2,553 research outputs found
Language and Culture
No full textLanguage pervades social life. It is a primary means by which we gain access to the contents of others\u27 minds and establish shared understanding of the reality. Meanwhile, there is an enormous amount of linguistic diversity among human populations. Depending on what counts as a language, there are 3,000 to 10,000 living languages in the world, although a quarter of the world’s languages have fewer than 1,000 speakers and half have fewer than 10,000 (Crystal, 1997). Not surprisingly, a key question in culture and psychology research concerns the role of language in cultural processes. The present chapter focuses on two issues that have received by far the greatest amount of research attention from cultural researchers. First, how does language and human cultures co-evolve? Second, what are the non-linguistic cognitive effects of using a certain language? Does speaking different languages orient individuals to see and experience the external reality differently? The scope of the present chapter does not permit a comprehensive review of all pertinent research; only a selected sample of studies will be used to illustrate the main ideas in the present chapter
New approaches to Q-matrix validation and estimation for cognitive diagnosis models
No full textA primary purpose of cognitive diagnosis models (CDMs) is to classify examinees based on their attribute patterns. The Q-matrix (Tatsuoka, 1985), a common component of all CDMs, specifies the relationship between the set of required dichotomous attributes and the test items. Since a Q-matrix is often developed by content-knowledge experts and can be influenced by their judgment (de la Torre & Chiu, 2016), this can lead to misspecifications in the Q-matrix that can have unintended consequences on examinees’ classifications. Incorrect classification of examinees can have tremendous impact since some assessments are high-stake and are used to make important decisions about students, such as selection and placement. Previous research based on the Trends in International Math and Science Study (TIMSS) has predominantly focused on comparing the performances of participating countries using their average scores.
This study focused on fitting data from the TIMSS with a CDM to obtain estimated attribute profiles that will provide information about skill proficiency of students in the participating countries. However, since the test is not specifically designed for use with a CDM, a provisional Q-matrix was developed with input from content experts. As a preliminary analysis, the TIMSS data was first fitted with the generalized deterministic inputs, noisy, “and” gate (G-DINA) model to obtain examinees’ estimated attribute profiles. An evaluation of the estimated attribute profiles however indicated that there are inconsistencies in classification, which may be due to misspecification in the provisional Q-matrix. To ensure that the provisional Q-matrix is appropriately developed, this dissertation proposes one Q-matrix validation method that can be used to correct possible misspecifications in a Q-matrix, and one Q-matrix estimation method for estimating a Q-matrix from scratch.
The proposed methods both integrate the Q-matrix validation procedure (Chiu, 2013) that is based on a nonparametric classification method. The first method, the integrated Q-matrix validation (IQV) technique, uses a joint maximum likelihood estimation (JMLE) procedure for diagnostic classification models (Chiu, Köhn, Zheng, and Henson, 2016) to determine examinees’ attribute profiles that are then integrated into the algorithm of Chiu’s Q-matrix validation method to validate the Q-matrix. In the second method, the two-step Q-matrix estimation (TSQE) method, factor analysis is first applied to the correlation matrix to obtain a provisional Q-matrix. The provisional Q-matrix is then incorporated into the algorithm of Chiu’s Q-matrix validation method, to obtain the true Q-matrix.
The viability of both methods was investigated using simulation studies with various conditions. The TIMSS data was re-analyzed with the G-DINA model using modified Q-matrices obtained from analysis with the proposed methods. An evaluation of the updated estimated attribute profiles indicated that some of the inconsistencies in classification that were previously identified have been resolved.Ph.D.Includes bibliographical reference
Subspace identification of 1D spatially-varying systems using Sequentially Semi-Separable matrices
No full textWe consider the problem of identifying 1D spatially-varying systems that exhibit no temporal dynamics. The spatial dynamics are modeled via a mixed-causal, anti-causal state space model. The methodology is developed for identifying the input-output map of e.g a 1D flexible beam described by the Euler-Bernoulli beam equation and equipped with a large number of actuators and sensors. It is shown that the static input-output map between the lifted inputs and outputs possess a so-called Sequentially Semi-Separable (SSS) matrix structure. This structure is of key importance to derive algorithms with linear computational complexity for controller synthesis of large-scale systems. A nuclear norm subspace identification method of the N2SID class is developed for estimating these state space models from input-output data. To enable the method to deal with a large number of repeated experiments a dedicated Alternating Direction Method of Multipliers (ADMM) algorithm is derived. It is shown in this paper that a nuclear norm relaxation on the SSS structure can be imposed which improves the estimates of the system matrices.Accepted Author ManuscriptTeam Raf Van de Pla
Are partner-country statistics useful for estimating"missing"trade data?
No full textBecause many developing countries fail to report trade statistics to the United Nations, there has been an interest in using partner-country data to fill these information gaps. The author used partner-country statistics for 30 developing countries to"estimate"actual (concealed) trade data and analyzed the magnitude of the resulting errors. The results indicate that partner-country data are unreliable even for estimating trade in broad aggregate product groups such as foodstuffs, fuels, or manufactures. Moreover, tests show that the reliability of partner-country statistics degenerates sharply as one moves to more finely distinguished trade categories (lower-level SITCs). Equally disturbing, about one-quarter of the partner-country comparisons take the wrong sign. That is, one country's reported free-on-board (f.o.b.) exports exceed the reported cost-insurance-freight (c.i.f.) value of partners'imports. Aside from product composition, tests show that partner-country data are equally inaccurate for estimating the direction of trade. Why are partner-country data so unreliable for approximating"missing"data? Evidence shows: 1) problems in reporting or processing COMTRADE data; 2) valuation differences (f.o.b. versus c.i.f.) for imports and exports; 3) problems relating to entrepot trade, or exports originating in export processing zones; 4) problems associated with exchange-rate changes; 5) intentional or unintentional misclassification of products; 6) efforts to"conceal"trade data for proprietary reasons; and 7) financial incentives to purposely falsify trade data. The author concludes that efforts to improve the general quality, or availability, of trade statistics using partner-country data holds little or no promise, although this information may be useful in specific cases where the trade statistics of a certain country are known to incorporate major errors. Significant progress in ugrading the accuracy, and coverage, of trade statistics can be achieved only by improving each country's procedures for data collection.ICT Policy and Strategies,Trade Policy,Economic Theory&Research,Environmental Economics&Policies,Statistical&Mathematical Sciences,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Trade Policy,Environmental Economics&Policies,Economic Theory&Research,ICT Policy and Strategies
OPTO-VIBRONIC INDUCTION OF CHIRALITY AND SPIN SELECTION RULE IN JAHN-TELLER EFFECT.
No full text Y.N. Chiu, J. Chem. Phys. 50, 5336 (1969) H.A. Jahn, Proc. Roy. Soc. (London) A164, 117 (1938) G. Herzberg ``Electronic Spectra and Electronic Structures of Polyatomic Molecules'' (D. Van Nostrand Co., Inc., Prentice Hall, N.J. 1966)Author Institution: Center for Molecular Dynamics and Energy Transfer, Department of Chemistry, The Catholic University of AmericaA mechanism is proposed for the production of chiral molecules through the cooperative action of polarized light and vibronic interaction. It requires a doubly-degenerate electronic state of an achiral molecule be splitted by a non-degenerate vibration of pseudoscalar symmetry in a Jahn-Teller Effect. The splitting results in symmetric double potential wells for the lower level, with one side of the well corresponding to one enantiomer and the other side to its mirror image, and with equal probability for each. It will be shown that the discrimination of one enantiomer from the other may be assisted either by the neutral-current coupling to nuclear weak interaction or by a second-order radiative both of which have pseudoscalar symmetry. It was found that only a limited class of molecules are amenable to this phenomenon. They belong to , and . Spin singlet and doublet states are both considered. For and transformation of spin , the most general selection rule consistent with time-reversal is derived. New tabulation is given to correct some misconceptions and minor errors in existing literature
Corrigendum to “The classical Artin approximation theorems”
No full textThe purpose of this note is to clarify and complement various places in the article The classical Artin approximation theorems, published in Bull. Amer. Math. Soc. 54 (2017), no. 4, 595–633. A few reasonings in the article may have been difficult to follow or were even problematic. The author is indebted to F. Castro-Jiménez, C. Chiu, R. Ephraim, B. Lamel, S. Perlega, G. Pfister, G. Rond, M. Singer, S. Woblistin, and particularly to an anonymous referee for valuable feedback.</p
MOLECULAR MULTICENTER INTEGRALS OF SPHERICAL GAUSSIAN FUNCTIONS BY GENERALIZED GRADIENT OPERATOR METHOD
No full text. G. Fieck, Theoret. Chim. Acta 54, 323 (1980). . M. Moharenzadeh and L.-Y. Chow Chiu, J. Chem. Phys. 104, 616 (1996).Author Institution: Department of Chemistry, Howard University; Natural Sciences and Mathematics Department, Bowie State UniversityThe spherical Laguerre Gaussian type function (LGTF) centered at nucleus , : can be generated by operating on the Gaussian exponential, exp () with a generalized gradient operator, . Through the vector coupling of the gradient operators, the Talmi coefficient of transforming the product of two LGTFs, one centered at and the other centered at , into a linear combination of the products of two different LGTFs, one centered at (center of mass of and ) and the other made of the internuclear coordinates, has been obtained. Multicenter molecular integrals of the overlap, the Coulomb repulsion, the spin-spin interaction and the spin-other-orbit interaction can be evaluated analytically. The integral results are simpler than those obtained by Fourier transform convolution $theorem.^{2}
Allosteric Modulation and Structural Determination of G-Protein Coupled Receptors
No full textabstract: G protein-coupled receptors (GPCRs) are known to be modulated by membrane cholesterol levels, but whether or not the effects are caused by specific receptor-cholesterol interactions or cholesterol’s general effects on the membrane is not well-understood. Results from coarse-grained molecular dynamics (CGMD) simulations coupled and structural bioinformatics offer new insights into how cholesterol modulates GPCR function by showing cholesterol interactions with β2AR that agree with previously published data. Additionally, differential and specific cholesterol binding in the CCK receptor subfamily was observed while revealing a previously unreported Cholesterol Recognition Amino-acid Consensus (CRAC) sequence that is also conserved across 38% of class A GPCRs. Mutation of this conserved CRAC sequence of the β2AR affects cholesterol stabilization of the receptor in a lipid bilayer. Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) has proven highly successful for structure determination of challenging membrane proteins crystallized in lipidic cubic phase, however, as most techniques, it has limitations. Using an optimized SFX experimental setup in a helium atmosphere we determined the room temperature structure of the adenosine A2A receptor (A2AAR) at 2.0 Å resolution and compared it with previous A2AAR structures determined in vacuum and/or at cryogenic temperatures. Specifically, we demonstrated the capability of utilizing high XFEL beam transmissions, in conjunction with a high dynamic range detector, to collect high-resolution SFX data while reducing crystalline material consumption and shortening the collection time required for a complete data set.
The results of these studies provide a better understanding of receptor-cholesterol interactions that can contribute to novel and improved therapeutics for a variety of diseases. Furthermore, the experimental setups presented herein can be applied to future molecular dynamics and SFX applications for protein nanocrystal samples to aid in structure-based discovery efforts of therapeutic targets that are difficult to crystallize.Dissertation/ThesisDoctoral Dissertation Biochemistry 202
Simulating the impact of climate change and adaptation strategies on farm productivity and income: A bioeconomic analysis
No full textThis study applied at the farm level in Tunisia aims at understanding the effects of climate change on agricultural productivity and income in Africa. Possible future climates are presented through different climate scenarios. The latter combines three levels of increasing temperature (1�centigrade (C), 2�C, and 3�C) with two levels of decreasing precipitation (10 and 20 percent) and a doubling of carbon dioxide concentration in the atmosphere (350 to 700 parts per million). The farming system of production is replicated through a bioeconomic model; that is, one that couples a cropping system model and an economic model run sequentially. The study reveals that land productivity and farm income decline under climate change. Depending on the changes in precipitation, farm productivity falls by 15 to 20 percent and farm income 5 to 20 percent when the temperature increases moderately (1�C). As the climate warms up (2�C and 3�C), farm productivity and income are severely affected, by 35 to 55 percent and 45 to 70 percent, respectively. When simple adaptation strategies based on new management techniques for hard wheat are tested - more irrigation and fertilization - compensations for the negative effects of climate change are found to be worthwhile only for a 1�C increase in temperature. However, the success of adaptation strategies highly depends on the availability of more water and lower additional cost to mobilize them at the farm level.adaptation strategies, Bioeconomic modeling, Agriculture, Climate change, farm income, productivity,
Agricultural trade liberalization in the Uruguay Round : one step forward, one step back?
No full textAfter evaluating the Uruguay Round's impact on agriculture and border protection in the next decade, the author concludes that while there was significant reform of the rules - particularly the conversion of nontariff barriers into tariffs and the reduction and binding of all tariffs - in practice, trade will probably be liberalized less than expected. The objective of the Round was to reverse protectionism and remove trade distortions. This may not be achieved in practice, at least not until further reductions are carried out in future rounds of negotiations. The major exception to this conclusion is in high-income Asian countries, where protection for major commodities will be significantly reduced. The tariffication and binding of all tariffs on agricultural products represents a significant step forward. Liberalization is implicit because countries are prohhibited from arbitrarily raising tariffs to new higher levels. But many of the newly established tariffs are so high in many countries as to effectively prohibit trade. Patterns of liberalization vary considerably by commodity and by country. Generally, the extent of liberalization was diminished by binding tariffs to the base period of 1986-88, when border protection was at a high point. In most OECD countries, this was worsened by"dirty tariffication:"the new base tariffs offered even greater protection than the nontariff barriers they replaced. Even after the commitments to tariff reductions in the Round, the ad valorem measure of the final binding tariffs will remain higher than the average rate of protection in 1982-93. A number of developing countries in East Asia, Latin America, and the Middle East chose to lock in prior liberalization efforts on some products. But for most commodities, there will be little actual liberalization, since most developing countries chose to bind their tariffs at a maximum level. Even when countries reduced already-bound rates, bound tariffs remained significantly higher than current applied rates, giving countries the flexibility to raise tariffs later. The high level of bound tariffs may allow countries to apply variable tariffs below the bound level, thus failing to stabilize tariffs and improve market access. Moreover, the Round did not touch many of the worst distortions in developing countries, such as import subsidies, export taxes, state-trading monopolies, and domestic policies that implicitly tax agriculture.Trade Policy,Environmental Economics&Policies,Economic Theory&Research,Export Competitiveness,Rules of Origin,Trade Policy,Rules of Origin,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Environmental Economics&Policies,Economic Theory&Research
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