Molecular surface tailoring of biomaterials via pulsed RF plasma discharges

A pulsed RF plasma glow discharge is employed to demonstrate molecular level controllability of surface film deposits. Molecular composition of plasma deposited films is shown to vary in a significant manner with the RF duty cycle. Three fluorocarbon monomers are used to illustrate the process. All three exhibit a trend towards increased surface CF₂ content with decreasing pulsed RF duty cycle, including exclusion of oxygen. Significant variations in carbon-fluorine surface functionalities are obtained over a controllable range of film thickness. Film growth rate measurements reveal the occurrence of surface reactions during significant portions of the off portion of the duty cycle. Albumin adsorption on fluorocarbon-treated PET films is unchanged from PET controls for a 100-fold range of bulk concentrations and 60-fold range of adsorption times. However, increased retention of albumin is observed following incubation with protein-denaturing sodium dodecyl sulfate solution, the retention decreasing with increasing bulk concentration of albumin. The increased retention of albumin suggests the treated surfaces may have promise as biocompatible materials.     

The Influence of Pituitary Adenoma Size on Vision and Visual Outcomes after Trans-Sphenoidal Adenectomy: A Report of 78 Cases

Objective

The aims of this study were to investigate the quantitative relationship between pituitary macroadenoma size and degree of visual impairment, and assess visual improvement after surgical resection of the tumor.

Methods

The medical records of patients with pituitary adenoma, who had undergone trans-sphenoidal adenectomy between January 2009 and January 2011, were reviewed. Patients underwent an ocular examination and brain MRI before and after surgery. The visual impairment score (VIS) was derived by combining the scores of best-corrected visual acuity and visual field. The relationship between VIS and tumor size/tumor type/position of the optic chiasm was assessed.

Results

Seventy-eight patients were included (41 male, 37 female). Thirty-two (41%) patients experienced blurred vision or visual field defect as an initial symptom. Receiver operating characteristic curve analysis showed that tumors <2.2 cm tended to cause minimal or no visual impairment. Statistical analysis showed that 1) poor preoperative vision is related to tumor size, displacement of the optic chiasm in the sagittal view on MRI and optic atrophy, and 2) poorer visual prognosis is associated with greater preoperative VIS. In multivariate analysis the only factor significantly related to VIS improvement was increasing pituitary adenoma size, which predicted decreased improvement.

Conclusion

Results from this study show that pituitary adenomas larger than 2 cm cause defects in vision while adenomas 2 cm or smaller do not cause significant visual impairment. Patients with a large macroadenoma or giant adenoma should undergo surgical resection as soon as possible to prevent permanent visual loss.     

Electromagnetic Environmental Effects Testing of Medical Devices Including Those Used for the Treatment of Diabetes

Background

Electromagnetic emissions from technologies that surround us can produce interference with implanted and externally worn medical devices. Electromagnetic environmental effects (E3) testing of medical devices at the Georgia Tech Research Institute (GTRI) began almost four decades ago and continues to incorporate new devices and new sources of electromagnetic emissions as they are developed and become available. The GTRI Medical Device Test Center provides real-world exposure fields to identify interactions and help manufacturers prevent disruptions from the environments in which their devices must function.

Methods

Typically, the medical device is mounted in or on a torso simulator containing a saline solution that simulates the electrical characteristics of the body. The torso simulator and the device under test are then moved through the fields generated by production security and logistical system technologies using a computer-controlled positioning system. These tests are conducted with different orientations of the medical device to the electromagnetic source, simulating the way in which device wearers interact with these systems in representative situations.

Results

Particular E3 test results measured on specific devices in the GTRI Medical Device Test Center are proprietary; however, the results of tests to date with current medical devices used for the treatment of diabetes have been encouraging. These devices have included implantable and externally worn insulin infusion pumps and continuous glucose monitoring systems from different manufacturers.

Conclusion

Since E3 tests of diabetes treatment devices to date in the test center have centered on devices from only a few of the many current manufacturers, further testing is warranted. In addition, increased functionality, which is being added to existing devices, will create new possibilities for interference in the future.     

Short‐term evaluation of electromagnetic field pretreatment of adipose‐derived stem cells to improve bone healing

An electromagnetic field is an effective stimulation tool because it promotes bone defect healing, albeit in an unknown way. Although electromagnetic fields are used for treatment after surgery, many patients prefer cell‐based tissue regeneration procedures that do not require daily treatments. This study addressed the effects of an electromagnetic field on adipose‐derived stem cells (ASCs) to investigate the feasibility of pretreatment to accelerate bone regeneration. After identifying a uniform electromagnetic field inside a solenoid coil, we observed that a 45 Hz electromagnetic field induced osteogenic marker expression via bone morphogenetic protein, transforming growth factor β, and Wnt signalling pathways based on microarray analyses. This electromagnetic field increased osteogenic gene expression, alkaline phosphate activity and nodule formation in vitro within 2 weeks, indicating that this pretreatment may provide osteogenic potential to ASCs on three‐dimensional (3D) ceramic scaffolds. This pretreatment effect of an electromagnetic field resulted in significantly better bone regeneration in a mouse calvarial defect model over 4 weeks compared to that in the untreated group. This short‐term evaluation showed that the electromagnetic field pretreatment may be a future therapeutic option for bone defect treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Research on Microstructure and Mechanical Properties of Rheological Die Forging Parts of Al-6.54Zn-2.40Cu-2.35Mg-0.10Zr(-Sc) Alloy

High-strength aluminum alloy (mainly refers to the 7xxx series) is the optimum material for lightweight military equipment. However, this type of aluminum alloy is a wrought aluminum alloy. If it is directly formed by traditional casting methods, there will inevitably be problems such as coarseness, unevenness, looseness, and hot cracking in the structure, which will greatly affect the final performance of the part. Based on the internal cooling with annular electromagnetic stirring (IC-AEMS) method, a new technology of rheological die forging is developed in this paper, and the scale-reduced parts of a brake hub of Al-6.54Zn-2.40Cu-2.35Mg-0.10Zr aluminum alloy were prepared. The influence of IC-AEMS and the addition of rare element Sc on the structure and mechanical properties of the parts was studied. An optical microscope and scanning electron microscope (SEM) were used to observe the microstructure evolution, energy dispersive spectroscopy (EDS) was used to analyze the phase distribution and composition, and the mechanical properties of the parts were tested by uniaxial tensile tests. The results show that the addition of Sc element can effectively refine the grains and improve the strength and elongation of the material; the application of IC-AEMS improves the cooling rate of the melt, increases the effective nucleation rate, and the grains are further refined. Through process optimization, scale-reduced parts of a brake hub with good formability and mechanical properties can be obtained, the ultimate tensile strength is 597.2 ± 3.1 MPa, the yield strength is 517.8 ± 4.3 MPa, and the elongation is 13.7 ± 1.3%.     

Collective many-body van der Waals interactions in molecular systems

Van der Waals (vdW) interactions are ubiquitous in molecules and condensed matter, and play a crucial role in determining the structure, stability, and function for a wide variety of systems. The accurate prediction of these interactions from first principles is a substantial challenge because they are inherently quantum mechanical phenomena that arise from correlations between many electrons within a given molecular system. We introduce an efficient method that accurately describes the nonadditive many-body vdW energy contributions arising from interactions that cannot be modeled by an effective pairwise approach, and demonstrate that such contributions can significantly exceed the energy of thermal fluctuations-a critical accuracy threshold highly coveted during molecular simulations-in the prediction of several relevant properties. Cases studied include the binding affinity of ellipticine, a DNA-intercalating anticancer agent, the relative energetics between the A- and B-conformations of DNA, and the thermodynamic stability among competing paracetamol molecular crystal polymorphs. Our findings suggest that inclusion of the many-body vdW energy is essential for achieving chemical accuracy and therefore must be accounted for in molecular simulations.     

静磁场对大鼠面颌骨骼肌细胞胞浆内游离钙离子浓度的影响

目的：利用激光共聚焦扫描显微镜（LCSM）技术观察静磁场作用下骨骼肌细胞胞浆内Ca2＋浓度的变化。方法：采用原代培养的大鼠面颌骨骼肌细胞,利用LCSM测定180、280、360mT磁场分别作用12、36、60h后,大鼠面颌骨骼肌细胞内游离Ca2＋浓度的变化。结果：12h组各磁场强度的骨骼肌细胞内游离Ca2＋浓度无明显变化。36h组细胞内Ca2＋浓度均有增加,且随着磁场强度的增加细胞内Ca2＋浓度增加明显。60h组细胞内Ca2＋浓度增加均非常明显,各磁场强度组相互之间无统计学意义。结论：静磁场促使大鼠面颌骨骼肌细胞胞浆内Ca2＋浓度增加,与时间呈正相关关系。