Biomedical subjects

F Qi

Publications and source records attributed to F Qi.

At least 19 recordsLinked to original sources

PubMed2006

Spin relaxation and ultra-slow Li motion in an aluminosilicate glass ceramic.

The ion dynamics in a lithium aluminosilicate glass ceramic was studied using stimulated-echo 7Li-NMR. For temperatures 300 K<T<450 K the hopping correlation times, tau(C), were determined from the decay of the quadrupolar spin-alignment amplitude. The decay times were thermally activated with an energy barrier of 0.61 eV, in agreement with conductivity measurements. For T<300 K the temperature dependence of the decay times, now corresponding to T1Q, was much weaker. The T1Q times followed the same trend as the independently measured spin-lattice relaxation times, T1, but were a factor of about three shorter than those. The theoretical ratio of T1/T1Q is shown to be 25/8 in the slow-motion regime if quadrupolar spin relaxation prevails. This result explains the present observation and similar ones made for several Li ion conductors. The relaxation of the octupolar spin-alignment order is discussed.

Aluminum↗

PubMed2006

Direct identification of propargyl radical in combustion flames by vacuum ultraviolet photoionization mass spectrometry.

We have developed an effusive laser photodissociation radical source, aiming for the production of vibrationally relaxed radicals. Employing this radical source, we have measured the vacuum ultraviolet (VUV) photoionization efficiency (PIE) spectrum of the propargyl radical (C(3)H(3)) formed by the 193 nm excimer laser photodissociation of propargyl chloride in the energy range of 8.5-9.9 eV using high-resolution (energy bandwidth = 1 meV) multibunch synchrotron radiation. The VUV-PIE spectrum of C(3)H(3) thus obtained is found to exhibit pronounced autoionization features, which are tentatively assigned as members of two vibrational progressions of C(3)H(3) in excited autoionizing Rydberg states. The ionization energy (IE = 8.674 +/- 0.001 eV) of C(3)H(3) determined by a small steplike feature resolved at the photoionization onset of the VUV-PIE spectrum is in excellent agreement with the IE value reported in a previous pulsed field ionization-photoelectron study. We have also calculated the Franck-Condon factors (FCFs) for the photoionization transitions C(3)H(3) (+)(X;nu(i),i = 1-12)<--C(3)H(3)(X). The comparison between the pattern of FCFs and the autoionization peaks resolved in the VUV-PIE spectrum of C(3)H(3) points to the conclusion that the resonance-enhanced autoionization mechanism is most likely responsible for the observation of pronounced autoionization features. We also present here the VUV-PIE spectra for the mass 39 ions observed in the VUV synchrotron-based photoionization mass spectrometric sampling of several premixed flames. The excellent agreement of the IE value and the pattern of autoionizing features of the VUV-PIE spectra observed in the photodissociation and flames studies has provided an unambiguous identification of the propargyl radical as an important intermediate in the premixed combustion flames. The discrepancy found between the PIE spectra obtained in flames and photodissociation at energies above the IE(C(3)H(3)) suggests that the PIE spectra obtained in flames might have contributions from the photoionization of vibrationally excited C(3)H(3) and/or the dissociative photoionization processes involving larger hydrocarbon species formed in flames.

Journal Article↗

PubMed2005

The Oral Fluid MEMS/NEMS Chip (OFMNC): diagnostic and translational applications.

The ability to monitor health status, disease onset and progression, and treatment outcome through non-invasive means is a most desirable goal in health-care promotion and delivery. There are three prerequisites for this goal to be realized: specific biomarkers associated with a health or disease state, a non-invasive approach to detect and monitor the biomarkers, and the technologies to discriminate between and among the biomarkers. We present a roadmap to achieve these goals using oral fluids as the diagnostic medium to scrutinize the health and/or disease status of individuals. This is an ideal opportunity to bridge state-of-the-art micro-/nano-electromechanical system (MEMS/NEMS) sensors to oral fluid for diagnostic applications. As the "mirror of body", oral fluid is a perfect medium to be explored for health and disease surveillance. The translational applications and opportunities are enormous.

Biomarkers↗

PubMed2004

193-nm photodissociation of acryloyl chloride to probe the unimolecular dissociation of CH2CHCO radicals and CH2CCO.

The work presented here uses photofragment translational spectroscopy to investigate the primary and secondary dissociation channels of acryloyl chloride (CH2==CHCOCl) excited at 193 nm. Three primary channels were observed. Two C-Cl fission channels occur, one producing fragments with high kinetic recoil energies and the other producing fragments with low translational energies. These channels produced nascent CH2CHCO radicals with internal energies ranging from 23 to 66 kcal/mol for the high-translational-energy channel and from 50 to 68 kcal/mol for the low-translational-energy channel. We found that all nascent CH2CHCO radicals were unstable to CH2CH + CO formation, in agreement with the G3//B3LYP barrier height of 22.4 kcal/mol to within experimental and computational uncertainties. The third primary channel is HCl elimination. All of the nascent CH2CCO coproducts were found to have enough internal energy to dissociate, producing CH2C: + CO, in qualitative agreement with the G3//B3LYP barrier of 39.5 kcal/mol. We derive from the experimental results an upper limit of 23 +/- 3 kcal/mol for the zero-point-corrected barrier to the unimolecular dissociation of the CH2CHCO radical to form CH2CH + CO.

Journal Article↗

PubMed2004

Objective facial paralysis grading based on Pface and eigenflow.

To provide physicians with an objective and quantitative measurement of single-sided facial paralysis, the paper presents a computer-based approach that is different from the nine existing, subjective and hand-performed international scales, such as House-Brackman. For voluntary expressions of a patient, this approach used Pface, which stems from Dface, to measure the asymmetry between two sides of the face and used eigenflow to measure the expression variations between the patient and normal subjects. The results from Pface and eigenflow were then combined by the support vector machine produce to Pdegree. A study of 25 subjects revealed that Pdegree could differentiate paralysis states (Pdegree > or = 0) and normal states (Pdegree < 0), with the ability to grade facial paralysis automatically. Moreover, the Pface of specific facial areas can be used in the supervision of the rehabilitation process.

Adolescent↗

PubMed2004

Simple modeling of dipolar coupled 7Li spins and stimulated-echo spectroscopy of single-crystalline beta-eucryptite.

Stimulated-echo spectroscopy has recently been applied to study the ultra-slow dynamics of nuclear spin-3/2 probes such as 7Li and 9Be in solids. Apart from the dominant first-order quadrupolar interaction in the present article also the impact of the homonuclear dipolar interactions is considered in a simple way: the time evolution of a dipole coupled pair of spins with I = 3/2 is calculated in an approximation, which takes into account that the satellite transitions usually do not overlap. Explicit analytical expressions describing various aspects of a coupled quadrupolar pair subjected to a Jeener-Broekaert pulse sequence are derived. Extensions to larger spin systems are also briefly discussed. These results are compared with experimental data on a single-crystalline Li ion conductor.

Journal Article↗

PubMed2004

Quantitative analyses of Streptococcus mutans biofilms with quartz crystal microbalance, microjet impingement and confocal microscopy.

Microbial biofilm formation can be influenced by many physiological and genetic factors. The conventional microtiter plate assay provides useful but limited information about biofilm formation. With the fast expansion of the biofilm research field, there are urgent needs for more informative techniques to quantify the major parameters of a biofilm, such as adhesive strength and total biomass. It would be even more ideal if these measurements could be conducted in a real-time, non-invasive manner. In this study, we used quartz crystal microbalance (QCM) and microjet impingement (MJI) to measure total biomass and adhesive strength, respectively, of S. mutans biofilms formed under different sucrose concentrations. In conjunction with confocal laser scanning microscopy (CLSM) and the COMSTAT software, we show that sucrose concentration affects the biofilm strength, total biomass, and architecture in both qualitative and quantitative manners. Our data correlate well with previous observations about the effect of sucrose on the adherence of S. mutans to the tooth surface, and demonstrate that QCM is a useful tool for studying the kinetics of biofilm formation in real time and that MJI is a sensitive, easy-to-use device to measure the adhesive strength of a biofilm.

Journal Article↗

PubMed2004

Transcriptional analysis of mutacin I (mutA) gene expression in planktonic and biofilm cells of Streptococcus mutans using fluorescent protein and glucuronidase reporters.

Streptococcus mutans is implicated as the primary pathogen involved in the development of dental caries. The production of specific bacteriocins (called mutacins) by S. mutans is one of the major virulence factors which facilitate the dominance of the bacterium within dental plaque. While much has been revealed about the biochemical structures of mutacins, little is known about the expression and regulation of mutacin genes, largely due to the lack of proper methods to monitor mutacin gene expression, especially under biofilm conditions. In this study, a set of reporter systems with the green fluorescent protein (gfp), the monomeric red fluorescent protein (mrfp1), and the glucuronidase (gusA) are introduced to S. mutans to study the transcriptional activities of the mutacin I gene (mutA). Although the mutA-reporter fusions are in single copy on the chromosome, these reporter systems display strong signals that allow us to effectively monitor mutA gene expression in S. mutans. Using these reporter systems, we show that mutA is expressed in both planktonic and biofilm cells, even though mutacin activities are normally detected only in biofilm cells. Furthermore, we confirm that mutR, the gene upstream of the mutacin operon, is required for mutacin I gene expression. The success of this study validates the feasibility of using these reporter systems to study gene expression and regulation in S. mutans.

Artificial Gene Fusion↗

PubMed2002

Stimulated-echo NMR spectroscopy of 9Be and 7Li in solids: method and application to ion conductors.

The generation of pure quadrupolar stimulated-echo spectra is successfully demonstrated for the spin-3/2 probe 9Be in a single crystal of triglycine fluoberyllate. This solid exhibits a paraelectric-to-ferroelectric phase transition. From experiments carried out for various mixing times no indications for a slow soft mode could be detected in this crystal. Then ion conducting lithium metal phosphates were studied using 7Li, another spin-3/2 probe which allows for a non-selective excitation of the entire NMR spectrum. In the indium and the scandium phosphates ultra-slow Li hopping processes could be detected directly via the stimulated-echo technique in a time range of up to four orders of magnitude. Due to the relatively large gyromagnetic ratio and thus strong dipolar interactions of 7Li no pure quadrupolar echoes could be generated. However, from a variation of the evolution times the quadrupolar effects could be separated from the dipolar ones. Finally, the differences in the ion hopping times of lithium indium phosphate and of lithium scandium phosphate are briefly discussed.

Beryllium↗

PubMed2001

Effects of noise on the off rate of Ca(2+) binding proteins in a coupled biochemical cell system.

We investigated numerically the kinetic properties of calcium binding proteins by using a three-calcium store model and discussed the response of a two-way coupled biochemical cell system, whose subsystems were coupled via diffusion-like cytosolic calcium transfer through gap junctions, to the external stimulation. When we used noise to modulate the off rate of the Ca(2+) binding proteins in simulation, an SR-like phenomenon of synchronous oscillations is observed. In addition, the interaction involving noise, coupling and the dynamics of Ca(2+) binding proteins is discussed.

Animals↗

PubMed2001

[Neurological manifestations of isolated sphenoiditis].

OBJECTIVE: To review the neurological manifestations of isolated sphenoiditis. METHODS: The symptoms, signs, imaging data, diagnoses and outcomes of 14 cases with sphenoiditis hospitalized in Peking Union Hospital June 1995-January 2001 were analyzed retrospectively. RESULTS: The chief complaints of this group included headache (12 cases), visual loss and/or diplopia (7 cases), blood in nasal discharge (3 cases), purulent nasal discharge (2 cases), exophthalmoptosis (1 case), fixation of eyeball (1 case), and pharyngodynia (1 case). Six patients presented deficits of the second and/or third, fourth, and sixth cranial nerves; one patient had hemiplegia and aphasia; no more presentation of nervous system was found in all patients. Only five patients showed signs of posterior sinusitis in rhinologic examination. CT and/or MRI revealed isolated sphenoiditis (11 cases) and sphenoiditis with posterior ethmoiditis (3 cases). The complications of this group were intracranial infection involving frontal, temporal, and parietal lobes and brainstem (1 case), aneurysm of cavernous carotid artery (1 case), nasal cerebrospinal fluid leakage (1 case), optic neuritis (5 eyes), abducent paralysis (2 cases), orbital cellulitis (1 case) and orbital apex syndrome (1 case). All of the patients underwent endoscopic sphenoid surgery. 13 patients were free of headache after surgery. One patient died because of hernia of brain. CONCLUSION: Headache can be the first or unique symptom of isolated sphenoiditis. Isolated sphenoiditis should be considered in diagnosis and differential diagnosis of headache. CT and MRI are the best tools in diagnosis of isolated sphenoiditis.

Adolescent↗

PubMed2001

Interrelations of vasoconstrictor sympathetic outflow to skin core temperature during unilateral sole heating in humans.

The purpose of the present study was to clarify how skin sympathetic nerve activity (SSNA) influences the core temperature during local heating of the unilateral sole of the foot for 60 min. We recorded SSNA microneurographically from the tibial or peroneal nerve simultaneously with skin blood flow, sweat rate at heated and non-heated sites, with tympanic temperature (Tty) as the core temperature. Sole heating began to suppress vasoconstrictive SSNA (vasoconstrictor) after 3.4 +/- 1.1 min, decrease Tty after 7.4 +/- 2.0 min, activate vasoconstrictor after 33.4 +/- 2.2 min, and increase Tty after 45.5 +/- 2.7 min. Regarding the interaction between vasoconstrictor and Tty during sole heating, we found the following: (1) the capability to suppress vasoconstrictors (decrease rate) showed positive correlations with the time delay from vasoconstrictor suppression to the Tty decrease (r = 0.752, p < 0.05), and with the Tty decrease rate (r = 0.795, p < 0.05), (2) the Tty decrease rate was inversely related to the capability to activate vasoconstrictors (increase rate) (r= -0.836, p < 0.05), and (3) the capability to activate vasoconstrictors was inversely related to the time delay from vasoconstrictor activation to the Tty increase (r = -0.856, p < 0.05) and showed a positive correlation with the Tty increase rate (r = 0.819, p < 0.05). These significant correlations indicate that the capability to control vasoconstrictors to the skin is one of the determinant factors maintaining core temperature in human thermoregulatory function. In conclusion, human thermoregulatory function is largely dependent on the suppression and activation capability of vasoconstrictors.

Adult↗

PubMed2001

Stochastic resonance induced by fluctuation in liquid membrane oscillator without input signals.

We investigated numerically the dynamic behavior of the oil/water liquid membrane, which is a promising model for excitable bio-membrane. When we use noise to modulate the parameters in simulation, noise-induced coherent oscillation is observed. With the increment of the noise intensity, the coherence of noise-induced oscillation can go through a maximum, which indicating the occurrence of stochastic resonance (SR) without input signals. We compared the SR effects under the condition that noise is added to different control parameters. When noise was added to both of the parameters, a complicated SR-like phenomemon was observed. The interaction of coherent SRs induced by two independent noises is discussed. The possibly constructive role of noise in some sensory cells is discussed also.

Computer Simulation↗

PubMed2001

Skin sympathetic outflow in Buerger's disease.

To clarify if sympathetic outflow is altered in Buerger's disease (thromboangitis obliterans, TAO), we measured skin sympathetic nerve activity (SSNA) in TAO patients, and observed the sweating and vasoconstrictive responses during resting and with activating maneuvers. Multiunit postganglionic sympathetic activity was recorded in a skin fascicle of the tibial nerve innervating the skin of the sole (glabrous skin) and peroneal nerve innervating the skin of the dorsum pedis (hairy skin) from five TAO patients and five healthy subjects simultaneously with skin blood flow and sweat expulsion. TAO patients showed significantly less vasoconstrictor SSNA than healthy subjects (17.0+/-1.9 vs. 31.5+/-5.8 bursts/min, P<0.001). Moreover, we found no relationship between vasoconstrictor SSNA and skin blood flow in some patients, while they were well correlated in healthy subjects. There was no evidence for increased sympathetic activity in TAO patients, and no hypersensitive relationship was found between SSNA and skin blood flow. These observations suggested that these TAO patients exhibiting no relationship between skin blood flow reduction and vasoconstrictor activity might not respond to sympathectomy, which is generally expected to result in an increase in skin blood flow. The absence of increased sympathetic nerve activity provides further indirect evidence of a local vascular abnormality in TAO.

Adult↗

PubMed2001

The ultraviolet photochemistry of phenylacetylene and the enthalpy of formation of 1,3,5-hexatriyne.

The ultraviolet photochemistry of phenylacetylene was studied in a molecular beam at 193 nm. The only primary photofragments observed were HCCH (acetylene) and C(6)H(4). Some of the C(6)H(4) molecules were found to decompose to 1,3,5-hexatriyne and molecular hydrogen. An enthalpy of formation of DeltaH(f) < or = 160 +/- 4 kcal mol(-1) was determined for 1,3,5-hexatriyne from the energetic threshold for this process. This experimentally determined value agrees well with our ab initio calculations performed at the G2 level of theory. Angular distribution measurements for the HCCH + C(6)H(4) channel yielded an isotropic distribution and were attributed to a long-lived intermediate and ground-state dissociation. An exhaustive search yielded no evidence for the phenyl + ethynyl or the atomic hydrogen elimination channels even though these were observed in the pyrolytic studies of phenylacetylene [Hofmann, J.; Zimmermann, G.; Guthier, K.; Hebgen, P.; Homann, K. H. Liebigs Ann. 1995, 631, 1995. Guthier, K.; Hebgen, P.; Hofmann, K. H.; Zimmermann, G. Liebigs Ann. 1995, 637, 1995].

Journal Article↗

PubMed2001

Photodissociation of ethylene sulfide at 193 nm: a photofragment translational spectroscopy study with VUV synchrotron radiation and ab initio calculations.

Photodissociation of ethylene sulfide at 193 nm has been studied using photofragment translational spectroscopy and ab initio theoretical calculations. Tunable synchrotron radiation was used as a universal but selective probe of the reaction products to reveal new aspects of the photodissociation dynamics. The channel giving S + C2H4 was found to be dominated by production of ground-state sulfur atoms (S(3P):S(1D) = 1.44:1), mostly through a spin-forbidden process. The results also suggest the presence of a channel giving S(3P) in conjunction with triplet ethylene C2H4 (3B(1u)) and allow insight into the energy of the latter species near its equilibrium geometry, in which the two methylene groups occupy perpendicular planes. In addition, a channel leading to the production of H2S with C2H2 also has been observed. Our experimental results are supported and elaborated by theoretical calculations.

Journal Article↗

PubMed2001

Complete nucleotide sequence and characterization of pUA140, a cryptic plasmid from Streptococcus mutans.

Approximately 5% of strains of Streptococcus mutans contain plasmid DNA. Strain UA140 harbors a 5.6-kb cryptic plasmid, pUA140, with an overall G+C content of 32.7%. Five open reading frames (ORF), encoding peptides of larger than 100 amino acid residues, were initially designated as ORF1 to ORF5. These five ORFs were located on the same strand of pUA140. ORF1 (258 amino acids) resembled a replication protein, Rep. Upstream of the putative Rep gene, a double-stranded origin for plasmid replication that showed strong similarity to those of a number of plasmids in the pT181 family was identified. Further upstream was a region constituting the single-stranded origin of replication. A single-stranded DNA intermediate was detected during plasmid replication. Taken together, these results suggest that pUA140 replicated by the rolling circle replication mechanism but exhibited several characteristics that differ from those of other members of the pT181 plasmid family.

Amino Acid Motifs↗

PubMed2001

Earth's orbital chirality and driving force of biomolecular evolution.

In our recent studies, it has been suggested that both symmetry breaking (violation) and biological rhythms could be caused by the natural rhythmic right-handed helical force field produced by the Earth's orbital chirality (EOC) (1--3). In this essay, according to the further theoretical and experimental studies, it was suggested that the natural EOC force field could serve as the diving force of biomolecular evolution via the chiral interactions. In addition, the following suggestions also were pointed out: (1) The EOC force field could cause the origin of non-coding repetitive DNA sequences ('Junk DNA') to increase the genomes stability and complexity; (2) The EOC force field could increase the structural order of biological systems via the biomolecular EOC stabilization energy effects; (3) The biological information could be spontaneously produced by the chiral interactions of the protogenes with the EOC force field.

Earth, Planet↗