Abstract. A population-based surveillance for typhoid fever was conducted in three rural communes of Dong Thap Province in southern Vietnam (population 28,329) for a 12-month-period starting on December 4, 1995. Cases of typhoid fever were detected by obtaining blood for culture from residents with fever Ն 3 days. Among 658 blood cultures, 56 (8.5%) were positive for Salmonella typhi with an overall incidence of 198 per 10 5 population per year. The peak occurrence was at the end of the dry season in March and April. The attack rate was highest among 5-9 year-olds (531/10 5 /year), and lowest in Ͼ 30 year-olds (39/10 5 /year). The attack rate was 358/10 5 /year in 2-4 yearolds. The isolation of S. typhi from blood cultures was highest (17.4%) in patients with 5 to 6 days of fever. Typhoid fever is highly endemic in Vietnam and is a significant disease in both preschool and school-aged children.

Salmonella typhi was isolated from 369 andSalmonella paratyphi A was isolated from 6 of 515 Vietnamese patients with suspected enteric fever. Compared with conventional broth culture of blood, direct plating of the buffy coat had a diagnostic sensitivity of 99.5% (95% confidence interval [CI], 97.1 to 100%). Blood bacterial counts were estimated by the pour plate method. The median S. typhi count in blood was 1 CFU/ml (range, <0.3 to 387 CFU/ml), of which a mean of 63% (95% CI, 58 to 67%) were intracellular. The mean number of bacteria per infected leukocyte was 1.3 (interquartile range [IQR], 0.7 to 2.4) CFU/cell (n = 81). Children (<15 years old;n = 115) had higher median blood bacterial counts than adults (n = 262): 1.5 (range, <0.3 to 387) versus 0.6 (range, <0.3 to 17.7) CFU/ml (P = 0.008), and patients who excreted S. typhi in feces had higher bacteremias than those who did not: a median of 3 (range, <0.3 to 32) versus 1 (range, <0.3 to 68) CFU/ml (P = 0.02). Blood bacterial counts declined with increasing duration of illness (P = 0.002) and were higher in infections caused by multidrug-resistant S. typhi (1.3 [range, <0.3 to 387] CFU/ml; n = 313) than in infections caused by antibiotic-sensitive S. typhi (0.5 [range, <0.3 to 32] CFU/ml; n = 62) (P = 0.006). In a multivariate analysis this proved to be an independent association, suggesting a relationship between antibiotic resistance and virulence in S. typhi.

Machine performance degradation assessment and remaining useful life (RUL) prediction are of crucial importance in condition-based maintenance to reduce the maintenance cost and improve the reliability. They provide a potent tool for operators in decision-making by specifying the present machine state and estimating the remaining time. For this ultimate purpose, a threestage method for assessing the machine health degradation and forecasting the RUL is proposed.In the first stage, only the normal operating condition of machine is used to create identification model for recognizing the dynamic system behavior. Degradation index which is used for indicating the machine degradation is subsequently created based on the root mean square of residual errors. These errors are the difference between identification model and behavior of system. In the second stage, the Cox's proportional hazard model is generated to estimate the survival function of the system. In the last stage, support vector machine, which is one of the remarkable machine learning techniques, in association with time-series techniques is utilized to forecast the RUL. The data of low methane compressor acquired from condition monitoring routine is used for validating the proposed method. The result shows that the proposed method could be used as a reliable tool to machine prognostics.

An open randomized comparison of 2 days (Ofx2) versus 3 days (Ofx3) of oral ofloxacin treatment (15 mg/kg/ day) was conducted with Vietnamese children between 1 and 15 years of age with suspected typhoid fever. Of 108 children enrolled, 100 were blood culture positive for Salmonella typhi, and 86% of the isolates were multidrug resistant. There were no significant adverse effects. The therapeutic responses were similar in both groups, with mean (؎ standard deviation) fever clearances of 107 ؎ 60 h in the Ofx3 group and 100 ؎ 64 h in the Ofx2 group (P > 0.2). There were six ''clinical'' failures in the Ofx2 group and two clinical failures in the Ofx3 group (P > 0.2), in which fever and symptoms persisted for more than 1 week after the start of treatment, but only one of these was culture positive (Ofx3). There was one suspected relapse, and one carrier was identified. Short courses of ofloxacin are simple, inexpensive, safe, and effective for the treatment of uncomplicated multidrug-resistant typhoid fever.

1165This paper deals with dynamic analysis of Pipeline Inspection Gauge (PIG) flow control in natural gas pipelines. The dynamic behaviour of PIG depends on the pressure differential generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze dynamic behaviour characteristics (e.g. gas flow, the PIG position and velocity) mathematical models are derived. Two types of nonlinear hyperbolic partial differential equations are developed for unsteady flow analysis of the PIG driving and expelled gas. Also, a non-homogeneous differential equation for dynamic analysis of the PIG is given. The nonlinear equations are solved by method of characteristics (MaC) with a regular rectangular grid under appropriate initial and boundary conditions. Runge-Kutta method is used for solving the steady flow equations to get the initial flow values and for solving the dynamic equation of the PIG. The upstream and downstream regions are divided into a number of elements of equal length. The sampling time and distance are chosen under Courant -Friedrich-Lewy (CFL) restriction. Simulation is performed with a pipeline segment in the Korea gas corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. The simulation results show that the derived mathematical models and the proposed computational scheme are effective for estimating the position and velocity of the PIG with a given operational condition of pipeline. A: Pipe cross section area [m 2 ] c : Wave speed [m/s] C : Linear damping coefficient of PIG [Ns/m] C c : Convection heat transfer coefficient [W/m 2 K] C; : Specific heat at constant volume [J/kgK] d : Internal diameter of pipe [rn] e : Internal energy per unit mass [J/kg] • Corresponding Author, FfPsta FfPdYn r, g h f k K I L PI G m M : Darcy friction coefficient : Braking force [N] : Friction force per unit pipe length [N/m] : Friction force between PIG and pipe wall' including [N] : Static friction force : Dynamic friction force : PIG driving force [N] : Gravity acceleration [m/S2] : Pipe head loss [m] : Pipe wall roughness [m] : Wear factor per distance travel [N/m] : Length of pipeline [m] : Length of PIG [m] : Hydraulic mean radius of pipe [m] : Weight of PIG [kg] P : Flow pressure [N/m 2 ] q : Compound rate of heat inflow per unit area of pipe wall [W'/m 2 ] R : Gas constant [J/kgK] S : Perimeter of pipe [m] T : Flow temperature [K] Text : Seabed temperature [K] u : Flow velocity [m/s] x : Distance from pipe inlet [m] XPiC : Position of PIG [m] VPlC : Velocity of PIG [rn/s] Greeks r : The ratio of specific heat !.I : Kinetic viscosity of flow [m 2/s] p : Fluid density [kg/m 3 ] SubscriptsL, R, M, N, S, 0, P: The grid points, and 0, I : The points at inlet and outlet of pipeline

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ABSTRACT. A total of 230 Salmonella isolates representing 33 serotypes originated from food (pork, beef, chicken meat, duck meat, and shrimp), domestic animals (pig, chicken, and duck), and human (children with diarrhea) in the Mekong Delta, Vietnam were examined for the antimicrobial resistance to 10 antibiotics. Of the 230 Salmonella isolates examined, 49 (21.3%) showed antimicrobial resistance. Thirty-eight isolates (16.5%) were resistant to oxytetracycline, 26 (11.3%) to chloramphenicol, 17 (7.4%) to nalidixic acid, 16 (7.0%) to streptomycin, 5 (2.2%) to kanamycin, and 4 (1.7%) to ampicillin. No isolate showed resistance to gentamicin, cefazolin, ceftriaxone, and ciprofloxacin. Among the resistant isolates, nineteen isolates were resistant to one antimicrobial agent, 10 to two, 15 to three, 3 to four, and 2 to five antimicrobial agents. The resistance rate of Salmonella isolates from the Mekong Delta, Vietnam to these antimicrobial agents seems to be relatively lower than the results of developed countries and even those of the neighboring countries.

An accurate and efficient new class of predictor-corrector schemes are proposed for solving nonlinear differential equations of fractional order. By introducing a new prediction method which is explicit and of the same accuracy order as that of the correction stage, the new schemes achieve a uniform accuracy order regardless of the values of fractional order