Density distribution of particles upon jamming after an avalanche in a 2D silo

We present a complete analysis of the density distribution of particles in a two dimensional silo after discharge. Simulations through a pseudo-dynamic algorithm are performed for filling and subsequent discharge of a plane silo. Particles are monosized hard disks deposited in the container and subjected to a tapping process for compaction. Then, a hole of a given size is open at the bottom of the silo and the discharge is triggered. After a clogging at the opening is produced, and equilibrium is restored, the final distribution of the remaining particles at the silo is analyzed by dividing the space into cells with different geometrical arrangements to visualize the way in which the density depression near the opening is propagated throughout the system. The different behavior as a function of the compaction degree is discussed.Comment: 11 pages, 10 figure

Identification and structural determination of the capsular polysaccharides from two Acinetobacter baumannii clinical isolates, MG1 and SMAL

The structures of the capsular polysaccharides (CPSs) of the two clinical isolates Acinetobacter baumannii SMAL and MG1 were elucidated. Hot phenol/water extractions of the dry biomasses, followed by enzymatic digestions and repeated ultracentrifugations led to the isolation of polysaccharides that were negative in Western blot analysis utilizing an anti-lipid A antibody, thus proving that they were not the LPS O-antigens but CPSs. Their structures were established on the basis of NMR spectroscopy and GC-MS analyses. The A. baumannii MG1 CPS consisted of a linear aminopolysaccharide with acyl substitution heterogeneity at the N-4 amino group of QuipN4N: 4)-alpha-D-GlcpNAc-(1 -> 4)-alpha-L-GalpNAcA-(1 -> 3)-beta-D-QuipNAc4NR-(1 -> R = -3-hydroxybutyrryl or acetyl. The repeating unit of the CPS produced by strain SMAL is a pentasaccharide, already reported for the O-antigen moiety from A. baumannii strain ATCC 17961: beta-D-GlcpNAc3NAcA-(1 down arrow 4) 6)-beta-D-Glcp-(1 -> 3)-beta-D-GalpNAc-(1 -> 3)-alpha-D-Galp-(1 -> 6)up arrow beta-D-GlcpNAc-(

An Integrated Approach to Risk and Impacts of Geo-Resources Exploration and Exploitation

Geo-resources are widely exploited in our society, with huge benefits for both economy and communities. Nevertheless, with benefits come risks and impacts. Understanding how such risks and impacts are intrinsically borne in a given project is of critical importance for both industry and society. In particular, it is crucial to distinguish between the specific impacts related to exploiting a given energy resource and those shared with the exploitation of other energy resources. A variety of different approaches can be used to identify and assess such risks and impacts. In particular, Life Cycle Assessment (LCA) and risk assessments (RAs) are the most commonly adopted. Although both are widely used to support decision making in environmental management, they are rarely used in combination perhaps because they have been developed by largely different groups of specialists. By analyzing the structure and the ratio of the two tools, we have developed an approach for combining and harmonizing LCA and MRA; the resulting protocol envisages building MRA upon LCA both qualitatively and quantitatively. We demonstrate the approach in a case study using a virtual site (based on a real one) for geothermal energy production

Perspectives in the use of biochars as low-cost CO2 adsorbents

The recognized versatility of biochar in environmental remediation issues opened up an increasing interest in its applications in multidisciplinary areas of science and engineering. Possible biochar applications include carbon sequestration, soil fertility improvement, pollution remediation and agricultural by-product/waste recycling. A proper application in specific environmental areas requires a fulfilled biochar chemico-physical characterization and overall properties. Please click on the file below for full content of the abstract

Human Bone-Marrow-Derived Stem-Cell-Seeded 3D Chitosan–Gelatin–Genipin Scaffolds Show Enhanced Extracellular Matrix Mineralization When Cultured under a Perfusion Flow in Osteogenic Medium

Tissue-engineered bone tissue grafts are a promising alternative to the more conventional use of natural donor bone grafts. However, choosing an appropriate biomaterial/scaffold to sustain cell survival, proliferation, and differentiation in a 3D environment remains one of the most critical issues in this domain. Recently, chitosan/gelatin/genipin (CGG) hybrid scaffolds have been proven as a more suitable environment to induce osteogenic commitment in undifferentiated cells when doped with graphene oxide (GO). Some concern is, however, raised towards the use of graphene and graphene-related material in medical applications. The purpose of this work was thus to check if the osteogenic potential of CGG scaffolds without added GO could be increased by improving the medium diffusion in a 3D culture of differentiating cells. To this aim, the level of extracellular matrix (ECM) mineralization was evaluated in human bone-marrow-derived stem cell (hBMSC)-seeded 3D CGG scaffolds upon culture under a perfusion flow in a dedicated custom-made bioreactor system. One week after initiating dynamic culture, histological/histochemical evaluations of CGG scaffolds were carried out to analyze the early osteogenic commitment of the culture. The analyses show the enhanced ECM mineralization of the 3D perfused culture compared to the static counterpart. The results of this investigation reveal a new perspective on more efficient clinical applications of CGG scaffolds without added GO

Easy tuning of nanotexture and N doping of carbonaceous particles produced by spark discharge

A better understanding of the effects of carbonaceous particulates in air pollution on human health and on the transmission of viruses requires studies with artificially produced aerosols that mimic the real ones. To produce such aerosols, methods to precisely tailor the morphology as well as the physical and chemical properties of carbon-based nanomaterials are crucial. Here we describe a facile and flexible approach to produce carbon-based nanoparticles with tailored N content by spark discharge utilizing graphite rods. Carbon-based nanoparticles with different nanotexture and N doping could be obtained by simply changing dilution gas (nitrogen, argon) and dilution gas purity (99 and 99.999%). The effect of the discharge frequency (50, 300 Hz) was also explored. The carbon-based nanoparticles were characterized by Fourier transform infrared and X-ray photoelectron spectroscopy, thermogravimetric analysis, and transmission electron microscopy. We find that the nanotexture is strictly linked to the chemical reactivity and to the surface chemistry. The use of N2 as dilution gas allowed for the incorporation of significant amounts of nitrogen (5–7 wt.%) in the carbonaceous particle network mainly as pyrrolic N, graphitic N and N-oxide functional groups

Grain Boundaries in Graphene on SiC(0001ˉ\bar{1}) Substrate

Grain boundaries in epitaxial graphene on the SiC(000$\bar{1}$) substrate are studied using scanning tunneling microscopy and spectroscopy. All investigated small-angle grain boundaries show pronounced out-of-plane buckling induced by the strain fields of constituent dislocations. The ensemble of observations allows to determine the critical misorientation angle of buckling transition $\theta_c = 19 \pm~2^\circ$. Periodic structures are found among the flat large-angle grain boundaries. In particular, the observed $\theta = 33\pm2^\circ$ highly ordered grain boundary is assigned to the previously proposed lowest formation energy structural motif composed of a continuous chain of edge-sharing alternating pentagons and heptagons. This periodic grain boundary defect is predicted to exhibit strong valley filtering of charge carriers thus promising the practical realization of all-electric valleytronic devices

Sex differences in stress-induced sleep deficits

Sleep disruptions are hallmarks in the pathophysiology of several stress-related disorders, including Major Depressive Disorder (MDD) and Post-Traumatic Stress Disorder (PTSD), both known to disproportionately affect female populations. Although previous studies have attempted to investigate disordered sleep in women, few studies have explored and compared how repeated stress affects sleep in both sexes in either human or animal models. We have previously shown that male rats exhibit behavioral and neuroendocrine habituation to 5 days of repeated restraint, whereas females do not; additional days of stress exposure are required to observe habituation in females. This study examined sex differences in sleep measures prior to, during, and after repeated restraint stress in adult male and female rats. Our data reveal that repeated stress increased time spent awake and decreased slow-wave sleep (SWS) and REM sleep (REMS) in females, and these effects persisted over 2 days of recovery. In contrast, the effects of stress on males were transient. These insomnia-like symptoms were accompanied by a greater number of exaggerated motor responses to waking from REMS in females, a phenotype similar to trauma-related nightmares. In sum, these data demonstrate that repeated stress produces disruptions in sleep that persist days after the stress is terminated in female rats. These disruptions in sleep produced by 5 days of repeated restraint may be due to their lack of habituation