bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of two cohorts of workers exposed to methyl methacrylate in acrylic sheet production
Authors: Tomenson J A , Bonner S M , Edwards J C , Pemberton M A , Cummings T F , Paddle G M
Published: July 2002

OBJECTIVES

To study mortality among 4324 workers at two United Kingdom factories, Darwen, Lancashire and Wilton, Cleveland, producing polymethyl methacrylate (PMMA) sheet. The Darwen factory is still active, but the Wilton one was closed in 1970. Also, to investigate patterns of mortality after exposure to methyl methacrylate; in particular, mortality from colon and rectal cancer.

METHODS

All male employees at the Darwen factory with a record of employment in 1949–88 and all men ever employed at the Wilton factory (1949–70) were investigated. The vital status of both cohorts was ascertained on 31 December 1995. The exposure of 1526 subjects at the Darwen plant who were engaged from 1949 onwards could be characterised. The mean duration of exposure was 7.6 years at 13.2 ppm (8 hour time weighted average), although exposures in some work groups were as high as 100 ppm. It was not possible to calculate the cumulative exposure of workers first employed at the Darwen plant before 1949 or workers at the Wilton factory.

RESULTS

In the Darwen cohort, 622 deaths were identified and a further 700 deaths in the Wilton cohort. Mortalities for the cohort were compared with national and local rates and expressed as standardised mortality ratios (SMRs). In the subcohort of Darwen workers with more than minimal exposure to MMA, reduced mortalities compared with national and local rates, were found for all causes (SMR 94), and colorectal cancer (SMR 92), but mortality from all cancers was slightly increased (SMR 104). No relations were found with cumulative exposure to MMA. In the subcohort of Wilton workers, mortality from all causes of death was significantly reduced (SMR 89), but mortality from all cancers (SMR 103) and colorectal cancer (SMR 124) were increased. The excess of colorectal cancer was confined to employees with less than 1 year of employment.

CONCLUSION

The study provided no clear evidence that employment at the factories or exposure to MMA had adversely affected the mortalities of workers.
Two cases of paraoccupational asthma due to toluene diisocyanate (TDI)
Authors: De Zotti R , Muran A , Zambon F
Published: July 2002

Two cases of paraoccupational asthma caused by toluene diisocyanate (TDI) are reported. The first patient was a metal worker in a machine shop situated near a factory producing polyurethane foam. Symptoms at work were not explainable by any specific exposure to irritants or allergens in the work site. As the patient recalled previous occasional work in the adjacent polyurethane factory with accompanying worsening of respiratory symptoms, a specific inhalation (SIC) test was performed with TDI, which confirmed the diagnosis of TDI asthma. The second case was a woman working part time as a secretary in the offices of her son's factory for varnishing wooden chairs. TDI was present in the products used in the varnishing shed. The SIC test confirmed the diagnosis of TDI asthma, despite the fact that the patient's job did not present risk of exposure to the substance. In both patients, symptoms disappeared when further exposure was avoided. These two cases confirm that paraoccupational exposure to TDI must be considered when evaluating patients with asthma not mediated by immunoglobulin E. They also suggest the need for more prospective studies evaluating the health risk for the general population living near polyurethane factories or other firms that use TDI.
Epidemiological response to a suspected excess of cancer among a group of workers exposed to multiple radiological and chemical hazards
Authors: Baysson H , Laurier D , Tirmarche M , Valenty M , Giraud J M
Published: July 2002

OBJECTIVE

An excess of cancer was suspected by workers of the metallurgy department at the French Atomic Energy Commissariat (CEA) after several deaths from cancer were reported in 1983 and 1984. After a descriptive study performed by the CEA in 1985 the results of which were not conclusive enough to put an end to the controversy, the present cohort study was undertaken in 1989.

METHODS

As no specific exposure, or a precise cancer site was suspected, it was decided to include all subjects who had worked at the metallurgy department for at least 1 year between 1950 and 1968. The cohort was followed up to 31 December 1990. Individual occupational exposures were determined retrospectively for each year from 1950 to 1990, both qualitatively (annual job, and hazard records, and assistance from former workers) and quantitatively (for external radiation). On the basis of these exposures, three types of occupational tasks were identified: handling of chemicals, radionuclides, and external radiation. Standardised mortality ratios (SMRs) were calculated to estimate the risk of death, and the existence of an association between risk of cancer and each of the three tasks was tested.

RESULTS

The cohort included 356 workers, followed up for an average of 30 years (total of 10 820 person-years). The number of deaths from all causes and from all cancer sites were respectively 44 and 21. No excess of cancer deaths was found for the study period (SMR 0.77), nor was there a peak in 1983–4. The risk of death from all cancer sites increased with the duration of exposure to chemicals.

CONCLUSION

The results do not justify the workers' impression of an excess of cancer. They suggest, however, that the duration of work at some tasks that involved handling chemicals may be an indicator of risk of cancer. Communication to the workers during the study played an important part in reducing their concern, contributing to their better understanding of the results.
Polychlorinated dibenzo-p-dioxin and dibenzofuran concentrations in the serum samples of workers at continuously burning municipal waste incinerators in Japan
Authors: Kumagai Shinji , Koda Shigeki , Miyakita Takashi , Yamaguchi Hideki , Katagi Kenichi , Yasuda Nobufumi
Published: July 2002

OBJECTIVES

To find whether concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in serum increased in workers at municipal incinerators that burn continuously.

METHODS

30 Workers employed at three municipal waste incineration plants (incinerator workers) and 30 control workers were studied. The incinerator workers had worn dust masks or airline masks during the periodic repair work inside the incinerators. Previous job, dietary habit, smoking habit, distance from residence to the incineration plant, and body weight and height were obtained from a questionnaire survey. Concentrations of PCDDs/PCDFs were measured in the serum of the workers and the dust deposited in the plants. The influence of various factors on serum concentrations of PCDDs/PCDFs was examined by multiple regression analysis.

RESULTS

Dust analysis showed the greatest amount of octachlorodibenzo-p-dioxin (OCDD), followed by 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD), 1,2,3,4,6,7,8-heptachlorodibenzofuran (HpCDF), and octachlorodibenzofuran (OCDF). The toxicity equivalents (TEQs) of PCDDs and PCDFs in the deposited dust were 4.8, 1.0, and 6.4 ng TEQs/g, respectively, for plants A, B, and C. The mean serum TEQs of PCDDs and PCDFs in the incinerator workers and control workers were 19.2 and 22.9 pg TEQs/g lipid, respectively, for area A, 28.8 and 24.5 pg TEQs/g lipid for area B, and 23.4 and 23.6 pg TEQs/g lipid for area C. No significant differences were found between the incinerator workers and the controls for TEQs of PCDDs and PCDFs separately, and TEQs of PCDDs and PCDFs together. However, the serum 1,2,3,4,6,7,8-HpCDF concentration was significantly higher in the incinerator workers than in the controls for all the three areas. When the exposure index to 1,2,3,4,6,7,8-HpCDF is defined as the product of the concentration of 1,2,3,4,6,7,8-HpCDF in the deposited dust and duration of employment, the concentration of 1,2,3,4,6,7,8-HpCDF in serum increased as the exposure index increased. Multivariate analysis suggested that the serum concentration of HpCDF increased with duration of employment at the incineration plants and OCDF increased with employment of ⩾21 years. The other significant variables (p<0.01 or p<0.001) were area for hexachlorodibenzo-p-dioxin (HxCDD) and tetrachlorodibenzofuran (TCDF), Brinkman index for HpCDD, and body mass index (BMI) for tetrachlorodibenzo-p-dioxin (TCDD), HpCDD, and TEQs of PCDDs.

CONCLUSION

The serum TEQs of PCDDs and PCDFs was not significantly higher among the incinerator workers, but the serum concentration of 1,2,3,4,6,7,8-HpCDF was. This suggests that the incinerator workers had inhaled dust containing PCDDs and PCDFs while working in plants equipped with incinerators that burn continuously.
Fatigue among working people: validity of a questionnaire measure
Authors: Beurskens Anna J H M , Bültmann Ute , Kant IJmert , Vercoulen Jan H M M , Bleijenberg Gijs , Swaen Gerard M H
Published: July 2002

OBJECTIVES

To evaluate the validity of the checklist individual strength questionnaire (CIS) in the working population. This 20 item self reported questionnaire has often been used in patients with chronic fatigue. To date, no research has focused on the validity of the CIS in occupational groups.

METHODS

To evaluate the discriminant validity the CIS was filled out by five groups of employees with expected differences in fatigue. The convergent validity was evaluated by comparing the results of the CIS with the results of three related measures: measured unidimensional fatigue, burnout, and need for recovery.

RESULTS

The CIS was able to discriminate between fatigued and non-fatigued employees in occupational groups. The expected agreement between the results of the CIS and related measures was confirmed.

CONCLUSIONS

The CIS seems to be an appropriate instrument for measuring fatigue in the working population.
Strategy for prevention and control of the risks due to noise
Authors: Malchaire J
Published: July 2002

OBJECTIVES

To propose a strategy for progressively controlling the exposure to noise in industry as much as possible. To propose a method that could, in the first stage, be used by the workers and management themselves to control exposures to noise as much as possible, and then, in later stages, when necessary, progressively call in the assistance of specialists and experts to identify more complex solutions and organise personal protection and medical surveillance.

METHODS

The strategy includes three stages. Stage 1 is observation, simple and easy to use by the workers to recognise the problems, identify straightforward solutions, and call for assistance when needed. Stage 2 is analysis, more complex but more costly, performed with the assistance of occupational health specialists to identify more technical control measures and set up a programme to conserve hearing. Stage 3 is expertise, performed with the assistance of acoustic experts for special measurements and control measures.

CONCLUSIONS

The proposed strategy enriches the assessment procedure that is usually recommended, by providing for one preliminary stage used by the people directly concerned. It explicitly recognises (a) the competence of the workers and management about their working conditions and (b) that knowledge and measurements of acoustics are not an absolute prerequisite for solving—at least partly—noise problems. It attempts to organise in sequence and optimise the cooperation between the workers, the occupational health specialists, and the experts in acoustics.
Lung function over the first 3 years of a professional diving career
Authors: Skogstad Marit , Thorsen Einar , Haldorsen Tor
Published: July 2002

OBJECTIVES

To characterise diving exposure and pulmonary function in professional divers at the start of their formal education and during the first 3 years of their professional career.

METHODS

The study included 87 men at the start of their education as professional divers. At follow up 1 and 3 years after the school 83 and 81 divers respectively were re-examined. Assessment of lung function included dynamic lung volumes and flows and transfer factor for carbon monoxide (TlCO).

RESULTS

69 Divers had preschool SCUBA diving experience and had a median number of 70 dives (range 2–3000) to a median maximal depth of 40 (range 10–73) metres. During the 15 week introductory diving course, they had 44 dives (range 38–50) in the depth range 10–50 metres. The median number of dives over the follow up period was 95 (range 0–722) to a maximal median depth of 38 (range 0–98) metres. At the start of the diving course there were no differences in forced vital capacity (FVC), forced expired volume in 1 second (FEV1), and in TlCObetween the 69 pre-exposed divers and the 18 never exposed divers. The FVC was significantly larger than predicted in both groups. At follow up at 3 years there was a significant reduction in mean (SD) FEV1of 1.8% (6.5), in forced mid-expiratory flow rate (FEF25–75%) of 6.5% (11.7) and in forced expiratory flow at 75% of FVC expired (FEF75%) of 10.4% (16.8). There was no change in FVC. The TlCOwas significantly decreased by 4.6% (8.8). No significant effects were found of cumulative diving exposure, including the number of dives, on the relative changes of any of the lung function variables.

CONCLUSIONS

The results indicate that divers initially belong to a selected group with large FVC. Exposure to diving may contribute to changes in pulmonary function, mostly affecting small airways conductance.
Mortality from cancer and chronic respiratory diseases among workers who manufacture carbon electrodes
Authors: Donato F , Monarca S , Marchionna G , Rossi A , Cicioni C , Chiesa R , Colin D , Boffetta P
Published: July 2002

OBJECTIVES

To investigate the risk of cancer and non-neoplastic respiratory diseases among workers who manufacture carbon electrodes, as this industry entails exposure to mixtures of polycyclic aromatic hydrocarbons.

METHODS

A historical cohort study was carried out of 1006 male workers employed for at least 1 year between 1945 and 1971 in a carbon (graphite) electrode production plant in central Italy, who were followed up for mortality between 1955 and 1996. The ratio of observed to expected deaths (standardised mortality ratios, SMRs) was computed from both national and (for the period 1964–96) regional age and period specific mortalities. A multivariate Poisson regression analysis was performed to investigate the relative risk (RR) of death according to duration of employment and time since first employment in the factory.

RESULTS

A total of 424 workers had died, 538 were still alive, and 44 were lost to follow up. Mortalities from all causes, all cancers, and respiratory tract cancer were in line with the regional figure. An excess was found over the expected deaths from skin cancer including melanoma (SMR 3.16, 95% confidence interval (95% CI) 0.65 to 9.23) and from non-neoplastic respiratory diseases (SMR 1.58, 95% CI 1.16 to 2.11). Poisson regression analysis including age as a covariate showed an increased risk of dying from gastric cancer with increasing duration of employment, and an increase in the RR of dying from lung cancer and from non-neoplastic respiratory diseases with increasing time since first employment, although the linear trend was not significant.

CONCLUSION

This study supports previous findings that working in the carbon electrode manufacturing industry may not increase the risk of dying from respiratory cancer. However, a possible association with non-malignant respiratory diseases cannot be excluded.
Occupational exposure to magnetic fields relative to mortality from brain tumours: updated and revised findings from a study of United Kingdom electricity generation and transmission workers, 1973–97
Authors: Sorahan T , Nichols L , van Tongeren M , Harrington J M
Published: July 2002

OBJECTIVE

To investigate whether risk of brain tumour is related to occupational exposure to magnetic fields.

METHODS

The mortality experienced by a cohort of 83 997 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1973–97. All workers were employed for at least 6 months with some employment in the period 1973–82. Computerised work histories were available for 79 972 study subjects for the period 1971–93. Detailed calculations had been performed by others to enable a novel assessment to be made of exposures to magnetic fields. Two analytical approaches were used, indirect standardisation (n=83 997) and Poisson regression (n=79 972).

RESULTS

Based on serial mortalities for England and Wales, deaths from brain cancer were close to expectation (observed 158, expected 146.4). No significant positive trends were shown for risks of brain tumours either with lifetime cumulative exposure to magnetic fields or with such exposures received in the most recent 5 years.

CONCLUSIONS

There are no discernible excess risks of brain tumours as a consequence of occupational exposure to magnetic fields in United Kingdom electricity generation and transmission workers.
Neurobehavioural changes and persistence of complaints in workers exposed to styrene in a polyester boat building plant: influence of exposure characteristics and microsomal epoxide hydrolase phenotype
Authors: Viaene M K , Pauwels W , Veulemans H , Roels H A , Masschelein R
Published: July 2002

OBJECTIVES

To investigate neurobehavioural effects and the persistence of complaints in workers exposed to styrene relative to exposure characteristics and the enzyme microsomal epoxide hydrolase (mEH) activity.

METHODS

A cross sectional study was performed in a retrospective cohort of workers of a polyester boat building plant 3 years after the main activity shut down in 1989. Workers still currently exposed to a much lower concentration of styrene in air than before (n=27) and formerly exposed workers (n=90) were compared with matched control workers (n=64). Currently and formerly exposed workers laminated 4700 and 3610 hours on average at mean exposure to styrene concentrations of 148 and 157 mg/m3respectively. A structured neurological anamnesis into former and present complaints, the NSC-60 questionnaire, and computer assisted neurobehavioural tests (NES) were administered. The mEH phenotype activity was measured in lymphocytes with a novel gas chromatography-mass spectroscopy (GC-MS) method.

RESULTS

For the period before 1989, currently and formerly exposed workers reported more complaints than control workers which related well with the mean exposure to airborn styrene concentration (p=0.03). Most complaints disappeared after the end of exposure, although the chest, equilibrium, and somatic category scores of NSC-60 and the number of workers reporting diminished sense of smell remained increased in formerly exposed workers (p⩽0.05). Symbol-digit substitution and digit span forwards test results were worse in currently and formerly exposed workers (p⩽0.01). In the combined group of currently and formerly exposed workers, the symbol-digit substitution and colour-word vigilance results related well to duration of exposure (p<0.01 and p=0.03) and mEH phenotype activity (p=0.01 and p=0.05), whereas the digit span forwards results only showed associations of borderline significance (duration of exposure (p=0.08) and mEH phenotype activity (p=0.08)).

CONCLUSION

Most subjective symptoms were reversible but some persisted after the end of exposure to styrene, whereas dysfunction of visuomotor performance and perceptual speed seemed to persist. Duration of exposure at lamination tasks and the interaction, duration of exposure×concentration of exposure, were found to be the best predictors of worsening visuomotor and perceptual speed performances. Activity of the mEH phenotype may play a modulating part in styrene neurotoxicity. The results suggested that less than 10 years of exposure to atmospheric styrene at an average concentration of 155 mg/m3may result in persistent neurotoxic effects.
A case-referent study of cancer mortality among sulfate mill workers in Sweden
Authors: Andersson E , Hagberg S , Nilsson T , Persson B , Wingren G , Torén K
Published: July 2002

OBJECTIVES

To investigate whether workers in Swedish sulfate mills have an increased risk of death from certain malignancies that have previously been linked to the pulping process.

METHODS

Subjects of the study (n=2480) were men aged 40–75 at death during 1960–89 in the parishes surrounding four sulfate mills. Exposure assessment was based on information from the personnel files in the mills— 35% of the subjects were recognised there, and work categories were created.

RESULTS

Among all sulfate mill workers, the odds ratio (OR) (90% confidence interval (90% CI)) for death from lung cancer was 1.6 (1.1 to 2.3), pleural mesotheliomas 9.5 (1.9 to 48), brain tumours 2.6 (1.2 to 5.3), and liver or biliary tract cancer 2.3 (1.0 to 5.2). There was an increased mortality from leukaemia among workers in the soda recovery plant (5.9 (2.6 to 13)) and bleaching plant and digester house (2.8 (1.0 to 7.5)).

CONCLUSIONS

Sulfate mill workers were at increased risk of dying from lung cancer and pleural mesotheliomas, probably due to exposure to asbestos. Increased risks of brain tumours and cancers of the liver or biliary tract were also found but the aetiology is not obvious.
Quantitative thermal perception thresholds relative to exposure to vibration
Authors: Nilsson T , Lundström R
Published: July 2002

OBJECTIVES

To assess the risk of disturbed thermal perception relative to exposure to vibration, to investigate a possible exposure-response relation and to analyse a possible relation between thermal perception and sensory symptoms.

METHODS

The study was based on a cross section of 123 male workers exposed to vibration and 62 male workers who were not exposed. Thermal perception of cold, warmth, and heat pain was bilaterally determined from the thenar eminence by the method of limits. Perception of cold and warmth were also tested in the second digit. Personal energy equivalent exposure to vibration was measured for all subjects. Vibration was measured in accordance with International Standards Organisation (ISO) 5349 and assessed separately for the left and right hand.

RESULTS

Combining exposure times and intensities gave the left hand an 0.80 exposure to vibration compared with the right. The risk of having contracted reduced thermal perception was increased at all test sites. The risk was higher for the thenar measurements than the finger measurements. A yearly extra contribution of 4000 mh/s2in cumulative exposure increases the risk of contracting a wider neutral zone by 18% (95% confidence interval (95% CI) 1.06 to 1.32) for the right and 18% (1.05 to 1.32) for the left hand side. Subjects with symptoms of nocturnal paraesthesia had a rate ratio (95% CI) of 2.80 (1.17 to 6.67) for the right hand and 2.72 (1.12 to 6.63) for the left hand for increased neutral zones at the thenar eminence.

CONCLUSIONS

The results indicate thermal sensory impairment related to cumulative exposure to vibration. The effect appeared at vibration levels below the current guiding standard. Quantitative sensory testing of thermal perception offers the chance to assess this specific hazard to the peripheral sensorineural system associated with hand intensive work entailing vibration.
Nasal, eye, and skin irritation in dockyard painters: Table 1
Authors: Chen R , Semple S , Dick F , Seaton A
Published: July 2002

OBJECTIVES

To determine whether the risk of irritant symptoms in painters is related to their exposure to paint.

METHODS

The prevalences of skin, eye and nasal symptoms were compared in 260 United Kingdom and 109 Chinese dockyard painters, 539 British community controls, and 255 Chinese dockyard controls, relative to their exposure to paints.

RESULTS

Painters showed an excess of irritant symptoms compared with controls. Adjusted relative risks (RRs) (95% confidence interval (95% CI) were: for skin irritation 1.58 (1.19 to 2.08) in British painters and 2.68 (1.73 to 4.09) in Chinese painters; for eye irritation, 1.41 (0.98 to 2.05) and 3.01 (1.90 to 4.76); and for nasal irritation, 1.53 (1.10 to 2.14) and 6.73 (3.53 to 12.82), respectively. Exposure duration-response relations were found for these symptoms; the risks decreased with time after exposure ended.

CONCLUSIONS

Irritant symptoms occur more often in dockyard painters than in controls, and this is likely to be a response to exposure to paint.
Survey of solvent related chronic encephalopathy as an occupational disease in European countries
Authors: Triebig G , Hallermann J
Published: July 2002

OBJECTIVES

To obtain information about solvent related chronic encephalopathy (SRCE) in the countries of the European Union (EU).

METHOD

A survey was conducted in 1998 and 1999 among medical experts, authorities for health and safety, and social security institutions.

RESULTS

SRCE is an acknowledged occupational disease in most of the participating countries. However, the numbers of compensated cases differ considerably. This is mainly a consequence of national social law rather than of differences in the criteria of diagnosis. In countries with relatively high reported incidences—such as Denmark, Finland, Norway, and Sweden—the number of acknowledged cases has declined over the past 5–10 years, although the most important criteria of diagnosis and causality, according to expert opinion, equivalent diagnostic procedures, and measures for prevention within the EU are not comparable.

CONCLUSIONS

There is a need for common guidelines for early diagnosis and the evaluation of causality. Actual figures of SRCE are not suitable to estimate prospective numbers of cases. For this reason a multicentre study in EU states is necessary after a consensus of diagnostic procedure. It is likely that the number of cases will decrease as a result of changes in legislation and preventive measures—such as substitution or reduction of solvents in the products, improvement of technical equipment, and regular health surveillance. Future research activities should focus on follow up studies of prognosis, randomised clinical trials of treatment, investigation of neurotoxic mechanisms, and of the interaction of solvent mixtures.
Identifying populations at risk from environmental contamination from point sources
Authors: Williams F L R , Ogston S A
Published: July 2002

Objectives: To compare methods for defining the population at risk from a point source of air pollution. A major challenge for environmental epidemiology lies in correctly identifying populations at risk from exposure to environmental pollutants. The complexity of today's environment makes it essential that the methods chosen are accurate and sensitive.

Methods: Environmental and mathematical methods were used to identify the population potentially exposed to a point source of airborne pollution emanating from a waste incinerator. Soil sampling was undertaken at 83 sites throughout the city and environs. The concentrations of arsenic and copper were measured at each site. Computer software produced smoothed contour plots of the distribution of arsenic and copper in the soil based on the information derived from the sampling sites. The population at risk was also identified using concentric rings of varying radii, with the source of pollution at the centre. Lastly, we used the sites that had previously been selected and measured the frequency of wind direction, speed and distance from the source of pollution at each site. Theoretical contour plots were constructed using the distance from the source of pollution at each site, with and without incorporating wind frequency as a function of direction.

Results: Each method identified different populations at risk from airborne pollution. The use of circles was a very imprecise way of identifying exposed populations. Mathematical modelling that incorporated wind direction was better. Soil sampling at many sites was accurate, as the method is direct; but it is very costly and the close proximity of high and low concentrations hindered interpretation. The smoothed contour plots derived from the soil sampling sites identified an exposed population that was similar to that derived from the spot sampling.

Conclusions: Using circles as the only means of identifying the exposed population leads to dilution of the potential health effect. The best approach is to use local knowledge about wind direction and speed to estimate the population likely to be at risk; to back up this estimate by judicious use of soil sampling; to use contour mapping to guide the final selection of exposed and non-exposed populations; and finally, to interpret the populations identified as being at risk by incorporating information about other potential sources of pollution (past and present) in the area.
The first observed complex of 11-crown-3 ether. X-ray crystal structure and NMR study of (benzo-11-crown-3)2·LiNCS
Authors: Buchanan G W , Azad M , Yap G PA
Published: July 2002

The title complex crystallizes in the monoclinic P21/c space group, with a = 7.7397(8), b = 18.287(2), c = 17.4726(19) Å, β = 94.008(2)°, and Z = 4. The coordination geometry around the lithium cation is pseudooctahedral. The effects of lithium complexation on the 1H and 13C solution NMR spectra are discussed. In the solid-state 13C NMR spectrum at 300 K, very long aliphatic proton spin lattice relaxation times are observed along with broadening of the aliphatic carbon resonances. These results are attributed to the dipolar washout phenomenon, where the presence of a low amplitude motion of the same frequency as the 1H decoupler, leads to less effective removal of the 1H13C dipolar coupling. At 330 K, there is some sharpening of the aliphatic resonances since there is less interference between the motion and the decoupling frequency.Key words: crown ether analog, lithium complex.
Conformational analysis of the bicyclo - [4.4.1]undecan-11-one ring system
Authors: Parvez Masood , Sorensen Ted S , Sun Fang
Published: July 2002

The first conformational analysis of a bicyclo[4.4.1]undecan-11-one system (1) is presented. Based on low-temperature13C NMR line-broadening measurements and an X-ray structure of the 1,6-dibromo derivative (2), this ketone adopts a chiral conformation with approximate C2symmetry about an axis containing the >C=0 bond. The observed NMR line-broadening results are consistent with a dynamic interchange of M and P enantiomeric C2conformations, or expressed another way, the "effective" development of an additional Cssymmetry plane bisecting the molecule at right angles to the plane containing the one carbon bridge (overall average C2vsymmetry). This process has a ΔHbarrier of 42 kJ mol1for ketone 1 (43 kJ mol1for 2).Key words: bicyclo[4.4.1]undecan-11-one, conformational analysis, NMR line broadening, X-ray structure, enantiomers.
Size and temperature dependence of hydrocarbon solubility in concentrated aqueous solutions of urea and guanidine hydrochloride
Authors: Graziano Giuseppe
Published: July 2002

At 25°C, methane and ethane are more soluble in water than in 7 M aqueous urea or 4.9 M aqueous guanidine hydrochloride (GuHCl); the reverse is true for larger hydrocarbons. In addition, the hydrocarbon solubility in 7 M aqueous urea or 4.9 M aqueous GuHCl increases compared with that in water on raising the temperature in the range of 545°C. These experimental data have not yet been rationalized. Using a well-founded theory of hydrophobic hydration, the present analysis indicates that the transfer of hydrocarbons from water to 7 M aqueous urea or to 4.9 M aqueous GuHCl is favored by the difference in the solutesolvent van der Waals interaction energy, and contrasted by the difference in the work of cavity creation. At room temperature, on increasing the hydrocarbon size, the first contribution rises in magnitude more rapidly than the second contribution, accounting for the threshold size occurrence. Moreover, the second contribution decreases in magnitude with an increase in temperature, becoming less unfavorable, while the first contribution is practically constant in the range of 545°C. The different temperature dependence of the work of cavity creation in such solvent systems is due to the fact that the density of 7 M aqueous urea and 4.9 M aqueous GuHCl decreases more rapidly than that of water when raising the temperature. The relationship between the density of a liquid and the work to create a cavity in it is discussed in detail.Key words: work of cavity creation, solute-solvent van der Waals interaction energy, H-bond reorganization.
An improved trap for large wood-boring insects, with special reference to Monochamus scutellatus (Coleoptera: Cerambycidae)
Authors: Morewood W D , Hein K E , Katinic P J , Borden J H
Published: July 2002

Commercially available multiple funnel traps have three potential limitations for trapping large wood-boring insects: (i) escape by captured insects from the dry collecting cup, (ii) low catches of insects that fall outside the trap, and (iii) poor visual orientation to the narrow funnel column. To test the importance of these limitations, we compared conventional multiple funnel traps to multiple funnel traps with water-filled collecting cups or large bottom funnels and to crossvane traps with a prominent silhouette. The experiment was conducted in a mill yard in the southern interior of British Columbia between 5 July and 2 October 2000. Differences in catch among different trap types indicated that the first and third of the three potential limitations were important for the capture of most target species. Crossvane traps captured significantly greater numbers of most Cerambycidae and Siricidae, and similar numbers of most Buprestidae, compared with the other traps. Of the two most abundant species, Xylotrechus longitarsus Casey was captured in consistently greater numbers in crossvane than in other traps, but Monochamus scutellatus (Say) showed little discrimination early in the flight season and much higher captures in crossvane traps late in the season. The change in behaviour of M. scutellatus may be related to a transition from maturation feeding to searching for oviposition sites.
Possible functions of the ultradense bone in the rostrum of Blainville's beaked whale (Mesoplodon densirostris)
Authors: MacLeod Colin D
Published: July 2002

The rostrum of Blainville's beaked whale, Mesoplodon densirostris, becomes secondarily ossified, particularly in males, as individuals mature. This mesorostral ossification forms the densest bone currently known and represents a considerable investment of resources for this species. Three functions for this mesorostral ossification have been proposed: prevention of damage to the rostrum during aggressive malemale interactions, ballast to aid deep diving, and sound transmission. These functions were assessed using data from museum specimens and observations of this species in the wild. Prevention of damage to the rostrum during aggressive malemale interactions was found to be the most likely function, based on the currently available data.
VARIANTS OF (A,B)-TREES WITH RELAXED BALANCE
Authors: JACOBSEN LARS , LARSEN KIM S.
Published: July 2002

New variants of (a,b)-trees with relaxed balance are proposed. These variants have better space utilization than the earlier proposals, while the asymptotic complexity of rebalancing is unchanged. The proof of complexity, which is derived, is much simpler than the ones previously published. Through experiments, some of the most interesting applications of this data structure are modeled, and it is demonstrated that the new variants are competitive.
DFT TECHNIQUES FOR SIZE ESTIMATION OF DATABASE JOIN OPERATIONS
Authors: SARAÇ KAMİl , EĞECİOĞLU ÖMER , ABBADI AMR EL
Published: July 2002

Novel algorithms based on the Discrete Fourier Transform (DFT) are proposed to estimate the size of relations resulting from join operations. We start with an approach in which the frequency distribution values are transformed using the DFT and the Fourier coefficients are used to construct histograms. Our main contribution is a direct approach which uses the amplitudes of the DFT coefficients iteratively. The proposed algorithm gives the exact join size using logarithmic space for the special case of self join. A generalization to compute the join of arbitrary relations is then used to develop two tree-based techniques that provide a spectrum of algorithms which interpolate storage requirements versus accuracy of the estimation obtained. Finally, we present experimental results to exhibit the effectiveness of our approach.
TRACE FORMULAS AND CONSERVATION LAWS FOR NONLINEAR EVOLUTION EQUATIONS
Authors: GESZTESY F. , HOLDEN H.
Published: July 2002

New trace formulas for linear operators associated with Lax pairs or zero-curvature representations of completely integrable nonlinear evolution equations and their relation to (polynomial) conservation laws are established. We particularly study the Korteweg–de Vries equation, the nonlinear Schrödinger equation, the sine–Gordon equation, and the infinite Toda lattice though our methods apply to any element of the AKNS–ZS class.

In the KdV context, we especially extend the range of validity of the infinite sequence of conservation laws to certain long-range situations in which the underlying one-dimensional Schrödinger operator has infinitely many (negative) eigenvalues accumulating at zero. We also generalize inequalities on moments of the eigenvalues of Schrödinger operators to this long-range setting. Moreover, our contour integration approach naturally leads to higher-order Levinson-type theorems for Schrödinger operators on the line.
TOPOLOGICAL QUANTUM DOUBLE
Authors: BONNEAU PHILIPPE
Published: July 2002

Following a preceding paper showing how the introduction of a t.v.s. topology on quantum groups led to a remarkable unification and rigidification of the different definitions, we adapt here, in the same way, the definition of quantum double. This topological double is dualizable and reflexive (even for infinite dimensional algebras).

In a simple case we show, considering the double as the "zero class" of an extension theory, the uniqueness of the double structure as a quasi-Hopf algebra.

A la suite d'un précédent article montrant comment l'introduction d'une topologie d'e.v.t. sur les groupes quantiques permet une unification et une rigidification remarquables des différentes définitions, on adapte ici de la même manière la définition du double quantique. Ce double topologique est alors dualisable et reflexif (même pour des algèbres de dimension infinie).

Dans un cas simple on montre, en considérant le double comme la "classe zéro" d'une théorie d'extensions, l'unicité de cette structure comme algèbre quasi-Hopf.
DEPOSITION OF HYDROGENATED NANOCRYSTALLINE SILICON CARBIDE BY ECR-CVD
Authors: YU M. B. , YOON S. F. , XU S. J. , CHEW K. , AHN J. , ZHANG Q.
Published: July 2002

In this work we report on the deposition of hydrogenated nanocrystalline silicon carbide (nc-SiC:H) films using an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system with silane (SiH4) and methane (CH4) as source gases. It was found that the conditions of strong hydrogen dilution and high microwave power are necessary for the fabrication of nanocrystalline SiC grains, which are found to be embedded in an amorphous matrix. The films have been studied using high resolution transmission electron microscopy, infrared absorption, Raman scattering and x-ray photoelectron spectroscopy. All the results have confirmed the prescence of SiC nanocrystallites. Very strong photoluminescence (PL) could be observed from these films at room temperature, with a peak energy of 2.64 eV. This energy, being higher than the optical bandgap of 3C-SiC, can be possibly due to quantum size effect in these crystals, which are embedded in an amorphous matrix of larger bandgap. Time-resolved PL at the peak emission energy exhibits a bi-exponential decay process with lifetimes that are in the order of picoseconds and nanoseconds, which are at least 2 orders of magnitude faster than that of bound excition transitions in bulk 3C-SiC at low temperature. The strong light emission and short PL lifetimes observed strongly suggest that the radiative recombination is a result of direct optical transitions in the SiC nanocrystallites. It was found that upon ultraviolet irradiation using an Ar + laser (351 nm), the PL intensity of the films was enhanced. After 20 minutes of irradiation, the PL intensity increased by about three times. This result suggests that the UV light may lead to modification of nonradiative recombination centers in the films.
Stress Rectification in MR Fluids under Tilted Magnetic Field
Authors: Takimoto J. , Takeda H. , Masubuchi Y. , Koyama K.
Published: July 2002

We have studied the shear stress and cluster structure of MR suspensions under tilted magnetic field by experiments, numerical simulations and a simple theory. The shear stress depends on the field direction asymmetrically, and shows a "rectification" effect; the fluids are easier to flow in one direction than in the reverse direction. Dispersed particles form stable chain-like clusters even under the tilted field condition, whose direction has some misalignment with the field direction due to the force exerted by the shear flow.
QUANTUM CRITICAL BEHAVIOR IN KONDO SYSTEMS
Authors: SI QIMIAO , SMITH J. LLEWEILUN , INGERSENT KEVIN
Published: July 2002

This article briefly reviews three topics related to the quantum critical behavior of certain heavy-fermion systems. First, we summarize an extended dynamical mean-field theory for the Kondo lattice, which treats on an equal footing the quantum fluctuations associated with the Kondo and RKKY couplings. The resulting dynamical mean-field equations describe a Kondo impurity model with an additional coupling to vector bosons. Two types of quantum phase transition appear to be possible within this approach — the first a conventional spin-density-wave transition, the second driven by local physics. For the second type of transition to be realized, the effective impurity model must have a quantum critical point exhibiting an anomalous local spin susceptibility. In the second part of the paper, such a critical point is shown to occur in two variants of the Kondo impurity problem. Finally, we propose an operational test for the existence of quantum critical behavior driven by local physics. Neutron scattering results suggest that CeCu 6-x Au x passes this test.
SPIN CORRELATIONS OF THE MAGNETORESISTIVE BILAYER MANGANITE La1.2Sr1.8Mn2O7
Authors: Rosenkranz S. , Osborn R. , Mitchell J. F. , Vasiliu-Doloc L. , Lynn J. W. , Sinha S. K.
Published: July 2002

We review our recent neutron and X-ray scattering studies of the 40% hole doped bilayer manganite La 1.2 Sr 1.8 Mn 2 O 7, which exhibits colossal magnetoresistance above the ferromagnetic transition at T C~113 K. In the paramagnetic region, static diffuse scattering reveals the existence of correlated charges. However, the good agreement of the in-plane spin correlations with the conventional model for quasi two-dimensional XY magnets indicates that the metal-insulator transition is driven by the growth of magnetic correlations. Across the transition, the competition between antiferromagnetic superexchange and ferromagnetic double exchange, observed as canted correlations between spins in neighboring layers within each bilayer, is strongly reduced, indicating a direct link of the double exchange interaction to the hole mobility.
DIRECT QUANTIZATION OF OPEN DISSIPATIVE SYSTEMS
Authors: MAGPANTAY JOSE A.
Published: July 2002

Open dissipative systems subject to a random force are directly quantized. The starting point is the effective action derived using the method of Parisi–Sourlas. Since the effective action is second order, the method of Ostrogradsky was used to quantize the system canonically. In the case of the harmonic oscillator, the relevant Green function can be computed exactly. In the general case, a perturbation expansion, involving time-dependent (memory) terms, can be defined.
DEPENDENCE OF SECOND HARMONIC GENERATION ON SIZE OF NANOCRYSTALLITES OF ZnO
Authors: MITRA ANIRBAN , THAREJA RAJ K.
Published: July 2002

We report second harmonic generation (SHG) from ZnO thin films deposited by the pulsed laser deposition technique at ambient oxygen pressures ranging from 10 mTorr to 1 Torr on glass substrate at room temperature (RT). The dependence of SHG on grain size and thickness of the film is discussed.
A NEW TYPE HYSTERESIS LOOP IN SiN/GdFeCoSi/SiN SANDWICH STRUCTURE
Authors: ZHAO YANLING , WANG SHIQI , SHONO KEIJI , YU XIANGYOU , LU MU , ZHAI HONGRU
Published: July 2002

A new type of inverted hysteresis loop was observed in an amorphous SiN/GdFeCoSi/SiN film, in which a magnetic GdFeCoSi layer with a thickness of 40 nm was sandwiched by SiN capping and buffer layers 5 nm thick. An inverted hysteresis loop with negative remanence appeared, when an applied field was perpendicular to the film plane, with remanance ratio of 0.4 and HC=120 Oe. An FMR experiment study showed that two magnetic phases existed in the system. A major magnetic phase had an easy-plane anisotropy and the other minor magnetic phase had an easy-normal anisotropy. By assuming an antiferromagnetic exchange coupling between them, the inverted loops can be explained.
MICROSTRUCTURE AND PROPERTIES OF FERROELECTRIC Bi4Ti3O12 THIN FILMS
Authors: JIANG B. , PENG J. L. , BURSILL L. A. , WANG H.
Published: July 2002

The film morphology and defect structure of ferroelectric bismuth titanate thin films are studied by high resolution transmission electron microscopy. As-grown and RTA-processed thin films have similar defect structures, consisting of stacking faults and complex intergrowth defect structures. The as-grown specimens prepared at low temperature had smaller particle size with higher density of these defects compared to RTA-processed samples. Detailed atomic structure models for the stacking faults and intergrowth defect structures are proposed and the computer-simulated images are compared with experiment.
RNA MODELING BY COMBINING STOCHASTIC CONTEXT-FREE GRAMMARS AND n-GRAM MODELS
Authors: SALVADOR ISMAEL , BENEDÍ JOSÉ-MIGUEL
Published: July 2002

The RNA sentences present structured regions caused by pairwise correlations, and nonstructured regions where any global relation can be found. In this paper, we present a combination of stochastic context-free grammars (SCFG) and bigram models. The SCFGs are used to represent the long-term relations of the structured part of RNA sequences, while the bigram models are used to capture the local relations of the nonstructured part. A stochastic version of Sakakibara's algorithm is used to study the SCFGs. Finally, experiments to evaluate the behavior of this proposal were carried out.
NONLINEAR COMPUTABILITY BASED ON CHAOS
Authors: MANGANARO GABRIELE , PINEDA DE GYVEZ JOSE
Published: July 2002

Two new computing models based on information coding and chaotic dynamical systems are presented. The novelty of these models lies on the blending of chaos theory and information coding to solve complex combinatorial problems. A unique feature of our computing models is that despite the nonpredictability property of chaos, it is possible to solve any combinatorial problem in a systematic way, and with only one dynamical system. This is in sharp contrast to methods based on heuristics employing an array of chaotic cells. To prove the computing power and versatility of our models, we address the systematic solution of classical NP-complete problems such as the three colorability and the directed Hamiltonian path in addition to a new chaotic simulated annealing scheme.