We have investigated the structural, magnetic, and electronic properties of nonstoichiometric iron oxide nanocrystals prepared by decomposition of iron(II) and iron(0) precursors in the presence of ...organic solvents and capping groups. The highly uniform, crystalline, and monodisperse nanocrystals that were produced enabled a full structural and compositional survey by electron microscopy and X-ray diffraction. The complex and metastable behavior of nonstoichiometric iron oxide (wüstite) at the nanoscale was studied by a combination of Mössbauer spectroscopy and magnetic characterization. Deposition from hydrocarbon solvents with subsequent self-assembly of iron oxide nanocrystals into superlattices allowed the preparation of continuous thin films suitable for electronic transport measurements.
A new polymer multilayer fabrication method that employs employing thin films of lamellar polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) is presented. The effectiveness of the technique is ...demonstrated by patterning nanometer‐scale silicon wire arrays. A multilayer patterning process that features defect‐free lamellar pattern formation is demonstrated (see figure).
Surface patterning of copolymers via self‐assembly is achieved by substrate design. The figure shows a polystyrene‐block‐poly(methyl methacrylate) symmetric diblock copolymer confined in a tapered ...structure. Engineering the channel structure provides local defectivity control for defect‐free striped lamellar patterns at the nanometer scale.
We describe a process for increasing power efficiency of concentrator photovoltaic (PV) systems by optimizing the lens-to-cell spacing. We find that there is an optimum defocus position with improved ...power output and reduced sensitivity to pointing errors, which, in combination, can result in a more than 10% enhancement. The improvement can be realized by minor changes to module cases which should not require changes to other manufacturing, installation, or component costs. In fact, optimizing the defocus position allows for lower costs per unit power due to increased power and relaxed system tolerances. This paper focuses on detailed data illuminating the behavior of ultrahigh concentration PV modules, while one can look forward to optimizing defocus through sufficiently detailed simulation; at present, we find that an empirical determination of optimum defocus is necessary. The data reveal that even without design parameters changing, supply chain changes can have a significant impact on the optimum defocus; data from five different module configurations with components from different manufacturing lots are presented. These different configurations serve to illustrate the consequences of component changes and the importance of verifying the optimum defocus. A detailed discussion of the effects that are important to determine the optimum defocus and which underlie these differences is included.
Our understanding of gene regulation in plants is constrained by our limited knowledge of plant cis-regulatory DNA and its dynamics. We mapped DNase I hypersensitive sites (DHSs) in A. thaliana ...seedlings and used genomic footprinting to delineate ∼700,000 sites of in vivo transcription factor (TF) occupancy at nucleotide resolution. We show that variation associated with 72 diverse quantitative phenotypes localizes within DHSs. TF footprints encode an extensive cis-regulatory lexicon subject to recent evolutionary pressures, and widespread TF binding within exons may have shaped codon usage patterns. The architecture of A. thaliana TF regulatory networks is strikingly similar to that of animals in spite of diverged regulatory repertoires. We analyzed regulatory landscape dynamics during heat shock and photomorphogenesis, disclosing thousands of environmentally sensitive elements and enabling mapping of key TF regulatory circuits underlying these fundamental responses. Our results provide an extensive resource for the study of A. thaliana gene regulation and functional biology.
Display omitted
•A. thaliana regulatory DNA, TF footprints, and cis-regulatory lexicon are elucidated•TF binding in protein-coding exons may have shaped A. thaliana codon usage•A. thaliana TF network architecture is strikingly similar to human•Light- and heat-cued regulatory DNA dynamics and TF network remodeling are revealed
Our understanding of plant gene regulation is constrained by our limited knowledge of plant cis-regulatory DNA and its dynamics in response to environmental cues. Sullivan et al. now establish nucleotide-resolution regulatory DNA landscapes for A. thaliana seedlings before and after exposure to light and heat, key environmental cues shaping plant growth and development. This study generates genome-wide, condition- and tissue-specific maps of TF occupancy, constructs condition-specific TF networks, and identifies hundreds of de novo TF motif models.
Cellular-state information between generations of developing cells may be propagated via regulatory regions. We report consistent patterns of gain and loss of DNase I-hypersensitive sites (DHSs) as ...cells progress from embryonic stem cells (ESCs) to terminal fates. DHS patterns alone convey rich information about cell fate and lineage relationships distinct from information conveyed by gene expression. Developing cells share a proportion of their DHS landscapes with ESCs; that proportion decreases continuously in each cell type as differentiation progresses, providing a quantitative benchmark of developmental maturity. Developmentally stable DHSs densely encode binding sites for transcription factors involved in autoregulatory feedback circuits. In contrast to normal cells, cancer cells extensively reactivate silenced ESC DHSs and those from developmental programs external to the cell lineage from which the malignancy derives. Our results point to changes in regulatory DNA landscapes as quantitative indicators of cell-fate transitions, lineage relationships, and dysfunction.
Display omitted
Display omitted
•Cell fate and lineage relationships can be derived from DHS patterns•The proportion of a cell’s DHSs shared with ESCs is a benchmark of maturity•Developmentally stable DHSs encode binding sites for self-regulating TFs•Cancer cells reactivate both ESC DHSs and those from noncognate lineages
Gains and losses of DNase I-hypersensitive sites (DHSs) during cellular differentiation provide a measure of developmental maturity and lineage relationships between cell types. Whereas developing cells exhibit a steady pruning of DHSs shared with ESCs, cancer cells show a disordered acquisition of multiple unrelated DHSs.
This paper represents the third in a three‐part series intended to challenge the social validity of the services provided by a university‐based practicum for addressing the challenging behavior of ...individuals with disabilities. In this paper, we surveyed referring stakeholders (e.g., parents, teachers) of past service recipients to explore the acceptability of the service model's goals, methods, and outcomes. We probed for tensions resultant from the model's threefold mission (service, training, and research) and explored how conflicts between these goals affected the quality of our services. Generally, results were favorable and appeared to support continued model implementation, but not without qualification. Emergent themes, areas for improvement, and future directions for intervention research are all discussed.
Practical multi receiver ultra high (1000+ Suns) concentration photovoltaic (UHCPV) systems experience large radiation, thermal and electrical loads in addition to large power density transients ...under routine operation. This report is a summary of the issues involved in determining the practical limits to concentration. How high is too high? Explorations into UHCPV have both theoretical and experimental aspects. Understanding the theoretical device physics and circuit limitations is often essential to determining which experiments to do and in interpreting results. On the experimental side the work can be divided into two fields depending on the type of light source. The first is artificial or simulated sources and the second is working in the field with direct solar irradiation. Both fields have advantages and disadvantages. Direct solar radiation was selected for the current experiments due to the low cost and ability to produce ultra high concentrations (4000+) over relatively large areas (25+ mm 2 ). Several experimental examples from these direct solar measurements shed light on some of the basic theories of how concentrated light affects the performance of multi junction photovoltaic cells. Out of these examples and theoretical foundations we conclude that for practical devices the first order constraint to optimum efficiency at ultra high concentrations is the series resistance. We also present a simple model based on published data and our results that can be used to predict the total system series resistance needed to optimize a system for a particular concentration.
•Fibromyalgia patients exhibit elevated cortical levels of 11CPBR28 signal.•11CPBR28 signal was correlated with subjective fatigue in patients.•Results from 11CPBR28 SUVR and VT analyses show strong ...regional overlap.•No differences in 11C-L-deprenyl-D2 signal implicate microglia, not astrocytes.•Our data support glial modulation as a potential therapeutic strategy for FM.
Fibromyalgia (FM) is a poorly understood chronic condition characterized by widespread musculoskeletal pain, fatigue, and cognitive difficulties. While mounting evidence suggests a role for neuroinflammation, no study has directly provided evidence of brain glial activation in FM. In this study, we conducted a Positron Emission Tomography (PET) study using 11CPBR28, which binds to the translocator protein (TSPO), a protein upregulated in activated microglia and astrocytes. To enhance statistical power and generalizability, we combined datasets collected independently at two separate institutions (Massachusetts General Hospital MGH and Karolinska Institutet KI). In an attempt to disentangle the contributions of different glial cell types to FM, a smaller sample was scanned at KI with 11C-L-deprenyl-D2 PET, thought to primarily reflect astrocytic (but not microglial) signal.
Thirty-one FM patients and 27 healthy controls (HC) were examined using 11CPBR28 PET. 11 FM patients and 11 HC were scanned using 11C-L-deprenyl-D2 PET. Standardized uptake values normalized by occipital cortex signal (SUVR) and distribution volume (VT) were computed from the 11CPBR28 data. 11C-L-deprenyl-D2 was quantified using λ k3. PET imaging metrics were compared across groups, and when differing across groups, against clinical variables.
Compared to HC, FM patients demonstrated widespread cortical elevations, and no decreases, in 11CPBR28 VT and SUVR, most pronounced in the medial and lateral walls of the frontal and parietal lobes. No regions showed significant group differences in 11C-L-deprenyl-D2 signal, including those demonstrating elevated 11CPBR28 signal in patients (p’s ≥ 0.53, uncorrected). The elevations in 11CPBR28 VT and SUVR were correlated both spatially (i.e., were observed in overlapping regions) and, in several areas, also in terms of magnitude. In exploratory, uncorrected analyses, higher subjective ratings of fatigue in FM patients were associated with higher 11CPBR28 SUVR in the anterior and posterior middle cingulate cortices (p’s < 0.03). SUVR was not significantly associated with any other clinical variable.
Our work provides the first in vivo evidence supporting a role for glial activation in FM pathophysiology. Given that the elevations in 11CPBR28 signal were not also accompanied by increased 11C-L-deprenyl-D2 signal, our data suggests that microglia, but not astrocytes, may be driving the TSPO elevation in these regions. Although 11C-L-deprenyl-D2 signal was not found to be increased in FM patients, larger studies are needed to further assess the role of possible astrocytic contributions in FM. Overall, our data support glial modulation as a potential therapeutic strategy for FM.
Globally, our knowledge on lake fisheries is still limited despite their importance to food security and livelihoods. Here we show that fish catches can respond either positively or negatively to ...climate and land-use changes, by analyzing time-series data (1970-2014) for 31 lakes across five continents. We find that effects of a climate or land-use driver (e.g., air temperature) on lake environment could be relatively consistent in directions, but consequential changes in a lake-environmental factor (e.g., water temperature) could result in either increases or decreases in fish catch in a given lake. A subsequent correlation analysis indicates that reductions in fish catch was less likely to occur in response to potential climate and land-use changes if a lake is located in a region with greater access to clean water. This finding suggests that adequate investments for water-quality protection and water-use efficiency can provide additional benefits to lake fisheries and food security.
PDF
