bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methylated Purines in Urinary Stones
Authors: Safranow Krzysztof , Machoy Zygmunt 
Published: May 2005

Abstract
Background: The aim of the study was to measure the content of methylated purines that appear as admixtures in uric acid stones.
Methods: We analyzed urinary calculi from 48 residents of Western Pomerania who underwent surgery at the urology ward in Szczecin. Stone samples were dissolved in 0.1 mol/L NaOH. Extracts were diluted in 50 mmol/L KH2PO4 and analyzed by reversed-phase HPLC with ultraviolet detection and use of a gradient of methanol concentration and pH.
Results: Uric acid was the main component of 9 stones. All 9 showed admixtures of 9 other purine derivatives: endogenous purine breakdown products (xanthine, hypoxanthine, and 2,8-dihydroxyadenine) and exogenous methyl derivatives of uric acid and xanthine (1-, 3-, and 7-methyluric acid; 1,3-dimethyluric acid; and 3- and 7-methylxanthine). Amounts of these purine derivatives ranged from the limit of detection to 12 mg/g of stone weight and showed a strong positive correlation (Spearman rank correlation coefficients, 0.63–0.94) with the uric acid content of the samples. The main methylated purine in the stones was 1-methyluric acid.
Conclusions: Urinary purines at concentrations below their saturation limits may coprecipitate in samples supersaturated with uric acid and appear as admixtures in urinary stones. The amount of each purine depends on its average urinary excretion, similarity to the chemical structure of uric acid, and concentration of the latter in the stone. These findings suggest that purines in stones represent a substitutional solid solution with uric acid as solvent. Methylxanthines, which are ubiquitous components of the diet, drugs, and uric acid calculi, may be involved in the pathogenesis of urolithiasis.
Die selbstverteilende virtuelle Maschine SDVM (Self Distributing Virtual Machine (SDVM))
Authors: Haase Jan , Eschmann Frank , Waldschmidt Klaus 
Published: May 2005

Zusammenfassung
Die Self Distributing Virtual Machine (SDVM) ist eine Middleware, die beliebige Standard-Rechner zu einem parallelen Rechnercluster verbindet. Die an der SDVM teilnehmenden Rechner können verschieden leistungsfähig sein und unter verschiedenen Betriebssystemen laufen. Ebenso kann die Netzwerktopologie beliebig gewählt werden und sich auch während der Laufzeit ändern. Die SDVM unterstützt dynamisches An- und Abmelden von Sites, sodass sich der Cluster während der Laufzeit vergrößern oder verkleinern kann. Außer dem SDVM-Daemon benötigen Rechner keine weiteren Voraussetzungen und können sich direkt in den SDVM-Cluster einfügen. Die SDVM besitzt eine automatische Verteilung von Daten und Instruktionsblöcken auf die teilnehmenden Sites, sowie einen dezentralen Scheduler. Aufgrund des Ausführungsparadigmas der SDVM können Applikationen ohne Änderungen auf beliebigen Cluster-Konfigurationen genutzt werden. Das Konzept der SDVM ist ebenfalls besonders für eng gekoppelte Systeme wie beispielsweise Multi-Prozessor-Systeme oder Systems-on-Chip (SoC) geeignet, kann aber auch für den Bereich des Grid Computing erweitert werden. Dieser Artikel beschreibt die Eigenschaften und die Struktur der SDVM.
Strukturierte Lehr- und Lernmodelle für die Ausbildung im Fachgebiet Technische Informatik (Structured Educational Models for Computer Engineering)
Authors: Lucke Ulrike , Nölting Kristin , Tavangarian Djamshid 
Published: May 2005

Zusammenfassung
Bewährte Entwurfsmechanismen für Rechentechnik weisen einen hohen Strukturierungsgrad auf. Zentrale, bleibende Anteile werden als fest verdrahtete Hardware realisiert, während dynamische Anteile rekonfigurierbar gestaltet werden. Modularität und Interoperabilität der Komponenten spielen dabei eine wichtige Rolle. Der Entwurfsprozess setzt Technologie-unabhängig auf einem hohen Abstraktionsniveau an. Der Artikel zeigt an aktuellen eLearning-Angeboten, wie diese Erfahrungen auf die Lehre übertragen werden können.
Transregional Collaborative Research Center SFB/TR 8 Spatial Cognition: Reasoning, Action, Interaction (Sonderforschungsbereich/Transregio SFB/TR 8 Raumkognition: Schließen, Handeln, Interagieren)
Authors: Barkowsky Thomas , Bateman John , Freksa Christian , Burgard Wolfram , Knauff Markus 
Published: May 2005

Summury
The Transregional Collaborative Research Center SFB/TR 8 Spatial Cognition was established by the German Science Foundation (DFG) at the Universities of Bremen and Freiburg in January 2003. 13 Research projects pursue interdisciplinary research on intelligent spatial information processing. This article introduces the research field of spatial cognition and reports on aspects from cognitive psychology, cognitive robotics, linguistics, and artificial intelligence.
An Overview on the Generation of BAC Transgenic Mice for Neuroscience Research
Authors: Yang X. William , Gong Shiaoching 
Published: May 2005

AbstractThis unit provides a comprehensive overview on the generation of transgenic mice using bacterial artificial chromosomes (BACs), and the application of BAC transgenic mice in neuroscience research. In the first section, advantages of the BAC transgenic approach compared to the conventional transgenic approach are summarized. In the second section, important considerations in designing BAC transgenic constructs are outlined. Four commonly used BAC transgenic construct designs are also outlined. Concepts of modifying BACs by homologous recombination in E. coli to introduce a variety of mutations into BACs, and important steps to characterize a modified BAC prior to the generation of transgenic mice are also presented. In the final section, some of the important applications of BAC transgenic mice in neuroscience research, including studying gene expression, gene function, mapping neuronal circuitry, and modeling human diseases, are described.
Modification of Bacterial Artificial Chromosomes (BACs) and Preparation of Intact BACDNA for Generation of Transgenic Mice
Authors: Gong Shiaoching , Yang X. William 
Published: May 2005

AbstractBAC transgenesis is a powerful tool for the study of gene expression and gene function in the mouse in vivo. In this unit, detailed protocols are provided for modification (i.e., marker gene insertion, deletion, or point mutation) of BACs by homologous recombination in E. coli. This method utilizes a shuttle vector that allows transient expression of the E. coli RecA gene to support homologous recombination in the BAC host bacteria. In addition, two protocols are provided for purification of BAC DNA for microinjection to generate transgenic mice. Since BAC DNA is prone to degradation, which may introduce positional effects in transgenic mice, two methods are given for purification of intact BAC DNA for subsequent microinjection.
Rule Out (R/O) Vasculitis
Authors: Thibodeau Steven , Grant Ellen , Schaefer Pamela W. 
Published: May 2005

AbstractWhen imaging patients for vasculitis, the goals are: (1) to determine if there is evidence of acute or subacute cerebral injury and (2) to assess the contour of the major intracranial arteries. An additional but still experimental goal is (3) to determine if there are areas of altered perfusion that suggest active small vessel disease. Standard MR images and diffusion‐weighted imaging are used to detect and determine the age of parenchymal lesions. The 3‐D TOF MRA helps evaluate the large and medium vessels. Perfusion‐weighted imaging may detect regions of altered relative blood flow and blood volume. This unit contains a basic protocol for the evaluation of stable patients as well as an alternative protocol for unstable patients.
Rule Out (R/O) Migraine
Authors: Thibodeau Steven , Grant Ellen 
Published: May 2005

AbstractWhen imaging patients with headaches, the goals are: (1) to rule out a more ominous etiology for their headaches and (2) to assess the degree of hemodynamic and parenchymal involvement when atypical or complicated migraine is suspected. The standard images allow other etiologies, such as mass lesions, to be excluded and an MR venogram can rule out venous sinus thrombosis. Contrast may be helpful in differentiating multiple small metastases, demylinating lesions with inflammatory components, and subcortical infarcts from the nonspecific foci of increased T2 associated with migraines that do not enhance. Perfusion‐weighted imaging allows detection assessment of hemodynamic compromise. Diffusion‐weighted imaging, in combination with the standard MR images, allows assessment of parenchymal involvement. This unit contains a basic protocol which can be used for the evaluation of patients as well as an alternative protocol for the assessment of cerebral perfusion in patients with visual auras.
Signal Detection
Authors: Cheng Yu‐Chung Norman , Haacke E. Mark 
Published: May 2005

AbstractThe bulk magnetization represents the equilibrium value of the magnetization when all spins have aligned themselves parallel to the main field. When this magnetization is tipped into the transverse plane, it precesses about the main field. This precession generates a changing flux through the face of an appropriately placed coil inducing an electromotive force (emf) in the coil. The measured signal is proportional to the induced emf. This unit discusses the basic physics behind detecting MR signal. The process of calculating induced emf based on Faradays law of induction is explained.
Phase Dependence on Motion
Authors: Cheng Yu‐Chung Norman , Haacke E. Mark 
Published: May 2005

AbstractThis unit introduces the sources of variable phase in the presence of motion. The sources of these phase changes can come from the read gradient, from the slice select gradient and from the phase encoding gradient. Motion during the gradient moves the spin from one location to another and, therefore, changes the effective field it sees. This field change leads to a frequency change in time during either the dephasing or rephasing gradient or both. As a result, the spins do not refocus at the expected time.
Recombineering: Genetic Engineering in Bacteria Using Homologous Recombination
Authors: Thomason Lynn , Court Donald L. , Bubunenko Mikail , Costantino Nina , Wilson Helen , Datta Simanti , Oppenheim Amos 
Published: May 2005

AbstractThe bacterial chromosome and plasmids can be engineered in vivo by homologous recombination using PCR products and synthetic oligonucleotides as substrates. This is possible because bacteriophage‐encoded recombination functions efficiently recombine sequences with homologies as short as 35 to 40 bases. This recombineering allows DNA sequences to be inserted or deleted without regard to location of restriction sites. This unit first describes preparation of electrocompetent cells expressing the recombineering functions and their transformation with double‐stranded DNA (dsDNA) or single‐stranded DNA (ssDNA). Support protocols describe a two‐step method of making genetic alterations without leaving any unwanted changes, and a method for retrieving a genetic marker (cloning) from the E. coli chromosome or a coelectroporated DNA fragment and moving it onto a plasmid. A method is also given to screen for unselected mutations. Additional protocols describe removal of defective prophage, methods for recombineering.
Basic Protein Sequence Analysis
Authors: Krishnamurthy Nandini , Sjölander Kimmen V. 
Published: May 2005

AbstractPrediction of molecular function of proteins has become an important task in the genomics era. A wide variety of sequence analysis tools are available to biologists for this task. We have selected one or two primary protocols for tasks such as domain detection, subcellular localization, and motif detection. We also present a strategy for integration of results from different protocols. All the resources needed for these protocols are accessible via publicly available Web servers and databases and require little or no computational expertise.
Analysis of Protein Co‐Occupancy by Quantitative Sequential Chromatin Immunoprecipitation
Authors: Geisberg Joseph V. , Struhl Kevin 
Published: May 2005

AbstractSequential Chromatin Immunoprecipitation (SeqChIP) is a powerful technique for analyzing the simultaneous association of two different proteins with genomic DNA sequences in vivo. Cellular Protein‐DNA complexes are cross‐linked with formaldehyde (UNIT ), and are purified via two successive immunoprecipitations, with each immunoprecipitation targeting a different protein. Protein‐DNA cross‐links are then reversed and DNA sequences of interest are analyzed by quantitative PCR. At each genomic region, calculated SeqChIP co‐occupancy values are compared to occupancy values of singly immunoprecipitated samples. The extent of enrichment brought about by the second immunoprecipitation relative to the singly immunoprecipitated sample is directly correlated with the degree of co‐occupancy between the two proteins at the genomic location assayed. In principle, the technique is not limited to Saccharomyces cerevisiae. Cells from a wide variety of organisms can be used.
Measurement of Cytokine Production Using Whole Blood
Authors: Thurm Cary W. , Halsey John F. 
Published: May 2005

AbstractWhole blood (WB) ex vivo stimulation assays are useful for measuring cytokine responses due to the easy access of samples from healthy donors and patients and the minimal processing of the sample required. Because the assay mimics the natural environment, WB culture may be the best milieu in which to study cell activation and cytokine production in vitro. Whole blood stimulation has been used to investigate the cellular responsiveness to a variety of stimuli, including bacterial endotoxin (LPS), antigens, allergens, and antibiotics. Various clinical uses of whole blood stimulation assays have been suggested, including the assessment of autoimmune diseases, the monitoring of drug and vaccine efficacy, and immunotoxicity. Thus, whole blood cell culture may be useful in studying the biological effects of potential allergenic and/or antigenic substances or drugs on immune cell activation and cytokine secretion.
Sources and Methods for Obtaining Stem and Progenitor Cells
Authors: Donahue Robert E. , Kuramoto Ken , Dunbar Cynthia E. 
Published: May 2005

AbstractExtrapolation of an understanding regarding hematopoiesis and, in particular, hematopoietic stem cells (HSCs) from rodent models or in vitro human cell models to applications in humans has proven very difficult. This is not surprising, given the differences between rodent and human hematopoietic physiology and the lack of true in vitro assays for HSCs. Therefore, translational preclinical development of genetic and cellular therapies is dependent on the utilization of practical and well‐defined large animal models. This chapter will introduce the most commonly used model species, including macaques, baboons, dogs, cats, and sheep, and explain the particular advantages and limitations of each. Specific protocols for the support of macaques through ablative cell and gene therapy procedures will be included to introduce investigators to the types of resources and support required to maintain a large animal facility dedicated to high‐intensity experimentation, and also to introduce investigators to the types of procedures that are possible.
Isolation of Prolymphocytes from Bone Marrow and Fetal Liver
Authors: Kouro Taku , Yokota Takafumi , Welner Robert , Kincade Paul W. 
Published: May 2005

AbstractIsolation of the lymphoid progenitors in their earliest stage of development is indispensable for understanding when and how hematopoietic cell lineages are committed. Recently developed immunofluorescent labeling and sorting has made it possible to identify and isolate rare progenitors of lymphocytes. In this unit, protocols for isolating lymphoid progenitors from three different sources are provided. These protocols are based on stepwise purification consisting of magnetic and fluorescence‐activated cell sorting techniques, optimized according to the nature of progenitors in each organ. Isolated progenitors may be analyzed in the lymphocyte differentiation cultures described in the following units and are useful for in vivo transfer experiments or microarray assays for gene expression.
In Vitro Differentiation and Measurement of B Cell Progenitor Activity in Culture
Authors: Kouro Taku , Yokota Takafumi , Welner Robert , Kincade Paul W. 
Published: May 2005

AbstractAs well as other blood cells, B lymphocytes originate from hematopoietic stem cells. However, it is not fully understood how their production is controlled. In the serum‐free, stromal‐cell‐free B cell differentiation culture described here, early steps of the B lineage differentiation process are reproduced under defined conditions. This assay is useful for examining the direct effects of various soluble factors on B cell progenitors because it does not contain stromal cells or unknown factors. Additionally, this assay yields sufficient cloning to measure B cell progenitors from single cell cultures. Stromal cell coculture assays are also described that cover a wider category of precursors such as human B cell progenitors.
Measurement of Natural Killer Cell Progenitor Activity in Culture
Authors: Kouro Taku , Yokota Takafumi , Welner Robert , Kincade Paul W. 
Published: May 2005

AbstractNatural killer cells are morphologically related to and have progenitors in common with B and T lymphocytes. In this unit, protocols describe how to induce natural killer cell differentiation from prolymphocytes. Since NK cell differentiation cultures also support B cell differentiation, this protocol is extremely useful for seeking the B and NK cell branch point in their differentiation pathway.
Responses of plant functional types to an environmental gradient on the Northeast China Transect
Authors: Wang Guo‐Hong , Ni Jian 
Published: May 2005

AbstractThe hypothesis that some plant traits such as life form are robust surrogates for plant functional type (PFT) has provoked an ongoing debate. Based on a dataset from the Northeast China Transect (NECT), we attempted to test the hypothesis by comparing an objective PFT identification framework in which large datasets of plant traits were considered with two subjective PFT frameworks in which only a few plant traits were involved. Additionally, we addressed the relations between the relative abundance of PFTs and the environmental gradient represented by actual evapotranspiration (AET) along the NECT. We also discuss the changes in ecosystem functioning associated with the PFT turnover along the environmental gradient. Based on an objective PFT classification, eight PFTs were identified: deciduous trees, shrubs, perennial forbs with lower net photosynthesis, perennial forbs with higher net photosynthesis, perennial bulb‐grasses, perennial tiller‐grasses, annual C4 herbs and evergreen trees. Our results indicated that some plant traits, such as life form and photosynthesis pathway, are robust surrogates for PFTs, implying that subjective approaches to PFT classification are useful. Nonetheless, caution should be used during the classification of PFTs. The framework adopted for PFT classification should depend on the specific scientific issues being dealt with. It is therefore meaningless to pursue a general framework for the identification of PFTs even within given plant communities. On the other hand, our quantitative classification of PFTs confirmed recurrent patterns with respect to PFT turnover along an environmental gradient. Furthermore, with the turnover in PFT along the NECT from the west to the east, ecosystem properties such as productivity and carbon storage are predicted to decrease, while photosynthesis is predicted to increase, suggesting that PFT turnover would inevitably lead to changes in ecosystem functioning.
SOME DUALITY CONJECTURES FOR FINITE GRAPHS AND THEIR GROUP THEORETIC CONSEQUENCES
Authors: Gersten S. M. , Riley T. R. 
Published: May 2005

AbstractWe pose some graph theoretic conjectures about duality and the diameter of maximal trees in planar graphs, and we give innovations in the following two topics in geometric group theory, where the conjectures have applications.Central extensions. We describe an electrostatic model concerning how van Kampen diagrams change when one takes a central extension of a group. Modulo the conjectures, this leads to a new proof that finitely generated class $c$ nilpotent groups admit degree $c+1$ polynomial isoperimetric functions.Filling functions. We collate and extend results about interrelationships between filling functions for finite presentations of groups. We use the electrostatic model in proving that the gallery length filling function, which measures the diameter of the duals of diagrams, is qualitatively the same as a filling function DlogA, concerning the sum of the diameter with the logarithm of the area of a diagram. We show that the conjectures imply that the space-complexity filling function filling length essentially equates to gallery length. We give linear upper bounds on these functions for a number of classes of groups including fundamental groups of compact geometrizable 3-manifolds, certain graphs of groups, and almost convex groups. Also we define restricted filling functions which concern diagrams with uniformly bounded vertex valence, and we show that, assuming the conjectures, they reduce to just two filling functions—the analogues of non-deterministic space and time.
THREE POSITIVE SOLUTIONS FOR A CLASS OF ELLIPTIC SYSTEMS IN ANNULAR DOMAINS
Authors: Marcos do Ó João , Lorca Sebastián , Ubilla Pedro 
Published: May 2005

AbstractIn this paper we study the existence and multiplicity of positive radial solutions for a class of semilinear elliptic systems in bounded annular domains with non-homogeneous boundary conditions by the use of a fixed-point theorem of cone expansion/compression type.
ON THE BEHAVIOUR OF THE OSCILLATORY SOLUTIONS OF SECOND-ORDER LINEAR UNSTABLE TYPE DELAY DIFFERENTIAL EQUATIONS
Authors: Philos Ch. G. , Purnaras I. K. , Sficas Y. G. 
Published: May 2005

AbstractSecond-order linear (non-autonomous as well as autonomous) delay differential equations of unstable type are considered. In the non-autonomous case, sufficient conditions are given in order that all oscillatory solutions are bounded or all oscillatory solutions tend to zero at $\infty$. In the case where the equations are autonomous, necessary and sufficient conditions are established for all oscillatory solutions to be bounded or all oscillatory solutions to tend to zero at $\infty$.
MULTIVARIATE SAMPLING THEOREMS ASSOCIATED WITH MULTIPARAMETER DIFFERENTIAL OPERATORS
Authors: Annaby M. H. 
Published: May 2005

AbstractWe investigate the multivariate sampling theory associated with multiparameter eigenvalue problems. A several-variable counterpart of the classical sampling theorem of Whittaker, Kotel’nikov and Shannon is given. It arose when the multiparameter system has order one. Two-dimensional sampling theorems associated with two-parameter systems of second-order differential operators will be established. The sampling formulae are of multivariate non-uniform Lagrange interpolation type. Unlike many of the known formulae, the interpolating functions are not necessarily products of single variable functions.
CLASSIFICATION OF LAGRANGIAN SURFACES OF CONSTANT CURVATURE IN THE COMPLEX EUCLIDEAN PLANE
Authors: Chen Bang-Yen 
Published: May 2005

AbstractOne of the most fundamental problems in the study of Lagrangian submanifolds from a Riemannian geometric point of view is the classification of Lagrangian immersions of real-space forms into complex-space forms. In this article, we solve this problem for the most basic case; namely, we classify Lagrangian surfaces of constant curvature in the complex Euclidean plane $\mathbb{C}^2$. Our main result states that there exist 19 families of Lagrangian surfaces of constant curvature in $\mathbb{C}^2$. Twelve of the 19 families are obtained via Legendre curves. Conversely, Lagrangian surfaces of constant curvature in $\mathbb{C}^2$ can be obtained locally from the 19 families.