Ground-Penetrating Radar Velocity Determination and Precision Estimates Using Common-Mid-Point (CMP) Collection with Hand-Picking, Semblance Analysis, and Cross-Correlation Analysis: a Case Study and Tutorial for Archaeologists

The most crucial parameter to be determined in an archaeological ground-penetrating radar (GPR) survey is the velocity of the subsurface material. Precision velocity estimates comprise the basis for depth estimation, topographic correction and migration, and can therefore be the difference between spurious interpretations and/or efficient GPR-guided excavation with sound archaeological interpretation of the GPR results. Here, we examine the options available for determining the GPR velocity and for assessing the precision of velocity estimates from GPR data, using data collected at a small-scale iron-working site in Rhode Island, United States. In the case study, the initial velocity analysis of common-offset GPR profile data, using the popular method of hyperbola fitting, produced some unexpectedly high subsurface signal velocity estimates, while analysis of common midpoint (CMP) GPR data yielded a more reasonable subsurface signal velocity estimate. Several reflection analysis procedures for CMP data, including hand and automated signal picking using cross-correlation and semblance analysis, are used and discussed here in terms of efficiency of processing and yielded results. The case study demonstrates that CMP data may offer more accurate and precise velocity estimates than hyperbola fitting under certain field conditions, and that semblance analysis, though faster than hand-picking or cross-correlation, offers less precision

Laser operation of a Tm:Y₂O₃ planar waveguide

We demonstrate the first Tm-doped yttria planar waveguide laser to our knowledge, grown by pulsed laser deposition. A maximum output power of 35 mW at 1.95 µm with 9% slope efficiency was achieved from a 12 µm-thick film grown on a Y3Al5O12 substrate

High-throughput, Efficient, and Unbiased Capture of Small RNAs from Low-input Samples for Sequencing.

MicroRNAs hold great promise as biomarkers of disease. However, there are few efficient and robust methods for measuring microRNAs from low input samples. Here, we develop a high-throughput sequencing protocol that efficiently captures small RNAs while minimizing inherent biases associated with library production. The protocol is based on early barcoding such that all downstream manipulations can be performed on a pool of many samples thereby reducing reagent usage and workload. We show that the optimization of adapter concentrations along with the addition of nucleotide modifications and random nucleotides increases the efficiency of small RNA capture. We further show, using unique molecular identifiers, that stochastic capture of low input RNA rather than PCR amplification influences the biased quantitation of intermediately and lowly expressed microRNAs. Our improved method allows the processing of tens to hundreds of samples simultaneously while retaining high efficiency quantitation of microRNAs in low input samples from tissues or bodily fluids

Highly Active Chiral Ruthenium Catalysts for Asymmetric Ring-Closing Olefin Metathesis

The synthesis of olefin metathesis catalysts containing chiral, monodentate N-heterocyclic carbenes and their application to asymmetric ring-closing metathesis (ARCM) are reported. These catalysts retain the high levels of reactivity found in the related achiral variants (1a and 1b). Using the parent chiral catalysts 2a and 2b and derivatives that contain steric bulk in the meta positions of the N-bound aryl rings (catalysts 3−5), five- through seven-membered rings were formed in up to 92% ee. The addition of sodium iodide to catalysts 2a−4a (to form 2b−4b in situ) caused a dramatic increase in enantioselectivity for many substrates. Catalyst 5a, which gave high enantiomeric excesses for certain substrates without the addition of NaI, could be used in loadings of ≤1 mol %. Mechanistic explanations for the large sodium iodide effect as well as possible mechanistic pathways leading to the observed products are discussed

catena-Poly[[(triaqua­cadmium)-μ-1,4-phenyl­enediacetato-κ4 O,O′:O′′,O′′′] dihydrate]

In the title compound, {[Cd(C10H8O4)(H2O)3]·2H2O}n, penta­gonal–bipyramidally coordinated CdII ions on a twofold rotation axis are linked by tethering 1,4-phenyl­enediacetate (1,4-phda) ligands into [Cd(1,4-phda)(H2O)3]n coordination polymer chains. The chain motifs are oriented parallel to the c-axis direction. Individual chains are connected into a supra­molecular network via O—H⋯O hydrogen bonding involving the aqua ligands

Geomorphology of icy debris fans: Delivery of ice and sediment to valley glaciers decoupled from icecaps

The pace and volume of mass flow processes contributing ice and sediment to icy debris fans (IDFs) were documented at sites in Alaska and New Zealand by integrating field observations, drone and time-lapse imagery, ground penetrating radar, and terrestrial laser scanning. Largely unstudied, IDFs are supraglacial landforms at the mouths of bedrock catchments between valley glaciers and icecaps. Time-lapse imagery recorded 300–2300 events reaching 15 fans during intervals from nine months to two years. Field observations noted hundreds of deposits trapped within catchments weekly that were later remobilized onto fans. Deposits were mapped on images taken three to four times per day. Most events were ice avalanches (58%–100%). Slush avalanches and/or flows were common in spring and fall (0%–65%). Icy debris flows were \u3c5% of the events, observed only at sites with geomorphically complex catchments. Rockfalls were common within catchments; few directly reached a fan. Site selection provided a spectrum of catchment relationships between icecaps and fans. The largest most active fans occur below hanging glaciers or short chutes between the icecap and glacier and were dominated by ice avalanches, slush avalanches, and slush flows. Larger, complex catchments allowed temporary storage of ice and sediment that were later remobilized into ice and slush avalanches and debris flows. Unlike alluvial settings where larger fans are associated with larger catchments, there are variable relationships between IDF area and catchment area. Exceptionally active and dynamic compared to alluvial fans, the studied IDFs exhibited annual resurfacing rates of 300%–\u3e4000%. Annual contributions by mass flows ranged from 133,200 to 5,200,000 m3, representing 3%–56% of fan volume. Although ablation occurred, mainly during summers, significant ice transfer occurred through fan subsurface areas to adjacent valley glaciers. Icy debris fans annually contributed \u3c1%–~24% of the mass of adjacent valley glaciers. Small glaciers (e.g., McCarthy Glacier, Alaska) showed minor thinning (\u3c1 m/yr) compared to larger glaciers (e.g., La Perouse, Douglas, and Mueller Glaciers, New Zealand) that lost \u3e5–10 m/yr over the hundreds of meters of valley glacier adjacent to the IDFs studied. Some IDFs lengthened in response to thinning of valley glaciers. Icy debris fans supplied significant ice and sediment to valley glaciers, slowing the rate of deglaciation. Results of this study have implications toward managing hazards and predicting glacial mass balance in alpine regions. For example, having quantitative information about the role of ice contribution from IDFs to valley glaciers may result in forecasting a lower rate of deglaciation than traditionally recognized for some glaciers decoupled from icecaps