Search

Formation behavior and photo-oxidation abilities of nanostructured TiO2 powders were investigated through a direct crystallization from aqueous TiOCl2 solutions containing various metal-chlorides at 100°C. The obtained TiO2 powders without any additives and those added with Ni2+, Fe3+ and Nb5+ ions, which have a similar positive ionic radius to Ti4+, were mainly crystallized with rutile phase, whereas those added with Al3+ and Zr4+ ions, which have a quite different positive ionic radius, were mainly crystallized with anatase phase. On the other hand, the secondary particles in the TiO2 powder consisted of acicular and spherical primary particles corresponding to rutile and anatase phases, respectively. From these results, it seems that the positive ionic radius of the additives would affect phase formation as well as morphology of TiO2 precipitates. Among the TiO2 powders prepared, Ni-added powder, which consisted mainly of rutile phase with a small amount of anatase phase, showed excellent photocatalytic ability in decomposition of 4-chlorophenol.

In this paper, a new control scheme of Class-E inverter for reducing the crest factor of electronic ballasts for fluorescent lamps using pulse-frequency-modulation (PFM) is introduced. The lifetime of the lamps is guaranteed by decreasing the lamp crest factor and also voltage stress of the switch is significantly decreased by a new scheme although conventional Class-E inverter is used in this paper. The proposed PFM control scheme doesn't used any auxiliary circuit. The proposed control strategy is executed by feeding back the input voltage, and the zero-voltage-switching (ZVS) is ensured by operating beyond resonant frequency. Therefore, the control principles of the proposed method are explained in detail and its validity is verified through several simulation and experimental results.

An improved MPPT converter with current compensation method for small-scaled PV-applications is presented in this paper. The proposed method implements maximum power point tracking (MPPT) by variable reference current which is continuously changed during one sampling period. Therefore, the proposed MPPT converter with current compensation method increases the power transferred to the load above 9%. As a result, the utilization efficiency of photovoltaic (PV)-module can be increased. In addition, as it doesn't use a digital signal processor (DSP), this MPPT method has the merits of both a cost efficiency and a simple control circuit design. Therefore, it is considered that the proposed MPPT method is proper to low power, low cost PV-applications. The concept and control principles of this improved MPPT method are explained in detail and the validity of the proposed method is verified through several simulated results.

An improved MPPT converter with current compensation method for small-scaled PV-applications is presented in this paper. The proposed method implements maximum power point tracking (MPPT) by variable reference current which is continuously changed during one sampling period. Therefore, the proposed MPPT converter with current compensation method increases the power transferred to the load above 9%. As a result, the utilization efficiency of the photovoltaic (PV)-module can be increased. In addition, as it doesn't use a digital signal processor (DSP), this MPPT method has the merits of both being cost efficient and having a simple control circuit design. Therefore, it is considered that the proposed MPPT method is proper to use for low power, low cost PV-applications. The concept and control principles of this improved MPPT method are explained in detail and the validity of the proposed method is verified through several simulated results.

This paper presents a new hybrid control scheme using active-clamped Class-E (ACCE) inverter for induction heating (IH) jar. The proposed hybrid control scheme has characteristics, which act as Class-E inverter at lower switch voltage and ACCE inverter at higher switch voltage than reference voltage of the main switch by feeding back voltage of the switch as well as advantages of conventional ACCE inverter such as zero-voltage-switching (ZVS) of the main switch and the reduced switch voltage due to clamping circuit. Moreover, the proposed hybrid control method using ACCE inverter has higher output power than conventional control scheme since ACCE inverter is operated like Class-E inverter at low input voltage condition. The principles of the proposed control are explained in detail and the validity of the proposed control scheme is verified through the several interesting simulated and experimental results.

In this paper, a new control scheme of Class-E inverter for induction heating (IH) jar applications with clamped voltage characteristics using pulse-frequency modulation (PFM) is introduced. To reduce the voltage stress of the switch, the proposed PFM control scheme doesn't need any auxiliary circuit in comparison to a family of active clamped Class E (ACCE) inverter. It can decrease voltage stress of switch through modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantages of not only the same output power when it is compared with a hybrid-active clamped Class-E (hybrid-ACCE) inverter but also zero-voltage-switching (ZVS), which are characteristics of conventional Class-E and active clamped Class-E (ACCE) inverter. The control principles of the proposed method are explained in detail and its validity is verified through experimental results.

This paper describes a data output buffer which shows a reduced switching noise over wide-range of loading conditions. The proposed output buffer employs load-adaptive circuitry to achieve bounded delay regardless of loading condition. For that purpose, a load monitoring circuit is embedded in the output buffer. The adaptive control of driving current enables the switching noise to be kept at a minimum value. The experimental chip with a 0.61 /spl mu/m CMOS technology shows a reduced switching noise level, 15%/spl sim/35% of conventional buffer while the transition time is bounded within 7 ns for loading capacitance up to 100 pF.

This paper presents new zero-voltage/zero-current-switching (ZVZCS) PWM DC-DC converters. The proposed soft-switching technique achieves ZVS and ZCS simultaneously at both turn-on and turn-off of the main switch and diode by use of only one auxiliary switch. Also, this technique is suitable for not only minority but also majority carrier semiconductor devices. The auxiliary circuit of the proposed topologies is placed out of the main power path, therefore, there are no voltage/current stresses on the main switch and diode. The operating principle of the proposed topologies is illustrated by a detailed study with a boost converter as an example. Theoretical analysis, simulation and experimental results are presented to explain the proposed schemes.

When electronic ballasts are used for fluorescent lamps, lifetime of the lamp is greatly affected by starting scenario and crest factor. A new method to reduce the crest factor of the lamp is proposed, and the proposed electronic ballast is controlled in the mode of pulse frequency modulation (PFM). Electronic ballasts with 50% valley-fill PFC are dealt with in this paper. The characteristics of electronic ballast with the proposed PFM control scheme are comprehensively investigated through several simulations and experiments.

In this paper, we introduce a state-of-the-art statistical modeling technique which is developed in order to evaluate the sensitivity of chip performance with device parameters using SPICE simulation. ET-based SPICE modeling links the shift of E-tests (Electrical tests) to a set of SPICE model parameters without additional measurements of I-V curves. Therefore, it is very useful and quick in analyzing the sensitivity of circuit characteristics to E-tests. In the case of an asynchronous DRAM, PMOS Idsat primarily contributes to the variation of the chip performance tRAC. This methodology not only enables circuit designers to analyze the circuit sensitivity with E-test, but also provides key device characteristics for the statistical process control during the yield ramp-up.

When using the optical tweezers, determing the exact value of the trap stiffiness is very important. In this work, displacements of micron size particle were measured as a function of time by using two different methods; the passive method which measures the trap stiffness of the trapped particle at a fixed position by optical tweezers and the active method which measures the trap stifffness by forcefully oscillating the trapped particle. When using the passive method, the trap stiffness which was determined from Boltzmann distribution and power spectrum was measured, respectively. When using the ative method, the trapstiffness which was analyzed through the data of the amplitude and phase information of the tradpped particle by using an lock-in amplifier was measured. The trap stiffness values obtained from two different methods were compared.

In this paper, a novel full-bridge (FB) zero-voltage-transition (ZVT) PWM DC/DC converter topology is proposed. The proposed FB-ZVT PWM DC/DC converter has ZVS of main switches for wide load and line ranges and an advantage of achieving zero voltage and zero current switching of the auxiliary switches using the auxiliary network. The auxiliary network is simply composed of saturable inductor, auxiliary capacitors and auxiliary diodes. With the help of the proposed auxiliary network, the improved FB-ZVT PWM DC/DC converter has so much improved characteristics with respect to the overall system efficiency. The operation principles are explained in detail and the several interesting simulation and experimental results verify the validity of the proposed circuit from a 83 kHz, 1 kW prototype converter using IGBTs.

In this paper, an improved full-bridge (FB) zero-voltage-transition (ZVT) PWM DC/DC power converter topology is proposed. The proposed FB-ZVT PWM DC/DC power converter has the advantage of achieving zero voltage and zero current switching of the auxiliary switches using an auxiliary network. The auxiliary network is simply composed of a saturable inductor, auxiliary capacitors and auxiliary diodes. With the help of the proposed auxiliary network, the improved FB-ZVT PWM DC/DC power converter has much improved characteristics with respect to the overall system efficiency. The operation principles are explained in detail and several interesting simulation and experimental results verify the validity of the proposed circuit from a 83 kHz, 1 kW prototype power converter using IGBTs.

This paper proposes a novel secondary clamping circuit for soft switching FB (full-bridge) PWM DC/DC converter. The proposed circuit eliminates the reflected output current which is reflected from the secondary side to the primary side so that it reduces the needless conduction losses of the primary side during the current circulating mode. Also, it ensures the zero-voltage/zero-current switching of the leading/lagging leg switches. The characteristics of the proposed clamping circuit are investigated and the validity is verified by the simulation and the experimental results.

This paper presents a new PWM DC/DC converter with dual output power using a single power stage, which has isolation characteristics between each of the dual outputs. The proposed converter topology is consists of only one switch and single secondary winding. The proposed converter, therefore, has the advantages of not only low cost and small size but also high power density because of using minimum components and devices compared with conventional methods, which use a multi winding transformer or several converters. The operating principle of the proposed converter topology, including the auxiliary circuit with the conventional ZVT (zero-voltage-transition) for soft switching of the main switch, is illustrated in detail and the validity of the converter is verified through several interesting simulated and experimental results.

In this paper, novel zero-current-transition (ZCT) PWM DC/DC converters without additional current stress and conduction loss on the main switch are presented during the resonance period of the auxiliary cell. The auxiliary cell consists of a resonant inductor, a resonant capacitor, an auxiliary switch and an auxiliary diode in parallel with the main switch and the zero-current-switching (ZCS) range of the main and the auxiliary switch of the proposed converters are entirely achieved by operating the auxiliary cell. Also the reduced di/dt, which is obtained by a resonant inductor, helps soft turn-on of the main switch. The theoretical analysis and the operation principle of the new ZCT technique are described in detail with a boost converter as an example. The simulation and the experiment were performed under 1 kW output power, 100 kHz switching frequency with a boost converter and 1 kW output power, 50 kHz switching frequency with a full-bridge (FB) converter to verify the validity of the proposed ZCT technique.

This paper presents an improved ZVS partial series resonant DC/DC converter (PSRC) with low conduction losses, suitable for high power and high frequency application. The proposed PSRC has advantages of zero-voltage-switching (ZVS) of the main switches for entire load ranges and low conduction losses of the main switches by decreasing current stresses. Also, reduction of the effective duty cycle does not occur during resonant period of the main circuit because the auxiliary circuit of the proposed converter is placed out of the main power path. The auxiliary network is only composed of passive components including the auxiliary inductor, auxiliary capacitors, auxiliary diodes and saturable inductor. Therefore, an improved ZVS PSRC has improved characteristics with respect to the overall system efficiency. The operation principles of the proposed converter are explained in detail and the validity of the proposed converter is verified by several interesting simulated and experimental results.

In this paper, a modified ZVZCS commutation cell with minimum additional components, which provides soft switching at both turn-on and turn-off of main and auxiliary switches as well as diodes in PWM converters, is presented. The proposed soft-switching technique is suitable for not only minority but also majority carrier semiconductor devices. The auxiliary switch of the proposed ZVZCS commutation cell is in parallel with the main switch, and therefore, there is no current stress on the main switch and diode. The operation principles of the proposed ZVZCS commutation cell are theoretically analyzed using the PWM boost converter topology as an example. Theoretical analysis, simulation and experimental results verify the validity of the PWM boost converter topology with the proposed ZVZCS commutation cell.

A practical statistical SPICE model has been developed for computer-aided design of high performance devices. This model accounts for both interdie and intra-die device variations, both of which contribute to statistical variations in chip performance. A new characterization method, ET-based SPICE modeling, is proposed in order to link the shift of E-tests (Electrical tests) to the SPICE input deck without additional measurements of I-V curves. Therefore, we can efficiently analyze the chip performance with respect to the process variations. The model is applied to a 2.0 V 1.6 GHz bandwidth DRAM which has 0.19 /spl mu/m triple-well, 4-poly, 2-metal CMOS process. The simulated chip performance variability agrees well with measured data.

This paper presents a new soft-switching partial series resonant DC/DC converter (PSRC) with zero-voltage/zero-current switching (ZV/ZCS), suitable for application in the high power and high frequency switching. The proposed converter has not only advantages of the conventional PSRC but also ZV/ZCS of the main switch for the entire load ranges by adding the auxiliary circuit, and zero-voltage-switching (ZVS) turn-on of the auxiliary switch. The auxiliary network consists of the auxiliary switches, two auxiliary capacitors, an auxiliary inductor, two auxiliary diodes and saturable inductor and added to ZV/ZCS of the main switch. The operation principles of the new converter are explained in detail and the several interesting simulated and experimental results verify the validity of the proposed circuit.

As a new approach to islet transplantation, biocompatible monomethoxy-poly(ethylene glycol) (mPEG) was chemically grafted onto the pancreatic islet capsule. The aim of this study was to determine the optimal conditions for completely covering the islet by the mPEG while maintaining a high viability of islets according to the reaction time and the repeating number of the reaction. By grafting the fluorescein-PEG instead of mPEG, we determined the optimal mPEG grafting time as 1 h, during which time the procedure did not reduce islet viability. Insulin secretion from islets where the mPEG was grafted on for 3 times was similar to that of control islets. Moreover, the mPEG-grafted islets rapidly responded to the changes in the glucose concentration in the same pattern as did control islets. These results showed that mPEG grafting did not damage the function of islets. In conclusion, when the mPEG grafting was performed for 1 h and repeated twice with 1-day culture between each mPEG-grafting step, the mPEG completely covered the islet capsules without any damage to the viability and function of the islets. The main advantage of mPEG grafting on the islet capsule is that it can protect the islet against the host's immune system without increasing the islet size so that it can be administered into the portal vein by the catheter.

There is increasing evidence that estrogen influences electrical activity of neurons via stimulation of membrane receptors. Although the presence of intracellular estrogen receptors and their responsiveness in dorsal root ganglion (DRG) primary sensory neurons were reported, rapid electrical responses of estrogen in DRG neurons have not been reported yet. Therefore the current study was initiated to examine the rapid effects of estrogen on Ca2+ channels and to determine its detailed mechanism in female rat DRG neurons using whole-cell patch-clamp recordings. Application of 17beta-estradiol (1 microM) caused a rapid inhibition on high-voltage-activated (HVA)-, but not on low-voltage-activated (LVA)-Ca2+ currents. This rapid estrogen-mediated inhibition was reproducible and dose-dependent. This effect was also sex- and stereo-specific; it was greater in cells isolated from intact female rats and was more effective than that of 17alpha-estradiol, the stereoisomer of the endogenous 17alpha-estradiol. In addition, ovariectomy reduced the inhibition significantly but this effect was restored by administration of estrogen in ovariectomized subjects. Occlusion experiments using selective blockers revealed 17beta-estradiol mainly targeted on both L- and N-type Ca2+ currents. Overnight treatment of cells with pertussis toxin profoundly reduced 17beta-estradiol-mediated inhibition of the currents. On the other hand, estradiol conjugated to bovine serum albumin (EST-BSA) produced a similar extent of inhibition as 17beta-estradiol did. These results suggest that 17beta-estradiol can modulate L- and N-type HVA Ca2+ channels in rat DRG neurons via activation of pertussis toxin-sensitive G-protein(s) and non-genomic pathways. It is likely that such effects are important in estrogen-mediated modulation of sensory functions at peripheral level.

The taxis response of Rhodobacter sphaeroides 2.4.1 and 2.4.3, Rhodopseudomonas palustris , and Agrobacterium tumefaciens to nitrate and nitrite was evaluated by observing the macroscopic behavior of cells suspended in soft agar and incubated under various conditions. R. sphaeroides 2.4.3, which is capable of both nitrate and nitrite reduction, showed a taxis response to both nitrate and nitrite. R. sphaeroides 2.4.1, which contains nitrate reductase but not nitrite reductase, did not show a taxis response towards either nitrogen oxide. Insertional inactivation of the nitrite reductase structural gene or its transcriptional regulator, NnrR, in strain 2.4.3 caused a loss of a taxis response towards both nitrate and nitrite. An isolate of 2.4.1 carrying a copy of the nitrite reductase gene from 2.4.3 showed a taxis response to both nitrogen oxides. The taxis response of 2.4.3 was observed under anaerobic conditions, suggesting that the taxis response was due to nitrate and nitrite respiration, not to inhibition of oxygen respiration by respiration of nitrogen oxides. Strain 2.4.3 showed a taxis response to nitrate and nitrite under photosynthetic and aerobic conditions. Changing the carbon source in the culture medium caused an unexpected subtle shift in the taxis response of 2.4.3 to nitrite. A taxis response to nitrogen oxides was also observed in R. palustris and A. tumefaciens. R. palustris exhibited a taxis response to nitrite but not to nitrate, while A. tumefaciens exhibited a response to both compounds.

Objectives: To evaluate the effects of transdermal estrogen therapy on bone mineral density (BMD) in postmenopausal Korean women. Methods: A total of 149 healthy postmenopausal women were retrospectively evaluated: 100 were on hormone therapy (HT) and 49 were the control group. For the HT group, 54 applied estrogen transdermally using either a patch (n = 21) or gel (n = 33), and 46 took estrogen orally (conjugated estrogen 0.625 mg or equivalent). Demographic profiles and changes in BMD over two years were compared according to the route of the estrogen. Results: No differences were found in age, age at menopause, parity, body mass index, and type of menopause among the oral, transdermal and control groups. Compared with controls, HT significantly increased BMD after 2 years in both the lumbar spine and the total hip. The increases in BMD at both lumbar spine and hip were comparable between the oral and transdermal groups. There were also no differences in BMD changes according to progestogen addition in either the oral or transdermal groups. Conclusion: Transdermal estrogen therapy increases BMD, comparable to oral estrogen, in postmenopausal Korean women. (J Menopausal Med 2014;20:111-117)

This paper presents new zero-voltage/zero-current-switching (ZVZCS) PWM DC-DC converters. The proposed soft-switching technique achieves ZVS and ZCS simultaneously at both turn-on and turn-off of the main switch and diode by using only one auxiliary switch. Also, this technique is suitable for not only minority but also majority carrier semiconductor devices. The auxiliary circuit of the proposed topologies is placed out the main power path, therefore, there are no voltage/current stresses on the main switch and diode. The operating principle of the proposed topologies is illustrated by a detailed study with a boost converter as an example. Theoretical analysis, simulation and experimental results are presented to explain the proposed schemes.

Objective The aim of this study was to evaluate the prevalence of hyperprolactinemia in adolescents and young women with menstrual problems. Study Design This study included 1704 young women with menstruation-related problems. The patients were classified into group I (age, 11-20 years) or group II (age, 21-30 years); the prevalence of hyperprolactinemia was analyzed according to age and categories of menstruation-related problems. Results For primary amenorrhea and oligomenorrhea, the prevalence of hyperprolactinemia was low in both groups. However, hyperprolactinemia was a relatively common cause of secondary amenorrhea (5.5% for group I and 13.8% for group II, respectively); it was more frequent in group II ( P = .001); the prevalence of prolactinoma was also higher in group II ( P = .015). For abnormal uterine bleeding, hyperprolactinemia was more common in group II (2.6% for group I and 9.4% for group II; P Conclusion Hyperprolactinemia is not rare in young women with menstruation-related problems; its prevalence varies according to age and manifestations.

Young-Hee Kang, M.S., Dong-Yun Lee, M.D., Doo Seok Choi, M.D., Byung-Koo Yoon, M.D., Young Joo Lee, Ph.D., Mee-Ra Rhyu, Ph.D. Samsung Biomedical Research Institute, Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Department of Bioscience and Biotechnology, Sejong University, Seoul, Divisions of Metabolism and Functionality Research, Korea Food Research Institute, Seongnam, Korea

The balance between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) regulates fibrinolysis. PAI-1 expression increases in atherosclerotic arteries and vascular smooth muscle cells (VSMCs) are one of major constituents of atheroma. We investigated the impact of lysophosphatidylcholine (lysoPC), an active component of oxidized low-density lipoprotein, on the plasminogen activator system of the rat VSMCs. The lysoPC stimulated the protein and gene expressions of PAI-1 but did not affect the protein expression of t-PA. Fibrin overlay zymography revealed that lysoPC increased the activity of PAI-1 in the conditioned media, while concurrently decreasing that of free t-PA. Vitamin E inhibited the lysoPC-induced PAI-1 expression. Further, lysoPC increased the intracellular reactive oxygen species (ROS) formation. Caffeic acid phenethyl ester, an inhibitor of NF-κB, blocked this lysoPC effect. Indeed, lysoPC induced the NF-κB-mediated transcriptional activity as measured by luciferase reporter assay. In addition, genistein, an inhibitor of protein-tyrosine kinase (PTK), diminished the lysoPC effect, while 7,12-dimethylbenz[a]anthracene, a stimulator of PTK, stimulated PAI-1 production. In conclusion, lysoPC does not affect t-PA expression but induces PAI-1 expression in the VSMC by mediating NF-κB and the genistein-sensitive PTK signaling pathways via oxidative stress. Importantly, lysoPC stimulates the enzyme activity of PAI-1 and suppresses that of t-PA.

Objectives: To investigate the cytotoxic effects of lysophosphatidylcholine (lysoPC), an active component of oxidized low-density lipoproteins (LDL), on vascular smooth muscle cells (VSMCs). Methods: VSMCs were derived from rat aorta. Cell death was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay, lactic dehydrogenase (LDH) assay, and DNA fragmentation assay. Apoptosis was quantified by propidium iodide staining and fluorescent activated cell sorting (FACS) analysis, and intracellular free radical production was determined using 2',7'-dichlorofluorescin diacetate (DCF-DA). In addition, the changes in caspases, bcl-2 and bax proteins were evaluated by western blot analysis. Results: LysoPC over 25 μM induced more than 50% of the cell death at 10 hours on MTT assay with no change in the level of LDH. The DNA ladder pattern showed that cell death induced by lysoPC was caused by apoptosis, which was associated with increased free radical production. Vitamin E, a potent antioxidant and caffeic acid phenylethyl ester (CAPE), an inhibitor of nuclear factor-kappaB (NF-kB), blocked apoptosis. The casepase-3 precursor decreased and the active form of caspase-8 increased. Total bcl-2 and bax proteins did not change with lysoPC treatment, but translocation of bax from cytosole to the mitochondria membrane was observed. Conclusion: LysoPC induces apoptosis in VSMCs via an oxidant mechanism, dependent on NF-kB. (J Korean Soc Menopause 2012;18:139-146)

A strategy for the on-surface synthesis of silver nanoparticles (AgNPs) on a variety of two- to three-dimensional material surfaces, utilizing polydopamine, an emerging surface modifying agent, is reported in this paper. This material-independent platform for AgNP synthesis is useful for fabricating organic/inorganic hybrid nanomaterials and for preparing substrates for laser desorption-ionization time-of-flight mass spectrometry (LDI-ToF MS).

Low voltage high mobility n-type thin film transistors (TFTs) based on sol-gel processed zinc oxide (ZnO) were fabricated using a high capacitance ion gel gate dielectric. The ion gel gated solution-processed ZnO TFTs were found to exhibit excellent electrical properties. TFT carrier mobilities were 13 cm2/V s, ON/OFF current ratios were 105, regardless of the sintering temperature used for the preparation of the ZnO thin films. Ion gel gated ZnO TFTs are successfully demonstrated on plastic substrates for the large area flexible electronics.

We investigated which of the three FRAX fracture risk assessment tool models is most applicable to Korean women. For 306 postmenopausal women (mean age, 77 yr) with a hip fracture, fracture probabilities were calculated using FRAX models from Japan, Turkey and China. Data on bone mineral density (BMD) at the femoral neck were available for 103 patients. Significant differences existed among the models, independent of the inclusion of BMD in the calculation of fracture probabilities. The probabilities of both major osteoporotic fractures and hip fractures were significantly higher in the Japanese model than in the Turkish or Chinese models. In all of the models, the probabilities of a major osteoporotic fracture, but not of a hip fracture, decreased significantly if calculated without BMD values. By applying the Japanese model, the ten-year probabilities for major osteoporotic and hip fractures increased significantly with age. Our results suggest that the Japanese FRAX model might be the most appropriate for Korean women.