Accurate low-power CMOS autozeroed comparator

A low-power CMOS autozeroed comparator suitable for high-frequency A/D convertors is discussed. The use of a source follower in the autozeroed inverter stage allows the circuit to provide an optimum tradeoff between speed, gain and power dissipation. Relationships are given that relate the time response, both in the autozeroing and comparating phase, to the circuit parameters. An experimental prototype, fabricated with a 2 mu m CMOS process is also presented.<>     

Gain-compensated sample-and-hold circuit for high frequency application

A novel and fast and accurate sample-and-hold circuit is presented which can be designed using conventional single stage amplifiers. The offset contribution to the output voltage is intrinsically compensated and the clock-feedthrough error can be reduced by slightly changing the clock phase scheme.<>     

From Stem Cells to Bone-Forming Cells

Bone formation starts near the end of the embryonic stage of development and continues throughout life during bone modeling and growth, remodeling, and when needed, regeneration. Bone-forming cells, traditionally termed osteoblasts, produce, assemble, and control the mineralization of the type I collagen-enriched bone matrix while participating in the regulation of other cell processes, such as osteoclastogenesis, and metabolic activities, such as phosphate homeostasis. Osteoblasts are generated by different cohorts of skeletal stem cells that arise from different embryonic specifications, which operate in the pre-natal and/or adult skeleton under the control of multiple regulators. In this review, we briefly define the cellular identity and function of osteoblasts and discuss the main populations of osteoprogenitor cells identified to date. We also provide examples of long-known and recently recognized regulatory pathways and mechanisms involved in the specification of the osteogenic lineage, as assessed by studies on mice models and human genetic skeletal diseases.     

An Enzyme Switch Employing Direct Electrochemical Communication between Horseradish Peroxidase and a Poly(aniline) Film

An enzyme switch, or microelectrochemical enzyme transistor, responsive to hydrogen peroxide was made by connecting two carbon band electrodes (～10 μm wide, 4.5 mm long separated by a 20-μm gap) with an anodically grown film of poly(aniline). Horseradish peroxidase (EC 1.11.1.7) was either adsorbed onto the poly(aniline) film or immobilized in an insulating poly(1,2-diaminobenzene) polymer grown electrochemically on top of the poly(aniline) film to complete the device. In the completed device, the conductivity of the poly(aniline) film changes from conducting (between - 0.05 and + 0.3 V vs SCE at pH 5) to insulating (>+0.3 V vs SCE at pH 5) on addition of hydrogen peroxide. The change in conductivity is brought about by oxidation of the poly(aniline) film by direct electrochemical communication between the enzyme and the conducting polymer. This was confirmed by measuring the potential of the poly(aniline) film during switching of the conductivity in the presence of hydrogen peroxide. The devices can be reused by rereducing the poly(aniline) electrochemically to a potential below +0.3 V vs SCE. A blind test showed that the device can be used to determine unknown concentrations of H(2)O(2) in solution and that, when used with hydrogen peroxide concentrations below 0.5 mmol dm(-)(3), the same device maybe reused several times. The possible development of devices of this type for use in applications requiring the measurement of low levels of hydrogen peroxide or horseradish peroxidase is discussed.     

EDTA excess Zn(II) back-titration in the presence of 4-(2-pyridylazo)-resorcinol indicator and naphthol green beta as inert dye for determining Cr(III) as Cr(III)/EDTA complex: application of the method to a leather industry wastewater

The colour changes of 4-(2-pyridylazo)-resorcinol and naphthol green beta as new screening metallochromic indicator in back-titration of EDTA excess with Zn(II) to determine Cr(III)/EDTA complex was investigated with the help of tristimulus colorimetry. Specific colour discrimination (SCD) and L*, a*, b* 1976 parameters were successfully applied to evaluate the quality of colour transition at the end-point in non-alkaline media and in the presence of Zn(II) and Ca(II) which resulted in non-interfering species at 1x10(-3) M and 2x10(-3) M, respectively. The above concentrations are comparable with those used for Cr(III). Validation of the fast and accurate reported method was performed by atomic absorption spectroscopy. Moreover, the method was applied for determining Cr as Cr(III) in a wastewater effluent deriving from a leather industry.     

High-frequency CMOS amplifier with improved bandwidth performance

A high-frequency CMOS amplifier is proposed which can be used as a gain stage in RF front-ends. The circuit is based on a traditional transconductance amplifier unconventionally arranged to achieve both accurate input biasing and single-to-differential conversion. It takes advantage of an innovative approach to greatly improve frequency performance. Owing to this technique, the operating frequency of a basic amplifier in a 0.8 μm CMOS process could be extended from 290 to 650 MHz without affecting the gain     

BIPV: merging the photovoltaic with the construction industry

BIPV (Building Integrated Photovoltaics) is a multifunctional technology that unifies the photovoltaic module with the overall building outer surface providing the building with several new functions while producing a portion or total building electricity usage. Increasing the aesthetic, functional and environmental value of a building at a much lower cost than in the recent past, new PV technologies will soon originate a market growth as intense as the growth of traditional PV market has been in the last 5 years. Copyright © 2009 John Wiley & Sons, Ltd.

     

Design Procedure for Two-Stage CMOS Transconductance Operational Amplifiers: A Tutorial

This paper deals with well-defined designcriteria for two-stage CMOS transconductance operational amplifiers. A novel and simple designprocedure is presented, which allows electricalparameters to be univocally related to the value ofeach circuit element and biasing value. Unlikeprevious methods, the proposed one is suited for apencil-and-paper design and yields accurateperformance optimization without introducingunnecessary circuit constraints. Bandwidthoptimization strategies are also discussed. SPICE simulations based on the proposed procedures aregiven which closely agree the expected results.     

Waste‐Free Electrochemical Oxidation of Alcohols in Water

We describe a new sol‐gel molecular electrode made of a thin layer of organosilica doped with the nitroxyl radical TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl) electrodeposited on the surface of an ITO‐coated glass and its employment as a selective and versatile oxidation catalyst in the electrochemical conversion of different alcohols to carbonyl compounds. Environmentally friendly water or a water/acetonitrile mixture buffered with bicarbonate is used as solvent. The electrode is highly stable and it can be reused for a prolonged period of time allowing easy separation from the products.