1,084 research outputs found
Bounding biomass in the Fisher equation
The FKPP equation with a variable growth rate and advection by an
incompressible velocity field is considered as a model for plankton dispersed
by ocean currents. If the average growth rate is negative then the model has a
survival-extinction transition; the location of this transition in the
parameter space is constrained using variational arguments and delimited by
simulations. The statistical steady state reached when the system is in the
survival region of parameter space is characterized by integral constraints and
upper and lower bounds on the biomass and productivity that follow from
variational arguments and direct inequalities. In the limit of
zero-decorrelation time the velocity field is shown to act as Fickian diffusion
with an eddy diffusivity much larger than the molecular diffusivity and this
allows a one-dimensional model to predict the biomass, productivity and
extinction transitions. All results are illustrated with a simple growth and
stirring model.Comment: 32 Pages, 13 Figure
Tetratheca gunnii Hook. f. on serpentine soils near Beaconsfield, Tasmania
The rediscovery of Tetratheca gunnii Hook. L, a species last collected in 1843 and presumed extinct, is
reported. The morphological variability among plants (lncluding) previously undescribed fruit is given to facilitate
comparison with descriptions of the type material. The habitat of the species is described and options for management to conserve viable populations are discussed
On waiting for something to happen
This paper seeks to examine two particular and peculiar practices in which the mediation of apparently direct encounters is made explicit and is systematically theorized: that of the psychoanalytic dialogue with its inward focus and private secluded setting, and that of theatre and live performance, with its public focus. Both these practices are concerned with ways in which “live encounters” impact on their participants, and hence with the conditions under which, and the processes whereby, the coming-together of human subjects results in recognizable personal or social change. Through the rudimentary analysis of two anecdotes, we aim to think these encounters together in a way that explores what each borrows from the other, the psychoanalytic in the theatrical, the theatrical in the psychoanalytic, figuring each practice as differently committed to what we call the “publication of liveness”. We argue that these “redundant” forms of human contact continue to provide respite from group acceptance of narcissistic failure in the post-democratic era through their offer of a practice of waiting
Falling behind and catching up : India’s transition from a colonial economy
India fell behind during colonial rule. The absolute and relative decline of Indian GDP per capita with respect to Britain began before colonization and coincided with the rising textile trade with Europe in the 18th century. The decline of traditional industries was not the main driver Indian decline and stagnation. Inadequate investment in agriculture and consequent decline in yield per acre stalled economic growth. Modern industries emerged and grew relatively fast. The falling behind was reversed after independence. Policies of industrialization and a green revolution in agriculture increased productivity growth in agriculture and industry, but Indian growth has been led by services. A strong focus on higher education under colonial policy had created an advantage for the service sector, which today has a high concentration of human capital. However, the slow expansion in primary education was a disadvantage in comparison with the high growth East Asian economies
The regulatory subunit of PKA-I remains partially structured and undergoes β-aggregation upon thermal denaturation
Background: The regulatory subunit (R) of cAMP-dependent protein kinase (PKA) is a modular flexible protein that responds with large conformational changes to the binding of the effector cAMP. Considering its highly dynamic nature, the protein is rather stable. We studied the thermal denaturation of full-length RIα and a truncated RIα(92-381) that contains the tandem cyclic nucleotide binding (CNB) domains A and B. Methodology/Principal Findings: As revealed by circular dichroism (CD) and differential scanning calorimetry, both RIα proteins contain significant residual structure in the heat-denatured state. As evidenced by CD, the predominantly α-helical spectrum at 25°C with double negative peaks at 209 and 222 nm changes to a spectrum with a single negative peak at 212-216 nm, characteristic of β-structure. A similar α→β transition occurs at higher temperature in the presence of cAMP. Thioflavin T fluorescence and atomic force microscopy studies support the notion that the structural transition is associated with cross-β-intermolecular aggregation and formation of non-fibrillar oligomers. Conclusions/Significance: Thermal denaturation of RIα leads to partial loss of native packing with exposure of aggregation-prone motifs, such as the B' helices in the phosphate-binding cassettes of both CNB domains. The topology of the β-sandwiches in these domains favors inter-molecular β-aggregation, which is suppressed in the ligand-bound states of RIα under physiological conditions. Moreover, our results reveal that the CNB domains persist as structural cores through heat-denaturation. © 2011 Dao et al
New Mechanics of Traumatic Brain Injury
The prediction and prevention of traumatic brain injury is a very important
aspect of preventive medical science. This paper proposes a new coupled
loading-rate hypothesis for the traumatic brain injury (TBI), which states that
the main cause of the TBI is an external Euclidean jolt, or SE(3)-jolt, an
impulsive loading that strikes the head in several coupled degrees-of-freedom
simultaneously. To show this, based on the previously defined covariant force
law, we formulate the coupled Newton-Euler dynamics of brain's micro-motions
within the cerebrospinal fluid and derive from it the coupled SE(3)-jolt
dynamics. The SE(3)-jolt is a cause of the TBI in two forms of brain's rapid
discontinuous deformations: translational dislocations and rotational
disclinations. Brain's dislocations and disclinations, caused by the
SE(3)-jolt, are described using the Cosserat multipolar viscoelastic continuum
brain model.
Keywords: Traumatic brain injuries, coupled loading-rate hypothesis,
Euclidean jolt, coupled Newton-Euler dynamics, brain's dislocations and
disclinationsComment: 18 pages, 1 figure, Late
Introduction to the special issue: after trust
“Trust” has long been seen as critical to the success and durability of trading networks, and conceptualised as a positive moral sentiment that is embedded in shared kinship, ethnicity or friendship, or in shared frameworks of morality. Other recent studies of business communities suggest that the ability to work in settings characterised by pervasive mistrust is a key factor in the development of commercial acumen and determining success. This Special Issue argues that the focus on trust and mistrust, and the underlying concern with ethics and morality, obscure equally critical aspects that inform the durability of trading networks. It offers ethnographic accounts of different inter-Asian trading networks active in the city of Yiwu. One of China’s most dynamic and diverse ‘international trade cities’, Yiwu is home to the largest wholesale market of small commodities in the world, and attracts traders and merchants from across the planet; over 12,000 foreign traders are also resident in the city. The collected articles analyse the durability of these networks in relation to broader geopolitical processes and contexts, arguing that success often depends on the ability to negotiate geopolitical shifts and the faultlines of political identity. The articles trace traders’ efforts to create institutions that allow them to withstand geopolitical transformations. They also document the ability of trading networks to operate flexibly across different social fields, showing that resilience often depends on the ability to navigate and profit from shifting relations between economic, political and familial domains
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