Generic theory of colloidal transport

We discuss the motion of colloidal particles relative to a two component fluid consisting of solvent and solute. Particle motion can result from (i) net body forces on the particle due to external fields such as gravity; (ii) slip velocities on the particle surface due to surface dissipative phenomena. The perturbations of the hydrodynamic flow field exhibits characteristic differences in cases (i) and (ii) which reflect different patterns of momentum flux corresponding to the existence of net forces, force dipoles or force quadrupoles. In the absence of external fields, gradients of concentration or pressure do not generate net forces on a colloidal particle. Such gradients can nevertheless induce relative motion between particle and fluid. We present a generic description of surface dissipative phenomena based on the linear response of surface fluxes driven by conjugate surface forces. In this framework we discuss different transport scenarios including self-propulsion via surface slip that is induced by active processes on the particle surface. We clarify the nature of force balances in such situations.Comment: 22 pages, 1 figur

Generalized Toda Theory from Six Dimensions and the Conifold

Recently, a physical derivation of the Alday-Gaiotto-Tachikawa correspondence has been put forward. A crucial role is played by the complex Chern-Simons theory arising in the 3d-3d correspondence, whose boundary modes lead to Toda theory on a Riemann surface. We explore several features of this derivation and subsequently argue that it can be extended to a generalization of the AGT correspondence. The latter involves codimension two defects in six dimensions that wrap the Riemann surface. We use a purely geometrical description of these defects and find that the generalized AGT setup can be modeled in a pole region using generalized conifolds. Furthermore, we argue that the ordinary conifold clarifies several features of the derivation of the original AGT correspondence.Comment: 27+2 pages, 3 figure

Pathogenicity of Entomopathogenic Fungi on the Weevil of the Andes (Premnotrypes vorax Hustache) of the Potato (Solanum tuberosum L.) in Chimborazo Province, Ecuador

From thirty native isolates of entomopathogenic fungi, which were obtained from corpses of larvae and adults of Andean weevil (Premnotrypes vorax Hustache); two fungi with entomopathogenic characteristics were selected through laboratory tests, which will be used in a program of integrated management of this pest in the Ecuadorian inter-Andean region. The pathogenicity of the 30 isolates was determined by the mortality that they caused in larvae and adults and it was expressed in percentage; for this, a complete randomized design (CRD) was used. The LC50 and TL50 were determined by Probit analysis. The two selected isolates corresponded to: Metarhizium anisopliae (Metschnikoff 1879) Sorokin 1883 (A13) and  Beauveria bassiana (Bals.-Criv.) Vuill. 1912 (A21), which proved to be the best, because they caused the highest mortality in larvae of the fourth instar and adults of P. vorax. The Probit analysis showed that LC50 for A21 isolate (B. bassiana) in fourth instar larvae was obtained with a concentration of 1,75x109 spores/ml and 1,08x109 spores/ml for adults. Instead for A13 isolate (M. anisopliae), the LC50 was obtained with a concentration of 1,65x109 spores/ml for larvae and 2,42x109 spores/ml for adults. The LT50 for the selected isolates at the indicated concentrations, was 4,84 and 4,32 days for larvae with A13 and A21 isolates respectively, while, for adults, the shortest time was obtained with A21 isolate in 4.36 days, compared with A13 isolate, that delayed 20,70 days. The larval stage of P. vorax was the most susceptible to A13 isolate, on the other hand, larvae and adults were equally susceptible to A21 isolate at the indicated concentrations. According to the results obtained, the two selected isolates can be used as an alternative to the use of conventional agrochemicals, which will contribute to a more ecological production

Plant Litter Quality Affects the Accumulation Rate, Composition, and Stability of Mineral-associated Soil Organic Matter

Mineral-associated organic matter (MAOM) is a relatively large and stable fraction of soil organic matter (SOM). Plant litters with high rates of mineralization (high quality litters) are hypothesized to promote the accumulation of MAOM with greater efficiency than plant litters with low rates of mineralization (low-quality litters) because litters with high rates of mineralization maximize the synthesis of microbial products and most MAOM is microbial-derived. However, the effect of litter quality on MAOM is inconsistent. We conducted four repeated short-term incubations (46-d each) of four plant litters (alfalfa, oats, maize and soybean) in two low-carbon subsoils (sandy loam and silty loam) with and without nutrient addition. Our short-term incubations focused on the initial stage of litter decomposition during the time when litter quality has a measureable effect on mineralization rates. Plant litter quality had a much greater effect on litter-C mineralization rate and MAOM-C accumulation than did soil type or nutrient addition. Soils amended with high-quality oat and alfalfa litters had greater MAOM-C accumulation than soils amended with low-quality maize and soybean litters. However, soils amended with high-quality litters also had greater litter-C mineralization than soils amended with low-quality litters. As a result, the accumulation of MAOM-C per unit of litter-C mineralization was lower in soils amended with high-vs. low-quality litters (0.65 vs. 1.39 g MAOM-C accumulated g−1 C mineralized). Cellulose and hemicelluose indices of accumulated MAOM were greater for maize and soybean than oats and alfalfa, however, most carbohydrates in MAOM were plant-derived regardless of litter quality. At the end of the incubations, more of the accumulated MAOM-N was potentially mineralizable in soils amended with high quality litters. Nevertheless, most of the litter-C remained as residual litter; just 12% was mineralized to CO2 and 13% was transferred to MAOM. Our results demonstrate several unexpected effects of litter quality on MAOM stabilization including the direct stabilization of plant-derived carbohydrates

Evaluación de tres dosis de potasio en la producción de lechuga (Lactuca sativa L. var. Crispa) bajo el sistema hidropónico recirculante NTF bajo invernadero

Three doses of potassium were evaluated in the production of lettuce (Lactuca sativa L. var. Crispa), under the recirculable NFT hydroponic system in the greenhouse of the Department of Horticulture of the ESPOCH. A completely randomized block design was used with three treatments and three replications. The doses evaluated were: low dose (LD) with 224,33 ppm, medium dose (MD) with 470,00 ppm, and high dose (HD) with 716,67 ppm. Evaluated parameters were: potassium content in leaves and root, fresh weights of the aerial part and root, yield per net plot and hectare. The economic analysis was carried out according to the relation benefit/cost. The best results for most of the parameters evaluated were obtained with the low dose (LD), obtaining fresh weights of the aerial part and root of 193,01 and 36,65 g respectively. It has a yield per net plot of 2,04 kilograms and per hectare of 15338,75 kilograms, and the highest cost benefit with 4,63 dollars equivalent to 362,75%. On the other hand, the highest content of potassium in leaves and root up to 40 days after transplant (DAT) was obtained with the medium dose (MD) with 5,13 and 6,00% of total potassium, respectively. In all treatments, maintaining turgor in the plants throughout the cycle is very important. From the agronomic and economic point of view, the use a nutritive solution containing 224,33 ppm of potassium was recommended

Degradación de la Clorofila Presente en (Spirogyra spp.) como Indicator Socio Ambiental de la Presencia de Plaguicidas organofosforados

En la presente investigación se estudió la alteración de la clorofila presente en Spirogyra spp. como indicador de la presencia de tres plaguicidas organofosforados: Curacrón, Malatión y Acefato, a través de ensayos realizados a diferentes concentraciones de los plaguicidas durante un lapso de 72 horas de exposición. Transcurrida la etapa experimental se pudo observar la pérdida de la coloración verde de las algas como resultado de la alteración de su pigmentación natural. El análisis de varianza realizado a los resultados de la medición de la absorbancia de las muestras demuestra una disminución de la concentración de clorofila, en comparación con las muestras testigo de los ensayos. La sensibilidad de las algas al ser expuestas a los plaguicidas organofosforados es una manifestación del alto potencial bioindicador de Spirogyra spp. Este estudio brinda a los agricultores de la comunidad de San Antonio la posibilidad de detectar de manera temprana la presencia de plaguicidas en sus fuentes de agua y abre las puertas a la investigación para posteriores aplicaciones. The alteration of the chlorophyll present in Spirogyra spp. was studied as an indicator of the presence of three organophosphorus pesticides, Curacron, Malathion and Acephate, with tests carried out at different concentrations of the pesticides during a period of 72 hours of exposure. After the experimental stage, it was possible to observe the loss of the green coloration of the algae as a result of the alteration of their natural pigmentation. The analysis of variance based on the results of the measurement of the absorbance of the samples demonstrated a decrease in the concentration of chlorophyll compared to the control samples from the trials. The sensitivity of algae to being exposed to organophosphorus pesticides is a manifestation of the high bioindicator potential of Spirogyra spp., which provides farmers in the community of San Antonio the possibility of early detection of the presence of pesticides in their sources of water, and it also opens the doors to research for subsequent applications

Quantizing higher-spin gravity in free-field variables

We study the formulation of massless higher-spin gravity on AdS$_3$ in a gauge in which the fundamental variables satisfy free field Poisson brackets. This gauge choice leaves a small portion of the gauge freedom unfixed, which should be further quotiented out. We show that doing so leads to a bulk version of the Coulomb gas formalism for $W_N$ CFT's: the generators of the residual gauge symmetries are the classical limits of screening charges, while the gauge-invariant observables are classical $W_N$ charges. Quantization in these variables can be carried out using standard techniques and makes manifest a remnant of the triality symmetry of $W_\infty[\lambda]$. This symmetry can be used to argue that the theory should be supplemented with additional matter content which is precisely that of the Prokushkin-Vasiliev theory. As a further application, we use our formulation to quantize a class of conical surplus solutions and confirm the conjecture that these are dual to specific degenerate $W_N$ primaries, to all orders in the large central charge expansion.Comment: 31 pages + appendices. V2: typos corrected, reference adde

Levantamiento por Compresión del piso del Seno del Maxilar. Técnica Transcrestal con Osteótomo. Descripción de un caso clínico.

Las limitaciones anatómicas causadas por la pérdida dental como la neumatizacion de seno maxilar y la poca altura del hueso alveolar en relacion con el seno del maxilar impide la colocacion del implante oseointegrado. No obstante el piso del seno del maxilar posee caracteristicas estructurales que permiten la compresion  ósea  y posicionan al implante con estabilidad primaria ideal. El objetivo de este artículo es describir un caso clínico donde se relata la preparacion, levantamiento y compresión del piso del seno del maxilar por intermedio de la Técnica Transcrestal y el uso de osteótomos con la finalidad de ganar altura y estabilidad primaria con la bicorticalización

N = 1 dualities in 2+1 dimensions

We consider minimally supersymmetric QCD in 2+1 dimensions, with Chern-Simons and superpotential interactions. We propose an infrared $SU(N) \leftrightarrow U(k)$ duality involving gauge-singlet fields on one of the two sides. It shares qualitative features both with 3d bosonization and with 4d Seiberg duality. We provide a few consistency checks of the proposal, mapping the structure of vacua and performing perturbative computations in the $\varepsilon$-expansion

Single-molecule experiments in biological physics: methods and applications

I review single-molecule experiments (SME) in biological physics. Recent technological developments have provided the tools to design and build scientific instruments of high enough sensitivity and precision to manipulate and visualize individual molecules and measure microscopic forces. Using SME it is possible to: manipulate molecules one at a time and measure distributions describing molecular properties; characterize the kinetics of biomolecular reactions and; detect molecular intermediates. SME provide the additional information about thermodynamics and kinetics of biomolecular processes. This complements information obtained in traditional bulk assays. In SME it is also possible to measure small energies and detect large Brownian deviations in biomolecular reactions, thereby offering new methods and systems to scrutinize the basic foundations of statistical mechanics. This review is written at a very introductory level emphasizing the importance of SME to scientists interested in knowing the common playground of ideas and the interdisciplinary topics accessible by these techniques. The review discusses SME from an experimental perspective, first exposing the most common experimental methodologies and later presenting various molecular systems where such techniques have been applied. I briefly discuss experimental techniques such as atomic-force microscopy (AFM), laser optical tweezers (LOT), magnetic tweezers (MT), biomembrane force probe (BFP) and single-molecule fluorescence (SMF). I then present several applications of SME to the study of nucleic acids (DNA, RNA and DNA condensation), proteins (protein-protein interactions, protein folding and molecular motors). Finally, I discuss applications of SME to the study of the nonequilibrium thermodynamics of small systems and the experimental verification of fluctuation theorems. I conclude with a discussion of open questions and future perspectives.Comment: Latex, 60 pages, 12 figures, Topical Review for J. Phys. C (Cond. Matt