Management discriminant properties in semiarid soils

The physical properties of coarse - textured soils in semiarid regions often deteriorate with use. We hypostatized that the changes in the physical properties of the soil were related to the cropping sistem employed. 5urface sampled of 52 Entic Haplustolls under three diferents uses (24 under continuous cultivation), 18 under rotation wuth grass Ieys (R), and 10 virgin soils M were analyzed for c1ay, silt, organic malter anrd water content, bulk density, compaction and aggregate stability. Data were analyzed statistically using principal components, canonical variables, and discriminant functions. A satisfactory segregation of the soils according to discriminant properties (coarse organic matter, aggregate stability, and suceptibility lo compaction) was obtained. The model developed satisfactory classified the soils under different uses (100% R, 83% e, and 88% V). Principal component analysis also showed that bulck density, compaction, and wet aggregate salability are related lo organic matter content. We conclude that, in the studied region, the lower the ratio of organic matter lo clay + soil content, the more severe the physical deterioration of the soils.Resúmenes de Trabajos presentados en otras publicaciones (por docentes de la UNLPam.)Publicado en Soil Science, Vol 163 N°7

Nitrogen cycle disruption through the application of de-icing salts on upland highways

It is hypothesized that episodic introductions of road salt severely disrupt the soil nitrogen cycle at a range of spatial and temporal scales. A field-scale study has confirmed impacts on the nitrogen cycle in soil, soil solution and river samples. There is evidence that ammonium-N retention on cation exchange sites has been reduced by the presence of sodium ions, and that ammonium-N has been flushed from the exchange sites. Increases in soil pH have been caused in naturally acidic uplands. These have enhanced mineralization of organic-N, especially nitrification, leading to a reduction in the mineralizable-N pool of roadside soils. There is evidence to support the hypothesis that organic matter content has been lowered over decades either through desorption or dispersal processes. Multiple drivers are identified that contribute to the disruption of nitrogen cycling processes, but their relative importance is difficult to quantify unequivocally. The influence of road salt on soil and soil solution declines with distance from the highway, but impacts on water chemistry in a local stream are still strongly evident at some distance from the road

Relationships between site factors and the growth of conifers introduced in Ventania (Province of Buenos Aires), Argentina

Se evaluó la influencia de factores de sitio sobre el crecimiento de 22 rodales de pino de Alepo (Plnus halepensis MUI), 20 de pino de Monterrey (Plnus radiata D.Don.), 15 de cedro del Himalaya (Cedrus deociara (Roxb) Loudon) y 15 de ciprés horizontal (Cupressus sempervirens i. horizontal (Mid.) Voos), ubicados en una vasta área del sistema serrano de Ventania. Las variables edáficas correlacionadas con el índice de sitio como indicador del crecimiento, fueron: profundidad deenraizamiento y pedregosldad a 0-30 y 30-60 cm de profundidad en P. halepensis; pedregosidad y contenidos de gravas finas y gravillas, y de arena en C. deodara, y profundidad de enraizamiento y color (value) del horizonte A en C. sempervirens. Ningún factor edáfico se correlacionó significativamente con el crecimiento de P. radiata. Los modelos de regresión utilizando únicamente aspectos edáficos permitieron explicar entre 23 y 70% de la variabilidad en el índice de sitio. Entre las variables geográficas, topográficas y climáticas se encontraron correlacionadas con el creci­miento de las distintas especies: latitud, longitud, altitud, longitud e inclinación de la pendiente, posición en el relieve, precipitación, suma anual de déficits y superávits hídricos, temperatura media del mes más cálido y otras variables climáticas, las que tuvieron particular incidencia en P. radiata. Incluyendo todas las variables ambientales en forma conjunta, la explicación de la varianza del índicede sitio se elevó a 60-85% según la especie.It was studied the influence of site factors on growth of stands of Aleppo pine (Plnus halepensis. Mill.), 20 stands of Monterey pine (Pinos radiate D. Don.), 15 stands of deodar cedar (Cedros deodara (Roxb) Loudon) and 15 stands of itaiian or common cypress (Cupressus sempervirens f. horizontalis (Mill.) Voos), located in a large area of the hilly system of Ventania Soil variables correlated with site index as growth estimator were: depth of rooting and stoniness at a depth of 0-30 and 30-60 cm for P. halepensis, stoniness, and gravel and sand content for C. deodara and depth of rooting and cotor (value) of A horizon for C. sempervirens. No soil factor was significantly correlated with the growth of P. radiate. Regression models including soil variables explained between 23 and 70% of foe variation in site index. Growth of the studied species was correlated with foe following geographic, topographic and climatic variables: latitude, longitude, altitude, slope length and gradient, slope position, rainfall, annual sum of water deficits and surpluses, mean temperature of the warmest month and other climatic variables which mainly affected growth of P. radiata. Including all the environmental variables, the explanation of the variation in site index grew up to 60-85%.Facultad de Ciencias Agrarias y Forestale

Ion exchange membranes derived from sulfonated polyaramides

Homo- and both random and block copolyaramides of high molecular weights, with sulfonated moieties in the backbone, were obtained by low temperature polycondensation technique in a dipolar aprotic solvent (NMP) using (a) free aromatic diamines in the presence of pyridine as acid acceptor and (b) N,N ′-bis-trimethylsilyl derivatives of the diamines without additional acid acceptor. The addition of low molecular weight electrolytes (LiCl or CaCl2) and in some cases trimesoyl chloride to the reaction mixture was found to be favorable for the synthesis of high molecular weight polyamides. The materials had a theoretical ion exchange capacity of up to 3.14 meq/g. The membranes were characterized in terms of morphology, thermal stability, water-uptake, and ion exchange capacities.Fil: Taeger, A.. Institute of Polymer Research Dresden; AlemaniaFil: Vogel, C.. Institute of Polymer Research Dresden; AlemaniaFil: Lehmann, D.. Institute of Polymer Research Dresden; AlemaniaFil: Jehnichen, D.. Institute of Polymer Research Dresden; AlemaniaFil: Komber, H.. Institute of Polymer Research Dresden; AlemaniaFil: Meier Haack, J.. Institute of Polymer Research Dresden; AlemaniaFil: Ochoa, Nelio Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Nunes, S.P.. GKSS Research Center; AlemaniaFil: Peinemann, K.-V.. GKSS Research Center; Alemani

3D Analysis of Ordered Porous Polymeric Particles using Complementary Electron Microscopy Methods

Highly porous particles with internal triply periodic minimal surfaces were investigated for sorption of proteins. The visualization of the complex ordered morphology requires complementary advanced methods of electron microscopy for 3D imaging, instead of a simple 2D projection: transmission electron microscopy (TEM) tomography, slice-and-view focused ion beam (FIB) and serial block face (SBF) scanning electron microscopy (SEM). The capability of each method of 3D image reconstruction was demonstrated and their potential of application to other synthetic polymeric systems was discussed. TEM has high resolution for details even smaller than 1 nm, but the imaged volume is relatively restricted (2.5 \u3bcm)3. The samples are pre-sliced in an ultramicrotome. FIB and SBF are coupled to a SEM. The sample sectioning is done in situ, respectively by an ion beam or an ultramicrotome, SBF, a method so far mostly applied only to biological systems, was particularly highly informative to reproduce the ordered morphology of block copolymer particles with 32\u201354 nm nanopores and sampling volume (20 \u3bcm)3

Self-Assembly of Supramolecular Triblock Copolymer Complexes

Four different poly(tert-butoxystyrene)-b-polystyrene-b-poly(4-vinylpyridine) (PtBOS-b-PS-b-P4VP) linear triblock copolymers, with the P4VP weight fraction varying from 0.08 to 0.39, were synthesized via sequential anionic polymerization. The values of the unknown interaction parameters between styrene and tert-butoxystyrene and between tert-butoxystyrene and 4-vinylpyridine were determined from random copolymer blend miscibility studies and found to satisfy 0.031<χS,tBOS<0.034 and 0.39<χ4VP,tBOS<0.43, the latter being slightly larger than the known 0.30<χS,4VP≤0.35 value range. All triblock copolymers synthesized adopted a P4VP/PS core/shell cylindrical self-assembled morphology. From these four triblock copolymers supramolecular complexes were prepared by hydrogen bonding a stoichiometric amount of pentadecylphenol (PDP) to the P4VP blocks. Three of these complexes formed a triple lamellar ordered state with additional short length scale ordering inside the P4VP(PDP) layers. The self-assembled state of the supramolecular complex based on the triblock copolymer with the largest fraction of P4VP consisted of alternating layers of PtBOS and P4VP(PDP) layers with PS cylinders inside the latter layers. The difference in morphology between the triblock copolymers and the supramolecular complexes is due to two effects: (i) a change in effective composition and, (ii) a reduction in interfacial tension between the PS and P4VP containing domains. The small angle X-ray scattering patterns of the supramolecules systems are very temperature sensitive. A striking feature is the disappearance of the first order scattering peak of the triple lamellar state in certain temperature intervals, while the higher order peaks (including the third order) remain. This is argued to be due to the thermal sensitivity of the hydrogen bonding and thus directly related to the very nature of these systems.

Secondhand Smoke Exposure and Coronary Artery Calcification among Nonsmoking Participants of a Population-Based Cohort

Background: Secondhand smoke (SHS) consists of fine particulate matter, carcinogens, and various toxins that affect large parts of the population. SHS increases the risk for acute cardiovascular events and may contribute to the development of atherosclerosis

Systematic assessment of training-induced changes in corticospinal output to hand using frameless stereotaxic transcranial magnetic stimulation.

Measuring changes in the characteristics of corticospinal output has become a critical part of assessing the impact of motor experience on cortical organization in both the intact and injured human brain. In this protocol we describe a method for systematically assessing training-induced changes in corticospinal output that integrates volumetric anatomical MRI with transcranial magnetic stimulation (TMS). A TMS coil is sited to a target grid superimposed onto a 3D MRI of cortex using a stereotaxic neuronavigation system. Subjects are then required to exercise the first dorsal interosseus (FDI) muscle on two different tasks for a total of 30 min. The protocol allows for reliably and repeatedly detecting changes in corticospinal output to FDI muscle in response to brief periods of motor training

Simply longer is not better: reversal of theta burst after-effect with prolonged stimulation

From all rTMS protocols at present, the theta burst stimulation (TBS) is considered the most efficient in terms of number of impulses and intensity required during a given stimulation. The aim of this study was to investigate the effects of inhibitory and excitatory TBS protocols on motor cortex excitability when the duration of stimulation was doubled. Fourteen healthy volunteers were tested under four conditions: intermittent theta bust stimulation (iTBS), continuous theta burst stimulation (cTBS), prolonged intermittent theta bust stimulation (ProiTBS) and prolonged continuous theta burst stimulation (ProcTBS). The prolonged paradigms were twice as long as the conventional TBS protocols. Conventional facilitatory iTBS converted into inhibitory when it was applied for twice as long, while the normally inhibitory cTBS became facilitatory when the stimulation duration was doubled. Our results show that TBS-induced plasticity cannot be deliberately enhanced simply by prolonging TBS protocols. Instead, when stimulating too long, after-effects will be reversed. This finding supplements findings at the short end of the stimulation duration range, where it was shown that conventional cTBS is excitatory in the first half and switches to inhibition only after the full length protocol. It is relevant for clinical applications for which an ongoing need for further protocol improvement is imminent