Simultaneous electronic and the magnetic excitation of a ferromagnet by intense THz pulses

The speed of magnetization reversal is a key feature in magnetic data storage. Magnetic fields from intense THz pulses have been recently shown to induce small magnetization dynamics in Cobalt thin film on the sub-picosecond time scale. Here, we show that at higher field intensities, the THz electric field starts playing a role, strongly changing the dielectric properties of the cobalt thin film. Both the electronic and magnetic responses are found to occur simultaneously, with the electric field response persistent on a time scale orders of magnitude longer than the THz stimulu

Effect of rapid solidification on microstructure, creep resistance and thermal properties of Sn-10 wt.% Sb- 3 wt.% X ( X= In, Ag, Bi and Zn) lead-free solder alloys

The harmful effects of lead on the environment and human health, coupled with the threat of legislation, have prompted a serious search of lead-free solders for electronic packaging applications. The melt-spinning processes of ternary Sn-10 wt.%Sb-3 wt.%X (X=In, Ag, Bi and Zn) were analyzed using x-ray diffractometer (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Vickers hardness tester (HV). The investigation showed that, the addition of a small amount of the third element enhances the ductility of the Sn–10 wt. % Sb lead-free solder due to the formation of a fine, homogeneous ternary microstructure. It is concluded that, the addition of 3.0 wt% Ag improves the grain size of the ternary microstructure. The fine precipitates from SnSb intermetallic compound suppresses the coarsening of the ternary structure and thus enhances solder ductility. Structural and microstructural analysis revealed that the origin of change in mechanical behaviors was due to refined beta-Sn grains and formation of intermetallic compounds(IMCs) SnSb, InSn19, ?-In3Sn and Ag3Sn. The results indicated that the melting point of Sn-10Sb-3 wt.% Ag and Sn-10 wt.%Sb- 3 wt.% Zn alloys reduced to 230 and 240 ?C respectively. In particular, the zinc addition at 3 wt.% is the most effective in improving solder ductility and good creep resistance correlated to a fine grain size and complete soluble of SnSb IMC particles in the ?-Sn matrix

Air nonlinear dynamics initiated by ultra-intense lambda-cubic THz pulses

Air turns into a nonlinear medium for electromagnetic waves under exceptionally strong fields. However up to present, its minuscule nonlinear response has limited the exploration to the optical frequency regime owing to the availability of intense near-infrared lasers. Here, we report on the observation of large-amplitude nonlinearity in air induced by an extremely intense light bullet at Terahertz frequencies (0.1-10 THz) provoking strong air birefringence. The observed nonlinearity manifests itself as third order susceptibility. The presented nonlinear observations break the barrier for the entire exciting THz-induced nonlinear phenomena in air ranging from THz-induced self-focusing and self-phase modulation to THz solitons and filamentation

Magneto-photonic phenomena at terahertz frequencies.

Magneto-terahertz phenomena are the main focus of the thesis. This work started as supporting research for the science of an X-ray laser (SwissFEL). X-ray lasers have recently drawn great attention as an unprecedented tool for scientific research on the ultrafast scale. A potential terahertz-pump / X-ray-probe experiment is foreseen to reveal the fundamentals of magnetic systems on the ultrafast time scale and benefits the ultrafast magnetic storage industry. The main objective of this work was to find the conditions and prove that a suitable terahertz pulse can induce ultrafast magnetization dynamics on the picoseconds scale. To answer this fundamental question, we performed original numerical simulations using a coupled Landau- Lifshitz-Gilbert Maxwell model. Calculations showed us that terahertz pulses can trigger ultrafast dynamics, but highlighted the requirements of properly shaped pulses and beyond-current-technology peak field intensities. Those requirements werethe motivations for the experiments performed in the second part of the thesis. To shape the terahertz pulses, we used time-resolved optical-pump / terahertz-probe of free carriers in semiconductors. We managed to temporally shape the terahertz pulses and even extend the technique to spectral shaping as well. Regarding the field intensities, we followed two approaches. The first deals with field enhancement in nanoslits arrays. We designed a sub-wavelength structure characterized by simultaneous high field enhancementand high transmission at terahertz frequencies to suit nonlinear sources. The second approach depended on up-scaling the generation from laser-induced plasma by increasing the pump wavelengths. Numerical calculations have also brought to our attention the importance of linear magneto-terahertz effects. In particular, the simulations showed that the ultrafast dynamics could lead to significant rotation of the polarization plane of the triggering terahertz pulse. Motivated by this finding, we focused in the last part of the thesis on the linear effects. We performed three original studies coming out with first demonstrations of broadband non-reciprocal terahertz phase retarders, terahertzmagnetic modulators, and the non-reciprocal terahertz isolators. In the first two experiments, we extended the unique properties of the magnetic liquids (Ferrofluids) to the terahertz regime. In the latter experiment, we used a permanent magnet (Ferrite) to experimentally show complete isolation (unidirectional transmission) of the terahertz waves

Synthetic versus biological mesh-related erosion after laparoscopic ventral mesh rectopexy. A systematic review

Purpose: This review reports the incidence of mesh-related erosion after ventral mesh rectopexy to determine whether any difference exists in the erosion rate between synthetic and biological mesh. Methods: A systematic search of the MEDLINE and the Ovid databases was conducted to identify suitable articles published between 2004 and 2015. The search strategy capture terms were laparoscopic ventral mesh rectopexy, laparoscopic anterior rectopexy, robotic ventral rectopexy, and robotic anterior rectopexy. Results: Eight studies (3,956 patients) were included in this review. Of those patients, 3,517 patients underwent laparoscopic ventral rectopexy (LVR) using synthetic mesh and 439 using biological mesh. Sixty-six erosions were observed with synthetic mesh (26 rectal, 32 vaginal, 8 recto-vaginal fistulae) and one (perineal erosion) with biological mesh. The synthetic and the biological mesh-related erosion rates were 1.87% and 0.22%, respectively. The time between rectopexy and diagnosis of mesh erosion ranged from 1.7 to 124 months. No mesh-related mortalities were reported. Conclusion: The incidence of mesh-related erosion after LVR is low and is more common after the placement of synthetic mesh. The use of biological mesh for LVR seems to be a safer option; however, large, multicenter, randomized, control trials with long follow-ups are required if a definitive answer is to be obtained

Modification in Bi-Ag Lead-Free Solder-Bearing Alloying Elements

The development of lead-free solder has an urgent task for material scientist due to health and environmental concerns over the lead content of traditional solders. The objective of this study is to examine Bi-Ag-rare earth (RE) element considered as one of the more attractive lead-free solders since it can easily replace Sn-Pb eutectic alloy with increasing soldering temperature while causes for high-temperature applications. In order to enhance the soldering properties of Bi-Ag alloys, a trace eare earth (RE) element of Ho added into Bi-Ag alloys. The results indicated that the addition of RE led to the refining of coarse Bi-Ag grains, in the microstructure. The tensile strength, Hv and creep resistance increased with a decrease in melting point and electrical resistance. This paper brief the influences of rare earth alloying element and rapid solidification on both of the microstructure, intermetallic compounds, creep resistance, melting behavior, electrical resistance and mechanical behavior