Superluminescent Diodes are high power semiconductor optical sources with relatively broad spectral linewidth used for a variety of applications. The basic, crucial device feature needed to achieve high-power superluminescent operation is low facet reflectivity to prevent lasing and optical gain saturation. Theoretical calculations show that by appropriately designing the device length and output facet reflectivity a significant increase in optical output power and wall-plug efficiency can be obtained. This paper presents theoretical and preliminary experimental results indicating that it is possible to further improve the operational characteristics of superluminescent diodes and achieve high optical output power with high conversion efficiency. The control of the facet reflectivity and the overall device optical geometry are obtained by using Focused Ion Beam post-fabrication processing. Results obtained from the characterisation of superluminescent diodes before and after facet reflectivity alteration achieved by creating patterns on the subwavelength scale will be discussed.
he possibility of a pressure monitoring system by differential pressure sensors to detect contaminant effects on cellular cultures metabolic activity is discussed using Saccharomyces cerevisiae, lymphocyte, and AHH1 cell cultures. Metabolic (aerobic and anaerobic) processes in cells are accompanied by CO2 production that induces changes in pressure values when cells are cultured in sealed vessels. These values are subsequently converted in voltage units and plotted pressure dynamics versus time. This procedure leads to a standard curve, typical of the cellular line, which characterizes cellular metabolism when all parameters are controlled, such as temperature and nutrients. Different phases appear in the S. cerevisiae differential pressure curve: an initial growth up to a maximum, followed by a decrement that leads to a typical "depression" (pressure values inside the test-tubes are lower than the initial one) after about 35 h from the beginning. The S. cerevisiae differential pressure curve is successfully used to test the effects of chemical (Amuchina®, trieline) and physical (UV radiation, blue light, magnetic fields) contaminants. The same technique is applied to lymphocytes and AHH1 cultures to investigate the effects generated by a 72-h exposure to a 50-Hz, 60-µT electromagnetic field. Lymphocyte samples, cultured in a PHA medium, grow less than control ones, but exhibit a greater metabolic activity: changes in the exposure system configuration influence neither sample growth differences nor metabolic response variations between control and irradiated samples, while all the other irradiation parameters remain constant. Control and irradiated lymphocyte samples, without PHA in culture medium, show the same behavior both during irradiation and metabolic test. AHH1 control and irradiated samples show no difference both in growth percentage during irradiation and in metabolic activity. Different cell cultures respond to the same stimulus in different manners.
A wealth of data point to Delayed Luminescence (DL) as a good candidate for early and reliable detection technique in neoplastic cells and tissues sorting. Aiming at a DL experimental set up for such a kind of information, a testing technique for morphological analysis should be provided. This could certify the early identification of pathologies and abnormalities in cells and tissues by DL. DL technique may be coupled with FIB (Focused Ion Beam) imaging
analysis to give a correlated, both spectroscopic and morphological investigation, at the submicron scale.
A strong link among others has been reported to exist between DL signal characteristics and cytoskeleton structure and dynamics: FIB (Focused Ion Beam) imaging is for the moment being the best non invasive check at all and it can detect morphological alterations as early as possible since its resolution can go down to 2-5 nm.
The cells, that can be highlighted by the fast DL and slow and efficient FIB, can be in parallel analysed by a metabolic manometric technique that uses differential pressure sensors: the different cellular activity of normal and abnormal cells can be recorded and this allows fast and non-invasive investigations, although requiring a minimal number of cells.
In addition it’s possible to study, by the confocal microscopy spectroscopic analysis, DNA fragments, exploiting the optical characteristics of a dye, like ethidium bromide, to detect dynamic and conformational changes in DNA chains. These changes can be artificially induced in cells (e.g. by irradiation) or found in neoplastic cells. The acquired experience allows an independent check of spectroscopic, morphologic and metabolic testing by a control on nucleic acid defects.
These four techniques may be used together creating a "protocol" in order to permit an early and reliable alterations diagnosis of cells and tissues, guaranteeing an high accuracy standard.
Our work is devoted to the study of Saccharomyces cerevisiae and human lymphocytes cellular metabolism in order to develop a reference model to assess biological systems responses to chemical or physical agents exposure. CO2 variations inside test-tubes are measured by differential pressure sensors; pressure values are subsequently converted in voltage. The system allows to test up to 16 samples at the same time. Sampling manages up to 100 acquisitions per second. Values are recorded by a data acquisition card connected to a computer. This procedure leads to a standard curve (pressure variation versus time), typical of the cellular line, that describe cellular metabolism. The longest time lapse used is of 170 h. Different phases appear in this curve: an initial growth up to a maximum, followed by a decrement that leads to a typical depression (pressure value inside the test-tubes is lower than the initial one) after about 35 h from the beginning of yeast cells. The curve is reproducible within an experimental error of 4%. The analysis of many samples and the low cost of the devices allow a good statistical significance of the data. In particular as a test we will compare two sterilizing agents effects: UV radiation and amuchina.
The possibility of using a pressure monitoring system based on differential pressure sensors to detect contaminant effects on cellular cultures metabolic activity is discussed using Saccharomyces cerevisiae cell cultures: differential pressure curves' shape, starting slope and maximum are affected both by physical and chemical contamination. Aim of the present study is the investigation of the effects generated by a 72h exposition of Saccharomyces cerevisiae, human lymphocytes and AHH1 cellular line cultures to 50Hz, 60(mu) T electromagnetic field. No significant differences have been recorded between irradiated and control yeast samples. On other hand irradiated lymphocytes samples, cultures in a PHA medium, grow less than control ones, but exhibit a greater metabolic activity: changes in the exposure system configuration influence neither sample growth differences nor metabolic response variations between control and irradiated samples. Control and irradiated lymphocyte samples, without PHA in culture medium, show the same behavior both during irradiation and metabolic test. AHH1 control and irradiated samples show no difference both in growth percentage during irradiation and in metabolic test. Different cell cultures respond to the same stimulus in different manners.
Delayed Luminescence is a well established technique based on the illumination of biological sample and on the subsequent count of the number of photons re-emitted by the sample after the light source has been switched off together with their spectral distribution. Investigations have been performed on yeast cells and algae so that correlations can be established between biological activities and physical parameters of the samples. Moreover nonlinear mechanisms of interaction between optical fields and cells can be figured out. Further investigations will be reported on yeast cell samples deposited on paper filters after irradiation by soft X-rays. The results will be discussed by cross correlating the experimental evidence from Delayed Luminescence with those obtained by metabolic activity recording. Luminescence and Delayed Luminescence are strictly correlated with early insurgence of morphological alterations of normal or pathological nature in cells and tissues; a novel technique for morphological analysis has been developed by means of Focused Ion Beam machines. A straightforward approach to morphology at the nanoscale both of membranes and cellular inner structures is then made possible. The final aim is an experimental set up for an early and reliable detection technique for neoplastic cells and tissues sorting.
Nitrogen lasers have been used since many years to make dye solutions to lase. A nitrogen laser (337.1 nm) TEA at atmospheric pressure has been built in our laboratory. It has been characterized and used to pump cells of different sizes containing different dyes: Rhodamine 6G, Coumarin 440, DOTCI and pyranine. As a preliminary result it has been shown that pyranine can lase, and this happens at very low threshold. Moreover, we have found that, independently on the dye concentration in the solvent, the dyes under consideration can be grouped into two major classes of behavior: Rhodamine 6G and DOTCI can lase both axially and transversally; Coumarin 440 and pyranine can lase only axially. Other intriguing features will be discussed and attention will be devoted to simultaneous multiple beam generation, superfluorescence and distributed axial pumping of dye solutions.
Mass spectrometry identifies atomic and molecular species and relative concentrations in a given atmosphere. The analysis of the composition and of the atmosphere variations in a batch system, that contains a suspension of yeast cells or lymphocytes, allows to identify and to track cell metabolic processes. Such a technique has proven to be efficient in radiobiology experiments to investigate soft X- ray non-nuclear damages, as complimentary to other physical and chemical assessments.
Recently the demand for hyperpolarized noble gases is arising to improve NMR spectroscopy resolution for imaging. Hyperpolarization of noble gases is achieved by spin- exchange with alkali metal. atoms that undergo optical pumping by circularly polarized radiation. Optical pumping is usually achieved by high power semiconductor lasers. These sources have a bandwidth very large when compared with the transition bandwidth of the optically active species. This has two serious consequences: (i) the request of high power lasers, (ii) the losses that the unemployed energy delivered to the Rb vapor can provide in the efficiency of the energy transfer. Object of our investigation will be the comparison of two experimental set ups for optical pumping of Rb vapor where pumping is given in one case by a dye laser pumped by a UV nitrogen laser built in our laboratory according to the Blumlein scheme and in the other case by a semiconductor laser. Major elements that will be discussed are (1) the role of stimulated emission of Rb vapor to increase the pumping efficiency, (2) the fate of resonant photons that are emitted during Rb decays, (3) the role of applied magnetic fields in the efficiency of pumping processes.
The results are discussed of a systematic investigation on the electromagnetic field exposure consequences on human lymphocytes. These artificial fields have intensities comparable with the Earth magnetic field one, and are used for exposures up to 4 days. Different and complementary techniques are used to safely assess the consequences of ElectroMagnetic Fields (EMF) on the cells; in particular morphology, metabolism and population dynamics are investigated. The recourse to ultra microscopy, pressure monitoring in sealed bottles, atomic mass spectroscopy. Far IR Fourier Transform and cytofluorimetry techniques give a good insight in the EMF induced changes. A statistically significant deviation of irradiated samples with respect to the control ones are reported. A critical analysis and a survey of similar experiments reported in literature lead us to the exam of the experimental set up with attention to the geometry of the irradiation system. Finally the role of different magnetic field detectors in the reproducibility of the experiments will be carefully discussed.
Delayed luminescence (D.L.) is a measure that provides important information on biological systems fields, structures and activities, by counting impinging and emitted photons. Many recent experimental works have shown the existence of a close connection, sometimes analytically expressed between the biological state of the system and D.L. parameters. Our investigations aim to show that D.L. is a workable analytical technique covering a large number of disciplinary fields, from agriculture to pollution control and from medical diagnostics to food quality control. The authors have conducted systematic research about D.L. from unicellular alga Acetabularia acetabulum to Saccharomyces cerevisiae yeast cultures and about more complex systems such as Soya seed (Glycine max, L.) and its dependence on sample preparation, history, intracellular signaling, metabolism and pollutant presence. We will discuss the most relevant results together with theoretical considerations on the basic interaction at work between biological systems and electromagnetic fields.
An overall approach into the differential investigation of membrane/cytoplasm related metabolism and of cell-cycle of yeast cells after two color soft X-ray irradiation is presented; the soft X-rays being generated in trains of picosecond pulses by laser-plasma interaction. The two color X-ray differential technique is based on the generation of approximately 0.6 KeV X-rays which are deposited only in the membrane-wall complex switching off the anaerobic (fermentative) activity of yeast cells and on the generation of approximately 1.2 KeV X-rays which are mainly deposited in the cytoplasm, mitochondria and nucleus of yeast cells, mainly affecting the aerobic metabolism. A synergetic analysis of the metabolism is discussed, mainly founded on the recording of different correlated metabolic parameters, both on-line and delayed. Among the relevant access, pressure monitoring in batch samples acquire a dominant role allowing the identification of metabolic oscillation, that represent a marker of physical and chemical actions performed on the samples at different times. The experience acquired on yeast cells metabolism is being used to investigate lymphocytes metabolism and the related oscillatory properties of relevant enzymatic complexes. Actually even if it is not exactly the same as the mammalian situation, it should really propel the whole field forward.
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