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Photofragmentation spectroscopy—the study of "half collisions" with polarized light of subdoppler line width—opens a window to look into the structure of molecules. The energy partitioning among the particular degrees of freedom of the products of the fragmentation reaction is described by the scalar properties, the direction and magnitude of a particular type of motion is described by the vector properties. The measurement of the scalar and vector properties allows a pictorial view of the intermediate state. The forces which make the fragments fly apart or rotate and vibrate can be "seen" from the line shapes. Information on the unstable intermediate state is gained from the stable fragments long after the dissociation of the parent molecule. In particular, information on the "lifetime" of the intermediate on a femtosecond time scale can be obtained.
A number of molecules, mainly three and four atomic, have been studied by this technique. Hydrogen peroxide has shown up as a textbook example. A complete analysis was possible including not only correlation of different types of fragment motion but also a correlation of the two coincident particles formed from the same parent molecule. The experimental results are in full agreement with recent calculations of the dynamics of the fragmentation on newly obtained potential energy surfaces. Hydrogen peroxide shows a strong dependence of its potential energy on the dihedral angle in the two electronic states amenable to laser excitation. This experiment further demonstrates that an analysis is also possible if two states are excited simultaneously.
Another good example is the fragmentation of hydrazoic acid for which also coincident pair correlation has been treated. Here again the results agree excellently with a qualitative picture which can be drawn from recently calculated ab initio potential energy surfaces. The HN3 example is much more complicated than the former one due to its higher structured upper potential energy surface. Strong rotational excitation is observed in the N2 fragment leaving the NH fragment rotationally cold.
The treatment of vector correlations in molecular photofragmentation is a powerful tool for the study of the dynamics of molecular dissociation reactions.
Timothy Findley's "The Wars" is a very powerful and disturbing book. Despite the novel's historically distant setting, the events of "The Wars" do not seem distant at all: the reader is brought close to the horrible violence of World War I and its devastating impact on a young mind. The question is why? The topic is certainly not new — we are аll too familiar with the World War I period. The theme is also an old one — a young man's loss of innocence and baptism by fire on the battlefield. The novelty and vividness of Findley's work are attributable to another source: its form. I hope to show that one artistic device in particular — de-automatization — is largely responsible for the novel's powerful impact on the modern reader.
Seven species of Radula are reported from the Galapagos Islands, including Radula santacruziana spec. nov. The majority of the species are common and widespread in the neotropics; two (including the new species) are endemic to the Galapagos. R. cornucopiae Spruce and R. mollis Lindenb. et Gott. are reduced to synonymy, resp. under R. episcia Spruce and R. quadrata Gott. et al.
A preliminary treatment of the Central American species of Octoblepharum (Musci: Calymperaceae)
(1991)
The species of Octoblepharum occurring in Central America have been critically examined. Six are recognized as valid species: O. albidum, O. cocuiense, O. cylindricum, O. erectifolium, O. pulvinatum and O. stramineum. Synonyms are given for these species: O. longifolium = O. albidum; O. mittenii, O. fragillimum, O. pellucidum and =O. pulvinatum var. angustifolium are synonyms of O. cocuiense; O. juruense and O. densum = O. pulvinatum and O. purpureo-brunneum = O. stramineum. All species are widely distributed in the area except for O. cylindricum and O. stramineum that are known only from Belize and Panama respectively.
The aim of this short and selected reference list is to guide bryologists in the very scattered African literature when they try to identify specimens, as no standard bryofloras are available for the whole of Tropical Africa. The idea to compile such a reference list was raised during the Tropical Bryology Workshop held by the British Bryological Society, in the Botany School of Cambridge University, on the 21st of September 1990. The list is based on the senior author’s private library and files. We hope that the publication and distribution of such a list, even if incomplete, will prove to be useful for the future taxonomic and floristic works in Tropical Africa with special reference to the Bryologia Africana Project. We also hope that it will encour- age further collecting and identification by those who are not well versed in or do not possess the very diversified taxonomic literature on African bryo- phytes.
A synopsis is provided of 88 species in 17 genera currently recognized in Lejeuneaceae subfamily Ptychanthoideae sensu lato (including Nipponolejeunea) of Asia. Taxonomic novelties include Thysananthus flavescens (Hatt.) comb. nov. (for Mastigolejeunea flavescens (Hatt.) Mizut.), Spruceanthus macrostipulus (Steph.) comb. nov. (for Archilejeunea macrostipula (Steph.) Verd.) and the reduction of Platylejeunea Mizut. to synonymy under Lopholejeunea.
Twenty-eight species of epiphyllous liverworts were identified from twenty-five sites in Kowloon Peninsula, Hong Kong. Twenty-four of these species are new records to Hong Kong, while four of them are new epiphyllous records to the Chinese mainland. The majority of the sites are located between 30-200 m above sea level, representing the lowest altitude of epiphyllous liverworts found in the Chinese mainland. Characteristics of the host plants bearing epiphyllous liverworts are briefly discussed. The following new combination is proposed: Cololejeunea pseudolatilobula (Chen & Wu) But & Gao comb. nov. (Pedinolejeunea pseudolatilobula Chen & Wu).
88.Campylopus hildebrandtii (C. Müll.) Jaeg. is reported as new to Ethiopia. 89. The combination Campylopus flexuosus (Hedw.) Brid. var. incacorralis (Herz.) J.-P. Frahm is validated. 90. Campylopus sedgwickii Dix., a species hitherto regarded as endemic to Sri Lanka, is recognized as a synonymous with C. recurvus (Mitt.) Jaeg. 91. The Campylopus fragilis complex in SE-.Asia has been revised. It consists of C.. fragilis (Brid.) B.S.G. in southern China, C. goughii (Mitt.) Jaeg. occurring from southern India to Sikkim and Bhutan and C. zollingerianus (C. Müll.) Bosch & Lac. occurring from Indonesia to the Philippines and also in Hawaii. Campylopus zollingerianus has proved to be the legitimate name for C. boswelii (C. Müll.) Par. and C. crispifolius Bartr. and not for C. goughii. All three species are distinguished mainly by the shape of the upper laminal cells only and accordingly, C. goughii and C. zollingerianus are placed as geographical vicariant races as subspecies to C. fragilis.