Space-qualified laser system for the BepiColombo Laser Altimeter

The space-qualified design of a miniaturized laser for pulsed operation at a wavelength of 1064 nm and at repetition rates up to 10 Hz is presented. This laser consists of a pair of diode-laser pumped, actively q-switched Nd:YAG rod oscillators hermetically sealed and encapsulated in an environment of dry synthetic air. The system delivers at least 300 million laser pulses with 50 mJ energy and 5 ns pulse width (FWHM). It will be launched in 2017 aboard European Space Agency’s Mercury Planetary Orbiter as part of the BepiColombo Laser Altimeter, which, after a 6-years cruise, will start recording topographic data from orbital altitudes between 400 and 1500 km above Mercury’s surface.

Collimated Field Emission Beams from Metal Double-Gate Nanotip Arrays Optically Excited via Surface Plasmon Resonance

The generation of collimated electron beams from metal double-gate nanotip arrays excited by near infrared laser pulses is studied. Using electromagnetic and particle tracking simulations, we showed that electron pulses with small rms transverse velocities are efficiently produced from nanotip arrays by laser-induced field emission with the laser wavelength tuned to surface plasmon polariton resonance of the stacked double-gate structure. The result indicates the possibility of realizing a metal nanotip array cathode that outperforms state-of-the-art photocathodes.

Tissue Crowding Induces Caspase-Dependent Competition for Space.

Regulation of tissue size requires fine tuning at the single-cell level of proliferation rate, cell volume, and cell death. Whereas the adjustment of proliferation and growth has been widely studied [1, 2, 3, 4 and 5], the contribution of cell death and its adjustment to tissue-scale parameters have been so far much less explored. Recently, it was shown that epithelial cells could be eliminated by live-cell delamination in response to an increase of cell density [6]. Cell delamination was supposed to occur independently of caspase activation and was suggested to be based on a gradual and spontaneous disappearance of junctions in the delaminating cells [6]. Studying the elimination of cells in the midline region of the Drosophila pupal notum, we found that, contrary to what was suggested before, Caspase 3 activation precedes and is required for cell delamination. Yet, using particle image velocimetry, genetics, and laser-induced perturbations, we confirmed [ 6] that local tissue crowding is necessary and sufficient to drive cell elimination and that cell elimination is independent of known fitness-dependent competition pathways [ 7, 8 and 9]. Accordingly, activation of the oncogene Ras in clones was sufficient to compress the neighboring tissue and eliminate cells up to several cell diameters away from the clones. Mechanical stress has been previously proposed to contribute to cell competition [ 10 and 11]. These results provide the first experimental evidences that crowding-induced death could be an alternative mode of super-competition, namely mechanical super-competition, independent of known fitness markers [ 7, 8 and 9], that could promote tumor growth.

Does a pulsed mode offer advantages over a continuous wave mode for excisional biopsies performed using a carbon dioxide laser?

Animal studies of excisional biopsies have shown less thermal damage when a carbon dioxide (CO(2)) laser (10.6 μm) is used in a char-free (CF) mode than in a continuous-wave (CW) mode. The authors' aim was to evaluate and compare clinical and histopathologic findings of excisional biopsies performed with CW and CF CO(2) laser (10.6 μm) modes.

The effect of different pulse durations in the treatment of nail psoriasis with 595-nm pulsed dye laser: a randomized, double-blind, intrapatient left-to-right study

Several studies have proven the efficacy of pulsed dye laser (PDL) in the treatment of plaque type psoriasis. However, only two published studies indicate the effectiveness of PDL on nail psoriasis.

Tight contact technique during side-to-side laser tissue soldering of rabbit aortas improves tensile strength

BACKGROUND: Cerebral revascularization may be indicated either for blood flow preservation or flow augmentation, often in clinical situations where neither endovascular nor standard surgical intervention can be performed. Cerebral revascularization can be performed by using a temporary occlusive or a non-occlusive technique. Both of these possibilities have their specific range of feasibility. Therefore non-occlusive revascularization techniques have been developed. To further reduce the risks for patients, less time consuming, sutureless techniques such as laser tissue soldering are currently being investigated. METHOD: In the present study, a new technique for side-to-side anastomosis was developed. Using a "sandwich technique", two vessels are kept in close contact during the laser soldering. Thoraco-abdominal aortas from 24 different rabbits were analyzed for laser irradiation induced tensile strength. Two different irradiation modes (continuous and pulsed) were used. The results were compared to conventional, noncontact laser soldering. Histology was performed using HE, Mason's Trichrome staining. FINDINGS: The achieved tensile strengths were significantly higher using the close contact "sandwich technique" as compared to the conventional adaptation technique. Furthermore, tensile strength was higher in the continuously irradiated specimen as compared to the specimen undergoing pulsed laser irradiation. The histology showed similar denaturation areas in both groups. The addition of a collagen membrane between vessel components reduced the tensile strength. CONCLUSION: These first results proved the importance of close and tight contact during the laser soldering procedure thus enabling the development of a "sandwich laser irradiation device" for in vivo application in the rabbit.

Pulsed versus continuous wave CO2 laser excisions of 100 oral fibrous hyperplasias: a randomized controlled clinical and histopathological study

BACKGROUND In experimental animal studies, pulsing the CO2 laser beam has been shown to reduce the thermal damage zone of excised oral mucosal tissue. However, there is still controversy over whether this is borne out under clinical conditions. OBJECTIVE To compare the outcome following excisional biopsies of fibrous hyperplasias using a pulsed (cf) versus a continuous wave (cw) CO2 laser mode regarding the thermal damage zone, duration of surgeries, intra- and postoperative complications, postoperative pain sensation, scarring and/or relapse during the initial 6 months. MATERIALS AND METHODS One hundred Swiss-resident patients with a fibrous hyperplasia in their buccal mucosa were randomly assigned to the cw mode (5 W) or the cf mode (140 Hz, 400 microseconds, 33 mJ, 4.62 W) group. All excisions were performed by one single oral surgeon. Postoperative pain (2 weeks) was recorded by visual analogue scale (VAS; ranging from 0 to 100). Intake of analgesics and postoperative complications were recorded in a standardized study form. The maximum width of the collateral thermal damage zone was measured (µm) in excision specimens by one pathologist. Intraoral photographs at 6-month follow-up examinations were evaluated regarding scarring (yes/no). RESULTS Median duration of the excision was 65 seconds in the cw and 81 seconds in the cf group (P = 0.13). Intraoperative bleeding occurred in 16.3% of the patients in the cw and 17.7% of the cf group. The median value of the thermal damage zone was 161(±228) μm in the cw and 152(± 105) μm in the cf group (P = 0.68). The reported postoperative complications included swelling in 19% and minor bleeding in 6% without significant differences between the two laser modes. When comparing each day separately or the combined mean VAS scores of both groups between Days 1-3, 1-7, and 1-15, there were no significant differences. However, more patients of the cw group (25%) took analgesics than patients of the cf group (9.8%) resulting in a borderline significance (P = 0.04). Scarring at the excision site was found in 50.6% of 77 patients after 6 months, and more scars were identified in cases treated with the cf mode (P = 0.03). CONCLUSIONS Excision of fibrous hyperplasias performed with a CO2 laser demonstrated a good clinical outcome and long-term predictability with a low risk of recurrence regardless of the laser mode (cf or cw) used. Scarring after 6 months was only seen in 50.6% of the cases and was slightly more frequent in the cf mode group. Based on the findings of the present study, a safety border of 1 mm appears sufficient for both laser modes especially when performing a biopsy of a suspicious soft tissue lesion to ensure a proper histopathological examination.

Laser ablation and induced nano-particle synthesis

Laser pulses are largely used for processing and analysis of materials and in particular for nano-particle synthesis. This paper addresses fundamentals of the generation of nano-materials following specific thermodynamic paths of the irradiated material. Computer simulations using the hydro code MULTI and the SESAME equation of state have been performed to follow the dynamics of a target initially heated by a short laser pulse over a distance comparable to the metal skin depth.

Measurement of the drift field in the ARGONTUBE LAr TPC with 266 nm pulsed laser beams

ARGONTUBE is a liquid argon time projection chamber (LAr TPC) with a drift field generated in-situ by a Greinacher voltage multiplier circuit. We present results on the measurement of the drift-field distribution inside ARGONTUBE using straight ionization tracks generated by an intense UV laser beam. Our analysis is based on a simplified model of the charging of a multi-stage Greinacher circuit to describe the voltages on the field cage rings.