Elevated Electron Temperature Coincident with Observed Fusion Reactions in a Sheared-Flow-Stabilized Z Pinch.

The sheared-flow-stabilized Z pinch concept has been studied extensively and is able to produce fusion-relevant plasma parameters along with neutron production over several microseconds. We present here elevated electron temperature results spatially and temporally coincident with the plasma neutron source. An optical Thomson scattering apparatus designed for the FuZE device measures temperatures in the range of 1-3 keV on the axis of the device, 20 cm downstream of the nose cone. The 17-fiber system measures the radial profiles of the electron temperature. Scanning the laser time with respect to the neutron pulse time over a series of discharges allows the reconstruction of the T_{e} temporal response, confirming that the electron temperature peaks simultaneously with the neutron output, as well as the pinch current and inductive voltage generated within the plasma. Comparison to spectroscopic ion temperature measurements suggests a plasma in thermal equilibrium. The elevated T_{e} confirms the presence of a plasma assembled on axis, and indicates limited radiative losses, demonstrating a basis for scaling this device toward net gain fusion conditions.

Sustained Neutron Production from a Sheared-Flow Stabilized Z Pinch.

The sheared-flow stabilized Z pinch has demonstrated long-lived plasmas with fusion-relevant parameters. We present the first experimental results demonstrating sustained, quasi-steady-state neutron production from the fusion Z-pinch experiment, operated with a mixture of 20% deuterium/80% hydrogen by pressure. Neutron emissions lasting approximately 5 µs are reproducibly observed with pinch currents of approximately 200 kA during an approximately 16 µs period of plasma quiescence. The average neutron yield is estimated to be (1.25±0.45)×10^{5} neutrons/pulse and scales with the square of the deuterium concentration. Coincident with the neutron signal, plasma temperatures of 1-2 keV and densities of approximately 10^{17} cm^{-3} with 0.3 cm pinch radii are measured with fully integrated diagnostics.

Probing local electron temperature and density inside a sheared flow stabilized Z-pinch using portable optical Thomson scattering.

We report the first optical Thomson scattering measurements inside a high electron temperature (≳1 keV) and moderate electron density (mid 1016 cm-3) plasma. This diagnostic has been built to provide critical plasma parameters, such as electron temperature and density, for Advanced Research Projects Agency-Energy-supported fusion-energy concepts. It uses an 8 J laser at 532 nm in 1.5 ns to measure the high frequency feature of the Thomson scattering profile at 17 locations along the probe axis. It is able to measure electron density from 5 × 1017 cm-3 to several 1019 cm-3 and electron temperatures from tens of eV to several keV. Here, we describe the design, deployment, and analysis on the sheared flow stabilized Z-pinch machine at Zap Energy named FuZE. The probe beam is aimed at an axial distance of 20 cm from the central electrode and is timed within the temporal envelope of neutron emission. The high temperature and moderate density plasmas generated on FuZE lie in an unconventional regime for Thomson scattering as they are between tokamaks and laser-produced plasmas. We described the analysis considerations in this regime, show that the electron density was below 5 × 1016 cm-3 at all times during these measurements, and present a sample shot where the inferred electron temperature varied from 167 ± 16 eV to 700 ± 85 eV over 1.6 cm.

Implementation of extreme ultraviolet spectroscopy on a sheared-flow-stabilized Z pinch.

A diagnostic for extreme ultraviolet spectroscopy was fielded on the sheared-flow-stabilized (SFS) fusion Z-pinch experiment (FuZE-Q) for the first time. The spectrometer collected time-gated plasma emission spectra in the 5-40 nm wavelength (30-250 eV) range for impurity identification, radiative power studies, and for plasma temperature and density measurements. The unique implementation of the diagnostic included fast (10 ns risetime) pulsed high voltage electronics and a multi-stage differential pumping system that allowed the vacuum-coupled spectrometer to collect three independently timed spectra per FuZE-Q shot while also protecting sensitive internal components. Analysis of line emission identifies oxygen (N-, C-, B-, Be-, Li-, and He-like O), peaking in intensity shortly after maximum current (>500 kA). This work provides a foundation for future high energy spectroscopy experiments on SFS Z-pinch devices.

Evidence for separatrix formation and sustainment with steady inductive helicity injection.

The first sustainment of toroidal plasma current of 50 kA at up to 3 times the injected currents, added in quadrature, using steady inductive helicity injection is described. Separatrix currents-currents not linking the helicity injectors-are sustained up to 40 kA. Decreases in the n=1 toroidal mode of the poloidal magnetic field at higher current amplifications indicate more quiescent, direct toroidal current drive. Results are achieved in HIT-SI (with a spheromak of major radius 0.3 m) during deuterium operations immediately after helium operation. These results represent a breakthrough in the development of this new current drive method for magnetic confinement fusion.

High-speed feedback control of an oscillating magnetic helicity injector using a graphics processing unit.

A real-time control system has been developed to control the amplitude, phase, and offset of bulk plasma parameters inside an oscillating magnetic helicity injector. Control software running entirely on an Nvidia Tesla P40 graphical processing unit is able to receive digitizer inputs and send response patterns to a Pulse Width Modulation (PWM) controller with a minimum control loop period of 12.8 µs. With an input digitization rate of 10 MS/s, a three-parameter proportional integral differential controller is shown to be sufficient to inform the PWM controller to drive the desired oscillating plasma waveform with a frequency of 16.6 kHz that is located near the resonance of a coupled RLC circuit. In particular, the temporal phase of the injector waveform is held within 10° of the target value. Control is demonstrated over the toroidal modal structure of the imposed magnetic perturbations of the helicity injection system, allowing a new class of discharges to be studied.

Demonstration of Tokamak ohmic flux saving by transient coaxial helicity injection in the national spherical torus experiment.

Transient coaxial helicity injection (CHI) started discharges in the National Spherical Torus Experiment (NSTX) have attained peak currents up to 300 kA and when coupled to induction, it has produced up to 200 kA additional current over inductive-only operation. CHI in NSTX has shown to be energetically quite efficient, producing a plasma current of about 10 A/J of capacitor bank energy. In addition, for the first time, the CHI-produced toroidal current that couples to induction continues to increase with the energy supplied by the CHI power supply at otherwise similar values of the injector flux, indicating the potential for substantial current generation capability by CHI in NSTX and in future toroidal devices.

Measuring material softening with nanoscale spatial resolution using heated silicon probes.

This article describes the use of heated silicon atomic force microscopy probes to perform local thermal analysis (LTA) of a thin film of polystyrene. The experiments measure film softening behavior with 100 nm spatial resolution, whereas previous research on LTA used probes that had a resolution near 10 microm, which was too large to investigate some types of features. This article demonstrates four methods by which heated silicon probes can perform thermal analysis with nanoscale spatial resolution. The polystyrene softening temperature measured from nanoscale LTA techniques is 120 degrees C, compared to 100 degrees C, measured with bulk ellipsometry. The discrepancy is attributed to the thermal contact resistance at the end of the silicon probe tip, on the order of 10(7)K/W, which modulates heat flow between the tip and sample and governs the fundamental limits of this technique. The use of a silicon probe for LTA enables bulk fabrication, parallelization for high-throughput analysis, and fabrication of a sharp tip capable of nanoscale spatial resolution.

High glucose and glucosamine induce insulin resistance via different mechanisms in 3T3-L1 adipocytes.

Sustained hyperglycemia induces insulin resistance, but the mechanism is still incompletely understood. Glucosamine (GlcN) has been extensively used to model the role of the hexosamine synthesis pathway (HSP) in glucose-induced insulin resistance. 3T3-L1 adipocytes were preincubated for 18 h in media +/- 0.6 nmol/l insulin containing either low glucose (5 mmol/l), low glucose plus GlcN (0.1-2.5 mmol/l), or high glucose (25 mmol/l). Basal and acute insulin-stimulated (100 nmol/l) glucose transport was measured after re-equilibration in serum and insulin-free media. Preincubation with high glucose or GlcN (1-2.5 mmol/l) inhibited basal and acute insulin-stimulated glucose transport only if insulin was present during preincubation. However, only preincubation with GlcN plus insulin inhibited insulin-stimulated GLUT4 translocation. GLUT4 and GLUT1 protein expression were not affected. GlcN (2.5 mmol/l) increased cellular UDP-N-acetylhexosamines (UDP-HexNAc) by 400 and 900% without or with insulin, respectively. High glucose plus insulin increased UDP-HexNAc by 30%. GlcN depleted UDP-hexoses, whereas high glucose plus insulin increased them. Preincubation with 0.5 mmol/l GlcN plus insulin maximally increased UDP-HexNAc without affecting insulin-stimulated or basal glucose transport. GlcN plus insulin (but not high glucose plus insulin) caused marked GlcN dose-dependent accumulation of GlcN-6-phosphate, which correlated with insulin resistance of glucose transport (r = 0.935). GlcN plus insulin (but not high glucose plus insulin) decreased ATP (10-30%) and UTP (>50%). GTP was not measured, but GDP increased. Neither high glucose plus insulin nor GlcN plus insulin prevented acute insulin stimulation (approximately 20-fold) of insulin receptor substrate 1-associated phosphatidylinositol (PI)-3 kinase. We have come to the following conclusions. 1) Chronic exposure to high glucose or GlcN in the presence of low insulin caused insulin resistance of glucose transport by different mechanisms. 2) GlcN inhibited GLUT4 translocation, whereas high glucose impaired GLUT4 "intrinsic activity" or membrane intercalation. 3) Both agents may act distally to PI-3 kinase. 4) GlcN has metabolic effects not shared by high glucose. GlcN may not model HSP appropriately, at least in 3T3-L1 adipocytes.

A novel variant of glutamine: fructose-6-phosphate amidotransferase-1 (GFAT1) mRNA is selectively expressed in striated muscle.

Glutamine:fructose-6-phosphate amidotransferase(GFAT) is the rate-limiting enzyme of the hexosamine synthesis pathway. Products of this pathway have been implicated in insulin resistance and glucose toxicity. GFAT1 is ubiquitous, whereas GFAT2 is expressed mainly in the central nervous system. In the course of developing a competitive reverse transcriptase-polymerase chain reaction assay, we noted that GFAT1 cDNA from muscle but not from other tissues migrated as a doublet. Subsequent cloning and sequencing revealed two GFAT1 mRNAs in both mouse and human skeletal muscles. The novel GFAT1 mRNA (GFAT1Alt [muscle selective variant of GFAT1]) is likely a splice variant. It is identical to GFAT1 except for a 48 or 54 bp insert in the mouse and human, respectively, at nucleotide position 686 of the coding sequence, resulting in a 16 or 18 amino acid insert at position 229 of the protein. GFAT1Alt is the predominant GFAT1 mRNA in mouse hindlimb muscle, is weakly expressed in the heart, and is undetectable in the brain, liver, kidney, lung, intestine, spleen, and 3T3-L1 adipocytes. In humans, it is strongly expressed in skeletal muscle but not in the brain. GFAT1 and GFAT1Alt expressed by recombinant adenovirus infection in COS-7 cells displayed robust enzyme activity and kinetic differences. The apparent K(m) of GFAT1Alt for fructose-6-phosphate was approximately twofold higher than that of GFAT1, whereas K(i) for UDP-N-acetylglucosamine was approximately fivefold lower. Muscle insulin resistance is a hallmark and predictor of type 2 diabetes. Variations in the expression of GFAT isoforms in muscle may contribute to predisposition to insulin resistance.

Childhood sexual and physical abuse as factors in adult psychiatric illness.

Using objective measures, the authors found a high rate of childhood sexual and physical abuse in a sample of 66 female psychiatric inpatients. Childhood abuse experiences were correlated with severity of adult psychiatric symptoms. The authors explore the usefulness of adult psychological symptoms, diagnoses, and prescribed medications as factors in the identification of patients who have histories of early sexual and physical abuse.

alpha-Lipoic acid prevents the development of glucose-induced insulin resistance in 3T3-L1 adipocytes and accelerates the decline in immunoreactive insulin during cell incubation.

Oxidative stress has been implicated in glucose toxicity. We tested the hypothesis that certain antioxidants may prevent insulin-resistant glucose transport that develops in adipocytes after sustained exposure to high glucose, provided insulin is present. The antioxidant alpha-lipoic acid has been proposed as an insulin sensitizer. 3T3-L1 adipocytes were preincubated 18 hours in media containing insulin (0.6 nmol/L) with low (5 mmol/L) or high (25 mmol/L) glucose with or without alpha-lipoate, dihydrolipoate (each 0.1 to 0.5 mmol/L), or N-acetylcysteine (1 to 5 mmol/L). After extensive re-equilibration in insulin and antioxidant-free media, basal and maximally insulin-stimulated (100 nmol/L) glucose transport was measured. Insulin was quantified by radioimmunoassay. Preincubation with alpha-lipoate and dihydrolipoate but not N-acetylcysteine increased subsequent basal glucose transport; the effect was much smaller than that of acute maximal insulin stimulation. Preincubation in high glucose without antioxidants inhibited acutely insulin-stimulated glucose transport by 40% to 50% compared with low glucose. This down- regulation was partially or completely prevented by each antioxidant. In cell-free media, the 2 reductants, dihydrolipoate and N-acetylcysteine, rapidly decreased immunoreactive insulin, but alpha-lipoate was ineffective. However, during incubation with adipocytes, alpha-lipoate, and dihydrolipoate promoted the decline in immunoreactive insulin nearly equally. Because insulin and high glucose are synergistic in inducing insulin resistance in this model, the reduction in immunoreactive insulin probably contributed to the protective effect of the antioxidants. 3T3-L1 adipocytes efficiently metabolize alpha-lipoate to dihydrolipoate, which may be released into the medium. The stimulation of glucose transport by alpha-lipoic acid may represent redox effects in subcellular compartments that are accessible to dihydrolipoate.

The role of needle purging in reducing transfer of microorganisms from local anesthetic cartridge diaphragms.

The literature is reviewed to demonstrate the significant amount of contamination on the external surface of the anesthetic cartridge diaphragm. Current methods of cartridge diaphragm decontamination to prevent injection of pathogens are discussed. A series of bacteriologic tests were conducted to determine the probability of transfer of pathogens from the diaphragm surface through the needle lumen of three different sizes to the deposition site. Results of needle purging suggest that a significant reduction in the transfer of microorganisms is possible using this technique.

A comprehensive program for pregnant adolescents: parenting and prevention.

Beginning in 1981 as an effort to reduce mortality rates of at-risk infants, the Teen Pregnancy Project of this agency has grown steadily into a multiservice program with many approaches, yet all services for its help-resistant population depend upon an outreach, home-visiting initiative to establish useful relationships with its clients.

A school-wide assessment of social media usage by students in a US dental school.

Social media sites have become an established means of communication due to the exponential growth in number of users across the world and the encouragement of interaction between users through site features. The purpose of this study was to determine the extent to which Loma Linda University School of Dentistry students use social media accounts, the types of accounts they prefer, their interest in incorporating social media into courses and their perceptions of the usefulness of social media in private practice. In addition, we wanted to determine the degree of student interest in the integration of these social tools into their instruction. One thousand one hundred and sixty-two students from Loma Linda University School of Dentistry were invited by e-mail to complete a confidential 18 item multiple choice survey through Surveymonkey.com. The overall response rate was 30% (n = 351) from the pooled response periods; the first in 2011 and the second in 2013. Similar to other studies, Facebook was used by 91% of the School of Dentistry students, and less than half used Google+, Twitter and LinkedIn. Of the respondents, 68% of students reported communicating on social media daily and 80% saw value for practising dentists to operate accounts. Time and privacy concerns were the largest barriers to usage at 16% and 12% respectively. One third of respondents were in favour of the incorporation of social media in their courses.

Design and operation of a fast electromagnetic inductive massive gas injection valve for NSTX-U.

Results from the operation of an electromagnetic valve, that does not incorporate ferromagnetic materials, are presented. Image currents induced on a conducting disc placed near a pancake solenoid cause it to move away from the solenoid and open the vacuum seal. A new and important design feature is the use of Lip Seals for the sliding piston. The pressure rise in the test chamber is measured directly using a fast time response Baratron gauge. The valve injects over 200 Torr l of nitrogen in less than 3 ms, which remains unchanged at moderate magnetic fields.

Spheromak formation by steady inductive helicity injection.

A spheromak is formed for the first time using a new steady state inductive helicity injection method. Using two inductive injectors with odd symmetry and oscillating at 5.8 kHz, a steady state spheromak with even symmetry is formed and sustained through nonlinear relaxation. A spheromak with about 13 kA of toroidal current is formed and sustained using about 3 MW of power. This is a much lower power threshold for spheromak production than required for electrode-based helicity injection. Internal magnetic probe data, including oscillations driven by the injectors, agree with the plasma being in the Taylor state. The agreement is remarkable considering the only fitting parameter is the amplitude of the spheromak component of the state.

Efficient generation of closed magnetic flux surfaces in a large spherical tokamak using coaxial helicity injection.

A method of coaxial helicity injection has successfully produced a closed flux current without the use of the central solenoid in the NSTX device, on a size scale closer to a spherical torus reactor, for a proof-of-principle demonstration of this concept. For the first time, a remarkable 60 times current multiplication factor was achieved. Grad-Shafranov plasma equilibrium reconstructions are used to verify the existence of closed flux current. In some discharges the generated current persists for a surprisingly long time approximately 400 ms.

The catalytic cysteine and histidine in the plant acyl-acyl carrier protein thioesterases.

The plant acyl-acyl carrier protein (acyl-ACP) thioesterases (TEs) play an essential role in chain termination during de novo fatty acid synthesis and are of biochemical interest because of their utilities in the genetic engineering of plant seed oils. Biochemical data have shown the possible involvement of an active-site cysteine and a histidine in catalysis, suggesting that these enzymes activate the hydrolysis of the thioester bond using the same basic catalytic machinery as those of proteases and lipases. To identify the cysteine and histidine residues that are critical in catalysis we substituted, in a 12:0 ACP TE (Uc FatB1), a conserved cysteine (Cys-320) to an Ala or a Ser, and three conserved histidines (His-140, His-285, and His-345) to an Ala or an Arg. Each Ala mutation caused a substantial loss of enzyme activity. However, only C320A and H285A completely inactivated the enzyme, indicating that these two residues are essential for catalysis. Considerable activity (>60%) still remained when Cys-320 was converted to a Ser, but this mutant (C320S) displayed a reversed sensitivity toward thiol or serine hydroxyl inhibitors compared with the wild-type enzyme. A pH optimal study demonstrates that while the wild-type enzyme has the highest activity between pH 8.5 and 9.5, the mutant H285A shows a shifted optimum to higher pH and a significant increase of activity around pH 12. This result suggests that Arg-285 (pKa 12) is deprotonated at high pH, thus partially mimicking the role of His-285 for proton abstraction in the wild-type enzyme. We conclude that the Cys-320 of the wild-type enzyme and Ser-320 of the mutant enzyme can attack the thioester bond of the substrate 12:0 ACP, assisted by His-285. Because plant TEs are highly conserved in length and sequence and the residues investigated here are completely conserved in all available TEs, it is reasonable to believe that homologues of Cys-320 and His-285 are present in the active sites of all plant acyl-ACP TEs.