Raman-tailored photonic crystal fiber for telecom band photon-pair generation

We report on the experimental characterization of a novel nonlinear liquid-filled hollow-core photonic crystal fiber for the generation of photon pairs at a telecommunication wavelength through spontaneous four-wave mixing (SFWM). We show that the optimization procedure in view of this application links the choice of the nonlinear liquid to the design parameters of the fiber, and we give an example of such an optimization at telecom wavelengths. Combining the modeling of the fiber and classical characterization techniques at these wavelengths, we identify for the chosen fiber and liquid combination SFWM phase-matching frequency ranges with no Raman scattering noise contamination. This is a first step toward obtaining a telecom band fibered photon-pair source with a high signal-to-noise ratio.

Photon extrabunching in ultrabright twin beams measured by two-photon counting in a semiconductor

For many years twin beams originating from parametric down-converted light beams have aroused great interest and attention in the photonics community. One particular aspect of the twin beams is their peculiar intensity correlation functions, which are related to the coincidence rate of photon pairs. Here we take advantage of the huge bandwidth offered by two-photon absorption in a semiconductor to quantitatively determine correlation functions of twin beams generated by spontaneous parametric down-conversion. Compared with classical incoherent sources, photon extrabunching is unambiguously and precisely measured, originating from exact coincidence between down-converted pairs of photons, travelling in unison. These results strongly establish that two-photon counting in semiconductors is a powerful tool for the absolute measurement of light beam photon correlations at ultrashort timescales.

[Information for patients about hospital infections in psychiatry: An assessment of healthcare professionals' knowledge, opinion and attitude]

INTRODUCTION

French legislation makes mandatory for healthcare providers the disclosure of hospital infection (HI) risk and actual occurrence to the patient. Given the specific diseases encountered in psychiatry, some difficulties may be expected in practical application of this regulation.

OBJECTIVES

The aim of our study was to describe the knowledge, declared practices and opinions of healthcare workers (HCW) in psychiatry concerning information for patients about HI.

METHODS

We randomly selected doctors, nurses and head nurses from four hospitals with psychiatric activity in Normandy. The HCW were asked to self-complete an anonymous questionnaire, including data describing the responding HCW and questions aiming at describing his/her knowledge, attitude in routine daily practice and opinion about information to patients about HI.

RESULTS

One hundred and forty-one HCW were initially selected, of which 114 (80.9%) eventually agreed to complete the questionnaire. Only eight HCW (7.0%) were considered to have a correct overall knowledge of legal obligations. Main errors concerned the obligation to inform the patient of the HI risk according to the medical procedures that are to be performed (43.9% of correct answers) and the obligation to inform the patient of the HI risk according to his/her medical condition (46.5%). The obligation to inform the patient of the occurrence of a HI was largely known (84.2%). HCW usually giving information about the risk of HI to patients without HI accounted for 5.3%. Main reasons advocated for not informing patients were a low level risk of HI in psychiatry (80.4%) and the lack of patients' demand (59.8%). In the case of HI occurrence, the percentage of HCW routinely informing patients was 13.2%. HCW systematically informing the patient's family about the occurrence of HI accounted for 9.6%. A large proportion of HCW supported delivering information to patients about HI (86.0%). HCW expected from information better approval of prevention programs by the patients (87.7%) but feared an increased anxiety in patients (75.4%) and a higher rate of care refusal (48.2%).

CONCLUSION

Whereas a very large proportion of HCW in psychiatry support delivering information to patients about HI, our study shows HCW's lack of awareness of regulations and lack of declared practices. Among factors explaining this contrast, a lower perceived HI risk and severity level are to be mentioned. Training programs focusing on risk and mechanisms of HI could be offered to professionals in psychiatry. The issue of specific communication difficulties with psychiatric patients should be addressed as well. In order to develop information on HI, specific methods suited to those patients should be developed.

What factors influence healthcare professionals' opinion and attitude regarding information for patients about hospital infection?

Although informing patients about medical risks is said to decrease the number of malpractice claims, most inpatients receive no information about hospital infection. Using a self-administered questionnaire, we surveyed 1270 healthcare workers randomly selected from 22 French hospitals to assess their opinion on information for patients about hospital infection risks, and their practice of informing patients with, or without, hospital infection. The influence of healthcare worker characteristics on opinion and practice was assessed using logistic regression. Response rate was 87.2%. Although 85.4% supported giving more information, only 17.0% routinely informed non-infected patients and 31.6% informed infected patients about infection. Attitudes were influenced by healthcare worker characteristics and environmental factors. Knowledge of obligations influenced practice when informing non-infected patients, but not those with hospital-acquired infection. Further research is needed to help healthcare professionals improve risk communication and disclosure of hospital infection.

Characterizing whispering-gallery modes in microspheres by direct observation of the optical standing-wave pattern in the near field

We demonstrated the use of a near-field probe to map the evanescent field of an optical standing wave in a fused-silica whispering-gallery mode microresonator. The periodicity of the observed standing wave allows us to estimate accurately the radial mode number of the whispering-gallery mode resonance that is being excited. We find that the use of a fiber half-coupler to excite these resonances in fused-silica microspheres results in only the lowest radial mode numbers' being strongly excited, as predicted.

Mapping whispering-gallery modes in microspheres with a near-field probe

We demonstrate the use of a near-field probe to map the angular dependence of high-Q whispering-gallery modes in fused-silica microspheres. The mapping is performed by placing a micrometer-sized tip formed on the end of a monomode fiber into the evanescent f ield at the microsphere surface, causing light to be coupled from the microsphere resonance into the fiber guided mode. The light output of the fiber is then measured while the tip is moved to different points on the microsphere surface. We have used this method to investigate the lifting of spherical degeneracy in the system.

Eroded monomode optical fiber for whispering-gallery mode excitation in fused-silica microspheres

We demonstrate the efficient excitation of high-Q whispering-gallery modes in near-spherical fused-silica microparticles in the size range 60-450 microm by the use of an eroded monomode optical fiber. When the sphere is placed in the evanescent field of the guided fiber mode, light is resonantly coupled from the fiber into the microparticle. We report a broadening of resonance modes and a shift of the resonance central frequency as the coupling strength is increased by reduction of the gap between the sphere and the fiber.

Vaccination against canine babesiosis: an overview of field observations

Pirodog (ND) is a novel vaccine against canine babesiosis. It is commercially distributed and has been used in France since May 1988. More than 150,000 dogs have now been vaccinated and the results of the immunization have been contradictory. Many things remain to be understood concerning individual susceptibility, the immunosuppressive effect of the disease, and the incidence of concomitant infections.

Protein p126: a parasitophorous vacuole antigen associated with the release of Plasmodium falciparum merozoites

The p126 protein is synthesized by P. falciparum between the 32nd and the 36th hour of the erythrocytic cycle, and is localized in the parasitophorous vacuole. It is processed when schizonts rupture and the major fragments (50, 47 and 18 kDa), which are released into culture supernatant, have been characterized using monoclonal antibodies. The 47 kDa fragment has been mapped at the N-terminus of the molecule. The portion of the protein p126 gene coding for this fragment contains 3 introns and is characterized by a sequence coding for 6 repeats of 8 aminoacids and by repeats of TCA/T-AGT coding for a polyserine sequence of 37 serines in a row for the FCR-3 strain. The 50 kDa fragment is also found in culture supernatant when merozoites are released from mature schizonts. The incubation of mature schizonts with leupeptin inhibits the release of merozoites and, in this case, a 56 kDa intermediate product is found. In those conditions, merozoites were observed free in the erythrocyte cytoplasm, the membrane of the parasitophorous vacuole being destroyed. The 50 kDa fragment can be obtained from the 56 kDa fragment by treatment with trypsin (a protease inhibited by leupeptin). Our results suggest that the processing of the 56 kDa fragment: 1) is protease-dependent, and could depend on a trypsin-like activity; 2) cannot occur after the release of merozoites because of the protease inhibitors contained in the serum; 3) does not occur before the release of merozoites, since no processed products of the protein p126 are observed in unruptured schizonts.(ABSTRACT TRUNCATED AT 250 WORDS)