bluuebunny/crossref_metadata_2025 huggingface dataset:
HIGHER DIMENSIONAL DUST COSMOLOGICAL IMPLICATIONS OF A DECAY LAW FOR THE Λ TERM: EXPRESSIONS FOR SOME OBSERVABLE QUANTITIES
Authors: KHADEKAR G. S. , PRADHAN ANIRUDH , MOLAEI M. R.
Published: March 2006

We have considered the multidimensional cosmological implications of a decay law for the Λ term that is proportional to [Formula: see text], where β is a constant and a is the scale factor of RW-space–time. We discuss the cosmological consequences of a model for the vanishing pressure for the case k = 0. It has been observed that such models are compatible with the result of recent observations and the cosmological term Λ gradually reduces as the universe expands. In this model, Λ varies as the inverse square of time, which matches its natural units. The proper distance, the luminosity distance-redshift, the angular diameter distance-redshift, and look back time-redshift for the model are presented in the framework of higher dimensional space–time. The model of the Freese et al. (Nucl. Phys. B287, 797 (1987)) for n = 2 is retrieved for the particular choice of A0and also the Einstein–de Sitter model is obtained for [Formula: see text]. This work has thus generalized to higher dimensions the well-known result in four-dimensional space–time. It is found that there may be a significant difference, in principle at least, to the analogous situation in four-dimensional space–time.
A FLUID OF STRINGS AS A VIABLE CANDIDATE FOR THE DARK SIDE OF THE UNIVERSE
Authors: CAPOZZIELLO S. , CARDONE V. F. , LAMBIASE G. , TROISI A.
Published: March 2006

We investigate the possibility that part of the dark matter is not made out of the usual cold dark matter (CDM) dust-like particles, but is in the form of a fluid of strings with barotropic factor ws= -1/3 of cosmic origin. To this aim, we split the dark matter density parameter into two terms and investigate the dynamics of a spatially flat universe filled with baryons, CDM, a fluid of strings and dark energy, modeling the latter as a cosmological constant or a negative pressure fluid with a constant equation of state w < 0. To test the viability of the models and to constrain their parameters, we use the Type Ia supernovae Hubble diagram and data on the gas mass fraction in galaxy clusters. We also discuss the weak field limit of a model comprising a significant fraction of dark matter in the form of a fluid of strings and show that this mechanism makes it possible to reduce the need for the elusive and up to now undetected CDM. We finally find that a model comprising both a cosmological constant and a fluid of strings fits the data very well and eliminates the need for phantom dark energy, thus representing a viable candidate for alleviating some of the problems plaguing the dark side of the universe.
MESON MASS AND CONFINEMENT FORCE DRIVEN BY DILATON
Authors: BREVIK IVER , GHOROKU KAZUO , NAKAMURA AKIHIRO
Published: March 2006

Meson spectra given as fluctuations of a D7-brane are studied under the background driven by the dilaton. This leads to a dual gauge theory with quark confinement due to the gauge condensate. We find that the effect of the gauge condensate on the meson spectrum is essential in order to make a realistic hadron spectrum in the non-supersymmetric case. In the supersymmetric case, however, only the spectra of the scalars are affected, but they are changed in an opposite way compared to the non-supersymmetric case.
A STUDY OF THE PIONEER ANOMALY: NEW DATA AND OBJECTIVES FOR NEW INVESTIGATION
Authors: TURYSHEV SLAVA G. , TOTH VIKTOR T. , KELLOGG LARRY R. , LAU EUNICE L. , LEE KYONG J.
Published: March 2006

The Pioneer 10/11 spacecraft yielded the most precise navigation in deep space to date. However, their radiometric tracking data has consistently indicated the presence of a small, anomalous, Doppler frequency drift. The drift is a blue shift, uniformly changing with a rate of ~6 × 10-9 Hz/s and can be interpreted as a constant sunward acceleration of each particular spacecraft of aP = (8.74±1.33) × 10-10 m/s 2 (or, alternatively, a time acceleration of at = (2.92±0.44) × 10-18 s/s 2). This signal has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. We discuss the current state of the efforts to retrieve the entire data sets of the Pioneer 10 and 11 radiometric Doppler data. We also report on the availability of recently recovered telemetry files that may be used to reconstruct the engineering history of both spacecraft using original project documentation and newly developed software tools. We discuss possible ways to further investigate the discovered effect using these telemetry files in conjunction with the analysis of the much extended Pioneer Doppler data. In preparation for this new upcoming investigation, we summarize the current knowledge of the Pioneer anomaly and review some of the mechanisms proposed for its explanation. We emphasize the main objectives of this new study, namely (i) analysis of the early data that could yield the true direction of the anomaly and thus, its origin, (ii) analysis of planetary encounters, which should say more about the onset of the anomaly (e.g. Pioneer 11's Saturn flyby), (iii) analysis of the entire dataset, which should lead to a better determination of the temporal behavior of the anomaly, (iv) comparative analysis of individual anomalous accelerations for the two Pioneers with the data taken from similar heliocentric distances, (v) the detailed study of on-board systematics, and (vi) development of a thermal-electric-dynamical model using on-board telemetry. The outlined strategy may allow for a higher accuracy solution for the anomalous acceleration of the Pioneer spacecraft and, possibly, will lead to an unambiguous determination of the origin of the Pioneer anomaly.
Regulation of water permeability in rabbit conjunctival epithelium by anisotonic conditions
Authors: Candia Oscar A. , Alvarez Lawrence J. , Zamudio Aldo C.
Published: March 2006

Effects of unilateral exposure to anisotonic conditions on diffusional water permeability of the isolated rabbit conjunctiva were determined. A segment of the bulbar-palpebral conjunctiva was mounted between Ussing-type hemichambers under short-circuit conditions. Unidirectional water fluxes ( Jdw) were measured in either direction by adding 3H2O to one hemichamber and sampling from the other. Electrical parameters were measured simultaneously. Jdw were determined under control isosmotic conditions and after introduction of either hyper- or hypotonic solutions against the tear or stromal sides of the preparations. In each of these four separate conditions, the anisotonic medium produced an ∼20–30% reduction in Jdw across the tissue, with the exception that to obtain such reduction with increased tonicity from the stromal side (medium osmolality increased by adding sucrose), conditions presumptively inhibiting regulatory volume increase mechanisms (e.g., pretreatment with amiloride and bumetanide) were also required. All reductions in Jdw elicited by the various anisotonic conditions were reversible on restoration of control tonicity. In experiments in which preparations were pretreated with the protein cross-linking agent glutaraldehyde, anisotonicity-elicited reductions in Jdw were not observed. Such reductions were also not observed in the presence of HgCl2, implying the involvement of aquaporins. However, it is possible that the mercurial may be toxic to the epithelium, preventing the tonicity response. Nevertheless, from concomitant changes in transepithelial electrical resistance, as well as [14C]mannitol fluxes, [14C]butanol fluxes, and Arrhenius plots, arguments are presented that the above effects are best explained as a cell-regulated reduction in membrane water permeability that occurs at the level of water-transporting channels. Presumably both apical and basolateral membranes can downregulate their water permeabilities as part of a protective mechanism to help maintain cell volume.
Cardiovascular responses to exercise and muscle metaboreflex activation during the recovery from pacing-induced heart failure
Authors: Augustyniak Robert A. , Ansorge Eric J. , Kim Jong-Kyung , Sala-Mercado Javier A. , Hammond Robert L. , Rossi Noreen F. , O'Leary Donal S.
Published: March 2006

Rapid recovery of resting hemodynamics from tachycardia- or arrhythmia-induced heart failure (HF) has been demonstrated in both humans and animals. However, little is known about cardiovascular responses to exercise in animals or about reflex control of the cardiovascular system during exercise while recovering from HF. Inasmuch as the reduced cardiac output (CO) during exercise in HF has been shown to lead to underperfusion of active skeletal muscle and tonic activation of the muscle metaboreflex, an improved CO during exercise in subjects recovering from HF may lead to higher skeletal muscle blood flows and to relief of this metabolic stimulus. We investigated cardiovascular responses to graded treadmill exercise and metaboreflex activation [evoked by imposed graded reductions in hindlimb blood flow (HLBF) during mild and moderate exercise] in chronically instrumented dogs during control, mild to moderate HF (induced by rapid ventricular pacing), and recovery from HF. Most hemodynamic responses to graded exercise returned to control within 24 h of disconnecting the pacemaker. After 2 wk of recovery, CO and HLBF at each workload were significantly higher than control. In addition, whereas the increase in CO that normally occurs with metaboreflex activation was markedly attenuated in HF, it completely returned in the recovery experiments. We conclude that cardiovascular responses to graded exercise during the recovery from pacing-induced HF return rapidly to near or above control and that the increased CO and HLBF in recovery likely relieved the metabolic stimulus and tonic metaboreflex activation that may have occurred during moderate exercise in HF.
Applications of Computed Tomography in Renal Imaging
Authors: Read Samantha , Allen Clare , Hare Christopher
Published: March 2006

There have been huge advances in CT technology since its introduction more than 30 years ago. Modern, multislice CT scanners are fast and produce truly volumetric data, allowing it to be reconstructed in almost any plane. In this article, we explore the impact of these developments on the use of CT in imaging of the renal tract. Whilst it may take the radiologist longer to review and process the increased amount of data that is produced, diagnostic accuracy is unquestionably improved and new and exciting challenges are presented to the radiologist as he learns to manipulate and interpret the data in a way that he has never done before.
Imaging Acute Renal Failure with Polyamine Dendrimer-Based MRI Contrast Agents
Authors: Dear James W. , Kobayashi Hisataka , Brechbiel Martin W. , Star Robert A.
Published: March 2006

Acute renal failure (ARF) induced by sepsis has a high mortality but lacks effective treatments. To develop novel therapies we must diagnose renal injury early and accurately in septic patients and identify any additional insults such as nephrotoxic drugs and ischemia. In this short review we describe our experience using MRI with dendrimer-based contrast agents in mouse models of ARF. This technique can diagnose early renal injury before serum creatinine is elevated, distinguish different ARF etiologies, track drug therapy and predict outcome. As an ARF biomarker, MRI with dendrimer-based contrast is a promising technique deserving further development.
Magnetic Resonance Imaging in Acute and Chronic Kidney Diseases: Present Status
Authors: Laissy Jean-Pierre , Idée Jean-Marc , Fernandez Pedro , Floquet Muriel , Vrtovsnik François , Schouman-Claeys Elisabeth
Published: March 2006

Magnetic resonance imaging (MRI) of normal and diseased kidneys shows great promise because of the combined value of anatomical and functional information provided, as well as of specific contrast patterns that can be observed non-invasively. Multicontrast MRI is able to show infiltrative kidney disorders. Diffusion-weighted imaging can assess alterations in renal function and can suggest obstruction or inflammation when present. Due to the low nephrotoxicity, contrast-enhanced MR studies using serial dynamic enhancement with non-specific gadolinium chelates are able to provide information on glomerular filtration. Furthermore, contrast agents such as ultrasmall particles of iron oxide, specific of inflammation, should be used in the near future to detect active from quiescent involvement, both in native kidneys and renal allografts. Early results should indicate that these compounds might differentiate acute tubular necrosis from other acute nephropathies, as well as active proliferative nephropathies from chronic ones. Ongoing studies will obviously demonstrate the value of the combination of these various MRI sequences in the diagnosis of acute renal failure and chronic kidney disease.
The Conundrum of Inducible Nitric Oxide Synthase in Chronic Leg Ulcers
Authors: Quatresooz Pascale , Paquet Philippe , Piérard Gérald E.
Published: March 2006

Nitric oxide (NO) is a potent biological mediator that can be produced in wounds by activation of inducible nitric oxide synthase (iNOS). Its presence appears to be beneficial to the healing process by promoting vasodilation and boosting both migration and synthetic activity of fibroblasts. Chronic leg ulcers differ from acute experimental wounds because the connective tissue and microvascularization of the ulcer bed are strikingly remod elled in chronic wounds. In addition, a critical bacterial colonization from the environment is also often present, and with deleterious effects. As such, NO release in leg ulcers may prove to be beneficial by improving the microvasculature and fibroblast functions, and by its antimicrobial effect. However, any excess in NO could become cytotoxic for keratinocytes, thus impeding re- epithelialization. Furthermore, chronic NO release could be involved in the cancerogenesis process leading to Marjolin ulcer. In conclusion, NO induced by environment factors mediates contrasted effects in wound healing that may be beneficial or detrimental for the patient.
Rapid Release of Active Tissue Factor From Human Arterial Smooth Muscle Cells Under Flow Conditions
Authors: Stampfuss Jan-Julius , Censarek Petra , Fischer Jens W. , Schrör Karsten , Weber Artur-Aron
Published: March 2006

Circulating tissue factor (TF) is an important determinant of coronary thrombosis. Among other cell types, such as monocytes, vascular smooth muscle cells (SMCs) are capable of releasing TF. When studied under static conditions, SMCs do release TF, but this process is slow and, thus, cannot explain the elevated levels of circulating TF, as observed in patients with acute coronary syndromes. The present study demonstrates that cultured human mammary artery SMCs very rapidly (minutes) release active, microparticle-bound TF when exposed to flow conditions. There was a clear log-linear correlation between the shear rate (range 10 s
−1
to 1500 s
−1
) and the procoagulant activity of SMC perfusates. Flow-dependent release of TF was transient (10 minutes) and did not measurably reduce cell surface TF content. Interestingly, a time-dependent (t
1/2
30 minutes) re-exposure of releasable TF was detected after a no-flow period. These data demonstrate that SMCs may become a pathophysiologically relevant source of TF that can be rapidly released into the circulation in situations in which endothelial damage occurs and SMCs come into a close contact with the flowing blood.
High-Density Lipoproteins Enhance Progenitor-Mediated Endothelium Repair in Mice
Authors: Tso Colin , Martinic Gary , Fan Wen-Hua , Rogers Campbell , Rye Kerry-Anne , Barter Philip J.
Published: March 2006

Objective—We quantified endothelial progenitor cell (EPC) engraftment into the endothelial layer as an index of progenitor-mediated endothelial repair. Studies were conducted in C57BL/6J and in apolipoprotein E–deficient (apoE−/−) mice. We also investigated the possibility that high-density lipoproteins (HDL) may promote progenitor-mediated endothelial repair.

Methods and Results—Thoracic aortic sections from C57BL/6J and apoE−/−mice were analyzed for evidence of progenitor-derived endothelium as determined by the number of stem cell antigen-1–positive (Sca-1+) cells in the endothelial layer. EPCs (Sca-1+ cells) were significantly increased after endothelial damage induced by lipopolysaccharide (LPS) administration in C57BL/6J mice. The number of EPCs was greater in the aortic endothelium of untreated apoE−/−than in untreated C57BL/6J mice and was similar to the number observed in LPS-treated C57BL/6J mice. The number of EPCs in the aortic endothelium of apoE−/−mice more than doubled after intravenous infusion of reconstituted HDL.

Conclusions—EPCs are recruited into the aortic endothelial layer of mice in response to an inflammatory insult. EPCs are also increased in the aortic endothelium of untreated apoE−/−mice. The observation that number is further increased in apoE−/−mice after injection of HDL suggests a role for HDL in promoting progenitor-mediated endothelial repair.
Desensitization of Platelet-Derived Growth Factor Receptor-β by Oxidized Lipids in Vascular Cells and Atherosclerotic Lesions
Authors: Vindis Cecile , Escargueil-Blanc Isabelle , Elbaz Meyer , Marcheix Bertrand , Grazide Marie-Helene , Uchida Koji , Salvayre Robert , Nègre-Salvayre Anne
Published: March 2006

The platelet-derived growth factor receptor-β (PDGFRβ) signaling pathway regulates smooth muscle cell (SMC) migration and proliferation and plays a role in the vascular wall response to injury. Oxidized low-density lipoprotein (oxLDL) in atherosclerotic lesions can activate the PDGFRβ pathway, but the long-term effects of oxLDL on PDGFRβ function are not well understood. We found that oxLDL induced a dual effect on PDGFRβ signaling. Initial activation of the PDGFR was followed by desensitization of the receptor. PDGFRβ desensitization was not attributable to PDGFRβ degradation or changes in localization to the caveolae but instead resulted from decreased PDGF binding and inhibition of PDGFRβ tyrosine kinase activity. This inhibition was associated with formation of (4HNE)– and acrolein–PDGFRβ adducts and was mimicked by preincubation of cells with 4HNE. These PDGFRβ adducts were also detected in aortae of apolipoprotein-deficient mice and hypercholesterolemic rabbits and in human carotid plaques. The aldehyde scavengers DNPH and Hydralazine prevented both oxLDL- and 4HNE-induced structural modification and PDGFRβ signaling dysfunction in cells and in vivo. OxLDL inhibition of PDGF signaling may contribute to defective SMC proliferation and decrease the stability of a vulnerable plaque.
Hearing Spaces: David Tudor's Collaboration on Sea Tails
Authors: Perloff Nancy
Published: March 2006

In 1983, David Tudor collaborated with kite artist Jackie Matisse and filmmaker Molly Davies on a six-monitor video piece called Sea Tails: Davies filmed Matisse's underwater kites, and Tudor recorded sea sounds from which he later mixed a score. Using notes and correspondence found at the Getty Research Institute, as well as interviews conducted with Matisse and Davies, the author reconstructs the collaborative process of making Sea Tails. Points of contact between the media of film, sculpture and sound reveal Tudor's postCagean form of collaboration, in which Tudor ceded control over compositional process and performance to outside forces—Matisse and Davies and the reverberation of the performance and sea spaces.
A Musical Technography of John Bischoff
Authors: Kahn Douglas
Published: March 2006

John Bischoff has been part of the formation and growth of electronic and computer music in the San Francisco Bay Area for over three decades. In an interview with the author, he describes his early development as a student of experimental music technology, including the impact of hearing and assisting in the work of David Tudor. Bischoff, like Tudor, explored the unpredictable potentials within electronic components, and he brought this curiosity to bear when he began working on one of the first available micro-computers. He was a key individual at the historical turning point when computer music escaped its institutional restric-tions and began becoming widespread.
The Folk Music of Chance Electronics: Circuit-Bending the Modern Coconut
Authors: Ghazala Qubais Reed
Published: March 2006

The author describes the philosophy and art of circuit-bending: shorting out conven-tional electronic devices to reveal unexpected sound and music. Starting from his first foray into chance electronics during his junior high school years, he details both his method of working and the wealth of instruments that have resulted.
RISK: The Use of High-Frequency Radio Electronics for Audio Recreation
Authors: Prins Gert-Jan
Published: March 2006

The author describes his career as an improvisational electronic musician.
Philippa Cullen: Dancing the Music
Authors: Jones Stephen
Published: March 2006

This paper discusses one aspect of the work of Philippa Cullen, a dancer, choreogra-pher, community artist and electronic experimenter who worked in Australia and in Europe for a brief period from 1969 to 1975. Covered here is her experimental work with electronic systems that allowed dancers to produce sound and music from their movements. Her primary instrument was the theremin, for which she and her collaborators produced a variety of innovative extensions, from very large aerials, to use with synthesizers. She was an important early exponent of interactivity in the arts, inspiring and teaching many others on her way.
David Tudor as Composer/Performer in Cage's Variations II.
Authors: Pritchett James
Published: March 2006

Understanding David Tudor's transition from performer to composer is critical to understanding his life and work. This task is made more complex, however, by the nature of Tudor's work as a performer. Because he specialized in the realization of indeterminate scores and entered into such close collaboration with avantgarde composers, the distinction between performer and composer is often unclear in Tudor's performances. The author discusses Tudor's realization of John Cage's Variations IIas a case study in identifying the overlapping of performer and composer roles, both within this specific realization and within the context of Tudor's history. Because this realization has much more in common with Tudor's own compositions than with Cage's musical ideas, it can be considered more a composition by David Tudor than a composition by John Cage.
David Tudor's Apprenticeship: The Years with Irma and Stefan Wolpe
Authors: Clarkson Austin
Published: March 2006

David Tudor's genius was evident from early childhood, but it was not until 1944, when he became a piano student of Irma Wolpe and a composition student of Stefan Wolpe, that Tudor began to realize his true potential. The Wolpes prepared Tudor for his extraordinary career as a path-breaking piano virtuoso and champion of the avant-garde. Tudor's years with the Wolpes culminated in the premiere of Battle Piece in 1950, Tudor's edition of which documents his collaboration with Wolpe in realizing the temporal dimensions of the score. Tudor's later path as a composer of live electronic music is traced back to his years of apprenticeship.
crash and bloom: A Self-Defeating Regenerative System
Authors: Repetto Douglas Irving
Published: March 2006

crash and bloom is an elec-tronic sculpture that undergoes population density cycles similar to those found in some natural systems. The system is made up of 42 boxes, their simple behaviors and the interconnec-tion topology of the boxes with one another, which enables them to pass “ping” messages around the network. Three simple rules determine how the boxes respond to the ping messages. These rules, coupled with a feedback loop topology, allow the emergence of crash and bloom cycles: The density of pings in the system rises rapidly, saturates the environ-ment, crashes and rises again.
David Tudor in the Late 1980s: Understanding a Secret Voice
Authors: Gray D'Arcy Philip
Published: March 2006

David Tudor's compositions of the late 1980s are somewhat mysterious. His artistic and technical approach was unique and can be seen as a precursor to much of the underground noise and avant-rock music that permeates the alternative club scene today. The author uses Tudor's Web pieces to explore his later work, studying his methodology and the possibility of reconstructing his systems.
How Does a Bicycle Light Sound?: Cracked Everyday Electronics
Authors: Möslang Norbert
Published: March 2006

Every electronic appliance contains a unique sonic poten-tial, which the author “cracks” to create music.
David Tudor: The Delicate Art of Falling
Authors: Viola Bill
Published: March 2006

The author discusses his early exposure to Tudor's work and its formative influence on his own work and thinking. This connection began with the author's collaboration in the presentation of Tudor's Rainforest, which provided an introduction to the provocative currents at work in Tudor's music and personality.
Open Sources: Words, Circuits and the Notation-Realization Relation in the Music of David Tudor
Authors: Kuivila Ron
Published: March 2006

As a pianist, David Tudor played a pivotal role in the development of the postwar musical avant-garde that has only recently received the scholarly response it warrants. The author traces the development of Tudor's approach to live electronic music from his work as a pianist and assesses the extent to which the indeterminate notations he so often realized entered into the development of his approach to electronic systems.
The Influence of Recording Technologies on the Early Development of Electroacoustic Music
Authors: Manning Peter
Published: March 2006

From the earliest experiments with the manipulation of 78-rpm disks during the 1920s, the technology of recording has played a major role in the evolution of electroacoustic music. This has extended not only to the recording and reproduction of materials but also to key components of the compositional process itself. Although such influences have become less prominent with the advent of digital technology, their impact during the formative years of electroacoustic music was significant and far-reaching. This article examines some key aspects of the pioneering era of creative development through the early 1950s, with particular reference to the Bauhaus sound artists, Pierre Schaeffer and musique concrète, and the Cologne studio for elektronische Musik
Christian Marclay's Early Years: An Interview
Authors: Kahn Douglas
Published: March 2006

The artist discusses with the author his early career and influences. Marclay explains his upbringing in Switzerland and his lack of familiarity with American mass culture, to which he credits his early experiments in art, music and performance using records. Marclay describes the evolution of his use of records and discusses other influences, such as art school and the New York club scene of the 1970s.
The Music of the Sphere: An Investigation into Asymptotic Harmonics, Brainwave Entrainment and the Earth as a Giant Bell
Authors: First David
Published: March 2006

The author discusses a conceptual framework for the organization and performance of music that has its basis in the frequency relationships of the Schumann Resonances and in the principle of binaural beats. He describes the steps he took in conceiving the project, the technical issues involved in realizing the goal of live data transmissions from a remote location and the creation of the three-dimensional overtone series that is the project's theoretical centerpiece. He also lays out his philosophy of improvisation and treads lightly into the curious gray areas where science mutates into leaps of faith.
Displaced Soundscapes: A Survey of Network Systems for Music and Sonic Art Creation
Authors: Barbosa Álvaro
Published: March 2006

The introduction of various collaborative tools, made possible by the expansion of computer network systems and communications technology, has led to new methods of musical composition and improvisation. The author describes a number of recent music and sound art projects involving the use of network systems that enable geographically displaced creators to collaboratively generate shared soundscapes. Various system designs, ideas and concepts associated with this interaction paradigm are presented and classified by the author.
Hand-Luggage: For a Generative Theory of Artifacts
Authors: Schulze Holger
Published: March 2006

This article presents the basic elements and strategies of a generative theory of artifacts, the Theorie der Werkgenese. Starting with a narrative reconstruction of Mike Mills's TV commercial for Adidas, the text briefly outlines a history of aleatoric games and heuristic strategies in the classical avantgarde as well as in postmodern follow-ups and late-20th-century pop music. Finally, the various fictions conveyed by the commercial are narrated in a new way, demonstrating generative analysis.
Bayesian Multiple Changepoint Analysis of Hurricane Activity in the Eastern North Pacific: A Markov Chain Monte Carlo Approach
Authors: Zhao Xin , Chu Pao-Shin
Published: March 2006

A Bayesian framework is developed to detect multiple abrupt shifts in a time series of the annual major hurricanes counts. The hurricane counts are modeled by a Poisson process where the Poisson intensity (i.e., hurricane rate) is codified by a gamma distribution. Here, a triple hypothesis space concerning the annual hurricane rate is considered: “a no change in the rate,” “a single change in the rate,” and “a double change in the rate.” A hierarchical Bayesian approach involving three layers—data, parameter, and hypothesis—is formulated to demonstrate the posterior probability of each possible hypothesis and its relevant model parameters through a Markov chain Monte Carlo (MCMC) method.

Based on sampling from an estimated informative prior for the Poisson rate parameters and the posterior distribution of hypotheses, two simulated examples are illustrated to show the effectiveness of the proposed method. Subsequently, the methodology is applied to the time series of major hurricane counts over the eastern North Pacific (ENP). Results indicate that the hurricane activity over ENP has very likely undergone a decadal variation with two changepoints occurring around 1982 and 1999 with three epochs characterized by the inactive 1972–81 epoch, the active 1982–98 epoch, and the inactive 1999–2003 epoch. The Bayesian method also provides a means for predicting decadal major hurricane variations. A lower number of major hurricanes are predicted for the next decade given the recent inactive period of hurricane activity.
The Probability Distribution of Sea Surface Wind Speeds. Part II: Dataset Intercomparison and Seasonal Variability
Authors: Monahan Adam Hugh
Published: March 2006

The statistical structure of sea surface wind speeds is considered, both in terms of the leading-order moments (mean, standard deviation, and skewness) and in terms of the parameters of a best-fit Weibull distribution. An intercomparison is made of the statistical structure of sea surface wind speed data from four different datasets: SeaWinds scatterometer observations, a blend of Special Sensor Microwave Imager (SSM/I) satellite observations with ECMWF analyses, and two reanalysis products [NCEP–NCAR and 40-yr ECMWF Re-Analysis (ERA-40)]. It is found that while the details of the statistical structure of sea surface wind speeds differs between the datasets, the leading-order features of the distributions are consistent. In particular, it is found in all datasets that the skewness of the wind speed is a concave upward function of the ratio of the mean wind speed to its standard deviation, such that the skewness is positive where the ratio is relatively small (such as over the extratropical Northern Hemisphere), the skewness is close to zero where the ratio is intermediate (such as the Southern Ocean), and the skewness is negative where the ratio is relatively large (such as the equatorward flank of the subtropical highs). This relationship between moments is also found in buoy observations of sea surface winds. In addition, the seasonal evolution of the probability distribution of sea surface wind speeds is characterized. It is found that the statistical structure on seasonal time scales shares the relationships between moments characteristic of the year-round data. Furthermore, the seasonal data are shown to depart from Weibull behavior in the same fashion as the year-round data, indicating that non-Weibull structure in the year-round data does not arise due to seasonal nonstationarity in the parameters of a strictly Weibull time series.
Climatology of Barrier Jets along the Alaskan Coast. Part I: Spatial and Temporal Distributions
Authors: Loescher Kenneth A. , Young George S. , Colle Brian A. , Winstead Nathaniel S.
Published: March 2006

This paper investigates the temporal and spatial climatology of coastal barrier jets in the Gulf of Alaska. The jets are divided into two categories based upon the origin of the air involved: “classic” barrier jets fed primarily by onshore flow and “hybrid” jets fed primarily by gap flow from the continental interior. The analyses are compiled from five years (1998–2003) of synthetic aperture radar images from the Radarsat-1 satellite totaling 3000 images. Thermodynamic and kinematic data from the NCEP reanalysis is used in the interpretation of the results.

The majority of coastal barrier jets occur during the cool season, with the coastline near Mount Fairweather and the Valdez–Cordova mountains experiencing the greatest number of barrier jets. Hybrid jets are even more strongly restricted to the cool season and are commonly found to the west of Cross Sound, Yakutat Bay, and Icy Bay. Some interannual variability in the total number of jets is observed.

Coastal barrier jet formation is associated with onshore wind directions and maximum terrain heights exceeding 2 km within 100 km of the coast, features that support low-level flow blocking. Hybrid jet formation requires the additional condition of an abnormally large offshore-directed pressure gradient force.

Half of the barrier and hybrid jets exhibit surface wind speeds in excess of 20 m s−1 (strong gale), although their widths are typically less than 100 km. The maximum speed of both types of jet tends to be 2–3 times that of the ambient synoptic flow. A small percentage of the jets detach from the coastline, with the typical detachment distance being 10 km.
Climatology of Barrier Jets along the Alaskan Coast. Part II: Large-Scale and Sounding Composites
Authors: Colle Brian A. , Loescher Kenneth A. , Young George S. , Winstead Nathaniel S.
Published: March 2006

This paper investigates the large-scale flow and thermodynamic structures associated with barrier jets along the Alaskan coast using the National Centers for Environmental Prediction (NCEP) reanalysis, as well as the average wind, moisture, and thermodynamic soundings at Yakutat, Alaska (YAK), and Whitehorse, Yukon Territory, Canada (YXY). Large-scale and sounding composites are constructed for all barrier jets objectively identified around YAK using synthetic aperture radar (SAR) imagery during the cool and warm seasons of 1998–2003. During the cool season the jet events are separated into those with sharp upstream wind gradients (shock jets), highly variable (“gustlike”) surface winds (variable jets), and the other jet events (other jets).

Those cool season barrier jets without shock or variable characteristics are associated with an anomalously deep upper-level trough approaching the Gulf of Alaska and an anomalous ridge over western Canada and interior Alaska. The associated surface cyclone and surface ridging result in strong low-level southerlies over southeast Alaska and the advection of 850-mb warm anomalies northward from the subtropics to Alaska. In contrast, the shock events have significant cold anomalies at 850 mb over the interior, while both the shock and variable jets have less upper-level ridging over the interior. The warm season other-jet composite is similar to that for the cool season, except that an 850-mb cool anomaly develops near the coast and the approaching upper-level trough is not significantly deeper than climatology.

The sounding composite at YAK of the other-jet type during the cool season is more stable, moist, and slightly cooler at lower levels than the nonjet events. The largest low-level cool, dry, and high stability anomalies are for the shock events at YAK and YXY, which suggests that this cold and dry air source over the interior is an important ingredient for the development of sharp frontlike boundaries to the barrier jet. In contrast, the variable jets have weaker low-level stability, which favors the subsequent mixing of higher momentum to the surface in localized areas. The warm season jets also have cooler lower levels than those for the nonjet events, but the lower levels are nearly well mixed with little stratification, especially over the interior.
Terrain Influences on Synoptic Storm Structure and Mesoscale Precipitation Distribution during IPEX IOP3
Authors: Shafer Jason C. , Steenburgh W. James , Cox Justin A. W. , Monteverdi John P.
Published: March 2006

The influence of topography on the evolution of a winter storm over the western United States and distribution of precipitation over northern Utah are examined using data collected during the third intensive observing period (IOP3) of the Intermountain Precipitation Experiment (IPEX). The analysis is based on high-density surface observations collected by the MesoWest cooperative networks, special radiosonde observations, wind profiler observations, Next-Generation Weather Radar (NEXRAD) data, and conventional data. A complex storm evolution was observed, beginning with frontal distortion and low-level frontolysis as a surface occluded front approached the Sierra Nevada. As the low-level occluded front weakened, the associated upper-level trough moved over the Sierra Nevada and overtook a lee trough. The upper-level trough, which was forward sloping and featured more dramatic moisture than temperature gradients, then moved across Nevada with a weak surface reflection as a pressure trough.

Over northern Utah, detailed observations revealed the existence of a midlevel trough beneath the forward-sloping upper-level trough. This midlevel trough appeared to form along a high-potential-vorticity banner that developed over the southern Sierra Nevada and moved downstream over northern Utah. A surface trough moved over northern Utah 3 h after the midlevel trough and delineated two storm periods. Ahead of the surface trough, orographic precipitation processes dominated and produced enhanced mountain precipitation. This period also featured lowland precipitation enhancement upstream of the northern Wasatch Mountains where a windward convergence zone was present. Precipitation behind the surface trough was initially dominated by orographic processes, but soon thereafter featured convective precipitation that was not fixed to the terrain. Processes responsible for the complex vertical trough structure and precipitation distribution over northern Utah are discussed.
Field Significance Revisited: Spatial Bias Errors in Forecasts as Applied to the Eta Model
Authors: Elmore Kimberly L. , Baldwin Michael E. , Schultz David M.
Published: March 2006

The spatial structure of bias errors in numerical model output is valuable to both model developers and operational forecasters, especially if the field containing the structure itself has statistical significance in the face of naturally occurring spatial correlation. A semiparametric Monte Carlo method, along with a moving blocks bootstrap method is used to determine the field significance of spatial bias errors within spatially correlated error fields. This process can be completely automated, making it an attractive addition to the verification tools already in use. The process demonstrated here results in statistically significant spatial bias error fields at any arbitrary significance level.

To demonstrate the technique, 0000 and 1200 UTC runs of the operational Eta Model and the operational Eta Model using the Kain–Fritsch convective parameterization scheme are examined. The resulting fields for forecast errors for geopotential heights and winds at 850, 700, 500, and 250 hPa over a period of 14 months (26 January 2001–31 March 2002) are examined and compared using the verifying initial analysis. Specific examples are shown, and some plausible causes for the resulting significant bias errors are proposed.
Assimilation with an Ensemble Kalman Filter of Synthetic Radial Wind Data in Anisotropic Turbulence: Perfect Model Experiments
Authors: Charron Martin , Houtekamer P. L. , Bartello Peter
Published: March 2006

The ensemble Kalman filter (EnKF) developed at the Meteorological Research Branch of Canada is used in the context of synthetic radial wind data assimilation at the mesoscale. A dry Boussinesq model with periodic boundary conditions is employed to provide a control run, as well as two ensembles of first guesses. Synthetic data, which are interpolated from the control run, are assimilated and simulate Doppler radar wind measurements.

Nine “radars” with a range of 120 km are placed evenly on the horizontal 1000 km × 1000 km domain. These radars measure the radial wind with assumed Gaussian error statistics at each grid point within their range provided that there is sufficient upward motion (a proxy for precipitation). These data of radial winds are assimilated every 30 min and the assimilation period extends over 4 days.

Results show that the EnKF technique with 2 × 50 members performed well in terms of reducing the analysis error for horizontal winds and temperature (even though temperature is not an observed variable) over a period of 4 days. However the analyzed vertical velocity shows an initial degradation. During the first 2 days of the assimilation period, the analysis error of the vertical velocity is greater when assimilating radar observations than when scoring forecasts initialized at t = 0 without assimilating any data. The type of assimilated data as well as the localization of the impact of the observations is thought to be the cause of this degradation of the analyzed vertical velocity. External gravity modes are present in the increments when localization is performed. This degradation can be eliminated by filtering the external gravity modes of the analysis increments.

A similar set of experiments is realized in which the model dissipation coefficient is reduced by a factor of 10. This shows the level of sensitivity of the results to the kinetic energy power spectrum, and that the quality of the analyzed vertical wind is worse when dissipation is small.
Synoptic Composites of the Extratropical Transition Life Cycle of North Atlantic Tropical Cyclones: Factors Determining Posttransition Evolution
Authors: Hart Robert E. , Evans Jenni L. , Evans Clark
Published: March 2006

A 34-member ensemble-mean trajectory through the cyclone phase space (CPS) is calculated using Navy Operational Global Atmospheric Prediction System (NOGAPS) analyses for North Atlantic tropical cyclones (TCs) undergoing extratropical transition (ET). Synoptic composites at four ET milestones are examined: 24 h prior to the beginning of ET (TB − 24), the beginning of ET (TB), the end of ET (TE), and 24 h after the end of ET (TE + 24). While the extratropically transitioning TC structure is tightly constrained in its tropical phase, it has a variety of evolutions after TE. Partitioning the ensemble based upon post-ET intensity change or structure discriminates among statistically significant ET precursor conditions. Compositing the various post-ET intensity regimes provides insight into the important environmental factors governing post-ET development.

A TC that intensifies (weakens) after TE begins transition (t = TB) with a negatively (positively) tilted trough 1000 km (1500 km) upstream. The negative tilt permits a contraction and intensification of the eddy potential vorticity (PV) flux, while the positive trough tilt prevents contraction and intensification of the forcing. In 6 of the 34 cases, the posttropical cold-core cyclone develops a warm-seclusion structure, rather than remaining cold core. Anticipation of this warm-seclusion evolution is critical since it represents a dramatically increased risk of middle- to high-latitude wind and wave damage. The warm-seclusion evolution is most favored when the scale of the interacting trough closely matches the scale of the transitioned TC, focusing the eddy PV flux in the outflow layer of the transitioning TC. The sensitivity of structural evolution prior to and after TE illustrated here gives insight into the degradation of global model midlatitude forecast accuracy during a pending ET event.

Eliassen–Palm flux cross sections suggest that ET is primarily driven by the eddy angular momentum flux of the trough, rather than the eddy heat flux associated with the trough. The response of the transitioning TC to the eddy angular momentum forcing is to produce adiabatic ascent and cooling radially inward and beneath the region of the forcing to restore thermal wind balance. In the case of ET, the forcing is maximized lower in the atmosphere, and spread over much greater depth, than in the case of trough-induced TC intensification. Only after TE is the eddy heat flux forcing as significant as the eddy angular momentum forcing, further supporting a physical foundation for the CPS description of cyclone evolution.
Low-Frequency Variability and Evolution of North American Cold Air Outbreaks
Authors: Portis Diane H. , Cellitti Michael P. , Chapman William L. , Walsh John E.
Published: March 2006

Hourly data from 17 relatively evenly distributed stations east of the Rocky Mountains during 54 winter seasons (1948/49 through 2001/02) are used to evaluate the low-frequency variability of extreme cold air outbreaks (CAOs). The results show no overall trend in CAO frequency, despite an increase in mean temperature over the Midwest and especially upstream into the CAO formation regions of high-latitude North America. However, there are regionally based trends in the intensity of long-duration (5 day) CAOs.

Daily heat budgets from reanalysis data are also used to investigate the thermodynamic and dynamic processes involved in the evolution of a subset of the major CAOs. The cooling of the air masses can be generally traced in the heat budget analysis as the air masses track southward along the Rocky Mountains into the Midwest. The earliest cooling begins in northwestern Canada more than a week before the cold air mass reaches the Midwest. Downstream in southwestern Canada, both diabatic and advective processes contribute to the cumulative cooling of the air mass. At peak intensity over the Midwest, diabatic processes and horizontal advection cool the air mass, but warming by subsidence offsets this cooling. By contrast, to the west of the CAO track into the Midwestern United States, vertical advection by orographic lifting cumulatively cools the air in the upslope flow regime associated with the low-level airflow around a cold air mass, and this cooling is offset by diabatic warming. Diabatic processes have strong positive correlations with temperature change over all regions (especially in central Canada) except for the mountainous regions in the United States that are to the west of the track of the cold air mass. Correlations of vertical advection with horizontal advection and diabatic processes are physically consistent and give credibility to the vertical advection field.