2,527 research outputs found
Dust-forming molecules in VY Canis Majoris (and Betelgeuse)
The formation of inorganic dust in circumstellar environments of evolved
stars is poorly understood. Spectra of molecules thought to be most important
for the nucleation, i.e. AlO, TiO, and TiO2, have been recently detected in the
red supergiant VY CMa. These molecules are effectively formed in VY CMa and the
observations suggest that non-equilibrium chemistry must be involved in their
formation and nucleation into dust. In addition to exploring the recent
observations of VY CMa, we briefly discuss the possibility of detecting these
molecules in the dust-poor circumstellar environment of Betelgeuse.Comment: contribution to Betelgeuse Workshop 2012: "The physics of Red
Supergiants: recent advances and open questions", 26-29 Nov 2012 Paris
(France
Pure rotational spectra of TiO and TiO_2 in VY Canis Majoris
We report the first detection of pure rotational transitions of TiO and TiO_2
at (sub-)millimeter wavelengths towards the red supergiant VY CMa. A rotational
temperature, T_rot, of about 250 K was derived for TiO_2. Although T_rot was
not well constrained for TiO, it is likely somewhat higher than that of TiO_2.
The detection of the Ti oxides confirms that they are formed in the
circumstellar envelopes of cool oxygen-rich stars and may be the "seeds" of
inorganic-dust formation, but alternative explanations for our observation of
TiO and TiO_2 in the cooler regions of the envelope cannot be ruled out at this
time. The observations suggest that a significant fraction of the oxides is not
converted to dust, but instead remains in the gas phase throughout the outflow.Comment: to appear in Astronomy and Astrophysic
Analysis of nanopore detector measurements using Machine-Learning methods, with application to single-molecule kinetic analysis
<p>Abstract</p> <p>Background</p> <p>A nanopore detector has a nanometer-scale trans-membrane channel across which a potential difference is established, resulting in an ionic current through the channel in the pA-nA range. A distinctive channel current blockade signal is created as individually "captured" DNA molecules interact with the channel and modulate the channel's ionic current. The nanopore detector is sensitive enough that nearly identical DNA molecules can be classified with very high accuracy using machine learning techniques such as Hidden Markov Models (HMMs) and Support Vector Machines (SVMs).</p> <p>Results</p> <p>A non-standard implementation of an HMM, emission inversion, is used for improved classification. Additional features are considered for the feature vector employed by the SVM for classification as well: The addition of a single feature representing spike density is shown to notably improve classification results. Another, much larger, feature set expansion was studied (2500 additional features instead of 1), deriving from including all the HMM's transition probabilities. The expanded features can introduce redundant, noisy information (as well as diagnostic information) into the current feature set, and thus degrade classification performance. A hybrid Adaptive Boosting approach was used for feature selection to alleviate this problem.</p> <p>Conclusion</p> <p>The methods shown here, for more informed feature extraction, improve both classification and provide biologists and chemists with tools for obtaining a better understanding of the kinetic properties of molecules of interest.</p
The Use of Backscattered Electron Imaging, X-Ray Microanalysis and X-Ray Microscopy in Demonstrating Physiological Cell Death
The cytochemical localization of enzymatic activity by means of backscattered electron imaging (BEi) is reviewed and the application of BEI to changes in acid phosphatase and ATPase distribution during physiological (programmed) cell death in Heliothis midgut is explored. Programmed cell death entails the release of nascent free acid phosphatase as extracisternal hydrolase. This shift can readily be detected by means of the atomic number contrast imparted by BEI of the lead phosphatase reaction product, thus enabling the distribution of dying cells to be mapped. BEI is particularly useful in this context as it allows the examination of bulk specimens at low magnification.
Death of cells is also accompanied by a collapse in ATPase activity which shows up as cytochemically negative areas in the X-ray microscope and by means of BEI. Acid phosphatase in normal cells is localized in the apical microvilli and lysosomes. Senescent or dying cells, however, clearly show a basally situated free hydrolase which migrates throughout the cell. Parallel TEM results confirm that this enzyme is ribosomal and extracisternal rather than lysosomal in origin.
ATPase activity is largely limited to the apical microvilli, although there is some activity associated with the basal plasma membranes. The apical ATPase, however is partially resistant to ouabain. Young and mature cells are positive although in the latter case some microvilli may be lost as the cells acquire a negative cap or dome. Inhibition by bromotetramizole indicates that apical activity is not to any significant extent contributed to by alkaline phosphatase. Degenerate or dead cells are negative and can be seen as a mozaic of black patches among normal cells when imaged by means of BEI or X-ray microscopy
Defense against predators incurs high reproductive costs for the aposematic moth<i> Arctia plantaginis</i>
Characterization of Hybrid Ferroelectric/HTS Thin Films for Tunable Microwave Components
Since the discovery of High-Temperature-Superconductors (HTS) in 1986, a diversity of HTS-based microwave components has been demonstrated. Because of their low conductor losses, HTS-based components are very attractive for integration into microwave circuits for space communication systems. Recent advancements have made deposition of ferroelectric thin films onto HTS thin films possible. Due to the sensitivity of the ferroelectric's dielectric constant (epsilon(sub r)) to an externally applied electric field (E), ferroelectric/superconducting structures could be used in the fabrication of low loss, tunable microwave components. In this paper, we report on our study of Ba(0.5)Sr(0.5)TiO3/YBa2Cu3O(7-delta) and Ba(0.08)Sr(0.92)TiO3/YBa2Cu3O(7-delta) ferroelectric/superconducting thin films on lanthanum aluminate (LaAlO3) substrates. For the (Ba:Sr, 0.50:0.50) epitaxial sample, a epsilon(sub r) of 425 and a loss tangent (tan delta) of 0.040 were measured at 298 K, 1.0 MHz, and zero applied E. For the same sample, a epsilon(sub r) of 360 and tan delta of 0.036 were obtained at 77 K, 1.0 MHz, and zero applied E. Variations in epsilon(sub r) from 180 to 360 were observed over an applied E range of 0V/cm less than or equal to E less than or equal to 5.62 x 10(exp 4) V/cm with little change in tan delta. However, the range of epsilon(sub r) variation for the polycrystalline (Ba:Sr, 0.08:0.92) sample over 0V/cm less than or equal to E less than or equal to 4.00 x 10(exp 4) V/cm was only 3.6 percent while tan delta increased markedly. These results indicate that a lack of epitaxy between the ferroelectric and superconducting layers decreases tuning and increases microwave losses
Ensemble Sales Forecasting Study in Semiconductor Industry
Sales forecasting plays a prominent role in business planning and business
strategy. The value and importance of advance information is a cornerstone of
planning activity, and a well-set forecast goal can guide sale-force more
efficiently. In this paper CPU sales forecasting of Intel Corporation, a
multinational semiconductor industry, was considered. Past sale, future
booking, exchange rates, Gross domestic product (GDP) forecasting, seasonality
and other indicators were innovatively incorporated into the quantitative
modeling. Benefit from the recent advances in computation power and software
development, millions of models built upon multiple regressions, time series
analysis, random forest and boosting tree were executed in parallel. The models
with smaller validation errors were selected to form the ensemble model. To
better capture the distinct characteristics, forecasting models were
implemented at lead time and lines of business level. The moving windows
validation process automatically selected the models which closely represent
current market condition. The weekly cadence forecasting schema allowed the
model to response effectively to market fluctuation. Generic variable
importance analysis was also developed to increase the model interpretability.
Rather than assuming fixed distribution, this non-parametric permutation
variable importance analysis provided a general framework across methods to
evaluate the variable importance. This variable importance framework can
further extend to classification problem by modifying the mean absolute
percentage error(MAPE) into misclassify error. Please find the demo code at :
https://github.com/qx0731/ensemble_forecast_methodsComment: 14 pages, Industrial Conference on Data Mining 2017 (ICDM 2017
Design approaches in technology enhanced learning
Design is a critical to the successful development of any interactive learning environment (ILE). Moreover, in technology enhanced learning (TEL), the design process requires input from many diverse areas of expertise. As such, anyone undertaking tool development is required to directly address the design challenge from multiple perspectives. We provide a motivation and rationale for design approaches for learning technologies that draws upon Simon's seminal proposition of Design Science (Simon, 1969). We then review the application of Design Experiments (Brown, 1992) and Design Patterns (Alexander et al., 1977) and argue that a patterns approach has the potential to address many of the critical challenges faced by learning technologists
The NTD Nanoscope: potential applications and implementations
<p>Abstract</p> <p>Background</p> <p>Nanopore transduction detection (NTD) offers prospects for a number of highly sensitive and discriminative applications, including: (i) single nucleotide polymorphism (SNP) detection; (ii) targeted DNA re-sequencing; (iii) protein isoform assaying; and (iv) biosensing via antibody or aptamer coupled molecules. Nanopore event transduction involves single-molecule biophysics, engineered information flows, and nanopore cheminformatics. The NTD Nanoscope has seen limited use in the scientific community, however, due to lack of information about potential applications, and lack of availability for the device itself. Meta Logos Inc. is developing both pre-packaged device platforms and component-level (unassembled) kit platforms (the latter described here). In both cases a lipid bi-layer workstation is first established, then augmentations and operational protocols are provided to have a nanopore transduction detector. In this paper we provide an overview of the NTD Nanoscope applications and implementations. The NTD Nanoscope Kit, in particular, is a component-level reproduction of the standard NTD device used in previous research papers.</p> <p>Results</p> <p>The NTD Nanoscope method is shown to functionalize a single nanopore with a channel current modulator that is designed to transduce events, such as binding to a specific target. To expedite set-up in new lab settings, the calibration and troubleshooting for the NTD Nanoscope kit components and signal processing software, the NTD Nanoscope Kit, is designed to include a set of test buffers and control molecules based on experiments described in previous NTD papers (the model systems briefly described in what follows). The description of the Server-interfacing for advanced signal processing support is also briefly mentioned.</p> <p>Conclusions</p> <p>SNP assaying, SNP discovery, DNA sequencing and RNA-seq methods are typically limited by the accuracy of the error rate of the enzymes involved, such as methods involving the polymerase chain reaction (PCR) enzyme. The NTD Nanoscope offers a means to obtain higher accuracy as it is a single-molecule method that does not inherently involve use of enzymes, using a functionalized nanopore instead.</p
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