Characterising room temperature ionic liquids with acoustic wave devices

Data for the physical properties of Room Temperature Ionic Liquids (RTILs) as a function of chemical composition is limited due to the expense and difficulty of producing large volumes of pure samples for characterization. RTILs comprise solely of ions and are liquid at room temperature. These are becoming of increasing interest for an extensive range of applications. This thesis looks at developing small scale characterization processes to find low cost and efficient methods for processing smaller sample volumes. Quartz crystal impedance analysis has been used to assess whether room temperature ionic liquids behave in a Newtonian manner to determine the values of their square root viscosity-density product using small volumes. Values are compared to traditional viscometer and densitometer measurements. A range of harmonics were studied for a 5 MHz fundamental crystal. The frequency shift of the third harmonic was found to provide the closest agreement between the two measurement methods with a limit seen at a square root viscosity-density product value of approximately 18 kg m??2 s??0:5. Further characterisation of the liquid was performed to separate values of density and viscosity using dual Quartz Crystal Microbalance (QCM) with fabricated surface features on one QCM; this required a total sample volume of only 240 L. Values were corroborated with standard measurement techniques demonstrating good agreement. A QCM was then incorporated into a microfluidic glass chip system to measure the square root of the viscosity-density product of RTILs

Advanced sandwich composite cores for patient support in advanced clinical imaging and oncology treatment

Ongoing advances in both imaging and treatment for oncology purposes have seen a significant rise in the use of not only the individual imaging modalities, but also their combination in single systems such as Positron Emission Tomography combined with Computed Tomography (PET–CT) and PET–MRI (Magnetic Resonance Imaging) when planning for advanced oncology treatment, the most demanding of which is proton therapy. This has identified issues in the availability of suitable materials upon which to support the patient undergoing imaging and treatment owing to the differing requirements for each of the techniques. Sandwich composites are often selected to solve this issue but there is little information regarding optimum materials for their cores. In this paper, we presented a range of materials which are suitable for such purposes and evaluated the performance for use in terms of PET signal attenuation, proton beam stopping, MRI signal shading and X-Ray CT visibility. We found that Extruded Polystyrene offers the best compromise for patient support and positioning structures across all modalities tested, allowing for significant savings in treatment planning time and delivering more efficient treatment with lower margins

Thermal conductivity measurement of liquids in a microfluidic device

A new microfluidic-based approach to measuring liquid thermal conductivity is developed to address the requirement in many practical applications for measurements using small (microlitre) sample size and integration into a compact device. The approach also gives the possibility of high-throughput testing. A resistance heater and temperature sensor are incorporated into a glass microfluidic chip to allow transmission and detection of a planar thermal wave crossing a thin layer of the sample. The device is designed so that heat transfer is locally one-dimensional during a short initial time period. This allows the detected temperature transient to be separated into two distinct components: a short-time, purely one-dimensional part from which sample thermal conductivity can be determined and a remaining long-time part containing the effects of three-dimensionality and of the finite size of surrounding thermal reservoirs. Identification of the one-dimensional component yields a steady temperature difference from which sample thermal conductivity can be determined. Calibration is required to give correct representation of changing heater resistance, system layer thicknesses and solid material thermal conductivities with temperature. In this preliminary study, methanol/water mixtures are measured at atmospheric pressure over the temperature range 30–50°C. The results show that the device has produced a measurement accuracy of within 2.5% over the range of thermal conductivity and temperature of the tests. A relation between measurement uncertainty and the geometric and thermal properties of the system is derived and this is used to identify ways that error could be further reduced

Analysis and in situ hybridization of cryptic satellites in Hordeum arizonicum

Three satellites, one (H1) on the heavy side of the main band of Hordeum arizonicum DNA and two (L1, L2) on the lighter side were purified using preparative silver-cesium sulphate density gradients. The native and the reassociated satellite DNAs were analysed in terms of buoyant densities and thermal dissociation. In cesium chloride gradients the H1 and L1 satellites formed single peaks corresponding to buoyant densities of 1.700 and 1.701 g · cm-3 respectively while the L2 satellite gave two peaks (1.680 and 1.661 g · cm-3). The H1 satellite showed three thermal components (Tm=82.5 °C, 87 °C and 91.5 °C) while the L1 and L2 had three (86.5, 92, 97.5 °C) and two (86, 95 °C) respectively. The H1 satellite was localized on the nuclei and chromosomes. The distribution of H1 onto approximately on third of the complement may reflect the genome specific origin of this satellite

Cleavage of plant chromosomes by restriction endonucleases

Cytological observations were made on the root-tip cells of Hordeum vulgare and H. bulbosum treated with a site-specific endonuclease preparation (restriction enzymes Hin<SUB>d</SUB> II and III from Haemophilus influenzae). The exogenously supplied endonuclease had cleaved the chromosomes in intact cells of both species into discrete fragments. Degradation was progressive with time. The number of breaks per vulgare chromosome was greater than per bulbosum chromosome. The possible implications of such differential susceptibility and practical applications of this technique are discussed

Evidence that the elevation of soluble MHC class I antigens in the serum precedes the onset of graft-versus-host disease and is correlated with the severity of the disease in rats

We examined the changes in the levels of soluble major histocompatibility antigen complex (MHC) class I antigens in the serum under a lethal or nonlethal state of graft-versus-host-disease (GVHD) induced by injecting various doses of PVG rat splenic lymphocytes into (DA × PVG)F rats. All rats receiving 4 × 10 lymphocytes (lethal dose) died on day 20-36 showing typical features of GVHD, while the injection of 4 × 10 cells (nonlethal dose) induced no sign of GVHD. When rats were inoculated with a nonlethal dose of lymphocytes prior to the injection of a lethal dose, all rats survived with or without showing transient GVHD. Preceding the onset of GVHD the levels of soluble class I antigens increased significantly to 1094 ± 487 ng/ml (mean ± SD, n = 4) from 3 days after the injection of a lethal dose to the time of death, whilst the levels in the nonlethal dose group remained unchanged. Rats with transient GVHD in the preinoculated group showed the increase of soluble class I antigens to the same extent as rats with lethal GVHD, suggesting that GVHD was systematically ongoing. The levels of soluble class I antigens also correlated with the severity of GVHD as judged by daily observation and histological studies. Rats receiving a lethal dose showed destructive alteration of spleen structure and cellular infiltration in the portal area of the liver before the animals started to show signs of GVHD, whereas rats in the nonlethal dose group exhibited no marked change. These data suggest the possibility of serum soluble class I antigens being not only a diagnostic but also a prognostic marker for GVHD

Simulação do serviço de correio eletrônico através de um modelo de filas

Estudamos, através da simulação de um modelo de filas, o serviço de correio eletrônico (e-mail) realizado pela rede de computadores do Instituto de Matemática e Estatística da Universidade de São Paulo, com o objetivo de identificar características estatísticas e avaliar seu desempenho. Uma análise do fluxo de mensagens foi feita para obter informações sobre o processo de chegadas, o tempo de serviço e a proporção de sucessos na entrega, além de outras características. Com base nessas informações, um modelo de filas é proposto e simulado para avaliar os tempos de espera das mensagens nesse sistema. O efeito de alterações nos parâmetros do modelo é também estudado.<br>We study, through simulation of a queuing model, the e-mail service provided by the Internet site of the Institute of Mathematics and Statistics of University of São Paulo, in order to identify statistics characteristics and to evaluate its performance. A data analysis of messages flow was done to obtain insight about the arrival process, the service time and the proportion of success, besides other characteristics. From this, a queuing model is proposed and simulated to evaluate waiting times of the messages in the system. The effect of changes in the parameters of the model is also studied

Separate Density and Viscosity Determination of Room Temperature Ionic Liquids using Dual Quartz Crystal Microbalances

The drive towards cleaner industrial processes has led to the development of room temperature ionic liquids (RTIL) as environmentally friendly solvents. They comprise solely of ions which are liquid at room temperature and with over one million simple RTIL alone it is important to characterize their physical properties using minimal sample volumes. Here we present a dual Quartz Crystal Microbalance (QCM) which allows separate determination of viscosity and density using a total sample volume of only 240µL. Liquid traps were fabricated on the sensing area of one QCM using SU-8 10 polymer with a second QCM having a flat surface. Changes in the resonant frequencies were used to extract separate values for viscosity and density. Measurements of a range of pure RTIL with minimal water content have been made on five different trap designs. The best agreement with measurements from the larger volume techniques was obtained for trap widths of around 50 µm thus opening up the possibility of integration into lab-on-a-chip systems