Biomedical subjects

Xuewu Liu

Publications and source records attributed to Xuewu Liu.

4 recordsLinked to original sources

PubMed2006

Spectrophotometric measurements of pH in-situ: laboratory and field evaluations of instrumental performance.

Automated in-situ instrumentation has been developed for precise and accurate measurements of a variety of analytes in natural waters. In this work we describe the use of 'SEAS' (spectrophotometric elemental analysis system) instrumentation for measurements of solution pH. SEAS-pH incorporates a CCD-based spectrophotometer, an incandescent light source, and dual pumps for mixing natural water samples with a sulfonephthalein indicator. The SEAS-pH optical cell consists of either a liquid core waveguide (LCW, Teflon AF-2400) or a custom-made PEEK cell. Long optical path lengths allow use of indicators at low concentrations, thereby precluding large indicator-induced pH perturbations. Laboratory experiments show that pH measurements obtained using LCW and PEEK optical cells are indistinguishable from measurements obtained using conventional spectrophotometric cells and high-performance spectrophotometers. Deployments in the Equatorial Pacific and the Gulf of Mexico demonstrate that SEAS-pH instruments are capable of obtaining vertical pH profiles with high spatial resolution. SEAS-pH deployments at a fixed river-site (Hillsborough River, FL) demonstrate the capability of SEAS for observations of diel pH cycles with high temporal resolution. The in-situ precision of SEAS-pH is assessed as 0.0014 pH units, and the system's measurement frequency is approximately 0.5 Hz. This work indicates that in-situ instrumentation can be used to provide accurate, precise, and highly resolved observations of carbon-system transformations in the natural environment.

Automation↗

PubMed2006

Clinical and EEG characteristics of benign rolandic epilepsy in Chinese patients.

We retrospectively evaluated the clinical and electroencephalogram (EEG) characteristics of benign rolandic epilepsy (BRE) in Chinese children. Two hundred and seventy-six patients with BRE were enrolled in this study. All patients had their first seizure between the ages of 3 and 12 years. 39.5% (109 cases) of patients ceased to have further BRE seizures by the age of 6 years, 93.1% (257 cases) recovered by the age of 12 years and 96.7% (267 cases) recovered by the age of 18 years. Two hundred and twenty-seven patients suffered only simple partial seizures, whereas 49 patients suffered generalized seizures from onset of BRE. The EEG scans of 239 patients showed repetitive diphasic spikes or sharp waves with high amplitude, which were most dominant in the central or centrotemporal areas. The spikes were confined to one hemisphere in 180 patients and occurred bilaterally in 59 patients. Ninety-eight patients were treated with antiepileptic drugs (AEDs): carbamazepine (CBZ) or valproate (VPA). The study showed that, in Chinese children, BRE is remarkably characteristic in its clinical and EEG presentation. Although BRE is usually benign in terms of ease of control with AEDs and spontaneous seizure remission, for those patients with a high frequency of seizures, AEDs should be prescribed positively.

Action Potentials↗

PubMed2006

Nanoporous surfaces as harvesting agents for mass spectrometric analysis of peptides in human plasma.

Silica-based nanoporous surfaces have been developed in order to capture low molecular weight peptides from human plasma. Harvested peptides were subjected to mass spectrometric analysis by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) as a means of detecting and assessing the bound molecules. Peptide profiles consisting of about 70 peaks in the range 800-10,000 m/z were generated. The method could allow detection of small peptides at ng/mL concentration levels, either in standard solutions or in plasma. The same molecular cutoff effect was observed for mixtures of standard proteins and peptides incubated with silicon-based nanoporous surfaces.

Blood Proteins↗

PubMed2006

Controlled-release microchips.

Efficient drug delivery remains an important challenge in medicine: continuous release of therapeutic agents over extended time periods in accordance with a predetermined temporal profile; local delivery at a constant rate to the tumour microenvironment to overcome much of the systemic toxicity and to improve antitumour efficacy; improved ease of administration, and increasing patient compliance required are some of the unmet needs of the present drug delivery technology. Microfabrication technology has enabled the development of novel controlled-release microchips with capabilities not present in the current treatment modalities. In this review, the current status and future prospects of different types of controlled-release microchips are summarised and analysed with reference to microneedle-based microchips, as well as providing an in-depth focus on microreservoir-based and nanoporous microchips.

Animals↗