Sick building syndrome: an emerging stress-related disorder?

BACKGROUND: This study examined the role of work-related psychosocial stress in the aetiology of sick building syndrome and tested the hypothesis that in buildings with no recognized environmental problems, health complaints typical of the syndrome were primarily stress-related. METHOD: A case-control study used data from confidential questionnaires to assess symptoms and perception of the physical and psychosocial environment among 2160 subjects in 67 offices. Working conditions were also inspected and indoor air quality monitored. RESULTS: We found an incremental trend in prevalence of sick building syndrome among office workers who reported high levels of physical and mental stress, and decreasing climate of co-operation. This association was confirmed after multivariate adjustment for significant personal and environmental exposure factors. Using a subsample, we further modelled interaction between stress and the other covariates but none achieved statistical significance. CONCLUSION: Our study confirmed stress to be a significant and independent determinant of the health complaints, and that symptoms compatible with the sick building syndrome in many cases were stress-related. Our findings underscore the importance of personal and organizational stress management to prevent ill health at the office.     

Stress–Strain Behavior During Compression of Polycrystalline La1−xCaxCoO3 Ceramics

Mechanical stress–strain behavior of LaCoO₃, La_0.8Ca_0.2CoO₃, and La_0.7Ca_0.3CoO₃ was studied under compression at 25° and 300°C. A hysteresis in the stress–strain relationship due to reorientation of ferroelastic domains (deformation twins) was observed, and a remanent strain is measured after unloading. The cohersive stress, defined as the maximum in effective elastic compliance during first loading, increases with substitution of Ca for La and decreases with increasing temperature. Domain reorientation was confirmed by X-ray diffraction of surfaces parallel and perpendicular to the loading direction. LaCoO₃ can be regarded as a soft ferroelastic material while the 30% Ca-substituted material is a hard ferroelastic. The hysteresis of the stress–strain relationship was clearly dependent on both composition and temperature.     

The investigation of chronic constipation for surgical management

Organic solvents, such as ethanol or dimethyl sulphoxide (DMSO), have been used in liquid embolic agents. To investigate the effects of these solvents on the cerebral blood vessels and cerebral tissue, we subjected Wistar rats weighing 250-300 g to internal carotid artery infusion of 0.2 ml diluted ethanol (10%, 40% or 70%) or anhydrous DMSO (100%). Some rats were sacrificed 5 min after the infusion and the remainder at 10 days. Rats injected with ethanol at high concentration or DMSO showed extensive exudation of Evans blue at the site of injection 5 min after infusion, together with full-thickness necrosis of the wall of vessels and swelling of brain cells. In contrast, rats injected with 10% or 40% ethanol solution showed necrosis of only the intimal layer and partial necrosis of the medial layer and no brain swelling was observed. These findings suggest that ethanol at low concentration can be used as a relatively safe solvent for liquid embolic substances.     

Recovery of 15N-labelled fertilizer applied to winter wheat and perennial ryegrass crops and residual 15N recovery by succeeding wheat crops under different crop residue management practices

The recovery of ¹⁵N-labelled fertilizer applied to a winter wheat (120 kg N ha^–1) and also a perennial ryegrass (60 kg N ha^–1) crop grown for seed for 1 year in the Canterbury region of New Zealand in the 1993/94 season was studied in the field. After harvests, ryegrass and wheat residues were subjected to four different residue management practices (i.e. ploughed, rotary hoed, mulched and burned) and three subsequent wheat crops were grown, the first succeeding wheat crop sown in 1994/95 to examine the effects of different crop residue management practices on the residual ¹⁵N recovery by succeeding wheat crops. Total ¹⁵N recoveries by the winter wheat and ryegrass (seed, roots and tops) were 52% and 41%, respectively. Corresponding losses of ¹⁵N from the crop-soil systems represented by un-recovered ¹⁵N in crop and soil were 12% and 35%, respectively. These losses were attributed to leaching and denitrification. The proportions of ¹⁵N retained in the soil (0-400 mm depth) at the time of harvest of winter wheat and ryegrass were 36% and 24%, respectively. Although the soil functioned as a substantial sink for fertilizer N, the recovery of this residual fertilizer by subsequent three winter wheat crops was low (1-5%) and this was not affected by different crop residue management practices.     

Turbulent flow generated in an annulus by a rotating screen

Summary The computational method for treating curved channel flow and flow in annuli driven by rotating screens is extended to cover turbulent flow, by making the viscosity a function of the average perimeter friction viscosity and using appropriate boundary conditions near the rigid walls, which are consistent with the logarithmic law. Although the turbulent flow model is very primitive, it serves to illustrate the big influence of the secondary flow on the obtained values of velocity distribution and friction factor.     

Chemical characterization of medium‐chain‐length polyhydroxyalkanoates (PHAs) recovered by enzymatic treatment and ultrafiltration

BACKGROUND: Medium‐chain‐length polyhydroxyalkanoates (PHAs) are biodegradable polyesters accumulated intracellularly as energy resources by bacterial species such as Pseudomonas putida. The most popular method for PHA recovery is solvent extraction using trichloromethane (chloroform) and methyl alcohol (methanol). An alternative method is enzymatic treatment, which eliminates usage of these hazardous solvents. This research focuses on the characterization of PHAs recovered by enzymatic treatments and ultrafiltration. Comparisons are made with conventional solvent extracted PHA. RESULTS: The purity of PHA in water suspension recovered by enzymatic treatments as analyzed by gas chromatography was 92.6%. Enzymatically recovered PHA was comparable to conventional solvent‐extracted PHA, which had a purity of 95.5%. PHA was further characterized for functional group analysis, structural composition analysis and molecular weight determination. It was found that the molecular weight of the PHA recovered by enzymatic treatment was less than solvent‐extracted PHA, probably due to degradation of the lipopolysaccharide layer. However, functional group and structural composition analyses showed similar results for PHA recovered by both methods. CONCLUSION: PHAs recovered through enzymatic digestion treatment have good comparability with solvent‐extracted PHAs. Thus enzymatic digestion has great potential as an alternative recovery method. Copyright © 2007 Society of Chemical Industry     

The effects of temperature on the water weakening of chalk by seawater

Seawater is injected into the high temperature North Sea chalk reservoirs to improve oil recovery with great success. Increased compaction of the rock, which also is a significant contribution to the oil displacement, is observed in the water-flooded area. Very recent laboratory studies at high temperature documented that enhanced compaction took place when chalk cores were flooded by seawater under stress. The special composition of seawater, regarding reactive ions towards the chalk surface, appeared to be the reason. In this paper, two different water-weakening mechanisms are discussed: (1) Substitution of Ca²⁺ at the inter-granular contacts by Mg²⁺ and (2) Chemical dissolution. The effect of temperature is opposite for the two mechanisms. The impact of temperature on chalk compaction is studied both in a static (cores aged in water) and dynamic (cores flooded with water) way by performing hydrostatic tests by use of standard triaxial cells. Distilled water was used as a reference fluid in the static tests at 80–130 °C. The mechanical strength of chalk containing seawater was opposite to chalk containing distilled water. With seawater, the chalk became weaker as the temperature increased, while using distilled water, the chalk became stronger as the temperature increased. In the dynamic creep tests, at 50–130 °C, the cores flooded with seawater were significantly weaker than cores flooded with seawater without sulfate, but the difference in mechanical strength decreased as the temperature decreased. The mechanism for enhanced chemical induced weakening of chalk by seawater is discussed.     

A differential-processing extraction approach to text and image segmentation

To efficiently store the information found in paper documents, text and non-text regions need to be separated. Non-text regions include half-tone photographs and line diagrams. The text regions can be converted (via an optical character reader) to a computer-searchable form, and the non-text regions can be extracted and preserved in compressed form using image-compression algorithms. In this paper, an effective system for automatically segmenting a document image into regions of text and non-text is proposed. The system first performs an adaptive thresholding to obtain a binarized image. Subsequently the binarized image is smeared using a run-length differential algorithm. The smeared image is then subjected to a text characteristic filter to remove error smearing of non-text regions. Next, baseline cumulative blocking is used to rectangularize the smeared region. Finally, a text block growing algorithm is used to block out a text sentence. The recognition of text is carried out on a text sentence basis.     

A goal oriented approach to software testing

There is a tendency to distribute the testing and validation effort in a software project uniformly over all system functions. However, to improve systems reliability and safety, testing effort must be focused on the functions with the highest failure consequences. This paper describes a method that computes the number of test cases given the accepted risk levels for each function. Input to the method are the total set of functions for the system, the set of possible accidents and their consequences plus the subset of accidents that can be caused by a failure in one particular function. Failure consequences and functions usage are then used to find the Potential Annual Loss Exposure (PALE) by using a simple diagram developed by AFSC. Given the PALE value, system functions can be ranked according to their risk. It is then possible to set goals for their failure probabilities and to compute the number of test cases needed for each function.     

An unusual CT and MR appearance of a posterior fossa dermoid

A study was made of the effect of transcutaneous diaphragmatic electrostimulation (2 mA, 0.3 ms, 20-30 V) on the external respiratory function in 12 asthmatic patients with respiratory insufficiency. The course comprised 7 daily sessions for 20 min. The improvement in respiratory function parameters was observed in the majority of the patients. The effect of electrostimulation was related to the quantity of the procedures.