The effects of selected aldehydes, ketones and carboxylic acids on off-flavours in water

The effects of selected aldehydes, ketones and carboxylic acids on the development of off‐flavours in water were studied. Combinations of hexanal, octanal, 2‐octanone, 5‐nonanone, hexanoic acid and nonanoic acid were rated by the off‐flavour intensities they created in water at concentrations just at or below the threshold value of each analyte. Two different sensory panels evaluated the off‐flavours induced by different combinations of the analytes. The observations of the two panels agreed well. From these studies, it could be concluded that aldehydes play an important role in the development of off‐flavours intensities in water. There were synergistic effects between aldehydes and ketones, as well as between aldehydes and carboxylic acids. Small amounts of aldehydes and carboxylic acids – well below their respective threshold values – caused an increase in the off‐flavour intensity. No synergism between ketones and carboxylic acids could be observed.     

A Molecular Perspective on the d-Band Model: Synergy Between Experiment and Theory

The d-band model of Hammer and Nørskov (Nature 376:238, 1995 [3]) relating adsorption energies to the d-band position, and the adsorption energies to barriers in catalytic reactions, has been extremely successful in predicting reactivities and catalysts. In the present contribution we review recent combined experimental and theoretical work on chemical bond-formation at surfaces. We focus on the adsorbate and how the adsorbate electronic structure can be rehybridized through mixing with unoccupied states to generate the radical state, real or virtual, that can then form electron pairs with the metal d-states, as described by the d-band model. We discuss five important bonding situations: (i) atomic radical, (ii) diatomics with unsaturated π-systems (Blyholder model), (iii) unsaturated hydrocarbons (Dewar–Chatt–Duncanson model), (iv) lone–pair interactions, and (v) saturated hydrocarbons (physisorption). Where the d-band model predicts trends along the series of transition metals, the present work provides intuitive tools for predicting trends among different adsorbates.     

Challenges and opportunities for productivity improvement studies in linear,repetitive, and location-based scheduling

Despite theoretical advancements in alternative project planning methods the extent of their practical implementation varies strongly; it has been limited especially in the US construction industry. The family of linear, repetitive, and location-based scheduling techniques holds significant but barely substantiated promise by containing multiple variables of interest for integrated analysis and optimization. Yet it is necessary to provide empirical evidence that using such techniques can improve productivity to increase credibility and acceptance by practitioners, because claims of conceptual superiority are only sporadically supported with detailed measures. An analysis is performed to identify relevant decision-making variables, extract challenges that currently limit the corpus of quantitative productivity studies on alternative scheduling to its insufficient size, and reveal opportunities to expand it in breadth and depth. Variables are categorized by their relevance to time, activity, resource and location, as well as the managerial approach. Challenges include the diverse definitions of productivity itself, issues related to achieving generalizability, and the detailed steps of data collection, preparation, and analysis. Opportunities include the guidance from existing but rare studies and well-established research methods such as case studies that can be applied. This is illustrated with a sample project of a high-rise apartment building in Brazil. If alternative methods can be proven to be measurably better for specific applications, there might be a paradigm shift from merely defaulting to traditional but problematic network-based scheduling toward consciously choosing the planning method based on its potential benefits for a project.     

Anodic Electrochromism for Energy‐Efficient Windows: Cation/Anion‐Based Surface Processes and Effects of Crystal Facets in Nickel Oxide Thin Films

Anodic electrochromic (EC) oxides are of major interest as counter electrodes for smart window applications owing to their unique optical properties upon charge insertion and extraction. However, performance optimization of such oxides has been hampered by limited understanding of their EC mechanism, particularly in Li⁺‐conducting electrolytes. This paper reports on NiO_x films with 1.16 ≤ x ≤ 1.32, prepared by sputter deposition. These films are immersed in an electrolyte of lithium perchlorate in propylene carbonate, and EC properties are studied by cyclic voltammetry and in situ optical transmittance measurements. The electrochromism is significantly enhanced at large values of x. It has been found that charge exchange in Ni oxide is mainly due to surface processes and involves both cations and anions from the electrolyte, which is different from the case of cathodic EC materials such as WO₃. Whereas previous studies of Ni oxide have focused on cation intercalation, the cation/anion‐based mechanism presented here offers a new paradigm for designing and developing EC devices such as smart windows for energy efficient buildings.     

Exergy analysis of chemical-looping combustion systems

A power plant based on chemical-looping combustion offers both a possibility of high net power efficiency and separation of the greenhouse gas CO₂. This is due to the way the oxidation of the fuel takes place. Instead of oxidizing the fuel with oxygen from the combustion air, the fuel is oxidized by an oxygen carrier, i.e., an oxygen-containing compound. The oxygen carriers that have been suggested in previous studies are metal oxides like NiO, Fe₂O₃ and Mn₃O₄. The reduced oxygen carrier is in the next step reoxidized by air in a second reactor and then recirculated to the first reactor. In this way, fuel and air are never mixed and the fuel oxidation products CO₂ and water leave the system undiluted by air. All that is needed to get an almost pure CO₂ product is to condense the water vapour and remove the liquid water.Chemical-looping combustion (CLC) is also claimed to reduce the fuel exergy destruction in the overall reaction of combustion of the fuel. This gives a possibility to increase the net power efficiency.This paper gives an introduction to chemical-looping combustion. Results from simulations and a detailed exergy analysis of two different CLC gas turbine (GT) systems are also presented. The first system utilizes methane as a fuel and NiO as oxygen carrier. The second system utilizes a fuel gas mixture consisting mainly of CO and H₂, simulating a fuel gas from for instance coal gasification. Results for this system are given for simulations with both NiO and Fe₂O₃ as oxygen carrier. The two systems are compared to comparable simulated systems with conventional combustion of the same fuel. The exergy analysis shows that the irreversibilities generated upon combustion of the fuel are reduced. The net power efficiency of the CLC–GT systems is similar or higher than for the corresponding GT systems with conventional combustion. The net power efficiency of CLC systems could be even further increased if the exergy remaining in the exhaust could be utilized in an efficient way.     

Relationships between milking frequency, lactation persistency and milk yield in Swedish Red heifers and cows milked in a voluntary attendance automatic milking system

A large dataset comprising output from an automatic milking (AM) system between 1999 and 2006 was examined and a total of 172 cow lactation curves and 68 heifer lactation curves were identified for further analysis. Relationships between milking frequency at different stages of lactation and lactation persistency and total lactation yield were determined. Cows had higher peak and total milk yields than heifers, but heifers had higher persistency (defined as the rate of decline in milk yield between days 100 and 300 post calving). Milking frequency did not differ significantly between cows and heifers in early lactation, but thereafter decreased significantly more in cows than in heifers. The effect of milking frequency on yield characteristics was analysed by comparing the highest and lowest quartiles for milking frequency. High milking frequency in early lactation was consistently associated with increased peak yield. High milking frequency averaged across the whole lactation was associated with increased peak yield in both cows and heifers, and with improved lactation persistency in cows only. This resulted in total lactation yield that was 21% greater in the high quartile cows compared with the low.     

Influence of sputtering conditions on the solar and luminous optical properties of amorphous LixWoy thin films

Thin films of amorphous tungsten oxide were deposited by sputtering onto glass substrates coated by conductive indium–tin oxide. The films were sputtered at different oxygen-to-argon flow ratios with different pressure and power. Elastic recoil detection analysis determined the density and the stoichiometry. X-ray diffraction measurements showed that the films were amorphous. The films were electrochemically intercalated with lithium ions. At several intercalation levels of each film, the optical reflectance and transmittance were measured in the wavelength range 0.3–2.5 μm. We study the effect of various sputtering conditions on the coloration efficiency of the films and on the luminous and solar optical properties. The O₂/Ar ratio and the sputter pressure determine to a large extent the optical absorption. As-deposited sputtered tungsten oxide with sufficiently little oxygen exhibits an absorption peak similar to the case of lithium intercalation.     

Short resolution proofs for a sequence of tricky formulas

 A class of propositional formulas, encoding the property that every finite, transitive digraph with no two-cycles must have a source, has been investigated by Krishnamurty and conjectured as hard for resolution. In this note we prove, opposed to that conjecture, that there are proofs of polynomial lengths (or even linear in the lengths of the formulas) of those formulas. Received March 15, 1994/November 28, 1994     

Electrical conductivity as a function of temperature in amorphous lithium tungsten oxide

Tungsten oxide is a widely used electrochromic material for smart windows. In order to study the charge carriers involved in the electrochromic process, it is important to characterize the electrical transport in tungsten oxide. Substoichiometric amorphous tungsten oxide films were prepared by DC-magnetron sputtering. The films were electrochemically intercalated with lithium. The Li/W intercalation ratios for the tungsten oxide films were in the range 0.15–0.53. Temperature dependent resistivity measurements were performed in the temperature range 77–300 K for samples at different lithium intercalation levels. It was found that the data are consistent with the variable range hopping model.