The role of surface charge of nucleation agents on the crystallization behavior of poly(vinylidene fluoride).

The effect of the surface charge of nucleation agents on the crystallization behavior of poly(vinylidene fluoride) (PVDF) has been investigated. Ion-dipole interaction between the positive surface of nucleation agents and the partially negative CF(2) dipoles of PVDF is established as a main factor for further lowering the free energy barrier for nucleation, and thus increasing significantly the crystallization kinetics. This is in contrast to the behavior observed for nucleation agents possessing either negative surface or neutral charges. Positive nucleation agents led to a remarkable increase in the crystallization temperature of PVDF (lower supercooling) as compared with that of neat PVDF. The dispersion of each type of nucleation agent is also important. The melting temperatures of nucleation agents need to be higher than the melting temperature of PVDF. The melting point and degree of crystallinity of PVDF can also be raised by using specific nucleation agents. The detailed crystallization kinetics and conformational changes of the PVDF chain have been investigated. With the addition of positive nucleation agents, the γ and ß chain conformations, instead of the α phase, dominate.

High field gradient targeting of magnetic nanoparticle-loaded endothelial cells to the surfaces of steel stents.

A cell delivery strategy was investigated that was hypothesized to enable magnetic targeting of endothelial cells to the steel surfaces of intraarterial stents because of the following mechanisms: (i) preloading cells with biodegradable polymeric superparamagnetic nanoparticles (MNPs), thereby rendering the cells magnetically responsive; and (ii) the induction of both magnetic field gradients around the wires of a steel stent and magnetic moments within MNPs because of a uniform external magnetic field, thereby targeting MNP-laden cells to the stent wires. In vitro studies demonstrated that MNP-loaded bovine aortic endothelial cells (BAECs) could be magnetically targeted to steel stent wires. In vivo MNP-loaded BAECs transduced with adenoviruses expressing luciferase (Luc) were targeted to stents deployed in rat carotid arteries in the presence of a uniform magnetic field with significantly greater Luc expression, detected by in vivo optical imaging, than nonmagnetic controls.

Predictors of early postpartum vitamin use among women of Mexican origin: implications for healthcare provider recommendations.

OBJECTIVE: High parity and short birth intervals among Hispanic women may deplete their folic-acid levels and place them at risk for neural tube defects (NTDs). The purposes of this study were to evaluate factors associated with multivitamin supplementation rates during the early (one to six weeks) postpartum period among Mexican-origin women and present their implications in preventing NTDs in subsequent pregnancies. DESIGN: A cross-sectional study was conducted among Hispanic mothers attending women, infant, and children (WIC) clinics in El Paso, Texas. Information was ascertained via interview on regular multivitamin use, and independent variables including sociodemographic characteristics, multivitamin knowledge, obstetric and health history, and birth control and infant feeding methods. RESULTS: Only 66% of 329 mothers took postpartum multivitamins. Multivitamin consumption declined by 29% for each postpartum week (P=.0003). Adjusted odds ratios indicated positive associations between multivitamin supplementation and prenatal care exclusively in the United States (P=.007), breastfeeding (P=.071), preconceptional (P=.005) and prenatal multivitamin use (P=.0002), and multivitamin recommendation from a healthcare provider (P < or = .0001). The majority of 247 women with multivitamin counsel (59%) were told to finish prenatal vitamins or to continue use while breastfeeding. Smokers were less likely to take multivitamins than nonsmokers (P=.007). CONCLUSIONS: A provider recommendation highly motivates early postpartum women to consume multivitamins. Since most women have more than one child, this period likely represents an interpregnancy interval and is an opportune time to educate and encourage women to take multivitamins. This simple and inexpensive measure could prevent birth defects in future pregnancies.

Evaluation of the microbial growth response to inorganic nanoparticles.

In order to enhance the utilization of inorganic nanoparticles in biological systems, it is important to develop a fundamental understanding of the influence they have on cellular health and function. Experiments were conducted to test silica, silica/iron oxide, and gold nanoparticles for their effects on the growth and activity of Escherichia coli (E. coli). Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize the morphology and quantify size distribution of the nanoparticles, respectively. TEM was also used to verify the interactions between composite iron oxide nanoparticles and E. coli. The results from DLS indicated that the inorganic nanoparticles formed small aggregates in the growth media. Growth studies measured the influence of the nanoparticles on cell proliferation at various concentrations, showing that the growth of E. coli in media containing the nanoparticles indicated no overt signs of toxicity.

Environmental health: a survey of Texas primary care physicians.

Although the role of environmental health hazards in cancer and other diseases is increasingly appreciated, most physicians have had little or no training in environmental health or in integrating exposure histories into their clinical practice. As part of the Texas Medical Association Physician Oncology Education Program, we mailed a questionnaire to 350 Texas primary care physicians (PCPs) to evaluate their attitudes, practice, training, and preferred sources for information regarding environmental health issues. Of the respondents, 86.1% reported that they had never received specific training in environmental health history-taking and 91.7% indicated a desire to learn more about environmental health hazards. The data also revealed that patients regularly raise questions about environmental topics that PCPs do not routinely discuss. Our findings identify a need for more environmental health education for Texas PCPs, and we suggest several possible mechanisms by which this might be accomplished.

Patient communication: a multidisciplinary approach using animated cartoons.

Communication is a major problem in the management of patients. Miscommunication occurs frequently in populations with low reading skills, illiteracy does not completely account for the observed low rates of recall of communicated information. Transmission of the message also plays an important role. Successful strategies to improve communication with patients include the use of videotapes, videotape modeling or cartoon illustrations. Do these products communicate effectively because they overcome illiteracy or because they also transmit a very clear message? Can good transmission of messages overcome illiteracy? In this study, we compared the effectiveness of a printed message about polio vaccinations with the same message converted into a production of animated cartoons using marketing and advertising techniques. The production that resulted from using this strategy showed that in the setting of this study, a well-designed animated cartoon is more effective in delivering a message than the same information provided in written instructional materials.

Electronic Structure of Luminescent d(0) Niobium and Tantalum Imido Compounds cis,mer-M(NR)Cl(3)L(2).

Electronic absorption and emission spectra are reported for luminescent d(0) monoimido group 5 compounds M(NR)Cl(3)L(2) (M = Nb, Ta; R = alkyl, aryl; L = dme, Cl(-), py). These compounds display weak (epsilon < 200 M(-)(1) cm(-)(1)), well-resolved lowest-energy transitions in the high-energy visible and near-UV regions (20 000 < E(abs) < 29 000 cm(-)(1)). The energy of this absorption band depends strongly on the nature of the imido substituent, with a significant decrease observed when aryl groups are present. Excitation into this transition results in long-lived luminescent excited states. Long emission lifetimes (50 ns to 17 &mgr;s) and high quantum yields (0.001-0.24) are observed, decreasing primarily as a function of the alkyl substituent, being lowest in the aryl imidos. Good overlap is observed with absorption, excitation, and emission mirror spectra, indicating absorption into and emission from the same excited state. The data are consistent with absorption into and emission from a (3)(nb, pi) state, or d(xy)() <-- Ta-N pi. Semiempirical molecular orbital calculations are presented which suggest that the imido compounds may be considered as having highly mixed but localized Ta=N pi-bonding. A significant difference is noted in [Ta(NPh)Cl(5)](2)(-), in which there is appreciable aryl character in Ta=N pi-type orbitals. This accounts for the difference in electronic properties of the aryl imidos compared to the alkyl imidos. An analysis of radiative and nonradiative excited-state deactivation pathways is presented. Significantly, an energy gap law correlation is observed for nonradiative decay in the imido compounds as a group, but a corresponding correlation of radiative rates with emission energy is not observed when aryl and alkyl imidos are compared, evidence of electronic perturbation by the aryl substituent.