4,008 research outputs found
Multirate Kalman filtering approach for optimal two-dimensional signal reconstruction from noisy subband systems
The International Conference on Image Processing, Santa Barbara, California, 26-29 October 1997Conventional synthesis filters in subband systems lose their optimality when additive noise due, for example, to signal quantization, disturbs the subband components. The multichannel representation of subband signal is combined with the statistical model of input signal to derive the multirate state-space model for filter bank system with additive noises. Thus the signal reconstruction problem in subband system can be formulated as the process of optimal state estimation in the equivalent multirate state-space model. With the input signal embedded in the state vector, the multirate Kalman filtering provides the minimum-variance reconstruction of input signal. Using the powerful Kronecker product notation, the results and derivations can then be extended to the 2-D cases. Incorporated with the vector dynamical model, the 2-D multirate state-space model for 2-D Kalman filtering is developed. Computer simulation with the proposed 2-D multirate Kalman filter gives favorable results.published_or_final_versio
Composition of the Essential Oil of Clausena Suffruticosa Leaf and Evaluation of its Antimicrobial and Cytotoxic Activities
Purpose: To investigate the essential oil content of Clausena suffruticosa leaf for its in-vitro antibacterial, antifungal and cytotoxic activities.Methods: The essential oil of Clausena suffruticosa leaf was extracted by hydrodistillation using a modified Clevenger-type apparatus and was analyzed by GC-MS using electron impact ionization method. Antibacterial, antifungal and cytotoxic screenings were made by disc diffusion technique,poisoned food technique and brine shrimp lethality bioassay, respectively. Minimum inhibitory concentration (MIC) of the oil was determined by measuring the zone of inhibition, with tetracycline as reference standard. Fluconazole served as standard in the antifungal assessment.Results: A total of twenty two compounds, of which Estragole, Anethole and â-Ocimene were the major ones, were found in the essential oil of C. suffruticosa. The oil showed higher antibacterial activity against Shigella flexneri than the reference, tetracycline (p < 0.05). Significant activity (p < 0.001) against other Gram-positive microbes - Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Bacillus polymyxa and Bacillus megaterium – was also observed. However, Gram-negative bacteria -Salmonella typhi, Shigella flexneri, Proteus mirabilis and Escherichia coli. Klebsiella pneumoniae and Shigella sonnei - showed no sensitivity to the oil. In the antifungal assay, the oil exhibited greater activity (p < 0.001) against Aspergillus ochraceus than the reference, fluconazole, Inhibition of other fungal strains tested was also statistically significant (p < 0.001). The lethal concentration (LC50) of the oil against brine shrimp was 41.2 ìg/ml in the cytotoxic assay.Conclusion: It is evident that the essential oil of C. suffruticosa is a potent antimicrobial and cytotoxic agent that should be further evaluated.Keywords: Clausena suffruticosa, Essential oil, Cytotoxicity, Antimicrobial, Brine shrim
Gamma-Ray Bursts in the Swift Era
With its rapid-response capability and multiwavelength complement of
instruments, the Swift satellite has transformed our physical understanding of
gamma-ray bursts (GRBs). Providing high-quality observations of hundreds of
bursts, and facilitating a wide range of follow-up observations within seconds
of each event, Swift has revealed an unforeseen richness in observed burst
properties, shed light on the nature of short-duration bursts, and helped
realize the promise of GRBs as probes of the processes and environments of star
formation out to the earliest cosmic epochs. These advances have opened new
perspectives on the nature and properties of burst central engines,
interactions with the burst environment from microparsec to gigaparsec scales,
and the possibilities for non-photonic signatures. Our understanding of these
extreme cosmic sources has thus advanced substantially; yet more than 40 years
after their discovery, GRBs continue to present major challenges on both
observational and theoretical fronts.Comment: 67 pages, 16 figures; ARAA, 2009;
http://arjournals.annualreviews.org/toc/astro/47/
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An Overview of the Use of Neural Networks for Data Mining Tasks
In the recent years the area of data mining has experienced a considerable demand for technologies that extract knowledge from large and complex data sources. There is a substantial commercial interest as well as research investigations in the area that aim to develop new and improved approaches for extracting information, relationships, and patterns from datasets. Artificial Neural Networks (NN) are popular biologically inspired intelligent methodologies, whose classification, prediction and pattern recognition capabilities have been utilised successfully in many areas, including science, engineering, medicine, business, banking, telecommunication, and many other fields. This paper highlights from a data mining perspective the implementation of NN, using supervised and unsupervised learning, for pattern recognition, classification, prediction and cluster analysis, and focuses the discussion on their usage in bioinformatics and financial data analysis tasks
TAXON version 1.1: A simple way to generate uniform and fractionally weighted three-item matrices from various kinds of biological data
An open-access program allowing three-item statement matrices to be generated
from data such as molecular sequences does not exist so far. The recently
developed LisBeth package (ver. 1.0) allows representing hypotheses of homology
among taxa or areas directly as rooted trees or as hierarchies; however, this
is not a standard matrix-based platform. Here we present "TAXON version 1.1"
(TAXON), a program designed for building three-item statement-matrices from
binary, additive (ordered) and non-additive (unordered) multistate characters,
with both fractional and uniform weighting of the resulted statements.Comment: 4 pages, 1 figure, 1 Supplement, 3 Supplemental example
No man’s land: information needs and resources of men with metastatic castrate resistant prostate cancer
The majority of men treated for prostate cancer will eventually develop castrate resistant disease (CRPC) with metastases (mCRPC). There are several options for further treatment: chemotherapy, third-line hormone therapy, radium, immunotherapy and palliation. Current ASCO guidelines for survivors of prostate cancer recommend that an individual’s information needs at all stages of disease are assessed, and that patients are provided with or referred to the appropriate sources for information and support. Earlier reviews have highlighted the dearth of such services and we wished to see if the situation had improved more recently. Unfortunately we conclude that there is still a lack of good quality congruent information easily accessible specifically for men with mCRPC and insufficient data regarding the risks, harms and benefits of different management plans. More research providing a clear evidence base about treatment consequences using patient reported outcome measures is required
Chandrasekhar-Kendall functions in astrophysical dynamos
Some of the contributions of Chandrasekhar to the field of
magnetohydrodynamics are highlighted. Particular emphasis is placed on the
Chandrasekhar-Kendall functions that allow a decomposition of a vector field
into right- and left-handed contributions. Magnetic energy spectra of both
contributions are shown for a new set of helically forced simulations at
resolutions higher than what has been available so far. For a forcing function
with positive helicity, these simulations show a forward cascade of the
right-handed contributions to the magnetic field and nonlocal inverse transfer
for the left-handed contributions. The speed of inverse transfer is shown to
decrease with increasing value of the magnetic Reynolds number.Comment: 10 pages, 5 figures, proceedings of the Chandrasekhar Centenary
Conference, to be published in PRAMANA - Journal of Physic
New insights into the role of androgen and oestrogen receptors in molecular apocrine breast tumours
Two recent studies on a rare androgen-dependent form of breast cancer have shed light on the biology of luminal tumours and reinforced the view that interfering with androgen signalling may have a place in the therapy of some forms of breast cancer
A comparison of 18F-FDG PET/MR with PET/CT in pulmonary tuberculosis
PURPOSE: PET/computed tomography (CT) has been shown to detect lesions in patients with pulmonary tuberculosis (PTB) and may be useful for assessing PTB disease in clinical research studies. However, radiation dose is of concern for clinical research in individuals with an underlying curable disease. This study aimed to determine whether PET/MR is equivalent to PET/CT in PTB. MATERIALS AND METHODS: Ten patients with microbiologically confirmed PTB were recruited. Patients received 129.0±4.1 MBq of fluorine-18-fluorodeoxyglucose. Five of the 10 patients underwent a PET/MR scan, followed by PET/CT. The remaining five were first imaged on the PET/CT, followed by the PET/MRI. PET acquisition began at 66.7±14.4 min (mean±SD) after injection when performing PET/MR first (PET/CT: 117.2±5.6 min) and 92.4±7.6 min when patients were imaged on PET/MR second (PET/CT: 61.1±3.9 min). PET data were reconstructed iteratively with Ordinary-Poisson Ordered-Subset Expectation-Maximization and reconstruction parameters were matched across the two scanners. A visual lesion detection task and a standardized uptake value (SUV) analysis were carried out. The CT Hounsfield unit values of PTB lesions were also compared with MR-based attenuation correction mu-map tissue classes. RESULTS: A total of 108 PTB lesions were detected on PET/MR and 112 on PET/CT. SUV analysis was carried out on 50 of these lesions that were observed with both modalities. Mean standardized uptake value (SUVmean) and maximum standardized uptake value (SUVmax) were significantly lower on PET/MR (SUVmean: 2.6±1.4; SUVmax: 4.3±2.5) than PET/CT (SUVmean: 3.5±1.5; SUVmax: 5.3±2.4). CONCLUSION: PET/MR visual performance was shown to be comparable to PET/CT in terms of the number of PTB lesions detected. SUVs were significantly lower on PET/MR. Dixon-based attenuation correction underestimates the linear attenuation coefficient of PTB lesions, resulting in lower SUVs compared with PET/CT. However, the use of PET/MR to measure the response of lung lesions to assess response to treatment in research studies is unlikely to be affected by these differences in quantification
Electronic Origin of High Temperature Superconductivity in Single-Layer FeSe Superconductor
The latest discovery of high temperature superconductivity signature in
single-layer FeSe is significant because it is possible to break the
superconducting critical temperature ceiling (maximum Tc~55 K) that has been
stagnant since the discovery of Fe-based superconductivity in 2008. It also
blows the superconductivity community by surprise because such a high Tc is
unexpected in FeSe system with the bulk FeSe exhibiting a Tc at only 8 K at
ambient pressure which can be enhanced to 38 K under high pressure. The Tc is
still unusually high even considering the newly-discovered intercalated FeSe
system A_xFe_{2-y}Se_2 (A=K, Cs, Rb and Tl) with a Tc at 32 K at ambient
pressure and possible Tc near 48 K under high pressure. Particularly
interesting is that such a high temperature superconductivity occurs in a
single-layer FeSe system that is considered as a key building block of the
Fe-based superconductors. Understanding the origin of high temperature
superconductivity in such a strictly two-dimensional FeSe system is crucial to
understanding the superconductivity mechanism in Fe-based superconductors in
particular, and providing key insights on how to achieve high temperature
superconductivity in general. Here we report distinct electronic structure
associated with the single-layer FeSe superconductor. Its Fermi surface
topology is different from other Fe-based superconductors; it consists only of
electron pockets near the zone corner without indication of any Fermi surface
around the zone center. Our observation of large and nearly isotropic
superconducting gap in this strictly two-dimensional system rules out existence
of node in the superconducting gap. These results have provided an unambiguous
case that such a unique electronic structure is favorable for realizing high
temperature superconductivity
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