Patterning of porous silicon nanostructures and eliminating microcracks on silicon nitride mask using metal assisted chemical etching

A method for selective formation of reproducible, high fidelity and controllable nano and micrometer size porous Si areas over n-type Si wafers is provided. A 400 nm thick Silicon Nitride layer was used as the mask layer while Platinum and Palladium nanoparticles were deposited over the unprotected areas to obtain porous areas through metal assisted chemical etching process. Nanoparticles were deposited by electroless plating solutions containing H₂PtCl₆ and PdCl₂. Good controls over pore size and depth were obtained with well defined and sharp edges of the patterned areas. The results were compared to porous structures obtained via electrochemical etching process, indicating the superiority of metal assisted etching in terms of its simplicity as well as the ability of Silicon Nitride layer acting as the mask layer.     

Effect of Microstructural Features on Magnetic Properties of High-Carbon Steel

Metallurgical and Materials Transactions A - Industrially produced high-carbon steel has been heat treated in order to obtain various microstructures of the single phase of martensite, bainite,...     

Cane molasses fermentation for continuous ethanol production in an immobilized cells reactor by Saccharomyces cerevisiae

Sodium-alginate immobilized yeast was employed to produce ethanol continuously using cane molasses as a carbon source in an immobilized cell reactor (ICR). The immobilization of Saccharomyces cerevisiae was performed by entrapment of the cell cultured media harvested at exponential growth phase (16 h) with 3% sodium alginate. During the initial stage of operation, the ICR was loaded with fresh beads of mean diameter of 5.01 mm. The ethanol production was affected by the concentration of the cane molasses (50, 100 and 150 g/l), dilution rates (0.064, 0.096, 0.144 and 0.192 h^?1) and hydraulic retention time (5.21, 6.94, 10.42 and 15.63 h) of the media. The pH of the feed medium was set at 4.5 and the fermentation was carried out at an ambient temperature. The maximum ethanol production, theoretical yield (Y_E/S), volumetric ethanol productivity (Q_P) and total sugar consumption was 19.15 g/l, 46.23%, 2.39 g l^?1 h^?1 and 96%, respectively.     

Target optimization for a 10-MeV E-beam neutron converter

Accelerator-based target design and optimization is an approach for neutron generation. The target plays an important role for a neutron source on an electron accelerator. For optimizing a neutron source using 10 MeV electron beams of Rhodotron-TT200, Pb, Ta, or W alloys with Be were calculated as photo-neutron converter. The neutron yield, flux and energy were simulated using the MCNPX code. The results indicate that a 10 MeV electron beam is capable of producing high-intensity neutron flux of 1013n·cm–2·s–1 with average energy of 0.8 MeV.     

Beta-carotene production within Dunaliella salina cells under salt stress condition in an indoor hybrid helical-tubular photobioreactor

For the cultivation of Dunaliella salina (a green unicellular eukaryote photosynthetic microalga), a 20 L indoor helical-tubular photobioreactor was designed. The inner diameter and the thickness of the PU (polyurethane) tube were 12 and 2 mm, respectively, and its length was 75 m. An open pond was located on the top of the PBR structure and a pump circulated the culture medium from the pond to the tubes. Another part of the tube was connected to an airlift column (which was connected to the bottom of the pond), and the culture medium completed its circulation by moving from the airlift column that connected the closed system (tubular) to the open system (open pond). Eight LED lamps with 10 000 lx were set around the tube and a 2000 lx LED was adjusted on the top of the pond. The culture salinity within the PBR was 1 mol L⁻¹ and four intermittent steps of 0.5 mol L⁻¹ salt stresses were injected into the culture medium. The highest beta-carotene production within this hybrid helical-tubular PBR was 4.85 µg of beta-carotene per mg of dry weight of microalgae at 2.5 mol L⁻¹ salinity.     

Experimental Investigation to Optimize Tool Life and Surface Roughness in Inconel 718 Machining

In addition to the cutting conditions, the surface quality is also affected significantly by a worn tool in machining processes. Identification of the desirable tool life so that the surface quality is maintained within a desirable level is an essential task, especially in the machining of hard materials. In this paper, an optimal tool life and surface quality were identified in the turning operation of Inconel 718 Superalloy by means of experimental investigations and intelligent methods. First, the effect of machining time (MT) at the different cutting parameters was widely investigated on the surface roughness using the neural network model. Then, the modified Non-dominated Sorting Genetic Algorithm (NSGA) was implemented to optimize tool life and surface roughness. For this purpose, a new approach was implemented and the MT was taken into account as the input and output parameters during the optimization. Finally, the results of optimization were classified and the suitable states of the machining outputs were found. The results indicate that the implemented strategy in this paper provides an efficient approach to determine a desirable criterion for tool life estimation in machining processes.     

Synthesis,in vitro characterization,and anti-tumor effects of novel polystyrene-poly(amide-ether-ester-imide) co-polymeric micelles for delivery of docetaxel in breast cancer in Balb/C mice

Objective: The goal of the present work was to make novel co-polymeric micellar carriers for the delivery of docetaxel (DTX).

Significance: Co-polymeric micelles can not only solubilize DTX and eliminate the need for toxic surfactants to dissolve it, but also cause passive targeting of the drug to the tumor and reduce its toxic side effects.

Methods: Poly(styrene-maleic acid) (SMA) was conjugated to poly (amide-ether-ester-imide)-poly ethylene glycol (PAEEI-PEG). Copolymer synthesis was proven by Fourier transform infrared (FTIR) and ¹H-nuclear magnetic resonance (¹H-NMR). The SMA-PAEEI-PEG micelles loaded with DTX were prepared and their critical micelle concentration (CMC), zeta potential, particle size, entrapment efficiency, and their release efficiency were studied. MCF-7 and MDA-MB231 breast cancer cells were used to evaluate the cellular uptake and cytotoxicity of the micelles. The antitumor activity of the DTX-loaded nanomicelles was measured in Balb/c mice.

Results: The FTIR and HNMR spectroscopy confirmed successful conjugation of SMA and PAEEI-PEG. The drug loading efficiency was in the range of 34.01–72.75% and drug release lasted for 120?h. The CMC value of the micelles was affected by the SMA/PAEEI-PEG ratio and was in the range of 29.85–14.28?µg/ml. The DTX-loaded micelles showed five times more cytotoxicity than the free drug. The DTX loaded micelles were more effective in tumor growth suppression in vivo and the animals showed an enhanced rate of survival.

Conclusion: The results show that the SMA-PAEEI-PEG micelles of DTX could potentially provide a suitable parenteral formulation with more stability, higher cytotoxicity, and improved antitumor activity.     

Relationship Between Time of Class and Student Grades in an Active Learning Course

Background

A factor related to students’ course performance that has seen limited research compared to other academic factors is the time of day a class is offered. Because of students’ chronotypes (i.e., preferred time of day to study or work), time of class can influence attendance, which has a strong correlation with students’ performance in a course.

Purpose/Hypothesis

The goal of this study was to investigate the relationship between class time, students’ attendance including individual and average class attendance, and students’ final grades in an active learning course.

Design/Method

The grade and attendance records of 1,577 first‐year engineering (FYE) students enrolled in 15 sections at different times of the day were analyzed using Tukey's Honestly Significant Difference and Multi‐Level Modeling to identify whether the performance and attendance of students in the early morning sections were significantly different from those in the other sections and to differentiate the individual and class attendance in relation to students’ grades.

Results

Students enrolled in early morning and late Friday afternoon classes had lower attendance and final grades than students in other sections. Class average attendance had a significant relationship with students’ grades. Thus, in active learning classes, both an individual student's and classmates’ absences have a negative relationship with an individual student's grade.

Conclusion

FYE students are more likely to miss early morning classes. In a course based on active learning, this lower attendance has a negative relationship with student performance for all students in the class, including the ones who attend the class regularly, suggesting active learning may amplify the negative effects of missing classes.     

Convergence of fuzzy-pyramid algorithms

Pyramid linking is an important technique for segmenting images and has many applications in image processing and computer vision. The algorithm is closely related to the ISODATA clustering algorithm and shares some of its properties. This paper investigates this relationship and presents a proof of convergence for the pyramid linking algorithm. The convergence of the hard-pyramid linking algorithm has been shown in the past; however, there has been no proof of the convergence of fuzzy-pyramid linking algorithms. The proof of convergence is based on Zangwill's theorem, which describes the convergence of an iterative algorithm in terms of a descent function of the algorithm. We show the existence of such a descent function of the pyramid algorithm and, further, show that all the conditions of Zangwill's theorem are met; hence the algorithm converges.This research was supported by the U.S. Army Research Office under contract DAAL 03-91-G0050.