Cellulose-based materials are produced industrially in countless varieties via top-down processing of natural lignocellulose substrates. By contrast, cellulosic materials are only rarely prepared via ...bottom up synthesis and oligomerization-induced self-assembly of cellulose chains. Building up a cellulose chain via precision polymerization is promising, however, for it offers tunability and control of the final chemical structure. Synthetic cellulose derivatives with programmable material properties might thus be obtained. Cellodextrin phosphorylase (CdP; EC 2.4.1.49) catalyzes iterative β-1,4-glycosylation from α-d-glucose 1-phosphate, with the ability to elongate a diversity of acceptor substrates, including cellobiose, d-glucose and a range of synthetic glycosides having non-sugar aglycons. Depending on the reaction conditions leading to different degrees of polymerization (DP), short-chain soluble cello-oligosaccharides (COS) or insoluble cellulosic materials are formed. Here, we review the characteristics of CdP as bio-catalyst for synthetic applications and show advances in the enzymatic production of COS and reducing end-modified, tailored cellulose materials. Recent studies reveal COS as interesting dietary fibers that could provide a selective prebiotic effect. The bottom-up synthesized celluloses involve chains of DP ≥ 9, as precipitated in solution, and they form ~5 nm thick sheet-like crystalline structures of cellulose allomorph II. Solvent conditions and aglycon structures can direct the cellulose chain self-assembly towards a range of material architectures, including hierarchically organized networks of nanoribbons, or nanorods as well as distorted nanosheets. Composite materials are also formed. The resulting materials can be useful as property-tunable hydrogels and feature site-specific introduction of functional and chemically reactive groups. Therefore, COS and cellulose obtained via bottom-up synthesis can expand cellulose applications towards product classes that are difficult to access via top-down processing of natural materials.
•Cellodextrin phosphorylases (EC 2.4.1.49) as biocatalyst for cello-oligomer synthesis•Structure, specificity and catalytic properties of cellodextrin phosphorylase•Synthesis of reducing end-modified cellulose oligomers for property-tunable materials•Synthesis of soluble cello-oligosaccharides by cascades of glycoside phosphorylases•Applied potential of products synthesized by cellodextrin phosphorylase
Spontaneous imbibition plays an important role in many subsurface and industrial applications. Unveiling pore‐scale wetting dynamics, and particularly its upscaling to the Darcy model, are still ...unresolved. We conduct image‐based pore‐network modeling of cocurrent spontaneous imbibition and the corresponding quasi‐static imbibition in homogeneous sintered glass beads and heterogeneous Estaillades carbonate. We find that pore‐scale heterogeneity significantly influences entrapment of the nonwetting fluid, which in Estaillades is mainly because of the poor connectivity of pores. We show that wetting dynamics significantly deviates capillary pressure and relative permeability away from their quasi‐static counterparts. Moreover, we propose a nonequilibrium model for wetting permeability that well incorporates flow dynamics. We implement the nonequilibrium model into two‐phase Darcy modeling of a 10 cm long medium. Sharp wetting fronts are numerically predicted, which are in good agreement with experimental observations. Our studies provide insights into developing a two‐phase imbibition model with measurable material properties.
Plain Language Summary
The flow of a fluid into a porous matrix by capillary force is encountered in many everyday processes, such as water‐flow to reach the tips of trees and water‐flow through soils. These processes are examples of spontaneous imbibition. Spontaneous imbibition is also crucial to many industrial applications, ranging from oil recovery and geological sequestration of carbon dioxide to inkjet printing, diapers, and paper sensors. Mostly, the imbibition rate, broadening of the wetting front, and entrapment of the nonwetting fluid are of great interest. In this work, we conduct extensive pore‐scale modeling of spontaneous flow in porous media. We illustrate how pore‐scale heterogeneity influences imbibition dynamics and entrapment of the nonwetting fluid. To bridge the gap between pore‐scale flow dynamics and the Darcy‐scale theory of spontaneous imbibition, we develop a nonequilibrium model for wetting permeability that can provide better modeling of spontaneous imbibition at the Darcy scale. Our studies have immediate implications for the applications of oil production from fractured reservoirs, capillary trapping of carbon dioxide, and remediation of nonaqueous liquids in soils.
Key Points
We conduct image‐based pore‐network modeling of spontaneous imbibition in sintered glass beads and Estaillades carbonate
We illustrate the influence of pore‐scale heterogeneity on wetting dynamics and nonwetting entrapment
We develop a new relative permeability model that incorporates wetting dynamics
The engineering of microbially induced calcium carbonate precipitation (MICP) has attracted much attention in a number of applications, such as sealing of CO2 leakage pathways, soil stabilization, ...and subsurface remediation of radionuclides and toxic metals. The goal of this work is to gain insight into pore‐scale processes of MICP and scale dependence of biogeochemical reaction rates. This will help us develop efficient field‐scale MICP models. In this work, we have developed a comprehensive pore‐network model for MICP, with geochemical speciation calculated by the open‐source PHREEQC module. A numerical pseudo‐3‐D micromodel as the computational domain was generated by a novel pore‐network generation method. We modeled a three‐stage process in the engineering of MICP including the growth of biofilm, the injection of calcium‐rich medium, and the precipitation of calcium carbonate. A number of test cases were conducted to illustrate how calcite precipitation was influenced by different operating conditions. In addition, we studied the possibility of reducing the computational effort by simplifying geochemical calculations. Finally, the effect of mass transfer limitation of possible carbonate ions in a pore element on calcite precipitation was explored.
Key Points
A comprehensive pore‐network model coupled with PHREEQC was developed to study microbially induced calcite precipitation in porous media
Scale dependence of biogeochemical reaction rates was studied
The possibility of reducing computational efforts by simplifying geochemical calculations was investigated
Whether nonalcoholic fatty liver disease (NAFLD) is associated with an increased risk of mortality remains controversial. The present study aimed to clarify this issue. A systematic search of PubMed ...and Embase was conducted through October 2018. Studies providing risk estimates of NAFLD and mortality were included. A random-effects model was employed to calculate summary risk estimates. Subgroup analyses were performed to identify potential effect modifiers. Fourteen studies, involving 498501 subjects and 24234 deaths, were included. Patients with NAFLD were found to be at an elevated risk of all-cause mortality compared with those without hazard ratio (HR) = 1.34; 95% confidence interval (CI) 1.17-1.54). The significantly positive association between NAFLD and all-cause mortality could not be modified by age, sex, follow-up duration, and adjustment for body mass index, diabetes, smoking or hypertension (all P
> 0.05), and remained in sensitivity analyses. No significant associations of NAFLD with CVD (HR = 1.13; 95% CI 0.92-1.38) and cancer (HR = 1.05; 95% CI 0.89-1.25) mortality were found. In conclusion, NAFLD is a predictor of increased all-cause mortality but not CVD and cancer mortality. These findings have important implications for decision making in public health and clinical practice, and highlight the urgency of developing effective treatments for NAFLD.
The senescence of dermal fibroblasts (DFLs) leads to an imbalance in the synthesis and degradation of extracellular matrix (ECM) proteins, presenting so-called senescence-associated secretory ...phenotype (SASP), which ultimately leads to skin aging. Recently, mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) have been recognized as a promising cell-free therapy for degenerative diseases, which opens a new avenue for skin aging treatment.
In this study, we utilized chitosan (CS) hydrogel for effective loading and sustained release of EVs. In vitro, we explored the rejuvenation effects of CS hydrogel-incorporated EVs (CS-EVs) on replicative senescence DFLs through a series of experiments such as senescence-associated β-galactosidase (SA-β-gal) staining, RT-PCR, and Western blot analysis. Besides, we employed local multi-site subcutaneous injection to treat skin aging of naturally aged mice with CS-EVs and DiI fluorescent dye was used to label EVs to achieve in vivo real-time tracking.
CS-EVs can significantly improve the biological functions of senescent fibroblasts, including promoting their proliferation, enhancing the synthesis of ECM proteins, and inhibiting the overexpression of matrix metalloproteinases (MMPs). Moreover, CS hydrogel could prolong the release of EVs and significantly increase the retention of EVs in vivo. After CS-EVs subcutaneous injection treatment, the aging skin tissues showed a rejuvenation state, manifested explicitly as the enhanced expression of collagen, the decreased expression of SASP-related factors, and the restoration of tissue structures.
CS hydrogel-encapsulated EVs could delay the skin aging processes by ameliorating the function of aging DFLs. Our results also highlight the potential of CS hydrogel-encapsulated EVs as a novel therapeutic strategy for improving aging skin to rejuvenation.
The difference between average pressures of two immiscible fluids is commonly assumed to be the same as macroscopic capillary pressure, which is considered to be a function of saturation only. ...However, under transient conditions, a dependence of this pressure difference on the time rate of saturation change has been observed by many researchers. This is commonly referred to as dynamic capillarity effect. As a first‐order approximation, the dynamic term is assumed to be linearly dependent on the time rate of change of saturation, through a material coefficient denoted by τ. In this study, a series of laboratory experiments were carried out to quantify the dynamic capillarity effect in an unsaturated sandy soil. Primary, main, and scanning drainage experiments, under both static and dynamic conditions, were performed on a sandy soil in a small cell. The value of the dynamic capillarity coefficient τ was calculated from the air‐water pressure differences and average saturation values during static and dynamic drainage experiments. We found a dependence of τ on saturation, which showed a similar trend for all drainage conditions. However, at any given saturation, the value of τ for primary drainage was larger than the value for main drainage and that was in turn larger than the value for scanning drainage. Each data set was fit a simple log‐linear equation, with different values of fitting parameters. This nonuniqueness of the relationship between τ and saturation and possible causes is discussed.
Key Points
A series of primary, main, and scanning drainage experiments, under both static and dynamic conditions, were performed on a sandy soil
The dynamic capillarity coefficient τ was calculated from the air‐water pressure differences and average saturation values
The relationship between τ and saturation was found to be nonunique for drainage processes
Atherosclerosis, a chronic inflammatory disease of the arterial wall, is among the leading causes of morbidity and mortality worldwide. The persistence of low-grade vascular inflammation has been ...considered to fuel the development of atherosclerosis. However, fundamental mechanistic understanding of the establishment of non-resolving low-grade inflammation is lacking, and a large number of atherosclerosis-related cardiovascular complications cannot be prevented by current therapeutic regimens. Trained immunity is an emerging new concept describing a prolonged hyperactivation of the innate immune system after exposure to certain stimuli, leading to an augmented immune response to a secondary stimulus. While it exerts beneficial effects for host defense against invading pathogens, uncontrolled persistent innate immune activation causes chronic inflammatory diseases. In light of the above, the long-term over-activation of the innate immune system conferred by trained immunity has been recently hypothesized to serve as a link between non-resolving vascular inflammation and atherosclerosis. Here, we provide an overview of current knowledge on trained immunity triggered by various exogenous and endogenous inducers, with particular emphasis on its pro-atherogenic effects and the underlying intracellular mechanisms that act at both the cellular level and systems level. We also discuss how trained immunity could be mechanistically linked to atherosclerosis from both preclinical and clinical perspectives. This review details the mechanisms underlying the induction of trained immunity by different stimuli, and highlights that the intracellular training programs can be different, though partly overlapping, depending on the stimulus and the biological system. Thus, clinical investigation of risk factor specific innate immune memory is necessary for future use of trained immunity-based therapy in atherosclerosis.
We propose a Lax representation of the two-component BKP hierarchy via pseudo-differential operators containing two derivations, and show that it is equivalent to the Lax representation via two types ...of pseudo-differential operators involving only one derivation given by Liu et al. (2011).
•Lax representation of the 2-BKP hierarchy via operators containing two derivations.•Equivalence between Lax equations and bilinear equation of the 2-BKP hierarchy.•Relationship between Baker–Akhiezer functions and tau function.
Abstract
Background
The associations of frailty with all-cause and cause-specific mortality remain unclear. Therefore, we performed this meta-analysis to fill this gap.
Methods
We searched the PubMed ...and Embase databases through June 2022. Prospective cohort studies or clinical trials examining frailty were evaluated, and the multiple adjusted risk estimates of all-cause and cause-specific mortality, such as death from cardiovascular disease (CVD), cancer, respiratory illness, dementia, infection, and coronavirus disease 2019 (COVID-19), were included. A random effects model was used to calculate the summary hazard ratio (HR).
Results
Fifty-eight studies were included for the qualitative systematic review, of which fifty-six studies were eligible for the quantitative meta-analysis, and the studies included a total of 1,852,951 individuals and more than 145,276 deaths. Compared with healthy adults, frail adults had a significantly higher risk of mortality from all causes (HR 2.40; 95% CI 2.17–2.65), CVD (HR 2.64; 95% CI 2.20–3.17), respiratory illness (HR 4.91; 95% CI 2.97–8.12), and cancer (HR 1.97; 95% CI 1.50–2.57). Similar results were found for the association between prefrail adults and mortality risk. In addition, based on the studies that have reported the HRs of the mortality risk per 0.1 and per 0.01 increase in the frailty index, we obtained consistent results.
Conclusions
The present study demonstrated that frailty was not only significantly related to an increased risk of all-cause mortality but was also a strong predictor of cause-specific mortality from CVD, cancer, and respiratory illness in community-dwelling adults. More studies are warranted to clarify the relationship between frailty and cause-specific mortality from dementia, infection, and COVID-19.
Trial registration
PROSPERO (CRD42021276021).
PDF
