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Burrowing Richardson's ground squirrels affect plant seedling assemblages via environmental but not seed bank changes

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Current Zoology 2020年第3期66卷 219-226页

作者： Levi j.Newediuk james F.Hare Department of Biological Sciences University of ManitobaWinnipegManitobaCanada R3T 2N2

In grassland ecosystems,burrowing mammals create disturbances,providing habitat for animal species and increasing plant community *** investigated whether seedling assemblages on Richardson's ground squirrel Urocitellus richardsonii mounds result from seed rearrangement or environmental changes that favor germination of certain species over *** test whether ground squirrels rearrange the seed bank by burrowing,we compared seed compositions among mounds,burrows,and undisturbed *** test whether ground squirrels change environmental conditions,we compared soil nitrate and bare ground cover on and off *** also compared seedlings that germinated on mounds with seedlings that germinated on artificial disturbances from which we removed aboveground *** nitrate and bare ground cover were significantly higher on mounds than artificial *** seed richness and abundance did not differ among mounds,burrows,and undisturbed soil,seedling richness was reduced on mounds relative to artificial *** disturbance favors seedlings that can capitalize on bare ground availability but are less able to immobilize nitrate,as opposed to perennial species that immobilize more nitrate but take longer to *** results suggest that Richardson's ground squirrels act as ecosystem engineers,although future research following succession on ground squirrel mounds is necessary to understand how they influence plant communities past the seedling stage.

关键词： burrowing disturbance ecosystem engineering Richardsons ground squirrel seed bank seedling species composition

The importance of large-diameter trees to the creation of snag and deadwood biomass

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Ecological Processes 2021年第1期10卷 380-393页

作者： james A.Lutz Soren Struckman Sara j.Germain Tucker j.Furniss Department of Wildland Resources S.J.and Jessie E.Quinney College of Natural ResourcesUtah State University5230 Old Main HillLoganUT 84322-5230USA

Background:Baseline levels of tree mortality can,over time,contribute to high snag densities and high levels of deadwood(down woody debris)if fire is infrequent and decomposition is *** can be important for tree recruitment,and it plays a major role in terrestrial carbon cycling,but deadwood is rarely examined in a spatially explicit ***:Between 2011 and 2019,we annually tracked all trees and snags≥1 cm in diameter and mapped all pieces of deadwood≥10 cm diameter and≥1 m in length in 25.6 ha of Tsuga heterophylla/Pseudotsuga menziesii *** analyzed the amount,biomass,and spatial distribution of deadwood,and we assessed how various causes of mortality that contributed uniquely to deadwood ***:Compared to aboveground woody live biomass of 481 Mg ha^(−1)(from trees≥10 cm diameter),snag biomass was 74 Mg ha^(−1) and deadwood biomass was 109 Mg ha^(−1)(from boles≥10 cm diameter).Biomass from large-diameter trees(≥60 cm)accounted for 85%,88%,and 58%,of trees,snags,and deadwood,*** aboveground woody live and dead biomass was 668 Mg ha^(−1).The annual production of downed wood(≥10 cm diameter)from tree boles averaged 4 Mg ha^(−1) yr^(−1).Woody debris was spatially heterogeneous,varying more than two orders of magnitude from 4 to 587 Mg ha^(−1) at the scale of 20 m×20 m *** all causes of deadwood creation varied in importance between large-diameter trees and small-diameter *** of standing stems and deadwood had weak inverse distributions,reflecting the long period of time required for trees to reach large diameters following antecedent tree mortalities and the centennial scale time required for deadwood ***:Old-growth forests contain large stores of biomass in living trees,as well as in snag and deadwood biomass pools that are stable long after tree *** biomass(or carbon)in deadwood pools can lead to substantial underestimations of sequestration and stability.

关键词： Carbon sequestration Old-growth forest Pseudotsuga menziesii Tree mortality Tsuga heterophylla Wind River Forest Dynamics Plot

Investigation of alkaline-crude oil reaction

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Petroleum 2015年第1期1卷 31-39页

作者： james j.Sheng Texas Tech University

One of the mechanisms of alkaline flooding relies on alkaline reaction with organic acids(saponifiable components) in the crude oil to produce an in situ surfactant called soap that lowers interfacial tensions. However, this mechanism is not quantified in the literature. For example, what is the fraction of acid components which react with alkaline solution to generate soap? How much soap can be generated?In this paper, this mechanism and related issues are discussed, analyzed or quantified. In particular, the numerical simulation approach is used. The results show that only a fraction of acid components can be converted into soap; the amount of generated soap could be low. A minimum pH(e.g. 9) is needed for the acids to be converted to soap. The literature information on the effect of amount of acid components(total acid number) on oil recovery is also discussed.

关键词： Alkali Alkaline flooding Crude oil Acid number Soap Surfactant

Optimization of huff-n-puff gas injection in shale oil reservoirs

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Petroleum 2017年第4期3卷 431-437页

作者： james j.Sheng Texas Tech University P.O.Box 43111LubbockTX 79409USA Southwest Petroleum University Chengdu 610500China

Earlier studies show that huff-n-puff injection is preferred to continuous gas flooding to improve liquid oil production in shale oil *** to gas flooding,huff-n-puff has more operational parameters to optimize so that liquid oil production can be *** paper is to discuss the optimum huff-n-puff times,number of cycles and soaking time under practical operational and reservoir *** operational and reservoir conditions dictate the maximum injection and production rates,and the maximum injection pressure and minimum production *** numerical simulation results and discussions show that the optimum huff time is so long that the pressure near the wellbore reaches the set maximum injection pressure during the huff period;and the optimum puff time is the time required for the pressure near the wellbore to reach the set minimum production pressure during the puff *** benefits of soaking may not compensate the loss in injection and production due to the time lost in the soaking ***,soaking may not be necessary during the huff-n-puff gas injection in shale oil *** number of huff-n-puff cycles is determined when an economic rate cut-off is reached.

关键词： shale reservoirs injection

Status of surfactant EOR technology

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Petroleum 2015年第2期1卷 97-105页

作者： james j.Sheng Texas Tech University P.O.Box 43111LubbockTX 79409United States

Surfactant enhanced oil recovery(EOR)includes surfactant flooding and surfactant *** main functions of surfactants are to reduce interfacial tension and wettability *** paper is to review the EOR technology related to surfactant *** reviewed topics include the following:Surfactant EOR mechanismsFactors affecting interfacial tension Trapping numberScreening criteriaLaboratory work Numerical simulation work Summary of pilot and large-scale applications Surfactants used Salinity gradientSurfactant EOR in carbonate reservoirs Surfactant EOR in shale reservoirs.

关键词： Surfactant flooding Surfactant EOR Review Enhanced oil recovery Chemical EOR

Low Cost, High Efficiency, Gain Flattened L Band EDFA Using FBGs as C Band Seed Generators

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光学学报 2003年第S1期23卷 271-272页

作者： j.j. Pan james Guo Lightwaves 2020 Inc. 1323 Great Mall Drive Milpitas CA 95035 USALightwaves 2020 Inc. 1323 Great Mall Drive Milpitas CA 95035 USA

A low cost, coolerless 980nm diode pumped, gain flattened L band EDFA with fast transient control, high pump efficiency and gain clamping effect was realized by using FBGs as C band seed generators.

关键词： EDFA in as with Gain Flattened L Band EDFA Using FBGs as C Band Seed Generators High Efficiency Low Cost

Recent Advancements in Optical Harmonic Generation Microscopy: Applications and Perspectives

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Biomedical Engineering Frontiers 2021年第1期2卷 65-88页

作者： Darian S.james Paul j.Campagnola Department of Biomedical Engineering University of Wisconsin-Madison1550 Engineering DrMadisonWI 53706USA

Second harmonic generation(SHG)and third harmonic generation(THG)microscopies have emerged as powerful imaging modalities to examine structural properties of a wide range of biological *** SHG and THG arise from very different contrast mechanisms,the two are complimentary and can often be collected simultaneously using a modified multiphoton *** this review,we discuss the needed instrumentation for these modalities as well as the underlying theoretical principles of SHG and THG in tissue and describe how these can be leveraged to extract unique structural *** provide an overview of recent advances showing how SHG microscopy has been used to evaluate collagen alterations in the extracellular matrix and how this has been used to advance our knowledge of cancers,fibroses,and the cornea,as well as in tissue engineering *** examples using polarization-resolved approaches and machine learning algorithms are ***,we review how THG has enabled developmental biology and skin cancer studies due to its sensitivity to changes in refractive index,which are ubiquitous in all cell and tissue ***,we offer perspectives and outlooks on future directions of SHG and THG microscopies and present unresolved questions,especially in terms of overall miniaturization and the development of microendoscopy instrumentation.

关键词： harmonic resolved directions

A Pressure Relaxation Closure Model for One-Dimensional, Two-Material Lagrangian Hydrodynamics Based on the Riemann Problem

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Communications in Computational Physics 2010年第5期7卷 927-976页

作者： james R.Kamm Mikhail j.Shashkov Applied Physics Division Los Alamos National LaboratoryLos AlamosNM 87545USA Theoretical Division Los Alamos National LaboratoryLos AlamosNM 87545USA

Despite decades of development, Lagrangian hydrodynamics of strengthfree materials presents numerous open issues, even in one dimension. We focus on theproblem of closing a system of equations for a two-material cell under the assumptionof a single velocity model. There are several existing models and approaches, eachpossessing different levels of fidelity to the underlying physics and each exhibitingunique features in the computed solutions. We consider the case in which the changein heat in the constituent materials in the mixed cell is assumed equal. An instantaneous pressure equilibration model for a mixed cell can be cast as four equations infour unknowns, comprised of the updated values of the specific internal energy andthe specific volume for each of the two materials in the mixed cell. The unique contribution of our approach is a physics-inspired, geometry-based model in which theupdated values of the sub-cell, relaxing-toward-equilibrium constituent pressures arerelated to a local Riemann problem through an optimization principle. This approachcouples the modeling problem of assigning sub-cell pressures to the physics associated with the local, dynamic evolution. We package our approach in the frameworkof a standard predictor-corrector time integration scheme. We evaluate our model using idealized, two material problems using either ideal-gas or stiffened-gas equationsof state and compare these results to those computed with the method of Tipton andwith corresponding pure-material calculations.

关键词： Lagrangian hydrodynamics compressible flow multi-material flow pressure relaxation

Placement of removable metal biliary stent in post-orthotopic liver transplantation anastomotic stricture

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World journal of Gastroenterology 2010年第28期16卷 3597-3600页

作者： Hoi-Poh Tee Martin W james Arthur j Kaffes Gastroenterology Unit Medical Department Hospital Tengku Ampuan AfzanJalan Tanah Putih25100 KuantanPahangMalaysia Wolfson Digestive Disease Biomedical Re search Unit Nottingham NG7 2UHUnited Kingdom AW Morrow Gastroenterology and Live Centre Royal Prince Alfred HospitalMissenden RoadCamp erdownNSW 2050Australia

Postoperative biliary strictures are the most common cause of benign biliary stricture in Western countries, secondary to either operative injury or bile duct anastomotic stricture following orthotopic liver transplantation(OLT).Surgery or endoscopic interventions are the mainstay of treatment for benign biliary *** aim to report the outcome of 2 patients with refractory anastomotic biliary stricture post-OLT,who had successful temporary placement of a prototype removable covered self-expandable metal stent(RCSEMS).These 2 patients(both men,aged 44 and 53 years)were given temporary placement of a prototype RCSEMS (8.5 Fr gauge delivery system,8 mm×40 mm stent dimensions)in the common bile duct across the biliary *** was no morbidity associated with stent placement and removal in these 2 *** parameters improved after the RCSEMS *** biliary patency was achieved in both the patients. No further biliary intervention was required within 14 and 18 mo follow-up after stent removal.

关键词： Anastomosis Biliary stent Biliary stricture Orthotopic liver transplantation Niti-S stent