This paper presents some new low noise GaAs FET radar burn-out results. The spread in burn-out energies is very large, as in earlier reported work. A simple model of the GaAs FET gate shows qualitative agreement with some aspects of observed failures. Interpulse degradation of gain and noise figure have been measured and a new circuit technique has been developed which significantly reduces the degradation.
Infrared spectral pathology has gained significant attention in the last few years, since it has been demonstrated to be able to readily identify cancerous tissue in biopsy samples. The Infrared technique, however, normally requires tissue sections to be mounted on infrared transparent slides. Unfortunately, these slides are both expensive and particularly frangible. In addition, mounting samples on specialist slides is an additional step in the sample preparation workflow, which ideally should be avoided. Applying infrared imaging directly to the H&E stained tissue on the glass slides that are normally used by pathologists, could help the infrared imaging technique be incorporated into current cancer diagnosis work flow and lower the total cost of detection. The disadvantage of using glass slides is that the spectral range available is restricted to just the high wavenumber region (2500–3600 cm −1 ). In this work a study has been conducted on 120 breast tissues biopsy cores from different patients, to demonstrate that with the limited spectral information, breast cancer can be identified from the H&E glass slides. A four-class histological Adboost classification model has been constructed. Optimisation of the classification threshold was carried out to reduce the number of false negatives. Using a threshold of 0.1 the cancerous cores could be detected with an accuracy of 95.8 %. This was incorporated into a simple traffic light system that could be used as a prescreening tool. This work, demonstrating the use of infrared spectral pathology on standard pathology samples slide, thus goes some way to overcome one of the barriers to successful translation of the infrared technique into the clinic.
Fourier transform infrared (FT-IR) microscopy, coupled with machine learning approaches, has been demonstrated to be a powerful technique for identifying abnormalities in human tissue. The ability to objectively identify the prediseased state, and diagnose cancer with high levels of accuracy, has the potential to revolutionise current histopathological practice. Despite recent technological advances in FT-IR microscopy, sample throughput and speed of acquisition are key barriers to clinical translation. Wide-field quantum cascade laser (QCL) infrared imaging systems with large focal plane array detectors utilising discrete frequency imaging, have demonstrated that large tissue microarrays (TMA) can be imaged in a matter of minutes. However this ground breaking technology is still in its infancy and its applicability for routine disease diagnosis is, as yet, unproven. In light of this we report on a large study utilising a breast cancer TMA comprised of 207 different patients. We show that by using QCL imaging with continuous spectra acquired between 912 and 1800 cm-1, we can accurately differentiate between 4 different histological classes. We demonstrate that we can discriminate between malignant and non-malignant stroma spectra with high sensitivity (93.56%) and specificity (85.64%) for an independent test set. Finally, we classify each core in the TMA and achieve high diagnostic accuracy on a patient basis with 100% sensitivity and 86.67% specificity. The absence of false negatives reported here opens up the possibility of utilising high throughput chemical imaging for cancer screening, thereby reducing pathologist workload and improving patient care.
We have demonstrated high-power, single-wavelength cw operation of an InGaAsP/InGaAs strained-layer multi-quantum-well active-grating surface-emitting amplifier operating at a wavelength of 1.7 μm. Single-wavelength operation was obtained with 38 dB suppression of amplified spontaneous emission at 107 mW cw power output.
The advent of thermo-electric, thermionic, and fuel cell power converters has led to the need for means of power inversion capable of high efficiencies at low input voltages. The advantages of tunnel diodes as low voltage power inversion elements and considerations governing their design are discussed. Performance data and electrical characteristics of germanium tunnel diodes having peak currents of 1-50 amperes are presented and results of low temperature operation are described. Methods of measuring the electrical parameters of these diodes are given, including a low-cost adapter for extending the current range of any curve tracer. Circuits for power conversion using these tunnel diodes are described, with theoretical and experimental efficiencies compared, construction problems outlined, and low temperature circuit operation discussed.
Studies of drug-cell interactions in cancer model systems are essential in the preclinical stage of rational drug design, which relies on a thorough understanding of the mechanisms underlying cytotoxic activity and biological effects, at a molecular level. This study aimed at applying complementary vibrational spectroscopy methods to evaluate the cellular impact of two Pt(ii) and Pd(ii) dinuclear chelates with spermine (Pt2Spm and Pd2Spm), using cisplatin (cis-Pt(NH3)2Cl2) as a reference compound. Their effects on cellular metabolism were monitored in a human triple-negative metastatic breast cancer cell line (MDA-MB-231) by Raman and synchrotron-radiation infrared microspectroscopies, for different drug concentrations (2-8 μM) at 48 h exposure. Multivariate data analysis was applied (unsupervised PCA), unveiling drug- and concentration-dependent effects: apart from discrimination between control and drug-treated cells, a clear separation was obtained for the different agents studied - mononuclear vs. polynuclear, and Pt(ii) vs. Pd(ii). Spectral biomarkers of drug action were identified, as well as the cellular response to the chemotherapeutic insult. The main effect of the tested compounds was found to be on DNA, lipids and proteins, the Pd(ii) agent having a more significant impact on proteins while its Pt(ii) homologue affected the cellular lipid content at lower concentrations, which suggests the occurrence of distinct and unconventional pathways of cytotoxicity for these dinuclear polyamine complexes. Raman and FTIR microspectroscopies were confirmed as powerful non-invasive techniques to obtain unique spectral signatures of the biochemical impact and physiological reaction of cells to anticancer agents.
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