Nonlinear high-temperature superconducting terahertz metamaterials

We report the observation of a nonlinear terahertz response of split-ring resonator arrays made of high-temperature superconducting films. Intensity-dependent transmission measurements indicate that the resonance strength decreases dramatically (i.e. transient bleaching) and the resonance frequency shifts as the intensity is increased. Pump–probe measurements confirm this behaviour and reveal dynamics on the few-picosecond timescale.Los Alamos National Laboratory. Laboratory Directed Research and Development ProgramUnited States. Office of Naval Research (Grant N00014-09-1-1103)National Science Foundation (U.S.) (American Competitiveness in Chemistry Fellowship 1041979

Garbage Collection for the Delft-Java Processor

ABSTRACT. The Delft Java Processor (DJP) is a hardware approach aiming at accelerating bytecode execution. One of the critical tasks in a JVM that could benefit from hardware support is garbage collection. To efficiently perform garbage collection in the DJP we have to better understand the general garbage collection related issues in real life situations. In this respect we provide in this paper a study of the dynamic allocation behavior of Java programs based on the SPECjvm98 benchmark suite. Age, size and type distribution of Java objects are presented and interpreted from the general point of view of garbage collection, together with other garbage collection related measurements. Thus we can identify the features of an efficient DJP dedicated garbage collector and propose supporting architectural extension(s) in the DJP. The study confirms the weak generational hypothesis according to which objects are most likely to die very young, suggesting that a collector with two generations could improve garbage collection performance with corresponding hardware support. To fully take advantage of the generational hypothesis efficient hardware-implemented write barriers are needed. Hardware support is also recommended for describing the dynamic layout of the stack (stack pointer map) for accurate garbage collection

Dataset of Observed Suspended Sediment and Particulate Organic Carbon Concentrations and Modeled Long-Term Suspended Sediment and Particulate Organic Carbon Yields (1994-2017) from the Reynolds Creek Experimental Watershed and Critical Zone Observatory in Southwestern Idaho, USA

Long-term datasets of suspended sediment (SS) and particulate organic carbon (POC) are valuable to understand the role the fluvial export plays in the landscape responses to changing climate and disturbance regimes such as fire. Here we report a dataset that includes raw SS and POC concentrations and estimated long-term (\u3e 23 years) SS and POC yields from 4 nested catchments that ranged from \u3c 1 to 54 km2 in area across the Reynolds Creek Experimental Watershed and Critical Zone Observatory (RCEW-CZO) in southwestern Idaho, USA. We also estimated SS and POC yields from a burned catchment in the first two years following fire. The RCEW-CZO is representative of many rangelands in the Intermountain West USA consisting of a mosaic of vegetation including Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and rabbitbrush (Chrysothamnus viscidiflorus) at lower elevations and mountain big sagebrush (Artemisia tridentata ssp. vaseyana), aspen (Populus tremuloides), bitter brush (Purshia tridentata), mountain mahogany (Cercocarpus ledifolius), Utah snowberry (Symphoricarpos oreophilus), and douglas-fir (Pseudotsuga menziesii) at higher elevation areas. Mean annual precipitation across these 4 catchments ranged from 616 to 911 mm yr-1 and mean annual temperature ranged from 7.16-4.75 degrees C. We first developed relationships between SS and POC for the five catchments from two years of data, one dry and one of the wettest water years on record. We then estimated SS yields using a composite model in loadflex that performs residual correction to improve estimates with the exception of burned catchment where we used a linear interpolation. We found strong relationships between log-transformed SS and POC (R2=0.38-0.86) that varied across catchments but did not vary across years, one dry and one of the wettest water years on record. Mean annual SS yields varied from 18-89 g SS m-2 yr-1 and POC from 0.61-11 g C m-2 yr-1 across the four unburned catchments. SS and POC yields were 611 g SS m-2 yr-1 and 35 g C m-2 yr-1, respectively, from the burned catchment in the first year following fire, and yields remained elevated in the second year, at 466 g SS m-2 yr-1 and 27.5 g C m-2 yr-1, owing to the large water year. These datasets are unique because few long-term records are available across nested catchments in rangelands in the Intermountain West US, and these datasets will aid in modeling and understanding linkages between climate, erosion, and carbon

Fourcross shaped metamaterial filters fabricated from high temperature superconducting YBCO and Au thin films for terahertz waves

In this study, we present a new, unique fourcross shaped metamaterial terahertz (THz) filter fabricated from both gold thin films and YBa2Cu3O7-δ high Tc superconducting thin films. A commercial electromagnetic simulation software, CST Microwave Studio, is used to design and optimize the metamaterial filter structures. The proposed fourcross shaped rectangular filter structure consists of periodic metallic rings where strip lines are located at the sides of the ring. Fourcross metamaterial filters are fabricated by using e-beam lithography and ion beam exhing techniques. Terahertz time-domain spectroscopy measurements validated the design predictions for both the center frequencies and bandwidths of the resonances due to the fourcross structures. The resonance switching of the transmission spectra was investigated by lowering the temperature below the critical transition temperature. This resonance switching effect is not observed in filters made up of metals. This novel fourcross rectangular resonator with a temperature-dependent resonance behavior holds great potential for active, tunable and low loss THz devices for imaging, sensing, and detection applications.TUBITAK (114F091); METU research office (BAP-08-011-2016-053); BAGEP Award of the Science Academy in Turkey; Turkish Academy of Science