Mathematical analysis of oxygen transfer through polydimethylsiloxane membrane between double layers of cell culture channel and gas chamber in microfluidic oxygenator

For successful cell culture in microfluidic devices, precise control of the microenvironment, including gas transfer between the cells and the surrounding medium, is exceptionally important. The work is motivated by a polydimethylsiloxane (PDMS) microfluidic oxygenator chip for mammalian cell culture suggesting that the speed of the oxygen transfer may vary depending on the thickness of a PDMS membrane or the height of a fluid channel. In this paper, a model is presented to describe the oxygen transfer dynamics in the PDMS microfluidic oxygenator chip for mammalian cell culture. Theoretical studies were carried out to evaluate the oxygen profile within the multilayer device, consisting of a gas reservoir, a PDMS membrane, a fluid channel containing growth media, and a cell culture layer. The corresponding semi-analytical solution was derived to evaluate dissolved oxygen concentration within the heterogeneous materials, and was found to be in good agreement with the numerical solution. In addition, a separate analytical solution was obtained to investigate the oxygen pressure drop (OPD) along the cell layer due to oxygen uptake of cells, with experimental validation of the OPD model carried out using human umbilical vein endothelial cells cultured in a PDMS microfluidic oxygenator. Within the theoretical framework, the effects of several microfluidic oxygenator design parameters were studied, including cell type and critical device dimensions.     

Electrospinning hollow and core/sheath nanofibers using hydrodynamic fluid focusing

Hollow poly (vinylpyrrolidone) (PVP) + TiO₂ and polypyrrole (core)/PVP (sheath) nanofibers were successfully electrospun using hydrodynamic fluid focusing. Utilizing a two-dimensional fluid focusing technique previously applied to aqueous solutions, intersecting microchannels cast in (poly)dimethylsiloxane were utilized to dynamically center core fluids in immiscible sheath fluids prior to electrospinning at the channel outlet. Advantages of using microfluidic channel networks for the electrospinning of composite nanofibers include spatiotemporal control over input reagents, ease of fabrication and the ability to focus the core stream into sheath layer without the need of complex co-annular nozzles.     

Choline derived from the phosphatidylcholine specific phospholipase D is not directly available for the CDP choline pathway in phorbol ester-treated C3H10T1/2 Cl 8 fibroblasts

To clarify the mechanism of capsaicin-induced primary neuronal cell death, newborn and adult rats were given a subcutaneous injection of capsaicin (50 mg/kg). Neonatal capsaicin injection induced neuronal apoptosis in the trigeminal ganglion. Apoptotic neurons had peripheral stacks of long parallel endoplasmic reticulum that are characteristic to primary neurons of the B-type, and exhibited nucleoplasmic condensation, nuclear shrinkage and cytoplasmic fragmentation. Light microscopically, apoptotic neurons exhibited a sign of DNA fragmentation as revealed by a nick end labelling method. The proportion of apoptotic cells was quite low during the first 12 h after capsaicin injection (<1%), rapidly increase to 10.44% by 24 h, and decreased to 0.29% by 48 h. Normal and vehicle control levels of apoptosis were <1%. Nerve growth factor (NGF, 0.5 mg/kg) simultaneously administered with capsaicin reduced the incidence of apoptosis by about 35% at 24 h post-injection. Neonatal transection of the infraorbital nerve induced neuronal apoptosis similar to that produced by the neonatal capsaicin in the maxillary division of the trigeminal ganglion. Unlike capsaicin, however, the neurotomy-induced apoptosis was seen in neurons of both the A- and B-types. Neither the capsaicin injection nor the neurotomy induced apoptosis in adult rats, though mitochondrial swelling similar to that seen at 0.5 h after neonatal capsaicin was observed after capsaicin injection in adults. The results indicate that the capsaicin-induced and nerve injury-induced primary neuronal damages in newborn rats share a common final pathway, apoptosis.     

Wool shrinkage control and surface modification by ozone

In treating fine wool top, more ozone is needed to achieve a given level of felting shrinkage control than with coarse wool. Treatment that allows no more than about 20% top shrinkage in three successive washes is usually satisfactory for controlling fabric shrinkage. A detergent rinse after treatment markedly decreases top and fabric shrinkage. Ozonization decreases fiber strength and wet friction against glass but increases fiber-to-fiber adhesion enough to increase yarn strength. Scanning electron microscopy (SEM) of fibers before and after treatment and laundering indicates that ozone makes the fiber surface more plastic (presumably when wet) but more liable to mechanical damage and erosion, which increase with the severity of treatment and with laundering. However, treatments most effective for shrinkage control are not distinguished from less effective treatments by the degree and character of surface changes shown by SEM. Ring dyeing of fiber cross sections shows that effects of ozone are greatest near the surface. X-ray photoelectron spectroscopy (XPS) and amino acid analysis show that cystine is oxidized to cysteic acid and that carbon is also oxidized at the surface. The increased dyeability (rate and uptake) is attributed to increased wettability, changed ionic balance, and crosslink scission, which, with cuticle damage, allow greater swelling and easier penetration. As found earlier with coarse wools, acid milling (leveling) dyestuffs further decrease shrinkage of treated fine wool. The position of wool in the triboelectric series is shifted toward the negative end by ozone treatment, expressing the higher electron work function of the added sulfonic acid groups. This shift is not simply related to shrinkage. Decreased feltability is attributed to softening of the wet cuticle layer and to increased surface charge, but the mechanism needs further study.     

A Novel Nanoprobe for Multimodal Imaging Is Effectively Incorporated into Human Melanoma Metastatic Cell Lines

To facilitate efficient drug delivery to tumor tissue, several nanomaterials have been designed, with combined diagnostic and therapeutic properties. In this work, we carried out fundamental in vitro and in vivo experiments to assess the labeling efficacy of our novel theranostic nanoprobe, consisting of glycogen conjugated with a red fluorescent probe and gadolinium. Microscopy and resazurin viability assays were used to study cell labeling and cell viability in human metastatic melanoma cell lines. Fluorescence lifetime correlation spectroscopy (FLCS) was done to investigate nanoprobe stability. Magnetic resonance imaging (MRI) was performed to study T₁ relaxivity in vitro, and contrast enhancement in a subcutaneous in vivo tumor model. Efficient cell labeling was demonstrated, while cell viability, cell migration, and cell growth was not affected. FLCS showed that the nanoprobe did not degrade in blood plasma. MRI demonstrated that down to 750 cells/μL of labeled cells in agar phantoms could be detected. In vivo MRI showed that contrast enhancement in tumors was comparable between Omniscan contrast agent and the nanoprobe. In conclusion, we demonstrate for the first time that a non-toxic glycogen-based nanoprobe may effectively visualize tumor cells and tissue, and, in future experiments, we will investigate its therapeutic potential by conjugating therapeutic compounds to the nanoprobe.     

利用电场感应器件MC33794测定液体高度

电场成像器件IC（MC33794）：Motorola公司提供行业内惟一可产生及检测低水平电场和功率并支持微控制器(MCU)的集成电路(IC)，所有这些功能均集成在单个芯片中。     

Changes in bone mass and serum markers of bone metabolism after parathyroidectomy

BACKGROUND: Primary hyperparathyroidism (PHPT) is associated with an increased bone turnover. The simultaneous use of biochemical and bone mass measurements before and after parathyroidectomy is sparsely reported. This study was carried out to evaluate changes in bone mass and markers of bone metabolism in postmenopausal women with PHPT after parathyroidectomy. METHODS: Twelve women, mean age of 63 years, were investigated. Measurements of bone mineral density (total body, spine, hip, and forearm bone mineral density) with dual-energy x-ray absorptiometry were performed before operation and at follow-up at a median of 23 months. Concomitantly, changes in serum intact parathyroid hormone, bone-specific alkaline phosphatase (B-ALP), osteocalcin, carboxyterminal propeptide of type I procollagen, and the immunoactive carboxyterminal telopeptide of type I collagen were recorded. RESULTS: At follow-up a significant increase in bone mineral density of the spine (p < 0.05), femoral neck (p < 0.05), Ward's triangle (p < 0.05), and trochanter (p < 0.01) was observed. No significant changes in the forearm were registered. Levels of parathyroid hormone, B-ALP, and osteocalcin were elevated and intercorrelated before operation. The serum levels of these parameters decreased significantly after operation. Serum levels of carboxyterminal propeptide of type I procollagen and the immunoactive carboxyterminal telopeptide of type I collagen did not significantly differ from a reference population, and no major changes were observed at follow-up. CONCLUSIONS: Bone mineral density in the spine and hip is improved after parathyroidectomy in postmenopausal women with primary hyperparathyrodism. Serum levels of B-ALP and osteocalcin are elevated in PHPT and decrease after operation. The clinical usefulness of serum markers of collagen metabolism in investigating bone metabolism in PHPT seems limited.     

All-optical frame synchronisation recovery

All-optical frame synchronisation recovery is demonstrated experimentally. A frame encoded input data signal forces a fibre laser to modelock. The fixed header is copied onto the laser output, whereas in the payload area the clock is recovered. The authors propose to use this frame synchronisation signal in an all-optical demultiplexer that unambiguously identifies each individual channel