Biomedical subjects

Wei Cai

Publications and source records attributed to Wei Cai.

42 records · Page 3Linked to original sources

PubMed2003

[Resting energy expenditure in healthy newborn infants].

OBJECTIVE: To establish the value of the resting energy expenditure (REE) in healthy newborns and evaluate relative factors of REE. METHODS: One hundred and fifty-four healthy newborns (75 boys, 79 girls; birth-weight 2,500-3,999 g) were enrolled in this study. The Apgar score at the 5th minute was equal to or more than 8; the postnatal age was equal to or more than 5 days. The newborns had no apparent defect. The mothers had no history of metabolic and endocrine diseases. REE was measured by Deltatrac II in child canopy mode for 30-45 minutes during asleep or quiet awake status. RESULTS: The average REE was (201.8 +/- 25.4) kJ/(kg.d), which was significantly lower than the predicted REE by Schofield formula[(226.1 +/- 4.8) kJ/(kg.d), P = 0.000], the predicted REE was 12.04% higher than the measured REE. There were no differences in sex and ways of delivery. The newborns whose birth-weight was between 2,500-2,999 g were measured in two modes: baby and child mode, and the REE values were significantly higher (122.6 +/- 25.0) kJ/(kg.d) and (208.8 +/- 26.4) kJ/(kg.d), respectively (P = 0.000). CONCLUSIONS: The prediction formula might be improper for calculating the REE in newborn infants. The indirect calorimetry was the better way to know the actual REE of newborns. The authors recommended that in child mode the measurement of REE in newborns would be the indirect calorimetry, and the REE in healthy newborns was (201.8 +/- 25.4) kJ/(kg.d).

Birth Weight↗

PubMed2002

Importance sampling of rare transition events in Markov processes.

We present an importance sampling technique for enhancing the efficiency of sampling rare transition events in Markov processes. Our approach is based on the design of an importance function by which the absolute probability of sampling a successful transition event is significantly enhanced, while preserving the relative probabilities among different successful transition paths. The method features an iterative stochastic algorithm for determining the optimal importance function. Given that the probability of sampling a successful transition event is enhanced by a known amount, transition rates can be readily computed. The method is illustrated in one- and two-dimensional systems.

Journal Article↗

PubMed2002

Nodal effects in dislocation mobility.

We show that, contrary to the prevailing perception, dislocations can become more mobile by zipping together to form junctions. In a series of direct atomistic simulations, the critical stress to move a junction network in a [110] plane of bcc molybdenum is found to be always smaller ( approximately 50%) than that required to move isolated dislocations. Our data support a previously proposed hypothesis about the nature of anomalous slip in bcc transition metals, yet offer a different atomistic mechanism for conservative motion of screw dislocation networks. The same data suggest a hierarchy of motion mechanisms in which lower-dimensional crystal imperfections control the rate of sliding along the low-angle twist boundaries.

Journal Article↗

PubMed2002

DNA-modified nanocrystalline diamond thin-films as stable, biologically active substrates.

Diamond, because of its electrical and chemical properties, may be a suitable material for integrated sensing and signal processing. But methods to control chemical or biological modifications on diamond surfaces have not been established. Here, we show that nanocrystalline diamond thin-films covalently modified with DNA oligonucleotides provide an extremely stable, highly selective platform in subsequent surface hybridization processes. We used a photochemical modification scheme to chemically modify clean, H-terminated nanocrystalline diamond surfaces grown on silicon substrates, producing a homogeneous layer of amine groups that serve as sites for DNA attachment. After linking DNA to the amine groups, hybridization reactions with fluorescently tagged complementary and non-complementary oligonucleotides showed no detectable non-specific adsorption, with extremely good selectivity between matched and mismatched sequences. Comparison of DNA-modified ultra-nanocrystalline diamond films with other commonly used surfaces for biological modification, such as gold, silicon, glass and glassy carbon, showed that diamond is unique in its ability to achieve very high stability and sensitivity while also being compatible with microelectronics processing technologies. These results suggest that diamond thin-films may be a nearly ideal substrate for integration of microelectronics with biological modification and sensing.

Base Sequence↗

PubMed2002

[Expression of matrix metaloproteinase and tissue inhibitors in ovarian tumors].

BACKGROUND & OBJECTIVE: Metalloproteinase(MMPs) is considered to be associated with the development of carcinoma, especially with the invasion and metastases of cancer. This study was designed to evaluate the relationship between the expression of MMP-2, MMP-9, and TIMP-2 and biological behavior of ovarian cancer. METHODS: The expression of MMP-2, MMP-9, and TIMP-2 in 128 patients with ovarian tumor was determined using immunohistochemical methods, and their relationship to many clinicopathological parameters was analyzed. RESULTS: Immunohistochemical studies revealed a diffuse granular distribution of MMP-2, MMP-9, and TIMP-2 in the cytoplasm of the carcinoma cells. The expression of MMP-2, MMP-9, and TIMP-2 was stronger in ovarian adenocarcinoma tissue than in ovarian benign tumor tissue (P < 0.01). MMP-2 and MMP-9 levels were found to be significantly higher in grade III-IV adenocarcinoma than in grade I-II adenocarcinoma (P < 0.01). MMP-2 and MMP-9 levels were significantly higher in G3 than in G1-2 tumors. Furthermore, the expression rate of MMP-2 and MMP-9 was higher in cases with lymph node metastases thanin those with non-lymph node metastasis. TIMP-2 expression was contrary to the expression of MMP-2 and MMP-9 on that three respects in ovarian carcinomas. CONCLUSION: The expression of MMP-2, MMP-9, and TIMP-2 correlate with tumor stage, poor differentiation, and lymphonodes metastases, which suggests that co-expression of MMP-2, MMP-9, and TIMP-2 within the same tumor seem to play an important role in the progression of ovarian cancer and could be useful prognostic markers for patients with ovarian carcinoma.

Adolescent↗

PubMedDate not supplied

Superstructure searching algorithm for generic reaction retrieval.

Chemical reaction knowledge is usually summarized and retrieved by chemists from references, journals, and reaction databases. To rigorously extract chemical reaction knowledge from large data sets, computer algorithms become much more important. This paper presents a new approach, superstructure searching (SSS) algorithm, for generic reaction retrieval. The algorithm considers all known reaction patterns from the targeted structure and assigns synthetic routes for new chemical compounds. This algorithm consists of screening, atom-by-atom comparison, and computation of R-groups' similarity.

Journal Article↗