1,366 research outputs found
Fabrication of novel sensors from nanomaterials
This thesis describes the fabrication and characterisation of novel sensors from nanomaterials. These are materials that have at least one length scale in the nanometre region, and in many cases they exhibit fascinating electrical, mechanical or optical properties due to their small size. While their small size makes them candidates for miniaturising macro-scale technologies, many researchers are concerned with exploiting their unique properties in larger scale applications. These might include strong, lightweight building materials based on their mechanical properties, or visual displays based on their electrical and/or optical properties. To achieve transfer of the properties from the nano-scale to the macro-scale however is not straight forward, and there are a number of obstacles that must be overcome. One obstacle is that of processing the nanomaterials, ensuring that their properties do not become lost when they are incorporated into bulk materials or composites due to aggregation or poor interactions with their host matrix. This obstacle will also be addressed in the thesis, as we fabricate and characterise composites incorporating nanomaterials, and develop methods to process these materials into novel sensors.The synthesis and characterisation of a number of different composites has been achieved, incorporating either carbon nanotubes or silver nanowires as the nanomaterials of interest. These have been fabricated using either mixing or in situ polymerisation routes, with surfactants, polysaccharides or conducting polymers as the dispersant. The composites are all soluble in either water or organic solvents to give stable dispersions, and show interesting properties including optical activity, high loading fractions of the nanomaterials and electrochromic behaviour.The methods that we have developed for processing the dispersions are drop deposition, inkjet printing and dielectrophoretic assembly. Drop deposition has been performed as it forms the basis of numerous solution-based processing techniques, and we have investigated specifically the effects of substrate hydrophobicity and the effect of aggregates in the dispersion on the resulting composite films that are formed. We have reported for the first time the inkjet printing of single wall carbon nanotubes, and have printed composite films that show good transparency and high conductivity. A novel method for arresting the structures formed through dielectrophoretic assembly within a gel solution has also been developed. This has led to the fabrication of electrically anisotropic gels, and free-standing 'strings' of yeast cells. Novel sensors have been fabricated through two of our processing methods.Thin films containing carbon nanotubes have been inkjet printed, and show sensitivity to water vapour (with gellan gum as the composite material) and alcohol vapour (with a water soluble conducting polymer as the composite material). A sensor based on biotin-functionalised silver nanowires assembled into a microwire and encapsulated within agarose gel has also been fabricated. This sensor showed sensitivity to streptavidin when the response was measured parallel to the formed microwire, but gave a much lower signal when the response was measured perpendicular to the microwire. This provides a proof of concept that a whole range of biosensors based on assembled silver nanowires into an anisotropic gel can be produced by employing an antigen-antibody strategy, similar to the one shown for biotin-streptavidin
A Note on Dialectics in Mathematics
A complete dialectical process is defined; it is shown that such a process is a function, and that every real function is a complete dialectical process. Some general implications of this result are discussed
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The effects of organizational structure on the leadership behavior of single-district and multi-district school superintendents in certain school districts of the Commonwealth of Massachusetts.
EducationDoctor of Education (Ed.D.
Acute lobar pneumonia: with special reference to its treatment
Acute Lobar Pneumonia is one of the most
important diseases with which we have to deal, on
account of the appalling mortality with which it is
attended. In his "Clinical Studiesā, Bramwell says
"There is perhaps no disease which cuts off so many
valuable lives as Acute Croupous Pneumonia, killing
as it does so many people at the height of their
full vigour, activity, and usefulnessā,In Great Britain alone, about 1,000 lives per week
are terminated by this malady.Although most fatal at the extremes of life, no
age escapes its ravages, and many of the apparently
most robust fall victims to it.The percentage mortality varies considerably in
different epidemics, and under different physicians,
but it is usually from 20 - 30
Fabrication and Electric Field Dependent Transport Measurements of Mesoscopic Graphite Devices
We have developed a unique micromechanical method to extract extremely thin
graphite samples. Graphite crystallites with thicknesses ranging from 10 - 100
nm and lateral size 2 m are extracted from bulk. Mesoscopic
graphite devices are fabricated from these samples for electric field dependent
conductance measurements. Strong conductance modulation as a function of gate
voltage is observed in the thinner crystallite devices. The temperature
dependent resistivity measurements show more boundary scattering contribution
in the thinner graphite samples.Comment: 3 pages, 3 figures included, submitted to Appl. Phys. Let
intraoperative Radiotherapy for Breast Cancer
Intraoperative radiotherapy (IORT) for early stage breast cancer is a technique for partial breast irradiation. There are several technologies in clinical use to perform breast IORT. Regardless of technique, IORT generally refers to the delivery of a single dose of radiation to the periphery of the tumor bed in the immediate intraoperative time frame, although some protocols have performed IORT as a second procedure. There are two large prospective randomized trials establishing the safety and efficacy of breast IORT in early stage breast cancer patients with sufficient follow-up time on thousands of women. The advantages of IORT for partial breast irradiation include: direct visualization of the target tissue ensuring treatment of the high-risk tissue and eliminating the risk of marginal miss; the use of a single dose coordinated with the necessary surgical excision thereby reduc- ing omission of radiation and the selection of mastectomy for women without access to a radiotherapy facility or unable to undergo several weeks of daily radiation; favorable toxicity profiles; patient convenience and cost savings; radiobiological and tumor micro- environment conditions which lead to enhanced tumor control. The main disadvantage of IORT is the lack of final pathologic information on the tumor size, histology, margins, and nodal status. When unexpected findings on final pathology such as positive margins or positive sentinel nodes predict a higher risk of local or regional recurrence, additional whole breast radiation may be indicated, thereby reducing some of the convenience and low-toxicity advantages of sole IORT. However, IORT as a tumor bed boost has also been studied and appears to be safe with acceptable toxicity. IORT has potential efficacy advantages related to overall survival related to reduced cardiopulmonary radia- tion doses. It may also be very useful in specific situations, such as prior to oncoplastic reconstruction to improve accuracy of adjuvant radiation delivery, or when used as a boost in higher risk patients to improve tumor control. Ongoing international clinical trials are studying these uses and follow-up data are accumulating on completed studies
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