bluuebunny/crossref_metadata_2025 huggingface dataset:
Elevated flux of cosmic spherules (micrometeorites) in Ordovician rocks of the Durness Group, NW Scotland
Authors: Dredge Ian , Parnell John , Lindgren Paula , Bowden Stephen
Published: May 2010

Synopsis

Limestone samples from the Cambro-Ordovician Durness Group were crushed, acid-digested and searched for evidence of micrometeorites. Eleven melted micrometeorites were extracted from the magnetic fraction of samples from the Balnakeil and Croisaphuill formations near the top of the group. Other formations in the Durness Group did not yield micrometeorites. Only melted spherules with a distinctive dendroidal crystalline structure (I-type cosmic spherules) were accepted as definite micrometeorites. They represent a flux of micrometeorites one to two orders of magnitude greater than at present. The micrometeorite-bearing formations are of Arenig age, coincident with the onset of an enhanced flux of extraterrestrial material identified by the occurrence of fossil meteorites in Sweden.
Discriminating faunal assemblages and their palaeoecology based on museum collections: the Carboniferous Hurlet and Index limestones of western Scotland
Authors: Dean M. T. , Owen A. W. , Bowdler-Hicks A. , Akhurst M. C.
Published: May 2010

Synopsis

Historical collections of Scottish Carboniferous macrofossils stored at the British Geological Survey (BGS), Edinburgh include the sole remaining sources of palaeontological data from numerous localities. Exploratory numerical analyses of such collections from the Hurlet and Index limestones of Ayrshire compare favourably with published qualitative assessments of faunal assemblages and palaeoenvironments; demonstrating that old collections can still be used in modern palaeoecological investigations. Macrofaunas from these formations comprise mainly brachiopods and molluscs and were collected from 67 localities that yielded 20 and 94 samples from the Hurlet and Index limestones respectively. Limitations of the presence/absence data were partly overcome by consolidation and restriction of aspects of the data set. Seriation indicates the lithological and environmental gradients of taxa. Cluster analysis reveals groups of samples linked to lithofacies. Principal Components Analysis (PCA) of diversity data derived from the data set in terms of numbers of genera in higher taxa highlights differences in gross taxonomic composition in terms of trophic structure, lithology and environment.

Supplementary material: lists of localities taxa and sample lithologies used in this study are available at
http://www.geolsoc.org.uk/SUP18401
.
Structure and evolution of the Lewisian Gairloch shear zone: variable movement directions in a strike-slip regime
Authors: Park R.G.
Published: May 2010

Synopsis

The Gairloch shear zone (GSZ) has long been regarded as a dextral strike-slip shear zone with a northwesterly plunging shear direction. However, the original strain analysis applies only to the northeastern third of the zone and the structure of the remaining two-thirds is considerably more complex. The 6.5 km wide GSZ was formed during late Laxfordian (D3) deformation at
c
. 1.7 Ga. It was a product of the interaction of D3 folding and dextral strike-slip shear under retrogressive greenschist-facies metamorphism on rocks previously intensely deformed by early Laxfordian (D2) deformation in amphibolite-facies.

The GSZ is divided into four units across strike: the
Northeastern shear zone
with NW-plunging D3 linear fabric; the
Flowerdale belt
with SE-plunging D2 linear fabric and low D3 strain; the
Ard belt
with steeply plunging F3 folds; and the
Southwestern shear zone,
with SE-plunging D3 lineation. Thus the GSZ consists of two high-strain D3 shear zones on either side of a central low-strain belt. Although consistently dextral strike-slip throughout, the D3 shear regime varies from NE-up in the Northeastern shear zone through sub-horizontal strike-slip in the Ard belt to SW-up in the Southwestern shear zone. This variation may have been caused by local uplift or depression induced by variations in geometry of the walls of the strike-slip system. A revised very approximate minimum estimate of the horizontal component of dextral shear is
c
. 9.5 km with a net NE-up vertical component of
c
. 5.5 km. Similarities in structure between the GSZ and the South Harris belt strengthen the case for these two zones to have been part of the same structure.
Uretero-Iliac Artery Fistula: A Diagnostic and Therapeutic Challenge
Authors: Aslam Muhammad Z. , Kheradmund Ferhad , Patel Nilay , Cranston David
Published: May 2010

Uretero-Iliac artery fistulas (UAFs) are very uncommon in urological practice. The rarity of this clinical entity may lead to a delayed or missed diagnosis which can result in life-threatening consequences. We present a case of a right ureteric and right external iliac artery fistula, its presentation, diagnosis, and management along with the review of the literature.
Maternal-Zygotic Epistasis and the Evolution of Genetic Diseases
Authors: Priest Nicholas K. , Wade Michael J.
Published: May 2010

Many birth defects and genetic diseases are expressed in individuals that do not carry the disease causing alleles. Genetic diseases observed in offspring can be caused by gene expression in mothers and by interactions between gene expression in mothers and offspring. It is not clear whether the underlying pattern of gene expression (maternal versus offspring) affects the incidence of genetic disease. Here we develop a 2-locus population genetic model with epistatic interactions between a maternal gene and a zygotic gene to address this question. We show that maternal effect genes that affect disease susceptibility in offspring persist longer and at higher frequencies in a population than offspring genes with the same effects. We find that specific forms of maternal-zygotic epistasis can maintain disease causing alleles at high frequencies over a range of plausible values. Our findings suggest that the strength and form of epistasis and the underlying pattern of gene expression may greatly influence the prevalence of human genetic diseases.
Parametric and Nonparametric Empirical Regression Models: Case Study of Copper Bromide Laser Generation
Authors: Gocheva-Ilieva S. G. , Iliev I. P.
Published: May 2010

In order to model the output laser power of a copper bromide laser with wavelengths of 510.6 and 578.2 nm we have applied two regression techniques—multiple linear regression and multivariate adaptive regression splines. The models have been constructed on the basis of PCA factors for historical data. The influence of first‐ and second‐order interactions between predictors has been taken into account. The models are easily interpreted and have good prediction power, which is established from the results of their validation. The comparison of the derived models shows that these based on multivariate adaptive regression splines have an advantage over the others. The obtained results allow for the clarification of relationships between laser generation and the observed laser input variables, for better determining their influence on laser generation, in order to improve the experimental setup and laser production technology. They can be useful for evaluation of known experiments as well as for prediction of future experiments. The developed modeling methodology is also applicable for a wide range of similar laser devices—metal vapor lasers and gas lasers.
Photoelastic Stress Analysis Surrounding Implant-Supported Prosthesis and Alveolar Ridge on Mandibular Overdentures
Authors: da Silva Dorival Pedroso , Cazal Claudia , Almeida Fernanda Campos Sousa de , Dias Reinaldo Brito e , Ballester Rafael Yagüe
Published: May 2010

The purpose of this research was to evaluate the maximum stress around osseointegrated implants and alveolar ridge, in a mandible with left partial resection through a photoelastic mandibular model. The first group consisted of two implants: traditional model (T), implants placed in the position of both canines; fulcrum model (F), implants placed in the position of left canine CL and right lateral incisor LiR. Both models linked through a bar and clips. The second group was consisted of three implants, with implants placed in the position of both canines (CR and CL) and the right lateral incisor (LiR), which composed four groups: (1) model with 3 “O” rings, (2) model 2 ERAs, bar with clips, (3) model 2 ERAs bar without clips; (4) model “O” ring bar and ERA. An axial and an oblique load of 6.8 kgf was applied on a overdenture at the 1st Pm, 2nd Pm, and 1st M. Results showed that the area around the left canine (CL) was practically free of stress; the left lateral incisor (LiL) developed only small tensions, and low stress in all the other cases; the right canine tooth suffered the largest concentrations of stress, mainly with the ERA retention mechanism.
Poor Accuracy of Methods Currently Used to Determine Umbilical Catheter Insertion Length
Authors: Verheij Gerdina H. , te Pas Arjan B. , Witlox Ruben S. G. M. , Smits-Wintjens Vivianne E. H. J. , Walther Frans J. , Lopriore Enrico
Published: May 2010

This study compares the methods of Dunn and Shukla in determining the appropriate insertion length of umbilical catheters. In July 2007, we changed our policy for umbilical catheter insertions from the method of Dunn to the method of Shukla. We report our percentage of inaccurate placement of umbilical-vein catheters (UVCs) and umbilical-artery catheters (UACs) before and after the change of policy. In the Dunn-group, 41% (28/69) of UVCs were placed directly in the correct position against 24% (20/84) in the Shukla-group. The position of the catheter-tip of UVCs in the Dunn-group and the Shukla-group was too high in 57% (39/69) and 75% (63/84) of neonates, respectively. UACs in the Dunn-group were placed directly in the correct position in 63% (24/38) compared to the 87% (39/45) of cases in Shukla-group. The position of the catheter-tip of UACs in the Dunn-group and the Shukla-group was too high in 34% (13/38) and 13% (6/45) of neonates, respectively. In conclusion, the Dunn-method is more accurate than the Shukla-method in predicting the insertion length for UVCs, whereas the Shukla-method is more accurate for UACs.
Minimally Cytotoxic Doses of Temozolomide Produce Radiosensitization in Human Glioblastoma Cells Regardless of MGMT Expression
Authors: Bobola Michael S. , Kolstoe Douglas D. , Blank A. , Silber John R.
Published: May 2010

Concurrent treatment with the methylating agent temozolomide during radiotherapy has yielded the first significant improvement in the survival of adult glioblastomas (GBM) in the last three decades. However, improved survival is observed in a minority of patients, most frequently those whose tumors display CpG methylation of the O6-methylguanine (O6-meG)-DNA methyltransferase (MGMT) promoter, and adult GBMs remain invariably fatal. Some, although not all, preclinical studies have shown that temozolomide can increase radiosensitivity in GBM cells that lack MGMT, the sole activity in human cells that removes O6-meG from DNA. Here, we systematically examined the temozolomide dose dependence of radiation killing in established GBM cell lines that differ in ability to remove O6-meG or tolerate its lethality. Our results show that minimally cytotoxic doses of temozolomide can produce dose-dependent radiosensitization in MGMT-deficient cells, MGMT-proficient cells, and MGMT-deficient cells that lack mismatch repair, a process that renders cells tolerant of the lethality of O6-meG. In cells that either possess or lack MGMT activity, radiosensitization requires exposure to temozolomide before but not after radiation and is accompanied by formation of double-strand breaks within 45 minutes of radiation. Moreover, suppressing alkyladenine-DNA glycosylase, the only activity in human cells that excises 3-methyladenine from DNA, reduces the temozolomide dose dependence of radiosensitization, indicating that radiosensitization is mediated by 3-methyladenine as well as by O6-meG. These results provide novel information on which to base further mechanistic study of radiosensitization by temozolomide in human GBM cells and to develop strategies to improve the outcome of concurrent temozolomide radiotherapy. Mol Cancer Ther; 9(5); 1208–18. ©2010 AACR.
Pluripotency of human embryonic and induced pluripotent stem cells for cardiac and vascular regeneration
Authors: Boheler Kenneth R.
Published: May 2010

Cardiac and vascular abnormalities and disease syndromes are major causes of death both during human development and with aging. To identify the cause of congenital defects and to combat this epidemic in the aging population, new models must be created for scientific investigation and new therapies must be developed. Recent advances in pluripotent stem cell biology offer renewed hope for tackling these problems. Of particular importance has been the creation of induced pluripotent (iPS) cells from adult tissues and organs through the forced expression of two to four transcription factors. Moreover, iPS cells, which are phenotypically indistinguishable from embryonic stem (ES) cells, can be generated from any patient. This unique capacity when coupled with samples from patients who have congenital and genetic defects of unknown aetiology should permit the creation of new model systems that foment scientific investigation. Moreover, creation of patient-specific cells should overcome many of the immunological limitations that currently impede therapeutic applications associated with other pluripotent stem cells and their derivatives. The aims of this paper will be to discuss cardiac and vascular diseases and show how iPS cells may be employed to overcome some of the most significant scientific and clinical hurdles facing this field.
Advances in cardiovascular molecular imaging for tracking stem cell therapy
Authors: Ransohoff Katherine J. , Wu Joseph C.
Published: May 2010

The high mortality rate associated with cardiovascular disease is partially due to the lack of proliferative cells in the heart. Without adequate repair following myocardial infarction, progressive dilation can lead to heart failure. Stem cell therapies present one promising option for treating cardiovascular disease, though the specific mechanisms by which they benefit the heart remain unclear. Before stem cell therapies can be used safely in human populations, their biology must be investigated using innovative technologies such as multi-modality molecular imaging. The present review will discuss the basic principles, labelling techniques, clinical applications, and drawbacks associated with four major modalities: radionuclide imaging, magnetic resonance imaging, bioluminescence imaging, and fluorescence imaging.
Comparison of methods for monitoring residual platelet reactivity after clopidogrel by point-of-care tests on whole blood in high-risk patients
Authors: Antonucci Emilia , Maggini Niccolò , Miranda Marco , Gori Anna , Marcucci Rossella , Giusti Betti , Balzi Daniela , Prisco Domenico , Abbate Rosanna , Paniccia Rita
Published: May 2010

Cardiovascular events are more frequent in high-risk coronary artery disease (CAD) patients on dual antiplatelet therapy with a residual platelet reactivity (RPR) than in those showing inhibition of ADP-inducible platelet activation. It is known that post-interventional RPR is a clinically important entity confirming it as a risk factor for thrombo-is-chaemic events. Multiple electrode platelet aggregometry (MEA) on whole blood has been recently proposed as a rapid tool to evaluate RPR in high-risk CAD patients on clopidogrel therapy. It was the aim of this study to detect RPR in 801 high-risk CAD patients on dual antiplatelet therapy comparing MEA with the VerifyNow P2Y12 assay on whole blood and classical light transmission aggregation (LTA) on plateletrich plasma. ADP (10 μM) was employed as agonist for MEA and LTA. The prevalence of RPR was 20.6% by MEA, 16.1% by LTA and 30.8% by VerifyNow. MEA showed a significant correlation (rho=0.62, p<0.0001) with VerifyNow and a moderate agreement (k=0.52, p<0.001) with 81.5% of concordant values. A significant correlation was found between MEA and LTA (rho=0.71, p<0.001) with a good agreement (k=0.63, p<0.001) and 88.8% of concordant values. MEA in relation to LTA showed a sensitivity of 80% and a specificity of 91%. MEA might represent a reliable method and valid alternative in comparison with other available platelet function assays. It might help to guide antiplatelet therapy and thus improve clinical outcome of high-risk CAD patients.
Characterisation and validity of inflammatory biomarkers in the prediction of post-operative atrial fibrillation in coronary artery disease patients
Authors: Kaireviciute Diana , D. Blann Andrew , Balakrishnan Balu , Lane Deirdre A. , Patel Jeetesh V. , Uzdavinys Giedrius , Norkunas Gediminas , Kalinauskas Gintaras , Sirvydis Vytautas , Aidietis Audrius , Lip Gregory Y. H.
Published: May 2010

Atrial fibrillation (AF) is a common complication of coronary artery bypass grafting (CABG). We sought to determine the diagnostic validity of plasma biomarkers of i) inflammation (marked by interleukin-6 [IL-6] and high-sensitivity C-reactive protein [hs-CRP]), ii) extracellular matrix remodelling (matrix metalloproteinase [MMP-9], tissue inhibitor of matrix metalloproteinase [TIMP-1]) and iii) the prothrombotic state (tissue factor and von Willebrand factor [vWF]) in the risk prediction of post-operative AF. Samples were obtained preoperatively from peripheral/femoral vein and from intracardiac chambers (right atrium [RA], the right atrial appendage [RAA], the left atrium [LA] and the left atrial appendage [LAA]) amongst 100 consecutive patients free of AF and inflammatory disease undergoing elective CABG. Biomarker concentrations were related to incident AF (30 days). At 30 days post CABG, 30 patients were proven to have had AF. Concentrations of tissue factor (TF) and vWF were unrelated to postoperative AF. Peripheral (p=0.018), and intracardiac levels (RAA (p=0.029) and LA (p=0.026)) of hs-CRP were associated with the presence of AF after CABG. Intracardiac levels of IL-6 in samples from the RAA (p=0.031), LA (p=0.042) and LAA (p=0.006), and MMP-9 in the LAA sample were also associated with AF (p=0.007). Our data suggest that an intra-cardiac inflammatory environment that is manifest peri-operatively may predispose to the development of post-operative AF. This intracardiac inflammatory state was reflected by increased peripheral hs-CRP levels. These differences may indicate local substrate abnormalities contributing to the development of AF post-operatively.
The effects of low-molecular-weight heparin at two different dosages on thrombin generation in cancer patients.
Authors: Traby Ludwig , Kaider Alexandra , Schmid Rainer , Kranz Alexander , Quehenberger Peter , Kyrle Paul A. , Eichinger Sabine
Published: May 2010

Non-surgical cancer patients are at high thrombotic risk. We hypothesised that the prothrombotic state is reflected by elevated thrombin generation and can be mitigated by increasing the low-molecularweight heparin (LMWH) dose. Non-surgical cancer patients were randomised to enoxaparin 40 or 80 mg. D-dimer, prothrombin fragment F1+2 (F1+2) and peak thrombin (PT) were measured 2, 4, 6 hours (h) after LMWH (day 1) and daily for 4 days. A total of 22 and 27 patients received enoxaparin 40 and 80 mg, respectively. D-dimer and F1+2 moderately decreased after 6 h in both groups. After enoxaparin 80 mg, D-dimer baseline levels [median (quartiles)] decreased from day 1 to 4 [1054.9 (549.5, 2714.0) vs. 613.0 (441.1, 1793.5) ng/ml] (p<0.0001), while no difference was seen after 40 mg. Baseline PT levels [median (quartiles)] were 426.2 nM (347.3, 542.3) (40 mg) and 394.0 nM (357.1, 448.8) (80 mg). After 80 mg, PT significantly decreased to 112.4 nM (68.5, 202.4), 57.1 nM (38.0, 101.2) and 43.6 nM (23.4, 112.8) after 2, 4 and 6 h, which was lower than after 40 mg (p=0.003). After 80 mg, PT decreased from day 1 to 4 [358.6 nM (194.2, 436.6); p=0.06] while no difference was seen after 40 mg. In conclusion, in cancer patients coagulation activation and thrombin generation is substantially increased. Peak thrombin levels are sensitive to the anticoagulant effects of LMWH at different dosages. The prothrombotic state is substantially attenuated by higher LMWH doses.
Magical Realism in Libya
Authors: Cooke Miriam
Published: May 2010

This essay argues that the writings of Libyan Ibrāhīm al-Kūnī, and particularly Nazīf al-hajar with its emphasis on animal-human juxtapositions and metamorphoses, should be considered examples of Arab magical realism. The circular narrative tells the story of a multi-generational struggle of a Touareg family with a legendary animal called a waddan. The last scion, he is taken on a trip to the border between the natural and the supernatural where he metamorphoses into the predator, the legendary animal and the history that both contain.
Beyond the Modernity Complex: Abd al-Hakīm Qāsim’s Re-Writing of the Nahdah Self-Narrative
Authors: al-Musawi Muhsin
Published: May 2010

The purpose of this paper is to study Abd al-Hakīm Qāsim’s Ayyām al-insān al-sabah (1969; The Seven Days of Man) and its sequel al-Mahdī (1977) as post-Nahdah self-narratives that leave behind the complex encounter with the West and bypass thereby the modernity binary of a backward tradition versus the offers of a European civilization. The schizophrenic narratives of encounter have confined Arabic narrative and limited its potential to engage individual experience in a dynamic social life. The post-Nahdah narrative interrogates other facts on the ground that relate to the nation-state, selfhood, family, communal life and religion. Abd al-Hakīm Qāsim’s Ayyām al-insān al-sabah is a pioneering text in this respect and deserves full attention in order to understand the radical shift in Arabic literature after 1967. Its mode of self-narration is not subservient to the canonical autobiography of Tāhā Husayn, and its unfolding takes place among contending powers where space implicates characters in action and enables human agency to have full play beyond the Nahdah legacy of cultural dependency.
One Face of the Hero: Reading Yahyā Haqqī’s Qindīl Umm Hāshimas Modern Myth
Authors: Bell Gregory J.
Published: May 2010

Yahyā Haqqī’s 1944 novella, Qindīl Umm Hāshim (The Lamp of Umm Hashim), tells the story of a young Egyptian, Ismail, who travels to England to study ophthalmology and returns to Egypt to practice medicine. The often fraught relationship between Egypt and the West is reflected in the difficulties Ismail faces, first in England and then in Egypt after his return. This paper argues that Qindīl Umm Hāshim is a modern myth which follows the universal “monomythic” pattern identified by Joseph Campbell. By reading the story as a myth, the paper provides insight into the meaning and structure of Haqqī’s novella. Why Haqqī chose to draw upon the genre of myth is discussed, as is his use and disruption of the monomythic pattern and the ways in which this allows him to comment upon Egypt’s relationship with the West.
Disorientation and the Metropolis in Hudā Barakāt’s Hārith al-miyāh
Authors: Amin Dina
Published: May 2010

In Hārith al-miyāh (The Tiller of Waters, 1998) Hudā Barakāt departs from traditional war narratives to unravel the horrors of war by depicting a protagonist whose life is reduced to an animal-like existence and whose relationship with space and time disorients both him and the reader. To preserve knowledge of his self, and to safeguard his homeland from complete annihilation, he reconstructs its history by telling stories to his beloved about Lebanon’s textiles industry. Through this alternative national ‘history,’ he tries to re-orient himself with (and within) his metropolis as it becomes a war-ravished wasteland. As he recreates his nation through oral narration, he also reintegrates its (now) scattered and conflicting communities as he recalls them into his narratives. This essay argues that the knowledge of history challenges disorientation and can become a means by which to defend the metropolis from erasure.
Loss and Memory: The Exilic Nihilism of Wadī Saādah, Australia’s Lebanese Émigré Poet
Authors: Burt Clarissa
Published: May 2010

Wadī Saādah, poet of the new Lebanese Mahjar, writes the loss and alienation which have been salient features of the experience the generation who came of age in the early 1970s and witnessed the horrors of recent Lebanese history. In his inimitable prose-poetic style, he documents the existential vortex which draws him in, but from which his poems escape as exquisite flares shot from afar, illuminating for us brilliantly, briefly where he has gone, tracers of personal, generational, and historical dissolution.
Three Recent Flavors of Drought in the Pacific Northwest
Authors: Bumbaco Karin A. , Mote Philip W.
Published: May 2010

In common with much of the western United States, the Pacific Northwest (defined in this paper as Washington and Oregon) has experienced an unusual number of droughts in the past decade. This paper describes three of these droughts in terms of the precipitation, temperature, and soil moisture anomalies, and discusses different drought impacts experienced in the Pacific Northwest (PNW). For the first drought, in 2001, low winter precipitation in the PNW produced very low streamflow that primarily affected farmers and hydropower generation. For the second, in 2003, low summer precipitation in Washington (WA), and low summer precipitation and a warm winter in Oregon (OR) primarily affected streamflow and forests. For the last, in 2005, a lack of snowpack due to warm temperatures during significant winter precipitation events in WA, and low winter precipitation in OR, had a variety of different agricultural and hydrologic impacts. Although the proximal causes of droughts are easily quantified, the ultimate causes are not as clear. Better precipitation observations in the PNW are required to provide timely monitoring of conditions leading to droughts to improve prediction in the future.
Particle Growth and Drop Collection Efficiency of Warm Clouds as Inferred from Joint CloudSat and MODIS Observations
Authors: Suzuki Kentaroh , Nakajima Takashi Y. , Stephens Graeme L.
Published: May 2010

This study describes an approach for combining CloudSat and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations to investigate the microphysical processes of warm clouds on the global scale. MODIS column optical thickness is vertically distributed between the cloud top and cloud bottom according to adiabatic and condensational growth assumptions and used as a vertical coordinate system to analyze profiles of CloudSat-observed radar reflectivity. The reflectivity profiles thus rescaled as a function of the in-cloud optical depth clearly depict how the cloud-to-rain particle growth processes take place within the cloud layer and how these processes vary systematically with variations in MODIS-derived effective particle radius. It is also found that the effective radii retrieved using two different wavelengths of MODIS tend to trace the microphysical change of reflectivity profiles in a different way because of the difference in the layer depth that characterizes these two effective radii.

The reflectivity profiles as a function of optical depth are also interpreted in terms of drop collection processes based on the continuous collection model. The slope of the reflectivity change with optical depth provides a gross measure of the collection efficiency factor. The systematic changes of reflectivity profiles with MODIS-derived particle sizes are then interpreted as demonstrating a strong dependency of the collection efficiency on particle size. These results provide a quantitative insight into the drop collection process of warm clouds in the real atmosphere.
Free and Forced Variability of the Tropical Atlantic Ocean: Role of the Wind–Evaporation–Sea Surface Temperature Feedback
Authors: Mahajan Salil , Saravanan R. , Chang Ping
Published: May 2010

The role of the wind–evaporation–sea surface temperature (WES) feedback in the low-frequency natural variability of the tropical Atlantic is studied using an atmospheric global climate model—the NCAR Community Climate Model, version 3 (CCM3)—thermodynamically coupled to a slab ocean model (SOM). The coupled model is modified to suppress the WES feedback and is compared to a control run. Singular value decomposition (SVD) analysis over the tropical Atlantic reveals that the coupled meridional mode of the Atlantic Ocean is amplified in the presence of the WES feedback. In its absence, the meridional mode still exists, but with a weaker amplitude. A feedback mechanism that involves the near-surface specific humidity is proposed to sustain the weaker Atlantic meridional mode in the absence of the WES feedback. Similar analysis of coupled model integrations when forced with an artificial El Niño–Southern Oscillation (ENSO)-like SST cycle in the Pacific reveals that in the presence of the WES feedback, the meridional mode is the preferred mode of response of the tropical Atlantic to ENSO forcing. In the absence of the WES feedback, the tropical Atlantic response is unlike the meridional mode and the effects of tropospheric warming and subsidence dominate. Regression analysis over the tropical Atlantic reveals that the meridional mode response to ENSO peaks in the spring and begins to decay in the fall in the coupled model in the presence of the WES feedback. The WES feedback also appears to be responsible for the northward migration of the ITCZ during ENSO events.
A Coupled Dynamical Ocean–Energy Balance Atmosphere Model for Paleoclimate Studies
Authors: Ritz Stefan P. , Stocker Thomas F. , Joos Fortunat
Published: May 2010

The Bern3D coupled three-dimensional dynamical ocean–energy balance atmosphere model is introduced and the atmospheric component is discussed in detail. The model is of reduced complexity, developed to perform extensive sensitivity studies and ensemble simulations extending over several glacial–interglacial cycles. On large space scales, the modern steady state of the model compares well with observations. In a first application, several 800 000-yr simulations with prescribed orbital, greenhouse gas, and ice sheet forcings are performed. The model shows an increase of Atlantic meridional overturning circulation strength at glacial inceptions followed by a decrease throughout the glaciation and ending in a circulation at glacial maxima that is weaker than at present. The sensitivity of ocean temperature to atmospheric temperature, Atlantic meridional overturning circulation (AMOC), and Antarctic bottom water (AABW) strength is analyzed at 23 locations. In a second application the climate sensitivities of the modern and of the Last Glacial Maximum (LGM) state are compared. The temperature rise for a doubling of the CO2 concentration from LGM conditions is 4.3°C and thus notably larger than in the modern case (3°C). The relaxation time scale is strongly dependent on the response of AABW to the CO2 change, since it determines the ventilation of the deep Pacific and Indian Ocean.
Notes on a Catastrophe: A Feedback Analysis of Snowball Earth
Authors: Roe Gerard H. , Baker Marcia B.
Published: May 2010

The language of feedbacks is ubiquitous in contemporary earth sciences, and the framework of feedback analysis is a powerful tool for diagnosing the relative strengths of the myriad mutual interactions that occur in complex dynamical systems. The ice albedo feedback is widely taught as the classic example of a climate feedback. Moreover, its potential to initiate a collapse to a completely glaciated snowball earth is widely taught as the classic example of a climate “tipping point.” A feedback analysis of the snowball earth phenomenon in simple, zonal mean energy balance models clearly reveals the physics of the snowball instability and its dependence on climate parameters. The analysis can also be used to illustrate some fundamental properties of climate feedbacks: how feedback strength changes as a function of mean climate state; how small changes in individual feedbacks can cause large changes in the system sensitivity; and last, how the strength and even the sign of the feedback is dependent on the climate variable in question.
Decadal Variability in a Central Greenland High-Resolution Deuterium Isotope Record and Its Relationship to the Frequency of Daily Atmospheric Circulation Patterns from the North Atlantic Region
Authors: Rimbu Norel , Lohmann Gerrit
Published: May 2010

The variability of an annual resolution deuterium time series from central Greenland is investigated in connection with the variability in the frequency of daily atmospheric circulation patterns in the North Atlantic region. Statistical analysis reveals that a large part of the decadal variability of the deuterium isotope record is related to decadal variability in the frequency of several identified daily circulation patterns. The study shows that these circulation patterns induce variations in the deuterium record by altering where isotopic fractionation occurs, mainly during the passage of the associated air masses over continental areas. The study identifies three significant periodic components in the deuterium isotope record at ∼12, ∼20, and ∼30 yr. It also shows that the ∼20-yr signal in the deuterium isotope record is related to the variability in the frequency of a winter circulation type. An analysis of six oxygen isotope records from central Greenland reveals decadal variations similar to the deuterium isotope record. The authors argue that high-resolution stable isotope records from Greenland ice cores can be used to obtain information about the frequency of certain daily circulation patterns during past periods.
Assessment of Extreme Quantitative Precipitation Forecasts and Development of Regional Extreme Event Thresholds Using Data from HMT-2006 and COOP Observers
Authors: Ralph F. M. , Sukovich E. , Reynolds D. , Dettinger M. , Weagle S. , Clark W. , Neiman P. J.
Published: May 2010

Extreme precipitation events, and the quantitative precipitation forecasts (QPFs) associated with them, are examined. The study uses data from the Hydrometeorology Testbed (HMT), which conducted its first field study in California during the 2005/06 cool season. National Weather Service River Forecast Center (NWS RFC) gridded QPFs for 24-h periods at 24-h (day 1), 48-h (day 2), and 72-h (day 3) forecast lead times plus 24-h quantitative precipitation estimates (QPEs) from sites in California (CA) and Oregon–Washington (OR–WA) are used. During the 172-day period studied, some sites received more than 254 cm (100 in.) of precipitation. The winter season produced many extreme precipitation events, including 90 instances when a site received more than 7.6 cm (3.0 in.) of precipitation in 24 h (i.e., an “event”) and 17 events that exceeded 12.7 cm (24 h)−1 [5.0 in. (24 h)−1]. For the 90 extreme events {>7.6 cm (24 h)−1 [3.0 in. (24 h)−1]}, almost 90% of all the 270 QPFs (days 1–3) were biased low, increasingly so with greater lead time. Of the 17 observed events exceeding 12.7 cm (24 h)−1 [5.0 in. (24 h)−1], only 1 of those events was predicted to be that extreme. Almost all of the extreme events correlated with the presence of atmospheric river conditions. Total seasonal QPF biases for all events {i.e., ≥0.025 cm (24 h)−1 [0.01 in. (24 h)−1]} were sensitive to local geography and were generally biased low in the California–Nevada River Forecast Center (CNRFC) region and high in the Northwest River Forecast Center (NWRFC) domain. The low bias in CA QPFs improved with shorter forecast lead time and worsened for extreme events. Differences were also noted between the CNRFC and NWRFC in terms of QPF and the frequency of extreme events. A key finding from this study is that there were more precipitation events >7.6 cm (24 h)−1 [3.0 in. (24 h)−1] in CA than in OR–WA. Examination of 422 Cooperative Observer Program (COOP) sites in the NWRFC domain and 400 in the CNRFC domain found that the thresholds for the top 1% and top 0.1% of precipitation events were 7.6 cm (24 h)−1 [3.0 in. (24 h)−1] and 14.2 cm (24 h)−1 [5.6 in. (24 h)−1] or greater for the CNRFC and only 5.1 cm (24 h)−1 [2.0 in. (24 h)−1] and 9.4 cm (24 h)−1 [3.7 in. (24 h)−1] for the NWRFC, respectively. Similar analyses for all NWS RFCs showed that the threshold for the top 1% of events varies from ∼3.8 cm (24 h)−1 [1.5 in. (24 h)−1] in the Colorado Basin River Forecast Center (CBRFC) to ∼5.1 cm (24 h)−1 [3.0 in. (24 h)−1] in the northern tier of RFCs and ∼7.6 cm (24 h)−1 [3.0 in. (24 h)−1] in both the southern tier and the CNRFC. It is recommended that NWS QPF performance in the future be assessed for extreme events using these thresholds.
Scale Dependence of Radar Rainfall Uncertainty: Initial Evaluation of NEXRAD’s New Super-Resolution Data for Hydrologic Applications
Authors: Seo Bong-Chul , Krajewski Witold F.
Published: May 2010

This study explores the scale effects of radar rainfall accumulation fields generated using the new super-resolution level II radar reflectivity data acquired by the Next Generation Weather Radar (NEXRAD) network of the Weather Surveillance Radar-1988 Doppler (WSR-88D) weather radars. Eleven months (May 2008–August 2009, exclusive of winter months) of high-density rain gauge network data are used to describe the uncertainty structure of radar rainfall and rain gauge representativeness with respect to five spatial scales (0.5, 1, 2, 4, and 8 km). While both uncertainties of gauge representativeness and radar rainfall show simple scaling behavior, the uncertainty of radar rainfall is characterized by an almost 3 times greater standard error at higher temporal and spatial resolutions (15 min and 0.5 km) than at lower resolutions (1 h and 8 km). These results may have implications for error propagation through distributed hydrologic models that require high-resolution rainfall input. Another interesting result of the study is that uncertainty obtained by averaging rainfall products produced from the super-resolution reflectivity data is slightly lower at smaller scales than the uncertainty of the corresponding resolution products produced using averaged (recombined) reflectivity data.
The University of South Alabama Mesonet and Coastal Observing System: A Technical and Statistical Overview
Authors: Kimball Sytske K. , Mulekar Madhuri S. , Cummings Shailer , Stamates Jack
Published: May 2010

The University of South Alabama Mesonet consists of 26 sites across the north-central Gulf of Mexico coast. Although the original purpose of the mesonet was monitoring landfalling tropical systems, meteorological data are collected and disseminated every 5 min year-round to serve a multitude of purposes, including weather forecasting, education, and research. In this paper a statistical analysis and like-sensor comparison demonstrates that variables, measured by different sensor types or by sensors at different heights, correlate well. The benefits of sensor redundancy are twofold, offering 1) backup sensors in the case of sensor failure during severe weather and 2) the ability to perform a large number of internal consistency checks for quality control purposes. An oceanographic compliment to the University of South Alabama Mesonet system, which was deployed by NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) to measure surface waves and ocean currents in an area south of Mobile, Alabama, is described. A preliminary comparison of mesonet wind data and ocean wave data show good agreement, offering promising opportunities for future research.
Deployment of a Tethered-Balloon System for Microphysics and Radiative Measurements in Mixed-Phase Clouds at Ny-Ålesund and South Pole
Authors: Lawson R. Paul , Stamnes Knut , Stamnes Jakob , Zmarzly Pat , Koskuliks Jeff , Roden Chris , Mo Qixu , Carrithers Michael , Bland Geoffrey L.
Published: May 2010

A tethered-balloon system capable of making microphysical and radiative measurements in clouds is described and examples of measurements in boundary layer stratus clouds in the Arctic and at the South Pole are presented. A 43-m3 helium-filled balloon lofts an instrument package that is powered by two copper conductors in the tether. The instrument package can support several instruments, including, but not limited to, a cloud particle imager; a forward-scattering spectrometer probe; temperature, pressure, humidity, and wind sensors; ice nuclei filters; and a 4-π radiometer that measures actinic flux at 500 and 800 nm. The balloon can stay aloft for an extended period of time (in excess of 24 h) and conduct vertical profiles up to about 1–2 km, contingent upon payload weight, wind speed, and surface elevation. Examples of measurements in mixed-phase clouds at Ny-Ålesund, Svalbard (79°N), and at the South Pole are discussed. The stratus clouds at Ny-Ålesund ranged in temperature from 0° to −10°C and were mostly mixed phase with heavily rimed ice particles, even when cloud-top temperatures were warmer than −5°C. Conversely, mixed-phase clouds at the South Pole contained regions with only water drops at temperatures as cold as −32°C and were often composed of pristine ice crystals. The radiative properties of mixed-phase clouds are a critical component of radiative transfer in polar regions, which, in turn, is a lynch pin for climate change on a global scale.
Determination of a Consistent Time for the Extratropical Transition of Tropical Cyclones. Part I: Examination of Existing Methods for Finding “ET Time”
Authors: Kofron David E. , Ritchie Elizabeth A. , Tyo J. Scott
Published: May 2010

As a tropical cyclone moves poleward and interacts with the midlatitude circulation, the question of whether it will undergo extratropical transition (ET) and, if it does, whether it will reintensify or dissipate, is a complex problem. Several quantities have been proposed in previous studies to describe extratropical transition including frontogenesis, 500-hPa geopotential heights, and cyclone phase-space parameters. In this study, these parameters are explored for their utility in defining an ET time using the Navy’s Operational Global Assimilation and Prediction System gridded analyses. The 500-hPa geopotential heights and frontogenesis currently do not have objective numerical definitions. Therefore, this study attempts to establish and examine threshold values that may be used to objectively define the ET time. Cyclone phase space already has numerical threshold values that can be examined.

Results show that the 500-hPa geopotential height open wave distinguishes 81 of 82 cases, but it fails to discriminate between transitioning ET and recurving non-ET cases and cannot be determined automatically. The 2D scalar frontogenesis distinguishes 77 of 82 cases but does not discriminate between transitioning ET and recurving non-ET cases. Finally, phase space successfully distinguishes 81 of 82 cases for the “ET time” defined by the asymmetry parameter but is only successful at capturing transitioning ET and recurving non-ET cases properly for 60 of 82 cases. All of the definitions are found to have disadvantages that preclude them from providing consistent guidance for when extratropical transition of a poleward-recurving tropical cyclone is occurring.
Retrospective Forecasts of the Hurricane Season Using a Global Atmospheric Model Assuming Persistence of SST Anomalies
Authors: Zhao Ming , Held Isaac M. , Vecchi Gabriel A.
Published: May 2010

Retrospective predictions of seasonal hurricane activity in the Atlantic and east Pacific are generated using an atmospheric model with 50-km horizontal resolution by simply persisting sea surface temperature (SST) anomalies from June through the hurricane season. Using an ensemble of 5 realizations for each year between 1982 and 2008, the correlations of the model mean predictions with observations of basin-wide hurricane frequency are 0.69 in the North Atlantic and 0.58 in the east Pacific. In the North Atlantic, a significant part of the degradation in skill as compared to a model forced with observed SSTs during the hurricane season (correlation of 0.78) can be explained by the change from June through the hurricane season in one parameter, the difference between the SST in the main development region and the tropical mean SST. In fact, simple linear regression models with this one predictor perform nearly as well as the full dynamical model for basin-wide hurricane frequency in both the east Pacific and the North Atlantic. The implication is that the quality of seasonal forecasts based on a coupled atmosphere–ocean model will depend in large part on the model’s ability to predict the evolution of this difference between main development region SST and tropical mean SST.
Dominican and Puerto Rican Mother-Adolescent Communication: Maternal Self-Disclosure and Youth Risk Intentions
Authors: Guilamo-Ramos Vincent
Published: May 2010

A communication framework was developed to examine the influence of maternal use of self-disclosure on adolescent intentions to smoke cigarettes and to engage in sexual intercourse. Data were collected from 516 Dominican and Puerto Rican mother-adolescent dyads. Statistical analyses were conducted in AMOS using structural equation modeling. Results indicated that maternal self-disclosure was associated with increased adolescent attributions of maternal trustworthiness and expertise, which in turn were associated with decreases in youths’ intentions to engage in the two risk behaviors.Adolescents’ perceptions were more salient for intentions to engage in risk behavior. Gender and ethnic differences emerged with mothers disclosing more to daughters than to sons and Puerto Rican mothers disclosing more than Dominican mothers. Implications for parent-adolescent communication are discussed.
Intergroup and Within-Group Perceived Discrimination Among U.S.-Born and Foreign-Born Latino Youth
Authors: Córdova David , Cervantes Richard C.
Published: May 2010

Despite the deleterious mental health and health consequences experiences of perceived discrimination can have on ethnic and racial minorities in the United States, a dearth of qualitative studies exist to develop a better understanding of such experiences. As part of a larger study examining psychosocial stress events, and in an effort to fill this gap, this study sought to explore stressful life experiences of intergroup and within-group perceived discrimination among a heterogeneous sample of U.S.-born and foreign-born Latino youth ( n = 170) residing in Los Angeles, California, and Trenton, New Jersey. Focus group methodology was implemented, and data were analyzed using grounded theory and constant comparison method. Findings suggest that Latino youths’ experiences of intergroup and within-group discrimination vary by nativity status and region of the United States. Findings may be helpful for researchers, practitioners, and others working with Latino youth.
The Immigration Debate and Its Relationship to the Ethnic Identity Development and Well-Being of Latino and White Youth
Authors: Roehling Patricia V. , Hernandez Jarvis Lorna , Sprik Jonathan M. , Campbell Precious H.
Published: May 2010

This study collected data from 422 seventh- and eighth-grade adolescents in 2005 and 391 seventh- and eighth-grade adolescents in 2006 in a medium-sized Midwestern community as part of a larger longitudinal study. The 2006 data collection occurred at the height of the national debate about immigration policy and practice. The fortuitous timing of the data collection allowed the authors to compare the responses of seventh- and eighth-grade Latino adolescents surveyed in 2005 with seventh- and eighth-grade students surveyed in 2006 to examine how the debate related to adolescent ethnic identity development and well-being. Using multiple regression analyses the study found evidence that the debate moved eighth-grade Latino students from the undifferentiated stage of ethnic identity development to the exploration stage. Furthermore, it was found that the debate was related to increased levels of acculturative stress and general stress among first-generation eighth-grade Latino students.