bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic Headache Relief After Section of Suboccipital Muscle Dural Connections: A Case Report
Authors: Hack Gary D. , Hallgren Richard C.
Published: January 2004

The presence of a connective tissue bridge, attaching suboccipital muscles to the dura mater, is now recognized as a feature of normal human anatomy. The role that this myodural bridge may play in headache production is uncertain; however, a new conceptual model is emerging. Postsurgical myodural adhesions have been reported as a complication resulting from excision of acoustic tumors. Extensive research now exists implicating these myodural adhesions as a possible source of postoperative headache. Integrating these 2 types of myodural unions (anatomic and pathologic) into a unified theory of headache production, we report a single patient who experienced relief from chronic headache after surgical separation of the myodural bridge from the suboccipital musculature.
Morbidity and Medication Preferences of Individuals With Headache Presenting to a Community Pharmacy
Authors: Wenzel Richard G. , Schommer Jon C. , Marks Thomas G.
Published: January 2004

Objective.—To assess the degree of debilitation and the treatment views of individuals with headache presenting to a community pharmacy.

Background.—Migraine and chronic daily headache are common poorly managed illnesses. Pharmacists recommend an over‐the‐counter “headache product” to customers more than 53 000 times daily, thus they are well positioned to help those with headache.

Design.—Pilot project of 22 self‐administered surveys of individuals presenting to a community pharmacy with a complaint of headache.

Results.—Thirteen persons had Migraine Disability Assessment scores of grade III or grade IV. Of the sample population, a substantial minority (41%) did not believe their headaches could be effectively managed with over‐the‐counter medications, 72% did not feel over‐the‐counter agents were safer than prescription products, 96% did not indicate that over‐the‐counter drugs were more effective than prescription drugs, and 50% disagreed that a physician's evaluation was not necessary. Only half of the population was satisfied with their current therapy, and individuals overwhelmingly (91%) wished they could prevent their headaches.

Conclusion.—The majority of individuals with headache presenting to a community pharmacy had high levels of morbidity and were in need of education regarding the proper role of over‐the‐counter medications, the advantages of prescription agents, and the benefits of a physician's referral. These preliminary results indicate that community pharmacies are potentially important locations for identification, education, and referral of individuals with headache.
Characterization of reaction products and their effects on the strength properties of transition joints formed between titanium and stainless steel
Authors: Ghosh and Mainak , Chatterjee Subrata
Published: January 2004

Transition joints were produced between commercially pure titanium and 304 stainless steel in the temperature range of 800–900°C for 30 min under 3 MPa uniaxial load in a vacuum. The diffusion bonds were characterized by optical and scanning electron microscopy, electron probe micro‐analyzer and tensile testing. At 850°C bonding temperature and above, a number of brittle intermetallics like FeTi and λ phases appear in the reaction zone and are mainly responsible for deterioration of bond strength. The highest bond strength (∼74% of titanium) was obtained for the diffusion‐bonded couple processed at 850°C due to the absence of discontinuities along the bond line and the formation of a finer size of intermetallic compounds.
Fine particulate metallurgical by‐products' influence on cement hydration and strength development: an initial study
Authors: Moosberg‐Bustnes Helena , Lind Lotta , Forssberg Eric
Published: January 2004

By‐products, such as dusts and sludges from metallurgical processes usually have a very fine particle size distribution and may be used, directly from the process of their origin, as a substitute for natural filler in concrete. To be able to promote the use of by‐products as fillers in concrete their effect on concrete properties has to be examined. This investigation has been made in order to gain knowledge of how fine particulate by‐products that contain metal oxides influence the cement hydration and concrete properties, such as strength development.
Effects of binders on balling behaviors of iron ore concentrates
Authors: Qiu Guanzhou , Jiang Tao , Fan Xiaohui , Zhu Deqing , Huang Zhucheng
Published: January 2004

An organic binder, Funa, has been developed and used in the production of iron ore pellets for direct reduction in China. This paper mainly describes the effects of the binder on balling behaviors of magnetite concentrates as compared to bentonite binder. Natural ballability and dynamic ballability of concentrates as well as the mechanical strengths of the balls have been included in the assessment. Results show that the organic binder markedly improved the natural ballability and the mechanical strengths but reduce the balling rate compared to bentonite. Investigation shows that the improvement in natural ballability by the binder is attributed to its increasing effect on the wettability on the surface of concentrates. Due to its effects of increasing liquid viscosity, however, the binder clearly reduced the balling rate of the concentrates. The binder clearly improved wet ball strength also due to its viscosity increasing effects, as well as its chemical bonding to the iron ore surface. High‐strength solid bridging of the binder and chemical bonding are the main reasons for much greater strengths of dry balls.
Continuous casting of tin strip using a heated mould
Authors: Motoyasu G. , Soda H. , McLean A.
Published: January 2004

A heated‐mould continuous casting process has been used to generate tin strips with a unidirectional morphology at casting speeds between 4 and 525 mm/min. It was found that the strips exhibited a striated substructure in various patterns influenced by cooling conditions and casting speed. The crystal orientation of strips examined by electron channeling pattern (ECP) analysis indicated that the orientation perpendicular to the top surface of the strips was in the vicinity of the [001] direction regardless of the casting speed used. The fluctuation in the orientation increased at higher casting speeds due to the development of a mosaic structure.
Strain‐based approach to crack growth and thermal fatigue life of hot work tool steels
Authors: Persson Anders
Published: January 2004

Thermal fatigue cracking is one of the most important life‐limiting tool failure mechanisms in die casting of aluminium and brass. It results from the rapid alternating heating and cooling of the die surface during the casting process, and it is observed as a network of fine cracks on the tool surfaces exposed to thermal cycling. The crack pattern deteriorates the surface finish of the tool and, therefore, that of the cast products. Hot work tool steels are frequently used as die materials to minimise this tool damage. In this study, thermal fatigue cracking of two hot work tool steel grades, hardened and tempered to various conditions, were evaluated using an experimental thermal fatigue test method based on cyclic induction heating and internal cooling of hollow cylindrical test rods. The surface strain is continuously recorded during the thermal cycling through a noncontact laser speckle technique. The thermal fatigue damage was characterised with respect to crack length and density of cracks. Based on the experimental findings estimations of crack growth and thermal fatigue life, and their temperature sensitivity were made. In addition, the crack growth and thermal fatigue life were represented using strain‐based models. It was found that the resistance against thermal cracking improves with initial tool steel hardness, in spite of the fact that thermal fatigue causes considerable softening, and that the initial ranking in hardness among the different steels is unaffected by thermal cycling. The cyclic thermal crack growth rate increases roughly with one order of magnitude when increasing the maximum cycle temperature from 700 to 850°C. In addition, an increase in the maximum cycle temperature from 600 to 700°C and from 700 to 850°C reduces the thermal fatigue life with roughly one order of magnitude, respectively.
The Yana RHS Site: Humans in the Arctic Before the Last Glacial Maximum
Authors: Pitulko V. V. , Nikolsky P. A. , Girya E. Yu. , Basilyan A. E. , Tumskoy V. E. , Koulakov S. A. , Astakhov S. N. , Pavlova E. Yu. , Anisimov M. A.
Published: January 2004

A newly discovered Paleolithic site on the Yana River, Siberia, at 71°N, lies well above the Arctic circle and dates to 27,000 radiocarbon years before present, during glacial times. This age is twice that of other known human occupations in any Arctic region. Artifacts at the site include a rare rhinoceros foreshaft, other mammoth foreshafts, and a wide variety of tools and flakes. This site shows that people adapted to this harsh, high-latitude, Late Pleistocene environment much earlier than previously thought.
Crystal Structure of Biotin Synthase, an
S
-Adenosylmethionine-Dependent Radical Enzyme
Authors: Berkovitch Frederick , Nicolet Yvain , Wan Jason T. , Jarrett Joseph T. , Drennan Catherine L.
Published: January 2004

The crystal structure of biotin synthase from
Escherichia coli
in complex with
S-
adenosyl-
L
-methionine and dethiobiotin has been determined to 3.4 angstrom resolution. This structure addresses how “AdoMet radical” or “radical SAM” enzymes use Fe
4
S
4
clusters and
S-
adenosyl-
L
-methionine to generate organic radicals. Biotin synthase catalyzes the radical-mediated insertion of sulfur into dethiobiotin to form biotin. The structure places the substrates between the Fe
4
S
4
cluster, essential for radical generation, and the Fe
2
S
2
cluster, postulated to be the source of sulfur, with both clusters in unprecedented coordination environments.
Dynamics of DNA Double-Strand Breaks Revealed by Clustering of Damaged Chromosome Domains
Authors: Aten Jacob A. , Stap Jan , Krawczyk Przemek M. , van Oven Carel H. , Hoebe Ron A. , Essers Jeroen , Kanaar Roland
Published: January 2004

Interactions between ends from different DNA double-strand breaks (DSBs) can produce tumorigenic chromosome translocations. Two theories for the juxta-position of DSBs in translocations, the static “contact-first” and the dynamic “breakage-first” theory, differ fundamentally in their requirement for DSB mobility. To determine whether or not DSB-containing chromosome domains are mobile and can interact, we introduced linear tracks of DSBs in nuclei. We observed changes in track morphology within minutes after DSB induction, indicating movement of the domains. In a subpopulation of cells, the domains clustered. Juxtaposition of different DSB-containing chromosome domains through clustering, which was most extensive in G1 phase cells, suggests an adhesion process in which we implicate the Mre11 complex. Our results support the breakage-first theory to explain the origin of chromosomal translocations.
Osmium Isotope Heterogeneity in the Constituent Phases of Mid-Ocean Ridge Basalts
Authors: Gannoun Abdelmouhcine , Burton Kevin W. , Thomas Louise E. , Parkinson Ian J. , van Calsteren Peter , Schiano Pierre
Published: January 2004

Radiogenic isotope variations in mid-ocean ridge basalts (MORB) are commonly attributed to compositional variations in Earth's upper mantle. For the rheniumosmium isotope system, constituent MORB phases are shown to possess exceptionally high Re/Os (parent/daughter) ratios, consequently radiogenic
187
Os is produced from the decay of
187
Re over short periods of time. Thus, in the absence of precise age constraints, Os isotope variations cannot be unambiguously attributed to their source, although Re–Os isotope data for constituent minerals can yield crystallization ages, details of equilibration, and initial Os isotope values that relate directly to the mantle source.
Foxg1
Suppresses Early Cortical Cell Fate
Authors: Hanashima Carina , Li Suzanne C. , Shen Lijian , Lai Eseng , Fishell Gord
Published: January 2004

During mammalian cerebral corticogenesis, progenitor cells become progressively restricted in the types of neurons they can produce. The molecular mechanism that determines earlier versus later born neuron fate is unknown. We demonstrate here that the generation of the earliest born neurons, the Cajal-Retzius cells, is suppressed by the telencephalic transcription factor Foxg1. In
Foxg1
null mutants, we observed an excess of Cajal-Retzius neuron production in the cortex. By conditionally inactivating
Foxg1
in cortical progenitors that normally produce deep-layer cortical neurons, we demonstrate that
Foxg1
is constitutively required to suppress Cajal-Retzius cell fate. Hence, the competence to generate the earliest born neurons during later cortical development is actively suppressed but not lost.
Partitioning the Energetics of Walking and Running: Swinging the Limbs Is Expensive
Authors: Marsh Richard L. , Ellerby David J. , Carr Jennifer A. , Henry Havalee T. , Buchanan Cindy I.
Published: January 2004

Explaining the energetics of walking and running has been difficult because the distribution of energy use among individual muscles has not been known. We estimated energy use by measuring blood flow to the hindlimb muscles in guinea fowl. Blood flow to skeletal muscles is controlled locally and varies directly with metabolic rate. We estimate that the swing-phase muscles consume 26% of the energy used by the limbs and the stance-phase muscles consume the remaining 74%, independent of speed. Thus, contrary to some previous suggestions, swinging the limbs requires an appreciable fraction of the energy used during terrestrial legged locomotion. Models integrating the energetics and mechanics of running will benefit from more detailed information on the distribution of energy use by the muscles.
Continental-Scale Partitioning of Fire Emissions During the 1997 to 2001 El Niño/La Niña Period
Authors: van der Werf Guido R. , Randerson James T. , Collatz G. James , Giglio Louis , Kasibhatla Prasad S. , Arellano Avelino F. , Olsen Seth C. , Kasischke Eric S.
Published: January 2004

During the 1997 to 1998 El Niño, drought conditions triggered widespread increases in fire activity, releasing CH
4
and CO
2
to the atmosphere. We evaluated the contribution of fires from different continents to variability in these greenhouse gases from 1997 to 2001, using satellite-based estimates of fire activity, biogeochemical modeling, and an inverse analysis of atmospheric CO anomalies. During the 1997 to 1998 El Niño, the fire emissions anomaly was 2.1 ± 0.8 petagrams of carbon, or 66 ± 24% of the CO
2
growth rate anomaly. The main contributors were Southeast Asia (60%), Central and South America (30%), and boreal regions of Eurasia and North America (10%).
Supramolecular Self-Assembly of Macroscopic Tubes
Authors: Yan Deyue , Zhou Yongfeng , Hou Jian
Published: January 2004

The macroscopic molecular self-assembly of an amphiphilic hyperbranched copolymer in acetone generated multiwalled tubes millimeters in diameter and centimeters in length. The thickness of the tube walls approaches 400 nanometers, and the walls have an inhomogeneous lamella structure that alternates between ordered hydrophilic domains and amorphous, partly irregular hydrophilic domains.
Coordination of Meiotic Recombination, Pairing, and Synapsis by PHS1
Authors: Pawlowski Wojciech P. , Golubovskaya Inna N. , Timofejeva Ljudmilla , Meeley Robert B. , Sheridan William F. , Cande W. Zacheus
Published: January 2004

Pairing, synapsis, and recombination are prerequisites for accurate chromosome segregation in meiosis. The
phs1
gene in maize is required for pairing to occur between homologous chromosomes. In the
phs1
mutant, homologous chromosome synapsis is completely replaced by synapsis between nonhomologous partners. The
phs1
gene is also required for installation of the meiotic recombination machinery on chromosomes, as the mutant almost completely lacks chromosomal foci of the recombination protein RAD51. Thus, in the
phs1
mutant, synapsis is uncoupled from recombination and pairing. The protein encoded by the
phs1
gene likely acts in a multistep process to coordinate pairing, recombination, and synapsis.
A Map of the Interactome Network of the Metazoan
C. elegans
Authors: Li Siming , Armstrong Christopher M. , Bertin Nicolas , Ge Hui , Milstein Stuart , Boxem Mike , Vidalain Pierre-Olivier , Han Jing-Dong J. , Chesneau Alban , Hao Tong , Goldberg Debra S. , Li Ning , Martinez Monica , Rual Jean-François , Lamesch Philippe , Xu Lai , Tewari Muneesh , Wong Sharyl L. , Zhang Lan V. , Berriz Gabriel F. , Jacotot Laurent , Vaglio Philippe , Reboul Jérôme , Hirozane-Kishikawa Tomoko , Li Qianru , Gabel Harrison W. , Elewa Ahmed , Baumgartner Bridget , Rose Debra J. , Yu Haiyuan , Bosak Stephanie , Sequerra Reynaldo , Fraser Andrew , Mango Susan E. , Saxton William M. , Strome Susan , van den Heuvel Sander , Piano Fabio , Vandenhaute Jean , Sardet Claude , Gerstein Mark , Doucette-Stamm Lynn , Gunsalus Kristin C. , Harper J. Wade , Cusick Michael E. , Roth Frederick P. , Hill David E. , Vidal Marc
Published: January 2004

To initiate studies on how protein-protein interaction (or “interactome”) networks relate to multicellular functions, we have mapped a large fraction of the
Caenorhabditis elegans
interactome network. Starting with a subset of metazoan-specific proteins, more than 4000 interactions were identified from high-throughput, yeast two-hybrid (HT=Y2H) screens. Independent coaffinity purification assays experimentally validated the overall quality of this Y2H data set. Together with already described Y2H interactions and interologs predicted
in silico
, the current version of the Worm Interactome (WI5) map contains ∼5500 interactions. Topological and biological features of this interactome network, as well as its integration with phenome and transcriptome data sets, lead to numerous biological hypotheses.
A Previously Unknown Maltose Transporter Essential for Starch Degradation in Leaves
Authors: Niittylä Totte , Messerli Gaëlle , Trevisan Martine , Chen Jychian , Smith Alison M. , Zeeman Samuel C.
Published: January 2004

A previously unknown maltose transporter is essential for the conversion of starch to sucrose in
Arabidopsis
leaves at night. The transporter was identified by isolating two allelic mutants with high starch levels and very high maltose, an intermediate of starch breakdown. The mutations affect a gene of previously unknown function,
MEX1
. We show that MEX1is a maltose transporter that is unrelated to other sugar transporters. The severe
mex1
phenotype demonstrates that MEX1is the predominant route of carbohydrate export from chloroplasts at night. Homologous genes in plants including rice and potato indicate that maltose export is of widespread significance.
Treasure Hunting to the Ends of the Earth
Authors: Wadhwa Meenakshi
Published: January 2004

Meteorites, Ice, and Antarctica
A Personal Account. by William A. Cassidy. Cambridge University Press, New York, 2003. 363 pp. $25, £19.95. ISBN 0-521-25872-3.

Cassidy offers a firsthand account of his 15 years of work collecting meteorites in the Antarctic and of the contributions Antarctic meteorites have made (and may yet make) to our understanding of the Moon, Mars, and the asteroids.
Coordinated Activation of Hsp70 Chaperones
Authors: Steel Gregor J. , Fullerton Donna M. , Tyson John R. , Stirling Colin J.
Published: January 2004

Hsp70s are a ubiquitous family of molecular chaperones involved in many cellular processes. Two Hsp70s, Lhs1p and Kar2p, are required for protein biogenesis in the yeast endoplasmic reticulum. Here, we found that Lhs1p and Kar2p specifically interacted to couple, and coordinately regulate, their respective activities. Lhs1p stimulated Kar2p by providinga specific nucleotide exchange activity, whereas Kar2p reciprocally activated the Lhs1p adenosine triphosphatase (ATPase). The two ATPase activities are coupled, and their coordinated regulation is essential for normal function in vivo.
The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way
Authors: Lineweaver Charles H. , Fenner Yeshe , Gibson Brad K.
Published: January 2004

We modeled the evolution of the Milky Way Galaxy to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun.
RNAi-Mediated Targeting of Heterochromatin by the RITS Complex
Authors: Verdel André , Jia Songtao , Gerber Scott , Sugiyama Tomoyasu , Gygi Steven , Grewal Shiv I. S. , Moazed Danesh
Published: January 2004

RNA interference (RNAi) is a widespread silencing mechanism that acts at both the posttranscriptional and transcriptional levels. Here, we describe the purification of an RNAi effector complex termed RITS (RNA-induced initiation of transcriptional gene silencing) that is required for heterochromatin assembly in fission yeast. The RITS complex contains Ago1 (the fission yeast
Argonaute
homolog), Chp1 (a heterochromatin-associated chromodomain protein), and Tas3 (a novel protein). In addition, the complex contains small RNAs that require the Dicer ribonuclease for their production. These small RNAs are homologous to centromeric repeats and are required for the localization of RITS to heterochromatic domains. The results suggest a mechanism for the role of the RNAi machinery and small RNAs in targeting of heterochromatin complexes and epigenetic gene silencing at specific chromosomal loci.
The Tale Behind the Worm
Authors: Herman Robert K.
Published: January 2004

In the Beginning Was the Worm
Finding the Secrets of Life in a Tiny Hermaphrodite. by Andrew Brown. Columbia University Press, New York, 2003. 252 pp. $27.95. ISBN 0-231-13146-1. Simon and Schuster, London. £15.99. ISBN 0-743-20716-5.

In this short narrative written for the general public, Brown tells the story of the work that led to our current understanding of the genome and development of the nematode
C. elegans
--and to the Nobel Prize awarded his principal protagonists, Bob Horvitz, Sydney Brenner, and John Sulston.
Lower Paleozoic stratigraphic and biostratigraphic correlations in the Canadian Cordillera: implications for the tectonic evolution of the Laurentian margin
Authors: Pyle Leanne J , Barnes Christopher R
Published: January 2004

The ancient Laurentian margin rifted in the latest Neoproterozoic to early Cambrian but appears not to have developed as a simple passive margin through a long, post-rift, drift phase. Stratigraphic and conodont biostratigraphic information from four platform-to-basin transects across the margin has advanced our knowledge of the early Paleozoic evolution of the margin. In northeastern British Columbia, two northern transects span the Macdonald Platform to Kechika Trough and Ospika Embayment, and a third transect spans the parautochthonous Cassiar Terrane. In the southern Rocky Mountains, new conodont biostratigraphic data for the Ordovician succession of the Bow Platform is correlated to coeval basinal facies of the White River Trough. In total, from 26 stratigraphic sections, over 25 km of strata were measured and > 1200 conodont samples were collected that yielded over 100 000 conodont elements. Key zonal species were used for regional correlation of uppermost Cambrian to Middle Devonian strata along the Cordillera. The biostratigraphy temporally constrains at least two periods of renewed extension along the margin, in the latest Cambrian and late Early Ordovician. Alkalic volcanics associated with abrupt facies changes across the ancient shelf break, intervals of slope debris breccia deposits, and distal turbidite flows suggest the margin was characterized by intervals of volcanism, basin foundering, and platform flooding. Siliciclastics in the succession were sourced by a reactivation of tectonic highs, such as the Peace River Arch. Prominent hiatuses punctuate the succession, including unconformities of early Late Ordovician, sub-Llandovery, possibly Early to Middle Silurian and Early Devonian ages.
The Burgess Shale and associated Cambrian formations west of the Fossil Gully Fault Zone on Mount Stephen, British Columbia
Authors: Fletcher Terence P , Collins Desmond H
Published: January 2004

West of the Fossil Gully Fault Zone on Mount Stephen, the three lowest members only of the Burgess Shale Formation are preserved: the Kicking Horse Shale, the Yoho River Limestone, and the Campsite Cliff Shale. The formation rests unconformably upon the Takakkaw Tongue Formation, whose dark basinal limestones conformably overlie paler shelf-like limestones of the Mount Whyte Formation. Mapping has resolved a long-standing problem and shown that the stratigraphical position of the famous Mount Stephen Trilobite Beds lies within the Campsite Cliff Shale. It has also revealed some of the complexities of the Fossil Gully Fault Zone, among which different periods and directions of component fault movements are indicated. Faunal evidence shows that the PlagiuraKochaspis to Albertella and Albertella to Glossopleura zonal boundaries lie within the Takakkaw Tongue sequence. Within the Burgess Shale, three distinct soft-bodied communities occur at different stratigraphical levels on this mountain slope. The oldest, characterized by the arthropod Alalcomenaeus and chelicerate Sanctacaris, occurs low in the Kicking Horse Shale Member and is best known from Collins Quarry. The others lie within the Campsite Cliff Shale Member. The Trilobite Beds, characterized by claws of the dinocarid Anomalocaris and moults of the trilobite Ogygopsis klotzi, onlap the sloping top of a proximal bench facies of the Yoho River Limestone Member close to the Cathedral Escarpment. Slightly older and farther out in the basin are beds characterized by the dinocarid Laggania and a tulip-like animal related to Dinomischus, excavated about 12 m above the top of a thin distal wedge facies of the Yoho River Limestone at the S7 site. Among the illustrated trilobites, a new corynexochine from the Campsite Cliff Shale Member is figured.
SmNd fluorite dating of Proterozoic low-sulfidation epithermal AuAg deposits and UPb zircon dating of host rocks at Mallery Lake, Nunavut, Canada
Authors: Turner William A , Heaman Larry M , Creaser Robert A
Published: January 2004

The Mallery Lake area contains precious metal-bearing quartzchalcedony stockworks that are pristine examples of ancient low-sulfidation epithermal deposits. Fluorite extracted from these epithermal deposits define a SmNd errorchron age of 1434 ± 23 Ma mean square of weighted deviates (MSWD) = 4.8. This date is interpreted to have age significance because (1) a simple linear trend does not exist between the 143Nd/144Nd ratios of the fluorite with respect to their 1/Nd concentrations as would be expected for mixing of two geochemical end members; (2) microthermometric studies indicate that the fluorite analysed in this study has an intimate association with a single high-salinity, calcic brinal fluid; and (3) the age determined from seven fluorite samples extracted from a single outcrop location yielded an identical age result (1434 ± 60 Ma; MSWD = 5.5) compared to the fluorite composite. Rhyodacites of the Pitz Formation and syenites from the Nueltin suite (intrusive equivalent to the rhyodacites) are the youngest volcanicplutonic rocks that are observed in outcrop in the Mallery Lake area, and they were dated by UPb zircon analysis at 1760 ± 43 Ma and 1755.4 ± 1.8 Ma, respectively. The ~320 million year age difference between the epithermal deposits and the hosting rhyodacitic flows suggests that the epithermal stockworks may have formed by a regional hydrothermal event unrelated to this earlier Paleoproterozoic volcanic activity. Uranium deposits in the Thelon and Athabasca basins, to the northwest and south of the Baker Lake Basin, were determined to have similar ore emplacement ages with no evident heat source.
Late Pleistocene coastal paleogeography of the Queen Charlotte Islands, British Columbia, Canada, and its implications for terrestrial biogeography and early postglacial human occupation
Authors: Hetherington Renée , Barrie J Vaughn , Reid Robert GB , MacLeod Roger , Smith Dan J , James Thomas S , Kung Robert
Published: January 2004

Molluscs, sediment lithology, and published sub-bottom profiles are used to deduce sea levels, outline the influence of glacially induced crustal displacement, and reconstruct the paleoenvironment of the northeast Pacific late Quaternary coastline. Geo-spatial modelling shows subaerially exposed land that could have been inhabited by plants and animals, and also coastally migrating early North American peoples. Ice-free terrain, present by at least 13 790 ± 150 14C years BP, a land bridge, and edible molluscs are identified. Queen Charlotte Islands (QCI) late Pleistocene coastal paleogeography may assist in explaining the biogeography of many terrestrial plant and animal species along the broader northeastern Pacific margin and provide evidence for researchers seeking late Pleistocene  early Holocene glacial refugia. Late Pleistocene  early Holocene coastlines that are not drowned and that may harbour early archaeological sites are identified along the western QCI, where migrants probably first travelled and the westernmost British Columbia mainland, where the effects of glacial ice were reduced.
Theoretical studies of model compounds of lathyrane-type diterpenes
Authors: Terada Yukimasa , Matsuura Tomoo , Mori Yukari , Yamamura Shosuke
Published: January 2004

The conformation of the 11-membered ring of the lathyrane skeleton has been investigated using NMR spectra and theoretical calculations. Some other skeletons, such as jatrophane, jatrapholane, and tigliane, seem to be derived from this framework, and the conformation is important in connection with the configuration of the resultant diterpenes. The conformation of lathyrane is principally defined by the orientation of the two methyl groups; namely, the methyl groups on C1 and C6 directed above or below the ring plane. Theoretical calculations revealed that the predominant conformation is altered depending on the oxygen functional groups on the ring. As far as the bond lengths, bond angles, and dihedral angles are concerned, all calculation methods afforded reasonable results. In contrast, as regards conformational stability, only the ab initio molecular orbital method (RHF/6-31G*) predicted the most stable conformation, consistent with NOE experiments. On the other hand, the stable conformations predicted by the ab initio method (RHF/STO-3G), the semi-empirical molecular orbital method (MOPAC(PM3)), and the molecular mechanics calculations (MM3) did not necessarily agree with the conformers suggested by the NOE experiments.Key words: ab initio MO, semi-empirical MO, molecular mechanics, 11-membered ring conformation, NOE.
Phosphorus magnetic shielding tensors for transition-metal compounds containing phosphine, phosphido, and phosphinidene ligands: Insights from computational chemistry
Authors: Feindel Kirk W , Wasylishen Roderick E
Published: January 2004

The present study examines the quality of the restricted HartreeFock (RHF) ab initio, B3LYP hybrid density functional theory (DFT), and relativistic zeroth-order regular approximation (ZORA) DFT methods for the calculation of phosphorus chemical shift (CS) tensors in phosphine, phosphido, and phosphinidene transition-metal complexes. A detailed comparison of calculated and experimental 31P CS tensors allows us to identify the characteristic advantages of each computational method. The results from B3LYP and ZORA-DFT calculations indicate that a double-ζ quality basis set reproduces experimental values of the principal components of the 31P CS tensor in many of the phosphorus-containing transition-metal complexes investigated, whereas the RHF method requires a triple-ζ doubly polarized basis set, yet fails in the case of the terminal phosphido group. Inclusion of the spin-orbit relativistic correction with the ZORA-DFT formalism requires a triple-ζ quality basis set to reproduce the experimental data. We demonstrate the merit of modern computational methods for investigating theoretically the effect of geometric variations upon the phosphorus CS tensor by systematically altering the WP bond length and the W-P-CMe bond angle in W(CO)5(PMe3). Additionally, a previously reported correlation, determined experimentally, relating the 31P CS tensor to the Fe-P-Fe bond angle in a series of iron phosphido-bridging compounds, has been reproduced with calculations using the model compound Fe2(CO)6(µ2-PPh2)(µ2-Cl). The results presented demonstrate the value of modern computational techniques for obtaining a greater understanding of the relationship between phosphorus chemical shifts and molecular structure.Key words: 31P chemical shift, phosphine, phosphido, phosphinidene, RHF, B3LYP, relativistic, ZORA-DFT.
Azabenzenes (azines)  The nitrogen derivatives of benzene with one to six N atoms: Stability, homodesmotic stabilization energy, electron distribution, and magnetic ring current; a computational study
Authors: Fabian Jürgen , Lewars E
Published: January 2004

The twelve azabenzenes  the species formed by replacing CH groups of benzene by N  were examined computationally (with emphasis on the six contiguous-nitrogen species). MP2(fc)/6-31G*, B3LYP/6-31G*, CCSD(T)/6-31G*//MP2(fc)/6-31G*, and G3(MP2) calculations were used to probe kinetic and thermodynamic stabilities, homodesmotic ring-opening energies, electron distribution (bond orders and lengths, Bird index), and NICS values, primarily to discern where the transition occurs from reasonably stable to highly fragile species. Some azabenzenes with three and those with four or more nitrogens are thermodynamically unstable, but kinetic stabilities indicated that, with the possible exception of hexaazabenzene, all the azabenzenes should be isolable, although some with four nitrogens might decompose at room temperature, and pentaazabenzene would require matrix isolation techniques. Although homodesmotic ring-opening reactions showed an almost monotonic decrease in the stability of the cyclic relative to the open-chain species (in appropriate ring-opening reactions) on going from benzene to hexaazabenzene, bond-order variation and NICS suggested this may be because of increasing destabilization by nitrogen lone pairs rather than because of a decrease in electron delocalization (in aromaticity). Key words: azines, azabenzenes, pentazine, hexazine, ab initio, DFT, aromaticity.
Inclusion complexation involving sugar-containing species: β-cyclodextrin and sugar surfactants
Authors: Reinsborough Vincent C , Stephenson Vanessa C
Published: January 2004

Surface tension, proton NMR, and computer modeling studies were undertaken in nonionic alkylpolyglycoside (APG) solutions containing β-cyclodextrin (β-CD) with a view to characterize the inclusion complexes formed and to determine if the sugar entities of the host and guest molecules played a significant role in the process. The APGs investigated were four glucopyranosides (octyl G8, decyl G10, dodecyl G12, tetradecyl G14) and two maltosides (decyl M10, dodecyl M12). Critical micelle concentrations (CMC) were obtained in the surfactantβ-CD systems, which in all cases increased with increasing β-CD concentration. The 1:1 APGβ-CD inclusion complex was principally formed with binding constants of 425 (mol L1)1 for the G12 complex, 340 (mol L1)1 for the G10 complex, and 125 (mol L1)1 for the M12 complex. The preferred configuration of the G-12β-CD complex has the surfactant tail coiled in the CD cavity with the surfactant sugar moiety sealing off the narrower opening of the CD torus.Key words: alkylpolyglycoside, β-cyclodextrin, NMR, critical micelle concentration, surface tension.
Spatial variability in soil nutrient availability in an oak-pine forest: potential effects of tree species
Authors: Washburn C SM , Arthur M A
Published: January 2004

Established species have been shown to affect soil nutrient availability, but the effects of "native invasive" species on soil nutrient availability are relatively unknown. Oak-dominated forests in the eastern deciduous forest are dynamic in their species composition, with increasing dominance of red maple (Acer rubrum L.) in the midstory and overstory. We hypothesized that higher quality red maple litter within a litter matrix dominated by oaks would accelerate N turnover, increase nutrient availability in the soil, and result in a thinner and less massive O horizon. We examined nutrient availability in soils under three overstory tree species (Quercus prinus L., A. rubrum, and Pinus echinata Mill. or Pinus rigida Mill.), under a shrub (Vaccinium spp.), and in locations without tree stems ("no tree"). Ex tract able nutrients (P, K, Mg, Ca) and total and available N were quantified in the O horizon and upper mineral soil at 0.5 m and 1.0 m from the base of individual trees or from the center of Vaccinium and no-tree locations. Despite low lignin concentration in red maple litter and low lignin/N ratio, the lowest N mineralization rates were found in red maple microsites; the highest N mineralization rates were found under oak. Extractable cations were generally highest under red maple and lowest under pines, and red maple had the highest levels of total N (but not NO3or NH4) in the upper mineral soil. Shifting species composition towards red maple and away from pines in these forests may alter nutrient cycling by increasing surface soil cation availability, but reducing soil N mineralization.
Litterfall, growth, and turnover of arboreal lichens after partial cutting in an Engelmann spruce  subalpine fir forest in north-central British Columbia
Authors: Stevenson Susan K , Coxson Darwyn S
Published: January 2004

Dynamics of canopy lichens were investigated for 2 years after group and single-tree selection harvesting in a Picea engelmannii Parry ex Engelm.  Abies lasiocarpa (Hook.) Nutt. forest in north-central British Columbia. Litter fall was collected in 1-m2traps set on the forest floor and estimates of Alectoria sarmentosa (Ach.) Ach. and Bryoria spp. litterfall adjusted for decomposition in the snowpack. Growth rates of A. sarmentosa and Bryoria fuscescens (Gyeln.) Brodo & D. Hawksworth were measured by repeatedly weighing samples maintained in mesh enclosures in the canopy. Standing crop of canopy lichens was measured in concurrent studies. There appeared to be a small postharvest pulse of litterfall in the single-tree selection area, but it was largely masked by natural variation. Ninety percent of the lichen litterfall was deposited within 10 m of the nearest tree. Annual relative growth rates of A. sarmentosa and B. fuscescens ranged from 2.7% to 10.4% and from 2.4% to 9.1%, respectively. Growth rates of both species were as high in the single-tree selection area as in the unlogged control area but were reduced along the edges of group selection openings. Growth and turnover (annual litterfall as a percentage of standing crop) of Alectoria were approximately in balance, but growth of Bryoria exceeded turnover. In situ decomposition of Bryoria may account for the difference.
Variability in organic matter lost by combustion in a boreal bog during the 2001 Chisholm fire
Authors: Benscoter Brian W , Wieder R Kelman
Published: January 2004

Fire directly releases carbon (C) to the atmosphere through combustion of biomass. An estimated 1470 ± 59 km2 of peatland burns annually in boreal, western Canada, releasing 4.7 ± 0.6 Tg C to the atmosphere via direct combustion. We quantified within-site variation in organic matter lost via combustion in a bog peatland in association with the 116 000-ha Chisholm, Alberta, fire in 2001. We hypothesized that for peatlands with considerable small-scale microtopography (bogs and treed fens), hummocks will burn less than hollows. We found that hollows exhibit more combustion than hummocks, releasing nearly twice as much C to the atmosphere. Our results suggest that spatial variability in species composition and site hydrology within a landform and across a landscape could contribute to considerable spatial variation in the amounts of C released via combustion during peatland fire, although the magnitude of this variation may be dependent on fire severity.
A behavioral and welfare analysis of progressive forest taxation
Authors: Koskela Erkki , Ollikainen Markku
Published: January 2004

We use the Hartman rotation model to study behavioral and social welfare effects of forest tax progression. The following new results are shown for harvest and timber taxes. First, a tax-revenue neutral increase in the timber tax rate, compensated by a higher tax exemption, will shorten the optimal private rotation age. A sufficient condition for this to hold for the yield and unit taxes is that the marginal valuation of amenities is nondecreasing with the age of the forest stand. Second, for the socially optimal forest taxation, if society can use the neutral site productivity tax to collect tax revenue, the proportional forest tax is enough to internalize the externality caused by private harvesting. Finally, even though site productivity tax is not available, the tax structure should be designed so that tax exemption is neutral, implying that the optimal corrective forest taxes remain unchanged.
Effects of late Holocene wildfires on diatom assemblages in Christina Lake, Alberta, Canada
Authors: Philibert Aline , Prairie Yves T , Campbell Ian , Laird Lana
Published: January 2004

The impact of forest fires on a boreal lake ecosystem was investigated in a discontinuous paleolimnological study of Christina Lake, in the mixedwood subregion of the boreal forest in northern Alberta (Canada). Diatom assemblages were examined below, within, and above charcoal-rich horizons in a sediment core, which represent local fire events. The total diatom concentration as well as the benthic to planktonic taxa ratio increased during charcoal peaks, but no detectable impact on taxa richness was observed. Diatom assemblage responses to fires generally lasted less than 5 years. Inter-taxa competition appears to be a major factor determining diatom assemblages in Christina Lake.
Impact of seed and seedling predation by small rodents on early regeneration establishment of black spruce
Authors: Côté Mathieu , Ferron Jean , Gagnon Réjean
Published: January 2004

Black spruce (Picea mariana (Mill.) BSP) postdispersal seed and juvenile seedling predation by small rodents (Peromyscus maniculatus (Wagner), Clethrionomys gapperi (Vigor), and Phenacomys intermedius (Merriam)) was assessed in three boreal habitats over a 2-year period using an extensive exclosurecontrol experiment. Small rodent relative abundance was measured during six periods using snap trapping. We found that seed and juvenile seedling predation by small rodents varied according to habitat type and over time. Indeed, seed predation was higher in sprucemoss forests than in other habitats, notably during the winter of 2002. During this period, seedling predation was higher in recent burns. This period of higher seed and juvenile seedling predation corresponded to an increase in small rodent abundance in our study area. We suggest that seeds and juvenile seedlings can become important food sources for small rodents during winter when fresh and succulent vegetation is rare, as shown by results of seed predation. The impact of small rodents on the early regeneration of black spruce in the eastern Canadian boreal forest is thus an important factor to consider to better understand the forest regeneration process in this particular biome. Rodents can have a major effect on regeneration following a burn and can also contribute to poor seedling establishment from natural seed rain under mature cover.
Temporal changes of forest net primary production and net ecosystem production in west central Canada associated with natural and anthropogenic disturbances
Authors: Li Zhong , Apps Michael J , Kurz Werner A , Banfield Ed
Published: January 2004

Temporal variations of net primary production (NPP) and net ecosystem production (NEP) in west central Canadian forests over the period of 19201995 and their responses to natural and anthropogenic disturbances were simulated using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2). The results show that forest NPP in the region was 215 g C·year1·m2 in 1920, varied between 105 and 317 g·C year1·m2 depending on ecoclimatic province, but gradually increased to 330 (158 to 395) g C·year1·m2 in the early 1980s before declining to 290 (148 to 395) g C·year1·m2 by 1995. Forest NEP was estimated to be 53 (13 to 88) g C·year1·m2 in 19201924, increased to 75 (5 to 98) g C·year1·m2 in 1960, and then declined to 26 (14 to 53) g C·year1·m2 in 19911995. Natural disturbances played a greater role than harvest in determining the temporal pattern of forest NPP and NEP during the period because of the larger area affected by natural disturbances. This study also indicated that ignoring disturbances would lead to an overestimation of forest NPP and NEP in ecosystem modeling.
Cadmium-containing wood ash in a pine forest: effects on humus microflora and cadmium concentrations in mushrooms, berries, and needles
Authors: Perkiömäki Jonna , Kiikkilä Oili , Moilanen Mikko , Issakainen Jorma , Tervahauta Arja , Fritze Hannu
Published: January 2004

The cadmium (Cd) concentration of wood ash (130 mg·kg1) is higher than allowed for agriculture fertilizers (3 mg·kg1). Therefore, the objectives of this field study were to test if the Cd of wood ash has the potential to affect the coniferous forest humus microflora and if Cd enters the human food chain. These objectives were tested with ash (A) and Cd-spiked ash (ACd, 400 mg Cd·kg1) at a fertilization rate of 3 t·ha1. Microbial community structure, respiration, needle litter decomposition, growth rates and Cd tolerance of bacteria, and the bioavailability of Cd were measured. Also, Cd concentrations of humus, soil percolation water, mushrooms, fruits and leaves of berries, and needles were determined. The amount of Cd in the percolation water or bioavailable Cd, measured with a bacterial biosensor, and Cd tolerance of bacteria did not increase, although the ACd treatment increased the amount of humus total and extractable Cd. Only the ACd and not the A treatment caused Cd concentration increment in Lactarius rufus and berries of Empetrum nigrum. In spite of the high Cd concentration of the spiked ash, it did not have harmful effects on humus microorganisms during this 4-year study. Thus, wood ash is safe to use as a fertilizer in forests.
The effects of initial tree spacing on the fibre properties of plantation-grown coastal western hemlock
Authors: Watson Paul , Garner Cameron , Robertson Robin , Reath Sandy , Gee Wai , Hunt Ken
Published: January 2004

Fundamental wood and fibre properties determine end product quality potential. They are affected by silvicultural practices. Initial stand stocking density has significant economic implications for both forest managers and industrial end users. An evaluation of the wood density and fibre properties of 38-year-old coastal western hemlock (Tsuga heterophylla (Raf.) Sarg.) planted at five different spacings was completed. We determined that the wood density was not affected by spacing. At the widest spacing, the outer wood fibre length was significantly shorter than at the four tighter spacings. Fibre coarseness and cell wall properties were similar at all spacings. This implies that wood chips prepared from a range of small-diameter thinnings material will not adversely affect kraft pulp fibre properties.