Truncated Gaussian-Bessel beams for short-pulse processing of small-aspect-ratio micro-channels in dielectrics.

In order to control the length of micro-channels ablated at the surface of dielectrics, we use annular filtering apertures for tailoring the depth of focus of micrometric Gaussian-Bessel beams. We identify experimentally and numerically the appropriate beam truncation that promotes a smooth axial distribution of intensity with a small elongation, suitable for processing micro-channels of small aspect ratio. Single-shot channel fabrication is demonstrated on the front surface of a fused silica sample, with sub-micron diameter, high-quality opening, and depth of few micrometers, using 1 ps low-energy (< 0.45 µJ) pulse. Finally, we realize 10 × 10 matrices of densely packed channels with aspect ratio ~5 and a spatial period down to 1.5 µm, as a prospective demonstration of direct laser fabrication of 2D photonic-crystal structures.

High photon flux Kα Mo x-ray source driven by a multi-terawatt femtosecond laser at 100 Hz.

We develop a pulsed hard x-ray Kα source at 17.4 keV produced by the interaction of a multi-terawatt peak power infrared femtosecond laser pulse with a thick molybdenum (Mo) target at a 100 Hz repetition rate. We measure the highest Mo Kα photon production reported to date corresponding to a Kα photon flux of 1×1011 ph/(sr·s) and an estimated peak brightness of ∼2.5×1017 ph/(s·mm2·mrad2(0.1% bandwidth)) at ∼5×1018 W/cm2 driving laser intensity.

Bulk laser-induced damage threshold of titanium-doped sapphire crystals.

The bulk laser-induced damage threshold (LIDT) fluence of Ti:sapphire is determined under single-pulse irradiation from the femtosecond to nanosecond temporal regimes in the visible and near-infrared spectral domains. In the range of explored laser conditions, the LIDT fluence increases with both pulse duration and wavelength. The results are also compared to laser interaction with sapphire samples and show an increased resistance to laser damage when the material is doped with Ti(3+) ions. These conclusions are of interest for robust operation of high-peak-power femtosecond Ti:sapphire laser chains.

Surface ablation of corneal stroma with few-cycle laser pulses at 800 nm.

We report measurements of crater diameter and surface ablation threshold as a function of laser fluence in porcine corneal stroma and fused silica with pulse durations of 7 fs (2.7 optical cycles), 30 fs and 100 fs at 800 nm. For laser pulses with Gaussian radial intensity profile, we show experimentally that the square of the crater diameter is a linear function of the logarithm of the fluence in fused silica, while it is closer to a linear function of the fluence in corneal stroma. Extrapolating these relations to zero diameter indicates that for both media the minimum fluence required for surface ablation is reduced with shorter pulse duration. A simple theoretical model suggests that this effect is due to a more significant contribution of photoionization as the laser pulse duration shortens.

Monitoring photonic nanojets from microsphere arrays by femtosecond laser ablation of thin films.

By comparing finite-difference time-domain near field simulations and femtosecond laser ablation of thin films, we characterize in three dimensional-space photonic nanojets from microsphere arrays. We demonstrate periodic drilling of transparent films with thickness up to 100 nm (onto absorbing substrates) is feasible with 1-microm diameter silica spheres. Working with larger polystyrene spheres, the apparent increase of the propagation length of the photonic nanojets makes possible to drill films as thick as 500 nm. Interestingly, the lateral width of the produced craters can be maintained below 400 nm evidencing the low divergence of the nanojets. For backside illumination of the arrays, the ablation features are located at the top of the microspheres. We reveal field enhancements in and out the spheres as well as laser energy confinement at the particle substrate interface. The wide variety of features observed in the experiments open routes to fabricating nanomaterials.

Experimental investigation of size broadening of a Kα x-ray source produced by high intensity laser pulses.

The size of a hard Kα x-ray source ([Formula: see text] = 17.48 keV) produced by a high intensity femtosecond laser interacting with a solid molybdenum target is experimentally investigated for a wide range of laser intensity (I ~ 1017-2.8 × 1019 W/cm2) and for four values of the temporal contrast ratio (6.7 × 107 < CR < 3.3 × 1010). Results point out the size enlargement of the x-ray source with the increase of laser intensity and with the deterioration of temporal contrast. It amounts up to sixteen times the laser spot size at the highest laser intensity and for the lowest temporal contrast ratio. Using hydrodynamic simulations, we evaluate the density scale length of the pre-plasma L/λ just before the main pulse peak. This allows us to show that a direct correlation with the laser absorption mechanisms is not relevant to explain the large size broadening. By varying the thickness of the molybdenum target down to 4 µm, the impact of hot electron scattering inside the solid is also proved irrelevant to explain the evolution of both the x-ray source size and the Kα photon number. We deduce that the most probable mechanism yielding to the broadening of the source size is linked to the creation of surface electromagnetic fields which confine the hot electrons at the solid surface. This assumption is supported by dedicated experiments where the evolution of the size enlargement of the x-ray source is carefully studied as a function of the laser focal spot size for the highest contrast ratio.

Exploring phase contrast imaging with a laser-based Kα x-ray source up to relativistic laser intensity.

This study explores the ability of a hard Kα x-ray source (17.48 keV) produced by a 10 TW class laser system operated at high temporal contrast ratio and high repetition rate for phase contrast imaging. For demonstration, a parametric study based on a known object (PET films) shows clear evidence of feasibility of phase contrast imaging over a large range of laser intensity on target (from ~1017 W/cm2 to 7.0 × 1018 W/cm2). To highlight this result, a comparison of raw phase contrast and retrieved phase images of a biological object (a wasp) is done at different laser intensities below the relativistic intensity regime and up to 1.3 × 1019 W/cm2. This brings out attractive imaging strategies by selecting suitable laser intensity for optimizing either high spatial resolution and high quality of image or short acquisition time.

Impact of the pulse contrast ratio on molybdenum Kα generation by ultrahigh intensity femtosecond laser solid interaction.

We present an extended experimental study of the absolute yield of Kα x-ray source (17.48 keV) produced by interaction of an ultrahigh intensity femtosecond laser with solid Mo target for temporal contrast ratios in the range of 1.7 × 107-3.3 × 109 and on three decades of intensity 1016-1019 W/cm². We demonstrate that for intensity I ≥ 2 × 1018 W/cm² Kα x-ray emission is independent of the value of contrast ratio. In addition, no saturation of the Kα photon number is measured and a value of ~2 × 1010 photons/sr/s is obtained at 10 Hz and I ~1019 W/cm². Furthermore, Kα energy conversion efficiency reaches the same high plateau equal to ~2 × 10-4 at I = 1019 W/cm² for all the studied contrast ratios. This original result suggests that relativistic J × B heating becomes dominant in these operating conditions which is supposed to be insensitive to the electron density gradient scale length L/λ. Finally, an additional experimental study performed by changing the angle of incidence of the laser beam onto the solid target highlights a clear signature of the interplay between collisionless absorption mechanisms depending on the contrast ratio and intensity.

Dynamic magnetic resonance imaging of the breast: Comparison of gadobutrol vs. Gd-DTPA. / Resonancia magnética dinámica de mama: estudio comparativo de gadobutrol y Gd-DTPA.

OBJECTIVE: To compare the pharmacokinetic profile of gadobutrol versus Gd-DTPA in dynamic contrast-enhanced MRI (DCE-MRI) in patients with breast cancer. Secondary objectives included comparing the safety profiles and diagnostic efficacy of the two contrast agents for detecting additional malignant lesions. MATERIAL AND METHODS: This retrospective observational study included 400 patients with histologically confirmed breast cancer; 200 underwent DCE-MRI with Gd-DTPA (Magnevist®) and 200 underwent DCE-MRI with gadobutrol (Gadovist®). Pharmacokinetic parameters and signal intensity were analyzed in a region of interest placed in the area within the lesion that had greatest signal intensity in postcontrast sequences. We compared the two groups on pharmacokinetic variables (Ktrans, Kep, and Ve), time-signal intensity curves, and the number of additional malignant lesions detected. RESULTS: The relative signal intensity (enhancement) was higher with gadobutrol than with Gd-DTPA. Washout was lower with gadobutrol than with Gd-DTPA (46% vs. 58,29%, respectively; p=0,0323). Values for Ktrans and Kep were higher for gadobutrol (p=0,001). There were no differences in the number of histologically confirmed additional malignant lesions detected (p=0,387). CONCLUSIONS: Relative enhancement is greater with gadobutrol, but washout is more pronounced with Gd-DTPA. The number of additional malignant lesions detected did not differ between the two contrast agents. Both contrasts are safe.

Dynamic photolytical actinometry of the vacuum-ultraviolet radiation produced by multichannel surface discharges of submicrosecond duration.

Absolute measurements of the vacuum-ultraviolet (VUV) radiation power produced by a planar broadband optical source of submicrosecond light pulse duration are carried out in the transient regime of formation of a photodissociation (bleaching) wave in a photodecomposing absorptive medium. The source is based on a multichannel surface discharge initiated in ArN(2) gas mixtures on the area of approximately 0.1 m(2). The energetic characteristics of the produced VUV radiation are determined on the basis of spatially and temporally resolved observations of the pulsed photolysis of XeF(2) vapors. It is shown that the photon flux intensity produced by the source within the spectral range of 120-200 nm reaches 1.1 x 10(23) photonscm(2) s corresponding to the effective brightness temperature of discharge plasma of 20 kK and to the intrinsic efficiency of the discharge VUV emission of 3.2%. Numerical simulations of the photolysis process show a rather weak sensitivity of the results to the fraction of discharge radiation emitted into the line spectrum, as well as to the angular distribution of emitted radiation. The spectral band of measurements can be selected according to the choice of parent photodecomposing particles.

Laser-synthesized oxide-passivated bright Si quantum dots for bioimaging.

Crystalline silicon (Si) nanoparticles present an extremely promising object for bioimaging based on photoluminescence (PL) in the visible and near-infrared spectral regions, but their efficient PL emission in aqueous suspension is typically observed after wet chemistry procedures leading to residual toxicity issues. Here, we introduce ultrapure laser-synthesized Si-based quantum dots (QDs), which are water-dispersible and exhibit bright exciton PL in the window of relative tissue transparency near 800 nm. Based on the laser ablation of crystalline Si targets in gaseous helium, followed by ultrasound-assisted dispersion of the deposited films in physiological saline, the proposed method avoids any toxic by-products during the synthesis. We demonstrate efficient contrast of the Si QDs in living cells by following the exciton PL. We also show that the prepared QDs do not provoke any cytoxicity effects while penetrating into the cells and efficiently accumulating near the cell membrane and in the cytoplasm. Combined with the possibility of enabling parallel therapeutic channels, ultrapure laser-synthesized Si nanostructures present unique object for cancer theranostic applications.

Sexual dimorphism in the maturation of the pituitary-gonadal axis, assessed by GnRH agonist challenge.

OBJECTIVE: To assess whether the maturational changes of the pituitary--gonadal axis in a healthy population show gender-specific changes and to establish normative data for the different Tanner stages. DESIGN: Prospective, cross-sectional study. METHODS: The GnRH agonist leuprolide acetate (500 microgram) was administered s.c. to 60 boys and 81 girls (age range, 5--17 years). Serum steroids and gonadotropins were determined at 0 and 24 h and at 0, 3 and 24 h after GnRH agonist challenge respectively, whereas IGF-I, IGF-binding protein-1 (IGFBP-1), IGFBP-3 and sex hormone-binding globulin were measured at baseline. RESULTS: Baseline and peak LH responses to the agonist in late puberty, and basal and peak FSH levels at all Tanner stages, were higher in girls than in boys. Girls showed higher IGF-I levels than boys throughout puberty, sharper decreases in IGFBP-1 and earlier and greater increases in 17-hydroxypregnenolone, dehydroepiandrosterone (DHEA) and DHEA-sulfate. Testosterone responses to the agonist increased during puberty in males, and showed no changes in females. Conversely, estradiol responses rose throughout puberty in females and remained unchanged until late puberty in males. CONCLUSION: Leuprolide acetate stimulates gonadotropin and gonadal steroid secretion during puberty in both sexes and increases FSH levels in prepubertal girls. Pubertal maturation of gonadotrope function is gender specific, as it appears to involve increases in both the releasable and reserve pools of LH in males, and of LH and FSH in females. The earlier increase in Delta(5)-steroids in girls may suggest a sharper rise in ovarian cytochrome P450c17 activity along the Delta(5)-steroid pathway, while the failure of estradiol to increase in response to leuprolide acetate in early pubertal males suggests a late maturation of aromatase activity.

Subcellular localization of brain mast cell histamine in developing rat.

The intracerebroventricular administration of compound 48/80 or polymixin B to rats 0 to 60 days old, produced a decrease both in the histamine which sediments in the crude nuclear fraction, as well as in the number of mast cells in the brain. In contrast, the histamine-releasers did not affect histamine levels in subcellular fractions where neuronal histamine is found. Once released, histamine disappeared rapidly (t 1/2 = 3.8 min). In untreated animals and in those treated with histamine releasers, the number of mast cells/g in the whole brains of developing rats and in the cerebral regions of adult rats showed a close correlation with the histamine levels in the crude nuclear fraction. The content of histamine per mast cell in adult rat brain was estimated to be about 13 pg/cell. Histologic examination of the subcellular fractions revealed the presence of intact mast cells in the crude nuclear fraction obtained from untreated animals, and of degranulated mast cells in the same fraction obtained from animals treated with histamine releasers. The mast cell contribution to adult rat brain histamine levels was about 22%. Our results strongly support that most of the histamine which sediments in the crude nuclear fraction of the rat brain is located in mast cells. Determination of histamine in the crude nuclear fraction and in the supernatant of this fraction is proposed as an easy way for identifying the cellular pool altered by any treatment affecting brain histamine levels.

Factors related to non-participation in a population-based breast cancer screening programme.

The main objectives were to describe the measures taken by women to detect breast disease prior to invitation to participate in a screening programme for breast cancer, and to identify factors related to non-participation in this programme. A cross-sectional study was designed at the Breast Cancer Early Detection Program of Sabadell-Cerdanyola (BCEDP), using data collected in interviews conducted face to face or over the telephone with 13 760 women participating in the programme and 280 non-participants. A total of 74.2% of the participants versus 70.4% of the non-participants reported having taken measures to detect breast disease, and 71.7% of the participants had undergone mammography versus 69.6% of the non-participants. Of the 10 057 women who had had mammograms, 58% had done so less than 2 years previously. Factors found to be associated to non-participation in the multivariate analysis were: higher level of education, higher occupational skills or working at home, self- or gynaecological examination of breasts, and having received hormone replacement therapy. Higher age group was the only factor that increased the probability of not having undergone mammography previously. Despite the high prevalence of prior measures to detect breast cancer and the similar prevalence between participating and non-participating women, this behaviour is much less prevalent in the group of women 60 years of age or older.

Hepatic angiomyolipoma: value of proton (fat/water) chemical shift fast low angle shot (FLASH) MR imaging technique in detecting fatty tissue content.

A case of angiomyolipoma of the liver in a 43-yr-old woman is reported. Findings on ultrasonography (US), computed tomography (CT), and magnetic resonance (MR) imaging techniques are presented and the usefulness of proton (fat/water) chemical shift FLASH imaging to confirm the presence of intratumoral fat is pointed out.

Primary lymphoma of the breast: MR imaging features. A case report.

Primary non-Hodgkin's lymphoma (NHL) of the breast are rare and represent less than 0.6% of all mammary malignancies. Secondary involvement of the breast in patients with diffuse disease occurs more frequently. The radiologic features of breast lymphoma are nonspecific, and the diagnosis is based on histologic criteria. We present the MR-imaging features of a case of primary NHL of the breast.

Fine needle aspiration of myofibroblastoma of the breast in a man. A report of two cases.

The cytopathologic features of fine needle aspiration biopsy of two myofibroblastomas of the breast in men are described. The cytologic findings consisted of monomorphic spindle cells with ovoid, grooved nuclei, isolated or in clusters, with an ill-defined, short fascicular pattern and abundant acellular, myxoid-appearing material. Atypical features were absent. No epithelial elements were present. We emphasize the value of aspiration cytology in association with clinical and mammographic data to establish a definitive diagnosis of this uncommon entity. This benign tumor should be considered in pure spindle cell, nontypical fine needle aspiration biopsy specimens of breast masses with sharp demarcation from the surrounding tissue, especially in men.

[Surgical treatment for compensatory hyperhidrosis in Adie syndrome]. / Tratamiento quirúrgico de la hiperhidrosis compensadora en el síndrome de Adie.

Ross syndrome is characterized by a triad of tonic pupil, areflexia and segmental hypohidrosis. Hypohidrosis may be accompanied by contralateral hyperhidrosis, probably due to a compensatory mechanism. We report a case of Ross syndrome with socially disabling left-sided hyperhidrosis. Sympathectomy of the second and third thoracic ganglia was performed with satisfactory results. With excellent results in primary hyperhidrosis and very low morbidity, thoracic sympathectomy is the definitive treatment for hyperhidrosis.

[Noninvasive diagnosis of posttraumatic thoracic splenosis]. / Diagnóstico no invasivo de la esplenosis torácica postraumática.

Thoracic splenosis is a rare occurrence that has usually been diagnosed by invasive procedures to allow a pathologic diagnosis to be reached. A firm diagnosis can now be made with the help of new, noninvasive imaging techniques. We report the case of a 34-year-old man with a history of severe thoracic-abdominal injury, including rupture of the spleen and left diaphragm. During computed tomography of the thorax related to a different diagnosis, nonspecific nodules were observed, although the patient was asymptomatic. A suspected diagnosis of thoracic splenosis was confirmed by technetium-99 sulfur colloid scintigraphy.

[Mediastinal enteric cyst: unusual clinical presentation and histopathology]. / Quiste entérico mediastínico: presentación clínica e histopatología inusuales.

A mediastinal enteric cyst is an uncommon entity which is rare in adults and usually found incidentally. In most cases the lesion is lined by gastrointestinal mucosa, and theories as to the origin of such lesions are diverse. We report an adult case of thoracic enteric cyst that presented with cardiac tamponade and for which histopathological examination revealed the presence of pancreatic tissue. Review of the literature yielded only 1 case of mediastinal enteric cyst with pancreatic tissue.