80-µs pulsewidth from a circulation-free diode-pumped liquid organic laser limited by thermal blooming.

Continuous-wave laser emission is challenging to obtain in organic lasers, whether in the solid or liquid form, a limitation caused by long-lived triplet states and by thermal effects. In liquid dye lasers, both issues can be fixed by rapidly flowing the dye, which is technically complex and prevents those lasers to be further miniaturized or easily integrated. Here we address the issue of the maximal pulsewidth that can be obtained in liquid dye lasers in the absence of any dye flow, in a compact and cost-effective diode-pumped laser system. Pulses as long as 80 µs have been obtained, thanks to the combination of a hemispherical resonator design, almost insensitive to thermal-lens effects, and an intentional mismatch between pump and cavity spatial modes. The limitation in pulse duration is shown to be entirely due to thermal blooming, and more specifically to diffraction losses brought by the spherical aberration of the thermal lens.

Enhancing brightness of Lambertian light sources with luminescent concentrators: the light extraction issue.

Luminescent concentrators (LC) enable breaking the limit of geometrical concentration imposed by the brightness theorem. They enable increasing the brightness of Lambertian light sources such as (organic) light-emitting diodes. However, for illumination applications, light emitted in the high-index material needs to be outcoupled to free space, raising important light extraction issues. Supported by an intuitive graphical representation, we propose a simple design for light extraction: a wedged output side facet, breaking the symmetry of the traditional rectangular slab design. Angular emission patterns as well as ray-tracing simulations are reported on Ce:YAG single crystal concentrators cut with different wedge angles, and are compared with devices having flat or roughened exit facets. The wedge output provides a simple and versatile way to simultaneously enhance the extracted power (up to a factor of 2) and the light directivity (radiant intensity increased by up to 2.2.).

Biosynthetic 4,6-dehydratase gene deletion: isolation of a glucosylated jadomycin natural product provides insight into the substrate specificity of glycosyltransferase JadS.

Deletion of the biosynthetic 4,6-dehydratase gene, jadT, present in the angucycline jadomycin dideoxysugar biosynthetic pathway, led to the isolation of a novel C12 glucosylated jadomycin. JadS was identified as the catalyst responsible for glucosylation due to a loss of production of the glucosylated natural product in a ΔjadSΔjadT deletion strain. This study demonstrates that a 2,6-dideoxy-l-sugar glycosyltransferase is able to transfer d-glucose, exemplifying remarkable substrate tolerance.

Kinetic evaluation of glucose 1-phosphate analogues with a thymidylyltransferase using a continuous coupled enzyme assay.

Cps2L, a thymidylytransferase, is the first enzyme in Streptococcus pneumoniae L-rhamnose biosynthesis and an antibacterial target. We herein report the evaluation of six sugar phosphate analogues selected to further probe Cps2L substrate tolerance. A modified continuous spectrophotometric assay was employed for facile detection of pyrophosphate (PPi) released from nucleotidylyltransfase-catalysed condensation of sugar 1-phosphates and nucleoside triphosphates to produce sugar nucleotides. Additionally, experiments using waterLOGSY NMR spectroscopy were investigated as a complimentary method to evaluate binding affinity to Cps2L.

[Obstetric anaesthesia in two patients with cerebral cavernomas: about two cases]. / Anesthésie obstétricale chez des patientes porteuses de cavernomes cérébraux : à propos de deux cas.

Prevalence of cerebral cavernous malformations is comprised in between 0.4 to 0.8% of the people. Anesthetic management of pregnant women suffering from this disease is often difficult. We have witnessed two cases of delivery concerning two patients suffering from a cerebral cavernous malformation, one with vaginal delivery under peridural analgesia and the other one with cesarean delivery under rachianesthesia. We recommend the realization of a magnetic resonance imaging the year before delivery. Without medullar cavernous malformations, perimedullar analgesia seems to be the preferred method of choice.

[Total parenteral nutrition for recurrent episodes of acute pancreatitis during pregnancy. A case report and literature review]. / Prise en charge d'épisodes récidivants de pancréatite aiguë par nutrition parentérale exclusive pendant la grossesse. Cas clinique et revue de la littérature.

We report on a 35-year-old woman who underwent at 15 weeks of pregnancy exclusive parenteral nutrition for recurrent episodes of acute pancreatitis. She had a pancreatico-jejunal anastomosis stenosis secondary to cephalic duodenopancreatectomy. Nocturnal exclusive parenteral nutrition was used 79 days during pregnancy and 12 days during post-partum. The fetal growth was normal and the foetal well-being was normal. She presented cholestasis at 30 weeks of pregnancy treated medically. She delivered at 33 weeks of pregnancy by cesarean section a healthy baby girl with normal birth weight.

Anticonical anchoring and surface transitions in a nematic liquid crystal.

Recent works reported planar and conical azimuthally degenerated nematic anchorings. Here we predict an additional "anticonical" degenerated anchoring. Its energy presents two minima, parallel and perpendicular to the substrate plane, separated by a conical energy barrier. We realize this bistable anchoring on a grafted polymer brush and we observe temperature-driven transitions between the conical, planar, and anticonical degenerated anchorings. Under electric field we break the anticonical anchoring and switch between its bistable states.

Fluorescence lifetime imaging with a low-repetition-rate passively mode-locked diode-pumped Nd:YVO4 oscillator.

We report a wide-field fluorescence lifetime imaging microscope based on a low-repetition-rate (3.7-MHz) passively mode-locked diode-pumped laser source. This inexpensive and compact laser source operating in the visible and UV range can excite a wide range of fluorophores of biological interest. We demonstrate that the power of this laser source is highly sufficient for studying biological systems with low quantum yields (autofluorescence of tissues and stained living cells). The maximum measurable lifetime is also strongly increased with this laser source, as fluorescence intensity measurement can occur 250 ns after the excitation pulse.

Passively mode-locked diode-pumped Nd:YVO4 oscillator operating at an ultralow repetition rate.

We demonstrate the operation of an ultralow-repetition-rate, high-peak-power, picosecond diode-pumped Nd:YVO4 passively mode-locked laser oscillator. Repetition rates lower than 1 MHz were achieved with the use of a new design for a multiple-pass cavity and a semiconductor saturable absorber. Long-term stable operation at 1.2 MHz with a pulse duration of 16.3 ps and an average output power of 470 mW, corresponding to 24-kW peak-power pulses, is reported. These are to our knowledge the lowest-repetition-rate high-peak-power pulses ever generated directly from apicosecond laser resonator without cavity dumping.

Prevalence of potential risk factors in victims of electrocution.

OBJECTIVE: To identify risk factors of fatal arrhythmia following electrical shock, by comparing the prevalence of transthoracic current, tetany, decreased skin resistance because of wet extremities, skin burns and heart disease in victims of electrocution with instant as opposed to delayed death. DESIGN: Retrospective case-control study, based on the charts from the coroner's office. RESULTS: A total of 124 deaths from electrocution occurred between 1987 and 1992. One victim presumably died from delayed arrhythmia and was excluded from the study. Twenty victims had decreased skin resistance because of wet extremities and five had tetany. Autopsy revealed coronary heart disease in 21 cases, and burns in 109; 10 did not have any skin lesion. There was no difference in risk factors between those who died instantly presumably from arrhythmia (n=114) and those who died later from other causes (n=9). CONCLUSION: No differences in risk factors were found between victims who died immediately from arrhythmia following electrical shock and those died later from other causes.

A missense mutation in FIC1 is associated with greenland familial cholestasis.

Greenland familial cholestasis is a severe form of intrahepatic cholestasis described among indigenous Inuit families in Greenland. Patients present with jaundice, pruritus, bleeding episodes, and steatorrhea, and die in childhood due to end-stage liver disease. We investigated the possibility that Greenland familial cholestasis is caused by a mutation in FIC1, the gene defective in patients with progressive familial intrahepatic cholestasis type 1 and many cases of benign recurrent intrahepatic cholestasis. Using single-strand conformation polymorphism analysis and sequencing of the FIC1 exons, a missense mutation, 1660 G-->A (D554N), was detected and was shown to segregate with the disease in Inuit patients from Greenland and Canada. Examination of liver specimens from 3 Inuit patients homozygous for this mutation revealed bland canalicular cholestasis and, on transmission electron microscopy, coarsely granular Byler bile, as previously described in patients with progressive familial intrahepatic cholestasis type 1. These data establish Greenland familial cholestasis as a form of progressive familial intrahepatic cholestasis type 1 and further underscore the importance of unimpeded FIC1 activity for normal bile formation.

Memory-free conic anchoring of liquid crystals on a solid substrate

We show that the anchoring memory of liquid crystals on solid substrates can be completely removed by grafting highly mobile polymer chains. Using grafted polystyrene, we obtain uniform, stable, and reproducible memory-free and conically degenerated anchoring of the nematic 5CB. The symmetry of the conic anchoring enables two different zenithal anchoring breakings, towards homeotropic and planar states. Under external torques we observe both of them, with weak thresholds.

The kidney in children with tyrosinemia: sonographic, CT and biochemical findings.

BACKGROUND: Tyrosinemia relates to a deficiency of fumarylacetoacetate hydrolase and presents early in life with central nervous system and liver abnormalities. Renal function is often impaired. Little is known about the architecture and function of the kidneys. OBJECTIVE: Imaging changes on US and CT are compared to the function of the kidneys in children with tyrosinemia, and followed after liver transplantation. MATERIALS AND METHODS: Renal sonography, CT and renal function tests in 32 children were reviewed. Renal length, volume, echogenicity and nephrocalcinosis were evaluated. Renal function was assessed by glomerular filtration rate, and the presence of aminoaciduria, acidosis and calciuria. Seventeen children had open renal biopsy during time of liver transplantation. Histology was reviewed. Statistical analyses relating renal structure to function were performed, and repeated after transplantation. RESULTS: The kidneys were enlarged (47 %), hyperechogenic (47 %) and showed nephrocalcinosis (16 %). There was delayed excretion of contrast medium at CT in 64 %. Aminoaciduria was present in 82 % of children, hypercalciuria in 67 %, tubular acidosis in 59 %, and low GFR in 48 %. Delayed excretion of contrast was associated with low GFR (P < 0.05). Renal biopsies showed dilated tubules (81 %), interstitial fibrosis (56 %), glomerulosclerosis (56 %) and tubular atrophy (56 %). During a mean observation period of 3 years following liver transplantation, GFR improved in 50 %, tubular acidosis in 50 % and hypercalciuria in 70 %. No change was noted in renal size or sonographic architecture. CONCLUSION: Renal architecture and function are abnormal in the majority of children with tyrosinemia. Liver transplantation improves renal function in about 50 % of patients, but abnormal renal size and architecture persist.

Imaging features of type 1 hereditary tyrosinemia: a review of 30 patients.

Hereditary tyrosinemia type 1, a common genetic disorder in the province of Quebec, is characterized by a deficiency of fumarylacetoacetate hydrolase. In this autosomal recessive disorder of tyrosine metabolism, the accumulation of succinylacetone leads to neurologic crises, acute and chronic liver failure, complex renal tubulopathy, rickets and a hemorrhagic syndrome. Liver trans- plantation has dramatically modified the spontaneous course of this lethal disease. The present paper describes the imaging features of tyrosinemia in 30 patients followed from 1980 to 1995 at Hôpital Sainte-Justine, Montreal, Canada.