The Use of Radiation-Induced Plastic Memory to Develop New Space Erectable Structures

Radiation induced plastic memory in polyethylene and use in space erectable structure

Analisis Penggunaan Aplikasi Evaluasi Belajar Online Pada Pembelajaran Biologi di SMA Kota Jambi: (Analysis of the Use of Online Learning Evaluation Applications in Biology Learning in Jambi City High Schools)

One of the measuring tools for evaluating learning outcomes is using a test. As information technology develops, written tests using paper media have changed to online-based tests. This research is quantitative descriptive. The data source for this research was obtained directly from teachers and students using interviews, survey questionnaires, and documentation results. The results of the study show that the online test applications used in Biology lessons at Jambi City Public High Schools are Google Forms, Google Classroom, Edmodo and e-exam applications. The online exam application is used during daily tests, midterm exams and final semester exams. The advantages of the online exam application used are that it does not use paper, fast, saves money, effort and time, exam results can be known quickly. Then the weakness is having to use a stable internet network, requiring internet quota and it is difficult to prevent students from cheating when exams are carried out at home. The obstacle felt by the teacher is that the exam questions must be typed one by one in the application, not all students have an Android smartphone, if the device has too many applications it will take a long time to open the exam application. And the network often lags. The effectiveness of implementing online exam applications is effective in technical terms such as speed of processing time, effort and cost. However, online exam applications are less effective in terms of increasing student learning outcomes and honesty. In general, the responses of teachers and students showed a positive response, respectively 70.52% and 65.78% with good criteria. Abstrak. Salah satu alat ukur evaluasi hasil belajar adalah menggunakan tes. Seiring berkembangnya teknologi informasi, tes terlulis dengan media kertas, berubah menjadi tes berbasis online. Penelitian ini merupakan penelitian deskriptif kuantitatif. Sumber data penelitian ini diperoleh langsung dari guru dan siswa dengan menggunakan wawancara, angket survei, dan hasil dokumentasi. Hasil penelitian menunjukkan aplikasi ujian online yang digunakan dalam pembelajaran Biologi di SMA Negeri Kota Jambi adalah Google Form, Google Classroom, Edmodo dan Aplikasi e-ujian. Aplikasi ujian online digunakan pada saat ulangan harian, ujian tengah semester dan ujian akhir semester. Kelebihan dari aplikasi ujian online yang digunakan adalah tidak menggunakan kertas, cepat, hemat biaya, tenaga dan waktu, hasil ujian dapat diketahui dengan cepat. Kemudian kelemahanya adalah harus menggunakan jaringan internet yang stabil, memerlukan kuota internet dan sulit menghindari siswa untuk berbuat curang ketika ujian dilaksanakan dirumah. Kendala yang dirasakan guru adalah soal ujian harus diketik satu persatu di aplikasi, tidak semua siswa memiliki smartphone android, apabila perangkat terlalu banyak aplikasi maka akan membutuhkan waktu yang lama untuk membuka aplikasi ujian. Serta jaringan sering ngelag. Efektivitas penerapan aplikasi ujian online efektif dalam hal teknis seperti kecepatan waktu pengerjaan, tenaga dan biaya. Namun, aplikasi  ujian online kurang efektif dalam hal peningkatan hasil belajar dan kejujuran siswa. Secara umum respon guru dan siswa menunjukkan respon yang positif masing-masing persentase 70,52% dan 65,78% dengan kriteria baik. Kata kunci: Aplikasi, Kota Jambi, Online, Ujian

Fabrication of micro-structures for optically driven micromachines using two-photon photopolymerization of UV curing resins

Two-photon photopolymerization of UV curing resins is an attractive method for the fabrication of microscopic transparent objects with size in the tens of micrometers range. We have been using this method to produce three-dimensional structures for optical micromanipulation, in an optical system based on a femtosecond laser. By carefully adjusting the laser power and the exposure time we were able to create micro-objects with well-defined 3D features and with resolution below the diffraction limit of light. We discuss the performance and capabilities of a microfabrication system, with some examples of its products.Comment: 12 pages, 10 figure

Radical polymerization of alkyl 2-cyanoacrylates

Cyanoacrylates (CAs) are well-known fast-setting adhesives, which are sold as liquids in the presence of stabilizers. Rapid anionic polymerization on exposure to surface moisture is responsible for instant adhesion. The more difficult, but synthetically more useful radical polymerization is only possible under acidic conditions. Recommendations on the handling of CAs and the resulting polymers are provided herein. In this review article, after a general description of monomer and polymer properties, radical homo- and copolymerization studies are described, along with an overview of nanoparticle preparations. A summary of our recently reported radical polymerization of CAs, using reversible addition-fragmentation chain transfer (RAFT) polymerization, is provided

Comparing Laser Diffraction and Optical Microscopy for Characterizing Superabsorbent Polymer Particle Morphology, Size, and Swelling Capacity

In this study, we determined the accuracy and practicality of using optical microscopy (OM) and laser diffraction (LD) to characterize hydrogel particle morphology, size, and swelling capacity (Q). Inverse-suspension-polymerized polyacrylamide particles were used as a model system. OM and LD showed that the average particle diameter varied with the mixing speed during synthesis for the dry (10–120 lm) and hydrated (34–240 lm) particles. The LD volume and number mean diameters showed that a few large particles were responsible for the majority of the water absorption. Excess water present in the gravimetric swelling measurements led to larger Qs (8.2 6 0.37 g/g), whereas the volumetric measurements with OM and LD resulted in reduced capacities (6.5 6 3.8 and 5.7 6 3.9 g/g, respectively). Results from the individual particle swelling measurements with OM (5.2 6 0.66 g/g) statistically confirmed that the volumetric methods resulted in a reduced and more accurate measurement of the Q than the gravimetric method

The Heavy Photon Search beamline and its performance

The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment searches for the e$^+$e$^-$ decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO$_4$ electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10 cm downstream of the target with the sensor edges only 500 $\mu$m above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05 GeV and 2.3 GeV beam energies, respectively. This paper describes the beam line and its performance during that data taking

Measurements of the Suitability of Large Rock Salt Formations for Radio Detection of High Energy Neutrinos

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10 PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient thermal noise in two salt formations. Measurements in the Waste Isolation Pilot Plant (WIPP), located in an evaporite salt bed in Carlsbad, NM yielded short attenuation lengths, 3-7 m over 150-300 MHz. However, measurements at United Salt's Hockley mine, located in a salt dome near Houston, Texas yielded attenuation lengths in excess of 250 m at similar frequencies. We have also analyzed early ground-penetrating radar data at Hockley mine and have found additional evidence for attenuation lengths in excess of several hundred meters at 440 MHz. We conclude that salt domes, which may individually contain several hundred cubic kilometer water-equivalent mass, provide attractive sites for next-generation high-energy neutrino detectors.Comment: 21 pages, 8 figures, to be submitted to Nuclear Instruments and Method

Adsorption of Multi-block and Random Copolymer on a Solid Surface: Critical Behavior and Phase Diagram

The adsorption of a single multi-block $AB$-copolymer on a solid planar substrate is investigated by means of computer simulations and scaling analysis. It is shown that the problem can be mapped onto an effective homopolymer adsorption problem. In particular we discuss how the critical adsorption energy and the fraction of adsorbed monomers depend on the block length $M$ of sticking monomers $A$, and on the total length $N$ of the polymer chains. Also the adsorption of the random copolymers is considered and found to be well described within the framework of the annealed approximation. For a better test of our theoretical prediction, two different Monte Carlo (MC) simulation methods were employed: a) off-lattice dynamic bead-spring model, based on the standard Metropolis algorithm (MA), and b) coarse-grained lattice model using the Pruned-enriched Rosenbluth method (PERM) which enables tests for very long chains. The findings of both methods are fully consistent and in good agreement with theoretical predictions.Comment: 27 pages, 12 figure

Molecular Architecture Manipulation in Free Radical Copolymerization: An Advanced Monte Carlo Approach to Screening Copolymer Chains with Various Comonomer Sequence Arrangements

This is the peer reviewed version of the following article: Saeb, M. R., Mohammadi, Y., Pakdel, A. S., & Penlidis, A. (2016). Molecular Architecture Manipulation in Free Radical Copolymerization: An Advanced Monte Carlo Approach to Screening Copolymer Chains with Various Comonomer Sequence Arrangements. Macromolecular Theory and Simulations, 25(4), 369–382, which has been published in final form at https://doi.org/10.1002/mats.201500096. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.A Kinetic Monte Carlo (KMC) simulation approach was adopted in this study to capture evolutionary events in the course of free radical copolymerization, through which batch and starved-feed semibatch processes were compared. The implementation of the KMC code developed in this work: (i) enables satisfactory control of the molecular weight of the copolymer by tracking the profiles of concentrations of macroradicals, monomers, and polymer as well as degree of polymerization, polydispersity, and chain length distribution; (ii) captures the bivariate distribution of chain length and copolymer composition; (iii) comprehensively tracks and analyzes detailed information on the molecular architecture of the growing chains, thus distinguishing between sequence length and polydispersity of chains produced in batch and starved-feed semibatch operations; (iv) makes possible the screening of products, based on such details as the number and weight fractions of products having different comonomer units located at various positions along the copolymer chains. The aforementioned characteristics were achieved by stochastic calculations through code developed in-house. This KMC simulator becomes a very useful tool for the development of tailored copolymers through free radical polymerization, with blocks separated with single units of a different type

Monodisperse Cylindrical Micelles and Block Comicelles of Controlled Length in Aqueous Media

Cylindrical block copolymer micelles have shown considerable promise in various fields of biomedical research. However, unlike spherical micelles and vesicles, control over their dimensions in biologically relevant solvents has posed a key challenge that potentially limits in depth studies and their optimization for applications. Here, we report the preparation of cylindrical micelles of length in the wide range of 70 nm to 1.10 μm in aqueous media with narrow length distributions (length polydispersities <1.10). In our approach, an amphiphilic linear-brush block copolymer, with high potential for functionalization, was synthesized based on poly­(ferrocenyldimethylsilane)-<i>b</i>-poly­(allyl glycidyl ether) (PFS-<i>b</i>-PAGE) decorated with triethylene glycol (TEG), abbreviated as PFS-<i>b</i>-(PEO-<i>g</i>-TEG). PFS-<i>b</i>-(PEO-<i>g</i>-TEG) cylindrical micelles of controlled length with low polydispersities were prepared in <i>N</i>,<i>N</i>-dimethylformamide using small seed initiators via living crystallization-driven self-assembly. Successful dispersion of these micelles into aqueous media was achieved by dialysis against deionized water. Furthermore, B–A–B amphiphilic triblock comicelles with PFS-<i>b</i>-poly­(2-vinylpyridine) (P2VP) as hydrophobic “B” blocks and hydrophilic PFS-<i>b</i>-(PEO-<i>g</i>-TEG) “A” segments were prepared and their hierarchical self-assembly in aqueous media studied. It was found that superstructures formed are dependent on the length of the hydrophobic blocks. Quaternization of P2VP was shown to cause the disassembly of the superstructures, resulting in the first examples of water-soluble cylindrical multiblock comicelles. We also demonstrate the ability of the triblock comicelles with quaternized terminal segments to complex DNA and, thus, to potentially function as gene vectors