An Exploration of Maximum Power Point Tracking Algorithms

This project investigated the performance of various solar maximum power point tracking algorithms on a single hardware platform. It also developed a low-cost hardware platform including a rudimentary solar cell emulator circuit and a maximum power point tracker circuit to test these algorithms. Additionally, the project covered the development of the two software algorithms that were tested in the project: the ”Sweep” algorithm and the ”Perturb and Observe” algorithm

A Fluorescent Aerogel for Capture and Identification of Interplanetary and Interstellar Dust

Contemporary interstellar dust has never been analyzed in the laboratory, despite its obvious astronomical importance and its potential as a probe of stellar nucleosynthesis and galactic chemical evolution. Here we report the discovery of a novel fluorescent aerogel which is capable of capturing hypervelocity dust grains and passively recording their kinetic energies. An array of these "calorimetric" aerogel collectors in low earth orbit would lead to the capture and identification of large numbers of interstellar dust grains.Comment: 13 pages, 4 figures, to appear in The Astrophysical Journa

Removing subordinate species in a biodiversity experiment to mimic observational field studies

Background: Positive effects of plant species richness on community biomass in biodiversity experiments are often stronger than those from observational field studies. This may be because experiments are initiated with randomly assembled species compositions whereas field communities have experienced filtering. Methods: We compared aboveground biomass production of randomly assembled communities of 2–16 species (controls) with experimentally filtered communities from which subordinate species were removed, resulting in removal communities of 1–8 species. Results: Removal communities had (1) 12.6% higher biomass than control communities from which they were derived, that is, with double species richness and (2) 32.0% higher biomass than control communities of equal richness. These differences were maintained along the richness gradient. The increased productivity of removal communities was paralleled by increased species evenness and complementarity. Conclusions: Result (1) indicates that subordinate species can reduce community biomass production, suggesting a possible explanation for why the most diverse field communities sometimes do not have the highest productivity. Result (2) suggests that if a community of S species has been derived by filtering from a pool of 2S randomly chosen species it is more productive than a community derived from a pool of S randomly chosen species without filtering

Detection of a glitch in the pulsar J1709-4429

We report the detection of a glitch event in the pulsar J1709$-$4429 (also known as B1706$-$44) during regular monitoring observations with the Molonglo Observatory Synthesis Telescope (UTMOST). The glitch was found during timing operations, in which we regularly observe over 400 pulsars with up to daily cadence, while commensally searching for Rotating Radio Transients, pulsars, and FRBs. With a fractional size of $\Delta\nu/\nu \approx 52.4 \times10^{-9}$, the glitch reported here is by far the smallest known for this pulsar, attesting to the efficacy of glitch searches with high cadence using UTMOST.Comment: 3 pages, 1 figur

LINCS Canvas Browser: interactive web app to query, browse and interrogate LINCS L1000 gene expression signatures

For the Library of Integrated Network-based Cellular Signatures (LINCS) project many gene expression signatures using the L1000 technology have been produced. The L1000 technology is a cost-effective method to profile gene expression in large scale. LINCS Canvas Browser (LCB) is an interactive HTML5 web-based software application that facilitates querying, browsing and interrogating many of the currently available LINCS L1000 data. LCB implements two compacted layered canvases, one to visualize clustered L1000 expression data, and the other to display enrichment analysis results using 30 different gene set libraries. Clicking on an experimental condition highlights gene-sets enriched for the differentially expressed genes from the selected experiment. A search interface allows users to input gene lists and query them against over 100 000 conditions to find the top matching experiments. The tool integrates many resources for an unprecedented potential for new discoveries in systems biology and systems pharmacology. The LCB application is available at http://www.maayanlab.net/LINCS/LCB. Customized versions will be made part of the http://lincscloud.org and http://lincs.hms.harvard.edu websites

Metabolic flexibility as a major predictor of spatial distribution in microbial communities

A better understand the ecology of microbes and their role in the global ecosystem could be achieved if traditional ecological theories can be applied to microbes. In ecology organisms are defined as specialists or generalists according to the breadth of their niche. Spatial distribution is often used as a proxy measure of niche breadth; generalists have broad niches and a wide spatial distribution and specialists a narrow niche and spatial distribution. Previous studies suggest that microbial distribution patterns are contrary to this idea; a microbial generalist genus (Desulfobulbus) has a limited spatial distribution while a specialist genus (Methanosaeta) has a cosmopolitan distribution. Therefore, we hypothesise that this counter-intuitive distribution within generalist and specialist microbial genera is a common microbial characteristic. Using molecular fingerprinting the distribution of four microbial genera, two generalists, Desulfobulbus and the methanogenic archaea Methanosarcina, and two specialists, Methanosaeta and the sulfate-reducing bacteria Desulfobacter were analysed in sediment samples from along a UK estuary. Detected genotypes of both generalist genera showed a distinct spatial distribution, significantly correlated with geographic distance between sites. Genotypes of both specialist genera showed no significant differential spatial distribution. These data support the hypothesis that the spatial distribution of specialist and generalist microbes does not match that seen with specialist and generalist large organisms. It may be that generalist microbes, while having a wider potential niche, are constrained, possibly by intrageneric competition, to exploit only a small part of that potential niche while specialists, with far fewer constraints to their niche, are more capable of filling their potential niche more effectively, perhaps by avoiding intrageneric competition. We suggest that these counter-intuitive distribution patterns may be a common feature of microbes in general and represent a distinct microbial principle in ecology, which is a real challenge if we are to develop a truly inclusive ecology

Broadband UBVR C I C Photometry of Horizontal-branch and Metal-poor Candidates from the HK and Hamburg/ESO Surveys. I

We report broadband UBVand/or BVRCIC CCD photometry for a total of 1857 stars in the thick-disk and halo populations of the Galaxy. The majority of our targets were selected as candidate field horizontal-branch or other A-type stars (FHB/A, N = 576), or candidate low-metallicity stars (N =1221), from the HK and Hamburg/ESO objective-prism surveys. Similar data for a small number of additional stars from other samples are also reported. These data are being used for several purposes. In the case of the FHB/A candidates they are used to accurately separate the lower gravity FHB stars from various higher gravity A-type stars, a subsample that includes the so-called blue metal poor stars, halo and thick-disk blue stragglers, main-sequence A-type dwarfs, and Am and Ap stars. These data are also being used to derive photometric distance estimates to high-velocity hydrogen clouds in the Galaxy and for improved measurements of the mass of the Galaxy. Photometric data for the metal-poor candidates are being used to refine estimates of stellar metallicity for objects with available medium-resolution spectroscopy, to obtain distance estimates for kinematic analyses, and to establish initial estimates of effective temperature for analysis of high-resolution spectroscopy of the stars for which this information now exists

Identification of a novel gene regulating amygdala-mediated fear extinction.

Recent years have seen advances in our understanding of the neural circuits associated with trauma-related disorders, and the development of relevant assays for these behaviors in rodents. Although inherited factors are known to influence individual differences in risk for these disorders, it has been difficult to identify specific genes that moderate circuit functions to affect trauma-related behaviors. Here, we exploited robust inbred mouse strain differences in Pavlovian fear extinction to uncover quantitative trait loci (QTL) associated with this trait. We found these strain differences to be resistant to developmental cross-fostering and associated with anatomical variation in basolateral amygdala (BLA) perineuronal nets, which are developmentally implicated in extinction. Next, by profiling extinction-driven BLA expression of QTL-linked genes, we nominated Ppid (peptidylprolyl isomerase D, a member of the tetratricopeptide repeat (TPR) protein family) as an extinction-related candidate gene. We then showed that Ppid was enriched in excitatory and inhibitory BLA neuronal populations, but at lower levels in the extinction-impaired mouse strain. Using a virus-based approach to directly regulate Ppid function, we demonstrated that downregulating BLA-Ppid impaired extinction, while upregulating BLA-Ppid facilitated extinction and altered in vivo neuronal extinction encoding. Next, we showed that Ppid colocalized with the glucocorticoid receptor (GR) in BLA neurons and found that the extinction-facilitating effects of Ppid upregulation were blocked by a GR antagonist. Collectively, our results identify Ppid as a novel gene involved in regulating extinction via functional actions in the BLA, with possible implications for understanding genetic and pathophysiological mechanisms underlying risk for trauma-related disorders

Sunny windy Sundays

Rapid expansion of wind and solar capacity in Great Britain presents challenges for managing electricity systems. One concern is the reduction in system inertia during periods where renewables provide a high proportion of demand which has led to some networks imposing system nonsynchronous penetration limits. However, given the lack of operational data, the relationship between renewable generation and demand for the full range of meteorological conditions experienced in Great Britain is poorly understood. This study uses reanalysis datasets to determine the proportion of demand from renewable generation on an hourly resolution for a 36-year period. The days with highest penetration of renewables tend to be sunny, windy weekend days between May and September, when there is a significant contribution of both wind and solar generation and demand is suppressed due to human behaviour. Based on the current distribution of wind and solar capacity, there is very little curtailment for all system non-synchronous penetration limits considered. However, as installed capacity of renewables grows the volume of generation curtailed also increases with a disproportionate volume occurring at weekends. The total volume of curtailment is highly dependent on ratio of wind and solar capacity, with the current blend close to the optimum level

The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b

Using radial velocity data from the Habitable Zone Planet Finder, we have measured the mass of the Neptune-sized planet K2-25b, as well as the obliquity of its M4.5 dwarf host star in the 600–800 Myr Hyades cluster. This is one of the youngest planetary systems for which both of these quantities have been measured and one of the very few M dwarfs with a measured obliquity. Based on a joint analysis of the radial velocity data, time-series photometry from the K2 mission, and new transit light curves obtained with diffuser-assisted photometry, the planet's radius and mass are 3.44 ± 0.12 R_⊕ and 24.5_(-5.2)^(+5.7) M_⊕. These properties are compatible with a rocky core enshrouded by a thin hydrogen–helium atmosphere (5% by mass). We measure an orbital eccentricity of e = 0.43 ± 0.05. The sky-projected stellar obliquity is λ = 3° ± 16°, compatible with spin–orbit alignment, in contrast to other "hot Neptunes" that have been studied around older stars