Integrators’ Air Transport Networks in Europe

Integrators are shipping carriers that control complete air and road delivery networks and offer a wide range of package delivery services. Despite the increasing relevance of small package delivery services in the European air transport market, very little has been written on integrated carriers’ air transport networks on the Old Continent. In this paper we examine the network configurations of DHL, FedEx, TNT, and UPS in terms of hubs, spokes, and market shares. Our results show that integrators operate hub-and-spoke networks. Network indices and centrality measures confirm that their network structures are more similar to those of full-service passenger carriers rather than those of low-cost carriers. However, the nature of their hub-and-spoke systems is different because freight tons, as compared to passengers, are more easily flown along multiple-stop and circular routes. As a consequence, FedEx, TNT, and UPS operate non-pure star networks with a dominant central hub and a set of intermediate airports acting as stops between the central hub and (usually) one “external airport”. DHL operates a multi-hub architecture, with a main dominant hub in Leipzig and a set of “secondary hubs” that provide several connections to other network nodes. Furthermore, we provide evidence of the most important intra-Europe and long-haul routes for each integrator, showing that DHL seems to have a more developed Europe-Asia connection, and is the only integrator to connect Europe to Sub-Saharan Africa. Finally, we show the high degree of complementarity existing between FedEx and TNT networks and that such complementarity is confirmed also by an analysis of their market shares in the different European sub-markets. Despite the significant level of market concentration, our analysis shows that the recent merger between FedEx and TNT is not expected to significantly modify market equilibrium in Europe.

     

Quantitative analysis of convective dose in hemofiltration and hemodiafiltration: "predilution" vs. "postdilution" reinfusion

In hemofiltration (HF) and hemodiafiltration (HDF), removal of medium and high-molecular-weight solutes is greatly enhanced by convective mechanisms as compared with simple diffusion; increasing convective flows may allow greater removal rates of these solutes. Use of "predilution" (pre-H[D]F) may allow higher ultrafiltration rates than the "postdilution" mode (post-H[D]F); yet, the dilution of plasma water may have unpredictable effects on "endogenous" water convection. We have applied a mathematical analysis to evaluate and compare endogenous water convective flow rates in pre-H(D)F vs. post-H(D)F. Endogenous plasma water recovered in ultrafiltrate was calculated according to patient (hematocrit, total protein level) and session parameters (blood flow, ultrafiltration rate, programmed weight loss), in absolute terms and as a fraction of endogenous plasma water delivery to the filter. Maximally efficient post-H(D)F was modelled according to a preset postfilter hematocrit or filtration fraction. Nomograms were constructed expressing endogenous water convective fluxes in relation to parameters of interest (ultrafiltration rate, blood flow, hematocrit) with both post-H(D)F and pre-H(D)F, and "efficiency" of pre-H(D)F vs. post-H(D)F (as the ratio of endogenous water convective flow rate with the 2 techniques) as a function of the ultrafiltration/reinfusion rate. In post-H(D)F, the model predicts maximal ultrafiltration rates within the limits of a preset hemoconcentration at the filter outlet; additionally, the model allows to calculate ultrafiltration/reinfusion quantities to be set in pre-H(D)F to equal and overcome maximal convective efficiency of post-H(D)F. This "equivalence" ultrafiltration rate may greatly vary according to patient's hematocrit and blood flow, so that the ultrafiltrate-reinfusate volume available in the system dictates, in any patient, which mode of reinfusion may attain higher "endogenous" convective flow rates. Pre-H(D)F may allow higher fractional and absolute "endogenous" convective flow rates as compared with post-H(D)F, provided that adequate amounts of reinfusate are available. For lower reinfusate volumes than "equivalence" values, post-H(D)F remains a better option.     

Evaluation of heat-induced changes in Spanish commercial milk: hydroxymethylfurfural and available lysine content

Hydroxymethyfurfural (HMF) content and loss of available lysine were measured as indices of heat damage in various Spanish commercial milks (pasteurized, UHT sterilized and in-bottle sterilized milks) with similar processing dates. HMF level was determined by the traditional colorimetric procedure and by the reversed-phase HPLC method. Available lysine was measured by an alternative method with o -phthaldialdehyde as fluorescent marker. A significative relationship has been found between the HMF content and loss of available lysine and both are suitable for use as heat-induced indices. When loss of lysine ( y ) was expressed as percentage and HMF ( x ) as μ m , the function of the correlation line was, y =0.47x−0.089 ( r =0.958, P <,0.005).     

Peroxyl radical scavenging activity of melanoidins in aqueous systems

Melanoidins are widely distributed in our diet, due to home or industrial processing of foods. Until recently, melanoidins were considered to be an inert, brown-coloured polymeric component. However, recent research into their nutritional, physiological, and functional properties has suggested that they have antioxidant properties, and we address this issue in this work. A sensitive procedure for assessing the inhibition of lipid peroxidation by melanoidins in watery media has been developed. Main drawbacks and critical steps of the procedure are discussed. Melanoidins can be classified according to the number of peroxyl radicals trapped per molecule. Coffee and sweet wine melanoidins show higher antioxidant activity than melanoidins isolated from beer. For the first time, a linear relationship between the peroxyl radical scavenging activity and the chromophore residues in the melanoidin skeleton responsible for browning has been established.     

Surface heat flow density at the phlegrean fields caldera (SOUTHERN ITALY)

The Phlegrean Fields area is a Holocene caldera located west of Naples, southern Italy. The recent post-caldera activity is characterized by several eruptive centers inside the collapsed area. In order to investigate the still active volcanic processes, surface heat flow measurements were carried out in 1995 in 30 sites of the Phlegrean Fields, and a heat flow map compiled. Filtering of the map reveals some well-defined anomalies superimposed on a general southward-increasing trend. Local anomalies are related to small magma bodies, whereas the observed general trend has been attributed to the effect of groundwater flow. This effect was calculated and removed. The undisturbed mean value of the surface heat flow density in the eastern sector is 149 mW\m², which is above the regional value of 85 mW\m² assigned to the eastern part of the Tyrrhenian Sea, and which is probably influenced by a very large, deep magmatic body.     

Characterization of industrial processed milk by analysis of heat-induced changes

Summary Thermal indicators in milk, which had been subjected to one of the six industrial processes of thermization, pasteurization, direct and indirect UHT-sterilization, pre-sterilization and in-bottle sterilization, were studied. The following three indices of heat damage were analyzed by high performance liquid chromatography (HPLC), hydroxymethylfurfural (HMF), lactulose and acid-soluble β-lactoglobulin(β-LG). Average amounts found were 1710 mg/l of β-LG and 2.49 μmol/l of HMF in pasteurized milk. In UHT milk, the amounts for direct and indirect processes were 389 and 322 mg/l of β-LG, 12.0 and 250 mg/l of lactulose and 5.6 and 8.7 μmol/l of HMF. In sterilized milk the amounts were 1120 mg/l of lactulose and 22 μmol/l of HMF, without any detectable presence of undenatured whey proteins. On the basis of the time/temperature profiles, a sterilization factor, expressed as seconds, was defined for each thermal treatment. By applying discriminant analysis each industrial process could be classified independently at the 95% confidence level (pasteurization, UHT-treatment and in-bottle sterilization), but direct-UHT treated milk could not be discriminated from indirect-UHT milk, nor thermized milk from raw bulk milk. The simultaneous application of several heat-induced parameters improves the classification of industrial processed milks, and is therefore a useful tool for optimization of the processing conditions.     

Preparation and properties of new acid catalysts obtained by grafting alkoxides and derivatives on the most common supports. Part II: Grafting zirconium and silicon alkoxides on γ-alumina

In this work, the preparation and properties of the acid catalysts obtained by grafting zirconium and silicon alkoxides and zirconium-sulfated alkoxide on γ-alumina were studied. The catalysts prepared were examined with electrochemical techniques to evaluate the hydroxyl density, the ZPC (zero point charge) and the intrinsic surface ionization constants. The catalysts were also submitted to TPD (temperature-programmed desorption) analysis using different organic bases to determine the distribution of acid sites. Some samples were also submitted to microcalorimetric analysis using pyridine as probe molecule, and to XPS measurements. Finally, the catalysts prepared were tested in three different reactions: methanol dehydration, n-hexane isomerization and cracking and skeletal isomerization of 1-butene to isobutene. The most relevant results obtained were: (i) grafted zirconia strongly promoted methanol dehydration up to an upper limit of grafting; (ii) grafted zirconium sulfated alkoxide showed a moderate activity, but good selectivity in n-hexane isomerization; (iii) silicated aluminas (prepared in the absence of solvents) showed high activity, selectivity and stability in the 1-butene skeletal isomerization reaction.     

A surface roughness predictive model in deterministic polishing of ground glass moulds

The introduction of deterministic NC grinding and polishing operations, in the manufacturing of free-form glass components for precision optics, requires the characterization of surface topography evolution as a function of process parameters. In this work, a model based on Reye's wear hypothesis is proposed for the assessment of surface roughness prediction as a function of operating parameters, in the deterministic polishing process of glass moulds. According to Reye's hypothesis, the removed material per unit area is proportional to the work due to the friction force: the removed material per unit area can be computed by adequately integrating the areal material ratio function (Abbott–Firestone curve) of the surface and can be associated with the amplitude roughness parameter; the work due to the friction force per unit area is proportional to the integral of the product of pressure and velocity in the time interval and can be derived from the process parameters by means of the Hertz theory. The model assessment was performed on ground glass flat samples polished with different operating parameters, mapping the surface roughness using an atomic force microscope (AFM). The developed model shows a satisfactory estimate of surface roughness evolution during the polishing process and confirms the experimental results found in the literature for the Preston coefficient.     

Tryptophan determination in milk-based ingredients and dried sport supplements by liquid chromatography with fluorescence detection

Sport supplements formulas are driven to a sector of consumers which a restrictive diet. Tryptophan is essential amino acid and its bioavailability should be assessed from these commercial products. A robust and fast HPLC procedure is applied to determine total tryptophan content from dairy-ingredients, mostly whey-based ingredients, and commercial dried-sport supplements, mostly whey-enriched sport supplements. The nutritional quality of the protein used in the formulation could be extrapolated to the expected tryptophan content by using a regression curve built from milk-based ingredients. Samples that not conform the correlation are suspected from inadequate industrial practices, such as over-processing, and/or the use of heat-damage ingredients.     

Development and characterization of a modular acquisition system for a 4D PET block detector

Next generation PET scanners should fulfill very high requirements in terms of spatial, energy and timing resolution. Modern scanner performances are inherently limited by the use of standard photomultiplier tubes. The use of Silicon Photomultiplier (SiPM) matrices is proposed for the construction of a 4D PET module based on LSO continuous crystals, which is envisaged to replace the standard PET block detector. The expected spatial resolution of the module for the photon hit position is below 1 mm, and it will perform at the same time, the Depth Of Interaction (DOI) calculation and the Time Of Flight (TOF) measurement. The use of large area multi-pixel Silicon Photomultiplier (SiPM) detectors requires the development of a multichannel Digital Acquisition system (DAQ) as well as of a dedicated front-end in order not to degrade the intrinsic detector performances. We have developed a flexible and modular DAQ system for the read-out of two modules in time coincidence for Positron Emission Tomography (PET) applications. The DAQ system is based on a previously developed custom front-end ASIC chip (BASIC) which allows to read-out SiPM matrices preserving their spectroscopy and timing capabilities. Here we describe the acquisition system architecture and its characterization measurements.