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Sample records for amplifying progenitor itap

  1. Induced adult stem (iAS) cells and induced transit amplifying progenitor (iTAP) cells-a possible alternative to induced pluripotent stem (iPS) cells?

    Science.gov (United States)

    Heng, Boon Chin; Richards, Mark; Ge, Zigang; Shu, Yimin

    2010-02-01

    The successful derivation of iPSC lines effectively demonstrates that it is possible to reset the 'developmental clock' of somatic cells all the way back to the initial embryonic state. Hence, it is plausible that this clock may instead be turned back half-way to a less immature developmental stage that is more directly applicable to clinical therapeutic applications or for in vitro pharmacology/toxicology screening assays. Such a suitable developmental state is postulated to be either the putative transit amplifying progenitor stage or adult stem cell stage. It is hypothetically possible to reprogram mature and terminally differentiated somatic cells back to the adult stem cell or transit amplifying progenitor stage, in a manner similar to the derivation of iPSC. It is proposed that the terminology 'Induced Adult Stem Cells' (iASC) or 'Induced Transit Amplifying Progenitor Cells' (iTAPC) be used to described such reprogrammed somatic cells. Of particular interest, is the possibility of resetting the developmental clock of mature differentiated somatic cells of the mesenchymal lineage, explanted from adipose tissue, bone marrow and cartilage. The putative adult stem cell sub-population from which these cells are derived, commonly referred to as 'mesenchymal stem cells', are highly versatile and hold much therapeutic promise in regenerative medicine, as attested to by numerous human clinical trials and animal studies. Perhaps it may be appropriate to term such reprogrammed cells as 'Induced Mesenchymal Stem Cells' (iMSC) or as 'Induced Mesenchumal Progenitor Cells' (iMPC). Given that cells from the same organ/tissue will share some commonalities in gene expression, we hypothesize that the generation of iASC or iTAPC would be more efficient as compared to iPSC generation, since a common epigenetic program must exist between the reprogrammed cells, adult stem cell or progenitor cell types and terminally differentiated cell types from the same organ/tissue.

  2. Interoperable Technologies for Advanced Petascale Simulations (ITAPS)

    Energy Technology Data Exchange (ETDEWEB)

    Shephard, Mark S

    2010-02-05

    Efforts during the past year have contributed to the continued development of the ITAPS interfaces and services as well as specific efforts to support ITAPS applications. The ITAPS interface efforts have two components. The first is working with the ITAPS team on improving the ITAPS software infrastructure and level of compliance of our implementations of ITAPS interfaces (iMesh, iMeshP, iRel and iGeom). The second is being involved with the discussions on the design of the iField fields interface. Efforts to move the ITAPS technologies to petascale computers has identified a number of key technical developments that are required to effectively execute the ITAPS interfaces and services. Research to address these parallel method developments has been a major emphasis of the RPI’s team efforts over the past year. Efforts to move the ITAPS technologies to petascale computers has identified a number of key technical developments that are required to effectively execute the ITAPS interfaces and services. Research to address these parallel method developments has been a major emphasis of the RPI’s team efforts over the past year. The development of parallel unstructured mesh methods has considered the need to scale unstructured mesh solves to massively parallel computers. These efforts, summarized in section 2.1 show that with the addition of the ITAPS procedures described in sections 2.2 and 2.3 we are able to obtain excellent strong scaling with our unstructured mesh CFD code on up to 294,912 cores of IBM Blue Gene/P which is the highest core count machine available. The ITAPS developments that have contributed to the scaling and performance of PHASTA include an iterative migration algorithm to improve the combined region and vertex balance of the mesh partition, which increases scalability, and mesh data reordering, which improves computational performance. The other developments are associated with the further development of the ITAPS parallel unstructured mesh

  3. RANK Signaling Amplifies WNT-Responsive Mammary Progenitors through R-SPONDIN1

    Directory of Open Access Journals (Sweden)

    Purna A. Joshi

    2015-07-01

    Full Text Available Systemic and local signals must be integrated by mammary stem and progenitor cells to regulate their cyclic growth and turnover in the adult gland. Here, we show RANK-positive luminal progenitors exhibiting WNT pathway activation are selectively expanded in the human breast during the progesterone-high menstrual phase. To investigate underlying mechanisms, we examined mouse models and found that loss of RANK prevents the proliferation of hormone receptor-negative luminal mammary progenitors and basal cells, an accompanying loss of WNT activation, and, hence, a suppression of lobuloalveologenesis. We also show that R-spondin1 is depleted in RANK-null progenitors, and that its exogenous administration rescues key aspects of RANK deficiency by reinstating a WNT response and mammary cell expansion. Our findings point to a novel role of RANK in dictating WNT responsiveness to mediate hormone-induced changes in the growth dynamics of adult mammary cells.

  4. Signaling Networks among Stem Cell Precursors, Transit-Amplifying Progenitors, and their Niche in Developing Hair Follicles

    Directory of Open Access Journals (Sweden)

    Amélie Rezza

    2016-03-01

    Full Text Available The hair follicle (HF is a complex miniorgan that serves as an ideal model system to study stem cell (SC interactions with the niche during growth and regeneration. Dermal papilla (DP cells are required for SC activation during the adult hair cycle, but signal exchange between niche and SC precursors/transit-amplifying cell (TAC progenitors that regulates HF morphogenetic growth is largely unknown. Here we use six transgenic reporters to isolate 14 major skin and HF cell populations. With next-generation RNA sequencing, we characterize their transcriptomes and define unique molecular signatures. SC precursors, TACs, and the DP niche express a plethora of ligands and receptors. Signaling interaction network analysis reveals a bird’s-eye view of pathways implicated in epithelial-mesenchymal interactions. Using a systematic tissue-wide approach, this work provides a comprehensive platform, linked to an interactive online database, to identify and further explore the SC/TAC/niche crosstalk regulating HF growth.

  5. Clinical-scale expansion of CD34(+) cord blood cells amplifies committed progenitors and rapid scid repopulation cells.

    Science.gov (United States)

    Casamayor-Genescà, Alba; Pla, Arnau; Oliver-Vila, Irene; Pujals-Fonts, Noèlia; Marín-Gallén, Sílvia; Caminal, Marta; Pujol-Autonell, Irma; Carrascal, Jorge; Vives-Pi, Marta; Garcia, Joan; Vives, Joaquim

    2017-03-25

    Umbilical cord blood (UCB) transplantation is associated with long periods of aplastic anaemia. This undesirable situation is due to the low cell dose available per unit of UCB and the immaturity of its progenitors. To overcome this, we present a cell culture strategy aimed at the expansion of the CD34(+) population and the generation of granulocyte lineage-committed progenitors. Two culture products were produced after either 6 or 14days of in vitro expansion, and their characteristics compared to non-expanded UCB CD34(+) controls in terms of phenotype, colony-forming activity and multilineage repopulation potential in NOD-scid IL2Rγ(null) mice. Both expanded cell products maintained rapid SCID repopulation activity similar to the non-expanded control, but 14-day cultured cells showed impaired long term SCID repopulation activity. The process was successfully scaled up to clinically relevant doses of 89×10(6) CD34(+) cells committed to the granulocytic lineage and 3.9×10(9) neutrophil precursors in different maturation stages. Cell yields and biological properties presented by the cell product obtained after 14days in culture were superior and therefore this is proposed as the preferred production setup in a new type of dual transplant strategy to reduce aplastic periods, producing a transient repopulation before the definitive engraftment of the non-cultured UCB unit. Importantly, human telomerase reverse transcriptase activity was undetectable, c-myc expression levels were low and no genetic abnormalities were found, as determined by G-banding karyotype, further confirming the safety of the expanded product.

  6. Clinical-scale cultures of cord blood CD34(+) cells to amplify committed progenitors and maintain stem cell activity.

    Science.gov (United States)

    Ivanovic, Zoran; Duchez, Pascale; Chevaleyre, Jean; Vlaski, Marija; Lafarge, Xavier; Dazey, Bernard; Robert-Richard, Elodie; Mazurier, Frédéric; Boiron, Jean-Michel

    2011-01-01

    We developed a clinical-scale cord blood (CB) cell ex vivo procedure to enable an extensive expansion of committed progenitors--colony-forming cells (CFCs) without impairing very primitive hematopoietic stem cells (HSCs). CD34(++) cells, selected from previously cryopreserved and thawed CB units, were cultured in two steps (diluted 1:4 after 6 days) in the presence of stem cell factor (SCF), fms-related tyrosine kinase 3 ligand (Flt-3L), megakaryocyte growth and development factor (MGDF) (100 ng/ml each), granulocyte-colony stimulating factor (G-CSF) (10 ng/ml) in HP01 serum-free medium. HSC activity was evaluated in a serial transplantation assay, by detection of human cells (CD45, CD33, CD19 and CFC of human origin) in bone marrow (BM) of primary and secondary recipient NOD/SCID mice 6-8 weeks after transplantation. A wide amplification of total cells (∼350-fold), CD34(+) cells (∼100-fold), and CFC (∼130-fold) without impairing the HSC activity was obtained. The activity of a particular HSC subpopulation (SRC(CFC)) was even enhanced.Thus, an extensive ex vivo expansion of CFCs is feasible without impairing the activity of HSCs. This result was enabled by associating antioxidant power of medium with an appropriate cytokine cocktail (i.e., mimicking physiologic effects of a weak oxygenation in hematopoietic environment).

  7. Lugares de frontera en la circulación entre Posadas (Misiones, Argentina y Encarnación (Itapúa, Paraguay

    Directory of Open Access Journals (Sweden)

    María Dolores Linares

    2015-06-01

    Full Text Available RESUMEN Este artículo se propone describir un tipo de movilidad espacial determinada, la circulación de las paseras paraguayas en el espacio fronterizo argentino-paraguayo de Posadas (Misiones, República Argentinay Encarnación (Itapúa, República del Paraguay, y analizarla en virtud de las territorialidades que ésta implica. Mediante una metodología cualitativa, basada en la realización de entrevistas en profundidad y en la observación participante, presentaremos una tipificación de los “lugares” que las paseras paraguayas transitan y construyen en la frontera. Para ordenar nuestra argumentación, en primer lugar, describiremos el marco legal-institucional que regula la frontera y cuáles son sus implicancias en la práctica laboral de las paseras. En segundo lugar, caracterizaremos la circulación en términos de trayectorias y motivaciones, incluyendo así mercaderías, medios de transporte y paradas. Por último, indicaremos y analizaremos los “lugares” que hemos identificado dentro de esta circulación internacional. ABSTRACT This article aims to describe a specific type of spatial mobility, the circulation of Paraguayan “paseras” in the Argentine-Paraguayan border area of Posadas (Misiones, Argentina andEncarnación (Itapúa, Paraguay, and analyze the new territorialities that it creates. Through a qualitative methodology based on interviews and participant observation, we present a typification of "places" that Paraguayan paseras walk along and build on the border. To organize our argument, first we describe the legal-institutional framework governing the border and its consequences for the paseras’ practice. Second, we characterize the cross-border circulation in terms of trajectories and motivations, thus including goods, transportation and stops. Finally, we indicate and discuss the "places" that we have identified within this international circulation.

  8. Solid Oxide Fuel Cell APU Feasibility Study for a Long Range Commercial Aircraft Using UTC ITAPS Approach. Volume 1; Aircraft Propulsion and Subsystems Integration Evaluation

    Science.gov (United States)

    Srinivasan, Hari; Yamanis, Jean; Welch, Rick; Tulyani, Sonia; Hardin, Larry

    2006-01-01

    The objective of this contract effort was to define the functionality and evaluate the propulsion and power system benefits derived from a Solid Oxide Fuel Cell (SOFC) based Auxiliary Power Unit (APU) for a future long range commercial aircraft, and to define the technology gaps to enable such a system. The study employed technologies commensurate with Entry into Service (EIS) in 2015. United Technologies Corporation (UTC) Integrated Total Aircraft Power System (ITAPS) methodologies were used to evaluate system concepts to a conceptual level of fidelity. The technology benefits were captured as reductions of the mission fuel burn and emissions. The baseline aircraft considered was the Boeing 777-200ER airframe with more electric subsystems, Ultra Efficient Engine Technology (UEET) engines, and an advanced APU with ceramics for increased efficiency. In addition to the baseline architecture, four architectures using an SOFC system to replace the conventional APU were investigated. The mission fuel burn savings for Architecture-A, which has minimal system integration, is 0.16 percent. Architecture-B and Architecture-C employ greater system integration and obtain fuel burn benefits of 0.44 and 0.70 percent, respectively. Architecture-D represents the highest level of integration and obtains a benefit of 0.77 percent.

  9. Operational amplifiers

    CERN Document Server

    Dostal, Jiri

    1993-01-01

    This book provides the reader with the practical knowledge necessary to select and use operational amplifier devices. It presents an extensive treatment of applications and a practically oriented, unified theory of operational circuits.Provides the reader with practical knowledge necessary to select and use operational amplifier devices. Presents an extensive treatment of applications and a practically oriented, unified theory of operational circuits

  10. Cross-differential amplifier

    Science.gov (United States)

    Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

    2013-01-01

    A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

  11. Portable musical instrument amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Christian, David E. (Danbury, CT)

    1990-07-24

    The present invention relates to a musical instrument amplifier which is particularly useful for electric guitars. The amplifier has a rigid body for housing both the electronic system for amplifying and processing signals from the guitar and the system's power supply. An input plug connected to and projecting from the body is electrically coupled to the signal amplifying and processing system. When the plug is inserted into an output jack for an electric guitar, the body is rigidly carried by the guitar, and the guitar is operatively connected to the electrical amplifying and signal processing system without use of a loose interconnection cable. The amplifier is provided with an output jack, into which headphones are plugged to receive amplified signals from the guitar. By eliminating the conventional interconnection cable, the amplifier of the present invention can be used by musicians with increased flexibility and greater freedom of movement.

  12. Amplification of neural stem cell proliferation by intermediate progenitor cells in Drosophila brain development

    Directory of Open Access Journals (Sweden)

    Bello Bruno C

    2008-02-01

    Full Text Available Abstract Background In the mammalian brain, neural stem cells divide asymmetrically and often amplify the number of progeny they generate via symmetrically dividing intermediate progenitors. Here we investigate whether specific neural stem cell-like neuroblasts in the brain of Drosophila might also amplify neuronal proliferation by generating symmetrically dividing intermediate progenitors. Results Cell lineage-tracing and genetic marker analysis show that remarkably large neuroblast lineages exist in the dorsomedial larval brain of Drosophila. These lineages are generated by brain neuroblasts that divide asymmetrically to self renew but, unlike other brain neuroblasts, do not segregate the differentiating cell fate determinant Prospero to their smaller daughter cells. These daughter cells continue to express neuroblast-specific molecular markers and divide repeatedly to produce neural progeny, demonstrating that they are proliferating intermediate progenitors. The proliferative divisions of these intermediate progenitors have novel cellular and molecular features; they are morphologically symmetrical, but molecularly asymmetrical in that key differentiating cell fate determinants are segregated into only one of the two daughter cells. Conclusion Our findings provide cellular and molecular evidence for a new mode of neurogenesis in the larval brain of Drosophila that involves the amplification of neuroblast proliferation through intermediate progenitors. This type of neurogenesis bears remarkable similarities to neurogenesis in the mammalian brain, where neural stem cells as primary progenitors amplify the number of progeny they generate through generation of secondary progenitors. This suggests that key aspects of neural stem cell biology might be conserved in brain development of insects and mammals.

  13. Wireless Josephson amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Narla, A.; Sliwa, K. M.; Hatridge, M.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H. [Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States)

    2014-06-09

    Josephson junction parametric amplifiers are playing a crucial role in the readout chain in superconducting quantum information experiments. However, their integration with current 3D cavity implementations poses the problem of transitioning between waveguide, coax cables, and planar circuits. Moreover, Josephson amplifiers require auxiliary microwave components, like directional couplers and/or hybrids, that are sources of spurious losses and impedance mismatches that limit measurement efficiency and amplifier tunability. We have developed a wireless architecture for these parametric amplifiers that eliminates superfluous microwave components and interconnects. This greatly simplifies their assembly and integration into experiments. We present an experimental realization of such a device operating in the 9–11 GHz band with about 100 MHz of amplitude gain-bandwidth product, on par with devices mounted in conventional sample holders. The simpler impedance environment presented to the amplifier also results in increased amplifier tunability.

  14. Oscillators and operational amplifiers

    DEFF Research Database (Denmark)

    Lindberg, Erik

    2005-01-01

    A generalized approach to the design of oscillators using operational amplifiers as active elements is presented. A piecewise-linear model of the amplifier is used so that it make sense to investigate the eigenvalues of the Jacobian of the differential equations. The characteristic equation...... of the general circuit is derived. The dynamic nonlinear transfer characteristic of the amplifier is investigated. Examples of negative resistance oscillators are discussed....

  15. Type Ia Supernovae Keep Memory of their Progenitor Metallicity

    Science.gov (United States)

    Piersanti, Luciano; Bravo, Eduardo; Cristallo, Sergio; Domínguez, Inmaculada; Straniero, Oscar; Tornambé, Amedeo; Martínez-Pinedo, Gabriel

    2017-02-01

    The ultimate understanding of SNe Ia diversity is one of the most urgent issues to exploit thermonuclear explosions of accreted White Dwarfs (WDs) as cosmological yardsticks. In particular, we investigate the impact of the progenitor system metallicity on the physical and chemical properties of the WD at the explosion epoch. We analyze the evolution of CO WDs through the accretion and simmering phases by using evolutionary models based on time-dependent convective mixing and an extended nuclear network including the most important electron captures, beta decays, and URCA processes. We find that, due to URCA processes and electron-captures, the neutron excess and density at which the thermal runaway occurs are substantially larger than previously claimed. Moreover, we find that the higher the progenitor metallicity, the larger the neutron excess variation during the accretion and simmering phases and the higher the central density and the convective velocity at the explosion. Hence, the simmering phase acts as an amplifier of the differences existing in SNe Ia progenitors. When applying our results to the neutron excess estimated for the Tycho and Kepler young supernova remnants, we derive that the metallicity of the progenitors should be in the range Z=0.030{--}0.032, close to the average metallicity value of the thin disk of the Milky Way. As the amount of {}56{Ni} produced in the explosion depends on the neutron excess and central density at the thermal runaway, our results suggest that the light curve properties depend on the progenitor metallicity.

  16. Optoisolators simplify amplifier design

    Science.gov (United States)

    Ting, Joseph Wee

    2007-09-01

    Simplicity and low parts count are key virtues to this high voltage amplifier. Optoisolators replace complex high voltage transistor biasing schemes. This amplifier employs only 2 optoisolators, 16 high voltage mosfets transistors, 2 low voltage ones, 6 linear IC's and a score of passive components. Yet it can amplify opamp signals to 5 kV peak-to-peak from DC to sine waves up to 20 kHz. Resistor feedback guarantees the fidelity of the signal. It can source and sink 10 mA of output current. This amplifier was conceived to power ion traps for biological whole cell mass measurements. It is a versatile tool for a variety of applications.

  17. RF Power Amplifier Analysis

    Directory of Open Access Journals (Sweden)

    M. Lokay

    1993-04-01

    Full Text Available The special program is presented for the demonstration of RF power transistor amplifiers for the purposes of the high-school education in courses of radio transmitters. The program is written in Turbo Pascal 6. 0 and enables to study the waveforms in selected points of the amplifier and to draw the trajectories of the working point in a plot of output transistor characteristics.

  18. Charge-sensitive amplifier

    Directory of Open Access Journals (Sweden)

    Startsev V. I.

    2008-02-01

    Full Text Available The authors consider design and circuit design techniques of reduction of the influence of the pyroelectric effect on operation of the charge sensitive amplifiers. The presented experimental results confirm the validity of the measures taken to reduce the impact of pyroelectric currents. Pyroelectric currents are caused by the influence of the temperature gradient on the piezoelectric sensor and on the output voltage of charge sensitive amplifiers.

  19. Electrospun amplified fiber optics.

    Science.gov (United States)

    Morello, Giovanni; Camposeo, Andrea; Moffa, Maria; Pisignano, Dario

    2015-03-11

    All-optical signal processing is the focus of much research aiming to obtain effective alternatives to existing data transmission platforms. Amplification of light in fiber optics, such as in Erbium-doped fiber amplifiers, is especially important for efficient signal transmission. However, the complex fabrication methods involving high-temperature processes performed in a highly pure environment slow the fabrication process and make amplified components expensive with respect to an ideal, high-throughput, room temperature production. Here, we report on near-infrared polymer fiber amplifiers working over a band of ∼20 nm. The fibers are cheap, spun with a process entirely carried out at room temperature, and shown to have amplified spontaneous emission with good gain coefficients and low levels of optical losses (a few cm(-1)). The amplification process is favored by high fiber quality and low self-absorption. The found performance metrics appear to be suitable for short-distance operations, and the large variety of commercially available doping dyes might allow for effective multiwavelength operations by electrospun amplified fiber optics.

  20. From progenitor to afterlife

    CERN Document Server

    Chevalier, R A

    2006-01-01

    The sequence of massive star supernova types IIP (plateau light curve), IIL (linear light curve), IIb, IIn (narrow line), Ib, and Ic roughly represents a sequence of increasing mass loss during the stellar evolution. The mass loss affects the velocity distribution of the ejecta composition; in particular, only the IIP's typically end up with H moving at low velocity. Radio and X-ray observations of extragalactic supernovae show varying mass loss properties that are in line with expectations for the progenitor stars. For young supernova remnants, pulsar wind nebulae and circumstellar interaction provide probes of the inner ejecta and higher velocity ejecta, respectively. Among the young remnants, there is evidence for supernovae over a range of types, including those that exploded with much of the H envelope present (Crab Nebula, 3C 58, 0540--69) and those that exploded after having lost most of their H envelope (Cas A, G292.0+1.8).

  1. Fourier plane image amplifier

    Science.gov (United States)

    Hackel, L.A.; Hermann, M.R.; Dane, C.B.; Tiszauer, D.H.

    1995-12-12

    A solid state laser is frequency tripled to 0.3 {micro}m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only about 1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power. 1 fig.

  2. Fourier plane image amplifier

    Science.gov (United States)

    Hackel, Lloyd A.; Hermann, Mark R.; Dane, C. Brent; Tiszauer, Detlev H.

    1995-01-01

    A solid state laser is frequency tripled to 0.3 .mu.m. A small portion of the laser is split off and generates a Stokes seed in a low power oscillator. The low power output passes through a mask with the appropriate hole pattern. Meanwhile, the bulk of the laser output is focused into a larger stimulated Brillouin scattering (SBS) amplifier. The low power beam is directed through the same cell in the opposite direction. The majority of the amplification takes place at the focus which is the fourier transform plane of the mask image. The small holes occupy large area at the focus and thus are preferentially amplified. The amplified output is now imaged onto the multichip module where the holes are drilled. Because of the fourier plane amplifier, only .about.1/10th the power of a competitive system is needed. This concept allows less expensive masks to be used in the process and requires much less laser power.

  3. Progenitors of type Ia supernovae

    CERN Document Server

    Maeda, Keiichi

    2016-01-01

    Natures of progenitors of type Ia Supernovae (SNe Ia) have not yet been clarified. There has been long and intensive discussion on whether the so-called single degenerate (SD) scenario or the double degenerate (DD) scenario, or anything else, could explain a major population of SNe Ia, but the conclusion has not yet been reached. With rapidly increasing observational data and new theoretical ideas, the field of studying the SN Ia progenitors has been quickly developing, and various new insights have been obtained in recent years. This article aims at providing a summary of the current situation regarding the SN Ia progenitors, both in theory and observations. It seems difficult to explain the emerging diversity seen in observations of SNe Ia by a single population, and we emphasize that it is important to clarify links between different progenitor scenarios and different sub-classes of SNe Ia.

  4. STABILIZED TRANSISTOR AMPLIFIER

    Science.gov (United States)

    Noe, J.B.

    1963-05-01

    A temperature stabilized transistor amplifier having a pair of transistors coupled in cascade relation that are capable of providing amplification through a temperature range of - 100 un. Concent 85% F to 400 un. Concent 85% F described. The stabilization of the amplifier is attained by coupling a feedback signal taken from the emitter of second transistor at a junction between two serially arranged biasing resistances in the circuit of the emitter of the second transistor to the base of the first transistor. Thus, a change in the emitter current of the second transistor is automatically corrected by the feedback adjustment of the base-emitter potential of the first transistor and by a corresponding change in the base-emitter potential of the second transistor. (AEC)

  5. Polarization effect in parametric amplifier

    Institute of Scientific and Technical Information of China (English)

    Junhe Zhou; Jianping Chen; Xinwan Li; Guiling Wu; Yiping Wang

    2005-01-01

    @@ Polarization effect in parametric amplifiers is studied. Coupled equations are derived from the basic propagation equations and numerical solutions are given for both one-wavelength-pump and two-wavelengthpump systems. Several parametric amplifiers driven by pumps at one wavelength and two wavelengths are analyzed and the polarization independent parametric amplifier is proposed.

  6. Radio Frequency Solid State Amplifiers

    CERN Document Server

    Jacob, J

    2015-01-01

    Solid state amplifiers are being increasingly used instead of electronic vacuum tubes to feed accelerating cavities with radio frequency power in the 100 kW range. Power is obtained from the combination of hundreds of transistor amplifier modules. This paper summarizes a one hour lecture on solid state amplifiers for accelerator applications.

  7. Multiple pass laser amplifier system

    Science.gov (United States)

    Brueckner, Keith A.; Jorna, Siebe; Moncur, N. Kent

    1977-01-01

    A laser amplification method for increasing the energy extraction efficiency from laser amplifiers while reducing the energy flux that passes through a flux limited system which includes apparatus for decomposing a linearly polarized light beam into multiple components, passing the components through an amplifier in delayed time sequence and recombining the amplified components into an in phase linearly polarized beam.

  8. Mesenchymal progenitor cells for the osteogenic lineage.

    Science.gov (United States)

    Ono, Noriaki; Kronenberg, Henry M

    2015-09-01

    Mesenchymal progenitors of the osteogenic lineage provide the flexibility for bone to grow, maintain its function and homeostasis. Traditionally, colony-forming-unit fibroblasts (CFU-Fs) have been regarded as surrogates for mesenchymal progenitors; however, this definition cannot address the function of these progenitors in their native setting. Transgenic murine models including lineage-tracing technologies based on the cre-lox system have proven to be useful in delineating mesenchymal progenitors in their native environment. Although heterogeneity of cell populations of interest marked by a promoter-based approach complicates overall interpretation, an emerging complexity of mesenchymal progenitors has been revealed. Current literatures suggest two distinct types of bone progenitor cells; growth-associated mesenchymal progenitors contribute to explosive growth of bone in early life, whereas bone marrow mesenchymal progenitors contribute to the much slower remodeling process and response to injury that occurs mainly in adulthood. More detailed relationships of these progenitors need to be studied through further experimentation.

  9. Simplified design of IC amplifiers

    CERN Document Server

    Lenk, John

    1996-01-01

    Simplified Design of IC Amplifiers has something for everyone involved in electronics. No matter what skill level, this book shows how to design and experiment with IC amplifiers. For experimenters, students, and serious hobbyists, this book provides sufficient information to design and build IC amplifier circuits from 'scratch'. For working engineers who design amplifier circuits or select IC amplifiers, the book provides a variety of circuit configurations to make designing easier.Provides basics for all phases of practical design.Covers the most popular forms for amplif

  10. Electronic amplifiers for automatic compensators

    CERN Document Server

    Polonnikov, D Ye

    1965-01-01

    Electronic Amplifiers for Automatic Compensators presents the design and operation of electronic amplifiers for use in automatic control and measuring systems. This book is composed of eight chapters that consider the problems of constructing input and output circuits of amplifiers, suppression of interference and ensuring high sensitivity.This work begins with a survey of the operating principles of electronic amplifiers in automatic compensator systems. The succeeding chapters deal with circuit selection and the calculation and determination of the principal characteristics of amplifiers, as

  11. Building valve amplifiers

    CERN Document Server

    Jones, Morgan

    2013-01-01

    Building Valve Amplifiers is a unique hands-on guide for anyone working with tube audio equipment--as an electronics hobbyist, audiophile or audio engineer. This 2nd Edition builds on the success of the first with technology and technique revisions throughout and, significantly, a major new self-build project, worked through step-by-step, which puts into practice the principles and techniques introduced throughout the book. Particular attention has been paid to answering questions commonly asked by newcomers to the world of the valve, whether audio enthusiasts tackling their first build or

  12. REGENERATIVE TRANSISTOR AMPLIFIER

    Science.gov (United States)

    Kabell, L.J.

    1958-11-25

    Electrical circults for use in computers and the like are described. particularly a regenerative bistable transistor amplifler which is iurned on by a clock signal when an information signal permits and is turned off by the clock signal. The amplifier porforms the above function with reduced power requirements for the clock signal and circuit operation. The power requirements are reduced in one way by employing transformer coupling which increases the collector circuit efficiency by eliminating the loss of power in the collector load resistor.

  13. Wideband amplifier design

    CERN Document Server

    Hollister, Allen L

    2007-01-01

    In this book, the theory needed to understand wideband amplifier design using the simplest models possible will be developed. This theory will be used to develop algebraic equations that describe particular circuits used in high frequency design so that the reader develops a ""gut level"" understanding of the process and circuit. SPICE and Genesys simulations will be performed to show the accuracy of the algebraic models. By looking at differences between the algebraic equations and the simulations, new algebraic models will be developed that include parameters originally left out of the model

  14. Nanoscale electromechanical parametric amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Aleman, Benjamin Jose; Zettl, Alexander

    2016-09-20

    This disclosure provides systems, methods, and apparatus related to a parametric amplifier. In one aspect, a device includes an electron source electrode, a counter electrode, and a pumping electrode. The electron source electrode may include a conductive base and a flexible conductor. The flexible conductor may have a first end and a second end, with the second end of the flexible conductor being coupled to the conductive base. A cross-sectional dimension of the flexible conductor may be less than about 100 nanometers. The counter electrode may be disposed proximate the first end of the flexible conductor and spaced a first distance from the first end of the flexible conductor. The pumping electrode may be disposed proximate a length of the flexible conductor and spaced a second distance from the flexible conductor.

  15. Modeling of semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Mørk, Jesper; Bischoff, Svend; Berg, Tommy Winther

    We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed.......We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed....

  16. The poster as modernist progenitor

    Directory of Open Access Journals (Sweden)

    Katherine Hauser

    2015-12-01

    Full Text Available Ruth E. Iskin’s The Poster: Art, Advertising. Design, and Collecting, 1860s-1900s positions the late-nineteenth-century advertising poster as the progenitor of valued modernist practices typically attached solely to photography and film. Modernist biases separating high art from mass culture account for scholars ignoring posters, however the poster ushered in an innovative reductive graphic style as well as pioneered the notion of multiple originals.

  17. The poster as modernist progenitor

    OpenAIRE

    Katherine Hauser

    2015-01-01

    Ruth E. Iskin’s The Poster: Art, Advertising. Design, and Collecting, 1860s-1900s positions the late-nineteenth-century advertising poster as the progenitor of valued modernist practices typically attached solely to photography and film. Modernist biases separating high art from mass culture account for scholars ignoring posters, however the poster ushered in an innovative reductive graphic style as well as pioneered the notion of multiple originals.

  18. Gamma-ray burst progenitors

    CERN Document Server

    Levan, Andrew; de Grijs, Richard; Langer, Norbert; Xu, Dong; Yoon, Sung-Chul

    2016-01-01

    We review our current understanding of the progenitors of both long and short duration gamma-ray bursts (GRBs). Constraints can be derived from multiple directions, and we use three distinct strands; i) direct observations of GRBs and their host galaxies, ii) parameters derived from modeling, both via population synthesis and direct numerical simulation and iii) our understanding of plausible analog progenitor systems observed in the local Universe. From these joint constraints, we describe the likely routes that can drive massive stars to the creation of long GRBs, and our best estimates of the scenarios that can create compact object binaries which will ultimately form short GRBs, as well as the associated rates of both long and short GRBs. We further discuss how different the progenitors may be in the case of black hole engine or millisecond-magnetar models for the production of GRBs, and how central engines may provide a unifying theme between many classes of extremely luminous transient, from luminous an...

  19. Gamma-Ray Burst Progenitors

    Science.gov (United States)

    Levan, Andrew; Crowther, Paul; de Grijs, Richard; Langer, Norbert; Xu, Dong; Yoon, Sung-Chul

    2016-12-01

    We review our current understanding of the progenitors of both long and short duration gamma-ray bursts (GRBs). Constraints can be derived from multiple directions, and we use three distinct strands; (i) direct observations of GRBs and their host galaxies, (ii) parameters derived from modelling, both via population synthesis and direct numerical simulation and (iii) our understanding of plausible analog progenitor systems observed in the local Universe. From these joint constraints, we describe the likely routes that can drive massive stars to the creation of long GRBs, and our best estimates of the scenarios that can create compact object binaries which will ultimately form short GRBs, as well as the associated rates of both long and short GRBs. We further discuss how different the progenitors may be in the case of black hole engine or millisecond-magnetar models for the production of GRBs, and how central engines may provide a unifying theme between many classes of extremely luminous transient, from luminous and super-luminous supernovae to long and short GRBs.

  20. Capacities of quantum amplifier channels

    Science.gov (United States)

    Qi, Haoyu; Wilde, Mark M.

    2017-01-01

    Quantum amplifier channels are at the core of several physical processes. Not only do they model the optical process of spontaneous parametric down-conversion, but the transformation corresponding to an amplifier channel also describes the physics of the dynamical Casimir effect in superconducting circuits, the Unruh effect, and Hawking radiation. Here we study the communication capabilities of quantum amplifier channels. Invoking a recently established minimum output-entropy theorem for single-mode phase-insensitive Gaussian channels, we determine capacities of quantum-limited amplifier channels in three different scenarios. First, we establish the capacities of quantum-limited amplifier channels for one of the most general communication tasks, characterized by the trade-off between classical communication, quantum communication, and entanglement generation or consumption. Second, we establish capacities of quantum-limited amplifier channels for the trade-off between public classical communication, private classical communication, and secret key generation. Third, we determine the capacity region for a broadcast channel induced by the quantum-limited amplifier channel, and we also show that a fully quantum strategy outperforms those achieved by classical coherent-detection strategies. In all three scenarios, we find that the capacities significantly outperform communication rates achieved with a naive time-sharing strategy.

  1. Small signal microwave amplifier design

    CERN Document Server

    Grosch, Theodore

    2000-01-01

    This book explains techniques and examples for designing stable amplifiers for high-frequency applications in which the signal is small and the amplifier circuit is linear. An in-depth discussion of linear network theory provides the foundation needed to develop actual designs. Examples throughout the book will show you how to apply the knowledge gained in each chapter leading to the complex design of low noise amplifiers. Many exercises at the end of each chapter will help students to practice their skills. The solutions to these design problems are available in an accompanying solutions book

  2. International Standardization Activities for Optical Amplifiers

    Institute of Scientific and Technical Information of China (English)

    Haruo Okamura

    2003-01-01

    International standardization activities for Optical Amplifiers at IECTC86 and ITU-T SG15 are reviewed. Current discussions include Optical Amplifier safety guideline, Reliability standard, Rest methods of Noise and PMD, Definitions of Raman amplifier parameters and OA classification.

  3. Characterization of SLUG microwave amplifiers

    Science.gov (United States)

    Hoi, I.-C.; Zhu, S.; Thorbeck, T.; McDermott, R.; Mutus, J.; Jeffrey, E.; Barends, R.; Chen, Y.; Roushan, P.; Fowler, A.; Sank, D.; White, T.; Campbell, B.; Chen, Z.; Chiaro, B.; Dunsworth, A.; Kelly, J.; Megrant, A.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Vainsencher, A.; Wenner, J.; Martinis, J. M.

    2015-03-01

    With the rapid growth of superconducting circuits quantum technology, a near quantum-limited amplifier at GHz frequency is needed to enable high fidelity measurements. We describe such an amplifier, the SQUID based, superconducting low inductance undulatory galvanometer (SLUG) amplifier. We measure the full scattering matrix of the SLUG. In particular, we measure both forward and reverse gain, as well as reflection. We see 15dB forward gain with added noise from one quanta to several quanta. The -1 dB compression point is around -95 dBm, about two orders of magnitude higher than that of typical Josephson parametric amplifiers. With these properties, SLUG is well suited for the high fidelity, simultaneous multiplexed readout of superconducting qubits.

  4. PID Controller with Operational Amplifier

    Directory of Open Access Journals (Sweden)

    Cristian Paul Chioncel

    2009-01-01

    Full Text Available The paper presents a PID controller made with LM741 operational amplifier that implement the PID controllers laws and allow for a widerange of applications of in the field of automatic control of technicalprocesses and systems.

  5. New Packaging for Amplifier Slabs

    Energy Technology Data Exchange (ETDEWEB)

    Riley, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Thorsness, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Suratwala, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Steele, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rogowski, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-03-18

    The following memo provides a discussion and detailed procedure for a new finished amplifier slab shipping and storage container. The new package is designed to maintain an environment of <5% RH to minimize weathering.

  6. TARC: Carlo Rubbia's Energy Amplifier

    CERN Multimedia

    Laurent Guiraud

    1997-01-01

    Transmutation by Adiabatic Resonance Crossing (TARC) is Carlo Rubbia's energy amplifier. This CERN experiment demonstrated that long-lived fission fragments, such as 99-TC, can be efficiently destroyed.

  7. Operational amplifiers theory and design

    CERN Document Server

    Huijsing, Johan

    2017-01-01

    This proven textbook guides readers to a thorough understanding of the theory and design of operational amplifiers (OpAmps). The core of the book presents systematically the design of operational amplifiers, classifying them into a periodic system of nine main overall configurations, ranging from one gain stage up to four or more stages. This division enables circuit designers to recognize quickly, understand, and choose optimal configurations. Characterization of operational amplifiers is given by macro models and error matrices, together with measurement techniques for their parameters. Definitions are given for four types of operational amplifiers depending on the grounding of their input and output ports. Many famous designs are evaluated in depth, using a carefully structured approach enhanced by numerous figures. In order to reinforce the concepts introduced and facilitate self-evaluation of design skills, the author includes problems with detailed solutions, as well as simulation exercises. Provides te...

  8. A KIND OF NEW AMPLIFIER

    Institute of Scientific and Technical Information of China (English)

    YIN XUN-HE; FENG RU-PENG; REN YONG

    2000-01-01

    Chaotic characteristics in the iteration of logistic map (one-dimensional discrete dynamic system) are simulatedand analyzed. The circuit implementation of a kind of chaotic amplifier model is based on the chaotic characteristicsthat chaos is sensitively dependent on its initial conditions, and the circuit simulation result is given using simulationprogram with integrated circuit emphasis for personal computer (PSPICE), and is compared with linear amplifier.Advantages and disadvantages of such a model are indicated.

  9. The progenitor of SN 2011ja: Clues from circumstellar interaction

    CERN Document Server

    Chakraborti, Sayan; Smith, Randall; Ryder, Stuart; Yadav, Naveen; Sutaria, Firoza; Dwarkadas, Vikram V; Chandra, Poonam; Pooley, David; Roy, Rupak

    2013-01-01

    Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until the time of core collapse produce Type IIP (Plateau) supernovae. The ejecta from these explosions shock the circumstellar matter originating from the mass loss of the progenitor during the final phases of its life. This interaction accelerates particles to relativistic energies which then lose energy via synchrotron radiation in the shock-amplified magnetic fields and inverse Compton scattering against optical photons from the supernova. These processes produce different signatures in the radio and X-ray part of the electromagnetic spectrum. Observed together, they allow us to break the degeneracy between shock acceleration and magnetic field amplification. In this work we use X-rays observations from the Chandra and radio observations from the ATCA to study the relative importance of particle acceleration and magnetic fields in producing the non-thermal radiation from SN 2011ja. We use radio observations to constrain the ...

  10. Neural and Oligodendrocyte Progenitor Cells: Transferrin Effects on Cell Proliferation

    Directory of Open Access Journals (Sweden)

    Lucas Silvestroff

    2013-02-01

    Full Text Available NSC (neural stem cells/NPC (neural progenitor cells are multipotent and self-renew throughout adulthood in the SVZ (subventricular zone of the mammalian CNS (central nervous system. These cells are considered interesting targets for CNS neurodegenerative disorder cell therapies, and understanding their behaviour in vitro is crucial if they are to be cultured prior to transplantation. We cultured the SVZ tissue belonging to newborn rats under the form of NS (neurospheres to evaluate the effects of Tf (transferrin on cell proliferation. The NS were heterogeneous in terms of the NSC/NPC markers GFAP (glial fibrillary acidic protein, Nestin and Sox2 and the OL (oligodendrocyte progenitor markers NG2 (nerve/glia antigen 2 and PDGFRα (platelet-derived growth factor receptor α. The results of this study indicate that aTf (apoTransferrin is able to increase cell proliferation of SVZ-derived cells in vitro, and that these effects were mediated at least in part by the TfRc1 (Tf receptor 1. Since OPCs (oligodendrocyte progenitor cells represent a significant proportion of the proliferating cells in the SVZ-derived primary cultures, we used the immature OL cell line N20.1 to show that Tf was able to augment the proliferation rate of OPC, either by adding aTf to the culture medium or by overexpressing rat Tf in situ. The culture medium supplemented with ferric iron, together with aTf, increased the DNA content, while ferrous iron did not. The present work provides data that could have a potential application in human cell replacement therapies for neurodegenerative disease and/or CNS injury that require the use of in vitro amplified NPCs.

  11. The involvement of multipotential progenitor cells in Mooren's ulcer.

    Science.gov (United States)

    Lee, In Gul; Ye, Juan; Kim, Jae Chan

    2005-06-30

    The aim of this study was to assess the involvement of multipotential progenitor cells in the pathogenesis of Mooren's ulcer using immunohistochemical staining techniques. Tissue specimens were collected from 3 Mooren's ulcer patients who underwent lamellar keratectomy. Immunohistochemical staining patterns were analyzed using antibodies: CD34, c-kit, STRO-1, CD45RO, VEGF and a-SMA. Strong positive CD34, c-kit and STRO-1 cells were revealed in Mooren's ulcer specimens, especially in the superficial stroma. A few weakly expressed CD34 stroma cells were seen in normal limbal cornea but no immunoreactivity for c-kit and STRO-1 could be found. CD45RO positive T cells were found to have infiltrated in Mooren's ulcer. The immunostaining pattern of VEGF and a- SMA was closely correlated with the degree of expression and the number of CD34 positive cells. Bone marrow-derived multipotential progenitor cells may be involved in the pathogenesis of Mooren's ulcer by synergizing with other factors to amplify autoimmune destructive reactions and to contribute to the regeneration process. Specific therapeutic strategies that target the role of these cells in the disease are warranted.

  12. Time-lapse imaging reveals symmetric neurogenic cell division of GFAP-expressing progenitors for expansion of postnatal dentate granule neurons.

    Directory of Open Access Journals (Sweden)

    Takashi Namba

    Full Text Available Granule cells in the hippocampus, a region critical for memory and learning, are generated mainly during the early postnatal period but neurogenesis continues in adulthood. Postnatal neuronal production is carried out by primary progenitors that express glial fibrillary acidic protein (GFAP and they are assumed to function as stem cells. A central question regarding postnatal dentate neurogenesis is how astrocyte-like progenitors produce neurons. To reveal cell division patterns and the process of neuronal differentiation of astrocyte-like neural progenitors, we performed time-lapse imaging in cultured hippocampal slices from early postnatal transgenic mice with mouse GFAP promoter-controlled enhanced green fluorescent protein (mGFAP-eGFP Tg mice in combination with a retrovirus carrying a red fluorescent protein gene. Our results showed that the majority of GFAP-eGFP+ progenitor cells that express GFAP, Sox2 and nestin divided symmetrically to produce pairs of GFAP+ cells (45% or pairs of neuron-committed cells (45%, whereas a minority divided asymmetrically to generate GFAP+ cells and neuron-committed cells (10%. The present results suggest that a substantial number of GFAP-expressing progenitors functions as transient amplifying progenitors, at least in an early postnatal dentate gyrus, although a small population appears to be stem cell-like progenitors. From the present data, we discuss possible cell division patterns of adult GFAP+ progenitors.

  13. Time-lapse imaging reveals symmetric neurogenic cell division of GFAP-expressing progenitors for expansion of postnatal dentate granule neurons.

    Science.gov (United States)

    Namba, Takashi; Mochizuki, Hideki; Suzuki, Ryusuke; Onodera, Masafumi; Yamaguchi, Masahiro; Namiki, Hideo; Shioda, Seiji; Seki, Tatsunori

    2011-01-01

    Granule cells in the hippocampus, a region critical for memory and learning, are generated mainly during the early postnatal period but neurogenesis continues in adulthood. Postnatal neuronal production is carried out by primary progenitors that express glial fibrillary acidic protein (GFAP) and they are assumed to function as stem cells. A central question regarding postnatal dentate neurogenesis is how astrocyte-like progenitors produce neurons. To reveal cell division patterns and the process of neuronal differentiation of astrocyte-like neural progenitors, we performed time-lapse imaging in cultured hippocampal slices from early postnatal transgenic mice with mouse GFAP promoter-controlled enhanced green fluorescent protein (mGFAP-eGFP Tg mice) in combination with a retrovirus carrying a red fluorescent protein gene. Our results showed that the majority of GFAP-eGFP+ progenitor cells that express GFAP, Sox2 and nestin divided symmetrically to produce pairs of GFAP+ cells (45%) or pairs of neuron-committed cells (45%), whereas a minority divided asymmetrically to generate GFAP+ cells and neuron-committed cells (10%). The present results suggest that a substantial number of GFAP-expressing progenitors functions as transient amplifying progenitors, at least in an early postnatal dentate gyrus, although a small population appears to be stem cell-like progenitors. From the present data, we discuss possible cell division patterns of adult GFAP+ progenitors.

  14. EMI-resilient amplifier circuits

    CERN Document Server

    van der Horst, Marcel J; Linnenbank, André C

    2014-01-01

    This book enables circuit designers to reduce the errors introduced by the fundamental limitations and electromagnetic interference (EMI) in negative-feedback amplifiers.  The authors describe a systematic design approach for application specific negative-feedback amplifiers, with specified signal-to-error ratio (SER).  This approach enables designers to calculate noise, bandwidth, EMI, and the required bias parameters of the transistors used in  application specific amplifiers in order to meet the SER requirements.   ·         Describes design methods that incorporate electromagnetic interference (EMI) in the design of application specific negative-feedback amplifiers; ·         Provides designers with a structured methodology to avoid the use of trial and error in meeting signal-to-error ratio (SER) requirements; ·         Equips designers to increase EMI immunity of the amplifier itself, thus avoiding filtering at the input, reducing the number of components and avoiding detr...

  15. A CMOS current-mode operational amplifier

    DEFF Research Database (Denmark)

    Kaulberg, Thomas

    1993-01-01

    current-mode feedback amplifier or a constant bandwidth in a transimpedance feedback amplifier. The amplifier is found to have a gain-bandwidth product of 3 MHz, an offset current of 0.8 μA (signal range ±700 μA), and a (theoretically) unlimited slew rate. The amplifier is realized in a standard CMOS 2...

  16. Mouse lung contains endothelial progenitors with high capacity to form blood and lymphatic vessels

    Directory of Open Access Journals (Sweden)

    Barleon Bernhard

    2010-07-01

    Full Text Available Abstract Background Postnatal endothelial progenitor cells (EPCs have been successfully isolated from whole bone marrow, blood and the walls of conduit vessels. They can, therefore, be classified into circulating and resident progenitor cells. The differentiation capacity of resident lung endothelial progenitor cells from mouse has not been evaluated. Results In an attempt to isolate differentiated mature endothelial cells from mouse lung we found that the lung contains EPCs with a high vasculogenic capacity and capability of de novo vasculogenesis for blood and lymph vessels. Mouse lung microvascular endothelial cells (MLMVECs were isolated by selection of CD31+ cells. Whereas the majority of the CD31+ cells did not divide, some scattered cells started to proliferate giving rise to large colonies (> 3000 cells/colony. These highly dividing cells possess the capacity to integrate into various types of vessels including blood and lymph vessels unveiling the existence of local microvascular endothelial progenitor cells (LMEPCs in adult mouse lung. EPCs could be amplified > passage 30 and still expressed panendothelial markers as well as the progenitor cell antigens, but not antigens for immune cells and hematopoietic stem cells. A high percentage of these cells are also positive for Lyve1, Prox1, podoplanin and VEGFR-3 indicating that a considerabe fraction of the cells are committed to develop lymphatic endothelium. Clonogenic highly proliferating cells from limiting dilution assays were also bipotent. Combined in vitro and in vivo spheroid and matrigel assays revealed that these EPCs exhibit vasculogenic capacity by forming functional blood and lymph vessels. Conclusion The lung contains large numbers of EPCs that display commitment for both types of vessels, suggesting that lung blood and lymphatic endothelial cells are derived from a single progenitor cell.

  17. Capacitively-coupled chopper amplifiers

    CERN Document Server

    Fan, Qinwen; Huijsing, Johan H

    2017-01-01

    This book describes the concept and design of the capacitively-coupled chopper technique, which can be used in precision analog amplifiers. Readers will learn to design power-efficient amplifiers employing this technique, which can be powered by regular low supply voltage such as 2V and possibly having a +\\-100V input common-mode voltage input. The authors provide both basic design concepts and detailed design examples, which cover the area of both operational and instrumentation amplifiers for multiple applications, particularly in power management and biomedical circuit designs. Discusses basic working principles and details of implementation for proven designs; Includes a diverse set of applications, along with measurement results to demonstrate the effectiveness of the technique; Explains advantages and drawbacks of the technique, given particular circumstances.

  18. Interface dynamos in supernova progenitors

    CERN Document Server

    Blackman, E G; Thomas, J H; Blackman, Eric G.; Nordhaus, Jason T.; Thomas, John H.

    2004-01-01

    Observational evidence for anisotropy in supernovae (SN) and their phenomenological connection to jetted sources such as gamma-ray bursts^Mhave revived considerations of the role magnetohydrodynamic outflows might play therein. Understanding the types of dynamos that might operate in supernova progenitors is therefore relevant. In contrast to previous work, here we study an ``interface dynamo'' for the conditions of a rapidly rotating neutron star surrounded by a convective envelope. Such dynamos have been studied for the Sun, naked white dwarfs,and post-AGB stars, where analogous configurations of strong shear layers surrounded by convective envelopes are present. The interface dynamo provides estimates of large-scale poloidal and toroidal fields, whose product enters the Poynting flux. Because the poloidal field is much weaker than the toroidal magnetic field, the actual average Poynting flux is lower than rough estimates which invoke the only the magnitude of the total magnetic energy. The lower value is s...

  19. Progenitors of Supernovae Type Ia

    CERN Document Server

    Toonen, S; Bours, M; Zwart, S Portegies; Claeys, J; Mennekens, N; Ruiter, A

    2013-01-01

    Despite the significance of Type Ia supernovae (SNeIa) in many fields in astrophysics, SNeIa lack a theoretical explanation. The standard scenarios involve thermonuclear explosions of carbon/oxygen white dwarfs approaching the Chandrasekhar mass; either by accretion from a companion or by a merger of two white dwarfs. We investigate the contribution from both channels to the SNIa rate with the binary population synthesis (BPS) code SeBa in order to constrain binary processes such as the mass retention efficiency of WD accretion and common envelope evolution. We determine the theoretical rates and delay time distribution of SNIa progenitors and in particular study how assumptions affect the predicted rates.

  20. Genetic Tagging During Human Mesoderm Differentiation Reveals Tripotent Lateral Plate Mesodermal Progenitors.

    Science.gov (United States)

    Chin, Chee Jia; Cooper, Aaron R; Lill, Georgia R; Evseenko, Denis; Zhu, Yuhua; He, Chong Bin; Casero, David; Pellegrini, Matteo; Kohn, Donald B; Crooks, Gay M

    2016-05-01

    Although clonal studies of lineage potential have been extensively applied to organ specific stem and progenitor cells, much less is known about the clonal origins of lineages formed from the germ layers in early embryogenesis. We applied lentiviral tagging followed by vector integration site analysis (VISA) with high-throughput sequencing to investigate the ontogeny of the hematopoietic, endothelial and mesenchymal lineages as they emerge from human embryonic mesoderm. In contrast to studies that have used VISA to track differentiation of self-renewing stem cell clones that amplify significantly over time, we focused on a population of progenitor clones with limited self-renewal capability. Our analyses uncovered the critical influence of sampling on the interpretation of lentiviral tag sharing, particularly among complex populations with minimal clonal duplication. By applying a quantitative framework to estimate the degree of undersampling we revealed the existence of tripotent mesodermal progenitors derived from pluripotent stem cells, and the subsequent bifurcation of their differentiation into bipotent endothelial/hematopoietic or endothelial/mesenchymal progenitors. Stem Cells 2016;34:1239-1250.

  1. Self-renewal of embryonic-stem-cell-derived progenitors by organ-matched mesenchyme.

    Science.gov (United States)

    Sneddon, Julie B; Borowiak, Malgorzata; Melton, Douglas A

    2012-11-29

    One goal of regenerative medicine, to use stem cells to replace cells lost by injury or disease, depends on producing an excess of the relevant cell for study or transplantation. To this end, the stepwise differentiation of stem cells into specialized derivatives has been successful for some cell types, but a major problem remains the inefficient conversion of cells from one stage of differentiation to the next. If specialized cells are to be produced in large numbers it will be necessary to expand progenitor cells, without differentiation, at some steps of the process. Using the pancreatic lineage as a model for embryonic-stem-cell differentiation, we demonstrate that this is a solvable problem. Co-culture with organ-matched mesenchyme permits proliferation and self-renewal of progenitors, without differentiation, and enables an expansion of more than a million-fold for human endodermal cells with full retention of their developmental potential. This effect is specific both to the mesenchymal cell and to the progenitor being amplified. Progenitors that have been serially expanded on mesenchyme give rise to glucose-sensing, insulin-secreting cells when transplanted in vivo. Theoretically, the identification of stage-specific renewal signals can be incorporated into any scheme for the efficient production of large numbers of differentiated cells from stem cells and may therefore have wide application in regenerative biology.

  2. Thermal recovery of NIF amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Sutton, S.; Marshall, C.; Petty, C.; Smith, L.; van Wonterghem, B.; Mills, S.

    1997-02-01

    The issue of thermal recovery of the NIF amplifiers has taken on increased emphasis as program goals move toward increasing the shot rate to once every four hours. This paper addresses the technical issues associated with achieving thermal recovery in the NIF amplifiers. We identify two temperature related thermal recovery quantities: (1) the difference between the average slab temperature and the temperature of other surfaces in the amplifier cavity, and (2) the temperature difference in the slab over the aperture. The first quantity relates to optical disturbances in the gas column in the system, while the second quantity is associated with optical aberrations in the laser media itself. Calculations and experiments are used to quantify recovery criteria, and develop cooling approaches. The cooling approaches discussed are (1) active cooling of the flashlamps with ambient gas and chilled gas, and (2) active cooling of the slab edge cladding. Calculations indicate that the NIF baseline cooling approach of 20 cfm per lamp ambient temperature gas flow in both the central and side flashlamp cassettes is capable of meeting thermal recovery requirements for an 8 hour shot period, while to achieve a 4 hour shot period requires use of chilled gas and edge cladding cooling. In addition, the effect of changing the amplifier cavity and beamtube fill gas from nitrogen to helium is addressed, showing that a factor of 8 reduction in the sensitivity to thermal disturbances is possible. 6 refs., 9 figs., 1 tab.

  3. CMOS Current-mode Operational Amplifier

    DEFF Research Database (Denmark)

    Kaulberg, Thomas

    1992-01-01

    current-mode feedback amplifier or a constant bandwidth in a transimpedance feedback amplifier. The amplifier is found to have a gain bandwidth product of 8 MHz, an offset current of 0.8 ¿A (signal-range ±700¿A) and a (theoretically) unlimited slew-rate. The amplifier is realized in a standard CMOS 2......A fully differential-input differential-output current-mode operational amplifier (COA) is described. The amplifier utilizes three second generation current-conveyors (CCII) as the basic building blocks. It can be configured to provide either a constant gain-bandwidth product in a fully balanced...

  4. Hematopoietic progenitor migration to the adult thymus

    OpenAIRE

    Zlotoff, Daniel A.; Bhandoola, Avinash

    2011-01-01

    While most hematopoietic lineages develop in the bone marrow (BM), T cells uniquely complete their development in the specialized environment of the thymus. Hematopoietic stem cells with long-term self-renewal capacity are not present in the thymus. As a result, continuous T cell development requires that BM-derived progenitors be imported into the thymus throughout adult life. The process of thymic homing begins with the mobilization of progenitors out of the bone marrow, continues with thei...

  5. Linearisation of RF Power Amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Per Asbeck

    2001-01-01

    This thesis deals with linearisation techniques of RF power amplifiers (PA), PA design techniques and integration of the necessary building blocks in a CMOS technology. The opening chapters introduces the theory of transmitter architectures, RF-signal representation and the principles of digital...... modulation. Furthermore different types of power amplifiers, models and measures of non-linearities are presented. A chapter is also devoted to different types of linearisation systems. The work carried out and described in this thesis can be divided into a more theoretical and system oriented treatment...... the polar loop architecture and it’s suitability to modern digital transmitters is discussed. A proposal of an architecture that is suitable for digital transmitters, which means that it has an interface to the digital back-end, defined by low-pass signals in polar form, is presented. Simulation guidelines...

  6. Single conversion stage amplifier - SICAM

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.

    2005-12-15

    This Ph.D. thesis presents a thorough analysis of the so called SICAM - SIngle Converter stage AMplifier approach to building direct energy conversion audio power amplifiers. The mainstream approach for building isolated audio power amplifiers today consists of isolated DC power supply and Class D amplifier, which essentially represents a two stage solution, where each of the components can be viewed as separate and independent part. The proposed SICAM solution strives for direct energy conversion from the mains to the audio output, by dedicating the operation of the components one to another and integrating their functions, so that the final audio power amplifier represents a single-stage topology with higher efficiency, lower volume, less board space, lower component count and subsequently lower cost. The SICAM approach is both applicable to non-isolated and isolated audio power amplifiers, but the problems encountered in these two cases are different. Non-isolated SICAM solutions are intended for both AC mains-connected and battery-powered devices. In non-isolated mains-connected SICAMs the main idea is to simplify the power supply or even provide integrated power factor correction (PFC) functions, while still maintaining low component stress and good audio performance by generally decreasing the input voltage level to the Class D audio power amplifier. On the other hand, non-isolated battery-powered SICAMs have to cope with the ever changing battery voltage and provide output voltage levels which are both lower and higher than the battery voltage, while still being simple and single-stage energy conversion solutions. In isolated SICAMs the isolation transformer adjusts the voltage level on the secondary side to the desired level, so the main challenges here are decreasing the size of the magnetic core and reducing the number and size of bulky reactive components as much as possible. The main focus of this thesis is directed towards the isolated SICAMs and

  7. 338-GHz Semiconductor Amplifier Module

    Science.gov (United States)

    Samoska, Lorene A.; Gaier, Todd C.; Soria, Mary M.; Fung, King Man; Rasisic, Vesna; Deal, William; Leong, Kevin; Mei, Xiao Bing; Yoshida, Wayne; Liu, Po-Hsin; Uyeda, Jansen; Lai, Richard

    2010-01-01

    Research findings were reported from an investigation of new gallium nitride (GaN) monolithic millimeter-wave integrated circuit (MMIC) power amplifiers (PAs) targeting the highest output power and the highest efficiency for class-A operation in W-band (75-110 GHz). W-band PAs are a major component of many frequency multiplied submillimeter-wave LO signal sources. For spectrometer arrays, substantial W-band power is required due to the passive lossy frequency multipliers.

  8. Supernova Remnant Progenitor Masses in M31

    CERN Document Server

    Jennings, Zachary G; Murphy, Jeremiah W; Dalcanton, Julianne J; Gilbert, Karoline M; Dolphin, Andrew E; Fouesneau, Morgan; Weisz, Daniel R

    2012-01-01

    Using HST photometry, we age-date 59 supernova remnants (SNRs) in the spiral galaxy M31 and use these ages to estimate zero-age main sequence masses (MZAMS) for their progenitors. To accomplish this, we create color-magnitude diagrams (CMDs) and use CMD fitting to measure the recent star formation history (SFH) of the regions surrounding cataloged SNR sites. We identify any young coeval population that likely produced the progenitor star and assign an age and uncertainty to that population. Application of stellar evolution models allows us to infer the MZAMS from this age. Because our technique is not contingent on precise location of the progenitor star, it can be applied to the location of any known SNR. We identify significant young SF around 53 of the 59 SNRs and assign progenitor masses to these, representing a factor of 2 increase over currently measured progenitor masses. We consider the remaining 6 SNRs as either probable Type Ia candidates or the result of core-collapse progenitors that have escaped ...

  9. Small and lightweight power amplifiers

    Science.gov (United States)

    Shams, Qamar A.; Barnes, Kevin N.; Fox, Robert L.; Moses, Robert W.; Bryant, Robert G.; Robinson, Paul C.; Shirvani, Mir

    2002-07-01

    The control of u wanted structural vibration is implicit in most of NASA's programs. Currently several approaches to control vibrations in large, lightweight, deployable structures and twin tail aircraft at high angles of attack are being evaluated. The Air Force has been examining a vertical tail buffet load alleviation system that can be integrated onboard an F/A-18 and flown. Previous wind tunnel and full-scale ground tests using distributed actuators have shown that the concept works; however, there is insufficient rom available onboard an F/A-18 to store current state-of- the-art system components such as amplifiers, DC-to-DC converter and a computer for performing vibration suppression. Sensor processing, power electronics, DC-to-DC converters, and control electronics that may be collocated with distributed actuators, are particularly desirable. Such electronic system would obviate the need for complex, centralized, control processing and power distribution components that will eliminate the weight associated with lengthy wiring and cabling networks. Several small and lightweight power amplifiers ranging from 300V pp to 650V pp have been designed using off the shelf components for different applications. In this paper, the design and testing of these amplifiers will be presented under various electrical loads.

  10. SPS RF System Amplifier plant

    CERN Multimedia

    1977-01-01

    The picture shows a 2 MW, 200 MHz amplifier plant with feeder lines. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also increased: to the first 2 MW plant a second 2 MW plant was added and by end 1979 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412016X, 7412017X, 7411048X.

  11. High power regenerative laser amplifier

    Science.gov (United States)

    Miller, J.L.; Hackel, L.A.; Dane, C.B.; Zapata, L.E.

    1994-02-08

    A regenerative amplifier design capable of operating at high energy per pulse, for instance, from 20-100 Joules, at moderate repetition rates, for instance from 5-20 Hertz is provided. The laser amplifier comprises a gain medium and source of pump energy coupled with the gain medium; a Pockels cell, which rotates an incident beam in response to application of a control signal; an optical relay system defining a first relay plane near the gain medium and a second relay plane near the rotator; and a plurality of reflectors configured to define an optical path through the gain medium, optical relay and Pockels cell, such that each transit of the optical path includes at least one pass through the gain medium and only one pass through the Pockels cell. An input coupler, and an output coupler are provided, implemented by a single polarizer. A control circuit coupled to the Pockels cell generates the control signal in timed relationship with the input pulse so that the input pulse is captured by the input coupler and proceeds through at least one transit of the optical path, and then the control signal is applied to cause rotation of the pulse to a polarization reflected by the polarizer, after which the captured pulse passes through the gain medium at least once more and is reflected out of the optical path by the polarizer before passing through the rotator again to provide an amplified pulse. 7 figures.

  12. Analog circuit design designing high performance amplifiers

    CERN Document Server

    Feucht, Dennis

    2010-01-01

    The third volume Designing High Performance Amplifiers applies the concepts from the first two volumes. It is an advanced treatment of amplifier design/analysis emphasizing both wideband and precision amplification.

  13. Higher order mode optical fiber Raman amplifiers

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Friis, Søren Michael Mørk; Usuga Castaneda, Mario A.;

    2016-01-01

    We review higher order mode Raman amplifiers and discuss recent theoretical as well as experimental results including system demonstrations.......We review higher order mode Raman amplifiers and discuss recent theoretical as well as experimental results including system demonstrations....

  14. Challenges in higher order mode Raman amplifiers

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Nielsen, Kristian; Friis, Søren Michael Mørk;

    2015-01-01

    A higher order Raman amplifier model that take random mode coupling into account ispresented. Mode dependent gain and signal power fluctuations at the output of the higher order modeRaman amplifier are discussed......A higher order Raman amplifier model that take random mode coupling into account ispresented. Mode dependent gain and signal power fluctuations at the output of the higher order modeRaman amplifier are discussed...

  15. Improved charge amplifier using hybrid hysteresis compensation

    Science.gov (United States)

    Amin-Shahidi, Darya; Trumper, David L.

    2013-08-01

    We present a novel charge amplifier, with a robust feedback circuit and a method for compensating piezoelectric actuator's hysteresis at low frequencies. The amplifier uses a modified feedback circuit which improves robustness to the addition of series load impedance such as in cabling. We also describe a hybrid hysteresis compensation method for enabling the charge amplifier to reduce hysteresis at low frequencies. Experimental results demonstrate the utility of the new amplifier design.

  16. European Research on THz Vacuum Amplifiers

    DEFF Research Database (Denmark)

    Brunetti, F.; Cojocarua, C.-S.; de Rossi, A.

    2010-01-01

    The OPTHER (OPtically Driven TeraHertz AmplifiERs) project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within this project is a consolidation of efforts at the international level from the main players of the Eu...... of the European research, academy and industry in vacuum electronics. This paper describes the status of the project and progress towards the THz amplifier realization....

  17. low pump power photonic crystal fibre amplifiers

    DEFF Research Database (Denmark)

    Hougaard, Kristian G.; Broeng, Jes; Bjarklev, Anders Overgaard

    2003-01-01

    Designs of low pump power optical amplifiers, based on photonic crystal fibres are presented. The potential of these fibre amplifiers is investigated, and it is demonstrated that such amplifiers may deliver gains of more than 15 dB at 1550 nm with less than 1 mW of optical pump power....

  18. A High-performance Small Signal Amplifier

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    According to questions in the design of high quality small signal amplifier, this paper gave a new-type high performance small signal amplifier. The paper selected the operational amplifier of ICL Company and designed a new-type circuit with simple, low cost and excellent performance.

  19. Log amplifier with pole-zero compensation

    Science.gov (United States)

    Brookshier, William

    1987-01-01

    A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifier circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedback loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point or pole is offset by a compensating break point or zero.

  20. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Borri, Paola; Ledentsov, N. N.

    2002-01-01

    -power surface emitting VCSELs. We investigated the ultrafast dynamics of quantum-dot semiconductor optical amplifiers. The dephasing time at room temperature of the ground-state transition in semiconductor quantum dots is around 250 fs in an unbiased amplifier, decreasing to below 50 fs when the amplifier...... is biased to positive net gain. We have further measured gain recovery times in quantum dot amplifiers that are significantly lower than in bulk and quantum-well semiconductor optical amplifiers. This is promising for future demonstration of quantum dot devices with high modulation bandwidth...

  1. An Implantable CMOS Amplifier for Nerve Signals

    DEFF Research Database (Denmark)

    Nielsen, Jannik Hammel; Lehmann, Torsten

    2003-01-01

    In this paper, a low noise high gain CMOS amplifier for minute nerve signals is presented. The amplifier is constructed in a fully differential topology to maximize noise rejection. By using a mixture of weak- and strong inversion transistors, optimal noise suppression in the amplifier is achieved....... A continuous-time current-steering offset-compensation technique is utilized in order to minimize the noise contribution and to minimize dynamic impact on the amplifier input nodes. The method for signal recovery from noisy nerve signals is presented. A prototype amplifier is realized in a standard digital 0...

  2. High temperature charge amplifier for geothermal applications

    Science.gov (United States)

    Lindblom, Scott C.; Maldonado, Frank J.; Henfling, Joseph A.

    2015-12-08

    An amplifier circuit in a multi-chip module includes a charge to voltage converter circuit, a voltage amplifier a low pass filter and a voltage to current converter. The charge to voltage converter receives a signal representing an electrical charge and generates a voltage signal proportional to the input signal. The voltage amplifier receives the voltage signal from the charge to voltage converter, then amplifies the voltage signal by the gain factor to output an amplified voltage signal. The lowpass filter passes low frequency components of the amplified voltage signal and attenuates frequency components greater than a cutoff frequency. The voltage to current converter receives the output signal of the lowpass filter and converts the output signal to a current output signal; wherein an amplifier circuit output is selectable between the output signal of the lowpass filter and the current output signal.

  3. Audio power amplifier design handbook

    CERN Document Server

    Self, Douglas

    2013-01-01

    This book is essential for audio power amplifier designers and engineers for one simple reason...it enables you as a professional to develop reliable, high-performance circuits. The Author Douglas Self covers the major issues of distortion and linearity, power supplies, overload, DC-protection and reactive loading. He also tackles unusual forms of compensation and distortion produced by capacitors and fuses. This completely updated fifth edition includes four NEW chapters including one on The XD Principle, invented by the author, and used by Cambridge Audio. Cro

  4. Endothelial progenitor cells in cardiovascular diseases

    Institute of Scientific and Technical Information of China (English)

    Poay; Sian; Sabrina; Lee; Kian; Keong; Poh

    2014-01-01

    Endothelial dysfunction has been associated with the development of atherosclerosis and cardiovascular diseases. Adult endothelial progenitor cells(EPCs) are derived from hematopoietic stem cells and are capable of forming new blood vessels through a process of vas-culogenesis. There are studies which report correlations between circulating EPCs and cardiovascular risk fac-tors. There are also studies on how pharmacotherapies may influence levels of circulating EPCs. In this review, we discuss the potential role of endothelial progenitor cells as both diagnostic and prognostic biomarkers. In addition, we look at the interaction between cardio-vascular pharmacotherapies and endothelial progenitor cells. We also discuss how EPCs can be used directly and indirectly as a therapeutic agent. Finally, we evalu-ate the challenges facing EPC research and how these may be overcome.

  5. High power RF solid state power amplifier system

    Science.gov (United States)

    Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

    2011-01-01

    A high power, high frequency, solid state power amplifier system includes a plurality of input multiple port splitters for receiving a high-frequency input and for dividing the input into a plurality of outputs and a plurality of solid state amplifier units. Each amplifier unit includes a plurality of amplifiers, and each amplifier is individually connected to one of the outputs of multiport splitters and produces a corresponding amplified output. A plurality of multiport combiners combine the amplified outputs of the amplifiers of each of the amplifier units to a combined output. Automatic level control protection circuitry protects the amplifiers and maintains a substantial constant amplifier power output.

  6. Quantum Noise in Amplifiers and Hawking/Dumb-Hole Radiation as Amplifier Noise

    CERN Document Server

    Unruh, W G

    2011-01-01

    The quantum noise in a linear amplifier is shown to be thermal noise. The theory of linear amplifiers is applied first to the simplest, single or double oscillator model of an amplifier, and then to linear model of an amplifier with continuous fields and input and outputs. Finally it is shown that the thermal noise emitted by black holes first demonstrated by Hawking, and of dumb holes (sonic and other analogs to black holes), arises from the same analysis as for linear amplifiers. The amplifier noise of black holes acting as amplifiers on the quantum fields living in the spacetime surrounding the black hole is the radiation discovered by Hawking. For any amplifier, that quantum noise is completely characterized by the attributes of the system regarded as a classical amplifier, and arises out of those classical amplification factors and the commutation relations of quantum mechanics.

  7. X Inactivation and Progenitor Cancer Cells

    Directory of Open Access Journals (Sweden)

    Ruben Agrelo

    2011-04-01

    Full Text Available In mammals, silencing of one of the two X chromosomes is necessary to achieve dosage compensation. The 17 kb non-coding RNA called Xist triggers X inactivation. Gene silencing by Xist can only be achieved in certain contexts such as in cells of the early embryo and in certain hematopoietic progenitors where silencing factors are present. Moreover, these epigenetic contexts are maintained in cancer progenitors in which SATB1 has been identified as a factor related to Xist-mediated chromosome silencing.

  8. Core-Collapse supernovae and its progenitors

    CERN Document Server

    Bose, Subhash; Misra, Kuntal

    2016-01-01

    Massive stars unable to sustain gravitational collapse, at the end of nuclear burning stage, turns out into core-collapse supernovae, leaving behind compact objects like neutron stars or black holes. The progenitor properties like mass and metallicity primarily governs the explosion parameters and type of compact remnant. In this contribution we summarize observational study of three Core Collapse type IIP SNe 2012aw, 2013ab and 2013ej, which are rigorously observed from ARIES and other Indian observatories and discuss their progenitor and explosion properties.

  9. YANG-MILLS FIELD AMPLIFIER

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2015-09-01

    Full Text Available The article presents a project of the Yang-Mills amplifier. Amplifier model is a multilayer spherical shell with increasing density towards the center. In the center of the amplifier is the core of high-density material. It is shown that in such a system, the amplitude of the Yang-Mills waves rises from the periphery to the center of several orders of magnitude. The role of the Yang-Mills field in the processes occurring in the nuclei of galaxies, stars and planets is discussed. The data modeling to strengthen the Yang-Mills field in the bowels of the planet, with an atomic explosion, and in some special devices such as the voltaic pile. To describe the mechanism of amplification chromodynamics field used as accurate results in Yang-Mills theory and numerical models developed based on an average and the exact equations as well. Among the exact solutions of the special role played by the centralsymmetric metric describing the contribution of the Yang-Mills field in the speed of recession of galaxies. Among the approximate numerical models can be noted the eight-scalar model we have developed for the simulation of non-linear color oscillations and chaos in the Yang-Mills theory. Earlier models were investigated spatio-temporal oscillations of the YangMills theory in the case of three and eight colors. The results of numerical simulation show that the nonlinear interaction does not lead to a spatial mixing of colors as it might be in the case of turbulent diffusion. Depending on the system parameters there is a suppression of the amplitude of the oscillations the first three by five colors or vice versa. The kinetic energy fluctuations or shared equally between the color components, or dominated by the kinetic energy of repressed groups of colors. In the present study, we found that amplification chromodynamic field leads to a sharp increase in the amplitude of the suppressed color, which can lead to an increase in entropy, excitation of nuclear

  10. Locoregional MYCN-amplified neuroblastoma.

    Science.gov (United States)

    Morales La Madrid, Andres; Volchenboum, Samuel; Gastier-Foster, Julie M; Pyatt, Robert; Liu, Don; Pytel, Peter; Lavarino, Cinzia; Rodriguez, Eva; Cohn, Susan L

    2012-10-01

    MYCN-amplification is strongly associated with other high-risk prognostic factors and poor outcome in neuroblastoma. Infrequently, amplification of MYCN has been identified in localized tumors with favorable biologic features. Outcome for these children is difficult to predict and optimal treatment strategies remain unclear. We report a 5-month-old who presented with an MYCN-amplified INSS stage 3, pelvic neuroblastoma. The tumor had favorable histology, hyperdiploidy, and lacked 1p36 and 11q23 aberrations. Although the patient met the criteria for high-risk neuroblastoma, because of the discordant prognostic markers we elected to treat her according to an intermediate-risk protocol. She remains event-free more than 18 months.

  11. Transverse pumped laser amplifier architecture

    Science.gov (United States)

    Bayramian, Andrew James; Manes, Kenneth; Deri, Robert; Erlandson, Al; Caird, John; Spaeth, Mary

    2013-07-09

    An optical gain architecture includes a pump source and a pump aperture. The architecture also includes a gain region including a gain element operable to amplify light at a laser wavelength. The gain region is characterized by a first side intersecting an optical path, a second side opposing the first side, a third side adjacent the first and second sides, and a fourth side opposing the third side. The architecture further includes a dichroic section disposed between the pump aperture and the first side of the gain region. The dichroic section is characterized by low reflectance at a pump wavelength and high reflectance at the laser wavelength. The architecture additionally includes a first cladding section proximate to the third side of the gain region and a second cladding section proximate to the fourth side of the gain region.

  12. Reflection amplifiers in self-regulated learning

    NARCIS (Netherlands)

    Verpoorten, Dominique

    2012-01-01

    Verpoorten, D. (2012). Reflection amplifiers in self-regulated learning. Doctoral thesis. November, 9, 2012, Heerlen, The Netherlands: Open Universiteit (CELSTEC). Datawyse / Universitaire Pers Maastricht.

  13. Enhanced Gain in Photonic Crystal Amplifiers

    DEFF Research Database (Denmark)

    Ek, Sara; Semenova, Elizaveta; Hansen, Per Lunnemann;

    2012-01-01

    study of a 1 QW photonic crystal amplifier. Net gain is achieved which enables laser oscillation in photonic crystal micro cavities. The ability to freely tailor the dispersion in a semiconductor optical amplifier makes it possible to raise the optical gain considerably over a certain bandwidth......We experimentally demonstrate enhanced gain in the slow-light regime of quantum well photonic crystal amplifiers. A strong gain enhancement is observed with the increase of the group refractive index, due to light slow-down. The slow light enhancement is shown in a amplified spontaneous emission...

  14. Design of an 1800nm Raman amplifier

    DEFF Research Database (Denmark)

    Svane, Ask Sebastian; Rottwitt, Karsten

    2013-01-01

    We present the experimental results for a Raman amplifier that operates at 1810 nm and is pumped by a Raman fiber laser at 1680 nm. Both the pump laser and the Raman amplifier is polarization maintaining. A challenge when scaling Raman amplifiers to longer wavelengths is the increase...... performance of the amplifier is also investigated for both configurations. Our results show an on/off gain exceeding 20 dB at 1810 nm for which the obtained effective noise figure is below 3 dB....

  15. Dynamics of Soliton Cascades in Fiber Amplifiers

    CERN Document Server

    Arteaga-Sierra, F R; Agrawal, Govind P

    2016-01-01

    We study numerically the formation of cascading solitons when femtosecond optical pulses are launched into a fiber amplifier with less energy than required to form a soliton of equal duration. As the pulse is amplified, cascaded fundamental solitons are created at different distances, without soliton fission, as each fundamental soliton moves outside the gain bandwidth through the Raman-induced spectral shifts. As a result, each input pulse creates multiple, temporally separated, ultrashort pulses of different wavelengths at the amplifier output. The number of pulses depends not only on the total gain of the amplifier but also on the width of input pulses.

  16. Characterization of hepatic progenitors from human fetal liver using CD34 as a hepatic progenitor marker

    Institute of Scientific and Technical Information of China (English)

    Parveen Nyamath; Ayesha AM; Aejaz Habeeb; Sanjeev Khosla; Aleem A Khan; CM Habibullah

    2007-01-01

    AIM: To enrich putative hepatic progenitors from the developing human fetal liver using CD34 as a marker.METHODS: Aborted fetuses of 13-20 wk were used for the isolation of liver cells. The cells were labeled with anti CD34; a marker used for isolating progenitor population and the cells were sorted using magnetic cell sorting. The positive fractions of cells were assessed for specific hepatic markers. Further, these cells were cultured in vitro for long term investigation.RESULTS: Flow cytometric and immunocytochemical analysis for alphafetoprotein (AFP) showed that the majority of the enriched CD34 positive cells were positive for AFP. Furthermore, these enriched cells proliferated in the long term and maintained hepatic characteristics in in vitro culture.CONCLUSION: The study shows that aborted human fetal liver is a potential source for isolation of hepatic progenitors for clinical applications. The study also demonstrates that CD34 can be a good marker for the enrichment of progenitor populations.

  17. Targeting human oligodendrocyte progenitors for myelin repair.

    Science.gov (United States)

    Dietz, Karen C; Polanco, Jessie J; Pol, Suyog U; Sim, Fraser J

    2016-09-01

    Oligodendrocyte development has been studied for several decades, and has served as a model system for both neurodevelopmental and stem/progenitor cell biology. Until recently, the vast majority of studies have been conducted in lower species, especially those focused on rodent development and remyelination. In humans, the process of myelination requires the generation of vastly more myelinating glia, occurring over a period of years rather than weeks. Furthermore, as evidenced by the presence of chronic demyelination in a variety of human neurologic diseases, it appears likely that the mechanisms that regulate development and become dysfunctional in disease may be, in key ways, divergent across species. Improvements in isolation techniques, applied to primary human neural and oligodendrocyte progenitors from both fetal and adult brain, as well as advancements in the derivation of defined progenitors from human pluripotent stem cells, have begun to reveal the extent of both species-conserved signaling pathways and potential key differences at cellular and molecular levels. In this article, we will review the commonalities and differences in myelin development between rodents and man, describing the approaches used to study human oligodendrocyte differentiation and myelination, as well as heterogeneity within targetable progenitor pools, and discuss the advances made in determining which conserved pathways may be both modeled in rodents and translate into viable therapeutic strategies to promote myelin repair.

  18. Single Degenerate Progenitors of Type Ia Supernovae

    Science.gov (United States)

    Bours, Madelon; Toonen, Silvia; Nelemans, Gijs

    2013-01-01

    There is a general agreement that Type Ia supernovae correspond to the thermonuclear runaway of a white dwarf (WD) in a compact binary. The details of these progenitor systems are still unclear. Using the population synthesis code SeBa and several assumption for the WD retention efficiency, we estimate the delay times and supernova rates for the single degenerate scenario.

  19. Direct Conversion of Fibroblasts to Megakaryocyte Progenitors

    Directory of Open Access Journals (Sweden)

    Julian Pulecio

    2016-10-01

    Full Text Available Current sources of platelets for transfusion are insufficient and associated with risk of alloimmunization and blood-borne infection. These limitations could be addressed by the generation of autologous megakaryocytes (MKs derived in vitro from somatic cells with the ability to engraft and differentiate in vivo. Here, we show that overexpression of a defined set of six transcription factors efficiently converts mouse and human fibroblasts into MK-like progenitors. The transdifferentiated cells are CD41+, display polylobulated nuclei, have ploidies higher than 4N, form MK colonies, and give rise to platelets in vitro. Moreover, transplantation of MK-like murine progenitor cells into NSG mice results in successful engraftment and further maturation in vivo. Similar results are obtained using disease-corrected fibroblasts from Fanconi anemia patients. Our results combined demonstrate that functional MK progenitors with clinical potential can be obtained in vitro, circumventing the use of hematopoietic progenitors or pluripotent stem cells.

  20. SUPERNOVA REMNANT PROGENITOR MASSES IN M31

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, Zachary G.; Williams, Benjamin F.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Fouesneau, Morgan; Weisz, Daniel R. [Department of Astronomy, University of Washington Seattle, Box 351580, WA 98195 (United States); Murphy, Jeremiah W. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Dolphin, Andrew E., E-mail: zachjenn@uw.edu, E-mail: adolphin@raytheon.com [Raytheon, 1151 East Hermans Road, Tucson, AZ 85706 (United States)

    2012-12-10

    Using Hubble Space Telescope photometry, we age-date 59 supernova remnants (SNRs) in the spiral galaxy M31 and use these ages to estimate zero-age main-sequence masses (M{sub ZAMS}) for their progenitors. To accomplish this, we create color-magnitude diagrams (CMDs) and employ CMD fitting to measure the recent star formation history of the regions surrounding cataloged SNR sites. We identify any young coeval population that likely produced the progenitor star, then assign an age and uncertainty to that population. Application of stellar evolution models allows us to infer the M{sub ZAMS} from this age. Because our technique is not contingent on identification or precise location of the progenitor star, it can be applied to the location of any known SNRs. We identify significant young star formation around 53 of the 59 SNRs and assign progenitor masses to these, representing a factor of {approx}2 increase over currently measured progenitor masses. We consider the remaining six SNRs as either probable Type Ia candidates or the result of core-collapse progenitors that have escaped their birth sites. In general, the distribution of recovered progenitor masses is bottom-heavy, showing a paucity of the most massive stars. If we assume a single power-law distribution, dN/dM{proportional_to}M{sup {alpha}}, then we find a distribution that is steeper than a Salpeter initial mass function (IMF) ({alpha} = -2.35). In particular, we find values of {alpha} outside the range -2.7 {>=} {alpha} {>=} -4.4 to be inconsistent with our measured distribution at 95% confidence. If instead we assume a distribution that follows a Salpeter IMF up to some maximum mass, then we find that values of M{sub Max} > 26 are inconsistent with the measured distribution at 95% confidence. In either scenario, the data suggest that some fraction of massive stars may not explode. The result is preliminary and requires more SNRs and further analysis. In addition, we use our distribution to estimate a

  1. Study of corneal epithelial progenitor origin and the Yap1 requirement using keratin 12 lineage tracing transgenic mice

    Science.gov (United States)

    Kasetti, Ramesh Babu; Gaddipati, Subhash; Tian, Shifu; Xue, Lei; Kao, Winston W.-Y.; Lu, Qingxian; Li, Qiutang

    2016-01-01

    Key issues in corneal epithelium biology are the mechanism for corneal epithelium stem cells to maintain the corneal epithelial homeostasis and wound healing responses, and what are the regulatory molecular pathways involved. There are apparent discrepancies about the locations of the progenitor populations responsible for corneal epithelial self-renewal. We have developed a genetic mouse model to trace the corneal epithelial progenitor lineages during adult corneal epithelial homeostasis and wound healing response. Our data revealed that the early corneal epithelial progenitor cells expressing keratin-12 originated from limbus, and gave rise to the transit amplifying cells that migrated centripetally to differentiate into corneal epithelial cells. Our results support a model that both corneal epithelial homeostasis and wound healing are mainly maintained by the activated limbal stem cells originating form limbus, but not from the corneal basal epithelial layer. In the present study, we further demonstrated the nuclear expression of transcriptional coactivator YAP1 in the limbal and corneal basal epithelial cells and its essential role for maintaining the high proliferative potential of those corneal epithelial progenitor cells in vivo. PMID:27734924

  2. Distributed feedback laser amplifiers combining the functions of amplifiers and channel filters

    DEFF Research Database (Denmark)

    Wang, Z.; Durhuus, T.; Mikkelsen, Benny;

    1994-01-01

    A dynamic model for distributed feedback amplifiers, including the mode coupled equations and the carrier rate equation, is established. The presented mode coupled equations have taken into account the interaction between fast changing optical signal and the waveguide with corrugations. By showin...... the possibility of amplifying 100 ps pulses without pulse broadening, we anticipate that a distributed feedback amplifier can be used as a combined amplifier and channel filter in high bit rate transmission systems....

  3. Amplified spontaneous emission and its restraint in a terawatt Ti:sapphire amplifier

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Amplified spontaneous emission (ASE) and its restraint in a femtosecond Ti: sapphire chirped_pulse amplifier were investigated. The noises arising from ASE were effectively filtered out in the spatial, temporal and spectral domain. Pulses as short as 38 fs were amplified to peak power of 1.4 TW. The power ratio between the amplified femtosecond pulse and the ASE was higher than 106:1.

  4. Self-pulsation in Raman fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.......Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated....

  5. BROADBAND TRAVELLING WAVE SEMICONDUCTOR OPTICAL AMPLIFIER

    DEFF Research Database (Denmark)

    2010-01-01

    Broadband travelling wave semiconductor optical amplifier (100, 200, 300, 400, 800) for amplification of light, wherein the amplifier (100, 200, 300, 400, 800) comprises a waveguide region (101, 201, 301, 401, 801) for providing confinement of the light in transverse directions and adapted...

  6. Ultrafast disk lasers and amplifiers

    Science.gov (United States)

    Sutter, Dirk H.; Kleinbauer, Jochen; Bauer, Dominik; Wolf, Martin; Tan, Chuong; Gebs, Raphael; Budnicki, Aleksander; Wagenblast, Philipp; Weiler, Sascha

    2012-03-01

    Disk lasers with multi-kW continuous wave (CW) output power are widely used in manufacturing, primarily for cutting and welding applications, notably in the automotive industry. The ytterbium disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency, and high reliability with low investment and operating costs. Fundamental mode picosecond disk lasers are well established in micro machining at high throughput and perfect precision. Following the world's first market introduction of industrial grade 50 W picosecond lasers (TruMicro 5050) at the Photonics West 2008, the second generation of the TruMicro series 5000 now provides twice the average power (100 W at 1030 nm, or 60 W frequency doubled, green output) at a significantly reduced footprint. Mode-locked disk oscillators achieve by far the highest average power of any unamplified lasers, significantly exceeding the 100 W level in laboratory set-ups. With robust long resonators their multi-microjoule pulse energies begin to compete with typical ultrafast amplifiers. In addition, significant interest in disk technology has recently come from the extreme light laser community, aiming for ultra-high peak powers of petawatts and beyond.

  7. Design and performance of the beamlet amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Erlandson, A.C.; Rotter, M.D.; Frank, M.D.; McCracken, R.W.

    1996-06-01

    In future laser systems, such as the National Ignition Facility (NIF), multi-segment amplifiers (MSAs) will be used to amplify the laser beam to the required levels. As a prototype of such a laser architecture, the authors have designed, built, and tested flash-lamp-pumped, Nd:Glass, Brewster-angle slab MSAs for the Beamlet project. In this article, they review the fundamentals of Nd:Glass amplifiers, describe the MSA geometry, discuss parameters that are important in amplifier design, and present our results on the characterization of the Beamlet MSAs. In particular, gain and beam steering measurements show that the Beamlet amplifiers meet all optical performance specifications and perform close to model predictions.

  8. Amplified OTDR systems for multipoint corrosion monitoring.

    Science.gov (United States)

    Nascimento, Jehan F; Silva, Marcionilo J; Coêlho, Isnaldo J S; Cipriano, Eliel; Martins-Filho, Joaquim F

    2012-01-01

    We present two configurations of an amplified fiber-optic-based corrosion sensor using the optical time domain reflectometry (OTDR) technique as the interrogation method. The sensor system is multipoint, self-referenced, has no moving parts and can measure the corrosion rate several kilometers away from the OTDR equipment. The first OTDR monitoring system employs a remotely pumped in-line EDFA and it is used to evaluate the increase in system reach compared to a non-amplified configuration. The other amplified monitoring system uses an EDFA in booster configuration and we perform corrosion measurements and evaluations of system sensitivity to amplifier gain variations. Our experimental results obtained under controlled laboratory conditions show the advantages of the amplified system in terms of longer system reach with better spatial resolution, and also that the corrosion measurements obtained from our system are not sensitive to 3 dB gain variations.

  9. Amplified OTDR Systems for Multipoint Corrosion Monitoring

    Directory of Open Access Journals (Sweden)

    Joaquim F. Martins-Filho

    2012-03-01

    Full Text Available We present two configurations of an amplified fiber-optic-based corrosion sensor using the optical time domain reflectometry (OTDR technique as the interrogation method. The sensor system is multipoint, self-referenced, has no moving parts and can measure the corrosion rate several kilometers away from the OTDR equipment. The first OTDR monitoring system employs a remotely pumped in-line EDFA and it is used to evaluate the increase in system reach compared to a non-amplified configuration. The other amplified monitoring system uses an EDFA in booster configuration and we perform corrosion measurements and evaluations of system sensitivity to amplifier gain variations. Our experimental results obtained under controlled laboratory conditions show the advantages of the amplified system in terms of longer system reach with better spatial resolution, and also that the corrosion measurements obtained from our system are not sensitive to 3 dB gain variations.

  10. Detection of Non-Amplified Genomic DNA

    CERN Document Server

    Corradini, Roberto

    2012-01-01

    This book offers a state-of-the-art overview on non amplified DNA detection methods and provides chemists, biochemists, biotechnologists and material scientists with an introduction to these methods. In fact all these fields have dedicated resources to the problem of nucleic acid detection, each contributing with their own specific methods and concepts. This book will explain the basic principles of the different non amplified DNA detection methods available, highlighting their respective advantages and limitations. The importance of non-amplified DNA sequencing technologies will be also discussed. Non-amplified DNA detection can be achieved by adopting different techniques. Such techniques have allowed the commercialization of innovative platforms for DNA detection that are expected to break into the DNA diagnostics market. The enhanced sensitivity required for the detection of non amplified genomic DNA has prompted new strategies that can achieve ultrasensitivity by combining specific materials with specifi...

  11. An Implantable CMOS Amplifier for Nerve Signals

    DEFF Research Database (Denmark)

    Nielsen, Jannik Hammel; Lehmann, Torsten

    2001-01-01

    In this paper, a low noise high gain CMOS amplifier for minute nerve signals is presented. By using a mixture of weak- and strong inversion transistors, optimal noise suppression in the amplifier is achieved. A continuous-time offset-compensation technique is utilized in order to minimize impact...... on the amplifier input nodes. The method for signal recovery from noisy nerve signals is presented. A prototype amplifier is realized in a standard digital 0.5 μm CMOS single poly, n-well process. The prototype amplifier features a gain of 80 dB over a 3.6 kHz bandwidth, a CMRR of more than 87 dB and a PSRR...

  12. Derivation of myoepithelial progenitor cells from bipotent mammary stem/progenitor cells.

    Directory of Open Access Journals (Sweden)

    Xiangshan Zhao

    Full Text Available There is increasing evidence that breast and other cancers originate from and are maintained by a small fraction of stem/progenitor cells with self-renewal properties. Recent molecular profiling has identified six major subtypes of breast cancer: basal-like, ErbB2-overexpressing, normal breast epithelial-like, luminal A and B, and claudin-low subtypes. To help understand the relationship among mammary stem/progenitor cells and breast cancer subtypes, we have recently derived distinct hTERT-immortalized human mammary stem/progenitor cell lines: a K5(+/K19(- type, and a K5(+/K19(+ type. Under specific culture conditions, bipotent K5(+/K19(- stem/progenitor cells differentiated into stable clonal populations that were K5(-/K19(- and exhibit self-renewal and unipotent myoepithelial differentiation potential in contrast to the parental K5(+/K19(- cells which are bipotent. These K5(-/K19(- cells function as myoepithelial progenitor cells and constitutively express markers of an epithelial to mesenchymal transition (EMT and show high invasive and migratory abilities. In addition, these cells express a microarray signature of claudin-low breast cancers. The EMT characteristics of an un-transformed unipotent mammary myoepithelial progenitor cells together with claudin-low signature suggests that the claudin-low breast cancer subtype may arise from myoepithelial lineage committed progenitors. Availability of immortal MPCs should allow a more definitive analysis of their potential to give rise to claudin-low breast cancer subtype and facilitate biological and molecular/biochemical studies of this disease.

  13. Measuring Optimal Length of the Amplifying Fiber in Different Working Conditions of the Amplifier

    Directory of Open Access Journals (Sweden)

    Radek Poboril

    2014-01-01

    Full Text Available The aim of this article is to highlight possible unwanted behaviour of an EDFA optical amplifier during temperature changes. After a brief introduction dealing with amplifiers and doped fibers in general we focus on the assembly of our own EDFA amplifier with standard construction and the IsoGain I-6 amplifying fiber, and on the parameters of its individual components. Since an erbium doped fiber has usually no direct thermal stabilization, temperature changes can affect performance of the entire amplifier. The next part of the article therefore describes the impacts of such changes on behaviour of our amplifier. At the very end we performed a measurement of the amplifier deployed in the actual WDM-PON the description of which can be found in the last chapter.

  14. Interneuron progenitor transplantation to treat CNS dysfunction

    Directory of Open Access Journals (Sweden)

    Muhammad O Chohan

    2016-08-01

    Full Text Available Due to the inadequacy of endogenous repair mechanisms diseases of the nervous system remain a major challenge to scientists and clinicians. Stem cell based therapy is an exciting and viable strategy that has been shown to ameliorate or even reverse symptoms of CNS dysfunction in preclinical animal models. Of particular importance has been the use of GABAergic interneuron progenitors as a therapeutic strategy. Born in the neurogenic niches of the ventral telencephalon, interneuron progenitors retain their unique capacity to disperse, integrate and induce plasticity in adult host circuitries following transplantation. Here we discuss the potential of interneuron based transplantation strategies as it relates to CNS disease therapeutics. We also discuss mechanisms underlying their therapeutic efficacy and some of the challenges that face the field.

  15. The endocannabinoid system drives neural progenitor proliferation.

    Science.gov (United States)

    Aguado, Tania; Monory, Krisztina; Palazuelos, Javier; Stella, Nephi; Cravatt, Benjamin; Lutz, Beat; Marsicano, Giovanni; Kokaia, Zaal; Guzmán, Manuel; Galve-Roperh, Ismael

    2005-10-01

    The discovery of multipotent neural progenitor (NP) cells has provided strong support for the existence of neurogenesis in the adult brain. However, the signals controlling NP proliferation remain elusive. Endocannabinoids, the endogenous counterparts of marijuana-derived cannabinoids, act as neuromodulators via presynaptic CB1 receptors and also control neural cell death and survival. Here we show that progenitor cells express a functional endocannabinoid system that actively regulates cell proliferation both in vitro and in vivo. Specifically, NPs produce endocannabinoids and express the CB1 receptor and the endocannabinoid-inactivating enzyme fatty acid amide hydrolase (FAAH). CB1 receptor activation promotes cell proliferation and neurosphere generation, an action that is abrogated in CB1-deficient NPs. Accordingly, proliferation of hippocampal NPs is increased in FAAH-deficient mice. Our results demonstrate that endocannabinoids constitute a new group of signaling cues that regulate NP proliferation and thus open novel therapeutic avenues for manipulation of NP cell fate in the adult brain.

  16. Noninvasive Imaging of Administered Progenitor Cells

    Energy Technology Data Exchange (ETDEWEB)

    Steven R Bergmann, M.D., Ph.D.

    2012-12-03

    The objective of this research grant was to develop an approach for labeling progenitor cells, specifically those that we had identified as being able to replace ischemic heart cells, so that the distribution could be followed non-invasively. In addition, the research was aimed at determining whether administration of progenitor cells resulted in improved myocardial perfusion and function. The efficiency and toxicity of radiolabeling of progenitor cells was to be evaluated. For the proposed clinical protocol, subjects with end-stage ischemic coronary artery disease were to undergo a screening cardiac positron emission tomography (PET) scan using N-13 ammonia to delineate myocardial perfusion and function. If they qualified based on their PET scan, they would undergo an in-hospital protocol whereby CD34+ cells were stimulated by the administration of granulocytes-colony stimulating factor (G-CSF). CD34+ cells would then be isolated by apharesis, and labeled with indium-111 oxine. Cells were to be re-infused and subjects were to undergo single photon emission computed tomography (SPECT) scanning to evaluate uptake and distribution of labeled progenitor cells. Three months after administration of progenitor cells, a cardiac PET scan was to be repeated to evaluate changes in myocardial perfusion and/or function. Indium oxine is a radiopharmaceutical for labeling of autologous lymphocytes. Indium-111 (In-111) decays by electron capture with a t{sub ½} of 67.2 hours (2.8 days). Indium forms a saturated complex that is neutral, lipid soluble, and permeates the cell membrane. Within the cell, the indium-oxyquinolone complex labels via indium intracellular chelation. Following leukocyte labeling, ~77% of the In-111 is incorporated in the cell pellet. The presence of red cells and /or plasma reduces the labeling efficacy. Therefore, the product needed to be washed to eliminate plasma proteins. This repeated washing can damage cells. The CD34 selected product was a 90

  17. On the progenitor of V838 Monocerotis

    CERN Document Server

    Tylenda, R; Szczerba, R

    2004-01-01

    We summarize and analyze the available observational data on the progenitor and the enviroment of V838 Mon, the object that erupted in January 2002. We show that the radio and infrared observed matter in the vicinity of V838 Mon could not have its origin in mass loss from V838 Mon but is of interstellar origin. Also from the light echo evolution we conclude that the reflecting dust is of the same nature and not blown by V838 Mon in the past. This is compatible with the photometric data for the progenitor of V838 Mon, from which we exclude the possibility that the object before eruption was an evolved red giant star (AGB or RGB star). We find that most likely it was a main sequence star of \\~5-10 M_sun.

  18. High power Ka band TWT amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Golkowski, C.; Ivers, J.D.; Nation, J.A.; Wang, P.; Schachter, L.

    1999-07-01

    Two high power 35 GHz TWT amplifiers driven by a relativistic pencil, 850 kV, 200A electron beam have been assembled and tested. The first had a dielectric slow wave structure and was primarily used to develop diagnostics, and to gain experience in working with high power systems in Ka band. The source of the input power for the amplifier was a magnetron producing a 30 kW, 200ns long pulse of which 10 kW as delivered to the experiment. The 30 cm long dielectric (Teflon) amplifier produced output power levels of about 1 MW with a gain of about 23 dB. These results are consistent with expectations from PIC code simulations for this arrangement. The second amplifier, which is a single stage disk loaded slow wave structure, has been designed. It consists of one hundred uniform cells with two sets of ten tapered calls at the ends to lower the reflection coefficient. The phase advance per cell is {pi}/2. The amplifier passband extends from 28 to 40 GHz. It is designed to increase the output power to about 20 MW. The amplifier is in construction and will be tested in the near future. Details of the design of both systems will be provided and initial results from the new amplifier presented.

  19. An Envelope Hammerstein Model for Power Amplifiers

    Institute of Scientific and Technical Information of China (English)

    Hua-Dong Wang; Song-Bai He; Jing-Fu Bao; Zheng-De Wu

    2007-01-01

    In this paper, an envelope Hammerstein(EH) model is introduced to describe dynamic inputoutput characteristics of RF power amplifiers. In the modeling approach, we use a new truncation method and an established nonlinear time series method to determine model structure. Then, we discuss the process of model parameter extraction in detailed. Finally, a 2 W WCDMA power amplifier is measured to verify the performance of EH model, and good agreement between model output and measurement result shows our model can accurately predict output characteristic of the power amplifier.

  20. Quantum electronics maser amplifiers and oscillators

    CERN Document Server

    Fain, V M; Sanders, J H

    2013-01-01

    Quantum Electronics, Volume 2: Maser Amplifiers and Oscillators deals with the experimental and theoretical aspects of maser amplifiers and oscillators which are based on the principles of quantum electronics. It shows how the concepts and equations used in quantum electronics follow from the basic principles of theoretical physics.Comprised of three chapters, this volume begins with a discussion on the elements of the theory of quantum oscillators and amplifiers working in the microwave region, along with the practical achievements in this field. Attention is paid to two-level paramagnetic ma

  1. Effect of Soliton Propagation in Fiber Amplifiers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The propagation of optical solitons in fiber amplifiers is discussed by considering a model that includes linear high order dispersion, two-photon absorption, nonlinear high-order dispersion, self-induced Ramam and five-order nonlinear effects. Based on travelling wave method, the solutions of the nonlinear Schrdinger equations, and the influence on soliton propagation as well as high-order effect in the fiber amplifier are discussed in detail. It is found that because of existing five-order nonlinear effect, the solution is not of secant hyperbola type, but shows high gain state of the fiber amplifier which is very favourable to the propagation of solitons.

  2. High Efficiency Microwave Power Amplifier (HEMPA) Design

    Science.gov (United States)

    Sims, W. Herbert

    2004-01-01

    This paper will focus on developing an exotic switching technique that enhances the DC-to-RF conversion efficiency of microwave power amplifiers. For years, switching techniques implemented in the 10 kHz to 30 MHz region have resulted in DC-to-RF conversion efficiencies of 90-95-percent. Currently amplifier conversion efficiency, in the 2-3 GHz region approaches, 10-20-percent. Using a combination of analytical modeling and hardware testing, a High Efficiency Microwave Power Amplifier was built that demonstrated conversion efficiencies four to five times higher than current state of the art.

  3. Fundamentals of RF and microwave transistor amplifiers

    CERN Document Server

    Bahl, Inder J

    2009-01-01

    A Comprehensive and Up-to-Date Treatment of RF and Microwave Transistor Amplifiers This book provides state-of-the-art coverage of RF and microwave transistor amplifiers, including low-noise, narrowband, broadband, linear, high-power, high-efficiency, and high-voltage. Topics covered include modeling, analysis, design, packaging, and thermal and fabrication considerations. Through a unique integration of theory and practice, readers will learn to solve amplifier-related design problems ranging from matching networks to biasing and stability. More than 240 problems are included to help read

  4. Experimental design of laminar proportional amplifiers

    Science.gov (United States)

    Hellbaum, R. F.

    1976-01-01

    An experimental program was initiated at Langley Research Center to study the effects of various parameters on the design of laminar proportional beam deflection amplifiers. Matching and staging of amplifiers to obtain high-pressure gain was also studied. Variable parameters were aspect ratio, setback, control length, receiver distance, receiver width, width of center vent, and bias pressure levels. Usable pressure gains from 4 to 19 per stage can now be achieved, and five amplifiers were staged together to yield pressure gains up to 2,000,000.

  5. Phase noise in RF and microwave amplifiers.

    Science.gov (United States)

    Boudot, Rodolphe; Rubiola, Enrico

    2012-12-01

    Understanding amplifier phase noise is a critical issue in many fields of engineering and physics, such as oscillators, frequency synthesis, telecommunication, radar, and spectroscopy; in the emerging domain of microwave photonics; and in exotic fields, such as radio astronomy, particle accelerators, etc. Focusing on the two main types of base noise in amplifiers, white and flicker, the power spectral density of the random phase φ(t) is Sφ(f) = b(0) + b(-1)/f. White phase noise results from adding white noise to the RF spectrum in the carrier region. For a given RF noise level, b(0) is proportional to the reciprocal of the carrier power P(0). By contrast, flicker results from a near-dc 1/f noise-present in all electronic devices-which modulates the carrier through some parametric effect in the semiconductor. Thus, b(-1) is a parameter of the amplifier, constant in a wide range of P(0). The consequences are the following: Connecting m equal amplifiers in parallel, b(-1) is 1/m times that of one device. Cascading m equal amplifiers, b(-1) is m times that of one amplifier. Recirculating the signal in an amplifier so that the gain increases by a power of m (a factor of m in decibels) as a result of positive feedback (regeneration), we find that b(-1) is m(2) times that of the amplifier alone. The feedforward amplifier exhibits extremely low b(-1) because the carrier is ideally nulled at the input of its internal error amplifier. Starting with an extensive review of the literature, this article introduces a system-oriented model which describes the phase flickering. Several amplifier architectures (cascaded, parallel, etc.) are analyzed systematically, deriving the phase noise from the general model. There follow numerous measurements of amplifiers using different technologies, including some old samples, and in a wide frequency range (HF to microwaves), which validate the theory. In turn, theory and results provide design guidelines and give suggestions for CAD and

  6. Achieving and maintaining cleanliness in NIF amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Burnham, A. K.; Horvath, J. A.; Letts, S. A.; Menapace, J. A.; Stowers, I. F.

    1998-07-28

    Cleanliness measurements made on AMPLAB prototype National Ignition Facility (NIF) laser amplifiers during assembly, cassette transfer, and amplifier operation are summarized. These measurements include particle counts from surface cleanliness assessments using filter swipe techniques and from airborne particle monitoring. Results are compared with similar measurements made on the Beamlet and Nova lasers and in flashlamp test fixtures. Observations of Class 100,000 aerosols after flashlamp firings are discussed. Comparisons are made between typical damage densities on laser amplifier optics from Novette, NOVA, Beamlet, and AMPLAB.

  7. Self-pulsation in Raman fiber amplifiers

    OpenAIRE

    Pedersen, Martin Erland Vestergaard; Ott, Johan Raunkjær; Rottwitt, Karsten

    2009-01-01

    Dynamic behavior caused by Brillouin scattering in Raman fiber amplifiers is studied. Modes of self-pulsation steady state oscillations are found. Their dependence on amplification scheme is demonstrated.

  8. Laser Cooled High-Power Fiber Amplifier

    CERN Document Server

    Nemova, Galina

    2009-01-01

    A theoretical model for laser cooled continuous-wave fiber amplifier is presented. The amplification process takes place in the Tm3+-doped core of the fluoride ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) glass fiber. The cooling process takes place in the Yb3+:ZBLAN fiber cladding. It is shown that for each value of the pump power and the amplified signal there is a distribution of the concentration of the Tm3+ along the length of the fiber amplifier, which provides its athermal operation. The influence of a small deviation in the value of the amplified signal on the temperature of the fiber with the fixed distribution of the Tm3+ions in the fiber cladding is investigated.

  9. High Energy Single Frequency Resonant Amplifier Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR phase I project proposes a single frequency high energy resonant amplifier for remote sensing. Current state-of-art technologies can not provide all...

  10. Regulation of the nascent brain vascular network by neural progenitors.

    Science.gov (United States)

    Santhosh, Devi; Huang, Zhen

    2015-11-01

    Neural progenitors are central players in the development of the brain neural circuitry. They not only produce the diverse neuronal and glial cell types in the brain, but also guide their migration in this process. Recent evidence indicates that neural progenitors also play a critical role in the development of the brain vascular network. At an early stage, neural progenitors have been found to facilitate the ingression of blood vessels from outside the neural tube, through VEGF and canonical Wnt signaling. Subsequently, neural progenitors directly communicate with endothelial cells to stabilize nascent brain vessels, in part through down-regulating Wnt pathway activity. Furthermore, neural progenitors promote nascent brain vessel integrity, through integrin αvβ8-dependent TGFβ signaling. In this review, we will discuss the evidence for, as well as questions that remain, regarding these novel roles of neural progenitors and the underlying mechanisms in their regulation of the nascent brain vascular network.

  11. Efficient Power Amplifier for Motor Control

    Science.gov (United States)

    Brown, R. J.

    1986-01-01

    Pulse-width-modulated amplifier supplies high current as efficiently as low current needed for starting and running motor. Key to efficiency of motor-control amplifier is V-channel metal-oxide/semiconductor transistor Q1. Device has low saturation resistance. However, has large gate input capacitance and small margin between its turn-on voltage and maximum allowable gate-to-source voltage. Circuits for output stages overcome limitations of VMOS device.

  12. Quantum cloning with an optical fiber amplifier

    CERN Document Server

    Fasel, S; Ribordy, G; Scarani, V; Zbinden, H; Fasel, Sylvain; Gisin, Nicolas; Ribordy, Gregoire; Scarani, Valerio; Zbinden, Hugo

    2002-01-01

    It has been shown theoretically that a light amplifier working on the physical principle of stimulated emission should achieve optimal quantum cloning of the polarization state of light. We demonstrate close-to-optimal universal quantum cloning of polarization in a standard fiber amplifier for telecom wavelengths. For cloning $1\\to 2$ we find a fidelity of 0.82, the optimal value being ${5/6}=0.83$.

  13. CMOS current amplifiers : speed versus nonlinearity

    OpenAIRE

    2000-01-01

    This work deals with analogue integrated circuit design using various types of current-mode amplifiers. These circuits are analysed and realised using modern CMOS integration technologies. The dynamic nonlinearities of these circuits are discussed in detail as in the literature only linear nonidealities and static nonlinearities are conventionally considered. For the most important open-loop current-mode amplifier, the second-generation current-conveyor (CCII), a macromodel is derived tha...

  14. MMIC Amplifiers for 90 to 130 GHz

    Science.gov (United States)

    Samoska, Lorene; Pukala, David; Peralta, Alejandro; Bryerton, Eric; Morgan, Matt; Boyd, T.; Hu, Ming; Schmitz, Adele

    2007-01-01

    This brief describes two monolithic microwave integrated-circuit (MMIC) amplifier chips optimized to function in the frequency range of 90 to 130 GHz, covering nearly all of F-band (90 - 140 GHz). These amplifiers were designed specifically for local-oscillator units in astronomical radio telescopes such as the Atacama Large Millimeter Array (ALMA). They could also be readily adapted for use in electronic test equipment, automotive radar systems, and communications systems that operate between 90 and 130 GHz.

  15. Some Notes on Wideband Feedback Amplifiers

    Science.gov (United States)

    Fitch, V.

    1949-03-16

    The extension of the passband of wideband amplifiers is a highly important problem to the designer of electronic circuits. Throughout the electronics industry and in many research programs in physics and allied fields where extensive use is made of video amplifiers, the foremost requirement is a passband of maximum width. This is necessary if it is desired to achieve a more faithful reproduction of transient wave forms, a better time resolution in physical measurements, or perhaps just a wider band gain-frequency response to sine wave signals. The art of electronics is continually faced with this omnipresent amplifier problem. In particular, the instrumentation techniques of nuclear physics require amplifiers with short rise times, a high degree of gain stability, and a linear response to high signal levels. While the distributed amplifier may solve the problems of those seeking only a wide passband, the requirements of stability and linearity necessitate using feedback circuits. This paper considers feedback amplifiers from the standpoint of high-frequency performance. The circuit conditions for optimum steady-state (sinusoidal) and transient response are derived and practical circuits (both interstage and output) are presented which fulfill these conditions. In general, the results obtained may be applied to the low-frequency end.

  16. Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells

    Science.gov (United States)

    2015-09-01

    AWARD NUMBER: W81XWH-13-1-0244 TITLE: Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells PRINCIPAL...2014 - 31 Aug 2015 4. TITLE AND SUBTITLE Identification, Characterization, and Utilization of Adult Meniscal Progenitor Cells 5a. CONTRACT NUMBER 5b...the development of knee osteoarthritis (OA). New treatments centered on the stem/ progenitor cell population resident within the adult meniscus will be

  17. Mobilization of hematopoietic progenitor cells in patients with liver cirrhosis

    Institute of Scientific and Technical Information of China (English)

    Ursula; M; Gehling; Marc; Willems; Kathleen; Schlagner; Ralf; A; Benndorf; Maura; Dandri; Jrg; Petersen; Martina; Sterneck; Joerg-Matthias; Pollok; Dieter; K; Hossfeld; Xavier; Rogiers

    2010-01-01

    AIM:To test the hypothesis that liver cirrhosis is associated with mobilization of hematopoietic progenitor cells. METHODS:Peripheral blood samples from 72 patients with liver cirrhosis of varying etiology were analyzed by flow cytometry.Identified progenitor cell subsets were immunoselected and used for functional assays in vitro. Plasma levels of stromal cell-derived factor-1(SDF-1) were measured using an enzyme linked immunosorbent assay.RESULTS:Progenitor cells with a CD133 + /CD45 + CD14 + phenotype we...

  18. Low Noise Optically Pre-amplified Lightwave Receivers and Other Applications of Fiber Optic Parametric Amplifiers

    Science.gov (United States)

    2010-07-27

    noise performance, optical gain bandwidth, and power efficiency. An interesting alternative to the mature Erbium-doped fiber amplifier ( EDFA ) is the...fibers (HNLF) and high power booster EDFAs . The FOPA can provide a very wide gain bandwidth [2], very high gain (70 dB was demonstrated in [3]), and...amplified spontaneous emission (ASE) noise in EDFAs is also generated. It is sometimes referred to as amplified quantum noise. Maximum gain (at the gain

  19. Genome-wide copy number profiling to detect gene amplifications in neural progenitor cells

    Directory of Open Access Journals (Sweden)

    U. Fischer

    2014-12-01

    Full Text Available DNA sequence amplification occurs at defined stages during normal development in amphibians and flies and seems to be restricted in humans to drug-resistant and tumor cells only. We used array-CGH to discover copy number changes including gene amplifications and deletions during differentiation of human neural progenitor cells. Here, we describe cell culture features, DNA extraction, and comparative genomic hybridization (CGH analysis tailored towards the identification of genomic copy number changes. Further detailed analysis of amplified chromosome regions associated with this experiment, was published by Fischer and colleagues in PLOS One in 2012 (Fischer et al., 2012. We provide detailed information on deleted chromosome regions during differentiation and give an overview on copy number changes during differentiation induction for two representative chromosome regions.

  20. Intermediate Progenitors Facilitate Intracortical Progression of Thalamocortical Axons and Interneurons through CXCL12 Chemokine Signaling.

    Science.gov (United States)

    Abe, Philipp; Molnár, Zoltán; Tzeng, Yi-Shiuan; Lai, Dar-Ming; Arnold, Sebastian J; Stumm, Ralf

    2015-09-23

    Glutamatergic principal neurons, GABAergic interneurons and thalamocortical axons (TCAs) are essential elements of the cerebrocortical network. Principal neurons originate locally from radial glia and intermediate progenitors (IPCs), whereas interneurons and TCAs are of extrinsic origin. Little is known how the assembly of these elements is coordinated. C-X-C motif chemokine 12 (CXCL12), which is known to guide axons outside the neural tube and interneurons in the cortex, is expressed in the meninges and IPCs. Using mouse genetics, we dissected the influence of IPC-derived CXCL12 on TCAs and interneurons by showing that Cxcl12 ablation in IPCs, leaving meningeal Cxcl12 intact, attenuates intracortical TCA growth and disrupts tangential interneuron migration in the subventricular zone. In accordance with strong CXCR4 expression in the forming thalamus and TCAs, we identified a CXCR4-dependent growth-promoting effect of CXCL12 on TCAs in thalamus explants. Together, our findings indicate a cell-autonomous role of CXCR4 in promoting TCA growth. We propose that CXCL12 signals from IPCs link cortical neurogenesis to the progression of TCAs and interneurons spatially and temporally. Significance statement: The cerebral cortex exerts higher brain functions including perceptual and emotional processing. Evolutionary expansion of the mammalian cortex is mediated by intermediate progenitors, transient amplifying cells generating cortical excitatory neurons. During the peak period of cortical neurogenesis, migrating precursors of inhibitory interneurons originating in subcortical areas and thalamic axons invade the cortex. Although defects in the assembly of cortical network elements cause neurological and mental disorders, little is known how neurogenesis, interneuron recruitment, and axonal ingrowth are coordinated. We demonstrate that intermediate progenitors release the chemotactic cytokine CXCL12 to promote intracortical interneuron migration and growth of thalamic axons

  1. Silencing BRE expression in human umbilical cord perivascular (HUCPV progenitor cells accelerates osteogenic and chondrogenic differentiation.

    Directory of Open Access Journals (Sweden)

    Elve Chen

    Full Text Available BRE is a multifunctional adapter protein involved in DNA repair, cell survival and stress response. To date, most studies of this protein have been focused in the tumor model. The role of BRE in stem cell biology has never been investigated. Therefore, we have used HUCPV progenitor cells to elucidate the function of BRE. HUCPV cells are multipotent fetal progenitor cells which possess the ability to differentiate into a multitude of mesenchymal cell lineages when chemically induced and can be more easily amplified in culture. In this study, we have established that BRE expression was normally expressed in HUCPV cells but become down-regulated when the cells were induced to differentiate. In addition, silencing BRE expression, using BRE-siRNAs, in HUCPV cells could accelerate induced chondrogenic and osteogenic differentiation. Hence, we postulated that BRE played an important role in maintaining the stemness of HUCPV cells. We used microarray analysis to examine the transcriptome of BRE-silenced cells. BRE-silencing negatively regulated OCT4, FGF5 and FOXO1A. BRE-silencing also altered the expression of epigenetic genes and components of the TGF-β/BMP and FGF signaling pathways which are crucially involved in maintaining stem cell self-renewal. Comparative proteomic profiling also revealed that BRE-silencing resulted in decreased expressions of actin-binding proteins. In sum, we propose that BRE acts like an adaptor protein that promotes stemness and at the same time inhibits the differentiation of HUCPV cells.

  2. Enhancing endothelial progenitor cell for clinical use

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    Circulating endothelial progenitor cells (EPCs) havebeen demonstrated to correlate negatively with vascularendothelial dysfunction and cardiovascular risk factors.However, translation of basic research into the clinicalpractice has been limited by the lack of unambiguousand consistent definitions of EPCs and reduced EPCcell number and function in subjects requiring them forclinical use. This article critically reviews the definitionof EPCs based on commonly used protocols, their valueas a biomarker of cardiovascular risk factor in subjectswith cardiovascular disease, and strategies to enhanceEPCs for treatment of ischemic diseases.

  3. Transpermeance Amplifier Applied to Magnetic Bearings

    Directory of Open Access Journals (Sweden)

    Jossana Ferreira

    2017-02-01

    Full Text Available The most conventional approach of controlling magnetic forces in active magnetic bearings (AMBs is through current feedback amplifiers: transconductance. This enables the operation of the AMB to be understood in terms of a relatively simple current-based model as has been widely reported on in the literature. The alternative notion of using transpermeance amplifiers, which approximate the feedback of gap flux rather than current, has been in commercial use in some form for at least thirty years, however is only recently seeing more widespread acceptance as a commercial standard. This study explores how such alternative amplifiers should be modeled and then examines the differences in behavior between AMBs equipped with transconductance and transpermeance amplifiers. The focus of this study is on two aspects. The first is the influence of rotor displacement on AMB force, commonly modeled as a constant negative equivalent mechanical stiffness, and it is shown that either scheme actually leads to a finite bandwidth effect, but that this bandwidth is much lower when transpermeance is employed. The second aspect is the influence of eddy currents. Using a very simple model of eddy currents (a secondary short-circuited coil, it is demonstrated that transpermeance amplifiers can recover significant actuator bandwidth compared with transconductance, but at the cost of needing increased peak current headroom.

  4. High power, high beam quality regenerative amplifier

    Science.gov (United States)

    Hackel, L.A.; Dane, C.B.

    1993-08-24

    A regenerative laser amplifier system generates high peak power and high energy per pulse output beams enabling generation of X-rays used in X-ray lithography for manufacturing integrated circuits. The laser amplifier includes a ring shaped optical path with a limited number of components including a polarizer, a passive 90 degree phase rotator, a plurality of mirrors, a relay telescope, and a gain medium, the components being placed close to the image plane of the relay telescope to reduce diffraction or phase perturbations in order to limit high peak intensity spiking. In the ring, the beam makes two passes through the gain medium for each transit of the optical path to increase the amplifier gain to loss ratio. A beam input into the ring makes two passes around the ring, is diverted into an SBS phase conjugator and proceeds out of the SBS phase conjugator back through the ring in an equal but opposite direction for two passes, further reducing phase perturbations. A master oscillator inputs the beam through an isolation cell (Faraday or Pockels) which transmits the beam into the ring without polarization rotation. The isolation cell rotates polarization only in beams proceeding out of the ring to direct the beams out of the amplifier. The diffraction limited quality of the input beam is preserved in the amplifier so that a high power output beam having nearly the same diffraction limited quality is produced.

  5. CXCR4/CXCL12 signaling impacts enamel progenitor cell proliferation and motility in the dental stem cell niche.

    Science.gov (United States)

    Yokohama-Tamaki, Tamaki; Otsu, Keishi; Harada, Hidemitsu; Shibata, Shunichi; Obara, Nobuko; Irie, Kazuharu; Taniguchi, Akiyoshi; Nagasawa, Takashi; Aoki, Kazunari; Caliari, Steven R; Weisgerber, Daniel W; Harley, Brendan A C

    2015-12-01

    Dental stem cells are located at the proximal ends of rodent incisors. These stem cells reside in the dental epithelial stem cell niche, termed the apical bud. We focused on identifying critical features of a chemotactic signal in the niche. Here, we report that CXCR4/CXCL12 signaling impacts enamel progenitor cell proliferation and motility in dental stem cell niche cells. We report cells in the apical bud express CXCR4 mRNA at high levels while expression is restricted in the basal epithelium (BE) and transit-amplifying (TA) cell regions. Furthermore, the CXCL12 ligand is present in mesenchymal cells adjacent to the apical bud. We then performed gain- and loss-of-function analyses to better elucidate the role of CXCR4 and CXCL12. CXCR4-deficient mice contain epithelial cell aggregates, while cell proliferation in mutant incisors was also significantly reduced. We demonstrate in vitro that dental epithelial cells migrate toward sources of CXCL12, whereas knocking down CXCR4 impaired motility and resulted in formation of dense cell colonies. These results suggest that CXCR4 expression may be critical for activation of enamel progenitor cell division and that CXCR4/CXCL12 signaling may control movement of epithelial progenitors from the dental stem cell niche.

  6. Endothelial Progenitor Cells Enter the Aging Arena.

    Directory of Open Access Journals (Sweden)

    Kate eWilliamson

    2012-02-01

    Full Text Available Age is a significant risk factor for the development of vascular diseases, such as atherosclerosis. Although pharmacological treatments, including statins and anti-hypertensive drugs, have improved the prognosis for patients with cardiovascular disease, it remains a leading cause of mortality in those aged 65 years and over. Furthermore, given the increased life expectancy of the population in developed countries, there is a clear need for alternative treatment strategies. Consequently, the relationship between aging and progenitor cell-mediated repair is of great interest. Endothelial progenitor cells (EPCs play an integral role in the cellular repair mechanisms for endothelial regeneration and maintenance. However, EPCs are subject to age-associated changes that diminish their number in circulation and function, thereby enhancing vascular disease risk. A great deal of research is aimed at developing strategies to harness the regenerative capacity of these cells.In this review, we discuss the current understanding of the cells termed ‘EPCs’, examine the impact of age on EPC-mediated repair and identify therapeutic targets with potential for attenuating the age-related decline in vascular health via beneficial actions on EPCs.

  7. The progenitors of supernovae Type Ia

    Science.gov (United States)

    Toonen, Silvia

    2014-09-01

    Despite the significance of Type Ia supernovae (SNeIa) in many fields in astrophysics, SNeIa lack a theoretical explanation. SNeIa are generally thought to be thermonuclear explosions of carbon/oxygen (CO) white dwarfs (WDs). The canonical scenarios involve white dwarfs reaching the Chandrasekhar mass, either by accretion from a non-degenerate companion (single-degenerate channel, SD) or by a merger of two CO WDs (double-degenerate channel, DD). The study of SNeIa progenitors is a very active field of research for binary population synthesis (BPS) studies. The strength of the BPS approach is to study the effect of uncertainties in binary evolution on the macroscopic properties of a binary population, in order to constrain binary evolutionary processes. I will discuss the expected SNeIa rate from the BPS approach and the uncertainties in their progenitor evolution, and compare with current observations. I will also discuss the results of the POPCORN project in which four BPS codes were compared to better understand the differences in the predicted SNeIa rate of the SD channel. The goal of this project is to investigate whether differences in the simulated populations are due to numerical effects or whether they can be explained by differences in the input physics. I will show which assumptions in BPS codes affect the results most and hence should be studied in more detail.

  8. Single degenerate supernova type Ia progenitors

    CERN Document Server

    Bours, M C P; Nelemans, G

    2013-01-01

    There is general agreement that supernovae Ia correspond to the thermonuclear runaway of a white dwarf that is part of a compact binary, but the details of the progenitor systems are still unknown and much debated. One of the proposed progenitor theories is the single-degenerate channel in which a white dwarf accretes from a companion, grows in mass, reaches a critical mass limit, and is then consumed after thermonuclear runaway sets in. However, there are major disagreements about the theoretical delay time distribution and the corresponding time-integrated supernova Ia rate from this channel. We investigate whether the differences are due to the uncertainty in the common envelope phase and the fraction of transferred mass that is retained by the white dwarf. This so-called retention efficiency may have a strong influence on the final amount and timing of supernovae Ia. Using the population synthesis code SeBa, we simulated large numbers of binaries for various assumptions on common envelopes and retention e...

  9. Magnetized massive stars as magnetar progenitors

    CERN Document Server

    Hu, Ren-Yu

    2009-01-01

    The origin of ultra-intense magnetic fields on magnetars is a mystery in modern astrophysics. We model the core collapse dynamics of massive progenitor stars with high surface magnetic fields in the theoretical framework of a self-similar general polytropic magnetofluid under the self-gravity with a quasi-spherical symmetry. With the specification of physical parameters such as mass density, temperature, magnetic field and wind mass loss rate on the progenitor stellar surface and the consideration of a rebound shock breaking through the stellar interior and envelope, we find a remnant compact object (i.e. neutron star) left behind at the centre with a radius of $\\sim 10^6$ cm and a mass range of $\\sim 1-3$ solar masses. Moreover, we find that surface magnetic fields of such kind of compact objects can be $\\sim 10^{14}-10^{15}$ G, consistent with those inferred for magnetars which include soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The magnetic field enhancement factor critically depend...

  10. Galactic Constraints on Supernova Progenitor Models

    CERN Document Server

    Acharova, I; Mishurov, Yu; Kovtyukh, V

    2013-01-01

    We undertake a statistical analysis of the radial abundance distributions in the Galactic disk within a theoretical framework for Galactic chemical evolution which incorporates the influence of spiral arms. 1) The mean mass of oxygen ejected per core-collapse SNe (CC SNe) event (which are concentrated within spiral arms) is $\\sim$0.27 M$_{\\odot}$; 2) the mean mass of iron ejected by `tardy' Type Ia SNe (SNeIa; progenitors of whom are older/longer-lived stars with ages $\\simgt$100 Myr and up to several Gyr, which do not concentrate within spiral arms) is $\\sim$0.58 M$_{\\odot}$; 3) the upper mass of iron ejected by prompt SNeIa (SNe whose progenitors are younger/shorter-lived stars with ages $\\simlt$100 Myr, which are concentrated within spiral arms) is $\\leq$0.23 M$_{\\odot}$ per event; 4) the corresponding mean mass of iron produced by CC SNe is $\\leq$0.04 M$_{\\odot}$ per event; (v) short-lived SNe (core-collapse or prompt SNeIa) supply $\\sim$85% of the Galactic disk's iron. The inferred low mean mass of oxyge...

  11. The OPTHER Project: Progress toward the THz Amplifier

    DEFF Research Database (Denmark)

    Paoloni, C; Brunetti, F; Di Carlo, A

    2011-01-01

    This paper describes the status of the OPTHER (OPtically driven TeraHertz AmplifiERs) project and progress toward the THz amplifier realization. This project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within th...

  12. Progenitor cells in arteriosclerosis: good or bad guys?

    Science.gov (United States)

    Campagnolo, Paola; Wong, Mei Mei; Xu, Qingbo

    2011-08-15

    Accumulating evidence indicates that the mobilization and recruitment of circulating or tissue-resident progenitor cells that give rise to endothelial cells (ECs) and smooth muscle cells (SMCs) can participate in atherosclerosis, neointima hyperplasia after arterial injury, and transplant arteriosclerosis. It is believed that endothelial progenitor cells do exist and can repair and rejuvenate the arteries under physiologic conditions; however, they may also contribute to lesion formation by influencing plaque stability in advanced atherosclerotic plaque under specific pathologic conditions. At the same time, smooth muscle progenitors, despite their capacity to expedite lesion formation during restenosis, may serve to promote atherosclerotic plaque stabilization by producing extracellular matrix proteins. This profound evidence provides support to the hypothesis that both endothelial and smooth muscle progenitors may act as a double-edged sword in the pathogenesis of arteriosclerosis. Therefore, the understanding of the regulatory networks that control endothelial and smooth muscle progenitor differentiation is undoubtedly fundamental both for basic research and for improving current therapeutic avenues for atherosclerosis. We update the progress in progenitor cell study related to the development of arteriosclerosis, focusing specifically on the role of progenitor cells in lesion formation and discuss the controversial issues that regard the origins, frequency, and impact of the progenitors in the disease.

  13. Retinal progenitor cell xenografts to the pig retina

    DEFF Research Database (Denmark)

    Warfvinge, Karin; Kiilgaard, Jens Folke; Lavik, Erin B;

    2005-01-01

    To investigate the survival, integration, and differentiation of mouse retinal progenitor cells after transplantation to the subretinal space of adult pigs.......To investigate the survival, integration, and differentiation of mouse retinal progenitor cells after transplantation to the subretinal space of adult pigs....

  14. Wideband pulse amplifiers for the NECTAr chip

    Science.gov (United States)

    Sanuy, A.; Delagnes, E.; Gascon, D.; Sieiro, X.; Bolmont, J.; Corona, P.; Feinstein, F.; Glicenstein, J.-F.; Naumann, C. L.; Nayman, P.; Ribó, M.; Tavernet, J.-P.; Toussenel, F.; Vincent, P.; Vorobiov, S.

    2012-12-01

    The NECTAr collaboration's FE option for the camera of the CTA is a 16 bits and 1-3 GS/s sampling chip based on analog memories including most of the readout functions. This works describes the input amplifiers of the NECTAr ASIC. A fully differential wideband amplifier, with voltage gain up to 20 V/V and a BW of 400 MHz. As it is impossible to design a fully differential OpAmp with an 8 GHz GBW product in a 0.35 CMOS technology, an alternative implementation based on HF linearized transconductors is explored. The output buffer is a class AB miller operational amplifier, with special non-linear current boost.

  15. Wideband pulse amplifiers for the NECTAr chip

    Energy Technology Data Exchange (ETDEWEB)

    Sanuy, A., E-mail: asanuy@ecm.ub.es [Dept. AM i Dept. ECM, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona. Marti i Franques 1, E08028, Barcelona (Spain); Delagnes, E. [IRFU/DSM/CEA, CE-Saclay, Bat. 141 SEN Saclay, F-91191, Gif-sur-Yvette (France); Gascon, D. [Dept. AM i Dept. ECM, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona. Marti i Franques 1, E08028, Barcelona (Spain); Sieiro, X. [Departament d' Electronica, Universitat de Barcelona. Marti i Franques 1, E08028, Barcelona (Spain); Bolmont, J.; Corona, P. [LPNHE, Universite Paris VI and Universite Paris VII and IN2P3/CNRS, Barre 12-22, 1er etage, 4 place Jussieu, 75252 Paris (France); Feinstein, F. [LUPM, Universite Montpellier II and IN2P3/CNRS, CC072, bat. 13, place Eugene Bataillon, 34095 Montpellier (France); Glicenstein, J-F. [IRFU/DSM/CEA, CE-Saclay, Bat. 141 SEN Saclay, F-91191, Gif-sur-Yvette (France); Naumann, C.L.; Nayman, P. [LPNHE, Universite Paris VI and Universite Paris VII and IN2P3/CNRS, Barre 12-22, 1er etage, 4 place Jussieu, 75252 Paris (France); Ribo, M. [Dept. AM i Dept. ECM, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona. Marti i Franques 1, E08028, Barcelona (Spain); and others

    2012-12-11

    The NECTAr collaboration's FE option for the camera of the CTA is a 16 bits and 1-3 GS/s sampling chip based on analog memories including most of the readout functions. This works describes the input amplifiers of the NECTAr ASIC. A fully differential wideband amplifier, with voltage gain up to 20 V/V and a BW of 400 MHz. As it is impossible to design a fully differential OpAmp with an 8 GHz GBW product in a 0.35 CMOS technology, an alternative implementation based on HF linearized transconductors is explored. The output buffer is a class AB miller operational amplifier, with special non-linear current boost.

  16. The Electron Beam Semiconductor (EBS) amplifier

    Science.gov (United States)

    True, R. M.; Baxendale, J. F.

    1980-07-01

    The Electron Beam Semiconductor (EBS) concept has existed for three decades; but only within the last decade has an active, well-defined program been underway to develop devices that can operate as high-power radio frequency(RF) amplifiers, fast risetime switches, and current and voltage pulse amplifiers. This report discusses the test procedures, data and results of reliability testing of RF and video pulse EBS amplifiers at Electronics Research and Development Command (ERADCOM), Fort Monmouth, New Jersey. Also, the experimental analysis of the series connected diode EBS device is described in detail. Finally, the report concludes with a discussion of the state-of-the-art of EBS and future trends of the technology.

  17. Design Of A Doherty Power Amplifier For GSM Systems

    Directory of Open Access Journals (Sweden)

    Saad Wasmi Osman

    2013-04-01

    Full Text Available This paper presents the design and analysis of Doherty power amplifier. The Doherty amplifier is used in  a base station for mobile system because of its high efficiency. The class AB power amplifier used in the configuration of the main and auxiliary amplifier. The result obtained shows that the Doherty power amplifier can be used on a wide band spectrum, the amplifier works at 900MHz and has very good power added efficiency (PAE and gain. The amplifier can also work at 1800MHz at input power greater than 20dBm. 

  18. GSK-3 is a master regulator of neural progenitor homeostasis

    Science.gov (United States)

    Kim, Woo-Yang; Wang, Xinshuo; Wu, Yaohong; Doble, Bradley W; Patel, Satish; Woodgett, James R; Snider, William D

    2016-01-01

    The development of the brain requires the exquisite coordination of progenitor proliferation and differentiation to achieve complex circuit assembly. It has been suggested that glycogen synthase kinase 3 (GSK-3) acts as an integrating molecule for multiple proliferation and differentiation signals because of its essential role in the RTK, Wnt and Shh signaling pathways. We created conditional mutations that deleted both the α and β forms of GSK-3 in mouse neural progenitors. GSK-3 deletion resulted in massive hyperproliferation of neural progenitors along the entire neuraxis. Generation of both intermediate neural progenitors and postmitotic neurons was markedly suppressed. These effects were associated with the dysregulation of β-catenin, Sonic Hedgehog, Notch and fibroblast growth factor signaling. Our results indicate that GSK-3 signaling is an essential mediator of homeostatic controls that regulate neural progenitors during mammalian brain development. PMID:19801986

  19. Effect of human neural progenitor cells on injured spinal cord

    Institute of Scientific and Technical Information of China (English)

    XU Guang-hui; BAI Jin-zhu; CAI Qin-lin; LI Xiao-xia; LI Ling-song; SHEN Li

    2005-01-01

    Objective: To study whether human neural progenitor cells can differentiate into neural cells in vivo and improve the recovery of injured spinal cord in rats.Methods: Human neural progenitor cells were transplanted into the injured spinal cord and the functional recovery of the rats with spinal cord contusion injury was evaluated with Basso-Beattie-Bresnahan (BBB) locomotor scale and motor evoked potentials. Additionally, the differentiation of human neural progenitor cells was shown by immunocytochemistry.Results: Human neural progenitor cells developed into functional cells in the injured spinal cord and improved the recovery of injured spinal cord in both locomotor scores and electrophysiological parameters in rats.Conclusions: Human neural progenitor cells can treat injured spinal cord, which may provide a new cell source for research of clinical application.

  20. Mast cell progenitors: origin, development and migration to tissues.

    Science.gov (United States)

    Dahlin, Joakim S; Hallgren, Jenny

    2015-01-01

    Mast cells in tissues are developed from mast cell progenitors emerging from the bone marrow in a process highly regulated by transcription factors. Through the advancement of the multicolor flow cytometry technique, the mast cell progenitor population in the mouse has been characterized in terms of surface markers. However, only cell populations with enriched mast cell capability have been described in human. In naïve mice, the peripheral tissues have a constitutive pool of mast cell progenitors. Upon infections in the gut and in allergic inflammation in the lung, the local mast cell progenitor numbers increase tremendously. This review focuses on the origin and development of mast cell progenitors. Furthermore, the evidences for cells and molecules that govern the migration of these cells in mice in vivo are described.

  1. Hepatic progenitor cells in human liver tumor development

    Institute of Scientific and Technical Information of China (English)

    Louis Libbrecht

    2006-01-01

    In recent years, the results of several studies suggest that human liver tumors can be derived from hepatic progenitor cells rather than from mature cell types.The available data indeed strongly suggest that most combined hepatocellular-cholangiocarcinomas arise from hepatic progenitor cells that retained their potential to differentiate into the hepatocytic and biliary lineages.Hepatic progenitor cells could also be the basis for some hepatocellular carcinomas and hepatocellular adenomas, although it is very difficult to determine the origin of an individual hepatocellular carcinoma. There is currently not enough data to make statements regarding a hepatic progenitor cell origin of cholangiocarcinoma.The presence of hepatic progenitor cell markers and the presence and extent of the cholangiocellular component are factors that are related to the prognosis of hepatocellular carcinomas and combined hepatocellularcholangiocarcinomas, respectively.

  2. Vascular Endothelial Growth Factor (VEGF) Bioavailability Regulates Angiogenesis and Intestinal Stem and Progenitor Cell Proliferation during Postnatal Small Intestinal Development

    Science.gov (United States)

    Holoyda, Kathleen A.; Hou, Xiaogang; Fowler, Kathryn L.; Grikscheit, Tracy C.

    2016-01-01

    Background Vascular endothelial growth factor (VEGF) is a highly conserved, master regulatory molecule required for endothelial cell proliferation, organization, migration and branching morphogenesis. Podocoryne carnea and drosophila, which lack endothelial cells and a vascular system, express VEGF homologs, indicating potential roles beyond angiogenesis and vasculogenesis. The role of VEGF in the development and homeostasis of the postnatal small intestine is unknown. We hypothesized regulating VEGF bioavailability in the postnatal small intestine would exhibit effects beyond the vasculature and influence epithelial cell stem/progenitor populations. Methods VEGF mutant mice were created that overexpressed VEGF in the brush border of epithelium via the villin promotor following doxycycline treatment. To decrease VEGF bioavailability, sFlt-1 mutant mice were generated that overexpressed the soluble VEGF receptor sFlt-1 upon doxycycline administration in the intestinal epithelium. Mice were analyzed after 21 days of doxycycline administration. Results Increased VEGF expression was confirmed by RT-qPCR and ELISA in the intestine of the VEGF mutants compared to littermates. The VEGF mutant duodenum demonstrated increased angiogenesis and vascular leak as compared to littermate controls. The VEGF mutant duodenum revealed taller villi and increased Ki-67-positive cells in the transit-amplifying zone with reduced Lgr5 expression. The duodenum of sFlt-1 mutants revealed shorter villi and longer crypts with reduced proliferation in the transit-amplifying zone, reduced expression of Dll1, Bmp4 and VE-cadherin, and increased expression of Sox9 and EphB2. Conclusions Manipulating VEGF bioavailability leads to profound effects on not only the intestinal vasculature, but epithelial stem and progenitor cells in the intestinal crypt. Elucidation of the crosstalk between VEGF signaling in the vasculature, mesenchyme and epithelial stem/progenitor cell populations may direct future

  3. Implementation of Digital Lock-in Amplifier

    Science.gov (United States)

    Bhattacharyya, Sabyasachi; Nasir Ahmed, Ragib; Bijoy Purkayastha, Basab; Bhattacharyya, Kaustubh

    2016-10-01

    The recovery of signal under the presence of noise is utmost essential for proper communication. The signals corrupted due to noise can be recovered using various techniques. However the weak signals are more prone to noise and hence they can be easily degraded due to noise. In such cases, a digital lock-in amplifier becomes an essential device for recovery of such weak signals. Keeping the cost, speed and other considerations, we will present the implementation of digital lock-in amplifier and how it recovers the weak signal under extreme noisy conditions.

  4. Double Clad Er-doped Fiber Amplifier

    Institute of Scientific and Technical Information of China (English)

    FU Yong-jun; MAO Xiang-qiao; WEI Huai; LI jian

    2007-01-01

    Presented is a theoretical study of double-clad Er-doped fiber power amplifier(EDFA). Two kinds of double clad fibers(DCF) with rectangular and "flower" inner clad shapes are studied, and these fibers have different coupling constants and propagation losses. We calculate the effective pump power absorption ratio along the fiber with different coupling constants from the first cladding to the doped core and with different propagation losses for the power in the inner cladding. Then the gains of the double clad Er-doped fiber amplifiers versus fiber lengths are calculated using the EDFA model based on propagation and rate equations of a homogeneous, two-level medium.

  5. Optimization of Pr3+:ZBLAN fiber amplifiers

    OpenAIRE

    Pedersen, B.; Miniscalco, J. W.; Quimby, R. S.

    1992-01-01

    Experimental parameters have been measured and used in a quantitative model of Pr3+-doped fluorozirconate fiber amplifiers. The optimum cutoff wavelength was determined to be 800 nm and the gain for 400 mW of pump was found to increase from 12 to 34 dB if the NA was increased from 0.15 to 0.25. Lengthening the metastable state lifetime from 110 to 300 μs would significantly improve amplifier performance while concentration quenching can appreciably degrade it

  6. Dynamic range meter for radiofrequency amplifiers

    Directory of Open Access Journals (Sweden)

    Drozd S. S.

    2009-04-01

    Full Text Available The new measurement setup having increased on 20…30 dB the own dynamic range in comparison with the standard circuit of the dynamic range meter is offered and the rated value of an error bringing by setup in the worst case does not exceed ± 2,8 dB. The measurement setup can be applied also to determinate levels of intermodulation components average power amplifiers and powerful amplifiers of a low-frequency at replacement of the quartz filter on meeting low-frequency the LC-filter and the spectrum analyzer.

  7. Analysis of bipolar and CMOS amplifiers

    CERN Document Server

    Sodagar, Amir M

    2007-01-01

    The classical approach to analog circuit analysis is a daunting prospect to many students, requiring tedious enumeration of contributing factors and lengthy calculations. Most textbooks apply this cumbersome approach to small-signal amplifiers, which becomes even more difficult as the number of components increases. Analysis of Bipolar and CMOS Amplifiers offers students an alternative that enables quick and intuitive analysis and design: the analysis-by-inspection method.This practical and student-friendly text demonstrates how to achieve approximate results that fall within an acceptable ran

  8. Linear Amplifier Model for Optomechanical Systems

    CERN Document Server

    Botter, Thierry; Brahms, Nathan; Schreppler, Sydney; Stamper-Kurn, Dan M

    2011-01-01

    We model optomechanical systems as linear optical amplifiers. This provides a unified treatment of diverse optomechanical phenomena. We emphasize, in particular, the relationship between ponderomotive squeezing and optomechanically induced transparency, two foci of current research. We characterize the amplifier response to quantum and deliberately applied fluctuations, both optical and mechanical. Further, we apply these results to establish quantum limits on external force sensing both on and off cavity resonance. We find that the maximum sensitivity attained on resonance constitutes an absolute upper limit, not surpassed when detuning off cavity resonance. The theory can be extended to a two-sided cavity with losses and limited detection efficiency.

  9. Operational amplifier circuits analysis and design

    CERN Document Server

    Nelson, J C C

    1995-01-01

    This book, a revised and updated version of the author's Basic Operational Amplifiers (Butterworths 1986), enables the non-specialist to make effective use of readily available integrated circuit operational amplifiers for a range of applications, including instrumentation, signal generation and processing.It is assumed the reader has a background in the basic techniques of circuit analysis, particularly the use of j notation for reactive circuits, with a corresponding level of mathematical ability. The underlying theory is explained with sufficient but not excessive, detail. A range of compu

  10. Feedback analysis of transimpedance operational amplifier circuits

    DEFF Research Database (Denmark)

    Bruun, Erik

    1993-01-01

    The transimpedance or current feedback operational amplifier (CFB op-amp) is reviewed and compared to a conventional voltage mode op-amp using an analysis emphasizing the basic feedback characteristics of the circuit. With this approach the paradox of the constant bandwidth obtained from CFB op...

  11. High-Performance Operational and Instrumentation Amplifiers

    NARCIS (Netherlands)

    Shahi, B.

    2015-01-01

    This thesis describes techniques to reduce the offset error in precision instrumentation and operational amplifiers. The offset error which is considered a major error source associated with gain blocks, together with other errors are reviewed. Conventional and newer approaches to remove offset and

  12. Holographic preamplifier for a quantum amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Zemskov, K.I.; Kazarian, M.A.; Orlova, N.G.; Liuksiutov, S.F.; Odulov, S.G.

    1988-08-01

    Successive amplification of a weak optical signal was realized experimentally in holographic and quantum amplifiers. The signal was a coherent one with an intensity less than the actual noise of the copper-vapor active medium; the technique involved the use of a coherent holographic preamplifier based on a lithium niobate/sodium photorefractive crystal. 8 references.

  13. Optimization of Pr3+:ZBLAN fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, B.; Miniscalco, J. W.; Quimby, R. S.

    1992-01-01

    Experimental parameters have been measured and used in a quantitative model of Pr3+-doped fluorozirconate fiber amplifiers. The optimum cutoff wavelength was determined to be 800 nm and the gain for 400 mW of pump was found to increase from 12 to 34 dB if the NA was increased from 0.15 to 0...

  14. Predistortion of a Bidirectional Cuk Audio Amplifier

    DEFF Research Database (Denmark)

    Birch, Thomas Hagen; Nielsen, Dennis; Knott, Arnold;

    2014-01-01

    Some non-linear amplifier topologies are capable of providing a larger voltage gain than one from a DC source, which could make them suitable for various applications. However, the non-linearities introduce a significant amount of harmonic distortion (THD). Some of this distortion could be reduce...

  15. A THEORY FOR BROADBAND VARACTOR PARAMETRIC AMPLIFIERS

    Science.gov (United States)

    design and synthesis of broadband varactor parametric amplifiers. The circuit considered in this thesis is that of linear variable capacitors embedded...second and more important inherent property is that, due to the frequency-coupling action of the variable capacitor , the scattering coefficient at the

  16. Offset Correction Techniques for Voltage Sense Amplifiers

    NARCIS (Netherlands)

    Groeneveld, S.

    2006-01-01

    This report deals with offset correction techniques for voltage sense amplifiers and is divided into two different parts: 1) mismatch and 2) offset correction techniques. First a literature study is done on the subject mismatch with specially focus on the future. Mismatch of a transistor is determin

  17. Ultra-low Voltage CMOS Cascode Amplifier

    DEFF Research Database (Denmark)

    Lehmann, Torsten; Cassia, Marco

    2000-01-01

    In this paper, we design a folded cascode operational transconductance amplifier in a standard CMOS process, which has a measured 69 dB DC gain, a 2 MHz bandwidth and compatible input- and output voltage levels at a 1 V power supply. This is done by a novel Current Driven Bulk (CDB) technique...

  18. New approaches to SNe Ia progenitors

    CERN Document Server

    Ruiz-Lapuente, Pilar

    2014-01-01

    Although Type Ia supernovae (SNe Ia) are a major tool in cosmology and play a key role in the chemical evolution of galaxies, the nature of their progenitor systems (apart from the fact that they must be close binaries containing at least one white dwarf) remains largely unknown. In the last decade, considerable efforts have been made, both observationally and theoretically, to solve this problem. Observations have, however, revealed a previously unsuspected variety of events, ranging from very underluminous outbursts to clearly overluminous ones, and spanning a range well outside the peak luminosity--decline rate of the light curve relationship, used to make calibrated candles of the SNe Ia. On the theoretical side, new explosion scenarios, such as violent mergings of pairs of white dwarfs, have been explored. We review those recent developments, emphasizing the new observational findings, but also trying to tie them to the different scenarios and explosion mechanisms proposed thus far.

  19. PET imaging of adoptive progenitor cell therapies.

    Energy Technology Data Exchange (ETDEWEB)

    Gelovani, Juri G.

    2008-05-13

    Objectives. The overall objective of this application is to develop novel technologies for non-invasive imaging of adoptive stem cell-based therapies with positron emission tomography (PET) that would be applicable to human patients. To achieve this objective, stem cells will be genetically labeled with a PET-reporter gene and repetitively imaged to assess their distribution, migration, differentiation, and persistence using a radiolabeled reporter probe. This new imaging technology will be tested in adoptive progenitor cell-based therapy models in animals, including: delivery pro-apoptotic genes to tumors, and T-cell reconstitution for immunostimulatory therapy during allogeneic bone marrow progenitor cell transplantation. Technical and Scientific Merits. Non-invasive whole body imaging would significantly aid in the development and clinical implementation of various adoptive progenitor cell-based therapies by providing the means for non-invasive monitoring of the fate of injected progenitor cells over a long period of observation. The proposed imaging approaches could help to address several questions related to stem cell migration and homing, their long-term viability, and their subsequent differentiation. The ability to image these processes non-invasively in 3D and repetitively over a long period of time is very important and will help the development and clinical application of various strategies to control and direct stem cell migration and differentiation. Approach to accomplish the work. Stem cells will be genetically with a reporter gene which will allow for repetitive non-invasive “tracking” of the migration and localization of genetically labeled stem cells and their progeny. This is a radically new approach that is being developed for future human applications and should allow for a long term (many years) repetitive imaging of the fate of tissues that develop from the transplanted stem cells. Why the approach is appropriate. The novel approach to

  20. A balanced wide-band amplifier for microwave applications

    Science.gov (United States)

    Panzariu, Mircea; Lupescu, Horia; Dumitrascu, Ana; Tamas, Razvan D.

    2015-02-01

    Due to its better performance, high fiability and large power capability, balanced amplifier is one of the most popular designs used in narrow band applications. However, with a balanced amplifier in class A operation, the band-pass is still narrow with classical coupler [1]. In this paper, we propose a new method for widen the band-pass and linearity of the amplifier, by using two Lange couplers and by adding two drivers, so that small signal could be amplified [2], [3], [4], [5]. The proposed amplifier works in the 0.9 - 2.4 GHz band, with good performances. We also propose an A class X-band amplifier, with Wilkinson power divider used as a combiner and divider. The amplifier will operate at 9,5 GHz with Continuous Wave (C.W). The two methods were validated by simulating the balanced amplifier with Lange coupler and the balanced amplifier with Wilkinson power divider, in class A operation.

  1. Multi-pass amplifier architecture for high power laser systems

    Science.gov (United States)

    Manes, Kenneth R; Spaeth, Mary L; Erlandson, Alvin C

    2014-04-01

    A main amplifier system includes a first reflector operable to receive input light through a first aperture and direct the input light along an optical path. The input light is characterized by a first polarization. The main amplifier system also includes a first polarizer operable to reflect light characterized by the first polarization state. The main amplifier system further includes a first and second set of amplifier modules. Each of the first and second set of amplifier modules includes an entrance window, a quarter wave plate, a plurality of amplifier slablets arrayed substantially parallel to each other, and an exit window. The main amplifier system additionally includes a set of mirrors operable to reflect light exiting the first set of amplifier modules to enter the second set of amplifier modules and a second polarizer operable to reflect light characterized by a second polarization state.

  2. The warm, rich sound of valve guitar amplifiers

    Science.gov (United States)

    Keeports, David

    2017-03-01

    Practical solid state diodes and transistors have made glass valve technology nearly obsolete. Nevertheless, valves survive largely because electric guitar players much prefer the sound of valve amplifiers to the sound of transistor amplifiers. This paper discusses the introductory-level physics behind that preference. Overdriving an amplifier adds harmonics to an input sound. While a moderately overdriven valve amplifier produces strong even harmonics that enhance a sound, an overdriven transistor amplifier creates strong odd harmonics that can cause dissonance. The functioning of a triode valve explains its creation of even and odd harmonics. Music production software enables the examination of both the wave shape and the harmonic content of amplified sounds.

  3. Low phase noise oscillator using two parallel connected amplifiers

    Science.gov (United States)

    Kleinberg, Leonard L.

    1987-01-01

    A high frequency oscillator is provided by connecting two amplifier circuits in parallel where each amplifier circuit provides the other amplifier circuit with the conditions necessary for oscillation. The inherent noise present in both amplifier circuits causes the quiescent current, and in turn, the generated frequency, to change. The changes in quiescent current cause the transconductance and the load impedance of each amplifier circuit to vary, and this in turn results in opposing changes in the input susceptance of each amplifier circuit. Because the changes in input susceptance oppose each other, the changes in quiescent current also oppose each other. The net result is that frequency stability is enhanced.

  4. Amplified spontaneous emission spectrum and gain characteristic of a two-electrode semiconductor optical amplifier*

    Institute of Scientific and Technical Information of China (English)

    Wang Hanchao; Huang Lirong; Shi Zhongwei

    2011-01-01

    A two-electrode multi-quantum-well semiconductor optical amplifier is designed and fabricated. The amplified spontaneous emission (ASE) spectrum and gain were measured and analyzed. It is shown that the ASE spectrum and gain characteristic are greatly influenced by the distribution of the injection current density. By changing the injection current density of two electrodes, the full width at half maximum, peak wavelength, peak power of the ASE spectrum and the gain characteristic can be easily controlled.

  5. Lineage tracing of neuromesodermal progenitors reveals novel Wnt-dependent roles in trunk progenitor cell maintenance and differentiation.

    Science.gov (United States)

    Garriock, Robert J; Chalamalasetty, Ravindra B; Kennedy, Mark W; Canizales, Lauren C; Lewandoski, Mark; Yamaguchi, Terry P

    2015-05-01

    In the development of the vertebrate body plan, Wnt3a is thought to promote the formation of paraxial mesodermal progenitors (PMPs) of the trunk region while suppressing neural specification. Recent lineage-tracing experiments have demonstrated that these trunk neural progenitors and PMPs derive from a common multipotent progenitor called the neuromesodermal progenitor (NMP). NMPs are known to reside in the anterior primitive streak (PS) region; however, the extent to which NMPs populate the PS and contribute to the vertebrate body plan, and the precise role that Wnt3a plays in regulating NMP self-renewal and differentiation are unclear. To address this, we used cell-specific markers (Sox2 and T) and tamoxifen-induced Cre recombinase-based lineage tracing to locate putative NMPs in vivo. We provide functional evidence for NMP location primarily in the epithelial PS, and to a lesser degree in the ingressed PS. Lineage-tracing studies in Wnt3a/β-catenin signaling pathway mutants provide genetic evidence that trunk progenitors normally fated to enter the mesodermal germ layer can be redirected towards the neural lineage. These data, combined with previous PS lineage-tracing studies, support a model that epithelial anterior PS cells are Sox2(+)T(+) multipotent NMPs and form the bulk of neural progenitors and PMPs of the posterior trunk region. Finally, we find that Wnt3a/β-catenin signaling directs trunk progenitors towards PMP fates; however, our data also suggest that Wnt3a positively supports a progenitor state for both mesodermal and neural progenitors.

  6. Design of an 1800 nm Raman Amplifier

    DEFF Research Database (Denmark)

    Svane, Ask Sebastian; Rottwitt, Karsten

    in the pump power requirement and deteriorated noise properties. Here we demonstrate a Raman amplifier designed for signal wavelengths around 1800 nm. The amplification fiber is an OFS PM Raman fiber, and is pumped by a Raman fiber laser emitting at 1680 nm [4]. The amplifier was pumped co......-polarized and backward, with respect to the singal. In Fig. 2 a measured Raman on/off gain exceeding 9 dB for 285 mW of injected pump power is obtained in a 4.35 km long fiber. A broadband supercontinuum source was used as a signal from 1700 nm to 1900 nm.......Different approaches are being explored to increase the capacity of communication systems [1,2], both long and short range systems. One approach is by exploiting new optical wavelength bands, outside the conventional communication window from 1530 nm to 1625 nm. Hollow core fibers have been...

  7. Behavioral modeling of Digitally Adjustable Current Amplifier

    Directory of Open Access Journals (Sweden)

    Josef Polak

    2015-03-01

    Full Text Available This article presents the digitally adjustable current amplifier (DACA and its analog behavioral model (ABM, which is suitable for both ideal and advanced analyses of the function block using DACA as active element. There are four levels of this model, each being suitable for simulation of a certain degree of electronic circuits design (e.g. filters, oscillators, generators. Each model is presented through a schematic wiring in the simulation program OrCAD, including a description of equations representing specific functions in the given level of the simulation model. The design of individual levels is always verified using PSpice simulations. The ABM model has been developed based on practically measured values of a number of DACA amplifier samples. The simulation results for proposed levels of the ABM model are shown and compared with the results of the real easurements of the active element DACA.

  8. Noise Gain Features of Fiber Raman Amplifier

    Directory of Open Access Journals (Sweden)

    Georgii S. Felinskyi

    2016-01-01

    Full Text Available The formation dynamics of the optical noise in a silica single mode fiber (SMF as function of the pump power variation in the counter pumped fiber Raman amplifier (FRA is experimentally studied. The ratio between the power of amplified spontaneous emission and the power of incoherent optical noise is quantitatively determined by detailed analysis of experimental data in the pump powers range of 100–300 mW within the full band of Stokes frequencies, including FRA working wavelengths over the C + L transparency windows. It is found out the maximum of Raman gain coefficient for optical noise does not exceed ~60% of corresponding peak at the gain profile maximum of coherent signal. It is shown that the real FRA noise figure may be considerably less than 3 dB over a wide wavelength range (100 nm at a pump power of several hundreds of mW.

  9. Cryogenic cooling for high power laser amplifiers

    Directory of Open Access Journals (Sweden)

    Perin J.P.

    2013-11-01

    Full Text Available Using DPSSL (Diode Pumped Solid State Lasers as pumping technology, PW-class lasers with enhanced repetition rates are developed. Each of the Yb YAG amplifiers will be diode-pumped at a wavelength of 940 nm. This is a prerequisite for achieving high repetition rates (light amplification duration 1 millisecond and repetition rate 10 Hz. The efficiency of DPSSL is inversely proportional to the temperature, for this reason the slab amplifier have to be cooled at a temperature in the range of 100 K–170 K with a heat flux of 1 MW*m−2. This paper describes the thermo-mechanical analysis for the design of the amplification laser head, presents a preliminary proposal for the required cryogenic cooling system and finally outlines the gain of cryogenic operation for the efficiency of high pulsed laser.

  10. Linear control of oscillator and amplifier flows*

    Science.gov (United States)

    Schmid, Peter J.; Sipp, Denis

    2016-08-01

    Linear control applied to fluid systems near an equilibrium point has important applications for many flows of industrial or fundamental interest. In this article we give an exposition of tools and approaches for the design of control strategies for globally stable or unstable flows. For unstable oscillator flows a feedback configuration and a model-based approach is proposed, while for stable noise-amplifier flows a feedforward setup and an approach based on system identification is advocated. Model reduction and robustness issues are addressed for the oscillator case; statistical learning techniques are emphasized for the amplifier case. Effective suppression of global and convective instabilities could be demonstrated for either case, even though the system-identification approach results in a superior robustness to off-design conditions.

  11. Fundamentals of fiber lasers and fiber amplifiers

    CERN Document Server

    Ter-Mikirtychev, Valerii (Vartan)

    2014-01-01

    This book covers the fundamental aspects of fiber lasers and fiber amplifiers, and includes a wide range of material from laser physics fundamentals to state-of-the-art topics in this rapidly growing field of quantum electronics. Emphasis is placed on the nonlinear processes taking place in fiber lasers and amplifiers, their similarities, differences to, and their advantages over other solid-state lasers. The reader will learn basic principles of solid-state physics and optical spectroscopy of laser active centers in fibers, main operational laser regimes, and practical recommendations and suggestions on fiber laser research, laser applications, and laser product development. The book will be useful for students, researchers, and professionals who work with lasers, in the optical communications, chemical and biological industries, etc.

  12. On Measuring the Metallicity of Supernovae Type Ia Progenitors

    CERN Document Server

    Miles, Broxton J; Townsley, Dean M; Timmes, F X; Jackson, Aaron P; Calder, Alan C; Brown, Edward F

    2015-01-01

    In Type Ia Supernovae (\\sneia), the relative abundances of chemical elements are affected by the neutron excess in the composition of the progenitor white dwarf. Since these products leave signatures in the spectra near maximum light, spectral features may be used to constrain the composition of the progenitor. We calculate the nucleosynthetic yields for three \\snia simulations for a wide range of progenitor metallicities, and calculate synthetic light curves and spectra to explore correlations between progenitor metallicity and the strength of spectral features. We use two 2D simulations of the deflagration-detonation-transition scenario with different $^{56}$Ni yields and the W7 simulation to control for differences between explosion models and total yields. While the overall yields of intermediate mass elements (16 $<$ A $\\leq$ 40) differ between the three cases, trends in the yields are similar. With increasing metallicity, $^{28}$Si yields remain nearly constant, $^{40}$Ca yields decline, and Ti and $...

  13. Luminal progenitors restrict their lineage potential during mammary gland development.

    Directory of Open Access Journals (Sweden)

    Veronica Rodilla

    2015-02-01

    Full Text Available The hierarchical relationships between stem cells and progenitors that guide mammary gland morphogenesis are still poorly defined. While multipotent basal stem cells have been found within the myoepithelial compartment, the in vivo lineage potential of luminal progenitors is unclear. Here we used the expression of the Notch1 receptor, previously implicated in mammary gland development and tumorigenesis, to elucidate the hierarchical organization of mammary stem/progenitor cells by lineage tracing. We found that Notch1 expression identifies multipotent stem cells in the embryonic mammary bud, which progressively restrict their lineage potential during mammary ductal morphogenesis to exclusively generate an ERαneg luminal lineage postnatally. Importantly, our results show that Notch1-labelled cells represent the alveolar progenitors that expand during pregnancy and survive multiple successive involutions. This study reveals that postnatal luminal epithelial cells derive from distinct self-sustained lineages that may represent the cells of origin of different breast cancer subtypes.

  14. Luminal progenitors restrict their lineage potential during mammary gland development.

    Science.gov (United States)

    Rodilla, Veronica; Dasti, Alessandro; Huyghe, Mathilde; Lafkas, Daniel; Laurent, Cécile; Reyal, Fabien; Fre, Silvia

    2015-02-01

    The hierarchical relationships between stem cells and progenitors that guide mammary gland morphogenesis are still poorly defined. While multipotent basal stem cells have been found within the myoepithelial compartment, the in vivo lineage potential of luminal progenitors is unclear. Here we used the expression of the Notch1 receptor, previously implicated in mammary gland development and tumorigenesis, to elucidate the hierarchical organization of mammary stem/progenitor cells by lineage tracing. We found that Notch1 expression identifies multipotent stem cells in the embryonic mammary bud, which progressively restrict their lineage potential during mammary ductal morphogenesis to exclusively generate an ERαneg luminal lineage postnatally. Importantly, our results show that Notch1-labelled cells represent the alveolar progenitors that expand during pregnancy and survive multiple successive involutions. This study reveals that postnatal luminal epithelial cells derive from distinct self-sustained lineages that may represent the cells of origin of different breast cancer subtypes.

  15. Senegenin promotes in vitro proliferation of human neural progenitor cells

    Institute of Scientific and Technical Information of China (English)

    Fang Shi; Zhigang Liang; Zixuan Guo; Ran Li; Fen Yu; Zhanjun Zhang; Xuan Wang; Xiaomin Wang

    2011-01-01

    Senegenin, an effective component of Polygala tenuifolia root extract, promotes proliferation and differentiation of neural progenitor cells in the hippocampus.However, the effects of senegenin on mesencephalon-derived neural progenitor cells remain poorly understood.Cells from a ventral mesencephalon neural progenitor cell line (ReNcell VM) were utilized as models for pharmaceutical screening.The effects of various senegenin concentrations on cell proliferation were analyzed,demonstrating that high senegenin concentrations (5, 10, 50, and 100 pmo/L), particularly 50 pmol/L, significantly promoted proliferation of ReNcell VM cells.In the mitogen-activated protein kinase signal transduction pathway, senegenin significantly increased phosphorylation levels of extracellular signal-regulated kinases.Moreover, cell proliferation was suppressed by extracellular signal-regulated kinase inhibitors.Results suggested that senegenin contributed to in vitro proliferation of human neural progenitor cells by upregulating phosphorylation of extracellular signal-regulated kinase.

  16. Observational clues to the progenitors of Type-Ia supernovae

    CERN Document Server

    Maoz, Dan; Nelemans, Gijs

    2013-01-01

    Type-Ia supernovae (SNe Ia) are important distance indicators, element factories, cosmic-ray accelerators, kinetic-energy sources in galaxy evolution, and endpoints of stellar binary evolution. It has long been clear that a SN Ia must be the runaway thermonuclear explosion of a degenerate carbon-oxygen stellar core, most likely a white dwarf (WD). However, the specific progenitor systems of SNe Ia, and the processes that lead to their ignition, have not been identified. Two broad classes of progenitor binary systems have long been considered: single-degenerate (SD), in which a WD gains mass from a non-degenerate star; and double-degenerate (DD), involving the merger of two WDs. New theoretical work has enriched these possibilities with some interesting updates and variants. We review the significant recent observational progress in addressing the progenitor problem. We consider clues that have emerged from the observed properties of the various proposed progenitor populations, from studies of their sites, pre...

  17. Design and simulation of a gyroklystron amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, M. S., E-mail: mschauhan.rs.ece@iitbhu.ac.in; Swati, M. V.; Jain, P. K. [Centre of Research in Microwave Tubes, Department of Electronics Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005 (India)

    2015-03-15

    In the present paper, a design methodology of the gyroklystron amplifier has been described and subsequently used for the design of a typically selected 200 kW, Ka-band, four-cavity gyroklystron amplifier. This conceptual device design has been validated through the 3D particle-in-cell (PIC) simulation and nonlinear analysis. Commercially available PIC simulation code “MAGIC” has been used for the electromagnetic study at the different location of the device RF interaction structure for the beam-absent case, i.e., eigenmode study as well as for the electron beam and RF wave interaction behaviour study in the beam present case of the gyroklystron. In addition, a practical problem of misalignment of the RF cavities with drift tubes within the tube has been also investigated and its effect on device performance studied. The analytical and simulation results confirmed the validity of the gyroklystron device design. The PIC simulation results of the present gyroklystron produced a stable RF output power of ∼218 kW for 0% velocity spread at 35 GHz, with ∼45 dB gain, 37% efficiency, and a bandwidth of 0.3% for a 70 kV, 8.2 A gyrating electron beam. The simulated values of RF output power have been found in agreement with the nonlinear analysis results within ∼5%. Further, the PIC simulation has been extended to study a practical problem of misalignment of the cavities axis and drift tube axis of the gyroklystron amplifier and found that the RF output power is more sensitive to misalignments in comparison to the device bandwidth. The present paper, gyroklystron device design, nonlinear analysis, and 3D PIC simulation using commercially available code had been systematically described would be of use to the high-power gyro-amplifier tube designers and research scientists.

  18. High-Performance Operational and Instrumentation Amplifiers

    OpenAIRE

    Shahi, B.

    2015-01-01

    This thesis describes techniques to reduce the offset error in precision instrumentation and operational amplifiers. The offset error which is considered a major error source associated with gain blocks, together with other errors are reviewed. Conventional and newer approaches to remove offset and low frequency noise are discussed, with a focus on the work of this thesis “Chopper-Stabilized Auto-Zeroed Chopper Instrumentation Amplifiers”. The technique is demonstrated through the application...

  19. Self-amplifying mRNA vaccines.

    Science.gov (United States)

    Brito, Luis A; Kommareddy, Sushma; Maione, Domenico; Uematsu, Yasushi; Giovani, Cinzia; Berlanda Scorza, Francesco; Otten, Gillis R; Yu, Dong; Mandl, Christian W; Mason, Peter W; Dormitzer, Philip R; Ulmer, Jeffrey B; Geall, Andrew J

    2015-01-01

    This chapter provides a brief introduction to nucleic acid-based vaccines and recent research in developing self-amplifying mRNA vaccines. These vaccines promise the flexibility of plasmid DNA vaccines with enhanced immunogenicity and safety. The key to realizing the full potential of these vaccines is efficient delivery of nucleic acid to the cytoplasm of a cell, where it can amplify and express the encoded antigenic protein. The hydrophilicity and strong net negative charge of RNA impedes cellular uptake. To overcome this limitation, electrostatic complexation with cationic lipids or polymers and physical delivery using electroporation or ballistic particles to improve cellular uptake has been evaluated. This chapter highlights the rapid progress made in using nonviral delivery systems for RNA-based vaccines. Initial preclinical testing of self-amplifying mRNA vaccines has shown nonviral delivery to be capable of producing potent and robust innate and adaptive immune responses in small animals and nonhuman primates. Historically, the prospect of developing mRNA vaccines was uncertain due to concerns of mRNA instability and the feasibility of large-scale manufacturing. Today, these issues are no longer perceived as barriers in the widespread implementation of the technology. Currently, nonamplifying mRNA vaccines are under investigation in human clinical trials and can be produced at a sufficient quantity and quality to meet regulatory requirements. If the encouraging preclinical data with self-amplifying mRNA vaccines are matched by equivalently positive immunogenicity, potency, and tolerability in human trials, this platform could establish nucleic acid vaccines as a versatile new tool for human immunization.

  20. Fast Electrocardiogram Amplifier Recovery after Defibrillation Shock

    Directory of Open Access Journals (Sweden)

    Ivan Dotsinsky

    2005-04-01

    Full Text Available A procedure for fast ECG amplifier recovery after defibrillation shocks was developed and simulated in the MATLAB environment. Exponentially decaying post-shock voltages have been recorded. Signals from the AHA database are taken and mixed with the recorded exponential disturbances. The algorithm applies moving averaging (comb filter on the compound input signal, thereby obtaining the samples of the disturbance. They are currently subtracted from the input signal. The results obtained show that its recovery is practically instantaneous.

  1. Amplifying the Hawking Signal in BECs

    Directory of Open Access Journals (Sweden)

    Roberto Balbinot

    2014-01-01

    Full Text Available We consider simple models of Bose-Einstein condensates to study analog pair-creation effects, namely, the Hawking effect from acoustic black holes and the dynamical Casimir effect in rapidly time-dependent backgrounds. We also focus on a proposal by Cornell to amplify the Hawking signal in density-density correlators by reducing the atoms’ interactions shortly before measurements are made.

  2. Electrically Pumped Vertical-Cavity Amplifiers

    DEFF Research Database (Denmark)

    Greibe, Tine

    2007-01-01

    In this work, the design of electrically pumped vertical cavity semiconductor optical amplifiers (eVCAs) for use in a mode-locked external-cavity laser has been developed, investigated and analysed. Four different eVCAs, one top-emitting and three bottom emitting structures, have been designed...... and discussed. The thesis concludes with recommendations for further work towards the realisation of compact electrically pumped mode-locked vertical externalcavity surface emitting lasers....

  3. Transportable setup for amplifier phase fidelity measurements

    OpenAIRE

    Troebs, Michael; Bogan, C.; Barke, S.; Kuehn, G.; Reiche, J.; Heinzel, Gerhard; Danzmann, Karsten

    2015-01-01

    One possible laser source for the Laser Interferometer Space Antenna (LISA) consists of an Ytterbium-doped fiber amplifier originally developed for inter-satellite communication, seeded by the laser used for the technology demonstrator mission LISA Pathfinder. LISA needs to transmit clock information between its three spacecraft to correct for phase noise between the clocks on the individual spacecraft. For this purpose phase modulation sidebands at GHz frequencies will be imprinted on the la...

  4. Short wavelength regenerative amplifier free electron lasers

    OpenAIRE

    Dunning, D J; McNeil, B. W. J.; Thompson, N. R.

    2008-01-01

    In this paper we discuss extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand.

  5. Endothelial progenitor cells with Alzheimer's disease

    Institute of Scientific and Technical Information of China (English)

    KONG Xiao-dong; ZHANG Yun; LIU Li; SUN Ning; ZHANG Ming-yi; ZHANG Jian-ning

    2011-01-01

    Background Endothelial dysfunction is thought to be critical events in the pathogenesis of Alzheimer's disease (AD).Endothelial progenitor cells (EPCs) have provided insight into maintaining and repairing endothelial function. To study the relation between EPCs and AD, we explored the number of circulating EPCs in patients with AD.Methods A total of 104 patients were recruited from both the outpatients and inpatients of the geriatric neurology department at General Hospital, rianjin Medical University. Consecutive patients with newly diagnosed AD (n=30),patients with vascular dementia (VaD, n=34), and healthy elderly control subjects with normal cognition (n=40) were enrolled after matching for age, gender, body mass index, medical history, current medication and Mini Mental State Examination. Middle cerebral artery flow velocity was examined with transcranial Doppler. Endothelial function was evaluated according to the level of EPCs, and peripheral blood EPCs was counted by flow cytometry.Results There were no significant statistical differences of clinical data in AD, VaD and control groups (P >0.05). The patients with AD showed decreased CD34-positive (CD34+) or CD133-positive (CD133+) levels compared to the control subjects, but there were no significant statistical differences in patients with AD. The patients with AD had significantly lower CD34+CD133+ EPCs(CD34 and CD133 double positive endothelial progenitor cells) than the control subjects (P <0.05). In the patients with AD, a lower CD34+CD133+ EPCs count was independently associated with a lower Mini-Mental State Examination score (r=0.514, P=0.004). Patients with VaD also showed a significant decrease in CD34+CD133+ EPCs levels, but this was not evidently associated with the Mini-Mental State Examination score. The changes of middle cerebral artery flow velocity were similar between AD and VaD. Middle cerebral artery flow velocity was decreased in the AD and VaD groups and significantly lower than

  6. Parallel reservoir computing using optical amplifiers.

    Science.gov (United States)

    Vandoorne, Kristof; Dambre, Joni; Verstraeten, David; Schrauwen, Benjamin; Bienstman, Peter

    2011-09-01

    Reservoir computing (RC), a computational paradigm inspired on neural systems, has become increasingly popular in recent years for solving a variety of complex recognition and classification problems. Thus far, most implementations have been software-based, limiting their speed and power efficiency. Integrated photonics offers the potential for a fast, power efficient and massively parallel hardware implementation. We have previously proposed a network of coupled semiconductor optical amplifiers as an interesting test case for such a hardware implementation. In this paper, we investigate the important design parameters and the consequences of process variations through simulations. We use an isolated word recognition task with babble noise to evaluate the performance of the photonic reservoirs with respect to traditional software reservoir implementations, which are based on leaky hyperbolic tangent functions. Our results show that the use of coherent light in a well-tuned reservoir architecture offers significant performance benefits. The most important design parameters are the delay and the phase shift in the system's physical connections. With optimized values for these parameters, coherent semiconductor optical amplifier (SOA) reservoirs can achieve better results than traditional simulated reservoirs. We also show that process variations hardly degrade the performance, but amplifier noise can be detrimental. This effect must therefore be taken into account when designing SOA-based RC implementations.

  7. Charge sensitive amplifies. The state of arts

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Kunishiro [Clear Pulse Co., Tokyo (Japan)

    1996-07-01

    In the radiation detectors, signals are essentially brought with charges produced by radiation, then it is naturally the best way to use a charge sensitive amplifier (CSA) system to extract those signals. The CSA is thought to be the best amplifier suitable to almost all the radiation detectors, if neglecting economical points of view. The CSA has been only applied to special fields like radiation detection because the concept of `charges` is not so universal against the concepts of `voltage` and `current`. The CSA, however, is low in noise and a high speed amplifier and may be applicable not only to radiation measurement but also piezoelectric devices and also bolometers. In this article, noise in the CSA, basic circuit on the CSA, concepts of `equivalent noise charge` (ENC), a method for the ENC, and importance of the `open-loop gain` in the CSA to achieve better performance of it and how to realize in a practical CSA were described. And, characteristics on a counting rate of the CSA, various circuit used in the CSA, and CSAs which are commercially available at present and special purpose CSAs were also introduced. (G.K.)

  8. Microstrip SQUID amplifiers for quantum information science

    Science.gov (United States)

    Defeo, M. P.; Plourde, B. L. T.

    2012-02-01

    Recent progress in SQUID amplifiers suggests that these devices might approach quantum-limited sensitivity in the microwave range, thus making them a viable option for measurement of superconducting quantum systems. In the microstrip SQUID amplifier configuration, gains of around 20dB are possible at frequencies of several hundred MHz, and the gain is limited by the maximum voltage modulation available from the SQUID. One route for increasing the voltage modulation involves using larger resistive shunts, however maintaining non-hysteretic device operation requires smaller junction capacitances than is possible with conventional photolithographically patterned junctions. Operating at higher frequencies requires a shorter input coil which reduces mutual inductance between the coil and washer and therefore gain. We have fabricated microstrip SQUID amplifiers using submicron Al-AlOx-Al junctions and large shunts. The input coil and SQUID washer are optimized for producing high gain at frequencies in the gigahertz range. Recent measurements of gain and noise temperature will be discussed as well as demonstrations of these devices as a first stage of amplification for a superconducting system

  9. Transistor circuit increases range of logarithmic current amplifier

    Science.gov (United States)

    Gilmour, G.

    1966-01-01

    Circuit increases the range of a logarithmic current amplifier by combining a commercially available amplifier with a silicon epitaxial transistor. A temperature compensating network is provided for the transistor.

  10. Human pancreatic islet progenitor cells demonstrate phenotypic plasticity in vitro

    Indian Academy of Sciences (India)

    Maithili P Dalvi; Malati R Umrani; Mugdha V Joglekar; Anandwardhan A Hardikar

    2009-10-01

    Phenotypic plasticity is a phenomenon that describes the occurrence of 2 or more distinct phenotypes under diverse conditions. This article discusses the work carried out over the past few years in understanding the potential of human pancreatic islet-derived progenitors for cell replacement therapy in diabetes. The phenotypic plasticity exhibited by pancreatic progenitors during reversible epithelial-to-mesenchymal transition (EMT) and possible role of microRNAs in regulation of this process is also presented herein.

  11. Endothelial Progenitor Cells for Diagnosis and Prognosis in Cardiovascular Disease

    OpenAIRE

    2015-01-01

    Objective. To identify, evaluate, and synthesize evidence on the predictive power of circulating endothelial progenitor cells (EPCs) in cardiovascular disease, through a systematic review of quantitative studies. Data Sources. MEDLINE was searched using keywords related to “endothelial progenitor cells” and “endothelium” and, for the different categories, respectively, “smoking”; “blood pressure”; “diabetes mellitus” or “insulin resistance”; “dyslipidemia”; “aging” or “elderly”; “angina p...

  12. Transplanted progenitors generate functional enteric neurons in the postnatal colon

    OpenAIRE

    2013-01-01

    Cell therapy has the potential to treat gastrointestinal motility disorders caused by diseases of the enteric nervous system. Many studies have demonstrated that various stem/progenitor cells can give rise to functional neurons in the embryonic gut; however, it is not yet known whether transplanted neural progenitor cells can migrate, proliferate, and generate functional neurons in the postnatal bowel in vivo. We transplanted neurospheres generated from fetal and postnatal intestinal neural c...

  13. Trasplante de progenitores hemopoyéticos Transplant of hemopoietic progenitors

    Directory of Open Access Journals (Sweden)

    J. J. Rifón

    2006-08-01

    Full Text Available En la segunda mitad del siglo XX el trasplante de progenitores hemopoyéticos ha pasado de ser un tratamiento desesperado con una alta incidencia de complicaciones que implicaba una elevada mortalidad, a ser un tratamiento curativo para miles de pacientes con neoplasias hematológicas y otras enfermedades. Desde entonces se han ampliado los conocimientos sobre las células madre hemopoyéticas, la sangre periférica ha sustituido a la médula ósea como fuente de progenitores, la sangre de cordón se ha establecido como fuente viable de progenitores, la realización de trasplantes no emparentados es una realidad para muchos pacientes. La mejora en los regímenes de acondicionamiento y la introducción de los regímenes no mieloablativos han disminuido las recaídas. Las nuevas técnicas diagnósticas y los nuevos tratamientos antimicrobianos han disminuido las complicaciones infecciosas y su mortalidad. Se han desarrollado los conocimientos en determinación de enfermedad mínima residual y el efecto antitumoral de los linfocitos del donante lo que ha permitido ampliar las indicaciones. Además, los nuevos conocimientos en la inmunobiología del trasplante han mejorado por un lado las opciones de controlar una de las principales complicaciones como es la enfermedad injerto contra huésped, y por otro un mejor aprovechamiento del efecto inmunoterápico del trasplante.In the second half of the XX century, the transplant of hemopoietic progenitors ceased to be a desperate treatment with a high incidence of complications implying a high mortality, and became a curative treatment for thousands of patients with hematological neoplasias and other diseases. Since then understanding of the hemopoietic stem cells has increased, peripheral blood has replaced bone marrow as a source of progenitors, cord blood has been established as a viable source of progenitors and the realisation of unrelated transplants is a reality for many patients. The improvement of

  14. Invited review: mesenchymal progenitor cells in intramuscular connective tissue development.

    Science.gov (United States)

    Miao, Z G; Zhang, L P; Fu, X; Yang, Q Y; Zhu, M J; Dodson, M V; Du, M

    2016-01-01

    The abundance and cross-linking of intramuscular connective tissue contributes to the background toughness of meat, and is thus undesirable. Connective tissue is mainly synthesized by intramuscular fibroblasts. Myocytes, adipocytes and fibroblasts are derived from a common pool of progenitor cells during the early embryonic development. It appears that multipotent mesenchymal stem cells first diverge into either myogenic or non-myogenic lineages; non-myogenic mesenchymal progenitors then develop into the stromal-vascular fraction of skeletal muscle wherein adipocytes, fibroblasts and derived mesenchymal progenitors reside. Because non-myogenic mesenchymal progenitors mainly undergo adipogenic or fibrogenic differentiation during muscle development, strengthening progenitor proliferation enhances the potential for both intramuscular adipogenesis and fibrogenesis, leading to the elevation of both marbling and connective tissue content in the resulting meat product. Furthermore, given the bipotent developmental potential of progenitor cells, enhancing their conversion to adipogenesis reduces fibrogenesis, which likely results in the overall improvement of marbling (more intramuscular adipocytes) and tenderness (less connective tissue) of meat. Fibrogenesis is mainly regulated by the transforming growth factor (TGF) β signaling pathway and its regulatory cascade. In addition, extracellular matrix, a part of the intramuscular connective tissue, provides a niche environment for regulating myogenic differentiation of satellite cells and muscle growth. Despite rapid progress, many questions remain in the role of extracellular matrix on muscle development, and factors determining the early differentiation of myogenic, adipogenic and fibrogenic cells, which warrant further studies.

  15. On the progenitor of the Type IIb supernova 2016gkg

    Science.gov (United States)

    Kilpatrick, Charles D.; Foley, Ryan J.; Abramson, Louis E.; Pan, Yen-Chen; Lu, Cicero-Xinyu; Williams, Peter; Treu, Tommaso; Siebert, Matthew R.; Fassnacht, Christopher D.; Max, Claire E.

    2017-03-01

    We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck adaptive optics system was used to perform relative astrometry between the Keck and HST imaging. We identify a single point source in the HST images coincident with the SN position to 0.89σ. The HST photometry is consistent with the progenitor star being an A0 Ia star with T = 9500 K and log (L/L⊙) = 5.15. We find that the SN 2016gkg progenitor star appears more consistent with binary than single-star evolutionary models. In addition, early-time light-curve data from SN 2016gkg revealed a rapid rise in luminosity within ∼0.4 d of non-detection limits, consistent with models of the cooling phase after shock break-out. We use these data to determine an explosion date of 2016 September 20.15 and progenitor-star radius of log (R/R⊙) = 2.41, which agrees with photometry from the progenitor star. Our findings are also consistent with detections of other SNe IIb progenitor stars, although more luminous and bluer than most other examples.

  16. Differential Apoptosis Radiosensitivity of Neural Progenitors in Adult Mouse Hippocampus

    Directory of Open Access Journals (Sweden)

    Yu-Qing Li

    2016-06-01

    Full Text Available Mammalian tissue-specific stem cells and progenitors demonstrate differential DNA damage response. Neural progenitors in dentate gyrus of the hippocampus are known to undergo apoptosis after irradiation. Using a mouse model of hippocampal neuronal development, we characterized the apoptosis sensitivity of the different neural progenitor subpopulations in adult mouse dentate gyrus after irradiation. Two different bromodeoxyuridine incorporation paradigms were used for cell fate mapping. We identified two apoptosis sensitive neural progenitor subpopulations after irradiation. The first represented non-proliferative and non-newborn neuroblasts and immature neurons that expressed doublecortin, calretinin or both. The second consisted of proliferative intermediate neural progenitors. The putative radial glia-like neural stem cells or type-1 cells, regardless of proliferation status, were apoptosis resistant after irradiation. There was no evidence of radiation-induced apoptosis in the absence of the Trp53 (p53 gene but absence of Cdkn1a (p21 did not alter the apoptotic response. Upregulation of nuclear p53 was observed in neuroblasts after irradiation. We conclude that adult hippocampal neural progenitors may demonstrate differential p53-dependent apoptosis sensitivity after irradiation.

  17. Hematopoietic progenitor cell mobilization for autologous transplantation - a literature review

    Directory of Open Access Journals (Sweden)

    Marco Aurélio Salvino

    2016-02-01

    Full Text Available ABSTRACT The use of high-dose chemotherapy with autologous support of hematopoietic progenitor cells is an effective strategy to treat various hematologic neoplasms, such as non-Hodgkin lymphomas and multiple myeloma. Mobilized peripheral blood progenitor cells are the main source of support for autologous transplants, and collection of an adequate number of hematopoietic progenitor cells is a critical step in the autologous transplant procedure. Traditional strategies, based on the use of growth factors with or without chemotherapy, have limitations even when remobilizations are performed. Granulocyte colony-stimulating factor is the most widely used agent for progenitor cell mobilization. The association of plerixafor, a C-X-C Chemokine receptor type 4 (CXCR4 inhibitor, to granulocyte colony stimulating factor generates rapid mobilization of hematopoietic progenitor cells. A literature review was performed of randomized studies comparing different mobilization schemes in the treatment of multiple myeloma and lymphomas to analyze their limitations and effectiveness in hematopoietic progenitor cell mobilization for autologous transplant. This analysis showed that the addition of plerixafor to granulocyte colony stimulating factor is well tolerated and results in a greater proportion of patients with non-Hodgkin lymphomas or multiple myeloma reaching optimal CD34+ cell collections with a smaller number of apheresis compared the use of granulocyte colony stimulating factor alone.

  18. Interstitial stromal progenitors during kidney development: here, there and everywhere.

    Science.gov (United States)

    Fanni, Daniela; Gerosa, Clara; Vinci, Laura; Ambu, Rossano; Dessì, Angelica; Eyken, Peter Van; Fanos, Vassilios; Faa, Gavino

    2016-12-01

    In recent years, the renal interstitium has been identified as the site of multiple cell types, giving rise to multiple contiguous cellular networks with multiple fundamental structural and functional roles. Few studies have been carried out on the morphological and functional properties of the stromal/interstitial renal cells during the intrauterine life. This work was aimed at reviewing the peculiar features of renal interstitial stem/progenitor cells involved in kidney development. The origin of the renal interstitial progenitor cells remains unknown. During kidney development, besides the Six2 + cells of the cap mesenchyme, a self-renewing progenitor population, characterized by the expression of Foxd1, represents the first actor of the non-nephrogenic lineage. Foxd1 + interstitial progenitors originate the cortical and the renal medullary interstitial progenitors. Here, the most important stromal/interstitial compartments present in the developing human kidney will be analyzed: capsular stromal cells, cortical interstitial cells, medullary interstitial cells, the interstitium inside the renal stem cell niche, Hilar interstitial cells and Ureteric interstitial cells. Data reported here indicate that the different interstitial compartments of the developing kidney are formed by different cell types that characterize the different renal areas. Further studies are needed to better characterize the different pools of renal interstitial progenitors and their role in human nephrogenesis.

  19. The Dynamics of Semiconductor Optical Amplifiers – Modeling and Applications

    DEFF Research Database (Denmark)

    Mørk, Jesper; Nielsen, Mads Lønstrup; Berg, Tommy Winther

    2003-01-01

    The importance of semiconductor optical amplifiers is discussed. A semiconductor optical amplifier (SOA) is a semiconductor laser with anti-reflection coated facets that amplifies an injected light signal by means of stimulated emission. SOAs have a number of unique properties that open up...

  20. Microwave parametric amplifiers using externally pumped Josephson junctions

    DEFF Research Database (Denmark)

    Sørensen, O. H.; Mygind, Jesper; Pedersen, Niels Falsig

    1978-01-01

    Externally pumped parametric amplifiers are discussed. Theory and experiments on the singly degenerate parametric amplifier based on a Josephson junction are presented. Advantages and limitations of the singly degenerate and doubly degenerate parametric amplifiers are discussed. Some plans and pr...... and proposals for future research are presented....

  1. An integrated charge amplifier for a pyroelectric sensor

    NARCIS (Netherlands)

    Setiadi, D.; Armitage, A.; Binnie, T.D.; Regtien, P.P.L.; Sarro, P.M.

    1997-01-01

    This paper presents an integrated charge amplifier that measures a small charge. This charge is generated by a pyroelectric detector. The charge amplifier consists of a single-stage c-annon source configuration with a passive feedback network. The charge amplifier has a bandwidth of 700 kHz and an o

  2. Polarization of Tapered Semiconductor Travelling-Wave Amplifiers

    Institute of Scientific and Technical Information of China (English)

    Huang Dexiu; Li Hong

    2001-01-01

    The polarization of a tapered semi-conductor travelling-wave amplifier has been investigated with the transfer matrix method based on convective equation. It is shown that the apparent polarization mode competition exists, and polarization-independent tapered semiconductor travellingwave amplifiers can be obtained through the optimization of amplifier parameters.

  3. Differential transimpedance amplifier circuit for correlated differential amplification

    Science.gov (United States)

    Gresham, Christopher A.; Denton, M. Bonner; Sperline, Roger P.

    2008-07-22

    A differential transimpedance amplifier circuit for correlated differential amplification. The amplifier circuit increase electronic signal-to-noise ratios in charge detection circuits designed for the detection of very small quantities of electrical charge and/or very weak electromagnetic waves. A differential, integrating capacitive transimpedance amplifier integrated circuit comprising capacitor feedback loops performs time-correlated subtraction of noise.

  4. Constraining GRB progenitors environment with Swift XRT

    CERN Document Server

    Saez, Dounia

    2015-01-01

    The characteristics of the Gamma-Ray Bursts (GRBs) environment may reflect the differences in GRB progenitors: long GRBs are expected to be found in high-density star-forming regions of the GRB host galaxies, while short ones may be associated with an older stellar population that may have had the time to travel far from stellar forming regions in potentially lower density regions. The latter is related to the hypothesis that short GRBs are associated to the merging of compact objects (BH-NS or NS-NS). We used the Swift XRT GRB afterglow archive to compare the intrinsic neutral hydrogen column density values for long and short GRBs within the redshift range 0.1- 1.3, performing a coherent analysis, and excluding from our analysis observations with poor statistics, which reduced our sample to 15 short GRBs. While short GRBs effectively show a median absorption value smaller than long ones the result is not statistically significant. In order to increase our sample we added short GRBs without redshift measure, ...

  5. Type Ia Supernovae: Colors, Rates, and Progenitors

    CERN Document Server

    Heringer, Epson; Kezwer, Jason; Graham, Melissa L; Sand, David; Bildfell, Chris

    2016-01-01

    The rate of type Ia supernovae (SNe Ia) in a galaxy depends not only on stellar mass, but also on star formation history. Here we show that two simple observational quantities ($g-r$ or $u-r$ host galaxy color, and $r$-band luminosity), coupled with an assumed delay time distribution (the rate of SNe Ia as a function of time for an instantaneous burst of star formation), are sufficient to accurately determine a galaxy's SN Ia rate, with very little sensitivity to the precise details of the star formation history. Using this result, we compare observed and predicted color distributions of SN Ia hosts for the MENeaCS cluster supernova survey, and for the SDSS Stripe 82 supernova survey. The observations are consistent with a continuous delay time distribution (DTD), without any cutoff. For old progenitor systems the power-law slope for the DTD is found to be $-1.50 ^{+0.19} _{-0.15}$. This result favours the double degenerate scenario for SN Ia, though other interpretations are possible. We find that the late-t...

  6. The Binary Progenitor of Tycho Brahe's Supernova

    Science.gov (United States)

    Ruiz-Lapuente, P.

    2006-08-01

    The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion. Unless the companion star is another white dwarf (in which case it should be destroyed by the mass-transfer process itself), it should survive and show distinguishing properties. Tycho's supernova (SN 1572) provides an opportunity to address observationally the identification of the surviving companion. Here we report a survey of the central region of its remnant, around the position of the explosion, which excludes red giants as the mass donor of the exploding white dwarf. We found a type G0-G2 star, similar to our Sun in surface temperature and luminosity (but lower surface gravity), moving at more than three times the mean velocity of the stars at that distance, which appears to be the surviving companion of the supernova.

  7. Binary progenitor models of type IIb supernovae

    CERN Document Server

    Claeys, J S W; Pols, O R; Eldridge, J J; Baes, M

    2011-01-01

    Massive stars that lose their hydrogen-rich envelope down to a few tenths of a solar mass explode as extended type IIb supernovae, an intriguing subtype that links the hydrogen-rich type II supernovae with the hydrogen-poor type Ib and Ic. The progenitors may be very massive single stars that lose their envelope due to their stellar wind, but mass stripping due to interaction with a companion star in a binary system is currently considered to be the dominant formation channel. We computed an extensive grid of binary models with the Eggleton binary evolution code. The predicted rate from our standard models, which assume conservative mass transfer, is about 6 times smaller than the current rate indicated by observations. It is larger but still comparable to the rate expected from single stars. To recover the observed rate we must generously allow for uncertainties and low accretion efficiencies in combination with limited angular momentum loss from the system. Motivated by the claims of detection and non-detec...

  8. Subretinal transplantation of mouse retinal progenitor cells

    Institute of Scientific and Technical Information of China (English)

    Caihui Jiang; Maonian Zhang; Henry Klassen; Michael Young

    2011-01-01

    The development of cell replacement techniques is promising as a potential treatment for photoreceptor loss. However, the limited integration ability of donor and recipient cells presents a challenge following transplantation. In the present study, retinal progenitor cells (RPCs) were harvested from the neural retinas of enhanced green fluorescent protein mice on postnatal day 1, and expanded in a neurobasal medium supplemented with fetal bovine serum without endothelial growth factor. Using a confocal microscope, immunohistochemistry demonstrated that expanded RPCs in vitro maintain retinal stem cell properties and can be differentiated into photoreceptor cells. Three weeks after transplantation, subretinal transplanted RPCs were found to have migrated and integrated into the outer nuclear layer of recipient retinas with laser injury, some of the integrated cells had differentiated into photoreceptors, and a subpopulation of these cells expressed photoreceptor specific synaptic protein, appearing to form synaptic connections with bipolar cells. These results suggest that subretinal transplantation of RPCs may provide a feasible therapeutic strategy for the loss of retinal photoreceptor cells.

  9. Hepatic progenitors for liver disease: current position

    Directory of Open Access Journals (Sweden)

    Alice Conigliaro

    2010-02-01

    Full Text Available Alice Conigliaro1, David A Brenner2, Tatiana Kisseleva21University “La Sapienza”, Dipartimento di Biotecnologie Cellulari ed Ematologia Policlinico Umberto I, V Clinica Medica, Rome, Italy; 2Department of Medicine, University of California, San Diego, La Jolla, CA, USAAbstract: Liver regeneration restores the original functionality of hepatocytes and cholangiocytes in response to injury. It is regulated on several levels, with different cellular populations contributing to this process, eg, hepatocytes, liver precursor cells, intrahepatic stem cells. In response to injury, mature hepatocytes have the capability to proliferate and give rise to new hepatocytes and cholangiocytes. Meanwhile, liver precursor cells (oval cells have become the most recognized bipotential precursor cells in the damaged liver. They rapidly proliferate, change their cellular composition, and differentiate into hepatocytes and cholangiocytes to compensate for the cellular loss and maintain liver homeostasis. There is a growing body of evidence that oval cells originate from the intrahepatic stem cell(s, which in turn give(s rise to epithelial, including oval cells, and/or other hepatic cells of nonepithelial origin. Since there is a close relationship between the liver and hematopoiesis, bone marrow derived cells can also contribute to liver regeneration by the fusion of myeloid cells with damaged hepatocytes, or differentiation of mesenchymal stem cells into hepatocyte-like cells. The current review discusses the contribution of different cells to liver regeneration and their characteristics.Keywords: hepatic progenitor, liver disease, liver precursor cells, oval cells, hepatocytes, intrahepatic stem cells, cholangiocytes

  10. Harmine stimulates proliferation of human neural progenitors

    Science.gov (United States)

    Dakic, Vanja; Maciel, Renata de Moraes; Drummond, Hannah; Nascimento, Juliana M.; Trindade, Pablo

    2016-01-01

    Harmine is the β-carboline alkaloid with the highest concentration in the psychotropic plant decoction Ayahuasca. In rodents, classical antidepressants reverse the symptoms of depression by stimulating neuronal proliferation. It has been shown that Ayahuasca presents antidepressant effects in patients with depressive disorder. In the present study, we investigated the effects of harmine in cell cultures containing human neural progenitor cells (hNPCs, 97% nestin-positive) derived from pluripotent stem cells. After 4 days of treatment, the pool of proliferating hNPCs increased by 71.5%. Harmine has been reported as a potent inhibitor of the dual specificity tyrosine-phosphorylation-regulated kinase (DYRK1A), which regulates cell proliferation and brain development. We tested the effect of analogs of harmine, an inhibitor of DYRK1A (INDY), and an irreversible selective inhibitor of monoamine oxidase (MAO) but not DYRK1A (pargyline). INDY but not pargyline induced proliferation of hNPCs similarly to harmine, suggesting that inhibition of DYRK1A is a possible mechanism to explain harmine effects upon the proliferation of hNPCs. Our findings show that harmine enhances proliferation of hNPCs and suggest that inhibition of DYRK1A may explain its effects upon proliferation in vitro and antidepressant effects in vivo. PMID:27957390

  11. Harmine stimulates proliferation of human neural progenitors

    Directory of Open Access Journals (Sweden)

    Vanja Dakic

    2016-12-01

    Full Text Available Harmine is the β-carboline alkaloid with the highest concentration in the psychotropic plant decoction Ayahuasca. In rodents, classical antidepressants reverse the symptoms of depression by stimulating neuronal proliferation. It has been shown that Ayahuasca presents antidepressant effects in patients with depressive disorder. In the present study, we investigated the effects of harmine in cell cultures containing human neural progenitor cells (hNPCs, 97% nestin-positive derived from pluripotent stem cells. After 4 days of treatment, the pool of proliferating hNPCs increased by 71.5%. Harmine has been reported as a potent inhibitor of the dual specificity tyrosine-phosphorylation-regulated kinase (DYRK1A, which regulates cell proliferation and brain development. We tested the effect of analogs of harmine, an inhibitor of DYRK1A (INDY, and an irreversible selective inhibitor of monoamine oxidase (MAO but not DYRK1A (pargyline. INDY but not pargyline induced proliferation of hNPCs similarly to harmine, suggesting that inhibition of DYRK1A is a possible mechanism to explain harmine effects upon the proliferation of hNPCs. Our findings show that harmine enhances proliferation of hNPCs and suggest that inhibition of DYRK1A may explain its effects upon proliferation in vitro and antidepressant effects in vivo.

  12. Dual-pump wave mixing in semiconductor optical amplifiers: performance enhancement with long amplifiers

    Science.gov (United States)

    Tomkos, Ioannis; Zacharopoulos, Ioannis; Syvridis, Dimitrios

    1999-05-01

    We demonstrate experimentally the improvement of the performance of the dual pump wave mixing scheme in semiconductor optical amplifiers, using long amplifier chips and high optical pump powers. The optical amplifiers used in the experiment had a ridge waveguide structure with bulk active layer and antireflective-coated angled facets. Measurements of the conversion efficiency and SBR as a function of wavelength shift are presented for a wavelength shift of more than 40 nm. The above measurements are carried out for three amplifier lengths (500 micrometers , 1000 micrometers , and 1500 micrometers ) and for different levels of the optical power of the two pumps. It will be shown that an increase in the amplifier length from 500 micrometers to 1500 micrometers results to an increase of more than 25 dB for the efficiency and more than 20 dB for the SBR. This improvement combined with the inherent advantages of the dual pump scheme (almost constant SBR and high efficiency for large wavelength shifts) results in a highly performing wavelength converter/phase conjugator, suitable for many applications.

  13. Enhanced propagation of photon density waves in random amplifying media

    CERN Document Server

    Renthlei, Lalruatfela; Ramakrishna, S A

    2013-01-01

    We demonstrate enhanced wave-like character of diffuse photon density waves (DPDW) in an amplifying random medium. The amplifying nature makes it contingent to choose the wave solution that grows inside the amplifying medium, and has a propagation vector pointing opposite to the growth direction. This results in negative refraction of the DPDW at an absorbing-amplifying random medium interface as well as the possibility of supporting "anti"-surface-like modes at the interface. A slab of amplifying random medium sandwiched between two absorbing random media supports waveguide resonances that can be utilized to extend the imaging capabilities of DPDW.

  14. Enhanced propagation of photon density waves in random amplifying media

    Science.gov (United States)

    Renthlei, Lalruatfela; Wanare, Harshawardhan; Ramakrishna, S. Anantha

    2015-04-01

    We demonstrate enhanced wavelike character of diffuse photon density waves (DPDW) in an amplifying random medium. The amplifying nature makes it necessary to choose the wave solution that grows inside the amplifying medium, and has a propagation vector pointing opposite to the growth direction. This results in negative refraction of the DPDW at an absorbing-amplifying random medium interface as well as the possibility of supporting "anti"-surface-like modes at the interface. A slab of an amplifying random medium sandwiched between two absorbing random media supports waveguide resonances that can be utilized to extend the imaging capabilities of DPDW.

  15. Cell-Surface Protein Profiling Identifies Distinctive Markers of Progenitor Cells in Human Skeletal Muscle

    Directory of Open Access Journals (Sweden)

    Akiyoshi Uezumi

    2016-08-01

    Full Text Available Skeletal muscle contains two distinct stem/progenitor populations. One is the satellite cell, which acts as a muscle stem cell, and the other is the mesenchymal progenitor, which contributes to muscle pathogeneses such as fat infiltration and fibrosis. Detailed and accurate characterization of these progenitors in humans remains elusive. Here, we performed comprehensive cell-surface protein profiling of the two progenitor populations residing in human skeletal muscle and identified three previously unrecognized markers: CD82 and CD318 for satellite cells and CD201 for mesenchymal progenitors. These markers distinguish myogenic and mesenchymal progenitors, and enable efficient isolation of the two types of progenitors. Functional study revealed that CD82 ensures expansion and preservation of myogenic progenitors by suppressing excessive differentiation, and CD201 signaling favors adipogenesis of mesenchymal progenitors. Thus, cell-surface proteins identified here are not only useful markers but also functionally important molecules, and provide valuable insight into human muscle biology and diseases.

  16. REARRANGEMENT IN THE B-GENOME FROM DIPLOID PROGENITOR TO WHEAT ALLOPOLYPOLID

    Directory of Open Access Journals (Sweden)

    Salina E.A.

    2012-08-01

    Full Text Available Three key periods that were accompanied by considerable rearrangements in the B genome of wheat and its progenitor can be considered. The first period covers the period from the divergence of diploid Triticum and Aegilops species from their common progenitor (2.5–6 million years ago to formation of the tetraploid T. diccocoides (about 500 thousand years ago. Significant genomic rearrangements in the diploid progenitor of the B genome, Ae. speltoides (SS genome, involved a considerable amplification of repeated DNA sequences, which led to an increase in the number of heterochromatin blocks on chromosomes relative to other diploid Aegilops and Triticum species. Our analysis has demonstrated that during this period the Spelt1 repeats intensively amplified as well as several mobile elements proliferated, in particular, the genome-specific gypsy LTR-retrotransposon Fatima and CACTA DNA-transposon Caspar. The second period in the B-genome evolution was associated with the emergence of tetraploid (BBAA genome and its subsequent evolution. The third most important event leading to the next rearrangement of the B genome took place relatively recently, 7000–9500 years ago, being associated with the emergence of hexaploid wheat with the genomic formula BBAADD. The evolution of the B/S genome involved intergenomic and intragenomic translocations and chromosome inversions. So far, five rearrangements in the B-genome chromosomes of polyploid wheats has been observed and described; the majority of them took place during the formation and evolution of tetraploid species. The mapping of the S-genome chromosomes and comparison with the B-genome chromosome maps have demonstrated that individual rearrangements pre-existed in Ae. speltoides; moreover, Ae. speltoides is polymorphic for these rearrangements.Chromosome 5B is nearly 870 Mbp (5BL = 580 Mbp and 5BS = 290 Mbp and is known to carry important genes controlling the key aspects of wheat biology, in

  17. Time amplifying techniques towards atomic time resolution

    Institute of Scientific and Technical Information of China (English)

    LI JingZhen

    2009-01-01

    High speed imaging technology has opened applications in many fields,such as collision,detonating,high voltage discharge,disintegration and transfer of phonon and exciton in solid,photosynthesis primitive reaction,and electron dynamics inside atom shell.In principle,all of the transient processes need to be explained theoretically and,st the same time,the time amplifying technique is required for observations of these processes.The present review concerns the atomic time amplifying mechanism of optical information and the extremely-high speed imaging methods,which are expressed in terms of the short time amplifying techniques.It is well-known that for extremely-high speed imaging with the converter tube,the temporal resolution is in the order of sub-picosecond of the streak imaging,and the imaging frequency is 6×10~8-5×10~9 fps(frame per second)of the frame imaging.On the other hand,for the tubeless extremely-high speed imaging,the imaging frequency is 10~7-10~(14) fps,and its mechanism of forming high speed and framing could involve a lot of factors of the light under investigation,for instance,light speed,light parallelism,the parameters of light wave such as amplitude,phase,polarization and wavelength,and even quantum properties of photon.In the cascaded system of electromagnetic wave and particle wave,it is possible to simultaneously realize extremely-high resolution in time and space,which is higher than a kite resolution.Then it would be possible to break the limit of the Heisenberg uncertainty relation of the optical frequency band.

  18. Time amplifying techniques towards atomic time resolution

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    High speed imaging technology has opened applications in many fields,such as collision,detonating, high voltage discharge,disintegration and transfer of phonon and exciton in solid,photosynthesis primitive reaction,and electron dynamics inside atom shell.In principle,all of the transient processes need to be explained theoretically and,at the same time,the time amplifying technique is required for observations of these processes.The present review concerns the atomic time amplifying mechanism of optical information and the extremely-high speed imaging methods,which are expressed in terms of the short time amplifying techniques.It is well-known that for extremely-high speed imaging with the converter tube,the temporal resolution is in the order of sub-picosecond of the streak imaging,and the imaging frequency is 6×10 8 ―5×10 9 fps(frame per second)of the frame imaging.On the other hand,for the tubeless extremely-high speed imaging,the imaging frequency is 10 7 ―10 14 fps,and its mechanism of forming high speed and framing could involve a lot of factors of the light under investigation,for instance,light speed,light parallelism,the parameters of light wave such as amplitude,phase,polari- zation and wavelength,and even quantum properties of photon.In the cascaded system of electro- magnetic wave and particle wave,it is possible to simultaneously realize extremely-high resolution in time and space,which is higher than a kite resolution.Then it would be possible to break the limit of the Heisenberg uncertainty relation of the optical frequency band.

  19. Interleukin-1 regulates proliferation and differentiation of oligodendrocyte progenitor cells.

    Science.gov (United States)

    Vela, José M; Molina-Holgado, Eduardo; Arévalo-Martín, Angel; Almazán, Guillermina; Guaza, Carmen

    2002-07-01

    Interleukin-1 (IL-1) is a pleiotropic cytokine expressed during normal CNS development and in inflammatory demyelinating diseases, but remarkably little is known about its effect on oligodendroglial cells. In this study we explored the role of IL-1beta in oligodendrocyte progenitors and differentiated oligodendrocytes. The effects of IL-1beta were compared to those of IL-1 receptor antagonist, the specific inhibitor of IL-1 activity, since progenitors and differentiated oligodendrocytes produce IL-1beta and express IL-1 receptors. Unlike other proinflammatory cytokines (TNFalpha and IFNgamma), IL-1beta was not toxic for oligodendrocyte lineage cells. However, this cytokine inhibited proliferation of oligodendrocyte progenitors in the presence of growth factors (PDGF plus bFGF). This was evidenced by a significant decrease in both cells incorporating bromodeoxyuridine (45%) and total cell numbers (57%) after 6 days of treatment. Interestingly, IL-1beta blocked proliferation at the late progenitor/prooligodendrocyte (O4+) stage but did not affect proliferation of early progenitors (A2B5+). Inhibition of proliferation paralleled with promotion of differentiation, as revealed by the increased percentage of R-mab+ cells (6.7-fold). Moreover, when oligodendrocyte progenitors were allowed to differentiate in the absence of growth factors, treatment with IL-1beta promoted maturation to the MBP+ stage (4.2-fold) and survival of differentiating oligodendrocytes (2.1-fold). Regarding intracellular signaling, IL-1beta activated the p38 mitogen-activated protein kinase (MAPK) but not the p42/p44 MAPK and, when combined with growth factors, intensified p38 activation but inhibited the growth-factor-induced p42/p44 activation. IL-1beta also induced a time-dependent inhibition of PFGF-Ralpha gene expression. These results support a role for IL-1beta in promoting mitotic arrest and differentiation of oligodendrocyte progenitors as well as maturation and survival of differentiating

  20. Investigations of electronic amplifiers supplying a piezobimorph actuator

    Science.gov (United States)

    Milecki, Andrzej; Regulski, Roman

    2016-10-01

    Piezoelectric bending actuators, also known as bimorphs, are characterized by very good dynamic properties and by displacements in a range of a few millimeters. Therefore these actuators are used in a wide range of applications. However their usage is limited because they require supplying amplifiers with output voltage of about 200 V, which are rather expensive. This paper presents investigation results of such amplifiers with high voltage output. The model of a piezobending actuator is proposed and implemented in Matlab-Simulink software in order to simulate the behavior of the actuator supplied by the amplifiers. The simulation results are presented and compared with investigation results of high voltage amplifier used for supplying a piezoactuator. The influence of current limitation of operational amplifier on the actuator current is tested. Finally, a low cost audio power amplifier is proposed to control the piezobender actuator (as a cheaper alternative to the high-voltage amplifier) and its investigations results are presented in the paper.

  1. Low power RF amplifier circuit for ion trap applications

    Science.gov (United States)

    Noriega, J. R.; García-Delgado, L. A.; Gómez-Fuentes, R.; García-Juárez, A.

    2016-09-01

    A low power RF amplifier circuit for ion trap applications is presented and described. The amplifier is based on a class-D half-bridge amplifier with a voltage mirror driver. The RF amplifier is composed of an RF class-D amplifier, an envelope modulator to ramp up the RF voltage during the ion analysis stage, a detector or amplitude demodulation circuit for sensing the output signal amplitude, and a feedback amplifier that linearizes the steady state output of the amplifier. The RF frequency is set by a crystal oscillator and the series resonant circuit is tuned to the oscillator frequency. The resonant circuit components have been chosen, in this case, to operate at 1 MHz. In testings, the class-D stage operated at a maximum of 78 mW at 1.1356 MHz producing 225 V peak.

  2. Gain flattened distributed fiber raman amplifiers

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An S band and a C band distributed fiber Raman amplifiers (DFRAs) with flattened gain and compensated dispersion have been studied and implemented with 1 427 nm and 1 455 nm mono-wavelength fiber Raman lasers as the pumped sources respectively. The gain of single-wave pumped S band and C band can reach 10 dB and 15 dB respectively. And a 50 nm gain flattened width was successfully obtained by using a chirp fiber Bragg grating (CFBG) gain flattened filter with gain ripple of 0.6 dB. The C band DFRA has been applied to CDMA wireless communication system successfully.

  3. Feedback analysis of transimpedance operational amplifier circuits

    OpenAIRE

    Bruun, Erik

    1993-01-01

    The transimpedance or current feedback operational amplifier (CFB op-amp) is reviewed and compared to a conventional voltage mode op-amp using an analysis emphasizing the basic feedback characteristics of the circuit. With this approach the paradox of the constant bandwidth obtained from CFB op-amps is explained. It is demonstrated in a simple manner that the constant gain-bandwidth product of the conventional op-amp and the constant bandwidth of the CFB op-amp are both in accordance with bas...

  4. Endothelial progenitor cells and integrins: adhesive needs

    Directory of Open Access Journals (Sweden)

    Caiado Francisco

    2012-03-01

    Full Text Available Abstract In the last decade there have been multiple studies concerning the contribution of endothelial progenitor cells (EPCs to new vessel formation in different physiological and pathological settings. The process by which EPCs contribute to new vessel formation in adults is termed postnatal vasculogenesis and occurs via four inter-related steps. They must respond to chemoattractant signals and mobilize from the bone marrow to the peripheral blood; home in on sites of new vessel formation; invade and migrate at the same sites; and differentiate into mature endothelial cells (ECs and/or regulate pre-existing ECs via paracrine or juxtacrine signals. During these four steps, EPCs interact with different physiological compartments, namely bone marrow, peripheral blood, blood vessels and homing tissues. The success of each step depends on the ability of EPCs to interact, adapt and respond to multiple molecular cues. The present review summarizes the interactions between integrins expressed by EPCs and their ligands: extracellular matrix components and cell surface proteins present at sites of postnatal vasculogenesis. The data summarized here indicate that integrins represent a major molecular determinant of EPC function, with different integrin subunits regulating different steps of EPC biology. Specifically, integrin α4β1 is a key regulator of EPC retention and/or mobilization from the bone marrow, while integrins α5β1, α6β1, αvβ3 and αvβ5 are major determinants of EPC homing, invasion, differentiation and paracrine factor production. β2 integrins are the major regulators of EPC transendothelial migration. The relevance of integrins in EPC biology is also demonstrated by many studies that use extracellular matrix-based scaffolds as a clinical tool to improve the vasculogenic functions of EPCs. We propose that targeted and tissue-specific manipulation of EPC integrin-mediated interactions may be crucial to further improve the usage of

  5. Intermediate Progenitor Cohorts Differentially Generate Cortical Layers and Require Tbr2 for Timely Acquisition of Neuronal Subtype Identity.

    Science.gov (United States)

    Mihalas, Anca B; Elsen, Gina E; Bedogni, Francesco; Daza, Ray A M; Ramos-Laguna, Kevyn A; Arnold, Sebastian J; Hevner, Robert F

    2016-06-28

    Intermediate progenitors (IPs) amplify the production of pyramidal neurons, but their role in selective genesis of cortical layers or neuronal subtypes remains unclear. Using genetic lineage tracing in mice, we find that IPs destined to produce upper cortical layers first appear early in corticogenesis, by embryonic day 11.5. During later corticogenesis, IP laminar fates are progressively limited to upper layers. We examined the role of Tbr2, an IP-specific transcription factor, in laminar fate regulation using Tbr2 conditional mutant mice. Upon Tbr2 inactivation, fewer neurons were produced by immediate differentiation and laminar fates were shifted upward. Genesis of subventricular mitoses was, however, not reduced in the context of a Tbr2-null cortex. Instead, neuronal and laminar differentiation were disrupted and delayed. Our findings indicate that upper-layer genesis depends on IPs from many stages of corticogenesis and that Tbr2 regulates the tempo of laminar fate implementation for all cortical layers.

  6. Intermediate Progenitor Cohorts Differentially Generate Cortical Layers and Require Tbr2 for Timely Acquisition of Neuronal Subtype Identity

    Directory of Open Access Journals (Sweden)

    Anca B. Mihalas

    2016-06-01

    Full Text Available Intermediate progenitors (IPs amplify the production of pyramidal neurons, but their role in selective genesis of cortical layers or neuronal subtypes remains unclear. Using genetic lineage tracing in mice, we find that IPs destined to produce upper cortical layers first appear early in corticogenesis, by embryonic day 11.5. During later corticogenesis, IP laminar fates are progressively limited to upper layers. We examined the role of Tbr2, an IP-specific transcription factor, in laminar fate regulation using Tbr2 conditional mutant mice. Upon Tbr2 inactivation, fewer neurons were produced by immediate differentiation and laminar fates were shifted upward. Genesis of subventricular mitoses was, however, not reduced in the context of a Tbr2-null cortex. Instead, neuronal and laminar differentiation were disrupted and delayed. Our findings indicate that upper-layer genesis depends on IPs from many stages of corticogenesis and that Tbr2 regulates the tempo of laminar fate implementation for all cortical layers.

  7. Chief sources of brachiopod recovery from the end Ordovician mass extinction with special references to progenitors

    Institute of Scientific and Technical Information of China (English)

    戎嘉余; 詹仁斌

    1999-01-01

    Survivor, Lazarus and progenitor taxa are sources of biotic recovery following mass extinction. Investigations of the benthic brachiopods through the latest Ordovician mass extinction shows that progenitors developed many evolutionary novelties and successful surviving mechanisms. They are superior to survivors and Lazarus taxa in their ability to adapt to environmental changes. They are the primary source of macroevolution and the ancestors of a number of new taxa. Three kinds of progenitors are recognized based on the Ordovician-Silurian brachiopods from South China: survivor-progenitors, crisis-progenitors and Lazarus-progenitors; the last has the strongest ability to resist adverse environments, and is the most diverse and abundant.

  8. Design criteria for ultrafast optical parametric amplifiers

    Science.gov (United States)

    Manzoni, C.; Cerullo, G.

    2016-10-01

    Optical parametric amplifiers (OPAs) exploit second-order nonlinearity to transfer energy from a fixed frequency pump pulse to a variable frequency signal pulse, and represent an easy way of tuning over a broad range the frequency of an otherwise fixed femtosecond laser system. OPAs can also act as broadband amplifiers, transferring energy from a narrowband pump to a broadband signal and thus considerably shortening the duration of the pump pulse. Due to these unique properties, OPAs are nowadays ubiquitous in ultrafast laser laboratories, and are employed by many users, such as solid state physicists, atomic/molecular physicists, chemists and biologists, who are not experts in ultrafast optics. This tutorial paper aims at providing the non-specialist reader with a self-consistent guide to the physical foundations of OPAs, deriving the main equations describing their performance and discussing how they can be used to understand their most important working parameters (frequency tunability, bandwidth, pulse energy/repetition rate scalability, control over the carrier-envelope phase of the generated pulses). Based on this analysis, we derive practical design criteria for OPAs, showing how their performance depends on the type of the nonlinear interaction (crystal type, phase-matching configuration, crystal length), on the characteristics of the pump pulse (frequency, duration, energy, repetition rate) and on the OPA architecture.

  9. Hot prospect for new gene amplifier

    Energy Technology Data Exchange (ETDEWEB)

    1991-11-29

    Molecular biologist Francis Barany is investigating one of the hottest areas in biotechnology: a gene-amplification technique called ligase chain reaction, or LCR. Already scientists have used LCR to detect the tiny mutation that causes sickle cell anemia and have adapted it to screen for a handful of other genetic diseases simultaneously - in a single test-tube. Some experts, in fact, are predicting that LCR will supplement the polymerase chain reaction (PCR), and in some cases even supplant it. LCR could revolutionize DNA diagnostics just as PCR transformed basic molecular biology following its introduction 6 years ago. With its ease of automation and ability to produce useful quantitative results, LCR could become a major player in the rapidly growing market for DNA diagnostics. LCR, like PCR, uses snippets of nucleic acid, or oligonucleotides, that anneal to a specific, complementary sequence on the target DNA to be amplified. But where PCR uses oligos that bracket the stretch to be amplified, LCR uses pairs of oligos that completely cover the target sequence.

  10. Backward Raman Amplifier for Laser Wakefield Accelerator

    Science.gov (United States)

    Ludwig, Joshua; Masson-Laborde, Paul-Edouard; Huller, Stefan; Rozmus, Wojciech; Wilks, Scott C.

    2016-10-01

    Particle in cell simulations via SCPIC and theoretical work on Raman amplification and laser wake field acceleration will be presented. Laser energy depletion has been shown to be a limiting factor during wake field acceleration. This work focuses on optimizing parameters for Raman amplification to work in conjunction with wake field acceleration in order in order to sustain an accelerating laser pulse as it generates plasma waves. It has been shown that laser pulses undergo red shifting during wake generation. Our work demonstrates that this red shifting results in a detuning between pump and seed in the backward Raman Amplifier. This detuning limits the amount of energy that can be transferred from the pump to the seed, and places new limits on backward Raman amplification. To overcome this limiting factor, this study makes use of a chirped pump allowing for extended coupling to the accelerating pulse. Three wave coupling model of Raman amplifier with a frequency shift term due to wake field will also be discussed and compared with PIC simulations.

  11. Amplified Fiber-Loop Ringdown Spectroscopy

    Science.gov (United States)

    Litman, Jessica; Barnes, Jack; Loock, Hans-Peter

    2009-06-01

    Many commercial liquid chemical analysis systems, such as high-performance liquid chromatography (HPLC) or capillary electrophoresis consist of a separation followed by optical detection. Besides small volumes and low detection limits, the system should also allow the detection of a large variety of analytes. Existing absorption and fluorescence detectors are often not very sensitive or require labelling. Here, an absorption detector is presented based on cavity ring-down spectroscopy (CRDS) where the optical cavity is made from fibre optic waveguides and the light source is a continuous wave (cw) diode laser. The purpose of this project is to increase the detection of analytes through their overtone absorption in the telecom region at 1300 to 1500 nm. This is done by increasing the ratio of desired loss (extinction caused by the sample), to undesirable loss (due to the waveguides or solvents) through amplification of the ringdown signal using a gain-clamped erbium doped fibre amplifier (EDFA). The amplified cavity has a round-trip time of 750 ns and we achieved a detection limit of at most 250 ppm when measuring acetylene at 1532.83 nm. The application of our method to detection of dissolved analytes or particles in liquids will be discussed.

  12. Development of 3 kW at 325 MHz solid-state RF power amplifier using four power amplifier modules

    Science.gov (United States)

    Ramarao, B. V.; Sonal, S.; Mishra, J. K.; Pande, M.; Singh, P.; Kumar, G.; Mukherjee, J.

    2014-01-01

    A high power solid-state RF power amplifier of 3 kW at 325 MHz has been developed using only four RF power amplifier modules of 850 W power output each. The design and characterization of RF power modules have been presented. A four way Wilkinson power combiner adds the output of four power amplifier modules with a total transmission loss of less than 6%. The combined power amplifier has a power gain of 20.2 dB at 1-dB compression point, and the corresponding output power is 2.8 kW at 325 MHz. The drain efficiency of the power amplifier is 65.3% at 3 kW. All the harmonics of this amplifier are below -40 dBc. The amplifier has better characteristics like fewer numbers of active devices per kilo watt, high efficiency, high gain, and ruggedness etc for RF accelerator applications.

  13. The Progenitor of the Type IIb SN 2008ax Revisited

    CERN Document Server

    Folatelli, Gastón; Kuncarayakti, Hanindyo; Benvenuto, Omar G; Maeda, Keiichi; Nomoto, Ken'ichi

    2015-01-01

    Hubble Space Telescope observations of the site of the supernova (SN) 2008ax obtained in 2011 and 2013 reveal that the possible progenitor object detected in pre-explosion images was in fact multiple. Four point sources are resolved in the new, higher-resolution images. We identify one of the sources with the fading SN. The other three objects are consistent with single supergiant stars. We conclude that their light contaminated the previously identified progenitor candidate. After subtraction of these stars, the progenitor appears to be significantly fainter and bluer than previously measured. Post-explosion photometry at the SN location indicates that the progenitor object has disappeared. If single, the progenitor is compatible with a supergiant star of B to mid-A spectral type, while a Wolf-Rayet (WR) star would be too luminous in the ultraviolet to account for the observations. Moreover, our hydrodynamical modelling shows the pre-explosion mass was $4-5$ $M_\\odot$ and the radius was $30-50$ $R_\\odot$, wh...

  14. THE TYPE IIb SUPERNOVA 2011dh FROM A SUPERGIANT PROGENITOR

    Energy Technology Data Exchange (ETDEWEB)

    Bersten, Melina C.; Nomoto, Ken' ichi; Folatelli, Gaston; Maeda, Keiichi [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Benvenuto, Omar G. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, B1900FWA La Plata (Argentina); Ergon, Mattias; Sollerman, Jesper [The Oskar Klein Centre, Department of Astronomy, AlbaNova, SE-106 91 Stockholm (Sweden); Benetti, Stefano; Ochner, Paolo; Tomasella, Lina [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Botticella, Maria Teresa [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Fraser, Morgan; Kotak, Rubina, E-mail: melina.bersten@ipmu.jp [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom)

    2012-09-20

    A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star-with R {approx} 200 R{sub Sun }-is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the yellow super-giant star detected at the location of the supernova (SN) in deep pre-explosion images is the progenitor star. From the main peak of the bolometric LC and expansion velocities, we constrain the mass of the ejecta to be Almost-Equal-To 2 M{sub Sun }, the explosion energy to be E = (6-10) Multiplication-Sign 10{sup 50} erg, and the {sup 56}Ni mass to be approximately 0.06 M{sub Sun }. The progenitor star was composed of a helium core of 3-4 M{sub Sun} and a thin hydrogen-rich envelope of Almost-Equal-To 0.1M{sub Sun} with a main-sequence mass estimated to be in the range of 12-15 M{sub Sun }. Our models rule out progenitors with helium-core masses larger than 8 M{sub Sun }, which correspond to M{sub ZAMS} {approx}> 25M{sub Sun }. This suggests that a single star evolutionary scenario for SN 2011dh is unlikely.

  15. The Type IIb Supernova 2011dh from a Supergiant Progenitor

    CERN Document Server

    Bersten, Melina C; Nomoto, Ken'ichi; Ergon, Mattias; Folatelli, Gastón; Sollerman, Jesper; Benetti, Stefano; Botticella, Maria Teresa; Fraser, Morgan; Kotak, Rubina; Maeda, Keiichi; Ochner, Paolo; Tomasella, Lina

    2012-01-01

    A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star ---with R ~200 Rsun---, is needed to reproduce the early light curve of SN 2011dh. This is consistent with the suggestion that the yellow super-giant star detected at the location of the SN in deep pre-explosion images is the progenitor star. From the main peak of the bolometric light curve and expansion velocities we constrain the mass of the ejecta to be ~2 Msun, the explosion energy to be E= 6-10 x 10^50 erg, and the 56Ni mass to be approximately 0.06 Msun. The progenitor star was composed of a helium core of 3 to 4 Msun and a thin hydrogen-rich envelope of ~0.1 M_sun with a main sequence mass estimated to be in the range of 12--15 Msun. Our models rule out progenitors with helium-core masses larger than 8 Msun, which correspond to M_ZAMS > 25 Msun. This suggests that a single star evolutionary scenario for SN 2011dh is unlikely.

  16. The progenitor mass of the magnetar SGR1900+14

    CERN Document Server

    Davies, Ben; Kudritzki, Rolf-Peter; Trombley, Christine; Kouveliotou, Chryssa; Wachter, Stefanie

    2009-01-01

    Magnetars are young neutron stars with extreme magnetic fields (B > 10^{14}-10^{15}G). How these fields relate to the properties of their progenitor stars is not yet clearly established. However, from the few objects associated with young clusters it has been possible to estimate the initial masses of the progenitors, with results indicating that a very massive progenitor star (M_prog >40Msun) is required to produce a magnetar. Here we present adaptive-optics assisted Keck/NIRC2 imaging and Keck/NIRSPEC spectroscopy of the cluster associated with the magnetar SGR 1900+14, and report that the initial progenitor star mass of the magnetar was a factor of two lower than this limit, M_prog=17 \\pm 2 Msun. Our result presents a strong challenge to the concept that magnetars can only result from very massive progenitors. Instead, we favour a mechanism which is dependent on more than just initial stellar mass for the production of these extreme magnetic fields, such as the "fossil-field" model or a process involving c...

  17. Ex vivo expansion of human peripheral blood progenitors.

    Science.gov (United States)

    Chabannon, C; Herrera-Rodriguez, D; Bardin, F; Mouren, M; Novakovitch, G; Blaise, D; Maraninchi, D; Mannoni, P

    1995-01-01

    Culture of human hematopoietic progenitors on a large scale could lead to several clinical applications within the near future, including the production of differentiated and functional cells, the increase in the number of early progenitors, especially stem cells, with such use as gene transfer, or the improvement of grafts used to limit the hematological toxicity associated with high-dose chemotherapy. In this case, one can still distinguish different objectives: improvement of grafts that contain low numbers of progenitors because of prior chemotherapies or because of marrow involvement for example, and qualitative changes in the graft content that would allow to envision the disappearance, or the further reduction, in the duration of absolute neutropenia that follows delivery of high dose chemotherapy ("nadir rescue"), despite substitution of mobilized blood cells to marrow cells and the in vivo use of hematopoietic growth factors. Additional advantages may be related to tumor purging in autologous expanded cells, and to the change in the ratio between hematopoietic progenitors and immunocompetent cells in allogeneic expanded populations. Therefore it appears that in vitro expansion currently raises two types of questions: the first ones are related to the definition of clinical or biological endpoints to be achieved, the second ones are related to "bioengineering", and deal with the efficiency and safety of progenitor cell cultures to be used for clinical applications. We here present preliminary results preparing future pilot clinical studies with ex vivo cultured human hematopoietic cells.

  18. On the Progenitor of the Type IIb Supernova 2016gkg

    CERN Document Server

    Kilpatrick, Charles D; Abramson, Louis E; Pan, Yen-Chen; Lu, Cicero-Xinyu; Williams, Peter; Treu, Tommaso; Siebert, Matthew R; Fassnacht, Christopher D; Max, Claire E

    2016-01-01

    We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck Adaptive Optics system was used to perform relative astrometry between the Keck and HST imaging. We identify a single point source in the HST images coincident with the SN position to 0.89-sigma. The HST photometry is consistent with the progenitor star being an A0Ia star with T=9500 K and log (L/Lsun)=5.15. We find that the SN 2016gkg progenitor star appears more consistent with binary than single-star evolutionary models. In addition, early-time light curve data from SN 2016gkg revealed a rapid rise in luminosity within ~0.4 days of non-detection limits, consistent with models of the cooling phase after shock break-out. We use these data to determine an explosion date of 20.15 September 2016 and progenitor star radius of log (R/Rsun)=2.41, which agrees with photometry from the progenitor star....

  19. Clusters of neural stem/progenitor cells cultured on a soft poly(vinyl alcohol) hydrogel crosslinked by gamma irradiation.

    Science.gov (United States)

    Mori, Hideki; Hara, Masayuki

    2016-05-01

    Neural stem/progenitor cells (NSPCs) in the central nervous system (CNS) have the capacity to self-renew by proliferation and are multipotent, giving rise to neurons, astrocytes, and oligodendrocytes. NSPCs can be amplified in neurosphere suspension cultures for cell transplantation therapy to treat CNS diseases as well as for in vitro pharmacological/toxicological assays; however, these suspension cultures have certain limitations, including the inconvenience of changing the culture medium as well as difficulty of live imaging. In the present study, we prepared a gamma-crosslinked poly(vinyl alcohol) (PVA) hydrogel and assessed its suitability as a substrate for adherent NSPC cultures. Differentiation was determined by evaluating the expression of the markers nestin (progenitors), βIII tubulin (neurons), and glial fibrillary acidic protein and S100β (glia) by immunocytochemistry and quantitative reverse transcriptase PCR. The levels of the marker genes were similar between the two types of culture; although some variability was observed, there were no fold differences in expression. NSPCs adhered to the PVA gel as clusters and grew without differentiating into neurons and glia. The proliferation rate of cells grown on the soft PVA gel [3.75-7.5% (w/v) PVA] was approximately 70% of that of neurospheres in suspension. We conclude that gamma-crosslinked PVA hydrogels can function as a novel scaffold for maintaining adherent NSPCs in an undifferentiated state.

  20. ID1 Is a Functional Marker for Intestinal Stem and Progenitor Cells Required for Normal Response to Injury

    Directory of Open Access Journals (Sweden)

    Ning Zhang

    2014-11-01

    Full Text Available LGR5 and BMI1 mark intestinal stem cells in crypt base columnar cells and +4 position cells, respectively, but characterization of functional markers in these cell populations is limited. ID1 maintains the stem cell potential of embryonic, neural, and long-term repopulating hematopoietic stem cells. Here, we show in both human and mouse intestine that ID1 is expressed in cycling columnar cells, +4 position cells, and transit-amplifying cells in the crypt. Lineage tracing revealed ID1+ cells to be self-renewing, multipotent stem/progenitor cells that are responsible for the long-term renewal of the intestinal epithelium. Single ID1+ cells can generate long-lived organoids resembling mature intestinal epithelium. Complete knockout of Id1 or selective deletion of Id1 in intestinal epithelium or in LGR5+ stem cells sensitizes mice to chemical-induced colon injury. These experiments identify ID1 as a marker for intestinal stem/progenitor cells and demonstrate a role for ID1 in maintaining the potential for repair in response to colonic injury.

  1. N-cadherin/FGFR promotes metastasis through epithelial-to-mesenchymal transition and stem/progenitor cell-like properties.

    Science.gov (United States)

    Qian, X; Anzovino, A; Kim, S; Suyama, K; Yao, J; Hulit, J; Agiostratidou, G; Chandiramani, N; McDaid, H M; Nagi, C; Cohen, H W; Phillips, G R; Norton, L; Hazan, R B

    2014-06-26

    N-cadherin and HER2/neu were found to be co-expressed in invasive breast carcinomas. To test the contribution of N-cadherin and HER2 in mammary tumor metastasis, we targeted N-cadherin expression in the mammary epithelium of the MMTV-Neu mouse. In the context of ErbB2/Neu, N-cadherin stimulated carcinoma cell invasion, proliferation and metastasis. N-cadherin caused fibroblast growth factor receptor (FGFR) upmodulation, resulting in epithelial-to-mesenchymal transition (EMT) and stem/progenitor like properties, involving Snail and Slug upregulation, mammosphere formation and aldehyde dehydrogenase activity. N-cadherin potentiation of the FGFR stimulated extracellular signal regulated kinase (ERK) and protein kinase B (AKT) phosphorylation resulting in differential effects on metastasis. Although ERK inhibition suppressed cyclin D1 expression, cell proliferation and stem/progenitor cell properties, it did not affect invasion or EMT. Conversely, AKT inhibition suppressed invasion through Akt 2 attenuation, and EMT through Snail inhibition, but had no effect on cyclin D1 expression, cell proliferation or mammosphere formation. These findings suggest N-cadherin/FGFR has a pivotal role in promoting metastasis through differential regulation of ERK and AKT, and underscore the potential for targeting the FGFR in advanced ErbB2-amplified breast tumors.

  2. Power amplifiers in CMOS technology : a contribution to power amplifier theory and techniques

    NARCIS (Netherlands)

    Acar, Mustafa

    2011-01-01

    In order to meet the demands from the market on cheaper, miniaturized mobile communications devices realization of RF power amplifiers(PAs) in the mainstream CMOS technology is essential. In general, CMOS PAs require high supply-voltage to decrease the matching network losses and for high output pow

  3. Rates and progenitors of type Ia supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Wood-Vasey, William Michael [Univ. of California, Berkeley, CA (United States)

    2004-01-01

    analyzing the true sensitivity of a multi-epoch supernova search and finds a Type Ia supernova rate from z ~ 0.01-0.1 of rV = 4.26$+1.39 +0.10\\atop{-1.93 -0.10}$h3 x 10-4 SNe Ia/yr/Mpc3 from a preliminary analysis of a subsample of the SNfactory prototype search. Several unusual supernovae were found in the course of the SNfactory prototype search. One in particular, SN 2002ic, was the first SN Ia to exhibit convincing evidence for a circumstellar medium and offers valuable insight into the progenitors of Type Ia supernovae.

  4. Close Binary Progenitors and Ejected Companions of Thermonuclear Supernovae

    Science.gov (United States)

    Geier, S.; Kupfer, T.; Heber, U.; Nemeth, P.; Ziegerer, E.; Irrgang, A.; Schindewolf, M.; Marsh, T. R.; Gänsicke, B. T.; Barlow, B. N.; Bloemen, S.

    2017-03-01

    Hot subdwarf stars (sdO/Bs) are evolved core helium-burning stars with very thin hydrogen envelopes, which can be formed by common envelope ejection. Close sdB binaries with massive white dwarf (WD) companions are potential progenitors of thermonuclear supernovae type Ia (SN Ia). We discovered such a progenitor candidate as well as a candidate for a surviving companion star, which escapes from the Galaxy. More candidates for both types of objects have been found by cross-matching known sdB stars with proper motion and light curve catalogues. We found 72 sdO/B candidates with high Galactic restframe velocities, 12 of them might be unbound to our Galaxy. Furthermore, we discovered the second-most compact sdB+WD binary known. However, due to the low mass of the WD companion, it is unlikely to be a SN Ia progenitor.

  5. Establishment of bipotent progenitor cell clone from rat skeletal muscle.

    Science.gov (United States)

    Murakami, Yousuke; Yada, Erica; Nakano, Shin-ichi; Miyagoe-Suzuki, Yuko; Hosoyama, Tohru; Matsuwaki, Takashi; Yamanouchi, Keitaro; Nishihara, Masugi

    2011-12-01

    The present study describes the isolation, cloning and characterization of adipogenic progenitor cells from rat skeletal muscle. Among the obtained 10 clones, the most highly adipogenic progenitor, 2G11 cells, were further characterized. In addition to their adipogenicity, 2G11 cells retain myogenic potential as revealed by formation of multinucleated myotubes when co-cultured with myoblasts. 2G11 cells were resistant to an inhibitory effect of basic fibroblast growth factor on adipogenesis, while adipogenesis of widely used preadipogenic cell line, 3T3-L1 cells, was suppressed almost completely by the same treatment. In vivo transplantation experiments revealed that 2G11 cells are able to possess both adipogenicity and myogenicity in vivo. These results indicate the presence of bipotent progenitor cells in rat skeletal muscle, and suggest that such cells may contribute to ectopic fat formation in skeletal muscle.

  6. Flow cytometric data analysis of circulating progenitor cell stability

    Directory of Open Access Journals (Sweden)

    Ernestine A. Mahar

    2017-02-01

    We performed a quality control assessment of the stability of circulating blood progenitor cells in blood samples stored at 4 °C, to determine the time period during which blood samples can be analyzed and yield consistent data for progenitor cell content. Healthy volunteers (n=6 were recruited and underwent phlebotomy, and blood was stored in EDTA tubes at 4 °C. Flow cytometry was performed to quantitate progenitor cell subsets at 0–4 h, 24 h, and 48 h post phlebotomy. All processed samples were fixed with 1% Paraformaldehyde and 1,000,000 total data events were collected. We found no significant differences in PC data for both CD34+ (P=0.68 for one-way ANOVA and CD34+/CD133+ (P=0.74 for one-way ANOVA.

  7. Wnt2 Regulates Progenitor Proliferation in the Developing Ventral Midbrain*

    Science.gov (United States)

    Sousa, Kyle M.; Villaescusa, J. Carlos; Cajanek, Lukas; Ondr, Jennifer K.; Castelo-Branco, Goncalo; Hofstra, Wytske; Bryja, Vitezslav; Palmberg, Carina; Bergman, Tomas; Wainwright, Brandon; Lang, Richard A.; Arenas, Ernest

    2010-01-01

    Wnts are secreted, lipidated proteins that regulate multiple aspects of brain development, including dopaminergic neuron development. In this study, we perform the first purification and signaling analysis of Wnt2 and define the function of Wnt2 in ventral midbrain precursor cultures, as well as in Wnt2-null mice in vivo. We found that purified Wnt2 induces the phosphorylation of both Lrp5/6 and Dvl-2/3, and activates β-catenin in SN4741 dopaminergic cells. Moreover, purified Wnt2 increases progenitor proliferation, and the number of dopaminergic neurons in ventral midbrain precursor cultures. In agreement with these findings, analysis of the ventral midbrain of developing Wnt2-null mice revealed a decrease in progenitor proliferation and neurogenesis that lead to a decrease in the number of postmitotic precursors and dopaminergic neurons. Collectively, our observations identify Wnt2 as a novel regulator of dopaminergic progenitors and dopaminergic neuron development. PMID:20018874

  8. Wnt2 regulates progenitor proliferation in the developing ventral midbrain.

    Science.gov (United States)

    Sousa, Kyle M; Villaescusa, J Carlos; Cajanek, Lukas; Ondr, Jennifer K; Castelo-Branco, Goncalo; Hofstra, Wytske; Bryja, Vitezslav; Palmberg, Carina; Bergman, Tomas; Wainwright, Brandon; Lang, Richard A; Arenas, Ernest

    2010-03-05

    Wnts are secreted, lipidated proteins that regulate multiple aspects of brain development, including dopaminergic neuron development. In this study, we perform the first purification and signaling analysis of Wnt2 and define the function of Wnt2 in ventral midbrain precursor cultures, as well as in Wnt2-null mice in vivo. We found that purified Wnt2 induces the phosphorylation of both Lrp5/6 and Dvl-2/3, and activates beta-catenin in SN4741 dopaminergic cells. Moreover, purified Wnt2 increases progenitor proliferation, and the number of dopaminergic neurons in ventral midbrain precursor cultures. In agreement with these findings, analysis of the ventral midbrain of developing Wnt2-null mice revealed a decrease in progenitor proliferation and neurogenesis that lead to a decrease in the number of postmitotic precursors and dopaminergic neurons. Collectively, our observations identify Wnt2 as a novel regulator of dopaminergic progenitors and dopaminergic neuron development.

  9. Gravitational Wave Constraints on the Progenitors of Fast Radio Bursts

    CERN Document Server

    Callister, Thomas; Weinstein, Alan

    2016-01-01

    The nature of fast radio bursts (FRBs) remains enigmatic. Highly energetic radio pulses of millisecond duration, fast radio bursts are observed with dispersion measures consistent with an extragalactic source. A variety of models have been proposed to explain their origin. One popular class of theorized FRB progenitor is the coalescence of compact binaries composed of neutron stars and/or black holes. We demonstrate that measurements made by the LIGO and Virgo gravitational wave observatories can be leveraged to severely constrain the validity of FRB binary coalescence models. Existing measurements rule out binary black holes as FRB progenitors, and results from Advanced LIGO's O1 and O2 observing runs will either confirm or strongly rule out binary neutron star and neutron star-black hole progenitors.

  10. Neural progenitors, neurogenesis and the evolution of the neocortex.

    Science.gov (United States)

    Florio, Marta; Huttner, Wieland B

    2014-06-01

    The neocortex is the seat of higher cognitive functions and, in evolutionary terms, is the youngest part of the mammalian brain. Since its origin, the neocortex has expanded in several mammalian lineages, and this is particularly notable in humans. This expansion reflects an increase in the number of neocortical neurons, which is determined during development and primarily reflects the number of neurogenic divisions of distinct classes of neural progenitor cells. Consequently, the evolutionary expansion of the neocortex and the concomitant increase in the numbers of neurons produced during development entail interspecies differences in neural progenitor biology. Here, we review the diversity of neocortical neural progenitors, their interspecies variations and their roles in determining the evolutionary increase in neuron numbers and neocortex size.

  11. Omega 3 fatty acids reduce myeloid progenitor cell frequency in the bone marrow of mice and promote progenitor cell differentiation

    Directory of Open Access Journals (Sweden)

    Sollars Vincent E

    2009-03-01

    Full Text Available Abstract Background Omega 3 fatty acids have been found to inhibit proliferation, induce apoptosis, and promote differentiation in various cell types. The processes of cell survival, expansion, and differentiation are of key importance in the regulation of hematopoiesis. We investigated the role of omega 3 fatty acids in controlling the frequency of various myeloid progenitor cells in the bone marrow of mice. Increased progenitor cell frequency and blocked differentiation are characteristics of hematopoietic disorders of the myeloid lineage, such as myeloproliferative diseases and myeloid leukemias. Results We found that increasing the proportion of omega 3 fatty acids relative to the proportion of omega 6 fatty acids in the diet caused increased differentiation and reduced the frequency of myeloid progenitor cells in the bone marrow of mice. Furthermore, this had no adverse effect on peripheral white blood cell counts. Conclusion Our results indicate that omega 3 fatty acids impact hematopoietic differentiation by reducing myeloid progenitor cell frequency in the bone marrow and promoting progenitor cell differentiation. Further exploration of this discovery could lead to the use of omega 3 fatty acids as a therapeutic option for patients that have various disorders of hematopoiesis.

  12. Differential Effects of Isoxazole-9 on Neural Stem/Progenitor Cells, Oligodendrocyte Precursor Cells, and Endothelial Progenitor Cells.

    Directory of Open Access Journals (Sweden)

    Seong-Ho Koh

    Full Text Available Adult mammalian brain can be plastic after injury and disease. Therefore, boosting endogenous repair mechanisms would be a useful therapeutic approach for neurological disorders. Isoxazole-9 (Isx-9 has been reported to enhance neurogenesis from neural stem/progenitor cells (NSPCs. However, the effects of Isx-9 on other types of progenitor/precursor cells remain mostly unknown. In this study, we investigated the effects of Isx-9 on the three major populations of progenitor/precursor cells in brain: NSPCs, oligodendrocyte precursor cells (OPCs, and endothelial progenitor cells (EPCs. Cultured primary NSPCs, OPCs, or EPCs were treated with various concentrations of Isx-9 (6.25, 12.5, 25, 50 μM, and their cell numbers were counted in a blinded manner. Isx-9 slightly increased the number of NSPCs and effectively induced neuronal differentiation of NSPCs. However, Isx-9 significantly decreased OPC number in a concentration-dependent manner, suggesting cytotoxicity. Isx-9 did not affect EPC cell number. But in a matrigel assay of angiogenesis, Isx-9 significantly inhibited tube formation in outgrowth endothelial cells derived from EPCs. This potential anti-tube-formation effect of Isx-9 was confirmed in a brain endothelial cell line. Taken together, our data suggest that mechanisms and targets for promoting stem/progenitor cells in the central nervous system may significantly differ between cell types.

  13. Enrichment and terminal differentiation of striated muscle progenitors in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Becher, Ulrich M.; Breitbach, Martin; Sasse, Philipp [Institute of Physiology I, Life and Brain Center, University of Bonn, Bonn (Germany); Garbe, Stephan [Department of Radiology, University of Bonn, Bonn (Germany); Ven, Peter F.M. van der [Institute for Cell Biology, University of Bonn, Bonn (Germany); Fuerst, Dieter O., E-mail: dfuerst@uni-bonn.de [Institute for Cell Biology, University of Bonn, Bonn (Germany); Fleischmann, Bernd K., E-mail: bernd.fleischmann@uni-bonn.de [Institute of Physiology I, Life and Brain Center, University of Bonn, Bonn (Germany)

    2009-10-01

    Enrichment and terminal differentiation of mammalian striated muscle cells is severely hampered by fibroblast overgrowth, de-differentiation and/or lack of functional differentiation. Herein we report a new, reproducible and simple method to enrich and terminally differentiate muscle stem cells and progenitors from mice and humans. We show that a single gamma irradiation of muscle cells induces their massive differentiation into structurally and functionally intact myotubes and cardiomyocytes and that these cells can be kept in culture for many weeks. Similar results are also obtained when treating skeletal muscle-derived stem cells and progenitors with Mitomycin C.

  14. Gender Differences on the Use of Amplifiers in Academic Writings

    Institute of Scientific and Technical Information of China (English)

    申利芬

    2012-01-01

      This study aims to investigate the use of amplifiers in term of gender and disciplinary groups in academic research arti⁃cles, which is based on the British Academic Written English Corpus (BAWE).18 amplifiers were examined across two dimen⁃sions:gender and disciplinary groups. The results show amplifiers are more common in males’ academic writings than in those of females in general, amplifiers are used more often in AH discipline. However, not all amplifiers show significant gender differ⁃ences between men and women. Six words show a significant difference between male and female writers:pretty, by far, perfect⁃ly, quite, a great deal, totally, which are used more often by males. However, the interesting is in LS discipline, most amplifiers are used more often by female than male writers and males tend to use by far more frequently than females.

  15. Multiple Differential-Amplifier MMICs Embedded in Waveguides

    Science.gov (United States)

    Kangaslahti, Pekka; Schlecht, Erich

    2010-01-01

    Compact amplifier assemblies of a type now being developed for operation at frequencies of hundreds of gigahertz comprise multiple amplifier units in parallel arrangements to increase power and/or cascade arrangements to increase gains. Each amplifier unit is a monolithic microwave integrated circuit (MMIC) implementation of a pair of amplifiers in differential (in contradistinction to single-ended) configuration. Heretofore, in cascading amplifiers to increase gain, it has been common practice to interconnect the amplifiers by use of wires and/or thin films on substrates. This practice has not yielded satisfactory results at frequencies greater than 200 Hz, in each case, for either or both of two reasons: Wire bonds introduce large discontinuities. Because the interconnections are typically tens of wavelengths long, any impedance mismatches give rise to ripples in the gain-vs.-frequency response, which degrade the performance of the cascade.

  16. ANALYSIS OF INTERNALLY GENERATED NOISE OF BIOELECTRIC AMPLIFIERS

    Institute of Scientific and Technical Information of China (English)

    Mashhour Mustafa; Bani Amer

    2003-01-01

    This paper deals with internally generated noise of bioelectric amplifiers that are usually used for processing of bioelectric events. The main purpose of this paper is to present a procedure for analysis of the effects of internal noise generated by the active circuits and to evaluate the output noise of the author's new designed bioelectric amplifier that caused by internal effects to the amplifier circuit itself in order to compare it with the noise generated by conventional amplifiers. The obtained analysis results of internally generated noise showed that the total output noise of bioelectric active circuits does not increase when some of their resistors have a larger value. This behavior is caused by the different transfer functions for the signal and the respective noise sources associated with these resistors. Moreover, the new designed bioelectric amplifier has an output noise less than that for conventional amplifiers. The obtained analysis results were also experimentally verified and the final conclusions were drawn.

  17. Low-noise amplifiers for satellite communications

    Science.gov (United States)

    Whelehan, J.

    1984-02-01

    It is pointed out that over the past several years significant advances have been made in the overall capability of both microwave and mm-wave receivers. This is particularly apparent in the telecom market. Integral parts of advanced receiver technology are low-noise receivers. The advances currently being achieved in low-noise technology are partly based on developments in GaAs semiconductor technology. The development of high-cutoff-frequency beam lead mixer diodes has led to the development of mm-wave low-noise mixers with excellent low-noise capability. The advanced techniques are now being employed in field-deployable systems. Low noise is an important factor in satellite communications applications. Attention is given to C-band fixed satellite service, C-band parametric amplifiers, C-band FET, and X band, the Ku band, and the 30/20 GHz band.

  18. Current feedback operational amplifiers and their applications

    CERN Document Server

    Senani, Raj; Singh, A K; Singh, V K

    2013-01-01

    This book describes a variety of current feedback operational amplifier (CFOA) architectures and their applications in analog signal processing/generation. Coverage includes a comprehensive survey of commercially available, off-the-shelf integrated circuit CFOAs, as well as recent advances made on the design of CFOAs, including design innovations for bipolar and CMOS CFOAs.  This book serves as a single-source reference to the topic, as well as a catalog of over 200 application circuits which would be useful not only for students, educators and researchers in apprising them about the recent developments in the area but would also serve as a comprehensive repertoire of useful circuits for practicing engineers who might be interested in choosing an appropriate CFOA-based topology for use in a given application.

  19. Stochastic phenomena in a fiber Raman amplifier

    CERN Document Server

    Kalashnikov, Vladimir; Ania-Castanón, Juan Diego; Jacobsen, Gunnar; Popov, Sergei

    2016-01-01

    The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering-based nonlinearity, the random birefringence of a fiber, and the pump-to-signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence-induced resonance-like enhancement of the gain fluctuations (stochastic anti-resonance) accompanied by pulse broadening and rare events in the form of low power outpu...

  20. Gain Characteristics of Fiber Optical Parametric Amplifier

    Institute of Scientific and Technical Information of China (English)

    高明义; 姜淳; 胡卫生

    2004-01-01

    The theory model of fiber optical parametric amplifier (FOPA) was introduced, which is based on optical nonlinear effect. And then numerical simulation was done to analyze and discuss the gain spectral characteristics of one-pump and two-pump FOPA. The results show that for one-pump FOPA, when pump wavelength is near to fiber zero-dispersion wavelength(ZDW), the gain flatness is better, and with the increase of the pump power, fiber length and its nonlinear coefficient, the gain value will increase while the gain bandwidth will become narrow. For two-pump FOPA, when the pump central wavelength is near to fiber ZDW, the gain flatness is better. Moreover, by decreasing the space of two pumps wavelength, the gain flatness can be improved. Finally, some problems existing in FOPA were addressed.

  1. End-stage renal disease causes an imbalance between endothelial and smooth muscle progenitor cells

    NARCIS (Netherlands)

    Westerweel, Peter E; Hoefer, Imo E; Blankestijn, Peter J; de Bree, Petra; Groeneveld, Dafna; van Oostrom, Olivia; Braam, Branko; Koomans, Hein A; Verhaar, Marianne C

    2007-01-01

    Patients with end-stage renal disease (ESRD) on hemodialysis have an increased risk of cardiovascular disease (CVD). Circulating endothelial progenitor cells (EPC) contribute to vascular regeneration and repair, thereby protecting against CVD. However, circulating smooth muscle progenitor cells (SPC

  2. Cellular plasticity : the good, the bad, and the ugly? Microenvironmental influences on progenitor cell therapy

    NARCIS (Netherlands)

    Moonen, Jan-Renier A. J.; Harmsen, Martin C.; Krenning, Guido

    2012-01-01

    Progenitor cell based therapies have emerged for the treatment of ischemic cardiovascular diseases where there is insufficient endogenous repair. However, clinical success has been limited, which challenges the original premise that transplanted progenitor cells would orchestrate repair. In this rev

  3. Inducible expression of noggin selectively expands neural progenitors in the adult SVZ

    Directory of Open Access Journals (Sweden)

    M. Morell

    2015-01-01

    Full Text Available Multipotent, self-renewing stem cells are present throughout the developing nervous system remaining in discrete regions of the adult brain. In the subventricular zone (SVZ signaling molecules, including the bone morphogenetic proteins and their secreted inhibitor, noggin appear to play a critical role in controlling neural stem cell (NSC behavior. To examine the function of this signaling pathway in the intact nervous system, we developed a transgenic mouse model in which noggin expression can be induced specifically in NSC via a nestin-driven reverse tetracycline-controlled transactivator (rtTA. In adult animals, the induction of noggin expression promotes the proliferation of neural progenitors in the SVZ, and shifts the differentiation of B cells (NSC from mature astrocytes to transit amplifying C cells and oligodendrocyte precursor cells without depleting the NSC population. Noggin expression significantly increases neuronal and oligodendrocyte differentiation both in vivo and in vitro when NSCs are grown as neurospheres. These results demonstrate that noggin/BMP interactions tightly control cell fate in the SVZ.

  4. Modeling and design techniques for RF power amplifiers

    CERN Document Server

    Raghavan, Arvind; Laskar, Joy

    2008-01-01

    The book covers RF power amplifier design, from device and modeling considerations to advanced circuit design architectures and techniques. It focuses on recent developments and advanced topics in this area, including numerous practical designs to back the theoretical considerations. It presents the challenges in designing power amplifiers in silicon and helps the reader improve the efficiency of linear power amplifiers, and design more accurate compact device models, with faster extraction routines, to create cost effective and reliable circuits.

  5. InP Heterojunction Bipolar Transistor Amplifiers to 255 GHz

    Science.gov (United States)

    Radisic, Vesna; Sawdai, Donald; Scott, Dennis; Deal, William; Dang, Linh; Li, Danny; Cavus, Abdullah; To, Richard; Lai, Richard

    2009-01-01

    Two single-stage InP heterojunction bipolar transistor (HBT) amplifiers operate at 184 and 255 GHz, using Northrop Grumman Corporation s InP HBT MMIC (monolithic microwave integrated circuit) technology. At the time of this reporting, these are reported to be the highest HBT amplifiers ever created. The purpose of the amplifier design is to evaluate the technology capability for high-frequency designs and verify the model for future development work.

  6. Numerical Analysis of Modal Instability Onset in Fiber Amplifiers

    Science.gov (United States)

    2014-03-11

    Evolution of the logarithmic frequency spectrum of the off-center optical intensity probe along the length of the co-pumped amplifier for the case of...Evolution of the logarithmic frequency spectrum of the off-center optical intensity probe along the length of the counter-pumped amplifier for the...ABSTRACT 16. SECURITY CLASSIFICATION OF: Numerical analysis of the onset of modal instability in fiber amplifiers is presented. Specifically calculations

  7. Dual Band High Efficiency Power Amplifier Based on CRLH Lines

    Directory of Open Access Journals (Sweden)

    D. Segovia-Vargas

    2009-12-01

    Full Text Available In this paper we propose the use of Composite Right/Left Hand (CRLH and Extended Composite Right/Left Hand (ECRLH transmission lines for the design of dual band high efficiency power amplifiers working in CE class. The harmonic termination can be synthesized using the meta-lines is particularly suitable for CE class amplifiers, which have a termination not as sensitive to the third harmonic as F class amplifier. This paper presents the design procedure and the design equations. The nonlinear phase response of a CRLH and ECRLH transmission line has been utilized to design arbitrary dual-band amplifiers.

  8. Nylon Sleeve for Cavity Amplifier Holds Tuning Despite Heat

    Science.gov (United States)

    Derr, Lloyd

    1964-01-01

    The problem: Detuning of cavity amplifiers with change in temperature. This results in deterioration of the performance of the amplifier at its design frequency. In cavity amplifiers and filters it is desirable that constant performance be maintained regardless of thermal changes. These changes often cause an "off resonance shift" in a cavity filter and a deterioration of performance in a cavity amplifier. The solution: Mount the tuning probe in a nylon sleeve. Thermal expansion and contraction of the nylon nullifies unwanted capacitive and inductive changes in the resonant elements.

  9. Modeling a Common-Source Amplifier Using a Ferroelectric Transistor

    Science.gov (United States)

    Sayyah, Rana; Hunt, Mitchell; MacLeond, Todd C.; Ho, Fat D.

    2010-01-01

    This paper presents a mathematical model characterizing the behavior of a common-source amplifier using a FeFET. The model is based on empirical data and incorporates several variables that affect the output, including frequency, load resistance, and gate-to-source voltage. Since the common-source amplifier is the most widely used amplifier in MOS technology, understanding and modeling the behavior of the FeFET-based common-source amplifier will help in the integration of FeFETs into many circuits.

  10. Controlling the dynamic range of a Josephson parametric amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Eichler, Christopher; Wallraff, Andreas [ETH Zuerich, Department of Physics, Zuerich (Switzerland)

    2014-12-01

    One of the central challenges in the development of parametric amplifiers is the control of the dynamic range relative to its gain and bandwidth, which typically limits quantum limited amplification to signals which contain only a few photons per inverse bandwidth. Here, we discuss the control of the dynamic range of Josephson parametric amplifiers by using Josephson junction arrays. We discuss gain, bandwidth, noise, and dynamic range properties of both a transmission line and a lumped element based parametric amplifier. Based on these investigations we derive useful design criteria, which may find broad application in the development of practical parametric amplifiers. (orig.)

  11. Pulse-distortion in a quantum-dot optical amplifier

    DEFF Research Database (Denmark)

    Romstad, Francis Pascal; Borri, Paola; Mørk, Jesper;

    2000-01-01

    Distortion of a -150fs optical pulse after propagation through an InAs/InGaAs quantum-dot optical amplifier is measured for different input energies an bias currents. Pulse distortion is observed and compared with results on a bulk amplifier.......Distortion of a -150fs optical pulse after propagation through an InAs/InGaAs quantum-dot optical amplifier is measured for different input energies an bias currents. Pulse distortion is observed and compared with results on a bulk amplifier....

  12. Combination ring cavity and backward Raman waveguide amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Kurnit, N.A.

    1981-03-13

    A combination regenerative ring and backward Raman waveguide amplifier and a combination regenerative ring oscillator and backward Raman waveguide amplifier which produce Raman amplification, pulse compression, and efficient energy extraction from the CO/sub 2/ laser pump signal for conversion into a Stokes radiation signal. The ring cavity configuration allows the CO/sub 2/ laser pump signal and Stokes signal to copropagate through the Raman waveguide amplifier. The backward Raman waveguide amplifier configuration extracts a major portion of the remaining energy from the CO/sub 2/ laser pump signal for conversion to Stokes radiation.

  13. Parametric Amplifiers for Microwave Kinectic Inductance Detector (MKID) Readout Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Find numerical solutions to the non-linear partial differential equations describing our amplifier transmission lines. Optimize periodic choke structure to block...

  14. Type Ia supernovae: explosions and progenitors

    Science.gov (United States)

    Kerzendorf, Wolfgang Eitel

    2011-08-01

    that they somehow need to acquire mass if they are to explode as SN Ia. Currently there are two major scenarios for this mass acquisition. In the favoured single degenerate scenario the white dwarf accretes matter from a companion star which is much younger in its evolutionary state. The less favoured double degenerate scenario sees the merger of two white dwarfs (with a total combined mass of more than 1.38 Msun). This thesis has tried to answer the question about the mass acquisition in two ways. First the single degenerate scenario predicts a surviving companion post-explosion. We undertook an observational campaign to find this companion in two ancient supernovae (SN 1572 and SN 1006). Secondly, we have extended an existing code to extract the elemental and energy yields of SNe Ia spectra by automating spectra fitting to specific SNe Ia. This type of analysis, in turn, help diagnose to which of the two major progenitor scenarios is right.

  15. Modeling and analysis of overmodulation in erbium-doped fiber amplifiers including amplified spontaneous emission

    Science.gov (United States)

    Sharma, Reena; Raghuwanshi, Sanjeev Kumar

    2017-02-01

    Line surveillance and management information in erbium-doped fiber amplifiers (EDFAs) can be broadcast by modulating the amplitude of the low-frequency lightwave information signal, the process termed as overmodulation in the literature. This paper presents systematic solutions for the overmodulated pump and information signal transfer functions for EDFA. It includes amplified spontaneous emission (ASE) that has an impact on outcomes in the high-gain system. To the extent of our belief, the methodical model simulated with the current approach leads to a distinct perspective of an outcome in the respective field. The test bed described here is realistic. It specifically represents the overmodulation behavior in an EDFA under the influence of ASE.

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  14. File list: His.Adp.10.AllAg.Adipose_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  15. File list: His.Adp.05.AllAg.Adipose_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  16. File list: Oth.Adp.05.AllAg.Adipose_progenitor_cells [Chip-atlas[Archive

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  17. File list: Oth.Adp.10.AllAg.Adipose_progenitor_cells [Chip-atlas[Archive

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  18. File list: His.Adp.20.AllAg.Adipose_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  19. File list: DNS.Adp.10.AllAg.Adipose_progenitor_cells [Chip-atlas[Archive

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  20. File list: Unc.Neu.50.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

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  1. File list: Pol.Neu.10.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  2. File list: ALL.Neu.20.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

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  3. File list: DNS.Neu.10.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

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  4. File list: DNS.Neu.50.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

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  5. File list: Oth.Neu.05.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  6. File list: His.Neu.10.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

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  7. File list: ALL.Neu.05.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  8. File list: His.Neu.20.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  9. File list: Unc.Neu.20.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  10. File list: His.Neu.05.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  11. File list: Oth.Neu.50.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  12. File list: Unc.Neu.05.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Unc.Neu.05.AllAg.Neural_progenitor_cells mm9 Unclassified Neural Neural progenitor ...cells http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Neu.05.AllAg.Neural_progenitor_cells.bed ...

  13. File list: Pol.Neu.20.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Neu.20.AllAg.Neural_progenitor_cells mm9 RNA polymerase Neural Neural progenito...r cells http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Neu.20.AllAg.Neural_progenitor_cells.bed ...

  14. File list: Oth.Neu.20.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.Neu.20.AllAg.Neural_progenitor_cells mm9 TFs and others Neural Neural progenito...r cells SRX109472,SRX315274,SRX802060,SRX109471 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.Neu.20.AllAg.Neural_progenitor_cells.bed ...

  15. File list: Pol.Neu.05.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Neu.05.AllAg.Neural_progenitor_cells mm9 RNA polymerase Neural Neural progenito...r cells http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Neu.05.AllAg.Neural_progenitor_cells.bed ...

  16. File list: DNS.Neu.20.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Neu.20.AllAg.Neural_progenitor_cells mm9 DNase-seq Neural Neural progenitor cel...ls SRX238870,SRX238868 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.20.AllAg.Neural_progenitor_cells.bed ...

  17. File list: DNS.Neu.05.AllAg.Neural_progenitor_cells [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Neu.05.AllAg.Neural_progenitor_cells mm9 DNase-seq Neural Neural progenitor cel...ls SRX238870,SRX238868 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.05.AllAg.Neural_progenitor_cells.bed ...

  18. File list: Unc.Oth.10.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Unc.Oth.10.AllAg.Multipotent_otic_progenitor mm9 Unclassified Others Multipotent ot...ic progenitor http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Oth.10.AllAg.Multipotent_otic_progenitor.bed ...

  19. File list: His.Oth.10.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Oth.10.AllAg.Multipotent_otic_progenitor mm9 Histone Others Multipotent otic pr...ogenitor http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Oth.10.AllAg.Multipotent_otic_progenitor.bed ...

  20. File list: Oth.Oth.50.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  1. File list: DNS.Oth.05.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available DNS.Oth.05.AllAg.Multipotent_otic_progenitor mm9 DNase-seq Others Multipotent otic ...progenitor http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Oth.05.AllAg.Multipotent_otic_progenitor.bed ...

  2. File list: Oth.Oth.20.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.Oth.20.AllAg.Multipotent_otic_progenitor mm9 TFs and others Others Multipotent ...otic progenitor SRX736459,SRX736458,SRX736460,SRX736461 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Oth.Oth.20.AllAg.Multipotent_otic_progenitor.bed ...

  3. File list: His.Oth.20.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Oth.20.AllAg.Multipotent_otic_progenitor mm9 Histone Others Multipotent otic pr...ogenitor http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Oth.20.AllAg.Multipotent_otic_progenitor.bed ...

  4. File list: Pol.Oth.10.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Oth.10.AllAg.Multipotent_otic_progenitor mm9 RNA polymerase Others Multipotent ...otic progenitor SRX736457,SRX736456 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Oth.10.AllAg.Multipotent_otic_progenitor.bed ...

  5. File list: Pol.Oth.50.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Oth.50.AllAg.Multipotent_otic_progenitor mm9 RNA polymerase Others Multipotent ...otic progenitor SRX736457,SRX736456 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Oth.50.AllAg.Multipotent_otic_progenitor.bed ...

  6. File list: His.Oth.05.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available His.Oth.05.AllAg.Multipotent_otic_progenitor mm9 Histone Others Multipotent otic pr...ogenitor http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/His.Oth.05.AllAg.Multipotent_otic_progenitor.bed ...

  7. File list: His.Oth.50.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  8. File list: Oth.Oth.10.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  9. File list: Unc.Oth.20.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  10. File list: Oth.Oth.05.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  11. File list: DNS.Oth.50.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  12. File list: Pol.Oth.20.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Pol.Oth.20.AllAg.Multipotent_otic_progenitor mm9 RNA polymerase Others Multipotent ...otic progenitor SRX736457,SRX736456 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Pol.Oth.20.AllAg.Multipotent_otic_progenitor.bed ...

  13. File list: Unc.Oth.50.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  14. File list: DNS.Oth.20.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  15. File list: Pol.Oth.05.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  16. File list: Unc.Oth.05.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

    Lifescience Database Archive (English)

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  17. File list: DNS.Oth.10.AllAg.Multipotent_otic_progenitor [Chip-atlas[Archive

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  18. File list: Unc.Neu.10.AllAg.Induced_neural_progenitors [Chip-atlas[Archive

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  19. File list: Pol.Neu.05.AllAg.Induced_neural_progenitors [Chip-atlas[Archive

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  20. File list: Oth.Neu.50.AllAg.Induced_neural_progenitors [Chip-atlas[Archive

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  1. File list: DNS.Neu.05.AllAg.Induced_neural_progenitors [Chip-atlas[Archive

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    Full Text Available DNS.Neu.05.AllAg.Induced_neural_progenitors mm9 DNase-seq Neural Induced neural pro...genitors http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/DNS.Neu.05.AllAg.Induced_neural_progenitors.bed ...

  2. File list: Unc.Neu.05.AllAg.Induced_neural_progenitors [Chip-atlas[Archive

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    Full Text Available Unc.Neu.05.AllAg.Induced_neural_progenitors mm9 Unclassified Neural Induced neural ...progenitors http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/assembled/Unc.Neu.05.AllAg.Induced_neural_progenitors.bed ...

  3. Optimal Relay Power Allocation for Amplify-and-Forward Relay Networks with Non-linear Power Amplifiers

    OpenAIRE

    Zhang, Chao; Ren, Pinyi; Peng, Jingbo; Wei, Guo; Du, Qinghe; Wang, Yichen

    2011-01-01

    In this paper, we propose an optimal relay power allocation of an Amplify-and-Forward relay networks with non-linear power amplifiers. Based on Bussgang Linearization Theory, we depict the non-linear amplifying process into a linear system, which lets analyzing system performance easier. To obtain spatial diversity, we design a complete practical framework of a non-linear distortion aware receiver. Consider a total relay power constraint, we propose an optimal power allocation scheme to maxim...

  4. Wideband high efficiency CMOS envelope amplifiers for 4G LTE handset envelope tracking RF power amplifiers

    OpenAIRE

    Hassan, Muhammad

    2012-01-01

    Fourth generation cellular networks offer performance similar to cable modems while allowing wide mobility. Although the use of orthogonal frequency division multiplexing in fourth generation increases its spectral efficiency but it also increases the peak-to-average power ratio of the transmitted signal. If a conventional power amplifier is used to transmit a high peak-to-average power ratio signal, then to meet the stringent linearity requirements, it will be operating 6 to 10 dB back-off f...

  5. Development of 3 kW at 325 MHz solid-state RF power amplifier using four power amplifier modules

    Energy Technology Data Exchange (ETDEWEB)

    Ramarao, B.V., E-mail: bvram@barc.gov.in [Ion Accelerator Development Division, Bhabha Atomic Research Center, Mumbai 400085 (India); Sonal, S.; Mishra, J.K.; Pande, M.; Singh, P. [Ion Accelerator Development Division, Bhabha Atomic Research Center, Mumbai 400085 (India); Kumar, G.; Mukherjee, J. [Indian Institute of Technology, Powai, Mumbai 400076 (India)

    2014-01-21

    A high power solid-state RF power amplifier of 3 kW at 325 MHz has been developed using only four RF power amplifier modules of 850 W power output each. The design and characterization of RF power modules have been presented. A four way Wilkinson power combiner adds the output of four power amplifier modules with a total transmission loss of less than 6%. The combined power amplifier has a power gain of 20.2 dB at 1-dB compression point, and the corresponding output power is 2.8 kW at 325 MHz. The drain efficiency of the power amplifier is 65.3% at 3 kW. All the harmonics of this amplifier are below −40 dBc. The amplifier has better characteristics like fewer numbers of active devices per kilo watt, high efficiency, high gain, and ruggedness etc for RF accelerator applications. -- Highlights: • High gain power amplifier, power gain at 20 dB. • High efficiency amplifier, efficiency >65%. • Minimum number of modules per kilo watt power output. • Heat sink with modules on both side, high density.

  6. Progenitor models of Wolf-Rayet+O binary systems

    NARCIS (Netherlands)

    Petrovic, J.; Langer, N.

    2007-01-01

    Since close WR+O binaries are the result of a strong interaction of both stars in massive close binary systems, they can be used to constrain the highly uncertain mass and angular momentum budget during the major mass- transfer phase. We explore the progenitor evolution of the three best suited WR+O

  7. In vitro pancreas organogenesis from dispersed mouse embryonic progenitors.

    Science.gov (United States)

    Greggio, Chiara; De Franceschi, Filippo; Figueiredo-Larsen, Manuel; Grapin-Botton, Anne

    2014-07-19

    The pancreas is an essential organ that regulates glucose homeostasis and secretes digestive enzymes. Research on pancreas embryogenesis has led to the development of protocols to produce pancreatic cells from stem cells (1). The whole embryonic organ can be cultured at multiple stages of development (2-4). These culture methods have been useful to test drugs and to image developmental processes. However the expansion of the organ is very limited and morphogenesis is not faithfully recapitulated since the organ flattens. We propose three-dimensional (3D) culture conditions that enable the efficient expansion of dissociated mouse embryonic pancreatic progenitors. By manipulating the composition of the culture medium it is possible to generate either hollow spheres, mainly composed of pancreatic progenitors expanding in their initial state, or, complex organoids which progress to more mature expanding progenitors and differentiate into endocrine, acinar and ductal cells and which spontaneously self-organize to resemble the embryonic pancreas. We show here that the in vitro process recapitulates many aspects of natural pancreas development. This culture system is suitable to investigate how cells cooperate to form an organ by reducing its initial complexity to few progenitors. It is a model that reproduces the 3D architecture of the pancreas and that is therefore useful to study morphogenesis, including polarization of epithelial structures and branching. It is also appropriate to assess the response to mechanical cues of the niche such as stiffness and the effects on cell´s tensegrity.

  8. Transcriptome analysis reveals transmembrane targets on transplantable midbrain dopamine progenitors.

    Science.gov (United States)

    Bye, Chris R; Jönsson, Marie E; Björklund, Anders; Parish, Clare L; Thompson, Lachlan H

    2015-04-14

    An important challenge for the continued development of cell therapy for Parkinson's disease (PD) is the establishment of procedures that better standardize cell preparations for use in transplantation. Although cell sorting has been an anticipated strategy, its application has been limited by lack of knowledge regarding transmembrane proteins that can be used to target and isolate progenitors for midbrain dopamine (mDA) neurons. We used a "FACS-array" approach to identify 18 genes for transmembrane proteins with high expression in mDA progenitors and describe the utility of four of these targets (Alcam, Chl1, Gfra1, and Igsf8) for isolating mDA progenitors from rat primary ventral mesencephalon through flow cytometry. Alcam and Chl1 facilitated a significant enrichment of mDA neurons following transplantation, while targeting of Gfra1 allowed for robust separation of dopamine and serotonin neurons. Importantly, we also show that mDA progenitors isolated on the basis of transmembrane proteins are capable of extensive, functional innervation of the host striatum and correction of motor impairment in a unilateral model of PD. These results are highly relevant for current efforts to establish safe and effective stem cell-based procedures for PD, where clinical translation will almost certainly require safety and standardization measures in order to deliver well-characterized cell preparations.

  9. Cosmic Supernova Rate History and Type Ia Supernova Progenitors

    OpenAIRE

    Kobayashi, Chiaki; Nomoto, Ken'ichi; Tsujimoto, Takuji

    2001-01-01

    Adopting a single degenerate scenario for Type Ia supernova progenitors with the metallicity effect, we make a prediction of the cosmic supernova rate history as a composite of the supernova rates in spiral and elliptical galaxies, and compare with the recent observational data up to z ~ 0.55.

  10. Characterization of Progenitor Cells during Canine Retinal Development

    Directory of Open Access Journals (Sweden)

    Mallely Ávila-García

    2012-01-01

    Full Text Available We identify the presence of progenitor cells during retinal development in the dog, as this species represents a natural model for studying several breed-specific degenerative retinal disorders. Antibodies to detected progenitor cells (Pax6, C-kit, and nestin and ganglion cells (BDNF, Brn3a, and Thy1 were used in combination with H3 for the purpose of identifying proliferating cells. Pax6, nestin, C-kit, and H3 were localized mainly in the neuroblastic layer of the retina during the embryonic stage. During the fetal stage, proteins were expressed in the inner neuroblastic layer (INL as well as in the outer neuroblastic layer; BDNF, Thy1, and Brn3a were also expressed in the INL. During the neonatal stage only C-kit was not expressed. Proliferating cells were present in both undifferentiated and differentiated retina. These results suggest that, during canine retinogenesis, progenitor cells are distributed along the retina and some of these cells remain as progenitor cells of the ganglion cells during the first postnatal days.

  11. The progenitor of Nova Cygni 2006 (=V2362 Cyg)

    NARCIS (Netherlands)

    Steeghs, D.; Greimel, R.; Drew, J.; Irwin, M.; Gaensicke, B.; Groot, P.J.; Knigge, C.

    2006-01-01

    We report on the detection of the likely progenitor to Nova Cygni 2006 = V2362 Cyg (IAUC #8697, #8698, ATel #792) using images from the INT Photometric H-Alpha Survey (IPHAS; http://www.iphas.org). The field containing the classical nova was observed as part of our galactic plane survey on Aug. 3rd

  12. Flow cytometric data analysis of circulating progenitor cell stability.

    Science.gov (United States)

    Mahar, Ernestine A; Mou, Liping; Hayek, Salim S; Quyyumi, Arshed A; Waller, Edmund K

    2017-02-01

    A recent publication by Mekonnen et al. demonstrated that among women with non-obstructive coronary artery disease, higher levels of circulating progenitor cells in the blood (CPC), were associated with impaired coronary flow reserve [1]. We performed a quality control assessment of the stability of circulating blood progenitor cells in blood samples stored at 4 °C, to determine the time period during which blood samples can be analyzed and yield consistent data for progenitor cell content. Healthy volunteers (n=6) were recruited and underwent phlebotomy, and blood was stored in EDTA tubes at 4 °C. Flow cytometry was performed to quantitate progenitor cell subsets at 0-4 h, 24 h, and 48 h post phlebotomy. All processed samples were fixed with 1% Paraformaldehyde and 1,000,000 total data events were collected. We found no significant differences in PC data for both CD34+ (P=0.68 for one-way ANOVA) and CD34+/CD133+ (P=0.74 for one-way ANOVA).

  13. Transcriptional Heterogeneity and Lineage Commitment in Myeloid Progenitors

    DEFF Research Database (Denmark)

    Paul, Franziska; Arkin, Ya'ara; Giladi, Amir;

    2015-01-01

    Within the bone marrow, stem cells differentiate and give rise to diverse blood cell types and functions. Currently, hematopoietic progenitors are defined using surface markers combined with functional assays that are not directly linked with in vivo differentiation potential or gene regulatory m...

  14. Endothelial progenitor cell-based neovascularization : implications for therapy

    NARCIS (Netherlands)

    Krenning, Guido; van Luyn, Marja J. A.; Harmsen, Martin C.

    2009-01-01

    Ischemic cardiovascular events are a major cause of death globally. Endothelial progenitor cell (EPC)-based approaches can result in improvement of vascular perfusion and might offer clinical benefit. However, although functional improvement is observed, the lack of long-term engraftment of EPCs int

  15. Neuregulin 1 Type II-ErbB Signaling Promotes Cell Divisions Generating Neurons from Neural Progenitor Cells in the Developing Zebrafish Brain.

    Science.gov (United States)

    Sato, Tomomi; Sato, Fuminori; Kamezaki, Aosa; Sakaguchi, Kazuya; Tanigome, Ryoma; Kawakami, Koichi; Sehara-Fujisawa, Atsuko

    2015-01-01

    Post-mitotic neurons are generated from neural progenitor cells (NPCs) at the expense of their proliferation. Molecular and cellular mechanisms that regulate neuron production temporally and spatially should impact on the size and shape of the brain. While transcription factors such as neurogenin1 (neurog1) and neurod govern progression of neurogenesis as cell-intrinsic mechanisms, recent studies show regulatory roles of several cell-extrinsic or intercellular signaling molecules including Notch, FGF and Wnt in production of neurons/neural progenitor cells from neural stem cells/radial glial cells (NSCs/RGCs) in the ventricular zone (VZ). However, it remains elusive how production of post-mitotic neurons from neural progenitor cells is regulated in the sub-ventricular zone (SVZ). Here we show that newborn neurons accumulate in the basal-to-apical direction in the optic tectum (OT) of zebrafish embryos. While neural progenitor cells are amplified by mitoses in the apical ventricular zone, neurons are exclusively produced through mitoses of neural progenitor cells in the sub-basal zone, later in the sub-ventricular zone, and accumulate apically onto older neurons. This neurogenesis depends on Neuregulin 1 type II (NRG1-II)-ErbB signaling. Treatment with an ErbB inhibitor, AG1478 impairs mitoses in the sub-ventricular zone of the optic tectum. Removal of AG1478 resumes sub-ventricular mitoses without precedent mitoses in the apical ventricular zone prior to basal-to-apical accumulation of neurons, suggesting critical roles of ErbB signaling in mitoses for post-mitotic neuron production. Knockdown of NRG1-II impairs both mitoses in the sub-basal/sub-ventricular zone and the ventricular zone. Injection of soluble human NRG1 into the developing brain ameliorates neurogenesis of NRG1-II-knockdown embryos, suggesting a conserved role of NRG1 as a cell-extrinsic signal. From these results, we propose that NRG1-ErbB signaling stimulates cell divisions generating neurons from

  16. Characterization of progenitor domains in the developing mouse thalamus.

    Science.gov (United States)

    Vue, Tou Yia; Aaker, Joshua; Taniguchi, Aya; Kazemzadeh, Christina; Skidmore, Jennifer M; Martin, Donna M; Martin, James F; Treier, Mathias; Nakagawa, Yasushi

    2007-11-01

    To understand the molecular basis of the specification of thalamic nuclei, we analyzed the expression patterns of various transcription factors and defined progenitor cell populations in the embryonic mouse thalamus. We show that the basic helix-loop-helix (bHLH) transcription factor Olig3 is expressed in the entire thalamic ventricular zone and the zona limitans intrathalamica (ZLI). Next, we define two distinct progenitor domains within the thalamus, which we name pTH-R and pTH-C, located caudal to the ZLI. pTH-R is immediately caudal to the ZLI and expresses Nkx2.2, Mash1, and Olig3. pTH-C is caudal to pTH-R and expresses Ngn1, Ngn2, and Olig3. Short-term lineage analysis of Olig3-, Mash1-, Ngn1-, and Ngn2-expressing progenitor cells as well as tracing the Pitx2 cell lineage suggests that pTH-C is the only major source of thalamic nuclei containing neurons that project to the cerebral cortex, whereas pTH-R and ZLI are likely to produce distinct postmitotic populations outside of the cortex-projecting part of the thalamus. To determine if pTH-C is composed of subdomains, we characterized expression of the homeodomain protein Dbx1 and the bHLH protein Olig2. We show that Dbx1 is expressed in caudodorsal-high to rostroventral-low gradient within pTH-C. Analysis of heterozygous Dbx1(nlslacZ) knockin mice demonstrated that Dbx1-expressing progenitors preferentially give rise to caudodorsal thalamic nuclei. Olig2 is expressed in an opposite gradient within pTH-C to that of Dbx1. These results establish the molecular heterogeneity within the progenitor cells of the thalamus, and suggest that such heterogeneity contributes to the specification of thalamic nuclei.

  17. Effect of Reishi polysaccharides on human stem/progenitor cells.

    Science.gov (United States)

    Chen, Wan-Yu; Yang, Wen-Bin; Wong, Chi-Huey; Shih, Daniel Tzu-Bi

    2010-12-15

    The polysaccharide fraction of Ganoderma lucidum (F3) was found to benefit our health in many ways by influencing the activity of tissue stem/progenitor cells. In this study, F3 was found to promote the adipose tissue MSCs' aggregation and chondrosphere formation, with the increase of CAM (N-CAM, I-CAM) expressions and autokine (BMP-2, IL-11, and aggrecan) secretions, in an in vitro chondrogenesis assay. In a stem cell expansion culture, it possesses the thrombopoietin (TPO) and GM-CSF like functions to enhance the survival/renewal abilities of primitive hematopoietic stem/progenitor cells (HSCs). F3 was found to promote the dendrite growth of blood mononuclear cells (MNCs) and the expression of cell adhesion molecules in the formation of immature dendritic cells (DC). On the other hand, F3 exhibited inhibitory effects on blood endothelial progenitor (EPC) colony formation, with concomitant reduction of cell surface endoglin (CD105) and vascular endothelial growth factor receptor-3 (VEGFR-3) marker expressions, in the presence of angiogenic factors. A further cytokine array analysis revealed that F3 indeed inhibited the angiogenin synthesis and enhanced IL-1, MCP-1, MIP-1, RANTES, and GRO productions in the blood EPC derivation culture. Collectively, we have demonstrated that the polysaccharide fraction of G. lucidum F3 exhibits cytokine and chemokine like functions which are beneficial to human tissue stem/progenitor cells by modulating their CAM expressions and biological activities. These findings provide us a better the observation that F3 glycopolysaccharides indeed possesses anti-angiogenic and immune-modulating functions and promotes hematopoietic stem/progenitor cell homing for better human tissue protection, reducing disease progression and health.

  18. Fas transduces dual apoptotic and trophic signals in hematopoietic progenitors.

    Science.gov (United States)

    Pearl-Yafe, Michal; Stein, Jerry; Yolcu, Esma S; Farkas, Daniel L; Shirwan, Haval; Yaniv, Isaac; Askenasy, Nadir

    2007-12-01

    Stem cells and progenitors are often required to realize their differentiation potential in hostile microenvironments. The Fas/Fas ligand (FasL) interaction is a major effector pathway of apoptosis, which negatively regulates the expansion of differentiated hematopoietic cells. The involvement of this molecular interaction in the function of hematopoietic stem and progenitor cells is not well understood. In the murine syngeneic transplant setting, both Fas and FasL are acutely upregulated in bone marrow-homed donor cells; however, the Fas(+) cells are largely insensitive to FasL-induced apoptosis. In heterogeneous populations of lineage-negative (lin(-)) bone marrow cells and progenitors isolated by counterflow centrifugal elutriation, trimerization of the Fas receptor enhanced the clonogenic activity. Inhibition of caspases 3 and 8 did not affect the trophic signals mediated by Fas, yet it efficiently blocked the apoptotic pathways. Fas-mediated tropism appears to be of physiological significance, as pre-exposure of donor cells to FasL improved the radioprotective qualities of hematopoietic progenitors, resulting in superior survival of myeloablated hosts. Under these conditions, the activity of long-term reconstituting cells was not affected, as determined in sequential secondary and tertiary transplants. Dual caspase-independent tropic and caspase-dependent apoptotic signaling place the Fas receptor at an important junction of activation and death. This regulatory mechanism of hematopoietic homeostasis activates progenitors to promote the recovery from aplasia and converts into a negative regulator in distal stages of cell differentiation. Disclosure of potential conflicts of interest is found at the end of this article.

  19. Gain characteristics of a saturated fiber optic parametric amplifier

    DEFF Research Database (Denmark)

    Rottwitt, Karsten; Lorenzen, Michael Rodas; Noordegraaf, Danny

    2008-01-01

    In this work we discuss saturation performance of a fiber optic parametric amplifier. A simple numerical model is described and applied to specific cases. A system experiment using a saturated amplifier illustrates a 4 dB improvement in required signal to noise ratio for a fixed bit error ratio....

  20. Optically amplifying planar glass waveguides: Laser on a chip

    DEFF Research Database (Denmark)

    Guldberg-Kjær, Søren Andreas

    The objective of this work was to devlop optically amplifying planar wavguides, using erbium-doped germano-silicate glass films deposited by PECVD (Plasma Enhanced Chemical Vapour Deposition). The waveguides should exhibit enough gain to be useful as optical amplifiers in integrated planar lightw...

  1. The design of erbium-doped fiber amplifiers

    DEFF Research Database (Denmark)

    Pedersen, Bo; Bjarklev, Anders Overgaard; Povlsen, Jørn Hedegaard

    1991-01-01

    An accurate model for the erbium-doped fiber amplifier is presented. The model is used to design the index profile of the doped fiber, optimizing with regard to efficiency for inline- and preamplifiers as well as for power booster amplifiers. The predicted pump efficiencies (maximum gain to pump...

  2. Amplifying Islam : Pluralism, Secularism, and Religious Sounds in The Netherlands

    NARCIS (Netherlands)

    Tamimi Arab, P.

    2015-01-01

    This dissertation is an ethnographic study of the amplified azan, the Islamic call to prayer, in the Netherlands, adding a sonic dimension to analyses of the politics of Islamic aesthetics in the western world. Often rejected by opponents as noise pollution, facilitating the amplified azan is an exa

  3. Ferroelectric Field-Effect Transistor Differential Amplifier Circuit Analysis

    Science.gov (United States)

    Phillips, Thomas A.; MacLeod, Todd C.; Ho, Fat D.

    2008-01-01

    There has been considerable research investigating the Ferroelectric Field-Effect Transistor (FeFET) in memory circuits. However, very little research has been performed in applying the FeFET to analog circuits. This paper investigates the use of FeFETs in a common analog circuit, the differential amplifier. The two input Metal-Oxide-Semiconductor (MOS) transistors in a general MOS differential amplifier circuit are replaced with FeFETs. Resistors are used in place of the other three MOS transistors. The FeFET model used in the analysis has been previously reported and was based on experimental device data. Because of the FeFET hysteresis, the FeFET differential amplifier has four different operating modes depending on whether the FeFETs are positively or negatively polarized. The FeFET differential amplifier operation in the different modes was analyzed by calculating the amplifier voltage transfer and gain characteristics shown in figures 2 through 5. Comparisons were made between the FeFET differential amplifier and the standard MOS differential amplifier. Possible applications and benefits of the FeFET differential amplifier are discussed.

  4. Saturation and noise properties of quantum-dot optical amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2004-01-01

    Based on extensive numerical calculations, quantum-dot (QD) amplifiers are predicted to offer higher output power and lower noise figure compared to bulk as well as quantum well amplifiers. The underlying physical mechanisms are analyzed in detail, leading to the identification of a few key...

  5. Energy Efficient and Compact RF High-Power Amplifiers

    NARCIS (Netherlands)

    Calvillo Cortés, D.A.

    2014-01-01

    The main objectives of this thesis are to improve the energy efficiency and physical form-factor of high-power amplifiers in base station applications. As such, the focus of this dissertation is placed on the outphasing amplifier concept, which can offer high-efficiency, good linearity and excellent

  6. Influence of higher order modes on angled-facet amplifiers

    DEFF Research Database (Denmark)

    Wang, Z.; Mikkelsen, B.; Stubkjær, Kristian

    1991-01-01

    The influence of the first-order mode on the residual reflectivity of angled-facet amplifiers is analyzed. For a 7 degrees angled-facet ridge waveguide amplifier with a single-layer antireflective (AR) coating, a gain ripple lower than 1-dB at 25-dB gain can be obtained independent...... by increasing the facet angles to 10 degrees...

  7. Design and Analysis of Hybrid CMOS SRAM Sense Amplifier

    Directory of Open Access Journals (Sweden)

    Karishma Bajaj

    2012-03-01

    Full Text Available Sense amplifiers are one of the very important peripheral components of CMOS memories. In a Hybrid Sense amplifier both current and voltage sensing techniques are used which makes it a better selection than a conventional current or voltage sense amplifiers. The hybrid sense amplifier works in three phases-Offset cancellation (200ps, Access phase (500ps and Evaluation phase. The offset cancellation is done simultaneously with word line decoding, so as to speed up the process. The sensing range of the hybrid sense amplifier is improved from 1.18mV to 92mV. Also hybrid sense amplifier consumes very low energy of about 6.84fj. This sense amplifier is analyzed with a column of 512 SRAM cells at 180nm technology node and compared to CMOS conventional voltage sense amplifier. The circuit consumes an average power of 1.57 µW with a negligible offset of 149.3µV.

  8. External Peltier Cooler For Low-Noise Amplifier

    Science.gov (United States)

    Soper, Terry A.

    1990-01-01

    Inexpensive Peltier-effect cooling module made of few commercially available parts used to reduce thermal noise in microwave amplifier. Retrofitted to almost any microwave low-noise amplifier or receiver preamplifier used in communication, telemetry, or radar. Includes copper or aluminum cold plate held tightly against unit to be cooled by strap-type worm-gear clamps.

  9. An RF Power Amplifier in a Digital CMOS Process

    DEFF Research Database (Denmark)

    Nielsen, Per Asbeck; Fallesen, Carsten

    2002-01-01

    A two stage class B power amplifier for 1.9 GHz is presented. The amplifier is fabricated in a standard digital EPI-CMOS process with low resistivity substrate. The measured output power is 29 dBm in a 50 Omega load. A design method to find the large signal parameters of the output transistor...

  10. Switching-mode Audio Power Amplifiers with Direct Energy Conversion

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2005-01-01

    This paper presents a new class of switching-mode audio power amplifiers, which are capable of direct energy conversion from the AC mains to the audio output. They represent an ultimate integration of a switching-mode power supply and a Class D audio power amplifier, where the intermediate DC bus...

  11. Phase Sensitive Amplifier Based on Ultrashort Pump Pulses

    CERN Document Server

    Gershikov, Alexander

    2016-01-01

    We demonstrate a narrow band phase sensitive amplifier in the pump degenerate configuration which employs ps pump pulses. Control of the amplifier bandwidth is achieved via changes of the pump spectral width. A phase sensitive gain between -6 and 6 decibels, with an overall system gain of 28dB was demonstrated.

  12. Series-Tuned High Efficiency RF-Power Amplifiers

    DEFF Research Database (Denmark)

    Vidkjær, Jens

    2008-01-01

    An approach to high efficiency RF-power amplifier design is presented. It addresses simultaneously efficiency optimization and peak voltage limitations when transistors are pushed towards their power limits.......An approach to high efficiency RF-power amplifier design is presented. It addresses simultaneously efficiency optimization and peak voltage limitations when transistors are pushed towards their power limits....

  13. A 300°C Dynamic-Feedback Instrumentation Amplifier

    NARCIS (Netherlands)

    Jong, P.C. de; Meijer, G.C.M.; Roermund, A.H.M. van

    1998-01-01

    A high-temperature instrumentation amplifier that uses dynamic feedback is presented. It realizes dynamic feedback by means of a rotating chain of resistors to compensate for resistor mismatches. An 11x dynamic-feedback instrumentation amplifier has been integrated in a standard junction-isolated 1.

  14. Implantable neurotechnologies: a review of integrated circuit neural amplifiers.

    Science.gov (United States)

    Ng, Kian Ann; Greenwald, Elliot; Xu, Yong Ping; Thakor, Nitish V

    2016-01-01

    Neural signal recording is critical in modern day neuroscience research and emerging neural prosthesis programs. Neural recording requires the use of precise, low-noise amplifier systems to acquire and condition the weak neural signals that are transduced through electrode interfaces. Neural amplifiers and amplifier-based systems are available commercially or can be designed in-house and fabricated using integrated circuit (IC) technologies, resulting in very large-scale integration or application-specific integrated circuit solutions. IC-based neural amplifiers are now used to acquire untethered/portable neural recordings, as they meet the requirements of a miniaturized form factor, light weight and low power consumption. Furthermore, such miniaturized and low-power IC neural amplifiers are now being used in emerging implantable neural prosthesis technologies. This review focuses on neural amplifier-based devices and is presented in two interrelated parts. First, neural signal recording is reviewed, and practical challenges are highlighted. Current amplifier designs with increased functionality and performance and without penalties in chip size and power are featured. Second, applications of IC-based neural amplifiers in basic science experiments (e.g., cortical studies using animal models), neural prostheses (e.g., brain/nerve machine interfaces) and treatment of neuronal diseases (e.g., DBS for treatment of epilepsy) are highlighted. The review concludes with future outlooks of this technology and important challenges with regard to neural signal amplification.

  15. Slow Light at High Frequencies in an Amplifying Semiconductor Waveguide

    DEFF Research Database (Denmark)

    Öhman, Filip; Yvind, Kresten; Mørk, Jesper

    2006-01-01

    We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz.......We demonstrate slow-down of a modulated light signal in a semiconductor waveguide. Concatenated amplifying and absorbing sections simultaneously achieve both amplification and a controllable time delay at 15 GHz....

  16. Coherent Beam Combination of Two Polarization Maintaining Ytterbium Fibre Amplifiers

    Institute of Scientific and Technical Information of China (English)

    HOU Jing; XIAO Rui; JIANG Zong-Fu; CHENG Xiang-Ai; SHU Bai-Hong; CHEN Jin-Bao; LIU Ze-Jin

    2005-01-01

    @@ We investigate coherent beam combination of fibre laser beams by phase locking. Phase noise of a polarization maintaining ytterbium fibre amplifier is inspected with a fibre interferometer. In a feed back control loop, two fibre polarization maintaining ytterbium amplifiers are phase locked and coherent combined when the phase noise is properly controlled by a LiNO3 phase modulator.

  17. A 24 channel acoustic/vibration test power amplifier

    Science.gov (United States)

    Barlett, F. R.

    1978-01-01

    In the present paper, the advantages and drawbacks of a multichannel amplifier operating in a vibration or acoustic facility are discussed. The configuration of the facility and the multichannel amplifier proposed is a compromise based on the particular requirements and anticipated work load in a specific case under consideration.

  18. Ultrafast Dynamics of Quantum-Dot Semiconductor Optical Amplifiers

    DEFF Research Database (Denmark)

    Poel, Mike van der; Hvam, Jørn Märcher

    2007-01-01

    We report on a series of experiments on the dynamical properties of quantum-dot semiconductor optical amplifiers. We show how the amplifier responds to one or several ultrafast (170 fs) pulses in rapid succession and our results demonstrate applicability and ultimate limitations to application...

  19. Genome relationships among Lotus species based on random amplified polymorphic DNA (RAPD).

    Science.gov (United States)

    Campos, L P; Raelson, J V; Grant, W F

    1994-06-01

    The ability of random amplified polymorphic DNA (RAPD) to distinguish among different taxa of Lotus was evaluated for several geographically dispersed accessions of four diploid Lotus species, L. tennis Waldst. et Kit, L. alpinus Schleich., L. japonicus (Regel) Larsen, and L. uliginosus Schkuhr and for the tetraploid L. corniculatus L., in order to ascertain whether RAPD data could offer additional evidence concerning the origin of the tetraploid L. corniculatus. Clear bands and several polymorphisms were obtained for 20 primers used for each species/accession. The evolutionary pathways among the species/accessions presented in a cladogram were expressed in terms of treelengths giving the most parsimonious reconstructions. Accessions within the same species grouped closely together. It is considered that L. uliginosus which is most distantly related to L. corniculatus, may be excluded as a direct progenitor of L. corniculatus, confirming previous results from isoenzyme studies. Lotus alpinus is grouped with accessions of L. corniculatus, which differs from previous studies. With this exception, these findings are in agreement with previous experimental studies in the L. corniculatus group. The value of the RAPD data to theories on the origin of L. corniculatus is discussed.

  20. Fishing amplifies forage fish population collapses.

    Science.gov (United States)

    Essington, Timothy E; Moriarty, Pamela E; Froehlich, Halley E; Hodgson, Emma E; Koehn, Laura E; Oken, Kiva L; Siple, Margaret C; Stawitz, Christine C

    2015-05-26

    Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches.

  1. Chemically amplified resist modeling in OPC

    Science.gov (United States)

    Zheng, Xin; Huang, Jason; Kuo, Fred; Kazarian, Aram; Chin, Fook; Fan, Yongfa

    2009-03-01

    The mechanism of chemically amplified resist plays a critical role in the modeling of the latent image. To achieve a practical model which can fit into the time frame of OPC, some simplifications and assumptions have to be made. We introduced regression kernels that take into account best exposure focus difference between isotropic pitch, dense, and line end features for the evaluation of image intensity. It compares the image intensity (signal) over small changes above and/or below the regressed "nominal" image position, which in principle corresponds to evaluating the intensity signal at various depths of a fixed resist profile thus can also be regressed for optimization during model development. Our calibration has shown that the model brought a great improvement in prediction for difficult structures such as dense features at or near the optical resolution limit and 2-dimensional features, which are the limiter of the overall model fitting accuracy for 45nm node and below. By replacing other existing techniques, total number of output kernels used for OPC operation is actually reduced with improvement of model accuracy. This model is proven to be a very effective yet accurate addition to the current OPC technology.

  2. Gold Nanoparticle Labels Amplify Ellipsometric Signals

    Science.gov (United States)

    Venkatasubbarao, Srivatsa

    2008-01-01

    The ellipsometric method reported in the immediately preceding article was developed in conjunction with a method of using gold nanoparticles as labels on biomolecules that one seeks to detect. The purpose of the labeling is to exploit the optical properties of the gold nanoparticles in order to amplify the measurable ellipsometric effects and thereby to enable ultrasensitive detection of the labeled biomolecules without need to develop more-complex ellipsometric instrumentation. The colorimetric, polarization, light-scattering, and other optical properties of nanoparticles depend on their sizes and shapes. In the present method, these size-and-shape-dependent properties are used to magnify the polarization of scattered light and the diattenuation and retardance of signals derived from ellipsometry. The size-and-shape-dependent optical properties of the nanoparticles make it possible to interrogate the nanoparticles by use of light of various wavelengths, as appropriate, to optimally detect particles of a specific type at high sensitivity. Hence, by incorporating gold nanoparticles bound to biomolecules as primary or secondary labels, the performance of ellipsometry as a means of detecting the biomolecules can be improved. The use of gold nanoparticles as labels in ellipsometry has been found to afford sensitivity that equals or exceeds the sensitivity achieved by use of fluorescence-based methods. Potential applications for ellipsometric detection of gold nanoparticle-labeled biomolecules include monitoring molecules of interest in biological samples, in-vitro diagnostics, process monitoring, general environmental monitoring, and detection of biohazards.

  3. Efficient and Compact Optical Amplifier Using EYDF

    Directory of Open Access Journals (Sweden)

    Sulaiman Wadi Harun

    2010-09-01

    Full Text Available An efficient Erbium/Ytterbium doped fiber amplifier (EYDFA is demonstrated using a 1058nm pumping wavelength, where the amplification is assisted by energy transfer between Yb and Er ions. The energy transfer increases the limit of erbium doping concentration that is imposed by concentration quenching in Erbium-doped fiber (EDF. Therefore, the gain and noise figure are severely degraded with 1480 nm pumping, where the energy transfer cannot be achieved. The use of optical isolator improves the small signal gain and noise figure by about 4.8 dB and 1.6 dB, respectively. By employing a double-pass configuration, a higher gain can be obtained with an expense of a noise figure penalty. The gain improvement of 17.0 dB is obtained at 20 mW and -50 dBm of pump and input signal powers. This shows that the double-pass configuration is an important aspect to consider when designing an efficient EYDFA.

  4. Globalization to amplify economic climate losses

    Science.gov (United States)

    Otto, C.; Wenz, L.; Levermann, A.

    2015-12-01

    Economic welfare under enhanced anthropogenic carbon emissions and associated future warming poses a major challenge for a society with an evolving globally connected economy. Unabated climate change will impact economic output for example through heat-stress-related reductions in productivity. Since meteorologically-induced production reductions can propagate along supply chains, structural changes in the economic network may influence climate-related losses. The role of the economic network evolution for climate impacts has been neither quantified nor qualitatively understood. Here we show that since the beginning of the 21st century the structural change of the global supply network has been such that an increase of spillover losses due to unanticipated climatic events has to be expected. We quantify primary, secondary and higher-order losses from reduced labor productivity under past and present economic and climatic conditions and find that indirect losses are significant and increase with rising temperatures. The connectivity of the economic network has increased in such a way as to foster the propagation of production loss. This supply chain connectivity robustly exhibits the characteristic distribution of self-organized criticality which has been shifted towards higher values since 2001. Losses due to this structural evolution dominated over the effect of comparably weak climatic changes during this decade. Our finding suggests that the current form of globalization may amplify losses due to climatic extremes and thus necessitate structural adaptation that requires more foresight than presently prevalent.

  5. Single Ion Quantum Lock-In Amplifier

    CERN Document Server

    Kotler, Shlomi; Glickman, Yinnon; Keselman, Anna; Ozeri, Roee

    2011-01-01

    We report on the implementation of a quantum analog to the classical lock-in amplifier. All the lock-in operations: modulation, detection and mixing, are performed via the application of non-commuting quantum operators on the electronic spin state of a single trapped Sr+ ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. With this technique we measure magnetic fields with sensitivity of 25 pT/sqrt(Hz) and light shifts with an uncertainty below 140 mHz after 1320 seconds of averaging. These sensitivities are limited by quantum projection noise and, to our knowledge, are more than two orders of magnitude better than with other single-spin probe technologies. In fact, our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic-spin one micrometer from an ion-detector with nanometer resolution. As a first application ...

  6. Status Report on the Energy Amplifier

    CERN Document Server

    Rubbia, Carlo

    1994-01-01

    0ne year after its first presentation,the Energy Amplifier (EA) Project holds its promises for a environmentally acceptable form of energy extraction from nuclei, namely to eliminate or at least greatly reduce(i) the environmental impact of the long-lived highly radioactive waste;(ii) the possibility of diversions toward military applications;(iii) the risks of an accidental divergence related to the critical operation of the chain reaction and (iv) make a more efficient use of a fuel which is less radio-toxic to extract and more abundant on Earth than Uranium. In these respects the EA (or equivalent scenarios from Los Alamos and elsewhere) is comparable in performance to Thermonuclear Fusion. Bot h approches offer pratically unl;imited fuel resources: the energetic content of Lithium on the Earth's crust needed by Fusion is estimated to be seven times the one of Thorium and they are both adequate for millions of years of very intensived utilisation.However the EA can be built economically,in a variety of siz...

  7. Pulse laser imaging amplifier for advanced ladar systems

    Science.gov (United States)

    Khizhnyak, Anatoliy; Markov, Vladimir; Tomov, Ivan; Murrell, David

    2016-05-01

    Security measures sometimes require persistent surveillance of government, military and public areas Borders, bridges, sport arenas, airports and others are often surveilled with low-cost cameras. Their low-light performance can be enhanced with laser illuminators; however various operational scenarios may require a low-intensity laser illumination with the object-scattered light intensity lower than the sensitivity of the Ladar image detector. This paper discusses a novel type of high-gain optical image amplifier. The approach enables time-synchronization of the incoming and amplifying signals with accuracy <= 1 ns. The technique allows the incoming signal to be amplified without the need to match the input spectrum to the cavity modes. Instead, the incoming signal is accepted within the spectral band of the amplifier. We have gauged experimentally the performance of the amplifier with a 40 dB gain and an angle of view 20 mrad.

  8. GHz bandwidth noise eater hybrid optical amplifier: design guidelines.

    Science.gov (United States)

    Danion, Gwennaël; Bondu, François; Loas, Goulc'hen; Alouini, Mehdi

    2014-07-15

    This Letter describes the design of an optical amplifier system optimized to reduce the relative intensity noise (RIN) of the input signal, and discloses its performance in terms of intensity noise reduction and bandwidth, without phase noise degradation. This polarization-maintaining amplifier is composed of an erbium-doped fiber amplifier (EDFA) cascaded with a semiconductor optical amplifier (SOA). The EDFA is sized to feed the SOA with a constant power corresponding to the optimal saturation level for noise reduction, through coherent population oscillations. When properly optimized, such an amplifier provides, simultaneously, 17 dB optical gain, 5.4 dB noise factor, and 20 dB reduction of the input-RIN across a 3 GHz bandwidth, without any electronics feedback loop.

  9. Quantum Dot Semiconductor Optical Amplifiers - Physics and Applications

    DEFF Research Database (Denmark)

    Berg, Tommy Winther

    2004-01-01

    This thesis describes the physics and applications of quantum dot semiconductor optical amplifiers based on numerical simulations. These devices possess a number of unique properties compared with other types of semiconductor amplifiers, which should allow enhanced performance of semiconductor...... respects is comparable to those of fiber amplifiers. The possibility of inverting the optically active states to a large degree is essential in order to achieve this performance. Optical signal processing through cross gain modulation and four wave mixing is modeled and described. For both approaches...... and QW devices and to experiments on quantum dot amplifiers. These comparisons outline the qualitative differences between the different types of amplifiers. In all cases focus is put on the physical processes responsible the differences....

  10. A Review of High Voltage Drive Amplifiers for Capacitive Actuators

    DEFF Research Database (Denmark)

    Huang, Lina; Zhang, Zhe; Andersen, Michael A. E.

    2012-01-01

    This paper gives an overview of the high voltage amplifiers, which are used to drive capacitive actuators. The amplifiers for both piezoelectric and DEAP (dielectric electroactive polymer) actuator are discussed. The suitable topologies for driving capacitive actuators are illustrated in detail, ......, including linear as well as switched mode amplifiers. In the past much attention has been paid on the driver for piezoelectric actuator. As DEAP is a type of new material, there is not much literature reference for it.......This paper gives an overview of the high voltage amplifiers, which are used to drive capacitive actuators. The amplifiers for both piezoelectric and DEAP (dielectric electroactive polymer) actuator are discussed. The suitable topologies for driving capacitive actuators are illustrated in detail...

  11. Digital Lock-in Amplifier Based on Microcontroller

    Institute of Scientific and Technical Information of China (English)

    An-li TAO; Guo-dong XU; Ke-xue LUO; Gang-ling ZHANG

    2010-01-01

    A method of implementing high cost-effective and highly integrated digital lock-in amplifier with microcontroller is discussed. And the digital lock-in amplifier is more suitable for measuring low-frequency weak signal.Digital signal sequence is obtained through sampling signal measured over an integer number of signal periods, but digital reference sequence is acquired through mathematical operation, then digital phase sensitive detection can be implemented by calculating the cross-correlation function of digital signal sequence and digital reference sequence.In addition, the frequency response and phase character of the digital lock-in amplifier is analyzed. Finally, the designed digital lock-in amplifier is achieved. Experimental results show that the digital lock-in amplifier can be used for measuring weak signal with low ignal-to-noise ratio.

  12. Uncovering the Number and Clonal Dynamics of Mesp1 Progenitors during Heart Morphogenesis

    Directory of Open Access Journals (Sweden)

    Samira Chabab

    2016-01-01

    Full Text Available The heart arises from distinct sources of cardiac progenitors that independently express Mesp1 during gastrulation. The precise number of Mesp1 progenitors that are specified during the early stage of gastrulation, and their clonal behavior during heart morphogenesis, is currently unknown. Here, we used clonal and mosaic tracing of Mesp1-expressing cells combined with quantitative biophysical analysis of the clonal data to define the number of cardiac progenitors and their mode of growth during heart development. Our data indicate that the myocardial layer of the heart derive from ∼250 Mesp1-expressing cardiac progenitors born during gastrulation. Despite arising at different time points and contributing to different heart regions, the temporally distinct cardiac progenitors present very similar clonal dynamics. These results provide insights into the number of cardiac progenitors and their mode of growth and open up avenues to decipher the clonal dynamics of progenitors in other organs and tissues.

  13. A Gallium Arsenide MESFET Operational Amplifier for Use in Composite Operational Amplifiers

    Science.gov (United States)

    1993-12-01

    F., Operational Amplifiers and Linear Integrated Circuits, 4th ed., Prentice Hall, 1991. 6. Sedra , A. S., and Smith , K. C., Microelectronic Circuits...7, pp. 1422-1429, July 1992. 17. McCamant, A. J., McCormack G. D., and Smith , D. H., "An Improved GaAs MESFET Model for SPICE," IEEE Transactions of...34Modeling Frequency Dependence of out Impedance of a Microwave MESFET at Low Frequencies," Electronics Letters, pp. 528-529, June 1985. 39. Smith , M. et al

  14. La violencia de hijos adolescentes contra sus progenitores La violencia de hijos adolescentes contra sus progenitores

    Directory of Open Access Journals (Sweden)

    Concepción Aroca Montolío

    2013-10-01

    Full Text Available According to Prosecutor’s Office of the Minor, the accusation interposed by mothers and/or fathers victims by theirs children, along 2007 were 2603, in 2008 amounted 4.211, in 2009 there were 5.209 and in 2010 there were 8.000 accusations. Suede this worrying increase, the principal aim of our article is to check the scientific international and national documentation, from 1957 until the year 2010 that analyses the phenomenon of the adolescent violence against parents, to achieve an approximation to its keys that there allows us the comprehension and analysis of this serious familiar problem. For it we will analyse: (a the importance of this crime by means of criminological mediators: prevalence and incidence; (b the age and sex variables’ aggressors to be able to establish a basic profile about theirs and, (c the violence types that the teenagers wield to damage, prejudice and suffering against their progenitors, with the aim to obtain what they want. The information obtained in this research review and qualitative analysis, change in base to the methodology used and the type of sample under study to obtain conclusions. Even though, we wantto do research into needs to investigate this type of familiar violence, and from there, to do researches with rigorous scientific methodologies, unifying criteria and variables to be investigating, to be able to anticipate in this increasing problem that the parents have. Según la Fiscalía del Menor en el año 2007, las denuncias interpuestas por madres y/o padres, víctimas de malos tratos por sus hijos e hijas menores de edad, fueron 2.683. En 2008 ascendieron a 4.211, en 2009 se presentaron 5.209 y en el año 2010 se registraron 8.000 denuncias. Ante éste preocupante incremento, el objetivo principal de nuestro artículo es revisar la documentación científica que analiza la violencia filio-parental,  desde 1957 hasta el año 2011, para lograr una aproximación a sus claves que nos permita la

  15. A modular positive feedback-based gene amplifier

    Directory of Open Access Journals (Sweden)

    Bhalerao Kaustubh D

    2010-02-01

    Full Text Available Abstract Background Positive feedback is a common mechanism used in the regulation of many gene circuits as it can amplify the response to inducers and also generate binary outputs and hysteresis. In the context of electrical circuit design, positive feedback is often considered in the design of amplifiers. Similar approaches, therefore, may be used for the design of amplifiers in synthetic gene circuits with applications, for example, in cell-based sensors. Results We developed a modular positive feedback circuit that can function as a genetic signal amplifier, heightening the sensitivity to inducer signals as well as increasing maximum expression levels without the need for an external cofactor. The design utilizes a constitutively active, autoinducer-independent variant of the quorum-sensing regulator LuxR. We experimentally tested the ability of the positive feedback module to separately amplify the output of a one-component tetracycline sensor and a two-component aspartate sensor. In each case, the positive feedback module amplified the response to the respective inducers, both with regards to the dynamic range and sensitivity. Conclusions The advantage of our design is that the actual feedback mechanism depends only on a single gene and does not require any other modulation. Furthermore, this circuit can amplify any transcriptional signal, not just one encoded within the circuit or tuned by an external inducer. As our design is modular, it can potentially be used as a component in the design of more complex synthetic gene circuits.

  16. Is black-hole ringdown a memory of its progenitor?

    Science.gov (United States)

    Kamaretsos, Ioannis; Hannam, Mark; Sathyaprakash, B S

    2012-10-05

    We perform an extensive numerical study of coalescing black-hole binaries to understand the gravitational-wave spectrum of quasinormal modes excited in the merged black hole. Remarkably, we find that the masses and spins of the progenitor are clearly encoded in the mode spectrum of the ringdown signal. Some of the mode amplitudes carry the signature of the binary's mass ratio, while others depend critically on the spins. Simulations of precessing binaries suggest that our results carry over to generic systems. Using Bayesian inference, we demonstrate that it is possible to accurately measure the mass ratio and a proper combination of spins even when the binary is itself invisible to a detector. Using a mapping of the binary masses and spins to the final black-hole spin allows us to further extract the spin components of the progenitor. Our results could have tremendous implications for gravitational astronomy by facilitating novel tests of general relativity using merging black holes.

  17. Endothelial progenitor cells: Exploring the pleiotropic effects of statins

    Science.gov (United States)

    Sandhu, Kully; Mamas, Mamas; Butler, Robert

    2017-01-01

    Statins have become a cornerstone of risk modification for ischaemic heart disease patients. A number of studies have shown that they are effective and safe. However studies have observed an early benefit in terms of a reduction in recurrent infarct and or death after a myocardial infarction, prior to any significant change in lipid profile. Therefore, pleiotropic mechanisms, other than lowering lipid profile alone, must account for this effect. One such proposed pleiotropic mechanism is the ability of statins to augment both number and function of endothelial progenitor cells. The ability to augment repair and maintenance of a functioning endothelium may have profound beneficial effect on vascular repair and potentially a positive impact on clinical outcomes in patients with cardiovascular disease. The following literature review will discuss issues surrounding endothelial progenitor cell (EPC) identification, role in vascular repair, factors affecting EPC numbers, the role of statins in current medical practice and their effects on EPC number. PMID:28163831

  18. Massive Binaries, Wolf-Rayet Stars and Supernova Progenitors

    Directory of Open Access Journals (Sweden)

    J.J. Eldridge

    2007-01-01

    Full Text Available La estrellas binarias son importantes para entender la evoluci on estelar. Presentamos un resumen de c omo las predicciones de las tasas relativas de supernova var an entre estrellas aisladas y binarias. Tambi en mostramos c omo el espacio de par ametros de tipos diferentes de supernovas di eren entre estrellas aisladas y binarias. Entonces, consideramos una pregunta importante sobre c omo saber las propiedades del progenitor de supernova a trav es de las im agenes previas a la explosi on y a trav es del trabajo reciente de producir colores sint eticos de nuestros modelos estelares para hacer una comparaci on directa con cualquier detecci on o l mite obtenido de las im agenes pre-explosi on de los progenitores de supernova

  19. Neuromesodermal progenitors and the making of the spinal cord

    Science.gov (United States)

    Henrique, Domingos; Abranches, Elsa; Verrier, Laure; Storey, Kate G.

    2016-01-01

    Neuromesodermal progenitors (NMps) contribute to both the elongating spinal cord and the adjacent paraxial mesoderm. It has been assumed that these cells arise as a result of patterning of the anterior neural plate. However, as the molecular mechanisms that specify NMps in vivo are uncovered, and as protocols for generating these bipotent cells from mouse and human pluripotent stem cells in vitro are established, the emerging data suggest that this view needs to be revised. Here, we review the characteristics, regulation, in vitro derivation and in vivo induction of NMps. We propose that these cells arise within primitive streak-associated epiblast via a mechanism that is separable from that which establishes neural fate in the anterior epiblast. We thus argue for the existence of two distinct routes for making central nervous system progenitors. PMID:26329597

  20. Epigenetic Reprogramming of Muscle Progenitors: Inspiration for Clinical Therapies

    Directory of Open Access Journals (Sweden)

    Silvia Consalvi

    2016-01-01

    Full Text Available In the context of regenerative medicine, based on the potential of stem cells to restore diseased tissues, epigenetics is becoming a pivotal area of interest. Therapeutic interventions that promote tissue and organ regeneration have as primary objective the selective control of gene expression in adult stem cells. This requires a deep understanding of the epigenetic mechanisms controlling transcriptional programs in tissue progenitors. This review attempts to elucidate the principle epigenetic regulations responsible of stem cells differentiation. In particular we focus on the current understanding of the epigenetic networks that regulate differentiation of muscle progenitors by the concerted action of chromatin-modifying enzymes and noncoding RNAs. The novel exciting role of exosome-bound microRNA in mediating epigenetic information transfer is also discussed. Finally we show an overview of the epigenetic strategies and therapies that aim to potentiate muscle regeneration and counteract the progression of Duchenne Muscular Dystrophy (DMD.

  1. Efficient performance simulation of class D amplifier output stages

    DEFF Research Database (Denmark)

    Nyboe, Flemming; Risbo, Lars; Andreani, Pietro

    2005-01-01

    Straightforward simulation of amplifier distortion involves transient simulation of operation on a sine wave input signal, and a subsequent FFT of the output voltage. This approach is very slow on class D amplifiers, since the switching behavior forces simulation time steps that are many orders...... of magnitude smaller than the duration of one period of an audio sine wave. This work presents a method of simulating the amplifier transfer characteristic using a minimum amount of simulation time, and then deriving THD from the results....

  2. Introduction to RF power amplifier design and simulation

    CERN Document Server

    Eroglu, Abdullah

    2015-01-01

    Introduction to RF Power Amplifier Design and Simulation fills a gap in the existing literature by providing step-by-step guidance for the design of radio frequency (RF) power amplifiers, from analytical formulation to simulation, implementation, and measurement. Featuring numerous illustrations and examples of real-world engineering applications, this book:Gives an overview of intermodulation and elaborates on the difference between linear and nonlinear amplifiersDescribes the high-frequency model and transient characteristics of metal-oxide-semiconductor field-effect transistorsDetails activ

  3. Investigation of a background suppression transimpedance amplifier for photovoltaic detectors

    Science.gov (United States)

    Metzger, Ferdinand J., Jr.

    1992-12-01

    The current generation of transimpedance amplifier based detector systems are limited by opamp saturation when operating at a high gain or in the presence of a large background signal. To eliminate saturation, an amplifier that is frequency dependent is developed. Additionally, the noise sources in the conventional transimpedance amplifier and photovoltaic detector are quantified for comparison to any modified circuit. Initial results indicate that the frequency dependent detector system is a viable system, however, further development is required. Further research of this technology is expected to support future infrared and long range detection applications.

  4. Design procedure for optimizing CMOS low noise operational amplifiers

    Institute of Scientific and Technical Information of China (English)

    Li Zhiyuan; Ye Yizheng; Ma Jianguo

    2009-01-01

    This paper presents and experimentally verifies an optimized design procedure for a CMOS low noise operational amplifier.The design procedure focuses on the noise performance,which is the key requirement for low noise operational amplifiers.Based on the noise level and other specifications such as bandwidth,signal swing,slew rate,and power consumption,the device sizes and the biasing conditions are derived.In order to verify the proposed design procedure,a three-stage operational amplifier has been designed.The device parameters obtained from the proposed design procedure closely agree with the simulated results obtained by using HSPICE.

  5. Optimization and Performance Analysis of Bulk-Driven Differential Amplifier

    Directory of Open Access Journals (Sweden)

    Antarpreet kaur

    2014-04-01

    Full Text Available In recent years, there has been an increasing demand for high-speed digital circuits at low power consumption. This paper presents a design of input stage of Operational Amplifier i.e cascode differential amplifier using a standard 65nm CMOS Technology.A comparison betweem gate-driven, bulk-driven and cascode bulk driven bulk-driven differential amplifier is described. The Results demonstrate that CMMR is 83.98 dB, 3-dB Bandwidth is 1.04 MHz. The circuit dissipate power of 28uWunder single supply of 1.0V.

  6. Amplifier circuit operable over a wide temperature range

    Science.gov (United States)

    Kelly, Ronald D.; Cannon, William L.

    1979-01-01

    An amplifier circuit having stable performance characteristics over a wide temperature range from approximately 0.degree. C up to as high as approximately 500.degree. C, such as might be encountered in a geothermal borehole. The amplifier utilizes ceramic vacuum tubes connected in directly coupled differential amplifier pairs having a common power supply and a cathode follower output stage. In an alternate embodiment, for operation up to 500.degree. C, positive and negative power supplies are utilized to provide improved gain characteristics, and all electrical connections are made by welding. Resistor elements in this version of the invention are specially heat treated to improve their stability with temperature.

  7. High power solid state rf amplifier for proton accelerator.

    Science.gov (United States)

    Jain, Akhilesh; Sharma, Deepak Kumar; Gupta, Alok Kumar; Hannurkar, P R

    2008-01-01

    A 1.5 kW solid state rf amplifier at 352 MHz has been developed and tested at RRCAT. This rf source for cw operation will be used as a part of rf system of 100 MeV proton linear accelerator. A rf power of 1.5 kW has been achieved by combining output power from eight 220 W rf amplifier modules. Amplifier modules, eight-way power combiner and divider, and directional coupler were designed indigenously for this development. High efficiency, ease of fabrication, and low cost are the main features of this design.

  8. 2250-MHz High Efficiency Microwave Power Amplifier (HEMPA)

    Science.gov (United States)

    Sims, W. Herbert; Bell, Joseph L. (Technical Monitor)

    2001-01-01

    Tnis paper will focus on developing an exotic switching technique that enhances the DC-to-RF conversion efficiency of microwave power amplifiers. For years, switching techniques implemented in the 10 kHz to 30 MHz region have resulted in DC-to-RF conversion efficiencies of 90-95-percent. Currently amplifier conversion efficiency, in the 2-3 GHz region approaches, 10-20-percent. Using a combination of analytical modeling and hardware testing, a High Efficiency Microwave Power Amplifier was built that demonstrated conversion efficiencies four to five times higher than current state of the art.

  9. Externally pumped millimeter-wave Josephson-junction parametric amplifier

    DEFF Research Database (Denmark)

    Levinsen, M.T; Pedersen, Niels Falsig; Sørensen, Ole;

    1980-01-01

    A unified theory of the singly and doubly degenerate Josephson-junction parametric amplifier is presented. Experiments with single junctions on both amplifier modes at frequencies 10, 35, and 70 GHz are discussed. Low-noise temperature (∼100 K, single sideband (SSB)) and reasonable gain (∼8 d......B) were obtained at 35 GHz in the singly degenerate mode. On the basis of the theory and experiments, a general procedure for optimizing junction parameters is discussed and illustrated by the specific design of a 100-GHz amplifier....

  10. Neural progenitor cells regulate microglia functions and activity.

    Science.gov (United States)

    Mosher, Kira I; Andres, Robert H; Fukuhara, Takeshi; Bieri, Gregor; Hasegawa-Moriyama, Maiko; He, Yingbo; Guzman, Raphael; Wyss-Coray, Tony

    2012-11-01

    We found mouse neural progenitor cells (NPCs) to have a secretory protein profile distinct from other brain cells and to modulate microglial activation, proliferation and phagocytosis. NPC-derived vascular endothelial growth factor was necessary and sufficient to exert at least some of these effects in mice. Thus, neural precursor cells may not only be shaped by microglia, but also regulate microglia functions and activity.

  11. In vitro pancreas organogenesis from dispersed mouse embryonic progenitors

    DEFF Research Database (Denmark)

    Greggio, Chiara; De Franceschi, Filippo; Figueiredo-Larsen, Evan Manuel;

    2014-01-01

    cells cooperate to form an organ by reducing its initial complexity to few progenitors. It is a model that reproduces the 3D architecture of the pancreas and that is therefore useful to study morphogenesis, including polarization of epithelial structures and branching. It is also appropriate to assess...... the response to mechanical cues of the niche such as stiffness and the effects on cell´s tensegrity....

  12. Glial progenitor cell-based treatment of the childhood leukodystrophies

    DEFF Research Database (Denmark)

    Osorio, M Joana; Goldman, Steven A

    2016-01-01

    The childhood leukodystrophies comprise a group of hereditary disorders characterized by the absence, malformation or destruction of myelin. These disorders share common clinical, radiological and pathological features, despite their diverse molecular and genetic etiologies. Oligodendrocytes...... genetic editing of pluripotent stem cells. Yet these challenges notwithstanding, the promise of glial progenitor cell-based treatment of the childhood myelin disorders offers hope to the many victims of this otherwise largely untreatable class of disease....

  13. Fate mapping by piggyBac transposase reveals that neocortical GLAST+ progenitors generate more astrocytes than Nestin+ progenitors in rat neocortex.

    Science.gov (United States)

    Siddiqi, Faez; Chen, Fuyi; Aron, Abraham W; Fiondella, Christopher G; Patel, Komal; LoTurco, Joseph J

    2014-02-01

    Progenitors within the neocortical ventricular zone (VZ) first generate pyramidal neurons and then astrocytes. We applied novel piggyBac transposase lineage tracking methods to fate-map progenitor populations positive for Nestin or glutamate and aspartate transpoter (GLAST) promoter activities in the rat neocortex. GLAST+ and Nestin+ progenitors at embryonic day 13 (E13) produce lineages containing similar rations of neurons and astrocytes. By E15, the GLAST+ progenitor population diverges significantly to produce lineages with 5-10-fold more astrocytes relative to neurons than generated by the Nestin+ population. To determine when birth-dated progeny within GLAST+ and Nestin+ populations diverge, we used a Cre/loxP fate-mapping system in which plasmids are lost after a cell division. By E18, birth-dated progeny of GLAST+ progenitors give rise to 2-3-fold more neocortical astrocytes than do Nestin+ progenitors. Finally, we used a multicolor clonal labeling method to show that the GLAST+ population labeled at E15 generates astrocyte progenitors that produce larger, spatially restricted, clonal clusters than the Nestin+ population. This study provides in vivo evidence that by mid-corticogenesis (E15), VZ progenitor populations have significantly diversified in terms of their potential to generate astrocytes and neurons.

  14. ENDOTHELIAL PROGENITOR CELLS AS SHUTTLE OF ANTICANCER AGENTS.

    Science.gov (United States)

    Laurenzana, Anna; Margheri, Francesca; Chilla', Anastasia; Biagioni, Alessio; Margheri, Giancarlo; Calorini, Lido; Fibbi, Gabriella; Del Rosso, Mario

    2016-08-08

    Cell therapies are treatments in which stem or progenitor cells are induced to differentiate into the specific cell type required to repair damaged or destroyed tissues. Following their discovery, endothelial progenitor cells (EPCs) have stimulated a worldwide interest as possible vehicles to perform an autologous cell-therapy of tumors. Taking into account the tumor-homing properties of EPCs, two different approaches to control cancer progression have been pursued by combining the cell-based therapy with gene therapy or with nanomedicine. The first one is based on the possibility to engineer EPCs to express different transgenes, the second one on the capacity of EPCs to uptake nanomaterials. Here we will review the most important progresses covering the following issues: the characterization of bona fide endothelial progenitor cells, their role in tumor vascularisation and metastasis, and preclinical data about their use in cell-based tumor therapy, considering anti-angiogenic, suicide, immune-stimulating and oncolytic virus gene-therapy. The mixed approach of EPC cell therapy and nanomedicine will be discussed in terms of plasmonic-dependent thermoablation and molecular imaging.

  15. Stem and progenitor cells: advancing bone tissue engineering.

    Science.gov (United States)

    Tevlin, R; Walmsley, G G; Marecic, O; Hu, Michael S; Wan, D C; Longaker, M T

    2016-04-01

    Unlike many other postnatal tissues, bone can regenerate and repair itself; nevertheless, this capacity can be overcome. Traditionally, surgical reconstructive strategies have implemented autologous, allogeneic, and prosthetic materials. Autologous bone--the best option--is limited in supply and also mandates an additional surgical procedure. In regenerative tissue engineering, there are myriad issues to consider in the creation of a functional, implantable replacement tissue. Importantly, there must exist an easily accessible, abundant cell source with the capacity to express the phenotype of the desired tissue, and a biocompatible scaffold to deliver the cells to the damaged region. A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key advances in stem and progenitor cell contribution to the field of bone tissue engineering. In this review, we briefly introduce various adult stem cells implemented in bone tissue engineering such as mesenchymal stem cells (including bone marrow- and adipose-derived stem cells), endothelial progenitor cells, and induced pluripotent stem cells. We then discuss numerous advances associated with their application and subsequently focus on technological advances in the field, before addressing key regenerative strategies currently used in clinical practice. Stem and progenitor cell implementation in bone tissue engineering strategies have the ability to make a major impact on regenerative medicine and reduce patient morbidity. As the field of regenerative medicine endeavors to harness the body's own cells for treatment, scientific innovation has led to great advances in stem cell-based therapies in the past decade.

  16. Functional analysis of retinal microglia and their effects on progenitors.

    Science.gov (United States)

    Carter, Debra A; Balasubramaniam, Balini; Dick, Andrew D

    2013-01-01

    The identification of stem/progenitor cells within the retinal neural environment has opened up the possibility of therapy via cellular replacement and/or reprogramming of resident cell populations. Within the neuro-retinal niche, following injury or in disease states (including inflammation and degeneration), cellular responses affect tissue homeostasis, reduce cell density, disrupt tissue architecture, and produce scar formation. Microglia (resident retinal immune cell tissue macrophage) are key to the maintenance of retinal homeostasis and are implicated in responses that may influence the control and behavior of retinal progenitors. Factors to consider in the generation of a transplantable cell resource with good migratory and integrative capacity include their yield, purity, and functional viability. Utilizing human postmortem retina, we have created a research platform to isolate, culture, and characterize adult retinal microglia as well as analyze their effect on retinal progenitors. Here, we describe techniques using magnetic labeled bead cell separation to isolate pure populations of retinal CD133(+) precursor cells and CD11b(+) microglia from primary adult retinal cell suspensions (RCSs), enabling flow cytometric cell phenotypic and qPCR genotypic analysis, as well as functional analysis by real-time ratiometric calcium imaging.

  17. Decoding the stellar fossils of the dusty Milky Way progenitors

    CERN Document Server

    de Bennassuti, Matteo; Valiante, Rosa; Salvadori, Stefania

    2014-01-01

    We investigate the metallicity distribution function (MDF) in the Galactic halo and the relative fraction of Carbon-normal and Carbon-rich stars. To this aim, we use an improved version of the semi-analytical code GAlaxy MErger Tree and Evolution (GAMETE), that reconstructs the hierarchical merger tree of the MW, following the star formation history and the metal and dust evolution in individual progenitors. The predicted scaling relations between the dust, metal and gas masses for MW progenitors show a good agreement with observational data of local galaxies and of Gamma Ray Burst (GRB) host galaxies at 0.1 140 M_{sun}, into the Pair-Instability SN progenitor mass range. The relative contribution of C-normal and C-enhanced stars to the MDF and its dependence on [Fe/H] points to a scenario where the Pop III/II transition is driven by dust-cooling and the first low-mass stars form when the dust-to-gas ratio in their parent clouds exceeds a critical value of D_crit = 4.4 x 10^{-9}.

  18. Endothelial Progenitor Cells for Diagnosis and Prognosis in Cardiovascular Disease

    Directory of Open Access Journals (Sweden)

    Caterina Oriana Aragona

    2016-01-01

    Full Text Available Objective. To identify, evaluate, and synthesize evidence on the predictive power of circulating endothelial progenitor cells (EPCs in cardiovascular disease, through a systematic review of quantitative studies. Data Sources. MEDLINE was searched using keywords related to “endothelial progenitor cells” and “endothelium” and, for the different categories, respectively, “smoking”; “blood pressure”; “diabetes mellitus” or “insulin resistance”; “dyslipidemia”; “aging” or “elderly”; “angina pectoris” or “myocardial infarction”; “stroke” or “cerebrovascular disease”; “homocysteine”; “C-reactive protein”; “vitamin D”. Study Selection. Database hits were evaluated against explicit inclusion criteria. From 927 database hits, 43 quantitative studies were included. Data Syntheses. EPC count has been suggested for cardiovascular risk estimation in the clinical practice, since it is currently accepted that EPCs can work as proangiogenic support cells, maintaining their importance as regenerative/reparative potential, and also as prognostic markers. Conclusions. EPCs showed an important role in identifying cardiovascular risk conditions, and to suggest their evaluation as predictor of outcomes appears to be reasonable in different defined clinical settings. Due to their capability of proliferation, circulation, and the development of functional progeny, great interest has been directed to therapeutic use of progenitor cells in atherosclerotic diseases. This trial is registered with registration number: Prospero CRD42015023717.

  19. Supernova 2008bk and Its Red Supergiant Progenitor

    CERN Document Server

    Van Dyk, Schuyler D; Elias-Rosa, Nancy; Taubenberger, Stefan; Li, Weidong; Howerton, Stanley; Pignata, Giuliano; Morrell, Nidia; Hamuy, Mario; Filippenko, Alexei V

    2010-01-01

    We have observed Supernova (SN) 2008bk in NGC 7793, both photometrically and spectroscopically, primarily at late times. We find that it is a Type II-Plateau (II-P) SN, which most closely resembles the low-luminosity SN 1999br in NGC 4900. Given the overall similarity between the observed light curves and colors of SNe 2008bk and 1999br, we infer that the total visual extinction to SN 2008bk must be almost entirely due to the Galactic foreground, similar to that for SN 1999br: A_V=0.065 mag, which is substantially less than the 1.0 +/- 0.5 mag assumed by Mattila et al. (2008). Furthermore, we confirm the identification of the putative red supergiant progenitor star of the SN in high-quality g'r'i' Gemini-South images from 2007. Little ambiguity exists in this progenitor identification; besides the connection between the star Sk -69 202 and SN 1987A, it qualifies as one of the best SN progenitor identifications to date. From a combination of the Gemini images with archival, pre-SN, Very Large Telescope JHK_s i...

  20. Transplanted progenitors generate functional enteric neurons in the postnatal colon

    Science.gov (United States)

    Hotta, Ryo; Stamp, Lincon A.; Foong, Jaime P.P.; McConnell, Sophie N.; Bergner, Annette J.; Anderson, Richard B.; Enomoto, Hideki; Newgreen, Donald F.; Obermayr, Florian; Furness, John B.; Young, Heather M.

    2013-01-01

    Cell therapy has the potential to treat gastrointestinal motility disorders caused by diseases of the enteric nervous system. Many studies have demonstrated that various stem/progenitor cells can give rise to functional neurons in the embryonic gut; however, it is not yet known whether transplanted neural progenitor cells can migrate, proliferate, and generate functional neurons in the postnatal bowel in vivo. We transplanted neurospheres generated from fetal and postnatal intestinal neural crest–derived cells into the colon of postnatal mice. The neurosphere-derived cells migrated, proliferated, and generated neurons and glial cells that formed ganglion-like clusters within the recipient colon. Graft-derived neurons exhibited morphological, neurochemical, and electrophysiological characteristics similar to those of enteric neurons; they received synaptic inputs; and their neurites projected to muscle layers and the enteric ganglia of the recipient mice. These findings show that transplanted enteric neural progenitor cells can generate functional enteric neurons in the postnatal bowel and advances the notion that cell therapy is a promising strategy for enteric neuropathies. PMID:23454768

  1. Transplantable NK cell progenitors in murine bone marrow.

    Science.gov (United States)

    Moore, T; Bennett, M; Kumar, V

    1995-02-15

    Differentiation of NK cells from pluripotent hematopoietic stem cells is a poorly understood process. Although it is known that NK cells are bone marrow derived and dependent upon an intact bone marrow microenvironment for complete maturation, it is not known if they arise from an intermediate lymphoid stem cell or from progenitors exclusively committed to the NK lineage. To determine whether phenotypically distinct committed NK progenitor cells exist in murine bone marrow, we sorted cells capable of repopulating recipient mice with mature NK cells upon i.v. transfer. We identified a rare population of bone marrow cells with the phenotype Ly6+ Lin- c-kit+ CD43high Fall-3high TSA-1- AA4.1low Rh123high that is highly enriched for the ability to generate NK cells after transplantation. Although these cells are relatively depleted of Rh123low pluripotent stem cells, they are highly enriched for both lymphoid and myeloid repopulating ability. Thus, we have found no evidence to support the existence of a phenotypically distinct transplantable progenitor population in mouse bone marrow that is either exclusively committed to the NK cell lineage or exhibits the functional characteristics of a common lymphoid stem cell.

  2. Neutronization During Carbon Simmering In Type Ia Supernova Progenitors

    Science.gov (United States)

    Martínez-Rodríguez, Héctor; Piro, Anthony L.; Schwab, Josiah; Badenes, Carles

    2016-07-01

    When a Type Ia supernova (SN Ia) progenitor first ignites carbon in its core, it undergoes ˜103-104 years of convective burning prior to the onset of thermonuclear runaway. This carbon simmering phase is important for setting the thermal profile and composition of the white dwarf. Using the MESA stellar evolution code, we follow this convective burning and examine the production of neutron-rich isotopes. The neutron content of the SN fuel has important consequences for the ensuing nucleosynthesis, and in particular, for the production of secondary Fe-peak nuclei like Mn and stable Ni. These elements have been observed in the X-ray spectra of SN remnants like Tycho, Kepler, and 3C 397, and their yields can provide valuable insights into the physics of SNe Ia and the properties of their progenitors. We find that weak reactions during simmering can at most generate a neutron excess of ≈ 3 × 10-4. This is ≈ 70% lower than that found in previous studies that do not take the full density and temperature profile of the simmering region into account. Our results imply that the progenitor metallicity is the main contributor to the neutron excess in SN Ia fuel for Z ≳ 1/3 Z ⊙. Alternatively, at lower metallicities, this neutron excess provides a floor that should be present in any centrally-ignited SN Ia scenario.

  3. Human fetal cardiac progenitors: The role of stem cells and progenitors in the fetal and adult heart.

    Science.gov (United States)

    Bulatovic, Ivana; Månsson-Broberg, Agneta; Sylvén, Christer; Grinnemo, Karl-Henrik

    2016-02-01

    The human fetal heart is formed early during embryogenesis as a result of cell migrations, differentiation, and formative blood flow. It begins to beat around gestation day 22. Progenitor cells are derived from mesoderm (endocardium and myocardium), proepicardium (epicardium and coronary vessels), and neural crest (heart valves, outflow tract septation, and parasympathetic innervation). A variety of molecular disturbances in the factors regulating the specification and differentiation of these cells can cause congenital heart disease. This review explores the contribution of different cardiac progenitors to the embryonic heart development; the pathways and transcription factors guiding their expansion, migration, and functional differentiation; and the endogenous regenerative capacity of the adult heart including the plasticity of cardiomyocytes. Unfolding these mechanisms will become the basis for understanding the dynamics of specific congenital heart disease as well as a means to develop therapy for fetal as well as postnatal cardiac defects and heart failure.

  4. Amplified spontaneous emission spectrum at the output of a diode amplifier saturated by an input monochromatic wave

    Science.gov (United States)

    Bogatov, A. P.; Drakin, A. E.; D'yachkov, N. V.; Gushchik, T. I.

    2016-08-01

    Expressions for the amplitudes of amplified spontaneous emission waves in a diode amplifier near the frequency ω0 of a 'strong' input monochromatic wave have been derived in terms of a random function of a stationary Gaussian process. We have found expressions for the spectral density of the amplitudes and shown that, on the red side of the spectrum with respect to frequency ω0, spontaneous emission waves obtain additional nonlinear gain, induced by the strong wave, whereas on the blue side of the spectrum an additional loss is induced. Such behaviour of the amplitudes of amplified waves agrees with previous results.

  5. Perioperative iloprost and endothelial progenitor cells in uremic patients with severe limb ischemia undergoing peripheral revascularization.

    Science.gov (United States)

    Coppolino, Giuseppe; Buemi, Antoine; Bolignano, Davide; Lacquaniti, Antonio; La Spada, Michele; Stilo, Francesco; De Caridi, Giovanni; Benedetto, Francesco; Loddo, Saverio; Buemi, Michele; Spinelli, Francesco

    2009-11-01

    The incidence of severe limb ischemia (SLI) is high among haemodialysis (HD) patients. Limb rescue rate after surgical revascularization is relatively poor compared with patients with normal renal function. Prostanoids are an interesting category as adjuvants to revascularization. New vessel growth develops not exclusively by proliferation of endothelial cells in vascular extremities but also by cells mobilized from the bone marrow (HSC), transformed into endothelial progenitor cells (EPC) contributing to both re-endothelialization and neovascularization. Basal number of HSC and EPC is significantly reduced in HD patients and correlated with a subsequent defective neovascularization. The aim of this study was to evaluate the effects of perioperative treatment with iloprost in uremic patients with acute ischemia of lower limbs, undergoing surgical revascularization, on endothelial progenitor cells, hypothesizing a possible biological mechanism induced by the prostanoids. A search was also made for vascular remodeling processes through the analysis of the concentrations of soluble adhesion molecules (i-CAM, v-CAM, e-selectin), biochemical markers of endothelial activation. Thirty HD patients with SLI undergoing peripheral revascularization were enrolled (15 were treated with iloprost and 15 with a placebo). Iloprost was administered as an intra-arterial bolus of 3000 ng over 1 to 3 min immediately after revascularization and in the same affected artery. Serum samples were taken before revascularization (T0), at 6 (T6) and 24 h (T24) after infusion to measure sICAM-1, sE-selectin, and sVCAM-1, and for quantification of HSC and EPC. Progenitors were identified by specific surface markers CD34+, CD133+ and VEGFR2+. Count was conducted using PROCOUNT performed in a TRUCOUNT tube and with a FACSort flow cytometer. Before revascularization, all patients showed a decreased number of HSC and EPC. After 6 h, HSC augmented significantly compared with T0 in both groups. The

  6. Amplifying waveguide optical isolator with an integrated electromagnet

    OpenAIRE

    2007-01-01

    We have demonstrated an amplifying waveguide optical isolator with an integrated electromagnet. This provides a solution to the generally poor magnetic remanence of this type of isolator. The proof of principle is presented and optimization routes are discussed.

  7. Fast terahertz imaging using a quantum cascade amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Yuan, E-mail: yr235@cam.ac.uk; Wallis, Robert; Jessop, David Stephen; Degl' Innocenti, Riccardo; Klimont, Adam; Beere, Harvey E.; Ritchie, David A. [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom)

    2015-07-06

    A terahertz (THz) imaging scheme based on the effect of self-mixing in a 2.9 THz quantum cascade (QC) amplifier has been demonstrated. By coupling an antireflective-coated silicon lens to the facet of a QC laser, with no external optical feedback, the laser mirror losses are enhanced to fully suppress lasing action, creating a THz QC amplifier. The addition of reflection from an external target to the amplifier creates enough optical feedback to initiate lasing action and the resulting emission enhances photon-assisted transport, which in turn reduces the voltage across the device. At the peak gain point, the maximum photon density coupled back leads to a prominent self-mixing effect in the QC amplifier, leading to a high sensitivity, with a signal to noise ratio up to 55 dB, along with a fast data acquisition speed of 20 000 points per second.

  8. A dual-amplifier hot-wire anemometer

    Science.gov (United States)

    Sadeh, W. Z.; Finn, C. L.

    1979-01-01

    The conceptual design of a dual-amplifier constant-temperature hot-wire anemometer is described. This hot-wire anemometer consists of three basic independent modules: a Wheatstone bridge in which the hot wire is one of its arms, an error-correction amplifier, and a voltage-controlled current source. The last two modules constitute the feedback network of this hot-wire anemometer. Thus the output voltage across the wire is a true function of the instantaneous changes in the wire resistance induced by the cooling effect of the flow. The dual-amplifier is capable of reaching relatively high frequency response through adequate selection of its active elements. Suitable gain of the error-correction amplifier and proper choice of the transfer function of the current source has yielded a frequency bandwidth up to 200 kHz.

  9. Distributed CMOS Bidirectional Amplifiers Broadbanding and Linearization Techniques

    CERN Document Server

    El-Khatib, Ziad; Mahmoud, Samy A

    2012-01-01

    This book describes methods to design distributed amplifiers useful for performing circuit functions such as duplexing, paraphrase amplification, phase shifting power splitting and power combiner applications.  A CMOS bidirectional distributed amplifier is presented that combines for the first time device-level with circuit-level linearization, suppressing the third-order intermodulation distortion. It is implemented in 0.13μm RF CMOS technology for use in highly linear, low-cost UWB Radio-over-Fiber communication systems. Describes CMOS distributed amplifiers for optoelectronic applications such as Radio-over-Fiber systems, base station transceivers and picocells; Presents most recent techniques for linearization of CMOS distributed amplifiers; Includes coverage of CMOS I-V transconductors, as well as CMOS on-chip inductor integration and modeling; Includes circuit applications for UWB Radio-over-Fiber networks.

  10. Experimental examinations of semiconductor laser amplifiers for optical communication technology

    Science.gov (United States)

    Ludwig, Reinhold

    1993-01-01

    Properties of SLA (Semiconductor Laser Amplifier), which are particularly interesting for application to linear repeaters in coherent multichannel systems, are studied and design rules for future optimized amplifier structure are deduced. Laser diode antireflection was examined and reflection factor was measured. Low signal properties were discussed considering injection current, wavelengths, temperature and polarization. The coupling between amplifiers and glass fibers was examined. The utilization of cascade amplifiers as linear repeaters in multichannel heterodyne systems and television distribution systems was investigatied. The following results are obtained: measurement and calculation of the paradiaphony between two signals radiated in a SLA; multichannel data transfer through a SLA; polarization independent amplification with SLA configurations; measurement of the frequency dependence of four wave mixing sidelines in a SLA; measurement of the system degradation through echoes in a bidirectional SLA chain; data transmission with frequency conversion and calculation of multichannel transmission systems with cascade SLA, taking into account saturation, signal to noise ratio, bandwidth reduction and echo.

  11. On the unlimited gain of a nonlinear parametric amplifier

    DEFF Research Database (Denmark)

    Sorokin, Vladislav

    2014-01-01

    The present paper is concerned with analysis of the response of a nonlinear parametric amplifier in abroad range of system parameters, particularly beyond resonance. Such analysis is of particular interestfor micro- and nanosystems, since many small-scale parametric amplifiers exhibit a distinctly...... nonlinearbehavior when amplitude of their response is sufficiently large. The modified method of direct separa-tion of motions is employed to study the considered system. As the result it is obtained that steady-stateamplitude of the nonlinear parametric amplifier response can reach large values in the case...... of arbitrarilysmall amplitude of external excitation, so that the amplifier gain tends to infinity. Very large amplifiergain can be achieved in a broad range of system parameters, in particular when the amplitude of para-metric excitation is comparatively small. The obtained results clearly demonstrate that very...

  12. A high-fidelity noiseless amplifier for quantum light states

    CERN Document Server

    Zavatta, A; Bellini, M

    2010-01-01

    Noise is the price to pay when trying to clone or amplify arbitrary quantum states. The quantum noise associated to linear phase-insensitive amplifiers can only be avoided by relaxing the requirement of a deterministic operation. Here we present the experimental realization of a probabilistic noiseless linear amplifier that is able to amplify coherent states at the highest level of effective gain and final state fidelity ever reached. Based on a sequence of photon addition and subtraction, and characterized by a significant amplification and low distortions, this high-fidelity amplification scheme may become an essential tool for quantum communications and metrology, by enhancing the discrimination between partially overlapping quantum states or by recovering the information transmitted over lossy channels.

  13. Fiber amplifiers under thermal loads leading to transverse mode instability

    DEFF Research Database (Denmark)

    Johansen, Mette Marie; Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard;

    2014-01-01

    Transverse mode instability (TMI) in rare-earth doped fiber amplifiers operating above an average power threshold is caused by intermodal stimulated thermal Rayleigh scattering due to quantum defect heating. We investigate thermally induced longitudinal waveguide perturbations causing power trans...

  14. 1.55 Micron High Peak Power Fiber Amplifier Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this proposal, we propose to demonstrate and build a 1.55 micron single frequency high energy and high peak power fiber amplifier by developing an innovative...

  15. Gain Variation with Raman Amplifier Parameters and Its Restoration

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We demonstrate that gain profile of a distributed Raman amplifier is sensitive to its parameter variation, such as loss/gain coefficients change or partial pump failure. Gain flatness can be restored by adjusting power of pump lasers.

  16. High-Frequency RIN Transfer in Fibre Optic Parametric Amplifiers

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Lund-Hansen, Toke; Kang, Ning

    2011-01-01

    ibre optic parametric amplifiers (FOPAs) are versatile devices for amplification at arbitrary wavelengths, as well as a wide range of optical signal processing applications, including switching, wavelength conversion, regeneration, pulse generation etc [1]. Transfer of intensity fluctuations from...

  17. A CMOS single-supply logarithmic amplifier for hearing aids

    Science.gov (United States)

    Jarng, Soon Suck; Chen, Lingfeng; Kwon, You Jung

    2005-12-01

    The Log Amplifier described in this paper is designed for hearing aids (HA) application. It works on a low single-supply voltage (1.3V). The input signal varies between 0.01mV and 100mV. To give enough compensation to the hearing impairment, the amplifier provides a very large gain. The output swing is limited because of the low supply voltage and the large gain. Therefore, the logarithmic amplifier introduced into the design of HA to compress input signal so that the output distortion can be avoid. Another factor we use it here is that the amplifier has enough sensitivity and gain to deal with the compressed input signal without getting extra distortion coursed by the pre-process on input signal. The short channel CMOS devices play an important role in reduction of the supply voltage. DONG-BU ANAM 0.18 μm process is selected.

  18. Design of low noise transimpedance amplifier for intravascular ultrasound

    KAUST Repository

    Reda, Dina

    2009-11-01

    In this paper, we study transimpedance amplifiers for capacitive sensing applications with a focus on Intravascular Ultra Sound (IVUS). We employ RF noise cancellation technique on capacitive feedback based transimpedance amplifiers. This technique eliminates the input-referred noise of TIAs completely and enhances the dynamic range of front-end electronics. Simulation results verify the proposed technique used in two different TIA topologies employing shunt-shunt feedback. ©2009 IEEE.

  19. Thermal Effects in High-Power Fiber Amplifiers

    DEFF Research Database (Denmark)

    Hansen, Kristian Rymann; Lægsgaard, Jesper

    2011-01-01

    The effect of temperature gradients in Yb-doped fiber amplifiers is studied numerically. We investigate the dependence of the mode area on the signal power, and compare forward and backward pumping schemes.......The effect of temperature gradients in Yb-doped fiber amplifiers is studied numerically. We investigate the dependence of the mode area on the signal power, and compare forward and backward pumping schemes....

  20. On the dual symmetry between absorbing and amplifying random media

    Indian Academy of Sciences (India)

    S Anantha Ramakrishna

    2004-06-01

    We re-examine the dual symmetry between absorbing and amplifying random media. By analysing the physically allowed choice of the sign of the square root to determine the complex wave vector in a medium, we draw a broad set of conclusions that enables us to resolve the apparent paradox of the dual symmetry and also to anticipate the large local electromagnetic field enhancements in amplifying random media.

  1. Ultrafast optical signal processing using semiconductor quantum dot amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Mørk, Jesper

    2002-01-01

    The linear and nonlinear properties of quantum dot amplifiers are discussed on the basis of an extensive theoretical model. These devices show great potential for linear amplification as well as ultrafast signal processing.......The linear and nonlinear properties of quantum dot amplifiers are discussed on the basis of an extensive theoretical model. These devices show great potential for linear amplification as well as ultrafast signal processing....

  2. Characterization of a multimode coplanar waveguide parametric amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Simoen, M., E-mail: simoen@chalmers.se; Krantz, P.; Bylander, Jonas; Shumeiko, V.; Delsing, P. [Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Göteborg SE-412 96 (Sweden); Chang, C. W. S.; Wilson, C. M. [Institute for Quantum Computing and Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Wustmann, W. [Department of Microtechnology and Nanoscience (MC2), Chalmers University of Technology, Göteborg SE-412 96 (Sweden); Laboratory for Physical Sciences, College Park, Maryland 20740 (United States)

    2015-10-21

    We characterize a Josephson parametric amplifier based on a flux-tunable quarter-wavelength resonator. The fundamental resonance frequency is ∼1 GHz, but we use higher modes of the resonator for our measurements. An on-chip tuning line allows for magnetic flux pumping of the amplifier. We investigate and compare degenerate parametric amplification, involving a single mode, and nondegenerate parametric amplification, using a pair of modes. We show that we reach quantum-limited noise performance in both cases.

  3. EXAMINING OF ASE AT THE ERBIUM DOPED FIBER AMPLIFIERS

    Directory of Open Access Journals (Sweden)

    H. Haldun GÖKTAŞ

    2004-02-01

    Full Text Available In this study, the effect of Amplified Spontaneous Emission (ASE which is the main cause of noise in Erbium Doped-Fiber Amplifiers (EDFA used in long distance signal transmission has been examined. For this purpose an EDFA pumped with a 1480nm pump source has been analysed to see the effect of ASE, by taking into account the noise and removing it from the simulation.

  4. An Artefact suppressing fast-recovery myoelectric amplifier

    OpenAIRE

    1999-01-01

    An amplifier for recording myoelectric signals using surface electrodes has been developed. The special features are suppression of stimulation artefacts and motion artefacts from electrodes. It is designed for recording of myoelectric signals from a muscle that is being stimulated with short impulses. The artifact suppression is achieved by using fast-recovery instrumentation amplifiers and having a nonlinear feedback loop for automatic compensation of changes in DC-offset

  5. Thermally induced nonlinear mode coupling in high power fiber amplifiers

    DEFF Research Database (Denmark)

    Johansen, Mette Marie; Hansen, Kristian Rymann; Alkeskjold, Thomas T.;

    2013-01-01

    Thermally induced nonlinear mode coupling leads to transverse mode instability (TMI) in high power fiber amplifiers. A numerical model including altering mode profiles from thermal effects and waveguide perturbations predicts a TMI threshold of ~200W.......Thermally induced nonlinear mode coupling leads to transverse mode instability (TMI) in high power fiber amplifiers. A numerical model including altering mode profiles from thermal effects and waveguide perturbations predicts a TMI threshold of ~200W....

  6. Design of 2.1 GHz CMOS Low Noise Amplifier

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper discusses the design of a fully differential 2.1 GHz CMOS low noise amplifier using the TSMC0.25 μm CMOS process. Intended for use in 3G, the low noise amplifier is fully integrated and without off-chip components. The design uses an LC tank to replace a large inductor to achieve a smaller die area, and uses shielded pad capacitances to improve the noise performance. This paper also presents evaluation results of the design.

  7. Calibration setup for ultralow-current transresistance amplifiers

    CERN Document Server

    Finardi, Ilaria

    2016-01-01

    We describe a calibration setup for the transresistance of low-current amplifiers, based on the capacitance-charging method. The calibration can be performed in the current range of typical interest for electron counting experiments. The setup implementation is simple and rugged, and is suitable to be embedded in larger experiments where the amplifier is employed. The calibration is traceable to units of capacitance and of time. The base relative accuracy of the implementation is in the 10^-5 range.

  8. Ferrite bead effect on Class-D amplifier audio quality

    OpenAIRE

    Haddad, Kevin El; Mrad, Roberto; Morel, Florent; Pillonnet, Gael; Vollaire, Christian; Nagari, Angelo

    2014-01-01

    International audience; This paper studies the effect of ferrite beads on the audio quality of Class-D audio amplifiers. This latter is a switch-ing circuit which creates high frequency harmonics. Generally, a filter is used at the amplifier output for the sake of electro-magnetic compatibility (EMC). So often, in integrated solutions, this filter contains ferrite beads which are magnetic components and present nonlinear behavior. Time domain measurements and their equivalence in frequency do...

  9. Progenitor-Explosion Connection and Remnant Birth Masses for Neutrino-Driven Supernovae of Iron-Core Progenitors

    CERN Document Server

    Ugliano, Marcella; Marek, Andreas; Arcones, Almudena

    2012-01-01

    We perform hydrodynamic supernova simulations in spherical symmetry for over 100 single stars of solar metallicity to explore the progenitor-explosion and progenitor-remnant connections established by the neutrino-driven mechanism. We use an approximative treatment of neutrino transport and replace the high-density interior of the neutron star (NS) by an inner boundary condition based on an analytic proto-NS core-cooling model, whose free parameters are chosen such that explosion energy, nickel production, and energy release by the compact remnant of progenitors around 20 solar masses are compatible with Supernova 1987A. Thus we are able to simulate the accretion phase, initiation of the explosion, subsequent neutrino-driven wind phase for 15-20 s, and the further evolution of the blast wave for hours to days until fallback is completed. Our results challenge long-standing paradigms. We find that remnant mass, launch time, and properties of the explosion depend strongly on the stellar structure and exhibit la...

  10. High Efficiency Microwave Power Amplifier: From the Lab to Industry

    Science.gov (United States)

    Sims, William Herbert, III; Bell, Joseph L. (Technical Monitor)

    2001-01-01

    Since the beginnings of space travel, various microwave power amplifier designs have been employed. These included Class-A, -B, and -C bias arrangements. However, shared limitation of these topologies is the inherent high total consumption of input power associated with the generation of radio frequency (RF)/microwave power. The power amplifier has always been the largest drain for the limited available power on the spacecraft. Typically, the conversion efficiency of a microwave power amplifier is 10 to 20%. For a typical microwave power amplifier of 20 watts, input DC power of at least 100 watts is required. Such a large demand for input power suggests that a better method of RF/microwave power generation is required. The price paid for using a linear amplifier where high linearity is unnecessary includes higher initial and operating costs, lower DC-to-RF conversion efficiency, high power consumption, higher power dissipation and the accompanying need for higher capacity heat removal means, and an amplifier that is more prone to parasitic oscillation. The first use of a higher efficiency mode of power generation was described by Baxandall in 1959. This higher efficiency mode, Class-D, is achieved through distinct switching techniques to reduce the power losses associated with switching, conduction, and gate drive losses of a given transistor.

  11. ANALYSIS OF INTERNALLY GENERATED NOISE OF BIOELECTRIC AMPLIFIERS

    Institute of Scientific and Technical Information of China (English)

    MashhourMustafaBaniAmer

    2003-01-01

    This papenr deals with internally generated noise of bioelectric amplifiers that are usually used for processing of bioelectric events.The main purpose of this paper is to present a procedure for analysis of the effects of internal noise generated by the active circuits and to evaluate the output noise of the author's new designed bioelectric amplifier that caused by internal effects to the amplifier circuit itself in order to compare it with the noise generated by conventional amplifiers.The obtained analysis results of internally generated noise showed that the total output noise of bioelectric active circuits does not increase when some of their resitors have a larger value.This behavior is caused by the different transfer functions for the signal and the respective noise sources associated with these resistors.Moreover,the new designed bioelectric amplifier haws an output noise less than that for conventional amplifiers.The obtained analysis results were also experimentally verified and the final conclusions were drawn.

  12. Photonic-Band-Gap Traveling-Wave Gyrotron Amplifier

    Science.gov (United States)

    Nanni, E. A.; Lewis, S. M.; Shapiro, M. A.; Griffin, R. G.; Temkin, R. J.

    2014-01-01

    We report the experimental demonstration of a gyrotron traveling-wave-tube amplifier at 250 GHz that uses a photonic band gap (PBG) interaction circuit. The gyrotron amplifier achieved a peak small signal gain of 38 dB and 45 W output power at 247.7 GHz with an instantaneous −3 dB bandwidth of 0.4 GHz. The amplifier can be tuned for operation from 245–256 GHz. The widest instantaneous −3 dB bandwidth of 4.5 GHz centered at 253.25 GHz was observed with a gain of 24 dB. The PBG circuit provides stability from oscillations by supporting the propagation of transverse electric (TE) modes in a narrow range of frequencies, allowing for the confinement of the operating TE03-like mode while rejecting the excitation of oscillations at nearby frequencies. This experiment achieved the highest frequency of operation for a gyrotron amplifier; at present, there are no other amplifiers in this frequency range that are capable of producing either high gain or high output power. This result represents the highest gain observed above 94 GHz and the highest output power achieved above 140 GHz by any conventional-voltage vacuum electron device based amplifier. PMID:24476286

  13. A Progenitor Cell Expressing Transcription Factor RORγt Generates All Human Innate Lymphoid Cell Subsets.

    Science.gov (United States)

    Scoville, Steven D; Mundy-Bosse, Bethany L; Zhang, Michael H; Chen, Li; Zhang, Xiaoli; Keller, Karen A; Hughes, Tiffany; Chen, Luxi; Cheng, Stephanie; Bergin, Stephen M; Mao, Hsiaoyin C; McClory, Susan; Yu, Jianhua; Carson, William E; Caligiuri, Michael A; Freud, Aharon G

    2016-05-17

    The current model of murine innate lymphoid cell (ILC) development holds that mouse ILCs are derived downstream of the common lymphoid progenitor through lineage-restricted progenitors. However, corresponding lineage-restricted progenitors in humans have yet to be discovered. Here we identified a progenitor population in human secondary lymphoid tissues (SLTs) that expressed the transcription factor RORγt and was unique in its ability to generate all known ILC subsets, including natural killer (NK) cells, but not other leukocyte populations. In contrast to murine fate-mapping data, which indicate that only ILC3s express Rorγt, these human progenitor cells as well as human peripheral blood NK cells and all mature ILC populations expressed RORγt. Thus, all human ILCs can be generated through an RORγt(+) developmental pathway from a common progenitor in SLTs. These findings help establish the developmental signals and pathways involved in human ILC development.

  14. Temporally Distinct Six2-Positive Second Heart Field Progenitors Regulate Mammalian Heart Development and Disease.

    Science.gov (United States)

    Zhou, Zhengfang; Wang, Jingying; Guo, Chaoshe; Chang, Weiting; Zhuang, Jian; Zhu, Ping; Li, Xue

    2017-01-24

    The embryonic process of forming a complex structure such as the heart remains poorly understood. Here, we show that Six2 marks a dynamic subset of second heart field progenitors. Six2-positive (Six2(+)) progenitors are rapidly recruited and assigned, and their descendants are allocated successively to regions of the heart from the right ventricle (RV) to the pulmonary trunk. Global ablation of Six2(+) progenitors resulted in RV hypoplasia and pulmonary atresia. An early stage-specific ablation of a small subset of Six2(+) progenitors did not cause any apparent structural defect at birth but rather resulted in adult-onset cardiac hypertrophy and dysfunction. Furthermore, Six2 expression depends in part on Shh signaling, and Shh deletion resulted in severe deficiency of Six2(+) progenitors. Collectively, these findings unveil the chronological features of cardiogenesis, in which the mammalian heart is built sequentially by temporally distinct populations of cardiac progenitors, and provide insights into late-onset congenital heart disease.

  15. Fetal hepatic progenitors support long-term expansion of hematopoietic stem cells.

    Science.gov (United States)

    Chou, Song; Flygare, Johan; Lodish, Harvey F

    2013-05-01

    We have developed a coculture system that establishes DLK(+) fetal hepatic progenitors as the authentic supportive cells for expansion of hematopoietic stem (HSCs) and progenitor cells. In 1-week cultures supplemented with serum and supportive cytokines, both cocultured DLK(+) fetal hepatic progenitors and their conditioned medium supported rapid expansion of hematopoietic progenitors and a small increase in HSC numbers. In 2- and 3-week cultures DLK(+) cells, but not their conditioned medium, continuously and significantly (>20-fold) expanded both hematopoietic stem and progenitor cells. Physical contact between HSCs and DLK(+) cells was crucial to maintaining this long-term expansion. Similar HSC expansion (approximately sevenfold) was achieved in cocultures using a serum-free, low cytokine- containing medium. In contrast, DLK(-) cells are incapable of expanding hematopoietic cells, demonstrating that hepatic progenitors are the principle supportive cells for HSC expansion in the fetal liver.

  16. Prolonged Mitosis of Neural Progenitors Alters Cell Fate in the Developing Brain.

    Science.gov (United States)

    Pilaz, Louis-Jan; McMahon, John J; Miller, Emily E; Lennox, Ashley L; Suzuki, Aussie; Salmon, Edward; Silver, Debra L

    2016-01-06

    Embryonic neocortical development depends on balanced production of progenitors and neurons. Genetic mutations disrupting progenitor mitosis frequently impair neurogenesis; however, the link between altered mitosis and cell fate remains poorly understood. Here we demonstrate that prolonged mitosis of radial glial progenitors directly alters neuronal fate specification and progeny viability. Live imaging of progenitors from a neurogenesis mutant, Magoh(+/-), reveals that mitotic delay significantly correlates with preferential production of neurons instead of progenitors, as well as apoptotic progeny. Independently, two pharmacological approaches reveal a causal relationship between mitotic delay and progeny fate. As mitotic duration increases, progenitors produce substantially more apoptotic progeny or neurons. We show that apoptosis, but not differentiation, is p53 dependent, demonstrating that these are distinct outcomes of mitotic delay. Together our findings reveal that prolonged mitosis is sufficient to alter fates of radial glia progeny and define a new paradigm to understand how mitosis perturbations underlie brain size disorders such as microcephaly.

  17. Dopamine Receptor Antagonists Enhance Proliferation and Neurogenesis of Midbrain Lmx1a-expressing Progenitors

    OpenAIRE

    Eva Hedlund; Laure Belnoue; Spyridon Theofilopoulos; Carmen Salto; Chris Bye; Clare Parish; Qiaolin Deng; Banafsheh Kadkhodaei; Johan Ericson; Ernest Arenas; Thomas Perlmann; András Simon

    2016-01-01

    Degeneration of dopamine neurons in the midbrain causes symptoms of the movement disorder, Parkinson disease. Dopamine neurons are generated from proliferating progenitor cells localized in the embryonic ventral midbrain. However, it remains unclear for how long cells with dopamine progenitor character are retained and if there is any potential for reactivation of such cells after cessation of normal dopamine neurogenesis. We show here that cells expressing Lmx1a and other progenitor markers ...

  18. In Vitro Modeling of Brain Progenitor Cell Development under the Effect of Environmental Factors.

    Science.gov (United States)

    Kuvacheva, N V; Morgun, A V; Komleva, Yu K; Khilazheva, E D; Gorina, Ya V; Lopatina, O L; Arutyunyan, S A; Salmina, A B

    2015-08-01

    We studied in vitro development of brain progenitor cells isolated from healthy 7-9-month-old Wistar rats and rats with experimental Alzheimer's disease kept under standard conditions and in enriched (multistimulus) environment in vivo. Progenitor cells from healthy animals more rapidly formed neurospheres. Considerable changes at the early stages of in vitro development of brain progenitor cells were observed in both groups kept in enriched environment.

  19. Interleukin-1 regulates hematopoietic progenitor and stem cells in the midgestation mouse fetal liver

    OpenAIRE

    Orelio, Claudia; Peeters, Marian; Haak, Esther; van der Horn, Karin; Dzierzak, Elaine

    2009-01-01

    Hematopoietic progenitors are generated in the yolk sac and aorta-gonad-mesonephros region during early mouse development. At embryonic day 10.5 the first hematopoietic stem cells emerge in the aorta-gonad-mesonephros. Subsequently, hematopoietic stem cells and progenitors are found in the fetal liver. The fetal liver is a potent hematopoietic site, playing an important role in the expansion and differentiation of hematopoietic progenitors and hematopoietic stem cells. However, little is know...

  20. Transplantation of Expanded Fetal Intestinal Progenitors Contributes to Colon Regeneration after Injury

    DEFF Research Database (Denmark)

    Fordham, Robert P; Yui, Shiro; Hannan, Nicholas R F

    2013-01-01

    Regeneration and homeostasis in the adult intestinal epithelium is driven by proliferative resident stem cells, whose functional properties during organismal development are largely unknown. Here, we show that human and mouse fetal intestine contains proliferative, immature progenitors, which can...... be expanded in vitro as Fetal Enterospheres (FEnS). A highly similar progenitor population can be established during intestinal differentiation of human induced pluripotent stem cells. Established cultures of mouse fetal intestinal progenitors express lower levels of Lgr5 than mature progenitors and propagate...

  1. Rare Earth Doped Fiber Amplifiers for the First Telecommunication Window

    Science.gov (United States)

    Sridhar, Balakrishnan

    A complete experimental and theoretical study of rare earth doped fiber-optic amplifiers for the first tele-communication window has been made. The thulium doped fluoride fiber amplifier is shown to provide amplification in the 800nm-820nm signal region. A complete steady state theoretical model has been presented and the model has been experimentally verified. The model predicts the gain, noise figure and the amplified spontaneous emission in the 800nm, 1470nm, 1900nm and 2300nm bands. The effect of population trapping at the ^3F_4 energy level of thulium ion is also shown with the help of the model. It has been shown that about 5 -15%o of the population is trapped at the ^3F _4 energy level. We have also shown theoretically, the expected gain and noise performance of Thulium doped fluoride fiber amplifiers pumped in the 680nm absorption band. The maximum gain at 806nm is slightly lower than with comparable 780 nm pumping. The gain bandwidth is however found to increase with 680nm pumping. The higher ASE at shorter wavelengths (flouride fiber amplifier in the 850nm signal band for the first time. The amplification is through an up-conversion process. The erbium doped flouride fiber amplifier was pumped with an estimated pump power of 35mW at 792nm. We have also considered a theoretical model for a single mode erbium doped fluoride fiber amplifier. Efficient amplification occurs because of the strong excited state absorption at the pump wavelength from the ^4I_{13/2} energy level.

  2. Generation of immortal cell lines from the adult pituitary: role of cAMP on differentiation of SOX2-expressing progenitor cells to mature gonadotropes.

    Directory of Open Access Journals (Sweden)

    Ginah L Kim

    Full Text Available The pituitary is a complex endocrine tissue composed of a number of unique cell types distinguished by the expression and secretion of specific hormones, which in turn control critical components of overall physiology. The basic function of these cells is understood; however, the molecular events involved in their hormonal regulation are not yet fully defined. While previously established cell lines have provided much insight into these regulatory mechanisms, the availability of representative cell lines from each cell lineage is limited, and currently none are derived from adult pituitary. We have therefore used retroviral transfer of SV40 T-antigen to mass immortalize primary pituitary cell culture from an adult mouse. We have generated 19 mixed cell cultures that contain cells from pituitary cell lineages, as determined by RT-PCR analysis and immunocytochemistry for specific hormones. Some lines expressed markers associated with multipotent adult progenitor cells or transit-amplifying cells, including SOX2, nestin, S100, and SOX9. The progenitor lines were exposed to an adenylate cyclase activator, forskolin, over 7 days and were induced to differentiate to a more mature gonadotrope cell, expressing significant levels of α-subunit, LHβ, and FSHβ mRNAs. Additionally, clonal populations of differentiated gonadotropes were exposed to 30 nM gonadotropin-releasing hormone and responded appropriately with a significant increase in α-subunit and LHβ transcription. Further, exposure of the lines to a pulse paradigm of GnRH, in combination with 17β-estradiol and dexamethasone, significantly increased GnRH receptor mRNA levels. This array of adult-derived pituitary cell models will be valuable for both studies of progenitor cell characteristics and modulation, and the molecular analysis of individual pituitary cell lineages.

  3. Aberrant lymphatic endothelial progenitors in lymphatic malformation development.

    Directory of Open Access Journals (Sweden)

    June K Wu

    Full Text Available Lymphatic malformations (LMs are vascular anomalies thought to arise from dysregulated lymphangiogenesis. These lesions impose a significant burden of disease on affected individuals. LM pathobiology is poorly understood, hindering the development of effective treatments. In the present studies, immunostaining of LM tissues revealed that endothelial cells lining aberrant lymphatic vessels and cells in the surrounding stroma expressed the stem cell marker, CD133, and the lymphatic endothelial protein, podoplanin. Isolated patient-derived CD133+ LM cells expressed stem cell genes (NANOG, Oct4, circulating endothelial cell precursor proteins (CD90, CD146, c-Kit, VEGFR-2, and lymphatic endothelial proteins (podoplanin, VEGFR-3. Consistent with a progenitor cell identity, CD133+ LM cells were multipotent and could be differentiated into fat, bone, smooth muscle, and lymphatic endothelial cells in vitro. CD133+ cells were compared to CD133- cells isolated from LM fluids. CD133- LM cells had lower expression of stem cell genes, but expressed circulating endothelial precursor proteins and high levels of lymphatic endothelial proteins, VE-cadherin, CD31, podoplanin, VEGFR-3 and Prox1. CD133- LM cells were not multipotent, consistent with a differentiated lymphatic endothelial cell phenotype. In a mouse xenograft model, CD133+ LM cells differentiated into lymphatic endothelial cells that formed irregularly dilated lymphatic channels, phenocopying human LMs. In vivo, CD133+ LM cells acquired expression of differentiated lymphatic endothelial cell proteins, podoplanin, LYVE1, Prox1, and VEGFR-3, comparable to expression found in LM patient tissues. Taken together, these data identify a novel LM progenitor cell population that differentiates to form the abnormal lymphatic structures characteristic of these lesions, recapitulating the human LM phenotype. This LM progenitor cell population may contribute to the clinically refractory behavior of LMs.

  4. Type Ia supernovae: Progenitors and evolution with redshift

    Science.gov (United States)

    Nomoto, Ken'ichi; Umeda, Hideyuki; Kobayashi, Chiaki; Hachisu, Izumi; Kato, Mariko; Tsujimoto, Takuji

    2000-06-01

    Relatively uniform light curves and spectral evolution of Type Ia supernovae(SNe Ia) have led to the use of SNe Ia as a ``standard candle'' to determine cosmological parameters. Whether a statistically significant value of the cosmological constant can be obtained depends on whether the peak luminosities of SNe Ia are sufficiently free from the effects of cosmic and galactic evolutions. Here we first review the single degenerate scenario for the Chandrasekhar mass white dwarf (WD) models of SNe Ia. We identify the progenitor's evolution and population with two channels: (1) the WD+RG (red-giant) and (2) the WD+MS (near main-sequence He-rich star) channels. In these channels, the strong wind from accreting WDs plays a key role, which yields important age and metallicity effects on the evolution. We then address the questions whether the nature of SNe Ia depends systematically on environmental properties such as metallicity and age of the progenitor system and whether significant evolutionary effects exist. We suggest that the variation of the carbon mass fraction X(C) in the C+O WD (or the variation of the initial WD mass) causes the diversity of the brightness of SNe Ia. This model can explain the observed dependences of SNe Ia brightness on the galaxy types and the distance from the galactic center. Finally, applying the metallicity effect on the evolution of SN Ia progenitors, we make a prediction of the cosmic supernova rate history as a composite of the supernova rates in different types of galaxies. .

  5. Circulating perivascular progenitors: a target of PDGFR inhibition.

    Science.gov (United States)

    Mancuso, Patrizia; Martin-Padura, Ines; Calleri, Angelica; Marighetti, Paola; Quarna, Jessica; Rabascio, Cristina; Braidotti, Paola; Bertolini, Francesco

    2011-09-15

    Cancer blood vessels consist of two interacting types of cells: inner lining endothelial cells (ECs) and surrounding perivascular cells (pericytes, vascular smooth muscle cells or mural cells). PDGFRbeta(CD140b)+ progenitor perivascular cells (PPC) can differentiate into pericytes and regulate vessel stability and vascular survival in tumors. Similarly to what we have done with circulating ECs and progenitors, we developed a flow cytometry procedure for the enumeration of circulating PPCs and the study of their viability in murine models of cancer and in cancer patients. DNA+CD45-CD31-CD140b+ cells were enumerated by six-colour flow cytometry, their morphology was studied by electron microscopy, PPC specificity confirmed by reverse trascription-PCR (RT-PCR) expression of CD140b mRNA, and viability assessed by Syto16 and 7AAD. In preclinical marrow transplantation studies, 9 ± 4% of circulating PPCs were derived from the marrow donor. PPCs were increased in cancer-bearing mice and in patients affected by some types of cancer. At variance with the kinetic of circulating endothelial progenitors, high-dose cyclophosphamide reduced the number of viable PPCs. The administration of sunitinib, a drug known to inhibit PDGFR, was associated in murine models and in cancer patients with an increase of apoptotic/necrotic circulating PPC, suggesting a direct targeting of these cells. PPC enumeration might be studied as a tool for the definition of the optimal biologic dose of anti-PDGFR drugs and investigated clinically as a possible predictive/prognostic tool in patients receiving anti-PDGFR drugs.

  6. Prostate progenitor cells proliferate in response to castration

    Directory of Open Access Journals (Sweden)

    Xudong Shi

    2014-07-01

    Full Text Available Androgen-deprivation is a mainstay of therapy for advanced prostate cancer but tumor regression is usually incomplete and temporary because of androgen-independent cells in the tumor. It has been speculated that these tumor cells resemble the stem/progenitor cells of the normal prostate. The purpose of this study was to examine the response of slow-cycling progenitor cells in the adult mouse prostate to castration. Proliferating cells in the E16 urogenital sinus were pulse labeled by BrdU administration or by doxycycline-controlled labeling of the histone-H2B GFP mouse. A small population of labeled epithelial cells in the adult prostate localized at the junction of the prostatic ducts and urethra. Fluorescence-activated cell sorting (FACS showed that GFP label-retaining cells were enriched for cells co-expressing stem cell markers Sca-1, CD133, CD44 and CD117 (4- marker cells; 60-fold enrichment. FACS showed, additionally, that 4-marker cells were androgen receptor positive. Castration induced proliferation and dispersal of E16 labeled cells into more distal ductal segments. When naïve adult mice were administered BrdU daily for 2 weeks after castration, 16% of 4-marker cells exhibited BrdU label in contrast to only 6% of all epithelial cells (P < 0.01. In sham-castrated controls less than 4% of 4-marker cells were BrdU labeled (P < 0.01. The unexpected and admittedly counter-intuitive finding that castration induced progenitor cell proliferation suggests that androgen deprivation therapy in men with advanced prostate cancer could not only exert pleiotrophic effects on tumor sub-populations but may induce inadvertent expansion of tumor stem cells.

  7. Several important in vitro improvements in the amplification, differentiation and tracing of fetal liver stem/progenitor cells.

    Directory of Open Access Journals (Sweden)

    Wei-hui Liu

    Full Text Available OBJECTIVE: We previously isolated fetal liver stem/progenitor cells (FLSPCs, but there is an urgent need to properly amplify FLSPCs, effectively induce FLSPCs differentiation, and steadily trace FLSPCs for in vivo therapeutic investigation. METHODS: FLSPCs were maintained in vitro as adherent culture or soft agar culture for large-scale amplification. To direct the differentiation of FLSPCs into hepatocytes, FLSPCs were randomly divided into four groups: control, 1% DMSO-treated, 20 ng/ml HGF-treated and 1% DMSO+20 ng/ml HGF-treated. To trace FLSPCs, the GFP gene was introduced into FLSPCs by liposome-mediated transfection. RESULTS: For amplifying FLSPCs, the soft agar culture were more suitable than the adherent culture, because the soft agar culture obtained more homogeneous cells. These cells were with high nuclear:cytoplasmic ratio, few cell organelles, high expression of CD90.1 and CD49f, and strong alkaline phosphatase staining. For inducing FLSPCs differentiation, treatment with HGF+DMSO was most effective (P<0.05, which was strongly supported by the typical morphological change and the significant decrease of OV-6 positive cells (P<0.01. In addition, the time of indocyanine green elimination, the percentage of glycogen synthetic cells, and the expressions of ALB, G-6-P, CK-8, CK-18 and CYP450-3A1 in HGF+DMSO-treated group were higher than in any other group. For tracing FLSPCs, after the selection of stable FLSPC transfectants, GFP expression continued over successive generations. CONCLUSIONS: FLSPCs can properly self-renew in soft agar culture and effectively differentiate into hepatocyte-like cells by HGF+DMSO induction, and they can be reliably traced by GFP expression.

  8. Methylene blue promotes quiescence of rat neural progenitor cells.

    Science.gov (United States)

    Xie, Luokun; Choudhury, Gourav R; Wang, Jixian; Park, Yong; Liu, Ran; Yuan, Fang; Zhang, Chun-Li; Yorio, Thomas; Jin, Kunlin; Yang, Shao-Hua

    2014-01-01

    Neural stem cell-based treatment holds a new therapeutic opportunity for neurodegenerative disorders. Here, we investigated the effect of methylene blue on proliferation and differentiation of rat neural progenitor cells (NPCs) both in vitro and in vivo. We found that methylene blue inhibited proliferation and promoted quiescence of NPCs in vitro without affecting committed neuronal differentiation. Consistently, intracerebroventricular infusion of methylene blue significantly inhibited NPC proliferation at the subventricular zone (SVZ). Methylene blue inhibited mTOR signaling along with down-regulation of cyclins in NPCs in vitro and in vivo. In summary, our study indicates that methylene blue may delay NPC senescence through enhancing NPCs quiescence.

  9. Directed Differentiation of Human Embryonic Stem Cells into Neural Progenitors.

    Science.gov (United States)

    Banda, Erin; Grabel, Laura

    2016-01-01

    A variety of protocols have been used to produce neural progenitors from human embryonic stem cells. We have focused on a monolayer culture approach that generates neural rosettes. To initiate differentiation, cells are plated in a serum-free nutrient-poor medium in the presence of a BMP inhibitor. Depending on the cell line used, additional growth factor inhibitors may be required to promote neural differentiation. Long-term culture and addition of the Notch inhibitor DAPT can promote terminal neuronal differentiation. Extent of differentiation is monitored using immunocytochemistry for cell type-specific markers.

  10. Power neodymium-glass amplifier of a repetitively pulsed laser

    Energy Technology Data Exchange (ETDEWEB)

    Vinogradov, Aleksandr V; Gaganov, V E; Garanin, Sergey G; Zhidkov, N V; Krotov, V A; Martynenko, S P; Pozdnyakov, E V; Solomatin, I I [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation)

    2011-11-30

    A neodymium-glass diode-pumped amplifier with a zigzag laser beam propagation through the active medium was elaborated; the amplifier is intended for operation in a repetitively pulsed laser. An amplifier unit with an aperture of 20 Multiplication-Sign 25 mm and a {approx}40-cm long active medium was put to a test. The energy of pump radiation amounts to 140 J at a wavelength of 806 nm for a pump duration of 550 {mu}s. The energy parameters of the amplifier were experimentally determined: the small-signal gain per pass {approx}3.2, the linear gain {approx}0.031 cm{sup -1} with a nonuniformity of its distribution over the aperture within 15%, the stored energy of 0.16 - 0.21 J cm{sup -3}. The wavefront distortions in the zigzag laser-beam propagation through the active element of the amplifier did not exceed 0.4{lambda} ({lambda} = 0.63 {mu}m is the probing radiation wavelength).

  11. Update on Waveguide-Embedded Differential MMIC Amplifiers

    Science.gov (United States)

    Kangaslahti, Pekka; Schleht, Erich

    2010-01-01

    There is an update on the subject matter of Differential InP HEMT MMIC Amplifiers Embedded in Waveguides (NPO-42857) NASA Tech Briefs, Vol. 33, No. 9 (September 2009), page 35. To recapitulate: Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high-electron-mobility transistors (HEMTs) in a differential configuration. The MMICs are designed integrally with, and embedded in, waveguide packages. The instant work does not mention InP HEMTs but otherwise reiterates part of the subject matter of the cited prior article, with emphasis on the following salient points: An MMIC is mounted in the electric-field plane ("E-plane") of a waveguide and includes a finline transition to each differential-amplifier stage. The differential configuration creates a virtual ground within each pair of transistor-gate fingers, eliminating the need for external radio-frequency grounding. This work concludes by describing a single-stage differential submillimeter-wave amplifier packaged in a rectangular waveguide and summarizing results of tests of this amplifier at frequencies of 220 and 305 GHz.

  12. Residual phase noise modeling of amplifiers using silicon bipolar transistors.

    Science.gov (United States)

    Theodoropoulos, Konstantinos; Everard, Jeremy

    2010-03-01

    In this paper, we describe the modeling of residual 1/f phase noise for Si bipolar amplifiers operating in the linear region. We propose that for Si bipolar amplifiers, the 1/f phase noise is largely caused by the base emitter recombination flicker noise. The up-conversion mechanism is described through linear approximation of the phase variation of the amplifier phase response by the variation of the device parameters (C(b)c, C(be), g(m), r(e)) caused by the recombination 1/f noise. The amplifier phase response describes the device over the whole frequency range of operation for which the influence of the poles and zeros is investigated. It is found that for a common emitter amplifier it is sufficient to only incorporate the effect of the device poles to describe the phase noise behavior over most of its operational frequency range. Simulations predict the measurements of others, including the flattening of the PM noise at frequencies beyond f(3dB), not predicted by previous models.

  13. Design and development of digital seismic amplifier recorder

    Energy Technology Data Exchange (ETDEWEB)

    Samsidar, Siti Alaa; Afuar, Waldy; Handayani, Gunawan, E-mail: gunawanhandayani@gmail.com [Department of Physics, ITB (Indonesia)

    2015-04-16

    A digital seismic recording is a recording technique of seismic data in digital systems. This method is more convenient because it is more accurate than other methods of seismic recorders. To improve the quality of the results of seismic measurements, the signal needs to be amplified to obtain better subsurface images. The purpose of this study is to improve the accuracy of measurement by amplifying the input signal. We use seismic sensors/geophones with a frequency of 4.5 Hz. The signal is amplified by means of 12 units of non-inverting amplifier. The non-inverting amplifier using IC 741 with the resistor values 1KΩ and 1MΩ. The amplification results were 1,000 times. The results of signal amplification converted into digital by using the Analog Digital Converter (ADC). Quantitative analysis in this study was performed using the software Lab VIEW 8.6. The Lab VIEW 8.6 program was used to control the ADC. The results of qualitative analysis showed that the seismic conditioning can produce a large output, so that the data obtained is better than conventional data. This application can be used for geophysical methods that have low input voltage such as microtremor application.

  14. Design and development of digital seismic amplifier recorder

    Science.gov (United States)

    Samsidar, Siti Alaa; Afuar, Waldy; Handayani, Gunawan

    2015-04-01

    A digital seismic recording is a recording technique of seismic data in digital systems. This method is more convenient because it is more accurate than other methods of seismic recorders. To improve the quality of the results of seismic measurements, the signal needs to be amplified to obtain better subsurface images. The purpose of this study is to improve the accuracy of measurement by amplifying the input signal. We use seismic sensors/geophones with a frequency of 4.5 Hz. The signal is amplified by means of 12 units of non-inverting amplifier. The non-inverting amplifier using IC 741 with the resistor values 1KΩ and 1MΩ. The amplification results were 1,000 times. The results of signal amplification converted into digital by using the Analog Digital Converter (ADC). Quantitative analysis in this study was performed using the software Lab VIEW 8.6. The Lab VIEW 8.6 program was used to control the ADC. The results of qualitative analysis showed that the seismic conditioning can produce a large output, so that the data obtained is better than conventional data. This application can be used for geophysical methods that have low input voltage such as microtremor application.

  15. Spectroscopic amplifier for pin diode; Amplificador espectroscopico para diodo Pin

    Energy Technology Data Exchange (ETDEWEB)

    Alonso M, M. S.; Hernandez D, V. M.; Vega C, H. R., E-mail: bebe.luna_s@hotmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2014-10-15

    The photodiode remains the basic choice for the photo-detection and is widely used in optical communications, medical diagnostics and field of corpuscular radiation. In detecting radiation it has been used for monitoring radon and its progeny and inexpensive spectrometric systems. The development of a spectroscopic amplifier for Pin diode is presented which has the following characteristics: canceler Pole-Zero (P/Z) with a time constant of 8 μs; constant gain of 57, suitable for the acquisition system; 4th integrator Gaussian order to waveform change of exponential input to semi-Gaussian output and finally a stage of baseline restorer which prevents Dc signal contribution to the next stage. The operational amplifier used is the TLE2074 of BiFET technology of Texas Instruments with 10 MHz bandwidth, 25 V/μs of slew rate and a noise floor of 17 nv/(Hz)1/2. The integrated circuit has 4 operational amplifiers and in is contained the total of spectroscopic amplifier that is the goal of electronic design. The results show like the exponential input signal is converted to semi-Gaussian, modifying only the amplitude according to the specifications in the design. The total system is formed by the detector, which is the Pin diode, a sensitive preamplifier to the load, the spectroscopic amplifier that is what is presented and finally a pulse height analyzer (Mca) which is where the spectrum is shown. (Author)

  16. Design of A Microwave Amplifier for Wireless Application

    Directory of Open Access Journals (Sweden)

    M. H. Ullah

    2012-01-01

    Full Text Available Problem statement: Low-Noise Amplifiers (LNA are very indispensable components in the design of numerous types of communication receivers employed in microwave technology. This paper is presents the design and development of low bias(Vce = 8v, Ic =10 mA single stage low noise microwave amplifier operating in 1.5GHZ frequency range, Gain 13dB ± 0.5dB, input/output return loss Approach: The principal design target is to obtain a minimum noise figure while concomitantly achieving a maximum gain by presenting the optimum noise impedance (Zopt which is characteristically implemented by adding a matching circuit between the source and the input of the amplifier. Results: The proposed low-noise amplifier for microwave wireless application is designed, simulated and optimized using Serenade Harmonica (by Ansoft Corporation and Advance Design System (ADS software by Agilent. Conclusion: In this paper a low-noise amplifier operated at 1.5 GHz. is designed because of the significant roles played in the field of microwave communication technology, which includes the application in the output stage of a transmitter where the signals needs to be strengthen before transmission.

  17. Modeling Distortion Effects in Class-D Amplifier Filter Inductors

    DEFF Research Database (Denmark)

    Knott, Arnold; Stegenborg-Andersen, Tore; Thomsen, Ole Cornelius

    2010-01-01

    Distortion is generally accepted as a quantifier to judge the quality of audio power amplifiers. In switchmode power amplifiers various mechanisms influence this performance measure. After giving an overview of those, this paper focuses on the particular effect of the nonlinearity of the output...... filter components on the audio performance. While the physical reasons for both, the capacitor and the inductor induced distortion are given, the practical in depth demonstration is done for the inductor only. This includes measuring the inductors performance, modeling through fitting and resulting...... into simulation models. The fitted models achieve distortion values between 0.03 % and 0.2 % as a basis to enable the design of a 200 W amplifier....

  18. Fiber optical parametric amplifiers in optical communication systems

    DEFF Research Database (Denmark)

    Marhic, Michel E.; Andrekson, Peter A.; Petropoulos, Periklis

    2015-01-01

    The prospects for using fiber optical parametric amplifiers (OPAs) in optical communication systems are reviewed. Phase-insensitive amplifiers (PIAs) and phase-sensitive amplifiers (PSAs) are considered. Low-penalty amplification at/or near 1 Tb/s has been achieved, for both wavelength- and time......-division multiplexed formats. High-quality mid-span spectral inversion has been demonstrated at 0.64 Tb/s, avoiding electronic dispersion compensation. All-optical amplitude regeneration of amplitude-modulated signals has been performed, while PSAs have been used to demonstrate phase regeneration of phase...... in excess of 14,000 Tb/s x km in realistic wavelength-division multiplexed long-haul networks. Technical challenges remaining to be addressed in order for fiber OPAs to become useful for long-haul communication networks are discussed....

  19. Spectrally tailored supercontinuum generation from single-mode-fiber amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Qiang; Guo, Zhengru; Zhang, Qingshan [Shanghai Key Laboratory of Modern Optical System, Engineering Research Center of Optical Instrument and System (Ministry of Education), School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093 (China); Liu, Yang; Li, Wenxue [State Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 Zhongshan North Road, Shanghai 200062 (China); Zeng, Heping, E-mail: hpzeng@phy.ecnu.edu.cn [Shanghai Key Laboratory of Modern Optical System, Engineering Research Center of Optical Instrument and System (Ministry of Education), School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093 (China); State Key Laboratory of Precision Spectroscopy, East China Normal University, 3663 Zhongshan North Road, Shanghai 200062 (China)

    2014-05-19

    Spectral filtering of an all-normal-dispersion Yb-doped fiber laser was demonstrated effective for broadband supercontinuum generation in the picosecond time region. The picosecond pump pulses were tailored in spectrum with 1 nm band-pass filter installed between two single-mode fiber amplifiers. By tuning the spectral filter around 1028 nm, four-wave mixing was initiated in a photonic crystal fiber spliced with single-mode fiber, as manifested by the simultaneous generation of Stokes wave at 1076 nm and anti-Stokes wave at 984 nm. Four-wave mixing took place in cascade with the influence of stimulated Raman scattering and eventually extended the output spectrum more than 900 nm of 10 dB bandwidth. This technique allows smooth octave supercontinuum generation by using simple single-mode fiber amplifiers rather than complicated multistage large-mode-area fiber amplifiers.

  20. Using MEMS Capacitive Switches in Tunable RF Amplifiers

    Directory of Open Access Journals (Sweden)

    Danson John

    2006-01-01

    Full Text Available A MEMS capacitive switch suitable for use in tunable RF amplifiers is described. A MEMS switch is designed, fabricated, and characterized with physical and RF measurements for inclusion in simulations. Using the MEMS switch models, a dual-band low-noise amplifier (LNA operating at GHz and GHz, and a tunable power amplifier (PA at GHz are simulated in m CMOS. MEMS switches allow the LNA to operate with 11 dB of isolation between the two bands while maintaining dB of gain and sub- dB noise figure. MEMS switches are used to implement a variable matching network that allows the PA to realize up to 37% PAE improvement at low input powers.