Revised age and stratigraphy of the classic Homo erectus-bearing succession at Trinil (Java, Indonesia)

Obtaining accurate age control for fossils found on Java (Indonesia) has been and remains challenging due to geochronologic and stratigraphic uncertainties. In the 1890s, Dubois excavated numerous faunal fossils—including the first remains of Homo erectus—in sediments exposed along the Solo River at Trinil. Since then, various, and often contradictory age estimates have been proposed for the Trinil site and its fossils. However, the age of the fossil-bearing layers and the fossil assemblage remains inconclusive. This study constructs a chronostratigraphic framework for the Trinil site by documenting new stratigraphic sections and test pits, and by applying 40Ar/39Ar, paleomagnetic, and luminescence (pIRIR290) dating methods. Our study identifies two distinct, highly fossiliferous channel fills at the Trinil site. The stratigraphically lower Bone-Bearing Channel 1 (BBC-1) dates to 830–773 ka, while Bone-Bearing Channel 2 (BBC-2) is substantially younger with a maximum age of 450 ± 110 ka and an inferred minimum age of 430 ± 50 ka. Furthermore, significantly younger T2 terrace deposits are present at similar low elevations as BBC-1 and BBC-2. Our results demonstrate the presence of Early and Middle Pleistocene, and potentially even late Middle to Late Pleistocene fossiliferous sediments within the historical excavation area, suggesting that Dubois excavated fossils from at least three highly fossiliferous units with different ages. Moreover, evidence for reworking suggests that material found in the fossil-rich strata may originate from older deposits, introducing an additional source of temporal heterogeneity in the Trinil fossil assemblage. This challenges the current assumption that the Trinil H.K. fauna –which includes Homo erectus-is a homogeneous biostratigraphic unit. Furthermore, this scenario might explain why the Trinil skullcap collected by Dubois is tentatively grouped with Homo erectus fossils from Early Pleistocene sediments at Sangiran, while Trinil Femur I shares affinities with hominin fossils of Late Pleistocene age

Quantitative and mechanistic studies using the oxygen-18 isotope shift in carbon-13 nuclear magnetic resonance spectroscopy

The \sp{18}O-isotope shift in \sp{13}C NMR spectroscopy was used to study the kinetics of oxygen exchange at the anomeric carbon atoms of several ketoses and aldoses. At 25-26\sp\circC and over the pH range from 2 to 10, the relative rates of oxygen exchange for the aldoses studied increased in the following sequence: D-glucose, D-mannose, D-ribose, D-2-deoxyribose. The hydration rates for the open chain forms of the sugars were calculated and the results were analyzed in terms of steric and inductive effects by drawing analogies with the hydration kinetics of simple aldehydes and ketones. Effective molarities associated with ring closure reactions of common monosaccharides are calculated. The position of bond cleavage in the acid-catalyzed hydrolysis of sucrose was elucidated by hydrolyzing the sugar in \sp{18}O-water and assaying the incorporation of \sp{18}O into the several anomeric products using \sp{13}C NMR. Independent supporting experimental evidence was obtained using \sp1H NMR. The results clearly indicated fructosyl-oxygen bond cleavage under the reaction conditions employed. A detailed investigation was made of the complex \sp{13}C NMR spectrum arising from the various \sp{18}O-isotopomers in a solution of \sp{18}O-labeled $\rm\lbrack 1,4$-\sp{13}C\sb2\rbrack succinic acid. These investigations reveal a way to measure the coupling constant between the carboxyl carbons of succinic acid. This coupling constant was found to increase dramatically with the solution pH. A complex spectrum was also observed in the carbonyl and olefinic regions of \sp{18}O-labeled (natural abundance \sp{13}C) dimethylmaleic anhydride. The eight signals in each region were interpreted in terms of isotope shifts over one, two, and even three bonds. The quantitative use of the \sp{18}\rm {O} isotope shift in \sp{13}C NMR was assessed. The substitution of \sp{16}O by \sp{18}O in a series of carboxylic acids and ketones did not result in an observable difference in the spin-lattice (T\sb1) relaxation behavior of the directly attached \sp{13}C nuclei. The use of peak heights to infer the relative proportions of isotopomers (in a sample of 90 spectra in which the relative intensity of one peak with respect to an adjacent peak in no case fell below 25%) gave the same results (within $\pm$4%) as the use of peak areas

Interfacial nanobubbles are leaky: Permeability of the gas/water interface

Currently there is no widespread agreement on an explanation for the stability of surface nanobubbles. One means by which several explanations can be differentiated is through the predictions they make about the degree of permeability of the gas-solutio

Phase State of Interfacial Nanobubbles

Interfacial nanobubbles represent an interesting state of matter: tiny bubbles decorating the interface between a solid and liquid. Yet, there is only sparse evidence supporting the idea that they are indeed gaseous. Here we present evidence that nanobubbles are composed of air rather than oil and that the solid surface underneath the nanobubbles is exposed to air rather than water. The differentiation between air and water was achieved by creating a sensor on the solid surface. The solid was coated in a hydrophobic monolayer containing dansyl fluorophores, which acts as a reporter for the environment around the fluorophore: at an excitation wavelength of 340 nm the emission maximum is 515 nm under water and 480 nm in dry or humid air. The difference in emission could thus be used to determine whether individual parts of the monolayer were in air or in water. Interfacial nanobubbles, created using the standard technique of ethanol exchange, were imaged with fluorescence microscopy, interference contrast microscopy, and phase contrast microscopy. Results show that the positions of nanobubbles shown by interference contrast microscopy or phase microscopy coincide with air pockets shown by fluorescence emission, thereby demonstrating that the interfacial nanobubbles are indeed bubbles. Differentiation between air and oils was achieved by absorption of a fluorescent dye, Nile blue. Whereas oils absorb Nile blue, the interfacial nanobubbles do not absorb the dye and therefore are not composed of oil

Sizing Individual Au Nanoparticles in Solution with Sub-Nanometer Resolution

Resistive-pulse sensing has generated considerable interest as a technique for characterizing nanoparticle suspensions. The size, charge, and shape of individual particles can be estimated from features of the resistive pulse, but the technique suffers from an inherent variability due to the stochastic nature of particles translocating through a small orifice or channel. Here, we report a method, and associated automated instrumentation, that allows repeated pressure-driven translocation of individual particles back and forth across the orifice of a conical nanopore, greatly reducing uncertainty in particle size that results from streamline path distributions, particle diffusion, particle asphericity, and electronic noise. We demonstrate ∼0.3 nm resolution in measuring the size of nominally 30 and 60 nm radius Au nanoparticles of spherical geometry; Au nanoparticles in solution that differ by ∼1 nm in radius are readily distinguished. The repetitive translocation method also allows differentiating particles based on surface charge density, and provides insights into factors that determine the distribution of measured particle sizes

Sizing Individual Au Nanoparticles in Solution with Sub-Nanometer Resolution

Resistive-pulse sensing has generated considerable interest as a technique for characterizing nanoparticle suspensions. The size, charge, and shape of individual particles can be estimated from features of the resistive pulse, but the technique suffers from an inherent variability due to the stochastic nature of particles translocating through a small orifice or channel. Here, we report a method, and associated automated instrumentation, that allows repeated pressure-driven translocation of individual particles back and forth across the orifice of a conical nanopore, greatly reducing uncertainty in particle size that results from streamline path distributions, particle diffusion, particle asphericity, and electronic noise. We demonstrate ∼0.3 nm resolution in measuring the size of nominally 30 and 60 nm radius Au nanoparticles of spherical geometry; Au nanoparticles in solution that differ by ∼1 nm in radius are readily distinguished. The repetitive translocation method also allows differentiating particles based on surface charge density, and provides insights into factors that determine the distribution of measured particle sizes