bluuebunny/crossref_metadata_2025 huggingface dataset:
AN INVERSE THEOREM FOR THE GOWERS $U^3(G)$ NORM
Authors: Green Ben , Tao Terence
Published: February 2008

There has been much recent progress in the study of arithmetic progressions in various sets, such as dense subsets of the integers or of the primes. One key tool in these developments has been the sequence of Gowers uniformity norms $U^d(G)$, $d=1,2,3,\dots$, on a finite additive group $G$; in particular, to detect arithmetic progressions of length $k$ in $G$ it is important to know under what circumstances the $U^{k-1}(G)$ norm can be large.

The $U^1(G)$ norm is trivial, and the $U^2(G)$ norm can be easily described in terms of the Fourier transform. In this paper we systematically study the $U^3(G)$ norm, defined for any function $f:G\to\mathbb{C}$ on a finite additive group $G$ by the formula

\begin{multline*} \qquad\|f\|_{U^3(G)}:=|G|^{-4}\sum_{x,a,b,c\in G}(f(x)\overline{f(x+a)f(x+b)f(x+c)}f(x+a+b) \\ \times f(x+b+c)f(x+c+a)\overline{f(x+a+b+c)})^{1/8}.\qquad \end{multline*}

We give an inverse theorem for the $U^3(G)$ norm on an arbitrary group $G$. In the finite-field case $G=\mathbb{F}_5^n$ we show that a bounded function $f:G\to\mathbb{C}$ has large $U^3(G)$ norm if and only if it has a large inner product with a function $e(\phi)$, where $e(x):=\mathrm{e}^{2\pi\ri x}$ and $\phi:\mathbb{F}_5^n\to\mathbb{R}/\mathbb{Z}$ is a quadratic phase function. In a general $G$ the statement is more complicated: the phase $\phi$ is quadratic only locally on a Bohr neighbourhood in $G$.

As an application we extend Gowers's proof of Szemerédi's theorem for progressions of length four to arbitrary abelian $G$. More precisely, writing $r_4(G)$ for the size of the largest $A\subseteq G$ which does not contain a progression of length four, we prove that

$$ r_4(G)\ll|G|(\log\log|G|)^{-c}, $$

where $c$ is an absolute constant.

We also discuss links between our ideas and recent results of Host, Kra and Ziegler in ergodic theory.

In future papers we will apply variants of our inverse theorems to obtain an asymptotic for the number of quadruples $p_1\ltp_2\ltp_3\ltp_4\leq N$ of primes in arithmetic progression, and to obtain significantly stronger bounds for $r_4(G)$.
d-FRATTINI CHIEF FACTORS
Authors: Bechtell H.
Published: February 2008

The concepts of d- and nd-Frattini chief factors of a finite group are introduced. Their ingrainment into that of the extended Frattini dual subgroup becomes the natural dual to Frattini and supplemented chief factors. Not only does a dual of the strengthened form of the Jordan–Hölder theorem arise, but also the $p$-nilpotent radical becomes the intersection of the centralizers of the nd-Frattini chief factors. As a result, a class $\mathfrak{F}$ of groups is a full integrated local formation $\mathrm{LF}(f)$ if and only if each nd-Frattini chief factor in $G\in\mathfrak{F}$ is $f$-central.
LOOP HOMOLOGY AS FIBREWISE HOMOLOGY
Authors: Crabb M. C.
Published: February 2008

The loop homology ring of an oriented closed manifold, defined by Chas and Sullivan, is interpreted as a fibrewise homology Pontrjagin ring. The basic structure, particularly the commutativity of the loop multiplication and the homotopy invariance, is explained from the viewpoint of the fibrewise theory, and the definition is extended to arbitrary compact manifolds.
A NEW CHARACTERIZATION FOR REGULAR BMO WITH NON-DOUBLING MEASURES
Authors: Hu Guoen , Wang Xin , Yang Dachun
Published: February 2008

Let $\mu$ be a positive Radon measure on $\mathbb{R}^d$ which satisfies $\mu(B(x,r))\le Cr^{n}$ for any $x\in\mathbb{R}^d$ and $r>0$ and some fixed constants $C>0$ and $n\in(0,d]$. In this paper, a new characterization of the space $\rbmo(\mu)$, which was introduced by Tolsa, is given. As an application, it is proved that the $L^p(\mu)$-boundedness with $p\in(1,\infty)$ of Calderón–Zygmund operators is equivalent to various endpoint estimates.
Spore ornamentation of Haplosporidium hinei n. sp. (Haplosporidia) in pearl oysters Pinctada maxima (Jameson, 1901)
Authors: BEARHAM D. , SPIERS Z. , RAIDAL S. , JONES J. B. , BURRESON E. M. , NICHOLLS P. K.
Published: February 2008

An infection of pearl oysters, Pinctada maxima, attributed to a Haplosporidium sp. by Hine and Thorne (1998) has been detected on 3 occasions and is considered to represent a serious concern to the pearling industry in Australia. The spore ornamentation of the parasite was determined by scanning electron microscopy and transmission electron microscopy. Spores of the parasite were pleomorphic, or elongated 3·5–4 μm×2·5–3·0 μm in size. Two filaments were wound around the spore and originated from 2 ‘knob-like’ posterior thickenings. Both filaments passed up one side of the spore together until just below the operculum whereupon each split and passed obliquely under the lip of the opercula lid. Each filament wrapped around the spore 4 times. The posterior thickenings seem to appear late in the development of the spore and were composed of spore wall material. A second set of branching tubular filaments composed of a different material was observed on the spore body although not on mature spores possessing a ‘knob-like’ posterior thickening. The ornamentation on the spores of the pearl oyster parasite was unique amongst described haplosporidian species where spore ornamentation is known. The parasite is named in this manuscript as Haplosporidium hinei n. sp.
Determination of the effects of temperature on viability, metabolic activity and proliferation of two Perkinsus species, and its significance to understanding seasonal cycles of perkinsosis
Authors: PEYRE M. K. LA , CASAS S. M. , VILLALBA A. , PEYRE J. F. LA
Published: February 2008

The range of water temperatures in which Perkinsus species can survive and proliferate remains ill-defined, particularly at lower temperatures. The in vitro viability, metabolic activity, and proliferation of 3 isolates each of P. marinus and P. olseni trophozoites at 28°C, and at 15 and 4°C, after transfer from 28°C, were compared. Both species showed declines in metabolic activity and proliferation from 28°C to 15°C. At 4°C, both species had viability after 30 days incubation time (P. marinus 49%, P. olseni 58%), but limited metabolic activity and no proliferation. Perkinsus marinus viability was further compared when transferred directly from 28°C, 18°C and progressively from 18°C (0·5°C/day) to 2, 4 and 6°C and maintained for up to 4 months. Viability was highest under progressive transfer (77% and 54% after 30 and 60 days exposure to test temperatures). The decrease in P. marinus viability at the lower temperatures in vitro only partially explains decreasing parasite infection intensities in eastern oysters in the colder months of the year. Moreover, the significant decrease in parasite infection intensities in late winter and early spring, as temperatures increase, is likely due to an active process of elimination by oyster host defences.
A non-constant invariant function for certain ergodic flows
Authors: SCHWARTZMAN SOL
Published: February 2008

Let U be the vector space of uniformly continuous real-valued functions on the real line $\mathbb {R}$ and let U0 denote the subspace of U consisting of all bounded uniformly continuous functions. If X is a compact differentiable manifold and we are given a flow on X, then we associate with the flow a function F:X→H1(X,U/U0) that is invariant under the flow. We give examples for which the flow on X is ergodic but there is no λ∈H1(X,U/U0) such that F(p)=λ for almost all points p.
Linearization of holomorphic germs with quasi-parabolic fixed points
Authors: RONG FENG
Published: February 2008

Letfbe a germ of a holomorphic diffeomorphism of$\mathbb {C}^n$with the originObeing a quasi-parabolic fixed point, i.e. the spectrum ofdfOconsists of 1 ande2iπθjwith$\theta _j\in \mathbb {R}\!\setminus \!\mathbb {Q}$. We show thatfis locally holomorphically conjugated to its linear part, iffis of some particular form and its eigenvalues satisfy certain arithmetic conditions. When the spectrum ofdfOdoes not consist of any 1’s, this is the classical result of Siegel [C. L. Siegel. Iteration of analytic functions.Ann. of Math.43(1942), 607–612] and Brjuno [A. D. Brjuno. Analytic form of differential equations.Trans. Moscow Math. Soc.25(1971), 131–288;26(1972), 199–239].
Expanding the scientific basis of health technology assessment: A research agenda for the next decade
Authors: Battista Renaldo N.
Published: February 2008

Objectives:The complexity of health technology assessment (HTA) has increased, in part because of its evolution through three distinct phases: the machine, the clinical outcomes, and the delivery models. However, the theoretical foundation for the field remains underdeveloped.

Methods:It is high time for HTA to bring together aspects of conceptual and theoretical works from other fields to strengthen the foundation of HTA.

Results:Many challenges await the further development of HTA. They can be captured around three research themes: adapting HTA to an evolving analysis object; translating HTA results into policy, management, and practice decisions; and evaluating organizational models of HTA.

Conclusions:Consolidating the scientific basis of HTA is essential if we are to succeed in increasing the relevance of HTA in some of the most challenging health-related decisions that we will make as individuals and societies.
Commentary
Authors: Banta H. David , Jonsson Egon
Published: February 2008

Battista has written a thoughtful and timely challenge to the field of health technology assessment (HTA). As the author points out, HTA is changing and evolving. One of the greatest challenges is that HTA now seems firmly established in a number of countries, and is being looked to more and more for the “answers.” We accept and endorse Battista's central thesis, and essentially all of his critical questions, including his ideas about future research topics. We hope to evoke further thoughts in the reader and perhaps stimulate other responses, either private and public.
Case study of the comparison of data from conference abstracts and full-text articles in health technology assessment of rapidly evolving technologies: Does it make a difference?
Authors: Dundar Yenal , Dodd Susanna , Williamson Paula , Dickson Rumona , Walley Tom
Published: February 2008

Objectives: The aim of this study was to examine (i) the consistency of reporting research findings presented in conference abstracts and presentations and subsequent full publications, (ii) the ability to judge methodological quality of trials from conference abstracts and presentations, and (iii) the effect of inclusion or exclusion of data from these sources on the pooled effect estimates in a meta-analysis.

Methods: This report is a case study of a selected health technology assessment review (TAR) of a rapidly evolving technology that had identified and included a meta-analysis of trial data from conference abstracts and presentations.

Results: The overall quality of reporting in abstracts and presentations was poor, especially in abstracts. There was incomplete or inconsistent reporting of data in the abstract/presentations. Most often inconsistencies were between conference slide presentations and data reported in published full-text articles. Sensitivity analyses indicated that using data only from published papers would not have altered the direction of any of the results when compared with those using published and abstract data. However, the statistical significance of three of ten results would have changed. If conference abstracts and presentations were excluded from the early analysis, the direction of effect and statistical significance would have changed in one result. The overall conclusions of the original analysis would not have been altered.

Conclusions: There are inconsistencies in data presented as conference abstracts/presentations and those reported in subsequent published reports. These inconsistencies could impact the final assessment results. Data discrepancies identified across sources included in TARs should be highlighted and their impact assessed and discussed. Sensitivity analyses should be carried out with and without abstract/presentation data included in the analysis. Incomplete reporting in conference abstracts and presentations limits the ability of reviewers to assess confidently the methodological quality of trials.
Doing mini–health technology assessments in hospitals: A new concept of decision support in health care?
Authors: Ehlers Lars , Vestergaard Malene , Kidholm Kristian , Bonnevie Birgitte , Pedersen Poul Holt , Jørgensen Torben , Jensen Malene Fabricius , Kristensen Finn Børlum , Kjølby Mette
Published: February 2008

Objectives:The purpose of this project was to evaluate local decision support tools used in the Danish hospital sector from a theoretical and an empirical point of view.

Methods:The use of local decision support was evaluated through questionnaires sent to all county health directors, all hospital managers, and all heads of clinical departments in cardiology, orthopedic surgery, and intensive care. In addition, respondents were asked to submit whatever decision support tools they were using (including mini-HTAs, other forms or checklists, and special procedures for decision making concerning new health technologies). A theoretical analysis of the decision support tools (decision theory) was performed as well as a comparison with the business case method used in private companies. Finally, the Danish mini-HTA was compared with foreign production and use of HTA and HTA-like assessments as local decision support.

Results:The response rate was high (87 percent, 94 percent, 85 percent, respectively). We collected sixty different forms (of which forty-nine were mini-HTAs) and twenty variants of written procedures. We found theoretical and empirical evidence that local involvement in the process of making the HTA could be important for the use of the results from the HTA and for the process of implementing the new technology.

Conclusions:Doing mini-HTA in hospitals seems to balance the need for quality and depth with the limited time and resources for assessment.
Ethics and health technology assessment: Handmaiden and/or critic?
Authors: Braunack-Mayer Annette J.
Published: February 2008

Objectives: This study examines the content and role of ethical analysis in health technology assessment (HTA) and horizon scanning publications. It proposes that ethical analysis in HTA is of at least two different types: an ethics of HTA and an ethics in HTA.

Methods: I examine the critical differences between these approaches through the examples of the analysis of genetic screening for breast cancer and home blood glucose testing in diabetes. I then argue that, although both approaches subscribe to similar views concerning HTA and ethics, they use different theoretical and methodological traditions to interpret and explain them.

Results and Conclusions: I conclude by suggesting that we need the interpretive insights of both these approaches, taken together, to explain why ethics has not been able yet to contribute fully to HTA and to demonstrate the scope and complexity of ethical work in this domain.
Early home-supported discharge of stroke patients: A health technology assessment
Authors: Larsen Torben , Olsen Tom S. , Sorensen Jan
Published: February 2008

Objectives: A comprehensive and systematic assessment (HTA) of early home-supported discharge by a multidisciplinary team that plans, coordinates, and delivers care at home (EHSD) was undertaken and the results were compared with that of conventional rehabilitation at stroke units.

Methods: A systematic literature search for randomized trials (RCTs) on “early supported discharge” was closed in April 2005. RCTs on EHSD without information on (i) death or institution at follow-up, (ii) change in Barthél Index, (iii) length of hospital stay, (iv) intensity of home rehabilitation, or (v) baseline data are excluded. Seven RCTs on EHSD with 1,108 patients followed 3–12 months after discharge are selected for statistical meta-analysis of outcomes. The costs are calculated as a function of the average number of home training sessions. Economic evaluation is organized as a test of dominance (both better outcomes and lower costs).

Results: The odds ratio (OR) for “Death or institution” is reduced significantly by EHSD: OR = .75 (confidence interval [CI], .46–.95), and number needed to treat (NNT) = 14. Referrals to institution have OR = .45 (CI, .31–.96) and NNT = 20. The reduction of the rate of death is not significant. Length of stay is significantly reduced by 10 days (CI, 2.6–18 days). All outcomes have a nonsignificant positive covariance. The median number of home sessions is eleven, and the average cost per EHSD is 1,340 USD. The “action mechanism” and financial barriers to EHSD are discussed.

Conclusions: EHSD is evidenced as a dominant health intervention. However, financial barriers between municipalities and health authorities have to be overcome. For qualitative reasons, a learning path of implementation is recommended where one stroke unit in a region initiates EHSD for dissemination of new experience to the other stroke units.
The economics of blood: Gift of life or a commodity?
Authors: Kanavos Panos , Yfantopoulos John , Vandoros Christina , Politis Costantina
Published: February 2008

Objectives:To calculate the costs of blood collection, testing, storage, and transfusion in Greece.

Methods:Costing information was collected from two large public hospitals, in Athens and Crete, that also act as blood banks. Given that private health care accounts for 40 percent of total health spending, the same costs were also considered in a private setting by collecting key reagent cost data from a leading private hospital in Athens. Mainly direct costs were considered (advertising campaigns, personnel, storage and maintenance, reagent costs, transportation costs from blood bank to end-use hospitals, and cross-matching and transfusion costs in receiving hospitals) and some indirect costs (opportunity cost of blood donorship).

Results:Captive donorship accounts for over 50 percent of the national blood supply. A unit of blood transfused would cost between €294.83 and €339.83 in public hospitals and could reach €413.93 in a private facility. This figure may be an underestimate, as it excludes opportunity costs of blood transfusion for patients and the healthcare system.

Conclusions:Blood has a significant cost to the health system. Policy makers and practitioners should encourage its rational use, build on current policies to further improve collection and distribution, encourage further volunteer donorship in Greece, and also consider alternatives to blood where the possibility exists.
Women's preferences for cervical cancer screening: A study using a discrete choice experiment
Authors: Wordsworth Sarah , Ryan Mandy , Skåtun Diane , Waugh Norman
Published: February 2008

Objectives: Recent policy recommendations for cervical screening include liquid-based cytology. This new approach could improve laboratory throughput, reducing the waiting time for test results. New guidelines also standardize the interval for screening, with women aged 25–50 offered screening every 3 years and women aged 50–64 every 5 years. Quantitative evidence on the preferences of women for alternative screening programs is limited; this study, therefore, elicits such preferences.

Methods: A postal questionnaire using a discrete choice experiment was mailed to 2,000 women in the Tayside Health Board region of Scotland.

Results: A response rate of 44 percent from those women who had previously had a smear was achieved. Women had a significant positive preference for reductions in recall rates and waiting time for results. Women preferred more frequent screening, particularly those aged 50+. Expected reductions in the chance of recall from the conventional Pap smear to the new liquid-based cytology were associated with a willingness to pay of £41. Women aged 50+ would be willing to pay £42 to increase the frequency of screening from every 5 to every 3 years. Service characteristics did not influence screening participation.

Conclusions: Guidance to move to liquid-based cytology will meet women's preferences for fewer repeat cervical smears and should reduce waiting time for results. However, proposals to increase screening intervals for those aged 50+ are inconsistent with the preferences for this age group. From a policy perspective, our study results suggest that the changes in attributes of the service such as unsatisfactory smear rates and frequency of screening, will improve service efficiency without affecting participation rates.
Decision makers' and scientists' opinion about contingent valuation and choice experiments for measuring willingness to pay in health care: Results from a survey in Germany
Authors: Günther Oliver H. , König Hans-Helmut
Published: February 2008

Objectives: Assessment of willingness to pay (WTP) by contingent valuation (CV) and choice experiments (CE) is increasingly performed in economic evaluation of health care. However, the question of whether the methods for measuring WTP are acceptable to decision makers and scientists has remained largely unacknowledged. The aim of this study was to learn more about decision makers' and scientists' opinion concerning these methods.

Methods: An expert group developed a questionnaire consisting of key items that may influence the opinion about CV and CE according to the constructs “attitude toward behavior,” “subjective norm,” and “behavioral intention” as defined by the Theory of Reasoned Action by Ajzen and Fishbein. In a survey, seventy-seven decision makers representing key institutions in the German healthcare system and forty-two scientists in health economics completed the questionnaire.

Results: Scientists and decision makers in particular did not show a high intention to use methods for measuring WTP. Skepticism regarding precision of the methods and subjects' capability to imagine paying an amount of money for a certain health commodity were stated along with the assertion that the hypothetical decision-making scenario was rather a distant reality. Nevertheless, the majority of scientists and decision makers did not state rejection of the methods.

Conclusions: Increasing the probability of using methods for measuring WTP in health care, the hypothetical scenarios should be made more realistic and payment vehicles should be used to help patients relate payment to a real health benefit. Moreover, an intensive discussion on the potential usefulness of CV/CE without excluding ethical concerns in comparison to existing alternatives has to be resumed.
Measuring quality of life: The development and initial validation of the Patient-Reported Erectile Function Assessment instrument
Authors: Torrance George W. , Keresteci Margaret-Anne , Casey Richard , Ryan Nancy C. , Tarride Jean-Eric
Published: February 2008

Objectives: Erectile dysfunction (ED) is a complex condition, which is variously influenced by physical, emotional, societal, and relationship factors. ED has serious implications for the quality of life (QoL) enjoyed by an affected male and his partner. It is very important, therefore, to understand the impact of ED on the QoL of those affected by it. Our objective was to determine if the eight-question Patient Reported Erectile Function Assessment (PREFA) could act as an independent, comprehensive disease-specific instrument in the assessment of QoL as it is impacted by ED.

Methods: During the development and validation of the Erectile Function–Visual Analog Scale (EF-VAS) (14), a new ED-specific preference-based instrument, a series of questions were included at the beginning of the assessment that would act as a way to encourage respondents to focus on their own experience with ED. Upon analysis of the EF-VAS data, it became apparent that the eight-question “warm up” section might act as a stand-alone assessment. Accordingly, the eight questions were named PREFA, and a validation analysis was undertaken to determine their consistency, feasibility, reliability, validity, and responsiveness.

Results: The PREFA questionnaire was found to be feasible and simple to complete, reliable, and valid, with excellent responsiveness. Overall, the PREFA has demonstrated that it can perform as a stand alone, validated assessment of the impact of ED on QoL, assessing areas of QoL not previously captured in existing instruments.

Conclusions: The PREFA is suitable for use in clinical and research settings as a disease-specific QoL assessment tool.
Priority setting for research in health care: An application of value of information analysis to glycoprotein IIb/IIIa antagonists in non-ST elevation acute coronary syndrome
Authors: Philips Zoë , Claxton Karl Philip , Palmer Stephen , Bojke Laura , Sculpher Mark John
Published: February 2008

Abstract:The purpose of this study is to explain the rationale for the value of information approach to priority setting for research and to describe the methods intuitively for those familiar with basic decision analytical modeling. A policy-relevant case study is used to show the feasibility of the method and to illustrate the type of output that is generated and how these might be used to frame research recommendations. The case study relates to the use of glycoprotein IIb/IIIa antagonists for the treatment of patients with non-ST elevation acute coronary syndrome. This is an area that recently has been appraised by the National Institute for Health and Clinical Excellence.
Uncertainty‐based multiobjective optimization of groundwater remediation design
Authors: Singh Abhishek , Minsker Barbara S.
Published: February 2008

Management of groundwater contamination often involves conflicting objectives and substantial uncertainty. The primary objective of this paper is to present a new approach, called the probabilistic multiobjective genetic algorithm (PMOGA), which incorporates uncertainty with multiobjective Pareto optimization. This type of approach is needed for water resources problems with multiple uncertain objectives; previous uncertainty‐based optimization approaches consider uncertainty only in the constraints (typically constraining reliability with respect to environmental standards) or in a single objective. The optimization algorithm uses a probabilistic ranking and crowding scheme that improves decision making within the genetic algorithm by identifying a set of solutions that are Pareto optimal despite the uncertainty in the objective values. The algorithm is applied to two groundwater remediation test cases with uncertain objectives: a hypothetical case study and a field‐scale pump‐and‐treat design problem at the Umatilla Chemical Depot situated at Hermiston, Oregon. For these case studies the primary source of uncertainty stems from uncertain aquifer hydraulic conductivity values, which affect both the remediation cost and efficiency. Results are analyzed, and the advantages of the PMOGA are discussed relative to an averaging‐based multiobjective approach, a stochastic single‐objective approach (similar to chance constrained optimization), and a deterministic multiobjective approach. The results demonstrate that using such an uncertainty‐based multiobjective optimization scheme can give valuable information about remediation options, giving results that are not only cost effective but that also have lower uncertainty.
Vertical transport of particulate organic matter regulated by fjord topography
Authors: Erlandsson Carina P.
Published: February 2008

The deepwater in many areas with restricted water exchange suffers from low oxygen concentrations due to degradation of organic matter. The objective of this study was to investigate how topography may influence the vertical transport, Fc, of particulate organic matter, POM, to the deepwater. A conceptual/analytical model for Fc was developed covering the combination of the three possible sources of POM/nutrients to an enclosed area; the coastal water, local supply, and nutrient rich local deepwater. The mathematical formulation of the conceptual model includes several factors describing to which degree various physical mechanisms in the fjord are influencing Fc. The model consists of submodels for the different sources of POM/nutrients. A one‐dimensional process oriented numerical model was used to test the conceptual model. Restricted water exchange with the coastal water led to decreased import of POM and thereby decreased vertical transport, Fc, of coastal POM. The contribution to Fc by local input of nutrients to the surface layer was described by a function of the residence time of the water above sill level, Tsw and the time Tp it takes for POM produced in the surface layer to settle below sill level. The recirculation of POM produced due to basin water renewals was shown to be a function of several factors: The relation between the depth of photic zone, Hp and the sill depth, Ht, the vertical velocity of the rising nutrient rich water mass versus the settling velocity of POM, etc. The results based on the conceptual submodels agreed well with the results from the process oriented numerical model. Methods to identify the trophic state of coastal waters, and also simple models to calculate the effect of a local point source, can be found in literature. However, using the model developed in this paper the effects of nutrient enrichment from different sources can be quantified in a simple and more efficient way than earlier. The model can thus be used to categorise areas with respect to sensitivity to local and large scale eutrophication, which is an important step towards better management and more sustainable exploitation of the coastal zone.
Measurement network design including traveltime determinations to minimize model prediction uncertainty
Authors: Janssen Gijs M. C. M. , Valstar Johan R. , van der Zee Sjoerd E. A. T. M.
Published: February 2008

Traveltime determinations have found increasing application in the characterization of groundwater systems. No algorithms are available, however, to optimally design sampling strategies including this information type. We propose a first‐order methodology to include groundwater age or tracer arrival time determinations in measurement network design and apply the methodology in an illustrative example in which the network design is directed at contaminant breakthrough uncertainty minimization. We calculate linearized covariances between potential measurements and the goal variables of which we want to reduce the uncertainty: the groundwater age at the control plane and the breakthrough locations of the contaminant. We assume the traveltime to be lognormally distributed and therefore logtransform the age determinations in compliance with the adopted Bayesian framework. Accordingly, we derive expressions for the linearized covariances between the transformed age determinations and the parameters and states. In our synthetic numerical example, the derived expressions are shown to provide good first‐order predictions of the variance of the natural logarithm of groundwater age if the variance of the natural logarithm of the conductivity is less than 3.0. The calculated covariances can be used to predict the posterior breakthrough variance belonging to a candidate network before samples are taken. A Genetic Algorithm is used to efficiently search, among all candidate networks, for a near‐optimal one. We show that, in our numerical example, an age estimation network outperforms (in terms of breakthrough uncertainty reduction) equally sized head measurement networks and conductivity measurement networks even if the age estimations are highly uncertain.
Antarctic sea ice elevation from satellite radar altimetry
Authors: Giles Katharine A. , Laxon Seymour W. , Worby Anthony P.
Published: February 2008

In situ measurements of sea ice thickness from ship and upward‐looking sonar are used to assess the potential for satellite radar altimetry to provide information on Antarctic sea ice thickness. A climatology of satellite ice elevation estimates is compared to an Antarctic sea ice thickness climatology made from the Antarctic Sea Ice Processes and Climate (ASPeCt) data set. In addition monthly, regional, satellite ice elevation estimates are compared to ULS ice draft data. The results show reasonable spatial agreement between the satellite and in‐situ data, and show regional signals of change in ice elevation in line with that which would be expected. The results show some promise for providing information on Antarctic ice thickness from radar altimetry missions such as CryoSat. However, further studies into snow and ice density and the radar penetration into the Antarctic snow cover are required.
Circulation in Lake Vostok: A laboratory analogue study
Authors: Wells Mathew G. , Wettlaufer J. S.
Published: February 2008

The waters of sub‐glacial Lake Vostok are thought to represent a unique biological habitat that has been out of contact with the atmosphere for millions of years. Although the water circulation within the lake will determine how nutrients are redistributed and hence where life may exist, the handful of existing studies conflict regarding whether the lake is stratified or well mixed, whether there is a clockwise or anti‐clockwise circulation, or whether the sloping roof leads to a flow intensified along the eastern boundary. Here, an experimental analogue model of Lake Vostok is used to show a qualitatively different mode of circulation than described previously. The dominant mode of dispersion, and hence bio‐ and chemical redistribution, is controlled by the presence of columnar vortex structures that arise from rotating convection. This form of circulation does not occur in any other lake on Earth. We estimate that a water parcel takes 20–30 days to travel from the base to the roof of Lake Vostok and will experience minimal lateral mixing during this time. As the nutrient supply to the lake via melting ice is predicted to be less than that required for active growth within the entire lake, we speculate that this form of slow columnar convection would lead to the presence of thin biological boundary layers within the waters of the lake. This has important implications for the interpretation of any direct water samples taken near the roof of Lake Vostok.
Influence of leads in sea ice on the temperature of the atmospheric boundary layer during polar night
Authors: Lüpkes C. , Vihma T. , Birnbaum G. , Wacker U.
Published: February 2008

The maximum effect of open leads within sea ice on the near‐surface atmospheric temperature is estimated using a 1D atmospheric model coupled with a thermodynamic snow/sea ice model. The study is restricted to clear‐sky conditions during polar night. The model is initialized with a typical wintertime atmospheric temperature profile. Results are analyzed at different integration times corresponding to different fetches over the fractured sea ice as a function of wind speed and sea ice concentration A. The results demonstrate that for A > 90% small changes in the sea ice fraction have a strong effect on the near‐surface temperature. A change by 1% causes a temperature signal of up to 3.5 K. A threshold value of about 4 m s−1 for the 10‐m wind speed divides the air‐ice interaction process into a weak‐wind and strong‐wind regime.
Summer sea ice motion from the 18 GHz channel of AMSR‐E and the exchange of sea ice between the Pacific and Atlantic sectors
Authors: Kwok Ron
Published: February 2008

We demonstrate that sea ice motion in summer can be derived reliably from the 18GHz channel of the AMSR‐E instrument on the EOS Aqua platform. The improved spatial resolution of this channel with its lower sensitivity to atmospheric moisture seems to have alleviated various issues that have plagued summer motion retrievals from shorter wavelength observations. Two spatial filters improve retrieval quality: one reduces some of the microwave signatures associated with synoptic‐scale weather systems and the other removes outliers. Compared with daily buoy drifts, uncertainties in motion are ∼3–4 km/day. Using the daily motion fields, we examine five years of summer ice area exchange between the Pacific and Atlantic sectors of the Arctic Ocean. With the sea‐level pressure patterns during the summer of 2006 and 2007 favoring the export of sea ice into the Atlantic Sector, the regional outflow is ∼21% and ∼15% of the total sea ice retreat in the Pacific sector.
Arctic perennial ice cover over the last 14 million years
Authors: Darby Dennis A.
Published: February 2008

Knowledge of the long‐term history of the perennial ice is an important issue that has eluded study because the Cenozoic core material needed has been unavailable until the recent Arctic Coring Expedition (ACEX). Detrital Fe oxide mineral grains analyzed by microprobe from the last 14 Ma (164 m) of the ACEX composite core on the Lomonosov Ridge were matched to circum‐Arctic sources with the same mineral and 12‐element composition. These precise source determinations and estimates of drift rates were used to determine that these sand grains could not be rafted to the ACEX core site in less than a year. Thus the perennial ice cover has existed since 14 Ma except for the unlikely rapid return to seasonal ice between the average sampling interval of about 0.17 Ma. Both North America and Russia contributed significant Fe grains to the ACEX core during the last 14 Ma.
On the geostatistical characterization of hierarchical media
Authors: Neuman Shlomo P. , Riva Monica , Guadagnini Alberto
Published: February 2008

The subsurface consists of porous and fractured materials exhibiting a hierarchical geologic structure, which gives rise to systematic and random spatial and directional variations in hydraulic and transport properties on a multiplicity of scales. Traditional geostatistical moment analysis allows one to infer the spatial covariance structure of such hierarchical, multiscale geologic materials on the basis of numerous measurements on a given support scale across a domain or “window” of a given length scale. The resultant sample variogram often appears to fit a stationary variogram model with constant variance (sill) and integral (spatial correlation) scale. In fact, some authors, who recognize that hierarchical sedimentary architecture and associated log hydraulic conductivity fields tend to be nonstationary, nevertheless associate them with stationary “exponential‐like” transition probabilities and variograms, respectively, the latter being a consequence of the former. We propose that (1) the apparent ability of stationary spatial statistics to characterize the covariance structure of nonstationary hierarchical media is an artifact stemming from the finite size of the windows within which geologic and hydrologic variables are ubiquitously sampled, and (2) the artifact is eliminated upon characterizing the covariance structure of such media with the aid of truncated power variograms, which represent stationary random fields obtained upon sampling a nonstationary fractal over finite windows. To support our opinion, we note that truncated power variograms arise formally when a hierarchical medium is sampled jointly across all geologic categories and scales within a window; cite direct evidence that geostatistical parameters (variance and integral scale) inferred on the basis of traditional variograms vary systematically with support and window scales; demonstrate the ability of truncated power models to capture these variations in terms of a few scaling parameters; show that exponential and truncated power variograms are often difficult to distinguish from each other, which helps explain why hierarchical data may appear to fit the former; note that truncated power models are unique in their ability to represent multiscale random fields having either Gaussian or heavy‐tailed symmetric Levy stable probability distributions; detail the way in which these models allow conditioning the spatial statistics of such fields on multiscale measurements via cokriging; and illustrate these capabilities on multiscale hydraulic data from an unconfined aquifer near Tübingen, Germany.
Long‐term groundwater storage trends estimated from streamflow records: Climatic perspective
Authors: Brutsaert Wilfried
Published: February 2008

Base flow, also known as low flow or drought flow, in a natural river system originates mainly from drainage of the riparian aquifers in the upstream basin. Base flow data can therefore provide a quantitative estimate of the basin‐scale groundwater storage changes that have taken place over the period of record. The concept was implemented and validated with data from two large river basins in Illinois. On average over the past 2/3 century, shallow groundwater storage in Illinois, derived from the drought flows, has been increasing at an average rate of around 0.05 to 0.10 mm a‐1. However, the trend has not been stationary throughout this period; for instance, the more recent trend from the mid nineteen nineties until now appears to have been negative. The groundwater storage changes inferred from the base flows are generally consistent with the average groundwater level changes measured in an observation well network over the same area.
Influence of combined hypertension and renal failure on functional α1‐adrenoceptor subtypes in the rat kidney
Authors: Hye Khan M A , Sattar M A , Abdullah N A , Johns E J
Published: February 2008

Background and purpose:This study investigated whether the α1‐adrenoceptor responsiveness of the renal vasculature was altered in the state of hypertension combined with renal failure.

Experimental approach:Male spontaneously hypertensive rats (SHR) received cisplatin (5 mg kg−1i.p.) to induce renal failure. Seven days later, the rats were anaesthetized and the reductions in renal blood flow (RBF) to electrical renal nerve stimulation (RNS) and intrarenal administration of three adrenoceptor agonists (noradrenaline, phenylephrine and methoxamine) were determined before and after amlodipine, 5‐methylurapidil, chloroethylclonidine or BMY 7378.

Key results:In renal failure SHR (RFSHR), RBF and creatinine clearance were significantly reduced (approximately 70%), while urine output and fractional sodium excretion were four and twenty‐fold higher, respectively, compared to SHR. Vasoconstrictions induced by RNS or the adrenoceptor agonists were greater in RFSHR than SHR, and these responses were blunted by 5‐methylurapidil, BMY 7378 and amlodipine in the SHR, while chloroethylclonidine had no effect. In the RFSHR, all renal vasoconstrictions were reduced by amlodipine and BMY 7378 but 5‐methylurapidil attenuated those caused by RNS, noradrenaline and methoxamine while those to phenylephrine were enhanced. Chloroethylclonidine potentiated renal vasoconstrictor responses to methoxamine and phenylephrine but not RNS or noradrenaline in RFSHR.

Conclusions and implications:These findings suggest α1A‐ and α1D‐adrenoceptors mediated the renal vasoconstrictor responses in SHR and RFSHR. In the RFSHR, other α1‐adrenoceptor subtypes, for example, α1B‐adrenoceptors appeared to play a greater role.

British Journal of Pharmacology(2008)153, 1232–1241; doi:10.1038/bjp.2008.13; published online 11 February 2008
Cholinergic nitric oxide release from the urinary bladder mucosa in cyclophosphamide‐induced cystitis of the anaesthetized rat
Authors: Andersson M C , Tobin G , Giglio D
Published: February 2008

Background and purpose: Previous reports have suggested that nitric oxide (NO) may be released by cholinergic stimuli in the rat bladder in cyclophosphamide‐induced cystitis, affecting bladder function. In the current study, we evaluated the effects of cyclophosphamide‐induced cystitis on muscarinic whole bladder contractile responses in vivo, and further, if NO might be released from the mucosa by cholinergic stimuli.

Experimental approach: Male rats were pre‐treated either with cyclophosphamide (100 mg kg−1; to induce cystitis) or saline (serving as controls). 60 h later, rats were anaesthetized and bladder pressure monitored.

Key results: The muscarinic receptor agonist methacholine (MeCh; 0.5–5 μg kg−1 i.v.) induced similar contractions (i.e. bladder pressure increases) in inflamed bladders as in controls, which were attenuated dose‐dependently by the muscarinic M1/M3/M5 antagonist 4‐diphenylacetoxy‐N‐methylpiperidine (4‐DAMP; 0.1–1000 μg kg−1 i.v.). In inflamed bladders, the cholinergic bladder contractions were enhanced after removing the mucosa, while cholinergic contractions were similar in intact and urothelium‐denuded inflamed bladders in the presence of the NO synthase inhibitor Nω‐nitro‐L‐arginine methyl ester (L‐NAME; 30 mg kg−1 i.v.). L‐NAME attenuated the antagonistic effect of 4‐DAMP on MeCh‐induced contractions in intact inflamed bladders. However L‐NAME did not affect the antagonism by 4‐DAMP of MeCh‐induced contractions of urothelium‐denuded bladders, under control conditions or with cyclophosphamide‐induced cystitis.

Conclusions and implications: In cyclophosphamide‐induced cystitis, the cholinergic function of the bladder is altered. In the inflamed bladder, NO seems to be released via cholinergic stimuli through mucosal muscarinic M3/M5 receptors, presumably on urothelial cells, affecting bladder function.

British Journal of Pharmacology (2008) 153, 1438–1444; doi:10.1038/bjp.2008.6; published online 4 February 2008
Pioglitazone opposes neurogenic vascular dysfunction associated with chronic hyperinsulinaemia
Authors: Takatori S , Zamami Y , Yabumae N , Hanafusa N , Mio M , Egawa T , Kawasaki H
Published: February 2008

Background and purpose: We previously demonstrated that chronic hyperinsulinaemia induced by drinking high levels of fructose augments adrenergic nerve‐mediated vasoconstriction and suppresses vasodilatation mediated by calcitonin gene‐related peptide (CGRP)‐containing (CGRPergic) vasodilator nerves. In this study, the effects of pioglitazone on vascular responses induced by stimulation of adrenergic nerves, CGRPergic nerves and vasoactive agents were investigated in pithed rats given 15% fructose solution to drink (FDR).

Experimental approach: To assess the effect of pioglitazone on the altered vascular responsiveness in the hyperinsulinaemic state in vivo, changes in vascular responses to spinal cord stimulation (SCS) and intravenous bolus injections of noradrenaline, angiotensin II and CGRP were evaluated in pithed control rats and FDR either untreated or treated with pioglitazone.

Key results: In the pithed FDR, vasoconstrictor responses to SCS and to injections of noradrenaline and angiotensin II were significantly greater than those of pithed control rats. In pithed FDR with artificially increased blood pressure and blockade of the autonomic ganglia, the vasodilator responses to SCS and CGRP injection were significantly smaller than those of pithed control rats. Oral administration of pioglitazone to FDR for two weeks markedly decreased plasma levels of insulin, triglycerides and blood glucose. In FDR pioglitazone diminished the augmented vasoconstrictor responses to SCS, noradrenaline and angiotensin II, and ameliorated the decrease in vasodilator responses to SCS.

Conclusions and implications: The present results suggest that pioglitazone improves not only insulin resistance, but also the dysfunctions in vascular control regulated by adrenergic and CGRPergic nerves in the hyperinsulinaemic state.

British Journal of Pharmacology (2008) 153, 1388–1398; doi:10.1038/bjp.2008.8; published online 4 February 2008
Enhanced angiotensin converting enzyme 2 regulates the insulin/Akt signalling pathway by blockade of macrophage migration inhibitory factor expression
Authors: Zhong J‐C , Yu X‐Y , Lin Q‐X , Li X‐H , Huang X‐Z , Xiao D‐Z , Lin S‐G
Published: February 2008

British Journal of Pharmacology (2008) 153, 621; doi:10.1038/sj.bjp.0707614