HST1, a new member of the SIR2 family of genes

A novel Saccharomyces cerevisiae gene, HST1, was identified from among anonymous cDNAs and the complete corresponding genomic clone was isolated and sequenced. HST1 is very closely related to SIR2, showing 71% sequence identity over 84% of its length. Polymerase chain reaction with degenerate primers on S. cerevisiae DNA identified three additional SIR2-related genes designated HST2, HST3 and HST4. The sequences of HST2, HST3 and HST4 correspond to sequences previously released by the S. cerevisiae genome sequencing project as U33335, NCBI gi:965078; X87331, NCBI gi:829135; and Z48784, YD9346.03, respectively. Disruption of HST1 has shown no phenotype with respect to mechanisms in which SIR2 has a role, namely, regional silencing of HMLα, or in rDNA recombination. The sequence of HST1 has been deposited in the DDBJ, EMBL and GenBank at NCBI database under Accession Number L47120.     

High pressure ammonia dissociation experiments for solar energy transport and storage

Work relating to the application of the ammonia dissociation reaction to the thermochemical transport and storage of solar energy is reported. A two-dimensional pseudo-homogeneous packed-bed catalytic reactor model has been adapted to predict the behaviour of ammonia dissociation and synthesis reactors. A series of steady-state experiments, with a high-pressure ammonia dissociator operated in an ‘open-loop’ experimental configuration, have been used to verify the model. These experiments involved operating pressures up to 16 MPa and temperatures up to 720°C. The results indicated an activation energy of 192 kJ mol⁻¹ and a pre-exponential factor of 3.0 × 10⁷mol s⁻¹ cm⁻³ atm⁻¹ for the nickel-on-alumina dissociation catalyst used. The experiments also indicated that the experimental configuration is suitable for development into a ‘closed-loop’ energy storage experiment operating at a power level of approximately 1kW_chem.     

Who will drive technological advance?

Electronic materials and packaging have been inexorably drawn along with the relentless march of technology. The complexity and capability of electronics increases with technology, yet it reduces the size and simplifies the shape of the materials and components that go to make up electronics. Whilst basic research into materials and packaging can be targeted into the areas of concern the main thrust for improvements is, of necessity, controlled by the specific needs of the product and the market.     

Problems with the mass spectrometric determination of tritium from cold fusion

Among the attempts to measure particles produced in the cold fusion of deuterium in palladium metal is the mass spectrometric observation of tritium. An experiment which has been reported in the popular press involves attaching a hollow Pd electrode to a vacuum chamber and measuring the tritium produced during electrolysis using a mass spectrometer. We present data demonstrating that mass 5 and 6, which could be mistaken for the ions DT⁺ and T₂ ⁺, can arise from ion-molecule reactions in the ionizer of the mass spectrometer giving the ions HD₂ ⁺ and D₃ ⁺. With H₂ and D₂ present in the vacuum chamber, there are at least eight reactions which lead to these triatomic species, and these may contribute to a complex time and pressure dependence of the signals.     

The effect of electrode ohmic losses and the role of the electrical connection in bipolar connected parallel plate electrodes

A mathematical model is used to predict current and potential distributions in electrochemical cell banks consisting of bipolar connected parallel plate electrodes. It is shown that the adoption of bipolar connection rather than monopolar connection alleviates the problems of a maldistribution of potential caused by limitations in electrode conductivity for a majority of cells in large cell banks. However, for the outer cells potential distribution is still not uniform regardless of the number of cells in the bank.     

Molecular mass calibration in size-exclusion chromatography of coal derivatives

A number of procedures have been investigated for the calibration of a size-exclusion chromatography (s.e.c.) column in the determination of molecular mass (MM) distributions of coal derivatives. The behaviour of narrow fractions of coal extracts in the MM range 200–3000 was compared with a variety of the more generally available calibration standards. Calibration with preparative s.e.c. subfractions of materials similar to those under study has been recommended. Polystyrene standards are satisfactory, however, for MM < 1000, but above this range other polymer standards should be sought. Universal and molar volume calibration do not apply to coal-derived materials.     

Characterization of protein immobilization on nanoporous gold using atomic force microscopy and scanning electron microscopy

Nanoporous gold (NPG), made by dealloying low carat gold alloys, is a relatively new nanomaterial finding application in catalysis, sensing, and as a support for biomolecules. NPG has attracted considerable interest due to its open bicontinuous structure, high surface-to-volume ratio, tunable porosity, chemical stability and biocompatibility. NPG also has the attractive feature of being able to be modified by self-assembled monolayers. Here we use scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize a highly efficient approach for protein immobilization on NPG using N-hydroxysuccinimide (NHS) ester functionalized self-assembled monolayers on NPG with pore sizes in the range of tens of nanometres. Comparison of coupling under static versus flow conditions suggests that BSA (Bovine Serum Albumin) and IgG (Immunoglobulin G) can only be immobilized onto the interior surfaces of free standing NPG monoliths with good coverage under flow conditions. AFM is used to examine protein coverage on both the exterior and interior of protein modified NPG. Access to the interior surface of NPG for AFM imaging is achieved using a special procedure for cleaving NPG. AFM is also used to examine BSA immobilized on rough gold surfaces as a comparative study. In principle, the general approach described should be applicable to many enzymes, proteins and protein complexes since both pore sizes and functional groups present on the NPG surfaces are controllable.     

A highly sensitive ultraviolet sensor based on a facile in situ solution-grown ZnO nanorod/graphene heterostructure

The weak photon absorption and fast carrier kinetics of graphene limit its application in photodetection. This limitation can be overcome by introducing photosensitive nanostructures to graphene. Herein we report the synthesis of a ZnO nanorod/graphene heterostructure by a facile in situ solution growth method. By combining the attributes of photosensitive ZnO nanorods and highly conductive graphene, we for the first time demonstrate a highly sensitive visible-blind ultraviolet (UV) sensor based on graphene related heterostructure. The photoresponsibility of the UV sensor can reach 22.7 A W(-1), which is over 45,000 fold higher than that of single graphene sheet based photodetectors.     

Effects of selected water chemistry variables on copper pitting propagation in potable water

The pit propagation behavior of copper (UNS C11000) was investigated from an electrochemical perspective using the artificial pit method. Pit growth was studied systematically in a range of HCO₃⁻, SO₄²⁻ and Cl⁻ containing-waters at various concentrations. Pit propagation was mediated by the nature of the corrosion products formed both inside and over the pit mouth (i.e., cap). Certain water chemistry concentrations such as those high in sulfate were found to promote fast pitting that could be sustained over long times at a fixed applied potential but gradually stifled in all but the lowest concentration solutions. In contrast, Cl⁻ containing waters without sulfate ions resulted in slower pit growth and eventual repassivation. These observations were interpreted through understanding of the identity, amount and porosity of corrosion products formed inside and over pits. These factors controlled their resistive nature as characterized using electrochemical impedance spectroscopy. A finite element model (FEM) was developed which included copper oxidation kinetics, transport by migration and diffusion, Cu(I) and Cu(II) solid corrosion product formation and porosity governed by equilibrium thermodynamics and a saturation index, as well as pit current and depth of penetration. The findings of the modeling were in good agreement with artificial pit experiments. Malachite, bronchantite, cuprite, nantokite and atacamite corrosion products were both observed in experiment and predicted by the model. Stifling and/or repassivation occurred when the resistance of the corrosion product layer became high enough to lower the pit bottom potential and pit current density such as 10^-5 A/cm² could be attained with thick and dense layer. The ramifications of these findings towards pit propagation characteristics in potable waters will be discussed with improved insight into the roles of Cl⁻ and SO₄²⁻ ions.