Response of the Asian Summer Monsoons to a High-latitude Thermal Forcing: Mechanisms and Nonlinearities

This study investigates mechanisms and nonlinearities in the response of the Asian Summer Monsoons (ASM) to high-latitude thermal forcings of different amplitudes. Using a suite of runs carried out with an intermediate-complexity atmospheric general circulation model, we find that the imposed forcings produce a strong precipitation response over the eastern ASM but a rather weak response over the southern ASM. The forcing also causes a precipitation dipole with wet conditions over the eastern Tibetan Plateau (TP) and dry conditions over the Bay of Bengal (BoB) and southeast Asia. A moderate increase of precipitation along the southern margin of the TP is also produced. Simulations designed to isolate the causal mechanisms show that thermodynamic interactions involving the tropical surface oceans are far less important than the water-vapour feedback for the transmission of information from the high-latitudes to the ASM. Additionally, we assess the nonlinearity of the ASM precipitation response to the forcing amplitude using a novel application of the empirical orthogonal function method. The response can be decomposed in two overlapping patterns. The first pattern represents a precipitation dipole with wet conditions over the eastern TP and dry conditions over BoB, which linearly increases with forcing amplitude becoming quasi-stationary for large forcing amplitudes (i.e. amplitudes leading to Arctic temperature anomalies larger than 10 degrees C). The second pattern is associated with increased precipitation over the southeastern TP and is nonlinearly dependent on forcing, being most important for intermediate forcing amplitudes (i.e. amplitudes leading to Arctic temperature anomalies between 5 and 10 degrees C)

ENSO influence on Europe during the last centuries

El Niño/Southern Oscillation (ENSO) affects climate not only in the Pacific region and the tropics, but also in the North Atlantic-European area. Studies based on twentieth-century data have found that El Niño events tend to be accompanied in late winter by a negative North Atlantic Oscillation index, low temperatures in northeastern Europe and a change in precipitation patterns. However, many questions are open, for example, concerning the stationarity of this relation. Here we study the relation between ENSO and European climate during the past 500 years based on statistically reconstructed ENSO indices, early instrumental station series, and reconstructed fields of surface air temperature, sea-level pressure, precipitation, and 500hPa geopotential height. After removing years following tropical volcanic eruptions (which systematically mask the ENSO signal), we find a consistent and statistically significant ENSO signal in late winter and spring. The responses to El Niño and La Niña are close to symmetric. In agreement with studies using twentieth-century data only, the ENSO signal in precipitation is different in fall than in late winter. Moving correlation analyses confirm a stationary relationship between ENSO and late winter climate in Europe during the past 300 years. However, the ENSO signal is modulated significantly by the North Pacific climate. A multi-field cluster analysis for strong ENSO events during the past 300 years yields a dominant pair of clusters that is symmetric and represents the ‘classical' ENSO effects on Europ

European climate response to tropical volcanic eruptions over the last half millennium

We analyse the winter and summer climatic signal following 15 major tropical volcanic eruptions over the last half millennium based on multi-proxy reconstructions for Europe. During the first and second post-eruption years we find significant continental scale summer cooling and somewhat drier conditions over Central Europe. In the Northern Hemispheric winter the volcanic forcing induces an atmospheric circulation response that significantly follows a positive NAO state connected with a significant overall warm anomaly and wetter conditions over Northern Europe. Our findings compare well with GCM studies as well as observational studies, which mainly cover the substantially shorter instrumental period and thus include a limited set of major eruptions

Engineering of ecological niches to create stable artificial consortia for complex biotransformations

The design of controllable artificial microbial consortia has attracted considerable interest in recent years to capitalize on the inherent advantages in comparison to monocultures such as the distribution of the metabolic burden by division of labor, the modularity and the ability to convert complex substrates. One promising approach to control the consortia composition, function and stability is the provision of defined ecological niches fitted to the specific needs of the consortium members. In this review, we discuss recent examples for the creation of metabolic niches by biological engineering of resource partitioning and syntrophic interactions. Moreover, we introduce a complementing process engineering approach to provide defined spatial niches with differing abiotic conditions (e.g. O2, T, light) in stirred tank reactors harboring biofilms. This enables the co-cultivation of microorganisms with non-overlapping abiotic requirements and the control of the strain ratio in consortia characterized by substrate competition

Optimisation of epoxy blends for use in extrinsic self-healing fibre-reinforced composites

AbstractA range of epoxy blends were investigated to determine their mechanical properties and suitability for use as healing agents for the repair of fibre-reinforced polymer (FRP) composites. Key requirements for an effective healing agent are low viscosity, and good mechanical performance. A base epoxy resin was selected and blended with a variety of diluents and a toughening agent, and the physical and mechanical properties of the resulting polymers were investigated. Single lap shear strengths of up to 139% of the base epoxy values were demonstrated, while double cantilever beam testing showed specimens healed with optimised epoxy blends can provide recoveries in fracture toughness of up to 269%, compared to 56% in specimens healed with the base epoxy resin. Cross-ply FRP laminate tensile specimens were used to highlight the potential to recover stiffness decay caused by intraply cracking. Following infusion of the damage via embedded vascules, the toughened epoxies were capable of providing complete recovery of stiffness

Dual Valorization of Lignin as a Versatile and Renewable Matrix for Enzyme Immobilization and (Flow) Bioprocess Engineering

Lignin has emerged as an attractive alternative in the search for more eco-friendly and less costly materials for enzyme immobi- lization. In this work, the terephthalic aldehyde-stabilization of lignin is carried out during its extraction to develop a series of functionalized lignins with a range of reactive groups (epoxy, amine, aldehyde, metal chelates). This expands the immobiliza- tion to a pool of enzymes (carboxylase, dehydrogenase, trans- aminase) by different binding chemistries, affording immobiliza- tion yields of 64–100%. As a proof of concept, a ω- transaminase reversibly immobilized on polyethyleneimine- lignin is integrated in a packed-bed reactor. The stability of the immobilized biocatalyst is tested in continuous-flow deamina- tion reactions and maintains the same conversion for 100 cycles. These results outperform previous stability tests carried out with the enzyme covalently immobilized on methacrylic resins, with the advantage that the reversibility of the immobilized enzyme allows recycling and reuse of lignin beyond the enzyme inactivation. Additionally, an in-line system also based on lignin is added into the downstream process to separate the reaction products by catch-and-release. These results demonstrate a fully closed-loop sustainable flow- biocatalytic system based exclusively on lignin

Evidences for a quasi 60-year North Atlantic Oscillation since 1700 and its meaning for global climate change

The North Atlantic Oscillation (NAO) obtained using instrumental and documentary proxy predictors from Eurasia is found to be characterized by a quasi 60-year dominant oscillation since 1650. This pattern emerges clearly once the NAO record is time integrated to stress its comparison with the temperature record. The integrated NAO (INAO) is found to well correlate with the length of the day (since 1650) and the global surface sea temperature record HadSST2 and HadSST3 (since 1850). These findings suggest that INAO can be used as a good proxy for global climate change, and that a 60-year cycle exists in the global climate since at least 1700. Finally, the INAO ~60-year oscillation well correlates with the ~60- year oscillations found in the historical European aurora record since 1700, which suggests that this 60-year dominant climatic cycle has a solar-astronomical origin

Slowing the Kinetics of Alumina Sol-Gel Chemistry for Controlled Catalyst Overcoating and Improved Catalyst Stability and Selectivity

Catalyst overcoating is an emerging approach to engineer surface functionalities on supported metal catalyst and improve catalyst selectivity and durability. Alumina deposition on high surface area material by sol–gel chemistry is traditionally difficult to control due to the fast hydrolysis kinetics of aluminum‐alkoxide precursors. Here, sol–gel chemistry methods are adapted to slow down these kinetics and deposit nanometer‐scale alumina overcoats. The alumina overcoats are comparable in conformality and thickness control to overcoats prepared by atomic layer deposition even on high surface area substrates. The strategy relies on regulating the hydrolysis/condensation kinetics of Al(sBuO)3 by either adding a chelating agent or using nonhydrolytic sol–gel chemistry. These two approaches produce overcoats with similar chemical properties but distinct physical textures. With chelation chemistry, a mild method compatible with supported base metal catalysts, a conformal yet porous overcoat leads to a highly sintering‐resistant Cu catalyst for liquid‐phase furfural hydrogenation. With the nonhydrolytic sol–gel route, a denser Al2O3 overcoat can be deposited to create a high density of Lewis acid–metal interface sites over Pt on mesoporous silica. The resulting material has a substantially increased hydrodeoxygenation activity for the conversion of lignin‐derived 4‐propylguaiacol into propylcyclohexane with up to 87% selectivity

A mild biomass pretreatment using gamma-valerolactone for concentrated sugar production

Here we report that gamma-valerolactone (GVL), a biomass-derived solvent, can be used to facilitate the mild pretreatment of lignocellulosic biomass. An 80% GVL, 20% water solvent system was used to pretreat hardwood at the mild temperature of 120 degrees C with an acid loading of 75 mM H2SO4. Up to 80% of original lignin was removed with 96-99% of original cellulose retained in the pretreated substrates. The use of a mild temperature and low acid concentrations caused negligible degradation of sugars. Up to 99% of the original glucan and 96% of the original xylan could be recovered after pretreatment. The pretreated substrate was quantitatively converted to sugars (99% and 100% total glucose and xylose yield) with an enzyme loading of 15 FPU g(-1) glucan. These digestibilities were three times higher than those obtained when using other organic solvents such as tetrahydrofuran or ethanol, and 20 times higher than when pure water was used during pretreatment. Over 99.5% of GVL could be recovered by liquid-CO2 extraction of the pretreated slurries while removing less than 1% of the sugars. This approach produced pretreatment slurries that could easily undergo high-solids (30% w/v) enzymatic hydrolysis without any substrate washing or drying. We obtained glucose and xylose yields of up to 90% and 97%, respectively, and generated sugar streams with sugar concentrations up to 182 g L-1