bluuebunny/crossref_metadata_2025 huggingface dataset:
Global transition zone tomography
Authors: Ritsema Jeroen , van Heijst Hendrik Jan , Woodhouse John H.
Published: February 2004

Our understanding of large‐scale mantle dynamics depends on accurate models of seismic velocity variation in the upper mantle transition zone (400–1000 km depth). With the Mode Branch Stripping technique (MBS) of van Heijst and Woodhouse [1997] it is possible to extract the dispersion characteristics of overtone surface wave signals from single source‐receiver overtone waveforms. Such data provide new global transition zone constraints. We combined more than a million measurements of path‐average overtone phase velocity with normal‐mode splitting functions and body wave travel times to construct model S20RTSb of shear velocity heterogeneity throughout the mantle. We discuss in detail the resolution of structural heterogeneity in the transition zone. The main observations are the following: (1) Large‐scale shear velocity variations (15%) in the upper 250 km of the mantle are at least 5 times larger than deeper in the mantle. High‐velocity keels of Archean cratons extend to about 200 km depth. Low velocities related to mid‐ocean ridge upwelling are confined to the upper 150 km of the mantle. (2) The 220‐km discontinuity in PREM cannot be reconciled with Rayleigh wave dispersion, especially in oceans. (3) The velocity below the oceanic lithosphere (350–400 km depth) is 1–1.5% lower than beneath the continental lithosphere. (4) High‐velocity slabs of former oceanic lithosphere are conspicuous structures just above the 670‐km discontinuity. They extend to about 1100 km depth in the South American, Indonesian, and Kermadec subduction zones, indicating that slabs penetrate through the 670‐km phase transition in several subduction zones. (5) We observe lower‐than‐average shear velocity below the lithosphere at eight hot spots (including Hawaii, Iceland, Easter, and Afar). It is, however, difficult to accurately estimate their depth extent in the transition zone because of the limited vertical resolution.
Seismotectonics and stress field of the Yellowstone volcanic plateau from earthquake first‐motions and other indicators
Authors: Waite Gregory P. , Smith Robert B.
Published: February 2004

We have found spatial variations in seismic stress indicators at the Yellowstone volcanic field, Wyoming, by examining source mechanisms of 25 years of network‐recorded earthquakes, 1973–1998. Yellowstone seismicity is characterized by swarms of earthquakes (MC < 3) within the 0.64 Ma Yellowstone caldera and between the caldera and the eastern end of the 44‐km‐long rupture of the 1959 MS7.5 Hebgen Lake earthquake. We relocated more than 12,000 earthquake hypocenters using three‐dimensional velocity models. Focal mechanisms calculated for 364 earthquakes, carefully selected for location accuracy, reveal predominantly normal faulting; however, fault orientations vary across the Yellowstone caldera. Specifically, focal mechanism T axes trend N‐S in the vicinity of the Hebgen Lake earthquake fault zone NW of the Yellowstone caldera and rotate to ENE‐WSW 35 km east of there. This rotation of the T axis trends occurs in the area of densest seismicity north of the caldera. Stress inversions performed using earthquake first‐motion data reveal a similar pattern in the minimum principal stress orientations. The extension directions derived from the focal mechanisms and stress inversions are generally consistent with extension directions determined from geodetic measurements, extension inferred from alignments of volcanic vents within the caldera, and extension directions determined from regional normal faults. The N‐S trending Gallatin normal fault north of the caldera is a notable exception; we find extension to be perpendicular to the direction of past extension on the Gallatin fault in the area immediately south of it. We interpret this N‐S extension north of the caldera to be related to postseismic viscoelastic relaxation in the upper mantle and lower crust following the Hebgen Lake earthquake. The dominantly extensional tectonic regime at Yellowstone inferred from these results demonstrates the influence of NE‐SW Basin and Range extension in this area.
Formation of an aggregate scale in Arctic sea ice
Authors: Hopkins Mark A. , Frankenstein Susan , Thorndike Alan S.
Published: February 2004

The ice pack covering northern seas is a mixture of thick ridged and rafted ice, undeformed ice, and open water. Conventional Eulerian Arctic sea ice models use a plastic yield surface to characterize the constitutive behavior of the pack. An alternative is to adopt a discontinuous Lagrangian approach and explicitly model the formation of leads and pressure ridges. We use a Lagrangian ice model that consists of thousands of discrete polygonal floes 1–4 km in width. At the beginning of a simulation the ice floes are frozen together in a square domain. We apply a linearly varying wind stress that deforms the pack by stretching the viscous‐elastic joints between adjacent floes. Fractures propagate along joints forming a crack pattern in the model ice pack. The crack pattern defines a system of large plates 10–100 km in width that are aggregates of many individual floes. The average size of the plates is determined by a competition between the rate of crack creation and the speed of the relaxation wave that travels outward from a newly broken joint and reduces stresses in the surrounding pack. Simulation results are used to characterize the formation of the aggregate structure and to determine how the rate of crack creation and the average area of the aggregate plates depends on tensile strength, the wind stress gradient, and the size of the individual floes. After the formation of the aggregate‐scale plate structure, subsequent deformation occurs at the plate boundaries. Since the usual state of the ice pack is a state of failure, an interesting situation is created in which the initial wind‐driven deformation creates the material conditions or aggregate structure under which subsequent deformation occurs.
Infragravity rip current pulsations
Authors: MacMahan Jamie H. , Reniers Ad J. H. M. , Thornton Edward B. , Stanton Tim P.
Published: February 2004

The origins of rip current pulsations within the infragravity frequency band (0.004–0.04 Hz) are determined from measurements made with arrays of colocated pressure and velocity sensors deployed on a beach with persistent rip current channels. The observations indicate significant energy in cross‐shore infragravity velocities that varies spatially in the alongshore due to the presence of rip channels. Infragravity velocities are smaller within the rip channel than on the shore‐connected shoal owing to differences in water depth. Rip current pulsations at infragravity frequencies are linked to standing infragravity motions but not to the ponding and subsequent release of water by wave group pumping.
A k‐distribution technique for radiative transfer simulation in inhomogeneous atmosphere: 1. FKDM, fast k‐distribution model for the longwave
Authors: Fomin Boris A.
Published: February 2004

A new technique for developing k‐distributions is described. This new technique requires almost half of the computational effort yet is at least as accurate as other published k‐distribution methods. Its novelty consists in the use of real atmospheric flux calculations to guide both the position of spectral bands and the k terms within each band; previous methods have not used such a guiding principle. Wave number subintervals which have similar atmospheric absorption behavior are chosen, then a representative absorption coefficient for such a wave number interval is set to the value which best fit the results of line‐by‐line calculations of fluxes and heating rates. This method of choosing one absorption coefficient to represent a large wave number subinterval contrasts with other published methods and is responsible in large part for the improved computational efficiency. It is worth noting that this new technique works as well in the stratosphere as the troposphere, so it can be applied to the processing of satellite data retrievals as well as in weather and climate forecasting. An example of the application of the new technique to the longwave part of the spectrum is presented. A fast k‐distribution model (FKDM) suitable for use in weather and climate prediction has been created using 23 k‐distribution terms, which is nearly half as many as other k‐distribution models. The molecular species represented in the model are H2O, CO2, O3, N2O, CH4, and CFC‐11,12,113. FKDM has been developed and validated using a fast line‐by‐line model (FLBLM). Validations have covered the tropical, midlatitude summer, midlatitude winter, subarctic summer, subarctic winter standard atmospheres, four atmospheres from the Spectral Radiance Experiment campaign, and one case of real tropical atmosphere. It has been found that the FKDM cooling rate accuracy is as follows: 0.15 and 0.2 K day−1 in troposphere for standard and real atmospheres, respectively, and 0.9 K day−1 in all the cases at altitudes below 70 km. Upward and downward flux errors are below 4 W m−2 (usually 1–2 W m−2) in every case.
Instability layers and airglow imaging
Authors: Hecht J. H.
Published: February 2004

For over 30 years it has been recognized that atmospheric gravity waves (AGWs) in the 80–110 km region significantly perturb the basic atmospheric state, perhaps causing instability regions and subsequent turbulence. It has also been recognized for nearly as long that AGWs cause strong fluctuations in the airglow emissions that originate in this altitude region. Airglow images have been obtained since 1973, and they have shown structures that have mainly been attributed to the passage of AGWs through this region as predicted theoretically. The AGWs have been assumed to originate largely in the troposphere because of either convective activity or the flow of air over large mountain ranges. However, intensive analysis of the properties of a class of small‐scale features currently known as ripples [Taylor et al., 1997; Nakamura et al., 1999] suggests that these features are not AGWs but are rather instability features generated in situ. The basis for this hypothesis is examined in this review, and it is concluded that while there is support for the instability hypothesis as the origin of ripple features, at present the exact nature of the instabilities causing these features is not known.
Neogene and Quaternary rollback evolution of the Tyrrhenian Sea, the Apennines, and the Sicilian Maghrebides
Authors: Rosenbaum Gideon , Lister Gordon S.
Published: February 2004

Reconstruction of the evolution of the Tyrrhenian Sea shows that the major stage of rifting associated with the opening of this basin began at ∼10 Ma. It involved two episodes of back arc extension, which were induced by the rollback of a west dipping subducting slab. The first period of extension (10–6 Ma) was prominent in the northern Tyrrhenian Sea and in the western part of the southern Tyrrhenian Sea. The second period of extension, mainly affected the southern Tyrrhenian Sea, began in the latest Messinian (6–5 Ma) and has been accompanied by subduction rollback at rates of 60–100 km Myr−1. Slab reconstruction, combined with paleomagnetic and paleogeographic constraints, indicates that in the central Apennines, the latest Messinian (6–5 Ma) arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike‐slip faults. These processes resulted in the formation of a narrow subducting slab beneath the Ionian Sea that has undergone faster subduction rollback and induced extreme rates of back arc extension.
Spatial distribution of the largest rainfall‐runoff floods from basins between 2.6 and 26,000 km2 in the United States and Puerto Rico
Authors: O'Connor Jim E. , Costa John E.
Published: February 2004

We assess the spatial distribution of the largest rainfall‐generated streamflows from a database of 35,663 flow records composed of the largest 10% of annual peak flows from each of 14,815 U.S. Geological Survey stream gaging stations in the United States and Puerto Rico. High unit discharges (peak discharge per unit contributing area) from basins with areas of 2.6 to 26,000 km2 (1–10,000 mi2) are widespread, but streams in Hawaii, Puerto Rico, and Texas together account for more than 50% of the highest unit discharges. The Appalachians and western flanks of Pacific coastal mountain systems are also regions of high unit discharges, as are several areas in the southern Midwest. By contrast, few exceptional discharges have been recorded in the interior West, northern Midwest, and Atlantic Coastal Plain. Most areas of high unit discharges result from the combination of (1) regional atmospheric conditions that produce large precipitation volumes and (2) steep topography, which enhances precipitation by convective and orographic processes and allows flow to be quickly concentrated into stream channels. Within the conterminous United States, the greatest concentration of exceptional unit discharges is at the Balcones Escarpment of central Texas, where maximum U.S. rainfall amounts apparently coincide with appropriate basin physiography to produce many of the largest measured U.S. floods. Flood‐related fatalities broadly correspond to the spatial distribution of high unit discharges, with Texas having nearly twice the average annual flood‐related fatalities of any other state.
A stochastic approach for assessing the uncertainty of rainfall‐runoff simulations
Authors: Montanari Alberto , Brath Armando
Published: February 2004

Rainfall‐runoff models have received a great deal of attention by researchers in the last decades. However, the analysis of their reliability and uncertainty has not been treated as thoroughly. In the present study, a technique for assessing the uncertainty of rainfall‐runoff simulations is presented that makes use of a meta‐Gaussian approach in order to estimate the probability distribution of the model error conditioned by the simulated river flow. The proposed technique is applied to the case study of an Italian river basin, for which the confidence limits of simulated river flows are derived and compared with the respective actual observations.
Properties of pregelatinized rice flour made by hot air or gum puffing
Authors: Lai Hsi‐Mei , Cheng Hsiao‐Hsien
Published: February 2004

Three varieties of rice, TCW 70, TN 67 and TCN 1, with an amylose content of 1.0, 20.3 and 32.0%, were used to produce pregelatinized rice flour by using hot air fluidized‐bed puffing or gun‐puffing methods. Serious molecular degradation was introduced by the gun‐puffing process. However, there were no significant differences in the molecular weights of rice flour before or after the hot air fluidized‐bed puffing process. Pasting properties of pregelatinized rice flours were dependent on the rice variety and the types of pretreatment, and were significantly affected by the puffing method. Hydrothermal pretreatment had different effects on the pasting and hydration properties of pregelatinized rice flour, depending on whether it was made from waxy or non‐waxy rice. Various properties of pregelatinized rice flour could be attributed to the combined effects of gelatinization, retrogradation and degradation of starch molecules during processing.
Effect of spraying on chemical properties and bactericidal efficacy of electrolysed oxidizing water
Authors: Hsu Shun‐Yao , Kim Chyes , Hung Yen‐Con , Prussia Stanley E.
Published: February 2004

A three‐factor, three‐by‐three‐by‐two‐level factorial designs were used for studying the effects of air pressure, sprayer orifice size and electrostatic charge of a spray gun on pH, oxidation‐reduction potential (ORP), electric conductivity and residual chlorine of electrolysed oxidizing (EO) waters with either low (9 mg L−1) or high concentration (88 mg L−1) of chlorine. Results indicated that a smaller orifice produced higher reduction in ORP and chlorine concentration than larger orifices. Electrostatic charge, in general, did not cause a significant reduction in chlorine concentration. High air pressure spray retained more chlorine and gave a higher ORP than low air pressure. EO water with high initial chlorine concentration achieved at least a 3–4 log10 CFU mL−1 reduction in Listeria monocytogenes populations when sprayed with the spray gun, while spraying with a commercial backpack sprayer or a poly‐tank sprayer eliminated Listeria population (9.4 log10 CFU mL−1 reductions) completely. These results demonstrated that although spraying reduced the chlorine in EO water by 20–97%, application of EO water through spraying has potential for reducing bacteria in food‐processing operations.
Beef and sheep mortadella: formulation, processing and quality aspects
Authors: Abdullah Basem Moh'd
Published: February 2004

Beef and lamb mortadella samples were prepared under controlled conditions and stored for 16 weeks under refrigeration. Moisture, protein, fat, ash and sodium chloride contents were measured initially and pH, percentage of free fatty acids, thiobarbituric acid values, total volatile nitrogen content, residual nitrite concentration and microbiological status were determined at regular intervals throughout storage. The sensory quality of the mortadellas during the first 2 months of storage was evaluated. The results of these tests permitted assessment of the quality and safety of beef and lamb mortadella. The products were satisfactory with regard to chemical and microbiological analyses, but after 2 months storage, the poor colour of lamb mortadella limited the sensory acceptability. Measurements of rancidity, caused by lipid deterioration and protein breakdown, were the best indicators of product quality.
Sweet potato‐based pasta product: optimization of ingredient levels using response surface methodology
Authors: Singh Sukhcharn , Raina Charanjit Singh , Bawa Amrinder Singh , Saxena Dharmesh Chandra
Published: February 2004

Sweet potato flour was used for the development of a pasta product. The system known as response surface methodology was used to analyse the effect of sweet potato flour, soyflour, water, Arabic gum and carboxy methyl cellulose (CMC) on quality responses (sensory, solids loss and hardness) of the pasta product. A rotatable central‐composite design was used to develop models for the responses. Responses were affected most by changes in soyflour and gum levels and to a lesser extent by sweet potato flour and water levels. Individual contour plots of the different responses were superimposed and regions meeting the maximum sensory score (33.8), minimum solids loss (16.6%) and maximum texture hardness (5616 g) were identified at 674 g kg−1 sweet potato flour, 195 g kg−1 water, 110 g kg−1 soyflour, 10.6 g kg−1 Arabic gum and 10.1 g kg−1 CMC levels.
Evaluation of physico‐chemical and sensory quality of frozen green grass pea (Lathyrus sativus L.)
Authors: Kmiecik Waldemar , Korus Anna , Lisiewska Zofia
Published: February 2004

The quality of grass peas (cv. Krab) intended for freezing was estimated at four degrees of seed maturity. The retention of basic physico‐chemical in dices such as dry matter, sugars, dietary fibre, total acids, total nitrogen, protein nitrogen and ash, as well as the sensory quality of frozen seeds prepared for consumption were used as the criteria in determining the overall quality value. Relative to fresh grass peas, the losses in cooked frozen seeds reached 47–64% for the content of reducing sugars, 36–53% of total sugars, 7–14% of starch, 2–4% of dietary fibre, 13–16% of total acids, 8–9% of total nitrogen and 4–6% of protein nitrogen. In cooked frozen seeds, differences between the first and the fourth maturity degree reached 47% in the case of dry matter content, 71% for starch, 166% for dietary fibre, 12% for acids, 51% for total nitrogen and 94% for protein nitrogen. The sensory quality of the cooked frozen grass peas was estimated to be from 4.17 to 4.77 on a 5‐score scale, and decreased with increasing seed maturity.
Effect of flour blending on functional, baking and organoleptic characteristics of bread
Authors: Dhingra Shfali , Jood Sudesh
Published: February 2004

Soybean (full‐fat and defatted) and barley flours were incorporated into wheat flour at 5, 10, 15 and 20% substitution levels. The gluten content, sedimentation value and water absorption capacity of the flour blends and the mixing time of the dough decreased with increase in the level of soybean and barley flour separately and in combinations. Protein and glutelin contents increased significantly on blending of soyflour (full‐fat and defatted) to bread wheat flour. The breads prepared from the blends also varied in their loaf weight, loaf volume and sensory characteristics. The bread volume decreased with increasing amount of non‐wheat flour substitution. The crumb colour changed from creamish white to dull brown and a gradual hardening of crumb texture was observed as the addition of soybean (full‐fat and defatted) and barley flours increased. At the higher levels, the acceptability declined because of the compact texture of the crumb and the strong flavour of the product. The addition of 10% of soyflour (full‐fat and defatted) or 15% of barley flour, full‐fat soy + barley or defatted soy + barley flour to bread flour produced acceptable bread.
Effects of heat treatment on the quality of fresh‐cut Chinese water chestnut
Authors: Peng Litao , Jiang Yueming
Published: February 2004

A heat treatment to inhibit browning and maintain the quality of fresh‐cut Chinese water chestnut was developed. Slices of Chinese water chestnut, cv. Guilin, were immersed in boiling water for 30 s, placed into film‐wrapped trays and then stored at 4 °C for up to 12 days. Changes in browning, eating quality and disease incidence were measured. The effect of heat treatment on the content of total phenolics and activities of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) was also evaluated. The heat treatment effectively prevented browning associated with PAL, PPO and POD activities and total phenolic content and delayed the decrease in eating quality, which is associated with reduced total soluble solids, titratable acidity and ascorbic acid, compared with fresh‐cut Chinese water chestnut. Inhibition of browning by heat treatment without microbial growth was achieved for 12 days of storage at 4 °C. These results showed that heat treatment effectively maintained the quality of fresh‐cut Chinese water chestnut.
Chemical composition, functional properties and baking potential of African breadfruit kernel and wheat flour blends
Authors: Akubor Peter I. , Badifu Gabriel I. O.
Published: February 2004

The chemical composition and functional properties of African breadfruit kernel flour (ABKF), wheat flour (WF) and their blends were determined. Cookies prepared from the blends were evaluated for their protein contents, physical and sensory characteristics. The flour blends had higher protein, fat and ash contents than WF. The level of these nutrients improved with increased amounts of ABKF in the blends. Foaming, water and oil absorption capacities of the flour blends increased, while the foam stability decreased with increased level of ABKF. The protein contents of the composite flour cookies were higher than that of the all WF cookie. There were no significant differences (P > 0.05) in the flavour of the composite flour cookies and that of all WF cookies. However, sensory scores differed significantly (P < 0.05) amongst them for colour, texture and overall acceptability.
Physicochemical parameters and pollen analysis of Moroccan honeydew honeys
Authors: Díez María Josefa , Andrés Cristina , Terrab Anass
Published: February 2004

The honeydew elements in 152 honeys from Morocco were studied. The main honeydew indicators are mycelia and fungal spores and, generally speaking, they were found in small percentages. Five mixed or forest honey samples were found by a sediments study, with a proportion of honeydew elements/number of pollen grains from nectariferous species of 1.04–1.83. Their origin (floral or honeydew) could not be confirmed in all cases by physicochemical parameters (pH, mineral content, electrical conductivity, sugars and colour) that were analysed, but recommendations for their characterization are presented.
Qualities and antioxidant properties of bread as affected by the incorporation of yam flour in the formulation
Authors: Hsu Chin‐Lin , Hurang Shu‐Lin , Chen Wenlung , Weng Yih‐Ming , Tseng Chin‐Yin
Published: February 2004

Yams (the tubers of Dioscorea spp.) are widely consumed but are also regarded as a medicinal food in China. Traditional Chinese herbal medicines using yams are only available on a seasonal basis, as yams quickly deteriorate during winter storage. Yam (Dioscorea purpurea, a major variety of yams in Taiwan) was freeze‐dried and ground to obtain yam flour. Bread was made by replacing up to 25% of wheat flour with yam flour. Although the loaf volume decreased with the addition of yam flour, the results showed that up to 20% of yam flour could be included in bread formulation without altering the sensory acceptance of the blended bread. The incorporation of yam flour in bread markedly increased the antioxidant capacity of the bread as tested by both DPPH free radical scavenging and total antioxidation tests. Breads containing yam flour can broaden the utilization of yams and may be regarded as possible health‐promoting foods.
Preparation of tofu using chitosan as a coagulant for improved shelf‐life
Authors: No Hong Kyoon , Meyers Samuel P.
Published: February 2004

The potential of chitosan as a coagulant in commercial tofu preparation was investigated with six chitosans of different molecular weights using various treatments. The following optimum processing conditions for tofu preparation were proposed: chitosan with a molecular weight of 28 kDa; chitosan solution type, 1% chitosan/1% acetic acid; chitosan solution to soymilk ratio, 1 : 8; coagulation temperature, 80 °C; coagulation time, 15 min. However, the sensory quality of tofu was notably improved using a 1 : 1 mixture of 1% acetic acid and 1% lactic acid instead of 1% acetic acid alone as a chitosan solvent. Tofu prepared with chitosan had lower ash and higher protein content than those of commercial products tested. In storage tests, the chitosan‐tofu had a longer shelf‐life, about 3 days, than tofu made with CaCl2. This added shelf‐life is significant in view of the magnitude (366 000 tonnes year−1) of tofu produced from commercial tofu plants (1407 plants as of 1998) in Korea.
Use of scanning electron microscopy to indicate the similarities and differences in pseudocereal and cereal proteins
Authors: Gorinstein Shela , Pawelzik Elke , Delgado‐Licon Efren , Yamamoto Kazutaka , Kobayashi Shoichi , Taniguchi Hajime , Haruenkit Ratiporn , Park Yong‐Seo , Jung Soon‐Teck , Drzewiecki Jerzy , Trakhtenberg Simon
Published: February 2004

Isolated and separated protein fractions from cereal and pseudocereal grains were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis and scanning electron microscopy. Prolamin, the main storage protein in cereal such as maize, showed a difference in electrophoretic patterns and fine structure in comparison with those from amaranth and soybean. In contrast glutelins from amaranth, soybean and maize showed some similarity in the distribution of protein bands and in microstructure. Amaranth and soybean were closely similar in distribution of protein fractions and their microscopic structure. As an addition to chemical analyses, microscopy helped to understand and visualize structural changes and textural differences in protein fractions. Pseudocereals can be used as a nutritive substitute of some cereals in functional foods.
Cold Acclimation Ability and Photosynthesis among Species of the Tropical Coffea Genus
Authors: Ramalho J. C. , Quartin V. L. , Leitão E. , Campos P. S. , Carelli M. L. C. , Fahl J. I. , Nunes M. A.
Published: February 2004

Abstract: Three Coffea species (C. arabica cv. Icatu, C. canephora cv. Apoatã and C. dewevrei) were tested in order to identify and study the mechanisms of tolerance to low, non‐freezing temperatures. Several photosynthesis‐related parameters were monitored during a 20‐day period of gradual temperature decrease, from 25/20 °C (day/night) down to 15/10 °C, during chilling treatments (15/4 °C), and upon rewarming (25/20 °C). Differences were found among species, both during low temperature exposure and during rewarming. In general, Coffea species showed cold‐induced photoinhibition of photosynthesis, which was attributable to biochemical (in vivo ribulose‐1,5‐bisphosphate carboxylase/oxygenase activity and carbohydrate synthesis) and biophysical (antennae functioning, photosystem II efficiency and linear electron transport) inactivation, rather than to stomatal constraints. The moderately low temperature of 15/10 °C was enough to cause a negative impact on net photosynthesis (A), mostly due to low (initial) rubisco activity in all species. However, C. arabica cv. Icatu showed a higher tolerance to chilling and recovered quickly and completely upon rewarming, as assessed from the impacts on the photosynthetic machinery (e.g. Amax, Fo, Fv/Fm, Fv′/Fm′, qP, ϕe, rubisco activity) and on carbohydrate metabolism. Such lesser effects are likely to be related to the strong increases and higher contents of zeaxanthin, lutein and β‐carotene that presumably increased the ability to dissipate excitation energy and contributed to protect the photosynthetic apparatus. During cold exposure, a significant reduction of the α/β carotene ratio, which is considered an acclimation feature, was observed solely in C. arabica cv. Icatu. However, C. canephora cv. Apoatã and, especially, C. dewevrei showed to be highly cold‐sensitive. In these latter species, the photoinhibitory impairments to photosynthesis were stronger, probably due to the lower contents of protecting pigments during chilling conditions that lead to a higher vulnerability to excess excitation energy. Moreover, the mesophyll impairments (e.g. Amax, Fv/Fm, ϕe) became significant even at moderately low temperatures of 15/10 °C, and a lower ability to recover after chilling exposure was observed. The limitation of in vivo rubisco activity and Amax may have been due to substrate limitation, but disturbances in sugar metabolism could also play an important role in the expression of chilling sensitivity in C. canephora cv. Apoatã and C. dewevrei.
Genetic Isolation and Diffusion of Wild Grapevine Italian and Spanish Populations as Estimated by Nuclear and Chloroplast SSR Analysis
Authors: Grassi F. , Imazio S. , Failla O. , Scienza A. , Ocete Rubio R. , Lopez M. A. , Sala F. , Labra M.
Published: February 2004

Abstract: Genetic structure of six Italian and five Spanish populations of wild grapevine (Vitis vinifera ssp. silvestris) was investigated using nuclear and chloroplast SSR analysis. Results show that the Italian populations are characterised by high genomic diversity within populations, with a peak of heterozygosity (Ho = 0.7637) for a population collected in southern Italy. However, the low haplotype richness and the high level of genetic distance detected among the Spanish populations, combined with their low gene flow, shows that these populations suffered from a genetic erosion. Genetic relationship between Italian and Spanish populations was investigated and results showed genetic differentiation between the two populations. Using nuclear and chloroplast SSR markers, the ratio between pollen and seed diffusion was estimated. High pollen flow, as compared with seed flow, suggests that seed diffusion is made difficult, probably due to low germinability and survival of seedlings in the wild. Seed germination and young plant survival must be considered a priority target for in situ conservation programmes. By providing information on population history, genetic structure and gene flow, and by identifying areas harbouring high levels of wild grape variability, this study provides the basis for the preservation of biodiversity of the wild grapevine.
Analysis of Expressed Sequence Tags Derived from Developing Seed and Pollen Cones of Cryptomeria japonica
Authors: Ujino‐Ihara T. , Taguchi Y. , Yoshimura K. , Tsumura Y.
Published: February 2004

Abstract: We obtained 1210 expressed sequence tags (ESTs), representing 1173 transcripts, from two cDNA libraries, which derive from developing seed and pollen cones of sugi (Cryptomeria japonica). Among these 1173 transcripts, 807 showed notable similarity to known sequences, including those of genes expressed in developing flower tissues of other plant species, such as CONSTANS and the genes for MADS‐domain proteins. This result indicates that, in spite of differences in morphology, the development of reproductive organs is regulated by a family of homologous transcription factors common to both gymnosperm and angiosperm species. The remaining 366 transcripts showed no significant similarity to any known sequences in public databases. Furthermore, we compared the 1173 transcripts to those derived from other tissues of C. japonica to investigate the possibility of tissue‐specific transcripts, and found that 882 did not occur among ESTs derived from other tissues, such as the inner bark and seedlings. The ESTs developed during the present study most likely include tissue‐ and stage‐specific transcripts, and these will contribute to a further understanding of the reproductive organ development of C. japonica.
A Top‐Down Hierarchy in Fruit Set on Inflorescences in Iris fulva (Iridaceae)
Authors: Wesselingh R. A. , Arnold M. L.
Published: February 2004

Abstract: In Iris fulva, the apical flower on an inflorescence opens first, and the flowering sequence then proceeds from the most basal flower upward to the apex (acropetally). Flowering order and flower position are thus partially decoupled, and this provides an opportunity to separately investigate the effects of these two factors upon fruit formation. We recorded natural patterns of fruit set and seed production, and found that fruit set patterns were determined by what appears to be a form of apical dominance. The first, apical flower had the highest fruit set and seed production. Fruit set decreased towards the base of the inflorescence, with later‐opening flowers having a higher fruit set. This is contrary to the pattern usually observed in other acropetally flowering plants, which is a higher fruit set for basal, early flowers. By performing additional hand pollinations and counting pollen grains on naturally pollinated flowers, we found that pollen deposition was not a major factor limiting fruit set, and that it could not explain the large difference in fruit set between the apical and basal flowers. Removing the first flower after it had wilted increased fruit set in the remaining flowers, but mainly in the more apical flowers. Only by removing the two topmost flowers could we obtain an increase in fruit set for the basal flower. The fact that the basal flower rarely sets fruit, despite being closer to resources, suggests that the apical meristem is either a strong sink for resources or produces hormones that form a gradient along the inflorescence, which is comparable with apical dominance.
Mechanical Properties of the Rhizome of Arundo donax L.
Authors: Speck O. , Spatz H.‐C.
Published: February 2004

Abstract: The mechanical properties of rhizome segments of Arundo donax L. were studied in three dimensions: longitudinal (X), transverse‐vertical (Y), transverse‐horizontal (Z). Tensile, cyclic loading and torsional tests demonstrate that the distinct anisotropy found in the hollow stems is less pronounced in the rhizome. Morphological and anatomical examinations suggest that the mechanical anisotropy of the stem is caused by the arrangement parallel to the stem of the vascular bundles and sclerenchymatous fibres, embedded in lignified parenchyma. Anatomical inhomogeneity is less pronounced in the rhizome due to the short internode lengths, and predominance of nodal regions, where sclerenchymatous fibres form a complex three‐dimensional arrangement embedded in unlignified starch‐storing parenchyma. Cyclic loading experiments indicate viscoelastic behaviour of the rhizomatous tissues under tensile stress. Additionally, viscoelastic behaviour under torsional stress was studied. Mechanical behaviour of the rhizome under tension up to fracture is discussed with regard to the fracture surfaces, analysed by SEM.
Pattern of Flower and Fruit Production in Stryphnodendron adstringens, an Andromonoecious Legume Tree of Central Brazil
Authors: Ortiz P. L. , Arista M. , Oliveira P. E. , Talavera S.
Published: February 2004

Abstract: Patterns of flower and fruit production in racemes of Stryphnodendron adstringens, an andromonoecious Brazilian savanna tree species, were studied in two natural areas near Uberlândia‐MG. Racemes were divided in three parts: apex, centre, and base. Number of flowers, gender, and nectar and pollen production were analyzed for each section. Frequency of visitors to each part of the inflorescence was also quantified. Hand self‐ and cross‐pollinations were performed in complete racemes and fruit set used to determine breeding system. The racemes produced a mean of 329 flowers, more densely packed in the central portion. Hermaphrodite and male flowers occur along the inflorescence but hermaphrodite flowers are more common in the centre. Fruit set was markedly low but does not seem to be limited by pollination service, since free open‐pollinated racemes and hand cross‐pollinated ones do not differ in fruit production rates. Fruits resulted mostly from cross‐pollinated flowers and fruit production was biased to the central portion of the raceme. Nectar yield was higher in the central portion of the raceme and visitors arrived more commonly on this portion of the inflorescence. However, most flowers did not produce nectar. The pattern of fruit production seems to be a consequence of the hermaphrodite flower distribution in the raceme and it is not constrained by pollen flow or flower opening sequence.
N‐Glycosylation in the Moss Physcomitrella patens is Organized Similarly to that in Higher Plants
Authors: Koprivova A. , Altmann F. , Gorr G. , Kopriva S. , Reski R. , Decker E. L.
Published: February 2004

Abstract: Allergenicity of plant glycoproteins in humans may prevent the use of plants as production factories for pharmaceutically important proteins. The major difference between plant and mammalian N‐glycans is the presence of xylosyl and α1,3‐fucosyl residues in the former. In a first step towards “humanization” of the N‐glycosylation pathway in the moss Physcomitrella patens, which could be an excellent system for industrial production of therapeutic proteins, we isolated the cDNAs and genes for N‐acetylglucosaminyltransferase I (GNTI), α1,3‐fucosyltransferase, and β1,2‐xylosyltransferase. Sequence analysis revealed that all three proteins are homologous to their counterparts from higher plants, however, the conservation of the primary structure was only 35 ‐ 45 %. The gene encoding the key enzyme of the pathway, gntI, was disrupted in P. patens by homologous recombination. Although the mutation of this gene in mouse or A. thaliana led to a significantly altered pattern of N‐glycans, the glycosylation pattern in the gntI knockouts did not differ from that in wild‐type moss and was identical to that in higher plants. Protein secretion, analysed in assays with recombinant human VEGF121 protein, was not affected in the knockouts. We conclude from our findings that the N‐glycosylation pathway in P. patens is identically organized to that in higher plants. However, P. patens probably possesses more than one isoform of GNTI which complicates a straightforward knockout. Therefore, and since complex type structures appear more desirable than oligomannosidic N‐glycans, future modifications of the pathway should target α1,3‐fucosyltransferase and/or β1,2‐xylosyltransferase.
Timing and ultrastructure of events following intracytoplasmic sperm injection in a marsupial, the tammar wallaby (Macropus eugenii)
Authors: Magarey Genevieve M. , Mate Karen E.
Published: February 2004

The aim of the present study was to determine the timing of oocyte activation, sperm decondensation and pronucleus formation after intracytoplasmic sperm injection (ICSI) in the tammar wallaby and to determine the fate of sperm structures at an ultrastructural level. Metaphase II-stage tammar wallaby oocytes were injected with spermatozoa and cultured for 1 (n = 15), 2 (n = 24), 4 (n = 30), 6 (n = 14), 8 (n = 32), 10 (n = 25), 12 (n = 29) or 19 h (n = 12). Oocytes were assessed using light, fluorescence and electron microscopy. The timing of oocyte activation and sperm decondensation after ICSI in the tammar wallaby is relatively similar to that of some eutherian species. Resumption of meiosis II was observed from 1 h and the first female pronucleus was seen 6 h after ICSI. Most oocytes (88%) possessed a female pronucleus by 10 h. Intact acrosomes persisted with intact sperm heads up to 2 h after ICSI. At 10 h, 80% of oocytes possessed a male pronucleus. The sperm tail had undergone considerable degeneration by 10 h after ICSI, including breakdown of the fibrous sheath dense fibres. The identification of sperm tail and midpiece remnants adjacent to pronuclei confirms that the events observed in wallaby oocytes after ICSI are not due to parthenogenetic activation.
Clustering of Nck by a 12-residue Tir phosphopeptide is sufficient to trigger localized actin assembly
Authors: Campellone Kenneth G. , Rankin Susannah , Pawson Tony , Kirschner Marc W. , Tipper Donald J. , Leong John M.
Published: February 2004

Enteropathogenic Escherichia coli (EPEC) translocates effector proteins into mammalian cells to promote reorganization of the cytoskeleton into filamentous actin pedestals. One effector, Tir, is a transmembrane receptor for the bacterial surface adhesin intimin, and intimin binding by the extracellular domain of Tir is required for actin assembly. The cytoplasmic NH2 terminus of Tir interacts with focal adhesion proteins, and its tyrosine-phosphorylated COOH terminus binds Nck, a host adaptor protein critical for pedestal formation. To define the minimal requirements for EPEC-mediated actin assembly, Tir derivatives were expressed in mammalian cells in the absence of all other EPEC components. Replacement of the NH2 terminus of Tir with a viral membrane-targeting sequence promoted efficient surface expression of a COOH-terminal Tir fragment. Artificial clustering of this fusion protein revealed that the COOH terminus of Tir, by itself, is sufficient to initiate a complete signaling cascade leading to pedestal formation. Consistent with this finding, clustering of Nck by a 12-residue Tir phosphopeptide triggered actin tail formation in Xenopus egg extracts.
Cleavage furrow positioning
Authors: Glotzer Michael
Published: February 2004

To complete the cell cycle, the cleavage furrow draws the plasma membrane toward the cell center, pinching the cytoplasm into two lobes that are subsequently separated into two cells. The position of the cleavage furrow is induced by the mitotic spindle during early anaphase. Although the mechanism of cleavage furrow positioning is not understood at a molecular level, recent results suggest that it might be mediated by local relief from the inhibitory effects of microtubules.
Rap1 up-regulation and activation on plasma membrane regulates T cell adhesion
Authors: Bivona Trever G. , Wiener Heidi H. , Ahearn Ian M. , Silletti Joseph , Chiu Vi K. , Philips Mark R.
Published: February 2004

Rap1 and Ras are closely related GTPases that share some effectors but have distinct functions. We studied the subcellular localization of Rap1 and its sites of activation in living cells. Both GFP-tagged Rap1 and endogenous Rap1 were localized to the plasma membrane (PM) and endosomes. The PM association of GFP-Rap1 was dependent on GTP binding, and GFP-Rap1 was rapidly up-regulated on this compartment in response to mitogens, a process blocked by inhibitors of endosome recycling. A novel fluorescent probe for GTP-bound Rap1 revealed that this GTPase was transiently activated only on the PM of both fibroblasts and T cells. Activation on the PM was blocked by inhibitors of endosome recycling. Moreover, inhibition of endosome recycling blocked the ability of Rap1 to promote integrin-mediated adhesion of T cells. Thus, unlike Ras, the membrane localizations of Rap1 are dynamically regulated, and the PM is the principle platform from which Rap1 signaling emanates. These observations may explain some of the biological differences between these GTPases.
Man the nanoscopes
Authors: Wells William A.
Published: February 2004

New light microscopy techniques are pushing the limits of resolution to 50 nm and below. Fluorescence microscopy that rivals electron microscopy in resolution but operates on intact cells may be within reach.
Differential Regulation of TCR-mediated Gene Transcription by Vav Family Members
Authors: Zakaria Shaheen , Gomez Timothy S. , Savoy Doris N. , McAdam Simon , Turner Martin , Abraham Robert T. , Billadeau Daniel D.
Published: February 2004

Although all three Vav family members are expressed in T lymphocytes, the role that Vav3 plays in T cell activation is poorly defined. Here we show that, like Vav1, Vav3 undergoes rapid tyrosine phosphorylation after T cell receptor (TCR) cross-linkage and interacts with the adaptor molecules SLP76 and 3BP2 in a SH2-dependent manner. However, depletion of Vav1 but not Vav3 protein by RNA interference affects TCR-mediated IL-2 promoter activity. In contrast, Vav3 function is specifically required for coupling TCR stimulation to serum response element–mediated gene transcription. These data indicate that, although both Vav proteins are biochemically coupled to the TCR, they regulate distinct molecular pathways leading to defined gene transcriptional events.
GATA-3 in Human T Cell Helper Type 2 Development
Authors: Skapenko Alla , Leipe Jan , Niesner Uwe , Devriendt Koen , Beetz Rolf , Radbruch Andreas , Kalden Joachim R. , Lipsky Peter E. , Schulze-Koops Hendrik
Published: February 2004

The delineation of the in vivo role of GATA-3 in human T cell differentiation is a critical step in the understanding of molecular mechanisms directing human immune responses. We examined T cell differentiation and T cell–mediated effector functions in individuals lacking one functional GATA-3 allele. CD4 T cells from GATA-3+/− individuals expressed significantly reduced levels of GATA-3, associated with markedly decreased T helper cell (Th)2 frequencies in vivo and in vitro. Moreover, Th2 cell–mediated effector functions, as assessed by serum levels of Th2-dependent immunoglobulins (Igs; IgG4, IgE), were dramatically decreased, whereas the Th1-dependent IgG1 was elevated compared with GATA-3+/+ controls. Concordant with these data, silencing of GATA-3 in GATA-3+/+ CD4 T cells with small interfering RNA significantly reduced Th2 cell differentiation. Moreover, GATA-3 mRNA levels increased under Th2-inducing conditions and decreased under Th1-inducing conditions. Taken together, the data strongly suggest that GATA-3 is an important transcription factor in regulating human Th2 cell differentiation in vivo.