Towards implementation of a nickel silicide process for CMOS technologies

In this paper, we review some of the advantages and disadvantages of nickel silicide as a material for the electrical contacts to the source, drain and gate of current and future CMOS devices. We first present some of the limitations imposed on the current cobalt silicide process because of the constant scaling, of the introduction of new substrate geometries (i.e. thin silicon on insulator) and of the modifications to the substrate material (i.e. SiGe). We then discuss the advantages of NiSi and for each of the CoSi₂ limitations, we point out why Ni is believed to be superior from the point of view of material properties, miscibility of phases and formation mechanisms. Discussion follows on the expected limitations of NiSi and some of the possible solutions to palliate these limitations.     

Screening of supports for the immobilization of pectinmethylesterase from acerola (Malpighia glabra L)

A partially purified extract of pectinmethylesterase (PME) from acerola fruit was immobilized on various supports: glass, celite, chrysotile, agarose, concanavalin A Sepharose 4B, egg shell, polyacrylamide and gelatin. In addition, reticulation with glutaraldehyde was assessed, as well as the use of gelatin in the presence of celite, glass and silica. The highest immobilization yields were obtained when the pectinmethylesterase was immobilized in concanavalin A Sepharose 4B (81.7%) and in gelatin‐water (78.0%). Copyright © 2004 Society of Chemical Industry     

Liquid–liquid extraction of a recombinant protein with reverse micelles

Recombinant cytochrome b₅ was extracted into the reversed micelle phase of an anionic surfactant (AOT) in octane and back-extracted to a final aqueous phase. The extraction of the protein was controlled by an electrostatic mechanism, since it was dependent on the global charge of the protein. This was directly demonstrated by experiments with native and mutant cytochromes obtained by site directed mutagenesis. The back-extraction of cytochrome b₅ to a fresh aqueous phase was decreased by factors that reduced the size of the water pool of the organic phase, such as high salt concentrations (1–2 mol dm^?3 NaCl) and low temperatures (4°C), probably because of an increase in a favourable interaction of this protein with the surfactant at closer distances.     

An integrated downstream processing strategy for the recovery and partial purification of penicillin acylase from crude media

An integrated process strategy for the recovery of penicillin acylase was developed, based on precipitation of non‐enzymatic proteins directly from Escherichia coli homogenates or crude extracts using Rolquat (quaternary ammonium salt) and adsorption of the enzyme on Amp‐Seph (3.8 µmole ampicillin cm^?3) under pseudo‐affinity conditions. The effect of pH, concentrations of ammonium sulfate and Rolquat, and also concentrations of protein and cell debris on the precipitation of non‐enzymatic proteins from homogenates and crude extracts of penicillin acylase were analysed. The method of addition of Rolquat to homogenates and crude extracts significantly influenced the size of the precipitated particles. Improved results on the specific activity of penicillin acylase were obtained for 22% and 1% (w/v) of ammonium sulfate and Rolquat, respectively, added sequentially to enzyme solutions and at room temperature. Under these experimental conditions, the specific activity of penicillin acylase in homogenates and crude extracts was enhanced 2.5–3.0‐fold. Finally, the integrated process strategy was implemented first by precipitation of non‐enzymatic proteins and recovery of penicillin acylase directly from the enzyme solution treated with Rolquat using an adsorption/filtration system with an overall yield of 86%. This system allows simultaneously the filtration of cell debris and fine precipitated particles, in situ recovery of penicillin acylase by its adsorption on Amp‐Seph, and selective desorption of the enzyme with a specific activity of 11 IU (mg prot)^?1 and a desorption yield of 95%. © 2002 Society of Chemical Industry     

Comparative study of the electrical properties of diamond films grown by microwave plasma assisted and hot-filament chemical vapor deposition

Schottky diodes were built on different polycrystalline diamond films grown by Microwave Plasma and Hot Filament Chemical Vapor Deposition and their electrical properties were studied. The barrier height increased with the diamond film quality and the corresponding ideality factor decreased. Even though the lower-quality HFCVD film displayed poor rectifying properties, it was found to be much less sensitive to variations in the operating conditions (air vs. vacuum). The activation energies of the films depend on morphological parameters, as preferable grain size or orientation. The bulk conduction also depends on the quality of the deposited films, changing from ohmic to trap-free or shallow trap SCLC and SCLC with an exponential distribution of traps. The hypothesis of using the electrical measurements as an indicator for film quality has been discussed.     

Genotoxic effect of Physalis angulata L. (Solanaceae) extract on human lymphocytes treated in vitro

Physalis angulata L (Solanaceae) is a medicinal plant from North of Brazil, whose different extracts and infusions are commonly used in the popular medicine for the treatment of malaria, asthma, hepatitis, dermatitis and rheumatism. However, the genotoxic effects of P. angulata on human cells is not well known. The main purpose of the present study was to evaluate the in vitro genotoxic effects of aqueous extract of P. angulata using the comet assay and the micronucleus assay in human lymphocytes provided from 6 healthy donors. Treatments with P. angulata extracts were performed in vitro in order to access the extent of DNA damage. The comet assay has shown that treatments with P. angulata at 0.5, 1.0, 2.0, 3.0 and 6.0 microg/mL in culture medium were genotoxic. Lymphocytes treated with P. angulata at the concentrations of 3.0 and 6.0 microg/mL in culture medium showed a statistically significant increase in the frequency of micronucleus (p<0.05), however, the cytokinesis blocked proliferation index (CBPI) was not decreased after P. angulata treatment. In conclusion, the present work demonstrated the genotoxic effects of P. angulata extract on human lymphocytes in vitro.     

Second primitive malignant tumour in patients with gynaecological cancer

OBJECTIVE: The purpose of this study was to characterise the occurrence of multiple primitive gynaecological malignant neoplasias, restricted to the genital tract and breast or associated with other organs, and to detect which types of association are most frequent concerning location, histology and staging. POPULATION AND METHODS: The records of patients with gynaecological cancer at the Portuguese Institute of Oncology--Lisbon Centre, between 1986 and 1993 were used in this study. RESULTS: Of the 10,746 women with gynaecological cancer, 91 (0.8%) were found to have a second primitive malignant neoplasia. Of these neoplasias, 64% (58 cases) were also located at a gynaecological site. The most frequent associations were endometrium/breast (13 cases), bilateral breast (12 cases) and ovary/endometrium (11 cases). The majority of primitive multiple gynaecological tumours were synchronous. Regarding gynaecological cancer and non-gynaecological cancer, in 28 cases (31%), the most common non-gynaecological location was the colon/rectum. Five patients had triple tumours. CONCLUSION: Although these situations are relatively rare the possibility of multiple primitive cancers should be considered with the presence of malignant tumours in two or more organs. This distinction between multiple primitive or metastatic cancers could be important for treatment as well as prognosis.     

Dielectric loss and phase transition of sodium potassium niobate ceramic investigated by impedance spectroscopy

The dielectric permittivity of Na_0.80K_0.20NbO₃ ceramic was investigated by impedance spectroscopy. The dielectric characterization was performed from room temperature to 800 °C, in the frequency range 5 Hz–13 MHz. The bulk permittivity was derived by the variation of the imaginary part of the impedance as a function of reciprocal angular frequency. The permittivity values as a function of temperature showed two maxima. The first maximum is very similar at 200 °C and the second one positioned at around 400 °C, which was associated to Curie’s temperature. The evolution of the complex permittivity as a function of frequency and temperature was investigated. At low frequency dispersion was investigated in terms of dielectric loss. The Na_0.80K_0.20NbO₃ showed a dissipation factor between 5 and 40 over a frequency range from 1 to 10² kHz.     

Chemically functionalized carbon nanotubes and their characterization using thermogravimetric analysis, fourier transform infrared, and raman spectroscopy

This article reports key findings on the chemical functionalization of carbon nanotubes (CNT). The functionalization of chemical vapor-deposited CNT was carried out by treating tubes with polyvinyl alcohol through ultrasonication in water with the aid of a surfactant. The surfactant is expected to promote the unbundling of aggregated CNT. The characterization of functionalized samples using thermogravimetric analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy revealed that the CNT were functionalized by the interaction of carboxylic acid and hydroxyl groups. From the characterization studies, it is apparent that there is a strong interaction between these functional groups and the covalently bonded carbon in the CNT network. The functionalization process enabled good CNT dispersion in the solution, and the CNT remained in suspension for many days. To support the effective functionalization of the tubes, the interaction of functionalized CNT with Ni ions is also demonstrated. This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in St. Paul, MN.