| 1. |
- Bandyopadhyay, S., et al.
(författare)
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A statistical approach to determine process parameter impact in Nd : YAG laser drilling of IN718 and Ti-6Al-4V sheets
- 2005
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Ingår i: Optics and lasers in engineering. - 0143-8166 .- 1873-0302. ; 43:2, s. 163-182
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Tidskriftsartikel (refereegranskat)abstract
- The numerous unique advantages afforded by pulsed Nd:YAG laser systems have led to their increasing utility for producing high aspect ratio holes in a wide range of materials. Notwithstanding the growing industrial acceptance of the technique, the increasingly tighter geometrical tolerances and more stringent hole quality requirements of modern industrial components demand that "defects" such as taper, recast, spatter etc., in laser-drilled holes are minimized. Process parameters like pulse energy, pulse repetition rate, pulse duration, focal position, nozzle standoff, type of gas and gas pressure of the assist gas are known to significantly influence hole quality during laser drilling. The present study reports the use of Taguchi design of experiments technique to study the effects of the above process variables on the quality of the drilled holes and ascertain optimum processing conditions. Minimum taper in the drilled hole was considered as the desired target response. The entire study was conducted in three phases:(a) screening experiments, to identify process variables that critically influence taper in laser drilled holes, (b) Optimization experiments, to ascertain the set of parameters that would yield minimum taper and (c) validation trials, to assess the validity of the experimental procedures and results. Results indicate that laser drilling with focal position on the surface of the material being drilled and employing low level values of pulse duration and pulse energy represents the ideal conditions to achieve minimum taper in laser-drilled holes. Thorough assessment of results also reveals that the laser-drilling process, optimized considering taper in the drilled hole as the target response, leads to very significant improvements in respect of other hole quality attributes of interest such as spatter and recast as well. © 2004 Elsevier Ltd. All rights reserved.
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| 2. |
- Andreasson, Joakim, 1973, et al.
(författare)
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A molecule-based 1 : 2 digital demultiplexer
- 2007
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:38, s. 14274-14278
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Tidskriftsartikel (refereegranskat)abstract
- A trichromophoric molecule consisting of a porphyrin linked to both a dihydropyrene and a dihydroindolizine-type photochrome, in combination with a third harmonic generating crystal, functions as a 1:2 digital demultiplexer with photonic inputs and outputs. Each of the two photochromes may be cycled independently between two metastable forms, leading to four photoisomers, three of which are used in the demultiplexer. These isomers interact photochemically with the porphyrin in order to yield the demultiplexer function. With the address input (1064-nm light) turned off, one Output of the device (porphyrin fluorescence) tracks the state of the data input (532-nm light). When the address input is turned on, the second output (absorbance at 572 nm) tracks the state of the data input, while the first output remains off. The demultiplexer does not require chemical or electrical inputs, and can cycle through its operational sequences multiple times.
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| 3. |
- Andreasson, Joakim, 1973, et al.
(författare)
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Molecular 2 : 1 digital multiplexer
- 2007
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Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 46:6, s. 958-961
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Tidskriftsartikel (refereegranskat)abstract
- (Chemical Equation Presented) Two into one: A porphyrin linked to two photochromic moieties performs as a 2:1 digital multiplexer (MUX). It takes heat and red light as the two inputs (in 1 and in 2), and a third switchable input (green light, sel) selects whether the output (porphyrin fluorescence) reports the state of in 1 or in 2. Each photochromic moiety may be independently photoisomerized to isomers that quench the porphyrin fluorescence. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
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| 4. |
- Carroll, DC, et al.
(författare)
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Active manipulation of the spatial energy distribution of laser-accelerated proton beams
- 2007
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 76:065401(R), s. 1-065401
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Tidskriftsartikel (refereegranskat)abstract
- The spatial energy distributions of beams of protons accelerated by ultrahigh intensity (>10^19 W/cm2) picosecond laser pulse interactions with thin foil targets are investigated. Using separate, low intensity (<10^13 W/cm2) nanosecond laser pulses, focused onto the front surface of the target foil prior to the arrival of the high intensity pulse, it is demonstrated that the proton beam profile can be actively manipulated. In particular, results obtained with an annular intensity distribution at the focus of the low intensity beam are presented, showing smooth proton beams with a sharp circular boundary at all energies, which represents a significant improvement in the beam quality compared to irradiation with the picosecond beam alone.
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| 5. |
- McKenna, P., et al.
(författare)
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Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets
- 2008
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 26:4, s. 591-596
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Tidskriftsartikel (refereegranskat)abstract
- The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients due, to self-focusing Of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy.
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| 6. |
- Straight, S. D., et al.
(författare)
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Molecular AND and INHIBIT gates based on control of porphyrin fluorescence by photochromes
- 2005
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Ingår i: Journal of the American Chemical Society. ; 127:26, s. 9403-9409
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Tidskriftsartikel (refereegranskat)abstract
- A molecular triad consisting of a porphyrin (P) covalently linked to two photochromes - one from the dihydroindolizine family (DHI) and one from the dihydropyrene family (DHP) - has been synthesized and found to act as either a molecular AND logic gate or an INHIBIT gate, depending on the inputs and initial state of the photochromes. The basis of these functions is quenching of porphyrin fluorescence (output of the gates) by the photochromes. The spiro form of DHI does not quench porphyrin fluorescence, whereas its betaine isomer strongly quenches by photoinduced electron transfer. DHP also quenches porphyrin fluorescence, but its cyclophanediene isomer does not. The triad has been designed using suitable energetics and electronic interactions, so that although these quenching phenomena may be observed, independent isomerization of the attached photochromes still occurs. This makes it possible to switch porphyrin fluorescence on or off by isomerization of the photochromes using various combinations of inputs such as UV light, red light, and heat.
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| 7. |
- Nandula, Seshagiri R., et al.
(författare)
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Female mice are more susceptible to developing inflammatory disorders due to impaired transforming growth factor beta signaling in salivary glands
- 2007
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Ingår i: Arthritis and Rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 56:6, s. 1798-1805
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Transforming growth factor 13 (TGF)3) plays a key role in the onset and resolution of autoimmune diseases and chronic inflammation. The aim of this study was to delineate the precise function of TGF beta signaling in salivary gland inflammation. Methods. We impaired TGF beta signaling in mouse salivary glands by conditionally inactivating expression of TGF beta receptor type I (TGF beta RI), either by using mouse mammary tumor virus-Cre mice or by delivering adenoviral vector containing Cre to mouse salivary glands via retrograde infusion of the cannulated main excretory ducts of submandibular glands. Results. TGF beta RI-conditional knockout (TGF beta RI-coko) mice were born normal; however, female TGF beta RI-coko mice developed severe multifocal inflammation in salivary and mammary glands and in the heart. The inflammatory disorder affected normal growth and resulted in the death of the mice at ages 4-5 weeks. Interestingly, male TGF beta RI-coko mice did not exhibit any signs of inflammation. The female TGF beta RI-coko mice also showed an increase in Th1 proinflammatory cytokines in salivary glands and exhibited an up-regulation of peripheral T cells. In addition, these mice showed an atypical distribution of aquaporin 5 in their salivary glands, suggesting likely secretory impairment. Administration of an adenoviral vector encoding Cre recombinase into the salivary glands resulted in inflammatory foci only in the glands of female TGF beta RI-loxP-flanked (floxed) mice (TGF beta RI-f/f mice), but not in those of male and female wild-type mice or male TGF beta RI-f/f mice. Conclusion. These results suggest that female mice are uniquely more susceptible to developing inflammatory disorders due to impaired TGF beta signaling in their salivary glands.
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