The value of location in keyword auctions

Sponsored links on search engines are an emerging advertising tool, whereby a number of slots are put on sale through keyword auctions. This is also known as contextual advertising. Slot assignment and pricing in keyword auctions are then essential for the search engine\u2019s management since provide the main stream of revenues, and are typically accomplished by the Generalized Second Price (GSP) mechanism. In GSP the price of slots is a monotone function of the slot location, being larger for the highest slots. Though a higher location is associated with larger revenues, the lower costs associated with the lowest slots may make them more attractive for the advertiser. The contribution of this research is to show, by analytical and simulation results based on the theory of order statistics, that advertisers may not get the optimal slot they aim at (the slot maximizing their expected profit) and that the GSP mechanism may be unfair to all the winning bidders but the one who submitted the lowest bid

Efeito da epoca de colheita e da vedacao da pastagem na producao de sementes de capim andropogon.

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Heat and helium production during exothermic reactions between gases through palladium geometrical elements loaded with hydrogen

In this research, thexffect of the shape of hydrogenloaded palladium elements on exothennic reactions between gases is shown. It was found that an element with parts of its sulface next to each other spontaneously triggers reactions, whereas an element whose su$aces are not next to each other needs outside triggering. The heat developed makes the temperature of the elements rise even by a few hundredths of a degree centigrade. Through photographic techniques, it was shown that the elements, when releasing heat, emit radiation connected to nuclearfusion reactions. These reactions, confirmed also by the analysis of the used hydrogen, showed helium formation. All these tests have confirmed the reproducibility of the phenomenon

VARIAZIONI NEL FLUSSO DI CO2 OSSERVATE NEL MARZO-APRILE 2009 IN ITALIA CENTRALE

In tutto il mondo nelle aree di collisione tettonica è stata osservata la presenza di sorgenti di acque calde o di gas di origine endogena (Italiano et al., 2001 e riferimenti citati). Il gas emesso più importante sotto il profilo quantitativo è l’anidride carbonica il cui ruolo è stato spesso sottolineato per giustificare la generazione di anomalìe di carattere geochimico osservate nelle acque sotterranee o nelle emissioni gassose. Nell’Italia centro-meridionale esistono numerose emissioni spontanee di anidride carbonica note come mofete o mefite. Nel corso della sequenza sismica del 1997 verificatasi in Umbria-Marche sono state monitorate le caratteristiche fisiche e composizionali di alcune emissioni di CO2 presenti nel territorio interessato dai principali eventi di carattere tettonico (Martinelli e Albarello, 1997). In particolare nel corso del 1997 sono state osservate variazioni di flusso di gas totale nelle emissioni di Monte Castello di Vibio, Umbertide e Massa Martana. Nelle stesse aree sono state osservate variazioni significative di carattere composizionale in grado di confermare la non stazionarietà dell’origine dei gas emessi (Italiano et al., 2004; Italiano et al., 2009 e bibliografia citata). Nel Comune di Massa Martana è localizzata l’emissione spontanea di anidride carbonica di San Faustino. L’emissione principale è captata da una opera di presa composta da una stanza sotterranea e da un insieme di tubi che convogliano il gas verso l’esterno. Alla fine del percorso di tubi è stata installata una strumentazione in grado di misurare la portata del gas. Il sensore è del tipo a “filo caldo”. Altri parametri di carattere ambientale sono monitorati nel sito e nella zona. Nel periodo 2005-2008 sono state osservate variazioni nei valori di portata del gas emesso in parte probabilmente ascrivibili alla attività tettonica della zona. Nel corso del 2009 sono stati affrontati e risolti problemi tecnici di alimentazione elettrica, ripristinata nel corso del mese di marzo. Alla fine del mese di Marzo 2009 e nel mese di aprile 2009 i valori di portata registrati sono stati pari a circa il doppio della normalità. I valori di portata sono poi ridiscesi entro la normalità entro un mese dalla data dell’evento principale della sequenza sismica del 2009 che ha interessato vaste aree dell’Abruzzo. La distanza tra il sito di osservazione e l’area epicentrale dell’evento principale della sequenza simica dell’aprile 2009 è di circa 80 km. Nella letteratura scientifica sono state riportateanomalìe di carattere geofisico e geochimico rilevate a distanze paragonabili a quelle descritte in concomitanza con eventi simici significativi. Fenomeni di possibile degassamento terrestre sono stati rilevati in quasi contemporaneità da altre unità di ricerca in grado di monitorare fenomenologie di area vasta con l’ausilio di tecniche satellitari (Aliano et al., 2009; Tramutoli et al., 2009). Il fenomeno osservato è iniziato alcuni giorni prima dell’evento sismico (Mw=6.3) del 6 aprile 2009 e può essere, in principio, interpretato come esito di processi di deformazione crostale osservati da altre unità di ricerca (e.g. Caporali, 2009). La composizione chimica di gas campionati nell’area epicentrale indica l’esistenza di fenomeni di fratturazione profonda e di liberazione di anidride carbonica di origine non superficiale (Bonfanti et al., 2009 e bibliografia citata, Italiano et al., 2009). La generazione e liberazione di gas di origine profonda è, in principio, in grado di confermare l’esistenza di possibili ulteriori anomalìe osservate nei fluidi della zona (e.g. Plastino et al., 2009). Il fenomeno osservato potrebbe essere interpretato come un fenomeno precursore dell’evento principale registrato e analizzato a posteriori. La possibile applicabilità del fenomeno osservato come strumento utile per migliorare le valutazioni di hazard è discussa e commentata

Insights into mantle-type volatiles contribution from dissolved gases in artesian waters of the Great Artesian Basin, Australia

The geochemical features of the volatiles dissolved in artesian thermal waters discharged over three basins (Millungera, Galilee and Cooper basin) of the Australian Great Artesian Basin (GAB) consistently indicate the presence of fluids from multiple gas sources located in the crust (e.g. sediments, oil reservoirs, granites) as well as minor but detectable contributions of mantle/magma-derived fluids. The gases extracted from 19 water samples and analyzed for their chemical and isotopic composition exhibit amounts of CO up to about 340mlSTP/L marked by a δC (Total Dissolved Carbon) ranging from -16.9 to +0.18‰ vs PDB, while CH concentrations vary from 4.4×10 to 4.9mlSTP/L. Helium contents were between 9 and >2800 times higher than equilibrium with Air Saturated Water (ASW), with a maximum value of 0.12mlSTP/L. Helium isotopic composition was in the 0.02-0.21 Ra range (Ra = air-normalized He/He ratio). The three investigated basins differ from each other in terms of both chemical composition and isotopic signatures of the dissolved gases whose origin is attributed to both mantle and crustal volatiles. Mantle He is present in the west-central and hottest part of the GAB despite no evidence of recent volcanism. We found that the partial pressure of helium, significantly higher in crustal fluids than in mantle-type volatiles, enhances the crustal He signature in the dissolved gases, thus masking the original mantle contribution. Neotectonic activity involving deep lithospheric structures and magma intrusions, highlighted by recent geophysical investigations, is considered to be the drivers of mantle/magmatic volatiles towards the surface. The results, although pertaining to artesian waters from a vast area of >542,000km, provide new constraints on volatile injection, and show that fluids' geochemistry can provide additional and independent information on the geo-tectonic settings of the Great Artesian Basin and its geothermal potential

An overview of the geochemical characteristics of oceanic carbonatites: New insights from Fuerteventura carbonatites (Canary islands)

The occurrence of carbonatites in oceanic settings is very rare if compared with their continental counterpart, having been reported only in Cape Verde and Canary Islands. This paper provides an overview of the main geochemical characteristics of oceanic carbonatites, around which many debates still exist regarding their petrogenesis. We present new data on trace elements in minerals and whole-rock, together with the first noble gases isotopic study (He, Ne, Ar) in apatite, calcite, and clinopyroxene from Fuerteventura carbonatites (Canary Islands). Trace elements show a similar trend as Cape Verde carbonatites, almost tracing the same patterns on multi-element and REE abundance diagrams.3He/4He isotopic ratios of Fuerteventura carbonatites reflect a shallow (sub-continental lithospheric mantle, SCLM) He signature in their petrogenesis, and they clearly differ from Cape Verde carbonatites, i.e., fluids from a deep and low degassed mantle with a primitive plume-derived He signature are involved in their petrogenesis

Dominating sets and connected dominating sets in dynamic graphs

In this paper we study the dynamic versions of two basic graph problems: Minimum Dominating Set and its variant Minimum Connected Dominating Set. For those two problems, we present algorithms that maintain a solution under edge insertions and edge deletions in time O( 06\ub7polylog n) per update, where 06 is the maximum vertex degree in the graph. In both cases, we achieve an approximation ratio of O(log n), which is optimal up to a constant factor (under the assumption that P 6= NP). Although those two problems have been widely studied in the static and in the distributed settings, to the best of our knowledge we are the first to present efficient algorithms in the dynamic setting. As a further application of our approach, we also present an algorithm that maintains a Minimal Dominating Set in O(min( 06, m)) per update

Anomalous fluid emission of a deep borehole in a seismically active area of Northern Apennines (Italy)

The Miano borehole, 1047 m deep, is located close to the river Parma in the Northern Apennines, Italy. A measuring station has been installed to observe the discharge of fluids continuously since November 2004. The upwelling fluid of this artesian well is a mixture of thermal water and CH4 as main components. In non-seismogenic areas, a relatively constant fluid emission would be expected, perhaps overlaid with long term variations from that kind of deep reservoir over time. However, the continuous record of the fluid emission, in particular the water discharge, the gas flow rate and the water temperature, show periods of stable values interrupted by anomalous periods of fluctuations in the recorded parameters. The anomalous variations of these parameters are of low amplitude in comparison to the total values but significant in their long-term trend. Meteorological effects due to rain and barometric pressure were not detected in recorded data probably due to reservoir depth and relatively high reservoir overpressure. Influences due to the ambient temperature after the discharge were evaluated by statistical analysis. Our results suggest that recorded changes in fluid emission parameters can be interpreted as a mixing process of different fluid components at depth by variations in pore pressure as a result of seismogenic stress variation. Local seismicity was analyzed in comparison to the fluid physico-chemical data. The analysis supports the idea that an influence on fluid transport conditions due to geodynamic processes exists. Water temperature data show frequent anomalies probably connected with possible precursory phenomena of local seismic events

Long-term geochemical monitoring and extensive/compressive phenomena: case study of the Umbria Region (Central Apennines, Italy)

Long-term geochemical monitoring performed in the seismic area of the Umbria-Marche region of Italy (i.e. Central Apennines) has allowed us to create a model of the circulation of fluids and interpret the temporal chemical and isotopic variations of both the thermal springs as well as the gas vents. Coincident with the last seismic crisis, which struck the region in 1997-1998, an enhanced CO2 degassing on a regional scale caused a pH-drop in all the thermal waters as a consequence of CO2 dissolution. Furthermore, much higher 3He/4He isotope ratios pointed to a slight mantle-derived contribution. Radon activity increased to well above the ±2 sinterval of the earlier seismic period, after which it abruptly decreased to very low levels a few days before the occurrence of the single deep-located shock (March 26, 1998, 51 km deep). The anomalous CO2 discharge was closely related to the extensional movement of the normal faults responsible for the Mw 5.7, 6.0 and 5.6 main shocks that characterized the earlier seismic phase. In contrast, a clear compressive sign is recognizable in the transient disappearance of the deep-originating components related to the Mw 5.3, 51 km-deep event that occurred on March 26, 1998. Anomalies were detected concomitantly with the seismicity, although they also occurred after the seismic crisis had terminated. We argue that the observed geochemical anomalies were driven by rock permeability changes induced by crustal deformations, and we describe how, in the absence of any release of elastic energy, the detection of anomalies reveals that a seismogenic process is developing. Indeed, comprehensive, long-term geochemical monitoring can provide new tools allowing us to better understand the development of seismogenesis

Mud volcanoes and methane seeps in Romania: main features and gas flux

Romania is one of the European countries with the most vigorous natural seepage of methane, uprising from pressurised natural gas and petroleum reservoirs through deep faults. The largest seepage zone is represented by large mud volcanoes, with CH4 >80% v/v, occurring on the Berca-Arbanasi hydrocarbon-bearing faulted anticline, in the Carpathian Foredeep. Smaller mud volcanoes have been identified in other areas of the Carpathian Foredeep, in the Transylvanian Depression and on the Moldavian Platform. New surveys carried out in Transylvania allowed us to discover the richest N2 mud volcano zone in the world (N2>90% v/v), with a remarkably high He content and a helium isotopic signature which highlights a contribution of mantle-derived source. The large mud volcanoes are generally quiescent, with rare explosive episodes and provide a methane flux in the order of 102-103 t km−2 y−1. Independently from mud volcanism, a remarkable dry macroseepage, however, has been found, with a degassing rate up to three orders of magnitude higher than that of mud volcanoes (i.e. 103-105 t km−2 y−1). The total gas flux from all investigated macroseepage zones in Romania is estimated in the range of 1500-2500 t y−1. The emission from microseepage, pervasively occurring throughout the hydrocarbon-prone basins, has yet to be assessed and added to the total gas output to the atmosphere