Functional Units (functional + unit)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Process Cost Comparison for Conventional and Near-Net-Shape Cermet Fabrication,

ADVANCED ENGINEERING MATERIALS, Issue 3 2010
Yuhong Xiong
Tungsten carbide,cobalt (WC,Co) is a widely used cermet that is generally fabricated into bulk parts via conventional powder metallurgy (P/M) methods. Because this material (and other cermets) is very hard and wear resistant, diamond grinding is generally required to fabricate complex parts. As an alternative, studies have shown the Laser Engineering Net Shaping (LENS) process to be a technically feasible method, allowing for fabrication of near-net-shape parts. The economic trade-offs, however, have not been previously characterized. In this work, technical cost modeling (TCM) is applied to compare the costs of fabricating WC,Co parts with the P/M process to those of the LENS process. Cost drivers are identified and sensitivity analysis is conducted. Results reveal that the uncertainty in functional unit has a significant effect on relative process costs, and the cost is sensitive to order size only if less than ten parts are produced. It is concluded that the LENS process is economically preferable if part size is small or part shape is complex. The P/M process is more suitable to produce large parts in simple shapes. [source]


ON THE ORIGIN OF MODULAR VARIATION

EVOLUTION, Issue 8 2002
Hod Lipson
Abstract We study the dynamics of modularization in a minimal substrate. A module is a functional unit relatively separable from its surrounding structure. Although it is known that modularity is useful both for robustness and for evolvability (Wagner 1996), there is no quantitative model describing how such modularity might originally emerge. Here we suggest, using simple computer simulations, that modularity arises spontaneously in evolutionary systems in response to variation, and that the amount of modular separation is logarithmically proportional to the rate of variation. Consequently, we predict that modular architectures would appear in correlation with high environmental change rates. Because this quantitative model does not require any special substrate to occur, it may also shed light on the origin of modular variation in nature. This observed relationship also indicates that modular design is a generic phenomenon that might be applicable to other fields, such as engineering: Engineering design methods based on evolutionary simulation would benefit from evolving to variable, rather than stationary, fitness criteria, as a weak and problem-independent method for inducing modularity. [source]


Gene, region and pathway level analyses in whole-genome studies

GENETIC EPIDEMIOLOGY, Issue 3 2010
Omar De la Cruz
Abstract In the setting of genome-wide association studies, we propose a method for assigning a measure of significance to pre-defined sets of markers in the genome. The sets can be genes, conserved regions, or groups of genes such as pathways. Using the proposed methods and algorithms, evidence for association between a particular functional unit and a disease status can be obtained not just by the presence of a strong signal from a SNP within it, but also by the combination of several simultaneous weaker signals that are not strongly correlated. This approach has several advantages. First, moderately strong signals from different SNPs are combined to obtain a much stronger signal for the set, therefore increasing power. Second, in combination with methods that provide information on untyped markers, it leads to results that can be readily combined across studies and platforms that might use different SNPs. Third, the results are easy to interpret, since they refer to functional sets of markers that are likely to behave as a unit in their phenotypic effect. Finally, the availability of gene-level P -values for association is the first step in developing methods that integrate information from pathways and networks with genome-wide association data, and these can lead to a better understanding of the complex traits genetic architecture. The power of the approach is investigated in simulated and real datasets. Novel Crohn's disease associations are found using the WTCCC data. Genet. Epidemiol. 34: 222,231, 2010. © 2009 Wiley-Liss, Inc. [source]


Optoelectrothermic Control of Highly Integrated Polymer-Based MEMS Applied in an Artificial Skin

ADVANCED MATERIALS, Issue 9 2009
Andreas Richter
A large-scale integration technology for MEMS based on the optoelectrothermic control of a temperature-sensitive hydrogel is described and exemplified using an imaging array system, a so-called artificial skin. The hydrogel itself acts as active functional unit, i.e., as actuator. The artificial skin comprises more than 4,000 individual actuators and provides both, visual and palpable artificial impressions of a surface. [source]


Bone Strength at Clinically Relevant Sites Displays Substantial Heterogeneity and Is Best Predicted From Site-Specific Bone Densitometry

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2002
Felix Eckstein Ph.D.
Abstract In this study we test the hypotheses that mechanical bone strength in elderly individuals displays substantial heterogeneity among clinically relevant skeletal sites, that ex situ dual-energy X-ray absorptiometry (DXA) provides better estimates of bone strength than in situ DXA, but that a site-specific approach of bone densitometry is nevertheless superior for optimal prediction of bone failure under in situ conditions. DXA measurements were obtained of the lumbar spine, the left femur, the left radius, and the total body in 110 human cadavers (age, 80.6 ± 10.5 years; 72 female, 38 male), including the skin and soft tissues. The bones were then excised, spinal and femoral DXA being repeated ex situ. Mechanical failure tests were performed on thoracic vertebra 10 and lumbar vertebra 3 (compressive loading of a functional unit), the left and right femur (side impact and vertical loading configuration), and the left and right distal radius (fall configuration, axial compression, and 3-point-bending). The failure loads displayed only very moderate correlation among sites (r = 0.39 to 0.63). Ex situ DXA displayed slightly higher correlations with failure loads compared with those of in situ DXA, but the differences were not significant and relatively small. Under in situ conditions, DXA predicted 50-60% of the variability in bone failure loads at identical (or closely adjacent) sites, but only around 20-35% at distant sites, advocating a site-specific approach of densitometry. These data suggest that mechanical competence in the elderly is governed by strong regional variation, and that its loss in osteoporosis may not represent a strictly systemic process. [source]


Differential correlates of diet and phylogeny on the shape of the premaxilla and anterior tooth in sparid fishes (Perciformes: Sparidae)

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2004
M. Linde
Abstract We explore the correlational patterns of diet and phylogeny on the shape of the premaxilla and anterior tooth in sparid fishes (Perciformes: Sparidae) from the western Mediterranean Sea. The premaxilla is less variable, and in spite of the presence of species-specific features, a common structural pattern is easily recognizable in all species (i.e. the ascending and the articular processes are fused in a single branch, as in many percoid fishes). In contrast, tooth shape is more variable, and different structural types can be recognized (e.g. canine-like or incisive). Coupling geometric morphometric and comparative methods we found that the relationship between shape, diet and phylogeny also differs between premaxilla and tooth. Thus, the shape of the premaxilla is significantly correlated with food type, whereas the shape of the teeth is not correlated with diet, and probably reflects the species phylogenetic relationships. Two biological roles, resistance against compressive forces generated in the buccal cavity and the size of the oral gape, would explain the ecomorphological patterns of the premaxilla. The premaxilla and anterior tooth appear to evolve at different rates (mosaic evolution) and represent an example of morphological traits belonging to the same functional unit but following uncoupled evolutionary pathways. [source]


Comparative Energy, Environmental, and Economic Analysis of Traditional and E-commerce DVD Rental Networks

JOURNAL OF INDUSTRIAL ECOLOGY, Issue 3 2007
Deepak Sivaraman
This study is a comparative life-cycle assessment (LCA) of two competing digital video disc (DVD) rental networks: the e-commerce option, where the customer orders the movies online, and the traditional business option, where the customer goes to the rental store to rent a movie. The analytical framework proposed is for a customer living in the city of Ann Arbor, Michigan in the United States. The primary energy and environmental performance for both networks are presented using a multicriterion LCA. The package selected by the traditional network is responsible for 67% of the difference in total energy consumption of the two alternatives. Results show that the e-commerce alternative consumed 33% less energy and emitted 40% less CO2 than the traditional option. A set of sensitivity analyses test the influence of distance traveled, transportation mode, and reuse of DVD and DVD packaging on the final results. The mode of transportation used by the customer in the traditional business model also affects global emissions and energy consumption. The customer walking to the store is by far the best option in the traditional network; however, the e-commerce option performed comparatively better despite all transportation modes tested. A novel economic indicator, ESAL, is used to compare different transportation modes based on the level of stress exerted on the pavement. The two networks are compared on the basis of cost accounting; consistent with its energy and environmental advantages, the e-commerce network also exerts lesser economic impact, by $1.17, for the functional unit tested. [source]


Green Energy or Organic Food?: A Life-Cycle Assessment Comparing Two Uses of Set-Aside Land

JOURNAL OF INDUSTRIAL ECOLOGY, Issue 3 2001
Richard van den Broek
Summary Bioenergy has a large worldwide potential in future climate change abatement, although its application may become limited by demands for land for other functions. The aim of this study was to make an environmental assessment of the use of energy crops in the Netherlands in a context that incorporates scarcity of land. A base case system was defined, consisting of conventional winter wheat production, set-aside land (1 hectare, together), and the production of coal-based electricity. Using life-cycle assessment, we compared this system with (1) a green energy system in which willow is cultivated on the set-aside land to replace the coal-based electricity and (2) an organic agriculture system in which the full hectare produces wheat under the Dutch EKO organic agriculture standard. In this way, the functional unit and the amount of land used is the same in each system. The final system comparison was based on normalized scores per environmental theme. The green energy system scored the best with respect to acidification, climate change, and energy carrier depletion. The organic food system scored best on terrestrial eco-toxicity and slightly better on the mutually related themes of seawater and seawater sediment eco-toxicity. The base case system performed slightly better with regard to eutrophication. Preferences, from an environmental point of view, for one of the systems should be determined by environmental policy priorities and the severity of local environmental problems. The case studied here shows that when climate change, energy carrier depletion, and acidification are the main drivers behind environmental policy, one should focus not on the extensification of agriculture, but rather dedicate more land to energy crops. Extensification of agriculture would be the preferred system when toxicity from pesticides is considered the main problem. [source]


Distribution patterns of ,- and ,-herpesviruses within Waldeyer's ring organs

JOURNAL OF MEDICAL VIROLOGY, Issue 8 2007
Christoph Berger
Abstract The Waldeyer's ring designates a functional unit of lymphoid tissue within the pharynx including the adenoids and tonsils. To gain insight into distribution patterns of ,- and ,-human herpesviruses (HHVs) and their potential mutual influences at their natural portal of entry, quantitative polymerase chain reaction (qPCR) assays were applied to adenoids and tonsils obtained from 30 children. DNA of Epstein-Barr virus (EBV), cytomegalovirus (CMV), HHV-6, HHV-7, and HHV-8 was detected in adenoids, tonsils, or both of 24 (80%), 19 (63%), 23 (77%), 23 (77%), and 0 (0%) children, respectively. EBV, CMV, HHV-6, and -7 localized in both adenoids and tonsils from 92%, 37%, 52%, and 70% of children, respectively, with the virus detectable by qPCR. The amount of EBV was 2,10-fold higher than of other HHVs and correlated in autologous organs (P,=,0.01) as did the amount of HHV-7 (P,=,0.002). The amount of CMV correlated with the HHV-6 amount in adenoids (P,=,0.028) and tonsils (P,=,0.007), and with the amount of HHV-7 in adenoids (P,<,0.01). Levels of HHV-6 DNA were lower in adenoids with detectable CMV DNA than in adenoids without detectable CMV DNA (P,=,0.0062). Inversely, CMV and HHV-7 levels were higher in adenoids with than in adenoids without detectable EBV DNA (P,=,0.019 and P,=,0.039, respectively).Thus, ,- and ,-HHV exhibit distinct distribution behaviors in Waldeyer's ring organs and seem to interact. This may be of medical importance in immunocompromised hosts who are likely to reactivate HHVs causing severe morbidity and death. J. Med. Virol. 79: 1147,1152, 2007. © 2007 Wiley-Liss, Inc. [source]


Development of the cypriniform protrusible jaw complex in Danio rerio: Constructional insights for evolution

JOURNAL OF MORPHOLOGY, Issue 7 2010
Katie Lynn Staab
Abstract Studies on the evolution of complex biological systems are difficult because the construction of these traits cannot be observed during the course of evolution. Complex traits are defined as consisting of multiple elements, often of differing embryological origins, with multiple linkages integrated to form a single functional unit. An example of a complex system is the cypriniform oral jaw apparatus. Cypriniform fishes possess an upper jaw characterized by premaxillary protrusion during feeding. Cypriniforms effect protrusion via the kinethmoid, a synapomorphy for the order. The kinethmoid is a sesamoid ossification suspended by ligaments attaching to the premaxillae, maxillae, palatines, and neurocranium. Upon mouth opening, the kinethmoid rotates as the premaxillae move anteriorly. Along with bony and ligamentous elements, there are three divisions of the adductor mandibulae that render this system functional. It is unclear how cypriniform jaws evolved because although the evolution of sesamoid elements is common, the incorporation of the kinethmoid into the protrusible jaw results in a function that is atypical for sesamoids. Developmental studies can show how biological systems are assembled within individuals and offer clues about how traits might have been constructed during evolution. We investigated the development of the protrusible upper jaw in zebrafish to generate hypotheses regarding the evolution of this character. Early in development, the adductor mandibulae arises as a single unit. The muscle divides after ossification of the maxillae, on which the A1 division will ultimately insert. A cartilaginous kinethmoid first develops within the intermaxillary ligament; it later ossifies at points of ligamentous attachment. We combine our structural developmental data with published kinematic data at key developmental stages and discuss potential functional advantages in possessing even the earliest stages of a system for protrusion. J. Morphol. 2010. © 2010 Wiley-Liss, Inc. [source]


Comparative and functional morphology of the buccal cavity of Diplogastrina (Nematoda) and a first outline of the phylogeny of this taxon*

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 1 2000
A. Fürst Von Lieven
The Diplogastrina include about 290 species of free living nematodes. Traditional classifications of this taxon are not based upon hypotheses of phylogenetic relationships. The highly variable structures of the buccal cavity were examined in 21 species using light microscopy and SEM. The function of the stomatal structures was studied with the aid of video recordings of living worms. The morphological data were used to reconstruct a first outline of the phylogenetic relationships of the Dipolgastrina. A rhabditoid gymnostomatal tube which is longer than wide, a short stegostom and a small dorsal tooth as in Pseudodiplogasteroides belong to the stem species pattern of Diplogastrina. Diplogastrina with a ,Rhabditis'-like gymnostomatal tube feed on bacteria and small fungal spores. A short and broad gymnostom as well as a right subventral tooth which forms a functional unit with the dorsal tooth were acquired step by step in the ancestral line leading to Mononchoides and Tylopharynx. The cuticularized cheilostom was divided into six plates connected by pliable regions twice independently within the Diplogastrina. The teeth-bearing posterior part of the buccal capsule can move forewards by pushing apart the plates of the cheilostom so that the teeth can get in contact with food items that are too big to be sucked into the buccal cavity. Diplogastrina with a divided cheilostom can feed not only on bacteria, but also on larger fungal spores, ciliates or other nematodes. Tylopharynx is specialized to rip apart the cell wall of fungal hyphae with the movements of a dorsal and a subventral tooth in order to suck out the contents of the fungus. This shows that the transformation of the buccal cavity in Diplogastrina is linked with an expansion of ecological niches. [source]


Sources of urinary proteins and their analysis by urinary proteomics for the detection of biomarkers of disease

PROTEOMICS - CLINICAL APPLICATIONS, Issue 9 2009
Bruce A. Julian
Abstract Renal disorders account for a substantial fraction of the budget for health care in many countries. Proteinuria is a frequent manifestation in afflicted patients, but the origin of the proteins varies based on the nature of the disorder. The emerging field of urinary proteomics has the potential to replace kidney biopsy as the diagnostic procedure of choice for patients with some glomerular forms of renal disease. To fully realize this potential, it is vital to understand the basis for the urinary excretion of protein in physiological and pathological conditions. In this review, we discuss the structure of the nephron, the functional unit of the kidney, and the process by which proteins/peptides enter the urine. We discuss several aspects of proteinuria that impact the proteomic analysis of urine of patients with renal diseases. [source]


Structural characterization of tartrate dehydrogenase: a versatile enzyme catalyzing multiple reactions

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2010
Radhika Malik
The first structure of an NAD-dependent tartrate dehydrogenase (TDH) has been solved to 2,Å resolution by single anomalous diffraction (SAD) phasing as a complex with the intermediate analog oxalate, Mg2+ and NADH. This TDH structure from Pseudomonas putida has a similar overall fold and domain organization to other structurally characterized members of the hydroxy-acid dehydrogenase family. However, there are considerable differences between TDH and these functionally related enzymes in the regions connecting the core secondary structure and in the relative positioning of important loops and helices. The active site in these complexes is highly ordered, allowing the identification of the substrate-binding and cofactor-binding groups and the ligands to the metal ions. Residues from the adjacent subunit are involved in both the substrate and divalent metal ion binding sites, establishing a dimer as the functional unit and providing structural support for an alternating-site reaction mechanism. The divalent metal ion plays a prominent role in substrate binding and orientation, together with several active-site arginines. Functional groups from both subunits form the cofactor-binding site and the ammonium ion aids in the orientation of the nicotinamide ring of the cofactor. A lysyl amino group (Lys192) is the base responsible for the water-mediated proton abstraction from the C2 hydroxyl group of the substrate that begins the catalytic reaction, followed by hydride transfer to NAD. A tyrosyl hydroxyl group (Tyr141) functions as a general acid to protonate the enolate intermediate. Each substrate undergoes the initial hydride transfer, but differences in substrate orientation are proposed to account for the different reactions catalyzed by TDH. [source]


Modulation of calcium signalling by intracellular organelles seen with targeted aequorins

ACTA PHYSIOLOGICA, Issue 1 2009
M. T. Alonso
Abstract The cytosolic Ca2+ signals that trigger cell responses occur either as localized domains of high Ca2+ concentration or as propagating Ca2+ waves. Cytoplasmic organelles, taking up or releasing Ca2+ to the cytosol, shape the cytosolic signals. On the other hand, Ca2+ concentration inside organelles is also important in physiology and pathophysiology. Comprehensive study of these matters requires to measure [Ca2+] inside organelles and at the relevant cytosolic domains. Aequorins, the best-known chemiluminescent Ca2+ probes, are excellent for this end as they do not require stressing illumination, have a large dynamic range and a sharp Ca2+ -dependence, can be targeted to the appropriate location and engineered to have the proper Ca2+ affinity. Using this methodology, we have evidenced the existence in chromaffin cells of functional units composed by three closely interrelated elements: (1) plasma membrane Ca2+ channels, (2) subplasmalemmal endoplasmic reticulum and (3) mitochondria. These Ca2+ -signalling triads optimize Ca2+ microdomains for secretion and prevent propagation of the Ca2+ wave towards the cell core. Oscillatory cytosolic Ca2+ signals originate also oscillations of mitochondrial Ca2+ in several cell types. The nuclear envelope slows down the propagation of the Ca2+ wave to the nucleus and filters high frequencies. On the other hand, inositol-trisphosphate may produce direct release of Ca2+ to the nucleoplasm in GH3 pituitary cells, thus providing mechanisms for selective nuclear signalling. Aequorins emitting at different wavelengths, prepared by fusion either with green or red fluorescent protein, permit simultaneous and independent monitorization of the Ca2+ signals in different subcellular domains within the same cell. [source]


Comparative expression analysis of transcription factor genes in the endostyle of invertebrate chordates

DEVELOPMENTAL DYNAMICS, Issue 3 2005
Jin Hiruta
Abstract The endostyle of invertebrate chordates is a pharyngeal organ that is thought to be homologous with the follicular thyroid of vertebrates. Although thyroid-like features such as iodine-concentrating and peroxidase activities are located in the dorsolateral part of both ascidian and amphioxus endostyles, the structural organization and numbers of functional units are different. To estimate phylogenetic relationships of each functional zone with special reference to the evolution of the thyroid, we have investigated, in ascidian and amphioxus, the expression patterns of thyroid-related transcription factors such as TTF-2/FoxE4 and Pax2/5/8, as well as the forkhead transcription factors FoxQ1 and FoxA. Comparative gene expression analyses depicted an overall similarity between ascidians and amphioxus endostyles, while differences in expression patterns of these genes might be specifically related to the addition or elimination of a pair of glandular zones. Expressions of Ci-FoxE and BbFoxE4 suggest that the ancestral FoxE class might have been recruited for the formation of thyroid-like region in a possible common ancestor of chordates. Furthermore, coexpression of FoxE4, Pax2/5/8, and TPO in the dorsolateral part of both ascidian and amphioxus endostyles suggests that genetic basis of the thyroid function was already in place before the vertebrate lineage. Developmental Dynamics 233:1031,1037, 2005. © 2005 Wiley-Liss, Inc. [source]


Syntheses of Triostin A Antibiotic and Nucleobase-Functionalized Analogs as New DNA Binders

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 28 2009
Anmol Kumar Ray
Abstract A total synthesis of the natural product triostin A, wherein the N -methylated depsipeptide scaffold is constructed by solution-phase peptide chemistry followed by disulfide formation and macrocyclization, is described. Finally, the quinoxalines were attached to provide the DNA bisintercalator. Analogs of triostin A were obtained by the successive functionalization of the cyclic depsipeptide with pyrimidine or purine recognition units. The attachment of functional units was achieved by the orthogonal protection of the respective side chain amino functionalities. The nucleobase-functionalized triostin analogs have the potential to recognize double-stranded DNA by hydrogen bonding. The interaction with DNA was investigated by UV spectroscopy and fluorescence intercalator displacement. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


Evolving modular networks with genetic algorithms: application to nonlinear time series

EXPERT SYSTEMS, Issue 4 2004
A.S. Cofiño
Abstract: A key problem of modular neural networks is finding the optimal aggregation of the different subtasks (or modules) of the problem at hand. Functional networks provide a partial solution to this problem, since the inter-module topology is obtained from domain knowledge (functional relationships and symmetries). However, the learning process may be too restrictive in some situations, since the resulting modules (functional units) are assumed to be linear combinations of selected families of functions. In this paper, we present a non-parametric learning approach for functional networks using feedforward neural networks for approximating the functional modules of the resulting architecture; we also introduce a genetic algorithm for finding the optimal intra-module topology (the appropriate balance of neurons for the different modules according to the complexity of their respective tasks). Some benchmark examples from nonlinear time-series prediction are used to illustrate the performance of the algorithm for finding optimal modular network architectures for specific problems. [source]


Design syntheses and mitochondrial complex I inhibitory activity of novel acetogenin mimics

FEBS JOURNAL, Issue 9 2000
Kaoru Kuwabara
Some natural acetogenins are the most potent inhibitors of mitochondrial complex I. These compounds are characterized by two functional units [i.e. hydroxylated tetrahydrofuran (THF) and ,,,-unsaturated ,-lactone ring moieties] separated by a long alkyl spacer. To elucidate which structural factors of acetogenins, including their active conformation, are crucial for the potent inhibitory activity we synthesized a novel bis-acetogenin and its analogues possessing two ,-lactone rings connected to bis-THF rings by flexible alkyl spacers. The inhibitory potency of the bis-acetogenin with bovine heart mitochondrial complex I was identical to that of bullatacin, one of the most potent natural acetogenins. This result indicated that one molecule of the bis-acetogenin does not work as two reactive inhibitors, suggesting that a ,-lactone and the THF ring moieties act in a cooperative manner on the enzyme. In support of this, either of the two ring moieties synthesized individually showed no or very weak inhibitory effects. Moreover, combined use of the two ring moieties at various molar ratios exhibited no synergistic enhancement of the inhibitory potency. These observations indicate that both functional units work efficiently only when they are directly linked by a flexible alkyl spacer. Therefore, some specific conformation of the spacer must be important for optimal positioning of the two units in the enzyme. Furthermore, the ,,,-unsaturated ,-lactone, the 4-OH group in the spacer region, the long alkyl tail attached to the THF unit and the stereochemistry surrounding the hydroxylated bis-THF rings were not crucial for the activity, although these are the most common structural features of natural acetogenins. The present study provided useful guiding principles not only for simplification of complicated acetogenin structure, but also for further wide structural modifications of these molecules. [source]


Clean and Flexible Modification Strategy for Carboxyl/Aldehyde-Functionalized Upconversion Nanoparticles and Their Optical Applications

ADVANCED FUNCTIONAL MATERIALS, Issue 24 2009
Huan-Ping Zhou
Abstract Rare-earth upconversion nanoparticles (UCNPs) exhibit great potential in luminescent biolabels and other multifunctional probes; however, their applications are limited by their low water solubility and the lack of binding groups. To address these problems, a clean and flexible strategy to modify hydrophobic monodisperse UCNPs into hydrophilic ones that are capped with functional groups is developed. The modification process is implemented by direct oxidation of oleic acid ligands with ozone under specific conditions, where the oleic acid (OA) ligands on the surface of the UCNPs can be converted into azelaic acid ligands (HOOC(CH2)7COOH) or azelaic aldehyde HOOC(CH2)7CHO, as is revealed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) measurements. This oxidation process has no significant side-effects on the morphology, phase, composition, or luminescent properties of the UCNPs. Free carboxylic acid groups on the surface endow the UCNPs with good water solubility, while aldehyde groups at the surface provide binding sites for amino-containing molecules via Schiff-base condensation, such as 2-(4-aminophenylethylyl)-5-methoxy-2-(2-pyridyl)thiazole (MPTEA) and 2-aminoethanethiol hydrochloride (NH2CH2CH2SH·HCl, HEMA). A Ce4+ sensor is constructed based on the dual-emission arising from the different spectral responses of MPTEA and the UCNPs. Facilitated by the covalent linkage between the terminal aldehyde group on the UCNPs and the amino group in HEMA, a hybrid structure of UCNPs and Au NPs is fabricated. The effective coupling between the aldehyde group and the amino group suggests that these functionalized UCNPs have potential in combining other functional units for simultaneous biolabeling, or other optical applications. [source]


Aligned Carbon Nanotubes with Ferromagnetic Behavior

ADVANCED MATERIALS, Issue 4 2010
Eleni C. Vermisoglou
Magnetic carbon nanotube (CNT) arrays are grown by in situ encapsulation of ferromagnetic iron carbide nanoparticles within the tube walls (see figure). The resulting structures, combining the inherently unique characteristics of aligned and open-ended CNTs with the fact that magnetic functionality is provided from "inside the walls", are promising functional units in highly efficient flow systems, for example, as parallel magnetic nanoreactors and in biological separations. [source]


Highly Periodic Fullerene Nanomesh,

ADVANCED MATERIALS, Issue 2 2006
N. Néel
Fullerene nanomesh: Fullerene islands with rectangular shapes organize themselves on a vicinal gold surface in an extraordinarily well-ordered mesh with unprecedented periodicity and low defect density (see Figure). This adsorbate system is a promising candidate for guiding subsequent deposition of functional units. [source]


Modular changes of cis-regulatory elements from two functional Pit1 genes in the duplicated genome of Cyprinus carpio

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2006
G. Kausel
Abstract The pituitary-specific transcription factor Pit1 is involved in its own regulation and in a network of transcriptional regulation of hypothalamo-hypophyseal factors including prolactin (PRL) and growth hormone (GH). In the ectotherm teleost Cyprinus carpio, Pit1 plays an important role in regulation of the adaptive response to seasonal environmental changes. Two Pit1 genes exist in carp, a tetraploid vertebrate and transcripts of both genes were detected by RT-PCR analysis. Powerful comparative analyses of the 5,-flanking regions revealed copy specific changes comprising modular functional units in the naturally evolved promoters. These include the precise replacement of four nucleotides around the transcription start site embedded in completely conserved regions extending upstream of the TATA-box, an additional transcription factor binding site in the 5,-UTR of gene-I and, instead, duplication of a 9 bp element in gene-II. Binding of nuclear factors was assessed by electro mobility shift assays using extracts from rat pituitary cells and carp pituitary. Binding was confirmed at one conserved Pit1, one conserved CREB and one consensus MTF1. Interestingly, two functional Pit1 sites and one putative MTF1 binding site are unique to the Pit1 gene-I. In situ hybridization experiments revealed that the expression of gene-I in winter carp was significantly stronger than that of gene-II. Our data suggest that the specific control elements identified in the proximal regulatory region are physiologically relevant for the function of the duplicated Pit1 genes in carp and highlight modular changes in the architecture of two Pit1 genes that evolved for at least 12 MYA in the same organism. J. Cell. Biochem. 99: 905,921, 2006. © 2006 Wiley-Liss, Inc. [source]


Ultrastructure of the hindgut of Drosophila larvae, with special reference to the domains identified by specific gene expression patterns

JOURNAL OF MORPHOLOGY, Issue 2 2001
Ryutaro Murakami
Abstract The hindgut of Drosophila larvae consists of nine domains that have been distinguished by specific gene expression patterns. In the present study, we examined the ultrastructure of the hindgut of Drosophila larvae, with special reference to the domains, in order to determine whether or not the domains are morphologically distinct functional units. Each domain showed specific ultrastructural features that suggested specific corresponding functions. According to the morphological features, terms are proposed for each domain: the imaginal ring; the "pylorus," which has a thick cuticular layer and well-developed sphincter muscles; the "large intestine," which occupies a major middle portion of the hindgut and has a unique dorsal and ventral subdivision; "border cells," which delineate the anterior and posterior borders of the large intestine and the border between the dorsal and ventral domains of the large intestine; and the "rectum," which is situated at the posterior end of the hindgut and has a thick cuticular layer and sphincter muscles. The morphological features indicate that the large intestine has active absorptive activities. The domains, which have been distinguished by gene expressions, were demonstrated to be functional tissue units of the gut. J. Morphol. 248:144,150, 2001. © 2001 Wiley-Liss, Inc. [source]


Axon or dendrite? cell biology and molecular pathways for neuronal cell asymmetry

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2008
Masashi Kishi
Abstract Young neurons polarize by specializing axons and dendrites from immature neurites. After synapse formations, they transmit electrical activity along the axon-dendrite axis, thereby working as functional units of the neural circuits. This axon-dendrite asymmetry is referred to as neuronal polarity. Although a great number of cell biological studies in vitro had been performed, little was known about the molecular events that establish the polarity. In the last several years, rapid advancement in molecular and genetic studies has unraveled the multiple signaling pathways. This paper summarizes current perspectives on the cell and molecular biological mechanisms of the neuronal polarization, to clarify future directions in this growing research field. © 2007 Wiley-Liss, Inc. [source]


Mapping at glomerular resolution: fMRI of rat olfactory bulb

MAGNETIC RESONANCE IN MEDICINE, Issue 3 2002
Ikuhiro Kida
Abstract The rat olfactory bulb contains ,2000 functional units called glomeruli which are used to recognize specific characteristics of odorants. Activity localization of individual glomerulae (,0.002 ,L) has important consequences for understanding mechanisms in olfactory information encoding. High-resolution functional MRI (fMRI) data from the rat olfactory bulb are presented using the blood oxygenation level dependent (BOLD) method at 7 T. Either individual or clusters of fMRI voxels suggestive of activity in the olfactory nerve and glomerular layers were reproducibly detected with repeated 2-min exposures of iso-amyl acetate at spatial resolution of 0.001,0.003 ,L. The importance of glomerular clustering for olfaction and the implications of BOLD mapping with even higher spatial resolution (i.e., ,0.001 ,L voxels) are discussed. High-resolution in vivo mapping of the rat olfactory bulb with fMRI at high magnetic field promises to provide novel data for understanding olfaction. Magn Reson Med 48:570,576, 2002. © 2002 Wiley-Liss, Inc. [source]


Patterning by genetic networks

MATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2006
S. Genieys
Abstract We consider here the morphogenesis (pattern formation) problem for some genetic network models. First, we show that any given spatio-temporal pattern can be generated by a genetic network involving a sufficiently large number of genes. Moreover, patterning process can be performed by an effective algorithm. We also show that Turing's or Meinhardt's type reaction,diffusion models can be approximated by genetic networks. These results exploit the fundamental fact that the genes form functional units and are organized in blocks. Due to this modular organization, the genes always are capable to construct any new patterns and even any time sequences of new patterns from old patterns. Computer simulations illustrate some analytical results. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Fine-scale spatial genetic structure and dispersal among spotted salamander (Ambystoma maculatum) breeding populations

MOLECULAR ECOLOGY, Issue 2 2007
KELLY R. ZAMUDIO
Abstract We examined fine-scale genetic variation among breeding aggregations of the spotted salamander (Ambystoma maculatum) to quantify dispersal, interpopulation connectivity and population genetic structure. Spotted salamanders rely on temporary ponds or wetlands for aggregate breeding. Adequate breeding sites are relatively isolated from one another and field studies suggest considerable adult site fidelity; therefore, we expected to find population structure and differentiation at small spatial scales. We used microsatellites to estimate population structure and dispersal among 29 breeding aggregations in Tompkins County, New York, USA, an area encompassing 1272 km2. Bayesian and frequency-based analyses revealed fine-scale genetic structure with two genetically defined demes: the North deme included seven breeding ponds, and the South deme included 13 ponds. Nine ponds showed evidence of admixture between these two genetic pools. Bayesian assignment tests for detection of interpopulation dispersal indicate that immigration among ponds is common within demes, and that certain populations serve as sources of immigrants to neighbouring ponds. Likewise, spatial genetic correlation analyses showed that populations , 4.8 km distant from each other show significant genetic correlation that is not evident at higher scales. Within-population levels of relatedness are consistently larger than expected if mating were completely random across ponds, and in the case of a few ponds, within-population processes such as inbreeding or reproductive skew contribute significantly to differentiation from neighbouring ponds. Our data underscore the importance of these within-population processes as a source of genetic diversity across the landscape, despite considerable population connectivity. Our data further suggest that spotted salamander breeding groups behave as metapopulations, with population clusters as functional units, but sufficient migration among demes to allow for potential rescue and recolonization. Amphibian habitats are becoming increasingly fragmented and a clear understanding of dispersal and patterns of population connectivity for taxa with different ecologies and life histories is crucial for their conservation. [source]


Role of motor unit structure in defining function

MUSCLE AND NERVE, Issue 7 2001
Ryan J. Monti PhD
Abstract Motor units, defined as a motoneuron and all of its associated muscle fibers, are the basic functional units of skeletal muscle. Their activity represents the final output of the central nervous system, and their role in motor control has been widely studied. However, there has been relatively little work focused on the mechanical significance of recruiting variable numbers of motor units during different motor tasks. This review focuses on factors ranging from molecular to macroanatomical components that influence the mechanical output of a motor unit in the context of the whole muscle. These factors range from the mechanical properties of different muscle fiber types to the unique morphology of the muscle fibers constituting a motor unit of a given type and to the arrangement of those motor unit fibers in three dimensions within the muscle. We suggest that as a result of the integration of multiple levels of structural and physiological levels of organization, unique mechanical properties of motor units are likely to emerge. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 848,866, 2001 [source]


Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americana

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 19 2010
Hidehiro Watanabe
Abstract Glomeruli are structural and functional units in the primary olfactory center in vertebrates and insects. In the cockroach Periplaneta americana, axons of different types of sensory neurons housed in sensilla on antennae form dorsal and ventral antennal nerves and then project to a number of glomeruli. In this study, we identified all antennal lobe (AL) glomeruli based on detailed innervation patterns of sensory tracts in addition to the shape, size, and locations in the cockroach. The number of glomeruli is ,205, and no sex-specific difference is observed. Anterograde dye injections into the antennal nerves revealed that axons supplying the AL are divided into 10 sensory tracts (T1,T10). Each of T1,T3 innervates small, oval glomeruli in the anteroventral region of the AL, with sensory afferents invading each glomerulus from multiple directions, whereas each of T4,T10 innervates large glomeruli with various shapes in the posterodorsal region, with a bundle of sensory afferents invading each glomerulus from one direction. The topographic branching patterns of all these tracts are conserved among individuals. Sensory afferents in a sub-tract of T10 had axon terminals in the dorsal margin of the AL and the protocerebrum, where they form numerous small glomerular structures. Sensory nerve branching pattern should reflect developmental processes to determine spatial arrangement of glomeruli, and thus the complete map of glomeruli based on sensory nerve branching pattern should provide a basis for studying the functional significance of spatial arrangement of glomeruli and its developmental basis. J. Comp. Neurol. 518:3907,3930, 2010. © 2010 Wiley-Liss, Inc. [source]


Compartmentalization of the precheliceral neuroectoderm in the spider Cupiennius salei: Development of the arcuate body, optic ganglia, and mushroom body

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 13 2010
Carola Doeffinger
Abstract Similarly to vertebrates, arthropod brains are compartmentalized into centers with specific neurological functions such as cognition, behavior, and memory. The centers can be further subdivided into smaller functional units. This raises the question of how these compartments are formed during development and how they are integrated into brain centers. We show here for the first time how the precheliceral neuroectoderm of the spider Cupiennius salei is compartmentalized to form the distinct brain centers of the visual system: the optic ganglia, the mushroom bodies, and the arcuate body. The areas of the visual brain centers are defined by the formation of grooves and vesicles and express the proneural gene CsASH1, followed by expression of the neural differentiation marker Prospero. Furthermore, the transcription factor dachshund, which is strongly enriched in the mushroom bodies and the outer optic ganglion of Drosophila, is expressed in the optic anlagen and the mushroom bodies of the spider. The developing brain centers are further subdivided into single neural precursor groups, which become incorporated into the grooves and vesicles but remain distinguishable throughout development, suggesting that they encode spatial information for neural subtype identity. Several molecular and morphological aspects of the development of the optic ganglia and the mushroom bodies are similar in the spider and in insects. Furthermore, we show that the primary engrailed head spot contributes neurons to the optic ganglia of the median eyes, whereas the secondary head spot, which has been associated with the optic ganglia in insects and crustaceans, is absent. J. Comp. Neurol. 518:2612,2632, 2010. © 2010 Wiley-Liss, Inc. [source]