Spatial price dynamics in the EU F&V sector: the cases of tomato and cauliflower

The paper explores the characteristics of spatial price dynamics for fresh vegetables. The analysis is carried out on selected EU prices for tomatoes and cauliflowers collected on some of the main production and consumption markets. It is based on the estimation of an time-varying threshold autoregressive econometric specification that is shown capable to underline the asymmetries in inter-Countries price transmission. The model shows that that horizontal price transmissions among net producer and net consumer markets is asymmetric and how such characteristic differs for markets closer to production areas or to consumption locations. This paper allowed to assess the average elapsing time for shocks to be transmitted among spatially separated markets, and, in particular, it shows the speed of transmission of price raises and price falls.price transmission, TVECM, vegetables, Agribusiness, Agricultural and Food Policy, Community/Rural/Urban Development, Food Consumption/Nutrition/Food Safety, Labor and Human Capital,

The entry price threshold in EU F&V sector: deterrence or effective barrier?

The paper investigates the effects of the entry price scheme for fresh fruit and vegetables. The analysis is conducted on the EU prices of tomatoes, lemons and apples for some of the main competing countries on the EU domestic markets: Morocco, Argentina, Turkey and China. The econometric analysis is based on testing and estimating a switching vector autoregressive model with endogenous threshold entry price level. The model shows the isolation effects and the accumulation of SIVs above the trigger entry price. This paper contributes to clarify the role played by the EPS in avoid or deter low priced imports from main EU partner Countries.Fruits and vegetables, Entry price system, trade policy, TVAR, Agricultural and Food Policy, F13, Q17, Q18,

Design of an innovative polymerase chain reaction device based on buoyancy driven flow

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Polymerase Chain Reaction (PCR) plays a central role in the field of molecular biology. The miniaturization of PCR systems is promising as it potentially minimizes costly reagent consumption and time required for analysis. In PCR microdevices a sample solution is usually handled by external pumps. An alternative solution relies on temperature-induced density difference in the presence of a body force to induce buoyancy driven flow. This alternative method is easy to be used and does not require expensive setup, but, to date, the thermo-fluid-dynamic field in the micro-channels still needs to be optimized. The present study focuses on the design of micro-channels, having innovative and optimized shapes to obtain proper fluid actuation and DNA sample amplification within buoyancy driven flow PCR devices. A parametric study is carried out by means of computational thermal fluid dynamic modeling: several channel geometry configurations were compared in terms of time required for analysis, temperature distribution and priming volume. The advantages and disadvantages of such configurations are discussed

engineering thoughts on hydrogen embrittlement

Abstract Hydrogen Embrittlement (HE) is a topical issue for pipelines transporting sour products. Engineers need a simple and effective approach in materials selection at design stage. In other words, they must know if a material is susceptible to cracking, to be able of: selecting the right material and apply correct operational measures during the service life. Following ASTM F2078, HE is "a permanent loss of ductility in a metal or alloy caused by hydrogen in combination with stress, either externally applied or internal residual stress". In many cases, hydrogen can play a role in crack propagation, as for instance in Stress Corrosion Cracking (SCC) and Corrosion Fatigue (CF). Three parameters are required to cause failure: presence of hydrogen, tensile stress, and material susceptibility. The two previous ones are triggering the failure, while the root cause is usually material susceptibility. This is why material selection is the important step to safely manage engineering structural materials. As an example, material selection for sour service pipeline is the object of well-known standards, e.g. by Nace International and EFC: they pose some limits in the sour service of steels, with reference to surface hardness. These standards have shown some weak points, namely: In the definition of sour service; In defining the role of crack initiation and propagation, considering that in Hydrogen embrittlement, stress state and stress variations are very important. As for the second point, in hydrogen generation anodic processes shall be taken into account too. For instance, there is a relationship between corrosion resistance and crack susceptibility. In carbon and low alloy steels, cracking will not normally occur when there is a significant corrosion rate. If a brittle layer (or a brittle spot) is present on the metal surface, this one can initiate a crack

Computational and experimental investigation of mixing in microchannels

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Mixing is a key process for the successful of all chemical or biochemical reactions, so effective micromixers represent essential components for micro total analysis systems (μTAS) or lab-on-a-chip. In the present study a combined computational and experimental approach was adopted to evaluate how the efficiency of a Y-mixer can be enhanced by modifying its downstream geometry. Three different geometries were studied and compared: Y-straight channel, Y-sine channel and Y-wrinkled wall channel. For each of them the influence of perfusing flow rates and channel cross section aspect ratio was investigated. Physical prototypes were built using a simple technique based on a xerographic process, and their mixing performance was experimentally evaluated. Computational models of the designed micromixers were generated: the Navier-Stokes equations for an incompressible Newtonian fluid and the advection-diffusion equation were solved with an uncoupled approach by means of the finite volume method. The computational and experimental results were critically compared, revealing Y-wrinkled wall mixer as the best performer among those considered and suggesting criteria of possible improvements and optimization

Regularity bounds by minimal generators and Hilbert function

Let $\rho_C$ be the regularity of the Hilbert function of a projective curve $C$ in \mbox {P}^n_K over an algebraically closed field $K$ and $\beta_1, \ldots, \beta_{n-1}$ be degrees for which there exists a complete intersection of type ($\beta_1, \ldots, \beta_{n-1}$) containing properly $C$. Then the Castelnuovo-Mumford regularity of $C$ is bounded above by max $\{\rho_C +1, \beta 1 + \ldots + \beta_n-1 -(n-1)\}$ .We investigate the sharpness of the above bound, which is achieved by curves algebraically linked to ones having degenerate general hyperplane section

Non-continuous Froude number scaling for the closure depth of a cylindrical cavity

A long, smooth cylinder is dragged through a water surface to create a cavity with an initially cylindrical shape. This surface void then collapses due to the hydrostatic pressure, leading to a rapid and axisymmetric pinch-off in a single point. Surprisingly, the depth at which this pinch-off takes place does not follow the expected Froude$^{1/3}$ power-law. Instead, it displays two distinct scaling regimes separated by discrete jumps, both in experiment and in numerical simulations (employing a boundary integral code). We quantitatively explain the above behavior as a capillary waves effect. These waves are created when the top of the cylinder passes the water surface. Our work thus gives further evidence for the non-universality of the void collapse