Home About us Contact
|
Home About us Contact | ||
|
|
||
Very Challenging (very + challenging)
Selected AbstractsCurve skeleton skinning for human and creature charactersCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2006Xiaosong Yang Abstract The skeleton driven skinning technique is still the most popular method for animating deformable human and creature characters. Albeit an industry de facto due to its computational performance and intuitiveness, it suffers from problems like collapsing elbow and candy wrapper joint. To remedy these problems, one needs to formulate the non-linear relationship between the skeleton and the skin shape of a character properly, which however proves mathematically very challenging. Placing additional joints where the skin bends increases the sampling rate and is an ad hoc way of approximating this non-linear relationship. In this paper, we propose a method that is able to accommodate the inherent non-linear relationships between the movement of the skeleton and the skin shape. We use the so-called curve skeletons along with the joint-based skeletons to animate the skin shape. Since the deformation follows the tangent of the curve skeleton and also due to higher sampling rates received from the curve points, collapsing skin and other undesirable skin deformation problems are avoided. The curve skeleton retains the advantages of the current skeleton driven skinning. It is easy to use and allows full control over the animation process. As a further enhancement, it is also fairly simple to build realistic muscle and fat bulge effect. A practical implementation in the form of a Maya plug-in is created to demonstrate the viability of the technique. Copyright © 2006 John Wiley & Sons, Ltd. [source] Pulmonary Regurgitation after Tetralogy of Fallot Repair: Clinical Features, Sequelae, and Timing of Pulmonary Valve ReplacementCONGENITAL HEART DISEASE, Issue 6 2007Naser M. Ammash MD ABSTRACT Pulmonary regurgitation following repair of tetralogy of Fallot is a common postoperative sequela associated with progressive right ventricular enlargement, dysfunction, and is an important determinant of late morbidity and mortality. Although pulmonary regurgitation may be well tolerated for many years following surgery, it can be associated with progressive exercise intolerance, heart failure, tachyarrhythmia, and late sudden death. It also often necessitates re-intervention. Identifying the appropriate timing of such intervention could be very challenging given the risk of prosthetic valve degeneration and the increased risk of reoperation. Comprehensive informed and regular assessment of the postoperative patient with tetralogy of Fallot, including evaluation of pulmonary regurgitation, right heart structure and function, is crucial to the optimal care of these patients. Pulmonary valve replacement performed in an experienced tertiary referral center is associated with low operative morbidity and mortality and very good long-term results. Early results of percutaneous pulmonary valve replacement are also promising. [source] Differentiating reactive mesothelial cells from metastatic adenocarcinoma in serous effusions: The utility of immunocytochemical panel in the differential diagnosis,DIAGNOSTIC CYTOPATHOLOGY, Issue 5 2009F.I.A.C., Husain A. Saleh M.D., M.B.A. Abstract Differentiating reactive mesothelial cells (RMs) from metastatic adenocarcinoma cells (MAC) in serous fluids based on cytomorphologic features alone can be very challenging. Various immunocytochemical (ICC) markers have been used to maximize the diagnostic accuracy, however, cytopathologists still encounter difficulties in effusion cytologic diagnosis. The aim of this study was to evaluate previous and recent ICC stains to identify the most sensitive and specific markers and the best panel for differentiating RM from MAC. Cell block sections from 41 MAC and 43 RM effusions cases were subjected to ICC staining for MOC-31, BerEp4, carcinoembryonic antigen (CEA), calretinin, HBME-1, CK5/6, and D2-40. For the MAC cases, the sensitivity of BerEp4, MOC-31, and CEA was 82.9, 92.6, and 17%, respectively, and the specificity was 95.3, 93, and 100%, respectively. For the RM cases, the sensitivity of calretinin, CK5/6, D2-40, and HBME-1 was 95.3, 27.9, 58.1, and 93%, respectively, and the specificity was 70.7, 73.1, 75.6, and 82.9%, respectively. The results show that BerEp4 and MOC-31 are highly sensitive and specific for detecting MAC, whereas calretinin and HBME1 are highly sensitive but only modestly specific for detecting RM cases (P < 0.05). Forced entry logistic regression revealed that using MOC-31, BerEp4, HBME-1, and calretinin, is an excellent panel for making correct diagnosis with 97.6% sensitivity in detecting MAC and 90.7% specificity in detecting RM. We conclude that adding a panel of MOC-31, BerEp4, calretinin, and HBME-1 immunostains to routine cytomorphologic features can greatly enhance the diagnostic accuracy of serous effusions. Diagn. Cytopathol. 2009. © 2009 Wiley-Liss, Inc. [source] Removal of high-abundance proteins for nuclear subproteome studies in rice (Oryza sativa) endospermELECTROPHORESIS, Issue 3 2008Guosheng Li Abstract Endosperm is a highly specialized storage organ with three sets of genomes. It is one of the most economically important organs in plants. Endosperm development involves parental imprinting and endoreduplication. A thorough study of the endosperm proteome, particularly the nuclear proteome, may provide critical insight into the regulation of seed development. Unfortunately, endosperm is extremely rich in starch grains and protein bodies of different sizes, making proteome studies on nonstorage proteins, particularly the low-abundance proteins, very challenging. Here we have developed a chromatographic method to remove large starch grains and an electrophoresis method to recover low-abundance proteins, respectively. Using these methods, we have identified 468 proteins from the nuclear enriched fraction of rice endosperm, including transcription factors, histone modification proteins, kinetochore proteins, centromere/microtubule binding proteins, and transposon proteins. Among the 468 proteins, 208 (44%) are hypothetical proteins, indicating that the endosperm proteome is poorly explored. In addition, analyses of the MS/MS data using BioWorks 3.1 have identified 59 putative acetylated proteins and 40 putative methylated proteins. Our studies have developed a method to remove starch grains and recover low-abundance proteins, respectively. The methods should be applicable to other organisms. [source] An allosteric DNAzyme with dual RNA-cleaving and DNA-cleaving activitiesFEBS JOURNAL, Issue 11 2010Dazhi Jiang A series of RNA-cleaving or DNA-cleaving DNAzymes have been obtained by in vitro selection. However, engineering an allosteric DNAzyme with dual RNA-cleaving and DNA-cleaving activities is very challenging. We used an in vitro -selected pistol-like (PL) DNAzyme as a DNA scaffold for designing a DNAzyme with dual catalytic activities. We prepared the 46-nucleotide DNAzyme with DNA-cleaving activity (PL DNAzyme), and then grafted the deoxyribonucleotide residues from an 8,17 variant DNAzyme into the region of stem,loop I and the catalytic core of the PL DNAzyme scaffold. This deoxyribonucleotide residue grafting resulted in a DNAzyme with dual RNA-cleaving and DNA-cleaving activities (DRc DNAzyme). Drc DNAzyme has properties different from those of the original PL DNAzyme, including DNA cleavage sites and the required metal ion concentration. Interestingly, the RNA substrate and RNase A can act as effectors to mediate the DNA cleavage. Our results show that RNA-cleaving and DNA-cleaving activities simultaneously coexist in DRc DNAzyme, and the DNA cleavage activity can be reversibly regulated by a conformational transition. [source] A measurement-communication-recognition framework of corporate culture change: An empirical studyHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2002Kwai-Sang Chin Company culture, consisting of a shared pattern of basic values, beliefs, and organizational assumptions, is widely accepted as a powerful force to drive performance-enhancing behavior in an organization. Changing a well-established culture is, however, a highly complex issue. It is thus very challenging to implement a new organizational culture. This article presents the measurement-communication-recognition (MCR) framework to manage culture changes in an organization. Ten cultural elements are strategically identified, whereas a four-stage approach of implementation methodology is proposed in the framework. © 2002 Wiley Periodicals, Inc. [source] Zero Shrinkage of LTCC by Self-Constrained SinteringINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2005Torsten Rabe Low shrinkage in x and y direction and low tolerances of shrinkage are an indispensable precondition for high-density component configuration. Therefore, zero shrinkage sintering technologies as pressure-assisted sintering and sacrificial tapes have been introduced in the low-temperature co-fired ceramics (LTCC) production by different manufacturers. Disadvantages of these methods are high costs of sintering equipment and an additional process step to remove the sacrificial tapes. In this article, newly developed self-constrained sintering methods are presented. The new technology, HeraLock®, delivers LTCC modules with a sintering shrinkage in x and y direction of less than 0.2% and with a shrinkage tolerance of ±0.02% without sacrificial layers and external pressure. Each tape is self-constrained by integration of a layer showing no shrinkage in the sintering temperature range of the LTCC. Large area metallization, integration of channels, cavities and passive electronic components are possible without waviness and camber. Self-constrained laminates are an alternative way to produce zero shrinkage LTCC. They consist of tapes sintering at different temperature intervals. Precondition for a successful production of a self-constrained LTCC laminate is the development of well-adapted material and tapes, respectively. This task is very challenging, because sintering range, high-temperature reactivity and thermal expansion coefficient have to be matched and each tape has to fulfill specific functions in the final component, which requires the tailoring of many properties as permittivity, dielectric loss, mechanical strength, and roughness. A self-constrained laminate is introduced in this article. It consists of inner tapes sintering at especially low-temperature range between 650°C and 720°C and outer tapes with an as-fired surface suitable for thin-film processes. [source] Talairach-Based Parcellation of Neonatal Brain Magnetic Resonance Imaging Data: Validation of a New ApproachJOURNAL OF NEUROIMAGING, Issue 4 2005Haissam Haidar PhD ABSTRACT Background and Purpose. Talairach-based parcellation (TP) of human brain magnetic resonance imaging (MRI) data has been used increasingly in clinical research to make regional measurements of brain structures in vivo. Recently, TP has been applied to pediatric research to elucidate the changes in regional brain volumes related to several neurological disorders. However, all freely available tools have been designed to parcellate adult brain MRI data. Parcellation of neonatal MRI data is very challenging owing to the lack of strong signal contrast, variability in signal intensity within tissues, and the small size and thus difficulty in identifying small structures used as landmarks for TP. Hence the authors designed and validated a new interactive tool to parcellate brain MRI data from newborns and young infants. Methods. The authors' tool was developed as part of a postprocessing pipeline, which includes registration of multichannel MR images, segmentation, and parcellation of the segmented data. The tool employs user-friendly interactive software to visualize and assign the anatomic landmarks required for parcellation, after which the planes and parcels are generated automatically by the algorithm. The authors then performed 3 sets of validation experiments to test the precision and reliability of their tool. Results. Validation experiments of intra-and interrater reliability on data obtained from newborn and 1-year-old children showed a very high sensitivity of >95% and specificity >99.9%. The authors also showed that rotating and reformatting the original MRI data results in a statistically significant difference in parcel volumes, demonstrating the importance of using a tool such as theirs that does not require realignment of the data prior to parcellation. Conclusions. To the authors' knowledge, the presented approach is the first TP method that has been developed and validated specifically for neonatal brain MRI data. Their approach would also be valuable for the analysis of brain MRI data from older children and adults. [source] Three metaphors and a (mis)quote: thinking about staffing-outcomes research, health policy and the future of nursingJOURNAL OF NURSING MANAGEMENT, Issue 2 2009FAAN, SEAN P. CLARKE RN Conducting research on nurse staffing and outcomes is very challenging, and the application of staffing-outcomes research in practice is both fraught with controversy and vitally important for the safety of our patients and the future of the profession. As I stand back and think about being involved in staffing-outcomes research for nearly a decade and sharing many of my thoughts about this rapidly growing literature in reviews and commentaries in print, certain metaphors for trends in this field come to mind. I won't claim originality for the insights that follow or attempt to thoroughly trace the genealogy of the stories and metaphors here, but offer them to provide what I hope is a fresh perspective to material that I and many of my colleagues have visited and revisited on numerous occasions. [source] Up against the edge: invasive species as testbeds for basic questions about evolution in heterogeneous environmentsMOLECULAR ECOLOGY, Issue 21 2009ROBERT D. HOLT Yogi Berra is often credited, with having opined that ,prediction is very difficult, especially about the future'. There is no discipline for which this statement holds with more force than invasion biology, where it has been historically very challenging to predict the fate of introduced species (Williamson 2006). Some species after introduction quickly go extinct. Other relatively similar species may persist, but with little spread from their initial beachheads. Yet others can become aggressive invaders, with devastating consequences for native communities and ecosystems. This lack of predictability may of course sometimes reflect a simple lack of knowledge, both about key features of a species' basic biology, and about the environmental and community milieu in which invasion occurs (Williamson 2006). However, unpredictability may also arise from a fundamental fact about populations of living organisms , they almost always contain genetic variation, and so are not fixed entities responding to an environmental template, but instead labile in how they cope with the environment, over many spatial and temporal scales. Chance vicissitudes in the origination, maintenance and spatial organization of genetic variation could play a large role in generating the observed unpredictability in the fates of introduced species. The degree to which a particular introduced species becomes ,invasive', to the extent of coming to the attention of worried land managers, governmental officials and the public , may reflect in part its capacity for adaptive evolution across a wide range of environmental conditions. [source] Effectual dispersion of carbon nanofibers in polyetherimide composites and their mechanical and tribological propertiesPOLYMER ENGINEERING & SCIENCE, Issue 10 2010Bin Li The use of proliferation of nanotechnology in commercial applications is driving requirements for minimal chemical processing and simple processes in industry. Carbon nanofiber (CNF) products possess very high purity levels without the need of purification processing before use and are in growing demand for this quality. Polyetherimide (PEI) has excellent mechanical and thermal performance, but its high viscosity makes its nanocomposites processing very challenging. In this study, a facile melt-mixing method was used to fabricate PEI nanocomposites with as received and physically treated CNFs. The dispersion of CNFs was characterized by scanning electron microscopy, transmitted optical microscopy, and electrometer with large-area electrodes. The results showed that the facile and powerful melt-mixing method is effective in homogeneously dispersing CNFs in the PEI matrix. The flexural and tribological characteristics were investigated and the formation of spatial networks of CNFs and weak interfacial bonding were considered as competitive factors to enhanced flexural properties. The composites with 1.0 wt% CNFs showed flexural strength and toughness increased by more than 50 and 550%, respectively, but showed very high wear rate comparable with that of pure PEI. The length of the CNFs also exerted great influences on both mechanical and tribological behaviors. POLYM. ENG. SCI., 50:1914,1922, 2010. © 2010 Society of Plastics Engineers [source] Targeted lipidomics using electron capture atmospheric pressure chemical ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2003Seon Hwa Lee There is an increasing need to be able to conduct quantitative lipidomics analyses as a complement to proteomics studies. The highest specificity for proteomics analysis can be obtained using methodology based on electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) coupled with liquid chromatography/tandem mass spectrometry (LC/MS/MS). For lipidomics analysis it is often necessary to be able to separate enantiomers and regioisomers. This can be very challenging when using methodology based on conventional reversed-phase chromatography. Normal-phase chromatography using chiral columns can provide dramatic improvements in the resolution of enantiomers and regioisomers. However, conventional ESI- and APCI-MS/MS has limited sensitivity, which makes it difficult to conduct studies in cell culture systems where only trace amounts of non-esterified bioactive lipids are present. The use of electron capture APCI-MS/MS overcomes this problem. Enantiomers and regioisomers of diverse bioactive lipids can be quantified using stable isotope dilution methodology coupled with normal-phase chiral chromatography and electron capture APCI-MS/MS. This methodology has allowed a lipidomics profile from rat epithelial cells maintained in culture to be delineated and allowed the effect of a non-selective lipoxygenase inhibitor to be assessed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Possible health impact of phytoestrogens and xenoestrogens in food,APMIS, Issue 3 2001Dolores Ibarreta Plants produce estrogen-like substances, denominated phytoestrogens, which are present in many human foodstuffs. The consumption of phytoestrogens has been associated with a variety of protective effects. Their relative estrogenic potency combined with their concentrations in food and human plasma indicate biological relevance. However, their biological properties differ from those of estradiol or other endogenous estrogens in humans. For instance, their possible effects on SHBG, inhibition of steroid metabolizing enzymes, anti-proliferative and anti-angiogenetic and other side effects have been described. Furthermore, phytoestrogens can exert estrogenic and antiestrogenic activities at the same time and their potency and metabolism have not been yet elucidated in all cases. In recent decades growing evidence has accumulated on the hormone-like effects of synthetic chemicals that appeared in the environment. The possible impact of xenoestrogens, to which humans are also exposed through the food chain, needs to be further clarified as well. The molecular effects and control mechanisms of these substances, their pharmacokinetics, threshold levels and dose-response differences are issues that require further research before a full assessment of their effect on humans can be drawn. Evaluating the total exposure and impact of this estrogenic effect is very challenging because of the lack of specific knowledge in some areas and the differences in the biological activity among these substances, as pinpointed in this review. [source] Subtype-selective targeting of voltage-gated sodium channelsBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2009Steve England Voltage-gated sodium channels are key to the initiation and propagation of action potentials in electrically excitable cells. Molecular characterization has shown there to be nine functional members of the family, with a high degree of sequence homology between the channels. This homology translates into similar biophysical and pharmacological properties. Confidence in some of the channels as drug targets has been boosted by the discovery of human mutations in the genes encoding a number of them, which give rise to clinical conditions commensurate with the changes predicted from the altered channel biophysics. As a result, they have received much attention for their therapeutic potential. Sodium channels represent well-precedented drug targets as antidysrhythmics, anticonvulsants and local anaesthetics provide good clinical efficacy, driven through pharmacology at these channels. However, electrophysiological characterization of clinically useful compounds in recombinant expression systems shows them to be weak, with poor selectivity between channel types. This has led to the search for subtype-selective modulators, which offer the promise of treatments with improved clinical efficacy and better toleration. Despite developments in high-throughput electrophysiology platforms, this has proven very challenging. Structural biology is beginning to offer us a greater understanding of the three-dimensional structure of voltage-gated ion channels, bringing with it the opportunity to do real structure-based drug design in the future. This discipline is still in its infancy, but developments with the expression and purification of prokaryotic sodium channels offer the promise of structure-based drug design in the not too distant future. [source] Correlative analysis of gene expression profile and prognosis in patients with gliomatosis cerebriCANCER, Issue 16 2009Oscar Fernando D'Urso PhD Abstract BACKGROUND: In modern clinical neuro-oncology, the pathologic diagnoses are very challenging, creating significant clinical confusion and affecting therapeutic decisions and prognosis. METHODS: TP53 and PTEN gene sequences were analyzed, and microarray expression profiling was also performed. The authors investigated whether gene expression profiling, coupled with class prediction methodology, could be used to determine the prognosis of gliomatosis cerebri in a more consistent manner than standard pathology. RESULTS: The authors reported the results of a molecular study in 59 cases of gliomatosis cerebri, correlating these results with prognosis. The well-known prognostic factors of gliomas (ie, age, Karnofsky performance status, histology [grade 2 vs 3], and contrast enhancement) were found to be predictive of response or outcome in only a percentage of patients but not in all patients. The authors identified a 23-gene signature that was able to predict patient prognosis with microarray gene expression profiling. With the aim of producing a prognosis tool that is useful in clinical investigation, the authors studied the expression of this 23-gene signature by real-time quantitative polymerase chain reaction. Real-time expression values relative to these 23 gene features were used to build a prediction method able to distinguish patients with a good prognosis (those more likely to be responsive to therapy) from patients with a poor prognosis (those less likely to be responsive to therapy). CONCLUSIONS: The results of the current study demonstrated not only a strong association between gene expression patterns and patient survival, but also a robust replicability of these gene expression,based predictors. Cancer 2009. © 2009 American Cancer Society. [source] Surgical treatment of recurrent endometrial carcinomaCANCER, Issue 1 2004Elio Campagnutta M.D. Abstract BACKGROUND Surgery does not have a definite role in the treatment of patients with recurrent endometrial carcinoma, except for those with central pelvic recurrences. The authors describe their experience with surgery in patients with abdominal endometrial recurrences. METHODS Between 1988 and 2000, 75 patients with abdominal and pelvic endometrial recurrences underwent secondary rescue surgery. Patients were classified according to the presence or absence of residual tumor after surgery. Therapy after rescue surgery was undertaken at the discretion of the medical oncologist. The progression-free interval and overall survival were defined as the time from secondary rescue surgery to the specific event and were evaluated by the Kaplan,Meier method and the log-rank test. A Cox proportional hazards regression model was used to compare survival with covariates. RESULTS Fifty-six patients (74.7%) underwent optimal debulking. Major surgical complications were observed in 23 patients (30.7%). Only 1 postoperative death was observed, although the mortality rate for surgical complications after the postoperative period was 8%. Patients who underwent optimal debulking had a significantly better cumulative survival rate compared with patients who had residual disease (36% vs. 0% at 60 months; P < 0.05). Residual disease, chemotherapy after rescue surgery, and central pelvis,vagina as the only site of recurrence were associated significantly with survival. CONCLUSIONS The authors found that this approach was very challenging in terms of the procedures involved, the incidence of major surgical complications, and the high mortality rate. It was useful in increasing overall survival, provided that patients were free of macroscopic disease. Careful selection of patients is needed to minimize mortality. Cancer 2004;100:89,96. © 2003 American Cancer Society. [source] | |||||||||||||||||||