Kilohertz femtosecond UV-pumped visible beta-barium borate and lithium triborate optical parametric generator and amplifier

We demonstrate optical parametric generation and amplification of femtosecond pulses in the entire visible range using type-I phase-matched beta-barium borate and lithium triborate crystals pumped by the frequency-doubled output of a Ti:sapphire regenerative amplifier at 395 nm. The output is tunable from 470 to 770 nm with a pulse width of ~170 fs at a repetition rate of 1 kHz and a maximum output energy of ~1.1 muJ/pulse. The visible optical parametric amplifier output was then frequency doubled and sum frequency mixed with the fundamental output of Ti:sapphire at 790 nm to produce UV pulses with a conversion efficiency of greater than 25%. The second harmonic generated UV pulses are tunable from 240 to 380 nm with a maximum pulse energy of ~260 nJ/pulse.

[Comparison of total N-nitrosamides in fasting gastric juice from subjects in high and low risk areas for gastric cancer]

OBJECTIVE

The status of human exposure to N-nitrosamides (NAD) is almost unknown, although they are probably carcinogenic to human stomach. This study is to elucidate the relationship between NAD exposure and causes of gastric carcinomas (GC).

METHODS

The total amount of natural NAD was detected with a photohydrolysis-TEA method (184 nmole/l, detection limit) in fasting gastric juice samples from subjects aged 35-68 by fibroendoscope both in a high and low risk area for GC with the same geographical and socioeconomic conditions in Shangdon Province, China.

RESULTS

A) More NAD-positive samples in the high risk area (Linqu County, n = 176) were observed than in the low risk area (Chongshan County, n = 99), the difference was significantly after age-adjustment (40.9% vs. 30.3%, P = 0.0324). B)84% of samples was pH < or = 3 in Chongshan, whereas only 48% in Linqu (P < 0.001). In the acidic samples more NAD-positive ones in Linqu were found than in Chongshan (46.2% vs 27.4%, P < 0.01). NAD-positive rate was higher in samples with pH > or = 5 than those with pH < or = 3 only in the low but not in the high risk area. C)NAD-positive rate was also higher in samples from subjects with chronic atrophic gastritis (CAG) with or without dysplasia than those from normal subjects and from those with superficial gastritis or CAG with intestinal metaplasia both in the high and low risk areas.

CONCLUSION

The results suggest that human endogenous exposure to NAD in the high risk area for GC be higher than that in the low risk area; CAG and dysplasia may play a role in human gastric carcinogenesis by N-nitrosamides.

[Observation of compensatory head posture in superior oblique muscle paralysis]

PURPOSE

Superior oblique muscle paralysis is the most common disease in clinic. We analysed the cause, machanism and regularity of compensatory head posture in superior oblique muscle paralysis.

METHODS

All of 27 cases with superior oblique muscle paralysis aere examined regularly, and special muscle, binocular single vision function with synoptophore examined. Bielschowsky test was made.

RESULTS

In our cases, the incidence rate of compensatory head posture was 40.7%, which had relations with age when a patient had disease, period and function of binocular single vision.

CONCLUSION

The existance of binocular single vision function is the physiological bases leading to compensatory head posture, and the patients whose ages are older than 3 years and the course is less than 10 years may present the compensatory head posture. So we should pay attention to early diagnosis and training to restore the binocular single vision function.

[Synthesis and positive inotropic activity of 3,4-dimethoxybenzoyl-piperazine derivatives]

We designed and synthesized twelve new 3,4-dimethoxybenzoyl-piperazine derivatives. These chemical structures (TM-1-TM-12) were confirmed by means of IR, MS, H-NMR and elemental analysis. Compounds (OPC-8212 TM-1, TM-2, VPA) were tested for positive inotropic activity. The results showed that compounds OPC-8212 and VPA possessed positive inotropic activity (P < 0.05). Further pharmacological studies will be made.

[Preliminary studies on microbe-mediated N-nitrosamide synthesis]

Chemical synthesis of N-nitrosamide and influences on it by bacteria and fungi isolated from human gastric juice were studied with trace analysis method to explore the pathway of its endogenous formation. Results showed in synthesis of N-methyl-N-nitrosourea (MNU) with precursors of methylurea (0.42 mmol/L) and sodium nitrite (25 mmol/L) in a condition simulating human stomach, pH of the reaction system played an important role in the synthesis, the amount of synthetic chemical maximized at a pH of 1-3 and almost no synthesis was found at pH of 5-7. A study on the ability to synthesize MNU catalyzed by bacteria isolated from the patients with stomach cancer living in a high-risk area showed its synthesis could be accelerated by Pseudomonas aeruginosa at pH of 6-7 with its catalyzing activity existed in heat liable component of living bacteria. This is the first report showing microorganisms to catalyze the formation of N-nitrosamide from its precursors.

Social aspects of malaria in Heping, Hainan

This paper presents findings from a study conducted in Heping Town, Qiongzhong County, Hainan Province, China. The study, conducted in 1992, used qualitative as well as quantitative methods to gather social, cultural and behavioural data associated with the acquisition, transmission and prevention of malaria, and the diagnosis and treatment of disease. These methods included focus groups, key informant and other in-depth interviews, and observations, a household survey and tests of school children of knowledge of malaria. The study is among the first to our knowledge that has utilized this broad mix of methods for tropical disease research in China.

[A study on the degradation kinetics of nicotinamide powder]

The effect of temperature and humidity on the degradation of nicotinamide powder was studied below the critical relative humidity at temperatures 50-80 degrees C and relative humidities 50-80%. The rate equation of the degradation of nicotinamide under isothermal and constant humidity conditions is -dC/dt=k(Co-C)-1, where k is the apparent rate constant of degradation, Co and C are initial concentration and concentration at time t of nicotinamide, respectively. The relationship between the apparent rate constant of degradation and relative humidity RH is in K=a + m (RH), where a and m are constants. When RH are 50.35, 66.85, 75.33 and 80.35%, the apparent activation energies of degradation from Arrhenius equation are 219.94, 181.86, 168.99 and 153.89 kJ/mol, respectively. The rate equation the photodegradation of nicotinamide under room temperature is -dR/dt=K' (Ro-R)-1, where K' is the apparent rate constant of photodegradation, Ro and R are initial reflectance and reflectance at time t of nicotinamide, respectively.

[A study on pathogen antigen and serodiagnosis of Malleus and Melioidosis with McAbs]

A study on pathogen antigen and serodiagnosis of Malleus and Mlioidosis was made with McAbs which are against Ps. mallei or Ps. pseudomallei. The results showed that (1) Ps. mallei and Ps. pseudomallei express different surface antigen types respectively, and there are antigen overlapping in some degree between them; (2) Epitope 2D4 is common to Ps. mallei and Ps. pseudomallei; (3) The antibody which is similar to McAbs 4D4 or 1A9 might be a common serum antibody of Malleus and Melioidosis; and (4) McAb 3A1 is a high specific one which reacts with Ps. pseudomallei only, and with it, it is possible to resolve the immunological problem of distinguishing diagnosis between Malleus and Melioidosis.

Highly efficient ultraviolet generation at 355 nm in LiB(3)O(5)

Highly efficient generation of UV radiation at 355 nm has been achieved in a LiB(3)O(5) crystal through the frequency mixing of the fundamental and second-harmonic radiation of a Nd:YAG laser. An energy conversion efficiency of 60% has been obtained under the experimental conditions described here. Thus the usefulness of LiB(3)O(5) for frequency-conversion applications is demonstrated.