A laser system for the parametric amplification of electromagnetic fields in a microwave cavity.

We describe recent improvements in the development of the high power laser system used in the motion induced radiation (MIR) experiment to amplify electromagnetic fields inside a microwave cavity. The improvements made on the oscillator stabilization, the pulse train shaping device, and the spatial beam uniformity are reported.

50-mJ macro-pulses at 1064 nm from a diode-pumped picosecond laser system.

Pulse-picking from a 100-mW cw mode-locked seeder, a hybrid master-oscillator power-amplifier (MOPA) system, based on Nd:YVO4 and Nd:YAG amplifier modules, has been developed, delivering single-pulses of 8.6 ps at 455-MHz repetition-rate, bunched into ~1-µs trains of 50 mJ ("macro-pulses"). The output beam is linearly polarized and nearly diffraction limited up to the maximum macro-pulse repetition-rate of 50 Hz. The single-pulse peak power and the macro-pulse duration and energy are quite suitable for high-energy nonlinear optical applications such as low-threshold synchronously-pumped parametric converters in the mid infrared. The impact on the overall efficiency of saturation distortion of the macro-pulse envelope as well as of amplified spontaneous emission (ASE) is considered. The managing of the envelope distortion compensation and of the ASE suppression by means of fast saturable absorbers is reported.

Compact, 1.5 mJ, 450 MHz, CdSiP2 picosecond optical parametric oscillator near 6.3 µm.

We report a compact, efficient, high-energy, and high-repetition-rate mid-IR picosecond optical parametric oscillator (OPO) based on the new nonlinear material CdSiP(2) (CSP). The OPO is synchronously pumped by a master oscillator power amplifier system at 1064.1 nm, providing 1 µs long macropulses constituting 8.6 ps micropulses at 450 MHz, and it can be tuned over 486 nm across 6091-6577 nm, covering the technologically important wavelength range for surgical applications. Using a compact (∼30 cm) cavity and improved, high-quality nonlinear crystal, idler macropulse energy as high as 1.5 mJ has been obtained at 6275 nm at a photon conversion efficiency of 29.5%, with >1.2 mJ over more than 68% of the tuning range, for an input macropulse energy of 30 mJ. Both the signal and idler beams are recorded to have good beam quality with a Gaussian spatial profile, and the extracted signal pulses are measured to have durations of 10.6 ps. Further, from the experimentally measured transmission data at 1064 nm, we have estimated the two-photon absorption coefficient of CSP to be ß=2.4 cm/GW, with a corresponding energy bandgap, E(g)=2.08 eV.

Can cognitive and behavioural disorders differentiate frontal variant-frontotemporal dementia from Alzheimer's disease at early stages?

Frontal variant-Frontotemporal dementia (fvFTD) and Alzheimer's disease (AD) patients matched for severity of dementia at the Clinical Dementia Rating (CDR) received neuropsychological testing in order to explore if the dysexecutive disorder might characterise fvFTD at early stage, when AD is dominated by the episodic memory defect. We also determined if the behavioural syndrome was more severe in fvFTD than AD, and if specific patterns of behavioural symptoms could differentiate the two types of dementia, using the Neuropsychiatry Inventory (NPI). AD patients performed worse than fvFTD not only in memory but also in executive tasks. Apathy and eating disorders proved to be more severe or frequent in fvFTD even if the two groups did not differ in the total NPI score. CDR score significantly correlated with the NPI score in fvFTD and with the MMSE in AD. Our data confirm that the memory disorders may differentiate the two types of dementia; however, the dysexecutive syndrome is as severe, and even more severe in AD. The severity of the behavioural syndrome is comparable in the two groups but the nature of the behavioural disorders may vary to some extent. We conclude that AD dementia at early stage is a behavioural-cognitive syndrome, while in fvFTD the behavioural disorders appear when the cognitive deficit is still relatively mild.

Peripheral blood stem cell collection from G-CSF-stimulated unrelated donors for second transplant.

Peripheral blood stem cells (PBSCs) collected following stimulation with cytokines are commonly used for autologous haematopoietic transplants. Currently, PBSCs are being used for syngeneic or allogeneic transplants from matched or haploidentical donors. However, many issues are still unanswered regarding the early or late side-effects cytokines have on recipients and on healthy donors. The aims of this paper were to evaluate the experience acquired worldwide in this field, to define the acceptability of stem cell donation by G-CSF-stimulated apheresis from unrelated donors after the failure of a first donation, and to assess side-effects of G-CSF on unrelated donors. The use of PBSCs has increased tremendously over the last few years and in the near future PBSCs will probably become the most relevant source of stem cells. Studies conducted so far have definitely concluded that G-CSF is safe and well tolerated. Results observed in transplants utilizing marrow stem cells compared with results obtained in transplants utilizing PBSCs have shown that patients undergoing this latter procedure recover earlier, require a lower number of transfusions and spend fewer days in hospital with a consequent decrease in costs. We concluded that a second transplant by G-CSF-stimulated apheresis from an unrelated donor is definitely acceptable and we designed a prospective study to better define all controversial aspects. Donors will be given 10 microg/kg/day of G-CSF subcutaneously for 5 days. One or two PBSC collection procedures will be performed: the first on day 5 and the second, if necessary, on day 6. Donors will be surveyed and blood counts monitored in a standardized manner during the process.

High-Repetition-Rate Q-Switched Diode-Pumped Nd:YAG Laser at 1.444 mum.

A diode-pumped Q-switched Nd:YAG laser that operates at the eye-safe 1444 nm wavelength has been developed. When pumped by a 10-W fiber-coupled array at 808 nm, it generated 1 W in cw operation and 560 mW at 20-kHz repetition rate with active Q-switching. Design issues such as thermal lensing characterization and beam quality are discussed.

Bankart-Delitala surgery in the treatment of recurrent anterior dislocation of the shoulder.

The study analyzes the results obtained when Bankart-Delitala surgery was used to treat recurrent anterior dislocation of the shoulder. A group of 30 patients were submitted to clinical and functional follow-up based on the Rowe system; 15 of the patients also underwent isokinetic testing. The data obtained were interpreted based on the Rowe system, but also analytically and statistically. The authors conclude that Bankart-Delitala surgery constitutes an effective surgical option in the treatment of recurrent anterior dislocation of the shoulder.

Design and characterization of a diode-pumped, single longitudinal and transverse mode, intracavity-doubled cw Nd:YAG laser.

We report on the experimental results of a diode-pumped, intracavity-doubled cw Nd:YAG laser, pumped by a 10-W fiber-coupled semiconductor laser at 808 nm and emitting as much as 600 mW in a stable single longitudinal mode and TEM(00) spatial mode. We discuss the main issues of the resonator design and the optimization of the intracavity second harmonic conversion by interpreting our results using simple models. Improvements for the current project are also discussed.

All-solid-state picosecond tunable source of near-infrared radiation.

A quasi-cw diode-pumped Nd:YAG laser, mode locked by a nonlinear mirror and stabilized by an acousto-optic modulator, has been developed that generates 31-ps, 23-microJ pulses. Employing this source with a periodically poled lithium niobate crystal in a traveling-wave geometry, we obtained extracavity frequency conversion with pump depletion of as much as 62% in the near infrared (1.46- 1.56 microm) with a pulse spectral width of 1.5nm and a beam quality M(2)=1.7.

High-power diode-pumped picosecond Nd(3+):YVO(4) laser.

A diode-pumped Nd(3+):YVO(4) laser passively mode locked by a nonlinear mirror based on second-harmonic generation has been developed. Pumping with a fiber-coupled 10-W diode array, we generated nearly diffraction limited, linearly polarized 11-ps pulses at 1064nm, with average power of 2.7 W at a 150-MHz repetition rate. Pulses as short as 7.9 ps were measured with reduced output power (1.35 W) by optimal focusing in the nonlinear crystal.

Allogeneic transplants of rhG-CSF-mobilized peripheral blood stem cells (PBSC) from normal donors. GITMO. Gruppo Italiano Trapianto di Midollo Osseo.

There is a growing interest in the use of peripheral blood stem cells (PBSC) for allogeneic transplantation. This is due in part to the idea that, as with autologous transplantation, increasing the number of allogeneic hemopoietic progenitors infused may lead to reduced complications. However, introducing the PBSC technique into allogeneic transplants implies theoretical as well as ethical problems involving both patient and donor. We are still uncertain whether the PBSC technique will result in an increase of GVHD or (better) of GVL. G-CSF, necessary for effective PBSC mobilization, is safe but its use in normal subjects should be regarded with caution. For this reason, a Study Committee promoted by the GITMO (Gruppo Italiano Trapianto di Midollo Osseo) evaluated the key aspects of allogeneic PBSC collection and transplantation. The present paper summarizes the scientific data and suggests some guidelines for the introduction of allogeneic PBSC transplantation into clinical practice. The procedure should be considered experimental and the Committee strongly recommends the use of allogeneic PBSC in experienced centers, initially in patients with advanced disease. The donor should be given a complete explanation of the advantages and risks of G-CSF therapy, leukapheresis and general anesthesia. A careful monitoring of both patient and donor should also be included to watch for short-term and long-term side effects.

Ultrasound guided fineneedle aspiration of impalpable breast nodules.

AIMS: This study was designed in an attempt to improve the sensitivity of cytologic examination of fineneedle aspiration biopsies. METHODS AND RESULTS: A prospective study was carried out on 79 patients with breast lesions less than 1 cm in diameter and clinically impalpable who were referred to the Radiodiagnostics Section of the Ca' Granda Hospital of Milan in 1990 and 1991 for mammographic and ultrasound verification. The examination was carried out using a high frequency (10 MHz) ultrasound probe to which an aspiration needle had been soldered. This made it possible to quickly and accurately reach the target nodule and thus gave a high sensitivity of the examination (93%). However, attachment of the needle to the probe prevented sampling from other points of the nodule and was responsible for the slight increase in number of inadequate samplesfi which in turn worsened the specificity of the test (86%). To check the gold standard of the examination, all the patients with positive or doubtful aspirations underwent surgical biopsy, whereas strict radiologic controls were performed in the negative cases. CONCLUSIONS: Ultrasound-guided fineneedle aspiration may have advantages over needle aspiration performed with the stereotactic radiologic technique. The needle can be monitored even if the patient moves; even deep, peripheral nodules as well as those near a prosthesis can be reached; repeated samples can be taken, and costs are limited.

Exploiting the Z-scan method for mode-locked laser design.

We present a novel interpretation of Kerr lens mode locking based on the Z-scan operating principle and derive a few practical criteria for application to mode-locked solid-state laser systems.

Time-resolved M(2) of nanosecond pulses from a Q-switched variable-reflectivity-mirror Nd:YAG laser.

Time-resolved M(2) numerical computation and experimental measurements of nanosecond pulses from a Q-switched variable-reflectivity-mirror Nd:YAG laser are presented for the first time to our knowledge. The beam quality parameter is seen to vary approximately from 1 at the beginning to 2 at the end of a high-energy pulse, with a value of 1.35 at the peak of the pulse, which also corresponds to the M(2) obtained from the time-averaged detection of the pulse profile.

Beam quality measurement of laser pulses by nonlinear optical techniques.

A novel method for measuring the beam quality of short, powerful laser pulses is presented. The method is based on the Z-scan technique used to investigate the nonlinear susceptibilities of optical materials. It is shown that both two-photon absorption and nonlinear refraction of a nonlinear sample can be used to obtain information about the spatial quality of the pulses.