bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscous Scaling Phenomena in Miniature Centrifugal Flow Cooling Fans: Theory, Experiments and Correlation
Authors: Walsh Patrick A. , Walsh Edmond J. , Grimes Ronan
Published: June 2010

This paper analyzes the scale effects that occur in miniature centrifugal flow fans and investigates the possibility of optimizing blade geometry so that performance can be enhanced. Such fans are typically employed in small scale heat sinks such as those used for processor cooling applications or in portable electronics. The specific design parameter varied is the blade chord length, and the resulting fan performance is gauged by examining the flow rate, pressure rise, and power consumption characteristics. The former two are measured using a BS 848 fan characterization rig and the latter, by directly measuring the power consumed. These characteristics are studied for three sets of scaled fans with diameters of 15 mm, 24 mm, and 30 mm, and each set considers six individual blade chord lengths. A novel theory is put forward to explain the anticipated effect of changing this parameter, and the results are analyzed in terms of the relevant dimensionless parameters: Reynolds number, chord length to diameter of fan ratio, flow coefficient, pressure coefficient, and power coefficient. When these characteristic parameters are plotted against the Reynolds number, similar trends are observed as the chord length is varied in all sets of scaled fans. The results show that the flow coefficient for all the miniature fans degrade at low Re values, but the onset of this degradation was observed at higher Re values for longer blade chord designs. Conversely, it was found that the pressure coefficient is elevated at low Re, and the onset Re for this phenomenon correlates well with the drop off in flow coefficient. Finally, the trend in power coefficient data is similar to that for the flow coefficient. The derived theory is used to correlate this data for which all data points fall within 6% of the correlation. Overall, the findings reported herein provide a good understanding of how changing the blade chord length affects the performance of miniature centrifugal fans; hence, providing fan designers with guidelines to aid in developing optimum blade designs, which minimize adverse scaling phenomena.
An Experimental Investigation in the Performance of Water-Filled Silicon Microheat Pipe Arrays
Authors: Harris D. K. , Palkar A. , Wonacott G. , Dean R. , Simionescu F.
Published: June 2010

This study details the fabrication and measurements of a water-filled 5 mm wide by 10 mm long silicon microheat pipe (MHP) array consisting of 22–100 μm square channels. This study is unique in that many experimental results reported in open literature are for single channel microheat pipes. The number of channels in the array and the fluid charge used here were optimized under a separate study. A number of experiments were carried out on the specimen MHPs to determine their effective thermal conductivity and comparisons were made with previous results found in literature. The testing methodology was designed to remove systematic biases and the array thermal performance measurements are reported in terms of a silicon equivalence by identically measuring an uncharged empty silicon array as a baseline measurement. Two separate water-filled specimens were made, independently tested, and are reported to have thermal conductivities of 261 W/m K and 324 W/m K, representing a silicon equivalence of 1.8 and 2.2, respectively. All testing was performed in a horizontal orientation.
Experimental Analysis Model of an Active Cooling Method for 3D-ICs Utilizing Multidimensional Configured Thermoelectric Coolers
Authors: Phan Huy N. , Agonafer Dereje
Published: June 2010

Presently, stack dice are used widely as low-power memory applications because thermal management of 3D architecture such as high-power processors inherits many thermal challenges. Inadequate thermal management of three-dimensional integrated circuits (3D-ICs) leads to reduction in performance, reliability, and ultimately system catastrophic failure. Heat dissipation of 3D systems is highly nonuniform and nonunidirectional due to many factors such as power architectures, transistors packing density, and real estate available on the chip. In this study, the development of an experimental model of an active cooling method to cool a 25 W stack-dice to approximately 13°C utilizing a multidimensional configured thermoelectric will be presented.
Multi-Objective Optimization to Improve Both Thermal and Device Performance of a Nonuniformly Powered Micro-Architecture
Authors: Karajgikar Saket , Agonafer Dereje , Ghose Kanad , Sammakia Bahgat , Amon Cristina , Refai-Ahmed Gamal
Published: June 2010

Integration of different functional components such as level two (L2) cache memory, high-speed I/O interfaces, and memory controller has enhanced microprocessor performance. In this architecture, certain functional units on the microprocessor dissipate a significant fraction of the total power while other functional units dissipate little or no power. This highly nonuniform power distribution results in a large temperature gradient with localized hot spots that may have detrimental effects on computer performance, product reliability, and yield. Moving the functional units may reduce the junction temperature but can affect performance by a factor as much as 30%. In this paper, a multi-objective optimization is performed to minimize the junction temperature without significantly altering the computer performance. The analysis was performed for 90 nm Pentium IV Northwood architecture operating at 3 GHz clock speed. Each functional unit on the die has a specific role, so functional units with similar roles were grouped together. Thus, the actual Pentium IV die was divided into four groups (front end, execution cores, bus and L2, and out-of-order engine). Repositioning constraints were determined using circuit delay models of major functional units in a micro-architectural simulator. Thus, depending on the scenario, relocating functional units can result in virtually no performance loss (less than 2% is assumed to be minimal and is reported as 0%) to as much as 30% performance loss. From the results, the minimum and the maximum temperatures were 56.6°C and 62.2°C. This ΔT corresponds to thermal design power of 60.2 W. For microprocessors with higher thermal design power (115 W) and operating at higher clock speed, higher ΔT can be realized. Based on this paper’s analysis, the optimized scenario resulted in a junction temperature of 56.6°C at the cost of a 14% performance loss.
The Structure of
cbb
3
Cytochrome Oxidase Provides Insights into Proton Pumping
Authors: Buschmann Sabine , Warkentin Eberhard , Xie Hao , Langer Julian D. , Ermler Ulrich , Michel Hartmut
Published: June 2010

C-Family Oxidase Structure

The heme-copper oxidases (HCOs) play a key role in aerobic respiration by coupling oxygen reduction to transmembrane proton pumping to generate electrochemical ion gradients across biological membranes that provide energy for many cellular processes. Based on subunit composition, electron donor, and heme type, the HCOs are divided into three families, of which families A and B have been structurally characterized.

Buschmann
et al.

(p.
327
, published online 24 June) now report the crystal structure of the C-family
cbb3
oxidase from
Pseudomonas stutzeri
. The structure suggests a different redox-driven pumping mechanism from A and B HCOs, and gives insight into why C HCOs are catalytically active at low oxygen concentrations.
Genetic Reactivation of Cone Photoreceptors Restores Visual Responses in Retinitis Pigmentosa
Authors: Busskamp Volker , Duebel Jens , Balya David , Fradot Mathias , Viney Tim James , Siegert Sandra , Groner Anna C. , Cabuy Erik , Forster Valérie , Seeliger Mathias , Biel Martin , Humphries Peter , Paques Michel , Mohand-Said Saddek , Trono Didier , Deisseroth Karl , Sahel José A. , Picaud Serge , Roska Botond
Published: June 2010

Let There Be Light

Retinitis pigmentosa, a disease that can result from a wide variety of genetic defects, causes degeneration of photoreceptor cells in the retina and leads to blindness. In the course of the disease, it is generally the rod photoreceptor cells that degenerate first. Cone photoreceptor cells may persist, but in a damaged and nonfunctional state.

Busskamp
et al.

(p.
413
, published online 24 June; see the cover; see the Perspective by

Cepko

) have now applied a gene therapy approach to mouse models of retinitis pigmentosa. Inducing expression of a bacterial light-activated ion pump, halorho dopsin, in the damaged cone cells improved visual responses in the diseased mouse retinas. Thus, it may be possible to rescue cone photoreceptors therapeutically, even after they have already been damaged.
Cancer incidence among women flax textile manufacturing workers in Lithuania: Table 1
Authors: Kuzmickiene Irena , Stukonis Mecys
Published: June 2010

Objective

To determine site-specific cancer incidence among women spinning-weaving and dyeing-finishing workers in the largest flax textile factory in Lithuania.

Method

The cancer incidence of a cohort of 3447 women workers from a flax textile factory was investigated for the period 1978–2002. All subjects were employed at the plant in the period 1957–2000 for a minimum of 12 months. Standardised incidence ratios (SIRs) were estimated by use of the corresponding national rates. SIRs were calculated for the spinning-weaving and dyeing-finishing work categories, and for two durations of employment categories (<10 years, ≥10 years).

Results

The cancer SIRs among spinning-weaving and dyeing-finishing workers were 0.84 (95% CI 0.69 to 1.00) and 0.90 (95% CI 0.52 to 1.44). An incidence deficit for non-melanoma skin cancer was found for the spinning-weaving unit (SIR 0.45, 95% CI 0.18 to 0.92). The risk of oral cavity and pharynx cancer was significantly increased in spinning-weaving unit workers with <10 years of employment (SIR 5.71, 95% CI 1.56 to 14.60). A significant excess of thyroid cancer and nervous system cancer was found among dyeing-finishing workers.

Conclusions

The overall cancer and non-melanoma skin cancer incidence rate among flax spinning-weaving workers was lower compared with the Lithuanian population. The present findings lend some support to an excess of thyroid and nervous system cancers among dyeing-finishing workers and of oral cavity and pharynx cancer in spinning-weaving workers.
The Employment Precariousness Scale (EPRES): psychometric properties of a new tool for epidemiological studies among waged and salaried workers
Authors: Vives Alejandra , Amable Marcelo , Ferrer Montserrat , Moncada Salvador , Llorens Clara , Muntaner Carles , Benavides Fernando G , Benach Joan
Published: June 2010

Background

Despite the fact that labour market flexibility has resulted in an expansion of precarious employment in industrialised countries, to date there is limited empirical evidence concerning its health consequences. The Employment Precariousness Scale (EPRES) is a newly developed, theory-based, multidimensional questionnaire specifically devised for epidemiological studies among waged and salaried workers.

Objective

To assess the acceptability, reliability and construct validity of EPRES in a sample of waged and salaried workers in Spain.

Methods

A sample of 6968 temporary and permanent workers from a population-based survey carried out in 2004–2005 was analysed. The survey questionnaire was interviewer administered and included the six EPRES subscales, and measures of the psychosocial work environment (COPSOQ ISTAS21) and perceived general and mental health (SF-36).

Results

A high response rate to all EPRES items indicated good acceptability; Cronbach's α coefficients, over 0.70 for all subscales and the global score, demonstrated good internal consistency reliability; exploratory factor analysis using principal axis analysis and varimax rotation confirmed the six-subscale structure and the theoretical allocation of all items. Patterns across known groups and correlation coefficients with psychosocial work environment measures and perceived health demonstrated the expected relations, providing evidence of construct validity.

Conclusions

Our results provide evidence in support of the psychometric properties of EPRES, which appears to be a promising tool for the measurement of employment precariousness in public health research.
Petrology of the Grenville swarm of gabbro dikes, Canadian Precambrian Shield
Authors: Kretz R. , Hartree R. , Garrett D. , Cermignani C.
Published: June 2010

The Grenville tholeiitic dikes of Late Proterozoic or early Paleozoic age cut marbles and gneisses of the Grenville Province within and adjacent to the Ottawa rift structure. Where traversed the swarm consists of about 40 large dikes (up to 100 m wide) representing a crustal extension of 1 km. The principal minerals are olivine, augite, pigeonite, plagioclase, magnetite, ilmenite, K-feldspar, and quartz. Crystals of pigeonite around olivine and complex augite–pigeonite composite grains suggest that the reactions olivine + melt → pigeonite and pigeonite + melt → augite have taken place. Conspicuous zoning and grain to grain variation in the composition of augite are consistent with fractional crystallization, but crystal – melt equilibrium during crystal growth is indicated by a restricted range in pyroxene paleotemperatures of 1180–1060 °C. Rock textures (subophitic, combined ophitic–subophitic, and equigranular) in dike centres are related to dike width and are determined principally by the influence of cooling rate on the nucleation of augite. The K2O content of the gabbro (centres of 15 dikes, 3–100 mm wide) ranges from 0.2 to 1.2% and is closely correlated with other elements, positively with Ti, Na, P, Rb, Sr, Y, Zr, and Ba, and negatively with Mg, Ca, and Cr. Relatively minor within-dike variation exists in the form of local (centimetre-scale) inhomogeneity, slight enrichment in K and Na, and depletion in Ca and Mg in the centre of one large dike and complex rhythmic variation in K, Na, Ca, and Fe across one small dike. Centre–margin comparisons in several large dikes indicate minor residence con tamination (Ca, Mg) in the margins of some dikes cutting marble. Of the various possible causes for variation in composition, those favoured at present are Fractional crystallization at depth (separation of augite and plagioclase), the partial preservation of compositional heterogeneity during intrusion, and the gravitational sinking of early formed crystals (with the upward displacement of K-enriched melt) in the central regions of large dikes.
Sm/Nd isotopic investigation of the age and origin of the Meguma Zone metasedimentary rocks
Authors: Clarke D. B. , Halliday A. N.
Published: June 2010

The Meguma Zone of southern Nova Scotia is a suspect terrane in the eastern Appalachians. Sm/Nd isotopic data on six samples from the thick sequence of flyschoid metasediments of the Meguma Group show that these rocks have a mean crustal residence age of TDM = 1773 ± 95 Ma, considerably older than their Cambro-Ordovician depositional age. This information should be useful in locating the matching terrane for the Meguma and ultimately in determining whether it was derived from one or more Precambrian sources with different crustal residence times.
Source parameters of the Ensenada Bay earthquake swarm, Baja California, Mexico
Authors: Rebollar Cecilio J.
Published: June 2010

Seismic data collected from the Ensenada Bay earthquake swarm of late 1981 were used to calculate the spectra of ground displacement. Data from the stations of Ensenada (ENX) and Cerro Bola (CBX), at epicentral distances of 14 and 57 km, respectively, were used to evaluate source parameters. The focal depths determined for these events were less than 10 km. The focal mechanism was a strike-slip fault type, with the plane of motion striking N52°W, parallel to the Agua Blanca Fault. Seismic moments ranging from 3.44 × 1019 to 5.99 × 1020 dyn∙cm (3.44 × 1014 to 5.99 × 1015 N∙cm) were estimated for events with local magnitudes in the range 1.7–2.3. The source dimensions were found to be 186 ± 36 m and the stress drops between 3 and 66 bar (0.3 and 6.6 MPa), comparable to results obtained in previous studies of shallow events (depths <10 km). The Ensenada swarm could be attributed to a localized zone of high-strain energy at the intersection of two faults. Ratios of P to S corner frequencies were evident for only five events; they were 1.39 ± 0.38. Magnitude and seismic moment from other studies were compared with the Ensenada data in the range of magnitudes 0–3. All the data can be accommodated by log M0 = 1.5 ML + (16.9 ± 1.1). The Ensenada earthquake swarm and the Victoria earthquake swarm, which occurred in the Mexicali valley in 1978, have similar source radii and corner frequencies for the same range of seismic moments.
A lightweight gravity corer for undisturbed sampling of soft sediments
Authors: Pedersen T. F. , Malcolm S. J. , Sholkovitz E. R.
Published: June 2010

A lightweight, portable gravity corer is described that collects up to 3 m long, 10 cm diameter undisturbed cores from sediments of exceptionally high porosity. The corer employs a triple O-ring seal to hold sediments in an unsupported, catcher-free plastic barrel simply by suction.
Implications of spore evidence for Late Devonian age of the Piskahegan Group, southwestern New Brunswick
Authors: McGregor D. C. , McCutcheon S. R.
Published: June 2010

The predominantly volcanic Piskahegan Group has commonly been considered Early Carboniferous, based on its stratigraphic position. However, spores recently discovered in the Carrow Formation, an alluvial fan deposit in the exocaldera facies, indicate that most, if not all, of the group is of Late Devonian (late Famennian) age. The spore assemblage includes several species reported previously from Ireland, Belgium, and eastern Europe, some of them apparently restricted to the southern parts of the Old Red Sandstone Continent in Late Devonian time. Comparison of records of earliest occurrences suggests that the incoming of some species was diachronous. Volcanic rocks of the Piskahegan Group are coeval with post-Acadian, tin–tungsten-bearing granites elsewhere in New Brunswick and are considered the surface expression of plutonism that resulted from Acadian continental collison.
Archean and Proterozoic crust in North-West Greenland: evidence from Rb–Sr whole-rock age determinations
Authors: Dawes Peter R. , Larsen Ole , Kalsbeek Feiko
Published: June 2010

The geochronological understanding of the Precambrian crystalline shield of North-West Greenland (75–79°N) is at a rudimentary stage. Isotopic data from three major rock complexes—the Etah meta-igneous complex, the Kap York meta-igneous complex, and the Kivioq Havn gneiss and supracrustal complex—all show scatter indicating disturbed Rb–Sr isotope systems. This may reflect widespread reactivation of the crust in Proterozoic (Hudsonian) time. However, the majority of the samples define errorchrons that are regarded as geologically significant, and although the ages are poorly constrained, the data demonstrate the presence of both Archean and Proterozoic terranes.The Etah complex is Proterozoic in age (errorchron age ca. 1850 Ma), whereas the Kap York and Kivioq Havn complexes represent late Archean material (errorchron age ca. 2700 Ma). These ages compare favourably with isotopic age information from adjacent Canada in southeast Ellesmere Island and Devon Island, where correlatable Archean and Proterozoic rock complexes occur.
Subaqueous outwash deposits in the Ingraham ridge, Chazy, New York
Authors: Diemer John A.
Published: June 2010

A 1.5 km segment of Ingraham ridge, a stratified sand and gravel ridge in northeastern New York, is composed dominantly of subaqueous outwash deposits. The core of the ridge segment may include subordinate subglacial tunnel deposits. The subaqueous outwash is composed mainly of interbedded sediment gravity flow, bar, dune, and ripple deposits that occur in channels. Sheetlike cross-stratified and cross-laminated deposits also are common, particularly on the distal western margin of the ridge segment. The ridge segment is draped by glaciolacustrine laminated sand, silt, and clay and glaciomarine massive mud. Westward decrease in grain size and scale of sedimentary structures is attributed to confining ice walls of an asymmetric embayment. Sediments are deformed in part by the melting of adjacent and buried ice. The ridge was modified during Champlain Sea regression and the reworked deposits were colonized by shallow-water organisms. Reworking may have been minor, and the broad, low morphology of the ridge may be due to subaqueous outwash deposition along its full length during retreat of the ice margin.
Mesofabric, microfabric, and submicrofabric of ice-thrust bedrock, Highvale mine, Wabamun Lake area, Alberta
Authors: Tsui Po C. , Cruden David M. , Thomson Stanley
Published: June 2010

The fabric of the ice-thrust argillaceous bedrock from a shear zone was studied in hand specimens, under a polarizing microscope and a scanning electron microscope. The fabric included principal displacement shears, Riedel shears, conjugate sets of particle alignments, cutans, lithorelics, and aggregations which dense cores of randomly oriented groups of clay platelets wrapped by an external layer of oriented clay particles in a turbostatic arrangement. In addition, the bedrock has been disturbed by permafrost, cycles of loading and unloading, and weathering, causing the magnitude of deformation to vary within the ice-thrust shear zone.The fabric of the ice-thrust shear zone is similar to that of shear zones formed by tectonic activity and by laboratory shear tests, suggesting that all these shear zones were formed under conditions of similar kinematic restraint.
Faunal assemblages of the Upper Gaspé Limestones, Early Devonian of eastern Gaspé, Quebec
Authors: Lespérance Pierre J. , Sheehan Peter M.
Published: June 2010

The 500–2000 m thick Early Devonian Upper Gaspé Limestones of the Gaspé Peninsula, Quebec, were deposited in moderately deep water, below wave base. The brachiopod–trilobite–dominated faunas lived during the long interval of community stasis that has been termed ecologic–evolutionary unit (EEU) VI. Synecologic analysis of these faunas by Q-mode cluster analysis produced 10 distinct brachiopod-dominated faunal assemblages (FA's). Most of these can be assigned to previously recognized communities or community sequences. An eleventh FA, artificially recognized, is dominated by trilobites, and it includes a newly recognized Roncellia gaspensis Community. Synecologic changes during the interval under investigation were gradual. FA's either extended through most of the interval or were derived directly from previous FA's. This evolutionary pattern probably represents evolutionary fine tuning, such as is expected during the long intervals of EEU stasis. Even though most of the Phanerozoic is composed of these intervals of EEU stasis, few studies have examined these intervals. Most synecologic work has concentrated on either intervals of reorganization of EEU's or times when the local environments caused changes in the local community composition. This study of a uniform habitat during an interval of EEU stasis serves to document the background rates of synecologic change and could serve as a standard against which the times of more dramatic synecologic reorganization can be compared.
Boron and lithium in high-grade rocks and minerals from the Wawa–Kapuskasing region, Ontario
Authors: Shaw D. M. , Truscott M. G. , Gray E. A. , Middleton T. A.
Published: June 2010

There is no preferential partitioning of boron among the principal rock-forming minerals in high-grade rocks of the Kapuskasing Structural Zone (KSZ) and the Wawa Domal Gneiss region (WDG). Lithium is strongly concentrated in biotite and other ferromagnesian minerals but does not show consistent partitioning between these and the sialic minerals.The distribution of B and Li within a rock may be studied using an alpha-track image, which shows that the inconsistencies in partitioning may be largely attributed to disturbance of mineral equilibria by postmetamorphic low-grade alteration that deposited B and Li.Boron has similar concentrations in all the rock types studied, although it is an incompatible element that elsewhere accumulates in pegmatites. Lithium concentrations are low in the anorthositic rocks but are otherwise very variable. In some but not all rocks higher than usual B and Li can be attributed to introduction during alteration.Boron occurs at low concentrations (2–3 ppm) throughout both the KSZ and the WDG areas and has an abundance similar to that in other granulite terranes. It is significantly lower than in average upper crustal rocks (9–15 ppm), and this is attributed to loss by fluid transport during formation of lower crustal material. Lithium occurs at similar concentrations in upper crustal rocks (20–22 ppm) as in the WDG area (27 ppm) but is lower in the KSZ (13 ppm), suggesting again a loss by fluid transport in the deep crust. Both estimates of loss are minima because of the evidence of reintroduction of the elements during later alteration.Although there is field and petrological evidence of anatectic melting in the KSZ–WDG region the distribution patterns of B and Li show no evidence of this: this is not unexpected for elements that readily partition into a fluid phase.
Microscopic planar features in quartz from Scollard Canyon, Alberta, and the Cretaceous–Tertiary boundary event
Authors: Grieve R. A. F. , Alexopoulos J.
Published: June 2010

Quartz grains separated from the Cretaceous–Tertiary (K/T) boundary clay at Scollard Canyon, Alberta, have prominent, microscopic planar features. These occur in 15–30% of the grains from the lower 1.5 cm of the boundary clay. They commonly correspond to the ω and π orientations found at known meteorite impact sites and differ from deformation features produced by other dynamic geologic processes. Basal planar features, however, are absent here and at other K/T sites. One possible explanation is that quartz at boundary sites is an incomplete sample of shocked quartz from the postulated K/T impact and unshocked detrital quartz. The source of the shocked quartz most likely was close to the point of impact and near surface. This and previous isotopic data suggest the K/T target site contained a relatively thin upper unit of quartz-bearing crystalline rocks overlying basaltic material, corresponding possibly to thinned continent or a continental margin.
Geochronology at the Namew Lake Ni–Cu orebody, Flin Flon area, Manitoba, Canada: thermal history of a metamorphic terrane
Authors: Cumming G. L. , Krstic D.
Published: June 2010

Intermediate composition orthogneisses of the southward extension of the Flin Flon greenstone belt surround the ultramafic host rock of the Namew Lake Ni–Cu deposit in northern Manitoba. The gneisses began cooling from elevated temperatures of approximately 700 °C at 1860 Ma when growth of new zircons ceased, after a protracted period of formation starting at ca. 1890 Ma. Zircons in the ultramafic rock itself indicate that it was intruded into the gneisses at 1847 Ma. Subsequently, the temperature decreased very slowly, with a relaxation time of 160 Ma, cooling through the blocking temperature for Ar loss in hornblende at 1799 Ma and for that in biotite at 1735 Ma. Using published values for blocking temperatures, we find that the temperature–time data are consistent with simple exponential decrease in temperature and do not require discreet pulses of thermal activity during the first 150 Ma of cooling. There is no indication of temperature as high as the blocking temperature for biotite, subsequent to 1735 Ma.Data from sphenes yield a range of ages between 1828 and 1820 Ma, correlated with the color of the sphene grains. This age range is intermediate between that of zircon and hornblende and is consistent with a blocking temperature of about 525 °C, whereas apatite gives an age of ca. 1810 Ma and therefore a blocking temperature between that of sphene and hornblende. The good precision on all the ages obtained provides rather precise relative blocking temperatures for zircon, sphene, apatite, hornblende, and biotite and provides a detailed thermal history for this region of the Flin Flon belt.
Helicosporous fungi and Early Eocene pollen, Eureka Sound Group, Axel Heiberg Island, Northwest Territories
Authors: Kalgutkar R. M. , McIntyre D. J.
Published: June 2010

Two types of helicosporous fungal spores were recovered from a sample from the Iceberg Bay Formation, Eureka Sound Group, at Strand Fiord, Axel Heiberg Island. These spores appear to be identical to those produced by the Recent genera Helicoön, Helicodendron, and Helicosporium. The associated pollen flora indicates an Early Eocene age for the sample and interval from which it was collected. The pollen and spores suggest that swamp forest vegetation, dominated by trees of Taxodiaceae–Cupressaceae and growing in a temperate climate, was present at or close to the site of deposition.
Structural analysis of the central and southwestern Sudbury Structure, Southern Province, Canadian Shield
Authors: Shanks W. S. , Schwerdtner W. M.
Published: June 2010

The Sudbury Structure (SS) is an unusual crater structure which acquired its present oval surface shape during northwest-directed ductile thrusting. Lower amphibolite-facies metamorphism accompanied the thrusting which generated a major reverse shear zone. At least 50 km long, the South Range shear zone (SRSZ) transects the South Range of the Sudbury Structure and exhumes a low level of the Sudbury Igneous Complex (SIC). Assuming heterogeneous simple shear in the northwest–southeast vertical plane on northeasterly striking glide surfaces, minimal estimates of net displacement across the SRSZ exceed 8 km. This displacement magnitude and the map pattern of the SIC require the southwest closure of the SS to be steeply plunging, in accord with a hypothetical funnel shape of the SIC. The rocks of the metasedimentary core of the SS are deformed into a family of second-order buckle folds, the tangent surface of which forms an upright open flexure within the first-order structure of the Sudbury synclinorium. The original orientation and bulk rotation of contacts in the SIC are unknown, so its participation in large-scale folding remains uncertain.
A magmatic sheet origin for thin metagabbroic anorthosite units in the Fishog subdomain of the southern Central Gneiss Belt, Grenville Province, Ontario
Authors: Van Kranendonk Martin J.
Published: June 2010

Thin (tens of metres wide by tens of kilometres long) sheets of metagabbroic anorthosite are a common and intriguing feature of the Central Gneiss Belt (CGB), southwestern Grenville Province. Their origin, however, as either tectonic remnants of originally much larger parent masses or as moderately strained magmatic sheets is controversial because regional high strain has largely obliterated original contact relationships and modified primary textures. The origin of three sheets of metagabbroic anorthosite within the Fishog subdomain of the CGB is examined. Field relationships and geochemical analyses indicate that the sheets are composed of two distinct subunits (A = anorthositic, with An57–63; B = dioritic, with An41–47) that may be genetically related but have been contaminated by a significant crustal component during intrusion. Grenvillian deformation was accommodated by the sheets through early ductile flow and subsequent brittle rupturing during folding that was accompanied by the intrusion of pegmatite veins. Field observations and the results of Robin's method of strain analysis applied to representative samples of the least strained of these sheets, the Head River unit (HRU), show that internal strain was low. Preserved contact relationships of gabbroic anorthosite magma into dioritic country rocks and of granitic sheets into the HRU can be used to infer that ductile thrusting was not an important mechanism in the formation of the sheets' narrow geometry but that it simply modified the shape of magmatic sheets. A magmatic sheet hypothesis is proposed for the origin of meta-anorthositic sheets and associated rocks of the Fishog subdomain and may serve as a viable model for the precursors to some of the more highly strained sheets of meta-anorthositic gneiss found throughout the CGB.
Seismic stratigraphy of Lake Huron – Georgian Bay and postglacial lake level history
Authors: Moore Jr. Theodore C. , Rea David K. , Mayer Larry A. , Lewis C. F. Michael , Dobson David M.
Published: June 2010

Five seismic reflectors in the basinal sedimentary section have been identified as representing erosional surfaces in shoaler regions of the lake basins and can be traced throughout most of the study area. The reflectors representing these erosional surfaces, and their conformable equivalents in the deep lake basins, are caused by intervals of coarser grain size in the sediments and are thought to represent lowering of lake levels prior to, and following, the Main Algonquin highstand (about 10.2 – 11.0 ka). These reflectors are used to define seismic sequences in the postglacial sedimentary fill of the basins. Two additional erosional surfaces, which closely follow the initial fall of the Main Algonquin lake level, are most clearly seen in thicker sections found in the northern part of the basins. The two oldest (pre-Main Algonquin) sequences appear to onlap highs and fill in lows within the basins, whereas the younger sequences (associated with the Main Algonquin through Mattawa times) tend to drape the topography and show little difference in thickness between the lows and their adjacent highs. The most recent sedimentary sequence represents deposition occurring since about 7.5 ka. It laps out against topographic highs and leaves older sequences exposed at the lake floor in many areas. The most pronounced erosional surfaces are associated with the Light Green and the Light Blue sequence boundaries. The Light Green sequence has a pair of coarser layers at its top, which are dated at 9.6 – 9.8 ka and 9.05 – 9.2 ka. The coarser interval at the top of the Light Blue sequence is dated at 7.45 – 7.80 ka. These layers are thought to mark maximum lake level lowstands and to represent the times of Ottawa–Marquette to latest Mattawa lake level fluctuation.
Reconstruction of post-Iroquois shoreline evolution in western Lake Ontario
Authors: Coakley John P. , Karrow Paul F.
Published: June 2010

When Lake Iroquois drained between 11.7 and 11.4 ka BP, lake level in the Ontario basin fell from a high of more than 40 m above present lake level to a minimum close to the then-existing sea level, which was approximately 40 m below present sea level. Since that time, lake level has been rising at an exponentially decreasing rate in the western portion of the basin as a result of postglacial and neotectonic uplift of the outlet near Kingston, at the eastern end. The published lake level history has been combined with other less well-known parameters (the post-Iroquois regional topography, erosion – deposition rates, and distribution of resistive shore materials) to reconstruct the evolution of the western Lake Ontario shoreline. Borehole, long piston core, and other subsurface data sources, primarily from the western portion of the lake near Hamilton Harbour, provide most of the physical constraints. Time references were provided by radiocarbon dates on shallow-water organics in the subsurface sediments. A computer program was designed to calculate and contour the changing elevations of the rebounding post-Iroquois topographic surface, allowing the time-dependent water-plane elevation to be superimposed. Semiquantitative allowance was made for differential erosion and deposition along the advancing shoreline. The reconstruction provides a perspective on past and future shoreline evolution in the basin and possibly on the location of potentially commercial offshore deposits of aggregate.
Inferred subglacial meltwater origin of lakes on the southern border of the Canadian Shield
Authors: Gilbert Robert , Shaw John
Published: June 2010

Paleozoic rocks form an escarpment up to 35 m high at the border with the Frontenac Axis of the Canadian Shield in southeastern Ontario. The escarpment, which lies nearly transverse to the flow direction of Pleistocene ice and subglacial meltwater in the region, is cut by a series of deep channels locally incised into the bedrock at the escarpment. A subbottom acoustic survey of two of these channels and mapping of a third, partly flooded channel revealed the shape of the bedrock surface beneath the water and glacial and postglacial sediments of lakes now occupying the channels. Most cross sections show a smooth-walled, dominant depression eroded up to 100 m below the land surface nearby, and flanked by one or more secondary depressions. The pattern changes considerably in detail, making secondary depressions especially difficult to trace along the length of the lake. The pattern is similar to that of subglacial fluvial erosion marks more than three orders of magnitude smaller found in bedrock throughout the region. We ascribe the origin of these channels cut across the escarpment to periodic, large flows of water beneath the Laurentide Ice Sheet. The escarpment formed a barrier through which the flow was forced at regular intervals, eroding large-scale channels at these sites of confined and accelerated flow, while the ice was still largely in contact with the surrounding surface. At the highest flows the entire surface was flooded and eroded.
The Dogtooth Duplex, a model for the structural development of the northern Purcell Mountains
Authors: Kubli Thomas E. , Simony Philip S.
Published: June 2010

Structural analysis based on recent detailed mapping of part of the Dogtooth Range of the northern Purcell Mountains confirms and refines a previous interpretation of a duplex structure, which, after its formation, was carried passively in the hanging wall of the out-of-sequence Purcell Thrust. Several parameters, such as thrust spacing, thrust displacement, and fold shape, place geometric constraints on the Dogtooth Duplex. Thrust spacing/displacement ratios indicate that the older structures of the western Dogtooth Range can be approximated by an antiformal stack model, whereas the younger structures of the eastern Dogtooth Range fit a hinterland-dipping duplex. The sole thrust of the Dogtooth Duplex is inferred to follow incompetent rocks in or below the basal part of the Hadrynian Windermere Supergroup. The roof thrust is inferred to follow shaley rocks, probably in the Middle Cambrian Chancellor Formation. From balanced, restored cross sections, total shortening within the duplex is estimated at 18–23 km or 50% of the initial width of the deformed strata. This shortening is interpreted to have been transferred during an early stage of deformation from the sole thrust of the Dogtooth Duplex to an upper detachment in Middle Cambrian strata of the Porcupine Creek Anticlinorium in the western Rocky Mountains. While subsequent shortening was partly accommodated within the Porcupine Creek Anticlinorium and partly transferred to the structures of the Main and Front ranges, the Dogtooth Duplex was carried passively on top of a "parautochthonous" wedge.
Fabrics and kinematic indicators associated with the local structures along Finlay – Ingenika fault, McConnell Creek area, north-central British Columbia
Authors: Zhang Guowei , Hynes Andrew
Published: June 2010

Structures associated with dextral transcurrent displacement on the Finlay – Ingenika fault are characterized predominantly by subvertical to vertical faults. Intersections of the fault planes with planar fabrics are all subvertical. This geometry, together with the common occurrence of subhorizontal slickenlines and stretching lineations in some strongly deformed fault zones, indicates their strike-slip nature. Principal directions of the strain ellipsoids determined from the deformed volcanic fragments along one of the faults are in accordance with those of the magnetic susceptibility ellipsoids from the adjacent plutonic rocks, indicating that the plutonic rocks experienced the same deformation as the Late Triassic Takla Group volcanics. Regional cleavage within the fault-bounded blocks indicates that the blocks were nonuniformly rotated clockwise about subvertical axes in response to progressive dextral transcurrent displacement on the Finlay – Ingenika fault. The mode of deformation observed in the area may characterize many parts of the Intermontane Belt.
A two-stage emplacement for the Cabonga allochthon (central part of the Grenville Province): evidence for orthogonal and oblique collision during the Grenville orogeny
Authors: Martignole J. , Pouget P.
Published: June 2010

The Cabonga allochthon (central part of the Grenville Province) is a Proterozoic unit of high-grade metasedimentary and metaigneous rocks resting on top of reworked parautochthonous Archean migmatites of the Réservoir Dozois terrane. The geometry and final assembly of terranes in this area result from the following succession of strains and displacements: (1) thrusting towards the northwest of a Proterozoic terrane; (2) northwest – southeast shortening of the transported terrane as indicated by large-scale northeast-trending buckle folds and by coeval development of a décollement within the upper layers of the Archean footwall; (3) reactivating of this décollement in the form of an east-dipping thrust, the Cabonga thrust (piggy-back sequence); the detached basement and the Proterozoic allochthon forming the Cabonga thrust sheet; (4) northeast-trending sinistral wrenching in the parautochthon, responsible for the sinuous contour of the overlying Cabonga thrust and probably also for the westward thrusting itself.The first two stages are best understood in a regime of northwest-directed shortening tectonics, well documented in other parts of the Grenville Province. The last two stages are correlated with a regional sinistral wrenching affecting the Grenvillian parautochthon and thus the footwall of the Cabonga allochthon. During this episode, the southern part of the parautochthon, sinking towards the northeast, may have acted as a northeast-dipping indenter responsible for the westward thrusting, which can be visualized as a lateral extrusion of the Cabonga thrust sheet. The above succession of events suggests a switch from orthogonal to oblique collision tectonics.
Distribution of relative growth rates and variation of cytohistological zonation in apical meristems of seedlings of two contrasting open-pollinated jack pine (Pinusbanksiana) families
Authors: Kremer Antoine
Published: June 2010

A general method is developed to obtain relative growth rates in different parts of an apical meristem, bare apical dome, internode, and whole apical dome. Expressions are given for transverse, longitudinal, and volume growth. It is shown that these growth rates depend on only four parameters, radius (Ro) and height (Ho) of the bare apical dome and transverse (r) and longitudinal (h) plastochron ratios. A method is described to obtain relative volumes of different zones in apices showing cytohistological zonation using relative area measurements on median longitudinal sections. Both methods are applied to a practical example, on ontogenetical variation of seedlings originating from two open-pollinated families of jack pine (Pinusbanksiana Lamb.) that exhibited a contrasting pattern of height growth in previous studies. Both families differ in their plastochron duration (PD) and this difference can be related to different distributions of growth rates in the apical meristem. PD values range, between 16–6 h in the first family, and between 12–4 h in the second one. Most family differences appear on bare apical dome growth rates and on allometric coefficients between bare apical dome growth and intermode growth. As an example, bare apical dome radial relative growth rates per PD varies during ontogeny from 0.004 to 0.008 and then decreases to −0.011 during the first 70 days after germination for the first family. Corresponding values for the second family are 0.001, 0.007, and −0.004. There are also ontogenetical variations in cytohistological zonation. Both families show an increase in the apical initial plus central mother cell zone relative volume following the decrease of plastochron duration. However, no significant differences between families are obtained for relative volumes of cytohistological zones. Relationships between distributions of growth rates and changes of cytohistological zonation are discussed.
Disequilibrium cutting rules
Authors: Johansson Per-Olov
Published: June 2010

This paper derives cost–benefit rules to be used when examining whether unemployment and other market imbalances provide justification for national forest managers to depart from the classical Faustmann rotation rule. It turns out that a high level of unemployment in a particular year is not normally a sufficient condition to justify increased cutting in that year (even if full employment is expected to prevail in the future). Moreover, it may very well be socially unprofitable to increase cutting when there is excess demand for timber. These results are in stark contrast with those found in textbooks on applied welfare economics, saying that unemployment and (or) excess demand for goods always justify a higher level of production than the profit maximizing one. This is so because the latter rules are derived for ordinary produced goods in single-period models, while forest management must be considered in an explicit intertemporal framework.
Summer soil moisture content and the water table in a forested wetland peat
Authors: Munro D. S.
Published: June 2010

Soil samples were collected from the peat of the Beverly Swamp, at weekly intervals, over three successive summers. The samples were analyzed to determine the distribution of soil moisture within the peat above the water table. A calculation scheme for the soil mositure deficit is defined and utilized to describe the behaviour of the soil moisture regime over time. Linear regressions of soil moisture deficit against water table level are found to be statistically strong, but the slopes of the regressions change significantly from one summer to the next. Therefore, it is concluded that the position of the water table is not necessarily a consistent indicator of storage capacity in wetlands.
Effects of CO2 enrichment on growth of Liquidambarstyraciflua and Pinustaeda seedlings under different irradiance levels
Authors: Tolley Leslie C. , Strain B. R.
Published: June 2010

Mathematical growth analysis techniques were used to assess the effects of atmospheric carbon dioxide enrichment on growth and biomass partitioning of Liquidambarstyraciflua L. (sweetgum) and Pinustaeda L. (loblolly pine) seedlings. Plants were grown from seed under high (1000 μmol•m−2•s−1) and low (250 μmol•m−2•s−1) photosynthetic photon flux density at CO2 concentrations of 350, 675, and 1000 μL•L−1 for 84 or 112–113 days. Elevated atmospheric CO2 concentration significantly increased height, leaf area, basal stem diameter, and total dry weight of sweetgum seedlings grown under high irradiance and to a lesser extent under low irradiance. Increases in dry matter accumulation were associated with early CO2 enhancement of net assimilation rate, but increases in amount of leaf surface area contributed more towards maintenance of larger size as seedlings aged. For sweetgum seedlings in particular, reduction of growth by low irradiance under normal atmospheric CO2 was compensated for by growing plants with elevated CO2. In contrast, elevated CO2 concentration produced no significant increase in growth of loblolly pine seedlings.