Inkjet Metrology II: Resolved Effects of Ejection Frequency, Fluidic Pressure, and Droplet Number on Reproducible Drop-on-Demand Dispensing

We report highly reproducible gravimetric and optical measurements of microdroplets that lend insights into the fundamentals of drop-on-demand (DOD) printing. Baseline fluidic pressure within the DOD dispenser was controlled to within 0.02 hPa, enabling long-term stability in dispensed droplet mass with observed variations near 1% (RSD) for isobutanol. The gravimetric measurements were sensitive enough to detect and avoid unwanted effects from air bubbles within the dispenser. The gravimetric and optical velocity measurements enabled consistent determination of droplet kinetic energy that governed baseline behavior across the operational variables. Mass and velocity were influenced in a nonlinear manner by the frequency of droplet ejection, the fluidic pressure within the dispensing device, and the number of droplets dispensed in a burst. Resolved effects were attributable to several possible mechanisms including acoustic resonances, energy partitioning from systematic orifice refill dynamics, pressure wavelets created within the dispenser cavity during “first-drop” formation, and residual ring-down after last-drop emergence

TRACE ELEMENT CHARACTERIZATION OF FORSTERITE CHONDRITES AND METEORITES OF SIMILAR REDOX STATE

From a systematic mineralogic/petrologic study of nine chondritic inclusions in the Cumberland Falls aubrite, Neal and Lipschutz (1981) reported that these inclusions constituted a new primitive chondritic suite--the forsterite (F) chondrites. The authors concluded that F chondrites acquired their chemical characteristics during nebular condensation and accretion into a parent body which later collided with the enstatite meteorite parent body, thereby being shocked and mixed. We report compositional data for volatile/mobile Ag, As, Au, Bi, Cd, Co, Cs, Ga, In, Rb, Sb, Se, Te, Tl, U, and Zn in: eight F chondrites studied by Neal and Lipschutz (1981) and another studied by Binns (1969); the Pontlyfni and Kakangari meteorites (putative forsterite chondrites of Graham et al., 1977); Acapulco and ALH A77081 (with similar redox state); and a chondritic inclusion from the aubrite ALH A78113. Our data show trace element contents of F chondrites to be unusually coherent (only Bi, Cd, In, and Tl vary \u3e10x) and distinct. Few elements in F chondrites vary with Fs content of low-Ca pyroxene or with the ferromagnesian silicate disequilibration parameter. Five elements (Cd, Rb, Sb, As, and Se) are present in F chondrites at ordinary chondrite levels; siderophiles are slightly lower while volatile/mobile chalcophiles are substantially lower. Lithophiles (U, Rb, and Cs) and Te are higher in F chondrites than in other type 3 material. The composition of F chondrites differs markedly from those of other meteorite populations considered, indicting \u3e2 parent populations of similar redox state. Compositionally, the chondritic inclusion from ALH A78113 is different from F chondrites, although interesting similarities exist; further mineralogic and chemical information should detail their relationship. These trace element data are consistent with the idea that F chondrites are a unique primitive chondrite group, affected negligibly by the considerable shock generated during the collision between their parent body and that of the enstatite meteorites. Therefore, these data provide the first compositional information for these primitive representatives from a hitherto-unknown portion of the early solar nebula

Iron-Manganese System for Preparation of Radiocarbon AMS Targets: Characterization of Procedural Chemical-Isotopic Blanks and Fractionation

We report a practical system to mass-produce accelerator mass spectrometry (AMS) targets with 10-100 micrograms carbon samples. Carbon dioxide is reduced quantitatively to graphite on iron fibers via manganese metal, and the Fe-C fibers are melted into a bead suitable for AMS. Pretreatment, reduction and melting processes occur in sealed quartz tubes, allowing parallel processing for otherwise time-intensive procedures. Chemical and isotopic (13C, 14C) blanks, target yields and isotopic fractionation were investigated with respect to levels of sample size, amounts of Fe and Mn, pretreatment and reduction time, and hydrogen pressure. With 7-day pretreatments, carbon blanks exhibited a lognormal mass distribution of 1.44 micrograms (central mean) with a dispersion of 0.50 micrograms (standard deviation). Reductions of 10 micrograms carbon onto targets were complete in 3-6 h with all targets, after correction for the blank, reflecting the 13C signature of the starting material. The 100 micrograms carbon samples required at least 15 h for reduction; shorter durations resulted in isotopic fractionation as a function of chemical yield. The trend in the 13C data suggested the presence of kinetic isotope effects during the reduction. The observed CO2-graphite 13C fractionation factor was 3-4% smaller than the equilibrium value in the simple Rayleigh model. The presence of hydrogen promoted methane formation in yields up to 25%. Fe-C beaded targets were made from NIST Standard Reference Materials and compared with graphitic standards. Although the 12C ion currents from the beads were one to two orders of magnitude lower than currents from the graphite, measurements of the beaded standards were reproducible and internally consistent. Measurement reproducibility was limited mainly by Poisson counting statistics and blank variability, translating to 14C uncertainties of 5-1% for 10-100 micrograms carbon samples, respectively. A bias of 5-7% (relative) was observed between the beaded and graphitic targets, possibly due to variations in sputtering fractionation dependent on sample size, chemical form and beam geometry.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

New Guidelines for δ13C Measurements

Consistency of δ13C measurements can be improved 39-47% by anchoring the δ13C scale with two isotopic reference materials differing substantially in 13C/12C. It is recommended that δ13C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of -46.6‰ to L-SVEC lithium carbonate and +1.95‰ to NBS 19 calcium carbonate. Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted: the δ13C of NBS 22 oil is -30.03‰.