Photocatalytic degradation of dyes by using a membrane reactor

Dyes are organic compounds used in textile, food and drug industries, and their abatement represents one of the main problems in the treatment processes because generally they are very stable toxic compounds. In this work, two commercial azo-dyes, i.e. Congo Red (C32H22N6Na2O6S2) and Patent Blue (C27H31N2NaO6S2), in aqueous solution were degraded in a photocatalytic membrane reactor by using TiO2 Degussa P25 as the catalyst. Different system con\ufb01gurations and irradiating sources were studied, and the in\ufb02uence of some operational parameters such as the pressure in the membrane cell and the initial concentration of the substrates was determined. A comparison between suspended and entrapped TiO2 was also done. The experimental results showed a satisfactory degradation ef\ufb01ciency of the photocatalytic membrane process. The in\ufb02uence of various parameters (e.g. feed concentration, recirculation rate) has been discussed to obtain high reaction rates, operating stability and high membrane rejection, both for substrates and by-products. Congo Red was photodegraded with higher rate under the same experimental conditions probably due to its higher adsorption onto the catalyst surface. It was possible to treat successfully highly concentrated solutions (500 mg/L) of both dyes by means of a continuous process obtaining good values of permeate \ufb02uxes (30\u201370 L/m2 h); this could be interesting for industrial applications. The reactor containing the suspended photocatalyst was signi\ufb01cantly more ef\ufb01cient than the reactor containing the catalyst entrapped into the membrane

Is the dependence on the temperature of the friction important in stress triggering phenomena? The case of the 2000 Iceland seismic sequence

We perform numerical experiments by using a mass–spring fault model subject to an external coseismic stress perturbation due to a remote seismic event happening on another fault, the causative fault. In particular, the aim of this study is to investigate the instantaneous fault interaction and possible triggering that happens when a fault perturbed by a stress change fails before the so–called unperturbed instability. As a realistic example we focus our attention on the instantaneous dynamic triggering phenomena occurred during the 17 June 2000 south Iceland seismic sequence in the South Iceland Seismic Zone (SISZ, Reykjanes Peninsula). The main event (Ms 6.6) was followed by three large events within a few tens of seconds (8, 26 and 30 s, respectively) located in a neighborhood of several tens of km. Among them the 26 s event was the best constrained (Bizzarri and Belardinelli, 2008). In the present study, conditions to simulate the instantaneous dynamic triggering connected to the former three events, have been investigated using the simple 1–D spring–slider analogue model representing a fault governed by the rate– and state–dependent friction laws. In previous studies suitable constitutive parameters of the modeled fault which allow the instantaneous triggering of the three events, have been found (Antonioli et al., 2006) and, furthermore, it was also shown how the dynamics of the 26 s event strongly depends on the assumed constitutive law and stress conditions (Bizzarri and Belardinelli, 2008) by considering the Dieterich–Ruina (DR henceforth) and the Ruina–Dieterich (RD henceforth) governing laws. In this context take place the present study original contribution that is to better understand if the conditions of instantaneous dynamic triggering (focusing on the case of the 26 s triggered event) provide any significant differences if modeled with a different rate– and state–dependent governing equation, the Chester and Higgs law (CH henceforth; see Chester and Higgs, 1992; Bizzarri, 2010b; Bizzarri, 2010c) which accounts for the thermal effect for frictional heating which may occur during seismic sliding

Time occurrence of earthquake instabilities in rate– and state–dependent friction models

Since the latter half of last century many studies and laboratory experiments have focused on the understanding of the evolution of frictional strength during sliding events on active faults. Such events may occur through aseismic fault creep, high-velocity slip and, in some cases, as a combination of both. According to the concept that earthquakes are frictional instabilities, their time occurrence may show a periodical pattern (the seismic cycle) whose behavior can be referred to the stick-slip dynamic. The dynamic evolution of a fault is often modeled considering its formal analogy with a physical system known as the spring-slider model (namely, a damped harmonic oscillator). Many experimental studies have been conducted using the spring-slider model, most of them simulating the interaction between slip surfaces with the surrounding elastic medium with a single-degree-of-freedom system. Despite its obvious limitations, such a model has provided important insights on dynamics of stick-slip cycle [Gu et al., 1984; Carlson et al., 1994], nucleation of earthquakes and triggered earthquake phenomena [e.g. Belardinelli et al., 2003]. On the basis of several experimental results on rock friction, Dieterich (1979) and Ruina (1983) formulated rate- and state-dependent friction laws, in which the frictional resistance is expressed through the evolution of the sliding rate and its history. Afterwards, Chester and Higgs (1992) figured out that also the temperature variation, produced by frictional heating, can affect the duration of the seismic cycle and the evolution of the frictional strength as well and consequently they incorporate such a thermal effect, improving the previous Ruina’s constitutive law. The present study is aimed to: 1. investigate the spring-slider physical response depending on the adopted constitutive law; 2. show the influence that the constitutive laws can exert on the time occurrence of a seismic instability and on the seismic cycle duration; 3. compare the constitutive laws in order to show their different features in simulating the evolution of slip velocity, stress drop and seismic cycle

GPS-based monitoring of land subsidence in the Po Plain (Northern Italy)

We use regional and local networks of continuously-operating GPS stations (CGPS) distributed in the northern–central part of the Italian peninsula to investigate the subsidence phenomenon of the Po plain sedimentary basin and vertical movements of the surrounding areas. The observations of 146 scientific and commercial stations are analyzed and compared, adopting analytical techniques widely used to study GPS coordinate time series. The use of simple antenna supports in commercial installations, instead of a more rigorous geodetic monument, does not seem to induce significant differences in the noise characteristics and in the amplitudes of annual and semi-annual periodic signals. The vertical velocity field deduced from 129 sites with observation time spans greater than one year, located in the Central–Northern Italian Peninsula, indicates the presence of two mainly subsidence areas: the Po Plain and the Arno Plain, while the sites located in the Alps and Apennine domains show relatively low uplift. The areas of the Po Plain monitored by GPS seem to indicate that the subsidence rate is constant or, in some cases, decreasing with respect to the values obtained from the last measurements, performed up to 2006 by means of both SAR and levelling techniques. Only the central part of the eastern Po Plain close to the Apennine border (Modena city area) is characterized by a peak in subsidence consisting in a velocity of about 15 mm/yr

Geodetic deformation Across the Central Apennines from GPS Data in the time span 1999-2003

Abstract During the time span 1999-2003 was set up and repeatedly surveyed a not permanent GPS network located across one of the highest seismic areas of the central Apennines (Italy). The Central Apennine Geodetic Network (CA-GeoNet), extends across Umbria, Abruzzo, Marche and Lazio regions, in an area of ∼180x130 km, from Tyrrhenian to the Adriatic sea. It consists in 125 GPS stations distributed at 3-5 km average grid and includes 7 permanent GPS stations operated by the Italian Space Agency (ASI) and the Istituto Nazionale di Geofisica and Vulcanologia (INGV). With the aim to estimate the active strain rate across this part of the chain, the GPS sites have been located on the main geological units of the area and across the typical basin and range structures, related with the main seismogenic faults. In this paper we show the network and the first results obtained for a subset of 23 stations that have been occupied at least during three repeated campaigns, in the time span 1999-2003. Data analysis, performed by Bernese 4.2 software, shows an extensional rate normal to the chain, in agreement with geological and seismic data. The strain rates in the inner chain are ranging from 12x10-9±11yr-1 to 16x10-9±11yr-1 and from -14x10-9±11yr-1 to -3x10-9±11yr-1. This result provides an improved estimation of the ongoing deformation of this area with respect to previous studies and is in agreement with the style of deformation inferred from seismicity and with the features of the main seismogenic sources from recent geological and seismological investigations

LA SUBSIDENZA NELL’ITALIA CENTRO-SETTENTRIONALE DA MISURE GPS

La grande diffusione negli ultimi anni di reti di stazioni GPS permanenti istituite per scopi commerciali come il posizionamento in tempo reale, può rappresentare un’importante integrazione alla già esistente rete scientifica di monitoraggio della deformazione crostale. Le stazioni commerciali sono solitamente equipaggiate con ricevitori a doppia frequenza e antenne tipo choke ring. Una possibile differenza fra queste e le stazioni scientifiche consiste nell’approccio utilizzato per la scelta del sito e per la monumentazione. Per questo motivo prima di utilizzare le osservazioni acquisite dalle stazioni commerciali per analisi di tipo scientifico bisogna verificare se i protocolli di installazione e gestione di questi non introducano nuove sorgenti di rumore nei dati o aumentino quelle già esistenti. In questo studio, abbiamo confrontato le caratteristiche principali delle serie temporali di 112 stazioni commerciali situate nell’Italia Centro–Settentrionale con quelle di 81 stazioni scientifiche presenti nella medesima zona (Fig. 1). Le osservazioni delle 112 stazioni commerciali prese in esame sono fornite dalle seguenti agenzie pubbliche e private: ASSOGEO, LABTOPO, Rete Regione Veneto, SOGER, IREALP, Rete Arpa Piemonte e Regione Abruzzo; e i dati delle 81 stazioni scientifiche sono stati invece acquisiti dagli archivi informatici di 5 diverse istituzioni pubbliche: ASI, INGV – RING, EUREF, FREDNET e Rete Toscana. Le osservazioni di tutte le stazioni considerate in questo lavoro sono state analizzate mediante il software GAMIT/GLOBK versione 10.34 e successive utilizzando la procedura denominata distributed processing (Dong et alii, 1998), che consente di analizzare reti con un alto numero di stazioni suddividendole in diverse sottoreti distinte, compensando successivamente i risultati ottenuti in un’unica soluz

CMS endcap RPC gas gap production for upgrade

The CMS experiment will install a RE4 layer of 144 new Resistive Plate Chambers (RPCs) on the existing york YE3 at both endcap regions to trigger high momentum muons from the proton-proton interaction. In this paper, we present the detailed procedures used in the production of new RPC gas gaps adopted in the CMS upgrade. Quality assurance is enforced as ways to maintain the same quality of RPC gas gaps as the existing 432 endcap RPC chambers that have been operational since the beginning of the LHC operation

ESA SENTINEL 2 IMAGERY AND GBGEOAPP: INTEGRATED TOOLS FOR THE DEOSAI NATIONAL PARK MANAGEMENT PLAN

Deosai plateau, in the Gilgit-Baltistan Province of Pakistan, for its average elevation of 4,114 meters, is the second highest plateau in the world after Changtang Tibetan Plateau. Two biogeographically important mountain ranges merge in Deosai: the Himalayan and Karakorum–Pamir highlands. The Deosai National Park, with its first recognition in 1993, encompasses an area of about 1620 km2, with the altitude ranging from 3500 to 5200 meters a.s.l. It is known and visited by tourists for the presence of brown bear, but a large number of species of fauna and flora leave, and can be seen during the summer season. This high-altitude ecosystem is particularly fragile and can be considered a sentinel for the effects of climate changes. Due to its geographic position and high altitude, the area of Deosai has never been studied in all its ecosystem components, producing high resolution maps. The first land cover map of Deosai with 10 meters of resolution is discussed in this study. This map has been obtained from Sentinel-2 imagery and improved through the new tool developed in this study: the GBGEOApp. This application for mobile has been done with three main ambitions: the validation of the new land cover map, its improvement with land use information, and the collection of new data in the field. On the basis of the results, the use of the GBGEOApp, as a tool for validation and increasing of environmental data collection, seems to be completely applicable involving the local technicians in a process of data sharing