Dimethyl formamide-free, urea-NaCl fluorescence in situ hybridization assay for Staphylococcus aureus.

AIMS: To test the feasibility of identifying Staphylococcus aureus with a fluorescence in situ hybridization (FISH) assay that uses a single hot-plate and urea-NaCl reagents. METHODS AND RESULTS: Slides spotted with S. aureus and treated with methanol and lysozyme were incubated with urea-NaCl reagents on a hot-plate with a precise temperature control and identified with specific DNA probes. CONCLUSIONS: Staphylococcus aureus was detected and differentiated from Staphylococcus epidermidis in 1 h with a novel FISH method that used a single hot-plate and in the absence of dimethyl formamide. SIGNIFICANCE AND IMPACT OF STUDY: A rapid hot-plate FISH assay with urea-NaCl and without toxic dimethyl formamide might be useful if FISH is run infrequently or where resources are limited.

The differential sensitivity of cultured chick mesodermal cells to actinomycin D.

Cells were isolated from the somite mesoderm and from the unsegmented (presomite) mesoderm of early chick embryos and exposed to actinomycin D in single cell culture. Actinomycin D inhibited proliferation in cell cultures derived from the unsegmented mesoderm, although the same concentrations of this antibiotic did not inhibit cultures derived from the somite mesoderm. This differential sensitivity parallels the regionally specific necrosis and degeneration observed in the unsegmented mesoderm of intact chick embryos exposed to actinomycin D. In culture, both cell types exhibited approximately the same permeability to labeled actinomycin D and showed comparable inhibition of RNA, DNA, and protein syntheses in the presence of the antibiotic. However, freshly isolated mesodermal cells from the somite region had a higher content of RNA than did cells from the unsegmented region, and the somite cells maintained a higher rate of macromolecular synthesis in untreated cultures.

Increased wavelength options in the visible and ultraviolet for Raman lasers operating on dual Raman modes.

We report increased wavelength options from Raman lasers for Raman media having two Raman modes of similar gain coefficient. For an external-cavity potassium gadolinium tungstate Raman laser pumped at 532 nm, we show that two sets of Stokes orders are generated simultaneously by appropriate orientation of the Raman crystal, and also wavelengths that correspond to sums of the two Raman modes. Up to 14 visible Stokes lines were observed in the wavelength range 555-675 nm. The increase in Stokes wavelengths also enables a much greater selection of wavelengths to be accessed via intracavity nonlinear sum frequency and difference frequency mixing. For example, we demonstrate 30 output wavelength options for a wavelength-selectable 271-321 nm Raman laser with intracavity sum frequency mixing in BBO. We also present a theoretical analysis that enables prediction of wavelength options for dual Raman mode systems.

High efficiency, multi-Watt CW yellow emission from an intracavity-doubled self-Raman laser using Nd:GdVO4.

Efficient multi-Watt continuous-wave (CW) yellow emission at 586.5 nm is demonstrated through intracavity frequency-doubling of a Nd:GdVO(4) self-Raman laser pumped at 880 nm. 2.51 W of CW yellow emission with an overall diode-to-yellow conversion efficiency of 12.2% is achieved through the use of a 20 mm long Nd:GdVO(4) self-Raman crystal and an intracavity mirror which facilitates collection of yellow emission generated within the resonator, and reduces thermal loading of the laser crystal.

Sutureless microvascular anastomoses by a biodegradable laser-activated solid protein solder.

A new sutureless technique to successfully anastomose the abdominal aorta of rats (1.3 mm in diameter) by using a fully biodegradable, laser-activated protein solder is presented. A total of 90 rats were divided into two groups randomly. In group one, the anastomoses were performed by using conventional microsuturing technique, whereas in group two, the anastomoses were performed by using a new laser welding technique. In addition, each of the two groups were divided into five subgroups and evaluated at different follow-up periods (10 minutes, 1 hour, 1 day, 1 week, and 6 weeks). At these intervals, the anastomoses were evaluated for patency and tensile strength. Three anastomoses in each subgroup were processed for light and electron microscopy. All anastomoses were found to be patent. The mean clamp time of the anastomoses performed with conventional suturing was 20.6 minutes compared with 7.2 minutes for the laser-activated welded anastomoses (p < 0.001). The strain measurements showed a stronger mechanical bond of the sutured anastomoses in the initial phase. However, at 6 weeks the tensile strength of the laser-welded anastomoses was higher compared with the conventional suture technique. Histologic evaluations revealed a near complete resorption of the solder after 6 weeks. The junction site of the vessel ends cannot be determined on the luminal side of the artery. In conclusion, a resorbable protein used as a solder, activated by a diode laser, can provide a reliable, safe, and rapid arterial anastomosis, which could be performed by any microsurgeon faster than conventional suturing after a short learning curve.

Thermal modeling of solid nonfocusing pump-light collectors used for diode-pumped Nd:YAG lasers.

We have developed a thermal model for the determination of the temperature distribution of a diode side-pumped Nd:YAG laser in which the laser rod is fixed in a solid nonfocusing (prismatic) pump-light collector. The model permits the temperature to be determined as a function of both spatial and temporal parameters for a wide range of boundary conditions and different collector materials. Interferometric measurements were carried out to obtain the averaged rod temperatures for comparison with results from the model and to fix a convective-cooling rate for ambient air that best fits the experimental results. Two cases were studied both theoretically and experimentally with artificial sapphire and BK7 as prism materials, and good agreement was achieved between model and experimental results. The use of artificial sapphire as the prism material reduces by a factor of ~7 both the rod temperature and the warm-up time compared with BK7 glass. Peltier cooling of the underside of the BK7 glass prism yields thermal Characteristics of the device that are similar to those devices with sapphire prisms. Calculations also show that the thermal properties of the fixant are not critical for moderate fixant thermal diffusivities (i.e., k(f) > 10(-8)-10(-7) m(2) s(-1)), thus the choice of an appropriate fixant can be based on its mechanical and index-matching properties alone.

Coherent phenomena between incoherent pulses.

A coherent interaction is observed between two incoherent, temporally separated pulses, which increases the stimulated Raman scattering conversion efficiency of the delayed pulse from 14% to 27%. This coupling occurs through long-lived coherence in the Raman medium. The influence of temporal pulse spacing on the enhancement is measured.

Large-volume longitudinally excited Ca(+) discharge-recombination laser.

An experimental investigation of a longitudinally excited Ca(+) discharge-recombination laser with an active volume of 1000 cm(3) is reported. Single-pulse output energy densities greater than 4 microJ/cm(3) at energy-conversion efficiencies of 0.05% have been obtained on the lambda373.7-nm transition for low-pulse-rate (1-Hz) operation at helium buffergas pressures up to 400 Torr. Mean powers greater 0.5 W have been obtained at 500 Hz in preliminary studies of high-pulse-rate operation.

Theoretical modeling of a diode-pumped Nd:YAG laser with a solid nonfocusing pump light collector.

We report theoretical modeling for a diode-side-pumped Nd:YAG laser in which the laser rod is fixed in a solid nonfocusing (prismatic) light collector. The geometry provides for pumping the rod from four sides, which gives a relatively uniform gain profile across the transverse section of the rod and enables a high tolerance of the laser output to resonator and pump diode misalignment. The numerical model is developed to illustrate how the pumping uniformity and the transfer efficiency are affected when changes in the collector and lasing materials are made. We use small-signal gain measurements to test the predictions of the model and to examine the extent to which surface scattering from the rough rod barrel further spatially averages the deposited pump energy. The effects of the different refractive indices of the rod, collector, and fixant and the absorption properties of the laser material on optical transfer efficiencies are discussed.

Thermally induced strain and birefringence calculations for a Nd:YAG rod encapsulated in a solid pump light collector.

Calculations and experimental measurements of the thermally induced strain and birefringence are presented for a diode-pumped Nd:YAG rod that is encapsulated in a prismatic pump light collector. A numerical model is developed to determine the spatiotemporal stress-induced strain distribution across the prism, index-matching fixant, and laser rod, and the birefringence that arises from the stress-induced strain within the laser rod. Calculations of the birefringence are compared with polarscopic measurements and display good agreement. Support for the rod on all sides is provided by the prism and fixant, and the distribution and degree of the stress-induced strain (and birefringence) within the laser rod are therefore influenced by the geometry and composition of the prism and fixant. These strains are thermomechanical in origin and are primarily a function of the elastic modulus of the fixant and the temperature of the system. Such stress-induced strains are additional to those strains that are produced from temperature gradients across the laser rod and result from the laser rod being constrained from expanding. Collectors utilizing index-matching fluid as the encapsulant display the smallest measure of birefringence relating to the temperature gradients in the rod. However, for collectors utilizing solid fixants (with significant elastic modulus), an increase in the birefringence results. In this case collector designs that have the laser rod located in a symmetrically shaped prism are effective in reducing the nonuniform pressures on the sides of the rod and therefore the birefringence.

Encapsulated rod for efficient thermal management in diode-side-pumped Nd:YAG lasers.

Theoretical calculations of energy deposition, temperature, and thermally induced birefringence are presented for a diode-side-pumped Nd:YAG laser that has the laser rod optically fixed into a right-rectangular prism with a square cross section. The design provides uniform cooling of the rod and allows for a number of conduction-cooling techniques to be used. Average output powers >5 W are feasible at optical-to-optical efficiencies of ~20% for long-pulse operation and ~10% for Q-switched operation for quite simple and convenient cooling arrangements (e.g., Peltier cooling).

Comparison of prism-expander and grazing-incidence grating cavities for copper laser pumped dye lasers.

Operating characteristics of a variety of rhodamine 590 dye laser oscillators transversely pumped by a pulsed copper bromide laser at low repetition rates are reported and compared. The cavities investigated include simple prism-expander and grazing-incidence grating arrangements as well as double-prism and prism preexpanded grazing-incidence grating configurations. Linewidths of ~0.01 A at energy conversion efficiencies up to 10% were obtained for a prism preexpanded grazing-incidence grating cavity with good beam quality and low background superluminescence (<0.01%).

Prism preexpanded grazing-incidence grating cavity for pulsed dye lasers.

A modification to the grazing-incidence grating cavity for pulsed dye lasers is described whereby a prism is employed to expand the intracavity beam by a small factor before illumination of the grating. Suitable choice of the angles of incidence at both prism and grating permits good spectral resolution to be obtained while overall cavity losses are minimized. The performance characteristics of the modified cavity are analyzed and compared with those of simple grazing-incidence grating cavities. Spectral linewidths <0.01 A have been obtained at relatively high efficiencies (7-10%) for coumarin 500 dye pumped with a pulsed N(2) laser.

Efficient all-solid-state yellow laser source producing 1.2-W average power.

We report a practical and efficient all-solid-state laser source operating at 578 nm. The source comprises a diode-pumped Nd:YAG laser gain medium producing fundamental output at 1064 nm, an intracavity LiIO (3) Raman-active crystal that generates first-Stokes output at 1155 nm, and an intracavity LiB(3)O(5) frequency-doubling crystal, which frequency doubles the first-Stokes output to 578 nm. Q -switched output with as much as 1.2-W average power has been obtained; conversion efficiencies from the fundamental to the yellow as high as 33% have been obtained.

Proposal for a magnesium photoionization laser at 24.7 nm.

A system is proposed in which resonantly excited Mg atoms are rapidly photoionized by soft x rays from a laserproduced plasma, causing inversion and superfluorescent laser action at 24.7 nm in Mg II. Calculations show that significant gains should occur when a moderately sized (10-J, 200-psec) 1064-nm pump laser is used.

Accumulation of Raman gain between closely spaced pulse pairs.

The short-pulse conversion efficiency of stimulated Raman scattering in Pb vapor is increased from 15% to 35% by using a novel technique that employs a closely spaced pair of pump pulses. The second pulse scatters off the coherent excitation induced in the medium by the first pulse, with a resultant enhancement in efficiency. To our knowledge these results give the first observation of such long-lived cooperative phenomena in stimulated Raman scattering. We have also observed this phenomenon in H(2) and show that this technique is readily applicable to other Raman-active media.

Fixed-wavelength operation of a copper-laser-pumped dye laser injection seeded by low-power He-Ne lasers.

The design and operating characteristics of a dye laser pumped by a 3-W copper-vapor laser (CVL) and injection seeded by low-power (1-5 mW) He-Ne lasers at 633 nm are reported. An extremely simple optical arrangement is used wherein the output mirror of the He-Ne laser and a third mirror form the dye laser cavity. Laser efficiency in fixed-wavelength operation has been investigated for variable CVL pump power, He-Ne injection power and polarization, and cavity output coupling for a standard Rhodamine 590/Rhodamine 640 dye solution. Over 90% of free-running (unseeded) laser power is obtained in fixed-wavelength (seeded) operation at low CVL pump powers (≤1 W), dropping to approximately 60% at 3-W pump power. Maximum CVL pump to dye laser optical conversion efficiency in narrow-band, fixed-wavelength operation at 633 nm was 12%.

Measurements of the divergence evolution of a copper-vapor laser output by using a cylindrical imaging technique.

The temporal evolution of divergence of the output of a copper-vapor laser (CVL) operating with a high-magnification (M = 26.5) unstable resonator is measured by using a one-dimensional imaging system together with a fast gated linear diode array detector. The CVL output is found to consist of several temporally resolved components, with each successive component having lower divergence. The final component of the output has essentially diffraction-limited divergence. The divergence behavior is modeled by using an unfolded resonator-equivalent lens guide, with geometric constraints on the propagation of spontaneous emission within the lens guide, and is found to match the experimentally determined behavior.

A common strategic language for clinicians and senior managers.

Effective strategic analysis of existing and potential services requires a framework which is relevant and understandable to both clinicians and senior managers. Our work with NHS trusts has developed a framework based on analysis of services into four principal service streams--emergency general hospital, non-emergency general hospital, specialist general hospital and tertiary. Relating service streams to clinical specialties provides a matrix which can provide a basis for an initial analysis of the current and prospective clinical services portfolio, allowing drilling down into the detail and back up to the overall picture. Portfolio effectiveness is assessed by considering overall viability consisting of three interrelated elements--clinical, market and financial viability. The interrelationship of service streams, clinical specialties and viability allows the trust board and key clinicians to share insights into the current and potential systemic linkages between these three elements and to develop a vision of future strategic direction.

Repetition-rate scaling of a kinetically enhanced copper-vapor laser.

The output power of a kinetically enhanced Cu-vapor laser is shown to increase linearly with pulse repetition frequency to an experimental limit of 22 kHz. Output power of >150 W has been produced by a medium-scale (38-mm diameter, 1.55-m long) device operating at 22 kHz.