Wiedemann-Franz relation and thermal-transistor effect in suspended graphene.

We extract experimentally the electronic thermal conductivity, Ke, in suspended graphene that we dope using a back-gate electrode. We make use of two-point dc electron transport at low bias voltages and intermediate temperatures (50-160 K), where the electron and lattice temperatures are decoupled. The thermal conductivity is proportional to the charge conductivity times the temperature, confirming that the Wiedemann-Franz relation is obeyed in suspended graphene. We extract an estimate of the Lorenz coefficient as 1.1-1.7 × 10(-8) W ΩK(-2). Ke shows a transistor effect and can be tuned with the back-gate by more than a factor of 2 as the charge carrier density ranges from ∼0.5 to 1.8 × 10(11) cm(-2).

Few-hundred GHz carbon nanotube nanoelectromechanical systems (NEMS).

We study 23-30 nm long suspended single-wall carbon nanotube quantum dots and observe both their stretching and bending vibrational modes. We use low-temperature DC electron transport to excite and measure the tubes' bending mode by making use of a positive feedback mechanism between their vibrations and the tunneling electrons. In these nanoelectromechanical systems (NEMS), we measure fundamental bending frequencies f(bend) ≈ 75-280 GHz and extract quality factors Q ∼ 10(6). The NEMS's frequencies can be tuned by a factor of 2 with tension induced by mechanical breakjunctions actuated by an electrostatic force or tension from bent suspended electrodes.

High power DC and ns-pulsed 2 MV accelerator for light ions.

High Voltage Engineering developed, built, and tested a unique 2 MV single-ended accelerator (SingletronTM) for light ions. The system combines a beam current of up to 2 mA for protons and helium in direct-current mode with nanosecond-pulsing capability. Compared to other chopper-buncher applications with Tandem accelerators, the single-ended accelerator increases the charge per bunch by about a factor of 8. The all-solid-state Singletron 2 MV power supplyTM supports high-current operation and features a large dynamic range of the terminal voltage and good transient performance to support the high-current operation. The terminal accommodates an in-house developed 2.45 GHz electron cyclotron resonance ion source and a chopping-bunching system. The latter features phase-locked loop stabilization and temperature compensation of the excitation voltage and its phase. The chopping bunching system further features the selection of hydrogen, deuterium, and helium as well as a pulse repetition rate, ranging from 125 kHz to 4 MHz, that are fully computer controlled. In the testing phase, the system demonstrated smooth operation for 2 mA proton and helium beams at terminal voltages from 0.5 to 2.0 MV, and somewhat reduced current at a voltage down to 250 kV. In pulsing mode, pulses with a full width at half maximum of 2.0 ns reached a peak current of ∼10 and ∼5.0 mA for protons and helium, respectively. This is equivalent to a pulse charge of about 20 and 10 pC. Applications range from various fields requiring direct current at multi-mA levels and MV light ions, including nuclear astrophysics research, boron neutron capture therapy, and deep implantation for semiconductor applications.

Development of a variable-energy, high-intensity, pulsed-mode ion source for low-energy nuclear astrophysics studies.

The primary challenge in directly measuring nuclear reaction rates near stellar energies is their small cross sections. The signal-to-background ratio in these complex experiments can be significantly improved by employing high-current (mA-range) beams and novel detection techniques. Therefore, the electron cyclotron resonance ion source at the Laboratory for Experimental Nuclear Astrophysics underwent a complete upgrade of its acceleration column and microwave system to obtain high-intensity, pulsed proton beams. The new column uses a compression design with O-ring seals for vacuum integrity. Its voltage gradient between electrode sections is produced by the parallel resistance of channels of chilled, deionized water. It also incorporates alternating, transverse magnetic fields for electron suppression and an axially adjustable beam extraction system. Following this upgrade, the operational bremsstrahlung radiation levels and high-voltage stability of the source were vastly improved, over 3.5 mA of target beam current was achieved, and an order-of-magnitude increase in normalized brightness was measured. Beam optics calculations, structural design, and further performance results for this source are presented.

A LATS biosensor screen identifies VEGFR as a regulator of the Hippo pathway in angiogenesis.

The Hippo pathway is a central regulator of tissue development and homeostasis, and has been reported to have a role during vascular development. Here we develop a bioluminescence-based biosensor that monitors the activity of the Hippo core component LATS kinase. Using this biosensor and a library of small molecule kinase inhibitors, we perform a screen for kinases modulating LATS activity and identify VEGFR as an upstream regulator of the Hippo pathway. We find that VEGFR activation by VEGF triggers PI3K/MAPK signaling, which subsequently inhibits LATS and activates the Hippo effectors YAP and TAZ. We further show that the Hippo pathway is a critical mediator of VEGF-induced angiogenesis and tumor vasculogenic mimicry. Thus, our work offers a biosensor tool for the study of the Hippo pathway and suggests a role for Hippo signaling in regulating blood vessel formation in physiological and pathological settings.

New determination of the astrophysical S factor SE1 of the 12C(alpha,gamma)16O reaction.

A new measurement of the beta-delayed alpha decay of 16N has been performed using a set of high efficiency ionization chambers. Sources were made by implantation of a 16N beam, yielding very clean alpha spectra down to energies as low as 400 keV. Our data are in good agreement with earlier results. For the S factor S(E1), we obtain a value of 74 +/- 21 keV b. In spite of improvements in the measurement, the error in S(E1) remains relatively large because of the correlations among the fit parameters and the uncertainties inherent to the extrapolation.

Giant electron-hole transport asymmetry in ultra-short quantum transistors.

Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e-h charging energy asymmetry). We parameterize the e-h transport asymmetry by the ratio of the hole and electron charging energies ηe-h. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, ηe-h reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV.

Cloning, sequencing and expression of the two genes encoding the mitochondrial single-stranded DNA-binding protein in Xenopus laevis.

In Xenopus laevis the single-stranded DNA binding protein imported into the mitochondria consists of two highly related polypeptides. The establishment of the genomic nucleotide sequences reveals that they are encoded by two different genes, XLSSB1 and XLSSB2. The deduced amino acid sequence is identical to the direct amino acid sequence determined by Edman degradation of the mitochondrial polypeptides [Ghrir. R., Lecaer, J.P., Dufresne, C. and Gueride, M. (1991) Primary structure of the two variants of Xenopus laevis mtSSB, a mitochondrial DNA binding protein. Arch. Biochem. Biophys. 291, 395-400]. Both genes are organized in seven exons and six introns, the sequence of the peptide leader is interrupted by an intervening sequence (intron 2). The exon/intron junctions are in exactly conserved positions, splitting the same codon. A high level of identity is observed between corresponding introns of the two genes over part or most of their lengths. Structural features of intronic sequences reveal multiple rearrangements and exchanges during the evolution of X. laevis species. A CCAAT box and the potential regulatory elements NRF-2 and Sp 1 are observed in the 5'-flanking region of both genes. During oogenesis, XLSSB gene expression is correlated with the replicative activity of the mitochondrial DNA.

Proteolytic activity of bacteria isolated from the oral cavities of BALB/c mice toward salivary proteins.

The proteolytic activities of 350 bacterial isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavities of BALB/c mice were tested against different proteins found in saliva (immunoglobulins A, M, G, albumin, lysozyme, mucin, lactoferrin, and lactoperoxidase), some of which are considered to possess antibacterial activity. The results indicate that: (1) lysozyme, lactoferrin, and lactoperoxidase are hydrolyzed by from 46 to 70% of the indigenous flora of the oral cavities of BALB/c mice; (2) IgA and IgM appeared less sensitive to the proteolytic activities of these strains than did the other proteins tested; (3) the colonization of the oral cavity does not seem to be correlated with the proteolytic activity; and (4) the presence of specific Ig proteases is relatively scarce within this population.

[Management of lymphedema: experience of the Cognacq-Jay Hospital]. / Prise en charge des lymphoedèmes: l'expérience de l'hôpital Cognacq-Jay.

Treatment of lymphedema includes practical advices, manual lymph drainage, bandaging, self-bandaging, elastic compression garment, skin care and physical exercises. Weight loss may be useful if obesity. Surgery is indicated in genital lymphedema more than in limb lymphedema. In 2001, in Lymphology Unit, 248 women were treated for secondary upper limb lymphedema after breast cancer. Excess of volume of lymphedema was reduced by 31.3% after a mean time of 2.1 weeks. For lower limb lymphedema (primary or secondary), 136 patients were treated with a mean reduction of excess of lymphedema by 29.8% after a mean time of 2.2 weeks. After this treatment, long term follow-up is necessary to maintain results and the motivation of the patient.

Mechanical control of spin states in spin-1 molecules and the underscreened Kondo effect.

The ability to make electrical contact to single molecules creates opportunities to examine fundamental processes governing electron flow on the smallest possible length scales. We report experiments in which we controllably stretched individual cobalt complexes having spin S = 1, while simultaneously measuring current flow through the molecule. The molecule's spin states and magnetic anisotropy were manipulated in the absence of a magnetic field by modification of the molecular symmetry. This control enabled quantitative studies of the underscreened Kondo effect, in which conduction electrons only partially compensate the molecular spin. Our findings demonstrate a mechanism of spin control in single-molecule devices and establish that they can serve as model systems for making precision tests of correlated-electron theories.

Evidence for a finite-temperature phase transition in a bilayer quantum Hall system.

We study the Josephson-like interlayer tunneling signature of the strongly correlated nuT=1 quantum Hall phase in bilayer two-dimensional electron systems as a function of the layer separation, temperature, and interlayer charge imbalance. Our results offer strong evidence that a finite temperature phase transition separates the interlayer coherent phase from incoherent phases which lack strong interlayer correlations. The transition temperature is dependent on both the layer spacing and charge imbalance between the layers.

Tuning the Kondo effect with a mechanically controllable break junction.

We study electron transport through C(60) molecules in the Kondo regime using a mechanically controllable break junction. By varying the electrode spacing, we are able to change both the width and the height of the Kondo resonance, indicating modification of the Kondo temperature and the relative strength of coupling to the two electrodes. The linear conductance as a function of T/T(K) agrees with the scaling function expected for the spin-1/2 Kondo problem. We are also able to tune finite-bias Kondo features which appear at the energy of the first C(60) intracage vibrational mode.

Direct measurement of the 14N(p,gamma)15O S factor.

The 14N(p,gamma)15O reaction regulates the rate of energy generation in the stellar CN cycle. Because discrepancies have been found in the analysis and interpretation of previous capture data, we have measured the 14N(p,gamma)15O excitation function for energies in the range E(lab)(p)=155-524 keV. Fits of these data using R-matrix theory yield a value for the S factor at zero energy of 1.68+/-0.09(stat)+/-0.16(syst) keV b, which is significantly smaller than the previous result. The corresponding reduction in the stellar reaction rate for 14N(p,gamma)15O has a number of interesting consequences, including an impact on estimates for the age of the Galaxy derived from globular clusters.

Rhodamine 123 uptake and mitochondrial DNA content in rabbit articular chondrocytes evolve differently upon transfer from cartilage to culture conditions.

Mitochondrial DNA (mtDNA) represents 0.15% of the total cell DNA (at least an order of magnitude less than in liver or heart) of rabbit articular chondrocytes. Besides the already well-documented low respiratory activity, chondrocyte differentiation thus involves a specific control of mitochondrial biogenesis. When transferred to in vitro conditions, chondrocytes increase their stock of mtDNA at the same time they resume growth, even more efficiently (8 times) than they do for cell volume (4.4 times). On the contrary, overall mitochondrial activity, estimated as the uptake of rhodamine 123, does not follow the same trend (2.5 times increase). Chondrocytes apparently keep these functional characteristics for some generations in culture.

Direct repeats in the non-coding region of rabbit mitochondrial DNA. Involvement in the generation of intra- and inter-individual heterogeneity.

In rabbit we observed heteroplasmy at an exceptionally high level, the heterogeneity occurring within the non-coding region of the DNA. Mitochondrial DNA (mt DNA) was cloned in pBR322 and the nucleotide sequence analysis of an EcoRI-Hind III fragment encompassing the non-coding region revealed that although there are common features with other mammalian mtDNAs (termed large central-conserved-sequence block, conserved-sequence blocks 1, 2 and 3 and termination-associated elements) the non-coding region shows an unusual organization; two stretches of tandem repeats of 20 bp and 153 bp are present in a part containing the origin of H-strand replication (OH) and probably the promoters for transcription as judged from other vertebrates. The long repeats are located between tRNA(Phe) and conserved sequence block 3 and the short repeats are located between conserved sequence blocks 1 and 2. When cloned in Escherichia coli (recA or recBC sbcb) DNA fragments containing the short repeats show length differences corresponding to various copy numbers of repeats. Electrophoretic analysis of the appropriate restriction fragments of rabbit mtDNA reveals extended intra- and inter-individual length heterogeneity. Both sets of repeats are involved in the generation of heterogeneity and are present in variable copy numbers from one mtDNA molecule to another. Moreover, rearrangement of the motives of the short repeat are observed to different extents in the mtDNA from one animal to another. The occurrence, maintenance and possible involvement of these repeated sequences, capable of forming stable secondary structures, are discussed in relation to their location in the region of control signals.

Co-linear organization of Xenopus laevis and mouse mitochondrial genomes.

Cloned fragments of Xenopus laevis mitochondrial DNA and Pleurodeles waltlii mitochondrial cDNAs have been hybridized together and with mouse mtDNA. In the three cases cross-hybridization was observed. The overall organization of the X. laevis fragments appeared to be co-linear with the mouse mtDNA, most sequences being conserved except for the D-loop and the URF6 regions. The use of mouse mtDNA has enabled us to identified several mitochondrial genes in X. laevis and P. waltlii.

Mitochondrial biogenesis in rabbit articular chondrocytes transferred to culture.

The effect of the switch to aerobic growth conditions was examined in rabbit articular chondrocytes transferred to culture. Spectroscopic analysis of the cytochromes of the respiratory chain shows that only cytochrome b is present in chondrocytes from cartilage, cytochromes c, c1, and a.a3 being undetectable as compared with the typical spectrum found in a primary cell culture on day 4. Steady state levels of RNA transcripts of nuclear (cytochrome c) and mitochondrial genes (cytochrome b and cytochrome oxidase subunits II and III) involved in the oxidative metabolism were determined relative to the RNA transcripts of the nuclear gene for glyceraldehyde phosphate dehydrogenase involved in the glycolytic pathway and to mitochondrial ribosomal RNAs. Chondrocytes transferred to culture showed a general increase in the levels of all transcripts, but the effect on mitochondrial transcripts was much greater (x 20) than the effect on nuclear transcripts (x 3-4). These results show the absence of a coordinate regulation of the expression of mitochondrial and nuclear genes coding for components of the respiratory chain. The increase in mitochondrial DNA triggered by culture conditions does not appear to be sufficient to account for the enhanced transcription. Concomitant with these mitochondrial changes, the level of transcripts for the collagen II gene involved in the differentiation function decreases dramatically (3% of the control on day 3).

Lifetime of the 6793-keV state in 15O.

The energy derived from the CN cycle at low stellar temperatures is regulated by the 14N(p,gamma)15O reaction. A previous direct measurement of this reaction has been interpreted as showing evidence for a subthreshold resonance which makes a major contribution to the reaction rate at low temperatures. This resonance, at E(c.m.) = -504 keV would correspond to the known Ex = 6793-keV state in 15O. We have measured a mean lifetime of 1.60(+0.75)(-0.72) fs (90% C.L.) for this state using the Doppler-shift attenuation method. This lifetime is a factor of 15 longer than that inferred from the (p,gamma) data and implies that the contribution of the subthreshold resonance is negligible.