Shyam Gouri Suresh

ARTSENS - An image-free system for noninvasive evaluation of arterial compliance

Evaluation of arterial compliance is significant in cardiovascular diagnosis for early detection of coronary heart disease. We present ARTSENS, an image-free system for non-invasive evaluation of arterial compliance in-vivo. The system utilizes a single element ultrasound probe with intelligent measurement algorithms to ensure accurate evaluation of local arterial compliance without an image. The ability of the system to detect artery anatomy and measure compliance was verified by in-vivo measurements conducted on 106 subjects. The accuracy of compliance estimates were evaluated by comparison with a state of art imaging system. The measurements made using ARTSENS showed strong correlation with those made using the imaging system. The ability of ARTSENS to detect age-related trends in arterial compliance was also investigated.

Firm performance, macroeconomic conditions, and “animal spirits” in a Post Keynesian model of aggregate fluctuations

Abstract: We construct a multiagent system (MAS) model of cyclical growth in which aggregate fluctuations result from variations in activity at the firm level. The latter, in turn, result from changes in “animal spirits” or the state of long-run expectations (SOLE) and their effect on firms’ investment behavior. We focus on the impact of publicly available information about macroeconomic conditions—analogous to the press releases of national statistical agencies—on changes in the SOLE and hence the amplitude of aggregate fluctuations. Our results suggest that the amplitude of fluctuations is reduced by extremes of attention or inattention to aggregate economic performance, but that this relationship is subject to complicated (and possibly complex) phase transitions exhibiting extreme sensitivity to initial conditions.

Aggregate Structural Macroeconomic Modelling: A Reconsideration and Defence

Aggregate structural macroeconomic modelling (ASMM) is frequently criticized for being ad hoc and justified (if at all) only as a pragmatic expedient. This paper argues instead that ASMM is consistent with the principles of well-established bodies of social theory. Appeal to these principles reveals that aggregate-level analysis of the type exemplified by ASMM is likely necessary and (in some circumstances) certainly sufficient for the successful prosecution of macroeconomic enquiry.

Non-invasive estimation of arterial compliance

The evaluation of arterial compliance is very important in cardiovascular screening of “at-risk” patients. Existing techniques for local arterial stiffness estimation put a premium on technology and operator expertise. Regional stiffness, measured in terms of the pulse wave velocity, is prone to errors in both path-length and delay estimation. Here, we present a Virtual Instrument (VI) for automated estimation of both local and regional arterial compliance measures. Local arterial compliance is evaluated by utilizing an ultrasound transducer to measure the distension and lumen diameter of the carotid artery. The regional stiffness is estimated from the pulse wave velocity, measured using two magnetic transducers in a dual-channel arrangement. The automated measurement algorithms are thoroughly analyzed, to identify and minimize possible error sources as well as to optimize the design of both the transducer and the virtual instrument. The results of a few human trials are also presented to illustrate the capability of the VI to measure arterial compliance in-vivo.

The Consequences of Social Pressures on Partisan Opinion Dynamics

We simulate an agent-based model of opinion dynamics in a two-party framework to analyze party- and polity-wide consequences of social pressures that compel individuals to publicly conform to their party line. The model indicates that opinions polarize over time despite being initialized uniformly across most members of both parties. Further, the socially acceptable range of opinions in each party and the level of partisanship prevalent in the polity play an important role in determining the membership sizes of both parties, the median opinions of both parties and the polity, and the level of polarization within and across parties.

Did CNBC Contribute to the Great Moderation or the Great Recession

We construct a multi-agent system (MAS) model of cyclical growth in which aggregate fluctuations result from variations in activity at firm level. The latter, in turn, result from changes in the state of long run expectations (SOLE) or “animal spirits” and their effect on firms’ investment behaviour. We focus on the impact of a common source of information – analogous to the mass media – on the amplitude of aggregate fluctuations. Our results suggest that the amplitude of growth cycles is reduced by extremes of attention or inattention to aggregate economic performance, but that this relationship is subject to complicated (and possibly complex) phase transitions.