An intelligent assistant for exploratory data analysis

In this paper we present an account of the main features of SNOUT, an intelligent assistant for exploratory data analysis (EDA) of social science survey data that incorporates a range of data mining techniques. EDA has much in common with existing data mining techniques: its main objective is to help an investigator reach an understanding of the important relationships ina data set rather than simply develop predictive models for selectd variables. Brief descriptions of a number of novel techniques developed for use in SNOUT are presented. These include heuristic variable level inference and classification, automatic category formation, the use of similarity trees to identify groups of related variables, interactive decision tree construction and model selection using a genetic algorithm

Modularity and community detection in bipartite networks

The modularity of a network quantifies the extent, relative to a null model network, to which vertices cluster into community groups. We define a null model appropriate for bipartite networks, and use it to define a bipartite modularity. The bipartite modularity is presented in terms of a modularity matrix B; some key properties of the eigenspectrum of B are identified and used to describe an algorithm for identifying modules in bipartite networks. The algorithm is based on the idea that the modules in the two parts of the network are dependent, with each part mutually being used to induce the vertices for the other part into the modules. We apply the algorithm to real-world network data, showing that the algorithm successfully identifies the modular structure of bipartite networks.Comment: RevTex 4, 11 pages, 3 figures, 1 table; modest extensions to conten

The effect of multiple sclerosis on carotid baroreflex control of heart rate and blood pressure

Multiple sclerosis (MS) is marked by conduction abnormalities within the central nervous system that can lead to impaired blood pressure regulation. However, the impact of this disease on dynamic neural control—responsiveness and timing (i.e., latency)—of blood pressure has not been examined. Utilizing a variable neck chamber system, we tested the hypothesis that patients with MS (MS: n=4) exhibit an altered response following baroreflex perturbation compared to sex and age matched healthy controls (CON: n=4). At rest, 5-sec pulses of neck suction (NS; -60 Torr) and neck pressure (NP; +40 Torr) were applied to simulate carotid hypertension and hypotension, respectively. Mean arterial pressure (MAP; Finometer) and heart rate (HR) were continuously measured in response to the perturbations. Carotid baroreflex (CBR) latencies (i.e., time-to-peak responses) were examined using carotid-cardiac (peak HR responses), carotid-vasomotor (peak MAP responses), and change in MAP at the peak HR response of the corresponding stimuli (MAP@HRpeak), all of which were not significant for both NP and NS. Following NS, responses in MAP (MS: -12±5, CON: -10±3 mmHg; p=0.43) and HR (MS: -9±3, CON: -8±4 BPM; p=0.58) were similar between groups. Following administration of NP, HR responses (MS: 4±2, CON: 5±4 BPM; p=0.47) were no different. However, the differences found in MAP were significant (MS: 5±2, CON: 8±2 mmHg; p=0.05), providing some evidence that baroreceptor responsiveness may be compromised when faced with a hypotensive challenge

Reduced Muscle Sympathetic Nerve Activity Response to a Cold Pressor Test in Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative autoimmune disease characterized by demyelination in the central nervous system leading to potential impairments in the autonomic control of cardiovascular function. We have previously demonstrated individuals with MS exhibit a diminished ability to increase blood pressure in response to a hypotensive stimulus compared with healthy controls likely due to impaired sympathetic modulation of the vasculature. PURPOSE: The aim of the current investigation was to test the hypothesis that muscle sympathetic nerve activity (MSNA) responses to a cold pressor test (CPT) are reduced in individuals with MS compared to healthy controls. METHODS: Four patients with relapsing-remitting MS (2 females/2 males, EDSS \u3c 4) and 4 sex-, age- and mass-matched controls were instrumented for MSNA (peroneal nerve), mean arterial blood pressure (MAP; Finometer), and heart rate (HR). Subjects were exposed to a CPT by immersing a hand in ice water for 2 min. Mean cardiovascular and MSNA responses (burst frequency) at baseline and at 30 sec intervals during the CPT were compared between groups. RESULTS: Heart rate (P\u3c0.001) and MAP (P\u3c0.001) responses increased from baseline throughout the CPT but no group differences were observed (P=0.10 and P=0.78, respectively). At baseline, MSNA was similar between groups (MS: 2 ± 2 vs. CON: 14 ± 9 bursts/min; P=0.239). However, individuals with MS had blunted MSNA responses to CPT compared to healthy controls at 60 seconds (MS: 18 ± 14 vs. CON: 42 ± 10 bursts/min; P=0.033), at 90 seconds (MS: 16 ± 12 vs. CON: 44 ± 10 bursts/min; P=.017) and at 120 seconds (MS: 13 ± 12 vs. CON: 43 ± 13 bursts/min; P=.012). CONCLUSION: Individuals with MS appear to have an attenuated muscle sympathetic response to CPT. However, MAP appears to respond similarly to healthy controls potentially through other compensatory mechanisms