On the nature of gravitational forces

In this paper I show how the statistics of the gravitational field is changed when the system is characterized by a non-uniform distribution of particles. I show how the distribution functions W(dF/dt) giving the joint probability that a test particle is subject to a force F and an associated rate of change of F given by dF/dt, are modified by inhomogeneity. Then I calculate the first moment of dF/dt to study the effects of inhomogenity on dynamical friction. Finally I test, by N-Body simulations, that the theoretical W(F) and dF/dt describes correctly the experimental data and I find that the stochastic force distribution obtained for the evolved system is in good agreement with theory. Moreover, I find that in an inhomogeneous background the friction force is actually enhanced relative to the homogeneous case

Rapid post-glacial bedrock weathering in coastal Norway

Quantifying bedrock weathering rates under diverse climate conditions is essential to understanding timescales of landscape evolution. Yet, weathering rates are often difficult to constrain, and associating a weathered landform to a specific formative environment can be complicated by overprinting of successive processes and temporally varying climate. In this study, we investigate three sites between 59°N and 69°N along the Norwegian coast that display grussic saprolite, tafoni, and linear weathering grooves on diverse lithologies. These weathering phenomena have been invoked as examples of geomorphic archives predating Quaternary glaciations and consequently as indicators of minimal glacial erosion. Here we apply cosmogenic nuclide chronometry to assess the recent erosional history. Our results demonstrate that all three sites experienced sufficient erosion to remove most cosmogenic nuclides formed prior to the Last Glacial Maximum. This finding is inconsistent with preservation of surficial (<1–2 m) weathered landforms under non-erosive ice during the last glacial period, while simultaneously demonstrating that post-glacial weathering and erosion rates can be locally rapid (4–10 cm kyr−1) in cold temperate to subarctic coastal locations

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

Female reproductive pattern of Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae) in Iskenderun Bay, Eastern Mediterranean

We studied the female reproductive pattern of Callinectes sapidus, which was introduced to the Mediterranean in the 20th century. We assessed female size at first maturity, fecundity, and fecundity relationship to size in Iskenderun Bay, eastern Mediterranean, Turkey. Samples were collected between July 2014 and June 2015 using bottom trawling at depths ranging from 1 to 50 m. A total of 322 crabs were caught of which 308 (95.7%) were females including 116 ovigerous ones. The minimum carapace width of the mature females was 39.1 mm and the mean carapace width 123.8 mm. The carapace width of ovigerous females varied between 95.1 and 144.5 mm, with a mean of 120.3 mm. The highest number of ovigerous females was observed in July and August. Mean fecundity was 1.91 million (667,950–4,669,853) eggs per female. A weak positive linear relationship between fecundity and carapace width was noted, as well as a high correlation with total egg weight. In the eastern Mediterranean, maturity sizes of females were smaller than those in the native region of the species. © 2017 Taylor & Francis.SÜF2013BAP25Funding was provided by the Research Fund of Çukurova University, project number SÜF2013BAP25

Potential interaction between plastic litter and green turtle Chelonia mydas during nesting in an extremely polluted beach

PubMedID: 30803627This study examines the extent of macroplastic pollution on Samandağ beach and the potential effects on green sea turtles during nesting. For this purpose, a total of 39 different turtle tracks were studied. Mean plastic concentration was found to be 19.5 ± 1.2 pcs m-2. Among the different types of crawling, the highest concentrations of plastics were found on the tracks of turtles that did not attempt to dig nests (25.9 ± 8.4 pcs m-2). In total, 7 different types of plastics (disposable, film, fishing-related, foam, fragments, miscellaneous, and textile) were found, with film-type plastics being the most prevalent (11 pcs m-2). Samandağ beach was found to be greatly more polluted than any other beach in the Mediterranean Sea. We concluded that this pollution can cause negative effects, especially entanglement and entrapment, on green sea turtle females and hatchlings. © 2019 Elsevier LtdRufford Foundation: 23605-1This study was supported by Rufford Foundation with grant number 23605-1

Distribution and population density of the ghost crab, Ocypode cursor (Linneaus, 1758) in Yumurtalik Beach, Turkey

The distribution and population density of the ghost crab, Ocypode cursor were studied in Yumurtalik Beach, Turkey during summer, 2009. Burrow densities of ghost crab were measured at three beach zones in relation to the Reference Datum (RD) with middle heights of 2, 4, and 9 m, which were located at medi-olittoral, supra-littoral, and sub-terrestrial fringe, respectively. Generally, individuals occurred above 1 m in height in relation to RD and peaked between 2 and 4 m. A range from 0 to 4.2 burrows/m2 was obtained, and the total number of crabs on this beach (approximately is 2256 km2) ranging from 18.99 burrows/m2 to 56.41 burrows/m2. Significant differences in the mean burrow density were found among three zones. Low densities were recorded in the sub-terrestrial zone in September and peak density in the supralittoral zone in August. In general crabs followed a clumped dispersion on Yumurtalik beach. In total 986 burrow diameters were measured where diameter ranged from 3 to 97.8 mm. The results provided evidence that Yumurtalik Beach can provide suitable habitats for O. cursor population. Ocypode cursor is not vulnerable to the anthropogenic disturbances and environmental alterations found at Yumurtalik Beach