bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling spatial patterns of biodiversity for conservation prioritization in North‐eastern Mexico
Authors: Ortega‐Huerta Miguel A. , Peterson A. T.
Published: January 2004

Relationships between spatial patterns of bird and mammal species richness in north‐eastern Mexico were analysed in relation to the location of three biosphere reserves (El Abra‐Tanchipa, El Cielo, and Sierra Gorda) and 13 priority areas recently identified for conservation. Ecological niches were modelled and potential distributions delimited for 285 bird and 114 mammal species using a genetic algorithm based on locality information from museum specimens and 15 selected environmental attributes. Potential distributions were transformed into hypothesized current distributions based on species–habitat associations as reflected in a recent land‐use map. Although species richness was lower when distributions were reduced from potential to current, spatial patterns of potential and current richness were similar. Heuristic, complementarity‐based prioritization procedures were used to identify combinations of areas and sites with maximal species representation: the biosphere reserves included 79% of birds and 74% of mammal species; eight priority areas provided an additional 11% of birds and 13% of mammals; the remaining 10% of birds and 13% of mammals were concentrated in new sites across the study area.
Introduced plants of the invasive Solidago gigantea (Asteraceae) are larger and grow denser than conspecifics in the native range
Authors: Jakobs Gabi , Weber Ewald , Edwards Peter J.
Published: January 2004

Introduced plant species that became successful invaders appear often more vigorous and taller than their conspecifics in the native range. Reasons postulated to explain this better performance in the introduced range include more favourable environmental conditions and release from natural enemies and pathogens. According to the Evolution of Increased Competitive Ability hypothesis (EICA hypothesis) there is a trade‐off between investment into defence against herbivores and pathogens, and investment into a stronger competitive ability. In this study, we conducted field surveys to investigate whether populations of the invasive perennial Solidago gigantea Ait (Asteraceae) differ with respect to growth and size in the native and introduced range, respectively. We assessed size and morphological variation of 46 populations in the native North American range and 45 populations in the introduced European range. Despite considerable variation between populations within continents, there were pronounced differences between continents. The average population size, density and total plant biomass were larger in European than in American populations. Climatic differences and latitude explained only a small proportion of the total variation between the two continents. The results show that introduced plants can be very distinct in their growth form and size from conspecifics in the native range. The apparently better performance of this invasive species in Europe may be the result of changed selection pressures, as implied by the EICA hypothesis.
Morphological responses of Leymus chinensis (Poaceae) to the large‐scale climatic gradient along the North‐east China Transect (NECT)
Authors: Renzhong Wang , Qiong Gao
Published: January 2004

A field experiment was conducted to examine the morphological variations of Leymus chinensis along the climatic gradient of the North‐east China Transect (NECT), from 115° to 125° E, in the vicinity of 43.5° N, in north‐eastern China. Ten sites selected for plant sampling along the gradient have approximately uniform theoretical radiation, but differ in precipitation and geographical elevation. The results of analyses showed that vegetative and reproductive shoot heights, flag leaf lengths and widths and seed numbers per inflorescence increased from the west to the east with precipitation, but decreased with aridity. Leaf lengths and widths for most leaf types from 115° to 124° E exhibited little variations. Significant correlations of plant heights, flag leaf lengths and widths and seed numbers per inflorescence with large‐scale climatic variables (e.g. annual precipitation, aridity) and geographical variation (longitude) found in this study indicated that climatic factors have significant effects on some morphological traits of L. chinensis along the NECT.
The Impact of Visit Frequency on the Relationship between Service Quality and Outpatient Satisfaction: A South Korean Study
Authors: Cho Woo Hyun , Lee Hanjoon , Kim Chankon , Lee Sunhee , Choi Kui‐Son
Published: January 2004

Objective. To examine the relative impact of four service quality dimensions on outpatient satisfaction and to test the invariance of the structural relationships between the service quality dimensions and satisfaction across three patient groups of varying numbers of prior visits to the same hospital as outpatients.

Data Sources/Study Setting. Survey of 557 outpatients using a self‐administered questionnaire over a 10‐day period at a general hospital in Sungnam, South Korea.

Data Collection. Patients answered questions related to two main constructs, patient satisfaction and health care service quality. The health care service quality measures (30 items) were developed based on the results of three focus group interviews and the SERVQUAL scale, while satisfaction (3 items) was measured using a previously validated scale.

Study Design. Confirmatory factor analysis was used to assess the construct validity of the service quality scale by testing convergent and divergent validity. A structural equation model specifying the four service quality dimensions as exogenous variables and patient satisfaction as an endogenous variable was estimated to assess the relative impact of each of the service quality dimensions on satisfaction. This was followed by a multigroup LISREL analysis that tested the invariance of structural coefficients across three groups with different frequencies of outpatient visits to the hospital.

Principal Findings. Findings support the causal relationship between service quality and satisfaction in the context of the South Korean health care environment. The four service quality dimensions showed varying patterns of impact on patient satisfaction across the three different outpatient groups.

Conclusion. The hospital management needs to be aware of the relative importance of each of the service quality dimensions in satisfaction formation of outpatients, which varies across different hospital utilization groups, and use this in strategic considerations.
Do Drug‐Free Workplace Programs Prevent Occupational Injuries? Evidence from Washington State
Authors: Wickizer Thomas M. , Kopjar Branko , Franklin Gary , Joesch Jutta
Published: January 2004

Objective. To evaluate the effect of a publicly sponsored drug‐free workplace program on reducing the risk of occupational injuries.

Data Sources. Workers' compensation claims data from the Washington State Department of Labor and Industries covering the period 1994 through 2000 and work‐hours data reported by employers served as the data sources for the analysis.

Study Design. We used a pre–post design with a nonequivalent comparison group to assess the impact of the intervention on injury risk, measured in terms of differences in injury incidence rates. Two hundred and sixty‐one companies that enrolled in the drug‐free workplace program during the latter half of 1996 were compared with approximately 20,500 nonintervention companies. We tested autoregressive, integrated moving‐average (ARIMA) models to assess the robustness of our findings.

Principal Findings. The drug‐free workplace intervention was associated (p<.05) with a statistically significant decrease in injury rates for three industry groups: construction, manufacturing, and services. It was associated (p<.05) with a reduction in the incidence rate of more serious injuries involving four or more days of lost work time for two industry groups: construction and services. The ARIMA analysis supported these findings.

Conclusions. The drug‐free workplace program we studied was associated with a selective, industry‐specific preventive effect. The strongest evidence of an intervention effect was for the construction industry. Estimated net cost savings for this industry were positive though small in magnitude.
The Costs of Decedents in the Medicare Program: Implications for Payments to Medicare+Choice Plans
Authors: Beeuwkes Buntin Melinda , Garber Alan M. , Mcclellan Mark , Newhouse Joseph P.
Published: January 2004

Objective. To discuss and quantify the incentives that Medicare managed care plans have to avoid (through selective enrollment or disenrollment) people who are at risk for very high costs, focusing on Medicare beneficiaries in the last year of life—a group that accounts for more than one‐quarter of Medicare's annual expenditures.

Data Source. Medicare administrative claims for 1994 and 1995.

Study Design. We calculated the payment a plan would have received under three risk‐adjustment systems for each beneficiary in our 1995 sample based on his or her age, gender, county of residence, original reason for Medicare entitlement, and principal inpatient diagnoses received during any hospital stays in 1994. We compared these amounts to the actual costs incurred by those beneficiaries. We then looked for clinical categories that were predictive of costs, including costs in a beneficiary's last year of life, not accounted for by the risk adjusters.

Data Extraction Methods. The analyses were conducted using claims for a 5 percent random sample of Medicare beneficiaries who died in 1995 and a matched group of survivors.

Principal Findings. Medicare is currently implementing the Principal Inpatient Diagnostic Cost Groups (PIP‐DCG) risk adjustment payment system to address the problem of risk selection in the Medicare+Choice program. We quantify the strong financial disincentives to enroll terminally ill beneficiaries that plans still have under this risk adjustment system. We also show that up to one‐third of the selection observed between Medicare HMOs and the traditional fee‐for‐service system could be due to differential enrollment of decedents. A risk adjustment system that incorporated more of the available diagnostic information would attenuate this disincentive; however, plans could still use clinical information (not included in the risk adjustment scheme) to identify beneficiaries whose expected costs exceed expected payments.

Conclusions. More disaggregated prospective risk adjustment methods and alternative payment systems that compensate plans for delivering care to certain classes of patients should be considered to ensure access to high‐quality managed care for all beneficiaries.
Impact of Managed Care on the Treatment, Costs, and Outcomes of Fee‐for‐Service Medicare Patients with Acute Myocardial Infarction
Authors: Kate Bundorf M. , Schulman Kevin A. , Stafford Judith A. , Gaskin Darrell , Jollis James G. , Escarce José J.
Published: January 2004

Objective. To examine the effects of market‐level managed care activity on the treatment, cost, and outcomes of care for Medicare fee‐for‐service acute myocardial infarction (AMI) patients.

Data Sources/Study Setting. Patients from the Cooperative Cardiovascular Project (CCP), a sample of Medicare beneficiaries discharged from nonfederal acute‐care hospitals with a primary discharge diagnosis of AMI from January 1994 to February 1996.

Study Design. We estimated models of patient treatment, costs, and outcomes using ordinary least squares and logistic regression. The independent variables of primary interest were market‐area managed care penetration and competition. The models included controls for patient, hospital, and other market area characteristics.

Data Collection/Extraction Methods. We merged the CCP data with Medicare claims and other data sources. The study sample included CCP patients aged 65 and older who were admitted during 1994 and 1995 with a confirmed AMI to a nonrural hospital.

Principal Findings. Rates of revascularization and cardiac catheterization for Medicare fee‐for‐service patients with AMI are lower in high‐HMO penetration markets than in low‐penetration ones. Patients admitted in high‐HMO‐competition markets, in contrast, are more likely to receive cardiac catheterization for treatment of their AMI and had higher treatment costs than those admitted in low‐competition markets.

Conclusions. The level of managed care activity in the health care market affects the process of care for Medicare fee‐for‐service AMI patients. Spillovers from managed care activity to patients with other types of insurance are more likely when managed care organizations have greater market power.
Reexamining Organizational Configurations: An Update, Validation, and Expansion of the Taxonomy of Health Networks and Systems
Authors: Dubbs Nicole L. , Bazzoli Gloria J. , Shortell Stephen M. , Kralovec Peter D.
Published: January 2004

Objectives. To (a) assess how the original cluster categories of hospital‐led health networks and systems have changed over time; (b) identify any new patterns of cluster configurations; and (c) demonstrate how additional data can be used to refine and enhance the taxonomy measures.

Data Sources. 1994 and 1998 American Hospital Association (AHA) Annual Survey of Hospitals.

Study Design. As in the original taxonomy, separate cluster solutions are identified for health networks and health systems by applying three strategic/structural dimensions (differentiation, integration, and centralization) to three components of the health service/product continuum (hospital services, physician arrangements, and provider‐based insurance activities).

Data Extraction Methods. Factor, cluster, and discriminant analyses are used to analyze the 1998 data. Descriptive and comparative methods are used to analyze the updated 1998 taxonomy relative to the original 1994 version.

Principal Findings. The 1998 cluster categories are similar to the original taxonomy, however, they reveal some new organizational configurations. For the health networks, centralization of product/service lines is occurring more selectively than in the past. For the health systems, participation has grown in and dispersed across a more diverse set of decentralized organizational forms. For both networks and systems, the definition of centralization has changed over time.

Conclusions. In its updated form, the taxonomy continues to provide policymakers and practitioners with a descriptive and contextual framework against which to assess organizational programs and policies. There is a need to continue to revisit the taxonomy from time to time because of the persistent evolution of the U.S. health care industry and the consequent shifting of organizational configurations in this arena. There is also value in continuing to move the taxonomy in the direction of refinement/expansion as new opportunities become available.
Metamorphic evolution of garnet‐bearing ultramafic rocks from the Gongen area, Sanbagawa belt, Japan
Authors: Enami M. , Mizukami T. , Yokoyama K.
Published: January 2004

Garnet‐bearing ultramafic rocks including clinopyroxenite, wehrlite and websterite locally crop out in the Higashi‐akaishi peridotite of the Besshi region in the Cretaceous Sanbagawa metamorphic belt. These rock types occur within dunite as lenses, boudins or layers with a thickness ranging from a few centimetres to 1 metre. The wide and systematic variation of bulk‐rock composition and the overall layered structure imply that the ultramafic complex originated as a cumulate sequence. Garnet and other major silicates contain rare inclusions of edenitic amphibole, chlorite and magnetite, implying equilibrium at relatively low P–T conditions during prograde metamorphism. Orthopyroxene coexisting with garnet shows bell‐shaped Al zoning with a continuous decrease of Al from the core towards the rim, consistent with rims recording peak metamorphic conditions. Estimated P–T conditions using core and rim compositions of orthopyroxene are 1.5–2.4 GPa/700–800 °C and 2.9–3.8 GPa/700–810 °C, respectively, implying a high P/T gradient (> 3.1 GPa/100 °C) during prograde metamorphism. The presence of relatively low P–T conditions at an early stage of metamorphism and the steep P/T gradient together trace a concave upwards P–T path that shows increasing P/T with higher T, similar to P–T paths reported from other UHP metamorphic terranes. These results suggest either (1) down dragging of hydrated mantle cumulate parallel to the slab–wedge interface in the subduction zone by mechanical coupling with the subducting slab or (2) ocean floor metamorphism and/or serpentinization at early stage of subduction of oceanic lithosphere and ensuing HP–UHP prograde metamorphism.
Hydrothermal alteration, fluid flow and volume change in shear zones: the layered mafic–ultramafic Kettara intrusion (Jebilet Massif, Variscan belt, Morocco)
Authors: Essaifi A. , Capdevila R. , Fourcade S. , Lagarde J. L. , Ballèvre M. , Marignac CH.
Published: January 2004

During emplacement and cooling, the layered mafic–ultramafic Kettara intrusion (Jebilet, Morocco) underwent coeval effects of deformation and pervasive fluid infiltration at the scale of the intrusion. In the zones not affected by deformation, primary minerals (olivine, plagioclase, clinopyroxene) were partially or totally altered into Ca‐amphibole, Mg‐chlorite and CaAl‐silicates. In the zones of active deformation (centimetre‐scale shear zones), focused fluid flow transformed the metacumulates (peridotites and leucogabbros) into ultramylonites where insoluble primary minerals (ilmenite, spinel and apatite) persist in a Ca‐amphibole‐rich matrix. Mass‐balance calculations indicate that shearing was accompanied by up to 200% volume gain; the ultramylonites being enriched in Si, Ca, Mg, and Fe, and depleted in Na and K. The gains in Ca and Mg and losses in Na and K are consistent with fluid flow in the direction of increasing temperature.

When the intrusion had cooled to temperatures prevailing in the country rock (lower greenschist facies), deformation was still active along the shear zones. Intense intragranular fracturing in the shear zone walls and subsequent fluid infiltration allowed shear zones to thicken to metre‐scale shear zones with time. The inner parts of the shear zones were transformed into chlorite‐rich ultramylonites. In the shear zone walls, muscovite crystallized at the expense of Ca–Al silicates, while calcite and quartz were deposited in ‘en echelon’ veins. Mass‐balance calculations indicate that formation of the chlorite‐rich shear zones was accompanied by up to 60% volume loss near the centre of the shear zones; the ultramylonites being enriched in Fe and depleted in Si, Ca, Mg, Na and K while the shear zones walls are enriched in K and depleted in Ca and Si. The alteration observed in, and adjacent to the chlorite shear zones is consistent with an upward migrating regional fluid which flows laterally into the shear zone walls. Isotopic (Sr, O) signatures inferred for the fluid indicate it was deeply equilibrated with host lithologies.
Diffusion creep and partial melting in high temperature mylonitic gneisses, Hope Valley shear zone, New England Appalachians, USA
Authors: Garlick S. R. , Gromet L. P.
Published: January 2004

Field, petrographic, microstructural and isotopic studies of mylonitic gneisses and associated pegmatites along the Hope Valley shear zone in southern Rhode Island indicate that late Palaeozoic deformation (c. 275 Ma) in this zone occurred at very high temperatures (>650 °C). High‐energy cuspate/lobate phase boundary microstructures, a predominance of equant to sub‐equant grains with low internal lattice strain, and mixed phase distributions indicate that diffusion creep was an important and possibly predominant deformation mechanism. Field and petrographic evidence are consistent with the presence of an intergranular melt phase during deformation, some of which collected into syntectonic pegmatites. Rb/Sr isotopic analyses of tightly sampled pegmatites and wall rocks confirm that the pegmatites were derived as partial melts of the immediately adjacent, isotopically heterogeneous mylonitic gneisses. The presence of syntectonic interstitial melts is inferred to have permitted a switch from dislocation creep to melt‐enhanced diffusion creep as the dominant mechanism in these relatively coarse‐grained mylonitic gneisses (200–500 µm syn‐deformational grain size). A switch to diffusion creep would lead to significant weakening, and may explain why the Hope Valley shear zone evolved into a major regional tectonic boundary. This work identifies conditions under which diffusion creep operates in naturally deformed granitic rocks and illuminates the deformation processes involved in the development of a tectonic boundary between two distinct Late Proterozoic (Avalonian) basement terranes.
Women's Issues of Migraine in Tertiary Care
Authors: Kelman Leslie
Published: January 2004

Objective.—To document the frequency and types of symptoms of migraine in a large group of female migraineurs in tertiary care.

Background.—Hormonal changes remain a significant accompaniment in the life cycle of the female migraineur. Little is documented on the relationship of women's issues to other features of migraine or to the lives of patients with migraine. Successful management of migraine mandates attention to women's issues from menarche to beyond menopause. The more information available to this end, the more confidently the clinician can prognosticate, guide, and treat the female patient.

Methods.—Women's issues were evaluated in 504 women with migraine diagnosed according to the criteria of the International Headache Society (codes 1.1 and 1.2). The variables graded on a scale of 0 to 3 at the initial visit included premenstrual syndrome, menopausal symptoms, use of birth control pills, use of hormone replacement therapy, hormonal triggering of headaches, worsening of headaches with birth control pills or hormone replacement therapy, headaches with menses only, headaches with menses and at other times, headaches in pregnancy, headaches unchanged in pregnancy, headaches worse in pregnancy, and headaches better in pregnancy. These variables were stratified by age and headache diagnosis.

Results.—Premenstrual syndrome was reported in 68.7% of patients, menopausal symptoms in 29.0%, and headaches attributed to birth control pills or hormone replacement therapy in 24.4% of patients. Sixty‐four point nine percent of women had headaches with menses as well as at other times, while 3.4% of women had headaches exclusively with menses. A pregnancy was reported in 61.3% of the women; 20.4% did not experience headache in pregnancy. Of the 79.6% who did experience headache, 17.8% reported that headaches improved in pregnancy, 27.8% reported headaches to be unchanged, and 34% reported a worsening of headaches. Hormone replacement therapy or birth control pills triggered headaches in 64% of the study group. Patients with 100% aura were significantly different from patients with 0% aura, being less likely to have headaches worsening with birth control pills or hormone replacement therapy (P < .01) and more likely to have headaches occurring during pregnancy (P < .05). When patients with 100% aura were matched for age, headache frequency, use of birth control pills or hormone replacement therapy, and use of prophylactic medications with patients having 0% aura, the former were significantly less likely to have menopausal symptoms (P < .05), less likely to have headaches worsening with birth control pills or hormone replacement therapy (P < .01), and more likely to have headaches occurring only during pregnancy (P < .05).

Conclusions.—This study provides a documentation of women's issues in a large cohort of patients. Stratification by headache type, presence of aura, and age refine the study.
Consequences of Transforming Measures of Efficacy for Acute Therapies: 5‐HT1B/1D Agonists as a Worked Example
Authors: Fox Anthony W. , Keywood Charlotte , Sheftell Fred D. , Spierings Egilius L. H.
Published: January 2004

Objective.—To examine whether the distributions of active and placebo response rates change after transformation into therapeutic gains, numbers needed to treat, and therapeutic ratios for 51 published clinical trials of 5‐HT1B/1D agonists in the acute treatment of migraine.

Background.—Acute migraine therapies have been compared using meta‐analysis. Before pooling the results of noncontemporaneous clinical trials for meta‐analysis, reconciliation of active response rates with concurrent placebo controls is done because of fluctuations in placebo response rates. The 3 common methods of reconciliation are to find for each clinical trial the therapeutic gain, the number needed to treat, or the therapeutic ratio.

Methods.—Raw active and placebo response rates were tabulated and displayed as histograms. The distributions of the therapeutic gains, numbers needed to treat, and therapeutic ratios were similarly plotted. These distributions were then compared with normal distributions using chi‐squared goodness‐of‐fit methodology.

Results.—The distribution of active response rates was consistent with a normal distribution (passing a goodness‐of‐fit test). Placebo response rates were not normally distributed. The distribution of therapeutic gains failed a test of normality (P= .018), as did the numbers needed to treat (P < .001); the skews of these distributions were toward opposite ends of the scale for relative efficacy. The therapeutic ratios also failed a test for normality, but passed a test for log‐normal distribution.

Conclusion.—Choice of transformation is a potential source of bias in meta‐analysis of acute migraine therapies.
Treatment of Primary Headache Disorders With Intravenous Valproate: Initial Outpatient Experience
Authors: Stillman Mark J. , Zajac Deborah , Rybicki Lisa A.
Published: January 2004

Objective.—To evaluate the effectiveness of intravenous valproate in managing moderate to severe headaches.

Background.—Despite major strides in the understanding of primary headache disorders, there have been few additions to acute headache management other than introduction of the triptans. An intravenous antiepileptic preparation, sodium valproate, has been reported to be effective in the management of status epilepticus and acute headache.

Methods.—Between March 13, 2000 and October 11, 2000, we prospectively treated, in a nonrandomized and open‐label study, every patient with a moderate to severe headache (4 or greater on a visual analog scale of head pain from 1 to 10) who wanted treatment with intravenous valproate. Using a verbal visual analog scale for pain (0 = no headache and 10 = most severe headache), we measured head pain before treatment and at time of discharge. The treating nurse monitored vital signs and side effects. A positive response was defined as a 50% or greater reduction at discharge in baseline pain. Information was collected regarding patient demographics, type of headache (according to criteria of the International Headache Society and that recently proposed for chronic headache), observation time in the treatment suite, cumulative dose of valproate, and use of concurrent medications. Univariable and multivariable correlates of response to treatment were identified using logistic regression analysis.

Results.—One hundred thirty treatments were given to 89 women and 17 men, aged 17 to 76 years; 92 patients received only one treatment. Valproate doses ranged between 300 and 1200 mg. Thirty‐three patients (31%) presented with episodic migraine, with or without aura; 45 patients (42%) presented with chronic daily headache with a history of episodic migraine, with or without aura (transformed migraine); 22 (21%) with unclassifiable chronic headache; 2 (2%) with episodic cluster headache; and 4 (4%) with chronic tension‐type headache. For first treatments only, 61 patients (57.5%) responded to treatment, whereas for all treatments, 82 patients (63.1%) responded. Age and gender did not affect likelihood of response, whereas increasing duration of treatment (P= .003) and the additional use of analgesics (P= .021) were each negatively associated with response. Among headache types, unclassifiable chronic headache segregated from all other classified headaches in terms of poor response. Aside from rare dizziness (n = 2) and one spell interpreted as a pseudoseizure, no side effects were noted.

Conclusions.—Intravenous valproate is a safe, rapidly effective, abortive headache agent. It appears to be an effective analgesic for identifiable primary headaches, especially episodic headache, and less effective for unclassifiable chronic headache. Randomized, double‐blind, controlled studies are warranted.
Migraine: A Chronic Sympathetic Nervous System Disorder
Authors: Peroutka Stephen J.
Published: January 2004

Objective.—To determine the degree of diagnostic and clinical similarity between chronic sympathetic nervous system disorders and migraine.

Background.—Migraine is an episodic syndrome consisting of a variety of clinical features that result from dysfunction of the sympathetic nervous system. During headache‐free periods, migraineurs have a reduction in sympathetic function compared to nonmigraineurs. Sympathetic nervous system dysfunction is also the major feature of rare neurological disorders such as pure autonomic failure and multiple system atrophy. There are no known reports in the medical literature, however, comparing sympathetic nervous system function in individuals with migraine, pure autonomic failure, and multiple system atrophy.

Methods.—A detailed review of the literature was performed to compare the results of a wide variety of diagnostic tests and clinical signs that have been described in these 3 heretofore unrelated disorders.

Results.—The data indicate that migraine shares significant diagnostic and clinical features with both pure autonomic failure and multiple system atrophy, yet represents a distinct subtype of chronic sympathetic dysfunction. Migraine is most similar to pure autonomic failure in terms of reduced supine plasma norepinephrine levels, peripheral adrenergic receptor supersensitivity, and clinical symptomatology directly related to sympathetic nervous system dysfunction. The peripheral sympathetic nervous system dysfunction is much more severe in pure autonomic failure than in migraine. Migraine differs from both pure autonomic failure and multiple system atrophy in that migraineurs retain the ability, although suboptimal, to increase plasma norepinephrine levels following physiological stressors.

Conclusions.—The major finding of the present study is that migraine is a disorder of chronic sympathetic dysfunction, sharing many diagnostic and clinical characteristics with pure autonomic failure and multiple system atrophy. However, the sympathetic nervous system dysfunction in migraine differs from pure autonomic failure and multiple system atrophy in that occurs in an anatomically intact system. It is proposed that the sympathetic dysfunction in migraine relates to an imbalance of sympathetic co‐transmitters. Specifically, it is suggested that a migraine attack is characterized by a relative depletion of sympathetic norepinephrine stores in conjunction with an increase in the release of other sympathetic cotransmitters such as dopamine, prostaglandins, adenosine triphosphate, and adenosine. An enhanced understanding of the sympathetic dysfunction in migraine may help to more effectively diagnose, prevent, and/or treat migraine and other types of headache.
Lateral Medullary Infarction Secondary to Vertebral Artery Dissection Presenting as a Trigeminal Autonomic Cephalalgia
Authors: Galende Alberto Villarejo , Camacho Ana , Gomez‐Escalonilla Carlos , Penas Marta , Juntas Raúl , Ramos Ana , Esteban Jesús
Published: January 2004

A 51‐year‐old woman had an attack of severe hemifacial pain with autonomic features as the presenting symptom of a lateral medullary infarction. A bilateral vertebral artery dissection was demonstrated. The existence of secondary cases may lead to a better understanding of the pathophysiology of trigeminal autonomic cephalalgias.
Changes of Cerebrovascular Response to Visual Stimulation in Migraineurs After Repetitive Sessions of Somatosensory Stimulation (Acupuncture): A Pilot Study
Authors: Bäcker M. , Hammes M. , Sander D. , Funke D. , Deppe M. , Tölle T. R. , Dobos G. J.
Published: January 2004

Objectives.—To evaluate the effect of repetitive somatosensory stimulation (acupuncture) on cerebrovascular response in migraineurs by functional transcranial Doppler.

Methods.—Changes of cerebral blood flow velocity in the right posterior and left middle cerebral arteries were measured by functional transcranial Doppler during visual stimulation (flickering light over 57 seconds) in 10 migraineurs before and after 10 acupuncture sessions. The same stimulation paradigm was performed in 10 control subjects. Cerebral blood flow velocity data were analyzed with a previously validated technique based on automated stimulus‐related averaging. To evaluate the clinical effect of the treatment, a headache diary monitored the frequency and intensity of the migraine attacks. A positive treatment effect was defined as a reduction of at least 50% in the attack frequency or the mean headache intensity (or both).

Results.—Before treatment, migraineurs showed overshooting cerebral blood flow velocity changes at the beginning and at the end of the stimulation and a delayed decline to baseline compared with control subjects. After treatment, this response pattern was significantly diminished (P≤ .05) in those who benefited from treatment (n = 6). Those who did not benefit from treatment (n = 4) showed a significantly (P≤ .05) more marked alteration of the cerebral blood flow velocity pattern.

Conclusions.—Data indicate that repetitive somatosensory stimulation (acupuncture) might positively influence the abnormal cerebrovascular response in migraineurs. In a subgroup of migraineurs, however, the dysfunction of the cerebrovascular system might deteriorate under the treatment.
Studies on leaching of massive rich copper ore in acidic ferric sulfate solutions
Authors: Arslan Fatma , Bulut Gülay , Kangal M. Olgaç , Perek K. Tahsin , Gül Alim , Gürmen Sebahattin
Published: January 2004

Representative samples of Küre (Turkey) massive rich copper ore were leached in acidic ferric sulfate solutions in order to recover copper and its associated metals (Zn, Co, Ni) present in the ore. The effects of leaching time, ferric ion concentration, acid concentration, solid/liquid ratio, temperature and silver sulfaste addition on metal leaching recoveries were investigated. Optimum leaching conditions and leaching kinetics were determined. Formation of elemental sulfur, which creates a diffusion barrier, was elucidated. In order to remove the retarding effect of elemental sulfur, silver ions were introduced to the leach medium and significant improvements were observed, especially in copper dissolution. Activation energies were found to be 36.7 kJ/mole for Cu and 43.3 kJ/mole for Zn dissolutions. The rate‐controlling step was found as the diffusion of ferric ions into the solution filling the pores of sulfur layer formed on the surface of partially leached ore particles.
The effect of swirl flow in an immersion nozzle on the heat and fluid flow in a billet continuous casting mold
Authors: Yokoya S. , Jönsson P. G. , Sasaki K. , Tada K. , Takagi S. , Iguchi M.
Published: January 2004

A numerical analysis and a water model study of the mold region of a billet continuous caster was performed with a novel injection concept using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mold. The following results were found:

A weak impinging flow can be observed near the corner of the mold wall, which results in the promotion of uniform heat and mass transfer all around across the plane, particularly at the casting corner.

An upward flow directed from the vicinity of the nozzle outlet to the meniscus can be observed near the corner of the upper part of the mold, which leads to the active heat and mass transfer into the meniscus.

A uniform velocity and heat distribution can be obtained within a short distance of 200 mm downward from the outlet of the nozzle.

Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable than that using the straight nozzle.
Coupled deformation and temperature analysis of strip rolling with a local perturbation of deformation using a 3D rigid‐plastic FEM
Authors: Jiang Z. Y. , Hu W. P. , Zhang X. M. , Liu X. H. , Wang G. D.
Published: January 2004

Coupling of the temperature and velocity fields is one of the advanced areas in the modeling of metal forming in recent years. The rolling of ribbed strip is a new forming process that has the deformation characteristics of strip and shape rolling and a major feature of this strip is that there is a local perturbation of the deformation on the flat strip. The innovation of this paper is a combination of the temperature and velocity fields for the rolling of ribbed strip employing a 3D rigid‐plastic Finite Element Method (FEM). From the new method of simulation for ribbed strip rolling, the fields of stress, strain rate, velocity and temperature are obtained. The rolling force obtained from the coupled analysis is compared with that from the noncoupled simulation, which shows that the coupled results are closer to the measured values.
Effect of Bone Mineral Content on the Tensile Properties of Cortical Bone: Experiments and Theory
Authors: Kotha S. P. , Guzelsu N.
Published: January 2004

The effect of mineral volume fraction on the tensile mechanical properties of cortical bone tissue is investigated by theoretical and experimental means. The mineral content of plexiform, bovine bone was lowered by 18% and 29% by immersion in fluoride solutions for 3 days and 12 days, respectively. The elastic modulus, yield strength and ultimate strength of bone tissue decreased, while the ultimate strain increased with a decrease in mineral content. The mechanical behavior of bone tissue was modeled by using a micro-mechanical shear lag theory consisting of overlapped mineral platelets reinforcing the organic matrix. The decrease in yield stress, by the 0.002 offset method, of the fluoride treated bones were matched in the theoretical curves by lowering the shear yield stress of the organic matrix. The failure criterion used was based on failure stresses determined from a failure envelope (Mohr’s circle), which was constructed using experimental data. It was found that the model predictions of elastic modulus got worse with a decrease in mineral content (being 7.9%, 17.2% and 33.0% higher for the control, 3-day and 12-day fluoride-treated bones). As a result, the developed theory could not fully predict the yield strain of bones with lowered mineral content, being 12.9% and 21.7% lower than the experimental values. The predicted ultimate stresses of the bone tissues with lower mineral contents were within ±10% of the experimental values while the ultimate strains were 12.7% and 26.3% lower than the experimental values. Although the model developed in this study did not take into account the presence of hierarchical structures, voids, orientation of collagen molecules and micro cracks, it still indicated that the mechanical properties of the organic matrix depend on bone mineral content.
Endometrial Thermal Balloon Ablation Using a High Temperature, Pulsed System: A Mathematical Model
Authors: Reinders Daniel M. , Baldwin Susan A. , Bert Joel L.
Published: January 2004

A new endometrial thermal balloon ablation treatment for menorrhagia is modeled mathematically to predict its efficacy and safety. A device preheats a fluid to 173°C within a reservoir external to the uterus, and then pulses this fluid without further heating between the reservoir and the balloon for 2.1 min of treatment time. The model predicted this treatment to result in consistent immediate tissue death (coagulation) depths of 3.4±0.1 mm for uterine cavities of 7 to 26 mL, and that eventual necrosis (tissue death that would occur 1–5 days post burn) may occur to depths of 6.5±0.2 mm. Whereas, burn depths varied with uterine cavity volume when a low temperature treatment (constant 75°C for 15 min) was modeled (2.3–2.9 mm and 6.8–8.2 mm, for immediate tissue death and eventual necrosis respectively). Similarly, the high temperature, pulsed treatment was less sensitive to blood perfusion rate than the low temperature treatment. Predicted eventual necrosis depth was 1.5 mm less for the high temperature, pulsed treatment than that predicted for a low temperature treatment (constant 87°C for 7 min) for the same immediate tissue death depth (3.5 mm), indicating that the new high temperature treatment may result in less damage to non targeted tissues.
Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 1: Basic Theory
Authors: Berkouk K. , Carpenter P. W. , Lucey A. D.
Published: January 2004

Our work is motivated by ideas about the pathogenesis of syringomyelia. This is a serious disease characterized by the appearance of longitudinal cavities within the spinal cord. Its causes are unknown, but pressure propagation is probably implicated. We have developed an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. This is intended as a simple model of the intraspinal cerebrospinal-fluid system. Our approach is based on the classic theory for the propagation of longitudinal waves in single, fluid-filled, elastic tubes. We show that for small-amplitude waves the governing equations reduce to the classic wave equation. The wave speed is found to be a strong function of the ratio of the tubes’ cross-sectional areas. It is found that the leading edge of a transmural pressure pulse tends to generate compressive waves with converging wave fronts. Consequently, the leading edge of the presure pulse steepens to form a shock-like elastic jump. A weakly nonlinear theory is developed for such an elastic jump.
Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 2: Mechanisms for the Pathogenesis of Syringomyelia
Authors: Carpenter P. W. , Berkouk K. , Lucey A. D.
Published: January 2004

Our aim in this paper is to use a simple theoretical model of the intraspinal cerebrospinal-fluid system to investigate mechanisms proposed for the pathogenesis of syringomyelia. The model is based on an inviscid theory for the propagation of pressure waves in co-axial, fluid-filled, elastic tubes. According to this model, the leading edge of a pressure pulse tends to steepen and form an elastic jump, as it propagates up the intraspinal cerebrospinal-fluid system. We show that when an elastic jump is incident on a stenosis of the spinal subarachnoid space, it reflects to form a transient, localized region of high pressure within the spinal cord that for a cough-induced pulse is estimated to be 50 to 70 mm Hg or more above the normal level in the spinal subarachnoid space. We propose this as a new mechanism whereby pressure pulses created by coughing or sneezing can generate syrinxes. We also use the same analysis to investigate Williams’ suck mechanism. Our results do not support his concept, nor, in cases where the stenosis is severe, the differential-pressure-propagation mechanism recently proposed by Greitz et al. Our analysis does provide some support for the piston mechanism recently proposed by Oldfield et al. and Heiss et al. For instance, it shows clearly how the spinal cord is compressed by the formation of elastic jumps over part of the cardiac cycle. What appears to be absent for this piston mechanism is any means whereby the elastic jumps can be focused (e.g., by reflecting from a stenosis) to form a transient, localized region of high pressure within the spinal cord. Thus it would seem to offer a mechanism for syrinx progression, but not for its formation.
In Vitro Measurements of Porcine Anterior Column Units Under Free Swelling
Authors: Reiter David A. , Sarigul-Klijn Nesrin , Gupta Munish C. , Fathallah Fadi A.
Published: January 2004

The objectives of this study are to present a 2-D optical method for measuring gross kinematics of porcine anterior column units (ACUs) exposed to swelling with no applied load, provide a detailed error analysis of the 2-D optical measurement technique, and present a 2-D radiographic technique for measuring the distribution of x-ray intensity through an axial slice of the disc. The 2-D optical technique was sufficient for detecting the flexion-extension behavior of the ACUs tested. The error analysis concluded that the use of a second camera to quantify out of plane movement of the specimen would greatly improve the accuracy of the measurement of angle. The 2-D radiographic technique provided limited information on changes in intradiscal material. It was also limited in its accuracy and dependability (i.e., only 5 out of 13 specimens provided radiographs suitable for this analysis). The results of this study indicate that a relationship might exist between the flexion-extension behavior observed from swelling and intradiscal shifts of matter. Further work is needed to confirm this relationship.
A New Method to Measure Post-Traumatic Joint Contractures in the Rabbit Knee
Authors: Hildebrand Kevin A. , Holmberg Michael , Shrive Nigel
Published: January 2004

A new device and method to measure rabbit knee joint angles are described. The method was used to measure rabbit knee joint angles in normal specimens and in knee joints with obvious contractures. The custom-designed and manufactured gripping device has two clamps. The femoral clamp sits on a pinion gear that is driven by a rack attached to a materials testing system. A 100 N load cell in series with the rack gives force feedback. The tibial clamp is attached to a rotatory potentiometer. The system allows the knee joint multiple degrees-of-freedom (DOF). There are two independent DOF (compression-distraction and internal-external rotation) and two coupled motions (medial-lateral translation coupled with varus-valgus rotation; anterior-posterior translation coupled with flexion-extension rotation). Knee joint extension-flexion motion is measured, which is a combination of the materials testing system displacement (converted to degrees of motion) and the potentiometer values (calibrated to degrees). Internal frictional forces were determined to be at maximum 2% of measured loading. Two separate experiments were performed to evaluate rabbit knees. First, normal right and left pairs of knees from four New Zealand White (NZW) rabbits were subjected to cyclic loading. An extension torque of 0.2 Nm was applied to each knee. The average change in knee joint extension from the first to the fifth cycle was 1.9deg±1.5degmean±sd with a total of 49 tests of these eight knees. The maximum extension of the four left knees (tested 23 times) was 14.6deg±7.1deg, and of the four right knees (tested 26 times) was 12.0deg±10.9deg. There was no significant difference in the maximum extension between normal left and right knees. In the second experiment, nine skeletally mature NZW rabbits had stable fractures of the femoral condyles of the right knee that were immobilized for five, six or 10 weeks. The left knee served as an unoperated control. Loss of knee joint extension (flexion contracture) was demonstrated for the experimental knees using the new methodology where the maximum extension was 35deg±9deg, compared to the unoperated knee maximum extension of 11deg±7deg, 10 or 12 weeks after the immobilization was discontinued. The custom gripping device coupled to a materials testing machine will serve as a measurement test for future studies characterizing a rabbit knee model of post-traumatic joint contractures.