Analysis of dynamic stiffness effect of primary suspension helical springs on railway vehicle vibration

Helical springs within the primary suspension are critical components for isolating the whole vehicle system from vibration generated at the wheel/rail contact. As train speeds increase, the frequency region of excitation becomes larger, and a simplified static stiffness can no longer represent the real stiffness property in a vehicle dynamic model. Coil springs in particular exhibit strong internal resonances, which lead to high vibration amplitudes within the spring itself as well as degradation of the vibration isolation. In this paper, the dynamic stiffness matrix method is used to determine the dynamic stiffness of a helical spring from a vehicle primary suspension. Results are confirmed with a finite element analysis. Then the spring dynamic stiffness is included within a vehicle-track coupled dynamic model of a high speed train and the effect of the dynamic stiffening of the spring on the vehicle vibration is investigated. It is shown that, for frequencies above about 50 Hz, the dynamic stiffness of the helical spring changes sharply. Due to this effect, the vibration transmissibility increases considerably which results in poor vibration isolation of the primary suspension. Introducing a rubber layer in series with the coil spring can attenuate this effect

Food and Nutrition Research Institute, Philippines

Poster created by students in the 2016 IWU Freeman Asia Internship Program

Towards Efficient Data Valuation Based on the Shapley Value

"How much is my data worth?" is an increasingly common question posed by organizations and individuals alike. An answer to this question could allow, for instance, fairly distributing profits among multiple data contributors and determining prospective compensation when data breaches happen. In this paper, we study the problem of data valuation by utilizing the Shapley value, a popular notion of value which originated in coopoerative game theory. The Shapley value defines a unique payoff scheme that satisfies many desiderata for the notion of data value. However, the Shapley value often requires exponential time to compute. To meet this challenge, we propose a repertoire of efficient algorithms for approximating the Shapley value. We also demonstrate the value of each training instance for various benchmark datasets

Combating infectious diseases in aquaculture with an original probiotic product

Oyster production in Rhode Island accounts for over $2.5 million in annual revenue, making it the top aquaculture product in the state. However, larval tank infections significantly constrain production and create substantial economic losses for commercial hatcheries. In most cases antibiotics may not be used to prevent or treat larval tank infections. A probiotic, or beneficial microbe which competes with pathogens, is a safer and “green” approach to preventing infections. Vibriosis, a common cause of oyster larval mortality, is the result of Vibrio species infections. Previous studies have shown that a native Rhode Island microbe, Bacillus pumilus RI06-95, protects oyster larvae against infection by the pathogen Vibrio tubiashii RE22. In this study, a freeze-dried formulation of this probiotic agent was evaluated for use in commercial hatchery tanks. Stability, dispersion and pilot-scale hatchery studies were performed to evaluate this product. A viability analysis of the freeze-dried product over time revealed that when stored at 4 ºC, the product will maintain viable probiotic cells at greater than the minimum effective concentration, 108 CFU/mL per single-use tube, for at least two months. The dispersion of this product in seawater was investigated using light microscopy, and qualitatively showed that the product readily and rapidly disperses within 30 seconds, without any shaking or added energy. A pilot-scale hatchery study revealed that the freeze-dried product increased survival of three-day-old and eight-day-old larvae after challenged with Vibrio tubiashii RE22 by 26 % (± 15 %) and 47 % (± 28 %) respectively, compared to larvae which received no probiotic treatment. Based on these results, we conclude that our freeze-dried formulation of Bacillus pumilus RI06-95 is a stable, easy-to-use, safe and efficacious probiotic product for sustainable oyster aquaculture

Sodium acetate infusion in critically ill trauma patients for hyperchloremic acidosis

<p>Abstract</p> <p>Introduction</p> <p>Sodium acetate has been shown to cause hemodynamic instability when used as a hemodialysis buffer. The pattern of hemodynamic response to injury will be evaluated between those who received sodium acetate and those who did not.</p> <p>The primary purpose of the study is to analyze the effect of sodium acetate on hemodynamic parameters. Secondarily we looked at the effects on prevention and treatment of hyperchloremic metabolic acidosis.</p> <p>Methods</p> <p>The study arm was comprised of patients who had received sodium acetate infusions in place of normal saline between March 2005 and December 2009. A control arm was created based on matching three pre-treatment variables: injury severity score (ISS), pH (+/- 0.03) and base deficit (+/- 3). A retrospective chart review was performed for patients in both arms. Blood pressure, arterial blood gas data and chemistry values were recorded for the time points of -6, -1, 0, 1, 6, 12, 24, 48, and 72 hours from start of sodium acetate infusion. Patients were excluded based on the following criteria: patients who were given sodium bicarbonate within 48 hours of starting sodium acetate, those given sodium acetate as a bolus, non-trauma patients, burn patients, patients who expired within 24 hours of arrival to the ICU, patients diagnosed with rhabdomyolysis and patients whose medical record could not be obtained.</p> <p>Results</p> <p>A total of 78 patients were included in the study, 39 in the study arm and 39 in the control arm. There were no statistically significant drops in blood pressure within either group. The median pH between the two groups at the start of infusion was equal. Both groups trended towards normal pH with the study arm improving faster than the control arm. The median serum bicarbonate at start of sodium acetate infusion was 19 mmol/L and 20 mmol/L at time zero for the study and control arms respectively with both trending upward during the study period. Chloride trended up initially in both groups but the study arm began to correct sooner at 24 hours compared to 48 hours for the control arm.</p> <p>Conclusion</p> <p>We analyzed the use of sodium acetate as an alternative to normal saline or lactated ringers during resuscitation of critically ill trauma patients at a single center. Our data shows that the hemodynamic profile remained favorable, without evidence of instability at any point during the study period. Normalization of hyperchloremia and metabolic acidosis occurred faster in the patients who received sodium acetate.</p

Parallel and pseudorandom discrete event system specification vs. networks of spiking neurons: Formalization and preliminary implementation results

International audienceUsual Parallel Discrete Event System Specification (P-DEVS) allows specifying systems from modeling to simulation. However, the framework does not incorporate parallel and stochastic simulations. This work intends to extend P-DEVS to parallel simulations and pseudorandom number generators in the context of a spiking neural network. The discrete event specification presented here makes explicit and centralized the parallel computation of events as well as their routing, making further implementations more easy. It is then expected to dispose of a well defined mathematical and computational framework to deal with networks of spiking neurons

The MYST histone acetyltransferases are essential for gametophyte development in Arabidopsis

<p>Abstract</p> <p>Background</p> <p>Histone acetyltransferases (HATs) play critical roles in the regulation of chromatin structure and gene expression. Arabidopsis genome contains 12 HAT genes, but the biological functions of many of them are still unknown. In this work, we studied the evolutionary relationship and cellular functions of the two Arabidopsis HAT genes homologous to the MYST family members.</p> <p>Results</p> <p>An extensive phylogenetic analysis of 105 MYST proteins revealed that they can be divided into 5 classes, each of which contains a specific combination of protein modules. The two Arabidopsis MYST proteins, HAM1 and HAM2, belong to a "green clade", clearly separated from other families of HATs. Using a reverse genetic approach, we show that <it>HAM1 </it>and <it>HAM2 </it>are a functionally redundant pair of genes, as single Arabidopsis <it>ham1 </it>and <it>ham2 </it>mutants displayed a wild-type phenotype, while no double mutant seedling could be recovered. Genetic analysis and cytological study revealed that <it>ham1ham2 </it>double mutation induced severe defects in the formation of male and female gametophyte, resulting in an arrest of mitotic cell cycle at early stages of gametogenesis. RT-PCR experiments and the analysis of transgenic plants expressing the <it>GUS </it>reporter gene under the <it>HAM1 </it>or the <it>HAM2 </it>promoter showed that both genes displayed an overlapping expression pattern, mainly in growing organs such as shoots and flower buds.</p> <p>Conclusion</p> <p>The work presented here reveals novel properties for MYST HATs in Arabidopsis. In addition to providing an evolutionary relationship of this large protein family, we show the evidence of a link between MYST and gamete formation as previously suggested in mammalian cells. A possible function of the Arabidopsis MYST protein-mediated histone acetylation during cell division is suggested.</p