Conceptual Drawbacks Research Articles

To what extent the conventional gas permeation testing method is reliable for membrane systems?

This work intends to analyze the inaccuracy which appears in the predictions of the conventional gas permeation testing (GPT) method. A theoretical combined with an experimental analysis were presented to study the capability of the conventional GPT method with reference to the membrane structural parameters. Although, the conventional GPT method is relatively easy and fast to be implemented, it normally prone to some inaccuracy caused by inadequate experimental and theoretical techniques. Therefore, it suffers from several conceptual drawbacks. In comparison to the Wakao et al. model, it can be concluded that the modified rp and (ε/lp) were different from the conventional one by a factor of 3π/16, and (16/3π)2 respectively. In addition, depending on which part of the J versus P is selected, different rp and (ε/lp) will be resulted in. Finally, at the regions which the slope is negative or zero, the conventional GPT method is not capable to establish any prediction.

Estimating the time since discharge of spent cartridges: A logical approach for interpreting the evidence

Estimating the time since discharge of a spent cartridge or a firearm can be useful in criminal situations involving firearms. The analysis of volatile gunshot residue remaining after shooting using solid-phase microextraction (SPME) followed by gas chromatography (GC) was proposed to meet this objective. However, current interpretative models suffer from several conceptual drawbacks which render them inadequate to assess the evidential value of a given measurement. This paper aims to fill this gap by proposing a logical approach based on the assessment of likelihood ratios. A probabilistic model was thus developed and applied to a hypothetical scenario where alternative hypotheses about the discharge time of a spent cartridge found on a crime scene were forwarded. In order to estimate the parameters required to implement this solution, a non-linear regression model was proposed and applied to real published data. The proposed approach proved to be a valuable method for interpreting aging-related data.

A landscape scale spatial model for semi-natural broadleaf woodland expansion in Wales, UK

Conservation assessment based on complex species distribution models suffers from a number of conceptual drawbacks when applied to setting conservation priorities. The rule-based model described in this paper uses a set of simple and easily understood ecological rules developed in consultation with local ecologists that are directly applicable to the local landscape. The model determines the suitability for the expansion of target semi-natural habitats, modified by landscape differences, for a selected study site in Wales, UK. The results in a pilot study area for semi-natural broadleaf woodland (SNBW) indicated that the model successfully identifies potential sites for expansion at the scale of the land parcel that represents the dominant management unit. The model generated high suitability scores for broadleaf woodland expansion along river valleys which contain proportionately more remnant broadleaf woodland and other semi-natural vegetation than other, more intensively farmed parts of the contemporary landscape. The results demonstrate that within this landscape type there is the potential to increase woodland area by c. 6.5%. By contrast a landscape type characterised by gentle relief and deep fertile soils currently under intensive agricultural use, shows the potential for lower levels of broadleaf woodland expansion equivalent to c. 3.3% of the area of the landscape unit. The model is flexible and can be re-run to reflect changed circumstances, in particular changes in policy relating to agri-environment targets for habitats and species. Future work is required to refine the model to reflect differences in the cultural as well as the physical characteristics of the underlying landscape.

A neorepublican cultural citizenship: beyond Marxism and liberalism

The idea of cultural citizenship is often associated with a present-day context of multiculturalism, and seen as a novel issue for political philosophy. Within political philosophy it has been mainly conceptualised within a liberal tradition focusing on (cultural) rights. The concept also features in cultural studies, to articulate the importance of artistic and media practices to citizenship. This article aims to orient the debate to wider theoretical concerns, and to a long-standing political-philosophical interest in the relation of politics and culture. It proposes a ‘broad view’ of cultural citizenship, which moreover locates cultural citizenship in concerns about the public sphere. It revisits historical philosophical positions on the relation of politics and culture, viz those of Karl Marx and John Stuart Mill. The distinct conceptual models ensuing from their work both expound ‘broad views’, which take the relation between politics and culture to impact on all citizens. The article subsequently discusses a recent Dutch policy report on cultural citizenship, which shows that these models still have topical relevance. Next, a fourfold grid is elaborated of weak and strong, positive and negative views on how citizenship is to be related to issues of culture. The article concludes by arguing for a neorepublican approach of cultural citizenship that adopts a ‘weak positive’ view and may repair the conceptual drawbacks of both the liberal and Marxist views.

Detecting network communities by propagating labels under constraints

We investigate the recently proposed label-propagation algorithm (LPA) for identifying network communities. We reformulate the LPA as an equivalent optimization problem, giving an objective function whose maxima correspond to community solutions. By considering properties of the objective function, we identify conceptual and practical drawbacks of the label-propagation approach, most importantly the disparity between increasing the value of the objective function and improving the quality of communities found. To address the drawbacks, we modify the objective function in the optimization problem, producing a variety of algorithms that propagate labels subject to constraints; of particular interest is a variant that maximizes the modularity measure of community quality. Performance properties and implementation details of the proposed algorithms are discussed. Bipartite as well as unipartite networks are considered.

A Theory-Driven Approach to Tree-Ring Standardization: Defining the Biological Trend from Expected Basal Area Increment

One of the main elements of dendrochronological standardization is removing the biological trend, i.e. the progressive decline of ring width along a cross-sectional radius that is caused by the corresponding increase in stem size and tree age over time. The “conservative” option for removing this biological trend is to fit a modified negative exponential curve (or a straight line with slope ≤ 0) to the ring-width measurements. This method is based on the assumption that, especially for open-grown and/or shade-intolerant species, annual growth rate of mature trees fluctuates around a specific level, expressed by a constant ring width. Because this method has numerical and conceptual drawbacks, we propose an alternative approach based on the assumption that constant growth is expressed by a constant basal area increment distributed over a growing surface. From this starting point, we derive a mathematical expression for the biological trend of ring width, which can be easily calculated and used for dendrochronological standardization.The proposed C-method is compared to other standardization techniques, including Regional Curve Standardization (RCS), of tree-ring width from ponderosa pines (Pinus ponderosa Douglas ex P.Lawson & C.Lawson) located at the Gus Pearson Natural Area (GPNA) in northern Arizona, USA. Master ring-index chronologies built from ring area, RCS, and C-method reproduced stand-wide patterns of tree growth at the GPNA, whereas other standardization options, including the “conservative” one, failed to do so. In addition, the C-method has the advantage of calculating an expected growth curve for each tree, whereas RCS is based on applying the same growth curve to all trees. In conclusion, the C-method replaces the purely empirical “conservative” option with a theory-based approach, which is applicable to individual ring-width measurement series, does not require fitting a growth curve using nonlinear regression, and can be rigorously tested for improving tree-ring records of environmental changes.

Neurogenesis in adult CNS: From denial to opportunities and challenges for therapy

The discovery of neurogenesis and neural stem cells (NSC) in the adult CNS has overturned a long-standing and deep-routed "dogma" in neuroscience, established at the beginning of the 20(th) century. This dogma lasted for almost 90 years and died hard when NSC were finally isolated from the adult mouse brain. The scepticism in accepting adult neurogenesis has now turned into a rush to find applications to alleviate or cure the devastating diseases that affect the CNS. Here we highlight a number of methodological, technical and conceptual drawbacks responsible for the historical denial of adult neurogenesis. Furthermore, we discuss old and new issues that need to be faced before NSC or endogenous neurogenesis can safely enter into the doctor's bag for therapies.

A Generalized Hidden Markov Model Approach to Transmembrane Region Prediction with Poisson Distribution as State Duration Probabilities

We present a novel algorithm to predict transmembrane regions from a primary amino acid sequence. Previous studies have shown that the Hidden Markov Model (HMM) is one of the powerful tools known to predict transmembrane regions; however, one of the conceptual drawbacks of the standard HMM is the fact that the state duration, i.e., the duration for which the hidden dynamics remains in a particular state follows the geometric distribution. Real data, however, does not always indicate such a geometric distribution. The proposed algorithm utilizes a Generalized Hidden Markov Model (GHMM), an extension of the HMM, to cope with this problem. In the GHMM, the state duration probability can be any discrete distribution, including a geometric distribution. The proposed algorithm employs a state duration probability based on a Poisson distribution. We consider the two-dimensional vector trajectory consisting of hydropathy index and charge associated with amino acids, instead of the 20 letter symbol sequences. Also a Monte Carlo method (Forward/Backward Sampling method) is adopted for the transmembrane region prediction step. Prediction accuracies using publicly available data sets show that the proposed algorithm yields reasonably good results when compared against some existing algorithms.

Affine Markov chain model of multifirm credit migration

This paper introduces and explores a natural extension of the Chen–Filipovic affine models for credit migration, credit spreads and credit default correlation. The essential addition proposed here is to introduce a Markov chain for the “credit rating” of each firm, which are independent conditioned on a stochastic time change. The stochastic time change is then combined with other stochastic factors, here the interest rate and the recovery rate, into a multidimensional affine process. The resulting general framework has the computational effectiveness of the Chen–Filipovic models, but without certain of their conceptual drawbacks. This paper, as the first of the series, aims to illustrate the potential of the general framework by exploring a minimal implementation which is still capable of combining stochastic interest rates, stochastic recovery rates and the multifirm default process. Already within this minimal version we see very good reproduction of essential features such as credit spread curves, default correlations and multifirm default distributions. 1This research was supported by the Natural Sciences and Engineering Research Council of Canada and the MITACS National Centre of Excellence, Canada.

The theory of general kriging, with applications to the determination of a local geoid

SUMMARY Two techniques are commonly used to predict values of a random field u(t) from a vector of observations Y; one, mainly used in geodesy, is collocation, the other, mainly used in hydrology and geology, is kriging. Both techniques are based on the same optimization principle, that is minimizing the mean square prediction error, and use the same class of predictors, namely linear in Y. However, in collocation theory u(t) is assumed to have zero average and the main statistic to be used is covariance; once covariance is estimated, it is easy to switch from one functional to another, through covariance propagation. In kriging theory, on the contrary, the average of the field can be an arbitrary constant (or even a function in a suitable finite space) and the main statistic to be estimated is the variogram. Due to its shape, there is no simple rule for variogram propagation from one functional to another; for this reason kriging has mainly dealt with simple evaluations of u(t), or possibly with block averages. This paper treats the unification of the two techniques under a method called by the authors general kriging. After an introduction discussing some typical problems where such theories can be usefully applied, in Section 2 we formalize our proposal in general mathematical terms. Basically one could say that a proper functional propagation based on variograms is established. A first 1-D simulated example follows. In Section 3, our proposal is contrasted on a conceptual basis with cokriging, showing that this method solves a different problem, and step-wise collocation with parameters, recalling some conceptual drawbacks of this approach. In Section 4, numerical examples taken from the problem of estimating a local gravimetric geoid are presented. In such a problem, in fact, both hypotheses, non-zero average and change of functionals, occur and general kriging has proved to be able to deal with them. Finally a short discussion of the results and on-going problems closes the paper.

Epidemiologic measures and policy formulation: lessons from potential outcomes

This paper provides a critique of the common practice in the health-policy literature of focusing on hypothetical outcome removal at the expense of intervention analysis. The paper begins with an introduction to measures of causal effects within the potential-outcomes framework, focusing on underlying conceptual models, definitions and drawbacks of special relevance to policy formulation based on epidemiologic data. It is argued that, for policy purposes, one should analyze intervention effects within a multivariate-outcome framework to capture the impact of major sources of morbidity and mortality. This framework can clarify what is captured and missed by summary measures of population health, and shows that the concept of summary measure can and should be extended to multidimensional indices.

Caliber of Quality-of-Life Assessments in Congenital Heart Disease

Interest in quality-of-life issues in children, adolescents, and adults with congenital heart disease has increased significantly during the past decades. In general, quality-of-life research is stimulated by an overall interest in outcomes. More specifically, quality-of-life studies add to mortality and morbidity data by taking reported physical, psychological, and social problems into consideration. However, quality of life can be an ambiguous concept that is hindered by methodological weaknesses, a situation that can prevent the drawing of firm conclusions. To appraise the conceptual and methodological rigor of published quality-of-life assessments in patients with congenital heart disease. A review of 70 articles published in the medical literature, using the 10 criteria previously developed by Gill and Feinstein. For each criterion, the number of articles complying with that criterion was counted, and the percentage was calculated. To indicate how well individual articles performed on the respective criteria, a summary score was calculated by summing the number of criteria an article fulfilled and dividing this sum by the number of criteria for which the article was eligible to be evaluated; the resulting value was then multiplied by 100. Summary scores ranging from 0, for articles complying with none of the criteria, to 100, for articles complying with all of the criteria. We found that quality-of-life assessments in patients with congenital heart disease showed major conceptual and methodological drawbacks (median summary score, 0). Moreover, we found that the term quality of life was often used inappropriately, an observation supported by several articles in which the authors drew conclusions about patients' quality of life, even though quality of life was not specifically measured. A poor conceptual and methodological basis for quality of life implies that many results from quality-of-life studies performed in patients with congenital heart disease contribute little to the scientific knowledge base of quality of life in this patient population. Future quality-of-life studies need to invest in a rigorous conceptualization, an adequate operational definition, and a sound measurement of quality of life.

Is Communalism Dead? Reflections on the Present and Future Practice of Crime Prevention: Part Two

This paper, of which this is the second part, takes up a strange paradox or dissonance that characterises contemporary crime prevention, particularly perhaps in Australia. On the one hand, there is an ample literature pointing out the conceptual and practical drawbacks of community, or more broadly of communalism (incorporating social capital), in crime prevention; on the other, policy and practice seem largely oblivious to these difficulties and hence, by extension, to the need for more appropriate conceptual formulations upon which to base collective approaches to crime prevention. Part One of the article (Carson, 2004) traced the allure and the difficulties of communalism in general and in crime prevention in particular. Part Two takes up the challenge of developing new and more appropriate foundations for a collectively-based approach in this policy arena. This it does by drawing selectively on the insights of radical communitarianism (shorn of its utopian communal overtones), on attempts to go beyond the close ties of social capital to a looser collective efficacy, and on discursive possibilities that address issues of difference, rights and democratisation in relation to crime prevention. By this means, it is argued, crime prevention may be reconnected to questions of social justice and collective capacity without surrendering to the false attractions of an anachronistic communalism.

Is Communalism Dead? Reflections on the Present and Future Practice of Crime Prevention: Part One

This article takes up a strange paradox or dissonance that characterises contemporary crime prevention, particularly in Australia. On the one hand, there is an ample literature pointing out the conceptual and practical drawbacks of “community” or more broadly of “communalism” (incorporating social capital) in crime prevention; on the other, policy and practice seem largely oblivious to these difficulties and hence, by extension, to the need for more appropriate conceptual formulations upon which to base collective approaches to crime prevention.The article is in two parts. The first traces the allure and the difficulties of communalism in general and in crime prevention in particular. In traversing what may be in some respects well enough known terrain, it underlines that until we recognise the innate difficulties with this conceptual framework, crime prevention will not face up to the challenge of developing new and more appropriate foundations for a collectively based approach in this policy arena. An attempt to address this challenge is taken up in the second part of the article.

Tests of Bell inequalities

According to recent reports, the last loopholes in testing Bell's inequality are closed. It is argued that the really important task in this field has not been tackled yet and that the leading experiments claiming to close locality and detection efficiency loopholes, although making very significant progress, have conceptual drawbacks. The important task is constructing quantum devices which will allow winning games of certain correlated replies against any classical team. A novel game of this type is proposed.

Cultural Factors in Educational Effectiveness: A framework for comparative research

ABSTRACT Following rapid social and economic development in the Asia-Pacific region in the past decades, there is a growing interest in the cultural differences in schooling between East and West. This interest extends to the cultural forces shaping the features of school processes and dominating the effectiveness of education in terms of students’ academic achievements. Unfortunately, many recent studies and debates about culture suffer from a number of major methodological and conceptual drawbacks, including confusion in conceptions, arbitrary use of cultural terms, over-attribution to cultural effects, and ignorance of levels of analysis. Few studies seem capable of deepening our understanding of cultural or cross-cultural factors in educational effectiveness.

On Measuring Species Evenness and Other Associated Parameters of Community Structure

The concepts of evenness, diversity and dominance have been traditionally regarded as basic parameters of community structure in interspecific competition, and during the past several decades there has been an impressive development of their measurements. It is quite depressing to realize, however, that there is still no consensus on how to measure and interrelate these parameters. In consequence, an increasing number of field ecologists are questioning the utility of evenness, dominance and diversity statistics to evaluate changes in the functional structure of biological communities with competing species. Recently, in this journal, Bulla (1994) has proposed a new index of species evenness and its associated diversity measurement to clarify the current confusion and, at the same time, reverse the loss of interest in the use of evenness and diversity statistics. Bulla properly justifies the development of a new evenness index because older ones, such as Pielou's (1969) J index, Hill's (1973) E index, Alatalo's (1981) F index and Molinari's (1989) G index, exhibit serious shortcomings. Nevertheless, it seems to me that Bulla's contribution only brings more confusion to the subject because it has both conceptual and practical drawbacks, overlooking the importance of the complementary relationship between evenness and dominance. Furthermore, Bulla's contribution is not entirely original since I had already proposed and utilized the same measurement of species diversity (Camargo 1992a, b, 1993a, b). To explain the derivation of his evenness index, Bulla begins with a graphical representation of the relative abundances of ten plant species in a real community and in a theoretical community (Fig. 1). Two different distributions are represented, the observed distribution and the expected distribution (equiprobability between species). Bulla correctly argues that the closer the observed distribution approaches the expected distribution, the 0.5

An Index of Evenness and Its Associated Diversity Measure

Evenness is an important property of all ecological communities. It may be defined as degree to which the abundances are equal among the species present in sample or (Molinari 1989). The most accepted measures of evenness are the J index (H'/H'max) (Pielou 1969), and Alatalo's (1981) simple but important modification of Hill's (1973) E21 ratio. Molinari (1989) studied the behavior of these indices over gradient of increasing evenness and found that both J and F21 have two important shortcomings: a) they tend to strongly overestimate evenness specially when its real value is low, and b) their behavior is decidedly nonlinear, the indices grow very fast at low equitabilities and then level off and change very slowly. Consequently, he developed G21 a calibrated version of F21, to overcome these limitations. G21 is an empirical mathematical transformation of F21 that effectively linearizes it and greatly improves its accuracy, at least in collections of only two species. As practical tool it is the best index already available, but it has both conceptual and practical drawbacks. The most important are: 1) It is purely empirical measure, without any clear ecological meaning. As pointed out by Molinari (1989), the usual interpretation of F21 as ratio of very abundant to abundant species is not correct and should be avoided. For G21 the problem is even greater, because of the complexity of the mathematical transformations involved. 2) The statistical properties of G21 are unknown. Consequently, it is impossible to make formal statistical comparisons among samples or communities. This is problem shared by many other indices. 3) G21 (as F21) measures evenness within those species with intermediate and high proportional abundances. Its value is little influenced by the species with low abundances. Consequently, the index fails to discriminate between communities whose main difference rests in the relative proportion of rare species. This last point is of great importance. In many ecological communities the proportion of rare species is an important component of evenness, perhaps the one that most clearly distingishes one community from another (Medina and Huber 1992; and see Fig. 4 for real example). Besides, the rare species are very sensitive to perturbations or environmental changes. Their sudden decrease or even disappearance produce changes in evenness, that good index should be able to detect. In the past, the lack of sensitivity to rare species was considered as desirable property in an evenness index, because it makes it robust against sampling bias. However, the occurrence of rare species in sample is not an effect of sampling bias, but consequence of important characteristics of the community that should not be ignored. This article proposes new evenness index that tries to overcome these problems. It is much simpler than the already discussed indices. It shows linear behaviour over gradients of increasing equitability, and has an immediate and realistic ecological interpretation. It also gives equal weight to all species independently of their abundances. It allows the derivation of simple diversity index, and its statistical distribution is known (Appendix 1).

RFLP approach to breeding for quantitative traits in plants—a critique

A number of recent papers suggest that use of RFLPs as markers offers a clear advantage in breeding for improvement in quantitative traits (QTs). The concepts underlying establishment of linkage between RFLP markers and QT loci stem from three papers on tomato published during 1987–1991. Essentially, continuously varying QT phenotypes are assigned to RFLP genotype classes, which can be considered to be determined by a single, diallelic gene with codominant alleles. Linkage is inferred through statistical analysis. Similarly, interaction between markers and QT is also tested by an analysis of variance. Here, the statistical methods employed in these three papers to detect linkage are critically evaluated, especially because subsequent investigations take the concepts developed in these papers as proven. In this paper, we examine the three fundamental papersde novo. We scrutinize the methods employed and the inferences drawn to bring to light what we believe are conceptual drawbacks.

Social impact and social preference as determinants of children's peer group status.

Three sociometric procedures, which utilize a two-dimensional social-impact and social-preference framework, were evaluated on three independent samples of fourthand fifth-grade children (N = 334, 173, 89). The stability and distribution of classification, the relationship between dimensions, the validation of dimensions, and the validation of classificatio n groups were considered. Overall, the Peery (1979) method appeared most problematic, due to both conceptual and practical drawbacks. The Coie, Dodge, and Coppotelli (1982) procedure was found to have nonexhaustive groups and had the potential of misrepresenting children's social networks when standardized scores were used. Furthermore, little support was found for the proposed controversial group in the Coie et al. classification system. An alternative two-dimensional sociometric model based on probability theory was proposed and was found to have excellent performance characteristics while still providing a constant frame of reference across social networks. The social reputational correlates of the impact and preference dimensions and the sociometric groups proposed by each model were also investigated. Although social impact and social preference are found to be reliable and valid determinants of peer group status, the need for alternative indicators of children's social standing in the peer group is discussed. The current empirical interest in children's friendships and peer relations has resulted in the increased use of sociometric classification schemes to categorize children both for nomothetic research and for clinical interventions. The further development of sociometric procedures and their appropriate use are important concerns for developmental and clinical psychologists because of the association between children's peer relations and subse