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Peak magnetic field exposure was associated with increased risk of miscarriage in 2 recent studies. Reduced physical activity levels in healthy pregnancies may affect measured exposure and thus bias results.

Citing the need for a basic, K-12 developmental framework for service learning, this article describes such a model. This model, an inclusive typology of service learning, distinguishes three levels of service learning: Community Service, Community Exploration, and Community Action. The authors correlate this typology to Piaget's cognitive developmental stages tying in Bradley's three-factor Criteria for Assessing Levels of Reflection. Two types of service, direct and indirect, are explained. Implications for education, research, and the community are discussed.

Service learning, a method of instruction that combines learning with service to the community, can foster mutual respect and caring between gifted students and their communities. Using examples from various service learning experiences conducted by young gifted adolescents, the authors relate how service learning can be instrumental in infusing the qualities of caring in gifted youth. A K-12 best-practice model for service learning that incorporates the Creative Problem Solving process, the cognitive apprenticeship model, cooperative learning, reflection, and celebration is described.

Despite extensive research on tobacco smoking during pregnancy, few studies address risks among African-American and white women, groups that differ in brand preference and smoking habits. The Pregnancy, Infection, and Nutrition Study is a prospective cohort study that included 2,418 women with detailed information on smoking during pregnancy, including brand, number of cigarettes per day, and changes during pregnancy. We analyzed risk of preterm birth (<37 and <34 weeks’ gestation) and small-for-gestational-age deliveries in relation to tobacco use. Pregnant African-American smokers differed markedly from whites in brand preference (95vs26 smoked menthol cigarettes) and number of cigarettes per day (1 of African-Americans and 12 of whites smoked 20 cigarettes per day). Smoking was not related to risk of preterm birth overall, but cotinine measured at the time of delivery was (adjusted odds ratio 2.2, 95 confidence interval 1.1–4.5). A clear association and dose-response gradient was present for risk of fetal growth restriction (risk ratio for 20 cigarettes/day 2.4, 95 confidence interval 1.4–4.0). Associations of tobacco use with preterm premature rupture of amniotic membrane resulting in preterm birth were notably stronger than the associations with other types of preterm birth.

This article examines service learning from the perspective of gifted adolescents who have participated in what I have termed Community Action service learning projects. Using a case study design, I investigated adolescents' perspectives concerning their involvement in service learning projects grounded in creative problem solving. A service learning typology based on the degrees of student involvement is described. The importance of service learning to the participants in this study is highlighted in the following themes that emerged from the data: methodology, attitudes, personal and social development, commitment, and empowerment. Implications for educators are discussed.

The tris(tert-butoxy)siloxy complex Ti[OSi(O^tBu)3]4 (1) was pyrolytically converted at low temperatures to the theoretical yield of homogeneous TiO2·4SiO2 materials. 1 also serves as a soluble model for isolated, tetrahedral titanium atoms in a silica matrix. The solid-state transformation of 1 to TiO2·4SiO2 affords a low-surface-area material (2a, 22 m² g^-1 for samples heated to 500 °C) consisting of roughly spherical particles with an average diameter of ca. 25 nm (by transmission electron microscopy). The solution-phase thermolysis of 1 affords a xerogel (2b) consisting of smaller primary particles (≤ca. 5 nm) and possessing a much higher surface area (552 m² g^-1 for samples heated to 500 °C). Acid catalysis of the pyrolytic conversion in solution affords a xerogel (2c) with a lower surface area (399 m² g^-1 for samples heated to 500 °C). Supercritical drying of the “wet-gel” in CO2 affords an aerogel (2d) with a morphology similar to that of the xerogel and a slightly higher surface area (677 m² g^-1 for samples heated to 500 °C). The TiO2·4SiO2 materials are amorphous as initially formed, and subsequent crystallizations of anatase (2a, 2b), rutile, and cristobalite (2a) occur at relatively high temperatures. 1 is a homogeneous catalyst for the selective epoxidation of cyclohexene to cyclohexene oxide (64% yield; 20 turnovers after 2 h) using cumene hydroperoxide (CHP) as the limiting reagent. 2a−d are heterogeneous catalysts that produce 6% (2a)−49% (2d) yields of cyclohexene oxide after 2 h (with 0.05 g of catalyst). Supporting 1 on silica affords a highly active epoxidation catalyst that provides yields of 94% cyclohexene oxide after 2 h (with a standard amount of 0.05 g of catalyst). The molecular route to homogeneous titania−silica materials described here represents an alternative to the sol−gel method, affording materials with surface areas comparable to those of related aerogels and moderate-to-excellent activities for the epoxidation of cyclohexene.

The single source precursor OV[OSi(O^tBu)3]3 was synthesized in high yield from OVCl3 and HOSi(O^tBu)3. This tri(alkoxy)siloxy complex was characterized by ¹H, ¹³C, ²⁹Si, and ⁵¹V NMR, FT-Raman, FT-IR, EXAFS, and UV−vis spectroscopies and by mass spectrometry. In the Raman spectrum of OV[OSi(O^tBu)3]3, V&dbd;O (1038 cm^-1) and V−O (651, 674, and 705 cm^-1) vibrations were observed. The ⁵¹V NMR shift was observed at −777 ppm and the ²⁹Si NMR resonance appears at −98 ppm. Thermolysis in n-octane at 180 °C resulted in formation of a green gel which upon drying in air formed a xerogel with a surface area of 320 m² g^-1, an average pore size of 140 Å, and a total pore volume of 2.25 cm³ g^-1. The calcined xerogel is similar to bulk V2O5 in catalytic performance for propane oxidative dehydrogenation.

By reaction of PbCl2 with 3 equivalents of NaOSi(OtBu)3, the ate complex NaPb[OSi(OiBu)3]3 was obtained. This compound possesses a structure containing a 3-coordinate, trigonal prismatic lead center, and a 6-coordinate Na atom encapsulated in an oxygen matrix formed by the bridging siloxy and tert-butoxy groups of the -OSi(OtBu)3 ligands. The neutral lead complex Pb[OSi(OtBu)3]2·tBuOH·CH3CN was obtained from reaction of Pb3(μ-OtBu)6 with HOSi(OtBu)3. The tin complex KSn[OSi(OtBu)3]3, prepared from SnCl2 and KOSi(OtBu)3, is isomorphous with NaPb[OSi(OtBu)3]3. The bismuth compounds Bi[OSi(OtBu)3]3 and Bi[OSi(OtBu)2Ph]3 were obtained by similar methods.

A scanning electron microscope procedure has been developed to measure the particle size distribution of dusts collected on filter media. The technique is applicable to inspirable dust samples and to individual stages of cascade impactors. Results from monazite dusts (density of 5200 kg m-3) confirm that the manufacturer's specified cut-points for impactor stages are correct for equivalent aerodynamic diameters.

The (tert-butoxy)siloxy complex [CuOSi(O^tBu)3]4 (1) was prepared by silanolysis of [CuO^tBu]4 with (^tBuO)3SiOH and examined as a single-source precursor to Cu/SiO2 and CunO/SiO2 (n = 1, 2) materials. The related complex {Cu[μ-OSiPh(O^tBu)2]}4 (4), obtained similarly, was characterized by X-ray crystallography as having a planar Cu4O4 core with oxygen-bridged Cu atoms. The highly associated, sublimable {NaCu[OSi(O^tBu)3]2}6 (3) was obtained by the addition of NaOSi(O^tBu)3 to 1 or by reaction of 2 equiv of NaOSi(O^tBu)3 with CuCl. Thermogravimetric analysis (TGA) of 1 under both oxygen and argon reveals rather sharp, low-temperature conversions to the final ceramic compositions (onset temperatures:  ca. 100 °C under oxygen; ca. 150 °C under argon). Under argon, the resulting material consists of Cu⁰ and Cu2O nanoparticles dispersed in silica, whereas an oxygen atmosphere leads to CuO nanoparticles in silica. These materials are carbon- and hydrogen-free and are produced by elimination of isobutene, tert-butyl alcohol, water, and silanol. The pyrolytic conversion of compound 4 occurs at higher temperature and more gradually but gives relatively clean conversion to a CuO/SiO2 composite under an oxygen atmosphere. The volatility of 1 allows its use in CVD preparations of thin films. Amorphous thin films with a Cu/Si ratio of 1:0.85 (microprobe analysis) and thicknesses ranging from 200 nm to 6 μm have been obtained.

The deletion of a conserved sequence of ca. 30 nucleotides in the 5' noncoding leader region of an avian sarcoma virus DNA clone resulted in a loss of infectivity after transfection of chicken embryo fibroblasts. Genetic and biochemical analysis of a representative mutant demonstrated that the env gene was expressed normally. Thus, viral RNA transcription, splicing, and translation were not impaired. The amount of mutant viral RNA encapsidated into virions, however, was severely reduced despite the presence of helper-virus. We conclude that the deleted sequence is an essential cis-acting packaging signal.

The primary purpose of pre-placement back x-ray screening is to reduce the incidence of low back problems. This study was designed to address the specific question of whether or not this objective is achieved, without directly looking at the predictive value of radiological abnormalities of the lumbar spine. Two retrospective cohorts of steelworkers were identified: one group hired before, and one after, introduction of back x-rays into an otherwise identical pre-placement medical examination. The two cohorts were stratified by age and work activity, and by use of a modified life table method were followed for 12 years. All health incidents, modified work, lost time, or permanent job changes were noted. Analysis revealed no statistically significant differences between cohorts for the parameters studied. The inclusion of low back x-ray screening into a comprehensive pre-placement medical examination had no significant effect on the subsequent incidence of low back pain in the cohort of steelworkers studied.

VCAM-1 is an immunoglobulin superfamily member that mediates adhesion of a variety of leukocytes to endothelial cells. VCAM expression has been associated with a variety of disease states and has been implicated in a number of normal processes. The predominant form of VCAM produced in human endothelial cells is a transmembrane protein containing seven immunoglobulin domains. In this study the murine VCAM gene has been characterized to allow the function(s) of VCAM to be studied in a small genetically accessible animal. While expression of an mRNA encoding a seven-immunoglobulin-domain transmembrane VCAM protein was seen in most tissues, the predominant change in VCAM expression upon interleukin 1 beta treatment was the induction of an alternatively spliced VCAM mRNA containing only the first three immunoglobulin domains. This message encodes a glycosylphosphatidylinositol (GPI)-anchored form of VCAM, VCAMGPI. VCAMGPI was efficiently cleaved from the cell surface by phosphatidylinositol-specific phospholipase C, mediated adhesion to leukocytes in a very late antigen 4-dependent manner, and was produced by mouse endothelial cell lines in culture. These data demonstrate that alternate forms of VCAM are produced under different physiological conditions and suggest that VCAMGPI may have a distinct role in inflammatory processes.

The author who was the former president of the Colorado Bar Association (CBA) explores his experiences as a CBA president and discusses responsibilities of the president. Topics discussed include the retirement of Chuck Turner who has served as the executive director for more than thirty-three years, responsibility of the CBA president to visit local bar associations in Colorado and opportunities provided by attorneys and judges working together in the CBA to develop lifelong relationships.

Serum folic‐acid and vitamin B12levels have been estimated and hæmatological investigations have been carried out for 411 psychiatric patients. Of the patients Investigated, 33·23% had folic‐acid levels of 3·5 ng/ml or less, and showed also hæmatological changes in the peripheral blood, indicating folic‐acid deficiency. Only five had serum vitamin B12levels of 200 pg/ml or less. The possible causes for this widespread deficiency are briefly discussed. More detailed investigations are essential to determine the significance of folic‐acid deficiency In psychiatric patients.

Autotrophic cultures of Euglena in continuous light (LL) were exposed to temperature cycles spanning different temperature intervals in the physiological range. Each cycle consisted of a regular alternation between equal phases of two temperatures differing by 7°. Different temperature combinations varied in the degree to which they were capable of phasing cell division. The most effective combinations tested, 18/25° and 28/35°, produced almost as good a synchrony as has been observed from the use of light/dark cycles (at constant temperature) in this system. Both batch and chemostat cultures with a wide range of generation times were phased, and cycles with period lengths ranging from 8 to 24 hr appeared to be equally effective.

Temperature cycles which produced synchrony of cell division in autotrophic Euglena (preceding paper, Terry and Edmunds, 1970) usually also evoked a cellular settling rhythm. The rhythm was expressed as a recurrent cycle of cell attachment to culture-vessel surfaces, with nearly the same phase angle to each of the different temperature cycles. Attachment occurred in cultures stirred rapidly enough for thorough mixing of the cell suspension, but it was possible to prevent attachment by increased agitation. The settling rhythm was entrained by temperature cycles with periods shorter than the minimum period length required to phase cell division, but the rhythm also persisted with a circadian period at constant temperature in continuous light following entrainment by 12,12 hr temperature cycles. The rhythm appeared in stationary-phase cultures exposed to either cold-synchronizing or heat-synchronizing temperature cycles, and also in growth-phase cultures exposed to cold-synchronizing cycles. The settling rhythm was generally not observable in heat-synchronized growth-phase cultures although it often appeared in the same cultures as they approached the stationary phase.