bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for Cortical Functional Changes in Patients With Migraine and White Matter Abnormalities on Conventional and Diffusion Tensor Magnetic Resonance Imaging
Authors: Rocca Maria A. , Colombo Bruno , Pagani Elisabetta , Falini Andrea , Codella Maria , Scotti Giuseppe , Comi Giancarlo , Filippi Massimo
Published: March 2003

Background—

In this study, we used functional MRI (fMRI) to investigate the pattern of cortical activations after a simple motor task in patients with migraine and white matter (WM) abnormalities on conventional MRI scans of the brain. We also investigated whether the extent of brain activations was correlated with WM structural pathology measured using diffusion tensor (DT) MRI.

Methods—

From 15 right-handed patients with migraine and 15 sex- and age-matched, right-handed healthy volunteers, we obtained the following: (1) fMRI (repetitive flexion-extension of the last 4 fingers of the right hand), (2) dual-echo turbo spin echo scans, and (3) pulsed-gradient spin-echo echo-planar sequence to calculate DT-MRI maps. fMRI analysis was performed using SPM99 and cluster detection. We measured the volume, the average mean diffusivity (

), and the average fractional anisotropy of all lesions seen on the dual-echo scans.

histograms of the normal-appearing WM were also produced.

Results—

Compared with healthy volunteers, migraine patients had a larger relative activation of the contralateral primary sensorimotor cortex (
P
=0.01) and a rostral displacement of the supplementary motor area (
P
=0.03). The shapes of the curves reflecting the time course for fMRI signal intensity changes were similar between migraine patients and controls for all of the cortical areas we studied. Compared with healthy subjects, migraine patients had significantly lower

histogram peak height of the normal-appearing WM histogram (
P
=0.02), which was found to be correlated with the extent of displacement of the supplementary motor area (
r
=−0.80,
P
<0.001).

Conclusions—

This study suggests that functional cortical changes occur in patients with migraine and brain MRI abnormalities and that they might be secondary to the extent of subcortical structural damage.
Quality of Life During and After Inpatient Stroke Rehabilitation
Authors: Hopman Wilma M. , Verner Jane
Published: March 2003

Background and Purpose—

Very limited longitudinal data are available that assess the health-related quality of life (HRQOL) of stroke survivors after discharge from inpatient rehabilitation. The purpose of this research was to assess changes in HRQOL during inpatient rehabilitation and again 6 months after discharge.

Methods—

This was a prospective study of all eligible patients admitted to an inpatient stroke rehabilitation hospital over a 3-year period. HRQOL was assessed by means of the Medical Outcomes Study 36-item Short Form (SF-36). Dependent
t
tests were used to compare the scores at admission and discharge and at discharge and 6 months. Changes in HRQOL were calculated for the period of admission to discharge and of discharge to the 6-month follow-up.

Results—

Complete data were available for 85 patients. During rehabilitation, there were improvements in all 8 domains of the SF-36, with 5 attaining statistical significance. After discharge, 3 domains continued to improve, with 1 attaining statistical significance. However, there were marked and statistically significant declines in the other 5 domains of the SF-36. Feedback was obtained from a subset of the patients as to the reasons for these declines.

Conclusions—

Substantial gains in HRQOL during inpatient stroke rehabilitation may be followed by equally substantial declines in the 6 months after discharge. There is a need for longitudinal research into the HRQOL of stroke survivors and their families, as well as a need to ensure that adequate community services and support are available.
Changes Related to Age and Cerebrovascular Symptoms in the Extracellular Matrix of Human Carotid Plaques
Authors: Gonçalves Isabel , Moses Jonatan , Dias Nuno , Pedro Luís M. , Fernandes e Fernandes José , Nilsson Jan , Ares Mikko P.S.
Published: March 2003

Background and Purpose—

Many processes involved in the pathogenesis of atherosclerosis result in modifications of the extracellular matrix. These changes not only determine the mechanical stability of atherosclerotic lesions but can directly or indirectly influence further development of the lesions. The purpose of the present study was to compare the matrix composition of human carotid plaques from symptomatic patients with those obtained from patients without symptoms. Furthermore, matrix changes related to age were studied.

Methods—

Thirty atherosclerotic carotid plaques were removed by endarterectomy from 27 patients and divided into 2 groups on the basis of the presence of ipsilateral symptoms. The plaques were homogenized, and the total levels of the major components of the extracellular matrix were determined.

Results—

Plaques associated with symptoms were characterized by increased levels of elastin (1.58±0.46 versus 1.24±0.40 mg/g wet wt;
P
=0.03) and decreased levels of hydroxyapatite (45.1±46.3 versus 131.4±111.7 mg/g wet wt;
P
=0.02) compared with asymptomatic plaques. The increase in elastin in plaques from symptomatic patients was due to elevated levels of an intermediate-size fraction, as determined by liquid chromatography. Collagen and sulfated glycosaminoglycans were present in equal amounts in both groups. Elastin content in carotid plaques decreased with age.

Conclusions—

Carotid plaques from symptomatic patients have lower levels of hydroxyapatite than those from asymptomatic patients. The present study also raises the possibility that non–cross-linked forms of elastin, increased in plaques associated with symptoms, could be a marker of plaque vulnerability and/or directly induce harmful cellular activities or increase lipoprotein retention in the vascular wall.
Cerebral Hemodynamics and Metabolism in Patients With Symptomatic Occlusion of the Internal Carotid Artery
Authors: Rutgers D.R. , van Osch M.J.P. , Kappelle L.J. , Mali W.P.T.M. , van der Grond J.
Published: March 2003

Background and Purpose—

The goals of this study were to investigate (1) whether the concentrations of choline, creatine, and
N
-acetyl aspartate (NAA) in cerebral white matter are changed in patients with symptomatic occlusion of the internal carotid artery (ICA) and (2) whether possible changes in metabolite concentration are related to regional cerebral perfusion or cerebral vasoreactivity.

Methods—

In 19 patients (mean±SD age, 60±9 years), white matter metabolite concentrations were measured with proton MR spectroscopic imaging on average 4±2 months after symptoms occurred. In selected voxels, corresponding cerebral blood flow and volume, mean transit time, and time-to-bolus peak were determined with dynamic susceptibility contrast MRI. Cerebral CO
2
reactivity was determined with transcranial Doppler sonography.

Results—

No significant changes in choline and creatine concentrations were observed. NAA concentration was significantly reduced in the hemisphere on the side of the symptomatic ICA (9.1±1.7 mmol/L) compared with the contralateral hemisphere (10.5±1.7 mmol/L,
P
<0.005) and control subjects (10.5±0.9 mmol/L,
P
<0.01). Although no significant interhemispheric difference in NAA concentration was found in patients who presented with retinal ischemia, patients with cerebral ischemia had a significantly lower NAA concentration in the symptomatic hemisphere (9.0±1.7 mmol/L) compared with the asymptomatic hemisphere (10.4±1.6 mmol/L,
P
<0.05). In all patients, NAA concentration was not significantly correlated with quantitative cerebral perfusion parameters or CO
2
reactivity.

Conclusions—

Patients with symptomatic ICA occlusion may show chronic neuronal damage in cerebral white matter as evidenced by reduced NAA concentration. This seems to be related to previous symptomatology rather than to the cerebral hemodynamic status in a chronic stage.
Associations of a Human G Protein β3 Subunit Dimorphism With Insulin Resistance and Carotid Atherosclerosis
Authors: Wascher Thomas C. , Paulweber Bernhard , Malaimare Liliane , Stadlmayr Andreas , Iglseder Bernhard , Schmoelzer Isabella , Renner Wilfried
Published: March 2003

Background and Purpose—

The C825T dimorphism of the gene encoding the human G protein β3 subunit (
GNB3
) is associated with hypertension and obesity. Although these findings suggest an association with insulin resistance and atherosclerosis, this hypothesis has yet been tested only partially.

Methods—

To investigate this hypothesis, the C825T dimorphism was determined in a population of 932 middle-aged white subjects of middle European (Austrian) origin. Insulin sensitivity was measured with the short insulin tolerance test; intima-media thickness of the carotid artery and morphological plaque burden were measured by ultrasound.

Results—

Insulin sensitivity was found to be significantly lower in carriers of the T allele (3.55±1.27 versus 3.92±1.30%/min,
P
=0.012) in the group of male subjects with abdominal body fat distribution (waist-to-hip ratio >0.9). No effect was observed in women or men with a waist-to-hip ratio <0.9. Advanced carotid artery plaques were more frequent (odds ratio, 1.606; 95% confidence interval, 1.002 to 2.575;
P
=0.04) in carriers of the T allele regardless of sex. No effect was observed with regard to carotid artery intima-media thickness.

Conclusions—

In summary, our results demonstrate that the
GNB3
825T allele is associated with reduced insulin sensitivity in men with abdominal fat distribution and with more advanced carotid atherosclerosis in middle-aged white men and women.
Early Outcome of Carotid Angioplasty and Stenting With and Without Cerebral Protection Devices
Authors: Kastrup Andreas , Gröschel Klaus , Krapf Hilmar , Brehm Bernhard R. , Dichgans Johannes , Schulz Jörg B.
Published: March 2003

Background—

Carotid angioplasty and stenting (CAS) is increasingly being used for treatment of symptomatic and asymptomatic carotid artery disease (CAD). To evaluate the efficacy of cerebral protection devices in preventing thromboembolic complications during CAS, we conducted a systematic review of studies reporting on the incidence of minor stroke, major stroke, or death within 30 days after CAS.

Summary of Review—

We searched for studies published between January 1990 and June 2002 by means of a PubMed search and a cumulative review of reference lists of all relevant publications. In 2357 patients a total of 2537 CAS procedures had been performed without protection devices, and in 839 patients 896 CAS procedures had been performed with protection devices. Both groups were similar with respect to age, sex distribution, cerebrovascular risk factors, and indications for CAS. In many studies the periprocedural complication rates had not been presented separately for patients with symptomatic and asymptomatic CAD. The combined stroke and death rate within 30 days in both symptomatic and asymptomatic patients was 1.8% in patients treated with cerebral protection devices compared with 5.5% in patients treated without cerebral protection devices (χ
2
=19.7,
P
<0.001). This effect was mainly due to a decrease in the occurrence of minor strokes (3.7% without cerebral protection versus 0.5% with cerebral protection; χ
2
=22.4,
P
<0.001) and major strokes (1.1% without cerebral protection versus 0.3% with cerebral protection; χ
2
=4.3,
P
<0.05), whereas death rates were almost identical (≈0.8%; χ
2
=0.3,
P
=0.6).

Conclusions—

On the basis of this early analysis of single-center studies, the use of cerebral protection devices appears to reduce thromboembolic complications during CAS. These technical aspects should be taken into account before the initiation of further randomized trials comparing CAS with carotid endarterectomy.
Is Breakdown of the Blood-Brain Barrier Responsible for Lacunar Stroke, Leukoaraiosis, and Dementia?
Authors: Wardlaw J.M. , Sandercock P.A.G. , Dennis M.S. , Starr J.
Published: March 2003

Background—The pathogenesis of and relationship between small deep (lacunar) infarcts, cerebral white matter disease (leukoaraiosis or white matter hyperintensities), and progressive cognitive impairment or dementia are much debated.

Summary of Comment—We hypothesize that cerebral small-vessel endothelial (ie, blood-brain barrier) dysfunction, with leakage of plasma components into the vessel wall and surrounding brain tissue leading to neuronal damage, may contribute to the development of 3 overlapping and disabling cerebrovascular conditions: lacunar stroke, leukoaraiosis, and dementia. This hypothesis could explain the link between ischemic cerebral small-vessel disease and several apparently clinically distinct dementia syndromes. This hypothesis is supported by pathological, epidemiological, and experimental studies in lacunar stroke and leukoaraiosis and observations on the blood-brain barrier with MRI. We suspect that the potential significance of blood-brain barrier failure as a pathogenetic step linking vascular disease with common, disabling brain diseases of insidious onset has been overlooked. For example, lipohyalinosis, which has a pathological appearance of uncertain origin and is possibly responsible for some discrete lacunar infarcts, may be one end of a clinical spectrum of illness manifested by blood-brain barrier failure.

Conclusions—Proof that blood-brain barrier failure is key to these conditions could provide a target for new treatments to reduce the effects of vascular disease on the brain and prevent cognitive decline and dementia.
Increased Risk of Atherosclerosis Is Confined to CagA-Positive
Helicobacter pylori
Strains
Authors: Mayr Manuel , Kiechl Stefan , Mendall Michael A. , Willeit Johann , Wick Georg , Xu Qingbo
Published: March 2003

Background and Purpose—

Accumulating evidence indicates that a variety of infections contribute to the pathogenesis of atherosclerosis, but there is controversy concerning the impact of
Helicobacter pylori
infections in atherosclerosis.

Methods—

We evaluated seropositivity to
H pylori
and to its cytotoxin-associated gene A (CagA) product in a large, prospective, population-based study (n=684). Intima-media thickness and atherosclerosis of carotid arteries were thoroughly assessed by high-resolution duplex scanning.

Results—

In our study population,
H pylori
infections defined by seropositivity have no relationship with levels of classic cardiovascular risk factors or markers of systemic inflammation, except for elevated levels of immune reactions to mycobacterial heat shock protein 65. The latter showed a trend toward highest levels in those harboring virulent
H pylori
strains (
P
=0.08). Common carotid artery intima-media thickness—both absolute values and changes between 1995 and 2000—were significantly enhanced in subjects seropositive to CagA but not in those infected with CagA-negative
H pylori
strains. There was a clear dose-response relation between anti-CagA antibodies and both intima-media thickness and atherosclerosis risk. Notably, the risk of atherosclerosis associated with CagA seropositivity was amplified by elevated C-reactive protein levels.

Conclusions—

Infections with virulent CagA-bearing
H pylori
strains may contribute to the pathogenesis of early atherosclerosis by aggravating immune-inflammatory reactions.
Ischemic Lacunar Stroke in Patients With and Without Potential Mechanism Other Than Small-Artery Disease
Authors: Baumgartner Ralf W. , Sidler Claude , Mosso Maria , Georgiadis Dimitrios
Published: March 2003

Background and Purpose—

Autopsy studies found that lacunar strokes differ in the size of the underlying brain infarct and that small lacunes are usually caused by hypertensive small-artery disease (SAD) and larger ones by atheromatous or embolic perforator occlusion. These findings suggest that larger lacunar infarcts might cause more severe neurological deficits and a higher detection rate on brain imaging compared with lacunar strokes caused by SAD. This prospective observational study was performed to investigate whether (1) neurological outcome, (2) prevalence of stroke risk factors, (3) prevalence of clinically asymptomatic occlusive cerebral artery disease, and (4) detection rate of underlying lacunar infarcts at brain imaging differ in ischemic lacunar strokes with (non-SAD) and without potential etiologies other than SAD.

Methods—

Consecutive patients with lacunar stroke (n=244), defined by both clinical findings and brain imaging, were studied. Neurological deficit was quantified at presentation with the use of the National Institutes of Health Stroke Scale (NIHSS) and after 3 months with the NIHSS and the modified Rankin Scale (mRS). Cerebral arteries were investigated by ultrasound.

Results—

Compared with patients with SAD lacunar strokes (n=155; 64%), patients with non-SAD lacunar strokes (n=89; 36%) had (1) higher NIHSS scores at presentation and higher NIHSS and mRS scores after 3 months (
P
<0.05); a higher prevalence of (2) hypertension (
P
<0.05), (3) coronary artery disease (
P
<0.0001), (4) previous transient ischemic attacks (
P
<0.01), and (5) asymptomatic stenoses of intracranial cerebral (
P
<0.01 to
P
<0.0001) and extracranial carotid (30% to 50% narrowing;
P
<0.01) arteries; and (6) a higher detection rate of the underlying lesion at brain imaging (
P
<0.01).

Conclusions—

Our data suggest that patients with non-SAD lacunar strokes have a worse clinical outcome and a higher prevalence of large cerebral and coronary artery disease than patients with SAD lacunar strokes.
Cardiac Baroreceptor Sensitivity Predicts Long-Term Outcome After Acute Ischemic Stroke
Authors: Robinson Thompson G. , Dawson Suzanne L. , Eames Penelope J. , Panerai Ronney B. , Potter John F.
Published: March 2003

Background and Purpose—

The baroreceptor reflex arc is important in the short-term regulation of the cardiovascular system, and small studies have reported impaired cardiac baroreceptor sensitivity (BRS) after acute stroke. However, the prognostic significance of impaired BRS is uncertain.

Methods—

One hundred twenty-four patients underwent simultaneous ECG and noninvasive beat-to-beat blood pressure (BP) monitoring within 72 hours of neuroradiologically confirmed acute ischemic stroke. Cardiac BRS was assessed from the combined α-index by means of power spectral analysis techniques. Baseline data for acute stroke patients were compared with those of a control group matched for age, sex, and casual BP. Patients were followed up for a median of 1508 days (range, 9 to 2656 days), and outcome was compared between patients with and without impaired BRS.

Results—

Median BRS values were significantly lower in stroke patients than in controls (5 [interquartile range, 3.5 to 7.4] versus 6.2 [interquartile range, 4.5 to 8.3] ms/mm Hg;
P
=0.04). Sixty-one (33 male) patients (mean age, 70.2 [SD 10.5] years) had impaired BRS (≤5.0 ms/mm Hg) compared with 63 (35 male) patients (mean age, 70.6 [SD 11.7] years) without impaired BRS (>5.0 ms/mm Hg). Stroke patients with impaired BRS values had a significantly poorer prognosis (28% versus 8% mortality rate during the follow-up period) although there were no differences in age, stroke severity, stroke type, or casual or 24-hour BP parameters between the 2 groups.

Conclusions—

Impaired cardiac BRS is associated with increased long-term mortality after acute ischemic stroke, irrespective of age, sex, stroke type, and BP. This may reflect cardiac arrhythmias, but the mechanisms underlying this association are unknown, although therapies that improve cardiac BRS after stroke warrant further investigation.
Pulse Pressure and Risk of Alzheimer Disease in Persons Aged 75 Years and Older
Authors: Qiu Chengxuan , Winblad Bengt , Viitanen Matti , Fratiglioni Laura
Published: March 2003

Background and Purpose—

Elevated blood pressure has been found to increase the risk of dementia, including Alzheimer disease. We sought to investigate whether pulse pressure was predictive of Alzheimer disease and dementia.

Methods—

A community-based, dementia-free cohort (n=1270) aged ≥75 years was clinically examined twice over 6 years to detect incident dementia with the use of the criteria of the
Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition
. Cox proportional hazards models were used to analyze pulse pressure in association with incident Alzheimer disease and dementia after adjustment for several potential confounders, including systolic pressure and diastolic pressure.

Results—

During the 5464.6 person-years (median, 4.7 years) of follow-up, 339 subjects developed dementia, including 256 Alzheimer disease cases. Pulse pressure as a continuous variable was not statistically related to the risk of Alzheimer disease and dementia. In the categorical analysis, however, in comparison with median tertile of pulse pressure (70 to 84 mm Hg), subjects with higher pulse pressure had adjusted relative risks (95% CI) of 1.4 (1.0 to 2.0;
P
=0.04) for Alzheimer disease and 1.3 (0.9 to 1.7) for dementia. The corresponding figures related to lower pulse pressure were 1.7 (1.2 to 2.3) for Alzheimer disease and 1.4 (1.0 to 1.9;
P
=0.03) for dementia. This association was particularly pronounced among women.

Conclusions—

Higher pulse pressure is associated with increased risk for Alzheimer disease and dementia in old adults, which is probably due to artery stiffness and severe atherosclerosis. Poor cerebral perfusion related to decreased pulse pressure may explain the association between lower pulse pressure and increased dementia risk.
Prospective Study of Serum Homocysteine and Risk of Ischemic Stroke Among Patients With Preexisting Coronary Heart Disease
Authors: Tanne David , Haim Moti , Goldbourt Uri , Boyko Valentina , Doolman Ram , Adler Yehuda , Brunner Daniel , Behar Solomon , Sela Ben-Ami
Published: March 2003

Background and Purpose—

Substantial evidence is accumulating suggesting that hyperhomocysteinemia may be a risk factor for ischemic stroke. Results of prospective studies are, however, conflicting, and the role of hyperhomocysteinemia in patients with preexisting atherosclerotic vascular disease is not clear. Our aim was to assess prospectively the risk of incident ischemic stroke conferred by serum total homocysteine among patients with preexisting stable coronary heart disease (CHD).

Methods—

We obtained baseline fasting serum samples from patients with chronic CHD enrolled in the Bezafibrate Infarction Prevention (n=3090) secondary prevention study cohort. With a nested case-control design, we measured baseline total homocysteine concentration by a high-performance liquid chromatography–based method in sera (n=160) of matched case-control pairs: patients who developed ischemic stroke during a mean follow-up of 8.2 years (cases) and age- and sex-matched controls without subsequent cardiovascular events.

Results—

An increase of 1 natural log unit in homocysteine concentration was associated with a >3-fold increase in relative odds of incident ischemic stroke (3.3; 95% CI, 1.2 to 10.2). Homocysteine concentrations at the highest quartile (>17.4 μmol/L) were associated with significantly higher odds of ischemic stroke compared with the lowest quartile in matched-pair analysis (3.1; 95% CI, 1.1 to 9.8) and after multivariable adjustments (4.6; 95% CI, 1.3 to 18.9). Adding fibrinogen or soluble intercellular adhesion molecule-1 concentrations, markers of inflammation, to the model did not attenuate this association. The linear trends across the quartiles were significant for all models (
P
<0.05).

Conclusions—

Serum total homocysteine concentration is a strong predictor for incident ischemic stroke among patients at increased risk because of chronic CHD. The graded association observed is independent of traditional risk factors or inflammatory markers and indicates the importance of serum homocysteine levels in patients with preexisting vascular disease.
Aggravated Brain Damage After Hypoxic Ischemia in Immature Adenosine A
2A
Knockout Mice
Authors: Ådén Ulrika , Halldner Linda , Lagercrantz Hugo , Dalmau Ishar , Ledent Catherine , Fredholm Bertil B.
Published: March 2003

Background and Purpose—

Cerebral hypoxic ischemia (HI) is an important cause of brain injury in the newborn infant. Adenosine is believed to protect against HI brain damage. However, the roles of the different adenosine receptors are unclear, particularly in young animals. We examined the role of adenosine A
2A
receptors (A2AR) using 7-day-old A
2A
knockout (A2AR
(−/−)
) mice in a model of HI.

Methods—

HI was induced in 7-day-old CD1 mice by exposure to 8% oxygen for 30 minutes after occlusion of the left common carotid artery. The resulting unilateral focal lesion was evaluated with the use of histopathological scoring and measurements of residual brain areas at 5 days, 3 weeks, and 3 months after HI. Behavioral evaluation of brain injury by locomotor activity, rotarod, and beam-walking test was made 3 weeks and 3 months after HI. Cortical cerebral blood flow, assessed by laser-Doppler flowmetry, and rectal temperature were measured during HI.

Results—

Reduction in cortical cerebral blood flow during HI and rectal temperature did not differ between wild-type (A2AR
(+/+)
) and knockout mice. In the A2AR
(−/−)
animals, brain injury was aggravated compared with wild-type mice. The A2AR
(−/−)
mice subjected to HI displayed increased forward locomotion and impaired rotarod performance in adulthood compared with A2AR
(+/+)
mice subjected to HI, whereas beam-walking performance was similarly defective in both groups.

Conclusions—

These results suggest that, in contrast to the situation in adult animals, A2AR play an important protective role in neonatal HI brain injury.
The Craft of Ruling in Plato's Euthydemus and Republic
Authors: Parry Richard
Published: March 2003

We will investigate the relation between the notion of the craft of ruling in the Euthydemus and in the Republic. In the Euthydemus, Socrates' search for an account of wisdom leads to his identifying it as the craft of ruling in the city. In the Republic, the craft of ruling in the city is the virtue of wisdom in the city and the analogue of wisdom in the soul. Still, the craft of ruling leads to aporia in the former dialogue while in the latter it is a central feature of Socrates' account of justice - both in the city and in the soul. Some commentators hold that the aporia at the end of the second protreptic interlude of the Euthydemus shows that Socrates' account of wisdom is fatally flawed and must be rejected. However, the difficulty for this position is that the craft of ruling from the Euthydemus is a hardy notion that plays an extremely important role in the Republic. Indeed, reflecting this fact, other commentators hold that the aporia is solved in the Republic. Still, what is so far missing is an analysis that clearly shows the way to this solution in the Republic. In what follows, we will analyze the two protreptic interludes in the Euthydemus in order to see how the aporia arises. As we shall see, Socrates presents the aporia as a labyrinth. Indeed, it is a labyrinth with a little noticed step that - once it is noticed - shows the way out. The result will be that the aporia of the Euthydemus points to a solution in which ruling in the soul implies a command of one's appetites and emotions.
Du vin pour le Collège de veille? Mise en lumière d'un lien occulté entre le Choeur de Dionysos et le νυκτερινος συλλογος dans les Lois de Platon
Authors: Larivée Annie
Published: March 2003

Ce texte cherche à montrer que plusieurs allusions textuelles indiquent l'existence d'un lien significatif entre le Choeur de Dionysos et le νυκτερινος συλλογος dans les Lois de Platon. Cette hypothèse inédite se trouve confirmée par un examen attentif des diverses correspondances entre les deux instances, examen qui permet en outre de préciser la nature de leur lien. Il semble d'abord que le Choeur de Dionysos ait pour rôle d'apporter un complément pédagogique de «musique appliquée» à l'élite politique et scientifique de la cité. Plus important encore, le Choeur Dionysien paraît être l'organe idéologique privilégié par lequel les gouvernants du Collège de veille peuvent donner une forme persuasive à leur science et exercer une influence civique puissante sur l'ensemble de la population.
Numerical analysis of heat transfer process for double sided tungsten inert gas – metal inert gas weld pool
Authors: Zhou F. M. , Yu Z. S. , Feng Y. H. , Huang Y. C. , Qian Y. Y.
Published: March 2003

Double sided arc welding is a new type of technology developed in recent years. Many experiments show that this technology has great advantages over single arc welding for the joining of intermediate thickness stainless steel and aluminium alloy base metals. In the present work, a three-dimensional transient numerical model is created to reveal the heat transfer process for a double sided tungsten inert gas (TIG) - metal inert gas (MIG) weld pool from the viewpoint of heat transfer literature and hydrodynamics. Considering of the features of the model, effective calculation software using finite element technology is adopted. The temperature fields in the weld pool for double sided TIG - MIG welding are successfully calculated; in addition, the configuration of the weld pool is also calculated.Comparisons show that thecalculatedresults agree approximately with the experimentally measured results. STWJ/310
Improved weldability diagram for pulsed laser welded austenitic stainless steels
Authors: Lienert T. J. , Lippold J. C.
Published: March 2003

Pulsed Nd:YAG laser welds were produced on 23 different austenitic stainless steel alloys of known composition. The primary solidification mode (PSM) and solidification cracking susceptibility of individual welds on each alloy were identified and correlated with their compositions. Single phase austenite solidification occurred in alloys with Cr equivalent to Ni equivalent ratios (Creq/Nieq) below approximately 1.59 (Hammar and Svennson equivalency relations). Alloys having a Creq/Nieq value above approximately 1.69 exhibited single phase ferrite PSM, whereas alloys for which Creq/Nieq was between 1.59 and 1.69 displayed either single phase ferrite PSM or a dual PSM with grains of single phase austenite adjacent to grains of single phase ferrite. The results of the present work were combined with those of a previous study to construct an improved weldability diagram for pulsed Nd:YAG laser welding of austenitic stainless steels. Consistent with previous observations, alloys that solidified as primary austenite were more prone to solidification cracking. Alloys that solidified as austenite (Creq/Nieq < 1.59) generally cracked when the combined impurity content (P + S) was greater than approximately 0.02%. However, cracking was not found in alloys that solidified as primary austenite with combined impurity content less than approximately 0.02%. Solidification cracking behaviour of alloys that solidified in a dual mode (1.59 < Creq/Nieq < 1.69) appeared to vary with impurity content. No cracking was observed in any of the alloys that solidified as primary ferrite (Creq/Nieq > 1.59).
Comparison of constant current and pulsed gas metal arc welding processes on basis of electrode resistive dissipation
Authors: Bingul Z. , Cook G. E. , Strauss A. M.
Published: March 2003

The dependence of electrode electrical parameters (resistivity and action) on temperature results in a variation of voltage drop along the electrode extension. In the present work, effects and interactions of the temperature dependent electrical parameters in constant current gas metal arc welding and pulsed gas metal arc welding of mild steel are examined and the differences between these two welding processes are determined using the above mentioned electrical parameters, which are calculated based on a resistivity model. The temperature dependent electrical parameters are also used to compute the electrode voltage drop and the arc voltage, which are very difficult to measure directly in practice. Furthermore, the processes are compared using electrode resistive dissipation. Use of the same input in both processes assists in the comparison of the two processes.
Mitigation of welding induced buckling distortion using transient thermal tensioning
Authors: Deo M. V. , Michaleris P.
Published: March 2003

Welding induces residual stresses in structures and may cause buckling distortion if the stresses exceed the critical buckling stress of the structure. Reducing the welding heat input or increasing the structural stiffness reduces or eliminates buckling distortion. However, where, because of the design constraints, structure geometry and weld size are fixed, the transient thermal tensioning process is effective in reducing buckling distortion. An experimental verification and demonstration of transient thermal tensioning for minimising welding induced buckling distortion is presented. Conventional welding was carried out to demonstrate buckling distortion and establish a baseline case. Buckling distortion was eliminated using transient thermal tensioning during welding under the same welding conditions. After buckling distortion was eliminated, angular distortion became evident, which was eliminated using mechanical restraints alongside transient thermal tensioning. Residual stress measurements were obtained using the blind hole drilling method and a comparison of residual stresses for the baseline panel and for the panel with transient thermal tensioning is presented.
Finite element modelling of tungsten inert gas welding of aluminium alloy 2024
Authors: Preston R. V. , Shercliff H. R. , Withers P. J. , Smith S. D.
Published: March 2003

A finite element model to predict the evolution of stress and distortion for a bead on plate tungsten inert gas (TIG) weld in aluminium alloy 2024 plate is described. The thermal model was calibrated against thermocouple measurements, and the mechanical model was validated against direct measurements of residual strain made using synchrotron X-ray diffraction. Particular attention has been paid to the clamping arrangement, the transfer of heat between the plate and the copper backing plate, and the selection of appropriate thermal history dependent mechanical properties. The validated model has been used to determine the optimal arrangement for ‘low stress no distortion’ welding using laser heating applied to both sides of the joint line ahead of the TIG torch. In this manner it is predicted that the peak longitudinal tensile stresses in the weld region can be reduced to 15% of their normal values.
Computer aided alloy design of insert metal for transient liquid phase bonding of γ/γ'/β type high aluminium nickel base superalloy
Authors: Nishimoto K. , Saida K. , Shinohara Y.
Published: March 2003

A computer aided alloy design technique was used to develop an insert metal for transient liquid phase bonding of γ/γ'/β type high Al, Ni base superalloy. A mathematical programming method was used to obtain an optimal chemical composition through rationally compromising the plural objective performances of an insert metal using the grid search method. This approach was based on data estimation from limited experimental data using the interpolation method. The objective function Z, which was introduced as an index of bonding performance of an insert metal, involved the melting point, hardness, formability of brittle phases, and void ratio in the bond layer as the evaluating factors. Using this method, the chemical composition Ni-3.0Cr -4.0B-0.5Ce (mass%), designated HY- 20, was determined as the optimal composition for the insert metal. Observations using SEM revealed that the joints bonded with the newly developed insert metal exhibited sound microstructures without the formation of brittle phases and voids in the bond layer. The creep rupture properties of the joints bonded using the HY- 20 insert metal were much improved as compared with the commercial Ni base amorphous insert metal MBF -80 (Ni-15.5Cr-3.7B), and were fairly comparable to those of the base metal.
Prediction of buckling distortion of welded structures
Authors: Deo M. V. , Michaleris P. , Sun J.
Published: March 2003

A predictive distortion analysis approach for welded structures is presented. Two-dimensional thermomechanical welding process simulations were performed to determine the residual stress. The critical buckling stress and the buckling mode are computed in a three-dimensional eigenvalue analysis. A technique employing decoupled two- and three-dimensional approaches is used to predict the occurrence of buckling distortion. Experimental validation of the prediction has been carried out in the laboratory. Welding experiments were carried out using welding conditions identical to those in the finite element model. The computational results are then verified by experimental observations.
Evaluation of effects of niobium and manganese addition on nickel base weldments
Authors: Kuo T.-Y. , Lee H.-T. , Tu C.-C.
Published: March 2003

The present work investigates the influence of different concentrations of Nb (from 0.1 to 3.35 wt-%) or Mn (from 0.78 to 3.32 wt-%) on the microstructure and mechanical properties of an Inconel 690 weldment. Welding electrodes are produced by coating Inconel filler metal 52 with a flux containing various percentages of Nb or Mn. Weldments with a bevel edge are butt welded via a manual shielded metal arc welding process, using identical parameters and procedures. The microstructure and mechanical properties of the resulting weldments are then analysed. The experimental results indicate that the subgrain structures of the welds are primarily dendritic. Under tensile testing, it is found that each specimen ruptures in the fusion zone and that the fracture surfaces exhibit entirely ductile features. It is noted that as the content of Nb increases, the welds tend to show a finer subgrain structure, i.e. having smaller dendritic spacing. Consequently, the tensile strength and microhardness of the fusion zone increase slightly and the tensile rupture mode changes from slant to flat fracture. It is determined that the interdendritic precipitates are mainly Nb rich eutectic type and Nb rich type constituents. The presence of these precipitates increases with higher concentrations of Nb in the flux and results in a significant decrease in the ductility of the weldment. Regarding the relative influence of the Mn additions, there appears to be no significant change in the subgrain structure as the percentage of Mn increases. However, the ductility tends to increase and it is also found that the tensile strength and microhardness of the fusion zone also increase slightly. Accordingly, the tensile rupture mode exhibits a slight tendency to change from flat to slant fracture. Although the interdendritic precipitates identified in the Mn series are similar to those in the Nb series, it should be noted that the precipitates appear in lower numbers and are smaller than their Nb counterparts.
Direct evidence for the role of pigment cells in the brain of ascidian larvae by laser ablation
Authors: Tsuda Motoyuki , Sakurai Daisuke , Goda Muneki
Published: March 2003

The anterior sensory vesicle of ascidian larvae contains a single large vesicle in which lie two distinct types of pigment cells, anterior and posterior. The ultrastructure of these pigment cells suggests that the anterior pigment cell is an otolith, presumably used for gravity detection,and the posterior pigment cell is an ocellus, used for photoreception. However, there is no direct experimental evidence for this assignment of function. Upward swimming behaviour occurring during the initial period of larval life was examined before and after laser ablation of the anterior pigment and posterior pigment cells. Posterior pigment cell-ablated larvae retained the upward swimming behaviour, but anterior pigment cell-ablated larvae lost it. These results suggest that the anterior pigment acts as a gravity sensor. The negatively phototactic swimming during the latter part of larval life was also examined before and after laser ablation of the anterior pigment or posterior pigment cells. Anterior pigment cell-ablated larvae retained the phototactic response, but posterior pigment cell-ablated larvae lost it. These results suggest that the posterior pigment of the sensory vesicle is involved in the negatively phototactic, downward swimming behavior. The effect of pressure on swimming behaviour was studied, and a putative pressure-detection organ was found not to be involved in the larval swimming behaviour. These are the first published experimental results that permit a functional role in ascidian larval behavior to be assigned to the sensory organs.
Honeybee navigation: properties of the visually driven `odometer'
Authors: Si Aung , Srinivasan Mandyam V. , Zhang Shaowu
Published: March 2003

Recent work has revealed that honeybees determine distance flown by gauging the extent to which the image of the environment moves in the eye as they fly toward their destination. Here we examine the properties of this visually driven `odometer', by training bees to fly to a feeder in a tunnel lined with a range of different visual patterns, and analysing their dances when they return to the hive. We find that the odometric signal is relatively unaffected by variations in the contrast and spatial frequency content of the patterns. Furthermore, a strong signal is generated even when the walls or the floor of the tunnel provide only weak optic-flow cues. Thus, distance flown is measured by a visually driven odometer that is surprisingly robust to variations in the texture or sparseness of the visual environment through which the bee flies.
Non-invasive imaging of blood cell concentration and blood distribution in zebrafishDanio rerioincubated in hypoxic conditionsin vivo
Authors: Schwerte Thorsten , Überbacher Dietmar , Pelster Bernd
Published: March 2003

This is the first study to use a combination of digital imaging techniques and vital video microscopy to study hypoxia-induced changes in blood cell concentration, angiogenesis and blood redistribution in entire animals. Zebrafish Danio rerio, which are known to be independent of convective oxygen transport until about 2 weeks post-fertilization, were raised under chronic hypoxia (PO2=8.7 kPa)starting at 1 day after fertilization (d.p.f.) until 15 d.p.f. In control animals, the concentration of red cells (i.e. the number of red cells per nl blood) remained constant until 7 d.p.f., and than decreased by approximately 70% until 15 d.p.f. In hypoxic animals, however, the concentration of red cells remained significantly elevated compared to control animals at 12 and 15 d.p.f. Assuming that the hemoglobin content of the red cells is similar,hypoxic animals have a higher oxygen carrying capacity in their blood. Red cell distribution within the various parts of the circulatory system, taken as an indicator for blood distribution, revealed a significant modification in the number of blood cells perfusing the organs in hypoxic animals. At 12 d.p.f., gut perfusion was reduced by almost 50% in hypoxic animals, while perfusion of the segmental muscle tissue was increased to 350% of control values. No significant changes in brain perfusion were observed under these conditions. At 15 d.p.f., the reduction in gut perfusion was abolished,although muscle perfusion was still significantly elevated. At this time,growth of hypoxic animals was less compared to control animals, revealing that hypoxia had become deleterious for further development. The vascular bed of various organs was not obviously different in hypoxic animals compared to normoxic animals.
The role of the subelytral spiracles in respiration in the flightless dung beetle Circellium bacchus
Authors: Byrne Marcus J. , Duncan Frances D.
Published: March 2003

The role of the subelytral cavity in flightless beetle species as an adaptation to water saving in arid habitats is still in dispute. We found that relatively little CO2 was released from the subelytral cavity of a large apterous beetle Circellium bacchus during simultaneous measurements of CO2 emission from the anterior mesothoracic spiracles and posterior body, which included the subelytral spiracles. However, when we sampled air directly from inside the subelytral cavity, we discovered that this pattern was reversed. A discontinuous gas exchange cycle(DGC) was recorded from the posterior body half, revealing a flutter phase that had been absent from the anterior mesothoracic DGC. The anterior mesothoracic and posterior subelytral spiracles act in synchrony to maintain high CO2 and water vapour levels inside the subelytral cavity. In addition, the O2 concentration of the air within the subelytral cavity is lower than the air around the elytral case, irrespective of the time of sampling. These findings lead us to conclude that the subelytral spiracles work in a coordinated fashion with the anterior spiracles to create a DGC,which allows us to extend the hypothesis of the function of the subelytral cavity as a respiratory water-saving device.
Serotonin modulates the electric waveform of the gymnotiform electric fishBrachyhypopomus pinnicaudatus
Authors: Stoddard Philip K. , Markham Michael R. , Salazar Vielka L.
Published: March 2003

The gymnotiform electric fish Brachyhypopomus pinnicaudatuscommunicates with a sexually dimorphic electric waveform, the electric organ discharge (EOD). Males display pronounced circadian rhythms in the amplitude and duration of their EODs. Changes in the social environment influence the magnitudes of these circadian rhythms and also produce more transient responses in the EOD waveforms. Here we show that injections of serotonin produce quick, transient, dose-dependent enhancements of the male EOD characters similar to those induced by encounters with another male. The response to serotonin administered peripherally begins 5-10 min post injection and lasts approximately 3 h. The magnitude of the response to serotonin is tightly associated with the magnitude of the day-to-night swing of the circadian rhythm prior to injection. Taken together these findings suggest that the male's social environment influences his response to serotonin by altering the function of some part of the downstream chain between the serotonin receptors and the ion channels involved in control of the EOD waveform. Although chronic activation of serotonin circuitry is widely known to elicit subordinate behavior, we find that 5-HT initially increases a dominance signal in these fish. These findings are consistent with the emerging view that serotonin facilitates different adaptive responses to acute and chronic social challenge and stress.
Minimal shortening in a high-frequency muscle
Authors: Moon Brad R. , Conley Kevin E. , Lindstedt Stan L. , Urquhart Michael R.
Published: March 2003

Reducing the cost of high-frequency muscle contractions can be accomplished by minimizing cross-bridge cycling or by recycling elastic strain energy. Energy saving by contractile minimization has very different implications for muscle strain and activation patterns than by elastic recoil. Minimal cross-bridge cycling will be reflected in minimal contractile strains and highly reduced force, work and power output, whereas elastic energy storage requires a period of active lengthening that increases mechanical output. In this study, we used sonomicrometry and electromyography to test the relative contributions of energy reduction and energy recycling strategies in the tailshaker muscles of western diamondback rattlesnakes (Crotalus atrox). We found that tailshaker muscle contractions produce a mean strain of 3%, which is among the lowest strains ever recorded in vertebrate muscle during movement. The relative shortening velocities(V/Vmax) of 0.2-0.3 were in the optimal range for maximum power generation, indicating that the low power output reported previously for tailshaker muscle is due mainly to contractile minimization rather than to suboptimal V/Vmax. In addition, the brief contractions(8-18 ms) had only limited periods of active lengthening (0.2-0.5 ms and 0.002-0.035%), indicating little potential for elastic energy storage and recoil. These features indicate that high-frequency muscles primarily reduce metabolic energy input rather than recycle mechanical energy output.