Academic literature on the topic 'Past perfect compound'

John Eccles's active theatrical career spanned a period of about sixteen years, though he continued to compose occasionally for the theater after his semi-retirement in 1707. During his career he wrote incidental music for more than seventy plays, writing songs that fit perfectly within their dramatic contexts and that offered carefully tailored vehicles for his singers’ talents while remaining highly accessible in tone. This edition includes music composed by Eccles for plays beginning with the letters H–P. These plays were fundamentally collaborative ventures, and multiple composers often su

For the past almost fifty years, scientists have been trying to explain the phenomenon of superconductivity. The mechanism is the key ingredient of microscopic theory, which was developed by Bardeen, Cooper, and Schrieffer in 1957. The theory also introduced the basic concepts of pairing, coherence length, energy gap, and so on. Since then, microscopic theory has undergone an intensive development. This book provides a very detailed theoretical treatment of the key mechanisms of superconductivity, including the current state of the art (phonons, magnons, plasmons). In addition, the book contai

Verbal idioms are usually lemmatized in dictionaries with their infinitive form (eg., nacer de pie). However, some of them are eventually registered with their perfect infinitive form (eg., haber nacido de pie), conveying the idea that they are preferably used with compound or past tenses. Our hypothesis is that not all idioms of this type are actually used in the same way. To prove it, thirty idioms, lemmatized once at least by the perfect infinitive, have been extracted from five different European Spanish phraseological dictionaries. The information collected is compared with the data obtained from a web text corpus. The main results are: firstly, the chosen lemma sign does not always correspond to the actual use of several idioms; secondly, there are clear differences among dictionaries regarding the treatment that they give to this kind of idioms; thirdly, it seems not to be a common pattern even within the same dictionary; finally, the information provided by a lemma sign sometimes does not fit properly with the definition and/or the example.

Thermochemistry has been defined in one of the most popular physical chemistry textbooks as “the study of the heat produced or required by chemical reactions”. The use of heat, instead of the more general word energy, immediately suggests a close association between thermochemistry and calorimetry—the oldest experimental technique for investigating the thermodynamics of chemical reactions. This view is, in fact, shared by many of our students and some of their teachers, together with the belief that thermochemistry, founded in the eighteenth century by Black, Lavoisier, and Laplace, has seen few major developments since the days of Berthelot and Thomsen, over 100 years ago. The notion that calorimetric studies are almost the sole source of thermochemical information prevails beyond the classroom. Also, the idea of thermochemistry as a science of the past is even conveyed by distinguished scientists and lecturers. Figure 1.1, taken from a delightful account by Herschbach, depicts thermochemistry as a mountain that was necessary to climb to conquer the structure and dynamics summits and reach the ultimate goal—the understanding of chemical synthesis. The picture is enlightening, but the timeline suggests that the climax of the thermochemical era dates back to the early decades of the last century, coinciding with the publication of Lewis and Randall’s Thermodynamics and the Free Energy of Chemical Substances. However, the golden years of calorimetry started in the 1930s, thanks to the work on organic compounds and key molecules, such as water and carbon dioxide, by Rossini and his colleagues at the National Bureau of Standards, and continued in the 1960s and 1970s. Thermochemical studies of organometallic compounds were pioneered by Skinner and his coworkers at Manchester University. Figure 1.1 can also be regarded from a different perspective, which is more correct and probably in keeping with Herschbach’s thoughts: Thermochemistry is not only the first mountain to climb but also the solid ground from which the remaining heights can be reached. The heaven, or the perfect understanding of chemical synthesis, rests on a detailed knowledge of thermochemistry, structure, dynamics, and their relationships.

Anaerobic methanotrophs are not the only ecologically important archaea to surprise microbiologists in the last decade. And their isoprenoid ethers are not the only useful lipids—and certainly not the strangest—to have joined the lexicon of microbial biomarkers. Though much of that lexicon is still too generic to be of much use in understanding geologic history, some of these structures have allowed geochemists to transcend biological complexity and garner clues to past climates and environments. In the 1990s, when Stefan Schouten first started finding ring-containing biphytanyl ethers in his sediment samples, he was still working on his doctorate at NIOZ. Like everyone else at the time, he assumed that they derived from the lipids of methanogenic archaea and that it was only a matter of time before ring-containing biphytanyl tetraethers would be identified among the lipids of some newly isolated culture of methanogens, as Guy Ourisson had predicted. Schouten was studying oxygen- and sulfur-bound biomarkers, which meant he treated his sediment extracts chemically to cleave the ether and sulfur bonds, and the treatments often turned up biphytanes. But then, he says, he and another student started finding the ring-containing compounds in some really unlikely places, such as the oxic surface layer of marine sediments where neither methanogens nor extreme thermophilic and halophilic archaea were likely to make a home. The only thing they could think of at the time was that the tetraethers had come from methanogens that lived in the oxygen minimum zone, the layer of water beneath the photic zone where heterotrophic bacteria are active, sometimes to the point of using up all of the oxygen. When Schouten presented these ideas at the 1995 organic geochemistry meeting, Stuart Wakeham immediately piped up with the suggestion that they look for the lipids in the water column—and offered the perfect samples for the enterprise. He had collected particulate matter at different depths in the Black Sea and Cariaco Basin, just the sort of anoxic environments where one might expect to find methanogens in the water column. . . .

This part includes a discussion of the main experimental methods that have been used to study the energetics of chemical reactions and the thermodynamic stability of compounds in the condensed phase (solid, liquid, and solution). The only exception is the reference to flame combustion calorimetry in section 7.3. Although this method was designed to measure the enthalpies of combustion of substances in the gaseous phase, it has very strong affinities with the other combustion calorimetric methods presented in the same chapter. Most published enthalpies of formation and reaction in the condensed phase were determined by calorimetry (see databases indicated in appendix B). It is therefore not surprising that the discussion of calorimetric methods occupies a large fraction of part II. The heart of a calorimeter is the calorimeter proper (also called measuring system or sample cell), which contains the reaction vessel, where the chemical reaction or phase transition under study occurs. Sometimes the calorimeter proper coincides with the reaction vessel. For example, in the setup shown in figure 6.1a, which is typical of many combustion calorimeters, the reaction vessel is placed inside the calorimeter proper. In the arrangement of figure 6.1b, used in many reaction-solution calorimeters, the calorimeter proper is also the reaction vessel. Normally, a controlled-temperature jacket surrounds the calorimeter proper. Other parts besides thermometers, commonly found in calorimeters, are stirring, heating, cooling, and ignition devices. Some of these devices are placed inside the calorimeter proper or cross its boundaries and are also considered to be part of it. In modern instruments, the data acquisition and many steps of the calorimetric experiments are usually computer-controlled. Calorimeters of many different designs have been constructed and operated. However, these are all variations of a few basic categories. For example, based on the heat exchange mode between the calorimeter proper and the surrounding jacket, it is convenient to distinguish three main classes of calorimeters: adiabatic, heat conduction, and isoperibol. In a perfectly adiabatic calorimeter no heat is transferred between the calorimeter proper and the jacket (the corresponding heat flow rate Φ = dQ/dt = 0, where Q represents the heat exchanged and t is time).

Though the concept of the biomarker emerged from attempts to infer the provenance of petroleum and the incidence of life on the young earth—for all the successes and disappointments of the early studies on Precambrian rocks, lunar dust, and oil shales—it was in the sediments of the deep sea that biomarkers really came into their own. The Deep Sea Drilling Project (DSDP) was initiated in the 1960s by a consortium of American oceanographic research institutions, but institutions in Russia, the United Kingdom, France, and Germany were quick to sign on. In what began as an effort to understand the makeup and dynamics of the earth’s crust and mantle, the DSDP’s special research ship traveled the world’s oceans, drilling thousands of meters into the seafloor to retrieve sediment cores that soon became coveted objects of study for geologists, oceanographers, biologists, paleontologists, and geochemists around the world. When Geoff’s group started analyzing the DSDP sediments in the early 1970s, most of the organic chemists involved with the program were from the oil industry and formed part of the drill ship’s safety program, monitoring the cores as they were brought on deck to ensure that dangerous accumulations of gas or liquid hydrocarbons weren’t being penetrated. But Geoff saw the DSDP as the perfect opportunity to wean his Bristol lab of its dependence on NASA’s Apollo program—a chance to bring his full attention back to Earth and its still largely unexplored realm of fossil molecules. The British Natural Environment Research Council had earmarked a large pot of funding for work on the cores, which would be unencumbered by the narrow commercial goals and secrecy that surrounded the limited offerings from oil-company bore holes. Geoff’s budding Organic Geochemistry Unit would be aligned with a multidisciplinary community of scientists who were all studying the same cores, working cooperatively, and publishing freely. And, unlike the lunar samples, ocean sediments were rife with interesting organic compounds, including many entirely unforeseen structures. Most of the cores consisted of sediments that had been laid down and buried sequentially without ever being subjected to the tectonic turmoil of stretching and subsidence, and the overlying kilometers of cold water had kept their temperatures relatively low.

To secure the highly challenging 2°C climate change limit, the automotive sector is expected to further improve the efficiency of the internal combustion engines. Over the past decade, internal combustion engine downsizing through turbocharging has become one of the major solutions that the industry has offered to fulfil its carbon commitment. Although the various new turbocharging technologies has changed the sluggish image of conventional turbocharged engines, the turbocharger system is far from perfect. From the perspective of engine energy flow, the copious amount of waste energy is habitu