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Periodontitis, or conventionally “Gum Disease,” is the infection and inflammation of gingival tissue, and is currently the leading cause of tooth loss in the United States. One of the most effective treatments of periodontitis is guided bone regeneration (GBR); however, current GBR barrier membranes lack high biocompatibility and cell impermeability. The authors of this study evaluated the in vitro viability of previously synthesized Gelatin-Pluronic® F127 hybrid hydrogels as potential GBR barrier membranes through a novel three-partition test involving migration of fluorescent-dyed human dermal fibroblasts. Results showed that cells were unable to migrate across the Gelatin-Pluronic® F127 hybrid hydrogel barrier, whereas control setups with gelatin hydrogel barriers showed cell permeability. In addition, cytotoxicity tests were conducted with fibroblasts plated in both cell mediums that had been incubated while in contact hybrid gels and cell mediums suspended on the surface of hybrid gels during swelling procedures. Fluorescence cell plate readings showed similar cell viability across data from both tests, indicating that Gelatin-Pluronic® F127 hybrid hydrogels are not toxic to cells, and thus biocompatible.
It has not been well established whether dietary folate intake reduces the risk of diabetes development. We aimed to clarify the prospective association between dietary folate intake and type 2 diabetes (T2D) risk among 7333 Korean adults aged 40 years or older who were included in the Multi-Rural Communities Cohort. Dietary folate intake was estimated from all 106 food items listed on a FFQ, not including folate intake from supplements. Two different measurements of dietary folate intake were used: the baseline consumption and the average consumption from baseline until just before the end of follow-up. The association between folate intake and T2D risk was determined through a modified Poisson regression model with a robust error estimator controlling for potential confounders. For 29 745 person years, 319 cases of diabetes were ascertained. In multivariable analyses, dietary folate intake was inversely associated with risk of T2D for women, not for men. For women, the incidence rate ratio of diabetes in the third tertile compared with the first tertile was 0·57 (95 % CI 0·38–0·87, Pfor trend=0·0085) in the baseline consumption model and 0·64 (95 % CI 0·43–0·95, Pfor trend=0·0244) in the average consumption model. These inverse associations was found in both normal fasting blood glucose group and impaired fasting glucose group among women. Among non-users of multinutrients and vitamin supplements, the significant inverse association remained. Thus, higher dietary intake of folate is prospectively associated with lower risk of diabetes for women.
Introduction: Point-of-care ultrasound (POCUS) has been suggested as an initial investigation in the management of renal colic. Our objectives were: 1) to determine the accuracy of POCUS for the diagnosis of nephrolithiasis, and 2) to assess its prognostic value in the management of renal colic (PROSPERO: 42016035331). Methods: An electronic database search of MEDLINE, EMBASE, and PubMed was conducted utilizing subject headings, keywords, and synonyms that address our research question. Bibliographies of included studies and narrative reviews were manually examined. Studies of adult emergency department patients with renal colic symptoms were included. Any degree of hydronephrosis was considered a positive POCUS finding. Accepted criterion standards were CT evidence of renal stone or hydronephrosis, direct stone visualization, or surgical findings. Screening of abstracts, quality assessment with the QUADAS-2 instrument, and data extraction were performed by two reviewers, with discrepancies resolved by conference with a third reviewer.Test performance was assessed by pooled sensitivity and specificity, calculated likelihood ratios, and a summary receiver operator curve (SROC). The secondary outcome of prognostic value was reported as a narrative summary. Results: The electronic search yielded 627 unique titles. After relevance screening, 25 papers underwent full-text review, and 8 articles met all inclusion criteria. Of these, 5 high-quality studies (N=1773) were included in the meta-analysis for diagnostic accuracy, and three yielded data on prognostic value. The pooled results for sensitivity and specificity were 70.2% (95% CI=67.1% to 73.2%) and 75.4% (95% CI=72.5% to 78.2%), respectively. The calculated positive and negative likelihood ratios were 2.85 and 0.39. The SROC generated did not show evidence of a threshold effect.Three studies examining prognostic value noted a higher likelihood of a large stone or surgical intervention with positive POCUS findings. The largest randomized trial showed lower cumulative radiation exposure and no increase in adverse events in those who received POCUS investigation as the initial renal colic investigation. Conclusion: Point-of-care ultrasound is of modest accuracy for the diagnosis of nephrolithiasis. While positive POCUS findings are associated with larger stones and greater likelihood for intervention, the clinical importance of this is unclear.
Molecular pathways underlying carcinogenesis: signal transduction
Fabiola Cecchi, Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda,MD, USA,
Young H. Lee, Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA,
Donald P. Bottaro, Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
Hepatocyte growth factor (HGF), also known as scatter factor (SF), was discovered on the basis of its ability to promote liver regeneration, and independently for its mitogenic activity on epithelial cells and its ability to induce cell scatter (1). HGF is secreted primarily by mesenchymal cells and drives cell motility, proliferation, survival, and morphogenesis by binding to the Met receptor tyrosine kinase (TK) present on a variety of target cell types (1–6). HGF/Met signaling is critical for normal development and adult homeostasis: deletion of either gene lethally disrupts embryogenesis (4,6) and up-regulation of HGF expression after kidney, liver, or heart injury protects against tissue damage and promotes repair and regeneration in adults (1,7–11). Under normal conditions, Met activation is tightly regulated by paracrine ligand delivery, ligand activation, and receptor internalization, dephosphorylation, and degradation (1). Despite this, HGF/Met signaling contributes to tumorigenesis, tumor angiogenesis, and metastasis in several prevalent cancers, a realization that has driven rapid growth in the development of experimental therapeutics targeting the pathway.
HGF and Met structure and function
The human HGF gene consists of 18 exons and 16 introns spanning 68 Mb on chromosome 7q21.11 (1). Five mRNA transcripts arise from alternative splicing: two encode full-length HGF forms and three encode truncated isoforms that bind Met, but differ in their biological activities (1). HGF protein is a plasminogen family member consisting of an amino-terminal heparin-binding domain (N), four kringle domains (K1–4) and a carboxyl-terminal serine-protease-like domain (Figure 17.1a). Unlike other plasminogen family members, HGF has no proteolytic activity (1). The HGF N and K1 domains contain the primary Met binding sites (12), and the protease-like domain contains an important secondary Met binding site (13). Proteolytic processing of the single-chain HGF precursor results in the active disulfide-linked heterodimer; the amino-terminal α-chain contains N and K1–4, and the β-chain contains the protease-like region (1).
Electron microscopes are proving themselves indispensible tools in the world of nanotechnology. In this brief overview, we explore the potential of electrons within in situ transmission electron microscopy (TEM) with the electrons provided either from the imaging electron beam or from electrical currents across contacted specimens to nanoengineered graphene based on work at our labs. The use of electrons is demonstrated to be enormously versatile to pattern, heal, and even fabricate graphene. In essence, electrons provide a useful engineering tool box that with further development will enable device fabrication and modification inside a TEM, thus allowing one to study structure–property relationships of graphene as well as other low dimensional materials in near real time with atomic precision.
Three types of Ganium Nitride (GaN) transistors were studied in this work. The devices were fabricated and exhibited unique characteristics over on-state current and off-state blocking performances. We also compared the performance differences of devices fabricated by multiepitaxial GaN/AlGaN layers on different substrates (Sapphire and Si) and evaluated the correlations among starting substrate, device variation, and manufacturing uniformity. The first device is a normally-on device with Sapphire substrate which shows good drain saturation current (Idsat) and breakdown characteristics, but the gate leakage current is quite large. The second device is a normally-off GaN transistor named metal-insulate-semiconductor (MIS) heterojunction field-effect transistor (MIS-HFET) which exhibits good performance with threshold voltage (Vth) of 3V and breakdown voltage (Vbd) of over 1800V. However the third device is a normally-off GaN metal-oxide-semiconductor field-elect transistor (MOSFET) structure which is rather difficult to exhibit good blocking characteristic due to inadequate doping process control of the reduce-surface-field (RESURF) region.
The photoluminescent properties of erbium doped silicon rich silicon oxide (SRSO) is investigated. The silicon content of SRSO was varied from 43 to 33 at. % and Er concentration was 0.4–0.7 at. % in all cases. We observe strong 1.54 μ m luminescence due to 4I13/2⇒4I15/2 Er3+ 4f transition, excited via energy transfer from carrier recombination in silicon nanoclusters to Er 4f shells. The luminescent lifetimes at the room temperature are found to be 4–7 msec, which is longer than that reported from Er in any semiconducting host material, and comparable to that of Er doped SiO2 and A12O3. The dependence of the Er3+ luminescent intensities and lifetimes on temperature, pump power and on background illumination shows that by using SRSO, almost all non-radiative decay paths of excited Er3+ can be effectively suppressed, and that such suppression is more important than increasing excitation rate of Er3+. A planar waveguide using Er doped SRSO is also demonstrated.
Electron traps in ALD and MOCVD HfO2 and HfSiO high-k dielectrics were investigated using both conventional DC and pulse measurements. It was found that the traps in the gate stack could be associated with defects of different activation energies and capture cross-sections. This points to potentially different origins of the electrically active defects, which can be either intrinsic or process-related. Structural non-uniformity of the high-k film, associated with grain formation and phase separation, may lead to variation of electrical properties of the gate dielectric along the transistor channel. Effects of such dielectric non-uniformity, as well as electron trapping, on the measured transistor mobility were evaluated.
We successfully fabricated a-IGZO TFTs employing a Ti/Cu source/drain (S/D) and SiNx passivation in order to reduce the line-resistance, as compared to most oxide TFTs that use Mo (or TCO) and SiO2 for their S/D and passivation, respectively. Although passivated with SiNx, the TFT exhibits good transfer characteristics without a negative shift. However, the TFT employing a Mo S/D exhibited conductor-like characteristics when passivated with SiNx. Our investigation suggests that the IGZO oxygen vacancies found in the Ti/Cu S/D are controlled, resulting in low concentrations, and so prevent the SiNx-passivated TFT from having a negative shift.
Abstract:GaN thin films on sapphire were grown by RF magnetron sputtering with ZnO buffer layer. The tremendous mismatch between the lattices of GaN and sapphire can be partly overcome by the use of thin buffer layer of ZnO. The dependence of GaN film quality on ZnO buffer layer was investigated by X-ray diffraction(XRD). The properties of the sputtered GaN are strongly dependent on ZnO buffer layer thickness. The optimum thickness of ZnO buffer layer is around 30nm. Using XRD analysis, we have found the optimal substrate temperature which can grow high quality GaN thin film. In addition, the effect of excimer laser annealing(ELA) on structural and electrical properties of GaN thin films was investigated. The surface roughness and images according to the laser energy density were investigated by atomic force microscopy(AFM) and it was confirmed that the crystallization was improved by increasing laser energy density.
Reservoir length dependencies of electromigration lifetime in multilevel interconnect were compared for two passivation dielectrics, that is, FOX (Flowable Oxide) and HDP FSG (High Density Plasma Fluorinated Silicate Glass). The higher electromigration resistance of interconnects passivated by FOX can be best explained by their lower stress and vacancy concentration levels than the case for FSG. It was also proposed that lower levels of stress and vacancy concentration in the longer reservoir could partially contribute to the better electromigration reliability of interconnect with the longer reservoir.
A pattern specific corrosion of aluminum wires was found during aluminum chemical mechanical polishing process. This paper presents and discusses the particular pattern dependency of the corrosion behavior and effective control methods in order to reduce the corrosion. An aluminum single damascene structure on silicon dioxide thin film was prepared and the effects of process variables and pattern configuration on corrosion behavior were extensively explored. The corrosion behavior was quantitatively analyzed using sheet resistance of corroded line. It was demonstrated that corrosion of aluminum wire was associated with cleaning media and pattern configuration. The area ratio between sub-micron size line and pads was the most important factors to determine the corrosion behavior. A post cleaning chemical including corrosion inhibitor couldn't prevent the corrosion perfectly. It was found that sacrificial dummy lines could reduce the aluminum corrosion, which suggests that the aluminum corrosion could be controlled by the structural consideration in aluminum damascene.
ECR silane plasmas for the deposition of a-Si:H and μc-Si films were investigated by in-situ mass spectroscopy (MS) using a quadrupole residual gas analyzer. The results showed that the intensities of ionic and neutral species (H, H2, He, Ar, Si and SiHx) in the 2 % SiH4/He plasma are strongly dependent on the deposition conditions such as chamber pressure, input power and hydrogen dilution. In all cases, the prevalence of Si ions was observed over SiH, SiH2 and SiH3 ions, suggesting a high decomposition rate of the silane in the plasma. In particular, the population of atomic hydrogen in the plasma seems to play a key role in the properties of both a-Si:H and μc-Si films. For example, the increased intensity of atomic hydrogen, compared to that of molecular hydrogen, resulted in the better quality a-Si:H film, showing a higher photo and dark conductivity ratio of ~105. The intensity of the hydrogen species was especially sensitive to the chamber pressure. The correlation between MS spectra and film properties is presented.
We have demonstrated a uniform, robust interface for high-k deposition with significant improvements in device electrical performance compared to conventional surface preparation techniques. The interface was a thin thermal oxide that was grown and then etched back in a controlled manner to the desired thickness. Utilizing this approach, an equivalent oxide thickness (EOT) as low as 0.87 nm has been demonstrated on high-k gate stacks having improved electrical characteristics as compared to more conventionally prepared starting surfaces.
Rough-surface polycrystalline silicon films have been used for fabrication of electrically erasable-programmable read-only-memories (EEPROM). Silicon-Rich Oxides (SRO), also known as semi-insulating polycrystalline silicon (SIPOS), have been recommended for use as electron injectors. The advantage of SRO as injectors is that both the bottom and top surfaces of the film can be used to obtain high field enhancement. An ultra-thin multi-layer structure of silicon and silicon dioxide has been fabricated by low pressure chemical vapor deposition (LPCVD). High resolution TEM shows alternating layers of 50 A thick SiO2 and polycrystalline Si (grain size ∼ 80 A) films were deposited and MOS capacitors using this multilayer dielectric were studied to understand their electrical characteristics. Both I-V and C-V measurements show that the Fowler-Nordheim tunneling current is proportional to the number of polycrystalline layers. The “turn-on” voltage of the tunneling current is determined by the thickness of first SiO2 layer, and the effective dielectric constant varies from 3.9 to 9.1, proportional to the number of poly-Si layers within the multi-layer structure (MLS). For a 350 Å stack (7 layers), the interface trap density, Dit, was 3×1010 traps/cm2, and the effective dielectric constant was roughly 9.
Monoclinic gallium oxide (β-Ga2O3) nanowires were catalytically synthesized by electric arc discharge of GaN powders mixed with a small amount (less than 5 %) of transition metals under a pressure of 500 Torr (80 %-Ar + 20 %-O2). Scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images showed that the average diameter of the wires were about 30 nm and their lengths were as long as up to one hundred micrometer, resulting in extremely large aspect ratio. Fourier diffractogram was indicative of single crystalline nature of the β-Ga2O3 wire. HRTEM image also showed β-Ga2O3 with twin defects at the center of the wire which might play as nucleation seeds. Both X-ray diffraction (XRD) patterns and FT-Raman spectra of the wires identified the observed nanowires as monoclinic crystalline gallium oxides.