Chemical flocculation for removing bentonite spills in water

A potential environmental impact associated with horizontal directional drilling is the inadvertent return of bentonite-based drilling fluid to the surface via naturally occurring fractures or fissures. This study investigated a range of flocculants consisting of water-soluble linear polyacrylamides (PAMs) differing in charge (anionic, neutral, and cationic), biopolymer (chitosan) and gypsum for treating the bentonite suspension that might release with runoff or into stream water. Laboratory jar test were conducted with a 0.4 % (w/v) bentonite suspension having an average initial turbidity of 1,217 nephelometric turbidity units (NTU). None of the PAMs by themselves were effective in flocculating bentonite suspension (\u3e 690 NTU), but adding gypsum in a combination with anionic PAM enhanced the flocculation reaction (\u3c 120 NTU). The biopolymer performed better than the PAMs alone by lowering turbidity to 437 NTU. A simple, passive dosing system was tested in which bentonite-laden turbid water was pumped into a length of pipe with a jute lining treated with the chemical and passed through a geotextile dewatering bag. Both the biopolymer and the combination of gypsum and anionic PAM were effective, reducing turbidity by 86-95 % relative to influent bentonite suspension (1,188 NTU). These results suggest that simple, inexpensive flocculation systems can be deployed to reduce turbidity caused by bentonite spills

Demographic characteristics of exploited tropical lutjanids: a comparative analysis

Demographic parameters from seven exploited coral reef lutjanid species were compared as a case study of the implications of intrafamily variation in life histories for multispecies harvest management. Modal lengths varied by 4 cm among four species (Lutjanus fulviflamma, L. vitta, L. carponotatus, L. adetii), which were at least 6 cm smaller than the modal lengths of the largest species (L. gibbus, Symphorus nematophorus, Aprion virescens). Modal ages, indicating ages of full selection to fishing gear, were 10 years or less for all species, but maximum ages ranged from 12 (L. gibbus) to 36 years (S. nematophorus). Each species had a unique growth pattern, with differences in length-at-age and mean asymptotic fork length (L∞), but smaller species generally grew fast during the first 1–2 years of life and larger species grew more slowly over a longer period. Total mortality rates varied among species; L. gibbus had the highest mortality and L. fulviflamma, the lowest mortality. The variability in life history strategies of these tropical lutjanids makes generalizations about lutjanid life histories difficult, but the fact that all seven had characteristics that would make them particularly vulnerable to fishing indicates that harvest of tropical lutjanids should be managed with caution

Optimization of the Lucy Interplanetary Trajectory via Two-Point Direct Shooting

Lucy is NASAs next Discovery-class mission and will explore the Trojan asteroids in the Sun-Jupiter L4 and L5 regions. This paper details the design of Lucys interplanetary trajectory using a two-point direct shooting transcription, nonlinear programming, and monotonic basin hopping. These techniques are implemented in the Evolutionary Mission Trajectory Generator (EMTG), a trajectory optimization tool developed at NASA Goddard Space Flight Center. We present applications to the baseline trajectory design, Monte Carlo analysis, and operations

Integrating Sequence Capture and Restriction Site-Associated DNA Sequencing to Resolve Recent Radiations of Pelagic Seabirds

The diversification of modern birds has been shaped by a number of radiations. Rapid diversification events make reconstructing the evolutionary relationships among taxa challenging due to the convoluted effects of incomplete lineage sorting (ILS) and introgression. Phylogenomic data sets have the potential to detect patterns of phylogenetic incongruence, and to address their causes. However, the footprints of ILS and introgression on sequence data can vary between different phylogenomic markers at different phylogenetic scales depending on factors such as their evolutionary rates or their selection pressures. We show that combining phylogenomic markers that evolve at different rates, such as paired-end double-digest restriction site-associated DNA (PE-ddRAD) and ultraconserved elements (UCEs), allows a comprehensive exploration of the causes of phylogenetic discordance associated with short internodes at different timescales. We used thousands of UCE and PE-ddRAD markers to produce the first well-resolved phylogeny of shearwaters, a group of medium-sized pelagic seabirds that are among the most phylogenetically controversial and endangered bird groups. We found that phylogenomic conflict was mainly derived from high levels of ILS due to rapid speciation events. We also documented a case of introgression, despite the high philopatry of shearwaters to their breeding sites, which typically limits gene flow. We integrated state- of-the-art concatenated and coalescent-based approaches to expand on previous comparisons of UCE and RAD-Seq data sets for phylogenetics, divergence time estimation, and inference of introgression, and we propose a strategy to optimize RAD-Seq data for phylogenetic analyses. Our results highlight the usefulness of combining phylogenomic markers evolving at different rates to understand the causes of phylogenetic discordance at different timescales.

Palaeoceanographic changes in the late Pliocene promoted rapid diversification in pelagic seabirds

Aim: Palaeoceanographic changes can act as drivers of diversification and speciation, even in highly mobile marine organisms. Shearwaters are a group of globally distributed and highly mobile pelagic seabirds. Despite a recent well-resolved phylogeny, shearwaters have controversial species limits, and show periods of both slow and rapid diversification. Here, we explore the role of palaeoceanographic changes on shearwaters' diversification and speciation. We investigate shearwater biogeography and the evolution of a key phenotypic trait, body size, and we assess the validity of their current taxonomy

A new framework for assessing the contributions of professionals in the natural sciences

No abstract available

Higher education in Indonesia: Contemporary challenges in governance, access, and quality

This chapter presents the development of Indonesian higher education since its origins to current challenges in the fields of governance, autonomy, access, equity, quality, and internationalization. Indonesia has a massive and diversified tertiary education, including experiments in community colleges and online programs. The higher educational system remains mainly centralized, with the exception of some reforms towards financial autonomy. Insufficient public funding hinders the capacity to provide adequate teaching, research, and facilities among other aspects. The consequential rise in student fees contributes to an overrepresentation of students from Java, urban centers, and higher social classes

Period and chemical evolution of SC stars

The SC and CS stars are thermal-pulsing AGB stars with C/O ratio close to unity. Within this small group, the Mira variable BH Cru recently evolved from spectral type SC (showing ZrO bands) to CS (showing weak C2). Wavelet analysis shows that the spectral evolution was accompanied by a dramatic period increase, from 420 to 540 days, indicating an expanding radius. The pulsation amplitude also increased. Old photographic plates are used to establish that the period before 1940 was around 490 days. Chemical models indicate that the spectral changes were caused by a decrease in stellar temperature, related to the increasing radius. There is no evidence for a change in C/O ratio. The evolution in BH Cru is unlikely to be related to an on-going thermal pulse. Periods of the other SC and CS stars, including nine new periods, are determined. A second SC star, LX Cyg, also shows evidence for a large increase in period, and one further star shows a period inconsistent with a previous determination. Mira periods may be intrinsically unstable for C/O ~ 1; possibly because of a feedback between the molecular opacities, pulsation amplitude, and period. LRS spectra of 6 SC stars suggest a feature at wavelength > 15 micron, which resembles one recently attributed to the iron-sulfide troilite. Chemical models predict a large abundance of FeS in SC stars, in agreement with the proposed association.Comment: 14 pages, 20 figures. MNRAS, 2004, accepted for publication. Janet Mattei, one of the authors, died on 22 March, 2004. This paper is dedicated to her memor

Influence of tip clearance on flow behavior and noise generation of centrifugal compressors in near-surge conditions

CFD has become an essential tool for researchers to analyze centrifugal compressors. Tip leakage flow is usually considered one of the main mechanisms that dictate compressor flow field and stability. However, it is a common practice to rely on CAD tip clearance, even though the gap between blades and shroud changes when compressor is running. In this paper, sensitivity of centrifugal compressor flow field and noise prediction to tip clearance ratio is investigated. 3D CFD simulations are performed with three different tip clearance ratios in accordance to expected operating values, extracted from shaft motion measurements and FEM predictions of temperature and rotational deformation. Near-surge operating conditions are simulated with URANS and DES. DES shows superior performance for acoustic predictions. Cases with reduced tip clearance present higher pressure ratio and isentropic efficiency, but no significant changes in compressor acoustic signature are found when varying clearance. In this working point, tip clearance is immersed in a region of strongly swirling backflow. Therefore, tip leakage cannot establish any coherent noise source mechanism.The equipment used in this work has been partially supported by FEDER project funds "Dotacion de infraestructuras cientifico tecnicas para el Centro Integral de Mejora Energetica y Medioambiental de Sistemas de Transporte (CiMeT), (FEDER-ICTS-2012-06)", framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain. The authors wish to thank Mr. Pau Raga for his worthy assistance during the meshing process.Galindo, J.; Tiseira Izaguirre, AO.; Navarro García, R.; López Hidalgo, MA. (2015). Influence of tip clearance on flow behavior and noise generation of centrifugal compressors in near-surge conditions. International Journal of Heat and Fluid Flow. 52:129-139. https://doi.org/10.1016/j.ijheatfluidflow.2014.12.004S1291395