36 research outputs found
Controlling Chemical Reactions by Short, Intense Mid-Infrared Laser Pulses: Comparison of Linear and Circularly Polarized Light in Simulations of ClCHO<sup>+</sup> Fragmentation
Enhanced
mode selective fragmentation of oriented ClCHO<sup>+</sup> →
Cl + HCO<sup>+</sup>, H + ClCO<sup>+</sup>, HCl<sup>+</sup> + CO with
linear polarized intense mid-IR pulses was demonstrated in our previous
computational study (J.
Phys. Chem. Lett. 2012, 3, 2541). Simulations of angle-dependent strong field
ionization of ClCHO indicate the ionization rate in the molecular
plane is nearly twice as large as perpendicular to the plane, suggesting
a degree of planar alignment can be obtained experimentally for ClCHO<sup>+</sup>, starting from neutral molecules. Classical trajectory
calculations with a 4 cycle 7 μm laser pulse (peak intensity
of 1.26 × 10<sup>14</sup> W/cm<sup>2</sup>) show that circularly
polarized light with the electric field in the plane of the molecule
deposits more energy and yields larger branching ratios for higher
energy fragmentation channels than linearly polarized light with the
same maximum field strength. These results suggest circularly polarized
mid-IR pulses can not only achieve control on reactions but also provide
an experimentally accessible implementation
Biomimetic Microfluidic Device for in Vitro Antihypertensive Drug Evaluation
Microfluidic devices have emerged
as revolutionary, novel platforms
for in vitro drug evaluation. In this work, we developed a facile
method for evaluating antihypertensive drugs using a microfluidic
chip. This microfluidic chip was generated using the elastic material
polyÂ(dimethylsiloxane) (PDMS) and a microchannel structure that simulated
a blood vessel as fabricated on the chip. We then cultured human umbilical
vein endothelial cells (HUVECs) inside the channel. Different pressures
and shear stresses could be applied on the cells. The generated vessel
mimics can be used for evaluating the safety and effects of antihypertensive
drugs. Here, we used hydralazine hydrochloride as a model drug. The
results indicated that hydralazine hydrochloride effectively decreased
the pressure-induced dysfunction of endothelial cells. This work demonstrates
that our microfluidic system provides a convenient and cost-effective
platform for studying cellular responses to drugs under mechanical
pressure
Stretchable and Micropatterned Membrane for Osteogenic Differentation of Stem Cells
Stem cells have emerged as potentially
useful cells for regenerative
medicine applications. To fully harness this potential, it is important
to develop in vitro cell culture platforms with spatially regulated
mechanical, chemical, and biological cues to induce the differentiation
of stem cells. In this study, a cell culture platform was constructed
that used polydopamine (PDA)-coated parafilm. The modified parafilm
supports cell attachment and proliferation. In addition, because of
the superb plasticity and ductility of the parafilm, it can be easily
micropatterned to regulate the spatial arrangements of cells, and
can exert different mechanical tensions. Specifically, we constructed
a PDA-coated parafilm with grooved micropatterns to induce the osteogenic
differentiation of stem cells. Adipose-derived mesenchymal stem cells
that were cultured on the PDA-coated parafilm exhibited significantly
higher osteogenic commitment in response to mechanical and spatial
cues compared to the ones without stretch. Our findings may open new
opportunities for inducing osteogenesis of stem cells in vitro using
the platform that combines mechanical and spatial cues
Fabrication of Uniform Casein/CaCO<sub>3</sub> Vaterite Microspheres and Investigation of Its Formation Mechanism
Uniform
Casein/CaCO<sub>3</sub> microspheres were fabricated with
well tuned properties and the formation mechanism based on the templating
effect of casein micelles was proposed. In bone tissue engineering,
vaterite microspheres were promising because of the biocompatibility
and easy fabrication. Here Casein/CaCO<sub>3</sub> microspheres were
precipitated by mixing CaCl<sub>2</sub> and Na<sub>2</sub>CO<sub>3</sub> solutions under stirring in the presence of casein. All samples
were mainly in vaterite, composed of aggregates of nanosized crystals.
With the increase of casein concentration, the amount of calcite and
microsphere size decreased while the loading content of casein increased,
suggesting that casein induced the formation of vaterite and also
stabilized the crystal phase. The formation mechanism was further
investigated. With the increase of CaCl<sub>2</sub> amount, the size
of the forming microspheres increased while the zeta potential was
stabilized, the polycrystalline nature was shown, and the presence
of Ca inside microspheres was confirmed. Hence, the formation mechanism
based on casein micelles which demonstrated the template effect was
proposed. Casein/CaCO<sub>3</sub> microspheres enhanced the deposition
of hydroxyapatite crystals and sample II-8 was tested as the most
cytocompatible on mesenchymal stem cells. The properties of Casein/CaCO<sub>3</sub> microspheres could be well controlled; for better performance
in bone tissue engineering, formation of composite scaffolds may be
preferred
Microfluidic Generation of Polydopamine Gradients on Hydrophobic Surfaces
Engineered surface-bound molecular
gradients are of great importance
for a range of biological applications. In this paper, we fabricated
a polydopamine gradient on a hydrophobic surface. A microfluidic device
was used to generate a covalently conjugated gradient of polydopamine
(PDA), which changed the wettabilty and the surface energy of the
substrate. The gradient was subsequently used to enable the spatial
deposition of adhesive proteins on the surface. When seeded with human
adipose mesenchymal stem cells, the PDA-graded surface induced a gradient
of cell adhesion and spreading. The PDA gradient developed in this
study is a promising tool for controlling cellular behavior and may
be useful in various biological applications
The Frequency Spectral Properties of Electrode-Skin Contact Impedance on Human Head and Its Frequency-Dependent Effects on Frequency-Difference EIT in Stroke Detection from 10Hz to 1MHz - Fig 6
<p>(a)(b) The contact impedance of all subjects at all electrodes. The dashed lines represent the measurement results of the electrodes at the forehead. (c)(d) The measurement results of electrochemical impedance and conductive gel impedance in the case of conductive gel with the thickness of 0.4 mm.</p
The effects of contact impedance on the boundary voltages because of imbalance between contact impedances.
<p>The effects of contact impedance on the boundary voltages because of imbalance between contact impedances.</p
Measuring circuit of contact impedance.
<p>In this study, an impedance analyzer was used, and the voltage excitation mode (500 mV) was applied.</p
The dielectric parameters of head tissues, hemorrhagic tissue and ischemic tissue.
<p>The dielectric parameters of head tissues, hemorrhagic tissue and ischemic tissue.</p
Reconstructed results of the ischemic stroke and the effects of the contact impedance.
<p><b>The contact impedance imbalance was simulated by varying the resistor in series with Electrode 1</b>.</p