DRI Renewable Energy Center (REC) (NV)

The primary objective of this project was to utilize a flexible, energy-efficient facility, called the DRI Renewable Energy Experimental Facility (REEF) to support various renewable energy research and development (R&D) efforts, along with education and outreach activities. The REEF itself consists of two separate buildings: (1) a 1200-ft2 off-grid capable house and (2) a 600-ft2 workshop/garage to support larger-scale experimental work. Numerous enhancements were made to DRI's existing renewable power generation systems, and several additional components were incorporated to support operation of the REEF House. The power demands of this house are satisfied by integrating and controlling PV arrays, solar thermal systems, wind turbines, an electrolyzer for renewable hydrogen production, a gaseous-fuel internal combustion engine/generator set, and other components. Cooling needs of the REEF House are satisfied by an absorption chiller, driven by solar thermal collectors. The REEF Workshop includes a unique, solar air collector system that is integrated into the roof structure. This system provides space heating inside the Workshop, as well as a hot water supply. The Workshop houses a custom-designed process development unit (PDU) that is used to convert woody biomass into a friable, hydrophobic char that has physical and chemical properties similar to low grade coal. Besides providing sufficient space for operation of this PDU, the REEF Workshop supplies hot water that is used in the biomass treatment process. The DRI-REEF serves as a working laboratory for evaluating and optimizing the performance of renewable energy components within an integrated, residential-like setting. The modular nature of the system allows for exploring alternative configurations and control strategies. This experimental test bed is also highly valuable as an education and outreach tool both in providing an infrastructure for student research projects, and in highlighting renewable energy features to the public

Diameter dependence of the optoelectronic properties of single walled carbon nanotubes determined by ellipsometry

International audienceWe report ellipsometric measurement on single walled carbon nanotube (SWCNT) films performed in a large spectral range from 0.07eV to 4.97eV. The complex dielectric functions of SWCNTs are correlated to their diameter distribution extracted from transmission electron microscopy. Here we show that the transition energies between Van Hove singularities are directly related to the strong one dimensional confinement. In the infrared spectral range, the real part of the dielectric function becomes negative. The electronic properties of SWCNTs are extracted from ellipsometry by using a Drude model. The mobility and the mean free path of charge carriers are limited by the high number of SWCNT contacts. In accordance with tight binding simulation, the conductivity and the charge carrier concentration increase with the SWCNT diameter. Finally, we demonstrate that the S-plasmon energy depends on the charge carrier concentration.

Real-time, label-free, intraoperative visualization of peripheral nerves and microvasculatures using multimodal optical imaging techniques

Accurate, real-time identification and display of critical anatomic structures, such as the nerve and vasculature structures, are critical for reducing complications and improving surgical outcomes. Human vision is frequently limited in clearly distinguishing and contrasting these structures. We present a novel imaging system, which enables noninvasive visualization of critical anatomic structures during surgical dissection. Peripheral nerves are visualized by a snapshot polarimetry that calculates the anisotropic optical properties. Vascular structures, both venous and arterial, are identified and monitored in real-time using a near-infrared laser-speckle-contrast imaging. We evaluate the system by performing in vivo animal studies with qualitative comparison by contrast-agent-aided fluorescence imaging

Dynamic and volumetric variables reliably predict fluid responsiveness in a porcine model with pleural effusion

Background: The ability of stroke volume variation (SVV), pulse pressure variation (PPV) and global end-diastolic volume (GEDV) for prediction of fluid responsiveness in presence of pleural effusion is unknown. The aim of the present study was to challenge the ability of SVV, PPV and GEDV to predict fluid responsiveness in a porcine model with pleural effusions. Methods: Pigs were studied at baseline and after fluid loading with 8 ml kg−1 6% hydroxyethyl starch. After withdrawal of 8 ml kg−1 blood and induction of pleural effusion up to 50 ml kg−1 on either side, measurements at baseline and after fluid loading were repeated. Cardiac output, stroke volume, central venous pressure (CVP) and pulmonary occlusion pressure (PAOP) were obtained by pulmonary thermodilution, whereas GEDV was determined by transpulmonary thermodilution. SVV and PPV were monitored continuously by pulse contour analysis. Results: Pleural effusion was associated with significant changes in lung compliance, peak airway pressure and stroke volume in both responders and non-responders. At baseline, SVV, PPV and GEDV reliably predicted fluid responsiveness (area under the curve 0.85 (p<0.001), 0.88 (p<0.001), 0.77 (p = 0.007). After induction of pleural effusion the ability of SVV, PPV and GEDV to predict fluid responsiveness was well preserved and also PAOP was predictive. Threshold values for SVV and PPV increased in presence of pleural effusion. Conclusions: In this porcine model, bilateral pleural effusion did not affect the ability of SVV, PPV and GEDV to predict fluid responsiveness

Role for ribosome-associated quality control in sampling proteins for MHC class I-mediated antigen presentation

Pathogens and tumors are detected by the immune system through the display of intracellular peptides on MHC-I complexes. These peptides are generated by the ubiquitin−proteasome system preferentially from newly synthesized polypeptides. Here we show that the ribosome-associated quality control (RQC) pathway, responsible for proteasomal degradation of polypeptide chains that stall during translation, mediates efficient antigen presentation of model proteins independent of their intrinsic folding properties. Immunopeptidome characterization of RQC-deficient cells shows that RQC contributes to the presentation of a wide variety of proteins, including proteins that may otherwise evade presentation due to efficient folding. By identifying endogenous substrates of the RQC pathway in human cells, our results also enable the analysis of common principles causing ribosome stalling under physiological conditions.publishedVersio

Investigation of the thermoelectric response in conducting polymers doped by solid-state diffusion

The thermoelectric effect is a physical phenomenon which intricately relates the thermal energy of charge carriers to their charge transport. Understanding the mechanism of this interaction in different systems lies at the heart of inventing novel materials which can revolutionize thermoelectric power gener- ation technology. Despite a recent surge of interest in organic thermoelectric materials, the community has had difficulties in formulating the charge trans- port mechanism in the presence of a significant degree of disorder. Here, we analyze the thermoelectric properties of various conducting polymers doped by a solid-state diffusion of dopant molecules based on a transport model with a power-law energy-dependence of transport function. A fine control of the degree of doping via post-doping annealing provides an accurate empirical evidence of a strong energy dependence of the carrier mobility in the conducting polymers. A superior thermoelectric power factor of conducting polymers doped by solid-state diffusion to that of other doping methods can be attributed to a resulting higher intrinsic mobility and higher free carrier concentration.The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n 610115. Keehoon Kang thanks the for financial support from Samsung Scholarship Foundation and the National Creative Research Laboratory program (Grant No. 2012026372) through the National Research Foundation of Korea, funded by the Korean Ministry of Science and ICT. K.B. acknowledges funding by the German Research Foundation (BR 4869/1-1)

Investigation of potential interferences in the detection of atmospheric ROx_{x} radicals by laser-induced fluorescence under dark conditions

Direct detection of highly reactive, atmospheric hydroxyl radicals (OH) is widely accomplished by laser-induced fluorescence (LIF) instruments. The technique is also suitable for the indirect measurement of HO2 and RO2 peroxy radicals by chemical conversion to OH. It requires sampling of ambient air into a low pressure cell, where OH fluorescence is detected after excitation by 308 nm laser radiation. Although the residence time of air inside the fluorescence cell is typically only on the order of milliseconds, there is potential that additional OH is internally produced, which would artificially increase the measured OH concentration. Here, we present experimental studies investigating potential interferences in the detection of OH and peroxy radicals for the LIF instruments of Forschungszentrum Jülich for nighttime conditions. For laboratory experiments, the inlet of the instrument was overflown by excess synthetic air containing one or more reactants. In order to distinguish between OH produced by reactions upstream of the inlet and artificial signals produced inside the instrument, a chemical titration for OH was applied. Additional experiments were performed in the simulation chamber SAPHIR where simultaneous measurements by an open-path differential optical absorption spectrometer (DOAS) served as reference for OH to quantify potential artifacts in the LIF instrument. Experiments included the investigation of potential interferences related to the nitrate radical (NO3, N2O5), related to the ozonolysis of alkenes (ethene, propene, 1-butene, 2,3-dimethyl-2-butene, α-pinene, limonene, isoprene), and the laser photolysis of acetone. Experiments studying the laser photolysis of acetone yield OH signals in the fluorescence cell, which are equivalent to 0.05 × 106 cm−3 OH for a mixing ratio of 5 ppbv acetone. Under most atmospheric conditions, this interference is negligible. No significant interferences were found for atmospheric concentrations of reactants during ozonolysis experiments. Only for α-pinene, limonene, and isoprene at reactant concentrations which are orders of magnitude higher than in the atmosphere artificial OH could be detected. The value of the interference depends on the turnover rate of the ozonolysis reaction. For example, an apparent OH concentration of approximately 1 × 106 cm−3 is observed, if 5.8 ppbv limonene reacts with 600 ppbv ozone. Experiments with the nitrate radical NO3 reveal a small interference signal in the OH, HO2 and RO2 detection. Dependencies on experimental parameters point to artificial OH formation by surface reactions at the chamber walls or in molecular clusters in the gas expansion. The signal scales with the presence of NO3 giving equivalent radical concentrations of 1.1 × 105 cm−3 OH, 1 × 107 cm−3 HO2, and 1.7 × 107 cm−3 RO2 per 10 pptv NO3