3,141 research outputs found
Multivariate Design of Experiments for Engineering Dimensional Analysis
We consider the design of dimensional analysis experiments when there is more
than a single response. We first give a brief overview of dimensional analysis
experiments and the dimensional analysis (DA) procedure. The validity of the DA
method for univariate responses was established by the Buckingham -Theorem
in the early 20th century. We extend the theorem to the multivariate case,
develop basic criteria for multivariate design of DA and give guidelines for
design construction. Finally, we illustrate the construction of designs for DA
experiments for an example involving the design of a heat exchanger
The Probable Detection of SN 1923A: The Oldest Radio Supernova?
Based upon the results of VLA observations, we report the detection of two
unresolved radio sources that are coincident with the reported optical position
of SN 1923A in M83. For the source closest to the SN position, the flux density
was determined to be 0.30 +/- 0.05 mJy at 20 cm and 0.093 +/- 0.028 mJy at 6
cm. The flux density of the second nearby source was determined to be 0.29 +/-
0.05 at 20 cm and 0.13 +/- 0.028 at 6 cm. Both sources are non-thermal with
spectral indices of alpha = -1.0 +/- 0.30 and -0.69 +/- 0.24, respectively. SN
1923A has been designated as a Type II-P. No Type II-P (other than SN 1987A)
has been detected previously in the radio. The radio emission from both sources
appears to be fading with time. At an age of approximately 68 years when we
observed it, this would be the oldest radio supernova (of known age) yet
detected
Corneoscleral laceration and ocular burns caused by electronic cigarette explosions
PURPOSE: To report cases of acute globe rupture and bilateral corneal burns from electronic cigarette (EC) explosions. METHODS: Case series. RESULTS: We describe a series of patients with corneal injury caused by EC explosions. Both patients suffered bilateral corneal burns and decreased visual acuity, and one patient sustained a unilateral corneoscleral laceration with prolapsed iris tissue and hyphema. A review of the scientific literature revealed no prior reported cases of ocular injury secondary to EC explosions; however, multiple media and government agency articles describe fires and explosions involving ECs, including at least 4 with ocular injuries. CONCLUSIONS: Given these cases and the number of recent media reports, ECs pose a significant public health risk. Users should be warned regarding the possibility of severe injury, including sight-threatening ocular injuries ranging from corneal burns to full-thickness corneoscleral laceration
Classical field theory. Advanced mathematical formulation
In contrast with QFT, classical field theory can be formulated in strict
mathematical terms of fibre bundles, graded manifolds and jet manifolds. Second
Noether theorems provide BRST extension of this classical field theory by means
of ghosts and antifields for the purpose of its quantization.Comment: 30 p
11HDL-induced cardioprotection is independent of the HDL receptor, scavenger receptor B1
Purpose: High-density lipoproteins (HDL) are atheroprotective. New evidence shows that HDL has widespread actions, including protection against cardiac ischemia reperfusion injury (IRI). This cardioprotective role has been attributed to several constituents of the HDL particle, including apolipoprotein A1 (apoA1) the major protein constituent and sphingosine-1-phosphate (S1P). However, the exact mechanisms of HDL-induced cardioprotection are still unknown and are under intensive investigation. A particular unresolved question remains the specific role of the HDL receptor, Scavenger Receptor BI (SR-BI), in the heart. The latter mediates many of the intracellular effects of HDL. The aim of this study was to evaluate the specific role of SR-BI in the protective impact of HDL on the heart. Methods and Results: The effects of HDL on the heart was evaluated in vitro using rat cultured neonatal cardiomyocytes and ex vivo in mice using the isolated heart Langendorff model of IRI (global no flow ischemia 35min, reperfusion 60min). In this model, HDL (400μg/mL) was injected during the first 7min of reperfusion and infarct size was assessed by triphenyltetrazolium chloride (TTC) staining. The specific role of SR-BI was investigated in vitro using specific siRNA facilitated knockdown and ex vivo using SR-BI knockout (SR-BI KO) mice. We confirmed that SR-BI is expressed in the cardiomyocytes and that HDL binds specifically to these cells. Treatment of cardiomyocytes with HDL induced the activation of several prosurvival signalling proteins, including Akt, STAT3 and ERK1/2 and protected the cells against oxidative stress induced by doxorubicin. Although specific binding of HDL was significantly reduced in SR-BI knockdown cardiomyocytes, activation of the prosurvival pathways was not affected. Similarly, SR-BI knockdown did not reduce the in vitro protective influence of HDL against oxidative stress induced by doxorubicin. Ex vivo, IRI induced an infarct size of 17.3±0.6% in isolated hearts of wildtype mice. HDL treatment during the first phase of reperfusion significantly reduced the infarct size by approximately 35% (p<0.05). This protective effect induced by HDL is maintained in SR-BI KO mice (40% of infarct size reduction (p<0.05) compared to non-treated SR-BI-KO mice). Conclusion: This is the first time that the specific role of SR-BI in the impact of HDL on the heart is investigated. Our results do not support a role for the HDL receptor SR-BI in the protective influence of HDL. Further investigations will be required to elucidate the exact mechanisms of HDL-induced cardioprotectio
Phonons in intrinsic Josephson systems with parallel magnetic field
Subgap resonances in the I-V curves of layered superconductors are explained
by the coupling between Josephson oscillations and phonons with dispersion in
c-direction. In the presence of a magnetic field applied parallel to the layers
additional structures due to fluxon motion appear. Their coupling with phonons
is investigated theoretically and a shift of the phonon resonances in strong
magnetic fields is predicted.Comment: Invited Paper to the "2nd International Symposium on Intrinsic
Josephson Effects and Plasma Oscillations in High-Tc Superconductors", 22-24
August 2000, Sendai, Japan, to be published in Physica
On the map: Nature and Science editorials
Bibliometric mapping of scientific articles based on keywords and technical terms in abstracts is now frequently used to chart scientific fields. In contrast, no significant mapping has been applied to the full texts of non-specialist documents. Editorials in Nature and Science are such non-specialist documents, reflecting the views of the two most read scientific journals on science, technology and policy issues. We use the VOSviewer mapping software to chart the topics of these editorials. A term map and a document map are constructed and clusters are distinguished in both of them. The validity of the document clustering is verified by a manual analysis of a sample of the editorials. This analysis confirms the homogeneity of the clusters obtained by mapping and augments the latter with further detail. As a result, the analysis provides reliable information on the distribution of the editorials over topics, and on differences between the journals. The most striking difference is that Nature devotes more attention to internal science policy issues and Science more to the political influence of scientists
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