Novel insights on new particle formation derived from a pan-european observing system.

The formation of new atmospheric particles involves an initial step forming stable clusters less than a nanometre in size (<~1 nm), followed by growth into quasi-stable aerosol particles a few nanometres (~1-10 nm) and larger (>~10 nm). Although at times, the same species can be responsible for both processes, it is thought that more generally each step comprises differing chemical contributors. Here, we present a novel analysis of measurements from a unique multi-station ground-based observing system which reveals new insights into continental-scale patterns associated with new particle formation. Statistical cluster analysis of this unique 2-year multi-station dataset comprising size distribution and chemical composition reveals that across Europe, there are different major seasonal trends depending on geographical location, concomitant with diversity in nucleating species while it seems that the growth phase is dominated by organic aerosol formation. The diversity and seasonality of these events requires an advanced observing system to elucidate the key processes and species driving particle formation, along with detecting continental scale changes in aerosol formation into the future.

An unbiased and efficient computerised tomography method to quantify muscle and adipose tissue volume in neuromuscular patients.

The objective was to evaluate the applicability and reliability of an unbiased stereological computerised tomography (CT) method for estimating total human body (HB), skeletal muscle (SM) and adipose tissue (AT) volumes in groups of neuromuscular patients. In 10 neuromuscular patients HB, SM and AT volumes were estimated using systematic sampling on equidistant CT sections throughout the total body axis using a counting grid with systematically ordered intersection points. Each intersection point hitting HB, SM or AT represented a known volume dependent on intersection point distance and sum of section thickness and gap. Random and systematic intra- and interobserver errors for volume estimates were below 0.035. These errors were negligible to the coefficient of variation of the group mean, being 0.190 for HB, 0.323 for SM and 0.471 for AT. Even in the presence of intrafascicular and intramuscular fat in neuromuscular patients, unbiased and reliable quantification of HB, SM and AT is possible.

Pulsed heterodyne CO(2) laser rangefinder and velocimeter with chirp correction.

A pulsed hybrid CO(2) transversely excited atmosphere (TEA) laser has been used in a bistatic laser rangefinder-velocimeter system with heterodyne detection. Several techniques have been applied to improve the performance of the system. These include the stabilization of the hybrid CO(2) TEA-laser and the stabilization of the frequency offset of the local oscillator (better than ±74 kHz peak to peak), phase-front matching at the detector surface resulting in a heterodyne beat efficiency of 0.4-0.6, and chirp correction. With this system, targets at distances of up to 25 km can be detected with an accuracy of 15 m. The velocity of the targets can be estimated with an accuracy of approximately ±0.5 m/s.

Inversion of lidar signals with the slope method.

In homogeneous atmospheres, backscatter and extinction coefficients are commonly determined by the inversion of lidar signals by using the slope method, i.e., from a linear least-squares fit to the logarithm on the range-compensated lidar return. We investigate the accuracy of this method. A quantitative analysis is presented of the influence of white noise and atmospheric extinction on the accuracy of the slope method and on the maximum range of lidar systems. To meet this objective, we simulate lidar signals with extinction coefficients ranging from 10(-3) km(-1) to 10 km(-1) with different signal-to-noise ratios. It is shown that the backscatter coefficient can be determined by using the slope method with an ccuracy of better than ~ 10% if the extinction coefficient is smaller than 1 km(-1) and the signal-to-noise ratio is better than ~ 1000. The accuracy in the calculated extinction coefficient is only better than ~ 10% if the extinction is larger than 1 km(-1) and the signal-to-noise ratio is better than ~2000. If th atmospheric extinction coefficient is smaller than 0.1 km(-1), then it is not possible to invert the extinction from lidar measurements with an accuracy of 10% or better unless the signal-to-noise ratio isunrealistically high.

Modeling of extinction and backscatter profiles in the marine mixed layer.

A steady state model is presented which describes the vertical structure of aerosol particle size distributions in the marine mixed layer. A balance is assumed between the fluxes at the top of the mixed layer and at the airsea interface. Effects of surface stability and entrainment are taken into account. The concentration gradients are further determined by the interaction of the aerosol size distribution and the humidity field. Results of numerical calculations are compared to profiles of 1.06-microm backscatter coefficients which were measured with lidar over the North Atlantic. The correct trends are predicted in 65% of the cases.

Scanning electron microscopy of Acholeplasma colonies on agar.

The colony formation and morphology of Acholeplasma laidlawii and of an Acholeplasma species was studied by scanning electron microscopy. In the colonies of both Acholeplasma spp. large irregularly shaped cells, spherical cells, chains of beads, and long filaments with small bulbous distensions were seen. The membrane of some of the large cells seemed to be perforated, giving the cell a pitted appearance.

Demonstration of acid phosphatase activity induced by 20-hydroxyecdysone in the fat body of Calliphora.

In the larval fat body of Calliphora erythrocephala, protein accumulation and autophagic activity occur prior to the onset of puparium formation. The involvement of the lysosomal system in the degradation of sequestered protein and cell organelles can be demonstrated by the electron-microscopical cytochemical localization of the lysosomal marker enzyme acid phosphatase in so-called protein granules. These granules contain not only newly synthetized or absorbed protein but also remnants of cell organelles such as mitochondria and endoplasmic reticulum. Ligation of the larvae behind the brain-ring gland complex prevents the appearance of these acid phosphatase-positive granules. They can be induced in ligated larvae by the injection of 20-hydroxyecdysone into the abdomen. These findings are briefly discussed in relation to the role of moulting hormones in normal development, especially with regard to the induction of autophagic activity.