A novel process for preparing PZT thick films

2000-2001 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Boundaries of Disk-like Self-affine Tiles

Let $T:= T(A, {\mathcal D})$ be a disk-like self-affine tile generated by an integral expanding matrix $A$ and a consecutive collinear digit set ${\mathcal D}$, and let $f(x)=x^{2}+px+q$ be the characteristic polynomial of $A$. In the paper, we identify the boundary $\partial T$ with a sofic system by constructing a neighbor graph and derive equivalent conditions for the pair $(A,{\mathcal D})$ to be a number system. Moreover, by using the graph-directed construction and a device of pseudo-norm $\omega$, we find the generalized Hausdorff dimension $\dim_H^{\omega} (\partial T)=2\log \rho(M)/\log |q|$ where $\rho(M)$ is the spectral radius of certain contact matrix $M$. Especially, when $A$ is a similarity, we obtain the standard Hausdorff dimension $\dim_H (\partial T)=2\log \rho/\log |q|$ where $\rho$ is the largest positive zero of the cubic polynomial $x^{3}-(|p|-1)x^{2}-(|q|-|p|)x-|q|$, which is simpler than the known result.Comment: 26 pages, 11 figure

Cubic exact solutions for the estimation of pairwise haplotype frequencies: implications for linkage disequilibrium analyses and a web tool 'CubeX'

<p>Abstract</p> <p>Background</p> <p>The frequency of a haplotype comprising one allele at each of two loci can be expressed as a cubic equation (the 'Hill equation'), the solution of which gives that frequency. Most haplotype and linkage disequilibrium analysis programs use iteration-based algorithms which substitute an estimate of haplotype frequency into the equation, producing a new estimate which is repeatedly fed back into the equation until the values converge to a maximum likelihood estimate (expectation-maximisation).</p> <p>Results</p> <p>We present a program, "CubeX", which calculates the biologically possible exact solution(s) and provides estimated haplotype frequencies, D', r²and <it>χ</it>²values for each. CubeX provides a "complete" analysis of haplotype frequencies and linkage disequilibrium for a pair of biallelic markers under situations where sampling variation and genotyping errors distort sample Hardy-Weinberg equilibrium, potentially causing more than one biologically possible solution. We also present an analysis of simulations and real data using the algebraically exact solution, which indicates that under perfect sample Hardy-Weinberg equilibrium there is only one biologically possible solution, but that under other conditions there may be more.</p> <p>Conclusion</p> <p>Our analyses demonstrate that lower allele frequencies, lower sample numbers, population stratification and a possible |D'| value of 1 are particularly susceptible to distortion of sample Hardy-Weinberg equilibrium, which has significant implications for calculation of linkage disequilibrium in small sample sizes (eg HapMap) and rarer alleles (eg paucimorphisms, q < 0.05) that may have particular disease relevance and require improved approaches for meaningful evaluation.</p

A new anisotropy index on trabecular bone radiographic images using the fast Fourier transform

BACKGROUND: The degree of anisotropy (DA) on radiographs is related to bone structure, we present a new index to assess DA. METHODS: In a region of interest from calcaneus radiographs, we applied a Fast Fourier Transform (FFT). All the FFT spectra involve the horizontal and vertical components corresponding respectively to longitudinal and transversal trabeculae. By visual inspection, we measured the spreading angles: Dispersion Longitudinal Index (DLI) and Dispersion Transverse Index (DTI) and calculated DA = 180/(DLI+DTI). To test the reliability of DA assessment, we synthesized images simulating radiological projections of periodic structures with elements more or less disoriented. RESULTS: Firstly, we tested synthetic images which comprised a large variety of structures from highly anisotropic structure to the almost isotropic, DA was ranging from 1.3 to 3.8 respectively. The analysis of the FFT spectra was performed by two observers, the Coefficients of Variation were 1.5% and 3.1 % for intra-and inter-observer reproducibility, respectively. In 22 post-menopausal women with osteoporotic fracture cases and 44 age-matched controls, DA values were respectively 1.87 ± 0.15 versus 1.72 ± 0.18 (p = 0.001). From the ROC analysis, the Area Under Curve (AUC) were respectively 0.65, 0.62, 0.64, 0.77 for lumbar spine, femoral neck, total femoral BMD and DA. CONCLUSION: The highest DA values in fracture cases suggest that the structure is more anisotropic in osteoporosis due to preferential deletion of trabeculae in some directions

Health insurance, neighborhood income, and emergency department usage by Utah children 1996–1998

BACKGROUND: It is estimated that approximately half of emergency department (ED) usage in the U.S. and other developed countries is for non-urgent conditions and that this usage is related to availability, social, and economic factors. We examined pediatric ED usage in a U.S. state with respect to income, health insurance status, types of medical conditions, and whether introduction of managed care affected utilization by Medicaid children. METHODS: Emergency department usage rates were calculated from 1996 through 1998 using Utah ED data for children with commercial health insurance, Medicaid, for uninsured children, and by income group estimating neighborhood household income from Zip code of residence. We analyzed usage following the July 1996 transition of Utah Medicaid to managed care. RESULTS: Children with Medicaid had approximately 50% greater ED utilization rates than children with commercial health insurance or uninsured children. The majority of usage for Medicaid and uninsured children was for non-traumatic conditions. Only 35% of total ED usage was for non-emergent or non-urgent conditions and this was related to both Medicaid and low household income. Children lacking health insurance were more likely to be discharged against medical advice (OR = 2.36, 95% C.I. 1.88–2.96). There was no reduction in Medicaid ED usage following the transition to managed care. CONCLUSION: Usage of ED services is related to both health insurance status and income. Children lacking health insurance and Medicaid children have excessive usage for conditions which could be treated in a primary care setting. That managed care does not reduce Medicaid ED usage is consistent with findings of other studies

Synthetic lethality: a framework for the development of wiser cancer therapeutics

The challenge in medical oncology has always been to identify compounds that will kill, or at least tame, cancer cells while leaving normal cells unscathed. Most chemotherapeutic agents in use today were selected primarily for their ability to kill rapidly dividing cancer cells grown in cell culture and in mice, with their selectivity determined empirically during subsequent animal and human testing. Unfortunately, most of the drugs developed in this way have relatively low therapeutic indices (low toxic dose relative to the therapeutic dose). Recent advances in genomics are leading to a more complete picture of the range of mutations, both driver and passenger, present in human cancers. Synthetic lethality provides a conceptual framework for using this information to arrive at drugs that will preferentially kill cancer cells relative to normal cells. It also provides a possible way to tackle 'undruggable' targets. Two genes are synthetically lethal if mutation of either gene alone is compatible with viability but simultaneous mutation of both genes leads to death. If one is a cancer-relevant gene, the task is to discover its synthetic lethal interactors, because targeting these would theoretically kill cancer cells mutant in the cancer-relevant gene while sparing cells with a normal copy of that gene. All cancer drugs in use today, including conventional cytotoxic agents and newer 'targeted' agents, target molecules that are present in both normal cells and cancer cells. Their therapeutic indices almost certainly relate to synthetic lethal interactions, even if those interactions are often poorly understood. Recent technical advances enable unbiased screens for synthetic lethal interactors to be undertaken in human cancer cells. These approaches will hopefully facilitate the discovery of safer, more efficacious anticancer drugs that exploit vulnerabilities that are unique to cancer cells by virtue of the mutations they have accrued during tumor progression

Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

The decay channel $\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p})$ is studied using a sample of $1.06\times 10^8$ $\psi^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $\Gamma<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics

Lysophosphatidic Acid Acyltransferase β (LPAATβ) Promotes the Tumor Growth of Human Osteosarcoma

Osteosarcoma is the most common primary malignancy of bone with poorly characterized molecular pathways important in its pathogenesis. Increasing evidence indicates that elevated lipid biosynthesis is a characteristic feature of cancer. We sought to investigate the role of lysophosphatidic acid acyltransferase β (LPAATβ, aka, AGPAT2) in regulating the proliferation and growth of human osteosarcoma cells. LPAATβ can generate phosphatidic acid, which plays a key role in lipid biosynthesis as well as in cell proliferation and survival. Although elevated expression of LPAATβ has been reported in several types of human tumors, the role of LPAATβ in osteosarcoma progression has yet to be elucidated.Endogenous expression of LPAATβ in osteosarcoma cell lines is analyzed by using semi-quantitative PCR and immunohistochemical staining. Adenovirus-mediated overexpression of LPAATβ and silencing LPAATβ expression is employed to determine the effect of LPAATβ on osteosarcoma cell proliferation and migration in vitro and osteosarcoma tumor growth in vivo. We have found that expression of LPAATβ is readily detected in 8 of the 10 analyzed human osteosarcoma lines. Exogenous expression of LPAATβ promotes osteosarcoma cell proliferation and migration, while silencing LPAATβ expression inhibits these cellular characteristics. We further demonstrate that exogenous expression of LPAATβ effectively promotes tumor growth, while knockdown of LPAATβ expression inhibits tumor growth in an orthotopic xenograft model of human osteosarcoma.Our results strongly suggest that LPAATβ expression may be associated with the aggressive phenotypes of human osteosarcoma and that LPAATβ may play an important role in regulating osteosarcoma cell proliferation and tumor growth. Thus, targeting LPAATβ may be exploited as a novel therapeutic strategy for the clinical management of osteosarcoma. This is especially attractive given the availability of selective pharmacological inhibitors

Using a human cardiovascular-respiratory model to characterize cardiac tamponade and pulsus paradoxus

<p>Abstract</p> <p>Background</p> <p>Cardiac tamponade is a condition whereby fluid accumulation in the pericardial sac surrounding the heart causes elevation and equilibration of pericardial and cardiac chamber pressures, reduced cardiac output, changes in hemodynamics, partial chamber collapse, pulsus paradoxus, and arterio-venous acid-base disparity. Our large-scale model of the human cardiovascular-respiratory system (H-CRS) is employed to study mechanisms underlying cardiac tamponade and pulsus paradoxus. The model integrates hemodynamics, whole-body gas exchange, and autonomic nervous system control to simulate pressure, volume, and blood flow.</p> <p>Methods</p> <p>We integrate a new pericardial model into our previously developed H-CRS model based on a fit to patient pressure data. Virtual experiments are designed to simulate pericardial effusion and study mechanisms of pulsus paradoxus, focusing particularly on the role of the interventricular septum. Model differential equations programmed in C are solved using a 5^th-order Runge-Kutta numerical integration scheme. MATLAB is employed for waveform analysis.</p> <p>Results</p> <p>The H-CRS model simulates hemodynamic and respiratory changes associated with tamponade clinically. Our model predicts effects of effusion-generated pericardial constraint on chamber and septal mechanics, such as altered right atrial filling, delayed leftward septal motion, and prolonged left ventricular pre-ejection period, causing atrioventricular interaction and ventricular desynchronization. We demonstrate pericardial constraint to markedly accentuate normal ventricular interactions associated with respiratory effort, which we show to be the distinct mechanisms of pulsus paradoxus, namely, series and parallel ventricular interaction. Series ventricular interaction represents respiratory variation in right ventricular stroke volume carried over to the left ventricle via the pulmonary vasculature, whereas parallel interaction (via the septum and pericardium) is a result of competition for fixed filling space. We find that simulating active septal contraction is important in modeling ventricular interaction. The model predicts increased arterio-venous CO₂due to hypoperfusion, and we explore implications of respiratory pattern in tamponade.</p> <p>Conclusion</p> <p>Our modeling study of cardiac tamponade dissects the roles played by septal motion, atrioventricular and right-left ventricular interactions, pulmonary blood pooling, and the depth of respiration. The study fully describes the physiological basis of pulsus paradoxus. Our detailed analysis provides biophysically-based insights helpful for future experimental and clinical study of cardiac tamponade and related pericardial diseases.</p