Evidence of the CH···O HydrogenBonding in Imidazolium-Based Ionic Liquids from Far-Infrared Spectroscopy Measurements and DFT Calculations

Knowledge of all the intermolecular forces occurring in ionic liquids (ILs) is essential to master their properties. Aiming at investigating the weaker hydrogen bonding in aprotic liquids, the present work combined computational study and far-infrared spectroscopy on four imidazolium-based ILs with different anions. The DFT calculations of the ionic couples, using the ωB97X-D functional and considering both the empirical dispersion corrections and the presence of a polar solvent, show that, for all samples, the lowest energy configurations of the ion pair present H atoms, directly bound to C atoms of the cation and close to O atoms of the anion, capable of creating moderate to weak hydrogen bonding with anions. For the liquids containing anions of higher bonding ability, the absorption curves generated from the calculated vibrational frequencies and intensities show absorption bands between 100 and 125 cm⁻¹ corresponding to the stretching of the hydrogen bond. These indications are in complete agreement with the presently reported temperature dependence of the far-infrared spectrum, where the stretching modes of the hydrogen bonding are detected only for samples presenting a moderate interaction and become particularly prominent at low temperatures. Moreover, from the analysis of the infrared spectra, the occurrence of various phase transitions as a function of temperature was detected, and the difference in the average energy between the H-bonded and the dispersion-governed molecular configurations was evaluated.     

Low-voltage high-drive CMOS current feedback op-amp

A novel CMOS current feedback op-amp is presented. The solution works using a low supply voltage and provides a wide input/output swing as well as a high current driving capability. Experimental results from a prototype implemented in a 0.35-/spl mu/m technology and powered with 1.5 V are also given. The circuit exhibits a better than 500 kHz closed-loop bandwidth and a /spl plusmn/1 mA current drive capability.     

Simple and accurate modeling of the output transition time in nanometer CMOS gates

In this paper, a model of the output transition time on nanometer CMOS gates is proposed. The development of this model follows the general approach used by Auvergne in (IEE Electron. Lett. 2002; 38 (4):175–177, IEEE Trans. Circuits Systems—part I 2000; 47 (9):1362–1369, IEEE Proc. ISCAS 2001; 5 :363–366, IEEE Trans. Computer‐Aided Design Integr. Circuits Systems 2002; 21 (11):1352–1363), which separately models the output transition time under fast and slow inputs. The proposed model is based on a combined transient and DC circuit analysis, and requires a few simulations. This approach allows for strongly reducing the number of required parameters and simulations compared with other models proposed in the literature. The analytical model proposed is very simple and has a clear physical meaning, thereby allowing an efficient implementation in CAD tools performing timing analysis, as well as an easy scalability through different processes and technology generations. Spectre simulations on a 65 nm CMOS technology and the 45, 32, 22 nm Berkeley Predictive Technology Models (BPTM) [Berkeley Predictive Technology Model (BPTM). ONLINE@11/25/2008: http://www.eas.asu.edu/～ptm/ ] show that the model accuracy is the same as the state‐of‐the‐art models, with an average error of only 4%. Comparison with currently used table‐based models showed also a significant reduction in the CPU time needed to simulate and characterize CMOS logic gates. Copyright © 2009 John Wiley & Sons, Ltd.     

Very fast carry energy efficient computation based on mixed dynamic=transmission-gate full adders

A circuit approach based on the adoption of mixed dynamic and transmission-gate full adder topologies to achieve very fast computation in carry chains is discussed. From a design point of view, the approach is very simple and allows the design to exceed the speed performance of fast Domino logic by more than 30% without degrading the energy efficiency. Post-layout simulations on a 90%nm CMOS technology are presented to validate the results.     

A Design Methodology for MOS Current-Mode Logic Frequency Dividers

In this work, a methodology for the design of MOS current-mode logic frequency dividers is presented. A mix of hand calculations and circuit simulations is used to relate the power consumption and the frequency of operation. Each latch in the dividers is sized separately in order to minimize the overall power consumption. Furthermore, the effect on the power consumption of circuit parameters such as output swing and voltage gain of the input differential pair is analyzed in detail. The methodology has been applied to dividers by two and dividers by three with 50% output duty cycle     

Surface plasmon resonance detection of metal ions: layer-by-layer assembly of polyelectrolyte sensing layers on a multichannel chip

A single-chip multichannel surface plasmon resonance sensor (SPR) has been used to detect metal ions in aqueous solutions. The equipment was designed around a commercial light-emitting diode and a CCD camera and incorporated no moving parts. The sensing materials were based on molecular architectures of polyelectrolyte films, deposited by the layer-by-layer self-assembly technique. Two bilayer architectures, poly(ethyleneimine) (PEI)/poly(ethylenealt-maleic acid) and PEI/poly(styrenesulfonate), were shown to produce different responses to solutions containing copper, nickel, and iron. The SPR equipment was able to measure concentrations of these metals down to levels of at least 2/spl times/10/sup -5/ M.     

New CMOS current mirrors with improved high-frequency response

A new CMOS current mirror is presented which has the static characteristic of the cascode current mirror and a high-frequency performance equivalent to or better than that of the simple current mirror. Moreover, the circuit proposed does not present the instability problem of the improved cascode utilized to increase the high-frequency response. The circuit is designed using CMOS 2 μm technology with various aspect ratios and simulated with the SPICE programme.     

Tandem mass spectrometry strategies for phosphoproteome analysis

Protein phosphorylation is involved in nearly all essential biochemical pathways and the deregulation of phosphorylation events has been associated with the onset of numerous diseases. A multitude of tandem mass spectrometry (MS/MS) and multistage MS/MS (i.e., MSⁿ) strategies have been developed in recent years and have been applied toward comprehensive phosphoproteomic analysis, based on the interrogation of proteolytically derived phosphopeptides. However, the utility of each of these MS/MS and MSⁿ approaches for phosphopeptide identification and characterization, including phosphorylation site localization, is critically dependant on the properties of the precursor ion (e.g., polarity and charge state), the specific ion activation method that is employed, and the underlying gas‐phase ion chemistries, mechanisms and other factors that influence the gas‐phase fragmentation behavior of phosphopeptide ions. This review therefore provides an overview of recent studies aimed at developing an improved understanding of these issues, and highlights the advantages and limitations of both established (e.g., CID) and newly maturing (e.g., ECD, ETD, photodissociation, etc.) yet complementary, ion activation techniques. This understanding is expected to facilitate the continued refinement of existing MS/MS strategies, and the development of novel MS/MS techniques for phosphopeptide analysis, with great promise in providing new insights into the role of protein phosphorylation on normal biological function, and in the onset and progression of disease. © 2011 Wiley Periodicals, Inc., Mass Spec Rev 30:600–625, 2011