2,118 research outputs found
Complete asymptotic expansions for eigenvalues of Dirichlet Laplacian in thin three-dimensional rods
We consider Dirichlet Laplacian in a thin curved three-dimensional rod. The
rod is finite. Its cross-section is constant and small, and rotates along the
reference curve in an arbitrary way. We find a two-parametric set of the
eigenvalues of such operator and construct their complete asymptotic
expansions. We show that this two-parametric set contains any prescribed number
of the first eigenvalues of the considered operator. We obtain the complete
asymptotic expansions for the eigenfunctions associated with these first
eigenvalues
Simultaneous fNIRS and thermal infrared imaging during cognitive task reveal autonomic correlates of prefrontal cortex activity
Functional Near Infrared-Spectroscopy (fNIRS) represents a powerful tool to non-invasively study task-evoked brain activity. fNIRS assessment of cortical activity may suffer for contamination by physiological noises of different origin (e.g. heart beat, respiration, blood pressure, skin blood flow), both task-evoked and spontaneous. Spontaneous changes occur at different time scales and, even if they are not directly elicited by tasks, their amplitude may result task-modulated. In this study, concentration changes of hemoglobin were recorded over the prefrontal cortex while simultaneously recording the facial temperature variations of the participants through functional infrared thermal (fIR) imaging. fIR imaging provides touch-less estimation of the thermal expression of peripheral autonomic. Wavelet analysis revealed task-modulation of the very low frequency (VLF) components of both fNIRS and fIR signals and strong coherence between them. Our results indicate that subjective cognitive and autonomic activities are intimately linked and that the VLF component of the fNIRS signal is affected by the autonomic activity elicited by the cognitive task. Moreover, we showed that task-modulated changes in vascular tone occur both at a superficial and at larger depth in the brain. Combined use of fNIRS and fIR imaging can effectively quantify the impact of VLF autonomic activity on the fNIRS signals
Preliminary analysis of Skylab RADSCAT results over the ocean
Preliminary observations at 13.9 GHz of the radar backscatter and microwave emission from the sea were analyzed using data obtained by the radiometer scatterometer on Skylab. Results indicate approximately a square-law relationship between differential scattering coefficient and windspeed at angles of 40 deg to 50 deg, after correction for directional effect, over a range from about 4 up to about 25 meters/sec. The brightness temperature response was also observed, and considerable success was achieved in correcting it for atmospheric attenuation and emission. Measurements were made in June, 1973, over Hurricane Ava off the west coast of Mexico and over relatively calm conditions in the Gulf of Mexico and Caribbean Sea
A people-oriented paradigm for smart cities
Most works in the literature agree on considering the Internet of Things (IoT) as the base technology to collect information related to smart cities. This information is usually offered as open data for its analysis, and to elaborate statistics or provide services which improve the management of the city, making it more efficient and more comfortable to live in. However, it is not possible to actually improve the quality of life of smart cities’ inhabitants if there is no direct information about them and their experiences. To address this problem, we propose using a social and mobile computation model, called the Internet of People (IoP) which empowers smartphones to recollect information about their users, analyze it to obtain knowledge about their habits, and provide this knowledge as a service creating a collaborative information network. Combining IoT and IoP, we allow the smart city to dynamically adapt its services to the needs of its citizens, promoting their welfare as the main objective of the city.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Dermoscopy and methyl aminolevulinate: A study for detection and evaluation of field cancerization
Actinic keratosis (AK) is a keratinocyte intraepidermal neoplasia UV light
–
induced that frequently appears in
sun-exposed areas of the skin. Although historically AK was de
fi
ned as
“
precancerous
”
, actually it is considered
as the earliest stage of squamous cell carcinoma (SCC) in situ. Since AKs can progress into invasive SCC, their
treatment isrecommended. AKsrarely developasa singlelesion;usually multiplelesions commonly affect anen-
tire area of chronically actinic damaged skin. This has led to the concept of
“
fi
eld cancerization
”
, an area chroni-
cally sun-exposed that surrounds peripherally visible lesions, in which are individualized subclinical alterations.
One of the main principles endpoint in the management of AKs is the evaluation and the treatment of
fi
eld
cancerization. In this view, in order to detect and quantify
fi
eld cancerization, we employed a method based
on the topical application of methyl aminolevulinate (MAL) and the detection of the
fl
uorescence emitted by
its metabolite Protoporphyrin IX (PpIX); then, considering the extension and the intensity of measured
fl
uores-
cence, we create a score of
fi
eld cancerization. The results show that patients underwent to daylight PDT had a
reduction of total score, from T0 to T2. Whereas in the group untreated we observed a stability of total score or
a slightly worse. So, the method and the score used allows to evaluate with a good approximation the dimension
of
fi
eld cancerization and show the modi
fi
cation of it after treatment
Superluminal behavior and the Minkowski space-time
Bessel X-waves, or Bessel beams, have been extensively studied in last years,
especially with regard to the topic of superluminality in the propagation of a
signal. However, in spite of many efforts devoted to this subject, no definite
answer has been found, mainly for lack of an exact definition of signal
velocity. The purpose of the present work is to investigate the field of
existence of Bessel beams in order to overcome the specific question related to
the definition of signal velocity. Quite surprisingly, this field of existence
can be represented in the Minkowski space-time by a Super-Light Cone which
wraps itself around the well-known Light Cone. So, the change in the upper
limit of the light velocity does not modify the fundamental low of the
relativity and the causal principle.Comment: 3 pages, 2 figure
Preliminary report on Skylab S-193 Radscat measurements of Hurricane Ava
The author has identified the following significant results. The Skylab RADSCAT instrument S-193 was operated on 6 June 1973 while the spacecraft flew past Hurricane Ava in the eastern Pacific Ocean. Scatterometer returns at all polarizations and radiometer measurements were obtained from a section through the storm with winds up to 48 knots at 52 deg incident angle and 35 knots at 45.5 deg incident angle. These first hurricane scatterometer measurements indicate reasonable correlation between wind speed and backscatter, with horizontal response much stronger than the vertical response at 52 deg. Each of the sections through the hurricane contains an as yet unexplained dip in cross section at a point 200 to 300 km prior to passing the eye. The response at a point where the radiometer signal's dramatic increase indicates strong rain is also accompanied by a strong increase in the backscattered signal. No attempt has been made to make a thorough correlation of radiometric response with wind speed, but the atmospheric contribution to the radiometer signal is quite apparent
Quinstant Dark Energy Predictions for Structure Formation
We explore the predictions of a class of dark energy models, quinstant dark
energy, concerning the structure formation in the Universe, both in the linear
and non-linear regimes. Quinstant dark energy is considered to be formed by
quintessence and a negative cosmological constant. We conclude that these
models give good predictions for structure formation in the linear regime, but
fail to do so in the non-linear one, for redshifts larger than one.Comment: 9 pages, 14 figures, "Accepted for publication in Astrophysics &
Space Science
Optical Guidance System /OGS/ for rendezvous and docking Final report
Optical guidance system for Apollo rendezvous and dockin
Skylab S-193 Radscat microwave measurements of sea surface winds
The S-193 Radscat made extensive measurements of many sea conditions. Measurements were taken in a tropical hurricane (Ava), a tropical storm (Christine), and in portions of extratropical cyclones. Approximately 200 scans of ocean data at 105 kilometer spacings were taken during the first two Skylab missions and another 200 during the final mission when the characteristics of the measurements changed due to damage of the antenna. Backscatter with four transmit/receive polarization combinations and emissions with horizontal and vertical receive polarizations were measured. Other surface parameters investigated for correlation with the measurements included sea temperature, air/sea temperature difference, and gravity-wave spectrum. Methods were developed to correct the microwave measurements for atmospheric effects. The radiometric data were corrected accurately for clear sky and light cloud conditions only. The radiometer measurements were used to recover the surface scattering characteristics for all atmospheric conditions excluding rain. The radiometer measurements also detected the presence of rain which signaled when the scattering measurement should not be used for surface wind estimation. Regression analysis was used to determine empirically the relation between surface parameters and the microwave measurements, after correction for atmospheric effects. Results indicate a relationship approaching square-law at 50 deg between differential scattering coefficient and wind speed with horizontally polarized scattering data showing slightly more sensitivity to wind speed than vertically polarized data
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