2,980 research outputs found
Risk pathways for gonorrhea acquisition in sex workers: can we distinguish confounding from an exposure effect using a priori hypotheses?
The population distribution of sexually transmitted infections (STIs) varies broadly across settings. Although there have been many studies aiming to define subgroups at risk of infection that should be a target for prevention interventions by identifying risk factors, questions remain about how these risk factors interact, how their effects jointly influence the risk of acquisition, and their differential importance across populations. Theoretical frameworks describing the interrelationships among risk determinants are useful in directing both the design and analysis of research studies and interventions. In this article, we developed such a framework from a review looking at determinants of risk for STI acquisition, using gonorrhea as an index infection. We also propose an analysis strategy to interpret the associations found to be significant in uniform analyses of observational data. The framework and the hierarchical analysis strategy are of particular relevance in the understanding of risk formation and might prove useful in identifying determinants that are part of the causal pathway and therefore amenable to prevention strategies across populations
Characterization of radially symmetric finite time blowup in multidimensional aggregation equations,
This paper studies the transport of a mass in by a
flow field . We focus on kernels for
for which the smooth densities are known to develop
singularities in finite time. For this range This paper studies the transport
of a mass in by a flow field . We
focus on kernels for for which the
smooth densities are known to develop singularities in finite time. For this
range we prove the existence for all time of radially symmetric measure
solutions that are monotone decreasing as a function of the radius, thus
allowing for continuation of the solution past the blowup time. The monotone
constraint on the data is consistent with the typical blowup profiles observed
in recent numerical studies of these singularities. We prove monotonicity is
preserved for all time, even after blowup, in contrast to the case
where radially symmetric solutions are known to lose monotonicity. In the case
of the Newtonian potential (), under the assumption of radial
symmetry the equation can be transformed into the inviscid Burgers equation on
a half line. This enables us to prove preservation of monotonicity using the
classical theory of conservation laws. In the case and at
the critical exponent we exhibit initial data in for which the
solution immediately develops a Dirac mass singularity. This extends recent
work on the local ill-posedness of solutions at the critical exponent.Comment: 30 page
Kants view of space about 1769
Kant was trying t o hunt with the hounds and run with
the hare. He was trying to show that space is prior to
the sensuous manifold, and yet that space presupposes a
synthesis. He was trying to show that the parts of space
are dependent upon the whole, and yet to say that the whole
of space is determined by a synthesis cf the parts. It
cannot be done. His attempt to combine these views failed.
His only alternative was the view of the Diss. that the conditions of synthesis can be entirely intellectual,
and that the conditions of the resulting whole can be entirely
sensitive. On such a view, sense and intellect
are dogmatically assumed to be separate and complete in
themselves. But in the Aₙₐ. where they are bound inseparably
together, the assumption is false.These conflicting views of space in theCritique
make clearer the two views of space in Diss. 15. In 1770,
Kant could answer Euler s Question in two ways . Space is
not abstracted from sensation; in reference to the
sensible world, it is not abstracted at all. There is,
however, an intellectual synthesis which yields it. It is determined by this synthesis. Kant reconciled these two
answers by means of the dualism of 1770. To know the
sensible world, the mind requires only intuitions. Knowledge
of the sensible world is synthetic, and not analytic. On
the other hand, to know the intelligible, real world, the
mind requires only concepts . Knowledge of the intelligible
world is analytic and not synthetic. These two kinds of
knowledge do not overlap.In every section of Diss. 15. save two Kant treated
the pure intuition of space as presented or contemplated,
and not constructed. In two parts he treated it as yielded by an activity of the mind. By following out
this assumption, he discovered the weakness in his dualism. At the end of the Corollary, he suggested that the concepts
of space and time, which are not abstracted from sense,
and which are not gained by reflection (like the usual
general concepts) are abstracted. from an activity of the
mind on the occasion of sensation. He assumed that an
intellectual activity can yield a sensitive whole. After
1770, he realized that this is impossible. He realized,
however, that the fault lay not in the assumption of an
activity of the mind, but in the deeper assumption of a
thoroughgoing dualism. The assumption of an activity of
the mind must -- he realized -- be retained, but the
dualism rejected. He could not isolate conception and
intuition. There is an activity of t'he understanding
which begins with the manifold of sense and which determines
space. The understanding represents space as a pure
manifold (in pure Mathematics) in contrast to the sensuous
manifold; and as a pure form of the sensuous manifold
(in applied Mathematics.) . At the end cf the Corollary
to Diss. 15., Kant was correct in saying that there is an
activity of the mind. He was wrong Only in regard to its
nature. The rest of Diss. 15. is based upon the false assumption that there is no activity of the mini. Diss.
15., as a whole, is based upon the false assumption
that conception and intuition can be isolated. The doctrine
that space is prior to sensation is based also upon this
false assumption. The doctrine that the whole of space
determines the parts is based also upon it. The same is
true of the doctrine that an infinite number of representations
are in space instead of under it. Once Kant corrected
this assumption, and joined conceptions and intuitions,
the representations cf space and time are subjected to the
conditions of conception as well as to the conditions of
sense. He could preserve the doctrines of space in the
Aes . only by reverting to the point of view of the Dissertation
and separating conception from intuition. He would never
have done this. He retained the views of the Aes.,
either because he did not realize that he had contradicted
them; or because, realizing it, he knew that the alteration
required was too far-reaching to be undertaken.Kant failed to unify his doctrines of space in the
Critique. Space is either prior to the manifold of
sense:- in which case, it is not determined by any kind
of synthesis; or space is determined by synthesis which
begins with the prior existing manifold cf sense. The
first is the teaching of Diss. 15. A., and Aes.1., the
second is the teaching of the Aₙₐ. Either space remains
after the objects of sense have been abstracted, or
nothing remains after they have been abstracted. The
first is the view of Diss. 15. A., and Aes. 11; the
second is the view of the Aₙₐ. Either the whole of space
determines the parts:- in which case there is no synthesis; or the parts precede the whole, and it is
determined by a synthesis of then. If the whole (aggregate)
has been reached by a synthesis, then it cannot precede
the parts, but is preceded and determined by them. If the
synthesis is carried further, a new whole results, and
what had been previously considered as the whole, is found
to have been merely an aggregate, determined by the extent
of the previous synthesis of the parts. Space cannot presuppose
an activity of the understanding (even in pure
Geometry) unless the parts determine the whole. This contradicts Diss. 15. C. n. and 15. cor. (first -paragraph).
Space cannot presuppose an activity of the understanding
unless particular representations cf space are under "space" and not in it. This contradicts Aes. B. IV
Elevated Paracellular Glucose Flux across Cystic Fibrosis Airway Epithelial Monolayers Is an Important Factor for Pseudomonas aeruginosa Growth.
People with cystic fibrosis (CF) who develop related diabetes (CFRD) have accelerated pulmonary decline, increased infection with antibiotic-resistant Pseudomonas aeruginosa and increased pulmonary exacerbations. We have previously shown that glucose concentrations are elevated in airway surface liquid (ASL) of people with CF, particularly in those with CFRD. We therefore explored the hypotheses that glucose homeostasis is altered in CF airway epithelia and that elevation of glucose flux into ASL drives increased bacterial growth, with an effect over and above other cystic fibrosis transmembrane conductance regulator (CFTR)-related ASL abnormalities. The aim of this study was to compare the mechanisms governing airway glucose homeostasis in CF and non-CF primary human bronchial epithelial (HBE) monolayers, under normal conditions and in the presence of Ps. aeruginosa filtrate. HBE-bacterial co-cultures were performed in the presence of 5 mM or 15 mM basolateral glucose to investigate how changes in blood glucose, such as those seen in CFRD, affects luminal Ps. aeruginosa growth. Calu-3 cell monolayers were used to evaluate the potential importance of glucose on Ps. aeruginosa growth, in comparison to other hallmarks of the CF ASL, namely mucus hyperviscosity and impaired CFTR-dependent fluid secretions. We show that elevation of basolateral glucose promotes the apical growth of Ps. aeruginosa on CF airway epithelial monolayers more than non-CF monolayers. Ps. aeruginosa secretions elicited more glucose flux across CF airway epithelial monolayers compared to non-CF monolayers which we propose increases glucose availability in ASL for bacterial growth. In addition, elevating basolateral glucose increased Ps. aeruginosa growth over and above any CFTR-dependent effects and the presence or absence of mucus in Calu-3 airway epithelia-bacteria co-cultures. Together these studies highlight the importance of glucose as an additional factor in promoting Ps. aeruginosa growth and respiratory infection in CF disease
Developing the structural capital of higher education institutions to support work based learning
This chapter considers issues related to the provision of work-based learning [WBL] programmes by higher education institutions and discusses these programmes using the concept of structural capital. ‘Structural capital’ is defined as the organising and structuring capability of the organisation as expressed in formal instruments, policies,
regulations, procedures, codes, functional business units, task groups, committees or less formal culture, networks and practices (Stewart, 1997) that influence practices and
procedures. Our experiences of operating work-based learning programmes in two very different higher education institutions provide illustrations of structural factors
that enable and facilitate work-based learning. The discussion outlines the forms of work-based learning that both universities employ, and considers some key aspects of
WBL delivery that are directly impacted upon by the structures and processes within institutions, and contribute to intra-institutional structural capital. A summary of practical examples is given as an appendix to the chapter
Cooperative Set Function Optimization Without Communication or Coordination
We introduce a new model for cooperative agents that seek to optimize a common goal without communication or coordination. Given a universe of elements V, a set of agents, and a set function f, we ask each agent i to select a subset Si ⊂ V such that the size of Si is constrained (i.e., |Si| < k). The goal is for the agents to cooperatively choose the sets Si to maximize the function evaluated at the union of these sets, ∪iSi; we seek max f(∪iSi). We assume the agents can neither communicate nor coordinate how they choose their sets. This model arises naturally in many real-world settings such as swarms of surveillance robots and colonies of foraging insects. Even for simple classes of set functions, there are strong lower bounds on the achievable performance of coordinating deterministic agents. We show, surprisingly, that for the fundamental class of submodular set functions, there exists a near-optimal distributed algorithm for this problem that does not require communication. We demonstrate that our algorithm performs nearly as well as recently published algorithms that allow full coordination
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