Showing papers by "Hanyang University published in 2003"

Antibacterial effect of nanosized silver colloidal solution on textile fabrics

Abstract: This paper deals with the antibacterial efficacy of nanosized silver colloidal solution on the cellulosic and synthetic fabrics Two kinds of Bacteria; Gram-positive and Gram-negative, were used TEM observation of silver nanoparticles showed their shape, and size distribution The particles were very small (2–5 nm) and had narrow distribution SEM images of treated fabrics indicated silver nanoparticles were well dispersed on the surfaces of specimens WAXS patterns did not show any peak of silver as the fabric had very small quantity of silver particles However, ICP-MS informed the residual concentration of silver particles on fabrics before/after laundering The antibacterial treatment of the textile fabrics was easily achieved by padding them with nanosized silver colloidal solution The antibacterial efficacy of the fabrics was maintained after many times laundering

Image-guided tumor ablation: proposal for standardization of terms and reporting criteria

Abstract: The field of image-guided tumor ablation requires standardization of terms and reporting criteria to facilitate effective communication of ideas and appropriate comparison between treatments with different technologies, such as chemical ablation (ethanol or acetic acid) and thermal therapies, such as radiofrequency, laser, microwave, ultrasound, and cryoablation. On the basis of this premise, a working committee was established with the goal of producing a proposal on such standardization. The intent of the Working Group is to provide a framework that will facilitate the clearest communication between investigators and will provide the greatest flexibility in comparisons between the many new, exciting, and emerging technologies. The members of the Working Group now propose a vehicle for reporting the various aspects of image-guided ablation therapy, including classifications of therapies and procedures, appropriate descriptors of image guidance, and terms to define imaging and pathologic findings. Methods for standardizing the reporting of follow-up findings and complications and other important aspects that require attention when reporting clinical results are addressed. It is the group's hope and intention that adherence to the recommendations of this proposal will facilitate achievement of the group's main objective: improved precision and communication in this field that lead to more accurate comparison of technologies and results and ultimately to improved patient outcomes.

The changepoint model for statistical process control

Abstract: Statistical process control (SPC) requires statistical methodologies that detect changes in the pattern of data over time. The common methodologies, such as Shewhart, cumulative sum (cusum), and exponentially weighted moving average (EWMA) charting, require the in-control values of the process parameters, but these are rarely known accurately. Using estimated parameters, the run length behavior changes randomly from one realization to another, making it impossible to control the run length behavior of any particular chart. A suitable methodology for detecting and diagnosing step changes based on imperfect process knowledge is the unknown-parameter changepoint formulation. Long recognized as a Phase I analysis tool, we argue that it is also highly effective in allowing the user to progress seamlessly from the start of Phase I data gathering through Phase II SPC monitoring. Despite not requiring specification of the post-change process parameter values, its performance is never far short of that of the optimal cusum chart which requires this knowledge, and it is far superior for shifts away from the cusum shift for which the cusum chart is optimal. As another benefit, while changepoint methods are designed for step changes that persist, they are also competitive with the Shewhart chart, the chart of choice for isolated non-sustained special causes.

Major Complications after Radio-frequency Thermal Ablation of Hepatic Tumors: Spectrum of Imaging Findings

Abstract: Although radio-frequency (RF) ablation has been accepted as a promising and safe technique for treatment of unresectable hepatic tumors, investigation of its complications has been limited. According to the multicenter (1,139 patients in 11 institutions) survey data of the Korean Study Group of Radiofrequency Ablation, a spectrum of complications occurred after RF ablation of hepatic tumors. The prevalence of major complications was 2.43%. The most common complications were hepatic abscess (0.66%), peritoneal hemorrhage (0.46%), biloma (0.20%), ground pad burn (0.20%), pneumothorax (0.20%), and vasovagal reflex (0.13%). Other complications were biliary stricture, diaphragmatic injury, gastric ulcer, hemothorax, hepatic failure, hepatic infarction, renal infarction, sepsis, and transient ischemic attack. One procedure-related death (0.09%) occurred (due to peritoneal hemorrhage). Three important strategies for decreasing the rate of complications are prevention, early detection, and proper management. A ph...

Preparation of nanocomposite fibers for permanent antibacterial effect

Abstract: The polypropylene/silver nanocomposite fibers were prepared for the attainment of permanent antibacterial activity to common synthetic textile. The fibers were melt-spun by co-extrusion of polypropylene (PP) and PP/Ag master-batches using general conjugate spinning. Master-batches were made up of mixture of PP chips and nano-sized silver powder. The antibacterial efficacy of spun fibers was excellent not when the master-batch used as the core, but when used as the sheath. The antibacterial activity of nano-silver in fibers was evaluated after certain contact time and calculated by percent reduction of two kinds of bacteria; Staphylococus aureus and Klebsiela pneumoniae. For the characterization, differential scanning calorimetry (DSC) and wide-angle X-ray diffractometer (WAXD) were used for analysis of structure, thermal and crystallization behavior of the spun-fibers. Scanning electron microscopy (SEM) was carried out to observe particle distribution on the nanocomposite fibers.

Low-temperature growth of ZnO nanowire array by a simple physical vapor-deposition method

Abstract: Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire array was successfully fabricated on an Al2O3 substrate by a simple physical vapor-deposition method at a low temperature of 450 °C...

Erythropoietin reduces myocardial infarction and left ventricular functional decline after coronary artery ligation in rats

Abstract: Erythropoietin (EPO), well known for its role in stimulation of erythropoiesis, has recently been shown to have a dramatic neuroprotective effect in animal models of cerebral ischemia, mechanical trauma of the nervous system, and excitotoxins, mainly by reducing apoptosis. We studied the effect of single systemic administration of recombinant human EPO (rhEPO) on left ventricular (LV) size and function in rats during 8 weeks after the induction of a myocardial infarction (MI) by permanent ligation of the left descending coronary artery. We found that an i.p. injection of 3,000 units/kg of rhEPO immediately after the coronary artery ligation resulted, 24 h later, in a 50% reduction of apoptosis in the myocardial area at risk. Eight weeks after the induction of MI, rats treated with rhEPO had an infarct size 15–25% of the size of that in untreated animals. The reduction in myocardial damage was accompanied by reductions in LV size and functional decline as measured by repeated echocardiography. Thus, a single dose of rhEPO administered around the time of acute, sustained coronary insufficiency merits consideration with respect to its therapeutic potential to limit the extent of resultant MI and contractile dysfunction.

An Asia-Pacific, double blind, placebo controlled, randomised study to evaluate the efficacy, safety, and tolerability of tegaserod in patients with irritable bowel syndrome

Abstract: Background: Tegaserod has been shown to be an effective therapy for the multiple symptoms of irritable bowel syndrome (IBS) in Western populations. However, little information is available regarding the use of tegaserod in the Asia-Pacific population. Aims: To evaluate the efficacy, safety, and tolerability of tegaserod versus placebo in patients with IBS from the Asia-Pacific region. Patients: A total of 520 patients from the Asia-Pacific region with IBS, excluding those with diarrhoea predominant IBS. Methods: Patients were randomised to receive either tegaserod 6 mg twice daily (n=259) or placebo (n=261) for a 12 week treatment period. The primary efficacy variable (over weeks 1–4) was the response to the question: “Over the past week do you consider that you have had satisfactory relief from your IBS symptoms?” Secondary efficacy variables assessed overall satisfactory relief over 12 weeks and individual symptoms of IBS. Results: The mean proportion of patients with overall satisfactory relief was greater in the tegaserod group than in the placebo group over weeks 1–4 (56% v 35%, respectively; p<0.0001) and weeks 1–12 (62% v 44%, respectively; p<0.0001). A clinically relevant effect was observed as early as week 1 and was maintained throughout the treatment period. Reductions in the number of days with at least moderate abdominal pain/discomfort, bloating, no bowel movements, and hard/lumpy stools were greater in the tegaserod group compared with the placebo group. Headache was the most commonly reported adverse event (12.0% tegaserod v 11.1% placebo). Diarrhoea led to discontinuation in 2.3% of tegaserod patients. Serious adverse events were infrequent (1.5% tegaserod v 3.4% placebo). Conclusions: Tegaserod 6 mg twice daily is an effective, safe, and well tolerated treatment for patients in the Asia-Pacific region suffering from IBS and whose main bowel symptom is not diarrhoea.

On the robustness and performance of disturbance observers for second-order systems

Abstract: The disturbance observer (DOB) has been widely utilized for high-precision and high-speed motion control applications. In this note, we suggest the robustness measure of the DOB as a criterion to design the robust DOB systems. Also, we suggest its design guidelines especially for second-order systems. Experimental results for an optical disk drive system show the validity of design guidelines.

Silica nanofibers from electrospinning/sol-gel process

Abstract: The fabrication of materials with one-dimensional nanoscale structures is of great promise for the fundamental understanding of the roles of dimensionality and size in an optical, electrical, and mechanical properties with reference to applications in semiconductor mechanical and chemical industries. Polymer nanofibers are of considerable interest for various kinds of applications including filters, reinforcing agents, biomedical materials, and fiber templates to prepare nanotubes [1–6]. Recently, there has been a growing interest in one-dimensional, inorganic nanosized materials such as carbon nanotubes, carbide nanorods, silica and titania nanofibers/nanotubes [7–11]. These one-dimensional nanomaterials exhibit some novel physical and chemical properties due to their peculiar structure and size effect, and are of great importance in nanodevices and mesoscopic theoretical research. Electrospinning technique is an effective method to produce nanofibers [12–16]. The electrospinning process involves the application of a strong electrostatic field to a capillary connected with a reservoir containing a polymer solution or melt. Under the influence of the electrostatic field, a pendant droplet of the polymer solution at the capillary tip is deformed into a conical shape (Taylor cone). If the voltage surpasses a threshold value, electrostatic forces overcome the surface tension, and a fine charged jet is ejected. The jet moves towards a ground plate acting as counter electrode. Due to the extensional viscosity of the polymer solution and the presence of entanglements, the jet remains stable and does not transform into spherical droplets as expected for a liquid cylindrical thread. The solvent begins to evaporate immediately after the jet is formed. The result is the deposition of a thin polymer fiber on a substrate located above the counter electrode. The sol-gel method has widely been used as an alternative technology for the preparation of a wide variety of forms including monoliths, powders, coatings, and fibers [17–20]. The typical sol-gel method is hydrolysis and condensation of tetraethyl orthosilicate (TEOS), Si(OCH2CH3)4. In recent years, there have been efforts to synthesize metal oxide (silica or titania) nanofibers and nanotubes by the sol-gel template method [11, 21, 22]. Meanwhile, micron-scale silica fibers have been achieved by extruding the spinnable sol through an orifice [23–25]. In the present work, we study formation of silica nanofibers using the sol-gel method and electrospinng technique. We note that the TEOS solution used in this study does not contain any gelator or binder to help spinnability. Kobayashi and coworkers synthesized titania fibers via the sol-gel method from a physical gel of titanium tetraisopropoxide by a low molecular weight organogelator [10]. Zhang and coworkers synthesized silica and titania nanorods with the sol-gel method and anodic alumina template membrane [11, 21]. The silica sol was prepared from tetraethyl orthosilicate (TEOS), distilled water, ethanol, and HCl. The sol composition in molar ratio was 1:2:2:0.01 (TEOS:ethanol:water:HCl). First, TEOS was mixed with ethanol in a beaker. The HCl/water solution was then added drop by drop to the TEOS/ethanol solution under vigorous stirring. The solution was heated at 80 ◦C for 30 min and then cooled down to room temperature. The silica sol was placed in a pasteur pipet and the electrode was directly connected with the solution. A tubular shaped counter electrode with a diameter of 22 cm was located below the reservoir. The winding drum was rotated at speed of 10 rpm during the electrospinning. The fibers were collected on aluminum foil covered the tubular layer. The distance between the tip of the capillary and the counter electrode (tip-tocollector distance, TCD) was 10 cm and the applied voltages ranged from 10 kV to 16 kV. The morphology and diameter of silica fiber were measured with SEM (S-2350 of Hitachi). The composition of silica fiber was determined with FTIR (Travel IR of SensIR Technol.). The structure of silica fiber was analyzed with XRD (DMAX 2000 of Rigaku Denki). The thermal property was analyzed with a thermogravimetric analyzer of TGA 2050 of TA Instrument. TGA analysis was performed at 50–800 ◦C with 20 ◦C/min in air. It has been known that silica fibers obtained by the conventional technique through the sol-gel process are affected by composition of sol and ripening condition [20, 24]. In the current study, silica nanofibers were obtained successufully by electrospinning technique and

Swelling behavior of interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and chitosan

Abstract: Interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and chitosan were prepared by UV irradiation. The characteristics of IPN hydrogels were investigated by swelling experiments, Fourier transform infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC). IPN hydrogels exhibited a relatively high swelling ratio in the range of 210–350% at 35 °C. The swelling ratio of PVA/chitosan IPN hydrogels depended on pH and temperature. DSC was used for the quantitative determination of the amounts of freezing and non-freezing water. Free water contents in IPN1, IPN2 and IPN3 were 62.0, 69.6 and 72.3% in pure water, respectively.

Low-temperature growth and Raman scattering study of vertically aligned ZnO nanowires on Si substrate

Abstract: High-density ZnO nanowires (ZnONWs) were aligned onto Au-catalyzed Si substrate through a simple low-temperature physical vapor deposition method. Scanning electron microscope (SEM) observations, x-ray diffraction (XRD) analysis, and photoluminescence spectra showed that the ZnONWs were single-crystalline, with a hexagonal wurzite structure. All of the results inferred from the SEM observations, the XRD rocking curves, and the Raman spectra for the investigated samples confirm that the ZnONWs are well aligned and c-axis oriented. The Raman spectra also indicated that the ZnONWs on Si substrates are under the biaxial compressive stress. Since it takes the advantage of low-cost, easily controlled deposition spot (due to the selective deposition trait of the Au layer), potential for scale-up production, and ability to integrate with Si substrate, this technique has a potential in future for fabricating the ZnONW array-based optoelectronic devices.

Evaluation of normalization methods for microarray data.

Abstract: Microarray technology allows the monitoring of expression levels for thousands of genes simultaneously. This novel technique helps us to understand gene regulation as well as gene by gene interactions more systematically. In the microarray experiment, however, many undesirable systematic variations are observed. Even in replicated experiment, some variations are commonly observed. Normalization is the process of removing some sources of variation which affect the measured gene expression levels. Although a number of normalization methods have been proposed, it has been difficult to decide which methods perform best. Normalization plays an important role in the earlier stage of microarray data analysis. The subsequent analysis results are highly dependent on normalization. In this paper, we use the variability among the replicated slides to compare performance of normalization methods. We also compare normalization methods with regard to bias and mean square error using simulated data. Our results show that intensity-dependent normalization often performs better than global normalization methods, and that linear and nonlinear normalization methods perform similarly. These conclusions are based on analysis of 36 cDNA microarrays of 3,840 genes obtained in an experiment to search for changes in gene expression profiles during neuronal differentiation of cortical stem cells. Simulation studies confirm our findings.

Elastic biodegradable poly(glycolide‐co‐caprolactone) scaffold for tissue engineering

Abstract: Cyclic mechanical strain has been demonstrated to enhance the development and function of engineered smooth muscle (SM) tissues, and it would be necessary for the development of the elastic scaffolds if one wishes to engineer SM tissues under cyclic mechanical loading. This study reports on the development of an elastic scaffold fabricated from a biodegradable polymer. Biodegradable poly(glycolide-co-caprolactone) (PGCL) copolymer was synthesized from glycolide and epsilon-caprolactone in the presence of stannous octoate as catalyst. The copolymer was characterized by (1)H-NMR, gel permeation chromatography and differential scanning calorimetry. Scaffolds for tissue engineering applications were fabricated from PGCL copolymer using the solvent-casting and particle-leaching technique. The PGCL scaffolds produced in this fashion had open pore structures (average pore size = 250 microm) without the usual nonporous skin layer on external surfaces. Mechanical testing revealed that PGCL scaffolds were far more elastic than poly(lactic-co-glycolic acid) (PLGA) scaffolds fabricated using the same method. Tensile mechanical tests indicated that PGCL scaffolds could withstand an extension of 250% without cracking, which was much higher than withstood by PLGA scaffolds (10-15%). In addition, PGCL scaffolds achieved recoveries exceeding 96% at applied extensions of up to 230%, whereas PLGA scaffolds failed (cracked) at an applied strain of 20%. Dynamic mechanical tests showed that the permanent deformation of the PGCL scaffolds in a dry condition produced was less than 4% of the applied strain, when an elongation of 20% at a frequency of 1 Hz (1 cycle per second) was applied for 6 days. Moreover, PGCL scaffolds in a buffer solution also had permanent deformations less than 5% of the applied strain when an elongation of 10% at a frequency of 1 Hz was applied for 2 days. The usefulness of the PGCL scaffolds was demonstrated by engineering SM tissues in vivo. This study shows that the elastic PGCL scaffolds produced in this study could be used to engineer SM-containing tissues (e.g. blood vessels and bladders) in mechanically dynamic environments.

Hydrolysis and acidogenesis of particulate organic material in mesophilic and thermophilic anaerobic digestion

Abstract: The purpose of this study was to evaluate the effect of pH and inorganic nutrient supplementations for anaerobic hydrolysis and addogenesis of paniculate organic materials at both mesophilic (35 °C) and thermophilic (55 °C) temperatures. Hydrolysis and addogenesis of a synthetic sludge was observed in batch operation for the evaluation of the pH effect. pH was uncontrolled in one reactor and controlled at 4.5, 5.5, and 6.5 in the other three reactors at both temperatures. The greatest degree of hydrolysis and addogenesis occurred when the pH was controlled at 6.5. The pH of the uncontrolled reactor dropped to 3.4 at both temperatures severely retarding hydrolysis and addogenesis. Concentrations of acetic and n‐butyric adds predominated with lower concentrations of propionic add at both temperatures in all reactors. Lactic add was produced as the earliest intermediate but as the reaction proceeded, short chain VF As were produced as final end products with a decrease in lactic add. The higher the ...

A virtual reality system for the assessment and rehabilitation of the activities of daily living.

Abstract: Successful rehabilitation with respect to the activities of daily living (ADL) requires accurate and effective assessment and training. A number of studies have emphasized the requirement for rehabilitation methods that are both relevant to the patient's real world environment, and that can also be transferred to other daily living tasks. Virtual reality (VR) has many advantages over other ADL rehabilitation techniques, and offers the potential to develop a human performance testing and training environment. Therefore, in this study, the virtual supermarket was developed and the possibility of using a VR system to assess and train cognitive ability in ADL investigated. This study demonstrates that VR technology offers great promise in the field of ADL training.

Electrical properties and EMI shielding characteristics of polypyrrole-nylon 6 composite fabrics

Abstract: Polypyrrole (PPy) was polymerized both chemically and electrochemically in sequence on nylon 6 woven fabrics, giving rise to polypyrrole–nylon 6 composite fabrics (PPy–N) with a high electric conductivity. The stability of the composite prepared by electrochemical polymerization (ECP) on chemical oxidative polymerization (COP) fabric was better than that of the composite prepared solely by the COP process, since the AQSA dopant was able to strongly interact with the PPy main chain and had a large molecular structure. The temperature dependence of the conductivity of the composites was verified over four heating and cooling cycles. The change in conductivity over these four repeated heating and cooling cycles was affected by the interaction between the thermal stability of the dopant and the rearrangement of the PPy main chain. The electromagnetic interference shielding efficiency (EMI SE) values were in the range 5–40 dB and depended on the conductivity and the layer array sequence of the conductive fabric. The composites with a high conductivity represented reflection-dominant EMI shielding characteristics, which are typical of the EMI shielding characteristics of metals. However, composites with low conductivity showed absorption-dominant EMI shielding characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1969–1974, 2003

Dopaminergic neuronal differentiation from rat embryonic neural precursors by Nurr1 overexpression.

Abstract: In vitro expanded CNS precursors could provide a renewable source of dopamine (DA) neurons for cell therapy in Parkinson's disease. Functional DA neurons have been derived previously from early midbrain precursors. Here we demonstrate the ability of Nurr1, a nuclear orphan receptor essential for midbrain DA neuron development in vivo, to induce dopaminergic differentiation in naive CNS precursors in vitro. Independent of gestational age or brain region of origin, Nurr1-induced precursors expressed dopaminergic markers and exhibited depolarization-evoked DA release in vitro. However, these cells were less mature and secreted lower levels of DA than those derived from mesencephalic precursors. Transplantation of Nurr1-induced DA neuron precursors resulted in limited survival and in vivo differentiation. No behavioral improvement in apomorphine-induced rotation scores was observed. These results demonstrate that Nurr1 induces dopaminergic features in naive CNS precursors in vitro. However, additional factors will be required to achieve in vivo function and to unravel the full potential of neural precursors for cell therapy in Parkinson's disease.

Prevalence of intestinal parasite infections on a national scale among primary schoolchildren in Laos

Abstract: In order to investigate the epidemiological situation of intestinal parasite infections in Laos, parasitological surveys were carried out on a national scale including 17 provinces and the Vientiane Municipality. A total of 29,846 stool specimens were collected from primary schoolchildren from May 2000 to June 2002 and examined once with the cellophane thick smear technique. The cumulative egg positive rate for intestinal helminths was 61.9%. By species, the rate for Ascaris lumbricoides was 34.9%, hookworm 19.1%, Trichuris trichiura 25.8%, Opisthorchis viverrini 10.9%, Taenia spp. 0.6% and Hymenolepis spp. 0.2%. The northern mountainous regions such as Phongsaly, Huaphan or Saysomboune Province showed a higher prevalence (over 70%) of soil- transmitted helminths. The regions along the Mekong River such as Khammuane, Saravane or Savannakhet Province showed a higher prevalence (over 20%) of fish-borne parasites. On the other hand, Schistosoma mansoni eggs were detected in 1.7% of schoolchildren only in Champassak Province, a previously endemic area. The highest prevalence was noted in Phongsaly Province (96.0%) and the lowest in Bolikhamxay Province (27.5%). An additional small-scale survey by cellophane anal swab detected Enterobius vermicularis eggs in 35.7% of 451 schoolchildren aged 6-8 years in Khammuane, Vientiane, Champassak Province and the Vientiane Municipality. Meanwhile, the mean blood haemoglobin level of hookworm-infected children was not lower than that of children not infected with hookworm, suggesting that nutritional factors are more important than parasite infection per se. Nevertheless, the above results indicate that a nationwide parasite control project is necessary to reduce possible morbidity due to parasitic diseases in the country.