Relationship among research collaboration, number of documents and number of citations. A case study in Spanish computer science production in 2000-2009.

This paper analyzes the relationship among research collaboration, number of documents and number of citations of computer science research activity. It analyzes the number of documents and citations and how they vary by number of authors. They are also analyzed (according to author set cardinality) under different circumstances, that is, when documents are written in different types of collaboration, when documents are published in different document types, when documents are published in different computer science subdisciplines, and, finally, when documents are published by journals with different impact factor quartiles. To investigate the above relationships, this paper analyzes the publications listed in the Web of Science and produced by active Spanish university professors between 2000 and 2009, working in the computer science field. Analyzing all documents, we show that the highest percentage of documents are published by three authors, whereas single-authored documents account for the lowest percentage. By number of citations, there is no positive association between the author cardinality and citation impact. Statistical tests show that documents written by two authors receive more citations per document and year than documents published by more authors. In contrast, results do not show statistically significant differences between documents published by two authors and one author. The research findings suggest that international collaboration results on average in publications with higher citation rates than national and institutional collaborations. We also find differences regarding citation rates between journals and conferences, across different computer science subdisciplines and journal quartiles as expected. Finally, our impression is that the collaborative level (number of authors per document) will increase in the coming years, and documents published by three or four authors will be the trend in computer science literature.

Sea ice habitat characteristics and number of narwhal (Monodon monoceros) sightings in Disko Bay, West Greenland

There is a paucity of information on abundance, densities, and habitat selection of narwhals Monodon monoceros in the offshore pack ice of Baffin Bay, West Greenland, despite the critical importance of winter foraging regions and considerable sea ice declines in the past decades. We conducted a double-platform visual aerial survey over a narwhal wintering ground to obtain pack ice densities and develop the first fully corrected abundance estimate using point conditional mark-recapture distance sampling. Continuous video recording and digital images taken along the trackline allowed for in situ quantification of winter narwhal habitat and for the estimation of fine-scale narwhal habitat selection and habitat-specific sighting probabilities. Abundance at the surface was estimated at 3484 (coefficient of variation [CV] = 0.46) including whales missed by observers. The fully corrected abundance of narwhals was 18 044 (CV = 0.46), or approximately one-quarter of the entire Baffin Bay population. The narwhal wintering ground surveyed (~9500 km**2) had 2.4 to 3.2% open water based on estimates from satellite imagery (NASA Moderate Resolution Imaging Spectroradiometer) and 1565 digital photographic images collected on the trackline. Thus, the ~18 000 narwhals had access to 233 km**2 of open water, resulting in an average density of ~77 narwhals/km**2 open water. Narwhal sighting probability near habitats with <10% or 10 to 50% open water was significantly higher than sighting probability in habitats with >50% open water, suggesting narwhals select optimal foraging areas in dense pack ice regardless of open water availability. This study provides the first quantitative ecological data on densities and habitat selection of narwhals in pack ice foraging regions that are rapidly being altered with climate change.

Glomerular number and size in autopsy kidneys: The relationship to birth weight

Background. In the Southeast United States, African Americans have an estimated incidence of hypertension and end-stage renal disease (ESRD) that is five times greater than Caucasians. Higher rates of low birth weight (LBW) among African Americans is suggested to predispose African Americans to the higher risk, possibly by reducing the number of glomeruli that develop in the kidney. This study investigates the relationships between age, race, gender, total glomerular number (N-glom), mean glomerular volume (V-glom), body surface area (BSA), and birth weight. Methods. Stereologic estimates of N-glom and V-glom were obtained using the physical disector/fractionator combination for autopsy kidneys from 37 African Americans and 19 Caucasians. Results. N-glom was normally distributed and ranged from 227,327 to 1,825,380, an 8.0-fold difference. A direct linear relationship was observed between N-glom and birth weight (r=0.423, P=0.0012) with a regression coefficient that predicted an increase of 257,426 glomeruli per kilogram increase in birth weight (alpha=0.050:0.908). Among adults there was a 4.9-fold range in V-glom , and in adults, V-glom was strongly and inversely correlated with N-glom (r=-0.640, P=0.000002). Adult V-glom showed no significant correlation with BSA for males (r=-0.0150, P=0.936), although it did for females (r=0.606, P=0.022). No racial differences in average N-glom or V-glom were observed. Conclusion. Birth weight is a strong determinant of N-glom and thereby of glomerular size in the postnatal kidney. The findings support the hypothesis that LBW by impairing nephron development is a risk factor for hypertension and ESRD in adulthood.

Meeting Physical Activity Guidelines and Average Daily Steps in a Working Population

Purpose: The aims of this study were to investigate the relationships and agreement between average number of steps taken per day and compliance with Australian physical activity guidelines in a sample of working Australian adults. Methods: One hundred-eighty-five adults wore a pedometer and recorded the number of steps taken each day for 7 d. On the 8th day, they completed a self-report survey that asked about frequency and duration of different activities during the previous week. Results: The average number of steps per day was 8543 (standard deviation = 2466) for men (n = 74) and 9093 (2926) for women (n = 111; no significant difference). Just over half the men (53%) and 45% of the women met the current national physical activity guidelines (no significant difference). Average number of steps per day was higher in those who met the guidelines [9547 (2655), n = 89] than in those who did not [8220 (2702), n = 96; P

The specification of vector autoregressive moving average models

In this paper we propose a new identification method based on the residual white noise autoregressive criterion (Pukkila et al. , 1990) to select the order of VARMA structures. Results from extensive simulation experiments based on different model structures with varying number of observations and number of component series are used to demonstrate the performance of this new procedure. We also use economic and business data to compare the model structures selected by this order selection method with those identified in other published studies.

The association between number of homework assignments completed during a lifestyle physical activity intervention and scores on transtheoretical measures

An assumption of theory-based physical activity interventions is that active participation positively affects the theoretical constructs upon which the intervention is based. This assumption is rarely tested. This study assessed whether participation, defined as completion of homework, in a lifestyle physical activity intervention was associated with changes over 6 months in constructs the homework addressed: the behavioral and cognitive processes of change, self-efficacy, and decisional balance (the pros and cons). Participants were 244 sedentary adults aged 25 to 75 years. They completed an average of 12 of 20 homework assignments. Those completing at least two-thirds of the homework (n = 113) had greater changes in the theoretical constructs from pretest to posttest than those completing less (n = 90). Post-hoc analyses suggest that completing theory-based homework may impact the processes of change and self-efficacy in lifestyle physical activity interventions and, therefore, are warranted in future interventions.

Hypertension, glomerular number, and birth weight in African Americans and white subjects in the southeastern United States

Low nephron number has been related to low birth weight and hypertension. In the southeastern United States, the estimated prevalence of chronic kidney disease due to hypertension is five times greater for African Americans than white subjects. This study investigates the relationships between total glomerular number (N-glom), blood pressure, and birth weight in southeastern African Americans and white subjects. Stereological estimates of N-glom were obtained using the physical disector/fractionator technique on autopsy kidneys from 62 African American and 60 white subjects 30-65 years of age. By medical history and recorded blood pressures, 41 African Americans, and 24 white subjects were identified as hypertensive and 21 African Americans and 36 white subjects as normotensive. Mean arterial blood pressure ( MAP) was obtained on 81 and birth weights on 63 subjects. For African Americans, relationships between MAP, N-glom, and birth weight were not significant. For white subjects, they were as follows: MAP and N-glom ( r = -0.4551, P = 0.0047); Nglom and birth weight ( r = 0.5730, P = 0.0022); MAP and birth weight ( r = -0.4228, P = 0.0377). For African Americans, average N-glom of 961 840 +/- 292 750 for normotensive and 867 358 +/- 341 958 for hypertensive patients were not significantly different ( P = 0.285). For white subjects, average N-glom of 923 377 +/- 256 391 for normotensive and 754 319 +/- 329 506 for hypertensive patients were significantly different ( P = 0.03). The data indicate that low nephron number and possibly low birth weight may play a role in the development of hypertension in white subjects but not African Americans.

Reduced nephron number and glomerulomegaly in Australian Aborigines: A group at high risk for renal disease and hypertension

Aborigines in remote areas of Australia have much higher rates of renal disease, as well as hypertension and cardiovascular disease, than non-Aboriginal Australians. We compared kidney findings in Aboriginal and non-Aboriginal people in one remote region. Glomerular number and mean glomerular volume were estimated with the disector/fractionator combination in the right kidney of 19 Aborigines and 24 non-Aboriginal people undergoing forensic autopsy for sudden or unexpected death in the Top End of the Northern Territory. Aborigines had 30% fewer glomeruli than non-Aborigines-202000 fewer glomeruli per kidney, or an estimated 404000 fewer per person (P=0.036). Their mean glomerular volume was 27% larger (P=0.016). Glomerular number was significantly correlated with adult height, inferring a relationship with birthweight, which, on average, is much lower in Aboriginal than non-Aboriginal people. Aboriginal people with a history of hypertension had 30% fewer glomeruli than those without-250000 fewer per kidney (P=0.03), or 500000 fewer per person, and their mean glomerular volume was about 25% larger. The lower nephron number in Aboriginal people is compatible with their susceptibility to renal failure. The additional nephron deficit associated with hypertension is compatible with other reports. Lower nephron numbers are probably due in part to reduced nephron endowment, which is related to a suboptimal intrauterine environment. Compensatory glomerular hypertrophy in people with fewer nephrons, while minimizing loss of total filtering surface area, might be exacerbating nephron loss. Optimization of fetal growth should ultimately reduce the florid epidemic of renal disease, hypertension, and cardiovascular disease.

Particle number emissions and source signatures of an industrial facility

The work presented was conducted within the scope of a larger study investigating impacts of the Stuart Oil Shale project, a facility operating to the north of the industrial city of Gladstone, Australia. The aims of the investigations were threefold: (a) the identification of the plant signatures in terms of particle size distributions in the submicrometer range (13-830 nm) through stack measurements, (b) exploring the applicability of these signatures in tracing the source contributions at locations of interest, at a distance from the plant, and (c) assessing the contribution of the plant to the total particle number concentration at locations of interest. The stack measurements conducted for three different conditions of plant operation showed that the particle size distributions were bimodal with average modal count median diameters (CMDs) of 24 (SD 4) and 52 (SD 9) nm. The average of all the particle size distributions recorded within the plant sector at a site located 4.5 km from the plant, over the sampling period when the plant was operating, also showed a bimodal distribution. The modal CMDs in this case were 27 and 50 nm, similar to those at the stack. This bimodal size distribution is distinct from the size distribution of the most common ambient anthropogenic emission source, which is vehicle emissions, and can be considered as a signature of this source. The average contribution of the plant (for plant sector winds) was estimated to be (10.0 +/- 3.8) x 10(2) particles cm(-3) and constituted approximately a 50% increase over the local particle ambient concentration for plant sector winds. This increase in particle number concentration compared to the local background concentration, while high compared to the clean environment concentration, is not significant when compared to concentrations generally encountered in the urban environment of Brisbane.

Effect of the average soft-segment length on the morphology and properties of segmented polyurethane nanocomposites

Two organically modified layered silicates (with small and large diameters) were incorporated into three segmented polyurethanes with various degrees of microphase separation. Microphase separation increased with the molecular weight of the poly(hexamethylene oxide) soft segment. The molecular weight of the soft segment did not influence the amount of polyurethane intercalating the interlayer spacing. Small-angle neutron scattering and differential scanning calorimetry data indicated that the layered silicates did not affect the microphase morphology of any host polymer, regardless of the particle diameter. The stiffness enhancement on filler addition increased as the microphase separation of the polyurethane decreased, presumably because a greater number of urethane linkages were available to interact with the filler. For comparison, the small nanofiller was introduced into a polyurethane with a poly(tetramethylene oxide) soft segment, and a significant increase in the tensile strength and a sharper upturn in the stress-strain curve resulted. No such improvement occurred in the host polymers with poly(hexamethylene oxide) soft segments. It is proposed that the nanocomposite containing the more hydrophilic and mobile poly(tetramethylene oxide) soft segment is capable of greater secondary bonding between the polyurethane chains and the organosilicate surface, resulting in improved stress transfer to the filler and reduced molecular slippage. (c) 2006 Wiley Periodicals, Inc.

Typical kernel size and number of sparse random matrices over Galois fields: a statistical physics approach

Using methods of statistical physics, we study the average number and kernel size of general sparse random matrices over GF(q), with a given connectivity profile, in the thermodynamical limit of large matrices. We introduce a mapping of GF(q) matrices onto spin systems using the representation of the cyclic group of order q as the q-th complex roots of unity. This representation facilitates the derivation of the average kernel size of random matrices using the replica approach, under the replica symmetric ansatz, resulting in saddle point equations for general connectivity distributions. Numerical solutions are then obtained for particular cases by population dynamics. Similar techniques also allow us to obtain an expression for the exact and average number of random matrices for any general connectivity profile. We present numerical results for particular distributions.

Approximate, Average, Dynamic Models of Uncontrolled Rectifiers for Aircraft Applications

To carry out stability and voltage regulation studies on more electric aircraft systems in which there is a preponderance of multi-pulse, rectifier-fed motor-drive equipment, average dynamic models of the rectifier converters are required. Existing methods are difficult to apply to anything other than single converters with a low pulse number. Therefore an efficient, compact method for deriving the approximate, linear, average model of 6- and 12-pulse rectifiers, based on the assumption of a small duration of the overlap angle is presented. The models are validated against detailed simulations and laboratory prototypes.

Nonlinear speech analysis algorithms mapped to a standard metric achieve clinically useful quantification of average Parkinson's disease symptom severity

The standard reference clinical score quantifying average Parkinson's disease (PD) symptom severity is the Unified Parkinson's Disease Rating Scale (UPDRS). At present, UPDRS is determined by the subjective clinical evaluation of the patient's ability to adequately cope with a range of tasks. In this study, we extend recent findings that UPDRS can be objectively assessed to clinically useful accuracy using simple, self-administered speech tests, without requiring the patient's physical presence in the clinic. We apply a wide range of known speech signal processing algorithms to a large database (approx. 6000 recordings from 42 PD patients, recruited to a six-month, multi-centre trial) and propose a number of novel, nonlinear signal processing algorithms which reveal pathological characteristics in PD more accurately than existing approaches. Robust feature selection algorithms select the optimal subset of these algorithms, which is fed into non-parametric regression and classification algorithms, mapping the signal processing algorithm outputs to UPDRS. We demonstrate rapid, accurate replication of the UPDRS assessment with clinically useful accuracy (about 2 UPDRS points difference from the clinicians' estimates, p < 0.001). This study supports the viability of frequent, remote, cost-effective, objective, accurate UPDRS telemonitoring based on self-administered speech tests. This technology could facilitate large-scale clinical trials into novel PD treatments.

Reductions of peak-to-average power ratio and optical beat interference in cost-effective OFDMA-PONs

The peak-to-average power ratio (PAPR) and optical beat interference (OBI) effects are examined thoroughly in orthogonal frequency-division multiplexing access (OFDMA)-passive optical networks (PONs) at a signal bit rate up to ∼ 20 Gb/s per channel using cost-effective intensity-modulation and direct-detection (IM/DD). Single-channel OOFDM and upstream multichannel OFDM-PONs are investigated for up to six users. A number of techniques for mitigating the PAPR and OBI effects are presented and evaluated including adaptive-loading algorithms such as bit/power-loading, clipping for PAPR reduction, and thermal detuning (TD) for the OBI suppression. It is shown that the bit-loading algorithm is a very efficient PAPR reduction technique by reducing it at about 1.2 dB over 100 Km of transmission. It is also revealed that the optimum method for suppressing the OBI is the TD + bit-loading. For a targeted BER of 1 × 10-3, the minimum allowed channel spacing is 11 GHz when employing six users. © 2013 Springer Science+Business Media New York.