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Snow-albedo feedback (SAF) is examined in 25 climate change simulations participating in the Coupled Model Intercomparison Project version 5 (CMIP5). SAF behavior is compared to the feedback’s behavior in the previous (CMIP3) generation of global models. SAF strength exhibits a fivefold spread across CMIP5 models, ranging from 0.03 to 0.16 W m −2  K −1  (ensemble-mean = 0.08 W m −2  K −1 ). This accounts for much of the spread in 21st century warming of Northern Hemisphere land masses, and is very similar to the spread found in CMIP3 models. As with the CMIP3 models, there is a high degree of correspondence between the magnitudes of seasonal cycle and climate change versions of the feedback. Here we also show that their geographical footprint is similar. The ensemble-mean SAF strength is close to an observed estimate of the real climate’s seasonal cycle feedback strength. SAF strength is strongly correlated with the climatological surface albedo when the ground is covered by snow. The inter-model variation in this quantity is surprisingly large, ranging from 0.39 to 0.75. Models with large surface albedo when these regions are snow-covered will also have a large surface albedo contrast between snow-covered and snow-free regions, and therefore a correspondingly large SAF. Widely-varying treatments of vegetation masking of snow-covered surfaces are probably responsible for the spread in surface albedo where snow occurs, and the persistent spread in SAF in global climate models.

Current methods for bioprinting functional tissue lack appropriate biofabrication techniques to build complex 3D microarchitectures essential for guiding cell growth and promoting tissue maturation1. 3D printing of central nervous system (CNS) structures has not been accomplished, possibly owing to the complexity of CNS architecture. Here, we report the use of a microscale continuous projection printing method (μCPP) to create a complex CNS structure for regenerative medicine applications in the spinal cord. μCPP can print 3D biomimetic hydrogel scaffolds tailored to the dimensions of the rodent spinal cord in 1.6 s and is scalable to human spinal cord sizes and lesion geometries. We tested the ability of µCPP 3D-printed scaffolds loaded with neural progenitor cells (NPCs) to support axon regeneration and form new ‘neural relays’ across sites of complete spinal cord injury in vivo in rodents1,2. We find that injured host axons regenerate into 3D biomimetic scaffolds and synapse onto NPCs implanted into the device and that implanted NPCs in turn extend axons out of the scaffold and into the host spinal cord below the injury to restore synaptic transmission and significantly improve functional outcomes. Thus, 3D biomimetic scaffolds offer a means of enhancing CNS regeneration through precision medicine.Fast scalable 3D bioprinting generates biocompatible and biomimetic scaffolds to precisely fit the geometries of spinal cord lesions, promote axonal regeneration, and support stem cell grafts to promote recovery from spinal cord injury in rodents.

This study aimed to investigate the influence of different coarse aggregate mineral compositions on the skid resistance performance of asphalt pavement. The imprint method was utilized to assess the contact probability between various graded asphalt surface aggregates and tires. Additionally, macroscopic adhesive friction coefficients between polished surfaces of three types of rock slabs (basalt, limestone, granite) and rubber were determined using a pendulum friction tester. Molecular dynamics simulations were employed to model the main aggregate minerals and rubber, and a “sandwich” type constrained shear model was constructed to evaluate micro-scale adhesive friction coefficients. Results indicated a 40% contact probability between aggregate and tire in a unit area of the road surface, highlighting the importance of studying adhesive friction between minerals and rubber. Macroscopically, basalt exhibited the highest adhesive friction coefficient, followed by limestone and granite. At the molecular level, feldspar showed the highest micro-scale friction coefficient with rubber, while quartz exhibited the lowest. The micro-scale adhesive friction coefficients correlated well with the macroscopic findings (correlation coefficient of 0.81), providing theoretical support for optimizing coarse aggregate selection to enhance skid resistance in road applications.

Multipotent mesenchymal stem cells (MSCs) have high self-renewal and multi-lineage differentiation potentials and low immunogenicity, so they have attracted much attention in the field of regenerative medicine and have a promising clinical application. MSCs originate from the mesoderm and can differentiate not only into osteoblasts, cartilage, adipocytes, and muscle cells but also into ectodermal and endodermal cell lineages across embryonic layers. To design cell therapy for replacement of damaged tissues, it is essential to understand the signaling pathways, which have a major impact on MSC differentiation, as this will help to integrate the signaling inputs to initiate a specific lineage. Hedgehog (Hh) signaling plays a vital role in the development of various tissues and organs in the embryo. As a morphogen, Hh not only regulates the survival and proliferation of tissue progenitor and stem populations but also is a critical moderator of MSC differentiation, involving tri-lineage and across embryonic layer differentiation of MSCs. This review summarizes the role of Hh signaling pathway in the differentiation of MSCs to mesodermal, endodermal, and ectodermal cells.

The functional maturation and preservation of hepatic cells derived from human induced pluripotent stem cells (hiPSCs) are essential to personalized in vitro drug screening and disease study. Major liver functions are tightly linked to the 3D assembly of hepatocytes, with the supporting cell types from both endodermal and mesodermal origins in a hexagonal lobule unit. Although there are many reports on functional 2D cell differentiation, few studies have demonstrated the in vitro maturation of hiPSC-derived hepatic progenitor cells (hiPSC-HPCs) in a 3D environment that depicts the physiologically relevant cell combination and microarchitecture. The application of rapid, digital 3D bioprinting to tissue engineering has allowed 3D patterning of multiple cell types in a predefined biomimetic manner. Here we present a 3D hydrogel-based triculture model that embeds hiPSC-HPCs with human umbilical vein endothelial cells and adipose-derived stem cells in a microscale hexagonal architecture. In comparison with 2D monolayer culture and a 3D HPC-only model, our 3D triculture model shows both phenotypic and functional enhancements in the hiPSC-HPCs over weeks of in vitro culture. Specifically, we find improved morphological organization, higher liver-specific gene expression levels, increased metabolic product secretion, and enhanced cytochrome P450 induction. The application of bioprinting technology in tissue engineering enables the development of a 3D biomimetic liver model that recapitulates the native liver module architecture and could be used for various applications such as early drug screening and disease modeling.

Mohr–Coulomb (MC) strength criterion has been widely used in many classical analytical expressions and numerical modeling due to its simple physical calculation, but the MC criterion is not suitable for describing the failure envelope of rock masses. In order to directly apply MC parameters to analytical expressions or numerical modeling in rock slope stability analysis, scholars established a criterion for converting Hoek–Brown (HB) parameters to equivalent MC parameters. However, the consistency of HB parameters and equivalent MC parameters in calculating critical acceleration of slope needs to be further explored and confirmed. Therefore, HB parameters are converted into equivalent MC parameters by considering the influence of slope angle (1# case and 2# case when slope angle is not considered and slope angle is considered respectively). Then, the lower-bound of finite element limit analysis is used for numerical modeling, and the results of calculating critical acceleration using HB parameters and equivalent MC parameters are compared, and the influence of related parameters on the calculation of critical acceleration is studied. Finally, the influence of different critical accelerations on the calculation of slope permanent displacement is further analyzed through numerical cases and engineering examples. The results show that: (1) In the 1# case, the critical acceleration obtained by the equivalent MC parameters are significantly larger than that obtained by the 2 #case and the HB parameters, and this difference becomes more obvious with the increase of slope angle. The critical acceleration obtained by the 2# case is very close to the HB parameters; (2) In the 1# case, slope height is inversely proportional to ΔAc (HB (Ac)  − 1# (Ac) ), and with the increase of slope height, ΔAc decreases, while in the 2# case, the difference of ΔAc (HB (Ac)  − 2# (Ac) ) is not significant; (3) In the 1# case, the sensitivity of the HB parameters to ΔAc is D  >  GSI  >  m i  >  σ ci , but in the 2# case, there is no sensitivity-related regularity; (4) The application of HB parameters and equivalent MC parameters in slope permanent displacement is studied through numerical cases and engineering examples, and the limitations of equivalent MC parameters in rock slope stability evaluation are revealed.

At present, the method for calculating long-term tunnel settlement predictions under metro loading considers only one working condition of passenger loading, which is inconsistent with actual working conditions. To establish a tunnel settlement model that accounts for variations in passenger flow, this study uses data mining methods to categorize metro operation into three working conditions: \"peak period, secondary period, and low period.\" The impact of these passenger flow conditions on the dynamic response of the soil around the tunnel is analyzed. Then, based on the principles of calculus, a calculus-based prediction model is established to consider the changing patterns of metro passenger flow. The model is applied to analyze the long-term settlement characteristics of Shanghai Metro Line 10. The results indicate that, under identical conditions, soil displacement and dynamic deviatoric stress around the tunnel increase with passenger capacity. The calculus prediction model aligns more closely with actual working conditions than the conventional model. The predicted tunnel settlement of Shanghai Metro Line 10 after 20 years of operation is approximately 37.07 mm, with most settlement occurring in the early stages, primarily due to cumulative plastic deformation of the soil.

The magnitude of global precipitation increase predicted by climate models has a large uncertainty that has been difficult to constrain, but much of the range in predictions is now shown to arise from shortcomings in the modelling of atmospheric absorption of shortwave radiation; if the radiative transfer algorithms controlling the absorption were more accurate, the model spread would narrow and the mean estimate could be about 40% lower. Model answer for future precipitation Increased precipitation is a central feature of climate model projections. But the magnitude of the increase has a large uncertainty that has been difficult to reduce or even understand. Anthony DeAngelis et al . now show that much of the range in predictions arises from a seemingly basic process: atmospheric absorption of shortwave radiation. A moistening atmosphere, as is predicted for the future, should increase precipitation due to higher humidity, however, the higher humidity should then increase shortwave absorption. The present analysis shows that, when compared to observational constraints, models simulate a too-small increase in shortwave absorption, and thus a too-large increase in precipitation. If the radiative transfer algorithms controlling the absorption could be better constrained and more standardized, the uncertainty would drop and the mean estimate would probably be about 40% lower. Intensification of the hydrologic cycle is a key dimension of climate change, with substantial impacts on human and natural systems 1 , 2 . A basic measure of hydrologic cycle intensification is the increase in global-mean precipitation per unit surface warming, which varies by a factor of three in current-generation climate models (about 1–3 per cent per kelvin) 3 , 4 , 5 . Part of the uncertainty may originate from atmosphere–radiation interactions. As the climate warms, increases in shortwave absorption from atmospheric moistening will suppress the precipitation increase. This occurs through a reduction of the latent heating increase required to maintain a balanced atmospheric energy budget 6 , 7 . Using an ensemble of climate models, here we show that such models tend to underestimate the sensitivity of solar absorption to variations in atmospheric water vapour, leading to an underestimation in the shortwave absorption increase and an overestimation in the precipitation increase. This sensitivity also varies considerably among models due to differences in radiative transfer parameterizations, explaining a substantial portion of model spread in the precipitation response. Consequently, attaining accurate shortwave absorption responses through improvements to the radiative transfer schemes could reduce the spread in the predicted global precipitation increase per degree warming for the end of the twenty-first century by about 35 per cent, and reduce the estimated ensemble-mean increase in this quantity by almost 40 per cent.

Rationally designed nanoparticles that can bind toxins show great promise for detoxification. However, the conventional intravenous administration of nanoparticles for detoxification often leads to nanoparticle accumulation in the liver, posing a risk of secondary poisoning especially in liver-failure patients. Here we present a liver-inspired three-dimensional (3D) detoxification device. This device is created by 3D printing of designer hydrogels with functional polydiacetylene nanoparticles installed in the hydrogel matrix. The nanoparticles can attract, capture and sense toxins, while the 3D matrix with a modified liver lobule microstructure allows toxins to be trapped efficiently. Our results show that the toxin solution completely loses its virulence after treatment using this biomimetic detoxification device. This work provides a proof-of-concept of detoxification by a 3D-printed biomimetic nanocomposite construct in hydrogel, and could lead to the development of alternative detoxification platforms. Nanoparticles capable of selectively binding target chemicals have potential for detoxification processes, but can lead to accumulation in the liver. Here the authors show a 3D-printed device containing functional nanoparticles, allowing the detox potential to be realised while holding the particles in place.

Bacterial cellulose (BC) and silk fibroin (SF) double-network hydrogel with high mechanical strength and biocompatibility was synthesized by using BC as the novel polymer substrate to absorb aqueous SF solution as the modifier. Fundamental physical characterizations were carried out by scanning electron microscopy, energy dispersive spectrometry, fourier transform infrared spectrometry, X-ray diffraction and X-ray photoelectron spectroscopy. Thermogravimetric and differential thermal analysis was used to investigate the stability of the hydrogel. Strength and biocompatibility of the BC/SF hydrogel for cartilage tissue engineering were evaluated by tensile strength tester and cell culture experiments. Results reveal that the BC/SF double-network hydrogel was prepared successfully, and the hydrogel could be used as a cartilage repair material in clinical application.Graphic abstract