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Xiaoming Chen

Publications and source records attributed to Xiaoming Chen.

36 records · Page 2Linked to original sources
PubMed2004

Preparation of a positively charged cellulose derivative chiral stationary phase with copolymerization reaction for capillary electrochromatographic separation of enantiomers.

A positively charged chiral stationary phase (CSP) was prepared by chemically immobilizing cellulose 3,5-dimethylphenylcarbamate onto methacryloyldiethylenetriaminopropylated silica (MCDEAPS) via a radical copolymerization reaction. The prepared CSP was evaluated for enantiomer separation in nonaqueous capillary electrochromatography (CEC). Electroosmotic flow (EOF) generated on the prepared CSP could be significantly improved with introduction of positive charges into the CSP, and separation of enantiomers in CEC has been achieved with mobile phases of ethanol and hexane-ethanol, respectively. In addition, we investigated the solvent versatility of the immobilized CSP on enantioseparations in CEC and capillary liquid chromatography (CLC) due to the elimination of dissolution of chiral selector in a number of solvents. Chiral resolution of some enantiomers was improved by adopting tetrahydrofuran (THF) and chloroform as mobile-phase modifiers, respectively.

Cellulose↗
PubMed2004

Enantiomer separation of dimethyl dicarboxy alpha-biphenyl (DDB) and its analogues on a covalently bonded cellulose tris-(3,5-dimethylphenylcarbamate) CSP.

Dimethyl dicarboxy alpha-biphenyl (DDB) and its analogues represent atropisomers which have been resolved on the covalently bonded cellulose tris-(3,5-dimethylphenylcarbamate) (CDMPC) CSP. Different kinds of alcohols, tetrahydrofuran (THF), and chloroform were employed as mobile phase modifiers (MPMs), and their influence on the retention and separation of the enantiomers was investigated. Ternary mobile phases (hexane/2-propanol/THF, hexane/2-propanol/chloroform) were employed to investigate the separation of the five enantiomers. The advantages of the broader choice of solvents offered by the covalently bonded CDMPC CSP were discussed. The effect of structural variation of the enantiomers on their retention and separation was investigated.

Buffers↗
PubMed2004

Combined use of MRI and PET to monitor response and assess residual disease for locally advanced breast cancer treated with neoadjuvant chemotherapy.

RATIONALE AND OBJECTIVES: The purpose of the study was to evaluate the hypothesis that magnetic resonance imaging (MRI) and positron emission tomography (PET) are complementary and valuable in monitoring response and assessing residual disease of locally advanced breast cancer (LABC) treated with neoadjuvant chemotherapy. We sought to determine if the combination of the two modalities was more accurate than either alone and could provide better guidance in patient management. MATERIALS AND METHODS: Sixteen lesions in 15 women with LABC were evaluated with MRI, PET, and clinical breast examination (CBE) before and after neoadjuvant chemotherapy. The pre- and posttherapy maximal tumor sizes on MRI and CBE and standard uptake values (SUVs) on PET served as the measurements for clinical response classification and residual disease assessment. Pathologic assessment provided the reference for macroscopic and microscopic pathologic tumor response and residual disease. RESULTS: PET correctly predicted lack of pathologic response in five of six cases (83%); CBE predicted correctly in one of six (17%) cases, and MRI predicted correctly in zero of six cases. When PET predicted response, MRI defined the extent of macroscopic pathologic residual disease accurately in 9 of 10 cases (90%). When posttherapy MRI showed complete response (CR) in eight cases, macroscopic pathologic complete response (mCR) was observed in all eight cases (100%). CONCLUSION: Our study suggests that combined use of MRI and PET is complementary and offers advantages over CBE. PET was more accurate in predicting pathologic nonresponse. Complete response by MRI correlated well with macroscopic pathologic complete response.

Adolescent↗
PubMed2004

Social and legal control in China: a comparative perspective.

This article exposes the reader to a different social and legal control system and a different way of thinking about crime--that of China. Chinese think positively about the nature of humans and their potential, and China's social control system weaves together a unique combination of formal and informal mechanisms with a strong emphasis on the latter. The criminal justice system constitutes a key element of the social control system, but it appears to be more of a last resort. It is hoped that through a comparative analysis, the reader can develop a deeper understanding of different social and legal systems.

China↗
PubMed2004

MRI-guided breast biopsy: clinical experience with 14-gauge stainless steel core biopsy needle.

OBJECTIVE: Core needle biopsy has proven advantages for wire localization and excision; however, MRI-guided core biopsy has been limited by less satisfactory sampling efficiency and less availability of MRI-compatible biopsy needles. We evaluated the feasibility and diagnostic yield of MRI-guided biopsy using 14-gauge stainless steel core biopsy needles and MRI-compatible coaxial sheaths in a closed 1.5-T scanner. MATERIALS AND METHODS: Thirty-five consecutive breast biopsies performed in 29 women between March 2001 and August 2002 were retrospectively reviewed. For each procedure, an MRI-compatible sheath was placed under MRI guidance using a dedicated breast coil and biopsy guidance system. With the patient out of the magnet, a 14-gauge steel core biopsy needle was used to obtain multiple samples. Lesion characteristics, including size, morphology, and enhancement, were recorded. Histology of all the lesions was obtained; and surgical, imaging, or clinical follow-up was performed. RESULTS: Targeted masses and enhancing foci ranged from 3 to 17 mm. Regional enhancement ranged from 14 to 70 mm. Thirty-four of the 35 biopsies were technically successful. Histology revealed malignancy in eight lesions (23%), atypical ductal hyperplasia in five lesions (14%), and benign entities in 21 lesions (60%). Surgery confirmed all eight core biopsies with malignant findings. Two of five lesions with atypical ductal hyperplasia were upgraded to malignancy after surgery. CONCLUSION: This new method of MRI-guided breast biopsy with a 14-gauge stainless steel core biopsy needle and a closed 1.5-T MRI scanner is feasible, safe, and effective and produces satisfactory diagnostic yield. This method offers an alternative to MRI-guided wire localization and to MRI-guided core biopsy with nonferrous needles.

Adult↗
PubMed2004

[Preparation of covalently bonded cellulose tris (4-methylbenzoate) derivative chiral stationary phases through a polymerization reaction].

Cellulose tris (4-methylbenzoate) derivatives (CTMB) having methacryloyl groups were synthesized with regio-selective or nonselective procedures, and were immobilized on gamma-methacrylatepropylated silica (gamma-MAPS) through a polymerization reaction. The obtained chiral stationary phases ( CSPs) were evaluated by high performance liquid chromatographic (HPLC) resolution of 9 racemates (3-butyl-phthalide, ketoprofen, trans-stilbene oxide, benzoin, benzoin analogue, Tröger' s base, warfarin, 4,4'-dimethoxy-5,6,5',6'-dimethylenedioxy-biphenyl-2,2'-dicarboxylate and 4,4'-dimethoxy-5,6,5',6'-dimethylenedioxy-biphenyl-2-methylcarboxylate-2'-ethylcarboxylate). For regio-nonselective procedure, increasing the content of vinyl group on CTMB would lead to higher immobilization efficiency and enantio-selectivity. CSPs prepared by regio-selective procedure possessed slightly higher enantioselectivities than those prepared by regio-nonselective procedure, while the latter showed some advantages for rapid and facile preparation. CSPs prepared with silica gel II (Fuji, 5 microm, 30 nm, ca. 150 m2/g) showed higher enantioselectivities than those prepared with silica gel I (Kromasil, 5 microm, 20 nm, ca. 240 m2/g). The prepared CSPs could keep stable under different eluents, even with 40% of tetrahydrofuran (THF) in mobile phases.

Benzoates↗
PubMed2003

Synthesis of covalently bonded cellulose derivative chiral stationary phases with a bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate.

A bifunctional reagent of 3-(triethoxysilyl)propyl isocyanate (TEPI) was initially adopted as a spacer reagent to prepare the bonded types of chiral stationary phases (CSPs) with cellulose derivatives. The silica-based CSPs were chemically prepared with non-regioselective and regioselective approaches and their chiral resolving capabilities were evaluated in terms of HPLC resolution of test enantiomers. It was observed that the chiral recognition capabilities of the non-regioselectively prepared CSPs were influenced by the amount of TEPI used. And also, the regioselectively prepared CSP generally showed a slightly higher resolution power than the non-regioselectively prepared CSP, while the non-regioselective procedures were highly advantageous to rapid preparation. In addition, chiral recognition of the prepared CSPs was affected by the properties of the used silica matrices.

Cellulose↗
PubMed2003

Molecularly imprinted monolithic stationary phases for liquid chromatographic separation of enantiomers and diastereomers.

The method for preparation of molecularly imprinted monolithic stationary phase has been improved to achieve liquid chromatographic separation of enantiomers and diastereomers. By adopting low polar porogenic solvents of toluene and dodecanol and optimal polymerization conditions, the molecularly imprinted monolithic stationary phases with good flow-through properties and high resolution were prepared. Enantiomers of amino acid derivatives and diastereomers of cinchona alkaloids were completely resolved using the monolithic stationary phases. The influence of porogenic composition, monomer-template ratio and polymerization conditions on the chromatographic performance was investigated. Some chromatographic conditions such as the composition of the mobile phase and the temperature were characterized. Scanning electron microscopy showed that the molecularly imprinted monolithic stationary phase has a large through-pore structure to allow the mobile phase to flow through the column at very low backpressure. Accelerated separations of enantiomers and diastereomers were therefore achieved at elevated flow rates. Finally, the chiral recognition performance of the prepared stationary phase in aqueous media was investigated. Hydrophobic interaction, and ionic and/or hydrogen bonding interactions were proposed to be responsible for the recognition mechanism.

Chromatography, High Pressure Liquid↗
PubMed2003

Capillary electrochromatographic separation of enantiomers on chemically bonded type of cellulose derivative chiral stationary phases with a positively charged spacer.

Positively charged chiral stationary phases (CSPs) were prepared for capillary electrochromatography (CEC) separation of enantiomers by chemically immobilizing cellulose derivatives onto diethylenetriaminopropylated silica (DEAPS) with tolylene-2,4-diisocyanate (TDI) as a spacer reagent. Anodic electroosmotic mobility was observed in both nonaqueous and aqueous mobile phases due to the positively charged amines on the surface of the prepared CSPs. For comparison, the traditionally used 3-aminopropyl silica (APS) was also adopted as the base material instead of DEAPS to prepare CSP. It was observed that the EOF on the DEAPS-based CSP was 18%-60% higher than that on the APS-based CSP under nonaqueous mobile phase conditions. Separation of enantiomers in CEC was performed on the positively charged CSPs with the nonaqueous mobile phases of pure ethanol or mixture of hexane-alcohol and the aqueous phases of acetonitrile-water or 95% ethanol. Fast separation of enantiomers was achieved on the newly prepared CSPs.

Cellulose↗
PubMed2002

Reactivity differences of indomethacin solid forms with ammonia gas.

The present study deals with the acid-base reaction of three solid-state forms of the nonsteroidal antiinflammatory drug indomethacin with ammonia gas. X-ray powder diffraction, optical microscopy, gravimetry, and spectroscopic methods were employed to establish the extent of the reaction as well as the lattice changes of the crystal forms. The glassy amorphous form readily reacts with ammonia gas to yield a corresponding amorphous ammonium salt. In addition, the metastable crystal form of indomethacin (the alpha-form) also reacts with ammonia gas, but produces the corresponding microcrystalline ammonium salt. This reaction is anisotropic and propagates along the a-axis of the crystals. The stable crystal form (the gamma-form), however, is inert to ammonia gas. Amorphous indomethacin can react with ammonia gas because it has more molecular mobility and free volume. The reactivity differences between the alpha- and gamma-forms are dictated by the arrangement of the molecules within the respective crystal lattices. The recently determined crystal structure of the metastable alpha-form of indomethacin (monoclinic P2(1) with Z = 6, V = 2501.8 A(3), D(c) = 1.42 g.cm(-3)) has three molecules of indomethacin in the asymmetric unit. Two molecules form a mutually hydrogen-bonded carboxylic acid dimer, while the carboxylic acid of the third molecule is hydrogen bonded to one of the amide carbonyls of the dimer. The carboxylic acid groups of the alpha-form are exposed on the [100] faces and are accessible to attack by ammonia gas. After one layer of molecules reacts, the reactive groups in the subsequent layer are accessible to the ammonia gas. This process proceeds along the a-axis until the ammonia gas has penetrated the entire crystal. In contrast to the alpha-form, the gamma-form has a centrosymmetric crystal structure in which the hydrogen-bonded carboxylic acid dimers are not accessible to ammonia gas because they are caged inside a hydrophobic shield comprising the remainder of the indomethacin molecule. In view of the significantly lower density of the stable gamma-form as compared to the metastable alpha-form (1.37 and 1.42 g cm(-3), respectively), it became apparent that the reactivity of the crystal forms depends exclusively on the molecular arrangement and not on the packing density of the indomethacin crystals.

Ammonia↗
PubMed2002

Separation of enantiomers by nanoliquid chromatography and capillary electrochromatography using a bonded cellulose trisphenylcarbamate stationary phase.

A cellulose trisphenylcarbamate-bonded chiral stationary phase was applied to nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) with nonaqueous and aqueous solutions as the mobile phases. Several chiral compounds were successfully resolved on the prepared phase by nano-LC. The applicability of nonaqueous CEC on a cellulose derivative stationary phase was investigated with the organic solvents methanol, hexane, 2-propanol, and tetrahydrofuran (THF) containing acetic acid, as well as triethylamine as the mobile phases. Enantiomers of warfarin and praziquantel were baseline-resolved with plate numbers of 82,300 and 38,800 plates/m, respectively, for the first eluting enantiomer. The influence of applied voltage, concentration of nonpolar solvent, apparent pH, and buffer concentration in the mobile phase on the electroosmotic flow (EOF) and the mobility of the enantiomers was evaluated. Enantioseparations of trans-stilbene oxide and praziquantel were also achieved in aqueous CEC with plate numbers of 111,100 and 107,400 plates/m, respectively, for the first eluting enantiomer. A comparison between nonaqueous CEC and aqueous CEC based on a cellulose trisphenylcarbamate stationary phase was discussed. Pressure-assisted CEC was examined for the chiral separation of praziquantel and faster analysis with high enantioselectivity was acquired with the proper pressurization of the inlet vial.

Carbamates↗
PubMed2002

Synthesis of chemically bonded cellulose trisphenylcarbamate chiral stationary phases for enantiomeric separation.

Cellulose trisphenylcarbamate is regioselectively bonded to 3-aminopropyl silica gel and underivatized silica gel, respectively, at the 6-position of the primary hydroxyl group on the glucose unit of cellulose with 4,4'-diphenylmethane diisocyanate (DPDI) as a spacer. Enantioseparations are evaluated on these prepared chiral stationary phases (CSPs) with several organic acids as the modifiers in the mobile phase by high-performance liquid chromatography. The influence of the amount of DPDI used on chiral resolution is investigated. Also, the corresponding coated-type phase is also prepared for the aim of comparison. It is observed that the bonded-type phase shows a lower chiral recognition power but a better column efficiency than the coated-type phase under the liquid chromatographic mobile phase with hexane-alcohol. However, the bonded-type CSPs are compatible with a wider number of solvents such as tetrahydrofuran (THF) or chloroform, which generally result in the solubility or swelling of the cellulose derivatives on the coated-type CSPs. The results obtained from this study indicate that the bonded-type CSP may provide complementary enantioselectivity over the coated-type phase by adopting THF as a component in the mobile phase.

Journal Article↗
PubMed2002

Social control in China: applications of the labeling theory and the reintegrative shaming theory.

This article delineates the underlying philosophy and functions of social control in the Chinese society. This topic is particularly interesting because specific control functions are grounded in a unique macro-control system, which is totally different from that typical of Western countries. The article also scrutinizes the implications of labeling theory and reintegrative shaming theory, as they are elaborated in the West, and tests their sensitivity to cross-cultural differences. Although some caveats are in order, the evidence presented here tends to support the reintegrative shaming theory rather than labeling theory.

China↗
PubMed2002

[Clinical observation of transcatheter uterine artery embolization for uterine myoma].

OBJECTIVE: To investigate the efficiency and safety of transcatheter uterine artery embolization (TUAE) for uterine myomas. METHODS: Thirty-eight cases of uterine myomas were treated by TUAE using lipiodol-pingyangmycin emulsion. 5 of 38 cases underwent hysterectomy or myomectomy from 1 to 3 weeks after TUAE. The specimens were studied pathologically. Thirty-three of 38 patients were followed for 3 to 6 months to observe the changes of myoma size and uterine volume and overian function. RESULTS: Symptom released in 90.6% (29/32), that was controlled of menorrhagia in 90.3% (28/31), disappeared of lumbago and lower abdominal pain in 83.3% (25/30), relieved of freguency and urgency of micturition in 45.5% (5/11). The mean reduction of myoma and uterine volume at 6 months was 59.1% and 49.3%, respectively, and at 12 months was 61.8% and 49.9% respectively. There was no significant difference in hormone level pre-embolization and post-embolization. Pathological studies of specimens showed that lipiodol deposition was found in myomas but not in myometrium. Myomas occurred spotty necrosis 2 weeks after embolization and extensive patchy necrosis 3 weeks after embolization. Degeneration or necrosis were not seen in myometrium. CONCLUSIONS: TUAE possesses a good effect for uterine myomas and doesn't result in the damage of ovarian hormone secretion and the myometrium.

Adult↗
PubMed2002

[Optimum mode of interventional treatment for hepatocellular carcinoma].

OBJECTIVE: To establish a reasonable protocol for interventional treatment of hepatocellular carcinoma (HCC). METHODS: The data of 1 000 HCC patients treated by different kinds of interventional treatment were reviewed with their results of biochemistry, imaging, pathology and survival rate evaluated. The value as well as the pros and cons of these various kinds of interventional treatment were compared in order to find an optimum protocol. RESULTS: Segmental-transcatheter oil chemoembolization (S-TOCE) was much effective eradicate the tumor yet inflicting less damage on the noncancerous hepatic tissue and giving much higher survival rate than the conventional transcatheter oil chemoembolization (C-TOCE). Percutaneous ethanol injection (PEI) played an important role in eradicating the residual tumor and improving the survival rate without damaging the noncancerous hepatic tissue. The survival quality or survival rate could be improved by choosing different ways of interventional treatments to cut down the complications. CONCLUSION: The selection of different interventional treatments should be done according to the size and type of HCC. Active management is indicated for different complications presenting along with HCC.

Carcinoma, Hepatocellular↗
PubMed2002

[Isolation, purification and analysis of polysaccharides from Adenophora potaninii Korsh].

Polysaccharides, AP-1 and AP-3, were obtained through extraction of the roots of Adenophora potaninii Korsh by hot water, followed by the isolation and purification by DEAE-cellulose and Sephadex G-200 column chromatography. It was proved to be homogeneous by gel filtration chromatography and their average MW was estimated to be 8.3 x 10(4) and 6.3 x 10(4) respectively. Analysis of sugar composition showed that AP-1 is D-glucan, while AP-3 is composed of glucose, rhamnose, arabinose and glucronic acid in the molar ratio of 5:1:1:3.

Campanulaceae↗