1,313 research outputs found
Determination of cloud microphysical properties by laser backscattering and extinction measurements
The extinction and backscattering of 514 nm laser radiation in polydisperse water droplet clouds was studied in the laboratory. Three cloud size distributions with modal diameters of 0.02, 5.0, and 12.0 microns were investigated. The relationships between the cloud optical parameters (attentuation coefficient, sigma and volume backscattering coefficient, Beta (sub pi)) and the cloud water content, C, were measured for each size distribution. It was found that a linear relationship exists between sigma and C and between beta (sub pi) and C for cloud water content values up to 3gm/cubic m. The linear relationships obtained, however, have slopes which depend on the droplet size distribution. For a given water content both sigma and beta (sub pi) increase as the modal diameter decreases. The measured data are compared with existing theoretical analyses and discussed in terms of thie application to lidar measurements of atmospheric clouds. It is concluded that the empirical information obtained can serve as a basis for quantitative lidar measurements
Surveying Caulerpa (Chlorophyta) species along the shores of the eastern Mediterranean
Caulerpa (Chlorophyta) species inhabiting intertidal and shallow subtidal areas along the Israeli Mediterranean shores were surveyed (i.e. presence/absence) on a seasonal basis from 2007-2009. We recorded the presence of three speciesC. prolifera, C. mexicana, and C. scalpelliformis. These species were noticeable in autumn and inconspicuous during winter, thus, revealing seasonality and population dynamics. There were no indications of well-known invasive species such as Caulerpa racemosa var.cylindracea and Caulerpa taxifolia. This study is the first of a kind that assesses the geographical distribution and seasonality of the genus Caulerpa along the Israeli shores
Final-sate radiation in electron-positron annihilation into a pion pair
The process of annihilation into a pair with radiation
of a photon is considered. The amplitude of the reaction
consists of the model independent initial-state
radiation (ISR) and model-dependent final-state radiation (FSR). The general
structure of the FSR tensor is constructed from Lorentz covariance, gauge
invariance and discrete symmetries in terms of the three invariant functions.
To calculate these functions we apply Chiral Perturbation Theory (ChPT) with
vector and axial-vector mesons. The contribution of
process to the muon anomalous magnetic moment is evaluated, and results are
compared with the dominant contribution in the framework of a hybrid model,
consisting of VMD and point-like scalar eletrodynamics. The developed approach
allows us also to calculate the charge asymmetry.Comment: 21 pages, 8 figure
Inclusion theorems for absolutely λ-summing maps
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46213/1/208_2005_Article_BF02052868.pd
Sexual reproduction and biometry of the nonzooxanthellate papillose cup coral Paracyathus pulchellus
Basic information on the reproductive biology of many scleractinian corals
species is limited or entirely lacking, particularly from temperate zones, though
it is essential for a better understanding of their ecology. This study describes
the morphological aspects and the annual cycle of gametogenesis and
biometric parameters of the papillose cup coral Paracyathus pulchellus
collected at Palinuro (Italy, Southern Tyrrhenian Sea), filling a knowledge gap
about the reproductive biology of a widespread Mediterranean and Northern
Atlantic coral. Samples of P. pulchellus were collected by SCUBA diving
between 5- and 10-meters depth during 18 monthly collections from June
2010 to December 2011. Sexually active polyps displayed either oocytes or
spermaries, indicating that P. pulchellus was gonochoric. The sex ratio of
sexually active polyps was 1:1. Gametogenesis began with undifferentiated
germ cells arose in the gastrodermis that migrated towards the mesoglea of the
mesentery where they completed the development. During spermatogenesis,
spermary diameter increased from 25 to 83 µm. Oocyte diameter ranged from
9 to 146 µm and during oogenesis the nucleus/cytoplasm ratio decreased due
to the accumulation of yolk. The nucleus migrated to the periphery of the
oocyte adhering closely to the cell membrane. No embryo was observed in the
coelenteric cavity of the polyps, suggesting an external development of
planktotrophic larvae due to the small-sized mature oocytes and a possible
broadcast spawning reproductive mode. Gonadal index of both females and
males increased significantly from August until November and fertilization took
place from November to January. Only sexually inactive individuals were
observed from February to April, suggesting a quiescence period in both
males and females. Seasonal variations in water temperature and
photoperiod may have a key role in regulating gametogenesis. The analysis
of the main biometric parameters (polyp width, height, dry skeletal mass, volume, surface/volume ratio and bulk skeletal density) showed a negative
correlation between size and skeletal density, and no sexual dimorphism
Reproduction of the azooxanthellate coral Caryophyllia inornata is not affected by temperature along an 850 km gradient on the Western Italian coast
The Intergovernmental Panel on Climate Change (IPCC) predicted that ocean surface
temperature will rise of 0.6–2.0◦C by 2100. Ocean warming is expected to produce
strong impacts on marine ecosystems such as coral reefs, affecting their physiological
events including reproductive processes. To date, relatively few studies have examined
the effects of climate change on the reproductive success of temperate corals
and even less in the azooxanthellate ones. This study examined the reproductive
output of the azooxanthellate Mediterranean coral Caryophyllia inornata along a wide
latitudinal gradient of seawater temperature and solar radiation. A total of 260 samples,
collected from five populations along the Western Italian coast, have been analyzed
through histological techniques. The intriguing aspects characterizing all populations
of C. inornata along the latitudinal gradient are a strong male-biased sex ratio and
the presence of embryos in all stages of development throughout the year in females,
males, and sexually inactive individuals. This peculiarity could suggest a mixed strategy
of sexual and asexual reproduction in this species as has been observed for some
anemones of the genus Actinia. Fecundity and spermary abundance (i.e., the number
of reproductive elements per body volume unit), gonadal index (i.e., the percentage of
body volume occupied by the germ cells) and fertility (i.e., the number of embryos per
body volume unit) in females, males and sexually inactive individuals were unrelated
to solar radiation and temperature along the latitudinal gradient. These results suggest
that the reproduction in C. inornata is not affected by increasing solar radiation and
temperature. The lack of zooxanthellae could make this species less dependent on
these environmental parameters, as previously hypothesized for another azooxanthellate
species, Leptopsammia pruvoti, investigated along the same gradient
Ocean warming and acidification detrimentally affect coral tissue regeneration at a Mediterranean CO2 vent
Among the main phenomena that are causing significant changes in ocean waters are warming and acidification, largely due to anthropogenic activities. Growing evidence suggests that climate change is having more substantial and rapid effects on marine communities than on terrestrial ones, triggering several physiological responses in these organisms, including in corals. Here we investigated, for first time in the field, the combined effect of increasing seawater acidification and warming on tissue regeneration rate of three Mediterranean scleractinian coral species characterized by different trophic strategies and growth modes. Balanophyllia europaea (solitary, zooxanthellate), Leptopsammia pruvoti (solitary, non-zooxanthellate) and Astroides calycularis (colonial, non-zooxanthellate) specimens were transplanted, during a cold, intermediate, and warm period, along a natural pH gradient generated by an underwater volcanic crater at Panarea Island (Mediterranean Sea, Italy), characterized by continuous and localized CO2 emissions at ambient temperature. Our results show a decrease in regenerative capacity, especially in the zooxanthellate species, with increasing seawater temperature and acidification, with demonstrated species-specific differences. This finding suggests that increasing seawater temperature and acidification could have a compounding effect on coral regeneration following injury, potentially hindering the capacity of corals to recover following physical disturbance under predicted climate change
Electromagnetic form factors of charged and neutral kaons in an extended vector-meson-dominance model
A model is developed for electromagnetic form factors of the charged and
neutral K-mesons. The formalism is based on ChPT Lagrangians with vector
mesons. The form factors, calculated without fitting parameters, are in a good
agreement with experiment for space-like and time-like photon momenta.
Contribution of the two-kaon channels to the muon anomalous magnetic moment
a_\mu is calculated.Comment: 23 pages, 11 figures, accepted for publication in Eur. Phys. J.
Low and variable pH decreases recruitment efficiency in populations of a temperate coral naturally present at a CO2 vent
Atmospheric carbon dioxide enrichment alters seawater carbonate chemistry, thus threatening calcifying
organisms such as corals. Coral populations at carbon dioxide vents are natural acidification experiments that
mimic organism responses to seawater pH values projected for 2100. Even if demographic traits are paramount
information to assess ecological relationships and habitat suitability, population dynamics studies on corals
thriving under acidified conditions are lacking. Here, we investigate the demography and reproduction of popu-
lations of the solitary, symbiotic, temperate coral Balanophyllia europaea naturally living along a pH gradient at a
Mediterranean CO2 vent. Gametogenesis and larval production were unaffected while recruitment efficiency
collapsed at low and variable pH, contributing to coral abundance decline and suggesting that life stages
between larval release and early polyp growth are hindered by acidification. Exploring these processes is crucial
to assess coral fate in the forthcoming acidified oceans, to preserve coral ecosystems and the socioeconomic ser-
vices they provide
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