The development of hydrogels for cartilage replacement and soft robotics has highlighted a challenge: load-bearing hydrogels need to be both stiff and tough. Several approaches have been reported to ...improve the toughness of hydrogels, but simultaneously achieving high stiffness and toughness remains difficult. Here we report that alginate-polyacrylamide hydrogels can simultaneously achieve high stiffness and toughness. We combine short- and long-chain alginates to reduce the viscosity of pregel solutions and synthesize homogeneous hydrogels of high ionic cross-link density. The resulting hydrogels can have elastic moduli of ∼1 MPa and fracture energies of ∼4 kJ m–2. Furthermore, this approach breaks the inverse relation between stiffness and toughness: while maintaining constant elastic moduli, these hydrogels can achieve fracture energies up to ∼16 kJ m–2. These stiff and tough hydrogels hold promise for further development as load-bearing materials.
The East Asian Summer Monsoon driven by temperature and moisture gradients between the Asian continent and the Pacific Ocean, leads to approximately 50% of the annual rainfall in the region across ...20-40°N. Due to its increasing scientific and social importance, there have been several previous studies on identification of moisture sources for summer monsoon rainfall over East Asia mainly using Lagrangian or Eulerian atmospheric water vapor models. The major source regions for EASM previously proposed include the North Indian Ocean, South China Sea and North western Pacific. Based on high-precision and high-frequency 6-year measurement records of hydrofluorocarbons (HFCs), here we report a direct evidence of rapid intrusion of warm and moist tropical air mass from the Southern Hemisphere (SH) reaching within a couple of days up to 33°N into East Asia. We further suggest that the combination of direct chemical tracer record and a back-trajectory model with physical meteorological variables helps pave the way to identify moisture sources for monsoon rainfall. A case study for Gosan station (33.25°N, 126.19°E) indicates that the meridional transport of precipitable water from the SH accompanying the southerly/southwesterly flow contributes most significantly to its summer rainfall.
Hardening evolution of AZ31B Mg sheet Lou, X.Y.; Li, M.; Boger, R.K. ...
International journal of plasticity,
2007, 2007-01-00, 20070101, Letnik:
23, Številka:
1
Journal Article
Recenzirano
The monotonic and cyclic mechanical behavior of O-temper AZ31B Mg sheet was measured in large-strain tension/compression and simple shear. Metallography, acoustic emission (AE), and texture ...measurements revealed twinning during in-plane compression and untwinning upon subsequent tension, producing asymmetric yield and hardening evolution. A working model of deformation mechanisms consistent with the results and with the literature was constructed on the basis of predominantly basal slip for initial tension, twinning for initial compression, and untwinning for tension following compression. The activation stress for twinning is larger than that for untwinning, presumably because of the need for nucleation. Increased accumulated hardening increases the twin nucleation stress, but has little effect on the untwinning stress. Multiple-cycle deformation tends to saturate, with larger strain cycles saturating more slowly. A novel analysis based on saturated cycling was used to estimate the relative magnitude of hardening effects related to twinning. For a 4% strain range, the obstacle strength of twins to slip is 3
MPa, approximately 1/3 the magnitude of textural hardening caused by twin formation (10
MPa). The difference in activation stress of twinning versus untwinning (11
MPa) is of the same magnitude as textural hardening.
Collisionless shocks are ubiquitous in the Universe as a consequence of supersonic plasma flows sweeping through interstellar and intergalactic media. These shocks are the cause of many observed ...astrophysical phenomena, but details of shock structure and behavior remain controversial because of the lack of ways to study them experimentally. Laboratory experiments reported here, with astrophysically relevant plasma parameters, demonstrate for the first time the formation of a quasiperpendicular magnetized collisionless shock. In the upstream it is fringed by a filamented turbulent region, a rudiment for a secondary Weibel-driven shock. This turbulent structure is found responsible for electron acceleration to energies exceeding the average energy by two orders of magnitude.
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There is an increased interest in the use of natural surfactant as replacements for synthetic surfactants due to their biosustainable and biocompatible properties. A category of ...natural surfactants which are attracting much current interest is the triterpenoid saponins; surface active components found extensively in a wide range of plant species. A wide range of different saponin structures exist, depending upon the plant species they are extracted from; but regardless of the variation in structural details they are all highly surface active glycosides. Greater exploitation and application requires a characterisation and understanding of their basic adsorption and self-assembly properties.
Glycyrrhizic acid, extracted from Licorice root, is a monodesmosidic triterpenoid saponin. It is widely used in cosmetic and pharmaceutical applications due to its anti-inflammatory properties, and is an ingredient in foods as a sweetener additive. It has an additional attraction due to its gel forming properties at relatively low concentrations. Although it has attracted much recent attention, many of its basic surface active characteristics, adsorption and self-assembly, remain relatively unexplored. How the structure of the Glycyrrhizic acid saponin affects its surface active properties and the impact of gelation on these properties are important considerations, and to investigate these are the focus of the study.
In this paper the adsorption properties at the air–water interface and the self-assembly in solution have been investigated using by neutron reflectivity and small angle neutron scattering; in non-gelling and gelling conditions.
The adsorption isotherm is determined in water and in the presence of gelling additives, and compared with the adsorption behaviour of other saponins. Gelation has minimal impact on the adsorption; apart from producing a rougher surface with a surface texture on a macroscopic length scale. Globular micelles are formed in aqueous solution with modest anisotropy, and are compared with the structure of other saponin micelles. The addition of gelling agents results in only minimal micelle growth, and the solutions remain isotropic under applied shear flow.
Abstract
In this paper, we present a long-term multiwavelength investigation focusing on 12 distinct samples of Fermi-4LAC bright flat-spectrum radio quasars (FSRQs). Detailed variability and ...spectral analyses of
γ
-ray, X-ray, and ultraviolet/optical data obtained by the Fermi Large Area Telescope, the Swift X-ray Telescope, and the Swift Ultraviolet and Optical Telescope were performed over a period of about 14 yr, spanning from 2008 October to 2022 October. These analyses provide insights into characterizing the variations within different activity states. To efficiently reproduce the multiwavelength simultaneous/quasi-simultaneous spectral energy distributions (SEDs) of the samples, we propose a novel approach for constraining the model parameters. By analyzing the parameters of the energy spectral curvature (
β
), the peak frequency (
ν
pk
), the peak luminosity (
L
pk
), the Compton dominance parameter (
A
C
), and the variability timescale (
t
var
) in different activity states, we can estimate the values of the jet radiation region parameters for the samples. Subsequently, we utilize the synchrotron-self-Compton and external Compton processes, employing a logarithmic-parabolic spectral shape to approximate the observed spectra of the sample sources, while considering the induced regime for the physical parameters. The model results show that: (1) by effectively reproducing SEDs in various active states of bright FSRQs, the parameters within the emission region were reasonably constrained; (2) compared to other active states, the emission region of the jet exhibits a reduced radius during the high state, while the magnetic field strength increases during the low state; and (3) for bright FSRQs in a high-activity state, there is an enhancement of the Doppler factor, often exhibiting a tendency toward energy equipartition.
Autologous bone marrow cells (BMCs) transplanted into ventricular scar tissue may differentiate into cardiomyocytes and restore myocardial function. This study evaluated cardiomyogenic ...differentiation of BMCs, their survival in myocardial scar tissue, and the effect of the implanted cells on heart function.
BMCs from adult rats were cultured in cell culture medium (control) and medium with 5-azacytidine (5-aza, 10 micromol/L), TGFbeta1 (10 ng/mL), or insulin (1 nmol/L) (n=6, each group). Only BMCs cultured with 5-aza formed myotubules which stained positively for troponin I and myosin heavy chain. In vivo studies: a cryoinjury-derived scar was formed in the left ventricular free wall. At 3 weeks after injury, fresh BMCs (n=9), cultured BMCs (n=9), 5-aza-induced BMCs (n=12), and medium (control, n=12) were autologously transplanted into the scar. Heart function was measured at 8 weeks after myocardial injury. Cardiac-like muscle cells which stained positively for myosin heavy chain and troponin I were observed in the scar tissue of the 3 groups of BMC transplanted hearts. Only the 5-aza-treated BMC transplanted hearts had systolic and developed pressures which were higher (P<0.05) than that of the control hearts. All transplanted BMCs induced angiogenesis in the scar.
Transplantation of BMCs induced angiogenesis. BMCs cultured with 5-aza differentiated into cardiac-like muscle cells in culture and in vivo in ventricular scar tissue and improved myocardial function.
•Tests were conducted on seawater sea sand concrete (SWSSC) filled FRP tubes exposed to artificial seawater.•Three types of FRP namely GFRP, CFRP and BFRP were used in the testing program.•Strength ...and ultimate axial strain of SWSSC-filled FRP tubes were reduced by environmental exposure.•Load-axial strain curves and ultimate capacity of SWSSC-filled FRP tubes were predicted.•The environmental factor specified in current guidelines for FRP degradation was assessed.
Application of the hybrid structure system utilizing seawater and sea sand concrete (SWSSC) and fiber reinforced polymer (FRP) is promising as it is resource beneficial as well as FRPs are corrosion resistant. This paper presents an experimental study on the durability of SWSSC-filled glass/carbon/basalt-FRP tubes exposed to artificial seawater (3.5% salt solution) at 40 °C for up to 6 months. The mechanical properties of conditioned and unconditioned plain concrete, FRPs, and concrete-filled FRP tubes (fully filled and double-skin tubes) were measured by means of compressive test and split-disk test. Compressive strength of SWSSC did not degrade after exposure, but an obvious degradation in hoop strength was observed for GFRP and BFRP. Mechanical properties, such as strength and ultimate axial strain of SWSSC-filled FRP tubes were reduced by environmental aging and the major mechanism is the hoop strength deterioration of FRP. Load-axial strain curves and ultimate capacity of SWSSC-filled FRP tubes were predicted by using an existing method with proper modification to account for the environmental effects. The predictions were in good agreement with experimental results. Finally, the environmental factor specified in current guidelines for FRP degradation was assessed using the data obtained in this study.
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