Biomedical subjects

Zhigang Wu

Publications and source records attributed to Zhigang Wu.

9 recordsLinked to original sources

PubMed2005

Pressure-induced anomalous phase transitions and colossal enhancement of piezoelectricity in PbTiO3.

We find an unexpected tetragonal-to-monoclinic-to-rhombohedral-to-cubic phase transition sequence induced by pressure, and a morphotropic phase boundary in a pure compound using first-principles calculations. Huge dielectric and piezoelectric coupling constants occur in the transition regions, comparable to those observed in the new complex single-crystal solid-solution piezoelectrics such as Pb(Mg(1/3)Nb(2/3))O3-PbTiO3, which are expected to revolutionize electromechanical applications. Our results show that morphotropic phase boundaries and giant piezoelectric effects do not require intrinsic disorder, and open the possibility of studying this effect in simple systems.

Journal Article↗

PubMed2005

Hard superconducting nitrides.

Detailed study of the equation of state, elasticity, and hardness of selected superconducting transition-metal nitrides reveals interesting correlations among their physical properties. Both the bulk modulus and Vickers hardness are found to decrease with increasing zero-pressure volume in NbN, HfN, and ZrN. The computed elastic constants from first principles satisfy c11 > c12 > c44 for NbN, but c11 > c44 > c12 for HfN and ZrN, which are in good agreement with the neutron scattering data. The cubic delta-NbN superconducting phase possesses a bulk modulus of 348 GPa, comparable to that of cubic boron nitride, and a Vickers hardness of 20 GPa, which is close to sapphire. Theoretical calculations for NbN show that all elastic moduli increase monotonically with increasing pressure. These results suggest technological applications of such materials in extreme environments.

Journal Article↗

PubMed2005

Rapid mixing using two-phase hydraulic focusing in microchannels.

Rapid mixing is important in biomedical analysis. In this study, rapid mixing is obtained through two-phase hydraulic focusing in microchannels. Two mixing streams are focused by two sheath streams. Assuming a laminar flow in the channel, the spreading behavior of the two immiscible fluids is modeled and solved analytically. The results show that both viscosity ratio and flow rate ratio between the sheath flow and the sample flow can affect the focusing ratio. Thus, the mixing path of the sample flows can be adjusted by either viscosity ratio or flow rate ratio. Furthermore, an analytical model was proposed and solved for convective/diffusive mixing between the sample streams. According to this model, the focusing ratio is a key parameter for rapid mixing. A fully polymeric micro mixer was fabricated and tested for verification of the presented analytical models. The micromixer was fabricated by laser micromachining and adhesive bonding. The characterization results show the promising potential of mixing in microscale using two-phase hydraulic focusing.

Complex Mixtures↗

PubMed2005

Opportunities for disease state management in prostate cancer.

In this paper, we examine how the management of prostate cancer lends itself to a disease state management (DSM)-based approach, and propose a framework that emphasizes the patient-provider-caregiver triad in managing the long-term implications of the condition. There is often no clearly superior approach to the management of patients with prostate cancer (eg, watchful waiting and hormonal therapy), and each option entails different trade-offs in quality of life. Ideally, the physician and patient discuss the options, issues, and patient preferences for treatment through the shared decision-making process. A family caregiver such as the spouse of the patient is often involved in the treatment decision and in the long-term management of the cancer experience. In order to develop a DSM program supporting both patient and caregiver, educational, psychosocial, and health care system support needs should be tailored to each phase of cancer treatment/management. To embrace the unique aspects of prostate cancer management, the proposed framework emphasizes communication among the patient-caregiver-provider triad, inclusion of family caregivers in the program, cancer phase-specific support, and psychosocial services as a basis for implementation and evaluation of a DSM program in prostate cancer.

Delivery of Health Care↗

PubMed2005

[Effect of polymeric scaffolds on attachment and growth of bone marrow mesenchymal stem cells].

To investigate the effect of three kinds of polymeric scaffolds on attachment, proliferation and differentiation of bone marrow mesenchymal stem cells, the cells were different polymeric scaffolds of PLA-PEG, PLA, PLGA, respectively. The proliferation of cell was evaluated by cell count; the attachment and morphology of BMSCs were observed by SEM; and differentiation was detected by alkaline phosphatase activity, fluorescence, and RT-PCR methods. Results showed that the cells in PLGA group spread better among BMSCs adhered to the three polymeric scaffolds. The activity of ALP was detected after 3 days culture in these three groups. There were no significant differences between PLA-PEG and PLGA groups, but the activity of ALP was higher than PLA group. The gene expressions of osteocalicin and collagen I were also observed in the early culture time. Calcium nodes formation in these polymeric scaffolds were detected. BMSC spreading first, then overlapping growth and secretion of matrix around the bottom and surface of scaffolds were observed through SEM. In summary, PLA-PEG and PLGA are better polymeric scaffolds for the bone tissue engineering, compared with PLA.

Bone Marrow Cells↗

PubMed2004

Characterization of vegetable oils: detailed compositional fingerprints derived from electrospray ionization fourier transform ion cyclotron resonance mass spectrometry.

Adulteration of vegetable oil is of concern for both commercial and health reasons. Compositional based fingerprints can potentially reveal both the oil source and its possible adulteration. Here, electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) resolves and identifies literally thousands of distinct chemical components of commercial canola, olive, and soybean oils, without extraction or other wet chemical separation pretreatment. In negative-ion ESI FT-ICR MS, the acidic components of soybean oil are easily distinguished from those of canola and olive oil based on relative abundances of C(18) fatty acids, whereas olive oil differs from canola and soybean oil based on relative abundances of tocopherols. In positive-ion ESI FT-ICR MS, the three oils are readily distinguished according to the relative abundances of di- and triacylglycerols with various numbers of double bonds in the fatty acid chains. We demonstrate the detection of soybean oil as an adulterant of olive oil, based on relative abundances of members of each of several chemical families. We suggest that the detailed chemical compositions of vegetable oils can be used to characterize them and to detect and identify adulterants.

Cyclotrons↗

PubMed2004

Two- and three-dimensional van krevelen diagrams: a graphical analysis complementary to the kendrick mass plot for sorting elemental compositions of complex organic mixtures based on ultrahigh-resolution broadband fourier transform ion cyclotron resonance mass measurements.

Ultrahigh-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry has resolved and identified the elemental compositions of over 10000 organic constituents of coal and petroleum crude oil. A plot of Kendrick mass defect versus Kendrick nominal mass sorts compounds into homologous series according to compound class (i.e., numbers of N, O, and S heteroatoms), type (number of rings plus double bonds), and degree of alkylation (number of CH(2) groups), to yield unique elemental assignments from ultrahigh-resolution mass measurements in the 200-900 Da range. Interpretation of such a vast compilation requires a simple (preferably graphical) means to differentiate between complex organic mixtures of different origin or processing. In an extension of the recently revived van Krevelen plot, each elemental composition is projected onto two or three axes according to its H/C, O/C, and/or N/C atomic ratios. The H/C ratio separates compounds according to degree of saturation, whereas O/C or N/C ratios separate according to O and N classes. We show that the three-dimensional van Krevelen diagram can completely separate different classes in pyridine-extracted coal or petroleum samples and can also graphically distinguish fossil fuels according to their nature (coal vs petroleum), maturation (coals of different rank), and processing (the same coal at two stages of liquefaction). The van Krevelen diagram thus appears well suited to amplifying and exposing compositional differences within and between complex organic mixtures.

Journal Article↗

PubMed2004

Rapid screening method for Schistosoma japonicum infection using questionnaires in flood area of the People's Republic of China.

A rapid, simple, and effective method using questionnaires is described for screening of high-risk individuals of schistosomiasis japonica after the occurrence of major flooding. A case-control study design was adopted in two randomly selected villages from Dongting Lake area in the People's Republic of China that are endemic for Schistosoma japonicum. Information about contagious water exposure history and several other risk factors were collected retrospectively from 246 individuals, aged 9-60 years. A probability model was developed by logistic regression analysis, which included six variables, namely (i) knowledge of Schistosoma transmission, (ii) education attainment, (iii) annual income before flood year per person, (iv) duration of contagious water exposure due to swimming and paddling, (v) intensity of contagious water exposure due to occupational activities, and (vi) duration of contagious water exposure due to recreational activities. The receiver-operating characteristic (ROC) curve was plotted and the sensitivity and specificity were calculated. The internal consistency of the probability model was good. The area below the ROC curve was 0.90. If the probability cutoff value of diagnosing an infection with S. japonicum was defined as 0.35, both sensitivity and specificity were above 82%, whereas positive and negative predictive values were 70 and 91%, respectively. We conclude that questionnaires are a viable tool for screening of high-risk individuals of S. japonicum infections in lake communities of China after flooding occurred, opening new avenues for schistosomiasis control.

Adolescent↗

PubMed2002

Composition of explosives by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

Commercial explosives are complex mixtures that contain not only the active explosive agent(s) but also a host of other organic and inorganic compounds. The ultrahigh mass resolving power (m/delta m50% >200,000) and mass accuracy (<1 ppm) of electrospray ionization Fourier transform ion cyclotron resonance (ESI FTICR) mass spectrometry allow for definitive identification of various species in TNT, RDX, and HMX. We are thereby able to correct prior misassignments of the elemental compositions of the most abundant negative ions from electrospray of RDX and HMX. Although the (known) active agents of many explosives may be identified by low-resolution MS or MS/MS, it is the other characteristic components (indigenous or artificial additives) whose presence and elemental composition can potentially identify the source of the product. ESI FTICR mass spectrometry of smokeless powder, TNT, and Powermite resolves and identifies numerous nonactive ingredients, many of which are recovered in a postblast residue. In contrast, the residue recovered from an explosion of military C4 yielded several species derived from RDX but virtually none from other ingredients.

Journal Article↗