A comparative study of complex multiple-band noise-shaping sigma-delta modulators for multi-tone input signals

This paper presents a comparative study of complex single-bit and multi-bit sigma-delta modulators that are capable of providing concurrent multiple-band noise-shaping for multi-tone narrow-band input signals. The concepts applied for the three design methodologies are based on the noise transfer functions of complex comb, complex slink and complex multi-notch filters.

Methods for the transfer function design of multiple narrow-band bandpass sigma-delta modulators

This paper presents the design analysis of novel tunable narrow-band bandpass sigma-delta modulators, which can achieve concurrent multiple noise-shaping for multi-tone input signals. Four different design methodologies based on the noise transfer functions of comb filters, slink filters, multi-notch filters and fractional delay comb filters are applied for the design of these multiple-band sigma-delta modulators. The latter approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter-based sigma-delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies. The merits and drawbacks of each technique for the various sigma-delta topologies are assessed in terms of in-band signal-to-noise ratios, accuracy of tunability and coefficient complexity for ease of implementation.

Increasing the variability of centre frequency locations in multiple-band sigma-delta modulators via the use of fractional delay filters

This paper presents the design analysis of novel tunable narrow-band bandpass sigma-delta modulators, that can achieve concurrent multiple noise-shaping for multi-tone input signals. This approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter based sigma-delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies.

Labour and the free churches 1918-1939: radicalism, righteousness and religion

It is a commonplace that the labour movement was somehow nurtured within the witness for liberty of the Free Churches. Exploring this at a range of levels - including organisation, rhetoric, policies, electoral politics and people - this book demonstrates the extent to which this remained a reality into the inter-war years. The distinctive religious setting in which it emerged indeed helps to explain the differences between Labour and more Marxist counterparts on the Continent. It is shown here that this setting continued to influence Labour approaches towards welfare, nationalisation and industrial relations between the wars. In the process Labour also adopted some of the righteousness of tone of the Free Churches. This setting was, however, changing. Dropping their traditional suspicion of the State, Nonconformists instead increasingly invested it with religious values, turning it through its growing welfare functions into the provider of practical Christianity. This nationalisation of religion continues to shape British attitudes to the welfare state as well as imposing narrowly utilitarian and material tests of relevance upon the churches and other social institutions. The elevation of the State was not, however, intended as an end in itself. What mattered were the social and individual outcomes. Socialism, for those Free Churchmen and women who helped to shape Labour in the early twentieth century, was about improving society as much as systems.

Unnoticed apocalypse: the science fiction politics of urban crisis

The slogan ‘capitalism is crisis’ is one that has recently circulated swiftly around the global Occupy movement. From Schumpeter to Marx himself, the notion that the economic cycles instituted by capitalism require periodic crises as a condition of renewed capital accumulation is a commonplace. However, in a number of recent texts, this conception of crisis as constituting the very form of urban capitalist development itself has taken on a more explicitly apocalyptic tone, exemplified by the Invisible Committee's influential 2007 book The Coming Insurrection, and its account of what it calls simply ‘the metropolis’. ‘It is useless to wait’, write the text's anonymous authors, ‘for a breakthrough, for the revolution, the nuclear apocalypse or a social movement.… The catastrophe is not coming, it is here.’ In considering such an apocalyptic tone, this paper thus situates and interrogates the text in terms both of its vision of the metropolis as a terrain of total urbanization and its effective spatialization of the present as itself a kind of ‘unnoticed’ apocalypse: the catastrophe which is already here. It does so by approaching this not only apropos its place within contemporary debates surrounding leftist politics and crisis theory but also via its imaginative intersection with certain post-1960s science fiction apocalyptic motifs. What, the paper asks, does it mean to think apocalypse as the ongoing condition of the urban present itself, as well as the opening up of political and cultural opportunity for some speculative exit from its supposedly endless terrain?

Circulating pancreatic polypeptide concentrations predict visceral and liver fat content

CONTEXT AND OBJECTIVE: No current biomarker can reliably predict visceral and liver fat content, both of which are risk factors for cardiovascular disease. Vagal tone has been suggested to influence regional fat deposition. Pancreatic polypeptide (PP) is secreted from the endocrine pancreas under vagal control. We investigated the utility of PP in predicting visceral and liver fat. PATIENTS AND METHODS: Fasting plasma PP concentrations were measured in 104 overweight and obese subjects (46 men and 58 women). In the same subjects, total and regional adipose tissue, including total visceral adipose tissue (VAT) and total subcutaneous adipose tissue (TSAT), were measured using whole-body magnetic resonance imaging. Intrahepatocellular lipid content (IHCL) was quantified by proton magnetic resonance spectroscopy. RESULTS: Fasting plasma PP concentrations positively and significantly correlated with both VAT (r = 0.57, P < .001) and IHCL (r = 0.51, P < .001), but not with TSAT (r = 0.02, P = .88). Fasting PP concentrations independently predicted VAT after controlling for age and sex. Fasting PP concentrations independently predicted IHCL after controlling for age, sex, body mass index (BMI), waist-to-hip ratio, homeostatic model assessment 2-insulin resistance, (HOMA2-IR) and serum concentrations of triglyceride (TG), total cholesterol (TC), and alanine aminotransferase (ALT). Fasting PP concentrations were associated with serum ALT, TG, TC, low- and high-density lipoprotein cholesterol, and blood pressure (P < .05). These associations were mediated by IHCL and/or VAT. Fasting PP and HOMA2-IR were independently significantly associated with hepatic steatosis (P < .01). CONCLUSIONS: Pancreatic polypeptide is a novel predictor of visceral and liver fat content, and thus a potential biomarker for cardiovascular risk stratification and targeted treatment of patients with ectopic fat deposition.

Estrogen protects the blood–brain barrier from inflammation-induced disruption and increased lymphocyte trafficking

Sex differences have been widely reported in neuroinflammatory disorders, focusing on the contributory role of estrogen. The microvascular endothelium of the brain is a critical component of the blood–brain barrier (BBB) and it is recognized as a major interface for communication between the periphery and the brain. As such, the cerebral capillary endothelium represents an important target for the peripheral estrogen neuroprotective functions, leading us to hypothesize that estrogen can limit BBB breakdown following the onset of peripheral inflammation. Comparison of male and female murine responses to peripheral LPS challenge revealed a short-term inflammation-induced deficit in BBB integrity in males that was not apparent in young females, but was notable in older, reproductively senescent females. Importantly, ovariectomy and hence estrogen loss recapitulated an aged phenotype in young females, which was reversible upon estradiol replacement. Using a well-established model of human cerebrovascular endothelial cells we investigated the effects of estradiol upon key barrier features, namely paracellular permeability, transendothelial electrical resistance, tight junction integrity and lymphocyte transmigration under basal and inflammatory conditions, modeled by treatment with TNFα and IFNγ. In all cases estradiol prevented inflammation-induced defects in barrier function, action mediated in large part through up-regulation of the central coordinator of tight junction integrity, annexin A1. The key role of this protein was then further confirmed in studies of human or murine annexin A1 genetic ablation models. Together, our data provide novel mechanisms for the protective effects of estrogen, and enhance our understanding of the beneficial role it plays in neurovascular/neuroimmune disease.