bluuebunny/crossref_metadata_2025_split huggingface dataset:
A white light confocal microscope for spectrally resolved multidimensional imaging
Authors: FRANK J. H. , ELDER A. D. , SWARTLING J. , VENKITARAMAN A. R. , JEYASEKHARAN A. D. , KAMINSKI C. F. 
Published: August 2007

SummarySpectrofluorometric imaging microscopy is demonstrated in a confocal microscope using a supercontinuum laser as an excitation source and a custom‐built prism spectrometer for detection. This microscope system provides confocal imaging with spectrally resolved fluorescence excitation and detection from 450 to 700 nm. The supercontinuum laser provides a broad spectrum light source and is coupled with an acousto‐optic tunable filter to provide continuously tunable fluorescence excitation with a 1‐nm bandwidth. Eight different excitation wavelengths can be simultaneously selected. The prism spectrometer provides spectrally resolved detection with sensitivity comparable to a standard confocal system. This new microscope system enables optimal access to a multitude of fluorophores and provides fluorescence excitation and emission spectra for each location in a 3D confocal image. The speed of the spectral scans is suitable for spectrofluorometric imaging of live cells. Effects of chromatic aberration are modest and do not significantly limit the spatial resolution of the confocal measurements.
Cryo‐FIB‐nanotomography for quantitative analysis of particle structures in cement suspensions
Authors: HOLZER L. , GASSER PH. , KAECH A. , WEGMANN M. , ZINGG A. , WEPF R. , MUENCH B. 
Published: August 2007

SummaryCryo‐FIB‐nanotomography is a novel high‐resolution 3D‐microscopy technique, which opens new possibilities for the quantitative microstructural analysis of complex suspensions. In this paper, we describe the microstructural changes associated with dissolution and precipitation processes occurring in a fresh cement paste, which has high alumina and sulphate contents. During the first 6 min, precipitation of ettringite leads to a general decrease of the particle size distribution. In the unhydrated cement paste almost no particles smaller than 500 nm are present, whereas after 6 min this size class already represents 9 vol%. The precipitation of ettringite also leads to a significant increase of the particle number density from 0.294*109/mm3 at t0min to 20.55*109/mm3 at t6min. Correspondingly the surface area increases from 0.75 m2/g at t0min to 2.13 m2/g at t6min. The small ettringite particles tend to form agglomerates, which strongly influence the rheological properties. The particular strength of cryo‐FIB‐nt is the potential to quantify particle structures in suspension and thereby also to describe higher‐order topological features such as the particle–particle interfaces, which is important for the study of agglomeration processes.
AFM investigation of Martian soil simulants on micromachined Si substrates
Authors: VIJENDRAN S. , SYKULSKA H. , PIKE W. T. 
Published: August 2007

SummaryThe micro and nanostructures of Martian soil simulants with particles in the micrometre‐size range have been studied using a combination of optical and atomic force microscopy (AFM) in preparation for the 2007 NASA Phoenix Mars Lander mission. The operation of an atomic force microscope on samples of micrometre‐sized soil particles is a poorly investigated area where the unwanted interaction between the scanning tip and loose particles results in poor image quality and tip contamination by the sample. In order to mitigate these effects, etched silicon substrates with a variety of features have been used to facilitate the sorting and gripping of particles. From these experiments, a number of patterns were identified that were particularly good at isolating and immobilizing particles for AFM imaging. This data was used to guide the design of micromachined substrates for the Phoenix AFM. Both individual particles as well as aggregates were successfully imaged, and information on sizes, shapes and surface morphologies were obtained. This study highlights both the strengths and weaknesses of AFM for the potentialin situinvestigation of Martian soil and dust. Also presented are more general findings of the limiting operational constraints that exist when attempting the AFM of high aspect ratio particles with current technology. The performance of the final designs of the substrates incorporated on Phoenix will be described in a later paper.
Quasi‐cleavage fracture planes in spheroidized A533B steel
Authors: KUMAR A. , WILKINSON A. J. , ROBERTS S. G. 
Published: August 2007

SummaryElectron backscattered diffraction (EBSD) has been used to acquire crystal orientation information around unusual microcracks induced by tensile deformation of notched specimens of spheroidized A533B steel. This unusual fracture mode has been called quasi‐cleavage and occurs at relatively low temperatures with fracture energies below that of the upper shelf. EBSD measurements on sectioned samples showed that the quasi‐cleavage cracks were intragranular. A two‐dimensional analysis technique was used in which EBSD measured crystal orientations were combined with secondary electron imaging to obtain the trace of the crack facet on the section plane. The measurements revealed that the observed crack facets were consistent with crack propagation along the {001} and {011} planes.
Accuracy of orientation distribution function determination based on EBSD data‐A case study of a recrystallized low alloyed Zr sheet
Authors: BOZZOLO N. , GERSPACH F. , SAWINA G. , WAGNER F. 
Published: August 2007

SummaryThe question of the statistical accuracy of EBSD data for global texture calculation was re‐explored on the basis of a very large grain population (83 000 grains measured on a recrystallized low‐alloyed Zr sheet). Previous works aimed mainly at identifying and quantifying the main texture components and were based on much smaller data sets. The present work attempts to quantify the accuracy of the complete texture, including low‐density regions of the orientation space. For that purpose, a new statistical parameter, VΔ, based on the calculation of texture difference functions is proposed. This parameter has two main advantages: it is equally sensitive to both high and low peaks of the orientation density function (ODF), and it has a physical interpretation because it is the material volume fraction corresponding to the difference between a given ODF and a reference ODF (considered, or known to be close to the truth). Two main variables were studied: the number of grains taken into account and the peak width ϕ0 of Bunge's ‘Gaussian’ model density used as kernel for the actual analysis. The orientation distribution functions were computed by nonparametric kernel density estimation with harmonics up to the order of 34. Minimizing the value of VΔ serves as the objective function for optimizing the peak width ϕ0 as a function of the number of grains. The properties of the VΔ parameter also allows for the definition of a method for estimating the accuracy of a given texture that has been obtained from a limited number of grains, without knowing the true texture of the investigated material.
Determination of parent orientation maps in advanced titanium‐based alloys
Authors: GERMAIN L. , DEY S. R. , HUMBERT M. , GEY N. 
Published: August 2007

SummaryIn the past few years, reconstruction methods have been developed and applied successfully to restore the β microtexture in titanium alloys. This contribution shows how these methods are extended to other transformations often encountered in advanced titanium alloys: the α (hcp)→γ (tetragonal) and the β (bcc)→O (orthorhombic) transformation.The efficiency of the restitution depends on specific crystallographic features of the investigated phase transformations. Therefore, the paper outlines these crystallographic specificities for some advanced titanium alloys. To illustrate the capability of the method to reconstruct the parent phase, different restored parent microtextures of these alloys are presented. The results show that the reconstruction methods are an efficient tool to study the microstructure and texture modifications induced by these phase transformations.
The preferred CSL misorientation distribution in polycrystalline SrTiO3
Authors: PARK MYUNG‐BEOM , SHIH SHAO‐JU , COCKAYNE DAVID J. H. 
Published: August 2007

SummaryElectron backscattered diffraction is used to investigate the preferred CSL (coincidence site lattice) distribution of polycrystalline SrTiO3 as a function of annealing times (1 h and 16 h). Comparison of the CSL misorientations suggests that the CSL boundary energy plays a role in the preferred grain growth.
NONPARAMETRIC REGRESSION ON FUNCTIONAL DATA: INFERENCE AND PRACTICAL ASPECTS
Authors: Ferraty Frédéric , Mas André , Vieu Philippe 
Published: August 2007

SummaryWe consider the problem of predicting a real random variable from a functional explanatory variable. The problem is tackled using a nonparametric kernel approach, which has been recently adapted to this functional context. We derive theoretical results from a deep asymptotic analysis of the behaviour of the estimate, including mean squared convergence (with rates and precise evaluation of the constant terms) as well as asymptotic distribution. Practical use of these results relies on the ability to estimate these constants. Some perspectives in this direction are discussed. In particular, a functional version of wild bootstrapping ideas is proposed and used both on simulated and real functional datasets.
SEMIPARAMETRIC ESTIMATION OF THE ERROR DISTRIBUTION IN MULTIVARIATE REGRESSION USING COPULAS
Authors: Kim Gunky , Silvapulle Mervyn J. , Silvapulle Paramsothy 
Published: August 2007

SummaryA semiparametric method is developed to estimate the dependence parameter and the joint distribution of the error term in the multivariate linear regression model. The nonparametric part of the method treats the marginal distributions of the error term as unknown, and estimates them using suitable empirical distribution functions. Then the dependence parameter is estimated by either maximizing a pseudolikelihood or solving an estimating equation. It is shown that this estimator is asymptotically normal, and a consistent estimator of its large sample variance is given. A simulation study shows that the proposed semiparametric method is better than the parametric ones available when the error distribution is unknown, which is almost always the case in practice. It turns out that there is no loss of asymptotic efficiency as a result of the estimation of regression parameters. An empirical example on portfolio management is used to illustrate the method.
BIOCHEMICAL COMPOSITION AND PHOTOSYNTHETIC CARBON METABOLISM OF NUTRIENT LIMITED CULTURES OF MERISMOPEDIA TENUISSIMA (CYANOPHYCEAE)1
Authors: Konopka Allan , Schnur Marilyn 
Published: August 2007

ABSTRACTContinuous cultures of Merismopedia tenuissima Lemmerman, limited by phosphorus, nitrogen, sulfur, or carbon, were compared to non limited batch cultures by two methods. The cellular content of photosynthetic pigments (chlorophyll and phycocyanin) was found to decrease in all nutrient limited cultures, except for the carbon limited culture. The ratio of carbohydrate to protein was 4‐ to 7‐fold higher in P, N or S limited cultures than in non‐limited or C limited cultures. The macromolecular products of photosynthesis were determined in samples to which NaH14CO3 was added. Relative incorporation into protein decreased in P or N limited cultures, increased accumulation of low molecular weight compounds was found in S and P limited cultures, and little change was noted in C limited cultures as compared to non‐limited cultures. Although relative incorporation into protein was significantly greater at 20μEin·m−2·s−1 light intensity than at 180 μEin·m−2.s−1 in non‐limited cultures, this effect was abolished in all nutrient limited cultures. These results suggest that measurement of the cellular carbohydrate to protein ratio and the products of photosynthesis would be useful in the analysis of algal population dynamics in nature.
TRANSPORT OF INORGANIC CARBON AND THE ‘CO2 CONCENTRATING MECHANISM’ IN CHLORELLA EMERSONII (CHLOROPHYCEAE)1
Authors: Beardall John , Raven John A. 
Published: August 2007

ABSTRACT Chlorella emersonii Shihira et Krauss var. emersonii exhibits ‘C4‐like’ gas exchange characteristics when grown at air levels of CO2, but is ‘C3‐like’ when grown with extra CO2. The total inorganic carbon concentration, and the free CO2 concentration, averaged over the cell interior are higher in air‐adapted cells than can be accounted for by passive CO2 equilibration from the medium and the mean intracellular pH value. The ‘extra’ inorganic C in the air‐grown cells probably cannot all be accounted for in terms of binding to proteins and requires an active transport process to account for it. The electrical potential of the cell interior becomes more negative when the ‘CO2 concentrating mechanism’ is operative; this is most readily explained if the active step in inorganic C accumulation is primary active uniport of HCO3−. Since the ‘CO2 concentrating mechanism’ can operate when CO2 is the species crossing the outer permeation barrier, it is suggested that the site of active HCO3− transport in Chlorella (and other eukaryotes) is the chloroplast envelope, and the plasmalemma in cyanobacteria. This scheme explains the obligatory role of the de‐repressed carbonic anhydrase in C4‐like photosynthesis in algae, but some other data support an explanation of C4‐like photosynthesis in terms of special properties of carbonic anhydrase as a carbon donor to RuBP carboxylase‐oxygenase.
THE FLAGELLAR APPARATUS OF CHILOMONAS PARAMECIUM (CRYPTOPHYCEAE) AND ITS COMPARISON WITH CERTAIN ZOOFLAGELLATES1
Authors: Roberts Keith R. , Stewart Kenneth D. , Mattox Karl R. 
Published: August 2007

ABSTRACTThe major components of the internal flagellar apparatus of Chilomonas paramecium Ehr. are two large microtubular roots and a striated root paralleled by three microtubules. The two microtubular roots overlap at the basal bodies. One microtubular root follows a curved path in the anterior of the cell, and the other extends straight to the posterior passing through a groove in the nucleus. The striated root extends laterally from the basal bodies. Except that it is smaller, the posteriorly directed root bears a strong resemblance to the axostyle of oxymonads. The overall arrangement and structure of the flagellar roots is similar to the pelta, axostyle and costa of trichomonads and the pelta and axostyle of oxymonads, groups of mitochondrion‐less, largely parasitic or symbiotic protozoans. An affinity between cryptomonads and oxymonads or trichomonads would have many phylogenetic implications, some of which are discussed.
ULTRASTRUCTURAL STUDIES ON SPHAEROPLEA ANNULINA (CHLOROPHYCEAE). II. SPERMATOGENESIS AND MALE GAMETE STRUCTURE1,2
Authors: Cáceres Eduardo J. , Robinson David G. 
Published: August 2007

ABSTRACTThe development and ultrastructure of the male gamete of Sphaeroplea annulina (Roth) Agardh have been investigated. Multiple mitoses each associated with phycoplast microtubules occur as a result of nitrogen deficiency in the culture medium. A regular cleavage of the cytoplasm delineated by microtubules then occurs, resulting in many young male gametes. During maturation the gametes are retained within a vacuolar envelope. Maturation entails reduction in nuclear size and chromatin condensation, loss of chloroplast thylakoids, endoplasmic reticulum and Golgi apparatus. The apical region where the two flagella are inserted consists of an apical cone and fibrous connections which lie distal to the basal bodies. The study supports the suggestion put forward in a previous paper: namely that the genus Sphaeroplea be retained in a separate order the Sphaeropleales.
LIGHT AND ELECTRON MICROSCOPIC STUDIES OF THE FUSION CELL IN ASTEROCOLAX GARDNERI SETCH. (RHODOPHYTA, CERAMIALES)12
Authors: Kugrens Paul , Arif Ibrahim 
Published: August 2007

ABSTRACTThe fusion cell in Asterocolax gardneri Setch, is a large, multinucleate, irregularly‐shaped cell resulting from cytoplasmic fusions of haploid and diploid cells. Subsequent enlargement takes place by incorporating adjacent gonimoblast cells. The resultant cell consists of two parts—a central portion of isolated cytoplasm, surrounded by an electron dense cytoplasmic barrier, and the main component of the fusion cell cytoplasm surrounding the isolated cytoplasm. The fusion cell contains many nuclei, large quantities of floridean starch, endoplasmic reticulum, and vesicles, but few mitochondria, plastids and dictyosomes. The endoplasmic reticulum forms vesicles that apparently secrete large quantities of extracellular mucilage which surrounds the entire carposporophyte. The isolated cytoplasm also is multinucleate but lacks starch and a plasma membrane. Few plastids, ribosomes and mitochondria are found in this cytoplasm. However, numerous endoplasmic reticulum cisternae occur near the cytoplasmic barrier and they appear to secrete material for the barrier. In mature carposporophytes, all organelles in the isolated cytoplasm have degenerated.
EFFECTS OF COPPER TOXICITY ON SILICIC ACID UPTAKE AND GROWTH IN THALASSIOSIRA PSEUDONANA11
Authors: Rueter John G. , Chisholm Sallie W. , Morel Francois M. M. 
Published: August 2007

ABSTRACTThe toxicity of Cu to Thalassiosira pseudonana (Hustedt) Hasle and Heimdal was investigated by examining both short and long term effects of Cu on cellular processes. Toxic levels of Cu (pCu* < 13) were found to inhibit short term Si(OH)4 uptake rates with kinetics characteristic of irreversible inhibition at a hypothetical Cu‐sensitive Si(OH)4 transport site. Residual Si(OH)4 concentrations (those below which no uptake could occur) were found to increase with increasing levels of Cu, and the toxic effects of Cu could be reversed by increasing the concentrations of Si(OH)4 in the medium. The actual uptake of Cu by the cells was found to vary inversely with the ambient Si(OH)4 concentration. Copper did not inhibit the uptake of NO3− or PO43‐.The long term inhibition of growth rate by Cu in this species was shown not to be a result of Si deficiency caused by the inhibition of Si(OH)4 uptake. Cu inhibited cells were found to have higher Si cell quotas (including a sizable soluble pool) than the control cultures. They were, however, observed to have aberrant frustules, significantly larger than the control cells, suggesting interference with the silification process as a possible mechanism for inhibition of growth by Cu.A conceptual model is proposed for the Cu‐Si(OH)4‐growth relationship. It includes a Cu sensitive Si(OH)4 transport site that may also serve to transport Cu into the cell, and growth inhibition mediated by intracellular Cu concentrations which may block cell division or cause general cellular disfunction.
NEW RECORD OF THE MARINE RED ALGA CUBICULOSPORUM (GIGARTINALES) FROM THE SOUTHERN GREAT BARRIER REEF1
Authors: Kraft Gerald T. , Huisman John M. 
Published: August 2007

ABSTRACT Cubiculosporum koronicarpis Kraft (Cubiculosporaceae, Gigartinales), known previously only from the type locality (southeastern Luzon, Philippines), has been collected at North West Island on the southern Great Barrier Reef. The habitat, distribution and taxonomic status of the species are discussed, and habit features of the new specimens are illustrated.
CULTURE STUDIES ON REPRODUCTION OF SPERMATOCHNUS PARADOXUS (PHAEOPHYCEAE, CHORDARIALES)1
Authors: Müller Dieter G. 
Published: August 2007

ABSTRACTThe life history of Spermatochnus paradoxus (Roth) Kütz. isolated from the Mediterranean Sea was studied in culture. Meiospores develop to a microscopic stage (microthallus) which at 20°C perpetuates asexually by plurilocular sporangia and formation of new microthalli. At 9°C microthalli act as homothallic gametophytes. Fusion of isogametes results in a diploid microthallus which, after differentiation of an apical cell, leads back to Spermatochnus plants. In addition, gametes develop without fusion to form haploid macrothalli, the further fate of which has not been determined. Chromosome numbers alternate between n = 20 ± 2 in the microthalli and 2n = 41 ± 4 in macrothalli.
THE FLAGELLAR APPARATUS OF THE ZOOSPORE OF UROSPORA PENICILLIFORMIS(CHLOROPHYTA)1
Authors: Sluiman Hans J. , Roberts Keith R. , Stewart Kenneth D. , Mattox Karl R. , Lokhorst Gijsbert M. 
Published: August 2007

ABSTRACTThe flagellar apparatus of Urospora penicilliformis (Roth) Aresch. is unique, or at least very unusual among green algae. The flagellar axonemes are rigid, and contain wing‐like projections. There are no central microtubules in the most proximal part of the axoneme. The transition region contains a series of electron dense transverse lamellae rather than a single septum, and lacks a stellate pattern. There is no cartwheel pattern in the proximal part of the basal bodies. The latter are associated with four different types of fibrous elements: ascending striated fibers that attach to an electron dense plate in the papillar center, lateral striated fibers that parallel microtubular roots, fibrous elements that link adjacent basal bodies, and finally two massive striated fibers that descend into the cell, passing closely along the nucleus (system II fibers, or rhizoplasts). Each of the four microtubular flagellar roots is sandwiched between two system I striated structures. The roots are probably equal; they contain proximally four, and distally up to eight microtubules. Based on the zoospore flagellar apparatus, it is concluded that the multinucleate U. penicilliformis is related to the Ulvaphyceae. Finally, a possible explanation in functional terms is given for the peculiar external morphology and behavior of the zoospore.
AMPHIDINIUM CRYOPHILUM SP. NOV. (DINOPHYCEAE) A NEW FRESHWATER DINOFLAGELLATE. II. ULTRASTRUCTURE1
Authors: Wilcox Lee W. , Wedemayer Gary J. , Graham Linda E. 
Published: August 2007

ABSTRACTThe dinoflagellate Amphidinium cryophilum sp. nov. is one of the few gymnodinians to be studied at the ultrastructural level. It resembles other dinoflagellates in the structure of the nucleus, trichocysts, storage materials, flagella, mitochondria, and microbodies. Other features of A. cryophilum less commonly observed in related organisms include a network of small interconnected vesicles, a system of large, peripheral vacuoles, chloroplasts bound by two rather than three membranes, an accumulation body, thylakoid‐associated plastoglobuli, a vesiculated nuclear envelope, a complex tubular pusule, striated flagellar collars, collared pits, and a peduncle. The occurrence of a peduncle, a structure implicated in phagotrophy, in this autotrophic organism is noteworthy. The ultrastructure of the peduncle of A. cryophilum differs significantly from that reported in another dinoflagellate.