Spatially resolved optical spectroscopy in extreme environment of low temperature, high magnetic fields and high pressure

We present an experimental setup developed to perform optical spectroscopy experiments (Raman scattering and photoluminescence measurements) with a micrometer spatial resolution in an extreme environment of low temperature, high magnetic field, and high pressure. This unique experimental setup, to the best of our knowledge, allows us to deeply explore the phase diagram of condensed matter systems by independently tuning these three thermodynamic parameters while monitoring the low-energy excitations (electronic, phononic, or magnetic excitations) to spatially map the Raman scattering response or to investigate objects with low dimensions. We apply this technique to bulk FePS₃, a layered antiferromagnet with a Néel temperature of T ≈ 120 K.

Measurement of the spin-forbidden dark excitons in MoS2 and MoSe2 monolayers

Excitons with binding energies of a few hundreds of meV control the optical properties of transition metal dichalcogenide monolayers. Knowledge of the fine structure of these excitons is therefore essential to understand the optoelectronic properties of these 2D materials. Here we measure the exciton fine structure of MoS2 and MoSe2 monolayers encapsulated in boron nitride by magneto-photoluminescence spectroscopy in magnetic fields up to 30 T. The experiments performed in transverse magnetic field reveal a brightening of the spin-forbidden dark excitons in MoS2 monolayer: we find that the dark excitons appear at 14 meV below the bright ones. Measurements performed in tilted magnetic field provide a conceivable description of the neutral exciton fine structure. The experimental results are in agreement with a model taking into account the effect of the exchange interaction on both the bright and dark exciton states as well as the interaction with the magnetic field.

Chemical synthesis, NMR analysis and evaluation on a cancer xenograft model (HL-60) of the aminosteroid derivative RM-133

The aminosteroid derivative RM-133 has been reported to be a promising pro-apoptotic agent showing activity on various cancer cell lines. Following the development of solid-phase synthesis that generated a series of libraries of aminosteroid derivatives, we now report the development of a convenient liquid phase chemical synthesis of RM-133, the most promising candidate, in order to obtain sufficient quantities to proceed with the first preclinical assays. A simple and convergent six-step synthesis was designed and allowed the preparation of a gram-quantity scale of RM-133. This aminosteroid derivative was also fully characterized by NMR experiments which revealed an interesting mixture of conformers. Finally, the in vivo potency of RM-133 was evaluated on a xenograft model in nude mice with HL-60 tumors, which has resulted in the blocking of tumor progression by 57%.

Reproductive management of silver foxes (Vulpes vulpes) in captivity

Specific protocols need to be developed that take into consideration the requirements of silver foxes. This study was designed to investigate the reproduction of 26 pairs of silver foxes (Vulpes vulpes). Reproduction parameters (breeding season, age at puberty, fecundity and fertility) of the foxes were examined under experimental conditions, and new techniques to optimize fox breeding were assessed. Staining of the vaginal smears with the double Harris-Schorr stain allowed for the precise detection of estrus and proved to be more reliable than simply measuring vaginal resistance. Ultrasonography was demonstrated to be useful for pregnancy diagnosis and prediction of parturition. Results demonstrate that the methods reported in this paper are easily applicable to similar studies carried out on small groups of animals within the framework of fox animal experimentation.

Temporal variations of LH and testosterone in arabian oryx (Oryx leucoryx) from birth to adulthood

To determine the onset of puberty in Arabian oryx (Oryx leucoryx), a longitudinal study was conducted in 5 captive males at the National Wildlife Research Centre, Taif (Saudi Arabia). From birth to 20 months of age, twice weekly, animals were weighed and blood was assayed for LH and testosterone. Four periods were defined by analysis of the hormonal profile. During the first 5 months (corresponding to prepuberty), mean LH concentrations increased significantly while testosterone remained basal. Testosterone increased significantly during the second period (from 6 to 7 months) while LH decreased significantly. The testosterone pattern suggests that the animals reached puberty at around 7 months old. Mean LH concentrations remained at a similar level before and after puberty and increased significantly between the 12th and 13th months of life. This increment correspond to the transition between two further periods. The third period (8-12 months) was characterized by testosterone peaks of 2.4 +/- 0.1 ng ml-1 which irregularly occurred over a period of 26.6 +/- 2.7 days and was followed by a fourth period, during which peaks were seen at 24.1 +/- 1.6-day intervals and reached 4.7 +/- 0.2 ng ml-1. This last period probably corresponds to the mature stage of puberty. The testosterone cyclicity in oryx, coinciding with the estrous cycle length of the female, would permit the male to be fertile throughout the year and could be an adaptive response to the opportunistic and aseasonal reproductive cycle of the female.

Length of estrous cycle and gestation in the Arabian oryx (Oryx leucoryx) and the importance of the male presence for induction of postpartum estrus

The reproduction of the Arabian oryx (Oryx leucoryx) has been studied in a breeding center in Taif (Saudi Arabia). In the first experiment, three groups of females were assigned to groups immediately after calving. In group 1, from the day of calving the females had visual and olfactory but not physical contact with a male. The calves were removed on the day of birth and each female was placed with a male on Day 45. In group 2, females and their calves were placed individually with a male the day after calving. In group 3, females and their calves were kept with neither visual nor olfactory contact with a male and then placed with a male on Day 90. The estrous cycle was deduced from assays of plasma progesterone up to Day 120 after calving. All females exhibited a postpartum estrus a few days after parturition but the occurrence of the estrus was significantly delayed in females of group 3. The length of the estrous cycle was 23.7 +/- 1.3 days and the gestation length was 255.2 +/- 1.5 days. In the second experiment, a group of adult females was formed in 1987 and the intervals between calving recorded over a period of 5 years. The mean interval between calving was 285 +/- 2 days (n = 99 gestations). However, 66.6% of these intervals averaged 276 days whereas 19.2% had averaged 294 and 13% averaged 321 days.

An outbreak of tuberculosis in a captive herd of Arabian oryx (Oryx leucoryx): management

An outbreak of tuberculosis due to Mycobacterium bovis in a herd of Arabian oryx (Oryx leucoryx) was managed by sanitary and medical measures. The sanitary measures included the isolation of infected animals, the monitoring of animals with a range of diagnostic tests and the hand-rearing of the progeny of the infected herd. All the infected oryx were treated with a mixture of isoniazid at 10 mg/kg bodyweight, ethambutol hydrochloride at 15 mg/kg bodyweight and rifampicin at 10 mg/kg bodyweight administered daily in the drinking water. These measures resulted in the cessation of mortalities, a decrease in the numbers of moderate and high risk animals and the production of tuberculosis-free animals for reintroduction into the wild.