1,341 research outputs found
Using PIV to measure granular temperature in saturated unsteady polydisperse granular flows
The motion of debris flows, gravity-driven fast
moving mixtures of rock, soil and water can be interpreted
using the theories developed to describe the shearing motion
of highly concentrated granular fluid flows. Frictional, collisional
and viscous stress transfer between particles and
fluid characterizes the mechanics of debris flows. To quantify
the influence of collisional stress transfer, kinetic models
have been proposed. Collisions among particles result in random
fluctuations in their velocity that can be represented by
their granular temperature, T. In this paper particle image
velocimetry, PIV, is used to measure the instantaneous velocity
field found internally to a physical model of an unsteady
debris flow created by using âtransparent soilââi.e. a mixture
of graded glass particles and a refractively matched fluid.
The ensemble possesses bulk properties similar to that of
real soil-pore fluid mixtures, but has the advantage of giving
optical access to the interior of the flow by use of plane laser
induced fluorescence, PLIF. The relationship between PIV
patch size and particle size distribution for the front and tail
of the flows is examined in order to assess their influences
on the measured granular temperature of the system. We find
that while PIV can be used to ascertain values of granular
temperature in dense granular flows, due to increasing spatial
correlation with widening gradation, a technique proposed to
infer the true granular temperature may be limited to flows
of relatively uniform particle size or large bulk
Neural development features: Spatio-temporal development of the Caenorhabditis elegans neuronal network
The nematode Caenorhabditis elegans, with information on neural connectivity,
three-dimensional position and cell linage provides a unique system for
understanding the development of neural networks. Although C. elegans has been
widely studied in the past, we present the first statistical study from a
developmental perspective, with findings that raise interesting suggestions on
the establishment of long-distance connections and network hubs. Here, we
analyze the neuro-development for temporal and spatial features, using birth
times of neurons and their three-dimensional positions. Comparisons of growth
in C. elegans with random spatial network growth highlight two findings
relevant to neural network development. First, most neurons which are linked by
long-distance connections are born around the same time and early on,
suggesting the possibility of early contact or interaction between connected
neurons during development. Second, early-born neurons are more highly
connected (tendency to form hubs) than later born neurons. This indicates that
the longer time frame available to them might underlie high connectivity. Both
outcomes are not observed for random connection formation. The study finds that
around one-third of electrically coupled long-range connections are late
forming, raising the question of what mechanisms are involved in ensuring their
accuracy, particularly in light of the extremely invariant connectivity
observed in C. elegans. In conclusion, the sequence of neural network
development highlights the possibility of early contact or interaction in
securing long-distance and high-degree connectivity
Where to from here? A quality improvement project investigating burns treatment and rehabilitation practices in India
Abstract Objective To describe the capacity of the Indian healthcare system in providing appropriate and effective burns treatment and rehabilitation services. Results Health professionals involved in burns treatment or rehabilitation at seven hospitals from four states in India were invited to participate in consultative meetings. Existing treatment and rehabilitation strategies, barriers and enablers to patient flow across the continuum of care and details on inpatient and outpatient rehabilitation were discussed during the meetings. Seventeen health professionals from various clinical backgrounds were involved in the consultation process. Key themes highlighted (a) a lack of awareness on burn first aid at the community level, (b) a lack of human resource to treat burn injuries in hospital settings, (c) a gap in burn care training for medical staff, (d) poor hospital infrastructure and (e) a variation in treatment practices and rehabilitation services available between hospitals. A number of opportunities exist to improve burns treatment and rehabilitation in India. Improvements would most effectively be achieved through promoting multidisciplinary care across a number of facilities and service providers. Further research is required to develop context-specific burn care models, determining how these can be integrated into the Indian healthcare system
Accidental stability of dark matter
We propose that dark matter is stable as a consequence of an accidental Z2
that results from a flavour-symmetry group which is the double-cover group of
the symmetry group of one of the regular geometric solids. Although
model-dependent, the phenomenology resembles that of a generic Higgs portal
dark matter scheme.Comment: 12 pages, final version, published in JHE
STK295900, a Dual Inhibitor of Topoisomerase 1 and 2, Induces G<inf>2</inf> Arrest in the Absence of DNA Damage
STK295900, a small synthetic molecule belonging to a class of symmetric bibenzimidazoles, exhibits antiproliferative activity against various human cancer cell lines from different origins. Examining the effect of STK295900 in HeLa cells indicates that it induces G2 phase arrest without invoking DNA damage. Further analysis shows that STK295900 inhibits DNA relaxation that is mediated by topoisomerase 1 (Top 1) and topoisomerase 2 (Top 2) in vitro. In addition, STK295900 also exhibits protective effect against DNA damage induced by camptothecin. However, STK295900 does not affect etoposide-induced DNA damage. Moreover, STK295900 preferentially exerts cytotoxic effect on cancer cell lines while camptothecin, etoposide, and Hoechst 33342 affected both cancer and normal cells. Therefore, STK295900 has a potential to be developed as an anticancer chemotherapeutic agent. © 2013 Kim et al
Reductionist and system approaches to study the role of infection in preterm labor and delivery
A substantial number of patients with preterm labor and delivery do not show clinical signs of infection, however, it is the subclinical form which is the main causative factor and often results in premature delivery. The hitherto commonly applied methods of inflammation detection are based either on potentially hazardous amniocentesis or still insufficient inflammation-related protein measurement in the serum or other biological fluids
Human Cytomegalovirus UL18 Utilizes US6 for Evading the NK and T-Cell Responses
Human cytomegalovirus (HCMV) US6 glycoprotein inhibits TAP function, resulting in down-regulation of MHC class I molecules at the cell surface. Cells lacking MHC class I molecules are susceptible to NK cell lysis. HCMV expresses UL18, a MHC class I homolog that functions as a surrogate to prevent host cell lysis. Despite a high level of sequence and structural homology between UL18 and MHC class I molecules, surface expression of MHC class I, but not UL18, is down regulated by US6. Here, we describe a mechanism of action by which HCMV UL18 avoids attack by the self-derived TAP inhibitor US6. UL18 abrogates US6 inhibition of ATP binding by TAP and, thereby, restores TAP-mediated peptide translocation. In addition, UL18 together with US6 interferes with the physical association between MHC class I molecules and TAP that is required for optimal peptide loading. Thus, regardless of the recovery of TAP function, surface expression of MHC class I molecules remains decreased. UL18 represents a unique immune evasion protein that has evolved to evade both the NK and the T cell immune responses
Consumer perceptions of co-branding alliances: Organizational dissimilarity signals and brand fit
This study explores how consumers evaluate co-branding alliances between dissimilar partner firms. Customers are well aware that different firms are behind a co-branded product and observe the partner firmsâ characteristics. Drawing on signaling theory, we assert that consumers use organizational characteristics as signals in their assessment of brand fit and for their purchasing decisions. Some organizational signals are beyond the control of the co-branding partners or at least they cannot alter them on short notice. We use a quasi-experimental design and test how co-branding partner dissimilarity affects brand fit perception. The results show that co-branding partner dissimilarity in terms of firm size, industry scope, and country-of-origin image negatively affects brand fit perception. Firm age dissimilarity does not exert significant influence. Because brand fit generally fosters a benevolent consumer attitude towards a co-branding alliance, the findings suggest that high partner dissimilarity may reduce overall co-branding alliance performance
Problematic social media use: results from a large-scale nationally representative adolescent sample
Despite social media use being one of the most popular activities among adolescents, prevalence estimates among teenage samples of social media (problematic) use are lacking in the field. The present study surveyed a nationally representative Hungarian sample comprising 5,961 adolescents as part of the European School Survey Project on Alcohol and Other Drugs (ESPAD). Using the Bergen Social Media Addiction Scale (BSMAS) and based on latent profile analysis, 4.5% of the adolescents belonged to the at-risk group, and reported low self-esteem, high level of depression symptoms, and elevated social media use. Results also demonstrated that BSMAS has appropriate psychometric properties. It is concluded that adolescents at-risk of problematic social media use should be targeted by school-based prevention and intervention programs
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