de BOSAWAS (SETAB) y el Proyecto Reserva de Biósfera Transfronteriza “Corazón del Corredor Biológico Mesoamericano” (PRBT - CCBM) , consideraron como objetivo principal d el presente estudio adecuar un instrumento de e valuación de la efectividad de manejo de la Reserva de Biosfera BOSAWAS (RB B), considerando las prácticas, costumbres y tradiciones de los pueblos ind��genas Mayangnas y Miskitus d e Jinotega y RAAN, que habitan dentro de este valioso espacio natural d e Nicaragua . Fueron seleccionados tres modelos metodológicos de evaluación (CIPIPPR, RAPPAM y CIPP) para adecuar y aplicar un solo modelo denominado “ c iclo de evaluación – CPPPR” . Con la implementación del nuevo mode lo : (1) se evaluó el c ontexto de los pueblos ind��genas desde el punto de vista de su cosmovisión , cultura y administración ind��gena ; (2) se p lanific aron los p rocesos logísticos, financieros, informantes claves o grupo meta, metodologías participativas para cada taller programado y las formas de recabar la información de manera flexible en cada encuentro ; (3) se obtuvieron los p roductos requeridos para ir generando el instrumento de evaluación de la efectividad de manejo en conjunto con los participantes ind ígenas y se realizaron tres evaluaciones en los períodos 2010, 2011 y 2012 ; (4) y con los r esultados de los 5 talleres - encuentros realizados se identificaron los ámbitos, criterios e indicadores propios para estos pueblos ind��genas. La propuesta del nuevo Instrumento denominado e valuación de la e fectividad de m anejo de la RBB por los pueblos ind��genas Mayangnas y Miskitos, fue oficializado por l os gobiernos territoriales ind��genas (GTI) por su ley de autonomía y publicado por MARENA como “Los ind��gena de BO SAWAS, apropiados y restituidos en el derecho de seguimiento al cuido, amor y resguardo de la madre tierra. Est e instrumento orienta a los GTI c ó mo monitorear y evalua r cuantitativa mente (valores numéricos y p onderaciones ) y cualitativa mente ( revisión y an álisis de sus condiciones en función de su ponderación adquirida y escenario óptimo ) . El instrumento comprende 4 ámbitos , 12 Criterios y 36 indicadores constru idos conjunta y consensuadamente por los líderes ind��genas participantes con su propio sentir, co nceptos, tradiciones, necesidades y cosmovisión que les caracterizan . Participaron un promedio de 18 líderes ind��genas de 7 territorios convocados, con poca as istencia de mujeres ind��genas . La calificación ponderada resultante de la s tres evaluaciones real izadas indica que el pueblo Miskitus desde su perspectiva valora su efectividad de manejo de ntro del Área protegida RBB con e l 68% del cumplimiento , alcanzando una calificación de 122 puntos ; y el territorio Mayangna la evalúa con el 52%, equivalente a 96 puntos. S in embargo al ubicar el valor del cumplimiento en función de la escala de calificaciones , amb a s etnias se ubican en la ponderación de ACEPTABLE. Los líderes coincide n que el instrumento es una vía para el desar roll o de capacidades de auto gestiones locales y regionales para alcanzar el manejo Satisfactorio u óptimo para sus pueblos

Influencia de rotación de cultivos y métodos de control sobre la dinámica de las malezas y el crecimiento, desarrollo y rendimiento del sorgo (Sorghum bicolor (L) Moench) var. D-55)

En la Estación Experimental de Las Mercedes municipio de Managua, se inició en la época de postrera en 1991, un experimento de rotación de cultivos bajo diferentes niveles de control de malezas. El presente trabajo evaluó el efecto de los cultivos antecesores sorgo, maíz y pepino con tres niveles de control de malezas : químico, período crítico y limpias periódicas a la dinámica de la cenosis de malezas, crecimiento y rendimiento del cultivo sucesor sorgo. Cuando antecedió el pepino la abundancia de maleza fue mayor con 504 Ind/m2 reduciéndose considerablemente a la cosecha obteniendo una biomasa promedio de 133.9 gr/m2. Sucedió lo contrario con maíz como cultivo antecesor ya que al principio la abundancia fue de 201 Ind/m2 y se obtuvo la mayor biomasa con 259.8 gr/m2 y para sorgo-sorgo tuvo valores de 232 Ind/m2 y a la cosecha en menor valor en biomasa de sorgo 130.0 gr/m2. En el rendimiento se enmarcó una tendencia a favor de maíz como cultivo antecesor con 1878 Kg/ha de sorgo, mientras sorgo-sorgo obtuvo un rendimiento de 1839 Kg/ha comparándose con pepino como antecesor con 1832 Kg/ha de sorgo. Comparando los controles aquí hubo diferencias significativas y en mayor valor le correspondió al control químico con 2048.0 Kg/ha, control período crítico con 1786 Kg/ha y el menor valor le correspondió a limpia periódica con sólo 1715 Kg/ha. En el control período crítico presentó mayor abundancia la maleza al inicio con 444 Ind/m2, teniendo una reducción hasta 62 Ind/m2 en la cosecha. El control químico tuvo un comportamiento similar que el control período crítico con 295 Ind/m2, reduciendo al final del ciclo con 135 Ind/m2. El control limpias periódicas tuvo al inicio la menor abundancia con 200 Ind/m2, reduciendo a la cosecha a 3 Ind/m2.