Boise State University

About: Boise State University is a education organization based out in Boise, Idaho, United States. It is known for research contribution in the topics: Population & Computer science. The organization has 3698 authors who have published 8664 publications receiving 210163 citations. The organization is also known as: BSU & Boise State.

Interactions of Biological Soil Crusts with Vascular Plants

Abstract: Biocrusts and vascular plants interact on many levels. The nature and consequences of these interactions vary with biocrust and plant characteristics and environmental conditions and throughout the plants’ life cycle. Biocrust structure and surface texture—shaped by its species composition and the environment—interacting with seed shape and size, determine whether the crust facilitates or deters seed capture and thus seedling establishment. In general, biocrusts tend to enhance plant growth through improved availability of nutrients, but root architecture plays a role in determining the effect of crusts on nutrient uptake. Furthermore, exchange of nutrients between biocrusts and vascular plants can occur through different pathways, including fungal linkages. Vascular plant communities also affect biocrust development, composition, and function through canopy shading, litterfall, and root activity and their effects on microclimate. The vascular plant canopy tends to favor certain biocrust species groups over others and usually enhances biocrust formation; however, a dense canopy can deprive crusts of adequate light for photosynthesis. Likewise, light litterfall may protect or favor biocrusts by improving the microclimatic conditions, while heavy litterfall can bury, damage, or destroy the crusts.

Fermi Large Area Telescope observations of the supernova remnant G8.7–0.1

Abstract: We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 ± 0.6 (stat) ± 1.2 (sys) GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of π0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Rating-based collaborative filtering: Algorithms and evaluation

Abstract: Recommender systems help users find information by recommending content that a user might not know about, but will hopefully like. Rating-based collaborative filtering recommender systems do this by finding patterns that are consistent across the ratings of other users. These patterns can be used on their own, or in conjunction with other forms of social information access to identify and recommend content that a user might like. This chapter reviews the concepts, algorithms, and means of evaluation that are at the core of collaborative filtering research and practice. While there are many recommendation algorithms, the ones we cover serve as the basis for much of past and present algorithm development. After presenting these algorithms we present examples of two more recent directions in recommendation algorithms: learning-to-rank and ensemble recommendation algorithms. We finish by describing how collaborative filtering algorithms can be evaluated, and listing available resources and datasets to support further experimentation. The goal of this chapter is to provide the basis of knowledge needed for readers to explore more advanced topics in recommendation.

Field Calibration of Water Content Reflectometers

Abstract: Field monitoring of volumetric soil water content (VWC) is critical for a variety of applications. Recently developed electronic soil water sensors provide a relatively inexpensive monitoring option. However, the calibration of these sensors is more sensitive to variations in soil properties than for time domain reflectometry (TDR), which is generally regarded as the best electronic means of VWC measurement and which has a relatively robust calibration. Field calibration incorporates the effects of within-profile and between-site soil variations and individual variability on sensor response. The objective of this study was to evaluate the effectiveness of using TDR to field-calibrate the Campbell Scientific water content reflectometer (WCR), or CS-615, which is an example of a newly developed sensor in widespread use. We found that (i) there was a strong, linear correlation between the WCR-measured period and TDR-measured VWC; (ii) the WCR calibration varied with soil type; (iii) calibration of individual sensors resulted in excellent agreement between TDR and the WCR measurements; and (iv) calibration resulted in improved description of soil water dynamics and improved precision of VWC estimates.