bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conodont bio-events, cladistics and response to glacio-eustasy, Ordovician-Silurian boundary through Llandovery, Anticosti Basin, Québec
Authors: Zhang Shunxin , Barnes Christopher R. 
Published: September 2007

Abstract

Conodont diversity was severely reduced during the terminal Ordovician mass extinction. Few species, mainly coniform taxa, survived across the Ordovician-Silurian boundary. The nature and timing of the post-extinction recovery and diversification have previously been difficult to assess, due to limited knowledge and preservation of the earliest Silurian faunas. Recent documentation of early Llandovery conodont faunas from a complete stratigraphic succession on Anticosti Island, Québec, along with the data re-examined from earlier detailed studies, provides the basis for a new analysis. Five evolutionary cycles are recognized through the Llandovery, together with a distinct set of bio-events that are interpreted as immigration, emigration, origination, and extinction events through consideration of global occurrence data for Llandovery conodonts. These events are supported by the detailed sampling and stratigraphic range data, as well as the first cladistic analysis of the four key genera:
Oulodus, Ozarkodina, Pterospathodus
, and
Rexroadus
. The Anticosti Basin may have been an important centre of evolutionary radiation, given that several genera and species have first appearances in this region and that initial evolutionary lineages can be established for many taxa. Many faunal variations appear to be correlated to eustatic events as well as the changing ocean-climate state through this boundary interval.
Palynostratigraphy of the classic Portland and Purbeck sequences of Dorset, southern England, and the correlation of Jurassic-Cretaceous boundary beds in the Tethyan and Boreal realms
Authors: Hunt Chris O. 
Published: September 2007

Abstract

Placement of the Jurassic-Cretaceous boundary and its correlation between the Tethyan and Boreal realms are still contentious. The distribution of stratigraphically significant dinoflagellate cysts in the Portland Stone and Purbeck formations of the Isle of Purbeck, Dorset, UK provides a basis for direct correlation between these sections and the type Berriasian in southeast France. The base of the Berriasian — and thus of the currently accepted Jurassic-Cretaceous boundary — most probably lies at the base of the Cypris Freestones in the Purbeck Formation. Miospore correlation between the Dorset sections and ammonite-bearing rocks in the Spilsby Province suggests that the base of the Cretaceous lies close to the base of the
Subcraspidites preplicomphalus
zone in the Boreal Realm.
Chronostratigraphy of proposed Turonian-Coniacian (Upper Cretaceous) stage boundary stratotypes: Salzgitter-Salder, Germany, and Wagon Mound, New Mexico, USA
Authors: Sikora Paul J. , Howe Richard W. , Gale Andrew S. , Stein Jeffrey A. 
Published: September 2007

Abstract

A knowledgeable choice for a stage boundary stratotype is dependent upon obtaining high-resolution stratigraphic data. Detailed analyses conducted for the two potential Turonian-Coniacian stage boundary stratotypes that were considered at the Second Cretaceous Stage Boundary Symposium provide both positive and negative insights for consideration. The Salzgitter-Salder Quarry in central Germany (which was recommended by the symposium) contains abundant bivalve fossils, including the recommended boundary datum: the lowest occurrence of the inoceramid bivalve
Cremnoceramus deformis erectus
. Foraminifera are also abundant, but extensive diagenetic recrystallization seriously degrades nannofossil and palynomorph recovery and limits the potential of the section for stable isotope stratigraphy and radiometric dating. Furthermore, palaeoenvironmental analysis indicates that much of the Salzgitter stage boundary interval has resulted from allochthonous sedimentation, indicating that the well-developed lithological cyclicity between limestone and marlstone that occurs in the section is largely autocyclic. The orbital cyclostratigraphic potential of the section is therefore also in question.

The Wagon Mound outcrop in northeastern New Mexico, USA, has good recovery and biostratigraphic control for all three microfossil groups, but the base of
C. deformis erectus
occurs above the section, by definition placing the section entirely in the Upper Turonian Well-preserved ammonites and inoceramid bivalves are also recoverable in over half of this section. Facies have not been recrystallized and represent continuous autochthonous sedimentation with sharply defined lithological cyclicity between limestone/marlstone couplets on a fine stratigraphic scale. In addition, a number of bentonites with proven datability occur in the section. Thus the bio- and chemostratigraphic dating potential, as well as the radiometric dating potential, of the section are good. However, much of the section is composed of carbonaceous, dysoxic facies with abnormal marine micro- and macrofossil assemblages, limiting study of the stratigraphic or palaeoecological trends leading up to the boundary.

The absence of the datum at Wagon Mound is puzzling, because microfossil biostratigraphy suggests that the section is substantially coeval with the Salzgitter-Salder section. The
C. deformis erectus
datum may thus be diachronous. Until the suitability of the recommended boundary datum is addressed, a reasoned choice of a section for the boundary stratotype is not possible. In any case, the absence of
C. deformis erectus
and the abnormal facies in the lower part of the Wagon Mound section, and the extensive diagenesis and partly allochthonous nature of the Salzgitter-Salder section, are serious enough problems to warrant rejection of both sections as stratotypes.
Upper Palaeocene and Lower Eocene interval in the Dieppe–Hampshire Basin: biostratigraphic analysis based on pyritized diatoms
Authors: van Eetvelde Y. , Dupuis C. 
Published: September 2007

Abstract

Assemblages of brackish and marine pyritized diatoms have been examined from Thanetian and Ypresian sediments in the Dieppe–Hampshire Basin. Two sites were studied: the borehole of Saint-Josse and sections at Ailly, both located in northern France. Pyritized diatoms are preserved in the deposits by epigenesis or as internal moulds by the growth of pyrite crystals in internal cavities. In both sites studied, most groups of
in situ
microfossils (e.g. dinoflagellates, foraminifera, nannoplankton) were extremely rare or absent, in contrast to pyritized diatoms, which showed good recovery, thereby proving their utility across this interval. The Palaeocene-Eocene boundary referred to this study is the official boundary defined by the Carbon Isotope Excursion. This is recorded in both sites studied. Diatom assemblages change character through the stratigraphic sequence, with three major diatom assemblages being defined which provide a key reference marker for the Palaeocene-Eocene boundary sediments from the Dieppe–Hampshire Basin. The first assemblage, D1, is characterized by the abundance peak of
Coscinodiscus morsianus
var.
moelleri
and
Coscinodiscus morsianus
var.
morsianus
. This assemblage is recorded in Thanetian and Lower Sparnacian facies. The second assemblage, D2, is defined by the abundance peak of
Fenestrella antiqua
, the downhole occurrence of
Coscinodiscus morsianus
sp., and a great diversity of circular diatoms. The upper part of this zone is marked by the greatest occurrence of
Fenestrella antiqua
and the extinction of
Coscinodiscus morsianus
var.
moelleri
. This assemblage corresponds with the upper part of the Sparnacian facies. The last assemblage (D3), of Early Ypresian age, is characterized by the presence of
Aulacodiscus, Trinacria, Craspedodiscus
and the great diversity of triangular, oval and bipolar species; these are held to indicate a marked increase in marine influence. These diatom assemblages from the Dieppe–Hampshire Basin show similarities to those from the North Sea Basin. Correlations between these two basins are possible by the use of pyritized diatoms. Thanks to these correlations, it is now possible to locate the Carbon Isotope Excursion in the North Sea Basin.
Palaeobiotope analysis and palaeoenvironmental reconstruction of the Palaeocene-Early Eocene ostracodes from east-central Sinai, Egypt
Authors: Elewa Ashraf M. T. , Morsi Abdel-Mohsen M. 
Published: September 2007

Abstract
Quantitative study of the ostracode assemblages from the Palaeocene to Early Eocene succession exposed along the area of east-central Sinai extending from the Egma Plateau in the south to Areif El Naqa in the north, using cluster analysis based on the customary presence/absence data matrix of frequencies (the Jaccard coefficient of similarity), has resulted in the distinction of five ecozones in the Early Palaeocene to Early Eocene intervals. Correspondence analysis applied to the same data matrix has led to the identification of five environmental factors affecting the distribution of the whole ostracode assemblage of the study area. These are the time factor or vertical distribution (second latent vector), water depth (third latent vector), degree of energy (fourth latent vector), water temperature as a function of depth (fifth latent vector), and oxygen concentration (sixth latent vector). From this, the prevailing palaeoenvironments in the study area during the Early Palaeocene to Early Eocene times have been reconstructed. A distinct faunal change has been detected at the Palaeocene-Eocene thermal maximum (PETM) as indicated by the second latent vector.
Highlighting the Early-Middle Pleistocene transition in Italian and French large-mammal faunas: similarities and faunal renewals
Authors: Palombo Maria R. , Valli Andrea M. F. 
Published: September 2007

Abstract
A similarity analysis between the large-mammal faunas of France and the Italian peninsula for the Pliocene to Middle Pleistocene highlights the taxonomic and structural renewal of large-mammal assemblages that took place at the Early-Middle Pleistocene transition. This faunal renewal coincides with a period of climatic deterioration revealed by the spread of grasslands that supported more abundant ‘cold’ taxa. Nevertheless, both in France and in Italy, this passage is not marked by a real turnover (i.e. the complete or almost complete renewal of a mammal fauna), but by an extinction phase followed by a dispersal event.
Hominin responses to Pleistocene environmental change in Arabia and South Asia
Authors: Petraglia Michael D. 
Published: September 2007

Abstract
Palaeoanthropologists typically outline human evolution within a framework of Pleistocene environmental change. Environmental change occurring across the Early-Middle Pleistocene transition is examined relative to patterns of hominin dispersal, ecological adaptations, cognitive advances and behavioural flexibility. Although climatic information has been used as the backdrop to human evolution, major lacunae exist in our understanding of the ecological settings where hominins evolved. Data from investigations conducted in the Arabian peninsula and the Indian subcontinent are reviewed, indicating the nature of Palaeolithic localities and their physical settings. Although much information remains to be obtained from these terrestrial records, significant changes are recognized in the environmental and archaeological record. The Early-Middle Pleistocene transition shows some conservative trends in hominin adaptations and technology, yet it is also an interval that evidences an increasing ability to transcend environmental controls through a greater level of behavioural flexibility and innovation.
In Situ Investigation of the Passive Films Formed on Chromium in Aqueous (pH8.4) Borate Buffer and Aqueous Chloride Solutions
Authors: Wang Feng , Harrington Scott , Devine Thomas M. 
Published: September 2007

The films formed on chromium in the passive and transpassive regions in borate buffer (pH8.4) were investigated by a combination of cyclic polarization and in situ EQCM and SERS. In the passive region, chromium dissolves as well as forms a passive film. The passive film thickness increases slowly with potential (approximately 6Aå/V). At low passive potentials, the identity of the film is not yet known.	At high passive potentials the film is very similar to Cr2O3. In the transpassive region chromium forms a thick Cr(III) film, tentatively identified as Cr(OH)3, plus two Cr(VI) species. Significant changes occur to the passive film when the sample is removed from the aqueous solution and exposed to air.
Electrochemical Studies of Lewis Acid / Ketone Interactions in Ionic Liquids
Authors: Cheek Graham 
Published: September 2007

The voltammetric behavior of 9-fluorenone, benzophenone, and benzil has been investigated in the ionic liquids 1-ethyl-3- methylimidazolium tetrafluoroborate (EMIm BF4) and 1-butyl- 2,3-dimethylimidazolium tetrafluoroborate (BDMIm BF4). At	100 mV/s, protonation of the radical anions of benzophenone and benzil by the EMIm cation is extensive; however, the	protonation reaction is slow and is not significant at 1000 mV/s. Use of BDMIm BF4, in which the acidic 2 position is substituted, precludes protonation of these radical anions. It has been found that addition of BF3 etherate to solutions of benzophenone in BDMIm BF4 , and to benzil in EMIm BF4,	results in formation of ketone : BF3 complexes.
Voltammetric Determination of Hydroxylamine at Platinum
Authors: ul Haque Inam , Bano Kiran 
Published: September 2007

The electrochemical oxidation of hydroxylamine at a platinum semi-micro disk electrode in nitric acid solution has been	studied. The plot of the peak, limiting and summit currents from cyclic voltammetry, normal pulse, and differential pulse voltammetry shows linear variation with the concentration of hydroxylamine. The peak current in DPV scaled linearly with the concentration of hydroxylamine from 25 micro-molar to 2.5 milli-molar. Lower limit of detection was found to be 15 micro- molar. The lowest detectable signal was observed at S/N=10.
Nebivolol Reverses Endothelial Dysfunction in Essential Hypertension
Authors: Tzemos Nikolaos , Lim Pitt O. , MacDonald Thomas M. 
Published: September 2007

BackgroundVascular endothelial dysfunction may predict future atherosclerosis. Hence, an antihypertensive agent that reverses endothelial dysfunction and lowers blood pressure might improve the prognosis of patients with hypertension. We hypothesized that nebivolol, a vasodilating β-blocker, could improve endothelial dysfunction. We tested this hypothesis by comparing the effects of nebivolol and atenolol on endothelial function.Methods and ResultsTwelve hypertensive patients with a mean ambulatory blood pressure of 154±7/97±10 mm Hg were randomized after a 2-week placebo run-in period (baseline) in a double-blind, crossover fashion to 8-week treatment periods with either 5 mg of nebivolol with 2.5 mg of bendrofluazide or 50 mg of atenolol with 2.5 mg of bendrofluazide. Forearm venous occlusion plethysmography and intra-arterial infusions of acetylcholine and NG-monomethyl-l-arginine (L-NMMA) were used to assess stimulated and basal endothelium-dependent nitric oxide release, respectively. Sodium nitroprusside was used as an endothelium-independent control. Nebivolol/bendrofluazide and atenolol/bendrofluazide each lowered the clinic blood pressure to the same extent (132±7/82±6 and 132±9/83±8 mm Hg, respectively;P<0.001 from baseline). The vasodilatory response to acetylcholine was significantly increased with nebivolol/bendrofluazide (maximum percentage change in forearm blood flow [mean±SEM], 435±27%,P<0.001) but not with atenolol/bendrofluazide. Similarly, the endothelium-dependent vasoconstrictive response to L-NMMA was significantly improved only with nebivolol treatment (percentage change in forearm blood flow, −54±5%;P<0.001). The response to sodium nitroprusside was not different between treatments, suggesting that the endothelium-independent pathway was unaffected.ConclusionsNebivolol/bendrofluazide increased both stimulated and basal endothelial nitric oxide release, whereas for the same degree of blood pressure control, atenolol/bendrofluazide had no effect on nitric oxide bioactivity. Thus, nebivolol may offer additional vascular protection in treating hypertension.
Folic Acid Prevents Nitroglycerin-Induced Nitric Oxide Synthase Dysfunction and Nitrate Tolerance
Authors: Gori Tommaso , Burstein Jason M. , Ahmed Sofia , Miner Steve E.S. , Al-Hesayen Abdul , Kelly Susan , Parker John D. 
Published: September 2007

Background—In healthy humans, continuous treatment with nitroglycerin (GTN) causes nitric oxide synthase dysfunction, probably through the reduced bioavailability of tetrahydrobiopterin. Recent studies proposed that folic acid is involved in the regeneration of tetrahydrobiopterin in different disease states. Therefore, we investigated whether folic acid administration would prevent this phenomenon. We also sought to determine if folic acid supplementation could prevent the development of tolerance to GTN.Methods and Results—On the first visit, 18 healthy male volunteers (aged 19 to 32 years) were randomized to receive either oral folic acid (10 mg once a day) or placebo for 1 week in a double-blind designed study. All subjects also received continuous transdermal GTN (0.6 mg/h). On the second visit, forearm blood flow was measured with venous occlusion strain gauge plethysmography in response to incremental infusions of acetylcholine (7.5, 15, and 30 μg/min),N-monomethyl-l-arginine (1, 2, and 4 μmol/min), and GTN (11 and 22 nmol/min). Folic acid prevented GTN-induced endothelial dysfunction, as assessed by responses to intraarterial acetylcholine andN-monomethyl-l-arginine (P<0.01). Moreover, in the subjects treated with folic acid plus transdermal GTN, responses to intraarterial GTN were significantly greater than those observed after transdermal GTN plus placebo (P<0.05).Conclusion—Our data demonstrate that supplemental folic acid prevents both nitric oxide synthase dysfunction induced by continuous GTN and nitrate tolerance in the arterial circulation of healthy volunteers. We hypothesize that the reduced bioavailability of tetrahydrobiopterin is involved in the pathogenesis of both phenomena. Our results confirm the view that oxidative stress contributes to nitrate tolerance.
Role of Endothelin-1 in the Active Constriction of Human Atherosclerotic Coronary Arteries
Authors: Kinlay Scott , Behrendt Dominik , Wainstein Marco , Beltrame John , Fang James C. , Creager Mark A. , Selwyn Andrew P. , Ganz Peter 
Published: September 2007

Background—Atherosclerotic coronary arteries are prone to constriction but the underlying causes are incompletely understood. We tested the hypothesis that endothelin-1 (ET-1), a potent vasoconstrictor, contributes to the heightened tone of atherosclerotic human coronary arteries.Methods and Results—In 8 patients with coronary artery disease (CAD) and 8 patients with angiographically smooth coronary arteries (normal), we infused BQ-123, an antagonist of the ETAreceptor, into a major coronary artery (infused artery) at 40 nmol/min for 60 minutes. The infused artery in the CAD patients contained a >50% stenosis. Using quantitative angiography, we compared the dilation of the infused artery with another, noninfused coronary artery. To estimate the magnitude of the contribution of ET-1 to coronary tone, we compared the dilation to BQ-123 with that elicited by intracoronary nitroglycerin (200 μg). BQ-123 induced significant dilation in the normal arteries (7.3% at 60 minutes,P<0.001 versus noninfused arteries) and a greater dilation in the CAD arteries (16.3% at 60 minutes,P<0.001 versus infused normal arteries). The dilation at stenoses was particularly pronounced (21.6% at 60 minutes,P<0.001 versus infused CAD arteries). Compared with the dilation from nitroglycerin, ET-1 contributed to 39% of the coronary tone in normal arteries, 74% of tone in CAD arteries, and 106% of tone at stenoses (P<0.01).Conclusions—ET-1 accounts for nearly all the resting tone in atherosclerotic coronary arteries, especially at stenoses. Inhibitors of ET-1, by relieving constriction, may significantly lessen the hemodynamic significance of coronary stenoses and thereby reduce myocardial ischemia.
Pharmacological Stress Myocardial Perfusion Imaging With the Potent and Selective A2AAdenosine Receptor Agonists ATL193 and ATL146e Administered by Either Intravenous Infusion or Bolus Injection
Authors: Glover David K. , Ruiz Mirta , Takehana Kazuya , Petruzella Frank D. , Riou Laurent M. , Rieger Jayson M. , Macdonald Timothy L. , Watson Denny D. , Linden Joel , Beller George A. 
Published: September 2007

Background—Adenosine (Ado) and dipyridamole are alternatives to exercise stress for myocardial perfusion imaging. Though generally safe, side effects frequently occur that cause patient discomfort and sometimes lead to premature termination of the study or require aminophylline administration. Recently, a new class of A2AAdo receptor agonists was synthesized. ATL193 and ATL146e are 2-propynylcyclohexyl-5′-N-ethylcarboxamido derivatives of Ado. The study goals were to evaluate the potency and selectivity of these new compounds on recombinant canine Ado receptors and to evaluate their hemodynamic properties in dogs to assess their usefulness as vasodilators for myocardial perfusion imaging.Methods and Results—In assays of recombinant canine Ado receptors, ATL-193 and ATL-146e were highly selective for the A2Aover the A1and A3receptors and were more potent than MRE-0470 and CGS-21680. In 16 anesthetized dogs, the agonists were administered by infusion (ATL-193; n=7 normal) or bolus injection (ATL-146e; n=9 critical left anterior descending coronary artery stenosis), and hemodynamic responses were compared with those of Ado. Both agonists produced dose-dependent coronary flow (CF) elevation without provoking the hypotension observed with Ado. After an ATL-146e bolus, the CF increase was sustained for several minutes, providing ample time for injection and myocardial uptake of99mTc-sestamibi, and CF returned to baseline within 20 minutes. The CF increase was completely blocked by the selective A2Aantagonist ZM241385 (3 μg · kg−1· min−1).Conclusions—ATL-193 and ATL-146e are highly potent and selective Ado A2Areceptor agonists with excellent potential for use as vasodilators for myocardial perfusion imaging. An important advantage of ATL-146e is the ability to administer it by bolus injection.