Maternal knowledge and the relationship between home environment and child development

2013 Spring.Includes bibliographical references.Research has identified parenting abilities and the home environment as two of the most important contributors to a child's kindergarten abilities. However, little is understood about how these predictors, which contribute to school readiness, are formed, and even less is understood about how they interact with each other. This study explores the relation between socioeconomic status (SES) and maternal knowledge of child development; the relation between maternal knowledge of child development and age-appropriate stimulation in the home; if the relation between SES and cognitive stimulation in the home is mediated by mothers' accurate knowledge of development; and whether cognitive stimulation in the home mediates the relation between accurate developmental knowledge and child cognitive developmental level. Data collected from 1,387 families who participated in the Early Head Start study, from 1996 to 2010, were used. For the present study, each of these families' scores from the 14-month KIDI, 36-month Bayley MDI, 36-month PPVT, and 24-month HOME were used. Each mother was tested. Propensity scores were examined to account for attrition. Mediation was tested using multiple regression analysis

TiCl4 Reaction Order in Living Isobutylene Polymerization at Low [TiCl4]:[Chain End] Ratios

Isobutylene (IB) polymerization kinetics at -80 degrees C were monitored in real time using midinfrared ATR-FTIR spectroscopy, with diamond-composite insertion probe and light conduit technology. Monomer concentration as a function of time was obtained by monitoring the absorbance at 887 cm(-1) associated with the = CH2 wag of IB. Polymerizations were initiated using 5-tert-butyl-1,3-bis(2-chloro-2-propyl)benzene (t-Bu-m-DCC) or 2-chloro-2,4,4-trimethylpentane (TMPC1) in conjunction with TiCl4 co-initiator, in hexane/methyl chloride or methylcyclohexane/methyl chloride (60:40 v/v) cosolvents. Either 2,4-dimethylpyridine (DMP) or 2,6-di-tert-butylpyridine (DTBP) was used as an electron donor (ED). Reaction conditions were [ED] = 2.00 x 10(-3) M, [IB](0) = 1.0 M, and [TMPC1] (or 2[t-Bu-m-DCC]) = 2.08 x 10(-2) M. Go-initiator concentrations were designed to be less than or equal to the growing chain end concentration and ranged from [TiCl4] = 7.20 x 10(-3) to 2.28 x 10(-2) M. Steady-state polymerization kinetics were found to be independent of the nature of initiator, slightly faster when conducted with the noncomplexing DTBP rather than DMP and slightly faster when methylcyclohexane rather than hexane was utilized as the hydrocarbon diluent. In all cases, polymerizations exhibited a second-order dependence on the effective TiCl4 concentration ([TiCl4](eff)). The latter was defined in terms of the nominal amount of TiCl4 added to the reactor minus the fraction calculated to be unavailable for co-initiation of the polymerization due to formation of a neutral complex with the ED and/or pyridinium salts as a result of proton scavenging. Second-order dependence on the effective TiCl4 concentration was attributed to the predominance in the propagation reaction of active carbocations associated with dimeric counteranions of the form Ti2Cl9-

Initiation Effects in the Living Cationic Polymerization of Isobutylene

Isobutylene (IB) polymerization kinetics were monitored in real time using mid-infrared ATR-FTIR spectroscopy, with diamond-composite insertion probe and light conduit technology. Monomer concentration as a function of time was obtained by monitoring the absorbance at 887 cm(-1) associated with the =CH2 wag of IB. The measured intensity of this band was found to decrease slightly with increasing temperature (0.42% per 1.0 degrees C). Polymerizations were initiated using the aromatic difunctional initiator 5-tert-butyl-1,3-bis(2-chloro-2-propyl)benzene (t-Bu-m-DCC) and a series of monofunctional aliphatic initiators: tert-butyl chloride (t-BuCl), 2-chloro-2,4,4-trimethylpentane (TMPCl), and 2-chloro-2,4,4,6,6-pentamethylheptane (TIBCl). The co-initiatior was TiCl4 and the Lewis base 2,4-dimethylpyridine (DMP) was used as an electron donor. Polymerizations were performed in methylcyclohexane/methyl chloride (60:40 v/v) cosolvents at temperatures ranging from -80 to -40 degrees C. Reaction conditions were consistently [DMP] = 2.00 x 10(-3) M and [IB](0) = 1.0 M. Initiator concentrations were [TIBCl] = [TMPCl] = [t-BuCl] = a[t-Bu-m-DCC] = 2.08 x 10(-2) M. Go-initiator concentrations ranged from [TiCl4] = 7.20 x 10-3 to 6.79 x 10-2 M. Inspection of the monomer concentration vs time data revealed a number of deviations from first,order decay, depending on initiator. It was observed that polymerizations initiated with t-Bu-m-DCC exhibited an initial regime of rapid monomer consumption (RMC), which is accompanied by a significant reaction exotherm. This phenomenon was attributed to a higher ionization equilibrium constant for the tert-benzylic chloride initiator relative to tert-alkyl chloride PIE chain ends. It was proposed that cations formed from the initiator undergo a number of propagation steps prior to the first ion-pair collapse and that this number yields an estimate of the number of IB units consumed per successful ionization during propagation. This number was observed to decrease with increasing temperature. It was also proposed that the RMC event may offer a means for the experimental determination of the absolute rate constant for IB propagation in TiCl4-co-initiated polymerizations. RMC behavior was completely absent with aliphatic initiators; initiation was extremely slow with t-BuCl and sluggish with TMPCl, relative to TIBCl

Real-Time Monitoring of Carbocationic Polymerization of Isobutylene Using In Situ FTIR-ATR Spectroscopy with Conduit and Diamond-Composite Sensor Technology

Isobutylene (IB) polymerization kinetics were monitored in real time using mid-infrared FTIR-ATR spectroscopy, with a diamond-composite insertion probe and light conduit technology. Polymerization was initiated using the 5-tert-butyl-1,3-bis(2-chloro-2-propyl)benzene (t-Bu-m-DCC)2,4-dimethylpyridine (DMP)/TiCl4 (1:2:20) system in hexane/methyl chloride (60:40 v/v) cosolvents at -80 degrees C, with [t-Bu-m-DCC] = 1.90 x 10(-3) M and [IB](o) = 1.0 M. Monomer concentration as a function of time was obtained by monitoring the absorbance at 887 cm(-1) associated with the =CH2 wag of IB. The calculated apparent first-order rate constant of 8.4 x 10(-4) s(-1) was within 3% of the value determined from traditional gravimetric methods (8.6 x 10(-4) s(-1)) withing the same range of conversion. Inspection of the first-order plot generated from the FTIR data revealed a number of deviations from linearity, which were attributed primarily to a transient rise and subsequent fall in reactor temperature caused by the initial large exotherm of polymerization. An artifact associated with the method of data analysis was also identified. These small differences in instantaneous rate were not detected by the gravimetric method due to insufficient accuracy and density of data points

Synthesis and Characterization of Carboxylic Acid-Terminated Polyisobutylenes

tert-Chloride-terminated polyisobutylenes (PIB) (1020 \u3c= M-n \u3c= 6700 g/mol) were dehydrochlorinated nonregiospecifically using basic alumina, or regiospecifically either via potassium tert-butoxide or in situ quenching of quasiliving PIB. Olefin-terminated PIBs were quantitatively ozonized at -78 degrees C using hexane/methylene chloride/methanol, 62/31/7 (v/v/v) cosolvents, and an ozone generator, employing pure oxygen as source gas. The primary ozonides were reduced using trimethyl phosphite to yield pure PIB methyl ketone from exo-olefin PIB, and a mixture of PIB methyl ketone and PIB aldehyde from mixed olefin-PIB. PIB methyl ketone was oxidized to carboxylate via the haloform reaction; titration revealed near-quantitative functionalization, but the reaction was slow. Tetrahalomethane oxidation was identified as a preferred alternative method, and was conducted using either CCl4 as the reaction solvent, THF as the solvent with CCl4 in reagent amounts, or hexane as the solvent with a phase-transfer catalyst and CCl4 in reagent amounts. The system using hexane, with tetra-n-butyl ammonium chloride as phase-transfer catalyst, showed complete conversion in similar to 4 h. PIB carboxylic acid was recovered by acidification and isolation. (C) 2008 Wiley Periodicals, Inc

Conjoint Analysis Applications in Health - How are Studies being Designed and Reported?: An Update on Current Practice in the Published Literature between 2005 and 2008

Despite the increased popularity of conjoint analysis in health outcomes research, little is known about what specific methods are being used for the design and reporting of these studies. This variation in method type and reporting quality sometimes makes it difficult to assess substantive findings. This review identifies and describes recent applications of conjoint analysis based on a systematic review of conjoint analysis in the health literature. We focus on significant unanswered questions for which there is neither compelling empirical evidence nor agreement among researchers. We searched multiple electronic databases to identify English-language articles of conjoint analysis applications in human health studies published since 2005 through to July 2008. Two independent reviewers completed the detailed data extraction, including descriptive information, methodological details on survey type, experimental design, survey format, attributes and levels, sample size, number of conjoint scenarios per respondent, and analysis methods. Review articles and methods studies were excluded. The detailed extraction form was piloted to identify key elements to be included in the database using a standardized taxonomy. We identified 79 conjoint analysis articles that met the inclusion criteria. The number of applied studies increased substantially over time in a broad range of clinical applications, cancer being the most frequent. Most used a discrete-choice survey format (71%), with the number of attributes ranging from 3 to 16. Most surveys included 6 attributes, and 73% presented 7-15 scenarios to each respondent. Sample size varied substantially (minimum - 13, maximum - 1258), with most studies (38%) including between 100 and 300 respondents. Cost was included as an attribute to estimate willingness to pay in approximately 40% of the articles across all years. Conjoint analysis in health has expanded to include a broad range of applications and methodological approaches. Although we found substantial variation in methods, terminology, and presentation of findings, our observations on sample size, the number of attributes, and number of scenarios presented to respondents should be helpful in guiding researchers when planning a new conjoint analysis study in health.Conjoint-analysis