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Obstructive salivary gland diseases are common conditions that arise following the disruption of the secretary ductal system and usually results in the swelling and pain of the affected gland(s). There has been an increase in the use of sialendoscopy for the treatment and diagnosis of obstructive salivary gland infection. If damage occurs to a duct or papilla following sialendoscopy, a stent may be necessary to prevent restenosis and for maintaining the salivary duct open after complete sialendoscopy. Currently, there are only non-biodegradable salivary duct stents available. The aim of the current study was to establish a methodology for the fabrication of a biodegradable poly-L-lactide (PLLA) salivary duct stent and to examine its function in an animal model. In the current study, PLLA was used to fabricate a salivary duct stent, which was compared with other commercially available non-biodegradable products. The mechanical tests revealed that the tensile strength of the PLLA stent was similar to that of the commercially available non-biodegradable stents. The Young's modulus, which measures the stiffness of a solid material, was significantly higher for the PLLA stent compared with the commercially available non-biodegradable stents. In addition, the current study demonstrated that the PLLA salivary duct stent was easily used with current sialendoscopy techniques, allowing accurate stent placement in an animal model.

Background: In order to improve the clinical treatment level of urinary system injury, it is necessary to build up an animal model of urinary system wound, which is not only analogous to real clinical practice, but also simple and practical. Methods: We have developed the third generation of firearm fragment wound generator based on the first and the second producer. The best explosive charge of the blank cartridge was selected by gradient powder loading experiments. The firearm fragment injuries were made to the bulbous urethra of 10 New Zealand male rabbits. One week preoperatively and 2, 4 and 8 weeks postoperatively, all the animals underwent urethroscopy and urethrography. At 2, 4 and 8 weeks postoperatively, two animals were randomly selected and killed, and the urethra was cut off for pathological examination. Results: The shooting distance of the third generation of firearm fragment wound generator is 2 cm. The best explosive charge of the blank cartridge is 1 g of nitrocotton. All rabbits survived the procedures and stayed alive until they were killed. Injuries were limited to bulbous urethra and distal urethra. Round damaged areas, 1-1.5 cm in length, on the ventral wall were observed. Ureteroscopy results showed that canal diameter gradually shrank by over 50% in 9 rabbits. The rate of success was 90%. Urethrography result noted that a 1-1.3 cm stricture was formed at the bulbous urethra. Histology results of injured stricture urethra showed that fibrous connective tissue hyperplasia and hyaline degeneration caused further stricture in the canal. Conclusions: The third generation of firearm fragment wound generator imitates the bullet firing process and is more accurate and repeatable. The corresponding rabbit model of traumatic complex urethral stricture simulates the real complex clinical conditions. This animal model provides a standardized platform for clinical researches on treating traumatic injuries to the urinary system.

Background Mesenchymal stromal cells (MSCs) are multipotent and have great potential in cell therapy. Previously we reported the differentiation potential of human MSCs into hepatocytes in vitro and that these cells can rescue fulminant hepatic failure. However, the conventional static culture method neither maintains growth factors at an optimal level constantly nor removes cellular waste efficiently. In addition, not only is the duration of differentiating hepatocyte lineage cells from MSCs required to improve, but also the need for a large number of hepatocytes for cell therapy has not to date been addressed fully. The purpose of this study is to design and develop an innovative microfluidic device to overcome these shortcomings. Methods We designed and fabricated a microfluidic device and a culture system for hepatic differentiation of MSCs using our protocol reported previously. The microfluidic device contains a large culture chamber with a stable uniform flow to allow homogeneous distribution and expansion as well as efficient induction of hepatic differentiation for MSCs. Results The device enables real-time observation under light microscopy and exhibits a better differentiation efficiency for MSCs compared with conventional static culture. MSCs grown in the microfluidic device showed a higher level of hepatocyte marker gene expression under hepatic induction. Functional analysis of hepatic differentiation demonstrated significantly higher urea production in the microfluidic device after 21 days of hepatic differentiation. Conclusions The microfluidic device allows the generation of a large number of MSCs and induces hepatic differentiation of MSCs efficiently. The device can be adapted for scale-up production of hepatic cells from MSCs for cellular therapy.

Is supplementary materials and methods: Table S1 presenting the sequence of quantitative PCR primers for MSCs, Figure S1 showing the microfluidic device with larger culture chamber used for the study, Figure S2 showing the processes of proliferation (A) and hepatic differentiation (B) of MSCs in the culture dish and microfluidic device, Figure S3 showing the growth curve of human MSCs cultured in the microfluidic device and culture dish from 0 to 9Â days, Figure S4 showing the comparative expression of surface markers in mouse MSCs cultured in static culture dish and microfluidic device at day 0Â and day 3, and Figure S5 showing the simulation of culture medium diffusion in a circle cultural chamber. The flow field showed an uneven flow profile in a circle cultural chamber. The dimension and parameters of flow field were based on a previous study [20]. (DOCX 979 kb)

Using the improved LP method, the authors seek to salve a class of problems of square strongly nonlinear free oscillations and of strongly nonlinear nonoscillations . Their first-order approximate solutions which has high accuracy are obtained. The method of this paper is different from the known L-P methods.

In this paper, using the integration method, it is sought to solve the problem for the laminar boundary-layer on a flat plate. At first, a trial function of the velocity profile which satisfies the basical boundary conditions is selected. The coefficients in the trial function awaiting decision are decided by using some numerical results of the boundary-layer differential equations. It is similar to the method proposed by Peng Yichuan, but the former is simpler. According to the method proposed by Peng, when the awaiting decision coefficients of the trial function are decided, it is sought to solve a third power algebraic equation. On the other hand, in this paper, there is only need for solving a linear algebraic equation. Moreover, the accuracy of the results of this paper is higher than that of Peng.

In this paper, using the interpolation perturbation method, the author seeks to solve several nonlinear problems. Numerical examples show that the method of this paper has good accuracy.

When there is small quantity term contained in differential equation, we may solve it by using the M. E. Shvez iterative method. If the small quantity term has singularity, or in the certain region where the small quantity term is not small, using this method to solve such differential equation, we may meet difficulties. In this paper, the author improves the M. E. Shvez method. Several examples are given to demonstrate the algorithm.

In this paper, on the basis of Ref. [1], the author studies the boundary value problems of the second-order differential equations, the highest order derivatives of which contain the small parameters. The numerical examples show that the calculating process of this method is quite simple and its accuracy is even higher than that of the multiple scales method.

In reference [1], the wave solutions of nonlinear heat conduction equation are studied. In it, the similar variable ξ is wave variable and it is assumed that the heat conduction coefficient is only the function of the similar variable ξ.

In this paper, the author obtains the more general displacement solutions for the isotropic plane elasticity problems. The general solution obtained in ref. [1] is merely the particular case of this paper. In comparison with ref. [1], the general solutions of this paper contain more arbitrary constants. Thus they may satisfy more boundary conditions.

The present article researches the problems of the lateral instability of cantilever rectangular plates under a concentrated force or a uniformly distributed load respectively. We select the polynomial (2.1) instead of the cosecant function in Ref. [1] as the flexural functions. The minimum critical load obtained here is more exact than the results obtained in Ref.[1]

Using the pressure gradient as the new variable instead of the ordinary longitudinal coordinate x. Liu transformed the ordinary laminar boundary equations into a new form. On this base Liu obtained the frictional stress factor by using the graphical method.

In this paper, we propose some formulas for seeking a part of the particular solutions of the heavy harmonics and Tricomi equations and obtain the precise polynomial solutions of the finite-item number for rectangular strip bending problem when the intensity of the distributed load varies with the fourth, power of longitudinal coordinote.

In ref. l. under the condition that the components of velocity are only the functions of time and polar angle 0. Dvornikov solved eqs. (1.1)–(1.3) of the ideal gas unsteady planar parallel potential flow. It was pointed out in ref.[1] that in general cases, the evident solutions could not be obtained. Only for two especial cases, the evident solutions were obtained. In this paper, the author studies the same problem as that in ref. [1]. In the first section we obtain the evident solution of equations (1.1)–(1.3) under the condition that the sonic velocity is restricted by some complemental conditions. In the second section, we obtain the first-order approximate solutions of the fundamental equation for the case that

Chernyi's series method[1] is not proper for the case that(γ−1)/(γ+1)〈2/(γ+1)×M2sin2Β (γ=cp/cv — adiabatic index number, M — Mach number, Β — shock incidence). In this paper, we only suppose that in the neighbour of the shock, there exists a shock layer in which the density of the gas is very big, but we do not remove the case that (γ−1)/(γ+1)〈2/(γ+1)M2sin2Β.

In [1], under the condition that all the perfectly plastic stress components at a crack tip are functions of ϕ only, making use of equilibrium equations, stress-strain rate relations, compatibility equations and yield condition. Lin derived the general analytical expressions of the perfectly plastic stress field at a mixed-mode crack tip under plane and anti-plane strain. But in [1] there were several restrictions on the proportionality factor γ in the stress-strain rate relations, such as supposing that γ is independent of ϕ and supposing that γ=c or cr−1. In this paper, we abolish these restrictions. The cases in [1], γ=crd (n=0 or-1) are the special cases of this paper.

For the practical metallic material, preceding the fracture, there always exist the domains of plasticity. For the plasticity limited in scope, the linear elastic mechanics is still applicable, but it is neccesary to correct the influence of the domain of plasticity. The traditional method of correction (Irwin’s method) is to introduce the conception of the effective fracture length, namely, owing to the existence of the domain of plasticity, the practical length of the fracture increases. If we take the length of the fracture to be equal to the effective fracture length 2(a + ry), where 2a is the original length of the fracture and 2ry is the added length, we may not regard the existence of the domain of plasticity and still use the linear elastic fracture mechanics to deal with.

In ref. [1], Lin obtained an approximate analytical solution of the ideal potential flow around a circular cylinder between two parallel flat flates.

In this paper, we obtain a third-order approximate solution for the laminar boundary layer between two planes perpendicular to each other. In boundary layer equations, the viscous and the inertial terms have the same quantity step. In this paper, at first, supposing that the inertial terms are bigger than the viscous terms, we solve the boundary layer equations, and then we suppose that the viscous terms are bigger than the inertial terms. At last, we take the mean value as the valid solution of the boundary layer equations. The first- and the second-order approximate solutions obtained in this paper coincide with the results in ref. [1], while the third-order solution obtained in this paper is better than that in ref. [1].

In ref. [1], V. E. Najenov studied the conditions that when the viscosity of the liquid is an exponential function of temperature, the pipe flow, having steady heat transfer, is one dimensional and with nonuniform temperature. For plane canal and circular pipe he still studied the velocity and the temperature fields.

In this paper, the same problem in ref. [1] is studied. The author’s solution approximately satisfies the whole fundamental equations (1.1) and (1.2) and the whole hound values conditions (1.3-1.5). But the Liu’s solution[1] does not satisfy the equation of continuity (1.2).