Slight Shrinkage Research Articles

Hospital-based case control study and animal study on the relationship between nonylphenol exposure and depression.

ObjectivesThe aim of this work is to explore the association between chronic exposure to nonylphenol (NP), a representative environmental endocrine disruptor (EED), and the risk of depression and its potential mechanism.MethodsA hospital-based case control study was conducted from August to December 2018. Forty-one patients with confirmed depression and 47 healthy volunteers were recruited. In vitro, 20 rats were randomly divided into the control group (corn oil) and NP exposure group (n=10 per group), which were gavaged at a dose of 4 mg/kg w/day for 180 days.ResultsThe depressed patient group had higher Zung Self-Rating Depression Scale (SDS) (P<0.001) and Self-Rating Anxiety Scale (SAS) (P<0.001) scores than the healthy group. The serum NP level (P=0.009) in the depressed group was higher than that in the healthy group, and the BDNF level (P=0.001) was lower. The serum levels of monoamine neurotransmitters dopamine (DA) (P=0.070), epinephrine (E) (P=0.001), and noradrenaline (NE) (P=0.000) were lower than those in the healthy group. In the sucrose preference test, the sucrose preference time for the exposure group of rats was lower than that of the control group (P<0.001). In the forced swim test, a longer resting time was measured for the exposure group of rats as compared to the control group (P<0.05). The level of NP (P<0.001) in the brain tissue of the NP exposure group was higher than that in the control group, and the serum level of brain-derived neurotrophic factor (BDNF) (P=0.004) was lower. Histopathological examination of the brain biopsies illustrated that the neuronal cells and nuclei in the hippocampus of the exposed group exhibited slight shrinkage.ConclusionChronic exposure to NP at environmental doses will result in the accumulation of NP in the brain and blood, and induction of depression, which might be associated with the alterations in the expression levels of BDNF and monoamine neurotransmitters.

Antimicrobial hydroxyapatite reinforced-polyelectrolyte complex nanofibers with long-term controlled release activity for potential wound dressing application

The prevention of wound infection has remained to be a critical step for facilitating wound healing following the application of wound dressing. To overcome such challenge, nano-hydroxyapatite (n-HAP) with high specific surface area, excellent biocompatibility, high mechanical strength and strong adsorption capacity was developed into a novel controlled release system for antimicrobial therapy. In general, n-HAP was loaded with a model antibiotic, tetracycline hydrochloride and was subsequently encapsulated inside chitosan/gelatin polyelectrolyte complex (PEC) nanofibers with a typical core-shell geometry. Firstly, the encapsulation of either tetracycline hydrochloride (TCH) or n-HAP led to the slight shrinkage of fiber diameter and enhancement in the thermotropic stability of PEC nanofiber. Secondly, the good water retention and air transmission properties of PEC was not impaired by the inclusion of n-HAP and TCH. Finally, the n-HAP reinforced PEC nanofiber membrane with encapsulated tetracycline hydrochloride has achieved the effect of long-term drug release, thereby improving the antibacterial efficacy against S. aureus, a common pathogen. Based on the good water retention, high rigidity, long term sustained drug release and prolonged antibacterial therapeutic efficacy, n-HAP reinforced PEC nanofiber membranes will serve as a promising platform for developing into novel antimicrobial wound dressings.

High temperature in situ SEM assessment followed by ex situ AFM and EBSD investigation of the nucleation and early growth stages of Fe-Al intermetallics

A dedicated in situ heating setup in a scanning electron microscope (SEM) followed by an ex situ atomic force microscopy (AFM) and electron backscatter diffraction (EBSD) is used to characterize the nucleation and early growth stages of Fe-Al intermetallics (IMs) at 596°C. A location tracking is used to interpret further characterization. Ex situ AFM observations reveal a slight shrinkage and out of plane protrusion of the IM at the onset of IM nucleation followed by directional growth. The formed interfacial IM compounds were identified by ex situ EBSD. It is now clearly demonstrated that the θ-phase nucleates first prior to the diffusion-controlled growth of the η-phase. The θ-phase prevails the intermetallic layer.

In Situ X‐Ray Observations and Microstructural Characterizations for Understanding Combustion Foaming and Reaction Processes to Synthesize Porous Al3Ti Composites From Al–Ti–B4C Powders

The combustion foaming behaviors to synthesize closed‐cellular porous Al3Ti composites are observed in situ using X‐ray radioscopy. The in situ observation of the thermal explosion (TE) mode foaming reveals that the combustion foaming process consists of six steps. The shape of the sample changes uniformly in the first three steps before the sample foams. First, the sample expands uniformly 1) gradual expansion) and maintains an almost constant volume for a fixed period 2) temporary steady state at a constant volume). During these stages, bubbles are not generated inside the sample. Subsequently, the sample shrinks uniformly 3) slight shrinkage). After these three steps, the bubbles are rapidly generated inside the sample 4) rapid foaming). Immediately after foaming, the sample shrinks drastically while bubbles are ruptured and combined 5) severe shrinkage and bubble coarsening). Finally, the sample solidifies as a porous metal 6) solidification). The sample fabricated under the self‐propagating high‐temperature synthesis (SHS) mode includes graded microstructures corresponding to steps (1)–(4). The microstructures of the samples foamed under the TE and SHS modes are characterized. These results are used for discussing the elementary reaction steps arising at steps (1)–(4).

Monitoring and driving force analysis of spatial and temporal change of water area of Hongjiannao Lake from 1973 to 2019

Hongjiannao Lake is the largest desert freshwater lake in China and the world's largest breeding habitat for gulls, which is of great significance to the local ecological environment and the breeding of key protected birds, and was listed as a national key protected lake in 2012. This study uses Landsat series satellite remote sensing data from 1973 to 2019 in combination with the NDWI water body index and OSTU adaptive threshold methods to obtain a 46-year area dataset for the study area. On this basis, the temporal and spatial evolution of the lake and its coupling relationship with natural factors and human activities were studied. The results show that (1) during the period 1973–2019, Hongjiannao Lake has undergone three stages: slight shrinkage (1973–1997), sharp shrinkage (1997–2015), and expansion (2015–2019); (2) The shrinkage of the Hongjiannao Lake is mainly caused by anthropogenic factors, followed by natural factors. The anthropogenic factors mainly consist of the upstream river construction reservoirs, industrial development of water and vegetation growth increased water demand; (3) For the first time, the preliminary results of the conservation measures implemented since 2012 were analyzed. This is mainly reflected in the positive growth of the Hongjiannao Lake for the first time since its long-term shrinkage in 1997. This phenomenon is mainly due to measures such as artificially increasing rainfall and ecological water replenishment. Climate change (high evaporation, low precipitation) and human activities (construction of upstream water conservancy projects, coal mining, lagoon road construction, irrigation water use, etc.) are the key factors contributing to the changes in lake area during the shrinkage period. It is suggested that the study area should carry out artificial rain enhancement and surface ecological water replenishment to scientifically and rationally utilize water resources in the basin, effectively suppress the shrinkage of Hongjiannao Lake, and achieve long-term sustainable restoration of the wetland ecology.

Effects of acetolysis on starch granules

The ability to concurrently analyze multiple microfossils from the same palaeoecological or archaeological sample would allow for faster and multi-evidenced analyses. Most microfossils require chemical processing to become identifiable under different types of microscopy; acetolysis is commonly employed in palynological study. We present the effects of acetolysis on starch-rich elements of four economic taxa. Acetolysis caused slight shrinkage in the average size of starch granules, at statistically significant levels for three of the four taxa explored. The capacity to conduct starch analysis from acetolyzed samples is discussed for archaeological and palaeoecological study.

Discrete fracture matrix modelling of fully-coupled CO2 flow – Deformation processes in fractured coal

CO2 interaction causes complex mechanical deformations and flow modifications in coal, depending on the spatial disposition of the fracture-matrix system. Sorption-induced matrix swelling reduces the local fracture aperture and correspondingly the fracture permeability, consequently influencing gas flow throughout the seam. Since these modifications are highly -heterogeneous and -localized, an explicitly-represented geometric model is essential for the accurate modelling of the fully-coupled process. In this study, the CO2 flow – coal deformation process is implemented in a numerical model at the scale of coal constituents (i.e. matrix blocks and cleats), through the inclusion of a spatially distributed 3D – discrete fracture matrix (DFM) network. Fracture geometry is generated from a stochastically simplified 2D fracture network obtained from micro-CT imaging. The approach is initially validated against experimental results from a single-fractured coal specimen and the analysis extended to the complex fracture geometry. The spatial and temporal evolutions of fracture/matrix pressure, adsorbed mass of CO2, adsorption-induced swelling, alterations in local fracture aperture and permeability, and contact modelling at fully fracture closure are specifically analysed with comparison against no-swelling behaviour. Results indicate that the high-permeability fracture pathways provide initial easy access for the CO2 to diffuse into the coal matrix, causing sorption-induced matrix swelling. Although the individual matrix blocks exhibit a slight shrinkage immediately upon injection of high fluid pressures within the fractures, sorption-induced swelling rapidly overcomes this, resulting in an overall volume expansion at full pressure equilibration. This is turn causes a significant reduction in fracture aperture and permeability. The magnitude of the local fracture aperture reduction depends on the swelling behaviour of the bounding matrix, that leads to essentially full-closure of small fractures, causing significant localized flow modifications to further CO2 injection in the vicinity of the particular fractures. The contact modelling approach identifies the timing and locations of fully-closing fractures in the complex geometry, where butt cleats exhibiting initial small apertures are prone to fully-close, compared to larger aperture face cleats that retain flow.

Quantitative identification and evolution trend simulation of shrinking cities at the county scale, China

Urban shrinkage became increasingly obvious during the process of rapid urbanization. It is important to understand the mechanism behind the formation and evolution of shrinking cities to realize urban transformation and sustainable development. This paper establishes a shrinking cities index to measure generalized urban shrinkage by using the population change rate at the county scale in China. First, on the spatial scale, the shrinking intensity and pattern distribution are analyzed. Second, on the temporal scale, the shrinking trajectories of shrinking cities are analyzed, and a trend is predicted for shrinking cities for 2020 and 2025 based on the gray model (GM (1,1)). Finally, economic, institutional, and social factors are selected to identify the major influences on the different shrinking trajectories using a spatial panel data model. The results show the following. (1) Between 2000 and 2015, shrinking cities in China were mainly distributed in four regions: the three northeastern provinces, the Shaanxi-Gansu-Ningxia region, the Sichuan-Chongqing region, and the middle and lower reaches of the Yangtze River. They thus appear to have connecting piece and axis distribution characteristics. (2) The dominant shrinking city types are slight and moderate shrinking, which together account for 80 %–90 % of all shrinking cities. These types have less severe or extreme shrinkage. Considering the different trajectories, temporary shrinking cities represent 75.26 % of all shrinking cities and predominantly occurred in 2010−2015. Episodic shrinking cities represent 19.74 % of all shrinking cities. Continuous shrinking cities represent 5.00 % of all shrinking cities and occurred in 2005−2015. (3) From 2015 to 2025, the number of shrinking cities is projected to be 272, with slight shrinkage accounting for 43.38 % of the total shrinking cities, and extreme shrinkage accounting for 4.78 %. Examining the spatial distribution of shrinking cities shows that they are mainly distributed in the three northeastern provinces, the Shaanxi-Gansu-Ningxia region, Xinjiang and the middle and lower reaches of the Yangtze River in the future. (4)Total GDP, GDP per capita, fiscal expenditures, employment, and built-up area have a significant impact on the population of shrinking cities. Among them, the total GDP has the largest impact, and the built-up area has the smallest impact. In addition, the total GDP, GDP per capita, fiscal revenue, and employment have a significant spatial spillover effect in temporary shrinking cities. This study provides empirical evidence to support Chinese policy makers in implementing urban sustainable development goals.

Salinity bias with negative pressure dependency caused by anisotropic deformation of CTD measuring cell under pressure examined with a dual-cylinder cell model

Measurements made by deep floats had a salinity bias with a negative pressure dependency. Salinity is affected by conductivity measurements via changes in the CTD measuring cell geometry under pressure. To remove the effect, a canceling factor for pressure CPcor is prepared theoretically by the manufacturer considering the isotropic deformation of a single-cylinder measuring cell under pressure; the observed negative pressure dependency, however, requires an even smaller CPcor. This study examined the causes of the inconsistency for salinity measurements with a dual-cylinder cell model, considering that the actual CTD measuring cell is a glass cell covered by a polyurethane jacket. The dual-cylinder cell model clarifies that the CTD measuring cell deforms anisotropically to yield a smaller CPcor; mainly because the inner glass cell deforms radially to a greater extent than the single-cylinder model due to the radial stress from the outer cylinder (jacket) being stronger than the hydrographic pressure. The observed fresh bias at the sea surface is attributed to a slight shrinkage of the outer jacket because of compression set of polyurethane in deep ocean. The shrunken polyurethane jacket is elongated over time due to a creep phenomenon, which causes less-freshening of the fresh bias found at the sea surface. The observed linear relationship between the smaller CPcor and the fresher bias at the sea surface is attributed to the variation of the wall thickness of the polyurethane jacket when it shrinks similarly. The study suggests another idea to improve the salinity accuracy of CTD sensors greatly: a change of the jacket material into an elastomer. The improvement makes the present setting of CPcor be more valid and reliable, because the elastomer jacket hardly affects the change of the measuring cell geometry under pressure, which in turn removes the pressure effects on salinity measurements.

Salinity effect on the liquid limit of soils

Previous studies stated that, with increasing salinity, the decreased liquid limit for expansive soils was attributed to the shrinkage of diffuse double layer, while the increased liquid limit for non-expansive soils was explained by the growing particle flocculation. These two mechanisms seem to be controversial and it is difficult to understand how an increasing salinity can promote soil flocculation. This study aims at clarifying the mechanism controlling liquid limit by conducting cone penetration test, sedimentation and rheological tests on MX80 Na-bentonite and silty soil. Results showed that the liquid limit and yield stress of MX80 increased then decreased with increasing salinity, while they increased slightly for the silty soil. In sedimentation test, faster settling rate and smaller sediment volume were identified for MX80 and silt suspensions in NaCl solution, evidencing the shrinkage of diffuse double layer and the formation of denser aggregated structure. This suggested that the change of liquid limit is the result of two mechanisms in competition, which depend on the compression rate of diffuse double layer: (1) the water storage in nano-fissures which correspond to the nanoscale spaces among interlayers of clay particles resulting from the slight shrinkage of diffuse double layer, and (2) the water expulsion into larger pores with significant shrinkage of diffuse double layer. For the MX80 at low salinity and for the silt soil, the first mechanism prevailed and the increasing liquid limit was attributed to the requirement of more water to fill the nano-fissures. In contrast, for MX80 at high salinity, the second mechanism prevailed—the diffuse double layer was compressed significantly, changing the double-layer water to free water and giving rise to the decrease in liquid limit.

Early-age deformation of cement emulsified asphalt mortar with aluminum powder and expansive agent

Early-age deformation of cement emulsified asphalt mortar (CA mortar) is a key parameter for its application in the CRTS I and CRTS II slab ballastless tracks of China. In this paper, the buoyancy method was used to measure the early-age deformation behaviors of CA mortars with aluminum powder (AP) and/or U-type expansive agent (UEA). The results indicate that the buoyancy method accurately and stably reflects the early-age deformation of CA mortar. The deformations of CA mortars with AP and/or UEA are composed of four stages: slight shrinkage stage, fast expansion stage, gradual shrinkage stage, and stable stage. Further analyses of relative expansions of samples reveal that different mechanisms of AP and UEA take effect at the gradual shrinkage stage of CA mortar deformation. Thermal effect induced by internal heat accumulation increases the air pressure in voids entrained by AP in CA mortar, thereby increasing the peak deformation values. Then the deformation tends to decrease with heat dissipation at the gradual shrinkage stage. Similar shrinkage stage is also observed in field tests. The buoyancy method can reflect the entire early-age deformation process of CA mortar with AP. This method is more suitable for engineering applications than the graduated flask method which is standardized in the specifications of China.

Optimization of cementitious composite for heavyweight concrete preparation using conduction calorimetry

The present work investigates the hydration heat of different cement composites by means of conduction calorimetry to optimize the composition of binder in the design of heavyweight concrete as biological shielding. For this purpose, Portland cement CEM I 42.5 R was replaced by a different portion of supplementary cementitious materials (blast furnace slag, metakaolin, silica fume/limestone) at 75%, 65%, 60%, 55%, and 50% levels to obtain low hydration heat lower than 250 j g−1. All ingredients were analyzed by energy dispersive X-ray fluorescence (EDXRF) and nuclear activation analysis (NAA) to assess the content of major elements and isotopes. A mixture of two high-density aggregates (barite and magnetite) was used to prepare three heavyweights concretes with compressive strength exceeding 45 MPa and bulk density ranging between 3400 and 3500 kg m−3. After a short period of volume expansion (up to 4 h), a slight shrinkage (max. 0.3°/°°) has been observed. Also, thermophysical properties (thermal conductivity, volumetric specific heat, thermal diffusivity) and other properties were determined. The results showed that aggregate content and not binder is the main factor influencing the engineering properties of heavyweight concretes.

Texture Modification of 3D Printed Air-Fried Potato Snack by Varying Its Internal Structure with the Potential to Reduce Oil Content

An air-fried 3D printed snack was developed to potentially provide consumer an alternative choice of potato snack with reduced oil. One cylindrical shape was firstly 3D printed with variable internal structures, followed by air-frying post-printing. The unfried printed samples well matched the designed geometry but with a slight shrinkage after air-frying process. Hardness and fracturability of air-fried potato snack, significantly affected by infill pattern, also significantly decreased when infill level decreased. The 100% infill printed and cast samples were observed with a serious puffing phenomenon during air-frying process. Finally, one kind of a food structure comprised of different parts illustrating multiple textures was developed by varying infill structure. The results suggested that the textural properties of the air-fried 3D printed potato snack could be modified by altering its internal structure, possibly offering a new way of oil reduction for potato-based snacks by creating customized internal structure by applying 3D printing.

Tuning interfacial chemistry and electrochemical properties of solid oxide cells via cation interdiffusion

Electrochemical performance of solid oxide cells is sensitive to electrode/electrolyte interfacial chemistry. Herein, taking SmBaCoCuO5+δ (SBCC) oxygen electrode and Gd0.1Ce0.9O1.95 (GDC) electrolyte as an example, the role of cation interdiffusion in tuning interfacial chemistry and electrochemical properties of solid oxide cells was studied. An increase in cation diffusion between SBCC and GDC layers results in bigger and better-connected SBCC particles with slight shrinkage in unit cell and denser GDC layer with distorted crystal structure. Cation diffusion is also responsible for abnormal deviation in electrochemical impedance spectroscopy that can be used to characterize catalytic properties of the electrode for oxygen redox reactions in SBCC/GDC/SBCC symmetric cell. The internal mechanism that contributes to this phenomenon was revealed through a series of well-designed tests and theoretical modeling. Single cell, SBCC/GDC/GDC-NiO, has high cation interdiffusion, works well in both solid oxide fuel cell and solid oxide electrolysis cell model; it also exhibits decreased catalytic activity and open-circuit voltage. This work provides helpful guides for the design of advanced solid oxide cells and other related devices.

Glacier Variations at Xinqingfeng and Malan Ice Caps in the Inner Tibetan Plateau Since 1970

The inner Tibetan Plateau is a glacierized region where glaciers show heterogeneous change. The Xinqingfeng and Malan ice caps are located in this region, and a transition zone exists with shifting influences between the westerlies and Indian summer monsoon. However, there is a lack of detailed information regarding glacier area and mass changes in this region before 2000. In the present study, we describe an integrated view of the glacier area and its mass changes for Mt. Xinqingfeng and Mt. Malan as derived from topographic maps, Landsat, ASTER, SRTM DEM, and TerraSAR-X/TanDEM-X from 1970 to 2012 and from 1970 to 2018, respectively. Our results show that the glaciers experienced a slight shrinkage in area by 0.09 ± 0.03% a−1 from 1970 to 2018 with a median mass loss rate of 0.22 ± 0.17 m w.e. a−1 and 0.29 ± 0.17 m w.e. a−1 between 1999 and 2012 at Mt. Xinqingfeng and Mt. Malan, respectively. The glaciers of Mt. Malan had a total mass loss of 0.19 ± 0.14 m w.e. a−1 during the period 1970–1999. A minimum of seven glaciers at Mt. Xinqingfeng and Mt. Malan showed heterogeneous variations with either surging or advancing during the observation period. Among them, the West Monuomaha Glacier, Monuomaha Glacier, and Zu Glacier were identified as surging glaciers, and the others may also be surging glaciers, although more evidence is required. These glaciers showed a long active period and low velocities. Therefore, we suggested that thermal controls are important for surge initiation and recession.

Supporting B–TiO2 on iM16K glass bubbles to prepare B–TiO2(x%)/iM16K hollow spheres for ofloxacin degradation

B–TiO2(x%)/iM16K hollow spheres were prepared by loading boron-doped TiO2 on iM16K glass bubbles using a sol-gel route. The density of the hollow spheres was controlled by changing the content of B–TiO2 in the composite material to facilitate photocatalyst-water separation after treatment. The loading of B–TiO2 on the surface of iM16K glass bubbles results in a slight shrinkage in anatase TiO2 cell volume and crystallite size. The distribution of the B–TiO2 layer on the surface of the iM16K glass bubbles is proven by EDS (energy dispersive spectrometry) mapping. The band gap energies of B–TiO2, B–TiO2(50%)/iM16K and B–TiO2(20%)/iM16K are 2.83, 2.97 and 3.10 eV. The N2 adsorption-desorption isotherms of B–TiO2(x%)/iM16K and B–TiO2 present the classical type IV isotherm that is subjected to mesoporous material. All the materials with different B–TiO2 contents have a narrow pore size range between 2 and 7 nm, and the porosity in the B–TiO2 layer is higher than the porosity in the B–TiO2 powder. The first order reaction rate constants for photocatalytic degradation of ofloxacin on B–TiO2(20%)/iM16K, B–TiO2(50%)/iM16K and B–TiO2 powder are 0.00861, 0.0233 and 0.0248 min−1, respectively. All the ofloxacin molecules can be almost degraded after 180 min of reaction on both B–TiO2(50%)/iM16K and B–TiO2 powder. UV–Visible and FTIR spectra of the ofloxacin solution during photocatalytic oxidation indicate decomposition of major functional groups in the ofloxacin molecule. Disruption of the C–F bond and the C–N bond results in the formation of F−, NH4+ and NO2− ions.

Biomimetic nanochannels for the discrimination of sialylated glycans via a tug-of-war between glycan binding and polymer shrinkage.

Sialylated glycans that are attached to cell surface mediate diverse cellular processes such as immune responses, pathogen binding, and cancer progression. Precise determination of sialylated glycans, particularly their linkage isomers that can trigger distinct biological events and are indicative of different cancer types, remains a challenge, due to their complicated composition and limited structural differences. Here, we present a biomimetic nanochannels system integrated with the responsive polymer polyethyleneimine-g-glucopyranoside (Glc-PEI) to solve this problem. By using a dramatic “OFF–ON” change in ion flux, the nanochannels system achieves specific recognition for N-acetylneuraminic acid (Neu5Ac, the predominant form of sialic acid) from various monosaccharides and sialic acid species. Importantly, different “OFF–ON” ratios of the conical nanochannels system allows the precise and sensitive discrimination of sialylated glycan linkage isomers, α2–3 and α2–6 linkage (the corresponding ion conductance increase ratios are 96.2% and 264%, respectively). Analyses revealed an unusual tug-of-war mechanism between polymer-glycan binding and polymer shrinkage. The low binding affinity of Glc-PEI for the α2–6-linked glycan caused considerable shrinkage of Glc-PEI layer, but the high affinity for the α2–3-linked glycan resulted in only a slight shrinkage. This competition mechanism provides a simple and versatile materials design principle for recognition or sensing systems that involve negatively charged target biomolecules. Furthermore, this work broadens the application of nanochannel systems in bioanalysis and biosensing, and opens a new route to glycan analysis that could help to uncover the mysterious and wonderful glycoworld.

Effect of accelerated ageing by cyclic variations of temperature and humidity on shrinkage of concretes

The objective of our research work is, on the one hand, to develop an experimental protocol to simulate the Moroccan climate, that we'll use to subject the studied concretes to accelerated ageing by exposure to cyclic variations of temperature (+5 to + 40 °C) and humidity (60 to 98% HRS). On the other hand, we aim to evaluate the impact of exposure to cyclic variations of temperature and humidity on concretes (with and without heat curing) behaviors in particular their shrinkage. For this purpose, three resistance classes of concrete were studied (C30, C40 and C60) without and with 10% silica Fume. Concrete samples were subjected to three types of conditioning prior to the tests. The reference concretes (Ct) were removed after 24 h and kept under stable temperature and humidity conditions (20 ± 2 °C and 80% ± 5 RH). Treated concretes (CV) were removed after 24 h and exposed to 300 cycles of 12 h of temperature and humidity variation in a climatic chamber. And finally, concretes that have undergone a heat cure (CTV) were maintained for 5 h at 90 °C, then exposed to the same temperature of the treated concrete (CV). The results obtained show that the accelerated ageing by cyclic variations of temperature and humidity resulted in a slight increase in shrinkage compared to the reference concretes. These differences were smoothed out after 300 cycles for C30 and C40 and after 200 cycles for C60. Slight shrinkage is recorded for concrete C60 with silica fume compared to concrete without it.

In situ TEM observation of void formation and migration in phase change memory devices with confined nanoscale Ge2Sb2Te5.

The reliability of Ge–Sb–Te phase-change memory (PCM) devices has been limited by failure due to void formation and this still remains one of the critical issues affecting their use in storage-class memory applications. To directly observe the void formation processes in real-time, we implemented in situ switching of PCM devices by applying set and reset voltage pulses to a Ge2Sb2Te5 (GST) cell inside a transmission electron microscope (TEM). The in situ TEM observations directly show that a void nucleates preferentially near the TiN bottom electrode in the GST cell, where the temperature is the highest. The nucleated void grows gradually until it reaches a certain size while migrating slowly toward the positively biased electrode. The fully grown void then continues migrating toward the positively biased electrode in subsequent set pulses. The observed polarity-dependent void migration can be explained by the field-induced redistribution of the constituent elements, especially by the electromigration of under-coordinated Te− ions which have vacancies around them. When the reset pulse with the same voltage polarity is applied, the voids exhibit a slight volume shrinkage but are not completely eliminated, resulting in a reset-stuck failure. The present in situ TEM observations revealing the nucleation, growth, and polarity-dependent migration of voids will contribute to the fundamental understanding of the failure by void formation in nanoscale GST-based PCM devices and help improving the design of reliable PCM devices.

Alkali-activated Portland cement with adjustable proper deformations for anchoring application

The application of alkali-activated Portland cement (hereinafter AAPC) for anchoring grouts was investigated with obtaining of non-shrinking high performance cementing systems. The AAPC system “ordinary Portland cement clinker – sodium metasilicate” was modified by the complexes of mineral and organic compounds to ensure specified properties of anchoring grouts. It was revealed that the most effective multifunctional additives are represented by the system “salt-electrolyte – surfactant”. Alongside with slowing down of AAPC paste setting time, the effect of compensated shrinkage of AAPC mortar, i.e. expansion within 0.062 mm/m and slight shrinkage within 0.017 mm/m, was ensured when Na2SO4 and NaNO3 were used in the mentioned system respectively. The effect of compensated shrinkage is explained by greater crystallization of hydrosilicates and hydroaluminates, additional formation of sulfate-containing sodium-calcium hydroaluminate (for Na2SO4-based system) and crystalline calcium hydronitroaluminate (for NaNO3-based system). The advantages of the modified AAPC for anchoring application are indicated in the paper.