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A role of the Qв binding protein in the mechanism of cyanobacterial adaptation to light intensity?
(1986)
Growth of the unicellular blue-green alga Anacystis nidulans in media containing sublethal concentrations of DCMU-type inhibitors of photosynthetic electron transport in strong white light gave rise to shade type appearance in this organism, as characterized by an increased ratio of phycocyanin to chlorophyll and reduced ratios, both, of carotenoids to chlorophyll and of total chlorophyll to P700. Shade type in Anacystis was caused neither by phenolic inhibitors tested nor by those known to bind to the cytochrome b6/f-complex. Surprisingly enough, the molar ratio of phycocyanin to chlorophyll in artificially shade adapted Anacystis1 grown in strong white light in the presence of 10-6 м atrazine, was found to increase with temperature for a given light intensity and with light intensity for a given temperature.
Mutants of Anaeystis with a reduced binding capacity for DCMU-type herbicides due to an amino acid exchange in the 32 kDa Qв-binding polypeptide, also called D-1 protein, were ob- served to show shade type appearance in strong light, to respond very little to changes in light intensity and to show a reduced capability to further change their appearance to shade type by binding of competitors of Ob to the 32 kDa polypeptide.
In Anaeystis a concentration of atrazine (10-7 м), ten times lower than the one causing the highest rate of shade adaptation (10-6 м), was shown to induce an optimum in cell density, which in turn resulted in an optimum in light-dependent O2 evolution. Both factors together might be responsible for the so-called greening effect observed in higher plants treated with sublethal concentrations of DCMU-type inhibitors of photosynthetic electron transport.
The cyanobacteria Anabaena cylindrica and Synechococcus leopoliensis (= Anacystis nidulans) were grown at different levels of UV-B radiation (439. 717, 1230 and 1405 J m -2d-1 weighted according Caldwell, 1971) for 2 days. Dry weight was hardly affected but phycocyanin content of both species decreased linearly to the level of UV-B radiation. Contents of protein, carotenoids and chlorophyll a were reduced only after exposure to high doses (1230 J m-2d-1) of UV-B radiation. Photosynthetic 14CO2 fixation of Anabaena cells was reduced linearly with increasing UV-B dose whereas no effect could be observed in Synechococcus. A depression of photosynthetic 15N-nitrate uptake was found after UV-B stress in both species. UV-B irradiance caused an increase of 15N-incorporation into glutamine, but no effect was noted for incorporation into alanine or aspartic acid. An increase of 15N-excess in glutamic acid linear with the UV-B dose was observed in Synechococcus, only. Patterns of 14C-labelled photosynthetic products were either less affected by UV-B radiation (Anabaena) or an enhancement of 14C-label in total amino acids was detected (Synechococcus). The amount of total free amino acids increased parallel to the level of UV-B radiation. Only, the high dose of UV-B (1405 J m-2d-1, weighted) results in a decrease of the glutamine pool. Our results indicate an inhibition of glutamate synthase by UV-B irradiation in Anabaena, only. Results were discussed with reference to the damage of the photosynthetic apparatus.
Potential energy, dipole moment, and electronic transition moment functions for the A 3Πand X3Σ- states of PH have been calculated from highly correlated electronic wavefunctions. The electric dipole moments in the vibrational ground state of PH are calculated to be 0.637 Debye (A 3Π) and 0.403 Debye (X3Σ-). The predicted rates of spontaneous emission between low lying vibrational states of the X state lie in the range of 46 to 109 sec-1 (PH) and 12 to 30 sec-1 (PD). The calculated radiative lifetime of the v' = 0 level in the A 3Π state of 400 ns is lower by about 10 percent than the most recent experimental value. The classical intersection of the 5Σ- and the A 3Πstate has been calculated to lie between v' = 2 and 3 with an expected uncertainty of about 500 cm−1, whereas the onset of the rotationally dependent predissociation lies at v' = 0, J' = 11.
This paper describes the reaction of Pulegium vulgare and a number of species from the same locality upon the different flooding regimes of four consecutive years. These species mainly belong to the Lolio-Cynosuretum and the Ranunculo-Alopecuretum. The results show that the effect of a flood on the vegetation strongly depends on the month (the date of the year) during which the inundation occurs. A flood of shorter duration in late summer has a stronger impact than a longer inundation in spring and early summer.
Pulegium vulgare strongly decreased after being flooded in July and August and did not recover in the subsequent year. On account of the behaviour of the species after a summer inundation, seven groups were broadly distinguished.
The Bethylidae are a primitive family of aculeate Hymenoptera which presently consists of about 2,200 nominal species. They are worldwide in distribution and all species are primary, external parasites of Lepidoptera and Coleoptera larvae. Due t o their host associations, bethylids are potentially useful for the biological control of various agricultural pests in the aforementioned groups. Unfortunately, the true potential of bethylids in applied biological control cannot be ascertained now because they have been used infrequently. Some species show strong promise, but t h e i r use is handicapped by a relative lack of basic taxonomic and biological knowledge. The most recent world catalog for bethylids is Kieffer (1914). A world catalog is forthcoming (Gordh, in prep.). There has never been a compilation of the world literature.
The only published checklist of the Hydradephaga from the Maryland area is Ulke (1902) who records 65 species from the District of Columbia. The present paper lists 121 species as occurring in Maryland. Comparable lists for other states are as follows: Young (1954), 120 species from Florida; Folkerts (1978), 120 species from New York; and Brigham (1982) and Sanderson (1982), 115 species from North and South Carolina. Some of the identifications are questionable until generic revisions are completed. This is especially true of Hydroporus and Gyrinus.
Presently, only a single species of the genus Diplocentrus is known from northeastern Mexico, D. whitei (Gervais) (Hoffman 1931 ). This species is dark brown to black and is quite large, with adults 65-75 mm long. Recent collecting in the mountains near Monterrey and El Potosi, Nuevo Leon, Mexico has revealed the presence of a much smaller, more lightly-colored species. The description of this new species is the subject of the present paper. Nomenclature and mensuration essentially follows that of Stahnke (1970), with the following exceptions: carinal terminology and cheliceral measurements are after Francke (1975, 1977) and trichobothrial terminology is after Vachon (1974). All measurements were taken with an American Optical Model 569 dissecting microscope equipped with an ocular micrometer calibrated at 10x.
This paper is a catalog of the Ephemeroptera known from the British Crown Colony of Hong Kong. It includes all known references for each species, along with an indication of the type localities and depositions of type specimens. For each reference the stage (male, female, or nymph) is indicated if relevant. Keys which include the species also are indicated. The recorded distribution for each species is listed. For each genus are given the reference to the original description, information on the type species, and any synonyms. Abbreviations of places of type deposition are as follows: (BMNH), British Museum (Natural History), London; (Cornell), Cornell University, Ithaca, New York; (DEI), Deutsches Entomologisches Institut, Eberswalde; (Hamburg), Zoologisches Staatsinstitut und Zoologisches Museum, Hamburg; (Hsu), personal collection of Y.-C. Hsu [the late Prof. Hsu indicated (personal communication) that because of events in China over the past few decades these specimens should be considered destroyed or lost]; (Utah), University of Utah, Salt Lake City. Although the taxonomic knowledge of the Hong Kong mayflies is still somewhat sketchy, there are substantial ecological studies ongoing at this time. Therefore, in order to facilitate future studies and comparisons of data, I have included in this catalog the "morphospecies" of Dudgeon (1982a, b, 1983, 1984a, b). The reader should be aware that many of the taxonomic assignments of these morphospecies are preliminary and actual placement will have to await future taxonomic studies. This paper is one in a continuing series of catalogs of the Ephemeroptera (cf. Hubbard & Peters 1978, Hubbard & Pescador 1978, Hubbard & Savage 1981, Hubbard 1982a,b).
This paper updates and summarizes the ant fauna of Alachua County, Florida, with two basic objectives. The first objective is presentation of a current, documented check-list consistent with existing taxonomy and an insight on species groups where taxonomic changes are likely in subsequent revisions. The second objection objective seeks to identify changes in the fauna since Van Pelt’s pioneer survey of 1948, and provide a basis for similar comparisons in the future. The county consists of 902 square miles in north-central Florida and embraces essentially all inland habitats of the northern peninsula. This rich habitat variability is reflected in its ant fauna of 110 species. Few other regions of comparable size and latitude support a larger ant diversity also documented in part for greater than 50 years. A review of the earlier work, current taxonomic authorities, and questionable or rejected records precede the new list.
This supplement concerns species of the family Sphingidae (pages 425-444) introduced to Hawaii since 1958 and now firmly established. The introductions are connected with the rapid growth of air traffic between Hawaii and SE Asia since the mid-1970s. Of special interest is the fast interisland colonization as reported in the HAWAII COOPERATIVE ECONOMIC INSECT REPORT (HCEIR), published by the State Department of Agriculture, Honolulu, HI until 1980, subsequently called HAWAII PEST REPORT.
The generic name Brachycoryna was first published by Guerin-Meneville (1844) who at that time also described B. pumila which was the only included species (type species by monotypy). The locality data given by Guerin's material is "Carthagene" (Cartagena, Columbia). Guerin correctly receives authorship of Brachycoryna since a single combined description of a new genus and new species published before 1930 is considered an "indication" for each name (Intern. Code 2001. Nomen., Article 12). Some authors (Weise, 1911 a,b; Papp, 1953) had assigned authorship to Baly (1885) who published the first generic description and reported B. pumila from Mexico, Guatemala, and Nicaragua. There have only been two other generic descriptions published: Weise (1911b) and Monros and Viana (1947).
The definition of the Tribe Pheidologetini in the ant subfamily Myrmicinae has always been problematic. Emery (1922) erected the tribe to contain the genera Pheidologeton, Oligomyrmex, Aneleus, Lophomyrmex, Trigonogaster, Ekebomyrma, Carebara and Paedalgus, but Wheeler (1922) put all these genera in the Solenopsidini. Neither Emery nor Wheeler satisfactorily defined either tribe. More recently, Ettershank (1966) proposed the "Pheidologeton genus group" composed of Pheidologeton, Oligomyrmex (including most Aneleus), Lophomyrmex, Carebara, Paedalgus and Anisopheidole, but still uncertainty remains as to relationships of these genera and even the definitions of the genera themselves. New characters and new means of analysis are needed to help resolve this problem.
The receipt, recently, of several requests for information and assistance in rearing blister beetles (Meloidae) has prompted me to prepare the following account of the rearing method used in my laboratory. In order to make the account as useful as possible to new students. I have included a considerable amount of information on meloid bionomics. Larval phases are designated as triungulin (TI, first grub (FG), coarctate (C), and second grub (SG). Where necessary, instar is indicated by a numerical subscript. The pupa and adult are symbolized by P and A, respectively. I assume that the reader has some knowledge of the taxonomy of the Meloidae.
The genera Paratella and Sephena were established by Melichar (1902) for complexes of species having distribution principally in New Guinea. However, three of Melichar’s new species of Paratella, i.e., fumaria, fusconigra and modesta, were known only from localities in Australia and/or New Zealand. Kirkaldy (1906) described Sephena argue, cinerea and rubida from specimens collected in Australia. He commented that they had the appearance of Paratella while having the characters of Sephena assigned by Melichar. Melichar (1923) and Metcalf (1957) each retained the above named species in Paratella and Sephena The type specimens of the species named above were examined in connection with my research on Kirkaldy and Melichar types, results of which are given in articles that have been submitted for publication elsewhere. To avoid duplicate citation of new synonymies, all synonymies given in this article should be considered to have prior designation by Medler, in press.
Fourteen new species of Adelphe are described, from several Caribbean islands, Central and South America.
Crepidodera Chevrolat is a genus of small metallic-colored flea beetles belonging to the family Chrysomelidae. Although these insects are quite common in the field and numerous in museum collections, the members of the genus in North America are, until now, poorly known. Heikertinger (1948-1950) recognized 4 taxa and recently, Lazorko (1974) described 3 additional species. These 7 species were recognized primarily on the basis of genital differences and were otherwise difficult to identify. Examination of a large accumulation of museum material and investigations in the field have indicated the presence of several additional species in the North American fauna. A detailed study of external characters, male genitalia and female spermathecae has revealed, in material previously referred to the Palaearctic species, C. fulvicornis (F.), a complex of closely related species. Essentially nothing was known about the biology of the North American species. General information on host plants was available and the general seasonal occurrence and habits of adults were described by Loan (1967b). However, the immature stages and life histories of all members of the genus were unknown. This has now been remedied with the discovery, during the course of this study, of the larvae of two species. The main purpose of this paper, therefore, is to consolidate the existing information on the genus in North America, describe 8 new species, redefine the previously described species, provide a key and illustrations to aid in their identification, and to describe the immature stages for 2 species. A discussion of the host plant relationships and the general life history of members of the genus is also presented.
Praestochrysis Linsenmaier contains those species of Chrysidinae with five teeth on the posterior margin of tergum III, first flagellomere (F-I) less than 3 times as long as broad (often much shorter), and clypeal length below antennal sockets (subantennal distance) not more than diameter of the midocellus (MOD). The genus is widespread in the Old World, but a majority of the known species are in the Ethiopian Region. Host records are rather few, but it is likely that nearly all species attack moth larvae and emerge from their cocoons. Praestochrysis shanghaiensis (F. Smith) is a well known parasitoid of the silk moth in the Far East.
Descriptions of species in the genus Sclerosococcus are primarily based on the female morphology (McKenzie 1958, Lambdin 1980). The lack of descriptions for males is attributed to their brief seasonal appearances (lasting only a few hours) and their small size that makes collection of adult specimens difficult. As a result, adequate descriptions for only a few males of Asterolecaniidae are available for comparisons. Of those species where males are known, most descriptions are of the tests or general morphological aspects (Russell, 1941). The most comprehensive descriptions for adult males in the family were provided for Asterolecanium proteae (Giliomee 1968) and for two species of Grammococcus (Miller and Lamdin 1978). The genus Sclerosococcus contains 4 species known from the Neotropical Region where they feed on bromelid hosts. Until now, no reference was made as to the existence of males of the species. My objective was to provide a description of the adult male of this rare species to better define the taxa. Measurements and illustration were made by microscopic examination of the allotype male. Terminology used to describe the external morphology, with few exceptions, was adapted from Theron (1958). All measurements are presented in micrometers.
A number of years ago we received a large lot of material collected by Robert G. and Clo M. Wind during their 1939-1940 expedition to the “East Indies” and published on the Danaidae and Satyridae of that trip (L. and J. Miller, 1978). One of the insects that the Winds considered to be of special significance was a male of a thecline that Bob Wind had intended to describe for his then wife. Both Bob and Clo asked us to describe the butterfly, but before we had an opportunity to describe the insect both Bob and Clo died. We now dedicate the description of this magnificent insect to their memories.
GLYPHICNEMIS Foerster is a small Holarctic genus in the subtribe Endaseina of the Gelini. Nearctic species were placed in PHYGADEUON Gravenhorst until Townes (1944) placed them in the subgenus GLYPHICNEMIS within ENDASYS Foerster. However, earlier Cushman (1925) had transferred PHYGADEUON CRASSIPES Provancher, a junior synonym of G. MANDIBULARIS (Cresson), to GLYPHICNEMIS, and the Palearctic species, at first placed in PHYGADEUON, were included by Habermehl (1916) i n GLYPHICNEMIS, reduced t o a subgenus within STYLOCRYPTUS Thomson (1873). This status was continued until Townes (1970) listed and described GLYPHICNEMIS as a seperate genus.
The key description and illustrations of mouthparts, ocelli, and terminal abdominal segments by Bovinq & Craighead (1931) have been the only information on the larval stages of the genus Hemipeplus Latreille, except for the observation by van Emden (1942) that individuals of the genus would not key properly in Boving & Craighead's key. Their example was of an undescribed species from Cuba. The semidiagrammatic illustrations make it difficult to identify the species illustrated, although it may be H. marginipennis (LeConte). This paper is based on larvae collected by the authors, in each case associated with adults. From the family diagnosis of larval Mycteridae (Crowson & Viedma 1964). Hemipeplus larvae differ noticeably in the form of the sensorium, which Crowson & Viedma describe as “very short, dome-shaped”; in Hemipeplus it is elongate and conical. From the larva of Mycterus (described by Crowson & Viedma 1964) those of Hemipeplus also differ in having five ocelli on each side (cf. two), mala with an uncus and medial pit (cf. without uncus or medial pit), mola ridged (cf. not ridged), cardines not divided (cf. distinctly divided, labial palpi with only one distinct palpomere (cf. with two palpomeres), abdominal asperities absent (cf. asperities present), and different form of spiracle (compare fig. 13 with fig. 4 in Crowson & Viedma 1964). Larvae of Hemipeplus are more similar to that of Eurypus muelleri Seldlitz (described by Costa & Vanin 1977) than to that of Mycterus. As in Hemipeplus, Eurypus larvae possess five ocelli arranged in rows of three and two on each side; two pairs of tubercles at posterior margin of abdominal sternite IX; mala with an uncus, and cardines divided. Hemipeplus larvae differ from those of Mycterus most notably in the form of abdominal tergite IX (see Costa & Vanin 1977:fig. 2 ) . The uncus is located on the mesal margin of the mala in Hemipeplus, whereas it is located on the ventral aspect of the mala in Eurypus.
A recently found fossil from the old Scudder pit (?) appears to be a large female horntail. It shows the ventral aspect. Compared with modern Siricidae, the length of its ovipositor in relation to the body proper suggests modern Xeris spectrum. Unfortunately the venation is incompletely preserved on both wings. In addition to this the forewings and hindwings overlap to some extent on each side. What venation is decipherable is seen in the two sketches. It does not seem to agree with any of the modern genera examined but approaches that of Sirex more closely than any other. Both antennae are faintly indicated. They are stout, many-segmented and in keeping with those of Siricidae. Both hind legs are preserved faintly almost throughout their length. They are stout, and the individual segments are clearly defined.
The only lists of Hydrophiloidae (Coleoptera: Hydrophilidae, Helophoridae, Hydrochidae, and Hydraenidae) from the mid-Atlantic region are Ulke (1902) who reported 46 species from the District of Columbia and Matta (1974) who presented keys and short descriptions for the 49 aquatic species of Hydrophilidae of Virginia. The following checklist records 103 species (75 aquatic) from Maryland. Comparable lists of aquatic species for other states are as follows: 53 species recorded from Florida by Young (1954); 20 species recorded from Ithaca, New York by Swenson (1982); 67 species from North and South Carolina by Brigham (1982); and 47 species from Illinois by Wooldridge (1967). Hatch (1965) recorded 128 species (of all habitats, 102 aquatic) from the Pacific Northwest; and 88 species (67 aquatic) reported from New York by Leng (1928).
The recently increased importance of sunflowers (Helianthus annuus Linnaeus) as a crop has brought with it an increased interest in the sunflower maggot, a long-recognized common name for Strauzia longipennis (Wiedemann). The larva of this species bores downward in the stem and feeds upon the pith of sunflowers. Until recently the genus Strauzia was considered to include only the type-species S. longipennis, with 7 varieties (Foote, 1965). It is now known that some of these varieties should be classed as distinct species, differing morphologically and biologically.
Early dietary Islamic law
(1986)
Various multivariate statistical procedures are used to distinguish species in the reef-coral family Poritidae through a continuous Neogene sequence (five myr time interval) in the Cibao Valley of the northern Dominican Republic. Some older (by approximately 10 myr) material from the same region is also included in the analyses. The material consists of approximately 450 colonies (120 of which are measured) from 92 localities in four river sections. The colonies are first sorted into three genera, and approximately 30 characters measured on five calices per colony. The data are analyzed using cluster and canonical discriminant analyses to group the colonies into clusters representing species. Five species are so defined in Porites and three in Goniopora. These groupings are then used statistically to reclassify type specimens for 22 of the 25 described species of Neogene Caribbean poritids. Eight described species are thereby synonymized with four previously-described species in Porites and one new species of Porites, Porites convivatoris. n. sp., is discovered. Five described species are synonymized with two previously-described species in Goniopora. The stratigraphic range of three species of Porites and three species of Goniopora is also shown to extend back to the late Oligocene, thereby diminishing the significance of any presumed early Miocene adaptive radiation. Only one species was found to be endemic to the Dominican Republic and only one confined to the northern Caribbean. The rest are widely distributed throughout the Caribbean. Thus, the endemism previously believed common during the Neogene is shown to be far less extensive. Evolutionary trends within each species are preliminarily analyzed for various characters using non parametric statistical procedures. In general, the results show that seven species experienced little or no evolutionary change (= stasis) through the sequence. Slight increases in corallite size are detected in two species, an increase in colony height in one species, and a more rounded colony shape in one species. These trends may be related to the general deepening of the environment; however, little correlation is found between lithology and morphology within species. Preliminary analyses of the relationship between intraspecific variation and poritid abundance and diversity yield significant results, suggesting that intraspecific trends may be environmental and that future study of coral species associations may offer insight into paleoenvironmental interpretations. Statistical comparisons with the Miocene Mediterranean poritids show that no species co-occur in the two provinces during the Neogene. Similarly, none of the studied Neogene species of Porites resemble modem Caribbean species of Porites, signifying that all nine poritid species studied must have become extinct and the modem Caribbean species of Porites radiated during the late Pliocene or early Pleistocene. This study represents part ofa multidisciplinary project on the stratigraphy of the northern Dominican Republic, coordinated by P. Jung and J. B. Saunders of the Naturhistorisches Museum Basel, Switzerland.
The genus Squamidium, a group of mosses with a tropical to subtropical American-African distribution, consists of two sections and seven species (prior to this study 27 species were recognized): sect. Squamidium (S. leucotrichum, S. livens, S. isocladum, S. nigricans, S. brasiliense) and sect. Macrosquamidium (S. macrocarpum and S. diversicoma). Twenty-four names are treated as syn. nov., three are provisionally excluded pending an examination of their types, and one new combination is made: Orthostichopsis pilotrichelloides (Sehnem) Allen & Crosby. Section Squamidium ist characterized by immersed capsules, stolon leaves with entire margins, and a relatively high basal membrane. Section Macrosquamidium is characterized by exserted capsules, stolon leaves with sharply recurved marginal teeth, and a relatively low basal membrane. The genus is retained in the Meteoriaceae. Within the Meteoriaceae Squamidium, is most closely related to Zelotmeteorium from which it differs only by its lack of squarrose-recurved leaves and its more well-developed alar cells. Squamidium, which in the absence of sporophytes has been confused consistently with Orthostichopsis, is separated from that genus on the basis of its lack of pseudoparaphyllia, weaker costae, lack of a distinct region of reddish cells across the leaf base, and strongly decurrent alar cells.
We discuss the possibility that nuclei with very large baryon numbers can exist in the form of large quark blobs in their ground states. A calculation based on the picture of quark bags shows that, in principle, the appearance of such exotic nuclear states in present laboratory experiments cannot be excluded. Some speculations in connection with the recently observed anomalous positron production in heavy-ion experiments are presented.
If the local color symmetry in a quark-gluon matter is broken, the expectation value of the gluon field 〈Aμa(x)〉 may be different from zero. Such a gluon-condensed phase has been found in mean field approximation. The gluon-condensed phase is characterized by a static, periodic chromomagnetic field, which is coupled to a periodic spin-color density distribution of quarks and antiquarks. Transitions of first and second order type have been found between the gluon-condensed and normal phases, the latter characterized by the vanishing value of the mean gluon field.
We formulate a group-theoretical projection technique for the quantum-statistical description of systems with exactly conserved charges corresponding to local non-Abelian gauge symmetries. The formalism is specified for SU(N) internal symmetry and a partition function related to a mixed canonical–grand-canonical ensemble is defined. Its perturbation expansion is derived, and we point out potential applications. We also study single-particle Green’s functions for the calculation of mixed ensemble averages with the help of a generalized Wick’s theorem and find that a connected-graphs expansion is impossible.
Conversion processes in light nuclei with transition energies above the e+, e- pair creation threshold are investigated within an analytical framework. In particular, we evaluate the ratio of electron transition probabilities from the negative energy continuum into the atomic K shell and into the positive energy continuum, respectively. The possible role of monoenergetic positron conversion with respect to the striking peak structures observed in e+ spectra from very heavy collision systems is examined.
The inelastic excitation of the (1/2)+ (871 keV) state of 17O in the reaction of 13C on 17O is described by a time-dependent quantum mechanical model with two diabatic states and a classical treatment of the radial relative motion. The structures in the angle-integrated cross section are interpreted as caused by the barriers of the angular momentum-dependent potentials. The transition strength is enhanced by the Landau-Zener effect between the levels considered.
Phenomenological consequences of a hypothetical light neutral particle in heavy ion collisions
(1986)
We discuss the possibility that the line structure observed in the spectrum of the positrons produced in heavy ion collisions is due to the decay of a new neutral elementary particle. We argue that this can be ruled out unless one is willing to accept fine tuning of parameters, or to assume the dominance of nonlinear effects.
We compute the energy spectrum of photons which originate from the quark-annihilation process ss¯→γg in quark-gluon plasma. The spectrum peaks at an energy Eγmax∼2ms∼400 MeV in the rest frame of the plasma. We expect one photon from the above process in the energy range of 2ms±0.25ms per hundred quark-gluon plasmas of a size R=3 fm and a lifetime τ=6 fm/c formed in nuclear collisions.
The novel momentum analysis technique introduced by Danielewicz and Odyniec can be used to detect and exhibit collective flow in the light system Ar(1800 MeV/nucleon) + KCl where the usual kinetic energy flow analysis fails. The microscopic Vlasov-Uehling-Uhlenbeck theory which includes the nuclear mean field, two-body collisions, and Pauli blocking is used to study this phenomenon. The resulting transverse momentum transfers turn out to be quite sensitive to the nuclear equation of state. From a comparison with experimental data, evidence is presented for a rather stiff nuclear equation of state. The cascade model is unable to describe the data.
The influence of fluctuations of the shape degree of freedom in collisions of deformed nuclei with energies between 0.8 and 2.1 GeV/nucleon is analyzed on the basis of an intranuclear cascade simulation for the strongly deformed systems 46Ti+ 46Ti and 166Er+ 166Er. While there is a considerable sensitivity of the global event variables to the orientation for polarized beams and targets, this dependence disappears in the average over all orientations for impact parameter selected and integrated events. The dependence of the nuclear stopping and thermalization on the size of the system under consideration and on the bombarding energy is also investigated.
We study the recent claim that the intranuclear cascade model exhibits collective sidewards flow. 4000 intranuclear cascade simulations of the reaction Nb(400 MeV/nucleon)+Nb are performed employing bound and unbound versions of the Cugnon cascade. We show that instability of the target and projectile nuclei in the unbound cascade produces substantial spurious sidewards flow angles, for spectators as well as for participants. Once the nuclear binding is included, the peak of the flow angle distributions for the participants alone is reduced from 35° to 17°. The theoretical ‘‘data’’ are subjected to the experimental multiplicity and efficiency cuts of the plastic ball 4π electronic spectrometer system. The flow angular distributions obtained from the bound cascade—with spectators and participants subjected to the plastic ball filter—are forward peaked, in contrast to the plastic ball data. We discuss the uncertainties encountered with the application of the experimental efficiency and multiplicity filter. The influence of the Pauli principle on the flow is also discussed. The lack of flow effects in the cascade model clearly reflects the absence of the nuclear compression energy that can cause substantially larger collective sidewards motion—there is too little intrinsic pressure built up in the cascade model.
Time dependent dirac equation with relativistic mean field dynamics applied to heavy ion scattering
(1986)
We treat the relativistic propagation of nucleons coupled to scalar- and vector-meson fields in a mean-field approximation. The time-dependent Dirac and mean-meson-field equations are solved numerically in three dimensions. Collisions of 16O(300, 600, and 1200 MeV/nucleon) + 16O are studied for various impact parameters. The results are compared to other recent theoretical approaches. The calculations predict spallation, large transverse-momentum transfer, and positive-angle sidewards flow, in qualitative agreement with the data in this energy regime.
Nuclear resonance fluorescence measurements with linearly polarized bremsstrahlung were performed to determine parities of bound dipole transitions in 206Pb. A new 1+ level at 5800 keV was found, which has almost the same strength as the isoscalar M1 transition in 208Pb. Twenty-four further dipole states in 206Pb below 7.6 MeV possess negative parity.
Nuclear resonance fluorescence experiments with linearly polarized bremsstrahlung were performed to determine parities of strong dipole transitions in 40Ar. A total of 14 transitions—ten of them previously unknown—in the energy range from 4.7 to 10.2 MeV could be identified. From this experiment it is evident that the main dipole strength to bound states is due to E1 excitations. An upper limit of B(M1) [up arrow] <0.5 µN2 was found for individual magnetic dipole excitations in 40Ar in the energy region below neutron threshold.
A detailed study of pion production in inelastic and central nucleus-nucleus collisions was carried out using a 2 m streamer spectrometer. Nuclear targets mounted inside the streamer chamber were exposed to nuclear beams of 4.5 GeV/c/nucleon momentum. A systematic study of the influence of the central trigger on observed data is performed. The data on multiplicities, rapidities, transverse momenta, and emission angles of negative pions are presented for various pairs of colliding nuclei. Intercorrelations between various characteristics are studied and discussed. The results are compared with predictions of some theoretical models. It is shown that the main features of the pion production in nuclear collisions can be satisfactorily described by a model assuming independent nucleon-nucleon collisions with subsequent cascading process. However, the observed correlation between Lambda and pion characteristics seems to be unexplained by this picture.