Cost Sharing Mechanisms for Fair Pricing of Resource Usage

We propose a simple and intuitive cost mechanism which assigns costs for the competitive usage of m resources by n selfish agents. Each agent has an individual demand; demands are drawn according to some probability distribution. The cost paid by an agent for a resource it chooses is the total demand put on the resource divided by the number of agents who chose that same resource. So, resources charge costs in an equitable, fair way, while each resource makes no profit out of the agents. We call our model the Fair Pricing model. Its fair cost mechanism induces a non-cooperative game among the agents. To evaluate the Nash equilibria of this game, we introduce the Diffuse Price of Anarchy, as an extension of the Price of Anarchy that takes into account the probability distribution on the demands. We prove:

Transition between stratified and non-stratified horizontal oil-water flows. Part II: Mechanism of drop formation

The conditions and mechanism of drop formation at the interface of oil-water wavy stratified flows that lead to the onset of drop entrainment and the transition to dual continuous flow pattern were investigated both experimentally and theoretically. Experimentally, high-speed video imaging was used to capture the mechanism of drop detachment from waves during oil and water stratified flow in a diameter horizontal acrylic pipe. The visual observations revealed that the faster phase undercuts the other one while the waves present in both phases deform until drops are detached. The wave deformation was attributed to the drag force, that originates from the relative movement between the two phases, exceeding the stabilising surface tension force. Based on this force balance an equation was developed that related the wavelength to the amplitude that can lead to drop detachment. This drop entrainment equation and the wave stability equation suggested in part I of the paper [Al-Wahaibi, T., Angeli, P., 2007. Transition between stratified and non-stratified horizontal oil-water flows. Part I: Stability analysis. Chemical Engineering Science, in press, doi:10.1016/j.ces.2007.01.024 ], defined three regions in a wave amplitude versus length graph, namely the stable waves, the unstable waves and the drop entrainment region. The intersection of the lines produced by these two equations gives the critical minimum wave characteristics for drop formation. These agreed well with experimental data when a new correlation for the drag coefficient on the waves was used, suitable for liquid-liquid flows. Also the characteristics of waves that were experimentally found to form drops fell within the predicted entrainment region.     

Enhanced Ca2+ Entry Sustains the Activation of Akt in Glucose Deprived SH-SY5Y Cells

The two crucial cellular insults that take place during cerebral ischemia are the loss of oxygen and loss of glucose, which can both activate a cascade of events leading to neuronal death. In addition, the toxic overactivation of neuronal excitatory receptors, leading to Ca²⁺ overload, may contribute to ischemic neuronal injury. Brain ischemia can be simulated in vitro by oxygen/glucose deprivation, which can be reversible by the re-establishment of physiological conditions. Accordingly, we examined the effects of glucose deprivation on the PI3K/Akt survival signaling pathway and its crosstalk with HIF-1α and Ca²⁺ homeostasis in SH-SY5Y human neuroblastoma cells. It was found that glucose withdrawal decreased HIF-1α protein levels even in the presence of the ischemia-mimicking CoCl_2. On the contrary, and despite neuronal death, we identified a strong activation of the master pro-survival kinase Akt, a finding that was also confirmed by the increased phosphorylation of GSK3, a direct target of p-Akt. Remarkably, the elevated Ca²⁺ influx recorded was found to promptly trigger the activation of Akt, while a re-addition of glucose resulted in rapid restoration of both Ca²⁺ entry and p-Akt levels, highlighting the plasticity of neurons to respond to ischemic challenges and the important role of glucose homeostasis for multiple neurological disorders.     

Bioimaging and Biodistribution of the Metal-Ion-Controlled Self-Assembly of PYY3–36 Studied by SPECT/CT

The controlled self-assembly of peptide- and protein-based pharmaceuticals is of central importance for their mode of action and tuning of their properties. Peptide YY_3–36 (PYY_3–36) is a 36-residue peptide hormone that reduces food intake when peripherally administered. Herein, we describe the synthesis of a PYY_3–36 analogue functionalized with a metal-ion-binding 2,2’-bipyridine ligand that enables self-assembly through metal complexation. Upon addition of Cu^II, the bipyridine-modified PYY_3–36 peptide binds stoichiometric quantities of metal ions in solution and contributes to the organization of higher-order assemblies. In this study, we aimed to explore the size effect of the self-assembly in vivo by using non-invasive quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) imaging. For this purpose, bipyridine-modified PYY_3–36 was radiolabeled with a chelator holding ¹¹¹In^III, followed by the addition of Cu^II to the bipyridine ligand. SPECT/CT imaging and biodistribution studies showed fast renal clearance and accumulation in the kidney cortex. The radiolabeled bipyridyl-PYY_3–36 conjugates with and without Cu^II presented a slightly slower excretion 1 h post injection compared to the unmodified-PYY_3–36, thus demonstrating that higher self-assemblies of the peptide might have an effect on the pharmacokinetics.     

A comparative presentation of implementation of ISO 22000 versus HACCP and FMEA in a small size Greek factory producing smoked trout: a case study

ISO 22000 is the new standard bound to replace HACCP on issues related to food safety. Although several companies, especially the big ones, have either implemented or are on the point of implementing ISO 22000, there are many others which are rather timid and/or reluctant to implement it. The main reason behind that is the lack of information and the fear that the new standard is too demanding in terms of bureaucratic work. This paper aims at making a comparative presentation of how the two systems can be applied to a small smoked salmon producing company thereby facilitating the emergence of the differences. The main difference is that in ISO 22000 systems like Good Manufacturing Practice and Good Hygiene Practice are prerequisites thus leading to lower number of CCPs. In this case study for example, the number of CCPs dropped from eight (8) in HACCP to four (4) in ISO 22000. Furthermore, the Failure Mode and Effect Analysis was applied to the smoked trout manufacturing process in an attempt to calculate quantitatively the Risk Priority Number (RPN) and to find out whether it can be effectively correlated to ISO 22000 and/or HACCP. RPN was found to be higher than 130 for eight steps, in close agreement with HACCP, thereby indicating that corrective actions will have to be undertaken.     

Study of aflatoxin B1 and ochratoxin A production by natural microflora and Aspergillus parasiticus in black and green olives of Greek origin

Aflatoxin B1 (AFB1) is a carcinogenic metabolite produced by certain Aspergillus species. Ochratoxin A (OTA) is classified as "possible carcinogen" and it is a metabolite of Aspergillus ochraceus and Penicillium verrucosum. Fungi contaminate natural and processed olives which support AFB1 and OTA production. The aim of this study was to compare and investigate AFB1 and OTA production in three different varieties of damaged olives. For each variety two different treatments were applied: (1) olives with natural microflora and (2) olives inoculated with A. parasiticus after natural microflora elimination. AFB1 and OTA have been extracted simultaneously from olives, purified with immunoaffinity columns and quantitated by HPLC using fluorescence detector. The recoveries and detection limits of AFB1 and OTA were 94% and 0.15 ng AFB1 g(-1) and 102.7%, 0.41 ng OTA g(-1) respectively. Results showed that, meanwhile OTA was not found in any olive sample, AFB(1) production within the three varieties of olives with natural microflora was significantly (P< or =0.05) different regarding their substrate and time of incubation (18 days). AFB1 production in two different varieties of black olives after inoculation by A. parasiticus was not significantly higher compared with control samples. On the contrary, AFB1 production in green olives was stimulated after the 12th day. Additionally, investigation on the occurrence of AFB1 and OTA in 30 samples of olives and olive pasta from Athens market showed OTA's presence in two samples of olives contaminated at the levels of 1.18 and 1.86 ng OTA g(-1). Aflatoxin B1 was found at levels 0.15-1.13 ng AFB1 g(-1) in all samples tested.