252 research outputs found
The incoherence of institutional reform: decentralization as a structural solution to immediate political needs
Institutional reforms are structural changes in the rules and norms of authority, with effects that are long-term and unpredictable on government, politics, and society. But leaders may undertake them to solve unrelated, discrete, short-term political problems. Understanding the latter is key to understanding the characteristics of many real reforms, and hence their fate. We introduce the concept of instrumental incoherence and use it to construct a theory of decentralization where reform is motivated by orthogonal objectives. We show that reformersโ incentives map onto the specifics of reform design via their side effects, not their main effects, which in turn lead to the medium- and long-term consequences eventually realized. We characterize downwardly accountable decentralization, which ties the hands of the center to empower local voters, vs. upwardly accountable decentralization, which ties the hands of local government to empower the center. We use these ideas to explain highly divergent outcomes in two extreme cases, Bolivia and Pakistan, using detailed, original evidence. Our analysis likely extends to a broader class of reforms where the incentives of agents pursuing a change, and the effects of that change, are highly asymmetric in time and dimension
Instrumental incoherence in institutional reform: decentralization as a structural solution to political exigency
If the effects of institutional reforms are long-term and unpredictable, why do leaders undertake them? We analyze reforms where the incentives of agents pursuing a change, and the effects of that change, are highly asymmetric in time and policy dimensions. We examine detailed evidence from decentralization in Bolivia and Pakistan, and explain very different outcomes with a simple game-theoretic model of the incentives and interactions amongst ruling and opposition parties, and civil society, over multiple periods. Politicians decentralize to solve a discrete, often short-term political problem. But decentralization is neither short-term nor discrete, but rather a deep change in the structure of public finance and authority with long-term effects on government, politics and society. Understanding the original problem is key to understanding the characteristics of the reform implemented, as well as its ultimate success or failure. Our analysis likely extends to a broader class of deep reforms with long-term consequences
JS-K, a Nitric Oxide Prodrug, Has Enhanced Cytotoxicity in Colon Cancer Cells with Knockdown of Thioredoxin Reductase 1
The selenoenzyme thioredoxin reductase 1 has a complex role relating to cell growth. It is induced as a component of the cellular response to potentially mutagenic oxidants, but also appears to provide growth advantages to transformed cells by inhibiting apoptosis. In addition, selenocysteine-deficient or alkylated forms of thioredoxin reductase 1 have also demonstrated oxidative, pro-apoptotic activity. Therefore, a greater understanding of the role of thioredoxin reductase in redox initiated apoptotic processes is warranted.The role of thioredoxin reductase 1 in RKO cells was evaluated by attenuating endogenous thioredoxin reductase 1 expression with siRNA and then either inducing a selenium-deficient thioredoxin reductase or treatment with distinct redox challenges including, hydrogen peroxide, an oxidized lipid, 4-hydroxy-2-nonenol, and a nitric oxide donating prodrug. Thioredoxin redox status, cellular viability, and effector caspase activity were measured.In cells with attenuated endogenous thioredoxin reductase 1, a stably integrated selenocysteine-deficient form of the enzyme was induced but did not alter either the thioredoxin redox status or the cellular growth kinetics. The oxidized lipid and the nitric oxide donor demonstrated enhanced cytotoxicity when thioredoxin reductase 1 was knocked-down; however, the effect was more pronounced with the nitric oxide prodrug. These results are consistent with the hypothesis that attenuation of the thioredoxin-system can promote apoptosis in a nitric oxide-dependent manner
Galactic Center Pulsars with the ngVLA
Pulsars in the Galactic Center (GC) are important probes of General
Relativity, star formation, stellar dynamics, stellar evolution, and the
interstellar medium. Despite years of searching, only a handful of pulsars in
the central 0.5 deg are known. The high-frequency sensitivity of ngVLA will
open a new window for discovery and characterization of pulsars in the GC. A
pulsar in orbit around the GC black hole, Sgr A*, will provide an unprecedented
probe of black hole physics and General Relativity.Comment: To be published in the ASP Monograph Series, "Science with a
Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA
Temporal and Spectral Properties of the Persistent Radio Source Associated with FRB 20190520B with the VLA
Among more than 800 known fast radio bursts (FRBs), only two, namely FRB
20121102A and FRB 20190520B, are confirmed to be associated with a persistent
radio sources (PRS). Here we report evidence of apparent temporal variability
in the PRS associated with the bursting FRB 20190520B based on the Karl G.
Jansky Very Large Array (VLA) observations taken in 2020 and 2021. Based on the
analysis of epoch-to-epoch variability of the PRS at L, S, C, and X band in
1-12 GHz, we detected not only overall marginal variability but also a likely
radio flux decrease ( 3.2 ) between the observations taken in
2020 and 2021 at 3 GHz. Assuming no spectral variation in the PRS during these
observations, we found the evidence for an overall broadband radio flux
decrease by about 20 percent between the 2020 and the 2021 observations,
suggesting that the PRS probably evolves on the yearly time scale. If we
attribute the marginal variability at 3 GHz as intrinsic or due to
scintillation, the size of potential variable component of the PRS is
constrained to be sub-parsec. On the other hand, the size of the PRS can be
also constrained to be larger than about 0.22 parsec from the averaged radio
spectrum and the integrated radio luminosity in the 1-12 GHz band based on
equipartition and self-absorption arguments. We discuss potential origins of
the PRS and suggest that an accreting compact object origin might be able to
explain the PRS's temporal and spectral properties. Confirmation of variability
or flux decline of the PRS would be critical to our understanding of the PRS
and its relation to the bursting source.Comment: 12 pages, 3 figures, accepted for publication in Ap
Multi-Messenger Gravitational Wave Searches with Pulsar Timing Arrays: Application to 3C66B Using the NANOGrav 11-year Data Set
When galaxies merge, the supermassive black holes in their centers may form
binaries and, during the process of merger, emit low-frequency gravitational
radiation in the process. In this paper we consider the galaxy 3C66B, which was
used as the target of the first multi-messenger search for gravitational waves.
Due to the observed periodicities present in the photometric and astrometric
data of the source of the source, it has been theorized to contain a
supermassive black hole binary. Its apparent 1.05-year orbital period would
place the gravitational wave emission directly in the pulsar timing band. Since
the first pulsar timing array study of 3C66B, revised models of the source have
been published, and timing array sensitivities and techniques have improved
dramatically. With these advances, we further constrain the chirp mass of the
potential supermassive black hole binary in 3C66B to less than using data from the NANOGrav 11-year data set. This
upper limit provides a factor of 1.6 improvement over previous limits, and a
factor of 4.3 over the first search done. Nevertheless, the most recent orbital
model for the source is still consistent with our limit from pulsar timing
array data. In addition, we are able to quantify the improvement made by the
inclusion of source properties gleaned from electromagnetic data to `blind'
pulsar timing array searches. With these methods, it is apparent that it is not
necessary to obtain exact a priori knowledge of the period of a binary to gain
meaningful astrophysical inferences.Comment: 14 pages, 6 figures. Accepted by Ap
VAST: An ASKAP Survey for Variables and Slow Transients
The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an
unprecedented opportunity to investigate the transient sky at radio
wavelengths. In this paper we present VAST, an ASKAP survey for Variables and
Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP
to enable the discovery and investigation of variable and transient phenomena
from the local to the cosmological, including flare stars, intermittent
pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar
scintillation, radio supernovae and orphan afterglows of gamma ray bursts. In
addition, it will allow us to probe unexplored regions of parameter space where
new classes of transient sources may be detected. In this paper we review the
known radio transient and variable populations and the current results from
blind radio surveys. We outline a comprehensive program based on a multi-tiered
survey strategy to characterise the radio transient sky through detection and
monitoring of transient and variable sources on the ASKAP imaging timescales of
five seconds and greater. We also present an analysis of the expected source
populations that we will be able to detect with VAST.Comment: 29 pages, 8 figures. Submitted for publication in Pub. Astron. Soc.
Australi
Bioadhesive Controlled Metronidazole Release Matrix Based on Chitosan and Xanthan Gum
Metronidazole, a common antibacterial drug, was incorporated into a hydrophilic polymer matrix composed of chitosan xanthan gum mixture. Hydrogel formation of this binary chitosan-xanthan gum combination was tested for its ability to control the release of metronidazole as a drug model. This preparation (MZ-CR) was characterized by in vitro, ex vivo bioadhesion and in vivo bioavailability study. For comparison purposes a commercial extended release formulation of metronidazole (CMZ) was used as a reference. The in vitro drug-release profiles of metronidazole preparation and CMZ were similar in 0.1 M HCl and phosphate buffer pH 6.8. Moreover, metronidazole preparation and CMZ showed a similar detachment force to sheep stomach mucosa, while the bioadhesion of the metronidazole preparation was higher three times than CMZ to sheep duodenum. The results of in vivo study indicated that the absorption of metronidazole from the preparation was faster than that of CMZ. Also, MZ-CR leads to higher metronidazole Cmax and AUC relative to that of the CMZ. This increase in bioavailability might be explained by the bioadhesion of the preparation at the upper part of the small intestine that could result in an increase in the overall intestinal transit time. As a conclusion, formulating chitosan-xanthan gum mixture as a hydrophilic polymer matrix resulted in a superior pharmacokinetic parameters translated by better rate and extent of absorption of metronidazole
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