Investigation of the Thermal Degradation of Polyurea: The Effect of Ammonium Polyphosphate and Expandable Graphite

Polyurea was compounded with ammonium polyphosphate and expandable graphite and the morphology was studied by atomic force microscopy. The thermal degradation of polyurea and polyurea compounded with the additives has been investigated using thermogravimetry coupled with Fourier Transform infrared spectroscopy and mass spectrometry. The study of the thermal degradation and the parameters affecting the thermal stability of PU is essential in order to effectively design flame retarded polyurea. In general, thermal decomposition of polyurea occurs in two steps assigned to the degradation of the hard segment and soft segment, respectively. Adding these additives accelerates the decomposition reaction of polyurea. However, it is clear that more char is formed. This char is thermally more stable than the carbonaceous structure obtained from neat PU. The intumescent shield traps the polymer fragments and limits the evolution of small flammable molecules that are able to feed the flame

A model curriculum for a Syrian experimental master\u27s degree program in education

The purpose of this study was to develop a model curriculum for a Syrian experimental master\u27s degree program in education. The study required answers to questions concerned with: required subjects; definition of the role of research, thesis writing, and practica; inservice education for untrained teachers; admissions requirements; expected competencies of the graduates of the program; definition of methods and materials of instruction; criteria to evaluate the competencies; incorporation of CBI elements into the program; type and mode of supervision; and adoption/adaption of elements of the American MAT program for Syria;The findings of this study were gathered from a sample of American scholars, a sample of Syrian students studying in the U.S.A., surveys of selected MAT programs and teaching assistant programs, and reinforced by literature review. The findings were: the model included courses: Educational Research, Philosophy of Education, Learning Theories, Educational Psychology, Methods of College Teaching, Curriculum Construction, six courses in area of concentration, three seminars, two practica, two practice teaching periods, and foreign language; research skills, thesis requirement, and practica were seen necessary to prepare college teachers; inservice education for untrained teachers was deemed necessary; entrance requirements were to possess a B.A. or B.S. and to pass an achievement test; the most favorable competency was the ability to communicate effectively; competencies may be achieved by informal lectures; achievement of competencies could be evaluated by observing the achievement of students taught by the new teacher; incorporation of CBI elements could start by incorporating field experience; supervision may be total during practicum and periodic during practice teaching; and the inclusion of practicum, course work practice teaching, and thesis writing was seen necessary for the program;The findings of this study led to the following recommendations: prior to the implementation process the minimum performance level of required competencies should be specified; implementation should be followed by performance evaluation of the graduates as opposed to graduates from traditional programs; grading should be centered on mastery of competencies, hence, the grades of pass-incomplete; and if initial experimentation is proven successful the program should ultimately be adopted by all Syrian universities;Further research should be concerned with: developing programs of competency-based nature at various levels in Syria with emphasis on professional development of Syrian faculty; developing MAT programs in Arab countries with special consideration to the needs of the Arab women; developing programs for general faculty development as far as methods of teaching, developing the curricula, community services, and research are concerned; and a doctorate program should be developed with emphasis on advanced theories and practices of college teaching and research

Pulse Morphology of the Galactic Center Magnetar PSR J1745-2900

We present results from observations of the Galactic Center magnetar, PSR J1745-2900, at 2.3 and 8.4 GHz with the NASA Deep Space Network 70 m antenna, DSS-43. We study the magnetar's radio profile shape, flux density, radio spectrum, and single pulse behavior over a ~1 year period between MJDs 57233 and 57621. In particular, the magnetar exhibits a significantly negative average spectral index of $\langle\alpha\rangle$ = -1.86 $\pm$ 0.02 when the 8.4 GHz profile is single-peaked, which flattens considerably when the profile is double-peaked. We have carried out an analysis of single pulses at 8.4 GHz on MJD 57479 and find that giant pulses and pulses with multiple emission components are emitted during a significant number of rotations. The resulting single pulse flux density distribution is incompatible with a log-normal distribution. The typical pulse width of the components is ~1.8 ms, and the prevailing delay time between successive components is ~7.7 ms. Many of the single pulse emission components show significant frequency structure over bandwidths of ~100 MHz, which we believe is the first observation of such behavior from a radio magnetar. We report a characteristic single pulse broadening timescale of $\langle\tau_{d}\rangle$ = 6.9 $\pm$ 0.2 ms at 8.4 GHz. We find that the pulse broadening is highly variable between emission components and cannot be explained by a thin scattering screen at distances $\gtrsim$ 1 kpc. We discuss possible intrinsic and extrinsic mechanisms for the magnetar's emission and compare our results to other magnetars, high magnetic field pulsars, and fast radio bursts.Comment: 18 pages, 12 figures, Accepted for publication in ApJ on 2018 August 30. v2: Updated to match published versio