On the reliability of electrostatic NEMS/MEMS devices: Review of present knowledge on the dielectric charging and stiction failure mechanisms and novel characterization methodologies

This paper reviews the state of the art knowledge related to critical failure mechanisms in electrostatic micro- and nano-electromechanical systems (MEMS and NEMS) which are the dielectric charging and stiction. It describes also the recent employed nanoscale characterization techniques for these phenomena based on Kelvin probe force microscopy (KPFM) and force–distance curve measurements. The influence of relative humidity and dielectric deposition conditions on the charging/discharging processes is discussed. Moreover, different stiction mechanisms induced by electrostatic force and/or meniscus formation are analyzed. Finally, novel characterization methods are presented and used to correlate between the results from MEMS devices and metal–insulator–metal (MIM) capacitors. These methods are employed in view of application in electrostatic capacitive MEMS switches and could be easily extended to explore other NEMS/MEMS devices. The study provides an accurate understanding of the charging and stiction related failure mechanisms, presents guidelines for a proper packaging environment, and reveals precise explanations for the literature reported device level measurements of electrostatic MEMS devices.     

Development of a Wear Test Apparatus for Screening Bearing-Flange Materials in Computer Tape Drives

An accelerated-wear test apparatus was developed to screen bearing-flange materials. During the test, tape edges rub against two flat test specimens (which are easy to fabricate). The clamping arrangement of the specimens provides the same contact with the tape during repeated tests. The tape is loaded against the sample by deadweight loading, which ensures constant loading, irrespective of tape guiding. Acceleration in wear is obtained by increasing the load at the interface of the tape and the test specimen. Wear tests were conducted on several metals, ceramics and cermets, coatings, and surface treatments. We find that ceramics and cermets have the lowest wear.     

Electricity prices and state commitment to energy efficiency in the U.S.

This paper studies the effect of electricity prices on state commitment to energy efficiency in the USA. Using panel data we find that electricity prices have a significant positive effect on state energy efficiency expenditures. Moreover, we find that this effect is particularly pronounced beyond a certain threshold level of prices. The rationale for these findings is that higher prices increase the cost-effectiveness of energy efficiency programs. These findings have important implications for state expenditures on energy efficiency if electricity prices rise in response to carbon and other stringent environmental regulations.     

Metal Core Recession and Head Stain Studies of MIG Heads Sliding against Cobalt-Doped Gamma Iron Oxide and Metal Particle Tapes

Metal-in-gap (MIG) heads are commonly used for high-density magnetic recording. Metal core recession and head stains increase the gap between the tape and the head, resulting in signal loss. In this study, accelerated sliding wear tests of Co-γFe₂O₃, and metal particle (MP) tapes against MIC heads made of three different amorphous and, nanocrystalline metals were conducted under various operating conditions. Metal core recess and propensity for head staining were measured. The degree of tape contact with a recessed core was also measured by pressing the tape against a glass slide with Cr grids and using an optical interference technique. The authors found that the core recess was about the same for all three core metals. Core recess by MP tape was larger than that, by oxide tape. The tape speed appeared to have little effect on the recess value. The authors also found that significant recess may occur during initial contouring of the head surface; however, after sliding for about 250 km, core recess reaches a steady-stale value which may be either higher or lower than the initial values. The mechanism of core recession was studied. The authors believe that core recession occurs as a consequence of the debris trapped, between the tape and the core, in addition to that caused by some tape contact. Formation of head stains was observed in all combinations. The stains fanned on the metal cores were heaviest for CoNbZr metal, followed by CoTaZr and FeTaC. Co-γFe₂O₃ tape produced a more severe stain than the MP tape. The apparent roughening of head rubbing surface observed for CoNbZr heads sliding against Co-γFe₂O₃, tape was due to the formation of stains.     

Antibody responses of cows during an outbreak of neosporosis evaluated by indirect fluorescent antibody test and different enzyme-linked immunosorbent assays

Hairpin ribozymes with high cleavage activities were designed. An extra sequence was introduced at the 3'-end of the hairpin ribozyme to increase the binding to the substrate RNA, as compared to the wild-type hairpin ribozyme. A three-way junction (TWJ) was formed between the newly designed ribozyme and the substrate RNA. The complex with a solid TWJ showed less RNA cleavage activity than the wild-type hairpin ribozyme. However, the ribozyme with a TWJ with five unpaired bases or propandiol phosphate linkers had higher cleavage activity than the parent ribozyme without the TWJ. When a cis-cleavage system, in which the 5'-end of the substrate RNA was conjugated to the 3'-end of the ribozyme, was employed, the complex with the TWJ containing unpaired bases was also cleaved faster than the complex with the solid TWJ. This suggested that these differences in the cleavage activities were derived from the confirmation, and this was proven by nondenaturing gel electrophoresis. The TWJ hairpin ribozyme containing unpaired bases is able to bind strongly with substrate RNAs and to cleave them efficiently. Since the three-way ribozyme presented here is more active than the wild-type ribozyme, this type of ribozyme can serve as a more efficient tool to control RNA activities in vitro and in vivo.     

Growth of undoped and Te doped InSb crystals by vertical directional solidification technique

We have successfully grown high mobility undoped and Te doped InSb crystals of size 10–12 mm dia. and 60 mm length under inert argon atmosphere in closed quartz ampoules, by vertical directional solidification (VDS) technique. The crystals showed predominantly (220) orientation along the growth axis. The surface defects, such as voids were reduced drastically by selecting proper lowering rate, rotational speed and cone angle of the ampoule. The high mobility and quality crystals were obtained with the ampoule conical angle less than 20°, lowering rate 5mm/h, and rotational speed 10 rpm.     

Corrections to "BER performance of a uniform circular array versus a uniform linear array in a mobile radio environment"

This paper presents some corrections on the equations given in a previous paper for the BER performance of a UCA and ULA in a mobile radio.     

Modes of Operation and Analysis of a Separately Excited Motor Fed by a Three-Phase Converter with a Freewheeling Diode

Low-speed performance of a three-phase fully controlled converter-fed dc separately excited motor drive can be improved by connecting a freewheeling diode. This paper describes the modes of operation and a method of analysis taking these modes of operation into account. Normalized curves are presented which allow the selection of a suitable value of filter inductor to keep the ripple within permissible values.     

Exact analysis for downlink MC-CDMA in Rayleigh fading channels

In this letter, downlink multicarrier code-division multiple access (MC-CDMA) systems with maximal ratio combining (MRC) in frequency-selective Rayleigh fading channels is considered. An exact bit error rate (BER) is provided based on the characteristic function (CF) and residue calculation method. The BER performance is evaluated in the time domain instead of the frequency domain. This method does not require any assumption regarding the statistical or spectral behavior of multiple access interference (MAI).     

Toxoplasma gondii isolates of free-ranging chickens from Rio de Janeiro, Brazil: mouse mortality, genotype, and oocyst shedding by cats

Most isolates of Toxoplasma gondii can be grouped into 3 genetic lineages. In the present study, 67 isolates of T. gondii were obtained by bioassay in mice inoculated with brains and hearts of 96 asymptomatic chickens from an area highly endemic to human infection in Rio de Janeiro, Brazil. Of the 48 isolates genotyped using the SAG2 locus, 34 (70%) were of type I and 13 (27%) were of type III. No isolate of type II was recovered. Isolates from 1 chicken contained a type I and type III mixed infection, indicating natural multiparasite infection in the same animal. Cats fed mice infected with 11 type I strains shed 19-535 million oocysts in their feces, indicating that type I isolates can circulate in the environment.