On the Relationship Between the Grain Size and Gas-Sensitivity of Chemo-Resistive Metal-Oxide Gas Sensors with Nanosized Grains

In this work we elaborate the effect of grain size on the sensitivity of chemo-resistive metal-oxide gas sensors with nanosized grains. The effective carrier concentration in nanocrystalline SnO₂ sensors with various grain sizes is calculated as a function of the surface state density. This involves numerical computation of the charge balance equation (i.e., the electroneutrality condition) using approximated analytical solutions of Poissons equation for small spherical crystallites. The calculations demonstrate a sharp decrease in the carrier concentration when the surface state density reaches a critical value that corresponds to a condition of fully depleted grains, namely when nearly all the electrons are trapped at the surface. Assuming that the variations in the surface state density are induced by surface interactions with the gas phase, these calculations enable to simulate the response curves of nanocrystalline SnO₂ gas sensors. The simulations show that the conductivity increases linearly with decreasing trapped charge densities, and that the sensitivity to the gas-induced variations in the trapped charge density is proportional to 1/D, where D is the average grain size.     

Breathing during sleep in patients with nocturnal desaturation

BACKGROUND: The global DNA methylation of 136 breast lesions (117 primary invasive carcinomas, 5 benign phyllodes tumors, 11 fibroadenomas, and 3 sclerosing adenosis) and their respective adjacent parenchyma was analyzed using an in vitro enzyme assay. METHODS: In the group of patients with breast carcinoma, DNA hypomethylation was correlated with clinical and pathologic parameters known to affect disease prognosis. Histopathologic type, disease stage, and tumor grade were evaluated according to the World Health Organization classification, the TNM system, and the criteria of Elston and Ellis' criteria, respectively. DNA flow cytometry was performed in fresh/frozen samples stained with propidium iodide. Hormone receptor (estrogen and progesterone receptor) status was determined by immunocytochemistry. RESULTS: The comparative study of DNA methylation showed that the DNA of breast carcinomas was statistically significantly less methylated than the DNA of the respective adjacent parenchyma (P=0.0001), the DNA of breast benign lesions (P=0.0002), and the DNA of normal parenchyma (P < 0.0001). A statistically significant correlation was found between the global DNA hypomethylation and the disease stage (P=0.0009), tumor size (P=0.0026), and histologic grade (P=0.0097) of malignant neoplasms. A trend for DNA from breast carcinomas with positive axillary lymph nodes (N1) to be more hypomethylated than those without nodal involvement (NO) (P=0.055) was verified. In contrast, no significant association was found between DNA methylation and histologic type of tumors, hormone receptors, DNA ploidy, and S-phase fraction. CONCLUSIONS: The current shows that DNA hypomethylation is increased in breast carcinomas, playing a potentially important role in tumor development. These findings also suggest that DNA methylation status may be a biologic marker with prognostic significance in this group of neoplasms.     

Complications of internal fixation of maxillofacial fractures with microplates

PURPOSE: The aim of this retrospective study was to evaluate the complications of open reduction and internal fixation of maxillofacial fractures with microplates. PATIENTS AND METHODS: In 44 patients with maxillofacial trauma, fractures of the maxillofacial skeleton were treated by open reduction and internal fixation using a 1.0-mm and 1.5-mm microsystem. Simultaneously occurring fractures of the mandible or frontozygomatic suture were treated with a 2.0-mm miniplate system. Perioperative and postoperative complications were traced using patient charts, operation reports, and radiographs. The average follow-up was 46.8 months (range, 31 to 54 months). RESULTS: A total of 124 1.0-mm microplates and 546 1.0-mm microscrews, and 17 1.5-mm microplates and 75 1.5-mm microscrews, was used. The perioperative complication rate was 1.2% for the 1.0-mm screws (use of four emergency screws, breakage of one screw in the dense frontozygomatic suture area, and an insertion of a screw in a premolar root). The postoperative complication rate was 0.8% for the 1.0-mm screws (screw dislocation without clinical implication). No complications were observed with the 1.5-mm system. Plate-related infection did not occur. All fractures healed well. Three patients asked for plate removal because of a vague, persisting pain in the treated area. After removal, only one patient was free of pain. A loose 1.5-mm screw was found in this patient. CONCLUSION: The overall complication rate for microsystems was 2.0%. Both microsystems proved to be a reliable modality to fix fractures of the maxillofacial skeleton. Complications can be considered incidental and of neglectable clinical significance.     

Agreement and repeatability of infrared pupillometry and the comparison method

OBJECTIVE: To evaluate the accuracy and repeatability of the widely used comparison method of measuring pupil size. DESIGN: Cross-sectional study. PARTICIPANTS: Fourteen eyes of seven healthy myopic subjects were examined. INTERVENTION: Two examiners made two repeated measures of pupil diameters of 14 eyes using Rosenbaum card comparison pupillometry and infrared pupillometry. Subjects fixated on a distant visual acuity chart, and pupils were measured under three luminance conditions. The agreement and inter-rater repeatability of both methods were determined. MAIN OUTCOME MEASURES: Outcomes were pupil diameters, limits of agreement, and coefficient of repeatability of two examiners. RESULTS: The mean difference between the two techniques ranged from 0.3 to 0.5 mm. The limits of agreement within two standard deviations ranged from 2.4 to 2.8 mm. Coefficient of repeatability ranged from 0.6 to 1.4 mm for infrared pupillometry and 1.0 to 1.2 mm for Rosenbaum pupillometry. Inter-rater repeatability of Rosenbaum pupillometry was consistently pupil diameter biased. Pupil diameters measured with the Rosenbaum method were consistently larger than diameters measured with the infrared technique for both examiners under all luminance conditions. CONCLUSIONS: Results indicate that although the mean difference in techniques was small, the range of the agreement between the Rosenbaum and the infrared techniques was large. The Rosenbaum method consistently overestimated pupil diameters and was subject to inter-rater repeatability bias. Rosenbaum pupillometry may not be appropriate when accurate pupil measurements are required. The results have implications for many clinical trials in ophthalmology, including those evaluating refractive surgery that use Rosenbaum comparison pupillometry.     

Expansion and deletion of triplet repeat sequences in Escherichia coli occur on the leading strand of DNA replication

Expansions and deletions of triplet repeat sequences that cause human hereditary neurological diseases were previously suggested to be mediated by the formation of DNA hairpins on the lagging strand during replication. The replication properties of CTG.CAG, CGG.CCG, and TTC.GAA repeats were studied in Escherichia coli using an in vivo phagemid system as a model for continuous leading strand synthesis. The repeats were substantially deleted when the CTG, CGG, and GAA repeats were the templates for rolling circle replication from the f1 phage origin. The deletions may be mediated by hairpins formed by these repeat tracts. The distributions of the deletion products of the CTG.CAG and CGG.CCG tracts indicated that hairpins of discrete sizes mediate deletions during complementary strand synthesis. Deletions during rolling circle synthesis are caused by larger hairpins of specific sizes. Thus, most deletion products were of defined lengths, suggesting a preference for specific hairpin intermediates. Small expansions of the CTG.CAG and CGG.CCG repeats were also observed, presumably due to the formation of CTG and CGG hairpins on the nascent complementary strand. Since rolling circle replication has been established in vitro as a model for leading strand synthesis, we conclude that triplet repeat instability can also occur on the leading strand of DNA replication.     

Latissimus dorsi pedicled graft. An unusual cause of shoulder pain

An unusual complication after the use of a pedicled latissimus dorsi flap is reported. The flap was used to reconstruct a facial defect after excision of a high grade mucoepidermoid carcinoma of a parotid gland. The tendinous insertion of the latissimus dorsi on the humerus was left intact and the flap pivoted around this point. Subsequent use of his arm caused the patient disabling shoulder pain from traction on the tendon. Symptoms resolved after the tendon was divided.     

Compositional dependence of work function and Fermi level position of the HfNx/SiO2 system

In situ Kelvin Probe (KP) measurements performed on HfN_x showed an increase of the vacuum work function as a function of N content from a value of 3.9 eV (silicon conduction band edge) for pure Hf to a value of 5 eV (silicon valence band edge) for x ～ 2. In contrast, capacitance–voltage (C–V) measurements showed that the effective work function increased only until x < 1 and saturated around a value of 4.6 eV (silicon midgap). This behavior is attributed to Fermi level pinning, which is probably due to oxidation of the HfN_x during the reactive sputtering deposition step.     

Highly enhanced electrochemical performance of silicon-free platinum–yttria stabilized zirconia interfaces

In the drive to achieve economically viable solid oxide fuel cells, efforts have been directed towards substantially decreasing their operating temperature. Unfortunately, these efforts have been hindered by extremely sluggish electrode kinetics at reduced temperatures. In this report, we show that silicon impurities on the surface of the electrolyte play a critical role in influencing electrode kinetics. More specifically, improvements by as much as three orders of magnitude are reported for the performance of platinum electrodes on yttria-stabilized zirconia electrolytes prepared as high purity thin films with a largely Si-free surface. These improvements in performance are estimated to enable operation of a solid oxide fuel cell down to approximately 400 °C.