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Predicting the isotopic modification of ice by melting processes is important for improving the accuracy in paleoclimate reconstruction. To this end, we present results from cold room laboratory observations of changes in the isotopic ratio (D/H and 18O/16O) of ice cubes by isotopic exchange between liquid water and ice in nearly isothermal conditions. A 1-D model was fit to the isotopic results by adjusting the values of two parameters, the isotopic exchange rate constant (kr) and the fraction of ice participating in the exchange (f). We found that the rate constant for hydrogen isotopic exchange between liquid water and ice may be greater (up to 40%) than that for the oxygen isotopic exchange. The range of the rate constant obtained from four melt experiments is from 0.21 to 0.82 h–1. The model results also suggest that f decreases with the increasing wetness of the ice. This is because with increasing water saturation in ice, water may be present only in the small pores or some of the water that was exchanged with ice may be bypassed, decreasing the effective surface area over which the isotopic exchange can occur. The relationship between the two water isotopes (δ18O vs δD) was observed and modeled and the slope was <8, which is significantly different from the slope of the meteoric waterline. We note that these slopes were obtained without considering the sublimation process.
The present study was performed to investigate whether breast-feeding is associated with early pubertal development among children 7–9 years old in Korea.
Children were divided into those who did and did not receive breast-feeding for 6 months or longer in accordance with the recommendations of the WHO. Pubertal status was determined by clinical examination using Tanner staging.
Prospective observational study.
We conducted a follow-up study of children aged 7–9 years in 2011 who had taken part in the Ewha Birth & Growth Cohort study.
Fifty (22·8 %) of the total of 219 children were in early puberty, with the proportion being slightly higher for girls (24·1 %) than boys (21·4 %). Children who had entered early puberty were taller, weighed more and had a higher concentration of insulin-like growth factor 1. Moreover, the change in weight Z-score from birth to follow-up was significantly lower in children who were breast-fed than in those who were not (weight Z-score change: 0·32 (sd 1·59) v. 0·77 (sd 1·61), respectively, P=0·04). Comparison of breast-feeding by puberty status indicated a preventive association with early puberty in children who were breast-fed for 6 months or longer (OR=0·37; 95 % CI 0·18, 0·74). This association remained significant after adjustment for relevant covariates.
These results demonstrate a beneficial association between breast-feeding and early pubertal development, especially in those breast-fed for 6 months or longer. The study suggests that interventions would need to start early in life to prevent early pubertal development.
The study's aim was to examine the association of alcohol consumption with verbal and visuospatial memory impairment in older people.
Participants were 1,572, aged ≥60 years, in the hospital-based registry of the Clinical Research Center for Dementia of South Korea (CREDOS). Moderate drinking was defined as no more than seven drinks per week and three drinks per day. Memory impairment was defined as performance with more than 1 standard deviation below the mean value on the Seoul Verbal Learning Test and Rey Complex Figure Test.
Those who consumed alcohol moderately, compared with abstainers, had a lower odds of verbal memory impairment (Odds Ratio [OR] = 0.64; 95% Confidence Interval [CI]: 0.46–0.87), adjusting for covariates. Visuospatial memory, however, was not significantly associated with alcohol consumption.
Moderate alcohol drinking is associated with a reduced likelihood of verbal memory impairment among older people attending memory clinics.
Genetic variation in wild soybean (Glycine soja Sieb. and Zucc.) is a valuable resource for crop improvement efforts. Soybean is believed to have originated from China, Korea, and Japan, but little is known about the diversity or evolution of Korean wild soybean. Therefore, in this study, we evaluated the genetic diversity and population structure of 733 G. soja accessions collected in Korea using 21 simple sequence repeat (SSR) markers. The SSR loci produced 539 alleles (25.7 per locus) with a mean genetic diversity of 0.882 in these accessions. Rare alleles, those with a frequency of less than 5%, represented 75% of the total number. This collection was divided into two populations based on the principal coordinate analysis. Accessions from population 1 were distributed throughout the country, whereas most of the accessions from population 2 were distributed on the western side of the Taebaek and Sobaek mountains. The Korean G. soja collection evaluated in this study should provide useful background information for allele mining approach and breeding programmes to introgress alleles into the cultivated soybean (G. max (L). Merr.) from wild soybean.
Non-destructive high-throughput phenotyping based on phenomics is an emerging technology for assessing the genetic diversity of various traits and screening in breeding programmes. In this study, non-destructive measurements of leaf temperature and chlorophyll fluorescence were conducted to investigate the physiological responses of soybean (Glycine max) to salt stress so as to set up a non-destructive screening method. Two-week-old seedlings of soybean in the V2 stage were treated with 0, 12.5, 25, 50 and 100 mM NaCl to induce salt stress. Three parameters, photosynthesis rate, stomatal conductance and chlorophyll fluorescence, decreased significantly, while soybean leaf temperature increased by exhibiting a positive correlation with NaCl concentration (P< 0.001). Soybean leaf temperature increased significantly at 50 mM NaCl when compared with the untreated control, although no visual symptom was observed. We selected leaf temperature as a major physiological parameter of salt stress as its measurement is much easier, faster and cheaper than that of other physiological parameters. Therefore, leaf temperature can be used for evaluating the responses to salt stress in soybean as a non-destructive and phenomic parameter. The results of this study suggest that non-destructive parameters such as chlorophyll fluorescence and leaf temperature are useful tools for assessing the genetic diversity of soybean with regard to salt stress tolerance and to screen salt stress-tolerant soybean for breeding.
We investigated microstructures, compositional distributions, and electrical properties of dielectric CaCu3Ti4O12 (CCTO) thin films deposited on Pt/TiO2/SiO2/Si substrates from 700 to 800 °C by pulsed laser deposition. With increasing the deposition temperature from 700 to 750 °C, the dielectric constants (εr) of CCTO films were greatly enhanced from ∼300 to ∼2000 at 10 kHz, respectively. However, the εr values of CCTO films were gradually decreased above 750 °C, which was surely attributable to the formation of a TiO2-rich dead layer at the interface between CCTO and Pt electrode. Compositional analyses by Auger electron spectroscopy, energy dispersive spectroscopy, and electron energy loss spectroscopy revealed that the TiO2-rich dead layer became thicker because of severe Cu diffusion from CCTO films to Pt electrode. The leakage current behaviors of CCTO films are in good agreement with Poole–Frenkel conduction mechanism, where both the TiO2-rich dead layer and rutile TiO2 nanocrystalline particles are considered to play a role of charge trapping centers.
It is widely recognized that the processor has a key role to play in creating and strengthening the mapping between form and meaning that is integral to language use. Adopting an emergentist approach to heritage language acquisition, the current study considers the extent to which the operation of the processor can contribute to an account of what is acquired, what is subsequently retained or lost, and what is never acquired in the first place. These questions are explored from two perspectives. First, morphosyntactic phenomena for which there is apparently substantial input are considered, with a focus on the relevance of salience, frequency, and transparency to the establishment of form-meaning mappings. Second, a phenomenon for which there appears to be relatively little input (i.e., scope) is examined with a view to understanding its fate in heritage language acquisition. In both cases, the emergentist perspective appears to offer promising insights into why heritage language learners succeed—and fail—in the way that they do.
The diatoms are an ecologically important group of algae that have been extensively studied by ecologists and taxonomists. However, the large-scale patterns of diatom distribution and the factors underlying this distribution are largely unknown. The aims of this study were to identify the large-scale spatial patterns of benthic diatom assemblages in Korean streams and rivers, and to assess the importance of numerous environmental factors on diatom distribution. We classified 720 study sites based on diatom flora. Benthic diatoms, water chemistry, altitude, and riparian land cover and use were characterized by multivariate analyses, Monte Carlo permutation tests, and indicator species analysis. In total, we identified 531 diatom taxa. Diatom assemblages were mostly dominated by species of the genera Achnanthes, Navicula, Nitzschia, Cocconeis, Fragilaria (Synedra included), Cymbella, Gomphonema, and Melosira. Cluster analysis partitioned all 720 sites into eight groups based on diatom species composition. Canonical correspondence analysis indicated that altitude, land cover and use, current velocity, electrical conductivity, and nutrient levels explained a significant amount of the variation in the composition of assemblages of benthic diatoms. At the national scale, a downstream ecological gradient was apparent, from fast-flowing, mostly oligotrophic highland streams to slow-flowing, mostly eutrophic lowland rivers. Our data suggest that spatial factors explain some of the variation in diatom distribution. The present investigation of the spatial patterns of benthic diatoms, the ecological determinants of diatom occurrence, and the identification of diatom indicator species contributes to development of a program for assessing the biological integrity of lotic ecosystems in Korea.
Anthropogenic land use within watersheds has substantial effects on aquatic habitats and biological communities. From September 2006 to December 2008, we investigated the effects of land use on benthic macroinvertebrate communities by comparing Song Stream and Odae Stream, two adjacent mountain streams in Korea whose watersheds have different land use patterns. Song Stream is significantly disturbed by agricultural activities in the watershed, whereas Odae Stream is relatively undisturbed and is surrounded by a well-conserved forest area. Song Stream had significantly higher levels of all nutrients and sediment-related factors due to the adjacent agricultural area. As a result, Song Stream had markedly lower species community indices, such as taxa richness and abundance. In Song Stream, macroinvertebrate scrapers and predators were most adversely affected, whereas collector-gatherers became a dominant group. Based on correlation and multivariate analyses, total dissolved solids had the strongest negative relationship with macroinvertebrate assemblages, followed by electrical conductivity, total nitrogen, and pH. The proportion of cobble in stream substrate was positively related to the richness and abundance of macroinvertebrates. Our results indicate that disturbances caused by agricultural land use, particularly sand deposition, had significant adverse effects on macroinvertebrate habitats and on the biotic integrity of benthic macroinvertebrate communities.
Licorice extracts are known to exhibit anti-carcinogenic activities. However, chronic licorice consumption can lead to serious side effects due to the presence of considerable quantities of glycyrrhizin, which causes severe hypokalaemia and hypertension. In the present study, we evaluated the effects of a hexane–ethanol extract of Glycyrrhiza uralensis (HEGU), which lacks glycyrrhizin, on the metastatic characteristics of DU145 prostate cancer cells. HEGU inhibited basal and epidermal growth factor-induced cell migration, invasion and adhesion in a dose-dependent fashion. HEGU significantly suppressed the secretion and activation of the matrix metalloproteinase (MMP)-2 and MMP-9. The secretion of tissue inhibitor of metalloproteinase (TIMP)-1 was reduced, but that of TIMP-2 was increased in HEGU-treated cells. HEGU reduced the protein levels of integrin-α2, the intercellular adhesion molecule, and the vascular cell adhesion molecule. An active fraction of HEGU was separated via column chromatography, and the structure of the active component, licoricidin, was identified via 1H NMR and 13C NMR. The treatment of DU145 cells with licoricidin induced a reduction in cell migration and the secretion of MMP-9, TIMP-1, urokinase-type plasminogen activator and vascular endothelial growth factor, as well as in the expression of adhesion molecules. These results indicate that HEGU, which contains licoricidin, is a potent anti-metastatic agent, which can markedly inhibit the metastatic and invasive capacity of malignant prostate cancer cells. The observed reductions in the activation of proteases and the levels of adhesion molecules may constitute a component of the mechanisms by which HEGU inhibits the migration and adhesion of prostate cancer cells.
In this study, we have investigated the structure of nickel-cobalt silicide to understand its behavior at high temperature. Nickel-cobalt silicide was formed after two-step RTP at 500°C and 700°C respectively. We could observe by TEM that nickel-cobalt silicide consists of a structure which seems to be a Ni-Co-Si ternary phase. No nickel silicide phases and cobalt silicide phases were detected in nickel-cobalt silicide by XRD. From XPS depth profile, we could confirm that there is a cobalt composition gradient along the silicide.
A mucin coat is deposited on rabbit embryos during passage through the oviduct; rabbit blastocysts cultured from the 1-cell stage in vitro have no mucin coat. When cultured blastocysts are transferred to recipients, the lack of mucin coat might account in part for subsequent failure of pregnancy. We have investigated the possibility that mucin coat deposition is induced following transfer of in vitro 72 h-cultured blastocysts to oviducts of asynchronous or synchronous recipients. One-cell embryos were collected by flushing oviducts 19–20 h post-coitus and were cultured in vitro for 72 h until they reached the blastocyst stage. The blastocysts were transferred to the oviducts of recipients that were synchronized either with the donors (synchronous) or 1 day later than the donors (asynchronous). They were recovered after 24–48 h and the mucin coat thickness and embryo degeneration rate were measured. The degeneration rate of blastocysts recovered from uteri of synchronous recipients was higher than that from asynchronous recipients (72.2% vs 40.0%). The mucin coats around embryos recovered from oviducts of asynchronous recipients after 48 h were thicker than those from synchronous recipients. More asynchronous recipients were pregnant and gave birth to more pups than synchronous recipients. These results indicate that the oviducts of asynchronous recipients secreted more mucin around the transferred embryos, causing higher rates of implantation of the in vitro-cultured blastocysts.
Structure and composition of the ferroelectric Pb(Zr, Ti)O3 layers in a capacitor of the ferroelectric random-access memory (FeRAM) device having a density of 64 k were investigated by transmission electron microscopy (TEM) together with the energy-dispersive spectroscopy (EDS) technique. The 250 nm thick PZT layer derived by the sol-gel route showed a 2–3% Pb-deficient, 3–4% Ti-deficient, and 5–7% Zr-excess composition at the top electrode interface compared to the bulk composition when they were as-fabricated. The local compositional nonuniformity became more critical as the integration process proceeded, which seriously degraded the ferroelectric hysteresis and the device yield. The major cause of the compositional variation was the outward diffusion of Pb through the capping barrier TiO2 layer during annealing at 650 °C. The AlN capping barrier layer was also not effective in suppressing the diffusion of Pb. However, the Al2O3/TiO2 double capping layer was very effective in suppressing the outward diffusion of Pb, and excellent ferroelectric characteristic was expected.
Zirconia (ZrO2) thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using ultrasonic nebulization with new source materials, Zr(OBu)4, Zr(OBu)3(acac), Zr(OBu)2(acac)2, and Zr(OBu) (acac)3. This process is a simple and economic method to prepare oxide thin films. Zr(OBu)4 was successfully reacted with acetylacetone at a molar ratio of 1: 3. Polycrystalline thin films were deposited at a substrate temperature range from 300 to 550 °C. The substitution of alkoxy radicals by acetylacetone made the deposition rate higher and insensitive to substrate temperature. The films deposited below 450 °C mostly had a monoclinic structure, and those deposited above 450 °C had a tetragonal structure. The measured optical energy band gap of zirconia film was 5.32 eV.
Bisethylacetoacetato Cu(II), referred to as Cu(etac)2, was synthesized and used as a novel metal-organic precursor to produce Cu films by PECVD processing. Cu(etac)2 is a nonfluoride compound that is solid at room temperature with reasonable volatility at 120–150 °C of 0.8 Torr. Effects of selected process variables on the characteristics of Cu film deposition were studied. Considered variables were plasma power, hydrogen flow rate, deposition time, substrate temperature, and precursor temperature. The process conditions to give Cu films of a high quality were determined. The electrical resistivity approached 2 μΩ · cm as the Cu film thickness became greater than 2500 Å. The conformality of the Cu film deposition by PECVD was sufficient to result in complete via-hole fillings of wafers patterned for 256 Mb DRAM.
We have produced Co1-xPtX (X = 0.53 and 0.75) alloy films using DC magnetron sputtering and investigated their magnetic properties using vibrating sample magnetometry(VSM) and Kerr hysteresis loop tracer. The as-deposited Co-Pt alloy films show a strong in-plane magnetization. By annealing the alloy samples, we have identified that the magnetic properties are drastically changed. While the magnetic properties of the Co0 25Pt0 75 alloy films show no noticeable changes, the coercivity and the squareness of the Co0.47Pt0.53 alloy films are drastically increased after annealing. Transmission electron microscopy(TEM) and x-ray diffractometry(XRD) analysis showed that CoPt(L10) and Co-Pt3 (L12) ordered phases, respectively, are formed in each case with a strong (11) texture. We suggest that the perpendicular magnetic anisotropy in the Co-Pt system does not depend on the mere textureness of the layer but strongly depends on the arrangement of Co and Pt at an atomic scale.
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