Study of a quadrupole ion trap with damping force by the two-point one block method.

RATIONALE: The capabilities and performances of a quadrupole ion trap under damping force based on collisional cooling is of particular importance in high-resolution mass spectrometry and should be analyzed by Mathieu's differential solutions. These solutions describe the stability and instability of the ion's trajectories confined in quadrupole devices. One of the methods for solving Mathieu's differential equation is a two-point one block method. In this case, Mathieu's stability diagram, trapping parameters a(z) and q(z) and the secular frequency of the ion motion w(z), can be derived in a precise manner. The two-point one block method (TPOBM) of Adams Moulton type is presented to study these parameters with and without the effect of damping force and compared to the 5th-order Runge-Kutta method (RKM5). The simulated results show that the TPOBM is more accurate and 10 times faster than the RKM5. The physical properties of the confined ions in the r and z axes are illustrated and the fractional mass resolutions m/Δm of the confined ions in the first stability region were analyzed by the RKM5 and the TPOBM. METHODS: The Lagrange interpolation polynomial was applied in the derivation of the proposed method. The proposed method will be utilized to obtain a series solution directly without reducing it to first order equations. RESULTS: The problem was tested with the ion trajectories in real time with and without the effect of damping force using constant step size. Numerical results from the two-point one block method have been compared with the fifth order Runge-Kutta method. CONCLUSIONS: The proposed two-point one block method has a potential application to solve complicated linear and nonlinear equations of the charged particle confinement in a quadrupole field especially in fine tuning accelerators, and, generally speaking, in physics of high energy.

A national epidemiological survey of oral mucosal lesions in Malaysia.

The prevalence of oral mucosal lesions in Malaysia was determined by examining a representative sample of 11,707 subjects aged 25 years and above throughout the 14 states over a period of 5 months during 1993/1994. A two-stage stratified random sampling was undertaken. A predetermined number of enumeration blocks, the smallest population unit in the census publication, was selected from each state. With the selected enumeration block, a systematic sample of living quarters was chosen with a random start. The survey instrument included a questionnaire on sociodemographic characteristics and a clinical examination. The clinical examination was carried out by 16 specially trained dental public health officers and the diagnosis calibrated with a final concordance rate of 92%. The age in the sample ranged from 25 to 115 years with a mean of 44.5+/-14.0. The sample comprised 40.2% males and 59.8% females; 55.8% were Malays, 29.4% Chinese, 10.0% Indians and 1.2% other ethnic groups. Oral mucosal lesions were detected in 1131 (9.7%) subjects, 5 (0.04%) had oral cancer, 165 (1.4%) had lesions or conditions that may be precancerous (leukoplakia, erythroplakia, submucous fibrosis and lichen planus) and 187 (1.6%) had betel chewer's mucosa. The prevalence of oral precancer was highest amongst Indians (4.0%) and other Bumiputras (the indigenous people of Sabah and Sarawak) (2.5%) while the lowest prevalence was amongst the Chinese (0.5%).

The prevalence of caries and enamel defects in 229 Malaysian children 16 years after water fluoridation (a pilot study).

Two hundred and twenty-nine children aged 12-15 years who were continuous residents of Penang island, in the north of Peninsular Malaysia were examined for caries and enamel defects. Caries prevalence was 82.2% with a DMFT score of 3.4 and DMFS score of 4.9; there were very few missing teeth and very little untreated caries in the population examined. Majority of DF (decayed/filled) lesions were pits and fissures with approximal and smooth surfaces relatively caries free. The prevalence of enamel defects was 76.4% with 19.1% of all teeth examined being affected. More posterior than anterior teeth were affected by enamel defects just as there were more maxillary than mandibular teeth affected by enamel defects. Diffuse patchy opacities were the most common defect diagnosed and this was found in 60.2% of the population examined. A bilateral distribution of diffuse patchy opacities was seen in 41.5% of the population examined. Tooth surfaces with enamel defects were no more susceptible to caries than defect-free surfaces.

Erupted compound odontoma.

A case is described in which a compound odontoma erupted into the oral cavity in an 8 1/2-year-old girl. The odontoma was initially discovered as a chance radiographic finding 2 years 8 months previously.

Crouzon syndrome. A review of literature and case report.

A sporadic case of Crouzon Syndrome without mental retardation is described. The patient, an 11 year old boy with grossly carious teeth and in severe pain was referred for dental treatment. A review of literature on Crouzon Syndrome is presented.

The cracked tooth syndrome--crown root vertical fracture.

A case of an incomplete tooth fracture followed by a complete fracture was presented. The difficulty of diagnosing this condition was discussed as well as the possible histological explanation of the symptoms experienced by the patient. It once again points out to practising dentists, that whilst deep pockets can give rise to severe periodontal pain, intense and excruciating pain should be investigated with the cracked tooth in mind.

Dental health in Malaysia.

Three epidemiological surveys have been carried out in Malaysia since 1971. All showed a high level of caries prevalence. Ninety per cent of school children between the ages of 6 and 18 suffered from dental caries, with a DMFT of approximately 3 and a dft of approximately 2. Ninety-five per cent of the adult population had caries experience, with the mean DMFT being 13.2. Approximately 55 per cent of children showed the presence of gingivitis with the mean number of inflamed gingival units per child ranging from 1.9 to 2.8, while 72.4 per cent of adults had some form of periodontal disease with 29 per cent having pockets deeper than 3 mm. The OHI-S score for adults was 2.2 and 81 per cent used toothbrushes to clean their teeth. A further 5.1 per cent used twigs and fingers with powdered charcoal or salt. One-third of the child population needed orthodontic treatment, with 0.3 per cent examined in peninsular Malaysia having cleft lip or palate or both. In the adult population 10.4 per cent of those examined required some form of orthodontic treatment. Twenty per cent of the children in the survey were in need of dentures; 54.7 per cent of the adults were either in need of dentures or were wearing dentures. Of these 25 per cent had complete dentures. The smoking habit was most commonly associated with pre-cancerous/cancerous lesions with alcohol consumption a close competitor; 114 adults, that is 1.3 per cent of those examined, suffer from leukoplakia but only one case of oral cancer was detected.(ABSTRACT TRUNCATED AT 250 WORDS)