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.
Intrinsic size effects in nanoglass plasticity have been connected to the structural length scales imposed by the interfacial network, and control over this behavior is critical to designing amorphous alloys with improved mechanical response. In this paper, atomistic simulations are employed to probe strain delocalization in nanoglasses with explicit correlation to the interfacial characteristics and length scales of the amorphous grain structure. We show that strength is independent of grain size under certain conditions, but scales with the excess free volume and degree of short-range ordering in the interfaces. Structural homogenization upon annealing of the nanoglasses increases their strength toward the value of the bulk metallic glass; however, continued partitioning of strain to the interfacial regions inhibits the formation of a primary shear band. Intrinsic size effects in nanoglass plasticity thus originate from biased plastic strain accumulation within the interfacial regions, which will ultimately govern strain delocalization and homogenous flow in nanoglasses.
Several studies have suggested that higher carotenoid levels may be beneficial for atherosclerosis patients, but few studies have examined this relationship in the Chinese population. This cross-sectional study examined the association between the levels of carotenoids in diet and serum and carotid intima–media thickness (IMT) in Chinese adults aged 50–75 years in Guangzhou, China. Dietary intake was assessed using a FFQ. HPLC was used to assay the serum concentrations of α-carotene, β-carotene, lutein+zeaxanthin, β-cryptoxanthin and lycopene. The IMT at the common carotid artery (CCA) and bifurcation of the carotid artery was measured by B-mode ultrasound. A total of 3707 and 2947 participants were included in the analyses of dietary and serum carotenoids. After adjustment for demographic, socio-economic and lifestyle factors, all the serum carotenoids levels except lycopene were found to be inversely associated with the IMT at the CCA and bifurcation (Ptrend<0·001 to 0·013) in both men and women. The absolute mean differences in the IMT between the subjects in the extreme quartiles of serum carotenoid levels were 0·034 mm (α-carotene), 0·037 mm (β-carotene), 0·032 mm (lutein+zeaxanthin), 0·030 mm (β-cryptoxanthin), 0·015 mm (lycopene) and 0·035 mm (total carotenoids) at the CCA; the corresponding values were 0·025, 0·053 0·043, 0·050, 0·011 and 0·042 mm at the bifurcation. The favourable associations were also observed between dietary carotenoids (except lycopene) and the CCA IMT. In conclusion, elevated carotenoid levels in diet and serum are associated with lower carotid IMT values (particular at the CCA) in Chinese adults.
A coaxial-output rolled strip pulse-forming line (RSPFL) with a dry structure is researched for the purpose of miniaturization and all-solid state of pulse-forming lines (PFL). The coaxial-output RSPFL consists of a coaxial-output electrode (COE) and a rolled strip line (RSL). The COE is characterized by quasi-coaxial structure, making the output pulse propagate along the axial direction with a small output inductance. The RSL is rolled on the COE, whose transmission characteristics are analyzed theoretically. It shows that the RSL can be regarded as a planar strip line when the rolling radius of the strip line is larger than 60 times of the thickness of the insulation dielectric layer of RSL. CST modeling was carried out to simulate the discharging characteristic of the coaxial-output RSPFL. It shows that the coaxial-output RSPFL can deliver a discharging pulse with a rise time <6 ns when the impedance of the RSL matches that of the COE, which confirms the theoretical analysis. A prototype of the coaxial-output RSPFL was developed. A 49-kV discharging pulse on a matched load was achieved when it was charged to 100 kV. The discharging waveform has a pulse width of 32 ns, with a rise time of 6 ns, which is consistent with the simulation waveform. An energy-storage density of 1.9 J/L was realized in the coaxial-output RSPFL. By the method of multi-stage connection in series, a much higher output voltage is convenient to be obtained.
This study aimed to investigate the effects of dietary live yeast (LY) supplementation on growth, intestinal permeability and immunological parameters of piglets challenged with enterotoxigenic Escherichia coli K88 (ETEC). Piglets weaned at 21 d were allocated into three treatments with six pens and six piglets per pen, receiving the control diet (CON), diets supplemented with antibiotics plus zinc oxide (ANT–ZnO) and LY (Saccharomyces cerevisiae strain CNCM I-4407), respectively, for a period of 2 weeks. On day 8, thirty-six piglets were selected as control without ETEC (CON), CON–ETEC, ANT–ZnO–ETEC and LY–ETEC groups challenged with ETEC until day 10 for sample collections. Piglets fed ANT–ZnO diet had the highest average daily gain and average daily feed intake (P<0·05) during the 1st week, but ADG of piglets fed the ANT–ZnO diet was similar as piglets fed LY diet during the second week. Piglets with LY–ETEC or ANT–ZnO–ETEC had markedly lower diarrhoea score (P<0·05) than piglets with CON–ETEC during the 24 h after ETEC challenge. Relative to piglets with CON, the counts of E. coli, urinary ratio of lactulose to mannitol, plasma IL-6 concentration, mRNA abundances of innate immunity-related genes in ileum and mesenteric lymph node tissues were increased (P<0·05), whereas the villous height of jejunum and relative protein expression of ileum claudin-1 were decreased (P<0·05) in piglets with CON–ETEC; however, these parameters did not markedly change in piglets with LY–ETEC or ANT–ZnO–ETEC. In summary, dietary LY supplementation could alleviate the severity of diarrhoea in piglets with ETEC, which may be associated with the improved permeability, innate immunity and bacterial profile.
Turbulent surface fluxes were studied using observations taken over sea ice in the Baltic Sea in March 1998. The fluxes of momentum and sensible heat were measured by a sonic anemometer and compared with fluxes derived from wind velocity and air-temperature profiles. The neutral 10 m drag coefficient showed no apparent dependence on wind speed (in the range 2–20 m s–1), resulting in a mean value of 1.0 × 10–3 for smooth snow-covered ice and 1.5 × 10−3 for deformed ice. The overall mean value was 1.28 × 10–3. The roughness length for temperature revealed a greater apparent dependence on wind speed and was slightly larger than the aerodynamic roughness for low wind speeds, and vice versa for moderate and high winds. We give an empirical expression that predicts how the scalar roughness depends on the aerodynamic roughness (drag coefficient) and wind speed. Agreement of the gradient-method results with the eddy-flux results supports the validity of the Monin-Obukhov similarity theory. Fluxes modelled by a coupled air-ice-sea model compared well with the eddy-flux and gradient methods. Surface temperature estimates by the three methods also agreed well. Tests and sensitivity analysis emphasize the need for especially accurate sensor calibration and strict information about the sensor heights for the gradient method.
Development of landfast sea ice and its snow cover was monitored in the Gulf of Bothnia, Baltic Sea, for a period of 4 weeks during the early melt season of 2004. During this period, approximately 90% of the snow layer was transformed into superimposed ice, while the rest sublimated. A one-dimensional thermodynamic snow/ice model was used to simulate this process. The modelled snowmelt and superimposed ice growth were consistent with the observations, but the net accumulation of superimposed ice was slightly overestimated. The errors in calculation of temporal variations of the refreezing were probably due to the uncertainties in the external forcing and simplification of snow processes in the model. The modelled snow thickness was sensitive to the atmospheric forcing, and the influence was amplified when the albedo was parameterized as a function of surface temperature. In the sensitivity tests without this feedback, the direct effect of the inaccuracy in the albedo parameterization was minor. Errors in the parameterized longwave radiation were critical for the modelled snow surface temperature during night-time, but did not have a large effect on the mass balance during this spring melt period.
In this paper, we present the results of a one-dimensional, thermodynamic sea-ice model applied to the Baltic Air-Sea-Ice Study (BASIS) field data. In general, the model results are in good agreement with the measurements, which were made during mild weather conditions with distinct areal and temporal variations in the snow and ice thickness. The total amount of refrozen ice calculated from the surface melting water gives a first-order estimate of snow-ice formation during the BASIS experiment, and this agreed well with the total observed variation in ice thickness. The model slightly overestimated ice growth at the bottom. This may be due to the variation in sea-ice thermal properties, affected by a slush layer between the snow and ice, or to the lack of ice-ocean interaction in the model.
The snow/ice albedo was studied during a 4 week field experiment over first-year sea ice in the Gulf of Bothnia, Baltic Sea, in spring 2004. Observations were made on radiative fluxes, cloud cover, wind, air temperature and humidity, as well as snow/ice temperature, thickness, density and grain size. The albedo variation during the observation period was large: the daily mean albedo ranged from 0.79 over a new snow cover to 0.30 over bare, melting ice. The evolution of the albedo was related to the surface properties, but existing parameterizations based on Arctic data did not explain the observations well. The snow thickness was found to be the most critical factor affecting the albedo. A new parameterization was derived for the albedo dependence on snow thickness, to be applied over the Baltic Sea in spring, when periods of melting and freezing alternate but the ice is still relatively thick (about 0.6 m). The diurnal cycle of solar radiation was large, and the snow/ice metamorphism due to the melting during daylight and refreezing during the night caused a diurnal albedo cycle with a maximum in the early morning and a minimum in the afternoon, with an albedo difference up to 0.14 between the two.
The development of land-fast sea ice and overlying snow was monitored during a 4 week period, until the snow cover had completely disappeared, at a site in the Gulf of Bothnia, Baltic Sea (63.57ú N, 19.85° E). The meteorological and radiative boundary conditions were continuously recorded. During the observation period, a 15 cm thick snow layer on the ice was transformed into a 7 cm thick granular ice layer (superimposed ice) on the ice surface, contributing significantly (about 11%) to the total ice thickness. Approximately 1 cm w.e. of the snow was sublimated. Neither snow-ice formation nor basal ice growth was significant during the same period. The salinity and isotopic (δ18O) composition of the ice indicated that prior to the experiment a 7 cm layer of superimposed ice had already formed. Hence, superimposed ice layers contributed 22% of the total ice thickness by the time all snow had disappeared. The advancing spring, decrease in surface albedo, diurnal cycle in the incoming solar radiation, and synoptic-scale changes in the cloud cover and the air–ice turbulent heat fluxes caused variations in the heat budget of the snowpack. Superimposed ice formation due to refreezing of meltwater occurred during most nights of the study period, and the most important refreezing periods were under such synoptic conditions that the air and snow surface temperatures also remained below zero during daytime. In contrast to typical summer conditions in polar oceans, low snow surface temperatures acted as the primary heat sink for the refreezing of meltwater.
The numerical integration of the heat-conduction equation is one of the main components in a thermodynamic sea-ice model. The spatial resolution in the ice normally varies from a minimum of three layers up to a few tens of layers. The temporal resolution varies from a few minutes up to hours. In this paper the impact of numerical resolution on the prediction of a one-dimensional thermodynamic ice model is studied. Analytical solutions for idealized cases were derived and compared with the numerical results. For the full ice model, groups of simulations were made, applying average climatic weather-forcing data corresponding to the ice-freezing, ice-thermal equilibrium and ice warm-up seasons. Special attention was paid to the effect of model spatial resolution. Early in the freezing season, the influence of resolution on model predictions is not significant. When the shortwave radiation becomes large, its absorption within the ice or snow cover was found to modulate the effect of numerical resolution on predictions of ice temperature and surface heat fluxes (e.g. the model run with a coarse spatial resolution yielded large daily variations in surface temperature). Resolution also affects the in-ice temperature profile. For process studies, a two-layer scheme for the solar radiation penetrating into the ice is suitable for a fine-spatial-resolution ice model.
We present a two-dimensional, coupled, mesoscale atmosphere–sea-ice model, and apply it to simulate the air–ice interaction during warm-air advection. The model was run into a steady state under various conditions with respect to the season, cloud cover and wind speed. The spatial and temporal evolution of the thermodynamics of the ice, snow and the atmospheric boundary layer (ABL) were investigated. The development of the stably stratified ABL downwind of the ice edge depended above all on the wind speed and cloud cover. If the turbulent heat flux from air to snow was large enough to compensate the radiative cooling of the surface, a downward conductive heat flux was generated in the upper ice and snow layers. The stronger was the surface heating (strong wind, overcast skies) and the shorter its duration (on a scale down to a few hours), the wider was the region where this downward flux occurred. From the point of view of ABL modelling, the interactive coupling between air and ice was most important when the wind was strong, while from the point of view of ice thermodynamic modelling the coupling was most important when the wind was weak.
We have studied the accuracy of ice thickness (hi) retrieval based on night-time MODIS (Moderate Resolution Imaging Spectroradiometer) ice surface temperature (Ts) images and HIRLAM (High Resolution Limited Area Model) weather forcing data from the Arctic. The study area is the Kara Sea and eastern part of the Barents Sea, and the study period spans November-April 2008–11 with 199 hi charts. For cloud masking of the MODIS data we had to use manual methods in order to improve detection of thin clouds and ice fog. The accuracy analysis of the retrieved hi was conducted with different methods, taking into account the inaccuracy of the HIRLAM weather forcing data. Maximum reliable hi under different air-temperature and wind-speed ranges was 35–50 cm under typical weather conditions (air temperature <–20cC, wind speed <5ms–1) present in the MODIS data. The accuracy is best for the 15–30 cm thickness range, ∼38%. The largest hi uncertainty comes from air temperature data. Our ice-thickness limits are more conservative than those in previous studies where numerical weather prediction model data were not used in the hi retrieval. Our study gives new detailed insight into the capability of Ts-based hi retrieval in the Arctic marginal seas during freeze-up and wintertime, and should also benefit work where MODIS hi charts are used.
Snow and ice thickness in the coastal Kara Sea, Russian Arctic, were investigated by applying the thermodynamic sea-ice model HIGHTSI. The external forcing was based on two numerical weather prediction (NWP) models: the High Resolution Limited Area Model (HIRLAM) and the European Centre for Medium-Range Weather Forecasts (ECMWF) model. A number of model experiments were carried out applying different snow parameterization schemes. The modelled ice thickness was compared with in situ measurements and the modelled snow thickness was compared with the NASA Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) snow thickness. The HIRLAM and ECMWF model results agreed with each other on air temperature and wind. The NWP model precipitation forecasts caught up the synoptic-scale snowfall events, but the magnitude was liable to errors. The ice growth was modelled reasonably well applying HIGHTSI either with a simple parameterization for snow thickness or with the HIRLAM or ECMWF model precipitation as input. For the latter, however, an adjustment of snow accumulation in early winter was necessary to avoid excessive accumulation and consequent underestimation of ice thickness. Applying effective snow heat conductivity improved the modelled ice thickness. The HIGHTSI-modelled snow thickness had a seasonal evolution similar to that of the AMSR-E snow thickness. New field data are urgently needed to validate NWP and ice models and remote-sensing products for snow and sea ice in the Kara Sea.
The seasonal cycle of fast ice thickness in Prydz Bay, East Antarctica, was observed between March and December 2012. In March, we observed a 0.16 m thickness gain of 0.22 m-thick first-year ice (FYI), while 1.16 m-thick second-year ice (SYI) nearby simultaneously ablated by 0.59 m. A 1-D thermodynamic sea-ice model was applied to identify the factors that led to the simultaneous growth of FYI and melt of SYI. The different evolutions were explained by the difference in the conductive heat flux between the FYI and SYI. As the FYI was thin, there was a large temperature gradient between the ice base and the colder ice surface. This generated an upward conductive heat flux, which was larger than the heat flux from the ocean to the ice base, yielding basal growth of ice. In the case of the thicker SYI the temperature gradient and, hence, the conductive heat flux were smaller, and not sufficient to balance the oceanic heat flux at the ice base, yielding basal ablation. Penetration of solar radiation affected the conductive heat flux in both cases, and the model results were sensitive to the initial ice temperature profile and the uncertainty of the oceanic heat flux.
The Myanmar snub-nosed monkey Rhinopithecus strykeri was discovered in 2010 on the western slopes of the Gaoligong Mountains in the Irrawaddy River basin in Myanmar and subsequently in the same river basin in China, in 2011. Based on 2 years of surveying the remote and little disturbed forest of the Gaoligong Mountains National Nature Reserve in China, with outline transect sampling and infrared camera monitoring, a breeding group comprising > 70 individuals was found on the eastern slopes of the Gaoligong Mountains in the Salween River Basin. Given the Critically Endangered status of this primate (a total of < 950 individuals are estimated to remain in the wild), efforts to protect the relatively undisturbed habitat of this newly discovered population and to prevent hunting are essential for the long-term survival of this species.
Ice algae have successfully adapted to the extreme environmental conditions in the Antarctic, however the underlying mechanisms involved in the regulation and response of thylakoid membranes and chloroplast to low-temperature stress are still not well understood. In this study, changes in pigment concentrations, lipids, fatty acids and pigment protein complexes in thylakoid membranes and chloroplast after exposure to low temperature conditions were investigated using the Antarctic ice algae Chlamydomonas sp. ICE-L. Results showed that the chloroplasts of Chlamydomonas sp. ICE-L are distributed throughout the cell except in the nuclear region in the form of thylakoid lamellas which exists in the gap between organelles and the starch granules. Also, the structure of mitochondria has no obvious change after cold stress. Concentrations of Chl a, Chl b, monogalactosyl diacylglycerol, digalactosyl diacylglycerol and fatty acids were also observed to exhibit changes with temperature, suggesting possible adaptations to cold environments. The light harvesting complex, lutein and β-carotene played an important role for adaptation of ICE-L, and increasing of monogalactosyl diacylglycerol and digalactosyl diacylglycerol improved the overall degree of unsaturation of thylakoid membranes, thereby maintaining liquidity of thylakoid membranes. The pigments, lipids, fatty acids and pigment-protein complexes maintained the stability of the thylakoid membranes and the normal physiological function of Chlamydomonas sp. ICE-L.
Stable carbon isotope (δ13C) values of organic matter in lacustrine sediments are commonly used to trace past changes in terrestrial and aquatic carbon cycles. Here we use a high-resolution, well-dated δ13C record from Lake Tengchongqinghai (TCQH) in southwestern China, together with other proxy indices, to reconstruct the paleolimnological history over the past 18.5 ka. Organic matter in the sediments of Lake TCQH is derived predominately from aquatic macrophytes. The lacustrine primary productivity is closely linked with lake-level changes affected by variations in the strength of the Asian summer monsoon and modified by evapotranspiration. Similar to lake sediments world-wide, a ca. − 3‰ shift occurred in the δ13C values of Lake TCQH in response to the significant increase in atmospheric CO2 concentration during the last deglaciation. In the Holocene, the availability of dissolved CO2 in the lake water of Lake TCQH was determined by variations in hydraulic energy: low water turbulence creates a thick, stagnant boundary layer around aquatic plants, which will restrict the rate of CO2 diffusion and result in more positive δ13C values of aquatic plants. In contrast, significant water turbulence dramatically reduces the boundary layer thickness leading to more negative δ13C values of aquatic plants.
Landfast sea ice forms and remains fixed along the coast for most of its life time. In Prydz Bay, landfast ice is seasonal due to melting, mechanical breakage and drift of ice in summer. Its annual cycle of thickness and temperature was examined using a one-dimensional thermodynamic model. Model calibration was made for March 2006 to March 2007 with forcing based on the Chinese National Antarctic Research Expedition data, which consisted of in situ ice and snow observations and meteorological records at the Zhongshan Station. The observed maximum annual ice thickness was 1.74 m. The ice broke and drifted out in summer when its thickness was 0.5–1.0 m. Oceanic heat flux was estimated by tuning the model with observed ice thickness. In the growth season, it decreased from 25 W m-2 to 5 W m-2, and in summer it recovered back to 25 W m-2. Albedo was important in summer; by model tuning the estimated value was 0.6, consistent with the ice surface being bare all summer. Snow cover was thin, having a minor role. The results can be used to further our understanding of the importance of landfast ice in Antarctica for climate research and high-resolution ice–ocean modelling.