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PubMed1990

Applications of covariance structure modeling in psychology: cause for concern?

Methods of covariance structure modeling are frequently applied in psychological research. These methods merge the logic of confirmatory factor analysis, multiple regression, and path analysis within a single data analytic framework. Among the many applications are estimation of disattenuated correlation and regression coefficients, evaluation of multitrait-multimethod matrices, and assessment of hypothesized causal structures. Shortcomings of these methods are commonly acknowledged in the mathematical literature and in textbooks. Nevertheless, serious flaws remain in many published applications. For example, it is rarely noted that the fit of a favored model is identical for a potentially large number of equivalent models. A review of the personality and social psychology literature illustrates the nature of this and other problems in reported applications of covariance structure models.

Analysis of Variance↗
PubMed2005

Patterns of continuity: a dynamic model for conceptualizing the stability of individual differences in psychological constructs across the life course.

In contemporary psychology there is debate over whether individual differences in psychological constructs are stable over extended periods of time. The authors argue that it is impossible to resolve such debates unless researchers focus on patterns of stability and the developmental mechanisms that may give rise to them. To facilitate this shift in emphasis, they describe a formal model that integrates 3 developmental processes: stochastic-contextual processes, person-environment transactions, and developmental constancies. The theoretical and mathematical analyses indicate that this model makes novel predictions about the way in which test-retest correlations are structured across a wide range of ages and test-retest intervals. The authors illustrate the utility of the model by comparing its predictions against meta-analytic data on Neuroticism. The discussion emphasizes the value of focusing on patterns of continuity, not only as phenomena to be explained but as data capable of clarifying the developmental processes underlying stability and change for a variety of psychological constructs.

Humans↗
PubMed2005

Methodology in family science: introduction to the special issue.

Methodology influences every facet of scientific inquiry including the processes of framing questions, operationalizing constructs, sampling individuals within populations and observations within persons, analyzing data, and bringing meaning to the results. This introduction to the special issue on methodology emphasizes the recursive interaction of research methodology and theories underlying family science. Because the science of family psychology is richly complex, so too must the methods for examining couple and family phenomena be equally diverse. Articles comprising this special issue vary in their emphasis on research design versus data-analytic techniques and on confirmatory versus discovery-oriented strategies. The special issue is intended to advance not only the conduct of family science but also the understanding and integration of an increasingly complex research literature by those engaged in education and clinical interventions. ((c) 2005 APA, all rights reserved).

Journal Article↗
PubMed2003

Assessing worry in older adults: confirmatory factor analysis of the Penn State Worry Questionnaire and psychometric properties of an abbreviated model.

The assessment of worry among older adults typically has involved measures designed with younger cohorts. Because of special concerns in assessing older adults, modifications to existing instruments may be necessary. Addressing equivocal factor analytic data on the Penn State Worry Questionnaire (PSWQ) among younger adults, the authors conducted confirmatory factor analyses to evaluate the generalizability of previous models to older adults with generalized anxiety disorder. Data fit poorly with established single- and two-factor models. The single-factor model was modified, resulting in the elimination of 8 items, strong fit indices, high internal consistency, adequate test-retest reliability, and good convergent and divergent validity. Further psychometric work is required to assess whether the revised model is a more parsimonious method to assess late-life anxiety.

Aged↗
PubMed1998

Dosage effects of methylphenidate on the social behavior of adolescents diagnosed with attention-deficit hyperactivity disorder.

Research participants were 46 adolescents (mean age = 13.8 years) who completed an intensive summer treatment program including a placebo-controlled, double-blind, crossover trial of 3 doses of methylphenidate (MPH) totaling 25, 50, or 75 mg per day. Dependent measures focused on social behavior and included observed behavior frequencies and ratings completed by counselors and parents, including side effects. Multiple data analytic methods were used with the goal of (a) describing the shape of the dose-response curves across multiple measures of social functioning, (b) determining the percentage of adolescents whose social behavior improved in response to MPH, and (c) assessing the incremental gains that result from increases in dose. The results show that (a) the shape of the dose-response curve is influenced by the measurement method, (b) the majority of adolescents exhibited improved social behavior when treated with MPH, (c) the bulk of the positive effects of MPH were achieved at the lowest dose, and (d) there appear to be diminishing positive effects and an increased risk of negative effects with successively higher doses.

Adolescent↗
PubMed2005

Publication bias in research synthesis: sensitivity analysis using a priori weight functions.

Publication bias, sometimes known as the "file-drawer problem" or "funnel-plot asymmetry," is common in empirical research. The authors review the implications of publication bias for quantitative research synthesis (meta-analysis) and describe existing techniques for detecting and correcting it. A new approach is proposed that is suitable for application to meta-analytic data sets that are too small for the application of existing methods. The model estimates parameters relevant to fixed-effects, mixed-effects or random-effects meta-analysis contingent on a hypothetical pattern of bias that is fixed independently of the data. The authors illustrate this approach for sensitivity analysis using 3 data sets adapted from a commonly cited reference work on research synthesis (H. M. Cooper & L. V. Hedges, 1994).

Data Interpretation, Statistical↗
PubMed1988

The nature and origin of interstellar diamond.

Microscopic diamond was recently discovered in oxidized acid residues from several carbonaceous chondrite meteorites (for example, the C delta component of the Allende meteorite). Some of the reported properties of C delta seem in conflict with those expected of diamond. Here we present high spatial resolution analytical data which may help to explain such results. The C delta diamond is an extremely fine-grained (0.5-10 nm) single-phase material, but surface and interfacial carbon atoms, which may comprise as much as 25% of the total, impart an 'amorphous' character to some spectral data. These data support the proposed high-pressure conversion of amorphous carbon and graphite into diamonds due to grain-grain collisions in the interstellar medium although a low-pressure mechanism of formation cannot be ruled out.

Carbon↗
PubMed1985

Antitumour imidazotetrazines, Part IX. The pharmacokinetics of mitozolomide in mice.

Mitozolomide is a novel antitumour agent showing a broad spectrum of activity against murine tumours and is currently undergoing Phase I clinical evaluation in the UK. We have conducted an animal pharmacokinetic study using male BALB/c mice as a pre-requisite to the clinical work. Mice were dosed i.p. at 5 dose levels (0.25-20 mg kg-1) and the oral and transdermal routes of administration were investigated at 20 mg kg-1. The analytical data produced a good fit to a simple open one-compartment pharmacokinetic model with an elimination half-life of the drug from plasma of between 0.68 and 0.88 h over the 0.25-20 mg kg-1 range covered. There was no evident dose dependency over this range and studies with two formulations showed mitozolomide to have good systemic availability when administered via the oral route (F values of 0.66 and 0.81). The drug was also found to be systemically available when administered topically in dimethylsulfoxide (F = 0.47). Mitozolomide shows many biochemical and biological similarities to the clinically used nitrosoureas BCNU and CCNU but our results show that it differs markedly in its kinetics from these two agents, with mitozolomide having relatively sustained plasma levels. It is hoped that this may be of therapeutic benefit if these levels are reflected in relative tumour concentrations.

Administration, Oral↗
PubMed1998

Plasma total-homocysteine in anorexia nervosa.

OBJECTIVE: The measurement of plasma total-homocysteine (tHcy) as a marker of folate and cobalamin status in patients with anorexia nervosa. DESIGN: Plasma tHcy, folate, cobalamin and other determinants of tHcy of a random group of patients with anorexia nervosa were compared with our own reference values. SETTING: The study was performed at the tertiary children's Hospital Sant Joan de Déu. SUBJECTS: All the female adolescents (n=43) coming to the Hospital during a one-year period, who were diagnosed with anorexia nervosa. Reference values for tHcy were simultaneously performed with apparently healthy adolescents (by history and analytical data) who underwent presurgical analysis for minor interventions, and other magnitudes we used our own reference values. INTERVENTIONS: Plasma tHcy was measured by reverse phase HPLC with fluorescence detection of the SBDF derivatives. Folate and cobalamin concentrations were determined by radioimmunoassay. RESULTS: tHcy was significantly increased in anorexic patients compared to reference values (Mann-Whitney, P < 0.0001-0.001). Values were above reference range in 34% of patients, and high-normal range in 53% of patients. tHcy concentrations lowered in 8 and 11 patients after nutritional rehabilitation. Cobalamin and folate were in the reference range except for one case. No significant correlation was found among tHcy, vitamins and other determinants of tHcy concentration. CONCLUSIONS: tHcy concentrations appear significantly increased in adolescents with anorexia nervosa, most probably owing to subclinical folate deficiency. This might be caused by both, intracellular folate deficiency and impaired availability. Abnormal plasma tHcy values were completely corrected after nutritional rehabilitation.

Adolescent↗
PubMed1998

Plasma amino acids in anorexia nervosa.

OBJECTIVE: To evaluate the amino acid profile in a group of adolescents with anorexia nervosa, and to apply alternative ways of presenting and assessing results, so as to increase the information available for understanding the metabolic abnormalities developed in these patients. DESIGN: Plasma amino acid concentrations of a random group of patients with anorexia nervosa compared with values obtained from a 'healthy' adolescent population. SETTING: The study was performed at the tertiary children's Hospital Sant Joan de Deu. SUBJECTS: Female adolescents (n = 92, age: 15+/-1.8 y) at diagnosis of anorexia nervosa. Reference values for amino acids were obtained from apparently healthy adolescents (by history and analytical data) who underwent presurgical analysis for minor operations. INTERVENTIONS: Plasma amino acid concentrations were measured by ion exchange chromatography. Basic laboratory analysis, carnitine and IGF-I were also determined. RESULTS: In anorexic patients plasma concentrations of taurine, asparagine, glutamine, glycine, methionine, phenylalanine, ornithine, and histidine were significantly higher than reference values (Mann-Whitney, P < 0.01-0.0001), whereas arginine and cystine were lower than our reference values (P < 0.0001). Relative amino acid values (the molar fraction of the patient medians relative to control medians) were plotted. The ratios of some amino acids were significantly greater than those obtained from the reference population: Phe/Tyr (P < 0.001), Met/Cys (P < 0.0001), and Gly/Val (P < 0.01). CONCLUSIONS: A trend to hyperaminoacidemia is a common feature in anorexia nervosa. Although absolute amino acid values cannot play a significant role in the assessment of nutritional status in this condition, the calculation of some ratios (Phe/Tyr, Met/Cys and Gly/Val) and the graphical representation of relative values may be useful. The plasma amino acid profile in anorexia nervosa is different from those of other severe malnutrition states, showing a marasmic pattern of balanced protein-energy undernutrition. Cystine and arginine may be considered limiting amino acids in this disease, and the consequences of their deficient concentrations for oxidative damage should be further evaluated.

Adolescent↗
PubMed2004

Vitamin D intakes in 18-64-y-old Irish adults.

OBJECTIVE: To estimate vitamin D intakes in a representative sample of Irish adults and to assess the contribution of foods to these intake estimates. DESIGN: Vitamin D intakes in 1379, 18-64-y-old adults from the North/South Ireland Food Consumption Survey were estimated using a combination of new analytical data for vitamin D in foods, determined by HPLC, and used to revise recipe calculations, together with existing data from McCance and Widdowson's The Composition of Foods, 5th Edition plus supplements. RESULTS: The total mean daily intake (MDI) of vitamin D (1 microg=40 IU) from all sources was 4.2 microg. The MDI was significantly higher (P<0.001) when the contribution from nutritional supplements was included (4.2 microg) compared with food sources only (3.2 microg). Men had significantly higher intakes (4.4 microg) than women (4.0 microg; P<0.001), which increased significantly (P<0.001) with age in both sexes. Meat/meat products (30.1%), fish/fish products (14.3%) and eggs/egg dishes (9.1%) were the main contributors to vitamin D intake. Supplements contributed 6.8 and 12% to MDI in men and women, respectively. In all, 74% of adults had an MDI of vitamin D that was less than the median (5 microg) of the recommended daily range of 0-10 microg. CONCLUSION: The findings of this study suggest that a large number of Irish adults have low vitamin D intakes. This, along with emerging evidence of low vitamin D status in at least some population subgroups, suggests that strategies to increase vitamin D intakes, including fortification of food, should be investigated.

Adolescent↗
PubMed2006

Methodological challenges in constructing effective treatment sequences for chronic psychiatric disorders.

Psychiatric disorders are often chronic conditions that require sequential decision making to achieve the best clinical outcomes. Sequential decisions are necessary to accommodate treatment response heterogeneity, a variable course of illness, and the often heavy burden associated with intensive or longer-term treatment. Yet, only a few studies in this field have been designed to address sequential decisions. Most of the experimental designs and data analytic methods that are best suited for improving sequential clinical decision making are often found in nonmedical fields such as engineering, computer science, and statistics. Promising designs and methods are surveyed with a focus on those areas most immediately useful for informing clinical decision making.

Chronic Disease↗
PubMed1999

Quality assurance in measuring the elemental composition of the alga Fucus vesiculosus.

Algae are increasingly used for the purpose of environmental biomonitoring, for instance in the long-term program of the Federal Environmental Specimen Bank of Germany. Therefore, for the studies presented here, freeze-dried samples of Fucus vesiculosus collected from the North Sea shores were analyzed for a broad range of elements by instrumental neutron activation analysis (INAA), while inductively coupled plasma atomic emission spectrometry (ICP-AES) and mass spectrometry (ICP-MS) were carried out on digests. The entire analytical procedures, including field sampling, cleaning of material, sample handling, determination of blanks and instrumental parameters, are described. Certified reference materials analyzed in parallel with real samples and intermethod comparisons were used for assuring the accuracy of the analytical data. Reproducibility of INAA measurements was between 4 and 6% depending on the element considered. Possible sources of uncertainty and variation of the contaminant origins are discussed. Boundary conditions for the performance of algae sampling within environmental monitoring programs and the application of this marine bioindicator for the purpose of controlling time-dependent and local differences in element patterns are presented.

Cryopreservation↗
PubMed2001

Enantioselective molecular sensing of aromatic amines using tetra-(S)-di-2-naphthylprolinol calix[4]arene.

This paper presents new analytical data, and evidence of the fluorescence quenching mechanism involved in enantioselective signals obtained with the chiral host tetra-(S)-di-2-naphthylprolinol calix[4]arene. Excellent selectivity is obtained with phenylglycinol and norephidrine in methanol, and samples of unknown enantiomeric composition have been determined with an average error of 1.08 and 0.62%, respectively (n = 6), on the basis of a single fluorescence measurement. The absence of any quenching observed with the related amines of phenylalaninol is attributed to a methylene spacer which inhibits efficient interaction between the aryl group of the guest and the naphthyl group of the host. The importance of the phenyl group of the guest in the quenching mechanism is confirmed by the complete absence of any quenching effect with cyclohexylethylamine.

Amines↗
PubMed2002

Inductively coupled plasma mass spectrometric determination of heavy metals in sea-water samples after pre-treatment with a chelating resin disk by an on-line flow injection method.

A new on-line flow injection (FI) pre-treatment system using a disk-type chelating resin (5 mm diameter, 0.5 mm thickness) was developed for the simultaneous multi-element determination of trace metals in sea-water samples by inductively coupled plasma mass spectrometry (ICP-MS). A chelating resin possessing an iminodiacetate (IDA) functional group was used for the collection of trace elements and the elimination of alkali and alkaline earth metals in highly concentrated salt solution. A 1 ml volume of a sea-water sample (pH 5.5) was applied to the chelating resin disk. Considering the removal efficiency for Ca, 50 mM ammonium acetate buffer solution (pH 5.5) was chosen as a sample carrier. The enriched trace metals were eluted with 0.1 M nitric acid and the eluate flowed into the ICP-MS system. The processing time for one sample was < 6 min (350 s). One of the important observations is the possibility of working with a low recovery, even lower than 50%. For example, several elements such as Mn, Cr, As, Mo, Ba and U, the recovery of which was < 50% in a batch-wise method, showed good linearity and reproducibility. The proposed method was evaluated by analyzing two kinds of sea-water certified reference materials, CASS-4 and NASS-5. Analytical data for eight heavy metals, V, Mn, Co, Ni, Cu, Mo, Cd and U, obtained from the present study agreed well with the certified values.

Flow Injection Analysis↗
PubMed2004

Determination of CH4, CO2 and N2O in air samples and soil atmosphere by gas chromatography mass spectrometry, GC-MS.

A method for determination of the climate gases CH4, CO2 and N2O in air samples and soil atmosphere was developed using GC-MS. The method uses straightforward gas chromatography (separation of the gases) with a mass spectrometric detector in single ion mode (specific determination). The gases were determined with high sensitivity and high sample throughput (18 samples h(-1)). The LOD (3sigma) for the gases were 0.10 micro L L(-1) for CH4, 20 microL L(-1) for CO2 and 0.02 microL L(-1) for N2O. The linear range (R2 = 0.999) was up to 500 microL L(-1) for CH4, 4000 microL L(-1) for CO2 and 80 microL L(-1) for N2O. The samples were collected in 10 mL vials and a 5 microL aliquot was injected on column. The method was tested against certified gas references, the analytical data gave an accuracy within +/-5% and a precision of +/-3%. The presence of < or = 10% by volume of C2H2 (often used experimentally to prevent N2 formation from N2O) did not interfere with detection for the targeted trace gases.

Air Pollutants↗
PubMed2004

Coordinative flexibility of 1,2-bis[1,4,7-triazacyclonon-1-yl]propan-2-ol in mononuclear and binuclear Ni(II) complexes.

Reaction of 1,2-bis[1,4,7-triazacyclonon-1-yl]propan-2-ol hexabromide (T(2)PrOH.6HBr) with Ni(ClO(4))(2)[middle dot]6H(2)O and adjustment of the pH to 7 resulted in the crystallization of pink and blue products from the one reaction mixture. The analytical data and X-ray structure determinations establish compositions corresponding to [Ni(T(2)PrOH)]Br(ClO(4))xH(2)O (pink crystals) and [Ni(2)(T(2)PrO)(OH(2))(3)Br]Br(ClO(4))x2H(2)O (blue crystals). A repeat synthesis of the latter yielded the diperchlorate monohydrate [Ni(2)(T(2)PrO)(OH(2))(3)Br](ClO(4))(2)xH(2)O. In the mononuclear complex, the 2-propanol group connecting the two 1,4,7-trizacyclononane (tacn) rings is protonated, the six nitrogen donors from the T(2)PrOH ligand coordinating to a single Ni(II) centre in a distorted octahedral geometry. In the binuclear complexes and, three coordination sites on each distorted octahedral Ni(II) centre are occupied fac by three nitrogen donors from the one tacn ring, the two metal centres being linked by an endogenous alkoxo bridge. A notable common feature of the two identical cations is that for one Ni(II) centre the remaining two sites are occupied by two water ligands, while in the other a bromo ligand replaces one ligated water. Similar binuclear systems have been recently defined [Zn(2)(T(2)PrO)X(H(2)O)(2)](ClO(4))(2)(X = Cl, Br), two complexes that exhibit coordination asymmetry with one pseudo-octahedral and one pseudo-square pyramidal Zn(ii) centre. The weak antiferromagnetic coupling in and is discussed and compared to di-phenoxo-bridged Ni(II) examples.

Journal Article↗
PubMed2005

Analytical chemistry of synthetic routes to psychoactive tryptamines. Part II. Characterisation of the Speeter and Anthony synthetic route to N,N-dialkylated tryptamines using GC-EI-ITMS, ESI-TQ-MS-MS and NMR.

The degree of alkylation of the side chain nitrogen in tryptamines is one important factor that affects psychoactivity. The method of Speeter and Anthony is considered to be one of the most important synthetic preparative methods. The final step in this reaction is based on the reduction of a (substituted) indole-3-yl-glyoxalylamide to the desired tryptamine with metal hydride. Twelve symmetrically and 13 asymmetrically N,N-disubstituted glyoxalylamides and their corresponding tryptamine derivatives have been synthesised and characterised by gas chromatography EI-ion trap mass spectrometry, electrospray-triple quadrupole-tandem mass spectrometry and NMR spectroscopy. Mass spectral and NMR similarities and differences between the investigated compounds are discussed. A solvent dependency is observed that has to be taken into consideration for the unambiguous assignment of (1)H- and (13)C-NMR chemical shifts. The (1)H-NMR study demonstrated that one can evaluate the rotamer populations of the asymmetrical glyoxalylamides. In a forensic or clinical scenario where single or multiple reaction monitoring approaches are contemplated, the appropriate ion transitions of choice may then focus on the two main fragmentations, namely beta-cleavage ([M+H](+)-->CH(2)N(+)R(2)R(3)) and/or alpha-cleavage ([M+H](+)-->[3-vinylindole](+)), respectively. The synthesis, NMR and MS analytical data presented provide the forensic analyst and clinical biochemist with a detailed and self-consistent body of information and mechanisms for the spectral identification of the more likely psychoactive tryptamines that may be met.

Gas Chromatography-Mass Spectrometry↗