Numerical verification of the condenser finite volume model

Numerical modelling of vapour compression systems is very useful for performance optimization through the implementation of suitable model-based control applications; in this context the heat exchangers are the most challenging component to devise, due to phase transition and ensuing discontinuities of the physical properties, and one tool which has proven itself suitable for the task is the finite volume method. A numerical verification of a finite volume model of a brazed plate condenser in counterflow arrangement is carried out, employing a fixed timestep solver; some useful guidelines are suggested to properly choose the solver order, the integration step size and the number of grid elements, balancing the accuracy of the predictions with computational time and model stability and flexibility during the transients, with the ultimate goal to provide a model suited for real-time simulations and control-oriented applications

Effects of pipe angular velocity and oven configuration on tube temperature distribution in the radiative heating of PVC pipes

Abstract Several manufacturing processes in polymer industry aim at obtaining products by deforming preforms or sheets after a heating process. A thorough knowledge of the operating parameters of such heating processes is fundamental to fulfill the often high production requirements with the least energy consumption and to avoid unacceptable defects in the final product. A common example of such an application is the end-forming process of polyvinyl chloride (PVC) tubes, which are enlarged at one end in order to allow pipes connections. The heating phase which comes before the deformation process is usually carried out in ovens equipped with short wave infrared lamps; to ensure uniform heating, pipes rotate with a given angular velocity, which represents a fundamental parameter for the success of the whole manufacturing process. In this work, a transient analysis of the radiative heat exchange between rotating PVC pipes and infrared lamps in an oven for end-forming process has been conducted by means of a finite element model, in order to investigate the influence of cylinder angular velocity on the temperature distribution in the tube. Local view factors have been calculated for different oven configurations and have been expressed as a function of angular velocity, allowing pipe rotation to be simulated as a time-dependent boundary condition, instead of using a moving mesh. Simulations were carried out for different tubes geometries and angular velocities and results were compared with the case of a uniformly irradiated tube in terms of temperature displacement. For a given oven configuration, the results obtained by the numerical model can be used to find a critical angular velocity over which further increase does not lead to appreciable improvements in temperature evenness. The effect of the lamps' relative position was also investigated, showing a significant influence on critical angular velocities obtained. The model realized represents a potential tool to characterize the end-forming process in terms of critical angular velocity, leading to reductions in machine set-up time and product waste due to thermal failure

Numerical model of an industrial refrigeration system for condensation temperature optimisation

Refrigeration plants in the food industry have a key role, yet are very energy-intensive, which poses a serious problem given the current steep rise of energy prices. In this framework, energy consumption minimisation represents a paramount goal for plant managers, yet most are loathe to test new control strategies in real-life plants, lest normal operation be disrupted and food be spoiled as a consequence. In this view, numerical models able to demonstrate the reduction in energy consumption which can be achieved with suitable conduction strategies, especially in the case when evaporative condensers are employed, appear the ideal tool to provide the manager with an estimation of the potential savings and spur them into adopting such strategies. In this work one such model is developed for the primary loop of the refrigeration plant of a warehouse for food storage located in northern Italy. The choice of the model type is discussed at length, as are modelling issues related to all main components of the loop. The model has been validated with operational data from the real-life plant and employed to determine the optimal condensation pressure corresponding to the minimum total energy consumption according to ambient conditions. The method and model can be applied to other, similar plants in order to minimise their energy consumption

TGF-β-responsive CAR-T cells promote anti-tumor immune function.

A chimeric antigen receptor (CAR) that responds to transforming growth factor beta (TGF-β) enables the engineering of T cells that convert this immunosuppressive cytokine into a potent T-cell stimulant. However, clinical translation of TGF-β CAR-T cells for cancer therapy requires the ability to productively combine TGF-β responsiveness with tumor-targeting specificity. Furthermore, the potential concern that contaminating, TGF-β?producing regulatory T (Treg) cells may preferentially expand during TGF-β CAR-T cell manufacturing and suppress effector T (Teff) cells demands careful evaluation. Here, we demonstrate that TGF-β CAR-T cells significantly improve the anti-tumor efficacy of neighboring cytotoxic T cells. Furthermore, the introduction of TGF-β CARs into mixed T-cell populations does not result in the preferential expansion of Treg cells, nor do TGF-β CAR-Treg cells cause CAR-mediated suppression of Teff cells. These results support the utility of incorporating TGF-β CARs in the development of adoptive T-cell therapy for cancer

Thermal characterization of the end-forming process of PVC pipes: influence of the number of lamps on critical angular velocities

Abstract The end-forming, or belling, of plastic pipes allows them to be joined together to form longer ducts. The first stage of the process entails softening the pipe wall through heating, and defines the properties of the final product. Because of the very low value of thermal conductivity of plastics and to speed heating up, the pipes are placed in ovens whose walls are lined with infra-red short-wave (SW) lamps. The radiation emitted partly penetrates the pipe wall, quickening the process. The heating elements have a straight configuration, and can only be laid axially flush over the oven's wall, the pipes, therefore, must rotate to obtain a circumferentially uniform heating and avoid damage. The threshold speed to avoid scorching while exceeding a desired temperature over the thickness of the pipe wall is defined as "critical angular velocity" and is strictly dependent on pipe geometry and oven characteristics such as the number and layout of lamps. The Authors have already investigated the problem extensively, as is well documented in the literature, yet one aspect still remains to be studied, namely the influence of the number of lamps on the heat flux distribution over the pipe's perimeter and on the critical velocity. In this work, the issue is investigated thoroughly using the same approach previously adopted and recalled in its main aspects in the paper. It is found that even a significant reduction in the number of lamps does not increase threshold velocities to technically unfeasible values. A non-negligible reduction in costs can therefore be achieved without significant impact on the process outcomes

PCR-Independent Detection of Bacterial Species-Specific 16S rRNA at 10 fM by a Pore-Blockage Sensor.

A PCR-free, optics-free device is used for the detection of Escherichia coli (E. coli) 16S rRNA at 10 fM, which corresponds to ~100-1000 colony forming units/mL (CFU/mL) depending on cellular rRNA levels. The development of a rapid, sensitive, and cost-effective nucleic acid detection platform is sought for the detection of pathogenic microbes in food, water and body fluids. Since 16S rRNA sequences are species specific and are present at high copy number in viable cells, these nucleic acids offer an attractive target for microbial pathogen detection schemes. Here, target 16S rRNA of E. coli at 10 fM concentration was detected against a total RNA background using a conceptually simple approach based on electromechanical signal transduction, whereby a step change reduction in ionic current through a pore indicates blockage by an electrophoretically mobilized bead-peptide nucleic acid probe conjugate hybridized to target nucleic acid. We investigated the concentration detection limit for bacterial species-specific 16S rRNA at 1 pM to 1 fM and found a limit of detection of 10 fM for our device, which is consistent with our previous finding with single-stranded DNA of similar length. In addition, no false positive responses were obtained with control RNA and no false negatives with target 16S rRNA present down to the limit of detection (LOD) of 10 fM. Thus, this detection scheme shows promise for integration into portable, low-cost systems for rapid detection of pathogenic microbes in food, water and body fluids

Extending Elliptic Curve Chabauty to higher genus curves

We give a generalization of the method of "Elliptic Curve Chabauty" to higher genus curves and their Jacobians. This method can sometimes be used in conjunction with covering techniques and a modified version of the Mordell-Weil sieve to provide a complete solution to the problem of determining the set of rational points of an algebraic curve $Y$.Comment: 24 page

Biosynthesis of the major brain gangliosides GD1a and GT1b

Gangliosides-sialylated glycosphingolipids-are the major glycoconjugates of nerve cells. The same four structures-GM1, GD1a, GD1b and GT1b-comprise the great majority of gangliosides in mammalian brains. They share a common tetrasaccharide core (Gal1-3GalNAc1-4Gal1-4Glc1-1′Cer) with one or two sialic acids on the internal galactose and zero (GM1 and GD1b) or one (GD1a and GT1b) 2-3-linked sialic acid on the terminal galactose. Whereas the genes responsible for the sialylation of the internal galactose are known, those responsible for terminal sialylation have not been established in vivo. We report that St3gal2 and St3gal3 are responsible for nearly all the terminal sialylation of brain gangliosides in the mouse. When brain ganglioside expression was analyzed in adult St3gal1-, St3gal2-, St3gal3-and St3gal4-null mice, only St3gal2-null mice differed significantly from wild type, expressing half the normal amount of GD1a and GT1b. St3gal1/2-double-null mice were no different than St3gal2-single-null mice; however, St3gal2/3-double-null mice were >95 depleted in gangliosides GD1a and GT1b. Total ganglioside expression (lipid-bound sialic acid) in the brains of St3gal2/3-double-null mice was equivalent to that in wild-type mice, whereas total protein sialylation was reduced by half. St3gal2/3-double-null mice were small, weak and short lived. They were half the weight of wild-type mice at weaning and displayed early hindlimb dysreflexia. We conclude that the St3gal2 and St3gal3 gene products (ST3Gal-II and ST3Gal-III sialyltransferases) are largely responsible for ganglioside terminal 2-3 sialylation in the brain, synthesizing the major brain gangliosides GD1a and GT1b. © 2012 The Author.Fil: Sturgill, Elizabeth R.. Johns Hopkins School Of Medicine; Estados Unidos. University Johns Hopkins; Estados UnidosFil: Aoki, Kazuhiro. University of Georgia; Estados UnidosFil: Lopez, Pablo. University Johns Hopkins; Estados UnidosFil: Colacurcio, Daniel. University Johns Hopkins; Estados UnidosFil: Vajn, Katarina. University Johns Hopkins; Estados UnidosFil: Lorenzini, Ileana. University Johns Hopkins; Estados UnidosFil: Majic, Senka. University Johns Hopkins; Estados UnidosFil: Yang, Won Ho. University of California; Estados UnidosFil: Heffer, Marija. J. J. Strossmayer University; CroaciaFil: Tiemeyer, Michael. University of Georgia; Estados UnidosFil: Marth, Jamey D.. University of California; Estados UnidosFil: Schnaar, Ronald L.. University Johns Hopkins; Estados Unido

The CoDyCo Project achievements and beyond: Towards Human Aware Whole-body Controllers for Physical Human Robot Interaction

International audienceThe success of robots in real-world environments is largely dependent on their ability to interact with both humans and said environment. The FP7 EU project CoDyCo focused on the latter of these two challenges by exploiting both rigid and compliant contacts dynamics in the robot control problem. Regarding the former, to properly manage interaction dynamics on the robot control side, an estimation of the human behaviours and intentions is necessary. In this paper we present the building blocks of such a human-in-the-loop controller, and validate them in both simulation and on the iCub humanoid robot using a human-robot interaction scenario. In this scenario, a human assists the robot in standing up from being seated on a bench