On the Mechanical Properties and Microstructure of Nitinol forBiomedical Stent Applications

This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents. The research is aimed at addressing two of the primary failure modes in Nitinol endovascular stents: fatigue-crack growth and overload fracture. The small dimensions of stents, coupled with their complex geometries and variability among manufacturers, make it virtually impossible to determine generic material constants associated with specific devices. Instead, the research utilizes a hybrid of standard test techniques (fracture mechanics and x-ray micro-diffraction) and custom-designed testing apparatus for the determination of the fracture properties of specimens that are suitable representations of self-expanding Nitinol stents. Specifically, the role of texture (crystallographic alignment of atoms) and the austenite-to-martensite phase transformation on the propagation of cracks in Nitinol was evaluated under simulated body conditions and over a multitude of stresses and strains. The results determined through this research were then used to create conservative safe operating and inspection criteria to be used by the biomedical community for the determination of specific device vulnerability to failure by fracture and/or fatigue

Cluster Analysis of Typhoon Tracks. Part II: Large-Scale Circulation and ENSO

A new probabilistic clustering method, based on a regression mixture model, is used to describe tropical cyclone (TC) propagation in the western North Pacific (WNP). Seven clusters were obtained and described in Part I of this two-part study. In Part II, the present paper, the large-scale patterns of atmospheric circulation and sea surface temperature associated with each of the clusters are investigated, as well as associations with the phase of the El Niño–Southern Oscillation (ENSO). Composite wind field maps over the WNP provide a physically consistent picture of each TC type, and of its seasonality. Anomalous vorticity and outgoing longwave radiation indicate changes in the monsoon trough associated with different types of TC genesis and trajectory. The steering winds at 500 hPa are more zonal in the straight-moving clusters, with larger meridional components in the recurving ones. Higher values of vertical wind shear in the midlatitudes also accompany the straight-moving tracks, compared to the recurving ones. The influence of ENSO on TC activity over the WNP is clearly discerned in specific clusters. Two of the seven clusters are typical of El Niño events; their genesis locations are shifted southeastward and they are more intense. The largest cluster is recurving, located northwestward, and occurs more often during La Niña events. Two types of recurving and one of straight-moving tracks occur preferentially when the Madden–Julian oscillation is active over the WNP region

Reverse doming of the anterior mitral leaflet with severe aortic regurgitation

The normal anatomic relation of the anterior mitral leaflet to the left ventricular outflow tract suggests that significant aortic regurgitation should have a predictable hemodynamic effect on the motion and configuration of the leaflet, an effect that should be seen by two-dimensional echocardiography. Previous reports have identified an abnormality of mitral opening in the short-axis view that was quite specific but not sensitive. This study was undertaken to evaluate mitral valve motion and configuration in aortic insufficiency using two-dimensional echocardiography. A characteristic pattern of anterior leaflet motion was found in patients with moderately severe and severe aortic regurgitation. This pattern, termed “reverse doming,” was seen in the apical and long-axis views in 19 of 22 such patients. The previously described “diastolic indentation” in the short-axis view was found in 16 of these 22 patients. Only 2 of 16 patients with lesser degrees of insufficiency had reverse doming. The sign was not seen in normal subjects nor in 16 patients with cardiomyopathy. For each of the few false positive and false negative findings, there is a seemingly logical hemodynamic explanation.It is concluded that reverse doming of the anterior mitral leaflet appears to be a sensitive and specific sign for moderately severe and severe aortic regurgitation

Overview of the spectrometer optical fiber feed for the Habitable-zone Planet Finder

The Habitable-zone Planet Finder (HPF) is a highly stabilized fiber fed precision radial velocity (RV) spectrograph working in the Near Infrared (NIR): 810 - 1280 nm . In this paper we present an overview of the preparation of the optical fibers for HPF. The entire fiber train from the telescope focus down to the cryostat is detailed. We also discuss the fiber polishing, splicing and its integration into the instrument using a fused silica puck. HPF was designed to be able to operate in two modes, High Resolution (HR- the only mode mode currently commissioned) and High Efficiency (HE). We discuss these fiber heads and the procedure we adopted to attach the slit on to the HR fibers.Comment: Presented at 2018 SPIE Astronomical Telescopes + Instrumentation, Austin, Texas, USA. 18 pages, 25 figures, and 2 table

The incidence and clinical burden of respiratory syncytial virus disease identified through hospital outpatient presentations in Kenyan children

There is little information that describe the burden of respiratory syncytial virus (RSV) associated disease in the tropical African outpatient setting. Methods We studied a systematic sample of children aged <5 years presenting to a rural district hospital in Kenya with acute respiratory infection (ARI) between May 2002 and April 2004. We collected clinical data and screened nasal wash samples for RSV antigen by immunofluorescence. We used a linked demographic surveillance system to estimate disease incidence. Results Among 2143 children tested, 166 (8%) were RSV positive (6% among children with upper respiratory tract infection and 12% among children with lower respiratory tract infection (LRTI). RSV was more likely in LRTI than URTI (p<0.001). 51% of RSV cases were aged 1 year or over. RSV cases represented 3.4% of hospital outpatient presentations. Relative to RSV negative cases, RSV positive cases were more likely to have crackles (RR = 1.63; 95% CI 1.34–1.97), nasal flaring (RR = 2.66; 95% CI 1.40–5.04), in-drawing (RR = 2.24; 95% CI 1.47–3.40), fast breathing for age (RR = 1.34; 95% CI 1.03–1.75) and fever (RR = 1.54; 95% CI 1.33–1.80). The estimated incidence of RSV-ARI and RSV-LRTI, per 100,000 child years, among those aged <5 years was 767 and 283, respectively. Conclusion The burden of childhood RSV-associated URTI and LRTI presenting to outpatients in this setting is considerable. The clinical features of cases associated with an RSV infection were more severe than cases without an RSV diagnosis

Downscaling projections of Indian monsoon rainfall using a non-homogeneous hidden Markov model

Downscaled rainfall projections for the Indian summer monsoon are generated using a non-homogeneous hidden Markov model (NHMM) and information from both a dense observational dataset and an ensemble of general circulation models (GCMs). The projections are conditioned on two types of GCM information, corresponding approximately to dynamic and thermodynamic components of precipitation change. These have opposing effects, with a weakening circulation compensating not quite half of the regional precipitation increase that might otherwise be expected. GCM information is taken at the largest spatial scales consistent with regional physics and modelling constraints, while the NHMM produces a disaggregation consistent with the observed fine-scale spatiotemporal variability. Projections are generated using multimodel mean predictors, with intermodel dispersion providing a measure of the uncertainty due to GCM differences. The downscaled simulations exhibit small increases in the number of dry days, in the average length of dry spells, in mean daily intensity and in the exceedance frequency of nearly all daily rainfall percentiles

Efficacy of CMX001 as a Prophylactic and Presymptomatic Antiviral Agent in New Zealand White Rabbits Infected with Rabbitpox Virus, a Model for Orthopoxvirus Infections of Humans

CMX001, a lipophilic nucleotide analog formed by covalently linking 3-(hexdecyloxy)propan-1-ol to cidofovir (CDV), is being developed as a treatment for smallpox. CMX001 has dramatically increased potency versus CDV against all dsDNA viruses and, in contrast to CDV, is orally available and has shown no evidence of nephrotoxicity in healthy volunteers or severely ill transplant patients to date. Although smallpox has been eliminated from the environment, treatments are urgently being sought due to the risk of smallpox being used as a bioterrorism agent and for monkeypox virus, a zoonotic disease of Africa, and adverse reactions to smallpox virus vaccinations. In the absence of human cases of smallpox, new treatments must be tested for efficacy in animal models. Here we first review and discuss the rabbitpox virus (RPV) infection of New Zealand White rabbits as a model for smallpox to test the efficacy of CMX001 as a prophylactic and early disease antiviral. Our results should also be applicable to monkeypox virus infections and for treatment of adverse reactions to smallpox vaccination

An Optical Backplane Demonstrator System Based on FET-SEED Smart Pixel Arrays and Diffractive Lenslet Arrays

We have demonstrated a representative portion of an optical backplane using FET-SEED smart pixels and free-space optics to interconnect printed circuit boards (PCB\u27s) in a two board, unidirectional link configuration. 4×4 arrays of FET-SEED transceivers were designed, fabricated, and packaged all the PCB level, The optical interconnection was constructed using diffractive microoptics, and custom optomechanics. The system was operated in two modes, one showing high data throughput, 100 MBit/sec, and the other demonstrating large connection densities, 2222 channel/cm2

Electronic structure and ferroelectricity in SrBi2Ta2O9

The electronic structure of SrBi2Ta2O9 is investigated from first-principles, within the local density approximation, using the full-potential linearized augmented plane wave (LAPW) method. The results show that, besides the large Ta(5d)-O(2p) hybridization which is a common feature of the ferroelectric perovskites, there is an important hybridization between bismuth and oxygen states. The underlying static potential for the ferroelectric distortion and the primary source for ferroelectricity is investigated by a lattice-dynamics study using the Frozen Phonon approach.Comment: 17 pages, 7 figures. Phys. Rev. B, in pres

Activation of an Endogenous Retrovirus-Associated Long Non-Coding RNA in Human Adenocarcinoma

Background Long non-coding RNAs (lncRNAs) are emerging as molecules that significantly impact many cellular processes and have been associated with almost every human cancer. Compared to protein-coding genes, lncRNA genes are often associated with transposable elements, particularly with endogenous retroviral elements (ERVs). ERVs can have potentially deleterious effects on genome structure and function, so these elements are typically silenced in normal somatic tissues, albeit with varying efficiency. The aberrant regulation of ERVs associated with lncRNAs (ERV-lncRNAs), coupled with the diverse range of lncRNA functions, creates significant potential for ERV-lncRNAs to impact cancer biology. Methods We used RNA-seq analysis to identify and profile the expression of a novel lncRNA in six large cohorts, including over 7,500 samples from The Cancer Genome Atlas (TCGA). Results We identified the tumor-specific expression of a novel lncRNA that we have named Endogenous retroViral-associated ADenocarcinoma RNA or ‘EVADR’, by analyzing RNA-seq data derived from colorectal tumors and matched normal control tissues. Subsequent analysis of TCGA RNA-seq data revealed the striking association of EVADR with adenocarcinomas, which are tumors of glandular origin. Moderate to high levels of EVADR were detected in 25 to 53% of colon, rectal, lung, pancreas and stomach adenocarcinomas (mean&thinsp;=&thinsp;30 to 144 FPKM), and EVADR expression correlated with decreased patient survival (Cox regression; hazard ratio&thinsp;=&thinsp;1.47, 95% confidence interval&thinsp;=&thinsp;1.06 to 2.04, P&thinsp;=&thinsp;0.02). In tumor sites of non-glandular origin, EVADR expression was detectable at only very low levels and in less than 10% of patients. For EVADR, a MER48 ERV element provides an active promoter to drive its transcription. Genome-wide, MER48 insertions are associated with nine lncRNAs, but none of the MER48-associated lncRNAs other than EVADR were consistently expressed in adenocarcinomas, demonstrating the specific activation of EVADR. The sequence and structure of the EVADR locus is highly conserved among Old World monkeys and apes but not New World monkeys or prosimians, where the MER48 insertion is absent. Conservation of the EVADR locus suggests a functional role for this novel lncRNA in humans and our closest primate relatives. Conclusions Our results describe the specific activation of a highly conserved ERV-lncRNA in numerous cancers of glandular origin, a finding with diagnostic, prognostic and therapeutic implications