28,903 research outputs found
Co-ordinating distributed knowledge: An investigation into the use of an organisational memory
This paper presents an ethnographically informed investigation into the use of an organisational memory, focusing in particular on how information was used in the performance of work. We argue that understanding how people make use of distributed knowledge is crucial to the design of an organisational memory. However, we take the perspective that an ‘organisational memory’ is not technology dependant, but is an emergent property of group interaction. In this sense, the technology does not form the organisational memory, but provides a novel means of augmenting the co-ordination of collaborative action. The study examines the generation, development and maintenance of knowledge repositories and archives. The knowledge and information captured in the organisational memory enabled the team members to establish a common understanding of the design and to gain an appreciation of the issues and concerns of the other disciplines. The study demonstrates why technology should not be thought of in isolation from its contexts of use, but also how designers can make use of the creative flexibility that people employ in their everyday activities. The findings of the study are therefore of direct relevance to both the design of knowledge archives and to the management of this information within organisations
Waste Management and Personal Hygiene for Extended Spacecraft Missions
Waste management and personal hygiene for extended manned spacecraft mission
Note on restoring manifest rotational symmetry in hyperfine and fine structure in light-front QED
We study the part of the renormalized, cutoff QED light-front Hamiltonian
that does not change particle number. The Hamiltonian contains interactions
that must be treated in second-order bound state perturbation theory to obtain
hyperfine structure. We show that a simple unitary transformation leads
directly to the familiar Breit-Fermi spin-spin and tensor interactions, which
can be treated in degenerate first-order bound-state perturbation theory, thus
simplifying analytic light-front QED calculations. To the order in momenta we
need to consider, this transformation is equivalent to a Melosh rotation. We
also study how the similarity transformation affects spin-orbit interactions.Comment: 17 pages, latex fil
Examining the Impact of Parental Socialization on the Coping Styles of Black Graduate Students Faced with Microaggressions
This article explores case examples of two graduate students who endure microaggressions from their math professor at a predominantly White university. The role that parental socialization plays in how these students developed their racial identities and the coping strategies they employed, is analyzed through the lens of Triple Quandary theory (Boykin and Toms 1 985). Findings from this investigation suggest that parental socialization is critical in preparing these students to cope with and respond to microaggressions in protective and adaptive ways. This paper illuminates coping styles, although divergent, that served these graduate students\u27 needs and protected their individual racial identities. Further, the support these students received from their faculty advisor who is also Black, exemplifies the importance of mentorship and advocacy from faculty of color to Black college students\u27 success. Direction for continuity in parental teachings for K-12 and university level educators are discussed
New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The role of epiphyseal skeletal immaturity in vascular obstruction
ObjectivesLegg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition.MethodsFinite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP.ResultsThe results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression.ConclusionThe findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease
Disability Onset Among Working Parents: Earnings Drops, Compensating Income Sources and Health Insurance Coverage
Examines the incidence of work-limiting disability by income level, demographics, and job characteristics; the impact on earnings and family finances; and the role of employer-sponsored insurance in decisions whether to reduce hours or to leave jobs
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Combined release of platelet-rich plasma and 3D-mesenchymal stem cell encapsulation in alginate hydrogels modified by the presence of silica
We report the modified release of platelet-rich plasma from alginate platelet-rich plasma hydrogels altered by the presence of silica. These PRP–alginate–silica compositions can be used as injectable carriers for viable mesenchymal stem cells
Analytic Treatment of Positronium Spin Splittings in Light-Front QED
We study the QED bound-state problem in a light-front hamiltonian approach.
Starting with a bare cutoff QED Hamiltonian, , with matrix elements
between free states of drastically different energies removed, we perform a
similarity transformation that removes the matrix elements between free states
with energy differences between the bare cutoff, , and effective
cutoff, \lam (\lam < \Lam). This generates effective interactions in the
renormalized Hamiltonian, . These effective interactions are derived
to order in this work, with . is renormalized
by requiring it to satisfy coupling coherence. A nonrelativistic limit of the
theory is taken, and the resulting Hamiltonian is studied using bound-state
perturbation theory (BSPT). The effective cutoff, \lam^2, is fixed, and the
limit, 0 \longleftarrow m^2 \alpha^2\ll \lam^2 \ll m^2 \alpha \longrightarrow
\infty, is taken. This upper bound on \lam^2 places the effects of
low-energy (energy transfer below \lam) emission in the effective
interactions in the sector. This lower bound on \lam^2
insures that the nonperturbative scale of interest is not removed by the
similarity transformation. As an explicit example of the general formalism
introduced, we show that the Hamiltonian renormalized to reproduces
the exact spectrum of spin splittings, with degeneracies dictated by rotational
symmetry, for the ground state through . The entire calculation is
performed analytically, and gives the well known singlet-triplet ground state
spin splitting of positronium, . We discuss remaining
corrections other than the spin splittings and how they can be treated in
calculating the spectrum with higher precision.Comment: 46 pages, latex, 3 Postscript figures included, section on remaining
corrections added, title changed, error in older version corrected, cutoff
placed in a windo
Quarkonia in Hamiltonian Light-Front QCD
A constituent parton picture of hadrons with logarithmic confinement
naturally arises in weak coupling light-front QCD. Confinement provides a mass
gap that allows the constituent picture to emerge. The effective renormalized
Hamiltonian is computed to , and used to study charmonium and
bottomonium. Radial and angular excitations can be used to fix the coupling
, the quark mass , and the cutoff . The resultant hyperfine
structure is very close to experiment.Comment: 9 pages, 1 latex figure included in the text. Published version (much
more reader-friendly); corrected error in self-energ
Water as an economic good: a solution, or a problem ?
Water resource management / Economic aspects / Economic analysis / Irrigated farming / Water rights / Pricing / Privatization / Marginal analysis / Water market / Water policy
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