566 research outputs found
Markerless View Independent Gait Analysis with Self-camera Calibration
We present a new method for viewpoint independent markerless gait analysis. The system uses a single camera, does not require camera calibration and works with a wide range of directions of walking. These properties make the proposed method particularly suitable for identification by gait, where the advantages of completely unobtrusiveness, remoteness and covertness of the biometric system preclude the availability of camera information and use of marker based technology. Tests on more than 200 video sequences with subjects walking freely along different walking directions have been performed. The obtained results show that markerless gait analysis can be achieved without any knowledge of internal or external camera parameters and that the obtained data that can be used for gait biometrics purposes. The performance of the proposed method is particularly encouraging for its appliance in surveillance scenarios
Reversible and Irreversible Spacetime Thermodynamics for General Brans-Dicke Theories
We derive the equations of motion for Palatini F(R) gravity by applying an
entropy balance law T dS= \delta Q+\delta N to the local Rindler wedge that can
be constructed at each point of spacetime. Unlike previous results for metric
F(R), there is no bulk viscosity term in the irreversible flux \delta N. Both
theories are equivalent to particular cases of Brans-Dicke scalar-tensor
gravity. We show that the thermodynamical approach can be used ab initio also
for this class of gravitational theories and it is able to provide both the
metric and scalar equations of motion. In this case, the presence of an
additional scalar degree of freedom and the requirement for it to be dynamical
naturally imply a separate contribution from the scalar field to the heat flux
\delta Q. Therefore, the gravitational flux previously associated to a bulk
viscosity term in metric F(R) turns out to be actually part of the reversible
thermodynamics. Hence we conjecture that only the shear viscosity associated
with Hartle-Hawking dissipation should be associated with irreversible
thermodynamics.Comment: 12 pages, 1 figure; v2: minor editing to clarify Section III, fixed
typos; v3: fixed typo
Growth and Demography of the Solitary Scleractinian Coral Leptopsammia pruvoti along a Sea Surface Temperature Gradient in the Mediterranean Sea
The demographic traits of the solitary azooxanthellate scleractinian Leptopsammia pruvoti were determined in six populations on a sea surface temperature (SST) gradient along the western Italian coasts. This is the first investigation of the growth and demography characteristics of an azooxanthellate scleractinian along a natural SST gradient. Growth rate was homogeneous across all populations, which spanned 7 degrees of latitude. Population age structures differed between populations, but none of the considered demographic parameters correlated with SST, indicating possible effects of local environmental conditions. Compared to another Mediterranean solitary scleractinian, Balanophyllia europaea, zooxanthellate and whose growth, demography and calcification have been studied in the same sites, L. pruvoti seems more tolerant to temperature increase. The higher tolerance of L. pruvoti, relative to B. europaea, may rely on the absence of symbionts, and thus the lack of an inhibition of host physiological processes by the heat-stressed zooxanthellae. However, the comparison between the two species must be taken cautiously, due to the likely temperature differences between the two sampling depths. Increasing research effort on determining the effects of temperature on the poorly studied azooxanthellate scleractinians may shed light on the possible species assemblage shifts that are likely to occur during the current century as a consequence of global climatic change
Kommerell’s diverticulum and aneurysmal right-sided aortic arch: A case report and review of the literature
AbstractRight-sided aortic arch is a rare variant of the thoracic vascular anatomy that may be accompanied by an aberrant origin of the left subclavian artery. We report a true aneurysm of the distal arch and descending thoracic aorta in a patient with right-sided arch and review previous descriptions of aneurysms of anomalous right-sided aortas. In our patient, the left subclavian artery originated at the junction between the distal arch and the descending thoracic aorta located in the right chest and was aneurysmal (Kommerell’s diverticulum); the thoracic aorta was also aneurysmal. Extra-anatomic left subclavian-to-carotid transposition was performed before the intrathoracic procedure. Subsequently, a right thoracotomy provided adequate exposure for repairing the aortic aneurysm and oversewing the aneurysmal origin of the subclavian artery. Because the distal aortic arch was involved, deep hypothermia and circulatory arrest were used. Only five previous instances of true aneurysms of a right-sided aortic arch have been reported; four of these patients underwent operative repair (via bilateral thoracotomy, median sternotomy, or right thoracotomy). We believe that a right thoracotomy provides good exposure and avoids the morbidity associated with bilateral thoracotomy. The reconstruction of the subclavian artery has not previously been reported in this setting. Performing subclavian reconstruction as an extrathoracic procedure before the intrathoracic repair would be expected to reduce the subsequent risk of distal ischemia or subclavian steal without increasing the overall morbidity associated with the procedure. (J Vasc Surg 2000;32:1208-14.
Extreme flooding events in coastal lagoons: seawater parameters and rainfall over a six-year period in the Mar Menor (SE Spain)
Climate change is one of the main problems currently strongly conditioning ecosystems all over the world. Coastal lagoons are amongst the most vulnerable habitats, and they are undergoing extensive human impact due to their high production rates and the close proximity of urban and agricultural centers. The Mar Menor, the largest saltwater lagoon in Europe, is an example of a highly impacted ecosystem. In December 2016 and September 2019, climate change-induced DANA
(upper-level isolated atmospheric depression) flooding events took place there, temporarily altering the lagoon oceanographic properties. Data gathered throughout the lagoon (11 stations inside and 1 outside the lagoon) from 2016 to 2021 were analyzed in order to assess the variability of seawater parameters: salinity, density, chlorophyll-a, turbidity, and dissolved oxygen, due to DANA events.
Results showed a change in seawater parameters that were reestablished at different rates, 4 and 10 months in 2016 and 2019, respectively, following a description of the environmental conditions and effects that have been reported after extreme rainfall in the lagoon. The amount of rainfall correlated with changes in the analyzed seawater parameters, such as an increase in turbidity and chlorophyll-a values. Furthermore, turbidity correlated with chlorophyll-a and oxygen saturation,
while density correlated with salinity. Such extreme weather events are worsened by climate change, growing more frequent and between shorter intervals in time. In order to decelerate ecosystem decline, comprehensive management plans are needed to address the various factors that might add to anthropic impacts in natural environments
Environmental infuence on calcifcation of the bivalve Chamelea gallina along a latitudinal gradient in the Adriatic Sea
Environmental factors are encoded in shells of marine bivalves in the form of geochemical properties, shell microstructure and shell growth rate. Few studies have investigated how shell growth is affected by habitat conditions in natural populations of the commercial clam Chamelea gallina. Here, skeletal parameters (micro-density and apparent porosity) and growth parameters (bulk density, linear extension and net calcification rates) were investigated in relation to shell sizes and environmental parameters along a latitudinal gradient in the Adriatic Sea (400 km). Net calcification rates increased with increasing solar radiation, sea surface temperature and salinity and decreasing Chlorophyll concentration in immature and mature shells. In immature shells, which are generally more porous than mature shells, enhanced calcification was due to an increase in bulk density, while in mature shells was due to an increase in linear extension rates. The presence of the Po river in the Northern Adriatic Sea was likely the main driver of the fluctuations observed in environmental parameters, especially salinity and Chlorophyll concentration, and seemed to negatively affect the growth of C. gallina
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
- …