Non-irradiated Areas Research Articles

Improving machining performance of single-crystal diamond tools irradiated by a focused ion beam

• Machining performance of the FIB irradiated tool was improved by the heat treatment. • Gallium ions were removed by the proposed heat treatment. • Wear resistance of the FIB affected area was inferior to the non-irradiated area. Tool shape is an important factor determining the shape and accuracy of machined areas in ultra-precision machining. Use of a focused ion beam (FIB) is an effective means to fabricate micro- to submicro-scale tool shapes. However, ion irradiation causes doping and defects in the tool that reduce tool performance. To use FIB machining on a single-crystal diamond tool without degrading tool performance, a combination of 500 °C heat treatment and aluminum deposition was used to remove gallium (Ga) ions induced by ion irradiation. The method was evaluated through machining experiments that showed that irradiation of Ga ions causes work materials to adhere to the tool surface. This adhesion and the resulting rapid tool wear were reduced by heat treatment. The proposed method also improved the transcription ability and wear resistance of the tool so it was capable of producing a surface quality better than or equal to that produced by non-irradiated tools, even over long cutting distances.

Phototriggered Base Proliferation: A Highly Efficient Domino Reaction for Creating Functionally Photo-Screened Materials

Phototriggered base proliferation as a highly efficient domino reaction is presented for creating functionally photo-screened materials, providing a strategy for the photopolymerization of shadow areas via chemically diffuse amines toward the nonirradiated areas during polymerization. By integrating proliferated amines with a peroxide initiator (dibenzoyl peroxide, BPO), phototriggered self-propagating polymerization of acrylate monomers in three-dimensional space was achieved. The advantages of this approach lie in its enhanced photosensitivity, increased propagating velocity, and elevated double-bond conversion (90%) while reducing the local high temperature and the minimum BPO concentration that sustain a traveling front. Astonishingly, the propagating velocity and local maximum temperature can be well-modulated by varied BPO concentration and the appropriate amount of BA-BPD (1-(9-fluorenylmethoxycarbonyl)-4-benzylpiperidine) concentration, respectively. Finally, functionally photo-screened material containing carbon nanotubes was successfully prepared by phototriggered base proliferation reactions.

Preparation of copper containing methacrylic polymers and their application for the copper patterns

Copper containing methacrylic polymers were prepared by the polymerization of a copper methacrylate complex (Cu[CH2C(CH3)COO](COD), where COD=1,5-cyclooctadiene) with different methylmethacrylate and methacrylic acid compositions. These polymers were found to be soluble in many organic solvents including THF and chloroform. Copper nano-networks or aggregated nanoparticles were obtained when a THF solution of the polymers was reduced using an aqueous sodium borohydride solution. When a thin film of the polymers coated on a silicon wafer was irradiated with an electron beam, nanoparticles were produced on the irradiated area, while the non-irradiated areas could be washed away with a weak base developer, such as a tetramethylammoniumhydroxyde (TMAH) aqueous solution, to produce a copper pattern through an electron beam lithography process.

Darkening effect on AZ31B magnesium alloy surface induced by nanosecond pulse Nd:YAG laser

Permanent darkening effect was achieved on surface of AZ31B Mg alloy irradiated with nanosecond pulse Nd:YAG laser, and special attention was made to examine how surface structure as well as oxidation affect the darkening effect. Experiments were carried out to characterize morphological evolution and chemical composition of the irradiated areas by optical reflection spectrometer, Talysurf surface profiler, SEM, EDS, and XPS. The darkening effect was found to be occurred at the surface under high laser energy. Optical spectra showed that the induced darkening surface was uniform over the spectral range from 200nm to 1100nm. SEM and surface profiler showed that surface morphology of darkening areas consisted of large number of micron scale cauliflower-like clusters and protruding particles. EDS and XPS showed that compared to non-irradiated area, oxygen content at the darkening areas increased significantly. It was proposed a mechanism that involved trapping of light in the surface morphology and chemistry variation of irradiated areas to explain the laser-induced darkening effect on AZ31B Mg alloy.

Selective use of postoperative neck radiotherapy in oral cavity and oropharynx cancer: a prospective clinical study

BackgroundIn cervical postoperative radiotherapy, the target volume is usually the same as the extension of the previous dissection. We evaluated a protocol of selective irradiation according to the risk estimated for each dissected lymph node level.MethodsEighty patients with oral/oropharyngeal cancer were included in this prospective clinical study between 2005 and 2008. Patients underwent surgery of the primary tumor and cervical dissection, with identification of positive nodal levels, followed by selective postoperative radiotherapy. Three types of selective nodal clinical target volume (CTV) were defined: CTV0, CTV1, and CTV2, with a subclinical disease risk of <10%, 10-25%, and 25% and a prescribed radiation dose of <35 Gy, 50 Gy, and 66–70 Gy, respectively. The localization of node failure was categorized as field, marginal, or outside the irradiated field.ResultsA consistent pattern of cervical infiltration was observed in 97% of positive dissections. Lymph node failure occurred within a high-risk irradiated area (CTV1-CTV2) in 12 patients, marginal area (CTV1/CTVO) in 1 patient, and non-irradiated low-risk area (CTV0) in 2 patients. The volume of selective lymph node irradiation was below the standard radiation volume in 33 patients (mean of 118.6 cc per patient). This decrease in irradiated volume was associated with greater treatment compliance and reduced secondary toxicity. The three-year actuarial nodal control rate was 80%.ConclusionThis selective postoperative neck irradiation protocol was associated with a similar failure pattern to that observed after standard neck irradiation and achieved a significant reduction in target volume and secondary toxicity.

A study on electric properties for pulse laser annealing of ITO film after wet etching

The electric properties of ITO thin film after UV or IR laser annealing and wet etching was analyzed via grazing incidence in-plane X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectra and residual stress measurement. The laser annealing process readily induced microcracks or quasi-microcracks on the ITO thin film due to the residual tension stress of crystalline phase transformation between irradiated and non-irradiated areas, and these defects then became the preferred sites for a higher etching rate, resulting in discontinuities in the ITO thin film after the wet etching process. The discontinuities in the residual ITO thin film obstruct carrier transmission and further result in electric failure.

Patterned immobilisation of silicon dioxide nanoparticles on the surface of a photosensitive polymer

A photosensitive co-polymer of styrene and 4-vinylbenzyl thiocyanate was synthesised and employed for the immobilisation of aminofunctionalised silica nanoparticles (SiO 2-NP) at the polymer surface. Upon UV irradiation of the co-polymer, isothiocyanate groups are generated by a photo-isomerisation reaction of the thiocyanate groups. The silica nanoparticles were selectively immobilised in irradiated areas by immersing the illuminated polymer surface in a solution of SiO 2-NP. Depending on the time of immersion and the nanoparticle concentration, different amounts of silica can be deposited in the irradiated areas, whilst no immobilisation of SiO 2-NP is observed in the non-irradiated areas. By using photolithographic methods, patterned silica structures (μm scale) were produced on the polymer surface. The SiO 2-NP covered surfaces are of potential interest to generate protective surface layers and to carry out further functionalisation reactions of the immobilised SiO 2-NP particles.

Nonlinear Behavior of Decrease in Reflectivity of Multilayer Mirrors for Extreme Ultraviolet Lithography Optics by High-Flux Extreme Ultraviolet Irradiation in Various Vacuum Environments

To estimate the optics lifetime of an extreme ultraviolet lithography (EUVL) system with a contaminated mirror surface, it is indispensable to carry out an acceleration test using high-flux EUV irradiation. In this study, Mo/Si multilayer mirrors were irradiated in various vacuum environments using a contamination evaluation system with an undulator light source, and changes in their reflectivity were evaluated. The dependence of the decrease in reflectivity per unit dose on the EUV irradiance was observed in high-flux irradiation experiments in vacuum with water vapor or n-decane gas introduction at pressures lower than about 10-5 Pa. The irradiance dependence disappeared when the pressures were increased for both water vapor and decane gas. A reflectivity distribution with a doughnut shape, namely, high at the irradiation center, low in the surrounding area, and high in the non-irradiated area, was observed in the irradiation experiments during the simultaneous introduction of water vapor and decane gas. These results can be generally explained by the mechanism of the supply-controlled limit.

The Thermal Effects of Therapeutic Lasers with 810 and 904 nm Wavelengths on Human Skin

To investigate the effect of therapeutic infrared class 3B laser irradiation on skin temperature in healthy participants of differing skin color, age, and gender. Little is known about the potential thermal effects of Low Level Laser Therapy (LLLT) irradiation on human skin. Skin temperature was measured in 40 healthy volunteers with a thermographic camera at laser irradiated and control (non-irradiated) areas on the skin. Six irradiation doses (2-12 J) were delivered from a 200 mW, 810 nm laser and a 60 mW, 904 nm laser, respectively. Thermal effects of therapeutic LLLT using doses recommended in the World Association for Laser Therapy (WALT) guidelines were insignificant; below 1.5°C in light, medium, and dark skin. When higher irradiation doses were used, the 60 mW, 904 nm laser produced significantly (p < 0.01) higher temperatures in dark skin (5.7, SD ± 1.8°C at 12 J) than in light skin, although no participants requested termination of LLLT. However, irradiation with a 200 mW, 810 nm laser induced three to six times more heat in dark skin than in the other skin color groups. Eight of 13 participants with dark skin asked for LLLT to be stopped because of uncomfortable heating. The maximal increase in skin temperature was 22.3°C. The thermal effects of LLLT at doses recommended by WALT-guidelines for musculoskeletal and inflammatory conditions are negligible (<1.5°C) in light, medium, and dark skin. However, higher LLLT doses delivered with a strong 3B laser (200 mW) are capable of increasing skin temperature significantly and these photothermal effects may exceed the thermal pain threshold for humans with dark skin color.

Caries inhibition in vital teeth using 9.6-μm CO2-laser irradiation

The aim of this study was to test the hypothesis that in a short-term clinical pilot trial short-pulsed 9.6 μm CO(2)-laser irradiation significantly inhibits demineralization in vivo. Twenty-four subjects scheduled for extraction of bicuspids for orthodontic reasons (age 14.9 ± 2.2 years) were recruited. Orthodontic brackets were placed on bicuspids (Transbond XT, 3M). An area next to the bracket was irradiated with a CO(2)-laser (Pulse System Inc, Los Alamos, New Mexico), wavelength 9.6 μm, pulse duration 20 μs, pulse repetition rate 20 Hz, beam diameter 1100 μm, average fluence 4.1 ± 0.3J∕cm(2), 20 laser pulses per spot. An adjacent nonirradiated area served as control. Bicuspids were extracted after four and twelve weeks, respectively, for a quantitative assessment of demineralization by cross-sectional microhardness testing. For the 4-week arm the mean relative mineral loss ΔZ (vol% × μm) for the laser treated enamel was 402 ± 85 (mean ± SE), while the control showed significantly higher mineral loss (ΔZ 738 ± 131; P = 0.04, t-test). The difference was even larger after twelve weeks (laser arm ΔZ 135 ± 98; control 1067 ± 254; P = 0.002). The laser treatment produced 46% demineralization inhibition for the 4-week and a marked 87% inhibition for the 12-week arm. This study shows, for the first time in vivo, that the short-pulsed 9.6 μm CO(2)-laser irradiation successfully inhibits demineralization of tooth enamel in humans.

Rewritable Photopatterning of a Bisanthracene-Functionalized Mesogenic Compound by Photodimerization and Thermal Back-Reaction of the Anthracene Moiety

ABSTRACTA new method for photopatterning of a bisanthracene-functionalized mesogenic compound 1 was developed. The monomer 1 had two anthracene moieties on each molecular end, and showed crystalline and liquid-crystalline phases at room temperature and at an elevated temperature, respectively. Upon UV irradiation of 1 in the molten state, intermolecular photodimerization of the anthracene moieties was induced, and consequently resulted in the formation of a linear polymer. In contrast to the monomer 1, the obtained polymer exhibited amorphous phase at room temperature. When 1 was irradiated with UV light through a photomask in the molten state, the irradiated areas changed to amorphous phase due to photopolymerization, whereas the non-irradiated areas remained the ordered phase. This phenomenon provided visual images with a clear contrast under polarized light. In addition, the images could be erased by heating the whole sample at a temperature above ca. 200 °C, because the amorphous phase changed to the ordered phase due to a reproduction of the monomer 1 from the polymer associated with thermal back-reaction of the anthracene photodimer. Photopatterning could be performed for the erased sample again and the process was found to be fairly reversible.

Low cost fabrication of SiO 2 optical waveguides by laser direct writing on Ti-doped Sol–Gel films

A commercial direct laser writing (DLW) system operating at 1070 nm was used to fabricate SiO 2 optical waveguides on silicon wafers. A Ti-doped SiO 2 Sol–Gel film was deposited on the SiO 2/Si substrate by the dip-coating technique, based on which SiO 2 optical waveguides were patterned by DLW using a Ytterbium fiber laser and followed by chemical etching. The effects of laser parameters and the preheated temperature of Sol–Gel films on the dimensions of optical waveguides were studied systematically. The differences of etching rate between laser irradiated and non-irradiated areas in Sol–Gel films preheated at various temperatures are characterized by measuring the thickness of the films. Results demonstrate that the available laser power density range for laser densification and the width of the patterned optical waveguides are influenced strongly by the preheated temperature of the Sol–Gel films. The width of the optimized optical waveguide in this work is 25 μm. The minimum propagation loss of the fabricated optical waveguides is 1.7 dB cm −1 at the wavelength of 1550 nm.

Prognostic factors in Hodgkin lymphoma

Depending on stage and risk factor profile, up to 95% of patients with Hodgkin lymphoma at first presentation reach complete remission after the initial standard treatment including radiotherapy, combination chemotherapy or combined modality therapy. Patients who relapse after first complete remission can achieve a second complete remission and long-term disease-free survival with salvage treatment including radiotherapy for localized relapse in previously nonirradiated areas, conventional salvage chemotherapy, or high-dose chemotherapy with stem cell transplantation. In general, risk-adapted treatment strategies are used in the treatment of patients with Hodgkin lymphoma. Adequate staging of newly diagnosed patients enables optimal treatment planning, which is of particular importance for finding a balance between treatment efficacy and toxicity. In this review, an overview is given of the current knowledge of clinical and biological risk factors and the role of imaging modalities during and after treatment.

ChemInform Abstract: Patterned Deposition of Copper on Poly(tetrafluoroethylene)

This paper reports on a three step process that has been developed for patterned deposition of Cu onto poly(tetrafluoroethylene) (PTFE). The first step involves patterned irradiation with low doses of x-rays of electrons which cross-link the PTFE surface; step tow involves chemical etching with the result that only the nonirradiated, noncross-linked areas are etched; and step three involves selective chemical vapor deposition (CVD) of Cu onto the etched surface at 200{degrees} C using (hexafluoroacetylacetonato) Cu(l) trimethylphosphine (hfac) Cu(PMe{sub 3}). The nonirradiated surface is a activated for selective Cu CVD by the chemical etching step, while the irradiated portions remain unactivated due to cross-linking. Continuous Cu films with resistivities of 4 {mu}ohm-cm are formed on the nonirradiated areas. X-ray photoelectron spectra show the nonirradiated areas of the surface to be covered by pure Cu with only surface impurities resulting from air transfer of the samples, while the irradiated areas show the presence of only C and F, characteristic of PTFE.

Development of a Porcine Delayed Wound-Healing Model and Its Use in Testing a Novel Cell-Based Therapy

A delayed full-thickness wound-healing model was developed and used for examining the capacity of adipose-derived stem cells (ASCs), either alone or in platelet-rich fibrin gels, to promote healing. Four pigs received electron beam radiation to the dorsal skin surface. Five weeks after radiation, subcutaneous fat was harvested from nonirradiated areas and processed to yield ASCs. Two weeks later, 28 to 30 full-thickness 1.5-cm(2) wounds were made in irradiated and nonirradiated skin. Wounds were treated with either saline solution, ASCs in saline solution, platelet-rich plasma (PRP) fibrin gel, ASCs in PRP, or non-autologous green fluorescence protein-labeled ASCs. The single radiation dose produced a significant loss of dermal microvasculature density (75%) by 7 weeks. There was a significant difference in the rate of healing between irradiated and nonirradiated skin treated with saline solution. The ASCs in PRP-treated wounds exhibited a significant 11.2% improvement in wound healing compared with saline solution. Enhancement was dependent on the combination of ASCs and PRP, because neither ASCs nor PRP alone had an effect. We have created a model that simulates the clinically relevant late radiation effects of delayed wound healing. Using this model, we showed that a combination of ASCs and PRP improves the healing rates of perfusion-depleted tissues, possibly through enhancing local levels of growth factors.

Controlled Precipitation of Lead Sulfide Quantum Dots in Glasses Using the Femtosecond Laser Pulses

We report the controlled precipitation of PbS quantum dots (QDs) in glasses using multiple irradiation of the femtosecond laser pulses followed by thermal treatment. Upon the irradiation of femtosecond laser, PbS QDs were found to preferentially precipitate in the irradiated area after thermal treatment. Photoluminescence spectra showed PbS QDs in the irradiated area emitted at the long wavelength side, and transmission electron microscope images also confirmed that PbS QDs formed in the irradiated area were larger than those formed in the nonirradiated area. This controlled precipitation of PbS QDs can lead to the development of advanced optical materials.

May the rectus abdominis myocutaneous flap be the best option for the reconstruction of complicated large defects of pelvic exenteration for vulvar malignancies after pelvic radiation?

Abstract Reconstruction of the large defects that develop after pelvic exenteration with local flaps may result in higher morbidity because of poor perineal wound healing after pelvic radiation. A well vascularised reconstructive flap originating from distant non-irradiated areas is needed. We report two cases of pelvic exenteration and rectus abdominis myocutaneous flap procedure in patients with recurrent vulvar malignancies that had undergone external beam pelvic radiation and subsequently developed pelvic fibrosis, necrosis and fistulas. Both flaps were totally viable postoperatively; the abdominal wound healed without any complication, no perineal wound complications developed with a follow-up of nine months. In conclusions, rectus abdominis myocutaneous flap reconstruction seems to be an ideal option for the large defects resulting from exenteration operations in patients with previous perineal radiation.

紫外線照射によるナノ液体潤滑膜のパターニングに関する粗視化分子動力学シミュレーション(機械要素,潤滑,設計,生産加工,生産システムなど)

The characteristics of monolayer liquid lubricant films coated on magnetic disks are basically determined by their interactions with disk surfaces. If the strength of the interactions could be patterned by ultraviolet (UV) irradiation through a photomask, it would be possible to attain desired tribological performance by rational design of the pattern. In this research, we developed coarse-grained molecular dynamics simulations to investigate the effect of masked UV irradiation on the distribution of monolayer lubricant films coated over solid surfaces. Consistent with experimental results, the simulation results showed that masked UV irradiation induces molecular flow from non-irradiated toward irradiated areas, and thereby a patterned surface structure with thicker lubricant in the irradiated area than in the non-irradiated area. The lubricant films, however, remained monolayer even in the UV-irradiated area. Our simulation results demonstrated that, rather than stacking of lubricant molecules, the patterned surface structure is caused by the stretch of the lubricant molecules in the film thickness direction following the increase of molecule density in the irradiated area.

A non-labeled DNA biosensor based on light addressable potentiometric sensor modified with TiO2 thin film

Titanium dioxide (TiO(2)) thin film was deposited on the surface of the light addressable potentiometric sensor (LAPS) to modify the sensor surface for the non-labeled detection of DNA molecules. To evaluate the effect of ultraviolet (UV) treatment on the silanization level of TiO(2) thin film by 3-aminopropyltriethoxysilane (APTS), fluorescein isothiocyanate (FITC) was used to label the amine group on the end of APTS immobilized onto the TiO(2) thin film. We found that, with UV irradiation, the silanization level of the irradiated area of the TiO(2) film was improved compared with the non-irradiated area under well-controlled conditions. This result indicates that TiO(2) can act as a coating material on the biosensor surface to improve the effect and efficiency of the covalent immobilization of biomolecules on the sensor surface. The artificially synthesized probe DNA molecules were covalently linked onto the surface of TiO(2) film. The hybridization of probe DNA and target DNA was monitored by the recording of I-V curves that shift along the voltage axis during the process of reaction. A significant LAPS signal can be detected at 10 micromol/L of target DNA sample.

The Proteasome Is an Integral Part of Solar Ultraviolet A Radiation-induced Gene Expression

Solar ultraviolet (UV) A radiation is a well known trigger of signaling responses in human skin fibroblasts. One important consequence of this stress response is the increased expression of matrix metalloproteinase-1 (MMP-1), which causes extracellular protein degradation and thereby contributes to photoaging of human skin. In the present study we identify the proteasome as an integral part of the UVA-induced, intracellular signaling cascade in human dermal fibroblasts. UVA-induced singlet oxygen formation was accompanied by protein oxidation, the cross-linking of oxidized proteins, and an inhibition of the proteasomal system. This proteasomal inhibition subsequently led to an accumulation of c-Jun and phosphorylated c-Jun and activation of activator protein-1, i.e. transcription factors known to control MMP-1 expression. Increased transcription factor activation was also observed if the proteasome was inhibited by cross-linked proteins or lactacystin, indicating a general mechanism. Most importantly, inhibition of the proteasome was of functional relevance for UVA-induced MMP-1 expression, because overexpression of the proteasome or the protein repair enzyme methionine sulfoxide reductase prevented the UVA-induced induction of MMP-1. These studies show that an environmentally relevant stimulus can trigger a signaling pathway, which links intracellular and extracellular protein degradation. They also identify the proteasome as an integral part of the UVA stress response.