Global coordination of transcriptional control and mRNA decay during cellular differentiation

We have systematically identified the targets of the Schizosaccharomyces pombe RNA-binding protein Meu5p, which is transiently induced during cellular differentiation. Meu5p-bound transcripts (>80) are expressed at low levels and have shorter half-lives in meu5 mutants, suggesting that Meu5p binding stabilizes its RNA targets.Most Meu5p targets are induced during differentiation by the activity of the Mei4p transcription factor. However, although most Mei4p targets display a sharp peak of expression, Meu5p targets are expressed for a longer period. In the absence of Meu5p, all Mei4p targets are expressed with similar kinetics (similar to non-Meu5p targets). Therefore, Meu5p determines the temporal profile of its targets.As the meu5 gene is itself a target of the transcription factor Mei4p, the RNA-binding protein Meu5p and their shared targets form a feed-forward loop (FFL), a network motif that is common in transcriptional networks.Our data highlight the importance of considering both transcriptional and posttranscriptional controls to understand dynamic changes in RNA levels, and provide insight into the structure of the regulatory networks that integrate transcription and RNA decay

Analytical method for perturbed frozen orbit around an Asteroid in highly inhomogeneous gravitational fields : A first approach

This article provides a method for nding initial conditions for perturbed frozen orbits around inhomogeneous fast rotating asteroids. These orbits can be used as reference trajectories in missions that require close inspection of any rigid body. The generalized perturbative procedure followed exploits the analytical methods of relegation of the argument of node and Delaunay normalisation to arbitrary order. These analytical methods are extremely powerful but highly computational. The gravitational potential of the heterogeneous body is rstly stated, in polar-nodal coordinates, which takes into account the coecients of the spherical harmonics up to an arbitrary order. Through the relegation of the argument of node and the Delaunay normalization, a series of canonical transformations of coordinates is found, which reduces the Hamiltonian describing the system to a integrable, two degrees of freedom Hamiltonian plus a truncated reminder of higher order. Setting eccentricity, argument of pericenter and inclination of the orbit of the truncated system to be constant, initial conditions are found, which evolve into frozen orbits for the truncated system. Using the same initial conditions yields perturbed frozen orbits for the full system, whose perturbation decreases with the consideration of arbitrary homologic equations in the relegation and normalization procedures. Such procedure can be automated for the first homologic equation up to the consideration of any arbitrary number of spherical harmonics coefficients. The project has been developed in collaboration with the European Space Agency (ESA)

X-ray radiography of cavitation in a beryllium alloy nozzle

[EN] Making quantitative measurements of the vapor distribution in a cavitating nozzle is difficult, owing to the strong scattering of visible light at gas-liquid boundaries and wall boundaries, and the small lengths and time scales involved. The transparent models required for optical experiments are also limited in terms of maximum pressure and operating life. Over the past few years, x-ray radiography experiments at Argonne's Advanced Photon Source have demonstrated the ability to perform quantitative measurements of the line of sight projected vapor fraction in submerged, cavitating plastic nozzles. In this paper, we present the results of new radiography experiments performed on a submerged beryllium nozzle which is 520m in diameter, with a length/diameter ratio of 6. Beryllium is a light, hard metal that is very transparent to x-rays due to its low atomic number. We present quantitative measurements of cavitation vapor distribution conducted over a range of non-dimensional cavitation and Reynolds numbers, up to values typical of gasoline and diesel fuel injectors. A novel aspect of this work is the ability to quantitatively measure the area contraction along the nozzle with high spatial resolution. Analysis of the vapor distribution, area contraction and discharge coefficients are made between the beryllium nozzle and plastic nozzles of the same nominal geometry. When gas is dissolved in the fuel, the vapor distribution can be quite different from that found in plastic nozzles of the same dimensions, although the discharge coefficients are unaffected. In the beryllium nozzle, there were substantially fewer machining defects to act as nucleation sites for the precipitation of bubbles from dissolved gases in the fuel, and as such the effect on the vapor distribution was greatly reduced.Raul Payri was funded by a Fulbright visiting scholar grant in collaboration with the Ministry of Education, Culture and Sports of Spain (reference PRX14/00331) while performing this work. Juan P Viera was funded by the Spanish MINECO (grant EEBB-I-15-0976 under project TRA2012-36932).Duke, DJ.; Matusik, KE.; Kastengren, AL.; Swantek, AB.; Sovis, N.; Payri, R.; Viera-Sotillo, JP.... (2017). X-ray radiography of cavitation in a beryllium alloy nozzle. International Journal of Engine Research. 18(1-2):39-50. https://doi.org/10.1177/1468087416685965S3950181-

Individualism and entrepreneurship: Does the pattern depend on the social context?

This article argues that cultural and personal values are relevant in the formation of entrepreneurial intentions; as such, the interplay between both value-levels deserves attention. Individualist values such as achievement, pleasure, self-direction and an exciting and stimulating life are related to entrepreneurial intention and activity, at both the cultural and personal levels. From a sample of 2069 adults with a university degree, the results support a double-effect of culture on entrepreneurial intention: the personal values effect (a more individualist culture leads to more members exhibiting higher entrepreneurial intentions) and the outlier effect (those who are more individualist than average in their culture will exhibit a higher entrepreneurial intention). Within the two individualist dimensions considered (self-enhancement and openness to change), the relationship of self-enhancement to entrepreneurial intention is stronger than that of openness to change. The implications of these results are discussed and avenues for future research are proposed

How does a cadaver model work for testing ultrasound diagnostic capability for rheumatic-like tendon damage?

To establish whether a cadaver model can serve as an effective surrogate for the detection of tendon damage characteristic of rheumatoid arthritis (RA). In addition, we evaluated intraobserver and interobserver agreement in the grading of RA-like tendon tears shown by US, as well as the concordance between the US findings and the surgically induced lesions in the cadaver model. RA-like tendon damage was surgically induced in the tibialis anterior tendon (TAT) and tibialis posterior tendon (TPT) of ten ankle/foot fresh-frozen cadaveric specimens. Of the 20 tendons examined, six were randomly assigned a surgically induced partial tear; six a complete tear; and eight left undamaged. Three rheumatologists, experts in musculoskeletal US, assessed from 1 to 5 the quality of US imaging of the cadaveric models on a Likert scale. Tendons were then categorized as having either no damage, (0); partial tear, (1); or complete tear (2). All 20 tendons were blindly and independently evaluated twice, over two rounds, by each of the three observers. Overall, technical performance was satisfactory for all items in the two rounds (all values over 2.9 in a Likert scale 1-5). Intraobserver and interobserver agreement for US grading of tendon damage was good (mean κ values 0.62 and 0.71, respectively), with greater reliability found in the TAT than the TPT. Concordance between US findings and experimental tendon lesions was acceptable (70-100 %), again greater for the TAT than for the TPT. A cadaver model with surgically created tendon damage can be useful in evaluating US metric properties of RA tendon lesions

Prognostic value of discharge heart rate in acute heart failure patients: More relevant in atrial fibrillation?

Aims: The prognostic impact of heart rate (HR) in acute heart failure (AHF) patients is not well known especially in atrial fibrillation (AF) patients. The aim of the study was to evaluate the impact of admission HR, discharge HR, HR difference (admission-discharge) in AHF patients with sinus rhythm (SR) or AF on long- term outcomes. Methods: We included 1398 patients consecutively admitted with AHF between October 2013 and December 2014 from a national multicentre, prospective registry. Logistic regression models were used to estimate the association between admission HR, discharge HR and HR difference and one- year all-cause mortality and HF readmission. Results: The mean age of the study population was 72+/-12years. Of these, 594 (42.4%) were female, 655 (77.8%) were hypertensive and 655 (46.8%) had diabetes. Among all included patients, 745 (53.2%) had sinus rhythm and 653 (46.7%) had atrial fibrillation. Only discharge HR was associated with one year all-cause mortality (Relative risk (RR)=1.182, confidence interval (CI) 95% 1.024-1.366, p=0.022) in SR. In AF patients discharge HR was associated with one year all cause mortality (RR=1.276, CI 95% 1.115-1.459, p</=0.001). We did not observe a prognostic effect of admission HR or HRD on long-term outcomes in both groups. This relationship is not dependent on left ventricular ejection fraction. Conclusions: In AHF patients lower discharge HR, neither the admission nor the difference, is associated with better long-term outcomes especially in AF patients

Cell lineage transport: a mechanism for molecular gradient formation

Gradient formation is a fundamental patterning mechanism during embryo development, commonly related to secreted proteins that move along an existing field of cells. Here, we mathematically address the feasibility of gradients of mRNAs and non-secreted proteins. We show that these gradients can arise in growing tissues whereby cells dilute and transport their molecular content as they divide and grow, a mechanism we termed ‘cell lineage transport.' We provide an experimental test by unveiling a distal-to-proximal gradient of Hoxd13 in the vertebrate developing limb bud driven by cell lineage transport, corroborating our model. Our study indicates that gradients of non-secreted molecules exhibit a power-law profile and can arise for a wide range of biologically relevant parameter values. Dilution and nonlinear growth confer robustness to the spatial gradient under changes in the cell cycle period, but at the expense of sensitivity in the timing of gradient formation. We expect that gradient formation driven by cell lineage transport will provide future insights into understanding the coordination between growth and patterning during embryonic development

Microbial catabolic activities are naturally selected by metabolic energy harvest rate

The fundamental trade-off between yield and rate of energy harvest per unit of substrate has been largely discussed as a main characteristic for microbial established cooperation or competition. In this study, this point is addressed by developing a generalized model that simulates competition between existing and not experimentally reported microbial catabolic activities defined only based on well-known biochemical pathways. No specific microbial physiological adaptations are considered, growth yield is calculated coupled to catabolism energetics and a common maximum biomass-specific catabolism rate (expressed as electron transfer rate) is assumed for all microbial groups. Under this approach, successful microbial metabolisms are predicted in line with experimental observations under the hypothesis of maximum energy harvest rate. Two microbial ecosystems, typically found in wastewater treatment plants, are simulated, namely: (i) the anaerobic fermentation of glucose and (ii) the oxidation and reduction of nitrogen under aerobic autotrophic (nitrification) and anoxic heterotrophic and autotrophic (denitrification) conditions. The experimentally observed cross feeding in glucose fermentation, through multiple intermediate fermentation pathways, towards ultimately methane and carbon dioxide is predicted. Analogously, two-stage nitrification (by ammonium and nitrite oxidizers) is predicted as prevailing over nitrification in one stage. Conversely, denitrification is predicted in one stage (by denitrifiers) as well as anammox (anaerobic ammonium oxidation). The model results suggest that these observations are a direct consequence of the different energy yields per electron transferred at the different steps of the pathways. Overall, our results theoretically support the hypothesis that successful microbial catabolic activities are selected by an overall maximum energy harvest rate

From correlation functions to Wilson loops

We start with an n-point correlation function in a conformal gauge theory. We show that a special limit produces a polygonal Wilson loop with $n$ sides. The limit takes the $n$ points towards the vertices of a null polygonal Wilson loop such that successive distances $x^2_{i,i+1} \to 0$. This produces a fast moving particle that generates a "frame" for the Wilson loop. We explain in detail how the limit is approached, including some subtle effects from the propagation of a fast moving particle in the full interacting theory. We perform perturbative checks by doing explicit computations in N=4 super-Yang-Mills.Comment: 37 pages, 10 figures; typos corrected, references adde

Holographic Brownian Motion in Magnetic Environments

Using the gauge/gravity correspondence, we study the dynamics of a heavy quark in two strongly-coupled systems at finite temperature: Super-Yang-Mills in the presence of a magnetic field and non-commutative Super-Yang-Mills. In the former, our results agree qualitatively with the expected behavior from weakly-coupled theories. In the latter, we propose a Langevin equation that accounts for the effects of non-commutativity and we find new interesting features. The equation resembles the structure of Brownian motion in the presence of a magnetic field and implies that the fluctuations along non-commutative directions are correlated. Moreover, our results show that the viscosity is smaller than the commutative case and that the diffusion properties of the quark are unaffected by non-commutativity. Finally, we compute the random force autocorrelator and verify that the fluctuation-dissipation theorem holds in the presence of non-commutativity.Comment: 34 pages. v2: typos corrected. v3: title and abstract slightly modified in order to better reflect the contents of the paper; footnote 3 and one reference were also added; version accepted for publication in JHE