To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Understanding the long-term ecological dynamics of boreal forests is essential for assessment of the possible responses and feedbacks of forest ecosystems to climate change. New data on past forest dynamics and peatland development were obtained from a peat sequence in the southern Valdai Hills (European Russia) based on pollen, plant macrofossil, micro-charcoal, peat humification, and testate amoeba analyses. The results demonstrate a dominance of broadleaved forests in the study area from 7000–4000 cal yr BP. Picea was initially a minor component of this forest but increased in cover rapidly with climatic cooling beginning at 4000 cal yr BP, becoming the dominant species. Broadleaved species persisted until 900 cal yr BP, with evidence for intensified felling and forest management over recent centuries. Over the last four hundred years there is evidence for widespread paludification and the establishment of Picea-Sphagnum forests. These data demonstrate how modern wet woodlands have been shaped by a combination of climatic and anthropogenic factors over several millennia. The results also demonstrate the value of a multiproxy approach in understanding long-term forest ecology.
A correlation has been found between strong molecular hydrogen emission and the morphological type of a planetary nebula. Those with an equatorial toroid and bipolar extensions have H2 1−0 S(1) stronger than Brackett γ. H2 maps of several objects, and NGC 2346 in particular, are consistent with a fast stellar wind interacting with an anisotropic medium.
A new astronomical system is nearing completion at U.N.S.W. in which a charge coupled device (CCD) array detector is matched to a Schmidt telescope, with the observations completely analyzed on-line. We have modified a Baker-Nunn satellite tracking camera, with its excellent 0.5m, f/1 super-Schmidt optics, converting it into a computer-controlled equatorially-mounted astronomical telescope. The telescope is expected to be located at Siding Spring Observatory in north-western New South Wales.
Universal screening for postpartum depression is recommended in many countries. Knowledge of whether the disclosure of depressive symptoms in the postpartum period differs across cultures could improve detection and provide new insights into the pathogenesis. Moreover, it is a necessary step to evaluate the universal use of screening instruments in research and clinical practice. In the current study we sought to assess whether the Edinburgh Postnatal Depression Scale (EPDS), the most widely used screening tool for postpartum depression, measures the same underlying construct across cultural groups in a large international dataset.
Ordinal regression and measurement invariance were used to explore the association between culture, operationalized as education, ethnicity/race and continent, and endorsement of depressive symptoms using the EPDS on 8209 new mothers from Europe and the USA.
Education, but not ethnicity/race, influenced the reporting of postpartum depression [difference between robust comparative fit indexes (∆*CFI) < 0.01]. The structure of EPDS responses significantly differed between Europe and the USA (∆*CFI > 0.01), but not between European countries (∆*CFI < 0.01).
Investigators and clinicians should be aware of the potential differences in expression of phenotype of postpartum depression that women of different educational backgrounds may manifest. The increasing cultural heterogeneity of societies together with the tendency towards globalization requires a culturally sensitive approach to patients, research and policies, that takes into account, beyond rhetoric, the context of a person's experiences and the context in which the research is conducted.
At least in conventional hydrostatic ice-sheet models, the numerical error associated with grounding line dynamics can be reduced by modifications to the discretization scheme. These involve altering the integration formulae for the basal traction and/or driving stress close to the grounding line and exhibit lower – if still first-order – error in the MISMIP3d experiments. MISMIP3d may not represent the variety of real ice streams, in that it lacks strong lateral stresses, and imposes a large basal traction at the grounding line. We study resolution sensitivity in the context of extreme forcing simulations of the entire Antarctic ice sheet, using the BISICLES adaptive mesh ice-sheet model with two schemes: the original treatment, and a scheme, which modifies the discretization of the basal traction. The second scheme does indeed improve accuracy – by around a factor of two – for a given mesh spacing, but
km resolution is still necessary. For example, in coarser resolution simulations Thwaites Glacier retreats so slowly that other ice streams divert its trunk. In contrast, with
km meshes, the same glacier retreats far more quickly and triggers the final phase of West Antarctic collapse a century before any such diversion can take place.
Holocene climatic variability and human impact on vegetation are reconstructed from a region in central European Russia, which lies at an important ecotone between broadleaf forest and steppe. For the first time in this region we adopt a multi-proxy approach that combines analysis of local mire conditions from plant macrofossil and testate amoeba analyses with pollen-based quantitative climate reconstruction. The proxies indicate a long-term warming trend from 9700 to 7500 cal yr BP, interrupted by a series of short-term cold events. From 7500 to 5000 cal yr BP the results imply a relatively stable climate, warmer and drier than present, spanning the Holocene Thermal Maximum. Since 5000 cal yr BP the data suggest a change to cooler climate, but with centennial-scale variability. This shift at around 5000 cal yr BP is supported by extensive evidence from other sites. In the early Holocene, the region was occupied mainly by pine and birch forests. Broad-leafed forests of oak, lime and elm expanded after 7800 cal yr BP and remained dominant until the last few centuries. During the historical period, vegetation changes have been driven mainly by human activities.
Using an ab-initio molecular dynamics approach based on the Car-Parrinello method, the detailed atomic and electronic structure of a high-angle grain boundary in germanium is determined by investigating its energy-translation surface. Information concerning the coordination of the lowest energy configuration, its translation state, volume change, structure factor and local density of states is obtained.
Molecular dynamics simulations performed on highly concentrated Coulomb/solvent systems are used to help interpret the transport mechanism in polymer ionics. Using simple Coulomb and Lennard-Jones forces among the ions and a solvent model of a fixed dipole contained in a spherical solvent particle, we investigated the nature of ion pair formation and stability. For a model NaI system, we find that ion pairs decrease with increase in solvent dipole moment or temperature. The latter observation is at variance with experimental results on polymer electrolytes, probably because of entropy terms that do not occur with our simple solvent molecule.
The effect of the crystal structure defects of different origin (dislocations, stresses, impurities, liquid phase inclusions) on the bulk laser damage threshold in big-size KDP crystals has been studied in the present paper. The quantitative dependence of the bulk laser damage threshold value on the internal stresses, density of dislocations and impurity concentration in crystals has been found.
UV-spectroscopy method is used to study the influence ofdifferent varying growth parameters (growth rate, crystallization temperature, pH of the solution, complexating additions) on the absorption spectra of KH2PO4 crystals. It is found that the minimal value of the absorption coefficient (k ˜ 0.01–0.02cm−1)may be achieved under the following growth conditions: 1) crystallization temperature ˜ 55°C, 2) growth rate ˜ 1mm/24hrs, 3)pH = 4.
We identify the binding sites for adsorption of a single Ge atom on the Si (100) surface using ab initio total energy calculations. The calculated diffusion barriers are in excellent agreement with experimental estimates. Using a large supercell we resolve the controversy regarding the binding geometry and migration path for the adatom, and investigate the influence of the adatom on the buckling of Si dimers. The adatom induces a buckling defect that is frequently observed using scanning tunneling Microscopy (STM); therefore the study of single adatoms may be experimentally accessible.
We are using total energy pseudopotential calculations to carry out an extensive investigation into grain boundary sliding in a number of different systems, in order to understand, at microscopic level, the fundamental mechanisms responsible for this process.
In this paper we present results for the sliding process at the ∑ = 5(001) twist grain boundary in germanium, chosen as a typical covalently bonded material, and contrast them with preliminary results obtained for the ∑ = 5 (001) twist grain boundary in aluminium, a typical metal.
We have performed total energy density functional theory calculations to investigate the sliding process at the ∑ = 5 (001) twist grain boundary in germanium. The accurate quantum mechanical description of the interatomic bonding provides valuable insights into the mechanisms of bond breaking and remaking that occur during the sliding.
In this paper we show how total energy calculations can be used to describe finite
temperature and strain rate effects in this grain boundary.
Recent developments in soft lithographic patterning enable the integration of functional ceramic thin films on a chip, rather than by adding discrete components to the system. As integrated device applications push the characteristic length scale of materials smaller and smaller, surface and interface effects play an important role, producing significant scientific challenges to the characterization of mechanical properties, performance and reliability. In this paper, we investigate the complex roles of microstructure, interface effects and residual stresses on ferroelectric thin film performance. Pb(Zr0.53Ti0.47)O3 films ranging in thickness from 190 nm to 500 nm were deposited by a sequential build up of sol-gel derived thin layers onto platinized Si substrates. Residual stresses in the films after thermal processing were observed and calculated from laser reflectance measurements of wafer curvature. Field-induced displacements were then measured by interferometric methods for films with well-characterized residual stress states. Results indicate significant increases in film performance with a decrease in measured residual tensile stress.
Inorganic calcite precipitation experiments were conducted to determine whether inducing specific orientations of calcite crystal growth can cause the enrichment of cations larger than Ca. Malonic acid (CH2(COOH)), a di-carboxylic acid, was used to poison growth on acute kink sites, promoting growth on obtuse kink sites, causing calcite crystals elongated along their c-axes to form in a mechanism similar to that seeninthe growth of E. huxleyi coccoliths. Calcite was precipitated with a range of malonic acid concentrations (0 to 10-1 M), and 9x10-5 M of either SrCl2 or MgCl2. The results show that calcite crystals precipitated in the presence of large malonic acid concentrations show significant elongation along the c axis, and suggest that increasing malonate concentrations corresponded with increasing DSr. Experiments with 10-1 M malonic acid caused elevated DSr comparable to that predicted for E. huxleyi coccolith calcite (Langer et al., 2006).
By extracting residues from pottery sherds the authors show that it is possible to say whether they had contained dairy or carcass fat residues. Correlation with faunal assemblages showed a good match between the incidence of dairy fat in pottery which implied a strong dairy fraction in the diet and a milking herd implied by the animal bones. They also show that dairy fat was more likely to be found in the smaller pots while carcass fats occurred in the larger ones. The method has demonstrated dairying in England from the fifth millennium BC, and offers a novel way of studying economies with pottery but few animal bones.