ALBERT

Description: The search for novel chemical architectures displaying improved biological properties is a never-ending synthetic challenge. In this context many new test structures are often conceived by selecting and replicating specific design elements from naturally occurring molecules and displaying them in an alternative format by way of a new chemical assembly. Constructing these newly designed compounds can be a timely and expensive process especially when a large quantity of the target material is required for physiochemical and property testing. To permit easier scale up and safer working practice many chemical researchers are employing flow chemistry approaches to aid in their synthesis challenges. Herein we report on the preparation of a key spirocyclic lactone using flow based reaction processing techniques.

Description: Mass transfer from single CO 2 Taylor bubbles in vertical mini channels was measured for channel hydraulic diameters, D h , from 5.5 to 8.0 mm. The effects of channel geometries on the mass transfer were also investigated by using square ducts and circular pipes. Bubble rising velocities, v B , in the ducts were much faster than those in the pipes due to large liquid flow areas in the corners of the ducts. The values of mass transfer coefficients, k L , in the pipes were almost the same as those in the ducts, in spite of a large difference in v B . Sherwood numbers, Sh D , using D h as a characteristic length are well correlated in terms of the Eötvös number. The proposed Sh D correlation can well predict a long-term dissolution process of a Taylor bubble.

Description: The phase-field method coupled with the Navier-Stokes equations is a rather new approach for scale-resolving numerical simulation of interfacial two-phase flows. The intention is to implement it as finite-volume method in the open source library for computational continuum mechanics OpenFOAM® and make it freely available. An overview on the governing equations is given and the numerical method is shortly discussed. The focus is on application and validation of the code for some fundamental wetting phenomena, namely the capillary rise in a narrow channel and the spreading of a droplet on a flat surface, which is chemically homogeneous or regularly patterned. The numerical results on static meshes agree well with analytical solutions and experimental/numerical results from literature. Also, first 3D finite-volume simulations with adaptive mesh refinement near the interface are presented as a key element to achieve CPU-time efficient simulations. A phase-field method for interface resolving numerical simulations of two-phase flows is presented and implemented in OpenFOAM®. The method is validated for several capillary flows with moving contact lines and is used to study dynamic droplet spreading on a flat surface by three-dimensional simulations with adaptive mesh refinement near the interface.

Description: The influence of water on the catalysis of biphasic Heck alkynylation, a family of palladium-catalyzed carbon-carbon bond formations, was investigated. Kinetic theory derived from Hatta moduli and pseudo-stationary-state approximations discovered that water, in coordination, reductive elimination, and product dissociation reaction steps of the deprotonation catalytic cycle, increases Gibbs energy barriers compared to values previously estimated by density functional theory calculations of purely organic syntheses involving an aryl iodide. On the contrary, water reduces the energy barrier of reductive elimination in the carbopalladation catalytic cycle. Quantum tunneling in proton transfer mechanism might account for the change. Water also influenced the rate-determining steps of the catalytic cycles, and its existence potentially switches the cross-coupling’s mechanism from deprotonation, previously thought to govern the reaction, to carbopalladation. Carbopalladation theory identified the ~35% of the Pd wasted during synthesis was ~10% greater than the amount predicted by deprotonation. Our discoveries enabled E-factor predictions that could someday help reduce chemical wastes generated during materials, natural products, and pharmaceutical manufactures. Theoretical groundwork is laid that enables data-driven research in the academic laboratory and data-driven development by the process chemist.

Description: A continuous process to produce carbon supported platinum catalysts by polyol reduction was examined. The reactant dispersion was rapidly heated up to reaction temperature while flowing through a directly electrically heated tube followed by a downstream isothermic tubular reactor. Appropriate inner diameters corresponding to desired short heating-up times were calculated. A certain lower limit for the inner diameter is caused by temporary pluggings of particle agglomerates circumventing steady-state operation. Tube diameters were evaluated with respect to heating-up times and plugging. It was proved that with a tubular reactor a continuous preparation of carbon nanotube supported platinum catalysts with a low particle size and evenly distributed particles is possible.

Description: This work focussed on the mathematical modeling of the separation process in counter-current decanter centrifuges, taking the influence of the sediment build-up and the flow pattern into account. Thus far, separation processes in centrifuges are calculated by means of simplified empirical models based on the so-called sigma-theory. To reduce experimental effort, we have developed a new model, which describes the separation process by considering material functions for sedimentation and the gel point. In addition to that, an arising sediment build-up and a change in the flow conditions are taken into account. The conducted numerical simulations are validated by experiments. Simplified models such as the sigma theory usually depend on experimental data of industrial machines. Our approach shows an enhanced accuracy while not depending on such information. The proposed simulation procedure is adaptable to other types of decanter centrifuges such as co-current machines.

Description: Catalyzed reaction of sulfite with oxygen is often used by industry for corrosion protection by chemical deoxygenation. The same reaction system is considered very important as a part of atmospheric chemistry due to SO2 immission modeling. In these applications, reaction kinetic data are of crucial importance. In deoxygenation, low concentrations of sulfite close to the stoichiometric ratio to oxygen are being used. Unfortunately, the values of kinetic constants for the reaction are sparse.The reaction kinetics was investigated in a rapid-mixing apparatus, where air or pure oxygen saturated solution containing the catalyst was mixed with aqueous sulfite solution. Mixing ratios with stoichiometric excess of dissolved oxygen were tested.Analysis of literature data suggests that the reaction is of 1.5 order in sulfite, 0 order in oxygen and 0.5 order in cobalt(II) catalyst. These reaction orders had been confirmed in the concentration range tested. The apparent kinetic constant and activation energy are also presented. Crucial importance of proper mixing of the two reacting solutions is reported, which was revealed during the development of the precise experimental technique providing reliable kinetic data.

Description: Inhibitory effects of high glucose and ethanol concentrations on ethanol production from wheat enzymatic hydrolysate by zygomycetes fungus Mucor hiemalis were investigated and modeled. Ethanol yield was decreased by increasing glucose concentration from 70 to 120 g.l -1 . Among different kinetic models, i.e., linear, Emerson, and modified Williams, modified Williams model was successfully described the fungal growth kinetics. Considering the inhibitory effect of glucose, a new model was developed for describing the rate of ethanol production. Moreover, the inhibitory effect of ethanol on ethanol yield, Y p/x , was modeled. The model prediction was successfully covered the experimental data.

Description: In this study experimental mass transfer data and literature data of airlift loop reactors are analyzed concerning an effect of gas-phase residence time on the volumetric mass transfer coefficient k L a. It becomes evident that a neglect of the oxygen depletion can be regarded as a diminishment of the mass transfer driving force. The latter is found to be an important cause of the mass transfer dependency on the actual apparatus height of airlift loop reactors. Therefore a new correlation is presented which describes the volumetric mass transfer coefficients of airlift loop reactors by including the effect of gas-phase transient component concentration depletion. In this work two geometrically similar experimental apparatuses of different absolute size are utilized. Both of them are driven as airlift loop reactors with aerated concentric draft tube. The operating method is schematically illustrated in Fig. 3. The essential geometric data of the reactors is listed in Tab. 1.

Description: Monolithic honeycomb reactors are characterized by small parallel channels, which make them an interesting approach to be applied as microstructured reactors. Besides the established manufacturing of ceramic honeycombs, these structures exhibit excellent mass transfer characteristics for multiphase reactions combined with degrees of freedom in the structural design. In this contribution the potential of monolithic honeycomb reactors operated in the beneficial slug flow regime is evaluated for heterogeneously catalyzed gas-liquid reactions. Therefore, results of the Fischer-Tropsch synthesis and hydrogenation of glucose to sorbitol were analyzed in order to obtain a more generalized picture of the interaction between mass transfer and reaction in small channels operated in multiphase flow.

Description: The concept of a multi-stage microstructured (MM) reactor has been tested in the bench-scale rig for combined steam and CO 2 reforming of methane (RM). In this reactor type the RM reaction is carried out in a series of adiabatic catalytic reaction steps with heat supply through fin-plate heat exchangers placed between the stages. RM reaction has been performed over a rhodium based catalyst in form of pellets. The experimental results have been described with a reaction engineering model that can be used as basis for model-supported scale-up. This paper describes an intermediate step in the development of the integrated reactor for thermal integration of oxidative coupling and reforming of methane. Conversion and yield near thermodynamical equilibrium have been achieved. Experiments confirmed advantages of the MM reactor against wall-coated micro reactors.

Description: This short review describes photocatalytic vs photosensitizing materials to be used respectively for gas-phase photooxidation and photo-oxygenation. The reactive oxygen species specific to photocatalysis and to photosensitization are summarized. Various kinds of gas-phase reactors and of photocatalytic materials are described in order to illustrate the great number of possible configurations and conditions of use. Some efforts towards standardization of gas-phase photocatalytic reactors devoted to indoor- or outdoor-air treatment are mentioned. Some examples of use of singlet oxygen in solvent-free photooxygenation reaction of volatile sulfides are given together with the properties of silica-based photosensitizing materials.

Description: Fluorine and fluorine-containing groups are omnipresent in pharmaceuticals, agrochemicals and many other high-value chemical products like liquid crystals and organic electronics. The unique properties of fluorine resulting from its tremendously high electronegativity make this element a key player in the quest of enabling new and advanced qualities for chemical compounds and materials. With the advent of fluorinating reagents a great diversity of synthetic methodologies has been developed to incorporate fluorine or fluorine-containing groups into small molecules with high conversion and selectivity. Especially photochemically catalyzed fluorination reactions proved their potential for the synthesis of fluorine-containing fine chemicals due to their mild reaction conditions. This tutorial review gives an overview of recently published synthesis strategies that use (visible-) light-absorbing catalysts for the activation of fluorinating reagents. A special focus is made on the use of continuous-flow microreactors for photochemically catalyzed fluorination reactions due to the excellent utilization of this reactor equipment for photochemistry.

Description: This manuscript addresses the evaluation of photocatalytic efficiency using Quantum Yields (QY) and the “Photochemical Thermodynamic Efficiency Factor” (PTEF). While the QY can be considered as an early photocatalytic reactor efficiency factor, developed in the 80’s, the PTEF was first introduced by Serrano and de Lasa in 1997 [29]. The PTEF allows establishing reactor efficiency as the ratio of utilized enthalpy for the formation of consumed OH • free radicals over the absorbed photon energy. In all cases, a key consideration for the evaluation of efficiency factors is the establishment of macroscopic energy balances together with an accurate assessment of evolved and absorbed photons. Of considerable help, as well, are the experimental devices developed at the Chemical Reactor Engineering Centre (CREC)-University of Western Ontario laboratories. Furthermore, photoconversion kinetics is a required information for the calculation of the OH • consumption rates and the establishment of the related kinetic parameters. In this respect, de Lasa et al (2005) [6] postulated a unified “in series-parallel” model for the kinetics in photocatalytic conversion. Until today, both PTEFs and QYs have been used by CREC-UWO researchers for efficiency calculations in photocatalytic reactors for the decontamination of air, water and hydrogen production. This methodology is very relevant, in particular, for the assessment of the effects of reactor scale, reactor configuration, irradiation source, type of photocatalyst and model pollutant compounds.

Description: Photoinitiated crosslinking of multifunctional acrylic esters in polymeric binders was investigated based on digital imaging using the Computer to Plate (CtP) technology applying laser exposure at 830 nm in the near infrared (NIR). All coating components were applied as thin double layer film on Al-plates with an anodized surface. Materials exposed exhibit a sensitivity between 30-100 mJ/cm 2 . Processing of the exposed materials occurred in a weak aqueous alkaline bath. Generation of initiating radicals occurs by electron transfer from the excited state of the NIR-sensitizer to the radical generator – an onium salt. Several onium salts with distinct cation and anion pattern were synthesized. Iodonium salts derived from several borates and those with the bis(trifluoromethylsulfonyl)imide anion resulted in lithographic materials with high sensitivity. Photoinduced electron transfer plays a major function to generate initiating radicals by a sensitized mechanism but thermal events also influence sensitivity of the coating. Particular the radiationless deactivation of the NIR-sensitizer possesses a major function for selective release of heat. Internal conversion (〉85%) was the major deactivation pathway while a certain fraction of NIR-dye fluorescence (〈15%) was also available. Moreover, a line shape focused laser system with emission in the NIR (808 nm) was successfully used to bake the materials. This was initiated by the absorption of the NIR-dye embedded in the coating.

Description: The cover represents on opening window which represents the Novel Process Windows concept. Inside the window, a photomicroreactor can be seen. In photochemistry, photons are used to activate organic substrates for reactions. More information on the photomicroreactor design and its application can be found in the paper by Su et al. Yuanhai Su, Ali Talla, Volker Hessel, and Timothy Noël Controlled Photocatalytic Aerobic Oxidation of Thiols to Disulfides in an Energy-Efficient Photomicroreactor Chem. Eng. Technol. 2015 , 38 (10) , 1733–1742 DOI: 10.1002/ceat.201500376

Description: The optimization of installation of baffles in UV rector is investigated. The flow field is obtained by solving continuity equation and momentum equation. The radiation intensity is solved by use of radiative transfer equation. The UV dosage is obtained by coupling Lagrangian particle tracking approach with the solved radiation intensity. One unbaffled reactor and two baffled reactors are simulated. The baffled UV reactor A has the biggest residence time and the smallest UV dosage while the baffled UV reactor B has the relatively bigger residence time and the biggest UV dosage. The unbaffled reactor performs between two baffled reactors in residence time and UV dosage. The baffled UV reactor B can get the best disinfection of microorganisms. The present study shows that the optimization must be coupled the flow field and the radiation intensity to attain a harmony between them.

Description: Stable isotope proving (SIP) enables function to be linked with identity without isolating the microorganisms responsible. This culture-independent approach has been adapted to identify the microorganisms involved in the degradation of numerous environmental contaminants. SIP studies have been performed in situ or in laboratory microcosms inoculated with soil, sediment, groundwater or bioreactor samples. This review focuses on the microorganisms that have been identified in those projects. SIP studies involving the degradation of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, gasoline associated contaminants, chlorinated solvents, RDX, phenol, uranium and pentachlorophenol are discussed. This review brings to light the significant diversity of contaminant degrading microorganisms.

Description: A continuous-flow microreactor was used to synthetize II–VI semiconductor quantum dots (CdSe). In order to improve the size distribution of the nanoparticles, the synthesis was carried out in a two-step procedure. A seed solution was obtained in a separate nucleation step, followed by a controllable growth step. Quantum dots that are synthesized with the two-step method show a much narrower size distribution in comparison to those obtained in a conventional batch synthesis. Quantum dots are nanocrystalline semiconductors that differ greatly from their bulk counterparts. To obtain CdSe quantum dots with a narrow size distribution, a two-step procedure was applied, in which CdSe seeds were synthesized in a separate process prior to the nanoparticle growing procedure. The seeds were mixed into the growing solution-containing droplet by coaxial injection.

Description: The chemical process industry is paying significant attention to the intensification of processes with the main aim of achieving increased productivity, improved economic status, and enhanced sustainability. The pharmaceutical industry is moving in the same direction and, therefore, dozens of processes are in a state of change. However, it is important to note that not all processes can be intensified easily, such as slow chemical reactions, processes with solids, slurries, and on the like. This review summarizes applications of promising tools for achieving process intensification in the small-scale pharmaceutical manufacturing of so-called small molecules. The focus is on microwave radiation, microreactors, ultrasounds, and meso-scale tubular reactors. Promising tools for accelerating slow chemical reactions in organic synthesis in order to achieve process intensification are reviewed with the focus on microwave radiation, meso-scale tubular reactors, microreactors, and ultrasounds. Applications of such tools for producing small molecules in the pharmaceutical industry are discussed and illustrated with examples.

Description: Process design management system is the essential computer-aided design type of software used in design and 3D modeling of process plants. Actually, it is a management center of process plant projects which allows designers and engineers from various disciplines to concurrently create, control, and manage changes to the plant design and other related engineering data. Some methods for achieving the inherently safer designs guide the location of process equipment and utilities. Therefore, there is room for close interactions between 3D modeling and methods to assess the inherent safety. The feasibility of integration of the Fire and Explosion Index into 3D modeling of industrial chemical processes is evaluated and supported by a case study. The importance of the presented concept as key part of such management philosophies like the lean design and the building information modeling is highlighted. In conventional process plant design, safety analysis is performed at the stage when the main design decisions were already made. The presented perspective allows placing the safety considerations using the Fire and Explosion Index (F&EI) in a 3D modeling environment. Results of the F&EI assessment can be visualized and shared between all disciplines involved in plant design.

Description: Energy optimization is a hot research topic for design and operation of crude oil distillation plants. Optimum energy utilization in a multistage crude oil distillation process is achieved by optimizing the distillation load of each distillation column as well as the yield of the sidestreams of distillation columns. A generalized multistage distillation energy consumption model is proposed, and the optimal distillation load distribution is accomplished by minimizing the total energy consumption. Based on the optimal distillation loads, a nonlinear programming model is then formulated to determine the yields of sidestreams by maximizing the thermal exergy recovery for the crude oil plant. Finally, a four-stage crude oil distillation plant is investigated to demonstrate the performance of the proposed approach. The results show a decrease in energy consumption and an increase in heat recovery. The distillation load distribution of the distillation columns in a multistage crude oil distillation process is directly related to the energy consumption, and the yields of the sidestreams of these columns affect the thermal exergy recovery for the crude oil plant. These problems are formulated by an energy optimization approach combining mathematical programming and exergy analysis.

Description: Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) was employed to investigate the velocity distribution (propagator) and dispersion coefficient of a model fluidized-bed reactor of low aspect ratio containing mustard seeds. Both propagator and dispersion were found to be strongly anisotropic due to slug-flow conditions, with the vertical/axial dispersion ratio becoming smaller with increasing air flow rate. The influence of air humidity and flow rate was discussed in the gas-solid system, and the concurrent effect of electrostatic charging of particles close to the reactor wall was shown. Dispersion was generally found to increase with growing humidity and superficial gas velocity. For comparison, results are presented for a gas-liquid-solid system with a water-to-particle mass ratio of 2:1 as a function of bed height. The results indicated that the addition of water enhanced the particle motion in the bed. Velocity distribution and dispersion coefficient of a model fluidized-bed reactor of low aspect ratio was investigated by pulsed-field gradient nuclear magnetic resonance. For the first time, the feasibility is demonstrated to describe statistically the behavior in three-phase reactors with a dominating water component. Addition of water enhanced the particle motion in the bed.

Description: 1-Hexene metathesis was performed over standard and potassium-doped WO 3 /SiO 2 catalysts. The samples were tested at various reaction temperatures, molar feed compositions, and space times. Under the applied reaction conditions, doping with potassium reduced the isomerization and cracking activity of the catalyst by at least half and improved the yield of detergent-range alkenes twofold. However, increasing the potassium loading to a higher amount resulted in a significant reduction in the metathesis activity as both Brønsted and Lewis acid sites were affected. Optimum operating conditions for the yield of detergent-range alkenes were identified using response surface methodology. The metathesis of terminal linear alkenes can be applied for the valorization of secondary Fischer-Tropsch product streams. The performance of silica-supported tungsten trioxide catalysts was investigated for the gas-phase metathesis of 1-hexene in a fixed-bed reactor. Metathesis of 1-hexene yielded valuable detergent-range alkenes. Doping WO 3 /SiO 2 with potassium was found to reduce isomerization and cracking of 1-hexene.

Description: A preliminary study based on a conceptual process design methodology that includes a technical evaluation and an economic study has been carried out for the use of the metal-organic framework NH 2 -MIL-53(Al) as adsorbent for the separation of carbon dioxide from methane. Among the alternatives considered, a vacuum pressure swing adsorption was chosen in the detailed design phase. The combination of a design with columns in parallel and the possibility of recirculating some of the streams ensures a high degree of separation and a final product with high quality without compromising the operation costs. A comparison with the state-of-the-art technology, amine scrubbing, and with a process based on membranes demonstrates that the proposed process is competitive as a result of its low operation costs and the energy demand. A vacuum pressure swing adsorption process, based on the usage of the metal-organic framework NH 2 -MIL-53(Al) for the separation of CO 2 from CH 4 , is proposed based on a conceptual process design methodology. The analysis includes a technical evaluation, an economic study, and a comparison with the most widely applied technologies, proving the competitiveness of the proposed process.

Description: The broken-and-intact-cell model is conventionally used for interpretation of overall extraction curves (OECs) observed in supercritical fluid extraction (SFE) of ground oilseeds. Another possibility, considered here, assumes that the packed beds of the ground material always contain a significant amount of very small particles, i.e., dust, which control the initial extraction rates. The bidisperse representation of particle ensembles allows accurate description of OECs on the basis of the modified shrinking core model. A simple asymptotic solution has been derived for bidisperse granulometric distributions under typical SFE conditions. Special microscopic observations have been performed to reveal and examine the dust fraction in ground seed substrates. A generalization of the shrinking core model for supercritical fluid extraction is introduced which takes into account the polydisperse nature of ground plant material. Model simplification adjusted for common extraction conditions, resulting in bidisperse approximation and simple asymptotic formulas is developed and successfully verified on experimental data from literature.

Description: An industrial-scale dead-end ultrafiltration system was optimized using statistically designed experiments. Given a certain level of pollutant, a two-level full factorial design and a central composite design were used to optimize the filtrate production of a single 8-inch industrial ultrafiltration membrane while manipulating the levels of four factors: feed pressure, backwash pressure, forward filtration time, and backwash time. Analysis of variance and residual analysis were used to validate and check the adequacy of the developed regression models. The optimal levels were later validated experimentally. The predicted filtrate production was in reasonable agreement with the experimental data. A two-level full factorial design and a central composite design were used to optimize the filtrate production of an industrial ultrafiltration membrane while manipulating the feed pressure, backwash pressure, forward filtration time, and backwash time. The obtained regression models were validated by analysis of variance and residual analysis. The optimal levels were then validated experimentally.

Description: The solubility behavior of salicylic acid (SAA)/4,4′-dipyridyl (4,4′-dipy) cocrystals is investigated in an ethanol solvent. The phase solubility diagram (PSD) of SAA/4,4′-dipy cocrystals is determined which are formed in a 2:1 stoichiometric ratio in ethanol. The objective is to improve the fundamentals of the formation mechanisms, solution behavior, and solid-state properties of SAA/4,4′-dipy cocrystals. The solubility behavior and solution chemistry of cocrystals are studied. It was found that the thermodynamic stability regions of the cocrystals and its components are defined by the phase solubility diagram. Besides the kinetic also the thermodynamic factor turned out to be important for the crystallization of cocrystals. Physical properties of active pharmaceutical ingredients can be tuned by pharmaceutical cocrystals without changing the chemical identity. The solubility behavior of salicylic acid/4,4′-dipyridyl (SAA/4,4′-dipy) cocrystals is investigated in an ethanol solvent to improve the fundamentals of the formation mechanisms, solution behavior, and solid-state properties of these cocrystals.

Description: The polymorphic formation of taltirelin (TTL) was monitored inline by Raman spectroscopy in batch cooling crystallization. The concentrations of the polymorphic forms and supersaturation were measured during crystallization and transformation processes. Polymorphic transformation was detected by monitoring the Raman spectra of the two polymorphs in slurry state. The effect of cooling rate and concentration on the polymorphic crystallization was assessed. At a slow cooling rate and a low concentration, the stable form, i.e., the β -form, was nucleated directly without transformation from the α -form. The nucleation mechanism of the two TTL polymorphs was studied using the supersaturation profile tracked by Raman spectroscopy. In cooling crystallization, supersaturation can be controlled by the cooling rate. Profiles of concentration are helpful for understanding polymorphic crystallization. At a low cooling rate, the α -form of taltirelin is nucleated and then transformed to the β -form. The α -form is formed at a high cooling rate, while the β -form is generated at a very slow cooling rate.

Description: Atorvastatin calcium (AC) spherical crystals were prepared by spherical agglomeration. CH 2 Cl 2 acting as bridging liquid was added together with the drug solution or after the antisolvent precipitation process. Polymorph transformation in antisolvent crystallization and agglomeration processes was observed by focused-beam reflectance measurement (FBRM). The results suggested the occurrence of an immediate agglomeration when CH 2 Cl 2 was added together with the drug solution. Size-controllable AC spherical crystals with improved flowability and compressibility can be obtained by adjusting the amount of CH 2 Cl 2 and the stirring speed. The improved compaction behavior of the AC particles can be applied for direct tableting. A higher stirring speed can reduce the amount of bridging liquid which is required for effective agglomeration. It was a prerequisite for fine particles to be wetted by the bridging liquid in the spherical agglomeration process. Spherical agglomeration is an effective method to improve the flowability and compressibility of Atorvastation calcium particles. A polymorph transformation occurred during the antisolvent precipitation and agglomeration process. The final size distribution of the particles is controllable by adjusting the amount of bridging liquid and stirring speed.

Description: The performance of a modified bioreactor inside a light enclosure for carbon dioxide (CO 2 ) bio-fixation by Chlorella vulgaris was investigated. The influence of different light intensities on CO 2 bio-fixation and biomass production rates was evaluated. The results showed that the photon flux available to microalgal cultures can be a key issue in properly optimizing microalgae photobioreactor performance, particularly at high cell concentrations. Although the optimal pH values for C. vulgaris range from 6-8, cell growth can take place even at pH 4 and 10. Batch microalgal cultivation in a photobioreactor was used to investigate the effect of different light intensities, including 30, 50, 100, 185 and 300 μmol m -2 s -1 . The maximum biomass concentration of 1.83 g L -1 was obtained at a light intensity of 100 μmol m -2 s -1 and 2 L min -1 of 2% CO 2 enriched air aeration. The performance of a modified bioreactor inside a light enclosure for carbon dioxide (CO 2 ) bio-fixation by Chlorella vulgaris was investigated. The influence of different light intensities on CO 2 bio-fixation and biomass production rates was evaluated. The results showed that the photon flux available to microalgal cultures can be a key issue in properly optimizing microalgae photobioreactor performance, particularly at high cell concentrations. Although the optimal pH values for C. vulgaris range from 6-8, cell growth can take place even at pH 4 and 10. Batch microalgal cultivation in a photobioreactor was used to investigate the effect of different light intensities, including 30, 50, 100, 185 and 300 μmol m -2 s -1 . The maximum biomass concentration of 1.83 g L -1 was obtained at a light intensity of 100 μmol m -2 s -1 and 2 L min -1 of 2% CO 2 enriched air aeration.

Description: Controlled silver particle geometries require at least a synthesis in two steps which strongly differ in their reaction kinetics. For the first step, the very fast seed formation, chaotic advection-based micromixers are tested in combination with a batch reactor for the growth step. Nanoparticles with narrow size distribution and excellent shape uniformity can be prepared in large batches. To achieve a highly reproducible and homogeneous particle solution, a microfluidic system containing three different micromixers for optimal mixing of the chemical precursors is established, allowing stringent control of every synthesis step. The produced silver particles can be used as seeds for forming anisotropic particles. Their further potential is demonstrated by preparation of anisotropic silver triangles. The thus generated seed particles are better suited for growing to triangles than those from conventional batch synthesis. The synthesis of silver nanoprisms is realized in a novel microfluidic platform consisting of three different micromixers. Uniform crystalline particles were prepared, acting as seed particles for a second batch reactor-based synthesis. This reproducible synthesis platform allows for large-scale synthesis of plasmonic nanoparticles with defined dimension and plasmon resonance.

Description: Fluid flow patterns and associated concentration fields in Y-mixers are investigated using lattice Boltzmann method (LBM) -based models. The focus lies on the impact of mixing angle on flow and concentration fields, which is varied between acute (θ = 10°) and obtuse (θ = 130°) angles. Residence time distributions are determined to study the effect of the angles on mixing and velocity patterns, in particular, different flow regimes, namely, stratified laminar, vortex and engulfment. The results from the simulations are validated with literature data and found to be in good agreement. Maximum mixing occurs in the 100 o -obtuse angle Y-mixer, attributed to the extensive engulfment of flows in the mixing channel.

Description: Pretreatment of lignocellulosic biomass is essential for overcoming its inherent recalcitrance prior to enzymatic hydrolysis and fermentation of its carbohydrate components into biofuels and bioproducts. Among the myriad of existing pretreatment methods, the hot water pretreatment with no-chemical usage is a particularly attractive approach due to its fewer safety and environmental concerns, as well as relative low cost. The hydronium ions dissociated from water at elevated temperatures can catalyze the deconstruction of lignocellulosic biomass into fermentable sugars, digestible cellulose, and lignin fragments. However, a prohibitive amount of sugar degradation products particularly generating in conventional batch systems limit the efficiency of hot water pretreatment. Although the advanced continuous reaction systems like flowthrough systems are prone to reduce the sugar degradation compounds thereby enhancing the sugar recovery, excessive water consumption accompanied with the over dilute sugar streams still impede the implementation of hot water pretreatment to be an economical viable pathway. These limitations of hot water pretreatment are considered to be associated with the scant attention of water-biomass interaction mechanism, as well as the engineering aspects regarding kinetic modeling and reactor configurations. Thus, extrapolating this information from scattered literatures would play a vital role to complete the comprehensive understanding of the hot water pretreatment. This review aims to fill in the blank of those critical factors influencing hot water pretreatment of lignocellulosic biomass, in terms of chemistry and engineering fundamentals to understand the correct axiomatic approaches needed to advance this technology. In particular, various reactor configurations and kinetic models are evaluated herein to explore the optimization strategies of hot water pretreatment toward application.

Description: During the past years cost pressure on the European chemical companies grew dramatically by increased competition from low-labor-cost BRIC countries on the one side and the U.S., favored by decreased energy costs due to shale gas exploitation, on the other side. Raising costs for energy consumption and wages come on top. Lonza, as a mid-sized chemical company located in a high-income-country, faced the need of cost reduction long time before and established highly efficient procedures in both, development and production, with the aim to decrease costs and already successfully applied since years. The paper describes some of the applied techniques in detail and shows their potential in terms of time and cost reduction. Furthermore, Lonza works with great emphasis on future solutions.

Description: Solid-liquid extraction using a laboratory robot, where anthocyanins are leached from dried red vine leaves ( vitis vinifera ), is evaluated with respect to precision and accuracy. The solid handling of the robot results in standard deviations between ± 0.6 and ± 1.8 depending on the particle size (max. 630 µm). For liquid handling standard deviations are from ± 0.8 to ± 2.6 depending on the volatility of the solvents. The validated, fully automated natural plant extraction-robot shows yields based on dry matter from 1.3 % to 0.8 %, 1.15 % to 0.55 % and 0.4 to 0.15 % for methanol, water (HCl, pH = 2.5) and ethanol and is improving with increasing particle size. Manually performed extraction kinetics experiments are compared with the robot and indicate a variance of 0.1 %. With respect to process intensification, a comparison of yields obtained by microwave and ultrasonic supported extraction in comparison to laboratory robot shaking and stirred single-stage batch experiments was performed.

Description: Aerial view of pipes of the thermal power plant. © Nickolay Vinokurov/Shutterstock

Description: Fire plays an important role in structuring vegetation in fire-prone regions worldwide. Progress has been made towards documenting the effects of individual fire events and fire regimes on vegetation structure; less is known of how different fire history attributes (e.g., time-since-fire, fire frequency) interact to affect vegetation. Using the temperate eucalypt ‘foothill’ forests of south-eastern Australia as a case-study system, we examine two hypotheses about such interactions: 1) that post-fire vegetation succession (e.g., time-since-fire effects) is influenced by other fire regime attributes, and 2) that the severity of the most recent fire overrides the effect of preceding fires on vegetation structure. Empirical data on vegetation structure were collected from 540 sites distributed across central and eastern Victoria, Australia. Linear mixed models were used to examine these hypotheses, and determine the relative influence of fire and environmental attributes on vegetation structure. Fire history measures, particularly time-since-fire, affected several vegetation attributes including ground and canopy strata; others such as low and sub-canopy vegetation were more strongly influenced by environmental characteristics like rainfall. There was little support for the hypothesis that post-fire succession is influenced by fire history attributes other than time-since-fire: only canopy regeneration was influenced by another variable (‘fire type’, representing severity). Our capacity to detect an overriding effect of the severity of the most recent fire was limited by a consistently weak effect of preceding fires on vegetation structure. Overall, results suggest the primary way that fire affects vegetation structure in foothill forests is via attributes of the most recent fire, both its severity and time since its occurrence: other attributes of fire regimes (e.g., fire interval, frequency) have less influence. The strong effect of environmental drivers such as rainfall and topography on many structural features show that foothill forest vegetation is also influenced by factors outside human control. While fire is amenable to human management, results suggest that at broad scales, structural attributes of these forests are relatively resilient to the effects of current fire regimes. Nonetheless, the potential for more frequent severe fires at short intervals, associated with a changing climate and/or fire management, warrant further consideration. This article is protected by copyright. All rights reserved.

Description: Integral projection models (IPMs) have a number of advantages over matrix-model approaches for analyzing size-structured population dynamics, because the latter require parameter estimates for each age or stage transition. However, IPMs still require appropriate data. Typically they are parameterized using individual-scale relationships between body size and demographic rates, but these are not always available. Here we present an alternative approach for estimating demographic parameters from time series of size-structured survey data using a Bayesian state-space IPM (SSIPM). By fitting an IPM in a state-space framework, we estimate unknown parameters and explicitly account for process and measurement error in a dataset to estimate the underlying process model dynamics. We tested our method by fitting SSIPMs to simulated data; the model fit the simulated size distributions well and estimated unknown demographic parameters accurately. We then illustrated our method using 9 years of annual surveys of the density and size distribution of two fish species (blue rockfish, Sebastes mystinus , and gopher rockfish, S. carnatus ) at seven kelp forest sites in California. The SSIPM produced reasonable fits to the data, and estimated fishing rates for both species that were higher than our Bayesian prior estimates based on coast-wide stock assessment estimates of harvest. That improvement reinforces the value of being able to estimate demographic parameters from local-scale monitoring data. We highlight a number of key decision points in SSIPM development (e.g., open vs. closed demography, number of particles in the state-space filter) so that users can apply the method to their own datasets. This article is protected by copyright. All rights reserved.

Description: Extensive outbreaks of bark beetles have killed trees across millions of hectares of forests and woodlands in western North America. These outbreaks have led to spirited scientific, public and policy debates about consequential increases in fire risk, especially in the wildland-urban interface (WUI), where homes and communities are at particular risk from wildfires. At the same time, large wildfires have become more frequent across this region. Widespread expectations that outbreaks increase extent, severity and/or frequency of wildfires are based partly on visible and dramatic changes in foliar moisture content and other fuel properties following outbreaks, as well as associated modeling projections. A competing explanation is that increasing wildfires are driven primarily by climatic extremes, which are becoming more common with climate change. However, the relative importance of bark beetle outbreaks versus climate on fire occurrence has not been empirically examined across very large areas and remains poorly understood. The most extensive outbreaks of tree-killing insects across the western United States have been of mountain pine beetle (MPB; Dendroctonus ponderosae ), which have killed trees over 〉 650,000 km 2 , mostly in forests dominated by lodgepole pine ( Pinus contorta ). Here we show that outbreaks of MPB in lodgepole pine forests of the western United States have been less important than climatic variability for the occurrence of large fires over the past 29 years. In lodgepole pine forests in general, as well as those in the WUI, occurrence of large fires was determined primarily by current and antecedent high temperatures and low precipitation but was unaffected by preceding outbreaks. Trends of increasing co-occurrence of wildfires and outbreaks are due to a common climatic driver rather than interactions between these disturbances. Reducing wildfire risk hinges on addressing the underlying climatic drivers, rather than treating beetle-affected forests. This article is protected by copyright. All rights reserved.

Description: Extensive mortality of whitebark pine, beginning in the early to mid-2000s, occurred in the Greater Yellowstone Ecosystem (GYE) of the western US, primarily from mountain pine beetle but also from other threats such as white pine blister rust. The climatic drivers of this recent mortality and the potential for future whitebark pine mortality from mountain pine beetle are not well understood, yet are important considerations in whether to list whitebark pine as a threatened or endangered species. We sought to increase the understanding of climate influences on mountain pine beetle outbreaks in whitebark pine forests, which are less well understood than in lodgepole pine, by quantifying climate-beetle relationships, analyzing climate influences during the recent outbreak, and estimating the suitability of future climate for beetle outbreaks. We developed a statistical model of the probability of whitebark pine mortality in the GYE that included temperature effects on beetle development and survival, precipitation effects on host tree condition, beetle population size, and stand characteristics. Estimated probability of whitebark pine mortality increased with higher winter minimum temperature, indicating greater beetle winter survival; higher fall temperature, indicating synchronous beetle emergence; lower two-year summer precipitation, indicating increased potential for host tree stress; increasing beetle populations; stand age; and increasing percent composition of whitebark pine within a stand. The recent outbreak occurred during a period of higher-than-normal regional winter temperatures, suitable fall temperatures, and low summer precipitation. In contrast to lodgepole pine systems, area with mortality was linked to precipitation variability even at high beetle populations. Projections from climate models indicate future climate conditions will likely provide favorable conditions for beetle outbreaks within nearly all current whitebark pine habitat in the GYE by the middle of this century. Therefore, when surviving and regenerating trees reach ages suitable for beetle attack, there is strong potential for continued whitebark pine mortality due to mountain pine beetle. This article is protected by copyright. All rights reserved.

Description: The prediction of mosquito abundance is of central interest in addressing mosquito population dynamics and in forecasting the associated emerging and re-emerging diseases. However, little work has focused on the systematic evaluation of how well adult mosquito abundance can be predicted as a function of observational resolutions, aggregation scales, and prediction lead time. Here we use a state space reconstruction (SSR) approach to compare the predictability of mosquito population dynamics at weekly, biweekly, and monthly scales. We focus on the analysis of Aedes vexans and Culiseta melanura populations monitored in Brunswick County (NC – USA) and find that prediction over a 7-day lead time is improved when daily observations are used, compared to the commonly used once-per-week sample. Our results demonstrate that daily observations of mosquito abundance contribute to improving mosquito predictability in two ways: (1) daily observations better capture fluctuations over short time scales, which are missed when sampling at coarser resolutions, (2) the aggregation of daily abundance observations reduces the impact of noise, thereby increasing the predictability of mosquito population dynamics as the aggregation scale is increased. We show that the evaluation of population dynamical models based on observed and predicted abundance can lead to a spuriously high apparent performance, due to the high auto-correlation in the observations used to update the model state at each successive time step. We show that the comparison of predicted and observed population change, expressed through per capita growth rates, leads to a more informative performance measure. This article is protected by copyright. All rights reserved.

Description: Climate conditions, such as temperature or precipitation averaged over several decades strongly affect species distributions, as evidenced by experimental results and a plethora of models demonstrating statistical relations between species occurrences and long-term climate averages. However, long-term averages can conceal climate changes that have occurred in recent decades and may not capture actual species occurrence well because the distributions of species, especially at the edges of their range, are typically dynamic and may respond strongly to short-term climate variability. Our goal here was to test whether bird occurrence models can be predicted by either covariates based on short-term climate variability or on long-term climate averages. We parameterized species distribution models (SDMs) based on either short-term variability or long-term average climate covariates for 320 bird species in the conterminous U.S., and tested whether any life-history trait-based guilds were particularly sensitive to short-term conditions. Models including short-term climate variability performed well based on their cross-validated AUC score (0.85), as did models based on long-term climate averages (0.84). Similarly, both models performed well compared to independent presence/absence data from the North American Breeding Bird Survey (independent AUC of 0.89 and 0.90, respectively). However, models based on short-term variability covariates more accurately classified true absences for most species (73% of true absences classified within the lowest quarter of environmental suitability versus 68%). In addition, they have the advantage that they can reveal the dynamic relationship between species and their environment because they capture the spatial fluctuations of species potential breeding distributions. With this information we can identify which species and guilds are sensitive to climate variability, identify sites of high conservation value where climate variability is low, and assess how species’ potential distributions may have already shifted due recent climate change. However, long-term climate averages require less data and processing time and may be more readily available for some areas of interest. Where data on short-term climate variability are not available, long-term climate information is a sufficient predictor of species distributions in many cases. However, short-term climate variability data may provide information not captured with long-term climate data for use in SDMs. This article is protected by copyright. All rights reserved.

Description: Increases in natural or non-crop habitat surrounding agricultural fields have been shown to be correlated with declines in insect crop pests. However, these patterns are highly variable across studies suggesting other important factors, such as abiotic drivers, which are rarely included in landscape models, may also contribute to variability in insect population abundance. The objective of this study was to explicitly account for the contribution of temperature and precipitation, in addition to landscape composition, on the abundance of a widespread insect crop pest, the soybean aphid ( Aphis glycines Matsumura), in Wisconsin soybean fields. We hypothesized that higher soybean aphid abundance would be associated with higher heat accumulation (e.g., growing degree days), and increasing non-crop habitat in the surrounding landscape, due to the presence of the overwintering primary hosts of soybean aphid. To evaluate these hypotheses, we used an ecoinformatics approach that relied on a large dataset collected across Wisconsin over a 9-year period (2003 – 2011), for an average of 235 sites per year (n=2,110 fields total). We determined surrounding landscape composition (1.5-km radius) using publicly available satellite-derived land cover imagery and interpolated daily temperature and precipitation information from the National Weather Service COOP weather station network. We constructed linear mixed models for soybean aphid abundance based on abiotic and landscape explanatory variables and applied model averaging for prediction using an information theoretic framework. Over this broad spatial and temporal extent in Wisconsin, we found that variation in growing season precipitation was positively related to soybean aphid abundance, while higher precipitation during the non-growing season had a negative effect on aphid populations. Additionally, we found that aphid populations were higher in areas with proportionally more forest, but were lower in areas where minor crops, such as small grains, were more prevalent. Thus, our findings support our hypothesis that including abiotic drivers increases our understanding of crop pest abundance and distribution. Moreover, by explicitly modeling abiotic factors, we may be able to explore how variable climate in tandem with land cover patterns may affect current and future insect populations, with potentially critical implications for crop yields and agricultural food webs. This article is protected by copyright. All rights reserved.

Description: Predator-prey interactions shape ecosystem structure and function, potentially limiting the productivity of valuable species. Simultaneously, stochastic environmental forcing affects species productivity, often through unknown mechanisms. The interacting effects of trophic and environmental conditions complicate management of exploited ecosystems and have motivated calls for more holistic management via ecosystem-based approaches, yet the limitations to these approaches are not widely appreciated. The Chignik salmon fishery in Alaska is managed to achieve maximum sustainable yield for sockeye salmon, though research suggests that predation by less economically valuable, and thus not targeted, coho salmon during juvenile rearing limits the productivity of sockeye salmon. We examined the relationship between historical sockeye salmon recruitment and coho salmon abundance observed in the Chignik system and could not detect a clear effect of coho salmon abundance on sockeye salmon productivity, given existing data. Using simulation models, we examined the probability of detecting a known predation effect on sockeye salmon recruitment in the presence of observation error in coho salmon abundance and stochasticity in sockeye salmon recruitment. Increased recruitment stochasticity reduced the ability to detect predator effects in recruitment, an effect further strengthened when low frequency environmental variation was added to the system. Further, increased observation error biased estimates of predator effects towards zero. Thus, in systems with high observation error on predator abundances, estimates of predation effects will be substantially weaker than true effects. We examined the effects of stochasticity on the ability of an adaptive management program to learn about ecosystem structure and detect an effect of management actions intended to release a prey species from its predators. Simulation models revealed that even under scenarios of large predation effects on sockeye salmon, stochastic recruitment masked detection of an effect of increased coho salmon harvest for nearly a decade. These results highlight the challenges inherent in ecosystem-based management of predator-prey systems due to mismatched time-scales of ecosystem dynamics and the willingness of stakeholders to risk losses in order to test uncertain hypotheses. It is critical for stakeholders considering EBFM and adaptive management strategies to be aware of the potential timelines of perceiving ecosystem change. This article is protected by copyright. All rights reserved.

Description: Timber harvest can adversely affect forest biota. Recent research and application suggest that retention of mature forest elements (‘retention forestry’), including unharvested patches (or ‘aggregates’) within larger harvested units, can benefit biodiversity compared to clearcutting. However, it is unclear whether these benefits can be generalized among the diverse taxa and biomes in which retention forestry is practiced. Lack of comparability in methods for sampling and analysing responses to timber harvest and edge creation presents a challenge to synthesis. We used a consistent methodology (similarly spaced plots or traps along transects) to investigate responses of vascular plants and ground-active beetles to aggregated retention at replicate sites in each of four temperate and boreal forest types on three continents: Douglas-fir forests in Washington, USA; aspen forests in Minnesota, USA; spruce forests in Sweden; and wet eucalypt forests in Tasmania, Australia. We assessed (i) differences in local (plot-scale) species richness and composition between mature (intact) and regenerating (previously harvested) forest; (ii) the lifeboating function of aggregates (capacity to retain species of unharvested forest); and whether intact forests and aggregates (iii) are susceptible to edge effects and (iv) influence the adjacent regenerating forest. Intact and harvested forests differed in composition but not richness of plants and beetles. The magnitude of this difference was generally similar among regions, but there was considerable heterogeneity of composition within and among replicate sites. Aggregates within harvest units were effective at lifeboating for both plant and beetle communities. Edge effects were uncommon even within the aggregates. In contrast, effects of forest influence on adjacent harvested areas were common and as strong for aggregates as for larger blocks of intact forest. Our results provide strong support for the widespread application of aggregated retention in boreal and temperate forests. The consistency of pattern in four very different regions of the world suggests that, for forest plants and beetles, responses to aggregated retention are likely to apply more widely. Our results suggest that through strategic placement of aggregates, it is possible to maintain the natural heterogeneity and biodiversity of mature forests managed for multiple objectives. This article is protected by copyright. All rights reserved.

Description: Distributions of foliar nutrients across forest canopies can give insight into their plant functional diversity and improve our understanding of biogeochemical cycling. We used airborne remote sensing and Partial Least Squares Regression (PLSR) to quantify canopy foliar nitrogen (N) across ~164 km 2 of wet lowland tropical forest in the Osa Peninsula, Costa Rica. We determined the relative influence of climate and topography on the observed patterns of canopy foliar N using a gradient boosting model (GBM) technique. At a local scale, where climate and substrate where constant, we explored the influence of slope position on canopy N by quantifying canopy N on remnant terraces, their adjacent slopes and knife edged ridges. In addition, we climbed and sampled 540 trees and analyzed foliar N in order to quantify the role of species identity (phylogeny) and environmental factors in predicting canopy N. Observed canopy N heterogeneity reflected environmental factors working at multiple spatial scales. Across the larger landscape, elevation and precipitation had the highest relative influence on predicting canopy foliar N (30 and 24%), followed by soils (15%), site exposure (9%), compound topographic index (8%), substrate (6%), and landscape dissection (6%). Phylogeny explained ~75% of the variation in the filed collected foliar N data, suggesting that phylogeny largely underpins the response to the environmental factors. Taken together, these data suggest that a large fraction of the variance in canopy N across the landscape is proximately driven by species composition, though ultimately this is likely a response to abiotic factors such as climate and topography. Future work should focus on the mechanisms and feedbacks involved, and how shifts in climate may translate to changes in forest function. This article is protected by copyright. All rights reserved.

Description: Escalating wildfire in subalpine forests with stand-replacing fire regimes is increasing the extent of early-seral forests throughout the western US. Post-fire succession generates the fuel for future fires, but little is known about fuel loads and their variability in young post-fire stands. We sampled fuel profiles in 24-year-old post-fire lodgepole pine ( Pinus contorta var. latifolia ) stands ( n =82) that regenerated from the 1988 Yellowstone Fires to answer three questions. (1) How do canopy and surface fuel loads vary within and among young lodgepole pine stands? (2) How do canopy and surface fuels vary with pre- and post-fire lodgepole pine stand structure and environmental conditions? (3) How have surface fuels changed between 8 and 24 years post-fire? Fuel complexes varied tremendously across the landscape despite having regenerated from the same fires. Available canopy fuel loads and canopy bulk density averaged 8.5 Mg ha -1 [range 0.0-46.6] and 0.24 kg m 3 [range: 0.0-2.3], respectively, meeting or exceeding levels in mature lodgepole pine forests. Total surface-fuel loads averaged 123 Mg ha -1 [range: 43 - 207], and 88% was in the 1000-hr fuel class. Litter, 1-hr, and 10-hr surface fuel loads were lower than reported for mature lodgepole pine forests, and 1000-hr fuel loads were similar or greater. Among-plot variation was greater in canopy fuels than surface fuels, and within-plot variation was greater than among-plot variation for nearly all fuels. Post-fire lodgepole pine density was the strongest positive predictor of canopy and fine surface fuel loads. Pre-fire successional stage was the best predictor of 100-hr and 1000-hr fuel loads in the post-fire stands and strongly influenced the size and proportion of sound logs (greater when late successional stands had burned) and rotten logs (greater when early successional stands had burned). Our data suggest that 76% of the young post-fire lodgepole pine forests have 1000-hr fuel loads that exceed levels associated with high-severity surface fire potential, and 63% exceed levels associated with active crown fire potential. Fire rotations in Yellowstone National Park are predicted to shorten to a few decades and this prediction cannot be ruled out by a lack of fuels to carry repeated fires. This article is protected by copyright. All rights reserved.

Description: Management of spatially structured species poses unique challenges. Despite a strong theoretical foundation, practitioners rarely have sufficient empirical data to evaluate how populations interact. Rather, assumptions about connectivity and source-sink dynamics are often based on incomplete, extrapolated or modeled data, if such interactions are even considered at all. Therefore, it has been difficult to evaluate whether spatially structured species are meeting conservation goals. We evaluated how estimated metapopulation structure responded to estimates of population sizes and dispersal probabilities, and to the set of populations included. We then compared outcomes of alternative management strategies that target conservation of metapopulation processes. We illustrated these concepts for Chinook salmon ( Oncorhynchus tshawytscha ) in the Snake River, USA. Our description of spatial structure for this metapopulation was consistent with previous characterizations. We found substantial differences in estimated metapopulation structure when we had incomplete information about all populations and when we used different sources of data (3 empirical, 2 modeled) to estimate dispersal, whereas responses to population size estimates were more consistent. Together, these findings suggest that monitoring efforts should target all populations occasionally and populations that play key roles frequently, and that multiple types of data should be collected when feasible. When empirical data are incomplete or of uneven quality, analyses using estimates produced from an ensemble of available datasets can help conservation planners and managers weigh near-term options. Doing so, we found tradeoffs in connectivity and source dominance in metapopulation-level responses to alternative management strategies that suggest which types of approaches may be inherently less risky. This article is protected by copyright. All rights reserved.

Description: Increasing tree density that followed fire exclusion after the 1880s in the southwestern United States (US) may have also altered nutrient cycles and led to a carbon (C) sink that constitutes a significant component of the US C budget. Yet, empirical data quantifying century-scale changes in C or nutrients due to fire exclusion are rare. We used tree-ring reconstructions of stand structure from five ponderosa pine–dominated sites from across northern Arizona to compare live tree C, nitrogen (N), and phosphorus (P) storage between the 1880s and 1990s. Live tree biomass in the 1990s contained up to 3 times more C, N, and P than in 1880s. However, the increase in C storage was smaller than values used in recent US C budgets. Furthermore, trees that had established prior to the 1880s accounted for a large fraction (28 to 66%) of the C, N, and P stored in contemporary stands. Overall, our century-scale analysis revealed that forests of the 1880s were on a trajectory to accumulate C and nutrients in trees even in the absence of fire exclusion, either because growing conditions became more favorable after the 1880s or because forests in the 1880s included age or size cohorts poised for accelerated growth. These results may lead to a reduction in the C sink attributed to fire exclusion, and they refine our understanding of reference conditions for restoration management of fire-prone forests. This article is protected by copyright. All rights reserved.

Description: The Conservation Effects Assessment Project (CEAP) was created in response to a request from the Office of Management and Budget that the U.S. Department of Agriculture - Natural Resource Conservation Service (USDA – NRCS) document the societal benefits anticipated to accrue from a major increase in conservation funding authorized by the 2002 Farm Bill. A comprehensive evaluation of the efficacy of rangeland conservation practices cost-shared with private landowners was unable to evaluate conservation benefits because outcomes were seldom documented. Four interrelated suppositions are presented to examine the causes underlying minimal documentation of conservations outcomes. These suppositions are: 1) benefits of conservation practices are considered a certainty so that documentation in not required, 2) minimal knowledge exchange between the USDA-NRCS and research organizations, 3) a paucity of conservation-relevant science, and 4) inadequate technical support for land owners following implementation of conservation practices. We then follow with recommendations to overcome potential barriers to documentation of conservation outcomes identified for each supposition. Collectively, this assessment indicates that the existing conservation practice standards are insufficient to effectively administer large conservation investments on rangelands and that modification of these standards alone will not achieve the goals explicitly stated by CEAP. We recommend that USDA-NRCS modify its conservation programs around a more comprehensive and integrative platform that is capable of implementing evidence-based conservation. Collaborative monitoring organized around landowner-agency-scientist partnerships would represent the focal point of a Conservation Program Assessment Network (CPAN). The primary network objective would be to establish missing information feedback loops between conservation practices and their agricultural and environmental outcomes to promote learning, adaptive management and innovation. Network information would be archived and made available to guide other, related conservation programs in relevant ecoregions. Restructuring conservation programs as recommend above would: 1) provide site specific information, learning and accountability that has been requested by CEAP and, 2) further advance balanced delivery of agricultural production and environmental quality goals. This article is protected by copyright. All rights reserved.

Description: To investigate the underlying mechanisms that control long-term recovery of tundra carbon (C) and nutrients after fire, we employed the Multiple Element Limitation (MEL) model to simulate 200-year post-fire changes in the biogeochemistry of three sites along a burn severity gradient in response to increases in air temperature, CO 2 concentration, nitrogen (N) deposition and phosphorus (P) weathering rates. The simulations were conducted for severely burned, moderately burned, and unburned arctic tundra. Our simulations indicated that recovery of C balance after fire was mainly determined by the internal redistribution of nutrients among ecosystem components (controlled by air temperature), rather than the supply of nutrients from external sources (e.g., nitrogen deposition and fixation, phosphorus weathering). Increases in air temperature and atmospheric CO 2 concentration resulted in 1) a net transfer of nutrient from soil organic matter to vegetation, and 2) higher C:nutrient ratios in vegetation and soil organic matter. These changes led to gains in vegetation biomass C but net losses in soil organic C stocks. Under a warming climate, nutrients lost in wildfire were difficult to recover because the warming-induced acceleration in nutrient cycles caused further net nutrient loss from the system through leaching. In both burned and unburned tundra, the warming-caused acceleration in nutrient cycles and increases in ecosystem C stocks were eventually constrained by increases in soil C:nutrient ratios, which increased microbial retention of plant-available nutrients in the soil. Accelerated nutrient turnover, loss of C, and increasing soil temperatures will likely result in vegetation changes, which further regulate the long-term biogeochemical succession. Our analysis should help in the assessment of tundra C budgets and of the recovery of biogeochemical function following fire, which is in turn necessary for the maintenance of wildlife habitat and tundra vegetation. This article is protected by copyright. All rights reserved.

Description: Restoring forest to hundreds of millions of hectares of degraded land has become a centerpiece of international plans to sequester carbon and conserve biodiversity. Forest landscape restoration will require scaling up ecological knowledge of secondary succession from small-scale field studies to predict forest recovery rates in heterogeneous landscapes. However, ecological field studies reveal widely divergent times to forest recovery, in part due to landscape features that are difficult to replicate in empirical studies. Seed rain can determine reforestation rate and depends on landscape features that are beyond the scale of most field studies. We develop mathematical models to quantify how landscape configuration affects seed rain and forest regrowth in degraded patches. The models show how landscape features can alter the successional trajectories of otherwise identical patches, thus providing insight into why some empirical studies reveal a strong effect of seed rain on secondary succession, while others do not. We show that seed rain will strongly limit reforestation rate when patches are near a threshold for arrested succession, when positive feedbacks between tree canopy cover and seed rain occur during early succession, and when directed dispersal leads to between-patch interactions. In contrast, seed rain has weak effects on reforestation rate over a wide range of conditions, including when landscape-scale seed availability is either very high or very low. Our modeling framework incorporates growth and survival parameters that are commonly estimated in field studies of reforestation. We demonstrate how mathematical models can inform forest landscape restoration by allowing land managers to predict where natural regeneration will be sufficient to restore tree cover. Translating quantitative forecasts into spatially-targeted interventions for forest landscape restoration could support target goals of restoring millions of hectares of degraded land and help mitigate global climate change. This article is protected by copyright. All rights reserved.

Description: Successful pest-mammal eradications from remote islands have resulted in important biodiversity benefits. Near-shore islands can also serve as refuges for native biota but require ongoing effort to maintain low-pest or pest-free status. Three management options are available in the presence of reinvasion risk: (1) control-to-zero density, in which immigration may occur but reinvaders are removed; (2) sustained population suppression (to relatively low numbers); or (3) no action. Biodiversity benefits can result from options 1 and 2. The management challenge is to make evidence-based decisions on the selection of an appropriate objective and to identify a financially feasible control strategy that has a high probability of success. This requires understanding the pest species population dynamics and how it will respond to a range of potential management strategies, each with an associated financial cost. We developed a 2-stage modelling approach that consisted of: (1) Bayesian inferential modelling to estimate parameters for a model of pest population dynamics and control; and (2) a forward projection model to simulate a range of plausible management scenarios and quantify the probability of obtaining zero density within four years. We applied the model to an ongoing, six-year trapping program to control stoats ( Mustela erminea ) on Resolution Island, New Zealand. Zero density has not yet been achieved. Results demonstrate that management objectives were impeded by a combination of a highly fecund population, insufficient trap attractiveness and a substantial proportion of the population that did not enter traps. Immigration is known to occur because the founding population arrived on the island by swimming from the mainland. However, immigration rate during this study was indistinguishable from zero. The forward projection modelling showed that control-to-zero density was feasible but required greater than a 2-fold budget increase to intensify the trapping rate relative to population growth. The 2-stage modelling provides the foundation for a management program in which broad-scale trials of additional trapping effort or improved trap lures would test model predictions and increase our understanding of system dynamics. This article is protected by copyright. All rights reserved.

Description: The electrochemical reduction of CO 2 is a promising method for its conversion which still suffers from important challenges that have to be solved before industrial realization becomes attractive. This study describes the optimization of gas diffusion electrodes with respect to catalyst dispersion and mass transport limitations allowing solubility issues to be circumvented and current densities to be increased to industrially relevant values. Consequently, the transfer of the promising results from semi-batch experiments into continuous mode of operation is demonstrated, and it is shown how the energetic efficiency can be significantly improved by the choice of electrolyte, in terms of concentration and type. Thereby ohmic losses can be decreased and the intrinsic activity improved.

Description: In a future energy system, flexible reactor operation may be needed if renewable electricity is converted to chemical energy carriers (synfuels). Limiting factors for the flexibility in a synfuel process can occur on different scales (catalyst, reactor, process). The present study addresses transient catalyst and reactor effects in 3-phase catalytic synthesis reactors with low-temperature Fischer-Tropsch synthesis as example reaction. A method was developed based on lab-scale experiments with step-changes and periodic-changes of inlet variables and mathematical models for experimental design and data analysis. Changes of feed gas flow, syngas H 2 /CO-ratio and temperature as inlet variables led, in some cases, to transient effects caused by catalyst changes or by reactor characteristics (e.g. residence times of gas components affected by their solubility in liquid hydrocarbon products). Catalyst changes include the reversible storage of carbon species during CO-rich intervals and hydrogenation of these carbon species during H 2 -rich intervals. The approach will help to scale-up for industrial applications and can be applied to other synthesis reactions.

Description: Profile measurements in a catalytic gauze reactor are conducted for catalytically assisted methane combustion over platinum. The reactor combines a capillary sampling technique with a novel fiber-optic Laser-Induced Fluorescence (LIF) Spectroscopy method for detection and quantification of gas phase OH[[[Wingdings;F09E]]] radicals serving as indicator species for gas phase reactions. The steep spatial gradients in the vicinity of the gauze are resolved at submillimeter scale. Experimental profiles are compared with three dimensional numerical reactor simulations including flow, mass transport, heat transport and microkinetic models for both surface and gas phase chemistry. The results provide insight into the interaction of chemistry and transport upstream, at and downstream the catalytic gauze and the interaction of surface and gas phase reactions by exchange of heat and radicals released from the catalyst surface.

Description: A packed bed algae biofilm reactor was developed using porous and non-porous dual packings. The biofilm was cultivated on reticulated polyurethane foam cubes of 0.01 m dimension. The non-porous glass raschigs were used as bed support that helps the removal of generated gas from the system. The effect of variables such as column L/D ratio, catalyst cube dimension and feed flow rate on the treatment of sewage water was studied. The reaction kinetics indicates that the nutrients uptake rate is dependent on both pore and film diffusion. The kinetics of uptake of nutrients follows a pseudo-first order reaction. From the pseudo reaction rate constant, Thiele Modulus and effectiveness factor were calculated and a kinetic model equation for fractional nutrients uptake was developed in terms of operating variables. It was observed that the model can predict the reaction rate with ±5% deviation. The packed bed column was operated continuously for 90 days with 76-83% of TN and 70-76% TP removal in 24 h of residence time and the results obtained may be useful for large-scale treatment of sewage water.

Description: With the high interest in renewable resources, the field of biosorption has undergone a huge leap in importance in recent years. The arsenic contamination in water causes many diseases. Various biosorbent materials have been tested for their ability to remove the two inorganic arsenic species commonly found in water; arsenite As (III) and arsenate As (V). The review evaluates source and various biosorbent used for arsenic removal from wastewater. The arsenic biosorption is influenced by the pH of aqueous phase, the concentration of arsenic, the presence of competing ions and arsenic speciation. The biosorption kinetic of As (III) and As (V) by biosorbents has been reported to be rapid, with greater than 80 % biosorption occurring between 30- 60 min, followed by second step which may take up several hours. The pseudo-second order model showed the best fit for kinetics of arsenic, which corresponds to a chemisorption process. Langmuir equation is widely used in a large number of equilibrium studies; this finding indicates that most arsenic ions are adsorbed in monolayer form and removal is better for As (III) than for As (V).

Description: The application of physiological measures to conservation monitoring has been gaining momentum and, while a suite of physiological traits are available to ascertain disturbance and condition in wildlife populations, glucocorticoids (i.e., GCs: cortisol and corticosterone) are the most heavily employed. The interpretation of GC levels as sensitive indicators of population change necessitates that GCs and metrics of population persistence are linked. However, the relationship between GCs and fitness may be highly context-dependent, changing direction, or significance, depending on the GC measure, fitness metric, life history stage, or other intrinsic and extrinsic contexts considered. We examined the relationship between baseline plasma corticosterone (CORT) levels measured at two periods of the breeding season and three metrics of fitness (offspring quality, reproductive output, and adult survival) in female tree swallows ( Tachycineta bicolor ). Specifically, we investigated whether: i) a relationship between baseline CORT metrics and fitness exists in our population; ii) whether the inclusion of energetic contexts such as food availability, reproductive investment, or body mass could alter or improve the strength of the relationship between CORT and fitness; iii) whether energetic contexts could better predict fitness compared to CORT metrics. Importantly, we investigated these relationships in both natural conditions and under an experimental manipulation of foraging profitability (feather clipping) to determine the influence of an environmental constraint on GC-fitness relationships. We found a lack of relationship between baseline CORT and both short- and long-term metrics of fitness in control and clipped birds. In contrast, loss in body mass over reproduction positively predicted reproductive output (number of chicks leaving the nest) in control birds; however, the relationship was characterized by a low R 2 (5%), limiting the predictive capacity, and therefore the application potential, of such a measure in a conservation setting. Our results stress the importance of ground-truthing GC-fitness relationships and indicate that baseline GCs will likely not be easily employed as conservation biomarkers across many species and life history stages. Given the accumulating evidence of temporally-dynamic, inconsistent, and context-dependent GC-fitness relationships, placing effort towards directly measuring fitness traits, rather than plasma GC levels, will likely be more worthwhile for many conservation endeavours. This article is protected by copyright. All rights reserved.

Description: Ecological processes operate across temporal and spatial scales. Anthropogenic disturbances impact these processes, but examinations of scale dependence in impacts are infrequent. Such examinations can provide important insight to wildlife-human interactions and guide management efforts to reduce impacts. We assessed spatiotemporal scale dependence in habitat selection of mule deer ( Odocoileus hemionus ) in the Piceance Basin of Colorado, USA, an area of ongoing natural gas development. We employed a newly developed animal movement method to assess habitat selection across scales defined using animal-centric spatiotemporal definitions ranging from the local (defined from 5 hour movements) to the broad (defined from weekly movements). We extended our analysis to examine variation in scale dependence between night and day and assess functional responses in habitat selection patterns relative to the density of anthropogenic features. Mule deer displayed scale invariance in the direction of their response to energy development features, avoiding well pads and the areas closest to roads at all scales, though with increasing strength of avoidance at coarser scales. Deer displayed scale-dependent responses to most other habitat features, including land cover type and habitat edges. Selection differed between night and day at the finest scales, but homogenized as scale increased. Deer displayed functional responses to development, with deer inhabiting the least developed ranges more strongly avoiding development relative to those with more development in their ranges. Energy development was a primary driver of habitat selection patterns in mule deer, structuring their behaviors across all scales examined. Stronger avoidance at coarser scales suggests that deer behaviorally mediated their interaction with development, but only to a degree. At higher development densities than seen in this area, such mediation may not be possible and thus maintenance of sufficient habitat with lower development densities will be a critical best management practice as development expands globally. This article is protected by copyright. All rights reserved.

Description: In saltmarsh plant communities bottom-up pressure from nutrient enrichment is predicted to increase productivity, alter community structure, decrease biodiversity, and alter ecosystem functioning. Previous work supporting these predictions has been based largely on short-term, plot-level (e.g., 1-300 m 2 ) studies, which may miss landscape-level phenomena that drive ecosystem-level responses. We implemented an ecosystem-scale, 9-year nutrient experiment to examine how saltmarsh plants respond to simulated conditions of coastal eutrophication. Our study differed from previous saltmarsh enrichment studies in that we applied realistic concentrations of nitrate (70-100 μM NO 3 - ), the most common form of coastal nutrient enrichment, via tidal water at the ecosystem scale ( ca . 60,000 m 2 creeksheds). Our enrichments added a total of 1,700 kg N creek −1 y −1 , which increased N loading 10-fold versus reference creeks (low-marsh: 171 g N m −2 y −1 ; high-marsh: 19 g N m −2 y −1 ). Nutrients increased the shoot mass and height of low marsh, tall Spartina alterniflora ; however, declines in stem density resulted in no consistent increase in aboveground biomass. High-marsh plants S. patens and stunted S. alterniflora did not respond consistently to enrichment. Nutrient enrichment did not shift community structure, contrary to the prediction of nutrient-driven dominance of S. alterniflora and Distichlis spicata over S. patens . Our mild responses may differ the results of previous studies for a number of reasons. First, the limited response of the high marsh may be explained by loading rates orders of magnitude lower than previous work. Low loading rates in the high marsh reflect infrequent inundation, arguing that inundation patterns must be considered when predicting responses to estuarine eutrophication. Additionally, we applied nitrate instead of the typically-used ammonium, which is energetically favored over nitrate for plant uptake. Thus, the form of nitrogen enrichment used, not just N-load, may be important in predicting plant responses. Overall, our results suggest that when coastal eutrophication is dominated by nitrate and delivered via flooding tidal water, aboveground saltmarsh plant responses may be limited despite moderate-to-high water-column N concentrations. Furthermore, we argue that the methodological limitations of nutrient studies must be considered when using results to inform management decisions about wetlands. This article is protected by copyright. All rights reserved.

Description: Most species that are negatively impacted when their densities are low aggregate to minimize this effect. Aggregation has the potential to change how Allee effects are expressed at the population level. We studied the interplay between aggregation and Allee effects in the mountain pine beetle ( Dendroctonus ponderosae Hopkins), an irruptive bark beetle that aggregates to overcome tree defenses. By cooperating to surpass a critical number of attacks per tree, the mountain pine beetle is able to breach host defenses,oviposit and reproduce. Mountain pine beetles and Hymenopteran parasitoids share some biological features, the most notable of which is obligatory host death as a consequence of parasitoid attack and development. We developed spatiotemporal models of mountain pine beetle dynamics that were based on the Nicholson-Bailey framework but which featured beetle aggregation and a tree-level attack threshold. By fitting our models to data from a local mountain pine beetle outbreak, we demonstrate that due to aggregation, attack thresholds at the tree level can be overcome by a surprisingly low ratio of beetles per susceptible tree at the stand level. This results confirms the importance of considering aggregation in models of organisms that are subject to strong Allee effects. This article is protected by copyright. All rights reserved.

Description: Ionotropic alginate microgels are commonly used for bioencapsulation applications and the air extrusion system is one of the common methods employed to produce these microgels. Although there have been many individual studies, no single report to date has comprehensively summarized the findings and results of the use of this system. Our review gives insight into the air extrusion methods, covering the setup, type and characteristics of the system, focussing on their innovative aspects. Characterization techniques for the resulting microgels are presented, along with the influence of process variables on their product size, and the development of empirical models for size prediction.

Description: For the purpose of a long-term heat storage system based on water sorption, a composite material consisting of 15 wt.% CaCl 2 and zeolite Ca-X (prepared by ion-exchange with Ca 2+ and subsequent impregnation with CaCl 2 of a binder-free granulated zeolite Na-X) was prepared on a technical scale. In a lab-scale apparatus, the heat storage density of the composite material reaches values up to 260 kWh m -3 for water vapor partial pressures up to 33 mbar. As compared to the pure zeolites Ca-X and Na-X, this corresponds to an increase in heat storage density of 45 % and 68 %, respectively. An engineering concept based on the mechanical transport of the composite heat storage material through a pre- and a main reactor was demonstrated in a “hardware in the loop” test bench.

Description: A model of the steam gasification of a single char particle driven by high intensity radiation was developed and experimentally verified with available measurements in literature. This was used to explore the sensitivity of particle surface temperature and heat transfer mechanisms to variations in particle diameters (100m to 1900m), radiative heat flux (1MW/m 2 to 4MW/m 2 ) and the concentration of the gasification agent, H 2 O (0.2 to 0.8 mole fraction) under typical conditions for solar gasification reactors. The results highlight the importance of particle diameter in influencing solar to chemical energy conversion efficiency and assist in the selection of appropriate feedstock particles to match the conditions in specific solar gasification reactors.

Description: Distillation of hydrocarbons was investigated to decrease energy consumption by applying the columns with the coupled heat and material flows. The elements of downstream processes were considered such as separation of the catalytic cracking gas and the recovery of benzene from petroleum and coking coal products by extractive distillation with N-methylpyrrolidone. It was found that the thermally coupled columns applied for the separation reduced energy consumption for the catalytic cracking gas separation up to 13.1% and for the benzene recovering up to 28.7%.

Description: Rapid granulation of biomass and reactor start-up has been studied in a novel denitrifying reactor. The effect of wastewater characteristics, reactor operating conditions and reactor geometry on microbial granulation has been studied. It was possible to achieve granulation in just 15 days of reactor start-up. In 15 days the settling velocity of the granules was 1.5 cm s -1 , which is almost 10 folds higher than that of seed sludge. The reactor was able to handle a nitrate loading rate of 50 g NO 3 -N m -3 day -1 in 3 days of reactor start-up with rates reaching up to 460 g NO 3 -N m -3 day -1 in just 30 days of reactor start-up with a removal efficiency of almost 100%. Based on the experimental observation, a hypothesis for the cause of rapid granulation has been proposed.

Description: K-solubilizing bacteria were isolated from solar salt pans of CSIR-CSMCRI’s experimental salt farm and Sambhar lake, mining areas of Naseerabad and wastewater from marble cutting machinery. Seven promising bacterial isolates from Makrana, three from Sambhar lake and three from Naseerabad were found to have comparatively better potassium solubilizing capacity. Out of these, three potential bacterial isolates were identified as Acinetobacter soli (MTCC 5918), Enterobacter xiangfangensis (MTCC 5917) and Acinetobacter baumannii (MTCC 5916). Thereafter, Acinetobacter soli was found to have maximum potassium releasing capacity of 80 mg/l in supernatant, which may be further applied as a biofertilizer.

Description: The development of floating liquefied natural gas (FLNG) plants has resulted in a focus on reducing the weight and size of the topside processing facilities for these units. The conventional fractionation of natural gas liquids (NGL) in LNG plants implies a direct sequence of three or more conventional distillation columns requiring different levels of refrigeration. The results of a feasibility study are described, indicating that a packed three-product dividing-wall column (DWC) could replace conventional de-ethanizer and depropanizer columns. This could provide significant energy, hardware, weight, and footprint benefits, but, very likely, at the expense of an unaffordable cold utilities demand. 1) A conventional demethanizer combined with a three-product dividing-wall column operated at moderate pressure appears to be a promising alternative for the conventional three-column sequence as encountered in natural gas liquids fractionation plants. In addition to the overall energy saving, such a configuration enables also weight, hardware, and footprint reduction.

Description: A 3D numerical model was developed for studying the multiphase flow and heat transfer process in a radiant syngas cooler (RSC). Realizable k-ϵ turbulent and discrete random walk models were adopted to simulate gas phase and particle phase flow fields, respectively. The surface temperature of the membrane wall was calculated by heat flux balance equations. The calculated temperature distribution was validated by comparing calculated values with measured data of an industrial RSC. Four different membrane wall arrangements of RSC, namely, ordinary membrane wall (OMW), partial division wall (PDW), annular division wall (ADW), and fin division wall (FDW), were designed for a specific condition. The radiant syngas cooler is one of the critical and expensive components of power plants. A three-dimensional numerical model was developed to predict the complex multiphase flow and heat transfer process in such a cooler of entrained-flow coal gasification for optimization. Four different membrane wall arrangements were designed and evaluated for a specific condition.

Description: Woody plant encroachment and overall declines in perennial vegetation in dryland regions can alter ecosystem properties and indicate land degradation, but the causes of these shifts remain controversial. Determining how changes in the abundance and distribution of grass and woody plants are influenced by conditions that regulate water availability at a regional scale provides a baseline to which compare how management actions alter the composition of these vegetation types at a more local scale and can be used to predict future shifts under climate change. Using a remote sensing-based approach, we assessed the balance between grasses and woody plants and how climate and topo-edaphic conditions affected their abundances across the northern Sonoran Desert from 1989 to 2009. Despite widespread woody plant encroachment in this region over the last 150 years, we found that leguminous trees, including mesquite ( Prosopis spp.), declined in cover in areas with prolonged drying conditions during the early 21st century. Creosote bush ( Larrea tridentata ) also had moderate decreases with prolonged drying but was buffered from changes on soils with low clay that promote infiltration, and high available water capacity that allows for retention of water at depth. Perennial grasses have expanded and contracted over the last two decades in response to summer precipitation, and were especially dynamic on shallow soils with high clay that have large fluctuations in water availability. Our results suggest that topo-edaphic properties can amplify or ameliorate climate-induced changes in woody plants and perennial grasses. Understanding these relationships has important implications for ecosystem function under climate change in the southwestern U.S. and can inform management efforts to regulate grass-woody plant abundances. This article is protected by copyright. All rights reserved.

Description: Species-area relationships have long been used to assess patterns of species diversity across scales. Here this concept is extended to spectral diversity using hyperspectral data collected by NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) over western Michigan. This mixture of mesic forest and agricultural lands offers two end-points on the local-scale diversity continuum – one set of well mixed forest patches and one set of highly homogeneous agricultural patches. Using the sum of the first three principal component values and the principal components’ convex hull volume, spectral diversity was compared within and among these plots and to null expectations for perfectly random and perfectly patchy landscapes. Overall the spectral diversity area relationship confirms the patterns that would be expected for this landscape, but this application suggests that this approach could be extended to less well understood landscapes and could reveal key insights about the relative importance of different drivers of community assembly, even in the absence of additional data about plant functional traits or species’ identities. This article is protected by copyright. All rights reserved.

Description: Understanding how habitat and nutritional condition affect ungulate populations is necessary for informing management, particularly in areas experiencing carnivore recovery and declining ungulate population trends. Variations in forage species availability, plant phenological stage, and the abundance of forage make it challenging to understand landscape-level effects of nutrition on ungulates. We developed an integrated spatial modeling approach to estimate landscape-level elk ( Cervus elaphus ) nutritional resources in two adjacent study areas that differed in coarse measures of habitat quality and related the consequences of differences in nutritional resources to elk body condition and pregnancy rates. We found no support for differences in dry matter digestibility between plant samples or in phenological stage based on ground sampling plots in the two study areas. Our index of nutritional resources, measured as digestible forage biomass, varied among landcover types and between study areas. We found that altered plant composition following fires was the biggest driver of differences in nutritional resources, suggesting that maintaining a mosaic of fire history and distribution will likely benefit ungulate populations. Study area, lactation status and year affected fall body fat of adult female elk. Elk in the study area exposed to lower summer range nutritional resources had lower nutritional condition entering winter. These differences in nutritional condition resulted in differences in pregnancy rate, with average pregnancy rates of 89% for elk exposed to higher nutritional resources and 72% for elk exposed to lower nutritional resources. Summer range nutritional resources have the potential to limit elk pregnancy rate and calf production, and these nutritional limitations may predispose elk to be more sensitive to the effects of harvest or predation. Wildlife managers should identify ungulate populations that are nutritionally limited and recognize that these populations may be more impacted by recovering carnivores or harvest than populations inhabiting more productive summer habitats. This article is protected by copyright. All rights reserved.

Description: Novel fire regimes are an important cause and consequence of global environmental change that involve interactions among biotic, climatic, and human components of ecosystems. Plant flammability is key to these interactions, yet few studies directly measure flammability or consider how multiple species with different flammabilities interact to produce novel fire regimes. Deserts of the southwestern USA are an ideal system for exploring how novel fire regimes can emerge when fire-promoting species invade ecosystems comprised of species that did not evolve with fire. In these deserts, exotic annual grasses provide fuel continuity across landscapes that did not historically burn. These fires often ignite a keystone desert shrub, the fire-intolerant creosote bush, Larrea tridentata (DC.) Coville. Ignition of Larrea is likely catalyzed by fuels produced by native plants that grow beneath the shrubs. We hypothesize that invasive and native species exhibit distinct flammability characteristics that in combination determine spatial patterns of fire spread and intensity. We measured flammability metrics of Larrea , two invasive grasses, Schismus arabicus and Bromus madritensis , and two native plants, the sub-shrub Ambrosia dumosa and the annual herb Amsinckia menziesii . Results of laboratory experiments show that the grasses carry fire quickly (1.32 cm/sec), but burn for short duration (0.5 min) at low temperatures. In contrast, native plants spread fire slowly (0.12 cm/sec), but burn up to eight times longer (4 min) and produced hotter fires. Additional experiments on the ignition requirements of Larrea suggest that native plants burn with sufficient temperature and duration to ignite dead Larrea branches (time to ignition: 2 min; temperature at ignition 692 °C). Once burning, these dead branches ignite living branches in the upper portions of the shrub. Our study provides support for a conceptual model in which exotic grasses are “spreaders” of fire and native plants growing beneath shrubs are “igniters” of dead Larrea branches. Once burning, flames produced by dead branches engulf the entire shrub, resulting in locally intense fires without historical precedent in this system. We suggest that fire models and conservation-focused management could be improved by incorporating the distinct flammability characteristics and spatial distributions of spreaders, igniters, and keystone shrubs. This article is protected by copyright. All rights reserved.

Description: Why some species and lineages are more likely to be invasive than others is one of the most important unanswered questions in basic and applied biology. In particular, the relative contributions to the invasion process of factors like preadaptation to invasiveness in the native range, evolution post-colonization, and random vs. non-random sampling of colonist lineages remain unclear. Here, we use a powerful common garden approach to address the potential for a role for sensitivity to nutrient limitation in determining the invasiveness of particular lineages of Potamopyrgus antipodarum , a New Zealand freshwater snail that has become globally invasive. We quantified specific growth rate (SGR), an important fitness-related trait in this species, under high phosphorus (P) vs. low-P conditions for a diverse set of native and invasive P. antipodarum . This study revealed that native-range P. antipodarum experience a more severe decline in SGR in low-P conditions relative to SGR in high-P conditions than their invasive range counterparts. Although these results suggest resilience to P limitation in invasive lineages, the absence of significant absolute differences in SGR between native and invasive lineages indicates that a straightforward connection between response to P limitation and invasiveness in P. antipodarum is unlikely. Regardless, our data do demonstrate that invasive vs. native lineages of P. antipodarum exhibit consistently different responses to an important environmental variable that is rarely studied in the context of invasion success. Further studies directed at exploring and disentangling the roles of sampling effects, selection on preexisting variation, and evolution after colonization will be required to provide a comprehensive picture of the role (or lack thereof) of nutrient limitation in the global invasion of P. antipodarum as well for as other invasive taxa. This article is protected by copyright. All rights reserved.

Description: An increasing number of studies have aimed to clarify the factors leading human groups to prioritize the use of some woody plant species when compared to others. Some of these studies have tested the apparency hypothesis in aiming to understand this phenomenon. According to the apparency hypothesis, the most commonly available local plant species on a forest path are the most useful to that local human population. However, the sparse and diverse nature of the results from studies investigating the factors that influence human exploitation of plant resources motivated us to perform a meta-analysis on the apparency hypothesis. We searched in the main databases (Scopus, Sciencedirect, Google Scholar and Scielo) for studies that correlated the environmental availability of woody species (estimated through vegetation parameters) with the importance degree of such species to the local human population (estimated by means of the use-value index). Overall, this meta-analysis supported the apparency hypothesis, although we also found high levels of heterogeneity in these studies. When the distinct uses of woody flora were considered separately, we found that local species availability is important for fuelwood (firewood and charcoal) and construction (houses, fences, etc.) purposes but does not explain medicinal and technological (object manufacture) plant use. We found no important differences in correlations values between the degree of species importance for people and the different vegetation parameters, although correlations are slightly higher for the dominance and importance value index. Our findings suggest that the exploitation of woody flora is influenced by local availability. This article is protected by copyright. All rights reserved.

Description: Ecological traps are threats to organisms, and exist in a range of biological systems. A subset of ecological trap theory is the “ethological trap”, whereby behaviors canalized by past natural selection become traps when environments change rapidly. Invasive predators are major threats to imperilled species and their ability to exploit canalized behaviors of naive prey is particularly important for the establishment of the predator and the decline of the native prey. Our study uses ecological theory to demonstrate that invasive predator controls require shifts in management priorities. Total predation rate (i.e., total response) is the product of both the functional response and numerical response of predators to prey. Functional responses are the changes in the rate of prey consumption by individual predators, relative to prey abundance. Numerical responses are the aggregative rates of prey consumption by all predators relative to prey density, which change with predator density via reproduction or migration, in response to changes in prey density. Traditional invasive predator management methods focus on reducing predator populations, and thus manage for numerical responses. These management efforts fail to manage for functional responses, and may not eliminate impacts of highly-efficient individual predators. We explore this problem by modelling the impacts of functional and numerical responses of invasive foxes depredating imperilled Australian turtle nests. Foxes exhibit exceptionally-efficient functional responses. A single fox can destroy 〉95% of turtle nests in a nesting area, which eliminates juvenile recruitment. In this case, the ethological trap is the ‘Arribada’ nesting strategy, an emergent behavior whereby most turtles in a population nest simultaneously in the same nesting grounds. Our models show that Arribada nesting events do not oversaturate foxes, and small numbers of foxes depredate all of the nests in a given Arribada. Widely scattering nests may reduce fox predation rates, but the long generation times of turtles combined with their rapid recent decline suggests that evolutionary changes in nesting strategy may be unlikely. Our study demonstrates that reducing populations of highly-efficient invasive predators is insufficient for preserving native prey species. Instead, management must reduce individual predator efficiency, independent of reducing predator population size. This article is protected by copyright. All rights reserved.

Description: Changed fire regimes have led to declines of fire-regime-adapted species and loss of biodiversity globally. Fire affects population processes of growth, reproduction and dispersal in different ways, but there is little guidance about the best fire regime(s) to maintain species population processes in fire-prone ecosystems. We use a process-based approach to determine the best range of fire intervals for keystone plant species in a highly-modified Mediterranean ecosystem in south-western Australia where current fire regimes vary. In highly-fragmented areas, fires are few due to limited ignitions and active suppression of wildfire on private land, while in highly connected protected areas fires are frequent and extensive. Using matrix population models, we predict population growth of seven Banksia species under different environmental conditions and patch connectivity, and evaluate the sensitivity of species survival to different fire management strategies and burning intervals. We discover that contrasting, complementary patterns of species life-histories with time since fire result in no single best fire regime. All strategies result in the local patch extinction of at least one species. A small number of burning strategies secure complementary species sets depending on connectivity and post-fire growing conditions. A strategy of no fire always leads to fewer species persisting than prescribed fire or random wildfire, while too-frequent or too-rare burning regimes lead to the possible local extinction of all species. In low landscape connectivity, we find a smaller range of suitable fire intervals, and strategies of prescribed or random burning result in a lower number of species with positive growth rates after 100 years on average compared with burning high connectivity patches. Prescribed fire may reduce or increase extinction risk when applied in combination with wildfire depending on patch connectivity. Poor growing conditions result in a significantly reduced number of species exhibiting positive growth rates after 100 years of management. By exploring the consequences of managing fire, we are able to identify which species are likely to disappear under a given fire regime. Identifying the appropriate complementarity of fire intervals, and their species-specific as well as community-level consequences, is crucial to reduce local extinctions of species in fragmented fire-prone landscapes. This article is protected by copyright. All rights reserved.

Description: Assessments of large-scale disasters, such as the Deepwater Horizon oil spill, are problematic because while measurements of post-disturbance conditions are common, measurements of pre-disturbance baselines are only rarely available. Without adequate observations of pre-disaster organismal and environmental conditions, it is impossible to assess the impact of such catastrophes on animal populations and ecological communities. Here, we use long-term biological tissue records to provide pre-disaster data for a vulnerable marine organism. Keratin samples from the carapace of loggerhead sea turtles record the foraging history for up to 18 years, allowing us to evaluate the effect of the oil spill on sea turtle foraging patterns. Samples were collected from 76 satellite-tracked adult loggerheads in 2011 and 2012, approximately one to two years after the spill. Of the ten individuals that foraged in areas exposed to surface oil, none demonstrated significant changes in foraging patterns post spill. The observed long-term fidelity to foraging sites indicates that loggerheads in the northern Gulf of Mexico likely remained in established foraging sites, regardless of the introduction of oil and chemical dispersants. More research is needed to address potential long-term health consequences to turtles in this region. Mobile marine organisms present challenges for researchers to monitor effects of environmental disasters, both spatially and temporally. We demonstrate that biological tissues can reveal long-term histories of animal behavior and provide critical pre-disaster baselines following an anthropogenic disturbance or natural disaster. This article is protected by copyright. All rights reserved.

Description: Increasing temperatures have resulted in reduced growth and increased tree mortality across large areas of western North American forests. Here we use tree-ring isotope chronologies (δ 13 C & δ 18 O) from live and dead trees from four locations in south-central Alaska to test whether white spruce trees killed by recent spruce beetle ( Dendroctonus rufipennis Kirby) outbreaks showed evidence of drought stress prior to death. Trees that were killed were more sensitive to spring/summer temperature and/or precipitation than trees that survived. At two of our sites we found greater correlations between the δ 13 C and δ 18 O chronologies and spring/summer temperatures in dead trees than in live trees, suggesting that trees that are more sensitive to temperature-induced drought stress are more likely to be killed. At one site, the difference between δ 13 C in live and dead trees was related to winter/spring precipitation, with dead trees showing stronger correlations between δ 13 C and precipitation, again suggesting increased water stress in dead trees. At all sites where δ 18 O was measured, δ 18 O chronologies showed the greatest difference in climate response between live and dead groups, with δ 18 O in live trees correlating more strongly with late winter precipitation than dead trees. Our results indicate that sites where trees are already sensitive to warm or dry early growing-season conditions experienced the most beetle-kill, which has important implications for forecasting future mortality events in Alaska. This article is protected by copyright. All rights reserved.

Description: Understanding the impacts of natural and human disturbances on forest biota is critical for improving forest management. Many studies have examined the separate impacts on fauna and flora of wildfire, conventional logging and salvage logging, but empirical comparisons across a broad gradient of simultaneous disturbances are lacking. We quantified species richness and frequency of occurrence of vascular plants, and functional group responses, across a gradient of disturbances that occurred concurrently in 2009 in the Mountain Ash forests of southeastern Australia. Our study encompassed replicated sites in undisturbed forest (~70 years post-fire), forest burned at low severity, forest burned at high severity, unburned forest that was clearcut logged, and forest burned at high severity that was clearcut salvage logged post-fire. All sites were sampled two and three years post-fire. Mean species richness decreased across the disturbance gradient from 30.1 spp/site on low severity burned sites and 28.9 spp/site on high severity burned sites, to 25.1 spp/site on clearcut sites and 21.7 spp/site on salvage logged sites. Low severity burned sites were significantly more species-rich than clearcut sites and salvage logged sites; high severity burned sites supported greater species richness than salvage logged sites. Specific traits influenced species’ sensitivity to disturbance. Resprouting species dominated undisturbed Mountain Ash forests, but declined significantly across the gradient. Fern and midstory trees decreased significantly in frequency of occurrence across the gradient. Ferns (excluding Bracken) decreased from 34% of plants in undisturbed forest to 3% on salvage logged sites. High severity burned sites supported a greater frequency of occurrence and species richness of midstory trees compared to clearcut and salvage logged sites. Salvage logging supported fewer midstory trees than any other disturbance category, and were distinctly different from clearcut sites. Plant life form groups, including midstory trees, shrubs and ferns, were dominated by very few species on logged sites. The differences in biotic response across the gradient of natural and human disturbances have significant management implications, particularly the need to reduce mechanical disturbance overall and to leave specific areas with no mechanical disturbance across the cut area during logging operations, to ensure the persistence of resprouting taxa. This article is protected by copyright. All rights reserved.

Description: We review and synthesize information on invasions of nonnative forest insects and diseases in the United States, including their ecological and economic impacts, pathways of arrival, distribution within the United States, and policy options for reducing future invasions. Nonnative insects have accumulated in United States forests at a rate of ~2.5 per yr over the last 150 yr. Currently the two major pathways of introduction are importation of live plants and wood packing material such as pallets and crates. Introduced insects and diseases occur in forests and cities throughout the United States, and the problem is particularly severe in the Northeast and Upper Midwest. Nonnative forest pests are the only disturbance agent that has effectively eliminated entire tree species or genera from United States forests within decades. The resulting shift in forest structure and species composition alters ecosystem functions such as productivity, nutrient cycling, and wildlife habitat. In urban and suburban areas, loss of trees from streets, yards, and parks affects aesthetics, property values, shading, stormwater runoff, and human health. The economic damage from nonnative pests is not yet fully known, but is likely in the billions of dollars per year, with the majority of this economic burden borne by municipalities and residential property owners. Current policies for preventing introductions are having positive effects but are insufficient to reduce the influx of pests in the face of burgeoning global trade. Options are available to strengthen the defenses against pest arrival and establishment, including measures taken in the exporting country prior to shipment, measures to ensure clean shipments of plants and wood products, inspections at ports of entry, and post-entry measures such as quarantines, surveillance, and eradication programs. Improved data collection procedures for inspections, greater data accessibility, and better reporting would support better evaluation of policy effectiveness. Lack of additional action places the nation, local municipalities, and property owners at high risk of further damaging and costly invasions. Adopting stronger policies to reduce establishments of new forest insects and diseases would shift the major costs of control to the source and alleviate the economic burden now borne by homeowners and municipalities.

Description: In order to improve the flow uniformity in plate-fin heat exchanger (PFHE), a modified header structure with a plain baffle inside is proposed in this study. Flow distribution and pressure drop in header were studied by using numerical method. Results show that the modified header is high-efficient in improving the flow uniformity in header of PFHE with negligible pressure drop increase. Then, a performance effectiveness factor was introduced to predict the effects of the modified structure on the performance of PFHE. Finally, influences of baffle structure parameters on modified structure performances were further discussed. Conclusions of this paper indicate that the modified header structure can effectively improve the performance of PFHE.

Description: Droughts and their negative effects on forest ecosystems are projected to increase under climate change for many regions. It has been suggested that intensive thinning could reduce drought impacts on established forests in the short-term. Most previous studies on the effect of thinning on drought impacts, however, have been confined to single forest sites. It is therefore still unclear how general and persisting the benefits of thinning are. This study assesses the potential of thinning to increase drought tolerance of the wide spread Scots pine ( Pinus sylvestris ) in Central Europe. We hypothesized 1) that increasing thinning intensity benefits the maintenance of radial growth of crop trees during drought (resistance) and its recovery following drought, 2) that those benefits to growth decrease with time elapsed since the last thinning and with stand age, and 3) that they may depend on drought severity as well as water limitations in pre- and post-drought periods. To test these hypotheses, we assessed the effects of thinning regime, stand age, and drought severity on radial growth of 129 Scots pine trees during and after drought events in 4 long-term thinning experiments in Germany. We find that thinning improved the recovery of radial growth following drought and to a lesser extent the growth resistance during a drought event. Growth recovery following drought was highest after the first thinning intervention and in recently and heavily thinned stands. With time since the last thinning, however, this effect decreased and could even become negative when compared to unthinned stands. Further, thinning helped to avoid an age-related decline in growth resistance (and recovery) following drought. The recovery following drought, but not the resistance during drought, was related to water limitations in the drought period. This is the first study that analyzed drought-related radial growth in trees of one species across several stands of different age. The interaction between thinning intensity and time since the last thinning underline the importance to distinguish between short- and long-term effects of thinning. According to our analysis, only thinning regimes, with relatively heavy and frequent thinning interventions would increase drought tolerance in pine stands. This article is protected by copyright. All rights reserved.