Time and laser ranging: a window of opportunity for geodesy, navigation and metrology.

Recent progress in the domain of time and frequency (T/F) standards requires important improvements of existing time distribution links. Among these, the accuracy of time transfer is actually an important part of the concerns in order to establish and maintain time & space references from ground and/or space facilities. Several time transfers by laser link projects have been carried out over the past 10 years with numerous scientific and metrological objectives. Satellite Laser ranging (SLR) has proven to be a fundamental tool, offering a straightforward, conceptually simple, highly accurate and unambiguous observable. Depending on the mission, LR is used to transmit time over two-way or one-way distances from 500 to several millions of km. The following missions and their objectives employed this technique: European Laser Timing (ELT) at 450 km, Time Transfer by Laser Link (T2L2) at 1,336 km, Laser Time Transfer (LTT) at 36,000 km, Lunar Reconnaissance Orbiter (LRO) at 350,000 km, and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) at tens of million km. This article describes the synergy between SLR and T/F technologies developed on the ground and in space and as well as the state of the art of their exploitation. The performance and sources of limitation of such space missions are analyzed. It shows that current and future challenges lie in the improvement of the time accuracy and stability of the time for ground geodetic observatories. The role of the next generation of SLR systems is emphasized both in space and at ground level, from the point of view of GGOS and valuable exploitation of the synergy between time synchronization, ranging and data transfer.

[Preformulation study of a potential local anesthetic from a group of phenylcarbamic acid derivatives]. / Predformulacné stúdiá potenciálneho lokálneho anestetika zo skupiny derivátov kyseliny fenylkarbámovej.

Within pre-formulation studies of phenylcarbamic acid derivatives with local anaesthetic effects, potential drug IV with the chemical name N-(2-(2-ethylphenylcarbamoyloxy)-ethyl)-piperidiniumchloride was examined. The study evaluated the effect of polyhydric alcohols--glycerol, propylene glycol, sorbitol and their concentrations of 5; 10; 15, and 20 wt % on the values of the partition coefficient in the system n-octanol/water, surface tension, and viscosity of the solutions of potential drug IV. The optimal auxiliary substance seems to be glycerol of a concentration of 15-20 wt %, as it does not affect the values of the partition coefficient and surface tension of potential drug IV solutions in a statistically significant manner.

Peltier-Cooled and Actively Quenched Operation of InGaAs/InP Avalanche Photodiodes as Photon Counters at a 1.55-mum Wavelength.

The performance of commercially available InGaAs/InP avalanche photodiodes as single-photon detectors at a 1.55-mum wavelength has been investigated. A new active quenching and gating circuit, tailored for operation of these diodes at temperatures in the range from room temperature to -60 degrees C and achievable by means of thermoelectrical cooling, has been developed. Careful tuning of the diodes' operating conditions resulted in a significant reduction of afterpulsing effects; it permitted operation of the detectors with high repetition rates. A noise-equivalent power of 7 x 10(-16) W/Hz(1/2) was obtained at a 1.55-mum wavelength.

The perception of discrimination in the HIV policy among Czech gay men.

The study aimed to evaluate the perception of discrimination in the Czech national HIV policy among gay men. The anonymous questionnaires were published in the gay journal and 191 respondents filled them and returned back. Their assessment of discrimination in the HIV policy and other life activities were ranked in 5-points scale. Assumed discrimination in the HIV policy was found to be one of the lowest one. Forty-one percent of men who answered did not find any discrimination in the HIV policy at all, eleven percent of them perceived it at the highest level. The personal perception of HIV discrimination was related to the fear of discrimination in the health facilities and to the general evaluation of political change for gay life. HIV policy is generally viewed as tolerant and without discriminative approach toward vulnerable minorities. The number of negative evaluations can play important role in the obstacles of preventive programs.

[Attitudes toward condoms and experience with their use among sex education teachers]. / Postoje ke kondomum a zkusenosti s jejich pouzíváním u sexuálních pedagogu.

BACKGROUND: The sex education is influenced by knowledge and attitudes. The aim of presented study was to evaluate the attitudes toward condom among sex education teachers and their personal experience with its use. METHODS AND RESULTS: Attitudes toward condoms were measured by 10-items anonymous questionnaires according to Zverina and Lippert. Personal experience was subjectively assumed in 5-point scale. The samples consists of 230 sex education teachers, among them 193 (84%) women. The average age was 40.5 +/- 9.7 years, in the range from 19 to 60 years. 37 teachers (16%) assigned themselves as religious. Condom was evaluated as a good protection against HIV and other STD in almost all answers. Three fifths of teachers considered condom to be an excellent contraception. 48% teachers did not know if the majority of women dislike condom. One tenth respondents rejected the opinion that the men dislike condoms. One tenth of teachers has never experienced condom personally. 12 percent stated to use it regularly, among them are more represented men. The opinions about quality of condom and decreased sensitivity by condom differ believers from atheists and users from non-users. CONCLUSIONS: Attitudes toward condom are predominantly liberal among Czech sex education teachers. The personal experience with use is common but not regular. The religion has small influence toward the attitudes and use.

Large-aperture germanium detector package for picosecond photon counting in the 0.5-1.6-microm range.

We report the design, construction, and parameters of a detector package based on a germanium avalanche photodiode operated in the Geiger mode cooled to 77 K. The new design of the active quenching circuit, proper diode structure, and cryogenic cooling setup permitted us to increase the detector's active area to 0.1-mm diameter while maintaining an acceptable dark-count rate, timing resolution, and photon-counting sensitivity at 1.54 microm. The active-area size and the compact design of the detector package permitted its application in satellite laser ranging at 0.532- and 1.543-microm wavelengths, yielding subcentimeter ranging precision.

[The effect of autolysis on the conduction system in young rats. An enzyme histochemistry study]. / Vliv autolýzy na prevodní systém mladých krys. Enzym-histochemická studie.

The conducting system of young rats was studied by histochemistry during autolysis at room temperature lasting 1, 3, 6, 24 and 48 hours. The results were compared with working muscle tissue. The most sensitive was the "glycogen-dependent" phosphorylase and the activity decreased after 1 hour. It was slightly detectable as late as after 24 hours when the working muscle was already negative. Other enzyme activities (oxidoreductases and hydrolases) were practically uninfluenced by 6 hour autolysis. A substantial decrease of activities was found in conducting system after 48 hours in comparison to the working muscle. A solitary relatively strong residual activity belonged to acetylcholine-esterase in the conducting system. Detection of acetylcholine-esterase can be useful in identification of the conducting system even later after death.