Effects of post-fire logging on forest surface air temperatures in the Siskiyou Mountains, Oregon, USA

Following stand-replacing wildfire, post-fire (salvage) logging of fire-killed trees is a widely implemented management practice in many forest types. A common hypothesis is that removal of fire-killed trees increases surface temperatures due to loss of shade and increased solar radiation, thereby influencing vegetation establishment and possibly stand development. Six years after a wildfire in a Mediterranean-climate mixed-conifer forest in southwest Oregon, USA, we measured the effects of post-fire logging (> 90 per cent dead tree (snag) removal) on growing season surface air temperatures. Compared with unlogged severely burned forest, post-fire logging did not lead to increased maximum daily surface air temperature. However, dead tree removal was associated with lower nightly minimum temperatures (similar to 1 degrees C) and earlier daytime heating, leading to a 1-2 degrees C difference during the warming portion of the day. Effects varied predictably by aspect. The patterns reported here represent a similar but muted pattern as previously reported for microclimatic changes following clear-cutting of green trees. Effects of microsites such as tree bases on fine-scale temperature regimes require further investigation

From colloidal dispersions to colloidal pastesthrough solid–liquid separation processes

Solid–liquid separation is an operation that starts with a dispersion of solid particles in a liquid and removes some of the liquid from the particles, producing a concentrated solid paste and a clean liquid phase. It is similar to thermodynamic processes where pressure is applied to a system in order to reduce its volume. In dispersions, the resistance to this osmotic compression depends on interactions between the dispersed particles. The first part of this work deals with dispersions of repelling particles, which are either silica nanoparticles or synthetic clay platelets, dispersed in aqueous solutions. In these conditions, each particle is surrounded by an ionic layer, which repels other ionic layers. This results in a structure with strong short-range order. At high particle volume fractions, the overlap of ionic layers generates large osmotic pressures; these pressures may be calculated, through the cell model, as the cost of reducing the volume of each cell. The variation of osmotic pressure with volume fraction is the equation of state of the dispersion. The second part of this work deals with dispersions of aggregated particles, which are silica nanoparticles, dispersed in water and flocculated by multivalent cations. This produces large bushy aggregates, with fractal structures that are maintained through interparticle surface– surface bonds. As the paste is submitted to osmotic pressures, small relative displacements of the aggregated particles lead to structural collapse. The final structure is made of a dense skeleton immersed in a nearly homogeneous matrix of aggregated particles. The variation of osmotic resistance with volume fraction is the compression law of the paste; it may be calculated through a numerical model that takes into account the noncentral interparticle forces. According to this model, the response of aggregated pastes to applied stress may be controlled through the manipulation of interparticle adhesion

Thin static charged dust Majumdar-Papapetrou shells with high symmetry in D >= 4

We present a systematical study of static D >= 4 space-times of high symmetry with the matter source being a thin charged dust hypersurface shell. The shell manifold is assumed to have the following structure S_(beta) X R^(D-2-beta), beta (in the interval ) is dimension of a sphere S_(beta). In case of (beta) = 0, we assume that there are two parallel hyper-plane shells instead of only one. The space-time has Majumdar-Papapetrou form and it inherits the symmetries of the shell manifold - it is invariant under both rotations of the S_(beta) and translations along R^(D-2-beta). We find a general solution to the Einstein-Maxwell equations with a given shell. Then, we examine some flat interior solutions with special attention paid to D = 4. A connection to D = 4 non-relativistic theory is pointed out. We also comment on a straightforward generalisation to the case of Kastor-Traschen space-time, i.e. adding a non-negative cosmological constant to the charged dust matter source.Comment: Accepted in Int. J. Theor. Phy

Lubrication in cold rolling: Elasto-plasto-hydrodynamic lubrication

A model has been developed with respect to hydrodynamic lubrication in cold rolling. The basic model describes the configuration of a rigid, perfectly plastic sheet rolled by a rigid work roll. The governing equations have been solved throughout the complete contact area, i.e. the inlet, the work zone and the outlet zone. Multi-level techniques have been applied to solve these equations together with boundary conditions, resulting in an algorithm solving the problem in O(n) operations. This means that the distribution of the pressure and the traction force in the lubricant film, and the shape of this film, as well as the plastic deformation of the sheet, can be accurately calculated for a large number of nodal points on a minicomputer. Subsequently elastic deformation, work hardening and dynamic behaviour of the flow stress have been incorporated in the model. It will be shown that the influence of these effects on the film thickness or the pressure distribution is considerable

Similarity of technical logics of cropping systems organization between conventional and recently converted organic farmers in a water catchment area

Organic farming is considered as a solution to preserve water quality in drinking water catchments. For local managers of these catchments it is thus important to identify conventional farmers for potential conversion to organic farming. The aim of this article is to assess technical similarity of conventional farmers concerned by a water catchment to organic farming. We build a typology of farmers based on technical logics related to cropping systems organization. We differentiated five types of farmers among 18 conventional dairy farmers and three recently converted organic farmers. According to our results, only two farmers can be considered as close to technical logics identified in organic farms. Nevertheless, we could identify partial technical similarities for two other farmer groups. These similarities may be useful for catchment managers to initiate transitions towards organic farming

Genética de las proteínas de reserva del cotiledón en castaño (Castanea sativa Miller)

A first approximation to the inheritance of cotyledon storage proteins was studied in European sweet chestnut (Castanea sativa Mill.) by evaluating the offspring of a controlled cross between two local chestnut varieties (Corriente and Pilonga) from southern Spain. The analysis was carried out in 15 polymorphic bands corresponding to the albumin fraction of the storage proteins. The relationship between bands displayed one case of allelism and four of linkage. These results should be considered as the baseline of the genetics of these proteins and suggest that they could be useful for the evaluation of the genetic variability in chestnut.Se ha efectuado una primera aproximación a la genética de las proteínas de reserva del cotiledón en castaño (Castanea sativa Mill.). Para ello, se ha evaluado la progenie resultante del cruzamiento controlado entre dos variedades locales del sur de España (Corriente y Pilonga). El análisis se ha realizado en 15 bandas polimórficas correspondientes a la fracción albúmina de las proteínas de reserva. El estudio de la combinación entre bandas ha permitido identificar un caso de alelismo y cuatro de ligamiento. Estos resultados suponen una contribución al estudio de la genética de estas proteínas y sugieren que podrían ser una herramienta útil para la evaluación de la variabilidad genética del castaño

Environmental Impact Assessment: Detecting Changes in Fish Community Structure in Response to Disturbance with an Asymmetric Multivariate BACI Sampling Design

One of the primary challenges to detecting anthropogenic environmental impacts is the high degree of spatial and temporal variability inherent in natural systems. Planned or routine events that result in disturbance to populations and communities provide an opportunity for scientists to apply well-replicated and statistically powerful sampling designs to assess subsequent biological effects. For example, a thick layer of sessile invertebrates is the prominent biotic feature of intertidal and shallow subtidal portions of offshore petroleum platforms in southern California. Given the central role of such invertebrates in providing food and shelter, their presence can reasonably be expected to influence associated fish community structure. At one platform on the San Pedro Shelf, invertebrate biomass was completely removed from support pilings and horizontal crossmembers to a depth of 20 m with high-pressure water during a standard “hydrocleaning” event in November 2007. Three nearby platforms remained undisturbed, providing a unique opportunity to test for disturbance-related changes in the local fish assemblage and the overall time course of community recovery. The potential impact of the abrupt and intense removal of the invertebrate layer was assessed with survey data collected periodically for one year prior- and one year post-hydrocleaning in a modified Before-After-Control-Impact (BACI) design. Asymmetrical multivariate analyses of variance revealed a significant effect of disturbance to fish, driven largely by reductions in the abundance of numerically dominant blacksmith (Chromis punctipinnis). Nevertheless, the system was surprisingly resilient, recovering to pre-disturbance conditions within ten months. Our results demonstrate that a well-replicated BACI sampling design can detect even subtle biological changes in response to disturbance, a key step towards developing a mechanistic understanding of community disassembly in the face of increasingly frequent and intense perturbations

Percutaneous Cervical Vertebroplasty in a MultifunctionalImage-Guided Therapy Suite: Hybrid Lateral Approach to C1 andC4 Under CT and Fluoroscopic Guidance

A 76-year-old patient suffering from two painful osteolytic metastases in C1 and C4 underwent percutaneous vertebroplasty by a hybrid technique in a multi-functional image-guided therapy suite (MIGTS). Two trocars were first placed into the respective bodies of C1 and C4 under fluoroscopic computed tomography guidance using a lateral approach. Thereafter, the patient was transferred on a moving table to the digital subtraction angiography unit in the same room for implant injection. Good pain relief was achieved by this minimally invasive procedure without complications. A hybrid approach for vertebroplasty in a MIGTS appears to be safe and feasible and might be indicated in selected cases for difficult accessible lesion