Yoon-Ho Choi

Genetic factors associated with endothelial dysfunction affect the early onset of coronary artery disease in Korean males.

The maintenance of balance between nitric oxide (NO) and the superoxide anion is required for proper functioning of the endothelium. To investigate the relationship between genetic factors associated with endothelial function and the development of coronary artery disease (CAD), endothelial nitric oxide synthase (ecNOS) gene a/b polymorphism and NADH/NADPH oxidase p22 phox gene C242T polymorphism were examined in 305 Korean male CAD patients and 215 healthy male control subjects. The β-fibrinogen gene H1/H2 polymorphism was also analyzed. Both ecNOS a/b and p22 phox C242T polymorphisms were found to be associated with the development of CAD in the study population (p = 0.020 and 0.011, respectively). When the association was analyzed by age, statistical significance was retained only in those <51 years (p = 0.021 and 0.025 for the a/b and the C242T polymorphism, respectively) and not in those >51 years of age (p =0.155 and 0.278 respectively). However, the distribution of the β-fibrinogen H1/H2 genotypes was not found to be associated with the development of CAD in either the ≤50 (p = 0.611) or >50 groups (p = 0.188). The ecNOS gene a/b polymorphism and the NADH/NADPH oxidase p22 phox gene C242T polymorphism were found to be significantly associated with the development of CAD in Korean male patients less than 51 years old.

Comparison of the coronary calcium score with the estimated coronary risk

ObjectivesThe role of coronary calcium scoring in coronary risk estimation is not well established. Calcium scoring could provide additional information in a certain subgroup of patients where the calcium score does not match the conventional Framingham risk estimates. We explored the characteristics of such a subgroup. MethodsThe study participants were 1653 asymptomatic persons who underwent routine health screening and calcium scoring using the 16-slice multidetector computed tomography. Risk stratification was performed in five categories both by 10-year Framingham coronary risk and the Agatston coronary calcium score. ResultsRisk stratifications by coronary calcium score and absolute risk showed a large discrepancy (difference ≥3 classes) in about 9% of participants. The proportion increased with age (P for trend <0.0001). An exploratory analysis revealed that age (partial R2=0.109, P<0.0001) and the presence of the metabolic syndrome (partial R2=0.025, P<0.001) were independent variables that accounted for the variance of the residual of regression between the log-transformed value of coronary calcium score and the absolute risk. ConclusionCalcium scoring may be clinically more useful in older (≥50 years) participants and/or in participants with the metabolic syndrome because of the relatively higher probability of obtaining additional information that the conventional Framingham risk estimation cannot provide.

A fast pattern matching algorithm with multi-byte search unit for high-speed network security

A signature-based intrusion detection system identifies intrusions by comparing the data traffic with known signature patterns. In this process, matching of packet strings against signature patterns is the most time-consuming step and dominates the overall system performance. Many signature-based network intrusion detection systems (NIDS), e.g., the Snort, employ one or multiple pattern matching algorithms to detect multiple attack types. So far, many pattern matching algorithms have been proposed. Most of them use single-byte standard unit for search, while a few algorithms such as the Modified Wu-Manber (MWM) algorithm use typically two-byte unit, which guarantees better performance than others even as the number of different signatures increases. Among those algorithms, the MWM algorithm has been known as the fastest pattern matching algorithm when the patterns in a rule set rarely appear in packets. However, the matching time of the MWM algorithm increases as the length of the shortest pattern in a signature group decreases. In this paper, by extending the length of the shortest pattern, we minimize the pattern matching time of the algorithm which uses multi-byte unit. We propose a new pattern matching algorithm called the L^+^1-MWM algorithm for multi-pattern matching. The proposed algorithm minimizes the performance degradation that is originated from the dependency on the length of the shortest pattern. We show that the L^+^1-MWM algorithm improves the performance of the MWM algorithm by as much as 20% in average under various lengths of shortest patterns and normal traffic conditions. Moreover, when the length of the shortest pattern in a rule set is less than 5, the L^+^1-MWM algorithm shows 38.87% enhancement in average. We also conduct experiments on a real campus network and show that 12.48% enhancement is obtained in average. In addition, it is shown that the L^+^1-MWM algorithm provides a better performance than the MWM algorithm by as much as 25% in average under various numbers of signatures and normal traffic conditions, and 20.12% enhancement in average with real on-line traffic.

Pre-treatments of polymers by atmospheric pressure ejected plasma for adhesion improvement

Polymers such as rubbers generally have low surface energy, thus high hydrophobicity and inherent low bondability. An atmospheric pressure ejected plasma (APEP) source is developed for pre-treatments of polymers to overcome these intractable properties and improve the adhesion ability between polymers as environmental-friendly and simple alternative methods to conventional treatments in spite of several limitations until now. Proper operational conditions are found by T-peel tests performed with various plasma parameters and high peel strength up to 3.5 kgf/cm is achieved at those conditions. Optical emission spectroscopy revealed that the amount of oxygen radicals and gas temperatures are found to be higher at proper conditions in T-peel tests and Fourier transform infrared spectroscopy using attenuated total reflection. Scanning electron microscopy is used for the measurement of surface composition and morphology of pre-treated polymer specimen. These results established the advantage of pre-treatments by APEP source in proper operation conditions when compared to the conventional treatments in terms of improvement of the adhesion ability between polymers.

Characterisations of atmospheric pressure ejected plasma sources

Atmospheric pressure ejected plasma sources have been developed for processing arbitrary shaped objects. Plasma sources with two coaxial electrodes are characterised experimentally by varying source design parameters such as discharge volume and discharge gap distance under various operating conditions such as RF power, gas flow rate, and gas compositions. Using optical emission spectroscopy (OES), gas temperatures and radical densities are qualitatively evaluated for flexible applications of the source. Discharge characteristics as glow has been confirmed with voltage and current (V–I) probes. Based on these source characteristics, specific design rules are presented for various applications such as polymer surface modification and metal surface decontamination. 2003 Elsevier Science B.V. All rights reserved.

Decontamination of radioactive metal surface by atmospheric pressure ejected plasma source

Abstract An atmospheric pressure ejected plasma source has been developed and applied to the decontamination of cobalt-contained oxide layer on metal surfaces. A helium-based discharge with relatively low gas temperature of approximately 200∼300 °C has been used for the decontamination. Small amounts of CF4 and O2 gases are added into helium plasmas as reactive species for carbonylation and fluorination of cobalt. Treatments are performed with various operating parameters such as RF power, treatment time and CF4/O2 gas flow ratio and so on. Decontamination ratios of approximately 95% have been achieved through both gasification and solidification. With the increased reactive gases, the decontamination processes are expedited via gasification, and decontamination ratios solely by gasification have reached up to approximately 70%, indicating the necessity of extra effort of removing solidified powder components.

Worm virulence estimation for the containment of local worm outbreak

A worm-infected host scanning globally may not cause any new infection in its underlying local network before it is detected and quarantined by a worm detector. To defend this type of scanning hosts, a number of worm scanner detection methods such as failed scan detection, honeypot, and dark port detection are proposed. However, for a stealthier worm limiting its scan inside an enterprise network, the chance of a successful local outbreak increases substantively due to the more limited scan space. To protect a local or enterprise network against a local outbreak, we need a coordinated and cost-conscious defense that entails an accurate estimate of worm virulence level. Unfortunately, many existing defense methods suffer from estimating the worm virulence level in a local or enterprise network. In this regard, we propose a maximum likelihood estimator to progressively estimate the size of susceptible host population in the local or enterprise network. From analysis and experimental evaluation, it is shown that the proposed estimator can report a reliable estimate of the size of susceptible population only after a few infections, sometimes only four, much faster than a similar method based on a Kalman filter. Also, based on maximum likelihood estimate, an appropriate containment threshold can be set to effectively stop the worm propagation while causing minimum service disruption to normal network users.

Determination of Losartan in Human Plasma by Liquid Chromatography Electrospray Ionization Mass Spectrometry (LC-ESI-MS): Application to Bioequivalence Study

Abstract A sensitive, simple, rapid, and specific liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) method was developed and validated for the identification and quantification of losartan in a small volume of human plasma. Losartan and I.S. were successfully separated on a CN column with a mobile phase of acetonitrile-0.2% formic acid solution (68:32, v/v). Detection was performed on a single quadrupole mass spectrometer by a selected ion monitoring (SIM) mode via electrospray ionization (ESI) source. The ESI source was set at positive ionization mode. The ion signal of m/z 422.79 and 194.81 were measured for losartan and I.S., respectively. The limit of detection (LOD) was 0.5 ng/mL (signal-to-noise ratio of 10.03) using only 200 μL of human plasma samples. The calibration curve was an excellent linear fit over the range of concentrations 1.0–1000 ng/mL (R2 = 0.9987) of losartan in human plasma. Consequently, all of our results fulfilled the common standard criteria of bioequivalence, 0.80 to 1.25 by the Korean and US Food and Drug Administration. In addition to the confidence intervals (C.I.) 90% of the pharmaceutical parameters, a two-way ANOVA showed no significant difference between the two formulations. This method was successfully applied to bioequivalence study of two brands of losartan potassium tablet (100 mg) formulations after a single oral administration.

Helicobacter pylori is associated with dyslipidemia but not with other risk factors of cardiovascular disease

Epidemiologic and clinical data suggest that Helicobacter pylori infection is a contributing factor in the progression of atherosclerosis. However, the specific cardiovascular disease risk factors associated with H. pylori remain unclear. We performed a cross-sectional study of 37,263 consecutive healthy subjects who underwent a routine health check-up. In multivariable log Poisson regression models adjusted for potential confounders, the associations of H. pylori seropositivity with higher LDL-C (relative risk [RR], 1.21; 95% confidence interval [CI], 1.12–1.30) and lower HDL-C level (RR, 1.10; 95% CI, 1.01–1.18) were significant and independent. In multiple linear regression analyses, H. pylori infection was significantly associated with higher total cholesterol level (coefficientu2009=u20092.114, Pu2009<u20090.001), higher LDL-C level (coefficientu2009=u20093.339, Pu2009<u20090.001), lower HDL-C level (coefficientu2009=u2009−1.237, Pu2009<u20090.001), and higher diastolic blood pressure (coefficientu2009=u20090.539, Pu2009=u20090.001). In contrast, H. pylori infection was not associated with obesity-related parameters (body mass index, waist circumference), glucose tolerance (fasting glucose, glycated hemoglobin), and systolic blood pressure. We found that H. pylori infection was significantly and independently associated with dyslipidemia, but not with other cardiometabolic risk factors, after adjusting for potential risk factors of atherosclerosis.

BLAST: B-LAyered bad-character SHIFT tables for high-speed pattern matching

In this study, the authors propose a new multi-pattern matching algorithm, called BLAST (B-LAyered bad-character Shift Tables with a single-byte search unit), which considers space-time tradeoff in the context of shift values during the search. Here, the term ‘bad character’ is a character that causes a mismatch. While checking multiple bytes in scanning the text at a time, the BLAST algorithm overcomes the reduction of the average shift value in a typical search, which is caused by the dependency on the multi-byte search unit (MBSU) and the large frequency of the last character of the given patterns. From the theoretical analysis, the authors validate the correctness of the BLAST algorithm. Also, from the experimental results across different setups, the authors show that the BLAST algorithm provides the faster search time than the other algorithms. For example, the authors obtain an enhancement by as much as 212.41% on average for various numbers of attack patterns and attack traffic conditions compared with that of the modified Wu-Manber algorithm. In addition, it is shown that the BLAST algorithm drastically reduces the amount of memory required for constructing the shift table based on a MBSU from 64 KB to 1 KB.