College students’ perceived threat and preference for seeking help in traditional,distributed, and distance learning environments

The purpose of the present study was to examine how college students’ help seeking behavior varied across different instructional learning environments. Four hundred and seventy four (N = 472) students enrolled in distance, distributed, and traditional classes were queried about their help seeking preferences, help seeking tendencies, personal threat in seeking help, and academic self-efficacy. It was hypothesized that students enrolled in courses with an online computer component would report (a) higher instances of help seeking behavior, particularly from instructors; and (b) feel less threatened to seek help than students in traditional learning environments. It was also expected that student achievement would be significantly correlated with formal help seeking, academic self-efficacy, and perceived threat to seek help. Lastly, it was postulated that students would report that they prefer to use electronic means to seek help and that they find it more effective. Overall the hypotheses of this study were supported. Educational implications and recommendations are provided regarding the type of technological tools that college instructors might consider using in their courses to promote help seeking.     

Nonlinearly viscoelastic analysis of asphalt mixes subjected to shear loading

This study presents the characterization of the nonlinearly viscoelastic behavior of hot mix asphalt (HMA) at different temperatures and strain levels using Schapery’s model. A recursive-iterative numerical algorithm is generated for the nonlinearly viscoelastic response and implemented in a displacement-based finite element (FE) code. Then, this model is employed to describe experimental frequency sweep measurements of two asphalt mixes with fine and coarse gradations under several combined temperatures and shear strain levels. The frequency sweep measurements are converted to creep responses in the time domain using a phenomenological model (Prony series). The master curve is created for each strain level using the time temperature superposition principle (TTSP) with a reference temperature of 40°C. The linear time-dependent parameters of the Prony series are first determined by fitting a master curve created at the lowest strain level, which in this case is 0.01%. The measurements at strain levels higher than 0.01% are analyzed and used to determine the nonlinear parameters. These parameters are shown to increase with increasing strain levels, while the time–temperature shift function is found to be independent of strain levels. The FE model with the calibrated time-dependent and nonlinear material parameters is used to simulate the creep experimental tests, and reasonable predictions are shown.     

Applicability and limitation of OSARs for the toxicity of electrophilic chemicals

The appropriate selection and application of quantitative structure-activity relationships (QSARs) for the prediction of toxicity is based on the prior assignment of a chemical to its mode of toxic action. This classification is often derived from structural characteristics with the underlying assumption that chemically similar compounds have similar mechanisms of action, which is often but not necessarily the case. Instead of using structural characteristics for classification toward a mode of toxic action, we used Escherichia coli based bioanalytical assays to classify electrophilic chemicals. Analyzing a series of reactive organochlorines, epoxides, and compounds with an activated double bond, three subclasses of reactive toxicity were distinguished: "glutathione depletion-related toxicity", "DNA damage", and "unspecific reactivity". For both subsets of specifically reacting compounds a direct correlation between effects and chemical reactivity was found. Reaction rate constants with either glutathione or 2'-deoxyguanosine, which was used as a model for complex DNA, served well to set up preliminary QSARs for either glutathione depletion-related toxicity or toxicity based on DNA damage in the model organism E. coli. The applicability of QSARs for electrophilic chemicals based on mechanistically relevant reaction rate constants is a priori limited to a small subset of compounds with strictly identical mechanism of toxic action and similar metabolic rates. In contrast, the proposed bioanalytical assays not only allowed the experimental identification of molecular mechanisms underlying the observable toxicity but also their toxicity values are applicable to quantitatively predict toxic effects in higher organisms by linear correlation models, independent of the assigned mode of toxic action.     

High-throughput double quantitative competitive polymerase chain reaction for determination of genetically modified organisms

Quantitative competitive polymerase chain reaction (PCR), especially the double competitive PCR methods (DC-PCR), have evolved as reliable approaches to quantification of genetically modified organisms (GMO) in food. However, DC-PCR is a low-throughput method because it requires titration of each sample with various amounts of a competitive internal standard, a protocol that involves several PCRs per sample followed by electrophoresis and densitometry. To address this drawback, we have developed a new method for GMO quantification, namely, a high-throughput double quantitative competitive PCR (HT-DCPCR). In HT-DCPCR, electrophoresis and densitometry are replaced by a rapid, microtiter well-based bioluminometric hybridization assay and there is no need for titration of each sample. The determination of GM soya was chosen as a model. We have constructed internal standards (DNA competitors) both for the 35S promoter sequence and for a plant-specific reference gene (lectin). The competitors have identical size and share the same primer binding sites with the target sequences but differ in a 24-bp internal segment. Each target sequence (35S and lectin) is coamplified with a constant amount (1000 copies) of the respective competitor. The four amplified fragments are hybridized with specific probes and captured on a universal solid phase to achieve simplicity and high throughput. The hybrids are determined by using streptavidin conjugated to the photoprotein aequorin. The ratio of the luminescence values obtained for the target and the competitor is linearly related to the starting amount of target DNA. The limit of quantification for the 35S promoter is 24 copies. The proposed method was evaluated by determining the GMO content of soybean powder certified reference materials. Also HT-DCPCR was compared to real-time PCR in a variety of real samples.     

Shelf-life extension of refrigerated Mediterranean mullet (Mullus surmuletus) using modified atmosphere packaging

The present work evaluated the quality and freshness characteristics and the effect of modified atmosphere packaging (MAP) on the shelf-life extension of refrigerated Mediterranean mullet using microbiological, biochemical, and sensory analyses. Fresh open sea red mullet (Mullus surmuletus) were packaged in four different atmospheres: M1, 10%/20%/70% (O2/ CO2/N2); M2, 10%/40%/50% (O2/CO2/N2); M3, 10%/60%/30% (O2/CO2/N2); identical fish samples were packaged in air. All fish were kept under refrigeration (4 +/- 0.5 degrees C) for 14 days. Of the three gas atmospheres, the 10%/40%/50% (M2) and 10%/ 60%/30% (M3) gas mixtures were the most effective for inhibiting growth of aerobic microflora in mullet samples until day 10 of refrigerated storage. H2S-producing bacteria and pseudomonads were part of the mullet microflora and their growth was partly inhibited under MAP conditions. Between these two bacterial groups, H2S-producing bacteria (including Shewanella putrefaciens) were dominant toward the end of the storage period, regardless of the packaging conditions. Brochothrix thermosphacta and lactic acid bacteria were found to be members of the final microbial flora of MAP and air-packaged mullet, whereas the Enterobacteriaceae population was lower than other bacterial groups. Of the chemical freshness indices determined, thiobarbituric acid values were variable in mullet samples irrespective of packaging conditions indicative of no specific oxidative rancidity trend. Based on sensorial data and aerobic plate count, trimethylamine nitrogen and total volatile basic nitrogen limit values in the range of ca. 15 to 23 and 52 to 60 mg N/100 g of fish muscle were obtained, respectively, for mullet packaged under modified atmosphere and air. Sensory analyses (odor and taste attributes) showed that the limit of sensorial acceptability was reached after ca. 6 days for the samples packaged in air, 8 days for the M1 and M3 samples, and after 10 days for the M2 samples. Respective shelf-life extension for fresh whole mullet was ca. 2 days (M1 and M3 gas mixtures), and 4 days (M2 gas mixture).     

Wear Protection by Fe‐B‐C Hard Phases

Four as‐cast iron alloys with (mass%) 1B + 3C, 2B + 2C, 3B + 1C and 4B + 1C were investigated in respect to their microstructure by optical and scanning electron microscopy with EDX and ESBD and by microprobe analysis. The microhardness of eutectic Fe₃(C,B) increased with the B/C ratio and raised the resistance to scratching by Flint particles. The low melting range of the castings was used for the powder metallurgical production of a metal matrix composite by liquid phase sintering of admixed hard particles in an Fe‐B‐C base material. Abrasive wear tests showed that the eutectic carborides in the base material raised the wear resistance even more than the admixed particles.     

Potential for acrylamide formation in potatoes: data from the 2003 harvest

Reducing sugars, free amino acids, and the potential for acrylamide formation were determined in more than 50 potato samples from the 2003 harvest in Switzerland. The reducing sugar content strongly correlated with acrylamide, whereas no correlation was found between acrylamide and free asparagine or the pool of free amino acids. The reducing sugar contents and the acrylamide potentials were higher in most of the cultivars tested than in the samples from 2002. This was probably due to the hot and dry summer of 2003. Monitoring sugars and amino acids during heating at 120 °C and 180 °C showed that glucose and fructose reacted much faster than sucrose and the amino acids. Glutamine was consumed to a larger extent than any of the other amino acids. During prolonged storage, the reducing sugars decreased considerably while only moderate changes in the free amino acids were observed. Altogether, glucose and fructose remain the critical factors for acrylamide formation in potatoes and represent the most feasible way of reducing the formation of acrylamide in potato products.     

Effect of the Alumosilicate Gels pH on Zeolite Phase Composition for the Co-crystallization of BEA/MOR Zeolites in Na2O-TEABr-Al2O3-SiO2-H2O System

This paper deals with the method of zeolites BEA （beta） and MOR （mordenite） synthesis and the co-crystallization method of zeolites BEA/MOR. Synthesized zeolites were studied based on the SEM （scanning electron microscopy）, XRD （x-ray diffraction） and chemical analysis. The porous structure of these zeolites was investigated by nitrogen low-temperature adsorption. It has been illustrated that regulation of the BEA/MOR co-crystalline zeolites phase composition is possible due to variations of the initial alumosilicate gels composition and hydrogen ions concentration. Zeolites containing the co-crystalline phases of BEA/MOR could to be attractive in the processes using the catalysts, which based on the pure phases BEA or MOR zeolites.     

Component-based waveform development: the Nucleus tool flow for efficient and portable software defined radio

With the advent of multi-processor systems on chip (MPSoCs) and due to the complexity and variety of modern wireless standards, academia and industry are moving towards software defined radio (SDR) solutions. It is the goal of the SDR approach to allow designers to describe a radio standard or waveform by means of a high level language. This allows faster waveform development cycles and makes it easier to migrate waveforms across different platforms. Out of many software paradigms, component-based software engineering (CBSE) is an attractive match for SDR, especially for baseband applications. It abstracts waveforms in the traditional way algorithm designers think of their applications and guarantees a high degree of portability. However, existing CBSE approaches for SDR have not been able to close the gap between specification and implementation so as to achieve the computational performance and the energy efficiency of handcrafted solutions. The main reason for this gap is that these flows rely on traditional compilers to lower the high level specification to the platform. The work presented in this paper builds on the Nucleus Concept (Ramakrishnan et al., IEEE Military Communications Conference (MILCOM 2009) [28]) in which computationally intensive kernels and their implementation characteristics on the target platform are known. This information allows a tool to close the performance gap, and thus enables efficient component-based SDR development. In this paper we present such a flow and its supporting environment, which includes state-of-the-art tools for system level design. The flow is demonstrated on a MIMO OFDM transceiver.