Relative Density

A process for interconnecting a three-dimensional pattern of self-propagating polymer waveguides was used to form micro-truss structures with two new unit cell architectures. The structures were formed using a two-dimensional mask with a hexagonal pattern of apertures. Distinct unit cell architectures were possible by exposing the mask to a different number of incident UV exposure beams, which are used to form the waveguides. One unit cell design featured three intersecting waveguides per node, resulting in a structure with threefold symmetry. The second unit cell design had six-fold symmetry and was characterized by primary nodes with six intersecting waveguides and secondary nodes with two intersecting waveguides. Compression loading experiments were conducted on micro-truss samples with comparable relative density values (q/q s = 6.5%), but different unit cell architectures. The addition of secondary nodes in the structures based on the second design led to an increase in compressive modulus of up to 70% and an average increase in peak strength of 42%. The increase in compressive strength and modulus was attributed to a reduction in the truss-member slenderness ratio achieved through increased waveguide connectivity.

The possibility of producing titanium alloy Ti ? 6Al ? 4V with minimal residual porosity from mixtures of elemental powders by the method of pressing and sintering without hot deformation during or after sintering was investigated. Various powder mixtures based on titanium and titanium hydride with alloying additions of either elemental powders having different particle sizes, or master alloys, were studied. It was shown that the synthesis of Ti ? 6Al ? 4V from mixtures of titanium hydride and master alloys is optimal with respect to the attainment of high relative density. In this case the sintered material has density up to 99%, homogeneous microstructure with relatively small (100-120 µm) ß-phase grains, and a low concentration of impurities, in particular oxygen, which provide a high level of mechanical properties s(ten = 970 MPa, d = 6%).

The effects of plantain starch obtained from the unripe fruit of the plantMusa paradisiaca L. (Musaceae) on the mechanical and disintegration properties of paracetamol tablets have been investigated in comparison with the effects of corn starch BP using a 23 factorial experimental design. The individual and combined effects of nature of starch binder (N), concentration of starch binder (C), and the relative density of tablet (RD) on the tensile strength (TS), brittle fracture index (BFI), and disintegration time (DT) of the tablets were investigated. The ranking of the individual effects on TS was RD>C≫N, on BFI was C≫RD>N and on DT was N>C>RD. The ranking for the interaction effects on TS and DT was N-C≫N-RD>C-RD, while that on BFI was N-C≫C-RD>N-RD. Changing nature of starch from a “low” (plantain starch) to a “high” (corn starch) level, increasing the concentration of starch binding agent from 2.5% to 10.0% wt/wt, and increasing relative density of the tablet from 0.80 to 0.90, led to increase in the values of TS and DT, but a decrease in BFI. Thus, tablets containing plantain starch had lower tensile strength and disintegration time values than those containing corn starch, but showed better ability to reduce the lamination and capping tendency in paracetamol tablet formulation. The interaction between N and C was significantly (P<.001) higher than those between N and RD and between C and RD. There is therefore the need to carefully choose the nature (N) and concentration (C) of starch used as binding agent in tablet formulations to obtain tablets of desired bond strength and disintegration properties. Furthermore, plantain starch could be useful as an alternative binding agent to cornstarch, especially where faster disintegration is required and the problems of lamination and capping are of particular concern.

We studied seasonal variation in population attributes of arbuscular mycorrhizal (AM) fungi over 2 years in four sites of temperate grasslands of the Argentinean Flooding Pampas. The sites represent a wide range of soil conditions, hydrologic gradients, and floristic composition. Lotus glaber, a perennial herbaceous legume naturalised in the Flooding Pampas, was dominant at the four plant community sites. Its roots were highly colonised by AM fungi. Temporal variations in spore density, spore type, AM root colonisation, floristic composition and soil chemical characteristics occurred in each site and were different among sites. The duration of flooding had no effect on spore density but depressed AM root colonisation. Eleven different types of spores were recognized and four were identified. Two species dominated at the four sites: Glomus fasciculatum and Glomus intraradices. Spore density was highest in summer (dry season) and lowest in winter (wet season) with intermediate values in autumn and spring. Colonisation of L. glaber roots was highest in summer or spring and lowest in winter or autumn. The relative density of G. fasciculatum and G. intraradices versus Glomus sp. and Acaulospora sp. had distinctive seasonal peaks. These seasonal peaks occurred at all four sites, suggesting differences among AM fungus species with respect to the seasonality of sporulation. Spore density and AM root colonisation when measured at any one time were poorly related to each other. However, spore density was significantly correlated with root colonisation 3 months before, suggesting that high colonisation in one season precedes high sporulation in the next season.

Empirical equations for estimating bubblepoint pressure, oil FVF at bubblepoint pressure, and total FVF for Middle East crude oils were derived as a function of reservoir temperature, total surface gas relative density, solution GOR, and stock-tank oil relative density. These empirical equations should be valid for all types of oil and gas mixtures with properties falling within the range of

The suppression of agricultural pests has often been proposed as an important service of natural enemy diversity, but few experiments have tested this assertion. In this study we present empirical evidence that increasing the richness of a particular guild of natural enemies can reduce the density of a widespread group of herbivorous pests and, in turn, increase the yield of an economically important crop. We performed an experiment in large field enclosures where we manipulated the presence/absence of three of the most important natural enemies (the coccinellid beetle Harmonia axyridis, the damsel bug Nabis sp., and the parasitic wasp Aphidius ervi) of pea aphids (Acyrthosiphon pisum) that feed on alfalfa (Medicago sativa). When all three enemy species were together, the population density of the pea aphid was suppressed more than could be predicted from the summed impact of each enemy species alone. As crop yield was negatively related to pea aphid density, there was a concomitant non-additive increase in the production of alfalfa in enclosures containing the more diverse enemy guild. This trophic cascade appeared to be influenced by an indirect interaction involving a second herbivore inhabiting the systemthe cowpea aphid, Aphis craccivora. Data suggest that high relative densities of cowpea aphids inhibited parasitism of pea aphids by the specialist parasitoid, A. ervi. Therefore, when natural enemies were together and densities of cowpea aphids were reduced by generalist predators, parasitism of pea aphids increased. This interaction modification is similar to other types of indirect interactions among enemy species (e.g. predatorpredator facilitation) that can enhance the suppression of agricultural pests. Results of our study, and those of others performed in agroecosystems, complement the broader debate over how biodiversity influences ecosystem functioning by specifically focusing on systems that produce goods of immediate relevance to human society.

Gadolinium oxide homogeneously mixed with uranium oxide nuclear fuel is used as burnable poison in modem LWR. Solid solutions of UOz with Gd20, additions of between 5 and 10 wt% have been prepared according to the following routes: (a) mechanical mixing of both ceramic powders; (b) AUC and ADU coprecipitation. Microstructural analyses have been carried out by optical ceramography and electron microprobe for observation of heterogeneities. Sintered densities as well as O/U ratios of the ceramic pellets have also been measured.

We investigate the random walk properties of a class of two-dimensional lattices with two different types of columns and discuss the dependence of the properties on the densities and detailed arrangements of the columns. We show that the row and column components of the mean square displacement are asymptotically independent of the details of the arrangement of columns. We reach the same conclusion for some other random walk properties (return to the origin and number of distinct sites visited) for various periodic arrangements of a given relative density of the two types of columns. We also derive exact asymptotic results for the occupation probabilities of the two types of distinct sites on our lattices which validate the basic conjecture on bond and step ratios made in the preceding paper in this series.

In the present work polyurethane foams containing variable concentrations of nano-sized clay and esparto wool were prepared and studied, with the objective of developing new multi-scalar rigid foams. The addition of montmorillonite clay favoured foaming and the formation of finer and homogeneous cellular structures, resulting in foams with compressive elastic moduli and collapse stresses lower than that of the polyurethane foams. Nevertheless, a comparative analysis versus the foams' relative density demonstrated that both properties follow one single trend for the two materials. The combination of esparto and montmorillonite further reduced the cell size of foams, at the same time promoting higher open cell contents, resulting in the foams with the lowest mechanical properties. Although no important differences in thermal conductivity were found with adding montmorillonite, its value decreasing with reducing the relative density, the incorporation of esparto led to higher thermal conductivities, independently of the relative density. The combination of esparto and montmorillonite resulted in foams with thermal conductivities halfway between the esparto-reinforced and the montmorillonite-reinforced foams, related to a higher open cell content.

Perovskite powders of La 0.3 Sr 0.7 CoO 3−d were prepared by the thermal decomposition of precursor complexes derived from nitrate solutions using ethylenediaminetetraacetic acid (EDTA) as a complexing agent. The calcination temperature is 920°C. Powders thus obtained have a low carbon contamination. Dense ceramics with a relative density of about 96% have been prepared after sintering at 1150°C.

Microstructural, magnetothermal and dielectric properties of YCrO 3 powders prepared by combustion and solid state methods have been studied by a combination of XRD, specific heat, magnetization and permittivity measurements. The TEM and XRD characterization confirm that the combustion powders are amorphous plate-like agglomerates of nano-sized crystalline particles. A more uniform grain size along with an increase of the relative density is observed by SEM in the sintered samples prepared by combustion route with respect to those produced by solid state reaction. Similar to the material obtained through solid state synthesis, the material prepared by the combustion method also shows spin canted antiferromagnetic ordering of Cr + 3 (S ¼ 3/2) at $ 140 K, which is shown by magnetization as well as l-type anomaly in the total specific heat. Furthermore, the magnetic contribution to the total specific heat reveals spin fluctuations above T N and a spin reorientation transition at about 60 K. Both YCrO 3 compounds show a diffuse phase transition at about 450 K, typical of a relaxor ferroelectric, which is characterized by a broad peak in the real part of the dielectric permittivity as a function of temperature, with the peak decreasing in magnitude and shifting to higher temperature as the frequency increases. The relaxor dipoles are due to the local non-centrosymmetric structure. Furthermore, the high loss tangent in a broad range of temperature as well as conductivity analysis indicates a hopping mechanism for the electronic conductivity as we believe it is a consequence of the outer d 3 -shell, which have detrimental effects on the polarization and the pooling process in the YCrO 3 bulk material. The more uniform particle size and higher density material synthesized through the combustion process leads to an improvement in the dielectric Properties.

One key strategy for increasing the application potential for biodegradable plastics lies in improving the physical and mechanical characteristics, which can be attained by inducing a cellular morphology in the pure polymer with the aid of a blowing agent, as well as by blending two or more polymers with the desirable properties. This paper examines the effect that blending two biodegradable polymers has on the thermal properties and morphology of the resultant foams blown with carbon dioxide (CO2). Polylactic acid (PLA), polyhydroxybutyrate-co-valerate (PHBV) and blends of both were foamed and characterized in terms of thermal characteristics, relative density, cell size, and foam morphology. The results indicate that although PLA and PHBV are immiscible, the presence of small quantities of PHBV (25 wt%) could lead to low density foams with finer, more uniform cells. Furthermore, the crystallinity of PHBV was found to be unaffected by the presence of PLA in the composite, which supports the immiscibility of PLA and PHBV.

The present work deals with studies on the manufacturing and investigation of mechanical and wear behavior of aluminum alloy matrix composites (AAMCs), produced using powder metallurgy technique of ball milled mixing in a high energy attritor and using a blend-press-sinter methodology. Matrix of pre-mechanical alloyed Al-4.5 wt.% Cu was used to which different fractions of nano and micron size TiC reinforcing particles (ranging from 0 to 10 wt.%) were added. The powders were mixed using a planetary ball mill. Consolidation was conducted by uniaxial pressing at 650 MPa. Sintering procedure was done at 400°C for 90 min. The results indicated that as TiC particle size is reduced to nanometre scale and the TiC content is increased up to optimum levels, the hardness and wear resistance of the composite increase significantly, whereas relative density, grain size and distribution homogeneity decrease. Using micron size reinforcing particulates from 5% to 10 wt.%, results in a significant hardness reduction of the composite from 174 to 98 HVN. Microstructural characterization of the as-pressed samples revealed reasonably uniform distribution of TiC reinforcing particulates and presence of minimal porosity. The wear test disclosed that the wear resistance of all specimens increases with the addition of nano and micron size TiC particles (up to 5 wt.%). Scanning electron microscopic observation of the worn surfaces was conducted and the dominant wear mechanism was recognized as abrasive wear accompanied by some delamination wear mechanism.

We present here both linear regressions and multivariate analyses correlating three global neuropsychological tests with a number of structural and neurochemical measurements performed on a prospective series of 15 patients with Alzheimer's disease and 9 neuropathologically normal subjects. The statistical data show only weak correlations between psychometric indices and plaques and tangles, but the density of neocortical synapses measured by a new immunocytochemical/densitometric technique reveals very powerful correlations with all three psychological assays. Multivariate analysis by stepwise regression produced a model including midfrontal and inferior parietal synapse density, plus inferior parietal plaque counts with a correlation coefficient of 0.96 for Mattis's Dementia Rating Scale. Plaque density contributed only 26% of that strength.

A comprehensive compositional and characterization study was carried out on five seed oils from varieties of the melons Citrullus lanatus and C. colocynth in order to evaluate their suitability for large-scale exploitation as edible vegetable oils. The oils were extracted by Soxhlet with a 3:1 mixture of n-hexane/2-propanol with yields that ranged from 24.8 to 30.0% (wt/wt). The refractive indices and relative densities of the oils fell within the narrow ranges of 1.465–1.469 and 0.874–0.954 g/cm3, respectively. Saponification values ranged between 182.1 and 193.8 mg KOH/g, whilst iodine values (IV) ranged from 95.8 to 124.0 (Wijs). The ranges of the values for free fatty acid (AV), 1.2–4.0 mg KOH/g, peroxide (PV), 1.1–10.9 meq/kg and p-anisidine (p-AV), 0.2–9.0, indicated that secondary oxidation products were barely present. GC analysis gave total unsaturation contents of 67.93–82.36%, with linoleic acid (18:2) being the dominant fatty acid (55.21–66.85%). The GC results agreed closely with those from proton NMR analysis of the fatty acid classes. The physicochemical and compositional properties determined in this study show that the qualities of the test Cucurbitacea seed oils are highly comparable to those of soybean, sunflower and groundnut seed oils. Therefore, the test melon seed oils could be developed into commercial products to serve as alternate vegetable oils in Southern and West Africa, the regions where these melons grow.

This research is to investigate the effects of deformable panels on reducing the seaward displacement, settlement and tilting of caisson quay walls. In this regard, a series of shaking table 1-g tests are performed for a 1 25 scaled-down caisson quay wall with two different seabed interface conditions. Here, the wall is tested in two cases: with and without (no-mitigation case) applying the deformable panels. Being installed behind the walls, the panels applied in the tests have different mechanical properties. In the model test, the harmonic base motions are used with constant frequency and amplitude. In all tests, the foundation soil beneath the caisson wall is assumed as dense and non liquefiable. However, in order to reproduce a loose backfill situation in the model, the backfill soil is constructed with relative density of 25%. Furthermore, to support the experimental results, a series of finite difference effective-stress analyses are performed in the prototype scale. The mitigation results show that the deformable panels can significantly decrease the seaward movement, settlement and inclination of wall as well as the total pressure recorded behind the caisson wall. Here, these panels are called Displacement Reducer Panels (DRP) based on the obtained results.

Estimation of the temperature field in the powder bed in selective laser sintering process is a key issue for understanding the sintering/binding mechanisms and for optimising the technique. Heat transfer may be strongly affected by formation and growth of necks between particles due to sintering when the contact conductivity becomes predominant in the powder bed effective thermal conductivity. The necks often remain small as compared to the particle size. To calculate the effective contact conductivity of such structures a model of independent small thermal contacts is proposed. The conductivity of the considered cubic-symmetry lattices and the random packing of equal spheres depends on the three structural parameters: the relative density, the coordination number, and the contact size. The present model agrees with the known numerical calculations in the range of contact radius to particle radius ratio below 0.3. The strong dependence on the contact size is qualitatively confirmed by experimental data.

Zirconium carbide (ZrC) and hafnium carbide (HfC) powders were produced by the carbothermal reduction reaction of carbon and the corresponding metal oxide (ZrO 2 and HfO 2 , respectively). Solution-based processing was used to achieve a fine-scale (i.e., nanometer-level) mixing of the reactants. The reactions were substantially completed at relatively low temperatures (<1500 • C) and the resulting products had small average crystallite sizes (∼50-130 nm). However, these products contained some dissolved oxygen in the metal carbide lattice and higher temperatures were required to complete the carbothermal reduction reactions. Dry-pressed compacts prepared using ZrC-based powders with ∼100 nm crystallite size could be pressurelessly sintered to ∼99% relative density at 1950

The distribution and abundance of thirteen species of regular
sea urchin were assessed on Sosoikula and Nukubuco reefs, Fiji. Their
morphology and behavior were contrasted relative to wave activity,
water depth, substratum composition, food, and predation through all the
reefs zones. Densities and relative densities of species in each zone were
determined and their significance tested relative to the species distribution.
Results indicated species associations with different reef areas, thus
habitat preferences, which reflected species’ competitive abilities and
resource partitioning. Echinometra mathaei was the most prolific and
adaptable species, having the greatest densities in all zones. Peak mean
densities occurred in the mid back reef area on the echinoderm flat (2.64
ind. m–2), comprising 93.6% of all echinoids found. Diadema savignyi
and Diadema setosum were found at maximum densities in the boulder
zone, utilizing the narrow elevated crevice space. Both these species of
Diadema showed an increase in test diameters and spine lengths from
the reef crest to the hard coral bommies, proportional to the increase in
observed crevice size. Echinothrix diadema and Echinothrix calamaris
(brown color morph) demonstrated a similar trend, but with continued
growth-related migration to the Porites and soft coral zone. The white
color morph of E. calamaris showed no apparent association between
size distribution and crevice space. This was due to behavioral adaptations,
where both juveniles and adults aggregated together in the few
very large crevices found. Algal and seagrass species distributions
appeared to have only a moderate influence on echinoid species distributions,
as most species diets appeared broad within habitat. Predation
pressure was assessed to be relatively low, with greatest predator densities
on the fore reef (0.24 ind. m–2). Refuge quality and availability,
moderated by predation, combined with different echinoid morphologies
and behaviors, determined species distributions through the reefs varied
habitats.

Experimental data on the drying behavior of suspension droplets is limited, despite its importance in industrial applications for material processing, chemical or the food industry involving spray dryers. This fact is particularly significant for high load and temperature conditions, as found in such industrial applications. In this work, the drying behavior of acoustically levitated multiphase droplets has been experimentally investigated. The acoustic tube levitator has been modified in order to allow experiments to be performed at high temperature conditions. The flow rate, temperature and relative humidity of this air stream can be controlled by an air conditioning system. A CMOS camera and a backlight illumination system are used to measure the droplet cross-sectional area and vertical position of the droplet during the drying process. The experiments have been performed using water-glass particle suspensions. The glass particles have a mean particle size and relative density of 13 mm and 2.5, respectively. The effect of the air temperature (60 1C o To 120 1C), initial volume of the droplet (0.05 mloV 0 o 0.7 ml), initial solid mass load (0.01 o Y S o 0.5) and relative humidity of the air (0.05 o HR o 0.45) on the mean porosity of the grain, first drying period duration and liquid evaporation rate has been analyzed by means of a parametric screening matrix and also by means of a central composite design (CCD) experimental design. The most important parameters to be considered for the porosity and the drying behavior in the range of variables analyzed are the initial solid mass load and the initial droplet volume. The relative humidity of the air exerts a moderate influence on the drying behavior of the droplet and the temperature has only a very low impact on the mean porosity. In addition, particular attention should be given to the drying behavior of small droplets, which result in a very low mean porosity values for high solid mass loads. The CCD confirms that the initial droplet volume, the solid mass load and their interaction exert significant influence on the three responses.

The interesting properties of metal foams as light weight, good energy absorption, low thermal conductivity, recyclability have spurred new process developments with the goal to obtain materials with a good relation between properties and costs.

The distribution and relative density of smooth-coated otters Lutra perspicillata Geoffroy were studied along a 425 km stretch of Chambal river within the National Chambal Sanctuary, Central India, between 1988 and 1992. Sample sites of l km were surveyed every 5 km. The study revealed that the distribution of otters along the river is patchy and largely restricted to the upper reaches. During the 1988 survey, 36% of sites were found with otter signs but only 24% in 1992. Recent increases in disturbance along the river due to construction of road bridges and mining activities might have put pressure on the population. Most of the positive sites (66%) were found on rocky banks, followed by clay banks (19%), banks with shoreline vegetation and marsh (11%) and sandy banks (3%). During intensive monitoring of four radio-implanted otters, c. 78% locations were made on rocky banks, 19% on banks with shoreline vegetation and marsh, with <3% on sandy banks and < 1% on clay banks, indicating greater preference for rocky banks owing to the greater availability of den sites. As a conservation measure, monitoring of the otter population should be done regularly and restrictions on cultivation, grazing and mining along the banks should be imposed within the Sanctuary limits, especially in the identified stretches.

The behavior of sodium silicate solutions in an alkaline medium has been studied in the 11.56-9 pH range by adding different amount of hydrochloric acid into a concentrated commercial solution ([Si] = 7 mol/L, Si/Na = 1.71, pH = 11.56). The formed products and their evolution during long ripening (up to 150 days) have been characterized by cryo-SEM, elementary analysis (ICP-AES), X-ray diffraction and surface area and relative density measurements. In the studied narrow ranges of pH (11.56-9) and silicon concentration (7-0.2 mol/L) four different situations have been observed: (i) a stable and clear solution, (ii) a reversible and transparent physical gel; (iii) a soluble white gel characterized by a significant contraction during ripening and (iv) an irreversible gel which presents a slow syneresis leading to a consolidate solid. The characterizations of the different solids, liquids and gels have shown that the observed behaviors were the results of the formation of nanometric soluble NaSi 1.87 O 4.24 particles and/or insoluble silica-like (NaSi 12.66 O 25.82 ) grains and of the contribution of a dissolution/precipitation mechanism.

A major operating cost in dense-medium separation is in replacement of lost medium solids. The loss of medium solids, being costly, plays a crucial role in determining the economics of any preparation operation. Coal washeries that employ dense-medium cyclones often attempt optimization of the processes by varying the vortex or the spigot diameter and the feed relative density. While these changes help in closer control of the separation process, they also result in medium losses due to changes in the medium split ratio (ratio of the medium flow rate in overflow to underflow). Since medium solids are lost by adhesion to products and as magnetic separator effluent, the effect of the change in medium split ratio on the drain-and-rinse screens and, hence, the magnetic separator circuit needs to be studied. In Tata Steel's coal washeries, at Jharkhand India, which employs primary and secondary dense-medium cyclones in series to produce clean coal, middlings and rejects, reducing the relative density of feed medium, had an insignificant effect on the medium split ratio. On the other hand, changing the cone ratio (ratio of the overflow diameter to the underflow diameter) changed the relative density and the flow rates through the cyclone outlets, thus affecting the performance of the magnetite recovery circuit.

The potential benefits of providing geocell reinforced sand mattress over clay subgrade with void have been investigated through a series of laboratory scale model tests. The parameters varied in the test programme include, thickness of unreinforced sand layer above clay bed, width and height of geocell mattress, relative density of the sand fill in the geocells, and influence of an additional layer of planar geogrid placed at the base of the geocell mattress. The test results indicate that substantial improvement in performance can be obtained with the provision of geocell mattress, of adequate size, over the clay subgrade with void. In order to have beneficial effect, the geocell mattress must spread beyond the void at least a distance equal to the diameter of the void. The influence of the void over the performance of the footing reduces for height of geocell mattress greater than 1.8 times the diameter of the footing. Better improvement in performance is obtained for geocells filled with dense soil.

This paper presents the results of shaking table tests on model reinforced soil retaining walls in the laboratory. The influence of backfill relative density on the seismic response was studied through a series of laboratory model tests on retaining walls. Construction of model retaining walls in the laminar box mounted on shaking table, instrumentation and results from the shaking table tests are described in detail. Three types of walls: wrap-and rigid-faced reinforced soil walls and unreinforced rigid-faced walls constructed to different densities were tested for a relatively small excitation. Wrap-faced walls are further tested for higher base excitation at different frequencies and relative densities. It is observed from these tests that the effect of backfill density on the seismic performance of reinforced retaining walls is pronounced only at very low relative density and at the higher base excitation. The walls constructed with higher backfill relative density showed lesser face deformations and more acceleration amplifications compared to the walls constructed with lower densities when tested at higher base excitation. The response of wrap-and rigid-faced retaining walls is not much affected by the backfill relative density when tested at smaller base excitation. The effects of facing rigidity were evaluated to a limited extent. Displacements in wrap-faced walls are many times higher compared to rigid-faced walls. The results obtained from this study are helpful in understanding the relative performance of reinforced soil retaining walls constructed to when subjected to smaller and higher base excitation for the range of relative density employed in the testing program. r

Sobre la base de observaciones y colectas se dan a conocer el estado de conservación, densidades relativas, preferencias de hábitat y dieta generalizada de 112 vertebrados de las Lomas de Atiquipa y Mejía en el departamento de Arequipa, sur del Perú. Que está constituida por 27 mamíferos, 73 aves, 10 reptiles, 1 anfibio y 1 pez.

Determinar la densidad relativa en suelos granulares gruesos es en general una difícil tarea dentro de la caracterización geotécnica de estos tipos de materiales, debido a que la presencia de partículas de gran tamaño no permiten el uso de los equipos convencionales para realizar ensayos de densidad máxima y mínima. Por otro lado, aunque existen ensayos de laboratorio no estandarizados para estimar la densidad mínima y máxima, no siempre se destinan los recursos necesarios para la realización de estos ensayos. Por esta razón el uso de correlaciones a partir de ensayos históricos representa una alternativa útil para el estudio de los rangos de densidades de estos materiales. El siguiente trabajo reúne una serie de resultados de ensayos de densidad máxima y mínima basados en las normas ASTM D4253 y ASTM D4254, para así establecer correlaciones que puedan ser usadas para determinar la densidad relativa (DR) de un suelo granular grueso. Finalmente se propone una metodología para estimar la densidad relativa de un material granular grueso, a partir de correlaciones obtenidas de ensayos a menor escala.

This paper presents the results from laboratory-model tests on a strip footing supported by a sand bed reinforced with a geocell mattress. The parameters varied in the testing program include pattern of geocell formation, pocket size, height and width of geocell mattress, the depth ...

Purpose. Pharmaceutical tablets are generally produced by compacting a mixture of several ingredients, including active drugs and excipients. It is of practical importance if the properties of such tablets can be predicted on the basis of the ones for constituent components. The purpose of this work is to develop a theoretical model which can predict the tensile strength of compacted multi-component pharmaceutical mixtures. Methods. The model was derived on the basis of the Ryshkewitch<Duckworth equation that was originally proposed for porous materials. The required input parameters for the model are the relative density or solid fraction (ratio of the volume of solid materials to the total volume of the tablets) of the multi-component tablets and parameters associated with the constituent single-component powders, which are readily accessible. The tensile strength of tablets made of various powder blends at different relative density was also measured using diametrical compression. Results. It has been shown that the tensile strength of the multi-component powder compacts is primarily a function of the solid fraction. Excellent agreement between prediction and experimental data for tablets of binary, ternary and four-component blends of some widely used pharmaceutical excipients was obtained.

The year-round food habits of lynx were studied using radio-telemetry and snow-tracking in the boreal forest of southeastern Norway. The main objectives of the study were to clarify the importance of domestic sheep and small prey species in the diet of lynx in an area with a very low density of roe deer. During the period 1995–1999, we found 193 scats and 358 kills made by lynx. Our results indicate that roe deer were the most common prey species (contributing to 83 and 34% of the biomass consumed in winter and summer, respectively), although a wide range of other species were also found, including mountain hares, tetranoids, red foxes, domestic sheep, wild reindeer, and even moose. Most of the diet was obtained by predation, although we did document several cases of scavenging. Roe deer were more important in the diet in winter than in summer, perhaps because they were easier to locate in winter as they clustered around feeding sites. In summer, domestic sheep and small prey increased in importance. Despite the very low density of roe deer in this study area, lynx seemed to still specialise on them, although domestic sheep did constitute a significant amount to their diet, especially for males and yearlings. However, the contribution of sheep to summer diet was far from that expected if their relative density was considered.

Seed oils from six legume cultivars of Phaseolus vulgaris, grown in the Kingdom of Lesotho, were extracted and their physicochemical properties and FA compositions were determined in order to compare their dietary lipids with those in P. vulgaris cultivars grown in other parts of the world. The oil content of the beans was very low, ranging from 1.5 to 2.0% (w/w). The acid values ranged from 11.0 to 19.2 mg KOH/g, whereas a combination of the PV and the p-anisidine values in Holm's equation gave oxidation values that ranged from 11.0 to 15.0. Thus, considerable enzymatic hydrolysis and oxidation had taken place in the beans during storage. Iodine values ranged from 80.5 to 92.3 (Wijs method), indicating moderate unsaturation in the oils. However, capillary GC analysis, supported by proton NMR analysis of the FAME, gave a total unsaturation range from 79.67 to 84.24%. The dominant FA were α-linolenic acid (36.47–48.81%) and linoleic acid (20.96–36.10%), with appreciable amounts of palmitic acid (14.33–18.23%). This FA composition pattern is quite similar to the FA distribution reported for low oil-bearing legume seeds. Thus, notwithstanding the different climatic and soil conditions, the general properties of lipids in the southern African legume cultivars were quite similar to those of lipids in P. vulgaris cultivars grown in other parts of the world. The high content of α-linolenic acid in the cultivars of P. vulgaris could very likely play a beneficial role in reducing the risk of coronary heart disease among the large populations consuming them in the southern African region.

The study presented here investigates the effect of density in cementitious mortar on its mechanical properties under quasi-static loading. The reduction in density was achieved through the addition of expanded perlite as a lightweight aggregate into cement paste by volume replacement of cement in the ratio from 0 to 8. This yielded a range of densities between 1000 and 2000 kg/m3. The compressive and flexural response of these mixes were determined for geometrically scaled specimens to study the size effect. Some mixes were reinforced with polymer microfibres and the Mode I fracture toughness parameters were evaluated through flexural testing of notched beams. When compared with a reference Portland cement paste, the compressive strength and elastic modulus scaled as the cube of the density, while the fracture toughness varied linearly with it. The study shows that the specimen size effect on compressive and flexural strength decreases with a drop in the density of the mix and also with fibre reinforcement. On the other hand, the specimen size effect on the critical crack mouth opening displacement was more pronounced at lower densities.

This article presents the mechanical behaviour of rigid polyurethane foams with relative density (q f /q s) above 0,3. The parameter taken into account is the density, which controls the foam architecture. The mechanical properties of the foams, characterised by large deformation compression tests and dynamic mechanical analyses, were compared to two theoretical models: (i) the Gibson and Ashby approach, widely used for foam description and (ii) the 2 + 1 phase model from Christensen and Lo, generally used for the description of particulate composite materials. In the studied density range, it is shown that the second approach is more appropriate. Moreover, the stress-strain curve and in particular yield stress have been modelled using two different approaches by extension of this model to the nonlinear domain.

The note pertains to an experimental study made on circular footings resting on semi-infinite layer of sand reinforced with geotextiles. Using the concept of homogenization of such soils, both analytical and numerical analyses have also been conducted to predict the loadsettlement behavior and compared with experimental observations. The study highlights the effect of the footing size, number of reinforcing layers, reinforcement placement pattern and bond length and the relative density of the soil on the load-settlement characteristics of the footings. r

The pull-out resistance of reinforcing elements is one of the most significant factors in increasing the bearing capacity of geosynthetic reinforced soils. In this research a new reinforcing element that includes elements (anchors) attached to ordinary geogrid for increasing the pull-out resistance of reinforcements is introduced. Reinforcement therefore consists of geogrid and anchors with cubic elements that attached to the geogrid, named (by the authors) Grid-Anchor. A total of 45 load tests were performed to investigate the bearing capacity of square footing on sand reinforced with this system. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, effect of relative density, low strain stiffness and stiffness after local shear were investigated. Laboratory tests showed that when a single layer of reinforcement is used there is an optimum reinforcement embedment depth for which the bearing capacity is the greatest. There also appeared to be an optimum vertical spacing of reinforcing layers for multi-layer reinforced sand. The bearing capacity was also found to increase with increasing number of reinforcement layer, if the reinforcement were placed within a range of effective depth. The effect of soil density also is investigated. Finally the results were compared with the bearing capacity of footings on non-reinforced sand and sand reinforced with ordinary geogrid and the advantages of the Grid-Anchor were highlighted. Test results indicated that the use of Grid-Anchor to reinforce the sand increased the ultimate bearing capacity of shallow square footing by a factor of 3.0 and 1.8 times compared to that for un-reinforced soil and soil reinforced with ordinary geogrid, respectively.

The theoretical maximum specific gravity (Gmm) is a parameter required for the calculation of the aggregate effective specific gravity, asphalt absortion, effective asphalt content and air voids content (Vv), within the design of a hot mix asphalt. From the Gmm and the bulk specific gravities of the aggregates and the compacted mixture, one can determine the volumetric characteristics and the

In this review I will describe the importance of seed banks and thepopulation dynamics of seeds on the distribution of species in salinehabitats. The main questions being examined in this review include: 1.Does the seed bank represent the flora of the entire salinity gradient or isit restricted to the species in each zonal community? 2. Is the size andspecies composition of the persistent seed bank regulated by the degree ofsalt stress in habitats along an environmental gradient? 3. Does thepopulation dynamics of seeds influence the temporal and spatial distributionof plant species in saline habitats? Seed banks may be transient orpersistent depending upon the physiological responses of species and thesoil environment in which the seeds are found. The formation of zonalcommunities in salt marsh environments is affected by changes in soilsalinity and flooding along an elevational gradient. Population dynamics ofseeds have been found to determine the spatial and temporal distributionof species along salinity gradients. The flora and relative density of speciesof zonal communities are significantly dependent upon the stress toleranceof species at different stages of development and the presence of transientor persistent seed banks. The occurrence of a seed bank is related to thesalinity tolerance of species at the germination stage of development, aseeds ability to tolerate hypersaline conditions and flooding, and whetheror not species are able to maintain a persistent seed bank until hypersalineconditions are alleviated.

The calcining and sintering behaviour of fluorapatite synthesised by precipitation has been studied. During the calcination process, in the temperature range 400-9008C, the specific surface area decreases with a rise in temperature. Below 7158C, the decrease is associated with grain growth according to a superficial diffusion mechanism. Above this temperature, several mechanisms may take part in the coarsening. Sintering of fluorapatite is performed between 690 and 13208C, under an argon atmosphere when the gas atmosphere is not fittingly dried; hydroxyfluorapatite can be formed during sintering. Densification appears to be governed by grain growth. At moderate temperatures coarsening leads to dense bodies. A relative density of about 97% is obtained at 10208C. Above 11008C densification is hindered by coarsening which becomes important and much quicker when the liquid phase is formed at 11808C.

Effect of Ag-doping on thermoelectric properties of n-type Bi 2 (Te 0.94 ,Se 0.06 ) 3 is studied. Bulk Bi 2 (Te 0.94 ,Se 0.06 ) 3 sample with single solid solution phase and high relative density (over 95%) is obtained by mechanical alloying and subsequent hot press sintering. The as-sintered sample has a microstructure of randomly distributed plate grains and its size is about 1 m. A V-shaped variation for the electrical properties with Ag doping is found which corresponds to different Ag atomic position in lattice among the doping range studied. A maximum figure of merit of about 1.7 × 10 −3 /K is achieved.

The mechanical behaviour of pharmaceutical powders during compaction is analysed using Finite Element Methods (FEM), in which the powder is modelled as an elastic-plastic continuum material. The Drucker-Prager Cap (DPC) model was chosen as the yield surface of the medium, which represents the failure and yield behaviours. Uniaxial compaction experiments were also carried out using a compaction simulator with an instrumented die. The objectives of these experiments were two-fold: (1) to investigate the pharmaceutical powder behaviour during compaction, for which the variation of relative density of the powder bed with applied pressure is analysed; and to calibrate the DPC model with the experimental measurements, from which realistic powder properties are generated and fed into finite element analysis (FEA). The relationship between relative density of powder bed and applied pressure is also obtained from FEA and compared with the experimental data. Good agreement between the experimental and FEA results is observed, which demonstrates that FEA can capture the major features of the powder behaviour during compaction. Furthermore, close examination of the evolution of the stress distribution during unloading reveals that there is a narrow band existing from the top edge towards the bottom centre of the tablet, in which there are localised, intensive shear stresses. It is in this band that potential failure regions, such as cracks, can initiate. This has been demonstrated with experimental evidence from X-ray microtomographical images and photography of fractured tablets. It is therefore demonstrated that FEA can predict the possible mechanism of failure, such as capping, during compaction. D