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Biomedical subjects

F Liu

Publications and source records attributed to F Liu.

At least 55 records · Page 3Linked to original sources
PubMed2005

Transient elastohydrodynamic lubrication analysis of metal-on-metal hip implant under simulated walking conditions.

The transient elastohydrodynamic lubrication (EHL) analysis was performed in this study for a typical metal-on-metal bearing employing a polyethylene backing underneath a metallic cup inlay under dynamic operating conditions of load and speed representative of normal walking. A ball-in-socket configuration was adopted to represent the articulation between the femoral head and the acetabular cup. The governing Reynolds and elasticity equations were solved simultaneously by using both finite difference and finite element methods. The predicted transient film thickness from the present study was compared with the estimation based on the quasi-static analysis. It was found that the polyethylene backing employed in the typical metal-on-metal hip bearing, combined with dynamic squeeze-film action, significantly improved the transient lubricant film thickness under cyclic walking and consequently a fluid film lubrication regime was possible for smooth bearing surfaces with an average roughness less than 0.005 microm.

Biocompatible Materials↗
PubMed2005

The role of nonsurface-active species at interfacial molecular recognition by melamine-type monolayers.

The main characteristics of Langmuir monolayers are radically changed by molecular recognition of hydrogen bond nonsurface-active species. The change in the thermodynamic, phase, and structural features by molecular recognition of dissolved uracil or barbituric acid by 2,4-di(n-undecylamino)-6-amino-1,3,5-triazine (2C11H23-melamine) monolayers is characterized by combination of surface pressure studies with Brewster angle microscopy (BAM) imaging and Grazing incidence X-ray diffraction (GIXD) measurements. Phase behavior of the 2C11H23-melamine monolayer and morphology of the condensed phase domains are changed drastically, but in a specific way, by molecular recognition of uracil or barbituric acid. The main characteristics of the interfacial system can be essentially affected by the kinetics of the recognition process. Pure 2C11H23-melamine monolayers show only small compact, but nontextured domains. The monolayers of 2C11H23-melamine-uracil assemblies develop well-shaped circular condensed-phase domains having an inner texture with alkyl chains essentially oriented parallel to the periphery and having a striking tendency to two-dimensional (2D) Ostwald ripening. The 2C11H23-melamine-barbituric acid monolayers form large homogeneous areas of condensed phase that transfer at smaller areas per molecule to a homogeneous condensed monolayer. BAM imaging of corresponding assemblies with ((CH3(CH2)11O(CH2)3)2-melamine having modified alkyl chains demonstrates the specific effect of the monolayer component. GIXD results reveal that molecular recognition of pyrimidine derivatives gives rise only to quantitative changes in the two-dimensional lattice structure. The striking differences in the main characteristics between the supramolecular species are related to their different chemical structures. Quantum chemical calculations using the semiempirical PM3 method provide information about the different nature of the hydrogen-bonding-based supramolecular structures.

Journal Article↗
PubMed2005

Measurement of absolute hadronic branching fractions of D mesons and e+e- -->DD cross sections at Ec.m.=3773 MeV.

Using 55.8 pb(-1) of e+e- collisions recorded at the psi(3770) resonance with the CLEO-c detector at CESR, we determine absolute hadronic branching fractions of charged and neutral D mesons using a double tag technique. Among measurements for three D0 and six D+ modes, we obtain reference branching fractions B(D0-->K-pi+)=(3.91+/-0.08+/-0.09)% and B(D+-->K-pi+pi+)=(9.5+/-0.2+/-0.3)%, where the uncertainties are statistical and systematic, respectively. Final state radiation is included in these branching fractions by allowing for additional, unobserved, photons in the final state. Using a determination of the integrated luminosity, we also extract the cross sections sigma(e+e- -->D0D0)=(3.60+/-0.07(+0.07)(-0.05)) nb and sigma(e+e- -->D+D-)=(2.79+/-0.07(+0.10)(-0.04)) nb.

Journal Article↗
PubMed2005

Identification of novel cAMP responsive element modulator (CREM) isoforms expressed by osteoblasts.

CREM, the cyclic adenosine monophosphate (cAMP) responsive element modulator, belongs to a multigene family of cAMP-responsive transcription factors. CREM encodes a variety of different isoforms by utilizing four promoters and a complex pattern of alternative messenger ribonucleic acid (mRNA) splicing. We showed previously that parathyroid hormone induces the CREM P2 promoter products known as ICER (inducible cAMP early repressor) in osteoblasts. Herein we report that osteoblasts also express at least 15 CREM transcripts initiated from the P1 promoter, including 7 novel transcripts that result from alternative splicing. It is of interest that we found that CREM-X contains both exon theta1, previously identified only in P3 promoter products, and a new exon termed L, which is located upstream of exon theta1.

3T3 Cells↗
PubMed2005

Molecular recognition kinetics of nonsurface active pyrimidine derivatives dissolved in the aqueous subphase by an amphiphilic melamine type monolayer: A theoretical approach.

Experimental studies show a drastic change of the characteristic features (Pi-A isotherms, morphology of the condensed phase domains) of the 2C11H23-melamine monolayers by molecular recognition of the pyrimidine derivatives uracil and thymine, largely affected by the reaction kinetics of the recognition process. A new approximate additive theoretical model is introduced for describing the molecular recognition kinetics. The theoretical approach is based on two assumptions: (i) first-order reaction kinetics for the molecular recognition of the nonsurface active pyrimidine derivatives dissolved in the aqueous subphase by the melamine type monolayer and (ii) applicability of the Pi-A isotherm equations derived previously for the description of melamine type monolayers in the fluid (gaseous, LE) state and the phase transition region to the condensed state. The rate constants for the molecular recognition reaction between the melamine type monolayer and the dissolved thymine and uracil are estimated, which are roughly proportional to the bulk concentrations of the pyrimidine derivatives and depend only slightly on the temperature. The theoretical estimates agree satisfactorily with the experimental results obtained under various conditions (Pi = const and dA/dt = const). This fact supports the validity of the first model proposed for the interfacial molecular recognition kinetics with nonsurface active substrates dissolved in the aqueous subphase by complementary hydrogen bonding.

Kinetics↗
PubMed2005

Small threat and contraband detection with TNA-based systems.

The detection of small threats, such as explosives, drugs, and chemical weapons, concealed or encased in surrounding material, is a major concern in areas from security checkpoints to UneXploded Ordnance (UXO) clearance. Techniques such as X-ray and trace detection are often ineffectual in these applications. Thermal neutron analysis (TNA) provides an effective method for detecting concealed threats. This paper shows the effectiveness of Ancore's SPEDS, based on TNA, in detecting concealed liquid threats and differentiating live from inert mortar shells.

Chemical Warfare↗
PubMed2005

Thermodynamic and structural characterization of amphiphilic melamine-type monolayers.

Monolayers of amphiphilic melamine derivatives are good candidates for the formation of supramolecular structures by hydrogen-bonding of nonsurface active species dissolved in the aqueous subphase by molecular recognition. In the present work, the thermodynamic and structural properties of the Langmuir monolayers of a homologous series of a selected amphiphilic melamine-type are characterized. Good candidates for such studies are the decyl, undecyl, and dodecyl homologues of the 2,4-di(n-alkylamino)-6-amino-1,3,5-triazine (2CnH(2n+1)-melamine) monolayers because of their two-phase coexistence region in the accessible temperature range. The characterization of the structural and phase behavior is performed by a combination of surface pressure studies with Brewster angle microscopy (BAM) imaging and Grazing incidence X-ray diffraction (GIXD) measurements. A comprehensive thermodynamic analysis provides good agreement between the experimental surface pressure - area (Pi-A) isotherms and the theoretical curves that were calculated on the basis of equations of state for a large region of monolayer stages developed by us in J. Phys. Chem. 1999, 103, 145. Theoretical curves calculated by application of equations of state only for the fluid monolayer state proposed recently by Rusanov (J. Chem Phys. 2004, 120, 10736) are in good agreement with the experiments in a limited temperature range. A rigorous equation is derived and applied to the experimental results for the calculation of the enthalpy of two-dimensional phase transition. The combination of BAM and GIXD illustrates that the microscopic long range ordering of the condensed monolayer phases is related to the lattice structure of the condensed monolayer.

Thermodynamics↗
PubMed2005

Interfacial molecular recognition of dissolved thymine by medium chain dialkyl melamine-type monolayers.

Systems consisting of an amphiphilic melamine-type monolayer and a pyrimidine derivative dissolved in the aqueous subphase are good candidates for the formation of interfacial supramolecular assemblies by molecular recognition of hydrogen-bond nonsurface-active species. In the present work, the change in the thermodynamic, phase, and structural properties as a result of molecular recognition of dissolved thymine by 2,4-di(n-undecylamino)-6-amino-1,3,5-triazine (2 C11H23-melamine) monolayers is studied. The combination of surface pressure studies with Brewster angle microscopy (BAM) imaging and grazing incidence X-ray diffraction (GIXD) measurements is optimal for the characterization of the change in structure and phase behavior at the interfacial recognition process. The molecular recognition of the nonsurface-active thymine dissolved in aqueous subphase changes drastically the characteristic features (surface pressure-area isotherms, morphology of the condensed phase domains) of the 2 C11H23-melamine monolayer. It is demonstrated that the kinetics of the recognition process affect largely the main characteristics (phase behavior, morphology of the condensed phase domains) of the interfacial system. The monolayers of 2 C11H23-melamine-thymine assemblies form dumbbell-shaped condensed phase domains not yet observed in other Langmuir monolayers so far. GIXD results show that the molecular recognition of thymine causes only quantitative changes in the two-dimensional lattice structure. Complementary hydrogen bonding of two thymine molecules by one 2 C11H23-melamine molecule is concluded from the chemical structure of both components. Additional information about the nature of the hydrogen bonding on the basis of supramolecular assemblies is obtained by using the quantum chemical PM3 approximation. Energy and lengths of the hydrogen bonds of the optimized thymine-2 C11H23-melamine-thymine structure are calculated.

Chemistry, Physical↗
PubMed2005

Improved measurement of the form factors in the decay lambda+c-->lambda + nue.

Using the CLEO detector at the Cornell Electron Storage Ring, we have studied the distribution of kinematic variables in the decay lambda(+)(c)lambda--> e(+)nu(e). By performing a four-dimensional maximum likelihood fit, we determine the form factor ratio, R= f(2)/f(1) = -0.31 +/- 0.05(stat) +/- 0.04(syst), the pole mass, M(pole) = [2.21 +/- 0.08(stat) +/- 0.14(syst)] GeV/c(2), and the decay asymmetry parameter of the lambda(+)(c), alpha (lambda(c)) = -0.86 +/-0.03(stat) +/- 0.02(syst), for q(2) = 0.67 (GeV/c(2))(2). We compare the angular distributions of the lambda(+)(c) and lambda(-)(c) and find no evidence for CP violation: A(lambda(c)) = (alpha(lambda(c)) + alpha (lambda(c)))/(alpha(lambda(c))-alpha(lambda(c))) = 0.00 +/- 0.03(stat) +/- 0.01(syst) +/- 0.02, where the third error is from the uncertainty in the world average of the CP-violating parameter, A(lambda), for ppi(-).

Journal Article↗
PubMed2005

Antioxidant activity of gallic acid from rose flowers in senescence accelerated mice.

The activities of the antioxidant enzymes catalase (CAT) and glutathione peroxidase (GPx) in the blood and liver of the aging model induced by injection of different doses of D-gal into normal mice, and in senescence accelerated mice (SAM) of different ages, were determined. The results showed that the enzyme activities in the D-gal treated mice did not alter appreciably but the enzyme activities in blood of the SAM declined significantly with the increase in age, especially in the 9-month-old SAM. When gallic acid purified from rose flowers was used to treat the 9-month-old male SAM, it not only reinstated the activities of CAT and GPx but also significantly reduced the amount of malondialdehyde (MDA) in the liver, brain and kidney. The results demonstrated that 9-month-old male SAM represent an appropriate animal model to evaluate the antioxidant activities of natural products.

Aging↗
PubMed2005

Visual perception of male body attractiveness.

Based on 69 scanned Chinese male subjects and 25 Caucasian male subjects, the present study showed that the volume height index (VHI) is the most important visual cue to male body attractiveness of young Chinese viewers among the many body parameters examined in the study. VHI alone can explain ca. 73% of the variance of male body attractiveness ratings. The effect of VHI can be fitted with two half bell-shaped exponential curves with an optimal VHI at 17.6 l m(-2) and 18.0 l m(-2) for female raters and male raters, respectively. In addition to VHI, other body parameters or ratios can have small, but significant effects on male body attractiveness. Body proportions associated with fitness will enhance male body attractiveness. It was also found that there is an optimal waist-to-hip ratio (WHR) at 0.8 and deviations from this optimal WHR reduce male body attractiveness.

Asian People↗
PubMed2005

Search for X(3872) in gammagamma fusion and radiative production at CLEO.

We report on a search for the recently reported X(3872) state using 15.1 fb(-1) of e(+)e(-) data taken in the sqrt[s] = 9.46-11.30 GeV region. Separate searches for the production of the X(3872) in untagged gammagamma fusion and e(+)e(-) annihilation following initial state radiation are made by taking advantage of the unique angular correlation between the leptons from the decay J/psi --> l(+)l(-) in X(3872) decay to pi(+)pi(-)J/psi. No signals are observed in either case, and 90% confidence upper limits are established as (2J+1)Gamma(gammagamma)(X(3872))B(X --> pi(+)pi(-)J/psi) < 12.9 eV and Gamma(ee)(X(3872))B(X- -> pi(+)pi(-)J/psi) < 8.3 eV.

Journal Article↗
PubMed2005

Study of the semileptonic charm decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu.

We investigate the decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu, where l is e or mu, using approximately 7 fb(-1) of data collected with the CLEO III detector. We find R(0) identical with B(D(0)-->pi(-)e(+)nu)/B(D(0)-->K(-)e(+)nu)=0.082+/-0.006+/-0.005. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and R(0) gives |f(pi)(+)(0)|(2)|V(cd)|(2)/|f(K)(+)(0)|(2)|V(cs)|(2)=0.038(+0.006+0.005)(-0.007-0.003).

Journal Article↗
PubMed2005

Measurement of the muonic branching fractions of the narrow upsilon resonances.

The decay branching fractions of the three narrow Upsilon resonances to mu(+)mu(-) have been measured by analyzing about 4.3 fb(-1) e(+)e(-) data collected with the CLEO III detector. The branching fraction B(Upsilon(1S)-->mu(+)mu(-))=(2.49+/-0.02+/-0.07)% is consistent with the current world average, but B(Upsilon(2S)-->mu(+)mu(-))=(2.03+/-0.03+/-0.08)% and B(Upsilon(3S)-->mu(+)mu(-))=(2.39+/-0.07+/-0.10)% are significantly larger than prior results. These new muonic branching fractions imply a narrower total decay width for the Upsilon(2S) and Upsilon(3S) resonances and lower other branching fractions that rely on these decays in their determination.

Journal Article↗
PubMed2005

An aqueous Chlorella extract inhibits IL-5 production by mast cells in vitro and reduces ovalbumin-induced eosinophil infiltration in the airway in mice in vivo.

An aqueous extract of the edible microalga (CP) (1), has recently been tested for its immunomodulatory effects in a human clinical trial. Here, the CP extract was dialyzed and fractionated using Sephadex G 100 chromatography. The effects of a dialyzed aqueous CP extract, fraction 2 , on mast cell mediator release in vitro and ovalbumin-induced allergic airway inflammation in vivo were examined. In vitro, treatment of mouse bone marrow-derived mast cells with 2 for 18 h significantly inhibited antigen (trinitrophenyl-BSA)-induced IL-5 production. In vivo, treatment of mice with 2 during ovalbumin sensitization and stimulation process significantly reduced eosinophil and neutrophil infiltration in the airways. Moreover, fractions obtained by size exclusion chromatography of 2 inhibited IgE-dependent cytokine GM-CSF production from human cord blood-derived mast cells. Taken together, these results suggest that 2 is composed of biopolymers with anti-allergic potential.

Animals↗
PubMed2005

An object-oriented designed finite-difference time-domain simulator for electromagnetic analysis and design in MRI--applications to high field analyses.

This paper presents a finite-difference time-domain (FDTD) simulator for electromagnetic analysis and design applications in MRI. It is intended to be a complete FDTD model of an MRI system including all RF and low-frequency field generating units and electrical models of the patient. The program has been constructed in an object-oriented framework. The design procedure is detailed and the numerical solver has been verified against analytical solutions for simple cases and also applied to various field calculation problems. In particular, the simulator is demonstrated for inverse RF coil design, optimized source profile generation, and parallel imaging in high-frequency situations. The examples show new developments enabled by the simulator and demonstrate that the proposed FDTD framework can be used to analyze large-scale computational electromagnetic problems in modern MRI engineering.

Algorithms↗
PubMed2005

An airport cargo inspection system based on X-ray and thermal neutron analysis (TNA).

A cargo inspection system incorporating a high-resolution X-ray imaging system with a material-specific detection system based on Ancore Corporation's patented thermal neutron analysis (TNA) technology can detect bulk quantities of explosives and drugs concealed in trucks or cargo containers. The TNA process utilises a 252Cf neutron source surrounded by a moderator. The neutron interactions with the inspected object result in strong and unique gamma-ray signals from nitrogen, which is a key ingredient in modern high explosives, and from chlorinated drugs. The TNA computer analyses the gamma-ray signals and automatically determines the presence of explosives or drugs. The radiation source terms and shielding design of the facility are described. For the X-ray generator, the primary beam, leakage radiation, and scattered primary and leakage radiation were considered. For the TNA, the primary neutrons and tunnel scattered neutrons as well as the neutron-capture gamma rays were considered.

Aircraft↗