Catalyzed Gasoline Particulate Filters Reduce Secondary Organic Aerosol Production from Gasoline Direct Injection Vehicles

The effects of photochemical aging on exhaust emissions from two light-duty vehicles with gasoline direct injection (GDI) engines equipped with and without catalyzed gasoline particle filters (GPFs) were investigated using a mobile environmental chamber. Both vehicles with and without the GPFs were exercised over the LA92 drive cycle using a chassis dynamometer. Diluted exhaust emissions from the entire LA92 cycle were introduced to the mobile chamber and subsequently photochemically reacted. It was found that the addition of catalyzed GPFs will significantly reduce tailpipe particulate emissions and also provide benefits in gaseous emissions, including nonmethane hydrocarbons (NMHC). Tailpipe emissions composition showed important changes with the use of GPFs by practically eliminating black carbon and increasing the fractional contribution of organic mass. Production of secondary organic aerosol (SOA) was reduced with GPF addition, but was also dependent on engine design which determined the amount of SOA precursors at the tailpipe. Our findings indicate that SOA production from GDI vehicles will be reduced with the application of catalyzed GPFs through the mitigation of reactive hydrocarbon precursors

Effects of driving conditions on secondary aerosol formation from a GDI vehicle using an oxidation flow reactor

A comprehensive study on the effects of photochemical aging on exhaust emissions from a vehicle equipped with a gasoline direct injection engine when operated over seven different driving cycles was assessed using an oxidation flow reactor. Both primary emissions and secondary aerosol production were measured over the Federal Test Procedure (FTP), LA92, New European Driving Cycle (NEDC), US06, and the Highway Fuel Economy Test (HWFET), as well as over two real-world cycles developed by the California Department of Transportation (Caltrans) mimicking typical highway driving conditions. We showed that the emissions of primary particles were largely depended on cold-start conditions and acceleration events. Secondary organic aerosol (SOA) formation also exhibited strong dependence on the cold-start cycles and correlated well with SOA precursor emissions (i.e., non-methane hydrocarbons, NMHC) during both cold-start and hot-start cycles (correlation coefficients 0.95–0.99), with overall emissions of ∼68–94 mg SOA per g NMHC. SOA formation significantly dropped during the hot-running phases of the cycles, with simultaneous increases in nitrate and ammonium formation as a result of the higher nitrogen oxide (NOx) and ammonia emissions. Our findings suggest that more SOA will be produced during congested, slow speed, and braking events in highways.acceptedVersionPeer reviewe

Analysis of complications after nailing of tibial shaft fractures

Fragestellung: Die aufgetretenen Komplikationen nach gebohrter und unaufgebohrter Marknagelung am Unterschenkelschaft sollten in Abhängigkeit von der Marknagelungstechnik untersucht werden, um ein verbessertes Qualitäts- und Komplikationsbewusstsein zu entwickeln. Zudem sollten die eigenen Ergebnisse mit internationalen Studien verglichen werden um eine bessere Therapieempfehlung aussprechen zu können. Material und Methoden: Von Januar 1995 bis Dezember 2001 wurde bei 110 Patienten (67 Männer, 43 Frauen, Durchschnittsalter: 40,7 Jahre) mit Unterschenkelschaftfrakturen eine Marknagelung durchgeführt. In 94 Fällen (85,5%) wurde primär ein unaufgebohrter und in 16 Fällen (14,5%) ein aufgebohrter Marknagel verwendet. In 55 Fällen (50,0%) erfolgte, vor allem bei schwerem Weichteilschaden, die primäre Versorgung mittels Fixateur externe. Nach durchschnittlich 10,9 Tagen erfolgte im weiteren Verlauf der Wechsel auf eine interne Osteosynthese. Primär additive Maßnahmen wurden in 46 Fällen (41,8%) durchgeführt. Bei radiologisch gesicherter knöcherner Konsolidierung erfolgte eine Nachuntersuchung bei 88 Patienten (80,0%) im Jahre 2004. Als Grundlage dienten die Kriterien von Merchant und Dietz (1989). Um statistisch zu beweisen ob ein signifikanter Zusammenhang besteht zwischen einem angewendeten Verfahren und einer aufgetretenen Komplikation wurde der x²-Test nach Pearson eingesetzt. Ergebnisse: In 21 Fällen kam es zur Ausbildung einer Komplikation Komplikationsrate (19,1%). Die Komplikationsrate in der unaufgebohrten Gruppe betrug 20,2% (19 Fälle) und in der aufgebohrten Gruppe 12,5% (2 Fälle). Als Komplikationen kam die Pseudarthrose (9,1%) am häufigsten vor, gefolgt von der Fehlstellung (8,2%) und der Infektion (1,8%). In allen 21 Fällen (19,1%) einer aufgetretenen Komplikation wurden sekundäre Interventionen erforderlich (1 alternative Plattenosteosynthese, 6 additive Plattenosteosynthesen, 12 aufgebohrte Umnagelungen, 2 temporäre Fixateur externe-Reosteosynthesen). Bei der primär aufgebohrten Marknagelung konnten lediglich 2 Außenrotationsfehlstellungen (12,5%) objektiviert und im weiteren Verlauf operativ korrigiert werden. Bei den Reosteosynthesen mittels aufgebohrter Umnagelung kam es in allen Fällen zur knöchernen Ausheilung der Frakturen. Der durchschnittliche Behandlungszeitraum in der Patientengruppe ohne Komplikationen (89 Fälle) vom Zeitpunkt der primären Versorgung bis zum Zeitpunkt der vollständigen Metallentfernung betrug 505,1 Tage. In der Gruppe der Komplikationen (21 Fälle) kam es durchschnittlich zu einem deutlich längeren Behandlungszeitraum von 847,5 Tagen. Vom Tage der primären Versorgung bis zum Zeitpunkt des Sekundärverfahrens vergingen in der Komplikationsgruppe durchschnittlich 137,1 Tage. Der überwiegende Teil der 88 nachuntersuchten Patienten (80,0%) war zum Zeitpunkt der Nachuntersuchung mit dem erreichten Behandlungsergebnis sehr zufrieden. In 75 Fällen (85,2%) schnitten die Patienten sehr gut bis gut, in 8 Fällen (9,1%) befriedigend und in 5 Fällen (5,7%) schlecht ab. Durch den x²-Test konnte kein signifikanter Einfluss der angewendeten Marknagelungstechnik für das Auftreten einer Komplikation nachgewiesen werden (p = 0,229). Zu berücksichtigen jedoch waren die geringen Fallzahlen in unserer Stichprobe. Generell und in Anbetracht der erzielten Quoten innerhalb unserer Studie, zeigte sich jedoch die Tendenz einer höheren Pseudarthrosenrate bei der unaufgebohrten Marknagelung. Schlussfolgerung: Die Therapie von Unterschenkelschaftfrakturen verlangt ein differenziertes Vorgehen. Durch eine primär aufgebohrte Marknagelung kann die Komplikationsrate hinsichtlich von Frakturheilungsstörungen bei korrekter Indikationsstellung wesentlich minimiert werden. Bei der operativen Versorgung einer Unterschenkelschaftfraktur sollte primär jedoch nicht immer aufgebohrt werden. Bei der Wahl zwischen aufgebohrtem und unaufgebohrtem Marknagel muss der behandelnde Chirurg vor jedem Eingriff individuell die Vor- und Nachteile des jeweiligen Systems jedes Mal neu in Einklang bringen um somit einen Weg zu finden Komplikationsraten zu verringern.Purpose: The occurence of complications after reamed and unreamed nailing of the tibial shaft should be analyzed to raise the awareness of quality and of occuring complications. In addition our own results should be compared to international studies in order to be able to pronounce a better recommendation of treatment. Material and methods: In between january 1995 and december 2001 110 patients suffering of tibial shaft fractures (67 male, 43 female, average age 40,7 years) were treated with tibial nailing. In 94 cases (85,5%) initially an unreamed nail, in 16 cases (14,5%) a reamed nail was used. 55 cases (50,0%) primarily with severe soft tissue damage were initially treated with external fixation. In these cases after an average of 10,9 days an intramedullary nailing followed. Primary additional procedures occured in 46 cases (41,8%). In 2004 a follow-up examination based on the criteria of Merchant and Dietz (1989) was performed on 88 patients (80,0%) with radiologically proved bony fracture consolidation. In order to prove if there is a statistically significant correlation between the applied nailing procedure and an occured complication a Pearson chi-square test was used. Results: A complication occured in 21 cases (complication rate 19,1%). The complication rate in the unreamed group was 20,2% (19 cases), in the reamed group 12,5% (2 cases). The complication occuring most freuquently was the pseudarthrosis (9,1%), followed by the malrotation (8,2%) and the infection (1,8%). In all 21 cases where a complication occured (19,1%) secondary interventions were necessary (1 case of alternative plate osteosynthesis, 6 cases of additive plate osteosynthesis, 12 cases of re-nailing with reamed nail, 2 cases of temporary osteosynthesis by external fixateur). In all 16 cases (14,5%) of reamed nailing 2 cases (12,5%) of lateral rotation occured which could be operatively corrected in the further course. In all cases of reamed re-nailing, healing was achieved by bony consolidation. The average time of treatment in the group without complications (89 cases) was 505,1 days, lasting from the day of initial treatment until the day of complete material extraction. In the group with complications (21 cases) the average time of treatment was 847,5 days. The average time between the day of initial treatment and the day of secondary procedure in the complication group was 137,1 days. At the time of follow-up examination most of the 88 patients (80,0%) were satisfied with the treatment results. The results after the criteria of Merchant and Dietz (1989) were excellent or good in 75 cases (85,2%), fair in 8 cases (9,1%) and poor in 5 cases (5,7%). In our study the Pearson chi-square test showed no significant correlation between the used nailing procedure and the occurence of a certain complication (p = 0,229). However, the low number of cases in our study should be considered. Generally and concerning the acquired rates inside of our study there is a tendency of higher pseudarthrosis rates after unreamed nailing. Conclusion: The treatment of tibial shaft fractures requires a differentiated approach. At primarily reamed nailing the complication rate concerning fracture healing disturbances can be essentially reduced by correct setting of indication. In our study there is a tendency of higher pseudarthrosis rates after unreamed nailing. Reamed nailing should not be used in every case of tibial shaft fractures. Deciding between unreamed and reamed nailing requires constant consideration of advantages and disadvantages of each procedure and reconciliation with the individual character of each case. Thereby complication rates can be decreased

Optimization of biodiesel production and its impact on exhaust emissions from diesel vehicles

The aim of this thesis is to offer an as complete and quantified as possible analysis regarding the investigation of various catalytic systems for biodiesel production, the effect of neat and blended biodiesel on the oxidation stability and the impact of biodiesel on the regulated and unregulated exhaust emissions from various passenger vehicles. During the first course of this study, several alkaline and acidic homogeneous catalysts were employed in order to identify the appropriate catalytic system for biodiesel production. Special consideration was placed on the use of amine-based catalysts for biodiesel production due to the fact that they present high catalytic activity. The experimental results, led to the conclusion that this technology reduces the separation and purifications steps downstream when compared to the conventional technology. This alternative way to process vegetable oils under mild reaction conditions can produce alkaline metals free methyl esters and glycerol. The second part of this study included the investigation of various heterogeneous catalysts loaded with different compounds for the transesterification of vegetable oils. It was found that these catalysts were easily recovered from the products at the end of the reaction and produce no soaps. It was determined that with the reusability of some of these catalysts, achieved high conversion rates. Finally, it was found a strong relationship between the concentration of the supported and the calcination temperature with methyl ester conversion. The third objective of this study emphasized on the oxidation stability of biodiesel and its blends with conventional diesel fuel. It was found that the stability of the biodiesel blends is a very complex process that is affected by a variety of factors, including the composition of biodiesel, the presence of antioxidant additives, and its stage of oxidation. In general, the stability of the biodiesel component is reflected on the stability of its blends with diesel fuel. Moreover, a strong correlation between biodiesel concentration and blend stability was observed. Increasing biodiesel concentration results in lower stability. Additionally, the stability of the blends may also be affected by certain characteristics of the diesel fuel. Higher refining to lower sulphur in the base diesel decreases oxidation stability of the final blend. The final objective of this research was to determine the effects of biodiesel on the exhaust emissions from different vehicles. It was determined that most of the regulated and unregulated emissions were dependent on the driving conditions and the biodiesel source material and quality. It was found that NOx emissions seemed to be influenced by the degree of unsaturation of biodiesel. The cold-start effect was found to be strong enough in order to significantly increase most of the emissions studied. Polycyclic aromatic hydrocarbon (PAHs) and carbonyl emissions negatively impacted by the presence of the oxidized biodiesel blends. It was also observed that the unregulated pollutants were impacted by the chemical composition of the biodiesel used.Η παρούσα διατριβή παρουσιάζει μια όσο το δυνατό ολοκληρωμένη μελέτη αναφορικά με την παραγωγή βιοντήζελ, την εξέταση και βελτιστοποίηση της κρίσιμης παραμέτρου της οξειδωτικής σταθερότητας και την αποτίμηση των περιβαλλοντικών του επιπτώσεων σε πετρελαιοκίνητα οχήματα νέας τεχνολογίας. Κατά τον πρώτο κλάδο μελέτης της διατριβής, επιλέχθηκε ένα πλήθος αλκαλικών και όξινων ομογενών καταλυτών με σκοπό την διερεύνηση του βέλτιστου καταλυτικού συστήματος για την παραγωγή βιοντήζελ. Ιδιαίτερη έμφαση δόθηκε στις αζωτούχες ενώσεις, καθώς διαπιστώθηκε ότι παρουσιάζουν εξαιρετική καταλυτική δράση ακόμα και σε προβληματικής ποιότητας πρώτες ύλες, όπως αυτές των χρησιμοποιημένων μαγειρικών ελαίων. Η πρόταση του συγκεκριμένου καταλυτικού συστήματος, οδηγεί στη διαπίστωση ότι η παραγωγή βιοντήζελ είναι εφικτό να πραγματοποιηθεί σε λιγότερα στάδια από όσα περιλαμβάνονται στις παραδοσιακές τεχνολογίες και κατ επέκταση σε χαμηλότερο κόστος. Η δεύτερη σειρά πειραματικών δοκιμών σχεδιάστηκε να συμπεριλάβει την μελέτη της καταλυτικής συμπεριφοράς στερεών ετερογενών καταλυτών και εμποτισμένων στερεών καταλυτών με διάφορους ενισχυτές. Η χρήση στερεών καταλυτών απλοποιεί την διαδικασία της μετεστεροποίησης, με την εξάλειψη των σταδίων πλύσης και ξήρανσης των μεθυλεστέρων. Με την εξέταση των εμποτισμένων καταλυτών διαπιστώθηκε ισχυρή συσχέτιση μεταξύ της συγκέντρωσης του ενισχυτή και της θερμοκρασία πύρωσης με την μετατροπή των τριγλυκεριδίων σε μεθυλεστέρες. Η τρίτη σειρά πειραμάτων επικεντρώθηκε στην μελέτη της οξειδωτικής σταθερότητας του βιοντήζελ και των μιγμάτων του με πετρελαϊκό ντήζελ. Οι μετρήσεις που πραγματοποιήθηκαν σε μίγματα πετρελαίου με διαφορετικές συγκεντρώσεις σε βιοντήζελ έδειξαν ότι η οξειδωτική σταθερότητα του τελικού μίγματος εξαρτάται από το ποσοστό του βιοντήζελ, από την ύπαρξη αντιοξειδωτικού προσθέτου, από την χημική σύσταση και από το στάδιο γήρανσης του βιοντήζελ. Πολύ σημαντικό ρόλο στην οξειδωτική συμπεριφορά του μίγματος κατείχαν και τα χαρακτηριστικά του πετρελαίου αναφοράς. Η τελευταία εργασία αυτής της διατριβής εξέτασε τα περιβαλλοντικά και λειτουργικά χαρακτηριστικά του βιοντήζελ σε πετρελαιοκίνητα οχήματα. Οι πειραματικές μετρήσεις έδειξαν πως η χρήση χαμηλών μιγμάτων βιοντήζελ δεν παρουσιάζει σημαντικές επιπτώσεις στη λειτουργία και τις εκπομπές των υπό δοκιμή οχημάτων. Εντούτοις, τα μίγματα βιοντήζελ άνω του 20 % κ.ό. οδήγησαν τις περισσότερες φορές σε εμφανείς μεταβολές σε σχέση με τα καύσιμο αναφοράς. Οι μη-νομοθετημένοι ρύποι φάνηκε να επηρεάζονται σημαντικά από την συγκέντρωση του βιοντήζελ στο τελικό μίγμα, από την σύσταση του βιοντήζελ, την πρώτη ύλη προέλευσης και την ποιότητα του, καθώς και από τις συνθήκες οδήγησης που εφαρμόστηκαν. Κατά την εκπόνηση αυτής της εργασίας εξήχθησαν χρήσιμα συμπεράσματα όσον αφορά την συσχέτιση του βαθμού ακορεστότητας του βιοντήζελ με τις εκπομπές οξειδίων του αζώτου, τις εκπομπές καρβονυλικών ενώσεων και τις εκπομπές πολυκυκλικών αρωματικών υδρογονανθράκων (ΡΑΗ). Γενικότερα, οι πληροφορίες που εξήχθησαν από τα πειραματικά δεδομένα, έδειξαν πως η χρήση του βιοντήζελ επηρεάζει μάλλον αρνητικά τον σχηματισμό τοξικών και καρκινογόνων ρύπων. Αξίζει να σημειωθεί ότι τα μίγματα των οξειδωμένων βιοντήζελ παρουσίασαν συστηματική αρνητική επίδραση στους μη-νομοθετημένους ρύπους των καρβονυλικών ενώσεων και ΡΑΗ

Reinforcing the Immunocompromised Host Defense against Fungi: Progress beyond the Current State of the Art

Despite the availability of a variety of antifungal drugs, opportunistic fungal infections still remain life-threatening for immunocompromised patients, such as those undergoing allogeneic hematopoietic cell transplantation or solid organ transplantation. Suboptimal efficacy, toxicity, development of resistant variants and recurrent episodes are limitations associated with current antifungal drug therapy. Adjunctive immunotherapies reinforcing the host defense against fungi and aiding in clearance of opportunistic pathogens are continuously gaining ground in this battle. Here, we review alternative approaches for the management of fungal infections going beyond the state of the art and placing an emphasis on fungus-specific T cell immunotherapy. Harnessing the power of T cells in the form of adoptive immunotherapy represents the strenuous protagonist of the current immunotherapeutic approaches towards combating invasive fungal infections. The progress that has been made over the last years in this field and remaining challenges as well, will be discussed

Cloud Forming Potential of Aerosol from Light-duty Gasoline Direct Injection Vehicles

In this study, the authors evaluate the hygroscopicity and droplet kinetics of fresh and aged emissions from new generation gasoline direct injector engines retrofitted with a gasoline particulate filter (GPF). Furthermore, ageing and subsequent secondary aerosol formation is explored in (NH4)2SO4-seeded and non-seeded experiments. The authors explore the impacts on measured and predicted hygroscopicity, CCN-activity, and droplet kinetics of secondary aerosol mixed with initially insoluble carbonaceous materials versus very soluble (NH4)2SO4 seed. The chemical composition and density of the secondary aerosol (SA) formed from aging is measured with an HR-TOF-AMS and a custom-built APM-SMPS system. The supersaturated and subsaturated hygroscopicity of the fresh and aged emission is measured with a DMT Streamwise Thermal Gradient CCN counter and a hygroscopicity tandem differential mobility analyzer (HTDMA), respectively. The measurements show that the fresh gasoline emissions are only slightly hygroscopic in both supersaturated and subsaturated environments. Photochemical aging and subsequent condensation of the secondary aerosol formed from the co-emitted gas phase precursors increases the hygroscopicity of gasoline emissions. Without the GPF, both subsaturated and supersaturated hygroscopicity. When the engine was retrofitted with the GPF, the secondary aerosol (SA) experiments were seeded with (NH4)2SO4. In these experiments the presence of the condensing SA depresses the hygroscopicity of the salt-secondary aerosol mixture. The hygroscopicity was also depressed in the subsaturated regime with time. These changes in the hygroscopicity with aging were additionally sensitive to aerosol dry size distribution. The authors also used threshold droplet growth analysis (TDGA) to evaluate the effects of the condensing SA on droplet kinetics. These results have important implications for the assessment of cloud-aerosol indirect effects of salt-seeded and black carbonaceous aerosol cores. The authors concluded that in the new generation GDI vehicles the point of aerosol emissions will have significant influence on the impacts of the secondary and primary aerosols on climate.View the NCST Project Webpag