bluuebunny/crossref_metadata_2025 huggingface dataset:
The novel human platelet septin SEPT8 is an interaction partner of SEPT4
Authors: Bläser Susanne , Horn Julia , Würmell Paul , Bauer Heike , Strümpell Sandra , Nurden Paquita , Pagenstecher Axel , Busse Anja , Wunderle Daniela , Hainmann Ina , Zieger Barbara
Published: March 2004

Septins are a family of GTP-binding proteins, which are essential for active membrane movement such as cytokinesis and vesicle trafficking. In non-dividing cells (such as platelets and neurons) septins are implicated in exocytosis. Platelets from a SEPT5 knockout mouse showed an altered serotonin secretion and platelet aggregation, suggesting that SEPT5 is involved in secretion in platelets. Septins form complexes consisting of multiple septin polypeptides. Using the yeast two-hybrid system we had demonstrated that SEPT5 partners with SEPT8.The aim of this study was to identify other interaction partners of the human platelet septin SEPT8. Using the yeast two-hybrid system with SEPT8 as bait protein we identified the human septin SEPT4 as an interaction partner of SEPT8. The interaction between SEPT4 and SEPT8 was confirmed by immunoprecipitation. Expression analysis revealed that SEPT4 is also expressed in human platelets. Thus, SEPT4 is the third described platelet septin besides SEPT5 and SEPT8.Transmission electron microscopy of platelets revealed that SEPT8 and SEPT4 are localized surrounding α-granules (as it had been shown for the septin SEPT5) suggesting that the three septins may be components of the septin complex in platelets and contribute in such a way to platelet biology. Activation of platelets by agonists resulted in the translocation of SEPT4 and SEPT8 to the platelet surface indicating a possible functional role of these proteins in platelet granular secretion.
Protective role of interleukin-6 in coagulatory and hemostatic disturbance induced by lipopolysaccharide in mice
Authors: Inoue Ken-ichiro , Yanagisawa Rie , Sakurai Miho , Shimada Akinori , Morita Takehito , Sato Masahiko , Yoshino Shin , Yoshikawa Toshikazu , Tohyama Chiharu , Takano Hirohisa
Published: March 2004

Although the role of interleukin (IL)-6 in inflammatory diseases has been previously examined, its role in hemostasis, fibrinolysis, and coagulation during inflammation remains to be established. The present study elucidated the role of IL-6 in hemostatic and coagulatory changes during severe inflammation induced by intraperitoneal administration of lipopolysaccharide (LPS: 1 mg/kg) using IL-6 null (-/-) mice. After LPS challenge, IL-6 (-/-) mice revealed significant prolongation of prothrombin time and activated partial thromboplastin time and a significant decrease in platelet counts as compared with wild type mice. LPS treatment induced marked pulmonary hemorrhage with neutrophilic inflammation in IL-6 (-/-) mice, in contrast, only mild neutrophilic infiltration in WT mice confirmed by macroscopic and histological findings.The protein levels of proinflammatory mediators, such as IL-1?, macrophage inflammatory protein (MIP)-1a., MIP-2, macrophage chemoattractant protein1, granulocyte/macrophage-colony-stimulating factor, and keratinocyte chemoattractant in the lungs were significantly greater in IL-6 (-/-) mice than in WT mice after LPS challenge. These results directly indicate that IL-6 is protective against coagulatory and hemostatic disturbance and subsequent pulmonary hemorrhage induced by bacterial endotoxin, at least partly, via the modulation of proinflammatory processes.
Pharmacogenetics of the CD14 endotoxin receptor polymorphism and progression of coronary atherosclerosis
Authors: Agema Willem , de Maat Moniek , Zwinderman Aeilko , Kastelein John , Rabelink Ton , van der Wall Ernst , Jukema J. Wouter
Published: March 2004

Atherosclerosis is at least in part an inflammatory disease. CD14 is an endotoxin receptor that after binding of lipopolysaccharides evokes endothelial activation and secretion of several cytokines. A polymorphism of CD14 has been associated with myocardial infarction. We evaluated the role of the -159 T/C polymorphism in the promoter region of the CD14 gene in relation to severity and progression of coronary atherosclerosis and response to the HMG CoA reductase inhibitor pravastatin. We recruited patients from the multicenter double-blind randomized placebo controlled REGRESS trial and genotyped the -159T/C CD14 polymorphism. DNA and angiographic follow-up were available from 759 patients with objectivated coronary artery disease. We measured changes in mean segment diameter (MSD) and minimum obstruction diameter (MOD) with quantitative coronary angiography and noted the occurrence of major adverse cardiac events. The genotype distribution was 28% TT, 49% CT, 23% CC. We did not find any association between genotype and MSD and MOD at baseline, frequency of previous myocardial infarction, changes in MSD and MOD or major clinical events. Treatment with the HMG CoA reductase inhibitor pravastatin reduced progression of coronary atherosclerosis and adverse events equally for all genotypes. We conclude, that the -159T/C polymorphism in the CD14 monocyte receptor gene was not associated with progression of coronary atherosclerosis in this population nor did it influence the efficacy of pravastatin in the treatment of atherosclerosis.
Platelet-endothelial cell interaction in pulmonary microcirculation: the role of PARS
Authors: Kiefmann Rainer , Heckel Kai , Schenkat Sonja , Dörger Martina , Węsierska-Gądek Józefa , Goetz Alwin
Published: March 2004

Accumulation of platelets might contribute to acute lung injury during systemic inflammation. The aim of the study was to elucidate the role of the poly (ADP-ribose) synthetase, a nucleotide-polymerizising enzyme, in mediation of platelet-endothelial cell interaction through regulation of adhesion molecules within the pulmonary microcirculation during endotoxemia. We used in vivo fluorescence microscopy to quantify kinetics of fluorescently labeled erythrocytes and platelets in rabbit pulmonary arterioles and venules. Six hours after onset of endotoxin infusion we observed a massive interaction of platelets with the microvascular endothelial cells, whereas under control conditions, no platelet sequestration was measured. An up-regulation of P- and E-selectin was detected in lung tissue following endotoxin infusion by immunohistochemistry and Western blot analysis. Blockade of endothelial P-selectin with fucoidin resulted in a reduction of the endotoxin-induced platelet-endothelial cell interaction. Inhibition of poly (ADP-ribose) synthetase by 3-aminobenzamide inhibited the endotoxin-induced expression of endothelial P- and E-selectin and the subsequent recruitment of platelets. In summary, we provide first in vivo evidence that platelets accumulate in pulmonary microcirculation following endotoxemia. Poly (ADP-ribose) synthetase seems to mediate this platelet-endothelial cell interaction via P- and E-selectin expressed on the surface of microvascular endothelium.
Factor V Leiden and prothrombin G20210A mutations in young adults with cryptogenic ischemic stroke
Authors: Mira Yolanda , Vayá Amparo , Corella Dolores , Ferrando Fernando , Villa Piedad , Estellés Amparo , Aznar Justo
Published: March 2004

The association between factor V Leiden (FVL) and prothrombin G20210A (PT 20210) mutations and ischemic stroke remains controversial, particularly in young adults with cryptogenic stroke. Prevalence of FVL (4.1%) and PT 20210 (8.2%) mutations was assessed in 49 patients under 50 years with cryptogenic stroke and compared with controls. Odd ratio (OR) for cryptogenic stroke was 2.62 (95% CI, 0.49-13.95) for FVL and 3.75 (95% CI, 1.05-13.34) for PT 20210 and 3.28 (95% CI, 1,17-9.20) for some recognized genetic thrombophilic defect. Moreover, the OR for cryptogenic stroke in young women using oral contraceptives (OC) was 3.59 (95% CI, 1.28-10.5). When some genetic thrombophilic defect was associated with OC, the OR was much higher (OR: 14.27; 95% CI, 0.66-309.99). Our results suggest that in the Mediterranean populations the PT 20210 mutation, but not FV Leiden, is a risk factor for cryptogenic stroke in young adults. OC use is also a significant risk factor for cryptogenic stroke, which is increased in women with some genetic thrombotic risk factor.
A systematic review of the accuracy of ultrasound in the diagnosis of deep venous thrombosis in asymptomatic patients
Authors: Boissel Jean-Pierre , Cucherat Michel , Sonie Sandrine , Shah Nirav , Leizorovicz Alain , Kassaï Behrouz
Published: March 2004

Evaluation of the accuracy of ultrasound has yielded heterogeneous results. Our objective was to summarize the evidence on the accuracy of ultrasound compared to venography in asymptomatic patients, taking into account the variation due to threshold differences. Searches of journal table of contents, computer databases (Medline, Embase, Biomed, Cochrane) and conference proceedings were performed. A study was eligible if it prospectively compared ultrasound to venography for the diagnosis of DVT in asymptomatic patients. Data of studies selected for inclusion were extracted independently by two authors. High quality studies with consecutive patient enrollment, blind evaluation of the two techniques, and absence of verification bias are summarized as Level 1, while those not fulfilling one or more of these criteria are considered Level 2. Original study authors were contacted to confirm accuracy and to provide missing data. A pooled estimate of the accuracy of ultrasound was obtained according to the method of Moses and coworkers. This method gives a summary diagnostic odds ratio (DOR). The DOR is a single indicator of test performance. It varies between 0 and infinity and exceeds 1, only when ultrasound is more often positive in patients with DVT relative to those without DVT. Higher DOR indicates better discriminatory test performance. Thirty one studies were rated as potentially unbiased and graded as Level 1.The mean prevalence of DVT as determined by venography was 22%. In Level 1 studies, the odds of positive ultrasound in proximal veins was 379 times higher (95% confidence limits 65, 2,200) and in distal veins 32 times higher (7.5, 135) among patients with DVT than those without. Our results suggest that, particularly for proximal veins, ultrasound is accurate for the diagnosis of DVT in asymptomatic postoperative orthopedic patients. More research is needed in other clinical settings.
Lower limb venous haemodynamic impairment on dependency: quantification and implications for the “economy class” position
Authors: Knaggs Alison , Sonecha Tans , Zervas Vasileios , Jenkins Michael , Wolfe John , Delis Konstantinos
Published: March 2004

The role of stasis in venous disease is undisputed, yet surprisingly, its haemodynamic quantitation remains largely undefined. We investigated the phenomenon of venous stasis in the lower limb upon sitting and standing and project its implications to economy class aircraft passengers. 26 normal limbs, 13 subjects, age 29-54, selected after duplex, plethysmography and ABPI, had peak[Vpeak], mean[Vmean] and minimum[Vmin] velocities, volumeflow[Qvenous], pulsatility index [PIvenous] and diameter obtained on horizontal, sitting (as in economy aircraft seats) and standing with duplex, at popliteal, femoral[FV] and common femoral[CFV]veins [differences in median %]. Vpeak, Vmean and Qvenous decreased from horizontal to sitting in the CFV [57%, 71%, 31%, respectively], FV [51%, 70%, 34%] and popliteal [31%, 58%, 42%] (all, p<.001). Vpeak, Vmean and Qvenous decreased further from sitting to standing in the CFV [26%, 44%, 25%, respectively], FV [21%, 42%, 27%] and popliteal [14%, 42%, 20%] (all, p <.001). Diameter, Vmin and PIvenous increased from horizontal to sitting in the CFV [50%, 63%, 38%, respectively], FV [39%, 23%, 66%] and popliteal [21%, 14%, 84%] (all, p <.001)]. Diameter, Vmin and PIvenous increased further from sitting to standing in CFV [10%, 22%, 19%, respectively; p ≤.004], FV [12%, 68%, 2%[ns]; p <.001)] and popliteal [14%, 50%, 24%; p ≤.017]. In all postures: Vpeak, Vmean, Qvenous and diameter at CFV exceeded FV (p <.025) and popliteal (p <.001) ones; also those at FV exceeded the popliteal ones (p ≤.003), except for the diameter on horizontal. Vmin in popliteal was higher than in CFV (p ≤.003) or FV (p <.025), on horizontal and standing. PIvenous in CFV was lower than in FV or popliteal (p <.025) on sitting. Right to left differences nonsignificant. [Wilcoxon+Bonferroni test: significance at p <.025] A shift from horizontal to sitting generates a most significant attenuation in Qvenous, Vpeak and Vmean linked to a reciprocal increase in Vmin, PIvenous and vein diameter, with further exacerbation on standing. Vpeak, Vmean and Qvenous decline with distance from groin enhancing venous stasis in the periphery. By restricting activation of the natural venous pumps, sitting cramped during long flights may protract the status of haemodynamic stagnation sustained on dependency which paired with marked venous dilatation generates a milieu that may promote thrombogenesis.
A review of the therapeutic uses of thrombin
Authors: Bradshaw Ralph , Gabriel Don , Ortel Thomas , Lawson Jeffrey , Mann Kenneth , Lundblad Roger
Published: March 2004

Thrombin is the product of the hemostatic response essential to the conversion of fibrinogen to fibrin. In addition, it is also responsible for the aggregation of blood platelets in the formation of the “platelet plug” as well as the activation of factor VIII, factor V, factor XI, factor XIII and protein C. The action of thrombin is not confined to the hemostatic response as it also has a critical function in the wound healing process by stimulating ‘mitogenic’ events through interaction with cell surface receptors. In this review, we consider the various biological activities of thrombin as they relate to current therapeutic use. While there has been considerable interest in the development of fibrin sealant products, there has been considerably less interest in documenting the continuing use of thrombin as a therapeutic. The use of thrombin for topical hemostasis and the treatment of pseudoaneurysms will be discussed in detail. It is concluded that the use of thrombin as a drug will not only continue but also will significantly increase. However, the availability of a safe human thrombin preparation will be critical for the continued use of thrombin as a therapeutic.
ICT4D: A Frontier for Higher Education in Developing Nations
Authors: Colle Royal , Roman Raul
Published: March 2004

Information and communication technologies (ICT) have become important features on the social and geographical landscapes of Africa and Asia in the early twenty-first century. This article discusses the various institutions and forces that play roles in applying these technologies to the challenges of community development. Case studies punctuate the text to provide concrete examples of the ideas and potential flowing out of the ICT environment, especially manifested by telecenters. The discussion highlights the low visibility of universities among the major actors and argues that they should build their capacities to be partners in the ICTs for Development movement.
Distance Learning and Virtual Education for Higher Education in Africa: Evaluation of Options and Strategies
Authors: Moyo Stanley
Published: March 2004

This paper briefly reviews the status of distance education and virtual education in the higher-education sector in Africa. The key issues affecting distance education in Sub-Saharan Africa (SSA) are identified and discussed. An analysis of the major issues facing distance education in SSA is made. It is noted that the full range of opportunities offered by information and communication technology (ICT) for higher education in Africa is largely underexploited. Factors responsible for this situation are identified and a range of strategies is recommended for resolving this situation. Finally, a model of distance education that can potentially enhance the use of ICT in higher education in SSA is proposed.
Strategies for Promoting Virtual Higher Education: General Considerations on Africa and Asia
Authors: Kuroda Kazuo , Shanawez Hossain
Published: March 2004

Education in general, and specifically higher education, plays an important role in the development process of all nations. Institutions of higher education have an important responsibility to support knowledge-driven economic growth strategies. This paper investigates the strategies of how by applying technologies on a large scale—with close attention to quality—virtual education can help higher education to find a way through the crisis of access, prohibitive cost, and lack of flexibility that we find all over the developing world. By addressing various issues related to planning, implementation, and quality with proper strategies, virtual education can provide immense opportunity to reduce the North-South knowledge gap and also to promote the development of the developing world. This paper reviews various issues related to promotion and quality control in virtual higher education and addresses possible strategies with general considerations of Africa and Asia.
Quality of life of survivors from severe sepsis and septic shock may be similar to that of others who survive critical illness
Authors: Granja Cristina , Dias Cláudia , Costa-Pereira Altamiro , Sarmento António
Published: March 2004

Introduction

The objective of the present study was to compare the health-related quality of life (HR-QoL) of survivors from severe sepsis and septic shock with HR-QoL in others who survived critical illness not involving sepsis.

Methods

From March 1997 to March 2001, adult patients in an eight-bed medical/surgical intensive care unit (ICU) of a tertiary care hospital admitted with severe sepsis or septic shock (sepsis group; n = 305) were enrolled and compared with patients admitted without sepsis (control group; n = 392). Patients younger than 18 years (n = 48) and those whose ICU stay was 1 day or less (n = 453) were excluded. In addition, patients exhibiting nonsevere sepsis on admission were excluded (n = 87). Finally, patients who developed nonsevere sepsis or severe sepsis/septic shock after admission were also excluded (n = 88).

Results

In-hospital mortality rates were 34% in the sepsis group and 26% in the control group. There were no differences in sex, age, main activity (work status), and previous health state between groups. Survivors in the sepsis group had a significantly higher Acute Physiology and Chronic Health Evaluation II score on admission (17 versus 12) and stayed significantly longer in the ICU. A follow-up appointment was held 6 months after ICU discharge, and an EQ-5D (EuroQol five-dimension) questionnaire was administered. A total of 104 sepsis survivors and 133 survivors in the control group answered the EQ-5D questionnaire. Sepsis survivors reported significantly fewer problems only in the anxiety/depression dimension. Although there were no significant differences in the other dimensions of the EQ-5D, there was a trend towards fewer problems being reported by sepsis survivors.

Conclusion

Evaluation using the EQ-5D at 6 months after ICU discharge indicated that survivors from severe sepsis and septic shock have a similar HR-QoL to that of survivors from critical illness admitted without sepsis.
Case mix, outcome and length of stay for admissions to adult, general critical care units in England, Wales and Northern Ireland: the Intensive Care National Audit & Research Centre Case Mix Programme Database
Authors: Harrison David A , Brady Anthony R , Rowan Kathy
Published: March 2004

Introduction

The present paper describes the methods of data collection and validation employed in the Intensive Care National Audit & Research Centre Case Mix Programme (CMP), a national comparative audit of outcome for adult, critical care admissions. The paper also describes the case mix, outcome and activity of the admissions in the Case Mix Programme Database (CMPD).

Methods

The CMP collects data on consecutive admissions to adult, general critical care units in England, Wales and Northern Ireland. Explicit steps are taken to ensure the accuracy of the data, including use of a dataset specification, of initial and refresher training courses, and of local and central validation of submitted data for incomplete, illogical and inconsistent values. Criteria for evaluating clinical databases developed by the Directory of Clinical Databases were applied to the CMPD. The case mix, outcome and activity for all admissions were briefly summarised.

Results

The mean quality level achieved by the CMPD for the 10 Directory of Clinical Databases criteria was 3.4 (on a scale of 1 = worst to 4 = best). The CMPD contained validated data on 129,647 admissions to 128 units. The median age was 63 years, and 59% were male. The mean Acute Physiology and Chronic Health Evaluation II score was 16.5. Mortality was 20.3% in the CMP unit and was 30.8% at ultimate discharge from hospital. Nonsurvivors stayed longer in intensive care than did survivors (median 2.0 days versus 1.7 days in the CMP unit) but had a shorter total hospital length of stay (9 days versus 16 days). Results for the CMPD were comparable with results from other published reports of UK critical care admissions.

Conclusions

The CMP uses rigorous methods to ensure data are complete, valid and reliable. The CMP scores well against published criteria for high-quality clinical databases.
Holocene glacier fluctuations, Waskey Lake, northeastern Ahklun Mountains, southwestern Alaska
Authors: Levy Laura B. , Kaufman Darrell S. , Werner Al
Published: February 2004

Lake sediments from Waskey Lake, Ahklun Mountains, southwestern Alaska were studied to decipher the history of upvalley glacier fluctuations during the Holocene. Several indicators of glacier activity were measured including: magnetic susceptibility, organic-matter content, grain-size distribution, bulk-sediment mineralogy and diatom assemblages. Seven radiocarbon ages on macrofossils, along with cross-checks by tephrochronology, provide the chronology of the cores. The results from core WL-1 indicate that glaciers lingered near Waskey Lake until 9100 cal. yr BP, perhaps under conditions of high winter accumulation. Peak organic-matter content occurs at 7400 cal. yr BP, when precipitation might have shifted to summer. The onset of Neoglaciation occurred 3100 cal. yr BP, and glaciers reached their maximum extenñ700 cal. yr BP. This chronology is consistent with the lichenometrically dated moraines from the glacier forefields. Although the ages are tentative, the youngest and most widespread group of moraines was deposited sometime between 650 and 200 cal. yr BP (during the‘Little Ice Age’). Since then, glaciers in the Waskey Lake area have shrunk bñ50% and equilibrium-line altitudes (ELA) have risen by 35± 22 m. This rise in ELA is much less than the 100 to 200 m rise observed elsewhere in Alaska and indicates considerable spatial variability in late-Holocene climatic change.
Late-Holocene dune activity linked to hydrological drought, Nebraska Sand Hills, USA
Authors: Mason Joseph A. , Swinehart James B. , Goble Ronald J. , Loope David B.
Published: February 2004

Dunefields of the Great Plains contain stratigraphic records of episodic Holocene aeolian activity, potentially providing a valuable record of climatic change. It has been dif” cult to establish unambiguous links between activity at speci” c sites and regional palaeoclimate, however. Here we demonstrate that widespread late-Holocene aeolian activity in the Nebraska Sand Hills, the largest dune” eld on the Great Plains of North America, occurred during a period of hydrological drought. Aeolian sand sheets are interbedded with peat that accumulated in interdunes throughout much of the Holocene. The youngest of these sand sheets was deposited between 950 and 650 cal. BP, about the same time as the most recent major episode of aeolian activity at upland sites up to 120 km apart. Sand sheets could only have advanced across the interdunes if the local groundwater‘ ow systems that maintain interdune wetlands were temporarily reduced or eliminated by a reduction in recharge. Both reduced recharge and upland aeolian activity are best explained by regional megadrought.
Techniques for estimation of tidal elevation and con” nement (∼salinity) histories of sheltered harbours and estuaries using benthic foraminifera: examples from New Zealand
Authors: Hayward Bruce W. , Scott George H. , Grenfell Hugh R. , Carter Rowan , Lipps Jere H.
Published: February 2004

Techniques for estimating tidal elevation and con” nement (proxy for salinity) using modern benthic foraminiferal census data from New Zealand harbours and lower-salinity estuaries are described and assessed for their utility for reconstructing the depositional settings of late-Holocene sequences. We describe a simple modern analogue technique for estimating tidal or subtidal elevation of Holocene fossil faunas, utilizing the modern data set most applicable to the Holocene setting (sheltered tidal harbours and inlets, or lower-salinity estuaries). Canonical correspondence analysis was used to extract a synthetic con” nement gradient from for aminiferal census data in transects down” ve New Zealand estuaries. This gradient was used to develop a New Zealand Con” nement Index that can be computed for New Zealand modern and Holocene estuarine and harbour samples based on their foraminiferal composition. The value of the method for estimating Holocene elevational and con” nement (palaeosalinity) histories was assessed for a tidal inlet and the middle reaches of an estuary. Two earthquake-related vertical displacements are recognized in a 1.1 m core from Ahuriri Inlet, Hawkes Bay: (1) a 1–2 m subsidence (c. 500 BP) from low tidal to subtidal; (2) a 1.5–2.5 m uplift (1931 Napier Earthquake) from subtidal to high tidal, followed by progressively increasing con” nement in a much smaller inlet. A substan tial con” nement increase (probable salinity decrease) is recognized in a 0.8 m core from Rangitopuni Estuary, Auckland, accompanying the widespread disappearance of cockle beds. Palynology shows that this event is associated with forest clearance in the watershed following earliest signi” cant human settlement (c. 600–800 BP). Taphonomic dissolution of calcareous tests was a signi” cant factor in the lesser accuracy of elevational estimates in our estuarine study core, although dissolution appears to correspond with increased freshwater runoff. Taphonomic disaggregation and loss of agglutinated foraminifera did not appear to be signi” cant in these short cores.
Common millennial-scale variability of Antarctic and Southern Ocean temperatures during the past 5000 years reconstructed from the EPICA Dome C ice core
Authors: Masson-Delmotte V. , Stenni B. , Jouzel J.
Published: February 2004

Measurements of the two water stable isotopes (dD and d18O) along EPICA (European Project for Ice Coring in Antarctica) Dome C ice core are combined with simple isotopic modelling (distillation models) to reconstruct the variability of both the site temperature (East Antarctica) and the moisture source temperature (nowadays probably the subantarctic Indian Ocean). We discuss the difference between the reconstructed site and source temperature pro” les with respect to the initial isotopic data. We show that (i) the early-Holocene optimum appears” rst in Antarctica and 800 years later in the Southern Ocean, and (ii) during the last 5000 years, the site and source temperatures co-vary at the centennial timescale. An 833-year periodicity is observed only on deuterium and site temperature and therefore probably of local origin.
Diatom evidence of hydrographic changes and ice conditions in Igaliku Fjord, South Greenland, during the past 1500 years
Authors: Jensen Karin G. , Kuijpers Antoon , Koç Nalân , Heinemeier Jan
Published: February 2004

Biostratigraphic diatom analyses were carried out on two sediment cores from Igaliku Fjord, South Greenland, in order to reconstruct hydrographic and climatic fluctuations during the late Holocene (AD 550 to present). Pronounced differences in hydrographic setting of the coring sites provide palaeoenvironmental information of both local and more regional character. Five diatom zones were identified from the subfossil diatom records, each describing a hydrographic setting. Two major climate periods, the ‘Mediaeval Warm Period’ (AD 800–1250) and the ‘Little Ice Age’ (ad 1580–1850), that were separated by a variable transitional period, were recognized. Prior to these periods, a cold and presumably moist climate regime prevailed between ad 500 and 700. Cooling events were identified during the ‘Mediaeval Warm Period’ in the period ad 960 to 1140. The diatom data demonstrate that marked hydrographic changes occurred in the course of a relatively short timespan beginning at about ad 1300 and culminating around ad 1500. These changes occur during a crucial period in which the Norse are believed to have disappeared from South Greenland. Thus, our results support the hypothesis proposing that one of the main reasons for the loss of the Norse settlements was climatic deterioration.
Palynofacies analysis and organic-walled dinoflagellate cysts in late-Holocene sediments from Igaliku Fjord, South Greenland
Authors: Roncaglia Lucia , Kuijpers Antoon
Published: February 2004

This study characterizes late-Holocene (past 3300 years) variations in organic matter deposition in the outer part of Igaliku Fjord, South Greenland, and uses this information to assess palaeohydrographic conditions. Except for two, all residues were characterized by abundant organic matter, with amorphous material dominating. The late-Holocene sediments in the deeper parts of the outer Igaliku Fjord have generally been deposited under anoxic to suboxic conditions with relatively low terrestrial/freshwater influx. The organic-walled dinoflagellate cyst assemblages suggest the continuous presence of water masses derived from the East Greenland Current, while changes in sea-surface temperature during the last 3300 years have also been interpreted. Terrestrial influx was reflected by the continuous occurrence of leaf tissue, which increased in abundance in sediments younger than ad 960. Pseudo-amorphous phytoclasts occurred in sediments older than ad 770, and sporomorphs were rare throughout.Acritarchs and organic-walled dinoflagellate cysts dominated the assemblages in the sediments. Relatively high amounts of benthic foraminiferal linings in the interval ad 960–1285 suggests increased nutrient availability, which may be ascribed to strong, wind-induced mixing of the water-column or higher fluxes of organic material. Sparse organic matter was recorded in sediments of age c.AD 1125 pointing to significant oxidation due to highly oxic bottom-water conditions.
Pre-industrial human and environment interactions in northern Peru during the late Holocene
Authors: Dillehay Tom , Kolata Alan L. , Q. Mario Pino
Published: February 2004

The result of long-term environmental and human interaction is a variety of potential human responses to major natural crises: population aggregation or dispersal, changes in economic strategies and land-use patterns, restructuring of social organization, increase in the incidence of conflict and warfare, and, in some instances, urban abandonment and cultural collapse. In the context of pre-industrial societies, two social processes with the greatest potential impact on the environment and on changing human-environmental interaction are urbanization and the development of diversified, regional-scale production systems such as intensive agriculture, pastoralism and exploitation of maritime resources. This paper employs archaeological and geological data from the Jequetepeque and Zana valleys on the north coast desert of Peru to study: (1) the specific responses of Moche, Chimu and Inca societies ( c. ad 250–1553) to major episodes of drought, El Niño flooding, and desertification; (2) the social processes of urban-rural relations and economic diversification; and (3) how these processes interacted within the dynamic arid north coast. Our research focuses on changing palaeoenvironmental regimes, agricultural infrastructures and domestic occupations to explore the complex interplay of cultural and natural forces that shaped the variable human responses and the history of urban-rural systems. Understanding the problem of how pre-industrial systems were sustained or failed in the context of interrelated social and environmental crises is an interdisciplinary objective, one that requires the integration of analytical techniques and theoretical frameworks of both the natural and social sciences as delineated in this study.
Sensitivity of raindrop formation in ascending cloud parcels to cloud condensation nuclei and thermodynamic conditions
Authors: Segal Y. , Khain A. , Pinsky M. , Sterkin A.
Published: March 2004

This paper uses a 2000‐bin spectral microphysics cloud parcel model to investigate the effects of aerosol particles on droplet spectrum evolution and warm rain formation in ascending cloud parcels under maritime, intermediate, and continental unstable thermodynamic conditions. Cloud parcels of different cloud depth are simulated for each thermodynamic condition. Concentration and size distribution of cloud condensation nuclei (CCN) were varied within a wide range for each cloud depth.

Cloud parcels were divided into three groups with respect to the relationship between cloud depth Hc and the distance of the collision triggering level Hcol above cloud base. The sensitivity of precipitation to CCN variations is quite different for the different groups. Parcels of the first group (Hc < Hcol) do not precipitate. Precipitation from cloud parcels belonging to the second group, in which collisions start at a small distance below the maximum cloud‐top height (Hc ≃ Hcol), turns out to be highly sensitive to the variation of CCN concentration and size distribution. For these parcels an increase in the concentration of large CCN can result in an increase in precipitation amount by several factors. Many cloud parcels arising under continental and intermediate conditions, as well as not very deep maritime clouds, can be assigned to this group. The precipitation amount from cloud parcels belonging to the third group (Hc ≫ Hcol), represented by deep tropical clouds, turns out to be insensitive to CCN distribution and droplet concentration within a wide range of their variations. Comparable effects of small and large CCN on precipitation formation are analysed for each group of cloud parcels.

These results are closely related to the problem of rain enhancement via hygroscopic seeding. It is shown that there is a certain range of cloud depths within which cloud seeding can potentially lead to a significant (several times) increase in rain within ascending parcels. Rain formed in cloud parcels with depths beyond this range is only slightly sensitive to the CCN concentration. Copyright © 2004 Royal Meteorological Society
Factors contributing to the onset of the Australian summer monsoon
Authors: Hung Chih‐Wen , Yanai Michio
Published: March 2004

Using the reanalyses from the European Centre for Medium‐Range Weather Forecasts, outgoing long‐wave radiation (OLR) and precipitation data for 1979–93, this paper examines major factors contributing to the onset of the Australian summer monsoon. The low‐level (850 hPa) westerly wind and convective activity (OLR, precipitation) over a region in northern Australia (NAU) are used to determine the onset dates. Composite results are then derived, based on these dates. Daily apparent heat source and apparent moisture sink values are obtained as residuals of the large‐scale heat and moisture budgets to help clarify the roles of the various heating processes in the onset. Four major factors contributing to the onset are identified: (1) land–sea thermal contrast, (2) barotropic instability, (3) arrival of the Madden–Julian oscillation (MJO) and (4) intrusion of midlatitude troughs. The thermal contrast due to differential heating between land and sea acts as a seasonal preconditioning for the onset. The sensible heating over the continent leads to a reversal of meridional temperature gradient between the Australian continent and the Arafura Sea in a layer below 800 hPa in September–March, and sets up a thermally induced meridional–vertical circulation which helps to transport low‐level moist air inland. The barotropic instability criterion is often met at 850 hPa in NAU several days prior to the onset. The sudden onset is then triggered by the arriving MJO and at times by the intrusion of a midlatitude trough. Copyright © 2004 Royal Meteorological Society
Three‐dimensional simulation of the ASTEX Lagrangian 1 field experiment with a regional numerical weather prediction model
Authors: Sigg Robert , Svensson Gunilla
Published: March 2004

The Atlantic Stratocumulus Transition Experiment (ASTEX) first Lagrangian experiment (Lagrangian 1) is here simulated with a modified version of the regional forecast model HIRLAM (High Resolution Limited Area Model). The main modification is that moist turbulent fluxes are accounted for in the model. Trajectory calculations show good agreement with earlier estimations. The initially rather shallow stratocumulus topped marine boundary layer is deepening along the trajectory, and in the end cumulus clouds are formed that penetrate the boundary‐layer top. The model predicts this change in cloudiness, but the boundary layer is too shallow in the model. A simulation with modified initial conditions shows improved results, but is still too slow in increasing the boundary‐layer depth. Additional factors that influence the boundary‐layer growth are: the increase in sea surface temperatures, lower modelled wind speeds, low entrainment rates due to coarse vertical resolution, and synoptic‐scale subsidence.

An anticyclone at the surface moved slightly northward during the simulation. The anticyclone was accompanied at 500 hPa by a deepening cyclone and, therefore, one would expect synoptic subsidence in the area of the Lagrangian 1. The modelled negative vertical wind component at the boundary‐layer top oscillates, and this is examined using spectral analysis. The results show that the vertical velocity is influenced by cumulus clouds on time‐scales up to 15 h with a peak at 9 h. The horizontal and vertical wavelengths of the vertical velocity disturbances are estimated from model output to be 400–500 km and 6–10 km, respectively. Using the estimated vertical wavelength and linear theory for hydrostatic inertia–gravity waves, a horizontal wavelength of 350–550 km was calculated for a frequency of 9 h. The model results thus indicate that these types of waves are responsible for the undulating vertical velocity.

Finally, an estimation of the synoptic‐scale vertical velocity is calculated by filtering out all scales smaller than 15 h from the vertical velocity signal. This results in subsidence both at the beginning and the end of the Lagrangian with vertical velocities between −0.1 and −0.4 cm s−1. Copyright © 2004 Royal Meteorological Society
Exploration of some convective regimes over the Alpine orography
Authors: Stein J.
Published: March 2004

A numerical exploration of several airflow regimes is performed by means of the non‐hydrostatic model Meso‐NH. The Alpine orography has been selected together with a uniform conditionally unstable profile extracted from the Mesoscale Alpine Programme database. The stationary solution is obtained at the fine scale after three successive simulations using three nested levels (40, 10 and 2.5 km). The variation of the non‐dimensional height of the Alps leads to the following regimes: no convection, upstream propagating convection and stationary convection over the Alps. The last two regimes correspond to regimes I and II of the Chu and Lin (2000) study. The sensitivity of the convective response to the fine‐scale orography is found to be more important for regime II than for regime I. Moisture budgets confirm the importance of the barrier wind to determine the rain distribution: in the centre of the Alpine orography for regime II and away from it for regime I. The drying ratio is more influenced by the comparative value of the advective time to a characteristic microphysical time‐scale than by the orographic forcing itself. Finally, for this sounding, the diabatic effects change the critical value of the non‐dimensional height for the transition between the ‘flow‐over’ and ‘flow‐around’ configurations. Copyright © 2004 Royal Meteorological Society
Estimation of the reliability of ensemble‐based probabilistic forecasts
Authors: Atger Frédéric
Published: March 2004

Reliability is an essential attribute of the quality of probabilistic forecasts. It is traditionally estimated by defining a number of arbitrary probability categories. Reliability is often difficult to estimate accurately with a small sample size. This occurs, for example, when evaluating high probabilities of rare events. Significance tests are used in this study in order to determine an appropriate categorization of forecast probabilities for the estimation of reliability. For events occurring frequently, this method leads to credible estimates of the performance for the whole range of forecast probabilities. On the other hand, the reliability of higher probabilities for infrequent events cannot be estimated with confidence. A statistical scheme has been designed for estimating reliability from limited samples, even in the case of rare events and higher probabilities. The procedure consists of fitting a Relative Operating Characteristic (ROC) curve under the bi‐normal assumption. The validity of the method is discussed by testing its ability to estimate reliability from truncated verification samples. The positive impact of a basic method of calibration is increased when it is applied after an estimation of reliability through a fitting of the ROC curve. Copyright © 2004 Royal Meteorological Society
Sensitivity of dynamical seasonal forecasts to ocean initial conditions
Authors: Alves Oscar , Balmaseda Magdalena Alonso , Anderson David , Stockdale Tim
Published: March 2004

The impact of ocean data assimilation on dynamical El Niño–Southern Oscillation forecasting is studied by looking at forecasts started from ocean initial conditions produced with and without data assimilation. Sensitivity is further examined by comparing coupled forecasts started from initial conditions obtained using different ocean‐forcing fields. A total of four ocean reanalyses for the period 1990–97, two analyses using sub‐surface data assimilation and two using only wind and sea‐surface‐temperature (SST) information are considered. Different wind‐stress forcing produces significantly different analyses when subsurface data are not assimilated, but these differences are much smaller when subsurface temperatures are assimilated.

The statistics of the forecast errors show that, with data assimilation, the forecasts of the NINO3 area (5°S–5°N,150°W–90°W) SST anomaly clearly beat persistence over all lead times (1–6 months), which is not the case when subsurface ocean observations are not used. The forecasts from the analyses using different wind forcing and no data assimilation differ considerably. The forecasts started from the analyses with data assimilation are generally similar irrespective of which wind product is used, suggesting that data assimilation is effective at reducing the impact of errors in the wind. For both wind forcings, data assimilation improves the forecast skill. Copyright © 2004 Royal Meteorological Society
Hydraulic aspects of föhn winds in an Alpine valley
Authors: Gohm A. , Mayr G. J.
Published: March 2004

This study examines the applicability of single‐layer hydraulic theory to Alpine föhn winds in the example of the flow in the Brenner Pass region (Austria/Italy). The south föhn is described as the gap flow over the Pass and along the associated Wipp Valley. Numerical shallow‐water simulations for a wide range of initial conditions, including shallow‐ and deep‐föhn cases, are discussed and compared with selected measurements collected within the Mesoscale Alpine Programme (MAP). The observational analyses are based on Doppler and aerosol‐backscatter lidar data for a specific föhn case, and on surface observations and radiosoundings for all föhn cases observed within the 70‐day MAP Special Observing Period (SOP).

Radiosoundings at a location upstream (south) and downstream (north) of the Brenner Pass reveal that the average MAP SOP föhn case had subcritical flow south and nearly critical flow north of the Brenner Pass. The hydraulic model indicates flow transition to a supercritical state near the Pass, a hydraulic jump 2 km further north, mainly subcritical flow in the upper Wipp Valley except near the Brenner and, especially for shallow föhn, a tendency to becoming supercritical in the lower Wipp Valley. The model results suggest that the vertical topographic contraction exerts stronger control for the flow at the Brenner gap than the lateral contraction. In accordance with Doppler lidar measurements, the hydraulic model captures the decrease of the wind speed in the across‐valley direction from east to west in the northern part of the valley. This asymmetric flow pattern is a result of the complex valley geometry rather than of the influence of upper‐level synoptic winds, as suggested in a previous study.

For some observed cases the strength of the temperature inversion at the top of the föhn layer decreased across the Brenner Pass, presumably due to entrainment processes. Consequently, the reduced‐gravity decreased as well. There are two major reasons for the only moderate agreement between the hydraulic parameters retrieved from soundings and those provided by the model: the model assumes a constant value of reduced‐gravity, and the calculation of hydraulic parameters for föhn cases without a strong and sharp temperature inversion is ambiguous. Essential flow patterns in the simulated fields, such as the location of the pressure minimum and wind speed maxima, compare well with the surface observations along a valley transect. Indications for a steeply amplified, or breaking, gravity wave resembling a hydraulic jump to the lee of the two mountain ridges are found in lidar observations as well as in the simulations. Copyright © 2004 Royal Meteorological Society
Adjoint sensitivity analysis of an observational operator for visible and infrared cloudy‐sky radiance assimilation
Authors: Greenwald Thomas J. , Vukićević Tomislava , Grasso Louis D. , Haar Thomas H. Vonder
Published: March 2004

An adjoint modelling system is developed for an observational operator at visible and infrared wavelengths to explore the connection between cloud microphysics and top of atmosphere (TOA) radiances at cloud‐resolving scales (2–5 km) in preparation for direct assimilation of cloudy‐sky radiance satellite data. Analysis was performed on complex simulated three‐dimensional cloud fields for different weather phenomena generated by the Regional Atmospheric Modeling System using two‐moment microphysics. Sensitivity of TOA radiances at 0.63, 3.92, and 10.7 µm to changes in cloud mixing ratio revealed that small liquid drops and ice particles for very optically thin clouds were the largest contributors to the radiative sensitivities. More importantly, the sensitivities at these wavelengths were found to be complementary; i.e. 0.63 µm reflectances possessed greatest sensitivity to optically thinner water and ice clouds, whereas 3.92 µm responded to thick water clouds and to ice clouds, while 10.7 µm was most sensitive to thinner, cold ice clouds. Implications for numerical weather prediction (NWP) models that do not predict particle number concentration are that radiative sensitivities change somewhat in magnitude but retain the same sign, provided reasonable concentrations are assumed for broad classes of particle types. Overall, results indicated that satellite radiances measured in visible/infrared spectral windows contain potential information regarding cloud microphysics, especially at solar wavelengths, suggesting that direct assimilation of these data may be useful in supplying unique cloud information to NWP models. Copyright © 2004 Royal Meteorological Society