Optical properties of the South pole ice at depths between 0.8 and 1 kilometer.

The optical properties of the ice at the geographical South Pole have been investigated at depths between 0.8 and 1 kilometer. The absorption and scattering lengths of visible light ( approximately 515 nanometers) have been measured in situ with the use of the laser calibration setup of the Antarctic Muon and Neutrino Detector Array (AMANDA) neutrino detector. The ice is intrinsically extremely transparent. The measured absorption length is 59 +/- 3 meters, comparable with the quality of the ultrapure water used in the Irvine-Michigan-Brookhaven and Kamiokande proton-decay and neutrino experiments and more than twice as long as the best value reported for laboratory ice. Because of a residual density of air bubbles at these depths, the trajectories of photons in the medium are randomized. If the bubbles are assumed to be smooth and spherical, the average distance between collisions at a depth of 1 kilometer is about 25 centimeters. The measured inverse scattering length on bubbles decreases linearly with increasing depth in the volume of ice investigated.

Analysis of low-molar-mass materials in commercial rubber samples by Soxhlet and headspace extractions followed by GC-MS analysis.

Very tight regulations apply to materials used for pharmaceutical packaging and for administering drugs. In this paper, we describe a simple and reliable procedure involving both gas- and liquid-phase extraction steps followed by an analysis step to identify the low-molar-mass materials in commercial-rubber samples. Representative commercial rubbers, that could be used for pharmaceutical packaging, have been selected and cryogenically powdered. Headspace and Soxhlet extractions have been carried out and the key parameters are discussed. The obtained extracts have been analyzed by gas chromatography (GC)-mass spectrometry (MS). More than 100 compounds have been detected and identified. Headspace allowed to extract the more-volatile compounds, whereas Soxhlet extraction recovered less-volatile compounds, but induced a loss of the volatile ones. Thus, both extraction techniques are required to fully characterize the low-molar-mass compounds present in rubber.

Seasonal variation of radionuclides in Fucus vesiculosus L. from the Oresund, Southern Sweden.

The activity concentrations of radionuclides (60Co, 54Mn, 137Cs, 40K) in whole plants of Fucus vesiculosus of different ages, and also in tissues of different ages from the same plants were investigated in the vicinity of the Barsebäck nuclear power plant in southern Sweden. Activity concentration differed between the tissues of different age of the plants, depending on the radionuclide as well as the time of year. The highest concentrations of 60Co and 54Mn were measured in the older parts of the plants in spring and summer, while the activity concentrations of 137Cs and 40K were highest in receptacles and new vegetative fronds. The discharge of radionuclides from the nuclear power plant was reflected in the measured activity concentration in the algae. For 60Co, the response seemed to be smoothed out when considering the whole plant, while the new vegetative tissue better reflected the discharge during the autumn. Thus, it is important to have knowledge about the autecology of the organism when it is used as an indicator for radionuclides.

Transmission of complex pressure waves through the perilymphatic fluid in cats.

The response of the perilymphatic fluid to complex pressure waves, composed of low-frequency sine waves superimposed on square-wave pressure pulses of varying amplitude was studied. In cats with a patent cochlear aqueduct a pronounced positive pressure change could be induced in the perilymphatic fluid when complex pressure waves were used. The time constants associated with the stabilization of the perilymphatic pressure after the application of pressure complexes were longer than those associated with square-wave pulses alone. The results indicate that the functional patency of the cochlear aqueduct could be influenced by the transmission of complex pressure waves. The results also indicate that when trying to influence the inner ear hydrodynamic balance in patients with Meniere's disease, the effect of complex pressure waves is far superior to the effect of square-wave pressure pulses in patients with an open cochlear aqueduct.

Transmission of square wave pressure pulses through the perilymphatic fluid in cats.

The inner ear hydrodynamics have been studied in a series of experiments on cats. A detailed analysis has been made of the perilymphatic pressure response to square wave pressure pulses applied to the ear canal and middle ear. It was found that the initial pressure response was followed by a rebound pressure response of the opposite phase. It was also found that in most cases each phase of the pressure response could be expressed in terms of two time constants. When the cochlear aqueduct was patent, the perilymphatic pressure response showed almost equal positive and negative pressure changes. However, when the cochlear aqueduct was surgically blocked, the perilymphatic pressure response consisted almost exclusively of the first phase of the response, while the rebound phase disappeared almost completely. The possibility of influencing the inner ear fluid balance in Meniere's disease by external pressure changes is discussed in the light of the present experimental results.

Patency tests of the maxillary ostium--model experiments.

The function of the maxillary ostia (phi 0.22-4.7 mm) has been evaluated in experiments on a nose-sinus model with variable sinusal volumes. A piston-pump producing to-and-fro volumes of 467 cm3 of air per revolution was used at a speed of 10 and 20 revolutions per minute (rpm). Three different techniques were used: simultaneous pressure recording in the sinus and the nose (Method I); simultaneous recording of the differential pressure between nose and sinus and the air-flow through the ostium (Method II); recording of the pressure rise inside the sinus upon the application of a constant artificial air-flow of 16,7 cm3 . s-1 or 2.0 cm3 . s-1 (Method III). All variables were recorded on an ink-jet recorder and onto tape when using methods I and II for later analysis on an x-y recorder. A pressure relationship of 1 : 1 was found between nose and sinus, independently of ostial diameters, sinusal volumes and piston-pump rates. The first method did not permit an isolated determination of the ostial function as the pressure values recorded are affected by ostial diameters, sinusal volumes and piston-pump rates. The pressure-flow relationship recorded with the second method was found to be dependent only on the ostial diameters. Hysteresis was observed at ostial diameters less than or equal to 1.63 mm. This is due to ostial diameter, sinusal volume and the rate of the nasal pressure changes. This method is suitable for an isolated determination of the ostial resistance, from which the equivalent ostial diameter can be calculated. With the third method using static air-flows and pressures the results are independent of the sinusal volume. This method is suitable for estimation of the ostial airway resistance and the equivalent ostial diameter. A striking similarity was observed between the results obtained with the last two methods in estimating equivalent ostial diameters.

The effect of static middle ear pressures on the hearing threshold.

The effect of static tympanic pressure gradients on hearing sensitivity was studied by introducing relative underpressure of 5, 10 and 15 cmH2O in the middle ear cavity of six normal ears. A self-recording Békésy audiometer was used to measure the hearing threshold shifts during middle ear pressure equilibrations. The threshold loss was most prominent for 0.5 and 1 kHZ and less for 4 kHZ. A threshold gain was shown for 2 and 6 kHZ. Over all test frequencies the threshold shifts were increased with higher relative underpressure in the middle ear cavity. In order to evaluate the hearing impairment caused by noise, it is therefore important to control the middle ear pressure before hearing is tested. A small change in middle ear pressure can be ignored when using the summed hearing thresholds between 2 and 8 kHZ.

Hair cell damage in the inner ear of the guinea pig due to noise in a workshop.

Guinea pigs were exposed to noise in various workshops at a shipyard. The equivalent sound level ranged from 87 to 90 dB(A) and the exposure time was 30 days of 8 hours. The numbers of lost outer hair cells were greater than in control animals, thus establishing a relation between the number of lost hair cells and the total noise dose. A comparison between the results obtained here and results obtained in laboratory experiments shows that although many physical sound parameters may be identical, the effect on the hair cells can be quite different. In particular, the total noise dose is not a parameter which can be directly related to hair cell loss. The most probable explanation for the difference in damage between the laboratory and workshop animals seems to be the rest periods of 16 hours between each of the 8-hour exposure periods.

Hair cell damage in the inner ear of the Guinea pig due to noise in a workshop.

Guinea pigs were exposed to noise in various workshops at a shipyard. The equivalent sound level ranged from 87 to 90 dB(A) and the exposure time was 30 days of 8 hours. The numbers of lost outer hair cells were greater than in control animals, thus establishing a relation between the number of lost hair cells and the total noise dose. A comparison between the results obtained here and results obtained in laboratory experiments shows that although many physical sound parameters may be identical, the effect on the hair cells can be quite different. In particular, the total noise dose is not a parameter which can be directly related to hair cell loss. The most probable explanation for the difference in damage between the laboratory and workshop animals seems to be the rest periods of 16 hours between each of the 8-hour exposure periods.

A 10-year study of the 137Cs distribution in soil and a comparison of Cs soil inventory with precipitation-determined deposition.

During a 10-year period, 1988-1998, surface soil samples have been collected at Blentarp in southern Sweden and analysed for 137Cs from the Chernobyl accident and from the nuclear weapons tests. The distance between the sampling plots on the different sampling occasions has been no more than 3 m. The results show that the depth distribution of 137Cs is very similar for each of the sampling occasions, indicating that the caesium migration at this site is very small. The total activity measured in the soil cores is in agreement with the calculated activity of 137Cs deposited at the site after nuclear weapons tests and the Chernobyl accident, based on air activity concentration and the amount of precipitation. The calculated deposition of 137Cs originating from the bomb tests amounts to 1.41 kBq m-2 for the period 1962-1986, which is in agreement with the activity of nuclear weapons fallout measured in the soil samples (1.60 kBq m-2 as a mean value of the first four years of sampling). The calculated activity of 137Cs of Chernobyl origin was 0.79 kBq m-2, which agrees well with the value of 0.79 kBq m-2 measured in the soil samples in 1988.

Studies of the radon concentration in drinking water from the horst Söderåsen in southern Sweden.

The radon activity concentration in ground water from drilled and dug wells on the horst Söderåsen in Southern Sweden has been determined with two different methods, gamma activity measurements with a germanium HPGe detector and alpha activity measurements with plastic track detectors. The results are consistent. High activity concentration is connected to granite bedrock. Dug wells have low concentrations and no trivial correlation between concentration and depth of the well is found. Large local variations exist. Activity concentrations > 700 Bq/l appear to be associated with leakage from layers of volcanic origin. The concentration from drilled wells is found to be quite constant over a 3 year period but short time variations appear to be significant. Evaporation from the open surface of a normal cooking vessel is slow with an activity gradient delta A/A of about 0.1-0.2 per hour at room temperature whereas even modest heating of water in e.g. a coffee machine is very efficient and reduces the radon activity concentration by > 90% in one process.

Long-term study of 99Tc in the marine environment on the Swedish west coast.

The activity concentration of (99)Tc in brown seaweed (Fucus vesiculosus and Fucus serratus) and seawater were analysed in samples collected in 1991, 1995 and 2001 at several stations along the Swedish west coast. In addition to these locations, a well-defined site (Särdal, 56.76 degrees N, 12.63 degrees E) was included with (99)Tc activity concentration data in seaweed from 1967 to 2000. Over the years, the major source of (99)Tc in the coastal waters of western Sweden has been the radioactive liquid discharge from the nuclear fuel reprocessing plant in Sellafield (UK) transported via ocean currents in the North Sea. The (99)Tc activity concentration in seaweed at the Särdal site increased from approximately 30 Bq kg(-1) up to 230 Bq kg(-1) (dry weight) between 1997 and 2000 due to the Sellafield EARP (Enhanced Actinide Removal Plant) discharges in 1995-1996, yielding an approximate transport time of 4-5 years between the Irish Sea and the Kattegat. Due to the very sharp gradient in (99)Tc concentration between the Baltic Sea and the North Sea, (99)Tc is presently one of the best transit tracers for the recent ventilation events in the Baltic Sea.

Application of accelerator mass spectrometry (AMS) for high-sensitivity measurements of 14CO2 in long-term studies of fat metabolism.

Long-term measurements of 14C in CO2 expired after ingestion of 14C-labelled triolein were performed using accelerator mass spectrometry (AMS). About 30% of a given amount of 14C-labelled triolein was catabolized rapidly, while the remaining 70% had a very slow turnover. The study shows the potential of the AMS technique for the study of the long-term biokinetics of 14C-labelled pharmaceuticals. The AMS technique allows the administered activity to be reduced by several orders of magnitude without compromising the study. It may also allow studies of rare drug metabolites.

Comparison between stationary and personal noise dose measuring systems.

In most of the investigations which have been made to survey occupational noise, a stationary sound level meter has been used either alone, or in combination with a stationary dosimeter. In this investigation, which was performed in a ship-building yard, an ear-borne noise dosimeter has been used. The Leq values which were obtained have been compared with those of the pocket-borne dosimeters. In many processes, considerable differences exist between pocket-borne and ear-borne dosimeters.

Comparison of the hearing threshold measured by pure-tone audiometry and by Békésy sweep audiometry.

The hearing thresholds of 115 subjects, workers in a shipyard, were determined both by Békésy sweep audiometry and by conventional individual pure-tone audiometry at fixed audiometric frequencies. The Békésy method gave the lowest values for the hearing thresholds. It has been possible to find a useful linear relation between pure-tone and Békésy hearing thresholds. With the help of a retest experiment it has been established that the standard deviations of hearing thresholds, obtained under similar conditions in a pure-tone investigation, are about twice as large as those obtained in a Békésy investigation.

Noise dose measurements with stationary and ear-borne microphones.

Precision measurement of noise doses with stationary and mobile, ear-borne, microphones were made on ten workers (emery-grinders, welders and platers). The workers selected in each group differed from one another in the amount they moved about during their working day. The differences in the reverberant field at their working places were also taken into account. Very large noise dose differences, up to 20 dB, between stationary and mobile dose measurements were found and it was not possible to find any correction factors for these differences.

The reliability of Békésy sweep audiometry recording and effects of the earphone position.

The hearing thresholds of subjects with hearing impairment of different severity were tested several times. The reliability of the hearing threshold measurements were analysed and compared to the inter-aural variations, the learning effects, the degree of noise-induced hearing impairment and the application of the earphones. The main factor determining the reliability of the hearing threshold is the application of the conventional earphone. A preliminary test-retest with the earphone adapted to an ear speculum for sound transmission to the external ear canal suggests that the precision of the Békésy sweep hearing threshold measurement can obviously be increased in the frequency range of 2 to 8 kHz.