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Layered ice has been used to investigate the initiation of fabrics in shear zones where there is preservation of a refolded layering The fabrics were measured using an apparatus that acquires pixel-based images that illustrate the variation of c-axis orientation within and between grains. In the centre of the shear zones there is dynamic recrystallization with the production of an asymmetric two-maxima fabric. The way dynamic recrystallization modifies the inherited folds and microstructure suggests that there is little effect of inheritance from a precursor grain microstructure or fabric No obvious evidence has been found for the occurrence of sub-grains, which implies that the role of sub-grain rotation is minimal or is obliterated by the recrystallization process. The final c-axis pattern is asymmetric with respect to the direction of shortening, with a strong maximum at ~5° to the pole of the shear zone, and a sense of asymmetry in the direction of the shear, and a secondary maximum inclined at ~45° to the plane of shearing. Distinct sets of nearest-neighbour c-axis distributions, namely, intermediate-angle (10–25°), high-angle (50–65°) and very high-angle (120–150°), suggest there may be special grain-boundary relationships.
Adulthood psychological health predicts labour force activity but few studies have examined childhood psychological health. We hypothesized that childhood psychological ill-health would be associated with labour force exit at 55 years.
Data were from the 55-year follow-up of the National Child Development Study (n = 9137). Labour force participation and exit (unemployment, retirement, permanent sickness, homemaking/other) were self-reported at 55 years. Internalizing and externalizing problems in childhood (7, 11 and 16 years) and malaise in adulthood (23, 33, 42, 50 years) were assessed. Education, social class, periods of unemployment, partnership separations, number of children, and homemaking activity were measured throughout adulthood.
Childhood internalizing and externalizing problems were associated with unemployment, permanent sickness and homemaking/other at 55 years, after adjustment for adulthood psychological health and education: one or two reports of internalizing was associated with increased risk for unemployment [relative risk (RR) 1.59, 95% confidence interval (CI) 1.12–2.25; RR 2.37, 95% CI 1.48–3.79] and permanent sickness (RR 1.32, 95% CI 1.00–1.74; RR, 1.48, 95% CI 1.00–2.17); three reports of externalizing was associated with increased risk for unemployment (RR 2.26, 95% CI 1.01–5.04), permanent sickness (RR 2.63, 95% CI 1.46–4.73) and homemaking/other (RR 1.95, 95% CI 1.00–3.78).
Psychological ill-health across the lifecourse, including during childhood, reduces the likelihood of working in older age. Support for those with mental health problems at different life stages and for those with limited connections to the labour market, including homemakers, is an essential dimension of attempts to extend working lives.
Lakes Barrine and Eacham and their small, discrete, forested catchments are sites of intensive sedimentological, palynological and ecological research. The studies that we present here concentrate on integrating population statistics of tree species of the living forest with their histories, as documented by fine-resolution pollen analysis (Green and Dolman 1988). Most of the work has been undertaken at Lake Barrine, where the last 5 ka is recorded in laminated sediments. Additional information about these sites and about aspects of the project is contained in Chen (1986, 1987, 1988), Goodfield (1988), Grindrod (1979), Timms (1976, 1979) and Walker (1988).
The 14C dating of organic fractions from paleosol layers containing <2% carbon in loess-paleosol sequences from the loess plateau in China has yielded results that are quite often much younger than the true age of the sediments. Percolation of modern organic materials from agricultural activities, and binding of these materials within the weathered clays of the paleosols has meant that conventional pretreatment techniques for 14C dating would not isolate a reliable chemical fraction. The total sequence from Bei Zhuang Cun, in Shaanxi Province, reflects the climatic history of the area for ca 30,000 years, ranging from the interstadial of the last glacial period to the postglacial period. Analysis of solvent extracts of organic material from this site indicates that they are mainly composed of carbohydrate residues originating from the relatively recent agricultural activity. Validity of the humic components for dating will be discussed.
The following list contains most of the measurements made during 1974, since our last list (R, 1973, v 15, p 241-251). All measurements were performed on a Beckman LS-200 Liquid Scintillation Spectrometer following previously published setting up (Polach, 1974), automatic cycling (Polach, 1969) and benzene synthesis (Polach and Stipp, 1966; Polach et al, 1972) procedures.
Loess deposition within the Loess Plateau of China records the history of environmental change over the last 2.5 Myr. Loess-paleosol sequences of the last 10 ka, which have preserved information of global climate change, relate closely to human occupation of the area. Hence, studies of the deposition and development of Holocene loess are significant for studying environmental change and problems associated with engineering geology. We present here stratigraphic relations among four profiles from the south, west and center of the Loess Plateau. On the basis of 14C radiometric and AMS dates of organic material extracted from the paleosols, together with magnetic susceptibility measurements down each profile, we discuss Holocene stratigraphic divisions within the Loess Plateau, and suggest that the Holocene optimum, characterized by paleosol complexes, occurred between 10 and 5 ka bp. From 5 ka BP to the present, neoglacial activity is characterized by recently deposited loess.
Through the establishment of radiocarbon chronozones relating common geological events within lacustrine and eolian sediments from five profiles representative of loess yuan (tablelands), river valley and northwest margin features of the Loess Plateau, we propose a series of stratigraphic divisions within the last 30 ka. The focus of this detailed study involves stratigraphic relationships contributing to evidence of Younger Dryas events, with the recognition of cold-dry, cool-wet and cold-dry periods represented within the Heiheze silt, Midiwan peat and Liushuwan eolian sand. The stratigraphic profiles reflect century-scale fluctuations of the East Asian monsoons. The precursor events enable us to place the Pleistocene/Holocene boundary at 10,000 bp.
A 14C measurement capability has been developed on the 14UD accelerator at the Australian National University. At present, this system operates on a medium-precision, low-throughput basis with slow cycling between isotopes. We describe unusual features of the system, and review preliminary experience with this mode of operation, in sample preparation, and with a recently installed injection system.
The Xi'an Laboratory of Loess and Quaternary Geology has developed a small sample 14C dating facility consisting of a Wallac 1220 Quantulus™ liquid scintillation spectrometer, and a miniature benzene synthesis line based on the synthesis procedures used at the Australian National University (ANU). This line can produce ca. 0.3-ml benzene samples, which are then measured for 14C activity using 0.3-ml Teflon vials developed by Wallac Oy. The counting performance of the Quantulus™ spectrometer using 0.3-ml vials has been evaluated, and a potential age limit of ca. 45,000 BP has been obtained for samples containing up to 250 mg carbon. This dating facility fills the gap between large sample (2.4–6 g carbon) and microsample (<1 mg carbon) handling to form a 14C dating method sequence.
δ13C and 14C activity measurements were made on terrestrial, marsh and aquatic plants growing in their natural habitat of the Plitvice Lakes in northwest Yugoslavia. δ13C values were ca −47 for aquatic mosses, which indicate that the carbon source was dissolved inorganic carbon (DIC) from alkaline karst waters, following a C3 pathway, and ca −25 for marsh plants, indicating the carbon source was atmospheric CO2. 14C activity of true aquatic plants and submerged parts of helophytes was close to 14C activity of DIC, whereas that of emergent parts of helophytes and terrestrial plants was similar to atmospheric CO2 activity. Aquatic plants which use DIC in freshwater for their photosynthesis are not suitable for 14C dating, unless the initial activity of incorporated carbon is known. δ13C values of plant material also depend on the carbon source and cannot be used for 14C age correction.
We tested the feasibility of dating freshwater and terrestrial molluscs from the semiarid and arid zone in China, since these types of shell material deposit only aragonite to form their shell structure, and shell integrity can be easily observed using X-ray diffraction. We also tested the possibility of estimating microenvironmental changes from shell δ13C values, but variations within shell populations preclude the use of these values as a reliable indicator. Reservoir ages were calculated for living shells of the same species as fossil shells by using their measured 14C ages, which were recalculated using an average value of atmospheric 14C activity for the years spanning their time of collection as the modern standard. The results indicate that freshwater and terrestrial shells are potentially useful as dating material, provided extreme care is taken in their collection and other datable material (in this case wood and pollen) is within the profile to act as a comparison.
The valley of the Baxie River, situated in the western region of the Loess Plateau in central China, contains a loess profile 15 m thick, which can be considered representative of loess-paleosol sequences formed over the last 17 ka. Both thermoluminescence (TL) determinations on fine-grained sediment (4–11 μm) and 14C determinations on various organic fractions of paleosols from the profile have provided an extremely useful chronological framework for these sequences. These sequences indicate a weakened summer monsoon during the last glacial maximum followed by a strengthening of the summer monsoon, beginning ca. 13 ka cal bp. An abrupt change to a weakened summer monsoon regime lasted from ca. 10.9 to 10.2 ka cal bp. The Asian summer monsoon circulation, recording the Holocene optimum, then increased and lasted from ca. 10.2 to 6 ka cal bp. The organic component of samples taken down the profile has δ13C values ranging from −21 to −24‰ with respect to the PDB standard. The more positive δ13C values suggest that the proportion of C4-type plants in river valleys of the Loess Plateau increased as Asian summer monsoon influence weakened, and C3-type vegetation increased as the summer monsoon influence strengthened. Magnetic susceptibility and organic content were low during loess deposition, also reflecting weakening of summer monsoon. Two 14C determinations on the humin fraction of the organic component near the top of the lower paleosol and the base of the upper paleosol complex gave ages of 10.2 and 10.9 ka cal BP, respectively. These ages mark the beginning and termination of a brief event involving increased dust influx under weakened summer monsoon conditions.
In a separate study, we conducted a series of high-precision radiocarbon measurements using wood from Britain and New Zealand to investigate interhemispheric offsets and possible temporal variations. To minimize variability associated with different species, the pretreatment of the oak (Quercus patraea) and cedar (Librocedrus bidwilli) was to α-cellulose for both. This study investigates the thoroughness of a range of pretreatment processes by the stable isotope analysis of the products.
It is generally recognised that spring grass does not provide a balanced ration for the grazing animal, since it contains excess of nitrogenous substances in relation to carbohydrate. Young lucerne similarly contains more nitrogen than is necessary to provide a balanced feed. When grazing these types of herbage, the animal wastes much of the ingested nitrogen. If the ration included carbohydrate rich foods in addition to the high quality herbage, the animal might be able to utilise more of the nitrogen it is consuming.
In this country little experimental evidence is available on the use of carbohydrate supplements for beef cattle, although several firms produce high carbohydrate cakes with low fibre content, for feeding in conjunction with young succulent grass.
High blood pressure (BP) variability, which may be an important determinant of hypertensive end-organ damage, is emerging as an important predictor of cardiovascular health. Dietary antioxidants can influence BP, but their effects on variability are yet to be investigated. The aim of the present study was to assess the effects of vitamin E, vitamin C and polyphenols on the rate of daytime and night-time ambulatory BP variation. To assess these effects, two randomised, double-blind, placebo-controlled trials were performed. In the first trial (vitamin E), fifty-eight individuals with type 2 diabetes were given 500 mg/d of RRR-α-tocopherol, 500 mg/d of mixed tocopherols or placebo for 6 weeks. In the second trial (vitamin C–polyphenols), sixty-nine treated hypertensive individuals were given 500 mg/d of vitamin C, 1000 mg/d of grape-seed polyphenols, both vitamin C and polyphenols, or neither (placebo) for 6 weeks. At baseline and at the end of the 6-week intervention, 24 h ambulatory BP and rate of measurement-to-measurement BP variation were assessed. Compared with placebo, treatment with α-tocopherol, mixed tocopherols, vitamin C and polyphenols did not significantly alter the rate of daytime or night-time systolic BP, diastolic BP or pulse pressure variation (P>0·05). Treatment with the vitamin C and polyphenol combination resulted in higher BP variation: the rate of night-time systolic BP variation (P= 0·022) and pulse pressure variation (P= 0·0036) were higher and the rate of daytime systolic BP variation was higher (P= 0·056). Vitamin E, vitamin C or grape-seed polyphenols did not significantly alter the rate of BP variation. However, the increase in the rate of BP variation suggests that the combination of high doses of vitamin C and polyphenols could be detrimental to treated hypertensive individuals.
Diagnosis of depressive disorder using interviewer-administered instruments is expensive and frequently impractical in large epidemiological surveys. The aim of this study was to assess the validity of three self-completion measures of depressive disorder and other psychiatric disorders in older people against an interviewer-administered instrument.
A random sample stratified by sex, age and social position was selected from the Whitehall II study participants. This sample was supplemented by inclusion of depressed Whitehall II participants. Depressive disorder and other mental disorders were assessed by the interviewer-administered structured revised Clinical Interview Schedule (CIS-R) in 277 participants aged 58–80 years. Participants also completed a computerized self-completion version of the CIS-R in addition to the General Health Questionnaire (GHQ) and the Center for Epidemiologic Studies Depression Scale (CES-D).
The mean total score was similar for the interviewer-administered (4.43) and self-completion (4.35) versions of the CIS-R [95% confidence interval (CI) for difference −0.31 to 0.16]. Differences were not related to sex, age, social position or presence of chronic physical illness. Sensitivity/specificity of self-completion CIS-R was 74%/98% for any mental disorder and 75%/98% for depressive episode. The corresponding figures were 86%/87% and 78%/83% for GHQ and 77%/89% and 89%/86% for CES-D.
The self-completion computerized version of the CIS-R is feasible and has good validity as a measure of any mental disorder and depression in people aged ⩾ 60 years. GHQ and CES-D also have good criterion validity as measures of any mental disorder and depressive disorder respectively.
Animal studies suggest that maternal separation is associated with alterations in the hypothalamic–pituitary–adrenal (HPA) axis through effects that occur in a critical period following birth. Evidence for an association of the diurnal cortisol rhythm with maternal separation in humans is equivocal.
We examined whether maternal separation in childhood is associated with diurnal cortisol pattern in 3712 middle-aged men and women. Two aspects of cortisol release were examined: the cortisol awakening response (CAR) and the diurnal slope in cortisol throughout the day.
Maternal separation in childhood was reported by 12% of participants. Those participants who reported maternal separation had a larger CAR and flatter slopes in cortisol levels compared to those who did not report maternal separation [adjusted mean CAR in those reporting no separation versus separation: 7.1, 95% confidence interval (CI) 6.7–7.5 v. 8.4, 95% CI 7.3–9.5, p = 0.02, corresponding to adjusted mean diurnal slope: −0.129 (95% CI −0.130 to −0.128) v. −0.126 (95% CI −0.128 to −0.124), p = 0.01]. In participants who reported maternal separation, the age of separation was not associated with either cortisol measure (p = 0.11). The association between maternal separation and slope in cortisol secretion was largely explained by smoking behaviour and marital status at the time of sample collection whereas that of the CAR was explained by childhood psychosocial, material factors and adult health behaviours.
Our findings suggest that maternal separation in childhood is associated with alterations in the diurnal cortisol pattern in middle age. These associations are predominantly accounted for by adult circumstances and behaviours.
Serological evaluations of foot-and-mouth disease type SAT 2 viruses isolated in Kenya between 1979 and 1982 were performed using the two-dimensional microneutralization test. Nine field isolates of epizootiological significance were compared with four vaccine viruses. The results obtained identified Tan 5/68 as the most appropriate reference vaccine virus strain since it had the broadest serological spectrum. Potent Tan 5/68 vaccines would be expected to provide adequate protection against the contemporary SAT 2 field viruses. In the case of K 83/74, which also was shown to have a broad spectrum with viruses isolated in Kenya, the results show that the 1982 isolate from central Kenya was significantly divergent (r < 1·00 at P = 0·01) and warranted tactical revaccination for its control. The study highlighted the fact that strain R1215 which had been isolated from the oesophageal-pharyngeal swabs of asymptomatic carrier cattle had a narrow serological spectrum suggesting that such viruses could be unsuitable as vaccine for the national campaign.
Cognitive performance has been associated with mental and physical health, but it is unknown whether the strength of these associations changes with ageing and with age-related social transitions, such as retirement. We examined whether cognitive performance predicted mental and physical health from midlife to early old age.
Participants were 5414 men and 2278 women from the Whitehall II cohort study followed for 15 years between 1991 and 2006. The age range included over the follow-up was from 40 to 75 years. Mental health and physical functioning were measured six times using SF-36 subscales. Cognitive performance was assessed three times using five cognitive tests assessing verbal and numerical reasoning, verbal memory, and phonemic and semantic fluency. Socio-economic status (SES) and retirement were included as covariates.
High cognitive performance was associated with better mental health and physical functioning. Mental health differences associated with cognitive performance widened with age from 39 to 76 years of age, whereas physical functioning differences widened only between 39 and 60 years and not after 60 years of age. SES explained part of the widening differences in mental health and physical functioning before age 60. Cognitive performance was more strongly associated with mental health in retired than non-retired participants, which contributed to the widening differences after 60 years of age.
The strength of cognitive performance in predicting mental and physical health may increase from midlife to early old age, and these changes may be related to SES and age-related transitions, such as retirement.