bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast nuclear magnetic resonance correlation spectroscopy without diagonal peaks: The “2-1” correlation spectroscopy
Authors: Liu Huili , Jiang Bin , Liu Maili , Mao Xi-an
Published: February 2008

A fast NMR experiment is proposed for measuring correlation spectroscopy (COSY) spectra with diagonal peaks completely removed or largely suppressed. This new pulse sequence is based on double quantum spectroscopy but with delayed detection, so that the double quantum coherence is effectively transferred to single quantum coherence. Therefore, the pulse sequence can be named “2-1” COSY.
High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment
Authors: Hosea J. , Bell R. E. , LeBlanc B. P. , Phillips C. K. , Taylor G. , Valeo E. , Wilson J. R. , Jaeger E. F. , Ryan P. M. , Wilgen J. , Yuh H. , Levinton F. , Sabbagh S. , Tritz K. , Parker J. , Bonoli P. T. , Harvey R. ,   NSTX Team
Published: February 2008

High harmonic fast wave heating and current drive (CD) are being developed on the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion 41, 1435 (2001)] for supporting startup and sustainment of the spherical torus plasma. Considerable enhancement of the core heating efficiency (η) from 44% to 65% has been obtained for CD phasing of the antenna (strap-to-strap ϕ=−90°, kϕ=−8m−1) by increasing the magnetic field from 4.5to5.5kG. This increase in efficiency is strongly correlated to moving the location of the onset density for perpendicular fast wave propagation (nonset∝B×k∥2∕ω) away from the antenna face and wall, and hence reducing the propagating surface wave fields. Radio frequency (RF) waves propagating close to the wall at lower B and k∥ can enhance power losses from both the parametric decay instability (PDI) and wave dissipation in sheaths and structures around the machine. The improved efficiency found here is attributed to a reduction in the latter, as PDI losses are little changed at the higher magnetic field. Under these conditions of higher coupling efficiency, initial measurements of localized CD effects have been made and compared with advanced RF code simulations.
Inductive sustainment of oblate field-reversed configurations with the assistance of magnetic diffusion, shaping, and finite-Larmor radius stabilization
Authors: Gerhardt S. P. , Belova E. V. , Yamada M. , Ji H. , Inomoto M. , Jacobson C. M. , Maqueda R. , McGeehan B. , Ren Y.
Published: February 2008

Oblate field-reversed configurations (FRCs) have been sustained for >300μs, or >15 magnetic diffusion times, through the use of an inductive solenoid. These argon FRCs can have their poloidal flux sustained or increased, depending on the timing and strength of the induction. An inward pinch is observed during sustainment, leading to a peaking of the pressure profile and maintenance of the FRC equilibrium. The good stability observed in argon (and krypton) does not transfer to lighter gases, which develop terminal co-interchange instabilities. The stability in argon and krypton is attributed to a combination of external field shaping, magnetic diffusion, and finite-Larmor radius effects.
Gazeau–Klauder coherent states for trigonometric Rosen–Morse potential
Authors: Chenaghlou A. , Faizy O.
Published: February 2008

The Gazeau–Klauder coherent states for the trigonometric Rosen–Morse potential are constructed. It is shown that the resolution of unity, temporal stability, and action identity conditions are satisfied for the coherent states. The Mandel parameter is also calculated for the weighting distribution function corresponding to the coherent states.
Pearl and mushroom instability patterns in two miscible fluids' core annular flows
Authors: d’Olce M. , Martin J. , Rakotomalala N. , Salin D. , Talon L.
Published: February 2008

We report on experiments with two miscible fluids of equal density but different viscosities. The fluids were injected co-currently and concentrically into a cylindrical pipe. The resulting base state is an axisymmetric parallel flow. The ratio of the two fluid flow rates determines the relative amount of the fluids, thus the radius of the inner core fluid. Depending on this radius and the total flow rate, two different and unstable axisymmetric patterns, denoted by mushrooms and pearls, were observed. We delineate the diagram of occurrence of the two patterns as a function of the various parameters.
Development of a 700MHz low-/high- temperature superconductor nuclear magnetic resonance magnet: Test results and spatial homogeneity improvement
Authors: Hahn S. , Bascuñán J. , Lee H. , Bobrov E. S. , Kim W. , Iwasa Y.
Published: February 2008

For the first time in nuclear magnetic resonance (NMR) magnet development, a magnet configuration comprising an insert wound with high-temperature superconductor (HTS) and a background-field magnet wound with low-temperature superconductor (LTS) has been proven viable for NMR magnets. This new LTS/HTS magnet configuration opens the way for development of 1GHz and above NMR magnets. Specifically, a 700MHz LTS/HTS NMR magnet (LH700), consisting of a 600MHz LTS magnet (L600) and a 100MHz HTS insert (H100), has been designed, built, and successfully tested, and its magnetic field characteristics were measured and analyzed. A field homogeneity of 172ppm in a cylindrical mapping volume of 17mm diameter by 30mm long was measured at 692MHz and corresponding H1 NMR signal with 1.9kHz half-width was captured. Two techniques, room-temperature and ferromagnetic shimming, were analytically examined to investigate if they would be effective for further improving spatial field homogeneity of the LH700.
Magnetism of CaRu1−xMnxO3: Magnetic Compton scattering study
Authors: Mizusaki S. , Taniguchi T. , Okada N. , Nagata Y. , Itou M. , Sakurai Y. , Ozawa T. C. , Noro Y. , Samata H.
Published: February 2008

The magnetism of CaRu1−xMnxO3 was studied using magnetic Compton scattering measurements for polycrystalline specimens at 10K under 2.5T using a synchrotron-radiation x ray. The spin moment deduced from the magnetic Compton profiles has a maximum at x=0.7 and the value agrees with the result of the magnetization measurement. The magnetic Compton profiles indicate that the Mn spin moment is dominant in magnetization and that Ru moment, which is induced with Mn doping, couples with Mn spin moment antiferromagnetically. The results suggest that a sort of ferrimagnetism is established in the CaRu1−xMnxO3 system.
A wide dynamic range x-ray streak camera system
Authors: Lihong Niu , Qinlao Yang , Hanben Niu , Hua Liao , Junlan Zhou , Yunkun Ding
Published: February 2008

An x-ray streak camera with wide dynamic range and a large slit photocathode of 30mm length has been developed and calibrated. In order to achieve wide dynamic range, a conventional streak tube has been improved and the camera system has been designed without microchannel plate electron amplifier. As a result, a dynamic range of 922 is achieved in a single shot mode with laser pulse of 30ps (full width at half maximum) at time resolution of better than 31ps.
Simulations of nonlinear pore-water convection in spherical shells
Authors: Dai Zifeng , Zhang Keke , Schubert Gerald , Liao Xinhao
Published: February 2008

Hydrothermal convection of pore water of uniform viscosity within a permeable, internally heated spherical shell bounded by two concentric spherical surfaces of inner radius ri and outer radius ro is investigated by fully three-dimensional numerical simulations based on a domain decomposition method. We first determine the critical Rayleigh number for the onset of hydrothermal convection by expressing linear solutions in terms of spherical Bessel functions. It is found that the basic motionless state becomes unstable with respect to an infinitesimal disturbance characterized by a spherical harmonic of degree l, the size of which is strongly dependent upon the aspect ratio ri∕ro. However, the three-dimensional structure of convection cannot be determined by the stability analysis because of the mathematical degeneracy of the linear solution. A new numerical scheme using a finite difference method is then employed to simulate three-dimensional nonlinear convection near the onset of convection. When the aspect ratio (ro−ri)∕ro is moderately small, a large number of different stable stationary patterns with exactly the same Rayleigh number are found by using different initial conditions. The solutions are relevant to the convectively forced circulation of water in the interiors of early solar system bodies and outer planet icy satellites.
Performance of write-line inserted magnetic tunneling junction for low-write-current magnetic random access memory cell
Authors: Honjo H. , Nebashi R. , Suzuki T. , Fukami S. , Ishiwata N. , Sugibayashi T. , Kasai N.
Published: February 2008

We have developed a write-line-inserted magnetic tunneling junction (MTJ) (WLIM) for use in low-write-current magnetoresistance random access memory (MRAM). The write current of the WLIM was reduced to 0.98mA and its thermal stability factor was 85 for a 0.32×0.48μm2 MTJ. We evaluated the switching property of the WLIM in an external magnetic field (Hsw̱ext) and an internal magnetic field (Hsw̱int). We found that Hsw̱ext was larger than Hsw̱int when the aspect ratio of the MTJs was less than 1.5. Furthermore, we obtained a high write-current magnetic-field efficiency of 13.0Oe∕mA when the aspect ratio of the MTJs was low. These properties mean that the WLIM structure has advantages for use in low-write-current MRAM.
Turbulent equipartition theory of toroidal momentum pinch
Authors: Hahm T. S. , Diamond P. H. , Gurcan O. D. , Rewoldt G.
Published: February 2008

The mode-independent part of the magnetic curvature driven turbulent convective (TurCo) pinch of the angular momentum density [Hahm et al., Phys. Plasmas 14, 072302 (2007)], which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of “magnetically weighted angular momentum density,” nmiU∥R∕B2, and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustrated that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms that exist in a simpler geometry.
A novel programmable pulse generator with nanosecond resolution for pulsed electron paramagnetic resonance applications
Authors: Devasahayam N. , Subramanian S. , Krishna M. C.
Published: February 2008

A pulse programmer with nanosecond time resolution needed for time-domain electron paramagnetic resonance (EPR) spectroscopic applications is described. This unit uses commercially available timing and input-output port modules and control software developed in our laboratory. The pulse programmer is operated through a personal computer front panel graphic user interface (GUI) inputs to control pulse widths, delays, and the associated acquisition trigger timings. Based on these parameters, all other associated gate and trigger timings are internally generated automatically without the need to enter them explicitly. The excitation pulse widths were of nanosecond resolution while all other gate pulses can be incremented in steps of 20ns without compromising spectrometer performance. In the current configuration, the pulse programmer permits generation of a single pulse or multiple pulse sequences for EPR imaging with minimal data entry via the front panel GUI.
Laser-launched flyer plate and confined laser ablation for shock wave loading: Validation and applications
Authors: Paisley Dennis L. , Luo Sheng-Nian , Greenfield Scott R. , Koskelo Aaron C.
Published: February 2008

We present validation and some applications of two laser-driven shock wave loading techniques: laser-launched flyer plate and confined laser ablation. We characterize the flyer plate during flight and the dynamically loaded target with temporally and spatially resolved diagnostics. With transient imaging displacement interferometry, we demonstrate that the planarity (bow and tilt) of the loading induced by a spatially shaped laser pulse is within 2–7mrad (with an average of 4±1mrad), similar to that in conventional techniques including gas gun loading. Plasma heating of target is negligible, in particular, when a plasma shield is adopted. For flyer plate loading, supported shock waves can be achieved. Temporal shaping of the drive pulse in confined laser ablation allows for flexible loading, e.g., quasi-isentropic, Taylor-wave, and off-Hugoniot loading. These techniques can be utilized to investigate such dynamic responses of materials as Hugoniot elastic limit, plasticity, spall, shock roughness, equation of state, phase transition, and metallurgical characteristics of shock-recovered samples.
New beam-charge interlock system for radiation safety at the KEKB injector linac
Authors: Suwada T. , Kadokura E. , Satoh M. , Furukawa K.
Published: February 2008

A new beam-charge interlock system is under development for radiation safety and machine protection at the KEKB injector linac. A hardware-based interlock system is required instead of the present software-based interlock system in order to boost its reliability. This system restricts the integrated amount of beam charges delivered to four different storage rings. The beam charges are measured using wall-current monitors and detection electronics at six locations along the linac. The detection electronics independently transmits a beam-abort request through a twisted hardwire cable directly to the safety control system of the linac, when the integrated amount of beam charges exceeds a certain threshold level prescribed for each location. We describe the characteristics and performance of the new beam-charge interlock system along with the details of the experimental tests.
High flux of relativistic electrons produced in femtosecond laser-thin foil target interactions: Characterization with nuclear techniques
Authors: Gerbaux M. , Gobet F. , Aléonard M. M. , Hannachi F. , Malka G. , Scheurer J. N. , Tarisien M. , Claverie G. , Méot V. , Morel P. , Faure J. , Glinec Y. , Guemnie-Tafo A. , Malka V. , Manclossi M. , Santos J. J.
Published: February 2008

We present a protocol to characterize the high energy electron beam emitted in the interaction of an ultraintense laser with matter at intensities higher than 1019Wcm−2. The electron energies and angular distributions are determined as well as the total number of electrons produced above a 10MeV threshold. This protocol is based on measurements with an electron spectrometer and nuclear activation techniques, combined with Monte Carlo simulations based on the GEANT3 code. The method is detailed and exemplified with data obtained with polypropylene and copper thin solid targets at a laser intensity of 2×1019Wcm−2. Special care is taken of the different sources of uncertainties. In particular, the reproducibility of the laser shots is considered.
Novel design of a compact “cylindrical mirror analyzer” array
Authors: Herting C. , Jüttemann F. , Petuker Z. , Schmitter S. , Hanne G. F.
Published: February 2008

The design of a compact multiangle electron analyzer array for simultaneous detection of scattered and ejected electrons at nine different angles is described. It consists of eight slim “simulated” cylindrical mirror analyzers (CMAs) providing electron detection for scattering/ejected angles of 14° apart from each other. A ninth analyzer is arranged to a scattering angle on the opposite side. A single analyzer has cylindrical symmetry equipotential lines in the region of the beam trajectories, whereas its electrodes are noncylindrical, except for the inner cylinder. The new spectrometer is easy to build because only a few electrodes of simple shape are needed for each of the analyzers. The electron optical properties of the new device are very close to those of a true CMA. Its geometric width, however, is only less than one-fifth of that of a conventional CMA, which allows one to arrange several analyzers close to each other. Example results with the new device are presented.
Novel rhenium gasket design for nuclear resonant inelastic x-ray scattering at high pressure
Authors: Tanis Elizabeth A. , Giefers Hubertus , Nicol Malcolm F.
Published: February 2008

For the first time, a highly absorbing element, rhenium, has been proven to be a strong, reliable, and safe gasket material for achieving high pressure in nuclear resonant inelastic x-ray scattering (NRIXS) experiments. Rhenium foil was cut into rectangular slices and in order to reduce absorption, the elevated imprint due to preindenting of the gasket is removed using electrical discharge machining. By utilizing this novel gasket design, transmission losses were mitigated while performing NRIXS experiments conducted on the Sn119 and Fe57 Mössbauer isotopes.
Inverse problems for the Schrödinger equations with time-dependent electromagnetic potentials and the Aharonov–Bohm effect
Authors: Eskin G.
Published: February 2008

We consider the inverse boundary value problem for the Schrödinger operator with time-dependent electromagnetic potentials in domains with obstacles. We extend the resuls of the author’s works [Inverse Probl. 19, 49 (2003); 19, 985 (2003); 20, 1497 (2004)] to the case of time-dependent potentials. We relate our results to the Aharonov–Bohm effect caused by magnetic and electric fluxes.
Two-axis probing system for atomic force microscopy
Authors: Jayanth G. R. , Jhiang Sissy M. , Menq Chia-Hsiang
Published: February 2008

A novel two-axis probing system is proposed for multiaxis atomic force microscopy (AFM). It employs a compliant manipulator that is optimally designed in terms of geometries and kinematics, and is actuated by multiple magnetic actuators to simultaneously control tip position and change tip orientation to achieve greater accessibility of the sample surface when imaging surfaces having large geometric variations. It leads to the creation of a multiaxis AFM system, which is a three-dimensional surface tool rather than a two-dimensional planar surface tool. The use of the system to scan the bottom corner of a grating step is reported.
Imaging the impact on cuprate superconductivity of varying the interatomic distances within individual crystal unit cells
Authors: Slezak J. A. , Lee Jinho , Wang M. , McElroy K. , Fujita K. , Andersen B. M. , Hirschfeld P. J. , Eisaki H. , Uchida S. , Davis J. C.
Published: February 2008

Many theoretical models of high-temperature superconductivity focus only on the doping dependence of the CuO
2
-plane electronic structure. However, such models are manifestly insufficient to explain the strong variations in superconducting critical temperature,
T
c
, among cuprates that have identical hole density but are crystallographically different outside of the CuO
2
plane. A key challenge, therefore, has been to identify a predominant out-of-plane influence controlling the superconductivity, with much attention focusing on the distance
d
A
between the apical oxygen and the planar copper atom. Here we report direct determination of how variations in interatomic distances within individual crystalline unit cells affect the superconducting energy-gap maximum Δ of Bi
2
Sr
2
CaCu
2
O
8+δ
. In this material, quasiperiodic variations of unit cell geometry occur in the form of a bulk crystalline “supermodulation.” Within each supermodulation period, we find ≈9 ± 1% cosinusoidal variation in local Δ that is anticorrelated with the associated
d
A
variations. Furthermore, we show that phenomenological consistency would exist between these effects and the random Δ variations found near dopant atoms if the primary effect of the interstitial dopant atom is to displace the apical oxygen so as to diminish
d
A
or tilt the CuO
5
pyramid. Thus, we reveal a strong, nonrandom out-of-plane effect on cuprate superconductivity at atomic scale.
CD4 T cells, lymphopenia, and IL-7 in a multistep pathway to autoimmunity
Authors: Calzascia Thomas , Pellegrini Marc , Lin Albert , Garza Kristine M. , Elford Alisha R. , Shahinian Arda , Ohashi Pamela S. , Mak Tak W.
Published: February 2008

There are many inhibitory mechanisms that function at the cellular and molecular levels to maintain tolerance. Despite this, self-reactive clones escape regulatory mechanisms and cause autoimmunity in certain circumstances. We hypothesized that the same mechanisms that permit T cells to expand during homeostatic proliferation may inadvertently promote autoimmunity under certain conditions. One major homeostatic cytokine is IL-7, and studies have linked it or its receptor to the development of multiple sclerosis and other autoimmune diseases. We show in a model of β-islet cell self-reactivity that the transfer of activated autoreactive CD4 T cells can prime and expand endogenous autoreactive CD8 T cells in a CD28- and CD40-dependent manner through the licensing of dendritic cells. Despite this, mice do not develop diabetes. However, the provision of exogenous IL-7 or the physiological production of IL-7 associated with lymphopenia was able to profoundly promote the expansion of self-reactive clones even in the presence of regulatory T cells. Autoimmune diabetes rapidly ensued with CD4 help and the subsequent activation of CD8 T cells, which contributed to disease progression. With the advent of many biologicals targeting TNFα, IL-6, and IL-1 and their effective use in the treatment of autoimmune diseases, we propose that IL-7 and its receptor may be promising targets for biological agents in the treatment of autoimmunity.
MicroRNAs and the advent of vertebrate morphological complexity
Authors: Heimberg Alysha M. , Sempere Lorenzo F. , Moy Vanessa N. , Donoghue Philip C. J. , Peterson Kevin J.
Published: February 2008

The causal basis of vertebrate complexity has been sought in genome duplication events (GDEs) that occurred during the emergence of vertebrates, but evidence beyond coincidence is wanting. MicroRNAs (miRNAs) have recently been identified as a viable causal factor in increasing organismal complexity through the action of these ≈22-nt noncoding RNAs in regulating gene expression. Because miRNAs are continuously being added to animalian genomes, and, once integrated into a gene regulatory network, are strongly conserved in primary sequence and rarely secondarily lost, their evolutionary history can be accurately reconstructed. Here, using a combination of Northern analyses and genomic searches, we show that 41 miRNA families evolved at the base of Vertebrata, as they are found and/or detected in lamprey, but not in either ascidians or amphioxus (or any other nonchordate taxon). When placed into temporal context, the rate of miRNA acquisition and the extent of phenotypic evolution are anomalously high early in vertebrate history, far outstripping any other episode in chordate evolution. The genomic position of miRNA paralogues in humans, together with gene trees incorporating lamprey orthologues, indicates that although GDEs can account for an increase in the diversity of miRNA family members, which occurred before the last common ancestor of all living vertebrates, GDEs cannot account for the origin of these novel families themselves. We hypothesize that lying behind the origin of vertebrate complexity is the dramatic expansion of the noncoding RNA inventory including miRNAs, rather than an increase in the protein-encoding inventory caused by GDEs.
Acid-sensing ion channels interact with and inhibit BK K
+
channels
Authors: Petroff Elena Yermolaieva , Price Margaret P. , Snitsarev Vladislav , Gong Huiyu , Korovkina Victoria , Abboud Francois M. , Welsh Michael J.
Published: February 2008

Acid-sensing ion channels (ASICs) are neuronal non-voltage-gated cation channels that are activated when extracellular pH falls. They contribute to sensory function and nociception in the peripheral nervous system, and in the brain they contribute to synaptic plasticity and fear responses. Some of the physiologic consequences of disrupting
ASIC
genes in mice suggested that ASIC channels might modulate neuronal function by mechanisms in addition to their H
+
-evoked opening. Within ASIC channel's large extracellular domain, we identified sequence resembling that in scorpion toxins that inhibit K
+
channels. Therefore, we tested the hypothesis that ASIC channels might inhibit K
+
channel function by coexpressing ASIC1a and the high-conductance Ca
2+
- and voltage-activated K
+
(BK) channel. We found that ASIC1a associated with BK channels and inhibited their current. Reducing extracellular pH disrupted the association and relieved the inhibition. BK channels, in turn, altered the kinetics of ASIC1a current. In addition to BK, ASIC1a inhibited voltage-gated Kv1.3 channels. Other ASIC channels also inhibited BK, although acidosis-dependent relief of inhibition varied. These results reveal a mechanism of ion channel interaction and reciprocal regulation. Finding that a reduced pH activated ASIC1a and relieved BK inhibition suggests that extracellular protons may enhance the activity of channels with opposing effects on membrane voltage. The wide and varied expression patterns of ASICs, BK, and related K
+
channels suggest broad opportunities for this signaling system to alter neuronal function.
Efficient Recovery of Fluoroquinolone-Susceptible and Fluoroquinolone-ResistantEscherichia coliStrains From Frozen Samples
Authors: Lautenbach Ebbing , Santana Evelyn , Lee Abby , Tolomeo Pam , Black Nicole , Babson Andrew , Perencevich Eli N. , Harris Anthony D. , Smith Catherine A. , Maslow Joel
Published: February 2008

We assessed the rate of recovery of fluoroquinolone-resistant and fluoroquinolone-susceptibleEscherichia coliisolates from culture of frozen perirectal swab samples compared with the results for culture of the same specimen before freezing. Recovery rates for these 2 classes ofE. coliwere 91% and 83%, respectively. The majority of distinct strains recovered from the initial sample were also recovered from the frozen sample. The strains that were not recovered were typically present only in low numbers in the initial sample. These findings emphasize the utility of frozen surveillance samples.
Ballast water risk assessment: principles, processes, and methods
Authors: Barry Simon C. , Hayes Keith R. , Hewitt Chad L. , Behrens Hanna L. , Dragsund Egil , Bakke Siri M.
Published: February 2008

Barry, S. C., Hayes, K. R., Hewitt, C. L., Behrens, H. L., Dragsund, E., and Bakke, S. M. 2008. Ballast water risk assessment: principles, processes, and methods. – ICES Journal of Marine Science, 65: 121–131. Two methods of assessing the risk of species introduction by ballast water are discussed, species-specific and environmental similarity assessments, each for alignment with four proposed principles of risk-based resource management: (i) society accepts that low risk scenarios exist; (ii) risk assessment is capable of identifying low risk scenarios; (iii) risk mitigation strategies exist; and (iv) mitigation costs are less than the cost of performing risk assessment. All four principles were met in some circumstances for both methods. Species-specific ballast water risk assessment is best suited to situations where the assessment can be restricted to a limited set of harmful species on journeys within bioregions where ballast water is a small component of natural genetic exchange. Environmental similarity risk assessment is appropriate for journeys that start and end in locations which have very little or no natural genetic exchange, such as journeys between non-contiguous bioregions. Because a large number of species are not assessed individually, environmental match assessments necessarily will be restricted to fundamental variables such as temperature and salinity. A number of bioregion classifications have been identified in the world’s oceans, some of which at a scale that may be appropriate for ballast water management. The suitability of any particular classification, however, needs further examination.
BMP signaling in dermal papilla cells is required for their hair follicle-inductive properties
Authors: Rendl Michael , Polak Lisa , Fuchs Elaine
Published: February 2008

Hair follicle (HF) formation is initiated when epithelial stem cells receive cues from specialized mesenchymal dermal papilla (DP) cells. In culture, DP cells lose their HF-inducing properties, but during hair growth in vivo, they reside within the HF bulb and instruct surrounding epithelial progenitors to orchestrate the complex hair differentiation program. To gain insights into the molecular program that maintains DP cell fate, we previously purified DP cells and four neighboring populations and defined their cell-type-specific molecular signatures. Here, we exploit this information to show that the bulb microenvironment is rich in bone morphogenetic proteins (BMPs) that act on DP cells to maintain key signature features in vitro and hair-inducing activity in vivo. By employing a novel in vitro/in vivo hybrid knockout assay, we ablate BMP receptor 1a in purified DP cells. When DPs cannot receive BMP signals, they lose signature characteristics in vitro and fail to generate HFs when engrafted with epithelial stem cells in vivo. These results reveal that BMP signaling, in addition to its key role in epithelial stem cell maintenance and progenitor cell differentiation, is essential for DP cell function, and suggest that it is a critical feature of the complex epithelial–mesenchymal cross-talk necessary to make hair.
PI3K pathway regulates survival of cancer stem cells residing in the perivascular niche following radiation in medulloblastoma in vivo
Authors: Hambardzumyan Dolores , Becher Oren J. , Rosenblum Marc K. , Pandolfi Pier Paolo , Manova-Todorova Katia , Holland Eric C.
Published: February 2008

Medulloblastomas are brain tumors that arise in the cerebellum of children and contain stem cells in a perivascular niche thought to give rise to recurrence following radiation. We used several mouse models of medulloblastomas in parallel to better understand how the critical cell types in these tumors respond to therapy. In our models, the proliferating cells in the tumor bulk undergo radiation-induced, p53-dependent apoptotic cell death. Activation of Akt signaling via PTEN loss transforms these cells to a nonproliferating extensive nodularity morphology. By contrast, the nestin-expressing perivascular stem cells survive radiation, activate PI3K/Akt pathway, undergo p53-dependent cell cycle arrest, and re-enter the cell cycle at 72 h. Furthermore, the ability of these cells to induce p53 is dependent on the presence of PTEN. These cellular characteristics are similar to human medulloblastomas. Finally, inhibition of Akt signaling sensitizes cells in the perivascular region to radiation-induced apoptosis.
Eph/ephrin signaling: networks
Authors: Arvanitis Dina , Davy Alice
Published: February 2008

Bidirectional signaling has emerged as an important signature by which Ephs and ephrins control biological functions. Eph/ephrin signaling participates in a wide spectrum of developmental processes, and cross-regulation with other communication pathways lies at the heart of the complexity underlying their function in vivo. Here, we review in vitro and in vivo data describing molecular, functional, and genetic interactions between Eph/ephrin and other cell surface signaling pathways. The complexity of Eph/ephrin function is discussed in terms of the pathways that regulate Eph/ephrin signaling and also the pathways that are regulated by Eph/ephrin signaling.
The pathways and outcomes of mycobacterial NHEJ depend on the structure of the broken DNA ends
Authors: Aniukwu Jideofor , Glickman Michael S. , Shuman Stewart
Published: February 2008

Mycobacteria can repair DNA double-strand breaks (DSBs) via a nonhomologous end-joining (NHEJ) system that includes a dedicated DNA ligase (LigD) and the DNA end-binding protein Ku. Here we exploit an improved plasmid-based NHEJ assay and a collection of Mycobacterium smegmatis strains bearing deletions or mutations in Ku or the DNA ligases to interrogate the contributions of LigD’s three catalytic activities (polymerase, ligase, and 3′ phosphoesterase) and structural domains (POL, LIG, and PE) to the efficiency and molecular outcomes of NHEJ in vivo. By analyzing in parallel the repair of blunt, 5′ overhang, and 3′ overhang DSBs, we discovered a novel end-joining pathway specific to breaks with 3′ overhangs that is Ku- and LigD-independent and perfectly faithful. This 3′ overhang NHEJ pathway is independent of ligases B and C; we surmise that it relies on NAD+-dependent LigA, the essential replicative ligase. We find that efficient repair of blunt and 5′ overhang DSBs depends stringently on Ku and the LigD POL domain, but not on the LigD polymerase activity, which mainly serves to promote NHEJ infidelity. The lack of an effect of PE-inactivating LigD mutations on NHEJ outcomes, especially the balance between deletions and insertions at blunt or 5′ overhang breaks, argues against LigD being the catalyst of deletion formation. Ligase-inactivating LigD mutations (or deletion of the LIG domain) have a modest impact on the efficiency of blunt and 5′ overhang DSB repair, because the strand sealing activity can be provided in trans by one of the other resident ATP-dependent ligases (likely LigC). Reliance on the backup ligase is accompanied by a drastic loss of fidelity during blunt end and 5′ overhang DSB repair. We conclude that the mechanisms of mycobacterial NHEJ are many and the outcomes depend on the initial structures of the DSBs and the available ensemble of end-processing and end-sealing components, which are not limited to Ku and LigD.
Allele-specific nuclear positioning of the monoallelically expressed astrocyte marker GFAP
Authors: Takizawa Takumi , Gudla Prabhakar R. , Guo Liying , Lockett Stephan , Misteli Tom
Published: February 2008

Chromosomes and genes are nonrandomly arranged within the mammalian cell nucleus. However, the functional significance of nuclear positioning in gene expression is unclear. Here we directly probed the relationship between nuclear positioning and gene activity by comparing the location of the active and inactive copies of a monoallelically expressed gene in single cell nuclei. We demonstrate that the astrocyte-specific marker GFAP (glial fibrillary acidic protein) is monoallelically expressed in cortical astrocytes. Selection of the active allele occurs in a stochastic manner and is generally maintained through cell division. Taking advantage of the monoallelic expression of GFAP, we show that the functionally distinct alleles occupy differential radial positions within the cell nucleus and differentially associate with intranuclear compartments. In addition, coordinately regulated astrocyte-specific genes on distinct chromosomes spatially associate in their inactive state and dissociate upon activation. These results provide direct evidence for function-related differential positioning of individual gene alleles within the interphase nucleus.
The uses of helium and xenon in current clinical practice
Authors: Harris P. D. , Barnes R.
Published: February 2008

The noble gases have always been an enigma. Discovered late in the history of chemistry and in seemingly small quantities in our atmosphere, they are some of the most unreactive elements known. However, despite being extremely inert, the noble gases (helium, neon, argon, krypton, xenon and radon) have found diverse and ever expanding applications in medicine. Of all of them, the gases that have found the greatest number of uses in the field of anaesthesia and related specialties are helium and xenon. This review focuses on the history of the discovery of both gases, their unique physicochemical properties and describes their uses in clinical practice with particular emphasis on those applicable to anaesthesia.
An investigation into the length of standard tracheostomy tubes in critical care patients*
Authors: Mallick A. , Bodenham A. , Elliot S. , Oram J.
Published: February 2008

A number of problems have been reported with the use of standard length tracheostomy tubes in adult critical care patients. We measured the depth from the skin surface to the tracheal wall and the angle of the tracheal stoma during percutaneous tracheostomy. In vitro measurements were also performed on standard tracheostomy tubes. Comparison of in vivo and in vitro dimensions demonstrated that standard length tracheostomy tubes are too short for the average critical care patient. We recommend that both the stomal and intratracheal lengths should be made longer by approximately 1 cm and tubes should be redesigned to an angle of 110–120° to allow optimal tracheal placement.
A national survey into the peri‐operative anaesthetic management of patients presenting for surgical correction of a fractured neck of femur*
Authors: Sandby‐Thomas M. , Sullivan G. , Hall J. E.
Published: February 2008

We conducted a national postal survey of trauma anaesthetists in the UK to ascertain current practice for the peri‐operative anaesthetic management in patients with fractured necks of femur. We received 155 replies from 218 questionnaires sent (71.1% response rate). Regional anaesthesia was preferred by 75.8% of respondents, with 95.5% of these employing a spinal technique. This was generally performed bad side down (45.7%) using ketamine (37.3%) and/or midazolam (41.2%) to aid positioning. In all, 31.4% used fentanyl in the intrathecal injectate, whereas only 5.9% used morphine. Paracetamol and morphine were the most commonly used postoperative analgesic regimens with non‐steroidal anti‐inflammatory drugs used by only 27.4%. Continuous epidural or nerve block infusions were used rarely. Of the anaesthetists, 50.6% would only request a pre‐operative echo if there were suspicious signs or symptoms in patients with a previously undiagnosed heart murmur. The peri‐operative management of these patients can be readily improved.
Pre‐oxygenation in pregnancy: an investigation using physiological modelling
Authors: McClelland S. H. , Bogod D. G. , Hardman J. G.
Published: February 2008

Hypoxaemia during anaesthetic induction in obstetrics is hazardous for mother and baby, but the onset of desaturation can be delayed by pre‐oxygenation. This study investigated pre‐oxygenation during pregnancy using computer simulation. The Nottingham Physiology Simulator was configured to replicate normal pregnant physiology. Three pregnant and three non‐pregnant subjects were created, representing population variation according to published physiological values. They underwent pre‐oxygenation by tidal and vital capacity breathing of 100% oxygen. Pre‐oxygenation during tidal breathing proceeded more rapidly in pregnancy, the median [range] time to achieve 95% of the maximum change in PÉo2 being 1 min 37 s [1:23–1:52] in pregnant subjects, compared to 2 min 51 s [2:28–3:15] in non‐pregnant subjects. Vital capacity pre‐oxygenation required seven breaths [5–10] in pregnant subjects, compared to six breaths [4–9] in non‐pregnant subjects, to achieve the same PÉo2 as after 95% complete tidal pre‐oxygenation. We recommend 2 min of tidal breathing for pre‐oxygenation in pregnancy.
The effect of warming local anaesthetic on the pain of injection during sub‐Tenon's anaesthesia for cataract surgery
Authors: Allen M. J. , Bunce C. , Presland A. H.
Published: February 2008

In a double blind, randomised controlled trial, we examined the effect of warming local anaesthetic solutions on the pain experienced by patients undergoing a sub‐Tenon's block for cataract surgery. In all, 140 patients were randomly allocated to receive either local anaesthetic stored at room temperature (control group) or local anaesthetic warmed to 37 °C (study group). Pain scores were assessed using a verbal analogue scale from 0 to 10. There was no significant difference in pain scores between the two groups. We conclude that the practice of warming local anaesthetic prior to performing a sub‐Tenon's block does not significantly reduce the amount of pain experienced by patients.
Anaesthesia – a sedentary specialty? Accelerometer assessment of the activity level of anaesthetists while at work
Authors: Cuthill J. A. , Fitzpatrick K. , Glen J.
Published: February 2008

Current guidance recommends that all adults should take a minimum of 10 000 steps a day to remain healthy. We assessed the activity levels of 45 anaesthetists while at work, using accelerometers. These devices also allowed us to measure sitting, standing and walking time – features of the working day that are also likely to contribute to health and well‐being. In addition, each anaesthetist was asked to guess how many steps they had taken and complete a questionnaire assessing current activity levels. Median (IQR [range]) number of steps taken per day at work was 3694 (2435–4646 [1444–7712]). Almost all anaesthetists underestimated the number of steps they had taken. We concluded that no anaesthetists in our study were able to take the recommended 10 000 steps solely during their working day. A concerted effort is required in recreational time to ensure anaesthetists stay fit and healthy.
An evaluation of the T‐Line® Tensymeter continuous noninvasive blood pressure device during induced hypotension*
Authors: Szmuk P. , Pivalizza E. , Warters R. D. , Ezri T. , Gebhard R.
Published: February 2008

A new continuous noninvasive blood pressure measurement device, the T‐Line® Tensymeter TL100 (Tensys Medical Inc., San Diego, CA, USA) which enables avoidance of arterial cannulation has been developed. We compared the values obtained using the T‐Line values to simultaneous arterial line measurements in patients undergoing general anaesthesia with induced hypotension. Twenty‐five patients, aged 18–70 years, were studied. The T‐Line and arterial line were positioned on the contralateral wrists. Intra‐operative, real‐time, blood pressure data were electronically captured and stored on a computer. Bland–Altman plots and 95% limits of agreement show that the majority of T‐Line data points were within 5 mmHg of the arterial line measurements (67%) and agreement was within 15 mmHg in 94.6% or more of all measurements. There was virtually no distinguishable error over the course of surgery using the device. In conclusion, the T‐Line measurements correlate with arterial measurements during anaesthesia in which there were periods of both normotensive and hypotensive anaesthesia. The T‐Line Tensymeter represents a noninvasive alternative to an arterial line in cases when arterial blood sampling is not required.
Metabolic acidosis in the critically ill: Part 1. Classification and pathophysiology
Authors: Morris C. G. , Low J.
Published: February 2008

Metabolic acidaemia (pH < 7.35 not primarily related to hypoventilation) is common amongst the critically ill and it is essential that clinicians caring for such patients have an understanding of the common causes. The exclusive elimination routes of volatile (carbon dioxide), organic (lactic and ketone) and inorganic (phosphate and sulphate) acids mean compensation for a defect in any one is limited and requires separate provision during critical illness. We discuss the models available to diagnose metabolic acidosis including CO2/HCO3–and physical chemistry‐derived (Stewart or Fencl‐Stewart) approaches, but we propose that the base excess and anion gap, corrected for hypoalbuminaemia and iatrogenic hyperchloraemia, remain most appropriate for clinical usage. Finally we provide some tips for interpreting respiratory responses to metabolic acidosis and how to reach a working diagnosis, the consequences of which are considered in Part 2 of this review.
The production and emission of nitrous oxide from headwater streams in the Midwestern United States
Authors: BEAULIEU J. J. , ARANGO C. P. , HAMILTON S. K. , TANK J. L.
Published: February 2008

The emission of nitrous oxide (N2O) from streams draining agricultural landscapes is estimated by the Intergovernmental Panel on Climate Change (IPCC) to constitute a globally significant source of this gas to the atmosphere, although there is considerable uncertainty in the magnitude of this source. We measured N2O emission rates and potential controlling variables in 12 headwater streams draining a predominantly agricultural basin on glacial terrain in southwestern Michigan. The study sites were nearly always supersaturated with N2O and emission rates ranged from −8.9 to 266.8 μg N2O‐N m−2 h−1 with an overall mean of 35.2 μg N2O‐N m−2 h−1. Stream water NO3− concentrations best‐predicted N2O emission rates. Although streams and agricultural soils in the basin had similar areal emission rates, emissions from streams were equivalent to 6% of the anthropogenic emissions from soils because of the vastly greater surface area of soils. We found that the default value of the N2O emission factor for streams and groundwater as defined by the IPCC (EF5‐g) was similar to the value observed in this study lending support to the recent downward revision to EF5‐g. However, the EF5‐g spanned four orders of magnitude across our study sites suggesting that the IPCC's methodology of applying one emission factor to all streams may be inappropriate.
Storage and mobility of black carbon in permafrost soils of the forest tundra ecotone in Northern Siberia
Authors: GUGGENBERGER GEORG , RODIONOV ANDREJ , SHIBISTOVA OLGA , GRABE MATTHIAS , KASANSKY OLEG A. , FUCHS HANS , MIKHEYEVA NATALIA , ZRAZHEVSKAYA GALINA , FLESSA HEINER
Published: February 2008

Boreal permafrost soils store large amounts of organic carbon (OC). Parts of this carbon (C) might be black carbon (BC) generated during vegetation fires. Rising temperature and permafrost degradation is expected to have different consequences for OC and BC, because BC is considered to be a refractory subfraction of soil organic matter. To get some insight into stocks, variability, and characteristics of BC in permafrost soils, we estimated the benzene polycarboxylic acid (BPCA) method‐specific composition and storage of BC, i.e. BPCA‐BC, in a 0.44 km2‐sized catchment at the forest tundra ecotone in northern Siberia. Furthermore, we assessed the BPCA‐BC export with the stream draining the catchment. The catchment is composed of various landscape units with south‐southwest (SSW) exposed mineral soils characterized by thick active layer or lacking permafrost, north‐northeast (NNE) faced mineral soils with thin active layer, and permafrost‐affected raised bogs in plateau positions showing in part thermokarst formation. There were indications of vegetation fires at all landscape units. BC was ubiquitous in the catchment soils and BPCA‐BC amounted to 0.6–3.0% of OC. This corresponded to a BC storage of 22–3440 g m−2. The relative contribution of BPCA‐BC to OC, as well as the absolute stocks of BPCA‐BC were largest in the intact bogs with a shallow active layer followed by mineral soils of the NNE aspects. In both landscape units, a large proportion of BPCA‐BC was stored within the permafrost. In contrast, mineral soils with thick active layer or lacking permafrost and organic soils subjected to thermokarst formation stored less BPCA‐BC. Permafrost is, hence, not only a crucial factor in the storage of OC but also of BC. In the stream water BPCA‐BC amounted on an average to 3.9% of OC, and a yearly export of 0.10 g BPCA‐BC m−2 was calculated, most of it occurring during the period of snow melt with dominance of surface flow. This suggests that BC mobility in dissolved and colloidal phase is an important pathway of BC export from the catchment. Such a transport mechanism may explain the high BC concentrations found in sediments of the Arctic Ocean.