Electron-beam induced synthesis of nanostructures: a review.

As the success of nanostructures grows in modern society so does the importance of our ability to control their synthesis in precise manners, often with atomic precision as this can directly affect the final properties of the nanostructures. Hence it is crucial to have both deep insight, ideally with real-time temporal resolution, and precise control during the fabrication of nanomaterials. Transmission electron microscopy offers these attributes potentially providing atomic resolution with near real time temporal resolution. In addition, one can fabricate nanostructures in situ in a TEM. This can be achieved with the use of environmental electron microscopes and/or specialized specimen holders. A rather simpler and rapidly growing approach is to take advantage of the imaging electron beam as a tool for in situ reactions. This is possible because there is a wealth of electron specimen interactions, which, when implemented under controlled conditions, enable different approaches to fabricate nanostructures. Moreover, when using the electron beam to drive reactions no specialized specimen holders or peripheral equipment is required. This review is dedicated to explore the body of work available on electron-beam induced synthesis techniques with in situ capabilities. Particular emphasis is placed on the electron beam-induced synthesis of nanostructures conducted inside a TEM, viz. the e-beam is the sole (or primary) agent triggering and driving the synthesis process.

[Anonymity and gamete donation]. / Anonymat du don de gamètes.

In France the gamete donation is based on the major principles: anonymity, no payment, solidarity and this mode of procreation can be used only if a medical indication is present in recipient couples. In prerequisite and during the revision of the law of bioethics, a wide debate took place about the anonymity of gamete donation. The objectives of this article is to review the concept of the anonymity and its links with the questions of the origin, the secret of the modalities of the conception and the mourning of the fertility, children, donors and the recipient couples waiting for gamete donation. The international situation is also addressed. The contribution of the CECOS, the centers which practice the sperm and the egg donations is highlighted. The anonymity cannot be discussed without addressing all these links and the complexity of this particular mode of conception. To date, the French society has maintained the anonymity in the new law of bioethics.

Multiscale modeling of nanowire-based Schottky-barrier field-effect transistors for sensor applications.

We present a theoretical framework for the calculation of charge transport through nanowire-based Schottky-barrier field-effect transistors that is conceptually simple but still captures the relevant physical mechanisms of the transport process. Our approach combines two approaches on different length scales: (1) the finite element method is used to model realistic device geometries and to calculate the electrostatic potential across the Schottky barrier by solving the Poisson equation, and (2) the Landauer-Büttiker approach combined with the method of non-equilibrium Green's functions is employed to calculate the charge transport through the device. Our model correctly reproduces typical I-V characteristics of field-effect transistors, and the dependence of the saturated drain current on the gate field and the device geometry are in good agreement with experiments. Our approach is suitable for one-dimensional Schottky-barrier field-effect transistors of arbitrary device geometry and it is intended to be a simulation platform for the development of nanowire-based sensors.

[ART with sperm donor after intraconjugal ICSI failure]. / Prise en charge en don de sperme après échec(s) d'ICSI intraconjugale.

OBJECTIVES: To evaluate the ART results with sperm donation for couples who do not succeed after IC ICSI treatment for male infertility. PATIENTS AND METHODS: Retrospective study of 71 couples (November 1994-February 2009). Two control populations were determined to analyse this two-steps treatment (IC and sperm donation) based on different criteria such as the date of ICSI, the female age at the time of the first attempt and the male indication. RESULTS: In IC-ICSI, the proportion of azoospermic subjects and/or carrying chromosomal abnormalities was significantly higher in the studied population as compared to control. The fertilization rate (FR) and the embryo quality were significantly lower in the studied population. After donation, 30 couples (42.2%) succeeded in being parents. The donor IA pregnancy rates were similar to those of the control population except for the azoospermic patients with poor results. When IVF/ICSI-D was performed, the pregnancy rates were lower than in the control population. DISCUSSION AND CONCLUSION: Sperm donation constitutes an option for half of the couples initially treated with IC-ICSI for male infertility. For couples who failed in sperm donation, a female implication cannot be excluded, even though not detected.

A small paramagnetic platinum cluster in an NaY zeolite: characterization and hydrogen adsorption and desorption.

A well-defined cluster containing 12 equivalent platinum atoms was prepared by ion exchange of an NaY zeolite, followed by hydrogen reduction. It was characterized by electron paramagnetic resonance (EPR) spectroscopy, hyperfine sublevel correlation (HYSCORE), and theoretical calculations. Combing the results of the experiments with density functional calculations, the likely structure of this cluster is icosahedral Pt13Hm, possibly with a low positive charge. The adsorbed H/D on the Pt cluster surface can be exchanged reversibly at room temperature. From H/D desorption experiments, an H2 binding energy of 1.36 eV is derived, in reasonable agreement with the calculated value but clearly larger than that for a (111) Pt single-crystal surface, revealing a finite size effect. While the hydrogen-covered cluster should clearly be regarded as a molecule, it is conceivable that the cluster adopts metallic character upon hydrogen desorption. It is likely that up to m=30 H atoms bind to this cluster with 12 surface atoms, which has important implications for the determination of the dispersion of small Pt catalyst particles by hydrogen chemisorption. Calculations as well as experiments give evidence of an interesting magnetic behavior with high-spin states playing a prominent role. There are strong indications that a reservoir of EPR silent but structurally similar clusters exists which can partly be converted to EPR visible species by H/D exchange or by gas adsorption.

[Management of reproduction disorders in spinal cord injured adolescents]. / Prise en charge des troubles de la reproduction chez l'adolescent blessé médullaire.

Adolescence is a period of research of sexual identity. How does a teenager build himself when a paraplegic or quadriplegic? How can the team of nursing staff help him? First we shall study the erection and the sexual relations and secondly we shall study the procreation issue. It is necessary to have early concrete information really suitable for a neurologic definition of a spinal cord injury and to conserve sperm before having complications of urinary infections. We inform 24 paraplegic or tetraplegic teenagers at the CMPA in Neufmoutiers and the CECOS at the Cochin Hospital in Paris.

Semen alterations in HIV-1 infected men.

BACKGROUND: Couples in whom the man is infected by human immunodeficiency virus (HIV) increasingly request assisted reproductive technology (ART) to allow safe procreation. Semen quality is critical in such situations. METHODS: Semen characteristics were evaluated in 189 HIV-infected men requesting ART. At the time of semen analysis all men were healthy and 177 were receiving anti-retroviral therapy. Comparisons were made with HIV-seronegative men, partners of women requiring IVF because of tubal infertility, after matching for age and sexual abstinence delay. RESULTS: The most significant semen alterations found in the HIV-infected men were reduced percentages of rapidly progressive sperm [median (range), 10% (0-30%) compared with 15% (5-30%) in the controls, P < 0.001], and increased concentrations of non-spermatic cells [3 x 10(6)/ml (0.2-16 x 10(6)/ml) compared with 1.1 x 10(6)/ml (0.1-14 x 10(6)/ml) in the controls, P < 0.001]. HIV-infected men also showed lower ejaculate volumes [2.8 ml (0.6-9.3 ml) compared with 3.6 ml (1.1-11 ml), P < 0.05] and total sperm counts [262.5 x 10(6) (0-1003 x 10(6)) compared with 310.5 x 10(6) (48.3-1679 x 10(6)), P < 0.05]. CONCLUSIONS: Semen evaluation in a large population of HIV-infected men requesting ART evidenced several alterations. Some of these anomalies might be related to anti-retroviral treatments.

Detection of hepatitis C virus in the semen of infected men.

We detected hepatitis C virus (HCV) RNA in the semen of one third of HCV viraemic men. Seminal viral loads were low, but the semen could be infectious and the role of sexual transmission in the spread of HCV infection should not be underestimated.

Decline in semen quality among fertile men in Paris during the past 20 years.

BACKGROUND: Several studies have suggested a population-wide decline in the quality of semen over the past 50 years, but clear evidence for decreasing semen quality in recent decades is lacking. METHODS: From 1973 through 1992 we measured the volume of seminal fluid, the sperm concentration, and the percentages of motile and morphologically normal spermatozoa in 1351 healthy fertile men. The data on the semen samples were collected at one sperm bank in Paris. The data in each calendar year were analyzed as a function of the year of donation, the age of each patient, the year of birth, and the duration of sexual abstinence before semen collection. RESULTS: There was no change in semen volume during the study period. The mean concentration of sperm decreased by 2.1 percent per year, from 89 x 10(6) per milliliter in 1973 to 60 x 10(6) per milliliter in 1992 (P < 0.001). During the same period the percentages of motile and normal spermatozoa decreased by 0.6 percent and 0.5 percent per year, respectively (both P < 0.001). After adjustment in multiple regression analyses for age and the duration of sexual abstinence, each successive calendar year of birth accounted for 2.6 percent of the yearly decline in the sperm concentration and for 0.3 percent and 0.7 percent, respectively, of the yearly declines in the percentages of motile and normal spermatozoa (all P < 0.001). CONCLUSIONS: During the past 20 years, there has been a decline in the concentration and motility of sperm and in the percentage of morphologically normal spermatozoa in fertile men that is independent of the age of the men.

Influence of sperm parameters on outcome of subzonal insemination in the case of previous IVF failure. off.

Subzonal insemination (SUZI) has been proposed for patients with sperm male factor infertility, and in cases of in-vitro fertilization (IVF) failures. However despite SUZI, there still remain couples with very low fertilization rates and even with fertilization failures. Since sperm parameters are known to influence the IVF fertilization rate, we investigated the relation between sperm parameters and the SUZI issue in cases of previous IVF failures with normal or subnormal sperm. Twenty-seven couples were included in the study and were split into two groups according to whether they had normal or subnormal sperm. In the first part of the study a randomized prospective trial comparing SUZI to classic IVF insemination was carried out (11 cycles). In the second part, all the oocytes had SUZI (35 cycles). None of the control inseminated oocytes fertilized. Including all the cases, the fertilization rate after SUZI was 29.8% with a pregnancy rate of 15.2% per cycle. We concluded that: (i) SUZI is efficient for achieving fertilization in cases of IVF failures; (ii) the post SUZI fertilization rate is inversely correlated to the percentage of acrosome defects in the semen (P < 0.001); and (iii) when the sperm is normal, the oocyte quality might be responsible for the previous IVF failures. In spite of a good fertilization rate for this indication, it seems that the chance of having a baby is low.

[Artificial insemination with the sperm of the husband (author's transl)]. / Insémination artificielle avec sperme du conjoint.

--128 women underwent artificial insemination with husband's semen (A I H) after an over 3 years period of sterility. --The most frequently recorded indication was low sperm density and/or reduced sperm motility. To increase sperm concentration and motility split ejaculates were most often utilised but also different other methods. --The pregnancy rate was 31 p. 100 and the success rate per cycle was 5 p. 100.