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Pineapple and hericium erinaceus (HE) produce a lot of residues in the process of food processing. These processed residues are good potential derivative precursors. In this investigation, a simple and non-toxic method was developed to prepare one new composite hydrogel by the Schiff base reaction between the aldehyde group of oxidized hydroxyethyl cellulose (OHEC) from processed pineapple peel residue and the amino group of carboxymethyl chitosan (CMCS) from processed HE residue. Subsequently, a series of experiments toward these new hydrogel polymers including structure characterization and performances were applied. The resultant hydrogel polymers were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy and confirmed with thermogravimetry. It was observed that the modification of cellulose and chitin was adequate, and the synthesis of OHEC/CMCS hydrogel polymers was successful. The gelation time experiments indicated that the shortest gel time was 33 s at a mass ratio of 4:6 (OHEC-70:CMCS). The hydrogel showed good swelling properties. The maximum swelling rate reached 11.58 g/g, and the swelling rate decreased with the increase of the oxidation degree of OHEC. The drug delivery applications of the prepared hydrogel were evaluated with bovine serum albumin (BSA) as a model drug releasing in vitro. It was discovered that the BSA release from the hydrogel was pH sensitive under simulated gastrointestinal conditions. All of these attributes indicate that the novel prepared hydrogel polymers have the potential as good carriers for oral delivery of protein-type drugs.

Permafrost has been warming and thawing globally, with subsequent effects on the climate, hydrology, and the ecosystem. However, the permafrost thermal state variation in the northern lower limit of the permafrost zone (Xidatan) on the Qinghai–Tibet Plateau (QTP) is unclear. This study attempts to explore the changes and variability in this permafrost using historical (1970–2019) and future projection datasets from remote-sensing-based land surface temperature product (LST) and climate projections from Earth system model (ESM) outputs of the Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5, CMIP6). Our model considers phase-change processes of soil pore water, thermal-property differences between frozen and unfrozen soil, geothermal flux flow, and the ground ice effect. Our model can consistently reproduce the vertical ground temperature profiles and active layer thickness (ALT), recognizing permafrost boundaries, and capture the evolution of the permafrost thermal regime. The spatial distribution of permafrost and its thermal conditions over the study area were controlled by elevation with a strong influence of slope orientation. From 1970 to 2019, the mean annual ground temperature (MAGT) in the region warmed by 0.49 ∘C in the continuous permafrost zone and 0.40 ∘C in the discontinuous permafrost zone. The lowest elevation of the permafrost boundary (on the north-facing slopes) rose approximately 47 m, and the northern boundary of discontinuous permafrost retreated southwards by approximately 1–2 km, while the lowest elevation of the permafrost boundary remained unchanged for the continuous permafrost zone. The warming rate in MAGT is projected to be more pronounced under shared socioeconomic pathways (SSPs) than under representative concentration pathways (RCPs), but there are no distinct discrepancies in the areal extent of the continuous and discontinuous permafrost and seasonally frozen ground among SSP and RCP scenarios. This study highlights the slow delaying process of the response of permafrost in the QTP to a warming climate, especially in terms of the areal extent of permafrost distribution.

Permafrost has been warming and thawing at a global scale with subsequent effects on the climate, hydrological, ecosystem and engineering system. However, the variation of permafrost thermal state in the northern lower limit of the permafrost zone (Xidatan) on the Qinghai–Tibetan Plateau (QTP) is unclear. To evaluate and project the permafrost changes, this study simulated the spatiotemporal dynamics of this marginal permafrost historically (1970–2019) based on the detailed investigation and monitoring datasets from 1987 in this study region, improved remote sensing-based Land Surface Temperature product (LST) and climate projections from Global Climate Model (GCM) outputs of Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5, CMIP6). Our model takes into consideration of phase change processes of soil pore water, thermal property difference between frozen and thawed soil, geothermal flux flow, and ground ice effect. The results indicate that 1) our model can consistently reproduce the ground temperature field and active layer thickness (ALT), is superior in recognizing permafrost boundaries, and would realistically capture the evolution of the permafrost thermal regime, 2) spatial distribution of permafrost and its thermal conditions over the study area were controlled by elevational with a strong influence of slope aspects, 3) from 1970 to 2019, the regional averaged means annual ground temperature (MAGT) had warmed by 0.49 °C in the continuous permafrost zone and 0.40 °C in the discontinuous permafrost zone, and the lowest elevation of permafrost boundary (on north-facing slopes) rose approximately 47 m, as well as the northern boundary of discontinuous permafrost has approximately retreated southwards 1~2 km, while the lowest elevation of permafrost boundary remains unchanged for continuous permafrost zone, 4) the warming rate in MAGT is projected to be slighter higher under Shared Socioeconomic Pathways (SSPs) than that of Representative Concentration Pathways (RCPs), but no distinct discrepancies in the areal extent of the continuous, discontinuous permafrost and seasonally frozen ground among SSP and RCP scenarios. This study highlights the slow delaying process in the response of mountain permafrost to a warming climate, especially in terms of the areal extent of permafrost distribution.