Fairs for e-commerce: the benefits of aggregating buyers and sellers

In recent years, many new and interesting models of successful online business have been developed. Many of these are based on the competition between users, such as online auctions, where the product price is not fixed and tends to rise. Other models, including group-buying, are based on cooperation between users, characterized by a dynamic price of the product that tends to go down. There is not yet a business model in which both sellers and buyers are grouped in order to negotiate on a specific product or service. The present study investigates a new extension of the group-buying model, called fair, which allows aggregation of demand and supply for price optimization, in a cooperative manner. Additionally, our system also aggregates products and destinations for shipping optimization. We introduced the following new relevant input parameters in order to implement a double-side aggregation: (a) price-quantity curves provided by the seller; (b) waiting time, that is, the longer buyers wait, the greater discount they get; (c) payment time, which determines if the buyer pays before, during or after receiving the product; (d) the distance between the place where products are available and the place of shipment, provided in advance by the buyer or dynamically suggested by the system. To analyze the proposed model we implemented a system prototype and a simulator that allow to study effects of changing some input parameters. We analyzed the dynamic price model in fairs having one single seller and a combination of selected sellers. The results are very encouraging and motivate further investigation on this topic

A Graph-Traversing Algorithm for Computing Some Stable Sets in Effectiveness Coalitional Games

We propose an algorithm for computing "main stable sets" recently introduced by Ciardiello, Di Liddo (2009) on effectiveness form coalitional games modeled through a directed pseudograph. The algorithm is based upon a graph traversing method exploring extended paths minimal in coalitions and we study some its interesting computational aspects for making these stability concepts as useful tools for decision theory.Algorithmic game theory; coalitional games; dominance relations; stable sets; graph theory.

Thermally activated vapor bubble nucleation: the Landau-Lifshitz/Van der Waals approach

Vapor bubbles are formed in liquids by two mechanisms: evaporation (temperature above the boiling threshold) and cavitation (pressure below the vapor pressure). The liquid resists in these metastable (overheating and tensile, respectively) states for a long time since bubble nucleation is an activated process that needs to surmount the free energy barrier separating the liquid and the vapor states. The bubble nucleation rate is difficult to assess and, typically, only for extremely small systems treated at atomistic level of detail. In this work a powerful approach, based on a continuum diffuse interface modeling of the two-phase fluid embedded with thermal fluctuations (Fluctuating Hydrodynamics) is exploited to study the nucleation process in homogeneous conditions, evaluating the bubble nucleation rates and following the long term dynamics of the metastable system, up to the bubble coalescence and expansion stages. In comparison with more classical approaches, this methodology allows on the one hand to deal with much larger systems observed for a much longer times than possible with even the most advanced atomistic models. On the other it extends contin- uum formulations to thermally activated processes, impossible to deal with in a purely determinist setting

Dynamics of a vapor nanobubble collapsing near a solid boundary

In the present paper a diffuse interface approach is used to address the collapse of a sub-micron vapor bubble near solid boundaries. This formulation enables an unprecedented description of interfacial flows that naturally takes into account topology modification and phase changes (both vapor/liquid and vapor/supercritical fluid transformations). Results from numerical simulations are exploited to discuss the complex sequence of events associated with the bubble collapse near a wall, encompassing shock-wave emissions in the liquid and reflections from the wall, their successive interaction with the expanding bubble, the ensuing asymmetry of the bubble and the eventual jetting phase

Introduction to neutrino astronomy

This writeup is an introduction to neutrino astronomy, addressed to astronomers and written by astroparticle physicists. While the focus is on achievements and goals in neutrino astronomy, rather than on the aspects connected to particle physics, we will introduce the particle physics concepts needed to appreciate those aspects that depend on the peculiarity of the neutrinos. The detailed layout is as follows: In Sect.~1, we introduce the neutrinos, examine their interactions, and present neutrino detectors and telescopes. In Sect.~2, we discuss solar neutrinos, that have been detected and are matter of intense (theoretical and experimental) studies. In Sect.~3, we focus on supernova neutrinos, that inform us on a very dramatic astrophysical event and can tell us a lot on the phenomenon of gravitational collapse. In Sect.~4, we discuss the highest energy neutrinos, a very recent and lively research field. In Sect.~5, we review the phenomenon of neutrino oscillations and assess its relevance for neutrino astronomy. Finally, we offer a brief overall assessment and a summary in Sect.~6. The material is selected - i.e., not all achievements are reviewed - and furthermore it is kept to an introductory level, but efforts are made to highlight current research issues. In order to help the beginner, we prefer to limit the list of references, opting whenever possible for review works and books.Comment: 15 pages, 5 figures. Accepted for publication The European Physical Journal Plus. Based on the lecture given at the "4th Azarquiel School of Astronomy", June 2017, Porto Paolo di Capo Passero, Syracuse (Italy) https://agenda.infn.it/conferenceDisplay.py?confId=1208

Characterising food web responses to climate change using a combination of traditional and molecular tools

Freshwater ecosystems are considered hot spots for biodiversity and provide a wide range of ecosystem services for human beings. A variety of natural and anthropogenic stressors are now threatening the stability and prosperity of these ecosystems. In particular, climate change and pollution are the main stressors impacting all freshwater ecosystems on Earth. In this mix of multiple stressors, climate change is already having profound impacts, and is predicted to result in large-scale population collapses, species range shifts, and local species extinctions, as well as altered ecosystem properties. Scientists have spent considerable efforts in recent years investigating how these perturbations might impact food web structures and dynamics to predict potential future scenarios, but much of this work has been hindered by the slow pace of data generation using traditional techniques. Thus, there is a need to adopt and develop new approaches that can answer questions and generate data at a much higher pace. Molecular tools can address this issue by generating millions of DNA sequences in a short period of time with the potential to build food webs in a very reliable way. Therefore, a detailed understanding of food webs and their interactions is critical to predict what effects climate change will have in the near future, and we need to find faster and cheaper ways of building the necessary evidence base. This will ultimately improve our ability to forecast how communities and ecosystems will respond to global change and anticipate which species (and systems) are more likely to deteriorate under these new conditions. In this thesis, I have used a combination of traditional and molecular tools to characterize the diet of a widely distributed generalist predator. DNA sequencing revealed a higher number of links compared to traditional microscopy, but protocols need to be refined to accurately quantify each link. In addition to this, I carried out two sets of laboratory experiments to quantify warming impacts on freshwater invertebrate interactions. Functional response experiments showed increased feeding rates with warming, while qPCR was not able to detect changes in DNA retention time in predator gut contents.Open Acces

in vitro models to evaluate the capacity of different sequestering agents to adsorb aflatoxins

Eight potential aflatoxin-sequestering agents (SAs) were tested for their ability to adsorb aflatoxin B1 (AfB1) and aflatoxin G1 (AfG1) in vitro. They belong to main SA classes: silicate minerals (calcium, magnesium and sodium bentonites, kaolinite, zeolite and clinoptinolite), activated carbon and yeast cell wall-derived. The AfB1 and AfG1 used in present work were extracted from a contaminated corn meal (82.21 mg/kg of AfB1 and 97.20 mg/kg of AfG11). Three single-concentration adsorption tests, consisting of a simply-water (W), a gastrointestinal simulating monogastric model (MM) and a ruminant model (RM), were used. The methods differed for dilution media, incubation steps and pH condition in which they were conducted. In particular, one step (2h at 39°C) at pH 7 for W; two steps (4h at 39°C) at pH 2 and 7 for MM; and a pre-incubation in rumen fluid (pH 7 for 2h at 39°C) + two steps (4h at 39°C) at pH 2 and 7 for RM, characterized each method. The AfB1:SA ratio (g/g) and dilution factor (ng of incubated AfB1:mL of volume) were chosen (1:500,000 and 4.1, respectively) to reflect field conditions. The AfB1 and AfG1 recovered in controls were 92.3% and 104.9% in W and 89.5% and 101.5% in MM; while in RM were 65.2% and 81.9%; respectively. This supported the idea of intrinsic rumen fluid factors could be involved in sequestering of aflatoxins. In the present study, three SAs (activated carbon, Mg bentonite and Na bentonite) were very efficient to sequester the available AfB1, with a sequestering activity of over 99.0% with each method. The Ca bentonite and clinoptinolite were able to bind available AfB1 in MM and RM methods, while they appeared inefficient (available AfB1 sequestered less than 80%) when W was used. The adsorption ability of zeolite was confirmed only with the W method. Ineffective or limited sequestering activity were obtained with kaolinite and yeast cell wall-derived products with each method. The AfB1 and AfG1 sequestering efficiencies observed in the present work resulted very similar showing strong and positive correlation (P<0.001) within methods (r=0.79, r=0.96 and r=0.99, respectively for W, MM and RM methods). The two simulated gastrointestinal methods (MM and RM, respectively) gave similar results and could be considered useful for in vitro pre-screening of potential sequestering agents. However, the major practical and analytical implications related to rumen fluid method suggested that MM method should be used

Supernova neutrino physics with a nuclear emulsion detector

The existence of the coherent neutrino-nucleus scattering reaction requires to evaluate, for any detector devoted to WIMP searches, the irreducible background due to conventional neutrino sources and at same time, it gives a unique chance to reveal supernova neutrinos. We report here a detailed study concerning a new directional detector, based on the nuclear emulsion technology. A Likelihood Ratio test shows that, in the first years of operations and with a detector mass of several tens of tons, the observation of the supernova signal can be achieved. The determination of the distance of the supernova from the neutrinos and the observation of $^8$B neutrinos are also discussed.Comment: 22 pages, 12 figure

Sperm glyceraldehyde 3-phosphate dehydrogenase gene expression in asthenozoospermic spermatozoa

It has been suggested that the energy required for sperm motility is produced by oxidative phosphorylation while glycolysis seems to be an important source for ATP transmission along the flagellum. Some studies have investigated the chemical and kinetic properties of the enzyme glyceraldehyde 3‐phosphate dehydrogenase to identify any changes in the regulation of glycolysis and sperm motility. In contrast, there are few studies analyzing the genetic basis of hypokinesis. For this reason, we investigated the glyceraldehyde 3‐phosphate dehydrogenase gene in human sperm to evaluate whether asthenozoospermia was correlated with any changes in its expression. Semen examination and glyceraldehyde 3‐phosphate dehydrogenase gene expression studies were carried out on 116 semen samples divided into two groups – Group A consisted of 58 normokinetic samples and Group B of 58 hypokinetic samples. Total RNA was extracted from spermatozoa, and real‐time PCR quantification of mRNA was carried out using specific primers and probes. The expression profiles for the Groups A and B were very similar. The mean delta Ct was as follows – Group A, 5.79 ± 1.04; Group B, 5.47 ± 1.27. Our study shows that in human sperm, there is no difference in glyceraldehyde 3‐phosphate dehydrogenase gene expression between samples with impaired motility and samples with normal kinetics. We believe that this study could help in the understanding of the molecular mechanisms of sperm kinetics, suggesting that hypomotility may be due to a possible posttranscriptional impairment of the control mechanism, such as mRNA splicing, or to posttranslational changes