Effective Timing Error Tolerance in Flip-Flop Based Core Designs

Timing errors turn to be a great concern in nanometer technology integrated circuits. This work presents a low-cost and power efficient, multiple timing error detection and correction technique for flip-flop based core designs. Two new flip-flop designs are introduced, which exploit a transition detector for timing error detection along with asynchronous local error correction schemes to provide timing error tolerance. The proposed, the Razor and the Time Dilation techniques were applied separately in the design of three versions of a 32-bit MIPS microprocessor core and the pci_bridge32 IWLS05 core, using a 90 nm CMOS technology. Comparisons based on simulation results validate the efficiency of the new design approach.     

Principles of demineralization: modern strategies for the isolation of organic frameworks. Part I. Common definitions and history

In contrast to biomineralization phenomena, that are among the most widely studied topics in modern material and earth science and biomedicine, much less is systematized on modern view of demineralization. Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Demineralization is the process of removing the inorganic part, or the biominerals, that takes place in nature via either physiological or pathological pathways in organisms. In vitro demineralization processes, used to obtain mechanistic information, consist in the isolation of the mineral phase of the composite biomaterials from the organic matrix. Physiological and pathological demineralization include, for example, bone resorption mediated by osteoclasts. Bioerosion, a more general term for the process of deterioration of the composite biomaterials represents chemical deterioration of the organic and mineral phase followed by biological attack of the composite by microorganisms and enzymes. Bioerosional organisms are represented by endolithic cyanobacteria, fungi, algae, plants, sponges, phoronids and polychaetes, mollusks, fish and echinoids.In the history of demineralization studies, the driving force was based on problems of human health, mostly dental caries. In this paper we summarize and integrate a number of events, discoveries, milestone papers and books on different aspect of demineralization during the last 400 years. Overall, demineralization is a rapidly growing and challenging aspect of various scientific disciplines such as astrobiology, paleoclimatology, geomedicine, archaeology, geobiology, dentistry, histology, biotechnology, and others to mention just a few.     

Learning automata-based polling protocols for wireless LANs

A learning automata-based polling (LEAP) protocol for wireless LANs, capable of operating efficiently under bursty traffic conditions, is introduced. We consider an infrastructure wireless LAN, where the access point (AP) is located at the center of a cell which comprises a number of mobile stations. According to the proposed protocol, the mobile station that is granted permission to transmit is selected by the AP by means of a learning automaton. The learning automaton takes into account the network feedback information in order to update the choice probability of each mobile station. It is proved that the learning algorithm asymptotically tends to assign to each station a portion of the bandwidth proportional to the station's needs. LEAP is compared to the randomly addressed polling and group randomly addressed polling protocols and is shown to exhibit superior performance under bursty traffic.     

A VHF Microstrip Antenna With Wide-Bandwidth and Dual-Polarization for Sea Ice Thickness Measurement

A VHF microstrip patch antenna was developed to achieve a bandwidth of 45 MHz (30%) from 127 to 172 MHz with dual-linear-polarization capability. This microstrip antenna, having a size of 117 cm times 117 cm times 27 cm, used low-dielectric-constant foam substrates and dual-stacked patches with capacitive probe feeds to achieve the required wide bandwidth. Four such capacitive feeds were used to achieve dual polarizations with less than -20 dB of cross-polarization level. Twenty-four shorting pins were uniquely used here on the lower patch to achieve 40 dB of isolation between the two polarization ports. This antenna has a measured gain of 8.5 dB at 137 MHz and 10.3 dB at 162 MHz. One advantage observed here at the low frequencies of VHF is that more electrical structures can be easily integrated into the microstrip antenna to improve its performance.     

Genetic transformation of xylose-fermenting yeastPichia stipitis

Applied Biochemistry and Biotechnology - A plasmid-mediated transformation system has been developed for the xylose-fermenting yeastPichia stipitis. We found that plasmid vectors containing...     

Electron difference densities and chemical bonding

In view of recent advances in X-ray technology it may be possible to deduce information regarding chemical bonding from experimentally determined electron densities. The construction of difference density maps represents a possible intermediate step in attaining this goal, but unresolved questions exist regarding appropriate definitions and interpretations of such maps. To shed light on these problems, theoretical difference densities are determined by ab-initio calculations for the molecules H₂, He₂, Li₂, Be₂, N₂ and F₂ at various internuclear distances. An examination of these difference density maps shows that the identification of those features of molecular electronic densities which are related to chemical bonding requires a judicious construction and a careful analysis of difference densities between molecules and their constituent atoms. Chemically relevant deformations can be small compared to density differences between different components of degenerate atomic groundstates and, consequently, chemical information can be swamped when difference densities are formed with spherically averaged atoms. To avoid such artifacts, oriented unaveraged atomic states must be subtracted for the formation of meaningful Chemical Difference Densities. The latter are explainable by means of a partitioning in terms of contributions from non-bonded inner shells, from lone pairs and from sigma and pi bonding shells. Such partitionings can be obtained through decompositions in terms of natural orbitals from correlated wavefunctions. Canonical SCF orbitals prove to be considerably less effective. Internuclear distances are found to have a great influence upon difference densities regardless of the attractive or repulsive nature of the interactions.     

Preparation and characterization of electrophoretically deposited high-temperature superconductor coatings

The high-temperature superconductor, YBa₂Cu₃O_7–x (x = 0.1–0.2) [YBCO], was prepared using an optimized calcination and sintering process. Thin layers of a few microns of this material were deposited on a silver substrate by applying a simplified electrophoretic deposition technique in a suspension of the fine, < 10 m, superconductor powder in a non-aqueous liquid. To get a uniform and strongly adherent coating, the deposition process is repeated several times, followed by an appropriate sintering procedure. The initially prepared YBCO powder and the coatings produced were characterized for their superconducting properties by X-ray diffraction analysis (XRD), magnetization measurements with a Superconducting Quantum Interference Device (SQUID) and electrical resistivity measurements. By scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) the grain size of the YBCO film, its thickness and impurity content, respectively, were estimated.     

Cooperative diversity schemes for asynchronous wireless networks

We construct cooperative diversity coding schemes that mitigate the effects of symbol asynchronicity among network users. We do so by modifying, at the expense of implementation practicality, the signaling complexity of well behaved existing schemes. The modification allows the same good performance (DMT optimality) in the presence of synchronicity, and almost-surely permits full-diversity gains for any event of symbol asynchronicity. This work was in part carried out while Petros Elia was at the University of Southern California. This research is supported in part by NSF-ITR CCR-0326628.     

HPLC study for evaluating the significance of pH in the inhibiting effect of phosphate buffer on the leaching pattern of resin composites

An HPLC method was applied to evaluate the inhibiting effect of phosphate buffer on the leaching pattern of resin composites and the significance of pH levels during the storage period in the solutions. Ten (10) disk-shaped specimens (2?mm?×?12?mm diameter) from Evetric restorative resin composite were immersed by means of a silk string in each of the following solutions: Distilled water (solution A), phosphate buffer of pH?=?4.5 (solution B) and phosphate buffer of pH?=?6.8 (solution C). After storage for 7, 30 and 60 days’ period, the eluates were examined by means of High Performance Liquid Chromatography (HPLC) at each time interval. The storage of the resin composite specimens in the phosphate buffer solution demonstrated an inhibiting effect on the leaching pattern compared to the distilled water solution. The results of this study suggest that HPLC is a useful tool to investigate the effect of the pH value of phosphate buffer solution, which resembles saliva, on the leaching pattern of resin composites.     

125-mJ diode-pumped injection-seeded Ho:Tm:YLF laser

We describe a diode-pumped, room-temperature Ho:Tm:YLF power oscillator with an optical-to-optical efficiency of 0.03. A Q -switched output energy of as much as 125 mJ at 6 Hz with a pulse width of 170 ns was obtained. Single-frequency, nearly transform-limited operation of the laser was achieved by injection seeding. Laser performance as a function of laser rod temperature and pump intensity was also investigated. The high power and high beam quality of this laser make it well suited for use as a coherent wind lidar transmitter on a space platform.