Insights into the growth of newly formed particles in a subtropical urban environment

The role of different chemical compounds, particularly organics, involved in the new particle formation (NPF) and its consequent growth are not fully understood. Therefore, this study was conducted to investigate the chemical composition of aerosol particles during NPF events in an urban subtropical environment. Aerosol chemical composition was measured along with particle number size distribution (PNSD) and several other air quality parameters at five sites across an urban subtropical environment. An Aerodyne compact Time-of-Flight Aerosol Mass Spectrometer (c-TOF-AMS) and a TSI Scanning Mobility Particle Sizer (SMPS) measured aerosol chemical composition (particles above 50 nm in vacuum aerodynamic diameter) and PNSD (particles within 9-414 nm in mobility diameter), respectively. Five NPF events, with growth rates in the range 3.3-4.6 nm, were detected at two of the sites. The NPF events happened on relatively warmer days with lower condensation sink (CS). Temporal percent fractions of organics increased after the particles grew enough to have a significant contribution to particles volume, while the mass fraction of ammonium and sulphate decreased. This uncovered the important role of organics in the growth of newly formed particles. Three organic markers, factors f43, f44 and f57, were calculated and the f44 vs f43 trends were compared between nucleation and non-nucleation days. K-means cluster analysis was performed on f44 vs f43 data and it was found that they follow different patterns on nucleation days compared to non-nucleation days, whereby f43 decreased for vehicle emission generated particles, while both f44 and f43 decreased for NPF generated particles. It was found for the first time that vehicle generated and newly formed particles cluster in different locations on f44 vs f43 plot and this finding can be potentially used as a tool for source apportionment of measured particles.

Accelerated drying of plantation grown Eucalyptus cloeziana and Eucalyptus pellita sawn timber

The objective of this study was to gain an understanding for drying sawn timber produced from fast-grown, well-managed Queensland hardwood plantations using accelerated drying methods. Due to limited resources, this was a preliminary study and further work will be required to optimize schedules for industrial implementation. Three conventional kiln trials, including two for 38-mm-thick, 19-year-old plantation Gympie messmate (Eucalyptus cloeziana F. Muell.) and one for 25mm thick, 15-year-old plantation red mahogany (Eucalyptus pellita F. Muell.), and two vacuum kiln drying trials, one each for 38- and 25mm thick Gympie messmate, were conducted. Measurements of final cross-sectional moisture content, moisture content gradient, residual drying stress, and internal and surface checking were used to quantify dried quality. Drying schedules were chosen based on either existing published schedules or, in the case of the vacuum drying trials, existing schedules for species with similar wood density and dying degrade properties, or manipulated schedules based on the results of trials conducted during this study. The findings indicate that both species can be dried using conventional drying techniques with acceptable grade quality in approximately 75 percent of the drying time that industry is currently achieving when drying native forest timber of the same species. The vacuum drying time was 60 percent less than conventional drying for 38-mm-thick, 19-year-old Gympie messmate, although drying quality needs improving. The findings have shown that through careful schedule manipulation and adjustment, the grade quality can be optimized to suit the desired expectation. Additional research is required to further optimize the schedules to ensure acceptable grade qualities can be reliably achieved across all drying criteria and exploit opportunities to reduce drying times further.

Cellular Cholesterol Accumulation and Egress from Endosomal Compartments

One of the most important factors determining the development of atherosclerosis is the amount of LDL particles in the circulation. In general, LDL particles are clinically regarded as “bad cholesterol” since these particles get entrapped within the vascular wall, leading to atherosclerosis. Circulating HDL particles are conversely regarded as “good cholesterol” because of their ability to transport cholesterol from peripheral tissues to the liver for secretion as bile salts. Once inside the artery wall LDL particles are engulfed by macrophages, resulting in macrophage foam cells. If the macrophage foam cells are not able to efflux the cholesterol back into the bloodstream, the excessive cholesterol ultimately leads to cell death, and the deposition of cellular debris within the atherosclerotic lesion. The cells ability to secrete cholesterol is mainly dependent on the ABCA1 transporter (ATP-binding cassette transporter A1) which transfers cellular cholesterol to extracellular apoA-I (apolipoprotein A-I) particles, leading to the generation of nascent HDL particles. The process of atherosclerotic plaque development is therefore to a large extent a cellular one, in which the capacity of the macrophages in handling the excessive cholesterol load determines the progression of lesion development. In this work we have studied the cellular mechanisms that regulate the trafficking of LDL-derived cholesterol from endosomal compartments to other parts of the cell. As a basis for the study we have utilized cells from patients with Niemann-Pick type C disease, a genetic disorder resulting from mutations in the NPC1 and NPC2 genes. In these cells, cholesterol is entrapped within the endosomal compartment, and is not available for efflux. By identifying proteins that bypass the cholesterol trafficking defect, we were able to identify the small GTPase Rab8 as an important protein involved in ABCA1 dependent cholesterol efflux. In the study, we show that Rab8 regulates cholesterol efflux in human macrophages by facilitating intracellular cholesterol transport, as well as by regulating the plasma membrane availability of ABCA1. Collectively, these results give new insight in to atherosclerotic lesion development and intracellular cholesterol processing.

A novel investigation of vapor-phase charge-transfer complexes of halogens with n-donors by electron energy loss spectroscopy

Complexes of I2 with diethyl ether and triethylamine and of Br, with diethyl ether have been investigated in the vapor phase for the first time by employing electron energy loss spectroscopy. Besides the CT bands, blue-shifted vacuum-UV bands of the halogens have been assigned; the amine-I, system appears to exhibit two CT bands,associated with two different excited states of the complex.

XPS and XAES studies of surface segregation and oxidation of Cu-Ge alloy

Surface segregation of Ge is seen in the Cu-5at%Ge alloy with an activation enthalpy equal to 17 kJ/mol. Oxidation of the alloy in the temperature range 400 to 600 K shows the formation of Cu2O and GeO which on further heating in vacuum at 650 K converts to GeO2 with the reduction of Cu2O to Cu.

Electron-Energy Loss Spectroscopy (Eels) Of Organic-Molecules In Vapor-Phase - Design And Fabrication Of An Indigenous Eel Spectrometer

An indigenous electron energy loss spectrometer has been designed and fabricated for the study of free molecules. The spectrometer enables the recording of low-resolution electronic spectra of molecules inthe vapour phase with ready access to the vacuum ultraviolet region. Electron energy loss spectra of aliphatic alcohols and carbonyl compounds as wellas of benzene derivatives have been recorded with the indigenous spectrometer and the electronic transitions in these molecules discussed.

Surface segregation and oxidation studies of Cu-Sn and Cu-Pd alloys by x-ray photoelectron and auger spectroscopy

X-ray photoelectron and Auger spectroscopic techniques have been employed to study surface segregation and oxidation of Cu-1 at%Sn, Cu-9at%Pd and Cu-25at%Pd alloys. Both Cu-Pd(9%) and Cu-Pd(25%) alloys show segregation of Cu when heated above 500 K. The Pd concentration was reduced by 50% at 750 K compared to the bulk composition; the enthalpy of segregation of Cu is around - 6kJ/mol. Sn segregation is seen from 470 to 650 K in the Cu-Sn(1%) alloy, and a saturation plateau of Sn concentration above 650 K is observed. Surface oxidation of Cu-Sn(1%) and Cu-Pd(9%) alloys at 500 K showed the formation of Cu2O on the surface with total suppression of Sn or Pd on the respective alloy surfaces. On vacuum annealing the oxidised Cu-Sn alloy surface at 550 K, a displacement reaction 2Cu2O+Sn→4Cu+SnO2 was observed. However, under similar annealing of the oxidised Cu-Pd(9%) alloy surface at 500 K, oxide oxygen was totally desorbed leaving the Cu-Pd alloy surface clean. In the case of the Cu-Pd(25%) alloy, only dissociatively chemisorbed oxygen was seen at 500 K which desorbed at the same temperature. Oxygen spill-over from copper to palladium is suggested as the mechanism of oxygen desorption from the oxidised Cu-Pd alloy surfaces.

Hardwood Drying Length Evaluation

Evaluating the length of time required to dry hardwood timber using vacuum drying compared to conventional drying facilities and technology.

FWPA Cullity Fellowship AR Redman

FWPA Cullity Fellowship research program - Characterisation of wood properties and transverse anatomy for vacuum drying modelling of commercially important Australian hardwood species.

Size effect on the lattice parameter of KCl during mechanical milling

The size effect on the lattice parameter of ionic KCl nanocrystals was studied systematically during mechanical milling of Pure KCl powder under vacuum. The results suggest anomalous lattice expansion, with the lattice parameter increasing from 6.278 angstrom at d = 6 mu m to 6.30307 angstrom at d = 85 mn. The defects generated during ball milling of KCl and surface stress are deemed to be responsible for this lattice parameter expansion. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Methicillin Resistance In Staphylococci : Horizontal Transfer of Mobile Genetic Element (SCCmec) Between Staphylococcal Species

Regardless of the existence of antibiotics, infectious diseases are the leading causes of death in the world. Staphylococci cause many infections of varying severity, although they can also exist peacefully in many parts of the human body. Most often Staphylococcus aureus colonises the nose, and that colonisation is considered to be a risk factor for spread of this bacterium. S. aureus is considered to be the most important Staphylococcus species. It poses a challenge to the field of medicine, and one of the most problematic aspects is the drastic increase of the methicillin-resistant S. aureus (MRSA) strains in hospitals and community world-wide, including Finland. In addition, most of the clinical coagulase-negative staphylococcus (CNS) isolates express resistance to methicillin. Methicillin-resistance in S. aureus is caused by the mecA gene that encodes an extra penicillin-binding protein (PBP) 2a. The mecA gene is found in a mobile genomic island called staphylococcal chromosome cassette mec (SCCmec). The SCCmec consists of the mec gene and cassette chromosome recombinase (ccr)gene complexes. The areas of the SCCmec element outside the ccr and mec complex are known as the junkyard J regions. So far, eight types of SCCmec(SCCmec I- SCCmec VIII) and a number of variants have been described. The SCCmec island is an acquired element in S. aureus. Lately, it appears that CNS might be the storage place of the SCCmec that aid the S. aureus by providing it with the resistant elements. The SCCmec is known to exist only in the staphylococci. The aim of the present study was to investigate the horizontal transfer of SCCmec between the S. aureus and CNS. One specific aim was to study whether or not some methicillin-sensitive S. aureus (MSSA) strains are more inclined to receive the SCCmec than others. This was done by comparing the genetic background of clinical MSSA isolates in the health care facilities of the Helsinki and Uusimaa Hospital District in 2001 to the representatives of the epidemic MRSA (EMRSA) genotypes, which have been encountered in Finland during 1992-2004. Majority of the clinical MSSA strains were related to the EMRSA strains. This finding suggests that horizontal transfer of SCCmec from unknown donor(s) to several MSSA background genotypes has occurred in Finland. The molecular characteristics of representative clinical methicillin-resistant S. epidermidis (MRSE) isolates recovered in Finnish hospitals between 1990 and 1998 were also studied, examining their genetic relation to each other and to the internationally recognised MRSE clones as well, so as to ascertain the common traits between the SCCmec elements in MRSE and MRSA. The clinical MRSE strains were genetically related to each other; eleven PFGE types were associated with sequence type ST2 that has been identified world-wide. A single MRSE strain may possess two SCCmec types III and IV, which were recognised among the MRSA strains. Moreover, six months after the onset of an outbreak of MRSA possessing a SCCmec type V in a long-term care facility in Northern Finland (LTCF) in 2003, the SCCmec element of nasally carried methicillin-resistant staphylococci was studied. Among the residents of a LTCF, nasal carriage of MR-CNS was common with extreme diversity of SCCmec types. MRSE was the most prevalent CNS species. Horizontal transfer of SCCmec elements is speculated to be based on the sharing of SCCmec type V between MRSA and MRSE in the same person. Additionally, the SCCmec element of the clinical human S. sciuri isolates was studied. Some of the SCCmec regions were present in S. sciuri and the pls gene was common in it. This finding supports the hypothesis of genetic exchange happening between staphylococcal species. Evaluation of the epidemiology of methicillin-resistant staphylococcal colonisation is necessary in order to understand the apparent emergence of these strains and to develop appropriate control strategies. SCCmec typing is essential for understanding the emergence of MRSA strains from CNS, considering that the MR-CNS may represent the gene pool for the continuous creation of new SCCmec types from which MRSA might originate.

Determination of baryon magnetic moments from QCD sum rules

The magnetic moment μB of a baryon B with quark content (aab) is written as μB=4ea(1+δB)eħ/2cMB, where ea is the charge of the quark of flavor type a. The experimental values of δB have a simple pattern and have a natural explanation within QCD. Using the ratio method, the QCD sum rules are analyzed and the values of δB are computed. We find good agreement with data (≊10%) for the nucleons and the Σ multiplet while for the cascade the agreement is not as good. In our analysis we have incorporated additional terms in the operator-product expansion as compared to previous authors. We also clarify some points of disagreement between the previous authors. External-field-induced correlations describing the magnetic properties of the vacuum are estimated from the baryon magnetic-moment sum rules themselves as well as by independent spectral representations and the results are contrasted.

Multivariate analysis of fresh-cut carambola slices stored under different temperatures.

Quality of fresh-cut carambola (Averrhoa carambola L) is related to many chemical and biochemical variables especially those involved with softening and browning, both influenced by storage temperature. To study these effects, a multivariate analysis was used to evaluate slices packaged in vacuum-sealed polyolefin bags, and stored at 2.5 degrees C, 5 degrees C and 10 degrees C, for up to 16 d. The quality of slices at each temperature was correlated with the duration of storage, O(2) and CO(2) concentration in the package, physical chemical constituents, and activity of enzymes involved in softening (PG) and browning (PPO) metabolism. Three quality groups were identified by hierarchical cluster analysis, and the classification of the components within each of these groups was obtained from a principal component analysis (PCA). The characterization of samples by PCA clearly distinguished acceptable and non-acceptable slices. According to PCA, acceptable slices presented higher ascorbic acid content, greater hue angles ((o)h) and final lightness (L-5) in the first principal component (PC1). On the other hand, non-acceptable slices presented higher total pectin content. PPO activity in the PC1. Non-acceptable slices also presented higher soluble pectin content, increased pectin solubilisation and higher CO(2) concentration in the second principal component (PC2) whereas acceptable slices showed lower total sugar content. The hierarchical cluster and PCA analyses were useful for discriminating the quality of slices stored at different temperatures.

Evaluation of wood characteristics of tropical post-mid rotation plantation Eucalyptus cloeziana and E. pellita: Part (b) Accelerated seasoning of sawn timber.

Drying trials were conducted using two species of plantation grown eucalypt timbers: 19-year-old Eucalyptus cloeziana (Gympie messmate) and 15-year-old Eucalyptus pellita (red mahogany). The objective of this study was to gain an understanding of the drying potential of young plantation grown material using accelerated seasoning methods, a process expected to be critcal to the success of plantation hardwood products entering value added markets. The findings are encouraging, indicating that both species can be dried using conventional drying techniques much faster than industry is currently achieving when drying native forest timber. The results suggest that there is a definite drying time advantatge in vacuum drying over conventional methods for 19-year-old E. cloeziana. The findings have shown that through careful schedule manipulation and adjustment, the grade quality can be optimised to suit the desired expectation. As this study was limited to only a small number of trials, time and quality improvements are expected to be realised for both conventional and vacuum drying methods as more research is conducted.

Mass transfer properties (permeability and mass diffusivity) of four Australian hardwood species

Characterisation of mass transfer properties was achieved in the longitudinal, radial, and tangential directions for four Australian hardwood species: spotted gum, blackbutt, jarrah and messmate. Measurement of mass transfer properties for these species was necessary to complement current vacuum drying modelling research. Water-vapour diffusivity was determined in steady state using a specific vapometer. Permeability values of some species and material directions were extremely low and undetectable by the mass flow meter device. Hence, a custom system based on volume evolution was conceived to determine very low, previously unpublished, wood permeability values. Mass diffusivity and permeability were lowest for spotted gum and highest for messmate. Except for messmate, in the radial direction, the four species measured were less permeable in all directions than the lowest published figures, demonstrating the high impermeability of Australian hardwoods and partly accounting for their relatively slow drying rates. Premeability, water-vapour diffusivity, and associated anisotropic ratio data obtained for messmate were extreme or did not follow typical trends and is consequently the most difficult of the four woods to dry in terms of collapse and checkinng degradation.