The Flood Last Time: ‘Muck’ and the uses of history in Kara Walker’s ‘Rumination’ on Katrina

Kara Walker describes her book After the Deluge (2007) as “rumination” on Hurricane Katrina structured in the form of a “visual essay.” The book combines Walker's own artwork and the works of other artists into “a narrative of fluid symbols” in which the overarching analogy of “murky, toxic waters” holds the potential to “become the amniotic fluid of a potentially new and difficult birth.” This essay considers Walker's use of history within this collection of images to show how the book opens up ways to interrogate Katrina's particular significance as a wholly new, and yet eerily familiar, historical “event.” Nuancing a reading of Walker's book with reference to James Baldwin's The Fire Next Time (1963), to which After the Deluge implicitly alludes, the essay examines Walker's artistic challenge to the notion that history is a narratable account of a past that precedes the present and demonstrates how that challenge encourages us to think about the potential uses of history within civil rights discourse after Katrina

Identification of the major cause of endemically poor mobilities in SiC/SiO2 structures

Materials with good carrier mobilities are desired for device applications, but in real devices the mobilities are usually limited by the presence of interfaces and contacts. Mobility degradation at semiconductor-dielectric interfaces is generally attributed to defects at the interface or inside the dielectric, as is the case in Si/SiO2 structures, where processing does not introduce detrimental defects in the semiconductor. In the case of SiC/SiO2 structures, a decade of research focused on reducing or passivating interface and oxide defects, but the low mobilities have persisted. By invoking theoretical results and available experimental evidence, we show that thermal oxidation generates carbon di-interstitial defects inside the semiconductor substrate and that they are a major cause of the poor mobility in SiC/SiO2 structures

Internal rationality, learning and imperfect information

We construct, estimate and explore the monetary policy consequences of a New Keynesian (NK) behavioural model with bounded-rationality and heterogeneous agents. We radically depart from most existing models of this genre in our treatment of bounded rationality and learning. Instead of the usual Euler learning approach, we assume that agents are internally rational (IR) given their beliefs of aggregate states and prices. The model is inhabited by fully rational (RE) and IR agents where the latter use simple heuristic rules to forecast aggregate variables exogenous to their micro-environment. We find that IR results in an NK model with more persistence and a smaller policy space for rule parameters that induce stability and determinacy. In the most general form of the model, agents learn from their forecasting errors by observing and comparing them with those under RE making the composition of the two types endogenous. In a Bayesian estimation with fixed proportions of RE and IR agents and a general heuristic forecasting rule we find that a pure IR model fits the data better than the pure RE case. However, the latter with imperfect rather than the standard perfect information assumption outperforms IR (easily) and RE-IR composites (slightly), but second moment comparisons suggest that the RE-IR composite can match data better. Our findings suggest that Kalman-filtering learning with RE can match bounded-rationality in matching persistence seen in the data

Designing Robust Monetary Policy Using Prediction Pools

How should a forward-looking policy maker conduct monetary policy when she has a finite set of models at her disposal, none of which are believed to be the true data generating process? In our approach, the policy makerfirst assigns weights to models based on relative forecasting performance rather than in-sample fit, consistent with her forward-looking objective. These weights are then used to solve a policy design prob- lem that selects the optimized Taylor-type interest-rate rule that is robust to model uncertainty across a set of well-established DSGE models with and without financial frictions. We find that the choice of weights has a significant impact on the robust optimized rule which is more inertial and aggressive than either the non-robust single model counterparts or the optimal robust rule based on backward-looking weights as in the common alternative Bayesian Model Averaging. Importantly, we show that a price-level rule has excellent welfare and robustness properties, and therefore should be viewed as a key instrument for policy makers facing uncertainty over the nature of financial frictions

Study of non-collinear parton dynamics in the prompt photon photoproduction at HERA

We investigate the prompt photon photoproduction at HERA within the framework of kt-factorization QCD approach. Our consideration is based on the off-shell matrix elements for the underlying partonic subprocesses. The unintegrated parton densities in a proton and in a photon are determined using the Kimber-Martin-Ryskin (KMR) prescription. Additionally, we use the CCFM-evolved unintegrated gluon as well as valence and sea quark distributions in a proton. A conservative error analisys is performed. Both inclusive and associated with the hadronic jet production rates are investigated. The theoretical results are compared with the recent experimental data taken by the H1 and ZEUS collaborations. We study also the specific kinematical properties of the photon-jet system which are strongly sensitive to the transverse momentum of incoming partons. Using the KMR scheme, the contribution from the quarks emerging from the earlier steps of the parton evolution is estimated and found to be of 15 - 20 approximately.Comment: 22 pages, 13 figures, 2 tabl

Relaxation paths for single modes of vibrations in isolated molecules

A numerical simulation of vibrational excitation of molecules was devised, and used to excite computational models of common molecules into a prescribed, pure, normal vibration mode in the ground electronic state, with varying, controlable energy content. The redistribution of this energy (either non-chaotic or irreversible IVR) within the isolated, free molecule is then followed in time with a view to determining the coupling strength between modes. This work was triggered by the need to predict the general characters of the infrared spectra to be expected from molecules in interstellar space, after being excited by photon absorption or reaction with a radical. It is found that IVR from a pure normal mode is very "restricted" indeed at energy contents of one mode quantum or so. However, as this is increased, or when the excitation is localized, our approach allows us to isolate, describe and quantify a number of interesting phenomena, known to chemists and in non-linear mechanics, but difficult to demonstrate experimentally: frequency dragging, mode locking or quenching or, still, instability near a potential surface crossing, the first step to generalized chaos as the energy content per mode is increased.Comment: 25 pages, 15 figures; accepted by J. Atom. Phys.

The WNK-regulated SPAK/OSR1 kinases directly phosphorylate and inhibit the K+-Cl- co-transporters

This is the final version of the article. Available from Portland Press via the DOI in this record.There is another ORE record for this publication: http://hdl.handle.net/10871/32310Precise homoeostasis of the intracellular concentration of Cl- is achieved via the co-ordinated activities of the Cl- influx and efflux. We demonstrate that the WNK (WNK lysine-deficient protein kinase)-activated SPAK (SPS1-related proline/alanine-rich kinase)/OSR1 (oxidative stress-responsive kinase 1) known to directly phosphorylate and stimulate the N[K]CCs (Na+-K+ ion co-transporters), also promote inhibition of the KCCs (K+-Cl- co-transporters) by directly phosphorylating a recently described C-terminal threonine residue conserved in all KCC isoforms [Site-2 (Thr1048)]. First, we demonstrate that SPAK and OSR1, in the presence of the MO25 regulatory subunit, robustly phosphorylates all KCC isoforms at Site-2 in vitro. Secondly, STOCK1S-50699, a WNK pathway inhibitor, suppresses SPAK/OSR1 activation and KCC3A Site-2 phosphorylation with similar efficiency. Thirdly, in ES (embryonic stem) cells lacking SPAK/OSR1 activity, endogenous phosphorylation of KCC isoforms at Site-2 is abolished and these cells display elevated basal activity of 86Rb+ uptake that was not markedly stimulated further by hypotonic high K+ conditions, consistent with KCC3A activation. Fourthly, a tight correlation exists between SPAK/OSR1 activity and the magnitude of KCC3A Site-2 phosphorylation. Lastly, a Site-2 alanine KCC3A mutant preventing SPAK/OSR1 phosphorylation exhibits increased activity. We also observe that KCCs are directly phosphorylated by SPAK/OSR1, at a novel Site-3 (Thr5 in KCC1/KCC3 and Thr6 in KCC2/KCC4), and a previously recognized KCC3-specific residue, Site-4 (Ser96). These data demonstrate that the WNK-regulated SPAK/OSR1 kinases directly phosphorylate the N[K]CCs and KCCs, promoting their stimulation and inhibition respectively. Given these reciprocal actions with anticipated net effects of increasing Cl- influx, we propose that the targeting of WNK-SPAK/OSR1 with kinase inhibitors might be a novel potent strategy to enhance cellular Cl- extrusion, with potential implications for the therapeutic modulation of epithelial and neuronal ion transport in human disease states.This work was supported by the Medical Research Council and the Wellcome Trust [grant number 091415] as well as the pharmaceutical companies supporting the Division of Signal Transduction Therapy Unit (AstraZeneca, Boehringer-Ingelheim, GlaxoSmithKline, Merck KgaA, Janssen Pharmaceutica and Pfizer). K.T.K. is supported by the Manton Center for Orphan Diseases at Children's Hospital Boston at Harvard Medical School, and the Harvard/MIT Joint Research Grants Program in Basic Neuroscience

Multi-gluon helicity amplitudes with one off-shell leg within high energy factorization

Basing on the Slavnov-Taylor identities, we derive a new prescription to obtain gauge invariant tree-level scattering amplitudes for the process g*g->Ng within high energy factorization. Using the helicity method, we check the formalism up to several final state gluons, and we present analytical formulas for the the helicity amplitudes for N=2. We also compare the method with Lipatov's effective action approach.Comment: 25 pages, quite a few figures, an appendix added, typos correcte

A comparative study of small x Monte Carlos with and without QCD coherence effects

We compare two Monte Carlo implementations of resummation schemes for the description of parton evolution at small values of Bjorken x. One of them is based on the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution equation and generates fully differential parton distributions in momentum space making use of reggeized gluons. The other one is based on the Catani-Ciafaloni-Fiorani-Marchesini (CCFM) partonic kernel where QCD coherence effects are introduced. It has been argued that both approaches agree with each other in the x -> 0 limit. We show that this is not the case for azimuthal angle dependent quantities since at high energies the BFKL approach is dominated by its zero conformal spin component while the CCFM gluon Green function receives contributions from all conformal spins even at very small x.Comment: 19 pages, 19 figure