796 research outputs found
Seismocardiographic Signal Timing with Myocardial Strain
Speckle Tracking Echocardiography (STE) is a relatively new method for
cardiac function evaluation. In the current study, STE was used to investigate
the timing of heart-induced mostly subaudible (i.e., below the frequency limit
of human hearing) chest-wall vibrations in relation to the longitudinal
myocardial strain. Such an approach may help elucidate the genesis of these
vibrations, thereby improving their diagnostic value
Physical properties of olive
B. Ghamary1,2, A. Rajabipour1, A. M. Borghei1, H. Sadeghi3(1. Agricultural Machinery Department., Faculty of Biosystems Engineering, University of Tehran, Karaj,Iran; 2. Ilam University, Ilam, Iran;3. Agricultural Machinery Department, Faculty of Agricultural Engineering, University of Mazandaran, Mazandaran, Iran) Abstract: Physical properties of olive, a fruit of paradise, and of other agricultural products are important factors in the design of processing, grading, transporting and other agricultural machinery. As an initial step to help improve the design of the machinery, in this research physical characteristics of two varieties of local olives, “yellow olive” and “oily olive”, were studied. Having been randomly collected during harvest season, for each olive sample three basic diameters, weight, and volume were measured and the following physical characteristics were estimated. For yellow olive and oily olive, the averages of geometric mean diameter were 20.04 mm and 18.28 mm respectively and their sphericties were 0.81 and 0.79 respectively. Application of regression analysis addressing the relationship between the volume and weight of each variety of olive yielded a significant relationship. Also, the volume of the olive samples was compared with that of an assumed ellipsoid shape, which again indicated a significant relationship. Finally, the correlation sought between olive flesh and the whole olive fruit was similarly found to be quite significant.Keywords: Olive, physical properties, geometric mean diameter, sphericity, Iran Citation: Ghamary B, A. Rajabipour, A. M. Borghei, H. Sadeghi. Physical properties of olive. Agric Eng Int: CIGR Journal, 2010, 12(2): 104-110.  
Beyond Gravitoelectromagnetism: Critical Speed in Gravitational Motion
A null ray approaching a distant astronomical source appears to slow down,
while a massive particle speeds up in accordance with Newtonian gravitation.
The integration of these apparently incompatible aspects of motion in general
relativity is due to the existence of a critical speed. Dynamics of particles
moving faster than the critical speed could then be contrary to Newtonian
expectations. Working within the framework of gravitoelectromagnetism, the
implications of the existence of a critical speed are explored. The results are
expected to be significant for high energy astrophysics.Comment: 13 pages, to appear in the Special December 2005 Issue of Int. J.
Mod. Phys.
Evidence for the Evolution of Young Early-Type Galaxies in the GOODS/CDF-S Field
We have developed an efficient photometric technique for identifying young
early-type galaxy candidates using a combination of photometric redshifts,
spectral-type classification, and optical/near-infrared colors. Applying our
technique to the GOODS HST/ACS and VLT/ISAAC data we have selected a complete
and homogeneous sample of young elliptical candidates among early-type field
galaxies. The distribution of structural parameters for these candidates shows
that their selection, which is based on early spectral types, is fully
consistent with early morphological types. We investigate the evolution of
their luminosities and colors as a function of redshift and galaxy mass and
find evidence for an increasing starburst mass fraction in these young
early-type galaxy candidates at higher redshifts, which we interpret in terms
of massive field galaxies experiencing more massive/intense starbursts at
higher redshifts. Moreover, we find indications for a systematically larger
young elliptical fraction among sub-L*/2 early-type galaxies compared to their
brighter counterparts. The total fraction among the field early-type galaxies
increases with redshift, irrespective of galaxy luminosity. Our results are
most consistent with galaxy formation scenarios in which stars in massive
early-type field galaxies are assembled earlier than in their low-mass
counterparts.Comment: 11 pages, 10 figures, accepted for publication in A
Helicity-Rotation-Gravity Coupling for Gravitational Waves
The consequences of spin-rotation-gravity coupling are worked out for linear
gravitational waves. The coupling of helicity of the wave with the rotation of
a gravitational-wave antenna is investigated and the resulting modifications in
the Doppler effect and aberration are pointed out for incident high-frequency
gravitational radiation. Extending these results to the case of a
gravitomagnetic field via the gravitational Larmor theorem, the rotation of
linear polarization of gravitational radiation propagating in the field of a
rotating mass is studied. It is shown that in this case the linear polarization
state rotates by twice the Skrotskii angle as a consequence of the spin-2
character of linear gravitational waves.Comment: 11 pages, no figures, accepted for publication in Phys. Rev. D; v2: a
few minor typos correcte
The MOSDEF Survey: Mass, Metallicity, and Star-formation Rate at z~2.3
We present results on the z~2.3 mass-metallicity relation (MZR) using early
observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey. We use an
initial sample of 87 star-forming galaxies with spectroscopic coverage of
H\beta, [OIII]\lambda 5007, H\alpha, and [NII]\lambda 6584 rest-frame optical
emission lines, and estimate the gas-phase oxygen abundance based on the N2 and
O3N2 strong-line indicators. We find a positive correlation between stellar
mass and metallicity among individual z~2.3 galaxies using both the N2 and O3N2
indicators. We also measure the emission-line ratios and corresponding oxygen
abundances for composite spectra in bins of stellar mass. Among composite
spectra, we find a monotonic increase in metallicity with increasing stellar
mass, offset ~0.15-0.3 dex below the local MZR. When the sample is divided at
the median star-formation rate (SFR), we do not observe significant SFR
dependence of the z~2.3 MZR among either individual galaxies or composite
spectra. We furthermore find that z~2.3 galaxies have metallicities ~0.1 dex
lower at a given stellar mass and SFR than is observed locally. This offset
suggests that high-redshift galaxies do not fall on the local "fundamental
metallicity relation" among stellar mass, metallicity, and SFR, and may provide
evidence of a phase of galaxy growth in which the gas reservoir is built up due
to inflow rates that are higher than star-formation and outflow rates. However,
robust conclusions regarding the gas-phase oxygen abundances of high-redshift
galaxies await a systematic reappraisal of the application of locally
calibrated metallicity indicators at high redshift.Comment: 12 pages, 6 figures, accepted for publication in the Astrophysical
Journal (ApJ
The MOSDEF Survey: Detection of [OIII]4363 and the direct-method oxygen abundance of a star-forming galaxy at z=3.08
We present measurements of the electron-temperature based oxygen abundance
for a highly star-forming galaxy at z=3.08, COSMOS-1908. This is the highest
redshift at which [OIII]4363 has been detected, and the first time
that this line has been measured at z>2. We estimate an oxygen abundance of
12+log(O/H). This galaxy is a low-mass (
M), highly star-forming ( M yr) system that
hosts a young stellar population ( Myr). We investigate the physical
conditions of the ionized gas in COSMOS-1908 and find that this galaxy has a
high ionization parameter, little nebular reddening (),
and a high electron density ( cm). We compare the ratios of
strong oxygen, neon, and hydrogen lines to the direct-method oxygen abundance
for COSMOS-1908 and additional star-forming galaxies at z=0-1.8 with
[OIII]4363 measurements, and show that galaxies at z1-3 follow
the same strong-line correlations as galaxies in the local universe. This
agreement suggests that the relationship between ionization parameter and O/H
is similar for z0 and high-redshift galaxies. These results imply that
metallicity calibrations based on lines of oxygen, neon, and hydrogen do not
strongly evolve with redshift and can reliably estimate abundances out to
z3, paving the way for robust measurements of the evolution of the
mass-metallicity relation to high redshift.Comment: 7 pages, 3 figures, 1 table, accepted to ApJ Letter
The MOSDEF Survey: Excitation Properties of Star-forming Galaxies
We present results on the excitation properties of z~2.3 galaxies using early
observations from the MOSFIRE Deep Evolution Field (MOSDEF) Survey. With its
coverage of the full suite of strong rest-frame optical emission lines, MOSDEF
provides an unprecedented view of the rest-frame optical spectra of a
representative sample of distant star-forming galaxies. We investigate the
locations of z~2.3 MOSDEF galaxies in multiple emission-line diagnostic
diagrams. These include the [OIII]/Hb vs. [NII]/Ha and [OIII]/Hb vs. [SII]/Ha
"BPT" diagrams, as well as the O_32 vs. R_23 excitation diagram. We recover the
well-known offset in the star-forming sequence of high-redshift galaxies in the
[OIII]/Hb vs. [NII]/Ha BPT diagram relative to SDSS star-forming galaxies.
However, the shift for our rest-frame optically selected sample is less
significant than for rest-frame-UV selected and emission-line selected galaxies
at z~2. Furthermore, we find that the offset is mass-dependent, only appearing
within the low-mass half of the z~2.3 MOSDEF sample, where galaxies are shifted
towards higher [NII]/Ha at fixed [OIII]/Hb. Within the [OIII]/Hb vs. [SII]/Ha
and O_32 vs. R_23 diagrams, we find that z~2.3 galaxies are distributed like
local ones, and therefore attribute the shift in the [OIII]/Hb vs. [NII]/Ha BPT
diagram to elevated N/O abundance ratios among lower-mass (M_*<10^10 M_sun)
high-redshift galaxies. The variation in N/O ratios calls into question the use
at high redshift of oxygen abundance indicators based on nitrogen lines, but
the apparent invariance with redshift of the excitation sequence in the O_32
vs. R_23 diagram paves the way for using the combination of O_32 and R_23 as an
unbiased metallicity indicator over a wide range in redshift. This indicator
will allow for an accurate characterization of the shape and normalization of
the mass-metallicity relationship over more than 10 Gyr.Comment: 14 pages, 9 figures, accepted to Ap
The MOSDEF Survey: Electron Density and Ionization Parameter at
Using observations from the MOSFIRE Deep Evolution Field (MOSDEF) survey, we
investigate the physical conditions of star-forming regions in
galaxies, specifically the electron density and ionization state. From
measurements of the [O II]3726,3729 and [S
II]6716,6731 doublets, we find a median electron density of
cm at , an increase of an order of magnitude
compared to measurements of galaxies at . While galaxies are
offset towards significantly higher O values relative to local galaxies
at fixed stellar mass, we find that the high-redshift sample follows a similar
distribution to the low-metallicity tail of the local distribution in the
O vs. R and O3N2 diagrams. Based on these results, we propose
that star-forming galaxies have the same ionization parameter as
local galaxies at fixed metallicity. In combination with simple photoionization
models, the position of local and galaxies in excitation diagrams
suggests that there is no significant change in the hardness of the ionizing
spectrum at fixed metallicity from to . We find that
galaxies show no offset compared to low-metallicity local galaxies
in emission line ratio diagrams involving only lines of hydrogen, oxygen, and
sulfur, but show a systematic offset in diagrams involving [N II]6584.
We conclude that the offset of galaxies from the local star-forming
sequence in the [N II] BPT diagram is primarily driven by elevated N/O at fixed
O/H compared to local galaxies. These results suggest that the local gas-phase
and stellar metallicity sets the ionization state of star-forming regions at
and .Comment: 26 pages, 14 figures, accepted to Ap
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