Search results for "MICROWAVE"
showing 10 items of 693 documents
Nanocrystallization of amorphous alloys using microwaves:In situtime-resolved synchrotron radiation studies
2009
Important energy and time savings can be achieved with the thermal treatment of materials by replacing conventional heating methods with microwave heating. The nano- crystallization of Co-Fe-W-B amorphous alloy powders under microwave irradiation was followed for the first time by in situ time-resolved synchrotron radiation powder diffraction. It is shown that even a very short exposure to the electromagnetic field (single pulse microwave application) typically of the order of a few seconds is sufficient to obtain the bulk nano- crystalline state. A metastable high-temperature Co-W-B orthorhombic phase forms during the microwave heating, which gradually transforms to the tetragonal Co2B sta…
Low-temperature microwave response of heavy-fermion compounds
2009
The electrodynamic properties of heavy fermions are distinct from those of normal metals due to the reduced transport relaxation rate that goes hand in hand with the enhanced mass. Using broadband microwave spectroscopy on thin-film samples of the heavy-fermion materials UPd2Al3 and UNi2Al3, we find that the frequency-dependent conductivity of these compounds at low temperatures follows a simple Drude prediction. The observed relaxation rates in the GHz frequency range are extremely low for a metal.
Experimental study of hydrogen plasma breakdown in a 2.45 GHz microwave discharge
2013
Temporal evolution of microwave-plasma coupling, vacuum ultraviolet (VUV) light emission and plasma electron temperature and density is reported for a 2.45GHz microwave hydrogen discharge pulsed at 50Hz. Directional couplers, a VUV spectrometer and a Langmuir probe are used for the diagnostics of the plasma breakdown. A 5‐10 µs transient peak of light emission exceeding the steady-state intensity by a factor of 3.3 is observed in coincidence with an abrupt drop in the microwave electric field. Observed light emission intensities combined with cross section data indicate that the electron temperature during the breakdown transient exceeds the steady-state value of 4‐6eV by a factor 3, which …
Plasma distributions observed in a 2.45 GHz hydrogen discharge
2014
The existence of various spatial distributions of hydrogen plasma in a pulsed 2.45 GHz microwave discharge is demonstrated. The data has been obtained through optical emission diagnostics utilizing an ultra-fast CCD camera system with multi-channel plate (MCP) intensifiers, and a wavelength-filtered photodiode recording temporal light emission signals of hydrogen atoms and molecules. It has been observed that the magnetic field topology and strength are determining the transitions between different plasma patterns and spectral saturation times while neutral gas pressure and microwave power show a weaker influence on the profiles but affect the emitted light intensity.
Microwave-induced thermoablation with Amica-probe is a safe and reproducible method to treat solid renal masses: results from a phase I study.
2012
Microwave thermal ablation (MWTA) could be considered in the future for treating small solid renal masses. The aim of the present study was to determine both the tolerability of the new Amica-probe applicator-induced MWTA used in vivo on patients with solid renal masses and the effects of heating on renal tumors and normal renal parenchyma. Fourteen patients with renal masses eligible for open radical nephrectomy were enrolled in this phase I study. All patients underwent MWTA of renal masses during the open surgery procedure before clamping of renal vascular pedicle. The effects of MWTA on patients' coagulation and tumor/renal vasculature were investigated. The histological effects of MWTA…
LOCAL MICROWAVE HYPERTHERMIA AND INTRAVESICAL CHEMOTHERAPY AS BLADDER SPARING TREATMENT FOR SELECT MULTIFOCAL AND UNRESECTABLE SUPERFICIAL BLADDER TU…
1998
Purpose: The role of a combined regimen of local hyperthermia and topical chemotherapy in patients with multifocal and recurrent superficial bladder tumors not curable by transurethral resection was evaluated in a neodjuvant organ sparing clinical study. Materials and Methods: A total of 19 patients with multifocal, superficial grades 1 to 3 bladder tumors that recurred after intravesical chemoprophylaxis or immunoprophylaxis underwent local combined administration of microwave induced hyperthermia and intravesical chemotherapy as a debulking approach. Due to extensive superficial involvement of the bladder walls complete transurethral resection of all tumors seemed technically unfeasible i…
Coaxial Slot Antenna Design for Microwave Hyperthermia using Finite- Difference Time-Domain and Finite Element Method
2011
Hyperthermia also called thermal therapy or thermotherapy is a type of cancer treatment in which body tissue is exposed to high temperatures. Research has shown that high temperatures can damage and kill cancer cells, usually with minimal injury to normal tissues. Otherwise, ablation or high temperature hyperthermia, including lasers and the use of radiofrequency, microwaves, and high-intensity focused ultrasound, are gaining attention as an alternative to standard sur- gical therapies. The electromagnetic microwave irradiation applied to the tumor tissue causes water molecules to vibrate and rotate, resulting in tissue heating and subsequently cell death via thermal-induced protein denatur…
Impact of Localized Microwave Hyperthermia on the Oxygenation Status of Malignant Tumors
1982
Considerable insight into the mechanisms of heat induced cell death in vitro has been gained during recent years (for reviews see 1–3). Besides the direct cell killing effect of heat, many microenvironmental or milieu factors seem to play an important role during heat treatment of solid tumors in vivo, such that a preferential effect of hyperthermia on tumors has been postulated for the in situ conditions. Environmental factors affecting the tumor milieu, such as tissue oxygen partial pressures, pH values, glucose (?) and lactate levels, nutrient supply and drainage of wastes, have thus become a subject of topical interest.
In situ synchrotron radiation monitoring of phase transitions during microwave heating of Al–Cu–Fe alloys
2008
The effect of rapid microwave heating has so far been evaluated mainly by comparing the state of materials before and after microwave exposure. Yet, further progress critically depends on the ability to follow the evolution of materials during ultrafast heating in real time. We describe the first in situ time-resolved monitoring of solid-state phase transitions during microwave heating of metallic powders using wide-angle synchrotron radiation diffraction. Single-phase Al–Cu–Fe quasicrystal powders were obtained by microwave heating of nanocrystalline alloy precursors at 650 °C in <20 s.
ChemInform Abstract: Microwave-Assisted Synthesis of 1,3-Disubstituted β-Carbolines from α-(Alkylideneamino)nitriles and Gramine.
2012
The title reaction produces indole derivatives of type (V) whose cyclization leads to formation of the desired alkaloid skeletons.