Sedimentation in an artificial lake -Lake Matahina, Bay of Plenty

Lake Matahina, an 8 km long hydroelectric storage reservoir, is a small (2.5 km2), 50 m deep, warm monomictic, gorge-type lake whose internal circulation is controlled by the inflowing Rangitaiki River which drains a greywacke and acid volcanic catchment. Three major proximal to distal subenvironments are defined for the lake on the basis of surficial sediment character and dominant depositional process: (a) fluvial-glassy, quartzofeld-spathic, and lithic gravel-sand mixtures deposited from contact and saltation loads in less than 3 m depth; (b) (pro-)deltaic-quartzofeldspathic and glassy sand-silt mixtures deposited from graded and uniform suspension loads in 3-20 m depth; and (c) basinal-diatomaceous, argillaceous, and glassy silt-clay mixtures deposited from uniform and pelagic suspension loads in 20-50 m depth. The delta face has been prograding into the lake at a rate of 35-40 m/year and vertical accretion rates in pro-delta areas are 15-20 cm/year. Basinal deposits are fed mainly from river plume dispersion involving overflows, interflows, and underflows, and by pelagic settling, and sedimentation rates behind the dam have averaged about 2 cm/year. Occasional fine sand layers in muds of basinal cores attest to density currents or underflows generated during river flooding flowing the length of the lake along a sublacustrine channel marking the position of the now submerged channel of the Rangitaiki River

OR15-5 Human Sex Determination at the Edge of Ambiguity: Impaired SRY Phosphorylation Attenuates Expression of the Male Program

A paradox is posed by metazoan gene-regulatory networks (GRNs) that are robust yet evolvable. Insight may be obtained through studies of bistable genetic circuits mediating developmental decisions. A model in organogenesis is provided by the sex-specific differentiation of the embryonic gonadal ridge to form a testis or ovary. Here, we investigated a Swyer mutation in human testis-determining factor SRY that impairs its phosphorylation in association with variable developmental outcomes: fertile male, intersex, or infertile female (46, XY pure gonadal dysgenesis). The mutation (R30I) abrogates serine phosphorylation within a putative target site for protein kinase A (PKA) N-terminal to the HMG box. Diverse processes can be regulated by protein phosphorylation, including DNA recognition by transcription factors (TFs). Phosphorylation of this site in human SRY (LRRSSSFLCT; italics) in vitro was previously shown to enhance specific DNA affinity. Biological consequences of the mutation were evaluated in SRY-responsive mammalian cell lines following transient transfection. The mutation attenuated in concert occupancy of a target enhancer (TESCO) and SOX9 transcriptional activation. These perturbations were mitigated by acidic substitution (LRIDDDFL) whereas Ala substitutions (RRAAAFL or RIAAAFL) attenuated activity to an extent similar to R30I alone. No differences were observed in nuclear localization. Mutagenesis suggested that the central Ser is most efficiently phosphorylated in accord with PKA targeting rules. Replacement of the native site by an optimized “Kemptide” PKA site (LRRASLGCT) enhanced both SRY phosphorylation and SOX9 transcriptional activation whereas a “swapped” protein-kinase C determinant (LRRSSFRRCT) blocked phosphorylation. Among SRY variants, extent of cellular phosphorylation mirrored relative in vitro efficiencies of synthetic SRY-derived peptides as PKA-specific substrates. Although several kinases are predicted in silico to target this tri-serine motif, cell-based studies implicate PKA as the relevant kinase in vivo. Our results provide evidence that primate Sry requires its phosphorylation for full gene-regulatory activity. A PKA site N-terminal to the SRY HMG box, unique to primates, exemplifies network “tinkering” through recruitment of a new regulatory linkage. Molecular characterization of the R30I inherited Swyer mutation in SRY thus demonstrates that impaired TF phosphorylation can attenuate a human developmental switch at the edge of ambiguity

Expanding research on corporate corruption, management and organizations

In this special issue introduction, we briefly describe a variety of research paths researchers have followed to study the multifaceted phenomenon of corruption. Furthermore, we classify the papers included in this special issue according to their contribution to these research paths and briefly preview them. Finally, drawing on these four research paths and the papers included in this special issue, we propose a six-item agenda for future research on corruption

First-principles calculation of DNA looping in tethered particle experiments

We calculate the probability of DNA loop formation mediated by regulatory proteins such as Lac repressor (LacI), using a mathematical model of DNA elasticity. Our model is adapted to calculating quantities directly observable in Tethered Particle Motion (TPM) experiments, and it accounts for all the entropic forces present in such experiments. Our model has no free parameters; it characterizes DNA elasticity using information obtained in other kinds of experiments. [...] We show how to compute both the "looping J factor" (or equivalently, the looping free energy) for various DNA construct geometries and LacI concentrations, as well as the detailed probability density function of bead excursions. We also show how to extract the same quantities from recent experimental data on tethered particle motion, and then compare to our model's predictions. [...] Our model successfully reproduces the detailed distributions of bead excursion, including their surprising three-peak structure, without any fit parameters and without invoking any alternative conformation of the LacI tetramer. Indeed, the model qualitatively reproduces the observed dependence of these distributions on tether length (e.g., phasing) and on LacI concentration (titration). However, for short DNA loops (around 95 basepairs) the experiments show more looping than is predicted by the harmonic-elasticity model, echoing other recent experimental results. Because the experiments we study are done in vitro, this anomalously high looping cannot be rationalized as resulting from the presence of DNA-bending proteins or other cellular machinery. We also show that it is unlikely to be the result of a hypothetical "open" conformation of the LacI tetramer.Comment: See the supplement at http://www.physics.upenn.edu/~pcn/Ms/TowlesEtalSuppl.pdf . This revised version accepted for publication at Physical Biolog

The Role of Narrative Fiction and Semi-Fiction in Organizational Studies

In this chapter, we discuss the use of narrative fiction and semi-fiction in organizational research and explore the strengths and weaknesses of these alternative approaches. We begin with an introduction reviewing the existing literature and clarifying what we mean by fiction and semi-fiction. We then present and discuss examples of fiction and semi-fiction focusing on how these approaches can be used in organizational research. We argue that fiction is more useful as a source of data and as a way of representing theory to an audience. Semi-fiction, on the other hand, provides a novel approach to the production and representation of theory. In both cases, researchers face a number of challenges, but also gain access to new and powerful techniques for developing insights into organizational topics

Text me! New consumer practices and change in organizational fields

While scholars have provided increasingly well-developed theoretical frameworks for understanding the role of institutional entrepreneurs and other purposeful actors in bringing about change in organizational fields, much less attention has been paid to the role of unorganized, nonstrategic actors in catalyzing change. In particular, the role of consumers remains largely uninvestigated. In this article, we draw on a case of the introduction of text messaging in the United Kingdom to explore the role of consumers in catalyzing change in organizational fields. Text messaging has become a widely diffused and institutionalized communication practice, in part changing mobile telephony from a voice-based, aural, and synchronous experience to a text-based, visual, and asynchronous experience. As consumers innovated and diffused new practices around this product, their actions led to significant changes in the field. We suggest how and under what conditions consumers are likely to innovate at the micro level and, with the subsequent involvement of other actors, catalyze change at the field level. Our primary contribution is to show how the cumulative effect of the spontaneous activities of one important and particularly dispersed and unorganized group can lead to changes in a field. By showing how change can result from the uncoordinated actions of consumers accumulating and converging over time, we provide an alternative explanation of change in organizational fields that does not privilege purposeful actors such as institutional entrepreneurs

Excluded-Volume Effects in Tethered-Particle Experiments: Bead Size Matters

The tethered-particle method is a single-molecule technique that has been used to explore the dynamics of a variety of macromolecules of biological interest. We give a theoretical analysis of the particle motions in such experiments. Our analysis reveals that the proximity of the tethered bead to a nearby surface (the microscope slide) gives rise to a volume-exclusion effect, resulting in an entropic force on the molecule. This force stretches the molecule, changing its statistical properties. In particular, the proximity of bead and surface brings about intriguing scaling relations between key observables (statistical moments of the bead) and parameters such as the bead size and contour length of the molecule. We present both approximate analytic solutions and numerical results for these effects in both flexible and semiflexible tethers. Finally, our results give a precise, experimentally-testable prediction for the probability distribution of the distance between the polymer attachment point and the center of the mobile bead.Comment: 4 pages, 3 figure

Paediatric treatment costs and the HIV epidemic

A CAJM on pediatric treatment costs and the effects of HIV pandemic in Malawi.As the AIDS epidemic puts additional strains on the already overburdened health care systems in sub-Saharan Africa, it becomes more important to estimate the cost of the epidemic in terms of health personnel and drug treatments. A retrospective review of 250 randomly selected paediatric admissions to a referral hospital in Malawi was undertaken. Groupings of “pos- sible/probable AIDS” and “probably not AIDS” were used in a comparative analysis of treatment costs. Estimated costs of treatments were significantly lower than those calculated in a study from Zimbabwe using different methodology. Meningitis was the most expensive condition to treat and accounted for a greater percentage of overall cost than either acute respiratory infection, diarihoeal disease or measles

Process of making a non-circular cross-sectional fiber

A melt extrusion composition made by combining about 99.9 to about 98.5 weight percent of at least one polyester and about 0.1 to about 1.5 weight percent additive provides for a polyester or copolyester non-circular cross-sectional fiber having at least four percent improved shape retention as compared to the same fiber made from a melt extrusion composition without the additive. The additive is present at the air-polymer interfacial surface during melt spinning. A method of making the fiber is also disclosed