Fused silica ablation by double ultrashort laser pulses with dual wavelength and variable delays.

Today, glass and other similar dielectric materials are widely used in modern manufacturing. However, glass is a brittle and a heat sensitive material. Laser technology is used to process glass but quality and throughput are still a key issue. In the present paper, we investigate dual-wavelength double ultrashort laser pulses in order to control free electrons dynamics and subsequent ablation for fused silica processing, and further improve the understanding of this laser-material interaction. We used a high average power Yb-doped femtosecond laser source (100 W) with two optical lines exhibiting different pulse durations and wavelengths (500 fs at 515 nm; and 1 or 10 ps at 1030 nm) with various fluences and delays. The best configuration in terms of ablation efficiency is expected to take place when the green pulse first induces free electrons, followed by their heating by the red pulse. The obtained results are discussed in terms of optical transmission as well as ablated volume, and are compared with single pulse ablation. Our experimental results are supported by absorbed energy density calculations based on a model considering the two-color laser induced electron dynamics, including photoionization, laser heating of free electrons, and their recombination. We demonstrate that there is an optimal cooperating effect between the two sub-pulses for a 1-ps delay, nevertheless there is no beneficial effect in splitting the beam for optimizing fused silica ablation compared with the single-pulse green configuration.

Pulse to pulse control for highly precise and efficient micromachining with femtosecond lasers.

Micromachining with high repetition rate femtosecond lasers and galvo scanners shows some limitations in the pulses positioning accuracy due to the galvo mirrors acceleration. This is particularly evident during scan speed or direction changes, resulting in a poor quality and overtreatment e.g. in corners. Several scanning approaches have been proposed to tackle these issues like the so-called skywriting (SW) and the pulse-on-demand (POD) being the last limited to ns lasers, moderate pulse repetition rates and scan speeds. Recently, POD approach has been extended to femtosecond laser sources with high power and high repetition rate. Here, for the first time, we explored the huge potential in laser micromachining of femtosecond POD technology associated to a fast galvo scanner. We tested an innovative set-up allowing for precise laser triggering at the requested time and position for MHz repetition rate and scan speed as high as 20 m/s. The pulse position accuracy of the system has been estimated to be ≤ 1µm whilst performances have been evaluated in comparison to conventional scanning and SW. Finally, we report the results of an engraving test on stainless steel. The advantages of the approach we propose are clearly shown in terms of machining quality and precision with respect to conventional scanning and reduction of the processing time by ≈ 40% with respect to SW.

Effective parameters for film-free femtosecond laser assisted bioprinting.

Optimal conditions for femtosecond laser bioprinting setup are reported on in terms of numerical aperture and accuracy of focal spot location for different bioinks to deposit without using a metallic absorbing layer.

Exogenous connective tissue growth factor preserves the hair-inductive ability of human dermal papilla cells.

Connective tissue growth factor influences human dermal papilla cells' hair inductive ability through several signaling pathways.

HIV prevention for injection drug users in China and Vietnam: policy and research considerations.

A pattern of serious injection drug user (IDU) driven HIV epidemics in Asia, with emerging evidence of generalization through heterosexual transmission, indicates the need for interventions focusing on both drug- and sex-related risk reduction. In a cross-border HIV prevention project for IDUs in northern Vietnam and southern China, peer educators disseminated risk reduction information to IDUs in the community and provided 20,000-25,000 sterile needles/syringes and 4,000-6,000 condoms per month. Since implementation of these interventions, the frequency of both injecting and sexual risk behaviours fell significantly, HIV prevalence among IDUs declined or stabilized, and HIV incidence dropped. There is official support for harm reduction interventions in both countries but this appears precarious in view of persistently powerful political and financial support for a law enforcement approach. Moreover, the simultaneous pursuit of inconsistent policies can have negative effects on the implementation of interventions. A harmonized and consistent policy environment is needed. Most of the evidence for efficacy of community-based HIV prevention comes from the developed world, but well-designed evaluations of such interventions in Asia and elsewhere in the developing world would have a better chance to influence policy decisions there. A synergistic approach to research, policy development, and service delivery is best calculated to achieve positive results in the struggle against HIV/AIDS in developing countries.

[Surgical therapy of malignant melanoma of the external ear]. / Zur chirurgischen Therapie des malignen Melanoms der Ohrmuschel.

METHOD: The data from our patients of the last 10 years were evaluated in relation to survival and recurrence. RESULTS: Very different surgical therapy-in some cases due to refusal of the therapy suggested-was performed in eight patients (including wedge shaped excision as well as ablation of the auricle). The mean survival ranged from 40 months up to the present. One patient died due to a local recurrence and regional and systemic metastases. One patient experienced local recurrence but is still well 16 months after he underwent surgical revision. Two patients died independently of the tumor. DISCUSSION: Comparison of our results with those of other studies confirms that the extent of the applied resection has of minor effect on recurrence and survival for this disease. Tumor thickness is the most important independent prognostic factor.

Interferometric Measurement of Resonance Transition Wavelengths in C iv, Si iv, Al iii, Al ii, and Si ii.

We have made the first interferomeric measurements of the wavelengths of the important ultraviolet diagnostic lines in the spectra C iv near 155 nm and Si iv near 139 nm with a vacuum ultraviolet Fourier transform spectrometer and high-current discharge sources. The wavelength uncertainties were reduced by 1 order of magnitude for the C iv lines and by 2 orders of magnitude for the Si iv lines. Our measurements also provide accurate wavelengths for resonance transitions in Al iii, Al ii, and Si ii.

Effects of a 2-hour cheerleading practice on dynamic postural stability, knee laxity, and hamstring extensibility.

STUDY DESIGN: One group; pretest, posttest design. OBJECTIVE: To assess the effect of a 2-hour cheerleading practice on the anterior knee laxity, hamstring extensibility, and dynamic postural stability (preferred stance leg during vision-denied unilateral stance) of 17 nonimpaired members of a college cheerleading team (8 females, 9 males; 18-25 years old). BACKGROUND: Anterior knee laxity and hamstring extensibility increase following exercise. The relationship between exercise induced anterior knee laxity, hamstring extensibility, and dynamic postural stability, however, has not been examined. METHODS AND MEASURES: Pre- and postpractice measurements were compared using paired t tests and Bonferroni's correction for multiple comparisons. A 3 x 2 analysis of variance (force level applied to the arthrometer by condition) and Tukey honest significant difference post hoc test were used to evaluate specific arthrometer force level by condition effects (P < .05). RESULTS: Mean laxity at 133 N and hamstring extensibility increased (mean +/- SD) 1.5 +/- 1 mm and 3 +/- 4 degrees, respectively, following practice. Mean medial-lateral stabiliometer platform angulation (frontal plane position) moved medially following practice (2.9 +/- 3 degrees) and produced a weak correlation with increased knee laxity (r = 0.58). Hamstring extensibility did not significantly relate to stabiliometry or knee laxity variables. CONCLUSIONS: The relationship between the medially directed platform angulation and the increase in anterior knee laxity following cheerleading practice suggests a relationship between subtalar joint position and anterior cruciate ligament strain.

[Prosthetic-implantology defect treatment concept for oral rehabilitation of the mandibular area after tumor treatment]. / Defektprothetisch-implantologisches Behandlungskonzept zur oralen Rehabilitation der unteren Mundhöhlenetage nach Tumorbehandlung.

Between 1988 and 1997, tumor resection was carried out in 18 irradiated patients group 1: 36-72 Gy. 83 implants) and 22 nonirradiated patients (group 2: 92 implants) in the mandible and floor of the mouth, and these patients subsequently underwent mandibular endosseous implant rehabilitation. A total of 23 patients were treated with exclusively implant-supported prostheses, and 16 with implant tissue-supported constructions. Between 1988 and 1991, group 1 and 2 patients received implant tissue-supported prostheses (using two to four implants). Due to prosthesis-related pressure lesions, the strategy has now been changed. Since 1992, group 1 patients have received exclusively implant-supported prostheses (using five to six implants), while group 2 patients have received implant tissue-supported constructions (using four implants). Special criteria for the success of implant-supported maxillofacial prosthetics were drawn up. With an average follow-up period of 37 months 160 fixtures (91%) were clinically osseointegrated. Both types of restoration provided sufficient oral rehabilitation. However, only completely implant-supported prostheses avoided soft tissue ulcers. The overall success rate was about 77% after 7 years in group 1 and about 87% after 9 years in group 2. With regard to implants placed after strategy change, the 5-year success rate was approximately 86% (group 1) and 94% (group 2). In irradiated patients, an exclusively implant-supported prosthesis without any mucosal contact (thus avoiding soft tissue ulcers with a potential to develop osteoradionecrosis) should therefore be fabricated. Implant tissue-supported restoration is also possible in nonirradiated oral cancer patients.

Surface tension measurements on pharyngeal and tracheal aspirate samples from newborns without and with respiratory distress syndrome.

A rapid test determining surfactant deficiency or dysfunction might help in controlling therapy of respiratory distress syndrome (RDS). Forty tracheal aspirate samples (TA) from 40 newborns with RDS (group 1) and 46 pharyngeal from 46 newborns without RDS (reference group) were analyzed by surface tension measurement with the pulsating bubble surfactometer. Five surface tension parameters were compared. Marked differences between both groups could be noted for the parameters: minimum surface tension (gamma min) and stability index (S), while maximum surface tension (gamma max), surface tension after a 10-second adsorption period and hysteresis area did not have striking differences. The parameters gamma min and S have the highest diagnostic value for determining surfactant deficiency or dysfunction. For a rapid test it is sufficient to compare gamma min with reference values, because S is calculated from gamma min and gamma max.

Radiometric characterization of a Penning discharge in the vacuum ultraviolet.

We present a Penning discharge as a possible radiometric transfer standard source in the vacuum UV, primarily in the spectral region below 20 nm. Following the concept of Finley et al., we have designed a Penning source using NdFeB permanent magnets. Emphasis was put on simple operation, quick electrode exchangeability, and easy source readjustment. The radiant intensities of the emission lines from different ionization stages of both buffer gas atoms and atoms sputtered from the cathodes have been studied in various discharge conditions. For selected Al and buffer gas emission lines we determined the absolute radiant intensities by a comparison with the calculable spectral radiant power of the Berlin Electron Storage Ring. A comparison with data from our hollow-cathode transfer standard source is given.

Quantitative glomerular morphology of the normal and diabetic baboon kidney.

This is a study of quantitative glomerular morphology in 14 normal and 6 long-term diabetic female baboons between 3 and 25 years of age. In the normal female baboon, peripheral glomerular capillary basement membrane thickness increased until around 10 years of age, reached a plateau between 10 and 20 years of age, and possibly decreased at 25 years of age. Mean value for young (3 to 7 years of age) and older (10 to 25 years of age) controls were 266 nm and 329 nm respectively. Fractional volumes of mesangial matrix (8.9%) and mesangial cells (6.8%) were not affected by age. Glomerular basement membrane thickness and the volume of mesangial matrix increased progressively in female baboons with poorly controlled pancreatectomy-induced diabetes, while the volume of mesangial cells remained unchanged. After 106 to 145 months of diabetes, glomerular basement membrane thickness and the volume of mesangial matrix were 558 nm and 18.7% respectively. These values were significantly greater than those of the age-matched controlled (p = less than 0.05). By light and electron microscopy, the normal baboon glomerular morphology, morphometric measurements and changes with age were similar to those in man. The renal changes in diabetic baboons were also similar in morphology and rate of development to those of mild to moderate diffuse diabetic glomerulosclerosis in humans, indicating that the baboon is an ideal model for the long-term study of diabetic glomerulosclerosis. The presence of considerable interanimal variability in the degree of glomerulosclerosis attained after prolonged diabetes suggested that glomerulosclerosis progressed at different rates in these models. The reason for this was not apparent.

Effects of a procaine preparation (Gerovital H3) in hospitalized geriatric patients: a double-blind study.

The effects of Gerovital H3 (a specially stabilized form of procaine hydrochloride) on geriatric psychiatric patients were assessed in a double-blind study at Bronx State Hospital. The mean age of the subjects was 73 years and the average rating for the severity of organic symptoms was "moderate." During the first six weeks of study, the patients were each given a 5-ml injection of either Gerovital or placebo (saline) intramuscularly three times a week. This dosage was doubled to 10 ml per injection during the second six weeks. Nine Gerovital and 10 control subjects completed the first six weeks; and 6 Gerovital and 7 control subjects completed the entire 12-week study. Objective rating scales were used to evaluate patients on measures of interpersonal functioning, cognitive ability, psychiatric symptoms, and urine and blood chemical findings. All subjects were assessed before treatment and at six weeks and twelve weeks of the study. Side effects were recorded at two-week intervals. On most measures the variability between subjects was quite large, whereas differences between average scores for the two groups usually were small The few significant differences showed no systematic pattern and would be expected to occur by chance alone when so many statistical comparisons are made. The overall results of this double-blind study strongly indicated that, among these hospitalized geriatric patients with organic symptoms, Gerovital H3 had no ameliorative effect on either psychologic or physiologic functioning.