bluuebunny/crossref_metadata_2025 huggingface dataset:
ℋ︁∞andl2–l∞filtering for two‐dimensional linear parameter‐varying systems
Authors: Wu Ligang , Wang Zidong , Gao Huijun , Wang Changhong
Published: February 2007

In this paper, the ℋ︁∞andl2–l∞filtering problem is investigated for two‐dimensional (2‐D) discrete‐time linear parameter‐varying (LPV) systems. Based on the well‐known Fornasini–Marchesini local state‐space (FMLSS) model, the mathematical model of 2‐D systems under consideration is established by incorporating the parameter‐varying phenomenon. The purpose of the problem addressed is to design full‐order ℋ︁∞andl2–l∞filters such that the filtering error dynamics is asymptotic stable and the prescribed noise attenuation levels in ℋ︁∞andl2–l∞senses can be achieved, respectively. Sufficient conditions are derived for existence of such filters in terms of parameterized linear matrix inequalities (PLMIs), and the corresponding filter synthesis problem is then transformed into a convex optimization problem that can be efficiently solved by using standard software packages. A simulation example is exploited to demonstrate the usefulness and effectiveness of the proposed design method. Copyright © 2007 John Wiley & Sons, Ltd.
A three‐outcome design for randomized comparative phase II clinical trials
Authors: Hong Shengyan , Wang Yanping
Published: February 2007

Randomized designs have been increasingly called for use in phase II oncology clinical trials to protect against potential patient selection bias. However, formal statistical comparison is rarely conducted due to the sample size restriction, despite its appeal. In this paper, we offer an approach to sample size reduction by extending the three‐outcome design of Sargent et al. (Control Clin. Trials 2001; 22:117–125) for single‐arm trials to randomized comparative trials. In addition to the usual two outcomes of a hypothesis testing (rejecting the null hypothesis or rejecting the alternative hypothesis), the three‐outcome comparative design allows a third outcome of rejecting neither hypotheses when the testing result is in some ‘grey area’ and leaves the decision to the clinical judgment based on the overall evaluation of trial outcomes and other relevant factors. By allowing a reasonable region of uncertainty, the three‐outcome design enables formal statistical comparison with considerably smaller sample size, compared to the standard two‐outcome comparative design. Statistical formulation of the three‐outcome comparative design is discussed for both the single‐stage and two‐stage trials. Sample sizes are tabulated for some common clinical scenarios. Copyright © 2007 John Wiley & Sons, Ltd.
She'‐e‐os: gender effects and investor reactions to the announcements of top executive appointments
Authors: Lee Peggy M. , James Erika Hayes
Published: February 2007

This study uses Kanter's token status theory to link announcements of top executives to shareholder reactions, highlighting possible gender effects. Using a sample of top executive announcements from 1990 to 2000, our results show that investor reactions to the announcements of female CEOs are significantly more negative than those of their male counterparts. Furthermore, women who have been promoted from within a firm are viewed more positively than women who come from outside. To supplement our analysis of investor reactions, we also analyze the text of popular press articles surrounding the announcements of male and female CEOs. These results show that articles about the appointment of a female CEO tend to emphasize gender, gender‐related and other job or organizational considerations. Copyright © 2007 John Wiley & Sons, Ltd.
Strategic schemas, strategic flexibility, and firm performance: the moderating role of industry clockspeed
Authors: Nadkarni Sucheta , Narayanan V. K.
Published: February 2007

We examine the moderating effect of industry clockspeed on the relationship between strategic schemas, strategic flexibility and firm performance. We employ two key properties of strategic schemas: complexity and focus. Using a sample of 225 firms from 14 industries, we show that the pattern of relationships among the theoretical constructs is different in fast‐ and slow‐clockspeed industries. The results suggest that complexity of strategic schemas promotes strategic flexibility and success in fast clockspeed industries, whereas focus of strategic schemas fosters strategic persistence, which is effective in slow‐clockspeed industries. Copyright © 2007 John Wiley & Sons, Ltd.
DNA Microarrays: Design Principles for Maximizing Ergodic, Chaotic Mixing
Authors: Hertzsch Jan‐Martin , Sturman Rob , Wiggins Stephen
Published: February 2007

In this article we show that models of flows in DNA microarrays generated by pulsed source–sink pairs can be studied as linked twist maps. The significance of this is that it enables us to relate the flow to mathematically precise notions of chaotic mixing that can be realized through specific design criteria. We apply these techniques to three different mixing protocols, two of which have been previously described in the literature, and we are able to isolate the features of each mixer that lead to “good” or “bad” mixing. Based on this, we propose a new design to generate a “well‐mixed” flow in a DNA microarray.
Gum Arabic as a Phytochemical Construct for the Stabilization of Gold Nanoparticles: In Vivo Pharmacokinetics and X‐ray‐Contrast‐Imaging Studies
Authors: Kattumuri Vijaya , Katti Kavita , Bhaskaran Sharanya , Boote Evan J. , Casteel Stan W. , Fent Genevieve M. , Robertson David J. , Chandrasekhar Meera , Kannan Raghuraman , Katti Kattesh V.
Published: February 2007

Gold nanoparticles (AuNPs) have exceptional stability against oxidation and therefore will play a significant role in the advancement of clinically useful diagnostic and therapeutic nanomedicines. Despite the huge potential for a new generation of AuNP‐based nanomedicinal products, nontoxic AuNP constructs and formulations that can be readily administered site‐specifically through the intravenous mode, for diagnostic imaging by computed tomography (CT) or for therapy via various modalities, are still rare. Herein, we report results encompassing: 1) the synthesis and stabilization of AuNPs within the nontoxic phytochemical gum‐arabic matrix (GA–AuNPs); 2) detailed in vitro analysis and in vivo pharmacokinetics studies of GA–AuNPs in pigs to gain insight into the organ‐specific localization of this new generation of AuNP vector, and 3) X‐ray CT contrast measurements of GA–AuNP vectors for potential utility in molecular imaging. Our results demonstrate that naturally occurring GA can be used as a nontoxic phytochemical construct in the production of readily administrable biocompatible AuNPs for diagnostic and therapeutic applications in nanomedicine.
Conditional Covariance Theory and Detect for Polytomous Items
Authors: Zhang Jinming
Published: February 2007

This paper extends the theory of conditional covariances to polytomous items. It has been proven that under some mild conditions, commonly assumed in the analysis of response data, the conditional covariance of two items, dichotomously or polytomously scored, given an appropriately chosen composite is positive if, and only if, the two items measure similar constructs besides the composite. The theory provides a theoretical foundation for dimensionality assessment procedures based on conditional covariances or correlations, such as DETECT and DIMTEST, so that the performance of these procedures is theoretically justified when applied to response data with polytomous items. Various estimators of conditional covariances are constructed, and special attention is paid to the case of complex sampling data, such as those from the National Assessment of Educational Progress (NAEP). As such, the new version of DETECT can be applied to response data sets not only with polytomous items but also with missing values, either by design or at random. DETECT is then applied to analyze the dimensional structure of the 2002 NAEP reading samples of grades 4 and 8. The DETECT results show that the substantive test structure based on the purposes for reading is consistent with the statistical dimensional structure for either grade.
Log-Multiplicative Association Models as Item Response Models
Authors: Anderson Carolyn J. , Yu Hsiu-Ting
Published: February 2007

Log-multiplicative association (LMA) models, which are special cases of log-linear models, have interpretations in terms of latent continuous variables. Two theoretical derivations of LMA models based on item response theory (IRT) arguments are presented. First, we show that Anderson and colleagues (Anderson & Vermunt, 2000; Anderson & Böckenholt, 2000; Anderson, 2002), who derived LMA models from statistical graphical models, made the equivalent assumptions as Holland (1990) when deriving models for the manifest probabilities of response patterns based on an IRT approach. We also present a second derivation of LMA models where item response functions are specified as functions of rest-scores. These various connections provide insights into the behavior of LMA models as item response models and point out philosophical issues with the use of LMA models as item response models. We show that even for short tests, LMA and standard IRT models yield very similar to nearly identical results when data arise from standard IRT models. Log-multiplicative association models can be used as item response models and do not require numerical integration for estimation.
Hexanal Synthesis in Isolated Soy Proteins
Authors: Boatright W. L. , Lu G.
Published: February 2007

Sodium erythrobate (2.3 mM) and dithiothreitol (6.5 mM) caused headspace hexanal from aqueous slurries of commercial isolated soy proteins (ISP) to increase by as much as 13‐fold compared with headspace hexanal in the controls. When linoleic acid was also added, headspace hexanal levels from commercial and laboratory‐prepared ISP were further increased by as much as 18‐ and 136‐fold, respectively, compared with the levels in the controls. When13C‐labeled linoleic acid was added to aqueous mixtures of laboratory‐prepared ISP along with reducing agents, 96% of the resulting hexanal contained the13C isotope. Commercial ISP samples had about 40% of the isotopically labeled carbon incorporated into hexanal. These large increases in hexanal were almost completely prevented by heating the aqueous ISP to 100 °C or above prior to adding the reducing agent and linoleic acid. Adding cysteine or sodium sulfite reduced headspace hexanal levels from aqueous ISP slurries by more than 88%. Thiol blockers, iodoacetic acid andN‐ethylmaleimide, did not affect hexanal levels.
Phosphatidic acid as a regulator of matrix metalloproteinase‐9 expression via the TNF‐α signaling pathway
Authors: Lee Jin-Gu , Lee Sun-Hye , Park Dae-Weon , Bae Yoe-Sik , Yun Sung-Su , Kim Jae-Ryong , Baek Suk-Hwan
Published: February 2007

Phosphatidic acid (PA) is implicated in pathophysiological processes associated with cellular signaling events and inflammation, which include the expressional regulation of numerous genes. Here, we show that PA stimulation increases matrix metalloproteinase‐9 (MMP‐9) expression in macrophages through tumor necrosis factor (TNF)‐α signaling. We performed antibody array analysis on proteins from macrophages stimulated with PA. PA was found to induce the production of TNF‐α, but not of TNF receptor (TNFR)1 and TNFR2 in a time‐dependent manner and stimulated significant, though delayed, MMP‐9 expression. PA induced the phosphorylations of both ERK1/2 and p38, but not of c‐jun amino‐terminal kinase. Moreover, only ERK1/2 inhibition by U0126 suppressed PA‐induced TNF‐α production and MMP‐9 expression. Neutralizing TNF‐α, TNFR1 or TNFR2 antibodies significantly suppressed PA‐induced MMP‐9 expression, suggesting that the production of TNF‐α in response to PA preceded the expression of MMP‐9. Moreover, lipopolysaccharide‐induced PA also led to TNF‐α release and resulted in MMP‐9 expression. Taken together, these observations suggest that PA may play a role in MMP‐9 regulation through ERKs/TNF‐α/TNFRs‐dependent signaling pathway.
Remaining life estimation of used components in consumer products: Life cycle data analysis by Weibull and artificial neural networks
Authors: Mazhar M.I. , Kara S. , Kaebernick H.
Published: February 2007

Environmental awareness and legislative pressures have made manufacturers responsible for the take‐back and end‐of‐life treatment of their products. To competitively exploit these products, one option is to incorporate used components in “new” or remanufactured products. However, this option is partly limited by a firm's ability to assess the reliability of used components. A comprehensive two‐step approach is proposed. The first stage phase statistically analyzes the behavior of components for reuse. A well‐known reliability assessment method, the Weibull analysis, is applied to the time‐to‐failure data to assess the mean life of components. In the second phase, the degradation and condition monitoring data are analyzed by developing an artificial neural network (ANN) model. The advantages of this approach over traditional approaches employing multiple regression analysis are highlighted with empirical data from a consumer product. Finally, the Weibull analysis and the ANN model are then integrated to assess the remaining useful life of components for reuse. This is a critical advance in sustainable management of supply chains since it allows for a better understanding of not only service requirements of product, but the remaining life in a product and hence its suitability for reuse or remanufacture. Future work should assess: (1) reduction in downtime of process equipment through the implementation of this technique as a means to better manage preventative maintenance; (2) reduce field failure of remanufactured product; (3) selling‐service strategy through implementation of the proposed methodology.
Displaced GAD65 amacrine cells of the guinea pig retina are
morphologically diverse
Authors: KAO YEN-HONG , STERLING PETER
Published: February 2007

The ganglion cell layer of mammalian retina contains numerous amacrine
cells. Many belong to one type, the cholinergic starburst cell, but the
other types have not been systematically identified. Using a new method to
target sparsely represented cell types, we filled about 200 amacrine
neurons in the ganglion cell layer of the guinea pig visual streak and
identified 11 types. Ten of these resemble types identified in other
species with somas in the inner nuclear layer, but one type has not been
previously reported. Most of the types and nearly all the injected cells
(95%) arborized low in the synaptic layer where they would co-stratify
with various classes of ON ganglion cell. The displaced somas (7% of all
amacrine cells) thus represent a heterogeneous pool, which are relatively
accessible for study of their interactions with ON ganglion cells.
Deciphering the Lapita Code: the Aitape Ceramic Sequence and Late Survival of the ‘Lapita Face’
Authors: Terrell John Edward , Schechter Esther M
Published: February 2007

Archaeological and ethnographic evidence from the Sepik coast of Papua New Guinea documents the survival in the western Pacific of a stylized symbol or motif — the so-called ‘Lapita face’ — on pottery and possibly other kinds of material items (such as wooden bowls and serving platters) for at least 3300 years. A plausible reason for the persistence of this iconography is that it has referred to ideas about the living and the dead, the human and the divine, and the individual and society that remained socially and spiritually profound and worth expressing long after the demise of Lapita as a distinct ceramic style. We detail evidence for saying that the ‘faces’ on Lapita vessels from thousands of years ago and certain stylized designs on historic and modern carved wooden bowls and platters from this coast are historically linked ways of alluding to sea turtles, creatures figuring prominently in the lore and cosmology of Pacific Islanders. Here we describe four prehistoric wares (or ‘phases’ or ‘periods’) in the Aitape ceramic sequence on the Sepik coast that, considered in series, fill the temporal gap between practices and beliefs in Lapita times and present-day realities in this part of the world.
Bradshaw and Bayes: Towards a Timetable for the Neolithic
Authors: Bayliss Alex , Bronk Ramsey Christopher , van der Plicht Johannes , Whittle Alasdair
Published: February 2007

The importance of chronology is reasserted as a means to achieving history and a sense of temporality. A range of current methods for estimating the dates and durations of archaeological processes and events are considered, including visual inspection of graphs and tables of calibrated dates and the summing of the probability distributions of calibrated dates. These approaches are found wanting. The Bayesian statistical framework is introduced, and a worked example presents simulated radiocarbon dates as a demonstration of the explicit, quantified, probabilistic estimates now possible on a routine basis. Using this example, the reliability of the chronologies presented for the five long barrows considered in this series of papers is explored. It is essential that the ‘informative’ prior beliefs in a chronological model are correct. If they are not, the dating suggested by the model will be incorrect. In contrast, the ‘uninformative’ prior beliefs have to be grossly incorrect before the outputs of the model are importantly wrong. It is also vital that the radiocarbon ages included in a model are accurate, and that their errors are correctly estimated. If they are not, the dating suggested by a model may also be importantly wrong. Strenuous effort and rigorous attention to archaeological and scientific detail are inescapable if reliable chronologies are to be built. The dates presented in the following papers are based on models. ‘All models are wrong, some models are useful’ (Box 1979, 202). We hope readers will find them useful, and will employ ‘worry selectivity’ to determine whether and how each model may be importantly wrong. The questions demand the timetable, and our prehistories deserve both.
Building for the Dead: Events, Processes and Changing Worldviews from the Thirty-eighth to the Thirty-fourth Centuries cal. bc in Southern Britain
Authors: Whittle Alasdair , Barclay Alistair , Bayliss Alex , McFadyen Lesley , Schulting Rick , Wysocki Michael
Published: February 2007

Our final paper in this series reasserts the importance of sequence. Stressing that long barrows, long cairns and associated structures do not appear to have begun before the thirty-eighth century cal. bc in southern Britain, we give estimates for the relative order of construction and use of the five monuments analysed in this programme. The active histories of monuments appear often to be short, and the numbers in use at any one time may have been relatively low; we discuss time in terms of generations and individual lifespans. The dominant mortuary rite may have been the deposition of articulated remains (though there is much diversity); older or ancestral remains are rarely documented, though reference may have been made to ancestors in other ways, not least through architectural style and notions of the past. We relate these results not only to trajectories of monument development, but also to two models of development in the first centuries of the southern British Neolithic as a whole. In the first, monuments emerge as symptomatic of preeminent groups; in the second model, monuments are put in a more gradualist and episodic timescale and related to changing kinds of self-consciousness (involving senses of self, relations with animals and nature, perceptions of the body, awareness of mortality and attitudes to the past). Both more distant and more recent and familiar possible sources of inspiration for monumentalization are considered, and the diversity of situations in which mounds were constructed is stressed. More detailed Neolithic histories can now begin to be written.
The impact of a community-based food skills intervention on cooking confidence, food preparation methods and dietary choices – an exploratory trial
Authors: Wrieden Wendy L , Anderson Annie S , Longbottom Pat J , Valentine Karen , Stead Martine , Caraher Martin , Lang Tim , Gray Bill , Dowler Elizabeth
Published: February 2007

Objective

To evaluate the feasibility of undertaking a food skills intervention study in areas of social deprivation aimed at altering cooking confidence, food preparation methods and dietary choices.

Design

A standardised skills programme was implemented in community-based settings. Pre- (T1) and post-intervention (T2) and 6-month follow-up (T3) measures (7-day diaries and self-administered questionnaires) were undertaken in intervention and comparison groups.

Setting

Eight urban communities in Scotland.

Subjects

One hundred and thirteen adults living in areas of social deprivation.

Results

It was clear that many subjects led fragmented lives and found commitment to intervention classes problematic. Sixty-three subjects completed the final (T3) assessments. The response to each component varied due to inability to attend sessions, illness, study requirements, employment, moving out of the area, change in circumstances, loss of interest and loss of postal questionnaires. At baseline, reported consumption of fruit and vegetables was low (mean frequency 8.1 ± 4.78 times per week). Fruit intake increased significantly (P < 0.05) between T1 and T2 in the intervention group (1.7 ± 2.36 to 2.7 ± 3.28 times per week) only. Between T1 and T3, there was a significant increase (P < 0.05) in intervention subjects who reported confidence in following a recipe (67–90%,).

Conclusions

This exploratory trial shows that a food skills intervention is likely to have a small but positive effect on food choice and confidence in food preparation. A full-scale randomised controlled trial in this hard-to-reach group would require a range of flexible approaches rather than a fully defined intervention, and presents challenges for trial design.
Food insecurity and subsequent weight gain in women
Authors: Jones Sonya J , Frongillo Edward A
Published: February 2007

Objective

Cross-sectional data indicate that a relationship between household food insecurity and overweight exists among women in the USA. Cross-sectional data cannot determine if food insecurity leads to overweight as some have hypothesised. The purpose of the present study was to examine the relationship of food insecurity with subsequent weight gain in women using data from the Panel Study of Income Dynamics (PSID).

Design, setting and subjects

Panel data from the 1999 and 2001 PSID, a nationally representative sample of households, were analysed using multivariate regression procedures.

Results

Average weight gain among all women (n = 5595) was 1.1 kg on average over the two years. There were no significant differences in the percentages of women who gained a clinically significant amount (2.3 kg) by food insecurity status. Overweight women who were on a weight-gain trajectory during the 2-year period gained less if they were food-insecure. This relationship was not observed among healthy-weight or obese women.

Conclusions

Overall, food insecurity does not appear to be strongly associated with subsequent weight gain in women.
Breast-feeding initiation and determinants of exclusive breast-feeding – a questionnaire survey in an urban population of western Nepal
Authors: Chandrashekhar TS , Joshi HS , Binu VS , Shankar PR , Rana MS , Ramachandran U
Published: February 2007

Objective

To assess rates of initiation of breast-feeding and exclusive breast-feeding within 2 months after delivery and to determine the factors influencing exclusive breast-feeding.

Design

A health worker-administered questionnaire survey was carried out during the time period 1 August–30 September 2005.

Setting

Immunisation clinics of Pokhara, a submetropolitan city in western Nepal.

Subjects

Three hundred and eighty-five mothers who had delivered a child within the previous 2 months.

Results

The rates of initiation within 1 h and within 24 h of delivery were 72.7 and 84.4%, respectively. Within 2 months after delivery, exclusive breast-feeding was practised by 82.3% of the mothers. Breast milk/colostrum was given as the first feed to 332 (86.2%) babies but 17.2% of them were either given expressed breast milk or were put to the breast of another lactating mother. Pre-lacteal feeds were given to 14% of the babies. The common pre-lacteal feeds given were formula feeds (6.2%), sugar water (5.9%) and cow's milk (2.8%). Complementary feeds were introduced by 12.7% of the mothers. By logistic regression analysis, friends' feeding practices, type of delivery and baby's first feed were the factors influencing exclusive breast-feeding practice of the mothers.

Conclusions

Despite the higher rates of initiation and exclusive breast-feeding, practices such as pre-lacteal feeds and premature introduction of complementary feeds are of great concern in this urban population. There is a need for promotion of good breast-feeding practices among expectant mothers and also the community, especially the families, taking into account the local traditions and customs.
Age-related changes in immunity: implications for vaccination in the elderly
Authors: Kovaiou Rania D. , Herndler-Brandstetter Dietmar , Grubeck-Loebenstein Beatrix
Published: February 2007

Average life expectancy is continuously rising in all developed countries, leading to an ever-increasing elderly population. Of the many functions of the body affected by the complex process of ageing, the immune system in particular undergoes various changes, collectively termed immunosenescence. As a result, elderly people are more susceptible to infections and are frequently less protected by vaccines. This review summarises the effect of ageing on immunity, emphasising the age-associated changes within T and B cells at a molecular and cellular level. Furthermore, it discusses strategies, such as the addition of immunostimulatory adjuvants and the use of potent antigen-delivery systems, that may counteract age-related defects in immune responses to vaccination. A proper understanding of how immunological memory is affected by ageing, and the introduction of strategies to ameliorate vaccine efficacy in the elderly, might reduce the incidence and the severity of infectious disease within this fragile age group and have a strong impact on the quality of life of elderly individuals.
Hyporheic exchange in gravel bed rivers with pool‐riffle morphology: Laboratory experiments and three‐dimensional modeling
Authors: Tonina Daniele , Buffington John M.
Published: February 2007

We report the first laboratory simulations of hyporheic exchange in gravel pool‐riffle channels, which are characterized by coarse sediment, steep slopes, and three‐dimensional bed forms that strongly influence surface flow. These channels are particularly important habitat for salmonids, many of which are currently at risk worldwide and which incubate their offspring within the hyporheic zone. Here we perform a set of laboratory experiments examining the effects of discharge and bed form amplitude on hyporheic exchange, with surface‐subsurface mixing measured directly from the concentration decay of a conservative tracer (fluorescein) injected into the surface flow. Near‐bed pressure measurements were also used to predict hyporheic exchange from a three‐dimensional pumping transport model. Comparison of the predicted and observed hyporheic exchange shows good agreement, indicating that the major mechanism for exchange is bed form–induced advection. However, the effect of bed forms is modulated by discharge and the degree of topographic submergence. We also tested the performance of the hydrostatic pressure as a proxy for the observed near‐bed pressure in driving hyporheic exchange, which would facilitate field measurement and analysis of hyporheic flow in natural rivers. We found agreement with measured hyporheic exchange only for low bed form amplitudes and high flows.
Progressive reduction in NE Atlantic intermediate water ventilation prior to Heinrich events: Response to NW European ice sheet instabilities?
Authors: Peck V. L. , Hall I. R. , Zahn R. , Scourse J. D.
Published: February 2007

We present high‐resolution benthic δ13C records from intermediate water depth core site MD01‐2461 (1153 m water depth), from the Porcupine Seabight, NE Atlantic, spanning 43 to 8 kyr B.P. At an average proxy time step of 160 ± 56 years this core provides information on the linkage between records from the Portuguese Margin and high‐latitude North Atlantic basin, allowing additional insights into North Atlantic thermohaline circulation (THC) variability during millennial‐scale climatic events of the last glacial. Together, these records document both discrete and progressive reductions in Glacial North Atlantic Intermediate Water (GNAIW) formation preceding Heinrich (H) events 1, 2, and 4, recorded through the apparent interchange of glacial northern and southern‐sourced intermediate water signatures along the European Margin. Close coupling of NW European ice sheet (NWEIS) instability and GNAIW formation is observed through transient advances of SCW along the European margin concurrent with pulses of ice‐rafted debris and meltwater release into the NE Atlantic between 27 and 16 kyr B.P., when the NWEIS was at maximum extent and proximal to Last Glacial Maximum convection zones in the open North Atlantic. It is such NWEIS instability and meltwater forcing that may have triggered reduced North Atlantic THC prior to collapse of the Laurentide ice sheet at H1 and H2. Precursory reduction in GNAIW formation prior to H4 may also be inferred. However, limited NWEIS ice volume prior to H4 and convection occurring in the Norwegian‐Greenland Sea require that if a meltwater trigger is invoked, as appears to be the case at H1 and H2, the source of meltwater prior to H4 is elsewhere, likely higher‐latitude ice sheets. Clarification of the sequencing and likely mechanisms of precursory decrease of the North Atlantic THC support theories of H event initiation relating to ice shelf growth during cold periods associated with reduced North Atlantic THC and subsequent ablation through subsurface warming and sea level rise associated with further reductions in meridional overturning.
Theory and observations of ice particle evolution in cirrus using Doppler radar: Evidence for aggregation
Authors: Westbrook C. D. , Hogan R. J. , Illingworth A. J. , O'Connor E. J.
Published: February 2007

Vertically pointing Doppler radar has been used to study the evolution of ice particles as they sediment through a cirrus cloud. The measured Doppler fall speeds, together with radar‐derived estimates for the altitude of cloud top, are used to estimate a characteristic fall time tc for the ‘average’ ice particle. The change in radar reflectivity Z is studied as a function of tc, and is found to increase exponentially with fall time. We use the idea of dynamically scaling particle size distributions to show that this behaviour implies exponential growth of the average particle size, and argue that this exponential growth is a signature of ice crystal aggregation.
Ground‐based observations at L ∼ 6 of multi‐band structures in VLF hiss
Authors: Titova E. E. , Demekhov A. G. , Pasmanik D. L. , Trakhtengerts V. Y. , Manninen J. , Turunen T. , Rycroft M. J.
Published: February 2007

We present ground‐based observations of banded structures (BS) in auroral hiss. This BS hiss was detected at Porojärvi station in Northern Finland, mainly in the local evening from 19 to 23 MLT, during magnetically quiet periods; half of all the events observed corresponded to AE < 50 nT. The structures, which resemble those observed by low‐altitude satellites, can be related to the cyclotron resonant interaction of VLF waves at frequencies near the lower‐hybrid resonance with suprathermal protons in the upper ionosphere and magnetosphere. The maximum probability distribution of band spacing for the events observed at Porojärvi is reached in the frequency range 200–300 Hz, which corresponds to proton gyrofrequencies at L ∼ 6 at altitudes of 4000–3000 km. We found that the BS hiss was detected in the region of evening‐side downward field‐aligned currents and rather intense precipitation of ions with energies 1–30 keV, detected by DMSP spacecraft. We propose that the observed BS hiss can be formed not only due to absorption at the proton gyroharmonics, as is usually assumed for similar structures observed onboard satellites, but also due to generation by energetic protons with an anisotropic velocity distribution.
Extreme lunar surface charging during solar energetic particle events
Authors: Halekas J. S. , Delory G. T. , Brain D. A. , Lin R. P. , Fillingim M. O. , Lee C. O. , Mewaldt R. A. , Stubbs T. J. , Farrell W. M. , Hudson M. K.
Published: February 2007

We analyzed a series of solar energetic particle events in late April and early May of 1998, during which lunar surface potentials reached values as large as ∼−4.5 kV (the largest recorded by Lunar Prospector). The two largest surface charging events during this time period correspond to energetic particle injections, when the electron flux between 50 keV and 5 MeV exceeded the proton flux over the same energy range. We searched the entire Lunar Prospector data set for other large negative surface charging events, and found that they occur almost exclusively during magnetotail crossings (when the Moon encounters the plasmasheet) and solar energetic particle events. Lunar surface charging (and its effect on the lunar dust environment) during inherently unpredictable space weather events represents a significant hazard for exploration.
Olivine friction at the base of oceanic seismogenic zones
Authors: Boettcher Margaret S. , Hirth Greg , Evans Brian
Published: February 2007

We investigate the strength and frictional behavior of olivine aggregates at temperatures and effective confining pressures similar to those at the base of the seismogenic zone on a typical ridge transform fault. Triaxial compression tests were conducted on dry olivine powder (grain size ≤60 μm) at effective confining pressures between 50 and 300 MPa (using Argon as a pore fluid), temperatures between 600°C and 1000°C, and axial displacement rates from 0.06 to 60 μm/s (axial strain rates from 3 × 10−6 to 3 × 10−3 s−1). Yielding shows a negative pressure dependence, consistent with predictions for shear enhanced compaction and with the observation that samples exhibit compaction during the initial stages of the experiments. A combination of mechanical data and microstructural observations demonstrate that deformation was accommodated by frictional processes. Sample strengths were pressure‐dependent and nearly independent of temperature. Localized shear zones formed in initially homogeneous aggregates early in the experiments. The frictional response to changes in loading rate is well described by rate and state constitutive laws, with a transition from velocity‐weakening to velocity‐strengthening at 1000°C. Microstructural observations and physical models indicate that plastic yielding of asperities at high temperatures and low axial strain rates stabilizes frictional sliding. Extrapolation of our experimental data to geologic strain rates indicates that a transition from velocity weakening to velocity strengthening occurs at approximately 600°C, consistent with the focal depths of earthquakes in the oceanic lithosphere.
Evidence for the Expression of Multiple Uracil Nucleotide‐Stimulated P2 Receptors Coupled to Smooth Muscle Contraction in Porcine Isolated Arteries
Authors: Rayment S J , Latif M L , Ralevic V , Alexander S P H
Published: February 2007

Background and purpose:

The uracil nucleotides UDP and UTP have been reported to activate P2Y2, P2Y4and P2Y6receptors to cause vasoconstriction. We have performed a comparative analysis of these receptors in endothelium‐denuded smooth muscle from porcine isolated coronary and ear arteries, using pharmacological and molecular tools.

Experimental approach:

Tissue segments were used to construct non‐cumulative concentration response curves for UTP and UDP, in the absence and presence of the P2 receptor antagonists PPADS or suramin. RT‐PCR and immunoblot analyses were employed to define gene expression and immunoreactivity for P2Y2, P2Y4and P2Y6receptors.

Key results:

In the coronary artery, UTP‐evoked contractile responses were reduced in the presence of suramin, but not PPADS, while the smaller responses to UDP were unaffected by either antagonist. In the ear artery, contractile responses to UDP were much smaller than those to UTP; responses to UTP were inhibited by both PPADS and suramin. RT‐PCR suggested predominant expression of P2Y2receptors in the coronary artery, while P2Y4and P2Y6receptor gene expression appeared equivalent in both tissues. Immunoblot analyses provided evidence for P2Y6receptors in both tissues, with equivocal evidence of P2Y2and P2Y4receptor immunoreactivities.

Conclusions and implications:

We conclude that UTP‐evoked contraction of porcine coronary artery smooth muscle appears to be predominantly P2Y2‐mediated, while the ear artery appears to express a uracil nucleotide‐sensitive P2 receptor(s) which fails to fit readily into the current classification.

British Journal of Pharmacology(2007)150, 604–612. doi:10.1038/sj.bjp.0707120
Thickness-dependent pinning in a superconductor thin film
Authors: Agassi D. , Christen D. K. , Pennycook S. J.
Published: February 2007

The dependence of critical current density jc on film thickness (d) is calculated for the simple configuration of a semi-infinite finite-thickness superconductor film and a single vortex. This film-thickness dependence reflects the impact of vortex broadening in a thin film on its pinning by the film’s edge or an internal surface. The calculated film-thickness variation of jc in the range d∕λ<2, where λ denotes the penetration depth, is found to be proportional to d−1∕2. A parameter-free estimate of the ensuing critical current is within a factor of 3 of observed values in YBa2Cu3O7 coated conductors. It is argued that this type of film-thickness scaling applies beyond the simple configuration considered here.
Conservation laws for steady flow and solitons in a multifluid plasma revisited
Authors: Mace R. L. , McKenzie J. F. , Webb G. M.
Published: February 2007

The conservation laws used in constructing the governing equations for planar solitons in multifluid plasmas are revisited. In particular, the concept of generalized vorticity facilitates the derivation of some general “Bernoulli theorems,” which reduce, in specific instances, to conservation laws previously deduced by other means. These theorems clarify the underlying physical principles that give rise to the conserved quantities. As an example of the usefulness of the techniques, even for relatively simple flows and progressive waves, the equations governing stationary nonlinear whistler waves propagating parallel to an ambient magnetic field are derived using generalized vorticity concepts.
Horizontally directional single-wall carbon nanotubes grown by chemical vapor deposition with a local electric field
Authors: Hongo Hiroo , Nihey Fumiyuki , Ochiai Yukinori
Published: February 2007

We studied the directional distribution of horizontally aligned single-wall carbon nanotubes (SWNTs) grown by thermal chemical vapor deposition (CVD) under an electric field. Electrodes formed on the sample surface were used to locally apply the electric field. We inserted spacer layers between the catalyst for the CVD and the substrate and investigated the spacer thickness dependence of the directional distribution width of the SWNTs. We found that a thicker spacer layer resulted in better alignment of the SWNTs. A sample having a 200-nm-thick spacer layer produced 7° of standard deviation along the electric field. The experimental results imply that suppression of the interaction between the substrate and the SWNT tips is important. We propose a simple model that describes this interaction during the growth. Based on this model, we explain our results and formulate a simple criterion for the experimental parameters to enable perfect controllability of the SWNTs direction.
Ion irradiation and thermally induced mixing of CoCrPt∕Cr multilayered films
Authors: Georgieva M. T. , Grundy P. J. , Telling N. D.
Published: February 2007

A set of CoCrPt∕Cr multilayered films with variable layer thicknesses has been used in an investigation of interlayer mixing and “patterning” of samples with relatively high coercivity and in-plane magnetization. The multilayers with the highest coercivities were irradiated with different doses of Ar++ ions in order to intermix the Cr and CoCrPt layers and push the CoCrPt stoichiometry into the nonmagnetic region of the phase diagram. Samples were also irradiated through a Ni-grating mask to obtain patterning by adjacent magnetic and nonmagnetic regions of the film. Thermal annealing experiments mirrored the change in magnetic properties of the irradiated samples.
Variable liquid crystal pretilt angles on various compositions of alignment layers
Authors: Kim Jong Bok , Kim Kyung Chan , Ahn Han Jin , Hwang Byoung Har , Hyun Dong Choon , Baik Hong Koo
Published: February 2007

The authors introduce variable liquid crystal (LC) pretilt angles via ion beam (IB) irradiation of silicon carbide (SiC) layers of various compositions. To control the composition of the SiC layer, the authors altered the rf power ratio between the graphite target and silicon target. The pretilt angle of the silicon-rich SiC layer was constant regardless of IB irradiation angle; however, the carbon-rich SiC layer showed variable pretilt angles, depending on IB irradiation angle. The authors attribute variable pretilt angle to the competition between van der Waals interactions, favoring the vertical alignment, and pi-pi interactions, favoring the LC alignment parallel to IB direction.
Giant magnetocaloric effect in ε-(Mn0.83Fe0.17)3.25Ge antiferromagnet
Authors: Du J. , Cui W. B. , Zhang Q. , Ma S. , Xiong D. K. , Zhang Z. D.
Published: February 2007

The magnetic phase transition and magnetocaloric effect are investigated on ε-(Mn0.83Fe0.17)3.25Ge compound. A large positive magnetic entropy change ΔSM is observed, which is accompanied with a field-induced metamagnetic transition from a collinear to a triangular antiferromagnetic configuration in this antiferromagnetic compound. The maximum value of ΔSM is 11.6J∕kgK at 93K for a magnetic field change of 7T. The study on systems with antiferromagnetic phases may open an important field in searching new materials for magnetic refrigeration.
All-optical switching in quantum cascade lasers
Authors: Zervos C. , Frogley M. D. , Phillips C. C. , Kundys D. O. , Wilson L. R. , Hopkinson M. , Skolnick M. S.
Published: February 2007

The authors demonstrate the switching of the midinfrared output of a quantum cascade laser (QCL) using a near infrared control laser. The present, unoptimized, device offers 100% modulation depths, at approximately 50% of the maximum QCL output power, and has a switching energy of ∼15nJ. It works as a resettable photon flux integrator which would give it a retiming function if used as a component for optical free space communications
Cylinder-shaped ultrasonic motors 4.8mm in diameter using electroactive piezoelectric materials
Authors: Luo Laihui , Zhu Hua , Zhao Chunsheng , Wang Haixia , Luo Haosu
Published: February 2007

Two cylinder-shaped ultrasonic motors 4.8mm in diameter were developed. This kind of motor was driven by four pieces of piezoelectric materials, which were used to excite the two first-bending vibrations. Pb(Mg1∕3Nb2∕3)O3–PbTiO3 (PMNT) crystal and Pb(Zr,Ti)O3 (PZT) ceramic piezoelectric materials were used as drive elements. The motor based on PMNT crystals could operate at a voltage of 25Vp-p (peak to peak). When driven by a 100Vp-p voltage, the motor could run at frequency ranging from 26to68kHz and the revolution speed reached 450rpm. Its maximum output torque was 0.6mNm. The motor based on the PZT ceramic did not exhibit high performance as the PMNT crystal motor. The piezoelectric materials affect the performance of the motors greatly.
Electric field gating with ionic liquids
Authors: Misra Rajiv , McCarthy Mitchell , Hebard Arthur F.
Published: February 2007

The authors show that ionic liquids are well suited to specialized electric field gating applications in which large surface charge densities can be induced on the surfaces of low-carrier density thin-film metals. Using either coplanar or overlay gate configurations, they demonstrate field-induced resistance changes on the order of a factor of 104 for thin conducting InOx films. The areal capacitances and field effect mobilities noticeably exceed those that can be achieved using AlOx dielectrics. In addition, the charge state can be frozen in by reducing the temperature, thus providing an opportunity for electric field tuning of metal-insulator transitions in a variety of thin-film systems.
Plasma catecholamine levels as indicators of the post-release survivorship of juvenile pelagic sharks caught on experimental drift longlines in the Southern California Bight
Authors: Hight Barbara V. , Holts David , Graham Jeffrey B. , Kennedy Brian P. , Taylor Valerie , Sepulveda Chugey A. , Bernal Diego , Ramon Darlene , Rasmussen Randall , Lai N. Chin
Published: February 2007

Between 1983 and 2004, nearly 12 000 shortf in mako (Isurus oxyrinchus), common thresher (Alopias vulpinus) and blue (Prionace glauca) sharks were tagged in the Southern California Bight; however, only 1.97% of these have been returned. One possible reason for this low return rate could be post-release mortality caused by capture stress from the experimental longline. Plasma catecholamine levels were analysed to evaluate stress levels in longline-captured, rod-and-reel-captured and unstressed docile sharks. The mean catecholamine values determined for the three tag–release species ranged from 6539 to 22 079 pg mL–1. The level of adrenaline found in moribund I. oxyrinchus (94 807 pg mL–1) was much higher than in either P. glauca (46 845 pg mL–1) or A. vulpinus (36 890 pg mL–1). In contrast, blood obtained from sharks that were landed within minutes had lower catecholamine values (P. glauca, 889 and 1347 pg mL–1; I. oxyrinchus, 2960 and 3946 pg mL–1, adrenaline and noradrenaline respectively). Among the nine I. oxyrinchus specimens that were recaptured long after their longline capture and release, the highest adrenaline level measured just before release was 33 352 pg mL–1. Because these mako sharks survived sufficiently long to be recaptured, their time-of-release catecholamine levels provide a conservative estimate of ~80% viability on the longline-captured and released population.
Spatial and seasonal distribution patterns of juvenile and adult raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa
Authors: Dicken M. L. , Booth A. J. , Smale M. J. , Cliff G.
Published: February 2007

Understanding the movement patterns of raggedtooth sharks (Carcharias taurus) is crucial in defining habitat use and evaluating the effects of exploitation and anthropogenic activities. Between 1984 and 2004, 1107 C. taurus juveniles (<1.8-m TL) and 2369 C. taurus maturing subadults and adults (>1.8-m TL) were tagged and released along the east coast of South Africa. In total, 125 C. taurus juveniles and 178 C. taurus maturing subadults and adults were recaptured, representing recapture rates of 11.2% and 7.5% respectively. The average distance travelled by juvenile sharks was 18.7 km (95% CI = 10.8–26.6 km). Juvenile sharks displayed site fidelity to summer nursery areas. The average distance travelled by maturing and adult sharks was 342 km (95% CI = 275–409 km). One female shark, however, was recaptured 1897 km from its original release site. The average rate at which pregnant sharks moved south from their gestation to pupping grounds was 2.6 km day–1 (95% CI = 2.04–3.16 km day–1). This study highlights the differences in movement patterns between C. taurus juveniles and adults and suggests philopatric behaviour in both life-history stages.