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81.
A Study of Student Engagement in Project‐Based Learning Across Multiple Approaches to STEM Education Programs
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Objective: In this study, we investigated the implementation of project‐based learning (PBL) activities in four secondary science, technology, engineering, and mathematics (STEM) education settings to examine the impact of inquiry based instructional practices on student learning. Method: Direct classroom observations were conducted during the 2013–2014 school year in STEM Traditional Courses, a STEM Platform School, an Engineering Optional Program (EOP), and a Virtual STEM Academy (VSA) to measure teacher instructional practices (School Observation Measure) and student engagement (The Rubric for Student‐Centered Activities). Results: The four approaches to STEM education showed significant differences in their implementation of PBL, with the EOP and VSA having higher incidences of PBL activities. Additionally, higher‐level questioning strategies, higher‐order instructional feedback, and integration of STEM subject areas was absent or rarely observed. Conclusions: Components of PBL are missing in STEM education, in traditional and non‐traditional STEM courses. In‐service teachers may benefit from professional development that enhances their understanding of PBL activities to maximize student learning opportunities. 相似文献
82.
Sally Noushini Soo Jean Park Jeanneth Perez Danielle Holgate Vivian Mendez Ian M. Jamie Joanne F. Jamie Phillip W. Taylor 《Molecules (Basel, Switzerland)》2021,26(16)
Pheromones are biologically important in fruit fly mating systems, and also have potential applications as attractants or mating disrupters for pest management. Bactrocera kraussi (Hardy) (Diptera: Tephritidae) is a polyphagous pest fruit fly for which the chemical profile of rectal glands is available for males but not for females. There have been no studies of the volatile emissions of either sex or of electrophysiological responses to these compounds. The present study (i) establishes the chemical profiles of rectal gland contents and volatiles emitted by both sexes of B. kraussi by gas chromatography–mass spectrometry (GC–MS) and (ii) evaluates the detection of the identified compounds by gas chromatography–electroantennogram detection (GC–EAD) and –electropalpogram detection (GC–EPD). Sixteen compounds are identified in the rectal glands of male B. kraussi and 29 compounds are identified in the rectal glands of females. Of these compounds, 5 were detected in the headspace of males and 13 were detected in the headspace of females. GC–EPD assays recorded strong signals in both sexes against (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-ethyl-7-mehtyl-1,6-dioxaspiro[4.5]decane isomer 2, (E,Z)/(Z,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, and (Z,Z)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane. Male antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane, 2-methyl-6-pentyl-3,4-dihydro-2H-pyran, 6-hexyl-2-methyl-3,4-dihydro-2H-pyran, 6-oxononan-1-ol, ethyl dodecanoate, ethyl tetradecanoate and ethyl (Z)-hexadec-9-enoate, whereas female antennae responded to (E,E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane and 2-methyl-6-pentyl-3,4-dihydro-2H-pyran only. These compounds are candidates as pheromones mediating sexual interactions in B. kraussi. 相似文献
83.
Lijun Duan Sunny N. Wallace Abigail Engelberth Justin K. Lovelady Edgar C. Clausen Jerry W. King Danielle Julie Carrier 《Applied biochemistry and biotechnology》2009,158(2):362-373
In an effort to increase revenues from a given feedstock, valuable co-products could be extracted prior to biochemical or
thermochemical conversion with subcritical water. Although subcritical water shows significant promise in replacing organic
solvents as an extraction solvent, compound degradation has been observed at elevated extraction temperatures. First order
thermal degradation kinetics from a model system, silymarin extracted from Silybum marianum, in water at pH 5.1 and 100, 120, 140, and 160 °C were investigated. Water pressure was maintained slightly above its vapor
pressure. Silymarin is a mixture of taxifolin, silichristin, silidianin, silibinin, and isosilibinin. The degradation rate
constants ranged from 0.0104 min−1 at 100 °C for silichristin to a maximum of 0.0840 min−1 at 160 °C for silybin B. Half-lives, calculated from the rate constants, ranged from a low of 6.2 min at 160 °C to a high
of 58.3 min at 100 °C, both for silichristin. The respective activation energies for the compounds ranged from 37.2 kJ/gmole
for silidianin to 45.2 kJ/gmole for silichristin. In extracting the silymarin with pure ethanol at 140 °C, no degradation
was observed. However, when extracting with ethanol/water mixtures at and 140 °C, degradation increased exponentially as the
concentration of water increased.
An erratum to this article can be found at 相似文献
84.
Ben Rebah F Prévost D Tyagi RD Belbahri L 《Applied biochemistry and biotechnology》2009,158(1):155-163
In our study, the potential of producing polyhydroxybutyrate (PHB) by cultivating fast-growing rhizobia (Sinorhizobium meliloti, Rhizobium leguminosarum bv. viciae, R. leguminosarum bv. phaseoli and R. leguminosarum bv. trifolii) in sludge and in industrial wastewater was evaluated. Results confirmed the possibility of using sludge as media for rhizobial
growth. During growth, substantial quantity of PHB was accumulated and yields varied depending on the media and rhizobial
species. Growing in sludge, PHB production did not exceed 3.7% w/w for all strains at the end of experiment (after 72 h). During the growth of S. meliloti, PHB yield varied and the maximum value reached 7.27% w/w after 60 h, with 1% Total Suspend Solid (TSS) sludge. Alkaline sludge pre-treatment affects rhizobial growth but did not
improve the PHB accumulation. While growing S. meliloti in industrial wastewater, the PHB yields varied and the highest value was obtained with slaughterhouse wastewater (10.7%
w/w) after 35 h of growth. Therefore, this work shows the potential of exploiting PHB production by rhizobia growing in wastewater
or sludge which could be applied to bioplastic industry, and confirms the potential of these recyclable wastes for high production
of rhizobial cells useable for legumes inoculants production. This study provides an environmentally sound way of sludge and
wastewater management and use in diverse biotechnological applications. 相似文献
85.
Bardet M Lundquist K Parkås J Robert D von Unge S 《Magnetic resonance in chemistry : MRC》2006,44(10):976-979
The 13C NMR signals from the aromatic ring carbons in a series of lignin model compounds of the arylglycerol beta-aryl ether type in DMSO solution have been assigned. The model compounds investigated are representative of the erythro and threo forms of differently substituted arylglycerol beta-aryl ethers. 相似文献
86.
Vugts DJ Koningstein MM Schmitz RF de Kanter FJ Groen MB Orru RV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(27):7178-7189
A broad range of differently substituted dihydropyrimidines and thiazines can be efficiently prepared by using a four-component reaction between phosphonates, nitriles, aldehydes, and iso(thio)cyanates. The scope and limitations of this multicomponent reaction are fully described. Variation of all four components has been investigated. The nitrile and aldehyde inputs can be varied extensively, but variation of the phosphonate input remains limited. An interesting rearrangement leading to phosphoramidates has been observed. Furthermore, the multicomponent reaction seems to be restricted to the use of isocyanates with strongly electron-withdrawing substituents, but an interesting additional exchange reaction under microwave conditions leads to dihydropyrimidines with less electron-withdrawing substituents at N3. In addition, a diastereoselective formation of dihydropyrimidines has been observed when using a chiral aldehyde as the input. Finally, by changing the isocyanate component to an isothiocyanate, thiazines are efficiently formed instead of the corresponding thio-dihydropyrimidines. 相似文献
87.
Danielle J. Moreau Zebb Prime Ric Porteous Con J. Doolan Vincent Valeau 《Journal of sound and vibration》2014
This paper presents an experimental investigation of the flow-induced noise created by a wall-mounted finite airfoil at low-to-moderate Reynolds number and zero angle of attack. Far-field noise measurements have been taken at a single observer location and with two perpendicular microphone arrays in an anechoic wind tunnel at Reynolds numbers of Rec=9.2×104–1.6×105, based on chord, and for a variety of airfoil aspect ratios (length to chord ratio of L/C=0.2–2, corresponding to length to thickness ratio of L/T=1.7–16.7). Additionally, surface oil-film visualisation images and unsteady velocity measurements taken in the near trailing edge wake are related to far-field noise measurements to determine the flow mechanisms responsible for noise generation. The results show that the wall-mounted finite airfoil radiates noise similar to a two-dimensional airfoil when L/T>8.3. Despite the incoming boundary layer height at the junction being 1.30≤δ/T≤1.46, junction and tip flow suppresses tonal noise production for airfoil?s up to L/T=8.3 at Rec=9.2×104–1.2×105. Trailing edge noise is found to be the dominant airfoil noise generation mechanism at frequencies above 1 kHz with the position of the noise source along the trailing edge determined by the proportion of the airfoil span influenced by flow at the airfoil–wall junction. 相似文献
88.
Ji He Danielle Zeng Xinhai Zhu Z. Cedric Xia Shuhui Li 《International Journal of Solids and Structures》2014
The path-dependence of the conventional Forming Limit Diagram (FLD) is an important issue for its applications in industry. Great efforts have been made to understand the nature of the path-dependence with both experimental and theoretical approaches, many of them attempting to find a path-independent way for the application of forming limits. In this paper, we focus on the nonlinear strain path effect on forming limit predictions using both isotropic and anisotropic hardening models. The Forming Limit Diagram (FLD), Forming Limit Stress Diagram (FLSD) and Forming Limit Effective Strain Diagram (epFLD) of sheet metals subject to linear and nonlinear strain paths are analyzed and compared using the Marciniak–Kuczynski approach. An anisotropic hardening model based on Yoshida and Uemori development is adopted in this study, and it is coupled with the traditional Hill’48 yield surface. This model is capable of describing the complex Bauschinger phenomenon after the material undergoes the reverse loading process such as the early re-yielding, work-hardening stagnation and permanent softening. Two different scenarios for the change of strain paths are also investigated. In the first scenario, the sheet material is initially loaded with a fixed strain increment ratio, unloaded to the free stress state, and then reloaded with a different strain increment ratio until the forming limit is reached. In the second scenario, the material does not undergo elastic unloading. Instead, the strain path is abruptly changed to a different strain increment ratio and the material undergoes continuous loading until the forming limit is reached. It is found that the work-hardening behavior after the pre-straining and the loading scenario plays an important role in the path dependent behavior of forming limits. Detailed analysis reveals that the M–K approach may have contributed to the significance of path-dependence observed in this study, especially at high pre-strain levels. 相似文献
89.
Ramon S. Vilela Thiago L. Oliveira Felipe T. Martins Javier A. Ellena Francesc Lloret Miguel Julve Danielle Cangussu 《Comptes Rendus Chimie》2012,15(10):856-865
The preparation, crystal structure and magnetic properties of a new oxalate-containing copper(II) chain of formula {[(CH3)4N]2[Cu(C2O4)2] · H2O}n (1) [(CH3)4N+ = tetramethylammonium cation] are reported. The structure of 1 consists of anionic oxalate-bridged copper(II) chains, tetramethylammoniun cations and crystallization water molecules. Each copper(II) ion in 1 is surrounded by three oxalate ligands, one being bidentate and the other two exhibiting bis-bidenate coordination modes. Although all the tris-chelated copper(II) units from a given chain exhibit the same helicity, adjacent chains have opposite helicities and then an achiral structure results. Variable-temperature magnetic susceptibility measurements of 1 show the occurrence of a weak ferromagnetic interaction through the oxalate bridge [J = +1.14(1) cm−1, the Hamiltonian being defined as H = –J ∑nmSi · Sj]. This value is analyzed and discussed in the light of available magneto-structural data for oxalate-bridged copper(II) complexes with the same out-of-plane exchange pathway. 相似文献
90.
Bassanese DN Crawford-Clark S Bowen BJ Henderson LC Barnett NW Conlan XA 《Journal of separation science》2012,35(9):1110-1117
The need to monitor biogenic amines levels is essential for many areas of the food industry for two main reasons: the caustic nature and potential toxicity of these amines, and the potential to use amine levels as markers for freshness and quality in foodstuffs. Optimised analysis conditions used for the determination of biogenic amines derivatised with 2-napthyloxycarbonyl chloride has been applied to different pet food samples to assess the effectiveness of this method for complex sample matrices. Further to this, the use of high-resolution mass spectrometry has enabled the previously unconfirmed derivatised form of seven biogenic amines to be established. The derivatised forms identified include as mono substituted (tryptamine and histamine), bisubstituted (putrescine, cadaverine and tyramine), trisubstituted (spermidine) and tetrasubstituted (spermine). The methodology of biogenic amine determination was performed successfully to a range of pet food products highlighting the applicability to a variety of complex sample matrices. 相似文献