Publications

This paper describes a microfluidic instrument that produces drops of supercooled water suspended in a moving stream of liquid fluorocarbon, and measures the temperatures at which ice nucleates in the drops. A microfluidic chip containing a monodisperse drop generator and a straight channel with 38 embedded resistance thermometers was placed in contact with a seven-zone temperature-control plate and imaged under a microscope with a high-speed camera. This instrument can record the freezing temperatures of tens of thousands of drops within minutes, with an accuracy of 0.4 °C. The ice-nucleation temperatures in ∼80-µm drops were reported for the freezing of 37 061 drops of pure water, and of 8898 drops of water seeded with silver iodide. Nucleation of ice in pure water was homogenous and occurred at temperatures between −36 and −37.8 °C, while water containing silver iodide froze between −10 and −19 °C. The instrument recorded the largest sets of individual freezing temperatures (37 061), had the fastest data acquisition rate (75 measurements/s), and the best optical (3 µm) and temporal (70 µs) resolutions among instruments designed to study nucleation of ice. The dendritic growth of ice in 150-µm drops of supercooled water at −35 °C was observed and imaged at a rate of 16 000 frames/s.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Fetal exposure to maternal smoking during pregnancy is associated with the development of noncommunicable diseases in the offspring. Maternal smoking may induce such long-term effects through persistent changes in the DNA methylome, which therefore hold the potential to be used as a biomarker of this early life exposure. With declining costs for measuring DNA methylation, we aimed to develop a DNA methylation score that can be used on adolescent DNA methylation data and thereby generate a score for

Background Artificial‐sweeteners are widely replacing caloric sweeteners, but emerging experimental data have linked them to metabolic perturbations. Epidemiologic data on long‐term intergenerational impact of artificially‐sweetened beverage (ASB) consumption during pregnancy on offspring obesity risk are lacking. We prospectively investigated intake of ASBs and sugar‐sweetened beverages (SSBs) during pregnancy in relation to offspring growth through age 7 years among high‐risk children born to women with gestational diabetes, serving as a unique model to study early origins of obesity. Methods In a prospective study of 918 mother‐singleton child dyads from the Danish National Birth Cohort, maternal dietary intake was assessed by a food frequency questionnaire during pregnancy. Offspring body mass index z‐scores (BMIZ) and overweight/obesity status were derived using weight and length/height measured at birth, 5 and 12 months, and 7 years. Linear regression and Poisson regression with robust standard errors were used, adjusting for major maternal and offspring risk factors. Results Approximately half of women reported consuming ASBs during pregnancy and 9% consumed daily. Compared to never consumption, daily ASB intake during pregnancy was positively associated with offspring large‐for‐gestational age [adjusted relative risk (aRR) 1.57; 95% CI: 1.05, 2.35], and BMIZ (adjusted β 0.59; 95% CI: 0.23, 0.96) and overweight/obesity (aRR 1.93; 95% CI; 1.24, 3.01) at 7 years. Further, per‐serving‐per‐day substitution of ASBs with water during pregnancy was related to a significantly lower risk of overweight/obesity at 7 years (aRR 0.83; 95% CI: 0.76, 0.91), whereas SSB substitution with ASBs was not related to a lower risk (aRR 1.14; 95% CI: 1.00, 1.31). Conclusions We observed positive associations between intrauterine exposure to ASBs and birth size and risk of overweight/obesity at 7 years. Findings further raise the questionability of promoting ASBs as “healthier” alternatives for SSBs, particularly among high‐risk pregnant women. Future studies with longer follow up beyond early childhood are warranted. Support or Funding Information The study is funded by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (contract # HHSN275201000020C). The DNBC is supported by grants from The Danish Research Council # 09‐067124 (Center for Fetal Programming) and 09‐075611.

This paper compares charge transport across self-assembled monolayers (SAMs) of n-alkanethiols containing odd and even numbers of methylenes. Ultraflat template-stripped silver (Ag(TS)) surfaces support the SAMs, while top electrodes of eutectic gallium-indium (EGaIn) contact the SAMs to form metal/SAM//oxide/EGaIn junctions. The EGaIn spontaneously reacts with ambient oxygen to form a thin (∼1 nm) oxide layer. This oxide layer enables EGaIn to maintain a stable, conical shape (convenient for forming microcontacts to SAMs) while retaining the ability to deform and flow upon contacting a hard surface. Conical electrodes of EGaIn conform (at least partially) to SAMs and generate high yields of working junctions. Ga(2)O(3)/EGaIn top electrodes enable the collection of statistically significant numbers of data in convenient periods of time. The observed difference in charge transport between n-alkanethiols with odd and even numbers of methylenes--the "odd-even effect"--is statistically discernible using these junctions and demonstrates that this technique is sensitive to small differences in the structure and properties of the SAM. Alkanethiols with an even number of methylenes exhibit the expected exponential decrease in current density, J, with increasing chain length, as do alkanethiols with an odd number of methylenes. This trend disappears, however, when the two data sets are analyzed together: alkanethiols with an even number of methylenes typically show higher J than homologous alkanethiols with an odd number of methylenes. The precision of the present measurements and the statistical power of the present analysis are only sufficient to identify, with statistical confidence, the difference between an odd and even number of methylenes with respect to J, but not with respect to the tunneling decay constant, β, or the pre-exponential factor, J(0). This paper includes a discussion of the possible origins of the odd-even effect but does not endorse a single explanation.

Die partielle Oxidation von subbituminöser Kohle durch FeIII-Ionen in 5 M H2SO4 bei 100 °C wurde als Anodenreaktion in einer prototypischen Kohle-Brennstoffzelle mit einer Lösung von VO2+/VO2+ in 5 M H2SO4 als kathodischer Halbzelle kombiniert (siehe Schema). Die Zelle arbeitete 1000 h bei 100 °C ohne Leistungsabfall, die maximale Stromdichte betrug 5 A L−1 und die Leistungsdichte 0.6 W L−1.

This paper describes a method for determining the density of contact trace objects with magnetic levitation (MagLev). MagLev measurements accurately determine the density (± 0.0002 g/cm(3) ) of a diamagnetic object and are compatible with objects that are nonuniform in shape and size. The MagLev device (composed of two permanent magnets with like poles facing) and the method described provide a means of accurately determining the density of trace objects. This method is inexpensive, rapid, and verifiable and provides numerical values--independent of the specific apparatus or analyst--that correspond to the absolute density of the sample that may be entered into a searchable database. We discuss the feasibility of MagLev as a possible means of characterizing forensic-related evidence and demonstrate the ability of MagLev to (i) determine the density of samples of glitter and gunpowder, (ii) separate glitter particles of different densities, and (iii) determine the density of a glitter sample that was removed from a complex sample matrix.