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Sample records for amplifying progenitor itap

  1. Interoperable Technologies for Advanced Petascale Simulations (ITAPS)

    SciTech Connect

    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

  2. Primary cilia regulate proliferation of amplifying progenitors in adult hippocampus: implications for learning and memory.

    PubMed

    Amador-Arjona, Alejandro; Elliott, Jimmy; Miller, Amber; Ginbey, Ashley; Pazour, Gregory J; Enikolopov, Grigori; Roberts, Amanda J; Terskikh, Alexey V

    2011-07-01

    Integration of new neurons into the adult hippocampus has been linked to specific types of learning. Primary cilia were found to be required for the formation of adult neural stem cells (NSCs) in the hippocampal dentate gyrus during development. However, the requirement of cilia in maintenance of adult NSCs is unknown. We developed a genetic mouse model in which fetal/perinatal brain development is unaffected, but adult hippocampal neurogenesis is constantly reduced by conditional ablation of primary cilia in adult GFAP(+) neural stem/progenitor cells. We found that this approach specifically reduces the number of hippocampal amplifying progenitors (also called type 2a cells) without affecting the number of radial NSCs (or type 1 cells). Constant reduction of adult hippocampal neurogenesis produced a delay rather than a permanent deficiency in spatial learning without affecting the retention of long-term memories. Decreased neurogenesis also altered spatial novelty recognition and hippocampus-independent cue conditioning. Here, we propose that adult hippocampal newborn neurons increase the efficiency of generating the new representations of spatial memories and that reduction of adult hippocampal neurogenesis may be biased toward cue-based strategies. This novel mouse model provides evidences that cognitive deficits associated with ciliary defects (ciliopathies) might be, in part, mediated by the deficiency of primary cilia in adult hippocampal stem/progenitor cells. PMID:21734285

  3. Primary cilia regulate proliferation of amplifying progenitors in adult hippocampus: implications for learning and memory.

    PubMed

    Amador-Arjona, Alejandro; Elliott, Jimmy; Miller, Amber; Ginbey, Ashley; Pazour, Gregory J; Enikolopov, Grigori; Roberts, Amanda J; Terskikh, Alexey V

    2011-07-01

    Integration of new neurons into the adult hippocampus has been linked to specific types of learning. Primary cilia were found to be required for the formation of adult neural stem cells (NSCs) in the hippocampal dentate gyrus during development. However, the requirement of cilia in maintenance of adult NSCs is unknown. We developed a genetic mouse model in which fetal/perinatal brain development is unaffected, but adult hippocampal neurogenesis is constantly reduced by conditional ablation of primary cilia in adult GFAP(+) neural stem/progenitor cells. We found that this approach specifically reduces the number of hippocampal amplifying progenitors (also called type 2a cells) without affecting the number of radial NSCs (or type 1 cells). Constant reduction of adult hippocampal neurogenesis produced a delay rather than a permanent deficiency in spatial learning without affecting the retention of long-term memories. Decreased neurogenesis also altered spatial novelty recognition and hippocampus-independent cue conditioning. Here, we propose that adult hippocampal newborn neurons increase the efficiency of generating the new representations of spatial memories and that reduction of adult hippocampal neurogenesis may be biased toward cue-based strategies. This novel mouse model provides evidences that cognitive deficits associated with ciliary defects (ciliopathies) might be, in part, mediated by the deficiency of primary cilia in adult hippocampal stem/progenitor cells.

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

    PubMed Central

    Joshi, Purna A.; Waterhouse, Paul D.; Kannan, Nagarajan; Narala, Swami; Fang, Hui; Di Grappa, Marco A.; Jackson, Hartland W.; Penninger, Josef M.; Eaves, Connie; Khokha, Rama

    2015-01-01

    Summary 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. PMID:26095608

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

    PubMed

    Rezza, Amélie; Wang, Zichen; Sennett, Rachel; Qiao, Wenlian; Wang, Dongmei; Heitman, Nicholas; Mok, Ka Wai; Clavel, Carlos; Yi, Rui; Zandstra, Peter; Ma'ayan, Avi; Rendl, Michael

    2016-03-29

    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. PMID:27009580

  6. Attenuation of the self-renewal of transit-amplifying osteoblast progenitors in the murine bone marrow by 17β-estradiol

    PubMed Central

    Di Gregorio, Gina B.; Yamamoto, Matsuo; Ali, A. Afshan; Abe, Etsuko; Roberson, Paula; Manolagas, Stavros C.; Jilka, Robert L.

    2001-01-01

    In agreement with evidence that estrogens slow the rate of bone remodeling by suppressing the production of both osteoclasts and osteoblasts, loss of estrogens leads to an increase in the number of osteoclast as well as early osteoblast progenitors (CFU-osteoblasts; CFU-OBs) in the murine bone marrow. Here we show that CFU-OBs are early transit-amplifying progenitors, i.e., dividing cells capable of limited self-renewal, and that 17β-estradiol acts in vivo and in vitro to attenuate their self-renewal by approximately 50%. Consistent with a direct receptor–mediated action of estrogens on early mesenchymal cell progenitors, anti–estrogen receptor-α (anti-ERα) Ab’s stain a small number of marrow cells that exhibit characteristics of primitive undifferentiated cells, including a high nucleus/cytoplasm ratio and lack of lineage-specific biochemical markers; the effect of 17β-estradiol on CFU-OB self-renewal is absent in mice lacking ERα. Because both osteoblasts and the stromal/osteoblastic cells that are required for osteoclast development are derived from CFU-OBs, suppression of the self-renewal of this common progenitor may represent a key mechanism of the anti-remodeling effects of estrogens. PMID:11285299

  7. HDAC inhibition amplifies gap junction communication in neural progenitors: Potential for cell-mediated enzyme prodrug therapy

    SciTech Connect

    Khan, Zahidul . E-mail: Zahidul.Khan@ki.se; Akhtar, Monira; Asklund, Thomas; Juliusson, Bengt . E-mail: Tomas.Ekstrom@ki.se

    2007-08-01

    Enzyme prodrug therapy using neural progenitor cells (NPCs) as delivery vehicles has been applied in animal models of gliomas and relies on gap junction communication (GJC) between delivery and target cells. This study investigated the effects of histone deacetylase (HDAC) inhibitors on GJC for the purpose of facilitating transfer of therapeutic molecules from recombinant NPCs. We studied a novel immortalized midbrain cell line, NGC-407 of embryonic human origin having neural precursor characteristics, as a potential delivery vehicle. The expression of gap junction protein connexin 43 (C x 43) was analyzed by western blot and immunocytochemistry. While C x 43 levels were decreased in untreated differentiating NGC-407 cells, the HDAC inhibitor 4-phenylbutyrate (4-PB) increased C x 43 expression along with increased membranous deposition in both proliferating and differentiating cells. Simultaneously, Ser 279/282-phosphorylated form of C x 43 was declined in both culture conditions by 4-PB. The 4-PB effect in NGC-407 cells was verified by using HNSC.100 human neural progenitors and Trichostatin A. Improved functional GJC is of imperative importance for therapeutic strategies involving intercellular transport of low molecular-weight compounds. We show here an enhancement by 4-PB, of the functional GJC among NGC-407 cells, as well as between NGC-407 and human glioma cells, as indicated by increased fluorescent dye transfer.

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

    PubMed

    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). PMID:21294956

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

    PubMed

    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).

  10. PULSE AMPLIFIER

    DOEpatents

    Johnstone, C.W.

    1958-06-17

    The improvement of pulse amplifiers used with scintillation detectors is described. The pulse amplifier circuit has the advantage of reducing the harmful effects of overloading cause by large signal inputs. In general the pulse amplifier circuit comprises two amplifier tubes with the input pulses applied to one amplifier grid and coupled to the second amplifier tube through a common cathode load. The output of the second amplifier is coupled from the plate circuit to a cathode follower tube grid and a diode tube in connected from grid to cathode of the cathode follower tube. Degenerative feedback is provided in the second amplifier by coupling a signal from the cathode follower cathode to the second amplifier grid. The circuit proqides moderate gain stability, and overload protection for subsequent pulse circuits.

  11. 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

    NASA Technical Reports Server (NTRS)

    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.

  12. Progenitor Epithelium

    PubMed Central

    Marty-Santos, Leilani

    2015-01-01

    Insulin-producing β cells within the vertebrate fetal pancreas acquire their fate in a step-wise manner. Whereas the intrinsic factors dictating the transcriptional or epigenetic status of pancreatic lineages have been intensely examined, less is known about cell–cell interactions that might constitute a niche for the developing β cell lineage. It is becoming increasingly clear that understanding and recapitulating these steps may instruct in vitro differentiation of embryonic stem cells and/or therapeutic regeneration. Indeed, directed differentiation techniques have improved since transitioning from 2D to 3D cultures, suggesting that the 3D microenvironment in which β cells are born is critical. However, to date, it remains unknown whether the changing architecture of the pancreatic epithelium impacts the fate of cells therein. An emerging challenge in the field is to elucidate how progenitors are allocated during key events, such as the stratification and subsequent resolution of the pre-pancreatic epithelium, as well as the formation of lumens and branches. Here, we assess the progenitor epithelium and examine how it might influence the emergence of pancreatic multipotent progenitors (MPCs), which give rise to β cells and other pancreatic lineages. PMID:26216134

  13. LOGARITHMIC AMPLIFIER

    DOEpatents

    De Shong, J.A. Jr.

    1957-12-31

    A logarithmic current amplifier circuit having a high sensitivity and fast response is described. The inventor discovered the time constant of the input circuit of a system utilizing a feedback amplifier, ionization chamber, and a diode, is inversely proportional to the input current, and that the amplifier becomes unstable in amplifying signals in the upper frequency range when the amplifier's forward gain time constant equals the input circuit time constant. The described device incorporates impedance networks having low frequency response characteristic at various points in the circuit to change the forward gain of the amplifler at a rate of 0.7 of the gain magnitude for every two times increased in frequency. As a result of this improvement, the time constant of the input circuit is greatly reduced at high frequencies, and the amplifier response is increased.

  14. Operational Amplifiers.

    ERIC Educational Resources Information Center

    Foxcroft, G. E.

    1986-01-01

    Addresses the introduction of low cost equipment into high school and college physical science classes. Examines the properties of an "ideal" operational amplifier and discusses how it might be used under saturated and non-saturated conditions. Notes the action of a "real" operational amplifier. (TW)

  15. Amplifier Distortion

    NASA Astrophysics Data System (ADS)

    Keeports, David

    2006-12-01

    By definition, a high fidelity amplifier's instantaneous output voltage is directly proportional to its instantaneous input voltage. While high fidelity is generally valued in the amplification of recorded music, nonlinearity, also known as distortion, is desirable in the amplification of some musical instruments. In particular, guitar amplifiers exploit nonlinearity to increase both the harmonic content and sustain of a guitar's sound. I will discuss how both modifications in sound result from saturation of triode tubes and transistors. Additionally, I will describe the difference in the symmetry of saturation curves for transistors and tubes and the reason why tube guitar amplifiers are generally considered to be superior to solid-state amplifiers. Finally, I will discuss attempts to use solid-state electronics to replicate the sound of tube amplifiers.

  16. Gyromagnetron amplifier

    SciTech Connect

    Lau, Y.-Y.; Barnett, L. R.

    1985-10-29

    A gyromagnetron amplifier for radiation at millimeter wavelengths comprising a tapered waveguide tube with longitudinally running vanes in the walls of the tube with the number of vanes chosen to coincide with a desired cyclotron harmonic frequency to be amplified. A beam of spiralling mildly relativistic electrons with an energy of 100 keV or less is directed into the small end of the tapered waveguide tube. A tapered axial magnetic field is set up within the waveguide tube with a low value appropriate to the amplification of a cyclotron harmonic frequency. An electromagnetic wave to be amplified is launched into the waveguide tube to co-propagate and be amplified by the spiralling electron beam. This device is characterized by a wide bandwidth, a low operating magnetic field, a relatively low operating beam voltage, with high power, and the capability of continuous wave operation.

  17. LOGARITHMIC AMPLIFIER

    DOEpatents

    Wade, E.J.; Stone, R.S.

    1959-03-10

    Electronic,amplifier circuits, especially a logai-ithmic amplifier characterizxed by its greatly improved strability are discussed. According to the in ention, means are provided to feed bach the output valtagee to a diode in the amplifier input circuit, the diode being utilized to produce the logarithmic characteristics. The diode is tics, The diode isition therewith and having its filament operated from thc same source s the filament of the logarithmic diode. A bias current of relatively large value compareii with the signal current is continuously passed through the compiting dioie to render the diode insensitivy to variations in the signal current. by this odes kdu to variaelled, so that the stability of the amlifier will be unimpaired.

  18. Bidirectional amplifier

    DOEpatents

    Wright, James T.

    1986-01-01

    A bilateral circuit is operable for transmitting signals in two directions without generation of ringing due to feedback caused by the insertion of the circuit. The circuit may include gain for each of the signals to provide a bidirectional amplifier. The signals are passed through two separate paths, with a unidirectional amplifier in each path. A controlled sampling device is provided in each path for sampling the two signals. Any feedback loop between the two signals is disrupted by providing a phase displacement between the control signals for the two sampling devices.

  19. Bidirectional amplifier

    DOEpatents

    Wright, J.T.

    1984-02-02

    A bilateral circuit is operable for transmitting signals in two directions without generation of ringing due to feedback caused by the insertion of the circuit. The circuit may include gain for each of the signals to provide a bidirectional amplifier. The signals are passed through two separate paths, with a unidirectional amplifier in each path. A controlled sampling device is provided in each path for sampling the two signals. Any feedback loop between the two signals is disrupted by providing a phase displacement between the control signals for the two sampling devices.

  20. Amplified Policymaking

    ERIC Educational Resources Information Center

    Prince, Katherine; Woempner, Carolyn

    2010-01-01

    This brief examines the policy implications of two drivers of change presented in the "2020 Forecast: Creating the Future of Learning"-- Pattern Recognition and Amplified Organization. These drivers point toward a series of cultural shifts and illuminate how we are developing new ways of organizing, constructing, and managing knowledge.…

  1. Low cost instrumentation amplifier

    NASA Technical Reports Server (NTRS)

    Sturman, J. C.

    1974-01-01

    Amplifier can be used for many applications requiring high input impedance and common mode rejection, low drift, and gain accuracy on order of one percent. Performance of inexpensive amplifier approaches that of some commercial instrumentation amplifiers in many specifications.

  2. SQUARE WAVE AMPLIFIER

    DOEpatents

    Leavitt, M.A.; Lutz, I.C.

    1958-08-01

    An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.

  3. Segmented amplifier configurations for laser amplifier

    DOEpatents

    Hagen, Wilhelm F.

    1979-01-01

    An amplifier system for high power lasers, the system comprising a compact array of segments which (1) preserves high, large signal gain with improved pumping efficiency and (2) allows the total amplifier length to be shortened by as much as one order of magnitude. The system uses a three dimensional array of segments, with the plane of each segment being oriented at substantially the amplifier medium Brewster angle relative to the incident laser beam and with one or more linear arrays of flashlamps positioned between adjacent rows of amplifier segments, with the plane of the linear array of flashlamps being substantially parallel to the beam propagation direction.

  4. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  5. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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.

  6. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  7. Cross-differential amplifier

    NASA Technical Reports Server (NTRS)

    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.

  8. Hybrid matrix amplifier

    DOEpatents

    Martens, J.S.; Hietala, V.M.; Plut, T.A.

    1995-01-03

    The present invention comprises a novel matrix amplifier. The matrix amplifier includes an active superconducting power divider (ASPD) having N output ports; N distributed amplifiers each operatively connected to one of the N output ports of the ASPD; and a power combiner having N input ports each operatively connected to one of the N distributed amplifiers. The distributed amplifier can included M stages of amplification by cascading superconducting active devices. The power combiner can include N active elements. The resulting (N[times]M) matrix amplifier can produce signals of high output power, large bandwidth, and low noise. 6 figures.

  9. Hybrid matrix amplifier

    DOEpatents

    Martens, Jon S.; Hietala, Vincent M.; Plut, Thomas A.

    1995-01-01

    The present invention comprises a novel matrix amplifier. The matrix amplifier includes an active superconducting power divider (ASPD) having N output ports; N distributed amplifiers each operatively connected to one of the N output ports of the ASPD; and a power combiner having N input ports each operatively connected to one of the N distributed amplifiers. The distributed amplifier can included M stages of amplification by cascading superconducting active devices. The power combiner can include N active elements. The resulting (N.times.M) matrix amplifier can produce signals of high output power, large bandwidth, and low noise.

  10. Portable musical instrument amplifier

    DOEpatents

    Christian, David E.

    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.

  11. The Crab Nebula's progenitor

    NASA Technical Reports Server (NTRS)

    Nomoto, K.; Sugimoto, D.; Sparks, W. M.; Fesen, R. A.; Gull, T. R.; Miyaji, S.

    1982-01-01

    The initial mass of the Crab Nebula's progenitor star is estimated by comparing the observed nebular chemical abundances with detailed evolutionary calculations for 2.4- and 2.6-solar-mass helium cores of stars with masses of 8 to 10 solar masses. The results indicate that the mass of the Crab's progenitor was between the upper limit of about 8 solar masses for carbon deflagration and the lower limit of about 9.5 solar masses set by the dredge-up of the helium layer before the development of the helium-burning convective region. A scenario is outlined for the evolution of the progenitor star. It is suggested that the Crab Nebula was probably the product of an electron-capture supernova.

  12. The evolution of basal progenitors in the developing non-mammalian brain

    PubMed Central

    Nomura, Tadashi; Ohtaka-Maruyama, Chiaki; Yamashita, Wataru; Wakamatsu, Yoshio; Murakami, Yasunori; Calegari, Federico; Suzuki, Kunihiro; Gotoh, Hitoshi; Ono, Katsuhiko

    2016-01-01

    The amplification of distinct neural stem/progenitor cell subtypes during embryogenesis is essential for the intricate brain structures present in various vertebrate species. For example, in both mammals and birds, proliferative neuronal progenitors transiently appear on the basal side of the ventricular zone of the telencephalon (basal progenitors), where they contribute to the enlargement of the neocortex and its homologous structures. In placental mammals, this proliferative cell population can be subdivided into several groups that include Tbr2+ intermediate progenitors and basal radial glial cells (bRGs). Here, we report that basal progenitors in the developing avian pallium show unique morphological and molecular characteristics that resemble the characteristics of bRGs, a progenitor population that is abundant in gyrencephalic mammalian neocortex. Manipulation of LGN (Leu-Gly-Asn repeat-enriched protein) and Cdk4/cyclin D1, both essential regulators of neural progenitor dynamics, revealed that basal progenitors and Tbr2+ cells are distinct cell lineages in the developing avian telencephalon. Furthermore, we identified a small population of subapical mitotic cells in the developing brains of a wide variety of amniotes and amphibians. Our results suggest that unique progenitor subtypes are amplified in mammalian and avian lineages by modifying common mechanisms of neural stem/progenitor regulation during amniote brain evolution. PMID:26732839

  13. The evolution of basal progenitors in the developing non-mammalian brain.

    PubMed

    Nomura, Tadashi; Ohtaka-Maruyama, Chiaki; Yamashita, Wataru; Wakamatsu, Yoshio; Murakami, Yasunori; Calegari, Federico; Suzuki, Kunihiro; Gotoh, Hitoshi; Ono, Katsuhiko

    2016-01-01

    The amplification of distinct neural stem/progenitor cell subtypes during embryogenesis is essential for the intricate brain structures present in various vertebrate species. For example, in both mammals and birds, proliferative neuronal progenitors transiently appear on the basal side of the ventricular zone of the telencephalon (basal progenitors), where they contribute to the enlargement of the neocortex and its homologous structures. In placental mammals, this proliferative cell population can be subdivided into several groups that include Tbr2(+) intermediate progenitors and basal radial glial cells (bRGs). Here, we report that basal progenitors in the developing avian pallium show unique morphological and molecular characteristics that resemble the characteristics of bRGs, a progenitor population that is abundant in gyrencephalic mammalian neocortex. Manipulation of LGN (Leu-Gly-Asn repeat-enriched protein) and Cdk4/cyclin D1, both essential regulators of neural progenitor dynamics, revealed that basal progenitors and Tbr2(+) cells are distinct cell lineages in the developing avian telencephalon. Furthermore, we identified a small population of subapical mitotic cells in the developing brains of a wide variety of amniotes and amphibians. Our results suggest that unique progenitor subtypes are amplified in mammalian and avian lineages by modifying common mechanisms of neural stem/progenitor regulation during amniote brain evolution. PMID:26732839

  14. Amplified spontaneous emission in Cassegrainian amplifiers

    NASA Astrophysics Data System (ADS)

    Eimerl, David

    1987-05-01

    The paper considers all possible paths for amplifed spontaneous emission (ASE) in multipass laser amplifiers using a Cassegranian telescope geometry. In particular, ASE which is reflected back into the medium off the telescope mirrors themselves is studied. These ASE components are unavoidable in this amplifier geometry. It is shown that there is a component of the ASE which makes approximately double the number of passes through the amplifier as the laser signal makes. It is also shown that these high-order ASE components are also present in amplifiers which are almost Cassegrainian. They cannot be eliminated by changing the ratio of the scraper and hole radii or the separation of the mirrors. It is likely that these ASE components will be more significant in pulsed lasers than CW lasers.

  15. Laser amplifier chain

    DOEpatents

    Hackel, R.P.

    1992-10-20

    A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain. 6 figs.

  16. Laser amplifier chain

    DOEpatents

    Hackel, Richard P.

    1992-01-01

    A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.

  17. Role of intermediate progenitor cells in cerebral cortex development.

    PubMed

    Pontious, Adria; Kowalczyk, Tom; Englund, Chris; Hevner, Robert F

    2008-01-01

    Intermediate progenitor cells (IPCs) are a type of neurogenic transient amplifying cells in the developing cerebral cortex. IPCs divide symmetrically at basal (abventricular) positions in the neuroepithelium to produce pairs of new neurons or, in amplifying divisions, pairs of new IPCs. In contrast, radial unit progenitors (neuroepithelial cells and radial glia) divide at the apical (ventricular) surface and produce only single neurons or single IPCs by asymmetric division, or self-amplify by symmetric division. Histologically, IPCs are most prominent during the middle and late stages of neurogenesis, when they accumulate in the subventricular zone, a progenitor compartment linked to the genesis of upper neocortical layers (II-IV). Nevertheless, IPCs are present throughout cortical neurogenesis and produce neurons for all layers. In mice, changes in the abundance of IPCs caused by mutations of Pax6, Ngn2, Id4 and other genes are associated with parallel changes in cortical thickness but not surface area. In gyrencephalic brains, IPCs may play broader roles in determining not only laminar thickness, but also cortical surface area and gyral patterns. We propose that regulation of IPC genesis and amplification across developmental stages and regional subdivisions modulates laminar neurogenesis and contributes to the cytoarchitectonic differentiation of cortical areas. PMID:18075251

  18. Wireless Josephson amplifier

    SciTech Connect

    Narla, A.; Sliwa, K. M.; Hatridge, M.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.

    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.

  19. Compact laser amplifier system

    DOEpatents

    Carr, R.B.

    1974-02-26

    A compact laser amplifier system is described in which a plurality of face-pumped annular disks, aligned along a common axis, independently radially amplify a stimulating light pulse. Partially reflective or lasing means, coaxially positioned at the center of each annualar disk, radially deflects a stimulating light directed down the common axis uniformly into each disk for amplification, such that the light is amplified by the disks in a parallel manner. Circumferential reflecting means coaxially disposed around each disk directs amplified light emission, either toward a common point or in a common direction. (Official Gazette)

  20. DIRECT COUPLED AMPLIFIER

    DOEpatents

    Dandl, R.A.

    1961-09-19

    A transistor amplifier is designed for vyery small currents below 10/sup -8/ amperes. The filrst and second amplifier stages use unusual selected transistors in which the current amplification increases markedly for values of base current below 10/sup -6/ amperes.

  1. Linearly polarized fiber amplifier

    SciTech Connect

    Kliner, Dahv A.; Koplow, Jeffery P.

    2004-11-30

    Optically pumped rare-earth-doped polarizing fibers exhibit significantly higher gain for one linear polarization state than for the orthogonal state. Such a fiber can be used to construct a single-polarization fiber laser, amplifier, or amplified-spontaneous-emission (ASE) source without the need for additional optical components to obtain stable, linearly polarized operation.

  2. DISTRIBUTED AMPLIFIER INCORPORATING FEEDBACK

    DOEpatents

    Bell, P.R. Jr.

    1958-10-21

    An improved distributed amplifier system employing feedback for stabilization is presented. In accordance with the disclosed invention, a signal to be amplified is applled to one end of a suitable terminated grid transmission line. At intervals along the transmission line, the signal is fed to stable, resistance-capacitance coupled amplifiers incorporating feedback loops therein. The output current from each amplifier is passed through an additional tube to minimize the electrostatic capacitance between the tube elements of the last stage of the amplifier, and fed to appropriate points on an output transmission line, similar to the grid line, but terminated at the opposite (input) end. The output taken from the unterminated end of the plate transmission line is proportional to the input voltage impressed upon the grid line.

  3. Digital automatic gain amplifier

    NASA Technical Reports Server (NTRS)

    Holley, L. D.; Ward, J. O. (Inventor)

    1978-01-01

    A circuit is described for adjusting the amplitude of a reference signal to a predetermined level so as to permit subsequent data signals to be interpreted correctly. The circuit includes an operational amplifier having a feedback circuit connected between an output terminal and an input terminal; a bank of relays operably connected to a plurality of resistors; and a comparator comparing an output voltage of the amplifier with a reference voltage and generating a compared signal responsive thereto. Means is provided for selectively energizing the relays according to the compared signal from the comparator until the output signal from the amplifier equals to the reference signal. A second comparator is provided for comparing the output of the amplifier with a second voltage source so as to illuminate a lamp when the output signal from the amplifier exceeds the second voltage.

  4. Tuning Broadband Microwave Amplifiers

    SciTech Connect

    Alaniz, Gabriel

    2003-09-05

    The PEP-II/DA {Phi} NE/ALS longitudinal feedback systems are complex wide bandwidth systems requiring analog, digital and microwave circuits. The solid-state amplifier is one of the components in the microwave circuit that is required to suppress the coupled bunch instabilities that exist in the PEP-II accelerator. The suppression is achieved by using an antenna as a kicker structure that provides an electric field in order to increase or decrease the energy of particles passing through the structure. The amplifier is made up of sixteen 30 to 35W microstrip GaAs FET modules that are combined to obtain 500W over a bandwidth of 850MHz to 1850MHz. The amplifier malfunctioned causing a reduction in the functionality and power output of the individual GaAs FET modules. The amplifier must be repaired. After repair, the amplifier must be tuned to optimize the gain while maintaining proper power output. The amplifier is tuned using microstrip circuit techniques. A variety of microstrip methods are used to obtain the proper line impedance. The result is a working amplifier that operates efficiently.

  5. Universal signal conditioning amplifier

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.; Hallberg, Carl; Cecil, Jim

    1994-01-01

    A state-of-the-art instrumentation amplifier capable of being used with most types of transducers has been developed at the Kennedy Space Center. This Universal Signal Conditioning Amplifier (USCA) can eliminate costly measurement setup item and troubleshooting, improve system reliability and provide more accurate data than conventional amplifiers. The USCA can configure itself for maximum resolution and accuracy based on information read from a RAM chip attached to each transducer. Excitation voltages or current are also automatically configured. The amplifier uses both analog and digital state-of-the-art technology with analog-to-digital conversion performed in the early stages in order to minimize errors introduced by offset and gain drifts in the analog components. A dynamic temperature compensation scheme has been designed to achieve and maintain 12-bit accuracy of the amplifier from 0 to 70 C. The digital signal processing section allows the implementation of digital filters up to 511th order. The amplifier can also perform real-time linearizations up to fourth order while processing data at a rate of 23.438 kS/s. Both digital and analog outputs are available from the amplifier.

  6. Multipass optical parametric amplifier

    SciTech Connect

    Jeys, T.H.

    1996-08-01

    A compact, low-threshold, multipass optical parametric amplifier has been developed for the conversion of short-pulse (360-ps) 1064-nm Nd:YAG laser radiation into eye-safe 1572-nm radiation for laser ranging and radar applications. The amplifier had a threshold pump power of as low as 45{mu}J, and at three to four times this threshold pump power the amplifier converted 30{percent} of the input 1064-nm radiation into 1572-nm output radiation. {copyright} {ital 1996 Optical Society of America.}

  7. Amplify Interest in STS.

    ERIC Educational Resources Information Center

    Chiappetta, Eugene L; Mays, John D.

    1992-01-01

    Presents activities in which students construct simple crystal radio sets and amplifiers out of diodes, transistors, and integrated circuits. Provides conceptual background, materials needed, instructions, diagrams, and classroom applications. (MDH)

  8. Fully relayed regenerative amplifier

    DOEpatents

    Glass, Alexander J.

    1981-01-01

    A regenerative laser apparatus and method using the optical relay concept to maintain high fill factors, to suppress diffraction effects, and to minimize phase distortions in a regenerative amplifier.

  9. The surface of articular cartilage contains a progenitor cell population.

    PubMed

    Dowthwaite, Gary P; Bishop, Joanna C; Redman, Samantha N; Khan, Ilyas M; Rooney, Paul; Evans, Darrell J R; Haughton, Laura; Bayram, Zubeyde; Boyer, Sam; Thomson, Brian; Wolfe, Michael S; Archer, Charles W

    2004-02-29

    It is becoming increasingly apparent that articular cartilage growth is achieved by apposition from the articular surface. For such a mechanism to occur, a population of stem/progenitor cells must reside within the articular cartilage to provide transit amplifying progeny for growth. Here, we report on the isolation of an articular cartilage progenitor cell from the surface zone of articular cartilage using differential adhesion to fibronectin. This population of cells exhibits high affinity for fibronectin, possesses a high colony-forming efficiency and expresses the cell fate selector gene Notch 1. Inhibition of Notch signalling abolishes colony forming ability whilst activated Notch rescues this inhibition. The progenitor population also exhibits phenotypic plasticity in its differentiation pathway in an embryonic chick tracking system, such that chondroprogenitors can engraft into a variety of connective tissue types including bone, tendon and perimysium. The identification of a chondrocyte subpopulation with progenitor-like characteristics will allow for advances in our understanding of both cartilage growth and maintenance as well as provide novel solutions to articular cartilage repair. PMID:14762107

  10. Electrospun amplified fiber optics.

    PubMed

    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.

  11. Electrospun Amplified Fiber Optics

    PubMed Central

    2015-01-01

    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. PMID:25710188

  12. Laser amplifier and method

    DOEpatents

    Backus, S.; Kapteyn, H.C.; Murnane, M.M.

    1997-07-01

    Laser amplifiers and methods for amplifying a laser beam are disclosed. A representative embodiment of the amplifier comprises first and second curved mirrors, a gain medium, a third mirror, and a mask. The gain medium is situated between the first and second curved mirrors at the focal point of each curved mirror. The first curved mirror directs and focuses a laser beam to pass through the gain medium to the second curved mirror which reflects and recollimates the laser beam. The gain medium amplifies and shapes the laser beam as the laser beam passes therethrough. The third mirror reflects the laser beam, reflected from the second curved mirror, so that the laser beam bypasses the gain medium and return to the first curved mirror, thereby completing a cycle of a ring traversed by the laser beam. The mask defines at least one beam-clipping aperture through which the laser beam passes during a cycle. The gain medium is pumped, preferably using a suitable pumping laser. The laser amplifier can be used to increase the energy of continuous-wave or, especially, pulsed laser beams including pulses of femtosecond duration and relatively high pulse rate. 7 figs.

  13. Laser amplifier and method

    DOEpatents

    Backus, Sterling; Kapteyn, Henry C.; Murnane, Margaret M.

    1997-01-01

    Laser amplifiers and methods for amplifying a laser beam are disclosed. A representative embodiment of the amplifier comprises first and second curved mirrors, a gain medium, a third mirror, and a mask. The gain medium is situated between the first and second curved mirrors at the focal point of each curved mirror. The first curved mirror directs and focuses a laser beam to pass through the gain medium to the second curved mirror which reflects and recollimates the laser beam. The gain medium amplifies and shapes the laser beam as the laser beam passes therethough. The third mirror reflects the laser beam, reflected from the second curved mirror, so that the laser beam bypasses the gain medium and return to the first curved mirror, thereby completing a cycle of a ring traversed by the laser beam. The mask defines at least one beam-clipping aperture through which the laser beam passes during a cycle. The gain medium is pumped, preferably using a suitable pumping laser. The laser amplifier can be used to increase the energy of continuous-wave or, especially, pulsed laser beams including pulses of femtosecond duration and relatively high pulse rate.

  14. STABILIZED FEEDBACK AMPLIFIER

    DOEpatents

    Fishbine, H.L.; Sewell, C. Jr.

    1957-08-01

    Negative feedback amplifiers, and particularly a negative feedback circuit which is economical on amode power consumption, are described. Basically, the disclosed circuit comprises two tetrode tubes where the output of the first tube is capacitamce coupled to the grid of the second tube, which in turn has its plate coupled to the cathode of the first tube to form a degenerative feedback circuit. Operating potential for screen of the second tube is supplied by connecting the cathode resistor of the first tube to the screen, while the screen is by-passed to the cathode of its tube for the amplified frequencies. Also, the amplifier incorporates a circuit to stabilize the transconductance of the tubes by making the grid potential of each tube interdependent on anode currents of both lubes by voltage divider circuitry.

  15. Hepatic progenitor cells express SerpinB3

    PubMed Central

    2014-01-01

    Background In the setting of liver injury hepatic progenitor cells are activated, counterbalancing the inhibited regenerative capacity of mature hepatocytes. Chronic activation of this compartment may give rise to a subset of liver tumours with poor prognosis. SerpinB3, a serpin over-expressed in injured liver and in primary liver cancer, has been shown to induce apoptosis resistance, epithelial to mesenchymal transition and to increase TGF-beta and Myc expression. Aim of the present study was to explore the presence of SerpinB3 in hepatic progenitor cells in human livers and in a mouse model of liver stem/progenitor cell activation. Hepatic progenitor cells were analysed in foetal and adult livers at protein and transcriptional levels. To induce experimental activation of the liver stem/progenitor compartment, C57BL/6J mice were injected with lipopolysaccharide plus D-galactosamine and were sacrificed at different time points. Liver cDNA was amplified using specific primers for mouse-homologous SerpinB3 isoforms and automatically sequenced. Results The presence of SerpinB3 in the progenitor cell compartment was detected in sorted human foetal and adult epithelial cell adhesion molecule (EpCAM) positive liver cells. By immunohistochemistry SerpinB3 was found in human cirrhotic livers in portal areas with progenitor cell activation showing ductular proliferation. CK-7, CK-19, EpCAM and CD-90 positive cell were also positive for SerpinB3. In the animal model, time course analysis in liver specimens revealed a progressive increase of SerpinB3 and a parallel decrease of activated caspase 3, which was barely detectable at 20 hours. Transcription analysis confirmed the presence of SerpinB3-homologous only in the liver of injured mice and sequence analysis proved its belonging to mouse Serpinb3b. Conclusion SerpinB3 is highly expressed in hepatic stem/progenitor cell compartment of both foetal and adult livers. PMID:24517394

  16. Spatial Light Amplifier Modulators

    NASA Technical Reports Server (NTRS)

    Eng, Sverre T.; Olsson, N. Anders

    1992-01-01

    Spatial light amplifier modulators (SLAM's) are conceptual devices that effect two-dimensional spatial modulation in optical computing and communication systems. Unlike current spatial light modulators, these provide gain. Optical processors incorporating SLAM's designed to operate in reflection or transmission mode. Each element of planar SLAM array is optical amplifier - surface-emitting diode laser. Array addressed electrically with ac modulating signals superimposed on dc bias currents supplied to lasers. SLAM device provides both desired modulation and enough optical gain to enable splitting of output signal into many optical fibers without excessive loss of power.

  17. A grid amplifier

    NASA Technical Reports Server (NTRS)

    Kim, Moonil; Weikle, Robert M., II; Hacker, Jonathan B.; Delisio, Michael P.; Rutledge, David B.; Rosenberg, James J.; Smith, R. P.

    1991-01-01

    A 50-MESFET grid amplifier is reported that has a gain of 11 dB at 3.3 GHz. The grid isolates the input from the output by using vertical polarization for the input beam and horizontal polarization for the transmitted output beam. The grid unit cell is a two-MESFET differential amplifier. A simple calibration procedure allows the gain to be calculated from a relative power measurement. This grid is a hybrid circuit, but the structure is suitable for fabrication as a monolithic wafer-scale integrated circuit, particularly at millimeter wavelengths.

  18. Universal signal conditioning amplifier

    NASA Technical Reports Server (NTRS)

    Larson, William E.; Hallberg, Carl; Medelius, Pedro J.

    1994-01-01

    Engineers at NASA's Kennedy Space Center have designed a signal conditioning amplifier which automatically matches itself to almost any kind of transducer. The product, called Universal Signal Conditioning Amplifier (USCA), uses state-of-the-art technologies to deliver high accuracy measurements. USCA's features which can be either programmable or automated include: voltage, current, or pulsed excitation, unlimited resolution gain, digital filtering and both analog and digital output. USCA will be used at Kennedy Space Center's launch pads for environmental measurements such as vibrations, strains, temperatures and overpressures. USCA is presently being commercialized through a co-funded agreement between NASA, the State of Florida, and Loral Test and Information Systems, Inc.

  19. Progenitors of type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Maeda, Keiichi; Terada, Yukikatsu

    2016-07-01

    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 paper 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.

  20. Fourier plane image amplifier

    DOEpatents

    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.

  1. Fourier plane image amplifier

    DOEpatents

    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.

  2. Mesenchymal progenitor cells for the osteogenic lineage

    PubMed Central

    Ono, Noriaki; Kronenberg, Henry M.

    2015-01-01

    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. PMID:26526380

  3. STABILIZED TRANSISTOR AMPLIFIER

    DOEpatents

    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)

  4. Man-Amplifying Exoskeleton

    NASA Astrophysics Data System (ADS)

    Rosheim, Mark E.

    1990-03-01

    This paper describes a design for a man-amplifying exoskeleton, an electrically powered, articulated frame worn by an operator. The design features modular construction and employ anthropomorphic pitch-yaw joints for arms and legs. These singularity-free designs offer a significant advancement over simple pivot-type joints used in older designs. Twenty-six degrees-of-freedom excluding the hands gives the Man-Amplifier its unique dexterity. A five hundred-pound load capacity is engineered for a diverse range of tasks. Potential applications in emergency rescue work, restoring functionality to the handicapped, and military applications ranging from material handling to an elite fighting core are discussed. A bibliography concludes this paper.

  5. PEAK LIMITING AMPLIFIER

    DOEpatents

    Goldsworthy, W.W.; Robinson, J.B.

    1959-03-31

    A peak voltage amplitude limiting system adapted for use with a cascade type amplifier is described. In its detailed aspects, the invention includes an amplifier having at least a first triode tube and a second triode tube, the cathode of the second tube being connected to the anode of the first tube. A peak limiter triode tube has its control grid coupled to thc anode of the second tube and its anode connected to the cathode of the second tube. The operation of the limiter is controlled by a bias voltage source connected to the control grid of the limiter tube and the output of the system is taken from the anode of the second tube.

  6. DRIFT COMPENSATED DIRECT COUPLED AMPLIFIER

    DOEpatents

    Windsor, A.A.

    1959-05-01

    An improved direct-coupled amplifier having zerolevel drift correction is described. The need for an auxiliary corrective-potential amplifier is eliminated thereby giving protection against overload saturation of the zero- level drift correcting circuit. (T.R.H.)

  7. Helical Fiber Amplifier

    DOEpatents

    Koplow, Jeffrey P.; Kliner, Dahy; Goldberg, Lew

    2002-12-17

    A multi-mode gain fiber is provided which affords substantial improvements in the maximum pulse energy, peak power handling capabilities, average output power, and/or pumping efficiency of fiber amplifier and laser sources while maintaining good beam quality (comparable to that of a conventional single-mode fiber source). These benefits are realized by coiling the multimode gain fiber to induce significant bend loss for all but the lowest-order mode(s).

  8. Multiple pass laser amplifier system

    DOEpatents

    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.

  9. Improved-Bandwidth Transimpedance Amplifier

    NASA Technical Reports Server (NTRS)

    Chapsky, Jacob

    2009-01-01

    The widest available operational amplifier, with the best voltage and current noise characteristics, is considered for transimpedance amplifier (TIA) applications where wide bandwidth is required to handle fast rising input signals (as for time-of-flight measurement cases). The added amplifier inside the TIA feedback loop can be configured to have slightly lower voltage gain than the bandwidth reduction factor.

  10. The Progenitors of Thermonuclear Supernovae

    SciTech Connect

    Piersanti, L.; Straniero, O.; Tornambe, A.; Dominguez, I.

    2009-05-03

    In the framework of the rotating Double Degenerate Scenario for type Ia Supernovae progenitors, we show that the dichotomy between explosive events in early and late type galaxies can be easily explained. Assuming that more massive progenitors produce slow-decline (high-luminosity) light curve, it comes out that, at the current age of the Universe, in late type galaxies the continuous star formation provides very massive exploding objects (prompt component) corresponding to slow-decline (bright) SNe; on the other hand, in early type galaxies, where star formation ended many billions years ago, only low mass ''normal luminosity'' objects (delayed component) are present.

  11. REGENERATIVE TRANSISTOR AMPLIFIER

    DOEpatents

    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.

  12. Amplifying Electrochemical Indicators

    NASA Technical Reports Server (NTRS)

    Fan, Wenhong; Li, Jun; Han, Jie

    2004-01-01

    Dendrimeric reporter compounds have been invented for use in sensing and amplifying electrochemical signals from molecular recognition events that involve many chemical and biological entities. These reporter compounds can be formulated to target specific molecules or molecular recognition events. They can also be formulated to be, variously, hydrophilic or amphiphilic so that they are suitable for use at interfaces between (1) aqueous solutions and (2) electrodes connected to external signal-processing electronic circuits. The invention of these reporter compounds is expected to enable the development of highly miniaturized, low-power-consumption, relatively inexpensive, mass-producible sensor units for diverse applications.

  13. Universal Signal Conditioning Amplifier

    NASA Technical Reports Server (NTRS)

    Kinney, Frank

    1997-01-01

    The Technological Research and Development Authority (TRDA) and NASA-KSC entered into a cooperative agreement in March of 1994 to achieve the utilization and commercialization of a technology development for benefiting both the Space Program and U.S. industry on a "dual-use basis". The technology involved in this transfer is a new, unique Universal Conditioning Amplifier (USCA) used in connection with various types of transducers. The project was initiated in partnership with I-Net Corporation, Lockheed Martin Telemetry & Instrumentation (formerly Loral Test and Information Systems) and Brevard Community College. The project consists of designing, miniaturizing, manufacturing, and testing an existing prototype of USCA that was developed for NASA-KSC by the I-Net Corporation. The USCA is a rugged and field-installable self (or remotely)- programmable amplifier that works in combination with a tag random access memory (RAM) attached to various types of transducers. This summary report comprises performance evaluations, TRDA partnership tasks, a project summary, project milestones and results.

  14. DIAMOND AMPLIFIED PHOTOCATHODES.

    SciTech Connect

    SMEDLEY,J.; BEN-ZVI, I.; BOHON, J.; CHANG, X.; GROVER, R.; ISAKOVIC, A.; RAO, T.; WU, Q.

    2007-11-26

    High-average-current linear electron accelerators require photoinjectors capable of delivering tens to hundreds of mA average current, with peak currents of hundreds of amps. Standard photocathodes face significant challenges in meeting these requirements, and often have short operational lifetimes in an accelerator environment. We report on recent progress toward development of secondary emission amplifiers for photocathodes, which are intended to increase the achievable average current while protecting the cathode from the accelerator. The amplifier is a thin diamond wafer which converts energetic (few keV) primary electrons into hundreds of electron-hole pairs via secondary electron emission. The electrons drift through the diamond under an external bias and are emitted into vacuum via a hydrogen-terminated surface with negative electron affinity (NEA). Secondary emission gain of over 200 has been achieved. Two methods of patterning diamond, laser ablation and reactive-ion etching (RIE), are being developed to produce the required geometry. A variety of diagnostic techniques, including FTIR, SEM and AFM, have been used to characterize the diamonds.

  15. Human Urine-Derived Renal Progenitors for Personalized Modeling of Genetic Kidney Disorders.

    PubMed

    Lazzeri, Elena; Ronconi, Elisa; Angelotti, Maria Lucia; Peired, Anna; Mazzinghi, Benedetta; Becherucci, Francesca; Conti, Sara; Sansavini, Giulia; Sisti, Alessandro; Ravaglia, Fiammetta; Lombardi, Duccio; Provenzano, Aldesia; Manonelles, Anna; Cruzado, Josep M; Giglio, Sabrina; Roperto, Rosa Maria; Materassi, Marco; Lasagni, Laura; Romagnani, Paola

    2015-08-01

    The critical role of genetic and epigenetic factors in the pathogenesis of kidney disorders is gradually becoming clear, and the need for disease models that recapitulate human kidney disorders in a personalized manner is paramount. In this study, we describe a method to select and amplify renal progenitor cultures from the urine of patients with kidney disorders. Urine-derived human renal progenitors exhibited phenotype and functional properties identical to those purified from kidney tissue, including the capacity to differentiate into tubular cells and podocytes, as demonstrated by confocal microscopy, Western blot analysis of podocyte-specific proteins, and scanning electron microscopy. Lineage tracing studies performed with conditional transgenic mice, in which podocytes are irreversibly tagged upon tamoxifen treatment (NPHS2.iCreER;mT/mG), that were subjected to doxorubicin nephropathy demonstrated that renal progenitors are the only urinary cell population that can be amplified in long-term culture. To validate the use of these cells for personalized modeling of kidney disorders, renal progenitors were obtained from (1) the urine of children with nephrotic syndrome and carrying potentially pathogenic mutations in genes encoding for podocyte proteins and (2) the urine of children without genetic alterations, as validated by next-generation sequencing. Renal progenitors obtained from patients carrying pathogenic mutations generated podocytes that exhibited an abnormal cytoskeleton structure and functional abnormalities compared with those obtained from patients with proteinuria but without genetic mutations. The results of this study demonstrate that urine-derived patient-specific renal progenitor cultures may be an innovative research tool for modeling of genetic kidney disorders.

  16. LIN28A marks the spermatogonial progenitor population and regulates its cyclic expansion

    PubMed Central

    Chakraborty, P; Buaas, F.W.; Sharma, M; Snyder, E; de Rooij, D.G.; Braun, R.E.

    2014-01-01

    One of the hallmarks of highly proliferative adult tissues is the presence of a stem cell population that produces progenitor cells bound for differentiation. Progenitor cells undergo multiple transit amplifying (TA) divisions before initiating terminal differentiation. In the adult male germline, daughter cells arising from the spermatogonial stem cells (SSCs) undergo multiple rounds of TA divisions to produce undifferentiated clones of interconnected 2, 4, 8 and 16 cells, collectively termed Aundifferentiated (Aundiff) spermatogonia, before entering a stereotypic differentiation cascade. Although the number of TA divisions markedly affects the tissue output both at steady state and during regeneration, mechanisms regulating the expansion of the TA cell population are poorly understood in mammals. Here, we show that mice with a conditional deletion of Lin28a in the adult male germline, display impaired clonal expansion of the progenitor transit amplifying Aundiff spermatogonia. The in vivo proliferative activity of Aundiff spermatogonial cells as indicated by BrdU incorporation during S phase was reduced in the absence of LIN28A. Thus contrary to the role of LIN28A as a key determinant of cell fate signals in multiple stem cell lineages, in the adult male germline it functions as an intrinsic regulator of proliferation in the population of Aundiff TA spermatogonia. In addition, neither precocious differentiation nor diminished capacity for self-renewal potential as assessed by transplantation was observed, suggesting that neither LIN28A itself, nor the pool of Aal progenitor cells, substantially contribute to the functional stem cell compartment. PMID:24715688

  17. Nanoscale electromechanical parametric amplifier

    DOEpatents

    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.

  18. Wavelength tunable alexandrite regenerative amplifier

    SciTech Connect

    Harter, D.J.; Bado, P.

    1988-11-01

    We describe a wavelength tunable alexandrite regenerative amplifier which is used to amplify nanosecond slices from a single-frequency cw dye laser or 50-ps pulses emitted by a diode laser to energies in the 10-mJ range. The amplified 5-ns slices generated by the cw-pumped line narrowed dye laser are Fourier transform limited. The 50-ps pulses emitted by a gain-switched diode laser are amplified by more than 10 orders of magnitude in a single stage.

  19. Optical Amplifier for Space Applications

    NASA Technical Reports Server (NTRS)

    Fork, Richard L.; Cole, Spencer T.; Gamble, Lisa J.; Diffey, William M.; Keys, Andrew S.

    1999-01-01

    We describe an optical amplifier designed to amplify a spatially sampled component of an optical wavefront to kilowatt average power. The goal is means for implementing a strategy of spatially segmenting a large aperture wavefront, amplifying the individual segments, maintaining the phase coherence of the segments by active means, and imaging the resultant amplified coherent field. Applications of interest are the transmission of space solar power over multi-megameter distances, as to distant spacecraft, or to remote sites with no preexisting power grid.

  20. Reflex ring laser amplifier system

    DOEpatents

    Summers, Mark A.

    1985-01-01

    A laser pulse is injected into an unstable ring resonator-amplifier structure. Inside this resonator the laser pulse is amplified, spatially filtered and magnified. The laser pulse is recirculated in the resonator, being amplified, filtered and magnified on each pass. The magnification is chosen so that the beam passes through the amplifier in concentric non-overlapping regions similar to a single pass MOPA. After a number of passes around the ring resonator the laser pulse is spatially large enough to exit the ring resonator system by passing around an output mirror.

  1. PROGENITORS OF RECOMBINING SUPERNOVA REMNANTS

    SciTech Connect

    Moriya, Takashi J.

    2012-05-01

    Usual supernova remnants have either ionizing plasma or plasma in collisional ionization equilibrium, i.e., the ionization temperature is lower than or equal to the electron temperature. However, the existence of recombining supernova remnants, i.e., supernova remnants with ionization temperature higher than the electron temperature, has been recently confirmed. One suggested way to have recombining plasma in a supernova remnant is to have a dense circumstellar medium at the time of the supernova explosion. If the circumstellar medium is dense enough, collisional ionization equilibrium can be established in the early stage of the evolution of the supernova remnant and subsequent adiabatic cooling, which occurs after the shock wave gets out of the dense circumstellar medium, makes the electron temperature lower than the ionization temperature. We study the circumstellar medium around several supernova progenitors and show which supernova progenitors can have a circumstellar medium dense enough to establish collisional ionization equilibrium soon after the explosion. We find that the circumstellar medium around red supergiants (especially massive ones) and the circumstellar medium dense enough to make Type IIn supernovae can establish collisional ionization equilibrium soon after the explosion and can evolve to become recombining supernova remnants. Wolf-Rayet stars and white dwarfs have the possibility to be recombining supernova remnants but the fraction is expected to be very small. As the occurrence rate of the explosions of red supergiants is much higher than that of Type IIn supernovae, the major progenitors of recombining supernova remnants are likely to be red supergiants.

  2. Progenitors of Recombining Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Moriya, Takashi J.

    2012-05-01

    Usual supernova remnants have either ionizing plasma or plasma in collisional ionization equilibrium, i.e., the ionization temperature is lower than or equal to the electron temperature. However, the existence of recombining supernova remnants, i.e., supernova remnants with ionization temperature higher than the electron temperature, has been recently confirmed. One suggested way to have recombining plasma in a supernova remnant is to have a dense circumstellar medium at the time of the supernova explosion. If the circumstellar medium is dense enough, collisional ionization equilibrium can be established in the early stage of the evolution of the supernova remnant and subsequent adiabatic cooling, which occurs after the shock wave gets out of the dense circumstellar medium, makes the electron temperature lower than the ionization temperature. We study the circumstellar medium around several supernova progenitors and show which supernova progenitors can have a circumstellar medium dense enough to establish collisional ionization equilibrium soon after the explosion. We find that the circumstellar medium around red supergiants (especially massive ones) and the circumstellar medium dense enough to make Type IIn supernovae can establish collisional ionization equilibrium soon after the explosion and can evolve to become recombining supernova remnants. Wolf-Rayet stars and white dwarfs have the possibility to be recombining supernova remnants but the fraction is expected to be very small. As the occurrence rate of the explosions of red supergiants is much higher than that of Type IIn supernovae, the major progenitors of recombining supernova remnants are likely to be red supergiants.

  3. Suicide Risk: Amplifiers and Attenuators.

    ERIC Educational Resources Information Center

    Plutchik, Robert; Van Praag, Herman M.

    1994-01-01

    Attempts to integrate findings on correlates of suicide and violent risk in terms of a theory called a two-stage model of countervailing forces, which assumes that the strength of aggressive impulses is modified by amplifiers and attenuators. The vectorial interaction of amplifiers and attenuators creates an unstable equilibrium making prediction…

  4. Laser amplifier developments at Mercury

    SciTech Connect

    Rose, E.A.; Brucker, J.P.; Honig, E.M.; McCown, A.W.; Romero, V.O.; York, G.W.

    1993-09-01

    Electron-beam pumped laser amplifiers have been modified to address the mission of krypton-fluoride excimer laser technology development. Methods are described for improving the performance and reliability of two pre-existing amplifiers at minimal cost and time. Preliminary performance data are presented to support the credibility of the approach.

  5. Hybrid thin-film amplifier

    NASA Technical Reports Server (NTRS)

    Cleveland, G.

    1977-01-01

    Miniature amplifier for bioelectronic instrumentation consumes only about 100 mW and has frequency response flat to within 0.5 dB from 0.14 to 450 Hz. Device consists of five thin film substrates, which contain eight operational amplifiers and seven field-effect transistor dice.

  6. Microchannels as axonal amplifiers.

    PubMed

    Fitzgerald, James J; Lacour, Stéphanie P; McMahon, Stephen B; Fawcett, James W

    2008-03-01

    An implantable neural interface capable of reliable long-term high-resolution recording from peripheral nerves has yet to be developed. Device design is challenging because extracellular axonal signals are very small, decay rapidly with distance from the axon, and in myelinated fibres are concentrated close to nodes of Ranvier, which are around 1 mum long and spaced several hundred micrometers apart. We present a finite element model examining the electrical behavior of axons in microchannels, and demonstrate that confining axons in such channels substantially amplifies the extracellular signal. For example, housing a 10-microm myelinated axon in a 1-cm-long channel with a 1000-microm(2) cross section is predicted to generate a peak extracellular voltage of over 10 mV. Furthermore, there is little radial signal decay within the channel, and a smooth axial variation of signal amplitude along the channel, irrespective of node location. Additional benefits include a greater extracellular voltage generated by large myelinated fibres compared to small unmyelinated axons, and the reduction of gain to unity at the end of the channel which ensures that there can be no crosstalk with electrodes in other channels nearby. A microchannel architecture seems well suited to the requirements of a peripheral nerve interface.

  7. DIAMOND AMPLIFIER FOR PHOTOCATHODES.

    SciTech Connect

    RAO,T.; BEN-ZVI,I.; BURRILL,A.; CHANG,X.; HULBERT,S.; JOHNSON,P.D.; KEWISCH,J.

    2004-06-21

    We report a new approach to the generation of high-current, high-brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron-volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating proper of the ''gun'' through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: (1) Reduction of the number of primary electrons by the large SEY, i.e. a very low laser power in a photocathode producing the primaries. (2) Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons. (3) Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. (4) Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. (5) Production of high average currents, up to ampere class. (6) Encapsulated design, making the ''load-lock'' systems unnecessary. This paper presents the criteria that need to be taken into account in designing the amplifier.

  8. Modeling renal progenitors - defining the niche.

    PubMed

    Tanigawa, Shunsuke; Perantoni, Alan O

    2016-01-01

    Significant recent advances in methodologies for the differentiation of pluripotent stem cells to renal progenitors as well as the definition of niche conditions for sustaining those progenitors have dramatically enhanced our understanding of their biology and developmental programing, prerequisites for establishing viable approaches to renal regeneration. In this article, we review the evolution of culture techniques and models for the study of metanephric development, describe the signaling mechanisms likely to be driving progenitor self-renewal, and discuss current efforts to generate de novo functional tissues, providing in depth protocols and niche conditions for the stabilization of the nephronic Six2+progenitor. PMID:26856661

  9. Characterization of SLUG microwave amplifiers

    NASA Astrophysics Data System (ADS)

    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.

  10. New Packaging for Amplifier Slabs

    SciTech Connect

    Riley, M.; Thorsness, C.; Suratwala, T.; Steele, R.; Rogowski, G.

    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.

  11. Amplifier arrays for CMB polarization

    NASA Technical Reports Server (NTRS)

    Gaier, Todd; Lawrence, Charles R.; Seiffert, Michael D.; Wells, Mary M.; Kangaslahti, Pekka; Dawson, Douglas

    2003-01-01

    Cryogenic low noise amplifier technology has been successfully used in the study of the cosmic microwave background (CMB). MMIC (Monolithic Millimeter wave Integrated Circuit) technology makes the mass production of coherent detection receivers feasible.

  12. Enhanced performance CCD output amplifier

    DOEpatents

    Dunham, Mark E.; Morley, David W.

    1996-01-01

    A low-noise FET amplifier is connected to amplify output charge from a che coupled device (CCD). The FET has its gate connected to the CCD in common source configuration for receiving the output charge signal from the CCD and output an intermediate signal at a drain of the FET. An intermediate amplifier is connected to the drain of the FET for receiving the intermediate signal and outputting a low-noise signal functionally related to the output charge signal from the CCD. The amplifier is preferably connected as a virtual ground to the FET drain. The inherent shunt capacitance of the FET is selected to be at least equal to the sum of the remaining capacitances.

  13. Progenitors of type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Raskin, Cody

    Type Ia supernovae are important, but mysterious cosmological tools. Their standard brightnesses have enabled cosmologists to measure extreme distances and to discover dark energy. However, the nature of their progenitor mechanisms remains elusive, with many competing models offering only partial clues to their origins. Here, type Ia supernova delay times are explored using analytical models. Combined with a new observation technique, this model places new constraints on the characteristic time delay between the formation of stars and the first type Ia supernovae. This derived delay time (500 million years) implies low-mass companions for single degenerate progenitor scenarios. In the latter portions of this dissertation, two progenitor mechanisms are simulated in detail; white dwarf collisions and mergers. From the first of these simulations, it is evident that white dwarf collisions offer a viable and unique pathway to producing type Ia supernovae. Many of the combinations of masses simulated produce sufficient quantities of 56 Ni (up to 0.51 solar masses) to masquerade as normal type Ia supernovae. Other combinations of masses produce 56 Ni yields that span the entire range of supernova brightnesses, from the very dim and underluminous, with 0.14 solar masses, to the over-bright and superluminous, with up to 1.71 solar masses. The 56 Ni yield in the collision simulations depends non-linearly on total system mass, mass ratio, and impact parameter. Using the same numerical tools as in the collisions examination, white dwarf mergers are studied in detail. Nearly all of the simulations produce merger remnants consisting of a cold, degenerate core surrounded by a hot accretion disk. The properties of these disks have strong implications for various viscosity treatments that have attempted to pin down the accretion times. Some mass combinations produce super-Chandrasekhar cores on shorter time scales than viscosity driven accretion. A handful of simulations also

  14. Reflex ring laser amplifier system

    SciTech Connect

    Summers, M.A.

    1983-08-31

    The invention is a method and apparatus for providing a reflex ring laser system for amplifying an input laser pulse. The invention is particularly useful in laser fusion experiments where efficient production of high-energy and high power laser pulses is required. The invention comprises a large aperture laser amplifier in an unstable ring resonator which includes a combination spatial filter and beam expander having a magnification greater than unity. An input pulse is injected into the resonator, e.g., through an aperture in an input mirror. The injected pulse passes through the amplifier and spatial filter/expander components on each pass around the ring. The unstable resonator is designed to permit only a predetermined number of passes before the amplified pulse exits the resonator. On the first pass through the amplifier, the beam fills only a small central region of the gain medium. On each successive pass, the beam has been expanded to fill the next concentric non-overlapping region of the gain medium.

  15. Prorenin receptor is critical for nephron progenitors.

    PubMed

    Song, Renfang; Preston, Graeme; Kidd, Laura; Bushnell, Daniel; Sims-Lucas, Sunder; Bates, Carlton M; Yosypiv, Ihor V

    2016-01-15

    Deficient nephrogenesis is the major factor contributing to renal hypoplasia defined as abnormally small kidneys. Nephron induction during kidney development is driven by reciprocal interactions between progenitor cells of the cap mesenchyme (CM) and the ureteric bud (UB). The prorenin receptor (PRR) is a receptor for renin and prorenin, and an accessory subunit of the vacuolar proton pump H(+)-ATPase. Global loss of PRR is lethal in mice and PRR mutations are associated with a high blood pressure, left ventricular hypertrophy and X-linked mental retardation in humans. To circumvent lethality of the ubiquitous PRR mutation in mice and to determine the potential role of the PRR in nephrogenesis, we generated a mouse model with a conditional deletion of the PRR in Six2(+) nephron progenitors and their epithelial derivatives (Six2(PRR-/-)). Targeted ablation of PRR in Six2(+) nephron progenitors caused a marked decrease in the number of developing nephrons, small cystic kidneys and podocyte foot process effacement at birth, and early postnatal death. Reduced congenital nephron endowment resulted from premature depletion of nephron progenitor cell population due to impaired progenitor cell proliferation and loss of normal molecular inductive response to canonical Wnt/β-catenin signaling within the metanephric mesenchyme. At 2 months of age, heterozygous Six2(PRR+/-) mice exhibited focal glomerulosclerosis, decreased kidney function and massive proteinuria. Collectively, these findings demonstrate a cell-autonomous requirement for the PRR within nephron progenitors for progenitor maintenance, progression of nephrogenesis, normal kidney development and function.

  16. Progenitor's Signatures in Type Ia Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Chiotellis, A.; Kosenko, D.; Schure, K. M.; Vink, J.

    2013-01-01

    The remnants of Type Ia supernovae (SNe Ia) can provide important clues about their progenitor histories. We discuss two well-observed supernova remnants (SNRs) that are believed to have resulted from SNe Ia, and use various tools to shed light on the possible progenitor histories. We find that Kepler's SNR is consistent with a symbiotic binary progenitor consisting of a white dwarf and an AGB star. Our hydrosimulations can reproduce the observed kinematic and morphological properties. For Tycho's remnant we use the characteristics of the X-ray spectrum and kinematics to show that the ejecta has likely interacted with dense circumstellar gas.

  17. Progenitor genealogy in the developing cerebral cortex.

    PubMed

    Laguesse, Sophie; Peyre, Elise; Nguyen, Laurent

    2015-01-01

    The mammalian cerebral cortex is characterized by a complex histological organization that reflects the spatio-temporal stratifications of related stem and neural progenitor cells, which are responsible for the generation of distinct glial and neuronal subtypes during development. Some work has been done to shed light on the existing filiations between these progenitors as well as their respective contribution to cortical neurogenesis. The aim of the present review is to summarize the current views of progenitor hierarchy and relationship in the developing cortex and to further discuss future research directions that would help us to understand the molecular and cellular regulating mechanisms involved in cerebral corticogenesis. PMID:25141969

  18. Laser system using regenerative amplifier

    DOEpatents

    Emmett, J.L.

    1980-03-04

    High energy laser system is disclosed using a regenerative amplifier, which relaxes all constraints on laser components other than the intrinsic damage level of matter, so as to enable use of available laser system components. This can be accomplished by use of segmented components, spatial filters, at least one amplifier using solid state or gaseous media, and separated reflector members providing a long round trip time through the regenerative cavity, thereby allowing slower switching and adequate time to clear the spatial filters, etc. The laser system simplifies component requirements and reduces component cost while providing high energy output. 10 figs.

  19. Laser system using regenerative amplifier

    DOEpatents

    Emmett, John L. [Pleasanton, CA

    1980-03-04

    High energy laser system using a regenerative amplifier, which relaxes all constraints on laser components other than the intrinsic damage level of matter, so as to enable use of available laser system components. This can be accomplished by use of segmented components, spatial filters, at least one amplifier using solid state or gaseous media, and separated reflector members providing a long round trip time through the regenerative cavity, thereby allowing slower switching and adequate time to clear the spatial filters, etc. The laser system simplifies component requirements and reduces component cost while providing high energy output.

  20. Coherent amplified optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Rao, Bin; Chen, Zhongping

    2007-07-01

    A technique to improve the signal-to-noise ratio (SNR) of a high speed 1300 nm swept source optical coherence tomography (SSOCT) system was demonstrated. A semiconductor optical amplifier (SOA) was employed in the sample arm to coherently amplify the weak light back-scattered from sample tissue without increasing laser power illuminated on the sample. The image quality improvement was visualized and quantified by imaging the anterior segment of a rabbit eye at imaging speed of 20,000 A-lines per second. The theory analysis of SNR gain is given followed by the discussion on the technologies that can further improve the SNR gain.

  1. Amplified gigabit PON systems [Invited

    NASA Astrophysics Data System (ADS)

    Suzuki, Ken-Ichi; Fukada, Youichi; Nesset, Derek; Davey, Russell

    2007-05-01

    We describe how a passive optical network (PON) extender box can be implemented at standard PON wavelengths (1310 and 1490nm) using either optical fiber amplifiers (praseodymium and thulium) or semiconductor optical amplifiers to further increase the physical reach and split of a current standardized PON system such as a G-PON or GE-PON. The transparency to PON protocol of this approach means no changes to the existing standards are required. This is attractive as operators and vendors are keen to fully exploit the investment made in current PON standards.

  2. PASOTRON{trademark} amplifier experiments

    SciTech Connect

    Ponti, E.S.; Goebel, D.M.; Feicht, J.R.; Santoru, J.; Eisenhart, R.L.

    1995-11-01

    Preliminary experimental studies are reported of an L-Band amplifier based on Hughes` Plasma-Assisted, Slow-Wave Oscillator (PASOTRON) technology. The amplifier system utilizes a hollow-cathode-plasma electron-gun, and a plasma-filled Slow-Wave Structure (SWS) to produce {>=} 100-{micro}sec-long, 50 to 75-kV, 30 to 100-A electron-beam pulses that propagate in a plasma channel without the use of any externally applied axial magnetic field. The electron-beam pulse coincides with a 100-{micro}sec-long RF drive signal provided by a 2.6-kW TWT, which is coupled into the amplifier upstream of the SWS. The SWS consists of a ring-bar design which is novel to the PASOTRON family of devices and is used for its short length compared to a helix. Simulations on HP`s High Frequency Structure Simulator were used to optimize the ring-bar SWS. Preliminary data are reported showing the new L-Band amplifiers gain, power, efficiency, and bandwidth. Methods of eliminating a Backward Wave Oscillation (BWO), which was found to limit the performance of the tube, are also presented.

  3. The School as an Amplifier.

    ERIC Educational Resources Information Center

    Vincent, William S.

    1966-01-01

    This paper attempts to show that adaptation of mathematics to the input-output model of the school can provide powerful assistance in the measurement and analysis of school quality and its determinants. The mathematical relationship described here relates an educational model to the field of electronics. More specifically, the amplifier, a device…

  4. Progenitor cells in pulmonary vascular remodeling.

    PubMed

    Yeager, Michael E; Frid, Maria G; Stenmark, Kurt R

    2011-01-01

    Pulmonary hypertension is characterized by cellular and structural changes in the walls of pulmonary arteries. Intimal thickening and fibrosis, medial hypertrophy and fibroproliferative changes in the adventitia are commonly observed, as is the extension of smooth muscle into the previously non-muscularized vessels. A majority of these changes are associated with the enhanced presence of α-SM-actin+ cells and inflammatory cells. Atypical abundances of functionally distinct endothelial cells, particularly in the intima (plexiform lesions), and also in the perivascular regions, are also described. At present, neither the origin(s) of these cells nor the molecular mechanisms responsible for their accumulation, in any of the three compartments of the vessel wall, have been fully elucidated. The possibility that they arise from either resident vascular progenitors or bone marrow-derived progenitor cells is now well established. Resident vascular progenitor cells have been demonstrated to exist within the vessel wall, and in response to certain stimuli, to expand and express myofibroblastic, endothelial or even hematopoietic markers. Bone marrow-derived or circulating progenitor cells have also been shown to be recruited to sites of vascular injury and to assume both endothelial and SM-like phenotypes. Here, we review the data supporting the contributory role of vascular progenitors (including endothelial progenitor cells, smooth muscle progenitor cells, pericytes, and fibrocytes) in vascular remodeling. A more complete understanding of the processes by which progenitor cells modulate pulmonary vascular remodeling will undoubtedly herald a renaissance of therapies extending beyond the control of vascular tonicity and reduction of pulmonary artery pressure. PMID:22034593

  5. Low Cost RF Amplifier for Community TV

    NASA Astrophysics Data System (ADS)

    Ch, Syafaruddin; Sasongko, Sudi Mariyanto Al; Made Budi Suksmadana, I.; Mustiko Okta Muvianto, Cahyo; Ariessaputra, Suthami

    2016-01-01

    he capability of television to deliver audio video makes this media become the most effective method to spread information. This paper presents an experiment of RF amplifier design having low-cost design and providing sufficient RF power particularly for community television. The RF amplifier consists of two stages of amplifier. The first stage amplifier was used to leverage output of TV modulator from 11dBm to enable to drive next stage amplifier. CAD simulation and fabrication were run to reach optimum RF amplifier design circuit. The associated circuit was made by determining stability circle, stability gain, and matching impedance. Hence, the average power of first stage RF amplifier was 24.68dBm achieved. The second stage used RF modules which was ready match to 50 ohm for both input and output port. The experiment results show that the RF amplifier may operate at frequency ranging from 174 to 230MHz. The average output power of the 2nd stage amplifier was 33.38 Watt with the overall gain of 20.54dB. The proposed RF amplifier is a cheap way to have a stable RF amplifier for community TV. The total budget for the designed RF amplifier is only a 1/5 compared to local design of final TV amplifier.

  6. Does surface roughness amplify wetting?

    SciTech Connect

    Malijevský, Alexandr

    2014-11-14

    Any solid surface is intrinsically rough on the microscopic scale. In this paper, we study the effect of this roughness on the wetting properties of hydrophilic substrates. Macroscopic arguments, such as those leading to the well-known Wenzel's law, predict that surface roughness should amplify the wetting properties of such adsorbents. We use a fundamental measure density functional theory to demonstrate the opposite effect from roughness for microscopically corrugated surfaces, i.e., wetting is hindered. Based on three independent analyses we show that microscopic surface corrugation increases the wetting temperature or even makes the surface hydrophobic. Since for macroscopically corrugated surfaces the solid texture does indeed amplify wetting there must exist a crossover between two length-scale regimes that are distinguished by opposite response on surface roughening. This demonstrates how deceptive can be efforts to extend the thermodynamical laws beyond their macroscopic territory.

  7. The novel Light Amplifier concept

    NASA Astrophysics Data System (ADS)

    Ferenc, Daniel; Kranich, Daniel; Laille, Alvin; Lorenz, Eckart

    2006-11-01

    Photon detectors are indispensable in many areas of fundamental physics research, particularly in the emerging field of particle astrophysics, as well as in medical imaging and nuclear nonproliferation. For a significant progress in all these areas a new, inexpensive industrial mass-production photosensor technology is needed, in many cases with a very large active area. In order to reach that goal we have introduced several innovations. This paper focuses on one of them, the hemispherical Light Amplifier. We report on the proof of principle tests of the prototype derived from an existing QUASAR phototube and a new Geiger-mode avalanche photodiode. Our experiments prove that Light Amplifier concept presents a promising solution for a next-generation low-cost photon detector offering superior performance.

  8. Neural Progenitors Adopt Specific Identities by Directly Repressing All Alternative Progenitor Transcriptional Programs.

    PubMed

    Kutejova, Eva; Sasai, Noriaki; Shah, Ankita; Gouti, Mina; Briscoe, James

    2016-03-21

    In the vertebrate neural tube, a morphogen-induced transcriptional network produces multiple molecularly distinct progenitor domains, each generating different neuronal subtypes. Using an in vitro differentiation system, we defined gene expression signatures of distinct progenitor populations and identified direct gene-regulatory inputs corresponding to locations of specific transcription factor binding. Combined with targeted perturbations of the network, this revealed a mechanism in which a progenitor identity is installed by active repression of the entire transcriptional programs of other neural progenitor fates. In the ventral neural tube, sonic hedgehog (Shh) signaling, together with broadly expressed transcriptional activators, concurrently activates the gene expression programs of several domains. The specific outcome is selected by repressive input provided by Shh-induced transcription factors that act as the key nodes in the network, enabling progenitors to adopt a single definitive identity from several initially permitted options. Together, the data suggest design principles relevant to many developing tissues. PMID:26972603

  9. Field-effect transistor improves electrometer amplifier

    NASA Technical Reports Server (NTRS)

    Munoz, R.

    1964-01-01

    An electrometer amplifier uses a field effect transistor to measure currents of low amperage. The circuit, developed as an ac amplifier, is used with an external filter which limits bandwidth to achieve optimum noise performance.

  10. High temperature current mirror amplifier

    DOEpatents

    Patterson, III, Raymond B.

    1984-05-22

    A high temperature current mirror amplifier having biasing means in the transdiode connection of the input transistor for producing a voltage to maintain the base-collector junction reversed-biased and a current means for maintaining a current through the biasing means at high temperatures so that the base-collector junction of the input transistor remained reversed-biased. For accuracy, a second current mirror is provided with a biasing means and current means on the input leg.

  11. High power gas laser amplifier

    DOEpatents

    Leland, Wallace T.; Stratton, Thomas F.

    1981-01-01

    A high power output CO.sub.2 gas laser amplifier having a number of sections, each comprising a plurality of annular pumping chambers spaced around the circumference of a vacuum chamber containing a cold cathode, gridded electron gun. The electron beam from the electron gun ionizes the gas lasing medium in the sections. An input laser beam is split into a plurality of annular beams, each passing through the sections comprising one pumping chamber.

  12. 338-GHz Semiconductor Amplifier Module

    NASA Technical Reports Server (NTRS)

    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.

  13. High power regenerative laser amplifier

    DOEpatents

    Miller, John L.; Hackel, Lloyd A.; Dane, Clifford B.; Zapata, Luis E.

    1994-01-01

    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.

  14. High power regenerative laser amplifier

    DOEpatents

    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.

  15. Small and lightweight power amplifiers

    NASA Astrophysics Data System (ADS)

    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.

  16. Improved charge amplifier using hybrid hysteresis compensation

    NASA Astrophysics Data System (ADS)

    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.

  17. NASA developments in solid state power amplifiers

    NASA Technical Reports Server (NTRS)

    Leonard, Regis F.

    1990-01-01

    Over the last ten years, NASA has undertaken an extensive program aimed at development of solid state power amplifiers for space applications. Historically, the program may be divided into three phases. The first efforts were carried out in support of the advanced communications technology satellite (ACTS) program, which is developing an experimental version of a Ka-band commercial communications system. These first amplifiers attempted to use hybrid technology. The second phase was still targeted at ACTS frequencies, but concentrated on monolithic implementations, while the current, third phase, is a monolithic effort that focusses on frequencies appropriate for other NASA programs and stresses amplifier efficiency. The topics covered include: (1) 20 GHz hybrid amplifiers; (2) 20 GHz monolithic MESFET power amplifiers; (3) Texas Instruments' (TI) 20 GHz variable power amplifier; (4) TI 20 GHz high power amplifier; (5) high efficiency monolithic power amplifiers; (6) GHz high efficiency variable power amplifier; (7) TI 32 GHz monolithic power amplifier performance; (8) design goals for Hughes' 32 GHz variable power amplifier; and (9) performance goals for Hughes' pseudomorphic 60 GHz power amplifier.

  18. Remote Acquisition Amplifier For 50-Ohm Cable

    NASA Technical Reports Server (NTRS)

    Amador, Jose J.

    1995-01-01

    Buffer-amplifier unit designed to drive 50-Ohm cables up to 100 ft. (30 m) long, compensating for attenuation in cables and enabling remote operation of oscilloscopes. Variable resistor provides for adjustment of gain of amplifier, such that overall gain from input terminals of amplifier to output end of cable set to unity.

  19. STELLAR BINARY COMPANIONS TO SUPERNOVA PROGENITORS

    SciTech Connect

    Kochanek, Christopher S.

    2009-12-20

    For typical models of binary statistics, 50%-80% of core-collapse supernova (ccSN) progenitors are members of a stellar binary at the time of the explosion. Independent of any consequences of mass transfer, this has observational consequences that can be used to study the binary properties of massive stars. In particular, the secondary companion to the progenitor of a Type Ib/c SN is frequently (approx50%) the more optically luminous star since the high effective temperatures of the stripped progenitors make it relatively easy for a lower luminosity, cooler secondary to emit more optical light. Secondaries to the lower mass progenitors of Type II SN will frequently produce excess blue emission relative to the spectral energy distribution of the red primary. Available data constrain the models weakly. Any detected secondaries also provide an independent lower bound on the progenitor mass and, for historical SN, show that it was not a Type Ia event. Bright ccSN secondaries have an unambiguous, post-explosion observational signature-strong, blueshifted, relatively broad absorption lines created by the developing SN remnant (SNR). These can be used to locate historical SN with bright secondaries, confirm that a source is a secondary, and, potentially, measure abundances of ccSN ejecta. Luminous, hot secondaries will re-ionize the SNR on timescales of 100-1000 yr that are faster than re-ionization by the reverse shock, creating peculiar H II regions due to the high metallicity and velocities of the ejecta.

  20. Circulating and tissue resident endothelial progenitor cells.

    PubMed

    Basile, David P; Yoder, Mervin C

    2014-01-01

    Progenitor cells for the endothelial lineage have been widely investigated for more than a decade, but continue to be controversial since no unique identifying marker has yet been identified. This review will begin with a discussion of the basic tenets originally proposed for proof that a cell displays properties of an endothelial progenitor cell. We then provide an overview of the methods for putative endothelial progenitor cell derivation, expansion, and enumeration. This discussion includes consideration of cells that are present in the circulation as well as cells resident in the vascular endothelial intima. Finally, we provide some suggested changes in nomenclature that would greatly clarify and demystify the cellular elements involved in vascular repair.

  1. A synthetic niche for nephron progenitor cells.

    PubMed

    Brown, Aaron C; Muthukrishnan, Sree Deepthi; Oxburgh, Leif

    2015-07-27

    FGF, BMP, and WNT balance embryonic nephron progenitor cell (NPC) renewal and differentiation. By modulating these pathways, we have created an in vitro niche in which NPCs from embryonic kidneys or derived from human embryonic stem cells can be propagated. NPC cultures expanded up to one billion-fold in this environment can be induced to form tubules expressing nephron differentiation markers. Single-cell culture reveals phenotypic variability within the early CITED1-expressing NPC compartment, indicating that it is a mixture of cells with varying progenitor potential. Furthermore, we find that the developmental age of NPCs does not correlate with propagation capacity, indicating that cessation of nephrogenesis is related to factors other than an intrinsic clock. This in vitro nephron progenitor niche will have important applications for expansion of cells for engraftment and will facilitate investigation of mechanisms that determine the balance between renewal and differentiation in these cells. PMID:26190145

  2. Exploring the Progenitors of Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Burke-Spolaor, Sarah; Kramer, Michael; Bhat, Ramesh; Kulkarni, S. R.; Keller, Stefan; Champion, David; Flynn, Chris; Kasliwal, Mansi

    2014-10-01

    Fast Radio Bursts (FRBs) are millisecond bursts that are broadly evidenced to arise from extragalactic, but yet unknown, progenitors. They have presented a true mystery in that so far no progenitor theory can adequately account for their observed properties. We request observations that will glean basic information on FRB progenitors. Our observations will execute a specific test of whether FRBs originate in nearby galaxies. We have also designed our target field and time request to enable a thorough exploration of optical counterparts before, during, and after any detected FRB episode. Additionally, with a number depending on the typical distance to FRBs, our observations will raise the running list of total FRB discoveries by 10-60%.

  3. Endothelial progenitor cells in cardiovascular diseases.

    PubMed

    Lee, Poay Sian Sabrina; Poh, Kian Keong

    2014-07-26

    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 vasculogenesis. There are studies which report correlations between circulating EPCs and cardiovascular risk factors. 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 cardiovascular pharmacotherapies and endothelial progenitor cells. We also discuss how EPCs can be used directly and indirectly as a therapeutic agent. Finally, we evaluate the challenges facing EPC research and how these may be overcome.

  4. Progenitor cells in the adult pancreas.

    PubMed

    Holland, Andrew M; Góñez, L Jorge; Harrison, Leonard C

    2004-01-01

    The beta-cell mass in the adult pancreas possesses the ability to undergo limited regeneration following injury. Identifying the progenitor cells involved in this process and understanding the mechanisms leading to their maturation will open new avenues for the treatment of type 1 diabetes. However, despite steady advances in determining the molecular basis of early pancreatic development, the identification of pancreatic stem cells or beta-cell progenitors and the molecular mechanisms underlying beta-cell regeneration remain unclear. Recent advances in the directed differentiation of embryonic and adult stem cells has heightened interest in the possible application of stem cell therapy in the treatment of type 1 diabetes. Drawing on the expanding knowledge of pancreas development, beta-cell regeneration and stem cell research, this review focuses on progenitor cells in the adult pancreas as a potential source of beta-cells. PMID:14737742

  5. Log amplifier with pole-zero compensation

    DOEpatents

    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.

  6. HIGH AVERAGE POWER OPTICAL FEL AMPLIFIERS.

    SciTech Connect

    BEN-ZVI, ILAN, DAYRAN, D.; LITVINENKO, V.

    2005-08-21

    Historically, the first demonstration of the optical FEL was in an amplifier configuration at Stanford University [l]. There were other notable instances of amplifying a seed laser, such as the LLNL PALADIN amplifier [2] and the BNL ATF High-Gain Harmonic Generation FEL [3]. However, for the most part FELs are operated as oscillators or self amplified spontaneous emission devices. Yet, in wavelength regimes where a conventional laser seed can be used, the FEL can be used as an amplifier. One promising application is for very high average power generation, for instance FEL's with average power of 100 kW or more. The high electron beam power, high brightness and high efficiency that can be achieved with photoinjectors and superconducting Energy Recovery Linacs (ERL) combine well with the high-gain FEL amplifier to produce unprecedented average power FELs. This combination has a number of advantages. In particular, we show that for a given FEL power, an FEL amplifier can introduce lower energy spread in the beam as compared to a traditional oscillator. This properly gives the ERL based FEL amplifier a great wall-plug to optical power efficiency advantage. The optics for an amplifier is simple and compact. In addition to the general features of the high average power FEL amplifier, we will look at a 100 kW class FEL amplifier is being designed to operate on the 0.5 ampere Energy Recovery Linac which is under construction at Brookhaven National Laboratory's Collider-Accelerator Department.

  7. High temperature charge amplifier for geothermal applications

    DOEpatents

    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.

  8. ULTRA-STABILIZED D. C. AMPLIFIER

    DOEpatents

    Hartwig, E.C.; Kuenning, R.W.; Acker, R.C.

    1959-02-17

    An improved circuit is described for stabilizing the drift and minimizing the noise and hum level of d-c amplifiers so that the output voltage will be zero when the input is zero. In its detailed aspects, the disclosed circuit incorporates a d-c amplifier having a signal input, a second input, and an output circuit coupled back to the first input of the amplifier through inverse feedback means. An electronically driven chopper having a pair of fixed contacts and a moveable contact alternately connects the two inputs of a difference amplifier to the signal input. The A. E. error signal produced in the difference amplifier is amplified, rectified, and applied to the second input of the amplifier as the d-c stabilizing voltage.

  9. Nondegenerate optical parametric chirped pulse amplifier

    DOEpatents

    Jovanovic, Igor; Ebbers, Christopher A.

    2005-03-22

    A system provides an input pump pulse and a signal pulse. A first dichroic beamsplitter is highly reflective for the input signal pulse and highly transmissive for the input pump pulse. A first optical parametric amplifier nonlinear crystal transfers part of the energy from the input pump pulse to the input signal pulse resulting in a first amplified signal pulse and a first depleted pump pulse. A second dichroic beamsplitter is highly reflective for the first amplified signal pulse and highly transmissive for the first depleted pump pulse. A second optical parametric amplifier nonlinear crystal transfers part of the energy from the first depleted pump pulse to the first amplified signal pulse resulting in a second amplified signal pulse and a second depleted pump pulse. A third dichroic beamsplitter receives the second amplified signal pulse and the second depleted pump pulse. The second depleted pump pulse is discarded.

  10. Resident mesenchymal progenitors of articular cartilage

    PubMed Central

    Candela, Maria Elena; Yasuhara, Rika; Iwamoto, Masahiro; Enomoto-Iwamoto, Motomi

    2015-01-01

    Articular cartilage has poor capacity of self-renewal and repair. Insufficient number and activity of resident mesenchymal (connective tissue) progenitors is likely one of the underlying reasons. Chondroprogenitors reside not only in the superficial zone of articular cartilage but also in other zones of articular cartilage and in the neighboring tissues, including perichondrium (groove of Ranvier), synovium and fat pad. These cells may respond to injury and contribute to articular cartilage healing. In addition, marrow stromal cells can migrate through subchondral bone when articular cartilage is damaged. We should develop drugs and methods that correctly stimulate resident progenitors for improvement of repair and inhibition of degenerative changes in articular cartilage. PMID:25179676

  11. Resident mesenchymal progenitors of articular cartilage.

    PubMed

    Candela, Maria Elena; Yasuhara, Rika; Iwamoto, Masahiro; Enomoto-Iwamoto, Motomi

    2014-10-01

    Articular cartilage has poor capacity of self-renewal and repair. Insufficient number and activity of resident mesenchymal (connective tissue) progenitors is likely one of the underlying reasons. Chondroprogenitors reside not only in the superficial zone of articular cartilage but also in other zones of articular cartilage and in the neighboring tissues, including perichondrium (groove of Ranvier), synovium and fat pad. These cells may respond to injury and contribute to articular cartilage healing. In addition, marrow stromal cells can migrate through subchondral bone when articular cartilage is damaged. We should develop drugs and methods that correctly stimulate resident progenitors for improvement of repair and inhibition of degenerative changes in articular cartilage. PMID:25179676

  12. Endothelial progenitor cells--an evolving story.

    PubMed

    Pearson, Jeremy D

    2010-05-01

    The first description of endothelial progenitor cells (EPC) in 1997 led rapidly to substantial changes in our understanding of angiogenesis, and within 5 years to the first clinical studies in humans using bone marrow derived EPC to enhance coronary neovascularisation and cardiac function after myocardial ischemia. However, to improve the success of this therapy a clearer understanding of the biology of EPC is needed. This article summarises recent data indicating that most EPC are not, in fact, endothelial progenitors but can be better described as angiogenic monocytes, and explores the implications this has for their future therapeutic use.

  13. Pigment Cell Progenitors in Zebrafish Remain Multipotent through Metamorphosis.

    PubMed

    Singh, Ajeet Pratap; Dinwiddie, April; Mahalwar, Prateek; Schach, Ursula; Linker, Claudia; Irion, Uwe; Nüsslein-Volhard, Christiane

    2016-08-01

    The neural crest is a transient, multipotent embryonic cell population in vertebrates giving rise to diverse cell types in adults via intermediate progenitors. The in vivo cell-fate potential and lineage segregation of these postembryonic progenitors is poorly understood, and it is unknown if and when the progenitors become fate restricted. We investigate the fate restriction in the neural crest-derived stem cells and intermediate progenitors in zebrafish, which give rise to three distinct adult pigment cell types: melanophores, iridophores, and xanthophores. By inducing clones in sox10-expressing cells, we trace and quantitatively compare the pigment cell progenitors at four stages, from embryogenesis to metamorphosis. At all stages, a large fraction of the progenitors are multipotent. These multipotent progenitors have a high proliferation ability, which diminishes with fate restriction. We suggest that multipotency of the nerve-associated progenitors lasting into metamorphosis may have facilitated the evolution of adult-specific traits in vertebrates. PMID:27453500

  14. High temperature current mirror amplifier

    DOEpatents

    Patterson, R.B. III.

    1984-05-22

    Disclosed is a high temperature current mirror amplifier having biasing means in the transdiode connection of the input transistor for producing a voltage to maintain the base-collector junction reversed-biased and a current means for maintaining a current through the biasing means at high temperatures so that the base-collector junction of the input transistor remained reversed-biased. For accuracy, a second current mirror is provided with a biasing means and current means on the input leg. 2 figs.

  15. Charge amplifier with bias compensation

    DOEpatents

    Johnson, Gary W.

    2002-01-01

    An ion beam uniformity monitor for very low beam currents using a high-sensitivity charge amplifier with bias compensation. The ion beam monitor is used to assess the uniformity of a raster-scanned ion beam, such as used in an ion implanter, and utilizes four Faraday cups placed in the geometric corners of the target area. Current from each cup is integrated with respect to time, thus measuring accumulated dose, or charge, in Coulombs. By comparing the dose at each corner, a qualitative assessment of ion beam uniformity is made possible. With knowledge of the relative area of the Faraday cups, the ion flux and areal dose can also be obtained.

  16. High power RF solid state power amplifier system

    NASA Technical Reports Server (NTRS)

    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.

  17. Pax6a and Pax6b are required at different points in neuronal progenitor cell proliferation during zebrafish photoreceptor regeneration.

    PubMed

    Thummel, Ryan; Enright, Jennifer M; Kassen, Sean C; Montgomery, Jacob E; Bailey, Travis J; Hyde, David R

    2010-05-01

    The light-damaged zebrafish retina results in the death of photoreceptor cells and the subsequent regeneration of the missing rod and cone cells. Photoreceptor regeneration initiates with asymmetric Müller glial cell division to produce neuronal progenitor cells, which amplify, migrate to the outer nuclear layer (ONL), and differentiate into both classes of photoreceptor cells. In this study, we examined the role of the Pax6 protein in regeneration. In zebrafish, there are two Pax6 proteins, one encoded by the pax6a gene and the other encoded by the pax6b gene. We intravitreally injected and electroporated morpholinos that were complementary to either the pax6a or pax6b mRNA to knockdown the translation of the corresponding protein. Loss of Pax6b expression did not affect Müller glial cell division, but blocked the subsequent first cell division of the neuronal progenitors. In contrast, the paralogous Pax6a protein was required for later neuronal progenitor cell divisions, which maximized the number of neuronal progenitors. Without neuronal progenitor cell amplification, proliferation of resident ONL rod precursor cells, which can only regenerate rods, increased inversely proportional to the number of INL neuronal progenitor cells. This confirmed that Müller glial-derived neuronal progenitor cells are necessary to regenerate cones and that distinct mechanisms selectively regenerate rod and cone photoreceptors. This work also defines distinct roles for Pax6a and Pax6b in regulating neuronal progenitor cell proliferation in the adult zebrafish retina and increases our understanding of the molecular pathways required for photoreceptor cell regeneration. PMID:20152834

  18. Proteoglycan synthesis by hematopoietic progenitor cells

    SciTech Connect

    Minguell, J.J.; Tavassoli, M. )

    1989-05-15

    The synthesis of proteoglycans (PG) by hematopoietic stromal cells has been reported. But PG synthesis by hematopoietic progenitor cells has not been explored. We have studied synthesis, cellular distribution, and molecular characteristics of PG by a cloned interleukin-3 (IL-3)-dependent hematopoietic progenitor cell line, FDCP-1, which is cloned from murine long-term marrow cultures. Under appropriate conditions the cell can differentiate into granulocytes and macrophages, and therefore, can be considered CFU-GM equivalent. The pattern of PG synthesis was studied by 35SO4 labeling. FDCP-1 cells actively synthesize PG, which are distributed in the intracellular, membrane-associated (MP), and extracellular pools. After purification of the 35S-labeled material by ion-exchange and gel filtration techniques, a single chondroitin sulfate-PG (CIS-PG) was observed to be present in the three studied pools. By Sepharose CL-4B chromatography, this PG has a Kav of 0.47, which after alkaline treatment is shifted to a Kav of 0.67. This indicates the proteoglycan nature of the 35SO4-labeled material. The MP CIS-PG is not stable. It is released to the culture medium where it is subsequently processed. However, in the presence of hematopoietic stromal cells D2X, the stability of MP proteoglycan of FDCP-1 cells is enhanced, suggesting that the synthesis of PG by progenitor cells and its accumulation in the membrane may have a role in the interaction between progenitor and stromal cells.

  19. SUPERNOVA REMNANT PROGENITOR MASSES IN M31

    SciTech Connect

    Jennings, Zachary G.; Williams, Benjamin F.; Dalcanton, Julianne J.; Gilbert, Karoline M.; Fouesneau, Morgan; Weisz, Daniel R.; Murphy, Jeremiah W.; Dolphin, Andrew E. E-mail: adolphin@raytheon.com

    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

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

    PubMed Central

    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

  1. Isolation of Dendritic Cell Progenitor and Bone Marrow Progenitor Cells from Mouse.

    PubMed

    Onai, Nobuyuki; Ohteki, Toshiaki

    2016-01-01

    Dendritic cells (DCs) comprise two major subsets, conventional DC (cDC) and plasmacytoid DC (pDC) in the steady-state lymphoid organ. These cells have a short half-life and therefore, require continuous generation from hematopoietic stem cells and progenitor cells. Recently, we identified DC-restricted progenitors called common DC progenitors (CDPs) in the bone marrow of mouse. The CDPs can be isolated from mouse bone marrow based on the hematopoietic cytokine receptors, such as Flt3 (Fms-related tyrosine kinase 3) (CD135), c-kit (CD117), M-CSF (macrophage colony-stimulating factor) receptor (CD115), and IL-7 (interleukin-7) receptor-α (CD127). The CDPs comprise of two progenitors, CD115(+) CDPs and CD115(-) CDPs, and give rise to only DC subsets in both in vitro and in vivo. The former CDPs are the main source of cDC, while the later CDPs are the main source of pDC in vivo. Here, we provide a protocol for the isolation of dendritic cell progenitor and bone marrow progenitor cells from mouse. PMID:27142008

  2. Multistaged stokes injected Raman capillary waveguide amplifier

    DOEpatents

    Kurnit, Norman A.

    1980-01-01

    A multistaged Stokes injected Raman capillary waveguide amplifier for providing a high gain Stokes output signal. The amplifier uses a plurality of optically coupled capillary waveguide amplifiers and one or more regenerative amplifiers to increase Stokes gain to a level sufficient for power amplification. Power amplification is provided by a multifocused Raman gain cell or a large diameter capillary waveguide. An external source of CO.sub.2 laser radiation can be injected into each of the capillary waveguide amplifier stages to increase Raman gain. Devices for injecting external sources of CO.sub.2 radiation include: dichroic mirrors, prisms, gratings and Ge Brewster plates. Alternatively, the CO.sub.2 input radiation to the first stage can be coupled and amplified between successive stages.

  3. High-efficiency solid state power amplifier

    NASA Technical Reports Server (NTRS)

    Wallis, Robert E. (Inventor); Cheng, Sheng (Inventor)

    2005-01-01

    A high-efficiency solid state power amplifier (SSPA) for specific use in a spacecraft is provided. The SSPA has a mass of less than 850 g and includes two different X-band power amplifier sections, i.e., a lumped power amplifier with a single 11-W output and a distributed power amplifier with eight 2.75-W outputs. These two amplifier sections provide output power that is scalable from 11 to 15 watts without major design changes. Five different hybrid microcircuits, including high-efficiency Heterostructure Field Effect Transistor (HFET) amplifiers and Monolithic Microwave Integrated Circuit (MMIC) phase shifters have been developed for use within the SSPA. A highly efficient packaging approach enables the integration of a large number of hybrid circuits into the SSPA.

  4. Optical latches using optical amplifiers

    NASA Astrophysics Data System (ADS)

    Li, Wenbo; Hu, Hongyu; Dutta, Niloy K.

    2013-05-01

    Optical latches are important for a wide range of applications including communication systems, optical logic systems, optical random access memory (RAM) and encryption. All optical logic operations using quantum dot (QD) based semiconductor optical amplifier (SOA) and Mach-Zehnder interferometer (MZI) have been studied. The building block of an optical latch such as NAND gate has been fabricated and their operation experimentally demonstrated at ~ 80 GHz. A rate equation model has been developed for the QD-SOA-MZI and it has been used to analyze the Boolean logic operation. The model has been used to analyze the Set-Reset (S-R) latch and the D-Flip-Flop (DFF) devices. The DFF is the basic device for building larger logic circuits. The results show that the latches would work to speeds of ~ 250 Gb/s.

  5. Transverse pumped laser amplifier architecture

    SciTech Connect

    Bayramian, Andrew James; Manes, Kenneth R.; Deri, Robert; Erlandson, Alvin; Caird, John; Spaeth, Mary L.

    2015-05-19

    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.

  6. Locoregional MYCN-amplified neuroblastoma.

    PubMed

    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.

  7. Transverse pumped laser amplifier architecture

    DOEpatents

    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.

  8. Hydraulically amplified PZT mems actuator

    DOEpatents

    Miles, Robin R.

    2004-11-02

    A hydraulically amplified microelectromechanical systems actuator. A piece of piezoelectric material or stacked piezo bimorph is bonded or deposited as a thin film. The piece is operatively connected to a primary membrane. A reservoir is operatively connected to the primary membrane. The reservoir contains a fluid. A membrane is operatively connected to the reservoir. In operation, energizing the piezoelectric material causing the piezoelectric material to bow. Bowing of the piezoelectric material causes movement of the primary membrane. Movement of the primary membrane results in a force in being transmitted to the liquid in the reservoir. The force in the liquid causes movement of the membrane. Movement of the membrane results in an operating actuator.

  9. A dc amplifier for nuclear particle measurement

    NASA Technical Reports Server (NTRS)

    Macnee, A. B.; Masnari, N. A.

    1978-01-01

    A monolithic preamplifier-postamplifier combination has been developed for use with solid state particle detectors. The direct coupled amplifiers employ interdigitated n-channel JFET's, diodes, and diffused resistors. The circuits developed demonstrate the feasibility of matching the performance of existing discrete component designs. The fabrication procedures for the monolithic amplifier fabrication are presented and the results of measurements on a limited number of sample amplifiers are given.

  10. Simulation of a regenerative MW FEL amplifier

    SciTech Connect

    Nguyen, R.T.; Colson, W.B.; Wong, R.K.; Sheffield, R.L.

    1997-08-01

    Both oscillator and regenerative amplifier configurations are being studied to optimize the design of a MW class FEL. The regenerative amplifier uses a longer undulator and relies on higher extraction efficiency to achieve high average power, whereas the oscillator is a more compact overall design requiring the transport of the high energy electron beam around bends for energy recovery. Using parameters extrapolated from the 1 kW LANL regenerative amplifier, simulations study the feasibility of achieving 1 MW average power.

  11. Log amplifier with pole-zero compensation

    DOEpatents

    Brookshier, W.

    1985-02-08

    A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifer circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedstock 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 is offset by a compensating break point or zero.

  12. Class E/F switching power amplifiers

    NASA Technical Reports Server (NTRS)

    Hajimiri, Seyed-Ali (Inventor); Aoki, Ichiro (Inventor); Rutledge, David B. (Inventor); Kee, Scott David (Inventor)

    2004-01-01

    The present invention discloses a new family of switching amplifier classes called class E/F amplifiers. These amplifiers are generally characterized by their use of the zero-voltage-switching (ZVS) phase correction technique to eliminate of the loss normally associated with the inherent capacitance of the switching device as utilized in class-E amplifiers, together with a load network for improved voltage and current wave-shaping by presenting class-F.sup.-1 impedances at selected overtones and class-E impedances at the remaining overtones. The present invention discloses a several topologies and specific circuit implementations for achieving such performance.

  13. Ping-pong auto-zero amplifier with glitch reduction

    DOEpatents

    Larson, Mark R.

    2008-01-22

    A ping-pong amplifier with reduced glitching is described. The ping-pong amplifier includes a nulling amplifier coupled to a switching network. The switching network is used to auto-zero a ping amplifier within a ping-pong amplifier. The nulling amplifier drives the output of a ping amplifier to a proper output voltage level during auto-zeroing of the ping amplifier. By being at a proper output voltage level, glitches associated with transitioning between a ping amplifier and a pong amplifier are reduced or eliminated.

  14. Galactic constraints on supernova progenitor models

    NASA Astrophysics Data System (ADS)

    Acharova, I. A.; Gibson, B. K.; Mishurov, Yu. N.; Kovtyukh, V. V.

    2013-09-01

    Aims: To estimate the mean masses of oxygen and iron ejected per each type of supernovae (SNe) event from observations of the elemental abundance patterns in the Galactic disk and constrain the relevant SNe progenitor models. Methods: 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. This framework has been shown to recover the non-linear behaviour in radial gradients, the mean masses of oxygen and iron ejected during SNe explosions to be estimated, and constraints to be placed on SNe progenitor models. Results: (i) The mean mass of oxygen ejected per core-collapse SNe (CC SNe) event (which are concentrated within spiral arms) is ~0.27 M⊙; (ii) the mean mass of iron ejected by tardy Type Ia SNe (SNeIa, whose progenitors are older/longer-lived stars with ages ≳100 Myr and up to several Gyr, which do not concentrate within spiral arms) is ~0.58 M⊙; (iii) the upper mass of iron ejected by prompt SNeIa (SNe whose progenitors are younger/shorter-lived stars with ages ≲100 Myr, which are concentrated within spiral arms) is ≤0.23 M⊙ per event; (iv) the corresponding mean mass of iron produced by CC SNe is ≤0.04 M⊙ per event; (v) short-lived SNe (core-collapse or prompt SNeIa) supply ~85% of the Galactic disk's iron. Conclusions: The inferred low mean mass of oxygen ejected per CC SNe event implies a low upper mass limit for the corresponding progenitors of ~23 M⊙, otherwise the Galactic disk would be overabundant in oxygen. This inference is the consequence of the non-linear dependence between the upper limit of the progenitor initial mass and the mean mass of oxygen ejected per CC SNe explosion. The low mean mass of iron ejected by prompt SNeIa, relative to the mass produced by tardy SNeIa (~2.5 times lower), prejudices the idea that both sub-populations of SNeIa have the same physical nature. We

  15. Sall1 in renal stromal progenitors non-cell autonomously restricts the excessive expansion of nephron progenitors.

    PubMed

    Ohmori, Tomoko; Tanigawa, Shunsuke; Kaku, Yusuke; Fujimura, Sayoko; Nishinakamura, Ryuichi

    2015-10-29

    The mammalian kidney develops from reciprocal interactions between the metanephric mesenchyme and ureteric bud, the former of which contains nephron progenitors. The third lineage, the stroma, fills up the interstitial space and is derived from distinct progenitors that express the transcription factor Foxd1. We showed previously that deletion of the nuclear factor Sall1 in nephron progenitors leads to their depletion in mice. However, Sall1 is expressed not only in nephron progenitors but also in stromal progenitors. Here we report that specific Sall1 deletion in stromal progenitors leads to aberrant expansion of nephron progenitors, which is in sharp contrast with a nephron progenitor-specific deletion. The mutant mice also exhibited cystic kidneys after birth and died before adulthood. We found that Decorin, which inhibits Bmp-mediated nephron differentiation, was upregulated in the mutant stroma. In contrast, the expression of Fat4, which restricts nephron progenitor expansion, was reduced mildly. Furthermore, the Sall1 protein binds to many stroma-related gene loci, including Decorin and Fat4. Thus, the expression of Sall1 in stromal progenitors restricts the excessive expansion of nephron progenitors in a non-cell autonomous manner, and Sall1-mediated regulation of Decorin and Fat4 might at least partially underlie the pathogenesis.

  16. Hematopoietic progenitor migration to the adult thymus

    PubMed Central

    Zlotoff, Daniel A.; Bhandoola, Avinash

    2010-01-01

    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 their circulation in the bloodstream, and concludes with their settling in the thymus. This review will discuss each of these steps as they occur in the unirradiated and post-irradiation scenarios, focusing on the molecular mechanisms of regulation. Improved knowledge about these early steps in T cell generation may accelerate the development of new therapeutic options in patients with impaired T cell number or function. PMID:21251013

  17. Noninvasive Imaging of Administered Progenitor Cells

    SciTech Connect

    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

  18. Interneuron Progenitor Transplantation to Treat CNS Dysfunction

    PubMed Central

    Chohan, Muhammad O.; Moore, Holly

    2016-01-01

    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. PMID:27582692

  19. Progenitor cells for ocular surface regenerative therapy.

    PubMed

    Casaroli-Marano, Ricardo P; Nieto-Nicolau, Nuria; Martínez-Conesa, Eva M

    2013-01-01

    The integrity and normal function of the corneal epithelium are essential for maintaining the cornea's transparency and vision. The existence of a cell population with progenitor characteristics in the limbus maintains a dynamic of constant epithelial repair and renewal. Currently, cell-based therapies for bio-replacement, such as cultured limbal epithelial transplantation and cultured oral mucosal epithelial transplantation, present very encouraging clinical results for treating limbal stem cell deficiencies. Another emerging therapeutic strategy consists of obtaining and implementing human progenitor cells of different origins using tissue engineering methods. The development of cell-based therapies using stem cells, such as human adult mesenchymal stromal cells, represents a significant breakthrough in the treatment of certain eye diseases and also offers a more rational, less invasive and more physiological approach to ocular surface regeneration. PMID:23257987

  20. POPULATION SYNTHESIS AND GAMMA RAY BURST PROGENITORS

    SciTech Connect

    C. L. FREYER

    2000-12-11

    Population synthesis studies of binaries are always limited by a myriad of uncertainties from the poorly understood effects of binary mass transfer and common envelope evolution to the many uncertainties that still remain in stellar evolution. But the importance of these uncertainties depends both upon the objects being studied and the questions asked about these objects. Here I review the most critical uncertainties in the population synthesis of gamma-ray burst progenitors. With a better understanding of these uncertainties, binary population synthesis can become a powerful tool in understanding, and constraining, gamma-ray burst models. In turn, as gamma-ray bursts become more important as cosmological probes, binary population synthesis of gamma-ray burst progenitors becomes an important tool in cosmology.

  1. Progenitor cells for ocular surface regenerative therapy.

    PubMed

    Casaroli-Marano, Ricardo P; Nieto-Nicolau, Nuria; Martínez-Conesa, Eva M

    2013-01-01

    The integrity and normal function of the corneal epithelium are essential for maintaining the cornea's transparency and vision. The existence of a cell population with progenitor characteristics in the limbus maintains a dynamic of constant epithelial repair and renewal. Currently, cell-based therapies for bio-replacement, such as cultured limbal epithelial transplantation and cultured oral mucosal epithelial transplantation, present very encouraging clinical results for treating limbal stem cell deficiencies. Another emerging therapeutic strategy consists of obtaining and implementing human progenitor cells of different origins using tissue engineering methods. The development of cell-based therapies using stem cells, such as human adult mesenchymal stromal cells, represents a significant breakthrough in the treatment of certain eye diseases and also offers a more rational, less invasive and more physiological approach to ocular surface regeneration.

  2. Human progenitor cells for bone engineering applications.

    PubMed

    de Peppo, G M; Thomsen, P; Karlsson, C; Strehl, R; Lindahl, A; Hyllner, J

    2013-06-01

    In this report, the authors review the human skeleton and the increasing burden of bone deficiencies, the limitations encountered with the current treatments and the opportunities provided by the emerging field of cell-based bone engineering. Special emphasis is placed on different sources of human progenitor cells, as well as their pros and cons in relation to their utilization for the large-scale construction of functional bone-engineered substitutes for clinical applications. It is concluded that, human pluripotent stem cells represent a valuable source for the derivation of progenitor cells, which combine the advantages of both embryonic and adult stem cells, and indeed display high potential for the construction of functional substitutes for bone replacement therapies.

  3. The endocannabinoid system drives neural progenitor proliferation.

    PubMed

    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.

  4. Noise figure of hybrid optical parametric amplifiers.

    PubMed

    Marhic, Michel E

    2012-12-17

    Following a fiber optical parametric amplifier, used as a wavelength converter or in the phase-sensitive mode, by a phase-insensitive amplifier (PIA) can significantly reduce four-wave mixing between signals in broadband systems. We derive the quantum mechanical noise figures (NF) for these two hybrid configurations, and show that adding the PIA only leads to a moderate increase in NF.

  5. Bridge/amplifier configuration for switched arrays

    NASA Technical Reports Server (NTRS)

    Bohning, O. D.

    1977-01-01

    Bridge network connected to differential amplifier and used with bubble-domain memories draws no power during standby and can be arrayed with other bridge amplifiers of like design. Two-node arrangement greatly simplifies conventional configurations where more than two nodes are involved.

  6. Method for reducing snap in magnetic amplifiers

    NASA Technical Reports Server (NTRS)

    Fischer, R. L. E.; Word, J. L.

    1968-01-01

    Method of reducing snap in magnetic amplifiers uses a degenerative feedback circuit consisting of a resistor and a separate winding on a magnetic core. The feedback circuit extends amplifier range by allowing it to be used at lower values of output current.

  7. Field effect transistors improve buffer amplifier

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Unity gain buffer amplifier with a Field Effect Transistor /FET/ differential input stage responds much faster than bipolar transistors when operated at low current levels. The circuit uses a dual FET in a unity gain buffer amplifier having extremely high input impedance, low bias current requirements, and wide bandwidth.

  8. Multipotent Hematopoietic Progenitors Divide Asymmetrically to Create Progenitors of the Lymphomyeloid and Erythromyeloid Lineages

    PubMed Central

    Görgens, André; Ludwig, Anna-Kristin; Möllmann, Michael; Krawczyk, Adalbert; Dürig, Jan; Hanenberg, Helmut; Horn, Peter A.; Giebel, Bernd

    2014-01-01

    Summary Hematopoietic stem and progenitor cells (HSPCs) can self-renew and create committed progenitors, a process supposed to involve asymmetric cell divisions (ACDs). Previously, we had linked the kinetics of CD133 expression with ACDs but failed to detect asymmetric segregation of classical CD133 epitopes on fixed, mitotic HSPCs. Now, by using a novel anti-CD133 antibody (HC7), we confirmed the occurrence of asymmetric CD133 segregation on paraformaldehyde-fixed and living HSPCs. After showing that HC7 binding does not recognizably affect biological features of human HSPCs, we studied ACDs in different HSPC subtypes and determined the developmental potential of arising daughter cells at the single-cell level. Approximately 70% of the HSPCs of the multipotent progenitor (MPP) fraction studied performed ACDs, and about 25% generated lymphoid-primed multipotent progenitor (LMPP) as wells as erythromyeloid progenitor (EMP) daughter cells. Since MPPs hardly created daughter cells maintaining MPP characteristics, our data suggest that under conventional culture conditions, ACDs are lineage instructive rather than self-renewing. PMID:25448068

  9. Design and performance of the beamlet amplifiers

    SciTech Connect

    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.

  10. Amplified OTDR Systems for Multipoint Corrosion Monitoring

    PubMed Central

    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. PMID:22737017

  11. Dual-range linearized transimpedance amplifier system

    DOEpatents

    Wessendorf, Kurt O.

    2010-11-02

    A transimpedance amplifier system is disclosed which simultaneously generates a low-gain output signal and a high-gain output signal from an input current signal using a single transimpedance amplifier having two different feedback loops with different amplification factors to generate two different output voltage signals. One of the feedback loops includes a resistor, and the other feedback loop includes another resistor in series with one or more diodes. The transimpedance amplifier system includes a signal linearizer to linearize one or both of the low- and high-gain output signals by scaling and adding the two output voltage signals from the transimpedance amplifier. The signal linearizer can be formed either as an analog device using one or two summing amplifiers, or alternately can be formed as a digital device using two analog-to-digital converters and a digital signal processor (e.g. a microprocessor or a computer).

  12. Post pulse shutter for laser amplifier

    DOEpatents

    Bradley, L.P.; Carder, B.M.; Gagnon, W.L.

    1981-03-17

    Disclosed are an apparatus and method for quickly closing off the return path for an amplified laser pulse at the output of an amplifier so as to prevent damage to amplifiers and other optical components appearing earlier in the chain by the return of an amplified pulse. The apparatus consists of a fast retropulse or post pulse shutter to suppress target reflection and/or beam return. This is accomplished by either quickly placing a solid across the light transmitting aperture of a component in the chain, such as a spatial filter pinhole, or generating and directing a plasma with sufficiently high density across the aperture, so as to, in effect, close the aperture to the returning amplified energy pulse. 13 figs.

  13. Post pulse shutter for laser amplifier

    DOEpatents

    Bradley, Laird P. [Livermore, CA; Carder, Bruce M. [Antioch, CA; Gagnon, William L. [Berkeley, CA

    1981-03-17

    Apparatus and method for quickly closing off the return path for an amplified laser pulse at the output of an amplifier so as to prevent damage to amplifiers and other optical components appearing earlier in the chain by the return of an amplified pulse. The apparatus consists of a fast retropulse or post pulse shutter to suppress target reflection and/or beam return. This is accomplished by either quickly placing a solid across the light transmitting aperture of a component in the chain, such as a spatial filter pinhole, or generating and directing a plasma with sufficiently high density across the aperture, so as to, in effect, close the aperture to the returning amplified energy pulse.

  14. EVOLUTION OF PROGENITORS FOR ELECTRON CAPTURE SUPERNOVAE

    SciTech Connect

    Takahashi, Koh; Umeda, Hideyuki; Yoshida, Takashi E-mail: umeda@astron.s.u-tokyo.ac.jp

    2013-07-01

    We provide progenitor models for electron capture supernovae (ECSNe) with detailed evolutionary calculation. We include minor electron capture nuclei using a large nuclear reaction network with updated reaction rates. For electron capture, the Coulomb correction of rates is treated and the contribution from neutron-rich isotopes is taken into account in each nuclear statistical equilibrium (NSE) composition. We calculate the evolution of the most massive super asymptotic giant branch stars and show that these stars undergo off-center carbon burning and form ONe cores at the center. These cores become heavier up to the critical mass of 1.367 M{sub Sun} and keep contracting even after the initiation of O+Ne deflagration. Inclusion of minor electron capture nuclei causes convective URCA cooling during the contraction phase, but the effect on the progenitor evolution is small. On the other hand, electron capture by neutron-rich isotopes in the NSE region has a more significant effect. We discuss the uniqueness of the critical core mass for ECSNe and the effect of wind mass loss on the plausibility of our models for ECSN progenitors.

  15. Endothelial progenitor cells in hematologic malignancies

    PubMed Central

    Saulle, Ernestina; Castelli, Germana; Pelosi, Elvira

    2016-01-01

    Studies carried out in the last years have improved the understanding of the cellular and molecular mechanisms controlling angiogenesis during adult life in normal and pathological conditions. Some of these studies have led to the identification of some progenitor cells that sustain angiogenesis through indirect, paracrine mechanisms (hematopoietic angiogenic cells) and through direct mechanisms, i.e., through their capacity to generate a progeny of phenotypically and functionally competent endothelial cells [endothelial colony forming cells (ECFCs)]. The contribution of these progenitors to angiogenetic processes under physiological and pathological conditions is intensively investigated. Angiogenetic mechanisms are stimulated in various hematological malignancies, including chronic myeloid leukemia (CML), acute myeloid leukemia (AML), myelodysplastic syndromes and multiple myeloma, resulting in an increased angiogenesis that contributes to disease progression. In some of these conditions there is preliminary evidence that some endothelial cells could derive from the malignant clone, thus leading to the speculation that the leukemic cell derives from the malignant transformation of a hemangioblastic progenitor, i.e., of a cell capable of differentiation to the hematopoietic and to the endothelial cell lineages. Our understanding of the mechanisms underlying increased angiogenesis in these malignancies not only contributed to a better knowledge of the mechanisms responsible for tumor progression, but also offered the way for the discovery of new therapeutic targets. PMID:27583252

  16. Endothelial progenitor cells in hematologic malignancies.

    PubMed

    Testa, Ugo; Saulle, Ernestina; Castelli, Germana; Pelosi, Elvira

    2016-01-01

    Studies carried out in the last years have improved the understanding of the cellular and molecular mechanisms controlling angiogenesis during adult life in normal and pathological conditions. Some of these studies have led to the identification of some progenitor cells that sustain angiogenesis through indirect, paracrine mechanisms (hematopoietic angiogenic cells) and through direct mechanisms, i.e., through their capacity to generate a progeny of phenotypically and functionally competent endothelial cells [endothelial colony forming cells (ECFCs)]. The contribution of these progenitors to angiogenetic processes under physiological and pathological conditions is intensively investigated. Angiogenetic mechanisms are stimulated in various hematological malignancies, including chronic myeloid leukemia (CML), acute myeloid leukemia (AML), myelodysplastic syndromes and multiple myeloma, resulting in an increased angiogenesis that contributes to disease progression. In some of these conditions there is preliminary evidence that some endothelial cells could derive from the malignant clone, thus leading to the speculation that the leukemic cell derives from the malignant transformation of a hemangioblastic progenitor, i.e., of a cell capable of differentiation to the hematopoietic and to the endothelial cell lineages. Our understanding of the mechanisms underlying increased angiogenesis in these malignancies not only contributed to a better knowledge of the mechanisms responsible for tumor progression, but also offered the way for the discovery of new therapeutic targets. PMID:27583252

  17. Fiber networks amplify active stress

    NASA Astrophysics Data System (ADS)

    Lenz, Martin; Ronceray, Pierre; Broedersz, Chase

    Large-scale force generation is essential for biological functions such as cell motility, embryonic development, and muscle contraction. In these processes, forces generated at the molecular level by motor proteins are transmitted by disordered fiber networks, resulting in large-scale active stresses. While fiber networks are well characterized macroscopically, this stress generation by microscopic active units is not well understood. I will present a comprehensive theoretical study of force transmission in these networks. I will show that the linear, small-force response of the networks is remarkably simple, as the macroscopic active stress depends only on the geometry of the force-exerting unit. In contrast, as non-linear buckling occurs around these units, local active forces are rectified towards isotropic contraction and strongly amplified. This stress amplification is reinforced by the networks' disordered nature, but saturates for high densities of active units. I will show that our predictions are quantitatively consistent with experiments on reconstituted tissues and actomyosin networks, and that they shed light on the role of the network microstructure in shaping active stresses in cells and tissue.

  18. Multi-pass light amplifier

    NASA Technical Reports Server (NTRS)

    Plaessmann, Henry (Inventor); Grossman, William M. (Inventor)

    1997-01-01

    A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A confocal resonator or White Cell resonator is provided, including two or three curvilinearly shaped mirrors facing each other along a resonator axis and an optical gain medium positioned on the resonator axis between the mirrors (confocal resonator) or adjacent to one of the mirrors (White Cell). In a first embodiment, two mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. The optical gain medium may be solid-state, liquid or gaseous medium and may be pumped longitudinally or transversely. In a second embodiment, first and second mirrors face a third mirror in a White Cell configuration, and the optical gain medium is positioned at or adjacent to one of the mirrors. Defocusing means and optical gain medium cooling means are optionally provided with either embodiment, to controllably defocus the light beam, to cool the optical gain medium and to suppress thermal lensing in the gain medium.

  19. Ultrafast laser and amplifier sources

    NASA Astrophysics Data System (ADS)

    Rundquist, A.; Durfee, C.; Chang, Z.; Taft, G.; Zeek, E.; Backus, S.; Murnane, M. M.; Kapteyn, H. C.; Christov, I.; Stoev, V.

    1997-08-01

    There has been remarkable progress in the development of high peak-power ultrafast lasers in recent years. Lasers capable of generating terawatt peak powers with unprecedented short pulse durations can now be built on a single optical table in a small laboratory. The rapid technological progress has made possible a host of new scientific advances in high-field science, such as the generation of coherent femtosecond X-ray pulses, and the generation of MeV-energy electron beams and high-energy ions. In this paper, we review progress in the development and design of ultrafast high-power lasers based on Ti:sapphire, including the ultrafast laser oscillators that are a very important enabling technology for high-power ultrafast systems, and ultrafast amplified laser systems that generate 20 fs duration pulses with several watts average power at kilohertz repetition-rates. Ultrafast waveform measurements of these pulses demonstrate that such short pulses can be generated with high fidelity. Finally, we discuss applications of ultrafast high-power pulses, including the generation of femtosecond to attosecond X-ray pulses.

  20. Ultrafast disk lasers and amplifiers

    NASA Astrophysics Data System (ADS)

    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.

  1. Progress on diamond amplified photo-cathode

    SciTech Connect

    Wang, E.; Ben-Zvi, I.; Burrill, A.; Kewisch, J.; Chang, X.; Rao, T.; Smedley, J.; Wu, Q.; Muller, E.; Xin, T.

    2011-03-28

    Two years ago, we obtained an emission gain of 40 from the Diamond Amplifier Cathode (DAC) in our test system. In our current systematic study of hydrogenation, the highest gain we registered in emission scanning was 178. We proved that our treatments for improving the diamond amplifiers are reproducible. Upcoming tests planned include testing DAC in a RF cavity. Already, we have designed a system for these tests using our 112 MHz superconducting cavity, wherein we will measure DAC parameters, such as the limit, if any, on emission current density, the bunch charge, and the bunch length. The diamond-amplified photocathode, that promises to support a high average current, low emittance, and a highly stable electron beam with a long lifetime, is under development for an electron source. The diamond, functioning as a secondary emitter amplifies the primary current, with a few KeV energy, that comes from the traditional cathode. Earlier, our group recorded a maximum gain of 40 in the secondary electron emission from a diamond amplifier. In this article, we detail our optimization of the hydrogenation process for a diamond amplifier that resulted in a stable emission gain of 140. We proved that these characteristics are reproducible. We now are designing a system to test the diamond amplifier cathode using an 112MHz SRF gun to measure the limits of the emission current's density, and on the bunch charge and bunch length.

  2. High power Ka band TWT amplifier

    SciTech Connect

    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.

  3. Quasi-optical constrained lens amplifiers

    NASA Astrophysics Data System (ADS)

    Schoenberg, Jon S.

    1995-09-01

    A major goal in the field of quasi-optics is to increase the power available from solid state sources by combining the power of individual devices in free space, as demonstrated with grid oscillators and grid amplifiers. Grid amplifiers and most amplifier arrays require a plane wave feed, provided by a far field source or at the beam waist of a dielectric lens pair. These feed approaches add considerable loss and size, which is usually greater than the quasi-optical amplifier gain. In addition, grid amplifiers require external polarizers for stability, further increasing size and complexity. This thesis describes using constrained lens theory in the design of quasi optical amplifier arrays with a focal point feed, improving the power coupling between the feed and the amplifier for increased gain. Feed and aperture arrays of elements, input/output isolation and stability, amplifier circuitry, delay lines and bias distribution are all contained on a single planar substrate, making monolithic circuit integration possible. Measured results of X band transmission lenses and a low noise receive lens are presented, including absolute power gain up to 13 dB, noise figure as low as 1.7 dB, beam scanning to +/-30 deg, beam forming and beam switching of multiple sources, and multiple level quasi-optical power combining. The design and performance of millimeter wave power combining amplifier arrays is described, including a Ka Band hybrid array with 1 watt output power, and a V Band 36 element monolithic array with a 5 dB on/off ratio.

  4. A Low-Noise Semiconductor Optical Amplifier

    SciTech Connect

    Ratowsky, R.P.; Dijaili, S.; Kallman, J.S.; Feit, M.D.; Walker, J.

    1999-03-23

    Optical amplifiers are essential devices for optical networks, optical systems, and computer communications. These amplifiers compensate for the inevitable optical loss in long-distance propagation (>50 km) or splitting (>10x). Fiber amplifiers such as the erbium-doped fiber amplifier have revolutionized the fiber-optics industry and are enjoying widespread use. Semiconductor optical amplifiers (SOAs) are an alternative technology that complements the fiber amplifiers in cost and performance. One obstacle to the widespread use of SOAs is the severity of the inevitable noise output resulting from amplified spontaneous emission (ASE). Spectral filtering is often used to reduce ASE noise, but this constrains the source spectrally, and improvement is typically limited to about 10 dB. The extra components also add cost and complexity to the final assembly. The goal of this project was to analyze, design, and take significant steps toward the realization of an innovative, low-noise SOA based on the concept of ''distributed spatial filtering'' (DSF). In DSF, we alternate active SOA segments with passive free-space diffraction regions. Since spontaneous emission radiates equally in all directions, the free-space region lengthens the amplifier for a given length of gain region, narrowing the solid angle into which the spontaneous emission is amplified [1,2]. Our innovation is to use spatial filtering in a differential manner across many segments, thereby enhancing the effect when wave-optical effects are included [3]. The structure quickly and effectively strips the ASE into the higher-order modes, quenching the ASE gain relative to the signal.

  5. Diode amplifier of modulated optical beam power

    SciTech Connect

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

    2014-11-30

    Analytical relations are obtained between characteristics of modulated light at the output and input of an optical diode power amplifier operating in the highly saturated gain regime. It is shown that a diode amplifier may act as an amplitude-to-phase modulation converter with a rather large bandwidth (∼10 GHz). The low sensitivity of the output power of the amplifier to the input beam power and its high energy efficiency allow it to be used as a building block of a high-power multielement laser system with coherent summation of a large number of optical beams. (lasers)

  6. Phase noise in RF and microwave amplifiers.

    PubMed

    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

  7. High Efficiency Microwave Power Amplifier (HEMPA) Design

    NASA Technical Reports Server (NTRS)

    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.

  8. Very high gain Nd:YLF amplifiers

    SciTech Connect

    Knights, M.G.; Thomas, M.D.; Chicklis, E.P.; Rines, G.A.; Seka, W.

    1988-05-01

    The authors report on high gain Nd:YLF rod amplifiers in which single-pass, small signal gains of over 1700 have been obtained along with stored energy densitiesgreater than or equal to0.4J/cm/sup 3/. The ability of Nd:YLF amplifiers to support such gains is a result of high parasitic oscillation thresholds, due primarily to the low refractive index of the material. These results suggest that Nd:YLF is an excellent candidate for amplifiers where high specific stored energies and/or very high gains are required.

  9. Achieving and maintaining cleanliness in NIF amplifiers

    SciTech Connect

    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.

  10. Phase-stable, microwave FEL amplifier

    SciTech Connect

    Carlsten, B.E.; Fazio, M.V.; Haynes, W.B.; May, L.; Potter, M.

    1995-07-01

    Free-electron laser (FEL) amplifiers have demonstrated high efficiency and high output power for microwave wavelengths. However, using present technology, microwave FEL amplifiers are not phase stable enough to be suitable for driving linear accelerators, where several much amplifiers need to be phase locked. The growing wave`s phase sensitivity to the beam voltage in the small-signal gain regime is responsible for the largest contribution to this phase instability. We discuss a scheme that reduces the phase sensitivity to the beam voltage by operating off synchronism and matching the phase variation resulting from the desynchronism to the phase variation from the reduced plasma wavenumber as the beam voltage changes.

  11. Progenitor Cells in Proximal Airway Epithelial Development and Regeneration

    PubMed Central

    Lynch, Thomas J.; Engelhardt, John F.

    2015-01-01

    Multiple distinct epithelial domains are found throughout the airway that are distinguishable by location, structure, function, and cell-type composition. Several progenitor cell populations in the proximal airway have been identified to reside in confined microenvironmental niches including the submucosal glands (SMGs), which are embedded in the tracheal connective tissue between the surface epithelium and cartilage, and basal cells that reside within the surface airway epithelium (SAE). Current research suggests that regulatory pathways that coordinate development of the proximal airway and establishment of progenitor cell niches may overlap with pathways that control progenitor cell responses during airway regeneration following injury. SMGs have been shown to harbor epithelial progenitor cells, and this niche is dysregulated in diseases such as cystic fibrosis. However, mechanisms that regulate progenitor cell proliferation and maintenance within this glandular niche are not completely understood. Here we discuss glandular progenitor cells during development and regeneration of the proximal airway and compare properties of glandular progenitors to those of basal cell progenitors in the SAE. Further investigation into glandular progenitor cell control will provide a direction for interrogating therapeutic interventions to correct aberrant conditions affecting the SMGs in diseases such as cystic fibrosis, chronic bronchitis, and asthma. PMID:24818588

  12. Multi-pass light amplifier

    NASA Technical Reports Server (NTRS)

    Plaessmann, Henry (Inventor); Grossman, William M. (Inventor); Olson, Todd E. (Inventor)

    1996-01-01

    A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. A second embodiment uses two curvilinear mirrors and one planar mirror, with a gain medium positioned in the optical path between each curvilinear mirror and the planar mirror. A third embodiment uses two curvilinear mirrors and two planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses a curvilinear mirror and three planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses four planar mirrors and a focusing lens system, with a gain medium positioned between the four mirrors. A fifth embodiment uses first and second planar mirrors, a focusing lens system and a third mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the third mirror. A sixth embodiment uses two planar mirrors and a curvilinear mirror and a fourth mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the fourth mirror. In a seventh embodiment, first and second mirrors face a third

  13. Radmis, a Novel Mitotic Spindle Protein that Functions in Cell Division of Neural Progenitors

    PubMed Central

    Yumoto, Takahito; Nakadate, Kazuhiko; Nakamura, Yuki; Sugitani, Yoshinobu; Sugitani-Yoshida, Reiko; Ueda, Shuichi; Sakakibara, Shin-ichi

    2013-01-01

    Developmental dynamics of neural stem/progenitor cells (NSPCs) are crucial for embryonic and adult neurogenesis, but its regulatory factors are not fully understood. By differential subtractive screening with NSPCs versus their differentiated progenies, we identified the radmis (radial fiber and mitotic spindle)/ckap2l gene, a novel microtubule-associated protein (MAP) enriched in NSPCs. Radmis is a putative substrate for the E3-ubiquitin ligase, anaphase promoting complex/cyclosome (APC/C), and is degraded via the KEN box. Radmis was highly expressed in regions of active neurogenesis throughout life, and its distribution was dynamically regulated during NSPC division. In embryonic and perinatal brains, radmis localized to bipolar mitotic spindles and radial fibers (basal processes) of dividing NSPCs. As central nervous system development proceeded, radmis expression was lost in most brain regions, except for several neurogenic regions. In adult brain, radmis expression persisted in the mitotic spindles of both slowly-dividing stem cells and rapid amplifying progenitors. Overexpression of radmis in vitro induced hyper-stabilization of microtubules, severe defects in mitotic spindle formation, and mitotic arrest. In vivo gain-of-function using in utero electroporation revealed that radmis directed a reduction in NSPC proliferation and a concomitant increase in cell cycle exit, causing a reduction in the Tbr2-positive basal progenitor population and shrinkage of the embryonic subventricular zone. Besides, radmis loss-of-function by shRNAs induced the multipolar mitotic spindle structure, accompanied with the catastrophe of chromosome segregation including the long chromosome bridge between two separating daughter nuclei. These findings uncover the indispensable role of radmis in mitotic spindle formation and cell-cycle progression of NSPCs. PMID:24260314

  14. Bone Marrow Stress Decreases Osteogenic Progenitors.

    PubMed

    Ng, Adeline H; Baht, Gurpreet S; Alman, Benjamin A; Grynpas, Marc D

    2015-11-01

    Age-related bone loss may be a result of declining levels of stem cells in the bone marrow. Using the Col2.3Δtk (DTK) transgenic mouse, osteoblast depletion was used as a source of marrow stress in order to investigate the effects of aging on osteogenic progenitors which reside in the marrow space. Five-month-old DTK mice were treated with one or two cycles of ganciclovir to conditionally ablate differentiated osteoblasts, whereas controls were saline-treated. Treatment cycles were two weeks in length followed by four weeks of recovery. All animals were sacrificed at 8 months of age; bone marrow stromal cells (BMSCs) were harvested for cell culture and whole bones were excised for bone quality assessment. Colony-forming unit (CFU) assays were conducted to investigate the osteogenic potential of BMSC in vitro, and RNA was extracted to assess the expression of osteoblastic genes. Bone quality assessments included bone histomorphometry, TRAP staining, microcomputed tomography, and biomechanical testing. Osteoblast depletion decreased CFU-F (fibroblast), CFU-ALP (alkaline phosphatase), and CFU-VK (von Kossa) counts and BMSC osteogenic capacity in cell culture. Ex vivo, there were no differences in bone mineral density of vertebrae or femurs between treatment groups. Histology showed a decrease in bone volume and bone connectivity with repeated osteoblast depletion; however, this was accompanied by an increase in bone formation rate. There were no notable differences in osteoclast parameters or observed bone marrow adiposity. We have developed a model that uses bone marrow stress to mimic age-related decrease in osteogenic progenitors. Our data suggest that the number of healthy BMSCs and their osteogenic potential decline with repeated osteoblast depletion. However, activity of the remaining osteoblasts increases to compensate for this loss in progenitor osteogenic potential.

  15. Bone Marrow Stress Decreases Osteogenic Progenitors.

    PubMed

    Ng, Adeline H; Baht, Gurpreet S; Alman, Benjamin A; Grynpas, Marc D

    2015-11-01

    Age-related bone loss may be a result of declining levels of stem cells in the bone marrow. Using the Col2.3Δtk (DTK) transgenic mouse, osteoblast depletion was used as a source of marrow stress in order to investigate the effects of aging on osteogenic progenitors which reside in the marrow space. Five-month-old DTK mice were treated with one or two cycles of ganciclovir to conditionally ablate differentiated osteoblasts, whereas controls were saline-treated. Treatment cycles were two weeks in length followed by four weeks of recovery. All animals were sacrificed at 8 months of age; bone marrow stromal cells (BMSCs) were harvested for cell culture and whole bones were excised for bone quality assessment. Colony-forming unit (CFU) assays were conducted to investigate the osteogenic potential of BMSC in vitro, and RNA was extracted to assess the expression of osteoblastic genes. Bone quality assessments included bone histomorphometry, TRAP staining, microcomputed tomography, and biomechanical testing. Osteoblast depletion decreased CFU-F (fibroblast), CFU-ALP (alkaline phosphatase), and CFU-VK (von Kossa) counts and BMSC osteogenic capacity in cell culture. Ex vivo, there were no differences in bone mineral density of vertebrae or femurs between treatment groups. Histology showed a decrease in bone volume and bone connectivity with repeated osteoblast depletion; however, this was accompanied by an increase in bone formation rate. There were no notable differences in osteoclast parameters or observed bone marrow adiposity. We have developed a model that uses bone marrow stress to mimic age-related decrease in osteogenic progenitors. Our data suggest that the number of healthy BMSCs and their osteogenic potential decline with repeated osteoblast depletion. However, activity of the remaining osteoblasts increases to compensate for this loss in progenitor osteogenic potential. PMID:26220824

  16. Adipose Tissue Residing Progenitors (Adipocyte Lineage Progenitors and Adipose Derived Stem Cells (ADSC)

    PubMed Central

    Berry, Ryan; Rodeheffer, Matthew S.; Rosen, Clifford J.; Horowitz, Mark C.

    2015-01-01

    The formation of brown, white and beige adipocytes have been a subject of intense scientific interest in recent years due to the growing obesity epidemic in the United States and around the world. This interest has led to the identification and characterization of specific tissue resident progenitor cells that give rise to each adipocyte population in vivo. However, much still remains to be discovered about each progenitor population in terms of their “niche” within each tissue and how they are regulated at the cellular and molecular level during healthy and diseased states. While our knowledge of brown, white and beige adipose tissue is rapidly increasing, little is still known about marrow adipose tissue and its progenitor despite recent studies demonstrating possible roles for marrow adipose tissue in regulating the hematopoietic space and systemic metabolism at large. This chapter focuses on our current knowledge of brown, white, beige and marrow adipose tissue with a specific focus on the formation of each tissue from tissue resident progenitor cells. PMID:26526875

  17. Operational Amplifier Experiments for the Chemistry Laboratory.

    ERIC Educational Resources Information Center

    Braun, Robert D.

    1996-01-01

    Provides details of experiments that deal with the use of operational amplifiers and are part of a course in instrumental analysis. These experiments are performed after the completion of a set of electricity and electronics experiments. (DDR)

  18. Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam; Reck, Theodore and; Schlecht, Erich; Lin, Robert; Deal, William

    2012-01-01

    The operating frequency of InP high electron mobility transistor (HEMT) based amplifiers has moved well in the submillimeter-wave frequencies over the last couple of years. Working amplifiers with usable gain in waveguide packages has been reported beyond 700 GHz. When cooled cryogenically, they have shown substantial improvement in their noise temperature. This has opened up the real possibility of cryogenic amplifier based heterodyne receivers at submillimeter wavelengths for ground-based, air-borne, and space-based instruments for astrophysics, planetary, and Earth science applications. This paper provides an overview of the science applications at submillimeter wavelengths that will benefit from this technology. It also describes the current state of the InP HEMT based cryogenic amplifier receivers at submillimeter wavelengths.

  19. Microwave diode amplifiers with low intermodulation distortion

    NASA Technical Reports Server (NTRS)

    Cooper, H. W.; Cohn, M.; Buck, D. C.

    1975-01-01

    Distortions can be greatly reduced in narrow-band applications by using the second harmonic. The ac behavior of simplified diode amplifier has negative resistance depending on slope of equivalent I-V curve.

  20. Noise in phase-preserving linear amplifiers

    SciTech Connect

    Pandey, Shashank; Jiang, Zhang; Combes, Joshua; Caves, Carlton M.

    2014-12-04

    The purpose of a phase-preserving linear amplifier is to make a small signal larger, so that it can be perceived by instruments incapable of resolving the original signal, while sacrificing as little as possible in signal-to-noise. Quantum mechanics limits how well this can be done: the noise added by the amplifier, referred to the input, must be at least half a quantum at the operating frequency. This well-known quantum limit only constrains the second moments of the added noise. Here we provide the quantum constraints on the entire distribution of added noise: any phasepreserving linear amplifier is equivalent to a parametric amplifier with a physical state σ for the ancillary mode; σ determines the properties of the added noise.

  1. Integrated CMOS amplifier for ENG signal recording.

    PubMed

    Uranga, A; Navarro, X; Barniol, N

    2004-12-01

    The development and in vivo test of a fully integrated differential CMOS amplifier, implemented with standard 0.7-microm CMOS technology (one poly, two metals, self aligned twin-well CMOS process) intended to record extracellular neural signals is described. In order to minimize the flicker noise generated by the CMOS circuitry, a chopper technique has been chosen. The fabricated amplifier has a gain of 74 dB, a bandwidth of 3 kHz, an input noise of 6.6 nV/(Hz)0.5, a power dissipation of 1.3 mW, and the active area is 2.7 mm2. An ac coupling has been used to adapt the electrode to the amplifier circuitry for the in vivo testing. Compound muscle action potentials, motor unit action potentials, and compound nerve action potentials have been recorded in acute experiments with rats, in order to validate the amplifier. PMID:15605867

  2. Sensor/amplifier for weak light sources

    NASA Technical Reports Server (NTRS)

    Desmet, D. J.; Jason, A. J.; Parr, A. C.

    1980-01-01

    Light sensor/amplifier circuit detects weak light converts it into strong electrical signal in electrically noisy environment. Circuit is relatively simple and uses inexpensive, readily available components. Device is useful in such applications as fire detection and photographic processing.

  3. Two-stage hybrid microcircuit amplifier

    SciTech Connect

    Pyo, M.L.

    1987-04-01

    This report documents the design, development, and fabrication of a two-stage amplifier operating at 400 to 600 MHz. Included are characterization data, predictions generated during design, and measured performance.

  4. How to characterize the nonlinear amplifier?

    NASA Technical Reports Server (NTRS)

    Kallistratova, Dmitri Kouznetsov; Cotera, Carlos Flores

    1994-01-01

    The conception of the amplification of the coherent field is formulated. The definition of the coefficient of the amplification as the relation between the mean value of the field at the output to the value at the input and the definition of the noise as the difference between the number of photons in the output mode and square of the modulus of the mean value of the output amplitude are considered. Using a simple example it is shown that by these definitions the noise of the nonlinear amplifier may be less than the noise of the ideal linear amplifier of the same amplification coefficient. Proposals to search another definition of basic parameters of the nonlinear amplifiers are discussed. This definition should enable us to formulate the universal fundamental lower limit of the noise which should be valid for linear quantum amplifiers as for nonlinear ones.

  5. Progenitor endothelial cell involvement in Alzheimer's disease

    SciTech Connect

    Budinger, Thomas F.

    2003-05-01

    There is compelling evidence that endothelial cells of the brain and periphery are dysfunctional in Alzheimer's Disease. There is evidence for a fundamental defect in, or abnormal aging of, endothelial progenitor cells in atherosclerosis. The possibility that endothelial cell defects are a primary cause for Alzheimer's Disease or other dementias can be researched by molecular and cell biology studies as well as cell trafficking studies using recently demonstrated molecular imaging methods. The evidence for abnormal endothelial function and the methods to explore this hypothesis are presented.

  6. Enhancing endothelial progenitor cell for clinical use

    PubMed Central

    Ye, Lei; Poh, Kian-Keong

    2015-01-01

    Circulating endothelial progenitor cells (EPCs) have been demonstrated to correlate negatively with vascular endothelial dysfunction and cardiovascular risk factors. However, translation of basic research into the clinical practice has been limited by the lack of unambiguous and consistent definitions of EPCs and reduced EPC cell number and function in subjects requiring them for clinical use. This article critically reviews the definition of EPCs based on commonly used protocols, their value as a biomarker of cardiovascular risk factor in subjects with cardiovascular disease, and strategies to enhance EPCs for treatment of ischemic diseases. PMID:26240678

  7. Enhancing endothelial progenitor cell for clinical use.

    PubMed

    Ye, Lei; Poh, Kian-Keong

    2015-07-26

    Circulating endothelial progenitor cells (EPCs) have been demonstrated to correlate negatively with vascular endothelial dysfunction and cardiovascular risk factors. However, translation of basic research into the clinical practice has been limited by the lack of unambiguous and consistent definitions of EPCs and reduced EPC cell number and function in subjects requiring them for clinical use. This article critically reviews the definition of EPCs based on commonly used protocols, their value as a biomarker of cardiovascular risk factor in subjects with cardiovascular disease, and strategies to enhance EPCs for treatment of ischemic diseases.

  8. MMIC Amplifiers for 90 to 130 GHz

    NASA Technical Reports Server (NTRS)

    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.

  9. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In Heon; Stock, Larry V.

    1989-01-01

    This semiannual progress report covers the period from September 1, 1988 to February 28, 1989 under NASA grant NAG-1-441 entitled, Direct Solar-Pumped Iodine Laser Amplifier. During this period, the research effort was concentrated on the solar pumped master oscillator power amplifier (MOPA) system using n-C3F7I. In the experimental work, the amplification measurement was conducted to identify the optimum conditions for amplification of the center's Vortek solar simulator pumped iodine laser amplifier. A modeling effort was also pursued to explain the experimental results in the theoretical work. The amplification measurement of the solar simulator pumped iodine laser amplifier is the first amplification experiment on the continuously pumped amplifier. The small signal amplification of 5 was achieved for the triple pass geometry of the 15 cm long solar simulator pumped amplifier at the n-C3F7I pressure of 20 torr, at the flow velocity of 6 m/sec and at the pumping intensity of 1500 solar constants. The XeCl laser pumped iodine laser oscillator, which was developed in the previous research, was employed as the master oscillator for the amplification measurement. In the theoretical work, the rate equations of the amplifier was established and the small signal amplification was calculated for the solar simulator pumped iodine laser amplifier. The amplification calculated from the kinetic equations with the previously measured rate coefficients reveals very large disagreement with experimental measurement. Moreover, the optimum condition predicted by the kinetic equation is quite discrepant with that measured by experiment. This fact indicates the necessity of study in the measurement of rate coefficients of the continuously pumped iodine laser system.

  10. High-Frequency, Conformable Organic Amplifiers.

    PubMed

    Reuveny, Amir; Lee, Sunghoon; Yokota, Tomoyuki; Fuketa, Hiroshi; Siket, Christian M; Lee, Sungwon; Sekitani, Tsuyoshi; Sakurai, Takayasu; Bauer, Siegfried; Someya, Takao

    2016-05-01

    Large-bandwidth, low-operation-voltage, and uniform organic amplifiers are fabricated on ultrathin foils. By the integration of short-channel OTFTs and AlOx capacitors, organic amplifiers with a bandwidth of 25 kHz are realized, demonstrating the highest gain-bandwidth product (GBWP) reported to date. Owing to material and process advancements, closed-loop architectures operate at frequencies of several kilohertz with an area smaller than 30 mm(2) . PMID:26922899

  11. High-Frequency, Conformable Organic Amplifiers.

    PubMed

    Reuveny, Amir; Lee, Sunghoon; Yokota, Tomoyuki; Fuketa, Hiroshi; Siket, Christian M; Lee, Sungwon; Sekitani, Tsuyoshi; Sakurai, Takayasu; Bauer, Siegfried; Someya, Takao

    2016-05-01

    Large-bandwidth, low-operation-voltage, and uniform organic amplifiers are fabricated on ultrathin foils. By the integration of short-channel OTFTs and AlOx capacitors, organic amplifiers with a bandwidth of 25 kHz are realized, demonstrating the highest gain-bandwidth product (GBWP) reported to date. Owing to material and process advancements, closed-loop architectures operate at frequencies of several kilohertz with an area smaller than 30 mm(2) .

  12. Athermal continuous-wave fiber amplifier

    NASA Astrophysics Data System (ADS)

    Nemova, Galina; Kashyap, Raman

    2009-07-01

    We present a new theoretical scheme for Yb 3+-doped athermal (radiation-balanced) continuous-wave fiber amplifier. This approach allows amplification with optical pumping of the fiber amplifier without detrimental heating of the fiber. Athermal amplification is realized by laser cooling in which waste heat is disposed of in the form of spontaneous fluorescence by balancing the radiated and absorbed power. The radiation-balanced fiber amplification can be realized using a specially designed distributed pumping scheme.

  13. Efficient Power Amplifier for Motor Control

    NASA Technical Reports Server (NTRS)

    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.

  14. Some Notes on Wideband Feedback Amplifiers

    DOE R&D Accomplishments Database

    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.

  15. V-band IMPATT power amplifier

    NASA Technical Reports Server (NTRS)

    Schell, S. W.

    1985-01-01

    This program is the result of the continuing demand and future requirement for a high data rate 60-GHz communications link. A reliable solid-state transmitter which delivers the necessary power over a wide bandwidth using the present IMPATT diode technology required the development of combining techniques. The development of a 60-GHz IMPATT power combiner amplifier is detailed. The results form a basis from which future wideband, high-power IMPATT amplifiers may be developed. As a result, several state-of-the-art advancements in millimeter-wave components technology were achieved. Specific achievements for the amplifier integration were: development of a nonresonant divider/combiner circuit; reproducible multiple junction circulator assemblies; and reliable high power 60-GHz IMPATT diodes. The various design approaches and tradeoffs which lead to the final amplifier configuration are discussed. A detailed circuit design is presented for the various amplifier components, and the conical line combiner, radial line combiner, and circulator development are discussed. The performance of the amplifier, the overall achievement of the program, the implications of the results, and an assessment of future development needs and recommendations are examined.

  16. Multiple excitation regenerative amplifier inertial confinement system

    DOEpatents

    George, V.E.; Haas, R.A.; Krupke, W.F.; Schlitt, L.G.

    1980-05-27

    The invention relates to apparatus and methods for producing high intensity laser radiation generation which is achieved through an optical amplifier-storage ring design. One or two synchronized, counterpropagating laser pulses are injected into a regenerative amplifier cavity and amplified by gain media which are pumped repetitively by electrical or optical means. The gain media excitation pulses are tailored to efficiently amplify the laser pulses during each transit. After the laser pulses have been amplified to the desired intensity level, they are either switched out of the cavity by some switch means, as for example an electro-optical device, for any well known laser end uses, or a target means may be injected into the regenerative amplifier cavity in such a way as to intercept simultaneously the counterpropagating laser pulses. One such well known end uses to which this invention is intended is for production of high density and temperature plasmas suitable for generating neutrons, ions and x-rays and for studying matter heated by high intensity laser radiation. 11 figs.

  17. Multiple excitation regenerative amplifier inertial confinement system

    DOEpatents

    George, Victor E. [Livermore, CA; Haas, Roger A. [Pleasanton, CA; Krupke, William F. [Pleasanton, CA; Schlitt, Leland G. [Livermore, CA

    1980-05-27

    The invention relates to apparatus and methods for producing high intensity laser radiation generation which is achieved through an optical amplifier-storage ring design. One or two synchronized, counterpropagating laser pulses are injected into a regenerative amplifier cavity and amplified by gain media which are pumped repetitively by electrical or optical means. The gain media excitation pulses are tailored to efficiently amplify the laser pulses during each transit. After the laser pulses have been amplified to the desired intensity level, they are either switched out of the cavity by some switch means, as for example an electro-optical device, for any well known laser end uses, or a target means may be injected into the regenerative amplifier cavity in such a way as to intercept simultaneously the counterpropagating laser pulses. One such well known end uses to which this invention is intended is for production of high density and temperature plasmas suitable for generating neutrons, ions and x-rays and for studying matter heated by high intensity laser radiation.

  18. Proposal of Switching Power Amplifier Using Small Capacity Linear Amplifier and LC Filter

    NASA Astrophysics Data System (ADS)

    Kamada, Jo; Funato, Hirohito; Ogasawara, Satoshi

    The higher efficiency and the low noise in output voltage and current has been required in some applications, i.e. audio-video equipment, medical equipment and so on. This paper proposes a power amplifier in which a PWM inverter is used as a main circuit. In the proposed power amplifier, a hybrid filter composed of a simple and general LC filter and a small capacity linear amplifier is connected to the output of the inverter. The linear amplifier is inserted in series to the filter capacitor to improve the filtering effect of the LC filter. Switching ripples and LC resonances are considerably suppressed by controlling the amplifier using the proposed method and a low distortion switching power amplifier is realized. The effects of the proposal circuit are verified by simulations and experiments. As a result, the proposed circuit achieves low noise about THD=0.68% in simulation and THD=1.7% in experiment.

  19. The Type Ia Supernovae Progenitor Problem: Searching for Progenitors in the Milky Way

    NASA Astrophysics Data System (ADS)

    Birchall, Alexander; Di Stefano, R.; Primini, F.; Scalzo, R.

    2013-01-01

    One of the most active areas of current astrophysical research is the search for the progenitors of Type Ia supernovae. Understanding the nature(s) of the progenitors is crucial if we are to use these supernovae to conduct high-precision measurements of the history of cosmic expansion, because in order to confirm them as standardizable candles we need to understand the mechanism by which they are produced. Type Ia supernovae occur when carbon/oxygen white dwarfs explode, having gained mass either by accretion from a companion or by merging with another white dwarf. The white dwarfs in all Type Ia progenitors must go through a stage of high-rate accretion and possibly of nuclear burning. They should then be detectable as bright objects, with luminosities as high as a few times 1038 erg s-1. Furthermore, whatever the correct model(s), more than 1000 bright progenitors (and other systems that may be equally bright but in which the white dwarf does not reach the critical mass) are expected in the Milky Way. We are conducting a comprehensive search through archived data to identify unusual bright sources that may correspond to white dwarfs accreting at high rates. A significant fraction of the progenitors may appear as x-ray sources that are either supersoft or quasisoft some of the time. We have therefore searched the ROSAT, Chandra, and XMM databases to identify all such soft sources in the Milky Way that are detectable from Earth. We report on our results and their implications.

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

    PubMed

    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.

  1. Neutrino emission from nearby supernova progenitors

    NASA Astrophysics Data System (ADS)

    Yoshida, Takashi; Takahashi, Koh; Umeda, Hideyuki

    2016-05-01

    Neutrinos have an important role for energy loss process during advanced evolution of massive stars. Although the luminosity and average energy of neutrinos during the Si burning are much smaller than those of supernova neutrinos, these neutrinos are expected to be detected by the liquid scintillation neutrino detector KamLAND if a supernova explosion occurs at the distance of ~100 parsec. We investigate the neutrino emission from massive stars during advanced evolution. We calculate the evolution of the energy spectra of neutrinos produced through electron-positron pair-annihilation in the supernova progenitors with the initial mass of 12, 15, and 20 M ⊙ during the Si burning and core-collapse stages. The neutrino emission rate increases from ~ 1050 s-1 to ~ 1052 s-1. The average energy of electron-antineutrinos is about 1.25 MeV during the Si burning and gradually increases until the core-collapse. For one week before the supernova explosion, the KamLAND detector is expected to observe 12-24 and 6-13 v¯e events in the normal and inverted mass hierarchies, respectively, if a supernova explosion of a 12-20 M ⊙ star occurs at the distance of 200 parsec, corresponding to the distance to Betelgeuse. Observations of neutrinos from SN progenitors have a possibility to constrain the core structure and the evolution just before the core collapse of massive stars.

  2. Endothelial progenitor cells in diabetic foot syndrome.

    PubMed

    Drela, Ewelina; Stankowska, Katarzyna; Kulwas, Arleta; Rość, Danuta

    2012-01-01

    In the late 20th century endothelial progenitor cells (EPCs) were discovered and identified as cells capable of differentiating into endothelial cells. Antigens characteristic of endothelial cells and hematopoietic cells are located on their surface. EPCs can proliferate, adhere, migrate and have the specific ability to form vascular structure, and they have a wide range of roles: They participate in maintaining hemostasis, and play an important part in the processes of vasculogenesis and angiogenesis. They are sources of angiogenic factors, especially vascular endothelial growth factor (VEGF). EPCs exist in bone marrow, from which they are recruited into circulation in response to specific stimuli. Tissue ischemia is thought to be the strongest inductor of EPC mobilization. Local ischemia accompanies many pathological states, including diabetic foot syndrome (DFS). Impaired angiogenesis--in which EPCs participate--is typical of DFS. An analysis of the available literature indicates that in diabetic patients the number of EPCs declines and their functioning is impaired. Endothelial progenitor cells are crucial to vasculogenesis and angiogenesis during ischemic neovascularization. The pathomechanisms underlying impaired angiogenesis in patients with DFS is complicated, but the discovery of EPCs has shed new light on the pathogenesis of many diseases, including diabetes foot syndrome.

  3. Progenitor Cell Dysfunctions Underlie Some Diabetic Complications

    PubMed Central

    Rodrigues, Melanie; Wong, Victor W.; Rennert, Robert C.; Davis, Christopher R.; Longaker, Michael T.; Gurtner, Geoffrey C.

    2016-01-01

    Stem cells and progenitor cells are integral to tissue homeostasis and repair. They contribute to health through their ability to self-renew and commit to specialized effector cells. Recently, defects in a variety of progenitor cell populations have been described in both preclinical and human diabetes. These deficits affect multiple aspects of stem cell biology, including quiescence, renewal, and differentiation, as well as homing, cytokine production, and neovascularization, through mechanisms that are still unclear. More important, stem cell aberrations resulting from diabetes have direct implications on tissue function and seem to persist even after return to normoglycemia. Understanding how diabetes alters stem cell signaling and homeostasis is critical for understanding the complex pathophysiology of many diabetic complications. Moreover, the success of cell-based therapies will depend on a more comprehensive understanding of these deficiencies. This review has three goals: to analyze stem cell pathways dysregulated during diabetes, to highlight the effects of hyperglycemic memory on stem cells, and to define ways of using stem cell therapy to overcome diabetic complications. PMID:26079815

  4. The progenitors of supernovae Type Ia

    NASA Astrophysics Data System (ADS)

    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.

  5. Red supergiants as type II supernova progenitors

    NASA Astrophysics Data System (ADS)

    Negueruela, Ignacio; Dorda, Ricardo; González-Fernández, Carlos; Marco, Amparo

    2015-08-01

    Recent searches for supernova IIp progenitors in external galaxies have led to the identification of red objects with magnitudes and colours indicative of red supergiants, in most cases implying quite low luminosities and hence masses well below 10Msol. Stellar models, on the other hand, do not predict explosions from objects below 9 Msol. What does our knowledge of local red supergiants tells us about the expected properties of such objects?We have carried out a comprehensive spectroscopic and photometric study of a sample of hundreds of red supergiants in the Milky Way and both Magellanic Clouds. We have explored correlations between different parameters and the position of stars in the HR diagrams of open clusters. At solar metallicty, there is strong evidence for a phase of very heavy mass loss at the end of the red supergiant phase, but the existence of such a phase is still not confirmed at SMC metallicities. Objects of ~ 7Msol, on the other hand, become very dusty in the SMC, and appear as very luminous Miras.Among Milky Way clusters, we find a surprising lack of objects readily identifiable as the expected 7 to 10 Msol red supergiants or AGB stars. We are carrying out an open cluster survey aimed at filling this region of the HR diagram with reliable data. Finally, we will discuss the implications of all this findings for the expected properties of supernova progenitors, as it looks unlikely that typical red supergiants may explode without undergoing further evolution.

  6. Mechanisms of cardiogenesis in cardiovascular progenitor cells.

    PubMed

    Taubenschmid, Jasmin; Weitzer, Georg

    2012-01-01

    Self-renewing cells of the vertebrate heart have become a major subject of interest in the past decade. However, many researchers had a hard time to argue against the orthodox textbook view that defines the heart as a postmitotic organ. Once the scientific community agreed on the existence of self-renewing cells in the vertebrate heart, their origin was again put on trial when transdifferentiation, dedifferentiation, and reprogramming could no longer be excluded as potential sources of self-renewal in the adult organ. Additionally, the presence of self-renewing pluripotent cells in the peripheral blood challenges the concept of tissue-specific stem and progenitor cells. Leaving these unsolved problems aside, it seems very desirable to learn about the basic biology of this unique cell type. Thus, we shall here paint a picture of cardiovascular progenitor cells including the current knowledge about their origin, basic nature, and the molecular mechanisms guiding proliferation and differentiation into somatic cells of the heart. PMID:22251563

  7. Radioprotection of hematopoietic progenitors by low dose amifostine prophylaxis

    PubMed Central

    Seed, Thomas M.; Inal, Cynthia E.

    2014-01-01

    Purpose Amifostine is a highly efficacious cytoprotectant when administered in vivo at high doses. However, at elevated doses, drug toxicity manifests for general, non-clinical radioprotective purposes. Various strategies have been developed to avoid toxic side-effects: The simplest is reducing the dose. In terms of protecting hematopoietic tissues, where does this effective, non-toxic minimum dose lie? Material and methods C3H/HEN mice were administered varying doses of amifostine (25–100 mg/kg) 30 min prior to cobalt-60 irradiation and euthanized between 4–14 days for blood and bone marrow collection and analyses. Results Under steady-state, amifostine had little effect on bipotential and multi-potential marrow progenitors but marginally suppressed a more primitive, lineage negative progenitor subpopulation. In irradiated animals, prophylactic drug doses greater than 50 mg/kg resulted in significant regeneration of bipotential progenitors, moderate regeneration of multipotential progenitors, but no significant and consistent regeneration of more primitive progenitors. The low amifostine dose (25 mg/kg) failed to elicit consistent and positive, radioprotective actions on any of the progenitor subtypes. Conclusions Radioprotective doses for amifostine appear to lie between 25 and 50 mg/kg. Mature, lineage-restricted progenitors appear to be more responsive to the protective effects of low doses of amifostine than the more primitive, multipotential progenitors. PMID:24597748

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

    PubMed Central

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

    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 were observed in 61% of the patients. Between 1% and 26% of the peripheral blood mononuclear cells (MNCs) displayed this phenotype. Furthermore, a distinct population of c-kit+ progenitor cells (between 1% and 38 % of the MNCs) could be detected in 91% of the patients. Additionally, 18% of the patients showed a population of progenitor cells (between 1% and 68% of the MNCs) that was characterized by expression of breast cancer resistance protein-1. Further phenotypic analysis disclosed that the circulating precursors expressed CXC chemokine receptor 4, the receptor for SDF-1. In line with this finding, elevated plasma levels of SDF-1 were present in all patients and were found to correlate with the number of mobilized CD133+ progenitor cells. CONCLUSION: These data indicate that in humans, liver cirrhosis leads to recruitment of various populations of hematopoietic progenitor cells that display markers of intrahepatic progenitor cells. PMID:20066741

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

    PubMed

    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.

  10. Real Time Calibration Method for Signal Conditioning Amplifiers

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J. (Inventor); Mata, Carlos T. (Inventor); Eckhoff, Anthony (Inventor); Perotti, Jose (Inventor); Lucena, Angel (Inventor)

    2004-01-01

    A signal conditioning amplifier receives an input signal from an input such as a transducer. The signal is amplified and processed through an analog to digital converter and sent to a processor. The processor estimates the input signal provided by the transducer to the amplifier via a multiplexer. The estimated input signal is provided as a calibration voltage to the amplifier immediately following the receipt of the amplified input signal. The calibration voltage is amplified by the amplifier and provided to the processor as an amplified calibration voltage. The amplified calibration voltage is compared to the amplified input signal, and if a significant error exists, the gain and/or offset of the amplifier may be adjusted as necessary.

  11. High-Efficiency Microwave Power Amplifier

    NASA Technical Reports Server (NTRS)

    Sims, Williams H.

    2005-01-01

    A high-efficiency power amplifier that operates in the S band (frequencies of the order of a few gigahertz) utilizes transistors operating under class-D bias and excitation conditions. Class-D operation has been utilized at lower frequencies, but, until now, has not been exploited in the S band. Nominally, in class D operation, a transistor is switched rapidly between "on" and "off" states so that at any given instant, it sustains either high current or high voltage, but not both at the same time. In the ideal case of zero "on" resistance, infinite "off" resistance, zero inductance and capacitance, and perfect switching, the output signal would be a perfect square wave. Relative to the traditional classes A, B, and C of amplifier operation, class D offers the potential to achieve greater power efficiency. In addition, relative to class-A amplifiers, class-D amplifiers are less likely to go into oscillation. In order to design this amplifier, it was necessary to derive mathematical models of microwave power transistors for incorporation into a larger mathematical model for computational simulation of the operation of a class-D microwave amplifier. The design incorporates state-of-the-art switching techniques applicable only in the microwave frequency range. Another major novel feature is a transmission-line power splitter/combiner designed with the help of phasing techniques to enable an approximation of a square-wave signal (which is inherently a wideband signal) to propagate through what would, if designed in a more traditional manner, behave as a more severely band-limited device (see figure). The amplifier includes an input, a driver, and a final stage. Each stage contains a pair of GaAs-based field-effect transistors biased in class D. The input signal can range from -10 to +10 dBm into a 50-ohm load. The table summarizes the performances of the three stages

  12. Nonuniform carrier distribution in semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Evankow, Joseph David, Jr.

    This work discusses the experimental results and theoretical analysis of the longitudinal distribution of the spontaneous emission, amplified spontaneous emission, hole-electron pairs, and gain in semiconductor optical amplifiers. A novel, yet simple, technique was developed enabling, for the first time, the measurement of these distributions. This was accomplished with a high degree of spatial resolution using a single-mode micro-lensed fiber tip positioned perpendicular to the active region and moved longitudinally along the stripe. The cornerstone of this study centers on the theoretical analysis of the small portion of the isotropic spontaneous emission, emanating from the optical cavity, which is captured by the lensed fiber. Spectral as well as integrated power measurements were made along the length of the cavity. These spectral and integrated power measurements provide a direct link to the carrier concentration and gain along the optical cavity. The distribution of this spontaneous emission along the amplifier, and its relationship to other parameters, provide information about the carriers. Since the common mode of operation for linear optical amplifiers is deep in saturation, the devices in this study were analyzed in regimes significantly below the small-signal gain. While large carrier density non- uniformity occur with output powers equal to or greater than Psat, a significant amount can occur in amplifiers even with small input signals. In these amplifiers, the higher carder concentrations produce much higher internal gain coefficients making them more prone to non-uniform carrier density distributions. Moreover, even in semiconductor lasers, where the carrier concentration and the gain are pinned at the onset of lasing to rather pedestrian levels (approximately 1 × 1018 cm-3 and of 3 dB, respectively), previous theoretical analysis for more than a decade postulated that a significant spatial distribution occur. These measurements and analysis

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

    PubMed Central

    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

  14. Vascular endothelial growth factors A and C are induced in the SVZ following neonatal hypoxia-ischemia and exert different effects on neonatal glial progenitors

    PubMed Central

    Bain, Jennifer M.; Moore, Lisamarie; Ren, Zhihua; Simonishvili, Sophia; Levison, Steven W.

    2012-01-01

    Episodes of neonatal hypoxia-ischemia (H-I) are strongly associated with cerebral palsy and a wide spectrum of other neurological deficits in children. Two key processes required to repair damaged organs are to amplify the number of precursors capable of regenerating damaged cells and to direct their differentiation towards the cell types that need to be replaced. Since hypoxia induces vascular endothelial growth factor (VEGF) production, it is logical to predict that VEGFs are key mediators of tissue repair after H-I injury. The goal of this study was to test the hypothesis that certain VEGF isoforms increase during recovery from neonatal H-I and that they would differentially affect the proliferation and differentiation of subventricular zone (SVZ) progenitors. During the acute recovery period from H-I both VEGF-A and VEGF-C were transiently induced in the SVZ, which correlated with an increase in SVZ blood vessel diameter. These growth factors were produced by glial progenitors, astrocytes and to a lesser extent, microglia. VEGF-A promoted the production of astrocytes from SVZ glial progenitors while VEGF-C stimulated the proliferation of both early and late oligodendrocyte progenitors, which was abolished by blocking the VEGFR-3. Altogether, these results provide new insights into the signals that coordinate the reactive responses of the progenitors in the SVZ to neonatal H-I. Our studies further suggest that therapeutics that extend VEGF-C production and/or agonists that stimulate the VEGFR-3 will promote oligodendrocyte progenitor cell development to enhance myelination after perinatal brain injury. PMID:23565129

  15. Thermal recovery of the NIF amplifiers

    SciTech Connect

    Beullier, J; Bicrel,; Erlandson, A; London, R; Manes, K; Marshall, C; Petty, C; Pierce, R; Smith, L; Sutton, S; Zapata, L

    1998-06-30

    With approximately 99% of the electrical energy supplied to the National Ignition Facility (NIF) appearing as heat in the amplifiers, thermal recovery of the NIF system is a major consideration in the design process. The NIF shot rate is one shot every 8 hours, with a goal of 4 hours between shots. This necessitates that thermal recovery take place in no more than 7 hours, with a goal of 3 hours for the accelerated shot rate. Residual optical distortions, which restrict the shot rate, are grouped into two discrete categories: (1) distortions associated with residual temperature gradients in the laser slabs, and (2) distortions associated with buoyantly driven convective currents in the amplifier cavity and beam-tube regions. Thermal recovery of the amplifiers is achieved by cooling the flashlamps and blastshields with a turbulent gas flow. The cooled blastshields then serve as a cold boundary to radiatively extract the residual heat deposited in the slabs and edge claddings. Advanced concepts, such as the use of slightly chilled gas to accelerate some aspects of recovery, are addressed. To quantify recovery rates of the amplifiers, experiments and numerical models are used to measure and calculate the temperatures and optical distortions in NIF-like amplifier elements. The calculation results are benchmarked against AMLAB temperature measurements, thus allowing a quantitative prediction of NIF thermal recovery. These results indicate that the NIF requirement of 7 hour thermal recovery can be achieved with chilled temperature cooling gas.

  16. High power, high beam quality regenerative amplifier

    DOEpatents

    Hackel, Lloyd A.; Dane, Clifford B.

    1993-01-01

    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.

  17. High power, high beam quality regenerative amplifier

    DOEpatents

    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.

  18. Injection- Seeded Optoplasmonic Amplifier in the Visible

    PubMed Central

    Gartia, Manas Ranjan; Seo, Sujin; Kim, Junhwan; Chang, Te-Wei; Bahl, Gaurav; Lu, Meng; Liu, Gang Logan; Eden, J. Gary

    2014-01-01

    A hybrid optoplasmonic amplifier, injection-seeded by an internally-generated Raman signal and operating in the visible (563–675 nm), is proposed and evidence for amplification is presented. Comprising a gain medium tethered to a whispering gallery mode (WGM) resonator with a protein, and a plasmonic surface, the optical system described here selectively amplifies a single (or a few) Raman line(s) produced within the WGM resonator and is well-suited for routing narrowband optical power on-a-chip. Over the past five decades, optical oscillators and amplifiers have typically been based on the buildup of the field from the spontaneous emission background. Doing so limits the temporal coherence of the output, lengthens the time required for the optical field intensity to reach saturation, and often is responsible for complex, multiline spectra. In addition to the spectral control afforded by injection-locking, the effective Q of the amplifier can be specified by the bandwidth of the injected Raman signal. This characteristic contrasts with previous WGM-based lasers and amplifiers for which the Q is determined solely by the WGM resonator. PMID:25156810

  19. Src kinase function controls progenitor cell pools during regeneration and tumor onset in the Drosophila intestine.

    PubMed

    Kohlmaier, A; Fassnacht, C; Jin, Y; Reuter, H; Begum, J; Dutta, D; Edgar, B A

    2015-04-30

    Src non-receptor kinases have been implicated in events late in tumor progression. Here, we study the role of Src kinases in the Drosophila intestinal stem cell (ISC) lineage, during tissue homeostasis and tumor onset. The adult Drosophila intestine contains only two progenitor cell types, division-capable ISCs and their daughters, postmitotic enteroblasts (EBs). We found that Drosophila Src42a and Src64b were required for optimal regenerative ISC division. Conversely, activation of Src42a, Src64b or another non-receptor kinase, Ack, promoted division of quiescent ISCs by coordinately stimulating G1/S and G2/M cell cycle phase progression. Prolonged Src kinase activation caused tissue overgrowth owing to cytokine receptor-independent Stat92E activation. This was not due to increased symmetric division of ISCs, but involved accumulation of weakly specified Notch(+) but division-capable EB-like cells. Src activation triggered expression of a mitogenic module consisting of String/Cdc25 and Cyclin E that was sufficient to elicit division not only of ISCs but also of EBs. A small pool of similarly division-capable transit-amplifying Notch(+) EBs was also identified in the wild type. Expansion of intermediate cell types that do not robustly manifest their transit-amplifying potential in the wild type may also contribute to regenerative growth and tumor development in other tissues in other organisms.

  20. Method to amplify variable sequences without imposing primer sequences

    DOEpatents

    Bradbury, Andrew M.; Zeytun, Ahmet

    2006-11-14

    The present invention provides methods of amplifying target sequences without including regions flanking the target sequence in the amplified product or imposing amplification primer sequences on the amplified product. Also provided are methods of preparing a library from such amplified target sequences.

  1. Ultrashort pulse amplification in cryogenically cooled amplifiers

    DOEpatents

    Backus, Sterling J.; Kapteyn, Henry C.; Murnane, Margaret Mary

    2004-10-12

    A laser amplifier system amplifies pulses in a single "stage" from .about.10.sup.-9 joules to more than 10.sup.-3 joules, with average power of 1-10 watts, and beam quality M.sup.2 <2. The laser medium is cooled substantially below room temperature, as a means to improve the optical and thermal characteristics of the medium. This is done with the medium inside a sealed, evacuated or purged cell to avoid moisture or other materials condensing on the surface. A "seed" pulse from a separate laser is passed through the laser medium, one or more times, in any of a variety of configurations including single-pass, multiple-pass, and regenerative amplifier configurations.

  2. Modulation instability in high power laser amplifiers.

    PubMed

    Rubenchik, Alexander M; Turitsyn, Sergey K; Fedoruk, Michail P

    2010-01-18

    The modulation instability (MI) is one of the main factors responsible for the degradation of beam quality in high-power laser systems. The so-called B-integral restriction is commonly used as the criteria for MI control in passive optics devices. For amplifiers the adiabatic model, assuming locally the Bespalov-Talanov expression for MI growth, is commonly used to estimate the destructive impact of the instability. We present here the exact solution of MI development in amplifiers. We determine the parameters which control the effect of MI in amplifiers and calculate the MI growth rate as a function of those parameters. The safety range of operational parameters is presented. The results of the exact calculations are compared with the adiabatic model, and the range of validity of the latest is determined. We demonstrate that for practical situations the adiabatic approximation noticeably overestimates MI. The additional margin of laser system design is quantified.

  3. Ultraflexible organic amplifier with biocompatible gel electrodes.

    PubMed

    Sekitani, Tsuyoshi; Yokota, Tomoyuki; Kuribara, Kazunori; Kaltenbrunner, Martin; Fukushima, Takanori; Inoue, Yusuke; Sekino, Masaki; Isoyama, Takashi; Abe, Yusuke; Onodera, Hiroshi; Someya, Takao

    2016-01-01

    In vivo electronic monitoring systems are promising technology to obtain biosignals with high spatiotemporal resolution and sensitivity. Here we demonstrate the fabrication of a biocompatible highly conductive gel composite comprising multi-walled carbon nanotube-dispersed sheet with an aqueous hydrogel. This gel composite exhibits admittance of 100 mS cm(-2) and maintains high admittance even in a low-frequency range. On implantation into a living hypodermal tissue for 4 weeks, it showed a small foreign-body reaction compared with widely used metal electrodes. Capitalizing on the multi-functional gel composite, we fabricated an ultrathin and mechanically flexible organic active matrix amplifier on a 1.2-μm-thick polyethylene-naphthalate film to amplify (amplification factor: ∼200) weak biosignals. The composite was integrated to the amplifier to realize a direct lead epicardial electrocardiography that is easily spread over an uneven heart tissue. PMID:27125910

  4. The Electron Beam Semiconductor (EBS) amplifier

    NASA Astrophysics Data System (ADS)

    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.

  5. Ultraflexible organic amplifier with biocompatible gel electrodes

    NASA Astrophysics Data System (ADS)

    Sekitani, Tsuyoshi; Yokota, Tomoyuki; Kuribara, Kazunori; Kaltenbrunner, Martin; Fukushima, Takanori; Inoue, Yusuke; Sekino, Masaki; Isoyama, Takashi; Abe, Yusuke; Onodera, Hiroshi; Someya, Takao

    2016-04-01

    In vivo electronic monitoring systems are promising technology to obtain biosignals with high spatiotemporal resolution and sensitivity. Here we demonstrate the fabrication of a biocompatible highly conductive gel composite comprising multi-walled carbon nanotube-dispersed sheet with an aqueous hydrogel. This gel composite exhibits admittance of 100 mS cm-2 and maintains high admittance even in a low-frequency range. On implantation into a living hypodermal tissue for 4 weeks, it showed a small foreign-body reaction compared with widely used metal electrodes. Capitalizing on the multi-functional gel composite, we fabricated an ultrathin and mechanically flexible organic active matrix amplifier on a 1.2-μm-thick polyethylene-naphthalate film to amplify (amplification factor: ~200) weak biosignals. The composite was integrated to the amplifier to realize a direct lead epicardial electrocardiography that is easily spread over an uneven heart tissue.

  6. FEL amplifier performance in the Compton regime

    NASA Astrophysics Data System (ADS)

    Cover, R. A.; Bhowmik, A.

    1984-01-01

    The Kroll-Morton-Rosenbluth equations of motion for electrons in a linearly polarized, tapered wiggler are utilized to describe gain in free-electron laser amplifiers. The three-dimensional amplifier model includes the effects of density variation in the electron beam, off-axis variations in the wiggler magnetic field, and betatron oscillations. The input electromagnetic field is injected and subsequently propagated within the wiggler by computing the Fresnel-Kirchhoff diffraction integral using the Gardner-Fresnel-Kirchhoff algorithm. The injected optical beam used in evaluating amplifier performance is initially a Gaussian which in general may be astigmatic. The importance of the above effects on extraction efficiency is computed both with rigorous three-dimensional electromagnetic wave propagation and a Gaussian treatment of the field.

  7. Single mode terahertz quantum cascade amplifier

    SciTech Connect

    Ren, Y. Wallis, R.; Shah, Y. D.; Jessop, D. S.; Degl'Innocenti, R.; Klimont, A.; Kamboj, V.; Beere, H. E.; Ritchie, D. A.

    2014-10-06

    A terahertz (THz) optical amplifier based on a 2.9 THz quantum cascade laser (QCL) structure has been demonstrated. By depositing an antireflective coating on the QCL facet, the laser mirror losses are enhanced to fully suppress the lasing action, creating a THz quantum cascade (QC) amplifier. Terahertz radiation amplification has been obtained, by coupling a separate multi-mode THz QCL of the same active region design to the QC amplifier. A bare cavity gain is achieved and shows excellent agreement with the lasing spectrum from the original QCL without the antireflective coating. Furthermore, a maximum optical gain of ∼30 dB with single-mode radiation output is demonstrated.

  8. Short pulse free electron laser amplifier

    DOEpatents

    Schlitt, Leland G.; Szoke, Abraham

    1985-01-01

    Method and apparatus for amplification of a laser pulse in a free electron laser amplifier where the laser pulse duration may be a small fraction of the electron beam pulse duration used for amplification. An electron beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f<1) of the electron beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, . . . , where substantially the same fraction f of the remainder of the electron beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron beam energy is substantially completely consumed by amplification of the laser pulse.

  9. High Bandwidth Differential Amplifier for Shock Experiments

    SciTech Connect

    Ross, P. W., Tran, V., Chau, R.

    2012-04-30

    We developed a high bandwidth differential amplifier for gas gun shock experiments/applications. The circuit has a bandwidth > 1 GHz, and is capable of measuring signals of ≤1.5 V with a common mode rejection of 250 V. Conductivity measurements of gas gun targets are measured by flowing high currents through the targets. The voltage is measured across the target using a technique similar to a four-point probe. Because of the design of the current source and load, the target voltage is approximately 250 V relative to ground. Since the expected voltage change in the target is < 1 V, the differential amplifier must have a large common mode rejection. High pass filters suppress internal ringing of operational amplifiers. Results of bench tests are shown.

  10. L1 Retrotransposition in Neural Progenitor Cells.

    PubMed

    Muotri, Alysson R

    2016-01-01

    Long interspersed nucleotide element 1 (LINE-1 or L1) is a family of non-LTR retrotransposons that can replicate and reintegrate into the host genome. L1s have considerably influenced mammalian genome evolution by retrotransposing during germ cell development or early embryogenesis, leading to massive genome expansion. For many years, L1 retrotransposons were viewed as a selfish DNA parasite that had no contribution in somatic cells. Historically, L1s were thought to only retrotranspose during gametogenesis and in neoplastic processes, but recent studies have shown that L1s are extremely active in the mouse, rat, and human neuronal progenitor cells (NPCs). These de novo L1 insertions can impact neuronal transcriptional expression, creating unique transcriptomes of individual neurons, possibly contributing to the uniqueness of the individual cognition and mental disorders in humans. PMID:26895053

  11. PET imaging of adoptive progenitor cell therapies.

    SciTech Connect

    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

  12. Stem/Progenitor cells in vascular regeneration.

    PubMed

    Zhang, Li; Xu, Qingbo

    2014-06-01

    A series of studies has been presented in the search for proof of circulating and resident vascular progenitor cells, which can differentiate into endothelial and smooth muscle cells and pericytes in animal and human studies. In terms of pluripotent stem cells, including embryonic stem cells, iPS, and partial-iPS cells, they display a great potential for vascular lineage differentiation. Development of stem cell therapy for treatment of vascular and ischemic diseases remains a major challenging research field. At the present, there is a clear expansion of research into mechanisms of stem cell differentiation into vascular lineages that are tested in animal models. Although there are several clinical trials ongoing that primarily focus on determining the benefits of stem cell transplantation in ischemic heart or peripheral ischemic tissues, intensive investigation for translational aspects of stem cell therapy would be needed. It is a hope that stem cell therapy for vascular diseases could be developed for clinic application in the future.

  13. Multipotent pancreas progenitors: Inconclusive but pivotal topic.

    PubMed

    Jiang, Fang-Xu; Morahan, Grant

    2015-12-26

    The establishment of multipotent pancreas progenitors (MPP) should have a significant impact not only on the ontology of the pancreas, but also for the translational research of glucose-responding endocrine β-cells. Deficiency of the latter may lead to the pandemic type 1 or type 2 diabetes mellitus, a metabolic disorder. An ideal treatment of which would potentially be the replacement of destroyed or failed β-cells, by restoring function of endogenous pancreatic endocrine cells or by transplantation of donor islets or in vitro generated insulin-secreting cells. Thus, considerable research efforts have been devoted to identify MPP candidates in the pre- and post-natal pancreas for the endogenous neogenesis or regeneration of endocrine insulin-secreting cells. In order to advance this inconclusive but critical field, we here review the emerging concepts, recent literature and newest developments of potential MPP and propose measures that would assist its forward progression. PMID:26730269

  14. Endothelial progenitor cell dysfunction in rheumatic disease.

    PubMed

    Westerweel, Peter E; Verhaar, Marianne C

    2009-06-01

    Rheumatic disease is characterized by inflammation and endothelial dysfunction, which contribute to accelerated atherosclerosis. Circulating endothelial progenitor cells (EPCs) can restore dysfunctional endothelium and thereby protect against atherosclerotic vascular disease. The number and function of EPCs are, however, affected in rheumatic diseases such as psoriatic arthritis, rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, and antineutrophil cytoplasmic autoantibody-associated vasculitis. rheumatic disease is often characterized by decreased numbers, and impaired function, of EPCs, although numbers of these cells might increase during the initial years of systemic sclerosis. Pioneering studies show that EPC dysfunction might be improved with pharmacological treatment. How best to restore EPC function, and whether achieving this aim can prevent long-term cardiovascular complications in rheumatic disease, remain to be established.

  15. Progenitor model of cosmic ray knee

    NASA Astrophysics Data System (ADS)

    Bijay, Biplab; Bhadra, Arunava

    2016-01-01

    The primary energy spectrum of cosmic rays exhibits a knee at about 3 PeV where a change in the spectral index occurs. Despite many efforts, the origin of such a feature in the spectrum is not satisfactorily solved yet. Here it is proposed that the steepening of the spectrum beyond the knee may be a consequence of the mass distribution of the progenitor of the cosmic ray source. The proposed speculative model can account for all the major observed features of cosmic rays without invoking any fine tuning to match flux or spectra at any energy point. The prediction of the proposed model regarding the primary composition scenario beyond the knee is quite different from most of the prevailing models of the knee, and thereby can be discriminated from precise experimental measurement of the primary composition.

  16. Redefining endothelial progenitor cells via clonal analysis and hematopoietic stem/progenitor cell principals.

    PubMed

    Yoder, Mervin C; Mead, Laura E; Prater, Daniel; Krier, Theresa R; Mroueh, Karim N; Li, Fang; Krasich, Rachel; Temm, Constance J; Prchal, Josef T; Ingram, David A

    2007-03-01

    The limited vessel-forming capacity of infused endothelial progenitor cells (EPCs) into patients with cardiovascular dysfunction may be related to a misunderstanding of the biologic potential of the cells. EPCs are generally identified by cell surface antigen expression or counting in a commercially available kit that identifies "endothelial cell colony-forming units" (CFU-ECs). However, the origin, proliferative potential, and differentiation capacity of CFU-ECs is controversial. In contrast, other EPCs with blood vessel-forming ability, termed endothelial colony-forming cells (ECFCs), have been isolated from human peripheral blood. We compared the function of CFU-ECs and ECFCs and determined that CFU-ECs are derived from the hematopoietic system using progenitor assays, and analysis of donor cells from polycythemia vera patients harboring a Janus kinase 2 V617F mutation in hematopoietic stem cell clones. Further, CFU-ECs possess myeloid progenitor cell activity, differentiate into phagocytic macrophages, and fail to form perfused vessels in vivo. In contrast, ECFCs are clonally distinct from CFU-ECs, display robust proliferative potential, and form perfused vessels in vivo. Thus, these studies establish that CFU-ECs are not EPCs and the role of these cells in angiogenesis must be re-examined prior to further clinical trials, whereas ECFCs may serve as a potential therapy for vascular regeneration. PMID:17053059

  17. Class E power amplifiers for wireless communications

    NASA Astrophysics Data System (ADS)

    Sowlati Hashjani, Tirdad

    In this thesis, the use of Class E power amplifiers for digital wireless communication applications is presented for the first time. A linear transmitter design using Class E amplifier is proposed for the North American Digital Cellular Standard. In this architecture, a phase correcting feedback loop is used to cancel the AM-PM distortion in Class E power amplifier. Several low voltage Class E power amplifiers, and the phase correcting feedback loop are designed and implemented in a commercially available 0.8 mum GaAs MESFET process. A fully integrated Class E power module operating at 835 MHz is presented. The power module consists of a Class F driver stage and a Class E power amplifier, and delivers 250 mW to the standard 50 Omega load with a power added efficiency of 51%. The design and implementation of a hybrid Class E power module operating at 835 MHz is also discussed. In this design, the output matching network is implemented on an alumina substrate, and has a lower power dissipation than its GaAs counterpart. The power module delivers 443 mW to the 50 Omega load with a power added efficiency of 67%. A 1.8 GHz fully integrated Class E power module is also presented. In this case, the power module delivers 200 mW of power to the 50 Omega load with a power added efficiency of 57%. The design and implementation of the phase correcting feedback loop, which consists of a limiting amplifier, a phase detector and two phase shifters, are discussed. The phase correcting feedback loop is used to linearize the 835 MHz Class E hybrid power module. With a loop gain of 20, the maximum phase distortion in the power module was reduced from 30sp° to 4sp° and the total power added efficiency was 65%.

  18. Transverse intensity transformation by laser amplifiers

    NASA Astrophysics Data System (ADS)

    Litvin, Igor A.; King, Gary; Collett, Oliver J. P.; Strauss, Hencharl J.

    2015-03-01

    Lasers beams with a specific intensity profile such as super-Gaussian, Airy or Dougnut-like are desirable in many applications such as laser materials processing, medicine and communications. We propose a new technique for laser beam shaping by amplifying a beam in an end-pumped bulk amplifier that is pumped with a beam that has a modified intensity profile. Advantages of this method are that it is relatively easy to implement, has the ability to reshape multimode beams and is naturally suited to high power/energy beams. Both three and four level gain materials can be used as amplifier media. However, a big advantage of using three level materials is their ability to attenuate of the seed beam, which enhances the contrast of the shaping. We first developed a numerical method to obtain the required pump intensity for an arbitrary beam transformation. This method was subsequently experimentally verified using a three level system. The output of a 2.07 μm seed laser was amplified in a Ho:YLF bulk amplifier which was being pumped by a 1.89 μm Tm:YLF laser which had roughly a TEM10 Hermit Gaussian intensity profile. The seed beam was amplified from 0.3 W to 0.55 W at the full pump power of 35 W. More importantly, the beam profile in one transverse direction was significantly shaped from Gaussian to roughly flat-top, as the model predicted. The concept has therefore been shown to be viable and can be used to optimise the beam profile for a wide range of applications.

  19. The dynamics of murine mammary stem/progenitor cells

    PubMed Central

    DONG, Qiaoxiang; SUN, Lu-Zhe

    2014-01-01

    The stem/progenitor cells in the murine mammary gland are a highly dynamic population of cells that are responsible for ductal elongation in puberty, homeostasis maintenance in adult, and lobulo-alveolar genesis during pregnancy. In recent years understanding the epithelial cell hierarchy within the mammary gland is becoming particularly important as these different stem/progenitor cells were perceived to be the cells of origin for various subtypes of breast cancer. Although significant advances have been made in enrichment and isolation of stem/progenitor cells by combinations of antibodies against cell surface proteins together with flow cytometry, and in identification of stem/progenitor cells with multi-lineage differentiation and self-renewal using mammary fat pad reconstitution assay and in vivo genetic labeling technique, a clear understanding of how these different stem/progenitors are orchestrated in the mammary gland is still lacking. Here we discuss the different in vivo and in vitro methods currently available for stem/progenitor identification, their associated caveats, and a possible new hierarchy model to reconcile various putative stem/progenitor cell populations identified by different research groups. PMID:25580105

  20. Neuraminidase enhances in vitro expansion of human erythroid progenitors.

    PubMed

    Bodivit, Gwellaouen; Chadebech, Philippe; Vigon, Isabelle; Yacia, Azzedine; Roziers, Nicolas Burin des; Pirenne, France; Fichelson, Serge

    2016-06-01

    In spite of recent key improvements, in vitro mass production of erythrocytes from human stem cells is still limited by difficulties in obtaining sufficient numbers of erythroid progenitors. In fact, such progenitors are as scarce in the bone marrow as in peripheral blood. We used a two-step culture model of human cord blood-derived erythroid progenitors in the presence or absence of high-purity neuraminidase, in a serum-free, defined culture medium. Granulocytic and megakaryocytic progenitor cell expansions were also studied. We show that significant enhancement of erythroid cell generation is obtained when CD34(+) human hematopoietic progenitors are cultured in the presence of neuraminidase. Interestingly, in so doing, expanded red cell progenitors remained erythropoietin-dependent for further expansion and survival, and cells thus generated displayed a normal phenotype. Moreover, the activity of neuraminidase on these cells can be reversed by simple cell washing. Finally, growth of cells of the other myeloid lineages (granulocytes and megakaryocytes) is either decreased or unchanged in the presence of neuraminidase. This specific feature of neuraminidase, that of stimulation of human red cell progenitor proliferation, provides a safe technique for producing greater numbers of in vitro-generated red blood cells for both basic research and transfusion use. PMID:27478075

  1. Caspase-1 mediates hyperlipidemia-weakened progenitor cell vessel repair

    PubMed Central

    Li, Ya-Feng; Huang, Xiao; Li, Xinyuan; Gong, Ren; Yin, Ying; Nelson, Jun; Gao, Erhe; Zhang, Hongyu; Hoffman, Nicholas E.; Houser, Steven R.; Madesh, Muniswamy; Tilley, Douglas G.; Choi, Eric T.; Jiang, Xiaohua; Huang, Cong-Xin; Wang, Hong; Yang, Xiao-Feng

    2015-01-01

    Caspase-1 activation senses metabolic danger-associated molecular patterns (DAMPs) and mediates the initiation of inflammation in endothelial cells. Here, we examined whether the caspase-1 pathway is responsible for sensing hyperlipidemia as a DAMP in bone marrow (BM)-derived Stem cell antigen-1 positive (Sca-1+) stem/progenitor cells and weakening their angiogenic ability. Using biochemical methods, gene knockout, cell therapy and myocardial infarction (MI) models, we had the following findings: 1) Hyperlipidemia induces caspase-1 activity in mouse Sca-1+ progenitor cells in vivo; 2) Caspase-1 contributes to hyperlipidemia-induced modulation of vascular cell death-related gene expression in vivo; 3) Injection of Sca-1+ progenitor cells from caspase-1−/− mice improves endothelial capillary density in heart and decreases cardiomyocyte death in a mouse model of MI; and 4) Caspase-1−/− Sca-1+ progenitor cell therapy improves mouse cardiac function after MI. Our results provide insight on how hyperlipidemia activates caspase-1 in Sca-1+ progenitor cells, which subsequently weakens Sca-1+ progenitor cell repair of vasculature injury. These results demonstrate the therapeutic potential of caspase-1 inhibition in improving progenitor cell therapy for MI. PMID:26709768

  2. Direct transcriptional reprogramming of adult cells to embryonic nephron progenitors.

    PubMed

    Hendry, Caroline E; Vanslambrouck, Jessica M; Ineson, Jessica; Suhaimi, Norseha; Takasato, Minoru; Rae, Fiona; Little, Melissa H

    2013-09-01

    Direct reprogramming involves the enforced re-expression of key transcription factors to redefine a cellular state. The nephron progenitor population of the embryonic kidney gives rise to all cells within the nephron other than the collecting duct through a mesenchyme-to-epithelial transition, but this population is exhausted around the time of birth. Here, we sought to identify the conditions under which adult proximal tubule cells could be directly transcriptionally reprogrammed to nephron progenitors. Using a combinatorial screen for lineage-instructive transcription factors, we identified a pool of six genes (SIX1, SIX2, OSR1, EYA1, HOXA11, and SNAI2) that activated a network of genes consistent with a cap mesenchyme/nephron progenitor phenotype in the adult proximal tubule (HK2) cell line. Consistent with these reprogrammed cells being nephron progenitors, we observed differential contribution of the reprogrammed population into the Six2(+) nephron progenitor fields of an embryonic kidney explant. Dereplication of the pool suggested that SNAI2 can suppress E-CADHERIN, presumably assisting in the epithelial-to-mesenchymal transition (EMT) required to form nephron progenitors. However, neither TGFβ-induced EMT nor SNAI2 overexpression alone was sufficient to create this phenotype, suggesting that additional factors are required. In conclusion, these results suggest that reinitiation of kidney development from a population of adult cells by generating embryonic progenitors may be feasible, opening the way for additional cellular and bioengineering approaches to renal repair and regeneration.

  3. Master-Oscillator/Power-Amplifier Laser System

    NASA Technical Reports Server (NTRS)

    Yu, Anthony W.; Krainak, Michael A.; Unger, Glenn L.

    1994-01-01

    Master-oscillator/power-amplifier (MOPA) laser system operates in continuous-wave mode or in amplitude-modulation (e.g., pulse) mode by modulation of oscillator current. Power amplifier is laser-diode-pumped neodymium:yttrium lithium fluoride (Nd:YLF) laser; oscillator is laser diode. Offers relatively high efficiency and power. Because drive current to oscillator modulated, external electro-optical modulator not needed. Potential uses include free-space optical communications, coded laser ranging, and generation of high-power, mode-locked pulses.

  4. Beyond nonlinear saturation of backward Raman amplifiers

    NASA Astrophysics Data System (ADS)

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A.; Fisch, Nathaniel J.

    2016-06-01

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. Pump detuning is employed to mitigate the relativistic phase mismatch and to overcome the associated saturation. The amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. This detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small.

  5. Beyond nonlinear saturation of backward Raman amplifiers.

    PubMed

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A; Fisch, Nathaniel J

    2016-06-01

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. Pump detuning is employed to mitigate the relativistic phase mismatch and to overcome the associated saturation. The amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. This detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small. PMID:27415380

  6. Cryogenic transimpedance amplifier for micromechanical capacitive sensors.

    PubMed

    Antonio, D; Pastoriza, H; Julián, P; Mandolesi, P

    2008-08-01

    We developed a cryogenic transimpedance amplifier that works at a broad range of temperatures, from room temperature down to 4 K. The device was realized with a standard complementary metal oxide semiconductor 1.5 mum process. Measurements of current-voltage characteristics, open-loop gain, input referred noise current, and power consumption are presented as a function of temperature. The transimpedance amplifier has been successfully applied to sense the motion of a polysilicon micromechanical oscillator at low temperatures. The whole device is intended to serve as a magnetometer for microscopic superconducting samples.

  7. Beyond nonlinear saturation of backward Raman amplifiers

    DOE PAGESBeta

    Barth, Ido; Toroker, Zeev; Balakin, Alexey A.; Fisch, Nathaniel J.

    2016-06-27

    Backward Raman amplification is limited by relativistic nonlinear dephasing resulting in saturation of the leading spike of the amplified pulse. We employed pump detuning in order to mitigate the relativistic phase mismatch and to overcome the associated saturation. In an amplified pulse can then be reshaped into a monospike pulse with little precursory power ahead of it, with the maximum intensity increasing by a factor of two. Finally, this detuning can be employed advantageously both in regimes where the group velocity dispersion is unimportant and where the dispersion is important but small.

  8. In vitro toxicity of trichothecenes on human haematopoietic progenitors.

    PubMed

    Parent-Massin, D; Fuselier, R; Thouvenot, D

    1994-01-01

    The culture of human haematopoietic progenitors, Colony-Forming-Unit Granulocyte and Macrophage (CFU-GM), has been performed in the presence of four trichothecenes, T-2 toxin, HT-2 toxin, diacetoxyscirpenol (DAS), and deoxynivalenol (DON). Our results showed that trichothecenes were cytotoxic for human haematopoietic progenitors. This work and the analysis of results described in the literature allowed us to propose that the haematologic lesions observed during human intoxication could be due to a destruction of haematopoietic progenitors such as granulocytic and macrophage colony-forming cells.

  9. Vascular smooth muscle progenitor cells: building and repairing blood vessels.

    PubMed

    Majesky, Mark W; Dong, Xiu Rong; Regan, Jenna N; Hoglund, Virginia J

    2011-02-01

    Molecular pathways that control the specification, migration, and number of available smooth muscle progenitor cells play key roles in determining blood vessel size and structure, capacity for tissue repair, and progression of age-related disorders. Defects in these pathways produce malformations of developing blood vessels, depletion of smooth muscle progenitor cell pools for vessel wall maintenance and repair, and aberrant activation of alternative differentiation pathways in vascular disease. A better understanding of the molecular mechanisms that uniquely specify and maintain vascular smooth muscle cell precursors is essential if we are to use advances in stem and progenitor cell biology and somatic cell reprogramming for applications directed to the vessel wall.

  10. Measuring the energy of amplified spontaneous emission (ASE) in a short pulse laser amplifier

    NASA Astrophysics Data System (ADS)

    Iliev, Marin; Adams, Daniel; Greco, Michael; Meier, Amanda; Squier, Jeff; Durfee, Charles

    2010-10-01

    In high-gain pulsed laser amplifiers, amplified spontaneous emission (ASE) tends to limit the gain in single stage fiber amplifiers. Even if ASE is not strong enough to deplete the gain of the amplifier, it still contributes strongly to a low-intensity background output in the amplified signal. The intensity contrast between the amplified short pulse and this background ASE pedestal can be measured with third-order autocorrelation, but this method cannot be used to completely specify the ASE's energy, which is distributed over many nanoseconds. We have developed a novel method that allows us to determine the energy and the spectrum of the ASE. We use a cross polarized wave (XPW) generating crystal such as BaF2 to ``clean up'' the ASE from the short pulse(SP). The input pulse (SP and ASE) and the cross-polarized signal are passed through a birefringent crystal such as sapphire. The relative group velocity difference along each crystal axis results in a delay between both channels. After passing through a polarizer, an interferogram is obtained in a spectrometer. This interferogram results from interference of the XPW pulse with the short-pulse content of the amplifier output, with a background of the ASE spectrum. Fourier analysis yields both the ASE energy and its spectrum.

  11. AMPLIFIED TELEPHONE AS A TEACHING MEDIUM.

    ERIC Educational Resources Information Center

    JOLLY, JOAN; MADDEN, CHARLES F.

    A GRANT TOTALING $58,400 FROM THE FUND FOR THE ADVANCEMENT OF EDUCATION ENABLED STEPHENS COLLEGE TO INITIATE AN EXPERIMENTAL EDUCATIONAL PROGRAM BY WHICH AMPLIFIED TELEPHONE COMMUNICATION BROUGHT HIGH-QUALITY INSTRUCTION TO GROUPS OF SMALL LIBERAL ARTS COLLEGES. A "MASTER TEACHER" ORGANIZED AND PRESENTED THE BASIC MATERIALS OF THE COURSE. PERSONS…

  12. Wide-Temperature-Range Integrated Operational Amplifier

    NASA Technical Reports Server (NTRS)

    Mojarradi, Mohammad; Levanas, Greg; Chen, Yuan; Kolawa, Elizabeth; Cozy, Raymond; Blalock, Benjamin; Greenwell, Robert; Terry, Stephen

    2007-01-01

    A document discusses a silicon-on-insulator (SOI) complementary metal oxide/semiconductor (CMOS) integrated- circuit operational amplifier to be replicated and incorporated into sensor and actuator systems of Mars-explorer robots. This amplifier is designed to function at a supply potential less than or equal to 5.5 V, at any temperature from -180 to +120 C. The design is implemented on a commercial radiation-hard SOI CMOS process rated for a supply potential of less than or equal to 3.6 V and temperatures from -55 to +110 C. The design incorporates several innovations to achieve this, the main ones being the following: NMOS transistor channel lengths below 1 m are generally not used because research showed that this change could reduce the adverse effect of hot carrier injection on the lifetimes of transistors at low temperatures. To enable the amplifier to withstand the 5.5-V supply potential, a circuit topology including cascade devices, clamping devices, and dynamic voltage biasing was adopted so that no individual transistor would be exposed to more than 3.6 V. To minimize undesired variations in performance over the temperature range, the transistors in the amplifier are biased by circuitry that maintains a constant inversion coefficient over the temperature range.

  13. Stereoscopy Amplifies Emotions Elicited by Facial Expressions

    PubMed Central

    Kätsyri, Jari; Häkkinen, Jukka

    2015-01-01

    Mediated facial expressions do not elicit emotions as strongly as real-life facial expressions, possibly due to the low fidelity of pictorial presentations in typical mediation technologies. In the present study, we investigated the extent to which stereoscopy amplifies emotions elicited by images of neutral, angry, and happy facial expressions. The emotional self-reports of positive and negative valence (which were evaluated separately) and arousal of 40 participants were recorded. The magnitude of perceived depth in the stereoscopic images was manipulated by varying the camera base at 15, 40, 65, 90, and 115 mm. The analyses controlled for participants’ gender, gender match, emotional empathy, and trait alexithymia. The results indicated that stereoscopy significantly amplified the negative valence and arousal elicited by angry expressions at the most natural (65 mm) camera base, whereas stereoscopy amplified the positive valence elicited by happy expressions in both the narrowed and most natural (15–65 mm) base conditions. Overall, the results indicate that stereoscopy amplifies the emotions elicited by mediated emotional facial expressions when the depth geometry is close to natural. The findings highlight the sensitivity of the visual system to depth and its effect on emotions. PMID:27551358

  14. Stereoscopy Amplifies Emotions Elicited by Facial Expressions.

    PubMed

    Hakala, Jussi; Kätsyri, Jari; Häkkinen, Jukka

    2015-12-01

    Mediated facial expressions do not elicit emotions as strongly as real-life facial expressions, possibly due to the low fidelity of pictorial presentations in typical mediation technologies. In the present study, we investigated the extent to which stereoscopy amplifies emotions elicited by images of neutral, angry, and happy facial expressions. The emotional self-reports of positive and negative valence (which were evaluated separately) and arousal of 40 participants were recorded. The magnitude of perceived depth in the stereoscopic images was manipulated by varying the camera base at 15, 40, 65, 90, and 115 mm. The analyses controlled for participants' gender, gender match, emotional empathy, and trait alexithymia. The results indicated that stereoscopy significantly amplified the negative valence and arousal elicited by angry expressions at the most natural (65 mm) camera base, whereas stereoscopy amplified the positive valence elicited by happy expressions in both the narrowed and most natural (15-65 mm) base conditions. Overall, the results indicate that stereoscopy amplifies the emotions elicited by mediated emotional facial expressions when the depth geometry is close to natural. The findings highlight the sensitivity of the visual system to depth and its effect on emotions. PMID:27551358

  15. NON-BLOCKING STABILIZED FEED BACK AMPLIFIER

    DOEpatents

    Fairstein, E.

    1960-03-01

    A plural stuge nonblocking degenerative feed-back amplifier was designed particularly suitable for counting circuits because of the stability and linearity in operation, characterized by the fact that the inltial stage employs a cathode coupled input circuit fed from a cathode follower and the final stage has a tline constant greater than those of the other stages.

  16. Stereoscopy Amplifies Emotions Elicited by Facial Expressions.

    PubMed

    Hakala, Jussi; Kätsyri, Jari; Häkkinen, Jukka

    2015-12-01

    Mediated facial expressions do not elicit emotions as strongly as real-life facial expressions, possibly due to the low fidelity of pictorial presentations in typical mediation technologies. In the present study, we investigated the extent to which stereoscopy amplifies emotions elicited by images of neutral, angry, and happy facial expressions. The emotional self-reports of positive and negative valence (which were evaluated separately) and arousal of 40 participants were recorded. The magnitude of perceived depth in the stereoscopic images was manipulated by varying the camera base at 15, 40, 65, 90, and 115 mm. The analyses controlled for participants' gender, gender match, emotional empathy, and trait alexithymia. The results indicated that stereoscopy significantly amplified the negative valence and arousal elicited by angry expressions at the most natural (65 mm) camera base, whereas stereoscopy amplified the positive valence elicited by happy expressions in both the narrowed and most natural (15-65 mm) base conditions. Overall, the results indicate that stereoscopy amplifies the emotions elicited by mediated emotional facial expressions when the depth geometry is close to natural. The findings highlight the sensitivity of the visual system to depth and its effect on emotions.

  17. LOW-LEVEL DIRECT CURRENT AMPLIFIER

    DOEpatents

    Kerns, Q.A.

    1959-05-01

    A d-c amplifier is described. Modulation is provided between a d-c signal and an alternating current to give an output signal proportional to the d- c signal. The circuit has high sensitivity and accuracy. (T.R.H.)

  18. Reflected-wave maser. [low noise amplifier

    NASA Technical Reports Server (NTRS)

    Clauss, R. C. (Inventor)

    1976-01-01

    A number of traveling-wave, slow-wave maser structures, containing active maser material but absent the typical ferrite isolators, are immersed in a nonuniform magnetic field. The microwave signal to be amplified is inserted at a circulator which directs the signal to a slow-wave structure. The signal travels through the slow-wave structure, being amplified according to the distance traveled. The end of the slow-wave structure farthest from the circulator is arranged to be a point of maximum reflection of the signal traveling through the slow-wave structure. As a consequence, the signal to be amplified traverses the slow-wave structure again, in the opposite direction (towards the circulator) experiencing amplification equivalent to that achieved by a conventional traveling-wave maser having twice the length. The circulator directs the amplified signal to following like stages of amplification. Isolators are used in between stages to prevent signals from traveling in the wrong direction, between the stages. Reduced signal loss is experienced at each stage. The high gain produced by each slow-wave structure is reduced to a moderate value by use of a nonuniform magnetic field which also broadens the line width of the maser material. The resulting bandwidth can be exceptionally wide. Cascaded stages provide high gain, exceptionally wide bandwith and very low noise temperature.

  19. Simulations of the LANL regenerative amplifier FEL

    SciTech Connect

    Kesselring, M.; Colson, W.B.; Wong, R.K.; Sheffield, R.L.

    1997-08-01

    The LANL regenerative amplifier FEL is designed to produce an average output power of 1 kW. Simulations study the transverse effects due to guiding by the intense electron beam and feedback. These simulations coupled with experimental measurements can be used to improve future high-power FEL designs.

  20. Analysis of a multistable semiconductor light amplifier

    SciTech Connect

    Otsuka, K.; Iwamura, H.

    1983-07-01

    A multistable operation in semiconductor laser amplifiers, based upon the carrier density dependence of the active region refractive index, is proposed. Simple analytical expressions describing the optical multistability are given, using the so-called antiguidance factor, which is the ratio of the decrease in the real refractive index to the increase in the imaginary refractive index.

  1. Narrow-linewidth master-oscillator power amplifier based on a semiconductor tapered amplifier.

    PubMed

    Wilson, A C; Sharpe, J C; McKenzie, C R; Manson, P J; Warrington, D M

    1998-07-20

    The output of a grating-stabilized external-cavity diode laser was injected into a semiconductor tapered amplifier in a master-oscillator power amplifier configuration, producing as much as 500 mW of power with narrow linewidth. The additional linewidth that is due to the tapered amplifier is much smaller than the typical linewidth of grating-stabilized laser diodes. To demonstrate the usefulness of the narrow linewidth and high output power, we used the system to perform Doppler-free two-photon spectroscopy with rubidium. PMID:18285950

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

    DOEpatents

    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.

  3. Stem and progenitor cell dysfunction in human trisomies

    PubMed Central

    Liu, Binbin; Filippi, Sarah; Roy, Anindita; Roberts, Irene

    2015-01-01

    Trisomy 21, the commonest constitutional aneuploidy in humans, causes profound perturbation of stem and progenitor cell growth, which is both cell context dependent and developmental stage specific and mediated by complex genetic mechanisms beyond increased Hsa21 gene dosage. While proliferation of fetal hematopoietic and testicular stem/progenitors is increased and may underlie increased susceptibility to childhood leukemia and testicular cancer, fetal stem/progenitor proliferation in other tissues is markedly impaired leading to the characteristic craniofacial, neurocognitive and cardiac features in individuals with Down syndrome. After birth, trisomy 21-mediated premature aging of stem/progenitor cells may contribute to the progressive multi-system deterioration, including development of Alzheimer's disease. PMID:25520324

  4. Identification and characterization of an injury-induced skeletal progenitor

    PubMed Central

    Marecic, Owen; Tevlin, Ruth; McArdle, Adrian; Seo, Eun Young; Wearda, Taylor; Duldulao, Christopher; Walmsley, Graham G.; Nguyen, Allison; Weissman, Irving L.; Chan, Charles K. F.; Longaker, Michael T.

    2015-01-01

    The postnatal skeleton undergoes growth, remodeling, and repair. We hypothesized that skeletal progenitor cells active during these disparate phases are genetically and phenotypically distinct. We identified a highly potent regenerative cell type that we term the fracture-induced bone, cartilage, stromal progenitor (f-BCSP) in the fracture callus of adult mice. The f-BCSP possesses significantly enhanced skeletogenic potential compared with BCSPs harvested from uninjured bone. It also recapitulates many gene expression patterns involved in perinatal skeletogenesis. Our results indicate that the skeletal progenitor population is functionally stratified, containing distinct subsets responsible for growth, regeneration, and repair. Furthermore, our findings suggest that injury-induced changes to the skeletal stem and progenitor microenvironments could activate these cells and enhance their regenerative potential. PMID:26216955

  5. Identification and characterization of an injury-induced skeletal progenitor.

    PubMed

    Marecic, Owen; Tevlin, Ruth; McArdle, Adrian; Seo, Eun Young; Wearda, Taylor; Duldulao, Christopher; Walmsley, Graham G; Nguyen, Allison; Weissman, Irving L; Chan, Charles K F; Longaker, Michael T

    2015-08-11

    The postnatal skeleton undergoes growth, remodeling, and repair. We hypothesized that skeletal progenitor cells active during these disparate phases are genetically and phenotypically distinct. We identified a highly potent regenerative cell type that we term the fracture-induced bone, cartilage, stromal progenitor (f-BCSP) in the fracture callus of adult mice. The f-BCSP possesses significantly enhanced skeletogenic potential compared with BCSPs harvested from uninjured bone. It also recapitulates many gene expression patterns involved in perinatal skeletogenesis. Our results indicate that the skeletal progenitor population is functionally stratified, containing distinct subsets responsible for growth, regeneration, and repair. Furthermore, our findings suggest that injury-induced changes to the skeletal stem and progenitor microenvironments could activate these cells and enhance their regenerative potential.

  6. Ultra-stripped supernovae: progenitors and fate

    NASA Astrophysics Data System (ADS)

    Tauris, Thomas M.; Langer, Norbert; Podsiadlowski, Philipp

    2015-08-01

    The explosion of ultra-stripped stars in close binaries can lead to ejecta masses <0.1 M⊙ and may explain some of the recent discoveries of weak and fast optical transients. In Tauris et al., it was demonstrated that helium star companions to neutron stars (NSs) may experience mass transfer and evolve into naked ˜1.5 M⊙ metal cores, barely above the Chandrasekhar mass limit. Here, we elaborate on this work and present a systematic investigation of the progenitor evolution leading to ultra-stripped supernovae (SNe). In particular, we examine the binary parameter space leading to electron-capture (EC SNe) and iron core-collapse SNe (Fe CCSNe), respectively, and determine the amount of helium ejected with applications to their observational classification as Type Ib or Type Ic. We mainly evolve systems where the SN progenitors are helium star donors of initial mass MHe = 2.5-3.5 M⊙ in tight binaries with orbital periods of Porb = 0.06-2.0 d, and hosting an accreting NS, but we also discuss the evolution of wider systems and of both more massive and lighter - as well as single - helium stars. In some cases, we are able to follow the evolution until the onset of silicon burning, just a few days prior to the SN explosion. We find that ultra-stripped SNe are possible for both EC SNe and Fe CCSNe. EC SNe only occur for MHe = 2.60-2.95 M⊙ depending on Porb. The general outcome, however, is an Fe CCSN above this mass interval and an ONeMg or CO white dwarf for smaller masses. For the exploding stars, the amount of helium ejected is correlated with Porb - the tightest systems even having donors being stripped down to envelopes of less than 0.01 M⊙. We estimate the rise time of ultra-stripped SNe to be in the range 12 h-8 d, and light-curve decay times between 1 and 50 d. A number of fitting formulae for our models are provided with applications to population synthesis. Ultra-stripped SNe may produce NSs in the mass range 1.10-1.80 M⊙ and are highly relevant for

  7. Low phase noise oscillator using two parallel connected amplifiers

    NASA Technical Reports Server (NTRS)

    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.

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

    PubMed

    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.

  9. Cochlear progenitor number is controlled through mesenchymal FGF receptor signaling

    PubMed Central

    Huh, Sung-Ho; Warchol, Mark E; Ornitz, David M

    2015-01-01

    The sensory and supporting cells (SCs) of the organ of Corti are derived from a limited number of progenitors. The mechanisms that regulate the number of sensory progenitors are not known. Here, we show that Fibroblast Growth Factors (FGF) 9 and 20, which are expressed in the non-sensory (Fgf9) and sensory (Fgf20) epithelium during otic development, regulate the number of cochlear progenitors. We further demonstrate that Fgf receptor (Fgfr) 1 signaling within the developing sensory epithelium is required for the differentiation of outer hair cells and SCs, while mesenchymal FGFRs regulate the size of the sensory progenitor population and the overall cochlear length. In addition, ectopic FGFR activation in mesenchyme was sufficient to increase sensory progenitor proliferation and cochlear length. These data define a feedback mechanism, originating from epithelial FGF ligands and mediated through periotic mesenchyme that controls the number of sensory progenitors and the length of the cochlea. DOI: http://dx.doi.org/10.7554/eLife.05921.001 PMID:25915623

  10. How Low Can They Go? Detecting low luminosity supernova progenitors

    NASA Astrophysics Data System (ADS)

    Fruchter, Andrew

    2013-10-01

    While we now discover thousands of supernovae {SNe} per year, in the history of astronomy a little more than a dozen SN progenitors have been identified, and all of these have been from Type II SNe. This dearth is largely due to the fact that the progenitors are destroyed in the SN, and so to study them one must have fortuitously taken data on them prior to their explosion. However, the fault may also partially lie with the methods employed to search for progenitors.In the past, searches have generally relied on looking at the location of a SNe in an archival image to see if a noticeable point source is at the right location. This method requires that the background field of the galaxy be relatively uniform, and if one wants an accurate estimate of the progenitor mangitude, that the star was not in an association or binary. Here we propose to take WFC3 images several years post explosion so that we can subtract them from archival WFPC2 images. We show that we can do this with extraordinary fidelity. We will apply this method to a well-chosen sample of three Type II SNe and two Type Ibc SNe, which lie on messy galaxy fields that may have camouflaged the presence of a progenitor. This method has the potential to detect or substantially deepen the limits on the progenitors of these objects, which already appear too faint for theoretical models.

  11. Age-related impairment of mesenchymal progenitor cell function.

    PubMed

    Stolzing, Alexandra; Scutt, Andrew

    2006-06-01

    In most mesenchymal tissues a subcompartment of multipotent progenitor cells is responsible for the maintenance and repair of the tissue following trauma. With increasing age, the ability of tissues to repair themselves is diminished, which may be due to reduced functional capacity of the progenitor cells. The purpose of this study was to investigate the effect of aging on rat mesenchymal progenitor cells. Mesenchymal progenitor cells were isolated from Wistar rats aged 3, 7, 12 and 56 weeks. Viability, capacity for differentiation and cellular aging were examined. Cells from the oldest group accumulated raised levels of oxidized proteins and lipids and showed decreased levels of antioxidative enzyme activity. This was reflected in decreased fibroblast colony-forming unit (CFU-f) numbers, increased levels of apoptosis and reduced proliferation and potential for differentiation. These data suggest that the reduced ability to maintain mesenchymal tissue homeostasis in aged mammals is not purely due to a decline in progenitor cells numbers but also to a loss of progenitor functionality due to the accumulation of oxidative damage, which may in turn be a causative factor in a number of age-related pathologies such as arthritis, tendinosis and osteoporosis.

  12. Harnessing endogenous stem/progenitor cells for tendon regeneration

    PubMed Central

    Lee, Chang H.; Lee, Francis Y.; Tarafder, Solaiman; Kao, Kristy; Jun, Yena; Yang, Guodong; Mao, Jeremy J.

    2015-01-01

    Current stem cell–based strategies for tissue regeneration involve ex vivo manipulation of these cells to confer features of the desired progenitor population. Recently, the concept that endogenous stem/progenitor cells could be used for regenerating tissues has emerged as a promising approach that potentially overcomes the obstacles related to cell transplantation. Here we applied this strategy for the regeneration of injured tendons in a rat model. First, we identified a rare fraction of tendon cells that was positive for the known tendon stem cell marker CD146 and exhibited clonogenic capacity, as well as multilineage differentiation ability. These tendon-resident CD146+ stem/progenitor cells were selectively enriched by connective tissue growth factor delivery (CTGF delivery) in the early phase of tendon healing, followed by tenogenic differentiation in the later phase. The time-controlled proliferation and differentiation of CD146+ stem/progenitor cells by CTGF delivery successfully led to tendon regeneration with densely aligned collagen fibers, normal level of cellularity, and functional restoration. Using siRNA knockdown to evaluate factors involved in tendon generation, we demonstrated that the FAK/ERK1/2 signaling pathway regulates CTGF-induced proliferation and differentiation of CD146+ stem/progenitor cells. Together, our findings support the use of endogenous stem/progenitor cells as a strategy for tendon regeneration without cell transplantation and suggest this approach warrants exploration in other tissues. PMID:26053662

  13. Amphidiploid Brassica juncea contains conserved progenitor genomes.

    PubMed

    Axelsson, T; Bowman, C M; Sharpe, A G; Lydiate, D J; Lagercrantz, U

    2000-08-01

    To perform a detailed study of genome evolution in the natural Brassica amphidiploid B. juncea, we have constructed two linkage maps based on RFLP (restriction fragment length polymorphism) markers; one generated from a cross between a resynthesized B. juncea (a chromosome doubled interspecific B. rapa x B. nigra hybrid) and a natural B. juncea cultivar, the other from a cross between two B. juncea cultivars. By using a common cultivar in both crosses, the two maps could be unambiguously integrated. All loci exhibited disomic inheritance of parental alleles in the natural x resynthesized cross, showing that B. rapa chromosomes paired exclusively with their A-genome homologues in B. juncea and that B. nigra chromosomes likewise paired with their B-genome homologues. The maps derived from the two crosses were also perfectly collinear. Furthermore, these maps were collinear with maps of the diploid progenitor species (B. nigra and B. rapa) produced using the same set of RFLP probes. These data indicate that the genome of B. juncea has remained essentially unchanged since polyploid formation. Our observations appear to refute the suggestion that the formation of polyploid genomes is accompanied by rapid change in genome structure.

  14. NFAT restricts osteochondroma formation from entheseal progenitors

    PubMed Central

    Tsang, Kelly; He, Lizhi; Garcia, Roberto A.; Ermann, Joerg; Mizoguchi, Fumitaka; Zhang, Minjie; Aliprantis, Antonios O.

    2016-01-01

    Osteochondromas are common benign osteocartilaginous tumors in children and adolescents characterized by cartilage-capped bony projections on the surface of bones. These tumors often cause pain, deformity, fracture, and musculoskeletal dysfunction, and they occasionally undergo malignant transformation. The pathogenesis of osteochondromas remains poorly understood. Here, we demonstrate that nuclear factor of activated T cells c1 and c2 (NFATc1 and NFATc2) suppress osteochondromagenesis through individual and combinatorial mechanisms. In mice, conditional deletion of NFATc1 in mesenchymal limb progenitors, Scleraxis-expressing (Scx-expressing) tendoligamentous cells, or postnatally in Aggrecan-expressing cells resulted in osteochondroma formation at entheses, the insertion sites of ligaments and tendons onto bone. Combinatorial deletion of NFATc1 and NFATc2 gave rise to larger and more numerous osteochondromas in inverse proportion to gene dosage. A population of entheseal NFATc1- and Aggrecan-expressing cells was identified as the osteochondroma precursor, previously believed to be growth plate derived or perichondrium derived. Mechanistically, we show that NFATc1 restricts the proliferation and chondrogenesis of osteochondroma precursors. In contrast, NFATc2 preferentially inhibits chondrocyte hypertrophy and osteogenesis. Together, our findings identify and characterize a mechanism of osteochondroma formation and suggest that regulating NFAT activity is a new therapeutic approach for skeletal diseases characterized by defective or exaggerated osteochondral growth. PMID:27158674

  15. The Binary Progenitor of Tycho Brahe's Supernova

    NASA Astrophysics Data System (ADS)

    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.

  16. Type Ia Supernova Models and Progenitor Scenarios

    NASA Astrophysics Data System (ADS)

    Nomoto, Ken'ichi; Kamiya, Yasuomi; Nakasato, Naohito

    2013-01-01

    We review some recent developments in theoretical studies on the connection between the progenitor systems of Type Ia supernovae (SNe Ia) and the explosion mechanisms. (1) DD-subCh: In the merging of double C+O white dwarfs (DD scenario), if the carbon detonation is induced near the white dwarf (WD) surface in the early dynamical phase, it could result in the (effectively) sub-Chandrasekhar mass explosion. (2) DD-Ch: If no surface C-detonation is ignited, the WD could grow until the Chandrasekhar mass is reached, but the outcome depends on whether the quiescent carbon shell burning is ignited and burns C+O into O+Ne+Mg. (3) SD-subCh: In the single degenerate (SD) scenario, if the He shell-flashes grow strong to induce a He detonation, it leads to the sub-Chandra explosion. (4) SD-Ch: If the He-shell flashes are not strong enough, they still produce interesting amounts of Si and S near the surface of the C+O WD before the explosion. In the Chandra mass explosion, the central density is high enough to produce electron capture elements, e.g., stable 58Ni. Observations of the emission lines of Ni in the nebular spectra provides useful diagnostics of the sub-Chandra vs. Chandra issue. The recent observations of relatively low velocity carbon near the surface of SNe Ia provide also an interesting constraint on the explosion models.

  17. Power-Amplifier Module for 145 to 165 GHz

    NASA Technical Reports Server (NTRS)

    Samoska, Lorene; Peralta, Alejandro

    2007-01-01

    A power-amplifier module that operates in the frequency range of 145 to 165 GHz has been designed and constructed as a combination of (1) a previously developed monolithic microwave integrated circuit (MMIC) power amplifier and (2) a waveguide module. The amplifier chip was needed for driving a high-electron-mobility-transistor (HEMT) frequency doubler. While it was feasible to connect the amplifier and frequency-doubler chips by use of wire bonds, it was found to be much more convenient to test the amplifier and doubler chips separately. To facilitate separate testing, it was decided to package the amplifier and doubler chips in separate waveguide modules. Figure 1 shows the resulting amplifier module. The amplifier chip was described in "MMIC HEMT Power Amplifier for 140 to 170 GHz" (NPO-30127), NASA Tech Briefs, Vol. 27, No. 11, (November 2003), page 49. To recapitulate: This is a three-stage MMIC power amplifier that utilizes HEMTs as gain elements. The amplifier was originally designed to operate in the frequency range of 140 to 170 GHz. The waveguide module is based on a previously developed lower frequency module, redesigned to support operation in the frequency range of 140 to 220 GHz. Figure 2 presents results of one of several tests of the amplifier module - measurements of output power and gain as functions of input power at an output frequency of 150 GHz. Such an amplifier module has many applications to test equipment for power sources above 100 GHz.

  18. Linear control of oscillator and amplifier flows*

    NASA Astrophysics Data System (ADS)

    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.

  19. Ideal photon number amplifier and duplicator

    NASA Technical Reports Server (NTRS)

    Dariano, G. M.

    1992-01-01

    The photon number-amplification and number-duplication mechanism are analyzed in the ideal case. The search for unitary evolutions leads to consider also a number-deamplification mechanism, the symmetry between amplification and deamplification being broken by the integer-value nature of the number operator. Both transformations, amplification and duplication, need an auxiliary field which, in the case of amplification, turns out to be amplified in the inverse way. Input-output energy conservation is accounted for using a classical pump or through frequency-conversion of the fields. Ignoring one of the fields is equivalent to considering the amplifier as an open system involving entropy production. The Hamiltonians of the ideal devices are given and compared with those of realistic systems.

  20. Review of two-stream amplifier performance

    NASA Astrophysics Data System (ADS)

    Phillips, Purobi M.; Freund, Henry P.; Zaidman, Ernest G.; Ganguly, Achintya K.; Vanderplaats, Norman R.

    1990-03-01

    The basic concept of the two-stream instability and its application in building a microwave/millimeter-wave amplifier are reviewed from the perspective of the general use of high-frequency devices. A historical review of the relevant literature is presented, with additional discussion of unpublished laboratory notebooks from the US Naval Research Laboratory. A summary of the theoretical background and its extension to the bounded three-dimensional case is given, along with results from one-dimensional nonlinear particle simulation, which is compared to nonlinear theory. The advantages, limitations, and shortcomings of a two-stream amplifier are discussed in comparison with other currently available devices that work in the same range of parameters.

  1. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Kim, K. H.; Stock, L. V.

    1986-01-01

    In order to evaluate the feasibility of the solar pumped dye laser, the parametric study of a dye laser amplifier pumped by a solar simulator and flashlamp was carried out, and the amplifier gains were measured at various pump beam irradiances on the dye cell. Rhodamine 6G was considered as a candidate for the solar pumped laser because of its good utilization of the solar spectrum and high quantum efficiency. The measurement shows that a solar concentration of 20,000 is required to reach the threshold of the dye. The work to construct a kinetic model algorithm which predicts the output parameter of laser was progressed. The kinetic model was improved such that there is good agreement between the theoretical model and experimental data for the systems defined previously as flashlamp pumped laser oscillator, and the long path length solar pumped laser.

  2. Solid state radiographic image amplifiers, part C

    NASA Technical Reports Server (NTRS)

    Szepesi, Z.

    1971-01-01

    The contrast sensitivity of the radiographic amplifiers, both the storage type and nonstorage type, their absolute sensitivity, and the reproducibility of fabrication were investigated. The required 2-2T quality level was reached with the radiographic storage screen. The sensitivity threshold was 100 to 200 mR with 45 to 100 kV filtered X-rays. The quality level of the radiographic amplifier screen (without storage) was 4-4T; for a 6 mm (0.25 in.) thick aluminum specimen, a 1 mm (0.040 in.) diameter hole in a 0.25 mm (0.010 in.) thick penetrameter was detected. Its sensitivity threshold was 2 to 6 mR/min. The developed radiographic screens are applicable for uses in nondestructive testing.

  3. First Lasing of the Regenerative Amplifier FEL

    SciTech Connect

    Nguyen, D.C.; Sheffield, R.L.; Fortang, C.M.; Goldstein, J.C.; Kinross-Wright, J.M.; Ebrahim, N.A.

    1998-08-17

    The Regenerative Amplifier Free-Electron Laser (RAFEL) is a high-gain RF-linac FEL capable of producing high optical power from a compact design. The combination of a high-gain and small optical feedback enables the FEL to reach saturation and produce a high optical power and high extraction efficiency without risk of optical damage to the mirrors. This paper summarizes the first lasing of the Regenerative Amplifier FEL and describes recent experimental results. The highest optical energy achieved thus far at 16.3 {micro}m is 1.7 J over an 9-{micro}s macropulse, corresponding to an average power during the macropulse of 190 kW. They deduce an energy of 1.7 mJ in each 16 ps micropulse, corresponding to a peak power of 110 MW.

  4. Magnetic Amplifier for Power Flow Control

    SciTech Connect

    2012-02-24

    GENI Project: ORNL is developing an electromagnet-based, amplifier-like device that will allow for complete control over the flow of power within the electric grid. To date, complete control of power flow within the grid has been prohibitively expensive. ORNL’s controller could provide a reliable, cost-effective solution to this problem. The team is combining two types of pre-existing technologies to assist in flow control, culminating in a prototype iron-based magnetic amplifier. Ordinarily, such a device would require expensive superconductive wire, but the magnetic iron core of ORNL’s device could serve as a low-cost alternative that is equally adept at regulating power flow.

  5. High power single-frequency Innoslab amplifier.

    PubMed

    Han, Ke-Zhen; Ning, Jian; Zhang, Bai-Tao; Wang, Yi-Ran; Zhang, Hai-Kun; Nie, Hong-Kun; Sun, Xiao-Li; He, Jing-Liang

    2016-07-10

    A laser diode array (LDA) end-pumped continuous-wave single-frequency Innoslab amplifier has been demonstrated. The Gaussian ray bundle method was used to model the light propagation in the Innoslab amplifier for the first time to the best of our knowledge. With discrete reflectors, the maximum output of 60 W with a linewidth of 44 MHz was achieved under the pump power of 245 W, corresponding to the optical-optical efficiency of 24.5%. The beam quality factor M2 at the output power of 51 W in the horizontal and vertical direction was measured to be 1.4 and 1.3, respectively. The long-term power instability in 2 h was less than 0.25%. PMID:27409308

  6. Matched wideband low-noise amplifiers for radio astronomy.

    PubMed

    Weinreb, S; Bardin, J; Mani, H; Jones, G

    2009-04-01

    Two packaged low noise amplifiers for the 0.3-4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300-4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<-10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range.

  7. Experimental research of a chain of diode pumped rubidium amplifiers.

    PubMed

    Li, Yunfei; Hua, Weihong; Li, Lei; Wang, Hongyan; Yang, Zining; Xu, Xiaojun

    2015-10-01

    In this paper, we have set up a diode pumped rubidium MOPA system with a chain of two amplifiers. The experimental results show an amplified laser power of 26W with amplification factor of 16.3 and power extraction efficiency of 53% for a single amplifier, and an amplified laser power of 11W with amplification factor of 7.9 and power extraction efficiency of 26% for a chain of two amplifiers. The reason for lower performance of cascade amplification is mainly due to the limited total pump power, which will be not sufficient for efficient pumping when assigned from a single amplifier into two amplifiers. The situation could be well improved by increasing the seed laser power as well as the pump power for each amplifier to realize high efficient saturated amplification. Such MOPA configuration has the potential for scaling high beam quality alkali laser into high powers. PMID:26480105

  8. Experimental research of a chain of diode pumped rubidium amplifiers.

    PubMed

    Li, Yunfei; Hua, Weihong; Li, Lei; Wang, Hongyan; Yang, Zining; Xu, Xiaojun

    2015-10-01

    In this paper, we have set up a diode pumped rubidium MOPA system with a chain of two amplifiers. The experimental results show an amplified laser power of 26W with amplification factor of 16.3 and power extraction efficiency of 53% for a single amplifier, and an amplified laser power of 11W with amplification factor of 7.9 and power extraction efficiency of 26% for a chain of two amplifiers. The reason for lower performance of cascade amplification is mainly due to the limited total pump power, which will be not sufficient for efficient pumping when assigned from a single amplifier into two amplifiers. The situation could be well improved by increasing the seed laser power as well as the pump power for each amplifier to realize high efficient saturated amplification. Such MOPA configuration has the potential for scaling high beam quality alkali laser into high powers.

  9. Erbium-doped-fiber optical limiting amplifiers

    NASA Astrophysics Data System (ADS)

    Graydon, Oliver C.; Nickolaos Zervas, Michael; Laming, Richard I.

    1995-05-01

    A novel configuration of an erbium-doped-fiber optical output-limiting amplifier (OLA) is presented which is realized by simply introducing a differential lump-loss between the signal and the pump power at a particular point along the fiber. The OLA exhibits an input-power dynamic range in excess of 40 dB and the capacity to control optically the level of the constant-output signal.

  10. Multiwatts narrow linewidth fiber Raman amplifiers.

    PubMed

    Feng, Yan; Taylor, Luke; Bonaccini Calia, Domenico

    2008-07-21

    Up to 4.8 W, approximately 10 MHz, 1178 nm laser is obtained by Raman amplification of a distributed feedback diode laser in standard single mode fibers pumped by an 1120 nm Yb fiber laser. More than 10% efficiency and 27 dB amplification is achieved, limited by onset of stimulated Brillouin scattering. The ratio of Raman to Brillouin gain coefficient of a fiber is identified as a figure of merit for building a narrow linewidth fiber Raman amplifier.

  11. Gas amplified ionization detector for gas chromatography

    DOEpatents

    Huston, Gregg C.

    1992-01-01

    A gas-amplified ionization detector for gas chromatrography which possesses increased sensitivity and a very fast response time. Solutes eluding from a gas chromatographic column are ionized by UV photoionization of matter eluting therefrom. The detector is capable of generating easily measured voltage signals by gas amplification/multiplication of electron products resulting from the UV photoionization of at least a portion of each solute passing through the detector.

  12. Phase stabilization of spatiotemporally multiplexed ultrafast amplifiers.

    PubMed

    Mueller, M; Kienel, M; Klenke, A; Eidam, T; Limpert, J; Tünnermann, A

    2016-04-18

    Actively stabilized, simultaneous spatial and temporal coherent beam combination is a promising power-scaling technique for ultrafast laser systems. For a temporal combination based on optical delay lines, multiple stable states of operation arise for common stabilization techniques. A time resolved Jones' calculus is applied to investigate the issue. A mitigation strategy based on a temporally gated error signal acquisition is derived and demonstrated, enabling to stabilize laser systems with arbitrary numbers of amplifier channels and optical delay lines. PMID:27137231

  13. Radiation and particle detector and amplifier

    NASA Technical Reports Server (NTRS)

    Schmidt, K. C. (Inventor)

    1973-01-01

    A radiation or charged particle detector is described which incorporates a channel multiplier structure to amplify the detected rays or particles. The channel multiplier structure has a support multiplying element with a longitudinal slot along one side. The element supports a pair of plates positioned contiguous with the slot. The plates funnel the particles or rays to be detected into the slotted aperture and the element, thus creating an effectively wide aperture detector of the windowless type.

  14. Reconfigurable Josephson Circulator/Directional Amplifier

    NASA Astrophysics Data System (ADS)

    Sliwa, K. M.; Hatridge, M.; Narla, A.; Shankar, S.; Frunzio, L.; Schoelkopf, R. J.; Devoret, M. H.

    2015-10-01

    Circulators and directional amplifiers are crucial nonreciprocal signal routing and processing components involved in microwave read-out chains for a variety of applications. They are particularly important in the field of superconducting quantum information, where the devices also need to have minimal photon losses to preserve the quantum coherence of signals. Conventional commercial implementations of each device suffer from losses and are built from very different physical principles, which has led to separate strategies for the construction of their quantum-limited versions. However, as recently theoretically, by establishing simultaneous pairwise conversion and/or gain processes between three modes of a Josephson-junction-based superconducting microwave circuit, it is possible to endow the circuit with the functions of either a phase-preserving directional amplifier or a circulator. Here, we experimentally demonstrate these two modes of operation of the same circuit. Furthermore, in the directional amplifier mode, we show that the noise performance is comparable to standard nondirectional superconducting amplifiers, while in the circulator mode, we show that the sense of circulation is fully reversible. Our device is far simpler in both modes of operation than previous proposals and implementations, requiring only three microwave pumps. It offers the advantage of flexibility, as it can dynamically switch between modes of operation as its pump conditions are changed. Moreover, by demonstrating that a single three-wave process yields nonreciprocal devices with reconfigurable functions, our work breaks the ground for the development of future, more complex directional circuits, and has excellent prospects for on-chip integration.

  15. Multiwatts narrow linewidth fiber Raman amplifiers.

    PubMed

    Feng, Yan; Taylor, Luke; Bonaccini Calia, Domenico

    2008-07-21

    Up to 4.8 W, approximately 10 MHz, 1178 nm laser is obtained by Raman amplification of a distributed feedback diode laser in standard single mode fibers pumped by an 1120 nm Yb fiber laser. More than 10% efficiency and 27 dB amplification is achieved, limited by onset of stimulated Brillouin scattering. The ratio of Raman to Brillouin gain coefficient of a fiber is identified as a figure of merit for building a narrow linewidth fiber Raman amplifier. PMID:18648406

  16. Self-amplifying mRNA vaccines.

    PubMed

    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.

  17. Design and simulation of a gyroklystron amplifier

    SciTech Connect

    Chauhan, M. S. Swati, M. V.; Jain, P. K.

    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. Amplifier/compressor fiber Raman lasers.

    PubMed

    Islam, M N; Mollenauer, L F; Stolen, R H; Simpson, J R; Shang, H T

    1987-10-01

    We show that the chirp from cross-phase modulation (XPM) dominates the operation of fiber Raman lasers (FRL's). Thus a FRL in the anomalous group-velocity regime is best described as a XPM-chirped Raman amplifier followed by a linear fiber compressor. While the output of such a laser is generally a narrow pulse with a broad pedestal, we show both experimentally and by computer simulation that negligible background is achievable.

  19. Self-amplifying mRNA vaccines.

    PubMed

    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. PMID:25620012

  20. Amplifying youth voices in the developing world.

    PubMed

    Fotenos, Saori; Rohatgi, Deepti

    2007-01-01

    Low-literacy youth in the slums of Brazil have been historically unequipped to share their ideas on how to improve their lives, because outside of the spoken word, it is difficult for them to express their thoughts persuasively. The Amplifying Voices afterschool video program piloted at Projeto Uerê in Rio de Janeiro shows that youth can leverage technological tools to voice their perspectives on social issues relevant to themselves and their communities.

  1. Variable Gain Semiconductor Optical Linear Amplifier (OLA)

    NASA Astrophysics Data System (ADS)

    Michie, W. Craig; Kelly, Tony; Tomlinson, Andy; Andonovic, Ivan

    2002-12-01

    The semiconductor optical amplifier (SOA) is a versatile component that can be deployed to meet the expanding applications associated with the introduction of additional functionalities at the optical level in wavelength division multiplexed systems. The future network requires low cost, small footprint, directly controllable amplification throughout the different application layers from long haul through to metro; the intrinsic size and integration capability advantages will ensure that the SOA plays a key role in this evolution. In multi-wavelength gating/amplification applications the gain dynamics, oscillating at timescales comparable to that of the data which is being amplified, introduce issues of pattern dependent waveform distortion (patterning) in single channel, and inter-channel cross-talk in multi-wavelength cases which require management through careful SOA design and understanding of the network application scenarios. In this paper, an optical linear amplifier (OLA) architecture with the unique capability to provide variable gain whilst maintaining linear operation at high output saturation powers will be described. Initial characterisation results for the OLA will be presented.

  2. Parallel reservoir computing using optical amplifiers.

    PubMed

    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.

  3. High gain holmium-doped fibre amplifiers.

    PubMed

    Simakov, Nikita; Li, Zhihong; Jung, Yongmin; Daniel, Jae M O; Barua, Pranabesh; Shardlow, Peter C; Liang, Sijing; Sahu, Jayanta K; Hemming, Alexander; Clarkson, W Andrew; Alam, Shaif-Ul; Richardson, David J

    2016-06-27

    We investigate the operation of holmium-doped fibre amplifiers (HDFAs) in the 2.1 µm spectral region. For the first time we demonstrate a diode-pumped HDFA. This amplifier provides a peak gain of 25 dB at 2040 nm with a 15 dB gain window spanning the wavelength range 2030 - 2100 nm with an external noise figure (NF) of 4-6 dB. We also compare the operation of HDFAs when pumped at 1950 nm and 2008 nm. The 1950 nm pumped HDFA provides 41 dB peak gain at 2060 nm with 15 dB of gain spanning the wavelength range 2050 - 2120 nm and an external NF of 7-10 dB. By pumping at the longer wavelength of 2008 nm the gain bandwidth of the amplifier is shifted to longer wavelengths and using this architecture a HDFA was demonstrated with a peak gain of 39 dB at 2090 nm and 15 dB of gain spanning the wavelength range 2050 - 2150 nm. The external NF over this wavelength range was 8-14 dB. PMID:27410557

  4. LLNL/Lion Precision LVDT amplifier

    SciTech Connect

    Hopkins, D.J.

    1994-04-01

    A high-precision, low-noise, LVDT amplifier has been developed which is a significant advancement on the current state of the art in contact displacement measurement. This amplifier offers the dynamic range of a typical LVDT probe but with a resolution that rivals that of non contact displacement measuring systems such as capacitance gauges and laser interferometers. Resolution of 0.1 {mu} in with 100 Hz bandwidth is possible. This level of resolution is over an order of magnitude greater than what is now commercially available. A front panel switch can reduce the bandwidth to 2.5 Hz and attain a resolution of 0.025 {mu} in. This level of resolution meets or exceeds that of displacement measuring laser interferometry or capacitance gauge systems. Contact displacement measurement offers high part spatial resolution and therefore can measure not only part contour but surface finish. Capacitance gauges and displacement laser interferometry offer poor part spatial resolution and can not provide good surface finish measurements. Machine tool builders, meteorologists and quality inspection departments can immediately utilize the higher accuracy and capabilities that this amplifier offers. The precision manufacturing industry can improve as a result of improved capability to measure parts that help reduce costs and minimize material waste.

  5. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In H.; Stock, Larry V.

    1988-01-01

    A XeCl laser which was developed earlier for an iodine laser oscillator was modified in order to increase the output pulse energy of XeCl laser so that the iodine laser output energy could be increased. The electrical circuit of the XeCl laser was changed from a simple capacitor discharge circuit of the XeCl laser to a Marx system. Because of this improvement the output energy from the XeCl laser was increased from 60 mj to 80 mj. Subsequently, iodine laser output energy was increased from 100 mj to 3 mj. On the other hand, the energy storage capability and amplification characteristics of the Vortek solar simulator-pumped amplifier was calculated expecting the calculated amplification factor is about 2 and the energy extraction efficiency is 26 percent due to the very low input energy density to the amplifier. As a result of an improved kinetic modeling for the iodine solar simulator pumped power amplifier, it is found that the I-2 along the axis of the tube affects seriously the gain profile. For the gas i-C3F7I at the higher pressures, the gain will decrease due to the I-2 as the pumping intensity increases, and at these higher pressures an increase in flow velocity will increase the gain.

  6. Sheet beam slow-wave amplifiers

    SciTech Connect

    Kirolous, H.; Joe, J.; Basten, M.A.; Booske, J.H.; Scharer, J.E.; Anderson, J.; True, R.; Scheitrum, G.

    1994-12-31

    Sheet electron beams used in conjunction with slow-wave (Cerenkov) structures are a promising way to realize higher average power millimeter-wave amplifiers. For example, a sheet beam with a meander line structure is proposed to obtain a 100 watt W-band power booster amplifier. A sheet beam with a tapered grating structure is also being considered as a wideband ({approximately} 10--20% instantaneous bandwidth) Ka-band amplifier with approximately 10 kW of average output power. The authors describe results of research that examine critical technological issues relevant to the realization of the proposed devices. The method of forming a sheet beam using magnetic quadrupole lenses and focusing it using periodically-cusped magnetic (PCM) fields are discussed. A pencil beam from a 10 kV, 0.25 A Pierce electron source is used for the initial investigations. The EGUN simulations with the measured magnetic field indicates that a thin (2 mm dia.) beam is available at the interaction region. Beam characterization has been performed using current density probes and an electrostatic velocity spread analyzer. Numerical modeling and cold test measurements of a tapered slow-wave structure together with the simulations and measurements of small-signal gain and bandwidth are also presented.

  7. Microstrip SQUID amplifiers for quantum information science

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

    Uezumi, Akiyoshi; Nakatani, Masashi; Ikemoto-Uezumi, Madoka; Yamamoto, Naoki; Morita, Mitsuhiro; Yamaguchi, Asami; Yamada, Harumoto; Kasai, Takehiro; Masuda, Satoru; Narita, Asako; Miyagoe-Suzuki, Yuko; Takeda, Shin'ichi; Fukada, So-Ichiro; Nishino, Ichizo; Tsuchida, Kunihiro

    2016-08-01

    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. PMID:27509136

  9. Epigenetic States of nephron progenitors and epithelial differentiation.

    PubMed

    Adli, Mazhar; Parlak, Mahmut; Li, Yuwen; El-Dahr, Samir S

    2015-06-01

    In mammals, formation of new nephrons ends perinatally due to consumption of mesenchymal progenitor cells. Premature depletion of progenitors due to prematurity or postnatal loss of nephrons due to injury causes chronic kidney disease and hypertension. Intensive efforts are currently invested in designing regenerative strategies to form new nephron progenitors from pluripotent cells, which upon further differentiation provide a potential source of new nephrons. To know if reprogramed renal cells can maintain their identity and fate requires knowledge of the epigenetic states of native nephron progenitors and their progeny. In this article, we summarize current knowledge and gaps in the epigenomic landscape of the developing kidney. We now know that Pax2/PTIP/H3K4 methyltransferase activity provides the initial epigenetic specification signal to the metanephric mesenchyme. During nephrogenesis, the cap mesenchyme housing nephron progenitors is enriched in bivalent chromatin marks; as tubulogenesis proceeds, the tubular epithelium acquires H3K79me2. The latter mark is uniquely induced during epithelial differentiation. Analysis of histone landscapes in clonal metanephric mesenchyme cell lines and in Wilms tumor and normal fetal kidney has revealed that promoters of poised nephrogenesis genes carry bivalent histone signatures in progenitors. Differentiation or stimulation of Wnt signaling promotes resolution of bivalency; this does not occur in Wilms tumor cells consistent with their developmental arrest. The use of small cell number ChIP-Seq should facilitate the characterization of the chromatin landscape of the metanephric mesenchyme and various nephron compartments during nephrogenesis. Only then we will know if stem and somatic cell reprogramming into kidney progenitors recapitulates normal development.

  10. 21 CFR 870.2060 - Transducer signal amplifier and conditioner.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Transducer signal amplifier and conditioner. 870.2060 Section 870.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Transducer signal amplifier and conditioner. (a) Identification. A transducer signal amplifier...

  11. 21 CFR 870.2050 - Biopotential amplifier and signal conditioner.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Biopotential amplifier and signal conditioner. 870.2050 Section 870.2050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Biopotential amplifier and signal conditioner. (a) Identification. A biopotential amplifier and...

  12. 21 CFR 870.2050 - Biopotential amplifier and signal conditioner.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Biopotential amplifier and signal conditioner. 870.2050 Section 870.2050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Biopotential amplifier and signal conditioner. (a) Identification. A biopotential amplifier and...

  13. 21 CFR 882.1835 - Physiological signal amplifier.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Physiological signal amplifier. 882.1835 Section 882.1835 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device...

  14. 21 CFR 870.2060 - Transducer signal amplifier and conditioner.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Transducer signal amplifier and conditioner. 870.2060 Section 870.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Transducer signal amplifier and conditioner. (a) Identification. A transducer signal amplifier...

  15. 21 CFR 882.1835 - Physiological signal amplifier.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Physiological signal amplifier. 882.1835 Section 882.1835 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device...

  16. 21 CFR 882.1835 - Physiological signal amplifier.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Physiological signal amplifier. 882.1835 Section 882.1835 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device...

  17. 47 CFR 2.815 - External radio frequency power amplifiers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false External radio frequency power amplifiers. 2... External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source...

  18. 21 CFR 882.1835 - Physiological signal amplifier.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Physiological signal amplifier. 882.1835 Section 882.1835 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device...

  19. 21 CFR 870.2050 - Biopotential amplifier and signal conditioner.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Biopotential amplifier and signal conditioner. 870.2050 Section 870.2050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Biopotential amplifier and signal conditioner. (a) Identification. A biopotential amplifier and...

  20. 21 CFR 870.2060 - Transducer signal amplifier and conditioner.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Transducer signal amplifier and conditioner. 870.2060 Section 870.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Transducer signal amplifier and conditioner. (a) Identification. A transducer signal amplifier...

  1. 21 CFR 870.2060 - Transducer signal amplifier and conditioner.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Transducer signal amplifier and conditioner. 870.2060 Section 870.2060 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Transducer signal amplifier and conditioner. (a) Identification. A transducer signal amplifier...

  2. 47 CFR 2.815 - External radio frequency power amplifiers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false External radio frequency power amplifiers. 2... External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source...

  3. 47 CFR 2.815 - External radio frequency power amplifiers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false External radio frequency power amplifiers. 2... External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source...

  4. 21 CFR 870.2050 - Biopotential amplifier and signal conditioner.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Biopotential amplifier and signal conditioner. 870.2050 Section 870.2050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... Biopotential amplifier and signal conditioner. (a) Identification. A biopotential amplifier and...

  5. 47 CFR 2.815 - External radio frequency power amplifiers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false External radio frequency power amplifiers. 2... External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source...

  6. 47 CFR 2.815 - External radio frequency power amplifiers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false External radio frequency power amplifiers. 2... External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which, (1) when used in conjunction with a radio transmitter as a signal source...

  7. 21 CFR 882.1835 - Physiological signal amplifier.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Physiological signal amplifier. 882.1835 Section 882.1835 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device...

  8. Signal Conditioning Amplifier and Recorder (SCAmpR)

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro J.; Voska, Ned (Technical Monitor)

    2002-01-01

    The Signal Conditioning Amplifier and Recorder (SCAmpR) system is presented. The topics include: 1) System Description; 2) Universal Signal Conditioning Amplifier (USCA); 3) Advanced Data Acquisition System (ADAS); and 4) Signal Conditioning Amplifier and Recorder (SCAmpR). This paper is presented in viewgraph form.

  9. Differential transimpedance amplifier circuit for correlated differential amplification

    DOEpatents

    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.

  10. Digital system provides superregulation of nanosecond amplifier-discriminator circuit

    NASA Technical Reports Server (NTRS)

    Forges, K. G.

    1966-01-01

    Feedback system employing a digital logic comparator to detect and correct amplifier drift provides stable gain characteristics for nanosecond amplifiers used in counting applications. Additional anticoincidence logic enables application of the regulation circuit to the amplifier and discriminator while they are mounted in an operable circuit.

  11. Molecular assembly of botulinum neurotoxin progenitor complexes

    PubMed Central

    Benefield, Desirée A.; Dessain, Scott K.; Shine, Nancy; Ohi, Melanie D.; Lacy, D. Borden

    2013-01-01

    Botulinum neurotoxin (BoNT) is produced by Clostridium botulinum and associates with nontoxic neurotoxin-associated proteins to form high-molecular weight progenitor complexes (PCs). The PCs are required for the oral toxicity of BoNT in the context of food-borne botulism and are thought to protect BoNT from destruction in the gastrointestinal tract and aid in absorption from the gut lumen. The PC can differ in size and protein content depending on the C. botulinum strain. The oral toxicity of the BoNT PC increases as the size of the PC increases, but the molecular architecture of these large complexes and how they contribute to BoNT toxicity have not been elucidated. We have generated 2D images of PCs from strains producing BoNT serotypes A1, B, and E using negative stain electron microscopy and single-particle averaging. The BoNT/A1 and BoNT/B PCs were observed as ovoid-shaped bodies with three appendages, whereas the BoNT/E PC was observed as an ovoid body. Both the BoNT/A1 and BoNT/B PCs showed significant flexibility, and the BoNT/B PC was documented as a heterogeneous population of assembly/disassembly intermediates. We have also determined 3D structures for each serotype using the random conical tilt approach. Crystal structures of the individual proteins were placed into the BoNT/A1 and BoNT/B PC electron density maps to generate unique detailed models of the BoNT PCs. The structures highlight an effective platform that can be engineered for the development of mucosal vaccines and the intestinal absorption of oral biologics. PMID:23509303

  12. Development and molecular composition of the hepatic progenitor cell niche.

    PubMed

    Vestentoft, Peter Siig

    2013-05-01

    End-stage liver diseases represent major health problems that are currently treated by liver transplantation. However, given the world-wide shortage of donor livers novel strategies are needed for therapeutic treatment. Adult stem cells have the ability to self-renew and differentiate into the more specialized cell types of a given organ and are found in tissues throughout the body. These cells, whose progeny are termed progenitor cells in human liver and oval cells in rodents, have the potential to treat patients through the generation of hepatic parenchymal cells, even from the patient's own tissue. Little is known regarding the nature of the hepatic progenitor cells. Though they are suggested to reside in the most distal part of the biliary tree, the canal of Hering, the lack of unique surface markers for these cells has hindered their isolation and characterization. Upon activation, they proliferate and form ductular structures, termed "ductular reactions", which radiate into the hepatic parenchyma. The ductular reactions contain activated progenitor cells that not only acquire a phenotype resembling that observed in developing liver but also display markers of differentiation shared with the cholangiocytic or hepatocytic lineages, the two parenchymal hepatic cell types. Interactions between the putative progenitor cells, the surrounding support cells and the extracellular matrix scaffold, all constituting the progenitor cell niche, are likely to be important for regulating progenitor cell activity and differentiation. Therefore, identifying novel progenitor cell markers and deciphering their microenvironment could facilitate clinical use. The aims of the present PhD thesis were to expand knowledge of the hepatic progenitor cell niche and characterize it both during development and in disease. Several animal models of hepatic injury are known to induce activation of the progenitor cells. In order to identify possible progenitor cell markers and niche components

  13. SUPERNOVA 2008bk AND ITS RED SUPERGIANT PROGENITOR

    SciTech Connect

    Van Dyk, Schuyler D.; Elias-Rosa, Nancy; and others

    2012-01-15

    We have obtained limited photometric and spectroscopic data for supernova (SN) 2008bk in NGC 7793, primarily at {approx}> 150 days after explosion. We find that it is a Type II-Plateau (II-P) SN that 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 (A{sub V} = 0.065 mag) must be almost entirely due to the Galactic foreground, similar to what has been assumed for SN 1999br. We confirm the identification of the putative red supergiant (RSG) progenitor star of the SN in high-quality g'r'i' images we had obtained in 2007 at the Gemini-South 8 m telescope. Little ambiguity exists in this progenitor identification, qualifying it as the best example to date, next to the identification of the star Sk -69 Degree-Sign 202 as the progenitor of SN 1987A. From a combination of photometry of the Gemini images with that of archival, pre-SN, Very Large Telescope JHK{sub s} images, we derive an accurate observed spectral energy distribution (SED) for the progenitor. We find from nebular strong-intensity emission-line indices for several H II regions near the SN that the metallicity in the environment is likely subsolar (Z Almost-Equal-To 0.6 Z{sub Sun }). The observed SED of the star agrees quite well with synthetic SEDs obtained from model RSG atmospheres with effective temperature T{sub eff} = 3600 {+-} 50 K. We find, therefore, that the star had a bolometric luminosity with respect to the Sun of log (L{sub bol}/L{sub Sun} ) = 4.57 {+-} 0.06 and radius R{sub *} = 496 {+-} 34 R{sub Sun} at {approx}6 months prior to explosion. Comparing the progenitor's properties with theoretical massive-star evolutionary models, we conclude that the RSG progenitor had an initial mass in the range of 8-8.5 M{sub Sun }. This mass is consistent with, albeit at the low end of, the inferred range of initial masses for SN II

  14. A clonal analysis of neural progenitors during axolotl spinal cord regeneration reveals evidence for both spatially restricted and multipotent progenitors.

    PubMed

    McHedlishvili, Levan; Epperlein, Hans H; Telzerow, Anja; Tanaka, Elly M

    2007-06-01

    Complete regeneration of the spinal cord occurs after tail regeneration in urodele amphibians such as the axolotl. Little is known about how neural progenitor cells are recruited from the mature tail, how they populate the regenerating spinal cord, and whether the neural progenitor cells are multipotent. To address these issues we used three types of cell fate mapping. By grafting green fluorescent protein-positive (GFP(+)) spinal cord we show that a 500 microm region adjacent to the amputation plane generates the neural progenitors for regeneration. We further tracked single nuclear-GFP-labeled cells as they proliferated during regeneration, observing their spatial distribution, and ultimately their expression of the progenitor markers PAX7 and PAX6. Most progenitors generate descendents that expand along the anterior/posterior (A/P) axis, but remain close to the dorsal/ventral (D/V) location of the parent. A minority of clones spanned multiple D/V domains, taking up differing molecular identities, indicating that cells can execute multipotency in vivo. In parallel experiments, bulk labeling of dorsally or ventrally restricted progenitor cells revealed that ventral cells at the distal end of the regenerating spinal cord switch to dorsal cell fates. Analysis of PAX7 and PAX6 expression along the regenerating spinal cord indicated that these markers are expressed in dorsal and lateral domains all along the spinal cord except at the distal terminus. These results suggest that neural progenitor identity is destabilized or altered in the terminal vesicle region, from which clear migration of cells into the surrounding blastema is also observed. PMID:17507409

  15. Derivation of endodermal progenitors from pluripotent stem cells†

    PubMed Central

    Ikonomou, Laertis; Kotton, Darrell N.

    2014-01-01

    Stem and progenitor cells play important roles in organogenesis during development and in tissue homeostasis and response to injury postnatally. As the regenerative capacity of many human tissues is limited, cell replacement therapies hold great promise for human disease management. Pluripotent stem cells such as embryonic stem (ES) cells and induced pluripotent stem (iPS) cells are prime candidates for the derivation of unlimited quantities of clinically relevant cell types through development of directed differentiation protocols, i.e. the recapitulation of developmental milestones in in vitro cell culture. Tissue-specific progenitors, including progenitors of endodermal origin, are important intermediates in such protocols since they give rise to all mature parenchymal cells. In this review, we focus on the in vivo biology of embryonic endodermal progenitors in terms of key transcription factors and signaling pathways. We critically review the emerging literature aiming to apply this basic knowledge to achieve the efficient and reproducible in vitro derivation of endodermal progenitors such as pancreas, liver and lung precursor cells. PMID:25160562

  16. Observational Clues to the Progenitors of Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Maoz, Dan; Mannucci, Filippo; Nelemans, Gijs

    2014-08-01

    Type Ia supernovae (SNe Ia) are important distance indicators, element factories, cosmic-ray accelerators, kinetic-energy sources in galaxy evolution, and end points 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 nondegenerate 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 SN Ia sites—pre- and postexplosion—from analysis of the explosions themselves and from the measurement of event rates. The recent nearby and well-studied event, SN 2011fe, has been particularly revealing. The observational results are not yet conclusive and sometimes prone to competing theoretical interpretations. Nevertheless, it appears that DD progenitors, long considered the underdog option, could be behind some, if not all, SNe Ia. We point to some directions that may lead to future progress.

  17. Hepatic stellate cells contribute to progenitor cells and liver regeneration.

    PubMed

    Kordes, Claus; Sawitza, Iris; Götze, Silke; Herebian, Diran; Häussinger, Dieter

    2014-12-01

    Retinoid-storing hepatic stellate cells (HSCs) have recently been described as a liver-resident mesenchymal stem cell (MSC) population; however, it is not clear whether these cells contribute to liver regeneration or serve as a progenitor cell population with hepatobiliary characteristics. Here, we purified HSCs with retinoid-dependent fluorescence-activated cell sorting from eGFP-expressing rats and transplanted these GFP(+) HSCs into wild-type (WT) rats that had undergone partial hepatectomy in the presence of 2-acetylaminofluorene (2AAF) or retrorsine, both of which are injury models that favor stem cell-based liver repair. Transplanted HSCs contributed to liver regeneration in host animals by forming mesenchymal tissue, progenitor cells, hepatocytes, and cholangiocytes and elevated direct bilirubin levels in blood sera of GUNN rats, indicating recovery from the hepatic bilirubin-handling defect in these animals. Transplanted HSCs engrafted within the bone marrow (BM) of host animals, and HSC-derived cells were isolated from BM and successfully retransplanted into new hosts with injured liver. Cultured HSCs transiently adopted an expression profile similar to that of progenitor cells during differentiation into bile acid-synthesizing and -transporting hepatocytes, suggesting that stellate cells represent a source of liver progenitor cells. This concept connects seemingly contradictory studies that favor either progenitor cells or MSCs as important players in stem cell-based liver regeneration.

  18. Inhibition of cyclooxygenase (COX)-2 affects endothelial progenitor cell proliferation

    SciTech Connect

    Colleselli, Daniela; Bijuklic, Klaudija; Mosheimer, Birgit A.; Kaehler, Christian M. . E-mail: C.M.Kaehler@uibk.ac.at

    2006-09-10

    Growing evidence indicates that inducible cyclooxygenase-2 (COX-2) is involved in the pathogenesis of inflammatory disorders and various types of cancer. Endothelial progenitor cells recruited from the bone marrow have been shown to be involved in the formation of new vessels in malignancies and discussed for being a key point in tumour progression and metastasis. However, until now, nothing is known about an interaction between COX and endothelial progenitor cells (EPC). Expression of COX-1 and COX-2 was detected by semiquantitative RT-PCR and Western blot. Proliferation kinetics, cell cycle distribution and rate of apoptosis were analysed by MTT test and FACS analysis. Further analyses revealed an implication of Akt phosphorylation and caspase-3 activation. Both COX-1 and COX-2 expression can be found in bone-marrow-derived endothelial progenitor cells in vitro. COX-2 inhibition leads to a significant reduction in proliferation of endothelial progenitor cells by an increase in apoptosis and cell cycle arrest. COX-2 inhibition leads further to an increased cleavage of caspase-3 protein and inversely to inhibition of Akt activation. Highly proliferating endothelial progenitor cells can be targeted by selective COX-2 inhibition in vitro. These results indicate that upcoming therapy strategies in cancer patients targeting COX-2 may be effective in inhibiting tumour vasculogenesis as well as angiogenic processes.

  19. High fat diet enhances stemness and tumorigenicity of intestinal progenitors

    PubMed Central

    Beyaz, Semir; Mana, Miyeko D.; Roper, Jatin; Kedrin, Dmitriy; Saadatpour, Assieh; Hong, Sue-Jean; Bauer-Rowe, Khristian E.; Xifaras, Michael E.; Akkad, Adam; Arias, Erika; Pinello, Luca; Katz, Yarden; Shinagare, Shweta; Abu-Remaileh, Monther; Mihaylova, Maria M.; Lamming, Dudley W.; Dogum, Rizkullah; Guo, Guoji; Bell, George W.; Selig, Martin; Nielsen, G. Petur; Gupta, Nitin; Ferrone, Cristina R.; Deshpande, Vikram; Yuan, Guo-Cheng; Orkin, Stuart H.; Sabatini, David M.; Yilmaz, Ömer H.

    2016-01-01

    Little is known about how pro-obesity diets regulate tissue stem and progenitor cell function. Here we find that high fat diet (HFD)-induced obesity augments the numbers and function of Lgr5+ intestinal stem-cells (ISCs) of the mammalian intestine. Mechanistically, HFD induces a robust peroxisome proliferator-activated receptor delta (PPAR-d) signature in intestinal stem and (non-ISC) progenitor cells, and pharmacologic activation of PPAR-d recapitulates the effects of a HFD on these cells. Like a HFD, ex vivo treatment of intestinal organoid cultures with fatty acid constituents of the HFD enhances the self-renewal potential of these organoid bodies in a PPAR-d dependent manner. Interestingly, HFD- and agonist-activated PPAR-d signaling endow organoid-initiating capacity to progenitors, and enforced PPAR-d signaling permits these progenitors to form in vivo tumors upon loss of the tumor suppressor Apc. These findings highlight how diet-modulated PPAR-d activation alters not only the function of intestinal stem and progenitor cells, but also their capacity to initiate tumors. PMID:26935695

  20. Chronic ethanol consumption transiently reduces adult neural progenitor cell proliferation.

    PubMed

    Rice, Ann C; Bullock, M Ross; Shelton, Keith L

    2004-06-11

    Adult neural stem/progenitor cells proliferate throughout the life of the animal in the subependymal zone and the subgranular zone of the dentate gyrus (DG). Treatments such as enriched environment, dietary restriction, running and anti-depressants increase proliferation, however, stress and opiates have been shown to decrease proliferation. While models of binge ethanol drinking decreases proliferation, few studies have characterized the effect chronic ethanol usage has on progenitor cell proliferation. In this study, we have examined changes in the progenitor cell proliferation rate following chronic ethanol consumption. Animals were given a nutritionally balanced liquid diet containing 6.5% v/v ethanol or an isocalorically balanced liquid diet. Bromodeoxyuridine (BrdU) was administered (150 mg/kg x 3) and the animals sacrificed 2 h after the last injection on days 3, 10 or 30 of the ethanol diet. Coronal brain blocks were paraffin embedded and 6 microm sections sliced and immunohistochemically stained for BrdU. Quantitation of the number of BrdU-labeled cells in the subgranular zone of the DG revealed a significant decrease only at the 3-day time-point, with recovery by the 10- and 30-day time-points. Thus, the progenitor cell proliferation rate is transiently decreased by chronic ethanol usage. This data suggests that chronic alcohol use results in a compensatory response that restores the progenitor cell proliferation rate.

  1. Impaired DNA replication within progenitor cell pools promotes leukemogenesis.

    PubMed

    Bilousova, Ganna; Marusyk, Andriy; Porter, Christopher C; Cardiff, Robert D; DeGregori, James

    2005-12-01

    Impaired cell cycle progression can be paradoxically associated with increased rates of malignancies. Using retroviral transduction of bone marrow progenitors followed by transplantation into mice, we demonstrate that inhibition of hematopoietic progenitor cell proliferation impairs competition, promoting the expansion of progenitors that acquire oncogenic mutations which restore cell cycle progression. Conditions that impair DNA replication dramatically enhance the proliferative advantage provided by the expression of Bcr-Abl or mutant p53, which provide no apparent competitive advantage under conditions of healthy replication. Furthermore, for the Bcr-Abl oncogene the competitive advantage in contexts of impaired DNA replication dramatically increases leukemogenesis. Impaired replication within hematopoietic progenitor cell pools can select for oncogenic events and thereby promote leukemia, demonstrating the importance of replicative competence in the prevention of tumorigenesis. The demonstration that replication-impaired, poorly competitive progenitor cell pools can promote tumorigenesis provides a new rationale for links between tumorigenesis and common human conditions of impaired DNA replication such as dietary folate deficiency, chemotherapeutics targeting dNTP synthesis, and polymorphisms in genes important for DNA metabolism. PMID:16277552

  2. Vascular wall progenitor cells in health and disease.

    PubMed

    Psaltis, Peter J; Simari, Robert D

    2015-04-10

    The vasculature plays an indispensible role in organ development and maintenance of tissue homeostasis, such that disturbances to it impact greatly on developmental and postnatal health. Although cell turnover in healthy blood vessels is low, it increases considerably under pathological conditions. The principle sources for this phenomenon have long been considered to be the recruitment of cells from the peripheral circulation and the re-entry of mature cells in the vessel wall back into cell cycle. However, recent discoveries have also uncovered the presence of a range of multipotent and lineage-restricted progenitor cells in the mural layers of postnatal blood vessels, possessing high proliferative capacity and potential to generate endothelial, smooth muscle, hematopoietic or mesenchymal cell progeny. In particular, the tunica adventitia has emerged as a progenitor-rich compartment with niche-like characteristics that support and regulate vascular wall progenitor cells. Preliminary data indicate the involvement of some of these vascular wall progenitor cells in vascular disease states, adding weight to the notion that the adventitia is integral to vascular wall pathogenesis, and raising potential implications for clinical therapies. This review discusses the current body of evidence for the existence of vascular wall progenitor cell subpopulations from development to adulthood and addresses the gains made and significant challenges that lie ahead in trying to accurately delineate their identities, origins, regulatory pathways, and relevance to normal vascular structure and function, as well as disease.

  3. Renal blood flow and oxygenation drive nephron progenitor differentiation.

    PubMed

    Rymer, Christopher; Paredes, Jose; Halt, Kimmo; Schaefer, Caitlin; Wiersch, John; Zhang, Guangfeng; Potoka, Douglas; Vainio, Seppo; Gittes, George K; Bates, Carlton M; Sims-Lucas, Sunder

    2014-08-01

    During kidney development, the vasculature develops via both angiogenesis (branching from major vessels) and vasculogenesis (de novo vessel formation). The formation and perfusion of renal blood vessels are vastly understudied. In the present study, we investigated the regulatory role of renal blood flow and O2 concentration on nephron progenitor differentiation during ontogeny. To elucidate the presence of blood flow, ultrasound-guided intracardiac microinjection was performed, and FITC-tagged tomato lectin was perfused through the embryo. Kidneys were costained for the vasculature, ureteric epithelium, nephron progenitors, and nephron structures. We also analyzed nephron differentiation in normoxia compared with hypoxia. At embryonic day 13.5 (E13.5), the major vascular branches were perfused; however, smaller-caliber peripheral vessels remained unperfused. By E15.5, peripheral vessels started to be perfused as well as glomeruli. While the interior kidney vessels were perfused, the peripheral vessels (nephrogenic zone) remained unperfused. Directly adjacent and internal to the nephrogenic zone, we found differentiated nephron structures surrounded and infiltrated by perfused vessels. Furthermore, we determined that at low O2 concentration, little nephron progenitor differentiation was observed; at higher O2 concentrations, more differentiation of the nephron progenitors was induced. The formation of the developing renal vessels occurs before the onset of blood flow. Furthermore, renal blood flow and oxygenation are critical for nephron progenitor differentiation. PMID:24920757

  4. Renal blood flow and oxygenation drive nephron progenitor differentiation.

    PubMed

    Rymer, Christopher; Paredes, Jose; Halt, Kimmo; Schaefer, Caitlin; Wiersch, John; Zhang, Guangfeng; Potoka, Douglas; Vainio, Seppo; Gittes, George K; Bates, Carlton M; Sims-Lucas, Sunder

    2014-08-01

    During kidney development, the vasculature develops via both angiogenesis (branching from major vessels) and vasculogenesis (de novo vessel formation). The formation and perfusion of renal blood vessels are vastly understudied. In the present study, we investigated the regulatory role of renal blood flow and O2 concentration on nephron progenitor differentiation during ontogeny. To elucidate the presence of blood flow, ultrasound-guided intracardiac microinjection was performed, and FITC-tagged tomato lectin was perfused through the embryo. Kidneys were costained for the vasculature, ureteric epithelium, nephron progenitors, and nephron structures. We also analyzed nephron differentiation in normoxia compared with hypoxia. At embryonic day 13.5 (E13.5), the major vascular branches were perfused; however, smaller-caliber peripheral vessels remained unperfused. By E15.5, peripheral vessels started to be perfused as well as glomeruli. While the interior kidney vessels were perfused, the peripheral vessels (nephrogenic zone) remained unperfused. Directly adjacent and internal to the nephrogenic zone, we found differentiated nephron structures surrounded and infiltrated by perfused vessels. Furthermore, we determined that at low O2 concentration, little nephron progenitor differentiation was observed; at higher O2 concentrations, more differentiation of the nephron progenitors was induced. The formation of the developing renal vessels occurs before the onset of blood flow. Furthermore, renal blood flow and oxygenation are critical for nephron progenitor differentiation.

  5. Hepatic stellate cells contribute to progenitor cells and liver regeneration

    PubMed Central

    Kordes, Claus; Sawitza, Iris; Götze, Silke; Herebian, Diran; Häussinger, Dieter

    2014-01-01

    Retinoid-storing hepatic stellate cells (HSCs) have recently been described as a liver-resident mesenchymal stem cell (MSC) population; however, it is not clear whether these cells contribute to liver regeneration or serve as a progenitor cell population with hepatobiliary characteristics. Here, we purified HSCs with retinoid-dependent fluorescence-activated cell sorting from eGFP-expressing rats and transplanted these GFP+ HSCs into wild-type (WT) rats that had undergone partial hepatectomy in the presence of 2-acetylaminofluorene (2AAF) or retrorsine, both of which are injury models that favor stem cell–based liver repair. Transplanted HSCs contributed to liver regeneration in host animals by forming mesenchymal tissue, progenitor cells, hepatocytes, and cholangiocytes and elevated direct bilirubin levels in blood sera of GUNN rats, indicating recovery from the hepatic bilirubin–handling defect in these animals. Transplanted HSCs engrafted within the bone marrow (BM) of host animals, and HSC-derived cells were isolated from BM and successfully retransplanted into new hosts with injured liver. Cultured HSCs transiently adopted an expression profile similar to that of progenitor cells during differentiation into bile acid–synthesizing and –transporting hepatocytes, suggesting that stellate cells represent a source of liver progenitor cells. This concept connects seemingly contradictory studies that favor either progenitor cells or MSCs as important players in stem cell–based liver regeneration. PMID:25401473

  6. Myostatin promotes the terminal differentiation of embryonic muscle progenitors

    PubMed Central

    Manceau, Marie; Gros, Jérôme; Savage, Kathleen; Thomé, Virginie; McPherron, Alexandra; Paterson, Bruce; Marcelle, Christophe

    2008-01-01

    Myostatin, a TGF-β family member, is an important regulator of adult muscle size. While extensively studied in vitro, the mechanisms by which this molecule mediates its effect in vivo are poorly understood. We addressed this question using chick and mouse embryos. We show that while myostatin overexpression in chick leads to an exhaustion of the muscle progenitor population that ultimately results in muscle hypotrophy, myostatin loss of function in chick and mouse provokes an expansion of this population. Our data demonstrate that myostatin acts in vivo to regulate the balance between proliferation and differentiation of embryonic muscle progenitors by promoting their terminal differentiation through the activation of p21 and MyoD. Previous studies have suggested that myostatin imposes quiescence on muscle progenitors. Our data suggest that myostatin’s effect on muscle progenitors is more complex than previously realized and is likely to be context-dependent. We propose a novel model for myostatin mode of action in vivo, in which myostatin affects the balance between proliferation and differentiation of embryonic muscle progenitors by enhancing their differentiation. PMID:18316481

  7. Characterization of a Common-Source Amplifier Using Ferroelectric Transistors

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    This paper presents empirical data that was collected through experiments using a FeFET in the established common-source amplifier circuit. The unique behavior of the FeFET lends itself to interesting and useful operation in this widely used common-source amplifier. The paper examines the effect of using a ferroelectric transistor for the amplifier. It also examines the effects of varying load resistance, biasing, and input voltages on the output signal and gives several examples of the output of the amplifier for a given input. The difference between a commonsource amplifier using a ferroelectric transistor and that using a MOSFET is addressed.

  8. Characterization of a Common-Gate Amplifier Using Ferroelectric Transistors

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    In this paper, the empirical data collected through experiments performed using a FeFET in the common-gate amplifier circuit is presented. The FeFET common-gate amplifier was characterized by varying all parameters in the circuit, such as load resistance, biasing of the transistor, and input voltages. Due to the polarization of the ferroelectric layer, the particular behavior of the FeFET common-gate amplifier presents interesting results. Furthermore, the differences between a FeFET common-gate amplifier and a MOSFET common-gate amplifier are examined.

  9. Experimental study of multipass copper vapour laser amplifiers

    SciTech Connect

    Karpukhin, Vyacheslav T; Malikov, Mikhail M

    2008-12-31

    Repetitively pulsed multipass copper vapour amplifiers are studied experimentally. A considerable increase in the peak power of laser pulses was achieved by using a special scheme of the amplifier. It is found that the main reasons preventing an increase in the peak power during many passages of the beam are the competitive development of lasing from spontaneous seeds in a parasitic resonator formed by the fold mirrors of a multipass amplifier, a decrease in the amplification during the last passages, and an increase in the pulse width at the amplifier output. (lasers. amplifiers)

  10. Power scaling of passively phased fiber amplifier arrays

    NASA Astrophysics Data System (ADS)

    Shakir, Sami A.; Culver, Bill; Nelson, Burke; Starcher, Yuji; Bates, George M.; Hedrick, Jerry W., Jr.

    2008-08-01

    Passive phasing of fiber amplifier arrays are promising for the power scaling of high power fiber laser systems. The broadband operation of passively phased systems mitigates nonlinear effects such as Stimulated Brillouin Scattering. This leads to the possibility of scaling the individual fiber amplifiers in the passively phased arrays to multi-kilowatt power levels. In effect, a smaller number of fiber amplifiers can be used compared to other methods of fiber amplifiers combining. We report the passive phasing of 16 Yb-doped fiber amplifiers at 5W each for a total of 80W.

  11. Properties of CD34+ CML stem/progenitor cells that correlate with different clinical responses to imatinib mesylate

    PubMed Central

    Forrest, Donna; Nicolini, Franck; Turhan, Ali; Guilhot, Joelle; Yip, Calvin; Holyoake, Tessa; Jorgensen, Heather; Lambie, Karen; Saw, Kyi Min; Pang, Emily; Vukovic, Ranko; Lehn, Paeta; Ringrose, Ashley; Yu, Miao; Brinkman, Ryan R.; Smith, Clay; Eaves, Allen; Eaves, Connie

    2010-01-01

    Imatinib mesylate (IM) induces clinical remissions in chronic-phase chronic myeloid leukemia (CML) patients but IM resistance remains a problem. We recently identified several features of CML CD34+ stem/progenitor cells expected to confer resistance to BCR-ABL-targeted therapeutics. From a study of 25 initially chronic-phase patients, we now demonstrate that some, but not all, of these parameters correlate with subsequent clinical response to IM therapy. CD34+ cells from the 14 IM nonresponders demonstrated greater resistance to IM than the 11 IM responders in colony-forming cell assays in vitro (P < .001) and direct sequencing of cloned transcripts from CD34+ cells further revealed a higher incidence of BCR-ABL kinase domain mutations in the IM nonresponders (10%-40% vs 0%-20% in IM responders, P < .003). In contrast, CD34+ cells from IM nonresponders and IM responders were not distinguished by differences in BCR-ABL or transporter gene expression. Interestingly, one BCR-ABL mutation (V304D), predicted to destabilize the interaction between p210BCR-ABL and IM, was detectable in 14 of 20 patients. T315I mutant CD34+ cells found before IM treatment in 2 of 20 patients examined were preferentially amplified after IM treatment. Thus, 2 properties of pretreatment CML stem/progenitor cells correlate with subsequent response to IM therapy. Prospective assessment of these properties may allow improved patient management. PMID:20574046

  12. Interactions of HIV and drugs of abuse: the importance of glia, neural progenitors, and host genetic factors.

    PubMed

    Hauser, Kurt F; Knapp, Pamela E

    2014-01-01

    Considerable insight has been gained into the comorbid, interactive effects of HIV and drug abuse in the brain using experimental models. This review, which considers opiates, methamphetamine, and cocaine, emphasizes the importance of host genetics and glial plasticity in driving the pathogenic neuron remodeling underlying neuro-acquired immunodeficiency syndrome and drug abuse comorbidity. Clinical findings are less concordant than experimental work, and the response of individuals to HIV and to drug abuse can vary tremendously. Host-genetic variability is important in determining viral tropism, neuropathogenesis, drug responses, and addictive behavior. However, genetic differences alone cannot account for individual variability in the brain "connectome." Environment and experience are critical determinants in the evolution of synaptic circuitry throughout life. Neurons and glia both exercise control over determinants of synaptic plasticity that are disrupted by HIV and drug abuse. Perivascular macrophages, microglia, and to a lesser extent astroglia can harbor the infection. Uninfected bystanders, especially astroglia, propagate and amplify inflammatory signals. Drug abuse by itself derails neuronal and glial function, and the outcome of chronic exposure is maladaptive plasticity. The negative consequences of coexposure to HIV and drug abuse are determined by numerous factors including genetics, sex, age, and multidrug exposure. Glia and some neurons are generated throughout life, and their progenitors appear to be targets of HIV and opiates/psychostimulants. The chronic nature of HIV and drug abuse appears to result in sustained alterations in the maturation and fate of neural progenitors, which may affect the balance of glial populations within multiple brain regions.

  13. Investigations of electronic amplifiers supplying a piezobimorph actuator

    NASA Astrophysics Data System (ADS)

    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.

  14. Low power RF amplifier circuit for ion trap applications

    NASA Astrophysics Data System (ADS)

    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.

  15. A new semicustom integrated bipolar amplifier for silicon strip detectors

    SciTech Connect

    Zimmerman, T.

    1989-07-11

    The QPA02 is a four channel DC coupled two stage transimpedance amplifier designed at Fermilab on a semicustom linear array (Quickchip 2S) manufactured by Tektronix. The chip was developed as a silicon strip amplifier but may have other applications as well. Each channel consists of a preamplifier and a second stage amplifier/sharper with differential output which can directly drive a transmission line (90 to 140 ohms). External bypass capacitors are the only discrete components required. QPA02 has been tested and demonstrated to be an effective silicon strip amplifier. Other applications may exist which can use this amplifier or a modified version of this amplifier. For example, another design is now in progress for a wire chamber amplifier, QPA03, to be reported later. Only a relatively small effort was required to modify the design and layout for this application. 11 figs.

  16. K-band FET amplifier for satellite downlink

    NASA Technical Reports Server (NTRS)

    Goel, J.; Cheung, R. P.

    1984-01-01

    State-of-the-art performance is demonstrated with solid-state amplifiers in K-band. The amplifier provides 8.2 watts of power with 39 dB gain over a frequency band of 1.4 GHz. Nonlinearity analyses of solid-state amplifiers suggest that system performance can be improved significantly by using an FET amplifier. Preliminary investigations reveal that the solid-state amplifiers can be space-qualified and can be expected to replace the TWTA in many communication links in the near future. It is pointed out that with improvements in device technology, the power, bandwidth and efficiency of solid-state amplifiers using FETs can be further improved. With FETs operating at a junction temperature of less than 125 C, solid-state amplifiers are inherently reliable, indicating a ten-year mean time to failure.

  17. Noiseless Optical Amplifier Operating on Hundreds of Spatial Modes

    NASA Astrophysics Data System (ADS)

    Corzo, N. V.; Marino, A. M.; Jones, K. M.; Lett, P. D.

    2012-07-01

    We implement a noiseless optical amplifier using a phase-sensitive four-wave mixing process in rubidium vapor. We observe performance near the quantum limit for this type of amplifier over a range of experimental parameters and show that the noise figure is always better than would be obtained with a phase-insensitive amplifier with the same gain. Additionally, we observe that the amplifier supports hundreds of spatial modes, making it possible to amplify complex two-dimensional spatial patterns with less than a 10% degradation of the input signal-to-noise ratio for gains up to 4.6. To confirm the multimode character of the amplifier, we study the noise figure as a function of spatially-varying losses. Additionally, we investigate the spatial resolution of the amplifier and show that it supports a range of spatial frequencies from 1.3 to more than 35 line pairs per millimeter.

  18. Identification of a common mesenchymal stromal progenitor for the adult haematopoietic niche

    PubMed Central

    Hu, Xingbin; Garcia, Mayra; Weng, Lihong; Jung, Xiaoman; Murakami, Jodi L.; Kumar, Bijender; Warden, Charles D.; Todorov, Ivan; Chen, Ching-Cheng

    2016-01-01

    Microenvironment cues received by haematopoietic stem cells (HSC) are important in regulating the choice between self-renewal and differentiation. On the basis of the differential expression of cell-surface markers, here we identify a mesenchymal stromal progenitor hierarchy, where CD45−Ter119−CD31−CD166−CD146−Sca1+(Sca1+) progenitors give rise to CD45−Ter119−CD31−CD166−CD146+(CD146+) intermediate and CD45−Ter119−CD31−CD166+CD146−(CD166+) mature osteo-progenitors. All three progenitors preserve HSC long-term multi-lineage reconstitution capability in vitro; however, their in vivo fates are different. Post-transplantation, CD146+ and CD166+ progenitors form bone only. While Sca1+ progenitors produce CD146+, CD166+ progenitors, osteocytes and CXCL12-producing stromal cells. Only Sca1+ progenitors are capable of homing back to the marrow post-intravenous infusion. Ablation of Sca1+ progenitors results in a decrease of all three progenitor populations as well as haematopoietic stem/progenitor cells. Moreover, suppressing production of KIT-ligand in Sca1+ progenitors inhibits their ability to support HSCs. Our results indicate that Sca1+ progenitors, through the generation of both osteogenic and stromal cells, provide a supportive environment for hematopoiesis. PMID:27721421

  19. Numerical simulation of cross field amplifiers

    SciTech Connect

    Eppley, K.

    1990-01-01

    Cross field amplifiers (CFA) have been used in many applications where high power, high frequency microwaves are needed. Although these tubes have been manufactured for decades, theoretical analysis of their properties is not as highly developed as for other microwave devices such as klystrons. One feature distinguishing cross field amplifiers is that the operating current is produced by secondary emission from a cold cathode. This removes the need for a heater and enables the device to act as a switch tube, drawing no power until the rf drive is applied. However, this method of generating the current does complicate the simulation. We are developing a simulation model of cross field amplifiers using the PIC code CONDOR. We simulate an interaction region, one traveling wavelength long, with periodic boundary conditions. An electric field with the appropriate phase velocity is imposed on the upper boundary of the problem. Evaluation of the integral of E{center dot}J gives the power interchanged between the wave and the beam. Given the impedance of the structure, we then calculate the change in the traveling wave field. Thus we simulate the growth of the wave through the device. The main advance of our model over previous CFA simulations is the realistic tracking of absorption and secondary emission. The code uses experimental curves to calculate secondary production as a function of absorbed energy, with a theoretical expression for the angular dependence. We have used this code to model the 100 MW X-band CFA under construction at SLAC, as designed by Joseph Feinstein and Terry Lee. We are examining several questions of practical interest, such as the power and spectrum of absorbed electrons, the minimum traveling wave field needed to initiate spoke formation, and the variation of output power with dc voltage, anode-cathode gap, and magnetic field. 5 refs., 8 figs.

  20. Rates and progenitors of type Ia supernovae

    SciTech Connect

    Wood-Vasey, William Michael

    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.

  1. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  2. Undulations from amplified low frequency surface waves

    SciTech Connect

    Coutant, Antonin; Parentani, Renaud

    2014-04-15

    We study the linear scattering of gravity waves in longitudinal inhomogeneous stationary flows. When the flow becomes supercritical, it is known that counterflow propagating shallow waves are blocked and converted into deep waves. Here we show that in the zero-frequency limit, the reflected waves are amplified in such a way that the free surface develops an undulation, i.e., a zero-frequency wave of large amplitude with nodes located at specific places. This amplification involves negative energy waves and implies that flat surfaces are unstable against incoming perturbations of arbitrary small amplitude. The relation between this instability and black hole radiation (the Hawking effect) is established.

  3. Noise rise in nondegenerate parametric amplifiers

    SciTech Connect

    Bryant, P.H. ); Movshovich, R.; Yurke, B. )

    1991-05-20

    The noise-rise phenomenon is a long-standing problem that was first observed in Josephson-junction-parametric amplifiers over ten years ago. We present here a case where noise-rise data from a Josephson junction is successfully explained, using a theory based on the universal properties of a dynamical system operated near a bifurcation point. The experiment and theory presented here is for a bifurcation of the Hopf type, a case not discussed previously. The predicted behavior is qualitatively different from that of previously studied bifurcations.

  4. Amplifying magneto-optical photonic crystal

    NASA Astrophysics Data System (ADS)

    Grishin, A. M.

    2010-08-01

    We modeled transmission and Faraday rotation characteristics of Er-doped all-garnet [Bi3Fe5O12/Gd3Ga5O12]m photonic crystals in view of their application in C-band magneto-optical amplifiers. It is found that 48 layered 11.4 μm thick crystal at λ =1532 nm provides 45° Faraday rotation and transmission as high as 85% being pumped with 100 mW/980 nm solid state laser diode.

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

    PubMed

    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. Myogenic Progenitors from Mouse Pluripotent Stem Cells for Muscle Regeneration.

    PubMed

    Magli, Alessandro; Incitti, Tania; Perlingeiro, Rita C R

    2016-01-01

    Muscle homeostasis is maintained by resident stem cells which, in both pathologic and non-pathologic conditions, are able to repair or generate new muscle fibers. Although muscle stem cells have tremendous regenerative potential, their application in cell therapy protocols is prevented by several restrictions, including the limited ability to grow ex vivo. Since pluripotent stem cells have the unique potential to both self-renew and expand almost indefinitely, they have become an attractive source of progenitors for regenerative medicine studies. Our lab has demonstrated that embryonic stem cell (ES)-derived myogenic progenitors retain the ability to repair existing muscle fibers and contribute to the pool of resident stem cells. Because of their relevance in both cell therapy and disease modeling, in this chapter we describe the protocol to derive myogenic progenitors from murine ES cells followed by their intramuscular delivery in a murine muscular dystrophy model. PMID:27492174

  7. Advances in hepatic stem/progenitor cell biology

    PubMed Central

    Verhulst, Stefaan; Best, Jan; van Grunsven, Leo A.; Dollé, Laurent

    2015-01-01

    The liver is famous for its strong regenerative capacity, employing different modes of regeneration according to type and extent of injury. Mature liver cells are able to proliferate in order to replace the damaged tissue allowing the recovery of the parenchymal function. In more severe scenarios hepatocytes are believed to arise also from a facultative liver progenitor cell compartment. In human, severe acute liver failure and liver cirrhosis are also both important clinical targets in which regeneration is impaired, where the role of this stem cell compartment seems more convincing. In animal models, the current state of ambiguity regarding the identity and role of liver progenitor cells in liver physiology dampens the enthusiasm for the potential use of these cells in regenerative medicine. The aim of this review is to give the basics of liver progenitor cell biology and discuss recent results vis-à-vis their identity and contribution to liver regeneration. PMID:26600740

  8. In vitro toxicity of trichothecenes on rat haematopoietic progenitors.

    PubMed

    Parent-Massin, D; Thouvenot, D

    1995-01-01

    The fusarial toxicosis induced by trichothecenes is characterized by common syndromes such as vomiting, inflammation, haemorrhages, diarrhoea and haematological changes. Subchronic ingestion of trichothecenes causes a decrease in circulating white cells. This leukopenic change of animals is reported as a characteristic feature in the best known human disorder: Alimentary Toxic Aleukia (ATA). The aim of the present study was to evaluate whether the haematologic disorders imputed to trichothecenes were a result of myelotoxicity by investigating in an in vitro model. Rat haematopoietic progenitors, Colony Forming Units-Granulocytes and Macrophages (CFU-GM), were cultured in the presence of several concentrations of four trichothecenes; T-2 toxin, HT-2 toxin, diacetoxyscirpenol (DAS) and deoxynivalenol (DON). All these trichothecenes were cytotoxic to rat haematopoietic progenitor cells. It is concluded that haematological disorders observed during trichothecene intoxication of animals are caused by the destruction of haematopoietic progenitors such as CFU-GM cells.

  9. Osteocytes serve as a progenitor cell of osteosarcoma

    PubMed Central

    Sottnik, Joseph L; Campbell, Brittany; Mehra, Rohit; Behbahani-Nejad, Omid; Hall, Christopher L.; Keller, Evan T.

    2016-01-01

    Osteosarcoma (OSA) is the most common primary bone tumor in humans. However, the cell of origin of OSA is not clearly defined although there is evidence that osteoblasts may serve as OSA progenitors. The role of osteocytes, terminally differentiated osteoblasts, as OSA progenitors has yet to be described. Analysis of patient cDNA from publicly available microarray data revealed that patients with OSA have increased expression of dentin matrix phosphoprotein 1 (DMP1), a marker of osteocytes. Analysis of multiple murine, human, and canine OSA cell lines revealed DMP1 expression. To test the tumorigenic potential of osteocytes, MLO-Y4, an SV-40 immortalized murine osteocyte cell line, was injected into subcutaneous and orthotopic (intratibial) sites of mice. Tumor growth occurred in both locations. Orthotopic MLO-Y4 tumors produced mixed osteoblastic/osteolytic radiographic lesions; a hallmark of OSA. Together, these data demonstrate for the first time that osteocytes can serve as OSA progenitors. PMID:24700678

  10. Immortalized neural progenitor cells for CNS gene transfer and repair.

    PubMed

    Martínez-Serrano, A; Björklund, A

    1997-11-01

    Immortalized multipotent neural stem and progenitor cells have emerged as a highly convenient source of tissue for genetic manipulation and ex vivo gene transfer to the CNS. Recent studies show that these cells, which can be maintained and genetically transduced as cell lines in culture, can survive, integrate and differentiate into both neurons and glia after transplantation to the intact or damaged brain. Progenitors engineered to secrete trophic factors, or to produce neurotransmitter-related or metabolic enzymes can be made to repopulate diseased or injured brain areas, thus providing a new potential therapeutic tool for the blockade of neurodegenerative processes and reversal of behavioural deficits in animal models of neurodegenerative diseases. With further technical improvements, the use of immortalized neural progenitors may bring us closer to the challenging goal of targeted and effective CNS repair.

  11. Glial Progenitors as Targets for Transformation in Glioma

    PubMed Central

    Ilkanizadeh, Shirin; Lau, Jasmine; Huang, Miller; Foster, Daniel J.; Wong, Robyn; Frantz, Aaron; Wang, Susan; Weiss, William A.; Persson, Anders I.

    2014-01-01

    Glioma is the most common primary malignant brain tumor and arises throughout the central nervous system (CNS). Recent focus on stem-like glioma cells has implicated neural stem cells (NSCs), a minor precursor population restricted to germinal zones, as a potential source of gliomas. In this review, we will focus on the relationship between oligodendrocyte progenitor cells (OPCs), the largest population of cycling glial progenitors in the postnatal brain, and gliomas. Recent studies suggest that OPCs can give rise to gliomas. Furthermore, signaling pathways often associated with NSCs also play key roles during OPC lineage development. Recent advances suggesting that gliomas can undergo a switch from progenitor- to stem-like phenotype after therapy, implicating that an OPC-origin is more likely than previously recognized. Future in-depth studies of OPC biology may shed light on the etiology of OPC-derived gliomas and reveal new therapeutic avenues. PMID:24889528

  12. Endothelial progenitor cells and burn injury - exploring the relationship.

    PubMed

    Banyard, Derek A; Adnani, Blake O; Melkumyan, Satenik; Araniego, Cheryl Ann; Widgerow, Alan D

    2016-01-01

    Burn wounds result in varying degrees of soft tissue damage that are typically graded clinically. Recently a key participant in neovascularization, the endothelial progenitor cell, has been the subject of intense cardiovascular research to explore whether it can serve as a biomarker for vascular injury. In this review, we examine the identity of the endothelial progenitor cell as well as the evidence that support its role as a key responder after burn insult. While there is conflicting evidence with regards to the delta of endothelial progenitor cell mobilization and burn severity, it is clear that they play an important role in wound healing. Systematic and controlled studies are needed to clarify this relationship, and whether this population can serve as a biomarker for burn severity. PMID:27574674

  13. Changes in Chondrogenic Progenitor Populations Associated with Aging and Osteoarthritis.

    PubMed

    Brady, Kyla; Dickinson, Sally C; Hollander, Anthony P

    2015-04-01

    Chondrogenic progenitor populations, including mesenchymal stem cells, represent promising cell-based transplantation or tissue engineering therapies for the regeneration of damaged cartilage. Osteoarthritis (OA) predominantly affects the elderly and is a leading cause of disability worldwide. Advancing age is a prominent risk factor that is closely associated with the onset and progression of the disease. Understanding the influence that aging and OA have on chondrogenic progenitor cells is important to determine how these processes affect the cellular mechanisms of the cells and their capacity to differentiate into functional chondrocytes for use in therapeutic applications. Here, we review the effect of age- and OA-related changes on the growth kinetics and differentiation potential of chondrogenic progenitor cell populations. Aging differentially influences the proliferative potential of progenitor cells showing reduced growth rates with increased senescence and apoptotic activity over time, while chondrogenesis appears to be independent of donor age. Cartilage tissue affected by OA shows evidence of progenitor populations with some potential for repair, however reports on the proliferative propensity of mesenchymal stem cells and their chondrogenic potential are contradictory. This is likely attributed to the narrow age ranges of samples assessed and deficits in definitively identifying donors with OA versus healthy patients across a wide scope of advancing ages. Further studies that investigate the mechanistic effects of chondrogenic progenitor populations associated with aging and the progression of OA using clearly defined criteria and age-matched control subject groups are crucial to our understanding of the clinical relevance of these cells for use in cartilage repair therapies. PMID:27340514

  14. Changes in Chondrogenic Progenitor Populations Associated with Aging and Osteoarthritis

    PubMed Central

    Brady, Kyla; Dickinson, Sally C.

    2015-01-01

    Chondrogenic progenitor populations, including mesenchymal stem cells, represent promising cell-based transplantation or tissue engineering therapies for the regeneration of damaged cartilage. Osteoarthritis (OA) predominantly affects the elderly and is a leading cause of disability worldwide. Advancing age is a prominent risk factor that is closely associated with the onset and progression of the disease. Understanding the influence that aging and OA have on chondrogenic progenitor cells is important to determine how these processes affect the cellular mechanisms of the cells and their capacity to differentiate into functional chondrocytes for use in therapeutic applications. Here, we review the effect of age- and OA-related changes on the growth kinetics and differentiation potential of chondrogenic progenitor cell populations. Aging differentially influences the proliferative potential of progenitor cells showing reduced growth rates with increased senescence and apoptotic activity over time, while chondrogenesis appears to be independent of donor age. Cartilage tissue affected by OA shows evidence of progenitor populations with some potential for repair, however reports on the proliferative propensity of mesenchymal stem cells and their chondrogenic potential are contradictory. This is likely attributed to the narrow age ranges of samples assessed and deficits in definitively identifying donors with OA versus healthy patients across a wide scope of advancing ages. Further studies that investigate the mechanistic effects of chondrogenic progenitor populations associated with aging and the progression of OA using clearly defined criteria and age-matched control subject groups are crucial to our understanding of the clinical relevance of these cells for use in cartilage repair therapies. PMID:27340514

  15. Hematopoietic stem/progenitor cell commitment to the megakaryocyte lineage.

    PubMed

    Woolthuis, Carolien M; Park, Christopher Y

    2016-03-10

    The classical model of hematopoiesis has long held that hematopoietic stem cells (HSCs) sit at the apex of a developmental hierarchy in which HSCs undergo long-term self-renewal while giving rise to cells of all the blood lineages. In this model, self-renewing HSCs progressively lose the capacity for self-renewal as they transit into short-term self-renewing and multipotent progenitor states, with the first major lineage commitment occurring in multipotent progenitors, thus giving rise to progenitors that initiate the myeloid and lymphoid branches of hematopoiesis. Subsequently, within the myeloid lineage, bipotent megakaryocyte-erythrocyte and granulocyte-macrophage progenitors give rise to unipotent progenitors that ultimately give rise to all mature progeny. However, over the past several years, this developmental scheme has been challenged, with the origin of megakaryocyte precursors being one of the most debated subjects. Recent studies have suggested that megakaryocytes can be generated from multiple pathways and that some differentiation pathways do not require transit through a requisite multipotent or bipotent megakaryocyte-erythrocyte progenitor stage. Indeed, some investigators have argued that HSCs contain a subset of cells with biased megakaryocyte potential, with megakaryocytes directly arising from HSCs under steady-state and stress conditions. In this review, we discuss the evidence supporting these nonclassical megakaryocytic differentiation pathways and consider their relative strengths and weaknesses as well as the technical limitations and potential pitfalls in interpreting these studies. Ultimately, such pitfalls will need to be overcome to provide a comprehensive and definitive understanding of megakaryopoiesis. PMID:26787736

  16. Possible Progenitor of Special Supernova Type Detected

    NASA Astrophysics Data System (ADS)

    2008-04-01

    caused by material being pulled off a companion star onto the white dwarf, fusion of this material on the surface of the star should heat the star and produce a strong source of X-radiation prior to the explosion. Once the supernova explosion occurs, the white dwarf is expected to be completely destroyed and then would be undetectable in X-rays. In the merger scenario, the intensity of X-ray emission prior to the explosion is expected to be much weaker. Based on the detection of a fairly strong X-ray source at approximately the position of SN 2007on 4 years before the explosion, Voss and Nelemans conclude that the data support the scenario where matter is pulled off a companion star. The small number of X-ray sources in the field implies that there is only a small chance of an unrelated source being so close by coincidence. Also, the X-ray source has similar properties to those expected for fusion on a white dwarf, unlike most X-ray sources in the sky. However, in follow-up studies, Voss, Nelemans and colleagues Gijs Roelofs (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.) and Cees Bassa (McGill University, Canada) used higher-quality optical images to better determine the supernova's position. This work, which is not yet published, shows a small, but significant difference in the measured positions of the supernova and the X-ray source, suggesting the source may not be the progenitor. Follow-up Chandra observations hint that the X-ray object has disappeared, but further observations are needed to finally decide whether the source was the progenitor or not. The team is also applying this new method to other supernovas and has high hopes that they will eventually succeed in identifying the elusive cause of at least some of these explosions. "We're very excited about opening up a new way of studying supernovas, even though we're not sure that we've seen this particular stellar bomb before it exploded," said Gijs Roelofs. "We're very confident that we

  17. Endothelial progenitor cells: a new player in lupus?

    PubMed

    Haque, Sahena; Alexander, M Yvonne; Bruce, Ian N

    2012-01-01

    Patients with systemic lupus erythematosus (SLE) have a greatly increased risk of cardiovascular disease. There is growing interest in the link between vascular damage and lupus-specific inflammatory factors. Impaired endothelial repair could account for the endothelial dysfunction in this patient group. This review describes the contribution that endothelial progenitor cells could play in the pathogenesis of premature vascular damage in this disease. The methods of isolation, detection, and characterization of endothelial progenitor cells, together with their potential role in repair of the endothelium and as a therapeutic target in SLE, are discussed. PMID:22356717

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

    SciTech Connect

    Becher, Ulrich M.; Breitbach, Martin; Sasse, Philipp; Garbe, Stephan; Ven, Peter F.M. van der; Fuerst, Dieter O.; Fleischmann, Bernd K.

    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.

  19. Subventricular zone progenitors in time and space: generating neuronal diversity

    PubMed Central

    Sequerra, Eduardo B.

    2014-01-01

    The adult mammalian brain harbors a population of cells around their lateral ventricles capable of giving rise to new neurons throughout life. The so-called subventricular zone (SVZ) is a heterogeneous germinative niche in regard to the neuronal types it generates. SVZ progenitors give rise to different olfactory bulb (OB) interneuron types in accordance to their position along the ventricles. Here, I review data showing the difference between progenitors located along different parts of the SVZ axes and ages. I also discuss possible mechanisms for the origin of this diversity. PMID:25565967

  20. ON IDENTIFYING THE PROGENITORS OF Type Ia SUPERNOVAE

    SciTech Connect

    Livio, Mario; Pringle, J. E.

    2011-10-10

    We propose two new means of identifying the main class of progenitors of Type Ia supernovae-single or double degenerate: (1) if the range of supernova properties is significantly determined by the range of viewing angles of non-spherically symmetric explosions, then the nature of the correlation between polarization and another property (for example, the velocity gradient) can be used to determine the geometry of the asymmetry and hence the nature of the progenitor, and (2) in the double- but not in the single-degenerate case, the range in the observed properties (e.g., velocity gradients) is likely to increase with the amount of carbon seen in the ejecta.

  1. Design criteria for ultrafast optical parametric amplifiers

    NASA Astrophysics Data System (ADS)

    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.

  2. Silicon on Insulator MESFETs for RF Amplifiers.

    PubMed

    Wilk, Seth J; Balijepalli, Asha; Ervin, Joseph; Lepkowski, William; Thornton, Trevor J

    2010-03-01

    CMOS compatible, high voltage SOI MESFETs have been fabricated using a standard 3.3V CMOS process without any changes to the process flow. A 0.6μm gate length device operates with a cut-off frequency of 7.3GHz and a maximum oscillation frequency of 21GHz. There is no degradation in device performance up to its breakdown voltage, which greatly exceeds that of CMOS devices on the same process. Other figures of merit of relevance to RF front-end design are presented, including the maximum stable gain and noise figure. An accurate representation of the device in SPICE has been developed using the commercially available TOM3 model. Using the SOI MESFET model, a source degenerated low noise RF amplifier targeting operation near 1GHz has been designed. The amplifier was fabricated on a PCB board and operates at 940MHz with a minimum NF of 3.8dB and RF gain of 9.9dB while only consuming 5mW of DC power. PMID:20657816

  3. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In Heon

    1990-01-01

    The optimum conditions of a solar pumped iodine laser are found in this research for the case of a continuous wave operation and a pulsed operation. The optimum product of the pressure(p) inside the laser tube and the tube diameter(d) was pd=40 approx. 50 torr-cm on the contrary to the case of a high intensity flashlamp pumped iodine laser where the optimum value of the product is known to be pd=150 torr-cm. The pressure-diameter product is less than 1/3 of that of the high power iodine laser. During the research period, various laser materials were also studied for solar pumping. Among the laser materials, Nd:YAG is found to have the lowest laser threshold pumping intensity of about 200 solar constant. The Rhodamine 6G was also tested as the solar pumped laser material. The threshold pumping power was measured to be about 20,000 solar constant. The amplification experiment for a continuously pumped iodine laser amplifier was performed using Vortek solar simulator and the amplification factors were measured for single pass amplification and triple pass amplification of the 15 cm long amplifier tube. The amplification of 5 was obtained for the triple pass amplification.

  4. Silicon on Insulator MESFETs for RF Amplifiers

    PubMed Central

    Balijepalli, Asha; Ervin, Joseph; Lepkowski, William; Thornton, Trevor J.

    2010-01-01

    CMOS compatible, high voltage SOI MESFETs have been fabricated using a standard 3.3V CMOS process without any changes to the process flow. A 0.6μm gate length device operates with a cut-off frequency of 7.3GHz and a maximum oscillation frequency of 21GHz. There is no degradation in device performance up to its breakdown voltage, which greatly exceeds that of CMOS devices on the same process. Other figures of merit of relevance to RF front-end design are presented, including the maximum stable gain and noise figure. An accurate representation of the device in SPICE has been developed using the commercially available TOM3 model. Using the SOI MESFET model, a source degenerated low noise RF amplifier targeting operation near 1GHz has been designed. The amplifier was fabricated on a PCB board and operates at 940MHz with a minimum NF of 3.8dB and RF gain of 9.9dB while only consuming 5mW of DC power. PMID:20657816

  5. Mechanical Amplifier for a Piezoelectric Transducer

    NASA Technical Reports Server (NTRS)

    Moore, James; Swain, Mark; Lawson, Peter; Calvet, Robert

    2003-01-01

    A mechanical amplifier has been devised to multiply the stroke of a piezoelectric transducer (PZT) intended for use at liquid helium temperatures. Interferometry holds the key to high angular resolution imaging and astrometry in space. Future space missions that will detect planets around other solar systems and perform detailed studies of the evolution of stars and galaxies will use new interferometers that observe at mid- and far-infrared wavelengths. Phase-measurement interferometry is key to many aspects of astronomical interferometry, and PZTs are ideal modulators for most methods of phase measurement, but primarily at visible wavelengths. At far infrared wavelengths of 150 to 300 m, background noise is a severe problem and all optics must be cooled to about 4 K. Under these conditions, piezos are ill-suited as modulators, because their throw is reduced by as much as a factor of 2, and even a wavelength or two of modulation is beyond their capability. The largest commercially available piezo stacks are about 5 in. (12.7 cm) long and have a throw of about 180 m at room temperature and only 90 m at 4 K. It would seem difficult or impossible to use PZTs for phase measurements in the far infrared were it not for the new mechanical amplifier that was designed and built.

  6. Hot prospect for new gene amplifier

    SciTech Connect

    Not Available

    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.

  7. Integrating and amplifying signal from riboswitch biosensors.

    PubMed

    Goodson, Michael S; Harbaugh, Svetlana V; Chushak, Yaroslav G; Kelley-Loughnane, Nancy

    2015-01-01

    Biosensors offer a built-in energy supply and inherent sensing machinery that when exploited correctly may surpass traditional sensors. However, biosensor systems have been hindered by a narrow range of ligand detection capabilities, a relatively low signal output, and their inability to integrate multiple signals. Integration of signals could increase the specificity of the sensor and enable detection of a combination of ligands that may indicate environmental or developmental processes when detected together. Amplifying biosensor signal output will increase detector sensitivity and detection range. Riboswitches offer the potential to widen the diversity of ligands that may be detected, and advances in synthetic biology are illuminating myriad possibilities in signal processing using an orthogonal parts-based engineering approach. In this chapter, we describe the design, building, and testing of a riboswitch-based Boolean logic AND gate in bacteria, where an output requires the activation of two riboswitches, and the biological circuitry required to amplify the output of the AND gate using natural extracellular bacterial communication signals to "wire" cells together. PMID:25605381

  8. Tuneable, non-degenerated, nonlinear, parametrically-excited amplifier

    NASA Astrophysics Data System (ADS)

    Dolev, Amit; Bucher, Izhak

    2016-01-01

    The proposed parametric amplifier scheme can be tuned to amplify a wide range of input frequencies by altering the parametric excitation with no need to physically modify the oscillator. Parametric amplifiers had been studied extensively, although most of the work focused on amplifiers that are parametrically excited at a frequency twice the amplifier's natural frequency. These amplifiers are confined to amplifying predetermined frequencies. The proposed parametric amplifier's bandwidth is indeed tuneable to nearly any input frequency, not bound to be an integer multiple of a natural frequency. In order to tune the stiffness and induce a variable frequency parametric excitation, a digitally controlled electromechanical element must be incorporated in the realization. We introduce a novel parametric amplifier with nonlinearity, Duffing type hardening, that bounds the otherwise unlimited amplitude. Moreover, we present a multi degree of freedom system in which a utilization of the proposed method enables the projection of low frequency vector forces on any eigenvector and corresponding natural frequency of the system, and thus to transform external excitations to a frequency band where signal levels are considerably higher. Using the method of multiple scales, analytical expressions for the responses have been retrieved and verified numerically. Parametric studies of the amplifiers' gain, sensitivities and spatial projection of the excitation on the system eigenvectors were carried out analytically. The results demonstrate the advantage of the proposed approach over existing schemes. Practical applications envisaged for the proposed method will be outlined.

  9. Type Ia supernovae: explosions and progenitors

    NASA Astrophysics Data System (ADS)

    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.

  10. Combination ring cavity and backward Raman waveguide amplifier

    DOEpatents

    Kurnit, Norman A.

    1983-01-01

    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. Additionally, the backward Raman amplifier configuration produces a Stokes radiation signal which has a high intensity and a short duration. Adjustment of the position of overlap of the Stokes signal and the CO.sub.2 laser pump signal in the backward Raman waveguide amplifiers alters the amount of pulse compression which can be achieved.

  11. Multiple Differential-Amplifier MMICs Embedded in Waveguides

    NASA Technical Reports Server (NTRS)

    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.

  12. Angle amplifier based on multiplexed volume holographic gratings

    NASA Astrophysics Data System (ADS)

    Cao, Liangcai; Zhao, Yifei; He, Qingsheng; Jin, Guofan

    2008-03-01

    Angle amplifier of laser beam scanner is a widely used device in optical systems. Volume holographic optical elements can be applied in the angle amplifier. Compared with the traditional angle amplifier, it has the advantages of high angle resolution, high diffraction efficiency, small size, and high angle magnification and flexible design. Bragg anglewavelength- compensating recording method is introduced. Because of the Bragg compensatory relation between angle and wavelength, this device could be recorded at another wavelength. The design of the angle amplifier recording at the wavelength of 514.2nm for the working wavelength of 632.8nm is described. An optical setup for recording the angle amplifier device is designed and discussed. Experimental results in the photorefractive crystal Fe:LiNbO 3 demonstrate the feasibility of the angle amplifier scheme.

  13. Intermodulation characteristics of X-band IMPATT amplifiers.

    NASA Technical Reports Server (NTRS)

    Trew, R. J.; Masnari, N. A.; Haddad, G. I.

    1972-01-01

    Measurement of the intermodulation products produced when two equal amplitude signals are applied to the input of an X-band IMPATT diode amplifier. A Si p(+)nn(+) IMPATT diode was operated in a double-slug-tuned reflection amplifier circuit that was tuned to provide 20 dB of small-signal gain at 9.340 GHz. The intermodulation tests consist of measurements of the magnitudes and frequencies of the amplifier output signals as a function of the input signal drive levels and frequency separations. The gain and single-frequency characteristics of the amplifier were also measured and are used along with the theoretical device and circuit admittance characteristics as a basis for explanation of the intermodulation results. A low-frequency dominance mechanism is found to exist in which the low-frequency signals are amplified more than the high-frequency signals. This mechanism becomes more significant as the amplifier drive level is increased.

  14. Josephson parametric amplifiers for the ADMX-HF experiment

    NASA Astrophysics Data System (ADS)

    Malnou, Maxime; Palken, Daniel; Hilton, Gene; Vale, Leila; Lehnert, Konrad

    2016-03-01

    Dark matter search in the ADMX-HF experiment aims at detecting power generated by the axion-photon conversion, of a few hundred of yoctowatts, in the 4 - 12 GHz band. The sensitivity of detection directly depends on the amplifier noise temperature, and therefore requires state of the art microwave amplifiers. In contrast to amplifiers with dissipation on-chip, superconducting Josephson parametric amplifiers (JPA) reach and even circumvent the quantum limit. Over the past years, we have developed JPAs fabricated with arrays of superconducting quantum interference devices. Their gain, bandwidth and tunability are particularly well suited for efficient amplification in the band of interest. In this talk we will present numerical modeling of the behavior of our amplifiers, along with the first results from new designs that cover the 4-12 GHz band. Finally, we will present the ongoing work to increase the gain-bandwidth product and gain stability of our amplifiers.

  15. Crystal oscillators using negative voltage gain, single pole response amplifiers

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L. (Inventor)

    1989-01-01

    A simple and inexpensive crystal oscillator is provided which employs negative voltage gain, single pole response amplifiers. The amplifiers may include such configurations as gate inverters, operational amplifiers and conventional bipolar transistor amplifiers, all of which operate at a frequency which is on the roll-off portion of their gain versus frequency curve. Several amplifier feedback circuit variations are employed to set desired bias levels and to allow the oscillator to operate at the crystal's fundamental frequency or at an overtone of the fundamental frequency. The oscillator is made less expensive than comparable oscillators by employing relatively low frequency amplifiers and operating them at roll-off, at frequencies beyond which they are customarily used. Simplicity is provided because operation at roll-off eliminates components ordinarily required in similar circuits to provide sufficient phase-shift in the feedback circuitry for oscillation to occur.

  16. Epithelial Sodium Channels in Pulmonary Epithelial Progenitor and Stem Cells

    PubMed Central

    Liu, Yang; Jiang, Bi-Jie; Zhao, Run-Zhen; Ji, Hong-Long

    2016-01-01

    Regeneration of the epithelium of mammalian lungs is essential for restoring normal function following injury, and various cells and mechanisms contribute to this regeneration and repair. Club cells, bronchioalveolar stem cells (BASCs), and alveolar type II epithelial cells (ATII) are dominant stem/progenitor cells for maintaining epithelial turnover and repair. Epithelial Na+ channels (ENaC), a critical pathway for transapical salt and fluid transport, are expressed in lung epithelial progenitors, including club and ATII cells. Since ENaC activity and expression are development- and differentiation-dependent, apically located ENaC activity has therefore been used as a functional biomarker of lung injury repair. ENaC activity may be involved in the migration and differentiation of local and circulating stem/progenitor cells with diverse functions, eventually benefiting stem cells spreading to re-epithelialize injured lungs. This review summarizes the potential roles of ENaC expressed in native progenitor and stem cells in the development and regeneration of the respiratory epithelium. PMID:27570489

  17. Progenitor Candidate for SN 2016gkg in NGC 613

    NASA Astrophysics Data System (ADS)

    Kilpatrick, C. D.; Siebert, M. R.; Foley, R. J.; Max, C. E.; Williams, P.; Abramson, L. E.; Lu, C.-X.; Treu, T.; Kassis, M.

    2016-09-01

    We have identified a candidate progenitor star of the Type II SN 2016gkg in NGC 613 (ATel #9521, #9526, #9528, #9529) in archival Hubble Space Telescope (HST) WFPC2 images in the F450W, F606W, and F814W filters.

  18. LPS induces pulp progenitor cell recruitment via complement activation.

    PubMed

    Chmilewsky, F; Jeanneau, C; Laurent, P; About, I

    2015-01-01

    Complement system, a major component of the natural immunity, has been recently identified as an important mediator of the dentin-pulp regeneration process through STRO-1 pulp cell recruitment by the C5a active fragment. Moreover, it has been shown recently that under stimulation with lipoteichoic acid, a complex component of the Gram-positive bacteria cell wall, human pulp fibroblasts are able to synthesize all proteins required for complement activation. However, Gram-negative bacteria, which are also involved in tooth decay, are known as powerful activators of complement system and inflammation. Here, we investigated the role of Gram-negative bacteria-induced complement activation on the pulp progenitor cell recruitment using lipopolysaccharide (LPS), a major component of all Gram-negative bacteria. Our results show that incubating pulp fibroblasts with LPS induced membrane attack complex formation and C5a release in serum-free fibroblast cultures. The produced C5a binds to the pulp progenitor cells' membrane and induces their migration toward the LPS stimulation chamber, as revealed by the dynamic transwell migration assays. The inhibition of this migration by the C5aR-specific antagonist W54011 indicates that the pulp progenitor migration is mediated by the interaction between C5a and C5aR. Our findings demonstrate, for the first time, a direct interaction between the recruitment of progenitor pulp cells and the activation of complement system generated by pulp fibroblast stimulation with LPS.

  19. cKit+ cardiac progenitors of neural crest origin

    PubMed Central

    Hatzistergos, Konstantinos E.; Takeuchi, Lauro M.; Saur, Dieter; Seidler, Barbara; Dymecki, Susan M.; Mai, Jia Jia; White, Ian A.; Balkan, Wayne; Kanashiro-Takeuchi, Rosemeire M.; Schally, Andrew V.; Hare, Joshua M.

    2015-01-01

    The degree to which cKit-expressing progenitors generate cardiomyocytes in the heart is controversial. Genetic fate-mapping studies suggest minimal contribution; however, whether or not minimal contribution reflects minimal cardiomyogenic capacity is unclear because the embryonic origin and role in cardiogenesis of these progenitors remain elusive. Using high-resolution genetic fate-mapping approaches with cKitCreERT2/+ and Wnt1::Flpe mouse lines, we show that cKit delineates cardiac neural crest progenitors (CNCkit). CNCkit possess full cardiomyogenic capacity and contribute to all CNC derivatives, including cardiac conduction system cells. Furthermore, by modeling cardiogenesis in cKitCreERT2-induced pluripotent stem cells, we show that, paradoxically, the cardiogenic fate of CNCkit is regulated by bone morphogenetic protein antagonism, a signaling pathway activated transiently during establishment of the cardiac crescent, and extinguished from the heart before CNC invasion. Together, these findings elucidate the origin of cKit+ cardiac progenitors and suggest that a nonpermissive cardiac milieu, rather than minimal cardiomyogenic capacity, controls the degree of CNCkit contribution to myocardium. PMID:26438843

  20. In Vitro Pancreas Organogenesis from Dispersed Mouse Embryonic Progenitors

    PubMed Central

    Grapin-Botton, Anne

    2014-01-01

    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. PMID:25079453

  1. Stem cells and progenitor cells in renal disease.

    PubMed

    Haller, Hermann; de Groot, Kirsten; Bahlmann, Ferdinand; Elger, Marlies; Fliser, Danilo

    2005-11-01

    Stem cells and progenitor cells are necessary for repair and regeneration of injured renal tissue. Infiltrating or resident stem cells can contribute to the replacement of lost or damaged tissue. However, the regulation of circulating progenitor cells is not well understood. We have analyzed the effects of erythropoietin on circulating progenitor cells and found that low levels of erythropoietin induce mobilization and differentiation of endothelial progenitor cells. In an animal model of 5/6 nephrectomy we could demonstrate that erythropoietin ameliorates tissue injury. Full regeneration of renal tissue demands the existence of stem cells and an adequate local "milieu," a so-called stem cell niche. We have previously described a stem cell niche in the kidneys of the dogfish, Squalus acanthus. Further analysis revealed that in the regenerating zone of the shark kidney, stem cells exist that can be induced by loss of renal tissue to form new glomeruli. Such animal models improve our understanding of stem cell behavior in the kidney and may eventually contribute to novel therapies. PMID:16221168

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

    PubMed

    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.

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

    PubMed

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

    2014-01-01

    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. PMID:25079453

  4. Epithelial Sodium Channels in Pulmonary Epithelial Progenitor and Stem Cells.

    PubMed

    Liu, Yang; Jiang, Bi-Jie; Zhao, Run-Zhen; Ji, Hong-Long

    2016-01-01

    Regeneration of the epithelium of mammalian lungs is essential for restoring normal function following injury, and various cells and mechanisms contribute to this regeneration and repair. Club cells, bronchioalveolar stem cells (BASCs), and alveolar type II epithelial cells (ATII) are dominant stem/progenitor cells for maintaining epithelial turnover and repair. Epithelial Na(+) channels (ENaC), a critical pathway for transapical salt and fluid transport, are expressed in lung epithelial progenitors, including club and ATII cells. Since ENaC activity and expression are development- and differentiation-dependent, apically located ENaC activity has therefore been used as a functional biomarker of lung injury repair. ENaC activity may be involved in the migration and differentiation of local and circulating stem/progenitor cells with diverse functions, eventually benefiting stem cells spreading to re-epithelialize injured lungs. This review summarizes the potential roles of ENaC expressed in native progenitor and stem cells in the development and regeneration of the respiratory epithelium. PMID:27570489

  5. TYPE IIb SUPERNOVAE WITH COMPACT AND EXTENDED PROGENITORS

    SciTech Connect

    Chevalier, Roger A.; Soderberg, Alicia M.

    2010-03-01

    The classic example of a Type IIb supernova is SN 1993J, which had a cool extended progenitor surrounded by a dense wind. There is evidence for another category of Type IIb supernova that has a more compact progenitor with a lower density, probably fast, wind. Distinguishing features of the compact category are weak optical emission from the shock heated envelope at early times, nonexistent or very weak H emission in the late nebular phase, rapidly evolving radio emission, rapid expansion of the radio shell, and expected nonthermal as opposed to thermal X-ray emission. Type IIb supernovae that have one or more of these features include SNe 1996cb, 2001ig, 2003bg, 2008ax, and 2008bo. All of these with sufficient radio data (the last four) show evidence for presupernova wind variability. We estimate a progenitor envelope radius {approx}1 x 10{sup 11} cm for SN 2008ax, a value consistent with a compact Wolf-Rayet progenitor. Supernovae in the SN 1993J extended category include SN 2001gd and probably the Cas A supernova. We suggest that the compact Type IIb events be designated Type cIIb and the extended ones Type eIIb. The H envelope mass dividing these categories is {approx}0.1 M {sub sun}.

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

    PubMed

    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.

  7. Method and apparatus for linear low-frequency feedback in monolithic low-noise charge amplifiers

    DOEpatents

    DeGeronimo, Gianluigi

    2006-02-14

    A charge amplifier includes an amplifier, feedback circuit, and cancellation circuit. The feedback circuit includes a capacitor, inverter, and current mirror. The capacitor is coupled across the signal amplifier, the inverter is coupled to the output of the signal amplifier, and the current mirror is coupled to the input of the signal amplifier. The cancellation circuit is coupled to the output of the signal amplifier. A method of charge amplification includes providing a signal amplifier; coupling a first capacitor across the signal amplifier; coupling an inverter to the output of the signal amplifier; coupling a current mirror to the input of the signal amplifier; and coupling a cancellation circuit to the output of the signal amplifier. A front-end system for use with radiation sensors includes a charge amplifier and a current amplifier, shaping amplifier, baseline stabilizer, discriminator, peak detector, timing detector, and logic circuit coupled to the charge amplifier.

  8. A photoelectric amplifier as a dye detector

    USGS Publications Warehouse

    Ebel, Wesley J.

    1962-01-01

    A dye detector, based on a modified photoelectric amplifier, has been planned, built, and tested. It was designed to record automatically the time of arrival of fluorescein dye at predetermined points in a stream system. Laboratory tests and stream trials proved the instrument to be efficient. Small changes in color can be detected in turbid or clear water. The unit has been used successfully for timing intervals of more than 17 hours; significant savings of time and manpower have resulted. Replacement of the clock, included in the original device, with a recording milliammeter increases the efficiency of the unit by contin,!ously recording changes in turbidity. The addition of this component would increase the cost from $75 to approximately $105.

  9. Compressed magnetic flux amplifier with capacitive load

    SciTech Connect

    Stuetzer, O.M.

    1980-03-01

    A first-order analysis is presented for a compressed magnetic flux (CMF) current amplifier working into a load with a capacitive component. Since the purpose of the investigation was to gain a general understanding of the arrangement, a number of approximations and limitations were accepted. The inductance of the transducer varies with time; the inductance/resistance/capacitance (LRC) circuit therefore is parametric and solutions are different for the stable regime (high C), the oscillation regime (low C), and the transition case. Solutions and performance depend strongly on circuit boundary conditions, i.e., energization of the circuit by either an injected current or by an applied capacitor charge. The behavior of current and energy amplification for the various cases are discussed in detail. A number of experiments with small CMF devices showed that the first-order theory presented predicts transducer performance well in the linear regime.

  10. Low-noise amplifiers for satellite communications

    NASA Astrophysics Data System (ADS)

    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.

  11. Wide-range lock-in amplifier

    DOEpatents

    McNeilly, David R.

    1985-01-01

    A lock-in amplifier is provided which allows detection of a signal buried in noise without preprocessing of the input signal. An analog signal multiplier is used to obtain a dc output which is the product of the signal being detected and a high-purity sine wave signal. A reference signal of a known selectable frequency is applied to a sine-wave generator to generate the sine wave of the same frequency. The sine wave is applied to a multiplier through a phase shift arrangement to allow the detection of both amplitude of the detected signal and the phases relative to the reference signal. The multiplier output is filtered by a low-pass filter to eliminate unwanted frequency components from the output signal.

  12. Wide-range lock-in amplifier

    DOEpatents

    McNeilly, D.R.

    1984-01-01

    A lock-in amplifier is provided which allows detection of a signal buried in noise without preprocessing of the input signal. An analog signal multiplier is used to obtain a dc output which is the product of the signal being detected and a high-purity sine wave signal. A reference signal of a known selectable frequency is applied to a sine-wave generator to generate the sine wave of the same frequency. The sine wave is applied to a multiplier through a phase shift arrangement to allow the detection of both amplitude of the detected signal and the phases relative to the reference signal. The multiplier output is filtered by a low-pass filter to eliminate unwanted frequency components from the output signal.

  13. Rippled beam free electron laser amplifier

    DOEpatents

    Carlsten, Bruce E.

    1999-01-01

    A free electron laser amplifier provides a scalloping annular electron beam that interacts with the axial electric field of a TM.sub.0n mode. A waveguide defines an axial centerline and, a solenoid arranged about the waveguide produces an axial constant magnetic field within the waveguide. An electron beam source outputs a annular electron beam that interacts with the axial magnetic field to have an equilibrium radius and a ripple radius component having a variable radius with a ripple period along the axial centerline. An rf source outputs an axial electric field that propagates within the waveguide coaxial with the electron beam and has a radial mode that interacts at the electron beam at the equilibrium radius component of the electron beam.

  14. InP Heterojunction Bipolar Transistor Amplifiers to 255 GHz

    NASA Technical Reports Server (NTRS)

    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.

  15. Cladding-pumped erbium-doped multicore fiber amplifier.

    PubMed

    Abedin, K S; Taunay, T F; Fishteyn, M; DiGiovanni, D J; Supradeepa, V R; Fini, J M; Yan, M F; Zhu, B; Monberg, E M; Dimarcello, F V

    2012-08-27

    A cladding pumped multicore erbium-doped fiber amplifier for simultaneous amplification of 6 channels is demonstrated. Peak gain over 32 dB has been obtained at a wavelength of 1560 nm and the bandwidth measured at 20-dB gain was about 35 nm. Numerical modeling of cladding pumped multicore erbium-doped amplifier was also performed to study the properties of the amplifier. The results of experiment and simulation are found to be in good agreement.

  16. Endometrial stem/progenitor cells: the first 10 years

    PubMed Central

    Gargett, Caroline E.; Schwab, Kjiana E.; Deane, James A.

    2016-01-01

    BACKGROUND The existence of stem/progenitor cells in the endometrium was postulated many years ago, but the first functional evidence was only published in 2004. The identification of rare epithelial and stromal populations of clonogenic cells in human endometrium has opened an active area of research on endometrial stem/progenitor cells in the subsequent 10 years. METHODS The published literature was searched using the PubMed database with the search terms ‘endometrial stem cells and menstrual blood stem cells' until December 2014. RESULTS Endometrial epithelial stem/progenitor cells have been identified as clonogenic cells in human and as label-retaining or CD44+ cells in mouse endometrium, but their characterization has been modest. In contrast, endometrial mesenchymal stem/stromal cells (MSCs) have been well characterized and show similar properties to bone marrow MSCs. Specific markers for their enrichment have been identified, CD146+PDGFRβ+ (platelet-derived growth factor receptor beta) and SUSD2+ (sushi domain containing-2), which detected their perivascular location and likely pericyte identity in endometrial basalis and functionalis vessels. Transcriptomics and secretomics of SUSD2+ cells confirm their perivascular phenotype. Stromal fibroblasts cultured from endometrial tissue or menstrual blood also have some MSC characteristics and demonstrate broad multilineage differentiation potential for mesodermal, endodermal and ectodermal lineages, indicating their plasticity. Side population (SP) cells are a mixed population, although predominantly vascular cells, which exhibit adult stem cell properties, including tissue reconstitution. There is some evidence that bone marrow cells contribute a small population of endometrial epithelial and stromal cells. The discovery of specific markers for endometrial stem/progenitor cells has enabled the examination of their role in endometrial proliferative disorders, including endometriosis, adenomyosis and Asherman

  17. Alteration of cardiac progenitor cell potency in GRMD dogs.

    PubMed

    Cassano, M; Berardi, E; Crippa, S; Toelen, J; Barthelemy, I; Micheletti, R; Chuah, M; Vandendriessche, T; Debyser, Z; Blot, S; Sampaolesi, M

    2012-01-01

    Among the animal models of Duchenne muscular dystrophy (DMD), the Golden Retriever muscular dystrophy (GRMD) dog is considered the best model in terms of size and pathological onset of the disease. As in human patients presenting with DMD or Becker muscular dystrophies (BMD), the GRMD is related to a spontaneous X-linked mutation of dystrophin and is characterized by myocardial lesions. In this respect, GRMD is a useful model to explore cardiac pathogenesis and for the development of therapeutic protocols. To investigate whether cardiac progenitor cells (CPCs) isolated from healthy and GRMD dogs may differentiate into myocardial cell types and to test the feasibility of cell therapy for cardiomyopathies in a preclinical model of DMD, CPCs were isolated from cardiac biopsies of healthy and GRMD dogs. Gene profile analysis revealed an active cardiac transcription network in both healthy and GRMD CPCs. However, GRMD CPCs showed impaired self-renewal and cardiac differentiation. Population doubling and telomerase analyses highlighted earlier senescence and proliferation impairment in progenitors isolated from GRMD cardiac biopsies. Immunofluorescence analysis revealed that only wt CPCs showed efficient although not terminal cardiac differentiation, consistent with the upregulation of cardiac-specific proteins and microRNAs. Thus, the pathological condition adversely influences the cardiomyogenic differentiation potential of cardiac progenitors. Using PiggyBac transposon technology we marked CPCs for nuclear dsRed expression, providing a stable nonviral gene marking method for in vivo tracing of CPCs. Xenotransplantation experiments in neonatal immunodeficient mice revealed a valuable contribution of CPCs to cardiomyogenesis with homing differences between wt and dystrophic progenitors. These results suggest that cardiac degeneration in dystrophinopathies may account for the progressive exhaustion of local cardiac progenitors and shed light on cardiac stemness in

  18. Gain of Olig2 function in oligodendrocyte progenitors promotes remyelination.

    PubMed

    Wegener, Amélie; Deboux, Cyrille; Bachelin, Corinne; Frah, Magali; Kerninon, Christophe; Seilhean, Danielle; Weider, Matthias; Wegner, Michael; Nait-Oumesmar, Brahim

    2015-01-01

    The basic helix-loop-helix transcription factor Olig2 is a key determinant for the specification of neural precursor cells into oligodendrocyte progenitor cells. However, the functional role of Olig2 in oligodendrocyte migration and differentiation remains elusive both during developmental myelination and under demyelinating conditions of the adult central nervous system. To decipher Olig2 functions, we generated transgenic mice (TetOlig2:Sox10(rtTA/+)) overexpressing Olig2 in Sox10(+) oligodendroglial cells in a doxycycline inducible manner. We show that Olig2 overexpression increases the generation of differentiated oligodendrocytes, leading to precocious myelination of the central nervous system. Unexpectedly, we found that gain of Olig2 function in oligodendrocyte progenitor cells enhances their migration rate. To determine whether Olig2 overexpression in adult oligodendrocyte progenitor cells promotes oligodendrocyte regeneration for myelin repair, we induced lysophosphatidylcholine demyelination in the corpus callosum of TetOlig2:Sox10(rtTA/+) and control mice. We found that Olig2 overexpression enhanced oligodendrocyte progenitor cell differentiation and remyelination. To assess the relevance of these findings in demyelinating diseases, we also examined OLIG2 expression in multiple sclerosis lesions. We demonstrate that OLIG2 displays a differential expression pattern in multiple sclerosis lesions that correlates with lesion activity. Strikingly, OLIG2 was predominantly detected in NOGO-A(+) (now known as RTN4-A) maturing oligodendrocytes, which prevailed in active lesion borders, rather than chronic silent and shadow plaques. Taken together, our data provide proof of principle indicating that OLIG2 overexpression in oligodendrocyte progenitor cells might be a possible therapeutic mechanism for enhancing myelin repair.

  19. UPDATE ON THE CETUS POLAR STREAM AND ITS PROGENITOR

    SciTech Connect

    Yam, William; Carlin, Jeffrey L.; Newberg, Heidi Jo; Dumas, Julie; O'Malley, Erin; Newby, Matthew; Martin, Charles

    2013-10-20

    We trace the Cetus Polar Stream (CPS) with blue horizontal branch and red giant stars from Data Release 8 of the Sloan Digital Sky Survey. Using a larger data set than was available previously, we are able to refine the measured distance and velocity to this tidal debris star stream in the south Galactic cap. Assuming that the tidal debris traces the progenitor's orbit, we fit an orbit to the CPS and find that the stream is confined between ∼24 and 36 kpc on a rather polar orbit inclined 87° to the Galactic plane. The eccentricity of the orbit is 0.20, and the period is ∼700 Myr. If we instead matched N-body simulations to the observed tidal debris, these orbital parameters would change by 10% or less. The CPS stars travel in the opposite direction to those from the Sagittarius tidal stream in the same region of the sky. Through N-body models of satellites on the best-fitting orbit, and assuming that mass follows light, we show that the stream width, line-of-sight depth, and velocity dispersion imply a progenitor of ∼> 10{sup 8} M{sub ☉}. However, the density of stars along the stream requires either a disruption time on the order of one orbit or a stellar population that is more centrally concentrated than the dark matter. We suggest that an ultrafaint dwarf galaxy progenitor could reproduce a large stream width and velocity dispersion without requiring a very recent deflection of the progenitor into its current orbit. We find that most Cetus stars have metallicities of –2.5 < [Fe/H] <–2.0, similar to the observed metallicities of the ultrafaint dwarfs. Our simulations suggest that the parameters of the dwarf galaxy progenitors, including their dark matter content, could be constrained by observations of their tidal tails through comparison of the debris with N-body simulations.

  20. Gain of Olig2 function in oligodendrocyte progenitors promotes remyelination

    PubMed Central

    Wegener, Amélie; Deboux, Cyrille; Bachelin, Corinne; Frah, Magali; Kerninon, Christophe; Seilhean, Danielle; Weider, Matthias; Wegner, Michael

    2015-01-01

    The basic helix-loop-helix transcription factor Olig2 is a key determinant for the specification of neural precursor cells into oligodendrocyte progenitor cells. However, the functional role of Olig2 in oligodendrocyte migration and differentiation remains elusive both during developmental myelination and under demyelinating conditions of the adult central nervous system. To decipher Olig2 functions, we generated transgenic mice (TetOlig2:Sox10rtTA/+) overexpressing Olig2 in Sox10+ oligodendroglial cells in a doxycycline inducible manner. We show that Olig2 overexpression increases the generation of differentiated oligodendrocytes, leading to precocious myelination of the central nervous system. Unexpectedly, we found that gain of Olig2 function in oligodendrocyte progenitor cells enhances their migration rate. To determine whether Olig2 overexpression in adult oligodendrocyte progenitor cells promotes oligodendrocyte regeneration for myelin repair, we induced lysophosphatidylcholine demyelination in the corpus callosum of TetOlig2:Sox10rtTA/+ and control mice. We found that Olig2 overexpression enhanced oligodendrocyte progenitor cell differentiation and remyelination. To assess the relevance of these findings in demyelinating diseases, we also examined OLIG2 expression in multiple sclerosis lesions. We demonstrate that OLIG2 displays a differential expression pattern in multiple sclerosis lesions that correlates with lesion activity. Strikingly, OLIG2 was predominantly detected in NOGO-A+ (now known as RTN4-A) maturing oligodendrocytes, which prevailed in active lesion borders, rather than chronic silent and shadow plaques. Taken together, our data provide proof of principle indicating that OLIG2 overexpression in oligodendrocyte progenitor cells might be a possible therapeutic mechanism for enhancing myelin repair. PMID:25564492

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

    NASA Technical Reports Server (NTRS)

    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.

  2. Precision absolute value amplifier for a precision voltmeter

    DOEpatents

    Hearn, William E.; Rondeau, Donald J.

    1985-01-01

    Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resister is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resister. The output current through the load resister is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resister. A second gain determining resister is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

  3. Precision absolute-value amplifier for a precision voltmeter

    DOEpatents

    Hearn, W.E.; Rondeau, D.J.

    1982-10-19

    Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resistor is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resistor. The output current through the load resistor is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resistor. A second gain determining resistor is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

  4. Ring cavity for a Raman capillary waveguide amplifier

    DOEpatents

    Kurnit, N.A.

    1981-01-27

    A regenerative ring amplifier and regenerative ring oscillator are described which function to feed back a portion of the Stokes signal to complete the ring cavity. The ring cavity configuration allows the CO/sub 2/ laser pump signal and Stokes signal to copropagate through the Raman capillary waveguide amplifier. A Raman capillary waveguide amplifier is also provided in the return leg of the ring cavity to increase gain without increasing the round trip time. Additionally, the ring cavity can be designed such that the amplified Stokes signal is synchronous with the mode-locked spikes of the incoming CO/sub 2/ laser pump signal.

  5. Ring cavity for a Raman capillary waveguide amplifier

    DOEpatents

    Kurnit, N.A.

    1983-07-19

    Disclosed is a regenerative ring amplifier and regenerative ring oscillator which function to feed back a portion of the Stokes signal to complete the ring cavity. The ring cavity configuration allows the CO[sub 2] laser pump signal and Stokes signal to copropagate through the Raman capillary waveguide amplifier. A Raman capillary waveguide amplifier is also provided in the return leg of the ring cavity to increase gain without increasing the round trip time. Additionally, the ring cavity can be designed such that the amplifier Stokes signal is synchronous with the mode-locked spikes of the incoming CO[sub 2] laser pump signal. 6 figs.

  6. Ring cavity for a raman capillary waveguide amplifier

    DOEpatents

    Kurnit, Norman A.

    1983-07-19

    A regenerative ring amplifier and regenerative ring oscillator which function to feed back a portion of the Stokes signal to complete the ring cavity. The ring cavity configuration allows the CO.sub.2 laser pump signal and Stokes signal to copropagate through the Raman capillary waveguide amplifier. A Raman capillary waveguide amplifier is also provided in the return leg of the ring cavity to increase gain without increasing the round trip time. Additionally, the ring cavity can be designed such that the amplifier Stokes signal is synchronous with the mode-locked spikes of the incoming CO.sub.2 laser pump signal.

  7. Nylon Sleeve for Cavity Amplifier Holds Tuning Despite Heat

    NASA Technical Reports Server (NTRS)

    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.

  8. Compensation of pulse-distortion in saturated laser amplifiers.

    PubMed

    Schimpf, Damian N; Ruchert, Clemens; Nodop, Dirk; Limpert, Jens; Tünnermann, Andreas; Salin, Francois

    2008-10-27

    We derive an expression describing pre-compensation of pulse-distortion due to saturation effects in short pulse laser-amplifiers. The analytical solution determines the optimum input pulse-shape required to obtain any arbitrary target pulse-shape at the output of the saturated laser-amplifier. The relation is experimentally verified using an all-fiber amplifier chain that is seeded by a directly modulated laser-diode. The method will prove useful in applications of high power, high energy laser-amplifier systems that need particular pulse-shapes to be efficient, e.g. micromachining and scientific laser-matter-interactions. PMID:18958044

  9. Digitally gain controlled linear high voltage amplifier for laboratory applications.

    PubMed

    Koçum, C

    2011-08-01

    The design of a digitally gain controlled high-voltage non-inverting bipolar linear amplifier is presented. This cost efficient and relatively simple circuit has stable operation range from dc to 90 kHz under the load of 10 kΩ and 39 pF. The amplifier can swing up to 360 V(pp) under these conditions and it has 2.5 μs rise time. The gain can be changed by the aid of JFETs. The amplifiers have been realized using a combination of operational amplifiers and high-voltage discrete bipolar junction transistors. The circuit details and performance characteristics are discussed.

  10. The solid-state Ku-band power amplifier

    NASA Technical Reports Server (NTRS)

    Geller, B. D.

    1975-01-01

    A survey of IMPATT diodes and negative resistance amplifiers is presented. The first phase of the amplifier effort is discussed in which a single diode reflection amplifier delivering 0.5 watt at 15 GHz with 10-dB gain over a 1-GHz band was developed. The design of a dominant mode resonant combiner is described along with the characterization of the IMPATT diodes. Results are given on the complete amplifier and on the thermal and graceful failure characteristics of the unit.

  11. MiR-128-2 inhibits common lymphoid progenitors from developing into progenitor B cells

    PubMed Central

    Chen, Huo; Fei, Xia; Tang, YuXu; Yan, Yunqiu; Zhang, Huimin; Zhang, Jinping

    2016-01-01

    A considerable number of studies revealed that B cell development is finely regulated by transcription factors (TFs). Recent studies suggested that TFs are coordinated with microRNAs to control the development of B cells in numerous checkpoints. In the present study, we first found that miR-128-2 was differentially expressed in various immune organs and immunocytes. B cell development was inhibited in miR-128-2-overexpressed chimera and transgenic (TG) mice in bone marrow with decreased preproB, preB, proB, immature B, and recirculating B cells, as well as increased common lymphoid progenitors (CLPs). Further experiments showed that the apoptosis of CLP decreased, but proliferation was not altered in miR-128-2-overexpressed mice. Extensive studies suggested that the inhibition of apoptosis of CLP may be caused by miR-128-2 targeting A2B and MALT1, thereby increasing the phosphorylation of ERK and P38 MAPK. Such findings have prompted future investigations on the function of miR-128-2 in lymph genesis. PMID:27008703

  12. Stem cell biology is population biology: differentiation of hematopoietic multipotent progenitors to common lymphoid and myeloid progenitors

    PubMed Central

    2013-01-01

    The hematopoietic stem cell (HSC) system is a demand control system, with the demand coming from the organism, since the products of the common myeloid and lymphoid progenitor (CMP, CLP respectively) cells are essential for activity and defense against disease. We show how ideas from population biology (combining population dynamics and evolutionary considerations) can illuminate the feedback control of the HSC system by the fully differentiated products, which has recently been verified experimentally. We develop models for the penultimate differentiation of HSC Multipotent Progenitors (MPPs) into CLP and CMP and introduce two concepts from population biology into stem cell biology. The first concept is the Multipotent Progenitor Commitment Response (MPCR) which is the probability that a multipotent progenitor cell follows a CLP route rather than a CMP route. The second concept is the link between the MPCR and a measure of Darwinian fitness associated with organismal performance and the levels of differentiated lymphoid and myeloid cells. We show that many MPCRs are consistent with homeostasis, but that they will lead to different dynamics of cells and signals following a wound or injury and thus have different consequences for Darwinian fitness. We show how coupling considerations of life history to dynamics of the HSC system and its products allows one to compute the selective pressures on cellular processes. We discuss ways that this framework can be used and extended. PMID:23327512

  13. Mesenchymal cells. Defining a mesenchymal progenitor niche at single-cell resolution.

    PubMed

    Kumar, Maya E; Bogard, Patrick E; Espinoza, F Hernán; Menke, Douglas B; Kingsley, David M; Krasnow, Mark A

    2014-11-14

    Most vertebrate organs are composed of epithelium surrounded by support and stromal tissues formed from mesenchyme cells, which are not generally thought to form organized progenitor pools. Here, we use clonal cell labeling with multicolor reporters to characterize individual mesenchymal progenitors in the developing mouse lung. We observe a diversity of mesenchymal progenitor populations with different locations, movements, and lineage boundaries. Airway smooth muscle (ASM) progenitors map exclusively to mesenchyme ahead of budding airways. Progenitors recruited from these tip pools differentiate into ASM around airway stalks; flanking stalk mesenchyme can be induced to form an ASM niche by a lateral bud or by an airway tip plus focal Wnt signal. Thus, mesenchymal progenitors can be organized into localized and carefully controlled domains that rival epithelial progenitor niches in regulatory sophistication. PMID:25395543

  14. X-Band, 17-Watt Solid-State Power Amplifier

    NASA Technical Reports Server (NTRS)

    Mittskus, Anthony; Stone, Ernest; Boger, William; Burgess, David; Honda, Richard; Nuckolls, Carl

    2005-01-01

    An advanced solid-state power amplifier that can generate an output power of as much as 17 W at a design operating frequency of 8.4 GHz has been designed and constructed as a smaller, lighter, less expensive alternative to traveling-wave-tube X-band amplifiers and to prior solid-state X-band power amplifiers of equivalent output power. This amplifier comprises a monolithic microwave integrated circuit (MMIC) amplifier module and a power-converter module integrated into a compact package (see Figure 1). The amplifier module contains an input variable-gain amplifier (VGA), an intermediate driver stage, a final power stage, and input and output power monitors (see Figure 2). The VGA and the driver amplifier are 0.5-m GaAs-based metal semiconductor field-effect transistors (MESFETs). The final power stage contains four parallel high-efficiency, GaAs-based pseudomorphic high-electron-mobility transistors (PHEMTs). The gain of the VGA is voltage-variable over a range of 10 to 24 dB. To provide for temperature compensation of the overall amplifier gain, the gain-control voltage is generated by an operational-amplifier circuit that includes a resistor/thermistor temperature-sensing network. The driver amplifier provides a gain of 14 dB to an output power of 27 dBm to drive the four parallel output PHEMTs, each of which is nominally capable of putting out as much as 5 W. The driver output is sent to the input terminals of the four parallel PHEMTs through microstrip power dividers; the outputs of these PHEMTs are combined by microstrip power combiners (which are similar to the microstrip power dividers) to obtain the final output power of 17 W.

  15. Ferroelectric Field-Effect Transistor Differential Amplifier Circuit Analysis

    NASA Technical Reports Server (NTRS)

    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.

  16. Reflection Amplifiers in Online Courses: A Classification Framework

    ERIC Educational Resources Information Center

    Verpoorten, Dominique; Westera, Wim; Specht, Marcus

    2011-01-01

    This paper provides a theoretical framework for "reflection amplifiers" that are used in online courses. Such reflection amplifiers are intervention techniques that aim at provoking reflective practices in learning, in order to enhance the quality and effectiveness of learning and promote meta-cognition. A literature survey identified a sample of…

  17. Conductively Cooled Ho:Tm:LuLiF Laser Amplifier

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Trieu, Bo; Petros, M.; Petzar, Paul; Lee, Hyung; Singh, U.

    2008-01-01

    A conductively-cooled Ho:Tm:LuLiF laser head can amplify 80mJ/340ns probe pulses into 400mJ when the pump pulse energy is close to amplified spontaneous emission (ASE) threshold, 5.6J. For a small signal, the double-pass amplification exceeds 25.

  18. Cross-talk free, low-noise optical amplifier

    DOEpatents

    Dijaili, Sol P.; Patterson, Frank G.; Deri, Robert J.

    1995-01-01

    A low-noise optical amplifier solves crosstalk problems in optical amplifiers by using an optical cavity oriented off-axis (e.g. perpendicular) to the direction of a signal amplified by the gain medium of the optical amplifier. Several devices are used to suppress parasitic lasing of these types of structures. The parasitic lasing causes the gain of these structures to be practically unusable. The lasing cavity is operated above threshold and the gain of the laser is clamped to overcome the losses of the cavity. Any increase in pumping causes the lasing power to increase. The clamping action of the gain greatly reduces crosstalk due to gain saturation for the amplified signal beam. It also reduces other nonlinearities associated with the gain medium such as four-wave mixing induced crosstalk. This clamping action can occur for a bandwidth defined by the speed of the laser cavity. The lasing field also reduces the response time of the gain medium. By having the lasing field off-axis, no special coatings are needed. Other advantages are that the lasing field is easily separated from the amplified signal and the carrier grating fluctuations induced by four-wave mixing are decreased. Two related methods reduce the amplified spontaneous emission power without sacrificing the gain of the optical amplifier.

  19. Cross-talk free, low-noise optical amplifier

    DOEpatents

    Dijaili, S.P.; Patterson, F.G.; Deri, R.J.

    1995-07-25

    A low-noise optical amplifier solves crosstalk problems in optical amplifiers by using an optical cavity oriented off-axis (e.g. perpendicular) to the direction of a signal amplified by the gain medium of the optical amplifier. Several devices are used to suppress parasitic lasing of these types of structures. The parasitic lasing causes the gain of these structures to be practically unusable. The lasing cavity is operated above threshold and the gain of the laser is clamped to overcome the losses of the cavity. Any increase in pumping causes the lasing power to increase. The clamping action of the gain greatly reduces crosstalk due to gain saturation for the amplified signal beam. It also reduces other nonlinearities associated with the gain medium such as four-wave mixing induced crosstalk. This clamping action can occur for a bandwidth defined by the speed of the laser cavity. The lasing field also reduces the response time of the gain medium. By having the lasing field off-axis, no special coatings are needed. Other advantages are that the lasing field is easily separated from the amplified signal and the carrier grating fluctuations induced by four-wave mixing are decreased. Two related methods reduce the amplified spontaneous emission power without sacrificing the gain of the optical amplifier. 11 figs.

  20. Efficient laser amplifier using sequential pulses of different wavelengths

    DOEpatents

    Stark, Jr., Eugene E.; Kephart, John F.; Leland, Wallace T.; Reichelt, Walter H.

    1980-01-01

    A laser oscillator output pulse is separated into a plurality of separate beams which are temporally or spatially individually amplified by a power amplifier. The beams may then be recombined to provide a more powerful output than conventional single beam amplification.

  1. External Peltier Cooler For Low-Noise Amplifier

    NASA Technical Reports Server (NTRS)

    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.

  2. 21 CFR 870.2050 - Biopotential amplifier and signal conditioner.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Biopotential amplifier and signal conditioner. 870.2050 Section 870.2050 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... conditioner is a device used to amplify or condition an electrical signal of biologic origin....

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

    PubMed Central

    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. PMID:26798055

  4. Amplified spontaneous emission in solar-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.

    1992-01-01

    The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

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

    PubMed

    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.

  6. Models of reduced-noise, probabilistic linear amplifiers

    NASA Astrophysics Data System (ADS)

    Combes, Joshua; Walk, Nathan; Lund, A. P.; Ralph, T. C.; Caves, Carlton M.

    2016-05-01

    We construct an amplifier that interpolates between a nondeterministic, immaculate linear amplifier and a deterministic, ideal linear amplifier and beyond to nonideal linear amplifiers. The construction involves cascading an immaculate linear amplifier that has amplitude gain g1 with a (possibly) nonideal linear amplifier that has gain g2. With respect to normally ordered moments, the device has output noise μ2(G2-1 ) where G =g1g2 is the overall amplitude gain and μ2 is a noise parameter. When μ2≥1 , our devices realize ideal (μ2=1 ) and nonideal (μ2>1 ) linear amplifiers. When 0 ≤μ2<1 , these devices work effectively only over a restricted region of phase space and with some subunity success probability p✓. We investigate the performance of our μ2 amplifiers in terms of a gain-corrected probability-fidelity product and the ratio of input to output signal-to-noise ratios corrected for success probability.

  7. CARM and harmonic gyro-amplifier experiments at 17 GHz

    SciTech Connect

    Menninger, W.L.; Danly, B.G.; Alberti, S.; Chen, C.; Rullier, J.L.; Temkin, R.J.; Giguet, E. |

    1993-11-01

    Cyclotron resonance maser amplifiers are possible sources for applications such as electron cyclotron resonance heating of fusion plasmas and driving high-gradient rf linear accelerators. For accelerator drivers, amplifiers or phase locked-oscillators are required. A 17 GHz cyclotron autoresonance maser (CARM) amplifier experiment and a 17 GHz third harmonic gyro-amplifier experiment are presently underway at the MIT Plasma Fusion Center. Using the SRL/MIT SNOMAD II introduction accelerator to provide a 380 kV, 180 A, 30 ns flat top electron beam, the gyro-amplifier experiment has produced 5 MW of rf power with over 50 dB of gain at 17 GHz. The gyro-amplifier operates in the TE{sub 31} mode using a third harmonic interaction. Because of its high power output, the gyro-amplifier will be used as the rf source for a photocathode rf electron gun experiment also taking place at MIT. Preliminary gyro-amplifier results are presented, including measurement of rf power, gain versus interaction length, and the far-field pattern. A CARM experiment designed to operate in the TE{sub 11} mode is also discussed.

  8. Efficient wide-aperture neodymium glass rod amplifiers

    SciTech Connect

    Potemkin, A K; Zhurin, K A; Kirsanov, A V; Kopelovich, E A; Kuznetsov, M V; Kuz'min, A A; Flat, F A; Khazanov, Efim A; Shaikin, A A

    2011-06-30

    Amplifiers based on neodymium phosphate glass rods 60 - 100 mm in diameter are experimentally studied. The amplifiers are pumped by INP-16/250 tubular flash lamps placed in a universal pump cavity with a two-section mirror reflector. A compact high-voltage capacitive energy storage with a preionisation circuit was developed to supply the lamps. (lasers)

  9. SLUG Microwave Amplifiers for Scalable Superconducting Qubit Readout

    NASA Astrophysics Data System (ADS)

    Zhu, Shaojiang; Hover, David; Ribeill, Guilhem; Thorbeck, Ted; McDermott, Robert; University of Wisconsin, Madison Team

    2014-03-01

    We describe a phase-insensitive microwave linear amplifier based on the Superconducting Low-inductance Undulatory Galvanometer (SLUG). The amplifier is well suited to the high fidelity quantum nondemolition measurement of superconducting qubits in a circuit quantum electrodynamics architecture. The amplifier has achieved instantaneous bandwidth greater than 400 MHz and system added noise of order one quantum in the GHz frequency range; moreover, the SLUG -1 dB compression point is around -95 dBm, about two orders of magnitude higher than that achieved with typical Josephson parametric amplifiers. We describe efforts to increase instantaneous bandwidth toward 1 GHz and discuss prospects for simultaneous measurement of multiple superconducting qubits using frequency-domain multiplexing with a broadband SLUG amplifier.

  10. Pulse laser imaging amplifier for advanced ladar systems

    NASA Astrophysics Data System (ADS)

    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.

  11. Capacitive Trans-Impedance Amplifier Circuit with Charge Injection Compensation

    NASA Technical Reports Server (NTRS)

    Milkov, Mihail M. (Inventor); Gulbransen, David J. (Inventor)

    2016-01-01

    A capacitive trans-impedance amplifier circuit with charge injection compensation is provided. A feedback capacitor is connected between an inverting input port and an output port of an amplifier. A MOS reset switch has source and drain terminals connected between the inverting input and output ports of the amplifier, and a gate terminal controlled by a reset signal. The reset switch is open or inactive during an integration phase, and closed or active to electrically connect the inverting input port and output port of the amplifier during a reset phase. One or more compensation capacitors are provided that are not implemented as gate oxide or MOS capacitors. Each compensation capacitor has a first port connected to a compensation signal that is a static signal or a toggling compensation signal that toggles between two compensation voltage values, and a second port connected to the inverting input port of the amplifier.

  12. Fiber optic signal amplifier using thermoelectric power generation

    DOEpatents

    Hart, M.M.

    1995-04-18

    A remote fiber optic signal amplifier for use as a repeater/amplifier, such as in transoceanic communications, powered by a Pu{sub 238} or Sr{sub 90} thermoelectric generator. The amplifier comprises a unit with connections on the receiving and sending sides of the communications system, and an erbium-doped fiber amplifier connecting each sending fiber to each receiving fiber. The thermoelectric generator, preferably a Pu{sub 238} or Sr{sub 90} thermoelectric generator delivers power to the amplifiers through a regulator. The heat exchange surfaces of the thermoelectric generator are made of materials resistant to corrosion and biological growth and are directly exposed to the outside, such as the ocean water in transoceanic communications. 2 figs.

  13. Fiber optic signal amplifier using thermoelectric power generation

    DOEpatents

    Hart, Mark M.

    1995-01-01

    A remote fiber optic signal amplifier for use as a repeater/amplifier, such as in transoceanic communications, powered by a Pu.sub.238 or Sr.sub.90 thermoelectric generator. The amplifier comprises a unit with connections on the receiving and sending sides of the communications system, and an erbium-doped fiber amplifier connecting each sending fiber to each receiving fiber. The thermoelectric generator, preferably a Pu.sub.238 or Sr.sub.90 thermoelectric generator delivers power to the amplifiers through a regulator. The heat exchange surfaces of the thermoelectric generator are made of materials resistant to corrosion and biological growth and are directly exposed to the outside, such as the ocean water in transoceanic communications.

  14. Fiber optic signal amplifier using thermoelectric power generation

    DOEpatents

    Hart, M.M.

    1993-01-01

    A remote fiber optic signal amplifier for use as a repeater/amplifier, such as in transoceanic communication, powered by a Pu{sub 238} or Sr{sub 90} thermoelectric generator. The amplifier comprises a unit with connections on the receiving and sending sides of the communications system, and an erbium-doped fiber amplifier connecting each sending fiber to each receiving fiber. The thermoelectric generator, preferably a Pu{sub 238} or Sr{sub 90} thermoelectric generator delivers power to the amplifiers through a regulator. The heat exchange surfaces of the thermoelectric generator are made of material resistant to corrosion and biological growth and are directly exposed to the outside, such as the ocean water in transoceanic communications.

  15. A neural amplifier with high programmable gain and tunable bandwidth.

    PubMed

    Perlin, Gayatri E; Sodagar, Amir M; Wise, Kensall D

    2008-01-01

    A neural recording amplifier having programmable gain and bandwidth is presented. The gain can be digitally programmed using 6 bits from 100x to 1100x in steps of 100x. The low-frequency cutoff can be varied from less than 10Hz to above 100Hz to accept or reject field potentials while the high-frequency cutoff is fixed at 9kHz. The input referred noise of this amplifier is 4.8microV(rms) and it consumes 50microW operating from +/-1.5V. Implemented in a 0.5microm technology, the amplifier occupies an area of 0.098mm(2). This amplifier has been successfully demonstrated in-vivo and compared to a commercial amplifier.

  16. Note: Differential amplified high-resolution tilt angle measurement system.

    PubMed

    Zhao, Shijie; Li, Yan; Zhang, Enyao; Huang, Pei; Wei, Haoyun

    2014-09-01

    A high-resolution tilt angle measurement system is presented in this paper. In this system, the measurement signal is amplified by two steps: (1) amplified by operational amplifier and (2) differential amplified by two MEMS-based inclinometers. The novel application not only amplifies the signal but, more importantly, substantially reduces the electrical interference and common-mode noise among the same circuit design. Thus, both the extremely high resolution and great long-term stability are achieved in this system. Calibrated by an autocollimator, the system shows a resolution of 2 arc sec. The accuracy is better than ±1.5 arc sec. The zero-drift error is below ±1 arc sec and ±2 arc sec in the short and long term, respectively.

  17. Note: Differential amplified high-resolution tilt angle measurement system

    NASA Astrophysics Data System (ADS)

    Zhao, Shijie; Li, Yan; Zhang, Enyao; Huang, Pei; Wei, Haoyun

    2014-09-01

    A high-resolution tilt angle measurement system is presented in this paper. In this system, the measurement signal is amplified by two steps: (1) amplified by operational amplifier and (2) differential amplified by two MEMS-based inclinometers. The novel application not only amplifies the signal but, more importantly, substantially reduces the electrical interference and common-mode noise among the same circuit design. Thus, both the extremely high resolution and great long-term stability are achieved in this system. Calibrated by an autocollimator, the system shows a resolution of 2 arc sec. The accuracy is better than ±1.5 arc sec. The zero-drift error is below ±1 arc sec and ±2 arc sec in the short and long term, respectively.

  18. Patch-clamp amplifiers on a chip.

    PubMed

    Weerakoon, Pujitha; Culurciello, Eugenio; Yang, Youshan; Santos-Sacchi, Joseph; Kindlmann, Peter J; Sigworth, Fred J

    2010-10-15

    We present the first, fully integrated, two-channel implementation of a patch-clamp measurement system. With this "PatchChip" two simultaneous whole-cell recordings can be obtained with rms noise of 8pA in a 10kHz bandwidth. The capacitance and series-resistance of the electrode can be compensated up to 10pF and 100MΩ respectively under computer control. Recordings of hERG and Na(v) 1.7 currents demonstrate the system's capabilities, which are on par with large, commercial patch-clamp instrumentation. By reducing patch-clamp amplifiers to a millimeter size micro-chip, this work paves the way to the realization of massively parallel, high-throughput patch-clamp systems for drug screening and ion-channel research. The PatchChip is implemented in a 0.5μm silicon-on-sapphire process; its size is 3×3mm(2) and the power consumption is 5mW per channel with a 3.3V power supply.

  19. Patch-clamp amplifiers on a chip

    PubMed Central

    Weerakoon, Pujitha; Culurciello, Eugenio; Yang, Youshan; Santos-Sacchi, Joseph; Kindlmann, Peter J.; Sigworth, Fred J.

    2010-01-01

    We present the first, fully-integrated, two-channel implementation of a patch-clamp measurement system. With this “PatchChip” two simultaneous whole-cell recordings can be obtained with rms noise of 8 pA in a 10 kHz bandwidth. The capacitance and series-resistance of the electrode can be compensated up to 10 pF and 100 MΩ respectively under computer control. Recordings of hERG and Nav 1.7 currents demonstrate the system's capabilities, which are on par with large, commercial patch-clamp instrumentation. By reducing patch-clamp amplifiers to a millimeter size micro-chip, this work paves the way to the realization of massively-parallel, high-throughput patch-clamp systems for drug screening and ion-channel research. The PatchChip is implemented in a 0.5 μm silicon-on-sapphire process; its size is 3 × 3 mm2 and the power consumption is 5 mW per channel with a 3.3 V power supply. PMID:20637803

  20. Fishing amplifies forage fish population collapses.

    PubMed

    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. Airborne Methane Measurements using Optical Parametric Amplifiers

    NASA Astrophysics Data System (ADS)

    Riris, H.; Numata, K.; Li, S.; Wu, S.; Ramanathan, A.; Dawsey, M.; Abshire, J. B.; Kawa, S. R.; Mao, J.

    2012-12-01

    We report on airborne methane measurements with an active sensing instrument using widely tunable, seeded optical parametric generation (OPG). Methane is a strong greenhouse gas on Earth and it is also a potential biogenic marker on Mars and other planetary bodies. Methane in the Earth's atmosphere survives for a shorter time than CO2 but its impact on climate change can be larger than CO2. Carbon and methane emissions from land are expected to increase as permafrost melts exposing millennial-age carbon stocks to respiration (aerobic-CO2 and anaerobic-CH4) and fires. Methane emissions from clathrates in the Arctic Ocean and on land are also likely to respond to climate warming. However, there is considerable uncertainty in present Arctic flux levels, as well as how fluxes will change with the changing environment and more measurements are needed. In this paper we report on an airborne demonstration of atmospheric methane column optical depth measurements at 1.65 μm using widely tunable, seeded optical parametric amplifier (OPA) and a photon counting detector. Our results show good agreement between the experimentally derived optical depth measurements and theoretical calculations and follow the expected changes for aircraft altitudes from 3 to 11 km. The technique has also been used to measure carbon dioxide and monoxide, water vapor, and other trace gases in the near and mid-infrared spectral regions on the ground.

  2. Single Ion Quantum Lock-In Amplifier

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    Invented by Dicke, the lock-in measurement is a phase-sensitive detection scheme that can extract a signal with a known carrier frequency from an extremely noisy environment. Here 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 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 /√{ 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. As a first application we perform light shift spectroscopy of a narrow optical quadruple transition. We remark that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor. (http://arxiv.org/abs/1101.4885)

  3. Compound hydraulic shear-modulated vortex amplifiers

    NASA Technical Reports Server (NTRS)

    Goldschmied, F. R.

    1977-01-01

    A novel two-stage shear-modulated hydraulic vortex amplifier (U.S. patent 3,520,317) has been fabricated and put through preliminary steady-state testing at the 1000 psi supply pressure level with flows up to 15 gpm. The invention comprises a conventional fluidic vortex power stage and a shear-modulated pilot stage. In the absence of any mechanical moving parts, water may be used as the hydraulic medium thus opening the way to many underseas applications. At blocked load, a control input from 0 to 150 psi was required to achieve an output from 0 to 900 psi; at wide-open load, a control input of 0 to 120 psi was needed to achieve an output from 0 to 15 gpm. The power stage has been found unsuitable for the proportional control mode because of its nonlinear performance in the intermediate load range and because of strong pressure fluctuations (plus or minus 150 psi) in the intermediate control range. The addition of the shear-modulated pilot stage improves intermediate load linearity.

  4. Gold Nanoparticle Labels Amplify Ellipsometric Signals

    NASA Technical Reports Server (NTRS)

    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.

  5. Identifying materials limits of chemically amplified photoresists

    NASA Astrophysics Data System (ADS)

    Wu, Wen-li; Prabhu, Vivek M.; Lin, Eric K.

    2007-03-01

    Chemically amplified photoresists are likely to remain the primary imaging materials for the semiconductor industry. As feature sizes decrease to dimensions comparable to the characteristic size of the molecules in the photoresist, a significant challenge lies in identifying the ultimate resolution limit of these materials. To address this challenge, we investigated model photoresist materials with high resolution measurements to examine the effect of individual factors among interdependent process steps on line-edge roughness (LER). Using a bilayer film sample geometry, we measured the internal deprotection interface with nanometer resolution as a function of photoacid size, initial resist copolymer composition, and amine base quencher by neutron reflectivity and infrared spectroscopy. After development, we found that the resist chemistry and additives can play an important role in LER through its influence on acid diffusion. However, these model experiments suggest that there is a limit in LER even with an idealized exposure image contrast and decreases in the width of the reaction-diffusion front. However, there may be opportunities to further decrease LER during development by tuning the response of the photoresist to the developer solution.

  6. Amplification uncertainty relation for probabilistic amplifiers

    NASA Astrophysics Data System (ADS)

    Namiki, Ryo

    2015-09-01

    Traditionally, quantum amplification limit refers to the property of inevitable noise addition on canonical variables when the field amplitude of an unknown state is linearly transformed through a quantum channel. Recent theoretical studies have determined amplification limits for cases of probabilistic quantum channels or general quantum operations by specifying a set of input states or a state ensemble. However, it remains open how much excess noise on canonical variables is unavoidable and whether there exists a fundamental trade-off relation between the canonical pair in a general amplification process. In this paper we present an uncertainty-product form of amplification limits for general quantum operations by assuming an input ensemble of Gaussian-distributed coherent states. It can be derived as a straightforward consequence of canonical uncertainty relations and retrieves basic properties of the traditional amplification limit. In addition, our amplification limit turns out to give a physical limitation on probabilistic reduction of an Einstein-Podolsky-Rosen uncertainty. In this regard, we find a condition that probabilistic amplifiers can be regarded as local filtering operations to distill entanglement. This condition establishes a clear benchmark to verify an advantage of non-Gaussian operations beyond Gaussian operations with a feasible input set of coherent states and standard homodyne measurements.

  7. Stokes injected Raman capillary waveguide amplifier

    DOEpatents

    Kurnit, Norman A.

    1980-01-01

    A device for producing stimulated Raman scattering of CO.sub.2 laser radiation by rotational states in a diatomic molecular gas utilizing a Stokes injection signal. The system utilizes a cryogenically cooled waveguide for extending focal interaction length. The waveguide, in conjunction with the Stokes injection signal, reduces required power density of the CO.sub.2 radiation below the breakdown threshold for the diatomic molecular gas. A Fresnel rhomb is employed to circularly polarize the Stokes injection signal and CO.sub.2 laser radiation in opposite circular directions. The device can be employed either as a regenerative oscillator utilizing optical cavity mirrors or as a single pass amplifier. Additionally, a plurality of Raman gain cells can be staged to increase output power magnitude. Also, in the regenerative oscillator embodiment, the Raman gain cell cavity length and CO.sub.2 cavity length can be matched to provide synchronism between mode locked CO.sub.2 pulses and pulses produced within the Raman gain cell.

  8. Fishing amplifies forage fish population collapses

    PubMed Central

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

    2015-01-01

    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. PMID:25848018

  9. Globalization to amplify economic climate losses

    NASA Astrophysics Data System (ADS)

    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.

  10. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.

    1987-01-01

    This semiannual progress report covers the period from March 1, 1987 to September 30, 1987 under NASA grant NAG1-441 entitled 'Direct solar-pumped iodine laser amplifier'. During this period Nd:YAG and Nd:Cr:GSGG crystals have been tested for the solar-simulator pumped cw laser, and loss mechanisms of the laser output power in a flashlamp-pumped iodine laser also have been identified theoretically. It was observed that the threshold pump-beam intensities for both Nd:YAG and Nd:Cr:GSGG crystals were about 1000 solar constants, and the cw laser operation of the Nd:Cr:GSGG crystal was more difficult than that of the Nd:YAG crystal under the solar-simulator pumping. The possibility of the Nd:Cr:GSGG laser operation with a fast continuously chopped pumping was also observed. In addition, good agreement between the theoretical calculations and the experimental data on the loss mechanisms of a flashlamp-pumped iodine laser at various fill pressures and various lasants was achieved.

  11. Folate deficiency inhibits proliferation of adult hippocampal progenitors.

    PubMed

    Kruman, Inna I; Mouton, Peter R; Emokpae, Roland; Cutler, Roy G; Mattson, Mark P

    2005-07-13

    Neurogenesis in the adult hippocampus may play important roles in learning and memory, and in recovery from injury. As recent findings suggest, the perturbance of homocysteine/folate or one-carbon metabolism can adversely affect both the developing and the adult brain, and increase the risk of neural tube defects and Alzheimer's disease. We report that dietary folic acid deficiency dramatically increased blood homocysteine levels and significantly reduced the number of proliferating cells in the dentate gyrus of the hippocampus in adult mice. In vitro, the perturbance of one-carbon metabolism repressed proliferation of cultured embryonic multipotent neuroepithelial progenitor cells and affected cell cycle distribution. Our results suggest that dietary folate deficiency inhibits proliferation of neuronal progenitor cells in the adult brain and thereby affects neurogenesis. PMID:15973147

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

    PubMed Central

    Consalvi, Silvia; Sandoná, Martina

    2016-01-01

    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). PMID:26839565

  13. Neuromesodermal progenitors and the making of the spinal cord

    PubMed Central

    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

  14. Imparting regenerative capacity to limbs by progenitor cell transplantation

    PubMed Central

    Lin, Gufa; Chen, Ying; Slack, Jonathan M.W.

    2012-01-01

    Summary The frog Xenopus can normally regenerate its limbs at early developmental stages but loses the ability during metamorphosis. This behavior provides a potential gain-of-function model for measures that can enhance limb regeneration. Here we show that frog limbs can be caused to form multidigit regenerates after receiving transplants of larval limb progenitor cells. It is necessary to activate Wnt/β -catenin signaling in the cells, and to add Sonic hedgehog, FGF10 and thymosin β4. These factors promote survival and growth of the grafted cells and also provide pattern information. The eventual regenerates are not composed solely of donor tissue; the host cells also make a substantial contribution despite their lack of regeneration-competence. Cells from adult frog legs or from regenerating tadpole tails do not promote limb regeneration, demonstrating the necessity for limb progenitor cells. These findings have obvious implications for the development of a technology to promote limb regeneration in mammals. PMID:23273877

  15. THE POPULATION OF HELIUM-MERGER PROGENITORS: OBSERVATIONAL PREDICTIONS

    SciTech Connect

    Fryer, Chris L.; Belczynski, Krzysztof; Bulik, Tomasz; Berger, Edo; Thoene, Christina

    2013-02-20

    The helium-merger gamma-ray burst (GRB) progenitor is produced by the rapid accretion onto a compact remnant (neutron star or black hole) when it undergoes a common envelope inspiral with its companion's helium core. This merger phase produces a very distinct environment around these outbursts and recent observations suggest that, in some cases, we are detecting the signatures of the past merger in the GRB afterglow. These observations allow us, for the first time, to study the specific features of the helium-merger progenitor. In this paper, we couple population synthesis calculations to our current understanding of GRB engines and common envelope evolution to make observational predictions for the helium-merger GRB population. Many mergers do not produce GRB outbursts and we discuss the implications of these mergers with the broader population of astrophysical transients.

  16. Single luminal epithelial progenitors can generate prostate organoids in culture

    PubMed Central

    Chua, Chee Wai; Shibata, Maho; Lei, Ming; Toivanen, Roxanne; Barlow, LaMont J.; Bergren, Sarah K.; Badani, Ketan K.; McKiernan, James M.; Benson, Mitchell C.; Hibshoosh, Hanina; Shen, Michael M.

    2014-01-01

    The intrinsic ability to display self-organizing morphogenetic properties in ex vivo culture may represent a general property of tissue stem cells. Here we show that single luminal stem/progenitor cells can generate prostate organoids in a three-dimensional culture system in the absence of stroma. Organoids generated from CARNs (castration-resistant Nkx3.1-expressing cells) or normal prostate epithelium exhibit tissue architecture containing luminal and basal cells, undergo long-term expansion in culture, and display functional androgen receptor signaling. Lineage-tracing demonstrates that luminal cells are favored for organoid formation, and generate basal cells in culture. Furthermore, tumor organoids can initiate from CARNs after oncogenic transformation, and from mouse models of prostate cancer, and can facilitate analyses of drug response. Finally, we provide evidence supporting the feasibility of organoid studies of human prostate tissue. Our studies underscore the progenitor properties of luminal cells, and identify in vitro approaches for studying prostate biology. PMID:25241035

  17. Progenitors of type Ia supernovae in elliptical galaxies

    SciTech Connect

    Gilfanov, M.; Bogdan, A.

    2011-09-21

    Although there is a nearly universal agreement that type Ia supernovae are associated with the thermonuclear disruption of a CO white dwarf, the exact nature of their progenitors is still unknown. The single degenerate scenario envisages a white dwarf accreting matter from a non-degenerate companion in a binary system. Nuclear energy of the accreted matter is released in the form of electromagnetic radiation or gives rise to numerous classical nova explosions prior to the supernova event. We show that combined X-ray output of supernova progenitors and statistics of classical novae predicted in the single degenerate scenario are inconsistent with X-ray and optical observations of nearby early type galaxies and galaxy bulges. White dwarfs accreting from a donor star in a binary system and detonating at the Chandrasekhar mass limit can account for no more than {approx}5% of type Ia supernovae observed in old stellar populations.

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

    PubMed

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

    2012-10-01

    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.

  19. Efficacy and Safety of Human Retinal Progenitor Cells

    PubMed Central

    Semo, Ma'ayan; Haamedi, Nasrin; Stevanato, Lara; Carter, David; Brooke, Gary; Young, Michael; Coffey, Peter; Sinden, John; Patel, Sara; Vugler, Anthony

    2016-01-01

    Purpose We assessed the long-term efficacy and safety of human retinal progenitor cells (hRPC) using established rodent models. Methods Efficacy of hRPC was tested initially in Royal College of Surgeons (RCS) dystrophic rats immunosuppressed with cyclosporine/dexamethasone. Due to adverse effects of dexamethasone, this drug was omitted from a subsequent dose-ranging study, where different hRPC doses were tested for their ability to preserve visual function (measured by optokinetic head tracking) and retinal structure in RCS rats at 3 to 6 months after grafting. Safety of hRPC was assessed by subretinal transplantation into wild type (WT) rats and NIH-III nude mice, with analysis at 3 to 6 and 9 months after grafting, respectively. Results The optimal dose of hRPC for preserving visual function/retinal structure in dystrophic rats was 50,000 to 100,000 cells. Human retinal progenitor cells integrated/survived in dystrophic and WT rat retina up to 6 months after grafting and expressed nestin, vimentin, GFAP, and βIII tubulin. Vision and retinal structure remained normal in WT rats injected with hRPC and there was no evidence of tumors. A comparison between dexamethasone-treated and untreated dystrophic rats at 3 months after grafting revealed an unexpected reduction in the baseline visual acuity of dexamethasone-treated animals. Conclusions Human retinal progenitor cells appear safe and efficacious in the preclinical models used here. Translational Relevance Human retinal progenitor cells could be deployed during early stages of retinal degeneration or in regions of intact retina, without adverse effects on visual function. The ability of dexamethasone to reduce baseline visual acuity in RCS dystrophic rats has important implications for the interpretation of preclinical and clinical cell transplant studies. PMID:27486556

  20. Neural progenitor cells regulate microglia functions and activity.

    PubMed

    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.