Intercontinental fligths from European Airports: Towards hub concentration or not?

This paper empirically analyzes changes in the supply of non-stop intercontinental flights from European airports. We take advantage of OAG data for air services from a rich sample of European airports to intercontinental destinations in the period 2004-2008. Results of the empirical analysis indicate a tendency towards a more balanced distribution of intercontinental flights across European airports. We also find that the demographic size of a region, its sector specialization, the political role of its central city and the proportion of connecting traffic explain the amount of and changes in long-haul air services supplied from European airports.

Sensibility and taste alterations after impacted lower third molar extractions. A prospective cohort study

Objectives: To determine the incidence, severity and duration of lingual tactile and gustatory function impairments after lower third molar removal. Study Design: Prospective cohort study with intra-subject measures of 16 patients undergoing lower third molar extractions. Sensibility and gustatory functions were evaluated in each subject preoperatively, one week and one month after the extraction, using Semmes-Weinstein monofilaments and 5 different concentrations of NaCl, respectively. Additionally, all patients filled a questionnaire to assess subjective perceptions. Results: Although patients did not perceive any sensibility impairments, a statistically significant decrease was detected when Semmes-Weinstein monofilaments. This alteration was present at one week after the surgical procedure and fully recovered one month after the extraction. There were no variations regarding the gustatory function. Conclusions: Lower third molar removal under local anesthesia may cause light lingual sensibility impairment. Most of these alterations remain undetected to patients. These lingual nerve injuries are present one week after the extraction and recover one month after surgery. The taste seems to remain unaffected after these procedures.

Sharp mandibular bone irregularities after lower third molar extraction: Incidence, clinical features and risk factors

Objectives: The purpose of this study was to determine the incidence and clinical symptoms associated with sharp mandibular bone irregularities (SMBI) after lower third molar extraction and to identify possible risk factors for this complication. Study Design: A mixed study design was used. A retrospective cohort study of 1432 lower third molar extractions was done to determine the incidence of SMBI and a retrospective case-control study was done to determine potential demographic and etiologic factors by comparing those patients with postoperative SMBI with controls. Results: Twelve SMBI were found (0.84%). Age was the most important risk factor for this complication. The operated side and the presence of an associated radiolucent image were also significantly related to the development of mandibular bone irregularities. The depth of impaction of the tooth might also be an important factor since erupted or nearly erupted third molars were more frequent in the SMBI group. Conclusions: SMBI are a rare postoperative complication after lower third molar removal. Older patients having left side lower third molars removed are more likely to develop this problem. The treatment should be the removal of the irregularity when the patient is symptomatic

New methods for the concentration of viruses from urban sewage using quantitative PCR.

Viruses are among the most important pathogens present in water contaminated with feces or urine and represent a serious risk to human health. Four procedures for concentrating viruses from sewage have been compared in this work, three of which were developed in the present study. Viruses were quantified using PCR techniques. According to statistical analysis and the sensitivity to detect human adenoviruses (HAdV), JC polyomaviruses (JCPyV) and noroviruses genogroup II (NoV GGII): (i) a new procedure (elution and skimmed-milk flocculation procedure (ESMP)) based on the elution of the viruses with glycine-alkaline buffer followed by organic flocculation with skimmed-milk was found to be the most efficient method when compared to (ii) ultrafiltration and glycine-alkaline elution, (iii) a lyophilization-based method and (iv) ultracentrifugation and glycine-alkaline elution. Through the analysis of replicate sewage samples, ESMP showed reproducible results with a coefficient of variation (CV) of 16% for HAdV, 12% for JCPyV and 17% for NoV GGII. Using spiked samples, the viral recoveries were estimated at 30-95% for HAdV, 55-90% for JCPyV and 45-50% for NoV GGII. ESMP was validated in a field study using twelve 24-h composite sewage samples collected in an urban sewage treatment plant in the North of Spain that reported 100% positive samples with mean values of HAdV, JCPyV and NoV GGII similar to those observed in other studies. Although all of the methods compared in this work yield consistently high values of virus detection and recovery in urban sewage, some require expensive laboratory equipment. ESMP is an effective low-cost procedure which allows a large number of samples to be processed simultaneously and is easily standardizable for its performance in a routine laboratory working in water monitoring. Moreover, in the present study, a CV was applied and proposed as a parameter to evaluate and compare the methods for detecting viruses in sewage samples.

New methods for the concentration of viruses from urban sewage using quantitative PCR.

Viruses are among the most important pathogens present in water contaminated with feces or urine and represent a serious risk to human health. Four procedures for concentrating viruses from sewage have been compared in this work, three of which were developed in the present study. Viruses were quantified using PCR techniques. According to statistical analysis and the sensitivity to detect human adenoviruses (HAdV), JC polyomaviruses (JCPyV) and noroviruses genogroup II (NoV GGII): (i) a new procedure (elution and skimmed-milk flocculation procedure (ESMP)) based on the elution of the viruses with glycine-alkaline buffer followed by organic flocculation with skimmed-milk was found to be the most efficient method when compared to (ii) ultrafiltration and glycine-alkaline elution, (iii) a lyophilization-based method and (iv) ultracentrifugation and glycine-alkaline elution. Through the analysis of replicate sewage samples, ESMP showed reproducible results with a coefficient of variation (CV) of 16% for HAdV, 12% for JCPyV and 17% for NoV GGII. Using spiked samples, the viral recoveries were estimated at 30-95% for HAdV, 55-90% for JCPyV and 45-50% for NoV GGII. ESMP was validated in a field study using twelve 24-h composite sewage samples collected in an urban sewage treatment plant in the North of Spain that reported 100% positive samples with mean values of HAdV, JCPyV and NoV GGII similar to those observed in other studies. Although all of the methods compared in this work yield consistently high values of virus detection and recovery in urban sewage, some require expensive laboratory equipment. ESMP is an effective low-cost procedure which allows a large number of samples to be processed simultaneously and is easily standardizable for its performance in a routine laboratory working in water monitoring. Moreover, in the present study, a CV was applied and proposed as a parameter to evaluate and compare the methods for detecting viruses in sewage samples.

Recovery of Hemicelluloses from Wood Hydrolysates by Membrane Filtration

Hemicelluloses are among the most important natural resources that contain polysaccharides. In this study the separation and purification of hemicelluloses from water extraction liquors containing wood hemicelluloses, lignin compounds and monosaccharide by using membrane filtration was investigated. The isolation of the hemicelluloses from the wood hydrolysates was performed in two steps: concentration of high molar mass hemicelluloses by ultrafiltration and separation of low molar mass hemicelluloses from monomeric sugars using tight ultrafiltration membranes. The purification of the retained hemicelluloses was performed by diafiltration. During the filtration experiments, the permeate flux through ultrafiltration and tight ultrafiltration membranes was relatively high. The fouling ability of the used membranes was relatively low. In our experiments, the retention of hemicelluloses using two filtration steps was almost complete. The separation of monosaccharides from hemicelluloses was relatively high and the purification of hemicelluloses by diafiltration was highly efficient. The separation of lignin from hemicelluloses was partially achieved. Diafiltration showed potential to purify retained hemicelluloses from lignin and other organics. The best separation of lignin from hemicelluloses in the first filtration step was obtained using the UC005 membrane. The GE-5 and ETNA01PP membranes showed potential to purify and separate lignin from hemicelluloses. However, the feed solution of the second filtration stages (from different ultrafiltration membranes) affected the permeate flux and the separation of various extracted compounds from hemicelluloses. The GE-5 and ETNA01PP membranes gave the efficient purification of the hemicelluloses when using diafiltration. Separation of degraded xylan from glucomannan (primary spruce hemicelluloses) was also possible using membrane filtration. The best separation was achieved using the GE-5 membrane. The retention of glucomannan was three times higher than xylan retention.

Determinação da massa molar por crioscopia: terc-butanol, um solvente extremamente adequado

We intend to divulge an easy experiment that permits the determination of molar masses of various compounds by cryoscopy. The major advantage of this is the use of the tert-butyl alcohol as a solvent, which requires simple apparatus and easy procedures. The melting point of this alcohol is around 25 ºC, which makes it easy to freeze and then melt the solutions. This solvent has a high cryoscopic constant and is miscible with both polar and non-polar compounds. The molar masses of acetone, water, chloroform, dichloro-methane, ethanol, hexane, carbon tetrachloride and toluene were determined. The results were good except for water. Even though there are reliable techniques of molar mass determination nowadays, this method is still frequently taught in undergraduate courses.

Reagenssin pinta-aktiivisuuden hyödyntäminen sinkin uutossa

Työssä tutkittiin sinkin uutossa käytettävän di(2-etyyliheksyyli)fosforihappo (D2EHPA) -uuttoreagenssin faasikäyttäytymistä ja miten laimentimen koostumus, lämpötila ja orgaanisen faasin sinkkipitoisuus vaikuttavat faasitasapainoon. Laimentimen vaikutuksen havaittiin olevan pientä, kun taas lämpötilan nostaminen yli huoneenlämpötilan leventää faasidiagrammin yksifaasialuetta. Pienet orgaanisen faasin sinkkipitoisuudet eivät juuri vaikuta faasitasapainoon. Sinkin ja D2EHPA:n moolisuhteen ollessa välillä 0,1–0,2 kompleksin rakenne ilmeisesti muuttuu. Sinkkipitoisuuden kasvaessa yksifaasialue muodostuu pienemmillä ammoniakkimäärillä. Suurilla orgaanisen faasin sinkkipitoisuuksilla ja ammoniakkimäärillä muodostuu orgaanisen faasin ja vesifaasin välille kolmas nestefaasi. D2EHPA:n (40 p %) vesipitoisuuden ja viskositeetin pH riippuvuutta tutkittiin, kun laimentimena oli alifaattinen hiilivetyliuotin. Nostettaessa pH yli 3,5:n uuttoreagenssi alkoi muodostaa käänteismisellejä, jolloin orgaanisen faasin vesipitoisuus ja viskositeetti kasvoivat eksponentiaalisesti. Sinkin mukana uuttautuu epäpuhtauksia kuten Al3+, Co2+, Cu2+, Na+, Ni2+, Cl- ja F-. Takaisinuuton kautta epäpuhtaudet joutuvat talteenottoelektrolyysiin, jossa ne voivat vaikuttaa tuotteen laatuun ja laskea virtahyötysuhdetta. Tarkoituksena oli tutkia väheneekö epäpuhtauksien myötäuuttautuminen jollakin tietyllä sinkin latausasteella. Fluoridin ja kuparin uuttautumisen havaittiin vähenevän vasta, kun sinkin pitoisuus orgaanisessa faasissa oli yli 20 g/L lämpötilasta riippumatta. Fluoridi uuttautuu mahdollisesti alumiinikompleksina ja/tai fluorihappona. Koboltin ja nikkelin myötäuuttautumisen havaittiin vähenevän, kun sinkin latausaste oli yli 10 g/L. Natrium ja kloridi eivät myötäuuttautuneet.

Has concentration evolved similarly in manufacturing and services? A sensitivity analysis

Our first objective is to compare the degree of concentration in manufacturing and services, with special emphasis on its evolution in these two sectors, using a sensitivity analysis for different concentration indices and different geographic units of analysis: municipalities and local labour systems of Catalonia in 1991 and 2001. Most concentration measures fail to consider the space in which a particular municipality is located. Our second objective is to overcome this problem by applying two different techniques: by using a clustering measure, and by analysing whether the location quotients computed for each municipality and sector present some kind of spatial autocorrelation process. We take special account of the differences in patterns of concentration according to the technological level of the sectors.

Automated flow-injection method for cadmium determination with pre-concentration and reagent preparation on-line

The spectrophotometric determination of Cd(II) using a flow injection system provided with a solid-phase reactor for cadmium preconcentration and on-line reagent preparation, is described. It is based on the formation of a dithizone-Cd complex in basic medium. The calibration curve is linear between 6 and 300 µg L-1 Cd(II), with a detection limit of 5.4 µg L-1, an RSD of 3.7% (10 replicates in duplicate) and a sample frequency of 11.4 h-1. The proposed method was satisfactorily applied to the determination of Cd(II) in surface, well and drinking waters.

Flow analysis by using solenoid valves for As(III) determination in natural waters by an on-line separation and pre-concentration system coupled to a tungsten coil atomizer

A flow system coupled to a tungsten coil atomizer in an atomic absorption spectrometer (TCA-AAS) was developed for As(III) determination in waters, by extraction with sodium diethyldithiocarbamate (NaDDTC) as complexing agent, and by sorption of the As(III)-DDTC complex in a micro-column filled with 5 mg C18 reversed phase (10 µL dry sorbent), followed by elution with ethanol. A complete pre-concentration/elution cycle took 208 s, with 30 s sample load time (1.7 mL) and 4 s elution time (71 µL). The interface and software for the synchronous control of two peristaltic pumps (RUN/ STOP), an autosampler arm, seven solenoid valves, one injection valve, the electrothermal atomizer and the spectrometer Read function were constructed. The system was characterized and validated by analytical recovery studies performed both in synthetic solutions and in natural waters. Using a 30 s pre-concentration period, the working curve was linear between 0.25 and 6.0 µg L-1 (r = 0.9976), the retention efficiency was 94±1% (6.0 µg L-1), and the pre-concentration coefficient was 28.9. The characteristic mass was 58 pg, the mean repeatability (expressed as the variation coefficient) was 3.4% (n=5), the detection limit was 0.058 µg L-1 (4.1 pg in 71 µL of eluate injected into the coil), and the mean analytical recovery in natural waters was 92.6 ± 9.5 % (n=15). The procedure is simple, economic, less prone to sample loss and contamination and the useful lifetime of the micro-column was between 200-300 pre-concentration cycles.

Size distribution of atmospheric particulate ionic species at a coastal site in Portugal

A Berner impactor was used to collect size-differentiated aerosol samples from March to August 2003 in the city of Aveiro, on the Portuguese west coast. The samples were analysed for the main water-soluble ion species. The average concentration of sulphate, nitrate, chloride and ammonium was 6.38, 3.09, 1.67 and 1.27 µg m-3, respectively. The results show that SO4(2-) and NH4+ were consistently present in the fine fraction < 1 µm, which represents, on average, 72 and 89% of their total atmospheric concentrations, respectively. The NO3-particles were concentrated in the coarse size. Chloride presented the characteristic coarse mode for marine aerosols. During some spring/summer events, an ammonium surplus was observed (NH4+/SO4(2-) molar ratios > 2), possibly due to greater availability of ammonia coming from agricultural activities or from the neighbouring chemical industrial complex. During the remaining periods, the aerosol was found to be somewhat acidic and predominantly in the form of ammonium bisulphate (NH4+/SO4(2-) molar ratios = 0.5-1.25). Samples collected under a major or exclusive influence of maritime air masses were essentially constituted by coarse particles with enrichment in sea salt, while for air masses of continental origin the contribution of water-soluble ionic species in the fine mode was more pronounced.

Alargamento da distribuição de massa molar de polímeros sintetizados com catalisadores metalocênicos dual-site

The main topics related to the use of dual-site catalysts in the production of polymers with broad molecular weight distribution are reviewed. The polymerization using dual-site catalysts is more economical and allows to produce a higher quality product than other processes, such as polymer blend and multistage reactors. However, the formulation of these catalysts is quite complicated since the same catalyst must produce distinct polymer grades. In addition, the release of patents concerning the combination of metallocenes and new technologies for polymerization shows that polymerization processes using dual-site catalysts are of current industrial interest.

Combined dielectrophoretic and impedance system for on-chip controlled bacteria concentration: Application to Escherichia coli

The present paper reports a bacteria autonomous controlled concentrator prototype with a user-friendly interface for bench-top applications. It is based on a micro-fluidic lab-on-a-chip and its associated custom instrumentation, which consists in a dielectrophoretic actuator, to pre-concentrate the sample, and an impedance analyser, to measure concentrated bacteria levels. The system is composed by a single micro-fluidic chamber with interdigitated electrodes and a instrumentation with custom electronics. The prototype is supported by a real-time platform connected to a remote computer, which automatically controls the system and displays impedance data used to monitor the status of bacteria accumulation on-chip. The system automates the whole concentrating operation. Performance has been studied for controlled volumes of Escherichia coli (E. coli) samples injected into the micro-fluidic chip at constant flow rate of 10 μL/min. A media conductivity correcting protocol has been developed, as the preliminary results showed distortion of the impedance analyser measurement produced by bacterial media conductivity variations through time. With the correcting protocol, the measured impedance values were related to the quantity of bacteria concentrated with a correlation of 0.988 and a coefficient of variation of 3.1%. Feasibility of E. coli on-chip automated concentration, using the miniaturized system, has been demonstrated. Furthermore, the impedance monitoring protocol had been adjusted and optimized, to handle changes in the electrical properties of the bacteria media over time.

Formação de micelas mistas entre o sal biliar colato de sódio e o surfactante aniônico dodecanoato de sódio

Mixed-micelle formation between sodium chlolate (NaC) and the anionic surfactant sodium dodecanoate (SDoD) in Tris-HCl buffer solutions, pH 9.00, varying the molar fraction of the surfactants, was investigated by means of electrical conductivity and steady-state fluorescence of pyrene. The critical micelar concentration (cmc) was measured from the equivalent conductance versus the square root of the molar surfactant concentration plots and the regular solution theory (RST) was used to predict the mixing behavior. The I1/I3 pyrene ratio-surfactant concentration plots were used as an additional technique to follow the behavior and the changes in the micropolarity of the mixed micelles.