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Closed-loop insulin delivery systems have the potential to address suboptimal glucose control in children and adolescents with type 1 diabetes. We compared safety and efficacy of the Cambridge hybrid closed-loop algorithm with usual care over 6 months in this population.In a multicentre, multinational, parallel randomised controlled trial, participants aged 6-18 years using insulin pump therapy were recruited at seven UK and five US paediatric diabetes centres. Key inclusion criteria were diagnosis of type 1 diabetes for at least 12 months, insulin pump therapy for at least 3 months, and screening HbAOf 147 people initially screened, 133 participants (mean age 13·0 years [SD 2·8]; 57% female, 43% male) were randomly assigned to either the closed-loop group (n=65) or the control group (n=68). Mean baseline HbAThe Cambridge hybrid closed-loop algorithm had an acceptable safety profile, and improved glycaemic control in children and adolescents with type 1 diabetes. To ensure optimal efficacy of the closed-loop system, usage needs to be consistently high, as demonstrated with CamAPS FX.National Institute of Diabetes and Digestive and Kidney Diseases.

In this paper, the design, fabrication, and characterization of a virtual pivot point micro electromechanical systems (MEMS) electrostatic actuator with externally mounted mirror is presented. The point of rotation of the movable arm of the actuator is distant from the physical actuator. This is a requirement for certain applications, such as an external cavity laser in Littman configuration. A maximum rotational radius of 5 mm from the virtual pivot point was achieved. A detailed analytical analysis for the displacement of the structure is presented. The dynamic characterization of the device with a finite element analysis simulation shows that the resonance frequency of the in-plane rotational mode is well separated from that of the out-of-plane bending mode, confirming high in-plane stability. The devices were fabricated on a silicon-on-insulator wafer with device layer thickness of 100 µm. Thin mirrors were fabricated by dicing a 100 µm thick silicon wafer. A resonance frequency of about 5.9 ´ 102 Hz for the maximum sized mounted mirror (1.7 mm ´ 100 µm ´ 1.0 mm) was determined by optical characterization.

Objective To examine demographic and clinical characteristics of diabetic patients undergoing diabetes-related major amputation in Far North Queensland to identify those at risk. Design A cohort was examined for differences between Indigenous and non-Indigenous groups in age, co-morbidities, indication for amputation and mortality. Attendance at the High Risk Foot Service was also reported. Setting Far North Queensland. Participants individuals with major amputations between 1998 and 2008. Main outcome measures Diabetes-related major amputations and mortality. Results Of the 143 individuals who underwent major amputation during the study period, 52% were Indigenous. On average, Indigenous amputees were 14 years younger than non-Indigenous amputees. There were more female Indigenous amputees compared with Indigenous male amputees. Indigenous amputees were more likely to suffer from chronic kidney disease (P

Laser Doppler perfusion imaging (LDI) is currently used in a variety of clinical applications, however, LDI instruments produce images of low resolution and have long scan times. A new optical perfusion imager using a laser speckle measurement technique and its use for in vivo blood flow measurements are described. Measurements of human skin and surgically exposed rabbit tissue made using this instrument were compared with a commercial laser Doppler perfusion imaging instrument. Results from blood flow measurements showed that the laser speckle imager measured an 11-67% decrease in blood flow under arterial occlusion. Under similar conditions, the laser Doppler imager measured blood flow decreases of 21-63%. In comparison with LDI, it was observed that the higher temporal resolution of the laser speckle imager was more sensitive to measuring the hyperaemic response immediately following occlusion. This in vivo study demonstrated some of the several advantages laser speckle imaging has over conventional LDI, making the new instrument more versatile in a clinical environment.

Additionally to the first total syntheses of the target compounds several novel syntheses of monoterpene fragments are described.

A full account of our oxidative radical cyclization approach to the synthesis of garcibracteatone and doitunggarcinone A is presented. This includes the first enantioselective synthesis of garcibracteatone, which allowed the absolute configuration of the natural compound to be determined. The first synthesis of doitunggarcinone A is also described, which confirms our reassignment of the relative configuration of this molecule. Novel syntheses of monoterpene fragments used to construct the target molecules are also reported.

Laser speckle perfusion imaging (LSPI) is a minimally invasive optical measure of relative changes in blood flow, providing real-time, high resolution, two-dimensional maps of vascular structure. Standard LSI imaging uses a light-reflective geometry that limits the measurement to a thin surface layer of 0.2-1 mm. The objective of this study was to test a new LSI instrument geometry with the laser source opposed to the image capture plane (light transmissive). Captured light then travels the entire tissue thickness (10-15 mm), sampling much deeper regions of interest than conventional optical imaging techniques.Reflective-light (conventional) and transmissive-light LSI modes were used to measure finger joint blood flow during a timed tourniquet occlusion of the brachial artery in volunteer participants.There was greatly increased visibility of vessels underlying the skin in the light-transmissive mode LSI mode. Established LSI algorithms were shown to still work in the light-transmissive mode, despite decorrelation due to finite laser coherence length and the light passing through a tissue thickness of 10-15 mm.Transmissive LSI can be used to measure blood flow deep (10-15 mm) into tissues. This could be useful for non-invasive measurements of finger joint synovial blood flow in diagnosing and treating peripheral vascular disorders, such as rheumatoid arthritis.

The performance of an rf‐excited CO2 waveguide laser which was synchronously pulsed and electro‐optically Q switched is described. Output power of up to 14 kW in 50 ns was achieved which was significantly higher than powers previously obtained from reported Q‐switched CO2 waveguide lasers. Acoustical perturbations were created in the optical waveguide by the pulsed discharge. This resulted in discontinuous variation in the laser pulse energy as the pulse repetition frequency was varied. Extremely marked thermal effects on Q‐switching performance were observed.

Background/purpose: The laser speckle perfusion imaging (LSPI) system is a new, non-invasive technique for rapidly and reproducibly measuring tissue perfusion. The high resolution and frame rate of the LSPI overcome many of the limitations of traditional laser Doppler imaging techniques. Therefore, LSPI is a useful means for evaluating blood flow in a variety of situations. The present study investigates the ability of the LSPI system to detect temporal changes in blood flow during the healing of cutaneous wounds in a well-characterized animal model. Methods: Full-thickness excisional skin wounds (2 × 2 cm) were created on the backs of juvenile female red Duroc pigs. Every week post-injury, the wounds were measured and photographed, and normalized blood flow values were determined using the LSPI system. Results: Tissue perfusion values were available after complete re-epithelialization and removal of the eschar, at day 21. At this point, wound blood flow was significantly elevated as compared with the surrounding, uninvolved skin. Wound blood flow declined steadily during healing, and approached normal values by day 35 post-injury. Conclusion: The kinetics of blood flow during excisional wound healing in the red Duroc model are comparable with that previously observed in laser Doppler imaging of healing human skin wounds and hypertrophic scars. These results therefore confirm that the red Duroc is a good model of human wound healing, and further indicates that the LSPI is an excellent technique for evaluating angiogenesis and neovascularization during healing in this and other models.

Laser Doppler perfusion imaging (LDI) is an established technique for early assessment of burn depth to help determine a course of treatment. Laser speckle perfusion imaging (LSPI) is an alternative laser based, non-invasive perfusion monitoring technique that offers rapid and high resolution images of tissue. We have evaluated the ability of the LSPI instrument in determining and monitoring burn scar perfusion over time and compared it with the LDI instrument as a standard. Methods: Ten patients with hypertrophic burn scars (time since injury: 1–8 months) were recruited. Burn scars were scanned with both instruments (LSPI and LDI) monthly over a period of 11 months. Clinical grading of the burn scars was assessed on every scan date using the Vancouver burn scar scale. Results: Comparison of the perfusion values determined by each instrument shows a strong positive correlation, r 2 = 0.86 ( n = 63). Each instrument's output also correlated significantly with the clinical grading of the scar, indicating the expected decrease in perfusion as the clinical condition of the scars improved with time. Significance: The new LSPI instrument compared favorably with the established LDI instrument, yielding similar results. The considerably faster scan time and higher resolution of the LSPI method provides a distinct clinical advantage, both in terms of patient comfort and for reliably matching perfusion characteristics to their associated anatomical features. The fast temporal response of the LSPI instrument could be used to monitor near real-time responses to mechanical or pharmacological interventions to study dynamic vascular changes to burn damaged tissues.

• Capture a User’s needs (e.g. new image acquisitions, products, services) in the form of an order. • Execute the steps required to “manufacture” and deliver the products and service. This involves interfacing to several other subsystems within the Ground Segment. • Track progress of the User’s order and provide feedback on the execution status to the User. • Facilitate the accounting (support billing, track usage, etc.) and provide management reports. Mission Planning provides the functions to

In earlier work, we demonstrated that radiance, calculated using the P3 approximation in a plane wave geometry, could be used to accurately predict the optical parameters of an Intralipid/methylene blue phantom. Plane wave geometry is impractical for clinical use but the results of this work encouraged us to further develop the P3 approximation for a spherical geometry, described in this paper. Radiance predicted by this model for a defined Intralipid/methylene blue phantom was compared with radiance measured in this phantom. The results demonstrate that the spherical derivation of the P3 approximation will reproducibly predict optical parameters of a tissue phantom as effectively as the slab geometry derivation of the P3 approximation. In a similar protocol, the P3 approximation was used to estimate the optical parameters of ex vivo human prostate. Radiance in this case was measured in the prostate samples using an after loading technique. Three prostate samples tested were found to be surprisingly optically homogeneous. The after loading protocol described in this paper could form the basis of a minimally invasive and effective clinical method to optically characterize human prostate.

Photodynamic therapy (PDT) has been considered as a potential therapy for superficial bladder carcinomas. Cutaneous photosensitivity and reduction of bladder capacity are the two well-known complications following systemic administration of the commonly used photosensitizer, Photofrin II (PII). The objective of the present study was to evaluate whether intravesical (i.b.) instillation of photosensitizers for PDT of bladder cancer might be a more suitable treatment method. Female Fischer rats were utilized to develop orthotopic and heterotopic bladder tumor models. Rats bearing orthotopic bladder tumors were treated either intravesically or intravenously with graded doses of 5-aminolevulinic acid (ALA) or PII. Normal rats received the same doses of ALA or PII. As well, rats bearing heterotopic tumor were studied for comparison. The biodistribution times (times allowed for tissue uptake and bioconversion following drug administration) were 2, 4 or 6 h. Porphyrin fluorescence intensities within tumor, urothelium, submucosa, bladder muscularis and abdominal muscle were quantitated by confocal laser scanning microscopy. Following intravenous (i.v.) injection of ALA, tumor protoporphyrin IX (PpIX) levels peaked at 4 h and diminished by 6 h. The PpIX ratios of tumor-to-bladder mucosa, submucosa and muscle layers were 3:1, 5:1 and 8:1, respectively, 4 h following 1000 mg/kg ALA injection. After ALA instillation, the optimal biodistribution time appeared to be 4 h. Bladder instillation provided comparable tumor labeling with the i.v. route, but lost selectivity of PpIX accumulation between tumor and normal urothelium. The PpIX ratio of tumor-to-bladder muscularis was 5:1. After i.b. instillation of PII, porphyrin fluorescence was detected only within tumor and urothelium, while porphyrin fluorescence was mainly located in bladder submucosa following i.v. injection. Intravesical administration of ALA or PII might be feasible for PDT of superficial bladder cancers.

Variations in the optical coefficients in tissue and the photosensitizer during photodynamic therapy (PDT) will require adjustment of the light dose during the course of therapy. We have studied the dynamics using light transmission spectra for two different tumor models when tetrasulfonated aluminum phthalocyanine (AlPcS4) was used as photosensitizer.Spectra were measured noninvasively in the EMT6/Ed murine tumor model, and with interstitially implanted source and probe fibers in the Dunning R3327-AT rat tumor model. Measurements were performed in the range 600-840 nm, using a tunable dye laser, a diode laser, and a Ti:Sapphire laser. AlPcS4 has absorption in the range 600-700 nm with an absorption peak at 670 nm in saline.The in vivo spectrum of AlPcS4 both in the EMT6/Ed tumor model and the Dunning R3327-AT tumor model differs from the spectrum of AlPcS4 in saline. The absorption at 670 nm was reduced, whereas the absorption at 640 nm increased. Exposure of phototherapeutic levels of light caused reduced light absorption by the photosensitizer and further spectral shift.We found that the AIPcS4 absorption spectrum changes in a biological environment, and we also observed increased light transmission at the treatment wavelength during PDT in both tumor models. Instability in the absorption spectrum of the photosensitizer may influence the effectiveness of PDT.

The goal of this study is to determine if flat cleaved fiber probes are appropriate for interstitial measurements of radiance in tissue. Flat cleaved probes have the advantage of high responsivity, and they are easy to insert into tissue. Owing to the non-isotropic response of flat cleaved probes, a calibration function is required, taking the anisotropy in the radiance in tissue into account.The method used to determine this function consists of radiance measurements in tissue, performed with a flat cleaved fiber probe mounted on a stereotactic stage for insertion into the tissue from different directions. Interstitial irradiation at 630 nm was delivered by a spherical source.We found that the degree of anisotropy in the radiance decreases with increasing distance from the interstitially implanted source in two different tissue phantoms and in the Dunning R3327-AT and R3327-H rat tumor models.A position-dependent calibration function is required for interstitially implanted flat cleaved fiber probes. An anisotropy function is presented, which modifies the measurements of radiance with a flat cleaved probe, to account for the change in anisotropy in the radiance. The anisotropy functions for the two tumor models differ substantially.

Although laser angioplasty has been demonstrated to be effective for the treatment of long, complex coronary arterial atherosclerotic stenoses, there is an associated risk of acute arterial spasm, dissection, and perforation as well as a significant restenosis rate. It has been postulated that the use of lasers emitting at wavelengths designed for radiation absorption by water would decrease local tissue trauma.We have examined the use of a Nd:YAG laser designed to emit at 1.44 microns, an absorption peak for water, and compared the results of laser ablation at 1.06 microns, 1.32 microns, and 1.44 microns wavelengths. Nd:YAG laser angioplasty was performed in the abdominal aorta of White Leghorn roosters. Acute and chronic vascular trauma was assessed by contrast angiography and histological analysis.There was a significant decrease in early mortality with 1.44 microns laser ablation. This decreased mortality after 1.44 microns ablation was associated with a decrease in vascular spasm, perforation, and thermal damage. Atherosclerotic plaque development at follow up was decreased with 1.44 microns ablation but this was not significant.1.44 microns laser ablation decreases early vascular trauma and mortality and may decrease subsequent atherosclerotic plaque development.

Objective. To report on the accuracy of reports of diabetes-related major amputations, rates per 100 000 people and trends over the 10-year period from 1998–99 to 2007–08 in Far North Queensland. Methods. Three data sources were cross-checked. Poisson regression was used to calculate the percentage change in trends in diabetes amputation hospitalisations over the period. Results. There was a discrepancy of 6 (3.7%) in 161 cases over 10 years. The number of diabetes-related hospitalisations for major lower limb amputation did not show a significant trend during this period, with an annual percentage change of –0.32%, P = 0.915. Conclusion. Amputation data in Far North Queensland were accurate. There was a modest reduction in the hospitalisation rate for major lower limb amputation over the 10-year period, demonstrating the need for improvements in the organisation of care. What is known about the topic? Diabetic foot complications resulting in amputation are recognised internationally as a costly, major health problem. Limited data are available in the Australian context, especially for regional high risk populations. What does this paper add? Accurate data on an Australian Institute of Health and Welfare recommended indicator, namely major amputations in people with diabetes. Confirmation of the accuracy of the data, enables benchmarking for future improvements. What are the implications for practitioners? A focus on major amputations is a useful indicator of the quality and safety of care for people with diabetes.

Dosimetry in photodynamic therapy as currently practiced is empirical in that it does not account for optical properties of the target lesion. However, since light attenuation in tissue is unpredictable, measurements of optical properties are needed to ensure optimal light dose delivery. Further improvements in the uniformity of light dose distribution in tumors can be afforded by implanting multiple light sources. A technique is described in which the use of multiple cylindrical sources was combined with measurements of light energy fluence rate in the tumor. Six sources were placed within translucent plastic needles, which were inserted into tumors in a parallel array. Tumor attenuation characteristics were measured by placing a miniature light detector in one needle, while illuminating a cylindrical source in another, nearby, needle. This process was repeated for different needle pairs. In one postmortem and two in vivo tumors the absorption coefficient, transport scattering coefficient and penetration depth ranged from 0.56-0.81 cm-1, 9.4-15.2 cm-1 and 1.7-2.3 mm, respectively. Apparent penetration depths for in vivo tumors changed with time, during experiments. Predictions of dosimetry were generally consistent with direct measurements of light in tumors. Somewhat better agreement was observed in an optical phantom.

This paper summarizes the results of a series of rf gas discharge experiments which were performed to assess the factors which influence the efficient operation of a transversely excited CO2 waveguide laser. Using multiple resonating inductors for impedance matching, the longitudinal voltage variations are shown to be affected by the rf operation frequency and the discharge geometry. The effect of the gas mixture and the rf input power density upon the discharge field to pressure ratio is also investigated.

Measurements of UV photoionization parameters for TEA CO 2 gas lasers are presented. Electron density and ionization decay times are given as a function of pressure for several gases and gas mixtures. Penetration depth of ionizing radiation in the gases is determined. The effect of selected additives on photoionization is demonstrated. The results show that a significant enhancement in electron density can be achieved. The X -band microwave interferometer data provide additional insight into the mechanisms involved and further substantiate the effectiveness of the technique in high-powered CO 2 laser design.

A high-pressure high-repetition-rate pulsed-discharge technique is described. Ultraviolet preionization and voltage switching are integrated using spark-gap switches in a geometry such that they will irradiate the discharge gas. A repetition rate of 4000 pulses per second (pps) has been achieved.

A mass spectrometer has been used to study the gas composition in a sealed rf‐excited CO2 waveguide laser during operation. CO2 dissociation levels, at 53% to 71%, are similar to those reported for dc‐excited waveguide lasers and substantiate prior measurements on rf‐excited discharges. The degree of dissociation decreases with increasing pressure and xenon content, but increases as the proportion of helium in the gas mixture is increased. Dissociation has been found to be insensitive to the rf input power per unit discharge length over the range of 2.7 to 4.7 W/cm. This is believed to be the result of increased rates of water vapor outgassing at higher input power levels.

Two prostate tumour models (Dunning R3327H and AT) were tested in rats to see if they were sensitive to hematoporphyrin-photoradiation therapy (HPD-PRT). The R3327H tumours were irradiated by implantation of a single fiber optic and the R3327 AT tumours were treated with implantation of four fiber optics simultaneously. Thermal measurements made at the tip of the fiber and up to 1 cm from the tip indicated temperature rises from 1.5 degree C to 20 degrees C at the tip and 0 degree to 8 degrees C distal to the tip, with power densities ranging from 100 mW to 500 mW. The R3327H tumour was controlled up to 8 weeks post-HPD-PRT, when the initial tumour size was 400-500 mm3. The R3327 AT tumours also respond to the HPD-PRT but a significant laser-induced thermal rise in the tumour is suspected.

The data and results of an extended investigation of the more salient parameters associated with the application of ultraviolet (UV) photoionization processes in TEA CO 2 lasers are presented. The study encompasses emission spectra, wavelength dependence, and influence of circuit parameters for a typical UV spark source. This investigation and a companion study utilizing a specialized charge collection apparatus on a monochromator provides further insight into the primary mechanisms involved in these photoinitiated laser devices and has, in addition, provided design criteria for the development of more efficient photoionization sources.

A mechanism for sustaining population inversions in contact charge‐transfer complexes in which the ground electronic state is not bound is described. The mechanism relies on picosecond radiationless depletion of the lower laser state. This generates an inversion even when the ground‐state potential curve, as plotted against the donor‐acceptor distance, is not repulsive vertically below the excited state minimum. Contact charge‐transfer lasers would offer high gain, high‐energy density, and tunable sources of coherent radiation in the uv and visible. A method for pumping such a laser is examined and applied to the pyrrole‐oxygen complex. A rate equation analysis is done and estimates for gain and energy density are presented.

An intracavity Fresnel loss-plate technique of measuring gain characteristics of a laser is described. The technique is applied to the CO2 laser and the results are found to agree well with other published measurements.The saturation parameter of the CO2 laser is found to increase with laser discharge current.

The design, construction, and operational parameters of a Rogowski‐type TEA CO2 laser are given. The device, which is simple and inexpensive to build, incorporates a provision for intracavity experiments and appears suited for studies in plasma physics and nonlinear optics.

The expansion of a hot mixture of CO2, N2, and H2O through a Laval nozzle is analyzed. Mixtures appropriate to the stoichiometric combustion of acetylene and propane are used. The calculations indicate that, despite the large quantities of water vapor present, the expansion will result in a population inversion on the CO2 laser transition for both fuels. The predicted maximum gain for these conditions is 3 dB/m which occurs for a reservoir temperature of 2000 °K. Design curves for this type of laser are given.

The saturated gain constant of the carbon dioxide laser is calculated using a thermodynamic approach. At low electron densities the gain constant is found to saturate according to a well-known and simple function. At higher electron densities, however, a more complicated form is assumed. The calculations are found to agree well with measured saturated gain.

Radiation induced air breakdown has been produced within the cavity of a TEA CO2 laser using an intracavity lens arrangement. Results indicate that this technique could be used for effective plasma heating because it permits fast energy dumping into low pressure sparks.

A high‐energy electron beam is generated using gas‐ionizing collisions to amplify a small cathode filament current. The technique makes use of a crossed magnetic and electric field to reduce the effective mean free path of electrons at the cathode. At a pressure of 5×10−5 Torr helium, for example, a filament current of 0.4 mA will produce a uniform beam of 100 mA. Accelerating voltages up to 100 kV are used.

The application of high‐repetition‐rate photoionized TEA laser techniques to continuous wave CO2 lasers is described. A PIE discharge approach is shown to provide a simple and convenient method for production of uniform large‐volume high‐density plasmas, suitable for continuous high‐powered CO2 laser operation. The approach may be suitable for discharge‐pumped noble‐gas–halide lasers.

A high‐pressure glow discharge in flowing gases is described. The cathode surface and the discharge glow are isolated by a mica sheet with a matrix of holes drilled into it. The cathode is differentially pumped to a pressure of approximately 1 Torr. This electrode structure has produced a discharge power density of 15 W/cm3 when the gas residence time is 3 ms.

A gas laser which oscillates on either the 5‐μ CO or the 10‐μ CO2 lines has been developed. The laser is sealed off, operates at room temperature, and has given over 4‐W total power, alternatively at 5 and 10 μ. Preliminary results indicate that performance characteristics and lifetimes comparable with conventional CO2 lasers should be achievable.

Radiation‐induced air breakdown has been produced within the cavity of a TEA CO2 laser using an intracavity lens arrangement. Results indicate that this technique could be used for effective plasma heating because it permits fast energy dumping into low‐pressure sparks.

A gas‐dynamic CO2 laser, in which the reservoir condition is achieved using an explosion, is described. Pulse energies of several joules have been obtained using common hydrocarbon fuels, including propane and natural gas.

Laser photoradiation of the brain via an optical fiber positioned 5 mm above a burr hole was performed after the injection of hematoporphyrin derivative (HpD) in 33 normal rats and 6 rats with an intracerebral glioma. Normal rats received HpD, 5 or 10 mg/kg of body weight, followed by laser exposure at various doses or were exposed to a fixed laser dose after the administration of HpD, 2.5 to 20 mg/kg. One control group received neither HpD nor laser energy, and another was exposed to laser energy only. The 6 rats bearing an intracranial 9L glioma were treated with HpD, 5 mg/kg, followed by laser exposure at various high doses. The temperature in the cortex or tumor was measured with a probe during laser exposure. The rats were killed 72 hours after photoradiation, and the extent of necrosis of cerebral tissue was measured microscopically. In the normal rats, the extent of brain damage correlated with increases in the dose of both the laser and the HpD. In all 6 glioma-bearing rats, the high laser doses produced some focal necrosis in the tumors but also damaged adjacent normal brain tissue. We conclude that damage to normal brain tissue may be a significant complication of high dose photoradiation therapy for intracranial tumors.

Fischer X Copenhagen rats bearing Dunning R3327-AT tumors were treated with hematoporphyrin derivative and red light (630 nm from an argon-driven dye laser) alone or in combination with the hypoxic cell radiosensitizer, misonidazole (MISO). In vitro studies had suggested that hypoxia might significantly decrease the cytotoxicity of photodynamic therapy (PDT) and labeling with [14C]MISO had revealed a significant fraction of viable hypoxic cells in this tumor. PDT alone resulted in a growth delay of 8.8 days but no tumor cures were observed. The administration of MISO (i.p. at 0.5 mg/g) 33 min prior to PDT resulted in an average growth delay of 15.2 days and tumor cures (local control at 33 days) in 20% of animals treated. If MISO at a similar dosage was administered 30 min after PDT an average growth delay of 16.3 days was measured and tumor cure was observed in 70% of the animals treated. These results suggest that the hypoxic cell fraction in R3327-AT tumors might be a limitation to their curability by PDT. The addition of MISO and/or other hypoxic cell cytotoxic agents to PDT procedures may provide an effective means of treating PDT-resistant hypoxic cells in solid tumors.

An approach to photodynamic treatment of tumors is the interstitial implantation of fiber optic light sources. Dosimetry is critical in identifying regions of low light intensity in the tumor which may prevent tumor cure. We describe a numerical technique for calculating light distributions within tumors, from multiple fiber optic sources. The method was tested using four translucent plastic needles, which were placed in a 0.94 X 0.94 cm grid pattern within excised Dunning R3327-AT rat prostate tumors. A cylindrical diffusing fiber tip, illuminated by 630 nm dye laser light was placed within one needle and a miniature light detector was placed within another. The average penetration depth in the tumor region between the two needles was calculated from the optical power measured by the detector, using a modified diffusion theory. Repeating the procedure for each pair of needles revealed significant variations in penetration depth within individual tumors. Average values of penetration depth, absorption coefficient, scattering coefficient, and mean scattering cosine were 0.282 cm, 0.469 cm-1, 250 cm-1 and 0.964, respectively. Calculated light distributions from four cylindrical sources in tumors gave reasonable agreement with direct light measurements using fiber optic probes.

The design and operational characteristics of a multielement cathode, suitable for high‐power electric discharge laser application is described. The compact structure utilizes a recirculating aqueous electrolyte for uniform current distribution, without the need for external resistive ballast. The simple and inexpensive geometry is suited for large‐area scaling.

Contact CT polyatomic complexes exhibit red-shifted emission spectra even when the ground electronic state potential curve, as plotted against the donor-acceptor distance, is not repulsive vertically below the CT state minimum. A population inversion can hence be sustained creating the possibility of lasing action.

The gases and cathode of a TEA CO2 laser are irradiated with uv radiation. The resulting photoionization and photoemission initiate and assist in sustaining a high‐energy low‐field‐strength discharge. Output energy of 50 J/liter at an efficiency of 15% has been obtained in an initial demonstration.

The threshold for laser‐induced breakdown has been found to be influenced by an electric field transverse to the laser focus. In air at a pressure of 20 Torr a field strength of 600 V/cm was found to completely suppress breakdown. At higher field strengths the electric field was found to induce breakdown rather than suppress it. These effects are explained as being due to charge removal and electron cascade.

Formation of a strong plasma prior to laser induced air breakdown has been observed using the CO 2 laser. Charge collection measurements reveal that the pressure dependence of charge generation is not compatible with cascade theory.

A small sealed off CO laser has given over 10 W continuous at room temperature. Preliminary results indicate that upon optimization, performance equivalent to that of the sealed off CO2 laser will be realized.

Gain saturation for filamentary parts of a Gaussian laser beam were measured in a CO 2 laser amplifier using a pinhole technique. The results show that the detailed growth of a Gaussian beam in the amplifier as well as the overall growth can be described by the well-known homogeneous saturation function. The small-signal gain constant was found to have the same value of 2 dB/m for all radial positions on the beam. The saturation parameter, however, decreased from a maximum Value of 40 W/cm2on the beam axis to 18 W/cm2on the beam wings. The profile of the saturation parameter had an approximately Gaussian shape with a width of 3.9 mm, the same as the width of the laser beam. Diffusion is suggested as the reason for this radial variation of saturation characteristics.