Pulse to pulse control for highly precise and efficient micromachining with femtosecond lasers.

Micromachining with high repetition rate femtosecond lasers and galvo scanners shows some limitations in the pulses positioning accuracy due to the galvo mirrors acceleration. This is particularly evident during scan speed or direction changes, resulting in a poor quality and overtreatment e.g. in corners. Several scanning approaches have been proposed to tackle these issues like the so-called skywriting (SW) and the pulse-on-demand (POD) being the last limited to ns lasers, moderate pulse repetition rates and scan speeds. Recently, POD approach has been extended to femtosecond laser sources with high power and high repetition rate. Here, for the first time, we explored the huge potential in laser micromachining of femtosecond POD technology associated to a fast galvo scanner. We tested an innovative set-up allowing for precise laser triggering at the requested time and position for MHz repetition rate and scan speed as high as 20 m/s. The pulse position accuracy of the system has been estimated to be ≤ 1µm whilst performances have been evaluated in comparison to conventional scanning and SW. Finally, we report the results of an engraving test on stainless steel. The advantages of the approach we propose are clearly shown in terms of machining quality and precision with respect to conventional scanning and reduction of the processing time by ≈ 40% with respect to SW.

Immunization in urban Southeast Asia.

By the year 2000 half the population in the world is expected to reside in large urban areas. "Improving immunization services to the disadvantaged in urban areas" is considered one of the priorities for the Expanded Programme on Immunization (EPI). A review of the current situation with regard to immunization coverage and disease surveillance in urban Southeast Asia shows that acceleration of immunization activities in urban areas is needed to achieve and sustain the goal of Universal Child Immunization by the year 1990.

Evaluation of cold chain monitoring in Kelantan, Malaysia.

An analysis was carried out on a total of 883 cold chain monitor (CCM) cards, which had been attached to batches of poliomyelitis, measles, DPT (diphtheria, pertussis, tetanus) and hepatitis B vaccines, during their transport and storage from the central store in Kuala Lumpur to Kelantan, a state in north-eastern Malaysia; 234 freeze watches attached to hepatitis B vaccines were also analysed. The monitor cards and freeze watches were observed at six levels between the central store and the periphery during distribution of the vaccines, and a colour change in any of the four windows (A, B, C, D) on the CCM cards or the freeze watches was recorded. In addition, 33 unopened vials of oral poliovirus vaccine (OPV), collected from refrigerators in 29 health facilities in Kelantan, were tested for potency using the tissue culture infective dose 50 (TCID50) method; 14 of them (42%) did not meet the WHO criteria for potent vaccines. The results showed that at the final destination 13.4% of all cards remained white while a colour change to blue was observed in 65% in window A, 16.6% in window B, and 4.4% in window C; none had turned blue in window D indicating that the vaccine had not been subjected to temperatures > or = 34 degrees C for 2 hours. All but 2 of the 234 freeze watches had turned purple, which indicates exposure of the hepatitis B vaccines to temperatures below 0 degree C. These results will assist health planners to correct the weaknesses identified in the cold chain system.

Poliomyelitis eradication in the Western Pacific Region.

Polio eradication activities in the Western Pacific Region (WPR) have reduced the transmission of wild poliovirus to one remaining focus of endemic transmission in the Mekong Delta area of South Vietnam and Cambodia. There has been a high level of government commitment for national immunization days in all WPR countries in which poliomyelitis was previously endemic and for continuous improvement in acute flaccid paralysis (AFP) surveillance quality. The total number of reported confirmed poliomyelitis cases in 1995 (as of June 1996) was 432, only 7% of the total of 5825 cases reported in 1990. In 1995, wild poliovirus was isolated from only 19 of 4800 AFP patients from whom specimens were collected and analyzed. There has been one importation of wild poliovirus type 1 into China from a neighboring country. An international Regional Commission for the Certification of Poliomyelitis Eradication in the WPR has been formed and met for the first time in April 1996.

Development and coordination of the Polio Laboratory Network in the Western Pacific Region of the World Health Organization.

A multitiered network of polio laboratories, consisting of specialized reference laboratories, regional reference laboratories, national laboratories and, in the case of China, provincial laboratories, was established in the Western Pacific Region of the World Health Organization (WHO) in 1992. The network currently consists of 43 laboratories within the Region and is coordinated through the WHO Regional Office in Manila. As the levels and extent of supplementary immunization and acute flaccid paralysis surveillance activities have increased, so has the work load of network laboratories. The total number of stool specimens collected and processed in Polio Laboratory Network laboratories in this WHO region in 1995 exceeded 15,000. With the Region now establishing the criteria necessary for certification of polio-free status, it is essential for the Polio Laboratory Network to establish international confidence in its ability to carry out its role in the eradication of polio.

The experience of countries in the Western Pacific Region in conducting national immunization days for poliomyelitis eradication.

Experience with national immunization days (NIDs) in six countries of the Western Pacific Region has shown that political support at all levels, detailed logistics plans, strategies appropriate to the local situation, and simple social mobilization messages have been key factors in the success of NIDs. Conventional strategies that may apply to conducting routine Expanded Programme on Immunization vaccinations do not necessarily apply to NIDs, in which the maximum number of children must be immunized in 1 or 2 days. Setting up temporary immunization posts at sites convenient to the local situation, moving the posts once or twice during the course of a day, and using volunteers to staff them are among many of the adaptations used successfully. Coverage figures published immediately after an NID can be misleading because of uncertainty about the true denominator. The true measure of the success of NIDs is in surveillance for wild poliovirus after the event.

Costs of polio immunization days in China: implications for mass immunization campaign strategies.

Ten provinces of China were selected to estimate the cost per immunization of the 1994-95 national immunization days (NIDs) at five levels (e.g. province, prefecture, county, township and village). Personnel costs accounted for the largest overall share of costs (39 per cent), followed by publicity and promotion costs (27 per cent), and logistic costs (15 per cent). Without consideration of vaccine costs, the major part of NID expenses were shouldered at the township level, which paid for 47 per cent of all incremental costs, while county and village level covered 28 per cent and 18 per cent respectively. Estimation of average costs per immunization was 2.86 RMB yuan, or $0.34, including vaccine costs, buildings and equipment amortization and salaries at all levels. The factors affecting average cost of NID included the output volume, socio-economic development and geographic features. Various approaches were recommended: to intensify the productivity of time and staff, to employ alternative inexpensive manpower resources, to make the best use of publicity and social promotion, the expansion of the age groups and utilization of multi-intervention strategies. Good planning at township level was a decisive factor to ensure an effective NID conducted in an efficient manner. The average cost of China's NID was the lowest among all mass immunization campaigns ever documented. Much of the reduced average cost was attributable to economies of scale.