Recent Times

In order to disprove this theory, Pasteur used swan-necked flasks unheated air could now enter the sterile culture solution. But in this case, the microorganisms in the air were deposited in the long S-shaped neck and did not enter the culture medium. If, however, the neck of a flask was broken off, they could enter the solution and multiply. 

In 1864, Louis Pasteur received the well-deserved prize of the Academy in recognition of his achievements. However, Pasteur s experiments provided no information on how life was formed. 

At around this time, there was much scientific debate about the theory of the origin of species proposed by Charles Darwin (1809-1882), a theory which was to change the world. Darwin himself was very cautious about making statements on biogenesis. It was still too early to answer such questions, because neither results from the science of cell biology nor an extensive knowledge of our planet, the solar system and the cosmos were available. 

The ideas of the well-known physiologist from Bonn, Eduard Pfliiger (1829-1910), seem to predate modem theories he assumed that, under the specific conditions of the primordial Earth, fundamental constituents of protoplasma could have developed from cyanide-type compounds or polymers derived from them (Pfliiger, 1875). 

The idea that microbes could migrate across the universe was supported by scientists with a worldwide reputation, such as H. von Helmholtz, W. Thomson (later Lord Kelvin) and Svante Arrhenius. This hypothesis was still accepted by Arrhenius in the year 1927, when he reported in the Zeitschrift fur Physikalische Chemie on his assumption that thermophilic bacteria could be transported within a few days from Venus (with a calculated surface temperature of 320 K) to the Earth by the radiation pressure of the sun (Arrhenius, 1927). The panspermia hypothesis, which seemed to have disappeared in the intervening decades, was reintroduced in the ideas of Francis Crick (Crick and Orgel, 1973). It still exists in a modified form (see Sect. 11.1.2.4). 

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A historical account of the development of organic nomenclature from the time preceding the Geneva Conference to faidy recent times is available... 

Coordinate Indexing and Boolean Logic. Three methods of indexing have been prominent in the chemical Hterature in recent times. The first, articulated indexing, has been used in printed Chemicaly hstracts subject indexes from their earliest days until well into the 1990s. A number of important concepts are identified as permissible index entries, including specific compounds, material types, reactions, and processes. One or more modifying statements foUow each basic index entry. Thus, eg. 

In more recent times, naphthalene has been used in condensation products from naphthalene sulfonic acids, utili2ing formaldehyde as additives to improve the flow properties of concrete these are referred to as superplastici2ers. Another newer appHcation is the production of diisopropylnaphthalenes. The mutual depression of the melting points in the mixture gives a Hquid which is used as a solvent for dyes in the production of carbonless copy paper. 

The principal marine deposits were formed during the Tertiary period and more particularly the upper Miocene epoch. Deposits of freshwater origin date from the PHocene to Miocene epochs to more recent times, dating to as late as 100,000 years ago. U.S. commercial deposits are at or comparatively near the surface. Bog deposits are exploited and lake beds are dredged for use in other parts of the world. 

The fact that only 11 structures were reported in (72PMH(5)l) whereas in Table 5, which is non-exhaustive, 36 more have been added shows the great development of X-ray structural determinations in recent times. Some of these structures deserve brief comment. 

There is a further complication in shallow lakes containing macrophytes (aquatic flowering plants, pteridophytes, and macroalgae). These take up and accumulate nutrients from the water and from the aquatic soil in which they are rooted (sediment). Although these plants are sometimes classed as nuisance weeds, they nevertheless act as an important alternative sink for nutrients which are denied to the plankton. In recent times, a key role of macrophytes in the successful and sustained management of water quality has been identified and explained. ... 

Flooded compressors use the asymmetric profile rotor extensively because the rotor s efficiency is most apparent in this size range. Flooded compressor size has, over the more recent times, been increased. The upper range is in the 7000 cfm range. While most applications are in air and refrigeration, certain modifications can make it applicable for process ga.s service. One of the considerations is the liquid used for the flooding. 

Butadiene and styrene may be polymerised in any proportion. The Tfs of the copolymers vary in an almost linear manner with the proportion of styrene present. Whereas SBR has a styrene content of about 23.5% and is rubbery, copolymers containing about 50% styrene are leatherlike whilst with 70% styrene the materials are more like rigid thermoplastics but with low softening points. Both of these copolymers are known in the rubber industry as high-styrene resins and are usually used blended with a hydrocarbon rubber such as NR or SBR. Such blends have found use in shoe soles, car wash brushes and other mouldings but in recent times have suffered increasing competition from conventional thermoplastics and to a less extent the thermoplastic rubbers. 

The polychloroprene suppliers have, however, faced several difficulties in recent times. These include ... 

In 1997 it was estimated that global production of PET was about 16.7 X 10 t.p.a., of which 12 million tonnes was used in textiles, 2 million tonnes for audio and video film (with a small quantity for technical mouldings) and 3 million tonnes for packaging, particularly bottles. The tremendous growth in the bottles market from zero in the late 1970s to 1.5 million tonnes in the USA alone in 1998 is, in consumption terms, one of the most spectacular examples of growth in plastics materials in recent times and will be considered later in this section. 

To minimize surface damage, static SIMS mass spectrometers should be as efficient as possible for detecting the total yield of secondary ions from a surface. Also, to be able to separate elemental from molecular species, and molecular species from each other, the mass resolution usually given as the mass m divided by the separable mass Am, should be very high. With this in mind, two types of mass spectrometer have been used - in early work mainly quadrupole mass filters and, more recently, time-of-flight mass spectrometers. 

In recent times the inspection and test activities have been transferred into the production departments of organizations, sometimes retaining the labels and sometimes reverting to the inspection and test labels. 

Fout-cenieted addition of RCu to an enone was widely discussed in tlie 1960s iSclieme 10.3a) [51-53], wb de discussions on six-centered ttansition states have continued imt d recent times iSclieme 10.3b) [54], Hiese meclianisms do not, bowevet, explain tbe fotciiation of E/Z mixtures of enolate stereoisomers [20, 55] and must now be considered obsolete. 

The connections between chemical constitution, on the one hand, and colour or physiological action on the other have been continually studied for many years, but the allied property of odour has only engaged occasional attention within quite recent times. 

For many years, gear shifting in the automatic transmission has been controlled hydraulically, typically in response to vehicle speed and the position of the engine inlet throttle. In recent times that control has been reassigned to an electronic computer, which facilitates gi eater smoothness and flexibility in shift control. 

In more recent times the location decision has been influenced by government intervention, e.g. ... 

Calorised Coatings The nickel- and cobalt-base superalloys of gas turbine blades, which operate at high temperatures, have been protected by coatings produced by cementation. Without such protection, the presence of sulphur and vanadium from the fuel and chloride from flying over the sea promotes conditions that remove the protective oxides from these superalloys. Pack cementation with powdered aluminium produces nickel or cobalt aluminides on the surfaces of the blade aerofoils. The need for overlay coatings containing yttrium have been necessary in recent times to deal with more aggressive hot corrosion conditions. 

In more recent times, large doses of vitamin C have been claimed to prevent the common cold, cure infertility, delay the onset of symptoms in acquired immunodeficiency syndrome (AIDS), and inhibit the development of gastric and cervical cancers. None of these claims have been backed by medical evidence, however. In the largest study yet done of the effect of vitamin C on the common cojd, a meta-analysis of more than 100 separate trials covering 40,000 people found no difference in the incidence of colds between those who took supplemental vitamin G regularly and those who did not. When taken during a cold, however, vitamin C does appear to decrease the cold s duration by 8%. 

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