WorldWideScience

Sample records for cell size control

  1. Stochastic Modeling of Bacteria Cell Size Control and Homeostasis

    Science.gov (United States)

    Chen, Yanyan; Buceta, Javier

    Besides recent breakthroughs, there is a gap of knowledge about the mechanisms underlying cell size control and homeostasis. In this context, recent studies support the incremental rule in rod-shaped bacteria: cells add a constant length to their size before dividing which is independent of their size at birth. This growing pattern, when coupled with the mid-cell division mechanism, leads to size convergence and homeostasis. However, some aberrantly long mutant strains of E. coli, e.g. ΔFtsW, do not typically divide at the middle. Whether cell size control and homeostasis apply to those mutant backgrounds, or the role played by biomechanical cues, remain open questions. Here we present a combination of theoretical, experimental, and computational approaches to address these questions. First, we introduce a Markov chain model that describes either wild-type (wt) strains or growth-defective strains. Second, we propose a polymer-like model to account for the mechanical inputs. Finally, we test experimentally some of our predictions by using wt and conditional mutant (ΔFtsW) strains. Altogether, our preliminary studies suggest a way to unify the principles of cell size control and homeostasis of wt and growth-defective cell strains.

  2. How Cells Can Control Their Size by Pumping Ions

    Directory of Open Access Journals (Sweden)

    Alan R. Kay

    2017-05-01

    Full Text Available The ability of all cells to set and regulate their size is a fundamental aspect of cellular physiology. It has been known for sometime but not widely so, that size stability in animal cells is dependent upon the operation of the sodium pump, through the so-called pump-leak mechanism (Tosteson and Hoffman, 1960. Impermeant molecules in cells establish an unstable osmotic condition, the Donnan effect, which is counteracted by the operation of the sodium pump, creating an asymmetry in the distribution of Na+ and K+ staving off water inundation. In this paper, which is in part a tutorial, I show how to model quantitatively the ion and water fluxes in a cell that determine the cell volume and membrane potential. The movement of water and ions is constrained by both osmotic and charge balance, and is driven by ion and voltage gradients and active ion transport. Transforming these constraints and forces into a set of coupled differential equations allows us to model how the ion distributions, volume and voltage change with time. I introduce an analytical solution to these equations that clarifies the influence of ion conductances, pump rates and water permeability in this multidimensional system. I show that the number of impermeant ions (x and their average charge have a powerful influence on the distribution of ions and voltage in a cell. Moreover, I demonstrate that in a cell where the operation of active ion transport eliminates an osmotic gradient, the size of the cell is directly proportional to x. In addition, I use graphics to reveal how the physico-chemical constraints and chemical forces interact with one another in apportioning ions inside the cell. The form of model used here is applicable to all membrane systems, including mitochondria and bacteria, and I show how pumps other than the sodium pump can be used to stabilize cells. Cell biologists may think of electrophysiology as the exclusive domain of neuroscience, however the electrical

  3. The TOR Signaling Pathway in Spatial and Temporal Control of Cell Size and Growth

    Directory of Open Access Journals (Sweden)

    Suam Gonzalez

    2017-06-01

    Full Text Available Cell size is amenable by genetic and environmental factors. The highly conserved nutrient-responsive Target of Rapamycin (TOR signaling pathway regulates cellular metabolic status and growth in response to numerous inputs. Timing and duration of TOR pathway activity is pivotal for both cell mass built up as well as cell cycle progression and is controlled and fine-tuned by the abundance and quality of nutrients, hormonal signals, growth factors, stress, and oxygen. TOR kinases function within two functionally and structurally discrete multiprotein complexes, TORC1 and TORC2, that are implicated in temporal and spatial control of cell size and growth respectively; however, recent data indicate that such functional distinctions are much more complex. Here, we briefly review roles of the two complexes in cellular growth and cytoarchitecture in various experimental model systems.

  4. Comparative analysis of cells and proteins of pumpkin plants for the control of fruit size.

    Science.gov (United States)

    Nakata, Yumiko; Taniguchi, Go; Takazaki, Shinya; Oda-Ueda, Naoko; Miyahara, Kohji; Ohshima, Yasumi

    2012-09-01

    Common pumpkin plants (Cucurbita maxima) produce fruits of 1-2 kg size on the average, while special varieties of the same species called Atlantic Giant are known to produce a huge fruit up to several hundred kilograms. As an approach to determine the factors controlling the fruit size in C. maxima, we cultivated both AG and control common plants, and found that both the cell number and cell sizes were increased in a large fruit while DNA content of the cell did not change significantly. We also compared protein patterns in the leaves, stems, ripe and young fruits by two-dimensional (2D) gel electrophoresis, and identified those differentially expressed between them with mass spectroscopy. Based on these results, we suggest that factors in photosynthesis such as ribulose-bisphosphate carboxylase, glycolysis pathway enzymes, heat-shock proteins and ATP synthase play positive or negative roles in the growth of a pumpkin fruit. These results provide a step toward the development of plant biotechnology to control fruit size in the future. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  5. Control of cell proliferation, endoreduplication, cell size, and cell death by the retinoblastoma-related pathway in maize endosperm

    KAUST Repository

    Sabelli, Paolo A.

    2013-04-22

    The endospermof cereal grains is one of the most valuable products of modern agriculture. Cereal endosperm development comprises different phases characterized by mitotic cell proliferation, endoreduplication, the accumulation of storage compounds, and programmed cell death. Although manipulation of these processes could maximize grain yield, how they are regulated and integrated is poorly understood. We show that the Retinoblastoma-related (RBR) pathway controls key aspects of endosperm development in maize. Down-regulation of RBR1 by RNAi resulted in up-regulation of RBR3-type genes, as well as the MINICHROMOSOME MAINTENANCE 2-7 gene family and PROLIFERATING CELL NUCLEAR ANTIGEN, which encode essential DNA replication factors. Both the mitotic and endoreduplication cell cycles were stimulated. Developing transgenic endosperm contained 42-58% more cells and ~70% more DNA than wild type, whereas there was a reduction in cell and nuclear sizes. In addition, cell death was enhanced. The DNA content of mature endosperm increased 43% upon RBR1 downregulation, whereas storage protein content and kernel weight were essentially not affected. Down-regulation of both RBR1 and CYCLIN DEPENDENT KINASE A (CDKA);1 indicated that CDKA;1 is epistatic to RBR1 and controls endoreduplication through an RBR1- dependent pathway. However, the repressive activity of RBR1 on downstream targets was independent from CDKA;1, suggesting diversification of RBR1 activities. Furthermore, RBR1 negatively regulated CDK activity, suggesting the presence of a feedback loop. These results indicate that the RBR1 pathway plays a major role in regulation of different processes during maize endosperm development and suggest the presence of tissue/organlevel regulation of endosperm/seed homeostasis.

  6. Tuning the Properties of Polymer Bulk Heterojunction Solar Cells by Adjusting Fullerene Size to Control Intercalation

    KAUST Repository

    Cates, Nichole C.

    2009-12-09

    We demonstrate that intercalation of fullerene derivatives between the side chains of conjugated polymers can be controlled by adjusting the fullerene size and compare the properties of intercalated and nonintercalated poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (pBTTT):fullerene blends. The intercalated blends, which exhibit optimal solar-cell performance at 1:4 polymer:fullerene by weight, have better photoluminescence quenching and lower absorption than the nonintercalated blends, which optimize at 1:1. Understanding how intercalation affects performance will enable more effective design of polymer:fullerene solar cells. © 2009 American Chemical Society.

  7. Structure and Electromagnetic Properties of Cellular Glassy Carbon Monoliths with Controlled Cell Size

    Directory of Open Access Journals (Sweden)

    Andrzej Szczurek

    2018-05-01

    Full Text Available Electromagnetic shielding is a topic of high importance for which lightweight materials are highly sought. Porous carbon materials can meet this goal, but their structure needs to be controlled as much as possible. In this work, cellular carbon monoliths of well-defined porosity and cell size were prepared by a template method, using sacrificial paraffin spheres as the porogen and resorcinol-formaldehyde (RF resin as the carbon precursor. Physicochemical studies were carried out for investigating the conversion of RF resin into carbon, and the final cellular monoliths were investigated in terms of elemental composition, total porosity, surface area, micropore volumes, and micro/macropore size distributions. Electrical and electromagnetic (EM properties were investigated in the static regime and in the Ka-band, respectively. Due to the phenolic nature of the resin, the resultant carbon was glasslike, and the special preparation protocol that was used led to cellular materials whose cell size increased with density. The materials were shown to be relevant for EM shielding, and the relationships between those properties and the density/cell size of those cellular monoliths were elucidated.

  8. The sexual identity of adult intestinal stem cells controls organ size and plasticity

    Science.gov (United States)

    Hudry, Bruno; Khadayate, Sanjay; Miguel-Aliaga, Irene

    2016-01-01

    SUMMARY Sex differences in physiology and disease susceptibility are commonly attributed to developmental and/or hormonal factors, but there is increasing realisation that cell-intrinsic mechanisms play important and persistent roles1,2. Here we use the Drosophila melanogaster intestine to investigate the nature and significance of cellular sex in an adult somatic organ in vivo. We find that the adult intestinal epithelium is a cellular mosaic of different sex differentiation pathways, and displays extensive sex differences in expression of genes with roles in growth and metabolism. Cell-specific reversals of the sexual identity of adult intestinal stem cells uncover its key roles in controlling organ size, its reproductive plasticity and its response to genetically induced tumours. Unlike previous examples of sexually dimorphic somatic stem cell activity, the sex differences in intestinal stem cell behaviour arise from intrinsic mechanisms, which control cell cycle duration and involve a new doublesex- and fruitless-independent branch of the sex differentiation pathway downstream of transformer. Together, our findings indicate that the plasticity of an adult somatic organ is reversibly controlled by its sexual identity, imparted by a new mechanism that may be active in more tissues than previously recognised. PMID:26887495

  9. Maternal genotype influences pea seed size by controlling both mitotic activity during early embryogenesis and final endoreduplication level/cotyledon cell size in mature seed.

    Science.gov (United States)

    Lemontey, C; Mousset-Déclas, C; Munier-Jolain, N; Boutin, J P

    2000-02-01

    When reciprocal crosses are made between different pea genotypes, there is a strong maternal influence on mature seed size of the reciprocal hybrids, i.e. their dry weights are similar to that of seeds obtained from their maternal parents. Reciprocal crosses between pea varieties having very different mature seed sizes were used to investigate how the maternal genotype controls seed development and mature seed size. The differences in dry seed weight between genotypes and reciprocal hybrids reflected differences in both cotyledon cell number and mean cell volume, and the maternal control on the establishment of these two traits was investigated. Using flow cytometry, data relative to endoreduplication kinetics in cotyledons during the transition between the cell division phase and maturation were obtained. The appearance of nuclei having an 8C DNA content indicates the initiation of the endoreduplication phenomenon and thus the end of the cell division phase. It was shown that the duration of the cell division phase was the same in the reciprocal hybrids, its value being intermediate between those recorded for their maternal parents. This result indicates that the timing of development of the embryo is not under maternal control, but depends on its own genotype. Consequently, maternal genotype must influence the mitotic rate during the cell division phase to achieve differences in cell number found in the cotyledons of mature F1-reciprocal hybrids. The final level of endoreduplication in cotyledons of mature seeds was also investigated. This study showed that there is a close relationship (r2 = 0.919) between the endoreduplication level in mature cotyledons and seed dry weight or mean volume of cotyledon cells, suggesting that both maternal and non-maternal factors could control the number of endoreduplicating cycles in the cotyledons and, hypothetically, the cotyledon cell size.

  10. Optimization of low frequency sound absorption by cell size control and multiscale poroacoustics modeling

    Science.gov (United States)

    Park, Ju Hyuk; Yang, Sei Hyun; Lee, Hyeong Rae; Yu, Cheng Bin; Pak, Seong Yeol; Oh, Chi Sung; Kang, Yeon June; Youn, Jae Ryoun

    2017-06-01

    Sound absorption of a polyurethane (PU) foam was predicted for various geometries to fabricate the optimum microstructure of a sound absorbing foam. Multiscale numerical analysis for sound absorption was carried out by solving flow problems in representative unit cell (RUC) and the pressure acoustics equation using Johnson-Champoux-Allard (JCA) model. From the numerical analysis, theoretical optimum cell diameter for low frequency sound absorption was evaluated in the vicinity of 400 μm under the condition of 2 cm-80 K (thickness of 2 cm and density of 80 kg/m3) foam. An ultrasonic foaming method was employed to modulate microcellular structure of PU foam. Mechanical activation was only employed to manipulate the internal structure of PU foam without any other treatment. A mean cell diameter of PU foam was gradually decreased with increase in the amplitude of ultrasonic waves. It was empirically found that the reduction of mean cell diameter induced by the ultrasonic wave enhances acoustic damping efficiency in low frequency ranges. Moreover, further analyses were performed with several acoustic evaluation factors; root mean square (RMS) values, noise reduction coefficients (NRC), and 1/3 octave band spectrograms.

  11. The BAR Domain Protein PICK1 Controls Vesicle Number and Size in Adrenal Chromaffin Cells

    NARCIS (Netherlands)

    Pinheiro, P.S.; Jansen, A.M.; de Wit, H.; Tawfik, B.; Madsen, K.L.; Verhage, M.; Gether, U.; Sørensen, J.B.

    2014-01-01

    Protein Interacting with C Kinase 1 (PICK1) is a Bin/Amphiphysin/Rvs (BAR) domain protein involved in AMPA receptor trafficking. Here, we identify a selective role for PICK1 in the biogenesis of large, dense core vesicles (LDCVs) in mouse chromaffin cells. PICK1 colocalized with syntaxin-6, a marker

  12. The Life Cycle of the Centric Diatom Thalassiosira Weissflogii: Control of Gametogenesis and Cell Size

    Science.gov (United States)

    1990-06-01

    were proven to possess isogamous or morphologically equivalent haploid gametes, arguments flourished as to the exact nature of sexual reproduction in...require vitamin B12, the number of bacteria -free clones of diatoms maintained in culture increased dramatically during the fifties and sixties (Lewin...these divisions is the creation of four uniflagellated haploid sperm from each spermatogonium. Thus, a C. pavillardlL cell, for example, can create as

  13. The BAR Domain Protein PICK1 Controls Vesicle Number and Size in Adrenal Chromaffin Cells

    DEFF Research Database (Denmark)

    da Silva Pinheiro, Paulo César; Jansen, Anna M; de Wit, Heidi

    2014-01-01

    Protein Interacting with C Kinase 1 (PICK1) is a Bin/Amphiphysin/Rvs (BAR) domain protein involved in AMPA receptor trafficking. Here, we identify a selective role for PICK1 in the biogenesis of large, dense core vesicles (LDCVs) in mouse chromaffin cells. PICK1 colocalized with syntaxin-6......, consistent with an upstream role for PICK1. Disrupting lipid binding of the BAR domain (2K-E mutation) or of the PDZ domain (CC-GG mutation) was sufficient to reproduce the secretion phenotype of the null mutant. The same mutations are known to eliminate PICK1 function in receptor trafficking, indicating...

  14. Fundamental principles in bacterial physiology—history, recent progress, and the future with focus on cell size control: a review

    Science.gov (United States)

    Jun, Suckjoon; Si, Fangwei; Pugatch, Rami; Scott, Matthew

    2018-05-01

    Bacterial physiology is a branch of biology that aims to understand overarching principles of cellular reproduction. Many important issues in bacterial physiology are inherently quantitative, and major contributors to the field have often brought together tools and ways of thinking from multiple disciplines. This article presents a comprehensive overview of major ideas and approaches developed since the early 20th century for anyone who is interested in the fundamental problems in bacterial physiology. This article is divided into two parts. In the first part (sections 1–3), we review the first ‘golden era’ of bacterial physiology from the 1940s to early 1970s and provide a complete list of major references from that period. In the second part (sections 4–7), we explain how the pioneering work from the first golden era has influenced various rediscoveries of general quantitative principles and significant further development in modern bacterial physiology. Specifically, section 4 presents the history and current progress of the ‘adder’ principle of cell size homeostasis. Section 5 discusses the implications of coarse-graining the cellular protein composition, and how the coarse-grained proteome ‘sectors’ re-balance under different growth conditions. Section 6 focuses on physiological invariants, and explains how they are the key to understanding the coordination between growth and the cell cycle underlying cell size control in steady-state growth. Section 7 overviews how the temporal organization of all the internal processes enables balanced growth. In the final section 8, we conclude by discussing the remaining challenges for the future in the field.

  15. The Rts1 regulatory subunit of protein phosphatase 2A is required for control of G1 cyclin transcription and nutrient modulation of cell size.

    Directory of Open Access Journals (Sweden)

    Karen Artiles

    2009-11-01

    Full Text Available The key molecular event that marks entry into the cell cycle is transcription of G1 cyclins, which bind and activate cyclin-dependent kinases. In yeast cells, initiation of G1 cyclin transcription is linked to achievement of a critical cell size, which contributes to cell-size homeostasis. The critical cell size is modulated by nutrients, such that cells growing in poor nutrients are smaller than cells growing in rich nutrients. Nutrient modulation of cell size does not work through known critical regulators of G1 cyclin transcription and is therefore thought to work through a distinct pathway. Here, we report that Rts1, a highly conserved regulatory subunit of protein phosphatase 2A (PP2A, is required for normal control of G1 cyclin transcription. Loss of Rts1 caused delayed initiation of bud growth and delayed and reduced accumulation of G1 cyclins. Expression of the G1 cyclin CLN2 from an inducible promoter rescued the delayed bud growth in rts1Delta cells, indicating that Rts1 acts at the level of transcription. Moreover, loss of Rts1 caused altered regulation of Swi6, a key component of the SBF transcription factor that controls G1 cyclin transcription. Epistasis analysis revealed that Rts1 does not work solely through several known critical upstream regulators of G1 cyclin transcription. Cells lacking Rts1 failed to undergo nutrient modulation of cell size. Together, these observations demonstrate that Rts1 is a key player in pathways that link nutrient availability, cell size, and G1 cyclin transcription. Since Rts1 is highly conserved, it may function in similar pathways in vertebrates.

  16. β-Glucan Size Controls Dectin-1-Mediated Immune Responses in Human Dendritic Cells by Regulating IL-1β Production

    Directory of Open Access Journals (Sweden)

    Matthew J. Elder

    2017-07-01

    Full Text Available Dectin-1/CLEC7A is a pattern recognition receptor that recognizes β-1,3 glucans, and its stimulation initiates signaling events characterized by the production of inflammatory cytokines from human dendritic cells (DCs required for antifungal immunity. β-glucans differ greatly in size, structure, and ability to activate effector immune responses from DC; as such, small particulate β-glucans are thought to be poor activators of innate immunity. We show that β-glucan particle size is a critical factor contributing to the secretion of cytokines from human DC; large β-glucan-stimulated DC generate significantly more IL-1β, IL-6, and IL-23 compared to those stimulated with the smaller β-glucans. In marked contrast, the secretion of TSLP and CCL22 were found to be insensitive to β-glucan particle size. Furthermore, we show that the capacity to induce phagocytosis, and the relative IL-1β production determined by β-glucan size, regulates the composition of the cytokine milieu generated from DC. This suggests that β-glucan particle size is critically important in orchestrating the nature of the immune response to fungi.

  17. Micro-environmental mechanical stress controls tumor spheroid size and morphology by suppressing proliferation and inducing apoptosis in cancer cells.

    Directory of Open Access Journals (Sweden)

    Gang Cheng

    Full Text Available Compressive mechanical stress produced during growth in a confining matrix limits the size of tumor spheroids, but little is known about the dynamics of stress accumulation, how the stress affects cancer cell phenotype, or the molecular pathways involved.We co-embedded single cancer cells with fluorescent micro-beads in agarose gels and, using confocal microscopy, recorded the 3D distribution of micro-beads surrounding growing spheroids. The change in micro-bead density was then converted to strain in the gel, from which we estimated the spatial distribution of compressive stress around the spheroids. We found a strong correlation between the peri-spheroid solid stress distribution and spheroid shape, a result of the suppression of cell proliferation and induction of apoptotic cell death in regions of high mechanical stress. By compressing spheroids consisting of cancer cells overexpressing anti-apoptotic genes, we demonstrate that mechanical stress-induced apoptosis occurs via the mitochondrial pathway.Our results provide detailed, quantitative insight into the role of micro-environmental mechanical stress in tumor spheroid growth dynamics, and suggest how tumors grow in confined locations where the level of solid stress becomes high. An important implication is that apoptosis via the mitochondrial pathway, induced by compressive stress, may be involved in tumor dormancy, in which tumor growth is held in check by a balance of apoptosis and proliferation.

  18. The Dynamical Mechanisms of the Cell Cycle Size Checkpoint

    International Nuclear Information System (INIS)

    Feng Shi-Fu; Yang Ling; Yan Jie; Liu Zeng-Rong

    2012-01-01

    Cell division must be tightly coupled to cell growth in order to maintain cell size, whereas the mechanisms of how initialization of mitosis is regulated by cell size remain to be elucidated. We develop a mathematical model of the cell cycle, which incorporates cell growth to investigate the dynamical properties of the size checkpoint in embryos of Xenopus laevis. We show that the size checkpoint is naturally raised from a saddle-node bifurcation, and in a mutant case, the cell loses its size control ability due to the loss of this saddle-node point

  19. Nuclear size regulation: from single cells to development and disease.

    Science.gov (United States)

    Edens, Lisa J; White, Karen H; Jevtic, Predrag; Li, Xiaoyang; Levy, Daniel L

    2013-04-01

    Cell size varies greatly among different cell types and organisms, especially during early development when cell division is rapid with little overall growth. A fundamental question is how organelle size is regulated relative to cell size. The nucleus exhibits exquisite size scaling during development and between species, and nuclear size is often altered in cancer cells. Recent studies have elucidated mechanisms of nuclear size regulation in a variety of experimental systems, opening the door to future research on how nuclear size impacts upon cell and nuclear function and subnuclear organization. In this review we discuss studies that have clarified nuclear size control mechanisms and how these results have or will contribute to our understanding of the functional significance of nuclear size. Copyright © 2012 Elsevier Ltd. All rights reserved.

  20. Fe(II)-regulated moderate pre-oxidation of Microcystis aeruginosa and formation of size-controlled algae flocs for efficient flotation of algae cell and organic matter.

    Science.gov (United States)

    Qi, Jing; Lan, Huachun; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2018-06-15

    The coagulation/flocculation/flotation (C/F/F) process is becoming a popular method for algae-laden water treatment. However, the efficiency of flotation is highly dependent on the ability of the preceding coagulation/flocculation process to form flocculated algae flocs. This study aims to improve the Microcystis aeruginosa flotation efficiency from algae cell and organic matter aspects by applying Fe(II)-regulated pretreatment enhanced Al coagulation process. The ability of the C/F/F process to remove cyanobacterial cells can be enhanced from 8% to 99% at a Fe(II) dose of 30 μM. The Al dose needed can be reduced by more than half while achieving successful flotation. The introduced Fe(II) after KMnO 4 can not only realize moderate pre-oxidation of cyanobacterial cells, but also form in-situ Fe(III). The DOC value can also be decreased significantly due to the formation of in-situ Fe(III), which is more efficient in dissolved organic matter (DOM) removal compared with pre-formed Fe(III). In addition, the gradually hydrolyzed in-situ Fe(III) can facilitate the hydrolysis of Al as a dual-coagulant and promote the clustering and cross-linking of Al hydrolyzates, which can enhance the formation of size-controlled algae flocs. Finally, the size-controlled algae flocs can be effectively floated by the bubbles released in the flotation process due to the efficient collision and attachment between flocs and bubbles. Therefore, the efficient flotation of algae cell and organic matter can be realized by the Fe(II) regulated moderate pre-oxidation of M. aeruginosa and formation of size-controlled algae flocs. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Cellular Allometry of Mitochondrial Functionality Establishes the Optimal Cell Size.

    Science.gov (United States)

    Miettinen, Teemu P; Björklund, Mikael

    2016-11-07

    Eukaryotic cells attempt to maintain an optimal size, resulting in size homeostasis. While cellular content scales isometrically with cell size, allometric laws indicate that metabolism per mass unit should decline with increasing size. Here we use elutriation and single-cell flow cytometry to analyze mitochondrial scaling with cell size. While mitochondrial content increases linearly, mitochondrial membrane potential and oxidative phosphorylation are highest at intermediate cell sizes. Thus, mitochondrial content and functional scaling are uncoupled. The nonlinearity of mitochondrial functionality is cell size, not cell cycle, dependent, and it results in an optimal cell size whereby cellular fitness and proliferative capacity are maximized. While optimal cell size is controlled by growth factor signaling, its establishment and maintenance requires mitochondrial dynamics, which can be controlled by the mevalonate pathway. Thus, optimization of cellular fitness and functionality through mitochondria can explain the requirement for size control, as well as provide means for its maintenance. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  2. Time evolution of cell size distributions in dense cell cultures

    Science.gov (United States)

    Khain, Evgeniy

    2015-03-01

    Living cells in a dense system are all in contact with each other. The common assumption is that such cells stop dividing due to a lack of space. Recent experimental observations have shown, however, that cells continue dividing for a while, but other cells in the system must shrink, to allow the newborn cells to grow to a normal size. Due to these ``pressure'' effects, the average cell size dramatically decreases with time, and the dispersion in cell sizes decreases, too. The collective cell behavior becomes even more complex when the system is expanding: cells near the edges are larger and migrate faster, while cells deep inside the colony are smaller and move slower. This exciting experimental data still needs to be described theoretically, incorporating the distribution of cell sizes in the system. We propose a mathematical model for time evolution of cell size distribution both in a closed and open system. The model incorporates cell proliferation, cell growth after division, cell shrinking due to ``pressure'' from other cells, and possible cell detachment from the interface of a growing colony. This research sheds light on physical and biological mechanisms of cell response to a dense environment and on the role of mechanical stresses in determining the distribution of cell sizes in the system.

  3. Fabrication and size control of Ag nanoparticles

    Directory of Open Access Journals (Sweden)

    M Farbod

    2012-06-01

    Full Text Available  The objective of this research was to fabricate Ag nanoparticles and control their sizes. Colloidal Ag nanoparticles with particle size of 30 nm were prepared by dissolving AgNO3 in ethanol and through the chemical reduction of Ag+ in alcohol solution. To control the nanoparticle size, different samples were fabricated by changing the AgNO3 and stabilizer concentrations and the effects of different factors on the shape and size of nanoparticles were investigated. The samples were characterized using SEM and EDX analysis. The results showed that by increasing the AgNO3 concentration, the average size of nanoparticles increases and nanoparticles lose their spherical shape. Also, we found that by using the stabilizer, it is possible to produce stable nanoparticles but increasing the stabilizer concentration caused an increase in size of nanoparticles. Fabrication of nanoparticles without using stabilizer was achieved but the results showed the nanoparticles size had a growth of 125 nm/h in the alcoholic media.

  4. Control of pore size in epoxy systems.

    Energy Technology Data Exchange (ETDEWEB)

    Sawyer, Patricia Sue; Lenhart, Joseph Ludlow (North Dakota State University, Fargo, ND); Lee, Elizabeth (North Dakota State University, Fargo, ND); Kallam, Alekhya (North Dakota State University, Fargo, ND); Majumdar, Partha (North Dakota State University, Fargo, ND); Dirk, Shawn M.; Gubbins, Nathan; Chisholm, Bret J. (North Dakota State University, Fargo, ND); Celina, Mathias C.; Bahr, James (North Dakota State University, Fargo, ND); Klein, Robert J.

    2009-01-01

    Both conventional and combinatorial approaches were used to study the pore formation process in epoxy based polymer systems. Sandia National Laboratories conducted the initial work and collaborated with North Dakota State University (NDSU) using a combinatorial research approach to produce a library of novel monomers and crosslinkers capable of forming porous polymers. The library was screened to determine the physical factors that control porosity, such as porogen loading, polymer-porogen interactions, and polymer crosslink density. We have identified the physical and chemical factors that control the average porosity, pore size, and pore size distribution within epoxy based systems.

  5. Controlling nanopore size, shape and stability

    International Nuclear Information System (INIS)

    Van den Hout, Michiel; Hall, Adam R; Wu Mengyue; Zandbergen, Henny W; Dekker, Cees; Dekker, Nynke H

    2010-01-01

    Solid-state nanopores are considered a promising tool for the study of biological polymers such as DNA and RNA, due largely to their flexibility in size, potential in device integration and robustness. Here, we show that the precise shape of small nanopores (∼5 nm diameter in 20 nm SiN membranes) can be controlled by using transmission electron microscope (TEM) beams of different sizes. However, when some of these small nanopores are immersed in an aqueous solution, their resistance is observed to decrease over time. By comparing nanopores of different shapes using (scanning) TEM both before and after immersion in aqueous solution, we demonstrate that the stability of small nanopores is related to their three-dimensional geometry, which depends on the TEM beam size employed during pore fabrication. Optimal stability is obtained using a TEM beam size of approximately the same size as the intended nanopore diameter. In addition, we show that thermal oxidation can serve as a means to independently control nanopore size following TEM fabrication. These observations provide key guidelines for the fabrication of stable solid-state nanopores on the scale of nucleic acids and small proteins.

  6. Size Matters, if you Control Your Junk

    DEFF Research Database (Denmark)

    Asness, Cliff; Frazzini, Andrea; Israel, Ronen

    The size premium has been challenged along many fronts: it has a weak historical record, varies significantly over time, in particular weakening after its discovery, is concentrated among microcap stocks, resides predominantly in January, is not present for non-price based measures of size, is weak...... internationally, and is argued to be subsumed by proxies for illiquidity. We find, however, that these challenges are systematically dismantled when controlling for the quality, or its inverse “junk”, of a firm. Across a wide variety of quality measures proposed in the literature a significant size premium...... emerges, which is: stable through time, robust to specification, more consistent across seasons and markets, not concentrated in microcaps, robust to non-price based measures of size, and not captured by an illiquidity premium. These results are replicated in 30 different industries and in 24 different...

  7. COCHLEATA controls leaf size and secondary inflorescence ...

    Indian Academy of Sciences (India)

    2012-10-18

    Oct 18, 2012 ... COCHLEATA controls leaf size and secondary inflorescence architecture via negative regulation of UNIFOLIATA (LEAFY ortholog) gene in garden pea Pisum sativum. VISHAKHA SHARMA, SWATI CHAUDHARY, ARVIND KUMAR and SUSHIL KUMAR*. Genetical Genomics Laboratory, National Institute of ...

  8. [Influence of slot size on torque control].

    Science.gov (United States)

    Tian, Jun; Liu, Zhong-Hao; Zhang, Ding; Wu, Chuan-Jun

    2009-12-01

    To study the influence of two slot size brackets on torque control when teeth interacted in the same arch. After the upper arch was aligned and leveled in Typodont study, the inclinations of upper teeth 5 +/- 5 were measured when 0.457 2 mm x 0.635 0 mm OPA-K brackets and 0.558 8 mmx0.711 2 mm OPA-K brackets were filled with 0.431 8 mm x 0.635 0 mm stainless steel wire. This experiment was duplicated 10 times. The inclin of each tooth were transformed to the absolute values of the torque play angle psi by computing program, and paired-t test was used. The two kinds of slot size brackets were different with statistical significance on torque control. When the brackets were filled with 0.431 8 mm x 0.635 0 mm stainless steel wire, the absolute values of the angle psi in 0.558 8 mm x 0.711 2 mm and 0.457 2 mm x 0.635 0 mm slot size brackets were 6.140 degrees +/- 3.758 degrees and 2.608 degrees +/- 1.479 degrees respectively, and the average difference of that between the two slot size brackets was 3.532 degrees. The absolute values of the angle psi in the upper left and right canine brackets were 2.560 degrees +/- 2.605 degrees, 4.230 degrees +/- 2.817 degrees, 1.260 degrees +/- 0.747 degrees and 2.070 degrees +/- 0.663 degrees respectively, and average differences between them were smaller than that in the other teeth. There was difference between the two kinds of slot size brackets on torque control, and 0.457 2 mm x 0.635 0 mm slot size bracket controls torque better when filled with the same size wire. In this study, the teeth interaction in the same arch probably caused the result that the difference of two slot size brackets on torque control was less than the study results of the theory calculations and material studys before.

  9. Cell size and growth regulation in the Arabidopsis thaliana apical stem cell niche

    Science.gov (United States)

    Willis, Lisa; Refahi, Yassin; Wightman, Raymond; Landrein, Benoit; Teles, José; Huang, Kerwyn Casey; Meyerowitz, Elliot M.

    2016-01-01

    Cell size and growth kinetics are fundamental cellular properties with important physiological implications. Classical studies on yeast, and recently on bacteria, have identified rules for cell size regulation in single cells, but in the more complex environment of multicellular tissues, data have been lacking. In this study, to characterize cell size and growth regulation in a multicellular context, we developed a 4D imaging pipeline and applied it to track and quantify epidermal cells over 3–4 d in Arabidopsis thaliana shoot apical meristems. We found that a cell size checkpoint is not the trigger for G2/M or cytokinesis, refuting the unexamined assumption that meristematic cells trigger cell cycle phases upon reaching a critical size. Our data also rule out models in which cells undergo G2/M at a fixed time after birth, or by adding a critical size increment between G2/M transitions. Rather, cell size regulation was intermediate between the critical size and critical increment paradigms, meaning that cell size fluctuations decay by ∼75% in one generation compared with 100% (critical size) and 50% (critical increment). Notably, this behavior was independent of local cell–cell contact topologies and of position within the tissue. Cells grew exponentially throughout the first >80% of the cell cycle, but following an asymmetrical division, the small daughter grew at a faster exponential rate than the large daughter, an observation that potentially challenges present models of growth regulation. These growth and division behaviors place strong constraints on quantitative mechanistic descriptions of the cell cycle and growth control. PMID:27930326

  10. Cell size and the initiation of DNA replication in bacteria.

    Directory of Open Access Journals (Sweden)

    Norbert S Hill

    Full Text Available In eukaryotes, DNA replication is coupled to the cell cycle through the actions of cyclin-dependent kinases and associated factors. In bacteria, the prevailing view, based primarily from work in Escherichia coli, is that growth-dependent accumulation of the highly conserved initiator, DnaA, triggers initiation. However, the timing of initiation is unchanged in Bacillus subtilis mutants that are ~30% smaller than wild-type cells, indicating that achievement of a particular cell size is not obligatory for initiation. Prompted by this finding, we re-examined the link between cell size and initiation in both E. coli and B. subtilis. Although changes in DNA replication have been shown to alter both E. coli and B. subtilis cell size, the converse (the effect of cell size on DNA replication has not been explored. Here, we report that the mechanisms responsible for coordinating DNA replication with cell size vary between these two model organisms. In contrast to B. subtilis, small E. coli mutants delayed replication initiation until they achieved the size at which wild-type cells initiate. Modest increases in DnaA alleviated the delay, supporting the view that growth-dependent accumulation of DnaA is the trigger for replication initiation in E. coli. Significantly, although small E. coli and B. subtilis cells both maintained wild-type concentration of DnaA, only the E. coli mutants failed to initiate on time. Thus, rather than the concentration, the total amount of DnaA appears to be more important for initiation timing in E. coli. The difference in behavior of the two bacteria appears to lie in the mechanisms that control the activity of DnaA.

  11. Cell control report

    CERN Document Server

    2013-01-01

    Please note this is a Short Discount publication. This extensive report provides an essential overview of cells and their use as factory automation building blocks. The following issues are discussed in depth: Cell integration Cell software and standards Future technologies applied to cells Plus Cell control applications including: - rotary parts manufacturing - diesel engine component development - general cell control development at the General Electric Corporation - a vendor list.

  12. Measuring bacterial cells size with AFM

    Directory of Open Access Journals (Sweden)

    Denise Osiro

    2012-03-01

    Full Text Available Atomic Force Microscopy (AFM can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe and the bacterium (Escherichia coli JM-109 strain to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

  13. Details Matter: Noise and Model Structure Set the Relationship between Cell Size and Cell Cycle Timing

    Directory of Open Access Journals (Sweden)

    Felix Barber

    2017-11-01

    Full Text Available Organisms across all domains of life regulate the size of their cells. However, the means by which this is done is poorly understood. We study two abstracted “molecular” models for size regulation: inhibitor dilution and initiator accumulation. We apply the models to two settings: bacteria like Escherichia coli, that grow fully before they set a division plane and divide into two equally sized cells, and cells that form a bud early in the cell division cycle, confine new growth to that bud, and divide at the connection between that bud and the mother cell, like the budding yeast Saccharomyces cerevisiae. In budding cells, delaying cell division until buds reach the same size as their mother leads to very weak size control, with average cell size and standard deviation of cell size increasing over time and saturating up to 100-fold higher than those values for cells that divide when the bud is still substantially smaller than its mother. In budding yeast, both inhibitor dilution or initiator accumulation models are consistent with the observation that the daughters of diploid cells add a constant volume before they divide. This “adder” behavior has also been observed in bacteria. We find that in bacteria an inhibitor dilution model produces adder correlations that are not robust to noise in the timing of DNA replication initiation or in the timing from initiation of DNA replication to cell division (the C+D period. In contrast, in bacteria an initiator accumulation model yields robust adder correlations in the regime where noise in the timing of DNA replication initiation is much greater than noise in the C + D period, as reported previously (Ho and Amir, 2015. In bacteria, division into two equally sized cells does not broaden the size distribution.

  14. MANOVA for Nested Designs with Unequal Cell Sizes and Unequal Cell Covariance Matrices

    Directory of Open Access Journals (Sweden)

    Li-Wen Xu

    2014-01-01

    satisfactorily for various cell sizes and parameter configurations and generally outperforms the AHT test in terms of controlling the nominal size. For the heteroscedastic cases, the PB test outperforms the AHT test in terms of power. In addition, the PB test does not lose too much power when the homogeneity assumption is actually valid.

  15. A solvent approach to the size-controllable synthesis of ultrafine Pt catalysts for methanol oxidation in direct methanol fuel cells

    International Nuclear Information System (INIS)

    Ye, Feng; Liu, Hui; Feng, Yan; Li, Jianling; Wang, Xindong; Yang, Jun

    2014-01-01

    Graphical abstract: - Highlights: • An ethylene glycol-based approach for the synthesis of Pt/C catalysts with uniform Pt nanoparticles. • Superior catalytic activity of Pt/C catalysts synthesized at EG/water volume ratio of 1/1 for methanol oxidation reaction. • High performance of MEA for DMFC using Pt/C catalysts synthesized at EG/water volume ratio of 1/1 at anode. - Abstract: An ethylene glycol (EG)-based approach has been developed for the synthesis of Pt/C catalysts with uniform Pt nanoparticles. A number of characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements are used to characterize the as-prepared Pt catalysts. The well-dispersed Pt nanoparticles with average size of approximate 2 nm could be obtained in the EG/water mixture with volume ratio of 1/1, which display higher activity for methanol oxidation than that of the Pt/C products prepared at other EG/water volume ratios (0:1, 2:1, and 1:0). In particular, the performance of the Pt nanoparticles prepared at EG/water volume ratio of 1/1 in the membrane electrode assembly for direct methanol fuel cells has also been evaluated and benchmarked by commercial Pt/C catalysts. This study offers a vivid example to synthesize Pt nanoparticles with fine size and good catalytic activity by simply tuning the solvent ratio in colloidal chemistry methods

  16. The duration of mitosis and daughter cell size are modulated by nutrients in budding yeast.

    Science.gov (United States)

    Leitao, Ricardo M; Kellogg, Douglas R

    2017-11-06

    The size of nearly all cells is modulated by nutrients. Thus, cells growing in poor nutrients can be nearly half the size of cells in rich nutrients. In budding yeast, cell size is thought to be controlled almost entirely by a mechanism that delays cell cycle entry until sufficient growth has occurred in G1 phase. Here, we show that most growth of a new daughter cell occurs in mitosis. When the rate of growth is slowed by poor nutrients, the duration of mitosis is increased, which suggests that cells compensate for slow growth in mitosis by increasing the duration of growth. The amount of growth required to complete mitosis is reduced in poor nutrients, leading to a large reduction in cell size. Together, these observations suggest that mechanisms that control the extent of growth in mitosis play a major role in cell size control in budding yeast. © 2017 Leitao and Kellogg.

  17. Cell Size Breathing and Possibilities to Introduce Cell Sleep Mode

    DEFF Research Database (Denmark)

    Micallef, Gilbert; Mogensen, Preben; Scheck, Hans-Otto

    2010-01-01

    regular upgrades in the infrastructure. While network equipment is in itself becoming more efficient, these upgrades still increase the overall energy consumption of the networks. This paper investigates the energy saving potential of exploiting cell size breathing by putting low loaded cells into sleep...... mode. The energy consumption and network performance of the resulting network are used to quantify the potential of this feature. The investigation is carried out on a tilt optimized network. Since putting cells into sleep mode results in a non-optimum antenna tilt configuration, this paper also...

  18. EPICS Controlled Collimator for Controlling Beam Sizes in HIPPO

    Energy Technology Data Exchange (ETDEWEB)

    Napolitano, Arthur Soriano [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vogel, Sven C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-08-03

    Controlling the beam spot size and shape in a diffraction experiment determines the probed sample volume. The HIPPO - High-Pressure-Preferred Orientation– neutron time-offlight diffractometer is located at the Lujan Neutron Scattering Center in Los Alamos National Laboratories. HIPPO characterizes microstructural parameters, such as phase composition, strains, grain size, or texture, of bulk (cm-sized) samples. In the current setup, the beam spot has a 10 mm diameter. Using a collimator, consisting of two pairs of neutron absorbing boron-nitride slabs, horizontal and vertical dimensions of a rectangular beam spot can be defined. Using the HIPPO robotic sample changer for sample motion, the collimator would enable scanning of e.g. cylindrical samples along the cylinder axis by probing slices of such samples. The project presented here describes implementation of such a collimator, in particular the motion control software. We utilized the EPICS (Experimental Physics Interface and Control System) software interface to integrate the collimator control into the HIPPO instrument control system. Using EPICS, commands are sent to commercial stepper motors that move the beam windows.

  19. Mevalonate Pathway Regulates Cell Size Homeostasis and Proteostasis through Autophagy.

    Science.gov (United States)

    Miettinen, Teemu P; Björklund, Mikael

    2015-12-22

    Balance between cell growth and proliferation determines cell size homeostasis, but little is known about how metabolic pathways are involved in the maintenance of this balance. Here, we perform a screen with a library of clinically used drug molecules for their effects on cell size. We find that statins, inhibitors of the mevalonate pathway, reduce cell proliferation and increase cell size and cellular protein density in various cell types, including primary human cells. Mevalonate pathway effects on cell size and protein density are mediated through geranylgeranylation of the small GTPase RAB11, which is required for basal autophagic flux. Our results identify the mevalonate pathway as a metabolic regulator of autophagy and expose a paradox in the regulation of cell size and proteostasis, where inhibition of an anabolic pathway can cause an increase in cell size and cellular protein density. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  20. Significance of tumor size and radiation dose to local control in stage I-III diffuse large cell lymphoma treated with CHOP-Bleo and radiation

    International Nuclear Information System (INIS)

    Fuller, Lillian M.; Krasin, Matthew J.; Velasquez, William S.; Allen, Pamela K.; McLaughlin, Peter; Rodriguez, M. Alma; Hagemeister, Fredrick B.; Swan, Forrest; Cabanillas, Fernando; Palmer, Judy L.; Cox, James D.

    1995-01-01

    Purpose: The purpose of this study was to evaluate the possible effect of adjunctive involved field (IF) radiotherapy on long-term local control for patients with Ann Arbor Stage I-III diffuse large cell lymphoma (DLCL) who achieved a complete remission on a combined modality program which included cyclophosphamide, doxorubicin, vincristine, prednisone, and Bleomycin (CHOP-Bleo). Methods and Materials: One hundred and ninety patients with Ann Arbor Stage I-III DLCL were treated with CHOP-Bleo and radiotherapy. Analyses were undertaken to determine (a) response to treatment according to stage, extent of maximum local disease, and irradiation dose either < 40 Gy or ≥ 40 Gy and (b) relapse patterns. Results: A complete remission (CR) was achieved in 162 patients. Among patients who achieved a CR, local control was better for those who received tumor doses of ≥ 40 Gy (97%) than for those who received < 40 Gy (83%) (p = 0.002.) Among those with extensive local disease, the corresponding control rates were 88% and 71%, respectively. A study of distant relapse patterns following a CR showed that the first relapse usually involved an extranodal site. Conclusion: Radiotherapy was an effective adjunctive treatment to CHOP-Bleo for patients with stage I-III DLCL who achieved a CR. Patterns of relapse suggested that total nodal irradiation (TNI) possibly could have benefited a small subset of patients

  1. Heterotrophic free-living and particle-bound bacterial cell size in the ...

    Indian Academy of Sciences (India)

    PRAKASH

    bacterial cell size was similar in all the five water courses, different sets of environmental variables apparently control the heterotrophic bacterial cell size ... major force controlling both the morphological and the taxonomic structure of ...... 18th edition, pp1–1000. Bennet S J, Sanders R W and Porter K G 1990 Heterotrophic,.

  2. Cell Control Engineering

    DEFF Research Database (Denmark)

    Lynggaard, Hans Jørgen Birk; Alting, Leo

    1996-01-01

    The engineering process of creating cell control systems is described, and a Cell Control Engineering (CCE) concept is defined. The purpose is to assist people, representing different disciplines in the organisation, to implement cell controllers by addressing the complexity of having many systems...... in physically and logically different and changing manufacturing environments. The defined CCE concept combines state-of-the-art of commercially available enabling technologies for automation system software development, generic cell control models and guidelines for the complete engineering process....... It facilitates the understanding of the task and structure of cell controllers and uses this knowledge directly in the implementation of the system. By applying generic models CCE facilitates reuse of software components and maintenance of applications. In many enterprises, software makes up an increasing part...

  3. Size control in development: lessons from Drosophila

    Indian Academy of Sciences (India)

    animals are differences in size, but for some reason the zoologists have paid singularly little attention to them” (Haldane 1927). Almost three quarters of a century later, one of the most important and fundamental aspects of development – how the size of a multicellular organism is determined – remains as mysterious as ever ...

  4. Cell-size distribution in epithelial tissue formation and homeostasis.

    Science.gov (United States)

    Puliafito, Alberto; Primo, Luca; Celani, Antonio

    2017-03-01

    How cell growth and proliferation are orchestrated in living tissues to achieve a given biological function is a central problem in biology. During development, tissue regeneration and homeostasis, cell proliferation must be coordinated by spatial cues in order for cells to attain the correct size and shape. Biological tissues also feature a notable homogeneity of cell size, which, in specific cases, represents a physiological need. Here, we study the temporal evolution of the cell-size distribution by applying the theory of kinetic fragmentation to tissue development and homeostasis. Our theory predicts self-similar probability density function (PDF) of cell size and explains how division times and redistribution ensure cell size homogeneity across the tissue. Theoretical predictions and numerical simulations of confluent non-homeostatic tissue cultures show that cell size distribution is self-similar. Our experimental data confirm predictions and reveal that, as assumed in the theory, cell division times scale like a power-law of the cell size. We find that in homeostatic conditions there is a stationary distribution with lognormal tails, consistently with our experimental data. Our theoretical predictions and numerical simulations show that the shape of the PDF depends on how the space inherited by apoptotic cells is redistributed and that apoptotic cell rates might also depend on size. © 2017 The Author(s).

  5. Size control in development: lessons from Drosophila

    Indian Academy of Sciences (India)

    which mediates dosage compensation in Drosophila; Mol. Cell 4 117–122. Kelley R L, Meller V H, Gordadze P R, Roman G, Davis R L and Kuroda M I 1999 Epigenetic spreading of the Drosophila dosage compensation complex from rox RNA genes into flanking chromatin; Cell 98. 513–522. Lucchesi J C 1998 Dosage ...

  6. size control. Disorders of the pathway in cancer diseases

    Directory of Open Access Journals (Sweden)

    Agnieszka Rybarczyk

    2014-05-01

    Full Text Available The Hippo pathway (also known as SWH – Salvador/Warts/Hippo, discovered for the first time in Drosophila melanogaster, is responsible for cell proliferation and organ size control in mammalian systems. The components of the pathway are two kinases and their adaptor proteins which inhibit the transcription co-activator YAP by phosphorylation. When the pathway is inactive (as an effect of upstream component gene expression disorders, activated YAP is translocated to the nucleus where it cooperates with TEAD transcription factor and promotes expression of genes that regulate cell proliferation and apoptosis. YAP acts generally as an oncogene, although there are some reports describing its role as a tumor suppressor. Since all of the core components are well known, the latest reports provide mostly information about upstream components of the Hippo pathway or its interaction with other biochemical pathways. Because of the Hippo pathway’s role in the cell cycle, it has become a very attractive object for studies of the genetic background of cancer. The under- or overexpression of genes involved in the Hippo pathway has been described in many different types of cancers. Moreover, it has been shown that there is a strong connection between cancer cell phenotype and highly activated YAP presence in the nucleus. This paper reviews the most important data about Hippo pathway regulation in Drosophila and mammals, including its numerous disorders and their implications for cell function.

  7. Green synthesis of size controllable gold nanoparticles.

    Science.gov (United States)

    Mohan Kumar, Kesarla; Mandal, Badal Kumar; Kiran Kumar, Hoskote A; Maddinedi, Sireesh Babu

    2013-12-01

    A facile rapid green eco-friendly method to synthesize gold nanoparticles (Au NPs) of tunable size using aqueous Terminalia arjuna fruit extracts has been demonstrated herein. Formation of Au NPs was confirmed by Surface Plasmon Resonance (SPR) study at 528 nm using UV-visible spectrophotometer. The time of reduction, size and morphological variations of Au NPs were studied with varying quantities of T. arjuna fruit aqueous extracts. Synthesized Au NPs were characterized using UV-visible spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDAX). Polyphenols responsible for reduction of Au(3+) to Au(0) were identified using High Performance Liquid Chromatography (HPLC) as ascorbic acid, gallic acid and pyrogallol. The oxidized forms of polyphenols formed coordination with surface of Au NPs which protected their further growth and aggregation. We also propose a plausible mechanism how to tune size and shape of Au NPs by varying the quantity of extracts. Thus obtained Au NPs were stable for more than four months. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Green synthesis of size controllable gold nanoparticles

    Science.gov (United States)

    Mohan Kumar, Kesarla; Mandal, Badal Kumar; Kiran Kumar, Hoskote A.; Maddinedi, Sireesh Babu

    2013-12-01

    A facile rapid green eco-friendly method to synthesize gold nanoparticles (Au NPs) of tunable size using aqueous Terminalia arjuna fruit extracts has been demonstrated herein. Formation of Au NPs was confirmed by Surface Plasmon Resonance (SPR) study at 528 nm using UV-visible spectrophotometer. The time of reduction, size and morphological variations of Au NPs were studied with varying quantities of T. arjuna fruit aqueous extracts. Synthesized Au NPs were characterized using UV-visible spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDAX). Polyphenols responsible for reduction of Au3+ to Au0 were identified using High Performance Liquid Chromatography (HPLC) as ascorbic acid, gallic acid and pyrogallol. The oxidized forms of polyphenols formed coordination with surface of Au NPs which protected their further growth and aggregation. We also propose a plausible mechanism how to tune size and shape of Au NPs by varying the quantity of extracts. Thus obtained Au NPs were stable for more than four months.

  9. Tailoring Porosity of Colloidal Boehmite Sol by Controlling Crystallite Size

    Energy Technology Data Exchange (ETDEWEB)

    Park, Myung Chul; Lee, Sung Reol; Kim, Hark; Park, In; Choy, Jin Ho [Ewha Womans University, Seoul (Korea, Republic of)

    2012-06-15

    Boehmite sols have been prepared by crystallization of amorphous aluminum hydroxide gel obtained by hydrolysis and peptization of aluminum using acetic acid. The size of the boehmite crystallites could be controlled by Al molar concentration in amorphous gel by means of controlling grain growth at nucleation stage. The size of boehmite increases as a function of Al molar concentration. With increasing boehmite crystallite size, the d{sub (020)} spacing and the specific surface area decreases, whereas the pore volume increases along with pore size. Especially, the pore size of the boehmite sol particles is comparable to the crystallite size along the b axis, suggesting that the fibril thickness along the b axis among the crystallite dimensions of the boehmite contributes to the pore size. Therefore, the physical properties of boehmite sols can be determined by the crystallite size controlled as a function of initial Al concentration

  10. Signalling and the control of skeletal muscle size

    Energy Technology Data Exchange (ETDEWEB)

    Otto, Anthony [School of Biological Sciences, Hopkins Building, University of Reading, Whiteknights Campus, Reading, Berkshire, RG6 6UB (United Kingdom); Patel, Ketan, E-mail: ketan.patel@reading.ac.uk [School of Biological Sciences, Hopkins Building, University of Reading, Whiteknights Campus, Reading, Berkshire, RG6 6UB (United Kingdom)

    2010-11-01

    Skeletal muscle is highly adaptive to environmental stimuli and can alter its mass accordingly. This tissue is almost unique in that it can increase its size through two distinct mechanisms. It can grow through a cellular process mediated by cell fusion, or it can increase its size simply by increasing its protein content. Understanding how these processes are regulated is crucial for the development of potential therapies against debilitating skeletal muscle wasting diseases. Two key signalling molecules, Insulin like Growth Factor (IGF) and GDF-8/myostatin, have emerged in recent years to be potent regulators of skeletal muscle size. In this review we bring together recent data highlighting the important and novel aspects of both molecules and their signalling pathways, culminating in a discussion of the cellular and tissue phenotypic outcomes of their stimulation or antagonism. We emphasise the complex regulatory mechanisms and discuss the temporal and spatial differences that control their action, understanding of which is crucial to further their use as potential therapeutic targets.

  11. Size-controlled synthesis of biodegradable nanocarriers for targeted ...

    Indian Academy of Sciences (India)

    Abstract. Research for synthesis of size-controlled carriers is currently challenging one. In this research paper, a method for size-controlled synthesis of biodegradable nanocarriers is proposed and described. Salting out method is suitable for both hydrophilic and hydrophobic drugs for the encapsulation on carriers.

  12. Size-controlled synthesis of biodegradable nanocarriers for targeted ...

    Indian Academy of Sciences (India)

    2016-08-26

    Aug 26, 2016 ... Research for synthesis of size-controlled carriers is currently challenging one. In this research paper, a method for size-controlled synthesis of biodegradable nanocarriers is proposed and described. Salting out method is suitable for both hydrophilic and hydrophobic drugs for the encapsulation on carriers.

  13. Use of surfactants to control island size and density

    Energy Technology Data Exchange (ETDEWEB)

    Merrell, Jason; Liu, Feng; Stringfellow, Gerald B.

    2017-08-15

    Methods of controlling island size and density on an OMVPE growth film may comprise adding a surfactant at a critical concentration level, allowing a growth phase for a first period of time, and ending the growth phase when desired island size and density are achieved. For example, the island size and density of an OMVPE grown InGaN thin film may be controlled by adding an antimony surfactant at a critical concentration level.

  14. Cell control with agents

    NARCIS (Netherlands)

    Ir Peter Boots; Ir. Dick van Schenk Brill

    2000-01-01

    A software system is described that uses the agent concept in the Cell Control layer. Important design goals are: the system continues as good as possible after a process crash, crashed processes are recreated whenever possible, and equivalent workstations are allocated dynamically. This project is

  15. A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division

    Science.gov (United States)

    Li, Yubing; Liu, Dianyi; López-Paz, Cristina; Olson, Bradley JSC; Umen, James G

    2016-01-01

    Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a ‘counting’ mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control. DOI: http://dx.doi.org/10.7554/eLife.10767.001 PMID:27015111

  16. Particle size control of detergents in mixed flow spray dryers

    Directory of Open Access Journals (Sweden)

    Mark Jonathan Crosby

    2015-03-01

    Full Text Available Particle size is a key quality parameter of a powder detergent as it determines its performance, the bulk density and the look and feel of the product. Consequently, it is essential that particle size is controlled to ensure the consistency of performance when comparing new formulations. The majority of study reported in the literature relating to particle size control, focuses on the spray produced by the atomisation technique. One approach advocated to achieve particle size control is the manipulation of the ratio of the mass slurry rate and mass flow rate of gas used for atomisation. Within this study, ratio control was compared with an automatic cascade loop approach using online measurements of the powder particle size on a small-scale pilot plant. It was concluded that cascade control of the mean particle size, based on manipulating the mass flow rate of gas, resulted in tighter, more responsive control. The effect of a ratio change varied with different formulations and different slurry rates. Furthermore, changes in slurry rate caused complications, as the impact on particle size growth in the dryer is non-linear and difficult to predict. The cascade loop enables further study into the effect of particle size on detergent performance.

  17. Economic Effects of Increased Control Zone Sizes in Conflict Resolution

    Science.gov (United States)

    Datta, Koushik

    1998-01-01

    A methodology for estimating the economic effects of different control zone sizes used in conflict resolutions between aircraft is presented in this paper. The methodology is based on estimating the difference in flight times of aircraft with and without the control zone, and converting the difference into a direct operating cost. Using this methodology the effects of increased lateral and vertical control zone sizes are evaluated.

  18. Revisionist integral deferred correction with adaptive step-size control

    KAUST Repository

    Christlieb, Andrew

    2015-03-27

    © 2015 Mathematical Sciences Publishers. Adaptive step-size control is a critical feature for the robust and efficient numerical solution of initial-value problems in ordinary differential equations. In this paper, we show that adaptive step-size control can be incorporated within a family of parallel time integrators known as revisionist integral deferred correction (RIDC) methods. The RIDC framework allows for various strategies to implement stepsize control, and we report results from exploring a few of them.

  19. Estradiol: a rhythmic, inhibitory, indirect control of meal size.

    Science.gov (United States)

    Eckel, Lisa A

    2004-08-01

    The classic analyses of the inhibitory effects of cholecystokinin (CCK) on meal size, conducted by Professor Gerard P. Smith and his colleagues at the Bourne Laboratory, inspired my initial interest in this field. My current research, which investigates the role of estradiol in the control of meal size, continues to be guided by Gerry's thoughtful, scientific approach to the study of ingestive behavior. In 1996, the year I arrived as a Postdoctoral Fellow at the Bourne Laboratory, Gerry published a new theory of the controls of meal size. In this important paper, Gerry proposed that the controls of meal size can be either direct or indirect. He argued that direct controls of meal size interact with peripheral, preabsorptive receptors that are sensitive to the chemical, mechanical, and colligative properties of ingested food and that indirect controls of meal size function to modulate the activity of direct controls. The purpose of this review is to illustrate how Gerry's theory has guided much of what is known about the mechanism by which estradiol inhibits food intake in female rats. I will provide evidence, primarily from behavioral studies of gonadally intact and ovariectomized rats, that estradiol exerts phasic and tonic inhibitory effects on food intake by acting as a rhythmic, inhibitory, indirect control of meal size.

  20. Phospholipid-assisted synthesis of size-controlled gold nanoparticles

    International Nuclear Information System (INIS)

    He Peng; Zhu Xinyuan

    2007-01-01

    Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV-vis spectra

  1. Quantum-size-controlled photoelectrochemical etching of semiconductor nanostructures

    Science.gov (United States)

    Fischer, Arthur J.; Tsao, Jeffrey Y.; Wierer, Jr., Jonathan J.; Xiao, Xiaoyin; Wang, George T.

    2016-03-01

    Quantum-size-controlled photoelectrochemical (QSC-PEC) etching provides a new route to the precision fabrication of epitaxial semiconductor nanostructures in the sub-10-nm size regime. For example, quantum dots (QDs) can be QSC-PEC-etched from epitaxial InGaN thin films using narrowband laser photoexcitation, and the QD sizes (and hence bandgaps and photoluminescence wavelengths) are determined by the photoexcitation wavelength.

  2. Effects of ultraviolet irradiation and postirradiation incubation on heterogeneous nuclear RNA size in murine cells

    International Nuclear Information System (INIS)

    Ali, R.; Sauerbier, W.

    1978-01-01

    We have analyzed the decrease in synthesis of individual size classes of heterogeneous nuclear RNA (hnRNA) in ultraviolet (uv)-irradiated Merwin plasmacytoma (MPC-11) cells at various times of postirradiation incubation. HnRNA from nonirradiated control cells is distributed over a wide range from approximately 60S to 5S, with 42S RNA carrying more label than any other size class. HnRNA from uv-irradiated cells shows a dose-dependent shift in size distribution toward lower molecular weight. The size distribution of hnRNA synthesized after prolonged times of postirradiation incubation is restored toward normal, i.e., synthesis of long RNA molecules increases relative to the synthesis of short ones. Analysis of the total number of hnRNA chains synthesized during a 20-min [ 3 H]uridine pulse shows a considerable eduction in their number with increasing uv dose. Murine cell lines are excision-repair-deficient but capable of post replication repair inhibited by caffeine. HnRNA transcripts of cells incubated in its presence were studied. The caffeine, which has no effect on hnRNA size in control cells, inhibits to a considerable extent the restoration of full-length transcripts during postirradiation incubation. The lack of excision repair in MPC-11 was confirmed by the analysis of pyrimidine dimers in trichloracetic acid-insoluble and soluble fractions within 8 h of postirradiation incubation. The size of parental and daughter strand DNA in uv-irradiated cells was correlated with RNA transcript size. The parental DNA in these experiments does not change its size as a consequence of uv exposure and postirradiation incubation. In contrast, daughter DNA strands are short in uv-irradiated cells and they increase in size during postirradiation incubation to reach the size of parental strands after 8 h

  3. Optimizing human embryonic stem cells differentiation efficiency by screening size-tunable homogenous embryoid bodies.

    Science.gov (United States)

    Moon, Sung-Hwan; Ju, Jongil; Park, Soon-Jung; Bae, Daekyeong; Chung, Hyung-Min; Lee, Sang-Hoon

    2014-07-01

    Human embryonic stem cells (hESCs) are generally induced to differentiate by forming spherical structures termed embryoid bodies (EBs) in the presence of soluble growth factors. hEBs are generated by suspending small clumps of hESC colonies; however, the resulting hEBs are heterogeneous because this method lacks the ability to control the number of cells in individual EBs. This heterogeneity affects factors that influence differentiation such as cell-cell contact and the diffusion of soluble factors, and consequently, the differentiation capacity of each EB varies. Here, we fabricated size-tunable concave microwells to control the physical environment, thereby regulating the size of EBs formed from single hESCs. Defined numbers of single hESCs were forced to aggregate and generate uniformly sized EBs with high fidelity, and the size of the EBs was controlled using concave microwells of different diameters. Differentiation patterns in H9- and CHA15-hESCs were affected by EB size in both the absence and presence of growth factors. By screening EB size in the presence of various BMP4 concentrations, a two-fold increase in endothelial cell differentiation was achieved. Because each hESC line has unique characteristics, the findings of this study demonstrate that concave microwells could be used to screen different EB sizes and growth factor concentrations to optimize differentiation for each hESC line. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Size-controlled synthesis of biodegradable nanocarriers for targeted ...

    Indian Academy of Sciences (India)

    1, February 2016, pp. 69–77. c Indian Academy of Sciences. Size-controlled synthesis of biodegradable nanocarriers for targeted and controlled cancer drug delivery using salting out cation. MADASAMY HARI BALAKRISHANAN and MARIAPPAN RAJAN∗. Department of Natural Products Chemistry, School of Chemistry, ...

  5. Unified changes in cell size permit coordinated leaf evolution.

    Science.gov (United States)

    Brodribb, Tim J; Jordan, Greg J; Carpenter, Raymond J

    2013-07-01

    The processes by which the functions of interdependent tissues are coordinated as lineages diversify are poorly understood. Here, we examine evolutionary coordination of vascular, epidermal and cortical leaf tissues in the anatomically, ecologically and morphologically diverse woody plant family Proteaceae. We found that, across the phylogenetic range of Proteaceae, the sizes of guard, epidermal, palisade and xylem cells were positively correlated with each other but negatively associated with vein and stomatal densities. The link between venation and stomata resulted in a highly efficient match between potential maximum water loss (determined by stomatal conductance) and the leaf vascular system's capacity to replace that water. This important linkage is likely to be driven by stomatal size, because spatial limits in the packing of stomata onto the leaf surface apparently constrain the maximum size and density of stomata. We conclude that unified evolutionary changes in cell sizes of independent tissues, possibly mediated by changes in genome size, provide a means of substantially modifying leaf function while maintaining important functional links between leaf tissues. Our data also imply the presence of alternative evolutionary strategies involving cellular miniaturization during radiation into closed forest, and cell size increase in open habitats. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  6. Size control of giant unilamellar vesicles prepared from inverted emulsion droplets.

    Science.gov (United States)

    Nishimura, Kazuya; Suzuki, Hiroaki; Toyota, Taro; Yomo, Tetsuya

    2012-06-15

    The production of giant lipid vesicles with controlled size and structure will be an important technology in the design of quantitative biological assays in cell-mimetic microcompartments. For establishing size control of giant vesicles, we investigated the vesicle formation process, in which inverted emulsion droplets are transformed into giant unilamellar vesicles (GUVs) when they pass through an oil/water interface. The relationship between the size of the template emulsion and the converted GUVs was studied using inverted emulsion droplets with a narrow size distribution, which were prepared by microfluidics. We successfully found an appropriate centrifugal acceleration condition to obtain GUVs that had a desired size and narrow-enough size distribution with an improved yield so that emulsion droplets can become the template for GUVs. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

  7. Isotropic 2D quadrangle meshing with size and orientation control

    KAUST Repository

    Pellenard, Bertrand

    2011-12-01

    We propose an approach for automatically generating isotropic 2D quadrangle meshes from arbitrary domains with a fine control over sizing and orientation of the elements. At the heart of our algorithm is an optimization procedure that, from a coarse initial tiling of the 2D domain, enforces each of the desirable mesh quality criteria (size, shape, orientation, degree, regularity) one at a time, in an order designed not to undo previous enhancements. Our experiments demonstrate how well our resulting quadrangle meshes conform to a wide range of input sizing and orientation fields.

  8. Shrinking microbubbles with microfluidics: mathematical modelling to control microbubble sizes.

    Science.gov (United States)

    Salari, A; Gnyawali, V; Griffiths, I M; Karshafian, R; Kolios, M C; Tsai, S S H

    2017-11-29

    Microbubbles have applications in industry and life-sciences. In medicine, small encapsulated bubbles (methods are distinguished due to their precise control and ease-of-fabrication. Nevertheless, sub-10 μm diameter bubble generation using microfluidics remains challenging, and typically requires expensive equipment and cumbersome setups. Recently, our group reported a microfluidic platform that shrinks microbubbles to sub-10 μm diameters. The microfluidic platform utilizes a simple microbubble-generating flow-focusing geometry, integrated with a vacuum shrinkage system, to achieve microbubble sizes that are desirable in medicine, and pave the way to eventual clinical uptake of microfluidically generated microbubbles. A theoretical framework is now needed to relate the size of the microbubbles produced and the system's input parameters. In this manuscript, we characterize microbubbles made with various lipid concentrations flowing in solutions that have different interfacial tensions, and monitor the changes in bubble size along the microfluidic channel under various vacuum pressures. We use the physics governing the shrinkage mechanism to develop a mathematical model that predicts the resulting bubble sizes and elucidates the dominant parameters controlling bubble sizes. The model shows a good agreement with the experimental data, predicting the resulting microbubble sizes under different experimental input conditions. We anticipate that the model will find utility in enabling users of the microfluidic platform to engineer bubbles of specific sizes.

  9. Development of orthogonal NISTmAb size heterogeneity control methods.

    Science.gov (United States)

    Turner, Abigail; Yandrofski, Katharina; Telikepalli, Srivalli; King, Jason; Heckert, Alan; Filliben, James; Ripple, Dean; Schiel, John E

    2018-03-01

    The NISTmAb is a monoclonal antibody Reference Material from the National Institute of Standards and Technology; it is a class-representative IgG1κ intended to serve as a pre-competitive platform for harmonization and technology development in the biopharmaceutical industry. The publication series of which this paper is a part describes NIST's overall control strategy to ensure NISTmAb quality and availability over its lifecycle. In this paper, the development of a control strategy for monitoring NISTmAb size heterogeneity is described. Optimization and qualification of size heterogeneity measurement spanning a broad size range are described, including capillary electrophoresis-sodium dodecyl sulfate (CE-SDS), size exclusion chromatography (SEC), dynamic light scattering (DLS), and flow imaging analysis. This paper is intended to provide relevant details of NIST's size heterogeneity control strategy to facilitate implementation of the NISTmAb as a test molecule in the end user's laboratory. Graphical abstract Representative size exclusion chromatogram of the NIST monoclonal antibody (NISTmAb). The NISTmAb is a publicly available research tool intended to facilitate advancement of biopharmaceutical analytics. HMW = high molecular weight (trimer and dimer), LMW = low molecular weight (2 fragment peaks). Peak labeled buffer is void volume of the column from L-histidine background buffer.

  10. Optical inline measurement procedures for counting and sizing cells in bioprocess technology.

    Science.gov (United States)

    Rudolph, Guido; Lindner, Patrick; Bluma, Arne; Joeris, Klaus; Martinez, Geovanni; Hitzmann, Bernd; Scheper, Thomas

    2009-01-01

    To observe and control cultivation processes, optical sensors are used increasingly. Important parameters for controlling such processes are cell count, cell size distribution, and the morphology of cells. Among turbidity measurement methods, imaging procedures are applied for determining these process parameters. A disadvantage of most previously developed imaging procedures is that they are only available offline which requires sampling. On the other hand, available imaging inline probes can so far only deliver a limited number of process parameters. This chapter presents new optical procedures for the inline determination of cell count, cell size distribution, and other parameters. In particular, by in situ microscopy an imaging procedure will be described which allows the determination of direct and nondirect cell parameters in real time without sampling.

  11. SCF(SAP) controls organ size by targeting PPD proteins for degradation in Arabidopsis thaliana.

    Science.gov (United States)

    Wang, Zhibiao; Li, Na; Jiang, Shan; Gonzalez, Nathalie; Huang, Xiahe; Wang, Yingchun; Inzé, Dirk; Li, Yunhai

    2016-04-06

    Control of organ size by cell proliferation and growth is a fundamental process, but the mechanisms that determine the final size of organs are largely elusive in plants. We have previously revealed that the ubiquitin receptor DA1 regulates organ size by repressing cell proliferation in Arabidopsis. Here we report that a mutant allele of STERILE APETALA (SAP) suppresses the da1-1 mutant phenotype. We show that SAP is an F-box protein that forms part of a SKP1/Cullin/F-box E3 ubiquitin ligase complex and controls organ size by promoting the proliferation of meristemoid cells. Genetic analyses suggest that SAP may act in the same pathway with PEAPOD1 and PEAPOD2, which are negative regulators of meristemoid proliferation, to control organ size, but does so independently of DA1. Further results reveal that SAP physically associates with PEAPOD1 and PEAPOD2, and targets them for degradation. These findings define a molecular mechanism by which SAP and PEAPOD control organ size.

  12. Controlling Infrastructure Costs: Right-Sizing the Mission Control Facility

    Science.gov (United States)

    Martin, Keith; Sen-Roy, Michael; Heiman, Jennifer

    2009-01-01

    Johnson Space Center's Mission Control Center is a space vehicle, space program agnostic facility. The current operational design is essentially identical to the original facility architecture that was developed and deployed in the mid-90's. In an effort to streamline the support costs of the mission critical facility, the Mission Operations Division (MOD) of Johnson Space Center (JSC) has sponsored an exploratory project to evaluate and inject current state-of-the-practice Information Technology (IT) tools, processes and technology into legacy operations. The general push in the IT industry has been trending towards a data-centric computer infrastructure for the past several years. Organizations facing challenges with facility operations costs are turning to creative solutions combining hardware consolidation, virtualization and remote access to meet and exceed performance, security, and availability requirements. The Operations Technology Facility (OTF) organization at the Johnson Space Center has been chartered to build and evaluate a parallel Mission Control infrastructure, replacing the existing, thick-client distributed computing model and network architecture with a data center model utilizing virtualization to provide the MCC Infrastructure as a Service. The OTF will design a replacement architecture for the Mission Control Facility, leveraging hardware consolidation through the use of blade servers, increasing utilization rates for compute platforms through virtualization while expanding connectivity options through the deployment of secure remote access. The architecture demonstrates the maturity of the technologies generally available in industry today and the ability to successfully abstract the tightly coupled relationship between thick-client software and legacy hardware into a hardware agnostic "Infrastructure as a Service" capability that can scale to meet future requirements of new space programs and spacecraft. This paper discusses the benefits

  13. Nuclear DNA Content Varies with Cell Size across Human Cell Types

    Science.gov (United States)

    Gillooly, James F.; Hein, Andrew; Damiani, Rachel

    2015-01-01

    Variation in the size of cells, and the DNA they contain, is a basic feature of multicellular organisms that affects countless aspects of their structure and function. Within humans, cell size is known to vary by several orders of magnitude, and differences in nuclear DNA content among cells have been frequently observed. Using published data, here we describe how the quantity of nuclear DNA across 19 different human cell types increases with cell volume. This observed increase is similar to intraspecific relationships between DNA content and cell volume in other species, and interspecific relationships between diploid genome size and cell volume. Thus, we speculate that the quantity of nuclear DNA content in somatic cells of humans is perhaps best viewed as a distribution of values that reflects cell size distributions, rather than as a single, immutable quantity. PMID:26134319

  14. Size Specific Transfection to Mammalian Cells by Micropillar Array Electroporation

    Science.gov (United States)

    Zu, Yingbo; Huang, Shuyan; Lu, Yang; Liu, Xuan; Wang, Shengnian

    2016-12-01

    Electroporation serves as a promising non-viral gene delivery approach, while its current configuration carries several drawbacks associated with high-voltage electrical pulses and heterogeneous treatment on individual cells. Here we developed a new micropillar array electroporation (MAE) platform to advance the electroporation-based delivery of DNA and RNA probes into mammalian cells. By introducing well-patterned micropillar array texture on the electrode surface, the number of pillars each cell faces varies with its plasma membrane surface area, despite their large population and random locations. In this way, cell size specific electroporation is conveniently carried out, contributing to a 2.5~3 fold increase on plasmid DNA transfection and an additional 10-55% transgene knockdown with siRNA probes, respectively. The delivery efficiency varies with the number and size of micropillars as well as their pattern density. As MAE works like many single cell electroporation are carried out in parallel, the electrophysiology response of individual cells is representative, which has potentials to facilitate the tedious, cell-specific protocol screening process in current bulk electroporation (i.e., electroporation to a large population of cells). Its success might promote the wide adoption of electroporation as a safe and effective non-viral gene delivery approach needed in many biological research and clinical treatments.

  15. Role of proteins in controlling selenium nanoparticle size

    Energy Technology Data Exchange (ETDEWEB)

    Dobias, J; Suvorova, E I; Bernier-Latmani, R, E-mail: rizlan.bernier-latmani@epfl.ch [Environmental Microbiology Laboratory, EPFL, Station 6, 1015 Lausanne (Switzerland)

    2011-05-13

    This work investigates the potential for harnessing the association of bacterial proteins to biogenic selenium nanoparticles (SeNPs) to control the size distribution and the morphology of the resultant SeNPs. We conducted a proteomic study and compared proteins associated with biogenic SeNPs produced by E. coli to chemically synthesized SeNPs as well as magnetite nanoparticles. We identified four proteins (AdhP, Idh, OmpC, AceA) that bound specifically to SeNPs and observed a narrower size distribution as well as more spherical morphology when the particles were synthesized chemically in the presence of proteins. A more detailed study of AdhP (alcohol dehydrogenase propanol-preferring) confirmed the strong affinity of this protein for the SeNP surface and revealed that this protein controlled the size distribution of the SeNPs and yielded a narrow size distribution with a three-fold decrease in the median size. These results support the assertion that protein may become an important tool in the industrial-scale synthesis of SeNPs of uniform size and properties.

  16. Determining the optimum cell size of digital elevation model for ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 120; Issue 4. Determining the optimum cell size of digital elevation model for hydrologic ... Technology, Bahal 127 028, Bhiwani, Haryana, India. Agricultural & Food Engineering Department, Indian Institute of Technology, Kharagpur-721302, West Bengal, India.

  17. Determining the optimum cell size of digital elevation model for ...

    Indian Academy of Sciences (India)

    obtained DEMs were explored for their intrinsic quality using four different methods, i.e., sink analy- sis, fractal dimension of derived stream network, entropy measurement and ... ters decrease, and many delicate landscape fea- tures are lost. However, as one can understand, it is not enough to model the cell size effects.

  18. System Size Resonance Associated with Canard Phenomenon in a Biological Cell System

    Science.gov (United States)

    Ma, Juan; Li, Hong-ying; Hou, Zhong-huai; Xin, Hou-wen

    2008-12-01

    The influence of internal noise on the calcium oscillations is studied. It is found that stochastic calcium oscillations occur when the internal noise is considered, while the corresponding deterministic dynamics only yields a steady state. Also, the performance of such oscillations shows two maxima with the variation of the system size, indicating the occurrence of system size resonance. This behavior is found to be intimately connected with the canard phenomenon. Interestingly, it is also found that one of the optimal system sizes matches well with the real cell size, and such a match is robust to the variation of the control parameters.

  19. Sonochemical synthesis of silica particles and their size control

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hwa-Min [Advanced Materials and Chemical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Lee, Chang-Hyun [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of); Kim, Bonghwan, E-mail: bhkim@cu.ac.kr [Electronic and Electrical Engineering, Catholic University of Daegu, Gyeongbuk 38430 (Korea, Republic of)

    2016-09-01

    Graphical abstract: - Highlights: • Silica particles were easily prepared by an ultrasound-assisted sol–gel method. • The particle size was controlled by the ammonium hydroxide/water molar ratio. • The size-controlled diameter of silica particles ranged from 40 to 400 nm. • The particles were formed in a relatively short reaction time. - Abstract: Using an ultrasound-assisted sol–gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  20. Using Micromanipulation to Analyze Control of Vertebrate Meiotic Spindle Size

    Directory of Open Access Journals (Sweden)

    Jun Takagi

    2013-10-01

    Full Text Available The polymerization/depolymerization dynamics of microtubules (MTs have been reported to contribute to control of the size and shape of spindles, but quantitative analysis of how the size and shape correlate with the amount and density of MTs in the spindle remains incomplete. Here, we measured these parameters using 3D microscopy of meiotic spindles that self-organized in Xenopus egg extracts and presented a simple equation describing the relationship among these parameters. To examine the validity of the equation, we cut the spindle into two fragments along the pole-to-pole axis by micromanipulation techniques that rapidly decrease the amount of MTs. The spheroidal shape spontaneously recovered within 5 min, but the size of each fragment remained small. The equation we obtained quantitatively describes how the spindle size correlates with the amount of MTs while maintaining the shape and the MT density.

  1. Combined Optimal Sizing and Control for a Hybrid Tracked Vehicle

    Directory of Open Access Journals (Sweden)

    Huei Peng

    2012-11-01

    Full Text Available The optimal sizing and control of a hybrid tracked vehicle is presented and solved in this paper. A driving schedule obtained from field tests is used to represent typical tracked vehicle operations. Dynamics of the diesel engine-permanent magnetic AC synchronous generator set, the lithium-ion battery pack, and the power split between them are modeled and validated through experiments. Two coupled optimizations, one for the plant parameters, forming the outer optimization loop and one for the control strategy, forming the inner optimization loop, are used to achieve minimum fuel consumption under the selected driving schedule. The dynamic programming technique is applied to find the optimal controller in the inner loop while the component parameters are optimized iteratively in the outer loop. The results are analyzed, and the relationship between the key parameters is observed to keep the optimal sizing and control simultaneously.

  2. SAW-controlled drop size for flow focusing.

    Science.gov (United States)

    Schmid, Lothar; Franke, Thomas

    2013-05-07

    We demonstrate the regularization of droplet formation by applying a surface acoustic wave (SAW) localized at the flow-focus junction of a drop maker. This allows electronic control of drop size in real time, without changing the flow rates or microchannel dimensions.

  3. Automated Control Surface Design and Sizing for the Prandtl Plane

    NARCIS (Netherlands)

    Van Ginneken, D.A.J.; Voskuijl, M.; Van Tooren, M.J.L.; Frediani, A.

    2010-01-01

    This paper presents a methodology for the design of the primary flight control surfaces, in terms of size, number and location, for fixed wing aircraft (conventional or unconventional). As test case, the methodology is applied to a 300 passenger variant of the Prandtl Plane. This box wing aircraft

  4. Size Controlled Synthesis of Transition Metal Nanoparticles for Catalytic Applications

    KAUST Repository

    Esparza, Angel

    2011-07-07

    Catalysis offers cleaner and more efficient chemical reactions for environmental scientists. More than 90% of industrial processes are performed with a catalyst involved, however research it is still required to improve the catalyst materials. The purpose of this work is to contribute with the development of catalysts synthesis with two different approaches. First, the precise size control of non-noble metals nanoparticles. Second, a new one-pot synthesis method based on a microemulsion system was developed to synthesize size-controlled metal nanoparticles in oxide supports. The one-pot method represents a simple approach to synthesize both support and immobilized nanometer-sized non-noble metal nanoparticles in the same reaction system. Narrow size distribution nickel, cobalt, iron and cobalt-nickel nanoparticles were obtained. High metal dispersions are attainable regardless the metal or support used in the synthesis. Thus, the methodology is adaptable and robust. The sizecontrolled supported metal nanoparticles offer the opportunity to study size effects and metal-support interactions on different catalytic reactions with different sets of metals and supports.

  5. Optically controlled grippers for manipulating micron-sized particles

    Science.gov (United States)

    Gibson, Graham; Barron, Louise; Beck, Fiona; Whyte, Graeme; Padgett, Miles

    2007-01-01

    We report the development of a joystick controlled gripper for the real-time manipulation of micron-sized objects, driven using holographic optical tweezers (HOTs). The gripper consists of an arrangement of four silica beads, located in optical traps, which can be positioned and scaled in order to trap an object indirectly. The joystick can be used to grasp, move (lateral or axial), and change the orientation of the target object. The ability to trap objects indirectly allows us to demonstrate the manipulation of a strongly scattering micron-sized metallic particle.

  6. Capabilities and Limitations of Tissue Size Control through Passive Mechanical Forces.

    Directory of Open Access Journals (Sweden)

    Jochen Kursawe

    2015-12-01

    Full Text Available Embryogenesis is an extraordinarily robust process, exhibiting the ability to control tissue size and repair patterning defects in the face of environmental and genetic perturbations. The size and shape of a developing tissue is a function of the number and size of its constituent cells as well as their geometric packing. How these cellular properties are coordinated at the tissue level to ensure developmental robustness remains a mystery; understanding this process requires studying multiple concurrent processes that make up morphogenesis, including the spatial patterning of cell fates and apoptosis, as well as cell intercalations. In this work, we develop a computational model that aims to understand aspects of the robust pattern repair mechanisms of the Drosophila embryonic epidermal tissues. Size control in this system has previously been shown to rely on the regulation of apoptosis rather than proliferation; however, to date little work has been done to understand the role of cellular mechanics in this process. We employ a vertex model of an embryonic segment to test hypotheses about the emergence of this size control. Comparing the model to previously published data across wild type and genetic perturbations, we show that passive mechanical forces suffice to explain the observed size control in the posterior (P compartment of a segment. However, observed asymmetries in cell death frequencies across the segment are demonstrated to require patterning of cellular properties in the model. Finally, we show that distinct forms of mechanical regulation in the model may be distinguished by differences in cell shapes in the P compartment, as quantified through experimentally accessible summary statistics, as well as by the tissue recoil after laser ablation experiments.

  7. Magnetic agglomeration method for size control in the synthesis of magnetic nanoparticles

    Science.gov (United States)

    Huber, Dale L [Albuquerque, NM

    2011-07-05

    A method for controlling the size of chemically synthesized magnetic nanoparticles that employs magnetic interaction between particles to control particle size and does not rely on conventional kinetic control of the reaction to control particle size. The particles are caused to reversibly agglomerate and precipitate from solution; the size at which this occurs can be well controlled to provide a very narrow particle size distribution. The size of particles is controllable by the size of the surfactant employed in the process; controlling the size of the surfactant allows magnetic control of the agglomeration and precipitation processes. Agglomeration is used to effectively stop particle growth to provide a very narrow range of particle sizes.

  8. Control valve sizing and specification: The first step

    International Nuclear Information System (INIS)

    Harkins, J.F.; Hoyle, E.D.

    1991-01-01

    Today's modern control valve can satisfy almost any application. Special trim, materials, operators, and body configurations have been developed to meet the most severe operating conditions. The missing link in the chain connecting design to application is often the interpretation and communication of the requirements for determining the proper valve for each application. This paper addresses an important but often neglected requirement for proper selection and sizing of control valves: the determination of correct input data. It presents criteria necessary to ensure that the data given the manufacturer accurately reflects the conditions under which the control valve will operate. It highlights the importance of communication between the system design engineer, the valve specifying engineer, and the control valve supplier, to ensure that the final system design meets the true requirements of the application. An example is provided of a simple liquid-handling system, for which line losses and variations in flow and equipment capacities are tabulated and requirements shown graphically on typical control valve characteristic curves. The effects of seemingly harmless, conservative assumptions regarding line losses, equipment capacities and selection, sizing practices, and the selection of various flow data can have on the final valve selection are illustrated. Also discussed is the proper selection of equipment and input data, based on the example

  9. Graphene-Based Flexible Micrometer-Sized Microbial Fuel Cell

    KAUST Repository

    Mink, Justine E.

    2013-10-23

    Microbial fuel cells harvest electrical energy produced by bacteria during the natural decomposition of organic matter. We report a micrometer-sized microbial fuel cell that is able to generate nanowatt-scale power from microliters of liquids. The sustainable design is comprised of a graphene anode, an air cathode, and a polymer-based substrate platform for flexibility. The graphene layer was grown on a nickel thin film by using chemical vapor deposition at atmospheric pressure. Our demonstration provides a low-cost option to generate useful power for lab-on-chip applications and could be promising to rapidly screen and scale up microbial fuel cells for water purification without consuming excessive power (unlike other water treatment technologies).

  10. A moonlighting enzyme links Escherichia coli cell size with central metabolism.

    Directory of Open Access Journals (Sweden)

    Norbert S Hill

    Full Text Available Growth rate and nutrient availability are the primary determinants of size in single-celled organisms: rapidly growing Escherichia coli cells are more than twice as large as their slow growing counterparts. Here we report the identification of the glucosyltransferase OpgH as a nutrient-dependent regulator of E. coli cell size. During growth under nutrient-rich conditions, OpgH localizes to the nascent septal site, where it antagonizes assembly of the tubulin-like cell division protein FtsZ, delaying division and increasing cell size. Biochemical analysis is consistent with OpgH sequestering FtsZ from growing polymers. OpgH is functionally analogous to UgtP, a Bacillus subtilis glucosyltransferase that inhibits cell division in a growth rate-dependent fashion. In a striking example of convergent evolution, OpgH and UgtP share no homology, have distinct enzymatic activities, and appear to inhibit FtsZ assembly through different mechanisms. Comparative analysis of E. coli and B. subtilis reveals conserved aspects of growth rate regulation and cell size control that are likely to be broadly applicable. These include the conservation of uridine diphosphate glucose as a proxy for nutrient status and the use of moonlighting enzymes to couple growth rate-dependent phenomena to central metabolism.

  11. A chemical screen probing the relationship between mitochondrial content and cell size.

    Directory of Open Access Journals (Sweden)

    Toshimori Kitami

    Full Text Available The cellular content of mitochondria changes dynamically during development and in response to external stimuli, but the underlying mechanisms remain obscure. To systematically identify molecular probes and pathways that control mitochondrial abundance, we developed a high-throughput imaging assay that tracks both the per cell mitochondrial content and the cell size in confluent human umbilical vein endothelial cells. We screened 28,786 small molecules and observed that hundreds of small molecules are capable of increasing or decreasing the cellular content of mitochondria in a manner proportionate to cell size, revealing stereotyped control of these parameters. However, only a handful of compounds dissociate this relationship. We focus on one such compound, BRD6897, and demonstrate through secondary assays that it increases the cellular content of mitochondria as evidenced by fluorescence microscopy, mitochondrial protein content, and respiration, even after rigorous correction for cell size, cell volume, or total protein content. BRD6897 increases uncoupled respiration 1.6-fold in two different, non-dividing cell types. Based on electron microscopy, BRD6897 does not alter the percent of cytoplasmic area occupied by mitochondria, but instead, induces a striking increase in the electron density of existing mitochondria. The mechanism is independent of known transcriptional programs and is likely to be related to a blockade in the turnover of mitochondrial proteins. At present the molecular target of BRD6897 remains to be elucidated, but if identified, could reveal an important additional mechanism that governs mitochondrial biogenesis and turnover.

  12. Crystal size control of sulfathiazole using high pressure carbon dioxide

    Science.gov (United States)

    Kitamura, M.; Yamamoto, M.; Yoshinaga, Y.; Masuoka, H.

    1997-07-01

    The effect of the pressurization method of carbon dioxide on the crystallization behavior and crystal size of sulphathiazole (SUT) was investigated. In the "stepwise pressurization" method exceptionally large pillar-like crystals of 2-6 mm were obtained as mainly a scaling on the wall of the crystallizer. In the "rapid pressurization" method, crystals with a size one third to half of that obtained in the stepwise method precipitated, indicating the accelerated nucleation rate by the rapid increase of the supersaturation degree with a vigorous bubbling. With the new method of "two-step pressurization", in the first step the nucleation is accelerated with a much larger pressure instantly created, and in the second step the growth rate is retarded with the lower pressure. By this method much more fine crystals (from a few tens to several hundred micrometers) were produced and the scaling was suppressed. In this method a large supersaturation degree at an interface between the gas (bubble) and liquid phase under a vigorous bubbling may play an important role in accelerating the nucleation. The average size of the crystals tended to become smaller with increase of the first pressure and the expansion ratio at a decompression point, and it tended to get larger with increase of the second pressure. These results show that the GAS method is very useful for the control of crystal size over a wide range.

  13. Cytotoxicity and cellular uptake of different sized gold nanoparticles in ovarian cancer cells

    Science.gov (United States)

    Kumar, Dhiraj; Mutreja, Isha; Chitcholtan, Kenny; Sykes, Peter

    2017-11-01

    Nanomedicine has advanced the biomedical field with the availability of multifunctional nanoparticles (NPs) systems that can target a disease site enabling drug delivery and helping to monitor the disease. In this paper, we synthesised the gold nanoparticles (AuNPs) with an average size 18, 40, 60 and 80 nm, and studied the effect of nanoparticles size, concentration and incubation time on ovarian cancer cells namely, OVCAR5, OVCAR8, and SKOV3. The size measured by transmission electron microscopy images was slightly smaller than the hydrodynamic diameter; measured size by ImageJ as 14.55, 38.13, 56.88 and 78.56 nm. The cellular uptake was significantly controlled by the AuNPs size, concentration, and the cell type. The nanoparticles uptake increased with increasing concentration, and 18 and 80 nm AuNPs showed higher uptake ranging from 1.3 to 5.4 μg depending upon the concentration and cell type. The AuNPs were associated with a temporary reduction in metabolic activity, but metabolic activity remained more than 60% for all sample types; NPs significantly affected the cell proliferation activity in first 12 h. The increase in nanoparticle size and concentration induced the production of reactive oxygen species in 24 h.

  14. Continuous Size Tuning of Monodispersed ZnO Nanoparticles and Its Size Effect on the Performance of Perovskite Solar Cells.

    Science.gov (United States)

    Zhang, Rong; Fei, Chengbin; Li, Bo; Fu, Haoyu; Tian, Jianjun; Cao, Guozhong

    2017-03-22

    ZnO has been demonstrated to be a promising candidate to fabricate high efficiency perovskite solar cells (PSCs) in terms of its better electron extraction and transport properties. However, the inability of synthesis of ZnO nanoparticles (NPs) with minimal surface defects and agglomeration remains a great challenge hindering the fabrication of highly efficient PSCs. In this work, highly crystalline and agglomeration-free ZnO NPs with controlled size were synthesized through a facile solvothermal method. Such ZnO NPs were applied in the fabrication of meso-structured PSCs. The solar cells with ∼40 nm ZnO NPs exhibit the highest power conversion efficiency (PCE) of 15.92%. Steady-state and time-resolved photoluminescence measurements revealed the faster injection and lower charge recombination at the interface of ∼40 nm ZnO NPs and perovskite, resulting in significantly enhanced J SC and V OC .

  15. A LCMT1-PME-1 methylation equilibrium controls mitotic spindle size.

    Science.gov (United States)

    Xia, Xiaoyu; Gholkar, Ankur; Senese, Silvia; Torres, Jorge Z

    2015-01-01

    Leucine carboxyl methyltransferase-1 (LCMT1) and protein phosphatase methylesterase-1 (PME-1) are essential enzymes that regulate the methylation of the protein phosphatase 2A catalytic subunit (PP2AC). LCMT1 and PME-1 have been linked to the regulation of cell growth and proliferation, but the underlying mechanisms have remained elusive. We show here an important role for an LCMT1-PME-1 methylation equilibrium in controlling mitotic spindle size. Depletion of LCMT1 or overexpression of PME-1 led to long spindles. In contrast, depletion of PME-1, pharmacological inhibition of PME-1 or overexpression of LCMT1 led to short spindles. Furthermore, perturbation of the LCMT1-PME-1 methylation equilibrium led to mitotic arrest, spindle assembly checkpoint activation, defective cell divisions, induction of apoptosis and reduced cell viability. Thus, we propose that the LCMT1-PME-1 methylation equilibrium is critical for regulating mitotic spindle size and thereby proper cell division.

  16. Cell cycle control by components of cell anchorage

    OpenAIRE

    Gad, Annica

    2005-01-01

    Extracellular factors, such as growth factors and cell anchorage to the extracellular matrix, control when and where cells may proliferate. This control is abolished when a normal cell transforms into a tumour cell. The control of cell proliferation by cell anchorage was elusive and less well studied than the control by growth factors. Therefore, we aimed to clarify at what points in the cell cycle and through which molecular mechanisms cell anchorage controls cell cycle pro...

  17. The Effects of Topographical Patterns and Sizes on Neural Stem Cell Behavior

    Science.gov (United States)

    Qi, Lin; Li, Ning; Huang, Rong; Song, Qin; Wang, Long; Zhang, Qi; Su, Ruigong; Kong, Tao; Tang, Mingliang; Cheng, Guosheng

    2013-01-01

    Engineered topographical manipulation, a paralleling approach with conventional biochemical cues, has recently attracted the growing interests in utilizations to control stem cell fate. In this study, effects of topological parameters, pattern and size are emphasized on the proliferation and differentiation of adult neural stem cells (ANSCs). We fabricate micro-scale topographical Si wafers with two different feature sizes. These topographical patterns present linear micro-pattern (LMP), circular micro-pattern (CMP) and dot micro-pattern (DMP). The results show that the three topography substrates are suitable for ANSC growth, while they all depress ANSC proliferation when compared to non-patterned substrates (control). Meanwhile, LMP and CMP with two feature sizes can both significantly enhance ANSC differentiation to neurons compared to control. The smaller the feature size is, the better upregulation applies to ANSC for the differentiated neurons. The underlying mechanisms of topography-enhanced neuronal differentiation are further revealed by directing suppression of mitogen-activated protein kinase/extracellular signaling-regulated kinase (MAPK/Erk) signaling pathway in ANSC using U0126, known to inhibit the activation of Erk. The statistical results suggest MAPK/Erk pathway is partially involved in topography-induced differentiation. These observations provide a better understanding on the different roles of topographical cues on stem cell behavior, especially on the selective differentiation, and facilitate to advance the field of stem cell therapy. PMID:23527077

  18. Revolving Vernier Mechanism Controls Size of Linear Homomultimer.

    Science.gov (United States)

    Uchida, Takeo; Abe, Keita; Endo, Yuma; Ichiseki, Shosei; Akita, Satoru; Liu, Shiyun; Aradachi, Sho; Saito, Masataka; Fukuchi, Akihiko; Kikkawa, Taiyo; Dammaretz, Theo; Kawamata, Ibuki; Suzuki, Yuki; Nomura, Shin-Ichiro M; Murata, Satoshi

    2017-11-01

    A new kind of the Vernier mechanism that is able to control the size of linear assembly of DNA origami nanostructures is proposed. The mechanism is realized by mechanical design of DNA origami, which consists of a hollow cylinder and a rotatable shaft in it connected through the same scaffold. This nanostructure stacks with each other by the shape complementarity at its top and bottom surfaces of the cylinder, while the number of stacking is limited by twisting angle of the shaft. Experiments have shown that the size distribution of multimeric assembly of the origami depends on the twisting angle of the shaft; the average lengths of the multimer are decamer, hexamer, and tetramer for 0°, 10°, and 20° twist, respectively. In summary, it is possible to affect the number of polymerization by adjusting the precise shape and movability of a molecular structure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Particle size tailoring of ursolic acid nanosuspensions for improved anticancer activity by controlled antisolvent precipitation.

    Science.gov (United States)

    Wang, Yancai; Song, Ju; Chow, Shing Fung; Chow, Albert H L; Zheng, Ying

    2015-10-15

    The present study was aimed at tailoring the particle size of ursolic acid (UA) nanosuspension for improved anticancer activity. UA nanosuspensions were prepared by antisolvent precipitation using a four-stream multi-inlet vortex mixer (MIVM) under defined conditions of varying solvent composition, drug feeding concentration or stream flow rate. The resulting products were characterized for particle size and polydispersity. Two of the UA nanosuspensions with mean particle sizes of 100 and 300 nm were further assessed for their in-vitro activity against MCF-7 breast cancer cells using fluorescence microscopy with 4',6-diamidino-2-phenylindole (DAPI) staining, as well as flow cytometry with propidium (PI) staining and with double staining by fluorescein isothiocyanate. It was revealed that the solvent composition, drug feeding concentration and stream flow rate were critical parameters for particle size control of the UA nanosuspensions generated with the MIVM. Specifically, decreasing the UA feeding concentration or increasing the stream flow rate or ethanol content resulted in a reduction of particle size. Excellent reproducibility for nanosuspension production was demonstrated for the 100 and 300 nm UA preparations with a deviation of not more than 5% in particle size from the mean value of three independent batches. Fluorescence microscopy and flow cytometry revealed that these two different sized UA nanosuspensions, particularly the 300 nm sample, exhibited a higher anti-proliferation activity against the MCF-7 cells and afforded a larger population of these cells in both early and late apoptotic phases. In conclusion, MIVM is a robust and pragmatic tool for tailoring the particle size of the UA nanosuspension. Particle size appears to be a critical determinant of the anticancer activity of the UA nanoparticles. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Walking control of small size humanoid robot: HAJIME ROBOT 18

    Science.gov (United States)

    Sakamoto, Hajime; Nakatsu, Ryohei

    2007-12-01

    HAJIME ROBOT 18 is a fully autonomous biped robot. It has been developed for RoboCup which is a worldwide soccer competition of robots. It is necessary for a robot to have high mobility to play soccer. High speed walking and all directional walking are important to approach and to locate in front of a ball. HAJIME ROBOT achieved these walking. This paper describes walking control of a small size humanoid robot 'HAJIME ROBOT 18' and shows the measurement result of ZMP (Zero Moment Point). HAJIME ROBOT won the Robotics Society of Japan Award in RoboCup 2005 and in RoboCup 2006 Japan Open.

  1. EXAFS Studies of Palladium Nanoparticles: Size Control and Hydrogenation

    Science.gov (United States)

    Harris, T.; Soussan, L.; Isseroff, R.; Sun, Y.; Rafailovich, M. H.; Frenkel, A. I.

    2007-02-01

    We synthesized several samples of thiol-stabilized Pd nanoparticles by controlling their size with the palladium/thiol ratio from 5:1 to 1:3. Size dependence on the Pd/thiol ratio was verified by comparing the Pd-S and Pd-Pd coordination numbers. The average size of free-standing nanoparticles decreased as the thiol concentration increased and stabilized at the 1:2 value of palladium/thiol ratio. In addition to the free-standing nanoparticles, we analyzed their thin films by depositing them as monolayers on Kapton film using Langmuir-Blodgett technique. We obtained that the structure of the nanoparticles was preserved, within the accuracy of the EXAFS measurement, after preparing Langmuir films. We also studied the effect of hydrogenation on the both type of the nanoparticles (the free standing ones and those in the monolayers). In both cases, exposure to 4 atm H2 pressure resulted in the elongation of the average Pd-Pd distance. The larger change (0.06±0.03 Å, relative to the non-hydrogenated films) was observed in the smaller clusters (with 1:1 Pd thiol ratio), and the smaller change (0.03±0.01 Å) — in the larger clusters (with 3:1 ratio). Such bond length expansion is attributed to the defects caused by H2 adsorption.

  2. Cell size and cell number in dwarf mutants of barley (Hordeum vulgare)

    International Nuclear Information System (INIS)

    Blonstein, A.D.; Gale, M.D.

    1984-01-01

    Sixteen height mutants, induced by sodium azide treatment of the two-rowed barley variety Proctor, have been used to investigate the relationship between the extent and nature of stem shortening with alterations in cell size and cell number, and the pleiotropic effects of dwarfing genes on vegetative development and agronomic performance. The studies on epidermal cell number and cell length in the developmentally earliest and latest elongated vegetative tissues - the coleoptile and peduncle resprectively - suggest that cell number may be the primary determinant of plant height. One semi-prostrate and one erectoides mutant are used to illustrate different cell number/cell size strategies and their relationships with gibberellin sensitivity, growth rate and lodging resistance are discussed. (author)

  3. Controlled regular locomotion of algae cell microrobots.

    Science.gov (United States)

    Xie, Shuangxi; Jiao, Niandong; Tung, Steve; Liu, Lianqing

    2016-06-01

    Algae cells can be considered as microrobots from the perspective of engineering. These organisms not only have a strong reproductive ability but can also sense the environment, harvest energy from the surroundings, and swim very efficiently, accommodating all these functions in a body of size on the order of dozens of micrometers. An interesting topic with respect to random swimming motions of algae cells in a liquid is how to precisely control them as microrobots such that they swim according to manually set routes. This study developed an ingenious method to steer swimming cells based on the phototaxis. The method used a varying light signal to direct the motion of the cells. The swimming trajectory, speed, and force of algae cells were analyzed in detail. Then the algae cell could be controlled to swim back and forth, and traverse a crossroad as a microrobot obeying specific traffic rules. Furthermore, their motions along arbitrarily set trajectories such as zigzag, and triangle were realized successfully under optical control. Robotize algae cells can be used to precisely transport and deliver cargo such as drug particles in microfluidic chip for biomedical treatment and pharmacodynamic analysis. The study findings are expected to bring significant breakthrough in biological drives and new biomedical applications.

  4. Quantifying size-dependent interactions between fluorescently labeled polystyrene nanoparticles and mammalian cells

    Directory of Open Access Journals (Sweden)

    Varela Juan A

    2012-09-01

    Full Text Available Abstract Background Nanoparticles (NPs are currently used in a wide variety of fields such as technology, medicine and industry. Due to the novelty of these applications and to ensure their success, a precise characterization of the interactions between NPs and cells is essential. Findings The current study explores the uptake of polystyrene NPs by 1321N1 human astrocytoma and A549 human lung carcinoma cell lines. In this work we show for the first time a comparison of the uptake rates of fluorescently labeled carboxylated polystyrene (PS NPs of different sizes (20, 40 and 100 nm in two different cell types, keeping the number of NPs per unit volume constant for all sizes. We propose a reliable methodology to control the dose of fluorescently labeled NPs, by counting individual NPs using automated particle detection from 3D confocal microscopy images. The possibility of detecting individual NPs also allowed us to calculate the size of each nanoparticle and compare the fluorescence of single NPs across different sizes, thereby providing a robust platform for normalization of NP internalization experiments as measured by flow cytometry. Conclusions Our findings show that 40 nm NPs are internalized faster than 20 nm or 100 nm particles in both cell lines studied, suggesting that there is a privileged size gap in which the internalization of NPs is higher.

  5. Environment friendly approach for size controllable synthesis of biocompatible Silver nanoparticles using diastase.

    Science.gov (United States)

    Maddinedi, Sireesh Babu; Mandal, Badal Kumar; Anna, Kiran Kumar

    2017-01-01

    A green, facile method for the size selective synthesis of silver nanoparticles (AgNPs) using diastase as green reducing and stabilizing agent is reported. The thiol groups present in the diastase are mainly responsible for the rapid reaction rate of silver nanoparticles synthesis. The variation in the size and morphology of AgNPs were studied by changing the pH of diastase. The prepared silver nanoparticles were characterized by using UV-vis, XRD, FTIR, TEM and SAED. The FTIR analysis revealed the stabilization of diastase molecules on the surface of AgNPs. Additionally, in-vitro cytotoxicity experiments concluded that the cytotoxicity of the as-synthesized AgNPs towards mouse fibroblast (3T3) cell lines is dose and size dependent. Furthermore, the present method is an alternative to the traditional chemical methods of size controlled AgNPs synthesis. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Cell cycle control factors and skeletal development

    Directory of Open Access Journals (Sweden)

    Toru Ogasawara

    2013-05-01

    Full Text Available In the oral and maxillofacial region, conditions such as delayed bone healing after tooth extraction, bone fracture, trauma-induced bone or cartilage defects, and tumors or birth defects are common, and it is necessary to identify the molecular mechanisms that control skeletogenesis or the differentiation of cells, in order to establish new treatment strategies for these conditions. Multiple studies have been conducted to investigate the involvement of factors that may be crucial for skeletogenesis or the differentiation of cells, including transcription factors, growth factors and cell cycle factors. Several genetically engineered mouse models of cell cycle factors have been generated in research seeking to identify cell cycle factor(s involved in the differentiation of cells, carcinogenesis, etc. Many groups have also reported the importance of cell cycle factors in the differentiation of osteoblasts, osteoclasts, chondrocytes and other cell types. Herein, we review the phenotypes of the genetically engineered mouse models of cell cycle factors with a particular focus on the size, body weight and skeletal abnormalities of the mice, and we discuss the potential of cell cycle factors as targets of clinical applications.

  7. Adsorption of hematite nanoparticles onto Caco-2 cells and the cellular impairments: effect of particle size

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Wen; Chen Yongsheng [School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Kalive, Madhavi; Capco, David G, E-mail: yongsheng.chen@ce.gatech.edu [School of Life Sciences, Arizona State University, Tempe, AZ 85287 (United States)

    2010-09-03

    control cells without the exposure to NPs. NPs initially triggered a dynamic reorganization and detachment of microvilli structures on Caco-2 cell surfaces. Following this impact, the drop in TEER occurred more significantly, particularly for the exposure to 26 nm NPs, which was consistent with the observations with confocal microscopy that the junctions were more severely disrupted by 26 nm NPs than other sizes. In conclusion, this paper demonstrates the interactions at the ultrastructural level from initial surface adsorption of NPs upon cells, to the subsequent microvilli reorganization, membrane penetration and the disruption of adherens junction and provides the fundamental information on size effects on NP behavior which is often poorly addressed for in vitro cytotoxicity studies of NPs.

  8. Adsorption of hematite nanoparticles onto Caco-2 cells and the cellular impairments: effect of particle size

    Science.gov (United States)

    Zhang, Wen; Kalive, Madhavi; Capco, David G.; Chen, Yongsheng

    2010-09-01

    The increasing applications of engineered nanomaterials nowadays have elevated the potential of human exposure through various routes including inhalation, skin penetration and digestion. To date there is scarce information on a quantitative description of the interactions between nanoparticles (NPs) and cell surfaces and the detrimental effects from the exposure. The purpose of this work was to study in vitro exposure of Caco-2 cells to hematite (α-Fe2O3) NPs and to determine the particle size effects on the adsorption behaviors. Cellular impairment was also investigated and compared. Hematite NPs were synthesized as part of this study with a discrete size distribution and uniform morphology examined by dynamic light scattering (DLS) and confirmed by transmission electron microscopy (TEM). Caco-2 cells were cultured as a model epithelium to mirror human intestinal cells and used to evaluate the impacts of the exposure to NPs by measuring transepithelial electrical resistance (TEER). Cell surface disruption, localization and translocation of NPs through the cells were analyzed with immunocytochemical staining and confocal microscopy. Results showed that hematite NPs had mean diameters of 26, 53, 76 and 98 nm and were positively charged with minor aggregation in the buffer solution. Adsorption of the four sizes of NPs on cells reached equilibrium within approximately 5 min but adsorption kinetics were found to be size-dependent. The adsorption rates expressed as mg m - 2 min - 1 were greater for large NPs (76 and 98 nm) than those for small NPs (26 and 53 nm). However, adsorption rates, expressed in units of m - 2 min - 1, were much greater for small NPs than large ones. After the adsorption equilibrium was reached, the adsorbed mass of NPs on a unit area of cells was calculated and showed no significant size dependence. Longer exposure time (>3 h) induced adverse cellular effects as indicated by the drop in TEER compared to the control cells without the exposure

  9. Surfactant effects in magnetite nanoparticles of controlled size

    International Nuclear Information System (INIS)

    Guardia, P.; Batlle-Brugal, B.; Roca, A.G.; Iglesias, O.; Morales, M.P.; Serna, C.J.; Labarta, A.; Batlle, X.

    2007-01-01

    Magnetite Fe 3 O 4 nanoparticles of controlled size within 6 and 20 nm in diameter were synthesised by thermal decomposition of an iron organic precursor in an organic medium. Particles were coated with oleic acid. For all samples studied, saturation magnetisation M s is size-independent, and reaches a value close to that expected for bulk magnetite, in contrast to results in small particle systems for which M s is usually much smaller due to surface spin disorder. The coercive field for the 6 nm particles is in agreement with coherent rotation, taking the bulk magnetocrystalline anisotropy into account. Both results suggest that the oleic acid molecules covalently bonded to the nanoparticle surface yield a strong reduction in the surface spin disorder. However, although the saturated state may be similar, the approach to saturation is different and, in particular, the high-field differential susceptibility is one order of magnitude larger than in bulk materials. The relevance of these results in biomedical applications is discussed

  10. Hippo signaling controls cell cycle and restricts cell plasticity in planarians.

    Directory of Open Access Journals (Sweden)

    Nídia de Sousa

    2018-01-01

    Full Text Available The Hippo pathway plays a key role in regulating cell turnover in adult tissues, and abnormalities in this pathway are consistently associated with human cancers. Hippo was initially implicated in the control of cell proliferation and death, and its inhibition is linked to the expansion of stem cells and progenitors, leading to larger organ size and tumor formation. To understand the mechanism by which Hippo directs cell renewal and promotes stemness, we studied its function in planarians. These stem cell-based organisms are ideal models for the analysis of the complex cellular events underlying tissue renewal in the whole organism. hippo RNA interference (RNAi in planarians decreased apoptotic cell death, induced cell cycle arrest, and could promote the dedifferentiation of postmitotic cells. hippo RNAi resulted in extensive undifferentiated areas and overgrowths, with no effect on body size or cell number. We propose an essential role for hippo in controlling cell cycle, restricting cell plasticity, and thereby preventing tumoral transformation.

  11. Scalable preparation of sized-controlled Co-N-C electrocatalyst for efficient oxygen reduction reaction

    Science.gov (United States)

    Ai, Kelong; Li, Zelun; Cui, Xiaoqiang

    2017-11-01

    Heat-treated metal-nitrogen-carbon (M-N-C) materials are emerging as promising non-precious catalysts to replace expensive Pt-based materials for oxygen reduction reaction (ORR) in energy conversion and storage devices. Despite recent progress, their activity and durability are still far from satisfactory. The activity site and particle size are among the most important factors for the ORR activity of M-N-C catalysts. Extensive efforts have been made to reveal the correlation of active site and activity. However, it remains unclear to what extent the particle size will influence the ORR activity of M-N-C materials. Moreover, to the best of our knowledge, controllable synthesis of M-N-C catalysts with high-density activity sites remains elusive. Herein, we develop a straightforward method to produce a monodisperse and size-controlled Co-N-C (Nano-P-ZIF-67) electrocatalyst, and systemically investigate its catalytic mechanisms. Only by optimizing the particle size, Nano-P-ZIF-67 outperforms the commercial 20 wt% Pt/C regarding all evaluating indicators for ORR catalysts in alkaline media including higher catalytic activity, durability, and stronger methanol tolerance. Nano-P-ZIF-67 is assembled into a cell, and the cell shows a power density of 45.5 mW/cm2, which is the highest value among currently studied cathode catalysts. We expect Nano-P-ZIF-67 to be a highly interesting candidate for the next generation of ORR catalysts.

  12. Recovery of aging-related size increase of skin epithelial cells: in vivo mouse and in vitro human study.

    Directory of Open Access Journals (Sweden)

    Igor Sokolov

    Full Text Available The size increase of skin epithelial cells during aging is well-known. Here we demonstrate that treatment of aging cells with cytochalasin B substantially decreases cell size. This decrease was demonstrated on a mouse model and on human skin cells in vitro. Six nude mice were treated by topical application of cytochalasin B on skin of the dorsal left midsection for 140 days (the right side served as control for placebo treatment. An average decrease in cell size of 56±16% resulted. A reduction of cell size was also observed on primary human skin epithelial cells of different in vitro age (passages from 1 to 8. A cell strain obtained from a pool of 6 human subjects was treated with cytochalasin B in vitro for 12 hours. We observed a decrease in cell size that became statistically significant and reached 20-40% for cells of older passage (6-8 passages whereas no substantial change was observed for younger cells. These results may be important for understanding the aging processes, and for cosmetic treatment of aging skin.

  13. The Influences of Cell Type and ZnO Nanoparticle Size on Immune Cell Cytotoxicity and Cytokine Induction

    Directory of Open Access Journals (Sweden)

    Thurber Aaron

    2009-01-01

    Full Text Available Abstract Nanotechnology represents a new and enabling platform that promises to provide a range of innovative technologies for biological applications. ZnO nanoparticles of controlled size were synthesized, and their cytotoxicity toward different human immune cells evaluated. A differential cytotoxic response between human immune cell subsets was observed, with lymphocytes being the most resistant and monocytes being the most susceptible to ZnO nanoparticle-induced toxicity. Significant differences were also observed between previously activated memory lymphocytes and naive lymphocytes, indicating a relationship between cell-cycle potential and nanoparticle susceptibility. Mechanisms of toxicity involve the generation of reactive oxygen species, with monocytes displaying the highest levels, and the degree of cytotoxicity dependent on the extent of nanoparticle interactions with cellular membranes. An inverse relationship between nanoparticle size and cytotoxicity, as well as nanoparticle size and reactive oxygen species production was observed. In addition, ZnO nanoparticles induce the production of the proinflammatory cytokines, IFN-γ, TNF-α, and IL-12, at concentrations below those causing appreciable cell death. Collectively, these results underscore the need for careful evaluation of ZnO nanoparticle effects across a spectrum of relevant cell types when considering their use for potential new nanotechnology-based biological applications.

  14. Dose dependency of the frequency of micronucleated binucleated clone cells and of division related median clone sizes difference. Pt. 2

    International Nuclear Information System (INIS)

    Hagemann, G,; Kreczik, A.; Treichel, M.

    1996-01-01

    Following irradiation of the progenitor cells the clone growth of CHO cells decreases as a result of cell losses. Lethally acting expressions of micronuclei are produced by heritable lethal mutations. The dependency of the frequency of micronucleated binucleated clone cells and of the median clone sizes difference on the radiation dose was measured and compared to non-irradiated controls. Using the cytokinesis-block-micronucleus-method binucleated cells with micronuclei were counted as ratio of all binucleated cells within a clone size distribution. This ratio (shortened: micronucleus yield) was determined for all clone size distributions, which had been exposed to different irradiation doses and incubation times. The micronucleus yields were compared to the corresponding median clone sizes differences. The micronucleus yield is linearly dependent on the dose and is independent of the incubation time. The same holds true for the division related median clone sizes difference, which as a result is also linearly dependent on the micronucleus yield. Due to the inevitably errors of the cell count of micronucleated binucleated cells, an automatic measurement of the median clone sizes differences is the preferred method for evaluation of cellular radiation sensitivity for heritable lethal mutations. This value should always be determined in addition, if clone survival fractions are used as predictive test because it allows for an estimation of the remission probability of surviving cells. (orig.) [de

  15. The Arabidopsis auxin-inducible gene ARGOS controls lateral organ size.

    Science.gov (United States)

    Hu, Yuxin; Xie, Qi; Chua, Nam-Hai

    2003-09-01

    During plant development, the final size of an organ is regulated and determined by various developmental signals; however, the molecular mechanisms by which these signals are transduced and the mediators involved are largely unknown. Here, we show that ARGOS, a novel Arabidopsis gene that is highly induced by auxin, is involved in organ size control. Transgenic plants expressing sense or antisense ARGOS cDNA display enlarged or reduced aerial organs, respectively. The alteration in organ size is attributable mainly to changes in cell number and the duration of organ growth. Ectopic expression of ARGOS prolongs the expression of AINTEGUMENTA (ANT) and CycD3;1 as well as the neoplastic activity of leaf cells. Moreover, organ enlargement in plants overexpressing ARGOS can be blocked by the loss of function of ANT, implying that ARGOS functions upstream of ANT to affect the meristematic competence of organ cells. The induction of ARGOS by auxin is attenuated or abolished in auxin-resistant1 (axr1), and overexpression of ARGOS partially restores axr1 organ development. These results suggest that ARGOS may transduce auxin signals downstream of AXR1 to regulate cell proliferation and organ growth through ANT during organogenesis.

  16. Hippo signaling controls cell cycle and restricts cell plasticity in planarians

    Science.gov (United States)

    de Sousa, Nídia; Rodríguez-Esteban, Gustavo; Rojo-Laguna, Jose Ignacio; Saló, Emili

    2018-01-01

    The Hippo pathway plays a key role in regulating cell turnover in adult tissues, and abnormalities in this pathway are consistently associated with human cancers. Hippo was initially implicated in the control of cell proliferation and death, and its inhibition is linked to the expansion of stem cells and progenitors, leading to larger organ size and tumor formation. To understand the mechanism by which Hippo directs cell renewal and promotes stemness, we studied its function in planarians. These stem cell–based organisms are ideal models for the analysis of the complex cellular events underlying tissue renewal in the whole organism. hippo RNA interference (RNAi) in planarians decreased apoptotic cell death, induced cell cycle arrest, and could promote the dedifferentiation of postmitotic cells. hippo RNAi resulted in extensive undifferentiated areas and overgrowths, with no effect on body size or cell number. We propose an essential role for hippo in controlling cell cycle, restricting cell plasticity, and thereby preventing tumoral transformation. PMID:29357350

  17. Regional variations in HDL metabolism in human fat cells: effect of cell size

    International Nuclear Information System (INIS)

    Despres, J.; Fong, B.S.; Julien, P.; Jimenez, J.; Angel, A.

    1987-01-01

    Abdominal obesity is related to reduced plasma high-density lipoprotein (HDL) cholesterol, and both are associated with cardiovascular disease risk. The authors have observed that plasma membranes from abdominal subcutaneous adipocytes have a greater HDL binding capacity than omental fat cell plasma membranes. The present study examined whether these binding characteristics could be due to differences in fat cell size or cholesterol concentration between the two adipose depots. Abdominal subcutaneous and deep omental fat were obtained from massively obese patients at surgery. Subcutaneous abdominal fat cells were significantly larger and their cellular cholesterol content greater than omental adipocytes. The uptake of HDL by collagenase-isolated fat cells was studied by incubating the cells for 2 h at 37 0 C with 10 μg/ml 125 I-HDL 2 or 125 I-HDL 3 . In both depots, the cellular uptake of 125 I-HDL 2 and 125 I-HDL 3 was specifically inhibited by addition of 25-fold excess unlabeled HDL and a close correlation was observed between the cellular uptake of 125 I-HDL 2 and 125 I-HDL 3 . In obese patients, the uptake of 125 I-HDL was higher in subcutaneous cells than in omental cells. The cellular 125 I-HDL uptake was significantly correlated with adipocyte size and fat cell cholesterol content but not with adipocyte cholesterol concentration. These results suggest that the higher HDL uptake observed in subcutaneous cells compared with omental cells in obesity is the result of differences in adipocyte size rather than differences in the cholesterol concentration (cholesterol-to-triglyceride ratio). The increased interaction of HDL with hypertrophied abdominal adipocytes may play an important role in determining the lipid composition of HDL in obesity

  18. Effects of Microbubble Size on Ultrasound-Mediated Gene Transfection in Auditory Cells

    Directory of Open Access Journals (Sweden)

    Ai-Ho Liao

    2014-01-01

    Full Text Available Gene therapy for sensorineural hearing loss has recently been used to insert genes encoding functional proteins to preserve, protect, or even regenerate hair cells in the inner ear. Our previous study demonstrated a microbubble- (MB-facilitated ultrasound (US technique for delivering therapeutic medication to the inner ear. The present study investigated whether MB-US techniques help to enhance the efficiency of gene transfection by means of cationic liposomes on HEI-OC1 auditory cells and whether MBs of different sizes affect such efficiency. Our results demonstrated that the size of MBs was proportional to the concentration of albumin or dextrose. At a constant US power density, using 0.66, 1.32, and 2.83 μm albumin-shelled MBs increased the transfection rate as compared to the control by 30.6%, 54.1%, and 84.7%, respectively; likewise, using 1.39, 2.12, and 3.47 μm albumin-dextrose-shelled MBs increased the transfection rates by 15.9%, 34.3%, and 82.7%, respectively. The results indicate that MB-US is an effective technique to facilitate gene transfer on auditory cells in vitro. Such size-dependent MB oscillation behavior in the presence of US plays a role in enhancing gene transfer, and by manipulating the concentration of albumin or dextrose, MBs of different sizes can be produced.

  19. A micro-sized bio-solar cell for self-sustaining power generation.

    Science.gov (United States)

    Lee, Hankeun; Choi, Seokheun

    2015-01-21

    Self-sustainable energy sources are essential for a wide array of wireless applications deployed in remote field locations. Due to their self-assembling and self-repairing properties, "biological solar (bio-solar) cells" are recently gaining attention for those applications. The bio-solar cell can continuously generate electricity from microbial photosynthetic and respiratory activities under day-night cycles. Despite the vast potential and promise of bio-solar cells, they, however, have not yet successfully been translated into commercial applications, as they possess persistent performance limitations and scale-up bottlenecks. Here, we report an entirely self-sustainable and scalable microliter-sized bio-solar cell with significant power enhancement by maximizing solar energy capture, bacterial attachment, and air bubble volume in well-controlled microchambers. The bio-solar cell has a ~300 μL single chamber defined by laser-machined poly(methyl methacrylate) (PMMA) substrates and it uses an air cathode to allow freely available oxygen to act as an electron acceptor. We generated a maximum power density of 0.9 mW m(-2) through photosynthetic reactions of cyanobacteria, Synechocystis sp. PCC 6803, which is the highest power density among all micro-sized bio-solar cells.

  20. What factors control the size of an eruption?

    Science.gov (United States)

    Gudmundsson, Agust

    2017-04-01

    For human society, eruption sizes (eruptive volumes or masses) are of the greatest concern. In particular, the largest eruptions, producing volumes of the order of hundreds or thousands of cubic kilometres, provide, together with meteoritic impacts, the greatest natural threats to mankind. Eruptive volumes tend to follow power laws so that most eruptions are comparatively small whereas a few are very large. It follows that a while during most ruptures of the source chambers a small fraction of the magma leaves the chamber, in some ruptures a very large fraction of the magma leaves the chamber. Most explosive eruptions larger than about 25 km3 are associated with caldera collapse. In the standard 'underpressure' ('lack of magmatic support') model, however, the collapse is the consequence, not the cause, of the large eruption. For poroelastic models, typically less than 4% of the magma in a felsic chamber and less than 0.1% of the magma in a mafic chamber leaves the chamber during rupture (and eventual eruption). In some caldera models, however, 20-70% of the magma is supposed to leave the chamber before the ring-fault forms and the caldera block begins to subside. In these models any amount of magma can flow out of the chamber following its rupture and there is apparently no way to forecast either the volume of magma injected from the chamber (hence the potential size of an eventual eruption) or the conditions for caldera collapse. An alternative model is proposed here. In this model normal (small) eruptions are controlled by standard poroelastity behaviour of the chamber, whereas large eruptions are controlled by chamber-volume reduction or shrinkage primarily through caldera/graben block subsidence into the chamber. Volcanotectonic stresses are then a major cause of ring-fault/graben boundary-fault formation. When large slips occur on these faults, the subsiding crustal block reduces the volume of the underlying chamber/reservoir, thereby maintaining its excess

  1. Mechanisms of Regulating Tissue Elongation in Drosophila Wing: Impact of Oriented Cell Divisions, Oriented Mechanical Forces, and Reduced Cell Size

    Science.gov (United States)

    Li, Yingzi; Naveed, Hammad; Kachalo, Sema; Xu, Lisa X.; Liang, Jie

    2014-01-01

    Regulation of cell growth and cell division plays fundamental roles in tissue morphogenesis. However, the mechanisms of regulating tissue elongation through cell growth and cell division are still not well understood. The wing imaginal disc of Drosophila provides a model system that has been widely used to study tissue morphogenesis. Here we use a recently developed two-dimensional cellular model to study the mechanisms of regulating tissue elongation in Drosophila wing. We simulate the effects of directional cues on tissue elongation. We also computationally analyze the role of reduced cell size. Our simulation results indicate that oriented cell divisions, oriented mechanical forces, and reduced cell size can all mediate tissue elongation, but they function differently. We show that oriented cell divisions and oriented mechanical forces act as directional cues during tissue elongation. Between these two directional cues, oriented mechanical forces have a stronger influence than oriented cell divisions. In addition, we raise the novel hypothesis that reduced cell size may significantly promote tissue elongation. We find that reduced cell size alone cannot drive tissue elongation. However, when combined with directional cues, such as oriented cell divisions or oriented mechanical forces, reduced cell size can significantly enhance tissue elongation in Drosophila wing. Furthermore, our simulation results suggest that reduced cell size has a short-term effect on cell topology by decreasing the frequency of hexagonal cells, which is consistent with experimental observations. Our simulation results suggest that cell divisions without cell growth play essential roles in tissue elongation. PMID:24504016

  2. Film Grain-Size Related Long-Term Stability of Inverted Perovskite Solar Cells.

    Science.gov (United States)

    Chiang, Chien-Hung; Wu, Chun-Guey

    2016-09-22

    The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H 2 Operovskite film having the grain size larger than 1 μm (D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H 2 O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Arabidopsis haiku Mutants Reveal New Controls of Seed Size by Endosperm1

    Science.gov (United States)

    Garcia, Damien; Saingery, Virginie; Chambrier, Pierre; Mayer, Ulrike; Jürgens, Gerd; Berger, Frédéric

    2003-01-01

    In flowering plants, maternal seed integument encloses the embryo and the endosperm, which are both derived from double fertilization. Although the development of these three components must be coordinated, we have limited knowledge of mechanisms involved in such coordination. The endosperm may play a central role in these mechanisms as epigenetic modifications of endosperm development, via imbalance of dosage between maternal and paternal genomes, affecting both the embryo and the integument. To identify targets of such epigenetic controls, we designed a genetic screen in Arabidopsis for mutants that phenocopy the effects of dosage imbalance in the endosperm. The two mutants haiku 1 and haiku 2 produce seed of reduced size that resemble seed with maternal excess in the maternal/paternal dosage. Homozygous haiku seed develop into plants indistinguishable from wild type. Each mutation is sporophytic recessive, and double-mutant analysis suggests that both mutations affect the same genetic pathway. The endosperm of haiku mutants shows a premature arrest of increase in size that causes precocious cellularization of the syncytial endosperm. Reduction of seed size in haiku results from coordinated reduction of endosperm size, embryo proliferation, and cell elongation of the maternally derived integument. We present further evidence for a control of integument development mediated by endosperm-derived signals. PMID:12692325

  4. Arabidopsis haiku mutants reveal new controls of seed size by endosperm.

    Science.gov (United States)

    Garcia, Damien; Saingery, Virginie; Chambrier, Pierre; Mayer, Ulrike; Jürgens, Gerd; Berger, Frédéric

    2003-04-01

    In flowering plants, maternal seed integument encloses the embryo and the endosperm, which are both derived from double fertilization. Although the development of these three components must be coordinated, we have limited knowledge of mechanisms involved in such coordination. The endosperm may play a central role in these mechanisms as epigenetic modifications of endosperm development, via imbalance of dosage between maternal and paternal genomes, affecting both the embryo and the integument. To identify targets of such epigenetic controls, we designed a genetic screen in Arabidopsis for mutants that phenocopy the effects of dosage imbalance in the endosperm. The two mutants haiku 1 and haiku 2 produce seed of reduced size that resemble seed with maternal excess in the maternal/paternal dosage. Homozygous haiku seed develop into plants indistinguishable from wild type. Each mutation is sporophytic recessive, and double-mutant analysis suggests that both mutations affect the same genetic pathway. The endosperm of haiku mutants shows a premature arrest of increase in size that causes precocious cellularization of the syncytial endosperm. Reduction of seed size in haiku results from coordinated reduction of endosperm size, embryo proliferation, and cell elongation of the maternally derived integument. We present further evidence for a control of integument development mediated by endosperm-derived signals.

  5. Size and compositionally controlled manganese ferrite nanoparticles with enhanced magnetization

    International Nuclear Information System (INIS)

    Vamvakidis, K.; Sakellari, D.; Angelakeris, M.; Dendrinou-Samara, C.

    2013-01-01

    A facile solvothermal approach was used to synthesize stable, superparamagnetic manganese ferrite nanoparticles with relatively small sizes ( 2 to Mn(acac) 3 , different sizes, 8 and 5 nm, of MnFe 2 O 4 nanoparticles were obtained respectively, while by tailoring the synthetic conditions iron-rich Mn 0.77 Fe 2.23 O 4 nanoparticles have been isolated with identical sizes and enhanced saturation magnetization. The magnetization values increased from 58.2 to 68.3 Am 2 /kg and from 53.3 to 60.2 Am 2 /kg for the nanoparticles of 8 and 5 nm, respectively. Blocking temperature (T B ), ranging from 80 to 180 K, and anisotropy constant (K eff ), ranging from 1.5 × 10 5 to 4.9 × 10 5 J/m 3 , were found higher for the iron-rich samples and associated with size and composition effects.

  6. Size-Controlled Dissolution of Organic-Coated Silver Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Rui; Levard, Clément; Marinakos, Stella M.; Cheng, Yingwen; Liu, Jie; Michel, F. Marc; Brown, Jr., Gordon E.; Lowry, Gregory V. (Duke)

    2012-04-02

    The solubility of Ag NPs can affect their toxicity and persistence in the environment. We measured the solubility of organic-coated silver nanoparticles (Ag NPs) having particle diameters ranging from 5 to 80 nm that were synthesized using various methods, and with different organic polymer coatings including poly(vinylpyrrolidone) and gum arabic. The size and morphology of Ag NPs were characterized by transmission electron microscopy (TEM). X-ray absorption fine structure (XAFS) spectroscopy and synchrotron-based total X-ray scattering and pair distribution function (PDF) analysis were used to determine the local structure around Ag and evaluate changes in crystal lattice parameters and structure as a function of NP size. Ag NP solubility dispersed in 1 mM NaHCO{sub 3} at pH 8 was found to be well correlated with particle size based on the distribution of measured TEM sizes as predicted by the modified Kelvin equation. Solubility of Ag NPs was not affected by the synthesis method and coating as much as by their size. Based on the modified Kelvin equation, the surface tension of Ag NPs was found to be {approx}1 J/m{sup 2}, which is expected for bulk fcc (face centered cubic) silver. Analysis of XAFS, X-ray scattering, and PDFs confirm that the lattice parameter, {alpha}, of the fcc crystal structure of Ag NPs did not change with particle size for Ag NPs as small as 6 nm, indicating the absence of lattice strain. These results are consistent with the finding that Ag NP solubility can be estimated based on TEM-derived particle size using the modified Kelvin equation for particles in the size range of 5-40 nm in diameter.

  7. Size-controlled magnetic nanoparticles with lecithin for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Park, S.I. [Department of Materials Science and Engineering, Chungnam National University, 305-764 Daejeon (Korea, Republic of); Kim, J.H. [Research Center for Advanced Magnetic Materials, Chungnam National University, 305-764 Daejeon (Korea, Republic of); Kim, C.G. [Department of Materials Science and Engineering, Chungnam National University, 305-764 Daejeon (Korea, Republic of); Kim, C.O. [Department of Materials Science and Engineering, Chungnam National University, 305-764 Daejeon (Korea, Republic of)]. E-mail: magkim@cnu.ac.kr

    2007-05-15

    Lecithin-adsorbed magnetic nanoparticles were prepared by three-step process that the thermal decomposition was combined with ultrasonication. Experimental parameters were three items-molar ratio between Fe(CO){sub 5} and oleic acid, keeping time at decomposition temperature and lecithin concentration. As the molar ratio between Fe(CO){sub 5} and oleic acid, and keeping time at decomposition temperature increased, the particle size increased. However, the change of lecithin concentration did not show the remarkable particle size variation.

  8. Effect of size and processing method on the cytotoxicity of realgar nanoparticles in cancer cell lines

    Directory of Open Access Journals (Sweden)

    Zhao W

    2011-08-01

    Full Text Available Weizhong Zhao1, Xun Lu3, Yuan Yuan1, Changsheng Liu1, Baican Yang3, Hua Hong1, Guoying Wang3, Fanyan Zeng21The State Key Laboratory of Bioreactor Engineering, 2Key Laboratory for Ultrafine Materials of Ministry of Education and Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, 3Pharmacy Department of Traditional Chinese Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, People’s Republic of ChinaAbstract: In this study, the effects of the size and Chinese traditional processing (including elutriation, water cleaning, acid cleaning, alkali cleaning on realgar nanoparticles (RN-induced antitumor activity in human osteosarcoma cell lines (MG-63 and hepatoma carcinoma cell lines (HepG-2 were investigated. The human normal liver cell line (L-02 was used as control. RN was prepared by high-energy ball milling technology. The results showed that with the assistance of sodium dodecyl sulfate, the size of realgar could be reduced to 127 nm after 12 hours’ ball milling. The surface charge was decreased from 0.83 eV to −17.85 eV and the content of As2O3 clearly increased. Except for elutriation, the processing methods did not clearly change the size of the RN, but the content of As2O3 was reduced dramatically. In vitro MTT tests indicated that in the two cancer cell lines, RN cytotoxicity was more intense than that of the coarse realgar nanoparticles, and cytotoxicity was typically time- and concentration-dependent. Also, RN cytotoxicities in the HepG-2 and L-02 cells all increased with increasing milling time. Due to the reduction of the As2O3 content, water cleaning, acid cleaning, and alkali cleaning decreased RN cytotoxicity in HepG-2, but RN after elutriation, with the lowest As2O3 (3.5 mg/g and the smallest size (109.3 nm, showed comparable cytotoxicity in HepG-2 to RN without treatment. Meanwhile, RN-induced cytotoxicity in L-02 cells was

  9. What Controls the Size of the Antarctic Ozone Hole?

    Science.gov (United States)

    Bhartia, P. K. (Technical Monitor); Newman, Paul A.; Kawa, S. Randolph; Nash, Eric R.

    2002-01-01

    The Antarctic ozone hole is a region of extremely large ozone depletion that is roughly centered over the South Pole. Since 1979, the area coverage of the ozone hole has grown from near zero size to over 24 Million square kilometers. In the 8-year period from 1981 to 1989, the area expanded by 18 Million square kilometers. During the last 5 years, the hole has been observed to exceed 25 Million square kilometers over brief periods. We will review these size observations, the size trends, and the interannual variability of the size. The area is derived from the area enclosed by the 220 DU total ozone contour. We will discuss the rationale for the choice of 220 DU: 1) it is located near the steep gradient between southern mid-latitudes and the polar region, and 2) 220 DU is a value that is lower than the pre- 1979 ozone observations over Antarctica during the spring period. The phenomenal growth of the ozone hole was directly caused by the increases of chlorine and bromine compounds in the stratosphere. In this talk, we will show the relationship of the ozone hole's size to the interannual variability of Antarctic spring temperatures. In addition, we will show the relationship of these same temperatures to planetary-scale wave forcings.

  10. Production of Concentrated Pickering Emulsions with Narrow Size Distributions Using Stirred Cell Membrane Emulsification.

    Science.gov (United States)

    Manga, Mohamed S; York, David W

    2017-09-12

    Stirred cell membrane emulsification (SCME) has been employed to prepare concentrated Pickering oil in water emulsions solely stabilized by fumed silica nanoparticles. The optimal conditions under which highly stable and low-polydispersity concentrated emulsions using the SCME approach are highlighted. Optimization of the oil flux rates and the paddle stirrer speeds are critical to achieving control over the droplet size and size distribution. Investigating the influence of oil volume fraction highlights the criticality of the initial particle loading in the continuous phase on the final droplet size and polydispersity. At a particle loading of 4 wt %, both the droplet size and polydispersity increase with increasing of the oil volume fraction above 50%. As more interfacial area is produced, the number of particles available in the continuous phase diminishes, and coincidently a reduction in the kinetics of particle adsorption to the interface resulting in larger polydisperse droplets occurs. Increasing the particle loading to 10 wt % leads to significant improvements in both size and polydispersity with oil volume fractions as high as 70% produced with coefficient of variation values as low as ∼30% compared to ∼75% using conventional homogenization techniques.

  11. Sorting of cells of the same size, shape, and cell cycle stage for a single cell level assay without staining

    Directory of Open Access Journals (Sweden)

    Yomo Tetsuya

    2006-06-01

    Full Text Available Abstract Background Single-cell level studies are being used increasingly to measure cell properties not directly observable in a cell population. High-performance data acquisition systems for such studies have, by necessity, developed in synchrony. However, improvements in sample purification techniques are also required to reveal new phenomena. Here we assessed a cell sorter as a sample-pretreatment tool for a single-cell level assay. A cell sorter is routinely used for selecting one type of cells from a heterogeneous mixture of cells using specific fluorescence labels. In this case, we wanted to select cells of exactly the same size, shape, and cell-cycle stage from a population, without using a specific fluorescence label. Results We used four light scatter parameters: the peak height and area of the forward scatter (FSheight and FSarea and side scatter (SSheight and SSarea. The rat pheochromocytoma PC12 cell line, a neuronal cell line, was used for all experiments. The living cells concentrated in the high FSarea and middle SSheight/SSarea fractions. Single cells without cell clumps were concentrated in the low SS and middle FS fractions, and in the higher FSheight/FSarea and SSheight/SSarea fractions. The cell populations from these viable, single-cell-rich fractions were divided into twelve subfractions based on their FSarea-SSarea profiles, for more detailed analysis. We found that SSarea was proportional to the cell volume and the FSarea correlated with cell roundness and elongation, as well as with the level of DNA in the cell. To test the method and to characterize the basic properties of the isolated single cells, sorted cells were cultured in separate wells. The cells in all subfractions survived, proliferated and differentiated normally, suggesting that there was no serious damage. The smallest, roundest, and smoothest cells had the highest viability. There was no correlation between proliferation and differentiation. NGF increases

  12. Lpar2b Controls Lateral Line Tissue Size by Regulating Yap1 Activity in Zebrafish

    Directory of Open Access Journals (Sweden)

    Xueqian Wang

    2018-02-01

    Full Text Available LPA signaling plays important roles during cell migration and proliferation in normal and pathological conditions. However, its role during sensory organ development remains unknown. Here we show a LPA receptor Lpar2b is expressed in the posterior lateral line primordium (pLLP and mechanosensory organs called neuromasts (NMs in zebrafish embryos. Lpar2b loss-of-function significantly reduces the number of NMs and hair cells in the posterior lateral line (pLL. Further analysis reveals that Lpar2b regulates the patterning and tissue size of the pLLP. Interestingly, we show that knocking down a Hippo effector Yap1 phenocopies the result of Lpar2b depletion, and Lpar2b regulates the phosphorylation and activity of Yap1 in the pLLP. Importantly, a phosphorylation-resistant Yap1 rescues pLLP size and NM number in Lpar2b-depleted embryos. Our results indicate Lpar2b controls primordium size and NM number by regulating Yap1 activity in the lateral line system.

  13. Cell surface engineering to control cellular interactions

    OpenAIRE

    Custódio, Catarina A.; Mano, João F.

    2016-01-01

    Cell surface composition determines all interactions of the cell with its environment, thus cell functions such as adhesion, migration and cell–cell interactions can potentially be controlled by engineering and manipulating the cell membrane. Cell membranes present a rich repertoire of molecules, therefore a versatile ground for modification. However the complex and dynamic nature of the cell surface is also a major challenge for cell surface engineering that should also involve strategies co...

  14. Preparation of leucite powders with controlled particle size distribution

    Czech Academy of Sciences Publication Activity Database

    Novotná, Martina; Kloužková, A.; Maixner, J.; Šatava, Vladimír

    2005-01-01

    Roč. 49, č. 4 (2005), s. 252-258 ISSN 0862-5468 R&D Projects: GA ČR GA104/03/0031 Institutional research plan: CEZ:AV0Z40320502 Keywords : leucite * preparation * particle size distribution Subject RIV: CA - Inorganic Chemistry Impact factor: 0.463, year: 2005

  15. Synthesis of size-controlled Bi particles by electrochemical deposition

    Indian Academy of Sciences (India)

    Wintec

    ... carried out using exfoliated graphite. (EG) as the working electrode. The EG particles were prepared according to a reported procedure (Fukuda et al. 1997) from natural graphite particles. The as-received graphite flakes were sieved to result in particles of size,. 300 μm. The natural graphite flakes were intercalated with.

  16. Nanoparticle size controls aggregation in lamellar nonionic surfactant mesophase.

    Science.gov (United States)

    Venugopal, Edakkal; Aswal, Vinod K; Kumaraswamy, Guruswamy

    2013-08-06

    We show that the size of silica nanoparticles influences the nature of their aggregation in an aqueous solution of a relatively hydrophobic nonionic surfactant, C12E4. We present results for dispersions of silica nanoparticles with sizes varying from 8 to 26 nm, in a 75: 25 C12E4/water system, that forms a lamellar phase, Lα, at room temperature. Addition of silica particles does not affect the formation of the Lα phase. Nanoparticles smaller than about 11 nm aggregate irreversibly in the C12E4/water system. However, nanoparticles larger than about 15 nm aggregate in the Lα phase, but are dispersed at temperatures above the Lα order-disorder temperature. Thus, in contrast to the smaller particles, aggregation of silica nanoparticles larger than about 15 nm is reversible with temperature. We use small-angle neutron scattering (SANS) to demonstrate that these results can be explained by the size-dependent wrapping of nanoparticles by surfactant bilayers. Larger particles, above 15 nm in size, are sterically stabilized by the formation of an adsorbed surfactant bilayer. The cost of bilayer bending inhibits adsorption onto the highly curved surfaces of smaller particles, and these "bare" particles aggregate irreversibly.

  17. Biotemplated fabrication of size controlled palladium nanoparticle chains

    NARCIS (Netherlands)

    Zhou, Xingfei; Zheng, Lifei; Li, Rong; Li, Bin; Pillai, Saju; Xu, Peng; Zhang, Yi

    2012-01-01

    Metal nanoparticles exhibit unique size- and spatial organization-dependent physical and chemical properties, and have a wide range of applications in various areas including single electron devices, chemical catalysts and biomedicines. In this paper, chains of palladium nanoparticles were obtained

  18. Synthesis of size-controlled Bi particles by electrochemical deposition

    Indian Academy of Sciences (India)

    The particles have been characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, UV-visible spectroscopy and X-ray diffraction technique. The particles, as deposited, are highly crystalline in nature and the particle size and shape ...

  19. Reversible Size Control of Silver Nanoclusters via Ligand-exchange

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2015-05-21

    The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

  20. Size-controllable polypyrrole nanospheres synthesized in the presence of phosphorylated chitosan and their size effect in different applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing; Cao, Yi; Lu, Yun, E-mail: yunlu@nju.edu.cn [Nanjing University, Department of Polymer Science and Engineering, State Key Laboratory of Coordination Chemistry, Key Laboratory of High Performance Polymer Materials and Technology of Ministry of Education, School of Chemistry and Chemical Engineering (China)

    2015-05-15

    The size-controllable polypyrrole (PPy) nanospheres are successfully synthesized by oxidative polymerization of pyrrole using N-methylene phosphonic chitosan (NMPC) as a structure-directing agent. By simply changing the amount of NMPC, the size of the PPy nanospheres can be adjusted from 190 to 50 nm in diameter. The spectrometric results suggest that the electrostatic interactions of phosphate groups in NMPC molecule with pyrrole ring might be a driving force for formation of the uniform and size-controllable PPy nanospheres. The PPy nanospheres with the diameter of 100 nm exhibit the largest capacity and a good cycling stability as electrode materials of supercapacitors. The as-prepared PPy nanospheres also can be combined with carbon dots to form composite nanospheres presenting enhanced fluorescence intensity, which show potential application in fluorescence detection.

  1. Structural and magnetic properties of size-controlled Mn0.5Zn0 ...

    Indian Academy of Sciences (India)

    5Fe2O4) because its magnetic properties can be modified significantly ei- ther with size or with different site occupancy. Three different sized particles were prepared by controlling synthesis parameters. 2. Methodology. In inverse spinel Fe3+.

  2. Human regulatory B cells control the TFH cell response.

    Science.gov (United States)

    Achour, Achouak; Simon, Quentin; Mohr, Audrey; Séité, Jean-François; Youinou, Pierre; Bendaoud, Boutahar; Ghedira, Ibtissem; Pers, Jacques-Olivier; Jamin, Christophe

    2017-07-01

    Follicular helper T (T FH ) cells support terminal B-cell differentiation. Human regulatory B (Breg) cells modulate cellular responses, but their control of T FH cell-dependent humoral immune responses is unknown. We sought to assess the role of Breg cells on T FH cell development and function. Human T cells were polyclonally stimulated in the presence of IL-12 and IL-21 to generate T FH cells. They were cocultured with B cells to induce their terminal differentiation. Breg cells were included in these cultures, and their effects were evaluated by using flow cytometry and ELISA. B-cell lymphoma 6, IL-21, inducible costimulator, CXCR5, and programmed cell death protein 1 (PD-1) expressions increased on stimulated human T cells, characterizing T FH cell maturation. In cocultures they differentiated B cells into CD138 + plasma and IgD - CD27 + memory cells and triggered immunoglobulin secretions. Breg cells obtained by Toll-like receptor 9 and CD40 activation of B cells prevented T FH cell development. Added to T FH cell and B-cell cocultures, they inhibited B-cell differentiation, impeded immunoglobulin secretions, and expanded Foxp3 + CXCR5 + PD-1 + follicular regulatory T cells. Breg cells modulated IL-21 receptor expressions on T FH cells and B cells, and their suppressive activities involved CD40, CD80, CD86, and intercellular adhesion molecule interactions and required production of IL-10 and TGF-β. Human Breg cells control T FH cell maturation, expand follicular regulatory T cells, and inhibit the T FH cell-mediated antibody secretion. These novel observations demonstrate a role for the Breg cell in germinal center reactions and suggest that deficient activities might impair the T FH cell-dependent control of humoral immunity and might lead to the development of aberrant autoimmune responses. Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  3. Forces and dynamics in epithelial domes of controlled size and shape

    Science.gov (United States)

    Latorre-Ibars, Ernest; Casares, Laura; Gomez-Gonzalez, Manuel; Uroz, Marina; Arroyo, Marino; Trepat, Xavier

    Mechanobiology of epithelia plays a central role in morphogenesis, wound healing, and tumor progression. Its current understanding relies on mechanical measurements on flat epithelial layers. However, most epithelia in vivo exhibit a curved 3D shape enclosing a pressurized lumen. Using soft micropatterned substrates we produce massive parallel arrays of epithelial domes with controlled size and basal shape. We measure epithelial traction, tension, and luminal pressure in epithelial domes. The local stress tensor on the freestanding epithelial membrane is then mapped by combining measured luminal pressure and local curvature. We show that tension and cell shape are highly anisotropic and vary along the meridional position of the domes. Finally, we establish constitutive relations between shape, tension, and pressure during perturbations of the contractile machinery, osmotic shocks, and spontaneous fluctuations of dome volume. Our findings contradict a description of the epithelium as a fluid capillary surface. Cells in the dome are unable to relax into a uniform and isotropic tensional state through sub- and supra-cellular rearrangements. Mapping epithelial shape, tension, and pressure will enable quantitative studies of mechanobiology in 3D epithelia of controlled size and shape.

  4. Preparation of size-controlled nanoparticles of magnetite

    OpenAIRE

    Andrade, Ângela Leão; Valente, Manuel Almeida; Ferreira, José Maria da Fonte; Fabris, José Domingos

    2012-01-01

    Samples of ferrofluids containing chemically stabilized nanoparticles of magnetite (Fe3O4) with tetramethylammonium hydroxide (TMAOH) were prepared by a direct reduction–precipitation method. The influences of aging time and temperature on the size and monodispersion characteristics of the produced nanoparticles were investigated. Transmission electron microscopy, powder X-ray diffraction, Fourier-transform infrared, and magnetization measurements with applied magnetic field up to 2 T were us...

  5. Size control synthesis of starch capped-gold nanoparticles

    International Nuclear Information System (INIS)

    Tajammul Hussain, S.; Iqbal, M.; Mazhar, M.

    2009-01-01

    Metallic gold nanoparticles have been synthesized by the reduction of chloroaurate anions [AuCl 4 ] - solution with hydrazine in the aqueous starch and ethylene glycol solution at room temperature and at atmospheric pressure. The characterization of synthesized gold nanoparticles by UV-vis spectroscopy, high resolution transmission electron microscopy (HRTEM), electron diffraction analysis, X-ray diffraction (XRD), and X-rays photoelectron spectroscopy (XPS) indicate that average size of pure gold nanoparticles is 3.5 nm, they are spherical in shape and are pure metallic gold. The concentration effects of [AuCl 4 ] - anions, starch, ethylene glycol, and hydrazine, on particle size, were investigated, and the stabilization mechanism of Au nanoparticles by starch polymer molecules was also studied by FT-IR and thermogravimetric analysis (TGA). FT-IR and TGA analysis shows that hydroxyl groups of starch are responsible of capping and stabilizing gold nanoparticles. The UV-vis spectrum of these samples shows that there is blue shift in surface plasmon resonance peak with decrease in particle size due to the quantum confinement effect, a supporting evidence of formation of gold nanoparticles and this shift remains stable even after 3 months.

  6. Control rod studies in small and medium sized fast reactors

    International Nuclear Information System (INIS)

    John, T.M.; Mohanakrishnan, P.; Mahalakshmi, B.; Singh, R.S.

    1988-01-01

    Control rods are the primary safety mechanism in the operation of fast reactors. Neutronic parameters associated with the control rods have to be evaluated precisely for studying the behaviour of the reactor under various operating conditions. Control rods are strong neutron absorbers discretely distributed in the reactor core. Accurate estimation of control rod parameters demand, in principle transport theory solutions in exact geometry. But computer codes for such evaluations usually consume exorbitantly large computer time and memory for even a single parameter evaluation. During the design of reactors, evaluation of these parameters will be required for many configurations of control rods. In this paper, the method used at Indira Gandhi Centre for Atomic Research for estimating the parameters associated with control rods is presented. Diffusion theory solutions were used for computations. A scheme using three dimensional geometry represented by triangular meshes and diffusion theory solutions in few energy groups for control rod parameter evaluation is presented. This scheme was employed in estimating the control rod parameters in a 500 Mw(e) fast reactor. Error due to group collapsing is estimated by comparing with 25 group calculations in three dimensions for typical cases. (author). 5 refs, 4 figs, 3 tabs

  7. Real-time laser cladding control with variable spot size

    Science.gov (United States)

    Arias, J. L.; Montealegre, M. A.; Vidal, F.; Rodríguez, J.; Mann, S.; Abels, P.; Motmans, F.

    2014-03-01

    Laser cladding processing has been used in different industries to improve the surface properties or to reconstruct damaged pieces. In order to cover areas considerably larger than the diameter of the laser beam, successive partially overlapping tracks are deposited. With no control over the process variables this conduces to an increase of the temperature, which could decrease mechanical properties of the laser cladded material. Commonly, the process is monitored and controlled by a PC using cameras, but this control suffers from a lack of speed caused by the image processing step. The aim of this work is to design and develop a FPGA-based laser cladding control system. This system is intended to modify the laser beam power according to the melt pool width, which is measured using a CMOS camera. All the control and monitoring tasks are carried out by a FPGA, taking advantage of its abundance of resources and speed of operation. The robustness of the image processing algorithm is assessed, as well as the control system performance. Laser power is decreased as substrate temperature increases, thus maintaining a constant clad width. This FPGA-based control system is integrated in an adaptive laser cladding system, which also includes an adaptive optical system that will control the laser focus distance on the fly. The whole system will constitute an efficient instrument for part repair with complex geometries and coating selective surfaces. This will be a significant step forward into the total industrial implementation of an automated industrial laser cladding process.

  8. The Size And Localisation Of Yellow Pigmented Lipid Cells 6 ...

    African Journals Online (AJOL)

    It was observed that the transverse sections of fresh ginger rhizomes contain spherical yellow-pigmented lipid cells (the spot of aroma and pungency mediating compounds), which were distributed more in the central than in the cortex regions of the rhizomes. The mean cell distribution showed that the proportion of these ...

  9. Cell Size Discrimination Based on the Measurement of the Equilibrium Velocity in Rectangular Microchannels

    Directory of Open Access Journals (Sweden)

    Lisa Schott

    2015-05-01

    Full Text Available Flow cytometry is a well-established diagnostic tool for cell counting and characterization. It utilizes fluorescence and scattered excitation light simultaneously emitted from cells passing an excitation laser focus to discriminate various cell types and estimate cell size. Here, we apply the principle of spatially modulated emission (SME to fluorescently stained SUP-B15 cells as a model system for cancer cells and Marinococcus luteus as model for bacteria. We demonstrate that the experimental apparatus is able to detect these model cells and that the results are comparable to those obtained by a commercially available CASY® TT Counter. Furthermore, by examining the velocity distribution of the cells, we observe clear relationships between cell condition/size and cell velocity. Thus, the cell velocity provides information comparable to the scatter signal in conventional flow cytometry. These results indicate that the SME technique is a promising method for simultaneous cell counting and viability characterization.

  10. Selective Rapid Eye Movement Sleep Deprivation Affects Cell Size and Number in Kitten Locus Coeruleus

    Directory of Open Access Journals (Sweden)

    James P Shaffery

    2012-05-01

    Full Text Available Cells in the locus coeruleus (LC constitute the sole source of norepinephrine (NE in the brain, and change their discharge rates according to vigilance state. In addition to its well established role in vigilance, NE affects synaptic plasticity in the postnatal critical period (CP of development. One form of CP synaptic plasticity affected by NE results from monocular occlusion, which leads to physiological and cytoarchitectural alterations in central visual areas. Selective suppression of rapid eye movement sleep (REMS in the CP kitten enhances the central effects of monocular occlusion. The mechanisms responsible for heightened cortical plasticity following REMS deprivation (REMSD remain undetermined. One possible mediator of an increase in plasticity is continuous NE outflow, which presumably persists during extended periods of REMSD. Tyrosine hydroxylase (TH is the rate-limiting enzyme in the synthesis of NE and serves as a marker for NE-producing cells. We selectively suppressed REMS in kittens for one week during the CP. The number and size of LC cells expressing immunoreactivity to tyrosine hydroxylase (TH-ir was assessed in age-matched REMS-deprived (RD-, treatment-control (TXC-, and home cage-reared (HCC animals. Sleep amounts and slow wave activity (SWA were also examined relative to baseline. Time spent in REMS during the study was lower in RD compared to TXC animals, and RD kittens increased SWA delta power in the latter half of the REMSD period. The estimated total number of TH-ir cells in LC was significantly lower in the RD- than in the TXC kittens and numerically lower than in HCC animals. The size of LC cells expressing TH-ir was greatest in the HCC group. They were significantly larger than the cells in the RD kittens. These data are consistent with a possible reduction in NE in forebrain areas, including visual cortex, caused by one week of REMSD.

  11. Constant pressure-controlled extrusion method for the preparation of Nano-sized lipid vesicles.

    Science.gov (United States)

    Morton, Leslie A; Saludes, Jonel P; Yin, Hang

    2012-06-22

    Liposomes are artificially prepared vesicles consisting of natural and synthetic phospholipids that are widely used as a cell membrane mimicking platform to study protein-protein and protein-lipid interactions, monitor drug delivery, and encapsulation. Phospholipids naturally create curved lipid bilayers, distinguishing itself from a micelle. Liposomes are traditionally classified by size and number of bilayers, i.e. large unilamellar vesicles (LUVs), small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs). In particular, the preparation of homogeneous liposomes of various sizes is important for studying membrane curvature that plays a vital role in cell signaling, endo- and exocytosis, membrane fusion, and protein trafficking. Several groups analyze how proteins are used to modulate processes that involve membrane curvature and thus prepare liposomes of diameters liposome-drug encapsulation, studying liposomes as vehicles to carry and deliver a drug of interest. Drug encapsulation can be achieved as reported during liposome formation. Our extrusion step should not affect the encapsulated drug for two reasons, i.e. (1) drug encapsulation should be achieved prior to this step and liposomes should retain their natural biophysical stability, securely carrying the drug in the aqueous core. These research goals further suggest the need for an optimized method to design stable sub-micron lipid vesicles. Nonetheless, the current liposome preparation technologies (sonication, freeze-and-thaw, sedimentation) do not allow preparation of liposomes with highly curved surface (i.e. diameter liposomes. Manual extrusion using gas-tight syringes and polycarbonate membranes, is a common practice but heterogeneity is often observed when using pore sizes liposomes whose diameters range between 30 and 400 nm. Dynamic light scattering (DLS), electron microscopy and nanoparticle tracking analysis (NTA) were used to quantify the liposome sizes as described in our protocol

  12. Efficiency optimized control of medium-size induction motor drives

    DEFF Research Database (Denmark)

    Abrahamsen, F.; Blaabjerg, Frede; Pedersen, John Kim

    2000-01-01

    The efficiency of a variable speed induction motor drive can be optimized by adaption of the motor flux level to the load torque. In small drives (<10 kW) this can be done without considering the relatively small converter losses, but for medium-size drives (10-1000 kW) the losses can not be disr......The efficiency of a variable speed induction motor drive can be optimized by adaption of the motor flux level to the load torque. In small drives (

  13. Molecular mechanisms controlling the cell cycle in embryonic stem cells.

    Science.gov (United States)

    Abdelalim, Essam M

    2013-12-01

    Embryonic stem (ES) cells are originated from the inner cell mass of a blastocyst stage embryo. They can proliferate indefinitely, maintain an undifferentiated state (self-renewal), and differentiate into any cell type (pluripotency). ES cells have an unusual cell cycle structure, consists mainly of S phase cells, a short G1 phase and absence of G1/S checkpoint. Cell division and cell cycle progression are controlled by mechanisms ensuring the accurate transmission of genetic information from generation to generation. Therefore, control of cell cycle is a complicated process, involving several signaling pathways. Although great progress has been made on the molecular mechanisms involved in the regulation of ES cell cycle, many regulatory mechanisms remain unknown. This review summarizes the current knowledge about the molecular mechanisms regulating the cell cycle of ES cells and describes the relationship existing between cell cycle progression and the self-renewal.

  14. Controlling the particle size of interpolymer complexes through host-guest interaction for drug delivery.

    Science.gov (United States)

    Chen, Yan; Pang, Yan; Wu, Jieli; Su, Yue; Liu, Jinyao; Wang, Ruibin; Zhu, Bangshang; Yao, Yefeng; Yan, Deyue; Zhu, Xinyuan; Chen, Qun

    2010-06-01

    A new method to adjust the particle size of interpolymer complexes has been developed by introduction of host-guest interaction into the dilute aqueous solution of poly(acrylic acid) (PAA) and poly(ethylene glycol) (PEG). Because of the cooperative hydrogen-bonding interaction, PAA can form the interpolymer complexes with PEG. Putting beta-cyclodextrin (beta-CD) into dilute PAA/PEG aqueous solution, the competition between host-guest and hydrogen-bonding interactions happens. The beta-CD/PAA/PEG ternary systems have been well characterized by ultraviolet-visible absorption spectroscopy (UV-vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), diffusion NMR spectroscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and solid-state (13)C NMR spectroscopy. The results indicate that the hydrophobic cavity of beta-CD is threaded by linear polymers so that the hydrophilicity of PAA/PEG interpolymer complexes is improved greatly. Adjusting the amounts of beta-CD, the particle size of the interpolymer complexes can be readily controlled. The low cytotoxicity of various beta-CD/PAA/PEG ternary complexes has been confirmed using the MTT assay in COS-7 cell line. Doxorubicin (DOX), an anticancer drug, has been encapsulated into the beta-CD/PAA/PEG ternary complexes. The DOX-loaded beta-CD/PAA/PEG ternary complexes have been analyzed by confocal laser scanning microscopy (CLSM), flow cytometry analysis, and the MTT assay against human cervical carcinoma cell (Hela). The results indicate that beta-CD/PAA/PEG ternary complexes with controlled particle size could be used as safe and promising drug carriers.

  15. Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hanguang [Department; Hwang, Sooyeon [Center; Wang, Maoyu [School; Feng, Zhenxing [School; Karakalos, Stavros [Department; Luo, Langli [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Qiao, Zhi [Department; Xie, Xiaohong [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Wang, Chongmin [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Su, Dong [Center; Shao, Yuyan [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Wu, Gang [Department

    2017-09-26

    To significantly reduce the cost of proton exchange membrane (PEM) fuel cells, current Pt must be replaced by platinum-metal-group (PGM)-free catalysts for the oxygen reduction reaction (ORR) in acid. We report here a new class of high-performance atomic iron dispersed carbon catalysts through controlled chemical doping of iron ions into zinc-zeolitic imidazolate framework (ZIF), a type of metal-organic framework (MOF). The novel synthetic chemistry enables accurate size control of Fe-doped ZIF catalyst particles with a wide range from 20 to 1000 nm without changing chemical properties, which provides a great opportunity to increase the density of active sites that is determined by the particle size. We elucidated the active site formation mechanism by correlating the chemical and structural changes with thermal activation process for the conversion from Fe-N4 complex containing hydrocarbon networks in ZIF to highly active FeNx sites embedded into carbon. A temperature of 800oC was identified as the critical point to start forming pyridinic nitrogen doping at the edge of the graphitized carbon planes. Further increasing heating temperature to 1100oC leads to increase of graphitic nitrogen, generating possible synergistic effect with FeNx sites to promote ORR activity. The best performing catalyst, which has well-defined particle size around 50 nm and abundance of atomic FeNx sites embedded into carbon structures, achieve a new performance milestone for the ORR in acid including a half-wave potential of 0.85 V vs RHE and only 20 mV loss after 10,000 cycles in O2 saturated H2SO4 electrolyte. The new class PGM-free catalyst with approaching activity to Pt holds great promise for future PEM fuel cells.

  16. Control size of silver nanoparticles in sol-gel glasses

    Science.gov (United States)

    Renteria, Victor M.; Celis, Antonio C.; Garcia-Macedo, Jorge A.

    2000-10-01

    By the sol-gel processing, silver ions in presence of stabilizing function (3-thiocyanatopropyl)triethoxysilane are reduced by heating gels at 180 C for several times in air atmosphere. The spectroscopic Uv-Vis observations, confirm silver nanoparticles presence with peak maximum around 350 nm. The optical properties of the metallic particles are observed at room temperature as function of time, and the absorption spectra practically do not change, which indicated they are trapped and stabilized within the fine porous silica cage. Mie theory calculations, considering the mean free path effect of the conduction electrons, are compatible with experimental spectra, indicating homogeneity in size and form of the metallic nanoparticles. Smithard correlation curve, between half width height (W1/2) of the optical absorption and the particle diameter 2r, predict silver particles size between 4 and 10 nm, during composite heating. Activation energy was measured and compared with previous data on similar systems and the probable reduction process are discussed.

  17. Effect of Different Support Morphologies and Pt Particle Sizes in Electrocatalysts for Fuel Cell Applications

    Directory of Open Access Journals (Sweden)

    G. Sevjidsuren

    2010-01-01

    Full Text Available The performance of a low temperature fuel cell is strongly correlated with parameters like the platinum particle size, platinum dispersion on the carbon support, and electronic and protonic conductivity in the catalyst layer as well as its porosity. These parameters can be controlled by a rational choice of the appropriate catalyst synthesis and carbon support. Only recently, particular attention has been given to the support morphology, as it plays an important role for the formation of the electrode structure. Due to their significantly different structure, mesoporous carbon microbeads (MCMBs and multiwalled carbon nanotubes (MWCNTs were used as supports and compared. Pt nanoparticles were decorated on these supports using the polyol method. Their size was varied by different heating times during the synthesis, and XRD, TEM, SEM, CV, and single cell tests used in their detailed characterization. A membrane-electrode assembly prepared with the MCMB did not show any activity in the fuel cell test, although the catalyst's electrochemical activity was almost similar to the MWCNT. This is assumed to be due to the very dense electrode structure formed by this support material, which does not allow for sufficient mass transport.

  18. Birth order, sibship size, and risk for germ-cell testicular cancer.

    Science.gov (United States)

    Richiardi, Lorenzo; Akre, Olof; Lambe, Mats; Granath, Fredrik; Montgomery, Scott M; Ekbom, Anders

    2004-05-01

    Several studies have reported an inverse association between birth order and testicular cancer risk, but estimates vary greatly and the biologic mechanism underlying the association is not established. We have evaluated the effect of birth order, sibship size, and the combined effect of these 2 variables in relation to risk for testicular cancer in a large, nested case-control study. Specifically, we compared 3051 patients with germ-cell testicular cancer (diagnosed between 1958 and 1998 and identified through the Swedish Cancer Registry) with 9007 population control subjects. Using record linkage with the Multi-Generation Register and the Census, we obtained information on number, order, and sex of the subjects' siblings, parental age, and paternal socioeconomic status. Both birth order and sibship size had an inverse and monotonically decreasing association with testicular cancer risk after adjusting for parental age, paternal socioeconomic status, and twin status. The associations were modified by subjects' cohort of birth and were not present among those born after 1959. The odds ratio for having at least 3 siblings, compared with none, was 0.63 (95% confidence interval = 0.53-0.75) among subjects born before 1960. Stratified analyses showed that birth order and number of younger siblings had a similar inverse association with the risk for testicular cancer. Sibship size, and not only birth order, is associated with testicular cancer risk. This suggests a higher prevalence of parental subfertility among patients with testicular cancer.

  19. Electronic structure and size of TiO sub 2 nanoparticles of controlled size prepared by aerosol methods

    CERN Document Server

    Soriano, L; Sanchez-Agudo, M; Sanz, J M; Ahonen, P P; Kauppinen, E I; Palomares, F J; Bressler, P R

    2002-01-01

    A complete characterization of nanostructures has to deal both with electronic structure and dimensions. Here we present the characterization of TiO sub 2 nanoparticles of controlled size prepared by aerosol methods. The electronic structure of these nanoparticles was probed by x-ray absorption spectroscopy (XAS), the particle size by atomic force microscopy (AFM). XAS spectra show that the particles crystallize in the anatase phase upon heating at 500 sup o C, whereas further annealing at 700 sup o C give crystallites of 70 % anatase and 30 % rutile phases. Raising the temperature to 900 sup o C results in a complete transformation of the particles to rutile. AFM images reveal that the mean size of the anatase particles formed upon heating at 500 sup o C is 30 nm, whereas for the rutile particles formed upon annealing at 900 sup o C 90 nm were found. The results obtained by these techniques agree with XRD data. (author)

  20. Immunosuppressive Activity of Size-Controlled PEG-PLGA Nanoparticles Containing Encapsulated Cyclosporine A

    Directory of Open Access Journals (Sweden)

    Li Tang

    2012-01-01

    Full Text Available We encapsulated cyclosporine A (CsA in poly(ethylene glycol-b-poly(d,l-lactide-co-glycolide (PEG-PLGA nanoparticles (NPs by nanoprecipitation of CsA and PEG-PLGA. The resulting CsA/PEG-PLGA-NPs were <100 nm in diameter with a narrow particle size distribution. The NP size could be controlled by tuning the polymer concentration, solvent, or water/solvent ratio during formulation. The PEGylated NPs maintained non-aggregated in salt solution. Solid NPs lyoprotected with bovine serum albumin were prepared for the convenience of storage and transportation. The release kinetics of CsA (55.6% released on Day 1 showed potential for maintaining therapeutic CsA concentrations in vivo. In T-cell assays, both free CsA and CsA/PEG-PLGA-NPs suppressed T-cell proliferation and production of inflammatory cytokines dose dependently. In a mixed lymphocyte reaction assay, the IC50 values for free CsA and CsA/PEG-PLGA-NPs were found to be 30 and 35 ng/mL, respectively. This nanoparticulate CsA delivery technology constitutes a strong basis for future targeted delivery of immunosuppressive drugs with improved efficiency and potentially reduced toxicity.

  1. Flexible PMP Approach for Large-Size Cell Formation

    NARCIS (Netherlands)

    Goldengorin, Boris; Krushinsky, Dmitry; Slomp, Jannes

    2012-01-01

    Lately, the problem of cell formation (CF) has gained a lot of attention in the industrial engineering literature. Since it was formulated (more than 50 years ago), the problem has incorporated additional industrial factors and constraints while its solution methods have been constantly improving in

  2. Impact of radiation therapy fraction size on local control of early glottic carcinoma

    International Nuclear Information System (INIS)

    Yu, Edward; Shenouda, George; Beaudet, Marie P.; Black, Martin J.

    1997-01-01

    Purpose: Different radiotherapy fractionation schedules were used over a 10-year period to treat patients with early squamous cell carcinoma of the vocal cords at McGill University. A retrospective analysis was performed to study the effect of fraction size on local control in this group of patients. Methods and Materials: A total of 126 previously untreated patients with T1 invasive squamous cell carcinoma of the true vocal cords were irradiated between January 1978 and December 1988 in the Department of Radiation Oncology at McGill University. All patients received megavoltage irradiation, 94 patients received daily fractions > 2 Gy (64 patients received 50 Gy with once-daily 2.5-Gy fractions, and 30 received 65.25 Gy in 29 fractions of 2.25 Gy each), and 32 patients were treated to a dose of 66 Gy in 33 fractions with 2 Gy/fraction. Patients' characteristics of prognostic importance were equally distributed between the two fractionation groups. Results: At a median follow-up of 84 months, the 10-year disease-free survival and overall survival were 76% and 93%, respectively. Local control for patients treated with > 2 Gy fraction was 84%, compared to 65.6% for those treated with 2-Gy fractions (p = 0.026). Among the prognostic factors tested, such as gender, age, stage, anterior and posterior commissure involvement, smoking history, and fraction size, the latter was the only significant predictor of local control for the whole group of patients in univariate (p = 0.041) and multivariate (p = 0.023) analysis. There was no observed difference in the incidence of complications between the two fraction groups. Conclusions: From the results of this retrospective review of patients treated with radiotherapy for T1 true vocal cord cancer, and within the range of total doses and overall treatment times used in our patients, it was found that fractionation schedules using daily fraction size > 2 Gy are associated with a better local control than schedules delivering 2 Gy

  3. Fuel cell with internal flow control

    Science.gov (United States)

    Haltiner, Jr., Karl J.; Venkiteswaran, Arun [Karnataka, IN

    2012-06-12

    A fuel cell stack is provided with a plurality of fuel cell cassettes where each fuel cell cassette has a fuel cell with an anode and cathode. The fuel cell stack includes an anode supply chimney for supplying fuel to the anode of each fuel cell cassette, an anode return chimney for removing anode exhaust from the anode of each fuel cell cassette, a cathode supply chimney for supplying oxidant to the cathode of each fuel cell cassette, and a cathode return chimney for removing cathode exhaust from the cathode of each fuel cell cassette. A first fuel cell cassette includes a flow control member disposed between the anode supply chimney and the anode return chimney or between the cathode supply chimney and the cathode return chimney such that the flow control member provides a flow restriction different from at least one other fuel cell cassettes.

  4. Size and shape control in the overgrowth of gold nanorods

    International Nuclear Information System (INIS)

    Ratto, Fulvio; Matteini, Paolo; Rossi, Francesca; Pini, Roberto

    2010-01-01

    We report on a new sustainable approach to manipulate the optical behaviour and geometrical properties of gold nanorods in aqueous solutions by fine control of their overgrowth. In our approach, the overgrowth is realized by modulation of the reduction of the gold ions which are left as Au 1+ after the primary step of the synthesis (typically as much as ∼80% of the gold ions available in the growth solution). The progress of the reduction requires the gradual addition of ascorbic acid, which transforms the Au 1+ into Au 0 and may be performed in the original growth solution with no need for any further manipulation. By control of the total amount and rate of administration of the ascorbic acid, we prove the possibility to realize a systematic modulation of the average lengths, diameters, shapes (rod or dog-bone like), and light extinction of the nanoparticles. A slow overgrowth leads to a gradual enlargement of the lengths and diameters at almost constant shape. In contrast, a faster overgrowth results into a more complex modification of the overall shape of the gold nanorods.

  5. Size and shape control in the overgrowth of gold nanorods

    Science.gov (United States)

    Ratto, Fulvio; Matteini, Paolo; Rossi, Francesca; Pini, Roberto

    2010-08-01

    We report on a new sustainable approach to manipulate the optical behaviour and geometrical properties of gold nanorods in aqueous solutions by fine control of their overgrowth. In our approach, the overgrowth is realized by modulation of the reduction of the gold ions which are left as Au1+ after the primary step of the synthesis (typically as much as 80% of the gold ions available in the growth solution). The progress of the reduction requires the gradual addition of ascorbic acid, which transforms the Au1+ into Au0 and may be performed in the original growth solution with no need for any further manipulation. By control of the total amount and rate of administration of the ascorbic acid, we prove the possibility to realize a systematic modulation of the average lengths, diameters, shapes (rod or dog-bone like), and light extinction of the nanoparticles. A slow overgrowth leads to a gradual enlargement of the lengths and diameters at almost constant shape. In contrast, a faster overgrowth results into a more complex modification of the overall shape of the gold nanorods.

  6. Size and shape control in the overgrowth of gold nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ratto, Fulvio; Matteini, Paolo; Rossi, Francesca; Pini, Roberto, E-mail: r.pini@ifac.cnr.i [Istituto di Fisica Applicata ' Nello Carrara' , Consiglio Nazionale delle Ricerche (Italy)

    2010-08-15

    We report on a new sustainable approach to manipulate the optical behaviour and geometrical properties of gold nanorods in aqueous solutions by fine control of their overgrowth. In our approach, the overgrowth is realized by modulation of the reduction of the gold ions which are left as Au{sup 1+} after the primary step of the synthesis (typically as much as {approx}80% of the gold ions available in the growth solution). The progress of the reduction requires the gradual addition of ascorbic acid, which transforms the Au{sup 1+} into Au{sup 0} and may be performed in the original growth solution with no need for any further manipulation. By control of the total amount and rate of administration of the ascorbic acid, we prove the possibility to realize a systematic modulation of the average lengths, diameters, shapes (rod or dog-bone like), and light extinction of the nanoparticles. A slow overgrowth leads to a gradual enlargement of the lengths and diameters at almost constant shape. In contrast, a faster overgrowth results into a more complex modification of the overall shape of the gold nanorods.

  7. Toxicity of nano- and micro-sized silver particles in human hepatocyte cell line L02

    Science.gov (United States)

    Liu, Pengpeng; Guan, Rongfa; Ye, Xingqian; Jiang, Jiaxin; Liu, Mingqi; Huang, Guangrong; Chen, Xiaoting

    2011-07-01

    Silver nanoparticles (Ag NPs) previously classified as antimicrobial agents have been widely used in consumers and industrial products, especially food storage material. Ag NPs used as antimicrobial agents may be found in liver. Thus, examination of the ability of Ag NPs to penetrate the liver is warranted. The aim of the study was to determine the optimal viability assay for using with Ag NPs in order to assess their toxicity to liver cells. For toxicity evaluations, cellular morphology, mitochondrial function (3-(4, 5-dimethylazol-2-yl)-2, 5-diphenyl-tetrazolium bromide, MTT assay), membrane leakage of lactate dehydrogenase (lactate dehydrogenase, LDH release assay), Oxidative stress markers (malonaldehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD)), DNA damage (single cell gel eletrophoresis, SCGE assay), and protein damage were assessed under control and exposed conditions (24 h of exposure). The results showed that mitochondrial function decreased significantly in cells exposed to Ag NPs at 25 μg·mL-1. LDH leakage significantly increased in cells exposed to Ag NPs (>= 25 μg mL-1) while micro-sized silver particles tested displayed LDH leakage only at higher doses (100 μg·mL-1). The microscopic studies demonstrated that nanoparticle-exposed cells at higher doses became abnormal in size, displaying cellular shrinkage, and an acquisition of an irregular shape. Due to toxicity of silver, further study conducted with reference to its oxidative stress. The results exhibited significant depletion of GSH level, increase in SOD levels and lead to lipid peroxidation, which suggested that cytotoxicity of Ag NPs in liver cells might be mediated through oxidative stress. The results demonstrates that Ag NPs lead to cellular morphological modifications, LDH leakage, mitochondrial dysfunction, and cause increased generation of ROS, depletion of GSH, lipid peroxidation, oxidative DNA damage and protein damage. Though the exact mechanism behind Ag NPs

  8. Toxicity of nano- and micro-sized silver particles in human hepatocyte cell line L02

    Energy Technology Data Exchange (ETDEWEB)

    Liu Pengpeng; Guan Rongfa; Jiang Jiaxin; Liu Mingqi; Huang Guangrong; Chen Xiaoting [Zhejiang Provincial Key Laboratory of Biometrology and Inspection and Quarantine, College of Life Sciences, China Jiliang University, Hangzhou 310018 (China); Ye Xingqian, E-mail: rfguan@163.com [Department of Food Science and Nutrition, School of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310029 (China)

    2011-07-06

    Silver nanoparticles (Ag NPs) previously classified as antimicrobial agents have been widely used in consumers and industrial products, especially food storage material. Ag NPs used as antimicrobial agents may be found in liver. Thus, examination of the ability of Ag NPs to penetrate the liver is warranted. The aim of the study was to determine the optimal viability assay for using with Ag NPs in order to assess their toxicity to liver cells. For toxicity evaluations, cellular morphology, mitochondrial function (3-(4, 5-dimethylazol-2-yl)-2, 5-diphenyl-tetrazolium bromide, MTT assay), membrane leakage of lactate dehydrogenase (lactate dehydrogenase, LDH release assay), Oxidative stress markers (malonaldehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD)), DNA damage (single cell gel eletrophoresis, SCGE assay), and protein damage were assessed under control and exposed conditions (24 h of exposure). The results showed that mitochondrial function decreased significantly in cells exposed to Ag NPs at 25 {mu}g{center_dot}mL{sup -1}. LDH leakage significantly increased in cells exposed to Ag NPs ({>=} 25 {mu}g mL{sup -1}) while micro-sized silver particles tested displayed LDH leakage only at higher doses (100 {mu}g{center_dot}mL{sup -1}). The microscopic studies demonstrated that nanoparticle-exposed cells at higher doses became abnormal in size, displaying cellular shrinkage, and an acquisition of an irregular shape. Due to toxicity of silver, further study conducted with reference to its oxidative stress. The results exhibited significant depletion of GSH level, increase in SOD levels and lead to lipid peroxidation, which suggested that cytotoxicity of Ag NPs in liver cells might be mediated through oxidative stress. The results demonstrates that Ag NPs lead to cellular morphological modifications, LDH leakage, mitochondrial dysfunction, and cause increased generation of ROS, depletion of GSH, lipid peroxidation, oxidative DNA damage and protein damage

  9. Robust organelle size extractions from elastic scattering measurements of single cells (Conference Presentation)

    Science.gov (United States)

    Cannaday, Ashley E.; Draham, Robert; Berger, Andrew J.

    2016-04-01

    The goal of this project is to estimate non-nuclear organelle size distributions in single cells by measuring angular scattering patterns and fitting them with Mie theory. Simulations have indicated that the large relative size distribution of organelles (mean:width≈2) leads to unstable Mie fits unless scattering is collected at polar angles less than 20 degrees. Our optical system has therefore been modified to collect angles down to 10 degrees. Initial validations will be performed on polystyrene bead populations whose size distributions resemble those of cell organelles. Unlike with the narrow bead distributions that are often used for calibration, we expect to see an order-of-magnitude improvement in the stability of the size estimates as the minimum angle decreases from 20 to 10 degrees. Scattering patterns will then be acquired and analyzed from single cells (EMT6 mouse cancer cells), both fixed and live, at multiple time points. Fixed cells, with no changes in organelle sizes over time, will be measured to determine the fluctuation level in estimated size distribution due to measurement imperfections alone. Subsequent measurements on live cells will determine whether there is a higher level of fluctuation that could be attributed to dynamic changes in organelle size. Studies on unperturbed cells are precursors to ones in which the effects of exogenous agents are monitored over time.

  10. The clone size of peripheral CD8 T cells is regulated by TCR promiscuity

    NARCIS (Netherlands)

    Hao, Yi; Legrand, Nicolas; Freitas, Antonio A.

    2006-01-01

    Positive selection in the thymus and peripheral T cell survival depend on T cell receptor (TCR)-major histocompatibility complex (MHC) interactions, but it is not yet clear if both events follow exactly the same rules. We studied peripheral T cell survival and clone sizes in conditions of

  11. Analysis of Cell Size in the Gastrula of Ten Frog Species Reveals a Correlation of Egg with Cell Sizes, and a Conserved Pattern of Small Cells in the Marginal Zone.

    Science.gov (United States)

    Vargas, Alexandra; Del Pino, Eugenia M

    2017-01-01

    We investigated the relationship between egg and cell sizes in the early gastrula of ten species of frogs with eggs of 1,100-3,500 μm diameters. We asked whether differences in cell size of the vegetal region, blastocoel roof, and marginal zone of the early gastrula were associated with egg size. Alternatively, we proposed that cell size differences may associate with gastrulation characteristics. The analyzed species were as follows: Xenopus laevis, Engystomops randi, Engystomops coloradorum, Espadarana callistomma, Epipedobates machalilla, Epipedobates anthonyi, Epipedobates tricolor, Dendrobates auratus, Gastrotheca riobambae, and Eleutherodactylus coqui. A positive correlation between egg and cell size was detected in the three regions of the gastrula. The correlation was strong in the vegetal region and blastocoel roof, and weak in the marginal zone. Large eggs allowed the evolution of frog terrestrial reproductive modes by storing nourishment for the developing embryos. Large cells, laden with yolk, occur in the vegetal region. However, small cell size characterized the marginal zone and blastocoel roof. We proposed that small cells of the marginal zone are required for involution and blastopore formation. The evolution pressure toward small cells in the marginal zone contributed to maintain the blastopore as a universal feature of frog gastrulation in eggs of different sizes and gastrulation modes. Our comparative analysis revealed two fundamental and conserved properties of the frog early gastrula, the correlation of egg with cell sizes, and the general small size of cells in the marginal zone. © 2016 Wiley Periodicals, Inc.

  12. How does a single cell know when the liver has reached its correct size?

    Directory of Open Access Journals (Sweden)

    Nadine Hohmann

    Full Text Available The liver is a multi-functional organ that regulates major physiological processes and that possesses a remarkable regeneration capacity. After loss of functional liver mass the liver grows back to its original, individual size through hepatocyte proliferation and apoptosis. How does a single hepatocyte 'know' when the organ has grown to its final size? This work considers the initial growth phase of liver regeneration after partial hepatectomy in which the mass is restored. There are strong and valid arguments that the trigger of proliferation after partial hepatectomy is mediated through the portal blood flow. It remains unclear, if either or both the concentration of metabolites in the blood or the shear stress are crucial to hepatocyte proliferation and liver size control. A cell-based mathematical model is developed that helps discriminate the effects of these two potential triggers. Analysis of the mathematical model shows that a metabolic load and a hemodynamical hypothesis imply different feedback mechanisms at the cellular scale. The predictions of the developed mathematical model are compared to experimental data in rats. The assumption that hepatocytes are able to buffer the metabolic load leads to a robustness against short-term fluctuations of the trigger which can not be achieved with a purely hemodynamical trigger.

  13. A qualitative study of psychological, social and behavioral barriers to appropriate food portion size control

    Science.gov (United States)

    2013-01-01

    Background Given the worldwide prevalence of overweight and obesity, there is a clear need for meaningful practical healthy eating advice - not only in relation to food choice, but also on appropriate food portion sizes. As the majority of portion size research to date has been overwhelmingly quantitative in design, there is a clear need to qualitatively explore consumers’ views in order to fully understand how food portion size decisions are made. Using qualitative methodology this present study aimed to explore consumers’ views about factors influencing their portion size selection and consumption and to identify barriers to appropriate portion size control. Methods Ten focus groups with four to nine participants in each were formed with a total of 66 persons (aged 19–64 years) living on the island of Ireland. The semi-structured discussions elicited participants’ perceptions of suggested serving size guidance and explored the influence of personal, social and environmental factors on their food portion size consumption. Audiotapes of the discussions were professionally transcribed verbatim, loaded into NVivo 9, and analysed using an inductive thematic analysis procedure. Results The rich descriptive data derived from participants highlight that unhealthy portion size behaviors emanate from various psychological, social and behavioral factors. These bypass reflective and deliberative control, and converge to constitute significant barriers to healthy portion size control. Seven significant barriers to healthy portion size control were apparent: (1) lack of clarity and irrelevance of suggested serving size guidance; (2) guiltless eating; (3) lack of self-control over food cues; (4) distracted eating; (5) social pressures; (6) emotional eating rewards; and (7) quantification habits ingrained from childhood. Conclusions Portion size control strategies should empower consumers to overcome these effects so that the consumption of appropriate food portion sizes

  14. A qualitative study of psychological, social and behavioral barriers to appropriate food portion size control.

    Science.gov (United States)

    Spence, Michelle; Livingstone, M Barbara E; Hollywood, Lynsey E; Gibney, Eileen R; O'Brien, Sinéad A; Pourshahidi, L Kirsty; Dean, Moira

    2013-08-01

    Given the worldwide prevalence of overweight and obesity, there is a clear need for meaningful practical healthy eating advice - not only in relation to food choice, but also on appropriate food portion sizes. As the majority of portion size research to date has been overwhelmingly quantitative in design, there is a clear need to qualitatively explore consumers' views in order to fully understand how food portion size decisions are made. Using qualitative methodology this present study aimed to explore consumers' views about factors influencing their portion size selection and consumption and to identify barriers to appropriate portion size control. Ten focus groups with four to nine participants in each were formed with a total of 66 persons (aged 19-64 years) living on the island of Ireland. The semi-structured discussions elicited participants' perceptions of suggested serving size guidance and explored the influence of personal, social and environmental factors on their food portion size consumption. Audiotapes of the discussions were professionally transcribed verbatim, loaded into NVivo 9, and analysed using an inductive thematic analysis procedure. The rich descriptive data derived from participants highlight that unhealthy portion size behaviors emanate from various psychological, social and behavioral factors. These bypass reflective and deliberative control, and converge to constitute significant barriers to healthy portion size control. Seven significant barriers to healthy portion size control were apparent: (1) lack of clarity and irrelevance of suggested serving size guidance; (2) guiltless eating; (3) lack of self-control over food cues; (4) distracted eating; (5) social pressures; (6) emotional eating rewards; and (7) quantification habits ingrained from childhood. Portion size control strategies should empower consumers to overcome these effects so that the consumption of appropriate food portion sizes becomes automatic and habitual.

  15. crm-1 facilitates BMP signaling to control body size in Caenorhabditis elegans.

    Science.gov (United States)

    Fung, Wong Yan; Fat, Ko Frankie Chi; Eng, Cheah Kathryn Song; Lau, Chow King

    2007-11-01

    We have identified in Caenorhabditis elegans a homologue of the vertebrate Crim1, crm-1, which encodes a putative transmembrane protein with multiple cysteine-rich (CR) domains known to have bone morphogenetic proteins (BMPs) binding activity. Using the body morphology of C. elegans as an indicator, we showed that attenuation of crm-1 activity leads to a small body phenotype reminiscent of that of BMP pathway mutants. We showed that the crm-1 loss-of-function phenotype can be rescued by constitutive supply of sma-4 activity. crm-1 can enhance BMP signaling and this activity is dependent on the presence of the DBL-1 ligand and its receptors. crm-1 is expressed in neurons at the ventral nerve cord, where the DBL-1 ligand is produced. However, ectopic expression experiments reveal that crm-1 gene products act outside the DBL-1 producing cells and function non-autonomously to facilitate dbl/sma pathway signaling to control body size.

  16. NiPt hollow nanocatalyst: Green synthesis, size control and electrocatalysis

    Directory of Open Access Journals (Sweden)

    Aixian Shan

    2014-04-01

    Full Text Available Nearly monodispersed hollow nanospheres of bimetallic NiPt have been synthesized by a one-pot wet chemical method at room temperature with a precursor Ni nanocompound as a sacrificial template. The size control is carried out via the sacrificial template, from about 35 nm to nearly 100 nm in diameter. The shell thickness of the NiPt hollow sphere reaches down to as thin as 2–3 nm slightly larger than a single layer of alloyed NiPt nanocrystallites. The product with the citric acid as surfactant exhibits enhanced oxygen reduction activities compared to a commercial Pt/C catalyst and the hollow nanospheres coated with PVP. It has potential applications in fuel cells, biotechnology and environmental chemistry with the facile synthesis, low cost and excellent electrocatalytic activity.

  17. The TEAD/TEF family of transcription factor Scalloped mediates Hippo signaling in organ size control.

    Science.gov (United States)

    Zhang, Lei; Ren, Fangfang; Zhang, Qing; Chen, Yongbin; Wang, Bing; Jiang, Jin

    2008-03-01

    The Hippo (Hpo) signaling pathway governs cell growth, proliferation, and apoptosis by controlling key regulatory genes that execute these processes; however, the transcription factor of the pathway has remained elusive. Here we provide evidence that the TEAD/TEF family transcription factor Scalloped (Sd) acts together with the coactivator Yorkie (Yki) to regulate Hpo pathway-responsive genes. Sd and Yki form a transcriptional complex whose activity is inhibited by Hpo signaling. Sd overexpression enhances, whereas its inactivation suppresses, tissue overgrowth caused by Yki overexpression or tumor suppressor mutations in the Hpo pathway. Inactivation of Sd diminishes Hpo target gene expression and reduces organ size, whereas a constitutively active Sd promotes tissue overgrowth. Sd promotes Yki nuclear localization, whereas Hpo signaling retains Yki in the cytoplasm by phosphorylating Yki at S168. Finally, Sd recruits Yki to the enhancer of the pathway-responsive gene diap1, suggesting that diap1 is a direct transcriptional target of the Hpo pathway.

  18. Cell therapy with allogenic canine periodontal ligament-derived cells in periodontal regeneration of critical size defects.

    Science.gov (United States)

    Nuñez, Javier; Sanchez, Nerea; Vignoletti, Fabio; Sanz-Martin, Ignacio; Caffesse, Raul; Santamaria, Silvia; Garcia-Sanz, Jose A; Sanz, Mariano

    2017-12-29

    The objective of this in vivo experimental study to evaluate the regenerative potential of a cell therapy combining allogenic periodontal ligament-derived cells within a xenogeneic bone substitute in a similar experimental model. In nine beagle dogs, critical size 6-mm supra-alveolar periodontal defects were created around the PIII and PIV. The resulting supra-alveolar defects were randomly treated with either 1.4 × 10 6 allogenic canine periodontal ligament-derived cells seeded on de-proteinized bovine bone mineral with 10% collagen (DBBM-C) (test group) or DBBM-C without cells (control group). Specimens were obtained at 3 months, and histological outcomes were studied. The histological analysis showed that total furcation closure occurred very seldom in both groups, being the extent of periodontal regeneration located in the apical third of the defect. The calculated amount of periodontal regeneration at the furcation area was comparable in both the test and control groups (1.93 ± 1.14 mm (17%) versus 2.35 ± 1.74 mm (22%), respectively (p = .37). Similarly, there were no significant differences in the amount of new cementum formation 4.49 ± 1.56 mm (41%) versus 4.97 ± 1.05 mm (47%), respectively (p = .45). This experimental study was unable to demonstrate the added value of allogenic cell therapy in supra-crestal periodontal regeneration. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  19. Asymmetric cell division during T cell development controls downstream fate

    Science.gov (United States)

    Pham, Kim; Shimoni, Raz; Charnley, Mirren; Ludford-Menting, Mandy J.; Hawkins, Edwin D.; Ramsbottom, Kelly; Oliaro, Jane; Izon, David; Ting, Stephen B.; Reynolds, Joseph; Lythe, Grant; Molina-Paris, Carmen; Melichar, Heather; Robey, Ellen; Humbert, Patrick O.; Gu, Min

    2015-01-01

    During mammalian T cell development, the requirement for expansion of many individual T cell clones, rather than merely expansion of the entire T cell population, suggests a possible role for asymmetric cell division (ACD). We show that ACD of developing T cells controls cell fate through differential inheritance of cell fate determinants Numb and α-Adaptin. ACD occurs specifically during the β-selection stage of T cell development, and subsequent divisions are predominantly symmetric. ACD is controlled by interaction with stromal cells and chemokine receptor signaling and uses a conserved network of polarity regulators. The disruption of polarity by deletion of the polarity regulator, Scribble, or the altered inheritance of fate determinants impacts subsequent fate decisions to influence the numbers of DN4 cells arising after the β-selection checkpoint. These findings indicate that ACD enables the thymic microenvironment to orchestrate fate decisions related to differentiation and self-renewal. PMID:26370500

  20. Biodegradable large compound vesicles with controlled size prepared via the self-assembly of branched polymers in nanodroplet templates.

    Science.gov (United States)

    Wang, Long-Hai; Xu, Xiao-Man; Hong, Chun-Yan; Wu, De-Cheng; Yu, Zhi-Qiang; You, Ye-Zi

    2014-09-04

    Generally, it is very difficult to control the size of large compound vesicles. Here, we introduce a novel method for the preparation of biodegradable large compound vesicles with controlled size and narrow size distribution by using aqueous nanodroplets as templates.

  1. Sample size reassessment for a two-stage design controlling the false discovery rate.

    Science.gov (United States)

    Zehetmayer, Sonja; Graf, Alexandra C; Posch, Martin

    2015-11-01

    Sample size calculations for gene expression microarray and NGS-RNA-Seq experiments are challenging because the overall power depends on unknown quantities as the proportion of true null hypotheses and the distribution of the effect sizes under the alternative. We propose a two-stage design with an adaptive interim analysis where these quantities are estimated from the interim data. The second stage sample size is chosen based on these estimates to achieve a specific overall power. The proposed procedure controls the power in all considered scenarios except for very low first stage sample sizes. The false discovery rate (FDR) is controlled despite of the data dependent choice of sample size. The two-stage design can be a useful tool to determine the sample size of high-dimensional studies if in the planning phase there is high uncertainty regarding the expected effect sizes and variability.

  2. Ontogeny of metabolic rate and red blood cell size in eyelid geckos: species follow different paths.

    Directory of Open Access Journals (Sweden)

    Zuzana Starostová

    Full Text Available While metabolism is a fundamental feature of all organisms, the causes of its scaling with body mass are not yet fully explained. Nevertheless, observations of negative correlations between red blood cell (RBC size and the rate of metabolism suggest that size variation of these cells responsible for oxygen supply may play a crucial role in determining metabolic rate scaling in vertebrates. Based on a prediction derived from the Cell Metabolism Hypothesis, metabolic rate should increase linearly with body mass in species with RBC size invariance, and slower than linearly when RBC size increases with body mass. We found support for that prediction in five species of eyelid geckos (family Eublepharidae with different patterns of RBC size variation during ontogenetic growth. During ontogeny, metabolic rate increases nearly linearly with body mass in those species of eyelid geckos where there is no correlation between RBC size and body mass, whereas non-linearity of metabolic rate scaling is evident in those species with ontogenetic increase of RBC size. Our findings provide evidence that ontogenetic variability in RBC size, possibly correlating with sizes of other cell types, could have important physiological consequences and can contribute to qualitatively different shape of the intraspecific relationship between metabolic rate and body mass.

  3. Ontogeny of metabolic rate and red blood cell size in eyelid geckos: species follow different paths.

    Science.gov (United States)

    Starostová, Zuzana; Konarzewski, Marek; Kozłowski, Jan; Kratochvíl, Lukáš

    2013-01-01

    While metabolism is a fundamental feature of all organisms, the causes of its scaling with body mass are not yet fully explained. Nevertheless, observations of negative correlations between red blood cell (RBC) size and the rate of metabolism suggest that size variation of these cells responsible for oxygen supply may play a crucial role in determining metabolic rate scaling in vertebrates. Based on a prediction derived from the Cell Metabolism Hypothesis, metabolic rate should increase linearly with body mass in species with RBC size invariance, and slower than linearly when RBC size increases with body mass. We found support for that prediction in five species of eyelid geckos (family Eublepharidae) with different patterns of RBC size variation during ontogenetic growth. During ontogeny, metabolic rate increases nearly linearly with body mass in those species of eyelid geckos where there is no correlation between RBC size and body mass, whereas non-linearity of metabolic rate scaling is evident in those species with ontogenetic increase of RBC size. Our findings provide evidence that ontogenetic variability in RBC size, possibly correlating with sizes of other cell types, could have important physiological consequences and can contribute to qualitatively different shape of the intraspecific relationship between metabolic rate and body mass.

  4. Cell responses to two kinds of nanohydroxyapatite with different sizes and crystallinities

    Directory of Open Access Journals (Sweden)

    Wei SC

    2012-03-01

    Full Text Available Xiaochen Liu1, Minzhi Zhao1, Jingxiong Lu2, Jian Ma4, Jie Wei2, Shicheng Wei1,31Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 2Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai, 3Department of Oral and Maxillofacial Surgery, School of Stomatology, Peking University, Beijing, 4Hospital of Stomatology, Tongji University, Shanghai, ChinaIntroduction:Hydroxyapatite (HA is the principal inorganic constituent of human bone. Due to its good biocompatibility and osteoconductivity, all kinds of HA particles were prepared by different methods. Numerous reports demonstrated that the properties of HA affected its biological effects.Methods: Two kinds of nanohydroxyapatite with different sizes and crystallinities were obtained via a hydrothermal treatment method under different temperatures. It was found that at a temperature of 140°C, a rod-like crystal (n-HA1 with a diameter of 23 ± 5 nm, a length of 47 ± 14 nm, and crystallinity of 85% ± 5% was produced, while at a temperature of 80°C, a rod-like crystal (n-HA2 with a diameter of 16 ± 3 nm, a length of 40 ± 10 nm, and crystallinity of 65% ± 3% was produced. The influence of nanohydroxyapatite size and crystallinity on osteoblast viability was studied by MTT, scanning electron microscopy, and flow cytometry.Results: n-HA1 gave a better biological response than n-HA2 in promoting cell growth and inhibiting cell apoptosis, and also exhibited much more active cell morphology. Alkaline phosphatase activity for both n-HA2 and n-HA1 was obviously higher than for the control, and no significant difference was found between n-HA1 and n-HA2. The same trend was observed on Western blotting for expression of type I collagen and osteopontin. In addition, it was found by transmission electron microscopy that large quantities of n-HA2 entered into the cell

  5. Effect of pore size and interpore distance on endothelial cell growth on polymers.

    Science.gov (United States)

    Narayan, D; Venkatraman, S S

    2008-12-01

    The endothelization of polymers using surface modification has received great attention. In particular, creation of physical surface features such as craters or pores has been an active area of research. However, there have been no reported studies of the effects of pore sizes (wide range) and interpore distance on endothelial cell growth. This report details the study done on endothelial cell attachment on the surfaces of polymers modified by porogen leaching. The polymeric system studied includes PLLA and PLGA (80/20). Factors such as porogen type, pore size, and interpore distance were varied, and the surface was evaluated for its influence on endothelial cell growth. Three groups of pore sizes were evaluated: small (5-20 mum), medium (20-45 mum), and large pores (45-90 mum). Two porogens were evaluated: sugar and gelatin. In addition to counting the attached endothelial cells, their proliferation was also quantified. Pore size and interpore distances were evaluated using scanning electron microscopy (SEM), and cell morphology was studied by staining with crystal violet. Analysis of variance demonstrated that the main parameters, pore size and interpore distance were significant in endothelial cell growth. In PLGA (80/20), it was found that endothelial cell growth was enhanced by smaller pore size and lower interpore distance, whereas the growth was poor on PLLA regardless of pore features. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008.

  6. Microprinted Stem Cell Niches Reveal Compounding Effect of Colony Size on Stromal Cells-Mediated Neural Differentiation.

    Science.gov (United States)

    Joshi, Ramila; Thakuri, Pradip Shahi; Buchanan, James C; Li, Jun; Tavana, Hossein

    2018-03-01

    Microenvironmental factors have a major impact on differentiation of embryonic stem cells (ESCs). Here, a novel phenomenon that size of ESC colonies has a significant regulatory role on stromal cells induced differentiation of ESCs to neural cells is reported. Using a robotic cell microprinting technology, defined densities of ESCs are confined within aqueous nanodrops over a layer of supporting stromal cells immersed in a second, immiscible aqueous phase to generate ESC colonies of defined sizes. Temporal protein and gene expression studies demonstrate that larger ESC colonies generate disproportionally more neural cells and longer neurite processes. Unlike previous studies that attribute neural differentiation of ESCs solely to interactions with stromal cells, it is found that increased intercellular signaling of ESCs significantly enhances neural differentiation. This study offers an approach to generate neural cells with improved efficiency for potential use in translational research. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. High-efficiency single cell encapsulation and size selective capture of cells in picoliter droplets based on hydrodynamic micro-vortices.

    Science.gov (United States)

    Kamalakshakurup, Gopakumar; Lee, Abraham P

    2017-12-05

    Single cell analysis has emerged as a paradigm shift in cell biology to understand the heterogeneity of individual cells in a clone for pathological interrogation. Microfluidic droplet technology is a compelling platform to perform single cell analysis by encapsulating single cells inside picoliter-nanoliter (pL-nL) volume droplets. However, one of the primary challenges for droplet based single cell assays is single cell encapsulation in droplets, currently achieved either randomly, dictated by Poisson statistics, or by hydrodynamic techniques. In this paper, we present an interfacial hydrodynamic technique which initially traps the cells in micro-vortices, and later releases them one-to-one into the droplets, controlled by the width of the outer streamline that separates the vortex from the flow through the streaming passage adjacent to the aqueous-oil interface (d gap ). One-to-one encapsulation is achieved at a d gap equal to the radius of the cell, whereas complete trapping of the cells is realized at a d gap smaller than the radius of the cell. The unique feature of this technique is that it can perform 1. high efficiency single cell encapsulations and 2. size-selective capturing of cells, at low cell loading densities. Here we demonstrate these two capabilities with a 50% single cell encapsulation efficiency and size selective separation of platelets, RBCs and WBCs from a 10× diluted blood sample (WBC capture efficiency at 70%). The results suggest a passive, hydrodynamic micro-vortex based technique capable of performing high-efficiency single cell encapsulation for cell based assays.

  8. Optimal Sizing and Control Strategy Design for Heavy Hybrid Electric Truck

    Directory of Open Access Journals (Sweden)

    Yuan Zou

    2012-01-01

    Full Text Available Due to the complexity of the hybrid powertrain, the control is highly involved to improve the collaborations of the different components. For the specific powertrain, the components' sizing just gives the possibility to propel the vehicle and the control will realize the function of the propulsion. Definitely the components' sizing also gives the constraints to the control design, which cause a close coupling between the sizing and control strategy design. This paper presents a parametric study focused on sizing of the powertrain components and optimization of the power split between the engine and electric motor for minimizing the fuel consumption. A framework is put forward to accomplish the optimal sizing and control design for a heavy parallel pre-AMT hybrid truck under the natural driving schedule. The iterative plant-controller combined optimization methodology is adopted to optimize the key parameters of the plant and control strategy simultaneously. A scalable powertrain model based on a bilevel optimization framework is built. Dynamic programming is applied to find the optimal control in the inner loop with a prescribed cycle. The parameters are optimized in the outer loop. The results are analysed and the optimal sizing and control strategy are achieved simultaneously.

  9. Comparison between direct methods for determination of microbial cell volume: electron microscopy and electronic particle sizing.

    OpenAIRE

    Montesinos, E; Esteve, I; Guerrero, R

    1983-01-01

    Size frequency distributions of different phototrophic and heterotrophic microorganisms were determined by means of scanning and transmission electron microscopy and electronic particle sizing. Statistically significant differences existed among the three techniques used in this study. Cells processed for electron microscopy showed lower mean cellular volumes than those processed for electronic particle sizing, reflecting a shrinkage by factors ranging from 1.1 to 6.2 (mean, 2.3). Processing ...

  10. The Influence of Genome and Cell Size on Brain Morphology in Amphibians.

    Science.gov (United States)

    Roth, Gerhard; Walkowiak, Wolfgang

    2015-08-10

    In amphibians, nerve cell size is highly correlated with genome size, and increases in genome and cell size cause a retardation of the rate of development of nervous (as well as nonnervous) tissue leading to secondary simplification. This yields an inverse relationship between genome and cell size on the one hand and morphological complexity of the tectum mesencephali as the main visual center, the size of the torus semicircularis as the main auditory center, the size of the amphibian papilla as an important peripheral auditory structure, and the size of the cerebellum as a major sensorimotor center. Nervous structures developing later (e.g., torus and cerebellum) are more affected by secondary simplification than those that develop earlier (e.g., the tectum). This effect is more prominent in salamanders and caecilians than in frogs owing to larger genome and cells sizes in the former two taxa. We hypothesize that because of intragenomic evolutionary processes, important differences in brain morphology can arise independently of specific environmental selection. Copyright © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.

  11. Size-dependent cellular uptake mechanism and cytotoxicity toward calcium oxalate on Vero cells

    Science.gov (United States)

    Sun, Xin-Yuan; Gan, Qiong-Zhi; Ouyang, Jian-Ming

    2017-02-01

    Urinary crystals with various sizes are present in healthy individuals and patients with kidney stone; however, the cellular uptake mechanism of calcium oxalate of various sizes has not been elucidated. This study aims to compare the internalization of nano-/micron-sized (50 nm, 100 nm, and 1 μm) calcium oxalate monohydrate (COM) and dihydrate (COD) crystals in African green monkey renal epithelial (Vero) cells. The internalization and adhesion of COM and COD crystals to Vero cells were enhanced with decreasing crystal size. Cell death rate was positively related to the amount of adhered and internalized crystals and exhibited higher correlation with internalization than that with adhesion. Vero cells mainly internalized nano-sized COM and COD crystals through clathrin-mediated pathways as well as micron-sized crystals through macropinocytosis. The internalized COM and COD crystals were distributed in the lysosomes and destroyed lysosomal integrity to some extent. The results of this study indicated that the size of crystal affected cellular uptake mechanism, and may provide an enlightenment for finding potential inhibitors of crystal uptake, thereby decreasing cell injury and the occurrence of kidney stones.

  12. Communication across the bacterial cell envelope depends on the size of the periplasm.

    Science.gov (United States)

    Asmar, Abir T; Ferreira, Josie L; Cohen, Eli J; Cho, Seung-Hyun; Beeby, Morgan; Hughes, Kelly T; Collet, Jean-François

    2017-12-01

    The cell envelope of gram-negative bacteria, a structure comprising an outer (OM) and an inner (IM) membrane, is essential for life. The OM and the IM are separated by the periplasm, a compartment that contains the peptidoglycan. The OM is tethered to the peptidoglycan via the lipoprotein, Lpp. However, the importance of the envelope's multilayered architecture remains unknown. Here, when we removed physical coupling between the OM and the peptidoglycan, cells lost the ability to sense defects in envelope integrity. Further experiments revealed that the critical parameter for the transmission of stress signals from the envelope to the cytoplasm, where cellular behaviour is controlled, is the IM-to-OM distance. Augmenting this distance by increasing the length of the lipoprotein Lpp destroyed signalling, whereas simultaneously increasing the length of the stress-sensing lipoprotein RcsF restored signalling. Our results demonstrate the physiological importance of the size of the periplasm. They also reveal that strict control over the IM-to-OM distance is required for effective envelope surveillance and protection, suggesting that cellular architecture and the structure of transenvelope protein complexes have been evolutionarily co-optimised for correct function. Similar strategies are likely at play in cellular compartments surrounded by 2 concentric membranes, such as chloroplasts and mitochondria.

  13. Developmental control of cell division

    NARCIS (Netherlands)

    Boxem, M. (Mike)

    2002-01-01

    During development of multicellular organisms, cell divisions need to be coordinated with the developmental program of the entire organism. Although the mechanisms that drive cells through the division cycle are well understood, very little is known about the pathways that link extracellular signals

  14. Detonation cell size measurements and predictions in hydrogen-air-steam mixtures at elevated temperatures

    International Nuclear Information System (INIS)

    Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Economos, C.; Sato, K.; Kinoshita, M.

    1994-01-01

    The effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures at 0.1 MPa has been investigated. Experiments were carried out in a 10-cm-inner-diameter, 6.1-m-long heated detonation tube with a maximum operating temperature of 700 K and spatial temperature uniformity of ± 14 K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300--650 K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at ay given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm-inside-diameter test vessel, based upon the onset of single-head spin, decreased from 15% hydrogen at 300 K down to about 9% hydrogen at 650 K. The experimental detonation cell size data were correlated suing a Zel'dovich-von Neumann-Doering (ZND) model for the detonation using detailed chemical-kinetic reaction mechanisms. The proportionality constants used to scale the reaction zone length calculations from the ZND model varied from 3o to 51 for the hydrogen-air cell size data at 650 and 300 K, respectively

  15. Detonation cell size measurements and predictions in hydrogen-air-steam mixtures at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Economos, C.; Sato, K.; Kinoshita, M. (Brookhaven National Lab., Upton, NY (United States). Safety and Risk Evaluation Division)

    1994-11-01

    The effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures at 0.1 MPa has been investigated. Experiments were carried out in a 10-cm-inner-diameter, 6.1-m-long heated detonation tube with a maximum operating temperature of 700 K and spatial temperature uniformity of [+-] 14 K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300--650 K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at ay given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm-inside-diameter test vessel, based upon the onset of single-head spin, decreased from 15% hydrogen at 300 K down to about 9% hydrogen at 650 K. The experimental detonation cell size data were correlated suing a Zel'dovich-von Neumann-Doering (ZND) model for the detonation using detailed chemical-kinetic reaction mechanisms. The proportionality constants used to scale the reaction zone length calculations from the ZND model varied from 3o to 51 for the hydrogen-air cell size data at 650 and 300 K, respectively.

  16. Process for control of cell division

    Science.gov (United States)

    Cone, C. D., Jr. (Inventor)

    1977-01-01

    A method of controlling mitosis of biological cells was developed, which involved inducing a change in the intracellular ionic hierarchy accompanying the cellular electrical transmembrane potential difference (Esubm) of the cells. The ionic hierarchy may be varied by imposing changes on the relative concentrations of Na(+), K(+) and Cl(-), or by directly imposing changes in the physical Esubm level across the cell surface.

  17. A Study on Cell Size of Irradiated Spacer Grid for PWR Fuel

    International Nuclear Information System (INIS)

    Jin, Y. G.; Kim, G. S.; Ryu, W. S. and others

    2014-01-01

    The spacer grids supporting the fuel rods absorb vibration impacts due to the reactor coolant flow, and grid spring force decreases under irradiation. This reduction of contact force might cause grid-to-rod fretting wear. The fretting failure of the fuel rod is one of the recent significant issues in the nuclear industry from an economical as well as a safety concern. Thus, it is important to understand the characteristics of cell spring behavior and the change in size of grid cells for an irradiated spacer grid. In the present study, the dimensional measurement of a spacer grid was conducted to investigate the cell size of an irradiated spacer grid in a hot cell at IMEF (Irradiated Materials Examination Facility) of KAERI. To evaluate the fretting wear performance of an irradiated spacer grid, hot cell tests were carried out at IMEF of KAERI. Hot cell examinations include dimensional measurements for the irradiated spacer grid. The change of cell sizes was dependent on the direction of the spacer grids, leading to significant gap variations. It was found that the change in size of the cell springs due to irradiation-induced stress relaxation and creep during the fuel residency in the reactor core affect the contact behavior between the fuel rod and the cell spring

  18. A method to increase reproducibility in adult ventricular myocyte sizing and flow cytometry: Avoiding cell size bias in single cell preparations.

    Directory of Open Access Journals (Sweden)

    Javier E López

    Full Text Available Flow cytometry (FCM of ventricular myocytes (VMs is an emerging technology in adult cardiac research that is challenged by the wide variety of VM shapes and sizes. Cellular variability and cytometer flow cell size can affect cytometer performance. These two factors of variance limit assay validity and reproducibility across laboratories. Washing and filtering of ventricular cells in suspension are routinely done to prevent cell clumping and minimize data variability without the appropriate standardization. We hypothesize that washing and filtering arbitrarily biases towards sampling smaller VMs than what actually exist in the adult heart.To determine the impact of washing and filtering on adult ventricular cells for cell sizing and FCM.Left ventricular cardiac cells in single-cell suspension were harvested from New Zealand White rabbits and fixed prior to analysis. Each ventricular sample was aliquoted before washing or filtering through a 40, 70, 100 or 200μm mesh. The outcomes of the study are VM volume by Coulter Multisizer and light-scatter signatures by FCM. Data are presented as mean±SD. Myocyte volumes without washing or filtering (NF served as the "gold standard" within the sample and ranged from 11,017 to 46,926μm3. Filtering each animal sample through a 200μm mesh caused no variation in the post-filtration volume (1.01+0.01 fold vs. NF, n = 4 rabbits, p = 0.999 with an intra-assay coefficient of variation (%CV of <5% for all 4 samples. Filtering each sample through a 40, 70 or 100μm mesh invariably reduced the post-filtration volume by 41±10%, 9.0±0.8% and 8.8±0.8% respectively (n = 4 rabbits, p<0.0001, and increased the %CV (18% to 1.3%. The high light-scatter signature by FCM, a simple parameter for the identification of ventricular myocytes, was measured after washing and filtering. Washing discarded VMs and filtering cells through a 40 or 100μm mesh reduced larger VM by 46% or 11% respectively (n = 6 from 2 rabbits, p<0

  19. Cdc42-mediated tubulogenesis controls cell specification

    DEFF Research Database (Denmark)

    Kesavan, Gokul; Sand, Fredrik Wolfhagen; Greiner, Thomas Uwe

    2009-01-01

    Understanding how cells polarize and coordinate tubulogenesis during organ formation is a central question in biology. Tubulogenesis often coincides with cell-lineage specification during organ development. Hence, an elementary question is whether these two processes are independently controlled......, or whether proper cell specification depends on formation of tubes. To address these fundamental questions, we have studied the functional role of Cdc42 in pancreatic tubulogenesis. We present evidence that Cdc42 is essential for tube formation, specifically for initiating microlumen formation and later...... for maintaining apical cell polarity. Finally, we show that Cdc42 controls cell specification non-cell-autonomously by providing the correct microenvironment for proper control of cell-fate choices of multipotent progenitors. For a video summary of this article, see the PaperFlick file with the Supplemental Data...

  20. Well-Controlled Cell-Trapping Systems for Investigating Heterogeneous Cell-Cell Interactions.

    Science.gov (United States)

    Kamiya, Koki; Abe, Yuta; Inoue, Kosuke; Osaki, Toshihisa; Kawano, Ryuji; Miki, Norihisa; Takeuchi, Shoji

    2018-03-01

    Microfluidic systems have been developed for patterning single cells to study cell-cell interactions. However, patterning multiple types of cells to understand heterogeneous cell-cell interactions remains difficult. Here, it is aimed to develop a cell-trapping device to assemble multiple types of cells in the well-controlled order and morphology. This device mainly comprises a parylene sheet for assembling cells and a microcomb for controlling the cell-trapping area. The cell-trapping area is controlled by moving the parylene sheet on an SU-8 microcomb using tweezers. Gentle downward flow is used as a driving force for the cell-trapping. The assembly of cells on a parylene sheet with round and line-shaped apertures is demonstrated. The cell-cell contacts of the trapped cells are then investigated by direct cell-cell transfer of calcein via connexin nanopores. Finally, using the device with a system for controlling the cell-trapping area, three different types of cells in the well-controlled order are assembled. The correct cell order rate obtained using the device is 27.9%, which is higher than that obtained without the sliding parylene system (0.74%). Furthermore, the occurrence of cell-cell contact between the three cell types assembled is verified. This cell-patterning device will be a useful tool for investigating heterogeneous cell-cell interactions. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Optical separation and controllable delivery of cells from particle and cell mixture

    Directory of Open Access Journals (Sweden)

    Li Yuchao

    2015-11-01

    Full Text Available Cell separation and delivery have recently gained significant attention in biological and biochemical studies. In thiswork, an optical method for separation and controllable delivery of cells by using an abruptly tapered fiber probe is reported. By launching a laser beam at the wavelength of 980 nm into the fiber, a mixture of cells with sizes of ~5 and ~3 μm and poly(methyl methacrylate particles with size of 5 μm are separated into three chains along the direction of propagation of light. The cell and particle chains are delivered in three dimensions over 600 μm distance. Experimental results are interpreted by numerical simulations. Optical forces and forward migration velocities of different particles and cells are calculated and discussed.

  2. In vitro toxicity of different-sized ZnO nanoparticles in Caco-2 cells

    Science.gov (United States)

    Kang, Tianshu; Guan, Rongfa; Chen, Xiaoqiang; Song, Yijuan; Jiang, Han; Zhao, Jin

    2013-11-01

    There has been rapid growth in nanotechnology in both the public and private sectors worldwide, but concern about nanosafety exists. To assess size-dependent cytotoxicity on human cancer cells, we studied the cytotoxic effect of three kinds of zinc oxide nanoparticles (ZnO NPs) on human epithelial colorectal adenocarcinoma (Caco-2) cells. Nanoparticles were first characterized by size, distribution, and intensity. Multiple assays have been adopted to measure the cell activity and oxidative stress. The cytotoxicity of ZnO NPs was time dependent and dose dependent. The 24-h exposure was chosen to confirm the viability and accessibility of the cells and taken as the appropriate time for the following test system. The IC50 value was found at a low concentration. The oxidative stress elicited a significant reduction in glutathione with increase in reactive oxygen species and lactate dehydrogenase. The toxicity resulted in a deletion of cells in the G1 phase and an accumulation of cells in the S and G2/M phases. One type of metallic oxide (ZnO) exerted different cytotoxic effects according to different particle sizes. Data from the previous experiments showed that 26-nm ZnO NPs appeared to have the highest toxicity to Caco-2 cells. The study demonstrated the toxicity of ZnO NPs to Caco-2 cells and the impact of particle size, which could be useful in the medical applications.

  3. Genetic algorithm with small population size for search feasible control parameters for parallel hybrid electric vehicles

    Directory of Open Access Journals (Sweden)

    Yu-Huei Cheng

    2017-11-01

    Full Text Available The control strategy is a major unit in hybrid electric vehicles (HEVs. In order to provide suitable control parameters for reducing fuel consumptions and engine emissions while maintaining vehicle performance requirements, the genetic algorithm (GA with small population size is applied to search for feasible control parameters in parallel HEVs. The electric assist control strategy (EACS is used as the fundamental control strategy of parallel HEVs. The dynamic performance requirements stipulated in the Partnership for a New Generation of Vehicles (PNGV is considered to maintain the vehicle performance. The known ADvanced VehIcle SimulatOR (ADVISOR is used to simulate a specific parallel HEV with urban dynamometer driving schedule (UDDS. Five population sets with size 5, 10, 15, 20, and 25 are used in the GA. The experimental results show that the GA with population size of 25 is the best for selecting feasible control parameters in parallel HEVs.

  4. Computer control of shielded cell operations

    International Nuclear Information System (INIS)

    Jeffords, W.R. III.

    1987-01-01

    This paper describes in detail a computer system to remotely control shielded cell operations. System hardware, software, and design criteria are discussed. We have designed a computer-controlled buret that provides a tenfold improvement over the buret currently in service. A computer also automatically controls cell analyses, calibrations, and maintenance. This system improves conditions for the operators by providing a safer, more efficient working environment and is expandable for future growth and development

  5. On the size distribution of one-, two- and three-dimensional Voronoi cells

    International Nuclear Information System (INIS)

    Marthinsen, K.

    1994-03-01

    The present report gives a presentation of the different cell size distribution obtained by computer simulations of random Voronoi cell structures in one-, two- and three-dimensional space. The random Voronoi cells are constructed from cell centroids randomly distributed along a string, in the plane and in three-dimensional space, respectively. The size distributions are based on 2-3 · 10 4 cells. For the spacial polyhedra both the distribution of volumes, areas and radii are presented, and the two latter quantities are compared to the distributions of areas and radii from a planar section through the three-dimensional structure as well as to the corresponding distributions obtained from a pure two-dimensional cell structure. 11 refs., 11 figs

  6. Night temperature and source-sink effects on overall growth, cell number and cell size in bell pepper ovaries.

    Science.gov (United States)

    Darnell, Rebecca L; Cruz-Huerta, Nicacio; Williamson, Jeffrey G

    2012-10-01

    Ovary swelling, and resultant fruit malformation, in bell pepper flowers is favoured by low night temperature or a high source-sink ratio. However, the interaction between night temperature and source-sink ratio on ovary swelling and the contribution of cell size and cell number to ovary swelling are unknown. The present research examined the interactive effects of night temperature and source-sink ratio on ovary size, cell number and cell size at anthesis in bell pepper flowers. Bell pepper plants were grown in growth chambers at night temperatures of either 20 °C (HNT) or 12 °C (LNT). Within each temperature treatment, plants bore either 0 (non-fruiting) or two developing fruits per plant. Ovary fresh weight, cell size and cell number were measured. Ovary fresh weights in non-fruiting plants grown at LNT were the largest, while fresh weights were smallest in plants grown at HNT with fruits. In general, mesocarp cell size in ovaries was largest in non-fruiting plants grown at either LNT or HNT and smallest in fruiting plants at HNT. Mesocarp cell number was greater in non-fruiting plants under LNT than in the rest of the night temperature/fruiting treatments. These responses were more marked in ovaries sampled after 18 d of treatment compared with those sampled after 40 d of treatment. Ovary fresh weight of flowers at anthesis increased 65 % in non-fruiting plants grown under LNT compared with fruiting plants grown under HNT. This increase was due primarily to increases in mesocarp cell number and size. These results indicate that the combined effects of LNT and high source-sink ratio on ovary swelling are additive. Furthermore, the combined effects of LNT and low source-sink ratio or HNT and high source-sink ratio can partially overcome the detrimental effects of LNT and high source-sink ratio.

  7. Detonation cell size measurements and predictions in hydrogen-air-steam mixtures at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Economos, C.

    1994-01-01

    The present research reports on the effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures. Experimental and theoretical research related to combustion phenomena in hydrogen-air-steam mixtures has been ongoing for many years. However, detonation cell size data currently exists or hydrogen-air-steam mixtures up to a temperature of only 400K. Sever accident scenarios have been identified for light water reactors (LWRs) where hydrogen-air mixture temperatures in excess of 400K could be generated within containment. The experiments in this report focus on extending the cell size data base for initial mixture temperatures in excess of 400K. The experiments were carried out in a 10-cm inner-diameter, 6.1-m long heated detonation tube with a maximum operating temperature of 700K and spatial temperature uniformity of {plus_minus}14K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300K--650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm inside-diameter test vessel, based upon the onset of single-head spin, decreased from 15 percent by hydrogen at 300K down to about 9 percent hydrogen at 650K. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments.

  8. Detonation cell size measurements and predictions in hydrogen-air-steam mixtures at elevated temperatures

    International Nuclear Information System (INIS)

    Ciccarelli, G.; Ginsberg, T.; Boccio, J.; Economos, C.

    1994-01-01

    The present research reports on the effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures. Experimental and theoretical research related to combustion phenomena in hydrogen-air-steam mixtures has been ongoing for many years. However, detonation cell size data currently exists or hydrogen-air-steam mixtures up to a temperature of only 400K. Sever accident scenarios have been identified for light water reactors (LWRs) where hydrogen-air mixture temperatures in excess of 400K could be generated within containment. The experiments in this report focus on extending the cell size data base for initial mixture temperatures in excess of 400K. The experiments were carried out in a 10-cm inner-diameter, 6.1-m long heated detonation tube with a maximum operating temperature of 700K and spatial temperature uniformity of ±14K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300K--650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm inside-diameter test vessel, based upon the onset of single-head spin, decreased from 15 percent by hydrogen at 300K down to about 9 percent hydrogen at 650K. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments

  9. Bone Microvasculature Tracks Red Blood Cell Size Diminution in Triassic Mammal and Dinosaur Forerunners.

    Science.gov (United States)

    Huttenlocker, Adam K; Farmer, C G

    2017-01-09

    Vertebrate red blood cells (RBCs) display a range of sizes, spanning orders of magnitude in volume in different clades [1]. The importance of this size variation to diffusion during exercise is reinforced by functional links between RBC and capillary diameters [2, 3]. Small RBCs, such as those of mammals (which lack nuclei) and birds, contribute to shorter diffusion distances and permit relatively fast O 2 uptake kinetics [4]. Although constraints on RBC size have been tied to the cell's need to attend capillary sizes for effective gas diffusion [3], as well as to genome size evolution [5, 6], major questions persist concerning patterns of RBC size evolution and its paleobiological significance. Here, we evaluate the relationship between RBC sizes and bone histometry and use microstructural evidence to trace their evolution in a phylogeny of extinct tetrapods. We find that several fossilizable aspects of bone microstructure, including the sizes of vascular and lacunar (cellular) spaces, provide useful indicators of RBC size in tetrapods. We also show that Triassic non-mammalian cynodonts had reduced and densely packed vascular canals identical to those of some mammals and likely accommodated smaller, more mammal-like RBCs. Reduced channel diameters accommodating smaller RBCs predated the origin of crown mammals by as much as 70 million years. This discovery offers a new proxy for the physiologic status of the mammal and avian stem groups and contextualizes the independent origins of their increased activity metabolism. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Size and Carbon Content of Sub-seafloor Microbial Cells at Landsort Deep, Baltic Sea

    DEFF Research Database (Denmark)

    Braun, Stefan; Morono, Yuki; Littmann, Sten

    2016-01-01

    small cell sizes as adaptation to the long-term subsistence at very low energy availability in the deep biosphere. We present for the first time depth-related data on the cell volume and carbon content of sedimentary microbial cells buried down to 60 m below the seafloor. Our data enable estimates...... of volume- and biomass-specific cellular rates of energy metabolism in the deep biosphere and will improve global estimates of microbial biomass....

  11. Size and Dynamics of Caveolae Studied Using Nanoparticles in Living Endothelial Cells

    OpenAIRE

    Wang, Zhenjia; Tiruppathi, Chinnaswamy; Minshall, Richard D.; Malik, Asrar B.

    2009-01-01

    Caveolae are plasma membrane invaginations prominent in all endothelial cells lining blood vessels. Caveolae characteristically bud to form free cytoplasmic vesicles capable of transporting carrier proteins such as albumin through the cell. However, caveolae size distribution and dynamics in living endothelial cells and ability of caveolae to internalize nanoparticles are not well understood. We demonstrate here the design of a dual-color nanoparticle pair to measure non-invasively caveolae s...

  12. Lithium-Ion Cell Charge Control Unit

    Science.gov (United States)

    Reid, Concha; Button, Robert; Manzo, Michelle; McKissock, Barbara; Miller, Thomas; Gemeiner, Russel; Bennett, William; Hand, Evan

    2006-01-01

    Life-test data of Lithium-Ion battery cells is critical in order to establish their performance capabilities for NASA missions and Exploration goals. Lithium-ion cells have the potential to replace rechargeable alkaline cells in aerospace applications, but they require a more complex charging scheme than is typically required for alkaline cells. To address these requirements in our Lithium-Ion Cell Test Verification Program, a Lithium-Ion Cell Charge Control Unit was developed by NASA Glenn Research Center (GRC). This unit gives researchers the ability to test cells together as a pack, while allowing each cell to charge individually. This allows the inherent cell-to-cell variations to be addressed on a series string of cells and results in a substantial reduction in test costs as compared to individual cell testing. The Naval Surface Warfare Center at Crane, Indiana developed a power reduction scheme that works in conjunction with the Lithium-Ion Cell Charge Control Unit. This scheme minimizes the power dissipation required by the circuitry to prolong circuit life and improve its reliability.

  13. Identification and characterization of the nano-sized vesicles released by muscle cells.

    Science.gov (United States)

    Romancino, Daniele P; Paterniti, Gaetano; Campos, Yvan; De Luca, Angela; Di Felice, Valentina; d'Azzo, Alessandra; Bongiovanni, Antonella

    2013-05-02

    Several cell types secrete small membranous vesicles that contain cell-specific collections of proteins, lipids, and genetic material. The function of these vesicles is to allow cell-to-cell signaling and the horizontal transfer of their cargo molecules. Here, we demonstrate that muscle cells secrete nano-sized vesicles and that their release increases during muscle differentiation. Analysis of these nanovesicles allowed us to characterize them as exosome-like particles and to define the potential role of the multifunctional protein Alix in their biogenesis. Copyright © 2013 Federation of European Biochemical Societies. All rights reserved.

  14. The Organization of Nanoporous Structure Using Controlled Micelle Size from MPEG-b-PDLLA Block Copolymers

    International Nuclear Information System (INIS)

    Chang, Jeong Ho; Kim, Kyung Ja; Shin, Young Kook

    2004-01-01

    Selected MPEG-b-PDLLA block copolymers have been synthesized by ring-opening polymerization with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are then controlled by the characteristics of the block copolymer template. All the materials prepared in this study showed the tunable pore size of 20-80 A with the increase of hydrophobic chain lengths and up to 660 m 2 /g of specific surface area. The formation mechanism of these nanoporous structures obtained by controlling the micelle size has been confirmed using both liquid and solid state 13 C and 29 Si NMR techniques. This work verifies the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of hydrophobic cores and hydrophilic shells of the block copolymer templates

  15. Size-controllable synthesis of bare gold nanoparticles by femtosecond laser fragmentation in water

    International Nuclear Information System (INIS)

    Maximova, Ksenia; Aristov, Andrei; Sentis, Marc; Kabashin, Andrei V

    2015-01-01

    We report a size-controllable synthesis of stable aqueous solutions of ultrapure low-size-dispersed Au nanoparticles by methods of femtosecond laser fragmentation from preliminary formed colloids. Such approach makes possible the tuning of mean nanoparticle size between a few nm and several tens of nm under the size dispersion lower than 70% by varying the fluence of pumping radiation during the fragmentation procedure. The efficient size control is explained by 3D geometry of laser fragmentation by femtosecond laser-induced white light super-continuum and plasma-related phenomena. Despite the absence of any protective ligands, the nanoparticle solutions demonstrate exceptional stability due to electric repulsion effect associated with strong negative charging of formed nanoparticles. Stable aqueous solutions of bare gold nanoparticles present a unique object with a variety of potential applications in catalysis, surface-enhanced Raman spectroscopy, photovoltaics, biosensing and biomedicine. (paper)

  16. Tailoring the rate-sensitivity of low density polyurea foams through cell wall aperture size

    Science.gov (United States)

    Ramirez, B. J.; Kingstedt, O. T.; Crum, R.; Gamez, C.; Gupta, V.

    2017-06-01

    The plateau stress and energy absorption of low density (≤300 kg/m3) polyurea (PU) foams and expanded polystyrene (EPS) were measured at deformation rates ranging from 0.004 s-1 to 5000 s-1. Low (≤10-1 s-1) strain rate testing was performed using an Instron load frame, intermediate (101-102 s-1) strain rates using a drop-weight impact tower, and high (≥103 s-1) strain rate conditions using a modified split-Hopkinson pressure bar. The plateau stress and energy absorption of low density PU foams exhibit a strong rate dependence across all deformation rates. This result has been previously unreported for low density polymer foams under low and intermediate strain rates. The strain rate sensitivity of PU foams was found to be strongly dependent on cell size for low strain rates and cell wall aperture size for intermediate and high strain rates. EPS type foam, however, remained nearly insensitive to strain rate. At low and intermediate strain rates, the plastic crushing in the EPS and the high plateau stress yield a much higher energy absorption capability than the viscoelastic dissipation in the PU foams. However, PU foams were found to display similar energy absorption properties as EPS based foams under high strain rates. Thus, controlling the strain rate sensitivity of PU foams through aperture diameter can lead to an increase in energy absorption properties at high strain rates, while simultaneously maintaining the peak stress below certain injury thresholds. Additionally, unlike EPS, which undergo plastic crushing after first impact, flexible polyurea foams will recover fully after each impact and thus will have multiple hit capabilities. This will allow these materials to have a wide range of applications, in advance body armors and protective headgears to use in low-cost protection systems for a wide range of military platforms, civilian, and space applications.

  17. Size Control and Fluorescence Labeling of Polydopamine Melanin-Mimetic Nanoparticles for Intracellular Imaging

    Directory of Open Access Journals (Sweden)

    Devang R. Amin

    2017-09-01

    Full Text Available As synthetic analogs of the natural pigment melanin, polydopamine nanoparticles (NPs are under active investigation as non-toxic anticancer photothermal agents and as free radical scavenging therapeutics. By analogy to the widely adopted polydopamine coatings, polydopamine NPs offer the potential for facile aqueous synthesis and incorporation of (biofunctional groups under mild temperature and pH conditions. However, clear procedures for the convenient and reproducible control of critical NP properties such as particle diameter, surface charge, and loading with functional molecules have yet to be established. In this work, we have synthesized polydopamine-based melanin-mimetic nanoparticles (MMNPs with finely controlled diameters spanning ≈25 to 120 nm and report on the pH-dependence of zeta potential, methodologies for PEGylation, and the incorporation of fluorescent organic molecules. A comprehensive suite of complementary techniques, including dynamic light scattering (DLS, cryogenic transmission electron microscopy (cryo-TEM, X-ray photoelectron spectroscopy (XPS, zeta-potential, ultraviolet–visible (UV–Vis absorption and fluorescence spectroscopy, and confocal microscopy, was used to characterize the MMNPs and their properties. Our PEGylated MMNPs are highly stable in both phosphate-buffered saline (PBS and in cell culture media and exhibit no cytotoxicity up to at least 100 µg mL−1 concentrations. We also show that a post-functionalization methodology for fluorophore loading is especially suitable for producing MMNPs with stable fluorescence and significantly narrower emission profiles than previous reports, suggesting they will be useful for multimodal cell imaging. Our results pave the way towards biomedical imaging and possibly drug delivery applications, as well as fundamental studies of MMNP size and surface chemistry dependent cellular interactions.

  18. Size Control and Fluorescence Labeling of Polydopamine Melanin-Mimetic Nanoparticles for Intracellular Imaging.

    Science.gov (United States)

    Amin, Devang R; Sugnaux, Caroline; Lau, King Hang Aaron; Messersmith, Phillip B

    2017-09-01

    As synthetic analogs of the natural pigment melanin, polydopamine nanoparticles (NPs) are under active investigation as non-toxic anticancer photothermal agents and as free radical scavenging therapeutics. By analogy to the widely adopted polydopamine coatings, polydopamine NPs offer the potential for facile aqueous synthesis and incorporation of (bio)functional groups under mild temperature and pH conditions. However, clear procedures for the convenient and reproducible control of critical NP properties such as particle diameter, surface charge, and loading with functional molecules have yet to be established. In this work, we have synthesized polydopamine-based melanin-mimetic nanoparticles (MMNPs) with finely controlled diameters spanning ≈25 to 120 nm and report on the pH-dependence of zeta potential, methodologies for PEGylation, and the incorporation of fluorescent organic molecules. A comprehensive suite of complementary techniques, including dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), X-ray photoelectron spectroscopy (XPS), zeta-potential, ultraviolet-visible (UV-Vis) absorption and fluorescence spectroscopy, and confocal microscopy, was used to characterize the MMNPs and their properties. Our PEGylated MMNPs are highly stable in both phosphate-buffered saline (PBS) and in cell culture media and exhibit no cytotoxicity up to at least 100 μg mL -1 concentrations. We also show that a post-functionalization methodology for fluorophore loading is especially suitable for producing MMNPs with stable fluorescence and significantly narrower emission profiles than previous reports, suggesting they will be useful for multimodal cell imaging. Our results pave the way towards biomedical imaging and possibly drug delivery applications, as well as fundamental studies of MMNP size and surface chemistry dependent cellular interactions.

  19. Control points within the cell cycle

    International Nuclear Information System (INIS)

    Van't Hof, J.

    1984-01-01

    Evidence of the temporal order of chromosomal DNA replication argues favorably for the view that the cell cycle is controlled by genes acting in sequence whose time of expression is determined by mitosis and the amount of nuclear DNA (2C vs 4C) in the cell. Gl and G2 appear to be carbohydrate dependent in that cells starved of either carbohydrate of phosphate fail to make these transitions. Cells deprived of nitrate, however, fail only at Gl to S transition indicating that the controls that operate in G1 differ from those that operate in G2. 46 references, 5 figures

  20. Planarians maintain a constant ratio of different cell types during changes in body size by using the stem cell system.

    Science.gov (United States)

    Takeda, Hiroyuki; Nishimura, Kaneyasu; Agata, Kiyokazu

    2009-12-01

    Planarians change in body size depending upon whether they are in feeding or starving conditions. To investigate how planarians regulate this flexible system, the numbers of total cells and specific cell types were counted and compared among worms 2 mm to 9 mm in body length. The total cell number increased linearly with increasing body length, but the ratio of cell numbers between the head and the trunk portion was constant (1:3). Interestingly, counting the numbers of specific neurons in the eye and brain after immunostaining using cell type-specific antibodies revealed that the ratio between different neuron types was constant regardless of the brain and body size. These results suggest that planarians can maintain proportionality while changing their body size by maintaining a constant ratio of different cell types. To understand this system and reveal how planarians restore the original ratio during eye and brain regeneration, the numbers of specialized cells were Investigated during regeneration. The results further substantiate the existence of some form of "counting mechanism" that has the ability to regulate both the absolute and relative numbers of different cell types in complex organs such as the brain during cell turnover, starvation, and regeneration.

  1. Single Atomic Iron Catalysts for Oxygen Reduction in Acidic Media: Particle Size Control and Thermal Activation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hanguang; Hwang, Sooyeon; Wang, Maoyu; Feng, Zhenxing; Karakalos, Stavros; Luo, Langli; Qiao, Zhi; Xie, Xiaohong; Wang, Chongmin; Su, Dong; Shao, Yuyan; Wu, Gang (BNL); (Oregon State U.); (SC); (PNNL); (Buffalo)

    2017-09-26

    It remains a grand challenge to replace platinum group metal (PGM) catalysts with earth-abundant materials for the oxygen reduction reaction (ORR) in acidic media, which is crucial for large-scale deployment of proton exchange membrane fuel cells (PEMFCs). Here, we report a high-performance atomic Fe catalyst derived from chemically Fe-doped zeolitic imidazolate frameworks (ZIFs) by directly bonding Fe ions to imidazolate ligands within 3D frameworks. Although the ZIF was identified as a promising precursor, the new synthetic chemistry enables the creation of well-dispersed atomic Fe sites embedded into porous carbon without the formation of aggregates. The size of catalyst particles is tunable through synthesizing Fe-doped ZIF nanocrystal precursors in a wide range from 20 to 1000 nm followed by one-step thermal activation. Similar to Pt nanoparticles, the unique size control without altering chemical properties afforded by this approach is able to increase the number of PGM-free active sites. The best ORR activity is measured with the catalyst at a size of 50 nm. Further size reduction to 20 nm leads to significant particle agglomeration, thus decreasing the activity. Using the homogeneous atomic Fe model catalysts, we elucidated the active site formation process through correlating measured ORR activity with the change of chemical bonds in precursors during thermal activation up to 1100 °C. The critical temperature to form active sites is 800 °C, which is associated with a new Fe species with a reduced oxidation number (from Fe3+ to Fe2+) likely bonded with pyridinic N (FeN4) embedded into the carbon planes. Further increasing the temperature leads to continuously enhanced activity, linked to the rise of graphitic N and Fe–N species. The new atomic Fe catalyst has achieved respectable ORR activity in challenging acidic media (0.5 M H2SO4), showing a half-wave potential of 0.85 V vs RHE and leaving only a 30 mV gap with Pt/C (60 μgPt/cm2). Enhanced stability

  2. Multi-objective energy management optimization and parameter sizing for proton exchange membrane hybrid fuel cell vehicles

    International Nuclear Information System (INIS)

    Hu, Zunyan; Li, Jianqiu; Xu, Liangfei; Song, Ziyou; Fang, Chuan; Ouyang, Minggao; Dou, Guowei; Kou, Gaihong

    2016-01-01

    Highlights: • Fuel economy, lithium battery size and powertrain system durability are incorporated in optimization. • A multi-objective power allocation strategy by taking battery size into consideration is proposed. • Influences of battery capacity and auxiliary power on strategy design are explored. • Battery capacity and fuel cell service life for the system life cycle cost are optimized. - Abstract: The powertrain system of a typical proton electrolyte membrane hybrid fuel cell vehicle contains a lithium battery package and a fuel cell stack. A multi-objective optimization for this powertrain system of a passenger car, taking account of fuel economy and system durability, is discussed in this paper. Based on an analysis of the optimum results obtained by dynamic programming, a soft-run strategy was proposed for real-time and multi-objective control algorithm design. The soft-run strategy was optimized by taking lithium battery size into consideration, and implemented using two real-time algorithms. When compared with the optimized dynamic programming results, the power demand-based control method proved more suitable for powertrain systems equipped with larger capacity batteries, while the state of charge based control method proved superior in other cases. On this basis, the life cycle cost was optimized by considering both lithium battery size and equivalent hydrogen consumption. The battery capacity selection proved more flexible, when powertrain systems are equipped with larger capacity batteries. Finally, the algorithm has been validated in a fuel cell city bus. It gets a good balance of fuel economy and system durability in a three months demonstration operation.

  3. Empirical evidence for multi-scaled controls on wildfire size distributions in California

    Science.gov (United States)

    Povak, N.; Hessburg, P. F., Sr.; Salter, R. B.

    2014-12-01

    Ecological theory asserts that regional wildfire size distributions are examples of self-organized critical (SOC) systems. Controls on SOC event-size distributions by virtue are purely endogenous to the system and include the (1) frequency and pattern of ignitions, (2) distribution and size of prior fires, and (3) lagged successional patterns after fires. However, recent work has shown that the largest wildfires often result from extreme climatic events, and that patterns of vegetation and topography may help constrain local fire spread, calling into question the SOC model's simplicity. Using an atlas of >12,000 California wildfires (1950-2012) and maximum likelihood estimation (MLE), we fit four different power-law models and broken-stick regressions to fire-size distributions across 16 Bailey's ecoregions. Comparisons among empirical fire size distributions across ecoregions indicated that most ecoregion's fire-size distributions were significantly different, suggesting that broad-scale top-down controls differed among ecoregions. One-parameter power-law models consistently fit a middle range of fire sizes (~100 to 10000 ha) across most ecoregions, but did not fit to larger and smaller fire sizes. We fit the same four power-law models to patch size distributions of aspect, slope, and curvature topographies and found that the power-law models fit to a similar middle range of topography patch sizes. These results suggested that empirical evidence may exist for topographic controls on fire sizes. To test this, we used neutral landscape modeling techniques to determine if observed fire edges corresponded with aspect breaks more often than expected by random. We found significant differences between the empirical and neutral models for some ecoregions, particularly within the middle range of fire sizes. Our results, combined with other recent work, suggest that controls on ecoregional fire size distributions are multi-scaled and likely are not purely SOC. California

  4. Nanotopographical Control of Stem Cell Differentiation

    Directory of Open Access Journals (Sweden)

    Laura E. McNamara

    2010-01-01

    Full Text Available Stem cells have the capacity to differentiate into various lineages, and the ability to reliably direct stem cell fate determination would have tremendous potential for basic research and clinical therapy. Nanotopography provides a useful tool for guiding differentiation, as the features are more durable than surface chemistry and can be modified in size and shape to suit the desired application. In this paper, nanotopography is examined as a means to guide differentiation, and its application is described in the context of different subsets of stem cells, with a particular focus on skeletal (mesenchymal stem cells. To address the mechanistic basis underlying the topographical effects on stem cells, the likely contributions of indirect (biochemical signal-mediated and direct (force-mediated mechanotransduction are discussed. Data from proteomic research is also outlined in relation to topography-mediated fate determination, as this approach provides insight into the global molecular changes at the level of the functional effectors.

  5. Cell-Sized confinement in microspheres accelerates the reaction of gene expression

    Science.gov (United States)

    Kato, Ayako; Yanagisawa, Miho; Sato, Yuko T.; Fujiwara, Kei; Yoshikawa, Kenichi

    2012-02-01

    Cell-sized water-in-oil droplet covered by a lipid layer was used to understand how lipid membranes affect biochemical systems in living cells. Here, we report a remarkable acceleration of gene expression in a cell-sized water-in-oil droplet entrapping a cell-free translation system to synthesize GFP (green fluorescent protein). The production rate of GFP (VGFP) in each droplet remained almost constant at least for on the order of a day, which implies 0th-order reaction kinetics. Interestingly, VGFP was inversely proportional to radius of droplets (R) when R is under 50 μm, and VGFP in droplets with R ~ 10 μm was more than 10 times higher than that in the bulk. The acceleration rates of GFP production in cell-sized droplets strongly depended on the lipid types. These results demonstrate that the membrane surface has the significant effect to facilitate protein production, especially when the scale of confinement is on the order of cell-size.

  6. Preoperative balance control compensation in patients with a vestibular schwannoma: does tumor size matter?

    Science.gov (United States)

    Ribeyre, Laurence; Frère, Julien; Gauchard, Gérome; Lion, Alexis; Perrin, Philippe; Spitz, Elisabeth; Parietti-Winkler, Cécile

    2015-04-01

    The influence of tumor size on postural control of patients with vestibular schwannoma (VS) remains to be determined. This study aimed to compare the postural performances of VS patients, according to the size of the tumor, with healthy subjects. The six conditions (C1-C6) of the sensory organization test (SOT) were carried out in 87 patients, split into four groups according to the Koos classification (stage I-IV), and in 72 aged-matched controls to evaluate postural control. The vestibular reflectivity and compensation were estimated with videonystagmography. Among patients, lower C5 and C6 scores were found in stage I and IV patients than in stage II and III patients, whereas vestibular compensation did not impact the tumor size influence on the postural control. The scores were significantly (pvestibular-related SOT conditions (C5-C6). Patients with an unilateral VS displayed altered postural performances compared to the control subjects and tumor size had a bell-like pattern effect on balance control. The tumor size could be seen as a determining factor in the implementation of adaptive mechanisms that lead to the postural compensation and might be dissociated from vestibular compensation. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  7. Confinement of surface waves at the air-water interface to control aerosol size and dispersity

    Science.gov (United States)

    Nazarzadeh, Elijah; Wilson, Rab; King, Xi; Reboud, Julien; Tassieri, Manlio; Cooper, Jonathan M.

    2017-11-01

    The precise control over the size and dispersity of droplets, produced within aerosols, is of great interest across many manufacturing, food, cosmetic, and medical industries. Amongst these applications, the delivery of new classes of high value drugs to the lungs has recently attracted significant attention from pharmaceutical companies. This is commonly achieved through the mechanical excitation of surface waves at the air liquid interface of a parent liquid volume. Previous studies have established a correlation between the wavelength on the surface of liquid and the final aerosol size. In this work, we show that the droplet size distribution of aerosols can be controlled by constraining the liquid inside micron-sized cavities and coupling surface acoustic waves into different volumes of liquid inside micro-grids. In particular, we show that by reducing the characteristic physical confinement size (i.e., either the initial liquid volume or the cavities' diameters), higher harmonics of capillary waves are revealed with a consequent reduction of both aerosol mean size and dispersity. In doing so, we provide a new method for the generation and fine control of aerosols' sizes distribution.

  8. Harnessing cell-material interaction to control cell fate: design ...

    Indian Academy of Sciences (India)

    Rajat K Das

    2017-10-26

    Oct 26, 2017 ... advancement in engineered hydrogel materials as such scaffold to control cell fate. Keywords. Extracellular matrix; hydrogel .... vided useful model systems to identify principles that would help design synthetic ..... tool to generate nanoscale periodic patterns that influ- enced stem cell differentiation.

  9. Harnessing cell-material interaction to control cell fate: design ...

    Indian Academy of Sciences (India)

    Rajat K Das

    2017-10-26

    Oct 26, 2017 ... Harnessing cell-material interaction to control cell fate: design principle of advanced functional hydrogel materials. †. RAJAT K DAS. ∗. Materials Science Centre, Indian Institute of Technology, Kharagpur, West Bengal, India. E-mail: rajat@matsc.iitkgp.ernet.in. MS received 15 August 2017; revised 29 ...

  10. Size distribution of retrovirally marked lineages matches prediction from population measurements of cell cycle behavior

    Science.gov (United States)

    Cai, Li; Hayes, Nancy L.; Takahashi, Takao; Caviness, Verne S Jr; Nowakowski, Richard S.

    2002-01-01

    Mechanisms that regulate neuron production in the developing mouse neocortex were examined by using a retroviral lineage marking method to determine the sizes of the lineages remaining in the proliferating population of the ventricular zone during the period of neuron production. The distribution of clade sizes obtained experimentally in four different injection-survival paradigms (E11-E13, E11-E14, E11-E15, and E12-E15) from a total of over 500 labeled lineages was compared with that obtained from three models in which the average behavior of the proliferating population [i.e., the proportion of cells remaining in the proliferative population (P) vs. that exiting the proliferative population (Q)] was quantitatively related to lineage size distribution. In model 1, different proportions of asymmetric, symmetric terminal, and symmetric nonterminal cell divisions coexisted during the entire developmental period. In model 2, the developmental period was divided into two epochs: During the first, asymmetric and symmetric nonterminal cell divisions occurred, but, during the second, asymmetric and symmetric terminal cell divisions occurred. In model 3, the shifts in P and Q are accounted for by changes in the proportions of the two types of symmetric cell divisions without the inclusion of any asymmetric cell divisions. The results obtained from the retroviral experiments were well accounted for by model 1 but not by model 2 or 3. These findings demonstrate that: 1) asymmetric and both types of symmetric cell divisions coexist during the entire period of neurogenesis in the mouse, 2) neuron production is regulated in the proliferative population by the independent decisions of the two daughter cells to reenter S phase, and 3) neurons are produced by both asymmetric and symmetric terminal cell divisions. In addition, the findings mean that cell death and/or tangential movements of cells in the proliferative population occur at only a low rate and that there are no

  11. Size control mechanism of ZnO nanoparticles obtained in microwave solvothermal synthesis

    Science.gov (United States)

    Wojnarowicz, Jacek; Chudoba, Tadeusz; Koltsov, Iwona; Gierlotka, Stanislaw; Dworakowska, Sylwia; Lojkowski, Witold

    2018-02-01

    The aim of the paper is to explain the mechanism of zinc oxide (ZnO) nanoparticle (NP) size control, which enables the size control of ZnO NPs obtained in microwave solvothermal synthesis (MSS) within the size range between circa 20 and 120 nm through the control of water content in the solution of zinc acetate in ethylene glycol. Heavy water was used in the tests. The mechanism of ZnO NPs size control was explained, discussed and experimentally verified. The discovery and investigation of this mechanism was possible by tracking the fate of water molecules during the whole synthesis process. All the synthesis products were identified. It was indicated that the MSS of ZnO NPs proceeded through the formation and conversion of intermediates such as Zn5(OH)8(CH3COO)2 · xH2O. Esters and H2O were the by-products of the MSS reaction of ZnO NPs. We justified that the esterification reaction is the decisive stage that is a prerequisite of the formation of ZnO NPs. The following parameters of the obtained ZnO NPs and of the intermediate were determined: pycnometric density, specific surface area, phase purity, average particles size, particles size distribution and chemical composition. The ZnO NPs morphology and structure were determined using scanning electron microscopy.

  12. A multi-agent based cell controller

    OpenAIRE

    Paulo Leitão; Francisco José de Oliveira Restivo; Goran Putnik

    2001-01-01

    This paper discusses the opportunity to use multi-agents technology in automation and distributed manufacturing systems and the expected improvements. To support the discussion, it is described a manufacturing cell control application developed using the multi-agent technology, and the results are compared with other control application developed in the past by some of the authors, using a traditional approach, for the same flexible manufacturing cell.

  13. Introducing micrometer-sized artificial objects into live cells: a method for cell-giant unilamellar vesicle electrofusion.

    Directory of Open Access Journals (Sweden)

    Akira C Saito

    Full Text Available Here, we report a method for introducing large objects of up to a micrometer in diameter into cultured mammalian cells by electrofusion of giant unilamellar vesicles. We prepared GUVs containing various artificial objects using a water-in-oil (w/o emulsion centrifugation method. GUVs and dispersed HeLa cells were exposed to an alternating current (AC field to induce a linear cell-GUV alignment, and then a direct current (DC pulse was applied to facilitate transient electrofusion. With uniformly sized fluorescent beads as size indexes, we successfully and efficiently introduced beads of 1 µm in diameter into living cells along with a plasmid mammalian expression vector. Our electrofusion did not affect cell viability. After the electrofusion, cells proliferated normally until confluence was reached, and the introduced fluorescent beads were inherited during cell division. Analysis by both confocal microscopy and flow cytometry supported these findings. As an alternative approach, we also introduced a designed nanostructure (DNA origami into live cells. The results we report here represent a milestone for designing artificial symbiosis of functionally active objects (such as micro-machines in living cells. Moreover, our technique can be used for drug delivery, tissue engineering, and cell manipulation.

  14. Retrieval of phytoplankton cell size from chlorophyll a specific absorption and scattering spectra of phytoplankton.

    Science.gov (United States)

    Zhou, Wen; Wang, Guifen; Li, Cai; Xu, Zhantang; Cao, Wenxi; Shen, Fang

    2017-10-20

    Phytoplankton cell size is an important property that affects diverse ecological and biogeochemical processes, and analysis of the absorption and scattering spectra of phytoplankton can provide important information about phytoplankton size. In this study, an inversion method for extracting quantitative phytoplankton cell size data from these spectra was developed. This inversion method requires two inputs: chlorophyll a specific absorption and scattering spectra of phytoplankton. The average equivalent-volume spherical diameter (ESD v ) was calculated as the single size approximation for the log-normal particle size distribution (PSD) of the algal suspension. The performance of this method for retrieving cell size was assessed using the datasets from cultures of 12 phytoplankton species. The estimations of a(λ) and b(λ) for the phytoplankton population using ESD v had mean error values of 5.8%-6.9% and 7.0%-10.6%, respectively, compared to the a(λ) and b(λ) for the phytoplankton populations using the log-normal PSD. The estimated values of C i ESD v were in good agreement with the measurements, with r 2 =0.88 and relative root mean square error (NRMSE)=25.3%, and relatively good performances were also found for the retrieval of ESD v with r 2 =0.78 and NRMSE=23.9%.

  15. Controllability analysis of decentralised linear controllers for polymeric fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Serra, Maria; Aguado, Joaquin; Ansede, Xavier; Riera, Jordi [Institut de Robotica i Informatica Industrial, Universitat Politecnica de Catalunya - Consejo Superior de Investigaciones Cientificas, C. Llorens i Artigas 4, 08028 Barcelona (Spain)

    2005-10-10

    This work deals with the control of polymeric fuel cells. It includes a linear analysis of the system at different operating points, the comparison and selection of different control structures, and the validation of the controlled system by simulation. The work is based on a complex non linear model which has been linearised at several operating points. The linear analysis tools used are the Morari resiliency index, the condition number, and the relative gain array. These techniques are employed to compare the controllability of the system with different control structures and at different operating conditions. According to the results, the most promising control structures are selected and their performance with PI based diagonal controllers is evaluated through simulations with the complete non linear model. The range of operability of the examined control structures is compared. Conclusions indicate good performance of several diagonal linear controllers. However, very few have a wide operability range. (author)

  16. Contact behavior modelling and its size effect on proton exchange membrane fuel cell

    Science.gov (United States)

    Qiu, Diankai; Peng, Linfa; Yi, Peiyun; Lai, Xinmin; Janßen, Holger; Lehnert, Werner

    2017-10-01

    Contact behavior between the gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance for proton exchange membrane fuel cells. Most current studies on contact behavior utilize experiments and finite element modelling and focus on fuel cells with graphite BPPs, which lead to high costs and huge computational requirements. The objective of this work is to build a more effective analytical method for contact behavior in fuel cells and investigate the size effect resulting from configuration alteration of channel and rib (channel/rib). Firstly, a mathematical description of channel/rib geometry is outlined in accordance with the fabrication of metallic BPP. Based on the interface deformation characteristic and Winkler surface model, contact pressure between BPP and GDL is then calculated to predict contact resistance and GDL porosity as evaluative parameters of contact behavior. Then, experiments on BPP fabrication and contact resistance measurement are conducted to validate the model. The measured results demonstrate an obvious dependence on channel/rib size. Feasibility of the model used in graphite fuel cells is also discussed. Finally, size factor is proposed for evaluating the rule of size effect. Significant increase occurs in contact resistance and porosity for higher size factor, in which channel/rib width decrease.

  17. NBT-II cell locomotion is modulated by restricting the size of focal contacts and is improved through EGF and ROCK signaling.

    Science.gov (United States)

    Liu, Hong-Wen; Lin, Chia-Ping; Liou, Yi-Jia; Hsu, Kuo-Wei; Yang, Jung-Yen; Lin, Chi-Hung

    2014-06-01

    Focal contacts, large macromolecular complexes that link the extracellular matrix and the internal cell cytoskeleton, are thought to govern cell locomotion. However, the maturation process through which focal contacts control the cellular migratory machinery by changes in size and molecular composition remain unclear. Here, we fabricated cell growth substrates that contained linear ECM strips of micron- or submicron-width in order to limit the enlargement of focal contacts. We found that NBT-II cells plated on the submicron substrate possessed smaller focal complexes that exhibited a highly dynamic turnover. These cells possessed various leading edges at multiple sites of the cell periphery, which prevented the cell from advancing. In contrast, cells grown on the micron-width substrate possessed large and stable focal adhesions. Most of these cells were elongated bipolar cells that were tethered at both ends and were immobile. Further, EGF and ROCK signaling pathways can modulate the cellular migratory responses according to the substrate guidance. On the submicron-width substrate, EGF treatment increased the focal contact size and the contractile force, causing these cells to develop one leading edge and migrate along the submicron-sized ECM paths. In contrast, inhibition of ROCK signaling decreased the focal contact size for cells plated on the micron substrate. These cells became less tethered and were able to migrate along or even across the micron-sized ECM paths. Our results indicate that formation and maturation of focal contacts is controlled by both ECM cues and intracellular signaling and they play a central role in directed cell motion. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Not all cells are equal: effects of temperature and sex on the size of different cell types in the Madagascar ground gecko Paroedura picta

    Directory of Open Access Journals (Sweden)

    Marcin Czarnoleski

    2017-08-01

    Full Text Available Cell size plays a role in evolutionary and phenotypically plastic changes in body size. To examine this role, we measured the sizes of seven cell types of geckos (Paroedura picta reared at three constant temperatures (24, 27, and 30°C. Our results show that the cell size varies according to the body size, sex and developmental temperature, but the pattern of this variance depends on the cell type. We identified three groups of cell types, and the cell sizes changed in a coordinated manner within each group. Larger geckos had larger erythrocytes, striated muscle cells and hepatocytes (our first cell group, but their renal proximal tubule cells and duodenal enterocytes (our second cell group, as well as tracheal chondrocytes and epithelial skin cells (our third cell group, were largely unrelated to the body size. For six cell types, we also measured the nuclei and found that larger cells had larger nuclei. The relative sizes of the nuclei were not invariant but varied in a complex manner with temperature and sex. In conclusion, we provide evidence suggesting that changes in cell size might be commonly involved in the origin of thermal and sexual differences in adult size. A recent theory predicts that smaller cells speed up metabolism but demand more energy for their maintenance; consequently, the cell size matches the metabolic demand and supply, which in ectotherms, largely depends on the thermal conditions. The complex thermal dependency of cell size in geckos suggests that further advancements in understanding the adaptive value of cell size requires the consideration of tissue-specific demand/supply conditions.

  19. Preparation and size control of highly monodisperse vinyl functionalized silica spheres

    International Nuclear Information System (INIS)

    Yin Jianbo; Deng Tiansong; Zhang Gengmin

    2012-01-01

    Vinyl functionalized silica spheres (VFSSs) are prepared by one-step reaction using the aqueous solution of organosilane. The synthetic method is effective and reproducible with one process used. The VFSSs could self-assemble into three-dimensional (3D) fcc photonic crystals. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that the VFSSs were highly monodisperse and their surfaces were sufficiently smooth. The size of the VFSSs could be controlled by adjusting the reaction temperature. The sphere size reached its minimum, 394 nm, around 45 °C and became larger when the temperature was either elevated or lowered. The maximum sphere size, 515 nm, was obtained around 15 °C. This work is expected to extend to the preparation and size control of other kinds of hybrid silica spheres.

  20. Cell size is positively correlated between different tissues in passerine birds and amphibians, but not necessarily in mammals.

    Science.gov (United States)

    Kozlowski, J; Czarnoleski, M; François-Krassowska, A; Maciak, S; Pis, T

    2010-12-23

    We examined cell size correlations between tissues, and cell size to body mass relationships in passerine birds, amphibians and mammals. The size correlated highly between all cell types in birds and amphibians; mammalian tissues clustered by size correlation in three tissue groups. Erythrocyte size correlated well with the volume of other cell types in birds and amphibians, but poorly in mammals. In birds, body mass correlated positively with the size of all cell types including erythrocytes, and in mammals only with the sizes of some cell types. Size of mammalian erythrocytes correlated with body mass only within the most taxonomically uniform group of species (rodents and lagomorphs). Cell volume increased with body mass of birds and mammals to less than 0.3 power, indicating that body size evolved mostly by changes in cell number. Our evidence suggests that epigenetic mechanisms determining cell size relationships in tissues are conservative in birds and amphibians, but less stringent in mammals. The patterns of cell size to body mass relationships we obtained challenge some key assumptions of fractal and cellular models used by allometric theory to explain mass-scaling of metabolism. We suggest that the assumptions in both models are not universal, and that such models need reformulation.

  1. The effective population size of malaria mosquitoes: large impact of vector control.

    Science.gov (United States)

    Athrey, Giridhar; Hodges, Theresa K; Reddy, Michael R; Overgaard, Hans J; Matias, Abrahan; Ridl, Frances C; Kleinschmidt, Immo; Caccone, Adalgisa; Slotman, Michel A

    2012-01-01

    Malaria vectors in sub-Saharan Africa have proven themselves very difficult adversaries in the global struggle against malaria. Decades of anti-vector interventions have yielded mixed results--with successful reductions in transmission in some areas and limited impacts in others. These varying successes can be ascribed to a lack of universally effective vector control tools, as well as the development of insecticide resistance in mosquito populations. Understanding the impact of vector control on mosquito populations is crucial for planning new interventions and evaluating existing ones. However, estimates of population size changes in response to control efforts are often inaccurate because of limitations and biases in collection methods. Attempts to evaluate the impact of vector control on mosquito effective population size (N(e)) have produced inconclusive results thus far. Therefore, we obtained data for 13-15 microsatellite markers for more than 1,500 mosquitoes representing multiple time points for seven populations of three important vector species--Anopheles gambiae, An. melas, and An. moucheti--in Equatorial Guinea. These populations were exposed to indoor residual spraying or long-lasting insecticidal nets in recent years. For comparison, we also analyzed data from two populations that have no history of organized vector control. We used Approximate Bayesian Computation to reconstruct their demographic history, allowing us to evaluate the impact of these interventions on the effective population size. In six of the seven study populations, vector control had a dramatic impact on the effective population size, reducing N(e) between 55%-87%, the exception being a single An. melas population. In contrast, the two negative control populations did not experience a reduction in effective population size. This study is the first to conclusively link anti-vector intervention programs in Africa to sharply reduced effective population sizes of malaria vectors.

  2. Controlling the spotlight of attention: visual span size and flexibility in schizophrenia.

    Science.gov (United States)

    Elahipanah, Ava; Christensen, Bruce K; Reingold, Eyal M

    2011-10-01

    The current study investigated the size and flexible control of visual span among patients with schizophrenia during visual search performance. Visual span is the region of the visual field from which one extracts information during a single eye fixation, and a larger visual span size is linked to more efficient search performance. Therefore, a reduced visual span may explain patients' impaired performance on search tasks. The gaze-contingent moving window paradigm was used to estimate the visual span size of patients and healthy participants while they performed two different search tasks. In addition, changes in visual span size were measured as a function of two manipulations of task difficulty: target-distractor similarity and stimulus familiarity. Patients with schizophrenia searched more slowly across both tasks and conditions. Patients also demonstrated smaller visual span sizes on the easier search condition in each task. Moreover, healthy controls' visual span size increased as target discriminability or distractor familiarity increased. This modulation of visual span size, however, was reduced or not observed among patients. The implications of the present findings, with regard to previously reported visual search deficits, and other functional and structural abnormalities associated with schizophrenia, are discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Pore size engineering applied to the design of separators for nickel-hydrogen cells and batteries

    Science.gov (United States)

    Abbey, K. M.; Britton, D. L.

    1983-01-01

    Pore size engineering in starved alkaline multiplate cells involves adopting techniques to widen the volume tolerance of individual cells. Separators with appropriate pore size distributions and wettability characteristics (capillary pressure considerations) to have wider volume tolerances and an ability to resist dimensional changes in the electrodes were designed. The separators studied for potential use in nickel-hydrogen cells consist of polymeric membranes as well as inorganic microporous mats. In addition to standard measurements, the resistance and distribution of electrolyte as a function of total cell electrolyte content were determined. New composite separators consisting of fibers, particles and/or binders deposited on Zircar cloth were developed in order to engineer the proper capillary pressure characteristics in the separator. These asymmetric separators were prepared from a variety of fibers, particles and binders. Previously announced in STAR as N83-24571

  4. Size-controlled fluorescent nanodiamonds: A facile method of fabrication and color-center counting

    KAUST Repository

    Mahfouz, Remi

    2013-01-01

    We present a facile method for the production of fluorescent diamond nanocrystals (DNCs) of different sizes and efficiently quantify the concentration of emitting defect color centers (DCCs) of each DNC size. We prepared the DNCs by ball-milling commercially available micrometer-sized synthetic (high pressure, high temperature (HPHT)) diamonds and then separated the as-produced DNCs by density gradient ultracentrifugation (DGU) into size-controlled fractions. A protocol to enhance the uniformity of the nitrogen-vacancy (NV) centers in the diamonds was devised by depositing the DNCs as a dense monolayer on amino-silanized silicon substrates and then subjecting the monolayer to He+ beam irradiation. Using a standard confocal setup, we analyzed the average number of NV centers per crystal, and obtained a quantitative relationship between the DNC particle size and the NV number per crystal. This relationship was in good agreement with results from previous studies that used more elaborate setups. Our findings suggest that nanocrystal size separation by DGU may be used to control the number of defects per nanocrystal. The efficient approaches described herein to control and quantify DCCs are valuable to researchers as they explore applications for color centers and new strategies to create them. © 2013 The Royal Society of Chemistry.

  5. Size-controlled fluorescent nanodiamonds: a facile method of fabrication and color-center counting

    Science.gov (United States)

    Mahfouz, Remi; Floyd, Daniel L.; Peng, Wei; Choy, Jennifer T.; Loncar, Marko; Bakr, Osman M.

    2013-11-01

    We present a facile method for the production of fluorescent diamond nanocrystals (DNCs) of different sizes and efficiently quantify the concentration of emitting defect color centers (DCCs) of each DNC size. We prepared the DNCs by ball-milling commercially available micrometer-sized synthetic (high pressure, high temperature (HPHT)) diamonds and then separated the as-produced DNCs by density gradient ultracentrifugation (DGU) into size-controlled fractions. A protocol to enhance the uniformity of the nitrogen-vacancy (NV) centers in the diamonds was devised by depositing the DNCs as a dense monolayer on amino-silanized silicon substrates and then subjecting the monolayer to He+ beam irradiation. Using a standard confocal setup, we analyzed the average number of NV centers per crystal, and obtained a quantitative relationship between the DNC particle size and the NV number per crystal. This relationship was in good agreement with results from previous studies that used more elaborate setups. Our findings suggest that nanocrystal size separation by DGU may be used to control the number of defects per nanocrystal. The efficient approaches described herein to control and quantify DCCs are valuable to researchers as they explore applications for color centers and new strategies to create them.

  6. Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique

    Science.gov (United States)

    Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

    2014-04-01

    Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin-avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin-biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.

  7. Effect of hydroxyapatite particle size, morphology and crystallinity on proliferation of colon cancer HCT116 cells

    Energy Technology Data Exchange (ETDEWEB)

    Dey, Sangeeta; Das, Mitun, E-mail: mitun@cgcri.res.in; Balla, Vamsi Krishna

    2014-06-01

    The aim of the present work is to chemically and physically characterize the synthesized Hydroxyapatite (HAp) micro and nanoparticles and to explore the inhibitory effect of nano-HAps on the in vitro growth of human colon cancerous cells HCT116. HAp powder was synthesized using three different routes to achieve micro and nanosized powders, with different morphologies and crystallinity. The synthesized powders were characterized using X-ray diffraction, FTIR spectroscopy and scanning electron microscope. The results showed that the average crystallite size of HAp powder varies from 11 nm to 177 nm and respective crystallinity of powder found to be in the range of 0.12 and 0.92. The effect of these physico-chemical properties of HAp powders on human colon cancer HCT116 cells inhibition was determined in vitro. It was found that decreasing the HAp powder crystallite size between 11 nm and 22 nm significantly increases the HCT116 cell inhibition. Our results demonstrate that apart from HAp powder size their crystallinity and morphology also play an important role in cellular inhibition of human colon cancer cells. - Highlights: • Chemically synthesized hydroxyapatite micro and nano-particles with different morphologies and crystallinity. • In vitro cell–material interaction showed that hydroxyapatite nano-particles inhibit colon cancer cells. • Human colon cancer cell inhibition also depends on crystallinity and morphology of HAp powder.

  8. Size and dynamics of caveolae studied using nanoparticles in living endothelial cells.

    Science.gov (United States)

    Wang, Zhenjia; Tiruppathi, Chinnaswamy; Minshall, Richard D; Malik, Asrar B

    2009-12-22

    Caveolae are plasma membrane invaginations prominent in all endothelial cells lining blood vessels. Caveolae characteristically bud to form free cytoplasmic vesicles capable of transporting carrier proteins such as albumin through the cell. However, caveolae size distribution and dynamics in living endothelial cells and ability of caveolae to internalize nanoparticles are not well understood. We demonstrate here the design of a dual-color nanoparticle pair to measure noninvasively caveolae size and dynamics. First, we coated nanoparticles with BSA (bovine serum albumin) to address whether albumin promoted their delivery. Albumin has been shown to bind to protein on endothelial cell surface localized in caveolae and activate albumin endocytosis. Imaging of BSA-coated nanoparticles varying from 20 to 100 nm in diameter in endothelial cells demonstrated that caveolae-mediated nanoparticle uptake was dependent on albumin coating of particles. We also showed that caveolae could accommodate up to 100 nm diameter nanoparticles, a size larger than the diameter of typical caveolae, suggesting compliant property of caveolae. Together, our results show the feasibility of tracking multicolored nanoparticles in living endothelial cells and potential usefulness for designing therapeutic nanoparticle cargo to cross the limiting vessel wall endothelial barrier.

  9. Influence of shear stress and size on viability of endothelial cells exposed to gold nanoparticles

    Science.gov (United States)

    Fede, C.; Albertin, Giovanna; Petrelli, L.; De Caro, R.; Fortunati, I.; Weber, V.; Ferrante, Camilla

    2017-09-01

    Screening nanoparticle toxicity directly on cell culture can be a fast and cheap technique. Nevertheless, to obtain results in accordance with those observed in live animals, the conditions in which cells are cultivated should resemble the one encountered in live systems. Microfluidic devices offer the possibility to satisfy this requirement, in particular with endothelial cell lines, because they are capable to reproduce the flowing media and shear stress experienced by these cell lines in vivo. In this work, we exploit a microfluidic device to observe how human umbilical vein endothelial cells (HUVEC) viability changes when subject to a continuous flow of culture medium, in which spherical citrate-stabilized gold nanoparticles of different sizes and at varying doses are investigated. For comparison, the same experiments are also run in multiwells where the cells do not experience the shear stress induced by the flowing medium. We discuss the results considering the influence of mode of exposure and nanoparticle size (24 and 13 nm). We observed that gold nanoparticles show a lower toxicity under flow conditions with respect to static and the HUVEC viability decreases as the nanoparticle surface area per unit volume increases, regardless of size.

  10. Nanotoxicity of silver nanoparticles to red blood cells: size dependent adsorption, uptake, and hemolytic activity.

    Science.gov (United States)

    Chen, Li Qiang; Fang, Li; Ling, Jian; Ding, Cheng Zhi; Kang, Bin; Huang, Cheng Zhi

    2015-03-16

    Silver nanoparticles (AgNPs) are increasingly being used as antimicrobial agents and drug carriers in biomedical fields. However, toxicological information on their effects on red blood cells (RBCs) and the mechanisms involved remain sparse. In this article, we examined the size dependent nanotoxicity of AgNPs using three different characteristic sizes of 15 nm (AgNPs15), 50 nm (AgNPs50), and 100 nm (AgNPs100) against fish RBCs. Optical microscopy and transmission electron microscopy observations showed that AgNPs exhibited a size effect on their adsorption and uptake by RBCs. The middle sized AgNPs50, compared with the smaller or bigger ones, showed the highest level of adsorption and uptake by the RBCs, suggesting an optimal size of ∼50 nm for passive uptake by RBCs. The toxic effects determined based on the hemolysis, membrane injury, lipid peroxidation, and antioxidant enzyme production were fairly size and dose dependent. In particular, the smallest sized AgNPs15 displayed a greater ability to induce hemolysis and membrane damage than AgNPs50 and AgNPs100. Such cytotoxicity induced by AgNPs should be attributed to the direct interaction of the nanoparticle with the RBCs, resulting in the production of oxidative stress, membrane injury, and subsequently hemolysis. Overall, the results suggest that particle size is a critical factor influencing the interaction between AgNPs and the RBCs.

  11. Cell size dependent toxicity thresholds of polycyclic aromatic hydrocarbons to natural and cultured phytoplankton populations

    Energy Technology Data Exchange (ETDEWEB)

    Echeveste, Pedro, E-mail: pedro.echeveste@uib.e [Department of Global Change Research, IMEDEA (CSIC-UIB) Instituto Mediterraneo de Estudios Avanzados, Miquel Marques 21, 07190 Esporles (Spain); Agusti, Susana, E-mail: sagusti@uib.e [Department of Global Change Research, IMEDEA (CSIC-UIB) Instituto Mediterraneo de Estudios Avanzados, Miquel Marques 21, 07190 Esporles (Spain); Dachs, Jordi, E-mail: jdmqam@cid.csic.e [Department of Environmental Chemistry, Institute of Environmental Assessment and Water Studies (IDAEA-CSIC), Jordi Girona Salgado 18, 08034 Barcelona (Spain)

    2010-01-15

    The toxicity of pyrene and phenanthrene to phytoplankton was studied by analyzing the effect on the growth, abundance and cell viability of cultured species and natural communities of the Atlantic Ocean and the Mediterranean Sea. A decrease in cell abundance, and growth rate was observed as concentration of PAHs increased, with catastrophic cell mortality induced at the highest PAH concentration tested. A strong positive linear relationship was observed between the LC50 (the PAH concentration at which cell population will decline by a half), and the species cell volume, for both phenanthrene and pyrene. Natural communities were however significantly more sensitive to PAHs than cultured phytoplankton, as indicated by the lower slope (e.g. 0.23 and 0.65, respectively, for pyrene) of the relationship LC50 vs. cell volume. The results highlight the importance of cell size in determining the phytoplankton sensitivity to PAHs identifying the communities from the oligotrophic ocean to be more vulnerable. - Cell size is the major factor determining phytoplankton sensitivity to PAHs.

  12. A novel layer-structured scaffold with large pore sizes suitable for 3D cell culture prepared by near-field electrospinning.

    Science.gov (United States)

    He, Feng-Li; Li, Da-Wei; He, Jin; Liu, Yang-Yang; Ahmad, Fiaz; Liu, Ya-Li; Deng, Xudong; Ye, Ya-Jing; Yin, Da-Chuan

    2018-05-01

    Electrospinning is a powerful method for preparing porous materials that can be applied as biomedical materials for implantation or tissue engineering or as scaffolds for 3D cell culture experiments. However, this technique is limited in practical applications because the pore size of 3D scaffolds directly prepared by conventional electrospinning is usually less than several tens of micrometres, which may not be suitable for 3D cell culture and tissue growth. To allow for satisfactory 3D cell culture and tissue engineering, the pore size of the scaffold should be controllable according to the requirement of the specific cells to be cultured. Here, we show that layer-structured scaffolds with pore sizes larger than 100μm can be obtained by stacking meshes prepared by direct-writing using the near-field electrospinning (NFES) technique. In the study, we prepared composite scaffolds made of polycaprolactone (PCL) and hydroxyapatite (HAp) via the above-mentioned method and tested the effectiveness of the novel scaffold in cell culture using mouse pre-osteoblast cells (MC3T3-E1). The pore size and the degradability of the PCL/HAp scaffolds were characterized. The results showed that the average pore size of the scaffolds was 167μm, which was controllable based on the required application; the degradation rate was controllable depending on the ratio of PCL to HAp. The biocompatibility of the scaffolds in vitro was studied, and it was found that the scaffolds showed no toxicity and that the cells could effectively attach, proliferate, and differentiate in the 3D skeleton of the scaffolds. Our studies showed that a simple modification of the preparation procedure can lead to a new way to fabricate novel layer-structured 3D scaffolds with controllable structures and pore sizes suitable for practical applications in implantation, tissue engineering and 3D cell culture. Copyright © 2017. Published by Elsevier B.V.

  13. Mercury induces proliferation and reduces cell size in vascular smooth muscle cells through MAPK, oxidative stress and cyclooxygenase-2 pathways

    Energy Technology Data Exchange (ETDEWEB)

    Aguado, Andrea; Galán, María; Zhenyukh, Olha; Wiggers, Giulia A.; Roque, Fernanda R. [Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Instituto de Investigación Hospital Universitario La Paz (IdiPAZ), 28029, Madrid (Spain); Redondo, Santiago [Departamento de Farmacología, Facultad de Medicina, Universidad Complutense, 28040, Madrid (Spain); Peçanha, Franck [Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Instituto de Investigación Hospital Universitario La Paz (IdiPAZ), 28029, Madrid (Spain); Martín, Angela [Departamento de Bioquímica, Fisiología y Genética Molecular, Universidad Rey Juan Carlos, 28922, Alcorcón (Spain); Fortuño, Ana [Área de Ciencias Cardiovasculares, Centro de Investigación Médica Aplicada, Universidad de Navarra, 31008, Pamplona (Spain); Cachofeiro, Victoria [Departamento de Fisiología, Facultad de Medicina, Universidad Complutense, 28040, Madrid (Spain); Tejerina, Teresa [Departamento de Farmacología, Facultad de Medicina, Universidad Complutense, 28040, Madrid (Spain); Salaices, Mercedes, E-mail: mercedes.salaices@uam.es [Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Instituto de Investigación Hospital Universitario La Paz (IdiPAZ), 28029, Madrid (Spain); and others

    2013-04-15

    Mercury exposure is known to increase cardiovascular risk but the underlying cellular mechanisms remain undetermined. We analyzed whether chronic exposure to HgCl{sub 2} affects vascular structure and the functional properties of vascular smooth muscle cells (VSMC) through oxidative stress/cyclooxygenase-2 dependent pathways. Mesenteric resistance arteries and aortas from Wistar rats treated with HgCl{sub 2} (first dose 4.6 mg kg{sup −1}, subsequent doses 0.07 mg kg{sup −1} day{sup −1}, 30 days) and cultured aortic VSMC stimulated with HgCl{sub 2} (0.05–5 μg/ml) were used. Treatment of rats with HgCl{sub 2} decreased wall thickness of the resistance and conductance vasculature, increased the number of SMC within the media and decreased SMC nucleus size. In VSMCs, exposure to HgCl{sub 2}: 1) induced a proliferative response and a reduction in cell size; 2) increased superoxide anion production, NADPH oxidase activity, gene and/or protein levels of the NADPH oxidase subunit NOX-1, the EC- and Mn-superoxide dismutases and cyclooxygenase-2 (COX-2); 3) induced activation of ERK1/2 and p38 MAPK. Both antioxidants and COX-2 inhibitors normalized the proliferative response and the altered cell size induced by HgCl{sub 2}. Blockade of ERK1/2 and p38 signaling pathways abolished the HgCl{sub 2}-induced Nox1 and COX-2 expression and normalized the alterations induced by mercury in cell proliferation and size. In conclusion, long exposure of VSMC to low doses of mercury activates MAPK signaling pathways that result in activation of inflammatory proteins such as NADPH oxidase and COX-2 that in turn induce proliferation of VSMC and changes in cell size. These findings offer further evidence that mercury might be considered an environmental risk factor for cardiovascular disease. - Highlights: ► Chronic HgCl{sub 2} exposure induces vascular remodeling. ► HgCl{sub 2} induces proliferation and decreased cell size in vascular smooth muscle cells. ► HgCl{sub 2} induces

  14. Heterotrophic free-living and particle-bound bacterial cell size in the ...

    Indian Academy of Sciences (India)

    Regression analysis revealed that 18% of the variation in mean heterotrophic free-living bacterial cell size was due to biological oxygen demand (BOD) in the river Arkavathy, 11% due to surface water velocity (SWV) in the river Cauvery and 11% due to temperature in the river Kapila. Heterotrophic particle-bound bacterial ...

  15. Sizing stack and battery of a fuel cell hybrid distribution truck

    NARCIS (Netherlands)

    Bram Veenhuizen; P. van den Bosch; T. Hofman; Edwin Tazelaar; Y. Shen

    2012-01-01

    An existing fuel cell hybrid distribution truck, built for demonstration purposes, is used as a case study to investigate the effect of stack (kW) and battery (kW, kWh) sizes on the hydrogen consumption of the vehicle. Three driving cycles, the NEDC for Low Power vehicles, CSC and JE05 cycle, define

  16. Three-Dimensional Culture Reduces Cell Size By Increasing Vesicle Excretion.

    Science.gov (United States)

    Mo, Miaohua; Zhou, Ying; Li, Sen; Wu, Yaojiong

    2018-02-01

    Our previous study has shown that three-dimensional (3D) culture decreases mesenchymal stem cell (MSC) size, leading to enhanced trafficking ability and reduced lung vascular obstructions. However, the underlying mechanisms are unclear. In this study, we proposed that 3D culture reduces MSC size by increasing vesicle excretion. Scanning electron microscope showed that 3D culture markedly increased the amount of membrane-bound vesicles on the cell surface. In consistence, tunable resistive pulse sensing quantifying analysis of vesicles in the culture medium indicated that there were higher levels of vesicles in the 3D culture MSC medium. 3D culture significantly lowered the level of actin polymerization (F-actin), suggestive of lowering actin skeleton tension may facilitate vesicle excretion. Indeed, treatment of MSCs with Cytochalasin D or functional blockade of integrin β1 caused increased vesicle secretion and decreased cell sizes. Thus, our results suggest that 3D culture reduces MSC size by increasing vesicle excretion which is likely mediated by lowering cytoskeleton tension. Stem Cells 2018;36:286-292. © 2017 AlphaMed Press.

  17. TUNING OF SIZE AND SHAPE OF AU-PT NANOCATALYST FOR DIRECT METHANOL FUEL CELLS

    Energy Technology Data Exchange (ETDEWEB)

    Murph, S.

    2011-04-20

    In this paper, we report the precise control of the size, shape and surface morphology of Au-Pt nanocatalysts (cubes, blocks, octahedrons and dogbones) synthesized via a seed-mediated approach. Gold 'seeds' of different aspect ratios (1 to 4.2), grown by a silver-assisted approach, were used as templates for high-yield production of novel Au-Pt nanocatalysts at a low temperature (40 C). Characterization by electron microscopy (SEM, TEM, HRTEM), energy dispersive X-ray analysis (EDX), UV-Vis spectroscopy, zeta-potential (surface charge), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS) were used to better understand their physico-chemical properties, preferred reactivities and underlying nanoparticle growth mechanism. A rotating disk electrode was used to evaluate the Au-Pt nanocatalysts electrochemical performance in the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) of direct methanol fuel cells. The results indicate the Au-Pt dogbones are partially and in some cases completely unaffected by methanol poisoning during the evaluation of the ORR. The ORR performance of the octahedron particles in the absence of MeOH is superior to that of the Au-Pt dogbones and Pt-black, however its performance is affected by the presence of MeOH.

  18. Small- and Medium-Sized Commercial Building Monitoring and Controls Needs: A Scoping Study

    Energy Technology Data Exchange (ETDEWEB)

    Katipamula, Srinivas; Underhill, Ronald M.; Goddard, James K.; Taasevigen, Danny J.; Piette, M. A.; Granderson, J.; Brown, Rich E.; Lanzisera, Steven M.; Kuruganti, T.

    2012-10-31

    Buildings consume over 40% of the total energy consumption in the U.S. A significant portion of the energy consumed in buildings is wasted because of the lack of controls or the inability to use existing building automation systems (BASs) properly. Much of the waste occurs because of our inability to manage and controls buildings efficiently. Over 90% of the buildings are either small-size (<5,000 sf) or medium-size (between 5,000 sf and 50,000 sf); these buildings currently do not use BASs to monitor and control their building systems from a central location. According to Commercial Building Energy Consumption Survey (CBECS), about 10% of the buildings in the U.S. use BASs or central controls to manage their building system operations. Buildings that use BASs are typically large (>100,000 sf). Lawrence Berkeley National Laboratory (LBNL), Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) were asked by the U.S. Department of Energy’s (DOE’s) Building Technologies Program (BTP) to identify monitoring and control needs for small- and medium-sized commercial buildings and recommend possible solutions. This study documents the needs and solutions for small- and medium-sized buildings.

  19. A concept of an automated function control for ambient aerosol measurements using mobility particle size spectrometers

    Science.gov (United States)

    Schladitz, A.; Merkel, M.; Bastian, S.; Birmili, W.; Weinhold, K.; Löschau, G.; Wiedensohler, A.

    2013-12-01

    An automated function control unit was developed to regularly check the ambient particle number concentration derived from a mobility particle size spectrometer as well as its zero-point behaviour. The aim of the new feature is to conduct unattended quality control experiments under field conditions at remote air quality monitoring or research stations. The automated function control also has the advantage of being able to get a faster system stability response than the recommended on-site comparisons with reference instruments. The method is based on a comparison of the total particle number concentration measured by a mobility particle size spectrometer and a condensation particle counter removing the diffusive particles approximately smaller than 25 nm in diameter. In practice, the small particles are removed by a set of diffusion screens, as traditionally used in a diffusion battery. The other feature of the automated function control is to check the zero-point behaviour of the ambient aerosol passing through a high-efficiency particulate air (HEPA) filter. An exemplary one-year data set is presented for the measurement site Annaberg-Buchholz as part of the Saxon air quality monitoring network. The total particle number concentration derived from the mobility particle size spectrometer overestimates the particle number concentration by only 2% (grand average offset). Furthermore, tolerance criteria are presented to judge the performance of the mobility particle size spectrometer with respect to the particle number concentration. An upgrade of a mobility particle size spectrometer with an automated function control enhances the quality of long-term particle number size distribution measurements. Quality assured measurements are a precondition for intercomparison studies of different sites. Comparable measurements will improve cohort health and also climate-relevant research studies.

  20. Coordination of size-control, reproduction and generational memory in freshwater planarians

    Science.gov (United States)

    Yang, Xingbo; Kaj, Kelson J.; Schwab, David J.; Collins, Eva-Maria S.

    2017-06-01

    Uncovering the mechanisms that control size, growth, and division rates of organisms reproducing through binary division means understanding basic principles of their life cycle. Recent work has focused on how division rates are regulated in bacteria and yeast, but this question has not yet been addressed in more complex, multicellular organisms. We have, over the course of several years, assembled a unique large-scale data set on the growth and asexual reproduction of two freshwater planarian species, Dugesia japonica and Girardia tigrina, which reproduce by transverse fission and succeeding regeneration of head and tail pieces into new planarians. We show that generation-dependent memory effects in planarian reproduction need to be taken into account to accurately capture the experimental data. To achieve this, we developed a new additive model that mixes multiple size control strategies based on planarian size, growth, and time between divisions. Our model quantifies the proportions of each strategy in the mixed dynamics, revealing the ability of the two planarian species to utilize different strategies in a coordinated manner for size control. Additionally, we found that head and tail offspring of both species employ different mechanisms to monitor and trigger their reproduction cycles. Thus, we find a diversity of strategies not only between species but between heads and tails within species. Our additive model provides two advantages over existing 2D models that fit a multivariable splitting rate function to the data for size control: firstly, it can be fit to relatively small data sets and can thus be applied to systems where available data is limited. Secondly, it enables new biological insights because it explicitly shows the contributions of different size control strategies for each offspring type.

  1. Controlled synthesis of graphene sheets with tunable sizes by hydrothermal cutting

    International Nuclear Information System (INIS)

    Ma Chen; Chen Zhongxin; Fang Ming; Lu Hongbin

    2012-01-01

    We report a hydrothermal method that directly reduces graphene oxide (GO) into graphene nanosheets (GNs) with different sizes. In the presence of NaOH and hydrazine, the hydrothermal reaction at 80 °C resulted in the formation of GNs with a lateral size of ∼1 μm but the size of GNs decreased to ∼300 and ∼100 nm upon increasing the reaction temperature to 150 and 200 °C, respectively. The morphology of the resulting GNs was observed by atomic force microscopy and transmission electron microscopy. The thickness of GNs is basically <3 nm, indicates the GNs stack together in a few-layer manner. XRD, XPS, FTIR, and Raman spectroscopy were used to characterize the structural changes before and after reduction. The results suggested that the defect stability in GO and reduced GNs could be responsible for the temperature dependence of the size of reduced GNs.Graphical AbstractA hydrothermal method is proposed to simultaneously reduce and cut graphene oxide into graphene sheets with different sizes in a controlled manner, in which the reaction temperature as a critical parameter is used to control the size of resulting graphene sheets.

  2. Cell lineage branching as a strategy for proliferative control.

    Science.gov (United States)

    Buzi, Gentian; Lander, Arthur D; Khammash, Mustafa

    2015-02-19

    How tissue and organ sizes are specified is one of the great unsolved mysteries in biology. Experiments and mathematical modeling implicate feedback control of cell lineage progression, but a broad understanding of what lineage feedback accomplishes is lacking. By exploring the possible effects of various biologically relevant disturbances on the dynamic and steady state behaviors of stem cell lineages, we find that the simplest and most frequently studied form of lineage feedback - which we term renewal control - suffers from several serious drawbacks. These reflect fundamental performance limits dictated by universal conservation-type laws, and are independent of parameter choice. Here we show that introducing lineage branches can circumvent all such limitations, permitting effective attenuation of a wide range of perturbations. The type of feedback that achieves such performance - which we term fate control - involves promotion of lineage branching at the expense of both renewal and (primary) differentiation. We discuss the evidence that feedback of just this type occurs in vivo, and plays a role in tissue growth control. Regulated lineage branching is an effective strategy for dealing with disturbances in stem cell systems. The existence of this strategy provides a dynamics-based justification for feedback control of cell fate in vivo.

  3. The effect of EIF dynamics on the cryopreservation process of a size distributed cell population.

    Science.gov (United States)

    Fadda, S; Briesen, H; Cincotti, A

    2011-06-01

    Typical mathematical modeling of cryopreservation of cell suspensions assumes a thermodynamic equilibrium between the ice and liquid water in the extracellular solution. This work investigates the validity of this assumption by introducing a population balance approach for dynamic extracellular ice formation (EIF) in the absence of any cryo-protectant agent (CPA). The population balance model reflects nucleation and diffusion-limited growth in the suspending solution whose driving forces are evaluated in the relevant phase diagram. This population balance description of the extracellular compartment has been coupled to a model recently proposed in the literature [Fadda et al., AIChE Journal, 56, 2173-2185, (2010)], which is capable of quantitatively describing and predicting internal ice formation (IIF) inside the cells. The cells are characterized by a size distribution (i.e. through another population balance), thus overcoming the classic view of a population of identically sized cells. From the comparison of the system behavior in terms of the dynamics of the cell size distribution it can be concluded that the assumption of a thermodynamic equilibrium in the extracellular compartment is not always justified. Depending on the cooling rate, the dynamics of EIF needs to be considered. Copyright © 2011 Elsevier Inc. All rights reserved.

  4. Chondrogenesis of adipose stem cells in a porous polymer scaffold: influence of the pore size.

    Science.gov (United States)

    Im, Gun-Ii; Ko, Ji-Yun; Lee, Jin Ho

    2012-01-01

    This study examined how the difference in pore size of porous scaffolds affected the in vitro chondrogenic differentiation of seeded adipose stem cells (ASCs) and the in vivo cartilage repair of ASC/scaffold construct. ASCs were isolated from 18 rabbits and seeded in a porous poly (ε-caprolactone) (PCL) scaffold with different pore sizes (100, 200, 400 μm). The ASCs underwent in vitro chondrogenic induction under TGF-β2 and BMP-7 for 21 days before analysis. The ASC/scaffold construct was also implanted on the osteochondral defect created on the distal femur of the same rabbits, and the quality of cartilage regeneration was analyzed after 8 weeks. At day 21, the ASCs proliferated and spread on the surface of the scaffolds with a pore size 100 and 200 μm, whereas there were many lumps of conglomerated ASCs on those with a pore size of 400 μm. The DNA content was significantly lower in the scaffold with a pore size of 400 μm than in that with a pore size of 100 or 200 μm. Proteoglycan production was significantly greater in the scaffold with a pore size of 400 and 200 μm than in that with a pore size of 100 μm. The chondrogenic marker gene expression including SOX9 and COL2A1 was greatest in the scaffold with a pore size of 400 μm followed by 200 μm. Immunofluorescent imaging showed that, while SOX9 was localized to nucleus, type II collagen was observed on the cytoplasm and secreted matrix around the cells most abundantly in the scaffold with a pore size of 400 μm followed by 200 μm. The gross and histological findings from the osteochondral defects showed that the cartilage repair was better in the scaffold with a pore size of 400 and 200 μm than in that with a pore size of 100 μm.

  5. Covariate adjustments in randomized controlled trials increased study power and reduced biasedness of effect size estimation.

    Science.gov (United States)

    Lee, Paul H

    2016-08-01

    This study aims to show that under several assumptions, in randomized controlled trials (RCTs), unadjusted, crude analysis will underestimate the Cohen's d effect size of the treatment, and an unbiased estimate of effect size can be obtained only by adjusting for all predictors of the outcome. Four simulations were performed to examine the effects of adjustment on the estimated effect size of the treatment and power of the analysis. In addition, we analyzed data from the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study (older adults aged 65-94), an RCT with three treatment arms and one control arm. We showed that (1) the number of unadjusted covariates was associated with the effect size of the treatment; (2) the biasedness of effect size estimation was minimized if all covariates were adjusted for; (3) the power of the statistical analysis slightly decreased with the number of adjusted noise variables; and (4) exhaustively searching the covariates and noise variables adjusted for can lead to exaggeration of the true effect size. Analysis of the ACTIVE study data showed that the effect sizes adjusting for covariates of all three treatments were 7.39-24.70% larger than their unadjusted counterparts, whereas the effect size would be elevated by at most 57.92% by exhaustively searching the variables adjusted for. All covariates of the outcome in RCTs should be adjusted for, and if the effect of a particular variable on the outcome is unknown, adjustment will do more good than harm. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Exposure to nano-size titanium dioxide causes oxidative damages in human mesothelial cells: The crystal form rather than size of particle contributes to cytotoxicity.

    Science.gov (United States)

    Hattori, Kenji; Nakadate, Kazuhiko; Morii, Akane; Noguchi, Takumi; Ogasawara, Yuki; Ishii, Kazuyuki

    2017-10-14

    Exposure to nanoparticles such as carbon nanotubes has been shown to cause pleural mesothelioma similar to that caused by asbestos, and has become an environmental health issue. Not only is the percutaneous absorption of nano-size titanium dioxide particles frequently considered problematic, but the possibility of absorption into the body through the pulmonary route is also a concern. Nevertheless, there are few reports of nano-size titanium dioxide particles on respiratory organ exposure and dynamics or on the mechanism of toxicity. In this study, we focused on the morphology as well as the size of titanium dioxide particles. In comparing the effects between nano-size anatase and rutile titanium dioxide on human-derived pleural mesothelial cells, the anatase form was shown to be actively absorbed into cells, producing reactive oxygen species and causing oxidative damage to DNA. In contrast, we showed for the first time that the rutile form is not easily absorbed by cells and, therefore, does not cause oxidative DNA damage and is significantly less damaging to cells. These results suggest that with respect to the toxicity of titanium dioxide particles on human-derived mesothelial cells, the crystal form rather than the particle size has a greater effect on cellular absorption. Also, it was indicated that the difference in absorption is the primary cause of the difference in the toxicity against mesothelial cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Myosin Vb mediated plasma membrane homeostasis regulates peridermal cell size and maintains tissue homeostasis in the zebrafish epidermis.

    Science.gov (United States)

    Sonal; Sidhaye, Jaydeep; Phatak, Mandar; Banerjee, Shamik; Mulay, Aditya; Deshpande, Ojas; Bhide, Sourabh; Jacob, Tressa; Gehring, Ines; Nuesslein-Volhard, Christiane; Sonawane, Mahendra

    2014-09-01

    The epidermis is a stratified epithelium, which forms a barrier to maintain the internal milieu in metazoans. Being the outermost tissue, growth of the epidermis has to be strictly coordinated with the growth of the embryo. The key parameters that determine tissue growth are cell number and cell size. So far, it has remained unclear how the size of epidermal cells is maintained and whether it contributes towards epidermal homeostasis. We have used genetic analysis in combination with cellular imaging to show that zebrafish goosepimples/myosin Vb regulates plasma membrane homeostasis and is involved in maintenance of cell size in the periderm, the outermost epidermal layer. The decrease in peridermal cell size in Myosin Vb deficient embryos is compensated by an increase in cell number whereas decrease in cell number results in the expansion of peridermal cells, which requires myosin Vb (myoVb) function. Inhibition of cell proliferation as well as cell size expansion results in increased lethality in larval stages suggesting that this two-way compensatory mechanism is essential for growing larvae. Our analyses unravel the importance of Myosin Vb dependent cell size regulation in epidermal homeostasis and demonstrate that the epidermis has the ability to maintain a dynamic balance between cell size and cell number.

  8. Hyperplasia of smooth muscle in mild to moderate asthma without changes in cell size or gene expression.

    Science.gov (United States)

    Woodruff, Prescott G; Dolganov, Gregory M; Ferrando, Ronald E; Donnelly, Samantha; Hays, Steven R; Solberg, Owen D; Carter, Roderick; Wong, Hofer H; Cadbury, Peggy S; Fahy, John V

    2004-05-01

    Bronchial hyperresponsiveness in mild to moderate asthma may result from airway smooth muscle cell proliferation or acquisition of a hypercontractile phenotype. Because these cells have not been well characterized in mild to moderate asthma, we examined the morphometric and gene expression characteristics of smooth muscle cells in this subgroup of patients with asthma. Using bronchial biopsies from 14 subjects with mild to moderate asthma and 15 control subjects, we quantified smooth muscle cell morphology by stereology and the expression of a panel of genes related to a hypercontractile phenotype of airway smooth muscle, using laser microdissection and two-step real-time polymerase chain reaction. We found that airway smooth muscle cell size was similar in both groups, but cell number was nearly twofold higher in subjects with asthma (p = 0.03), and the amount of smooth muscle in the submucosa was increased 50-83% (p 0.1). We conclude that airway smooth muscle proliferation is a pathologic characteristic of subjects with mild to moderate asthma. However, smooth muscle cells in mild to moderate asthma do not show hypertrophy or gene expression changes of a hypercontractile phenotype observed in vitro.

  9. Controlled shutdown of a fuel cell

    Science.gov (United States)

    Clingerman, Bruce J.; Keskula, Donald H.

    2002-01-01

    A method is provided for the shutdown of a fuel cell system to relieve system overpressure while maintaining air compressor operation, and corresponding vent valving and control arrangement. The method and venting arrangement are employed in a fuel cell system, for instance a vehicle propulsion system, comprising, in fluid communication, an air compressor having an outlet for providing air to the system, a combustor operative to provide combustor exhaust to the fuel processor.

  10. Multiple crown size variables of the upper incisors in patients with supernumerary teeth compared with controls

    NARCIS (Netherlands)

    Khalaf, K.; Smith, R. N.; Elcock, C.; Brook, A. H.

    2009-01-01

    Aims: As part of ongoing studies of the aetiology of dental anomalies the aims of this study were to identify multiple components of tooth size of the upper permanent incisors in 34 patients with supernumerary teeth and to compare them with those in a control group to determine whether the presence

  11. One-pot size and shape controlled synthesis of DMSO capped iron ...

    Indian Academy of Sciences (India)

    Abstract. We report here the capping of iron oxide nanoparticles with dimethyl sulfoxide (DMSO) to make chloroform soluble iron oxide nanoparticles. Size and shape of the capped iron oxide nanoparticles are well controlled by simply varying the reaction parameters. The synthesized nanocrystallites were characterized by.

  12. Structural and magnetic properties of size-controlled Mn 0.5 Zn 0.5 ...

    Indian Academy of Sciences (India)

    Mn0.5Zn0.5Fe2O4 ferrite nanoparticles with tunable Curie temperature and saturation magnetization are synthesized using hydrothermal co-precipitation method. Particle size is controlled in the range of 54 to 135 Å by pH and incubation time of the reaction. All the particles exhibit super-paramagnetic behaviour at room ...

  13. Gold nanoparticle size and shape influence on osteogenesis of mesenchymal stem cells

    Science.gov (United States)

    Li, Jingchao; Li, Jia'en Jasmine; Zhang, Jing; Wang, Xinlong; Kawazoe, Naoki; Chen, Guoping

    2016-04-01

    Gold nanoparticles (AuNPs) have been extensively explored for biomedical applications due to their advantages of facile synthesis and surface functionalization. Previous studies have suggested that AuNPs can induce differentiation of stem cells into osteoblasts. However, how the size and shape of AuNPs affect the differentiation response of stem cells has not been elucidated. In this work, a series of bovine serum albumin (BSA)-coated Au nanospheres, Au nanostars and Au nanorods with different diameters of 40, 70 and 110 nm were synthesized and their effects on osteogenic differentiation of human mesenchymal stem cells (hMSCs) were investigated. All the AuNPs showed good cytocompatibility and did not influence proliferation of hMSCs at the studied concentrations. Osteogenic differentiation of hMSCs was dependent on the size and shape of AuNPs. Sphere-40, sphere-70 and rod-70 significantly increased the alkaline phosphatase (ALP) activity and calcium deposition of cells while rod-40 reduced the ALP activity and calcium deposition. Gene profiling revealed that the expression of osteogenic marker genes was down-regulated after incubation with rod-40. However, up-regulation of these genes was found in the sphere-40, sphere-70 and rod-70 treatment. Moreover, it was found that the size and shape of AuNPs affected the osteogenic differentiation of hMSCs through regulating the activation of Yes-associated protein (YAP). These results indicate that the size and shape of AuNPs had an influence on the osteogenic differentiation of hMSCs, which should provide useful guidance for the preparation of AuNPs with defined size and shape for their biomedical applications.Gold nanoparticles (AuNPs) have been extensively explored for biomedical applications due to their advantages of facile synthesis and surface functionalization. Previous studies have suggested that AuNPs can induce differentiation of stem cells into osteoblasts. However, how the size and shape of AuNPs affect the

  14. Particle Size Affects Concentration-Dependent Cytotoxicity of Chitosan Nanoparticles towards Mouse Hematopoietic Stem Cells

    Directory of Open Access Journals (Sweden)

    Siti Sarah Omar Zaki

    2015-01-01

    Full Text Available Chitosan nanoparticles (CSNPs have been extensively applied in medical and pharmaceutical fields as promising drug delivery systems. Despite that, the safety of CSNPs remains inadequate and needs further investigation, particularly on hematopoietic stem cells (HSCs. CSNPs were prepared by ionic gelation method and later were characterized for their physical characteristics (particle size and zeta potential. Cytotoxicity of CSNPs was assessed by MTT assay. Particle size was highly influenced by chitosan concentration and molecular weight (medium and high molecular weight (MMW and HMW. Higher chitosan concentration and molecular weight produced larger nanoparticles. Zeta potential of CSNPs was not significantly affected by chitosan concentrations and molecular weights used in the present study. MMW had a better stability than HMW CSNPs as their particle size and zeta potential were not significantly altered after autoclaving. Cytotoxicity of CSNPs was influenced by zeta potential and particle size. On the other hand, chitosan concentration and molecular weight indirectly influenced cytotoxicity by affecting particle size and zeta potential of CSNPs. In conclusion, cytotoxicity of CSNPs was mainly attributed to their physical characteristics and this opens a strategy to ensure the safety of CSNPs applications in stem cell technology.

  15. Particle Size Affects Concentration-Dependent Cytotoxicity of Chitosan Nanoparticles towards Mouse Hematopoietic Stem Cells

    International Nuclear Information System (INIS)

    Zaki, S. S. O.; Ibrahim, M. N.; Katas, H.

    2015-01-01

    Chitosan nanoparticles (CSNPs) have been extensively applied in medical and pharmaceutical fields as promising drug delivery systems. Despite that, the safety of CSNPs remains inadequate and needs further investigation, particularly on hematopoietic stem cells (HSCs). CSNPs were prepared by ionic gelation method and later were characterized for their physical characteristics (particle size and zeta potential). Cytotoxicity of CSNPs was assessed by MTT assay. Particle size was highly influenced by chitosan concentration and molecular weight (medium and high molecular weight (MMW and HMW)). Higher chitosan concentration and molecular weight produced larger nanoparticles. Zeta potential of CSNPs was not significantly affected by chitosan concentrations and molecular weights used in the present study. MMW had a better stability than HMW CSNPs as their particle size and zeta potential were not significantly altered after autoclaving. Cytotoxicity of CSNPs was influenced by zeta potential and particle size. On the other hand, chitosan concentration and molecular weight indirectly influenced cytotoxicity by affecting particle size and zeta potential of CSNPs. In conclusion, cytotoxicity of CSNPs was mainly attributed to their physical characteristics and this opens a strategy to ensure the safety of CSNPs applications in stem cell technology.

  16. Development of gelatin-chitosan-hydroxyapatite based bioactive bone scaffold with controlled pore size and mechanical strength.

    Science.gov (United States)

    Maji, Kanchan; Dasgupta, Sudip; Kundu, Biswanath; Bissoyi, Akalabya

    2015-01-01

    Hydroxyapatite-chitosan/gelatin (HA:Chi:Gel) nanocomposite scaffold has potential to serve as a template matrix to regenerate extra cellular matrix of human bone. Scaffolds with varying composition of hydroxyapatite, chitosan, and gelatin were prepared using lyophilization technique where glutaraldehyde (GTA) acted as a cross-linking agent for biopolymers. First, phase pure hydroxyapatite-chitosan nanocrystals were in situ synthesized by coprecipitation method using a solution of 2% acetic acid dissolved chitosan and aqueous solution of calcium nitrate tetrahydrate [Ca(NO3)2,4H2O] and diammonium hydrogen phosphate [(NH4)2H PO4]. Keeping solid loading constant at 30 wt% and changing the composition of the original slurry of gelatin, HA-chitosan allowed control of the pore size, its distribution, and mechanical properties of the scaffolds. Microstructural investigation by scanning electron microscopy revealed the formation of a well interconnected porous scaffold with a pore size in the range of 35-150 μm. The HA granules were uniformly dispersed in the gelatin-chitosan network. An optimal composition in terms of pore size and mechanical properties was obtained from the scaffold with an HA:Chi:Gel ratio of 21:49:30. The composite scaffold having 70% porosity with pore size distribution of 35-150 μm exhibited a compressive strength of 3.3-3.5 MPa, which is within the range of that exhibited by cancellous bone. The bioactivity of the scaffold was evaluated after conducting mesenchymal stem cell (MSC) - materials interaction and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay using MSCs. The scaffold found to be conducive to MSC's adhesion as evident from lamellipodia, filopodia extensions from cell cytoskeleton, proliferation, and differentiation up to 14 days of cell culture.

  17. Size-dependence of volatile and semi-volatile organic carbon content in phytoplankton cells

    Directory of Open Access Journals (Sweden)

    Sergio eRuiz-Halpern

    2014-07-01

    Full Text Available The content of volatile and semivolatile organic compounds (VOC and SOC, measured as exchangeable dissolved organic carbon (EDOC, was quantified in 9 phytoplanktonic species that spanned 4 orders of magnitude in cell volume, by disrupting the cells and quantifying the gaseous organic carbon released. EDOC content varied 4 orders of magnitude, from 0.0015 to 14.12 pg C cell-1 in the species studied and increased linearly with increasing phytoplankton cell volume following the equation EDOC (pg C cell-1 = -2.35 x cellular volume (CV, µm3 cell-1 0.90 (± 0.3, with a slope (0.90 not different from 1 indicating a constant increase in volatile carbon as the cell size of phytoplankton increased. The percentage of EDOC relative to total cellular carbon was small but varied 20 fold from 0.28 % to 5.17 %, and no obvious taxonomic pattern in the content of EDOC was appreciable for the species tested. The cell release rate of EDOC is small compared to the amount of carbon in the cell and difficult to capture. Nonetheless, the results point to a potential flux of volatile and semivolatile phytoplankton-derived organic carbon to the atmosphere that has been largely underestimated and deserves further attention in the future.

  18. Gas-phase laser synthesis of aggregation-free, size-controlled hydroxyapatite nanoparticles

    International Nuclear Information System (INIS)

    Bapat, Parimal V.; Kraft, Rebecca; Camata, Renato P.

    2012-01-01

    Nanophase hydroxyapatite (HA) is finding applications in many areas of biomedical research, including bone tissue engineering, drug delivery, and intracellular imaging. Details in chemical composition, crystal phase makeup, size, and shape of HA nanoparticles play important roles in achieving the favorable biological responses required in these applications. Most of the nanophase HA synthesis techniques involve solution-based methods that exhibit substantial aggregation of particles upon precipitation. Typically these methods also have limited control over the particle size and crystal phase composition. In this study, we describe the gas-phase synthesis of aggregation-free, size-controlled HA nanoparticles with mean size in the 20–70 nm range using laser ablation followed by aerosol electrical mobility classification. Nanoparticle deposits with adjustable number concentration were obtained on solid substrates. Particles were characterized by transmission electron microscopy, atomic force microscopy, and X-ray diffraction. Samples are well represented by log-normal size distributions with geometric standard deviation σ g ≈ 1.2. The most suitable conditions for HA nanoparticle formation at a laser fluence of 5 J/cm 2 were found to be a temperature of 800 °C and a partial pressure of water of 160 mbar.

  19. Body size estimation in women with anorexia nervosa and healthy controls using 3D avatars.

    Science.gov (United States)

    Cornelissen, Katri K; McCarty, Kristofor; Cornelissen, Piers L; Tovée, Martin J

    2017-11-17

    A core feature of anorexia nervosa is an over-estimation of body size. However, quantifying this over-estimation has been problematic as existing methodologies introduce a series of artefacts and inaccuracies in the stimuli used for judgements of body size. To overcome these problems, we have: (i) taken 3D scans of 15 women who have symptoms of anorexia (referred to henceforth as anorexia spectrum disorders, ANSD) and 15 healthy control women, (ii) used a 3D modelling package to build avatars from the scans, (iii) manipulated the body shapes of these avatars to reflect biometrically accurate, continuous changes in body mass index (BMI), (iv) used these personalized avatars as stimuli to allow the women to estimate their body size. The results show that women who are currently receiving treatment for ANSD show an over-estimation of body size which rapidly increases as their own BMI increases. By contrast, the women acting as healthy controls can accurately estimate their body size irrespective of their own BMI. This study demonstrates the viability of combining 3D scanning and CGI techniques to create personalised realistic avatars of individual patients to directly assess their body image perception.

  20. Particle Size-Dependent Antibacterial Activity and Murine Cell Cytotoxicity Induced by Graphene Oxide Nanomaterials

    Directory of Open Access Journals (Sweden)

    Lin Zhao

    2016-01-01

    Full Text Available Recent studies have indicated that graphene and its derivative graphene oxide (GO engage in a wide range of antibacterial activities with limited toxicity to human cells. Here, we systematically evaluate the dependence of GO toxicity on the size of the nanoparticles used in treatments: we compare the cytotoxic effects of graphene quantum dots (GQDs, <15 nm, small GOs (SGOs, 50–200 nm, and large GOs (LGOs, 0.5–3 μm. We synthesize the results of bacterial colony count assays and SEM-based observations of morphological changes to assess the antibacterial properties that these GOs bring into effect against E. coli. We also use Live/Dead assays and morphological analysis to investigate changes to mammalian (Murine macrophage-like Raw 264.7 cells induced by the presence of the various GO particle types. Our results demonstrate that LGOs, SGOs, and GQDs possess antibacterial activities and cause mammalian cell cytotoxicity at descending levels of potency. Placing our observations in the context of previous simulation results, we suggest that both the lateral size and surface area of GO particles contribute to cytotoxic effects. We hope that the size dependence elucidated here provides a useful schematic for tuning GO-cell interactions in biomedical applications.

  1. Parallel nanogap fabrication with nanometer size control using III-V semiconductor epitaxial technology

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-MartInez, Ivan; Gonzalez, Yolanda; Briones, Fernando [Instituto de Microelectronica de Madrid (CNM-CSIC), Isaac Newton 8 PTM, E-28760 Tres Cantos, Madrid (Spain)], E-mail: ivan@imm.cnm.csic.es

    2008-07-09

    A nanogap fabrication process using strained epitaxial III-V beams is reported. The process is highly reproducible, allowing parallel fabrication and nanogap size control. The beams are fabricated from MBE-grown (GaAs/GaP)/AlGaAs strained heterostructures, standard e-beam lithography and wet etching. During the wet etching process, the relaxation of the accumulated stress at the epitaxial heterostructure produces a controlled beam breakage at the previously defined beam notch. After the breakage, the relaxed strain is proportional to the beam length, allowing nanogap size control. The starting structure is similar to a mechanically adjustable break junction but the stress causing the breakage is, in this case, built into the beam. This novel technique should be useful for molecular-scale electronic devices.

  2. Elevator Sizing, Placement, and Control-Relevant Tradeoffs for Hypersonic Vehicles

    Science.gov (United States)

    Dickeson, Jeffrey J.; Rodriguez, Armando A.; Sridharan, Srikanth; Korad, Akshay

    2010-01-01

    Within this paper, control-relevant vehicle design concepts are examined using a widely used 3 DOF (plus flexibility) nonlinear model for the longitudinal dynamics of a generic carrot-shaped scramjet powered hypersonic vehicle. The impact of elevator size and placement on control-relevant static properties (e.g. level-flight trimmable region, trim controls, Angle of Attack (AOA), thrust margin) and dynamic properties (e.g. instability and right half plane zero associated with flight path angle) are examined. Elevator usage has been examine for a class of typical hypersonic trajectories.

  3. Syringe and Needle Size, Syringe Type, Vacuum Generation, and Needle Control in Aspiration Procedures

    International Nuclear Information System (INIS)

    Haseler, Luke J.; Sibbitt, Randy R.; Sibbitt, Wilmer L.; Michael, Adrian A.; Gasparovic, Charles M.; Bankhurst, Arthur D.

    2011-01-01

    Purpose: Syringes are used for diagnostic fluid aspiration and fine-needle aspiration biopsy in interventional procedures. We determined the benefits, disadvantages, and patient safety implications of syringe and needle size on vacuum generation, hand force requirements, biopsy/fluid yield, and needle control during aspiration procedures. Materials and Methods: Different sizes (1, 3, 5, 10, and 20 ml) of the conventional syringe and aspirating mechanical safety syringe, the reciprocating procedure device, were studied. Twenty operators performed aspiration procedures with the following outcomes measured: (1) vacuum (torr), (2) time to vacuum (s), (3) hand force to generate vacuum (torr-cm 2 ), (4) operator difficulty during aspiration, (5) biopsy yield (mg), and (6) operator control of the needle tip position (mm). Results: Vacuum increased tissue biopsy yield at all needle diameters (P < 0.002). Twenty-milliliter syringes achieved a vacuum of −517 torr but required far more strength to aspirate, and resulted in significant loss of needle control (P < 0.002). The 10-ml syringe generated only 15% less vacuum (−435 torr) than the 20-ml device and required much less hand strength. The mechanical syringe generated identical vacuum at all syringe sizes with less hand force (P < 0.002) and provided significantly enhanced needle control (P < 0.002). Conclusions: To optimize patient safety and control of the needle, and to maximize fluid and tissue yield during aspiration procedures, a two-handed technique and the smallest syringe size adequate for the procedure should be used. If precise needle control or one-handed operation is required, a mechanical safety syringe should be considered.

  4. Cell cycle control by a minimal Cdk network.

    Directory of Open Access Journals (Sweden)

    Claude Gérard

    2015-02-01

    Full Text Available In present-day eukaryotes, the cell division cycle is controlled by a complex network of interacting proteins, including members of the cyclin and cyclin-dependent protein kinase (Cdk families, and the Anaphase Promoting Complex (APC. Successful progression through the cell cycle depends on precise, temporally ordered regulation of the functions of these proteins. In light of this complexity, it is surprising that in fission yeast, a minimal Cdk network consisting of a single cyclin-Cdk fusion protein can control DNA synthesis and mitosis in a manner that is indistinguishable from wild type. To improve our understanding of the cell cycle regulatory network, we built and analysed a mathematical model of the molecular interactions controlling the G1/S and G2/M transitions in these minimal cells. The model accounts for all observed properties of yeast strains operating with the fusion protein. Importantly, coupling the model's predictions with experimental analysis of alternative minimal cells, we uncover an explanation for the unexpected fact that elimination of inhibitory phosphorylation of Cdk is benign in these strains while it strongly affects normal cells. Furthermore, in the strain without inhibitory phosphorylation of the fusion protein, the distribution of cell size at division is unusually broad, an observation that is accounted for by stochastic simulations of the model. Our approach provides novel insights into the organization and quantitative regulation of wild type cell cycle progression. In particular, it leads us to propose a new mechanistic model for the phenomenon of mitotic catastrophe, relying on a combination of unregulated, multi-cyclin-dependent Cdk activities.

  5. Noisy-threshold control of cell death

    Directory of Open Access Journals (Sweden)

    Vilar Jose MG

    2010-11-01

    Full Text Available Abstract Background Cellular responses to death-promoting stimuli typically proceed through a differentiated multistage process, involving a lag phase, extensive death, and potential adaptation. Deregulation of this chain of events is at the root of many diseases. Improper adaptation is particularly important because it allows cell sub-populations to survive even in the continuous presence of death conditions, which results, among others, in the eventual failure of many targeted anticancer therapies. Results Here, I show that these typical responses arise naturally from the interplay of intracellular variability with a threshold-based control mechanism that detects cellular changes in addition to just the cellular state itself. Implementation of this mechanism in a quantitative model for T-cell apoptosis, a prototypical example of programmed cell death, captures with exceptional accuracy experimental observations for different expression levels of the oncogene Bcl-xL and directly links adaptation with noise in an ATP threshold below which cells die. Conclusions These results indicate that oncogenes like Bcl-xL, besides regulating absolute death values, can have a novel role as active controllers of cell-cell variability and the extent of adaptation.

  6. Evaluation of growth, cell size and biomass of Isochrysis aff. galbana (T-ISO with two LED regimes

    Directory of Open Access Journals (Sweden)

    Miguel Victor Cordoba-Matson

    2013-04-01

    Full Text Available In contrast to crops, there are fewer studies using LED-based light with green microalgae and none cultivating the microalga Isochrysis aff. galbana (T-ISO even though of its importance in marine aquaculture. The objective was to evaluate of white and red LEDs as an alternative source of light to cultivate I. aff. galbana (T-ISO. In order to carry this out white and red LEDs were used with a laboratory built Erlenmeyer-type photobioreactor to determine productivity, cell number and size and biomass composition. Results were compared with standard fluorescent lights of the same light intensity. The culture system consisted of 3 flasks for applying red LEDs and three for white LEDs and 3 control group flasks illuminated with the normal fluorescent lighting at the similar light intensity of ~60 mM m–2 s–1. It was found that the population cell density did not significantly increase with either red LEDs or white LEDs (p > 0.05, if at all. Standard fluorescent lighting (control group showed significant increases in population cell number (p < 0.05. Through microscopic observation cell size was found to be smaller for white LEDS and even smaller for red LEDs compared to fluorescent lighting. Biochemical composition of proteins, carbohydrates and lipids was similar for all light regimes. The authors suggest that the unexpected non-growth I. aff. galbana (T-ISO, a haptophyte microalga, with white and red LEDs is possibly due to fact that to initiate cell growth this microalgae requires other wavelengths (possibly green besides red and blue, to allow other pigments, probably fucoxanthin, to capture light

  7. Tracking T-cells in vivo with a new nano-sized MRI contrast agent.

    Science.gov (United States)

    Liu, Li; Ye, Qing; Wu, Yijen; Hsieh, Wen-Yuan; Chen, Chih-Lung; Shen, Hsin-Hsin; Wang, Shian-Jy; Zhang, Haosen; Hitchens, T Kevin; Ho, Chien

    2012-11-01

    Non-invasive in vivo tracking of T-cells by magnetic resonance imaging (MRI) can lead to a better understanding of many pathophysiological situations, including AIDS, cancer, diabetes, graft rejection. However, an efficient MRI contrast agent and a reliable technique to track non-phagocytic T-cells are needed. We report a novel superparamagnetic nano-sized iron-oxide particle, IOPC-NH2 series particles, coated with polyethylene glycol (PEG), with high transverse relaxivity (250 s(-1) mM(-1)), thus useful for MRI studies. IOPC-NH2 particles are the first reported magnetic particles that can label rat and human T-cells with over 90% efficiency, without using transfection agents, HIV-1 transactivator peptide, or electroporation. IOPC-NH2 particles do not cause any measurable effects on T-cell properties. Infiltration of IOPC-NH2-labeled T-cells can be detected in a rat model of heart-lung transplantation by in vivo MRI. IOPC-NH2 is potentially valuable contrast agents for labeling a variety of cells for basic and clinical cellular MRI studies, e.g., cellular therapy. In this study, a novel PEG coated superparamagnetic nano-sized iron-oxide particle was investigated as a T-cell labeling agent for MRI studies. The reported particles can label T-cells with over 90% efficiency, without using transfection agents, HIV-1 transactivator peptide, or electroporation, therefore may enable more convenient preclinical call labeling studies. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Size-dependent isolation of primordial germ cells from avian species.

    Science.gov (United States)

    Jung, Kyung M; Kim, Young M; Ono, Tamao; Han, Jae Y

    2017-06-01

    Primordial germ cells (PGCs), the precursors of sperm or ova, could be used to generate transgenic animals and interspecies germ-line chimeras, which would facilitate the recovery of endangered species by making their access and manipulation in vitro easier. During early embryogenesis in avian species, PGCs are transported via the bloodstream to the gonadal anlagen. PGCs of most avian species-particularly wild or endangered birds-are not readily isolated from the embryonic bloodstream because germ-cell markers have not yet been defined for them. Here, we report a rapid, efficient, and convenient method for PGC isolation from various avian species. Blood PGCs were isolated based on the difference in size between PGCs and other blood cells, using a microporous membrane. The efficiency of this size-dependent isolation for the White Leghorn chicken was not significantly different from that of magnetic-activated cell sorting, and the isolated cells expressed chicken PGC-related genes and PGC-specific markers. The utility of the method was then verified in Japanese quail (Coturnix japonica), Mallard duck (Anas platyrhynchos), and Muscovy duck (Cairina moschata). Immunocytochemistry and an in vivo migration assay indicated that this method was able to enrich for true embryonic blood PGCs without specific antibodies, and could be applied to the development of avian interspecies chimeras for restoration of wild or endangered species. © 2017 Wiley Periodicals, Inc.

  9. Exact, time-independent estimation of clone size distributions in normal and mutated cells.

    Science.gov (United States)

    Roshan, A; Jones, P H; Greenman, C D

    2014-10-06

    Biological tools such as genetic lineage tracing, three-dimensional confocal microscopy and next-generation DNA sequencing are providing new ways to quantify the distribution of clones of normal and mutated cells. Understanding population-wide clone size distributions in vivo is complicated by multiple cell types within observed tissues, and overlapping birth and death processes. This has led to the increased need for mathematically informed models to understand their biological significance. Standard approaches usually require knowledge of clonal age. We show that modelling on clone size independent of time is an alternative method that offers certain analytical advantages; it can help parametrize these models, and obtain distributions for counts of mutated or proliferating cells, for example. When applied to a general birth-death process common in epithelial progenitors, this takes the form of a gambler's ruin problem, the solution of which relates to counting Motzkin lattice paths. Applying this approach to mutational processes, alternative, exact, formulations of classic Luria-Delbrück-type problems emerge. This approach can be extended beyond neutral models of mutant clonal evolution. Applications of these approaches are twofold. First, we resolve the probability of progenitor cells generating proliferating or differentiating progeny in clonal lineage tracing experiments in vivo or cell culture assays where clone age is not known. Second, we model mutation frequency distributions that deep sequencing of subclonal samples produce.

  10. Driving an Industry: Medium and Heavy Duty Fuel Cell Electric Truck Component Sizing

    Energy Technology Data Exchange (ETDEWEB)

    Kast, James; Marcinkoski, Jason; Vijayagopal, Ram; Duran, Adam

    2016-06-22

    Medium and heavy duty (MD and HD respectively) vehicles are responsible for 26 percent of the total U.S. transportation petroleum consumption [1]. Hydrogen fuel cells have demonstrated value as part of a portfolio of strategies for reducing petroleum use and emissions from MD and HD vehicles. [2] [3], but their performance and range capabilities, and associated component sizing remain less clear when compared to other powertrains. This paper examines the suitability of converting a representative sample of MD and HD diesel trucks into Fuel Cell Electric Trucks (FCETs), while ensuring the same truck performance, in terms of range, payload, acceleration, speed, gradeability and fuel economy.

  11. Optical Flow Cell for Measuring Size, Velocity and Composition of Flowing Droplets

    Directory of Open Access Journals (Sweden)

    Sammer-ul Hassan

    2017-02-01

    Full Text Available Here an optical flow cell with two light paths is reported that can accurately quantify the size and velocity of droplets flowing through a microchannel. The flow cell can measure the time taken for droplets to pass between and through two conjoined light paths, and thereby is capable of measuring the velocities (0.2–5.45 mm/s and sizes of droplets (length > 0.8 mm. The composition of the droplet can also be accurately quantified via optical absorption measurements. The device has a small footprint and uses low-powered, low-cost components, which make it ideally suited for use in field-deployable and portable analytical devices.

  12. Flow perfusion culture of human mesenchymal stem cells on coralline hydroxyapatite scaffolds with various pore sizes

    DEFF Research Database (Denmark)

    Bjerre, Lea; Bünger, Cody; Baatrup, Anette

    2011-01-01

    Bone grafts are widely used in orthopaedic reconstructive surgery, but harvesting of autologous grafts is limited due to donor site complications. Bone tissue engineering is a possible alternative source for substitutes, and to date, mainly small scaffold sizes have been evaluated. The aim...... of this study was to obtain a clinically relevant substitute size using a direct perfusion culture system. Human bone marrowderived mesenchymal stem cells were seeded on coralline hydroxyapatite scaffolds with 200 μm or 500 μm pores, and resulting constructs were cultured in a perfusion bioreactor or in static...... number of cells was higher in 500 μm constructs as compared with 200 μm constructs. Alkaline phosphatase enzyme activity assays and real time RT-PCR on seven osteogenic markers showed that differentiation occurred primarily and earlier in statically cultured constructs with 200 μm pores compared with 500...

  13. Allometry and size control: what can studies of body size regulation teach us about the evolution of morphological scaling relationships?

    Science.gov (United States)

    Mirth, Christen K; Anthony Frankino, W; Shingleton, Alexander W

    2016-02-01

    The relationship between organ and body size, known as morphological allometry, has fascinated biologists for over a century because changes in allometry generate the vast diversity of organism shapes. Nevertheless, progress has been limited in understanding the genetic mechanisms that regulate allometries and how these mechanisms evolve. This is perhaps because allometry is measured at the population level, however adult organ and body size depends on genetic background and the developmental environment of individuals. Recent findings have enhanced our understanding of how insects regulate their organ and body sizes in response to environmental conditions, particularly nutritional availability. We argue that merging these developmental insights with a population genetics approach will provide a powerful system for understanding the evolution of allometry. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. Sexual Functioning and Behavior of Men with Body Dysmorphic Disorder Concerning Penis Size Compared with Men Anxious about Penis Size and with Controls: A Cohort Study

    Science.gov (United States)

    Veale, David; Miles, Sarah; Read, Julie; Troglia, Andrea; Wylie, Kevan; Muir, Gordon

    2015-01-01

    Introduction Little is known about the sexual functioning and behavior of men anxious about the size of their penis and the means that they might use to try to alter the size of their penis. Aim To compare sexual functioning and behavior in men with body dysmorphic disorder (BDD) concerning penis size and in men with small penis anxiety (SPA without BDD) and in a control group of men who do not have any concerns. Methods An opportunistic sample of 90 men from the community were recruited and divided into three groups: BDD (n = 26); SPA (n = 31) and controls (n = 33). Main Outcome Measures The Index of Erectile Function (IEF), sexual identity and history; and interventions to alter the size of their penis. Results Men with BDD compared with controls had reduced erectile dysfunction, orgasmic function, intercourse satisfaction and overall satisfaction on the IEF. Men with SPA compared with controls had reduced intercourse satisfaction. There were no differences in sexual desire, the frequency of intercourse or masturbation across any of the three groups. Men with BDD and SPA were more likely than the controls to attempt to alter the shape or size of their penis (for example jelqing, vacuum pumps or stretching devices) with poor reported success. Conclusion Men with BDD are more likely to have erectile dysfunction and less satisfaction with intercourse than controls but maintain their libido. Further research is required to develop and evaluate a psychological intervention for such men with adequate outcome measures. PMID:26468378

  15. Nanoscaffold matrices for size-controlled, pulsatile transdermal testosterone delivery: nanosize effects on the time dimension

    Science.gov (United States)

    Malik, Ritu; Tondwal, Shailesh; Venkatesh, K. S.; Misra, Amit

    2008-10-01

    Pulsatile transdermal testosterone (T) has applications in hormone supplementation and male contraception. Pulsatile T delivery was achieved by assembling crystalline and nanoparticulate T in nucleation-inhibiting polymer matrices of controlled porosity. Different interference patterns observed from various polymeric films containing T were due to the various particle sizes of T present in the polymer matrices. Scanning electron microscopy was used to determine the size and shape of T crystals. Skin-adherent films containing T nanoparticles of any size between 10-500 nm could be prepared using pharmaceutically acceptable vinylic polymers. Drug release and skin permeation profiles were studied. The dissolution-diffusion behavior of nanoparticles differed from crystalline and molecular states. Nanosize may thus be used to engineer chronopharmacologically relevant drug delivery.

  16. Grain Size Control of the Magnetic Nanoparticles by Solid State Route Modification

    Science.gov (United States)

    Barreto, A. C. H.; Santiago, V. R.; Freire, R. M.; Mazzetto, S. E.; Sasaki, J. M.; Vasconcelos, I. F.; Denardin, J. C.; Mele, Giuseppe; Carbone, Luigi; Fechine, P. B. A.

    2013-07-01

    The CoFe2O4 and NiFe2O4 nanoparticles were synthesized exploiting a co-precipitation method and afterward calcinated at 400 °C through two different experimental apparatus: a conventional muffle and rotatory oven. X-ray diffraction (XRD) analysis revealed that nanocrystalline ferrites grew with a face center cubic structure (fcc) and Fd3 m symmetry space group. XRD, transmission electron microscopy, and magnetic measurements confirmed the compositional homogeneity and the narrow size particle distribution (6-8 nm) of the sample thermally treated in a rotary oven, in all likelihood due to the sample's constant turning movement. The size of the magnetic particles is extremely important and influences the choice of a potential technological application. For this reason, our study emerges as a new and simple innovating procedure to control the size of magnetic nanoparticles.

  17. Nature of peptide wrapping onto metal nanoparticle catalysts and driving forces for size control.

    Science.gov (United States)

    Ramezani-Dakhel, Hadi; Bedford, Nicholas M; Woehl, Taylor J; Knecht, Marc R; Naik, Rajesh R; Heinz, Hendrik

    2017-06-22

    Colloidal metal nanocrystals find many applications in catalysis, energy conversion devices, and therapeutics. However, the nature of ligand interactions and implications on shape control have remained uncertain at the atomic scale. Large differences in peptide adsorption strength and facet specificity were found on flat palladium surfaces versus surfaces of nanoparticles of 2 to 3 nm size using accurate atomistic simulations with the Interface force field. Folding of longer peptides across many facets explains the formation of near-spherical particles with local surface disorder, in contrast to the possibility of nanostructures of higher symmetry with shorter ligands. The average particle size in TEM correlates inversely with the surface coverage with a given ligand and with the strength of ligand adsorption. The role of specific amino acids and sequence mutations on the nanoparticle size and facet composition is discussed, as well as the origin of local surface disorder that leads to large differences in catalytic reactivity.

  18. Size controlled biogenic silver nanoparticles as antibacterial agent against isolates from HIV infected patients

    Science.gov (United States)

    Suganya, K. S. Uma; Govindaraju, K.; Kumar, V. Ganesh; Dhas, T. Stalin; Karthick, V.; Singaravelu, G.; Elanchezhiyan, M.

    2015-06-01

    Silver nanoparticles (AgNPs) are synthesized using biological sources due to its high specificity in biomedical applications. Herein, we report the size and shape controlled synthesis of AgNPs using the aqueous extract of blue green alga, Spirulina platensis. Size, shape and elemental composition of AgNPs were characterized using UV-vis spectroscopy, Fluorescence spectroscopy, FT-IR (Fourier Transform-Infrared Spectroscopy), FT-RS (Fourier Transform-Raman Spectroscopy), SEM-EDAX (Scanning Electron Microscopy-Energy Dispersive X-ray analysis) and HR-TEM (High Resolution Transmission Electron Microscopy). AgNPs were stable, well defined and monodispersed (spherical) with an average size of 6 nm. The synthesized AgNPs were tested for its antibacterial potency against isolates obtained from HIV patients.

  19. Reciprocal control of cell proliferation and migration

    Directory of Open Access Journals (Sweden)

    De Donatis Alina

    2010-09-01

    Full Text Available Abstract In adult tissue the quiescent state of a single cell is maintained by the steady state conditions of its own microenvironment for what concern both cell-cell as well as cell-ECM interaction and soluble factors concentration. Physiological or pathological conditions can alter this quiescent state through an imbalance of both soluble and insoluble factors that can trigger a cellular phenotypic response. The kind of cellular response depends by many factors but one of the most important is the concentration of soluble cytokines sensed by the target cell. In addition, due to the intrinsic plasticity of many cellular types, every single cell is able, in response to the same stimulus, to rapidly switch phenotype supporting minimal changes of microenviromental cytokines concentration. Wound healing is a typical condition in which epithelial, endothelial as well as mesenchymal cells are firstly subjected to activation of their motility in order to repopulate the damaged region and then they show a strong proliferative response in order to successfully complete the wound repair process. This schema constitute the leitmotif of many other physiological or pathological conditions such as development vasculogenesis/angiogenesis as well as cancer outgrowth and metastasis. Our review focuses on the molecular mechanisms that control the starting and, eventually, the switching of cellular phenotypic outcome in response to changes in the symmetry of the extracellular environment.

  20. Body size perception and weight control in youth: 9-year international trends from 24 countries

    Science.gov (United States)

    Quick, Virginia; Nansel, Tonja R.; Liu, Danping; Lipsky, Leah M.; Due, Pernille; Iannotti, Ronald J.

    2014-01-01

    Objectives To examine nine-year trends and relationships regarding misperceptions of body size and dieting for weight loss among adolescents from 24 countries, and explore the influence of country-level overweight prevalence. Methods Socio-demographic characteristics, body size perception, and dieting for weight loss were assessed in the Health Behaviour in School-aged Children survey conducted in 24 countries cross-sectionally at three time points (2001/02, 2005/06, 2009/10). Logistic regression models examined change over time in overestimation of body size in non-overweight adolescents, underestimation of body size in overweight adolescents, dieting for weight loss in non-overweight and overweight adolescents, and relationships between body size perception and dieting. Analyses were stratified by weight status and sex. Covariates included country-level overweight prevalence, family affluence, and country level of development. Body mass index was only included in models examining dieting for weight loss. Results Country-level overweight prevalence increased over time (11.6% to 14.7%). Compared to Time 1, overweight adolescents had greater odds of body size underestimation at Time 3 (OR=1.68 for girls, OR=1.10 for boys), while non-overweight adolescents had lower odds of body size overestimation at Time 3 (OR=0.87 for girls, OR=0.89 for boys). Controlling for country-level overweight prevalence attenuated these relationships. Compared to Time 1, overweight and non-overweight boys were 10% more likely to diet at Time 3, while overweight and non-overweight girls were 19% and 16%, respectively, less likely to diet at Time 3. Controlling for country-level overweight prevalence did not impact trends in dieting for weight loss. Additionally, the association of self-perceived overweight with increased odds of dieting diminished over time. Conclusions Body size perceptions among adolescents may have changed over time concurrent with shifts in country-level body weight

  1. Effect of Mixture Pressure and Equivalence Ratio on Detonation Cell Size for Hydrogen-Air Mixtures

    Science.gov (United States)

    2015-06-01

    mixture pressure detonation cell sizes are important for scaling the combustion chambers, and before this research no data existed for hydrogen and air...Introduction General Issue Pressure gain combustors have the potential to replace traditional combustions systems in gas turbine engines (Tellefsen et al... combustion has not been fully incorporated into turbine engines. In order to fully integrate RDEs into turbine engines, RDEs must be able to function

  2. Tuning of glyconanomaterial shape and size for selective bacterial cell agglutination

    OpenAIRE

    Cid Martín, J.J.; Assali, Mohyeddin; Fernández García, E.; Valdivia Giménez, Victoria Esther; Sánchez Fernández, E. M.; García Fernández, José Manuel; Wellinger, Ralf Erik; Fernández Fernández, Inmaculada; Khiar, N.

    2016-01-01

    Multivalent glycosystems are potential candidates for anti-adhesive therapy, a non-lethal approach against the ever increasing antibiotic resistance of pathogenic bacteria. In order to fine-tune the glyconanomaterial size and shape for selective bacterial cell agglutination, herein we report the synthesis of sugar-coated dynamic and polymeric 3D-micelles and 1D-carbon nanotubes. The reported shot-gun like synthetic approach is based on the ability of diacetylenic-based neoglycolipids to self-...

  3. Na+ and K+ ion selectivity by size-controlled biomimetic graphene nanopores

    Science.gov (United States)

    Kang, Yu; Zhang, Zhisen; Shi, Hui; Zhang, Junqiao; Liang, Lijun; Wang, Qi; Ågren, Hans; Tu, Yaoquan

    2014-08-01

    Because biological ionic channels play a key role in cellular transport phenomena, they have attracted extensive research interest for the design of biomimetic nanopores with high permeability and selectivity in a variety of technical applications. Inspired by the structure of K+ channel proteins, we designed a series of oxygen doped graphene nanopores of different sizes by molecular dynamics simulations to discriminate between K+ and Na+ channel transport. The results from free energy calculations indicate that the ion selectivity of such biomimetic graphene nanopores can be simply controlled by the size of the nanopore; compared to K+, the smaller radius of Na+ leads to a significantly higher free energy barrier in the nanopore of a certain size. Our results suggest that graphene nanopores with a distance of about 3.9 Å between two neighboring oxygen atoms could constitute a promising candidate to obtain excellent ion selectivity for Na+ and K+ ions.Because biological ionic channels play a key role in cellular transport phenomena, they have attracted extensive research interest for the design of biomimetic nanopores with high permeability and selectivity in a variety of technical applications. Inspired by the structure of K+ channel proteins, we designed a series of oxygen doped graphene nanopores of different sizes by molecular dynamics simulations to discriminate between K+ and Na+ channel transport. The results from free energy calculations indicate that the ion selectivity of such biomimetic graphene nanopores can be simply controlled by the size of the nanopore; compared to K+, the smaller radius of Na+ leads to a significantly higher free energy barrier in the nanopore of a certain size. Our results suggest that graphene nanopores with a distance of about 3.9 Å between two neighboring oxygen atoms could constitute a promising candidate to obtain excellent ion selectivity for Na+ and K+ ions. Electronic supplementary information (ESI) available. See DOI

  4. Synthetic levers enabling independent control of phase, size, and morphology in nickel phosphide nanoparticles.

    Science.gov (United States)

    Muthuswamy, Elayaraja; Savithra, Galbokka H Layan; Brock, Stephanie L

    2011-03-22

    Simultaneous control of phase, size, and morphology in nanoscale nickel phosphides is reported. Phase-pure samples of discrete nanoparticles of Ni12P5 and Ni2P in hollow and solid morphologies can be prepared in a range of sizes (10-32 nm) by tuning key interdependent synthetic levers (P:Ni precursor ratio, temperature, time, oleylamine quantity). Size and morphology are controlled by the P:Ni ratio in the synthesis of the precursor particles, with large, hollow particles formed at low P:Ni and small, solid particles formed at high P:Ni. The P:Ni ratio also impacts the phase at the crystallization temperature (300-350 °C), with metal-rich Ni12P5 generated at low P:Ni and Ni2P at high P:Ni. Moreover, the product phase formed can be decoupled from the initial precursor ratio by the addition of more "P" at the crystallization temperature. This enables formation of hollow particles (favored by low P:Ni) of Ni2P (favored by high P:Ni). Increasing temperature and time also favor formation of Ni2P, by generating more reactive P and providing sufficient time for conversion to the thermodynamic product. Finally, increasing oleylamine concentration allows Ni12P5 to be obtained under high P:Ni precursor ratios that favor solid particle formation. Oleylamine concentration also acts to "tune" the size of the voids in particles formed at low P:Ni ratios, enabling access to Ni12P5 particles with different void sizes. This approach enables an unprecedented level of control over phase and morphology of nickel phosphide nanoparticles, paving the way for systematic investigation of the impact of these parameters on hydrodesulfurization activities of nickel phosphides.

  5. Portion size

    Science.gov (United States)

    ... with hummus. To control your portion sizes when eating out, try these tips: Order the small size. Instead of a medium or large, ask for the smallest size. By eating a small hamburger instead of a large, you ...

  6. Distributed Active Traction Control System Applied to the RoboCup Middle Size League

    Directory of Open Access Journals (Sweden)

    José Almeida

    2013-10-01

    Full Text Available This work addresses the problem of traction control in mobile wheeled robots in the particular case of the RoboCup Middle Size League (MSL. The slip control problem is formulated using simple friction models for ISePorto Team Robots with a differential wheel configuration. Traction was also characterized experimentally in the MSL scenario for relevant game events. This work proposes a hierarchical traction control architecture which relies on local slip detection and control at each wheel, with relevant information being relayed to a higher level responsible for global robot motion control. A dedicated one axis control embedded hardware subsystem allowing complex local control, high frequency current sensing and odometric information procession was developed. This local axis control board is integrated in a distributed system using CAN bus communications. The slipping observer was implemented in the axis control hardware nodes integrated in the ISePorto Robots and was used to control and detect loss of traction. An external vision system was used to perform a qualitative analysis of the slip detection and observer performance results are presented.

  7. Facile fabrication of BiVO4 nanofilms with controlled pore size and their photoelectrochemical performances

    Science.gov (United States)

    Feng, Chenchen; Jiao, Zhengbo; Li, Shaopeng; Zhang, Yan; Bi, Yingpu

    2015-12-01

    We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures.We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06584d

  8. Size control of Au NPs supported by pH operation

    Science.gov (United States)

    Ichiji, Masumi; Akiba, Hiroko; Hirasawa, Izumi

    2017-07-01

    Au NPs are expected to become useful functional particles, as particle gun used for plant gene transfer and also catalysts. We have studied PSD (particle size distribution) control of Au NPs by reduction crystallization. Previous study found out importance of seeds policy and also feeding profile. In this paper, effect of pH in the reduction crystallization was investigated to clarify the possibility of Au NPs PSD control by pH operation and also their growth process. Au NPs of size range 10-600 nm were obtained in single-jet system using ascorbic acid (AsA) as a reducing agent with adjusting pH of AsA. Au NPs are found to grow in the process of nucleation, agglomeration, agglomeration growth and surface growth. Au NPs tend to grow by agglomeration and become larger size in lower pH regions, and to grow only by surface growth and become smaller size in higher pH regions.

  9. Simultaneous phase and size control of upconversion nanocrystals through lanthanide doping

    KAUST Repository

    Wang, Feng

    2010-02-25

    Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase, modifying electronic properties, modulating magnetism as well as tuning emission properties. Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF 4 nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF 4 upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels to volumetric three-dimensional displays. © 2010 Macmillan Publishers Limited. All rights reserved.

  10. Experimental study of commercial size proton exchange membrane fuel cell performance

    International Nuclear Information System (INIS)

    Yan, Wei-Mon; Wang, Xiao-Dong; Lee, Duu-Jong; Zhang, Xin-Xin; Guo, Yi-Fan; Su, Ay

    2011-01-01

    Commercial sized (16 x 16 cm 2 active surface area) proton exchange membrane (PEM) fuel cells with serpentine flow chambers are fabricated. The GORE-TEX (registered) PRIMEA 5621 was used with a 35-μm-thick PEM with an anode catalyst layer with 0.45 mg cm -2 Pt and cathode catalyst layer with 0.6 mg cm -2 Pt and Ru or GORE-TEX (registered) PRIMEA 57 was used with an 18-μm-thick PEM with an anode catalyst layer at 0.2 mg cm -2 Pt and cathode catalyst layer at 0.4 mg cm -2 of Pt and Ru. At the specified cell and humidification temperatures, the thin PRIMEA 57 membrane yields better cell performance than the thick PRIMEA 5621 membrane, since hydration of the former is more easily maintained with the limited amount of produced water. Sufficient humidification at both the cathode and anode sides is essential to achieve high cell performance with a thick membrane, like the PRIMEA 5621. The optimal cell temperature to produce the best cell performance with PRIMEA 5621 is close to the humidification temperature. For PRIMEA 57, however, optimal cell temperature exceeds the humidification temperature.

  11. Experimental study of commercial size proton exchange membrane fuel cell performance

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei-Mon; Guo, Yi-Fan [Department of Greenergy, National University of Tainan, Tainan 700 (China); Wang, Xiao-Dong; Zhang, Xin-Xin [Department of Thermal Engineering, School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Lee, Duu-Jong [Department of Chemical Engineering, College of Engineering, National Taiwan University of Science and Technology, Taipei 106 (China); Su, Ay [Department of Mechanical Engineering, Fuel Cell Center, Yuan Ze University, Taoyuan 300 (China)

    2011-01-15

    Commercial sized (16 x 16 cm{sup 2} active surface area) proton exchange membrane (PEM) fuel cells with serpentine flow chambers are fabricated. The GORE-TEX registered PRIMEA 5621 was used with a 35-{mu}m-thick PEM with an anode catalyst layer with 0.45 mg cm{sup -2} Pt and cathode catalyst layer with 0.6 mg cm{sup -2} Pt and Ru or GORE-TEX registered PRIMEA 57 was used with an 18-{mu}m-thick PEM with an anode catalyst layer at 0.2 mg cm{sup -2} Pt and cathode catalyst layer at 0.4 mg cm{sup -2} of Pt and Ru. At the specified cell and humidification temperatures, the thin PRIMEA 57 membrane yields better cell performance than the thick PRIMEA 5621 membrane, since hydration of the former is more easily maintained with the limited amount of produced water. Sufficient humidification at both the cathode and anode sides is essential to achieve high cell performance with a thick membrane, like the PRIMEA 5621. The optimal cell temperature to produce the best cell performance with PRIMEA 5621 is close to the humidification temperature. For PRIMEA 57, however, optimal cell temperature exceeds the humidification temperature. (author)

  12. Microfluidic Isolation of Circulating Tumor Cell Clusters by Size and Asymmetry.

    Science.gov (United States)

    Au, Sam H; Edd, Jon; Stoddard, Amy E; Wong, Keith H K; Fachin, Fabio; Maheswaran, Shyamala; Haber, Daniel A; Stott, Shannon L; Kapur, Ravi; Toner, Mehmet

    2017-05-26

    Circulating tumor cell clusters (CTC clusters) are potent initiators of metastasis and potentially useful clinical markers for patients with cancer. Although there are numerous devices developed to isolate individual circulating tumor cells from blood, these devices are ineffective at capturing CTC clusters, incapable of separating clusters from single cells and/or cause cluster damage or dissociation during processing. The only device currently able to specifically isolate CTC clusters from single CTCs and blood cells relies on the batch immobilization of clusters onto micropillars which necessitates long residence times and causes damage to clusters during release. Here, we present a two-stage continuous microfluidic chip that isolates and recovers viable CTC clusters from blood. This approach uses deterministic lateral displacement to sort clusters by capitalizing on two geometric properties: size and asymmetry. Cultured breast cancer CTC clusters containing between 2-100 + cells were recovered from whole blood using this integrated two-stage device with minimal cluster dissociation, 99% recovery of large clusters, cell viabilities over 87% and greater than five-log depletion of red blood cells. This continuous-flow cluster chip will enable further studies examining CTC clusters in research and clinical applications.

  13. Synthesis and size control of monodisperse copper nanoparticles by polyol method.

    Science.gov (United States)

    Park, Bong Kyun; Jeong, Sunho; Kim, Dongjo; Moon, Jooho; Lim, Soonkwon; Kim, Jang Sub

    2007-07-15

    We describe herein the synthesis of metallic copper nanoparticles in the presence of poly(vinylpyrrolidone), employed as a protecting agent, via a polyol method in ambient atmosphere. The obtained copper particles were confirmed by XRD to be crystalline copper with a face-centered cubic (fcc) structure. We observed monodisperse spherical copper nanoparticles with a diameter range 45+/-8 nm. The particle size and its distribution are controlled by varying the synthesis parameters such as the reducing agent concentration, reaction temperature, and precursor injection rate. The precursor injection rate plays an important role in controlling the size of the copper nanoparticles. On the basis of XPS and HRTEM results, we demonstrate that the surface of the copper is surrounded by amorphous CuO and that poly(vinylpyrrolidone) is chemisorbed on the copper surface.

  14. A Method of MPPT Control Based on Power Variable Step-size in Photovoltaic Converter System

    Directory of Open Access Journals (Sweden)

    Xu Hui-xiang

    2016-01-01

    Full Text Available Since the disadvantage of traditional MPPT algorithms of variable step-size, proposed power tracking based on variable step-size with the advantage method of the constant-voltage and the perturb-observe (P&O[1-3]. The control strategy modify the problem of voltage fluctuation caused by perturb-observe method, at the same time, introducing the advantage of constant-voltage method and simplify the circuit topology. With the theoretical derivation, control the output power of photovoltaic modules to change the duty cycle of main switch. Achieve the maximum power stabilization output, reduce the volatility of energy loss effectively, and improve the inversion efficiency[3,4]. Given the result of experimental test based theoretical derivation and the curve of MPPT when the prototype work.

  15. Particle size distribution control of Pt particles used for particle gun

    Science.gov (United States)

    Ichiji, M.; Akiba, H.; Nagao, H.; Hirasawa, I.

    2017-07-01

    The purpose of this study is particle size distribution (PSD) control of submicron sized Pt particles used for particle gun. In this report, simple reaction crystallization is conducted by mixing H2PtCl6 and ascorbic acid. Without the additive, obtained Pt particles have broad PSD and reproducibility of experiment is low. With seeding, Pt particles have narrow PSD and reproducibility improved. Additionally, mean particle diameter of 100-700 nm is controlled by changing seeding amount. Obtained particles are successfully characterized as Pt by XRD results. Moreover, XRD spectra indicate that obtained particles are polycrystals. These experimental results suggest that seeding consumed nucleation, as most nuclei attached on the seed surface. This mechanism virtually restricted nucleation to have narrow PSD can be obtained.

  16. Highly size- and shape-controlled synthesis of silver nanoparticles via a templated Tollens reaction.

    Science.gov (United States)

    Dondi, Ruggero; Su, Wu; Griffith, Gerry A; Clark, Graham; Burley, Glenn A

    2012-03-12

    A mild, facile one-step synthetic strategy for the preparation of size- and shape-controlled silver nanoparticles (AgNPs) is presented. The high degree of size- and shape-control of these AgNPs is achieved by the use of triazole sugar ligands scaffolded by a central resorcinol ether core. Both the triazoles and the resorcinol ether core mediate the nucleation, growth, and passivation phases of the preparation of AgNP in the presence of the Tollens reagent as the silver source. Kinetic and (1)H NMR titration data is presented describing the nature of the interactions between the Tollens reagent and these ligands. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Copper reverses cardiomyocyte hypertrophy through vascular endothelial growth factor-mediated reduction in the cell size.

    Science.gov (United States)

    Zhou, Yang; Jiang, Youchun; Kang, Y James

    2008-07-01

    Previous studies have shown that dietary copper supplementation reversed heart hypertrophy induced by pressure overload in a mouse model. The present study was undertaken to understand the cellular basis of copper-induced regression of cardiac hypertrophy. Primary cultures of neonatal rat cardiomyocytes were treated with phenylephrine (PE) at a final concentration of 100 microM in cultures for 48 h to induce cellular hypertrophy. The hypertrophied cardiomyocytes were exposed to copper sulfate at a final concentration of 5 microM in cultures for additional 24 h. This copper treatment reduced the size of the hypertrophied cardiomyocytes, as measured by flow cytometry, protein content in cells, cell volume and cardiomyocyte hypertrophy markers including beta-myosin heavy chain protein, skeletal alpha-actin, and atrial natriuretic peptide. Cell cycle analysis and cell sorting of p-histone-3 labeled cardiomyocytes indicated that cell division was not involved in the copper-induced regression of cardiomyocyte hypertrophy. Copper also inhibited PE-induced apoptosis, determined by a TUNEL assay. Because copper stimulates vascular endothelial growth factor (VEGF) production through activation of hypoxia-inducible transcription factor, an anti-VEGF antibody at a final concentration of 2 ng/ml in cultures was used and shown to blunt copper-induced regression of cell hypertrophy. Conversely, VEGF alone at a final concentration of 0.2 microg/ml reversed cell hypertrophy as the same as copper did. This study demonstrates that both copper and VEGF reduce the size of hypertrophied cardiomyocytes, and copper regression of cardiac hypertrophy is VEGF-dependent.

  18. Size and composition-controlled fabrication of VO2 nanocrystals by terminated cluster growth

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre; Slack, Jonathan

    2013-05-14

    A physical vapor deposition-based route for the fabrication of VO2 nanoparticles is demonstrated, consisting of reactive sputtering and vapor condensation at elevated pressures. The oxidation of vanadium atoms is an efficient heterogeneous nucleation method, leading to high nanoparticle throughtput. Fine control of the nanoparticle size and composition is obtained. Post growth annealing leads to crystalline VO2 nanoparticles with optimum thermocromic and plasmonic properties.

  19. PEM fuel stack dynamics, constraining supervisory control for propulsion systems in fuel cell busses

    NARCIS (Netherlands)

    Edwin Tazelaar; E. Middelman; P. van den Bosch; Bram Veenhuizen

    2013-01-01

    The last decade several prototypes of fuel cell busses have been presented [1, 2]. A closer observation of these prototypes shows remarkable differences in both sizing and control of the system components. Some busses are essentially electric vehicles with a relative low power fuel cell system used

  20. Control of nanoparticle size, reactivity and magnetic properties during the bioproduction of magnetite by Geobacter sulfurreducens

    Energy Technology Data Exchange (ETDEWEB)

    Byrne, J. M.; Telling, N. D.; Coker, V. S.; Pattrick, R. A. D.; Laan, G. van der; Arenholz, E.; Tuna, F.; Lloyd, J. R.

    2011-08-02

    The bioproduction of nano-scale magnetite by Fe(III)-reducing bacteria offers a potentially tunable, environmentally benign route to magnetic nanoparticle synthesis. Here, we demonstrate that it is possible to control the size of magnetite nanoparticles produced by Geobacter sulfurreducens, by adjusting the total biomass introduced at the start of the process. The particles have a narrow size distribution and can be controlled within the range of 10-50 nm. X-ray diffraction analysis indicates that controlled production of a number of different biominerals is possible via this method including goethite, magnetite and siderite, but their formation is strongly dependent upon the rate of Fe(III) reduction and total concentration and rate of Fe(II) produced by the bacteria during the reduction process. Relative cation distributions within the structure of the nanoparticles has been investigated by X-ray magnetic circular dichroism and indicates the presence of a highly reduced surface layer which is not observed when magnetite is produced through abiotic methods. The enhanced Fe(II)-rich surface, combined with small particle size, has important environmental applications such as in the reductive bioremediation of organics, radionuclides and metals. In the case of Cr(VI), as a model high-valence toxic metal, optimised biogenic magnetite is able to reduce and sequester the toxic hexavalent chromium very efficiently in the less harmful trivalent form.

  1. Consultation for Small-Sized Penis in the Egyptian Males: A Case Control Study.

    Science.gov (United States)

    Salama, Nader

    2016-05-01

    This study aimed to report penile dimensions in adult Egyptian males consulting for small-sized penis (SSP) and describe their demographics and andrological profile. A case control study was designed through retrospective data analysis of patients (n = 239) seeking advice for SSP and a control group (n = 59). This included sociodemographics, other andrological complaints, and penile dimensions (pendulous length [PL], penopubic or total length [TL], and circumference [CF]) at flaccid and erect states and the size of the prepubic fatty pad. The results reported that most patients were single, students, and smokers and had not completed a university education. Several patients reported falsely premature ejaculation (PE), penile curvature (PC), and small-sized testes. Most penile dimensions of the patients (mean, cm) were significantly lower than those of the controls, whether in flaccid (PL: 7.4 vs. 8.05, p = .008; CF: 8.7 vs. 8.98, p = .026) or erect state (PL: 11.8 vs. 13, p = .000; TL: 14.2 vs. 15, p = .000; CF: 11.3 vs. 11.8, p = .003). However, no patient presented with a pendulous penile length <4 cm in flaccid or <7 cm in erect state. In conclusion, Egyptian men consulting for SSP did not have true small organs, but their penile dimensions were slightly smaller than those of men without such complaint. The proper sexual education program is highly advisable in these situations to avoid the myths and misconceptions about sexuality. © The Author(s) 2015.

  2. The synthesis and characterization of platinum nanoparticles: a method of controlling the size and morphology

    International Nuclear Information System (INIS)

    Long, Nguyen Viet; Hayakawa, Tomokatsu; Lakshminarayana, Gandham; Nogami, Masayuki; Chien, Nguyen Duc; Hirata, Hirohito

    2010-01-01

    In this paper, Pt nanoparticles with good shapes of nanocubes and nano-octahedra and well-controlled sizes in the range 5-7 and 8-12 nm, respectively, have been successfully synthesized. The modified polyol method by adding silver nitrate and varying the molar ratio of the solutions of silver nitrate and H 2 PtCl 6 has been used to produce Pt nanoparticles of the size and shape to be controlled. The size and morphology of Pt nanoparticles have been studied by transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The results have shown that their very sharp and good shapes exist in the main forms of cubic, cuboctahedral, octahedral and tetrahedral shapes directly related to the crystal nucleation along various directions of the {100} cubic, {111} octahedral and {111} tetrahedral facets during synthesis. In particular, various irregular and new shapes of Pt nanoparticles have been found. Here, it is concluded that the role of silver ions has to be considered as an important factor for promoting and controlling the development of Pt nanoparticles of {100} cubic, {111} octahedral and {111} tetrahedral facets, and also directly orienting the growth and formation of Pt nanoparticles.

  3. The synthesis and characterization of platinum nanoparticles: a method of controlling the size and morphology

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet; Hayakawa, Tomokatsu; Lakshminarayana, Gandham; Nogami, Masayuki [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Chien, Nguyen Duc [Institute of Engineering Physics, Hanoi University of Technology, Dai Co Viet 1, Hanoi City (Viet Nam); Hirata, Hirohito, E-mail: nguyen.longviet@nitech.ac.jp, E-mail: nogami@nitech.ac.jp [Advanced Material Engineering Division, Toyota Motor Corporation, Higashifuji Technical Center 1200, Mishuku, Susono, Shizuoka (Japan)

    2010-01-22

    In this paper, Pt nanoparticles with good shapes of nanocubes and nano-octahedra and well-controlled sizes in the range 5-7 and 8-12 nm, respectively, have been successfully synthesized. The modified polyol method by adding silver nitrate and varying the molar ratio of the solutions of silver nitrate and H{sub 2}PtCl{sub 6} has been used to produce Pt nanoparticles of the size and shape to be controlled. The size and morphology of Pt nanoparticles have been studied by transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The results have shown that their very sharp and good shapes exist in the main forms of cubic, cuboctahedral, octahedral and tetrahedral shapes directly related to the crystal nucleation along various directions of the {l_brace}100{r_brace} cubic, {l_brace}111{r_brace} octahedral and {l_brace}111{r_brace} tetrahedral facets during synthesis. In particular, various irregular and new shapes of Pt nanoparticles have been found. Here, it is concluded that the role of silver ions has to be considered as an important factor for promoting and controlling the development of Pt nanoparticles of {l_brace}100{r_brace} cubic, {l_brace}111{r_brace} octahedral and {l_brace}111{r_brace} tetrahedral facets, and also directly orienting the growth and formation of Pt nanoparticles.

  4. Fluidic control over cell proliferation and chemotaxis

    Science.gov (United States)

    Groisman, Alex

    2006-03-01

    Microscopic flows are almost always stable and laminar that allows precise control of chemical environment in micro-channels. We describe design and operation of several microfluidic devices, in which various types of environments are created for different experimental assays with live cells. In a microfluidic chemostat, colonies of non-adherent bacterial and yeast cells are trapped in micro-chambers with walls permeable for chemicals. Fast chemical exchange between the chambers and nearby flow-through channels creates essentially chemostatic medium conditions in the chambers and leads to exponential growth of the colonies up to very high cell densities. Another microfluidic device allows creation of linear concentration profiles of a pheromone (α-factor) across channels with non-adherent yeast cells, without exposure of the cells to flow or other mechanical perturbation. The concentration profile remains stable for hours enabling studies of chemotropic response of the cells to the pheromone gradient. A third type of the microfluidic devices is used to study chemotaxis of human neutrophils exposed to gradients of a chemoattractant (fMLP). The devices generate concentration profiles of various shapes, with adjustable steepness and mean concentration. The ``gradient'' of the chemoattractant can be imposed and reversed within less than a second, allowing repeated quantitative experiments.

  5. Cell cycle control across the eukaryotic kingdom.

    Science.gov (United States)

    Harashima, Hirofumi; Dissmeyer, Nico; Schnittger, Arp

    2013-07-01

    Almost two billion years of evolution have generated a vast and amazing variety of eukaryotic life with approximately 8.7 million extant species. Growth and reproduction of all of these organisms depend on faithful duplication and distribution of their chromosomes to the newly forming daughter cells in a process called the cell cycle. However, most of what is known today about cell cycle control comes from a few model species that belong to the unikonts; that is, to only one of five 'supergroups' that comprise the eukaryotic kingdom. Recently, analyzing species from distantly related clades is providing insights into general principles of cell cycle regulation and shedding light on its evolution. Here, referring to animal and fungal as opposed to non-unikont systems, especially flowering plants from the archaeplastid supergroup, we compare the conservation of central cell cycle regulator functions, the structure of network topologies, and the evolutionary dynamics of substrates of core cell cycle kinases. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Mice divergently selected for high and low basal metabolic rates evolved different cell size and organ mass.

    Science.gov (United States)

    Maciak, S; Bonda-Ostaszewska, E; Czarnołęski, M; Konarzewski, M; Kozłowski, J

    2014-03-01

    Evolution of metabolic rates of multicellular organisms is hypothesized to reflect the evolution of their cell architecture. This is likely to stem from a tight link between the sizes of cells and nuclei, which are expected to be inversely related to cell metabolism. Here, we analysed basal metabolic rate (BMR), internal organ masses and the cell/nucleus size in different tissues of laboratory mice divergently selected for high/low mass-corrected BMR and four random-bred mouse lines. Random-bred lines had intermediate levels of BMR as compared to low- and high-BMR lines. Yet, this pattern was only partly consistent with the between-line differences in cell/nucleus sizes. Erythrocytes and skin epithelium cells were smaller in the high-BMR line than in other lines, but the cells of low-BMR and random-bred mice were similar in size. On the other hand, the size of hepatocytes, kidney proximal tubule cells and duodenum enterocytes were larger in high-BMR mice than other lines. All cell and nucleus sizes were positively correlated, which supports the role of the nucleus in cell size regulation. Our results suggest that the evolution of high BMR involves a reduction in cell size in specialized tissues, whose functions are primarily dictated by surface-to-volume ratios, such as erythrocytes. High BMR may, however, also incur an increase in cell size in tissues with an intense transcription and translation, such as hepatocytes. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  7. Controlling particle size in the Stöber process and incorporation of calcium.

    Science.gov (United States)

    Greasley, Sarah L; Page, Samuel J; Sirovica, Slobodan; Chen, Shu; Martin, Richard A; Riveiro, Antonio; Hanna, John V; Porter, Alexandra E; Jones, Julian R

    2016-05-01

    The Stӧber process is commonly used for synthesising spherical silica particles. This article reports the first comprehensive study of how the process variables can be used to obtain monodispersed particles of specific size. The modal particle size could be selected within in the range 20-500 nm. There is great therapeutic potential for bioactive glass nanoparticles, as they can be internalised within cells and perform sustained delivery of active ions. Biodegradable bioactive glass nanoparticles are also used in nanocomposites. Modification of the Stӧber process so that the particles can contain cations such as calcium, whilst maintaining monodispersity, is desirable. Here, whilst calcium incorporation is achieved, with a homogenous distribution, careful characterisation shows that much of the calcium is not incorporated. A maximum of 10 mol% CaO can be achieved and previous reports are likely to have overestimated the amount of calcium incorporated. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Primary cilium and autophagy: The avengers of cell-size regulation.

    Science.gov (United States)

    Orhon, Idil; Dupont, Nicolas; Codogno, Patrice

    2016-11-01

    The maintenance of cellular homeostasis in response to extracellular stresses by autophagy is vital for the health of various tissues. Extracellular stimuli may include nutrient starvation, endoplasmic reticulum stress, hypoxia, cytotoxic agents, or mechanical stress. The primary cilium (PC) is a microtubule-based sensory organelle that regulates the integration of various extracellular stimuli. The interconnection between macroautophagy/autophagy and the PC is beginning to be illuminated. In this punctum, we discuss our recent study of PC-dependent autophagy in response to fluid flow in kidney epithelial cells. Urinary flow in kidney tubules creates a shear stress that regulates epithelial cell volume. PC-mediated autophagy is necessary for the regulation of cell size. The signal from the PC is transduced by the activation of STK11/LKB1 and by MTOR inhibition. Our results clarify the physiological role of PC-dependent autophagy in the kidney and suggest that autophagy manipulation may provide a route to the treatment of ciliopathies.

  9. Assessing T cell clonal size distribution: a non-parametric approach.

    Science.gov (United States)

    Bolkhovskaya, Olesya V; Zorin, Daniil Yu; Ivanchenko, Mikhail V

    2014-01-01

    Clonal structure of the human peripheral T-cell repertoire is shaped by a number of homeostatic mechanisms, including antigen presentation, cytokine and cell regulation. Its accurate tuning leads to a remarkable ability to combat pathogens in all their variety, while systemic failures may lead to severe consequences like autoimmune diseases. Here we develop and make use of a non-parametric statistical approach to assess T cell clonal size distributions from recent next generation sequencing data. For 41 healthy individuals and a patient with ankylosing spondylitis, who undergone treatment, we invariably find power law scaling over several decades and for the first time calculate quantitatively meaningful values of decay exponent. It has proved to be much the same among healthy donors, significantly different for an autoimmune patient before the therapy, and converging towards a typical value afterwards. We discuss implications of the findings for theoretical understanding and mathematical modeling of adaptive immunity.

  10. Assessing T cell clonal size distribution: a non-parametric approach.

    Directory of Open Access Journals (Sweden)

    Olesya V Bolkhovskaya

    Full Text Available Clonal structure of the human peripheral T-cell repertoire is shaped by a number of homeostatic mechanisms, including antigen presentation, cytokine and cell regulation. Its accurate tuning leads to a remarkable ability to combat pathogens in all their variety, while systemic failures may lead to severe consequences like autoimmune diseases. Here we develop and make use of a non-parametric statistical approach to assess T cell clonal size distributions from recent next generation sequencing data. For 41 healthy individuals and a patient with ankylosing spondylitis, who undergone treatment, we invariably find power law scaling over several decades and for the first time calculate quantitatively meaningful values of decay exponent. It has proved to be much the same among healthy donors, significantly different for an autoimmune patient before the therapy, and converging towards a typical value afterwards. We discuss implications of the findings for theoretical understanding and mathematical modeling of adaptive immunity.

  11. Microbial single-cell analysis in picoliter-sized batch cultivation chambers.

    Science.gov (United States)

    Kaganovitch, Eugen; Steurer, Xenia; Dogan, Deniz; Probst, Christopher; Wiechert, Wolfgang; Kohlheyer, Dietrich

    2018-03-14

    Microfluidics has enabled various research projects in the field of microbial single-cell analysis. In particular, single-use microfluidic cultivation devices combined with automated time-lapse imaging provide powerful approaches for analyzing microbial phenomena at the single-cell level. High spatiotemporal resolution facilitates individual cell identification and tracking, delivering detailed insights into areas like phenotypic population heterogeneity, which can be highly relevant to the fate of a microbial population and may negatively impact the efficiency of biotechnological fermentations. New tools need to be developed to access the origin of population heterogeneity and understand its functional role. In this study, we present a microfluidic device for batch cultivations inside picoliter-sized cultivation chambers that can be reversibly isolated from continuous medium supply. Therefore, the cultivation broth is simply replaced by a continuous flow of humidified air, removing any medium residue along the supply channels but preserving five picoliters of cultivation medium inside the cultivation chambers in a highly parallel manner. Living cells can grow inside our microfabricated batch chambers, which can accommodate up to several hundred cells. The chamber height approximately matches the diameter of a single cell, facilitating cell growth in monolayers that are ideal for image-based cell analysis. We successfully demonstrated the growth of Escherichia coli during continuous medium perfusion and batch cultivation conditions. As expected, the cells grew exponentially under continuous medium influx until the maximum chamber capacity was reached, but when they were cultivated under batch conditions, cellular growth underwent an exponential phase, followed by a stationary phase with obvious morphological changes. Copyright © 2018 Elsevier B.V. All rights reserved.

  12. Transcriptional control of the cell cycle.

    Science.gov (United States)

    Sánchez, I; Dynlacht, B D

    1996-06-01

    Although a significant amount of evidence has demonstrated that there are intimate connections between transcriptional controls and cell cycle regulation, the precise mechanisms underlying these connections remain largely obscure. A number of recent advances have helped to define how critical cell cycle regulators, such as the retinoblastoma family of tumor suppressor proteins and the cyclin-dependent kinases, might function on a biochemical level and how such mechanisms of action have been conserved not only in the regulation of transcription by all three RNA polymerases but also across species lines. In addition, the use of in vivo techniques has begun to explain how the activity of the E2F transcription factor family is tied to the cell cycle dependent expression of target genes.

  13. Cell intrinsic control of axon regeneration

    Science.gov (United States)

    Mar, Fernando M; Bonni, Azad; Sousa, Mónica M

    2014-01-01

    Although neurons execute a cell intrinsic program of axonal growth during development, following the establishment of connections, the developmental growth capacity declines. Besides environmental challenges, this switch largely accounts for the failure of adult central nervous system (CNS) axons to regenerate. Here, we discuss the cell intrinsic control of axon regeneration, including not only the regulation of transcriptional and epigenetic mechanisms, but also the modulation of local protein translation, retrograde and anterograde axonal transport, and microtubule dynamics. We further explore the causes underlying the failure of CNS neurons to mount a vigorous regenerative response, and the paradigms demonstrating the activation of cell intrinsic axon growth programs. Finally, we present potential mechanisms to support axon regeneration, as these may represent future therapeutic approaches to promote recovery following CNS injury and disease. PMID:24531721

  14. Receptor control in mesenchymal stem cell engineering

    Science.gov (United States)

    Dalby, Matthew J.; García, Andrés J.; Salmeron-Sanchez, Manuel

    2018-03-01

    Materials science offers a powerful tool to control mesenchymal stem cell (MSC) growth and differentiation into functional phenotypes. A complex interplay between the extracellular matrix and growth factors guides MSC phenotypes in vivo. In this Review, we discuss materials-based bioengineering approaches to direct MSC fate in vitro and in vivo, mimicking cell-matrix-growth factor crosstalk. We first scrutinize MSC-matrix interactions and how the properties of a material can be tailored to support MSC growth and differentiation in vitro, with an emphasis on MSC self-renewal mechanisms. We then highlight important growth factor signalling pathways and investigate various materials-based strategies for growth factor presentation and delivery. Integrin-growth factor crosstalk in the context of MSC engineering is introduced, and bioinspired material designs with the potential to control the MSC niche phenotype are considered. Finally, we summarize important milestones on the road to MSC engineering for regenerative medicine.

  15. Effect of pore size on the calculated pressure at biological cells pore wall.

    Science.gov (United States)

    El-Hag, Ayman H; Zheng, Zhong; Boggs, Steven A; Jayaram, Shesha H

    2006-09-01

    A transient nonlinear finite-element program has been used to calculate the electric field distribution as a function of time for a spherical cell with a pore in a conducting medium during application of a subnanosecond rise time "step" wave, including the effects of dipolar saturation in the water-based cytoplasm and cell medium. The time-dependent pressure on the pore wall has been computed as a function of time as the system polarizes from the change of the energy in the electric field to the left (inside the pore) and to the right (inside the membrane) of the pore wall. The computations suggest that dipolar saturation, while significant, has little effect on the time-dependent electric field distribution but a substantial effect on the field-induced pore wall pressure. Also, the effect of pore size on both the computed electric field and field-induced pressure was studied. As the pore size increases, a collapse in both the electric field and field-induced pressure has been noticed. This suggests that as the pore size increases, the driving force for further opening the pore is not electrical.

  16. Energy harvesting from organic liquids in micro-sized microbial fuel cells

    KAUST Repository

    Mink, J.E.

    2014-03-07

    Micro-sized microbial fuel cells (MFCs) are miniature energy harvesters that use bacteria to convert biomass from liquids into usable power. The key challenge is transitioning laboratory test beds into devices capable of producing high power using readily available fuel sources. Here, we present a pragmatic step toward advancing MFC applications through the fabrication of a uniquely mobile and inexpensive micro-sized device that can be fueled with human saliva. The 25-ll MFC was fabricated with graphene, a two-dimensional atomic crystal-structured material, as an anode for efficient current generation and with an air cathode for enabling the use of the oxygen present in air, making its operation completely mobile and free of the need for laboratory chemicals. With saliva as a fuel, the device produced higher current densities (1190 Am-3) than any previous aircathode micro-sized MFCs. The use of the graphene anode generated 40 times more power than that possible using a carbon cloth anode. Additional tests were performed using acetate, a conventional organic material, at high organic loadings that were comparable to those in saliva, and the results demonstrated a linear relationship between the organic loading and current. These findings open the door to saliva-powered applications of this fuel cell technology for Lab-on-a-Chip devices or portable point-of-care diagnostic devices. 2014 Nature Publishing Group All rights reserved 1884-4057/14.

  17. Sexual Functioning and Behavior of Men with Body Dysmorphic Disorder Concerning Penis Size Compared with Men Anxious about Penis Size and with Controls: A Cohort Study

    Directory of Open Access Journals (Sweden)

    David Veale, MD, FRCPsych

    2015-09-01

    Conclusion: Men with BDD are more likely to have erectile dysfunction and less satisfaction with intercourse than controls but maintain their libido. Further research is required to develop and evaluate a psychological intervention for such men with adequate outcome measures. Veale D, Miles S, Read J, Troglia A, Wylie K, and Muir G. Sexual functioning and behavior of men with body dysmorphic disorder concerning penis size compared with men anxious about penis size and with controls: A cohort study. Sex Med 2015;3:147–155.

  18. Size-Controlled and Optical Properties of Monodispersed Silver Nanoparticles Synthesized by the Radiolytic Reduction Method

    Science.gov (United States)

    Saion, Elias; Gharibshahi, Elham; Naghavi, Kazem

    2013-01-01

    Size-controlled and monodispersed silver nanoparticles were synthesized from an aqueous solution containing silver nitrate as a metal precursor, polyvinyl alcohol as a capping agent, isopropyl alcohol as hydrogen and hydroxyl radical scavengers, and deionized water as a solvent with a simple radiolytic method. The average particle size decreased with an increase in dose due to the domination of nucleation over ion association in the formation of the nanoparticles by gamma reduction. The silver nanoparticles exhibit a very sharp and strong absorption spectrum with the absorption maximum λmax blue shifting with an increased dose, owing to a decrease in particle size. The absorption spectra of silver nanoparticles of various particle sizes were also calculated using a quantum physics treatment and an agreement was obtained with the experimental absorption data. The results suggest that the absorption spectrum of silver nanoparticles possibly derived from the intra-band excitations of conduction electrons from the lowest energy state (n = 5, l = 0) to higher energy states (n ≥ 6; Δl = 0, ±1; Δs = 0, ±1), allowed by the quantum numbers principle. This demonstrates that the absorption phenomenon of metal nanoparticles based on a quantum physics description could be exploited to be added into the fundamentals of metal nanoparticles and the related fields of nanoscience and nanotechnology. PMID:23579953

  19. Mechanical weed control on small-size dry bean and its response to cross-flaming

    Energy Technology Data Exchange (ETDEWEB)

    Martelloni, L.; Frasconi, C.; Fontanelli, M.; Raffaelli, M.; Peruzzi, A.

    2016-11-01

    Dry bean (Phaseolus vulgaris L.) can be a profitable crop for farmers; however controlling weeds effectively without a decrease in yield remains a problem. An example where mechanical weed control is difficult to conduct is dry bean ‘Toscanello’, which is a small sized high-income niche product growing low to the ground. Concerning intra-row weed control, also flame weeding could be an opportunity but the dry bean heat tolerance needs to be studied. The aims of this research were to study the weed control efficacy of a spring-tine harrow and an inter-row cultivator in this bean variety, and to test the tolerance of dry bean cultivated under weed-free conditions to cross-flaming applied with different liquefied petroleum gas (LPG) doses. Flame weeding was applied at BBCH 13 and BBCH 14 bean growth stages by pairs of burners producing direct double flame acting into the intra-row space, with bean plants placed in the middle. The results suggest that the spring-tine harrow used two times at BBCH 13 and 14, respectively, lead to a yield similar to that of the weedy control. The inter-row cultivator could be an opportunity for small-sized dry bean crops producers, enabling them to obtain a similar yield compared to the hand-weeded control. Concerning the bean tolerance to cross-flaming the results showed that bean flamed at BBCH 13 stage had little tolerance to cross-flaming. Bean flamed at BBCH 14 stage was tolerant until an LPG dose of 39 kg/ha, giving yield responses similar to those observed in the non-flamed control. (Author)

  20. Pyruvate kinase isoenzyme M2 is a glycolytic sensor differentially regulating cell proliferation, cell size and apoptotic cell death dependent on glucose supply

    International Nuclear Information System (INIS)

    Spoden, Gilles A.; Rostek, Ursula; Lechner, Stefan; Mitterberger, Maria; Mazurek, Sybille; Zwerschke, Werner

    2009-01-01

    The glycolytic key regulator pyruvate kinase M2 (M2-PK or PKM2) can switch between a highly active tetrameric and an inactive dimeric form. The transition between the two conformations regulates the glycolytic flux in tumor cells. We developed specific M2-PK-binding peptide aptamers which inhibit M2-PK, but not the 96% homologous M1-PK isoenzyme. In this study we demonstrate that, at normal blood glucose concentrations, peptide aptamer-mediated inhibition of M2-PK induces a significant decrease of the population doubling (PDL rate) and cell proliferation rate as well as an increase in cell size, whereas under glucose restriction an increase in PDL and cell proliferation rates but a decrease in cell size was observed. Moreover, M2-PK inhibition rescues cells from glucose starvation-induced apoptotic cell death by increasing the metabolic activity. These findings suggest that M2-PK is a metabolic sensor which regulates cell proliferation, cell growth and apoptotic cell death in a glucose supply-dependent manner.

  1. Size-based cell sorting with a resistive pulse sensor and an electromagnetic pump in a microfluidic chip.

    Science.gov (United States)

    Song, Yongxin; Li, Mengqi; Pan, Xinxiang; Wang, Qi; Li, Dongqing

    2015-02-01

    An electrokinetic microfluidic chip is developed to detect and sort target cells by size from human blood samples. Target-cell detection is achieved by a differential resistive pulse sensor (RPS) based on the size difference between the target cell and other cells. Once a target cell is detected, the detected RPS signal will automatically actuate an electromagnetic pump built in a microchannel to push the target cell into a collecting channel. This method was applied to automatically detect and sort A549 cells and T-lymphocytes from a peripheral fingertip blood sample. The viability of A549 cells sorted in the collecting well was verified by Hoechst33342 and propidium iodide staining. The results show that as many as 100 target cells per minute can be sorted out from the sample solution and thus is particularly suitable for sorting very rare target cells, such as circulating tumor cells. The actuation of the electromagnetic valve has no influence on RPS cell detection and the consequent cell-sorting process. The viability of the collected A549 cell is not impacted by the applied electric field when the cell passes the RPS detection area. The device described in this article is simple, automatic, and label-free and has wide applications in size-based rare target cell sorting for medical diagnostics. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Enhancement of pig embryonic implants in factor VIII KO mice: a novel role for the coagulation cascade in organ size control.

    Science.gov (United States)

    Aronovich, Anna; Tchorsh, Dalit; Shezen, Elias; Rosen, Chava; Klionsky, Yael; Cohen, Sivan; Tal, Orna; Martinowitz, Uri; Katchman, Helena; Eventov-Friedman, Smadar; Amariglio, Ninette; Jacob-Hirsch, Jasmine; Rechavi, Gideon; Reisner, Yair

    2009-12-21

    Very little is known about the mechanisms that contribute to organ size differences between species. In the present study, we used a mouse model of embryonic pig tissue implantation to define the role of host Factor VIII in controlling the final size attained by the implant. We show here that pig embryonic spleen, pancreas, and liver all grow to an increased size in mice that are deficient in the Factor VIII clotting cascade. Similar results were obtained using the transplantation model after treatment with the low molecular weight heparin derivative Clexane which markedly enhanced transplant size. Likewise, enhanced size was found upon treatment with the direct thrombin inhibitor Dabigatran, suggesting that organ size regulation might be mediated by thrombin, downstream of Factor VIII. Considering that thrombin was shown to mediate various functions unrelated to blood clotting, either directly by cleavage of protease-activated receptors (PARs) or indirectly by cleaving osteopontin (OPN) on stroma cells, the role of PAR1 and PAR4 antagonists as well as treatment with cleaved form of OPN (tcOPN) were tested. While the former was not found to have an impact on overgrowth of embryonic pig spleen implants, marked reduction of size was noted upon treatment with the (tcOPN). Collectively, our surprising set of observations suggests that factors of the coagulation cascade have a novel role in organ size control.

  3. Integration of epigenetic and genetic controls of seed size by cytokinin in Arabidopsis.

    Science.gov (United States)

    Li, Jing; Nie, Xin; Tan, Jeanie Li Hui; Berger, Frédéric

    2013-09-17

    The development of seeds in flowering plants is placed under complex interactions between maternal tissues, the embryo, and the endosperm. The endosperm plays a major role in the regulation of seed size. In Arabidopsis thaliana, endosperm size depends on the coordination of the genetic pathway HAIKU (IKU) with epigenetic controls comprising genome dosage, DNA methylation, and trimethylated lysine 27 on histone H3 (H3K27me3) deposition. However, the effectors that integrate these pathways have remained unknown. Here, we identify a target of the IKU pathway, the cytokinin oxidase CKX2, that affects cytokinin signaling. CKX2 expression is activated by the IKU transcription factor WRKY10 directly and promotes endosperm growth. CKX2 expression also depends on H3K27me3 deposition, which fluctuates in response to maternal genome dosage imbalance and DNA demethylation of male gametes. Hence, the control of endosperm growth by CKX2 integrates genetic and epigenetic regulations. In angiosperms, cytokinins are highly active in endosperm, and we propose that IKU effectors coordinate environmental and physiological factors, resulting in modulation of seed size.

  4. Size-controlled synthesis and characterization of thiol-stabilized gold nanoparticles

    Science.gov (United States)

    Frenkel, A. I.; Nemzer, S.; Pister, I.; Soussan, L.; Harris, T.; Sun, Y.; Rafailovich, M. H.

    2005-11-01

    Size-controlled synthesis of nanoparticles of less than a few nanometers in size is a challenge due to the spatial resolution limit of most scattering and imaging techniques used for their structural characterization. We present the self-consistent analysis of the extended x-ray absorption fine-structure (EXAFS) spectroscopy data of ligand-stabilized metal nanoclusters. Our method employs the coordination number truncation and the surface-tension models in order to measure the average diameter and analyze the structure of the nanoparticles. EXAFS analysis was performed on the two series of dodecanethiol-stabilized gold nanoparticles prepared by one-phase and two-phase syntheses where the only control parameter was the gold/thiol ratio ξ, varied between 6:1 and 1:6. The two-phase synthesis resulted in the smaller particles whose size decreased monotonically and stabilized at 16Å when ξ was lowered below 1:1. This behavior is consistent with the theoretically predicted thermodynamic limit obtained previously in the framework of the spherical drop model of Au nanoparticles.

  5. A hybrid mathematical model for controlling particle size, particle size distribution, and color properties of toner particles

    Science.gov (United States)

    Ataeefard, Maryam; Shadman, Alireza; Saeb, Mohammad Reza; Mohammadi, Yousef

    2016-08-01

    A mathematical modeling approach was proposed combining the capabilities of response surface methodology (RSM) and desirability function (DF) and implemented successfully in production of printing toner particles. Toner powders were systematically synthesized through suspension copolymerization process. Applying RSM, a series of experiments were designed and toner particles were prepared and the effects of monomer ratio, colorant and surfactant content on the particle size (PS), particle size distribution (PSD), thermal and colorimetric properties (∆ E) of the resulting toner were monitored and discussed. The second-order models corresponding to each target characteristic, i.e., PS, PSD, and ∆ E of different types of toner powders, were obtained by individual optimization to express variation of each property in terms of polymerization parameters. Applying statistical calculations, the best reduced models were identified to be fed in the second step of optimization. Since toners with appropriate PS, PSD, and CP were needed, we applied multi-objective optimization based on DF approach. The results show that exact tuning of toner properties is closely possible with the aid of hybrid mathematical model developed in this work. Noticeably, desirabilities are very close to 100 %.

  6. Controlling pore size of activated carbon through self-activation process for removing contaminants of different molecular sizes.

    Science.gov (United States)

    Wu, Yingji; Xia, Changlei; Cai, Liping; Shi, Sheldon Q

    2018-05-15

    Self-activation was employed for the manufacturing of activated carbon (AC) using kenaf core fibers, which is more environmentally friendly and cost-effective than the conventional physical/chemical activations. It makes the use of the gases emitted from the thermal treatment to activate the converted carbon itself. The mechanism was illustrated by the Fourier transform infrared spectroscopy and mass spectrometry analysis of the emitted gases, showing that CO 2 served as an activating agent. The AC from self-activation presented high performance, for instance, the Brunauer-Emmett-Teller surface area was up to 2296 m 2 g -1 , Using the Density Functional Theory (DFT), the pore volume (PV) was determined to be 1.876 cm 3 g -1 . Linear relations of PV DFT-micropore /iodine number, and PV DFT-mesopore /tannin value were established, indicating a strong relationship between the pore structure of AC and its adsorbing preference. Adsorption results for copper (II) and rhodamine 6G also indicated that the pore size of AC should be designed based on the molecular size of the contaminants. Copyright © 2018 Elsevier Inc. All rights reserved.

  7. Active impulsive noise control using maximum correntropy with adaptive kernel size

    Science.gov (United States)

    Lu, Lu; Zhao, Haiquan

    2017-03-01

    The active noise control (ANC) based on the principle of superposition is an attractive method to attenuate the noise signals. However, the impulsive noise in the ANC systems will degrade the performance of the controller. In this paper, a filtered-x recursive maximum correntropy (FxRMC) algorithm is proposed based on the maximum correntropy criterion (MCC) to reduce the effect of outliers. The proposed FxRMC algorithm does not requires any priori information of the noise characteristics and outperforms the filtered-x least mean square (FxLMS) algorithm for impulsive noise. Meanwhile, in order to adjust the kernel size of FxRMC algorithm online, a recursive approach is proposed through taking into account the past estimates of error signals over a sliding window. Simulation and experimental results in the context of active impulsive noise control demonstrate that the proposed algorithms achieve much better performance than the existing algorithms in various noise environments.

  8. Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.

    Science.gov (United States)

    Parakhonskiy, B V; Svenskaya, Yu I; Yashchenok, A М; Fattah, H A; Inozemtseva, O A; Tessarolo, F; Antolini, R; Gorin, D A

    2014-06-01

    An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1μm. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Efficient size control of amphiphilic cyclodextrin nanoparticles through a statistical mixture design methodology.

    Science.gov (United States)

    Choisnard, Luc; Géze, Annabelle; Bigan, Muriel; Putaux, Jean-Luc; Wouessidjewe, Denis

    2005-12-06

    the aim of the study was to investigate size control of amphiphilic beta-cyclodextrin nanoparticles obtained by solvent displacement technique. An experimental design methodology for mixture design was undertaken using D-optimal approach with the following technique variables: water fraction X1 (40-70% v/v), acetone fraction X2 (0-60% v/v) and ethanol fraction X3 (0-60% v/v). The resulting quadratic model obtained after logarithmic transformation of data and partial least-square regression was statistically validated and experimentally checked. Also, the morphology of the colloidal nanoparticles from selected experiments was observed by cryo-transmission electron microscopy. This experimental design approach allowed to produce interesting amphiphilic beta-cyclodextrin nanoparticles with a predicted mean size varying from 60 to 400 nm.

  10. Nonthermal plasma synthesis of size-controlled, monodisperse, freestanding germanium nanocrystals

    International Nuclear Information System (INIS)

    Gresback, Ryan; Holman, Zachary; Kortshagen, Uwe

    2007-01-01

    Germanium nanocrystals may be of interest for a variety of electronic and optoelectronic applications including photovoltaics, primarily due to the tunability of their band gap from the infrared into the visible range of the spectrum. This letter discusses the synthesis of monodisperse germanium nanocrystals via a nonthermal plasma approach which allows for precise control of the nanocrystal size. Germanium crystals are synthesized from germanium tetrachloride and hydrogen entrained in an argon background gas. The crystal size can be varied between 4 and 50 nm by changing the residence times of crystals in the plasma between ∼30 and 440 ms. Adjusting the plasma power enables one to synthesize fully amorphous or fully crystalline particles with otherwise similar properties

  11. Deposition of SrTiO3 films by electrophoresis with thickness and particle size control

    International Nuclear Information System (INIS)

    Junior, W.D.M.; Pena, A.F.V.; Souza, A.E.; Santos, G.T.A.; Teixeira, S.R.; Senos, A.M.R.; Longo, E.

    2012-01-01

    The SrTiO3 (ST) is a material that exhibits semiconducting characteristics and interesting electrical properties. In room temperature has a structure of high cubic symmetry. The size of the crystallites of this material directly influences this symmetry, changing its network parameters. ST nanoparticles are obtained by hydrothermal method assisted by microwave (MAH). ST films are prepared by electrophoretic deposition (EPD). Approximately 1 g of the powder is dissolved in 100 ml of acetone and 1.5 ml of triethanolamine. The stainless steel substrates are arranged horizontally in the solution. The depositions are performed for 1-10 min and subjected to a potential difference of 20-100 V. The films were characterized by x-ray diffraction (XRD) and atomic force microscopy (AFM). The characterizations show that it is possible to control both the thickness and size of the crystallites of the film depending on the deposition parameters adopted. (author)

  12. Size and Cell Number of the Utricle in kinetotically swimming Fish: A parabolic Aircraft Flight Study

    Science.gov (United States)

    Baeuerle, A.; Anken, R.; Baumhauer, N.; Hilbig, R.; Rahmann, H.

    Humans taking part in parabolic aircraft flights (PAFs) may suffer from space motion sickness (SMS, a kinetosis). Since it has been repeatedly shown earlier that some fish of a given batch also reveal a kinetotic behaviour during PAFs (especially so-called spinning movements and looping responses), and due to the homology of the vestibular apparatus among all vertebrates, fish can be used as model systems to investigate the origin of susceptibility to motion sickness. Therefore, we examined the utricular maculae (they are responsible for the internalisation of gravity in teleosteans) of fish swimming kinetotically during the μg-phases in the course of PAFs in comparison with animals from the same batch who swam normally. On the light microscopical level, it was found that the total number of both sensory and supporting cells of the utricular maculae did not differ between kinetotic animals as compared to normally swimming fish. Cell density (sensory and supporting cells/100μm -μm), however, was reduced in kinetotic animals (p<0.0001), which seemed to be due to malformed epithelial cells (increase in cell size) of the kinetotic specimens. Susceptibility to kinetoses may therefore originate in asymmetric inner ear otoliths as has been suggested earlier, but also in genetically predispositioned, malformed sensory epithelia. This work was financially supported by the German Aerospace Center (DLR) e.V. (FKZ: 50 WB 9997).

  13. Estimation and control of droplet size and frequency in projected spray mode of a gas metal arc welding (GMAW) process.

    Science.gov (United States)

    Anzehaee, Mohammad Mousavi; Haeri, Mohammad

    2011-07-01

    New estimators are designed based on the modified force balance model to estimate the detaching droplet size, detached droplet size, and mean value of droplet detachment frequency in a gas metal arc welding process. The proper droplet size for the process to be in the projected spray transfer mode is determined based on the modified force balance model and the designed estimators. Finally, the droplet size and the melting rate are controlled using two proportional-integral (PI) controllers to achieve high weld quality by retaining the transfer mode and generating appropriate signals as inputs of the weld geometry control loop. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

  14. Metal–Organic Frameworks (MOFs) as Multivalent Materials: Size Control and Surface Functionalization by Monovalent Capping Ligands

    NARCIS (Netherlands)

    Rijnaarts, Timon; Weinhart-Mejia, R.; Egberink, Richard J.M.; van Roosmalen, W.P.E.; Huskens, Jurriaan

    2015-01-01

    Control over particle size and composition are pivotal to tune the properties of metal organic frameworks (MOFs), for example, for biomedical applications. Particle-size control and functionalization of MIL-88A were achieved by using stoichiometric replacement of a small fraction of the divalent

  15. Excellent endurance of MWCNT anode in micro-sized Microbial Fuel Cell

    KAUST Repository

    Mink, Justine E.

    2012-08-01

    Microbial Fuel Cells (MFCs) are a sustainable technology for energy production using bioelectrochemical reactions from bacteria. Microfabrication of micro-sized MFCs allows rapid and precise production of devices that can be integrated into Lab-on-a-chip or other ultra low power devices. We show a multi-walled carbon nanotubes (MWCNTs) integrated anode in a biocompatible and high power and current producing device. Long term testing of the MWCNT anode also reveals a high endurance and durable anode material that can be adapted as a long-lasting power source. © 2012 IEEE.

  16. High-speed counting and sizing of cells in an impedance flow microcytometer with compact electronic instrumentation

    DEFF Research Database (Denmark)

    Castillo-Fernandez, Oscar; Rodriguez-Trujíllo, Romén; Gomila, Gabriel

    2014-01-01

    Here we describe a high-throughput impedance flow cytometer on a chip. This device was built using compact and inexpensive electronic instrumentation. The system was used to count and size a mixed cell sample containing red blood cells and white blood cells. It demonstrated a counting capacity of...

  17. Soft landing of bare nanoparticles with controlled size, composition, and morphology

    Science.gov (United States)

    Johnson, Grant E.; Colby, Robert; Laskin, Julia

    2015-02-01

    Physical synthesis employing magnetron sputtering and gas aggregation in a modified commercial source has been coupled with size-selection and ion soft landing to prepare bare nanoparticles on surfaces with controlled coverage, size, composition, and morphology. Employing atomic force microscopy (AFM) and scanning electron microscopy (SEM), it is demonstrated that the size and coverage of nanoparticles on flat and stepped surfaces may be controlled using a quadrupole mass filter and the length of deposition, respectively. AFM shows that nanoparticles bind randomly to flat surfaces when soft landed at relatively low coverage (4 × 104 ions μm-2). On stepped surfaces at intermediate coverage (4 × 105 ions μm-2) nanoparticles bind along step edges forming extended linear chains. At the highest coverage (2 × 106 ions μm-2) nanoparticles form a continuous film on flat surfaces. On one surface with sizable defects, the presence of localized imperfections results in agglomeration of nanoparticles onto these features and formation of neighboring zones devoid of particles. Employing high resolution scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) the customized magnetron sputtering/gas aggregation source is demonstrated to produce bare single metal particles with controlled morphology as well as bimetallic alloy nanoparticles with defined core-shell structures of that are of interest to catalysis.Physical synthesis employing magnetron sputtering and gas aggregation in a modified commercial source has been coupled with size-selection and ion soft landing to prepare bare nanoparticles on surfaces with controlled coverage, size, composition, and morphology. Employing atomic force microscopy (AFM) and scanning electron microscopy (SEM), it is demonstrated that the size and coverage of nanoparticles on flat and stepped surfaces may be controlled using a quadrupole mass filter and the length of deposition, respectively. AFM shows

  18. Control of size and density of InAs/(Al,Ga)As self-organized islands

    International Nuclear Information System (INIS)

    Ballet, P.; Smathers, J. B.; Yang, H.; Workman, C. L.; Salamo, G. J.

    2001-01-01

    We report on the influence of the chemical composition of the (Al,Ga)As surface on the formation of strain induced three-dimensional (3D) InAs islands. The experiments have been carried out using a molecular beam epitaxy facility combined with a scanning tunneling microscope enabling in situ surface characterization. The evolution of the density and morphology of these islands is investigated as a function of the Al composition. The InAs deposition, substrate temperature, and annealing time effects on the island formation and morphology are studied. The morphologies of the (Al,Ga)As surface as well as that of the reconstructed InAs 'wetting layer' are also described. Results indicate that there are major differences between the InAs/GaAs and the InAs/AlAs systems despite the same lattice mismatch. We observe these differences varying the aluminum content in the starting (Al,Ga)As surface. We show that control of the Al fraction leads to control of the size and density of the 3D islands. The control of island density and size as well as the growth mode of these islands is explained by considering the difference in surface mobility and cation intermixing between these two systems. Our observation is that strain energy is not the only parameter governing the formation of 3D islands but the chemical nature of the different layers involved is proved to significantly affect island properties. [copyright] 2001 American Institute of Physics

  19. The Effect of Alcohols on Red Blood Cell Mechanical Properties and Membrane Fluidity Depends on Their Molecular Size

    Science.gov (United States)

    Sonmez, Melda; Ince, Huseyin Yavuz; Yalcin, Ozlem; Ajdžanović, Vladimir; Spasojević, Ivan; Meiselman, Herbert J.; Baskurt, Oguz K.

    2013-01-01

    The role of membrane fluidity in determining red blood cell (RBC) deformability has been suggested by a number of studies. The present investigation evaluated alterations of RBC membrane fluidity, deformability and stability in the presence of four linear alcohols (methanol, ethanol, propanol and butanol) using ektacytometry and electron paramagnetic resonance (EPR) spectroscopy. All alcohols had a biphasic effect on deformability such that it increased then decreased with increasing concentration; the critical concentration for reversal was an inverse function of molecular size. EPR results showed biphasic changes of near-surface fluidity (i.e., increase then decrease) and a decreased fluidity of the lipid core; rank order of effectiveness was butanol > propanol > ethanol > methanol, with a significant correlation between near-surface fluidity and deformability (r = 0.697; palcohol enhanced the impairment of RBC deformability caused by subjecting cells to 100 Pa shear stress for 300 s, with significant differences from control being observed at higher concentrations of all four alcohols. The level of hemolysis was dependent on molecular size and concentration, whereas echinocytic shape transformation (i.e., biconcave disc to crenated morphology) was observed only for ethanol and propanol. These results are in accordance with available data obtained on model membranes. They document the presence of mechanical links between RBC deformability and near-surface membrane fluidity, chain length-dependence of the ability of alcohols to alter RBC mechanical behavior, and the biphasic response of RBC deformability and near-surface membrane fluidity to increasing alcohol concentrations. PMID:24086751

  20. Scalable fabrication of size-controlled chitosan nanoparticles for oral delivery of insulin.

    Science.gov (United States)

    He, Zhiyu; Santos, Jose Luis; Tian, Houkuan; Huang, Huahua; Hu, Yizong; Liu, Lixin; Leong, Kam W; Chen, Yongming; Mao, Hai-Quan

    2017-06-01

    Controlled delivery of protein would find diverse therapeutic applications. Formulation of protein nanoparticles by polyelectrolyte complexation between the protein and a natural polymer such as chitosan (CS) is a popular approach. However, the current method of batch-mode mixing faces significant challenges in scaling up while maintaining size control, high uniformity, and high encapsulation efficiency. Here we report a new method, termed flash nanocomplexation (FNC), to fabricate insulin nanoparticles by infusing aqueous solutions of CS, tripolyphosphate (TPP), and insulin under rapid mixing condition (Re > 1600) in a multi-inlet vortex mixer. In comparison with the bulk-mixing method, the optimized FNC process produces CS/TPP/insulin nanoparticles with a smaller size (down to 45 nm) and narrower size distribution, higher encapsulation efficiency (up to 90%), and pH-dependent nanoparticle dissolution and insulin release. The CS/TPP/insulin nanoparticles can be lyophilized and reconstituted without loss of activity, and produced at a throughput of 5.1 g h -1 when a flow rate of 50 mL min -1 is used. Evaluated in a Type I diabetes rat model, the smaller nanoparticles (45 nm and 115 nm) control the blood glucose level through oral administration more effectively than the larger particles (240 nm). This efficient, reproducible and continuous FNC technique is amenable to scale-up in order to address the critical barrier of manufacturing for the translation of protein nanoparticles. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. A Cell-Enriched Engineered Myocardial Graft Limits Infarct Size and Improves Cardiac Function

    Directory of Open Access Journals (Sweden)

    Isaac Perea-Gil, MS

    2016-08-01

    Full Text Available Myocardial infarction (MI remains a dreadful disease around the world, causing irreversible sequelae that shorten life expectancy and reduce quality of life despite current treatment. Here, the authors engineered a cell-enriched myocardial graft, composed of a decellularized myocardial matrix refilled with adipose tissue-derived progenitor cells (EMG-ATDPC. Once applied over the infarcted area in the swine MI model, the EMG-ATDPC improved cardiac function, reduced infarct size, attenuated fibrosis progression, and promoted neovascularization of the ischemic myocardium. The beneficial effects exerted by the EMG-ATDPC and the absence of identified adverse side effects should facilitate its clinical translation as a novel MI therapy in humans.

  2. The Functionalization, Size Control and Properties of Metal-Organic Frameworks

    DEFF Research Database (Denmark)

    Xu, Hui; Iversen, Bo Brummerstedt

    Recent years, Metal-Organic Framework (MOF) materials have drawn great attentions due to their potential applications in gas sorption/separation and luminescent sensing. In this dissertation, the recent progress of MOF materials is reviewed, with specific focus on the functionalization, size...... control and properties of MOF materials. A cationic MOF material was synthesized, and small hydrocarbons C1/C2 sorption/separation properties were studied. A MOF with both open metal sites and Lewis basic pyridyl sites was developed, and C2H2, CO2 and CH4 gas sorption/separation properties were explored...

  3. Comparative analysis of non-destructive methods to control fissile materials in large-size containers

    Directory of Open Access Journals (Sweden)

    Batyaev V.F.

    2017-01-01

    Full Text Available The analysis of various non-destructive methods to control fissile materials (FM in large-size containers filled with radioactive waste (RAW has been carried out. The difficulty of applying passive gamma-neutron monitoring FM in large containers filled with concreted RAW is shown. Selection of an active non-destructive assay technique depends on the container contents; and in case of a concrete or iron matrix with very low activity and low activity RAW the neutron radiation method appears to be more preferable as compared with the photonuclear one.

  4. Quality control of radiopharmaceuticals with HPLC using aqueous size exclusion spherogel column

    International Nuclear Information System (INIS)

    Vallabhajosula, S.; Goldsmith, S.J.; Lipszyc, H.

    1982-01-01

    The application of HPLC for the analysis and quality control of 99 Tc-radiopharmaceuticals, using a weakly basic anion exchange column, has been reported. This HPLC method for the separation of the components is based on molecular size. 99 Tc-MDP, 99 Tc-HDP and 99 Tc-DTPA were analysed and UV absorption studies carried out on the components. Components of the 99 Tc-MDP separation were injected into rabbits and renal excretion and serial images studied. (U.K.)

  5. RETRACTED ARTICLE: Cu2ZnSnSe4 quantum dots with controllable size and quantum confinement effect

    Science.gov (United States)

    Zong, Kai; Lu, SiHeng; Wang, Hao; Sun, YuXiu; Liu, JingBing; Yan, Hui

    2013-09-01

    Cu2ZnSnSe4 quantum dots (QDs) with controllable sizes have been synthesized via a hot-injection method. The diameters of the QDs range from 3.2 to 10.1 nm with the tunable band gap from 1.27 to 1.54 eV by adjusting the reaction temperatures from 180 to 240 °C. Structural and Raman scattering data confirm that Cu2ZnSnSe4 is obtained without other secondary phases. The band gaps of the QDs with diameters less than 4.6 nm show an obvious blue shift to higher energy due to quantum confinement effect. It indicates that the Cu2ZnSnSe4 QDs can be a potential candidate for quantum-dot-sensitized solar cells in the future.

  6. JNK1 Controls Dendritic Field Size in L2/3 and L5 of the Motor Cortex, Constrains Soma Size and Influences Fine Motor Coordination

    Directory of Open Access Journals (Sweden)

    Emilia eKomulainen

    2014-09-01

    Full Text Available Genetic anomalies on the JNK pathway confer susceptibility to autism spectrum disorders, schizophrenia and intellectual disability. The mechanism whereby a gain or loss of function in JNK signaling predisposes to these prevalent dendrite disorders, with associated motor dysfunction, remains unclear. Here we find that JNK1 regulates the dendritic field of L2/3 and L5 pyramidal neurons of the mouse motor cortex (M1, the main excitatory pathway controlling voluntary movement. In Jnk1-/- mice, basal dendrite branching of L5 pyramidal neurons is increased in M1, as is cell soma size, whereas in L2/3, dendritic arborization is decreased. We show that JNK1 phosphorylates rat HMW-MAP2 on T1619, T1622 and T1625 (Uniprot P15146 corresponding to mouse T1617, T1620, T1623, to create a binding motif, that is critical for MAP2 interaction with and stabilization of microtubules, and dendrite growth control. Targeted expression in M1 of GFP-HMW-MAP2 that is pseudo-phosphorylated on T1619, T1622 and T1625 increases dendrite complexity in L2/3 indicating that JNK1 phosphorylation of HMW-MAP2 regulates the dendritic field. Consistent with the morphological changes observed in L2/3 and L5, Jnk1-/- mice exhibit deficits in limb placement and motor coordination, while stride length is reduced in older animals. In summary, JNK1 phosphorylates HMW-MAP2 to increase its stabilization of microtubules while at the same time controlling dendritic fields in the main excitatory pathway of M1. Moreover, JNK1 contributes to normal functioning of fine motor coordination. We report for the first time, a quantitative sholl analysis of dendrite architecture, and of motor behavior in Jnk1-/- mice. Our results illustrate the molecular and behavioral consequences of interrupted JNK1 signaling and provide new ground for mechanistic understanding of those prevalent neuropyschiatric disorders where genetic disruption of the JNK pathway is central.

  7. Uniform TiO2 nanoparticles induce apoptosis in epithelial cell lines in a size-dependent manner.

    Science.gov (United States)

    Sun, Qingqing; Ishii, Takayuki; Kanehira, Koki; Sato, Takeshi; Taniguchi, Akiyoshi

    2017-05-02

    The size of titanium dioxide (TiO 2 ) nanoparticles is a vital parameter that determines their cytotoxicity. However, most reported studies have employed irregular shapes and sizes of TiO 2 nanoparticles, as it is difficult to produce nanoparticles of suitable sizes for research. We produced good model TiO 2 nanoparticles of uniform shape and size for use in studying their cytotoxicity. In this work, spherical, uniform polyethylene glycol-modified TiO 2 (TiO 2 -PEG) nanoparticles of differing sizes (100, 200, and 300 nm) were prepared using the sol-gel method. A size-dependent decrease in cell viability was observed with increasing nanoparticle size. Furthermore, apoptosis was found to be positively associated with nanoparticle size, as evidenced by an increase in caspase-3 activity with increasing nanoparticle size. Larger nanoparticles exhibited higher cellular uptake, suggesting that larger nanoparticles more strongly induce apoptosis. In addition, the cellular uptake of different sizes of nanoparticles was energy dependent, suggesting that there are size-dependent uptake pathways. We found that 100 and 200 nm (but not 300 nm) nanoparticles were taken up via clathrin-mediated endocytosis. These results utilizing uniform nanoparticles suggest that the size-dependent cytotoxicity of nanoparticles involves active cellular uptake, caspase-3 activation, and apoptosis in the epithelial cell line (NCI-H292). These findings will hopefully aid in the future design and safe use of nanoparticles.

  8. Fast and Near-Optimal Timing-Driven Cell Sizing under Cell Area and Leakage Power Constraints Using a Simplified Discrete Network Flow Algorithm

    Directory of Open Access Journals (Sweden)

    Huan Ren

    2013-01-01

    Full Text Available We propose a timing-driven discrete cell-sizing algorithm that can address total cell size and/or leakage power constraints. We model cell sizing as a “discretized” mincost network flow problem, wherein available sizes of each cell are modeled as nodes. Flow passing through a node indicates the choice of the corresponding cell size, and the total flow cost reflects the timing objective function value corresponding to these choices. Compared to other discrete optimization methods for cell sizing, our method can obtain near-optimal solutions in a time-efficient manner. We tested our algorithm on ISCAS’85 benchmarks, and compared our results to those produced by an optimal dynamic programming- (DP- based method. The results show that compared to the optimal method, the improvements to an initial sizing solution obtained by our method is only 1% (3% worse when using a 180 nm (90 nm library, while being 40–60 times faster. We also obtained results for ISPD’12 cell-sizing benchmarks, under leakage power constraint, and compared them to those of a state-of-the-art approximate DP method (optimal DP runs out of memory for the smallest of these circuits. Our results show that we are only 0.9% worse than the approximate DP method, while being more than twice as fast.

  9. TELICS—A Telescope Instrument Control System for Small/Medium Sized Astronomical Observatories

    Science.gov (United States)

    Srivastava, Mudit K.; Ramaprakash, A. N.; Burse, Mahesh P.; Chordia, Pravin A.; Chillal, Kalpesh S.; Mestry, Vilas B.; Das, Hillol K.; Kohok, Abhay A.

    2009-10-01

    For any modern astronomical observatory, it is essential to have an efficient interface between the telescope and its back-end instruments. However, for small and medium-sized observatories, this requirement is often limited by tight financial constraints. Therefore a simple yet versatile and low-cost control system is required for such observatories to minimize cost and effort. Here we report the development of a modern, multipurpose instrument control system TELICS (Telescope Instrument Control System) to integrate the controls of various instruments and devices mounted on the telescope. TELICS consists of an embedded hardware unit known as a common control unit (CCU) in combination with Linux-based data acquisition and user interface. The hardware of the CCU is built around the ATmega 128 microcontroller (Atmel Corp.) and is designed with a backplane, master-slave architecture. A Qt-based graphical user interface (GUI) has been developed and the back-end application software is based on C/C++. TELICS provides feedback mechanisms that give the operator good visibility and a quick-look display of the status and modes of instruments as well as data. TELICS has been used for regular science observations since 2008 March on the 2 m, f/10 IUCAA Telescope located at Girawali in Pune, India.

  10. The CTA medium size telescope prototype, a test bench for the array control software

    Energy Technology Data Exchange (ETDEWEB)

    Birsin, Emrah; Oya, Igor; Schwanke, Ullrich [Institut fuer Physik, Humboldt-Universitaet zu Berlin (Germany); Behera, Bagmeet; Koeppel, Hendryk; Melkumyan, David; Schmidt, Torsten; Wegner, Peter; Wiesand, Stephan; Winde, Michael [Deutsches Elektronen-Synchrotron, DESY, Zeuthen (Germany)

    2012-07-01

    CTA (Cherenkov Telescope Array) will be the largest ground-based gamma-ray observatory ever built. Two arrays are foreseen to be build, one in the Southern and one in the Northern hemisphere. A prototype for the Medium Size Telescope (MST) type (diameter: 12 m) will be installed in Berlin in early 2012. This MST prototype will be composed of the mechanical structure, drive system and mirror facets with an active mirror control system. The stability of the mechanical structure will be investigated with CCD cameras and a weather station. Furthermore the ALMA Common Software (ACS) distributed control framework will used as readout and control system for the MST, allowing to evaluate the software with the future use for the whole CTA array in mind. The design of the control software is following the concepts and tools under evaluation within the CTA consortium, like the use of a UML based code generation framework for ACS component modeling, and the use of OPC Unified Architecture (OPC UA) for hardware access. In this contribution the progress in the implementation of the control system for this CTA prototype telescope is described.

  11. Cell size dependence of additive versus synergetic effects of UV radiation and PAHs on oceanic phytoplankton

    International Nuclear Information System (INIS)

    Echeveste, Pedro; Agusti, Susana; Dachs, Jordi

    2011-01-01

    Polycyclic Aromatic Hydrocarbons' (PAHs) toxicity is enhanced by the presence of ultraviolet radiation (UVR), which levels have arisen due to the thinning of the ozone layer. In this study, PAHs' phototoxicity for natural marine phytoplankton was tested. Different concentrations of a mixture of 16 PAHs were added to natural phytoplankton communities from the Mediterranean Sea, Atlantic, Arctic and Southern Oceans and exposed to natural sunlight received in situ, including treatments where the UVR bands were removed. PAHs' toxicity was observed for all the phytoplankton groups studied in all the waters and treatments tested, but only for the pico-sized group a synergetic effect of the mixture and UVR was observed (p = 0.009). When comparing phototoxicity in phytoplankton from oligotrophic and eutrophic waters, synergy was only observed at the oligotrophic communities (p = 0.02) where pico-sized phytoplankton dominated. The degree of sensitivity was related to the trophic degree, decreasing as Chlorophyll a concentration increased. - Highlights: → The smallest picocyanobacteria were the most sensitive to PAHs and UVR. → PAHs-UVR synergism for the picophytoplankton and the oligotrophic communities. → PAHs-UVR additivity for the nanophytoplankton and the eutrophic communities. → An irradiance threshold is suggested to determine the joint action of UVR and PAHs. - Cell size and UVR levels determine additive/synergetic effects of PAHs and UVR to oceanic phytoplankton.

  12. Cell size dependence of additive versus synergetic effects of UV radiation and PAHs on oceanic phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Echeveste, Pedro, E-mail: pecheveste@imedea.uib-csic.es [Department of Global Change Research, IMEDEA (CSIC-UIB) Instituto Mediterraneo de Estudios Avanzados, Miquel Marques 21, 07190 Esporles, Illes Balears (Spain); Agusti, Susana [Department of Global Change Research, IMEDEA (CSIC-UIB) Instituto Mediterraneo de Estudios Avanzados, Miquel Marques 21, 07190 Esporles, Illes Balears (Spain); Dachs, Jordi [Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research, IDAEA-CSIC, Barcelona, Catalunya (Spain)

    2011-05-15

    Polycyclic Aromatic Hydrocarbons' (PAHs) toxicity is enhanced by the presence of ultraviolet radiation (UVR), which levels have arisen due to the thinning of the ozone layer. In this study, PAHs' phototoxicity for natural marine phytoplankton was tested. Different concentrations of a mixture of 16 PAHs were added to natural phytoplankton communities from the Mediterranean Sea, Atlantic, Arctic and Southern Oceans and exposed to natural sunlight received in situ, including treatments where the UVR bands were removed. PAHs' toxicity was observed for all the phytoplankton groups studied in all the waters and treatments tested, but only for the pico-sized group a synergetic effect of the mixture and UVR was observed (p = 0.009). When comparing phototoxicity in phytoplankton from oligotrophic and eutrophic waters, synergy was only observed at the oligotrophic communities (p = 0.02) where pico-sized phytoplankton dominated. The degree of sensitivity was related to the trophic degree, decreasing as Chlorophyll a concentration increased. - Highlights: > The smallest picocyanobacteria were the most sensitive to PAHs and UVR. > PAHs-UVR synergism for the picophytoplankton and the oligotrophic communities. > PAHs-UVR additivity for the nanophytoplankton and the eutrophic communities. > An irradiance threshold is suggested to determine the joint action of UVR and PAHs. - Cell size and UVR levels determine additive/synergetic effects of PAHs and UVR to oceanic phytoplankton.

  13. Grain size controls on sediment supply from debris-mantled dryland hillslopes

    Science.gov (United States)

    Michaelides, K.

    2011-12-01

    characteristics, determine sediment transport dynamics and net flux, GSD supplied to the slope base and the changes in GSD on the hillslope. The results show a strong control of initial hillslope GSD on flux characteristics: (1) GSD controls the degree of non-linearity in the relationship between sediment flux and hillslope gradient. (2) Grain size uniformity controls the degree and form of non-linearity in the relationship between sediment flux and gradient. (3) Over multiple runoff events, slopes coarsen - steeper slopes become coarser than shallow slopes. For individual events, changes in GSD on the slope depend on the magnitude and duration of the runoff event and can result in variable coarsening and fining on different parts of the slope. (4) The GSD of sediment delivered to the slope base is dependent on the hillslope GSD and the hillslope attributes and runoff characteristics. For most runoff events, the GSD of fluxed sediment is finer than the hillslope GSD except for extreme runoff events on very steep slopes with intermediate GSD (not extremely coarse). These findings provide insights into hillslope responses to climatic forcing and have theoretical implications for modeling hillslope evolution in drylands.

  14. How to control chaotic behaviour and population size with proportional feedback

    International Nuclear Information System (INIS)

    Liz, Eduardo

    2010-01-01

    We study the control of chaos in one-dimensional discrete maps as they often occur in modelling population dynamics. For managing the population, we seek to suppress any possible chaotic behavior, leading the system to a stable equilibrium. In this Letter, we make a rigorous analysis of the proportional feedback method under certain conditions fulfilled by a wide family of maps. We show that it is possible to stabilize the chaotic dynamics towards a globally stable positive equilibrium, that can be chosen among a broad range of possible values. In particular, the size of the population can be enhanced by control in form of population reduction. This paradoxical phenomenon is known as the hydra effect, and it has important implications in the design of strategies in such areas as fishing, pest management, and conservation biology.

  15. Fabrication and characterization of size-controlled starch-based nanoparticles as hydrophobic drug carriers.

    Science.gov (United States)

    Han, Fei; Gao, Chunmei; Liu, Mingzhu

    2013-10-01

    Acetylated corn starch was successfully synthesized and optimized by the reaction of native corn starch with acetic anhydride and acetic acid in the presence of sulfuric acid as a catalyst. The optimal degree of substitution of 2.85 was obtained. Starch-based nanoparticles were fabricated by a simple and novel nanoprecipitation procedure, by the dropwise addition of water to acetone solution of acetylated starch under stirring. Fourier transform infrared spectrometry showed that acetylated starch had some new bands at 1750, 1375 and 1240 cm(-1) while acetylated starch nanoparticles presented the identical peaks as the drug-loaded acetylated starch nanoparticles and the acetylated starch. Wide angle X-ray diffraction indicated that A-type pattern of native starch was completely transformed into the V-type pattern of Acetylated starch and starch-based nanoparticles show the similar type pattern with the acetylated starch. The scanning electron microscopy showed that the different sizes of pores formed on the acetylated starch granules were utterly converted into the uniform-sized spherical nanoparticles after the nanoprecipitation. The encapsulation efficiency and diameter of nanoparticle can be adjusted by the degree of substitution, the volume ratio of nonsolvent to solvent and the weight ratio of acetylated starch to drug. It was also depicted that the release behaviors of drug-loaded nanoparticles depend on the size of nanoparticles and the degree of substitution of the acetylated starch. Release studies prove that the starch-based nanoparticles with uniform size can be used for the encapsulation of hydrophobic drug and attained the sustained and controllable drug release carriers.

  16. Epigenetic control of cell identity and plasticity

    KAUST Repository

    Orlando, Valerio

    2014-04-02

    The DNA centered dogma for genetic information and cell identity is now evolving into a much more complex and flexible dimension provided by the discovery of the Epigenome. This comprises those chromosome structural and topological components that complement DNA information and contribute to genome functional organization. Current concept is that the Epigenome constitutes the dynamic molecular interface allowing the Genome to interact with the Environment. Exploring how the genome interacts with the environment is a key to fully understand cellular and complex organism mechanisms of adaptation and plasticity. Our work focuses on the role of an essential, specialized group or chromatin associated proteins named Polycomb (PcG) that control maintenance of transcription programs during development and in adult life. In particular PcG proteins exert epigenetic “memory” function by modifying chromosome structures at various levels to maintain gene silencing in particular through cell division. While in the past decade substantial progress was made in understanding PcG mechanisms acting in development and partially during cell cycle, very little is known about their role in adult post-mitotic tissues and more in general the role of the epigenome in adaptation. To this, we studied the role of PcG in the context of mammalian skeletal muscle cell differentiation. We previously reported specific dynamics of PRC2 proteins in myoblasts and myotubes, in particular the dynamics of PcG Histone H3 K27 Methyl Transferases (HMT), EZH2 and EZH1, the latter apparently replacing for EZH2 in differentiated myotubes. Ezh1 protein, although almost identical to Ezh2, shows a weak H3K27 HMT activity and its primary function remains elusive. Recent ChIPseq studies performed in differentiating muscle cells revealed that Ezh1 associates with active and not repressed regulatory regions to control RNA pol II elongation. Since H3K27 tri-methylation levels are virtually steady in non

  17. Implication of oxidative stress in size-dependent toxicity of silica nanoparticles in kidney cells

    International Nuclear Information System (INIS)

    Passagne, Isabelle; Morille, Marie; Rousset, Marine; Pujalté, Igor; L’Azou, Béatrice

    2012-01-01

    Silica nanoparticles (nano-SiO 2 ) are one of the most popular nanomaterials used in industrial manufacturing, synthesis, engineering and medicine. While inhalation of nanoparticles causes pulmonary damage, nano-SiO 2 can be transported into the blood and deposit in target organs where they exert potential toxic effects. Kidney is considered as such a secondary target organ. However, toxicological information of their effect on renal cells and the mechanisms involved remain sparse. In the present study, the cytotoxicity of nano-SiO 2 of different sizes was investigated on two renal proximal tubular cell lines (human HK-2 and porcine LLC-PK 1 ). The molecular pathways involved were studied with a focus on the involvement of oxidative stress. Nanoparticle characterization was performed (primary nanoparticle size, surface area, dispersion) in order to investigate a potential relationship between their physical properties and their toxic effects. Firstly, evidence of particle internalization was obtained by transmission electron microscopy and conventional flux cytometry techniques. The use of specific inhibitors of endocytosis pathways showed an internalization process by macropinocytosis and clathrin-mediated endocytosis for 100 nm nano-SiO 2 nanoparticles. These nanoparticles were localized in vesicles. Toxicity was size- and time-dependent (24 h, 48 h, 72 h). Indeed, it increased as nanoparticles became smaller. Secondly, analysis of oxidative stress based on the assessment of ROS (reactive oxygen species) production (DHE, dihydroethidium) or lipid peroxidation (MDA, malondialdehyde) clearly demonstrated the involvement of oxidative stress in the toxicity of 20 nm nano-SiO 2 . The induction of antioxidant enzymes (catalase, GSTpi, thioredoxin reductase) could explain their lesser toxicity with 100 nm nano-SiO 2 .

  18. Determining peptide sequence effects that control the size, structure, and function of nanoparticles.

    Science.gov (United States)

    Coppage, Ryan; Slocik, Joseph M; Briggs, Beverly D; Frenkel, Anatoly I; Naik, Rajesh R; Knecht, Marc R

    2012-02-28

    The ability to tune the size, shape, and composition of nanomaterials at length scales particle morphology through controlling the biotic/abiotic interface. Here we demonstrate the ability to finely tune the size, surface structure, and functionality of single-crystal Pd nanoparticles between 2 and 3 nm using materials directing peptides. This was achieved by selectively altering the peptide sequence to change the binding motif, which in turn modifies the surface structure of the particles. The materials were fully characterized before and after reduction using atomically resolved spectroscopic and microscopic analyses, which indicated that the coordination environment prior to reduction significantly affects the structure of the final nanoparticles. Additionally, changes to the particle surface structure, as a function of peptide sequence, can allow for chloride ion coordination that alters the catalytic abilities of the materials for the C-C coupling Stille reaction. These results suggest that peptide-based approaches may be able to achieve control over the structure/function relationship of nanomaterials where the peptide sequence could be used to selectivity tune such capabilities.

  19. Size Controlled CaF2 Nanocubes and Their Dosimetric Properties Using Photoluminescence Technique

    Directory of Open Access Journals (Sweden)

    Najlaa D. Alharbi

    2015-01-01

    Full Text Available A new synthetic chemical coprecipitation route for the preparation of well-crystallized size controlled nano- and microcrystalline cubes of CaF2 is reported. Crystalline cubes in the range of 2 μm–20 nm could be synthesized and their sizes were controlled by varying the solvent : cosolvent ratio. The as-synthesized CaF2 nanocubes were characterized by different techniques. Photoluminescence (PL emission spectrum of CaF2 nanocrystalline powder showed strong emission band at 415 nm. Moreover, the effect of Eu as a dopant on the emission spectrum of CaF2 was investigated. This dopant was found to get incorporated in its Eu2+ and Eu3+ forms. The as-produced nanocubes were exposed to UV irradiation and the corresponding PL emission was studied. Excellent results are obtained, where CaF2:Eu nanocubes were found to be highly sensitive and might be suitable for esteeming the doses of UV irradiation using the PL technique.

  20. Anodic aluminum oxide with fine pore size control for selective and effective particulate matter filtering

    Science.gov (United States)

    Zhang, Su; Wang, Yang; Tan, Yingling; Zhu, Jianfeng; Liu, Kai; Zhu, Jia

    2016-07-01

    Air pollution is widely considered as one of the most pressing environmental health issues. Particularly, atmospheric particulate matters (PM), a complex mixture of solid or liquid matter suspended in the atmosphere, are a harmful form of air pollution due to its ability to penetrate deep into the lungs and blood streams, causing permanent damages such as DNA mutations and premature death. Therefore, porous materials which can effectively filter out particulate matters are highly desirable. Here, for the first time, we demonstrate that anodic aluminum oxide with fine pore size control fabricated through a scalable process can serve as effective and selective filtering materials for different types of particulate matters (such as PM2.5, PM10). Combining selective and dramatic filtering effect, fine pore size control and a scalable process, this type of anodic aluminum oxide templates can potentially serve as a novel selective filter for different kinds of particulate matters, and a promising and complementary solution to tackle this serious environmental issue.

  1. Designing artificial 2D crystals with site and size controlled quantum dots.

    Science.gov (United States)

    Xie, Xuejun; Kang, Jiahao; Cao, Wei; Chu, Jae Hwan; Gong, Yongji; Ajayan, Pulickel M; Banerjee, Kaustav

    2017-08-30

    Ordered arrays of quantum dots in two-dimensional (2D) materials would make promising optical materials, but their assembly could prove challenging. Here we demonstrate a scalable, site and size controlled fabrication of quantum dots in monolayer molybdenum disulfide (MoS 2 ), and quantum dot arrays with nanometer-scale spatial density by focused electron beam irradiation induced local 2H to 1T phase change in MoS 2 . By designing the quantum dots in a 2D superlattice, we show that new energy bands form where the new band gap can be controlled by the size and pitch of the quantum dots in the superlattice. The band gap can be tuned from 1.81 eV to 1.42 eV without loss of its photoluminescence performance, which provides new directions for fabricating lasers with designed wavelengths. Our work constitutes a photoresist-free, top-down method to create large-area quantum dot arrays with nanometer-scale spatial density that allow the quantum dots to interfere with each other and create artificial crystals. This technique opens up new pathways for fabricating light emitting devices with 2D materials at desired wavelengths. This demonstration can also enable the assembly of large scale quantum information systems and open up new avenues for the design of artificial 2D materials.

  2. Cell-cycle control by protein kinase B

    NARCIS (Netherlands)

    Kops, G.J.P.L.

    2001-01-01

    Numerous cells in the body divide, and do so in a well-controlled manner. In some situations where this control is deregulated, cells may divide continuously. Such uncontrolled proliferation of cells is thought to be responsible for the onset of cancer. In order for a cell to divide in a normal

  3. P27 in cell cycle control and cancer

    DEFF Research Database (Denmark)

    Møller, Michael Boe

    2000-01-01

    In order to survive, cells need tight control of cell cycle progression. The control mechanisms are often lost in human cancer cells. The cell cycle is driven forward by cyclin-dependent kinases (CDKs). The CDK inhibitors (CKIs) are important regulators of the CDKs. As the name implies, CKIs were...

  4. ALFY-Controlled DVL3 Autophagy Regulates Wnt Signaling, Determining Human Brain Size.

    Directory of Open Access Journals (Sweden)

    Rotem Kadir

    2016-03-01

    Full Text Available Primary microcephaly is a congenital neurodevelopmental disorder of reduced head circumference and brain volume, with fewer neurons in the cortex of the developing brain due to premature transition between symmetrical and asymmetrical cellular division of the neuronal stem cell layer during neurogenesis. We now show through linkage analysis and whole exome sequencing, that a dominant mutation in ALFY, encoding an autophagy scaffold protein, causes human primary microcephaly. We demonstrate the dominant effect of the mutation in drosophila: transgenic flies harboring the human mutant allele display small brain volume, recapitulating the disease phenotype. Moreover, eye-specific expression of human mutant ALFY causes rough eye phenotype. In molecular terms, we demonstrate that normally ALFY attenuates the canonical Wnt signaling pathway via autophagy-dependent removal specifically of aggregates of DVL3 and not of Dvl1 or Dvl2. Thus, autophagic attenuation of Wnt signaling through removal of Dvl3 aggregates by ALFY acts in determining human brain size.

  5. Ebf1 controls early cell differentiation in the embryonic striatum.

    Science.gov (United States)

    Garel, S; Marín, F; Grosschedl, R; Charnay, P

    1999-12-01

    Ebf1/Olf-1 belongs to a small multigene family encoding closely related helix-loop-helix transcription factors, which have been proposed to play a role in neuronal differentiation. Here we show that Ebf1 controls cell differentiation in the murine embryonic striatum, where it is the only gene of the family to be expressed. Ebf1 targeted disruption affects postmitotic cells that leave the subventricular zone (SVZ) en route to the mantle: they appear to be unable to downregulate genes normally restricted to the SVZ or to activate some mantle-specific genes. These downstream genes encode a variety of regulatory proteins including transcription factors and proteins involved in retinoid signalling as well as adhesion/guidance molecules. These early defects in the SVZ/mantle transition are followed by an increase in cell death, a dramatic reduction in size of the postnatal striatum and defects in navigation and fasciculation of thalamocortical fibres travelling through the striatum. Our data therefore show that Ebf1 plays an essential role in the acquisition of mantle cell molecular identity in the developing striatum and provide information on the genetic hierarchies that govern neuronal differentiation in the ventral telencephalon.

  6. Evaluation of a method to measure HHV-6B infection in vitro based on cell size.

    Science.gov (United States)

    Becerra-Artiles, Aniuska; Santoro, Tessa; Stern, Lawrence J

    2018-01-05

    Human herpesvirus 6 (HHV-6A and HHV-6B) infection of cell cultures can be measured by different methods, including immunofluorescence microscopy, flow cytometry, or quantification of virus DNA by qPCR. These methods are reliable and sensitive but require long processing times and can be costly. Another method used in the field relies on the identification of enlarged cells in the culture; this method requires little sample processing and is relatively fast. However, visual inspection of cell cultures can be subjective and it can be difficult to establish clear criteria to decide if a cell is enlarged. To overcome these issues, we explored a method to monitor HHV-6B infections based on the systematic and objective measurement of the size of cells using an imaging-based automated cell counter. The size of cells in non-infected and HHV-6B-infected cultures was measured at different times post-infection. The relatively narrow size distribution observed for non-infected cultures contrasted with the broader distributions observed in infected cultures. The average size of cultures shifted towards higher values after infection, and the differences were significant for cultures infected with relatively high doses of virus and/or screened at longer times post-infection. Correlation analysis showed that the trend observed for average size was similar to the trend observed for two other methods to measure infection: amount of virus DNA in supernatant and the percentage of cells expressing a viral antigen. In order to determine the performance of the size-based method in differentiating non-infected and infected cells, receiver operating characteristic (ROC) curves were used to analyze the data. Analysis using size of individual cells showed a moderate performance in detecting infected cells (area under the curve (AUC) ~ 0.80-0.87), while analysis using the average size of cells showed a very good performance in detecting infected cultures (AUC ~ 0.99). The size

  7. Preparation and formation mechanisms of metallic particles with controlled size, shape, structure and surface functionality

    Science.gov (United States)

    Lu, Lu

    Due to their excellent conductivity and chemical stability, particles of silver (Ag), gold (Au), copper (Cu) and their alloys are widely used in the electronic industry. Other unique properties extend their uses to the biomedical, optical and catalysis fields. All of these applications rely on particles with well controlled size, morphology, structure, and surface properties. Chemical precipitation from homogeneous solutions was selected as the synthetic route for the investigations described in this work. Based on the evaluation of key process parameters (temperature, reactant concentrations, reactant addition rate, mixing, etc.) the general formation mechanisms of metallic particles in various selected precipitation systems were investigated and elucidated. Five different systems for preparing particles with controlled size, morphology, structure and surface functionality are discussed. The first system involves the precipitation of Ag nanoparticles with spherical and anisotropic (platy or fiber-like) morphology. It will be shown that the formation of a stable Ag/Daxad complex has a significant impact on the reaction kinetics, and that the chromonic properties of Daxad molecules are responsible for the particle anisotropy. In the second system, Au-Ag core-shell nanoparticles were prepared in aqueous solution by a two-step precipitation process. The optical properties of these particles can be tailored by varying the thickness of the Ag shell. It was also determined that the stability of the bimetallic metallic sols depends on the Cl-ion concentration in solution. The third system discussed deals with preparation by the polyol process of well dispersed Cu nanospheres with high crystallinity and excellent oxidation resistance. We show that the heterogeneous nucleation (seeding) approach has significant merit in controlling particle size and uniformity. The functionalization of Au nanoparticle surfaces with glutathione molecules is discussed in the next section. The

  8. Improved Light Conversion Efficiency Of Dye-Sensitized Solar Cell By Dispersing Submicron-Sized Granules Into The Nano-Sized TiO2 Layer

    Directory of Open Access Journals (Sweden)

    Song S.A.

    2015-06-01

    Full Text Available In this work, TiO2 nanoparticles and submicron-sized granules were synthesized by a hydrothermal method and spray pyrolysis, respectively. Submicron-sized granules were dispersed into the nano-sized TiO2 layer to improve the light conversion efficiency. Granules showed better light scattering, but lower in terms of the dye-loading quantity and recombination resistance compared with nanoparticles. Consequently, the nano-sized TiO2 layer had higher cell efficiency than the granulized TiO2 layer. When dispersed granules into the nanoparticle layer, the light scattering was enhanced without the loss of dye-loading quantities. The dispersion of granulized TiO2 led to increase the cell efficiency up to 6.51%, which was about 5.2 % higher than that of the electrode consisting of only TiO2 nanoparticles. Finally, the optimal hydrothermal temperature and dispersing quantity of granules were found to be 200°C and 20 wt%, respectively.

  9. Comparative effects of macro-sized aluminum oxide and aluminum oxide nanoparticles on erythrocyte hemolysis: influence of cell source, temperature, and size

    Energy Technology Data Exchange (ETDEWEB)

    Vinardell, M. P., E-mail: mpvinardellmh@ub.edu; Sordé, A. [Universitat de Barcelona, Departament de Fisiologia, Facultat de Farmàcia (Spain); Díaz, J. [Universitat de Barcelona CCiT, Scientific and Technological Centers (Spain); Baccarin, T.; Mitjans, M. [Universitat de Barcelona, Departament de Fisiologia, Facultat de Farmàcia (Spain)

    2015-02-15

    Al{sub 2}O{sub 3} is the most abundantly produced nanomaterial and has been used in diverse fields, including the medical, military, and industrial sectors. As there are concerns about the health effects of nanoparticles, it is important to understand how they interact with cells, and specifically with red blood cells. The hemolysis induced by three commercial nano-sized aluminum oxide particles (nanopowder 13 nm, nanopowder <50 nm, and nanowire 2–6 × 200–400 nm) was compared to aluminum oxide and has been studied on erythrocytes from humans, rats, and rabbits, in order to elucidate the mechanism of action and the influence of size and shape on hemolytic behavior. The concentrations inducing 50 % hemolysis (HC{sub 50}) were calculated for each compound studied. The most hemolytic aluminum oxide particles were of nanopowder 13, followed by nanowire and nanopowder 50. The addition of albumin to PBS induced a protective effect on hemolysis in all the nano-forms of Al{sub 2}O{sub 3}, but not on Al{sub 2}O{sub 3}. The drop in HC{sub 50} correlated to a decrease in nanomaterial size, which was induced by a reduction of aggregation. Aluminum oxide nanoparticles are less hemolytic than other oxide nanoparticles and behave differently depending on the size and shape of the nanoparticles. The hemolytic behavior of aluminum oxide nanoparticles differs from that of aluminum oxide.

  10. Renal Epithelial Cell Injury Induced by Calcium Oxalate Monohydrate Depends on their Structural Features: Size, Surface, and Crystalline Structure.

    Science.gov (United States)

    Sun, Xin-Yuan; Ouyang, Jian-Ming; Gan, Qiong-Zhi; Liu, Ai-Jie

    2016-11-01

    Urinary crystals in normal and kidney stone patients often differ in crystal sizes and surface structures, but the effects of different crystal properties on renal tubular epithelial cells remain unclear. This study aimed to compare the cytotoxicity of micron/nano-calcium oxalate monohydrate (COM) crystals with sizes of 50 nm, 200 nm, 1 μm, 3 μm, and 10 μm to African green monkey renal epithelial (Vero) cells, to reveal the effect of crystal size and surface structure on cell injury, and to investigate the pathological mechanism of calcium oxalate kidney stones. Cell viability, cellular biochemical parameters, and internalized crystal amount in Vero cells were closely associated with the size of COM crystals. At the same concentration (200 μg/mL), COM-1 μm induced the most serious injury to Vero cells and caused the most significant change to cellular biochemical parameters, which were related to the specific porous structure and highest internalized amount in Vero cells. By contrast, COM-50 nm and COM-200 nm crystals lost their small size effect because of serious aggregation and weakened their toxicity to cells. COM-3 μm and COM-10 μm crystals were too large for cells to completely internalize; these crystals also exhibited a low specific surface area and thus weakened their toxicity. The excessive expression of intracellular ROS and reduction of the free-radical scavenger SOD were the main reasons for cell injury and eventually caused necrotic cell death. Crystal size, surface structure, aggregation, and internalization amount were closely related to the cytotoxicity of COM crystals.

  11. Structure Sensitivity Study of Waterborne Contaminant Hydrogenation Using Shape- and Size-Controlled Pd Nanoparticles

    KAUST Repository

    Shuai, Danmeng

    2013-03-01

    Catalytic reduction with Pd has emerged as a promising technology to remove a suite of contaminants from drinking water, such as oxyanions, disinfection byproducts, and halogenated pollutants, but low activity is a major challenge for application. To address this challenge, we synthesized a set of shape- and size-controlled Pd nanoparticles and evaluated the activity of three probe contaminants (i.e., nitrite, N-nitrosodimethylamine (NDMA), and diatrizoate) as a function of facet type (e.g., (100), (110), (111)), ratios of low- to high-coordination sites, and ratios of surface sites to total Pd (i.e., dispersion). Reduction results for an initial contaminant concentration of 100 μM show that initial turnover frequency (TOF0) for nitrite increases 4.7-fold with increasing percent of (100) surface Pd sites (from 0% to 95.3%), whereas the TOF0 for NDMA and for diatrizoate increases 4.5- and 3.6-fold, respectively, with an increasing percent of terrace surface Pd sites (from 79.8% to 95.3%). Results for an initial nitrite concentration of 2 mM show that TOF0 is the same for all shape- and size-controlled Pd nanoparticles. Trends for TOF0 were supported by results showing that all catalysts but one were stable in shape and size up to 12 days; for the exception, iodide liberation in diatrizoate reduction appeared to be responsible for a shape change of 4 nm octahedral Pd nanoparticles. Density functional theory (DFT) simulations for the free energy change of hydrogen (H2), nitrite, and nitric oxide (NO) adsorption and a two-site model based on the Langmuir-Hinshelwood mechanism suggest that competition of adsorbates for different Pd sites can explain the TOF0 results. Our study shows for the first time that catalytic reduction activity for waterborne contaminant removal varies with the Pd shape and size, and it suggests that Pd catalysts can be tailored for optimal performance to treat a variety of contaminants for drinking water. © 2013 American Chemical Society.

  12. Size, Shape, and Arrangement of Cellulose Microfibril in Higher Plant Cell Walls

    Energy Technology Data Exchange (ETDEWEB)

    Ding, S. Y.

    2013-01-01

    Plant cell walls from maize (Zea mays L.) are imaged using atomic force microscopy (AFM) at the sub-nanometer resolution. We found that the size and shape of fundamental cellulose elementary fibril (CEF) is essentially identical in different cell wall types, i.e., primary wall (PW), parenchyma secondary wall (pSW), and sclerenchyma secondary wall (sSW), which is consistent with previously proposed 36-chain model (Ding et al., 2006, J. Agric. Food Chem.). The arrangement of individual CEFs in these wall types exhibits two orientations. In PW, CEFs are horizontally associated through their hydrophilic faces, and the planar faces are exposed, forming ribbon-like macrofibrils. In pSW and sSW, CEFs are vertically oriented, forming layers, in which hemicelluloses are interacted with the hydrophobic faces of the CEF and serve as spacers between CEFs. Lignification occurs between CEF-hemicelluloses layers in secondary walls. Furthermore, we demonstrated quantitative analysis of plant cell wall accessibility to and digestibility by different cellulase systems at real-time using chemical imaging (e.g., stimulated Raman scattering) and fluorescence microscopy of labeled cellulases (Ding et al., 2012, Science, in press).

  13. Size-Controlled Synthesis of CoFe2O4 Nanoparticles Potential Contrast Agent for MRI and Investigation on Their Size-Dependent Magnetic Properties

    Directory of Open Access Journals (Sweden)

    Fujun Liu

    2013-01-01

    Full Text Available Cobalt ferrite nanoparticles (CoFe2O4 NPs were synthesized by coprecipitation followed by treatments with diluted nitric acid and sodium citrate. Transmission electron microscope (TEM and photon correlation spectroscopy (PCS characterization showed that the size distributions of these nanoparticles were monodisperse and that no aggregation occurred. This colloid showed a long-term stability. Through adjustment of the concentrations of reactants and reaction temperature, the size of the NPs can be tuned from 6 to 80 nm. The size-control mechanism is explained by a nucleation-growth model, where the local concentration of monomers is assumed to decide the size of nuclei, and reaction temperatures influence the growth of nuclei. Magnetization and relaxivity r1,2 measurements showed that the NPs revealed size-dependent magnetization and relaxivity properties, which are explained via a “dead magnetic layer” theory where reductions of saturation magnetization (Ms and r1,2 are assumed to be caused by the demagnetization of surface spins.

  14. Sample size requirements for studies of treatment effects on beta-cell function in newly diagnosed type 1 diabetes.

    Directory of Open Access Journals (Sweden)

    John M Lachin

    Full Text Available Preservation of β-cell function as measured by stimulated C-peptide has recently been accepted as a therapeutic target for subjects with newly diagnosed type 1 diabetes. In recently completed studies conducted by the Type 1 Diabetes Trial Network (TrialNet, repeated 2-hour Mixed Meal Tolerance Tests (MMTT were obtained for up to 24 months from 156 subjects with up to 3 months duration of type 1 diabetes at the time of study enrollment. These data provide the information needed to more accurately determine the sample size needed for future studies of the effects of new agents on the 2-hour area under the curve (AUC of the C-peptide values. The natural log(x, log(x+1 and square-root (√x transformations of the AUC were assessed. In general, a transformation of the data is needed to better satisfy the normality assumptions for commonly used statistical tests. Statistical analysis of the raw and transformed data are provided to estimate the mean levels over time and the residual variation in untreated subjects that allow sample size calculations for future studies at either 12 or 24 months of follow-up and among children 8-12 years of age, adolescents (13-17 years and adults (18+ years. The sample size needed to detect a given relative (percentage difference with treatment versus control is greater at 24 months than at 12 months of follow-up, and differs among age categories. Owing to greater residual variation among those 13-17 years of age, a larger sample size is required for this age group. Methods are also described for assessment of sample size for mixtures of subjects among the age categories. Statistical expressions are presented for the presentation of analyses of log(x+1 and √x transformed values in terms of the original units of measurement (pmol/ml. Analyses using different transformations are described for the TrialNet study of masked anti-CD20 (rituximab versus masked placebo. These results provide the information needed to

  15. Maternal Diet and Insulin-Like Signaling Control Intergenerational Plasticity of Progeny Size and Starvation Resistance.

    Directory of Open Access Journals (Sweden)

    Jonathan D Hibshman

    2016-10-01

    Full Text Available Maternal effects of environmental conditions produce intergenerational phenotypic plasticity. Adaptive value of these effects depends on appropriate anticipation of environmental conditions in the next generation, and mismatch between conditions may contribute to disease. However, regulation of intergenerational plasticity is poorly understood. Dietary restriction (DR delays aging but maternal effects have not been investigated. We demonstrate maternal effects of DR in the roundworm C. elegans. Worms cultured in DR produce fewer but larger progeny. Nutrient availability is assessed in late larvae and young adults, rather than affecting a set point in young larvae, and maternal age independently affects progeny size. Reduced signaling through the insulin-like receptor daf-2/InsR in the maternal soma causes constitutively large progeny, and its effector daf-16/FoxO is required for this effect. nhr-49/Hnf4, pha-4/FoxA, and skn-1/Nrf also regulate progeny-size plasticity. Genetic analysis suggests that insulin-like signaling controls progeny size in part through regulation of nhr-49/Hnf4, and that pha-4/FoxA and skn-1/Nrf function in parallel to insulin-like signaling and nhr-49/Hnf4. Furthermore, progeny of DR worms are buffered from adverse consequences of early-larval starvation, growing faster and producing more offspring than progeny of worms fed ad libitum. These results suggest a fitness advantage when mothers and their progeny experience nutrient stress, compared to an environmental mismatch where only progeny are stressed. This work reveals maternal provisioning as an organismal response to DR, demonstrates potentially adaptive intergenerational phenotypic plasticity, and identifies conserved pathways mediating these effects.

  16. Shape-and size-controlled Ag nanoparticles stabilized by in situ generated secondary amines

    International Nuclear Information System (INIS)

    Ramírez-Meneses, E.; Montiel-Palma, V.; Domínguez-Crespo, M.A.; Izaguirre-López, M.G.; Palacios-Gonzalez, E.; Dorantes-Rosales, H.

    2015-01-01

    Highlights: • Ag nanoparticles were generated from Ag amido complexes AgN i Pr 2 and AgN(SiMe 3 ) 2 . • Ag nanoparticles were stabilized by in situ generated HN i Pr 2 or HN(SiMe 3 ) 2 . • 1 or 5 equiv. of ethylenediamine as additional capping agent decreases the average size of the particles. • Ethylenediamine favor the formation of spherical particles. - Abstract: Silver amides such as AgN i Pr 2 and AgN(SiMe 3 ) 2 have been employed successfully as precursors for the yield synthesis of silver nanoparticles under mild conditions of dihydrogen gas reduction (2 atm) in organic media. Transmission electron microscopy (TEM) showed the formation of silver nanoparticles with FCC structure, variously sized from 26 to 35 nm for AgN i Pr 2 and from 14 to 86 nm for AgN(SiMe 3 ) 2 , the synthesis could take place in absence of added stabilizers due to the in situ formation of secondary amines from the reaction of dihydrogen gas with the amide ligands of the silver precursor. Indeed, the presence of HNR 2 (R = iPr 2 , N(SiMe 3 ) 2 ) on the surface of the nanoparticle was confirmed by spectroscopic means. Finally, the addition of ethylenediamine as additional capping agent allowed not only the control of the structural characteristics of the resulting Ag nanoparticles (well-dispersed with spherical shape), but that regarding the nanoparticle size as it inhibited overgrowth, limiting it to ca. 25 nm

  17. Shape-and size-controlled Ag nanoparticles stabilized by in situ generated secondary amines

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez-Meneses, E., E-mail: esther.ramirez@ibero.mx [Departamento de Ingeniería y Ciencias Químicas, Universidad Iberoamericana, Prolongación Paseo de la Reforma 880, Lomas de Santa Fe, Distrito Federal C.P. 01219 (Mexico); Montiel-Palma, V. [Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001 Col. Chamilpa, Cuernavaca, Morelos C.P. 62209 (Mexico); Domínguez-Crespo, M.A.; Izaguirre-López, M.G. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada-IPN, Unidad Altamira. Km 14.5 Carretera Tampico-Puerto Industrial, 89600 Altamira, Tamaulipas (Mexico); Palacios-Gonzalez, E. [Laboratorio de Microscopia de Ultra alta Resolución, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas No. 152, C.P. 07730 México D.F. (Mexico); Dorantes-Rosales, H. [Departamento de Metalurgia, E.S.I.Q.I.E.-I.P.N., Unidad Profesional Adolfo López Mateos, Zacatenco, Delegación. Gustavo A. Madero, C.P. 07738 México D.F. (Mexico)

    2015-09-15

    Highlights: • Ag nanoparticles were generated from Ag amido complexes AgN{sup i}Pr{sub 2} and AgN(SiMe{sub 3}){sub 2}. • Ag nanoparticles were stabilized by in situ generated HN{sup i}Pr{sub 2} or HN(SiMe{sub 3}){sub 2}. • 1 or 5 equiv. of ethylenediamine as additional capping agent decreases the average size of the particles. • Ethylenediamine favor the formation of spherical particles. - Abstract: Silver amides such as AgN{sup i}Pr{sub 2} and AgN(SiMe{sub 3}){sub 2} have been employed successfully as precursors for the yield synthesis of silver nanoparticles under mild conditions of dihydrogen gas reduction (2 atm) in organic media. Transmission electron microscopy (TEM) showed the formation of silver nanoparticles with FCC structure, variously sized from 26 to 35 nm for AgN{sup i}Pr{sub 2} and from 14 to 86 nm for AgN(SiMe{sub 3}){sub 2}, the synthesis could take place in absence of added stabilizers due to the in situ formation of secondary amines from the reaction of dihydrogen gas with the amide ligands of the silver precursor. Indeed, the presence of HNR{sub 2} (R = iPr{sub 2}, N(SiMe{sub 3}){sub 2}) on the surface of the nanoparticle was confirmed by spectroscopic means. Finally, the addition of ethylenediamine as additional capping agent allowed not only the control of the structural characteristics of the resulting Ag nanoparticles (well-dispersed with spherical shape), but that regarding the nanoparticle size as it inhibited overgrowth, limiting it to ca. 25 nm.

  18. Size control of MnFe2O4 nanoparticles in electric double layered magnetic fluid synthesis

    International Nuclear Information System (INIS)

    Aquino, R.; Tourinho, F.A.; Itri, R.; E Lara, M.C.F.L.; Depeyrot, J.

    2002-01-01

    We propose a method based on the pH of the synthesis to control the nanoparticle size during the ferrofluid elaboration. The particle diameter is determined by means of X-ray diffraction experiments. The measured mean size depends on the type of buffer used during the coprecipitation process. The results therefore confirm that the nanoparticle size can be monitored by the hydroxide concentration and suggest to consider the induced interplay between nucleation and crystal growth

  19. Nanometer-scale sizing accuracy of particle suspensions on an unmodified cell phone using elastic light scattering.

    Directory of Open Access Journals (Sweden)

    Zachary J Smith

    Full Text Available We report on the construction of a Fourier plane imaging system attached to a cell phone. By illuminating particle suspensions with a collimated beam from an inexpensive diode laser, angularly resolved scattering patterns are imaged by the phone's camera. Analyzing these patterns with Mie theory results in predictions of size distributions of the particles in suspension. Despite using consumer grade electronics, we extracted size distributions of sphere suspensions with better than 20 nm accuracy in determining the mean size. We also show results from milk, yeast, and blood cells. Performing these measurements on a portable device presents opportunities for field-testing of food quality, process monitoring, and medical diagnosis.

  20. Size-Controlled Production of Gold Bionanoparticles Using the Extremely Acidophilic Fe(III-Reducing Bacterium, Acidocella aromatica

    Directory of Open Access Journals (Sweden)

    Intan Nurul Rizki

    2018-02-01

    Full Text Available Recycling of gold-bearing “urban mine” resources, such as waste printed circuit boards (PCBs, is attracting an increasing interest. Some of the gold leaching techniques utilize acidic lixiviants and in order to eventually target such acidic leachates, the utility of the acidophilic Fe(III-reducing heterotrophic bacterium, Acidocella (Ac. aromatica PFBC was evaluated for production of Au(0 bionanoparticles (bio-AuNPs. Au(III ions (as AuCl4−, initially 10 mg/L, were readily adsorbed onto the slightly-positively charged Ac. aromatica cell surface and transported into cytoplasm to successfully form intracellular bio-AuNPs in a simple one-step microbiological reaction. Generally, increasing the initial concentration of formate as e-donor corresponded to faster Au(III bioreduction and a greater number of Au(0 nucleation sites with less crystal growth within 40–60 h: i.e., use of 1, 5, 10, or 20 mM formate led to production of bio-AuNPs of 48, 24, 13, or 12 nm in mean particle size with 2.3, 17, 62, and 97 particles/cell, respectively. Addition of Cu2+ as an enzymatic inhibitor significantly decreased the number of Au(0 nucleation sites but enhanced crystal growth of individual particles. As a result, the manipulation of the e-donor concentration combined with an enzyme inhibitor enabled the 3-grade size-control of bio-AuNPs (nearly within a normal distribution at 48, 26 or 13 nm by use of 1 mM formate, 20 mM formate (+Cu2+ or 10 mM formate, respectively, from highly acidic, dilute Au(III solutions.

  1. Gripe water as reducing and stabilizing agent for synthesis of size controlled gold nanoparticles.

    Science.gov (United States)

    Kirubha, E; Palanisamy, P K

    2013-03-01

    Green synthesis techniques are emerging as more facile and eco-friendly approach for the synthesis of metal nanoparticles compared to chemical reduction methods. Herein we report a new approach to synthesize gold nanoparticles (AuNPs) using gripe water as a reducing as well as stabilizing agent. Good control over the size of the nanoparticles from 3.2 nm to 25 nm has been achieved with this method by simply varying the experimental conditions. The Surface Plasmon Resonance bands of tunable gold nanospheres with high monodispersity and polydispersity have been obtained by this technique and monitored using UV-Visible spectrum. The morphology and the size of these AuNPs are determined using High Resolution Transmission Electron Microscope (HR-TEM). X-Ray Diffraction (XRD) analysis confirms the crystalline nature and the phase of the AuNPs. The as-synthesized AuNPs exhibit good optical nonlinearity. The nonlinear optical studies have been carried out by Z-scan technique to demonstrate its optical limiting property. The threshold limit of the AuNPs is obtained at a input intensity of 30 mW. The nonlinear refractive index of the nanoparticles is in the order of 10(-9) cm2/W and the third-order nonlinearity is estimated to be 7 x 10(-5) esu.

  2. Size-controlled synthesis of dextran sulfate coated iron oxide nanoparticles for magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jarrett, Benjamin R; Frendo, Michele; Vogan, Jacob; Louie, Angelique Y [Department of Biomedical Engineering, University of California, Davis, CA 95616 (United States)

    2007-01-24

    In the generation of nanoparticles for biological applications, the control over synthetic parameters influencing the particles' physicochemical properties are of great interest due to the strong influence of particle size and surface properties on cellular uptake and biodistribution. We have synthesized dextran sulfate coated particles and systematically evaluated synthetic parameters that may influence the properties of these nanoparticles as potential magnetic resonance (MR) contrast agents. The amount of base, polysaccharide content, ratio of iron salts, and reaction time were optimized to yield approximately 30 nm particles as determined by dynamic light scattering with good MR properties (r{sub 1} = 14.46 mM{sup -1} s{sup -1} and r{sub 2} = 72.55 mM{sup -1} s{sup -1}) and in good yield (50%). Particle sizes and relaxivities are compared with clinically available dextran coated particles and the resulting physical properties of the dextran sulfate coated particles show these particles could be used as potential MR contrast agents for cardiovascular imaging.

  3. The effect of particle size distribution on the design of urban stormwater control measures

    Science.gov (United States)

    Selbig, William R.; Fienen, Michael N.; Horwatich, Judy A.; Bannerman, Roger T.

    2016-01-01

    An urban pollutant loading model was used to demonstrate how incorrect assumptions on the particle size distribution (PSD) in urban runoff can alter the design characteristics of stormwater control measures (SCMs) used to remove solids in stormwater. Field-measured PSD, although highly variable, is generally coarser than the widely-accepted PSD characterized by the Nationwide Urban Runoff Program (NURP). PSDs can be predicted based on environmental surrogate data. There were no appreciable differences in predicted PSD when grouped by season. Model simulations of a wet detention pond and catch basin showed a much smaller surface area is needed to achieve the same level of solids removal using the median value of field-measured PSD as compared to NURP PSD. Therefore, SCMs that used the NURP PSD in the design process could be unnecessarily oversized. The median of measured PSDs, although more site-specific than NURP PSDs, could still misrepresent the efficiency of an SCM because it may not adequately capture the variability of individual runoff events. Future pollutant loading models may account for this variability through regression with environmental surrogates, but until then, without proper site characterization, the adoption of a single PSD to represent all runoff conditions may result in SCMs that are under- or over-sized, rendering them ineffective or unnecessarily costly.

  4. Preparation of Size-Controlled Silver Nanoparticles and Chitin-Based Composites and Their Antimicrobial Activities

    Directory of Open Access Journals (Sweden)

    Vinh Quang Nguyen

    2013-01-01

    Full Text Available A simple method for the preparation of size-controlled spherical silver nanoparticles (Ag NPs was reported for their generation by autoclaving a mixture of silver-containing glass powder and glucose. The particle size is regulated by the glucose concentration, with concentrations of 0.25, 1.0, and 4.0 wt% glucose providing small (3.48±1.83 nm in diameter, medium (6.53±1.78 nm, and large (12.9±2.5 nm particles, respectively. In this study, Ag NP/chitin composites were synthesized by mixing each of these three Ag NP suspensions with a <5% deacetylated (DAc chitin powder (pH 7.0 at room temperature. The Ag NPs were homogenously dispersed and stably adsorbed onto the chitin. The Ag NP/chitin composites were obtained as yellow or brown powders. Approximately 5, 15, and 20 μg of the small, medium, and large Ag NPs, respectively, were estimated to maximally adsorb onto 1 mg of chitin. The bactericidal and antifungal activities of the Ag NP/chitin composites increased as the amount of Ag NPs in the chitin increased. Furthermore, smaller Ag NPs (per weight in the chitin composites provided higher bactericidal and anti-fungal activities.

  5. Size control of surfactant vesicles made by a mixture of cationic surfactants and organic derivatives.

    Science.gov (United States)

    Kim, Tae-Hwan; Han, Young-Soo; Jang, Jong-Dae; Seong, Baek-Seok

    2014-10-01

    Spontaneous size-controllable vesicles that are prepared by a mixture of surfactants with different alkyl chain lengths (n-alkyltrimethylammonium bromide, C(n)TAB) and an organic derivative (5-methyl salicylic acid, 5mS) in aqueous solution have been investigated. When the organic derivative 5mS is mixed with the C(n)TAB surfactants in aqueous solution, the surfactant vesicles are spontaneously formed above a certain 5mS concentration. Small angle neutron scattering reveals that the core radius of surfactant vesicles is clearly increased from ca. 31 nm to ca. 97 nm with the alkyl chain length of surfactants while the bilayer thickness of the vesicles is nearly constant. The structure of surfactant vesicles maintains against temperature change ranging from 30 degrees C to 45 degrees C, showing no structural change. These results can provide thermally stable surfactant vesicles with various sizes and constant bilayer thickness that may possess a different permeability and may allow the surfactant vesicle to be used in gene or drug delivery for a variety of goods.

  6. Flexible and elastic metamaterial absorber for low frequency, based on small-size unit cell

    Science.gov (United States)

    Yoo, Y. J.; Zheng, H. Y.; Kim, Y. J.; Rhee, J. Y.; Kang, J.-H.; Kim, K. W.; Cheong, H.; Kim, Y. H.; Lee, Y. P.

    2014-07-01

    Using a planar and flexible metamaterial (MM), we obtained the low-frequency perfect absorption even with very small unit-cell size in snake-shape structure. These shrunken, deep-sub-wavelength and thin MM absorbers were numerically and experimentally investigated by increasing the inductance. The periodicity/thickness (the figure of merit for perfect absorption) is achieved to be 10 and 2 for single-snake-bar and 5-snake-bar structures, respectively. The ratio between periodicity and resonance wavelength (in mm) is close to 1/12 and 1/30 at 2 GHz and 400 MHz, respectively. The absorbers are specially designed for absorption peaks around 2 GHz and 400 MHz, which can be used for depressing the electromagnetic noise from everyday electronic devices and mobile phones.

  7. A case of gastric endocrine cell carcinoma which was significantly reduced in size by radiotherapy

    International Nuclear Information System (INIS)

    Azakami, Kiyoshi; Nishida, Kouji; Tanikawa, Ken

    2016-01-01

    In 2010, the World Health Organization classified gastric neuroendocrine tumors (NETs) into three types: NET grade (G) 1, NET G2 and neuroendocrine carcinoma (NEC). NECs are associated with a very poor prognosis. The patient was an 84-year-old female who was initially diagnosed by gastrointestinal endoscope with type 3 advanced gastric cancer with stenosis of the gastric cardia. Her overall status and performance status did not allow for operations or intensive chemotherapy. Palliative radiotherapy was performed and resulted in a significant reduction in the size of the tumor as well as the improvement of the obstructive symptoms. She died 9 months after radiotherapy. An autopsy provided a definitive diagnosis of gastric endocrine cell carcinoma, and the effectiveness of radiotherapy was pathologically-confirmed. Palliative radiotherapy may be a useful treatment option for providing symptom relief, especially for old patients with unresectable advanced gastric neuroendocrine carcinoma. (author)

  8. T cell immunosurveillance controls B lymphoma development

    OpenAIRE

    Kallies, Axel

    2014-01-01

    We recently showed a critical role for T cells in the immunosurveillance of nascent B cell lymphomas arising from mutations impacting plasma cell differentiation. Our data suggest that CD8+ T cells continuously eliminate mutated B cells that fail to downregulate their co-stimulatory machinery and the Fas death receptor, thus constraining B lymphoma pathogenesis.

  9. Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene

    KAUST Repository

    Cui, X.

    2016-05-20

    The trade-off between physical adsorption capacity and selectivity of porous materials is a major barrier for efficient gas separation and purification through physisorption. We report control over pore chemistry and size in metal coordination networks with hexafluorosilicate and organic linkers for the purpose of preferential binding and orderly assembly of acetylene molecules through cooperative host-guest and/or guest-guest interactions. The specific binding sites for acetylene are validated by modeling and neutron powder diffraction studies. The energies associated with these binding interactions afford high adsorption capacity (2.1 millimoles per gram at 0.025 bar) and selectivity (39.7 to 44.8) for acetylene at ambient conditions. Their efficiency for the separation of acetylene/ethylene mixtures is demonstrated by experimental breakthrough curves (0.73 millimoles per gram from a 1/99 mixture).

  10. Adaptive Traffic Control Systems in a medium-sized Scandinavian city

    DEFF Research Database (Denmark)

    Agerholm, Niels; Olesen, Anne Vingaard

    2018-01-01

    Adaptive Traffic Control Systems (ATCS) are aimed at reducing congestion. ATCS adapt to approaching traffic to continuously optimise the traffic flows in question. ATCS have been implemented in many locations, including the Scandinavian countries, with various effects. Due to congestion problems......, ATCS were installed in the eight signalised intersections of a 1.7 km stretch of the ring road in the medium-sized Danish city of Aalborg. To measure the effect of ATCS a with/without study was carried out. GPS data from a car following the traffic, recorded transportation times for buses in service......, and GPS data from a range of cars driving on the ring road formed the basis for the study. The result of ATCS implementation was a significant 17% reduction in transportation time on the ring road in the most congested period, the afternoon peak. Less significant effects were found regarding the morning...

  11. Functional polythiophene nanoparticles: size-controlled electropolymerization and ion selective response.

    Science.gov (United States)

    Si, Pengchao; Chi, Qijin; Li, Zheshen; Ulstrup, Jens; Møller, Preben Juul; Mortensen, John

    2007-04-04

    We have synthesized a thiophene derivative, (4-benzeno-15-crown-5 ether)-thiophene-3-methylene-amine (BTA), which was used as a monomer for electrochemical polymerization on metallic surfaces to prepare functional polymer films. Self-assembly of BTA monomers on Au(111) surfaces promotes ordered polymerization to form polymer nanoparticles or clusters by which the size of the polymer nanoparticles can further be controlled electrochemically. The electropolymerization was monitored in situ by scanning tunneling microscopy to unravel the dynamics of the process and possible mechanisms. These are further supported by calculations using a semiquantative model of polymer clusters and X-ray photoelectron spectroscopy analysis. On the basis of these observations, we have attempted to optimize the construction of BTA polymer based ion selective electrodes. The BTA based polymer films, prepared from both aqueous solution and organic phase on gold electrodes, displayed selective sensitivity to potassium ions with a linear dependence of ion concentration over 4 orders of magnitude.

  12. Rac1 Regulates the Activity of mTORC1 and mTORC2 and Controls Cellular Size

    Science.gov (United States)

    Saci, Abdelhafid; Cantley, Lewis C.; Carpenter, Christopher L.

    2013-01-01

    SUMMARY Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that exists in two separate complexes, mTORC1 and mTORC2, that function to control cell size and growth in response to growth factors, nutrients, and cellular energy levels. Low molecular weight GTP-binding proteins of the Rheb and Rag families are key regulators of the mTORC1 complex, but regulation of mTORC2 is poorly understood. Here, we report that Rac1, a member of the Rho family of GTPases, is a critical regulator of both mTORC1 and mTORC2 in response to growth-factor stimulation. Deletion of Rac1 in primary cells using an inducible-Cre/Lox approach inhibits basal and growth-factor activation of both mTORC1 and mTORC2. Rac1 appears to bind directly to mTOR and to mediate mTORC1 and mTORC2 localization at specific membranes. Binding of Rac1 to mTOR does not depend on the GTP-bound state of Rac1, but on the integrity of its C-terminal domain. This function of Rac1 provides a means to regulate mTORC1 and mTORC2 simultaneously. PMID:21474067

  13. Cell surface control of differentiation in Acanthamoeba.

    Science.gov (United States)

    Yang, S; Villemez, C

    1994-12-01

    Acanthamoeba castellanii (Neff) is a free-living soil amoeba with close relatives that are opportunistic pathogens. Trophozoites differentiate into cysts when deprived of nutrients; cysts convert into trophozoites, leaving the wall behind, in the presence of nutrients. The data presented here, which includes immunoaffinity purification of the receptor, indicate that cell surface molecular signals also control Acanthamoeba differentiation in both directions. Monoclonal antibodies that bind specifically to a 40 kD trophozoite protein initiate the encystment of trophozoites. When bound to cysts the same monoclonal antibodies prevent excystment. Washing away the antibody allows both trophozoites and cysts to resume normal activity. One of these monoclonal antibodies inhibits pinocytosis, while another has no effect on pinocytosis.

  14. Size-controlled synthesis of SnO{sub 2} quantum dots and their gas-sensing performance

    Energy Technology Data Exchange (ETDEWEB)

    Du, Jianping, E-mail: dujp518@163.com [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Zhao, Ruihua [Shanxi Kunming Tobacco Limited Liability Company, Taiyuan 030012, Shanxi (China); Xie, Yajuan [College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Li, Jinping, E-mail: jpli211@hotmail.com [Research Institute of Special Chemicals, Taiyuan University of Technology, Shanxi, 030024 (China)

    2015-08-15

    Graphical abstract: The gas-sensing property of quantum dots is related to their sizes. SnO{sub 2} quantum dots (TQDs) were synthesized and the sizes were controlled by a simple strategy. The results show that controlling QDs size is efficient to detect low-concentration hazardous volatile compounds selectively. - Highlights: • SnO{sub 2} quantum dots with controllable size were synthesized by hydrothermal route. • The sizes of SnO{sub 2} quantum dots (TQDs) were controlled by a simple strategy. • The responses to volatile chemicals strongly depend on the size of quantum dots. • Small-size TQDs exhibit a good selectivity and response to triethylamine. • Controlling size is efficient to detect low-concentration toxic gases selectively. - Abstract: Tin dioxide quantum dots (TQDs) with controllable size were synthesized by changing the amount of alkaline reagent in the hydrothermal process. The gas-sensing properties were investigated by operating chemoresistor type sensor. The morphology and structure were characterized by X-ray diffraction, scanning/transmission electron microscopy, UV–vis and Raman spectrometry. The as-synthesized SnO{sub 2} shows the characteristics of quantum dots and the narrowest size distribution is about 2–3 nm. The gas-sensing results indicate that the responses are strongly dependent on the size of quantum dots. TQDs with different sizes exhibit different sensitivities and selectivities to volatile toxic chemicals such as aldehyde, acetone, methanol, ethanol and amine. Especially, when the sensors are exposed to 100 ppm triethylamine (TEA), the sensing response value of TQDs with small size is two times higher than that of the large-size TQDs. The maximum response values of TQDs to 1 ppm and 100 ppm TEA are 15 and 153, respectively. The response time is 1 s and the recovery time is 47 s upon exposure to 1 ppm TEA. The results suggest that it is an effective method by regulating the size of SnO{sub 2} quantum dots to detect low

  15. Acoustofluidic devices controlled by cell phones.

    Science.gov (United States)

    Bachman, Hunter; Huang, Po-Hsun; Zhao, Shuaiguo; Yang, Shujie; Zhang, Peiran; Fu, Hai; Huang, Tony Jun

    2018-01-30

    Acoustofluidic devices have continuously demonstrated their potential to impact medical diagnostics and lab-on-a-chip applications. To bring these technologies to real-world applications, they must be made more accessible to end users. Herein, we report on the effort to provide an easy-to-use and portable system for controlling sharp-edge-based acoustofluidic devices. With the use of a cell phone and a modified Bluetooth® speaker, on-demand and hands-free pumping and mixing are achieved. Additionally, a novel design for a sharp-edge-based acoustofluidic device is proposed that combines both pumping and mixing functions into a single device, thus removing the need for external equipment typically needed to accomplish these two tasks. These applications serve to demonstrate the potential function that acoustofluidic devices can provide in point-of-care platforms. To further this point-of-care goal, we also design a portable microscope that combines with the cell phone and Bluetooth® power supply, providing a completely transportable acoustofluidic testing station. This work serves to bolster the promising position that acoustofluidic devices have within the rapidly changing research and diagnostics fields.

  16. Toward High Magnetic Moment, Controlled-Size, Blood Dispersible Nanoparticles: An Enabling Technology for Biomagnetics Interfacing Concepts

    Science.gov (United States)

    2006-03-02

    SUBTITLE Toward High Magnetic Moment, Controlled-Size, Blood Dispersible Nanoparticles: An Enabling Technology for Biomagnetics Interfacing...Dispersible Nanoparticles: An Enabling Technology for Biomagnetic Interfacing Concepts Final Report submitted to Dr. Hugh DeLong, AFOSR, and Dr

  17. Microwave Synthesized Monodisperse CdS Spheres of Different Size and Color for Solar Cell Applications

    Directory of Open Access Journals (Sweden)

    Carlos A. Rodríguez-Castañeda

    2015-01-01

    Full Text Available Monodisperse CdS spheres of size of 40 to 140 nm were obtained by microwave heating from basic solutions. It is observed that larger CdS spheres were formed at lower solution pH (8.4–8.8 and smaller ones at higher solution pH (10.8–11.3. The color of CdS products changed with solution pH and reaction temperature; those synthesized at lower pH and temperature were of green-yellow color, whereas those formed at higher pH and temperature were of orange-yellow color. A good photovoltage was observed in CdS:poly(3-hexylthiophene solar cells with spherical CdS particles. This is due to the good dispersion of CdS nanoparticles in P3HT solution that led to a large interface area between the organic and inorganic semiconductors. Higher photocurrent density was obtained in green-yellow CdS particles of lower defect density. The efficient microwave chemistry accelerated the hydrolysis of thiourea in pH lower than 9 and produced monodisperse spherical CdS nanoparticles suitable for solar cell applications.

  18. Impact of sickle cell anaemia on cardiac chamber size in the paediatric population.

    Science.gov (United States)

    Adjagba, Philippe M; Habib, Gaston; Robitaille, Nancy; Pastore, Yves; Raboisson, Marie-Josée; Curnier, Daniel; Dahdah, Nagib

    2017-07-01

    Purpose Sickle cell disease is known to cause various degrees of vasculopathy, including impact on heart function. The aims of this single-centre, retrospective study were to assess cardiac chamber size and function and the relationship with haematological indices such as haemoglobin, aspartate aminotransferase, reticulocytosis and bilirubin, lactate dehydrogenase in sickle cell disease. Right ventricle and left ventricle diastolic diameters, left ventricle mass estimate, left ventricle shortening fraction, myocardial performance index, and an index of myocardial relaxation (E/E') were calculated and correlated with haematological parameters. A total of 110 patients (65% haemoglobin SS, 29% haemoglobin SC) were studied at a mean age of 12.14±5.26 years. Right ventricle dilatation and left ventricle dilatation were present in 61.5 and 42.9%, respectively. Left ventricle mass was abnormal in 21.9%; all patients had normal myocardial performance index, 31.4% had abnormal E/E', and left ventricle shortening fraction was low in 38.1%. Cardiac dilatation was best correlated with haemoglobin, aspartate aminotransferase, reticulocytosis and bilirubin. Best subset regression analysis yielded significant additional prediction for right ventricle or left ventricle dilatation with haemoglobin, bilirubin, and lactate dehydrogenase. Abnormal E/E' was solely predictable with haemoglobin level. Hydroxyurea-treated patients had improved diastolic function. Right ventricle dilatation was more prevalent than left ventricle dilatation. The long-term consequences of right ventricular dilatation, clinical consequences, and association with pulmonary vasculopathy need to be further determined.

  19. Fabrication of large size alginate beads for three-dimensional cell-cluster culture

    Science.gov (United States)

    Zhang, Zhengtao; Ruan, Meilin; Liu, Hongni; Cao, Yiping; He, Rongxiang

    2017-08-01

    We fabricated large size alginate beads using a simple microfluidic device under a co-axial injection regime. This device was made by PDMS casting with a mold formed by small diameter metal and polytetrafluorothylene tubes. Droplets of 2% sodium alginate were generated in soybean oil through the device and then cross-linked in a 2% CaCl2 solution, which was mixed tween80 with at a concentration of 0.4 to 40% (w/v). Our results showed that the morphology of the produced alginate beads strongly depends on the tween80 concentration. With the increase of concentration of tween80, the shape of the alginate beads varied from semi-spherical to tailed-spherical, due to the decrease of interface tension between oil and cross-link solution. To access the biocompatibility of the approach, MCF-7 cells were cultured with the alginate beads, showing the formation of cancer cells clusters which might be useful for future studies.

  20. Lithium-Ion Cell Charge-Control Unit Developed

    Science.gov (United States)

    Reid, Concha M.; Manzo, Michelle A.; Buton, Robert M.; Gemeiner, Russel

    2005-01-01

    A lithium-ion (Li-ion) cell charge-control unit was developed as part of a Li-ion cell verification program. This unit manages the complex charging scheme that is required when Li-ion cells are charged in series. It enables researchers to test cells together as a pack, while allowing each cell to charge individually. This allows the inherent cell-to-cell variations to be addressed on a series string of cells and reduces test costs substantially in comparison to individual cell testing.

  1. The effect of alcohols on red blood cell mechanical properties and membrane fluidity depends on their molecular size.

    Directory of Open Access Journals (Sweden)

    Melda Sonmez

    Full Text Available The role of membrane fluidity in determining red blood cell (RBC deformability has been suggested by a number of studies. The present investigation evaluated alterations of RBC membrane fluidity, deformability and stability in the presence of four linear alcohols (methanol, ethanol, propanol and butanol using ektacytometry and electron paramagnetic resonance (EPR spectroscopy. All alcohols had a biphasic effect on deformability such that it increased then decreased with increasing concentration; the critical concentration for reversal was an inverse function of molecular size. EPR results showed biphasic changes of near-surface fluidity (i.e., increase then decrease and a decreased fluidity of the lipid core; rank order of effectiveness was butanol > propanol > ethanol > methanol, with a significant correlation between near-surface fluidity and deformability (r = 0.697; p<0.01. The presence of alcohol enhanced the impairment of RBC deformability caused by subjecting cells to 100 Pa shear stress for 300 s, with significant differences from control being observed at higher concentrations of all four alcohols. The level of hemolysis was dependent on molecular size and concentration, whereas echinocytic shape transformation (i.e., biconcave disc to crenated morphology was observed only for ethanol and propanol. These results are in accordance with available data obtained on model membranes. They document the presence of mechanical links between RBC deformability and near-surface membrane fluidity, chain length-dependence of the ability of alcohols to alter RBC mechanical behavior, and the biphasic response of RBC deformability and near-surface membrane fluidity to increasing alcohol concentrations.

  2. Partner Influence in Diet and Exercise Behaviors: Testing Behavior Modeling, Social Control, and Normative Body Size

    Science.gov (United States)

    Ciciurkaite, Gabriele; Brady, Christy Freadreacea; Garcia, Justin

    2016-01-01

    Previous research has documented social contagion in obesity and related health behaviors, but less is known about the social processes underlying these patterns. Focusing on married or cohabitating couples, we simultaneously explore three potential social mechanisms influencing obesity: normative body size, social control, and behavior modeling. We analyze the association between partner characteristics and the obesity-related health behaviors of focal respondents, comparing the effects of partners’ body type, partners’ attempts to manage respondents’ eating behaviors, and partners’ own health behaviors on respondents’ health behaviors (physical activity, fruit and vegetable consumption, and fast food consumption). Data on 215 partners are extracted from a larger study of social mechanisms of obesity in family and community contexts conducted in 2011 in the United States. Negative binomial regression models indicate that partner behavior is significantly related to respondent behavior (p social control in this sample, though generalizations about the relevance of these processes may be inappropriate. These results underscore the importance of policies and interventions that target dyads and social groups, suggesting that adoption of exercise or diet modifications in one individual is likely to spread to others, creating a social environment characterized by mutual reinforcement of healthy behavior. PMID:28033428

  3. Location-specific growth and transfer of arrayed MoS2 monolayers with controllable size

    Science.gov (United States)

    Wang, Xiaotian; Kang, Kyungnam; Chen, Siwei; Du, Ruozhou; Yang, Eui-Hyeok

    2017-06-01

    We present a controlled chemical vapor deposition (CVD) growth and transfer of arrayed MoS2 monolayers on predetermined locations. The patterned transition metal oxide (e.g. MoO3) source substrate was contacted face-to-face with an SiO2 growth substrate, where localized MoS2 flakes were synthesized on both source and growth substrates, following a CVD procedure. This growth technique enabled the growth of both single crystalline and polycrystalline MoS2 monolayer arrays with controlled size and location, exclusively on predetermined locations on the growth substrates. As-grown MoS2 arrays were transferred using a unique process that combines the wet and stamping transfer processes and dramatically enhanced the integrity of transferred MoS2 on microstructures, while protecting the microstructures during the transfer process. This fabrication technique can be applied to different transition metal dichalcogenides (TMDs) and allows the formation of TMDs on select locations, potentially eliminating a post-lithography step for device fabrication.

  4. Large-scale synthesis and quantitative characterization of size-controllable potassium tungsten bronze nanowires

    Science.gov (United States)

    Liu, Chang; Peng, Yuehua; Zhou, Fang; Yin, Yanling; Huang, Xingqing; Wang, Lizhou; Wang, Weike; Zhou, Weichang; Tang, Dongsheng

    2018-03-01

    Single-crystalline hexagonal potassium tungsten bronze K0.26WO3 nanowires with diameters of 10–30 nm and lengths to several micrometers have been successfully synthesized via a hydrothermal method. The diameters of K0.26WO3 nanowires can be well modulated by reducing potassium tungsten oxide K2OW7O21 nanowires in hydrogen atmosphere at different temperatures. X-ray quantitative characterization indicates that the lattice constants and crystal lattice microstrains of these K0.26WO3 nanowires exhibit anisotropic behaviors along the radial and axis directions, which can be well explained by the surface effect and K+ ion aggregating or ordering. It also indicates that oxygen vacancies will occur in the WO3 lattice when the reduction temperature is around 650 °C, and the oxygen vacancies will prevent K+ ions from aggregating or ordering. Controllable synthesis and quantitative analysis of size-controllable K x WO3 nanowires will contribute to deepen our understanding on their structures and properties, and explore their potential applications in nanoscale resistive switching devices based on the distribution of K+ ions.

  5. Chemo-mechanical control of neural stem cell differentiation

    Science.gov (United States)

    Geishecker, Emily R.

    Cellular processes such as adhesion, proliferation, and differentiation are controlled in part by cell interactions with the microenvironment. Cells can sense and respond to a variety of stimuli, including soluble and insoluble factors (such as proteins and small molecules) and externally applied mechanical stresses. Mechanical properties of the environment, such as substrate stiffness, have also been suggested to play an important role in cell processes. The roles of both biochemical and mechanical signaling in fate modification of stem cells have been explored independently. However, very few studies have been performed to study well-controlled chemo-mechanotransduction. The objective of this work is to design, synthesize, and characterize a chemo-mechanical substrate to encourage neuronal differentiation of C17.2 neural stem cells. In Chapter 2, Polyacrylamide (PA) gels of varying stiffnesses are functionalized with differing amounts of whole collagen to investigate the role of protein concentration in combination with substrate stiffness. As expected, neurons on the softest substrate were more in number and neuronal morphology than those on stiffer substrates. Neurons appeared locally aligned with an expansive network of neurites. Additional experiments would allow for statistical analysis to determine if and how collagen density impacts C17.2 differentiation in combination with substrate stiffness. Due to difficulties associated with whole protein approaches, a similar platform was developed using mixed adhesive peptides, derived from fibronectin and laminin, and is presented in Chapter 3. The matrix elasticity and peptide concentration can be individually modulated to systematically probe the effects of chemo-mechanical signaling on differentiation of C17.2 cells. Polyacrylamide gel stiffness was confirmed using rheological techniques and found to support values published by Yeung et al. [1]. Cellular growth and differentiation were assessed by cell counts

  6. Efficient All-Vacuum Deposited Perovskite Solar Cells by Controlling Reagent Partial Pressure in High Vacuum.

    Science.gov (United States)

    Hsiao, Sheng-Yi; Lin, Hong-Lin; Lee, Wei-Hung; Tsai, Wei-Lun; Chiang, Kai-Ming; Liao, Wei-Yu; Ren-Wu, Chen-Zheng; Chen, Chien-Yu; Lin, Hao-Wu

    2016-08-01

    All-vacuum-deposited perovskite solar cells produced by controlling reagent partial pressure in high vacuum with newly developed multi-layer electron and hole transporting structures show outstanding power conversion efficiency of 17.6% and smooth, pinhole-free, micrometer-sized perovskite crystal grains. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Insulin/IGF-regulated size scaling of neuroendocrine cells expressing the bHLH transcription factor Dimmed in Drosophila.

    Directory of Open Access Journals (Sweden)

    Jiangnan Luo

    Full Text Available Neurons and other cells display a large variation in size in an organism. Thus, a fundamental question is how growth of individual cells and their organelles is regulated. Is size scaling of individual neurons regulated post-mitotically, independent of growth of the entire CNS? Although the role of insulin/IGF-signaling (IIS in growth of tissues and whole organisms is well established, it is not known whether it regulates the size of individual neurons. We therefore studied the role of IIS in the size scaling of neurons in the Drosophila CNS. By targeted genetic manipulations of insulin receptor (dInR expression in a variety of neuron types we demonstrate that the cell size is affected only in neuroendocrine cells specified by the bHLH transcription factor DIMMED (DIMM. Several populations of DIMM-positive neurons tested displayed enlarged cell bodies after overexpression of the dInR, as well as PI3 kinase and Akt1 (protein kinase B, whereas DIMM-negative neurons did not respond to dInR manipulations. Knockdown of these components produce the opposite phenotype. Increased growth can also be induced by targeted overexpression of nutrient-dependent TOR (target of rapamycin signaling components, such as Rheb (small GTPase, TOR and S6K (S6 kinase. After Dimm-knockdown in neuroendocrine cells manipulations of dInR expression have significantly less effects on cell size. We also show that dInR expression in neuroendocrine cells can be altered by up or down-regulation of Dimm. This novel dInR-regulated size scaling is seen during postembryonic development, continues in the aging adult and is diet dependent. The increase in cell size includes cell body, axon terminations, nucleus and Golgi apparatus. We suggest that the dInR-mediated scaling of neuroendocrine cells is part of a plasticity that adapts the secretory capacity to changing physiological conditions and nutrient-dependent organismal growth.

  8. Epigenetic control of embryonic stem cell fate

    DEFF Research Database (Denmark)

    Christophersen, Nicolaj Strøyer; Helin, Kristian

    2010-01-01

    Embryonic stem (ES) cells are derived from the inner cell mass of the preimplantation embryo and are pluripotent, as they are able to differentiate into all cell types of the adult organism. Once established, the pluripotent ES cells can be maintained under defined culture conditions, but can als...

  9. Self-assembled nanofiber coatings for controlling cell responses

    NARCIS (Netherlands)

    Barros, Raquel C.; Gelens, Edith; Bulten, Erna; Tuin, Annemarie; de Jong, Menno R; Kuijer, Roel; van Kooten, Theo G

    Nanofibers are thought to enhance cell adhesion, growth, and function. We demonstrate that the choice of building blocks in self-assembling nanofiber systems can be used to control cell behavior. The use of 2 D-coated, self-assembled nanofibers in controlling lens epithelial cells, fibroblasts, and

  10. Patterns of hyperphagia in the Zucker obese rat: a role for fat cell size and number?

    Science.gov (United States)

    Vasselli, J R

    1985-06-01

    The hypothesis that adipocyte size and number influence feeding behavior, via as yet unidentified signals to the CNS, is reviewed. The proposal is made that, due to several metabolic alterations which favor lipid deposition, the genetically obese Zucker rat (fafa) may be an appropriate model in which to study feeding-adipose tissue relationships. Data from several studies are presented demonstrating that the developing male Zucker fatty rat displays hyperphagia during the growth period which reaches a peak, or "break point," and then declines such that intake of fatty and lean rats becomes comparable at approximately 20 weeks of age. Beyond week 20, cycles of hyperphagia of several weeks' duration can be detected in fatty rats. The above feeding changes are related to data showing that on a laboratory chow-type diet, adipocytes approach maximal size at 15-16 weeks in the fatty rat, while accelerated proliferation of adipocytes takes place following week 20. During growth, responding for food in an operant task by fatty rats varies in accord with the pattern of hyperphagia. Further studies in the fatty rat show that the duration and magnitude of developmental hyperphagia can be altered by manipulating the caloric density and macronutrient content of the diet, with fat containing diets leading to the earliest break point of developmental hyperphagia. Some theoretical problems with the notion of adipose tissue feedback control of feeding behavior are discussed.

  11. Advances on development of suction and temperature controlled oedometer cell

    International Nuclear Information System (INIS)

    Ye Weimin; Zhang Yawei; Chen Bao; Wang Min

    2010-01-01

    Oedometer cells for unsaturated soils can be classified into two types, that is, conventional unsaturated oedometer cells (high-suction unsaturated oedometer cell, high-suction and high-pressure unsaturated oedometer cell) and temperature controlled unsaturated oedometer cells. Among them, the osmotic, vapor equilibrium and axis translation techniques are often employed for suction control. The thermostat bath method and thermostatically controlled heater method are commonly used for temperature control. The lever loading system, hydraulic loading system and air pressure loading system are commonly means used for vertical pressure. Combination of osmotic (or axis translation) technique with vapor equilibrium method employed for the full range suction control, thermostatically liquid temperature control method, and the hydraulic loading system, could be used for suction, temperature and loading control in the design for unsaturated oedometer cells in the future, which can be used for study of buffer/backfill materials under high-temperature, high pressure and full range suction conditions. (authors)

  12. Size-controlled, magnetic, and core-shell nanoparticles synthesized by inert-gas condensation

    Science.gov (United States)

    Koten, Mark A.

    Interest in nanoparticles (2 to 100 nm in diameter) and clusters of atoms (0.5 to 2 nm in diameter) has heightened over the past two and a half decades on both fundamental and functional levels. Nanoparticles and clusters of atoms are an exciting branch of materials science because they do not behave like normal bulk matter, nor do they act like molecules. They can have shockingly different physical, chemical, optical, or magnetic properties from the same material at a larger scale. In the case of nanoparticles, the surface-to-volume ratio can change fundamental properties like melting temperature, binding energy, or electron affinity. The definitions of markers used to distinguish between metallic, semiconducting, and insulating bulk condensed matter, such as the band gap and polarizability, can even be blurred or confused on the nanoscale. Similarly, clusters of atoms can form in structures that are only stable at finite sizes, and do not translate to bulk condensed matter. Thermodynamics of finite systems changes dramatically in nanovolumes such as wires, rods, cubes, and spheres, which can lead to complex core-shell and onion-like nanostructures. Consequently, these changes in properties and structure have led to many new possibilities in the field of materials engineering. Inert-gas condensation (IGC) is a well-established method of producing nanoparticles that condense from the gas phase. Its first use dates back to the early 1990s, and it has been used to fabricate nanoparticles both commercially and in research and development for applications in magnetism, biomedicine, and catalysts. In this dissertation, IGC was used to produce a wide variety of nanoparticles. First, control over the size distributions of Cu nanoparticles and how it relates to the plasma properties inside the nucleation chamber was investigated. Next, the formation of phase pure WFe2 nanoparticles revealed that this Laves phase is ferromagnetic instead of non-magnetic. Finally, core

  13. Spatiotemporal control of cell-cell reversible interactions using molecular engineering

    Science.gov (United States)

    Shi, Peng; Ju, Enguo; Yan, Zhengqing; Gao, Nan; Wang, Jiasi; Hou, Jianwen; Zhang, Yan; Ren, Jinsong; Qu, Xiaogang

    2016-10-01

    Manipulation of cell-cell interactions has potential applications in basic research and cell-based therapy. Herein, using a combination of metabolic glycan labelling and bio-orthogonal click reaction, we engineer cell membranes with β-cyclodextrin and subsequently manipulate cell behaviours via photo-responsive host-guest recognition. With this methodology, we demonstrate reversible manipulation of cell assembly and disassembly. The method enables light-controllable reversible assembly of cell-cell adhesion, in contrast with previously reported irreversible effects, in which altered structure could not be reused. We also illustrate the utility of the method by designing a cell-based therapy. Peripheral blood mononuclear cells modified with aptamer are effectively redirected towards target cells, resulting in enhanced cell apoptosis. Our approach allows precise control of reversible cell-cell interactions and we expect that it will promote further developments of cell-based therapy.

  14. Particle Size Effects of TiO2 Layers on the Solar Efficiency of Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Ming-Jer Jeng

    2013-01-01

    Full Text Available Large particle sizes having a strong light scattering lead to a significantly decreased surface area and small particle sizes having large surface area lack light-scattering effect. How to combine large and small particle sizes together is an interesting work for achieving higher solar efficiency. In this work, we investigate the solar performance influence of the dye-sensitized solar cells (DSSCs by the multiple titanium oxide (TiO2 layers with different particle sizes. It was found that the optimal TiO2 thickness depends on the particle sizes of TiO2 layers for achieving the maximum efficiency. The solar efficiency of DSSCs prepared by triple TiO2 layers with different particle sizes is higher than that by double TiO2 layers for the same TiO2 thickness. The choice of particle size in the bottom layer is more important than that in the top layer for achieving higher solar efficiency. The choice of the particle sizes in the middle layer depends on the particle sizes in the bottom and top layers. The mixing of the particle sizes in the middle layer is a good choice for achieving higher solar efficiency.

  15. Polymer electrolyte membrane fuel cell control with feed-forward ...

    African Journals Online (AJOL)

    Feed-forward and feedback control is developed in this work for Polymer electrolyte membrane (PEM) fuel cell stacks. The feed-forward control is achieved using different methods, including look-up table, fuzzy logic and neural network, to improve the fuel cell stack breathing control and prevent the problem of oxygen ...

  16. Smooth muscle cell recruitment to lymphatic vessels requires PDGFB and impacts vessel size but not identity.

    Science.gov (United States)

    Wang, Yixin; Jin, Yi; Mäe, Maarja Andaloussi; Zhang, Yang; Ortsäter, Henrik; Betsholtz, Christer; Mäkinen, Taija; Jakobsson, Lars

    2017-10-01

    Tissue fluid drains through blind-ended lymphatic capillaries, via smooth muscle cell (SMC)-covered collecting vessels into venous circulation. Both defective SMC recruitment to collecting vessels and ectopic recruitment to lymphatic capillaries are thought to contribute to vessel failure, leading to lymphedema. However, mechanisms controlling lymphatic SMC recruitment and its role in vessel maturation are unknown. Here, we demonstrate that platelet-derived growth factor B (PDGFB) regulates lymphatic SMC recruitment in multiple vascular beds. PDGFB is selectively expressed by lymphatic endothelial cells (LECs) of collecting vessels. LEC-specific deletion of Pdgfb prevented SMC recruitment causing dilation and failure of pulsatile contraction of collecting vessels. However, vessel remodelling and identity were unaffected. Unexpectedly, Pdgfb overexpression in LECs did not induce SMC recruitment to capillaries. This was explained by the demonstrated requirement of PDGFB extracellular matrix (ECM) retention for lymphatic SMC recruitment, and the low presence of PDGFB-binding ECM components around lymphatic capillaries. These results demonstrate the requirement of LEC-autonomous PDGFB expression and retention for SMC recruitment to lymphatic vessels, and suggest an ECM-controlled checkpoint that prevents SMC investment of capillaries, which is a common feature in lymphedematous skin. © 2017. Published by The Company of Biologists Ltd.

  17. Multidimensional nanomaterials for the control of stem cell fate

    Science.gov (United States)

    Chueng, Sy-Tsong Dean; Yang, Letao; Zhang, Yixiao; Lee, Ki-Bum

    2016-09-01

    Current stem cell therapy suffers low efficiency in giving rise to differentiated cell lineages, which can replace the original damaged cells. Nanomaterials, on the other hand, provide unique physical size, surface chemistry, conductivity, and topographical microenvironment to regulate stem cell differentiation through multidimensional approaches to facilitate gene delivery, cell-cell, and cell-ECM interactions. In this review, nanomaterials are demonstrated to work both alone and synergistically to guide selective stem cell differentiation. From three different nanotechnology families, three approaches are shown: (1) soluble microenvironmental factors; (2) insoluble physical microenvironment; and (3) nano-topographical features. As regenerative medicine is heavily invested in effective stem cell therapy, this review is inspired to generate discussions in the potential clinical applications of multi-dimensional nanomaterials.

  18. Monocrystalline solar cells performance coated by silver nanoparticles: Effect of NPs sizes from point of view Mie theory

    Science.gov (United States)

    Elnoby, Rasha M.; Mourad, M. Hussein; Elnaby, Salah L. Hassab; Abou Kana, Maram T. H.

    2018-05-01

    Solar based cells coated by nanoparticles (NPs) acknowledge potential utilizing as a part of photovoltaic innovation. The acquired silicon solar cells (Si-SCs) coated with different sizes of silver nanoparticles (Ag NPs) as well as uncoated were fabricated in our lab. The sizes and optical properties of prepared NPs were characterized by spectroscopic techniques and Mie theory respectively. The reflectivity of Si-SCs showed reduction of this property as the size of NPs increased. Electrical properties as open circuit current, fill factor and output power density were assessed and discussed depending on point of view of Mie theory for the optical properties of NPs. Also, photostabilities of SCs were assessed using diode laser of wavelength 450 nm and power 300 mW. Coated SCs with the largest Ag NPs size showed the highest Photostability due to its highest scattering efficiency according to Mie theory concept.

  19. Size and dielectric properties of skeletal stem cells change critically after enrichment and expansion from human bone marrow: consequences for microfluidic cell sorting.

    Science.gov (United States)

    Xavier, Miguel; de Andrés, María C; Spencer, Daniel; Oreffo, Richard O C; Morgan, Hywel

    2017-08-01

    The capacity of bone and cartilage to regenerate can be attributed to skeletal stem cells (SSCs) that reside within the bone marrow (BM). Given SSCs are rare and lack specific surface markers, antibody-based sorting has failed to deliver the cell purity required for clinical translation. Microfluidics offers new methods of isolating cells based on biophysical features including, but not limited to, size, electrical properties and stiffness. Here we report the characterization of the dielectric properties of unexpanded SSCs using single-cell microfluidic impedance cytometry (MIC). Unexpanded SSCs had a mean size of 9.0 µm; larger than the majority of BM cells. During expansion, often used to purify and increase the number of SSCs, cell size and membrane capacitance increased significantly, highlighting the importance of characterizing unaltered SSCs. In addition, MIC was used to track the osteogenic differentiation of SSCs and showed an increased membrane capacitance with differentiation. The electrical properties of primary SSCs were indistinct from other BM cells precluding its use as an isolation method. However, the current studies indicate that cell size in combination with another biophysical parameter, such as stiffness, could be used to design label-free devices for sorting SSCs with significant clinical impact. © 2017 The Authors.

  20. When larger brains do not have more neurons: increased numbers of cells are compensated by decreased average cell size across mouse individuals

    Science.gov (United States)

    Herculano-Houzel, Suzana; Messeder, Débora J.; Fonseca-Azevedo, Karina; Pantoja, Nilma A.

    2015-01-01

    There is a strong trend toward increased brain size in mammalian evolution, with larger brains composed of more and larger neurons than smaller brains across species within each mammalian order. Does the evolution of increased numbers of brain neurons, and thus larger brain size, occur simply through the selection of individuals with more and larger neurons, and thus larger brains, within a population? That is, do individuals with larger brains also have more, and larger, neurons than individuals with smaller brains, such that allometric relationships across species are simply an extension of intraspecific scaling? Here we show that this is not the case across adult male mice of a similar age. Rather, increased numbers of neurons across individuals are accompanied by increased numbers of other cells and smaller average cell size of both types, in a trade-off that explains how increased brain mass does not necessarily ensue. Fundamental regulatory mechanisms thus must exist that tie numbers of neurons to numbers of other cells and to average cell size within individual brains. Finally, our results indicate that changes in brain size in evolution are not an extension of individual variation in numbers of neurons, but rather occur through step changes that must simultaneously increase numbers of neurons and cause cell size to increase, rather than decrease. PMID:26082686

  1. 40 CFR 141.81 - Applicability of corrosion control treatment steps to small, medium-size and large water systems.

    Science.gov (United States)

    2010-07-01

    ... treatment steps to small, medium-size and large water systems. 141.81 Section 141.81 Protection of... WATER REGULATIONS Control of Lead and Copper § 141.81 Applicability of corrosion control treatment steps... review and approve the addition of a new source or long-term change in water treatment before it is...

  2. Cell-Based Gene Therapy for Repair of Critical Size Defects in the Rat Fibula

    Science.gov (United States)

    Lazard, ZaWaunyka W.; Heggeness, Michael H.; Hipp, John A.; Sonnet, Corinne; Fuentes, Angie S.; Nistal, Rita P.; Davis, Alan R.; Olabisi, Ronke M.; West, Jennifer L.; Olmsted-Davis, Elizabeth A.

    2012-01-01

    More than a decade has passed since the first experiments using adenovirus-transduced cells expressing bone morphogenetic protein 2 were performed for the synthesis of bone. Since this time, the field of bone gene therapy has tackled many issues surrounding safety and efficacy of this type of strategy. We present studies examining the parameters of the timing of bone healing, and remodeling when heterotopic ossification (HO) is used for bone fracture repair using an adenovirus gene therapy approach. We use a rat fibula defect, which surprisingly does not heal even when a simple fracture is introduced. In this model, the bone quickly resorbs most likely due to the non-weight bearing nature of this bone in rodents. Using our gene therapy system robust HO can be introduced at the targeted location of the defect resulting in bone repair. The HO and resultant bone healing appeared to be dose dependent, based on the number of AdBMP2-transduced cells delivered. Interestingly, the HO undergoes substantial remodeling, and assumes the size and shape of the missing segment of bone. However, in some instances we observed some additional bone associated with the repair, signifying that perhaps the forces on the newly forming bone are inadequate to dictate shape. In all cases, the HO appeared to fuse into the adjacent long bone. The data collectively indicates that the use of BMP2 gene therapy strategies may vary depending on the location and nature of the defect. Therefore, additional parameters should be considered when implementing such strategies. PMID:21344484

  3. Improvement of endothelial progenitor outgrowth cell (EPOC)-mediated vascularization in gelatin-based hydrogels through pore size manipulation.

    Science.gov (United States)

    Fu, Jiayin; Wiraja, Christian; Muhammad, Hamizan B; Xu, Chenjie; Wang, Dong-An

    2017-08-01

    In addition to chemical compositions, physical properties of scaffolds, such as pore size, can also influence vascularization within the scaffolds. A larger pore has been shown to improve host vascular tissue invasion into scaffolds. However, the influence of pore sizes on vascularization by endothelial cells directly encapsulated in hydrogels remains unknown. In this study, micro-cavitary hydrogels with different pore sizes were created in gelatin-methacrylate hydrogels with dissolvable gelatin microspheres (MS) varying in sizes. The effect of pore sizes on vascular network formation by endothelial progenitor outgrowth cells (EPOCs) encapsulated in hydrogels was then investigated both in vitro and in vivo. When cultured in vitro, vascular networks were formed around pore structures in micro-cavitary hydrogels. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro. When implantation in vivo, functional connections between encapsulated EPOCs and host vasculature micro-cavitary hydrogels were established. Vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones. This study reveals that the optimal pore size for hydrogel vascularization in vitro and in vivo is different. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro, while vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that

  4. Synthetic RNA Controllers for Programming Mammalian Cell Fate and Function

    Science.gov (United States)

    2015-11-04

    Final report for “Synthetic RNA controllers for programming mammalian cell fate and function” Principal Investigator: Christina D. Smolke...SUBTITLE Synthetic RNA controllers for programming mammalian cell fate and function 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18   2 Synthetic RNA controllers for programming mammalian cell fate and function Task 1

  5. Cell cycle controls: potential targets for chemical carcinogens?

    OpenAIRE

    Afshari, C A; Barrett, J C

    1993-01-01

    The progression of the cell cycle is controlled by the action of both positive and negative growth regulators. The key players in this activity include a family of cyclins and cyclin-dependent kinases, which are themselves regulated by other kinases and phosphatases. Maintenance of balanced cell cycle controls may be directly linked to genomic stability. Loss of the check-points involved in cell cycle control may result in unrepaired DNA damage during DNA synthesis or mitosis leading to genet...

  6. Engineering models and methods for industrial cell control

    DEFF Research Database (Denmark)

    Lynggaard, Hans Jørgen Birk; Alting, Leo

    1997-01-01

    This paper is concerned with the engineering, i.e. the designing and making, of industrial cell control systems. The focus is on automated robot welding cells in the shipbuilding industry. The industrial research project defines models and methods for design and implemen-tation of computer based....... Further, an engineering methodology is defined. The three elements enablers, architecture and methodology constitutes the Cell Control Engineering concept which has been defined and evaluated through the implementation of two cell control systems for robot welding cells in production at ODENSE STEEL...

  7. Classical cadherins control nucleus and centrosome position and cell polarity.

    Science.gov (United States)

    Dupin, Isabelle; Camand, Emeline; Etienne-Manneville, Sandrine

    2009-06-01

    Control of cell polarity is crucial during tissue morphogenesis and renewal, and depends on spatial cues provided by the extracellular environment. Using micropatterned substrates to impose reproducible cell-cell interactions, we show that in the absence of other polarizing cues, cell-cell contacts are the main regulator of nucleus and centrosome positioning, and intracellular polarized organization. In a variety of cell types, including astrocytes, epithelial cells, and endothelial cells, calcium-dependent cadherin-mediated cell-cell interactions induce nucleus and centrosome off-centering toward cell-cell contacts, and promote orientation of the nucleus-centrosome axis toward free cell edges. Nucleus and centrosome off-centering is controlled by N-cadherin through the regulation of cell interactions with the extracellular matrix, whereas the orientation of the nucleus-centrosome axis is determined by the geometry of N-cadherin-mediated contacts. Our results demonstrate that in addition to the specific function of E-cadherin in regulating baso-apical epithelial polarity, classical cadherins control cell polarization in otherwise nonpolarized cells.

  8. Spectra study and size control of cobalt nanoparticles passivated with oleic acid and triphenylphosphine

    International Nuclear Information System (INIS)

    Su Yikun; Ouyang Xing; Tang Jiaoning

    2010-01-01

    This paper compares the performance of two surfactants-triphenylphosphine (TPP) and oleic acid (OA) as a pair of capping agents in the synthesis of magnetic Co nanoparticles (NPs). Magnetic colloids of cobalt NPs are prepared by reducing solute cobalt chloride in the presence of stabilizing agents at a high temperature and characterized by TEM. Infrared spectra reveal that a chemical bond can be formed between O of C=O band and Co atoms while a coordinate bond forms between P and Co atoms around the NPs on the surface. OA binds strongly to the particle surface during synthesis that hinders the particle from growing; the TPP reversibly coordinates neutral metal surface sites that favor rapid growth. We studied the influence of changing the TPP/OA concentration ratio on the particle size distribution and crystallinity of Co NPs. Our results indicate the presence of TPP/OA is able to control particle growth, stabilize the colloidal suspension and prevent the final product from oxidation by air.

  9. One-pot size-controlled growth of graphene-encapsulated germanium nanocrystals

    Science.gov (United States)

    Lee, Jae-Hyun; Lee, Eun-Kyung; Kang, Seog-Gyun; Jung, Su-Ho; Son, Seok-Kyun; Nam, Woo Hyun; Kim, Tae-Hoon; Choi, Byong Lyong; Whang, Dongmok

    2018-05-01

    To realize graphene-encapsulated semiconductor nanocrystals (NCs), an additional graphene coating process, which causes shape destruction and chemical contamination, has so far been inevitable. We report herein one-pot growth of uniform graphene-germanium core-shell nanocrystals (Ge@G NCs) in gram scale by the addition of methane as a carbon source during the thermal pyrolysis of germane. The methane plays a critical role in the growth of the graphene shell, as well as in the determination of the nucleation density and diameter of the NCs, similar to a surfactant in the liquid-phase growth of monodisperse NCs. By adjusting the gas ratio of precursors, a mixture of germane and methane, we can control the size of the Ge@G NCs in the range of ∼5-180 nm. The Ge@G NCs were characterized by various microscopic and spectroscopic tools, which indicated that the Ge core is single crystalline, and is completely covered by the graphene shell. We further investigated the merits of the graphene shell, which can enhance the electrical conductivity of nanocrystalline materials.

  10. Stochastic Lot-Sizing under Carbon Emission Control for Profit Optimisation in MTO Manufacturing

    Directory of Open Access Journals (Sweden)

    Qiao A.

    2017-01-01

    Full Text Available Aggravating global warming has heightened the imminent need by the world to step up forceful efforts on curbing emission of greenhouse gases. Although manufacturing is a major resource of carbon emission, few research works have studied the impacts of carbon constraints on manufacturing, leading to environmentally unsustainable production strategies and operations. This paper incorporates carbon emission management into production planning for make-to-order (MTO manufacturing. This paper proposes a model that solves lot-sizing problems to maximise profits under carbon emission caps. The model adopts stochastic interarrival times for customer orders to enhance the practicality of the results for real-world manufacturing. Numerical experiments show that reducing carbon emission undercuts short-term profits of a company. However, it is conducive to the company’s market image as being socially responsible which would attract more customers who concern about environmental protection. Hence, reducing carbon emission in manufacturing is beneficial to long-term profitability and sustainability. The results provide managerial insights into manufacture operations for balancing profitability and carbon control.

  11. Spectra study and size control of cobalt nanoparticles passivated with oleic acid and triphenylphosphine

    Energy Technology Data Exchange (ETDEWEB)

    Su Yikun, E-mail: yikun@szu.edu.cn [College of Materials Science and Engineering, Shenzhen University, Shenzhen Key Laboratory of Special Functional Materials, Shenzhen 518060 (China); Ouyang Xing; Tang Jiaoning [College of Materials Science and Engineering, Shenzhen University, Shenzhen Key Laboratory of Special Functional Materials, Shenzhen 518060 (China)

    2010-02-01

    This paper compares the performance of two surfactants-triphenylphosphine (TPP) and oleic acid (OA) as a pair of capping agents in the synthesis of magnetic Co nanoparticles (NPs). Magnetic colloids of cobalt NPs are prepared by reducing solute cobalt chloride in the presence of stabilizing agents at a high temperature and characterized by TEM. Infrared spectra reveal that a chemical bond can be formed between O of C=O band and Co atoms while a coordinate bond forms between P and Co atoms around the NPs on the surface. OA binds strongly to the particle surface during synthesis that hinders the particle from growing; the TPP reversibly coordinates neutral metal surface sites that favor rapid growth. We studied the influence of changing the TPP/OA concentration ratio on the particle size distribution and crystallinity of Co NPs. Our results indicate the presence of TPP/OA is able to control particle growth, stabilize the colloidal suspension and prevent the final product from oxidation by air.

  12. Control of crystallite orientation and size in Fe and FeCo nanoneedles

    International Nuclear Information System (INIS)

    Mendoza-Reséndez, Raquel; Luna, Carlos; Diaz Barriga-Castro, Enrique; Bonville, Pierre; Serna, Carlos J

    2012-01-01

    Uniform magnetic nanoneedles have been prepared by hydrogen reduction of elongated nanoarchitectures. These precursors are as-prepared or cobalt-coated aggregates of highly oriented haematite nanocrystals (∼5 nm). The final materials are flattened nanoneedles formed by chains of assembled Fe or FeCo single-domain nanocrystals. The microstructural properties of such nanoneedles were tailored using renewed and improved synthetic strategies. In this fashion, the needle elongation and composition, the crystallite size (from 15 up to 30 nm), the nanocrystal orientation (with the 〈110〉 or 〈001〉 directions roughly along the long axis of the nanoneedle) and their type of arrangement (single chains, frustrated double chains and double chains) were controlled by modifying the reduction time, the axial ratio of the precursor haematite and the presence of additional coatings of aluminum or yttrium compounds. The values of the coercivity H C found for these nanoneedles are compared with the values predicted by the chain of spheres model assuming a symmetric fanning mechanism for magnetization reversal. (paper)

  13. Nuclei size in relation to nuclear status and aneuploidy rate for 13 chromosomes in donated four cells embryos

    DEFF Research Database (Denmark)

    Agerholm, I.E.; Hnida, C.; Cruger, D.G.

    2008-01-01

    Purpose The aim was to elucidate if the nuclear size and number are indicative of aberrant chromosome content in human blastomeres and embryos. Methods The number of nuclei and the nucleus and blastomere size were measured by a computer controlled system for multilevel analysis. Then the nuclei...... were enumerated for 13 chromosomes by a combination of PNA and DNA probes. Results In the mononucleated embryos there was no difference in the mean size of chromosomally normal and abnormal nuclei but a significant difference in the mean nuclei size of nuclei that had gained chromosomes compared...... to nuclei that had lost chromosomes. The nuclei from multinucleated blastomeres had a significant smaller mean size and the frequency of chromosomally aberrant blastomeres was significantly higher. Conclusion The mean nuclear size is not a marker for the chromosome content in mononucleated embryos. However...

  14. Application of the Stage, Size, Grade, and Necrosis (SSIGN) Score for Clear Cell Renal Cell Carcinoma in Contemporary Patients.

    Science.gov (United States)

    Parker, William P; Cheville, John C; Frank, Igor; Zaid, Harras B; Lohse, Christine M; Boorjian, Stephen A; Leibovich, Bradley C; Thompson, R Houston

    2017-04-01

    The tumor stage, size, grade, and necrosis (SSIGN) score was originally defined using patients treated with radical nephrectomy (RN) between 1970 and 1998 for clear cell renal cell carcinoma (ccRCC), excluding patients treated with partial nephrectomy (PN). To characterize the original SSIGN score cohort with longer follow-up and evaluate a contemporary series of patients treated with RN and PN. Retrospective single-institution review of 3600 consecutive surgically treated ccRCC patients grouped into three cohorts: original RN, contemporary (1999-2010) RN, and contemporary PN. RN or PN. The association of the SSIGN score with risk of death from RCC was assessed using a Cox proportional hazards regression model, and predictive ability was summarized with a C-index. The SSIGN scores differed significantly between the original RN, contemporary RN, and contemporary PN cohorts (pcontemporary RN, and 1.70 for contemporary PN; all pcontemporary RN, and contemporary PN, respectively. After accounting for an era-specific improvement in survival among RN patients (HR: 0.53 for contemporary vs original RN; pcontemporary RN and PN patients, the score retained strong predictive ability. These results should assist in patient counseling and help guide surveillance for ccRCC patients treated with RN or PN. We evaluated the validity of a previously described tool to predict survival following surgery in contemporary patients with kidney cancer. We found that this tool remains valid even when extended to patients significantly different than were initially used to create the tool. Copyright © 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.

  15. Selective self-assembly of adenine-silver nanoparticles forms rings resembling the size of cells

    Science.gov (United States)

    Choi, Sungmoon; Park, Soonyoung; Yang, Seon-Ah; Jeong, Yujin; Yu, Junhua

    2015-01-01

    Self-assembly has played critical roles in the construction of functional nanomaterials. However, the structure of the macroscale multicomponent materials built by the self-assembly of nanoscale building blocks is hard to predict due to multiple intermolecular interactions of great complexity. Evaporation of solvents is usually an important approach to induce kinetically stable assemblies of building blocks with a large-scale specific arrangement. During such a deweting process, we tried to monitor the possible interactions between silver nanoparticles and nucleobases at a larger scale by epifluorescence microscopy, thanks to the doping of silver nanoparticles with luminescent silver nanodots. ssDNA oligomer-stabilized silver nanoparticles and adenine self-assemble to form ring-like compartments similar to the size of modern cells. However, the silver ions only dismantle the self-assembly of adenine. The rings are thermodynamically stable as the drying process only enrich the nanoparticles-nucleobase mixture to a concentration that activates the self-assembly. The permeable membrane-like edge of the ring is composed of adenine filaments glued together by silver nanoparticles. Interestingly, chemicals are partially confined and accumulated inside the ring, suggesting that this might be used as a microreactor to speed up chemical reactions during a dewetting process. PMID:26643504

  16. Effect of fertilization on cell size in wood of Eucalyptus grandis Hill Ex Maiden

    Directory of Open Access Journals (Sweden)

    Luiz Santini Junior

    2010-12-01

    Full Text Available The use of fertilization in forest stands results in yield gains, yet little attention has been directed to its potential effects on the quality of wood produced. Information is scarce about the effect of fertilization on anatomical structures of older Eucalyptus wood. This work aims to study the effect of fertilization on tissue cell size of wood from a Eucalyptus grandis stand at age 21 years, the management system of which is based on selective thinning and fertilizer application at the start of the thinning season. Factors to consider include: presence or absence of fertilizers, two log positions and five radial (pith to bark positions. Results led to the conclusion that fertilization significantly influenced only vessel frequency. Vessel elements length was influenced by tree height. Fiber length, fiber diameter, fiber wall thickness, vessel elements length, vessel diameter and vessel frequency were influenced by the radial position of the sample in relation to the log. A positive correlation was observed between fiber length, fiber diameter, fiber wall thickness, vessel elements length, vessel diameter, ray width and radial position, while a negative correlation was observed between ray frequency and radial position.

  17. Using cathode spacers to minimize reactor size in air cathode microbial fuel cells

    KAUST Repository

    Yang, Qiao

    2012-04-01

    Scaling up microbial fuel cells (MFCs) will require more compact reactor designs. Spacers can be used to minimize the reactor size without adversely affecting performance. A single 1.5mm expanded plastic spacer (S1.5) produced a maximum power density (973±26mWm -2) that was similar to that of an MFC with the cathode exposed directly to air (no spacer). However, a very thin spacer (1.3mm) reduced power by 33%. Completely covering the air cathode with a solid plate did not eliminate power generation, indicating oxygen leakage into the reactor. The S1.5 spacer slightly increased columbic efficiencies (from 20% to 24%) as a result of reduced oxygen transfer into the system. Based on operating conditions (1000ς, CE=20%), it was estimated that 0.9Lh -1 of air would be needed for 1m 2 of cathode area suggesting active air flow may be needed for larger scale MFCs. © 2012 Elsevier Ltd.

  18. Population size drives industrial Saccharomyces cerevisiae alcoholic fermentation and is under genetic control.

    Science.gov (United States)

    Albertin, Warren; Marullo, Philippe; Aigle, Michel; Dillmann, Christine; de Vienne, Dominique; Bely, Marina; Sicard, Delphine

    2011-04-01

    Alcoholic fermentation (AF) conducted by Saccharomyces cerevisiae has been exploited for millennia in three important human food processes: beer and wine production and bread leavening. Most of the efforts to understand and improve AF have been made separately for each process, with strains that are supposedly well adapted. In this work, we propose a first comparison of yeast AFs in three synthetic media mimicking the dough/wort/grape must found in baking, brewing, and wine making. The fermentative behaviors of nine food-processing strains were evaluated in these media, at the cellular, populational, and biotechnological levels. A large variation in the measured traits was observed, with medium effects usually being greater than the strain effects. The results suggest that human selection targeted the ability to complete fermentation for wine strains and trehalose content for beer strains. Apart from these features, the food origin of the strains did not significantly affect AF, suggesting that an improvement program for a specific food processing industry could exploit the variability of strains used in other industries. Glucose utilization was analyzed, revealing plastic but also genetic variation in fermentation products and indicating that artificial selection could be used to modify the production of glycerol, acetate, etc. The major result was that the overall maximum CO(2) production rate (V(max)) was not related to the maximum CO(2) production rate per cell. Instead, a highly significant correlation between V(max) and the maximum population size was observed in all three media, indicating that human selection targeted the efficiency of cellular reproduction rather than metabolic efficiency. This result opens the way to new strategies for yeast improvement.

  19. Effects of cell spatial organization and size distribution on ultrasound backscattering.

    Science.gov (United States)

    Saha, Ratan K; Kolios, Michael C

    2011-10-01

    In ultrasound tissue characterization dealing with cellular aggregates (such as tumors), it can be hypothesized that cell microstructure and spatial distribution dominate the backscatter signal. Effects of spatial organization and size distribution of nuclei in cell aggregates on ultrasound backscatter are examined in this work using 2-D computer simulations. The nuclei embedded in cytoplasm were assumed to be weak scatterers of incident ultrasound waves, and therefore multiple scattering could be neglected. The fluid sphere model was employed to obtain the scattering amplitude for each nucleus and the backscatter echo was generated by summing scattered signals originating from many nuclei. A Monte Carlo algorithm was implemented to generate realizations of cell aggregates. It was found that the integrated backscattering coefficient (IBSC) computed between 10 and 30 MHz increased by about 27 dB for a spatially random distribution of mono-disperse nuclei (radius = 4.5 μm) compared with that of a sample of periodically positioned mono-disperse nuclei. The IBSC also increased by nearly 7 dB (between 10 and 30 MHz) for a spatially random distribution of poly-disperse nuclei (mean radius ± SD = 4.5 ± 1.54 μm) compared with that of a spatially random distribution of mono-disperse nuclei. Two different Gaussian pulses with center frequencies 5 and 25 MHz were employed to study the backscatter envelope statistics. An 80% bandwidth was chosen for each case with approximately 0.32 mm as the full-width at half-maximum (FWHM) for the first pulse and 0.06 mm for the second. The incident beam was approximated as a Gaussian beam (FWHM = 2.11 and 1.05 mm for those pulses, respectively). The backscatter signal envelope histograms generally followed the Rayleigh distribution for mono-disperse and poly-disperse samples. However, for samples with partially ordered nuclei, if the irradiating pulse contained a frequency for which ultrasound wavelength and scatter periodicity became

  20. Improving Sunflower Halva Stability and Texture by Controlling Tahini Particle Size Distribution

    OpenAIRE

    Vlad Mureşan; Lucian Cuibus; Anna Olari; Emil Racolţa; Carmen Socaciu; Sabine Danthine; Sevastița Muste; Christophe Blecker

    2015-01-01

    Sunflower halva is an appreciated product, but shows currently a quality below the expectations of the new generation of consumers, having a hard texture and oil exuded on the surface (low stability). The aim of this work was to assess the influence of tahini particle size on sunflower halva texture and stability. Eight different particle size sunflower tahini samples were produced at pilot plant scale, the higher the number of passes through the colloidal mill, the smaller the particle size ...

  1. The effects of different size gold nanoparticles on mechanical properties of vascular smooth muscle cells under mechanical stretching

    Science.gov (United States)

    Kieu, Tri Minh

    Nanotechnology is an emerging and promising frontier for medicine and biomedical research due to its potential for applications such as drug delivery, imaging enhancement, and cancer treatment. While these materials may possess significant possibilities, the effects of these particles in the body and how the particles affect the cells is not fully understood. In this study, vascular smooth muscle cells (VSMCs) will be exposed to 5 and 20 nm diameter citrate AuNPs under mechanical conditions. The cytotoxicity properties of these particles will be investigated using LDH and MTT assays. Atomic force microscopy will be used to study how the size of the nanoparticles affect the mechanical properties of the VSMCs. Immunofluorescence staining for alpha actin will also be performed to enhance understanding of the phenotypic shift. The LDH and MTT cytotoxicity assay results demonstrated that neither 5 nor 20 nm diameter nanoparticles are cytotoxic to the cells. However, the mechanical properties and cell morphology of the VSMCs was altered. Under static conditions, both AuNP treatments decreased the mechanical properties of the cells. The size of the nanoparticles had a softening effect on elastic modulus of the cell and sign of a synthetic phenotype was observed. The VSMCs subjected to mechanical stretching exhibited higher elastic modulus compared to the static experimental groups. Again, both AuNPs treatments decreased the mechanical properties of the cells and signs of more synthetic phenotype was seen. However, the size of the nanoparticles did not have any influence on cell's elastic modulus unlike the static treated cells. The mechanical testing condition provided a better look at how these particles would affect the cells in vivo. While the nanoparticles are not cytotoxic to the VSMCs, they are altering the mechanical properties and phenotype of the cell.

  2. The effect of increasing the pore size of nanofibrous scaffolds on the osteogenic cell culture using a combination of sacrificial agent electrospinning and ultrasonication.

    Science.gov (United States)

    Aghajanpoor, Mahdiyeh; Hashemi-Najafabadi, Sameereh; Baghaban-Eslaminejad, Mohamadreza; Bagheri, Fatemeh; Mohammad Mousavi, Seyyed; Azam Sayyahpour, Foruogh

    2017-07-01

    One of the major problems associated with the electrospun scaffolds is their small pore size, which limits the cellular infiltration for bone tissue engineering. In this study, the effect of increasing the pore size on cellular infiltration was studied in poly/nanohydroxyapatite electrospun scaffolds, which were modified using ultrasonication, co-electrospinning with poly (ethylene oxide), and a combination of both. Ultrasonic process was optimized by central composite design. The ultrasonic output power and time of the process were considered as the effective parameters. The pore size of the scaffolds was evaluated by scanning electron microscope. The optimum conditions, according to the pore area and mechanical properties of the scaffolds were selected, and finally the groups that had the highest pore size and mechanical strength were selected for the combined method. Increasing the pore size enhanced the cellular proliferation, extension and infiltration, as well as the osteodifferentiation of stem cells. At the optimum condition, the average cellular infiltration was 36.51 µm compared to the control group with no cellular infiltration. In addition, alkaline phosphatase activity and the expression of osteocalcin and collagen I (COL I) were, respectively, 1.86, 2.54, and 2.16 fold compared to the control group on day 14. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1887-1899, 2017. © 2017 Wiley Periodicals, Inc.

  3. Size-controlled heating ability of CoFe2O4 nanoparticles for hyperthermia applications

    Science.gov (United States)

    Phong, P. T.; Phuc, N. X.; Nam, P. H.; Chien, N. V.; Dung, D. D.; Linh, P. H.

    2018-02-01

    The magnetic properties and heating capacity of cobalt ferrite (CoFe2O4) nanoparticles 13-24 nm in size were studied. Results showed that the specific absorption rate of the nanoparticles strongly depended on their magnetic properties and particle size. Specific absorption rate values decreased with increased particle size, and the smallest CoFe2O4 nanoparticles (13.5 nm) exhibited the highest specific absorption rate. The mechanism underlying the decrease in specific absorption rate of the CoFe2O4 nanoparticles with increased particle size was also discussed.

  4. The Size of Activating and Inhibitory Killer Ig-like Receptor Nanoclusters Is Controlled by the Transmembrane Sequence and Affects Signaling

    Directory of Open Access Journals (Sweden)

    Anna Oszmiana

    2016-05-01

    Full Text Available Super-resolution microscopy has revealed that immune cell receptors are organized in nanoscale clusters at cell surfaces and immune synapses. However, mechanisms and functions for this nanoscale organization remain unclear. Here, we used super-resolution microscopy to compare the surface organization of paired killer Ig-like receptors (KIR, KIR2DL1 and KIR2DS1, on human primary natural killer cells and cell lines. Activating KIR2DS1 assembled in clusters two-fold larger than its inhibitory counterpart KIR2DL1. Site-directed mutagenesis established that the size of nanoclusters is controlled by transmembrane amino acid 233, a lysine in KIR2DS1. Super-resolution microscopy also revealed two ways in which the nanoscale clustering of KIR affects signaling. First, KIR2DS1 and DAP12 nanoclusters are juxtaposed in the resting cell state but coalesce upon receptor ligation. Second, quantitative super-resolution microscopy revealed that phosphorylation of the kinase ZAP-70 or phosphatase SHP-1 is favored in larger KIR nanoclusters. Thus, the size of KIR nanoclusters depends on the transmembrane sequence and affects downstream signaling.

  5. Bacterial cell curvature through mechanical control of cell growth

    DEFF Research Database (Denmark)

    Cabeen, M.; Charbon, Godefroid; Vollmer, W.

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...... that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature...... can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics...

  6. Role of nano and micron-sized inclusions on the oxygen controlled preform optimized infiltration growth processed YBCO superconductors

    Science.gov (United States)

    Pavan Kumar Naik, S.; Bai, V. Seshu

    2017-02-01

    In the present work, with the aim of improving the local flux pinning at the unit cell level in the YBa2Cu3O7-δ (YBCO) bulk superconductors, 20 wt% of nanoscale Sm2O3 and micron sized (Nd, Sm, Gd)2BaCuO5 secondary phase particles were added to YBCO and processed in oxygen controlled preform optimized infiltration growth process. Nano Dispersive Sol Casting method is employed to homogeneously distribute the nano Sm2O3 particles of 30-50 nm without any agglomeration in the precursor powder. Microstructural investigations on doped samples show the chemical fluctuations as annuli cores in the 211 phase particles. The introduction of mixed rare earth elements at Y-site resulted in compositional fluctuations in the superconducting matrix. The associated lattice mismatch defects have provided flux pinning up to large magnetic fields. Magnetic field dependence of current density (Jc(H)) at different temperatures revealed that the dominant pinning mechanism is caused by spatial variations of critical temperatures, due to the spatial fluctuations in the matrix composition. As the number of rare earth elements increased in the YBCO, the peak field position in the scaling of the normalized pinning force density (Fp/Fp max) significantly gets shifted towards the higher fields. The curves of Jc(H) and Fp/Fp max at different temperatures clearly indicate the LRE substitution for LRE' or Ba-sites for δTc pinning.

  7. Engineering models and methods for industrial cell control

    DEFF Research Database (Denmark)

    Lynggaard, Hans Jørgen Birk; Alting, Leo

    1997-01-01

    This paper is concerned with the engineering, i.e. the designing and making, of industrial cell control systems. The focus is on automated robot welding cells in the shipbuilding industry. The industrial research project defines models and methods for design and implemen-tation of computer based...... control and monitor-ing systems for production cells. The project participants are The Danish Academy of Technical Sciences, the Institute of Manufacturing Engineering at the Technical University of Denmark and ODENSE STEEL SHIPYARD Ltd.The manufacturing environment and the current practice...... for engineering of cell control systems has been analysed as well as automation software enablers. A number of problems related to these issues are identified.In order to support engineering of cell control systems by the use of enablers, a generic cell control data model and an architecture has been defined...

  8. Fixation patterns, not clinical diagnosis, predict body size over-estimation in eating disordered women and healthy controls.

    Science.gov (United States)

    Cornelissen, Katri K; Cornelissen, Piers L; Hancock, Peter J B; Tovée, Martin J

    2016-05-01

    A core feature of anorexia nervosa (AN) is an over-estimation of body size. Women with AN have a different pattern of eye-movements when judging bodies, but it is unclear whether this is specific to their diagnosis or whether it is found in anyone over-estimating body size. To address this question, we compared the eye movement patterns from three participant groups while they carried out a body size estimation task: (i) 20 women with recovering/recovered anorexia (rAN) who had concerns about body shape and weight and who over-estimated body size, (ii) 20 healthy controls who had normative levels of concern about body shape and who estimated body size accurately (iii) 20 healthy controls who had normative levels of concern about body shape but who did over-estimate body size. Comparisons between the three groups showed that: (i) accurate body size estimators tended to look more in the waist region, and this was independent of clinical diagnosis; (ii) there is a pattern of looking at images of bodies, particularly viewing the upper parts of the torso and face, which is specific to participants with rAN but which is independent of accuracy in body size estimation. Since the over-estimating controls did not share the same body image concerns that women with rAN report, their over-estimation cannot be explained by attitudinal concerns about body shape and weight. These results suggest that a distributed fixation pattern is associated with over-estimation of body size and should be addressed in treatment programs. © 2016 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:507-518). © 2016 The Authors. International Journal of Eating Disorders published by Wiley Periodicals, Inc.

  9. Mesoporous Silica Supported Au Nanoparticles with Controlled Size as Efficient Heterogeneous Catalyst for Aerobic Oxidation of Alcohols

    Directory of Open Access Journals (Sweden)

    Xuefeng Chu

    2015-01-01

    Full Text Available A series of Au catalysts with different sizes were synthesized and employed on amine group functionalized ordered mesoporous silica solid supports as catalyst for the aerobic oxidation of various alcohols. The mesoporous silica of MCM-41 supported Au nanoparticles (Au-1 exhibited the smallest particle size at ~1.8 nm with superior catalytic activities owing to the confinement effect of the mesoporous channels. Au-1 catalyst is also very stable and reusable under aerobic condition. Therefore, this presented work would obviously provide us a platform for synthesizing more size-controlled metal catalysts to improve the catalytic performances.

  10. Sample Size Calculation: Inaccurate A Priori Assumptions for Nuisance Parameters Can Greatly Affect the Power of a Randomized Controlled Trial.

    Directory of Open Access Journals (Sweden)

    Elsa Tavernier

    Full Text Available We aimed to examine the extent to which inaccurate assumptions for nuisance parameters used to calculate sample size can affect the power of a randomized controlled trial (RCT. In a simulation study, we separately considered an RCT with continuous, dichotomous or time-to-event outcomes, with associated nuisance parameters of standard deviation, success rate in the control group and survival rate in the control group at some time point, respectively. For each type of outcome, we calculated a required sample size N for a hypothesized treatment effect, an assumed nuisance parameter and a nominal power of 80%. We then assumed a nuisance parameter associated with a relative error at the design stage. For each type of outcome, we randomly drew 10,000 relative errors of the associated nuisance parameter (from empirical distributions derived from a previously published review. Then, retro-fitting the sample size formula, we derived, for the pre-calculated sample size N, the real power of the RCT, taking into account the relative error for the nuisance parameter. In total, 23%, 0% and 18% of RCTs with continuous, binary and time-to-event outcomes, respectively, were underpowered (i.e., the real power was 90%. Even with proper calculation of sample size, a substantial number of trials are underpowered or overpowered because of imprecise knowledge of nuisance parameters. Such findings raise questions about how sample size for RCTs should be determined.

  11. Novel single-cell mega-size chambers for electrochemical etching of panorama position-sensitive polycarbonate ion image detectors

    Science.gov (United States)

    Sohrabi, Mehdi

    2017-11-01

    A novel development is made here by inventing panorama single-cell mega-size electrochemical etching (MS-ECE) chamber systems for processing panorama position-sensitive mega-size polycarbonate ion image detectors (MS-PCIDs) of potential for many neutron and ion detection applications in particular hydrogen ions or proton tracks and images detected for the first time in polycarbonates in this study. The MS-PCID is simply a large polycarbonate sheet of a desired size. The single-cell MS-ECE invented consists of two large equally sized transparent Plexiglas sheets as chamber walls holding a MS-PCID and the ECE chamber components tightly together. One wall has a large flat stainless steel electrode (dry cell) attached to it which is directly in contact with the MS-PCID and the other wall has a rod electrode with two holes to facilitate feeding and draining out the etching solution from the wet cell. A silicon rubber washer plays the role of the wet cell to hold the etchant and the electrical insulator to isolate the dry cell from the wet cell. A simple 50 Hz-HV home-made generator provides an adequate field strength through the two electrodes across the MS-ECE chamber. Two panorama single-cell MS-ECE chamber systems (circular and rectangular shapes) constructed were efficiently applied to processing the MS-PCIDs for 4π ion emission image detection of different gases in particular hydrogen ions or protons in a 3.5 kJ plasma focus device (PFD as uniquely observed by the unaided eyes). The panorama MS-PCID/MS-ECE image detection systems invented are novel with high potential for many applications in particular as applied to 4π panorama ion emission angular distribution image detection studies in PFD space, some results of which are presented and discussed.

  12. Genetic control of cowpea seed sizes Controle genético do tamanho das sementes de caupi

    Directory of Open Access Journals (Sweden)

    Francisco Cláudio da Conceição Lopes

    2003-01-01

    Full Text Available Cowpea [Vigna unguiculata (L. Walp.] is one of the most widely adapted grain legumes in hot regions of Africa, Asia and the Americas. In the semiarid Northeast of Brazil, it is the main subsistence crop, an excellent protein source of low cost, for the poor population. The objective of this work was to estimate genetic parameters to understand the inheritance of seed sizes in cowpea. The parents P1 and P2 and the generations, F1, F2, BC1 and BC2 of the cross TVx5058-09C X Manteiguinha formed the genetic material for this study. These six generates (P1, P2, F1, F2, BC1 and BC were evaluated in a completely randomized block-design with six replications, in Teresina - PI, Brazil, in 1998. The genetic parameters estimated were: phenotypic and total genetic variance, additive and dominance genetic components of variance and the variance attributed to the environment, heritability in the broad and narrow senses, average degree of dominance and the number of genes controlling the character. The additive - dominance model fitted the data for 100-seeds weight in as much as the midparental value and the additive effect were the more important genetic parameters for the determination of this character. The number of genes that control its expression is five. The occurrence of high values for narrow sense heritability indicates that the selection for seed size can be made in early generations.Caupi [Vigna unguiculata (L. Walp.] é uma das leguminosas mais adaptadas às regiões quentes da África, Ásia e das Américas. No semi-árido do nordeste do Brasil é a principal cultura de subsistência, por ser uma excelente fonte de proteína de baixo custo para a população mais carente. O objetivo deste trabalho foi estimar parâmetros genéticos que podem explicar a herança do tamanho das sementes de caupi. Os genótipos parentais P1 e P2 e as gerações F1, F2, RC1 e RC2 do cruzamento TVx5058-09C X Manteiguinha, constituíram o material genético utilizado

  13. Controlled Delivery of Human Cells by Temperature Responsive Microcapsules

    Science.gov (United States)

    Mak, W.C.; Olesen, K.; Sivlér, P.; Lee, C.J.; Moreno-Jimenez, I.; Edin, J.; Courtman, D.; Skog, M.; Griffith, M.

    2015-01-01

    Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line—human umbilical vein endothelial cells (HUVECs). While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation. PMID:26096147

  14. Controlled Delivery of Human Cells by Temperature Responsive Microcapsules

    Directory of Open Access Journals (Sweden)

    W.C. Mak

    2015-06-01

    Full Text Available Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line—human umbilical vein endothelial cells (HUVECs. While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation.

  15. A Modified Thermal Treatment Method for the Up-Scalable Synthesis of Size-Controlled Nanocrystalline Titania

    Directory of Open Access Journals (Sweden)

    Aysar Sabah Keiteb

    2016-10-01

    Full Text Available Considering the increasing demand for titania nanoparticles with controlled quality for various applications, the present work reports the up-scalable synthesis of size-controlled titanium dioxide nanocrystals with a simple and convenient thermal treatment route. Titanium dioxide nanocrystals with tetragonal structure were synthesized directly from an aqueous solution containing titanium (IV isopropoxide as the main reactant, polyvinyl pyrrolidone (PVP as the capping agent, and deionized water as a solvent. With the elimination of the drying process in a thermal treatment method, an attempt was made to decrease the synthesis time. The mixture directly underwent calcination to form titanium dioxide (TiO2 nanocrystalline powder, which was confirmed by FT-IR, energy dispersive X-ray spectroscopy (EDX, and X-ray diffraction (XRD analysis. The control over the size and optical properties of nanocrystals was achieved via variation in calcination temperatures. The obtained average sizes from XRD spectra and transmission electron microscopy (TEM images showed exponential variation with increasing calcination temperature. The optical properties showed a decrease in the band gap energy with increasing calcination temperature due to the enlargement of the nanoparticle size. These results prove that direct calcination of reactant solution is a convenient thermal treatment route for the potential large-scale production of size-controlled Titania nanoparticles.

  16. Controling stem cell proliferation - CKIs at work

    NARCIS (Netherlands)

    Bruggeman, SWM; van Lohuizen, M

    2006-01-01

    The cyclin-dependent kinase inhibitors or CKIs are well recognized as intrinsic regulators of the cell cycle. Here, we discuss recent data implicating their activity in restraining adult stem cell self-renewal, and the role that proteins regulating CKI expression play in this process.

  17. Control of cell proliferation by Myc

    DEFF Research Database (Denmark)

    Bouchard, C; Staller, P; Eilers, M

    1998-01-01

    Myc proteins are key regulators of mammalian cell proliferation. They are transcription factors that activate genes as part of a heterodimeric complex with the protein Max. This review summarizes recent progress in understanding how Myc stimulates cell proliferation and how this might contribute...

  18. Organic Based Solar Cells with Morphology Control

    DEFF Research Database (Denmark)

    Andersen, Thomas Rieks

    The field of organic solar cells has in the last years gone through an impressive development with efficiencies reported up to 12 %. For organic solar cells to take the leap from primarily being a laboratory scale technology to being utilized as renewable energy source, several issues need...... Microscopy and as solar cells in a blend with PCBM. It was concluded that these particles did not show a potential large enough for continuous work due to a high material loss and low efficiency when applied in solar cells. The second method to achieve was preparation of pre-arranged morphology organic...... nanoparticles consisting of a blend of donor and acceptor in an aqueous dispersion, thereby addressing two of the issues remaining in the field of organic solar cells. This approach was used on six different polymers, which all had the ability to prepare aqueous nanoparticle inks. The morphology...

  19. Muscle Stem Cell Fate Is Controlled by the Cell-Polarity Protein Scrib

    Directory of Open Access Journals (Sweden)

    Yusuke Ono

    2015-02-01

    Full Text Available Satellite cells are resident skeletal muscle stem cells that supply myonuclei for homeostasis, hypertrophy, and repair in adult muscle. Scrib is one of the major cell-polarity proteins, acting as a potent tumor suppressor in epithelial cells. Here, we show that Scrib also controls satellite-cell-fate decisions in adult mice. Scrib is undetectable in quiescent cells but becomes expressed during activation. Scrib is asymmetrically distributed in dividing daughter cells, with robust accumulation in cells committed to myogenic differentiation. Low Scrib expression is associated with the proliferative state and preventing self-renewal, whereas high Scrib levels reduce satellite cell proliferation. Satellite-cell-specific knockout of Scrib in mice causes a drastic and insurmountable defect in muscle regeneration. Thus, Scrib is a regulator of tissue stem cells, controlling population expansion and self-renewal with Scrib expression dynamics directing satellite cell fate.

  20. Experimental investigation of particle size distribution influence on diffusion controlled coarsening

    International Nuclear Information System (INIS)

    Fang, Zhigang; Patterson, B.R.

    1993-01-01

    The influence of initial particle size distribution on coarsening during liquid phase sintering has been experimentally investigated using W-14Ni-6Fe alloy as a model system. It was found that initially wider size distribution particles coarsened more rapidly than those of an initially narrow distribution. The well known linear relationship between the cube of the average particle radius bar r -3 , and time was observed for most of the coarsening process, although the early stage coarsening rate constant changed with time, as expected with concomitant early changes in the tungsten particle size distribution. The instantaneous transient rate constant was shown to be related to the geometric standard deviation, 1nσ, of the instantaneous size distributions, with higher rate constants corresponding to larger 1nσ values. The form of the particle size distributions changed rapidly during early coarsening and reached a quasi-stable state, different from the theoretical asymptotic distribution, after some time. A linear relationship was found between the experimentally observed instantaneous rate constant and that computed from an earlier model incorporating the effect of particle size distribution. The above results compare favorably with those from prior theoretical modeling and computer simulation studies of the effect of particle size distribution on coarsening, based on the DeHoff communicating neighbor model

  1. Short Term Motor-Skill Acquisition Improves with Size of Self-Controlled Virtual Hands.

    Science.gov (United States)

    Ossmy, Ori; Mukamel, Roy

    2017-01-01

    Visual feedback in general, and from the body in particular, is known to influence the performance of motor skills in humans. However, it is unclear how the acquisition of motor skills depends on specific visual feedback parameters such as the size of performing effector. Here, 21 healthy subjects physically trained to perform sequences of finger movements with their right hand. Through the use of 3D Virtual Reality devices, visual feedback during training consisted of virtual hands presented on the screen, tracking subject's hand movements in real time. Importantly, the setup allowed us to manipulate the size of the displayed virtual hands across experimental conditions. We found that performance gains increase with the size of virtual hands. In contrast, when subjects trained by mere observation (i.e., in the absence of physical movement), manipulating the size of the virtual hand did not significantly affect subsequent performance gains. These results demonstrate that when it comes to short-term motor skill learning, the size of visual feedback matters. Furthermore, these results suggest that highest performance gains in individual subjects are achieved when the size of the virtual hand matches their real hand size. These results may have implications for optimizing motor training schemes.

  2. Short Term Motor-Skill Acquisition Improves with Size of Self-Controlled Virtual Hands.

    Directory of Open Access Journals (Sweden)

    Ori Ossmy

    Full Text Available Visual feedback in general, and from the body in particular, is known to influence the performance of motor skills in humans. However, it is unclear how the acquisition of motor skills depends on specific visual feedback parameters such as the size of performing effector. Here, 21 healthy subjects physically trained to perform sequences of finger movements with their right hand. Through the use of 3D Virtual Reality devices, visual feedback during training consisted of virtual hands presented on the screen, tracking subject's hand movements in real time. Importantly, the setup allowed us to manipulate the size of the displayed virtual hands across experimental conditions. We found that performance gains increase with the size of virtual hands. In contrast, when subjects trained by mere observation (i.e., in the absence of physical movement, manipulating the size of the virtual hand did not significantly affect subsequent performance gains. These results demonstrate that when it comes to short-term motor skill learning, the size of visual feedback matters. Furthermore, these results suggest that highest performance gains in individual subjects are achieved when the size of the virtual hand matches their real hand size. These results may have implications for optimizing motor training schemes.

  3. Size-controllable synthesis of nanosized-TiO2 anatase using porous Vycor glass as template

    International Nuclear Information System (INIS)

    Mazali, I.O.; Filho, A.G. Souza; Viana, B.C.; Filho, J. Mendes; Alves, O.L.

    2006-01-01

    In this paper we report the synthesis and characterization of TiO 2 nanocrystal dispersed into a porous Vycor glass. We have obtained very small TiO 2 nanocrystals in the anatase form. The nanocrystal size is controlled via the mass increment only thus preventing the growth through the coalescence process. The nanocrystal size was monitored through transmission electron microscope and Raman scattering. The coalescence control is attributed due to the obtention of nanocrystals dispersed into the host and to the terminal bonds present in the porous which act as an anchor thus resulting in a low diffusion of the nanocrystals through the porous network

  4. Molecular Control of Interdigital Cell Death and Cell Differentiation by Retinoic Acid during Digit Development

    Directory of Open Access Journals (Sweden)

    Martha Elena Díaz-Hernández

    2014-04-01

    Full Text Available The precise coordination of cell death and cell differentiation during the formation of developing digits is essential for generating properly shaped limbs. Retinoic acid (RA has a fundamental role in digit development; it promotes or inhibits the molecular expression of several critical genes. This control of gene expression establishes molecular cascades that enable both the commencement of cell death and the inhibition of cell differentiation. In this review, we focus on the antagonistic functions between RA and fibroblast growth factor (FGF signaling in the control of cell death and between RA and transforming growth factor beta (TGFβ signaling in the control of cell differentiation.

  5. Energy, control and DNA structure in the living cell

    DEFF Research Database (Denmark)

    Wijker, J.E.; Jensen, Peter Ruhdal; Gomes, A. Vaz

    1995-01-01

    Maintenance (let alone growth) of the highly ordered living cell is only possible through the continuous input of free energy. Coupling of energetically downhill processes (such as catabolic reactions) to uphill processes is essential to provide this free energy and is catalyzed by enzymes either...... control cell physiology. Indeed, in the living cell homeostatic control mechanisms might exist for the free-energy transduction pathways so as to prevent perturbation of cellular function when the Gibbs energy sup