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PubMed2006

Indoor climate, psychosocial work environment and symptoms in open-plan offices.

To study the indoor climate, the psychosocial work environment and occupants' symptoms in offices a cross-sectional questionnaire survey was made in 11 naturally and 11 mechanically ventilated office buildings. Nine of the buildings had mainly cellular offices; five of the buildings had mainly open-plan offices, whereas eight buildings had a mixture of cellular, multi-person and open-plan offices. A total of 2301 occupants, corresponding to a response rate of 72%, completed a retrospective questionnaire. The questionnaire comprised questions concerning environmental perceptions, mucous membrane irritation, skin irritation, central nervous system (CNS) symptoms and psychosocial factors. Occupants in open-plan offices are more likely to perceive thermal discomfort, poor air quality and noise and they more frequently complain about CNS and mucous membrane symptoms than occupants in multi-person and cellular offices. The association between psychosocial factors and office size was weak. Open-plan offices may not be suited for all job types. PRACTICAL IMPLICATION: Open-plan offices may be a risk factor for adverse environmental perceptions and symptoms.

Cross-Sectional Studies↗
PubMed1994

Distribution of P and hobo mobile elements in environmentally manipulated long-term Drosophila melanogaster cage populations.

The copy number and the chromosome positions of the P and hobo insertions were determined by means of in situ hybridization to polytene chromosomes, in five long-term Drosophila melanogaster cage populations kept for 18 years under different culture conditions (temperature and relative humidity). The analysis revealed that the copy number of both P and hobo elements were similar between the populations kept under the same culture conditions and significantly different among the populations maintained under different culture conditions. A tendency for similar distribution of these elements along the major chromosome arms was also observed in the populations of the same environmental manipulation. The distribution of the insertions along the chromosomes was not random for both the P and hobo elements; sites with high insertion frequencies were found (hot spots of occupation). Some of them were common in all cage populations while others were characteristic of the populations kept under the same conditions. Finally, fixed sites of occupation were also observed in all populations and refer mostly to hobo distribution. The data are discussed on the basis of the possible involvement of the P and hobo elements, in some way, to the adaptation process and speciation.

Animals↗
PubMed1986

Contact lens wear in dry environments.

The relation between relative humidity at the place of work and subjective discomfort as well as a number of objective parameters was studied in 34 contact lens wearers. Subjects in a low relative humidity (less than about 30%) showed significantly shorter BUT on the lens and more prominent lens deposits than subjects in a higher relative humidity (greater than 40%). A short BUT on the lens was associated with lens deposits (and vice versa) and restricted lens movements. Discomfort was particularly prominent when humidity was less than about 25%, when BUT on the lens was less than 20 sec, and when lens deposits were present. An experiment where relative humidity was manipulated between about 20 and 50% showed that subjects with a short BUT on the lens and prominent lens deposits were much more sensitive to a low relative humidity than other subjects. Enzymatic cleaners, frequent lens replacements, and loose fits were valuable to lessen discomfort.

Adult↗
PubMed1986

Eye symptoms and signs in buildings with indoor climate problems ('office eye syndrome').

Break-up time measurements and Lissamine green staining were performed on 169 office workers in 4 town halls in Copenhagen where the occupants complained about the indoor air quality. In a questionnaire investigation one year before the study it was found that 25% of all the employees had eye irritation several times a week. A statistically significant association (P less than 0.025) was found between eye irritation and unstable precorneal film (reduced break-up time) and/or lissamine green stained epithelial damage. There was a significant rank correlation between eye irritation and different degrees of dry eyes (P less than 0.00006). The investigation proved that eye irritation associated with indoor climate problems can be related to objective pathological changes in the eyes as found in the dry eyes. The findings constitute a new syndrome which I propose to name the 'office eye syndrome'.

Adult↗
PubMed1989

Foam at inner eye canthus in office workers, compared with an average Danish population as control group.

Foam formation in the eye canthus is well-known. The presence of foam was observed in 169 office workers in 4 town halls in Copenhagen County compared with 112 control persons from the general population in the same area. The presence of foam depends on age and gender. A significant increase with age was observed in the control population (P = 0.0078). In both groups, females had a significantly lower occurrence of foam than males (P = 0.0043, P = 0.010). This difference was mainly caused by the use of eye make-up. After correction for age, gender and use of eye make-up, the prevalence of foam was significantly lower in the office population than in the control population (P less than 0.0001). Furthermore, low foam formation was significantly correlated to reported subjective eye irritation in the office population (P = 0.0074), but not in the control population (P = 0.40). Also, significant positive correlation between absence of foam and different degrees of dry eyes (expressed as a combination of premature break-up of the precorneal tearfilm and lissamine green stained epithelial damage of the bulbar conjunctiva) was found both in the office population and in the control population (P = 0.0090, P = 0.0034). However, after correction for the more frequent appearance of dry eyes in the office population, foam was still observed significantly less frequently in the office population than in the control population (P = 0.0001). It is concluded that the decreased foam formation in the office worker constitutes a key symptom in the development of 'office eye syndrome'. In what way the office environment influences the foam formation is unknown. Possible mechanisms are discussed.

Adult↗
PubMedDate not supplied

Neutron energies in medical electron accelerator rooms.

Two experimental methods are described for obtaining average energies of neutron spectra produced by an electron accelerator in a medical treatment room. In the first method, the dose equivalent is measured by means of indium activation foils in an Andersson-Braun moderator. Fluences are determined by the usual activation foil techniques. These data lead to the conversion factor, neutrons/(cm2s) per mrem/h, which uniquely defines the effective energy of the unknown spectrum. In the second method, the fast neutron broad-beam attenuation in polyethylene is obtained from measurement of the thermalized fluence versus depth curve, whose slope in the exponential region parallels that of the fast neutron spectrum. It was found for a 24-MV linear accelerator that the effective energy varied from 0.28 MeV at the isocenter under closed collimators to 0.016-0.024 MeV in the entrance maze. These results compare favorably with other measurements and calculations. It is concluded that the dose equivalent can be measured to within +/- 50% with an activation foil in an Andersson-Braun moderator and that the characteristic energy obtained by attenuation at the isocenter closely approximates the average energy of the neutron spectrum escaping the treatment head.

Electrons↗
PubMedDate not supplied

Approximations to saturation curves in gas-filled parallel-plate ionization chambers.

Saturation curves were measured for air and nitrogen in the exposure rate range from approximately 1 to approximately 500 R/min. Because of the differences between the ion-ion versus electron-ion recombination processes, the air and nitrogen saturation curves differ considerably even when measured under identical chamber and exposure rate conditions. A comparison between our experimental data and various approximations to saturation curves in air, developed by others, is given. It is then shown that the air saturation curve can be approximated by a sum of three simple exponential functions.

Air↗
PubMed1986

Space variances in the mean-square pressure at the boundaries of a rectangular reverberation room.

It was found that it was possible to reduce the number of samples needed for power measurements by sampling at the boundaries in a reverberation room. The space variances in the mean-square pressure of oblique wave fields in a rectangular reverberation room were calculated. The sound source was assumed to be a narrow-band noise source. Space variances throughout the room sigma 2A, on the floor sigma 2B, on the edge sigma 2C, and at the corner sigma 2G were compared with each other numerically. The numerical results confirmed that the relation sigma 2G less than sigma 2C less than sigma 2B less than sigma 2A holds well. Particularly, in a rectangular reverberation room, under the condition that the receiver position is fixed at the corner of the room (corner method), the number of samples reduces to 1/2-1/3 the number of samples needed under the condition that both receiver positions and source positions are changed throughout the room. Some experimental results regarding the power measurements by the corner method are also shown. The experimental results confirmed the suitable estimation of the power for a noise source at low frequencies.

Acoustics↗
PubMed1986

Nonlinear response in evaluating the subjective diffuseness of sound fields.

Tests were conducted to determine which horizontal reflection angles are most effective in stimulating subjective diffuseness for a listener in a room. Paired comparison tests were carried out where subjects were asked to judge in which of two sound fields they perceived more diffuseness. Results show that the most effective horizontal angle depends on the frequency of the one-third-octave-band noise, as is indicated by the interaural cross correlation. The remarkable finding in this investigation is that the scale value of subjective diffuseness may be formulated in terms of the 3/2 power of the magnitude of interaural cross correlation (IACC) and that the scale value does not vary with the frequency of the bandpass noise source.

Acoustics↗
PubMed1986

Predictors of speech intelligibility in rooms.

Three different types of acoustical measures were compared as predictors of speech intelligibility in rooms of varied size and acoustical conditions. These included signal-to-noise measures, the speech transmission index derived from modulation transfer functions, and useful/detrimental sound ratios obtained from early/late sound ratios, speech, and background levels. The most successful forms of each type of measure were of similar prediction accuracy, but the useful/detrimental ratios based on a 0.08-s early time interval were most accurate. Several physical measures, although based on very different calculation procedures, were quite strongly related to each other.

Acoustic Stimulation↗
PubMed1986

Speech intelligibility studies in classrooms.

Speech intelligibility tests and acoustical measurements were made in ten occupied classrooms. Octave-band measurements of background noise levels, early decay times, and reverberation times, as well as various early/late sound ratios, and the center time were obtained. Various octave-band useful/detrimental ratios were calculated along with the speech transmission index. The interrelationships of these measures were considered to evaluate which were most appropriate in classrooms, and the best predictors of speech intelligibility scores were identified. From these results ideal design goals for acoustical conditions for classrooms were determined either in terms of the 50-ms useful/detrimental ratios or from combinations of the reverberation time and background noise level.

Adolescent↗
PubMed1986

A design for a general digital filter for state estimation of an arbitrary stochastic sound system.

This article describes a new attempt at the design of a general digital filter for the state estimation of a nonstationary nonlinear stochastic sound system. A recursive algorithm for estimating the higher-order statistics of arbitrary-function type, mean, and variance is obtained by introducing a new expansion form of Bayes' theorem. Further, the state probability density function (PDF) can also be estimated in a unified form of orthogonal or nonorthogonal series expansions by using these estimates. This method is widely applicable for cases where the random-noise fluctuation is non-Gaussian. The estimation algorithm proposed in this article agrees completely with a well-known Kalman filtering theory [J. Basic Eng. 82, 35-45 (1960); Kalman and Buchy, J. Basic Eng. 83, 95-108 (1961)], as a simplified special case when the stochastic system is of linear type with Gaussian random excitation. The validity and effectiveness of the proposed theory were confirmed experimentally by applying it to actually observed room acoustic data and road-traffic noise data.

Algorithms↗
PubMed1986

An investigation of the sound field above the audience in large lecture halls with a scale model.

Measurements of steady-state sound pressure levels above the audience in large lecture halls show that the classical equation for predicting the sound pressure level is not accurate. The direct field above the seats was measured on a 1:10 scale model and was found to be dependent on the incidence angle and direction of sound propagation across the audience. The reverberant field above the seats in the model was calculated by subtracting the direct field from the measured total field and was found to be dependent on the magnitude and particularly on the placement of absorption. The decrease of sound pressure level versus distance in the total field depends on the angle (controlled by absorption placement) at which the strong reflections are incident upon the audience area. Sound pressure level decreases at a fairly constant rate with distance from the sound source in both the direct and reverberant field, and the decrease rate depends strongly on the absorption placement. The lowest rate of decay occurs when the side walls are absorptive, and both the ceiling and rear wall are reflective. These consequences are discussed with respect to prediction of speech intelligibility.

Climate↗
PubMed1987

The role of tactile aids in providing information about acoustic stimuli.

Devices that convert sound patterns into patterns of vibrotactile stimulation have been shown in laboratory and clinical studies to enable persons to appreciate many aspects of the acoustic environment, and thus are of potential benefit to deaf persons. In the present article, a framework is outlined for describing normal listening situations as a hierarchy of tasks requiring increasingly complex analysis of the acoustic waveform, including sound detection, environmental sound identification, syllable rhythm and stress categorization, phoneme and word identification, and comprehension of connected speech. The types of benefits provided by tactile aids in each of these tasks are exemplified using data from studies of single-channel commercially available devices and multichannel tactile vocoders in our own and other laboratories. The discussion of these data addresses such issues as the features of the acoustic environment that can or should be transmitted through a tactile aid, the differences in the information transmitted by commercially available versus experimental laboratory devices, the comparison of tactile aids and cochlear implants, and the technical problems that remain to be overcome in the design and evaluation of improved vibrotactile aids.

Acoustic Stimulation↗
PubMed1982

Influence of environmental storage relative humidity on biological indicator resistance, viability, and moisture content.

The effect of environmental storage relative humidity (RH) on the moisture content, viability, and moist heat and gaseous ethylene oxide (EO) resistance of biological indicators (BIs) was evaluated. No statistically significant difference was observed between the initial Bacillus stearothermophilus spore population and the spore population of BIs stored at 20 degrees C and 0, 20, 44, of 55% RH or under ambient, 4 degrees C, or -20 degrees C conditions after 12 months. A statistically significant decrease in moist heat resistance from initial starting levels was found for BIs stored at 20 degrees C and either 0 or 20% RH. There was a statistically significant decrease in the B. subtilis BI spore population, compared with initial levels, when the BIs were stored at 20 degrees C and 0% RH concomitant with a significant increase in their EO resistance. BI storage at 20 degrees C and 20 or 44% RH, or under ambient, 4 degrees C, or -20 degrees C conditions, had no significant effect on EO resistance. BIs stored at 20 degrees C and 66% RH demonstrated a significantly lower EO resistance compared with starting levels.

Cell Survival↗
PubMed1984

Bacterial endotoxin isolated from a water spray air humidification system as a putative agent of occupation-related lung disease.

Outbreaks of hypersensitivity pneumonitis or humidifier fever were attributed to the inhalation of organic material aerosolized by a chilled-water spray humidification system. The purpose of this study was to isolate and characterize the serologically detectable antigen(s) present in extracts obtained from the humidification system. By using bicarbonate or phenol-water extractions or both, the antigen was isolated and characterized, using colorimetry, gas-liquid chromatography, reverse-phase high-performance liquid chromatography, and X-ray fluorescence. Carbohydrates, hexosamines, phosphorus, and even-numbered saturated and unsaturated fatty acids were constituents of the serologically detectable antigen. When tested in in vivo and in vitro assays, the antigen had demonstrable endotoxin activity. All subjects with biopsy-proven lung disease and a majority of subjects suspected of having lung disease had antibodies directed toward the purified endotoxin. The data strongly suggest that an aerosolized bacterial endotoxin is a putative agent inducing lung disease.

Alveolitis, Extrinsic Allergic↗
PubMed1989

Environmental regulation of expression of virulence determinants in Bordetella pertussis.

The trans-activator vir is required for expression of all virulence-associated genes in Bordetella pertussis. The nature of the global regulation of these factors by vir and environmental signals was examined by Northern blot analysis and with beta-galactosidase transcriptional fusions in five vir-regulated genes. Northern blots suggested that vir regulates at the level of transcription since Vir- organisms did not exhibit detectable mRNA from vir-regulated loci. Environmental signals such as high levels of salts, nicotinic acid, and 6-chloronicotinic acid or growth at low temperatures were examined. Of all of the cations and anions examined, only SO4 ions eliminated transcription of vir-regulated genes and reduced transcription of vir itself, suggesting that global regulation is obtained by modifying expression of the essential component, vir. Organisms grown on 6-chloronicotinic acid or quinaldic acid did not have detectable transcription from vir-regulated loci. Modulation by nicotinic acid, on the other hand, was strain dependent, acting at the level of transcription in strain 18-323 but not in Tohama I derivatives. Growth at lower temperatures reduced, but did not eliminate, transcription from vir-regulated loci. At 28 degrees C the ratio of pertussis toxin mRNA to recA mRNA (a non-vir-regulated factor) was equivalent to that at 37 degrees C, suggesting that transcription at low temperatures is reduced in a proportional manner and need not involve vir.

Bordetella pertussis↗
PubMed2000

Use of a repetitive DNA probe to type clinical and environmental isolates of Aspergillus flavus from a cluster of cutaneous infections in a neonatal intensive care unit.

Aspergillus flavus is second to A. fumigatus as a cause of invasive aspergillosis, but no standard method exists for molecular typing of strains from human sources. A repetitive DNA sequence cloned from A. flavus and subcloned into a pUC19 vector, pAF28, was used to type 18 isolates from diverse clinical, environmental, and geographic sources. The restriction fragment length polymorphisms generated with EcoRI- or PstI-digested genomic DNA and probed with digoxigenin-labeled pAF28 revealed complete concordance between patterns. Eighteen distinct fingerprints were observed. The probe was used to investigate two cases of cutaneous A. flavus infection in low-birth-weight infants in a neonatal intensive care unit (NICU). Both infants were transported by the same ambulance and crew to the NICU on the same day. A. flavus strains of the same genotype were isolated from both infants, from a roll of tape used to fasten their umbilical catheters, from a canvas bag used to store the tape in the ambulance, and from the tape tray in the ambulance isolette. These cases highlight the need to consider exposures in critically ill neonates that might occur during their transport to the NICU and for stringent infection control practices. The hybridization profiles of strains from a second cluster of invasive A. flavus infections in two pediatric hematology-oncology patients revealed a genotype common to strains from a definite case patient and a health care worker. A probable case patient was infected with a strain with a genotype different from that of the strain from the definite case patient but highly related to that of an environmental isolate. The high degree of discrimination and reproducibility obtained with the pAF28 probe underscores its utility for typing clinical and environmental isolates of A. flavus.

Ambulances↗