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T Y Chen

Publications and source records attributed to T Y Chen.

At least 19 recordsLinked to original sources
PubMed2006

Three-dimensional conformal radiotherapy for the treatment of arteriovenous shunting in patients with hepatocellular carcinoma.

The objective of this study is to evaluate the efficacy of radiotherapy for the treatment of arteriovenous shunting (AVS) in patients with hepatocellular carcinoma (HCC). Between November 1997 and April 2005, 20 HCC patients with AVS were referred to our department for radiotherapy. The radiation was delivered with 10-15 MV X-ray given 5 days per week at 2 approximately 2.5 Gy per fraction. Total doses ranged from 45 to 64 Gy (median dose 60 Gy). The patients were followed up with color Doppler sonography. When non-invasive imaging suggested obliteration, X-ray angiography was performed to verify the results. Four of the 20 AVS proved to be completely obliterated at X-ray angiography in 1.9, 2.8, 1.8 and 2.9 months after radiotherapy. One of the remaining 16 showed obvious regression on Doppler sonography 0.5 months after radiotherapy, but X-ray angiography was not performed to verify the result. Radiation-related hepatic failure did not occur during the follow-up period. In conclusion, radiotherapy is a treatment alternative for AVS in HCC patients and gives patients with poor prognosis the chance to receive further transcatheter arterial embolization.

Adult↗
PubMed2006

Enhanced magnetoresistance induced by spin transfer torque in granular films with a magnetic field.

Spin-transfer torques (STT) provide a mechanism to alter the magnetic configurations of magnetic heterostructures, a result previously only achieved by an external magnetic field. In granular solids, we demonstrate a new form of STT effect that can be exploited to induce a large spin disorder when combined with a large magnetic field. We have obtained a very large magnetoresistance effect in excess of 400% at 4.2 K in a large magnetic field, the largest ever reported in any metallic systems. The STT characteristics of granular solids differ significantly from those of multilayers, showing no STT effect at low magnetic fields but prominent STT effects at high fields.

Journal Article↗
PubMed2006

Application of a constructed wetland for industrial wastewater treatment: a pilot-scale study.

The main objective of this study was to examine the efficacy and capacity of using constructed wetlands on industrial pollutant removal. Four parallel pilot-scale modified free water surface (FWS) constructed wetland systems [dimension for each system: 4-m (L)x1-m (W)x1-m (D)] were installed inside an industrial park for conducting the proposed treatability study. The averaged influent contains approximately 170 mg l(-1) chemical oxygen demand (COD), 80 mg l(-1) biochemical oxygen demand (BOD), 90 mg l(-1) suspend solid (SS), and 32 mg l(-1) NH(3)-N. In the plant-selection study, four different wetland plant species including floating plants [Pistia stratiotes L. (P. stratiotes) and Ipomoea aquatica (I. aquatica)] and emergent plants [Phragmites communis L. (P. communis) and Typha orientalis Presl. (T. orientalis)] were evaluated. Results show that only the emergent plant (P. communis) could survive and reproduce with a continuous feed of 0.4m(3)d(-1) of the raw wastewater. Thus, P. communis was used in the subsequent treatment study. Two different control parameters including hydraulic retention time (HRT) (3, 5, and 7d) and media [vesicles ceramic bioballs and small gravels, 1cm in diameter] were examined in the treatment study. Results indicate that the system with a 5-d HRT (feed rate of 0.4m(3)d(-1)) and vesicles ceramic bioballs as the media had the acceptable and optimal pollutant removal efficiency. If operated under conditions of the above parameters, the pilot-plant wetland system can achieve removal of 61% COD, 89% BOD, 81% SS, 35% TP, and 56% NH(3)-N. The treated wastewater meets the current industrial wastewater discharge standards in Taiwan.

Biodegradation, Environmental↗
PubMed2006

Intravitreal triamcinolone staining observation of residual undetached cortical vitreous after posterior vitreous detachment.

AIMS: To study the pattern of residual undetached cortical vitreous (RCV) after posterior vitreous detachment (PVD) in eyes with rhegmatogenous retinal detachment (RRD) and to examine the relationship between RCV and the development of epiretinal membrane (ERM). METHODS: A prospective study was conducted in 33 consecutive patients with clinically evident PVD who underwent pars plana vitrectomy for RRD. During vitrectomy, triamcinolone acetonide (0.2 cm(3), 10 mg/cm(3)) was applied to stain the RCV. The pattern of the staining were recorded. The formation of postoperative ERM was correlated with the staining pattern of RCV. Each case was followed for at least 6 months. RESULTS: In all, 23 of the 33 patients had RCV of variable size, with a single stain patch observed in 13 patients and multiple patches in seven patients. Large circumferential areas of staining at the mid-periphery were noted in three patients. A total of 10 cases had staining over the fovea and five patients had staining over the disc. ERM developed in seven patients during follow-up. None corresponded to RCV. CONCLUSION: RCV is common in eyes with PVD and RRD. The macula and disc area are the most frequent locations for these vitreous islands. The relationship between RCV and ERM remains to be investigated.

Adolescent↗
PubMed2006

Liver graft-to-recipient spleen size ratio as a novel predictor of portal hyperperfusion syndrome in living donor liver transplantation.

Portal hyperperfusion in a small-size liver graft is one cause of posttransplant graft dysfunction. We retrospectively analyzed the potential risk factors predicting the development of portal hyperperfusion in 43 adult living donor liver transplantation recipients. The following were evaluated: age, body weight, native liver disease, spleen size, graft size, graft-to-recipient weight ratio (GRWR), total portal flow, recipient portal venous flow per 100 g graft weight (RPVF), graft-to-recipient spleen size ratio (GRSSR) and portosystemic shunting. Spleen size was directly proportional to the total portal flow (p = 0.001) and RPVF (p = 0.014). Graft hyperperfusion (RPVF flow > 250 mL/min/100 g graft) was seen in eight recipients. If the GRSSR was < 0.6, 5 of 11 cases were found to have graft hyperperfusion (p = 0.017). The presence of portosystemic shunting was significant in decreasing excessive RPVF (p = 0.059). A decrease in portal flow in the hyperperfused grafts was achieved by intraoperative splenic artery ligation or splenectomy. Spleen size is a major factor contributing to portal flow after transplant. The GRSSR is associated with posttransplant graft hyperperfusion at a ratio of < 0.6.

Adolescent↗
PubMed2006

Application of monitored natural attenuation to remediate a petroleum-hydrocarbon spill site.

Contamination of groundwater by petroleum-hydrocarbons is a serious environmental problem. The Monitored Natural Attenuation (MNA) approach is a passive remediation to degrade and dissipate groundwater contaminants in situ. In this study, a full-scale natural bioremediation investigation was conducted at a gasoline spill site. Results show that concentrations of major contaminants (benzene, toluene, ethylbenzene, and xylenes) dropped to below detection limit before they reached the downgradient monitor well located 280 m from the spill location. The results also reveal that natural biodegradation was the major cause of the observed contaminant reduction. The calculated natural first-order attenuation rates for BTEX and 1,2,4-trimethylbenzene (1,2,4-TMB) ranged from 0.051 (benzene) to 0.189 1/day (1,2,4-TMB). Evidence for the occurrence of natural attenuation includes the following: (1) depletion of dissolved oxygen, nitrate, and sulfate; (2) production of dissolved ferrous iron, sulfide, and CO2; (3) decreased BTEX concentrations and BTEX as carbon to TOC ratio along the transport path; (4) increased alkalinity and microbial populations; (5) limited spreading of the BTEX plume; and (6) preferential removal of certain BTEX components along the transport path. Additionally, the biodegradation capacity (44.73 mg/L) for BTEX and 1,2,4-TMB was much higher than other detected contaminants within the plume. Hence, natural attenuation can effectively contain the plume, and biodegradation processes played an important role in contaminant removal.

Benzene Derivatives↗
PubMed2005

Natural attenuation of MTBE at two petroleum-hydrocarbon spill sites.

Methyl tert-butyl ether (MTBE) has been used as a gasoline additive to improve the combustion efficiency and to replace lead since 1978. Because it is widely used and it has been disposed inappropriately, MTBE has become a prevalent groundwater contaminant worldwide. In this study, two petroleum-hydrocarbon contaminated sites (Sites A and B) were selected to evaluate the occurrence and effectiveness of natural attenuation of MTBE at these two sites. Field investigation results indicate that the natural attenuation mechanisms of MTBE at both sites were occurring with the first-order attenuation rates of 0.0021 and 0.0048 1day(-1) at Sites A and B, respectively. Results also reveal that the intrinsic biodegradation pattern was the most important mechanism among the natural attenuation processes at both sites. Results from BIOSCREEN simulation suggest that biodegradation was responsible for 78 and 59% of MTBE mass reduction at Sites A and B, respectively. Investigation results show that MTBE plume at Site B could be effectively controlled via natural attenuation processes. However, MTBE plume at Site A has migrated to a farther downgradient area and passed the boundary line of the site. Thus, more active groundwater remedial technologies should be applied at Site A to protect the downgradient environment. Results from this study suggest that natural attenuation might be feasible to be used as a remedial option for the remediation of MTBE-contaminated site on the premise that (1) detailed site characterization has been conducted and (2) the occurrence and effectiveness of natural attenuation processes have been confirmed.

Biodegradation, Environmental↗
PubMed2005

Co1-xFexS2: a tunable source of highly spin-polarized electrons.

In the emerging field of spin-electronics ideal ferromagnetic electron sources would not only possess a high degree of spin polarization, but would also offer control over the magnitude of this polarization. We demonstrate here that a simple scheme can be utilized to control both the magnitude and the sign of the spin polarization of ferromagnetic CoS2, which we probe with a variety of techniques. The position of the Fermi level is fine-tuned by solid solution alloying with the isostructural diamagnetic semiconductor FeS2, leading to tunable spin polarization of up to 85%.

Journal Article↗
PubMed2005

The significance of hepatic vein outflow volume in hepatic outflow insufficiency of living right liver graft evaluated by Doppler ultrasound.

The color Doppler ultrasound has been used to evaluate hepatic vein (HV) outflow insufficiency based on flow velocity and waveforms. In our experience, some cases with flat waveforms are clinically asymptomatic. The parameters of HV flow velocity and waveforms are not always correlated with clinical problems. So, we proposed that total HV flow volume (HVFV) may be a more reliable index. From August 2001 to July 2003, 31 cases among 48 adult-to-adult living related transplants of a right liver graft had one HV anastomosis. HV velocity, waveforms, and HVFV were compared both before and after transplantation. We set the minimal HVFV ratio at 80% based on the original HVFV before graft retrieval. There was no significant difference in HVFV before liver graft retrieval between the 2 groups, but there was a significant change after transplantation. There were no cases of HV insufficiency among group A patients (>80%), whose HVFV ranged from 397 to 1181 mL/min with ratios from 75% to 180% (mean 115%). In group B, there were 4 complicated cases with prolonged severe ascites (<80%) with HVFV ratios from 56% to 76% (mean 66%). Fisher exact test showed a great significance (P < .001). Thus the preliminary criteria of 80% minimal HVFV ratio allows detection of HV insufficiency for further interventional management.

Adult↗
PubMed2005

Increasing taxes to reduce smoking prevalence and smoking attributable mortality in Taiwan: results from a tobacco policy simulation model.

OBJECTIVE: To develop a simulation model to predict the effects of tax policies on smoking prevalence rates and smoking attributable deaths. METHODS: Using data from Taiwan, a simulation model is developed that projects population using birth and death rate data, future smoking rates using initiation, cessation and relapse data, and smoking attributable deaths using smoking prevalence and relative risk estimates. The model projects the number of smokers and smoking related deaths from a baseline year forward. The effects of taxes of different sizes, indexed and unindexed, and temporary versus sustained are modelled using elasticities based on published studies of demand. RESULTS: The model predicts that sustained tax increases have the potential to substantially reduce the number of smokers and the number of premature deaths, with the effects growing over time. Indexing taxes to inflation stems erosion of the tax effect. In our model, when the tax increases by 10 times (NTD 50) over the recent tax increase (NTD 5) and taxes are indexed to inflation, the smoking prevalence rate falls by over 15% soon after the tax increase, and by about 30% in relative terms by the year 2040, resulting in 4500 lives saved per year. CONCLUSIONS: Tax rises have the ability to substantially affect smoking rates in Taiwan. These effects grow over time and lead to substantial savings in lives and health care costs.

Adolescent↗
PubMed2005

Sol/gel transition of chitosan solutions.

This work studies the occurrence of sol/gel transition and the gel rheology for chitosan solution under various conditions. Experiments were conducted in an oscillatory shear apparatus with small amplitude, using a Rheometrics SR-5 rheometer, with Couette and parallel plate geometries. The experimental results demonstrate that the sol/gel transition concentration and the elastic modulus (G') for CS gel decrease as the pH value and the molecular weight (Mw) increase. However, the sol/gel transition concentration and G' became independent of Mw when Mw exceeded a threshold. The higher ionization constant, Kp, is responsible for the higher sol/gel transition concentration in a formic acid solution than in an acetic acid solution with equivalent molar concentration. The elastic modulus G' of a CS gel increases with temperature, which relationship differs from that for many polysaccharides, and can be understood through classical rubber elastic theory. Finally, a gel whose concentration was barely above the sol/gel point exhibited aging, and its G' and G" declined rather than increase with time, accompanied by a reversal from the sol/gel state back to the sol state. This is an uncommon aging behavior for a polysaccharide and a detailed explanation is provided.

Acetic Acid↗
PubMed2005

Audit of hypertension in general practice.

An audit of hypertension management was done in October 2004 in nine general practice (GP) clinics. Two structure, ten process and two outcome indicators were assessed. Results showed that targets were achieved in only four indicators, i.e., weight recording (89%), BP monitoring (85.8%), follow-up interval not exceeding 6 months (87.9%) and mean diastolic BP (73.9%). The other indicators (hypertension registry, reminder mechanisms for defaulters, recording of smoking, height, fundoscopy, monitoring of lipid profile, blood sugar, ECG, renal function and achievement of target mean systolic pressure) showed adequacy percentages varying from 22.1 to 68.7. Out of the 1260 patients assessed, 743 (59%) achieved a mean BP < or = 140/90 (or < or = 130/80 mmHg with diabetes mellitus / renal insufficiency) in the last 3 recorded readings. There was a vast difference between individual clinics. Reasons for not achieving targets were discussed and remedial measures for implementation were recommended.

Family Practice↗
PubMed2004

Current-driven switching in a single exchange-biased ferromagnetic layer.

We demonstrate spin-transfer torque effects in a single exchange-biased ferromagnetic layer. A current through a point contact to the exchange-biased Co layer reverses the magnetization of a nanodomain in the layer hysteretically for low applied magnetic fields and reversibly for high fields (up to 9 T). These effects are the inverse of the domain wall magnetoresistance, in the same way that similar effects in multilayers are the inverse of giant magnetoresistance.

Journal Article↗
PubMed2004

Hepatic venous stenosis in partial liver graft transplantation detected by color Doppler ultrasound before and after radiological interventional management.

Hepatic outflow insufficiency remains one of the major complications causing postoperative graft failure especially among partial liver graft transplantations (PLT) including living donor liver transplantation (LDLT), reduced size liver transplantation (RLT), and split liver transplantation (SLT). These procedures are different from the whole liver graft transplantations (OLT), which include multiple vascular anastomoses. Color Doppler ultrasound (CDUS) was used to evaluate the hepatic venous outflow from grafts before and after radiological interventional management and to document treatment effects. From June 1994 to March 2003, our 136 cases of PLTs included 131 LDLTs, two RLTs, and three SLTs. Seven cases (six children and one adult) showed postoperative hepatic vein outflow obstruction and persistent massive ascites, as detected by color Doppler ultrasound (CDUS) and confirmed by interventional angiography. The CDUS showed a monophasic flat waveform with a relatively low hepatic vein average peak velocity (Va) in all cases (mean 11 cm/s). Successful interventional procedures included balloon dilatation in three cases and metallic stent replacement in four cases. CDUS was used with guidance during the procedure to confirm restoration of normal hepatic vein flow with a multiphasic waveform and an objective increase of average flow velocity (high to average 66 cm/s). Ascites disappeared dramatically after the procedure. In conclusion CDUS is the prime modality to diagnose and document a treatment response.

Adult↗
PubMed2004

The significance of transarterial embolization for advanced hepatocellular carcinoma in liver transplantation.

INTRODUCTION: Transarterial embolization (TAE) is the treatment of choice for advanced HCC to control or even induce tumor shrinkage. The aim of this study was to evaluate the effect of pretransplantation TAE for treatment of advanced HCC. MATERIAL AND METHODS: From 1996 to 2002, we studied 12 cirrhotic patients with HCC, including six who met and six who exceeded the Milan criteria. All patients had sufficient hepatic function to undergo TAE. Liver transplantations were performed subsequently and they were followed prospectively for a median of 22 months (range = 12 to 53 months). RESULTS: The explanted livers from the 12 patients who had undergone TAE were noted to have extensive tumor necrosis. The pathological specimens at LT showed downstaging of the HCC, which allowed those six patients to meet the Milan criteria. The overall 1- and 2-year survival rates were 92% and 73%, respectively. The overall 1- and 2-year disease-free survival rates were 92% and 73%, respectively. One death unrelated to liver disease at 2 years after LT was noted in the downgraded group. One patient of the initially eligible group developed lung metastasis at 6 months and died at 12 months after LT. CONCLUSION: TAE is effective to downstage advanced HCC and reduce the dropout rate on the LT waiting list. Pre-LT TAE may be considered as a better therapeutic strategy for patients with advanced HCC.

Carcinoma, Hepatocellular↗