bluuebunny/crossref_metadata_2025 huggingface dataset:
Lysophosphatidic Acid Receptors 1 and 2 Play Roles in Regulation of Vascular Injury Responses but Not Blood Pressure
Authors: Panchatcharam Manikandan , Miriyala Sumitra , Yang Fanmuyi , Rojas Mauricio , End Christopher , Vallant Christopher , Dong Anping , Lynch Kevin , Chun Jerold , Morris Andrew J. , Smyth Susan S.
Published: August 2008

Phenotypic modulation of vascular smooth muscle cells (SMCs) is essential for the development of intimal hyperplasia. Lysophosphatidic acid (LPA) is a serum component that can promote phenotypic modulation of cultured SMCs, but an endogenous role for this bioactive lipid as a regulator of SMC function in vivo has not been established. Ligation injury of the carotid artery in mice increased levels in the vessel of both autotaxin, the lysophospholipase D enzyme responsible for generation of extracellular LPA, and 2 LPA responsive G protein–coupled receptors 1 (LPA1) and 2 (LPA2). LPA1
−/−
2
−/−
mice were partially protected from the development of injury-induced neointimal hyperplasia, whereas LPA1
−/−
mice developed larger neointimal lesions after injury. Growth in serum, LPA-induced extracellular signal-regulated protein kinase activation, and migration to LPA and serum were all attenuated in SMCs isolated from LPA1
−/−
2
−/−
mice. In contrast, LPA1
−/−
SMCs exhibited enhanced migration resulting from an upregulation of LPA3. However, despite their involvement in intimal hyperplasia, neither LPA1 nor LPA2 was required for dedifferentiation of SMCs following vascular injury or dedifferentiation of isolated SMCs in response to LPA or serum in vitro. Similarly, neither LPA1 nor LPA2 was required for LPA to elicit a transient increase in blood pressure following intravenous administration of LPA to mice. These results identify a role for LPA1 and LPA2 in regulating SMC migratory responses in the context of vascular injury but suggest that additional LPA receptor subtypes are required for other LPA-mediated effects in the vasculature.
Chronic Hypoxia–Induced Angiogenesis Normalizes Blood Pressure in Spontaneously Hypertensive Rats
Authors: Vilar José , Waeckel Ludovic , Bonnin Philippe , Cochain Clément , Loinard Céline , Duriez Micheline , Silvestre Jean-Sébastien , Lévy Bernard I.
Published: August 2008

We hypothesized that activation of angiogenesis by chronic hypoxia may affect vascular resistance and, subsequently, blood pressure levels in spontaneously hypertensive rats (SHRs). Five-week-old prehypertensive SHRs and age-matched normotensive Wistar–Kyoto (WKY) rats (n=8 per group) were maintained under normobaric normoxic or hypoxic (10% O
2
) conditions for 8 weeks. Three weeks later, the systolic blood pressure was lower by 26% in hypoxic SHRs compared to normoxic SHRs (
P
<0.05) and remained at the normoxic WKY level. Total peripheral vascular resistance, calculated as the mean arterial pressure/cardiac output (assessed by ultrasound imaging and Doppler), was 30% lower in hypoxic than in normoxic SHRs (
P
<0.001) and returned to WKY levels. Interestingly, chronic hypoxia also significantly reduced systolic blood pressure in adult 12-week-old SHRs with established hypertension; blood pressure was normalized (versus normoxic WKY rats) after 4 weeks of hypoxia. Changes in hemodynamic parameters were associated with activation of proangiogenic pathways. Protein levels of vascular endothelial growth factor (VEGF)-A in the skeletal muscles were increased by 2.2-fold in hypoxic compared to normoxic SHRs (
P
<0.001). At the end of the hypoxic period, capillary density in the quadriceps muscle was 1.2-fold higher in hypoxic than in normoxic SHRs (
P
<0.001). Myocardial capillary density and VEGF-A protein contents were also 1.2- and 2.1-fold higher in hypoxic compared to normoxic SHRs (
P
<0.001 and
P
<0.05, respectively). Moreover, treatment with neutralizing VEGF-A antibody abrogated the hypoxia-induced angiogenesis and subsequently worsened arterial hypertension. Therefore, our results suggest that chronic normobaric hypoxia (1) activates VEGF-A–induced angiogenesis and thereafter (2) prevents the occurrence of hypertension in young prehypertensive SHRs and (3) normalizes blood pressure in adult SHRs with established hypertension.
Dose-Response Relationship Between Cigarette Smoking and Risk of Ischemic Stroke in Young Women
Authors: Bhat Viveca M. , Cole John W. , Sorkin John D. , Wozniak Marcella A. , Malarcher Ann M. , Giles Wayne H. , Stern Barney J. , Kittner Steven J.
Published: August 2008

Background and Purpose—

Although cigarette smoking is known to be a risk factor for ischemic stroke, there are few data on the dose-response relationship between smoking and stroke risk in a young ethnically diverse population.

Methods—

We used data from the Stroke Prevention in Young Women Study, a population-based case-control study of risk factors for ischemic stroke in women aged 15 to 49 years to examine the relationship between cigarette smoking and ischemic stroke. Historical data, including smoking history, was obtained through standardized interviews. Odds ratios (OR) were estimated using logistic regression. Cases (n=466) were women with stroke in the greater Baltimore-Washington area, and controls (n=604) were women free of a stroke history identified by random digit dialing.

Results—

After multivariable adjustment, the OR comparing current smokers to never smokers was 2.6 (
P
<0.0001); no difference in stroke risk was observed between former smokers and never smokers. Adjusted OR increased with increasing number of cigarettes smoked per day (OR=2.2 for 1 to 10 cigs/d; 2.5 for 11 to 20 cigs/d; 4.3 for 21 to 39 cigs/d; 9.1 for 40 or more cigs/d).

Conclusion—

These results suggest a strong dose-response relationship between cigarette smoking and ischemic stroke risk in young women and reinforce the need for aggressive smoking cessation efforts in young adults.
A Novel Endovascular Device for Emboli Rerouting
Authors: Grad Ygael , Sievert Horst , Nishri Boaz , Stone Gregg W. , Katzen Barry T. , Yodfat Ofer , Higashida Randall , Harris Dagan , Wakhloo Ajay K. , Assaf Yaron , Norbash Alexander , Bushi Doron , Lieber Baruch B.
Published: August 2008

Background and Purpose—

The feasibility and safety of a novel endovascularly delivered tubular mesh designed to reroute emboli away from a critical artery as a means of ischemic stroke prevention was tested in vitro and in vivo.

Methods—

Emboli rerouting efficacy was assessed in vitro. Perfusion through the external femoral artery that was jailed by the device, cellular proliferation rate over the jailing mesh, and the resulting tissue coverage of the orifice were assessed in the swine iliofemoral bifurcation. Device-induced embolization was assessed in a swine kidney model.

Results—

In vitro experiments demonstrated that particles as small as 60% of the pore dimension can be rerouted by the device, although at low efficacy, and rerouting efficacy approached 100% as the particle size approached the pore dimension. Repeat assessment of flow preimplantation and at various follow-up times by Doppler ultrasound showed no significant changes in the perfusion ratio of the jailed branch to the parent artery or the jailed branch to the naive contralateral artery either as a result of device implantation or at the follow-up times. Tissue coverage over the jailed ostium was limited to approximately 12% after stabilization. Cellular proliferation rate gradually decreased to diminishing level approximately 22 weeks postimplantation. The devices implanted across the renal arteries did not demonstrate any device-induced embolization after 1 month.

Conclusions—

It is proposed that this device could be used to reroute emboli away from important intracranial vessels as a means of stroke prevention.
Cardiac Reserve and Pulmonary Gas Exchange Kinetics in Patients With Stroke
Authors: Tomczak Corey R. , Jelani Anwar , Haennel Robert G. , Haykowsky Mark J. , Welsh Robert , Manns Patricia J.
Published: August 2008

Background and Purpose—

Cardiovascular and pulmonary factors contributing to impaired peak oxygen uptake (V̇O
2
) in patients with stroke (SP) are not well known. We assessed cardiovascular function, pulmonary gas exchange, and ventilation in SP and healthy age, gender, and activity-matched control subjects.

Methods—

Ten hemiparetic SP and 10 control subjects were enrolled. Subjects completed cycle ergometry testing to assess peak and reserve V̇O
2
, carbon dioxide production, ventilation (tidal volume; breathing frequency; minute ventilation), and cardiac output. V̇O
2
, carbon dioxide production, and minute ventilation were measured throughout peak exercise recovery (off-kinetics) and at exercise onset (on-kinetics) along with heart rate during low-level exercise.

Results—

Peak V̇O
2
was 43% lower (
P
<0.001) in SP secondary to reduced peak and reserve cardiac output and minute ventilation. The impaired cardiac output reserve (
P
<0.001) was due to a 34% lower heart rate reserve (
P
=0.001). The impaired minute ventilation reserve (
P
=0.013) was due to a 41% lower tidal volume reserve (
P
=0.009). Stroke volume and breathing frequency reserve were preserved. V̇O
2
off-kinetics were 29% slower in SP (
P
<0.001) and related to peak V̇O
2
(
R
=−0.72,
P
<0.001) and peak cardiac output (
R
=−0.75,
P
<0.001) for the study group. Additionally, carbon dioxide production (
P
=0.016) and minute ventilation (
P
=0.023) off-kinetics were prolonged in SP. V̇O
2
on-kinetics were 29% slower (
P
=0.031) during low-level exercise in SP.

Conclusions—

The impaired peak V̇O
2
in SP is secondary to a decline in peak and reserve cardiac output and ventilation. Prolonged V̇O
2
kinetics in SP are associated in part with deconditioning and may be mediated by reduced O
2
availability and/or the rate of muscle O
2
use.
Quantitative Assessment of Mixed Cerebral Vascular Territory Supply With Vessel Encoded Arterial Spin Labeling MRI
Authors: Kansagra Akash P. , Wong Eric C.
Published: August 2008

Background and Purpose—

Recent advances in arterial spin labeling MRI have permitted noninvasive evaluation of vascular territories. In the present study, we quantitatively assess mixing of internal carotid and basilar artery blood through cerebrovascular anastomoses using vessel-encoded arterial spin labeling and a new postprocessing method.

Methods—

Vessel-encoded arterial spin labeling was used to determine the territories of the internal carotid and basilar arteries in 14 healthy subjects and one patient with asymptomatic high-grade carotid artery stenosis before and after endarterectomy. Contributions to individual vascular territories were quantified using a voxelwise supply fraction algorithm and the results were correlated with MR angiography.

Results—

Vascular territories were consistent with cerebrovascular anatomy and the presence of pathology. The supply fraction method allowed quantification of mixed territorial supply arising from collateral flow and showed vascular supply changes in a patient with carotid artery stenosis after endarterectomy.

Conclusions—

Vascular territories obtained with vessel-encoded arterial spin labeling correlate with cerebrovascular anatomy and allow quantitative assessment of mixed territorial supply in subjects with and without pathology.
Acute Retinal Arteriolar Emboli After Cardiac Catheterization
Authors: Kreis Andreas J. , Nguyen Thanh , Rogers Sophie , Wang Jie Jin , Harper C. Alex , Clark David J. , Farouque H.M. Omar , Wong Tien Y.
Published: August 2008

Background and Purpose—

There are concerns that cardiac catheterization may cause retinal embolization, a risk marker for cerebrovascular emboli and stroke. We describe the incidence of acute retinal embolism after cardiac catheterization.

Methods—

One hundred unselected patients attending a tertiary referral center for diagnostic cardiac catheterization were recruited. Digital retinal photography (optic disc and macular fields) was performed precatheterization and within 3 hours postcatheterization. New retinal emboli were identified by a senior researcher and confirmed by a retinal specialist.

Results—

There was one case of retinal embolus precatheterization. Two patients (incidence 2.02%; 95% CI, 0.25 to 7.11) developed new retinal arteriolar emboli after catheterization. No patient developed clinically apparent visual or neurological changes.

Conclusions—

The risk of acute retinal embolism immediately after cardiac catheterization is 2%. This finding indicates that the retinal, and possibly the cerebral circulation, may be compromised more frequently than is clinically apparent as a complication of cardiac catheterization.
Low Incidence of Stroke in Southern Italy
Authors: Manobianca Giovanni , Zoccolella Stefano , Petruzzellis Antonella , Miccoli Annamaria , Logroscino Giancarlo
Published: August 2008

Background and Purpose—

Although a lower incidence of stroke has been observed in the Mediterranean area compared to other European countries, this is based on only a few studies. We sought to determine the incidence and 28-day case-fatality of stroke through a population-based stroke register in a rural area in Southern Italy, characterized by a stroke unit in the referral hospital.

Methods—

We established a multisource prospective population-based register in a well defined geographic area of 38 735 inhabitants in Puglia, Southern Italy. We identified all subjects in the study area with a first-ever stroke between January 1, 2001 and December 31, 2002.

Results—

We identified 127 first-ever strokes (77 males, 50 females) during the two-year study period. Hospitalization was 95%: 92 cases (72.4%) were cerebral infarction, 24 (18.9%) intracerebral hemorrhage, 3 (2.4%) subarachnoid hemorrhage, and 8 (6.3%) were unclassifiable strokes. The overall crude annual incidence was 1.6 per 1000 (95%CI: 1.4 to 1.9), 2.0 for males (95% CI:1.6 to 2.5), and 1.3 for females (95% CI:0.9 to 1.6). The incidence rates standardized to the 2001 European and world populations were respectively 1.5 (2.0 for males and 1.3 for females) and 0.8 (0.9 for males and 0.6 for females). Incidence rates progressively increased with age in both sexes, reaching their peak at 85 years or more (21.4/1000 overall, 35.0 for men and 13.4 for women). The 28-day case-fatality was 18.1%.

Conclusions—

Our study supports previous findings of lower incidence of stroke in the Mediterranean area, whereas the case-fatality in our study was lower than in previous studies from Italy. Further studies are needed to determine the role of prompt referral and stroke units on prognosis in population-based setting.
Hematoma Growth in Oral Anticoagulant Related Intracerebral Hemorrhage
Authors: Cucchiara Brett , Messe Steven , Sansing Lauren , Kasner Scott , Lyden Patrick
Published: August 2008

Background and Purpose—

Limited data suggest that intracerebral hemorrhage related to oral anticoagulant therapy (OAT ICH) is associated with more hemorrhage expansion and a worse prognosis than spontaneous ICH (SICH).

Methods—

We examined patients enrolled in the placebo arm of the CHANT study, a prospective randomized trial of a putative neuroprotectant in patients with ICH. All patients had neuroimaging within 6 hours of symptom onset and at 72 hours. Initial ICH volume and hemorrhage expansion were determined by a central reader. Multivariable logistic regression was used to determine factors associated with ICH expansion and mortality at 90 days.

Results—

Of 303 patients included, 21 (6.9%) had OAT ICH. Baseline median ICH volume was greater in patients with OAT ICH compared to SICH (30.6 versus 14.4 mL,
P
=0.03). Hemorrhage expansion (defined as >33% increase in ICH volume) occurred in 56% of patients with OAT ICH compared to 26% of SICH (
P
=0.006). Mortality was substantially higher in OAT ICH (62% versus 17%,
P
<0.001). In multivariable analysis, time to neuroimaging and oral anticoagulant use were independently associated with hemorrhage expansion, and age, gender, and oral anticoagulant use were independently associated with mortality.

Conclusions—

These findings confirm that OAT ICH is associated with more hemorrhage expansion and greater mortality than SICH.
Quality of Ischemic Stroke Care in Emerging Countries
Authors: Sposato Luciano A. , Esnaola María M. , Zamora Rafael , Zurrú María C. , Fustinoni Osvaldo , Saposnik Gustavo ,   the Argentinian Neurological Society
Published: August 2008

Background and Purpose—

Limited information is available on stroke management in developing countries. An accurate monitoring of quality of stroke care will become crucial, particularly with the emerging paradigm of pay-for-performance. Our aim was to explore the feasibility of measuring standardized indicators of quality of ischemic stroke care in acute care facilities in Argentina.

Methods—

ReNACer is a prospective, multicenter, countrywide, stroke registry comprising 74 academic and nonacademic institutions in Argentina. The registry includes patient-level information on demography, clinical characteristics, diagnostic procedures, treatment, and the selected key performance indicators of quality of ischemic stroke care (access to thrombolysis or aspirin use in the acute setting, admission to designated stroke units, length of stay, risk-adjusted in-hospital pneumonia, risk-adjusted in-hospital mortality, discharge on antithrombotics, and antihypertensive agents).

Results—

We included 1991 patients with ischemic stroke from 74 institutions in Argentina between November 2004 and October 2006. Seventy-nine per cent of the patients were prescribed antithrombotic therapy within 48 hours of admission, but only 1% received thrombolytics. No more than 5.7% were admitted to stroke units. In-hospital pneumonia was diagnosed in 14.3% of the patients and was higher in nonacademic facilities (16.4% versus 11.4%,
P
<0.02). The overall adjusted in-hospital mortality was 9.1%, also higher in nonacademic hospitals (10.6% versus 7.1%,
P
<0.008). At discharge, antithrombotics were prescribed in 90.2% and antihypertensive agents in 63.6% of the patients.

Conclusions—

In ReNACer, there was a limited access to stroke units and thrombolytics, and a relatively high incidence of in-hospital pneumonia. Differences in stroke care were observed between academic and nonacademic institutions. There is an urgent need to develop national stroke programs in Argentina.
On the Etiology of Incident Brain Lacunes
Authors: Gouw Alida A. , van der Flier Wiesje M. , Pantoni Leonardo , Inzitari Domenico , Erkinjuntti Timo , Wahlund Lars O. , Waldemar Gunhild , Schmidt Reinhold , Fazekas Franz , Scheltens Philip , Barkhof Frederik
Published: August 2008

Background and Purpose—

We investigated regional differences in MRI characteristics and risk factor profiles of incident lacunes over a 3-year period.

Methods—

Baseline and 3-year follow-up MRI were collected within the LADIS study (n=358). Incident lacunes were characterized with respect to brain region, their appearance within pre-existent white matter hyperintensities (WMH), surrounding WMH size, and risk factors.

Results—

106 incident lacunes were observed in 62 patients (58 subcortical white matter [WM], 35 basal ganglia, and 13 infratentorial). Incident subcortical WM lacunes occurred more often within preexisting WMH (
P
=0.01) and were mostly accompanied by new and expanded WMH (
P
<0.001), compared to incident basal ganglia and infratentorial lacunes. Risk factors for incident subcortical WM lacunes were history of hypertension and stroke, whereas atrial fibrillation predicted incident basal ganglia/infratentorial lacunes.

Conclusion—

Differences in relation to WMH and risk factor profiles may suggest that incident lacunes in the subcortical WM have a different pathogenesis than those in the basal ganglia and infratentorial region.
Warfare and Economy in Renaissance Italy, 1350–1450
Authors: Caferro William P.
Published: August 2008

The well-known cycle of plague and famine in fourteenth- and fifteenth-century Italy coincided with continuous and expensive warfare. These wars, largely ignored by scholars, had important economic consequences for the peninsula, reallocating resources on both the state and individual level. The spending habits of soldiers suggest, albeit tentatively at this stage, a “Renaissance” penchant for conspicuous consumption and display.
Never Again? The Legacy of the Argentine and Chilean Dictatorships for the Global Human Rights Regime
Authors: Cavallaro James L. , Brewer Stephanie Erin
Published: August 2008

Widespread forced disappearances, summary executions, and torture practiced by the military regimes in Argentina and Chile came to define human rights abuse during the 1970s and 1980s. Opposition to these practices and their parent regimes helped to shape the contemporary human rights movement and, by extension, human rights norms and institutions. Thomas C. Wright's State Terrorism in Latin America contends that the movement's struggle with the Argentine and Chilean dictatorships resulted in an era of greater deterrence and enforcement power for human rights institutions. Sonia Cardenas' Conflict and Compliance, however, maintains that despite the advance in norms and the creation of supranational structures to promote accountability for human rights abuse, the mechanisms for changing state practice have remained remarkably constant throughout the past three decades. Both in Latin America and elsewhere, domestic forces and cost-benefit analysis—at times aided by international pressure—continue to be the principal determinants of state behavior in the field of human rights.
Biogeography of Tropical Montane Cloud Forests. Part II: Mapping of Orographic Cloud Immersion
Authors: Nair Udaysankar S. , Asefi Salvi , Welch Ronald M. , Ray D. K. , Lawton Robert O. , Manoharan Vani Starry , Mulligan Mark , Sever Tom L. , Irwin Daniel , Pounds J. Alan
Published: August 2008

This study details two unique methods to quantify cloud-immersion statistics for tropical montane cloud forests (TMCFs). The first technique uses a new algorithm for determining cloud-base height using Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products, and the second method uses numerical atmospheric simulation along with geostationary satellite data. Cloud-immersion statistics are determined using MODIS data for March 2003 over the study region consisting of Costa Rica, southern Nicaragua, and northern Panama. Comparison with known locations of cloud forests in northern Costa Rica shows that the MODIS-derived cloud-immersion maps successfully identify known cloud-forest locations in the United Nations Environment Programme (UNEP) World Conservation Monitoring Centre (WCMC) database. Large connected regions of cloud immersion are observed in regions in which the trade wind flow is directly impinging upon the mountain slopes; in areas in which the flow is parallel to the slopes, a fractured spatial distribution of TMCFs is observed. Comparisons of the MODIS-derived cloud-immersion map with the model output show that the MODIS product successfully captures the important cloud-immersion patterns in the Monteverde region of Costa Rica. The areal extent of cloud immersion is at a maximum during morning hours and at a minimum during the afternoon, before increasing again in the evening. Cloud-immersion frequencies generally increase with increasing elevation and tend to be higher on the Caribbean Sea side of the mountains. This study shows that the MODIS data may be used successfully to map the biogeography of cloud forests and to quantify cloud immersion over cloud-forest locations.
Characterizing Variability of the Urban Physical Environment for a Suite of Cities in Rondônia, Brazil
Authors: Powell Rebecca L. , Roberts Dar A.
Published: August 2008

Urban environments are characterized by high spectral and spatial heterogeneity and, as a consequence, most urban pixels in moderate-resolution imagery contain multiple land-cover materials. Despite these complexities, virtually all urban land cover can be generalized as a combination of vegetation, impervious surfaces, and soil (V–I–S components), in addition to water. Previous work has demonstrated the potential of multiple endmember spectral mixture analysis (MESMA) to model the subpixel abundance of V–I–S components. Here, the authors test whether the technique is sufficiently robust to map V–I–S components for a diverse set of cities, selecting 10 urban centers in the state of Rondônia, Brazil, to represent a range of populations, development histories, and economic activities. For each urban sample, a 20 km × 20 km region centered over the built-up area was subset from Landsat Enhanced Thematic Mapper Plus (ETM+) imagery. MESMA was applied to all subscenes using the same spectral library, model constraints, and selection rules. Accuracy of the modeled V–I–S fractions was assessed using high-resolution images mosaicked from digital aerial videography. Modeled fractions and reference fractions were highly correlated, with R2 values exceeding 0.75 for all materials in multiple cities across a region. Model complexity, or the number of endmembers required to accurately model each pixel, was correlated with the degree of human impact on the landscape. Built-up areas, as delineated by model complexity, exhibited a strong fit to the well-established relationship between the built-up area of a settlement and its population. Finally, this work demonstrates that the V–I–S components as modeled by MESMA can capture both inter- and intraurban variability, suggesting that these data products could contribute to comparative studies of urbanizing areas through time and across regions.
Tropical Atmosphere–Ocean Interactions in a Conceptual Framework
Authors: Jansen Malte F. , Dommenget Dietmar , Keenlyside Noel
Published: August 2008

Statistical analysis of observations (including atmospheric reanalysis and forced ocean model simulations) is used to address two questions: First, does an analogous mechanism to that of El Niño–Southern Oscillation (ENSO) exist in the equatorial Atlantic or Indian Ocean? Second, does the intrinsic variability in these basins matter for ENSO predictability? These questions are addressed by assessing the existence and strength of the Bjerknes and delayed negative feedbacks in each tropical basin, and by fitting conceptual recharge oscillator models, both with and without interactions among the basins.

In the equatorial Atlantic the Bjerknes and delayed negative feedbacks exist, although weaker than in the Pacific. Equatorial Atlantic variability is well described by the recharge oscillator model, with an oscillatory mixed ocean dynamics–sea surface temperature (SST) mode present in boreal spring and summer. The dynamics of the tropical Indian Ocean, however, appear to be quite different: no recharge–discharge mechanism is found. Although a positive Bjerknes-like feedback from July to September is found, the role of heat content seems secondary.

Results also show that Indian Ocean interaction with ENSO tends to damp the ENSO oscillation and is responsible for a frequency shift to shorter periods. However, the retrospective forecast skill of the conceptual model is hardly improved by explicitly including Indian Ocean SST. The interaction between ENSO and the equatorial Atlantic variability is weaker. However, a feedback from the Atlantic on ENSO appears to exist, which slightly improves the retrospective forecast skill of the conceptual model.
The Control of Polar Haloclines by Along-Isopycnal Diffusion in Climate Models
Authors: Sijp Willem P. , England Matthew H.
Published: August 2008

Increasing the value of along-isopycnal diffusivity in a coupled model is shown to lead to enhanced stability of North Atlantic Deep Water (NADW) formation with respect to freshwater (FW) perturbations. This is because the North Atlantic (NA) surface salinity budget is dominated by upward salt fluxes resulting from winter convection for low values of along-isopycnal diffusivity, whereas along-isopycnal diffusion exerts a strong control on NA surface salinity at higher diffusivity values. Shutdown of wintertime convection in response to a FW pulse allows the development of a halocline responsible for the suppression of deep sinking. In contrast to convection, isopycnal salt diffusion proves a more robust mechanism for preventing the formation of a halocline, as surface freshening leads only to a flattening of isopycnals, leaving at least some diffusive removal of anomalous surface FW in place. As a result, multiple equilibria are altogether absent for sufficiently high values of isopycnal diffusivity. Furthermore, the surface salinity budget of the North Pacific is also dominated by along-isopycnal diffusion when diffusivity values are sufficiently high, leading to a breakdown of the permanent halocline there and the associated onset of deep-water formation.
Polarimetric and Dual-Doppler Radar Observations of the Lipscomb County, Texas, Supercell Thunderstorm on 23 May 2002
Authors: Frame Jeffrey , Markowski Paul , Richardson Yvette , Straka Jerry , Wurman Joshua
Published: August 2008

Polarimetric and dual-Doppler observations of a supercell observed by the National Center for Atmospheric Research (NCAR) S-band Polarimetric (SPOL) radar, two Doppler-On-Wheels (DOW) radars, and the Greek XPOL radar on 23 May 2002 during the International H2O Project (IHOP) are presented. The polarimetric radar observations began as the storm organized into a supercell and continued for over an hour while the storm was in its mature phase. The hydrometeor distribution within the mature storm was retrieved using a fuzzy logic hydrometeor classification algorithm. The dual-Doppler radar observations began around the time that the polarimetric radar observations concluded, and they covered the end of the mature phase and much of the dissipation phase of the storm. The dual-Doppler wind syntheses are used to evaluate the importance of the forward-flank outflow in augmenting the horizontal vorticity field near the storm above 400 m. In this case, having a relatively weak low-level mesocyclone, the parcel trajectories and the horizontal vorticity field observed within the forward-flank outflow are not what one would likely expect based on prior numerical studies (having generally stronger low-level mesocyclones) that have emphasized an important dynamical role for forward-flank downdrafts in terms of their horizontal vorticity generation. Instead, the observed trajectories could not be traced from the forward-flank outflow toward the storm’s updraft and the horizontal vorticity vectors within the forward-flank outflow generally did not point (westward) toward the storm’s updraft.
Microphysical and Thermodynamic Structure and Evolution of the Trailing Stratiform Regions of Mesoscale Convective Systems during BAMEX. Part I: Observations
Authors: Smith Andrea M. , McFarquhar Greg M. , Rauber Robert M. , Grim Joseph A. , Timlin Michael S. , Jewett Brian F. , Jorgensen David P.
Published: August 2008

This study used airborne and ground-based radar and optical array probe data from the spiral descent flight patterns and horizontal flight legs of the NOAA P-3 aircraft in the trailing stratiform regions (TSRs) of mesoscale convective systems (MCSs) observed during the Bow Echo and Mesoscale Convective Vortex Experiment (BAMEX) to characterize microphysical and thermodynamic variations within the TSRs in the context of the following features: the transition zone, the notch region, the enhanced stratiform rain region, the rear anvil region, the front-to-rear flow, the rear-to-front flow, and the rear inflow jet axis. One spiral from the notch region, nine from the enhanced stratiform rain region, and two from the rear anvil region were analyzed along with numerous horizontal flight legs that traversed these zones. The spiral performed in the notch region on 29 June occurred early in the MCS life cycle and exhibited subsaturated conditions throughout its depth. The nine spirals performed within the enhanced stratiform rain region exhibited saturated conditions with respect to ice above and within the melting layer and subsaturated conditions below the melting layer. Spirals performed in the rear anvil region showed saturation until the base of the anvil, near −1°C, and subsaturation below. These data, together with analyses of total number concentration and the slope to gamma fits to size distributions, revealed that sublimation above the melting layer occurs early in the MCS life cycle but then reduces in importance as the environment behind the convective line is moistened from the top down. Evaporation below the melting layer was insufficient to attain saturation below the melting layer at any time or location within the MCS TSRs. Relative humidity was found to have a strong correlation to the component of wind parallel to the storm motion, especially within air flowing from front to rear.
Low-Level Thermodynamic, Kinematic, and Reflectivity Fields of Hurricane Guillermo (1997) during Rapid Intensification
Authors: Sitkowski Matthew , Barnes Gary M.
Published: August 2008

From 0600 UTC 2 August to 1200 UTC 3 August Hurricane Guillermo (1997) deepened by 54 hPa over the eastern North Pacific Ocean, easily exceeding the thresholds that define rapid intensification (RI). The NOAA WP-3Ds observed a portion of this RI with similar two-aircraft missions on consecutive days. The aircraft jettisoned 70 successful global positioning system (GPS) dropwindsondes (or GPS sondes), which reveal how conditions in the lower troposphere on the octant to quadrant scale evolved within 250 km of the eye. Reflectivity fields demonstrate that the deepening is correlated with a spiraling in of the northern eyewall that reduces the eye diameter by 10 km. This behavior contrasts the more uniform contraction witnessed during eyewall replacement cycles. Mixing between the lower eye and eyewall, as detailed by other investigators, appears to have triggered the reduction in the eye diameter. After RI the eyewall remains asymmetrical with the tallest echo tops and heaviest rain rates located on the east or trailing side of the hurricane and to the left of the deep-layer shear vector. Net latent heat release within 60 km of the circulation center increases 21% from 2 to 3 August and is matched by a 30% increase in the inflow below 2 km at the 100-km radius. The GPS sondes, combined with aircraft in situ data for the eyewall region, reveal that the tropical cyclone (TC) establishes an annulus adjacent to and under the eyewall where the tangential wind component and equivalent potential temperature increase substantially. The radial extent of this annulus is constrained by the rainbands that remain robust throughout RI. The results support the argument that RI is controlled by processes within 100 km of the circulation center, and in particular within the eyewall.
Evaluation of Short-Range Quantitative Precipitation Forecasts from a Time-Lagged Multimodel Ensemble
Authors: Yuan Huiling , Lu Chungu , McGinley John A. , Schultz Paul J. , Jamison Brian D. , Wharton Linda , Anderson Christopher J.
Published: August 2008

Short-range quantitative precipitation forecasts (QPFs) and probabilistic QPFs (PQPFs) are investigated for a time-lagged multimodel ensemble forecast system. One of the advantages of such an ensemble forecast system is its low-cost generation of ensemble members. In conjunction with a frequently cycling data assimilation system using a diabatic initialization [such as the Local Analysis and Prediction System (LAPS)], the time-lagged multimodel ensemble system offers a particularly appealing approach for QPF and PQPF applications. Using the NCEP stage IV precipitation analyses for verification, 6-h QPFs and PQPFs from this system are assessed during the period of March–May 2005 over the west-central United States. The ensemble system was initialized by hourly LAPS runs at a horizontal resolution of 12 km using two mesoscale models, including the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) and the Weather Research and Forecast (WRF) model with the Advanced Research WRF (ARW) dynamic core. The 6-h PQPFs from this system provide better performance than the NCEP operational North American Mesoscale (NAM) deterministic runs at 12-km resolution, even though individual members of the MM5 or WRF models perform comparatively worse than the NAM forecasts at higher thresholds and longer lead times. Recalibration was conducted to reduce the intensity errors in time-lagged members. In spite of large biases and spatial displacement errors in the MM5 and WRF forecasts, statistical verification of QPFs and PQPFs shows more skill at longer lead times by adding more members from earlier initialized forecast cycles. Combing the two models only reduced the forecast biases. The results suggest that further studies on time-lagged multimodel ensembles for operational forecasts are needed.
The Gridding of MOS
Authors: Glahn Bob , Gilbert Kathryn , Cosgrove Rebecca , Ruth David P. , Sheets Kari
Published: August 2008

Model output statistics (MOS) guidance forecasts have been produced at stations and provided to National Weather Service forecasters and private entities for over three decades. As the numerical weather prediction models became more accurate, MOS followed that trend. Up until a few years ago, the MOS produced at observation locations met the basic need for guidance. With the advent of the Interactive Forecast Preparation System and the National Digital Forecast Database, gridded MOS forecasts became needed as guidance for forecasters. One method of providing such grids is to objectively analyze the MOS forecasts for points.

A basic successive correction method has been extended to analyze MOS forecasts and surface weather variables. This method is being applied to MOS forecasts to provide guidance for producing grids of sensible weather elements such as temperature, clouds, and snow amount. Guidance forecasts have been implemented for the conterminous United States for most weather elements contained in routine weather forecasts. This paper describes the method applied to daytime maximum temperature over the conterminous United States and gives example results.
Toward Achieving the “Beloved Community” in the Workplace
Authors: Jones James R. , Wilson David C. , Jones Peggy
Published: August 2008

In this study, the authors analyze data from a Gallup Organization public opinion poll commemorating the 40th anniversary of the Equal Employment Opportunity Commission to illustrate how businesses might incorporate Dr. Martin Luther King Jr.'s social justice themes of belongingness and connectedness in ways beneficial to desirable organizational outcomes (e.g., employee satisfaction, employee loyalty, employee retention). Results from a racially/ethnically diverse sample of more than 1,200 Americans indicate that, among other outcomes, racial and ethnic minority employees who feel a sense of engagement (i.e., belongingness and connectedness) with their workplaces, and who believe in their organization's commitment to diversity, feel a heightened affective connection at work. Furthermore, negative psychosocial outcomes because of perceived discrimination-based inequity in the workplace were mediated by engagement and trust in organization diversity policies. The authors discuss implications of these findings for future management research and practice.
Political Survival and Endogenous Institutional Change
Authors: de Mesquita Bruce Bueno , Smith Alastair
Published: August 2008

Incumbent political leaders risk deposition by challengers within the existing political rules and by revolutionary threats. Building on Bueno de Mesquita, Smith, Siverson, and Morrow's selectorate theory, the model here examines the policy responses of office-seeking leaders to revolutionary threats. Whether leaders suppress public goods such as freedom of assembly and freedom of information to hinder the organizational ability of potential revolutionaries or appease potential revolutionaries by increasing the provision of public goods depends, in part, on the sources of government revenues. Empirical tests show that governments with access to revenue sources that require few labor inputs by the citizens, such as natural resource rents or foreign aid, reduce the provision of public goods and increase the odds of increased authoritarianism in the face of revolutionary pressures. In contrast, without these sources of unearned revenues, governments respond to revolutionary pressures by increasing the provision of public goods and democratizing.
Chief Executive Organization and Advisory Arrangements for Foreign Affairs
Authors: Johansson Karl Magnus
Published: August 2008

As prime ministers are drawn into international relations and the foreign policy process, they are in need of advisory structures for foreign affairs in their offices. This article examines the system and the role of foreign affairs advisers to the Prime Minister (PM), the chief executive, in Sweden. The article centres on the organization for foreign affairs, in general terms of institutional and staffing arrangements, and on leader—adviser relationships. As the right hand of the PM, inner circle advisers in foreign affairs have a direct role in overseeing foreign policy on the key issues and do more than just serve in an advisory capacity by being operative in diplomacy and in policy coordination. These advisers can therefore wield influence on policy and the government based on their own expertise and position at the centre of power and at the frontier between the chief executive and the outside world.
Mikhail Gorbachev, the Murmansk Initiative, and the Desecuritization of Interstate Relations in the Arctic
Authors: Åtland Kristian
Published: August 2008

In October 1987, during a visit to the Kola Peninsula, the Secretary-General of the Soviet Communist Party, Mikhail Gorbachev, launched a series of policy initiatives which ultimately came to mark the beginning of the end of the Cold War era in the Arctic. The move was aimed at transforming the northern part of the globe from being a sensitive military theatre to becoming an international `zone of peace'. This objective was to be achieved through the establishment of a nuclear weapons-free zone in Northern Europe, restrictions on naval activities in Arctic seas, and the development of transborder cooperation in areas such as resource development, scientific exploration, indigenous people's affairs, environmental protection and marine transportation. This article analyses the contents of the Murmansk initiative, the context in which it was launched, the extent to which it materialized, and the degree to which it contributed to a normalization of interstate relations in the Arctic. In addition to being motivated by historical interest, the article aims at exploring the Copenhagen School concept of `desecuritization' and shedding light on the challenges and opportunities of turning security issues into non-security issues.
Africa's Evolving Security Architecture and the Concept of Multilayered Security Communities
Authors: Franke Benedikt
Published: August 2008

Following decades of feeble attempts, Africa's states have recently made great strides in establishing an elaborate security architecture to tackle the continent's many perils. I argue that the emergence and particular structure of this architecture and its institutional layers are best described by the constructivist concept of multilayered security communities. While this concept is based on the original idea of security communities by Karl Deutsch and its later adaptation by Emmanuel Adler and Michael Barnett, it recognizes the increasing prominence of elaborate multi-level security cooperation in the developing world and the difficulties of the original theoretical framework to account therefor. Consequently, it combines security community terminology with notions such as organized complementarity and multi-level governance to do conceptual justice to systems like Africa's decentralized collective security arrangement.
Homogenization and Pseudoelastic Behavior of Composite Materials Reinforced with Shape Memory Alloy Fibers
Authors: Jarali Chetan S. , Raja S.
Published: August 2008

Pseudoelastic behavior of cylindrical shape memory alloy (SMA) fiber embedded in a polymer matrix is investigated by using micromechanic approaches. A homogenization scheme based on Eshelby's equivalent inclusion method is adopted to derive the expressions for strains in the fiber and matrix in terms of the average strain in the composite. The constitutive laws for the SMA fiber and matrix are also expressed in terms of the average strain in the composite. The expressions for the SMA composite stiffness and the inelastic strains tensors are derived using dilute distribution theory and rule of mixtures approach. The composite stiffness and inelastic strain tensors are used in the generalized Hooke's law to compute the transformation stresses and associated hysteresis of the SMA composite. A comparison is also made with the strain energy approach. The computational results in terms of the composite stiffness and the stresses are presented within different fiber volume fraction, using the proposed methods. Finally, the modifications in the modeling approaches are highlighted with analytical case studies involving hysteretic stress—strain behaviors.
Strength Optimization of Laminated Composite Plates
Authors: Topal Umut , Uzman Ümit
Published: August 2008

A procedure to select the optimum fiber orientations and determine the maximum load-bearing capacity of the simply supported symmetrically laminated plates combined the bidirectional tension loads and bending moments is described. The fiber orientation is considered a design variable. The optimization problem consists of two stages. The objective of the first stage is to maximize the strength of the laminated plates by determining the fiber orientations optimally while the objective of the second stage is to maximize each of the bidirectional tension loads and bending moments subject to the Tsai—Wu failure criterion for the optimum fiber orientations obtained from the first stage. The modified feasible direction method (MFD) is used as an optimization procedure. Therefore, a FORTRAN program is used for the finite element analysis and optimization routine. Also, the optimum fiber orientations are obtained using the golden section (GS) method to compare the results. Finally, the effect of the different plate aspect ratio, width-to thickness ratio, the uncertainties in the material properties and the uncertainties in the fiber orientations on the optimum results is investigated and the results are compared.
Shear Behavior of 3-D Biaxial Spacer Weft Knitted Composite under High Strain Rates
Authors: Baozhong Sun  , Bohong Gu
Published: August 2008

The punch shear behavior of 3-D biaxial spacer weft knitted E-glass/ vinyl ester composite was investigated at quasi-static (0.01/s) and high strain rates ranging from 1200 to 3200/s in wale and course directions respectively. The quasi-static shear behavior was tested on a MTS 810.23 material tester and was compared with high strain rate shear behavior from a modified split Hopkinson pressure bar (SHPB) technique. The experimental results indicate that the shear stiffness, failure stress, and failure strain are rate sensitive both in wale and course directions. The shear stiffness and failure stress increase with the the increase of strain rate. The failure strains along the wale and course directions decrease with increasing strain rate. Furthermore, the shear failure becomes more severe in the course direction than in the wale direction at high strain rates. The damage mode in the wale direction at various strain rates is punch shear failure, while that of the course direction is filament tow breakage and matrix cracks. The unique features of this article are to conduct the punch shear tests at high strain rates successfully using a modified SHPB apparatus for the novel 3-D knitted composite and find the strain rate sensitivity both in shear behavior and failure mode. The results will benefit the structural design of the 3-D knitted composite owing to the higher in-plane tension stiffness and strength of the composite than any other 3-D textile structural composites.