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Multi-probe scanning tunneling microscopy can play a role in various electrical measurements and characterization of nanoscale objects. The consistent close placement of multiple probes relies on very sharp apexes with no other interfering materials along the shank of the tip. Electrochemically etched tips can prepare very sharp apex tips; however, other asperities on the shank can cause interference and limit the close positioning of multiple tips to beyond the measured radii. Gallium focused ion beam (FIB) milling is used to remove any interfering material and allow closely spaced tips with a consistent yield. The tip apex radius is evaluated with field ion microscopy, and the probe spacing is evaluated with STM on hydrogen terminated silicon surfaces. FIB prepared tips can consistently achieve the measured probe to probe spacing distances of 25 nm–50 nm.

The measurements of magnetic hysteresis for aggregates of nanoparticles deposited on a surface are reported. Magnetite nanoparticles derived from magnetotactic bacteria are studied using nanomechanical torque magnetometry. The nanoparticles are deposited on high-stress Si3N4 membranes, to allow inspection by electron microscopy, followed by focused ion-beam milling of torsional resonators precisely located to capture selected aggregates within the membrane area. Torque magnetometry is performed using the resonators. We investigate also the magnetic torque-driven AC resonant modes of the modified supporting membrane. The observations are compared to numerical simulations of the mechanical modes, and to micromagnetic modeling of the hysteresis of a specific measured cluster of ∼350 nanoparticles.

Controlling Magnetic Noise Ferromagnetic materials contain a number of magnetic domains, with individual domains switching stochastically as the field strength is increased. As magnetic memory elements shrink in size, it is important to understand, and ultimately control, this magnetic noise. Using a magnetic vortex core integrated with a nanomechanical torsion balance, Burgess et al. (p. 1051 , published online 17 January) created a two-dimensional map of the magnetic potential within the sample with nanoscale resolution. Moreover, introducing geometric defects (dimples) in the sample allowed the magnetization to be stabilized.

For several years, many types of solar powered water pumping systems were evaluated, and in this paper, diaphragm and helical solar photovoltaic (PV) powered water pumping systems are discussed. Data were collected on diaphragm and helical pumps which were powered by different solar PV arrays at multiple pumping depths to determine the pumping performance, efficiency, and reliability of the different systems. The highest diaphragm pump hydraulic efficiency measured was ∼48%, and the highest helical pump hydraulic efficiency measured was ∼60%. The peak total system efficiency (e.g. solar radiation to pumped water) measured for the diaphragm and helical pumps were ∼5% and ∼7%, respectively (based on PV modules with ∼12% efficiency). The daily water volume of the three-chamber high head diaphragm pump performed better than the dual-chamber high head diaphragm pump (∼5 to ∼100% depending on PV array input power and pumping depth). Use of a controller was shown to improve the quad diaphragm pump performance below a solar irradiance of 600 W/m 2 (20 m head) to 800 W/m 2 (30 m head). While diaphragm pumps made mostly of plastic demonstrated similar to much better pumping performance than diaphragm pumps made with a high proportion of metal, the metal pumps demonstrated a longer service life (>2 years) than the plastic pumps service life (

A simple decision-analysis model is used to determine the financial benefits accruing to one highway authority in Scotland from the use of weather radar imagery for u-inter-road-maintenance operations. Over a three-month period, the savings are some £23 000 greater than the benefits derived from the use of the particular OPEN ROAD forecast service employed by that authority.

The effectiveness of debris reduction using magnetically guided pulsed laser deposition (MGPLD) is reported here. KrF laser pulses (248 nm) of 100 mJ energy were focused to intensities of 6×109 W/cm2 onto the surface of a copper or a carbon source target and a magnetic field of 0.3 T as used to steer the plasma around a curved arc of 0.5 m length to the deposition substrate. Debris counts were compared for films produced by the MGPLD and conventional PLD (nonguided) techniques. A significant reduction in particulates of size greater than 0.1 μm was achieved using MGPLD. For the copper films, particulate count was reduced from 150 000 particles/cm2/nm to 50 particulates/cm2/nm and for diamond-like carbon thin films particulate count was reduced from 25 000 particles/cm2/nm to 1200 particles/cm2/nm.

Pulsed laser deposition (PLD) has been used together with the Glancing Angle Deposition (GLAD) technique [1,2] for the first time to produce highly porous structured films. A laser produced carbon plasma and vapour plume was deposited at a highly oblique incident angle onto rotating Si substrates, resulting in films exhibiting high bulk porosity and controlled columnar microstructure. By varying the substrate rotation rate, the shape of the microcolumns can be tailored. These results extend the versatility of the GLAD process to materials not readily deposited by means of traditional physical vapour deposition techniques.

The water pumping performance of two wind-electric systems is compared to the water pumping performance of two solar-PV systems. The wind-electric systems were rated at 1.0 kW and 1.5 kW at a wind speed of about 12 m/s, and the rotor diameters were 2.75 m and 3.05 m, respectively. The solar-PV systems were rated at 0.1 kW and 0.9 kW at a radiation level of about 1,000 W/m{sup 2}, and the total solar panel surface areas were 1 and 17 m{sup 2}, respectively. Both wind-electric systems powered three-phase 230 V a-c induction motors with centrifugal pumps. The smaller of the solar-PV systems powered a d-c motor with a diaphragm pump, and the larger one powered a single phase 230 V a-c induction motor with a centrifugal pump. Only a well pumping depth of 30 m was evaluated for both wind-electric and solar-PV water pumping systems. The 0.1 kW and the 0.9 kW solar water pumping systems can provide enough water for 25 and 75 cattle, respectively, if the incident solar radiation is similar to that of Bushland, TX. The 1.0 kW and 1.5 kW wind-electric water pumping systems can provide enough water for 300 and 400 cattle, respectively, if themore » wind regime is similar to that of Bushland, TX.« less

MEMS based laser projection is of high interest for automotive head-up displays and dashboard displays, as well as for an increasing number of personal mobile projection applications. These applications require scanning mirrors that offer high scan frequencies and wide scan angles while showing low power consumption. This paper presents a novel low-power high-Q scanning mirror that is vacuum encapsulated on wafer level and thereby exhibits Q-factors exceeding 145,000. A new glass forming process enables fabrication of glass wafers with inclined 3D-shaped windows needed to spatially separate the direct reflex from the projected image.

Micromechanical resonators are very useful for detection of magnetic torque. We have developed nanoscale torsional resonators fabricated within silicon nitride membranes, as a platform for magnetometry of nanoscale magnetic elements. We describe the rotational magnetic hysteresis of a 10 nm thick film deposited on a resonator, and a study of magnetic hysteresis in a single, 1 m diameter permalloy disk. The torsional resonator is patterned using a dual beam scanning electron/focused ion system. For the 1 m diameter disk, it is found to be possible to tune the conditions such that an apparent magnetic supercooling of vortex nucleation is observed, as would be suggested by the modified Landau theory of the C- to vortex-state switch as a first-order phase transition. Complementary transmission electron and Lorentz microscopy of the same structures have also been performed. © 2011 American Institute of Physics.

The formation and evolution of collisional structures in the coronas of laser-produced plasmas have been studied by irradiating multilayered targets with nonuniform laser beams. Spatially resolved x-ray emission patterns and spectra were recorded to infer the temperatures, ionization states, and time-integrated hydrodynamic histories of plasmas originating from tracer layers embedded in the targets. The conditions of the experiment have been simulated using a two-dimensional single-fluid hydrodynamic code. The experimental results and code predictions are in good agreement, showing the stagnation of colliding plasmas in the nonirradiated regions

We demonstrate that the transition from the high-field state to the vortex state in a nanomagnetic disk shows the magnetic equivalent of supercooling. This is evidence that this magnetic transition can be described in terms of a modified Landau first-order phase transition. To accomplish this we have measured the bulk magnetization of single magnetic disks using nanomechanical torsional resonator torque magnetometry. This allows observation of single vortex creation events without averaging over an array of disks or over multiple runs., Comment: 11 pages preprint, 4 figures, accepted to New Journal of Physics

Acoustical noise data have been collected and analyzed on small wind turbines used for water pumping at the USDA-ARS Conservation and Production Research Laboratory (CPRL) near Bushland, TX. This acoustical analysis differed from previous research in that the data were analyzed with rotor or tip speed being the independent variable in addition to analyzing the data with wind speed as the independent variable. Acoustical noise generation was analyzed for two different wind turbines which were tested with different blades. The averaging period for acoustical noise data was one second instead of one minute (smallest time increment recommended in IEC wind turbine noise standard) since the sound pressure level of small stand-alone wind turbines can vary significantly over just a few seconds. Disconnecting the wind turbine from the water pump motor by the pump controller was shown to significantly increase the noise of the wind turbine.

An axial magnetic field with a maximum strength of 2.2 kG was used to confine and guide a laser produced carbon plasma around a 30 deg bend. The plasma was produced by a 25 ns KrF laser pulse at a peak intensity of 1×109 W cm−2. An array of Faraday cups positioned at the exit of the guide field was used to determine that approximately 20% of the original plasma was confined by the magnetic field and guided along a 15 cm trajectory to a 5 cm2 area.

Summary form only given, as follows. The guiding of plasma produced by a KrF laser and Nd:YAG laser using straight and curved solenoidal magnetic field has been studied as a means of giving a debris free, controlled deposition source for the production of thin films. Details on the deflection and guiding of the laser produced plasma in curved and straight magnetic fields and initial coating results will be presented. These results will be presented and compared to predictions of plasma guiding using 2D and 3D numerical plasma simulation mode.

Most small wind turbines (1.0 kW and below) furl (aerodynamic/mechanical ability of wind turbine to turn out of the wind) for overspeed protection. Overspeed protection afforded by this furling action protects the rotor and other system components from being stressed beyond the limits for which they were designed. Testing wind turbines that furl has been performed by the USDA-Agricultural Research Service, Bushland, TX, since 1988. One 10 kW wind turbine being tested came close to destruction when a guy cable attachment failed due to excessive vibration. The excessive vibration was caused by the high wind speed necessary to cause the turbine to furl. In November 1997 experimental testing was started on two smaller wind turbines (rated at 0.85 kW and 1.5 kW) to analyze and investigate ways of altering the furling wind speed which could be incorporated in a redesign of the 10 kW wind turbine. These changes involved changing the rotor diameter, the direction of rotor rotation, and the wind turbine electrical load. Increasing the rotor diameter by about 20% resulted in a decrease in furling wind speed of 4 to 5 m/s for the 0.85 kW wind turbine and 2 to 3 m/s for the 1.5 kW wind turbine. Changing the rotor rotation direction gave different results for the two wind turbines, but the larger tilt angle of the 10 kW wind turbine rotor axis may make changing the rotor rotation direction more effective. Applying the electrical load at a lower frequency with a smart conuoller on the 0.85 kW wind turbine resulted in a delay in furling of at least 4 m/s.

Lateral energy transport in laser-produced plasmas has been studied by irradiating planar polystyrene foils with 0.53-\ensuremath{\mu}m-wavelength, spatially nonuniform laser beams. Spatially resolved x-ray emission patterns and spectra were recorded to infer the temperatures, ionization states, and time-integrated hydrodynamic histories of plasma originating from tracer layers embedded in the targets. The conditions of the experiment have been simulated using a two-dimensional single fluid hydrodynamic code. The experimental results and code predictions are in good agreement, indicating that a moderate amount of ablation occurs in the nonirradiated region of the target. (c) 1995 The American Physical Society

Magnetic torque is used to actuate nano-torsional resonators, which are fabricated by focused-ion-beam milling of permalloy coated silicon nitride membranes. Optical interferometry is used to measure the mechanical response of two torsion modes at resonance, which is proportional to the magnetization vector of the nanomagnetic volume. By varying the bias magnetic field, the magnetic behavior can be measured with excellent sensitivity ($\approx 10^8 \mu_B$) for single magnetic elements., Comment: 8 pages preprint, 4 figures, accepted to Appl. Phys. Letters

Reflectivity and red-shifted spectra of stimulated Brillouin scattering (SBS) from solid aluminum targets irradiated by 0.25 µm laser radiation at various angles of incidence have been measured. Higher reflectivity was observed for a larger angle of incidence (θ), whereas the spectral shift showed no significant dependence on θ. SBS energy reflectivity levels increased from ∼0.1% (θ=0°) to ∼1% (θ=45°) for a focused KrF laser intensity of ∼1014 W/cm2. The observed θ dependence of reflectivity and spectral shift is consistent with predictions of a two-dimensional hydrodynamic simulation code (CASTOR), in particular, a locally planar density profile and spherical plasma expansion. The observed reflectivity levels cannot be quantitatively explained by standard convective gain theory for inhomogeneous plasma.

Measurements of x-ray conversion efficAncies9have been made for plasmas produced by KrF laser pulses at intensities of 2.5-7.5x10 ''W cm Initial measurements of x-ray fluence have been made using a simple set of filtered x-ray diodes and an x-ray calorimeter for targets with atomic numbers from 4 to 82. More detailed measurements have been made of three elements: aluminum, titanium and gold. These have included measurements of the angular dependence of emission, the spectral characteristics of emission in the 100-1000 eV range and time dependent measurements of the spectrum using an x-ray streak camera. The angular and spectral characteristics have been used to more accurately determine the energy conversion efficiency for these elements.