Lower Levels Of Aggregation Research Articles

How Should We Measure District-Level Public Opinion on Individual Issues?

Due to insufficient sample sizes in national surveys, strikingly little is known about public opinion at the level of Congressional and state legislative districts in the United States. As a result, there has been virtually no study of whether legislators accurately represent the will of their constituents on individual issues. This article solves this problem by developing a multilevel regression and poststratification (MRP) model that combines survey and census data to estimate public opinion at the district level. We show that MRP estimates are excellent predictors of public opinion and referenda results for both congressional and state senate districts. Moreover, they have less error, higher correlations, and lower variance than either disaggregated survey estimates or presidential vote shares. The MRP approach provides American and Comparative Politics scholars with a valuable new tool to measure issue-specific public opinion at low levels of geographic aggregation.

TRQ-complications: who gets the benefits when the EU liberalizes Mercosur's access to the beef markets?

The European Union (EU) and the Mercosur countries resumed negotiations on trade liberalization in May 2010 after several years of interruption. The article analyzes who stands to benefit and who is likely to lose if the EU liberalizes Mercosur's access to domestic beef markets. This economic assessment is performed using a partial equilibrium model for beef operating at a low level of product aggregation, paying specific attention to the role of Tariff Rate Quotas (TRQs). Consultations with experts from the meat sector allowed us to identify the allocation of the quota rents to different stakeholders. Under an agreement based on the EU's negotiation proposal, trade impacts are projected to be small due to the present quota overfill. As expected, impacts are more pronounced under the conditions set out in Mercosur's proposal. The results confirm that the distribution of quota rents can be decisive in determining welfare effects.

Earthworm-induced N2O emissions in a sandy soil with surface-applied crop residues

Abstract Earlier research with endogeic and epigeic earthworm species in loamy arable soil has shown that both earthworm groups can increase nitrous oxide (N 2 O) emissions, provided that crop residue placement matches the feeding strategy of the earthworm ecological group(s). However, it is not yet clear whether these effects also occur in sandy soils which typically contain less soil organic matter and have low soil aggregation levels. Here, we aimed to quantify N 2 O emissions as affected by endogeic and/or epigeic earthworm species, and to relate changes in N 2 O emissions to earthworm-induced changes in soil properties in a sandy soil. A 90 day mesocosm study was conducted with sandy soil and 15 N-labeled radish ( Raphanus sativus cv. Adagio L.) residue applied on top. Treatments included: (i) no earthworm addition, (ii) addition of the endogeic species Aporrectodea caliginosa (Savigny), (iii) addition of the epigeic species Lumbricus rubellus (Hoffmeister), and (iv) both species combined. An additional treatment was included without earthworms and with residue manually incorporated into the soil. L. rubellus significantly increased cumulative N 2 O emissions from 228 to 859 μg N 2 O–N kg −1 ( F 1,12 = 83.12, P A. caliginosa did not affect N 2 O emissions. In contrast to earlier studies in loamy soil, no positive interaction between both species with regard to N 2 O emissions was found. This was probably related to high competition for organic resources in the relatively poor soil and a low potential for stable soil aggregate formation (and associated anaerobic microsites) by endogeic worms in sandy soil. 15 N isotope analysis revealed that the activity of L. rubellus significantly increased ( F 1,12 = 6.20, P = 0.028) the recovery of 15 N in the 250–8000 μm size fraction, indicating incorporation of crop residues into the mineral soil. When residues were manually incorporated, N 2 O emissions were significantly ( P 2 O–N kg −1 ) than when incorporated by L. rubellus . The high N 2 O emissions in the presence of L. rubellus , when compared to manual mixing, suggest a stimulation of microbial activity and/or changes in the microbial community composition. Insights on the earthworm effects on N 2 O emission from such soils are discussed.

Towards a new crown indicator: an empirical analysis

We present an empirical comparison between two normalization mechanisms for citation-based indicators of research performance. These mechanisms aim to normalize citation counts for the field and the year in which a publication was published. One mechanism is applied in the current so-called crown indicator of our institute. The other mechanism is applied in the new crown indicator that our institute is currently exploring. We find that at high aggregation levels, such as at the level of large research institutions or at the level of countries, the differences between the two mechanisms are very small. At lower aggregation levels, such as at the level of research groups or at the level of journals, the differences between the two mechanisms are somewhat larger. We pay special attention to the way in which recent publications are handled. These publications typically have very low citation counts and should therefore be handled with special care.

Exploring the geographical distribution of wealth using the output area classification

The results of the first wave of the Wealth and Assets Survey were published in the report, ‘Wealth in Great Britain’ in December 2009 with datasets released in March 2010. However, apart from the presentation of the aggregate results on a Government Office Region basis, no more disaggregated geographical analysis of the data has so far been carried out, not least because of the potential disclosivity of the data when presented for low level geographies. This paper aims to provide an understanding of the geographical distribution of wealth and its components by areas with common socio-economic and demographic characteristics from relatively high to low levels of aggregation while overcoming the disclosivity problem. This is achieved by using the Output Area Classification (OAC) groupings, based on the 2001 Census.

The empirical performance of the NEG with reference to small areas

The New Economic Geography (NEG) has moved from being almost purely theoretical to now becoming a basis for empirical research. The question is, given its origins in international economics, can the NEG model explain the economic geography of small regions within countries? This article reviews some of the literature relating to this question, concluding that we should consider simpler, easier to estimate rival models rather than assume that NEG will be successful at a low level of spatial aggregation.

CASH TRANSFERS AND POVERTY REDUCTION IN CHILE*

The headcount ratio in Chile has declined from 40 percent to 14 percent since 1987. However, most analysis of this reduction uses national and regional poverty statistics. In contrast, we employ poverty mapping methodologies to find heterogeneity in the effectiveness of transfers across counties. To better understand this variation, we explore the roles of characteristics of the local population, structural features of the county, and geography. The greatest reductions in poverty occur in rural households, yet population characteristics and geography are also important. These findings suggest that targeting at low levels of aggregation can deliver further reductions in poverty.

INTERFUEL SUBSTITUTION: A META‐ANALYSIS

Abstract This paper provides the first meta‐analysis of the interfuel substitutability literature. The sample includes 47 studies of interfuel substitution in the industrial sector, in manufacturing industry or manufacturing sub‐industries, or in the macro‐economy of a variety of developed and developing countries. Meta‐regressions are estimated for the six shadow elasticities of substitution between coal, oil, gas and electricity. I find that at the level of the industrial sector as a whole the oil–coal, oil–gas, oil–electricity and gas–electricity shadow elasticities of substitution are significantly greater than unity. The remaining elasticities – between coal and gas and coal and electricity – are insignificantly different from unity or zero due to their large standard errors. Substitution possibilities seem more constrained at the macro level and less constrained at lower levels of aggregation. Estimates of the elasticities of substitution from cross‐section regressions are generally largest whereas fixed effects panel estimates are intermediate in magnitude, and time‐series estimates are mostly much smaller. In order to obtain more precise and less biased estimates of long‐run elasticities of substitution, there is a need for additional primary studies using large samples and/or the between estimator which econometric research suggests is likely to provide the best estimates of long‐run elasticities.

Status groups and altruistic behaviour in dictator games

We provide evidence on the effects of social status in the dictator game. With regard to average donations from and to status groups, it turns out that (a) the higher the status of the dictator, the more she donates, and (b) the higher the status of the recipient, the less she receives in donations. Both tendencies are proposed by altruism. On a lower level of aggregation, we find that altruism has the highest proportion of correct predictions among all theoretical concepts under consideration (i.e. altruism, warm-glow giving, in-group bias, noblesse oblige). Surprisingly, there are rarely pure altruists on the individual level. This points at well-known problems of aggregation in social science research and challenges, among others, experimental studies on the in-group bias.

Can inverse density dependence at small spatial scales produce dynamic instability in animal populations?

All else being equal, inversely density-dependent (IDD) mortality destabilizes population dynamics. However, stability has not been investigated for cases in which multiple types of density dependence act simultaneously. To determine whether IDD mortality can destabilize populations that are otherwise regulated by directly density-dependent (DDD) mortality, I used scale transition approximations to model populations with IDD mortality at smaller “aggregation” scales and DDD mortality at larger “landscape” scales, a pattern observed in some reef fish and insect populations. I evaluated dynamic stability for a range of demographic parameter values, including the degree of compensation in DDD mortality and the degree of spatial aggregation, which together determine the relative importance of DDD and IDD processes. When aggregation-scale survival was a monotonically increasing function of density (a “dilution” effect), dynamics were stable except for extremely high levels of aggregation combined with either undercompensatory landscape-scale density dependence or certain values of adult fecundity. When aggregation-scale survival was a unimodal function of density (representing both “dilution” and predator “detection” effects), instability occurred with lower levels of aggregation and also depended on the values of fecundity, survivorship, detection effect, and DDD compensation parameters. These results suggest that only in extreme circumstances will IDD mortality destabilize dynamics when DDD mortality is also present, so IDD processes may not affect the stability of many populations in which they are observed. Model results were evaluated in the context of reef fish, but a similar framework may be appropriate for a diverse range of species that experience opposing patterns of density dependence across spatial scales.

Impaired sperm aggregation in Adam2 and Adam3 null mice

Previous studies have shown that sperm from Adam2 and Adam3 knockout mice have defective migration in the female reproductive tracts and cannot bind to the egg's zona pellucida (ZP), which leads to infertility. Here, we report that Adam2 and Adam3 knockout sperm have severely impaired sperm aggregation and that this defect is not restored over time during in vitro cultivation, suggesting the requirement of ADAM2 and ADAM3 in normal sperm association.

Inequality at Low Levels of Aggregation in Chile

Despite success in poverty reduction, inequality in Chile has remained virtually unchanged over the last 20 years. High levels of inequality have been shown to hamper further reductions in poverty as well as economic growth, and local inequality has been shown to affect such outcomes as violence and health. The study of inequality at the local level is thus crucial for understanding the economic wellbeing of a country. Local measures of inequality have been difficult to obtain, but recent theoretical advances have enabled the combination of survey and census data to generate estimates of inequality that are robust at disaggregated geographic levels. We employ this methodology to produce consistent and precise estimates of inequality for every county in Chile. We find considerable heterogeneity in county-level estimates of inequality, with Gini coefficients ranging from 0.41 to 0.64.

Hydrothermal Synthesis of Alpha Alumina (α‐Al2O3) Powders: Study of the Processing Variables and Growth Mechanisms

Alpha alumina (α‐Al2O3) powders and α‐Al2O3/boehmite (γ‐AlOOH) mixtures with controlled γ‐AlOOH contents were synthesized hydrothermally under alkaline or acidic conditions at 380°–435°C for 1–10 days, under 6.9–14.5 MPa pressure, from concentrated precursors without stirring. The precursors were formed by mixing different types of aluminum hydroxides with water, and optionally with α‐Al2O3 seeds, hydrogen peroxide, sulfuric acid, dopants (i.e., KMnO4), and/or other additives. The experiments were performed on industrial scale in large production autoclaves. The synthesized α‐Al2O3 powders exhibited up to 100% phase purity, 99.98% chemical purity, equiaxed morphology, low aggregation levels, narrow crystallite size distributions with primary particle sizes ranging between 100 nm and 40 μm, and high reproducibility. Precursor types, seeds, chemical additives, and temperature/time of the hydrothermal synthesis were found to govern properties of the powders. Different growth mechanisms for nanosized and rough powders are discussed. Results of this study enable the use of hydrothermal α‐Al2O3 powders in a multitude of applications, and make their hydrothermal production a commercial reality.

GSK3 and p53 - is there a link in Alzheimer's disease?

BackgroundRecent evidence suggests that glycogen synthase kinase-3β (GSK3β) is implicated in both sporadic and familial forms of Alzheimer's disease. The transcription factor, p53 also plays a role and has been linked to an increase in tau hyperphosphorylation although the effect is indirect. There is also evidence that GSK3β and p53 interact and that the activity of both proteins is increased as a result of this interaction. Under normal cellular conditions, p53 is kept at low levels by Mdm2 but when cells are stressed, p53 is stabilised and may then interact with GSK3β. We propose that this interaction has an important contribution to cellular outcomes and to test this hypothesis we developed a stochastic simulation model.ResultsThe model predicts that high levels of DNA damage leads to increased activity of p53 and GSK3β and low levels of aggregation but if DNA damage is repaired, the aggregates are eventually cleared. The model also shows that over long periods of time, aggregates may start to form due to stochastic events leading to increased levels of ROS and damaged DNA. This is followed by increased activity of p53 and GSK3β and a vicious cycle ensues.ConclusionsSince p53 and GSK3β are both involved in the apoptotic pathway, and GSK3β overactivity leads to increased levels of plaques and tangles, our model might explain the link between protein aggregation and neuronal loss in neurodegeneration.

Systematic study of hydrothermal crystallization of zinc oxide (ZnO) nano-sized powders with superior UV attenuation

Zinc oxide (ZnO) powders were synthesized by the hydrothermal method at 160–280 °C for 6–24 h, under 90–930 psi pressure, from concentrated precursors without stirring. The precursors were formed by mixing aqueous solutions of zinc acetate, chloride, sulfate, or nitrate with KOH (aq) under either controlled or rapid precipitation conditions. The precursor quantities were chosen to yield zinc concentration of 0.3–4.0 m, KOH concentration of 0.6–8.0 m, and pH between 4 and 14 after precipitation had been completed. Several of the synthesized powders exhibited equiaxed morphology, low aggregation levels, narrow crystallite size distributions in the range 60–200 nm, and excellent dispersability. Some of the ZnO powders consisted of nano-sized equiaxed crystallites mixed with large, mostly elongated crystals, 0.5–4.0 μm in size. Based on this systematic study encompassing a wide range of synthesis conditions, temperature-controlled growth rate and Ostwald ripening were found to dominate the hydrothermal crystallization of ZnO powders. Comparison with several commercially available ZnO powders revealed superior purity, particle size distributions, defect structure, and ultimately the UV attenuation, in selected powders synthesized hydrothermally. Results of this study enable the use of hydrothermally made ZnO powders in sunscreens or other UV absorption applications and make their hydrothermal production commercially feasible.

Service marks as indicators for innovation in knowledge-based services

It has long been a tradition in the field of innovation research to use quantitative indicators to measure the extent of innovation activities and analyze them in from a comparative cross-national perspective. For instance, using patents is an established way of assessing innovation output in the realm of technologies and products. With the growing relevance of services as an important economic activity, the need for specific indicators that can be used to measure innovation output in this context is growing. In this paper we discuss the possibilities and limits of using service marks as basic innovation indicators for services. As most macroanalyses on the basis of marks are not harnessing their full potential, improved methods for more detailed approaches are presented. In detail, the use of community trademarks proves to be insufficient for valid statistical analyses; international registrations combined with community trademarks should be used instead. Some examples are given to illustrate the potential of this approach on a lower level of aggregation.

Resource Dimensioning Through Buffer Sampling

Link dimensioning, i.e., selecting a (minimal) link capacity such that the users' performance requirements are met, is a crucial component of network design. It requires insight into the interrelationship among the traffic offered (in terms of the mean offered load M, but also its fluctuation around the mean, i.e., `burstiness'), the envisioned performance level, and the capacity needed. We first derive, for different performance criteria, theoretical dimensioning formulas that estimate the required capacity C as a function of the input traffic and the performance target. For the special case of Gaussian input traffic, these formulas reduce to C=M + alpha V, where alpha directly relates to the performance requirement (as agreed upon in a service level agreement) and V reflects the burstiness (at the timescale of interest). We also observe that Gaussianity applies for virtually all realistic scenarios; notably, already for a relatively low aggregation level, the Gaussianity assumption is justified.

Application of High Hydrostatic Pressure to Dissociate Aggregates and Refold Proteins

Non-denaturing pressures of around 2000 bar are effective for eliminating and refolding protein aggregates and may be applicable in various phases of protein manufacturing to decrease aggregate levels in products and improve process yields. Lower aggregate levels can result in reduced immunogenicity of proteins and enable the correct refolding of proteins that might not be recovered with traditional techniques. High pressure treatment can also be used to conduct selective PEGylation and protease cleavage reactions while minimizing protein aggregation. High pressure processes have been used in the food industry for over 50 years and large scale (300 L) systems are commercially available, enabling production of proteins on the kilogram scale. This review summarizes the utility of high pressure refolding to remove and refold protein aggregates, enhance therapeutic proteins, and facilitate manufacturing improvements at industrial scales.

The Impact of Surgeon Specialization on Patient Mortality

To examine the effect of surgeon specialization on patient outcomes, controlling for volume. There is great interest in the degree to which surgical specialization affects outcomes, particularly considering drives to measure and reward quality in healthcare. Although surgical specialization has been previously analyzed with respect to outcomes, most studies have treated it as a dichotomous variable based on academic credentials. We treat it here as a continuous variable defined quantitatively by procedural diversity. We used 2002 to 2005 patient data from the National Surgical Quality Improvement Program for the Department of Surgery, Barnes Jewish Hospital, St. Louis, Missouri. To quantitate procedural specialization, Herfindahl-Hirschman indices for surgeons were calculated using billing codes. These indices were calculated according to 3 different levels of procedural aggregation. Using conditional logit models, we examined the relationship between these indices and 30-day postoperative mortality rates. Surgeon specialization was inversely related to mortality rates after adjusting for case volume when indices were calculated using medium procedural aggregation (odds ratio for mortality = 0.580 per 0.1 unit Herfindahl increase; P = 0.025) or low aggregation (odds ratio for mortality = 0.510 per 0.1 unit Herfindahl increase; P = 0.015). No relationship was observed at the high level of aggregation. The procedural concentration component of surgical specialization is correlated with improved mortality rates independently of case volume. However, how broadly or narrowly "specialization" is defined has an impact on this relationship.

New hierarchical classification of food items for the assessment of exposure to packaging migrants: use of hub codes for different food groups

This paper describes development work undertaken to expand the capabilities of an existing two-dimensional probabilistic modelling approach for assessing dietary exposure to chemicals migrating out of food contact materials. A new three-level hub-coding system has been devised for coding different food groups with regards to their consumption by individuals. The hub codes can be used at three different levels representing a high, medium and low level of aggregation of individual food items. The hub codes were developed because they have a greater relevance to packaging migration than coding used (largely and historically) for nutritional purposes. Also, the hub codes will assist pan-europeanization of the exposure model in the future, when up to 27 or more different food coding systems from 27 European Union Member States will have to be assimilated into the modelling approach. The applicability of the model with the new coding system has been tested by incorporating newly released 2001 UK consumption data. The example used was exposure to a hypothetical migrant from coated metal packaging for foodstuffs. When working at the three hierarchical levels, it was found that the tiered approach gave conservative estimates at the cruder level of refinement and a more realistic assessment was obtained as the refinement progressed. The work overall revealed that changes in eating habits over time had a relatively small impact on estimates of exposure. More important impacts are changes over time in packaging usage, packaging composition and migration levels. For countries like the UK, which has sophisticated food consumption data, it is uncertainties in these other areas that need to be addressed by new data collection.