Water permeability of two different lipid bilayers of dipalmitoylphosphatidylcholine (DPPC) and palmitoylsphingomyelin (PSM) in the absence and presence of cholesterol (0–50 mol %) have been studied ...by molecular dynamics simulations to elucidate the molecular mechanism of the reduction in water leakage across the membranes by the addition of cholesterol. An enhanced free energy barrier was observed in these membranes with increased cholesterol concentration, and this was explained by the reduced cavity density around the cholesterol in the hydrophobic membrane core. There was an increase of trans conformers in the hydrophobic lipid chains adjacent to the cholesterol, which reduced the cavity density. The enhanced free energy barrier was found to be the main reason to reduce the water permeability with increased cholesterol concentration. At low cholesterol concentrations the PSM bilayer exhibited a higher free energy barrier than the DPPC bilayer for water permeation, while at greater than 30 mol % of cholesterol the difference became minor. This tendency for the PSM and DPPC bilayers to resemble each other at higher cholesterol concentrations was similar to commonly observed trends in several structural properties, such as order parameters, cross-sectional area per molecule, and cavity density profiles in the hydrophobic regions of bilayer membranes. These results demonstrate that DPPC and PSM bilayers with high cholesterol contents possess similar physical properties, which suggests that the solubility of cholesterol in these lipid bilayers has importance for an understanding of multicomponent lipid membranes with cholesterol.
The deuterium/hydrogen (D/H) ratio of primordial water partitioned into a planetary interior seems to be different on Earth and Mars. Water from volcanic rocks originating from Earth's deep mantle ...has a low D/H ratio with high 3He/4He ratios, implying that it was inherited partially from the solar nebula. In contrast, the D/H ratio of water in the Martian meteorites considered to represent the mantle does not trend toward that of the solar nebula. These differences may be owing to differences in the types of atmospheric structures formed on protoplanets accreting in the solar nebula. Using a 1D radiative-equilibrium model, we analyze the thermal structure of a hybrid-type protoatmosphere in which the solar nebula component dominates the upper layer while a degassed component dominates the lower layer. Our analysis implies Mars-sized protoplanets maintain a hybrid-type protoatmosphere and the D/H ratio of the lower atmosphere resembles that of the building blocks. Conversely, when the mass is larger than Mars-sized, the compositional stratification is collapsed by convective mixing of the solar nebula component with the degassed component, and the D/H ratio approaches that of the solar nebula. This tendency becomes stronger when the planetary mass is larger. If water vapor is distributed through a magma ocean into the planetary interior, Mars-sized protoplanets are likely to reflect the D/H ratios of the building blocks, while larger protoplanets are likely to have acquired a solar-nebula-like D/H ratio.
Stakeholder collaboration is acknowledged as an important part of tourism destination planning and management. However, not all destination stakeholders have the same level of power and influence in ...collaborative activities or decision-making, with some groups able to exert more influence over the process. The purpose of this study was to identify and categorise the various types of power that influence stakeholder collaborations in tourism destination planning and management and determine which stakeholder groups hold these powers. A case study approach was adopted and data was collected from publicly available secondary resources. The study results show that four different types of power (coercive, legitimate, induced and competent power) were evident in stakeholder collaborations. Coercive power was mainly held by government and public sector agencies while DMOs and large private organisations were found to hold strong legitimate power. Induced power was exerted by federal, state and local governments; educational institutions and consulting firms tended to possess competent power.
Abstract
Recent studies of the chronology of Martian meteorites suggest that the growth of Mars was almost complete within a few Myr after the birth of the Solar system. During such rapid accretion, ...proto-Mars likely gravitationally maintained both the solar nebula component and the impact degassing component, containing H2O vapour and reduced gas species, as a proto-atmosphere to be called a hybrid-type proto-atmosphere. Here we numerically analyse the mass and composition of the degassed component and the atmospheric thermal structure sustained by accretional heating. Our results predict that a growing Mars possibly acquired a massive and hot hybrid-type proto-atmosphere with surface pressure and temperature greater than several kbar and 2000 K, respectively, which is sufficient to produce a deep magma ocean. In such a high-temperature and high-pressure environment, a significant amount of H2O, CH4, CO, and H2 is expected to be partitioned into the planetary interior, although this would strongly depend on the dynamics of the magma ocean and mantle solidification. The dissolved H2O may explain the wet Martian mantle implied from basaltic Martian meteorites. Along with the remnant reduced atmosphere after the hydrodynamic atmospheric escape, dissolved reduced gas species may have maintained an earliest Martian surface environment that allowed prebiotic chemical evolution and liquid H2O activities.
There are prevalent financial relationships between dermatologists and pharmaceutical companies in Japan. However, little was known about the extent of whole picture of the personal payments made to ...dermatologists by pharmaceutical companies. This study aimed to examine the personal payments to the board-certified dermatologists by the Japanese Dermatological Association from the pharmaceutical companies between 2016 and 2019. Using the publicly disclosed payments data by the pharmaceutical companies between 2016 and 2019, we evaluated the magnitude, prevalence, and trends in the personal payments made to all board-certified dermatologists for the lecturing, writing, and consulting compensations. The payments were descriptively analyzed overall and by dermatologist demographics. Additionally, the payment trends were assessed by generalized estimating equation models. Of 6883 active board-certified dermatologists, 3121 (45.3%) received a total of $33,223,806 personal payments between 2016 and 2019. The median per-physician payments and number of payments (interquartile range) were $1737 ($613-$5287) and 4.0 (2.0-10.0) over the 4 years, respectively. Only top 1%, 5%, 10% of dermatologists received 41.7% (95% confidence interval CI 38.2-45.1%), 76.9% (95% CI 74.7-79.1%), and 87.6% (95% CI 86.2-88.9%) of overall payments. The number of dermatologists receiving payments and per-dermatologist payments increased by 4.3% (95% CI 3.1‒5.5%, p < 0.001) and 16.4% (95% CI 13.5‒19.4%, p < 0.001) each year. The board-certification in dermatology-oncology, in cosmetic dermatology, and male sex were significantly associated with higher personal payments with relative monetary values of 2.29 (95% CI 1.65-3.19, p < 0.001), 3.16 (95% CI 1.89-5.26, p < 0.001), and 5.38 (95% CI 4.12-7.04, p < 0.001). Less than half of Japanese board-certified dermatologists received lower personal payments from the pharmaceutical companies than those to other specialists. However, these personal payments were increasingly more prevalent and greater over the 4 years.
Although erosions and ulcerations are the most common small-bowel abnormalities found on wireless capsule endoscopy (WCE), a computer-aided detection method has not been established. We aimed to ...develop an artificial intelligence system with deep learning to automatically detect erosions and ulcerations in WCE images.
We trained a deep convolutional neural network (CNN) system based on a Single Shot Multibox Detector, using 5360 WCE images of erosions and ulcerations. We assessed its performance by calculating the area under the receiver operating characteristic curve and its sensitivity, specificity, and accuracy using an independent test set of 10,440 small-bowel images including 440 images of erosions and ulcerations.
The trained CNN required 233 seconds to evaluate 10,440 test images. The area under the curve for the detection of erosions and ulcerations was 0.958 (95% confidence interval CI, 0.947-0.968). The sensitivity, specificity, and accuracy of the CNN were 88.2% (95% CI, 84.8%-91.0%), 90.9% (95% CI, 90.3%-91.4%), and 90.8% (95% CI, 90.2%-91.3%), respectively, at a cut-off value of 0.481 for the probability score.
We developed and validated a new system based on CNN to automatically detect erosions and ulcerations in WCE images. This may be a crucial step in the development of daily-use diagnostic software for WCE images to help reduce oversights and the burden on physicians.
Display omitted
Background and Aim
Although small‐bowel angioectasia is reported as the most common cause of bleeding in patients and frequently diagnosed by capsule endoscopy (CE) in patients with obscure ...gastrointestinal bleeding, a computer‐aided detection method has not been established. We developed an artificial intelligence system with deep learning that can automatically detect small‐bowel angioectasia in CE images.
Methods
We trained a deep convolutional neural network (CNN) system based on Single Shot Multibox Detector using 2237 CE images of angioectasia. We assessed its diagnostic accuracy by calculating the area under the receiver operating characteristic curve (ROC‐AUC), sensitivity, specificity, positive predictive value, and negative predictive value using an independent test set of 10 488 small‐bowel images, including 488 images of small‐bowel angioectasia.
Results
The AUC to detect angioectasia was 0.998. Sensitivity, specificity, positive predictive value, and negative predictive value of CNN were 98.8%, 98.4%, 75.4%, and 99.9%, respectively, at a cut‐off value of 0.36 for the probability score.
Conclusions
We developed and validated a new system based on CNN to automatically detect angioectasia in CE images. This may be well applicable to daily clinical practice to reduce the burden of physicians as well as to reduce oversight.
The subtropical North Pacific has been historically considered as a stable and homogenous oligotrophic marine ecosystem. The consistently low phytoplankton biomass has been attributed to a close ...balance between phytoplankton growth and grazing mortality. However, phytoplankton summer blooms were frequently observed in the central North Pacific near the Hawaiian Islands. To determine whether this is a result of unbalanced phytoplankton growth and microzooplankton grazing, we conducted a trans-Pacific cruise through the subtropical North Pacific. The growth and microzooplankton grazing mortality rates of the phytoplankton community and specific groups in the surface layer (10 m), were examined by dilution experiments. Positive phytoplankton net growth rates (0.34 ± 0.29 day
−1
) were observed under the depletion of dissolved inorganic nitrogen (DIN, < 40 nM) throughout the study area. However, considering the grazing of micro- and mesozooplankton collectively, the phytoplankton growth was largely consumed (net growth rate of 0.08 ± 0.15 day
−1
), except in the central North Pacific (net growth rate of 0.42 ± 0.11 day
−1
). Phytoplankton biomass accumulation in this area was also demonstrated by the satellite-observed Chl
a
, although this was just sustained for a few days. The high phytoplankton growth rate in the central North Pacific (0.84 ± 0.26 day
−1
) was a result of the dominant
Prochlorococcus
, which contributed 88% of the community Chl
a
. The weak response of
Prochlorococcus
growth to ammonium addition indicates their growth (1.14 ± 0.55 day
−1
) was not limited by the ambient DIN and was likely a result of their advantage of utilizing various dissolved organic nitrogen.
PDF
