DIRECTED SELF-ASSEMBLY OF NANOSTRUCTURES AND THE OBSERVATIONS OF SELF-LIMITING GROWTH OF MOUNDS ON PATTERNED CRYSTAL SURFACE DURING EPITAXIAL GROWTH

In this thesis I describe an approach toward investigating moving interfaces, surface stabilities and directing self assembly of nanostructures, using lithographic patterning to perturb a flat crystalline surface over a range of spatial frequencies, followed by epitaxial growth. GaAs(001) shows a transient instability toward topographical perturbations. We model this behavior using an Ehrlich-Schwoebel (ES) barrier which impedes the diffusion of atoms across steps from above. We show via both kinetic Monte Carlo (kMC) simulations and molecular beam epitaxial (MBE) growth experiments that patterning in the presence of an ES barrier can be used to direct the self assembly of mounds. Second, as we track the time evolution of mound formation, we find the evidence of "Self-Limiting Growth" on surfaces - we find that in the initial stage of growth, the pattern directs the spontaneous formation of multilayer islands at 2-fold bridge sites between neighboring nanopits along [110] crystal orientation, seemingly due to the presence of an Ehrlich-Schwoebel barrier and the effect of heterogeneous nucleation sites on the surfaces. However, as growth continues, the height of mounds at 2-fold bridge sites "self-limits": the mounds cease to grow. Beyond this point an initially less favored 4-fold bridge sites dominate, and a different pattern of self assembled mounds begins. The observation of self-limiting behavior brings us new understanding of mechanism for crystal growth. We also find that the transient amplification of pattern corrugation during growth is correlated with self-limiting behavior of mounds. We propose that a minimum, `critical terrace size' at the top of each mound is responsible for the observed self-limiting growth behavior. Finally, the observation of the sequence of the mounds forming on the patterned surfaces gives us rather direct evidence that the formation of growth mounds on the surface is a nucleated process, rather than an instability

Association between interleukin-6 receptor gene variations and atherosclerotic lipid profiles among young adolescents in Taiwan

<p>Abstract</p> <p>Background</p> <p>To analyze the potential genetic associations between four polymorphisms of interleukin-6 receptor (IL-6R) gene and atherosclerotic lipid profiles among young adolescents in Taiwan.</p> <p>Methods</p> <p>Using data from the Taipei Children Heart Study-II - a cross-sectional survey in 2003. After multi-stage sampling, we selected 418 boys and 441 girls with an average age of 13.1 years. We genotyped the subjects for four IL-6R gene polymorphisms (rs4845617 G/A, rs4845623 A/G, rs8192284 A/C, and rs2229238 C/T) using a TaqMan 5' nuclease assay. Lipid profiles, including total cholesterol (CHOL), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C) were measured using standard methods. We also calculated CHOL/HDL-C ratio, LDL-C/HDL-C ratio, and TG/HDL-C ratio as atherosclerotic indexes.</p> <p>Results</p> <p>IL-6R rs8192284 A/C and rs2229238 C/T variants showed strong associations with high TG (additive model, OR = 1.58, 95%CI: 1.05-2.37; OR = 1.55, 95%CI: 1.04-2.29, respectively), low HDL-C (additive model, OR = 1.57, 95%CI: 1.03-2.39; OR = 1.68, 95%CI: 1.12-2.52, respectively), and high CHOL/HDL-C (additive model, OR = 1.68, 95%CI: 1.08-2.61, OR = 1.82, 95%CI: 1.18-2.79, respectively) in girls. We inferred five common haplotypes using rs4845617 G/A, rs4845623 A/G, and rs2229238 C/T (GAC, GAT, GGC, AAC, and AAT). In girls, the AAT haplotype was associated with a significant risk of high TG, low HDL-C, high CHOL/HDL-C, and abnormal lipid levels (high TG or low HDL-C) when compared with the GAC haplotype (OR range = 3.08-4.40, all p < 0.05).</p> <p>Conclusion</p> <p>The IL-6R rs8192284 A/C and rs2229238 C/T variants are associated with dyslipidemia in girls, but not in boys. The AAT haplotype of the IL-6R gene (rs4845617 G/A, rs4845623 A/G, and rs2229238 C/T) may play an important role in the pathogenesis of dyslipidemia and atherosclerosis in girls.</p

Ikbkap/Elp1 Deficiency Causes Male Infertility by Disrupting Meiotic Progression

Mouse Ikbkap gene encodes IKAP—one of the core subunits of Elongator—and is thought to be involved in transcription. However, the biological function of IKAP, particularly within the context of an animal model, remains poorly characterized. We used a loss-of-function approach in mice to demonstrate that Ikbkap is essential for meiosis during spermatogenesis. Absence of Ikbkap results in defects in synapsis and meiotic recombination, both of which result in increased apoptosis and complete arrest of gametogenesis. In Ikbkap-mutant testes, a few meiotic genes are down-regulated, suggesting IKAP's role in transcriptional regulation. In addition, Ikbkap-mutant testes exhibit defects in wobble uridine tRNA modification, supporting a conserved tRNA modification function from yeast to mammals. Thus, our study not only reveals a novel function of IKAP in meiosis, but also suggests that IKAP contributes to this process partly by exerting its effect on transcription and tRNA modification

Structural insights into the gating of DNA passage by the topoisomerase II DNA-gate.

Type IIA topoisomerases (Top2s) manipulate the handedness of DNA crossovers by introducing a transient and protein-linked double-strand break in one DNA duplex, termed the DNA-gate, whose opening allows another DNA segment to be transported through to change the DNA topology. Despite the central importance of this gate-opening event to Top2 function, the DNA-gate in all reported structures of Top2-DNA complexes is in the closed state. Here we present the crystal structure of a human Top2 DNA-gate in an open conformation, which not only reveals structural characteristics of its DNA-conducting path, but also uncovers unexpected yet functionally significant conformational changes associated with gate-opening. This structure further implicates Top2's preference for a left-handed DNA braid and allows the construction of a model representing the initial entry of another DNA duplex into the DNA-gate. Steered molecular dynamics calculations suggests the Top2-catalyzed DNA passage may be achieved by a rocker-switch-type movement of the DNA-gate

Estimating quality weights for EQ-5D (EuroQol-5 dimensions) health states with the time trade-off method in Taiwan

Background/PurposeEQ-5D (EuroQol-5 dimensions) is a preference-based measure of health, which is widely used in cost–utility analyses. It has been suggested that each country should develop its own value set. We therefore sought to develop the quality weights of the EQ-5D health states with the time trade-off (TTO) method in Taiwan.MethodsA total of 745 respondents consisting of employees and volunteers in 17 different hospitals were recruited and interviewed. Each of them valued 13 of 73 EQ-5D health states using the TTO method. Based on the three exclusion criteria for valuation data, only 456 (61.21%) respondents were considered eligible for data analysis. The quality weights for all EQ-5D health states were modeled by generalized estimating equations (GEEs).ResultsOver half of the responses were given negative values, and the medical personnel seemed to have a significantly higher TTO value (+0.1) than others after controlling for other predictors. The N3 model (level 3 occurred within at least 1 dimension) yielded an acceptable fit for the observed OTT data [mean absolute error (MAE) = 0.056, R2 = 0.35]. The magnitude of mean absolute differences (MADs) between Taiwan data and those from the UK, Japan, and South Korea ranged from 0.146 to 0.592, but the rank correlation coefficients were all above 0.811.ConclusionThis study reaffirms the differences in health-related preference values across countries. The high proportion of negative values might indicate that we have also partially measured the intensity of fear in addition to the utility of different health states

Low-energy Scattering of (D∗Dˉ∗)±(D^{*}\bar{D}^{*})^\pm System and the Resonance-like Structure Zc(4025)Z_c(4025)

In this paper, low-energy scattering of the $(D^{*}\bar{D}^{*})^\pm$ meson system is studied within L\"uscher's finite-size formalism using $N_{f}=2$ twisted mass gauge field configurations. With three different pion mass values, the $s$-wave threshold scattering parameters, namely the scattering length $a_0$ and the effective range $r_0$, are extracted in $J^P=1^+$ channel. Our results indicate that, in this particular channel, the interaction between the two vector charmed mesons is weakly repulsive in nature hence do not support the possibility of a shallow bound state for the two mesons, at least for the pion mass values being studied. This study provides some useful information on the nature of the newly discovered resonance-like structure $Z_c(4025)$ observed in various experiments.Comment: 11 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1403.131

Detection of subtle neurological alterations by the Catwalk XT gait analysis system

BACKGROUND: A new version of the CatWalk XT system was evaluated as a tool for detecting very subtle alteration in gait based on higher speed sample rate; the system could also demonstrate minor changes in neurological function. In this study, we evaluated the neurological outcome of sciatic nerve injury intervened by local injection of hyaluronic acid. Using the CatWalk XT system, we looked for differences between treated and untreated groups and differences within the same group as a function of time so as to assess the power of the Catwalk XT system for detecting subtle neurological change. METHODS: Peripheral nerve injury was induced in 36 Sprague–Dawley rats by crushing the left sciatic nerve using a vessel clamp. The animals were randomized into one of two groups: Group I: crush injury as the control; Group II: crush injury and local application with hyaluronic acid. These animals were subjected to neurobehavior assessment, histomorphology evaluation, and electrophysiology study periodically. These data were retrieved for statistical analysis. RESULTS: The density of neurofilament and S-100 over the distal end of crushed nerve showed significant differences either in inter-group comparison at various time points or intra-group comparison from 7 to 28 days. Neuronal structure architecture, axon counts, intensity of myelination, electrophysiology, and collagen deposition demonstrate significant differences between the two groups. There was significant difference of SFI and angle of ankle in inter- group analysis from 7 to 28 days, but there were no significant differences in SFI and angle of ankle at time points of 7 and 14 days. In the Cat Walk XT analysis, the intensity, print area, stance duration, and swing duration all showed detectable differences at 7, 14, 21, and 28 days, whereas there were no significant difference at 7 and 14 days with CatWalk 7 testing. In addition, there were no significant differences of step sequence or regularity index between the two versions. CONCLUSION: Hyaluronic acid augmented nerve regeneration as early as 7 days after crush injury. This subtle neurological alteration could be detected through the CatWalk XT gait analysis but not the SFI, angle of ankle, or CatWalk 7 methods

Clinical Outcome of Mycobacterium abscessus Infection and Antimicrobial Susceptibility Testing

Background/PurposeMycobacterium abscessus is the most resistant and rapidly growing mycobacterium and causes a wide range of clinical infectious diseases. The relationship between antimicrobial susceptibility and clinical outcome needs to be further evaluated.MethodsForty M. abscessus isolates were obtained from clinical specimens of 40 patients at the Taichung Veterans General Hospital from January 2006 to December 2008. Antimicrobial susceptibility testing was performed using the broth microdilution method according to the recommendations of the National Committee for Clinical Laboratory Standards. The clinical manifestations and outcomes were reviewed from medical records.ResultsTwenty-two patients were diagnosed with M. abscessus infection. Cough (86.3%), hemoptysis (31.8%) and fever (18.1%) were the most common symptoms. The radiographic findings included reticulonodular opacities (50.0%), consolidation (31.8%) and cavitary lesions (18.1%). The 40 isolates were susceptible to amikacin (95.0%), cefoxitin (32.5%), ciprofloxacin (10.0%), clarithromycin (92.5%), doxycycline (7.5%), imipenem (12.5%), moxifloxacin (22.5%), sulfamethoxazole (7.5%) and tigecycline (100%). The rate of treatment failure was 27.3% at the end of the 12th month after the start of treatment, although these patients were treated with a combination of clarithromycin and other antimicrobial agents.ConclusionM. abscessus is naturally susceptible to clarithromycin and amikacin, variably susceptible to cefoxitin and imipenem, and resistant to most other antimicrobial drugs. Combination therapy with clarithromycin, amikacin and other active antimicrobial agents may lead to clinical improvement; however, the rate of treatment failure is still high