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PubMed2003

The functional localization of neural networks using genetic algorithms.

We presented an algorithm for extracting Boolean functions (propositions, rules) from the units in trained neural networks. The extracted Boolean functions make the hidden units understandable. However, in some cases, the extracted Boolean functions are complicated, and so are not understandable, which means that the hidden units are not functionally localized. This paper presents an algorithm for the functional localization of (the hidden units of) neural networks. When a hidden unit is well approximated to a low-order Boolean function, the unit can be regarded as functionally localized. The functional localization of a hidden unit is evaluated by the error between the hidden unit and the low-order Boolean function extracted from the hidden unit. The optimization is executed by genetic algorithms. We applied it to vote data, mushroom data and chess data. Experimental results show that the algorithm works well.

Agaricales↗
PubMed1996

Assessment of the biodistribution and metabolism of 5-fluorouracil as monitored by 18F PET and 19F MRI: a comparative animal study.

The effective clinical use of the anticancer drug 5-fluorouracil (5-FU) requires the non-invasive assessment of its transport and metabolism, particularly in the tumor and the liver, where the drug is catabolized to alpha-fluoro-beta-alanine (FBAL). In this study, the potentials and limitations of dynamic 18F PET and metabolic 19F MRI examinations for noninvasive 5-FU monitoring were investigated in ACI and Buffalo rats with transplanted MH3924A and TC5123 Morris hepatomas, respectively. Selective 5-[19F]FU and [19F]FBAL MR images were acquired 5 and 70 min after 5-FU injection using a CHESS MRI sequence. After administration of 5-[18F]FU, the kinetics of the regional 5-[18F]FU uptake were measured by dynamic PET scanning over 120 min. To allow a comparison between PET and MRI data, standardized uptake values (SUV) were computed at the same points in time. The TC5123 hepatoma showed a significantly (p < 0.002) higher mean SUV at 5 and 70 min post-5-FU injection than the MH3924A cell lines, whereas there were no significant differences between the mean SUV measured in the liver of both animal populations. In contrast to the PET data, no significant differences in the mean 5-[19F]FU and [19F]FBAL MR signal values in the tumor of both models were observed. The MR images, however, yielded the additional information that 5-FU is converted to FBAL only in the liver and not in the hepatomas.

Animals↗
PubMed2001

Stabilization of isolated mixed-valence trimers in a novel nickel dithiolene complex with CF2 substituents.

The preparation of the novel paramagnetic nickel dithiolene complex Ni(F2pdt)2-* (F2pdt2-: 2,2-difluoro-1,3-propanediyldithioethylene-1,2-dithiolate) and its X-ray crystal structure as n-Bu4N+ salt are described. (n-Bu4N)[Ni(F2pdt)2] (2) crystallizes in the orthorhombic system, space group Pna2(1) with a = 21.379(4) A, b = 8.9702(18) A, and c = 18.527(4) A. The radical anions are isolated from each other by the bulky n-Bu4N+ cations and exhibit a Curie-type magnetic behavior. Two reversible redox waves corresponding to the redox couples Ni(F2pdt)2(2-/-*) and Ni(F2pdt)2(-*/0) are observed at -0.55 and 0.30 V vs SCE, illustrating the electron withdrawing effect of the CF2 substituents. As a consequence, (TTF)3(BF4)2 oxidation of the radical anion does not afford the neutral Ni(F2pdt)2(0) but a TTF salt formulated as [TTF](3)[Ni(F2pdt)2]3[CH2Cl2]. It crystallizes in the triclinic system, space group P1 with a = 12.330(3) A, b = 12.726(3) A, c =15.706(3) A, alpha = 91.10(3), beta = 110.78(3), and gamma = 116.01(3). Donor and acceptor moieties are organized into (TTF)3(2+) and [Ni(F2pdt)2]3(2-) trimers whose dicationic and dianionic charges have been inferred from the intramolecular bond lengths evolution and the singlet-triplet magnetic behavior. These trimers arrange orthogonally to each other into chess-board-like slabs, characterized by a segregation of the CF2 fragments and further stabilized by weak C-H.F interactions. Extended Hückel calculations show that only the nickel dithiolene complex trimer actually contributes to the magnetic susceptibility.

Journal Article↗
PubMed1999

Covalent Three-Dimensional Titanium(IV)-Aryloxide Networks.

Ti((i)OPr)(4) was treated with 2.58 equiv of hydroquinone in THF to yield a red-orange powder formulated as [Ti(OC(6)H(4)O)(a)()(OC(6)H(4)OH)(3.34)(-)(1.83)(a)()(O(i)Pr)(0.66)(-)(0.17)(a)() (THF)(0.2)](n)() (1, (0.91 </= a </= 1.82)) based upon D(2)O/DCl quenching studies. Treatment of 1 with an excess of hydroquinone in Et(2)O or DME afforded burgundy [Ti(2)(&mgr;(1,4)-OC(6)H(4)O)(2)(&mgr;(1,4)-OC(6)H(4)OH)(2)(&mgr;-OC(6)H(4)OH)(2)](infinity) (2). Burgundy [Ti(2)(&mgr;(1,4)-OC(6)H(4)O)(2)(&mgr;(1,4):eta(2),eta(1)-OC(6)H(4)O)(2)(OH(2))(2).(H(2)O)(2).(H-OC(6)H(4)OH).(MeCN)](infinity) (4) was prepared from 1 and excess wet hydroquinone in CH(3)CN. The acetonitrile in 4 can be exchanged for THF or DME. Treatment of Ti(O(i)Pr)(4) with approximately 4 equiv of 2,7-dihydroxynaphthalene in Et(2)O at 100 degrees C (2 days) in a sealed tube yielded orange crystals of [Ti(2)(&mgr;(1,7)-OC(10)H(6)O)(2)(&mgr;(1,7):eta(2),eta(1)-OC(10)H(6)OH)(2)(O(i)Pr)(2)](infinity) (5). Diffraction studies were conducted at the Cornell High Energy Synchrotron Source (CHESS) because of the small crystal sizes. 2 (C(18)H(14)O(6)Ti, monoclinic, P2(1)/n, a = 9.624 (2), b = 11.283 (2), c = 14.916 (3), beta = 90.47(3) degrees, Z = 4), 4 (C(32)H(33)NO(14)Ti(2), monoclinic, P2(1)/n, a = 16.137 (3), b = 10.762 (2), c = 20.368 (4), beta = 111.65(3) degrees, Z = 4), and 5 (C(23)H(20)O(5)Ti, orthorhombic, Pbca, a = 11.095 (2), b = 17.970 (4), c = 19.484 (4), Z = 8) are 3-dimensional materials based on diaryloxide connectivity between geometrically similar edge shared (i.e., Ti(2)(&mgr;-OAr)(2)) bioctahedral dititanium building blocks. While 2 and 5 possess a roughly body-centered arrangement of dititanium units, 4 has a hexagonal secondary structural motif. The nature of crystallization through alcoholysis is also discussed.

Journal Article↗
PubMed1998

How shall we speak of children's personalities in middle childhood? A preliminary taxonomy.

Developmental researchers have neglected the study of personality traits in middle childhood, thus leaving unanswered many questions about childhood personality structure. This article presents a developmental framework for understanding personality in middle childhood and critically reviews 5 models of temperament and personality structure in this age range: the models of A. Thomas and S. Chess, A. H. Buss and R. Plomin, M. K. Rothbart, J. Block and J. H. Block, and the Big Five. A number of robust personality dimensions common to these models and the broader developmental and adult personality literatures are then discussed: sociability, social inhibition, dominance, negative emotionality, aggressiveness, prosocial disposition, persistence/attention, mastery motivation, inhibitory control, and activity level. These dimensions represent a preliminary taxonomy of personality traits for exploring questions of individual development in childhood.

Age Factors↗
PubMed1995

Long-term working memory.

To account for the large demands on working memory during text comprehension and expert performance, the traditional models of working memory involving temporary storage must be extended to include working memory based on storage in long-term memory. In the proposed theoretical framework cognitive processes are viewed as a sequence of stable states representing end products of processing. In skilled activities, acquired memory skills allow these end products to be stored in long-term memory and kept directly accessible by means of retrieval cues in short-term memory, as proposed by skilled memory theory. These theoretical claims are supported by a review of evidence on memory in text comprehension and expert performance in such domains as mental calculation, medical diagnosis, and chess.

Aptitude↗
PubMed2005

Child temperament does not predict adolescent body composition in girls.

OBJECTIVES: Our previous cross-sectional analysis of MIT Growth and Development (MIT) Study girls showed that activity temperament, as assessed by a nine-item temperament questionnaire, was related to body composition and nonresting energy expenditure (NREE). In girls with lower levels of physical activity, having a high activity temperament was associated with a higher NREE. Percentage body fat was lower in girls with high vs low activity temperament. Based on these results, we hypothesized that, especially in girls with declining levels of physical activity over adolescence, high activity temperament in childhood would be protective against increased adiposity during adolescence. We tested this hypothesis with longitudinal data from the MIT study. DESIGN, SETTING, AND PARTICIPANTS: A total of 196 nonobese premenarcheal girls 8-12 y old were enrolled between 1990 and 1993. Girls were followed until 4 y postmenarche; average duration of follow-up was 7 y. MEASURES: Activity temperament was assessed at baseline by the girls' mothers with questions modified from those developed by Thomas and Chess that tapped predilection for movement. Temperament, the stylistic component of behavior, is considered relatively stable within an individual. Body composition was assessed by total body water at baseline and study completion (4 y postmenarche), and by bioelectrical impedance (BIA) annually. Physical activity was assessed annually by questionnaire, and by activity diary at baseline only. RESULTS: Child activity temperament was not associated with percentage body fat at 4 y postmenarche in multivariate regression models controlling for baseline percentage body fat, physical activity, parental obesity status, age at menarche, age at baseline, and race-ethnicity. Body composition of girls with low and high activity temperaments who reported declining levels of physical activity over adolescence was not statistically significantly different at study completion. In longitudinal models of percentage body fat by BIA, high activity temperament was not associated with lower adiposity. CONCLUSION: Although high activity temperament was associated cross-sectionally with lower percentage body fat and higher NREE, we did not find evidence to support our hypothesis that high child activity temperament would be protective for increased adiposity prospectively in our cohort of girls followed over the adolescent period.

Aging↗
PubMed2003

Translation and restandardization of an instrument: the Early Infant Temperament Questionnaire.

AIMS OF THE STUDY: To test the psychometric properties of a Danish translation of the Early Infant Temperament Questionnaire (EITQ) and to establish standards for scoring the questionnaire. RATIONALE: The general aim was to create a translation that remained close to the original version, was meaningful for the Danish participants, and had acceptable psychometric properties. BACKGROUND: Patterns of temperament can be discerned early in life and tend to persist over time and across situations. For the past 50 years, temperament has been studied by theorists, clinicians and nurse clinicians to predict behaviour, discover interventions that prevent serious behaviour disturbances, and help parents understand the implications of their child's temperament. Thomas and Chess's conceptualization of temperament in nine categories was the framework for the development of the English-language EITQ. Research methods. The translation followed a stepwise process of translation, back translation and consensus. A convenience sample of 204 Danish mothers with 1-4-month old infants completed the translated questionnaire and a demographic questionnaire in 1999. RESULTS: Alpha coefficients for the nine subscales ranged from 0.59 to 0.82. All alpha coefficients were comparable to or higher than those reported on the original United States standardization study. There were statistically significant differences between reported United States mean scores and those in the Danish sample. DISCUSSION: The psychometric properties of the Danish translation are equal to or better than those reported for the United States study. Differences in mean scores or most subscales point to the need to create Danish profiles for scoring. CONCLUSIONS: The Danish version of the EITQ has acceptable reliability and is ready for use in Denmark.

Denmark↗
PubMed1999

Classifications in psychiatry: a conceptual history.

BACKGROUND: Historical accounts of psychiatric classifications have hitherto been written in terms of a 'received view'. This contains two assumptions, that: (i) the activity of classifying is inherent to the human mind; and (ii) psychiatric 'phenomena' are stable natural objects. OBJECTIVES: The aim of this article is to provide an outline of the evolution of psychiatric classifications from the perspective of conceptual history. This is defined as a theoretical and empirical inquiry into the principles, sortal techniques and contexts in which alienists carried out their task. It assumes that all psychiatric classifications are cultural products, and endeavours to answer the question of whether classificatory models imported from the natural sciences can be applied to man-made constructs (such as mental illness) definitionally based on 'personalised semantics'. METHODS: Exemplars of classificatory activity are first mapped and contextualised. Then, it is suggested that in each historical period crafting classifications has been like playing a game of chess with each move being governed by rules. This is illustrated by offering an analysis of the 1860-1861 French debate on classification. RESULTS AND CONCLUSIONS: (1) Medicine is not a contemplative but a modificatory activity and hence classifications are only valuable if they can release new information about the object classified. (2) It should not be inferred from the fact that psychiatric classifications are not working well (i.e. that they only behave as actuarial devices) that they must be given up. Conceptual work needs to continue to identify 'invariants' (i.e. stable elements that anchor classifications to 'nature'. (3) Because mental disorders are more than unstable behavioural epiphenomena wrapped around stable molecular changes, 'neurobiological' invariants may not do. Stability depends upon time frames. Furthermore, it is unlikely that gene-based classifications will ever be considered as classifications of mental disorders. For once, they would have low predictive power because of their lack of information about the defining codes of mental illness. 'Social' and 'psychological' invariants have problems of their own.

History, 18th Century↗
PubMed2003

[Temperament and affective disorders--historical basis of current discussion].

The history of the temperament concept begins in ancient Greece. The humoral theory remained influential over the centuries. At the beginning of the 20 th century, both Wilhelm Wundt and his pupil Emil Kraepelin formulated new aspects. Wundt described two dimensions: "speed of variability of emotions" and "intensity of emotions". Kraepelin observed four fundamental states (depressive, manic, irritable and cyclothymic), which he linked to manic-depressive illness. Since then different lines of temperament research have evolved: (1) psychiatric-psychopathological theories (e. g. Ewald, Kretschmer and Sheldon), which tend to see temperament as a dilution of full-blown affective disorders; (2) neurobiological theories (e. g. Pavlov, Eysenck and Gray), which understand temperament as determined by underlying neurobiological processes - especially levels of arousal; and (3) developmental theories (e. g. Chess & Thomas, Rothbart and Kagan), which derived their temperament concept from early childhood observations. Recent theories (e. g. those of Cloninger or Akiskal) combine different aspects. After reviewing the historical temperament concepts we present underlying factors which are linked to affective disorders (such as emotional reactivity, cyclicity or trait affectivity). Finally, we illustrate the importance of temperament concepts for research in affective disorders.

History, 19th Century↗
PubMed2006

[In vivo proton MR spectroscopy of normal liver parenchyma: technique and results].

PURPOSE: To analyze the proton magnetic resonance spectroscopic data ( (1)H MRS) of normal liver parenchyma with regard to age, sex, body mass index and location in the liver. MATERIALS AND METHODS: 45 healthy volunteers age 24 to 65 years were examined with an optimized single-voxel (1)H MRS using a 1.5-T scanner. A spin echo sequence with a TR of 1500 ms and a TE of 135 ms was used, allowing in-phase detection of the choline signal. Weak water suppression was achieved using a chemical shift selective suppression (CHESS) technique. Each examination included the measurement of three voxels with a voxel size of 18 x 18 x 18 mm (3) in different areas of the liver. The volunteers were divided into different age-based groups (young: < or = 44 years; older: > or = 44 years), BMI (normal weighted: < 25 kg/m (2); obese: > 25 kg/m (2)) and sex. RESULTS: In the acquired spectra different lipid (e. g. [CH (2)] (n)), choline, glutamine, glutamate and glycogen-glucose-complex resonances were detected. The analysis of the spectra, however, only focused on the concentrations of choline and (CH (2)) (n) and the relative concentrations of the choline-to-(CH (2)) (n)-ratios. In the older volunteers the relative concentration of the choline-to-(CH (2)) (n)-ratio was significantly decreased by 0.213 +/- 0.193 in comparison to the younger subjects (p = 0,031). Further statistical analysis confirmed a significant decrease of the choline-to-(CH (2)) (n)-ratio by 0.223 +/- 0.180 in obese volunteers compared to volunteers of a standard weight (p = 0,016). The significant difference between the choline-to-(CH (2)) (n)-ratio in female versus male volunteers was calculated with an increase of 0.483 +/- 0.172 (p = 0,000). The location of the voxel in the liver parenchyma did not yield a significant difference in the choline-to-(CH (2)) (n)-ratio. CONCLUSION: The analysis of the proton liver MRS of healthy volunteers indicated a significant difference in the choline-to-(CH (2)) (n)-ratio depending on age, sex, and BMI with a confidence interval of 95 %. The different choline-to-(CH (2)) (n)-ratio could be the result of the body fat distribution depending on age and sex and also of the increased fat portion of the body in obese volunteers.

Adult↗
PubMed1974

The psychological concept of "losing move" in a game of perfect information.

From a game-theoretic standpoint, in any two-person game of perfect information, each position is won, lost, or drawn, and a move is to be considered an error only when it transfers the game from a more favorable to a less favorable state. A psychological concept of error is quite different, in that it must take into account the fallibility of the players as information processing systems. This paper introduces a psychological concept of error in such games based on the distinction between "obvious" and "problematic" moves, and proposes a formalism for this concept that appears to capture, at least to a first approximation, the notion of "losing move" as that phrase is actually used by players in games like chess.

Journal Article↗
PubMed2004

Chunks in expert memory: evidence for the magical number four ... or is it two?

This study aims to test the divergent predictions of the chunking theory (Chase & Simon, 1973) and template theory (Gobet & Simon, 1996a, 2000) with respect to the number of chunks held in visual short-term memory and the size of chunks used by experts. We presented game and random chessboards in both a copy and a recall task. In a within-subject design, the stimuli were displayed using two presentation media: (a) physical board and pieces, as in Chase and Simon's (1973) study; and (b) a computer display, as in Gobet and Simon's (1998) study. Results show that, in most cases, no more than three chunks were replaced in the recall task, as predicted by template theory. In addition, with game positions in the computer condition, chess Masters replaced very large chunks (up to 15 pieces), again in line with template theory. Overall, the results suggest that the original chunking theory overestimated short-term memory capacity and underestimated the size of chunks used, in particular with Masters. They also suggest that Cowan's (2001) proposal that STM holds four chunks may be an overestimate.

Adolescent↗
PubMed1984

Computation of statistical secondary structure of nucleic acids.

This paper presents a computer analysis of statistical secondary structure of nucleic acids. For a given single stranded nucleic acid, we generated "structure map" which included all the annealing structures in the sequence. The map was transformed into "energy map" by rough approximation; here, the energy level of every pairing structure consisting of more than 2 successive nucleic acid pairs was calculated. By using the "energy map", the probability of occurrence of each annealed structure was computed, i.e., the structure was computed statistically. The basis of computation was the 8-queen problem in the chess game. The validity of our computer programme was checked by computing tRNA structure which has been well established. Successful application of this programme to small nuclear RNAs of various origins is demonstrated.

Biological Evolution↗
PubMed1999

Adolescent social anxiety as an outcome of inhibited temperament in childhood.

OBJECTIVE: Chess and Thomas suggested that temperament might make a contribution to social phobia and other forms of extreme social anxiety. This study provides the first investigation of the outcomes in adolescents who had been inhibited (subdued to and avoidant of novelty) or uninhibited (approaching novelty) in the second year of life, utilizing both direct interview and direct observation. METHOD: Seventy-nine subjects, aged 13 years, who had been classified as inhibited or uninhibited in the second year were assessed with both standardized interview and direct observation. RESULTS: There was a significant association between earlier classification of a child as inhibited and generalized social anxiety at adolescence, but no association with specific fears, separation anxiety, or performance anxiety. The adolescents who were classified as socially anxious made fewer spontaneous comments than those without social anxiety; no relation was seen between any other type of fear and the number of spontaneous comments. Adolescent girls who had been inhibited as toddlers were more likely to be impaired by generalized social anxiety than boys. CONCLUSIONS: The interview and observational data indicate that important aspects of an inhibited temperament are preserved from the second year of life to early adolescence, which predispose an adolescent to social anxiety.

Adolescent↗
PubMed1983

Nitrogen Turnover and Assimilation during Regrowth in Trifolium subterraneum L. and Bromus mollis L.

Subterranean clover (Trifolium subterraneum L. cv Woogenellup) and soft chess grass (Bromus mollis L. cv Blando) were grown in monocultures with (15)NH(4)Cl added to the soil to study nitrogen movement during regrowth following shoot removal. Four clipping treatments were imposed. Essentially all available (15)N was assimilated from the soil prior to the first shoot harvest. Measurements of total reduced nitrogen and (15)N contained within that nitrogen fraction in roots, crowns, and shoots at each harvest showed large, significant (P </= 0.001) declines in excess (15)N of crowns and roots in both species between the first and fourth harvests. There was no significant decline in total reduced nitrogen in the same organs over that period. Similar responses were evident in plants defoliated three times. The simplest interpretation of these data is that reduced nitrogen compounds turn over in plant roots and crowns during shoot regrowth. Calculations for grass and clover plants clipped four times during the growing season indicated that 100 to 143% of the nitrogen present in crowns and roots turned over between the first and fourth shoot harvest in both species, assuming nitrogen in those organs was replaced with nitrogen containing the lowest available concentration of (15)N. If other potential sources of nitrogen were used for the calculations, it was necessary to postulate that larger amounts of total nitrogen flowed through the crown and root to produce the measured dilution of (15)N compounds. These data provide the first quantitative estimates of the amount of internal nitrogen used by plants, in addition to soil nitrogen or N(2), to regenerate shoots after defoliation.

Journal Article↗
PubMed2000

Increased resolution data from a large unit cell crystal collected at a third-generation synchrotron X-ray source.

A third-generation synchrotron source was used to collect data from crystals with a very large unit cell. There was an increase in the effective resolution of the data from 5 to 3.5 A. Data were collected on crystals of HK97 mature empty capsids, space group P2(1), with unit-cell parameters a = 580, b = 625, c = 790 A, beta = 90.0 degrees. Like other crystals with very large unit-cell dimensions, the intensity falls off rapidly as a function of resolution, with a precipitous drop beginning at 9 A resolution. Synchrotron data from these crystals were previously observed at the CHESS F1 beamline to about 3.5 A resolution, but the intensities could not be accurately measured beyond 5 A. In experiments conducted at the Advanced Photon Source (APS) beamline 14-BM-C, data from identical crystals could be processed to a resolution of 3.5 A. The lifetime of the crystals in the beam was increased from one exposure per crystal volume to between four and eight exposures per crystal volume. More than 500 images were collected in two trips, allowing the extension of the resolution of the data set and the structure determination to 3.5 A resolution. Factors in the increased resolution may include X-ray flux, beamline geometry and low background scatter. These results suggest that other crystals with large unit cells and pronounced intensity falloff with resolution may benefit from the use of this or similar beamlines.

Capsid↗
PubMed2002

Crystallization and preliminary crystallographic analysis of the ezrin FERM domain.

Ezrin is a member of the ERM (ezrin/radixin/moesin) family of proteins that cross-link the actin cytoskeleton to the plasma membrane and that also function, both upstream and downstream of the small G-protein Rho, in signaling cascades that regulate the assembly of actin stress fibers. In this study, crystals were obtained of the amino-terminal 297 residues (referred to as FERM) of ezrin. The crystals of the FERM domain of ezrin belong to the monoclinic space group P2(1), with unit-cell parameters a = 48.5, b = 112.8, c = 66.3 A, beta = 102.3 degrees, and contain two molecules in the asymmetric unit. A 2.3 A data set was collected using synchrotron radiation at CHESS A1.

Crystallization↗