Size-dependent hydroxyl radicals generation induced by SiO2 ultra-fine particles: The role of surface iron

2009 ◽  
Vol 52 (7) ◽  
pp. 1033-1041 ◽  
Author(s):  
Yu Shang ◽  
Tong Zhu ◽  
Yi Li ◽  
JinCai Zhao
2021 ◽  
Author(s):  
Lu Chen ◽  
Fang Zhang ◽  
Don Collins ◽  
Jieyao Liu ◽  
Sihui Jiang ◽  
...  

Abstract. Understanding the volatility and mixing state of atmospheric aerosols is important for elucidating the formation of fine particles and to help determining their effect on environment and climate. In this study, the volatility of the fine particles is characterized by the size-dependent volatility shrink factor (VSF) for summer and winter in the urban area of Beijing using measurements of a volatility tandem differential mobility analyzer (VTDMA). We show the volatility of aerosols is always with one high-volatile and one less- or non-volatile mode both in the summer and winter. On average, the particles are more volatile in the summer (with mean VSF of 0.3) than in the winter (with mean VSF of 0.6). The outstanding high-volatile mode around noontime illustrates the role of nucleation in producing more volatile particles in the summer. We further retrieve the mixing state of the ambient fine particles from the size-resolved VSF and find that the non-black carbon (BC) particles that formed from nucleation processes accounted for 52–69 % of the total number concentration in the summer. While, particles containing a refractory core that is thought to be BC-containing particles dominate and contribute 67–77 % toward the total number concentration in the winter. The diurnal cycles of the retrieved aerosol mixing state for the summer further supports the conclusion that nucleation process is the main contributors to non-BC particles. In addition, the extent of aging of BC particles was characterized as the ratio of the BC diameter before and after heating at 300 °C (Dp/Dc), showing that the average ratio of ~2.2 in the winter is higher than the average of ~1.5 in the summer, which indicates that BC aging is more efficient in wintertime, with resulting differences in light absorption enhancement between cold and warm seasons.


Author(s):  
Chihiro Kaito ◽  
Yoshio Saito

The direct evaporation of metallic oxides or sulfides does not always given the same compounds with starting material, i.e. decomposition took place. Since the controll of the sulfur or selenium vapors was difficult, a similar production method for oxide particles could not be used for preparation of such compounds in spite of increasing interest in the fields of material science, astrophysics and mineralogy. In the present paper, copper metal was evaporated from a molybdenum silicide heater which was proposed by us to produce the ultra-fine particles in reactive gas as shown schematically in Figure 1. Typical smoke by this method in Ar gas at a pressure of 13 kPa is shown in Figure 2. Since the temperature at a location of a few mm below the heater, maintained at 1400° C , were a few hundred degrees centigrade, the selenium powder in a quartz boat was evaporated at atmospheric temperature just below the heater. The copper vapor that evaporated from the heater was mixed with the stream of selenium vapor,and selenide was formed near the boat. If then condensed by rapid cooling due to the collision with inert gas, thus forming smoke similar to that from the metallic sulfide formation. Particles were collected and studied by a Hitachi H-800 electron microscope.Figure 3 shows typical EM images of the produced copper selenide particles. The morphology was different by the crystal structure, i.e. round shaped plate (CuSe;hexagona1 a=0.39,C=l.723 nm) ,definite shaped p1 ate(Cu5Se4;Orthorhombic;a=0.8227 , b=1.1982 , c=0.641 nm) and a tetrahedron(Cu1.8Se; cubic a=0.5739 nm). In the case of compound ultrafine particles there have been no observation for the particles of the tetrahedron shape. Since the crystal structure of Cu1.8Se is the anti-f1uorite structure, there has no polarity.


2021 ◽  
pp. 103836
Author(s):  
Ding Tang ◽  
Leilei Zhao ◽  
Huamiao Wang ◽  
Dayong Li ◽  
Yinghong Peng ◽  
...  

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Somruethai Sumkhemthong ◽  
Eakachai Prompetchara ◽  
Pithi Chanvorachote ◽  
Chatchai Chaotham

Abstract Background Accumulated evidence demonstrates cisplatin, a recommended chemotherapy, modulating pro-survival autophagic response that contributes to treatment failure in lung cancer patients. However, distinct mechanisms involved in cisplatin-induced autophagy in human lung cancer cells are still unclear. Results Herein, role of autophagy in cisplatin resistance was indicated by a decreased cell viability and increased apoptosis in lung cancer H460 cells pre-incubated with wortmannin, an autophagy inhibitor, prior to treatment with 50 µM cisplatin for 24 h. The elevated level of hydroxyl radicals detected via flow-cytometry corresponded to autophagic response, as evidenced by the formation of autophagosomes and autolysosomes in cisplatin-treated cells. Interestingly, apoptosis resistance, autophagosome formation, and the alteration of the autophagic markers, LC3-II/LC3-I and p62, as well as autophagy-regulating proteins Atg7 and Atg3, induced by cisplatin was abrogated by pretreatment of H460 cells with deferoxamine, a specific hydroxyl radical scavenger. The modulations in autophagic response were also indicated in the cells treated with hydroxyl radicals generated via Fenton reaction, and likewise inhibited by pretreatment with deferoxamine. Conclusions In summary, the possible role of hydroxyl radicals as a key mediator in the autophagic response to cisplatin treatment, which was firstly revealed in this study would benefit for the further development of novel therapies for lung cancer.


ChemInform ◽  
2015 ◽  
Vol 46 (22) ◽  
pp. no-no
Author(s):  
Kapileswar Seth ◽  
Manesh Nautiyal ◽  
Priyank Purohit ◽  
Naisargee Parikh ◽  
Asit K. Chakraborti

Materia Japan ◽  
1995 ◽  
Vol 34 (4) ◽  
pp. 455-460 ◽  
Author(s):  
Eiji Fuchita ◽  
Masaaki Oda ◽  
Chikara Hayashi

Gefahrstoffe ◽  
2020 ◽  
Vol 80 (01-02) ◽  
pp. 19-24 ◽  
Author(s):  
M. Köhler ◽  
A. Ohle ◽  
M. Beckmann ◽  
S. Steinau ◽  
F. Tettich ◽  
...  

Der Anteil an Kremationen (Feuerbestattungen) nimmt in Deutschland seit Jahren zu und umfasst bereits mehr als 65 % aller Bestattungen. Grenzwerte für die Emissionen von Feinstaub oder die Anzahl ultrafeiner Partikel (UFP) existieren nicht und bisher sind auch keine systematischen Untersuchungen bekannt, welche Partikelemissionen in Krematorien auftreten. Daher kann zum aktuellen Zeitpunkt nicht beurteilt werden, ob es sich bei Krematorien um nennenswerte Feinstaubquellen handelt. Um diese Lücke zu schließen, wurden die reingasseitigen UFP-Konzentrationen in zehn Krematorien unterschiedlichen Bau- bzw. Modernisierungsjahres und mit verschiedenen Abgasreinigungstechnologien gemessen. Über die Kremationsdauer gemittelte UFP-Konzentrationen zwischen 1,19 · 10³ und 4,26 · 107 cm–3 wurden erfasst. Die höchsten Konzentrationen zeigten sich bei Anlagen mit Flugstromverfahren, deren Filtereinheiten unmittelbar vor der nächsten Revision standen. Bei Anlagen gleichen Typs mit gewarteten Filtereinheiten lag die mittlere UFP-Konzentration zwei Größenordnungen darunter.


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