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81.
Reichert IL Robson MD Gatehouse PD He T Chappell KE Holmes J Girgis S Bydder GM 《Magnetic resonance imaging》2005,23(5):611-618
PurposeNormal adult cortical bone has a very short T2 and characteristically produces no signal with pulse sequence echo times (TEs) routinely used in clinical practice. We wished to determine whether it was possible to use ultrashort TE (UTE) pulse sequences to detect signal from cortical bone in human subjects and use this signal to characterise this tissue.Subjects and MethodsSeven volunteers and 10 patients were examined using ultrashort TE pulse sequences (TE=0.07 or 0.08 ms). Short and long inversion as well as fat suppression pulses were used as preparation pulses. Later echo images were also obtained as well as difference images produced by subtracting a later echo image from a first echo image. Saturation pulses were used for T1 measurement and sequences with progressively increasing TEs for T2* measurement. Intravenous gadodiamide was administered to four subjects.ResultsSignal in cortical bone was detected with UTE sequences in children, normal adults and patients. This signal was usually made more obvious by subtracting a later echo image from the first provided that the signal-to-noise ratio was sufficiently high.Normal mean adult T1s ranged from 140 to 260 ms, and mean T2*s ranged from 0.42 to 0.50 ms. T1 increased significantly with age (P<.01).Increased signal was observed after contrast enhancement in the normal volunteer and the three patients to whom it was administered.Reduction in signal from short T2 components was seen in acute fractures, and increase in signal in these components was seen with new bone formation after fracture malunion. In a case of osteoporosis, bone cross-sectional area and signal level appeared reduced.ConclusionSignal can be detected from normal and abnormal cortical bone with UTE pulse sequences, and this can be used to measure its T1 and T2* as well as observe contrast enhancement. Difference images are of value in increasing the conspicuity of cortical bone and observing abnormalities in disease. 相似文献
82.
Marsella MJ Reid RJ Estassi S Wang LS 《Journal of the American Chemical Society》2002,124(42):12507-12510
Tetra(2,3-thienylene) is a thiophene-fused [8]annulene capable of undergoing redox-induced dimensional changes. The feasibility of efficiently translating this intrinsic function into a single polymeric electromechanical actuator is investigated by both experiment and density functional theory (B3LYP 6-31G[d,p]). A study of tetra(2,3-thienylene) and its homodimer reveal that redox-induced conformational change is conserved upon dimerization, a result that implicates similar behavior in the corresponding polymer. Theoretical predictions yield a maximum redox-induced dimensional change of 5.92% per repeat unit for the homodimer. Cyclic voltammetry reveals complete reversibility for the corresponding redox cycle. The latter two facts establish tetra(2,3-thienylene) as a suitable building block for single-molecule electromechanical actuators. 相似文献
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86.
Samia Benbernou Maria Alessandra Ragusa Mekki Terbeche 《Mathematical Methods in the Applied Sciences》2014,37(17):2615-2618
In this note, we examine small self‐similar solutions of the 3D incompressible magnetohydrodynamic equations in homogenous function spaces and show the uniqueness of self‐similar solutions when the velocity field is small in some homogeneous function spaces. This extend the recent results given by C. He and Z. Xin. “On the self‐similar solutions of the magneto‐hydro‐dynamic equations. Acta Mathematica Scientia, série B English Edition 2009; 29 (3): 583–598”. It is a natural way to extend the space widely and improve the previous results. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
87.
Syed Hamad Bukhari Samia Aslam Faiza Mustafa Ayesha Jamil Salman Naeem Khan Muhammad Ashfaq Ahmad 《Optik》2014
Entangled coherent states (ECSs) with relative phase equal to the phase shift between two coherent states are constructed. We study the degree of entanglement and the nonclassical features exhibited by the so-constructed states keeping in view their role in quantum information processing (QIP). 相似文献
88.
Samia Lamraoui Rachid Bensalem Khadidja Hacini Hocine Meradji Sebti Ghemid Fouad El Haj Hassan 《Central European Journal of Physics》2014,12(1):70-79
Structural, electronic and thermal properties of Zn1?x Mg x S ternary alloys are studied by using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The Wu-Cohen generalized gradient approximation (WC-GGA) is used in this approach for the exchangecorrelation potential. Moreover, the modified Becke-Johnson approximation (mBJ) is adopted for band structure calculations. The dependence of the lattice constant, bulk modulus and band gap on the composition x showed that the first exhibits a small deviation from the Vegard’s law, whereas, a marginal deviation of the second from linear concentration dependence (LCD). The bowing of the fundamental gap versus composition predicted by our calculations agrees well with the available theoretical data. The microscopic origins of the gap bowing are explained by using the approach of Zunger and co-workers. Thermal effects on some macroscopic properties of Zn1?x Mg x S alloys are also investigated using the quasi-harmonic Debye model, in which the phononic effects are considered. As, this is the first quantitative theoretical prediction of the thermal properties of Zn1?x Mg x S alloys, no other calculated results and furthermore no experimental studies are available for comparison. 相似文献
89.
We have applied harmonic expansion to derive an analytical solution for the Lorenz-Haken equations. This method is used to describe the regular and periodic self-pulsing regime of the single mode homogeneously broadened laser. These periodic solutions emerge when the ratio of the population decay rate ? is smaller than 0:11. We have also demonstrated the tendency of the Lorenz-Haken dissipative system to behave periodic for a characteristic pumping rate “2C P ”[7], close to the second laser threshold “2C 2th ”(threshold of instability). When the pumping parameter “2C” increases, the laser undergoes a period doubling sequence. This cascade of period doubling leads towards chaos. We study this type of solutions and indicate the zone of the control parameters for which the system undergoes irregular pulsing solutions. We had previously applied this analytical procedure to derive the amplitude of the first, third and fifth order harmonics for the laser-field expansion [7, 17]. In this work, we extend this method in the aim of obtaining the higher harmonics. We show that this iterative method is indeed limited to the fifth order, and that above, the obtained analytical solution diverges from the numerical direct resolution of the equations. 相似文献
90.
Shirong Lu Tienan Jin Takeshi Yasuda Ashraful Islam Md. Akhtaruzzaman Liyuan Han Khalid A. Alamry Samia A. Kosa Abdullah Mohamed Asiri Yoshinori Yamamoto 《Tetrahedron》2013,69(4):1302-1306
A new series of functional 2-benzyl-1,2-dihydro[60]fullerenes, BnHCs, were synthesized efficiently via co-catalyzed selective monofunctionalization of C60 with functional benzyl bromides. Photophysical and electrochemical properties of the new BnHCs were investigated. PSCs based on 2-MeO–4-CO2Me–BnHC as new acceptor and P3HT as donor showed a power conversion efficiency of 3.75%, which is comparable to that of PC61BM under the same device conditions. 相似文献