bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of daily movement of dairy cattle to fresh grass in morning or afternoon on intake, grazing behaviour, rumen fermentation and milk production
Authors: ABRAHAMSE P. A. , TAMMINGA S. , DIJKSTRA J.
Published: August 2009

Twenty Holstein cows were split into two equal groups to test the effect of daily move to a previously ungrazed strip after morning milking (MA) or afternoon milking (AA) on herbage intake, grazing behaviour, rumen characteristics and milk production using a randomized block design with three periods of 14 days each. Milking took place at 06.00 and 16.00 h. The chemical composition of grass was similar between treatments, but an interaction between treatment and time of sampling was found in all variables except acid detergent lignin (ADL). The most pronounced differences existed in sugar content. Grass sugar content was greatest following afternoon milking. However, the difference in sugar content in grass was much larger in MA (158v114 g/kg dry matter (DM) at 16.00 and 06.00 h, respectively) than in AA (147v129 g/kg DM at 16.00 and 06.00 h, respectively). Neutral detergent fibre (NDF) was significantly higher at 06.00 h than at 16.00 h (469v425 g/kg DM) in AA, but was equal between morning and afternoon in MA (453 g/kg DM). Herbage intake, determined using the n-alkane technique, did not differ between treatments. Grazing behaviour observed using IGER graze recorders were similar between treatments, except for ruminating time, bite rate and the number of ruminations and boli per period of the day. However, interactions between treatment and time in grazing behaviour variables were found. Grazing time was longer and number of bites was greater following allocation to a new plot (after milking in the morning in MA or milking in the afternoon in AA) when compared to allocation to the same plot after the subsequent milking per treatment (after milking in the afternoon or morning in MA and AA, respectively). In comparison to AA, grazing time in MA was more evenly distributed during the day but lower during the night. The combined effects of differences in grazing behaviour and chemical composition of the grass between treatments in different periods of the day probably caused higher intake of sugars in AA, resulting in a significantly higher non-glucogenic to glucogenic volatile fatty acid ratio (NGR) in the rumen in AA than MA. Milk fat content was lower in MA than AA, but milk production and milk protein and lactose content did not differ. In conclusion, time of allocation to a fresh plot altered the distribution of grazing behaviour variables over the day, and affected NGR and milk fat content, but herbage intake and milk production were not changed.
Heterogeneous Beliefs and Momentum Profits
Authors: Verardo Michela
Published: August 2009

Recent theoretical models derive return continuation in a setting where investors have heterogeneous beliefs or receive heterogeneous information. This paper tests the link between heterogeneity of beliefs and return continuation in the cross-section of U.S. stock returns. Heterogeneity of beliefs about a firm’s fundamentals is measured by the dispersion in analyst forecasts of earnings. The results show that momentum profits are significantly larger for portfolios characterized by higher heterogeneity of beliefs. Predictive cross-sectional regressions show that heterogeneity of beliefs has a positive effect on return continuation after controlling for a stock’s visibility, the speed of information diffusion, uncertainty about fundamentals, information precision, and volatility. The results in this paper are robust to the potential presence of short-sale constraints and are not explained by arbitrage risk.
IMPRECISE MARKOV CHAINS AND THEIR LIMIT BEHAVIOR
Authors: de Cooman Gert , Hermans Filip , Quaeghebeur Erik
Published: August 2009

When the initial and transition probabilities of a finite Markov chain in discrete time are not well known, we should perform a sensitivity analysis. This can be done by considering as basic uncertainty models the so-calledcredal setsthat these probabilities are known or believed to belong to and by allowing the probabilities to vary over such sets. This leads to the definition of animprecise Markov chain. We show that the time evolution of such a system can be studied very efficiently using so-calledlowerandupper expectations, which are equivalent mathematical representations of credal sets. We also study how the inferred credal set about the state at timenevolves asn→∞: under quite unrestrictive conditions, it converges to a uniquely invariant credal set, regardless of the credal set given for the initial state. This leads to a non-trivial generalization of the classical Perron–Frobenius theorem to imprecise Markov chains.
Asymptotic growth of algebras associated to powers of ideals
Authors: CUTKOSKY STEVEN DALE , HERZOG JÜRGEN , SRINIVASAN HEMA
Published: August 2009

We study generalized symbolic powers and form ideals of powers and compare their growth with the growth of ordinary powers, and we discuss the question of when the graded rings attached to symbolic powers or to form ideals of powers are finitely generated.
Chern classes of blow-ups
Authors: ALUFFI PAOLO
Published: August 2009

We extend the classical formula of Porteous for blowing-up Chern classes to the case of blow-ups of possibly singular varieties along regularly embedded centers. The proof of this generalization is perhaps conceptually simpler than the standard argument for the nonsingular case, involving Riemann–Roch without denominators. The new approach relies on the explicit computation of an ideal, and a mild generalization of a well-known formula for the normal bundle of a proper transform ([8, B·6·10]).

We also discuss alternative, very short proofs of the standard formula in some cases: an approach relying on the theory of Chern–Schwartz–MacPherson classes (working in characteristic 0), and an argument reducing the formula to a straightforward computation of Chern classes for sheaves of differential 1-forms with logarithmic poles (when the center of the blow-up is a complete intersection).
Multisymplectic structures and the variational bicomplex
Authors: BRIDGES THOMAS J. , HYDON PETER E. , LAWSON JEFFREY K.
Published: August 2009

Multisymplecticity and the variational bicomplex are two subjects which have developed independently. Our main observation is that re-analysis of multisymplectic systems from the view of the variational bicomplex not only is natural but also generates new fundamental ideas about multisymplectic Hamiltonian PDEs. The variational bicomplex provides a natural grading of differential forms according to their base and fibre components, and this structure generates a new relation between the geometry of the base, covariant multisymplectic PDEs and the conservation of symplecticity. Our formulation also suggests a new view of Noether theory for multisymplectic systems, leading to a definition of multimomentum maps that we apply to give a coordinate-free description of multisymplectic relative equilibria. Our principal example is the class of multisymplectic systems on the total exterior algebra bundle over a Riemannian manifold.
Are snacking patterns associated with risk of overweight among Kahnawake schoolchildren?
Authors: Mercille Genevieve , Receveur Olivier , Macaulay Ann C
Published: August 2009

Objective

To understand more specifically how the quality, quantity and frequency of snack food consumption differs in different BMI categories.

Design

Four hundred and forty-nine school-aged children (grade 4–6) from a Kanien’kehaka (Mohawk) community provided a 24 h recall and their height and weight in 1994, 1998 and 2002, in three independent cross-sectional samples. Food consumed between two consecutive meals was defined as a snacking occasion. ANOVA and χ2 tests were used to compare food choices between BMI categories according to food quality criteria and food groups in 2006. Logistic regression models were performed to compare results between normal-weight children and those at risk of overweight and between normal-weight and overweight children.

Results

Energy intake from snacks tended to be higher for children at risk of overweight, compared with the other two BMI categories. Food groups with a higher energy density were also consumed more frequently by these children, with larger average portions of cereal bars (P < 0·05). Except for dessert consumption, which was less frequent among overweight children, no other variable distinguished risk of overweight in the two logistic regression models tested.

Conclusions

Differences detected in snack food intake between normal-weight children and children at risk of overweight could explain in part the relationship between food choices and risk of overweight. Studies of dietary differences in conjunction with body weight would benefit from considering children at risk of overweight and normal-weight children, rather than children with excess weight only.
Healthy Eating Index and abdominal obesity
Authors: Tande Desiree L , Magel Rhonda , Strand Bradford N
Published: August 2009

Objective

Although diet is a modifiable lifestyle factor to reduce abdominal obesity risk, the relationship between the Health Eating Index (HEI) and waist circumference (WC) has not been studied. The present study aimed to describe relationships between the HEI and abdominal obesity among adults.

Design

Secondary data analysis of a cross-sectional national survey, the Third National Health and Nutrition Examination Survey (NHANES III). The HEI data, including the total HEI score and HEI component scores, were collected with a 24 h recall. WC measures were taken during a physical examination. Abdominal obesity was defined as WC ≥ 102 cm for men and WC ≥ 88 cm for women. Other covariates were collected during an interview.

Subjects

In total 15 658 US adults, men (n 7470) and non-pregnant women (n 8188).

Results

The odds of abdominal obesity was 8·3 % (95 % CI 1·8, 14·9 %, P = 0·014) lower for women and 14·5 % (95 % CI 6·8, 21·9 %, P ≤ 0·001) lower for men with each 10-unit increase in total HEI score (HEI scale, 0–100). For each point increase for the fruit score, abdominal obesity risk decreased by 2·6 % (95 % CI 0·8, 4·4 %, P = 0·007) for women. Abdominal obesity risk decreased for men with each point increase in saturated fat and variety scores, by 3·1 % (95 % CI 0·1, 6·0 %, P = 0·042) and 4·0 % (95 % CI 0·1, 7·7 %, P = 0·043) respectively.

Conclusions

Dietary consumption that follows the HEI is associated with a lower risk for abdominal obesity.
Food insecurity prevalence among college students at the University of Hawai’i at Mānoa
Authors: Pia Chaparro M , Zaghloul Sahar S , Holck Peter , Dobbs Joannie
Published: August 2009

Objectives

To assess the prevalence and identify possible predictors of food insecurity among college students at the University of Hawai’i at Mānoa.

Design

Cross-sectional survey, including the US Department of Agriculture’s Household Food Security Survey Module, demographic and spending variables.

Setting

University of Hawai’i at Mānoa, Honolulu, Hawai’i (USA).

Subjects

Four hundred and forty-one non-freshmen students from thirty-one randomly selected classes.

Results

Twenty-one per cent of students surveyed were food-insecure, while 24 % were at risk of food insecurity. Students at higher risk of food insecurity included those who reported living on campus and those living off-campus with room mates. Those identifying themselves as Hawaiians and Pacific Islanders, Filipinos and mixed were also at increased risk of food insecurity.

Conclusions

Food insecurity is a significant problem among college students at the University of Hawai’i at Mānoa. Food availability and accessibility should be increased for these students through the establishment of on-campus food banks and student gardens. Future studies should assess the prevalence of food insecurity in other college campuses nationwide.
Relative validity of a self-completion 24 h recall questionnaire to assess beverage consumption among schoolchildren aged 7 to 9 years
Authors: Muckelbauer Rebecca , Libuda Lars , Kersting Mathilde
Published: August 2009

Objective

Drinking habits in children are associated with diet quality, but validated assessment tools for large-scale studies in young children are lacking. Therefore, we validated a self-completion 24 h recall questionnaire (RQ) focusing on beverage consumption with a 24 h weighed record (WR).

Design

Thirty-five voluntary participants from the DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) Study cohort aged 7–9 years completed the RQ. The illustrated RQ required ticking the number of glasses of seven beverage categories consumed in five time intervals in the previous 24 h. As a reference, parents completed weighed records of their child’s diet. Agreement between the RQ and WR was tested by classification into consumers and non-consumers (kappa coefficients, κ), by the children’s ability to estimate the exact beverage and total volume consumed (Wilcoxon signed-rank test, Spearman rank correlation), and by ranking children according to reported beverage volumes.

Results

The RQ and WR showed a good level of agreement for classifying participants into consumers and non-consumers of the single beverage categories (κ values between 0·78 and 0·94). Correlation coefficients for the volume of the single categories ranged between 0·81 and 0·91. The total beverage volume was overestimated in the RQ, on average, by 114 ml (P = 0·015). Agreement in ranking into tertiles by beverage volume was moderate to good for juice/soft drinks (κ = 0·44), milk (κ = 0·57) and water (κ = 0·70), but fair for the total beverage volume (κ = 0·23).

Conclusions

Our self-completion 24 h RQ could estimate the consumption of several beverage categories among young children at the group level, but quantification of total beverage volume was flawed.
Evaluation of a kindergarten-based nutrition education intervention for pre-school children in China
Authors: Hu Chuanlai , Ye Dongqing , Li Yingchun , Huang Yongling , Li Li , Gao Yongqing , Wang Sufang
Published: August 2009

Objective

To evaluate the impact of nutrition education in kindergartens and to promote healthy dietary habits in children.

Design

Prospective cohort study. Four kindergartens with 1252 children were randomized to the intervention group and three with 850 children to the control group. The personal nutritional knowledge, attitudes and dietary behaviours of the parents were also investigated. Each month, children and parents in the intervention group participated in nutrition education activities. The main outcome measures were anthropometrics and diet-related behaviours of the children and the nutritional knowledge and attitudes of the parents at baseline, 6 months (mid-term) and 1 year (post-test). Baseline demographic and socio-economic characteristics were also collected.

Setting

Seven kindergartens from Hefei, the capital city of Anhui Province, eastern China.

Subjects

Two thousand one hundred and two 4- to 6-year-old pre-schoolers from seven kindergartens participated.

Results

The prevalence of children’s unhealthy diet-related behaviours decreased significantly and good lifestyle behaviours increased in the group receiving nutrition education compared with controls. Parental eating habits and attitudes to planning their children’s diets also changed appreciably in the intervention group compared with the control group (P< 0·05). However, there were no statistically significant differences in children’s height, weight, height-for-ageZ-score or weight-for-ageZ-score between the two groups.

Conclusions

Kindergarten-based nutrition education improves pre-schoolers’ lifestyle behaviours and brings about beneficial changes in parents’ attitudes to planning their children’s diets and their own personal eating habits.
COVERINGS OF SKEW-PRODUCTS AND CROSSED PRODUCTS BY COACTIONS
Authors: PASK DAVID , QUIGG JOHN , SIMS AIDAN
Published: August 2009

Consider a projective limitGof finite groupsGn. Fix a compatible familyδnof coactions of theGnon aC*-algebraA. From this data we obtain a coactionδofGonA. We show that the coaction crossed product ofAbyδis isomorphic to a direct limit of the coaction crossed products ofAby theδn. IfA=C*(Λ) for somek-graph Λ, and if the coactionsδncorrespond to skew-products of Λ, then we can say more. We prove that the coaction crossed product ofC*(Λ) byδmay be realized as a full corner of theC*-algebra of a (k+1)-graph. We then explore connections with Yeend’s topological higher-rank graphs and theirC*-algebras.
BELLWETHERS FOR BOUNDEDNESS OF COMPOSITION OPERATORS ON WEIGHTED BANACH SPACES OF ANALYTIC FUNCTIONS
Authors: BOURDON PAUL S.
Published: August 2009

Let 𝔻 be the open unit disc, letv:𝔻→(0,∞) be a typical weight, and letHv∞be the corresponding weighted Banach space consisting of analytic functionsfon 𝔻 such that$\|f\|_v:=\sup _{z\in \mathbb {D}}v(z)\lvert f(z)\rvert \less \infty $. We callHv∞atypical-growth space. For ϕ a holomorphic self-map of 𝔻, letCφdenote the composition operator induced by ϕ. We say thatCφis abellwether for boundednessof composition operators on typical-growth spaces if for each typical weightv,Cφacts boundedly onHv∞only if all composition operators act boundedly onHv∞. We show that a sufficient condition forCφto be a bellwether for boundedness is that ϕ have an angular derivative of modulus less than 1 at a point on∂𝔻. We raise the question of whether this angular-derivative condition is also necessary forCφto be a bellwether for boundedness.
NORMALITY AND SHARED SETS
Authors: FANG MINGLIANG , ZALCMAN LAWRENCE
Published: August 2009

Let ℱ be a family of meromorphic functions defined in D, all of whose zeros have multiplicity at least k+1. Let a and b be distinct finite complex numbers, and let k be a positive integer. If, for each pair of functions f and g in ℱ, f(k) and g(k) share the set S={a,b}, then ℱ is normal in D. The condition that the zeros of functions in ℱ have multiplicity at least k+1 cannot be weakened.
PARTIAL ACTIONS OF INVERSE AND WEAKLY LEFT E-AMPLE SEMIGROUPS
Authors: GOULD VICTORIA , HOLLINGS CHRISTOPHER
Published: August 2009

We introduce partial actions of weakly left E-ample semigroups, thus extending both the notion of partial actions of inverse semigroups and that of partial actions of monoids. Weakly left E-ample semigroups arise very naturally as subsemigroups of partial transformation semigroups which are closed under the unary operation α↦α+, where α+ is the identity map on the domain of α. We investigate the construction of ‘actions’ from such partial actions, making a connection with the FA-morphisms of Gomes. We observe that if the methods introduced in the monoid case by Megrelishvili and Schröder, and by the second author, are to be extended appropriately to the case of weakly left E-ample semigroups, then we must construct not global actions, but so-called incomplete actions. In particular, we show that a partial action of a weakly left E-ample semigroup is the restriction of an incomplete action. We specialize our approach to obtain corresponding results for inverse semigroups.
Sedimentary, volcanic, and tectonic processes of the central Mariana Arc: Mariana Trough back‐arc basin formation and the West Mariana Ridge
Authors: Oakley A. J. , Taylor B. , Moore G. F. , Goodliffe A.
Published: August 2009

We present new multichannel seismic profiles and bathymetric data from the central Marianas that image the West Mariana Ridge (WMR) remnant arc, both margins of the Mariana Trough back‐arc basin, the modern arc, and Eocene frontal‐arc high. These data reveal structure and stratigraphy related to three periods of arc volcanism and two periods of arc rifting. We interpret the boundary between accreted back‐arc basin and rifted arc crust along the Mariana Trough and support these findings with drilling results and recent seismic refraction and gravity studies. We show that with the exception of a few volcanoes behind the volcanic front that straddle the boundary between crustal types, the modern Mariana Arc is built entirely on rifted arc crust between 14 and 19°N. Our data indicate that there is more accreted back‐arc seafloor to the west of the Mariana Trough spreading axis than to the east, confirming previous evidence for an asymmetric basin. The rifted margin of the WMR remnant arc forms a stepped pattern along the western boundary of the Mariana Trough, between 15°30′ and 19°N. In this region, linear volcanic cross chains behind the WMR are aligned with the trend of Mariana Trough spreading segments, and the WMR ridges extend into the back‐arc basin along the same strike. These ridges are magmatic accommodation zones which, to the north along the Izu‐Bonin Arc, punctuate tectonic extension. For the WMR we hypothesize that rift basins are more commonly the sites where spreading segment offsets nucleate, whereas magmatic centers of spreading segments are sites where magmatism continues from arc volcanism, through rifting to back‐arc spreading. The Mariana Trough is opening nonrigidly and is characterized by two predominant abyssal hill trends, NNW–SSE in the north and N–S in the south. Between the only two basin‐crossing fracture zones at ∼15.5 and 17.5°, N–S axes propagated north at the expense of NNW axes.
Buoyant replenishment in silicic magma reservoirs: Experimental approach and implications for magma dynamics, crystal mush remobilization, and eruption
Authors: Girard Guillaume , Stix John
Published: August 2009

We present new experiments on replenishment of rhyolite magma chambers by rhyolite magma using corn syrup‐water solutions. We emphasize small density contrasts and show that buoyancy is the key controlling factor for whether injections will rise to the top (if buoyant) or pond at the base (if denser). During emplacement, we observe little or no mixing of the injected liquid with the reservoir liquid, as predicted by the fact that our injections have low Reynolds numbers (<10, typically). At later stages, the low‐buoyancy (≤1 kg m−3) injected liquid, which has accumulated at the top of the reservoir, undergoes mixing with the reservoir liquid, which may originate by the gravitational destabilization of a thin layer of denser resident liquid trapped above the injected liquid layer. The presence of a basal crystal mush, modeled by acrylic beads in a corn syrup‐water solution matrix is also considered. Slightly buoyant injections entrain a small fraction of mush particles to the top of the overlying liquid layer. Entrainment efficiency increases dramatically for high‐buoyancy injections. We hypothesize that the injected liquid can entrain a maximum quantity of mush particles, which corresponds to the amount required for the injected liquid/mush particle suspension to attain neutral buoyancy in the resident liquid. Hence for silicic systems, a replenishing melt can entrain up to 12.5% crystals during its ascent through the mush. Our results have implications for rhyolites bearing crystals with disequilibrium features, as they may represent mush crystals remobilized by a replenishing silicic magma.
Thermal and metamorphic environment of subduction zone episodic tremor and slip
Authors: Peacock Simon M.
Published: August 2009

Episodic tremor and slip (ETS) have been detected in the Cascadia and southwest Japan subduction zones, where the subducting crust is relatively warm because of the young incoming lithosphere (<20 Ma) and modest plate convergence rates (∼40–60 mm/a). In the southwest Japan subduction zone, low‐frequency earthquakes occur on the plate interface at depths of 30–35 km beneath Shikoku where finite element thermal models predict temperatures of ∼425°C in the subducting oceanic crust and at depths of 30–40 km beneath the Kii Peninsula where predicted temperatures are ∼325°C. Warmer temperatures of ∼575°C are predicted at ETS depths beneath southern Vancouver Island in the Cascadia subduction zone, but here tremor also occurs within the overlying fore‐arc crust where temperatures are lower. In the southwest Japan and Cascadia subduction zones, subducting oceanic crust passes through the blueschist, greenschist, and amphibolite metamorphic facies where mineral dehydration reactions are complex. The different temperatures predicted for the two subduction zones suggest that ETS does not coincide with a specific temperature or metamorphic reaction. Several lines of evidence indicate that a free H2O‐rich fluid is present, at least transiently, in subducting oceanic crust and fluids released by prograde metamorphic dehydration reactions may help trigger or enable ETS within the subducting plate. Less clear is the role H2O may play in tremor observed in the Cascadia fore‐arc crust where free H2O may exist locally in faults and fractures, but retrograde hydration reactions are expected to consume H2O.
Simultaneous estimation of both soil moisture and model parameters using particle filtering method through the assimilation of microwave signal
Authors: Qin Jun , Liang Shunlin , Yang Kun , Kaihotsu Ichiro , Liu Ronggao , Koike Toshio
Published: August 2009

Soil moisture is a very important variable in land surface processes. Both field moisture measurements and estimates from modeling have their limitations when being used to estimate soil moisture on a large spatial scale. Remote sensing is becoming a practical method to estimate soil moisture globally; however, the quality of current soil surface moisture products needs to be improved in order to meet practical requirements. Data assimilation (DA) is a promising approach to merge model dynamics and remote sensing observations, thus having the potential to estimate soil moisture more accurately. In this study, a data assimilation algorithm, which couples the particle filter and the kernel smoothing technique, is presented to estimate soil moisture and soil parameters from microwave signals. A simple hydrological model with a daily time step is utilized to reduce the computational burden in the process of data assimilation. An observation operator based on the ratio of two microwave brightness temperatures at different frequencies is designed to link surface soil moisture with remote sensing measurements, and a sensitivity analysis of this operator is also conducted. Additionally, a variant of particle filtering method is developed for the joint estimation of soil moisture and soil parameters such as texture and porosity. This assimilation scheme is validated against field moisture measurements at the CEOP/Mongolia experiment site and is found to estimate near‐surface soil moisture very well. The retrieved soil texture still contains large uncertainties as the retrieved values cannot converge to fixed points or narrow ranges when using different initial soil texture values, but the retrieved soil porosity has relatively small uncertainties.
Marine ice sheet dynamics: Hysteresis and neutral equilibrium
Authors: Durand G. , Gagliardini O. , de Fleurian B. , Zwinger T. , Le Meur E.
Published: August 2009

The stability of marine ice sheets and outlet glaciers is mostly controlled by the dynamics of their grounding line, i.e., where the bottom contact of the ice changes from bedrock or till to ocean water. The last report of the Intergovernmental Panel on Climate Change has clearly underlined the poor ability of models to capture the dynamics of outlet glaciers. Here we present computations of grounding line dynamics on the basis of numerical solutions of the full Stokes equations for ice velocity, coupled with the evolution of the air ice– and sea ice–free interfaces. The grounding line position is determined by solving the contact problem between the ice and a rigid bedrock using the finite element code Elmer. Results of the simulations show that marine ice sheets are unstable on upsloping beds and undergo hysteresis under perturbation of ice viscosity, confirming conclusions from boundary layer theory. The present approach also indicates that a 2‐D unconfined marine ice sheet sliding over a downsloping bedrock does not exhibit neutral equilibrium. It is shown that mesh resolution around the grounding line is a crucial issue. A very fine grid size (<100 m spacing) is needed in order to achieve consistent results.
Probabilistic approach to estimating the effects of channel reaches on flood frequencies
Authors: Guo Yiping , Hansen David , Li Chuan
Published: August 2009

A host of physical parameters and characteristics of catchments and channel reaches are normally needed in watershed planning and stormwater management studies. Some of these are also design variables, such as channel cross‐section size, shape, roughness, and (to a lesser extent) bed slope. Conventional channel routing techniques employ continuity and some form of the momentum equation to determine the downstream impacts of individual flood events. With the introduction of the concept of storage‐induced delay time, a probabilistic approach is developed wherein the role of a given channel reach on the frequency distribution of floods from the catchment upstream can be directly determined. The approach uses the same kinds of channel‐reach parameters as are typically used by many conventional flood routing algorithms. Its physically based nature makes it suitable for watershed planning and stormwater management studies wherein little or no flow data are available for parameter estimation or flow frequency analysis. The validity of this probabilistic approach is demonstrated by comparing its outcomes with the results of a suite of conventional continuous simulations using rainfall data from Halifax, Canada.
Rethinking Water Scarcity: The Role of Storage
Authors: Taylor Richard
Published: August 2009

Water scarcity, in its simplest sense, can be defined as a shortage in the availability of freshwater relative to demand. Freshwater shortages directly affect food security, access to safe drinking water, hygiene and public health, and environmental well‐being. Water scarcity can also retard economic development and promote civil strife. Robust measures of water scarcity are therefore required to inform water policy and help allocate resources to mitigate these effects.
Economic Cost of an Algae Bloom Cleanup in China's 2008 Olympic Sailing Venue
Authors: Wang X. H. , Li L. , Bao X. , Zhao L. D.
Published: August 2009

In the summer of 2008, an algae bloom struck the coast of Qingdao, China, where the 2008 Olympic sailing events were to be held. The bloom was caused by the drift and proliferation of the green algae Enteromorpha (see http://precedings.nature.com/documents/2352/version/1). It lasted for more than 1 month and covered nearly the entire sailing venue. The Enteromorpha bloom was so intense that national and local governments invested a tremendous amount of labor and resources in a cleanup effort in order to achieve Olympic Games standards [Hu and He, 2008].
Earth Magnetic Anomaly Grid Released
Authors: Maus Stefan
Published: August 2009

An Earth Magnetic Anomaly Grid (EMAG2) compiled from satellite, ship, and airborne magnetic measurements during a 2‐year international collaborative effort was released in February 2009. Magnetic anomaly maps provide insights into the subsurface structure and composition of the Earths crust. They are widely used in the geological sciences and in resource exploration. Furthermore, the global magnetic map is useful in science education to illustrate plate tectonics, crustal interaction with the deep mantle, and other aspects of Earth evolution. Distinct patterns and magnetic signatures on magnetic anomaly maps can be attributed to the formation (seafloor spreading) and destruction (subduction zones) of oceanic crust, the formation of continental crust by accretion of terranes to cratonic areas, and large‐scale volcanism.
Understanding Methane Hydrates in the Arctic: Multidisciplinary Efforts Needed: Developing Long Term International Collaboration on Methane Hydrate Research and Monitoring in the Arctic Region; Texel, Netherlands, 18–20 February 2009
Authors: Coffin R. B. , Greinert J.
Published: August 2009

The Arctic is highly vulnerable to climate change, but the environmental, economic, and societal impacts of climate change may be global rather than just regional. Some scientists currently believe that destabilizing Arctic gas hydrates, both onshore and offshore, could significantly accentuate global warming. Justification of this belief needs a more thorough understanding of the permafrost and sediment hydrate distribution.

Many scientists currently believe that hydrates are extensive and by far the greatest potential source of methane in the Arctic. However, scientists have little understanding of their stability, particularly in relation to permafrost melt. Unlike their deep‐water equivalents, which are stabilized by hydrostatic pressure, polar hydrates are regulated by temperature; low temperatures are critical to their stability. The hydrates in the shallow seas that dominate the Arctic Ocean are highly vulnerable to warming because the protective layer of methane‐oxidizing and heat‐distributing water is very thin over the vast shelf area.
Ancient carbonate sedimentary signature in the Hawaiian plume: Evidence from Mahukona volcano, Hawaii
Authors: Huang Shichun , Abouchami Wafa , Blichert‐Toft Janne , Clague David A. , Cousens Brian L. , Frey Frederick A. , Humayun Munir
Published: August 2009

Lavas from Mahukona, a small Hawaiian volcano on the Loa trend, exhibit major and trace element abundance variations exceeding those in lavas from large Hawaiian shields, such as Mauna Loa and Mauna Kea. Mahukona lavas define three geochemically distinct groups of tholeiitic shield basalt and a transitional group of postsshield basalt. At 10% MgO the tholeiitic groups range from 9 to 12% CaO; such differences in CaO can reflect partial melts derived from garnet pyroxenite (low CaO) and peridotite (high CaO), but the negative CaO‐Yb (both at 10% MgO) trend formed by Mahukona lavas is inconsistent with this explanation. Within Mahukona lavas, radiogenic Nd‐Hf‐Pb isotopic ratios are highly correlated with each other; however, 87Sr/86Sr is decoupled from these radiogenic isotopic ratios. Rather, 87Sr/86Sr is correlated with trace element abundance ratios involving Sr, and importantly, Mahukona lavas define a negative Rb/Sr‐87Sr/86Sr trend, implying that a Sr‐rich source component characterized by high 87Sr/86Sr is important in the petrogenesis of Mahukona lavas. We infer that this Sr‐rich source component is recycled ancient carbonate‐rich sediments. Intershield heterogeneity among Hawaiian shields also shows a negative Rb/Sr‐87Sr/86Sr trend. For example, Makapuu‐stage Koolau lavas have higher 87Sr/86Sr but lower Rb/Sr than Mauna Kea lavas. Consequently, we infer that a recycled ancient carbonate‐rich sedimentary source component is important in the Hawaiian plume. Although most lavas from Loa and Kea trend volcanoes define distinct fields in isotopic ratios of Sr, Nd, Hf, and Pb, the majority of Mahukona lavas have isotopic ratios at the boundary between the fields defined by Loa and Kea trend lavas. However, a subgroup of Mahukona shield lavas have Kea‐like isotopic and trace element signatures, an observation that can be explained by vertical heterogeneity in a bilaterally asymmetrical plume.
Geomagnetic paleointensity between 1300 and 1750 A.D. derived from a bread oven floor sequence in Lübeck, Germany
Authors: Schnepp Elisabeth , Lanos Philippe , Chauvin Annick
Published: August 2009

Geomagnetic paleointensities have been determined from a single archaeological site in Lübeck, Germany, where a sequence of 25 bread oven floors has been preserved in a bakery from medieval times until today. Age dating confines the time interval from about 1300 A.D. to about 1750 A.D. Paleomagnetic directions have been published from each oven floor and are updated here. The specimens have very stable directions and no or only weak secondary components. The oven floor material was characterized rock magnetically using Thellier viscosity indices, median destructive field values, Curie point determinations, and hysteresis measurements. Magnetic carriers are mixtures of SD, PSD, and minor MD magnetite and/or maghemite together with small amounts of hematite. Paleointensity was measured from selected specimens with the double‐heating Thellier method including pTRM checks and determination of TRM anisotropy tensors. Corrections for anisotropy as well as for cooling rate turned out to be unnecessary. Ninety‐two percent of the Thellier experiments passed the assigned acceptance criteria and provided four to six reliable paleointensity estimates per oven floor. Mean paleointensity values derived from 22 oven floors show maxima in the 15th and early 17th centuries A.D., followed by a decrease of paleointensity of about 20% until 1750 A.D. Together with the directions the record represents about 450 years of full vector secular variation. The results compare well with historical models of the Earth's magnetic field as well as with a selected high‐quality paleointensity data set for western and central Europe.
Spread F, GPS phase fluctuations, and plasma bubbles near the crest of equatorial ionization anomaly during solar maximum
Authors: Lee C. C. , Chu F. D. , Chen W. S. , Liu J. Y. , Su S.‐Y. , Liou Y. A. , Yu S. B.
Published: August 2009

This work is the first attempt to concurrently study the occurrence probabilities of spread F, GPS phase fluctuations, and plasma bubbles near the crest of equatorial ionization anomaly (EIA). The data were observed by an ionosonde, a GPS receiver, and ROCSAT‐1 during 2000, the solar maximum year. Results show that the occurrences of the range spread F (RSF) differ from those of the frequency spread F (FSF). For the seasonal variation, the RSF occurrence has the maximum values in March and September, while the FSF occurrence peaks at June. For the nighttime variation, RSF and FSF peak at 2300 and 0300 LT, respectively. Regarding the GPS phase fluctuations, an index Fp is applied to characterize the irregularity strength. The similarity between the 50 < Fp ≤ 200 and RSF occurrences demonstrates that the characteristics of F region irregularities forming 50 < Fp ≤ 200 are mainly related to RSF. The occurrence of 200 < Fp is almost absent. The rare event is also found in the observation of plasma bubbles by ROCSAT‐1. Furthermore, the seasonal variations in GPS phase fluctuations at the EIA crest and the dip equator have similar trends. This indicates that the F region irregularities of RSF and 50 < Fp ≤ 200 at the EIA crest are originated from the equatorial ionosphere. On the other hand, the seasonal variation in occurrence probability of FSF at the EIA crest is close to that of spread F at midlatitudes. This suggests that the generation mechanisms of FSF and midlatitude spread F might be same, but the further study is required.
Mechanisms of nitrogen limitation affecting maize growth: a comparison of different modelling hypotheses
Authors: Li F. Y. , Jamieson P. D. , Johnstone P. R. , Pearson A. J.
Published: August 2009

Two hypothetical mechanisms exist for quantifying crop nitrogen (N) demand and N-deficit effects on crop growth. The Critical N mechanism uses a critical N concentration, while the Leaf N mechanism distinguishes active N in leaves from the N elsewhere in shoots. These two mechanisms were implemented in parallel in a maize model (Amaize) to evaluate their adequacy in predicting crop growth and development. In the Leaf N mechanism, two approaches for quantifying N-deficit effects, by reducing green leaf area (GAI) or diluting specific leaf nitrogen (SLN), were also examined. The model-predicted plant biomass, grain yield, and N uptake were compared with measurements from 47 maize crops grown on 16 sites receiving different N fertiliser treatments. The results showed that model-predicted plant biomass, grain yield and N uptake were insensitive to the approaches used for quantifying N-deficit effects in the Leaf N mechanism. The model-predicted plant biomass, grain yield and N uptake using either N approach were significantly related to measurements (P < 0.01) but had considerable deviations (r2 = 0.66–0.69 for biomass, 0.50–0.54 for grain yield: 0.17–0.33 for N uptake). The linear fits of the predicted against measured values showed no significant difference (P > 0.1) among the three N approaches, with the Leaf N mechanism predicting smaller deviation than the Critical N mechanism. However, the Critical N mechanism was better in simulating plant growth dynamics in early plant growth stages. The Leaf N mechanism distinguished functional from structural N pools in plants, having a sound physiological base. The simulation using the Leaf N mechanism with both SLN dilution and GAI reduction for quantifying N-deficit effects was the best in predicting crop growth and yield.
Cysteine modification of a specific repressor protein controls the translational status of nucleus-encoded LHCII mRNAs in
Chlamydomonas
Authors: Wobbe Lutz , Blifernez Olga , Schwarz Christian , Mussgnug Jan H. , Nickelsen Jörg , Kruse Olaf
Published: August 2009

The cytosolic RNA-binding protein NAB1 represses translation of LHCII (light-harvesting complex of photosystem II) encoding mRNAs by sequestration into translationally silent mRNP complexes in the green alga
Chlamydomonas reinhardtii
. NAB1 contains 2 cysteine residues, Cys-181 and Cys-226, within its C-terminal RRM motif. Modification of these cysteines either by oxidation or by alkylation in vitro was accompanied by a decrease in RNA-binding affinity for the target mRNA sequence. To confirm the relevance of reversible NAB1 cysteine oxidation for the regulation of its activity in vivo, we replaced both cysteines with serines. All examined cysteine single and double mutants exhibited a reduced antenna at PSII caused by a perturbed NAB1 deactivation mechanism, with double mutations and Cys-226 single mutations causing a stronger and more distinctive phenotype compared with the Cys-181 mutation. Our data indicated that the responsible redox control mechanism is mediated by modification of single cysteines. Polysome analyses and RNA co-immunoprecipitation experiments demonstrated the interconnection of the NAB1 thiol state and its activity as a translation repressor in vivo. NAB1 is fully active in its dithiol state and is reversibly deactivated by modification of its cysteines. In summary, this work is an example that cytosolic translation of nucleus encoded photosynthetic genes is regulated via a reversible cysteine-based redox switch in a RNA-binding translation repressor protein.
Overexpression of SOD-2 reduces hippocampal superoxide and prevents memory deficits in a mouse model of Alzheimer's disease
Authors: Massaad Cynthia A. , Washington Taneasha M. , Pautler Robia G. , Klann Eric
Published: August 2009

Alzheimer's disease (AD) is a neurodegenerative disease characterized by impaired cognitive function and the deposition of extracellular amyloid plaques and intracellular tangles. Although the proximal cause of AD is not well understood, it is clear that amyloid-β (Aβ) plays a critical role in AD pathology. Recent studies also implicate mitochondrial abnormalities in AD. We investigated this idea by crossing mice that overexpress mitochondrial superoxide dismutase (SOD-2) with the Tg2576 mouse model of AD that overexpresses the human amyloid precursor protein carrying the Swedish mutation (K670N:M671L). We found that overexpression of SOD-2 decreased hippocampal superoxide, prevented AD-related learning and memory deficits, and reduced Aβ plaques. Interestingly, SOD-2 overexpression did not affect the absolute levels of Aβ1–40and Aβ1–42, but did significantly reduce the Aβ1–42to Aβ1–40ratio, thereby shifting the balance toward a less amyloidogenic Aβ composition. These findings directly link mitochondrial superoxide to AD pathology and demonstrate the beneficial effects of a mitochondrial anti-oxidant enzyme, hence offering significant therapeutic implications for AD.
Synapse elimination in olivo-cerebellar explants occurs during a critical period and leaves an indelible trace in Purkinje cells
Authors: Letellier Mathieu , Wehrlé Rosine , Mariani Jean , Lohof Ann M.
Published: August 2009

During developmental synaptogenesis, the pre- and postsynaptic cells undergo specific interactions that lead to the establishment of the mature circuit. We have studied the roles of the pre- and postsynaptic cells in establishing this mature innervation by using an in vitro model of synaptic development. We describe climbing fiber (CF)-Purkinje cell (PC) synaptogenesis in cultured mouse hindbrain explants and show that synaptic competition occurs during early development in vitro. By manipulating the maturation stage of each of the synaptic partners in a coculture experimental paradigm, we found that multi-innervation does not occur when both synaptic partners are mature and have already experienced synapse elimination; in contrast, mature PCs can be multi-innervated when they have never experienced synapse elimination and/or when CFs are immature. However in these cases, the normal process of synapse elimination is impaired. These results show that CF-synapse elimination occurs only during a PC-dependant critical period and triggers indelible signals that prevent synapse competition in the mature system.
Repeated learning makes cultural evolution unique
Authors: Strimling Pontus , Enquist Magnus , Eriksson Kimmo
Published: August 2009

Although genetic information is acquired only once, cultural information can be both abandoned and reacquired during an individual's lifetime. Therefore, cultural evolution will be determined not only by cultural traits' ability to spread but also by how good they are at sticking with an individual; however, the evolutionary consequences of this aspect of culture have not previously been explored. Here we show that repeated learning and multiple characteristics of cultural traits make cultural evolution unique, allowing dynamical phenomena we can recognize as specifically cultural, such as traits that both spread quickly and disappear quickly. Importantly, the analysis of our model also yields a theoretical objection to the popular suggestion that biological and cultural evolution can be understood in similar terms. We find that the possibility to predict long-term cultural evolution by some success index, analogous to biological fitness, depends on whether individuals have few or many opportunities to learn. If learning opportunities are few, we find that the existence of a success index may be logically impossible, rendering notions of “cultural fitness” meaningless. On the other hand, if individuals can learn many times, we find a success index that works, regardless of whether the transmission pattern is vertical, oblique, or horizontal.
Structure of the C-terminal domain of transcription factor IIB from
Trypanosoma brucei
Authors: Ibrahim B. Syed , Kanneganti Nalini , Rieckhof Gabrielle E. , Das Anish , Laurents Douglas V. , Palenchar Jennifer B. , Bellofatto Vivian , Wah David A.
Published: August 2009

In trypanosomes, the production of mRNA relies on the synthesis of the spliced leader (SL) RNA. Expression of the SL RNA is initiated at the only known RNA polymerase II promoter in these parasites. In the pathogenic trypanosome,
Trypanosoma brucei
, transcription factor IIB (tTFIIB) is essential for SL RNA gene transcription and cell viability, but has a highly divergent primary sequence in comparison to TFIIB in well-studied eukaryotes. Here we describe the 2.3 Å resolution structure of the C-terminal domain of tTFIIB (tTFIIB
C
). The tTFIIB
C
structure consists of 2 closely packed helical modules followed by a C-terminal extension of 32 aa. Using the structure as a guide, alanine substitutions of basic residues in regions analogous to functionally important regions of the well-studied eukaryotic TFIIB support conservation of a general mechanism of TFIIB function in eukaryotes. Strikingly, tTFIIB
C
contains additional loops and helices, and, in contrast to the highly basic DNA binding surface of human TFIIB, contains a neutral surface in the corresponding region. These attributes probably mediate trypanosome-specific interactions and have implications for the apparent bidirectional transcription by RNA polymerase II in protein-encoding gene expression in these organisms.