University of Notre Dame

About: University of Notre Dame is a education organization based out in Notre Dame, Indiana, United States. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 22238 authors who have published 55201 publications receiving 2032925 citations. The organization is also known as: University of Notre Dame du Lac & University of Notre Dame, South Bend.

From Greenland to green lakes: Cultural eutrophication and the loss of benthic pathways in lakes

Abstract: Benthic community responses to lake eutrophication are poorly understood relative to pelagic responses. We compared phytoplankton and periphyton productivity along a eutrophication gradient in Greenland, U.S., and Danish lakes. Phytoplankton productivity increased along the phosphorus gradient (total phosphorus [TP] 5 2‐430 mg m 23 ), but whole-lake benthic algal productivity decreased, substantially depressing increases in primary productivity at the whole-lake scale. In shallow, oligotrophic Greenland lakes, periphyton was responsible for 80‐98% of primary production, whereas in Danish lakes with TP . 100 mg m 23 , phytoplankton were responsible for nearly 100% of primary production. Benthic contributions ranged from 5 to 80% depending on morphometry and littoral habitat composition in lakes with intermediate phosphorus concentrations. Thus, eutrophication was characterized by a switch from benthic to pelagic dominance of primary productivity. Carbon stable isotope analysis showed that the redistribution of primary production entailed a similar shift from periphyton to phytoplankton in the diets of zoobenthos. Benthic and pelagic habitats were energetically linked through food web interactions, but eutrophication eroded the benthic primary production pathway.

A Bayesian approach to image expansion for improved definition

Abstract: Accurate image expansion is important in many areas of image analysis. Common methods of expansion, such as linear and spline techniques, tend to smooth the image data at edge regions. This paper introduces a method for nonlinear image expansion which preserves the discontinuities of the original image, producing an expanded image with improved definition. The maximum a posteriori (MAP) estimation techniques that are proposed for noise-free and noisy images result in the optimization of convex functionals. The expanded images produced from these methods will be shown to be aesthetically and quantitatively superior to images expanded by the standard methods of replication, linear interpolation, and cubic B-spline expansion. >

Firm-Value Effects of Carbon Emissions and Carbon Disclosures

Abstract: Using hand-collected carbon emissions data for 2006 to 2008 that were voluntarily disclosed to the Carbon Disclosure Project by S&P 500 firms, we examine the effects on firm value of carbon emissions and of the act of voluntarily disclosing carbon emissions. Correcting for self-selection bias from managers' decisions to disclose carbon emissions, we find that, on average, for every additional thousand metric tons of carbon emissions, firm value decreases by $212,000, where the median emissions for the disclosing firms in our sample are 1.07 million metric tons. We also examine the firm-value effects of managers' decisions to disclose carbon emissions. We find that the median value of firms that disclose their carbon emissions is about $2.3 billion higher than that of comparable non-disclosing firms. Our results indicate that the markets penalize all firms for their carbon emissions, but a further penalty is imposed on firms that do not disclose emissions information. The results are consistent w...

Picosecond Dynamics of Silver Nanoclusters. Photoejection of Electrons and Fragmentation

Abstract: Silver colloids of particle diameter 40−60 nm have been synthesized using a chemical reduction method in aqueous medium. These nanoclusters are photoactive and exhibit transient bleaching in the 400−500 nm region followed by a strong absorption in the visible−near-infrared region when subjected to 355 nm laser-pulse excitation. The transient bleaching of the surface plasmon absorption band is a monophotonic process, while the absorption growth in the red region is a biphotonic process arising from the photoejection of electrons. The 40−60 nm clusters were observed to break up into smaller clusters (5−20 nm) with 355 nm laser-pulse excitation. The choice of excitation wavelength provides the size selectivity in the fragmentation of the clusters. For example, when the excitation wavelength was switched to 532 nm, only larger (or irregularly shaped) particles were found to break up.

A PML–PPAR-δ pathway for fatty acid oxidation regulates hematopoietic stem cell maintenance.

Abstract: Stem-cell function is an exquisitely regulated process. Thus far, the contribution of metabolic cues to stem-cell function has not been well understood. Here we identify a previously unknown promyelocytic leukemia (PML)–peroxisome proliferator-activated receptor δ (PPAR-δ)–fatty-acid oxidation (FAO) pathway for the maintenance of hematopoietic stem cells (HSCs). We have found that loss of PPAR-δ or inhibition of mitochondrial FAO induces loss of HSC maintenance, whereas treatment with PPAR-δ agonists improved HSC maintenance. PML exerts its essential role in HSC maintenance through regulation of PPAR signaling and FAO. Mechanistically, the PML–PPAR-δ–FAO pathway controls the asymmetric division of HSCs. Deletion of Ppard or Pml as well as inhibition of FAO results in the symmetric commitment of HSC daughter cells, whereas PPAR-δ activation increased asymmetric cell division. Thus, our findings identify a metabolic switch for the control of HSC cell fate with potential therapeutic implications.