Risk and Protective Factors for Gastrointestinal Symptoms associated with Antibiotic Treatment in Children: A Population Study

Bau, Mario,Moretti, Alex,Bertoni, Elisabetta,Vazzoler, Valentino,Luini, Chiara,Agosti, Massimo,Salvatore, Silvia The Korean Society of Pediatric Gastroenterology 2020 Pediatric gastroenterology, hepatology & nutrition Vol.23 No.1

Purpose: Gastrointestinal symptoms are often related to antibiotic treatment. Their incidence, risk and protective conditions in children are not well defined and represent the aims of this study. Methods: We prospectively enrolled inpatient children submitted to antibiotic treatment. Indication, type, dose and duration of treatment, probiotic supplementation and gastrointestinal symptoms were recorded at recruitment, after two and four weeks. Antibiotic-associated diarrhea (AAD) was defined as the presence of at least 3 loose/liquid stools within 14 days from antibiotic onset. Results: AAD occurred in 59/289 (20.4%) of patients, with increased risk in children younger than 3 years (relative risk [RR]=4.25), in lower respiratory (RR=2.11) and urinary infections (RR=3.67), intravenous administration (RR=1.81) and previous AAD episodes (RR=1.87). Abdominal pain occurred in 27/289 (9.3%), particularly in children >6 years (RR=4.15), with previous abdominal pain (RR=7.2) or constipation (RR=4.06). Constipation was recorded in 23/289 (8.0%), with increased risk in children having surgery (RR=2.56) or previous constipation (RR=7.38). Probiotic supplementation significantly reduced AAD (RR=0.30) and abdominal pain (RR=0.36). Lactobacillus rhamnosus GG (LGG) and L. reuteri significantly reduced AAD (RR=0.37 and 0.35) and abdominal pain (RR=0.37 and 0.24). Conclusion: AAD occurred in 20.4% of children, with increased risk at younger age, lower respiratory and urinary tract infections, intravenous treatment and previous AAD. LGG and L. reuteri reduced both AAD and associated abdominal pain.

Doped Two-dimensional Semiconductor Superlattice: Photo-stimulated Quantum Thermo-magnetoelectric Effects under the Influence of a Confined Phonon

Bau Nguyen Quang,Quynh Nguyen Thi Lam,Ba Cao Thi Vi,Hung Le Thai 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.12

Photo-stimulated quantum thermo-magnetoelectric effects in doped two-dimensional semiconductor superlattices, including the photo-stimulated quantum Ettingshausen effect and the photo-stimulated quantum Peltier effect, have been theoretically studied by using the quantum kinetic equation method. In this work, we assume that the electron-confined acoustic phonon scattering is essential. Moreover, the presence of the laser radiation (LR) is also taken into account to determine the influence of confined phonons on the aforementioned effects. We have defined the analytical expressions for the kinetic tensors and the Ettingshausen and the Peltier coefficients, presented the numerically calculated the theoretical results for the GaAs:Si/GaAs:Be doped semiconductor superlattice and compared them with these for the case of an unconfined acoustic phonon. The results obtained indicated that the formulas for the kinetic tensors, the Ettingshausen coefficient (EC) and the Peltier coefficient (PC) contain the quantum number m specifying the confinement of a phonon and approach the results for an unconfined phonon as m goes to zero. We found that the kinetic tensors, the EC and the PC oscillate with changing magnetic field and that the confinement of a phonon causes a shift of the peaks in these oscillations to lower energy. The dependences of both EC and PC on the temperature were found to be nonlinear. Moreover, all the coefficients level off when the temperature was less than 4.5 K or greater than 5.5 K. The EC also depended on the doping concentration in a nonlinear way and reaches a positive constant value when the semiconductor superlattice was doped with a high concentration. Most of the numerical results showed that the magnitude of the tensors, the EC as well as the PC, within a confined acoustic phonon varie significantly in comparison with the unconfined phonon case. This means that the confinement of the phonon affects the thermo-magnetoelectric effect quantitatively and qualitatively. These results contribute to completing the theory of the thermo-magnetoelectric effects in the low-dimensional semiconductor systems.

The Nonlinear Absorption Coeffcient of a Strong Electromagnetic Wave Caused by Confined Electrons in Quantum Wells

Bau Quang Nguyen,Hung Manh Do,Ngoe Bich Nguyen 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2

Analytic expressions for the nonlinear absorption coefficient of a strong electromagnetic wave (laser radiation) caused by confined electrons for the case of electron - optical phonon scattering and electron - acoustic phonon scattering in quantum wells are calculated by using the quantum kinetic equation for electrons. The problem is also considered for both the absence and the presence of an external magnetic field. The dependence of the nonlinear absorption coefficient on the intensity and the frequency of the external strong electromagnetic wave, the temperature T of the system and the cyclotron frequency for case of an external magnetic field is obtained. The analytic expressions are numerically evaluated, plotted and discussed for a specific quantum well AlAs/GaAs/ AlAs. The computations show that the nonlinear absorption coefficient in quantum wells is much more greater than to is in normal bulk semiconductor. The appearance of an external magnetic field causes surprising changes in the nonlinear absorption. All the results are compared with those for the normal bulk semiconductors to show the difference.

DNSs of the Ignition of a Lean PRF/Air Mixture under RCCI/SCCI Conditions

Minh Bau Luong,Kwang Hyeon Yu(유광현),Chun Sang Yoo(유광현) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11

A comparative DNS study of the ignition characteristics of dual-fueled reactivity controlled compression ignition (RCCI) and stratification charge compression ignition (SCCI) is investigated using a 116-species reduced primary reference fuel (PRF) mechanism. In the RCCI combustion, two PRF fuels (n-heptane and iso-octane) with opposite autoignition characteristics are separatedly supplied and in-cylinder blended such that spatial variations in fuel reactivity, fuel concentration and temperature are achieved. In the SCCI combustion, however, just a single fuel (PRF50) is used such that only fuel concentration and temperature inhomoginieties are obtained. Because three factors, rather than only two as in SCCI combustion, govern the overall RCCI combustion, combustion timing and combustion duration or heat release rate of RCCI combustion are flexibly and effectively controlled. It is found that the overall RCCI combustion occurs much earlier and its combustion duration is longer compared to SCC combustionI. Moreover, the negative temperature coefficient (NTC) has a positive effect on enhancing RCCI combustion by inducing a shorter combustion timing and a longer combustion duration as a result of the occurrence of a predominant low-speed deflagration-combustion mode.

Effects of the NTC Regime on the Ignition of a Lean n-Heptane/Air Mixture with Temperature and Composition Inhomogeneities

Minh Bau Luong,Kwang Hyeon Yu(유광현),Chun Sang Yoo(유춘상) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.5

The effect of the negative temperature coefficient (NTC) on the ignition of a stratified lean n-heptane/air mixture of temperature and equivalence ratio was investigated using 2-D direct numerical simulations (DNSs) with a 58-species reduced mechanism. It was found that for T? in the NTC regime, fuel stratification is more effective than thermal stratification in controlling the ignition delay and mitigating the heat release rate (HRR). One of the key finding in this study is that for the intermediate T?, the overall combustion becomes more advanced and mean heat release rate (HRR) is temporally more distributed with increasing Ø′ regardless of the negatively-correlated T-Ø relations. It is primarily because the deflagrative mode prevails at the reaction fronts for large Ø′ and hence the combustion occurs subsequently, rendering mean HRR more distributed over time.

철학 : 대노사광선생송명유학전석체계적방법론반성

두보서 ( Bau Ruei Duh ) 한국중국학회 2000 國際中國學硏究 Vol.3 No.-

A DNS study of ignition of lean biodiesel/air mixture with temperature and composition inhomogeneities

Minh Bau Luong,Chun Sang Yoo(유춘상) 한국연소학회 2013 KOSCOSYMPOSIUM논문집 Vol.2013 No.12

Two-dimensional direct numerical simulations of ignition of a biodiesel/air mixture with temperature (Τ) and equivalence ratio (Φ) stratifications are investigated using a 73-speices reduced chemistry. This study aims at three case studies (1) baseline cases With either only thermal stratification or only fuel concentration stratification: and the two highly feasible scenarios of the Τ-Φ distribution (2) uncorrelated Τ-Φ correlations; and (3) negatively correlated Τ-Φ correlations. The uncorrelated Τ-Φ distribution leads to a smooth combustion due to a mixed mode of combustion of deflagration and spontaneous ignition. The negatively-correlated Τ-Φ distribution results in a severe occurrence of heat release rate throught the whole domain because of spontaneous ignition.

A DNS Study of Ignition of a Lean PRF/Air Mixture under RCCI/SCCI Conditions

Minh Bau Luong,Gwang Hyeon Yu(유광현),Chun Sang Yoo(유춘상) 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.5

A comparative DNS study of the ignition characteristics of dual-fueled reactivity controlled compression ignition (RCCI) and stratification charge compression ignition (SCCI) is investigated using a 116-species reduced primary reference fuel(PRF) mechanism. It is found that the overall RCCI combustion is greatly enhanced and flexibly controlled, thereby significantly reducing the peak HRR. The negative temperature coefficient has a synergistic effect on advancing the overall combustion and smoothing RCCI/SCCI combustion by inducing more low-speed deflagrations. Compared to SCCI, the overall combustion of RCCI is more advanced in time regardless of T0. However, it is also found that the effects of reactivity and/or equivalence ratio stratifications on reducing the peak are nearly eliminated with T0 in the high temperature regime for both RCCI/SCCI due to the dominant spontaneous ignition mode.

A DNS Study of Ignition Characteristics of Lean PRF/Air Mixtures under HCCI Conditions

Minh Bau Luong,Chun Sang Yoo(유춘상) 한국연소학회 2012 KOSCOSYMPOSIUM논문집 Vol.- No.45

Direct numerical simulations (DNSs) of ignition of lean primary reference fuel (PRF)/air mixtures under homogeneous charge compression ignition (HCCI) conditions are performed using 116-species reduced chemistry. The influence of variations in the initial temperature field, imposed by changing the variance of temperature, and the fuel composition on ignition of lean PRF/air mixtures is studied using the displacement speed analysis.

A DNS Study of RCCI Combustion

Minh Bau Luong,Gwang Hyeon Yu(유광현),Chun Sang Yoo(유춘상) 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.12

The chemical aspects of primary reference fuel (PRF)/air mixture under RCCI conditions are investigated to provide fundamental insights into the ignition characteristics of RCCI combustion. Chemical explosive mode analysis (CEMA) is adopted to understand the ignition process of the lean PRF/air mixture by identifying controlling species and elementary reactions at different locations and times.