Prediction of the Spectrum of a Digital Delta–Sigma Modulator Followed by a Polynomial Nonlinearity

This paper presents a mathematical analysis of the power spectral density of the output of a nonlinear block driven by a digital delta-sigma modulator. The nonlinearity is a memoryless third-order polynomial with real coefficients. The analysis yields expressions that predict the noise floor caused by the nonlinearity when the input is constant

Mind the Gap: Another look at the problem of the semantic gap in image retrieval

This paper attempts to review and characterise the problem of the semantic gap in image retrieval and the attempts being made to bridge it. In particular, we draw from our own experience in user queries, automatic annotation and ontological techniques. The first section of the paper describes a characterisation of the semantic gap as a hierarchy between the raw media and full semantic understanding of the media's content. The second section discusses real users' queries with respect to the semantic gap. The final sections of the paper describe our own experience in attempting to bridge the semantic gap. In particular we discuss our work on auto-annotation and semantic-space models of image retrieval in order to bridge the gap from the bottom up, and the use of ontologies, which capture more semantics than keyword object labels alone, as a technique for bridging the gap from the top down

Maternal and perinatal outcome in severe preeclampsia and eclampsia at the Rivers State university teaching hospital, Nigeria

Background: Severe preeclampsia and eclampsia remain a challenge in tropical obstetric practice. It is a major contributor to feto-maternal morbidity and mortality in developing countries. This study seeks to determine the prevalence, associated risk factors and the feto-maternal outcome of severe preeclampsia and eclampsia at the rivers state university teaching hospital (RSUTH).Method: A retrospective study of all women who had severe preeclampsia and eclampsia and were delivered at the RSUTH in a two-year period, 1ST January 2018 to 31ST December 2019, was carried out. Data on patients’ age, parity, education, booking status, gestational age at delivery, diagnosis, complications, mode of delivery and fetal sex, birth weight and Apgar scores were retrieved using structured pro-forma. Data were analyzed using SPSS version 20.Results: There were 4496 deliveries of which 128 had severe preeclampsia and eclampsia, giving a prevalence of 2.85%. Of these, 94 (73.4%) had severe preeclampsia and 34 (26.6%) had eclampsia. The mean age of the women ± SD was 29.84±5.44 years, median parity was para 1, and mean gestational age ± SD was 35.38±3.84 weeks. There were 10 maternal deaths giving case fatality of 7.8%. The mean birth weight ± SD was 2.61±0.91 kg and stillborn rate was 14.4%. There was significant association with maternal age, education, booking status, method of delivery and Apgar score of the baby.Conclusion: The prevalence in this study is high with associated high maternal mortality and stillborn rates. Timely and appropriate intervention including primary management and judicious termination of pregnancy will reduce mortality of mother and fetus

Bridging the Semantic Gap in Multimedia Information Retrieval: Top-down and Bottom-up approaches

Semantic representation of multimedia information is vital for enabling the kind of multimedia search capabilities that professional searchers require. Manual annotation is often not possible because of the shear scale of the multimedia information that needs indexing. This paper explores the ways in which we are using both top-down, ontologically driven approaches and bottom-up, automatic-annotation approaches to provide retrieval facilities to users. We also discuss many of the current techniques that we are investigating to combine these top-down and bottom-up approaches

Killer Cell Inhibitory Receptor Recognition of Human Leukocyte Antigen (HLA) Class I Blocks Formation of a pp36/PLC-γ Signaling Complex in Human Natural Killer (NK) Cells

The killer cell inhibitory receptors (KIR) of human natural killer (NK) cells recognize human leukocyte antigen class I molecules and inhibit NK cell cytotoxicity through their interaction with protein tyrosine phosphatases (PTP). Here, we report that KIR recognition of class I ligands inhibits distal signaling events and ultimately NK cell cytotoxicity by blocking the association of an adaptor protein (pp36) with phospholipase C-γ in NK cells. In addition, we demonstrate that pp36 can serve as a substrate in vitro for the KIR-associated PTP, PTP-1C (also called SHP-1), and that recognition of class I partially disrupts tyrosine phosphorylation of NK cell proteins, providing evidence for KIR-induced phosphatase activity

Asymptotics of Canonical and Saturated RNA Secondary Structures

It is a classical result of Stein and Waterman that the asymptotic number of RNA secondary structures is $1.104366 n^{-3/2} 2.618034^n$. In this paper, we study combinatorial asymptotics for two special subclasses of RNA secondary structures - canonical and saturated structures. Canonical secondary structures were introduced by Bompf\"unewerer et al., who noted that the run time of Vienna RNA Package is substantially reduced when restricting computations to canonical structures. Here we provide an explanation for the speed-up. Saturated secondary structures have the property that no base pairs can be added without violating the definition of secondary structure (i.e. introducing a pseudoknot or base triple). Here we compute the asymptotic number of saturated structures, we show that the asymptotic expected number of base pairs is $0.337361 n$, and the asymptotic number of saturated stem-loop structures is $0.323954 1.69562^n$, in contrast to the number $2^{n-2}$ of (arbitrary) stem-loop structures as classically computed by Stein and Waterman. Finally, we show that the density of states for [all resp. canonical resp. saturated] secondary structures is asymptotically Gaussian. We introduce a stochastic greedy method to sample random saturated structures, called quasi-random saturated structures, and show that the expected number of base pairs of is $0.340633 n$.Comment: accepted: Journal of Bioinformatics and Computational Biology (2009) 22 page