Iron and ruthenium catalysts for hydrogen transfer reactions

The ruthenium catalysed oxidation of 1-phenylethanol derivatives with the release of hydrogen gas has been studied. A hydrogen acceptor was introduced in an effort to elucidate the rate-determining step of the reaction. The transfer of hydrogen from complex alcohols to simple aldehydes and ketones was pursued as a process for obtaining simple alcohols for fuel cell applications. The Shvo catalyst was identified as being the most efficient catalyst for the oxidation of difficult substrates. A family of iron analogues of the Shvo catalyst were synthesised and studied as precatalysts for the oxidation of alcohols. Catalyst activation was achieved by the removal of a CO ligand using trimethylamine-N-oxide and the oxidation of 1-phenylethanol derivatives with acetone was studied. Simple aldehydes were evaluated as hydrogen acceptors and a novel formylation reaction was discovered. Asymmetric iron analogues of the Shvo catalyst were synthesised and applied to the asymmetric transfer hydrogenation of acetophenone using 5:2 formic acid/triethylamine. The synthesis of further analogues with a tethering group was investigated to improve catalyst stability and enantioselectivity. Novel chiral diamine and amino-alcohol ligands containing 1,2,3-triazole functionalities were developed as ligands for the asymmetric transfer hydrogenation of ketones. Tridentate diaminotriazoles provided the best activity and selectivity in the reduction reactions with Ru3(CO)12

Application of ruthenium complexes of triazole-containing tridentate ligands to asymmetric transfer hydrogenation of ketones

The synthesis of a series of tridentate ligands based on a homochiral 1,2-diamine structure attached to a triazole group and their subsequent applications to the asymmetric transfer hydrogenation of ketones are described. In the best cases, alcohols of up to 93% ee were obtained. Although base is not required, the use of Ru3(CO)12 as metal source is essential, indicating a unique mechanism for the formation of the active catalyst

Control design of uncertain quantum systems with fuzzy estimators

published_or_final_versio

Temperature-based tuning of magnetic particle separation by on-chip free-flow magnetophoresis

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Free-flow magnetophoresis provides a fast and efficient means of continuous flow magnetic separation for the detection of biological analytes, due to the wide variety of magnetic particle surface properties available for binding specific targets. Here, we investigate the effect of temperature changes on the deflection behaviour of magnetic particles in a microfluidic magnetophoresis separation chamber. It was found that the extent of deflection was greatly increased at higher temperatures due to decreased solution viscosity and thus reduced resistance against particle motion. This concept was used to improve the resolution of the separation of 2.8 μm and 1 μm diameter magnetic particles. Hence, controlling the temperature of the separation system provides a simple but highly effective means of enhancing magnetic separation efficiency. This concept could also be applied to the temperature-based tuning of microparticle trajectories in many others types of continuous flow processes, such as those using optical, electrical or acoustic forces.This study is funded by the Engineering and Physical Sciences Research Council (EPSRC)

Iron and ruthenium catalysts for hydrogen transfer reactions

The ruthenium catalysed oxidation of 1-phenylethanol derivatives with the release of hydrogen gas has been studied. A hydrogen acceptor was introduced in an effort to elucidate the rate-determining step of the reaction. The transfer of hydrogen from complex alcohols to simple aldehydes and ketones was pursued as a process for obtaining simple alcohols for fuel cell applications. The Shvo catalyst was identified as being the most efficient catalyst for the oxidation of difficult substrates. A family of iron analogues of the Shvo catalyst were synthesised and studied as precatalysts for the oxidation of alcohols. Catalyst activation was achieved by the removal of a CO ligand using trimethylamine-N-oxide and the oxidation of 1-phenylethanol derivatives with acetone was studied. Simple aldehydes were evaluated as hydrogen acceptors and a novel formylation reaction was discovered. Asymmetric iron analogues of the Shvo catalyst were synthesised and applied to the asymmetric transfer hydrogenation of acetophenone using 5:2 formic acid/triethylamine. The synthesis of further analogues with a tethering group was investigated to improve catalyst stability and enantioselectivity. Novel chiral diamine and amino-alcohol ligands containing 1,2,3-triazole functionalities were developed as ligands for the asymmetric transfer hydrogenation of ketones. Tridentate diaminotriazoles provided the best activity and selectivity in the reduction reactions with Ru3(CO)12.EThOS - Electronic Theses Online ServiceEngineering and Physical Sciences Research Council (EPSRC)GBUnited Kingdo

Improvements on Low Cost CT Systems

Computed tomography (CT) is a radiographic method that provides an ideal examination technique whenever the goal is to locate and size volumetric detail in three dimensions. Because of the relatively good penetrability of X-rays, as well as the sensitivity of absorption to density and atomic number of matter, CT permits the nondestructive physical and, to a limited extent, chemical characterization of the internal structure of materials. Also, since the method is X-ray based, it applies both to metallic and nonmetallic specimens, solid and fibrous materials, and smooth and irregularly surfaced objects. X-ray CT provides quantitative, readily interpretable data and enables the inspections of structures that are not amenable to any other nondestructive evaluation technique. As a result CT has become well established as an inspection, evaluation, and analysis tool[1]

Time-delay control of a magnetic levitated linear positioning system

In this paper, a high accuracy linear positioning system with a linear force actuator and magnetic levitation is proposed. By locating a permanently magnetized rod inside a current-carrying solenoid, the axial force is achieved by the boundary effect of magnet poles and utilized to power the linear motion, while the force for levitation is governed by Ampere's Law supplied with the same solenoid. With the levitation in a radial direction, there is hardly any friction between the rod and the solenoid. The high speed motion can hence be achieved. Besides, the axial force acting on the rod is a smooth function of rod position, so the system can provide nanometer resolution linear positioning to the molecule size. Since the force-position relation is highly nonlinear, and the mathematical model is derived according to some assumptions, such as the equivalent solenoid of the permanently magnetized rod, so there exists unknown dynamics in practical application. Thus 'robustness' is an important issue in controller design. Meanwhile the load effect reacts directly on the servo system without transmission elements, so the capability of 'disturbance rejection; is also required. With the above consideration, a time-delay control scheme is chosen and applied. By comparing the input-output relation and the mathematical model, the time-delay controller calculates an estimation of unmodeled dynamics and disturbances and then composes the desired compensation into the system. Effectiveness of the linear positioning system and control scheme are illustrated with simulation results

The RNA binding protein Cwc2 interacts directly with the U6 snRNA to link the nineteen complex to the spliceosome during pre-mRNA splicing

Intron removal during pre-messenger RNA (pre-mRNA) splicing involves arrangement of snRNAs into conformations that promote the two catalytic steps. The Prp19 complex [nineteen complex (NTC)] can specify U5 and U6 snRNA interactions with pre-mRNA during spliceosome activation. A candidate for linking the NTC to the snRNAs is the NTC protein Cwc2, which contains motifs known to bind RNA, a zinc finger and RNA recognition motif (RRM). In yeast cells mutation of either the zinc finger or RRM destabilize Cwc2 and are lethal. Yeast cells depleted of Cwc2 accumulate pre-mRNA and display reduced levels of U1, U4, U5 and U6 snRNAs. Cwc2 depletion also reduces U4/U6 snRNA complex levels, as found with depletion of other NTC proteins, but without increase in free U4. Purified Cwc2 displays general RNA binding properties and can bind both snRNAs and pre-mRNA in vitro. A Cwc2 RRM fragment alone can bind RNA but with reduced efficiency. Under splicing conditions Cwc2 can associate with U2, U5 and U6 snRNAs, but can only be crosslinked directly to the U6 snRNA. Cwc2 associates with U6 both before and after the first step of splicing. We propose that Cwc2 links the NTC to the spliceosome during pre-mRNA splicing through the U6 snRNA

Antibodies to the Mr 64,000 (64K) protein in islet cell antibody positive non-diabetic individuals indicate high risk for impaired Beta-cell function

A prospective study of a normal childhood population identified 44 islet cell antibody positive individuals. These subjects were typed for HLA DR and DQ alleles and investigated for the presence of antibodies to the Mr 64,000 (64K) islet cell antigen, complement-fixing islet cell antibodies and radiobinding insulin autoantibodies to determine their potency in detecting subjects with impaired Beta-cell function. At initial testing 64K antibodies were found in six of 44 islet cell antibody positive subjects (13.6%). The same sera were also positive for complement-fixing islet cell antibodies and five of them had insulin autoantibodies. During the follow-up at 18 months, islet cell antibodies remained detectable in 50% of the subjects studied. In all six cases who were originally positive, 64K antibodies were persistently detectable, whereas complement-fixing islet cell antibodies became negative in two of six and insulin autoantibodies in one of five individuals. HLA DR4 (p < 0.005) and absence of asparic acid (Asp) at position 57 of the HLA DQ chain (p < 0.05) were significantly increased in subjects with 64K antibodies compared with control subjects. Of 40 individuals tested in the intravenous glucose tolerance test, three had a first phase insulin response below the first percentile of normal control subjects. Two children developed Type 1 (insulin-dependent) diabetes mellitus after 18 and 26 months, respectively. Each of these subjects was non-Asp homozygous and had persistent islet cell and 64K antibodies. We conclude that 64K antibodies, complement-fixing islet cell antibodies and insulin autoantibodies represent sensitive serological markers in assessing high risk for a progression to Type 1 diabetes in islet cell antibody positive non-diabetic individuals