bluuebunny/crossref_metadata_2025 huggingface dataset:
Projecting mammographic screens
Authors: Parr N. , Boyages J. , Taylor R. , Anura P. , Callaghan T.
Published: October 2002

Objective The purpose of mammographic screening is to reduce mortality from breast cancer. This study describes a method for projecting the number of screens to be performed by a mammographic screening programme, and applies this method in the context of New South Wales, Australia.

Method The total number of mammographic screens was projected as the sum of initial screens and re-screens, and is based on projections of the population, rates of new recruitment, rates of attrition within the programme, and the mix of screening intervals. The baseline scenario involved: 70% participation of women aged 50–69 years, 90% return rate for the second and subsequent re-screens, 5% annual screens (95% biennial screens), and a specified population projection. The results were assessed with respect to variations in these assumptions.

Results The projections were strongly influenced by: the rate of screening of the target age group; the proportion of women re-screened annually; and the rates of attrition within the programme. Although demographic change had a notable effect, there was little difference between different population projections. Standard assumptions about attrition within the programme suggest that the current target participation rates in NSW may not be achieved in the long term.

Conclusions A practical model for projecting mammographic screens for populations is described which is capable of forecasting the number of screens under different scenarios.

Implications Projections of mammographic screens provide important information for the planning and financing of equipment and personnel, and for testing the effects of variations in important operational parameters. Re-screening attrition is an important contributor to screening viability.
Breast screening attendance: making better use of an appointment system
Authors: Tinkler C. , Pegington K. , Baldwin R.
Published: October 2002

Objectives To improve the effective use of screening appointment time on mobile units and even out the daily workload.

Setting Ten sites screened by three Breast Test Wales mobile units between January and August 1999.

Methods Women who had never attended for screening in previous screening rounds were identified and block booked into dedicated sessions at a rate of up to eight women per five minute slot. After piloting in the first site, the number in each slot was varied depending on how many rounds of screening these women had failed to attend. The numbers of women attending the remaining days were compared before and after the introduction of the new booking system.

Results There was a noticeable difference in uptake rates for previous non-attenders depending on how many screening rounds they had missed. The uptake rate for women who had missed one round of screening was found to average 20%. For those who had missed two previous rounds it averaged 9% and for those who had missed three it averaged 3%. Before the change in booking procedure, the average attending each day was 51 (median 51), but after the change, the average was 57 (median 59). The overall time needed was decreased.

Conclusions Booking dedicated sessions for previous non-attenders results is a more effective use of resources, reducing screening time in every site and levelling out attendance.
Estimating risk of breast cancer from population incidence affected by widespread mammographic screening
Authors: Taylor R. , Boyages J.
Published: October 2002

Objectives To estimate the absolute risk of breast cancer in women, allowing for the effect on incidence of the introduction of widespread mammographic screening.

Design Annual breast cancer incidences were compared with numbers of annual mammograms in the population for 1980–96 to identify periods most likely to be affected by screening. Age specific breast cancer incidences 1972–96 were modelled by Poisson regression with an age, period, and cohort analysis. The 1996 age specific incidence was recalculated with the stable period effect 1972–89, and the age and cohort effects. Age specific incidence was converted to cumulative risk of breast cancer to age 79.

Setting Population based data from all women in New South Wales (NSW), Australia.

Patients or participants Breast cancer incidence in women 1972–96 obtained from the NSW Central Cancer Registry and female populations derived from successive censuses. Mammographic data from private sector mammograms (1985–96), and the mammographic screening service (1988–96) for NSW women.

Interventions Introduction of population mammographic screening.

Main outcome measures Recorded age specific incidence and absolute risk of breast cancer to age 79 was compared with underlying incidence and cumulative absolute risk, adjusted for recent period effects, most likely due to mammographic screening in the population.

Results The age, period, and cohort model showed an increasing effect for birth cohorts 1910–44 then a plateau, and prominent period effects in 1991 and 1994–6. Increased incidence of breast cancer coincided with an increase in mammographic examinations in the private sector (1991), and prevalent rounds of mammographic screening in the population (1994–6) after introduction of a statewide mammographic screening service. Recorded incidence produced a breast cancer risk to age 79 of 9.9% (1 in 10) for 1996, whereas estimation of underlying incidence yielded a risk of 8.5% (1 in 12).

Conclusions The introduction of mammographic screening in a population inflates the incidence of breast cancer because of diagnosis of prevalent cases. For the purpose of public and clinical communication, it is more reasonable and responsible to adjust for period effects (due to screening) rather than produce risk estimates based on recorded incidence, which may show an alarming increase in risk of breast cancer over a short period.
Improving attendance for breast screening among recent non-attenders: a randomised controlled trial of two interventions in primary care
Authors: Bankhead C. , Richards S.H. , Peters T.J. , Sharp D.J. , Hobbs F.D.R. , Brown J. , Roberts L. , Tydeman C. , Redman V. , Formby J. , Wilson S. , Austoker J.
Published: October 2002

Objectives To examine the effectiveness and cost-effectiveness of two primary care based interventions aimed at increasing breast screening uptake for women who had recently failed to attend.

Setting 13 General practices with low uptake in the second round of breast screening (below 60%) in north west London and the West Midlands, United Kingdom. Participants were women in these practices who were recent non-attenders for breast screening in the third round.

Methods Pragmatic factorial randomised controlled trial, with people randomised to a systematic intervention (general practitioner letter), an opportunistic intervention (flag in women's notes prompting discussion by health professionals), neither intervention, or both. Outcome measures were attendance for screening 6 months after randomisation and cost-effectiveness of the interventions.

Results 1158 Women were individually randomised as follows: 289 control; 291 letter; 290 flag; 288 both interventions. Attendance was ascertained for 1148 (99%) of the 1158 women. Logistic regression adjusting for the other intervention and practice produced an odds ratio (OR) for attendance of 1.51 (95% confidence interval (95% CI 1.02 to 2.26; p=0.04) for the letter, and 1.39 (95% CI 0.93 to 2.07; p=0.10) for the flag. Health service costs/additional attendance were £35 (letter) and £65 (flag).

Conclusions Among recent non-attenders, the letter was effective in increasing breast screening attendance. The flag was of equivocal effectiveness and was considerably less cost-effective than the letter.
False positive results do not have a negative effect on reattendance for subsequent breast screening
Authors: O'Sullivan I. , Sutton S. , Dixon S. , Perry N.
Published: October 2002

OBJECTIVES:To find out whether a false positive breast screening result has a negative effect on subsequent screening attendance. Also considered was the proportion of women who had ever failed to reattend for screening, having previously attended routinely. DESIGN:The study was a retrospective cohort design. SETTING:Data from the call and recall records of the Central and East London Breast Screening Service (CELBSS) were used. PARTICIPANTS:Women who had been invited to attend for breast screening by the CELBSS during 1997. Main outcome measures—Subsequent attendance or non-attendance for the next routine breast screen, after a false positive screening result. RESULTS:A substantial number of women failed to reattend for a breast screen during their screening history, having attended for their previous routine breast screen. No differences in the rates of reattendance were found between those who had previously received a false positive result and those who had not. CONCLUSION:From the results obtained in the present study it would seem that the experience of a false positive breast screen does not deter women from reattending in the future. However, many women living in inner city areas who attend for an initial breast screen are failing to attend for subsequent routine mammograms. This may have a deleterious effect for these women in terms of the benefits of attendance for regular screening.
Cancer screening coverage of south Asian women in Wakefield
Authors: Sutton G.C. , Storer A. , Rowe K.
Published: October 2002

OBJECTIVE:To measure the cervical and breast screening coverage of south Asian women in Wakefield, compared with other city residents. DESIGN:Pairwise measurement of screening histories of women whose names appeared to be south Asian, and of non-Asian women matched by date of birth and general practice. Data source—Computerised records of screening histories held by West Yorkshire Central Services Agency, for the eight general practices in central Wakefield. RESULTS:67% of south Asians and 75% of non-Asians had acceptable (not overdue) cervical screening histories (&khgr;2=13.75, p<0.001). 53% of south Asians and 78% of non-Asians had acceptable breast screening histories (&khgr;2=8.5, p<0.01) CONCLUSION:Interventions should be designed to improve coverage for breast screening among south Asian women. The need for such interventions for cervical screening is equivocal.
Model of estimated rates of colorectal cancer from polyp growth by year of surveillance
Authors: Wilson L.S. , Lightwood J.
Published: October 2002

OBJECTIVE:Most studies show protective effects of non-steroidal anti-inflamatory drugs (NSAIDs) against polyps and colorectal cancers (CRCs) of up to 50%. Current models are unable to directly estimate changes in effects of chemoprevention on CRCs. The purpose is to develop a model to examine effects of changes in growth rates of polyps on surveillance intervals and risk of CRC . METHODS:The growth model simulates 500 people after polypectomy, estimating number and size of polyps annually over 10 years. Each polyp is assigned a random growth rate consistent with distributions of empirically observed growth assumed to follow a log linear model. Rates of CRC were calculated from largest polyps distributed to people. RESULTS:Simulated distributions of polyps and CRCs closely match empirical estimates which confirms the usefulness of the model. If polyp growth is 25% of normal, the number of cancers by year 10 after index colonoscopy decrease from 146 to only 57/100 000 for those in risk group 0 (no polyps at index colonoscopy) and from 840 to 124/100 000 for those of risk group 3 (4 or more polyps). CONCLUSIONS:This is the first model based on polyp growth rates. The CRC rates suggest that for those with no polyps on index colonoscopy, surveillance may be as for people of average risk (7–10 years), whereas those with one polyp or more need more surveillance (2–5 years). The use of the model is the indication that surveillance intervals could be increased by as much as 2–10 years if the growth rates of polyps are slowed.
An investigation into the effect of extending routine mammographic screening to older women in the United Kingdom on the time it takes to screen
Authors: Brown J. , Garvican L. , Moss S.
Published: October 2002

Objective: To compare the time it takes to screen women aged 65–69 with women age 50–64. Setting: Screening centres participating in the Department of Health funded demonstration study of extending breast screening to women aged 65–69. Methods: Consecutive women of all ages were timed during November 1999 to February 2000, until about 50 women aged 65–69 had been screened at each of the sites. For each woman screened, her age, whether she had been screened before, the times when she checked in, started to get undressed, started screening, finished screening, and when she left the screening unit were recorded. The radiographers also recorded any difficulties associated with screening any of the women in the survey. Results: The total mean time spent at the centres and the time being screened was not significantly different between the two age groups overall or within each of the demonstration sites (p>0.05). The distribution of screen time was similar between the age groups within each of the sites. The proportion of screens reported as difficult by the radiographers differed between sites, with two out of the three sites reporting more problems screening older women. Conclusions: Despite some radiographers reporting more difficulties associated with screening older women, screening a woman aged 65–69 was found, on average, to take no longer than screening a women aged 50–64 years. Thus, when the NHS breast screening programme is extended to include older women, the same time interval for an appointment can be scheduled regardless of the woman's age.
A randomised trial of population screening for melanoma
Authors: Aitken J.F. , Elwood J.M. , Lowe J.B. , Firman D.W. , Balanda K.P. , Ring I.T.
Published: October 2002

Objectives: Melanoma is a significant cause of morbidity and mortality worldwide and incidence is increasing. Survival after treatment is inversely related to the thickness of the tumour at diagnosis. Population screening has the potential to reduce mortality but there is no conclusive evidence of benefit. Such evidence can come best from a randomised trial. Here we describe the design of a community based randomised trial of a population screening programme for melanoma in Queensland, Australia and early results of the first phase of the trial. Methods: A total of 44 communities (aggregate population 560 000 adults aged 30 years or more) will be randomised to receive either a community based screening programme for 3 years or normal practice. The screening programme promotes thorough skin self examination and whole body skin examination by a doctor and provides open access skin cancer screening clinics. In its first phase, the trial is underway in nine intervention and nine control communities. The primary outcome measure is mortality from melanoma during 15 years of follow up. Results: The first phase of the trial has shown the feasibility of implementing a population skin screening programme including regular skin cancer screening clinics, and has shown the strong support of communities and doctors for the programme. There has been a significant 2.5-fold increase in participation in screening in the intervention communities in this first phase after the first 12 months of the trial and no significant increase in participation in screening in control communities during this period. Conclusions: The design of a community based randomised trial of screening for melanoma has been successfully peer reviewed and the intervention has been shown to be feasible in practice. This randomised trial may be one of the last opportunities to develop the evidence required for public health recommendations for population screening for melanoma.
An interesting byproduct of screening: assessing the effect of HRT on arterial calcification in the female breast
Authors: Cox J. , Simpson W. , Walshaw D.
Published: October 2002

Arterial calcification in the female breast (BAC) is a common but unreported finding on breast screening mammograms. Accumulating evidence suggests that BAC may have importance as a marker for generalised vascular disease. In this study, we have assessed the influence of HRT usage on the prevalence of BAC in 4400 women undergoing mammography for breast cancer screening. Significantly increased levels of breast arterial calcification were observed in women who had never used HRT compared with a group of women presently using HRT.
Mortality among Japanese construction workers in Mie Prefecture
Authors: Sun J , Kubota H , Hisanaga N , Shibata E , Kamijima M , Nakamura K
Published: October 2002

Aims:A historical cohort mortality study was conducted among 17 668 members of the Construction Workers’ Health Insurance Society of Mie Prefecture in Japan, in order to verify the relation between occupations and mortality status.

Methods:The cohort was followed from 2 April 1973 to 1 April 1998. Standardised mortality ratios (SMR) were calculated for all members and each job classification.

Results:98.7% of the members were traced successfully until the date when the follow up terminated. When all members were considered together, significant excess mortality was observed for “accidents and adverse effects”. Significant excess mortalities were also observed for lung cancers among scaffold men and ironworkers, for cancer of the oesophagus among plumbers, and for “chronic liver disease and cirrhosis” among scaffold men and painters.

Conclusion:Results suggest that more detailed investigations, which would include some minor job classifications should be undertaken. This is an updated cohort study which was partially completed in 1997.
Personal exposure of Paris office workers to nitrogen dioxide and fine particles
Authors: Mosqueron L , Momas I , Le Moullec Y
Published: October 2002

Aims:(1) To obtain an overall estimate of variability of personal exposure of Paris office workers to fine particles (PM2.5) and nitrogen dioxide (NO2), and to quantify their microenvironmental determinants. (2) To examine the role of potential determinants of indoor concentrations.

Methods:Sixty two office workers in a Paris municipal administration (all non-smokers) were equipped with personal samplers: passive samplers for 48 hours for NO2(n = 62), and active pumps for 24 hours for PM2.5(n = 55). Simultaneous measurements were performed in homes and offices; the local air monitoring network provided ambient concentrations. A time activity diary was used to weight measured concentrations by time spent in each microenvironment in order to estimate exposure concentrations.

Results:On average, PM2.5personal exposure (30.4 μg/m3) was higher than corresponding in-home (24.7 μg/m3) and ambient concentrations (16.7 μg/m3). Personal exposure to NO2(43.6 μg/m3) was significantly higher than in-home concentrations (35.1 μg/m3) but lower than the background outdoor level (60.1 μg/m3). Personal exposures to PM2.5and NO2were not significantly different from in-office concentrations. PM2.5and NO2personal exposures were not significantly correlated. In-home, in-office, in-transit, outdoor time weighted concentrations, and time spent in other indoor microenvironments explain respectively 86% and 78% of personal variations in PM2.5and NO2. In-home PM2.5concentration was primarily influenced by exposure to environmental tobacco smoke, and secondly by the ambient level (R2= 0.20). NO2in-home concentration was affected mostly by the ambient level and gas cooking time (R2= 0.14).

Conclusion:While results show the major contribution of in-home and in-office concentrations to both NO2and PM2.5personal exposures, the identification of indoor level determinants was not very conclusive.
Elbow fistulas using autogeneous vein: patency rates and results of revision
Authors: Murphy G J , Saunders R , Metcalfe M , Nicholson M L
Published: October 2002

Background

The provision and maintenance of vascular access remains a major cost to end stage renal failure programmes. There are few reports regarding the surgical revision of the failing native elbow arteriovenous fistula (AVF).

Patients and methods

A retrospective case note review was performed on all patients identified from the hospital vascular access database as having undergone construction of an autogeneous vein elbow AVF. Over a seven year period 282 autogeneous vein AVFs were fashioned in 232 patients using the brachial artery as the in-flow conduit. Of these 208 were brachiocephalic fistulas, or a variant thereof, and 74 were fashioned using the transposed autologous basilic vein (136 male: 96 female; median age 60 years, range 14–94 years).

Results

Of 282 elbow fistulas 197 were successfully used for dialysis (70%). Cumulative primary patency of elbow fistulas using autogeneous vein in this series was 68%, 54%, and 44% at one, two, and three years respectively. A further 34 revision procedures were performed on 28 fistulas to maintain fistula function, and cumulative secondary patency after surgical revision was 75%, 60%, and 46% at one, two, and three years. Overall 21 out of 34 procedures (62%) successfully restored fistula function and cumulative primary patency of the revised fistulas was 56% at one year. Eighteen AVFs (brachiocephalic, n=12; autologous basilar vein, n=6) required revision for access dysfunction secondary to a short stenoses within 4 cm of the arteriovenous anastomoses. Of these 18 AVFs eight were revised by excision of the stenosed segment and either primary anastomoses of the two cut ends of arterialised vein or reanastomoses of the proximal venous limb proximally on the brachial artery. In another nine fistulas the excised segment was replaced with a short interposition graft (polytetrafluoroethylene, n=7; native basilic vein, n=1; bovine carotid artery, n=1). One fistula with postanastomotic stenoses and a more proximal needle site stenoses was revised using two vein patches. Overall 100% were patent at 24 hours, 13 provided successful dialysis (72%), and cumulative primary patency was 67% and 50% at six months and one year respectively.

Conclusions

Successful surgical revision of failing native elbow fistulas can restore patency and improve cumulative secondary patency with potential benefits in terms of patient morbidity and mortality. These results compare favourably to published patency rates after fistula salvage using interventional radiological techniques.
Idiopathic heterotopic ossification in the intensive care setting
Authors: Lane J E , Dean R J , Foulkes G D , Chandler P W
Published: October 2002

Heterotopic ossification is characterised by the periarticular deposition of ectopic bone. It typically occurs after trauma, neurogenic injury, or congenital causes. Idiopathic heterotopic ossification has been rarely reported. A patient who developed idiopathic heterotopic ossification in the intensive care unit without any known predisposing conditions is presented.
Eosinophilic gastroenteritis mimicking pancreatic cancer
Authors: Christopher V , Thompson M H , Hughes S
Published: October 2002

Eosinophilic gastroenteritis is a condition characterised by eosinophilic infiltration of the gastrointestinal tract. Biliary obstruction is an unusual presentation. A case where the initial investigations were consistent with carcinoma of the head of pancreas but the resection specimen showed no malignancy is presented. The diagnosis was suspected from a review of the patient’s past history and confirmed by re-examination of the histology.
Nitrogen retention bySphagnummosses: responses to atmospheric nitrogen deposition and drought
Authors: Aldous Allison R
Published: October 2002

Sphagnum mosses are assumed to be effective at acquiring low amounts of nitrogen (N) in precipitation to support annual growth. However, N concentrations in precipitation have increased from anthropogenic sources over the last 150 years. I hypothesized that N retention from wet atmospheric deposition decreases with increased N availability, by comparing Sphagnum mosses in a high N deposition region in the Adirondack Park, New York, to a low-deposition region in eastern Maine. A15NH415NO3tracer was applied to mosses in both regions, and retention after 24 h was estimated. Nitrogen retention ranged from 50 to 90% of N applied. Most15N was recovered from the apical capitula and upper stems. Nitrogen retention was greater in the Maine sites in 1998. However, in 1999, a drought year, particularly in Maine, N retention was less in Maine than in New York. The drier climate appeared to lower N retention, possibly through its physiological effects on the mosses. Although atmospheric deposition might be the only exogenous source of N, it satisfied only a small fraction of N required for annual growth. These data suggest that internal cycling processes, such as mineralization, may be much more important N sources to support Sphagnum growth.Key words: Sphagnum mosses, atmospheric nitrogen deposition, nitrogen-use efficiency, nitrogen retention, peatlands, bogs, drought.
A comparison of the 5S rDNA diversity in theHordeum brachyantherumcalifornicumcomplex with those of the eastern AsiaticHordeum roshevitziiand the South AmericanHordeum cordobense(Triticeae: Poaceae)
Authors: Baum Bernard R , Johnson Douglas A
Published: October 2002

Amplification of the 5S rDNA gene by the polymerase chain reaction, followed by cloning and sequencing, was used to generate data from 23 seed accessions of Hordeum brachyantherum Nevski, Hordeum californicum Covas et Stebbins, Hordeum cordobense Bothmer, Jacobsen et Nicora, and Hordeum roshevitzii Bowden. One hundred and fourteen clones were analyzed, resulting in the detection of four different 5S DNA unit classes. Three of them, long H1, long H2, and long Y2, had been previously reported. The long H3 class, described for the first time, is present only in H. roshevitzii but can be grouped with previously unassigned units of Hordeum bulbosum L. and Hordeum spontaneum C. Koch. Based upon the analyses of 5S rDNA sequences, we found that (i) the long H2 unit class was not found in the Asiatic H. roshevitzii and therefore may be restricted to the American species, (ii) there is no strong support that H. brachyantherum and H. californicum are worthy of species recognition, and (iii) cladistic analysis of the consensus sequences of the four paralogous unit classes demonstrated that long Y2 is the most distant from the three long H classes.Key words: 5S DNA gene, Hordeum, unit classes.
A model for the development of the rhizobial and arbuscular mycorrhizal symbioses in legumes and its use to understand the roles of ethylene in the establishment of these two symbioses
Authors: Guinel F C , Geil R D
Published: October 2002

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis  outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants.Key words: AM, epidermis, evolution, pea, rhizobia, sym mutant.
Influence of water stress on Dutch elm disease symptoms in Ulmus minor
Authors: Solla A , Gil L
Published: October 2002

The response of Ulmus minor Miller to Dutch elm disease was observed under combined heavy and light watering regimes. Ramets of two clones, planted in pots, were divided into two groups and each group underwent a different watering regime: heavy initial watering followed by light watering and light initial watering followed by heavy watering. The changeover in watering took place on May 29, 1998, 15 days after plants had been inoculated with a Ophiostoma novo-ulmi Brasier spore suspension. Greater wilting was evident in elms subjected to the heavy initial watering followed by light watering regime than those subjected to light initial watering followed by heavy watering. Non-inoculated plants subjected to heavy initial watering followed by light watering developed large vessel diameters during the heavy watering period and showed approximately 20% wilting during the light watering period. Non-inoculated plants subjected to light initial watering followed by heavy watering developed vessels with smaller diameters during the light watering period, and showed no wilting. The evidence suggests that large vessel formation prior to inoculation associated with water stress after infection increases Dutch elm disease symptoms. The role of water stress in the development of Dutch elm disease symptoms and the implications for elm resistance and breeding are discussed.Key words: field elm, Dutch elm disease, water relations, xylem vessels, breeding, Ophiostoma novo-ulmi.
Opposite effects of ocean temperature on survival rates of 120 stocks of Pacific salmon (Oncorhynchus spp.) in northern and southern areas
Authors: Mueter Franz J , Peterman Randall M , Pyper Brian J
Published: October 2002

To improve the understanding of linkages between ocean conditions and salmon productivity, we estimated effects of ocean temperature on survival rates of three species of Pacific salmon (Oncorhynchus spp.) across 120 stocks. This multistock approach permitted more precise estimates of effects than standard single-stock analyses. The estimated effects were opposite in sign between northern and southern stocks and were quite consistent across stocks within species and areas. Warm anomalies in coastal temperatures were associated with increased survival rates for stocks in Alaska and decreased survival rates in Washington and British Columbia, suggesting that different mechanisms determine survival rates in the two areas. Regional-scale sea surface temperatures (SST, within several hundred kilometres of a stock's ocean entry point) were a much better predictor of survival rates than large-scale climate anomalies associated with the Pacific Decadal Oscillation (PDO), suggesting that survival rates are primarily linked to environmental conditions at regional spatial scales. With appropriate cautions, these results may be used to predict the potential effects of climatic changes on salmon productivity in different areas of the Northeast Pacific.
Whole-lake algal responses to a century of acidic industrial deposition on the Canadian Shield
Authors: Vinebrooke Rolf D , Dixit Sushil S , Graham Mark D , Gunn John M , Chen Yu-Wei , Belzile Nelson
Published: October 2002

A century of cultural acidification is hypothesized to have altered algal community structure in boreal lakes. To date, this hypothesis has remained untested because of both the lack of data predating the onset of industrial pollution and incomplete estimates of whole-lake algal community structure. High-pressure liquid chromatography (HPLC) of sedimentary pigments was used to quantify whole-lake algal responses to acid deposition in six boreal lakes located in Killarney Park, Ontario, Canada. Concomitant significant increases in chlorophyll and carotenoid concentrations, diatom-inferred lake acidity, and metal levels since 1900 suggested that algal abundances in four acidified lakes and one small, circumneutral lake were enhanced by aerial pollution. An alternate explanation is that increased acidity and underwater light availability in the acidified lakes shifted algal abundance towards phytobenthos and deepwater phytoplankton, whose pigment signatures were better preserved in the sediments. Taxonomically diagnostic pigment stratigraphies were consistent with shifts in algal community structure towards filamentous green phytobenthos and deepwater phytoflagellates in the acidified lakes. Our findings suggest that decades of aerial pollution have altered the base of foodwebs in boreal lakes, potentially rendering them less resilient to other environmental stressors.
A trophic study of a marine ecosystem off southeastern Australia using stable isotopes of carbon and nitrogen
Authors: Davenport Stephanie R , Bax Nicholas J
Published: October 2002

The stable isotopes of carbon and nitrogen were used to investigate trophic relationships of fish and invertebrates on the continental shelf of southeastern Australia. We examined 87 fish species, marine mammals, penguins, invertebrates, algal samples, suspended particulate organic matter (POM), and sediments. The main source of primary production is oceanic phytoplankton, although there is evidence of a seagrass contribution to the benthos. Marine mammals, penguins, some benthic invertebrates, and some benthic fish filled the highest trophic positions. Sources of variability in isotope results included temporal (POM, some fish) and spatial (POM, sediments) elements, bottom depth (some fish), and size (some fish). Fish had muscle δ15N values of 9.6 to 14.7 and δ13C values of 20.6 to 14.6. Cluster analysis on fish stable isotope results produced fish groups that could be interpreted with trophic and habitat information. Trophic relationships in fish, suggested by stable isotope results, were supported by stomach contents analysis. Stable isotope results may indicate more representative trophic relationships, as stomach contents analyses tend to group prey by taxon rather than by trophodynamic position. In fish and invertebrates, stable isotope results related more to functional patterns of feeding than to taxonomic relationships.
The economics of fishing down the food chain
Authors: Hannesson Rögnvaldur
Published: October 2002

This paper uses a predatorprey model to discuss the fundamental economics of fishing down the food chain. Three regimes are compared: open access, global optimization, and partial optimization of rents from each stock. If the net price of prey species increases, fishing down the food chain would indeed be a desirable effect in economic terms. Under open access, however, fishing down the food chain could occur as a result of a higher net price of species higher up in the food chain. With partial optimization, there could be less fishing down the food chain than economically desirable.
Reconstructing the lives of fish using Sr isotopes in otoliths
Authors: Kennedy Brian P , Klaue Andrea , Blum Joel D , Folt Carol L , Nislow Keith H
Published: October 2002

For many species, understanding the processes underlying variation in life history strategies is limited by the difficulty of tracking individuals throughout their lives. Within the rapidly expanding field of otolith microchemistry, novel approaches are being combined with state-of-the-art analytical techniques to provide new and valuable information about the environmental history of fishes. However, no approach to date allows the reconstruction of fish movements at high temporal resolution (weeks to months) over relatively small spatial scales (110 km). We used micromilling techniques to extract strontium (Sr) isotopic signatures from the otoliths of four returning Atlantic salmon (Salmo salar) adults. Distinct Sr isotopic signatures were detectable from four life cycle stages, including prefeeding hatchery development, rearing stream growth, smolt out-migration, and ocean residence. High-resolution analyses of Sr isotope records establish that natal stream signatures are recoverable and show that both site fidelity within the freshwater stage and the timing of migration vary considerably among individuals. Results made possible with this approach provide insight into a long-standing debate on the mobility of salmon during their nonmigratory stage. The ability to resolve flexible behaviors of salmon increases our understanding of their population biology and conservation needs.
Hydrological and trophic characteristics of tuna habitat: consequences on tuna distribution and longline catchability
Authors: Bertrand Arnaud , Josse Erwan , Bach Pascal , Gros Philippe , Dagorn Laurent
Published: October 2002

We studied relationships between tropical tunas (albacore (Thunnus alalunga), bigeye (Thunnus obesus), and yellowfin (Thunnus albacares)) and their biotic and abiotic environments through simultaneous acoustic observations of tunas and their prey, experimental longline catch, and oceanographic data in French Polynesia. Vertical habitat limits were estimated based on temperature and dissolved oxygen at capture data. We then studied tuna-micronekton relationships to better understand how tuna occupy the pelagic space. At a regional scale, tunas were more abundant in areas rich in prey with favourable hydrological conditions. Inside such areas, at the scale of a longline set, however, the longline catches were maximal only when prey were not distributed in dense patches (except for yellowfin tuna). We interpreted this result by considering that areas with high prey abundance attract tunas, but at a small scale, if prey are patchy distributed, tunas are more inclined to feed on them rather than on longline baits. The effect of patches on yellowfin tuna catch per unit effort (CPUE) does not appear likely because this species also feeds on the mixed layer, where patch density was very low. Not only hydrological characteristics, but also prey density and prey patch characteristics, should be taken into account for interpreting longline CPUE data.
Predatory impact of the freshwater invaderDikerogammarus villosus(Crustacea: Amphipoda)
Authors: Dick Jaimie T.A , Platvoet Dirk , Kelly David W
Published: October 2002

To assess the increasing threats to aquatic ecosystems from invasive species, we need to elucidate the mechanisms of impacts of current and predicted future invaders. Dikerogammarus villosus, a PontoCaspian amphipod crustacean, is invading throughout Europe and predicted to invade the North American Great Lakes. European field studies show that populations of macroinvertebrates decline after D. villosus invasion. The mechanism of such impacts has not been addressed empirically; however, D. villosus is known to prey upon and replace other amphipods. Therefore, in this study, we used microcosm and mesocosm laboratory experiments, with both single and mixed prey species scenarios, to assess any predatory impact of D. villosus on a range of macroinvertebrate taxa, trophic groups, and body sizes. Dikerogammarus villosus predatory behaviour included shredding of prey and infliction of "bite" injuries on multiple victims. Dikerogammarus villosus killed significantly greater numbers of macroinvertebrates than did the native Gammarus duebeni, which is currently being replaced by D. villosus. This invader thus appears to impact on freshwater ecosystems through its exceptional predatory capabilities. We predict that future invasions by D. villosus will have serious direct and indirect effects on freshwaters, with its invasion facilitated in a larger "invasional meltdown" in regions like the North American Great Lakes.
Geological and evolutionary underpinnings for the success of Ponto-Caspian species invasions in the Baltic Sea and North American Great Lakes
Authors: Reid David F , Orlova Marina I
Published: October 2002

Between 1985 and 2000, ~70% of new species that invaded the North American Great Lakes were endemic to the Ponto-Caspian (Caspian, Azov, and Black seas) basins of eastern Europe. Sixteen Ponto-Caspian species were also established in the Baltic Sea as of 2000. Many Ponto-Caspian endemic species are characterized by wide environmental tolerances and high phenotypic variability. Ponto-Caspian fauna evolved over millions of years in a series of large lakes and seas with widely varying salinities and water levels and alternating periods of isolation and open connections between the Caspian Sea and Black Sea depressions and between these basins and the Mediterranean Basin and the World Ocean. These conditions probably resulted in selection of Ponto-Caspian endemic species for the broad environmental tolerances and euryhalinity many exhibit. Both the Baltic Sea and the Great Lakes are geologically young and present much lower levels of endemism. The high tolerance of Ponto-Caspian fauna to varying environmental conditions, their ability to survive exposure to a range of salinities, and the similarity in environmental conditions available in the Baltic Sea and Great Lakes probably contribute to the invasion success of these species. Human activities have dramatically increased the opportunities for transport and introduction and have played a catalytic role.
Rapid Communication / Communication RapideAmbient solar ultraviolet radiation and its effects on phosphorus flux into boreal lake phytoplankton communities
Authors: Frost Paul C , Xenopoulos Marguerite A
Published: October 2002

We examined the effects of ultraviolet radiation (UVR) on net phosphorus (P) flux into phytoplankton communities in two boreal lakes at the Experimental Lakes Area (ELA), Canada. We manipulated P available to and irradiance received by phytoplankton during four different three-day incubations of dilution bioassays. Net P flux was estimated by measuring the accumulation of particulate P (that retained on glass fiber filters) over the incubation period. No effects of UVR on net P flux were found at ambient P levels in any of the experiments. At the highest levels of P addition, less particulate phosphorus (PP) accumulated in both the minus-UVB (~1540%; photosynthetically active radiation (PAR) + UVA) and full-sunlight (~2545%; PAR + UVA + UVB) exposed phytoplankton compared with those that received PAR only. Neither chlorophyll- nor carbon-specific net P flux was affected by UVR exposure at ambient P levels. However, at the highest levels of P enrichment, chlorophyll-specific net P flux increased in response to UVR in both lakes, whereas carbon-specific net P flux declined in one of the lakes and was unaffected by UV exposure in the second lake. Our results indicate that UVR can affect total PP accumulation in enriched systems, but not at ambient P levels, and that UVR has a weak and variable effect on biomass-specific P uptake in phytoplankton under enriched conditions.
Evolutionary and physiological adaptations of aquatic invasive animals: r selection versus resistance
Authors: McMahon Robert F
Published: October 2002

Invasive species have been characterized as tolerant of environmental extremes. This hypothesis was evaluated for invasive aquatic species in North America, particularly Asian clams, Corbicula fluminea, and zebra mussels, Dreissena polymorpha. Both species have rapid growth, early maturity, short life spans, and elevated fecundity, allowing rapid population recovery after reductions by rarefractive, environmental extremes. Extensive resistance capacities offer little adaptive value to invasive, r-selected species, because population reductions occur in their unstable habitats regardless of degree of stress tolerance. Thus, both species have relatively poor physiologic resistance, depending instead on elevated growth and fecundity for rapid population recovery. In contrast, native North American bivalve species are often adapted to stable habitats where perturbation is infrequent (i.e., freshwater unionoidean bivalves). They are characterized by slow growth, extended life spans, and low effective fecundities, slowing population recoveries (K-selected), and have evolved extensive resistance adaptations to avoid extirpation during environmental extremes. Review of resistance adaptations in other North American aquatic invaders revealed poorer or equivalent physiological tolerance relative to taxonomically related native species, suggesting that extensive physiological tolerance is not required for invasive success.
A general expression for symmetry factors of Feynman diagrams
Authors: Palmer C D , Carrington M E
Published: October 2002

The calculation of the symmetry factor corresponding to a given Feynman diagram is well known to be a tedious problem. We have derived a simple formula for these symmetry factors. Our formula works for any diagram in scalar theory (ϕ3 and ϕ4 interactions), spinor QED, scalar QED, or QCD.

PACS Nos.: 11.10-z, 11.15-q, 11.15Bt
Electron excitation of the Group IV elements
Authors: Srivastava R , McEachran R P , Stauffer A D
Published: October 2002

We investigated the electron excitation of the fine-structure levels of the 3P ground state and the first excited 1D state of the first four elements of Group IV: carbon, silicon, germanium, and tin. These calculations were carried out in the jj coupling scheme using the relativistic distorted-wave method. Results are presented for the differential cross sections and spin-polarization parameters for incident electron energies of 25 and 40 eV.

PACS Nos.: 34.80Dp, 34.80Nz
M X-ray emission from low-energy, highly charged Taq+ (q = 4549) ions colliding with neutral atoms due to singly and doubly excited states formed through single-electron capture
Authors: Tawara H , Richard P , Safronova U I , Vasilyev A A , Stockli M
Published: October 2002

M X-rays have been observed from 140 keV/u 181Taq+ (q = 4549) ions colliding with neutral Ar atoms under single collisions. The most dominant X-rays have been found to be due to transitions of 4p3d and 4f3d when the projectiles bring 3d-shell vacancies into collisions. Though much weaker, M X-rays also have been observed in collisions with Ta45+ ions that initially have no 3d-shell vacancy and are understood to originate from transitions of the doubly excited states 3d9nln'l' formed through strong electronelectron interactions after single-electron capture. The observed M X-ray spectra have been compared and reproduced nicely with the synthesized spectra. It has been confirmed that transitions of such doubly excited states also contribute to X-rays at the lower energy region observed even for higher charge ions with 3d vacancies. PACS Nos.: 32.30Rj, 32.70Cs, 32.80Rm, 34.70+e
The RacahWigner category
Authors: Joyce W P , Butler P H , Ross H J
Published: October 2002

The RacahWigner calculus is formulated using category theory. The notion of recoupling requires a consistent choice of isomorphisms corresponding to regrouping of irreducible representations. This is the essential content of a ring category. Hence the RacahWigner calculus is inherently a ring category. Category theory places the emphasis on maps between representations. The diagrammatic approach of category theory lays bare underlying relationships in the RacahWigner calculus. Direct sum decomposition, coupling coefficients, recoupling coefficients, and group chain decomposition are simplified and clarified when represented by diagrams. The diagram techniques of category theory are unlike diagram techniques used for group calculations. The BiedenharnElliott sum rule, Racah backcoupling, Racah factorisation lemma, and the WignerEckart theorem are derived from properties of this category. PACS Nos.: 02.10Ws, 02.20Qs, 02.20Fh, 02.20Df, 03.65Fd, 31.15Hz
Parametric-time coherent states for Morse potential
Authors: Unal N
Published: October 2002

We transform the Lagrangian of the Morse-potential problem into two harmonic oscillators in a new parametric time and quantize this system by using path integrals over holomorphic coordinates of oscillators and derive coherent states.

PACS Nos.: 31.15-p, 03.65Ca, 03.65Ge