A History of Particle-Size Limits, Special Report, HR-99

Soils consist largely of mineral particles in a wide range of sizes. It is advantageous to assign names, such as "sand", etc., to describe particles which lie between certain size limits. These names are convenient to use and give more information than merely stating that the particles fit certain size limitations. Many systems of particle-size limits have been proposed and used, and have many discrepancies. For example, depending on the system used, a term such as "sand" may designate very different materials. Since no clear-cut divisions can be made between members of a continuous series all particle-size limit schemes are arbitrary. The originators of the various systems were influenced by many factors: convenience of investigation, methods and equipment available for analysis, ease of presenting data, convenience for statistical analysis, previous work, and systems in use. The complications were further compounded because of widely varying fields of endeavor with varying background, outlook, and goals. For example, many inconsistencies are found in engineering depending on whether the size limits are used to differentiate soils, or characterize aggregates for concrete. Some of the investigators have tried to place limits to correspond with the various properties of the soil components; others were more interested in the ease and convenience of obtaining and presenting data. The purpose of this paper is to review many of the systems which have been proposed and used, and if possible, to suggest what may have been the reasons for the selection of the particle-size limits.

Current directions in DNA gel particles

A general understanding of interactions between DNA andoppositely charged compounds forms the basis for developing novelDNA-based materials, including gel particles. The association strength,which is altered by varying the chemical structure of the cationiccosolute, determines the spatial homogeneity of the gelation process,creating DNA reservoir devices and DNA matrix devices that can bedesigned to release either single- (ssDNA) or double-stranded(dsDNA) DNA. This paper reviews the preparation of DNA gelparticles using surfactants, proteins and polysaccharides. Particlemorphology, swelling/dissolution behaviour, degree of DNAentrapment and DNA release responses as a function of the nature ofthe cationic agent used are discussed. Current directions in thehaemocompatible and cytotoxic characterization of these DNA gelparticles have been also included.

Particle exposure scenarios for research and production activities involving nanomaterials

Nanomaterials with structures in the nanoscale (1 to 100 nm) often have chemical, physical and bioactive characteristics different from those of larger entities of the same material. This is interesting for industry but raises questions about the health of exposed people. However, little is known so far about the exposure of workers to inhalable airborne nanomaterials. We investigated several activities in research laboratories and industry to learn about relevant exposure scenarios. Work process analyses were combined with measurements of airborne particle mass concentrations and number−size distributions. Background levels in research settings were mostly low, while in industrial production, levels were sometimes elevated, especially in halls near busy roads or in the presence of diesel fork lifts without particle filters. Peak levels were found in an industrial setting dealing with powders (up to 80,000 particles/cm³ and up to 15 mg/m³). Mostly low concentrations were found for activities involving liquid applications. However, centrifugation and lyophilization of nanoparticle containing solutions resulted in very high particle number concentrations (up to 300,000 particles/cm³), whereas no increases were seen for the same activities conducted with nanoparticle−free liquids. No significant increases of particle concentrations were found for processes involving nanoparticles bound to surfaces. Also no increases were observed in laboratories that were visualizing properties and structures of small amounts of nanomaterials. Conclusion: When studying exposure scenarios for airborne nanomaterials, the focus should not only be on processes involving nano−powders, but also on processes involving intensively treated nanoparticle−containing liquids. Acknowledgement: We thank Chantal Imhof, MSc and Guillaume Ferraris, MSc for their contributions.

External forcings, oceanographic processes and particle flux dynamics in Cap de Creus submarine canyon, NW Mediterranean Sea

Particle fluxes (including major components and grain size), and oceanographic parameters (near-bottom water temperature, current speed and suspended sediment concentration) were measured along the Cap de Creus submarine canyon in the Gulf of Lions (GoL; NW Mediterranean Sea) during two consecutive winter-spring periods (2009 2010 and 2010 2011). The comparison of data obtained with the measurements of meteorological and hydrological parameters (wind speed, turbulent heat flux, river discharge) have shown the important role of atmospheric forcings in transporting particulate matter through the submarine canyon and towards the deep sea. Indeed, atmospheric forcing during 2009 2010 and 2010 2011 winter months showed differences in both intensity and persistence that led to distinct oceanographic responses. Persistent dry northern winds caused strong heat losses (14.2 × 103 W m−2) in winter 2009 2010 that triggered a pronounced sea surface cooling compared to winter 2010 2011 (1.6 × 103 W m−2 lower). As a consequence, a large volume of dense shelf water formed in winter 2009 2010, which cascaded at high speed (up to ∼1 m s−1) down Cap de Creus Canyon as measured by a current-meter in the head of the canyon. The lower heat losses recorded in winter 2010 2011, together with an increased river discharge, resulted in lowered density waters over the shelf, thus preventing the formation and downslope transport of dense shelf water. High total mass fluxes (up to 84.9 g m−2 d−1) recorded in winter-spring 2009 2010 indicate that dense shelf water cascading resuspended and transported sediments at least down to the middle canyon. Sediment fluxes were lower (28.9 g m−2 d−1) under the quieter conditions of winter 2010 2011. The dominance of the lithogenic fraction in mass fluxes during the two winter-spring periods points to a resuspension origin for most of the particles transported down canyon. The variability in organic matter and opal contents relates to seasonally controlled inputs associated with the plankton spring bloom during March and April of both years.

Differential protein labeling with thiol-reactive infrared DY-680 and DY-780 maleimides and analysis by two-dimensional gel electrophoresis.

Differential protein labeling with 2-DE separation is an effective method for distinguishing differences in the protein composition of two or more protein samples. Here, we report on a sensitive infrared-based labeling procedure, adding a novel tool to the many labeling possibilities. Defined amounts of newborn and adult mouse brain proteins and tubulin were exposed to maleimide-conjugated infrared dyes DY-680 and DY-780 followed by 1- and 2-DE. The procedure allows amounts of less than 5 microg of cysteine-labeled protein mixtures to be detected (together with unlabeled proteins) in a single 2-DE step with an LOD of individual proteins in the femtogram range; however, co-migration of unlabeled proteins and subsequent general protein stains are necessary for a precise comparison. Nevertheless, the most abundant thiol-labeled proteins, such as tubulin, were identified by MS, with cysteine-containing peptides influencing the accuracy of the identification score. Unfortunately, some infrared-labeled proteins were no longer detectable by Western blots. In conclusion, differential thiol labeling with infrared dyes provides an additional tool for detection of low-abundant cysteine-containing proteins and for rapid identification of differences in the protein composition of two sets of protein samples.

Somatic embryogenesis and the effect of particle bombardment on banana Maçã regeneration

A plant regeneration method with cell suspension cultures of banana, and the effect of biobalistic on regeneration potential are described in this report. Somatic embryos of banana were obtained from indirect embryogenesis of male inflorescence of banana cultivar Maçã (AAB group). Part of the calluses formed (40%) showed embryogenic characteristics (nonfriable, compact and yellow color). The cell suspension, originated from embryogenic calluses, contained clusters of small tightly packed cells with dense cytoplasms, relatively large nuclei and very dense nucleoli. After four months of culture, somatic embryos started to regenerate. The maximum number of regenerated plants was observed between 45 and 60 days after embryo formation.In the first experiment, 401 plants were regenerated from approximately 10 mL of packed cells. In the second experiment, 399 plants were regenerated from a cell suspension six months older than that of the first experiment. Cell transformation using particle bombardment with three different plasmid constructions, containing the uid-A gene, resulted in a strong GUS expression five days after bombardment; however, plant regeneration from bombarded cells was much lower than nonbombarded ones.

In-vivo performance of high-density collagen gel tubes for urethral regeneration in a rabbit model.

Congenital malformations or injuries of the urethra can be treated using existing autologous tissue, but these procedures are sometimes associated with severe complications. Therefore, tissue engineering may be advantageous for generating urethral grafts. We evaluated engineered high-density collagen gel tubes as urethral grafts in 16 male New Zealand white rabbits. The constructs were either acellular or seeded with autologous smooth muscle cells, isolated from an open bladder biopsy. After the formation of a urethral defect by excision, the tissue-engineered grafts were interposed between the remaining urethral ends. No catheter was placed postoperatively. The animals were evaluated at 1 or 3 months by contrast urethrography and histological examination. Comparing the graft caliber to the control urethra at 3 months, a larger caliber was found in the cell-seeded grafts (96.6% of the normal caliber) than in the acellular grafts (42.3%). Histology of acellular and cell-seeded grafts did not show any sign of inflammation, and spontaneous regrowth of urothelium could be demonstrated in all grafts. Urethral fistulae, sometimes associated with stenosis, were observed, which might be prevented by urethral catheter application. High-density collagen gel tubes may be clinically useful as an effective treatment of congenital and acquired urethral pathologies.

Processus de "deuil gelé" chez les femmes bosniaques, épouses de disparus

Les femmes concernées par cette recherche sont des femmes bosniaques, requérantes d'asile en Suisse, suivies au sein de l'association « Appartenances ». Elles ont quitté leur pays à la suite de la prise de la ville de Srebrenica, en juillet 1995. Lors de cet exode, elles ont été séparées de leurs maris, qui sont aujourd'hui encore portés disparus. Ces femmes partagent une expérience douloureuse qui transparaît derrière un certain nombre de symptômes physiques et psychiques. Nous avons été frappés par la répétition de pertes importantes, sans que les conditions permettant un travail de deuil soient réunies. Aucune signification ne peut être attribuée aux disparitions et aux décès, masqués par le silence politique et par l'impossibilité d'accomplir un rituel. Le deuil peut ainsi se compliquer jusqu'à devenir un deuil impossible, dont le prototype pourrait être le « deuil gelé » lors d'une disparition. D'autre part, le stress et l'attaque de l'identité occasionnés par les traumatismes et l'exil ont coupé ces femmes de leurs ressources personnelles et culturelles. La perte d'une image entière de soi est prolongée par le statut précaire de requérant d'asile et par la perte des espoirs mis dans le pays d'accueil. Devant la complexité de cette problématique, nous nous sommes demandés sur quel aspect axer la prise en charge thérapeutique. Nous avons décidé de travailler sur le vécu et les deuils actuels de ces patientes (stress post-traumatique et statut précaire en Suisse). Le concept-clé qui a étayé cette recherche s'inspire de Pollock (7): « le processus de deuil devient très significatif, dans le sens qu 'il est apparemment une des formes les plus universelles de l'adaptation et de la croissance à travers la structuration, disponible pour l'homme. » Dès lors, nous avons fait l'hypothèse que si le deuil est une forme universelle d'adaptation, l'élaboration d'un travail de deuil ou d'un processus d'adaptation quel qu'il soit, pourra servir d'apprentissage pour l'élaboration d'autres deuils. Concrètement, en travaillant sur le rétablissement de leur identité, les femmes pourront retrouver un accès à leurs ressources personnelles et culturelles, tandis que travailler sur les espoirs et déceptions face au statut en Suisse permettra de développer des moyens permettant plus de contrôle sur l'environnement. Leur autonomie rétablie, elles pourront consacrer leurs énergies à attribuer une signification à leur vécu et faire face aux autres deuils paralysant leur guérison. Nous avons assisté aux entretiens thérapeutiques, en récoltant des témoignages sur la base d'un canevas d'entretien semi-structuré, puis nous avons transposé les éléments sur une grille d'analyse regroupant les informations en items. L'analyse de ces entretiens nous a permis de préciser notre hypothèse et de développer des pistes de réflexion pour l'accompagnement thérapeutique de personnes vivant une disparition. A l'issue de ce travail, nous pouvons tirer des parallèles entre les processus d'élaboration des divers deuils. Les femmes sont entrées peu à peu dans le souvenir de la personne aimée et non plus dans le souvenir des événements traumatiques qui ont marqué sa disparition. S'appuyant alors sur la « mémoire sereine » de Kristeva (1) une recherche de signification a pu être entreprise, rejoignant ce que Métraux et Fleuiy (43) définissent comme la santé : « ... se voir créateur du sens qu'on veut donner à sa propre existence, à ses actes et à ses projets. »

Optimization of particle bombardment parameters for the genetic transformation of Brazilian maize inbred lines

The objective of this work was to develop a genetic transformation system for tropical maize genotypes via particle bombardment of immature zygotic embryos. Particle bombardment was carried out using a genetic construct with bar and uidA genes under control of CaMV35S promoter. The best conditions to transform maize tropical inbred lines L3 and L1345 were obtained when immature embryos were cultivated, prior to the bombardment, in higher osmolarity during 4 hours and bombarded at an acceleration helium gas pressure of 1,100 psi, two shots per plate, and a microcarrier flying distance of 6.6 cm. Transformation frequencies obtained using these conditions ranged from 0.9 to 2.31%. Integration of foreign genes into the genome of maize plants was confirmed by Southern blot analysis as well as bar and uidA gene expressions. The maize genetic transformation protocol developed in this work will possibly improve the efficiency to produce new transgenic tropical maize lines expressing desirable agronomic characteristics.

Variabilidade genética em cultivares de soja determinada com marcadores microssatélites em gel de agarose

O objetivo deste trabalho foi avaliar a variabilidade genética de cultivares de soja com marcadores microssatélites selecionados e caracterizados quanto à informatividade para uso em gel de agarose. O DNA de 23 cultivares de soja foi amplificado com 283 marcadores microssatélites em gel de agarose a 3%. Posteriormente, 53 marcadores que apresentaram polimorfismo facilmente detectável nos géis de agarose foram utilizados na caracterização de 53 cultivares. Nessas cultivares foram detectados 124 alelos, com média de 2,34 alelos por loco, e os valores de conteúdo de informação polimórfica variaram entre 0,16 e 0,66, com média de 0,47. As frequências alélicas variaram de 0,02 a 0,91, com média de 0,43. A distância genética calculada variou de 0,02 a 0,73, com média de 0,47. A menor distância observada foi entre as cultivares CD201 e CD208, e a maior distância entre CD210 e BRSMT Uirapuru. Os marcadores utilizados possibilitaram a identificação das 53 cultivares avaliadas. Os locos microssatélites de soja, avaliados em gel de agarose, apresentam elevada informatividade. É possível detectar variabilidade significativa no germoplasma brasileiro de soja avaliado, mesmo entre cultivares elite, quando se usa marcadores moleculares microssatélites selecionados por sua informatividade.

Probabilistic evidential assessment of gunshot residue particle evidence (Part I): likelihood ratio calculation and case pre-assessment using Bayesian networks

Well developed experimental procedures currently exist for retrieving and analyzing particle evidence from hands of individuals suspected of being associated with the discharge of a firearm. Although analytical approaches (e.g. automated Scanning Electron Microscopy with Energy Dispersive X-ray (SEM-EDS) microanalysis) allow the determination of the presence of elements typically found in gunshot residue (GSR) particles, such analyses provide no information about a given particle's actual source. Possible origins for which scientists may need to account for are a primary exposure to the discharge of a firearm or a secondary transfer due to a contaminated environment. In order to approach such sources of uncertainty in the context of evidential assessment, this paper studies the construction and practical implementation of graphical probability models (i.e. Bayesian networks). These can assist forensic scientists in making the issue tractable within a probabilistic perspective. The proposed models focus on likelihood ratio calculations at various levels of detail as well as case pre-assessment.

Forecasting the Earth"s radiation belts and modeling solar energetic particle events: Recent results from SPACECAST

High-energy charged particles in the van Allen radiation belts and in solar energetic particle events can damage satellites on orbit leading to malfunctions and loss of satellite service. Here we describe some recent results from the SPACECAST project on modelling and forecasting the radiation belts, and modelling solar energetic particle events. We describe the SPACECAST forecasting system that uses physical models that include wave-particle interactions to forecast the electron radiation belts up to 3 h ahead. We show that the forecasts were able to reproduce the >2 MeV electron flux at GOES 13 during the moderate storm of 7-8 October 2012, and the period following a fast solar wind stream on 25-26 October 2012 to within a factor of 5 or so. At lower energies of 10- a few 100 keV we show that the electron flux at geostationary orbit depends sensitively on the high-energy tail of the source distribution near 10 RE on the nightside of the Earth, and that the source is best represented by a kappa distribution. We present a new model of whistler mode chorus determined from multiple satellite measurements which shows that the effects of wave-particle interactions beyond geostationary orbit are likely to be very significant. We also present radial diffusion coefficients calculated from satellite data at geostationary orbit which vary with Kp by over four orders of magnitude. We describe a new automated method to determine the position at the shock that is magnetically connected to the Earth for modelling solar energetic particle events and which takes into account entropy, and predict the form of the mean free path in the foreshock, and particle injection efficiency at the shock from analytical theory which can be tested in simulations.