Enhanced effect of dimension of receptor-ligand complex and depletion effect on receptor-mediated endocytosis of nanoparticles

We present an extended analytical model including the depletion effect and the dimension of ligand-receptor complex, aiming to elucidate their influences on endocytosis of spherocylindrical nanoparticles （NPs）. It is found that the dimension of ligand-receptor complex （δ） and the depletion effect interrelatedly govern the optimal conditions of NP endocytosis. The endocytosis phase diagram constructed in the space of NP radius and relative aspect ratio indicates that the endocytosis of NP is enhanced evidently by reducing the optimal radius and the threshold radius of endocytosed NP. Meanwhile, through thermodynamic and kinetic analysis of the diffusion of receptors, the dependence of diffusion length on depletion effect and the dimension of ligand-receptor complex can be identified in great detail. For small aspect ratio, diffusion length decreases with increasing concentration c of small bioparticles in cellular environment. Endocytosis speed corresponding to large radius R and high concentration c of small bioparticles strongly depends on the increasing （2r-δ）. These results may show some highlights into the conscious design of NPs for diagnostic agents and therapeutic drug delivery applications.

Simultaneous Impedance Analysis of Three Parallel Piezoelectric Quartz Crystals for Electrochemical Depletion Layer Effect Study

Simultaneous impedance analysis of three one-face sealed resonating piezoelectric quartz crystals (PQCs) in parallel is proposed through admittance measurements of the three PQCs on one impedance analyzer and then non-linear fitting according to the parallel combination of three Butterworth-Van Dyke circuits. Responses of each PQC obtained from the three-PQC mode agreed well with those measured separately in series sucrose aqueous solutions. This novel method has been used for the study of depletion-layer effect during ferri-/ferrocyanide electrochemical reactions.

Coupling effects of depletion interactions in a three-sphere colloidal system

In a three-sphere system, the middle sphere is acted upon by two opposite depletion forces from the other two spheres. It is found that, in this system, the two depletion forces are coupled with each other and result in a strengthened depletion force. So the difference of the depletion forces of the three-sphere system and its corresponding two two-sphere systems is introduced to describe the coupling effect of the depletion interactions. The numerical results obtained by Monte- Carlo simulations show that this coupling effect is affected by both the concentration of small spheres and the geometrical confinement. Meanwhile, it is also found that the mechanisms of the coupling effect and the effect on the depletion force from the ~eometry factor are the same.

Biologically effective radiation of solar ultraviolet radiation and the depletion of stratospheric ozone

Based on the biological action spectra and total UV-B radiation in the atmosphere,the effective UV-dose for DNA, erythema,and plant at different seasons in the last decade,and their future change in Beijing area were calculated.Computation results indicate that the maxi- mum of biologically effective radiation dose at noontime is in July and the minimum is in January. From 1980 to 1989 biologically effective radiation dose have increased with the average rates of about 0.6,0.7 and 1.1 mW/m￣2 per year for January, April and October,while in July the trend of radiation dose is not ln evidence. For 1% reduction of ozone concentration radiation amplification factor for DNA,erythema and plant are 2.3,2.3 and 1.4 and for 30% reduction of ozone concentration the RAF for DNA,erythema and plant are 4.2,4.0 and 2.1,respectively.

Effect of Certain Toxicants on Gonadotropin-Induced Ovarian Non-Esterified Cholesterol Depletion and Steroidogenic Enzyme Stimulation of the Common Carp Cyprinus carpio in vitro

Isolated ovarian tissues from the common carp, Cyprinus carpio were incubated in vitro to obtain a discrete effect of four common toxicants of industrial origin, namely phenol, sulfide, mercuric chloride and cadmium chloride, on gonadotropin-induced alteration of nonesterified and esterified cholesterol and steroidogenic enzymes, △5-3β-HSD and 17β-HSD activity. Stage II ovarian tissue containing 30-40% mature oocytes were shown to be most responsive to gonadotropins in depleting only nonesterified cholesterol moiety and stimulating the activity of both. Safe doses of above mentioned toxicants when added separately to stage II ovarian tissue with oLH (1 μg/incubation) gonadotropin-induced depletion of nonesterified cholesterol and gonadotropin-induced stimulation of the activity of both enzymes was significantly inhibited. Esterified cholesterol remained almost unaltered. Findings clearly indicate the impairment of gonadotropin induced fish ovarian steroidogenesis by the four toxicants separately.

Low on-resistance high-voltage lateral double-diffused metal oxide semiconductor with a buried improved super-junction layer

A novel low specific on-resistance （Ron,sp） lateral double-diffused metal oxide semiconductor （LDMOS） with a buried improved super-junction （BISJ） layer is proposed. A super-junction layer is buried in the drift region and the P pillar is split into two parts with different doping concentrations. Firstly, the buried super-junction layer causes the multiple-direction assisted depletion effect. The drift region doping concentration of the BISJ LDMOS is therefore much higher than that of the conventional LDMOS. Secondly, the buried super-junction layer provides a bulk low on-resistance path. Both of them reduce Ron,sp greatly. Thirdly, the electric field modulation effect of the new electric field peak introduced by the step doped P pillar improves the breakdown voltage （BV）. The BISJ LDMOS exhibits a BV of 300 V and Ron,sp of 8.08 mΩ·cm2 which increases BV by 35% and reduces Ron,sp by 60% compared with those of a conventional LDMOS with a drift length of 15 μm, respectively.

Ultralow specific on-resistance high voltage trench SOI LDMOS with enhanced RESURF effect

A RESURF-enhanced high voltage SOl LDMOS （ER-LDMOS） with an ultralow specific on-resistance （Ron, sp） is proposed. The device features an oxide trench in the drift region, a P-pillar at the sidewall of the trench, and a buried P-layer （BPL） under the trench. First, the P-pillar adjacent to the P-body not only acts as a vertical junction termination extension （JTE）, but also forms a vertical reduced surface field （RESURF） structure with the N- drift region. Both of them optimize the bulk electric field distributions and increase the doping concentration of the drift region. Second, the BPL together with the N-drift region and the buried oxide layer （BOX） exhibits a triple- RESURF effect, which further improves the bulk field distributions and the doping concentration. Additionally, multiple-directional depletion is induced owing to the P-pillar, the BPL, and two MIS-like structures consisting of the N-drift region combined with the oxide trench and the BOX. As a result, a significantly enhanced-RESURF effect is achieved, leading to a high breakdown voltage （BV） and a low Ron, sp. Moreover, the oxide trench folds the drift region in the vertical direction, resulting in a reduced cell pitch and thus Ron, sp. Simulated results show that the ER-LDMOS improves BV by 67% and reduces Ron, sp by 91% compared with the conventional trench LDMOS at the same cell pitch.

A Simple and Effective Boundary Model in Nonequilibrium Molecular Dynamics Method

Abstract We propose a simple and effective boundary model in a nonequilibrium molecular dynamics （NEMD） simulation to study the out-of-equilibrium dynamics of polymer fluids. The present boundary model can effectively weaken the depletion effect and the slip effect near the boundary, and remove the unwanted heat instantly. The validity of the boundary model is checked by investigating the flow behavior of dilute polymer solution driven by an external force. Reasonable density distributions of both polymer and solvent particles, velocity profiles of the solvent and temperature profiles of the system are obtained. Furthermore, the studied polymer chain shows a cross-streaming migration towards center of the tube, which is consistent with that predicted in previous literatures. These numerical results give powerful evidences for the validity of the present boundary model. Besides, the boundary model can also be used in other flows in addition to the Poiseuille flow.

Super junction LDMOS with enhanced dielectric layer electric field for high breakdown voltage

The lateral super junction （SJ） power devices suffer the substrate-assisted depletion （SAD） effect, which breaks the charge balance of SJ resulting in the low breakdown voltage （BV）. A solution based on enhancing the electric field of the dielectric buried layer is investigated for improving the BV of super junction LDMOSFET （SJ-LDMOS）. High density interface charges enhance the electric field in the buried oxide （BOX） layer to increase the block voltage of BOX, which suppresses the SAD effect to achieve the charge balance of SJ. In order to obtain the linear enhancement of electric field, SO1 SJ-LDMOS with trenched BOX is presented. Because the trenched BOX self-adaptively collects holes according to the variable electric field strength, the approximate linear charge distribution is formed on the surface of the BOX to enhance the electric field according to the need. As a result, the charge balance between N and P pillars of SJ is achieved, which improves the BV of SJ-LDMOS to close that of the idea SJ structure.

Dimensions of receptor-ligand complex and the optimal radius of endocytosed virus-like particle

Recent experiments have pointed out that cellular uptake is strongly dependent on the physical dimensions of endocytosed nanoparticles and tile optimal radius of endocytosed virus-like particle coated by transferrin is around 50 nm. As the same time, the dimensions of receptor-ligand complex have strong effects on the size-dependent exclusion of proteins ill cell environments. Inspired by these experimental results, a continuum elastic model is constructed to resolve the relationship between the dinlensions of receptor-ligand complex and the optimal radius of endocytosed virus-like particle. These results demonstrate that the optimal radius of endocytosed virus-like particle depends on the dimensions of reeeptor-ligand complex and the dimension of receptor-ligand complex reduces the depletion zone.

Optimal aspect ratio of endocytosed spherocylindrical nanoparticle

Recent simulations have demonstrated that bioparticle size and shape modulate the process of endocytosis, and studies have provided more quantitative information that the endocytosis efficiency of spherocylindrical bioparticles is decided by its aspect ratio. At the same time, the dimensions of the receptor-ligand complex have strong effects on the size-dependent exclusion of proteins within the cellular environment. However, these earlier theoretical works including simulations did not consider the effects of ligand-receptor complex dimension on the endocytosis process. Thus, it is necessary to resolve the effects of ligand-receptor complex dimension and determine the optimal aspect ratio of spherocylindrical bioparticles in the process of endocytosis. Accordingly, we proposed a continuum elastic model, of which the results indicate that the aspect ratio depends on the ligand-receptor complex dimension and the radius of the spherocylindrical bioparticle. This model provides a phase diagram of the aspect ratio of endocytosed spherocylindrical bioparticles, the larger aspect ratio of which appears in the phase diagram with increasing ligand density, and highlights the bioparticle design.