bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships between circadian rhythms and modulation of gene expression by glucocorticoids in skeletal muscle
Authors: Almon Richard R. , Yang Eric , Lai William , Androulakis Ioannis P. , Ghimbovschi Svetlana , Hoffman Eric P. , Jusko William J. , DuBois Debra C.
Published: July 2008

The existence and maintenance of biological rhythms linked to the 24-h light-dark cycle are essential to the health and functioning of an organism. Although much is known concerning central clock mechanisms, much less is known about control in peripheral tissues. In this study, circadian regulation of gene expression was examined in rat skeletal muscle. A rich time series involving 54 animals euthanized at 18 distinct time points within the 24-h cycle was performed, and mRNA expression in gastrocnemius muscles was examined using Affymetrix gene arrays. Data mining identified 109 genes that were expressed rhythmically, which could be grouped into eight distinct temporal clusters within the 24-h cycle. These genes were placed into 11 functional categories, which were examined within the context of temporal expression. Transcription factors involved in the regulation of central rhythms were examined, and eight were found to be rhythmically expressed in muscle. Because endogenous glucocorticoids are a major effector of circadian rhythms, genes identified here were compared with those identified in previous studies as glucocorticoid regulated. Of the 109 genes identified here as circadian rhythm regulated, only 55 were also glucocorticoid regulated. Examination of transcription factors involved in circadian control suggests that corticosterone may be the initiator of their rhythmic expression patterns in skeletal muscle.
Cerebromicrovascular endothelial cells are resistant tol-glutamate
Authors: Domoki Ferenc , Kis Béla , Gáspár Tamás , Bari Ferenc , Busija David W.
Published: July 2008

Cerebral microvascular endothelial cells (CMVECs) have recently been implicated as targets of excitotoxic injury by l-glutamate (l-glut) or N-methyl-d-aspartate (NMDA) in vitro. However, high levels of l-glut do not compromise the function of the blood-brain barrier in vivo. We sought to determine whether primary cultures of rat and piglet CMVECs or cerebral microvascular pericytes (CMVPCs) are indeed sensitive to l-glut or NMDA. Viability was unaffected by 8-h exposure to 1–10 mM l-glut or NMDA in CMVECs or CMVPCs isolated from both species. Furthermore, neither 1 mM l-glut nor NMDA augmented cell death induced by 12-h oxygen-glucose deprivation in rat CMVECs or by 8-h medium withdrawal in CMVPCs. Additionally, transendothelial electrical resistance of rat CMVEC-astrocyte cocultures or piglet CMVEC cultures were not compromised by up to 24-h exposure to 1 mM l-glut or NMDA. The Ca2+ionophore calcimycin (5 μM), but not l-glut (1 mM), increased intracellular Ca2+levels in rat CMVECs and CMVPCs assessed with fluo-4 AM fluorescence and confocal microscopy. CMVEC-dependent pial arteriolar vasodilation to hypercapnia and bradykinin was unaffected by intracarotid infusion of l-glut in anesthetized piglets by closed cranial window/intravital microscopy. We conclude that cerebral microvascular cells are insensitive and resistant to glutamatergic stimuli in accordance with their in vivo role as regulators of potentially neurotoxic amino acids across the blood-brain barrier.
Rosiglitazone reduces renal and plasma markers of oxidative injury and reverses urinary metabolite abnormalities in the amelioration of diabetic nephropathy
Authors: Zhang Hongyu , Saha Jharna , Byun Jaeman , Schin MaryLee , Lorenz Matthew , Kennedy Robert T. , Kretzler Matthias , Feldman Eva L. , Pennathur Subramaniam , Brosius Frank C.
Published: July 2008

Recent studies suggest that thiazolidinediones ameliorate diabetic nephropathy (DN) independently of their effect on hyperglycemia. In the current study, we confirm and extend these findings by showing that rosiglitazone treatment prevented the development of DN and reversed multiple markers of oxidative injury in DBA/2J mice made diabetic by low-dose streptozotocin. These diabetic mice developed a 14.2-fold increase in albuminuria and a 53% expansion of renal glomerular extracellular matrix after 12 wk of diabetes. These changes were largely abrogated by administration of rosiglitazone beginning 2 wk after the completion of streptozotocin injections. Rosiglitazone had no effect on glycemic control. Rosiglitazone had similar effects on insulin-treated diabetic mice after 24 wk of diabetes. Podocyte loss and glomerular fibronectin accumulation, other markers of early DN, were prevented by rosiglitazone in both 12- and 24-wk diabetic models. Surprisingly, glomerular GLUT1 levels did not increase and nephrin levels did not decrease in the diabetic animals; neither changed with rosiglitazone. Plasma and kidney markers of protein oxidation and lipid peroxidation were significantly elevated in the 24-wk diabetic animals despite insulin treatment and were reduced to near-normal levels by rosiglitazone. Finally, urinary metabolites were markedly altered by diabetes. Of 1,988 metabolite features identified by electrospray ionization time of flight mass spectrometry, levels of 56 were altered more than twofold in the urine of diabetic mice. Of these, 21 were returned to normal by rosiglitazone. Thus rosiglitazone has direct effects on the renal glomerulus to reduce reactive oxygen species accumulation to prevent type 1 diabetic mice from development of DN.
IL-8 amplifies CD40/CD154-mediated ICAM-1 production via the CXCR-1 receptor and p38-MAPK pathway in human renal proximal tubule cells
Authors: Li Hongye , Nord Edward P.
Published: July 2008

Activation of the CD40 receptor by its cognate ligand, CD154, results in interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) production and increased intercellular adhesion molecule-1 (ICAM-1) expression in proximal tubule cells (PTCs). The independent role of these two proinflammatory chemokines, IL-8 and MCP-1, in inciting an inflammatory response in PTCs was explored. Exposure of primary cultures of human renal PTCs to recombinant IL-8 and MCP-1 resulted in increased ICAM-1 expression measured by quantitative real-time PCR, but confirmed only for IL-8 by immunoblot. The mechanism of action of IL-8 was explored in further detail. Immunohistochemistry identified both the CXCR-1 and CXCR-2 receptors, confirmed by RT-PCR, immunoprecipitation, immunoblot, and FACS analysis. IL-8 increased ICAM-1 expression only via the CXCR-1 receptor, which in turn resulted in activation of the p38 mitogen-activated protein kinase (MAPK) pathway; neither the extracellular signal-related kinase (ERK) 1/2 MAPK pathway nor the stress-activated protein kinase (SAPK)/c-Jun NH2 terminal kinase (JNK) pathway was involved. CD154/CD40-mediated ICAM-1 upregulation was not affected by preincubation of monolayers with the CXCR-1 blocking antibody, indicating that ICAM-1 expression occurs independent of CD154-mediated IL-8 production. Coincubation of monolayers with both CD154 and IL-8 resulted in a greater ICAM-1 response than either compound alone. We conclude that in human renal PTCs, IL-8 upregulates ICAM-1 production by engaging the CXCR-1 receptor and p38 MAPK signaling pathway. This cascade of events is independent of CD40/CD154-mediated IL-8 stimulation and ICAM-1 production and serves to amplify the inflammatory response.
Radicicol, a heat shock protein 90 inhibitor, reduces glomerular filtration rate
Authors: Ramírez Victoria , Mejía-Vilet Juan M. , Hernández Damián , Gamba Gerardo , Bobadilla Norma A.
Published: July 2008

The heat shock protein subfamily of 90 kDa (HSP90) is composed of five isoforms. The more abundant proteins of this subfamily are cytosolic isoforms known as HSP90α and HSP90β. More than 100 client proteins have been found to be regulated by HSP90. Several studies have shown that HSP90 regulates nitric oxide synthesis that is dependent on endothelial nitric oxide synthase (eNOS). Because eNOS regulates renal vascular tone and glomerular filtration rate (GFR), the present study was designed to evaluate the effect of acute HSP90 inhibition with radicicol on GFR and the eNOS pathway. Twenty male Wistar rats were divided into two groups: control vehicle animals and radicicol-infused animals (25 μg·ml−1·min−1). Basal levels were taken before experimental measurements. Mean arterial pressure and renal blood flow (RBF) were recorded, as well as GFR, urinary nitrite and nitrate excretion (UNO2/NO3V). Additionally, we evaluated eNOS expression, Ser1177 and Thr495 eNOS phosphorylation levels, the eNOS dimer-to-monomer ratio, as well as oxidative stress by assessing renal lipoperoxidation and urinary isoprostane F2α and hydrogen peroxide. HSP90 inhibition with radicicol produced a fall in RBF and GFR that was associated with a significant reduction of UNO2/NO3V. The effects of radicicol were in part mediated by a significant decrease in eNOS phosphorylation and in the eNOS dimer-to-monomer ratio. Our findings suggest that GFR is in part maintained by HSP90-eNOS interaction.
Regulation of the epithelial Na+channel by endothelin-1 in rat collecting duct
Authors: Bugaj Vladislav , Pochynyuk Oleh , Mironova Elena , Vandewalle Alain , Medina Jorge L. , Stockand James D.
Published: July 2008

We used patch-clamp electrophysiology to investigate regulation of the epithelial Na+channel (ENaC) by endothelin-1 (ET-1) in isolated, split-open rat collecting ducts. ET-1 significantly decreases ENaC open probability by about threefold within 5 min. ET-1 decreases ENaC activity through basolateral membrane ETBbut not ETAreceptors. In rat collecting duct, we find no role for phospholipase C or protein kinase C in the rapid response of ENaC to ET-1. ET-1, although, does activate src family tyrosine kinases and their downstream MAPK1/2 effector cascade in renal principal cells. Both src kinases and MAPK1/2 signaling are necessary for ET-1-dependent decreases in ENaC open probability in the split-open collecting duct. We conclude that ET-1 in a physiologically relevant manner rapidly suppresses ENaC activity in native, mammalian principal cells. These findings may provide a potential mechanism for the natriuresis observed in vivo in response to ET-1, as well as a potential cause for the salt-sensitive hypertension found in animals with impaired endothelin signaling.
Kv4 Accessory Protein DPPX (DPP6) is a Critical Regulator of Membrane Excitability in Hippocampal CA1 Pyramidal Neurons
Authors: Kim Jinhyun , Nadal Marcela S. , Clemens Ann M. , Baron Matthew , Jung Sung-Cherl , Misumi Yoshio , Rudy Bernardo , Hoffman Dax A.
Published: July 2008

A-type K+ currents have unique kinetic and voltage-dependent properties that allow them to finely tune synaptic integration, action potential (AP) shape and firing patterns. In hippocampal CA1 pyramidal neurons, Kv4 channels make up the majority of the somatodendritic A-type current. Studies in heterologous expression systems have shown that Kv4 channels interact with transmembrane dipeptidyl-peptidase-like proteins (DPPLs) to regulate the surface trafficking and biophysical properties of Kv4 channels. To investigate the influence of DPPLs in a native system, we conducted voltage-clamp experiments in patches from CA1 pyramidal neurons expressing short-interfering RNA (siRNA) targeting the DPPL variant known to be expressed in hippocampal pyramidal neurons, DPPX (siDPPX). In accordance with heterologous studies, we found that DPPX downregulation in neurons resulted in depolarizing shifts of the steady-state inactivation and activation curves, a shallower conductance-voltage slope, slowed inactivation, and a delayed recovery from inactivation for A-type currents. We carried out current-clamp experiments to determine the physiological effect of the A-type current modifications by DPPX. Neurons expressing siDPPX exhibited a surprisingly large reduction in subthreshold excitability as measured by a decrease in input resistance, delayed time to AP onset, and an increased AP threshold. Suprathreshold DPPX downregulation resulted in slower AP rise and weaker repolarization. Computer simulations supported our experimental results and demonstrated how DPPX remodeling of A-channel properties can result in opposing sub- and suprathreshold effects on excitability. The Kv4 auxiliary subunit DPPX thus acts to increase neuronal responsiveness and enhance signal precision by advancing AP initiation and accelerating both the rise and repolarization of APs.
Storage of Energy in Disk‐Shaped Laser Materials
Authors: Kouznetsov Dmitrii
Published: July 2008

Thin disk laser is analyzed, assuming that the heat is drained in the same direction, as the optical pulse, withdrawing the stored energy, comes.
Amplified spontaneous emission, the background loss, and overheating are taken into account with simple model. The scaling laws of the basic parameters are deduced. For the case of fixed repetition rate, the upper bound of thickness is obtained. Key parameters are suggested. The key energy parameter is promoted as criterion for evaluation of different laser materials for the high energy, high mean power disk lasers. The maximum energy per active element is estimated. For the scaling up the power and/or energy withdrawn from a single active element, the background loss should scale down inversely proportional to the cube of the background loss. This scaling law gives the criterion whether the heat should be drained in the direction orthogonal to the beam that withdraws the energy.
Mebendazole Induces Apoptosis via Bcl-2 Inactivation in Chemoresistant Melanoma Cells
Authors: Doudican Nicole , Rodriguez Adrianna , Osman Iman , Orlow Seth J.
Published: July 2008

Most metastatic melanoma patients fail to respond to available therapy, underscoring the need for novel approaches to identify new effective treatments. In this study, we screened 2,000 compounds from the Spectrum Library at a concentration of 1 μmol/L using two chemoresistant melanoma cell lines (M-14 and SK-Mel-19) and a spontaneously immortalized, nontumorigenic melanocyte cell line (melan-a). We identified 10 compounds that inhibited the growth of the melanoma cells yet were largely nontoxic to melanocytes. Strikingly, 4 of the 10 compounds (mebendazole, albendazole, fenbendazole, and oxybendazole) are benzimidazoles, a class of structurally related, tubulin-disrupting drugs. Mebendazole was prioritized to further characterize its mechanism of melanoma growth inhibition based on its favorable pharmacokinetic profile. Our data reveal that mebendazole inhibits melanoma growth with an average IC50 of 0.32 μmol/L and preferentially induces apoptosis in melanoma cells compared with melanocytes. The intrinsic apoptotic response is mediated through phosphorylation of Bcl-2, which occurs rapidly after treatment with mebendazole in melanoma cells but not in melanocytes. Phosphorylation of Bcl-2 in melanoma cells prevents its interaction with proapoptotic Bax, thereby promoting apoptosis. We further show that mebendazole-resistant melanocytes can be sensitized through reduction of Bcl-2 protein levels, showing the essential role of Bcl-2 in the cellular response to mebendazole-mediated tubulin disruption. Our results suggest that this screening approach is useful for identifying agents that show promise in the treatment of even chemoresistant melanoma and identifies mebendazole as a potent, melanoma-specific cytotoxic agent. (Mol Cancer Res 2008;6(8):1308–15)
Applying Computational Models of Spatial Prepositions to Visually Situated Dialog
Authors: Kelleher John D. , Costello Fintan J.
Published: July 2008

This article describes the application of computational models of spatial prepositions to visually situated dialog systems. In these dialogs, spatial prepositions are important because people often use them to refer to entities in the visual context of a dialog. We first describe a generic architecture for a visually situated dialog system and highlight the interactions between the spatial cognition module, which provides the interface to the models of prepositional semantics, and the other components in the architecture. Following this, we present two new computational models of topological and projective spatial prepositions. The main novelty within these models is the fact that they account for the contextual effect which other distractor objects in a visual scene can have on the region described by a given preposition. We next present psycholinguistic tests evaluating our approach to distractor interference on prepositional semantics, and illustrate how these models are used for both interpretation and generation of prepositional expressions.
Exploiting Semantic Role Resources for Preposition Disambiguation
Authors: O'Hara Tom , Wiebe Janyce
Published: July 2008

This article describes how semantic role resources can be exploited for preposition disambiguation. The main resources include the semantic role annotations provided by the Penn Treebank and FrameNet tagged corpora. The resources also include the assertions contained in the Factotum knowledge base, as well as information from Cyc and Conceptual Graphs. A common inventory is derived from these in support of definition analysis, which is the motivation for this work.

The disambiguation concentrates on relations indicated by prepositional phrases, and is framed as word-sense disambiguation for the preposition in question. A new type of feature for word-sense disambiguation is introduced, using WordNet hypernyms as collocations rather than just words. Various experiments over the Penn Treebank and FrameNet data are presented, including prepositions classified separately versus together, and illustrating the effects of filtering. Similar experimentation is done over the Factotum data, including a method for inferring likely preposition usage from corpora, as knowledge bases do not generally indicate how relationships are expressed in English (in contrast to the explicit annotations on this in the Penn Treebank and FrameNet). Other experiments are included with the FrameNet data mapped into the common relation inventory developed for definition analysis, illustrating how preposition disambiguation might be applied in lexical acquisition.
First Steps in Writing Arabic Narrative Fiction: The Case of Hadīqat al-Akhbār
Authors: Bawardi Basiliyus
Published: July 2008

This study tracks the significant literary activity of the Beirut newspaper Hadīqat al-Akhbār (1858-1911) in its first ten years. A textual examination of the newspaper reveals that Khalīl al-Khūrī (1836-1907), a central figure of the nahda and the owner of Hadīqat al-Akhbār, believed that an adoption of a new Western literary genre into the traditional Arabic literary tradition would provide the Arab culture with tools for reviving the Arabic language and create new styles of expression. The textual analysis of numerous narrative fictions that were published in the newspaper demonstrates two significant matters: first, Hadīqat al-Akhbār was the first Arabic newspaper to publish translations from Western narrative fiction, especially from the French Romance stories. Secondly, it will be shown how Khalīl al-Khūrī constructed a fetal model of Arabic narrative fiction by publishing a fictional narrative of his own, Wayy, idhan lastu bi-ifranjī (Alas, I'm not a foreigner), in 1859-1861. The literary activity in Hadīqat al-Akhbār, as the following study illustrates, played a substantial role in changing the aesthetic literary taste, and paved the way for the birth of an authentic Arabic narrative fiction.
The Myth of “The Triumph of Fanaticism” in the Seventeenth-Century Ottoman Empire
Authors: El-Rouayheb Khaled
Published: July 2008

Since Halil İnalcık's classic The Ottoman Empire: The Classical Age (1973), the received view amongst historians has been that Ottoman scholars lost interest in the rational sciences after around 1600, largely as an effect of the rise of the puritanical Kādīzādeli movement. In the present article, I argue that there was in fact no decline of interest in the rational sciences amongst seventeenth century Ottoman scholars. On the contrary, interest in logic, dialectic, philosophy and rational theology seems to have been on the rise. Sunni Persian, Azeri and Kurdish scholars fleeing Safavid Iran brought with them new scholarly works in the rational sciences and gained a reputation as accomplished teachers. The number of Ottoman colleges in which works on the rational sciences were studied and taught also seems to have risen dramatically in the course of the 17th century.
Mit der Waffe des Islams gegen Zionisten und Anthropomorphisten. Die politische Relevanz mittelalterlicher Theologie im ibāditischen Islam der Gegenwart
Authors: Berger Lutz
Published: July 2008

Starting from the polemics of the Ibādī mufti of Oman, Ahmad al-Khalīlī, with Ibn Bāz and other Wahhābī 'ulamā' this paper addresses how representatives of contemporary Islam try to overcome sectarian differences and how they make sense of medieval theological precepts in a radically changed intellectual and political environment. The paper stresses the role of (invented traditions of) resistance against external and internal foes (imperialism and—to a lesser degree—Sufism) as ideological basis for modernist Islamic ecumenism. Remaining sectarian differences are explained by pretending that rival sects are in reality agents of external enemies of Islam. An example of this argumentation is Ahmad al-Khalīlī's effort to remove the Wahhābīs from the fold of Islam by making Wahhābism a Jewish sect with Islamic trappings. For this purpose Ahmad al-Khalīlī recycles premodern Ibādī polemic against the Sunnis at large. Medieval theologoumena are thereby given a present-day political meaning. Without openly attacking the Sultan, the mufti al-Khalīlī's arguments against the Wahhābīs can at the same time be read as a document of opposition against the Omani regime's policies, in a situation where the Sultanate is confronted by a resurgence of political Ibādism.
“Ignatio atque immo Deo volente”: Canisius's Tertia probatio in Rome and His Mission to Sicily
Authors: van de Schoor Rob
Published: July 2008

Canisius's first mission to Sicily (1548-49), where he taught at the Jesuit college in Messina, can be seen as the culmination of the tertia probatio that he had undergone in Rome under Ignatius of Loyola. During that period, he had been trained and groomed by Ignatius, who had made him toe the Jesuit line through obedience and detachment. Just how the young man felt about all this is uncertain, although there are passages in his letters indicating that he found the various rites de passage difficult to bear. He in fact failed to achieve full detachment, for his love for his native Germany (in particular the lower Rhineland), could not be stifled. Ignatius then made a virtue of necessity by calling Canisius back from Sicily and sending him to Ingolstadt.
Climatology of Lake-Effect Precipitation Events over Lake Champlain
Authors: Laird Neil F. , Desrochers Jared , Payer Melissa
Published: July 2008

This study provides the first long-term climatological analysis of lake-effect precipitation events that developed in relation to a small lake (having a surface area of ≤1500 km2). The frequency and environmental conditions favorable for Lake Champlain lake-effect precipitation were examined for the nine winters (October–March) from 1997/98 through 2005/06. Weather Surveillance Radar-1988 Doppler (WSR-88D) data from Burlington, Vermont, were used to identify 67 lake-effect events. Events occurred as 1) well-defined, isolated lake-effect bands over and downwind of the lake, independent of larger-scale precipitating systems (LC events), 2) quasi-stationary lake-effect bands over the lake embedded within extensive regional precipitation from a synoptic weather system (SYNOP events), or 3) a transition from SYNOP and LC lake-effect precipitation. The LC events were found to occur under either a northerly or a southerly wind regime. An examination of the characteristics of these lake-effect events provides several unique findings that are useful for comparison with known lake-effect environments for larger lakes. January was the most active month with an average of nearly four lake-effect events per winter, and approximately one of every four LC events occurred with southerly winds. Event initiation and dissipation occurred on a diurnal time scale with an average duration of 12.1 h. In general, Lake Champlain lake-effect events 1) typically yielded snowfall, with surface air temperatures rarely above 0°C, 2) frequently had an overlake mesolow present with a sea level pressure departure of 3–5 hPa, 3) occurred in a very stable environment with a surface inversion frequently present outside the Lake Champlain Valley, and 4) averaged a surface lake–air temperature difference of 14.4°C and a lake–850-hPa temperature difference of 18.2°C. Lake Champlain lake-effect events occur within a limited range of wind and temperature conditions, thus providing events that are more sensitive to small changes in environmental conditions than are large-lake lake-effect events and offering a more responsive system for subsequent investigation of connections between mesoscale processes and climate variability.
Impact of Urban Growth on Surface Climate: A Case Study in Oran, Algeria
Authors: Bounoua Lahouari , Safia Abdelmounaine , Masek Jeffrey , Peters-Lidard Christa , Imhoff Marc L.
Published: July 2008

The authors develop a land use map discriminating urban surfaces from other cover types over a semiarid region in North Africa and use it in a land surface model to assess the impact of urbanized land on surface energy, water, and carbon balances. Unlike in temperate climates where urbanization creates a marked heat island effect, this effect is not strongly marked in semiarid regions. During summer, the urban class results in an additional warming of 1.45°C during daytime and 0.81°C at night relative to that simulated for needleleaf trees under similar climate conditions. Seasonal temperatures show that urban areas are warmer than their surrounding areas during summer and slightly cooler in winter. The hydrological cycle is practically “shut down” during summer and is characterized by relatively large amounts of runoff in winter. The authors estimate the annual amount of carbon uptake to be 1.94 million metric tons with only 11.9% assimilated during the rainy season. However, if urbanization expands to reach 50% of the total area excluding forests, the annual total carbon uptake will decline by 35% and the July mean temperature would increase only 0.10°C relative to the current situation. In contrast, if urbanization expands to 50% of the total land excluding forests and croplands but all short vegetation is replaced by native broadleaf deciduous trees, the annual carbon uptake would increase by 39% and the July mean temperature would decrease by 0.9°C relative to the current configuration. These results provide guidelines for urban planners and land use managers and indicate possibilities for mitigating the urban heat.
Practical Application of Two-Turning-Point Theory to Mountain-Wave Transmission through a Wind Jet
Authors: Broutman Dave , Eckermann Stephen D. , Rottman James W.
Published: July 2008

A Fourier method is used to model mountain waves that have nearby turning points in a wind jet. In Fourier space, the propagation equations are solved by ray theory. To correct for the ray singularity at a turning point without time-consuming special-function evaluations, the ray solution is linearly interpolated across the breakdown region. The Fourier solutions for the spatial wavefield are compared with mesoscale model simulations in two cases: two-dimensional flow over idealized topography with uniform stratification and a sech-squared wind profile and three-dimensional flow over the island of Jan Mayen with stratification and wind profiles taken from radiosonde measurements. The latter case reveals the partial transmission of trapped mountain waves into the stratosphere.
A New Algorithm for Low-Frequency Climate Response
Authors: Abramov Rafail V. , Majda Andrew J.
Published: July 2008

The low-frequency response to changes in external forcing for the climate system is a fundamental issue. In two recent papers the authors developed a new blended response algorithm for predicting the response of a nonlinear chaotic forced-dissipative system to small changes in external forcing. This new algorithm is based on the fluctuation–dissipation theorem and combines the geometrically exact general response formula using integration of a linear tangent model at short response times and the classical quasi-Gaussian response algorithm at longer response times. This algorithm overcomes the inherent numerical instability in the geometric formula arising because of positive Lyapunov exponents at longer times while removing potentially large systematic errors from the classical quasi-Gaussian approximation at moderate times.

Here the new blended method is tested on the low-frequency response for a T21 barotropic truncation on the sphere with realistic topography in two dynamical regimes corresponding to the mean climate behavior at 300- and 500-hPa geopotential height. The 300-hPa regime has robust strongly mixing behavior with a nearly Gaussian equilibrium state distribution, whereas the 500-hPa regime is weakly chaotic with slowly decaying time autocorrelation functions and strongly non-Gaussian climatology. It is found that the blended response algorithm has significant skill beyond the classical quasi-Gaussian algorithm for the response of the climate mean state and its variance. Additionally, the predicted response of the T21 barotropic model in the low-frequency regime for these functionals does not seem to be affected by the model’s structural instability. Thus, the results here suggest the use of the fluctuation–dissipation theorem–based blended response algorithm for more complex nonlinear geophysical models.
ISO Modulation on the Submonthly Wave Pattern and Recurving Tropical Cyclones in the Tropical Western North Pacific
Authors: Ko Ken-Chung , Hsu Huang-Hsiung
Published: July 2008

This study demonstrates the multiscale nature, from synoptic to intraseasonal time scales, of the atmospheric flow in the tropical western North Pacific. The multiscale features include intraseasonal oscillations (ISO), northwestward-propagating submonthly wave patterns, and recurving tropical cyclones (TCs). In the ISO westerly phase, the wave pattern was better organized and the TCs were clustered near the cyclonic circulation of the wave pattern during the genesis, development, and propagation. On the other hand, the wave pattern and TCs were weak and poorly organized in the ISO easterly phase. The distinct characteristics between the westerly and easterly phases could be attributed to the ISO modulation on the monsoon trough and the subtropical anticyclonic ridge. The ISO in the westerly phase provided a favorable background (e.g., enhanced monsoon trough and moisture confluent zone) for the wave–TC pattern development, while the ISO in the easterly phase provided a less favorable environment.
Predicting Extreme Phases of the Indian Summer Monsoon*
Authors: Ding Qinghua , Wang Bin
Published: July 2008

Extreme active and break phases of the Indian summer monsoon (ISM) often bring about devastating floods and severe draughts. Here it is shown that these extreme phases exhibit distinctive precursory circulation conditions in both the tropics and extratropics over a range of antecedent periods. The extremely active monsoon over northern India is preceded by a strengthening of the upper-tropospheric central Asian high and enhancement of the tropical convection over the equatorial Indian Ocean and the South China Sea. The concurrent buildup of the anomalous high over central Asia and the arrival of tropical convection over northern India increase the likelihood of occurrence of a heavy rainy period there. Similarly, the concurrent anomalous low over central Asia and the arrival of suppressed convection originating from the equatorial Indian Ocean and the South China Sea precede extremely strong monsoon breaks over northern India. Two predictors can be used to predict the extreme active/break phases of the northern ISM: normalized 200-hPa geopotential height over central Asia and outgoing longwave radiation over southern India. Once the mean of the two predictors exceeds a threshold unit (1.0), an extreme phase is anticipated to occur over northern India after 4–5 days and reach peak intensity after an additional 2 days. In general, an event forecast by this simple scenario has a 40% probability of developing into an extreme phase, which is normally a small probability event (a less than 4% occurrence).
Comparing Occurrences and Vertical Structures of Hydrometeors between Eastern China and the Indian Monsoon Region Using CloudSat/CALIPSO Data
Authors: Luo Yali , Zhang Renhe , Wang Hui
Published: July 2008

Seasonal variations in the occurrence frequency, vertical location, and radar reflectivity factor (dBZ) of hydrometeors covering eastern China and the Indian monsoon region are described using two CloudSat standard products [Geometrical Profiling Product (GEOPROF) and GEOPROF-lidar] during the period July 2006–August 2007. The 14-month averaged hydrometeor occurrence frequency is 80% (for eastern China) and 70% (for Indian region), respectively, to which multilayer (mostly double or triple layers) hydrometeors contribute 37% and 47%. A significant increase in the multilayer hydrometeor amount from winter to summer in the Indian region causes a pronounced seasonal variation in its total hydrometeor amount. The nearly opposite phases in the seasonal variations of single- and multilayer hydrometeor amounts result in little change with season in total hydrometeor amount in eastern China. Although the passive sensor-based satellite cloud product is able to provide the major seasonal features in the hydrometeor occurrence frequency (HOF) as revealed by the CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) product, it generally underestimates the HOF.

The maxima in the amounts of both high-level and thick hydrometeor layers occur during summer in both regions, reflecting the impact of the Asian summer monsoon. The abundance of low-level cloud layers and scarcity of hydrometeors at higher levels in eastern China during autumn to winter reflect the general subsidence motion in the middle and upper troposphere. The hydrometeors are geometrically thin in both regions. Cirrus containing small ice crystals is the most common cloud type in the Indian region over the year, while the eastern China hydrometeors are located lower and distributed more evenly in the dBZ–altitude phase space. Although the Indian region has deeper convection and more anvils than eastern China during summer, the averaged dBZ–altitude distributions of deep convection and anvils are nearly identical between the two regions.
Gravity Waves in a Horizontal Shear Flow. Part I: Growth Mechanisms in the Absence of Potential Vorticity Perturbations
Authors: Bakas Nikolaos A. , Farrell Brian F.
Published: July 2008

Interaction of internal gravity waves with a horizontal shear flow in the absence of potential vorticity perturbations is investigated making use of closed-form solutions. Localized wave packet trajectories are obtained, the energy growth mechanisms occurring are identified, and the potential role of perturbation growth in wave breaking is assessed.

Regarding meridional propagation, the wave packet motion is limited by turning levels where the waves are reflected and trapping levels where the waves stagnate. Regarding perturbation energy amplification, two growth mechanisms can be distinguished: growth due to advection of zonal velocity and growth due to downgradient Reynolds stresses. The three-dimensional perturbations producing optimal energy growth reveal that these two mechanisms produce large and robust amplification of zonal velocity and/or density and vertical velocity, potentially leading to shear or convective instability.

For large static stability, amplification of density perturbations in conjunction with vertical orientation of the constant phase lines close to the trapping level potentially leads to a convective collapse of the wave packet near the trapping level, in agreement with existing direct numerical simulation studies. For lower static stability and for waves with phase lines oriented horizontally, growth due to advection of zonal velocity dominates, leading to rapid growth of streamwise streaks within the localized wave packet and potentially to shear instability.
Multiscale Processes and Nonlinear Dynamics of the Circulation and Upwelling Events off Monterey Bay
Authors: San Liang X. , Robinson Allan R.
Published: July 2008

The nonlinear multiscale dynamics of the Monterey Bay circulation during the Second Autonomous Ocean Sampling Network (AOSN-II) Experiment (August 2003) is investigated in an attempt to understand the complex processes underlying the highly variable ocean environment of the California coastal region. Using a recently developed methodology, the localized multiscale energy and vorticity analysis (MS-EVA) and the MS-EVA-based finite-amplitude hydrodynamic instability theory, the processes are reconstructed on three mutually exclusive time subspaces: a large-scale window, a mesoscale window, and a submesoscale window. The ocean is found to be most energetic in the upper layers, and the temporal mesoscale structures are mainly trapped above 200 m. Through exploring the nonlinear window–window interactions, it is found that the dynamics underlying the complex surface circulation is characterized by a well-organized, self-sustained bimodal instability structure: a Bay mode and a Point Sur mode, which are located near Monterey Bay and west of Point Sur, respectively. Both modes are of mixed types, but they are distinctly different in dynamics. The former is established when the wind relaxes, while the latter is directly driven by the wind. Either way, the wind instills energy into the ocean, which is stored within the large-scale window and then released to fuel temporal mesoscale processes. Upon wind relaxation, the generated mesoscale structures propagate northward along the coastline, in a form with dispersion properties similar to that of a free thermocline-trapped coastal-trapped wave. Between these two modes, a secondary instability is identified in the surface layer during 15–21 August, transferring energy to the temporal submesoscale window. Also studied is the deep-layer flow, which is unstable all the time throughout the experiment within the Bay and north of the deep canyon. It is observed that the deep temporal mesoscale flow within the Bay may derive its energy from the submesoscale window as well as from the large-scale window. This study provides a real ocean example of how secondary upwelling can be driven by winds through nonlinear instability and how winds may excite the ocean via an avenue distinctly different from the classical paradigms.
Noise-Induced Multidecadal Variability in the North Atlantic: Excitation of Normal Modes
Authors: Frankcombe Leela M. , Dijkstra Henk A. , von der Heydt Anna
Published: July 2008

In this paper it is proposed that the stochastic excitation of a multidecadal internal ocean mode is at the origin of the multidecadal sea surface temperature variability in the North Atlantic. The excitation processes of the spatial sea surface temperature pattern associated with this multidecadal mode within an idealized three-dimensional model are studied by adding noise to the surface heat flux forcing. In the regime where the internal mode is damped, the amplitude of its sea surface temperature pattern depends on the type of noise forcing applied. While the mode is weakly excited by white noise, only the introduction of spatial and temporal coherence in the forcing, with characteristics of the North Atlantic Oscillation in particular, causes the amplitude of the variability to increase to levels comparable to those observed. Within this idealized model the physical mechanism of the excitation can be determined: the presence of the noise rectifies the background state and consequently changes the growth factor of the internal mode.
Validation of Jason-1 and Envisat Remotely Sensed Wave Heights
Authors: Durrant Tom H. , Greenslade Diana J. M. , Simmonds Ian
Published: July 2008

Satellite altimetry provides an immensely valuable source of operational significant wave height (Hs) data. Currently, altimeters on board Jason-1 and Envisat provide global Hs observations, available within 3–5 h of real time. In this work, Hs data from these altimeters are validated against in situ buoy data from the National Data Buoy Center (NDBC) and Marine Environmental Data Service (MEDS) buoy networks. Data cover a period of three years for Envisat and more than four years for Jason-1.

Collocation criteria of 50 km and 30 min yield 3452 and 2157 collocations for Jason-1 and Envisat, respectively. Jason-1 is found to be in no need of correction, performing well throughout the range of wave heights, although it is notably noisier than Envisat. An overall RMS difference between Jason-1 and buoy data of 0.227 m is found. Envisat has a tendency to overestimate low Hs and underestimate high Hs. A linear correction reduces the RMS difference by 7%, from 0.219 to 0.203 m.

In addition to wave height–dependent biases in the altimeter Hs estimate, a wave state–dependent bias is also identified, with steep (smooth) waves producing a negative (positive) bias relative to buoys.

A systematic difference in the Hs being reported by MEDS and NDBC buoy networks is also noted. Using the altimeter data as a common reference, it is estimated that MEDS buoys are underestimating Hs relative to NDBC buoys by about 10%.
The Riding Wave Removal Technique: Recent Developments
Authors: Schulz Eric Werner
Published: July 2008

Recent advances in a technique to identify and catalog waves that ride on larger-scale carrier waves are described in detail. The latest developments allow the riding wave removal technique to correctly identify and replace riding waves at the Nyquist frequency scale. Examples of the technique are provided for two diverse datasets: the Black Sea and Lake George. A sample of the riding wave characteristics extracted using this method is presented.
Potential Impacts of the Saharan Air Layer on Numerical Model Forecasts of North Atlantic Tropical Cyclogenesis
Authors: Pratt Aaron S. , Evans Jenni L.
Published: July 2008

Tropical cyclones have devastating impacts on countries across large parts of the globe, including the Atlantic basin. Thus, forecasting of the genesis of Atlantic tropical cyclones is important, but this problem remains a challenge for researchers and forecasters due to the variety of weather systems that can lead to tropical cyclogenesis (e.g., stalled frontal boundaries, African easterly waves, and extratropical cyclones), as well as the role of the surrounding environment in promoting or inhibiting the development into a tropical depression and beyond. In the North Atlantic, the effects of the Saharan air layer (SAL), a hot, dry dusty layer that moves into the eastern Atlantic basin, must be taken into account when forecasting whether genesis will occur. There are several characteristics of SAL that impact tropical cyclones (decreased midtropospheric moisture, increased midlevel shear, and enhanced stability). The purpose of this study is to examine the forecasting skill of the National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) model for the 2002 and 2003 Atlantic hurricane seasons, with particular regard paid to possible SAL effects on model genesis forecast accuracy. Cyclone phase space analyses of GFS 6-hourly forecasts were divided into three possible outcomes: S (successful forecasts that verified in cyclogenesis), F1 (cyclogenesis events that were not forecast to occur), and F2 (forecasted cyclogenesis that did not occur). The spatial variabilities of these outcomes for the early, middle, and late season were analyzed for both years, as well as the background environmental conditions. The large number of F2 forecasts that were seen in both years can be partly explained by the GFS model not capturing the detrimental effects of the SAL on cyclogenesis.
The Impact of Exposure To Violence On a Trajectory of (Declining) Parental Monitoring
Authors: Spano Richard , Rivera Craig , Vazsonyi Alexander T. , Bolland John M.
Published: July 2008

Five waves of longitudinal data collected from 348 African American youth living in extreme poverty are used to examine the impact of exposure to violence on parenting over time. Semiparametric group-based modeling is used to identify trajectories of parental monitoring and exposure to violence from Time 1 (T1) to Time 5 (T5). Results indicate that for youth (a) 48% had a trajectory of declining parental monitoring and (b) 7% had sharply increasing exposure to violence from T1 to T5. Multivariate findings are consistent with the ecological—transactional model of community violence. Exposure to violence T1 was a precursor of a trajectory of declining parental monitoring T1 to T5. Youth with a trajectory of stable and sharply increasing exposure to violence were more than 200% more likely to have declining parental monitoring T1 to T5. The theoretical implications of these findings as well as areas for future research are also discussed.
Exploring Cramming
Authors: McIntyre Shelby H. , Munson J. Michael
Published: July 2008

Cramming for finals is common on college campuses, and many students seem to cram for their final in the Principles of Marketing course. This article addresses the question of defining and measuring a “cramming study strategy.” Scales are developed to assess (a) cramming for courses in general and (b) cramming specifically in the Principles of Marketing course relative to two other study strategies. Several research questions about cramming are addressed, including (a) How widespread is the practice? (b) How effective do students perceive it to be? (c) How effective is it actually, both in the short and long term, for students' GPA and grade in the Principles of Marketing course? and (d) Is there a deterioration in retention, as measured by a master test, of content learned in the Principles course from using more of a cramming study strategy? Implications are discussed, particularly in light of various pedagogical approaches to combating learning decay, and areas for future research are suggested.
A Rose by Any Other Name? The Influence of Brand Name versus Chemical Differences in the Prescription of Antidepressants
Authors: Ward Steven , Pecotich Anthony , O'Cass Aron , Julian Craig C.
Published: July 2008

The effect that marketing has had on the prescription decisions of the medical profession is an area of great social and governmental concern and has been the subject of substantial international debate. In this study, the importance of brand name as a factor influencing the prescription habits of general practitioners and psychiatrists is examined. Data on antidepressant prescriptions supplied by the Australian Governments Pharmaceutical Benefit Scheme and results derived from MANOVA and ANOVA analyses suggest that the brand name as much as chemical differences influenced the prescription of choice of antidepressants by both general practitioners and psychiatrists. The use of a well-promoted brand name may be an important evaluation shortcut by both groups regardless of detailed training resulting in medical practices, which may undermine the social imperative of affordable medical care for all. The authors suggest that clinical appropriateness of prescriptions for antidepressants by brand name needs further investigation.