bluuebunny/crossref_metadata_2025 huggingface dataset:
TRPV4 Channels Mediate Cyclic Strain–Induced Endothelial Cell Reorientation Through Integrin-to-Integrin Signaling
Authors: Thodeti Charles K. , Matthews Benjamin , Ravi Arvind , Mammoto Akiko , Ghosh Kaustabh , Bracha Abigail L. , Ingber Donald E.
Published: April 2009

Cyclic mechanical strain produced by pulsatile blood flow regulates the orientation of endothelial cells lining blood vessels and influences critical processes such as angiogenesis. Mechanical stimulation of stretch-activated calcium channels is known to mediate this reorientation response; however, the molecular basis remains unknown. Here, we show that cyclically stretching capillary endothelial cells adherent to flexible extracellular matrix substrates activates mechanosensitive TRPV4 (transient receptor potential vanilloid 4) ion channels that, in turn, stimulate phosphatidylinositol 3-kinase–dependent activation and binding of additional β1 integrin receptors, which promotes cytoskeletal remodeling and cell reorientation. Inhibition of integrin activation using blocking antibodies and knock down of TRPV4 channels using specific small interfering RNA suppress strain-induced capillary cell reorientation. Thus, mechanical forces that physically deform extracellular matrix may guide capillary cell reorientation through a strain-dependent “integrin-to-integrin” signaling mechanism mediated by force-induced activation of mechanically gated TRPV4 ion channels on the cell surface.
A Role for Gab1/SHP2 in Thrombin Activation of PAK1
Authors: Wang Dong , Paria Biman C. , Zhang Qiuhua , Karpurapu Manjula , Li Quanyi , Gerthoffer William T. , Nakaoka Yoshikazu , Rao Gadiparthi N.
Published: April 2009

To understand the role of epidermal growth factor receptor (EGFR) transactivation in G protein-coupled receptor (GPCR) agonist-induced signaling events, we have studied the capacity of thrombin in the activation of Gab1-SHP2 in vascular smooth muscle cells (VSMCs). Thrombin activated both Gab1 and SHP2 in EGFR-dependent manner. Similarly, thrombin induced Rac1 and Cdc42 activation, and these responses were suppressed when either Gab1 or SHP2 stimulation is blocked. Thrombin also induced PAK1 activation in a time- and EGFR-Gab1-SHP2-Rac1/Cdc42-dependent manner. Inhibition of activation of EGFR, Gab1, SHP2, Rac1, Cdc42, or PAK1 by pharmacological or genetic approaches attenuated thrombin-induced VSMC stress fiber formation and motility. Thrombin activated RhoA in a time-dependent manner in VSMCs. LARG, a RhoA-specific GEF (guanine nucleotide exchange factor), was found to be associated with Gab1 and siRNA-mediated depletion of its levels suppressed RhoA, Rac1 and PAK1 activation. Dominant negative mutant-mediated interference of RhoA activation inhibited thrombin-induced Rac1 and PAK1 stimulation in VSMCs and their stress fiber formation and migration. Balloon injury induced PAK1 activity and interference with its activation led to attenuation of SMC migration from media to intima, resulting in reduced neointima formation and increased lumen size. Inhibition of thrombin signaling by recombinant hirudin also blocked balloon injury-induced EGFR tyrosine phosphorylation and PAK1 activity. These results show that thrombin-mediated PAK1 activation plays a crucial role in vascular wall remodeling and it could be a potential target for drug development against these vascular lesions.
Neuropathological Correlates of Temporal Pole White Matter Hyperintensities in CADASIL
Authors: Yamamoto Yumi , Ihara Masafumi , Tham Carina , Low Roger W.C. , Slade Janet Y. , Moss Tim , Oakley Arthur E. , Polvikoski Tuomo , Kalaria Raj N.
Published: April 2009

Background and Purpose—

White matter (WM) hyperintensities on MRI or leukoaraiosis is characteristic of stroke syndromes. Increased MRI signals in the anterior temporal pole are suggested to be diagnostic for cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), with 90% sensitivity and 100% specificity. The structural correlates of these specific WM hyperintensities seen on T2-weighted and FLAIR sequences in the temporal pole of CADASIL are unclear. We assessed pathological changes in postmortem tissue from the temporal pole to reveal the cause of CADASIL-specific WM hyperintensities.

Methods—

A combination of tinctorial and immunostaining approaches and in vitro imaging methods were used to quantify the extent of perivascular space (PVS), arteriosclerosis determined as the sclerotic index, WM myelination as the myelin index, and damage within the WM as accumulated degraded myelin basic protein in samples of the anterior temporal pole from 9 CADASIL and 8 sporadic subcortical ischemic vascular dementia cases, and 5 similarly aged (young) and 5 older controls. Luxol fast blue-stained serial sections from a CADASIL case were also used to reconstruct the temporal pole, which was then compared to the MR images.

Results—

Luxol fast blue sections used to reconstruct the temporal pole revealed an abundance of enlarged PVS in the WM that topographically appeared as indistinct opaque regions. The mean and total areas of the PVS per WM area (%PVS) were significantly greater in CADASIL compared to the controls. The myelin index was severely reduced in CADASIL in relation to the subcortical ischemic vascular dementia and control sample that was consistent with increased immunoreactivity of degraded myelin basic protein, indicating myelin degeneration. Cerebral microvessels associated with the PVS exhibited a 4.5-fold greater number of basophilic (hyalinized) vessels and a 57% increase in the sclerotic index values in CADASIL subjects compared to young controls. A significant correlation between the quantity of hyalinized vessels and sclerotic index values was also apparent (
P
<0.05).

Conclusions—

Our findings suggest that MRI hyperintensities in the temporal pole of CADASIL patients are explained by enlarged PVS and degeneration of myelin accompanied by lack of drainage of the interstitial fluid rather than lacunar infarcts. Consistent with the lack of MR hypersignals in the temporal pole of older subcortical ischemic vascular dementia subjects, our observations imply greater progression of pathological changes in CADASIL patients.
Identifying Patients at High Risk for Poor Outcome After Intra-Arterial Therapy for Acute Ischemic Stroke
Authors: Hallevi Hen , Barreto Andrew D. , Liebeskind David S. , Morales Miriam M. , Martin-Schild Sheryl B. , Abraham Anitha T. , Gadia Jignesh , Saver Jeffrey L. ,   the UCLA Intra-Arterial Therapy Investigators, Grotta James C. , Savitz Sean I.
Published: April 2009

Background and Purpose—

Intra-arterial recanalization therapy (IAT) is increasingly used for acute stroke. Despite high rates of recanalization, the outcome is variable. We attempted to identify predictors of outcome that will enable better patient selection for IAT.

Methods—

All patients who underwent IAT at the University of Texas Houston Stroke Center were reviewed. Poor outcome was defined as modified Rankin Scale score 4 to 6 on hospital discharge. Findings were validated in an independent data set of 175 patients from the University of California at Los Angeles Stroke Center.

Results—

One hundred ninety patients were identified. Mean age was 62 years and median baseline National Institutes of Health Stroke Scale score was 0.18. Recanalization rate was 75%, symptomatic hemorrhage rate was 6%, and poor outcome rate was 66%. Variables associated with poor outcome were: age, baseline National Institutes of Health Stroke Scale, admission glucose, diabetes, heart disease, previous stroke, and the absence of mismatch on the pretreatment MRI. Logistic regression identified 3 variables independently associated with poor outcome: age (
P
=0.049; OR, 1.028), National Institutes of Health Stroke Scale (
P
=0.013; OR, 1.084), and admission glucose (
P
=0.031; OR, 1.011). Using these data, we devised the Houston IAT score: 1 point for age >75 years; 1 for National Institutes of Health Stroke Scale score >18, and 1 point for glucose >150 mg/dL (range, 0 to 3 mg/dL). The percentage of poor outcome by Houston IAT score was: score of 0, 44%; 1, 67%; 2, 97%; and 3, 100%. Recanalization rates were similar across the scores (
P
=0.4). Applying Houston IAT to the external cohort showed comparable trends in outcome and nearly identical rates in the Houston IAT therapy 3 tier.

Conclusions—

The Houston IAT score estimates the chances of poor outcome after IAT, even with recanalization. It may be useful in comparing cohorts of patients and when assessing the results of clinical trials.
Recent Respiratory Infection Predicts Atherothrombotic Stroke
Authors: Zurrú María Cristina , Alonzo Claudia , Brescacín Laura , Romano Marina , Cámera Luis Alberto , Waisman Gabriel , Cristiano Edgardo , Ovbiagele Bruce
Published: April 2009

Background and Purpose—

Increasing evidence links infections to atherosclerosis. Case–control and cohort studies have found that infections, especially respiratory and dental, are associated with coronary heart disease. However, data on the association of infections with cerebrovascular disease are limited, especially beyond Europe and the United States. We assessed the relationship between recent infections and atherothrombotic disease in a South American cohort.

Methods—

We conducted a case–control study of 105 cases and 354 control subjects in a Buenos Aires healthcare system matched by age (mean age, 73.2±12.3 and 72.9±12.8 years), sex, and major cardiovascular risk factors. Cases were patients hospitalized with atherothrombotic ischemic stroke from December 2006 to October 2007. Control subjects were randomly assigned from an electronic outpatient database. Data from the preceding year on inpatient and ambulatory respiratory, urinary and abdominal infections as well as peripheral white blood cell count were collected.

Results—

Infections were more frequent in cases than control subjects (29% versus 13%; OR, 2.6; 95% CI, 1.4 to 4.5;
P
=0.0004); however, this was driven by community-acquired respiratory tract infections (19% versus 6%; OR, 3.9; 95% CI, 1.9 to 8;
P
<0.001) because there were no differences between cases and control subjects for other types of infection. Respiratory tract infections were the most prevalent type of infection during the 3 months before an atherothrombotic ischemic event, occurring more in cases compared with control subjects (17% versus 4%; OR, 5; 95% CI, 2.2 to 11.3;
P
<0.001). In multivariable analysis adjusting for major vascular risk factors, history of respiratory infection in the prior year was associated more with cases than control subjects (OR, 4.9; 95% CI, 2.3 to 10.2;
P
<0.001). White blood cell count was slightly higher in cases versus control subjects (7602±2058 versus 7121.6±1947,
P
=0.01).

Conclusion—

In this South American cohort, recent respiratory tract infections were significantly associated with atherothrombotic stroke, suggesting that prompt identification and treatment of individuals with or at risk for these infections may mitigate the burden from this type of stroke.
Hippocampal Lesion Patterns in Acute Posterior Cerebral Artery Stroke
Authors: Szabo Kristina , Förster Alex , Jäger Theodor , Kern Rolf , Griebe Martin , Hennerici Michael G. , Gass Achim
Published: April 2009

Background and Purpose—

Reports of ischemic stroke affecting the hippocampus are rare. In this study we used diffusion-weighted MRI (DWI) to characterize patients with posterior circulation stroke involving the hippocampus.

Methods—

Fifty-seven consecutive acute stroke patients with hippocampal infarct (HI) on DWI were analyzed with regard to clinical features and ischemic lesion patterns. The last 20 of these underwent additional neuropsychological testing of short-term, working, and episodic long-term memory.

Results—

We found unilateral HI in 54 and bilateral HI in 3 patients. Visual analysis identified 4 patterns of DWI lesion affecting (1) the complete hippocampus (15/60), (2) the lateral (19/60) or (3) dorsal (22/60) parts of the hippocampal body and tail, and (4) circumscribed lesions in the lateral hippocampus (4/60), corresponding well to hippocampal vascular anatomy. In all cases DWI showed further ischemic lesions in the posterior circulation. Symptoms from lesions outside the hippocampus were the common leading clinical signs. Whereas mnestic deficits were prominent in only 11/57 patients, neuropsychological examination in 20 patients showed deficits of verbal episodic long-term memory in left and of nonverbal episodic long-term memory in right HI.

Conclusion—

Several phenotypic lesion patterns can be distinguished in HI that usually occur as part of multifocal PCA ischemia. A careful neuropsychological examination is necessary to detect resulting memory deficits.
Economic Burden of Intracranial Vascular Malformations in Adults
Authors: Miller Clare E. , Quayyum Zahidul , McNamee Paul , Al-Shahi Salman Rustam
Published: April 2009

Background and Purpose—

Although intracranial vascular malformations (IVMs) are the leading cause of intracerebral hemorrhage (ICH) in young adults, there has not been a cost-of-illness study on an unselected cohort.

Methods—

We measured the direct healthcare costs (inpatient, outpatient, intervention, and brain imaging) incurred by every adult within 3 years after their first presentation with a brain arteriovenous malformation (AVM) or cavernous malformation (CM) in a prospective, population-based study. We estimated the indirect cost of lost productivity for the whole cohort over the same period by projecting questionnaire responses from living consenting adults.

Results—

369 adults (AVM=229 [62%], CM=140 [38%]) incurred healthcare costs of £5.96 million over 3 years, of which AVMs accounted for 90%, inpatient care accounted for 75%, and the first year of care accounted for 69%. Median 3-year healthcare costs were statistically significantly higher for adults presenting with ICH, aged <65 years, receiving interventional treatment, and adults with AVMs rather than CMs (£15 784 versus £1385,
P
<0.0005). Healthcare costs diminished with increasing AVM nidus size (
P
=0.005). Mean 3-year costs of lost productivity per questionnaire respondent (n=145) were £17 111 for AVMs and £6752 for CMs (
P
=0.1), and the projected 3-year cost of lost productivity for all 369 adults was £8.7 million.

Conclusions—

The costs of healthcare and lost productivity attributable to IVMs are considerable, and highest in those aged <65 years, presenting with ICH, receiving interventional treatment, and harboring AVMs rather than CMs. Long-term studies of the cost-effectiveness of interventional treatment are needed.
Role of Health Insurance in Averting Economic Hardship in Families After Acute Stroke in China
Authors: Heeley Emma , Anderson Craig S. , Huang Yining , Jan Stephen , Li Yan , Liu Ming , Sun Jian , Xu En , Wu Yangfeng , Yang Qidong , Zhang Jingfen , Zhang Shihong , Wang Jiguang
Published: April 2009

Background and Purpose—

Stroke is a major health burden in China, but there are limited data on its economic effects on households. We aimed to examine the economic impact of stroke and to assess the influence of health insurance.

Methods—

In a nationwide, prospective, 62-hospital registry study of acute stroke in China, we recorded information on patient demographics, clinical features, socioeconomic factors, management, and costs of medical care. Information on out-of-pocket health expenses was obtained in surviving patients at 3- and 12-month follow-up. Catastrophic healthcare payments, defined as ≥30% of total household annual income, were estimated from reported household annual income.

Results—

Among 4739 3-month survivors of stroke with outcome data, average hospital and medication costs were 16 525 Chinese Yuan Renminbi (US $2361) and out-of-pocket costs were 14 478 Chinese Yuan Renminbi (US $2068). Overall, 3384 (71%) patients had experienced catastrophic out-of-pocket expenditure. Workers without health insurance were 7 times (OR, 6.9; 95% CI, 4.6 to 10.3) more likely to experience catastrophic payments than workers with insurance. Health insurance also protected against catastrophic payments in patients who were either retired or not working (no insurance: OR, 4.7; 95% CI, 3.1 to 7.2; OR, 1.82; 95% CI, 1.3 to 2.6, respectively).

Conclusions—

Because healthcare costs are high relative to income in China, families face considerable economic hardship after stroke. Health insurance protects families against catastrophic healthcare payments, thus highlighting the need to accelerate the ongoing process of building a comprehensive healthcare system in both urban and rural settings in China.
Relative Importance of Proteinase-Activated Receptor-1 Versus Matrix Metalloproteinases in Intracerebral Hemorrhage-Mediated Neurotoxicity in Mice
Authors: Xue Mengzhou , Hollenberg Morley D. , Demchuk Andrew , Yong V. Wee
Published: April 2009

Background and Purpose—To reduce bleeding and damage to central nervous system tissue in intracerebral hemorrhage, the coagulant effect of thrombin is essential. However, thrombin itself can kill neurons in intracerebral hemorrhage as can the matrix metalloproteinases (MMPs), which are also elevated in this condition, in part due to thrombin-mediated activation of MMPs. It is thus important to understand and block the neurotoxic effects of thrombin without inhibiting its therapeutic outcomes. In this study, we have investigated the relative roles of proteinase activated receptor-1, a thrombin receptor, and MMPs in brain injury induced by thrombin or blood.

Methods—Mice were subjected to stereotactic intracerebral injections of saline, thrombin, and autologous blood, with or without hirudin, a thrombin inhibitor, or GM6001, an MMP inhibitor. Twenty-four hours later, tissue sections were obtained to evaluate the area of brain damage and extent of dying neurons. Data from wild-type mice were compared with results obtained with proteinase activated receptor-1 null mice.

Results—In blood-induced damage to the brain parenchyma, both hirudin and GM6001 significantly reduced injury to a comparable extent (>40%) implicating both thrombin and MMPs in neurotoxicity. In proteinase activated receptor-1 null mice, blood-induced brain damage was reduced by 22.6% relative to wild-type animals; by comparison, the blood-induced brain damage was reduced by 48.3% using GM6001.

Conclusions—The neurotoxicity of blood in intracerebral hemorrhage involves both proteinase activated receptor-1 and MMP activation, with the latter appearing more prominent in causing death.
Invasive Cortical Stimulation to Promote Recovery of Function After Stroke
Authors: Plow Ela B. , Carey James R. , Nudo Randolph J. , Pascual-Leone Alvaro
Published: April 2009

Background and Purpose—

Residual motor deficits frequently linger after stroke. Search for newer effective strategies to promote functional recovery is ongoing. Brain stimulation, as a means of directing adaptive plasticity, is appealing. Animal studies and Phase I and II trials in humans have indicated safety, feasibility, and efficacy of combining rehabilitation and concurrent invasive cortical stimulation. However, a recent Phase III trial showed no advantage of the combination. We critically review results of various trials and discuss the factors that contributed to the distinctive result.

Summary of Review—

Regarding cortical stimulation, it is important to determine the (1) location of peri-infarct representations by integrating multiple neuroanatomical and physiological techniques; (2) role of other mechanisms of stroke recovery; (3) viability of peri-infarct tissue and descending pathways; (4) lesion geometry to ensure no alteration/displacement of current density; and (5) applicability of lessons generated from noninvasive brain stimulation studies in humans. In terms of combining stimulation with rehabilitation, we should understand (1) the principle of homeostatic plasticity; (2) the effect of ongoing cortical activity and phases of learning; and (3) that subject-specific intervention may be necessary.

Conclusions—

Future cortical stimulation trials should consider the factors that may have contributed to the peculiar results of the Phase III trial and address those in future study designs.
Cacophony or Coherence: Ethnographic Writing and Competing Claims to Ritual and Textual Authority
Authors: Allocco Amy
Published: April 2009

This essay describes the challenges to ethnographic writing that are raised by multiplicity, contradiction, and conflicting narratives in the fieldwork process. Specifically, the essay examines multiple and sometimes opposing articulations of the causes for, and ritual treatments of, a malignant horoscopic condition called nāga dōsam (snake blemish) in contemporary South India. This examination raises questions about the relationships between textual knowledge and ritual performance, as well as the nature of competing claims to ritual and textual authority. At the heart of these interpretive questions lies the issue of representation, or how best to characterize such multiplicity and inconsistency in the ethnographic texts which grow from our field research. Drawing on excerpts from fieldwork interviews with two Brahmin religious specialists, this essay considers how best to evoke the realities of the Tamil ritual field without simply inscribing these power dynamics on the ethnographic text.
Reading and Writing (to) the Devi: Reflections on Unanticipated Ritualized Ethnography
Authors: Dempsey Corinne
Published: April 2009

This article relates an event that effectively erases the distinguishing markers between the practices of fieldwork, writing, and ritual. This merging of performance genres provides an opportunity to consider three themes that surface regularly in recent ethnographic and ritual theory: bodily knowledge, reflexivity, and indeterminacy. In this article I will explore how these themes are relevant not only to ritual and ethnographic practice in general but to rituals performed at a Sri Lankan goddess temple in the town of Rush outside Rochester, New York, where I have conducted fieldwork since 1998. My aim in speaking about ritual and ethnography in the same breath, framed by my experience of collapsing practices, is to highlight what these endeavors have to say about our multifaceted ways of perceiving and knowing.
“On Thursdays We Worship the Banana Plant”: Encountering Lived Hinduism in a Canadian Suburb
Authors: Gunn Janet
Published: April 2009

Classic models of ethnography have the anthropologist going off into “the field” to encounter “the native.” How is the project of ethnography altered when one's field site is one's own city? This paper draws on fieldwork in a Canadian city to probe the entailments of conducting anthropological research in one's own backyard, throwing the conventional understanding of the ethnographer into question. What does this type of encounter reveal about the Othering process that is so often inherent in the ethnographic project? Unexamined notions of the anthropologist's role are challenged in ways both necessary and unnerving, blurring conventional boundaries of home and field. Such “dis-orientalization” is crucial to reaching a more honest position vis-à-vis the individuals and communities to whom ethnographers bring their questions. The various confusions it presents are generative. By foiling attempts at tidy categorizations, these encounters speak of the multiplicity and fluidity of lived religious identities and experiences.
Experiencing the Mango Festival as a Ritual Dramatization of Hagiography
Authors: Pechilis Karen
Published: April 2009

The author traveled to the coastal town of Kāraikkāl in Tamilnadu, south India in summer 2006 in order to explore the ways in which a festival celebrating a classical Hindu female saint would “tell” the story of her life as represented in a medieval canonical hagiography that the author had previously translated. By highlighting the oral mode of “telling” as a characterization of the festival's presentation, the author signals the performative, personal, and public aspects of its rendering of her story. At the festival's center is an emphasis on the visual, not in the sense of a staged drama, but as a persistent focus on sacred images, or what the author calls “moments of awe.” The “all at once” perception experience enabled by the visual mirrors the simultaneity of experience enabled by these moments of awe inscribed by bhakti (devotion) in that they are opportunities for the enactment of worship, the engagement of participation, and the creation of a public.
The Hermeneutics of Touch: Uncovering Abhinavagupta's Tactile Terrain
Authors: Skora Kerry Martin
Published: April 2009

This article introduces a “hermeneutics of touch” in order to uncover the place of tactile experience in the work of Abhinavagupta, the Kashmiri Hindu Tantric sage (c. 975-1025 C.E.). I focus on his understanding of the liberation of touch, especially as articulated in his Trankāloka (TĀ), his encyclopedic synthesis of Trika Śiva discourse and ritual. Inspired by the scholarship of the new emerging fields of anthropology of the senses as well as religion and the senses, I purposely break with the primary emphasis on vision and cognition seen in Abhinavagupta Studies, to reconsider the significance of the tactile sense.
Ensemble Variance Calibration for Representing Meteorological Uncertainty for Atmospheric Transport and Dispersion Modeling
Authors: Kolczynski Walter C. , Stauffer David R. , Haupt Sue Ellen , Deng Aijun
Published: April 2009

In the event of the release of a dangerous atmospheric contaminant, an atmospheric transport and dispersion (ATD) model is often used to provide forecasts of the resulting contaminant dispersion affecting the population. These forecasts should also be accompanied by accurate estimates of the forecast uncertainty to allow for more informed decisions about the potential hazardous area. This study examines the calculation of uncertainty in the meteorological data as derived from an ensemble, and its effects when used as additional input to drive an ATD model. The first part of the study examines the capability of a linear function to relate ensemble spread to error variance of the ensemble mean given ensemble spread from 24 days of forecasts from the National Centers for Environmental Prediction (NCEP) Short-Range Ensemble Forecast (SREF). This linear function can then be used to calibrate the ensemble spread to produce a more accurate estimate of the meteorological uncertainty. Results for the linear relationship of wind variance are very good, with values of the coefficient of determination R2 generally exceeding 0.94 for forecast lengths of 12 h and greater. The calibration is shown to be more sensitive to forecast hour than vertical level within the lower troposphere. The second part presents a 24-h case study to assess the impact of meteorological uncertainty calculations on Second-Order Closure Integrated Puff (SCIPUFF) ATD model predictions. Both uncalibrated ensemble wind variances and wind variances calibrated based on the results of the first part show improvement in mean concentration forecasts relative to a control experiment using the default hazard mode uncertainty when compared with a baseline SCIPUFF integration based on a high-resolution dynamic analysis of the meteorological conditions. The SCIPUFF experiments that use a wind variance calibration show both qualitative and quantitative improvement in most of the mean concentrations and patterns over the control experiment and the SCIPUFF experiment using uncalibrated wind variances. The SCIPUFF experiments using meteorological ensemble uncertainty information also produce mean concentrations and patterns that compare favorably to those of an explicit SCIPUFF ensemble based on each SREF member. Use of the uncalibrated variance information within a single ATD prediction produces mean ATD predictions most similar to those of the explicit ATD ensemble, and use of calibrated ensemble variance is shown to have some advantages over the explicit ATD ensemble.
On Climate Impacts of a Potential Expansion of Urban Land in Europe
Authors: Trusilova K. , Jung M. , Churkina G.
Published: April 2009

Over the last two decades, a disproportional increase of urban land area in comparison with the population growth has been observed in many countries of Europe, and this trend is predicted to continue. The conversion of vegetated land into urban land leads to a higher proportion of impervious surface area, to decline and change of vegetation cover, to artificial heat sources, and therefore to changes in climate. This study focuses on the implications of the expansion of urban land for the European climate at the local and regional scales. Regional climate simulations with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) coupled to the Town Energy Budget model are used to isolate effects of urban land expansion on temperature and precipitation. The study suggests that the expansion of current urban land by 40% would lead to an enlargement of regions affected by thermal stress by a factor of 2, whereas the intensity of the thermal stress does not change significantly. Precipitation in urban areas would be reduced by 0.2 mm day−1 in summer as a result of disturbances of the water cycle caused by urban surfaces. The area in which precipitation was altered increased nearly linearly with the urban land increment.
Spectra, Spatial Scales, and Predictability in a Quasigeostrophic Model
Authors: Morss Rebecca E. , Snyder Chris , Rotunno Richard
Published: April 2009

Results from homogeneous, isotropic turbulence suggest that predictability behavior is linked to the slope of a flow’s kinetic energy spectrum. Such a link has potential implications for the predictability behavior of atmospheric models. This article investigates these topics in an intermediate context: a multilevel quasigeostrophic model with a jet and temperature perturbations at the upper surface (a surrogate tropopause). Spectra and perturbation growth behavior are examined at three model resolutions. The results augment previous studies of spectra and predictability in quasigeostrophic models, and they provide insight that can help interpret results from more complex models. At the highest resolution tested, the slope of the kinetic energy spectrum is approximately at the upper surface but −3 or steeper at all but the uppermost interior model levels. Consistent with this, the model’s predictability behavior exhibits key features expected for flow with a shallower than −3 slope. At the highest resolution, upper-surface perturbation spectra peak below the energy-containing scales, and the error growth rate decreases as small scales saturate. In addition, as model resolution is increased and smaller scales are resolved, the peak of the upper-surface perturbation spectra shifts to smaller scales and the error growth rate increases. The implications for potential predictive improvements are not as severe, however, as in the standard picture of flows exhibiting a finite predictability limit. At the highest resolution, the model also exhibits periods of much faster-than-average perturbation growth that are associated with faster growth at smaller scales, suggesting predictability behavior that varies with time.
The Late-Spring Maximum of Rainfall over the U.S. Central Plains and the Role of the Low-Level Jet
Authors: Wang Shih-Yu , Chen Tsing-Chang
Published: April 2009

The seasonal rainfall over the U.S. central plains features a late-spring maximum. A spring–fall annual mode revealed from the empirical orthogonal function analysis on rainfall delineates a maximum center over the central plains that coincides with the large late-spring rainfall. This paper examines the large-scale dynamical and hydrological processes in forming the rainfall center. The NCEP–Department of Energy (DOE) reanalysis 2 data reveal that the baroclinic structure of the continental-scale circulation during late spring (May and June) induces a vertically out-of-phase divergent circulation forming strong convergence of water vapor flux over the central plains. Such circulation features generate concentrated convective activity in this region. The upper-level anticyclone development with the North American monsoon in July replaces the late-spring baroclinic structure and, in turn, reduces the convective activity. The Great Plains low-level jet (LLJ) plays a role in the downscaling process that connects the continental-scale circulation to rainfall. The LLJ coupled with approaching baroclinic waves leads to stronger moisture convergence in the central plains than that occurring under the upper-level anticyclone. The former type of the LLJ occurs most frequently in late spring and contributes to more than 60% of the rainfall. During midsummer (July and August), such a coupling is hindered by the well-developed upper-level anticyclone, subsequently decreasing the rainfall.
Overturning and Dissipation Caused by Baroclinic Tidal Flow near the Sill of a Fjord Basin
Authors: Arneborg Lars , Liljebladh Bengt
Published: April 2009

Dissipation time series and moored velocity and density time series on the inner slopes of the Gullmar Fjord sill showed that the internal tides generated at the sill radiated to the head of the fjord, were reflected, and then radiated back to the sill, where they dissipated their energy mainly below sill level. A large amount of the dissipation was caused by a transitional flow at a particular phase of the internal tide, when the bottom layer descended down the sill slope and had to pass a constriction set up by a submarine hill. The inward, baroclinic bottom-layer flow transformed into a supercritical bottom jet, which separated from the bottom just downstream of the constriction. A large fraction of the dissipation took place in the successive rebounding region (the hydraulic jump) above the bottom jet, where overturns of the same size as the vertical extent of the rebounding region were observed. More than half of the dissipation was happening in the bottom boundary layer below the jet. During the transitional flow, there were clear pulsations of the jet with periods of about 15 min. The amount of diapycnal mixing caused by the turbulence was reduced by the large fraction of dissipation within the bottom boundary layer and perhaps also by the high-buoyancy Reynolds numbers within the rebounding region. When using a relatively new parameterization of mixing, the mixing was significantly reduced compared to using the traditional constant mixing efficiency method.
Interplay of Resonant and Quasi-Resonant Interaction of the Directional Ocean Waves
Authors: Waseda Takuji , Kinoshita Takeshi , Tamura Hitoshi
Published: April 2009

Recent experimental study of the evolution of random directional gravity waves in deep water provides new insight into the nature of the spectral evolution of the ocean waves and the relative significance of resonant and quasi-resonant wave interaction. When the directional angle containing half the total energy is broader than ∼20°, the spectrum evolves following the energy transfer that can be described by the four-wave resonant interaction alone. In contrast, in the case of a directionally confined spectrum, the effect of quasi-resonant wave–wave interaction becomes important, and the wave system becomes unstable. When the temporal change of the spectral shape due to quasi resonance becomes irreversible owing to energetic breaking dissipation, the spectrum rapidly downshifts. Under such extreme conditions, the likelihood of a freak wave is high.
Modeling Influence of Stratification on Lateral Circulation in a Stratified Estuary
Authors: Cheng Peng , Wilson Robert E. , Chant Robert J. , Fugate David C. , Flood Roger D.
Published: April 2009

The dynamics of lateral circulation in the Passaic River estuary is examined in this modeling study. The pattern of lateral circulation varies significantly over a tidal cycle as a result of the temporal variation of stratification induced by tidal straining. During highly stratified ebb tides, the lateral circulation exhibits a vertical two-cell structure. Strong stratification suppresses vertical mixing in the deep channel, whereas the shoal above the halocline remains relatively well mixed. As a result, in the upper layer, the lateral asymmetry of vertical mixing produces denser water on the shoal and fresher water over the thalweg. This density gradient drives a circulation with surface currents directed toward the shoal, and the currents at the base of the pycnocline are directed toward the thalweg. In the lower layer, the lateral circulation tends to reduce the tilting of isopycnals and gradually diminishes at the end of the ebb tide. A lateral baroclinic pressure gradient is a dominant driving force for lateral circulation during stratified ebb tides and is generated by differential diffusion that indicates a lateral asymmetry in vertical mixing. Over the thalweg, vertical mixing is strong during the flood and weak during the ebb. Over the shoal, the tidally periodical stratification shows an opposite cycle of that at the thalweg. Lateral straining tends to enhance stratification during flood tides and vertical diffusion maintains the relatively well-mixed water column over the shoal during the stratified ebb tides.
Numerical Simulations and Observations of Surface Wave Fields under an Extreme Tropical Cyclone
Authors: Fan Yalin , Ginis Isaac , Hara Tetsu , Wright C. Wayne , Walsh Edward J.
Published: April 2009

The performance of the wave model WAVEWATCH III under a very strong, category 5, tropical cyclone wind forcing is investigated with different drag coefficient parameterizations and ocean current inputs. The model results are compared with field observations of the surface wave spectra from an airborne scanning radar altimeter, National Data Buoy Center (NDBC) time series, and satellite altimeter measurements in Hurricane Ivan (2004). The results suggest that the model with the original drag coefficient parameterization tends to overestimate the significant wave height and the dominant wavelength and produces a wave spectrum with narrower directional spreading. When an improved drag parameterization is introduced and the wave–current interaction is included, the model yields an improved forecast of significant wave height, but underestimates the dominant wavelength. When the hurricane moves over a preexisting mesoscale ocean feature, such as the Loop Current in the Gulf of Mexico or a warm- and cold-core ring, the current associated with the feature can accelerate or decelerate the wave propagation and significantly modulate the wave spectrum.
On the Quantitative Low-Level Aerosol Measurements Using Ceilometer-Type Lidar
Authors: Sundström Anu-Maija , Nousiainen Timo , Petäjä Tuukka
Published: April 2009

The objective of this work is to investigate whether a commercial ceilometer-type lidar can be used as a quantitative aerosol measurement instrument. To this end, lidar backscattering measurements are compared with exact theoretical calculations of backscattering, which are based on in situ–measured size distributions and account for uncertainties in particle composition and shape. The results show that the differences between simulated and measured backscattering remain nearly constant and within the uncertainties involved. The differences are most plausibly explained by an error in the overlap function of the lidar and/or errors in the calibration of either the lidar or the in situ instruments used to measure the aerosol size distribution. Occasionally, large differences occur that are obviously connected to the unrepresentativeness of the in situ and lidar measurement volumes because of insufficient atmospheric mixing. The results imply that the absolute accuracy of the instrument investigated might be sufficient for quantitative aerosol measurements in some applications. A fix for the overlap function, however, would be desirable.
Overview of the CALIPSO Mission and CALIOP Data Processing Algorithms
Authors: Winker David M. , Vaughan Mark A. , Omar Ali , Hu Yongxiang , Powell Kathleen A. , Liu Zhaoyan , Hunt William H. , Young Stuart A.
Published: April 2009

The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is a two-wavelength polarization lidar that performs global profiling of aerosols and clouds in the troposphere and lower stratosphere. CALIOP is the primary instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite, which has flown in formation with the NASA A-train constellation of satellites since May 2006. The global, multiyear dataset obtained from CALIOP provides a new view of the earth’s atmosphere and will lead to an improved understanding of the role of aerosols and clouds in the climate system. A suite of algorithms has been developed to identify aerosol and cloud layers and to retrieve a variety of optical and microphysical properties. CALIOP represents a significant advance over previous space lidars, and the algorithms that have been developed have many innovative aspects to take advantage of its capabilities. This paper provides a brief overview of the CALIPSO mission, the CALIOP instrument and data products, and an overview of the algorithms used to produce these data products.
Next-Day Convection-Allowing WRF Model Guidance: A Second Look at 2-km versus 4-km Grid Spacing
Authors: Schwartz Craig S. , Kain John S. , Weiss Steven J. , Xue Ming , Bright David R. , Kong Fanyou , Thomas Kevin W. , Levit Jason J. , Coniglio Michael C.
Published: April 2009

During the 2007 NOAA Hazardous Weather Testbed (HWT) Spring Experiment, the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma produced convection-allowing forecasts from a single deterministic 2-km model and a 10-member 4-km-resolution ensemble. In this study, the 2-km deterministic output was compared with forecasts from the 4-km ensemble control member. Other than the difference in horizontal resolution, the two sets of forecasts featured identical Advanced Research Weather Research and Forecasting model (ARW-WRF) configurations, including vertical resolution, forecast domain, initial and lateral boundary conditions, and physical parameterizations. Therefore, forecast disparities were attributed solely to differences in horizontal grid spacing. This study is a follow-up to similar work that was based on results from the 2005 Spring Experiment. Unlike the 2005 experiment, however, model configurations were more rigorously controlled in the present study, providing a more robust dataset and a cleaner isolation of the dependence on horizontal resolution. Additionally, in this study, the 2- and 4-km outputs were compared with 12-km forecasts from the North American Mesoscale (NAM) model. Model forecasts were analyzed using objective verification of mean hourly precipitation and visual comparison of individual events, primarily during the 21- to 33-h forecast period to examine the utility of the models as next-day guidance. On average, both the 2- and 4-km model forecasts showed substantial improvement over the 12-km NAM. However, although the 2-km forecasts produced more-detailed structures on the smallest resolvable scales, the patterns of convective initiation, evolution, and organization were remarkably similar to the 4-km output. Moreover, on average, metrics such as equitable threat score, frequency bias, and fractions skill score revealed no statistical improvement of the 2-km forecasts compared to the 4-km forecasts. These results, based on the 2007 dataset, corroborate previous findings, suggesting that decreasing horizontal grid spacing from 4 to 2 km provides little added value as next-day guidance for severe convective storm and heavy rain forecasters in the United States.
Radar Refractivity Retrievals in Oklahoma: Insights into Operational Benefits and Limitations
Authors: Heinselman P. L. , Cheong B. L. , Palmer R. D. , Bodine D. , Hondl K.
Published: April 2009

The 2007 and 2008 spring refractivity experiments at KTLX investigated the potential utility of high-resolution, near-surface refractivity measurements to operational forecasting. During these experiments, forecasters at the Norman, Oklahoma, National Weather Service Forecast Office (NWSFO) assessed refractivity and scan-to-scan refractivity change fields retrieved from the Weather Surveillance Radar-1988 Doppler weather radar near Oklahoma City—Twin Lakes, Oklahoma (KTLX). Both quantitative and qualitative analysis methods were used to analyze the 41 responses from seven forecasters to a questionnaire designed to measure the impact of refractivity fields on forecast operations. The analysis revealed that forecasts benefited from the refractivity fields on 25% of the days included in the evaluation. In each of these cases, the refractivity fields provided complementary information that somewhat enhanced the forecasters’ capability to analyze the near-surface environment and boosted their confidence in moisture trends. A case in point was the ability to track a retreating dryline after its location was obscured by a weak reflectivity bloom caused by biological scatterers. Forecasters unanimously agreed, however, that the impact of this complementary information on their forecasts was too insignificant to justify its addition as an operational dataset. The applicability of these findings to other NWSFOs may be limited to locations with similar weather situations and access to surface data networks like the Oklahoma Mesonet.
Illuminating the Downside of Social Capital
Authors: Browning Christopher R.
Published: April 2009

The potential “downside” of social capital has received relatively limited attention in research to date. In this article, the author presents a theoretical approach to urban crime and criminogenic conditions that emphasizes the potential for competition between two types of social capital, social network—based reciprocated exchange and collective efficacy, in the regulation of neighborhood crime. This “negotiated coexistence” approach hypothesizes that as network interaction and reciprocated exchange among neighborhood residents increase, offenders and conventional residents become increasingly interdependent. In turn, the social capital provided by network integration of offenders may diminish the regulatory effectiveness of collective efficacy. Using data from the 1990 Census and the 1994-1995 Project on Human Development in Chicago Neighborhoods Community Survey, the author tests the negotiated-coexistence model against competing expectations regarding the association between networks, collective efficacy, and crime. Consistent with the negotiated-coexistence approach, ordinary least squares and spatial regression models of property crime and social disorder indicate that the regulatory effects of collective efficacy on crime are reduced in neighborhoods characterized by high levels of network interaction and reciprocated exchange.