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The definition of UTC was implemented in 1972, principally to accommodate celestial navigation and follows recommendation 460 of the International Radio Consultative Committee (CCIR) in 1970. Since 1972 the use of electronic means to navigate has overtaken celestial navigation. This fact along with increasing public dissatisfaction with the possible disruption to modern electronic communications and navigation systems caused by the insertion of a leap second has called into question the current definition of UTC. An extensive review of the background and issues relating to the leap second can be found in Nelson, et al (2001).

The most intensely discussed and controversial issue in time keeping has been the proposal before the International Telecommunications Union (ITU) to redefine Coordinated Universal Time (UTC) so as to replace leap seconds by leap hours. Should this proposal be adopted, the practice of inserting leap seconds would cease after a specific date. Should the Earth's rotation continue to de-accelerate at its historical rate, the next discontinuity in UTC would be an hour inserted several centuries from now. Advocates of this proposal cite the need to synchronize satellite and other systems, such as GPS, Galileo, and GLONASS, which did not exist and were not envisioned when the current system was adopted. They note that leap second insertions can be and have been incorrectly implemented or accounted for. Such errors have to date had localized impact, but they could cause serious mishaps involving loss of life. For example, some GPS receivers have been known to fail simply because there was no leap second after a long enough interval, other GPS receivers failed because the leap second information was broadcast more than three months in advance, and some commercial software used for internet time-transfer Network Time Protocol (NTP) could either discard all data received after a leap second or interpret it as a frequency change. The ambiguity associated with the extra second could also disrupt financial accounting and certain forms of encryption. Those opposed to the proposal question the need for a change, and also point out the costs of adjusting to the proposed change and its inconvenience to amateur astronomers and others who rely upon astronomical calculations published in advance. Reports have been circulated that the cost of checking and correcting software to accommodate the new definition of UTC would be many millions of dollars for some systems. In October 2005 American Astronomical Society asked the ITU for a year's time to study the issue. This commission has supported the efforts of the IAU's Committee on the Leap Second to make an informed recommendation, and anticipates considerable discussion at the IAU's 26th General Assembly in 2006.

The author explains why light pulses are an important tool for time coordination and discuss the activities and the problems in this field. The author reviews the scientific and technical problems propelling the search for very accurate time comparison. A laser comparison method is discussed which is very simple in principle. This is followed by a discussion of the first experiments performed in France, the United States, Spain, and China. A new space based experimental method is presented along with the first results, and some specific problems in laser timing along with the kinds of errors one would expect are discussed. >

Background Nowadays polytherapy is widely used in older patients affected by comorbidity but it implies changing kinetics and dynamics which can increase the probability of negative drug interactions resulting in therapeutic failure and/or adverse drug reactions. Purpose The aim of this study was to retrospectively assess the prescriptions of discharged patients to assess potential drug interactions in terms of frequency and characteristics. Materials and methods The retrospective study was carried out considering the data within the period from 1 January to 31 March 2011. The study examined prescriptions with at least two drugs for patients older than 65 who were discharged from the General Medicine Unit of Azienda Ospedaliero Universitaria S. Maria della Misericordia in Udine. Drug interactions were identified and assessed using the Micromedex DrugReax System. Results The data involved 181 patients (44% male and 56% female): 12% in the range between 65 and 70 years, 79% in the range between 71 and 90 years and 9% of patients older than 90 years. Most patients had between 5 and 10 drugs (69%). The rest of them: 16% of patients had fewer than five drugs, 14% between 11 and 15 drugs and 1% more than 15 drugs. The authors analysed 1348 prescriptions. The therapeutic classes most frequently prescribed were: antithrombotic agent (161 prescriptions, 11.9%), diuretics (129 prescriptions, 9.6%), drugs for acid-related disorders and drugs for the heart (121 prescriptions, 9%). Furosemide (8.0%), pantoprazole (7.0%), acetylsalicylic acid and ramipril (5.3%) were the most frequently prescribed drugs. According to the Micromedex DrugReax database, only the treatments of 34 patients (19%) did not show potential drug interactions. The database responses pointed out 633 potential drug interactions, 47% of total prescriptions: 2% of minor, 78% of moderate and 20% of major severity. This meant that major-severity drug reactions were possible in 74 different prescriptions: ramipril-spironolactone (eight prescriptions) and simvastatin-warfarin (five prescriptions) being the most frequent. Conclusions The percentage of major-severity potential drug interactions was low. However, in order to improve the quality of healthcare, the key reading of the results was the opportunity to initiate a control procedure to prevent negative effects from the drug interaction. Clinical pharmacists should have a key role, using their expertise in a proactive exchange with the clinical prescriber when the treatment is decided. This might avoid potentially dangerous drug interactions that might lead to therapeutic failure and/or adverse drug reactions. Possible suggestions might include modification of time scheduling for drug administration. Finally clinical pharmacists should also educate patients to promote compliance with the drug administration regimen.

In the first part of this paper the characteristics of frequency deviation and modulation bandwidth required for phase-locking optically pumped far infrared lasers to reference synthesized signals are examined. Then different fast modulation techniques suitable for this purpose are discussed pointing out their particular features. Experimental results concerning laser frequency modulation by Stark effect, injection locking and electrically variable reactances (e.g Schottky diodes, plasma cell) are reported and compared.

On the basis of the height difference between the CNR cosmic-ray laboratory at Plateau Rosa, 3500 m, and Turin, 250 m above s.l., a direct measurement of the terrestrial gravitational shift has been made by the comparison of the time scales of two cesium beam atomic frequency standards of the Istituto Elettrotecnico Nazionale «Galileo Ferraris». The principle of equivalence predicts the effect Δt/t=−ΔU/c 2 =3.54·10−13, corresponding to the gain of the standard at mountain altitudes Δt/t=30.6 ns/d. The results Δt/t=(33.8±6.8) ns/d and Δt/t=(36.5±5.8) ns/d, derived with two independent operating criteria, have been obtained from 1584 h of actual measurement, with reference to an atomic time scale whose linearity was continuously and carefully tested. The results are discussed in terms of the current gravitational theories and in view of future experimental researches, which will be permitted by the advancements of the metrology of time.

It is reported that the X-ray pulses from the PSR 0531+21 pulsar have been detected by means of a VLF sounding of the ionospheric region with which they interact. VLF waves impinging on theD-region with a very large angle of incidence and recorded at a location (Turin, Italy) where a big natural obstacle (the Mont Blanc) scatters away the associate ground wave have been instrumental in fostering the success of the operation. The existence of some specific electron density profiles that are likely to be found in theD-region of the ionosphere is also required for the ground-based detection of the X-ray pulses from PSR 0531+21.

A time comparison method, which is based on TV synchronization pulses sent along radio links, was proposed and successfully tested in Czechoslovakia in 1967. Experiments performed afterwards in Europe and the U. S. confirmed the significance of this method. The instability of the overall propagation time delay along the radio links (including the equipment) is the major source of errors for long-term timekeeping between remote laboratories. In 1969, a research project on this subject was initiated in Italy, using the comparison of simultaneous time measurements by the TV method and integrated phase measurements via a coaxial cable between two remote laboratories that were located in Rome and Turin, Italy. The results show that the discrepancy between the TV results and the direct comparison by cable, over periods of 100 days, is usually less than 3 ?s.

L’esposizione degli argomenti trattati nel presente articolo e stata di proposito molto contenuta, ma la varieta dei soggetti lascia facilmente immaginare quanto vasta e feconda possa essere la ricerea in questo settore metrologico che ha le piu strette connessioni con la fisica della materia, l’elettronica e la radiotecnica.

Countless are nowadays the applications of Time/Frequency methods and systems to science and technology: the daily production of more than 300 000 quartz units, with precisions ranging from 10E-5 to 10E-10, barely satisfies the needs of factories making wristwatches, cars, PCs, dishwashers, etc..