Anomalous stable hydrogen-oxygen isotope characteristics and water vapor sources of autumn precipitation in the Weihe River basin, Northwest China.

The extreme changes in autumn rain have significant impacts on the ecological environment of Weihe River basin. Based on 117 autumn rain samples and corresponding meteorological data from 2015 to 2021 at Yangling located in the middle of Weihe River basin, we investigated the stable hydrogen and oxygen isotope composition and water vapor sources of precipitation. The results showed that, (1) extreme changes in autumn rainfall in the study area occurred frequently in recent years, which could be divided into extreme-high autumn precipitation year (HAP, 2021), general autumn precipitation year (GAP, 2015-2017, 2019-2020) and extreme-low autumn precipitation year (LAP, 2018) based on the autumn rain index (ARI); (2) the stable isotopes of different types of precipitation differed significantly, with a pattern of LAP>GAP>HAP for both δH and δO values.

Measurements of Enthalpy of Sublimation of Ne, N, O, Ar, CO, Kr, Xe, and HO using a Double Paddle Oscillator.

We report precise experimental values of the enthalpy of sublimation (Δ ) of quenched condensed films of neon (Ne), nitrogen (N), oxygen (O), argon (Ar), carbon dioxide (CO), krypton (Kr), xenon (Xe), and water (HO) vapor using a single consistent measurement platform. The experiments are performed well below the triple point temperature of each gas and fall in the temperature range where existing experimental data is very limited. A 6 cm and 400 µm thick double paddle oscillator (DPO) with high quality factor (Q ≈ 4 × 10 at 298K) and high frequency stability (33 parts per billion) is utilized for the measurements.

Application of the double paddle oscillator for quantifying environmental, surface mass variation.

Sub-monolayer sensitivity to controlled gas adsorption and desorption is demonstrated using a double paddle oscillator (DPO) installed within an UHV (ultra-high vacuum) environmental chamber equipped with film deposition, (multi)gas admission and temperature control. This effort is intended to establish a robust framework for quantitatively comparing mass changes due to gas loading and unloading on different materials systems selected or considered for use as mass artifacts. Our apparatus is composed of a UHV chamber with gas introduction and temperature control and materials deposition for future materials testing enabling preparation of virgin surfaces that can be monitored during initial exposure to gasses of interest.

Time- and angle-resolved x-ray diffraction to probe structural and chemical evolution during Al-Ni intermetallic reactions.

We present novel time- and angle-resolved x-ray diffraction (TARXD) capable of probing structural and chemical evolutions during rapidly propagating exothermic intermetallic reactions between Ni-Al multilayers. The system utilizes monochromatic synchrotron x-rays and a two-dimensional (2D) pixel array x-ray detector in combination of a fast-rotating diffraction beam chopper, providing a time (in azimuth) and angle (in distance) resolved x-ray diffraction image continuously recorded at a time resolution of ~30 μs over a time period of 3 ms. Multiple frames of the TARXD images can also be obtained with time resolutions between 30 and 300 μs over three to several hundreds of milliseconds.

Photoemission spectroscopy and atomic force microscopy investigation of vapor-phase codeposited silver/poly(3-hexylthiophene) composites.

Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase codeposition. Change in microstructure, chemical nature, and electronic properties with increasing filler (Ag) content were investigated using in situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer, but no evidence of interaction between Ag and carbon (in P3HT) was found.

Electric field and tip geometry effects on dielectrophoretic growth of carbon nanotube nanofibrils on scanning probes.

Single-wall carbon nanotube (SWNT) nanofibrils were assembled onto a variety of conductive scanning probes including atomic force microscope (AFM) tips and scanning tunnelling microscope (STM) needles using positive dielectrophoresis (DEP). The magnitude of the applied electric field was varied in the range of 1-20 V to investigate its effect on the dimensions of the assembled SWNT nanofibrils. Both length and diameter grew asymptotically as voltage increased from 5 to 18 V.

Ultrasharp and high aspect ratio carbon nanotube atomic force microscopy probes for enhanced surface potential imaging.

The resolution of scanning surface potential microscopy (SSPM) is mainly limited by non-local electrostatic interactions due to the finite probe size. Here we present high resolution surface potential imaging with ultrasharp and high aspect ratio carbon nanotube (CNT) atomic force microscopy (AFM) probes fabricated via dielectrophoresis. Enhancement of surface potential contrast by several factors is reported for integrated circuit structures and purple membrane fragments for these CNT AFM probes as compared to conventional probes.