Effect of soil moisture on seasonal variation in indoor radon concentration: modelling and measurements in 326 Finnish houses.

The effect of soil moisture on seasonal variation in soil air and indoor radon is studied. A brief review of the theory of the effect of soil moisture on soil air radon has been presented. The theoretical estimates, together with soil moisture measurements over a period of 10 y, indicate that variation in soil moisture evidently is an important factor affecting the seasonal variation in soil air radon concentration. Partitioning of radon gas between the water and air fractions of soil pores is the main factor increasing soil air radon concentration. On two example test sites, the relative standard deviation of the calculated monthly average soil air radon concentration was 17 and 26%. Increased soil moisture in autumn and spring, after the snowmelt, increases soil gas radon concentrations by 10-20 %. In February and March, the soil gas radon concentration is in its minimum. Soil temperature is also an important factor. High soil temperature in summer increased the calculated soil gas radon concentration by 14%, compared with winter values. The monthly indoor radon measurements over period of 1 y in 326 Finnish houses are presented and compared with the modelling results. The model takes into account radon entry, climate and air exchange. The measured radon concentrations in autumn and spring were higher than expected and it can be explained by the seasonal variation in the soil moisture. The variation in soil moisture is a potential factor affecting markedly to the high year-to-year variation in the annual or seasonal average radon concentrations, observed in many radon studies.

The classification of osteonecrosis in patients with cancer: validation of a new radiological classification system.

AIM: To validate a new, non-joint-specific radiological classification system that is suitable regardless of the site of the osteonecrosis (ON) in patients with cancer. MATERIAL AND METHODS: Critical deficiencies in the existing ON classification systems were identified and a new, non-joint-specific radiological classification system was developed. Seventy-two magnetic resonance imaging (MRI) images of patients with cancer and ON lesions were graded, and the validation of the new system was performed by assessing inter- and intra-observer reliability. RESULTS: Intra-observer reliability of ON grading was good or very good, with kappa values of 0.79-0.86. Interobserver agreement was lower but still good, with kappa values of 0.62-0.77. Ninety-eight percent of all intra- or interobserver differences were within one grade. Interobserver reliability of assessing the location of ON was very good, with kappa values of 0.93-0.98. CONCLUSION: All the available radiological ON classification systems are joint specific. This limitation has spurred the development of multiple systems, which has led to the insufficient use of classifications in ON studies among patients with cancer. The introduced radiological classification system overcomes the problem of joint-specificity, was found to be reliable, and can be used to classify all ON lesions regardless of the affected site.

A software tool for tomographic axial superresolution in STED microscopy.

A method for generating three-dimensional tomograms from multiple three-dimensional axial projections in STimulated Emission Depletion (STED) superresolution microscopy is introduced. Our STED< method, based on the use of a micromirror placed on top of a standard microscopic sample, is used to record a three-dimensional projection at an oblique angle in relation to the main optical axis. Combining the STED< projection with the regular STED image into a single view by tomographic reconstruction, is shown to result in a tomogram with three-to-four-fold improved apparent axial resolution. Registration of the different projections is based on the use of a mutual-information histogram similarity metric. Fusion of the projections into a single view is based on Richardson-Lucy iterative deconvolution algorithm, modified to work with multiple projections. Our tomographic reconstruction method is demonstrated to work with real biological STED superresolution images, including a data set with a limited signal-to-noise ratio (SNR); the reconstruction software (SuperTomo) and its source code will be released under BSD open-source license.

Evaluation of the TPX MRSA assay for the detection of methicillin-resistant Staphylococcus aureus.

The aim of this study was to evaluate a new type of assay for the phenotypic detection of methicillin-resistant Staphylococcus aureus (MRSA). The assay is based on a point-of-care compatible two-photon excitation fluorescence detection technology (TPX). A collection of 243 epidemic MRSA isolates was tested in addition to 138 sporadic MRSA and 101 negative control strains. The assay proved to be both sensitive (97.9%) and specific (94.1%) in the identification of MRSA, with adequate positive (98.4%) and negative (92.2%) predictive values. The time required for obtaining a positive test result was less than 14 h for 99.0% of the MRSA true-positive samples. After a test run, the selectively enriched reaction mixtures may be recovered and further studied by molecular or standard phenotypic methods. The main benefits of the TPX methodology include a simple assay procedure, low reagent consumption, and a high-throughput capacity.

Two-photon fluorescence excitation in detection of biomolecules.

Two-photon fluorescence excitation has been found to be a very powerful method for enhancing the sensitivity and resolution in far-field light microscopy. Two-photon fluorescence excitation also provides a substantially background-free detection on the single-molecule level. It allows direct monitoring of formation of labelled biomolecule complexes in solution. Two-photon excitation is created when, by focusing an intensive light source, the density of photons per unit volume and per unit time becomes high enough for two photons to be absorbed into the same chromophore. In this case, the absorbed energy is the sum of the energies of the two photons. In two-photon excitation, dye molecules are excited only when both photons are absorbed simultaneously. The probability of absorption of two photons is equal to the product of probability distributions of absorption of the single photons. The emission of two photons is thus a quadratic process with respect to illumination intensity. Thus in two-photon excitation, only the fluorescence that is formed in the clearly restricted three-dimensional vicinity of the focal point is excited. We have developed an assay concept that is able to distinguish optically between the signal emitted from a microparticle in the focal point of the laser beam, and the signal emitted from the surrounding free labelled reagent. Moreover, the free labels outside the focal volume do not contribute any significant signal. This means that the assay is separation-free. The method based on two-photon fluorescence excitation makes possible fast single-step and separation-free immunoassays, for example, for whole blood samples. Since the method allows a separation-free assay in very small volumes, the method is very useful for high-throughput screening assays. Consequently we believe that two-photon fluorescence excitation will make a remarkable impact as a research tool and a routine method in many fields of analysis.

A new microvolume technique for bioaffinity assays using two-photon excitation.

Bioaffinity binding assays such as the immunoassay are widely used in life science research. In an immunoassay, specific antibodies are used to bind target molecules in the sample, and quantification of the binding reaction reveals the amount of the target molecules. Here we present a method to measure bioaffinity assays using the two-photon excitation of fluorescence. In this method, microparticles are used as solid phase in binding the target molecules. The degree of binding is then quantified from individual microparticles by use of two photon excitation of fluorescence. We demonstrated the effectiveness of the method using the human alpha-fetoprotein (AFP) immunoassay, which is used to detect fetal disorders. The sensitivity and dynamic range we obtained with this assay indicate that this method can provide a cost-effective and simple way to measure various biomolecules in solution for research and clinical applications.

Photon-burst analysis in two-photon fluorescence excitation flow cytometry.

We studied the use of a dramatically reduced testing zone in combination with two-photon excitation and photon-burst analysis in high-throughput rare-event detection simulation using a modified flow cytometer. Two-photon excitation measurements were performed with a mode-locked titanium:sapphire laser. Fluorescence emission was measured with a photon-counting avalanche photodiode. Measured signal was analysed offline by autocorrelation and burst detection methods. Test samples were composed of full blood and orange fluorescent polystyrene nanospheres mixed in full blood. Results show that two-photon fluorescence excitation and time-correlation analysis provide a good signal-to-noise ratio for rare-event particle detection in a turbid sample environment.

A new design of the flow cuvette and optical set-up for the scanning flow cytometer.

We introduce a new design for the optical cuvette and a new optical lay-out for the Scanning Flow Cytometer (SFC) that permits measurement of the angular dependency of the scattered light from individual moving particles. The improved optical scheme of the SFC allows measurement of the angular scattering pattern of individual particles at polar angles from 10 degrees to 120 degrees with integration at azimuthal angles from 0 degrees to 360 degrees and with angular resolution of better than 0.5 degrees. The performance of the SFC is demonstrated using certified polystyrene particles as reference material The aim of this work is to develop a flow cytometer, which, by recording the entire light scattering pattern of individual biological particles, would provide more information about the particle structure than the ordinary wide angle, forward and side scattering concepts.

Image formation and data acquisition in a stage scanning 4Pi confocal fluorescence microscope.

We describe the three-dimensional (3-D) image formation and data acquisition in a stage scanning 4Pi confocal fluorescence microscope with the use of two-photon excitation. The 3-D point-spread functions of the 4Pi confocal and regular confocal microscope are measured and compared. Particular emphasis is given to the data acquisition procedure. 4Pi confocal microscopy results in a point-spread function that is 4 times sharper than that of a regular confocal microscope, ultimately leading to superior 3-D imaging of translucent fluorescent specimens. For a two-photon excitation wavelength of approximately 800 nm, we obtain an axial resolution of 140 nm.

Group F beta-hemolytic streptococcus, tonsillitis and myocarditis.

A case of tonsillitis and myocarditis is reported, where the only positive microbiological finding was a throat swab growing group F beta-hemolytic streptococci. The patient made an uneventful recovery after treatment with benzylpenicillin and clindamycin.

Roxithromycin in the treatment of pneumonia.

An open multicentre study of the efficacy and side effects of roxithromycin, a new macrolide antibiotic, in the treatment of community acquired pneumonia was undertaken. The diagnosis was verified by transtracheal aspiration. Fifty-three patients were studied. In the 49 patients evaluable the clinical efficacy rate was 92% (95% confidence limits 84-100%). Only by measurement of the fall in serum C-reactive protein was it possible to detect a difference in response between pneumonia due to Streptococcus pneumoniae and Haemophilus influenzae. The drug was well tolerated clinically and laboratory abnormalities included transient eosinophilia and elevated liver enzymes in two patients.

Penetration of sulbactam into cerebrospinal fluid of patients with viral meningitis or without meningitis.

In a study designed to determine the penetration of sulbactam into the central nervous system, a single intramuscular dose of 0.5-1.0 g was given to 19 patients: nine with viral meningitis and 10 with normal cerebrospinal fluid (CSF). Drug levels in CSF were first detectable 2 hr after administration in patients with viral meningitis and 4 hr after administration in patients with normal CSF. The sulbactam levels were low (0-3.7 mg/ml), and no significant differences were found between levels in the two groups of patients. For the achievement of therapeutic concentrations of sulbactam in CSF, doses larger than those administered in this study should be used in conjunction with a beta-lactam antibiotic.