bluuebunny/crossref_metadata_2025 huggingface dataset:
Diel rhythms in shallow Mediterranean rocky-reef fishes: a chronobiological approach with the help of trained volunteers
Authors: Azzurro Ernesto , Aguzzi Jacopo , Maynou Francesc , Chiesa Juan José , Savini Dario
Published: September 2012

Behavioural rhythms in marine species have been mostly investigated in laboratory organisms and their expression within the animals' natural environments remains largely unknown. Here, we studied diel (i.e. 24-hours-based) and intra-diel (i.e. 12-hours-based) rhythmic variations in the abundance of seven shallow rocky-reef fish species, namelyCoris julis, Epinephelus marginatus, Sarpa salpa, Serranus cabrilla, Serranus scriba, Sparisoma cretenseandThalassoma pavo, along the rocky shores of Linosa Island (Mediterranean Sea). Data were visually collected by trained volunteers along fixed transects at 3-hourly intervals throughout six consecutive 24-hours periods. Density estimates can vary greatly between consecutive days and during 24-hours periods according not only to the major day–night changeover but also to minor intra-diel variations at the daylight hours. In the case ofT. pavo, C. julis, S. cabrillaand S. salpa waveform analyses showed midday troughs in abundance within the 24-hours period but significant variation within the hours of daylight was highlighted only forT. pavo. Although results were not conclusive at the intra-dial level, the employment of volunteers represented a valuable tool for chronobiology, suitable to improve our understanding of fish behaviour in natural systems.
Stimulated Raman forward scattering of laser in a pre-formed plasma channel
Authors: Panwar Anuraj , Kumar Ashok , Ryu C.M.
Published: September 2012

Stimulated Raman forward scattering (SRFS) of an intense short pulse laser in a plasma channel formed by two pre-laser pulses is investigated. The density nonuniformity of a plasma channel increases the focusing of main laser pulse. Main laser pulse excites a plasma wave and two electromagnetic sideband waves. Laser and the sidebands exert an axial ponderomotive force on electrons driving the plasma wave. The nonlinear currents arise at sideband frequencies. The density perturbation due to plasma wave beats with the oscillatory velocity due to pump to drive the sidebands. The normalized growth rate of SRFS increases with the density nonuniformity of a plasma channel. However, in the presence of a deep plasma channel the focusing is ineffective to laser intensity, but the growth rate increases with the intensity of main laser pulse.
Polarization effects in collisions between very intense laser beams and relativistic electrons
Authors: Popa Alexandru
Published: September 2012

The interaction between laser and relativistic electron beams is a promising source of very energetic X rays. We present an accurate model for the collisions between very intense linearly polarized laser beams, corresponding to relativistic parameters of the order of unity or greater, and electrons having energies up to 100 MeV. Our approach uses only one approximation, namely it neglects the radiative corrections. We consider the two cases in which the laser field polarization is either perpendicular or parallel to the plane defined by the directions of propagation of the laser beam and electron beam, and calculate accurately the properties of the σ and π polarized scattered beams. The angle between the directions of the laser and electron beams, denoted by θL, is allowed to have arbitrary values, so that the widely analyzed 180° and 90° geometries, in which the two beams collide, respectively, head on and perpendicularly, are particular cases. We prove that the polarization properties of the scattered beam depend on the angle θL. By varying this angle, the polarization of the scattered beam can be varied between the two limit configurations in which the electromagnetic field of the scattered beam is σ or π polarized with respect to the scattering plane. Our theoretical results are in good agreement with experimental results published in literature. Our model shows that current technologies can be used to produce hard harmonics of the scattered radiations. These harmonics can have relatively high intensities comparable to the intensities of the first harmonics, and energies higher than 1 MeV. Our results lead to the possibility to realize an adjustable photon source with both the energy and polarization of the scattered radiations accurately controlled by the value of the θL angle.
Experimental verification of a low-impedance transit-time oscillator without foils
Authors: Cao Yibing , He Juntao , Zhang Jiande , Ling Junpu
Published: September 2012

The low-impedance transit-time oscillator without foils is a new high-power microwave generator. In a previous report, a radiation power of 2.7 GW at 1.64 GHz has been achieved and the corresponding power conversion efficiency is 18.75%. Recently, the further experiments are continued in our laboratory. By increasing the cathode-anode gap properly, the operating voltage of device is enhanced to about 628 kV, and the corresponding radiation power reaches 3.6 GW. The device efficiency approaches 23%. In the newest experiments, because of the higher power level, the radiation power has been obviously influenced by RF breakdown in the vicinity of the dielectric window. By using a plastic bag filled with sulfur-hexafluoride (SF6), such an influence can be minimized.
OPTIMAL POLICY FOR A PRODUCTION–INVENTORY SYSTEM WITH SETUP COST AND AVERAGE COST CRITERION
Authors: Chao Xiuli , Xu Yifan , Yang Baimei
Published: September 2012

One of the most fundamental results in inventory theory is the optimality of (s, S) policy for inventory systems with setup cost. This result is established under a key assumption of infinite ordering/production capacity. Several studies have shown that, when the ordering/production capacity is finite, the optimal policy for the inventory system with setup cost is very complicated and indeed, only partial characterization for the optimal policy is possible. In this paper, we consider a continuous review production/inventory system with finite capacity and setup cost. The demand follows a Poisson process and a demand that cannot be satisfied upon arrival is backlogged. We show that the optimal control policy has a very simple structure when the holding/shortage cost rate is quasi-convex. We also develop efficient algorithms to compute the optimal control parameters.
AN URN MODEL FOR CASCADING FAILURES ON A LATTICE
Authors: Cirillo Pasquale , Hüsler Jürg
Published: September 2012

A cascading failure is a failure in a system of interconnected parts, in which the breakdown of one element can lead to the subsequent collapse of the others. The aim of this paper is to introduce a simple combinatorial model for the study of cascading failures. In particular, having in mind particle systems and Markov random fields, we take into consideration a network of interacting urns displaced over a lattice. Every urn is Pólya-like and its reinforcement matrix is not only a function of time (time contagion) but also of the behavior of the neighboring urns (spatial contagion), and of a random component, which can represent either simple fate or the impact of exogenous factors. In this way a non-trivial dependence structure among the urns is built, and it is used to study default avalanches over the lattice. Thanks to its flexibility and its interesting probabilistic properties, the given construction may be used to model different phenomena characterized by cascading failures such as power grids and financial networks.
PROPERTIES OF SECOND-ORDER REGULAR VARIATION AND EXPANSIONS FOR RISK CONCENTRATION
Authors: Lv Wenhua , Mao Tiantian , Hu Taizhong
Published: September 2012

The purpose of this study is two-fold. First, we investigate further properties of the second-order regular variation (2RV). These properties include the preservation properties of 2RV under the composition operation and the generalized inverse transform, among others. Second, we derive second-order expansions of the tail probabilities of convolutions of non-independent and identically distributed (i.i.d.) heavy-tail random variables, and establish second-order expansions of risk concentration under mild assumptions. The main results extend some ones in the literature from the i.i.d. case to non-i.i.d. case.
APPROXIMATE DYNAMIC PROGRAMMING TECHNIQUES FOR SKILL-BASED ROUTING IN CALL CENTERS
Authors: Roubos D. , Bhulai S.
Published: September 2012

We consider the problem of dynamic multi-skill routing in call centers. Calls from different customer classes are offered to the call center according to a Poisson process. The agents are grouped into pools according to their heterogeneous skill sets that determine the calls that they can handle. Each pool of agents serves calls with independent exponentially distributed service times. Arriving calls that cannot be served directly are placed in a buffer that is dedicated to the customer class. We obtain nearly optimal dynamic routing policies that are scalable with the problem instance and can be computed online. The algorithm is based on approximate dynamic programming techniques. In particular, we perform one-step policy improvement using a polynomial approximation to relative value functions. We compare the performance of this method with decomposition techniques. Numerical experiments demonstrate that our method outperforms leading routing policies and has close to optimal performance.
Public Ritual and Urbanization in Central Mexico: Temple and Plaza Offerings from La Laguna, Tlaxcala
Authors: Carballo David M.
Published: September 2012

Urbanization of the world's first cities involved the social integration of greater scales of community membership as well as the social differentiation of individuals along the continua of wealth, power, and occupational specialization that define urban landscapes. This article considers the causal role of public ritual in these processes during the period of incipient urbanism in central Mexico (c. 600 BC–AD 100) by examining temple and plaza offerings at La Laguna, a town within an urbanizing cultural landscape whose inhabitants participated in the transformative exchanges that resulted in urban state capitals such as Teotihuacan.
The Domestication of Personhood: a View from the Northern Iroquoian Longhouse
Authors: Creese John L.
Published: September 2012

This article examines how personhood was shaped in the routine dispositional relations of longhouse life among the Iroquoian societies of eastern North America. Drawing on scholarship that situates the emergence of culturally-specific modes of personhood within relational networks of people and things, I present evidence that over seven centuries, a deep resonance developed between the ‘polyvalence’ of Iroquoian domestic spaces and a broadly ‘fractal’ (sensu Fowler 2004) or ‘part-in-whole’ sense of personhood in Iroquoian societies. An ethnohistoric review of seventeenth-century Ontario Iroquoian concepts of personhood is followed by an archaeological analysis of the development of longhouses between the tenth and sixteenth centuries. I report the results of a kernel density estimation (KDE) analysis of the spatial distribution of post and pit features across longhouse living floors in a diachronic study of 45 hearth areas. The results indicate that everyday practices within the longhouse came to follow several characteristic patterns by the mid-twelfth century ad. These patterns served to define ‘polyvalent’ relationships in which resident persons and nuclear families were at once identifiable as distinct social atoms and as inextricable components of larger hypostatic wholes — most especially house and lineage. A fundamental coherence was thereby established between the embodied experience of domestic taskscapes and a mode of personhood in which any social whole was understood as a dynamic and partible alliance of elements.
Daily sugar-sweetened beverage consumption and insulin resistance in European adolescents: the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) Study
Authors: Kondaki Katerina , Grammatikaki Evangelia , Jiménez-Pavón David , De Henauw Stefaan , González-Gross Marcela , Sjöstrom Michael , Gottrand Frédéric , Molnar Dénes , Moreno Luis A , Kafatos Anthony , Gilbert Chantal , Kersting Mathilde , Manios Yannis
Published: September 2012

Objective

The present study aimed to evaluate the relationship between the consumption of selected food groups and insulin resistance, with an emphasis on sugar-sweetened beverages (SSB).

Design

The present research is a large multicentre European study in adolescents, the HELENA-CSS (Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study).

Setting

Homeostasis model assessment–insulin resistance index (HOMA-IR) was calculated. Several anthropometric and lifestyle characteristics were recorded. Dietary assessment was conducted by using a short FFQ.

Subjects

The participants were a subset of the original sample (n546) with complete data on glucose, insulin and FFQ. All participants were recruited at schools.

Results

Median (25th, 75th percentile) HOMA-IR was 0·62 (0·44, 0·87). Mean HOMA-IR was significantly higher among adolescents consuming brown bread ≤1 time/week than among those consuming 2–6 times/week (P= 0·011). Mean values of HOMA-IR were also higher in adolescents consuming SSB >5 times/week compared with those consuming less frequently, although a statistically significant difference was detected between those consuming SSB 5–6 times/week and 2–4 times/week (P= 0·049). Multiple linear regression analysis showed that only the frequency of SSB consumption was significantly associated with HOMA-IR after controlling for potential confounders. In particular, it was found that HOMA-IR levels were higher among adolescents consuming SSB 5–6 times/week and ≥1 time/d compared with those consuming ≤1 time/week by 0·281 and 0·191 units, respectively (P= 0·009 and 0·046, respectively).

Conclusions

The present study revealed that daily consumption of SSB was related with increased HOMA-IR in adolescents.
School food and nutrition policy, monitoring and evaluation in the USA
Authors: Hirschman Jay , Chriqui Jamie F
Published: September 2012

Objective

To provide an overview of school food and nutrition monitoring from 1980 to the Healthy Hunger-Free Kids Act of 2010 and data on school food availability in the USA.

Design

A review of the history of school food and nutrition policy, monitoring and evaluation efforts in the USA over the past three decades.

Setting

USA.

Subjects

School food service, school districts and schools nationwide.

Results

The school food environment in the USA is governed by a patchwork of federal, state and local laws and policies. The federal government has primary authority over the school meal programmes and has recently issued updated regulations governing the food and nutrient requirements for meals sold or served through the National School Lunch and School Breakfast Programs. Competitive foods (i.e. foods and beverages sold/served outside the meal programmes) are governed primarily by state and district laws and policies, although new federal regulations are expected to set minimum standards in this area. The USA has a long history of data monitoring and evaluation funded by government and private foundations which has enabled decision makers to monitor progress and opportunities to improve the foods and beverages made available to students in school.

Conclusions

School food-related monitoring and evaluation research has been highly influential in influencing legislation and policy, leading to improvements in the foods and beverages available to children at school as part of planned meals and individual items sold outside the meal programmes. The lessons learned from the US experience provide insights that may be valuable for implementation, monitoring and evaluation of school food programmes in other countries.
Design, testing and validation of an innovative web-based instrument to evaluate school meal quality
Authors: Patterson Emma , Quetel Anna-Karin , Lilja Karin , Simma Marit , Olsson Linnea , Elinder Liselotte Schäfer
Published: September 2012

Objective

To develop a feasible, valid, reliable web-based instrument to objectively evaluate school meal quality in Swedish primary schools.

Design

The construct ‘school meal quality’ was operationalized by an expert panel into six domains, one of which was nutritional quality. An instrument was drafted and pilot-tested. Face validity was evaluated by the panel. Feasibility was established via a large national study. Food-based criteria to predict the nutritional adequacy of school meals in terms of fat quality, iron, vitamin D and fibre content were developed. Predictive validity was evaluated by comparing the nutritional adequacy of school menus based on these criteria with the results from a nutritional analysis. Inter-rater reliability was also assessed.

Setting

The instrument was developed between 2010 and 2012. It is designed for use in all primary schools by school catering and/or management representatives.

Subjects

A pilot-test of eighty schools in Stockholm (autumn 2010) and a further test of feasibility in 191 schools nationally (spring 2011).

Results

The four nutrient-specific food-based criteria predicted nutritional adequacy with sensitivity ranging from 0·85 to 1·0, specificity from 0·45 to 1·0 and accuracy from 0·67 to 1·0. The sample in the national study was statistically representative and the majority of users rated the questionnaire positively, suggesting the instrument is feasible. The inter-rater reliability was fair to almost perfect for continuous variables and agreement was ≥67 % for categorical variables.

Conclusions

An innovative web-based system to comprehensively monitor school meal quality across several domains, with validated questions in the nutritional domain, is available in Sweden for the first time.
On the Search for the Authentic Liturgy of the Apostles: The Diversity of the Early Church as Normative for Anglicans
Authors: Barrington Bates J.
Published: September 2012

This essay examines the Anglican claim for the early church as the normative standard for liturgy, as reiterated throughout our history from the time of Thomas Cranmer through the liturgical revisions of the late twentieth century. A secondary claim of general uniformity through similarity in texts of common prayer is then discussed as a point of historic resonance for Anglican identity. Some very general examples of early church evidence follow, as a means of debunking the notion of a unified and simple structure for primitive liturgy. I will then discuss the notion of ‘early church’, and what we mean by terms like it, and follow this with a consideration of liturgical diversity. The gospel call to privilege Christian unity, I will assert, remains the primary stumbling block to the full embracing of the God-given diversity of the one holy, catholic and apostolic church.
The impact of maternal synthetic glucocorticoid administration in late pregnancy on fetal and early neonatal hypothalamic–pituitary–adrenal axes regulatory genes is dependent upon dose and gestational age at exposure
Authors: Li S. , Moss T. J. M. , Nitsos I. , Matthews S. G. , Challis J. R. G. , Newnham J. P. , Sloboda D. M.
Published: September 2012

In this study, we determined the gene and/or protein expression of hypothalamic–pituitary–adrenal (HPA) axis regulatory molecules following synthetic glucocorticoid exposures. Pregnant sheep received intramuscular saline or betamethasone (BET) injections at 104 (BET-1), 104 and 111(BET-2) or 104, 111 and 118 (BET-3) days of gestation (dG). Samples were collected at numerous time-points between 75 dG and 12 weeks postnatal age. In the BET-3 treatment group, fetal plasma cortisol levels were lower at 145 dG than controls and gestational length was lengthened significantly. The cortisol:adrenocorticotropic hormone (ACTH) ratio in fetal plasma of control and BET-3 fetuses rose significantly between132 and 145 dG, and remained elevated in lambs at 6 and 12 weeks of age; this rise was truncated at day 145 in fetuses of BET-3 treated mothers. After BET treatment, fetal and postnatal pituitary proopiomelanocortin mRNA levels were reduced from 109 dG to 12 weeks postnatal age; pituitary prohormone convertase 1 and 2 mRNA levels were reduced at 145 dG and postnatally; hypothalamic arginine vasopressin mRNA levels were lowered at all time-points, but corticotrophin-releasing hormone mRNA levels were reduced only in postnatal lambs. Maternal BET increased late fetal and/or postnatal adrenal mRNA levels of ACTH receptor and 3β hydroxysteroid dehydrogenase but decreased steroidogenic acute regulatory protein and P450 17-α hydroxylase. The altered mRNA levels of key HPA axis regulatory proteins after maternal BET injections suggests processes that may subserve long-term changes in HPA activity in later life after prenatal exposure to synthetic glucocorticoids.
Self-Concept, Implicit Leadership Theories, and Follower Preferences for Leadership
Authors: Ehrhart Mark G.
Published: September 2012

The purpose of this study was to investigate the factors that shape followers’ initial reactions to leaders. Based on the literature on self-concept and leader categorization theory, it was hypothesized that followers’ self-concepts (specifically their self-esteem and self-construal) would predict their conceptualization of an ideal leader (i.e., their implicit leadership theory, ILT), which would then predict followers’ preferences for specific leadership styles. Using a sample of 206 university students, results indicated that the effects of independent self-construal on charismatic leader preference were partially mediated by the dedication ILT dimension, and the effects of interdependent self-construal were fully mediated by the sensitivity ILT dimension. Additional findings and directions for future research are discussed.
Despite Leaders’ Good Intentions?
Authors: Peus Claudia , Braun Susanne , Frey Dieter
Published: September 2012

This article introduces the concept of adverse leadership. Adverse leadership arises when followers (1) perceive their leader to violate leadership prototypes or to concur with antiprototypes, and (2) attribute this violation to internal stable conditions within the leader (i.e., actor-observer bias), even though (3) the leader had no intention to cause harm. Adverse leadership goes above and beyond earlier leadership concepts because it focuses on (a) the role of followers’ implicit leadership theories and attributions in negative leadership, and on (b) leader behavior that is not intended to be harmful by the leader; it is conceptualized on (c) multiple levels of analysis, and posited to have (d) differential negative and positive effects on outcomes in organizations. Implications for future research and practice are discussed.
From Radical to Mainstream?
Authors: Bligh Michelle C. , Kohles Jeffrey C.
Published: September 2012

While the prevalent approach in leadership studies has focused on the leader figure, a growing number of studies challenge the implicit assumption that leaders are always singularly most central and critical to the leadership process. In this article, we review the development of follower-centered approaches that challenge the study of leadership without a concomitant emphasis on the importance of followership. From its roots as a critical challenge to the “mainstream” leadership tradition, the study of followership has helped to sharpen the focus of both leader and follower roles. Follower-centered approaches deepen almost any leader-centric analysis, for when the view is shifted from leaders to followers, assumptions are challenged, new perspectives are developed, and new questions are raised. Here, we provide an overview of followercentric approaches which either directly or indirectly challenge the study of leadership as primarily the study of leaders.
Contributions of natural and anthropogenic sources to atmospheric methane variations over western Siberia estimated from its carbon and hydrogen isotopes
Authors: Umezawa Taku , Machida Toshinobu , Aoki Shuji , Nakazawa Takakiyo
Published: September 2012

Aircraft measurements of carbon and hydrogen isotopic ratios of atmospheric CH4 (δ13CH4 and δD‐CH4), with the respective precisions of 0.08‰ and 2.2‰, as well as CH4 concentration were made at 1 and 2 km altitudes over western Siberia during 2006–2009. δ13CH4 and δD‐CH4 were almost always lower at lower altitudes, while the CH4 concentration was higher, implying strong sources on the ground with low isotopic values. δ13CH4 showed a clear seasonal minimum in the late summer, while seasonality of CH4 and δD‐CH4 was ambiguous due to the local disturbances. By inspecting the relationships between the CH4 concentration and isotopes, we found that isotopic source signatures in the winter (December–April) are −41.2 ± 1.8 and −187 ± 18‰ for δ13CH4 and δD‐CH4, respectively, and the corresponding values in the summer (June–October) are −65.0 ± 2.5 and −282 ± 25‰. These values indicate predominant CH4emissions from fossil fuel facilities in the winter and wetlands in the summer. It was also found that the shorter‐term CH4 variations are more influenced by fossil CH4 than that from wetlands. The finding presumably reflects the fact that the former is released from limited areas such as leakage from fossil fuel facilities, while the latter is released from a vast expanse of wetland. By employing a CH4 emission data set used in an atmospheric chemistry transport model, we calculated seasonal isotopic changes of CH4 sources in western Siberia and compared them to the estimates obtained in this study. The results indicated that the seasonal change in the CH4 emission data set is reasonable, at least in terms of a ratio of fossil to biogenic emissions.
Linking the northern Alps with their foreland: The latest exhumation history resolved by low‐temperature thermochronology
Authors: von Hagke C. , Cederbom C. E. , Oncken O. , Stöckli D. F. , Rahn M. K. , Schlunegger F.
Published: September 2012

The evolution of the Central Alpine deformation front (Subalpine Molasse) and its undeformed foreland is recently debated because of their role for deciphering the late orogenic evolution of the Alps. Its latest exhumation history is poorly understood due to the lack of late Miocene to Pliocene sediments. We constrain the late Miocene to Pliocene history of this transitional zone with apatite fission track and (U‐Th)/He data. We used laser ablation inductively coupled mass spectrometry for apatite fission track dating and compare this method with previously published and unpublished external detector method fission track data. Two investigated sections across tectonic slices show that the Subalpine Molasse was tectonically active after the onset of folding of the Jura Mountains. This is much younger than hitherto assumed. Thrusting occurred at 10, 8, 6–5 Ma and potentially thereafter. This is contemporaneous with reported exhumation of the External Crystalline Massifs in the central Alps. The Jura Mountains and the Subalpine Molasse used the same detachments as the External Crystalline Massifs and are therefore kinematically coupled. Estimates on the amount of shortening and thrust displacement corroborate this idea. We argue that the tectonic signal is related to active shortening during the late stage of orogenesis.
Effect of experimental wood addition on hyporheic exchange and thermal dynamics in a losing meadow stream
Authors: Sawyer Audrey H. , Cardenas M. Bayani
Published: September 2012

Stream restoration structures such as large wood can enhance shallow river‐groundwater exchange, or hyporheic exchange, and alter temperature dynamics in restored reaches. We added and then removed channel‐spanning logs in a second‐order mountain meadow stream to test short‐term impacts on hyporheic exchange, streambed temperatures, and surface water temperatures. Based on vertical seepage measurements and numerical simulations of hyporheic fluid and heat flow, large wood addition increased hyporheic exchange and altered streambed temperatures. In this losing stream, meter‐scale hyporheic exchange cells formed beneath large wood. Upwelling pore water downstream of logs stabilized diel temperature cycles across <8% of the streambed, creating localized but potentially valuable thermal refuge. Exchange rates were <0.1% of channel discharge—too small to impact the range of diel temperature signals in surface water. However, the lag between downstream and upstream diel temperature signals was slightly greater with large wood, which may indicate that surface storage zones rather than hyporheic storage zones increased thermal retardation. Losing conditions limited the spatial extent and rates of hyporheic exchange near large wood. Impacts of large wood reintroduction on hyporheic exchange depend on ambient groundwater discharge or recharge, streambed permeability, channel Froude number, large wood blockage ratio, and large wood spacing. In many streams, large wood reintroduction may increase hyporheic habitat volume and complexity but may not increase exchange rates enough to alter surface water temperature or chemistry. Surface storage zones such as eddies and pools can still influence heat and solute retention in the channel.
Trends in the global tropopause thickness revealed by radiosondes
Authors: Feng Sha , Fu Yunfei , Xiao Qingnong
Published: September 2012

The first global trends in the thickness of the tropopause layer (TL) are analyzed based on radiosonde data in the Integrated Global Radiosonde Archive (IGRA) for the period of 1965–2004. It reveals that TL has been thickening for the entire globe with positive trends of 0.16 ± 0.12 km/decade during this period. Statistically significant thickening is observed in the tropics, North Hemisphere (NH) extratropics, and NH poles. Accompanied by overall cooling of −0.58 ± 0.40 K/decade in TL's top, remarkable rising trends of 0.35 ± 0.29 km/decade are observed in the correspoding height. However, the anti‐correlation of the trends in the tropopause temperature and the corresponding height is not observed in its lower boundary, namely the first lapse rate tropopause (LRT), for all the latitude bands as suggested by the previous studies. The results imply that the temperature of the TL is primarily couple with the height of its upper boundary as the thickness of the TL is more correlated with the temperature of the lower stratosphere than with the tempeature of the upper troposphere. Long‐term changes in TL may in turn carry more information how tropopause change in response to climate change than in the sharp “tropopause surface” only.
Can a halo CME from the limb be geoeffective?
Authors: Cid C. , Cremades H. , Aran A. , Mandrini C. , Sanahuja B. , Schmieder B. , Menvielle M. , Rodriguez L. , Saiz E. , Cerrato Y. , Dasso S. , Jacobs C. , Lathuillere C. , Zhukov A.
Published: September 2012

The probability for a halo coronal mass ejection (CME) to be geoeffective is assumed to be higher the closer the CME launch site is located to the solar central meridian. However, events far from the central meridian may produce severe geomagnetic storms, like the case in April 2000. In this work, we study the possible geoeffectiveness of full halo CMEs with the source region situated at solar limb. For this task, we select all limb full halo (LFH) CMEs that occurred during solar cycle 23, and we search for signatures of geoeffectiveness between 1 and 5 days after the first appearance of each CME in the LASCO C2 field of view. When signatures of geomagnetic activity are observed in the selected time window, interplanetary data are carefully analyzed in order to look for the cause of the geomagnetic disturbance. Finally, a possible association between geoeffective interplanetary signatures and every LFH CME in solar cycle 23 is checked in order to decide on the CME's geoeffectiveness. After a detailed analysis of solar, interplanetary, and geomagnetic data, we conclude that of the 25 investigated events, there are only four geoeffective LFH CMEs, all coming from the west limb. The geoeffectiveness of these events seems to be moderate, turning to intense in two of them as a result of cumulative effects from previous mass ejections. We conclude that ejections from solar locations close to the west limb should be considered in space weather, at least as sources of moderate disturbances.
In situ measurements of plasma irregularity growth in the cusp ionosphere
Authors: Oksavik K. , Moen J. , Lester M. , Bekkeng T. A. , Bekkeng J. K.
Published: September 2012

The Investigation of Cusp Irregularities (ICI‐2) sounding rocket was launched on 5 December 2008 from Ny‐Ålesund, Svalbard. The high‐resolution rocket data are combined with data from an all‐sky camera, the EISCAT Svalbard Radar, and the SuperDARN Hankasalmi radar. These data sets are used to characterize the spatial structure ofFregion irregularities in the dayside cusp region. We use the data set to test two key mechanisms for irregularity growth; the Kelvin‐Helmholtz (KH) and gradient drift (GD) instabilities. Except for a promising interval of 4–6 km irregularities, the KH growth rate was found to be too slow to explain the observed plasma irregularities. The time history of the plasma gives further support that structured particle precipitation could be an important source of kilometer‐ to hectometer‐scale “seed” irregularities, which are then efficiently broken down into decameter‐scale irregularities by the GD mechanism.
Magnetic field fluctuations observed in the heliosheath by Voyager 1 at 114 ± 2 AU during 2010
Authors: Burlaga L. F. , Ness N. F.
Published: September 2012

The radial component of the flow speed VR in the heliosheath was decreasing between 2009.0 (108.5 AU) and 2010.3, at which time it reached the “stagnation region” where VR ≈ 0 km/s from 2010.3 to at least to 2011.0 (115.7 AU). The fluctuations of the hour averages of the magnetic fieldBobserved by Voyager 1 (V1) each day throughout 2010 were primarily compressive (longitudinal) fluctuations, along theT(averageB) direction in HG coordinates. The yearly average of the daily standard deviations (SD) of the compressive component ofBwas 〈SDc〉 = 〈SD(BT)〉 ≈ 〈SD(B)〉 ≈ 0.015 nT. The corresponding standard deviations of the transverse components 〈SDt〉 = SD(BR) > ≈ 〈SD(BN)〉 ≈ 0.006 nT. During 2010, 〈SDc〉/〈SDt〉 > 2.6 and 〈SDc〉/〈B〉 = 0.15. The counting rate of cosmic rays >70 MeV/nuc tends to increase with increasing B and SDc, contrary to expectations.
A global shear velocity model of the upper mantle from fundamental and higher Rayleigh mode measurements
Authors: Debayle Eric , Ricard Yanick
Published: September 2012

We present DR2012, a global SV‐wave tomographic model of the upper mantle. We use an extension of the automated waveform inversion approach of Debayle (1999) which improves our mapping of the transition zone with extraction of fundamental and higher‐mode information. The new approach is fully automated and has been successfully used to match approximately 375,000 Rayleigh waveforms. For each seismogram, we obtain a path average shear velocity and quality factor model, and a set of fundamental and higher‐mode dispersion and attenuation curves. We incorporate the resulting set of path average shear velocity models into a tomographic inversion. In the uppermost 200 km of the mantle, SV wave heterogeneities correlate with surface tectonics. The high velocity signature of cratons is slightly shallower (≈200 km) than in other seismic models. Thicker continental roots are not required by our data, but can be produced by imposinga priori a smoother model in the vertical direction. Regions deeper than 200 km show no velocity contrasts larger than ±1% at large scale, except for high velocity slabs within the transition zone. Comparisons with other seismic models show that current surface wave datasets allow to build consistent models up to degrees 40 in the upper 200 km of the mantle. The agreement is poorer in the transition zone and confined to low harmonic degrees (≤10).
Upper crustal structure of Newberry Volcano from P‐wave tomography and finite difference waveform modeling
Authors: Beachly Matthew W. , Hooft Emilie E. E. , Toomey Douglas R. , Waite Gregory P.
Published: September 2012

Seismic tomography combined with waveform modeling constrains the dimensions and melt content of a magma body in the upper crust at Newberry Volcano. We obtain a P‐wave tomographic image by combining travel‐time data collected in 2008 on a line of densely spaced seismometers with active‐source data collected in the 1980s. The tomographic analysis resolves a high‐velocity intrusive ring complex surrounding a low‐velocity caldera‐fill zone at depths above 3 km and a broader high‐velocity intrusive complex surrounding a central low‐velocity anomaly at greater depths (3–6 km). This second, upper‐crustal low‐velocity anomaly is poorly resolved and resolution tests indicate that an unrealistically large, low‐velocity body representing ∼60 km3of melt could be consistent with the available travel times. The 2008 data exhibit low amplitude first arrivals and an anomalous secondary P wave phase originating beneath the caldera. Two‐dimensional finite difference waveform modeling through the tomographic velocity model does not reproduce these observations. To reproduce these phases, we predict waveforms for models that include synthetic low‐velocity bodies and test possible magma chamber geometries and properties. Three classes of models produce a transmittedP‐phase consistent with the travel time and amplitude of the observed secondary phase and also match the observed lower amplitude first arrivals. These models represent a graded mush region, a crystal‐suspension region, and a melt sill above a thin mush region. The three possible magma chamber models comprise a much narrower range of melt volumes (1.6–8.0 km3) than could be constrained by travel‐time tomography alone.
Probabilistic surface reconstruction from multiple data sets: An example for the Australian Moho
Authors: Bodin T. , Salmon M. , Kennett B. L. N. , Sambridge M.
Published: September 2012

Interpolation of spatial data is a widely used technique across the Earth sciences. For example, the thickness of the crust can be estimated by different active and passive seismic source surveys, and seismologists reconstruct the topography of the Moho by interpolating these different estimates. Although much research has been done on improving the quantity and quality of observations, the interpolation algorithms utilized often remain standard linear regression schemes, with three main weaknesses: (1) the level of structure in the surface, or smoothness, has to be predefined by the user; (2) different classes of measurements with varying and often poorly constrained uncertainties are used together, and hence it is difficult to give appropriate weight to different data types with standard algorithms; (3) there is typically no simple way to propagate uncertainties in the data to uncertainty in the estimated surface. Hence the situation can be expressed by Mackenzie (2004): “We use fantastic telescopes, the best physical models, and the best computers. The weak link in this chain is interpreting our data using 100 year old mathematics”. Here we use recent developments made in Bayesian statistics and apply them to the problem of surface reconstruction. We show how the reversible jump Markov chain Monte Carlo (rj‐McMC) algorithm can be used to let the degree of structure in the surface be directly determined by the data. The solution is described in probabilistic terms, allowing uncertainties to be fully accounted for. The method is illustrated with an application to Moho depth reconstruction in Australia.
Oxygen trends over five decades in the North Atlantic
Authors: Stendardo I. , Gruber N.
Published: September 2012

We investigate long‐term trends in dissolved oxygen in the North Atlantic from 1960 to 2009 on the basis of a newly assembled high‐quality dataset consisting of oxygen data from three different sources: CARINA, GLODAP and the World Ocean Database. Oxygen trends are determined along isopycnal surfaces for eight regions and five water masses using a general least‐squares linear regression method that accounts for temporal auto‐correlation. Our results show a significant decrease of oxygen in the Upper (UW), Mode (MW) and Intermediate (IW) waters in almost all regions over the last 5 decades. Over the same period, oxygen increased in the Lower Intermediate Water (LIW) and Labrador Sea Water (LSW) throughout the North Atlantic. The observed oxygen decreases in the MW and IW of the northern and eastern regions are largely driven by changes in circulation and/or ventilation, while changes in solubility are the main driver for the oxygen decrease in the UW and the increases in the LIW and LSW. From 1960 until 2009 the UW, MW, and IW horizons have lost a total of −57 ± 34 Tmol, while the LIW and LSW horizons have gained 46 ± 47 Tmol, integrating to a roughly constant oxygen inventory in the North Atlantic. Comparing our oxygen trends with those of the oceanic heat content, we find an O2 to heat change ratio of −3.6 ± 2.8 nmol J−1 for the UW, MW and IW, and a ratio of −2.8 ± 3.4 nmol J−1 for the LIW and LSW. These ratios are substantially larger than those expected from solubility alone.
Retrieval of the spectral diffuse attenuation coefficientKd(λ) in open and coastal ocean waters using a neural network inversion
Authors: Jamet C. , Loisel H. , Dessailly D.
Published: September 2012

The diffuse attenuation coefficient,Kd(λ) is a fundamental radiometric parameter that is used to assess the light availability in the water column. A neural network approach is developed to assessKd(λ) at any visible wavelengths from the remote sensing reflectances as measured by the SeaWiFS satellite sensor. The neural network (NN) inversion is trained using a combination of simulated and in‐situ data sets covering a broad range ofKd(λ), between 0.0073 m−1at 412 nm and 12.41 m−1at 510 nm. The performance of the retrieval is evaluated against two data sets, one consisting of mainly synthetic data while the other one contains in‐situ data only and is compared to those obtained with previous published empirical (NASA, Morel and Maritorena (2001) and Zhang and Fell (2007)) and semi‐analytical (Lee et al., 2005b) algorithms. On the in‐situ data set from the COASTLOOC campaign, the retrieval accuracy of the present algorithm is quite similar to published algorithms for oligotrophic and mesotrophic ocean waters. But for Kd(490) > 0.25 m−1, the NN approach allows to retrieve Kd(490) with a much better accuracy than the four other methods. The results are consistent when compared with other SeaWiFS wavelengths. This new inversion is as suitable in the open ocean waters as in the turbid waters. The work here is straightforwardly applicable to the MERIS sensor and with few changes to the MODIS‐AQUA sensor. The algorithm in matlab and C code is provided as auxiliary material.
An evaluation of the barotropic and internal tides in a high‐resolution global ocean circulation model
Authors: Shriver J. F. , Arbic B. K. , Richman J. G. , Ray R. D. , Metzger E. J. , Wallcraft A. J. , Timko P. G.
Published: September 2012

Global comparisons of barotropic and internal tides generated in an eddy‐resolving ocean circulation model are made with tidal estimates obtained from altimetric sea surface heights and an altimetry‐constrained tide model. As far as we know, our Hybrid Coordinate Ocean Model (HYCOM) simulations shown here and in an earlier paper are the only published high‐resolution global simulations to contain barotropic tides, internal tides, the general circulation, and mesoscale eddies concurrently. Comparing the model barotropic tide with a global data‐assimilative shallow water tide model shows that the global tidal elevation differences are approximately evenly split between discrepancies in tidal amplitude and phase. Both the model and observations show strong generation of internal tides at a limited number of “hot spot” regions with propagation of beams of energy for thousands of kilometers away from the sources. The model internal tidal amplitudes compare well with observations near these energetic tidal regions. Averaged over these regions, the model and observation internal tide amplitude estimates agree to approximately 15% for the four largest semidiurnal constituents and 23% for the four largest diurnal constituents. Away from the hot spots, the comparison between the model and altimetric amplitude is not as good due, in part, to two problems, errors in the model barotropic tides and overestimation of the altimetric tides in regions of strong mesoscale eddy activity. Examining the general energy distribution of the simulated internal tide is an important first step in the evaluation of internal tides in HYCOM.
Simulating the 1998 spring bloom in Lake Michigan using a coupled physical‐biological model
Authors: Luo Lin , Wang Jia , Schwab David J. , Vanderploeg Henry , Leshkevich George , Bai Xuezhi , Hu Haoguo , Wang Dongxiao
Published: September 2012

A coupled physical‐biological model is used to simulate the ecosystem characteristics in Lake Michigan. The physical model is the unstructured grid, Finite‐Volume Coastal Ocean Model (FVCOM). The biological model is a NPZD model, including phosphorus as the nutrient, which is the limiting element in Lake Michigan, phytoplankton, zooplankton and detritus. The models are driven by observed hourly meteorological forcing in 1998 and the model results are calibrated by satellite and in situ data. The main physical and ecological phenomena in the spring of 1998 are captured. During March to May, a circle‐like phytoplankton bloom appears in southern Lake Michigan, which looks like a ‘doughnut’. The formation mechanisms of the prolonged spring bloom are investigated. It is confirmed that the phytoplankton bloom is forced by rapidly increasing temperature and light intensity in spring. The thermal front that develops in spring inhibits the transport of nutrients and phytoplankton from the nearshore to the deeper water. The wind‐driven gyre circulation in southern Lake Michigan induces significant offshore transport, which contributes to the establishment of the circular bloom.
The detection of atmospheric rivers in atmospheric reanalyses and their links to British winter floods and the large‐scale climatic circulation
Authors: Lavers David A. , Villarini Gabriele , Allan Richard P. , Wood Eric F. , Wade Andrew J.
Published: September 2012

Atmospheric Rivers (ARs), narrow plumes of enhanced moisture transport in the lower troposphere, are a key synoptic feature behind winter flooding in midlatitude regions. This article develops an algorithm which uses the spatial and temporal extent of the vertically integrated horizontal water vapor transport for the detection of persistent ARs (lasting 18 h or longer) in five atmospheric reanalysis products. Applying the algorithm to the different reanalyses in the vicinity of Great Britain during the winter half‐years of 1980–2010 (31 years) demonstrates generally good agreement of AR occurrence between the products. The relationship between persistent AR occurrences and winter floods is demonstrated using winter peaks‐over‐threshold (POT) floods (with on average one flood peak per winter). In the nine study basins, the number of winter POT‐1 floods associated with persistent ARs ranged from approximately 40 to 80%. A Poisson regression model was used to describe the relationship between the number of ARs in the winter half‐years and the large‐scale climate variability. A significant negative dependence was found between AR totals and the Scandinavian Pattern (SCP), with a greater frequency of ARs associated with lower SCP values.