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Search Results: 1 - 10 of 358 matches for " Aram Papoyan "
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N -resonances in a buffered micrometric Rb cell: splitting in a strong magnetic field
Armen Sargsyan,Rafayel Mirzoyan,Aram Papoyan,David Sarkisyan
Physics , 2012, DOI: 10.1364/OL.37.004871
Abstract: N -resonances excited in rubidium atoms confined in micrometric-thin cells with variable thickness from 1 {\mu}m to 2 mm are studied experimentally for the cases of a pure Rb atomic vapor and of a vapor with neon buffer gas. Good contrast and narrow linewidth were obtained for thicknesses as low as 30 {\mu}m. The higher amplitude and sharper profile of N-resonances in the case of a buffered cell was exploited to study the splitting of the 85Rb D1 N-resonance in a magnetic field of up to 2200 G. The results are fully consistent with the theory. The mechanism responsible for forming N-resonances is discussed. Possible applications are addressed.
A method for the quantitative study of atomic transitions in a magnetic field based on an atomic vapor cell with L=lambda
Armen Sargsyan,Grant Hakhumyan,Aram Papoyan,David Sarkisyan,Aigars Atvars,Marcis Auzinsh
Physics , 2008,
Abstract: We describe the so-called "Lambda-Zeeman method" to investigate individual hyperfine transitions between Zeeman sublevels of atoms in an external magnetic field of 0.1 mT - 0.25 T. Atoms are confined in a nanocell with thickness L = Lambda, where Lambda is the resonant wavelength (794 nm or 780 nm for D1 or D2 line of Rb). Narrow resonances in the transmission spectrum of the nanocell are split into several components in a magnetic field; their frequency positions and probabilities depend on the B-field. Possible applications are described, such as magnetometers with nanometric spatial resolution and tunable atomic frequency references.
Sub-Doppler spectroscopy of Rb atoms in a sub-micron vapor cell in the presence of a magnetic field
David Sarkisyan,Aram Papoyan,Tigran Varzhapetyan,Janis Alnis,Kaspars Blush,Marcis Auzinsh
Physics , 2003, DOI: 10.1088/1464-4258/6/3/023
Abstract: We report the first use of an extremely thin vapor cell (thickness ~ 400 nm) to study the magnetic-field dependence of laser-induced-fluorescence excitation spectra of alkali atoms. This thin cell allows for sub-Doppler resolution without the complexity of atomic beam or laser cooling techniques. This technique is used to study the laser-induced-fluorescence excitation spectra of Rb in a 50 G magnetic field. At this field strength the electronic angular momentum J and nuclear angular momentum I are only partially decoupled. As a result of the mixing of wavefunctions of different hyperfine states, we observe a nonlinear Zeeman effect for each sublevel, a substantial modification of the transition probabilities between different magnetic sublevels, and the appearance of transitions that are strictly forbidden in the absence of the magnetic field. For the case of right- and left- handed circularly polarized laser excitation, the fluorescence spectra differs qualitatively. Well pronounced magnetic field induced circular dichroism is observed. These observations are explained with a standard approach that describes the partial decoupling of I and J states.
Magnetic field-induced mixing of hyperfine states of Cs 6 2^P_{3/2} level observed with a sub-micron vapor cell
Aram Papoyan,David Sarkisyan,Kaspars Blush,Marcis Auzinsh,Daniel Bloch,Martial Ducloy
Physics , 2003,
Abstract: The fluorescence spectra of a sub-micron atomic cesium vapor layer observable under resonant excitation on D2 line have been studied in the presence of an external magnetic field. Substantial changes in amplitudes and frequency positions of the individual (resolved) hyperfine transitions have been recorded in moderate magnetic fields (up to ~ 50 Gauss). These features are caused by mixing of the hyperfine states of the upper level resulting from comparable values of the hyperfine splitting of the 62^P_{3/2} manifold and Larmor frequencies of the magnetic sublevels. The results of simulation show a good agreement with the experimental spectra. Possible application of the results for high spatial resolution magnetometry is discussed.
High contrast D$_{1}$ line electromagnetically induced transparency in nanometric-thin rubidium vapor cell
Armen Sargsyan,Claude Leroy,Yevgenya Pashayan-Leroy,Rafayel Mirzoyan,Aram Papoyan,David Sarkisyan
Physics , 2011, DOI: 10.1007/s00340-011-4614-0
Abstract: Electromagnetically induced transparency (EIT) on atomic D$_{1}$ line of rubidium is studied using a nanometric-thin cell with atomic vapor column length in the range of L= 400 - 800 nm. It is shown that the reduction of the cell thickness by 4 orders as compared with an ordinary cm-size cell still allows to form an EIT resonance for $L= \lambda$ ($\lambda =794$ nm) with the contrast of up to 40%. Remarkable distinctions of EIT formation in nanometric-thin and ordinary cells are demonstrated. Despite the Dicke effect of strong spectral narrowing and increase of the absorption for $L=$ $\lambda /2$, EIT resonance is observed both in the absorption and the fluorescence spectra for relatively low intensity of the coupling laser. Well resolved splitting of the EIT resonance in moderate magnetic field for $L=$ $\lambda $ can be used for magnetometry with nanometric spatial resolution. The presented theoretical model well describes the observed results.
Active narrowband filtering, line narrowing and gain using ladder electromagnetically induced transparency in an optically thick atomic vapour
James Keaveney,Armen Sargsyan,David Sarkisyan,Aram Papoyan,Charles S. Adams
Physics , 2013, DOI: 10.1088/0953-4075/47/7/075002
Abstract: Electromagnetically induced transparency (EIT) resonances using the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}\rightarrow5\rm{D}_{5/2}$ ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the $5\rm{S}_{1/2}\rightarrow5\rm{P}_{3/2}$ transition wavelength due to an energy-pooling assisted frequency conversion with characteristics similar to four-wave mixing. As a result it is possible to observe tunable and switchable transparency resonances with amplitude close to $100\%$ and a linewidth of 15 MHz. In addition, the large line narrowing effect allows resolution of $^{85}$Rb $5\rm{D}_{5/2}$ hyperfine structure even in the presence of strong power broadening.
What Is the Best Surgical Approach for Bilateral Pulmonary Hydatid Cysts in Children?  [PDF]
Aram Baram
World Journal of Cardiovascular Surgery (WJCS) , 2015, DOI: 10.4236/wjcs.2015.53006
Abstract: Introduction: The most common site for hydatid cysts in children is the lungs while in adult hepatic cysts are predominant. Bilateral pulmonary involvement is relatively rare and its surgical management is poorly described in the current literature. Until now no definite consensus has been described in the literature for the ideal surgical approach in pediatric bilateral pulmonary hydatid cysts (BPHC). The aim of this prospective cohort study was to describe the problems encountered in treating pediatric BPHC by two different surgical techniques. Patients and Methods: Between June 2007 and June 2014, 60 children (group one = 31, group two = 29) with BPHC were operated on in our center. Group one included all children with BPHC operated by single session bilateral anterolateral mini-thoracotomy. Group two included all cases operated by two stage standard posterolateral thoracotomy at 21 days interval. Results: In group one (19 males and 12 females), the mean age was 8.9 years (3.5-17). In group two, there were 29 cases (18 males and 11 females), the mean age was 9.6 years (2-17). There was no significant statistical difference in terms of the presentations and age distribution. The duration of surgery in group one was significantly shorter and the duration of hospital stay was significantly shorter as well (group one 3.6 days versus 4.6 days in the second group). Pain scale was not more in the first group as it was believed to be. Conclusion: We believe that single session bilateral anterolateral thoracotomy is a better approach than either one stage successive thoracotomies, median sternotomy or clamshell thoracotomy as it involves less postoperative pain and does not precipitate a decrease in the respiratory capacity.
“Kurdistan” Technique for the Treatment of Unprotected Trifurcation Left Main Stem Coronary Artery Lesion: Case Report  [PDF]
Aram J. Mirza
World Journal of Cardiovascular Diseases (WJCD) , 2014, DOI: 10.4236/wjcd.2014.49058
Abstract:

The left main coronary artery (LMCA) is responsible for supplying about 75% to 100% of the left ventricular cardiac mass. Left main stem coronary artery (LMCA) disease reduces flow to a large portion of the myocardium, placing the patient at high risk for life-threatening events such as left ventricular dysfunction and arrhythmias with a high mortality approaching 50% in those treated medically. For several decades, coronary artery bypass grafting (CABG) has been considered as a gold standard treatment of unprotected left main coronary artery (ULMCA). However, successful percutaneous coronary interventions (PCI) have been increasingly reported recently due to improved stent technology and better operator expertise. In spite of these factors, management can be challenging especially in LMCA bifurcational & trifurcational lesions, and therefore an integrated approach combining special techniques, physiological evaluation and adjunctive pharmacological agents should be combined for better clinical outcome. Herein, we describe a new promising technique named (Kurdistan technique) for the treatment of trifurcation unprotected left main stem lesion. In the last 18 months, 21 patients with significant trifurcational LMS had underwent PCI using this technique in our hospital (Sulaimany Heart Hospital/Kurdistan). The procedural success rate was 100%, follow up coronary angiography done between 6 - 12 months after the procedure for all the patients with no significant in-stent restenosis in any patient. One case is presented here demonstrating the technique.

Incidence, Predictors, Treatment, and Long-Term Prognosis of Patients with Restenosis after Long Drug-Eluting Stent Implantation for Coronary Arteries  [PDF]
Aram J Mirza
World Journal of Cardiovascular Diseases (WJCD) , 2014, DOI: 10.4236/wjcd.2014.413075
Abstract: Background: Few data on the clinical course and management of patients experiencing restenosis after implantation of long drug-eluting stents treatment for coronary arteries was available. Objectives: The aim of this study was to evaluate the incidence, predictors, and long-term outcomes of patients with in-stent restenosis (ISR) after percutaneous coronary intervention (PCI) with long (33 mm & 38 mm) drug-eluting stents (DES) for long lesions in coronary arteries including left anterior descending artery (LAD), Lt circumflex artery (Lt Cx), right coronary artery (RCA), obtuse marginal artery (OM) & posterior descending artery (PDA). Methods: Between July 2009 and October 2010, 421 long DES had being implanted in 421 consecutive patients with significant coronary artery stenosis, with 371 patients (88%) undergoing routine follow up, clinical follow up done by exercise stress test at 6 & 12 months after stenting for 126 patients (34%), in 124 patients (33.5%) follow up was done by Computed Tomography angiography & 121 patients (32.5%) with clinically driven angiographic follow-up. A major adverse cardiac event was defined as the composite of death, myocardial infarction (MI), or target-lesion revascularization (TLR) within 15 months. Results: All patients who underwent clinical follow up were asymptomatic. The overall incidence of angiographic (CT or conventional) ISR with long (33 mm & 38 mm) DES was 4% (15 out of 371 stents) with 8 (53.3%) focal-type and 7 (46.7%) with diffuse-type ISR. Six patients (40%) under-went repeated PCI, seven (46.7%) underwent bypass surgery, and 2 (13.3%) were treated medically. During long-term follow-up (ranging from 12 - 26 months), there were no deaths, 3 (0.8%) MI, and 13 (3.5%) repeated target-lesion revascularization (PCI or CABG) cases. The incidence of major adverse cardiac event was 5.3% in the medical group, 10.1% in the repeated PCI group, and 21.4% in the bypass surgery group. Multivariate analysis showed that the occurrence of DES-ISR did not affect the risk of death or MI. Conclusions: The incidence of ISR was 4% after long DES stenting for coronary arteries. The long-term clinical prognosis of patients with long DES-ISR associated with coronary artery stenting might be benign, if the patient has optimal treatment.
FUNDAMENTAL PRINCIPLES OF THE CROSSING (PASSING) CAPACITY FOR WHEEL SPECIAL MILITARY VEHICLES
Cornel ARAM,Andreea ARAM
Journal of Defense Resources Management , 2010,
Abstract: In mountain corps, the combat surprise of the enemy is made, first of all, by mobility. For this, when the horses are not used, the access of vehicles in difficult access areas is sometimes vital because it is a surprise for the enemy, the attacks of special troops of mountaineers can be surprising or the mountain artillery companies can supply their troops better.This is the reason why my doctoral research has focused on the influences of ground features on the capacity of crossing, especially in the cold period of the year, because most of the time mountain rangers’ corps take action in this kind of conditions. The tests were made in real conditions, during the missions and the field exercises, in tough climatic and atmospheric conditions, exclusively in mountains in winter
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