457 research outputs found
Developing a 1-Megawatt Photovoltaic Power Plant for Liberty University
A photovoltaic power plant with a generation capacity of 1-megawatt is designed for Liberty University. Liberty Universityâs location and size are stated to provide context for the design. Design choices are presented, first with general information that is applicable to any photovoltaic plant design, then with significant factors that impact this design. Specific models of solar panels and inverters are selected after the necessary classifications are determined. The final design has 2,880 solar panels with a fixed angle 30â° above the horizon, has two central inverters, and takes up 2.57 acres. Future research is suggested for finances as well as expected technological advances
A Dominance Hierarchy of Auditory Spatial Cues in Barn Owls
Background: Barn owls integrate spatial information across frequency channels to localize sounds in space. Methodology/Principal Findings: We presented barn owls with synchronous sounds that contained different bands of frequencies (3â5 kHz and 7â9 kHz) from different locations in space. When the owls were confronted with the conflicting localization cues from two synchronous sounds of equal level, their orienting responses were dominated by one of the sounds: they oriented toward the location of the low frequency sound when the sources were separated in azimuth; in contrast, they oriented toward the location of the high frequency sound when the sources were separated in elevation. We identified neural correlates of this behavioral effect in the optic tectum (OT, superior colliculus in mammals), which contains a map of auditory space and is involved in generating orienting movements to sounds. We found that low frequency cues dominate the representation of sound azimuth in the OT space map, whereas high frequency cues dominate the representation of sound elevation. Conclusions/Significance: We argue that the dominance hierarchy of localization cues reflects several factors: 1) the relative amplitude of the sound providing the cue, 2) the resolution with which the auditory system measures the value of a cue, and 3) the spatial ambiguity in interpreting the cue. These same factors may contribute to the relative weighting of soun
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Hearing through your eyes: neural basis of audiovisual cross-activation, revealed by transcranial alternating current stimulation
Some people experience auditory sensations when seeing visual flashes or movements. This prevalent synaesthesia-like âvisual-evoked auditory responseâ (vEAR) could result either from over-exuberant cross-activation between brain areas, and/or reduced inhibition of normally-occurring cross-activation. We have used transcranial alternating current stimulation (tACS) to test these theories. We applied tACS at 10Hz (alpha-band frequency) or 40Hz (gamma-band), bilaterally either to temporal or occipital sites, while measuring same/different discrimination of paired auditory (A) versus visual (V) 'Morse code' sequences. At debriefing, participants were classified as vEAR or non-vEAR depending on whether they reported 'hearing' the silent flashes.
In non-vEAR participants, temporal 10Hz tACS caused impairment of A performance, which correlated with improved V; conversely under occipital tACS, poorer V performance correlated with improved A. This reciprocal pattern suggests that sensory cortices are normally mutually inhibitory, and that alpha-frequency tACS may bias the balance of competition between them. vEAR participants showed no tACS effects, consistent with reduced inhibition, or enhanced cooperation between modalities. In addition, temporal 40Hz tACS impaired V performance, specifically in individuals who showed a performance advantage for V (relative to A). Gamma-frequency tACS may therefore modulate the ability of these individuals to benefit from recoding flashes into the auditory modality, possibly by disrupting cross-activation of auditory areas by visual stimulation.
Our results support both theories, suggesting that vEAR may depend on disinhibition of normally-occurring sensory cross-activation, which may be expressed more strongly in some individuals. Furthermore, endogenous alpha and gamma-frequency oscillations may function respectively to inhibit or promote this cross-activation
The Role of Glyph Blocks in Punctuating Mayan Texts
This thesis investigates how glyph blocks organize Mayan texts. Understanding the factors that influence a glyph blockâs composition and its syntactic correspondence helps reveal the degree of metalinguistic awareness of Mayan scribes. To address these points, I sampled 60 texts from the Mayan Hieroglyphic Database, compiled by Matthew Looper and Martha Macri (2023). Each glyph block from each text was tagged for an array of variables, including syntactic value and graphic composition. Linear and logistic regressions revealed that scribes possessed a sound understanding of phrasal structure, evident in their utilization of graphic compacting to fit syntactic units within a single block. Additionally, the phrasal value of glyph blocks varied depending on region, class, and presence of purely phonological spellings, showing that scribal practices differ in their preference for phrasal blocks. In sum, Mayan scribes were keenly aware of syntactic structure, using glyph blocks as a means of punctuating their texts.Master of Art
Detection of CO from SMM J16359+6612, The Multiply Imaged Submillimeter Galaxy Behind A2218
We report the detection of CO (=32) line emission from all three
multiple images (A,B and C) of the intrinsically faint ( 0.8 mJy)
submillimeter-selected galaxy SMM J16359+6612. The brightest source of the
submm continuum emission (B) also corresponds to the brightest CO emission,
which is centered at =2.5168, consistent with the pre-existing redshift
derived from \Ha. The observed CO flux in the A, B and C images is 1.2, 3.5 and
1.6 Jy \kms respectively, with a linewidth of \kms. After
correcting for the lensing amplification, the CO flux corresponds to a
molecular gas mass of \Msun, while the
extent of the CO emission indicates that the dynamical mass of the system
\Msun. Two velocity components are seen in the CO spectra;
these could arise from either a rotating compact ring or disk of gas, or
merging substructure. The star formation rate in this galaxy was previously
derived to be 100--500 \Msun \yr. If all the CO emission arises from the
inner few kpc of the galaxy and the galactic CO-to-H conversion factor
holds, then the gas consumption timescale is a relatively short 40 Myr, and so
the submm emission from SMM J16359+6612 may be produced by a powerful, but
short-lived circumnuclear starburst event in an otherwise normal and
representative high-redshift galaxy.Comment: Appearing in the 2004 October 10 issue of the Astrophysical Journal
Letters, Volume 614, L5-L
Achieving good environmental status in the Black Sea: scale mismatches in environmental management
The Black Sea has suffered severe environmental degradation. Governance of the Black Sea region is complex and results in a series of scale mismatches which constrain management. This paper develops a simple classification of spatial scale mismatches incorporating the driver, pressure, state, welfare, response (DPSWR) framework. The scale mismatch classification is applied to two major environmental problems of the Black Sea, eutrophication and small pelagic fisheries. A number of scale mismatches are described and classified and potential solutions are identified
Group I aptazymes as genetic regulatory switches
BACKGROUND: Allosteric ribozymes (aptazymes) that have extraordinary activation parameters have been generated in vitro by design and selection. For example, hammerhead and ligase ribozymes that are activated by small organic effectors and protein effectors have been selected from random sequence pools appended to extant ribozymes. Many ribozymes, especially self-splicing introns, are known control gene regulation or viral replication in vivo. We attempted to generate Group I self-splicing introns that were activated by a small organic effector, theophylline, and to show that such Group I aptazymes could mediate theophylline-dependent splicing in vivo. RESULTS: By appending aptamers to the Group I self-splicing intron, we have generated a Group I aptazyme whose in vivo splicing is controlled by exogenously added small molecules. Substantial differences in gene regulation could be observed with compounds that differed by as little as a single methyl group. The effector-specificity of the Group I aptazyme could be rationally engineered for new effector molecules. CONCLUSION: Group I aptazymes may find applications as genetic regulatory switches for generating conditional knockouts at the level of mRNA or for developing economically viable gene therapies
Response and Resistance to Paradox-Breaking BRAF Inhibitor in Melanomas
FDA-approved BRAF inhibitors produce high response rates and improve overall survival in patients with BRAF V600E/K-mutant melanoma, but are linked to pathologies associated with paradoxical ERK1/2 activation in wild-type BRAF cells. To overcome this limitation, a next-generation paradox-breaking RAF inhibitor (PLX8394) has been designed. Here, we show that by using a quantitative reporter assay, PLX8394 rapidly suppressed ERK1/2 reporter activity and growth of mutant BRAF melanoma xenografts. Ex vivo treatment of xenografts and use of a patient-derived explant system (PDeX) revealed that PLX8394 suppressed ERK1/2 signaling and elicited apoptosis more effectively than the FDA-approved BRAF inhibitor, vemurafenib. Furthermore, PLX8394 was efficacious against vemurafenibresistant BRAF splice variant-expressing tumors and reduced splice variant homodimerization. Importantly, PLX8394 did not induce paradoxical activation of ERK1/2 in wild-type BRAF cell lines or PDeX. Continued in vivo dosing of xenografts with PLX8394 led to the development of acquired resistance via ERK1/2 reactivation through heterogeneous mechanisms; however, resistant cells were found to have differential sensitivity to ERK1/2 inhibitor. These findings highlight the efficacy of a paradox-breaking selective BRAF inhibitor and the use of PDeX system to test the efficacy of therapeutic agents. © 2017 American Association for Cancer Research
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