Numerical computation of temperature on steel and an insulator with simulation compared to experimental data.

In this report, we are computing the temperature from the heat equation for a disk of a given thickness. A laser beam of Gaussian profile is assumed at the surface of a circular sample. Prediction of temperature for a laser pulse with a Gaussian profile is shown for a circular symmetry. Temperature distributions are performed analytically and numerically for a power with a Gaussian profile at different depths from the surface. In the previous computation the laser beam was assumed to be small compared to the disk's radius. The calculations performed are useful to predict the proper spacing between marks during a laser procedure. Computations of the temperature for a beam spot size much larger than the sample dimensions are also shown for a modulated laser beam. The computation of temperature for the modulated laser beam is also compared to experimental data points obtained on bone.

Laser-induced emission spectra of stainless steels and aluminum irradiated with nanopulse lasers without setting delay: potential applications to remote sensing and laser micromachining.

Spectral lines from the impurities held in stainless steel and in aluminum can be clearly identified in the UV and the visible spectra when emission is laser induced. These spectroscopic lines can be initiated in metal irradiated at moderate laser optical densities of about 2.5×108W/cm2. In addition to the lines arising from impurities found in some metals, it was found that some spectroscopic lines from iron oxide formed during irradiation were also detected at the above-mentioned power density. It was found that lines observed from iron oxide are consistent with what is reported in the literature. The investigations reported were produced on samples at optical densities that are sufficient to create an electric field that is about 10 times the air electrical breakdown near the focal point. The results reported were obtained without setting any delay between the laser Q-switch and the data acquisition. The spectroscopic data are comparable to those shown in the literature by laser-induced breakdown spectroscopy in term of signal-to-noise ratio and are promising in detecting impurities such as heavy metals in remote sensing applications, where pulse delay is not always practical due to atmospheric conditions and power requirements. As a marking procedure is used during the investigations, the method demonstrates how spectroscopic monitoring in real time can be applied during a procedure in laser micromachining applications.

Precise determination of the focal point on a glass sample using spectroscopy analysis.

Laser marking of various materials is commonly used nowadays in commercial products. In the past two decades, CO2 lasers have been used extensively to mark insulators such as glass and wood during industrial production. Usually, a system of mirrors is used during a marking procedure. Although a laser beam can be characterized accurately using well-known methods, it is desirable to identify where the focal point is after reflecting on the scanning mirrors. The positioning of a motorized stage with a knife-edge and a sensing device to characterize a beam after reflecting through a mirror scanner system is impractical due to limited space. The method described here to determine the focal point accurately requires using only a large numerical aperture fiber connected to a motorized stage. In this paper, we investigate how spectroscopy of typical emission lines can be used to identify the position of the focal point in real time during laser marking procedures.

Laser micromachining of periodic surface radius change on the optical fiber circumference.

In this paper, we are showing that holes and marking spots with sizes that are comparable to the wavelength of a CO2 laser at λ=10.6 µm can be achieved reproducibly on a conventional optical fiber SMF28 when it is positioned at the focal point. Some theory on Gaussian beam propagation is briefly reviewed and readily applied to drill a fiber on its axis near the focal point. As the fiber was moved from the focal point, it was found that some features, such as ridges along the fiber circumference, were also micromachined by the laser. It was demonstrated that the fabrication of surface nanoaxial photonic fibers, long-pitch grating fibers, and pump laser strippers can be envisaged on a conventional SMF28 with a cladding diameter of 125 µm.

Very accurate temperature control of bones by a CO2 laser for medical applications.

In this paper, we show that the temperature of porcine bone samples can be maintained to a constant value within the range of 40°C-75°C. For this temperature range, it was also shown that a porcine bone sample could be kept at a given temperature within a fraction of a degree Celsius. This method relies on a real-time feedback computer control between a noncontact sensor and a CO2 laser operating at a typical repetition rate within the 5-20 kHz range. Results are shown for domesticated porcine bones that strongly absorb the CO2 radiation at λ=10.6 µm.

Controlling the temperature of bones using pulsed CO2 lasers: observations and mathematical modeling.

Temperature of porcine bone specimens are investigated by aiming a pulsed CO2 laser beam at the bone-air surface. This method of controlling temperature is believed to be flexible in medical applications as it avoids the uses of thermal devices, which are often cumbersome and generate rather larger temperature variations with time. The control of temperature using this method is modeled by the heat-conduction equation. In this investigation, it is assumed that the energy delivered by the CO2 laser is confined within a very thin surface layer of roughly 9 µm. It is shown that temperature can be maintained at a steady temperature using a CO2 laser and we demonstrate that the method can be adapted to be used in tandem with another laser beam. This method to control the temperature is believed to be useful in de-contamination of bone during the implantation treatment, in bone augmentation when using natural or synthetic materials and in low-level laser therapy.

Law of cooling, heat conduction and Stefan-Boltzmann radiation laws fitted to experimental data for bones irradiated by CO2 laser.

The rate of cooling of domesticated pig bones is investigated within the temperature range of 20°C-320°C. Within the afore-mentioned temperature range, it was found that different behaviors in the rate of cooling were taking place. For bones reaching a temperature within the lower temperature range of 20°C-50°C, it was found that the rate of cooling is mostly governed by the empirical Newton's law of cooling. It is also shown that a transition is taking place somewhere within 50°C-100°C, where both the heat conduction equation and Newton's law apply. As bones can be raised at a fairly high temperature before burning, it was found that the rate of cooling within the range 125°C-320°C is mostly behaving according to the heat conduction equation and Stefan-Boltzmann radiation law. A pulsed CO2 laser was used to heat the bones up to a given temperature and the change of temperature as a function of time was recorded by non-contact infrared thermometer during the cooling period.

Temperature control of water-based substances by CO2 laser for medical applications.

Temperature of water-based substances is investigated by aiming a pulsed CO(2) laser beam at the water-air surface. This method of controlling temperature is believed to be flexible in medical applications as it avoids the use of thermal devices, which are often cumbersome and generate rather larger temperature swing with time. The control of temperature in this laser method is modeled by the heat conduction equation. In this investigation, it is assumed that the energy delivered by the CO(2) laser is confined within a very thin surface layer of roughly 10 µm. It is shown that the temperature can be very well controlled by a CO(2) laser at a steady temperature, and we demonstrate that the method can be adapted to work in tandem with another laser beam.

Knockdown of RARB2 identifies a dual role in cancer.

Two chemoprevention trials have shown that retinoic acid (RA) may be harmful in patients at risk for lung cancer, and RA administration to this high-risk group results in RARB2 reactivation. Although RARB2 is thought to possess tumor suppressive activity, its expression has recently been correlated with poorer prognosis in patients with nonsmall cell lung cancer. We hypothesized that RARB2 expression is necessary for the growth and maintenance of the oncogenic phenotype in lung cancer cells in which RARB2 has not been inactivated. We tested various antisense oligodeoxynucleotides (ASO) against RARB2 in multiple lung cancer cell lines and used microarray technology to compare the patterns of gene expression following ASO treatment versus RA treatment in the A-549 lung cancer cell line. We show that ASO treatment reduces proliferation and causes apoptosis in 3 RARB2-expressing lung cancer cell lines but has no apparent effect in at least two other lung cancer cells lines having lost RARB2 expression or one normal lung RARB2-expressing cell line; we demonstrate a correlation between resulting RARB2 expression levels and cell growth; and identify transcriptional effects related to both RA and RARB2 signaling. In particular, five genes known to contribute to carcinogenesis or chemotherapeutic resistance are down-regulated following ASO treatment: three of these are up-regulated following RA treatment. This work demonstrates a dual role for RARB2 (tumor suppression and tumor promotion) and identifies a challenge with respect to using RARB2 as a target for treatment or prevention strategies.

Vascular smooth muscle contractility assays for inflammatory and immunological mediators.

The blood vessels are one of the important target tissues for the mediators of inflammation and allergy; further cytokines affect them in a number of ways. We review the use of the isolated blood vessel mounted in organ baths as an important source of pharmacological information. While its use in the bioassay of vasoactive substances tends to be replaced with modern analytical techniques, contractility assays are effective to evaluate novel synthetic drugs, generating robust potency and selectivity data about agonists, partial agonists and competitive or insurmountable antagonists. For instance, the human umbilical vein has been used extensively to characterize ligands of the bradykinin B(2) receptors. Isolated vascular segments are live tissues that are intensely reactive, notably with the regulated expression of gene products relevant for inflammation (e.g., the kinin B(1) receptor and inducible nitric oxide synthase). Further, isolated vessels can be adapted as assays of unconventional proteins (cytokines such as interleukin-1, proteases of physiopathological importance, complement-derived anaphylatoxins and recombinant hemoglobin) and to the gene knockout technology. The well known cross-talks between different cell types, e.g., endothelium-muscle and nerve terminal-muscle, can be extended (smooth muscle cell interaction with resident or infiltrating leukocytes and tumor cells). Drug metabolism and distribution problems can be modeled in a useful manner using the organ bath technology, which, for all these reasons, opens a window on an intermediate level of complexity relative to cellular and molecular pharmacology on one hand, and in vivo studies on the other.

Standing wave surface plasmon mediated forward and backward scattering.

Two superimposed gratings act to couple light to surface plasmon modes at a metal-air interface. A surface plasmon standing wave is created by generating two counter propagating plasmon waves. The wavelength and angle of incidence of the light that generates the surface plasmon standing wave can be selected by selecting the grating spacing of the couplers. The standing wave can then be out-coupled via the same gratings. In addition to affecting the transmission and reflection signals of the film the structure also enhances the light coupled into the forward- and the back-scattered direction.

32P-oligodeoxynucleotide-coated coils to prevent arterial recanalization after embolization.

BACKGROUND AND PURPOSE: Endovascular treatment of aneurysms with coils, a less invasive alternative to surgery, is too often associated with recurrences. In a canine model, recanalization after coil embolization can be inhibited by in situ beta radiation. METHODS: Radioactive platinum coils were produced by immersion in a (32)P-oligodeoxynucleotide solution. In vitro and in vivo (32)P-oligodeoxynucleotide elution profiles were assessed after incubation or arterial implantation for 14 days or less. Activities within arteries, thrombi, and coils were measured by scintillation counting. Angiographic and pathologic results no more than 12 weeks after standard platinum and radioactive coil embolization of canine maxillary, cervical, and vertebral arteries were compared among 17 animals. RESULTS: Exposure to (32)P-oligodeoxynucleotide solution at 65 degrees C yielded coils with an average activity of 0.3 microCi/cm. Elution profiles in vitro and in vivo showed that 50% of total activities eluted from coils within 24 hours at first, but coil activities then paralleled the natural decay of (32)P. Radioactivity was present in the thrombi and arterial wall throughout the 14-day observation period. Arteries that were embolized with standard coils recanalized at 2 weeks. Implantation of (32)P-oligodeoxynucleotide-coated coils produced total occlusions in 78.6% of arteries throughout the 12-week observation period. Most arteries that were implanted with radioactive coils were filled with fibrous tissue at 3 months. CONCLUSION: Radioactive coils can be produced by using the binding properties of a (32)P-oligodeoxynucleotide to platinum. Use of these coils in an animal model was effective in preventing recanalization. This method could be performed on site to provide coils tailored to each intervention.

Expression of kinin B(1) receptor in fresh or cultured rabbit aortic smooth muscle: role of NF-kappa B.

Kinin B(1) receptor (B(1)R) expression and the importance of the transcription factor nuclear factor (NF)-kappa B in this process were evaluated in models based on the rabbit aorta: freshly isolated tissue (postisolation induction) and cultured smooth muscle cells (SMCs). A 3-h incubation of freshly isolated tissues determined a sharp B(1)R mRNA increase (RT-PCR). Coincubation of tissues with a stimulus (interleukin-1 beta, fetal bovine serum, epidermal growth factor, or cycloheximide) further increased mRNA levels. Cultured SMCs possessed a basal population of surface B(1)Rs ([(3)H]Lys-des-Arg(9)-bradykinin binding) that was upregulated by treatments with the same set of stimuli (binding, mRNA, nuclear runon). Pharmacological inhibitors of NF-kappa B (MG-132, BAY 11-7082, dexamethasone) or actinomycin D reduced the postisolation induction of B(1)Rs in fresh aortic tissue (contractility or mRNA) and the cytokine effect on cells (mRNA, binding). NF-kappa B may be a common mediator of various stimuli that increase B(1)R gene transcription in the rabbit aorta, including tissue isolation, but cycloheximide also stabilizes B(1)R mRNA. The SMC models faithfully mimic the in vivo situation with regard to B(1)R regulation.