931 research outputs found
Roughness of sandstone fracture surfaces: Profilometry and shadow length investigations
The geometrical properties of fractured sandstone surfaces were studied by measuring the length distribution of the shadows appearing under grazing illumination. Three distinct domains of variation were found: at short length scales a cut-oïŹ of self-aïŹnity is observed due to the inter-granular rupture of sandstones, at long length scales, the number of shadows falls oïŹ very rapidly because of the non-zero illumination angle and of the ïŹnite roughness amplitude. Finally, in the intermediate domain, the shadow length distribution displays a power law decrease with an exponent related to the roughness exponent measured by mechanical proïŹlometry. Moreover, this method is found to be more sensitive to deviations from self-aïŹnity than usual methods
Traffic jams and intermittent flows in microfluidic networks
We investigate both experimentally and theoretically the traffic of particles
flowing in microfluidic obstacle networks. We show that the traffic dynamics is
a non-linear process: the particle current does not scale with the particle
density even in the dilute limit where no particle collision occurs. We
demonstrate that this non-linear behavior stems from long range hydrodynamic
interactions. Importantly, we also establish that there exists a maximal
current above which no stationary particle flow can be sustained. For higher
current values, intermittent traffic jams form thereby inducing the ejection of
the particles from the initial path and the subsequent invasion of the network.
Eventually, we put our findings in the broader context of the transport
proccesses of driven particles in low dimension
Recommended from our members
Basal rot of narcissus : understanding pathogenicity in fusarium oxysporum f. sp. narcissi
Fusarium oxysporum is a globally distributed soilborne fungal pathogen causing root rots, bulb rots, crown rots and vascular wilts on a range of horticultural plants. Pathogenic F. oxysporum isolates are highly host specific and are classified as formae speciales. Narcissus is an important ornamental crop and both the quality and yield of flowers and bulbs can be severely affected by a basal rot caused by F. oxysporum f. sp. narcissi (FON); 154 Fusarium isolates were obtained from different locations and Narcissus cultivars in the United Kingdom, representing a valuable resource. A subset of 30 F. oxysporum isolates were all found to be pathogenic and were therefore identified as FON. Molecular characterisation of isolates through sequencing of three housekeeping genes, suggested a monophyletic origin with little divergence. PCR detection of 14 Secreted in Xylem (SIX) genes, previously shown to be associated with pathogenicity in other F. oxysporum f. spp., revealed different complements of SIX7, SIX9, SIX10, SIX12 and SIX13 within FON isolates which may suggest a race structure. SIX gene sequences were unique to FON and SIX10 was present in all isolates, allowing for molecular identification of FON for the first time. The genome of a highly pathogenic isolate was sequenced and lineage specific (LS) regions identified which harboured putative effectors including the SIX genes. Real-time RT-PCR, showed that SIX genes and selected putative effectors were expressed in planta with many significantly upregulated during infection. This is the first study to characterise molecular variation in FON and provide an analysis of the FON genome. Identification of expressed genes potentially associated with virulence provides the basis for future functional studies and new targets for molecular diagnostics
Dispersion enhancement and damping by buoyancy driven flows in 2D networks of capillaries
The influence of a small relative density difference on the displacement of
two miscible liquids is studied experimentally in transparent 2D networks of
micro channels. Both stable displacements in which the denser fluid enters at
the bottom of the cell and displaces the lighter one and unstable displacements
in which the lighter fluid is injected at the bottom and displaces the denser
one are realized. Except at the lowest mean flow velocity U, the average
of the relative concentration satisfies a convection-dispersion
equation. The dispersion coefficient is studied as function of the relative
magnitude of fluid velocity and of the velocity of buoyancy driven fluid
motion. A model is suggested and its applicability to previous results obtained
in 3D media is discussed
The significance of seniority for women managersâ interpretations of organizational restructuring
This paper examines the impact of restructuring within the transport and logistics sector on women managers working at senior and less senior (middle/junior management) levels of the organization. The majority of women experienced increased performance pressures and heavier workloads as well as an increase in working hours. At the same time, there were pressures to work at home (i.e. week-ends and evenings) and reduced opportunities to work from home (i.e. during normal office hours). Management level emerged as an important factor in how these changes were interpreted. Senior managers perceived more positive outcomes in terms of increased motivation and loyalty. Despite a longer working week, they were less likely to report low morale as an outcome from long hours. In fact, irrespective of management level, women working shorter hours were more likely to report low morale as an outcome. Results are discussed in relation to literature on restructuring and careers, in terms of perceptual framing and in relation to different levels of investment in the organization
Draft genome sequence of an onion basal rot isolate of Fusarium proliferatum
Fusarium proliferatum is a component of the onion basal rot disease complex. We present an annotated F. proliferatum draft genome sequence, totaling 45.8 Mb in size, assembled into 597 contigs, with a predicted 15,418 genes. The genome contains 58 secondary metabolite clusters and homologs of the Fusarium oxysporum effector SIX2
Spin splitting in a polarized quasi-two-dimensional exciton gas
We have observed a large spin splitting between "spin" and
heavy-hole excitons, having unbalanced populations, in undoped GaAs/AlAs
quantum wells in the absence of any external magnetic field. Time-resolved
photoluminescence spectroscopy, under excitation with circularly polarized
light, reveals that, for high excitonic density and short times after the
pulsed excitation, the emission from majority excitons lies above that of
minority ones. The amount of the splitting, which can be as large as 50% of the
binding energy, increases with excitonic density and presents a time evolution
closely connected with the degree of polarization of the luminescence. Our
results are interpreted on the light of a recently developed model, which shows
that, while intra-excitonic exchange interaction is responsible for the spin
relaxation processes, exciton-exciton interaction produces a breaking of the
spin degeneracy in two-dimensional semiconductors.Comment: Revtex, four pages; four figures, postscript file Accepted for
publication in Physical Review B (Rapid Commun.
An Augmented Interface to Display Industrial Robot Faults
Technology advancement is changing the way industrial factories have to face an increasingly complex and competitive market. The fourth industrial revolution (known as industry 4.0) is also changing how human workers have to carry out tasks and actions. In fact, it is no longer impossible to think of a scenario in which human operators and industrial robots work side-by-side, sharing the same environment and tools. To realize a safe work environment, workers should trust robots as well as they trust human operators. Such goal is indeed complex to achieve, especially when workers are under stress conditions, such as when a fault occurs and the human operators are no longer able to understand what is happening in the industrial manipulator. Indeed, Augmented Reality (AR) can help workers to visualize in real-time robotsâ faults. This paper proposes an augmented system that assists human workers to recognize and visualize errors, improving their awareness of the system. The system has been tested using both an AR see-through device and a smartphone
- âŠ