Cellular Sensing Governs the Stability of Chemotactic Fronts

In contexts ranging from embryonic development to bacterial ecology, cell populations migrate chemotactically along self-generated chemical gradients, often forming a propagating front. Here, we theoretically show that the stability of such chemotactic fronts to morphological perturbations is determined by limitations in the ability of individual cells to sense and thereby respond to the chemical gradient. Specifically, cells at bulging parts of a front are exposed to a smaller gradient, which slows them down and promotes stability, but they also respond more strongly to the gradient, which speeds them up and promotes instability. We predict that this competition leads to chemotactic fingering when sensing is limited at too low chemical concentrations. Guided by this finding and by experimental data on E. coli chemotaxis, we suggest that the cells' sensory machinery might have evolved to avoid these limitations and ensure stable front propagation. Finally, as sensing of any stimuli is necessarily limited in living and active matter in general, the principle of sensing-induced stability may operate in other types of directed migration such as durotaxis, electrotaxis, and phototaxis

Sex differences in constitutive autophagy

Sex bias has been described nowadays in biomedical research on animal models, although sexual dimorphism has been confirmed widely under pathological and physiological conditions. The main objective of our work was to study the sex differences in constitutive autophagy in spinal cord and skeletalmuscle tissue fromwild type mice. To examine the influence of sex on autophagy, mRNA and proteins were extracted from male and female mice tissues.The expressions of microtubule-associated protein 1 light chain 3 (LC3) and sequestosome 1 (p62), markers to monitor autophagy, were analyzed at 40, 60, 90, and 120 days of age.We found significant sex differences in the expression of LC3 and p62 in both tissues at these ages. The results indicated that sex and tissue specific differences exist in constitutive autophagy.These data underlined the need to include both sexes in the experimental groups to minimize any sex bias

Performance assessment of Posidonia oceanica (L.) Delile restoration experiment on dead matte twelve years after planting\u2014structural and functional meadow features

Following the restoration of natural conditions by reducing human pressures, reforestation is currently considered a possible option to accelerate the recovery of seagrass habitats. Long-term monitoring programs theoretically represent an ideal solution to assess whether a reforestation plan has produced the desired results. Here, we report on the performance of a 20 m2 patch of Posidonia oceanica transplanted on dead matte twelve years after transplantation in the Gulf of Palermo, northwestern Sicily. Photo mosaic performed in the area allowed us to detect 23 transplanted patches of both regular and irregular shape, ranging from 0.1 to 2.7 m2 and an overall surface close to 19 m2. Meadow density was 331.6 \ub1 17.7 shoot m-2 (currently five times higher than the initial value of 66 shoots m-2), and it did not show statistical differences from a close by natural meadow (331.2 \ub1 14.9). Total primary production, estimated by lepidochronology, varied from 333.0 to 332.7 g dw m2/year, at the transplanted and natural stand, respectively. These results suggest that complete restoration of P. oceanica on dead matte is possible in a relatively short time (a decade), thus representing a good starting point for upscaling the recovery of the degraded meadows in the area

Occupational choice, number of entrepreneurs and output: theory and empirical evidence with Spanish data

This paper extends the (Lucas, Bell J Econ 9:508–523,1978) model of occupational choices by individuals with different skills, beyond the simple options of self-employment or wage-employment, by including a second choice for the self-employed. That is, an option to hire employees and so become self-employed with employees (SEWEs), or to be self-employed without employees (SEWNEs). We solve for the market equilibrium and examine the sensitivity of relative sizes of occupational groups, and of the level of productivity, to changes in the exogenous parameters. The results show that the positive (negative) association between number of SEWEs (SEWNEs) and productivity, observed in the Spanish data, can be explained, under certain conditions, as the result of cross-region and time differences in average skills. These findings point to the importance of distinguishing between SEWEs and SEWNEs in drawing valid conclusions concerning any link between entrepreneurship and economic development

Continuous Time Random Walks in periodic systems: fluid limit and fractional differential equations on the circle

In this article, the continuous time random walk on the circle is studied. We derive the corresponding generalized master equation and discuss the effects of topology, especially important when Levy flights are allowed. Then, we work out the fluid limit equation, formulated in terms of the periodic version of the fractional Riemann-Liouville operators, for which we provide explicit expressions. Finally, we compute the propagator in some simple cases. The analysis presented herein should be relevant when investigating anomalous transport phenomena in systems with periodic dimensions.Comment: 14 pages, 1 figure. References added. Published versio

Heart involvement in Rheumatoid Arthritis: Systematic review and meta-analysis.

OBJECTIVE: The aim of our study was to conduct a systematic review with meta-analysis of the current case-control studies about the valvular and pericardial involvement in patients with Rheumatoid Arthritis (RA), asymptomatic for cardiovascular diseases. METHODS: Case-control studies were identified by searching PubMed (1975-2010) and the Cochrane Central Register of Controlled Trials (CENTRAL) (1975-2010). Participants were adult patients with RA asymptomatic for cardiovascular diseases, and the outcome measure was the presence of cardiac involvement. RESULTS: Quantitative synthesis included 10 relevant studies out of 2326 bibliographic citations that had been found. RA resulted significantly associated to pericardial effusion (OR 10.7; 95% CI 5.0-23.0), valvular nodules (OR 12.5; 95% CI 2.8-55.4), tricuspidal valve insufficiency (OR 5.3; 95% CI 2.4-11.6), aortic valve stenosis (OR 5.2; 95% CI 1.1-24.1), mitral valve insufficiency (OR 3.4; 95% CI 1.7-6.7), aortic valve insufficiency (OR 1.7; 95% CI 1.0-2.7), combined valvular alterations (OR 4.3; 95% CI 2.3-8.0), mitral valve thickening and/or calcification (OR 5.0; 95% CI 2.0-12.7), aortic valve thickening and/or calcification (OR 4.4; 95% CI 1.1-17.4), valvular thickening and/or calcification (OR 4.8; 95% CI 2.2-10.5), and mitral valve prolapse (OR 2.2; 95% CI 1.2-4.0). CONCLUSIONS: Our systematic review pointed out the strength and the grade of both pericardial and cardiac valvular involvement in RA patients. Our findings underscore the importance of an echocardiographic assessment at least in clinical research when RA patients are involved. Moreover, further research is needed to understand the possible relationship of our findings and the increased cardiovascular mortality

“I am most grateful...” using gratitude to improve the sense of relatedness and motivation for online volunteerism

Volunteering benefits those who receive and those who provide help. Yet barriers can inhibit engagement with and motivation for volunteering activities. Online environments on one hand help to lower some of these barriers, but on the other hand they can introduce new obstacles specially when the medium transforms the social interactions important to volunteers. We study the motivational drivers of online volunteering, and how those are affected by design. Specifically, we focus on relatedness as a source of motivation. We describe two studies with volunteers that help medical students to learn and improve their communication skills through mock interviews in an educational program. The volunteers can participate in the program face-to-face or through an online platform. The first study consisted of a survey (n = 66 volunteers), two workshops and one interview (n = 12 volunteers) in which we explored volunteer demographics, motivations, psychological needs, and experiences. Findings suggested relatedness can be an important indicator of volunteer motivations. In the second study, we added a feature to the online platform to display personal gratitude messages from student beneficiaries to the volunteers in order to improve the experience of relatedness between them. In total, n = 30 volunteers completed 196 sessions. We used survey and system data to assess the impact of gratitude on perceived relatedness, motivation, and behavior (immediate, booked, and completed appointments). Results showed that the expression of gratitude by the beneficiary significantly affected the volunteer’s experience of relatedness which then correlated with immediate appointments booking behavior by each volunteer. The implications for design of online volunteering systems are discussed

Can the nile generate output, income, and employment in Egypt? A mixed multiplier analysis

Nile water availability is one of the major constraints for agricultural development in Egypt. This study conducts a mixed multiplier analysis, under water and land constraints, to identify the seasonal agricultural activities with high output and income multipliers. It uses a 2008/09 SAM for Egypt with a detailed rep-resentation of Nile-related production factors employed by agricultural activities across irrigation seasons. The results demonstrate the significance of addressing Nile water constraints, not only for agriculture, but also for the overall economy. Policies that enhance water productivity, particularly in the winter season, generate outstanding increases in output, income, and employment through sizable multiplier effects. © 2021, Bononia University Press. All rights reserved

Wetting to Non-wetting Transition in Sodium-Coated C_60

Based on ab initi and density-functional theory calculations, an empirical potential is proposed to model the interaction between a fullerene molecule and many sodium atoms. This model predicts homogeneous coverage of C_60 below 8 Na atoms, and a progressive droplet formation above this size. The effects of ionization, temperature, and external electric field indicate that the various, and apparently contradictory, experimental results can indeed be put into agreement.Comment: 4 pages, 4 postscript figure