880 research outputs found
A failure study of the railway rail serviced for heavy cargo trains
AbstractIn this case study, a failed railway rail which was used for heavy cargo trains was investigated in order to find out its root cause. The macroscopic beach marks and microscopic fatigue striations were not observed by macro and microscopic observations. The chevron patterns were observed by macro observations. The crack origin was at the tip of chevron patterns. The fan-shaped patterns, cleavage step and the river patterns were observed at the crack origin, which demonstrated the feature of cleavage fracture. The metallurgical structures at the crack origin were pearlite and ferrite networks. The crack is supposed to be initiated from the weaker ferrite networks. Given all of that, the failed railway rail is considered to be caused by overload. It is of great importance to improve the welding technology, and control the load of train in order to prevent similar failure in future
Functional changes in motor endplates of the target muscle after amputation of the C7 nerve root
There are limited data on structural and functional changes in motor endplates and
muscle fibers in the target muscle following amputation of the 7th cervical nerve root, a
transplantation-related procedure in surgical treatment in the case of avulsions of the brachial
plexus roots. We examined functional changes in these structures using stimulated singlefiber electromyography (sSF-EMG) in an animal model. Unilateral amputation of the 7th
cervical nerve root was performed in 36 male rats, and the m. triceps brachii muscle was
tested by sSF-EMG at different time points. We observed significant differences in the jitter
(mean consecutive difference, MCD, of the latencies between adjacent muscle fibers) at postamputation weeks 1, 2, 4, and 6. The post-operation fiber density (FD) values within the
zone of effective stimulation also gradually increased. At post-amputation weeks 8 and 12,
the jitter values returned to normal levels, whereas FD values continued to rise. Our results
indicate that the post-amputation compensatory processes in the target muscles of the 7th
cervical nerve root are completed at 9-12 weeks after amputation.Дані щодо структурних та функціональних змін у моторних
кінцевих пластинках та м’язових волокнах м’яза-цілі після ампутації сьомого шийного нервового корінця (процедури в рамках трансплантаційного хірургічного лікування
наслідків відриву корінців брахіального сплетіння) поки
що обмежені. Ми досліджували функціональні зміни в згаданих структурах, використовуючи методику стимуляційної „одноволоконної” електроміографії в умовах експериментальної моделі на тваринах. Унілатеральну ампутацію
сьомого цервікального нервового корінця було виконано на
36 щурах-самцях, і триголові м’язи плеча тестувалися за допомогою згаданої ЕМГ-методики в різні часові інтервали.
Ми виявили істотні відмінності середніх варіацій („дрижання”, jitter, різниць між послідовними величинами) латентних періодів, характерних для прилеглих одне до одного
м’язових волокон, у перший, другий, четвертий та шостий
тижні після операційного періоду. В цей час щільність волокон у зоні ефективної стимуляції також поступово зростала.
На восьмий–12-й тижні післяопераційного періоду значення варіацій („дрижання”) поверталися до нормальних, тоді
як значення щільності активованих волокон продовжували
зростати. Наші результати свідчать про те, що післяампутаційні компенсаторні процеси в м’язах-цілях волокон нервового корінця С7 завершуються через дев’ять–12 тижнів після ампутації останнього
Revisión sobre métodos de preparación, mecanismos y aplicaciones de péptidos antioxidantes en aceites
Natural antioxidants, especially those used in edible oil, are safer compared to chemically synthesized antioxidants. Therefore, research on natural antioxidants has become prevelant. Antioxidant peptides derived from food protein can effectively prevent oil oxidation. Protein hydrolyzation is widely applied for the production of antioxidant peptides in industry, and bioinformatics is employed nowadays to generate the desired peptide sequence. Furthermore, the mechanism of antioxidant peptides in the oil system is still controversial, which limits the further development of antioxidant peptides as food antioxidants. This review introduces the preparation method of antioxidant peptides and their mechanisms as well as applications in the oil. It will help to comprehensively understand the function of antioxidant peptides and promote their development in the oil field.Los antioxidantes naturales, especialmente utilizados en aceites comestibles, son más seguros en comparación con los antioxidantes sintetizados químicamente. Por lo tanto, la investigación sobre antioxidantes naturales se convierte en un punto de interés. Los péptidos antioxidantes derivados de las proteínas alimentarias pueden prevenir eficazmente la oxidación del aceite. La hidrolización de proteínas se usa ampliamente en la industria para la producción de péptidos antioxidantes y la bioinformática se emplea hoy en día para generar la secuencia de péptidos deseada. Además, el mecanismo de los péptidos antioxidantes en el sistema oleoso sigue siendo controvertido, lo que limita el desarrollo posterior de péptidos antioxidantes como antioxidantes alimentarios. Esta revisión presenta el método de preparación de péptidos antioxidantes y su mecanismo, así como las aplicaciones en aceite, lo que ayudará a comprender de manera integral la función de los péptidos antioxidantes y promoverá su desarrollo en el campo petrolero
Design Strategy for a Scalable Virtual Pharmacy Patient
This paper reports on the completion of the first stage of research of a pilot study undertaken in collaboration by 3 Australian universities. The pilot involves the development of a virtual pharmacy patient (VPP) as a study of its effects on student learning when it is used as a formative assessment tool for pharmacy students in interviewing and diagnosing a patient. The design criteria that have been incorporated into the virtual patient system are described. The novelty of this system is in its ability to track and report on the style and appropriateness of student questioning of a virtual pharmacy patient. One of the main problems in this type of system is recognition of free-text student questions. An overview of the pragmatic solution to this and the systems potential as a tool to generate a lexicon for more complex question recognition is presented
Resolution Tests of CsI(Tl) Scintillators Read Out by Pin Diodes
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Two-Particle Correlation Functions for the 200-MeV 3-He + Ag Reaction
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Charmless Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II
We provide a systematic study of charmless decays (
and denote pseudoscalar and vector mesons, respectively) based on an
approximate six-quark operator effective Hamiltonian from QCD. The calculation
of the relevant hard-scattering kernels is carried out, the resulting
transition form factors are consistent with the results of QCD sum rule
calculations. By taking into account important classes of power corrections
involving "chirally-enhanced" terms and the vertex corrections as well as weak
annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of decays into
PP, PV and VV final states, and also for the corresponding polarization
observables in VV final states. It is found that the weak annihilation
contributions with non-trivial strong phase have remarkable effects on the
observables in the color-suppressed and penguin-dominated decay modes. In
addition, we discuss the SU(3) flavor symmetry and show that the symmetry
relations are generally respected
Multiband tight-binding theory of disordered ABC semiconductor quantum dots: Application to the optical properties of alloyed CdZnSe nanocrystals
Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a
broad range of applications, as their spectrum and thus their excitation gap
can be tailored by variation of their size. Additionally, nanocrystals of the
type ABC can be realized by alloying of two pure compound semiconductor
materials AC and BC, which allows for a continuous tuning of their absorption
and emission spectrum with the concentration x. We use the single-particle
energies and wave functions calculated from a multiband sp^3 empirical
tight-binding model in combination with the configuration interaction scheme to
calculate the optical properties of CdZnSe nanocrystals with a spherical shape.
In contrast to common mean-field approaches like the virtual crystal
approximation (VCA), we treat the disorder on a microscopic level by taking
into account a finite number of realizations for each size and concentration.
We then compare the results for the optical properties with recent experimental
data and calculate the optical bowing coefficient for further sizes
Modulation instability induced by cross-phase modulation in a dual-wavelength dispersion-managed soliton fiber ring laser
We report on the observation of modulation instability induced by cross-phase
modulation in a dual-wavelength operation dispersion-managed soliton fiber ring
laser with net negative cavity dispersion. The passively mode-locked operation
is achieved by using nonlinear polarization rotation technique. A new type of
dual-wavelength operation, where one is femtosecond pulse and the other is
picosecond pulse operation, is obtained by properly rotating the polarization
controllers. When the dual-wavelength pulses are simultaneously circulating in
the laser ring cavity, a series of stable modulation sidebands appears in the
picosecond pulse spectrum at longer wavelength with lower peak power due to
modulation instability induced by cross-phase modulation between the two lasing
wavelengths. Moreover, the intensities and wavelength shifts of the modulation
sidebands can be tuned by varying the power of the femtosecond pulse or the
lasing central wavelengths of the dual-wavelength pulses. The theoretical
analysis of the modulation instability induced by cross-phase modulation in our
fiber laser is also presented.Comment: 26 pages, 10 figure
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