1,283 research outputs found
Experimental ischemia–reperfusion: biases and myths—the proximal vs. distal hypoxic tubular injury debate revisited
Although the understanding of processes associated with hypoxic tubular cell injury has remarkably improved, controversies remain regarding the appropriateness of various animal models to the human syndrome of acute kidney injury (AKI). We herein compare available experimental models of hypoxic acute kidney damage, which differ both conceptually and morphologically in the distribution of tubular cell injury. Tubular segment types differ in their capacity to mount hypoxia-adaptive responses, mediated by hypoxia-inducible factors (HIFs), and in cell type–specific molecules shed into the urine, which may serve as early biomarkers for renal damage. These differences may be of value in the perception of the human AKI, its detection, and prevention
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Why Is Diabetes Mellitus a Risk Factor for Contrast-Induced Nephropathy?
Contrast-induced nephropathy (CIN) remains a leading cause of iatrogenic acute kidney injury, as the usage of contrast media for imaging and intravascular intervention keeps expanding. Diabetes is an important predisposing factor for CIN, particularly in patients with renal functional impairment. Renal hypoxia, combined with the generation of reactive oxygen species, plays a central role in the pathogenesis of CIN, and the diabetic kidney is particularly susceptible to intensified hypoxic and oxidative stress following the administration of contrast media. The pathophysiology of this vulnerability is complex and involves various mechanisms, including a priori enhanced tubular transport activity, oxygen consumption, and the generation of reactive oxygen species. The regulation of vascular tone and peritubular blood flow may also be altered, particularly due to defective nitrovasodilation, enhanced endothelin production, and a particular hyperresponsiveness to adenosine-related vasoconstriction. In addition, micro- and macrovascular diseases and chronic tubulointerstitial changes further compromise regional oxygen delivery, and renal antioxidant capacity might be hampered. A better understanding of these mechanisms and their control in the diabetic patient may initiate novel strategies in the prevention of contrast nephropathy in these susceptible patients
Solving airline operations problems using specialized agents in a distributed multi-agent system
An airline schedule very rarely operates as planned. Problems related with aircrafts, crew members and passengers are common and the actions towards the solution of these problems are usually known as operations recovery. The Airline Operations Control Center (AOCC) tries to solve these problems with the minimum cost and satisfying all the required rules. In this paper we present the implementation of a Distributed Multi-Agent System (MAS) representing the existing roles in an AOCC, This MAS deals with several operational bases and for each type of operation problems it has several specialized software agents that implement different algorithms (heuristic, AI, OR, etc.), competing to find the best solution for each problem. We present a real case study taken from an AOCC where a crew recovery problem is solved. Computational results using a real airline schedule are presented, including a comparison with a solution for the same problem found by the human operators in the AOCC. We show that, even in simple problems and when comparing with solutions found by human operators, it is possible to find valid solutions, in less time and with a smaller cost
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Vagus nerve controls resolution and pro-resolving mediators of inflammation
Resolution of inflammation is now recognized as a biosynthetically active process involving pro-resolving mediators. Here, we show in zymosan-initiated peritoneal inflammation that the vagus nerve regulates local expression of netrin-1, an axonal guidance molecule that activates resolution, and that vagotomy reduced local pro-resolving mediators, thereby delaying resolution. In netrin-1+/− mice, resolvin D1 (RvD1) was less effective in reducing neutrophil influx promoting resolution of peritonitis compared with Ntn1+/+. Netrin-1 shortened the resolution interval, decreasing exudate neutrophils, reducing proinflammatory mediators, and stimulating the production of resolvins, protectins, and lipoxins. Human monocytes incubated with netrin-1 produced proresolving mediators, including resolvins and lipoxins. Netrin-1 and RvD1 displayed bidirectional activation in that they stimulated each other’s expression and enhanced efferocytosis. These results indicate that the vagus nerve regulates both netrin-1 and pro-resolving lipid mediators, which act in a bidirectional fashion to stimulate resolution, and provide evidence for a novel mechanism for local neuronal control of resolution
Single-shot carrier-envelope-phase measurement in ambient air
The ability to measure and control the carrier envelope phase (CEP) of
few-cycle laser pulses is of paramount importance for both frequency metrology
and attosecond science. Here, we present a phase meter relying on the
CEP-dependent photocurrents induced by circularly polarized few-cycle pulses
focused between electrodes in ambient air. The new device facilitates compact
single-shot, CEP measurements under ambient conditions and promises CEP tagging
at repetition rates orders of magnitude higher than most conventional CEP
detection schemes as well as straightforward implementation at longer
wavelengths
Microresonator solitons for massively parallel coherent optical communications
Optical solitons are waveforms that preserve their shape while propagating,
relying on a balance of dispersion and nonlinearity. Soliton-based data
transmission schemes were investigated in the 1980s, promising to overcome the
limitations imposed by dispersion of optical fibers. These approaches, however,
were eventually abandoned in favor of wavelength-division multiplexing (WDM)
schemes that are easier to implement and offer improved scalability to higher
data rates. Here, we show that solitons may experience a comeback in optical
communications, this time not as a competitor, but as a key element of
massively parallel WDM. Instead of encoding data on the soliton itself, we
exploit continuously circulating dissipative Kerr solitons (DKS) in a
microresonator. DKS are generated in an integrated silicon nitride
microresonator by four-photon interactions mediated by Kerr nonlinearity,
leading to low-noise, spectrally smooth and broadband optical frequency combs.
In our experiments, we use two interleaved soliton Kerr combs to transmit a
data stream of more than 50Tbit/s on a total of 179 individual optical carriers
that span the entire telecommunication C and L bands. Equally important, we
demonstrate coherent detection of a WDM data stream by using a pair of
microresonator Kerr soliton combs - one as a multi-wavelength light source at
the transmitter, and another one as a corresponding local oscillator (LO) at
the receiver. This approach exploits the scalability advantages of
microresonator soliton comb sources for massively parallel optical
communications both at the transmitter and receiver side. Taken together, the
results prove the significant potential of these sources to replace arrays of
continuous-wave lasers in high-speed communications.Comment: 10 pages, 3 figure
Tunable 2D Electron- and 2D Hole States Observed at Fe/SrTiO Interfaces
Oxide electronics provide the key concepts and materials for enhancing
silicon-based semiconductor technologies with novel functionalities. However, a
basic but key property of semiconductor devices still needs to be unveiled in
its oxidic counterparts: the ability to set or even switch between two types of
carriers - either negatively (n) charged electrons or positively (p) charged
holes. Here, we provide direct evidence for individually emerging n- or p-type
2D band dispersions in STO-based heterostructures using resonant photoelectron
spectroscopy. The key to tuning the carrier character is the oxidation state of
an adjacent Fe-based interface layer: For Fe and FeO, hole bands emerge in the
empty band gap region of STO due to hybridization of Ti and Fe-derived states
across the interface, while for FeO overlayers, an 2D electron system
is formed. Unexpected oxygen vacancy characteristics arise for the hole-type
interfaces, which as of yet had been exclusively assigned to the emergence of
2DESs. In general, this finding opens up the possibility to straightforwardly
switch the type of conductivity at STO interfaces by the oxidation state of a
redox overlayer. This will extend the spectrum of phenomena in oxide
electronics, including the realization of combined n/p-type all-oxide
transistors or logic gates.Comment: Advanced Materials (accepted
Public Benefits of Undeveloped Lands on Urban Outskirts: Non-Market Valuation Studies and their Role in Land Use Plans
Over the past three decades, the economics profession has developed methods for estimating the public benefits of green spaces, providing an opportunity to incorporate such information into land-use planning. While federal regulations routinely require such estimates for major regulations, the extent to which they are used in local land use plans is not clear. This paper reviews the literature on public values for lands on urban outskirts, not just to survey their methods or empirical findings, but to evaluate the role they have played--or have the potential to play-- in actual land use plans. Based on interviews with authors and representatives of funding agencies and local land trusts, it appears that academic work has had a mixed reception in the policy world. Reasons for this include a lack of interest in making academic work accessible to policy makers, emphasizing revealed preference methods which are inconsistent with policy priorities related to nonuse values, and emphasis on benefit-cost analyses. Nevertheless, there are examples of success stories that illustrate how such information can play a vital role in the design of conservation policies. Working Paper 07-2
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