Novel Methods for Efficient Changepoint Detection

This thesis introduces several novel computationally efficient methods for offline and online changepoint detection. The first part of the thesis considers the challenge of detecting abrupt changes in scenarios where there is some autocorrelated noise or where the mean fluctuates locally between the changes. In such situations, existing implementations can lead to substantial overestimation of the number of changes. In response to this challenge, we introduce DeCAFS, an efficient dynamic programming algorithm to deal with such scenarios. DeCAFS models local fluctuations as a random walk process and autocorrelated noise as an AR(1) process. Through theory and empirical studies we demonstrate that this approach has greater power at detecting abrupt changes than existing approaches. The second part of the thesis considers a practical, computational challenge that can arise with online changepoint detection within the real-time domain. We introduce a new procedure, called FOCuS, a fast online changepoint detection algorithm based on the simple Page-CUSUM sequential likelihood ratio test. FOCuS enables the online changepoint detection problem to be solved sequentially in time, through an efficient dynamic programming recursion. In particular, we establish that FOCuS outperforms current state-of-the-art algorithms both in terms of efficiency and statistical power, and can be readily extended to more general scenarios. The final part of the thesis extends ideas from the nonparametric changepoint detection literature to the online setting. Specifically, a novel algorithm, NUNC, is introduced to perform an online detection for changes in the distribution of real-time data. We explore the properties of two variants of this algorithm using both simulated and real data examples

CHASING THE RAINBOW: GENDER-RELIGIOSITY AND THE CONSTRUCTION OF IDENITY IN THE MUSIC AND RITUAL OF THE METROPOLITAN COMMUNITY CHURCH OF NORTHERN VIRGINIA

The intersection of belief, identity, and performance enacted in the Metropolitan Community Church of Northern Virginia (MCC NOVA) - a lesbian, gay, bisexual, transgender, queer community of faith, provides an arena for ethnomusicological inquiry into ritual performance and its relationship with identity construction. As a safe-haven for persons marginalized by mainstream religious traditions, MCC NOVA serves as an alternative to historically oppressive and suppressive worshipping environments where LGBTQ lifestyle is often considered antithetical to the goals of religiosity. It grounds ritual and musical practices in its core values: elastic theology, inclusiveness, diversity, community, member-ministers, and love and acceptance. These core values are the basis of a variety of performative events which allow for the self-fashioning of identity and spiritual exploration on both an individual and corporate level. Affected by a variety of "cradle traditions", this LBGTQ group draws on a complex assortment of sacred musics and ritual practices which form a unique gender-religiosity as MCCers journey to describe and re-invent their collective self. MCC NOVA intensifies the experience of faith through its multi-gendered condition, alternative spiritualities, and idiosyncratic performance events by fashioning a Judeo-Christian-based LBGTQ spirituality in light of freedoms which allow for exploration beyond the boundaries of the Christian ordo. This project deals with a series of unexplored important ethnomusicological questions concerning the significance, process, problems, negotiations, and repercussions involved in performing a variety of ritual musics and acts in light of MCC NOVA's central core values. Foremost is the question of the relationship between individual existenz and corporate identity and the role this relationship plays in ritual. The aesthetics which promote this process are a culmination of blended beliefs rooted in LBGTQ lifestyle, concerns about gender, religious priorities, and the historical faith traditions of the congregants. Performances vary in their ability to describe the intersection of these major contributions to identity construction. Therefore, the investigation of a truly gender-religious stance requires a consideration of the behavioral, ritual-musical, and ontological realities of MCC NOVA membership as they interact to construct an identity where liturgy is both source and outcome of this unique religiosity

Expandable intramedullary nailing and platelet rich plasma to treat long bone non-unions

Background Roentgenographic and functional outcomes of expandable self locking intramedullary nailing and platelet rich plasma (PRP) gel in the treatment of long bone non-unions are reported. Materials and methods Twenty-two patients suffering from atrophic diaphyseal long bone non-unions were enrolled in the study. Patients were treated with removal of pre-existing ardware, decortication of non-union fragments, and fixation of pseudoarthrosis with expandable intramedullary nailing (FixionTM, Disc’O Tech, Tel Aviv, Israel). At surgery, PRP was placed in the pseudoarthrosis rim. Results The thirteen-month follow-up showed 91% (20/22 patients) of patients attaining bony union. The average time to union was 21.5 weeks. No infection, neurovascular complication, rotational malalignment, or limb shortening [4 mm were observed. The healing rate of non-unions was comparable to that observed in previous studies but with a lower complication frequency. Conclusions The combined use of self locking intramedullary nailing and PRP in the management of atrophic diaphyseal long bone non-unions seems to produce comparable results with less complications than previously reported. Further data are warranted to investigate the single contribution of PRP gel and Fixion nail

Does a ferromagnet with spin-dependent masses produce a spin-filtering effect in a ferromagnetic/insulator/superconductor junction?

We analyze charge transport through a ballistic ferromagnet/insulator/superconductor junction by means of the Bogoliubov-de Gennes equations. We take into account the possibility that ferromagnetism in the first electrode may be driven by a mass renormalization of oppositely polarized carriers, i.e. by a spin bandwidth asymmetry, rather than by a rigid splitting of up-and down-spin electron bands as in a standard Stoner ferromagnet. By evaluating the averaged charge conductance for both an s- and a $d_{x^2-y^2}$-wave order parameter for the S side, we show that the mass mismatch in the ferromagnetic electrode may mimic a spin active barrier. Indeed, in the $s$-wave case we show that under suitable conditions the spin dependent conductance of minority carriers below the energy gap $\Delta_0$ can be larger than for majority carriers, and lower above $\Delta_0$. On the other hand, for a d_{x^2-y^2}-wave superconductor similar spin-dependent effects give rise to an asymmetric peak splitting in the conductance. These results suggest that the junction may work as a spin-filtering device.Comment: 7 pages, 5 figure

Online Multivariate Changepoint Detection: Leveraging Links With Computational Geometry

The increasing volume of data streams poses significant computational challenges for detecting changepoints online. Likelihood-based methods are effective, but their straightforward implementation becomes impractical online. We develop two online algorithms that exactly calculate the likelihood ratio test for a single changepoint in p-dimensional data streams by leveraging fascinating connections with computational geometry. Our first algorithm is straightforward and empirically quasi-linear. The second is more complex but provably quasi-linear: $\mathcal{O}(n\log(n)^{p+1})$ for $n$ data points. Through simulations, we illustrate, that they are fast and allow us to process millions of points within a matter of minutes up to $p=5$.Comment: 31 pages,15 figure

Two-Dimensional Shear Wave Elastography Versus Transient Elastography: A Non-Invasive Comparison for the Assessment of Liver Fibrosis in Patients With Chronic Hepatitis C

In recent years, several non-invasive methods have been developed for staging liver fibrosis in patients with chronic hepatitis C. A 2D-Shear wave elastography (SWE) technique has been recently introduced on the EPIQ 7 US system (ElastQ), but its accuracy has not been validated in patients with chronic hepatitis C virus (HCV) infection. We enrolled 178 HCV patients to assess their liver fibrosis stage with ElastQ software using transient elastography as a reference standard. The best cut-off values to diagnose ≥ F2, ≥ F3, and F4 were 8.15, 10.31, and 12.65 KPa, respectively. Liver stiffness values had a positive correlation with transient elastography (r = 0.57; p < 0.001). The area under the receiver operating characteristics (AUROC) was 0.899 for ≥ F2 (moderate fibrosis), 0.900 for ≥ F3 (severe fibrosis), and 0.899 for cirrhosis. 2D-SWE has excellent accuracy in assessing liver fibrosis in patients with chronic hepatitis C and an excellent correlation with transient elastograph

Odd-frequency triplet pairing in mixed-parity superconductors

We show that mixed-parity superconductors may exhibit equal-spin pair correlations that are odd-in-time and can be tuned by means of an applied field. The direction and the amplitude of the pair correlator in the spin space turn out to be strongly dependent on the symmetry of the order parameter, and thus provide a tool to identify different types of singlet-triplet mixed configurations. We find that odd-in-time spin-polarized pair correlations can be generated without magnetic inhomogeneities in superconducting/ferromagnetic hybrids when parity mixing is induced at the interface.Comment: 4 pages, 1 figur