Mean Field Approach for a Statistical Mechanical Model of Proteins

We study the thermodynamical properties of a topology-based model proposed by Galzitskaya and Finkelstein for the description of protein folding. We devise and test three different mean-field approaches for the model, that simplify the treatment without spoiling the description. The validity of the model and its mean-field approximations is checked by applying them to the $\beta$-hairpin fragment of the immunoglobulin-binding protein (GB1) and making a comparison with available experimental data and simulation results. Our results indicate that this model is a rather simple and reasonably good tool for interpreting folding experimental data, provided the parameters of the model are carefully chosen. The mean-field approaches substantially recover all the relevant exact results and represent reliable alternatives to the Monte Carlo simulations.Comment: RevTeX-4, 11 pages, 6 eps-figures, To Appear on J.Chem.Phy

Radio emission from satellite-Jupiter interactions (especially Ganymede)

Analyzing a database of 26 years of observations of Jupiter from the Nan\c{c}ay Decameter Array, we study the occurrence of Io-independent emissions as a function of the orbital phase of the other Galilean satellites and Amalthea. We identify unambiguously the emissions induced by Ganymede and characterize their intervals of occurrence in CML and Ganymede phase and longitude. We also find hints of emissions induced by Europa and, surprisingly, by Amalthea. The signature of Callisto-induced emissions is more tenuous.Comment: 14 pages, 7 figures, in "Planetary Radio Emissions VIII", G. Fischer, G. Mann, M. Panchenko and P. Zarka eds., Austrian Acad. Sci. Press, Vienna, in press, 201

Fine morphological assessment of quality of human mature oocytes after slow freezing or vitrification with a closed device: a comparative analysis

BACKGROUND: Human mature oocytes are very susceptible to cryodamage. Several reports demonstrated that vitrification might preserve oocyte better than slow freezing. However, this is still controversial. Thus, larger clinical, biological and experimental trials to confirm this concept are necessary. The aim of the study was to evaluate and compare fine morphological features in human mature oocytes cryopreserved with either slow freezing or vitrification. METHODS: We used 47 supernumerary human mature (metaphase II) oocytes donated by consenting patients, aged 27-32 years, enrolled in an IVF program. Thirtyfive oocytes were cryopreserved using slow freezing with 1.5 M propanediol +0.2 M sucrose concentration (20 oocytes) or a closed vitrification system (CryoTip Irvine Scientific CA) (15 oocytes). Twelve fresh oocytes were used as controls. All samples were prepared for light and transmission electron microscopy evaluation. RESULTS: Control, slow frozen/thawed and vitrified/warmed oocytes (CO, SFO and VO, respectively) were rounded, 90-100 mum in diameter, with normal ooplasm showing uniform distribution of organelles. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates and small mitochondria-vesicle (MV) complexes were the most numerous structures found in all CO, SFO and VO cultured for 3-4 hours. M-SER aggregates decreased, and large MV complexes increased in those SFO and VO maintained in culture for a prolonged period of time (8-9 hours). A slight to moderate vacuolization was present in the cytoplasm of SFO. Only a slight vacuolization was present in VO, whereas vacuoles were almost completely absent in CO. Amount and density of cortical granules (CG) appeared abnormally reduced in SFO and VO, irrespective of the protocol applied. CONCLUSIONS: Even though, both slow freezing and vitrification ensured a good overall preservation of the oocyte, we found that: 1) prolonged culture activates an intracellular membrane "recycling" that causes the abnormal transformation of the membranes of the small MV complexes and of SER into larger rounded vesicles; 2) vacuolization appears as a recurrent form of cell damage during slow freezing and, at a lesser extent, during vitrification using a closed device; 3) premature CG exocytosis was present in both SFO and VO and may cause zona pellucida hardenin

The role of Akt signalling in the mammalian ovary

The serine/threonine protein kinase Akt is involved in many cellular processes including cell growth, survival, proliferation and metabolism. Akt activity is modulated downstream of phosphatidylinositol-3-kinase (PI3K) in response to different extracellular stimuli. In the mammalian ovary, Akt collaborates with other kinases in the regulation of coordinate follicle and oocyte development. Akt determines the pool of primordial follicles and the transition from quiescent to growing phase. In addition, the kinase modulates granulosa cell apoptosis throughout folliculogenesis. In oocytes Akt participates in the control of meiosis resumption and, at metaphase II stage, regulates polar body emission and spindle organization. Its inhibition negatively affects preimplantation embryo development. As a consequence of such a central role, Akt dysregulation is associated with several human diseases including infertility and ovarian cancer.[...

Defining and identifying communities in networks

The investigation of community structures in networks is an important issue in many domains and disciplines. This problem is relevant for social tasks (objective analysis of relationships on the web), biological inquiries (functional studies in metabolic, cellular or protein networks) or technological problems (optimization of large infrastructures). Several types of algorithm exist for revealing the community structure in networks, but a general and quantitative definition of community is still lacking, leading to an intrinsic difficulty in the interpretation of the results of the algorithms without any additional non-topological information. In this paper we face this problem by introducing two quantitative definitions of community and by showing how they are implemented in practice in the existing algorithms. In this way the algorithms for the identification of the community structure become fully self-contained. Furthermore, we propose a new local algorithm to detect communities which outperforms the existing algorithms with respect to the computational cost, keeping the same level of reliability. The new algorithm is tested on artificial and real-world graphs. In particular we show the application of the new algorithm to a network of scientific collaborations, which, for its size, can not be attacked with the usual methods. This new class of local algorithms could open the way to applications to large-scale technological and biological applications.Comment: Revtex, final form, 14 pages, 6 figure

Sensorless variable speed single-phase induction motor drive system based on direct rotor flux orientation

The single-phase induction motor (SPIM) is one of the electrical machines more used in the World, and can be found in several fractional and sub-fractional horsepower applications in houses, offices, shoppings, farms, and industries. The introduction of more sophisticated applications has required the use of variable speed drives for SPIM, where the adoption of sensorless techniques is the more reasonable option for speed control due to the low cost of this electrical machine. A proposal for sensorless variable speed SPIM drive based on direct rotor field orientation techniques is presented in this paper. None transformation is used in order to eliminate the asymmetry of the stator windings of the SPIM. The rotor speed is estimated from an flux observer, which is based on two independent linear feedback control systems. The speed and flux estimatives are used in two control loop based on PID regulators, which determine the voltages to be applied to the SPIM windings by a three-legs VSI inverter. Using computer simulations, two situations are considered in order to demonstrate the satisfactory performance of the proposed sensorless speed control for SPIM drives: variations on rotor speed reference and the application of mechanical load

Non-ergodic site response model based on local recordings for Menta Dam site

The paper describes the development of a non-ergodic site response model for a strategic site in the Aspromonte mountains, in Southern Italy. Fractured metamorphic rocks belonging to Calabrian complex outcrop in this area, located in a region where Southern Apennines crustal faults and subduction of the Calabrian Arc contribute to the seismic hazard. At the site, three accelerometers are installed since 2016 as part of the monitoring system of the Menta Dam, a bituminous-faced rockfill dam constructed for the water supply of the region. Ground motions recorded at the site and elsewhere from regional crustal and subduction earthquakes have been used to evaluate region-specific source and path adjustment to global ground motion models (GMMs). Those regionally adjusted GMMs have, in turn, been used to evaluate the mean bias of site-specific recordings, which is used to estimate non-ergodic site response for the dam site. This analysis highlights that site-specific site response is appreciably larger than the global average prediction of GMMs for periods lower than 0.4s. A non-ergodic GMM is developed that accounts for these effects to be used in subsequent Probabilistic Site Hazard Analysis (PSHA)

Comparison of voter and Glauber ordering dynamics on networks

We study numerically the ordering process of two very simple dynamical models for a two-state variable on several topologies with increasing levels of heterogeneity in the degree distribution. We find that the zero-temperature Glauber dynamics for the Ising model may get trapped in sets of partially ordered metastable states even for finite system size, and this becomes more probable as the size increases. Voter dynamics instead always converges to full order on finite networks, even if this does not occur via coherent growth of domains. The time needed for order to be reached diverges with the system size. In both cases the ordering process is rather insensitive to the variation of the degreee distribution from sharply peaked to scale-free.Comment: 12 pages, 12 figure

The (endo)cannabinoid signaling in female reproduction: What are the latest advances?

Cannabis extracts like marijuana have the highest consumption rate worldwide. Yet, their societal acceptance as recreational and therapeutic drugs could represent a serious hazard to female human reproduction, because cannabis ingredients [termed (phyto)cannabinoids] can perturb an endogenous system of lipid signals known as endocannabinoids. Accumulated evidence on animal models and humans has demonstrated a crucial role of these endogenous signals on different aspects of female reproduction, where they act through an ensamble of proteins that synthesize, transport, degrade and traffic them. Several reports have recently evidenced the potential role of endocannabinoids as biomarkers of female infertility for disease treatment and prevention, as well as their possible epigenetic effects on pregnancy. The purpose of this review is to provide an update of data collected in the last decade on the effects of cannabinoids and endocannabinoids on female reproductive events, from development and maturation of follicles and oocytes, to fertilization, oviductal transport, implantation and labor. In this context, a particular attention has ben devoted to the ovary and the production of fertilizable oocytes, because recent studies have addressed this hot topic with conflicting results among species