bluuebunny/crossref_metadata_2025 huggingface dataset:
Holocene treeline dynamics in the mountains of northeastern British Columbia, Canada, inferred from fossil pollen and stomata
Authors: Pisaric Michael F. J. , Holt Catherine , Szeicz Julian M. , Karst Tammy , Smol John P.
Published: February 2003

Changes in pollen and stomata assemblages in sediment cores recovered from tundra and foresttundra lakes in alpine regions of northeastern British Columbia reflect vegetation and inferred climatic change throughout the Holocene. Pollen and stomata records are presented from two lakes, BC2 located in the alpinetundra zone and Dead Spruce Lake at the present elevation of subalpine treeline. The pollen and stomata records from BC2 indicate that an ephemeral shrub and herb assemblage was rapidly replaced by an aspen (Populus)-spruce (Picea)-birch (Betula) woodland at ~ 10600 cal. yr BP. The occurrence of stomata suggests that treeline was at least 235 m higher than present from ~10 600 until ~7500 cal. yr BP and temperatures were at least 1.4°C warmer than at present. Analyses from Dead Spruce Lake indicate that the density of trees was also higher between ~9000 and 4800 cal. yr BP. High concentrations of macroscopic charcoal between ~9800 and 8000 cal. yr BP suggest that conditions were also drier at this time. Changes in the position of treeline during the early to mid-Holocene appear to track closely shifts in climate, while forest development at our forest-tundra site reflects a combination of both heightened summer insolation and increased fire activity. The fossil stomata record from BC2 suggests that a rapid cooling event at ~8200 cal. yr BP may have been the trigger that resulted in the downslope movement of treeline to its present elevation. Increased Picea percent ages, pollen-accumulation rates (PARs) and concentration of stomata between ~3600 and 2700 cal. yr BP provide evidence for a late-Holocene increase in forest-tundra density in response to warmer temperatures.
Holocene timberline and palaeoclimate of the northern Uinta Mountains, northeastern Utah, USA
Authors: Munroe J. S.
Published: February 2003

Clastic and organic sediments exposed in two stream cutbanks above modern timberline in the headwaters of the Henrys Fork drainage record multiple episodes of fluvial, lacustrine and wetland deposition. The location of the upper Henrys Fork at the boundary between modern summer-wet/winter-dry and summer dry/winter-wet precipitation regimes suggests that changes in vegetation during the Holocene were due primarily to variations in growing-season temperature. A radiocarbon date of 9310 6 70 BP on a Salix fragment from the base of one exposure indicates that the upper reaches of the Henrys Fork were vegetated by riparian willows by the early Holocene. Four other dates on wood and bulk organics ranging up to 4070 6 70 BP indicate that deposition continued through the middle Holocene. High Picea/Pinus ratios and high percentages of Artemisia pollen suggest that an open Picea parkland was established at timberline by 9.5 ka cal. BP, in response to mean annual and July temperatures ~1.0°C greater than at present. Continued warmth through the middle Holocene allowed Pinus to expand upwards into the spruce parkland by 7.5 ka cal. BP. A period of maximum warmth was reached between 6.5 and 5.4 ka cal. BP, and near-modern conditions prevailed over the final ~1000 years of the record (until 3.8 ka cal. BP).
Holocene palaeoenvironmental changes in southern France: a palaeobotanical study of travertine at St-Antonin, Bouches-du-Rhône
Authors: Ali Adam A. , Terral Jean-Frédéric , Guendon Jean-Louis , Roiron Paul
Published: February 2003

Travertines are carbonate deposits formed generally during temperate climatic periods. They usually present a succession of travertinous units and detrital sedimentary levels containing leaf impressions and charcoal, respectively. The travertine of St-Antonin was formed during the Holocence in accordance with this model; snail shells and archaeological material have also been preserved, essentially in detrital levels. An interdisciplinary investigation combining two palaeobotanical approaches (identification of leaf imprints and charred wood) has been carried out to identify vegetation changes, at a local or microregional scale during the travertine formation. Our results were compared with those of previous malacological, geomorphological and archaeological studies. The Preboreal and Boreal sequence of the travertine shows evidence of a reduction of the riverside vegetation correlated with the establishment of a mesophilous vegetation dominated by the pubescent oak (Quercus pubescens). During the Boreal–Atlantic transition, the vegetation structure changed slightly under anthropogenic influence. From the Atlantic to the first part of the Subboreal, vegetation seems to have been profoundly affected by intensive human exploitation. This process has broken up the forested area into different plant communities and favoured the dominance of heliophilous and thermophilous species.
Chronological control of coral records using luminescent lines and evidence for non-stationary ENSO teleconnections in northeast Australia
Authors: Hendy E. J. , Gagan M. K. , Lough J. M.
Published: February 2003

Eight, multicentury, Porites coral cores were used to develop a 373-year chronology by cross-dating techniques adapted from dendrochronology.Characteristic patterns of distinct luminescent lines within the coral skeletons were matched between coral cores from inshore and mid-shelf reefs in the central Great Barrier Reef, Australia. Skeleton-plots of luminescent banding were produced for each core and combined into a master chronology back to ad 1615. In addition to improving dating control, the luminescence master chronology provides a proxy for Burdekin River runoff and Queensland summer rainfall. Variations in the magnitude of the correlation between the luminescence master and the Mann et al. (2000) NINO3 sea-surface temperature reconstruction provides insights into the long-term stability of El Niño-Southern Oscillation (ENSO) telecon nections. Burdekin River runoff was significantly inversely related to ENSO variability for much of the period from the ad 1650s to 1800, suggesting that ENSO-related teleconnections were as dominant then as in recent decades. The extremely dry mid-1760s to mid-1780s stand out as a period of anomalously positive correlation between river runoff and the NINO3 reconstruction. Weak ENSO teleconnections are apparent from the 1800s to 1870s, when conditions were possibly similar to those reported for the 1920s–1950s.
Mid-Holocene climate and the hemlock decline: the range limit of Tsuga canadensis in the western Great Lakes region, USA
Authors: Calcote Randy
Published: February 2003

Eastern hemlock (Tsuga canadensis) expanded rapidly across Upper Peninsula Michigan from ~6500 to 5500 cal. yr BP, followed by a sudden decline of hemlock pollen percentages that lasted over 1000 years. Hemlock declined throughout its range, apparently due to insect/pathogen outbreaks, which may have been affected by regional climatic shifts. Modern analogues were used to reconstruct submillennial climatic trends from fossil pollen sites spanning the western range limit of hemlock. Reconstructions from eight sites inside the range of hemlock at the time of the decline (5400 cal. yr BP) are compared with eight sites outside the range, which should be independent of variation in hemlock pollen percentages and the non-climatic effects of insects/pathogens. Expansion of hemlock before the decline occurred at a time of increasing precipitation and January temperature. Long-term precipitation averages stabilized at ~5500 cal. yr BP and remained fairly constant throughout the period of low hemlock abundance. January temperature reconstructions decrease at the time of the hemlock decline to approximately modern values at sites inside the range, as well as at oak dominated sites just outside the range. The lower-than-modern precipitation of the mid-Holocene may have reduced hemlock's tolerance for cold stress and winter desiccation and perhaps increased its susceptibility to insects or pathogens. January temperature reconstructions for pine-dominated sites outside the pre-decline hem lock range show little change, possibly due to the insensitivity of pine-dominated pollen assemblages to small climatic fluctuations. Hemlock began a new expansion across the region after 4000 cal. yr BP as July tempera ture decreased and precipitation increased.
Development history and carbon accumulation of a slope bog in oceanic British Columbia, Canada
Authors: Turunen Carrie , Turunen Jukka
Published: February 2003

Palaeoecological techniques and radiocarbon datings were used to reconstruct the initiation and development of a sloping bog system near Prince Rupert, British Columbia, Canada. Peat initiation began around 12 000 cal. BP, possibly as a result of a cool, wet climate prior to the insolation maximum. A Picea sitchensis-Tsuga heterophylla-Alnus minerotrophic wet fern forest occupied the study site from 9300 to 8300 cal. BP. Between 8300 and 7500 cal. BP, cooler and wetter climatic conditions promoted increased organic matter accumulation and paludification by Sphagnum species. Subsequent lateral expansion has been very slow in the later Holocene. Paludification resulted in a shift to a scrubby, less productive Pinus contorta-T. heterophylla-Cupressaceae-Cyperaceae bog woodland around approximately 7500–3000 cal. BP. The modern Cupressaceae-Pinus contorta-T. heterophylla-Ericaceae-Cyperaceae mire was well established by 2000 cal. BP and a modern oceanic climate was predominant. The initiation and development of the studied bog corresponds to regional climatic and successional trends. However, the average long-term apparent rate of carbon accumu lation (LORCA) was low compared to rates from other northern mires, only 6.3 6 0.6 (SE) g m-2 yr-1. About 53% of the present carbon store was already accumulated by 6200 cal. BP. This study emphasizes that mire initiation and slow forest paludification in north coastal British Columbia is a multidirectional process resulting from complex interactions between climatic and autogenic factors.
Oxygen-isotope (δ18O) evidence of Holocene hydrological changes at Signy Island, maritime Antarctica
Authors: Noon P. E. , Leng M. J. , Jones V. J.
Published: February 2003

A record of Holocene hydrological changes has been produced from variations in oxygen-isotope composition (δ18O) preserved in freshwater lake sediments from maritime Antarctica. Small amounts (<5%) of authigenic carbonate have been extracted from a non-marl sediment core from Sombre Lake, Signy Island (60°43'S, 45°38'W). Oxygen-isotope and particle-size analysis provide a sensitive record of hydrological events in the lake arising from local and regional climate phenomena. The climate affects δ18O through snowpack volume and glacier activity in the catchment, lakewater temperatures, the input versus evaporation balance and the duration of seasonal lake ice cover. The most depleted (negative) δ18O values are associated with influxes of meltwater at times of glacier advance or retreat. Enriched (positive) δ18O values occur during more arid, warmer conditions with longer periods of open water in summer. This isotope record can be used to determine century-scale to decadal variability in air circulation and moisture origin. Strong similarities with other Holo cene proxy records from the Weddell Sea and Antarctic Peninsula Region are apparent, including the mid-Holocene climate optimum followed by the Neoglacial and, most recently, late twentieth-century climatic warming. The oxygen-isotope record from Sombre Lake illustrates the importance of remote islands in contribu ting to our understanding of teleconnections in atmospheric and oceanographic circulation, sea-ice extent, air temperatures and precipitation in the Southern Ocean.
Reconstruction and palaeoclimatic interpretation of mid-Holocene vegetation and lake-level changes at Saint-Jorioz, Lake Annecy, French Pre-Alps
Authors: Magny Michel , Bégeot Carole , Guiot Joël , Marguet André , Billaud Yves
Published: February 2003

Pollen and sediment analyses were used to reconstruct vegetation and lake-level changes over the mid-Holocene period at Saint-Jorioz, Lake Annecy (northern French Pre-Alps). Episodes of forest clearings point to Neolithic cultural activities in the northern French Pre-Alps from c. 6500 cal. BP in agreement with other pollen and macrofossils records from eastern Switzerland and the Jura mountains. The lake-level record shows rises atc. 8300–8200, 6400, 5900 and after 5730 cal. BP. The rise at c. 8300–8200 cal. BP shows a tripartition. Lower water levels developed before 8300–8200 and 6665 cal. BP, at c. 6050 and 5730 cal. BP. Rises at c. 8300–8200, 6400, 5900 and after 5730 cal. BP can be related to the 8200-yr event and North Atlantic ice-rafted debris (IRD) events occurring at c. 6200, 5800 and 5500 cal. BP, respectively. Using a model based on pollen and lake-level data, the palaeoenvironmental changes reconstructed at Saint-Jorioz were translated into quantitative climate parameters. The results suggest that rises in lake level coincided with increasing annual precipitation, runoff and available moisture, and decreasing mean summer temperature and shortening of the growing season probably as a result of alternate southward/northward displacements of the Atlantic Westerly Jet. At Saint-Jorioz, the period around the 8200-yr event corresponded to a c. 2.5°C summer temperature cooling and a c. 130 mm P-E (precipitation-evaporation) increase in agreement with other European and marine palaeoclimate records; a c. 4°C summer-temperature cooling and a rise in annual precipitation by c. 175 mm are reconstructed at c. 5900 cal. BP and after 5730 cal. BP, i.e., close to the time of the North Atlantic IRD events dated at 5800 and 5500 cal. BP, and are to be tested by further investigations. A general trend toward temperature cooling and precipitation increase appears over the period documented by the sediment sequence of Saint-Jorioz possibly related to an orbitally induced reduction of summer insolation.
Rhyolitic tephra horizons in northwestern Europe and Iceland from the AD 700s–800s: a potential alternative for dating first human impact
Authors: Wastegård Stefan , Hall Valerie A. , Hannon Gina E. , van den Bogaard Christel , Pilcher Jonathan R. , Sigurgeirsson Magnús Á. , Hermanns-Auoardóttir Margrét
Published: February 2003

The distribution and geochemistry of four rhyolitic tephra horizons from Iceland dated to the ad 700s–800s is assessed. These include the rhyolitic phase of the Landnám tephra (ad 870s), the ad 860 layer, a previously unrecorded tephra called the GA4–85 layer (c. ad 700–800) and the Tjïrnuvík tephra (c. ad 800s). The ad 860 and GA4–85 layers were first found in peat bogs in north Ireland. They are here correlated with equivalent horizons on Iceland which were found below the Landnám tephra (c. ad 870s). This time period is considered important in the North Atlantic region, because it coincides with a phase of human settlement in Iceland and the Faroe Islands. The establishment of a detailed tephrochronology may provide a tool for exact dating of sediment successions and sediments associated with archaeological excavations. Caution must be taken especially on Iceland where the Landnám tephra is often used for dating archaeological sites. This investigation show that several rhyolitic tephra horizons occur close in time to the Landnám tephra, and that mistakes can be made if detailed geochemical analyses are not carried out, especially in areas which are distal to the source of the Landnám tephra (the Veidivötn and Torfajökull volcanic systems, southern Iceland).
Vegetation response to rainfall variation and human impact in central Kenya during the past 1100 years
Authors: Lamb Henry , Darbyshire Iain , Verschuren Dirk
Published: February 2003

Pollen data from a 625 cm sediment core from Crescent Island Crater, a subbasin of Lake Naivasha, Kenya, provide an 1100-year record of vegetation change at a mean time resolution of 15 years. Earlier data from the same core show a record of lake depth (and thus inferred rainfall variation) in the form of changing sedimentary facies, supported by salinity inferences based on diatom and chironomid assemblages. Stratigraphic variation in the abundances of aquatic and semi-aquatic plants and chlorophyte algae generally supports the reconstructed lake depths. Woody Afromontane and woodland plant taxa decreased relative to Poaceae (grasses) during low rainfall periods, and increased during high rainfall periods. A decrease in the extent of lower montane forest coincident with favourable climatic conditions after about ad 1700 was probably caused byKikuyu immigration and population expansion around that time, as indicated by simultaneous appearance of the food crop Zea mays (maize). Increases in ruderal herbaceous and exotic tree pollen during the twentieth century indicate increased local landscape disturbance during the colonial period. There is little direct pollen evidence for accelerating clearance of the montane forest during recent decades.
Treatment with sildenafil for the healing of refractory skin ulcerations in the antiphospholipid syndrome
Authors: Gertner E
Published: March 2003

Nonhealing skin ulceration is a cutaneous manifestation of the antiphospholipid syndrome (APS) and is associated with thrombosis of small dermal vessels. Numerous therapies have been described but are either ineffective or require a prolonged course of treatment with potential complications. We describe the efficacy of sildenafil, a phosphodiesterase inhibitor, in the treatments of such ulcers.
High prevalence of antiphospholipid antibodies in Asian cancer patients with thrombosis
Authors: Yoon K H , Wong A , Shakespeare T , Sivalingam P
Published: March 2003

Thrombotic complications are a significant cause of morbidity and mortality in cancer patients. Studies in Caucasian populations have shown that up to one-third of such patients test positive to antiphospholipid antibodies. Our aim was to determine the prevalence and serotypes of antiphospholipid antibodies in an unselected group of Asian cancer patients with thrombosis. All patients with cancer-related thrombosis seen in the Department of Hematology-Oncology and Radiation Oncology were enrolled in this study. The study period was from April 2000 to May 2001. Antiphospholipid antibodies tests were performed, namely lupus anticoagulant screen, anti-cardiolipin antibodies (IgG and IgM) and anti-beta-2 glycoprotein I antibodies (B2 GPI) IgG, IgM and IgA. Thirty-three patients were recruited. There were 14 males and 19 females, with an age range of 35-78 years of age. Of those enrolled, there were 25 Chinese, five Malays and three Indians. The patients had several cancer types: 11 (36.7%) patients had adenocarcinoma as the histological cell type. Of the 33 patients, 75.8% had stage IV disease. Arterial thrombosis was seen in eight patients (24.2%), and venous thrombosis occurred in 29 patients (87.9%). Antiphospholipid antibodies were positive in 60.6% of the patients, of which anti-B2GPI IgA antibody was the most prevalent antiphospholipid present (46.9%). The presence of anti-beta-2 glycoprotein I IgA antibody was associated with strokes, extensive and recurrent venous thrombosis, and coincident arterial and venous thrombosis. A high prevalence of antiphospholipid antibodies (60.6%) was found in Asian patients with cancer-related thrombosis. The presence of antiphospholipid antibodies, particularly anti B2GPI IgA, may identify a subset of cancer patients who are at high risk of developingthrombotic complications, and further studies are warranted.
Neurological involvement as a poor prognostic factor in catastrophic antiphospholipid syndrome: autopsy findings in 12 cases
Authors: Olguín-Ortega L , Jara L J , Becerra M , Ariza R , Espinoza L , Wilson W , Barile-Fabris L
Published: March 2003

CAPS is an uncommon disease, characterized by clinical evidence of multiple organ involvement and histopathological evidence of multiple vessel occlusions, in patients with either primary or secondary antiphospholipid syndrome. The present series describes the clinical manifestations and autopsy findings of 12 patients with CAPS. Neurological involvement was considered the main cause of death in all of them. CNS pathology revealed thrombotic microangiopathyas well as small and large vessel occlusions in several brain areas. Neurological involvement in CAPS is strongly associated with thrombotic microangiopathy and should be considered a potential cause of death in these patients.
Carbon monoxide and bile pigments: surprising mediators of vascular function
Authors: Durante William
Published: March 2003

Heme oxygenase (HO) catalyzes the degradation of heme to CO, iron, and biliverdin. Biliverdin is subsequently metabolized to bilirubin by the enzyme biliverdin reductase. Although long considered irrelevant byproducts of heme catabolism, recent studies indicate that CO and the bile pigments biliverdin and bilirubin may play an important physiological role in the circulation. The release of CO by vascular cells may modulate blood flow and blood fluidity by inhibiting vasomotor tone, smooth muscle cell proliferation, and platelet aggregation. CO may also maintain the integrity of the vessel wall by directly blocking vascular cell apoptosis and by inhibiting the release of pro-apoptotic inflammatory cytokines from the vessel wall. These effects of CO are mediated via multiple pathways, including activation of soluble guanylate cyclase, potassium channels, p38 mitogen-activated protein kinase, or inhibition of cytochrome P450. In addition, the release of bile pigments may serve to sustain vascular homeostasis by protecting vascular cells from oxidative stress and by inhibiting the adhesion and infiltration of leukocytes into the vessel wall. Induction of HO-1 gene expression and the subsequent release of CO and bile pigments are observed in numerous vascular disorders and may provide an important adaptive mechanism to preserve homeostasis at sites of vascular injury. Thus, the HO-catalyzed formation of CO and bile pigments by vascular cells may function as a critical endogenous vasoprotective system. Moreover, pharmacological or genetic approaches targeting HO-1 to the vessel wall may represent a novel therapeutic approach in treating vascular disease.
Toward a new blood vessel
Authors: MacNeill Briain D , Pomerantseva Irina , Lowe Harry C , Oesterle Stephen N , Vacanti Joseph P
Published: March 2003

Strategies to treat atherosclerotic coronary artery disease include coronary artery bypass grafting (CABG), in which grafts are used to bypass atherosclerotic vessels and restore blood flow to the ischemic myocardium. The grafts used include healthy arteries or veins harvested from a separate site. Results with arterial grafts have been superior to venous grafts; promoting the practice of total arterial revascularization using only arterial grafts. Suitable arterial grafts, however, are scarce and harvest procedures add to morbidity and cost. Tissue engineering combines the principles of engineering with life sciences for the development of biological substitutes and restore, maintain or improve tissue function. Advances in this field have included the development of tissue-engineered blood vessels, with the potential to serve as arterial grafts, conduits or fistulae. This review describes the history of tissue engineering arteries, the techniques used, and progress to date. The source of cells and the future direction of this field are explored.
L-Arginine in cardiovascular disease: dream or reality?
Authors: Tousoulis Dimitris , Antoniades Charalambos , Tentolouris Costas , Goumas George , Stefanadis Christodoulos , Toutouzas Pavlos
Published: March 2003

l-arginine is the substrate for endothelial nitric oxide synthase (eNOS), and the precursor for the synthesis of nitric oxide (NO). This amino acid exerts a number of actions in the cardiovascular system, mainly through the production of NO. However, it also has a number of NO-independent properties, such as the ability to regulate blood and intracellular pH and the effect on the depolarization of endothelial cell membranes. It also has antihypertensive and antioxidant properties, it influences blood viscosity and the coagulation/fibrinolysis system, and it affects the metabolism of glucose, lipids and proteins. L-arginine influences a number of atherosclerosis risk factors such as hypercholesterolemia, hypertension and smoking, improving endothelial function in these patients. However, it does not affect endothelial function in patients with diabetes mellitus. The role of L-arginine in coronary artery disease is still controversial, but it seems that oral or parenteral administration of this amino acid restores endothelial function in the brachial artery and improves coronary microcirculation. The role of L-arginine in heart failure is currently under investigation, and the first results are rather hopeful. In conclusion, L-arginine seems to provide a hopeful prospect for the treatment of cardiovascular diseases. However, more data derived from large-scale prospective studies evaluating the effects of long-term treatment with L-arginine are needed.
The contribution of nitric oxide to exercise hyperemia in the human forearm
Authors: Gordon Mary Beth , Jain Rajiv , Beckman Joshua A , Creager Mark A
Published: March 2003

The contribution of nitric oxide (NO) to exercise-induced hyperemia is debated. Previous conclusions that nitric oxide synthase (NOS) inhibition reduces endothelium-dependent vasodilation during exercise hyperemia may be confounded by inhibitor-mediated increases in resting vascular tone. In this study, nine healthy participants performed wrist flexion exercise before and during intra-arterial administration of the NOS-inhibitor NG-monomethyl-l-arginine (l-NMMA, 2 mg·min-1). Nine additional subjects performed this procedure while nitroprusside (0.2 mg·min-1) was co-infused with l-NMMA to maintain basal flow. Forearm blood flow was assessed with venous occlusion strain-gauge plethysmography at baseline, immediately after cessation of exercise, and continuously for 5 minutes thereafter. l-NMMA alone reduced resting flow by 26%, peak flow immediately after exercise by 20%, and integrated post-exercise hyper-emic volume by 50% (all p, 0.05). Stabilization of resting vasodilator tone by nitroprusside eliminated the effects of l-NMMA on peak flow after exercise, yet l-NMMA still attenuated total hyperemic volume. In a time-control study of 12 subjects, there was no change in peak blood flow or hyperemic volume. This study indicates that NO is not a major regulator of peak limb blood flow measured immediately after cessation of dynamic exercise. The contribution of NO to exercise hyperemia is limited to the recovery period after exercise.
Pharmaceutical ethnobotany in the Montseny biosphere reserve (Catalonia, Iberian Peninsula). General results and new or rarely reported medicinal plants
Authors: Bonet M Àngels , Vallès Joan
Published: March 2003

An ethnobotanical survey was carried out in the massif of Montseny, which is situated in north-east Catalonia (Iberian Peninsula), covers 826 km2 and has a population of 80 000. From 1993 to 2000 we interviewed 180 people and collected ethnobotanical information about 351 medicinal plants, with 4023 use-reports. Through comparison with a large set of studies, we detected 501 unreported or uncommon uses that corresponded to 201 plant species, 57 of which had never or very rarely been cited as medicinal or toxic. General results and key findings on the plant ethnopharmacology (number of medicinal plants, modes of consumption, types of illnesses treated) of this area are presented here, together with information on new or rarely reported medicinal plants.
Inhibition of TPA-induced NF-κB nuclear translocation and production of NO and PGE2 by the anti-rheumatic gold compounds
Authors: Yamashita Masamichi , Ashino Shigeru , Oshima Yuko , Kawamura Shunsuke , Ohuchi Kazuo , Takayanagi Motoaki
Published: March 2003

Auranofin, aurothioglucose and aurothiomalate (10 μM each) inhibited 12-O-tetradecanoylphorbol 13-acetate (TPA, 16.2 nM)-induced nuclear translocation of nuclear factor-kappa B (NF-κB), and production of nitric oxide (NO) and prostaglandin E2 (PGE2) in rat peritoneal macrophages when the cells were pre-incubated with each gold compound for 20h. Without pre-incubation for 20h, aurothioglucose and aurothiomalate, but not auranofin, failed to inhibit the TPA-induced NF-κB nuclear translocation and production of NO and PGE2. Auranofin, aurothioglucose and aurothiomalate did not affect the direct binding of NF-κB to the DNA probe. It was suggested that these gold compounds inhibit the TPA-induced production of NO and PGE2 by inhibiting the NF-κB nuclear translocation.
Structure-activity relationship determination within a group of substituted phenyl sulfamate based compounds against the enzyme oestrone sulfatase
Authors: Patel Chirag K , Galisson Angelique , James Karen , Owen Caroline P , Ahmed Sabbir
Published: March 2003

The enzyme oestrone sulfatase (ES) is responsible for the conversion of the stored (sulfated) form of oestrogens to the active form, namely oestrone. In our continuing quest to synthesize potent inhibitors of oestrone sulfatase and to determine the structural requirements for such inhibition, we have synthesized and evaluated several derivatives of phenyl sulfamate. We report the results of the synthesis and biochemical evaluation of a series of 3- and 4-aminosulfonated derivatives of phenol in an effort to investigate the role of the acid dissociation constant (pKa), and therefore the stability of the phenoxide ion, on the inhibitory activity of compounds against this enzyme. The results showed that there was a strong correlation between the observed pKa and inhibitory activity within the aminosulfonated compounds considered. This suggested that in the inhibition of oestrone sulfatase by these compounds, pKa was an important physicochemical property, and as such, the stability of the O− ion was a crucial factor in the inhibition, and therefore the drug design process.
Targeting of p0071 to desmosomes and adherens junctions is mediated by different protein domains
Authors: Hatzfeld Mechthild , Green Kathleen J. , Sauter Helmut
Published: March 2003

p0071, a member of the armadillo protein family, is most closely related to p120ctn and the plakophilins 1-3. Whereas plakophilins are desmosomal plaque proteins, p120ctn localizes to adherens junctions and interacts with classical cadherins. In contrast, p0071 has been described as a protein with dual localization in adherens junctions and desmosomes depending on the cell type examined. Here we have analyzed the localization of p0071 and its domains in detail. Although by sequence analysis, p0071 is more closely related to the adherens junction proteins p120ctn, ARVCF and δ-catenin, endogenous p0071 associated preferentially with desmosomes in MCF-7 epithelial cells. Overexpressed p0071 localized along cell borders and overlapped only partially with desmosomal markers but colocalized with non-desmosomal cadherins and recruited cadherins to the membrane. The head domain of p0071 was sufficient for desmosomal targeting, whereas the arm repeat domain associated with adherens junctions and enhanced membrane association of classical cadherins. The tail domain localized preferentially to the nucleus and associated with desmosomes. To examine the mechanism underlying this dual localization more closely we determined binding partners of p0071 by using yeast-two-hybrid and mom-targeting assays. These approaches show that the head domain interacted with desmosomal proteins desmocollin 3a and desmoplakin, whereas the armadillo repeat domain binds to non-desmosomal cadherins. Head and armadillo repeat domains both interacted with plakoglobin by binding to different sites. Our data suggest that, in addition to plakoglobin, p0071 is the second armadillo protein present in both types of adhesive junctions and may play a role in regulating crosstalk between adherens junctions and desmosomes.
Microtubule distribution during meiosis I in flea-beetle[Alagoasa(Oedionychus)] spermatocytes: evidence for direct connections between unpaired sex chromosomes
Authors: Wilson Paula J. , Forer Arthur , Wise Dwayne
Published: March 2003

The meiosis-I spindle in flea-beetle spermatocytes is unusual in that the autosomes and univalent sex chromosomes are separated by a mitochondrial sheath and move polewards at different times. To help understand the basis for this interesting chromosome behaviour, and to gather more detailed information about it, we studied microtubule distributions throughout meiosis I using immunofluorescence and confocal microscopy, and took careful measurements of pole and kinetochore positions at all stages of division. Our results show that, by late prophase, there is a spindle-shaped cytoplasmic array of microtubules in the central part of the cell, with the nucleus at the periphery. Following nuclear envelope breakdown, both autosomes and sex chromosomes become associated with cytoplasmic microtubules, although only the autosomes move centrally to the `cytoplasmic spindle'. The two unpaired sex chromosomes remain at the cell periphery and appear to be connected to each other by a microtubule bundle extending between their kinetochores. These bundles often persist into anaphase. Analysis of measurements taken from fixed/stained cells supports previous observations that sex chromosomes move part way to the pole in early prometaphase and then stop. The measurements also suggest that during autosomal anaphase, spindle elongation precedes autosome movement to the poles and polewards movement of sex chromosomes is limited or absent when autosomes are moving polewards.
Cytoskeletal proteins with N-terminal signal peptides: plateins in the ciliateEuplotesdefine a new family of articulins
Authors: Kloetzel John A. , Baroin-Tourancheau Anne , Miceli Cristina , Barchetta Sabrina , Farmar James , Banerjee Deben , Fleury-Aubusson Anne
Published: March 2003

Protistan cells employ a wide variety of strategies to reinforce and give pattern to their outermost cortical layers. Whereas some use common cytoskeletal elements such as microtubules, others are based on novel cytoskeletal proteins that are as-yet-unknown in higher eukaryotes. The hypotrich ciliate Euplotes possesses a continuous monolayer of scales or plates, located within flattened membranous sacs (`alveoli') just below the plasma membrane, and this provides rigidity and form to the cell. Using immunological techniques, the major proteins comprising these `alveolar plates' have been identified and termed α-, β-, andγ-plateins. The present report describes work leading to the molecular characterization of three plateins, α1 and α2 (predicted Mrs of 61 and 56 kDa) and a β/γ form(Mr=73 kDa). All three proteins have features that are hallmarks of articulins, a class of cytoskeletal proteins that has been identified in the cortex of a wide variety of protistan cells, including certain flagellates, ciliates, dinoflagellates and Plasmodium. Chief among these common features are a prominent primary domain of tandem 12-amino acid repeats, rich in valine and proline, and a secondary domain of fewer,shorter repeating units. However, variations in amino acid use within both primary and secondary repetitive domains, and a much more acidic character(predicted pIs of 4.7-4.9), indicate that the plateins represent the first proteins in a new subclass or family of articulins. This conclusion is supported by another novel feature of the plateins, the presence of a canonical hydrophobic signal peptide at the N-terminus of each derived platein sequence. This correlates well with the final cellular location of the plateins, which are assembled into plates within the membrane-limited alveolar sacs. To our knowledge, this is the first report in any eukaryote of cytoskeletal proteins with such start—transfer sequences. Confocal immunofluorescence microscopy, using antibodies to the plateins as probes,reveals that new alveolar plates (enlarging in cortical zones undergoing morphogenesis) label more faintly than mature parental plates. During plate assembly (or polymerization), the plateins thus appear to exist in a more soluble form.
Error attenuation in the control of a parallel robot manipulator using a dual-model-based structure
Authors: Li Q
Published: February 2003

Parallel structure robots have been receiving growing attention from both academia and industry in recent years. This is due to their advantages over serial structure robots, such as high stiffness, high motion accuracy and a high load-structure ratio. Control of parallel robots, however, produces difficulties to control engineers due to the modelling errors arising from the highly non-linear and complex structures. This paper proposes a dual-model-based structure for error attenuation in the trajectory-tracking control of a parallel robot manipulator. In this design, a conventional model-based control algorithm employing an estimated robot dynamic model is first implemented in the inner loop of the control structure. Then, in order to reduce the unwanted effects caused by modelling erros, another model-based structure, developed based on the concept of the internal model control, is appended in the outer loop of the control structure as a compensator. A combination of these two model-based components results in a novel dual-model-based structure for parallel robot control. Sensitivity analyses show that the effects due to modelling errors and external disturbances can be significantly reduced by applying this new control structure without relying on a high-gain control solution. The effectiveness of this control design is successfully demonstrated by numerical studies on a planar parallel robot with 2 degrees of freedom.
Exterior engine noise characterization using an acoustic tube to measure volume velocity distribution
Authors: Nakamura M , Nakano D R M
Published: February 2003

An acoustic tube was developed and applied using the volume velocity measurement method for the prediction of constant exterior engine noise. Using accelerometers to measure engine surface vibration is a difficult task, especially for places such as the exhaust manifold. The proposed method is as follows: an acoustic tube containing a microphone is set at a given distance from the engine and measurements are made in such a way that the whole engine surface is covered. Exterior engine noise at a certain distance from the vehicle was predicted by using the measured volume velocity values and propagation characteristics. The predicted results agreed well with previously experimental values.
Influences of nozzle flow and nozzle geometry on the shape and size of an air core in a hollow cone swirl nozzle
Authors: Halder M R , Dash S K , Som S K
Published: February 2003

Theoretical and experimental studies have been carried out to determine the influences of nozzle flow and nozzle geometry on the shape and size of a fully developed air core in a hollow cone swirl nozzle. The theoretical study is based on the numerical solution of conservation equations for mass and momentum along with the volume fraction of the liquid phase. An interface capturing method has been adopted in the numerical simulation of free surface flow in the nozzle. Experiments have been carried out with a number of nozzles fabricated in Perspex material. The air core diameter has been measured from photographs taken by a camera outside the nozzle. It has been observed that the shape of the fully developed air core in a conical swirl nozzle is cylindrical with a considerable bulging at the entrance to the orifice, while in the case of a conical nozzle without a finite length of orifice, the air core is uniform throughout the nozzle. The values of the air core diameter in the swirl chamber ( da1) and in the orifice ( da2) of a nozzle increase sharply with an increase in inlet Reynolds number ( Re) below 1.1 × 104, but become almost independent of Re above this (up to 1.7 × 104). The air core diameter, both in the swirl chamber and in the orifice, increases with an increase in the value of the ratio of orifice to swirl chamber diameter and the cone angle of the swirl chamber and with a decrease in the value of the ratio of entry port to swirl chamber diameter and the ratio of orifice length to swirl chamber diameter.
Topological synthesis of non-fractionated differential geared mechanisms for automotives
Authors: Chen D-Z , Yao K-L , Lee J-J
Published: February 2003

In this paper, a methodology on the topological synthesis of admissible non-fractionated differential geared mechanisms for automotives is presented. Based on the characteristics of differential geared mechanisms, characteristics of non-fractionated differential geared mechanisms are laid out. Admissible non-fractionated differential geared mechanisms can be identified from atlases of geared kinematic chains by checking the redundancy condition in a kinematic equation governing the terminals. The methodology presented here is systematic and efficient, and can be easily applied to the enumeration of innovative non-fractionated differential geared mechanisms.
A simple method for the design of gas burner injectors
Authors: Lawn C J
Published: February 2003

The performance of a fuel jet issuing through a nozzle and entraining the air for combustion in a gas burner has been systematically investigated, using well-established theory for such ‘injectors’ based on momentum conservation for one-dimensional flows. Earlier applications of this theory for injector calculations are reviewed. It is shown that neglect of property variations introducs only small errors for the cases that are likely to be considered in such combustion problems. Design charts are generated in which the ratio of entrained air flow to fuel to fuel flow is related to the area ratio of the two streams at the plane of the nozzle. The ratio is a function of generalized parameters describing the inlet and outlet resistances (ameliorated by a diffuser), the density ratio of the fluids and the Mach number of the nozzle. Predictions are compared with new experimental data for an injector with the mixing tube Reynolds number in the range 2000–12000 and shown to agree to within 10 per cent when the mixing tube is of optimum length.
Radiant heat flux to external surfaces from escaping and extrusive flashover flames
Authors: Chen A , Francis J
Published: February 2003

Current practice when predicting safe separation distances between buildings is to assess the radiant hazard posed by flames and hot gas visible across the vent. The vent is treated as a radiating vertical surface with a representative temperature. A method is proposed for calculating the radiant heat flux to external surfaces from hot gas and extrusive flame emerging from a vent in a compartment wall containing post-flashover fire. An experimental study has been made to examine the validity of the method for extrusive flames unaffected by wind.
A study of the impulsive wave discharged from the inclined exit of a tube
Authors: Kim H-D , Kweon Y-H , Setoguchi T
Published: February 2003

The propagation of the impulsive wave discharged from the inclined exit of a tube is investigated using a shock tube experiment and by numerical computations. The pressure histories and wavefront geometries of the impulsive wave propagating outside the exits of the tube with several different configurations are analysed for the range of an initial shock wave Mach number between 1.1 and 1.4. In the shock tube experiments, the impulsive waves are visualized by a Schlieren optical system for the purpose of validation of computational work. Computations using the two-dimensional, unsteady, compressible, Euler equations are carried out to represent the experimental impulsive waves. The results obtained show that the inclination angle of the tube exit reduces the magnitude of the impulsive wave and affects the wavefront geometry of the impulsive wave. It is also found that the propagation direction and magnitude of the impulsive wave depend on the Mach number of the initial shock wave, while the impulsive waveform does not significantly vary with the Mach number of the initial shock wave. The computed results obtained predict the experimental ones with quite good accuracy.
An experimental study of spray mixing in a direct injection engine
Authors: Probst D M , Ghandhi J B
Published: February 2003

The effects of injection timing, injector type, injection pressure and engine flowfield on fuel spray mixing in a direct injection engine were investigated using planar laser-induced fluorescence. The fluorescence images had sufficient resolution and quality to permit, for the first time in an engine, the calculation of the scalar dissipation rate. The probability density function of the scalar dissipation scaled by the mean showed excellent agreement with turbulent jet and shear layer data for late injection conditions, indicating that the same fundamental mixing process existed in the different flows. The effect of shot noise limited such comparisons for the more homogeneous early injection conditions. A dual-metric method was developed to characterize the degree of mixedness. The two metrics employed were the spatial variation, which describes the homogeneity of the scalar population, and the mean scalar dissipation, which describes the average magnitude of local scalar gradients and represents the rate of fine-scale mixing. Using this method, it was found that the presence of a strong bulk flowfield dominated the mixing rate in the test engine, while injector characteristics showed lesser effects. The data set averaged results of the two metrics for a wide range of conditions were found to define a single, unique curve that was accurately described by a quadratic relationship. This curve defines the path that turbulent mixing follows from an initial segregated state to the fully mixed limit.
Experimental optimization of a direct injection homogeneous charge compression ignition gasoline engine using split injections with fully automated microgenetic algorithms
Authors: Canakci M , Reitz R D
Published: February 2003

Homogeneous charge compression ignition (HCCI) is receiving attention as a new low-emission engine concept. Little is known about the optimal operating conditions for this engine operation mode. Combustion under homogeneous, low equivalence ratio conditions results in modest temperature combustion products, containing very low concentrations of NOx and particulate matter (PM) as well as providing high thermal efficiency. However, this combustion mode can produce higher HC and CO emissions than those of conventional engines.

An electronically controlled Caterpillar single-cylinder oil test engine (SCOTE), originally designed for heavy-duty diesel applications, was converted to an HCCI direct injection (DI) gasoline engine. The engine features an electronically controlled low-pressure direct injection gasoline (DI-G) injector with a 60° spray angle that is capable of multiple injections. The use of double injection was explored for emission control and the engine was optimized using fully automated experiments and a microgenetic algorithm optimization code. The variables changed during the optimization include the intake air temperature, start of injection timing and the split injection parameters (per cent mass of fuel in each injection, dwell between the pulses). The engine performance and emissions were determined at 700 r/min with a constant fuel flowrate at 10 MPa fuel injection pressure. The results show that significant emissions reductions are possible with the use of optimal injection strategies.