Augmented reality simulator for training in two-dimensional echocardiography.
Weidenbach, M; Wick, C; Pieper, S; Quast, K J; Fox, T; Grunst, G; Redel, D A
2000-02-01
In two-dimensional echocardiography the sonographer must synthesize multiple tomographic slices into a mental three-dimensional (3D) model of the heart. Computer graphics and virtual reality environments are ideal to visualize complex 3D spatial relationships. In augmented reality (AR) applications, real and virtual image data are linked, to increase the information content. In the presented AR simulator a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to establish spatial and temporal congruence. The heart model, together with an animated ultrasound sector represents a reference scenario, which displays the currently selected two-dimensional echocardiographic cutting plane calculated from the volume data set. Modifications of the cutting plane within the echocardiographic data are transferred and visualized simultaneously and in real time within the reference scenario. The trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by an animated ultrasound probe, whose position is controlled by an electromagnetic tracking system. The tracking system is attached to a dummy transducer and placed on a plastic puppet to give a realistic impression of a two-dimensional echocardiographic examination.
Computer-based training in two-dimensional echocardiography using an echocardiography simulator.
Weidenbach, Michael; Wild, Florentine; Scheer, Kathrin; Muth, Gerhard; Kreutter, Stefan; Grunst, Gernoth; Berlage, Thomas; Schneider, Peter
2005-04-01
Two-dimensional (2D) echocardiography is a user-dependent technique that poses some inherent problems to the beginner. The first problem for beginners is spatial orientation, especially the orientation of the scan plane in reference to the 3-dimensional (3D) geometry of the heart. The second problem for beginners is steering of the ultrasound probe. We have designed a simulator to teach these skills. On a computer screen a side-by-side presentation of a 3D virtual reality scene on the right side and a 2D echocardiographic view on the left side is given. The virtual scene consists of a 3D heart and an ultrasound probe with scan plane. The 2D echocardiographic image is calculated from 3D echocardiographic data sets that are registered with the heart model to achieve spatial and temporal congruency. The displayed 2D echocardiographic image is defined and controlled by the orientation of the virtual scan plane. To teach hand-eye coordination we equipped a dummy transducer with a 3D tracking system and placed it on a dummy torso. We have evaluated the usability of the simulator in an introductory course for final-year medical students. The simulator was graded realistic and easy to use. According to a subjective self-assessment by a standardized questionnaire the aforementioned skills were imparted effectively.
Marcus, K.A.; Barends, M.; Morava, E.; Feuth, T.; Korte, C.L. de; Kapusta, L.
2011-01-01
BACKGROUND: Myocardial dysfunction in children diagnosed with mitochondrial disease is an ominous sign and has been associated with substantial increased mortality rates. Early detection of cardiac involvement would therefore be desirable. Two dimensional strain echocardiography (2DSTE) has proven t
Marcus, K.A.; Janousek, J.; Barends, M.E.; Weijers, G.; Korte, C.L. de; Kapusta, L.
2012-01-01
Two-dimensional speckle tracking echocardiography (2DSTE) offers valuable information in the echocardiographic assessment of ventricular myocardial function. It enables the quantification and timing of systolic ventricular myocardial deformation. In addition, 2DSTE can be used to identify mechanical
Assessment of the Frank-Starling relationship by two-dimensional echocardiography.
Zipprich, D A; Owen, C H; Lewis, C W; Gall, S A; Davis, J W; Kisslo, J A; Glower, D D
1996-01-01
The Frank-Starling relationship between left ventricular stroke work and end-diastolic minor-axis cross-sectional area was evaluated as a load-insensitive measure of inotropic state by two-dimensional echocardiography in 10 conscious dogs. Stroke work was calculated as the product of systolic change in cross-sectional area and either (1) beat-to-beat mean arterial pressure or (2) initial systolic blood pressure. Both Frank-Starling relationships were highly linear during preload variation (mean r = 0.96), sensitive to the inotropic state (slope increase with calcium 51% +/- 43% and 62% +/- 53%, respectively), and insensitive to afterload (r < 0.4, slope or x intercept versus afterload). Thus the Frank-Starling relationships derived from two-dimensional echocardiographic images and peripheral arterial pressure may be a useful and practical means of assessing inotropic state with minimally invasive measurements.
The role of two-dimensional echocardiography in diagnostics of coarctation of the aorta in newborns
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Ilisić Tamara
2015-01-01
Full Text Available Introduction. Diagnosis of neonatal coarctation of the aorta (CoA still presents a challenge in routine practice because of absence of reliable morphologic and functional parameters for early detection of this congenital heart defect in newborns. Objective. The aim of this study is to identify easy obtainable two-dimensional echocardiographic parameters for detection of the CoA in newborns. Methods. Echocardiographic evaluation was performed in 30 newborns with CoA and 20 healthy neonates (control group. Measurements of the proximal transverse arch (PTA, distal transverse arch (DTA, isthmus, distance between the left common carotid artery (LCCA at the origin of the left subclavian artery (LSA, were obtained by two-dimensional echocardiography. Aortic arch hypoplasia was defined using Mouleart, Karl and Mee criteria, and Z-value. Index 1 was calculated as a ratio of DTA and distance between origins LCCA-LSA, Index 2 was calculated as a ratio of the ascending aorta and the distance between LCCA-LSA origins, and Index 3 was calculated as a ratio of PTA and distance between LCCA-LSA origins. Results. Index 1 was significantly lower in patients with CoA in comparison with control group (0.50 vs. 1.39; p≤0.01. A cutoff point at 0.39, for Index 1, showed a sensitivity of 92% and specificity of 99% for the diagnosis of neonatal CoA, while cut off points at 0.69 and 0.44, for Index 2 and Index 3, showed the highest sensitivity and specificity for the diagnosis of CoA in newborns. Conclusion. By using these echo indexes, two-dimensional echocardiographic aortic arch measurement becomes a simple, reliable noninvasive method for the evaluation of aortic coarctation in newborns and may lead to earlier diagnosis and subsequent surgical correction.
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Objective To evaluate the dimensions of atrial septal aneurysm (ASA), the presence and characteristics of interatrial shunt, the movement of the wall of the aneurysm, and correlation between these findings and sign and/or symptoms suggesting embolism in Manisa, a district of a western Anatolian city of Turkey. Methods Two thousand five hundred cases were examined by routine transthoracic echocardiography (TTE) in both pediatric and adult cardiology outpatient clinics. ASA was detected in 20 cases and evaluated by two-dimensional color Doppler echocardiography (CDE). The length of the base, the maximum radius and the maximum displacement of ASA were measured. The shunt between the atria was examined by CDE. In cases where a shunt could not be found, galactose and palmitic acid was injected. Standard 12-lead electrocardiogram (ECG) and exercise stress test were also performed. Results No clinical signs or symptoms were found, suggesting a systemic or cerebral embolism. The maximum displacement of ASA was between 2 and 5 mm. All of the aneurysms were localized in the right atrium, and the walls of the aneurysm did not move beyond the base of the left atrium during the maximum displacement. Interatrial shunt was detected in 14 of 20 patients (70%) by CDE and in the remaining six cases by contrast TTE. Frequent ventricular ectopic beats were observed in one patient. Conclusions During routine TTE we observed 0.8% asymptomatic ASA in our population. The use of a contrast agent was found to be a valuable additional method in patients with ASA when the shunt could not be detected by CDE. The risk for embolism is not high when the maximum displacement of the wall of ASA was 5 mm or less and no bulge into the left atrium was observed. Based on our experience with this method, TTE is easy to perform, well-tolerated and acceptable.
Institute of Scientific and Technical Information of China (English)
Rong LIU; Youbin DENG; Xiaojun BI; Yani LIU; Li XIONG; Liuping CHEN
2009-01-01
The clinically applied value of myocardial perfusion and systolic function in patients with coronary artery disease after coronary artery bypass surgery using real-time myocardial contrast echo-cardiography (RT-MCE) combined with two-dimensional strain echocardiography was assessed.Twenty patients underwent intravenous RT-MCE by intravenous injections of Sono Vue before and after coronary artery bypass surgery. Two-dimensional images were recorded from the left ventricular four-chamber view, two-chamber view and the apical view before, and two weeks and three months af-ter coronary artery bypass surgery, and the peak systolic longitudinal strain was measured. The results showed that myocardial perfusion was significantly increased after coronary artery bypass surgery in about 71.6% segments. In the group that myocardial perfusion was improved, the peak systolic longitu-dinal strain three months after bypass surgery was significantly higher than that before operation [(-15.78±5.91)% vs (-10.45±8.31)%, P0.05]. It was con-cluded that whether or not the improvement of myocardial perfusion can mirror the recovery trend of regional systolic function, two-dimensional strain echocardiography can observe dynamic change of re-gional systolic function. The combination of myocardial perfusion with two-dimensional strain echocar-diography can more accurately assess the curative effectiveness of coronary artery bypass surgery.
Aortic arch mechanics measured with two-dimensional speckle tracking echocardiography.
Teixeira, Rogério; Monteiro, Ricardo; Baptista, Rui; Pereira, Telmo; Ribeiro, Miguel A; Gonçalves, Alexandra; Cardim, Nuno; Gonçalves, Lino
2017-07-01
To study the feasibility of vascular mechanics at the aortic arch with two-dimensional speckle tracking echocardiography, as well as to define normal values and to compare results between hypertensive patients and healthy patients. We included 107 patients (61 healthy patients and 46 hypertensive patients) who underwent a complete echocardiographic exam, including a short-axis view of the aortic arch. The speckle tracking methodology was used to calculate aortic arch mechanics offline (EchoPAC; GE Healthcare). The analysis was performed for circumferential aortic strain and for the early circumferential aortic strain rate, and we used an average result of the six equidistant segments of the arterial wall. We also assessed the aortic pulse wave velocity with the Complior method. The 61 healthy patients had a mean age of 33 ± 9 years, and 59% were women. Of the total 366 aortic arch wall segments, 344 (94%) had adequate waveforms for the speckle tracking analysis. The hypertensive patients had a mean age of 45 ± 12 years, and 54% were women. Of the total 276 aortic wall segments, 261 (95%) had adequate waveforms for analysis. Aortic arch strain and strain rate were lower in the hypertensive patients group than in the healthy patients group (6.3 ± 2.0 vs. 11.2 ± 3.2% and 1.0 ± 0.3 vs. 1.5 ± 0.4 s, respectively, both P Speckle tracking analysis of aortic arch images is feasible and might serve as a new approach to evaluate arterial function.
Thind, Munveer; Ahmed, Mustafa I; Gok, Gulay; Joson, Marisa; Elsayed, Mahmoud; Tuck, Benjamin C; Townsley, Matthew M; Klas, Berthold; McGiffin, David C; Nanda, Navin C
2015-05-01
We report a case of a right atrial thrombus traversing a patent foramen ovale into the left atrium, where three-dimensional transesophageal echocardiography provided considerable incremental value over two-dimensional transesophageal echocardiography in its assessment. As well as allowing us to better spatially characterize the thrombus, three-dimensional transesophageal echocardiography provided a more quantitative assessment through estimation of total thrombus burden.
Pierard, L A; Albert, A; Henrard, L; Lempereur, P; Sprynger, M; Carlier, J; Kulbertus, H E
1986-09-01
To determine the incidence and clinical significance of pericardial effusion after acute myocardial infarction, two-dimensional echocardiography was serially performed in 66 consecutive patients. Pericardial effusion was observed in 17 (26%); the effusion was small in 13 patients, moderate in 3 and large with signs of cardiac tamponade in 1. In this patient, two-dimensional echocardiography strongly suggested myocardial rupture. The observation of pericardial effusion was not associated with age, sex, previous myocardial infarction, atrial fibrillation or treatment with heparin. It was more often a complication of anterior than of inferior acute infarction. Patients with pericardial effusion had higher peak levels of creatine kinase and lactic dehydrogenase and a higher wall motion score index. More patients with pericardial effusion had congestive heart failure or ventricular arrhythmias, developed a ventricular aneurysm or died within 1 year after their infarction. In conclusion, pericardial effusion is frequently visualized by two-dimensional echocardiography after acute myocardial infarction and its presence is associated with an increased occurrence of complications and cardiac death.
Teixeira, Rogério; Monteiro, Ricardo; Dinis, Paulo; Santos, Maria José; Botelho, Ana; Quintal, Nuno; Cardim, Nuno; Gonçalves, Lino
2016-11-24
Vascular mechanics assessed with two-dimensional speckle tracking echocardiography (2D-STE) could be used as a new imaging surrogate of vascular stiffening. The CHA2DS2-VASc score is considered accurate as an estimate of stroke risk in non-valvular AF, although many potential stroke risk factors have not been included in this scoring method. The purpose of this research is to study the feasibility of evaluating vascular mechanics at the descending aorta in non-valvular AF patients using transesophageal 2D-STE and to analyze the association between descending aortic mechanics and stroke. We prospectively recruited a group of 44 patients referred for a transesophageal echocardiogram (TEE) in the context of cardioversion for non-valvular AF. A short-axis view of the descending aorta, one to two centimeters after the aortic arch was selected for the vascular mechanics assessment with the 2D-STE methodology. The vascular mechanics parameters analyzed were circumferential aortic strain (CAS) and early circumferential aortic strain rate (CASR). A clinical assessment was performed with focus on the past stroke history and the CHA2DS2-VASc score. The mean age of our cohort was 65 ± 13 years and 75% were men; AF was known for 2.8 ± 2.5 years and it was considered paroxystic in 41% of cases. Waveforms adequate for measuring 2D-STE were present in 85% of the 264 descending aortic wall segments. The mean CAS was 3.5 ± 1.2% and the mean CASR was 0.7 ± 0.3 s(-1). The inter- and intra-observer variability for aortic mechanics was considered adequate. The median CHA2DS2VASc score was 2 (2-3). As the score increased we noted that both the CAS (r = -0.38, P = 0.01) and the CASR (r = -0.42, P mechanics assessed with transesophageal 2D-STE.
Enzensberger, Christian; Achterberg, Friederike; Degenhardt, Jan; Wolter, Aline; Graupner, Oliver; Herrmann, Johannes; Axt-Fliedner, Roland
2017-01-01
Objective The primary objective of this study was to determine the feasibility and reproducibility of 2-dimensional speckle tracking imaging based on the wall motion tracking (WMT) technique in fetal echocardiography. The secondary objective was to compare left and right ventricular global and segmental longitudinal peak strain values. Methods A prospective cross-sectional study was performed. Global and segmental longitudinal peak strain values of the left ventricle (LV) and right ventricle (RV) were assessed prospectively. Based on apical 4-chamber views, cine loops were acquired and digitally stored. Strain analysis was performed offline. Intra- and interobserver variabilities were analyzed. Results A total of 29 healthy fetuses with an echocardiogram performed between 19 and 37 weeks of gestation were included. Analysis was performed with a temporal resolution of 60 frames per second (fps). For both examiners, in all cases Cronbach’s alpha was>0.7. The interobserver variability showed a strong agreement in 50% of the segments (ICC 0.71–0.90). The global strain values for LV and RV were −16.34 and −14.65%, respectively. Segmental strain analysis revealed a basis to apex gradient with the lowest strain values in basal segments and the highest strain values in apical segments. Conclusion The assessment of fetal myocardial deformation parameters by 2D WMT is technically feasible with good reproducibility. PMID:28210715
Suzuki, Ryohei; Mochizuki, Yohei; Yoshimatsu, Hiroki; Teshima, Takahiro; Matsumoto, Hirotaka; Koyama, Hidekazu
2017-02-01
Objectives Hypertrophic cardiomyopathy, a primary disorder of the myocardium, is the most common cardiac disease in cats. However, determination of myocardial deformation with two-dimensional speckle-tracking echocardiography in cats with various stages of hypertrophic cardiomyopathy has not yet been reported. This study was designed to measure quantitatively multidirectional myocardial deformations of cats with hypertrophic cardiomyopathy. Methods Thirty-two client-owned cats with hypertrophic cardiomyopathy and 14 healthy cats serving as controls were enrolled and underwent assessment of myocardial deformation (peak systolic strain and strain rate) in the longitudinal, radial and circumferential directions. Results Longitudinal and radial deformations were reduced in cats with hypertrophic cardiomyopathy, despite normal systolic function determined by conventional echocardiography. Cats with severely symptomatic hypertrophic cardiomyopathy also had lower peak systolic circumferential strain, in addition to longitudinal and radial strain. Conclusions and relevance Longitudinal and radial deformation may be helpful in the diagnosis of hypertrophic cardiomyopathy. Additionally, the lower circumferential deformation in cats with severe hypertrophic cardiomyopathy may contribute to clinical findings of decompensation, and seems to be related to severe cardiac clinical signs. Indices of multidirectional myocardial deformations by two-dimensional speckle-tracking echocardiography may be useful markers and help to distinguish between cats with hypertrophic cardiomyopathy and healthy cats. Additionally, they may provide more detailed assessment of contractile function in cats with hypertrophic cardiomyopathy.
Stuckey, Daniel J; Carr, Carolyn A; Tyler, Damian J; Clarke, Kieran
2008-08-01
Two-dimensional echocardiography is the most commonly used non-invasive method for measuring in vivo cardiac function in experimental animals. In humans, measurements of cardiac function made using cine-MRI compare favourably with those made using echocardiography. However, no rigorous comparison has been made in small animals. Here, standard short-axis two-dimensional (2D) echocardiography (2D-echo) and cine-MRI measurements were made in the same rats, both control and after chronic myocardial infarction. Correlations between the two techniques were found for end diastolic area, stroke area and ejection fraction, but cine-MRI measurements of ejection fraction were 12+/-6% higher than those made using 2D-echo, because of the 1.8-fold higher temporal resolution of the MRI technique (4.6 ms vs 8.3 ms). Repeated measurements on the same group of rats over several days showed that the cine-MRI technique was more reproducible than 2D-echo, in that 2D-echo would require five times more animals to find a statistically significant difference. In summary, caution should be exercised when comparing functional results acquired using short-axis 2D-echo vs cine-MRI. The accuracy of cine-MRI allows identification of alterations in heart function that may be missed when using 2D-echo.
Internetwork magnetic field as revealed by two-dimensional inversions
Danilovic, S.; van Noort, M.; Rempel, M.
2016-09-01
Context. Properties of magnetic field in the internetwork regions are still fairly unknown because of rather weak spectropolarimetric signals. Aims: We address the matter by using the two-dimensional (2D) inversion code, which is able to retrieve the information on smallest spatial scales up to the diffraction limit, while being less susceptible to noise than most of the previous methods used. Methods: Performance of the code and the impact of various effects on the retrieved field distribution is tested first on the realistic magneto-hydrodynamic (MHD) simulations. The best inversion scenario is then applied to the real data obtained by Spectropolarimeter (SP) on board Hinode. Results: Tests on simulations show that: (1) the best choice of node position ensures a decent retrieval of all parameters; (2) the code performs well for different configurations of magnetic field; (3) slightly different noise levels or slightly different defocus included in the spatial point spread function (PSF) produces no significant effect on the results; and (4) temporal integration shifts the field distribution to a stronger, more horizontally inclined field. Conclusions: Although the contribution of the weak field is slightly overestimated owing to noise, 2D inversions are able to recover well the overall distribution of the magnetic field strength. Application of the 2D inversion code on the Hinode SP internetwork observations reveals a monotonic field strength distribution. The mean field strength at optical depth unity is ~ 130 G. At higher layers, field strength drops as the field becomes more horizontal. Regarding the distribution of the field inclination, tests show that we cannot directly retrieve it with the observations and tools at hand, however, the obtained distributions are consistent with those expected from simulations with a quasi-isotropic field inclination after accounting for observational effects.
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Jing-Jie Li
Full Text Available PURPOSE: The aim was to assess atrial fibrillation (AF and vulnerability in Wolff-Parkinson-White (WPW syndrome patients using two-dimensional speckle tracking echocardiography (2D-STE. METHODS: All patients were examined via transthoracic echocardiography and 2D-STE in order to assess atrial function 7 days before and 10 days after RF catheter ablation. A postoperative 3-month follow-up was performed via outpatient visit or telephone calls. RESULTS: Results showed significant differences in both body mass index (BMI and supraventricular tachycardia (SVT duration between WPW patients and DAVNP patients (both P<0.05. Echocardiography revealed that the maximum left atrial volume (LAVmax and the left ventricular mass index (LVMI in diastole increased noticeably in patients with WPW compared to patients with DAVNP both before and after ablation (all P<0.05. Before ablation, there were obvious differences in the levels of SRs, SRe, and SRa from the 4-chamber view (LA in the WPW patients group compared with patients in the DAVNP group (all P<0.05. In the AF group, there were significant differences in the levels of systolic strain rate (SRs, early diastolic strain rate (SRe, and late diastolic strain rate (SRa from the 4-chamber view (LA both before and after ablation (all P<0.05. In the non-AF group, there were decreased SRe levels from the 4-chamber view (LA/RA pre-ablation compared to post-ablation (all P<0.05. CONCLUSION: Our findings provide convincing evidence that WPW syndrome may result in increased atrial vulnerability and contribute to the development of AF. Further, RF catheter ablation of AAV pathway can potentially improve atrial function in WPW syndrome patients. Two-dimensional speckle tracking echocardiography imaging in WPW patients would be necessary in the evaluation and improvement of the overall function of RF catheter ablation in a long-term follow-up period.
Viossat, J; Chauvaud, S; Mihaileanu, S; Pillière, R; Sicre, P; Schnebert, B; Abbou, B; Lafont, A; Julien, J; Marino, J P
1986-09-01
20 patients who underwent reconstructive surgery for mitral regurgitation were peroperatively investigated by contrasted bidimensional echocardiography using intraventricular injection of 20 ml of physiologic saline. Before the valvuloplasty, the peroperative quantitation of mitral leakage was in all cases closely correlated with the data obtained preoperatively. After the mitral reparation, three groups of patients could be observed: group I (12 cases): absent or minimal regurgitation (0-+); group II (5 cases): moderate mitral regurgitation (++); group III (3 cases): marked regurgitation ( - +) necessitating an immediate ECC. In two cases it was possible to improve successfully the valvular function, in the third case valvular replacement was necessary. The correlation between the data of peroperative contrasted echography at one hand and the clinical examination and the postoperative paraclinical investigations on the other hand was excellent in all cases. Thus the contrasted bidimensional peroperative echocardiography represents a reliable method for predicting the immediate results of mitral reconstructive surgery.
Romero, M A; Espinosa Vázquez, A; Ramos Corrales, M A; Solorio, S; Lepe Montoya, L; Badui, E; Ocampo, S; Carrillo, A M
1996-01-01
Myocardial expansion in acute myocardial infarction (AMI) is present in about 45% of the patients within the first 72 hours. This is associated with ventricular aneurysm formation, myocardial rupture, heart failure and early death. Experimental studies in animals with AMI have used late reperfusion to decrease the incidence of expansion with success. The present is a prospective, longitudinal, open and randomized study in 21 patients with anterior AMI, to evaluate if the late reperfusion (6 to 12 hours) can decrease the incidence of myocardial expansion graded quantitatively with bidimensional echocardiography. Two groups were made: group A (n = 12) who received thrombolysis with streptokinase 1.5 mill. IU plus oral aspirin 150 mg OD (n = 9). Both groups had the same characteristics of AMI and functional class of Killip and Kimball (I-II class). Intrahospital treatment was given freely in both groups. The expansion was evaluated with bidimensional echocardiography used Jugdutt's method. In group A, expansion was present in 25% of the cases, while in group B was 66.6% (p < 0.0005). The distortion area, distortion peak, septal thickness and large asynergic segment were more sensitive parameters to identify myocardial expansion. Our results are similar to some experimental studies. We conclude that late thrombolysis can be useful in decreasing the incidence of myocardial expansion. Bidimensional echocardiography is a useful, fast and safe method to identify myocardial expansion.
D'hooge, Jan; Barbosa, Daniel; Gao, Hang; Claus, Piet; Prater, David; Hamilton, Jamie; Lysyansky, Peter; Abe, Yasuhiko; Ito, Yasuhiro; Houle, Helene; Pedri, Stefano; Baumann, Rolf; Thomas, James; Badano, Luigi P
2016-06-01
Speckle tracking echocardiography has already demonstrated its clinical potential. However, its use in routine practice is jeopardized by recent reports on high inter-vendor variability of the measurements. As such, the European Association of CardioVascular Imaging (EACVI) and the American Society of Echocardiography (ASE) set up a standardization task force, which was joined by all manufacturers of echocardiographic equipment as well as by companies offering software solutions only, with the ambition to tackle this problem by standardization and quality assurance (QA). In this study, a first step towards QA of all commercially available tracking solutions based on computer-generated ultrasound images is presented. The accuracy of the products was acceptable with relative errors below 10% and intra-vendor reproducibility within 5%. Whether these results can be extrapolated to the clinical setting is the topic of an ongoing study of the EACVI/ASE/Industry Task Force to standardize deformation imaging. This study was an important first step in the development of generally accepted tools for QA of speckle tracking echocardiography. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.
Thomas, W P; Gaber, C E; Jacobs, G J; Kaplan, P M; Lombard, C W; Moise, N S; Moses, B L
1993-01-01
Recommendations are presented for standardized imaging planes and display conventions for two-dimensional echocardiography in the dog and cat. Three transducer locations ("windows") provide access to consistent imaging planes: the right parasternal location, the left caudal (apical) parasternal location, and the left cranial parasternal location. Recommendations for image display orientations are very similar to those for comparable human cardiac images, with the heart base or cranial aspect of the heart displayed to the examiner's right on the video display. From the right parasternal location, standard views include a long-axis four-chamber view and a long-axis left ventricular outflow view, and short-axis views at the levels of the left ventricular apex, papillary muscles, chordae tendineae, mitral valve, aortic valve, and pulmonary arteries. From the left caudal (apical) location, standard views include long-axis two-chamber and four-chamber views. From the left cranial parasternal location, standard views include a long-axis view of the left ventricular outflow tract and ascending aorta (with variations to image the right atrium and tricuspid valve, and the pulmonary valve and pulmonary artery), and a short-axis view of the aortic root encircled by the right heart. These images are presented by means of idealized line drawings. Adoption of these standards should facilitate consistent performance, recording, teaching, and communicating results of studies obtained by two-dimensional echocardiography.
Kocabay, Gonenc; Muraru, Denisa; Peluso, Diletta; Cucchini, Umberto; Mihaila, Sorina; Padayattil-Jose, Seena; Gentian, Denas; Iliceto, Sabino; Vinereanu, Dragos; Badano, Luigi P
2014-08-01
Two-dimensional speckle-tracking echocardiography is a novel tool to assess myocardial function. The purpose of this study was to evaluate left ventricular myocardial strain and rotation parameters by two-dimensional speckle-tracking echocardiography in a large group of healthy adults across a wide age range to establish their reference values and to assess the influence of age, sex, and hemodynamic factors. Transthoracic echocardiograms were acquired in 247 healthy volunteers (139 women, 44 years [standard deviation, 16 years old] (range, 18-80 years). We measured longitudinal, circumferential, and radial peak systolic strain values, and left ventricular rotation and twist. Average values of global longitudinal, radial, and circumferential strain were -21.5% (standard deviation, 2.0%), 40.1% (standard deviation, 11.8%) and -22.2% (standard deviation, 3.4%), respectively. Longitudinal strain was significantly more negative in women, whereas radial and circumferential strain and rotational parameters were similar in both sexes. Accordingly, lower limits of normality for the strain components were -16.9% in men and -18.5% in women for longitudinal strain, and -15.4% for circumferential and 24.6% for radial strain, irrespective of sex. Longitudinal strain values were more negative at the base than at apical segments. Mean rotational values were -6.9° (standard deviation, 3.5°) for the base, 13.0° (standard deviation, 6.5°) for apical rotation, and 20.0° (standard deviation, 7.3°) for net twist. We report the comprehensive assessment of normal myocardial deformation and rotational mechanics in a large cohort of healthy volunteers. We found that women have more negative longitudinal strain, accounting for their higher left ventricular ejection fraction. Availability of reference values for these parameters may foster their implementation in the clinical routine. Copyright © 2013 Sociedad Española de Cardiología. Published by Elsevier Espana. All rights reserved.
Park, Kyu-Hwan; Son, Jang-Won; Park, Won-Jong; Lee, Sang-Hee; Kim, Ung; Park, Jong-Seon; Shin, Dong-Gu; Kim, Young-Jo; Choi, Jung-Hyun; Houle, Helene; Vannan, Mani A; Hong, Geu-Ru
2013-01-01
This article is the first clinical investigation of the quantitative left atrial (LA) vortex flow by two-dimensional (2-D) transesophageal contrast echocardiography (2-D-TECE) using vector particle image velocimetry (PIV). The aims of this study were to assess the feasibility of LA vortex flow analysis and to characterize and quantify the LA vortex flow in controls and in patients with atrial fibrillation (AF). Thirty-five controls and 30 patients with AF underwent transesophageal contrast echocardiography. The velocity vector was estimated by particle image velocimetry. The morphology and pulsatility of the LA vortex flow were compared between the control and AF groups. In all patients, quantitative LA vortex flow analysis was feasible. In the control group, multiple, pulsatile, compact and elliptical-shaped vortices were seen in the periphery of the LA. These vortices were persistently maintained and vectors were directed toward the atrioventricular inflow. In the AF group, a large, merged, lower pulsatile and round-shaped vortex was observed in the center of the LA. In comparisons of vortex parameters, the relative strength was significantly lower in the AF group (1.624 ± 0.501 vs. 2.105 ± 0.226, p < 0.001). It is feasible to characterize and quantify the LA vortex flow by transesophageal contrast echocardiography in patients with AF, which offers a new method to obtain additional information on LA hemodynamics. The approach has the potential for early detection of the LA dysfunction and in decisions regarding treatment strategy and guiding anticoagulation treatment in patients with AF.
Strain and strain rate by two-dimensional speckle tracking echocardiography in a maned wolf
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Matheus M. Mantovani
2012-12-01
Full Text Available The measurement of cardiovascular features of wild animals is important, as is the measurement in pets, for the assessment of myocardial function and the early detection of cardiac abnormalities, which could progress to heart failure. Speckle tracking echocardiography (2D STE is a new tool that has been used in veterinary medicine, which demonstrates several advantages, such as angle independence and the possibility to provide the early diagnosis of myocardial alterations. The aim of this study was to evaluate the left myocardial function in a maned wolf by 2D STE. Thus, the longitudinal, circumferential and radial strain and strain rate were obtained, as well as, the radial and longitudinal velocity and displacement values, from the right parasternal long axis four-chamber view, the left parasternal apical four chamber view and the parasternal short axis at the level of the papillary muscles. The results of the longitudinal variables were -13.52±7.88, -1.60±1.05, 4.34±2.52 and 3.86±3.04 for strain (%, strain rate (1/s, displacement (mm and velocity (cm/s, respectively. In addition, the radial and circumferential Strain and Strain rate were 24.39±14.23, 1.86±0.95 and -13.69±6.53, -1.01±0.48, respectively. Thus, the present study provides the first data regarding the use of this tool in maned wolves, allowing a more complete quantification of myocardial function in this species.
Dedeoglu, Reyhan; Şahin, Sezgin; Koka, Aida; Öztunç, Funda; Adroviç, Amra; Barut, Kenan; Cengiz, Dicle; Kasapçopur, Özgür
2016-08-01
The aim of this study was to investigate subclinical systolic and diastolic dysfunction in juvenile-onset systemic lupus erythematosus (j-SLE) patients with speckle tracking echocardiography (STE) and the effects of disease activity on left ventricular (LV) regional functions. Thirty-five patients with j-SLE and 30 healthy children (control group) were evaluated between January and August 2015. STE was performed on all patients and controls. Medical records, including diagnosis criteria, age at diagnosis, and duration of disease, were evaluated. SLE disease activity was assessed using the SLE Disease Activity Index (SLEDAI). j-SLE patients had lower ejection fraction than did control subjects but still within normal range. LV end-diastolic and end-systolic dimensions were significantly larger in j-SLE patients (32.43 ± 3.2 vs 28.3 ± 3.1 and 21.1 ± 1.9 vs 18.9.0 ± 2.2, respectively; p = 0.001). There was a significant reduction in longitudinal strain of LV segments in the j-SLE patients compared with controls. J-SLE patients were further divided into subgroups. Group 1 comprised patients having SLEDAI scores >8 at the onset of disease but who improved with therapy during follow-up. Group 2 included j-SLE patients with SLEDAI scores >8 at diagnosis and persistently >4 at the end of follow-up. In the LV mid-inferior and mid-inferolateral segments, STE strain measurements of group 2 were significantly lower than those of group 1 (15.9 ± 6.4 vs 20.0 ± 4.4, 17.9 ± 7.2 vs 23.2 ± 3.8; p = 0.075, p = 0.055, respectively). Simple and non-invasive STE would be helpful in predicting cardiovascular prognosis with new therapeutic medications/interventions or in objectively comparing the effects of immunosuppressive drugs in comparison with preceding STE evaluation.
Wu, Victor Chien-Chia; Otsuji, Yutaka; Takeuchi, Masaaki
2017-01-01
Background Newer 2D strain software has a potential to assess layer-specific strain. However, normal reference values for layer-specific strain have not been established. We aimed to establish the normal ranges of layer-specific longitudinal and circumferential strain (endocardial global longitudinal strain (GLS), transmural GLS, epicardial GLS, endocardial global circumferential strain (GCS), transmural GCS, and epicardial GCS). Methods and results We retrospectively analyzed longitudinal and circumferential strain parameters in 235 healthy subjects, with use of layer-specific 2D speckle tracking software (GE). The endocardial strain/epicardial strain (Endo/Epi) ratio was also measured to assess the strain gradient across the myocardium. The endocardial, transmural, and epicardial GLS values and the Endo/Epi ratio in the normal subjects were -23.1±2.3, -20.0±2.0, -17.6±1.9, and 1.31±0.07, respectively. The corresponding values of GCS were -28.5±3.0, -20.8±2.3, -15.3±2.0, and 1.88±0.17, respectively. The layer-specific global strain parameters exhibited no age dependency but did exhibit gender dependency except for endocardial GCS. A subgroup analysis revealed that basal and middle levels of endocardial LS was decreased in the middle and elderly aged group. However, apical endocardial LS was preserved even in the elderly subjects. Conclusions We proposed normal reference values for layer-specific strain based on both age and gender. This detailed strain analysis provides layer-oriented information with the potential to characterize abnormal findings in various cardiovascular diseases. PMID:28662186
Vieira-Filho, Normando G; Mancuso, Frederico J N; Oliveira, Wercules A A; Gil, Manuel A; Fischer, Cláudio H; Moises, Valdir A; Campos, Orlando
2014-03-01
The left atrial volume index (LAVI) is a biomarker of diastolic dysfunction and a predictor of cardiovascular events. Three-dimensional echocardiography (3DE) is highly accurate for LAVI measurements but is not widely available. Furthermore, biplane two-dimensional echocardiography (B2DE) may occasionally not be feasible due to a suboptimal two-chamber apical view. Simplified single plane two-dimensional echocardiography (S2DE) could overcome these limitations. We aimed to compare the reliability of S2DE with other validated echocardiographic methods in the measurement of the LAVI. We examined 143 individuals (54 ± 13 years old; 112 with heart disease and 31 healthy volunteers; all with sinus rhythm, with a wide range of LAVI). The results for all the individuals were compared with B2DE-derived LAVIs and validated using 3DE. The LAVIs, as determined using S2DE (32.7 ± 13.1 mL/m(2)), B2DE (31.9 ± 12.7 mL/m(2)), and 3DE (33.1 ± 13.4 mL/m(2)), were not significantly different from each other (P = 0.85). The S2DE-derived LAVIs correlated significantly with those obtained using both B2DE (r = 0.98; P < 0.001) and 3DE (r = 0.93; P < 0.001). The mean difference between the S2DE and B2DE measurements was <1.0 mL/m(2). Using the American Society of Echocardiography criteria for grading LAVI enlargement (normal, mild, moderate, severe), we observed an excellent agreement between the S2DE- and B2DE-derived classifications (κ = 0.89; P < 0.001). S2DE is a simple, rapid, and reliable method for LAVI measurement that may expand the use of this important biomarker in routine echocardiographic practice.
Orii, Makoto; Hirata, Kumiko; Tanimoto, Takashi; Shiono, Yasutsugu; Shimamura, Kunihiro; Yamano, Takashi; Ino, Yasushi; Yamaguchi, Tomoyuki; Kubo, Takashi; Tanaka, Atsushi; Imanishi, Toshio; Akasaka, Takashi
2015-06-01
The aim of this study was to determine whether two-dimensional speckle-tracking echocardiography can identify the myocardial damage detected by delayed enhancement (DE) magnetic resonance imaging via the differences in myocardial deformation in patients with extracardiac sarcoidosis who showed no structural and functional abnormalities in the heart. Forty-five patients with biopsy-proven extracardiac sarcoidosis were analyzed retrospectively. Patients with abnormal electrocardiographic and echocardiographic findings, including ventricular arrhythmias, heart block, regional wall motion abnormalities, valvular heart disease, and cardiomyopathy, were excluded. Ten age-matched healthy control subjects were recruited as a control group. Comprehensive echocardiography and DE magnetic resonance imaging were performed, and circumferential, longitudinal, and radial strain were consecutively assessed using two-dimensional speckle-tracking echocardiographic software in a 16-segment model of the left ventricle in accordance to the presence (DE+) or absence (DE-) of DE. Among the 45 patients, 36 segments in 13 patients showed DE. DE+ segments had lower peak circumferential strain than DE- and control segments (-14 ± 5% vs -28 ± 7% vs -30 ± 7%, P speckle-tracking echocardiography can identify the myocardial damage detected by DE magnetic resonance imaging in patients with extracardiac sarcoidosis. Copyright © 2015 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.
Marcus, K.A.; Mavinkurve-Groothuis, A.M.C.; Barends, M.; Dijk, A.P.J. van; Feuth, T.; Korte, C.L. de; Kapusta, L.
2011-01-01
BACKGROUND: The accurate evaluation of intrinsic myocardial contractility in children with or without congenital heart disease (CHD) has turned out to be a challenge. Two-dimensional strain echocardiographic (2DSTE) imaging or two-dimensional speckle-tracking echocardiographic imaging appears to hol
Nozawa, E; Kanashiro, R M; Murad, N; Carvalho, A C C; Cravo, S L D; Campos, O; Tucci, P J F; Moises, V A
2006-05-01
Although echocardiography has been used in rats, few studies have determined its efficacy for estimating myocardial infarct size. Our objective was to estimate the myocardial infarct size, and to evaluate anatomic and functional variables of the left ventricle. Myocardial infarction was produced in 43 female Wistar rats by ligature of the left coronary artery. Echocardiography was performed 5 weeks later to measure left ventricular diameter and transverse area (mean of 3 transverse planes), infarct size (percentage of the arc with infarct on 3 transverse planes), systolic function by the change in fractional area, and diastolic function by mitral inflow parameters. The histologic measurement of myocardial infarction size was similar to the echocardiographic method. Myocardial infarct size ranged from 4.8 to 66.6% when determined by histology and from 5 to 69.8% when determined by echocardiography, with good correlation (r = 0.88; P echocardiography (r = -0.87; P rats.
Nozawa E.; Kanashiro R.M.; Murad N.; Carvalho A.C.C.; Cravo S.L.D.; Campos O.; Tucci P.J.F.; Moises V.A.
2006-01-01
Although echocardiography has been used in rats, few studies have determined its efficacy for estimating myocardial infarct size. Our objective was to estimate the myocardial infarct size, and to evaluate anatomic and functional variables of the left ventricle. Myocardial infarction was produced in 43 female Wistar rats by ligature of the left coronary artery. Echocardiography was performed 5 weeks later to measure left ventricular diameter and transverse area (mean of 3 transverse planes), i...
Elsayed, Mahmoud; Bulur, Serkan; Kalla, Aditi; Ahmed, Mustafa I; Hsiung, Ming C; Uygur, Begum; Alagic, Nermina; Sungur, Aylin; Singh, Satinder; Nanda, Navin C
2016-08-01
We present two cases in whom live/real time three-dimensional transesophageal echocardiography (3DTEE) provided incremental value in the assessment of atherosclerotic disease in the aorta. In one patient, it identified additional atherosclerotic ulcers as well as thrombi within them which were missed by two-dimensional (2D) TEE. In both cases, the size of the large mobile atherosclerotic plaque was underestimated by 2DTEE as compared with 3DTEE. Furthermore, 3DTEE provided volume quantification of the thrombi and ulcers which is not possible by 2DTEE. The echocardiographic findings of atherosclerotic plaques were confirmed by computed tomography in one patient and by surgery in the other.
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Nozawa E.
2006-01-01
Full Text Available Although echocardiography has been used in rats, few studies have determined its efficacy for estimating myocardial infarct size. Our objective was to estimate the myocardial infarct size, and to evaluate anatomic and functional variables of the left ventricle. Myocardial infarction was produced in 43 female Wistar rats by ligature of the left coronary artery. Echocardiography was performed 5 weeks later to measure left ventricular diameter and transverse area (mean of 3 transverse planes, infarct size (percentage of the arc with infarct on 3 transverse planes, systolic function by the change in fractional area, and diastolic function by mitral inflow parameters. The histologic measurement of myocardial infarction size was similar to the echocardiographic method. Myocardial infarct size ranged from 4.8 to 66.6% when determined by histology and from 5 to 69.8% when determined by echocardiography, with good correlation (r = 0.88; P < 0.05; Pearson correlation coefficient. Left ventricular diameter and mean diastolic transverse area correlated with myocardial infarct size by histology (r = 0.57 and r = 0.78; P < 0.0005. The fractional area change ranged from 28.5 ± 5.6 (large-size myocardial infarction to 53.1 ± 1.5% (control and correlated with myocardial infarct size by echocardiography (r = -0.87; P < 0.00001 and histology (r = -0.78; P < 00001. The E/A wave ratio of mitral inflow velocity for animals with large-size myocardial infarction (5.6 ± 2.7 was significantly higher than for all others (control: 1.9 ± 0.1; small-size myocardial infarction: 1.9 ± 0.4; moderate-size myocardial infarction: 2.8 ± 2.3. There was good agreement between echocardiographic and histologic estimates of myocardial infarct size in rats.
Caspar, Thibault; Fichot, Marie; Ohana, Mickaël; El Ghannudi, Soraya; Morel, Olivier; Ohlmann, Patrick
2017-08-01
Acute myocarditis (AM) often involves the left ventricular (LV) subepicardium that might be displayed by cardiac magnetic resonance even late after the acute phase. In the absence of global or regional LV dysfunction, conventional transthoracic echocardiography (TTE) does not accurately identify tissue sequelae of AM. We sought to evaluate the diagnostic value of two-dimensional (2D) and three-dimensional (3D) speckle-tracking echocardiography to identify patients with a history of AM with preserved LV ejection fraction (LVEF). Fifty patients (group 1: age, 31.4 ± 10.5 years; 76% males) with a history of cardiac magnetic resonance-confirmed diagnosis of AM (according to the Lake Louise criteria) were retrospectively identified and then (21.7 ± 23.4 months later) evaluated by complete echocardiography including 2D and 3D speckle-tracking analysis, as well as 50 age- and gender-matched healthy controls (group 2: age, 31.2 ± 9.5 years: 76% males). Patients with a history of severe clinical presentation of AM (sudden death, ventricular arrhythmia, heart failure, alteration of LVEF) were excluded. At diagnosis, peak troponin and C-reactive protein were 11.97 (interquartile range, 4.52-25.92) μg/L and 32.3 (interquartile range, 14.85-70.45) mg/L, respectively. Mean delay between acute phase and follow-up study TTE was 21.7 ± 23.4 months. LVEF was not statistically different between groups (62.1% vs 63.5%, P = .099). Two-dimensional global longitudinal strain (GLS) was lower in magnitude in group 1 (-17.8% vs -22.1%, P speckle-tracking echocardiography, even though LVEF is conserved, adding incremental information over conventional TTE. Copyright © 2017 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.
Uusitalo, Valtteri; Luotolahti, Matti; Pietilä, Mikko; Wendelin-Saarenhovi, Maria; Hartiala, Jaakko; Saraste, Markku; Knuuti, Juhani; Saraste, Antti
2016-05-01
Two-dimensional speckle-tracking applied to dobutamine stress echocardiography (DSE) may aid in the detection of coronary artery disease (CAD). The aim of this study was to determine the value of strain, strain rate, and postsystolic strain index (PSI) measured by speckle-tracking during DSE in the evaluation of the presence, extent, and severity of myocardial ischemia. Fifty patients 63 ± 7 years of age with intermediate probability of CAD were prospectively recruited. All patients underwent DSE, quantitative positron emission tomographic perfusion imaging, and invasive angiography. Regional peak systolic longitudinal strain, strain rate, and PSI were measured at rest, at a dobutamine dose of 20 μg/kg/min, at peak stress, and at early recovery (1 min after stress). Obstructive CAD was defined as >75% stenosis or 40% to 75% stenosis combined with either fractional flow reserve speckle-tracking echocardiography during early recovery after DSE can help in the detection of hemodynamically significant coronary stenosis compared with visual wall motion analysis alone. Copyright © 2016 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.
Gong, Lei; Li, Dongye; Chen, Junhong; Wang, Xiaoping; Xu, Tongda; Li, Wenhua; Ren, Shaoyang; Wang, Cheng
2013-06-01
It is clinically important to determine the myocardial viability of regional wall motion abnormality segments in patients with acute myocardial infarction (AMI). The purpose of this study was to ascertain the ability and value of a combination of speckle tracking echocardiography (STE) and low dose dobutamine stress echocardiography (LDDSE) for the evaluation of viable myocardium in patients with AMI. Forty-two hospitalized patients with AMI and left ventricular systolic dysfunction (left ventricular ejection fraction <50%) were underwent STE in conjunction with LDDSE and dual isotope simultaneous acquisition single photon emission computed tomography (DISA-SPECT). Percutaneous coronary intervention (PCI) was performed subsequently in all patients. STE was used to measure radial, circumferential, and longitudinal end-systolic strain and peak systolic strain rate. The movement of each segment was observed by routine echocardiography 1, 3, and 6 months after PCI, and its improvement over time was the criterion of viable myocardium. The sensitivity, specificity and accuracy of DISA-SPECT for the assessment of viable myocardium were 83.6, 74.4, and 80.7%, respectively. Among the radial, circumferential, and longitudinal strain and strain rate parameters, only longitudinal strain (LS) and longitudinal strain rate (LSr) at rest and LDDSE emerged as independent predictors of viable myocardium, When combining LS and LSr at LDDSE, the sensitivity, specificity and accuracy for the assessment of viable myocardium rose to 89.8, 90.2 and 89.9%, respectively. The sensitivity of STE in conjunction with LDDSE was similar to DISA-SPECT for detecting viable myocardium in patients with AMI, but the specificity and accuracy of STE performed with LDDSE were higher than DISA-SPECT.
Hayashi, Hidetaka; Izumi, Chisato; Takahashi, Shuichi; Uchikoshi, Masato; Yamazaki, Ryou; Asanuma, Toshihiko; Ishikura, Fuminobu; Beppu, Shintaro; Nakatani, Satoshi
2011-09-01
Recently, it has become possible to evaluate left ventricular (LV) torsion by two-dimensional (2D) speckle tracking images. However, LV torsion is a three-dimensional (3D) performance, which per se cannot be assessed by the 2D speckle tracking method. The present study investigated the accuracy of the 2D speckle tracking method and real-time 3D echocardiography in measuring LV rotation, comparing with the MRI tagging method. We assessed LV apical rotation using the 2D speckle tracking method, real-time 3D echocardiography, and MRI tagging method in 26 normal subjects, and compared the results of these three methods. LV apical rotation was measured just before the level in which the posterior papillary muscle was absorbed into the free wall. The degree of LV apical rotation evaluated by the 2D speckle tracking method (Δθ 2D) was significantly smaller than that evaluated by 3D echocardiography (Δθ 3D) and the MRI tagging method (Δθ MRI) (Δθ 2D 7.3 ± 2.8°; Δθ 3D 8.8 ± 3.4°; Δθ MRI 9.0 ± 3.4°; Δθ 2D vs. Δθ 3D, p = 0.0001; Δθ 2D vs. Δθ MRI, p speckle tracking method compared with the MRI tagging method, whereas it could be precisely measured by 3D echocardiography.
Aurich, Matthias; Keller, Marius; Greiner, Sebastian; Steen, Henning; Aus dem Siepen, Fabian; Riffel, Johannes; Katus, Hugo A; Buss, Sebastian J; Mereles, Derliz
2016-12-01
Assessment of left ventricular (LV) systolic function plays a central role in cardiac imaging. Calculation of ejection fraction (EF) is the current method of choice; however, its limited intermodal comparability represents a major drawback. The assessment of myocardial mechanics by strain imaging may better reflect the complex myocardial contractility. We aimed to evaluate different methods for quantification of LV strain on global and regional levels with a focus on the new non-proprietary feature tracking (FT) algorithm. Measurements of LV deformation were performed by means of high-resolution two-dimensional (2D) speckle tracking echocardiography (STE) and compared with values obtained by 2D feature tracking echocardiography (FT-E) and feature tracking cardiac magnetic resonance imaging (FT-CMR). Assessments with echocardiography started within 30 min after CMR examination to minimize time-dependent variations in myocardial function. Forty-seven patients were included. Assessments by STE were -15.7 ± 5.0% for global longitudinal strain (GLS), -14.6 ± 4.5% for global circumferential strain (GCS), and 21.6 ± 13.3% for global radial strain (GRS), while values obtained with FT-E were -13.1 ± 4.0, -13.6 ± 4.0, 20.3 ± 9.5, and with FT-CMR -15.0 ± 4.0, -16.9 ± 5.4, and 35.0 ± 10.8, respectively. Linear regression and the Bland-Altman analysis showed the best intramodal association for STE GLS and FT-E GLS (r = 0.88, bias = -2.7%, LOA = ±4.7%). The correlation for GCS and GRS was weaker, and for regional strain was poor. In contrast to EF, GLS showed a better intermodal correlation between echocardiography and CMR (r = 0.81 by speckle tracking, r = 0.8 by FT, and r = 0.78 by EF). In our study, measurement of global longitudinal LV strain using the new FT algorithm with CMR and echocardiography was comparable with measurements obtained by high-resolution STE. Compared with echocardiographic EF determination, FT-E GLS shows a better reproducibility and a better
Nourian, Saeed; Hosseinsabet, Ali; Jalali, Arash; Mohseni-Badalabadi, Reza
2017-01-01
Right ventricular myocardial infarction (RVMI) damages the systolic and diastolic functions of the RV, so the right atrium interacts with the RV with an acutely altered function. The aim of our study was to compare right atrial function as evaluated by 2D speckle-tracking echocardiography (2DSTE) between patients with inferior wall myocardial infarction (INFMI) and patients affected by both inferior myocardial infarction and right ventricular myocardial infarction (INFMI + RVMI). Our study recruited 70 consecutive patients with INFMI (43 patients without RVMI and 27 patients with RVMI). Right atrial function was evaluated by 2DSTE. Early diastolic strain, systolic strain rate, absolute value of early diastolic strain rate, expansion index, and diastolic emptying index of the right atrium were reduced in the patients with INFMI + RVMI compared to the patients with INFMI. The area under the curve for early diastolic strain for INFMI diagnosis was 0.682 (p value = 0.011, 95 % CI 0.550-0.815). Right atrial early diastolic longitudinal strain right atrial reservoir and conduit functions were impaired in the patients with INFMI + RVMI compared with the patients with INFMI.
Mehlenbacher, Randy D.; McDonough, Thomas J.; Grechko, Maksim; Wu, Meng-Yin; Arnold, Michael S.; Zanni, Martin T.
2015-04-01
Thin film networks of highly purified semiconducting carbon nanotubes (CNTs) are being explored for energy harvesting and optoelectronic devices because of their exceptional transport and optical properties. The nanotubes in these films are in close contact, which permits energy to flow through the films, although the pathways and mechanisms for energy transfer are largely unknown. Here we use a broadband continuum to collect femtosecond two-dimensional white-light spectra. The continuum spans 500 to 1,300 nm, resolving energy transfer between all combinations of bandgap (S1) and higher (S2) transitions. We observe ultrafast energy redistribution on the S2 states, non-Förster energy transfer on the S1 states and anti-correlated energy levels. The two-dimensional spectra reveal competing pathways for energy transfer, with S2 excitons taking routes depending on the bandgap separation, whereas S1 excitons relax independent of the bandgap. These observations provide a basis for understanding and ultimately controlling the photophysics of energy flow in CNT-based devices.
Kansal, Mayank M; Lester, Steven J; Surapaneni, Phani; Sengupta, Partho P; Appleton, Christopher P; Ommen, Steven R; Ressler, Steven W; Hurst, R Todd
2011-11-01
Distinguishing the pathologic hypertrophy of hypertrophic cardiomyopathy (HC) from the physiologic hypertrophy of professional football players (PFP) can be challenging when septal wall thickness falls within a "gray zone" between 12 and 16 mm. It was hypothesized that 2-dimensional and speckle-tracking strain (ε) echocardiography could differentiate the hearts of PFPs from those of patients with HC with similar wall thicknesses. Sixty-six subjects, including 28 professional American football players and 21 patients with HC, with septal wall thicknesses of 12 to 16 mm, along with 17 normal controls, were studied using 2-dimensional echocardiography. Echocardiographic parameters, including modified relative wall thickness (RWT; septal wall thickness + posterior wall thickness/left ventricular end-diastolic diameter) and early diastolic annular tissue velocity (e'), were measured. Two-dimensional ε was analyzed by speckle tracking to measure endocardial and epicardial longitudinal ε and circumferential ε and radial cardiac ε. Septal wall thickness was higher in patients with HC than in PFPs (14.7 ± 1.1 vs 12.9 ± 0.9 mm, respectively, p <0.001), while posterior wall thickness showed no difference. RWT was larger in patients with HC than in PFPs (0.68 ± 0.10 vs 0.48 ± 0.06, p <0.001). Longitudinal endocardial ε and radial cardiac ε were significantly higher in PFPs than in patients with HC, while circumferential endocardial ε was no different. RWT was the parameter that most accurately differentiated PFPs from patients with HC. An RWT cut point of 0.6 differentiated PFPs from patients with HC, with an area under the curve of 0.97. In conclusion, a 2-dimensional echocardiographic measure of RWT (septal wall + posterior wall thickness/left ventricular end-diastolic dimension) accurately differentiated PFPs' hearts from those of patients with HC when septal wall thickness was in the gray zone of 12 to 16 mm. Two-dimensional strain analysis identifies
Phelan, Dermot; Collier, Patrick; Thavendiranathan, Paaladinesh; Popović, Zoran B; Hanna, Mazen; Plana, Juan Carlos; Marwick, Thomas H; Thomas, James D
2012-10-01
The diagnosis of cardiac amyloidosis (CA) is challenging owing to vague symptomatology and non-specific echocardiographic findings. To describe regional patterns in longitudinal strain (LS) using two-dimensional speckle-tracking echocardiography in CA and to test the hypothesis that regional differences would help differentiate CA from other causes of increased left ventricular (LV) wall thickness. 55 consecutive patients with CA were compared with 30 control patients with LV hypertrophy (n=15 with hypertrophic cardiomyopathy, n=15 with aortic stenosis). A relative apical LS of 1.0, defined using the equation (average apical LS/(average basal LS + mid-LS)), was sensitive (93%) and specific (82%) in differentiating CA from controls (area under the curve 0.94). In a logistic regression multivariate analysis, relative apical LS was the only parameter predictive of CA (p=0.004). CA is characterised by regional variations in LS from base to apex. A relative 'apical sparing' pattern of LS is an easily recognisable, accurate and reproducible method of differentiating CA from other causes of LV hypertrophy.
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Anthony F. Yu
2016-01-01
Full Text Available Two-dimensional speckle tracking echocardiography (2DSTE provides a sensitive measure of left ventricular (LV systolic function and may aid in the diagnosis of cardiotoxicity. 2DSTE was performed in a cross-sectional study of 134 patients (mean age: 31.4±8.8 years; 55% male; mean time since diagnosis: 15.4±9.4 years previously treated with anthracyclines (mean cumulative dose: 320±124 mg/m2, with (n=52 or without (n=82 mediastinal radiotherapy. The prevalence of LV systolic dysfunction, defined as fractional shortening < 27%, LV ejection fraction (LVEF < 55%, and global longitudinal strain (GLS ≤ 16%, was 5.2%, 6.0%, and 23.1%, respectively. Abnormal GLS was observed in 24 (18% patients despite a normal LVEF. Indices of LV systolic function were similar regardless of anthracycline dose. However, GLS was worse (18.0 versus 19.0, p=0.003 and prevalence of abnormal GLS was higher (36.5% versus 14.6%, p=0.004 in patients treated with mediastinal radiotherapy. Mediastinal radiotherapy was associated with reduced GLS (p=0.040 after adjusting for sex, age, and cumulative anthracycline dose. In adult survivors of childhood, adolescent, and young adult cancer, 2DSTE frequently detects LV systolic dysfunction despite a normal LVEF and may be useful for the long-term cardiac surveillance of adult cancer survivors.
Dark States in the Light-Harvesting complex 2 Revealed by Two-dimensional Electronic Spectroscopy
Ferretti, Marco; Hendrikx, Ruud; Romero, Elisabet; Southall, June; Cogdell, Richard J.; Novoderezhkin, Vladimir I.; Scholes, Gregory D.; van Grondelle, Rienk
2016-02-01
Energy transfer and trapping in the light harvesting antennae of purple photosynthetic bacteria is an ultrafast process, which occurs with a quantum efficiency close to unity. However the mechanisms behind this process have not yet been fully understood. Recently it was proposed that low-lying energy dark states, such as charge transfer states and polaron pairs, play an important role in the dynamics and directionality of energy transfer. However, it is difficult to directly detect those states because of their small transition dipole moment and overlap with the B850/B870 exciton bands. Here we present a new experimental approach, which combines the selectivity of two-dimensional electronic spectroscopy with the availability of genetically modified light harvesting complexes, to reveal the presence of those dark states in both the genetically modified and the wild-type light harvesting 2 complexes of Rhodopseudomonas palustris. We suggest that Nature has used the unavoidable charge transfer processes that occur when LH pigments are concentrated to enhance and direct the flow of energy.
Dark States in the Light-Harvesting complex 2 Revealed by Two-dimensional Electronic Spectroscopy.
Ferretti, Marco; Hendrikx, Ruud; Romero, Elisabet; Southall, June; Cogdell, Richard J; Novoderezhkin, Vladimir I; Scholes, Gregory D; van Grondelle, Rienk
2016-02-09
Energy transfer and trapping in the light harvesting antennae of purple photosynthetic bacteria is an ultrafast process, which occurs with a quantum efficiency close to unity. However the mechanisms behind this process have not yet been fully understood. Recently it was proposed that low-lying energy dark states, such as charge transfer states and polaron pairs, play an important role in the dynamics and directionality of energy transfer. However, it is difficult to directly detect those states because of their small transition dipole moment and overlap with the B850/B870 exciton bands. Here we present a new experimental approach, which combines the selectivity of two-dimensional electronic spectroscopy with the availability of genetically modified light harvesting complexes, to reveal the presence of those dark states in both the genetically modified and the wild-type light harvesting 2 complexes of Rhodopseudomonas palustris. We suggest that Nature has used the unavoidable charge transfer processes that occur when LH pigments are concentrated to enhance and direct the flow of energy.
L. Feyz (Lida); B.M. van Dalen (Bas); M.L. Geleijnse (Marcel); N.M. van Mieghem (Nicolas); R.T. van Domburg (Ron); J. Daemen (Joost)
2017-01-01
markdownabstractBackground: Speckle tracking echocardiography (STE) is an echocardiography modality that is able to measure left ventricular (LV) characteristics, including rotation, strain and strain rate. Strain measures myocardial fibre contraction and relaxation. This study aims to assess the
Institute of Scientific and Technical Information of China (English)
Chee Khoon LIEW; Kui Hian SIM; Rapaee ANNUAR; Tiong Kiam ONG; Sze Piaw CHIN; Tobias Seyfarth; Yean Yip FONG; Wei Ling CHAN; Choon Kiat ANG; Houng Bang LIEW
2006-01-01
Objectives To compare left ventricular ejection fraction (LVEF) determined from 64-row multi-detector computed tomography (64-row MDCT) with those determined from two dimensional echocardiography (2D echo) and cardiac magnetic resonance imaging (CMR). Methods Thirty-two patients with coronary artery disease underwent trans-thoracic 2D echo, CMR and contrast-enhanced 64-row MDCT for assessment of LVEF within 48 hours of each other. 64-row MDCT LVEF was derived using the Syngo Circulation software; CMR LVEF was by Area Length Ejection Fraction (ALEF) and Simpson method and 2D echo LVEF by Simpson method.Results The LVEF was 49.13 ± 15.91% by 2D echo, 50.72 ± 16.55% (ALEF method) and 47.65 ± 16.58%(Simpson method) by CMR and 50.00 ± 15.93% by 64-row MDCT. LVEF measurements by 64-row MDCT correlated well with LVEF measured with CMR using either the ALEF method (Pearson correlation r = 0.94, P ＜0.01) or Simpson method (r = 0.92, P＜0.01). It also correlated well with LVEF measured using 2D echo (r = 0.80, P ＜ 0.01). Conclusion LVEF measurements by 64-row MDCT correlated well with LVEF measured by CMR and 2D echo. The correlation between 64-row MDCT and CMR was better than the correlation between 2D echo with CMR. Standard data set from a 64-row MDCT coronary study can be reliably used to calculate the LVEF.
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Yonghuai Wang
Full Text Available Coronary slow-flow phenomenon (CSFP is an angiographic diagnosis characterised by a low rate of flow of contrast agent in the normal or near-normal epicardial coronary arteries. Many of the patients with CSFP may experience recurrent acute coronary syndromes. However, current clinical practice tends to underestimate the impact of CSFP due to the yet unknown effect on the cardiac function. This study was performed to evaluate left ventricular (LV and right ventricular (RV diastolic and systolic functions, using two-dimensional (2D longitudinal strain and strain rate, in patients with CSFP, and to determine the relationships between the thrombolysis in myocardial infarction (TIMI frame count (TFC and LV and RV diastolic and systolic functions.Sixty-three patients with CSFP and 45 age- and sex-matched controls without CSFP were enrolled in the study. Diagnosis of CSFP was made by TFC. LV and RV diastolic and systolic functions were assessed by 2D speckle-tracking echocardiography.LV peak early diastolic longitudinal strain rate (LSRe was lower in patients with CSFP than in controls (P = 0.01. LV peak systolic longitudinal strain (LS and LV peak systolic longitudinal strain rate (LSRs were lower in patients with CSFP than in controls (P = 0.004 and P = 0.03, respectively. There was no difference in LV ejection fraction. RV peak early diastolic longitudinal strain rate (RSRe was lower in patients with CSFP than in controls (P = 0.03. There were no differences in RV peak systolic longitudinal strain (RS, RV peak systolic longitudinal strain rate (RSRs, or RV fractional area change among the groups. The mean TFC correlated negatively with LSRe and RSRe in patients with CSFP (r = -0.26, P = 0.04 and r = -0.32, P = 0.01, respectively.LV diastolic and systolic functions were impaired in patients with CSFP. CSFP also affected RV diastolic function, but not RV systolic function.
Li, Yuman; Xie, Mingxing; Wang, Xinfang; Lu, Qing; Zhang, Li; Ren, Pingping
2015-01-01
Early detection of right ventricular (RV) and left ventricular (LV) dysfunction in patients with repaired tetralogy of Fallot (TOF) is essential because dysfunction is correlated with a poor clinical outcome. The aim of this study was to assess RV and LV function in asymptomatic children with repaired TOF by two-dimensional ultrasound speckle tracking echocardiography (STE). Fifty-six asymptomatic children with a preserved biventricular ejection fraction (EF) after repair of TOF and 35 healthy control subjects were studied. RV and LV strain and strain rate were measured by STE. RVEF and pulmonary regurgitation (PR) were assessed using cardiac magnetic resonance imaging. Compared with the control subjects, RV regional longitudinal strain and strain rate and global longitudinal strain (GLS) and strain rate (GLSR) were impaired in children with repaired TOF. Likewise, LV circumferential and radial strain and strain rate were reduced in patients with TOF. In contrast, longitudinal strain and strain rate did not differ between the groups. RV and LV GLSR were correlated with postoperative follow-up period (r1 = -0.44; r2 = -0.48). RV GLS and GLSR were associated with RVEF (r1 = 0.64; r2 = 0.60) and PR (r1 = -0.48; r2 = -0.49). LV circumferential strain rate was related to PR (r = -0.45). STE can identify abnormalities that may represent early impairment of RV and LV systolic function in postoperative TOF patients with a preserved EF. PR is associated with decreased biventricular performance in repaired patients. STE-derived strain and strain rate may be useful indices for detecting the early deterioration of biventricular performance in patients with TOF. © 2014, Wiley Periodicals, Inc.
Georgievska-Ismail, Ljubica; Zafirovska, Planinka; Hristovski, Zarko
2016-11-01
To evaluate additional role of left atrial two-dimensional speckle tracking echocardiography in patients with diabetes mellitus type 2, 218 patients with heart failure with preserved left ventricular ejection fraction divided according to the presence of diabetes mellitus (108 with and 110 without) were enrolled in the study. Traditional parameters using two-dimensional echocardiography and Doppler imaging were measured as expressions of left ventricular diastolic function as well as peak atrial longitudinal strain and peak atrial contraction strain were measured using two-dimensional speckle tracking echocardiography. Global average peak atrial longitudinal strain and peak atrial contraction strain were significantly lower in patients with diabetes mellitus (p = 0.002 and p = 0.001, respectively) and its reduced values were significantly associated with higher prevalence of diabetes mellitus (p = 0.002 and p = 0.001, respectively), its greater severity (p = 0.002 and p = 0.016, respectively) and longer duration only for global average peak atrial longitudinal strain (p = 0.030). Multiple linear regression analysis demonstrated that the presence of diabetes mellitus appeared as independent predictor of reduced global peak atrial longitudinal strain [B = -2.173; 95% confidence interval: -3.870 to (-0.477); p = 0.012] as well of reduced global peak atrial contraction strain [B = -1.30; 95% confidence interval: -2.234 to (-0.366); p = 0.007]. Two-dimensional speckle tracking echocardiography appeared as a useful additional tool for detection of left atrial dysfunction in patients with heart failure who have preserved left ventricular ejection fraction and diabetes mellitus who are especially prone to develop cardiovascular complications. © The Author(s) 2016.
Marcus, K.A.; Korte, C.L. de; Feuth, T.; Thijssen, J.M.; Oort, A.M. van; Tanke, R.B.; Kapusta, L.
2012-01-01
BACKGROUND: The aim of this study was to investige serial changes of myocardial deformation using two-dimensional speckle-tracking echocardiographic (2DSTE) imaging in children undergoing balloon valvuloplasty for congenital valvular aortic stenosis (VAS). METHODS: Thirty-seven children with isolate
Revealing origin of quasi-one dimensional current transport in defect rich two dimensional materials
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Lotz, Mikkel R.; Boll, Mads; Bøggild, Peter; Petersen, Dirch H., E-mail: dirch.petersen@nanotech.dtu.dk [Center for Nanostructured Graphene (CNG), Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); Hansen, Ole [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); Danish National Research Foundation' s Center for Individual Nanoparticle Functionality (CINF), Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Kjær, Daniel [Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kgs. Lyngby (Denmark); CAPRES A/S, Scion-DTU, Building 373, DK-2800 Kgs. Lyngby (Denmark)
2014-08-04
The presence of defects in graphene have for a long time been recognized as a bottleneck for its utilization in electronic and mechanical devices. We recently showed that micro four-point probes may be used to evaluate if a graphene film is truly 2D or if defects in proximity of the probe will lead to a non-uniform current flow characteristic of lower dimensionality. In this work, simulations based on a finite element method together with a Monte Carlo approach are used to establish the transition from 2D to quasi-1D current transport, when applying a micro four-point probe to measure on 2D conductors with an increasing amount of line-shaped defects. Clear 2D and 1D signatures are observed at low and high defect densities, respectively, and current density plots reveal the presence of current channels or branches in defect configurations yielding 1D current transport. A strong correlation is found between the density filling factor and the simulation yield, the fraction of cases with 1D transport and the mean sheet conductance. The upper transition limit is shown to agree with the percolation threshold for sticks. Finally, the conductance of a square sample evaluated with macroscopic edge contacts is compared to the micro four-point probe conductance measurements and we find that the micro four-point probe tends to measure a slightly higher conductance in samples containing defects.
Feyz, Lida; van Dalen, Bas M; Geleijnse, Marcel L; Van Mieghem, Nicolas M; van Domburg, Ron T; Daemen, Joost
2017-05-11
Speckle tracking echocardiography (STE) is an echocardiography modality that is able to measure left ventricular (LV) characteristics, including rotation, strain and strain rate. Strain measures myocardial fibre contraction and relaxation. This study aims to assess the effect of renal sympathetic denervation (RDN) on functional myocardial parameters, including STE, and to identify potential differences between responders and non-responders. The study population consisted of 31 consecutive patients undergoing RDN in the context of treatment for resistant hypertension. Patients were included between December 2012 and June 2014. Transthoracic echocardiography and speckle tracking analysis was performed at baseline and at 6 months follow-up. The study population consisted of 31 patients with treatment-resistant hypertension treated with RDN (mean age 64 ± 10 years, 15 men). The total study population could be divided into responders (n = 19) and non-responders (n = 12) following RDN. RDN reduced office blood pressure by 18.9 ± 26.8/8.5 ± 13.5 mmHg (p < 0.001). A significant decrease was seen in LV posterior wall thickness (LVPWd) (0.47 ± 1.0 mm; p = 0.020), without a significant change in the LV mass index (LVMI). In the total cohort, only peak late diastolic filling velocity (A-wave velocity) decreased significantly by 5.3 ± 13.2 cm/s (p = 0.044) and peak untwisting velocity decreased significantly by 14.5 ± 28.9°/s (p = 0.025). RDN reduced blood pressure and significantly improved functional myocardial parameters such as A-wave velocity and peak untwisting velocity in patients with treatment-resistant hypertension, suggesting a potential beneficial effect of RDN on myocardial mechanics.
Directory of Open Access Journals (Sweden)
Elaheh Malakan Rad
2016-11-01
Full Text Available Background: The late postoperative course for children with transposition of the great arteries (TGA with an intact ventricular septum (IVS is very important because the coronary arteries may be at risk of damage during arterial switch operation (ASO. We sought to investigate left ventricular function in patients with TGA/IVS by echocardiography.Methods: From March 2011 to December 2012, totally 20 infants (12 males and 8 females with TGA/IVS were evaluated via 2-dimensional speckle-tracking echocardiography (2D STE more than 6 months after they underwent ASO. A control group of age-matched infants and children was also studied. Left ventricular longitudinal strain (S, strain rate (SR, time to peak systolic longitudinal strain (TPS, and time to peak systolic longitudinal strain rate (TPSR were measured and compared between the 2 groups.Results: Mean ± SD of age at the time of study in the patients with TGA/IVS was 15 ± 5 months, and also age at the time of ASO was 12 ± 3 days. Weight was 3.13 ± 0.07 kg at birth and 8.83 ± 1.57 kg at the time of ASO. Global strain (S, Time to peak strain rate (TPSR, and Time to peak strain (TPS were not significantly different between the 2 groups, whereas global strain rate (SR was significantly different (p value < 0.001. In the 3-chamber view, the values of S in the lateral, septal, inferior, and anteroseptal walls were significantly different between the 2 groups (p value < 0.001, and SR in the posterior wall was significantly different between the 2 groups (p value < 0.001. There were no positive correlations between S and SR in terms of the variables of heart rate, total cardiopulmonary bypass time, and aortic cross-clamp time. There were no statistically significant differences between the 2 groups regarding S, SR, TPS, and TPSR in the anteroseptal and posterior walls in the 3-chamber view and in the lateral and septal walls in the 4-chamber view. Conclusion: We showed that between 6 and 18 months
Isaaz, K; Cloez, J L; Danchin, N; Marçon, F; Worms, A M; Pernot, C
1985-09-15
Evaluation of the right ventricular (RV) outflow tract in congenital heart disease is extremely important for surgical management. Therefore, the value of 2-dimensional echocardiography (2-D echo) to assess the RV outflow tract was studied using a new approach: the subcostal elongated right oblique view. Twenty normal children and 49 children with congenital heart disease, aged 1 day to 11 years, were studied. Significant pulmonary infundibular obstruction was present in 22 patients with conotruncal malformations. To obtain the subcostal elongated right oblique view from the short-axis view at the aortic valve level, the transducer was slightly rotated clockwise with an anterior angulation of about 30 degrees so that the ascending aorta was seen in its long axis, providing an image similar to that obtained by a right ventriculogram in the elongated right anterior oblique view. The deviation of infundibular septum was appreciated by measurement of the angle alpha, defined by the long axis of the infundibular septum and the plane of aortic cusps. This view could be obtained in 64 patients (92%). In correlation with angiographic or anatomic data, the subcostal elongated right oblique view permitted recognition of several types of RV outflow tract: type I--normally formed RV outflow tract; type II--disorganized RV outflow tract with obstruction (alpha less than 90 degrees); type III and IV--disorganized RV outflow tract with obstruction (alpha greater than 90 degrees). This view could visualize the crista supraventricularis in type I, but also the anatomic components of RV outflow tract that may contribute to obstruction in the other types: infundibular septum, septoparietal trabeculations and trabecula septomarginalis.(ABSTRACT TRUNCATED AT 250 WORDS)
Liu, Y J; Leng, X P; Du, G Q; Wang, X D; Tian, J W; Ren, M
2015-02-01
The reperfusion injury that occurs in the early reperfusion often results in myocardial dysfunction. This study evaluated global and regional left ventricular (LV) function using speckle tracking echocardiography (STE) in a rabbit ischemia-reperfusion (I/R) model with and without ischemic postconditioning (I-PostC). The aim is to investigate the potential benefit of I-PostC for myocardial function and validate whether regional longitudinal strain is an appropriate index to indicate myocardial dysfunction. Forty rabbits were divided into an ischemia-reperfusion group (group I) and an I-PostC group (group II). After the coronary arteries were ligated, LV systolic strain and twist parameters decreased, and absolute value of strain rate of isovolumetric relaxation period (SRivr) and post-systolic strain index (PSI) increased significantly in both groups (all pstrain rate (SRsys), systolic strain (Ssys), LV twist and untwisting rate increased, and SRivr and PSI decreased in group II. These changes were not seen in group I. All STE parameters were correlated with area of necrosis (AN)/area at risk (AR) (all p0.8 or 0.6. The sensitivities of GSRsys, GSsys, SRsys, Ssys, and LV twist to detect the myocardial infarction were 81.3%, 62.5%, 87.5%, 93.8% and 81.3%, respectively. And the specificities of those parameters were 75.0%, 81.2%, 75.0%, 87.5% and 68.7%. These results indicate that STE is useful for quantitative detection on myocardial function improvement induced by I-PostC in a rabbit I/R model. The regional index-Ssys is an appropriate parameter to indicate myocardial dysfunction because of its sensitivity, specificity, and repeatability.
Binnetoğlu, Fatih Köksal; Babaoğlu, Kadir; Altun, Gürkan; Kayabey, Özlem
2014-01-01
Whether the hypertrophy found in the hearts of athletes is physiologic or a risk factor for the progression of pathologic hypertrophy remains controversial. The diastolic and systolic functions of athletes with left ventricular (LV) hypertrophy usually are normal when measured by conventional methods. More precise assessment of global and regional myocardial function may be possible using a newly developed two-dimensional (2D) strain echocardiographic method. This study evaluated the effects that different types of sports have on the hearts of children and adolescents and compared the results of 2D strain and strain-rate echocardiographic techniques with conventional methods. Athletes from clubs for five different sports (basketball, swimming, football, wrestling, and tennis) who had practiced regularly at least 3 h per week during at least the previous 2 years were included in the study. The control group consisted of sedentary children and adolescents with no known cardiac or systemic diseases (n = 25). The athletes were grouped according to the type of exercise: dynamic (football, tennis), static (wrestling), or static and dynamic (basketball, swimming). Shortening fraction and ejection fraction values were within normal limits for the athletes in all the sports disciplines. Across all 140 athletes, LV geometry was normal in 58 athletes (41.4 %), whereas 22 athletes (15.7 %) had concentric remodeling, 20 (14.3 %) had concentric hypertrophy, and 40 (28.6 %) had eccentric hypertrophy. Global LV longitudinal strain values obtained from the average of apical four-, two-, and three-chamber global strain values were significantly lower for the basketball players than for all the other groups (p < 0.001).
Directory of Open Access Journals (Sweden)
Cramer Maarten J
2008-05-01
Full Text Available Abstract Background Dyssynchrony of myocardial deformation is usually described in terms of variability only (e.g. standard deviations SD's. A description in terms of the spatio-temporal distribution pattern (vector-analysis of dyssynchrony or by indices estimating its impact by expressing dyscoordination of shortening in relation to the global ventricular shortening may be preferential. Strain echocardiography by speckle tracking is a new non-invasive, albeit 2-D imaging modality to study myocardial deformation. Methods A post-processing toolbox was designed to incorporate local, speckle tracking-derived deformation data into a 36 segment 3-D model of the left ventricle. Global left ventricular shortening, standard deviations and vectors of timing of shortening were calculated. The impact of dyssynchrony was estimated by comparing the end-systolic values with either early peak values only (early shortening reserve ESR or with all peak values (virtual shortening reserve VSR, and by the internal strain fraction (ISF expressing dyscoordination as the fraction of deformation lost internally due to simultaneous shortening and stretching. These dyssynchrony parameters were compared in 8 volunteers (NL, 8 patients with Wolff-Parkinson-White syndrome (WPW, and 7 patients before (LBBB and after cardiac resynchronization therapy (CRT. Results Dyssynchrony indices merely based on variability failed to detect differences between WPW and NL and failed to demonstrate the effect of CRT. Only the 3-D vector of onset of shortening could distinguish WPW from NL, while at peak shortening and by VSR, ESR and ISF no differences were found. All tested dyssynchrony parameters yielded higher values in LBBB compared to both NL and WPW. CRT reduced the spatial divergence of shortening (both vector magnitude and direction, and improved global ventricular shortening along with reductions in ESR and dyscoordination of shortening expressed by ISF. Conclusion Incorporation
Al-Kassou, Baravan; Tzikas, Apostolos; Stock, Friederike; Neikes, Fabian; Völz, Alexander; Omran, Heyder
2017-04-20
Correct sizing of a left atrial appendage (LAA) closure system is important to avoid redeployment of the device and peri-device leaks. The aims of this study were to assess the significance of two-dimensional transoesophageal echocardiography (2D-TEE), real-time 3D transoesophageal echocardiography (RT 3D-TEE) and angiography for measuring the size of the LAA landing zone and to determine the impact on sizing an LAA closure device. Furthermore, we investigated the relevance of volume loading on LAA size. In a prospective study, 46 patients underwent 2D-TEE and RT 3D-TEE 24 hours prior to LAA closure, at the beginning of the procedure and just before the procedure after volume loading with an average of 1,035±246 ml. Angiography was performed immediately before the implantation. Maximal diameter (2.2±0.4 versus 2.3±0.4 cm; pcorrelation (R) between measurements and LAA device size was found for RT 3D-TEE-derived perimeter (R=0.97) and area (R=0.96), whereas the maximal diameter (R=0.78) measured by 2D-TEE and angiography (R=0.76) correlated less closely. Sizing based on an RT 3D-TEE-measured perimeter resulted only in 4% of undersizing the implanted device. Peri-device leaks occurred in seven cases (15%) and were associated with a lower compression of LAA devices (7±1.3% versus 14±3.2% for patients without leaks, pcorrelation to LAA closure device size than 2D-TEE or angiographic measurements.
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章晨; 孙寅光; 朱佳; 黄洁; 王琳; 葛卫力; 唐礼江
2012-01-01
. 3,22. 5±6. 4( P < 0. 05), while that in circumferential direction respectively 20. 1 ± 7. 7, 23. 4 ± 8.1, 27. 1 ± 7. 1 ( P <0. 01), but radial motion was different, the absolute value of strain in three levels respectively was 40. 9±17. 4,41. 8±17. 6,28. 8±17.1 ( P <0. 01). The systolic strain rate in three directions was completely inconsistent, there was no obvious rule. There was a trend for early diastolic strain rate in three directions increasing from the base to the apex. The reproductivity test indicated the peak longitudinal strain was the best. Conclusion Cardiac mechanical movement is a very complicated process, two-dimensional strain echocardiography helps reveal the myocardial movement characteristics in physiological and pathological states.
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张梅青; 王秋霜; 黄党生; 张丽伟; 欧阳巧红; 王宇玫; 安秀芝
2013-01-01
目的 评价心肌梗死患者超声二维心肌应变的变化与心肌梗死范围的相关性.方法 选择71例急性心肌梗死患者,于心肌梗死后3～6个月行超声心动图和单光子发射计算机断层摄影(SPECT)检查,根据心肌梗死面积将患者分为A组28例(心肌梗死面积＜12%),B组43例(心肌梗死面积≥12%).所有患者行超声二维斑点追踪分析,测量心肌收缩期整体纵向应变(GLS)、收缩期整体径向应变(GRS)、收缩期整体圆周应变(GCS),对心肌应变与SPECT检测的左心室壁缺血坏死心肌的面积占左心室壁的百分比(Extent)进行相关分析,并应用ROC曲线评价3种心肌应变检测心肌梗死范围的价值.结果 B组的GLS、GCS及GRS均低于A组(P＜0.05).GLS、GCS与Extent均相关(r=0.721、r=0.504,P＜0.01),GLS、GCS及GRS的ROC曲线下面积分别为0.818、0.749、0.678,诊断心肌梗死面积≥12%对应的界值分别为-13.83%、-11.65%、26.64%,敏感性和特异性分别为72.7%、88.9%,63.6%、88.9%,81.8%、55.6%.结论 超声二维心肌应变的变化能够反映心肌梗死范围的改变,其中GLS能够较好地评价心肌梗死范围.%Objective To assess the relation between myocardial strain and infarction size detected by two-dimensional echocardiography in patients with myocardial infarction .Methods Seventy-one acute myocardial infarction patients ,who underwent echocardiography and single photon e-mission computed tomography (SPECT ) 3 -6 months after onset of the disease ,were divided into group A with its myocardial infarction size<12% (n=28)and group B with its myocardial infarction size≥l2% (n=43).Their cardiac global longitudinal strain (GLS ),global radial strain (GRS) and global circumference strain (GCS ) were detected by two-dimensional echocardiography and compared with the left ventricular ischemic size detected by SPECT .ROC curves were plotted for the GLS ,GCS and GRS .Results The incidence of GLS ,GCS and GRS was significantly
Bollinger, A. T.; Božović, I.
2016-10-01
Various electronic phases displayed by cuprates that exhibit high temperature superconductivity continue to attract much interest. We provide a short review of several experiments that we have performed aimed at investigating the superconducting state in these compounds. Measurements on single-phase films, bilayers, and superlattices all point to the conclusion that the high-temperature superconductivity (HTS) in these materials is an essentially quasi-two dimensional phenomenon. With proper control over the film growth, HTS can exist in a single copper oxide plane with the critical temperatures as high as that achieved in the bulk samples.
Gomes, Douglas Fabiano; Batista, Jesiane Stefania da Silva; Torres, Adalgisa Ribeiro; de Souza Andrade, Diva; Galli-Terasawa, Lygia Vitoria; Hungria, Mariangela
2012-03-01
Rhizobium tropici strain PRF 81 is used in commercial inoculants for common-bean crops in Brazil because of its high efficiency in nitrogen fixation and, as in other strains belonging to this species, its tolerance of environmental stresses, representing a useful biological alternative to chemical nitrogen fertilizers. In this study, a proteomic reference map of PRF 81 was obtained by two-dimensional gel electrophoresis and MALDI-TOF/TOF-TOF mass spectrometry. In total, 115 spots representing 109 different proteins were successfully identified, contributing to a better understanding of the rhizobia-legume symbiosis and supporting, at proteomics level, a strong resemblance with agrobacteria.
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张梅青; 王秋霜; 黄党生; 安秀芝; 姬冬冬; 王淑华; 郭家瑞
2011-01-01
目的:探讨应用超声二维斑点追踪技术(STI)定量评价尿毒症患者心肌功能的价值.方法:尿毒症组(n=45)和健康对照组(n=38)分别行超声心动图,据左室射血分数(LVEF)将尿毒症组分为心功能正常组(n=29,LVEF≥50%)和心功能减退组(n=16,LVEFG50%),应用STI技术测量左室心肌各节段收缩期峰值应变,并计算出心肌整体纵向应变(LS)、径向应变(RS)及圆周应变(CS).结果:与健康对照组相比,心功能正常组及心功能减退组室间隔、左室后壁明显增厚,左房内径增大(P＜0.01);心肌应变比较,心功能正常组与健康对照组相比,心肌整体LS、CS均明显减低(P<0.01).心功能减退组较心功能正常组应变进一步降低(P＜0.05).结论:超声二维纵向、径向及圆周应变能够早期准确评价尿毒症患者心肌功能,其中纵向、径向应变较LVEF更早的发现心肌功能的减低.%Objective: To evaluate the accuracy and value of the two-dimensional speckle tracking imaging Echocardiography (STI) quantirative measurement of global systolic function in cardiac patients with uremia. Methods: Rourine parameters were determined by echocardiography in 45 uremic patients and 38 healthy controls. According to the left ejection fraction (LVEF) , the uremic group was divided into normal cardiac uremia group (n= 29 , LVEF ≥50％ ) and cardiac dysfunction group (n= 16, LVEF ＜50％). We measured left ventricular myocardial sections of peak systolic strain by STI.and calculated the cardiac global longitudinal strain, radial strain and circumferential strain. Results: Compared with healthy control group, ventricular wall thickness, left atrium diameter were significantly different in Normal cardiac group and cardiac dysfunction group; Compared with healthy control group, the global longitudinal myocardial strain, circumferential strain were significantly lower ( P ＜0.01) , cardiac dysfunction group compared with normal cardiac function
Institute of Scientific and Technical Information of China (English)
卢岷; 王志刚; 冉海涛; 曹小玲; 张群霞; 孙幼屏; 李宜蓁
2011-01-01
目的 探讨二维应变技术联合负荷超声评价犬急性心肌缺血再灌注模型存活心肌的应用价值.方法 24只健康杂种犬,阻断其左冠状动脉前降支90 min后再灌注120 min.运用二维斑点追踪显像(speckle tracking imaging,SRI)分别检测静息状态、再灌注状态和小剂量多巴酚丁胺负荷状态下左室前壁、前间壁各节段收缩期峰值纵向应变(peak-systolic longitudinal strain,SLpeak)、径向应变(peak-systolic radial strain,SRpeak)、圆周应变(peak-systolic circumferential strain,SCpeak).以用氯化三苯基四氮唑(2,3,5-triphenyltetrazoliumchloride,TTC)和伊文思蓝(Evans blue,EB)染色结果为标准,将前壁、前间隔各节段分为存活节段组和非存活节段组.结果 (1)基础状态下,存活节段组和非存活节段组之间SLpeak、SRpeak、SCpeak无显著性差异(P＞0.05)；(2)再灌注后,存活组和非存活组SLpeak、SRpeak、SCpeak均降低,但两组比较无显著性差异(P＞0.05);(3)与负荷试验前比较,多巴酚丁胺负荷后存活节段组SLpeak、SRpeak、SCpeak显著性增加(P＜0.05),非存活节段组各指标无明显变化(P＞0.05)；存活节段组与非存活节段组比较有显著性差异(P＜0.05).结论 小剂量多巴酚丁胺负荷超声联合二维应变可准确评价心肌存活性.%Objective To evaluate the myocardial viability by two-dimensional strain combined with low dose dobutamine stress echocardiography. Methods In twenty four anesthetized mongrel dogs, the left anterior descending artery was occluded for 90 min followed by 120 min reperfusion. Two-dimensional strain of anterior wall and anterior septum, include peak systolic longitudinal strain (Slpeak), circumferential strain (Scpeak) and radial strain (Srpeak), were measured at baseline, after reperfusion and dobutamine stress. To assess viable or nonviable myocardium, triph-enyl tetrazolium chloride (TTC) and Evans blue staining were applied. Results During baseline
Jun, Sunhong; Yang, Cheolhee; Kim, Tae Wu; Isaji, Megumi; Tamiaki, Hitoshi; Ihee, Hyotcherl; Kim, Jeongho
2015-07-21
Chlorosomes are the largest light harvesting complexes in nature and consist of many bacteriochlorophyll pigments forming self-assembled J-aggregates. In this work, we use two-dimensional electronic spectroscopy (2D-ES) to investigate ultrafast dynamics of excitation energy transfer (EET) in chlorosomes and their temperature dependence. From time evolution of the measured 2D electronic spectra of chlorosomes, we directly map out the distribution of the EET rate among the manifold of exciton states in a 2D energy space. In particular, it is found that the EET rate varies gradually depending on the energies of energy-donor and energy-acceptor states. In addition, from comparative 2D-ES measurements at 77 K and room temperature, we show that the EET rate exhibits subtle dependence on both the exciton energy and temperature, demonstrating the effect of thermal excitation on the EET rate. This observation suggests that active thermal excitation at room temperature prevents the excitation trapping at low-energy states and thus promotes efficient exciton diffusion in chlorosomes at ambient temperature.
Institute of Scientific and Technical Information of China (English)
程蕾蕾; 赵维鹏; 潘翠珍; 丁文军; 王春生; 舒先红
2011-01-01
IntroductionAorto-left ventricular tunnel(ALVT)is an extrenle rare(0.001%)congenital para-valvular conmmnication between aorta and the left ventricle.It was first reported by Edwards and his colleagues in 1961[ 1].Only about 100 cases have been reported until now.We re port Out"first ease of ALVT with infective endocarditis demonstrated by two-dimensional and three-dimensional echocardiography and confirmed by surgery.%@@ IntroductionAorto-left ventricular tunnel ( ALVT) is an extreme rare (0.001% ) congenital para-valvular communication between aorta and the left ventricle.It was first reported by Edwards and his colleagues in 1961[1].Only about 100 cases have been reported until now.We report our first case of ALVT with infective endocarditis demonstrated by two-dimensional and three-dimensional echocardiography and confirmed by surgery.
Ostroumov, Evgeny E; Mulvaney, Rachel M; Anna, Jessica M; Cogdell, Richard J; Scholes, Gregory D
2013-09-26
Excited state dynamics in LH2 complexes of two purple bacterial species were studied by broad-band two-dimensional electronic spectroscopy. The optical response was measured in the 500-600 nm spectral region on the 0-400 fs time scale. Global target analysis of two-dimensional (2D) transient spectra revealed the main energy transfer pathways between carotenoid S2, 1Bu(-) and S1 states and bacteriochlorophyll Qx state. Global analysis ascertained the evolutionary and vibration-associated spectra, which also indicated the presence of a higher-lying vibrational level in the carotenoid S1 state. The estimation of the spectral overlap between the 1Bu(-) state and the Qx state indicated a significant contribution of the 1Bu(-) state to the overall S2-to-Qx excitation energy transfer.
Trevisan-Silva, Dilza; Bednaski, Aline Viana; Gremski, Luiza Helena; Chaim, Olga Meiri; Veiga, Silvio Sanches; Senff-Ribeiro, Andrea
2013-12-15
Loxosceles bites have been associated with characteristic dermonecrotic lesions with gravitational spreading and systemic manifestations. Venom primarily comprises peptides and protein molecules (5-40 kDa) with multiple biological activities. Although poorly studied, metalloproteases have been identified in venoms of several Loxosceles species, presenting proteolytic effects on extracellular matrix components. The characterization of an Astacin-like protease (LALP) in Loxosceles intermedia venom was the first report of an Astacin family member as a component of animal venom. Recently, these proteases were described as a gene family in L. intermedia, Loxosceles laeta and Loxosceles gaucho. Herein, the whole venom complexity of these three Loxosceles species was analyzed using two-dimensional electrophoresis (2DE). Subproteomes of LALPs were explored through 2DE immunostaining using anti-LALP1 antibodies and 2DE gelatin zymogram. Proteins presented molecular masses ranging from 24 to 29 kDa and the majority of these molecules had basic or neutral isoelectric points (6.89-9.93). Likewise, the measurement of gelatinolytic effects of Loxosceles venom using fluorescein-gelatin showed that the three venoms have distinct proteolytic activities. The metalloprotease fibrinogenolytic activities were also evaluated. All venoms showed fibrinogenolytic activity with different proteolytic effects on Aα and Bβ chains of fibrinogen. The results reported herein suggest that the LALP family is larger than indicated in previously published data and that the complex profile of the gelatinolytic activity reflects their relevance in loxoscelism. Furthermore, our investigation implicates the brown spider venom as a source of Astacin-like proteases for use in loxoscelism studies, cell biology research and biotechnological applications.
Wardlaw, G. D.; Reddy, C. M.; Nelson, R. K.; Valentine, D. L.
2008-12-01
In 2003 the National Research Council reported more than 380 million gallons of oil is emitted into the ocean each year from natural seepage and as a result of anthropogenic activities. Many of the hydrocarbons making up this oil are persistent and toxic to marine life. Petroleum emitted into biologically sensitive areas can lead to environmental stress and ecosystem collapse. As a result many studies and a substantial amount of resources have been devoted to creating efficient and effective remediation tools and developing a better understanding of natural hydrocarbon weathering processes occurring in marine environments. The goal of this study is to elucidate patterns and extent of aerobic hydrocarbon degradation in marine sediments. In order to assess the specific molecular transformations occurring in petroleum emitted into oxic marine environments, we prepared microcosm experiments using sediments and seawater collected from the natural oil seeps offshore Coal Oil Point, California. Petroleum recovered from Platform Holly in the Santa Barbara Channel, was added to a sediment-seawater mixture and the microcosm bottles were allowed to incubate under aerobic conditions for slightly more than 100 days. Comprehensive, two-dimensional gas chromatography was employed in this study to quantify changes in the concentrations of individual hydrocarbon compounds because of the increased resolution and resolving power provided with this robust analytical method. We show significant hydrocarbon mass loss due to aerobic biodegradation for hundreds of tracked compounds in the microcosm bottles. The results shown here provide quantitative evidence for broad-scale metabolic specificity during aerobic hydrocarbon degradation in surface and shallow subsurface marine sediments.
Institute of Scientific and Technical Information of China (English)
冉红; 张平洋; 方玲玲; 马小五; 吴文芳; 冯王飞
2013-01-01
Objective Rcgional lcft vcntricular (LV) function could be detected by measuring peak-systolic strain by speckle tracking imaging (STI).We evaluated the value of STI combined with adenosine stress echocardiography on assessing myocardial viability in patients with myocardial infarction (MI).Methods Two dimensional echocardiography was performed at rest and after adenosine stress echocardiography (infused at 140 μg · kg-1 · min-1 over a period of 6 min) in 39 stable patients with previous MI.Peak-systolic (Speak-sys) circumferential strain,radial strain and longitudinal strain were assessed by STI.Radionuclide myocardial perfusion/metabolic imaging served as the “gold standard” to detection of myocardial viability.Results (1) There were 215 viable and 153 non-viable regions among 368abnormal motion segments out of 624 segments in 39 MI patients according to radionuclide imaging results.(2) Speak-sys was similar between viable and nonviable myocardium at rest (all P ＞ 0.05).After adenosine infusion,radial Speak-sys [(37.98 ± 5.45) ％ vs.(30.22 ± 5.47) ％],longitudinal Speak-sys [(-23.71 ±4.53) ％ vs.(-17.52 ± 4.34) ％] increased significantly (P ＜ 0.05) in viable segments compared to baseline levels and were significantly higher than in nonviable segments radial Speak-sys [(37.98 ± 5.45) ％vs.(30.12±5.37)％] and longitudinal Speak-sys[(-23.71 ±4.53)％ vs.(-16.95±4.62)％](P＜0.05),while remained unchanged in nonviable segments before and after adenosine infusion.Circumferential Speak-sys was similar before and after adenosine infusion in both viable and nonviable segments (all P ＞ 0.05).(3) Delta radial strain change ＞ 9.8％ has a sensitivity of 82.3％ and a specificity of 81.1％ whereas a delta change of longitudinal strain ＞ 16.5％ has a sensitivity of 83.5％ and a specificity of 92.3％ for detecting viable segments.Conclusions Speckle tracking imaging combined with adenosine stress echocardiography could serve as a new and
Clinical Stress Echocardiography
S.E. Karagiannis
2007-01-01
textabstractTwo-dimensional echocardiography is a commonly used non-invasive method for the assessment of left ventricular function. It provides precise information on both global and segmental myocardial function by displaying endocardial motion and wall thickening. Dobutamine stress
Moran, Sean D; Woys, Ann Marie; Buchanan, Lauren E; Bixby, Eli; Decatur, Sean M; Zanni, Martin T
2012-02-28
The structural eye lens protein γD-crystallin is a major component of cataracts, but its conformation when aggregated is unknown. Using expressed protein ligation, we uniformly (13)C labeled one of the two Greek key domains so that they are individually resolved in two-dimensional (2D) IR spectra for structural and kinetic analysis. Upon acid-induced amyloid fibril formation, the 2D IR spectra reveal that the C-terminal domain forms amyloid β-sheets, whereas the N-terminal domain becomes extremely disordered but lies in close proximity to the β-sheets. Two-dimensional IR kinetics experiments show that fibril nucleation and extension occur exclusively in the C-terminal domain. These results are unexpected because the N-terminal domain is less stable in the monomer form. Isotope dilution experiments reveal that each C-terminal domain contributes two or fewer adjacent β-strands to each β-sheet. From these observations, we propose an initial structural model for γD-crystallin amyloid fibrils. Because only 1 μg of protein is required for a 2D IR spectrum, even poorly expressing proteins can be studied under many conditions using this approach. Thus, we believe that 2D IR and protein ligation will be useful for structural and kinetic studies of many protein systems for which IR spectroscopy can be straightforwardly applied, such as membrane and amyloidogenic proteins.
Two dimensional echocardiographic detection of intraatrial masses.
DePace, N L; Soulen, R L; Kotler, M N; Mintz, G S
1981-11-01
With two dimensional echocardiography, a left atrial mass was detected in 19 patients. Of these, 10 patients with rheumatic mitral stenosis had a left atrial thrombus. The distinctive two dimensional echocardiographic features of left atrial thrombus included a mass of irregular nonmobile laminated echos within an enlarged atrial cavity, usually with a broad base of attachment to the posterior left atrial wall. Seven patients had a left atrial myxoma. Usually, the myxoma appeared as a mottled ovoid, sharply demarcated mobile mass attached to the interatrial septum. One patient had a right atrial angiosarcoma that appeared as a nonmobile mass extending from the inferior vena caval-right atrial junction into the right atrial cavity. One patient had a left atrial leiomyosarcoma producing a highly mobile mass attached to the lateral wall of the left atrium. M mode echocardiography detected six of the seven myxomas, one thrombus and neither of the other tumors. Thus, two dimensional echocardiography appears to be the technique of choice in the detection, localization and differentiation of intraatrial masses.
Foist, Rod B; Schulze, H Georg; Ivanov, Andre; Turner, Robin F B
2011-05-01
Two-dimensional correlation spectroscopy (2D-COS) is a powerful spectral analysis technique widely used in many fields of spectroscopy because it can reveal spectral information in complex systems that is not readily evident in the original spectral data alone. However, noise may severely distort the information and thus limit the technique's usefulness. Consequently, noise reduction is often performed before implementing 2D-COS. In general, this is implemented using one-dimensional (1D) methods applied to the individual input spectra, but, because 2D-COS is based on sets of successive spectra and produces 2D outputs, there is also scope for the utilization of 2D noise-reduction methods. Furthermore, 2D noise reduction can be applied either to the original set of spectra before performing 2D-COS ("pretreatment") or on the 2D-COS output ("post-treatment"). Very little work has been done on post-treatment; hence, the relative advantages of these two approaches are unclear. In this work we compare the noise-reduction performance on 2D-COS of pretreatment and post-treatment using 1D (wavelets) and 2D algorithms (wavelets, matrix maximum entropy). The 2D methods generally outperformed the 1D method in pretreatment noise reduction. 2D post-treatment in some cases was superior to pretreatment and, unexpectedly, also provided correlation coefficient maps that were similar to 2D correlation spectroscopy maps but with apparent better contrast.
Gibbs, Holly C.; Sing, Garwin; Armas, Juan Carlos González; Campbell, Colin J.; Ghazal, Peter; Yeh, Alvin T.
2013-03-01
The mechanisms that enable viruses to harness cellular machinery for their own survival are primarily studied in cell lines cultured in two-dimensional (2-D) environments. However, there are increasing reports of biological differences between cells cultured in 2-D versus three-dimensional (3-D) environments. Here we report differences in host-virus interactions based on differences in culture environment. Using ultrashort pulse microscopy (UPM), a form of two-photon microscopy that utilizes sub-10-fs pulses to efficiently excite fluorophores, we have shown that de novo development of extra-chromosomal virus replication compartments (VRCs) upon murine cytomegalovirus (mCMV) infection is markedly enhanced when host cells are cultured in 3-D collagen gels versus 2-D monolayers. In addition, time-lapse imaging revealed that mCMV-induced VRCs have the capacity to grow by coalescence. This work supports the future potential of 3-D culture as a useful bridge between traditional monolayer cultures and animal models to study host-virus interactions in a more physiologically relevant environment for the development of effective anti-viral therapeutics. These advances will require broader adoption of modalities, such as UPM, to image deep within scattering tissues.
Ruiz, Marcia T; Nichols, Amanda; Price, Gerald B; Zannis-Hadjopoulos, Maria
2002-08-01
Ors-binding activity (OBA) has been previously purified by its ability to specifically interact with A3/4, a 36-bp mammalian origin consensus sequence [1]. Peptide sequence analyses identified OBA as Ku86, the largest subunit of Ku antigen, a heterodimeric protein (Ku70/Ku86) involved in several autoimmune disorders [2-5]. The affinity-purified fraction containing OBA/Ku is also enriched for DNA-dependent protein kinase DNA-PKcs, the catalytic subunit of the DNA-PK holoenzyme, of which Ku antigen is the DNA-binding subunit [6-8]. Glycerol-gradient sedimentation analyses have demonstrated the presence of OBA/Ku in a high-molecular-weight complex. In order to investigate whether OBA/Ku and DNA-PKcs are associated in this fraction, we have used a modification of the two-dimensional gel electrophoresis technique originally described [9]. Electromobility shift assays were developed in native capillary gels, which were subsequently used for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in the second dimension. The gels were then processed for Western blotting using the Ku70, Ku86 and DNA-PKcs antibodies. This approach has revealed the association of OBA/Ku and DNA-PKcs to give rise to the DNA-PK holoenzyme irrespective of the presence, or the absence of DNA. Altogether, we have proven the utility of this technique for the study of protein-protein and protein-DNA interactions.
Hoffmann, Rainer; Altiok, Ertunc; Friedman, Zvi; Becker, Michael; Frick, Michael
2014-10-01
Myocardial deformation analysis by speckle-tracking echocardiography (STE) has been used for analysis of myocardial viability and myocardial fibrosis. Patients with severe aortic stenosis are known to develop myocardial fibrosis. This study evaluated the association between myocardial fibrosis determined by late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) and 2-dimensional STE in patients with severe aortic stenosis. In 30 patients (78±7 years) with severe aortic stenosis (mean gradient 53±21 mm Hg), peak systolic circumferential strain based on 2-dimensional echocardiographic parasternal short-axis views and peak systolic longitudinal strain based on apical views were determined for analysis of regional function. LGE CMR was performed to define the amount of fibrosis in each segment within 24 hours of echocardiography. Relative amount of fibrosis was determined based on LGE CMR as gray-scale threshold 6 SDs above the mean signal intensity of the normal remote myocardium. There was a decrease in LGE from base to apex (14.4±8.7% for basal segments, 3.4±3.0% for midventricular segments, and 2.1±3.0% for apical segments; pmyocardial deformation expressed as peak systolic longitudinal strain from base to apex (-11.6±7.0% for basal segments, -16.9±6.5% for midventricular segments, and -17.4±7.7% for apical segments; p=0.001). There was a negative correlation between the amount of myocardial fibrosis determined by LGE CMR and peak systolic longitudinal strain for the total left ventricle (r=-0.538, p=0.007). Myocardial fibrosis defined as LGE>10% could be identified by peak systolic longitudinal strain less than -11.6%, with a sensitivity of 65% and a specificity of 75% (area under the receiver operating characteristic curve 0.69). In conclusion, myocardial fibrosis increases from apical to basal left ventricular segments in patients with severe aortic stenosis. There is an association between severity of myocardial fibrosis defined by LGE CMR
Osserman, Robert
2011-01-01
The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o
Juday, Richard D. (Inventor)
1992-01-01
A two-dimensional vernier scale is disclosed utilizing a cartesian grid on one plate member with a polar grid on an overlying transparent plate member. The polar grid has multiple concentric circles at a fractional spacing of the spacing of the cartesian grid lines. By locating the center of the polar grid on a location on the cartesian grid, interpolation can be made of both the X and Y fractional relationship to the cartesian grid by noting which circles coincide with a cartesian grid line for the X and Y direction.
Clinical Stress Echocardiography
S.E. Karagiannis
2007-01-01
textabstractTwo-dimensional echocardiography is a commonly used non-invasive method for the assessment of left ventricular function. It provides precise information on both global and segmental myocardial function by displaying endocardial motion and wall thickening. Dobutamine stress echocardiograp
Directory of Open Access Journals (Sweden)
Matheus M. Mantovani
2012-12-01
Full Text Available The measurement of cardiovascular features of wild animals is important, as is the measurement in pets, for the assessment of myocardial function and the early detection of cardiac abnormalities, which could progress to heart failure. Speckle tracking echocardiography (2D STE is a new tool that has been used in veterinary medicine, which demonstrates several advantages, such as angle independence and the possibility to provide the early diagnosis of myocardial alterations. The aim of this study was to evaluate the left myocardial function in a maned wolf by 2D STE. Thus, the longitudinal, circumferential and radial strain and strain rate were obtained, as well as, the radial and longitudinal velocity and displacement values, from the right parasternal long axis four-chamber view, the left parasternal apical four chamber view and the parasternal short axis at the level of the papillary muscles. The results of the longitudinal variables were -13.52±7.88, -1.60±1.05, 4.34±2.52 and 3.86±3.04 for strain (%, strain rate (1/s, displacement (mm and velocity (cm/s, respectively. In addition, the radial and circumferential Strain and Strain rate were 24.39±14.23, 1.86±0.95 and -13.69±6.53, -1.01±0.48, respectively. Thus, the present study provides the first data regarding the use of this tool in maned wolves, allowing a more complete quantification of myocardial function in this species.A obtenção de parâmetros cardiovasculares em animais selvagens são importantes de serem avaliados, assim como em animais de companhia, para a obtenção da função miocárdica e determinação precoce de alterações cardíacas que poderiam evoluir para insuficiência cardíaca . A ecocardiografia speckle tracking (2D STE é uma ferramenta nova que tem sido utilizada em medicina veterinária, a qual tem demonstrado várias vantagens quanto ao seu uso, como a independência do ângulo de insonação e a possibilidade de se obter o diagnóstico precoce de altera
Institute of Scientific and Technical Information of China (English)
王健; 康春松; 董建红; 薛继平
2009-01-01
Objective To probe into the value of the evaluation of left ventricular myocardial function by two dimensional strain(2DS) for coronary artery disease(CAD) patients with different degrees of left anterior descending(LAD) branch stenosis. Methods Fifty-five eases without myocardial infarction among a total of 72 patients with CAD were divided in to 3 groups based on the extent of LAD stenosis,that was group A(stenosis75%, n = 12). Another 17 eases of CAD with myocardial infarction were selected as group D. Strain and strain rate of the whole 11 segments that blood supplied by LAD of all cases were measured with 2DS. Results The 2DS ultrasound showed that the peak strain(S), the peak systolic strain rate(SRs) and the peak early diastolic strain rate (SRE) in all the 11 segments of group A were high and sharp. The above mentioned parameters of group B decreased compared with that of group A, however, there was no statistical significant difference (P >0.05). The S, SRs and SRE of group C cases decreased in some segments compared with that of group A and group B (P0.05). While in group D cases, the SRA decreased markedly. The SRE/SRA was more than 1 in group A. However, in group B, C and D cases, the SRE/SRA were all less than 1. Conclusions 2DS can sensitively reflect the decrease of regional myocardial systolic and diastolic function caused by the reduction of perfusion,and it may be beneficial to find myocardial ischemia for patients as early as possible.%目的 探讨二维应变成像评价冠心病患者左前降支(LAD)不同程度狭窄时局部心功能改变的价值.方法 72例冠心病患者中非心肌梗死患者55例,根据LAD狭窄程度分组:A组(狭窄75%)12例;17例心肌梗死患者为D组.应用二维应变成像检测LAD参与供血的11个节段应变和应变率参数的变化.结果 A组各节段峰值应变(S)、收缩期峰值应变率(SRS)与舒张早期峰值应变牢(SRE)较高尖.B组与A组比较有所下降,
Two-dimensional optical spectroscopy
Cho, Minhaeng
2009-01-01
Discusses the principles and applications of two-dimensional vibrational and optical spectroscopy techniques. This book provides an account of basic theory required for an understanding of two-dimensional vibrational and electronic spectroscopy.
Institute of Scientific and Technical Information of China (English)
王玉静; 何燕萍; 叶季鲜; 谢晓莉
2012-01-01
Objective: To assess the short-term efficacy of cardiac resynchronization therapy (CRT) using two-dimensional strain echocardiography in patients with chronic heart failure (CHF). Methods: A total of 31 CHF patients treated with CRT were enrolled in this study. Left ventricular end-diastolic diameter (LVEDD),left ventricular end-systolic diameter (LVESD) and left ventricular ejection fraction(LVEF) were measured two weeks before and three months after CRT. Radial strain (RS) peak,circumferential strain (CS) peak and longitudinal systolic strain (LS) peak of 16 left ventricular segments were measured using two-dimensional echocardiography. Results: LVEF,LVEDD,LVESD,RS peak,CS peak,LS peak were improved after CRT. CRT increased LVEF,decreased LVEDD and LVESD. CRT also shortened LS peak after three months (P<0. 05). Cardiac resynchronization was achieved after CRT. Conclusions: CRT can significantly improve the cardiac function in patients with CHF. Two-dimensional strain echocardiography can provide unique quantitative information for assessing the short-term outcome of CRT.%目的:应用二维应变超声心动图评价慢性心力衰竭(chronic heart failure,CHF)患者在安装三腔起搏器进行左室再同步化治疗(cardiac resynchronization therapy,CRT)后的短期疗效.方法:选择行植入CRT的患者31例,分别在CRT术前、术后2周及术后3个月测量左室射血分数(left ventricular ejection fraction,LVEF)、左室舒张末内径(left ventricular end-diastolic diameter,LVEDD)、左室收缩末内径(left ventricular end-systolic diameter,LVESD),应用二维应变成像技术分析左室壁16个节段的径向应变(radial strain,RS)峰值、环向应变(circumferential strain,CS)峰值及纵向收缩期(longitudinal systolic strain,LS)峰值.结果:与术前相比,术后2周及术后3个月的LVEDD、LVESD和LVEF及左室壁16个节段的RS峰值、CS峰值和LS峰值均有不同程度改善.术后2周与术后3
Institute of Scientific and Technical Information of China (English)
肖蕾; 王玲; 闻小林; 崔亚云
2013-01-01
目的探讨二维超声心动图联合时间-空间关联成像(STIC)技术在胎儿先天性心脏病(CHD)筛查中的应用价值。方法采用多切面顺序扫查法对11036例胎儿进行心脏检查,部分胎儿进行STIC技术容积数据库采集及脱机分析,CHD胎儿引产后进行尸体解剖或出生后随访结果对照。结果单纯二维超声心动图筛查出176例胎儿先天性心脏大血管结构异常(不包括心律失常),其中97例在二维超声基础上进行 STIC 技术检查,92例两种方法检查结果一致(其中1例合并心内畸形漏诊)；检出的CHD胎儿中,87例记录二维筛查时间,平均每个胎儿心脏用时(9.68±2.13) min,79例记录STIC技术扫描时间,平均每次STIC扫描用时(7.76±2.42)min；不同孕周二维超声心动图与STIC技术各重要切面显示合格率差异无统计学意义。结论STIC技术可作为二维超声心动图的有效补充手段,二者联合可进一步提高胎儿CHD的产前诊断率。%Objective To explore the application value of two-dimensional echocardiography with spatio-temporal im-age correlation (STIC) in fetal congenital heart disease (CHD) prenatal ultrasonography. Methods 11 036 hearts of fetus were inspected by severalviews order scanning method and for STIC volume database acquisition and off-line a-nalysis congenital heart disease fetus for autopsy after induced labor or contrast the follow-up results after birth. Re-sults 97 cases with spatio-temp-oral image correlation in 176 cases congenital heart and great vessels exception (dysrhythmias not including) with simple two-dimensional echocardiography,92 cases were accordant (one case with incorporative intracardiac malformation missed diagnosis);in screened congenital heart disease fetus,STIC (n=79) and routine ultrasonography (n=87) took (7.76±2.42) min and (9.68±2.13) min per case,respectively;in dif-ferent gestational weeks,the quality of the images derived from volume datasets were comparable to
Takahashi, Kei; Kabashima, Fumie; Tsuchiya, Fumihiko
2016-03-01
Japanese sake is a traditional alcoholic beverage composed of a wide variety of metabolites, which give it many types of tastes and flavors. Previously, we have reported that medium-chain fatty acids contribute to a fatty odor in sake (Takahashi, K., et al., J. Agric. Food Chem., 62, 8478-8485, 2014). In this study, we have reanalyzed the data obtained using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. The relationship between the chemical components in sake and specific organoleptic properties such as off-flavor and quality has been explored. This led to the identification of the type of chemical compounds present and an assessment of the numerous candidate compounds that correlate with such organoleptic properties in sake. This research provides important fundamental knowledge for the sake-brewing industry. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.
Institute of Scientific and Technical Information of China (English)
黄冬梅; 夏稻子; 张宇虹; 礼广森; 崔洪岩
2011-01-01
目的 应用超声二维纵向应变探讨心绞痛患者冠状动脉介入治疗术(PCI)前后左心室心肌收缩功能改变情况.方法 32例心绞痛(左前降支病变)患者和30例正常人(对照组),分别记录PCI术前、术后3个月和正常人心尖四腔切面,二腔切面,左心室长轴高帧频图像,应用二维应变软件测量各个节段的收缩期峰值纵向应变值.结果 PCI术前患者(术前组)与对照组比较,心肌节段的纵向应变值减低(P＜0.05),且与冠状动脉造影左前降支病变分布范围相一致;与PCI术前相比,术后3个月患者(术后组)相应节段心肌收缩期纵向应变值较前改善(P＜0.05),且部分节段与对照组比较差异无统计学意义(P＞0.05).结论 超声斑点追踪二维纵向应变不但能定位诊断节段性室壁运动异常,而且能够定量地评价心绞痛患者PCI术后左心室心肌收缩功能改善情况.%Objective To explore the characteristics of two-dimensional strain of left ventricular myocardial function before and after percutaneous coronary intervention( PCI) in the patients with angina pectoris ( AP ) by speckle tracking echocardiography. Methods A total of 32 patients with AP and 30 healthy volunteers were involved. High frame rate two-dimensional images were recorded from the apical four-chamber view, two-chamber view and long-axis view of the left ventricle, respectively. The peak systolic longitudinal strain was measured in all of these views using two-dimensional strain software. Results Compared to the control group, the left ventricular peak systolic longitudinal strain values in part of segments were lower in patients with AP before and after PCI ( P ＜ 0.05 ). Left ventricular peak systolic longitudinal strain values in part of segments were significantly improved at 3 month after PCI compared to those patients before PCI ( P＜0. 05 ). Conclusions Two-dimensional strain echocardiography can be used to precisely quantify regional
Institute of Scientific and Technical Information of China (English)
袁彬彬; 张卫达; 张雪花; 王晓武
2012-01-01
目的:运用斑点追踪技术(STI)测量猪闭合性心肌挫伤前、后左心室短轴各节段的二维应变值,观察正常人室壁二维应变的规律,探讨斑点追踪技术对节段性心肌缺血的临床应用价值.方法:采用小型撞击器对9只贵州小型巴马猪进行撞击建立闭合性心肌损伤模型,记录猪撞击前及撞伤后左室短轴观3个水平的高帧频图像,应用二维应变分析软件测量各节段的径向应变(RS)、圆周应变(CS).结果:闭合性心肌挫伤前Rs在同一水平各节段间差异无统计学意义,乳头肌水平显著高于心尖水平(P＜0.05)；Cs在同一水平不同节段间差异有统计学意义(P＜0.05).闭合性心肌挫伤后的挫伤节段的Rs和Cs显著低于正常组相应节段(均为P＜0.01、P＜0.05).结论:STI能够准确测量左室短轴各节段的二维应变值、敏感评价心肌缺血程度.%Objective:To evaluate the clinical value of speckle tracking echocardiography for the measurement of two dimensional strain echocardiography (2D-SE) technique in pigs with close myocardial contusion and to estimate the left ventricle function of close myocardial contusion. Methods:9 small Guizhou-Panama pigs were used. The close myocardial contusion animal mode, was snccessfully set up using the small impactor. High frame rate two-dimensional images were recorded from the left ventricular short-axis views at three different levels before and after the MC. Radial strain (RS) and circumferential strain (CS) were measured in the left ventricular short-axis views using 2DS strain analysis software. Results: 2DS analysis software showed that there was no significant difference ( P >0. 05) of the RS at the same levels mentioned above in left ventricle before the MC. RS and CS after the strike were significantly decreased compared with pre-my-ocardial contusion ( P <0. 05. P<0. 01) at the same levels mentioned above in left ventricle. Conclusion: Speckle tracking imaging
Directory of Open Access Journals (Sweden)
Selina J Hein
Full Text Available Translucent zebrafish larvae represent an established model to analyze genetics of cardiac development and human cardiac disease. More recently adult zebrafish are utilized to evaluate mechanisms of cardiac regeneration and by benefiting from recent genome editing technologies, including TALEN and CRISPR, adult zebrafish are emerging as a valuable in vivo model to evaluate novel disease genes and specifically validate disease causing mutations and their underlying pathomechanisms. However, methods to sensitively and non-invasively assess cardiac morphology and performance in adult zebrafish are still limited. We here present a standardized examination protocol to broadly assess cardiac performance in adult zebrafish by advancing conventional echocardiography with modern speckle-tracking analyses. This allows accurate detection of changes in cardiac performance and further enables highly sensitive assessment of regional myocardial motion and deformation in high spatio-temporal resolution. Combining conventional echocardiography measurements with radial and longitudinal velocity, displacement, strain, strain rate and myocardial wall delay rates after myocardial cryoinjury permitted to non-invasively determine injury dimensions and to longitudinally follow functional recovery during cardiac regeneration. We show that functional recovery of cryoinjured hearts occurs in three distinct phases. Importantly, the regeneration process after cryoinjury extends far beyond the proposed 45 days described for ventricular resection with reconstitution of myocardial performance up to 180 days post-injury (dpi. The imaging modalities evaluated here allow sensitive cardiac phenotyping and contribute to further establish adult zebrafish as valuable cardiac disease model beyond the larval developmental stage.
Institute of Scientific and Technical Information of China (English)
袁彬彬; 张卫达; 王晓武; 李叶阔
2009-01-01
目的 运用斑点追踪技术测量实验动物猪左心室短轴各个节段二维应变.方法 选取健康贵州小型巴马猪9只,采集猪在正常状态下左室短轴二尖瓣水平、乳头肌水平及心尖水平心室节段二维图像(帧频>40帧/s),应用二维应变技术分析软件分析左室心肌各节段的径向应变(RS),圆周应变(CS)及旋转角度(Rot)的变化规律.结果 实验猪在正常状态下显示二维应变所测得左室短轴切面基底段、中间段、心尖段的径向应变依次递增,基底段最小,心尖段最大,但差异无统计学意义(P>0.05).从左室心尖来看,左室扭转运动主要表现为心底部顺时针旋转和心尖部逆时针旋转,心脏整体表现为心动周期内逆时针方向为主的扭转运动.结论 二维应变技术为定量评价左室收缩功能提供了一种快速准确、操作简便、可重复性的无角度依赖的的新方法,具有广阔的临床应用前景.%Objective To evaluate the two-dimensional strain by speckle tracking echocardiography in healthy piglets.Methods 9 small Guizhou-Panama pigs were used.High frame rate two-dimensional images were recorded from the left ventricular short-axis views at the levels of mitral annulus,papillary muscle and apex.Radial strain,circumferential strain and rotation were measured in the left ventricular short-axis views using two-dimensional strain software.Results Left ventricular two-dimensional radial strain gradually increased from the base to apex.As seenfromthe apex.LV performs a wringing motion with a clockwise rotation at the base and counterclockwise rotation at the apex.Conclusion 2DS technique is a rapid,accurate,easy,repeatable and no angle reliant method to quantitatively estimate the left ventrlcle function.
Institute of Scientific and Technical Information of China (English)
张群霞; 张茂惠; 阳文琳; 曹小玲; 苏蕾; 卢岷
2016-01-01
Objective To explore the accuracy of assessing viable myocardium by two -dimensional strain analysis combined with PLGA contrast enhanced low dose dobutamine stress echocardiography.Methods Thirty cute ischemia reperfusion canine models were reproduced successfully. Then myocardial contrast(enhanced with PLGA contrast agents) was performed through aortic root,images were acquired and saved at baseline,rest,and the period with low dose dobutamine administration.The dimentional strain parameters of myocardial segments were acquired by measurements of regional peak -systolic strain in longitudinal(LS),radial(RS)and circumferential(CS)motion on all segments respectively under different condition.Results The parameters of 24 dogs were measured successfully.Compared with nonviable myocardial segment,LS,RS and CS of viable segment increased significantly during dobutamine stress,there was significant difference (P<0.05),however,LS,RS and CS of the former did not present significant variance at the same time .The myocardial specimen staining results were selected as the gold standard, the LS,RS,and CS were selected as evaluation parameters,the sensitivities for LS,RS and CS were 81.03%,77.59% and 72.41%, the specificities were 81.30%,84.00% and 78.00%,respectively.Conclusion Two-dimensional strain analysis combined with low dose dobutamine stress echocardiography enhanced with PLGA contrast agent can improve the quality of ultrasound image,and also can improve the accuracy of assessing viable myocardium with acquired dimensional strain parameters.%目的：探讨乳酸/羟基乙酸共聚物（PLGA）经主动脉心肌造影联合多巴酚丁胺负荷条件下，二维应变评价犬节段心肌存活性的准确性。方法30只犬成功建立急性心肌缺血再灌注模型，经主动脉根部行 PLGA 心肌造影，通过多巴酚丁胺负荷试验，获取心肌节段二维应变参数：收缩期峰值纵向应变（LS）、径向应变（RS）及圆
Institute of Scientific and Technical Information of China (English)
张立敏; 李莎; 魏红; 刘楠; 王盈
2015-01-01
Objective To establish a diabetic and atherosclerosis rat models,so as to discuss the mechanism of the effect of Fasudil on left ventricle function using two?dimensional strain echocardiography(2D?SE). Methods Among the 27 Wistar rats selected for the study,9 were selected as control group(Cont group),the other 18 were used to establish diabetic and atherosclerosis models. Then the modeling group was equally divided in?to Model group(Mod group,n=9)and Fasudil group(Fas group,n=9). The Fas group was given Fasudil with the dose of 10 mg · kg-1 · d-1 for 4 weeks. The global radial strain(GRS),global circumferential strain(GCS)and blood levels of von Willebrand factor(vWF)were measured. The correlation between strain parameter and vWF were analyzed. Results The vWF level was significantly higher in Mod group compared to Cont group and Fas group(P0.05). The GRS and GCS were significantly decreased in Mod group compared to Cont group and Fas group(P0.05).Mod组与Cont组及Fas组相比GRS、GCS明显降低(P<0.05),Fas组GRS、GCS较Cont组降低(P<0.05).GRS、GCS与vWF呈负相关(P<0.05).结论 法舒地尔对糖尿病合并动脉硬化大鼠左心室功能的影响与改善内皮功能相关,2D?SE评价糖尿病合并动脉硬化大鼠的左心室功能是一种有效的方法.
Two-dimensional magma-repository interactions
Bokhove, O.
2001-01-01
Two-dimensional simulations of magma-repository interactions reveal that the three phases --a shock tube, shock reflection and amplification, and shock attenuation and decay phase-- in a one-dimensional flow tube model have a precursor. This newly identified phase ``zero'' consists of the impact of
Mobility anisotropy of two-dimensional semiconductors
Lang, Haifeng; Zhang, Shuqing; Liu, Zhirong
2016-12-01
The carrier mobility of anisotropic two-dimensional semiconductors under longitudinal acoustic phonon scattering was theoretically studied using deformation potential theory. Based on the Boltzmann equation with the relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was derived, showing that the influence of effective mass on mobility anisotropy is larger than those of deformation potential constant or elastic modulus. Parameters were collected for various anisotropic two-dimensional materials (black phosphorus, Hittorf's phosphorus, BC2N , MXene, TiS3, and GeCH3) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio is overestimated by the previously described method.
Institute of Scientific and Technical Information of China (English)
李燕; 吕清; 王静; 张艳容; 陈明; 张静; 方凌云
2009-01-01
目的 应用二维应变超声心动图(2D-Strain)结合实时心肌超声造影(MCE)评价静息状态下冠状动脉(冠脉)不同程度狭窄患者局部心肌血流灌注和应变的变化及两者之间的关系.方法 对25例冠心病患者及15例健康志愿者行MCE和2D-Strain检查.血供异常的心肌节段按供血冠狭窄程度分为轻度狭窄组(50%～75%)、中度狭窄组(76%～89%)和重度狭窄组(≥90%).从MCE再灌注允盈曲线获得A值和β值分析心肌灌注;应用2D-Strain测量心肌纵向收缩期峰值应变(SL)分析心功能.结果 在异常冠脉供血区,随着冠脉狭窄程度的加重;各组的A值与对照组相比呈递减趋势,但差异无统计意义(P>0.05);而中度狭窄组和重度狭窄组的β值和SL值均显著低于对照组(β值:0.75±0.67和0.67±0.53对0.97±0.65;SL值:11.60±5.89和9.58±6.51对19.46±6.17,均P75%的冠脉狭窄引起的心肌缺血,且两者具有较好的相关性.%Objective To estimate the impact of various extent of coronary stenosis at rest on myocardial perfusion and functional indices from myocardial contrast echocardiography(MCE) and two-dimensional strain echocardiography(2D-Strain) and characterize the relationship between them. Methods Three levels of coronary stenosis:mild (50%～75%),moderate (76%～89%),severe (≥90%) in 25 patients with coronary artery stenosis and 15 healthy subjects in the control group were examined. Plateau videointensity (value A) and time to plateau (value β) of the replenishment curve from MCE were calculated for perfusion analysis,and longitudinal peak systolic strain(SL) from 2D-Strain were measured for functional analysis. Results Value A tended to decrease with increasing severity of stenosis,ahhough these differences did not reach the level of statistical significance, β and SL were significantly increased in the context of moderate and severe coronary stenosis when compared with control group (β, moderate 0.75±0.67 and severe 0.67±0
Ostrander, Joshua S; Knepper, Robert; Tappan, Alexander S; Kay, Jeffrey J; Zanni, Martin T; Farrow, Darcie A
2017-02-16
Pentaerythritol tetranitrate (PETN) is a common secondary explosive and has been used extensively to study shock initiation and energy propagation in energetic materials. We report 2D IR measurements of PETN thin films that resolve vibrational energy transfer and relaxation mechanisms. Ultrafast anisotropy measurements reveal a sub-500 fs reorientation of transition dipoles in thin films of vapor-deposited PETN that is absent in solution measurements, consistent with intermolecular energy transfer. The anisotropy is frequency dependent, suggesting spectrally heterogeneous vibrational relaxation. Cross peaks are observed in 2D IR spectra that resolve a specific energy transfer pathway with a 2 ps time scale. Transition dipole coupling calculations of the nitrate ester groups in the crystal lattice predict that the intermolecular couplings are as large or larger than the intramolecular couplings. The calculations match well with the experimental frequencies and the anisotropy, leading us to conclude that the observed cross peak is measuring energy transfer between two eigenstates that are extended over multiple PETN molecules. Measurements of the transition dipole strength indicate that these vibrational modes are coherently delocalized over at least 15-30 molecules. We discuss the implications of vibrational relaxation between coherently delocalized eigenstates for mechanisms relevant to explosives.
Institute of Scientific and Technical Information of China (English)
李阳; 夏稻子
2011-01-01
Objective To access two-dimensional strain echocardiography(2DSE) in evaluating the clinical effect of emergency stent implantation and delayed stent implantation in patients with acute myocardial infarction(AMI).Methods With two-dimensional strain software, peak systolic radial strain of the left ventricular and parameters of conventional ultrasound were measured in 48 patients with AMI and 30 healthy age-matched volunteers.Results (1)Compared with the control group, the peak systolic radial strain of the left vent ricular segments,Left ventricle ejection fraction(LVEF) and fractional shortening(FS) in patients with emergency stent implantation group(A group)and delayed stent implantation group(B group) decreased.Left antrum and ventricular diameter were higher than those in A group and B group.Difference between them was significant(P＜0.05).(2) Compared A group and B group, left antrum and ventricular diameters of A group were lower than those in group B.LVEF and FS were higher than those in B group.Peak systolic radial strain of the left ventricular segments except posterior and inferior wall to basal segment,inferior wall to apical segment of B group decreased significantly(P＜0.05).Conclusions Emergency stent implantation is better than delayed stent implantation in patients with acute myocardial infarction.%目的 应用超声二维应变技术(2DSE)分析急性心肌梗死(AMI)患者急诊与延迟支架置入术后的局部心肌应变,评价急诊与延迟支架置入术的临床效果.方法 48例AMI患者和30例正常对照组应用二维应变软件测量左室短轴室壁各节段的径向峰值收缩应变及常规超声参数.结果 (1)与对照组比较,急诊支架置入术后患者(A组)与延迟支架置人术后患者(B组)的左房、左室内径增大,LVEF、FS降低,各节段室壁应变降低,差异有统计学意义(P＜0.05);(2)A组与B组比较,A组的左房、左室内径低于B组,LVEF、FS高于B组,A组各节段室壁应变除后
Institute of Scientific and Technical Information of China (English)
付倩; 谢明星; 王静; 王新房; 吕清; 卢晓芳; 方凌云; 程龙
2009-01-01
目的 探讨二维应变超声心动图定量评价大鼠急性心肌梗死模型左室局部心肌功能改变的应用价值.方法 60只Wistar大鼠随机分为两组:实验组50只,制备急性冠状动脉心肌梗死模型;假手术组10只.两组分别于术前及术后1周、4周、8周行超声心动图检查.解剖M型超声心动图测量左室舒张末期及收缩末期内径(LVIDd、LVIDs)、短轴缩短率(FS)、射血分数(EF)和左室质量(LVM).记录左室乳头肌短轴高帧频图像,应用二维应变分析软件测量各节段的收缩期峰值径向应变(PRS)、环向应变(PCS).实验组大鼠检查结束后处死,取出心脏行TTC染色并计算梗死面积;VG染色观察心肌组织中的胶原纤维.结果 根据TTC染色结果将实验组大鼠左窀分为梗死心肌、梗死周围和远处心肌.术后1周VG染色显示实验组大鼠左室各节段均出现不同程度的胶原纤维沉着.与术前及同时期假手术组相比,实验组大鼠于术后1周时梗死心肌、梗死周围及远处心肌的PRS、PCS均明显降低(P0. 01). Compared with baseline and sham-operated group,LVIDd,LVIDs and LVM of study group all increased significantly ( P <0. 05) in 4 weeks and 8 weeks after operation,and FS and EF reduced significantly ( P <0. 05). Two-dimensional strain obtained in interobserver and intraobserver both showed high agreement. Conclusions Two-dimensional strain echocardiography can assess regional function of myocardium with different perfusion in rats following acute myocardial infarction, and provides a sensitive and reliable method to follow up the process of left ventricular remodeling after myocardial infarction.
Two-dimensional liquid chromatography
DEFF Research Database (Denmark)
Græsbøll, Rune
of this thesis is on online comprehensive two-dimensional liquid chromatography (online LC×LC) with reverse phase in both dimensions (online RP×RP). Since online RP×RP has not been attempted before within this research group, a significant part of this thesis consists of knowledge and experience gained...
Institute of Scientific and Technical Information of China (English)
刘晓然; 马宁; 李嵘娟; 杨娅
2016-01-01
变、圆周应变率均低于对照组[(19.36±5.75)％比(37.31±9.97)％、(3.67±1.67) s-1比(7.18±2.04)s-1、(0.65±0.44) cm/s比(1.21±0.41) cm/s、(-14.63±6.98)％比(-25.43±2.07)％、(-3.33 ±0.67)s-1比(-6.31 ±0.96)s-1、(0.54±0.34) cm/s比(1.04 ±0.88) cm/s、(21.27±8.16)％比(44.40±7.86)％、(5.02±0.89) s-1比(8.24±0.48)s-1、(-16.91±8.08)％比(-24.27±9.49)％、(-4.21 ±0.46)s-1比(-7.00±0.80)s-1],差异均有统计学意义(均P＜0.05).结论 应激后左心室壁部分节段出现可逆性收缩功能减低.二维斑点追踪成像技术能够较常规超声更早、更敏感地检测捆绑应激大鼠早期左心室室壁运动及功能异常.%Objective To quantitatively evaluate the left ventricular function in immobilization stress (IMO) model of rats with two-dimensional speckle tracking echocardiography technique.Methods Forty-eight female Sprague Dawley rats (aged 30 weeks) were randomly divided into observation group (n =36) and control group (n=12);the rats in observation group were further randomly divided into instant, 24 h, 48 h, 72 h subgroup (n =9 in each group).IMO model was established by binding for 30 min in observation group, and the rats in control group were free movement.Echocardiography was performed immediately, 24 h, 48 h and 72 h after relief of stress in each subgroup.The interventricular septal thickness, left ventricular posterior wall thickness, left ventricular end diastolic dimension (LVEDD), left ventricular end systolic dimension (LVESD), left ventricular ejection fraction, fractional shortening, stroke volume (SV), end-systolic volume and left ventricular end-diastolic volume were determined;the images of left ventricular long axis plane (base, mid, apex of anterior septum and posterior wall) and left ventricular short axis plane (anterior wall, lateral wall, posterior wall, inferior wall, posterior septum, anterior septum) were saved, the radial strain and strain rate, longitudinal strain and strain
DEFF Research Database (Denmark)
Hoffmann, Søren; Mogelvang, Rasmus; Sogaard, Peter
2011-01-01
AIMS: To determine if echocardiographic tissue Doppler imaging (TDI) performed at rest detects reduced myocardial function in patients with reversible ischaemia. METHODS AND RESULTS: Eighty-four patients with angina pectoris, no previous history of ischaemic heart disease and normal left ventricu......AIMS: To determine if echocardiographic tissue Doppler imaging (TDI) performed at rest detects reduced myocardial function in patients with reversible ischaemia. METHODS AND RESULTS: Eighty-four patients with angina pectoris, no previous history of ischaemic heart disease and normal left...... velocities could be demonstrated in patients with a false-positive SPECT compared with controls. CONCLUSION: In patients with stable angina pectoris, preserved ejection fraction, and reversible ischaemia assessed by SPECT, echocardiographic colour TDI performed at rest reveals impaired cardiac function...
Two dimensional unstable scar statistics.
Energy Technology Data Exchange (ETDEWEB)
Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)
2006-12-01
This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.
Juday, Richard D.
1992-01-01
Modified vernier scale gives accurate two-dimensional coordinates from maps, drawings, or cathode-ray-tube displays. Movable circular overlay rests on fixed rectangular-grid overlay. Pitch of circles nine-tenths that of grid and, for greatest accuracy, radii of circles large compared with pitch of grid. Scale enables user to interpolate between finest divisions of regularly spaced rule simply by observing which mark on auxiliary vernier rule aligns with mark on primary rule.
Bachner-Hinenzon, Noa; Ertracht, Offir; Leitman, Marina; Vered, Zvi; Shimoni, Sara; Beeri, Ronen; Binah, Ofer; Adam, Dan
2010-09-01
The rat heart is commonly used as an experimental model of the human heart in both health and disease states, assuming that heart function of rats and humans is alike. When studying a rat model, echocardiography is usually performed on sedated rats, whereas standard echocardiography on adult humans does not require any sedation. Since echocardiography results of sedated rats are usually inferred to alert humans, in the present study, we tested the hypothesis that differences in left ventricular (LV) function may be present between rats sedated by a low dose of ketamine-xylazine and alert humans. Echocardiography was applied to 110 healthy sedated rats and 120 healthy alert humans. Strain parameters were calculated from the scans using a layer-specific speckle tracking echocardiography program. The results showed that layer longitudinal strain is equal in rats and humans, whereas segmental strain is heterogeneous (P rats and humans (P rats and humans (P rats (P rats and humans, in rats the rotation was larger at the apex (P rats and humans. Thus, when evaluating LV function of sedated rats under ketamine-xylazine, it is recommended to measure the global longitudinal strain, LV twist, and torsion-to-shortening ratio, since no scaling is required when converting these parameters and inferring them to humans.
Institute of Scientific and Technical Information of China (English)
李政; 潘翠珍; 舒先红; 陈昊; 王春生
2014-01-01
目的 应用二维斑点追踪技术及组织多普勒技术分别评价移植心脏左、右室纵向收缩功能.方法 56例心脏移植患者,根据心内膜心肌活检及长期临床随访结果分为无排异组(A组)和排异组(B组),随机入选36例健康志愿者归入C组,测量左室射血分数(LVEF)、肺动脉收缩压、三尖瓣瓣环位移(TAPSE)和三尖瓣瓣环收缩期速度(TA-S')等指标.应用Qlab 9.0软件分析获得左室整体纵向应变值(global longitudinal strain,GLS).结果 B组较C组LVEF降低(P＜0.01).三组间GLS、TAPSE及TA-S'值比较差异均有统计学意义(P均＜0.01),B组＜A组＜C组;GLS与LVEF、TAPSE、TA-S'有较好的负相关性(r分别为-0.64,-0.69,-0.71,P均＜0.01).结论 心脏移植患者左、右室纵向收缩功能均有不同程度降低.%Objective To investigate longitudinal systolic function of transplanted heart using two dimensional speckle tracking echocardiography and tissue Doppler imaging.Methods 56 consecutive patients with heart transplant were recruited,according to myocardial biopsy and 1 year's follow up,they were divided into non-rejection group (group A) and rejection group (group B).36 healthy controls (group C) were also randomly recruited.Left ventricular ejection fraction (LVEF),pulmonary arterial systolic pressure,tricuspid annular plane systolic excursion (TAPSE),tricuspid annular plane systolic velocity (TAS') and global longitudinal strain (GLS) were calculated via Qlab 9.0 analysis software offline.Results Compared with group C,LVEF was reduced in group B (P ＜0.01).Differences of GLS,TAPSE,and TA-S' among groups were all statistically significant (P ＜0.01),group B＜group A＜ group C.LVEF,TAPSE and TA-S' were correlated with GLS (r =-0.64,r =-0.69,r =-0.71 ; all P ＜ 0.01).Conclusions Left and right ventricles were a functional unity,the systolic function of which was impaired in patients with heart transplant.
Two-dimensional liquid chromatography
DEFF Research Database (Denmark)
Græsbøll, Rune
Two-dimensional liquid chromatography has received increasing interest due to the rise in demand for analysis of complex chemical mixtures. Separation of complex mixtures is hard to achieve as a simple consequence of the sheer number of analytes, as these samples might contain hundreds or even...... dimensions. As a consequence of the conclusions made within this thesis, the research group has, for the time being, decided against further development of online LC×LC systems, since it was not deemed ideal for the intended application, the analysis of the polar fraction of oil. Trap-and...
Institute of Scientific and Technical Information of China (English)
方玲玲; 张平洋; 王冲; 马小五; 史宏伟; 汪黎明; 冯雪虹
2010-01-01
Objective To explore the feasibility of evaluating viable myocardium with twodimensional strain imaging combined with adenosine stress echocardiography. Methods Acute myocardial infarction and reperfusion model was made by ligating anterior descending coronary artery for 90 minutes followed by 120-minute reperfusion in 15 healthy mongrel dogs. Images were acquired at baseline and after reperfusion Adenosine was then infused and image acquisition repeated. Regional peak-systolic strain in radial, circumferential and longitudinal motion on anterior wall and anterior septum were measured. TTC staining served as a "gold standard" to define viable and nonviable myocardium. The ratio of infarct area ( SN ) to total area (S) was calculated and viable myocardium was defined with SN/S ≤ 50%. Results At baseline, RSpeak sys, CSpeak sys and LSpeak syswere similar between viable ( n = 37 ) and nonviable myocardial segments (n = 53 ) and significantly decreased after reperfusion in both viable and nonviable myocardial segments. Compared with values obtained after reperfusion, LSpeak sys and RSpeak sys remained unchanged in nonviable myocardial segments and significantly increased in viable myocardial segments after adenosine (P<0.05). Post adenosine RSpeak sys was negatively correlated with SN/S and CSpeak sys and LSpeak syswere positively correlated with SN/S. With △RSpeak sys(before and after adenosine) ≥ 13.5%, the sensitivity was 83.8% and specificity was 83.0% for distinguishing viable from nonviable myocardial segment. With △LSpeak sys≥11% as cutoff value, the sensitivity was 78.4% and specificity was 88.7% for distinguishing viable from nonviable myocardial segment. Combining △RSpeak sys and △LSpeak sys, the sensitivity and specificity for distinguishing viable from nonviable myocardial segment were 91.9% and 79. 2%,respectively. Conclusions Two-dimensional strain imaging combined with adenosine stress echocardiography could quantitatively identify viable
Two-dimensional capillary origami
Energy Technology Data Exchange (ETDEWEB)
Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu
2016-01-08
We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.
Mobility anisotropy of two-dimensional semiconductors
Lang, Haifeng; Liu, Zhirong
2016-01-01
The carrier mobility of anisotropic two-dimensional (2D) semiconductors under longitudinal acoustic (LA) phonon scattering was theoretically studied with the deformation potential theory. Based on Boltzmann equation with relaxation time approximation, an analytic formula of intrinsic anisotropic mobility was deduced, which shows that the influence of effective mass to the mobility anisotropy is larger than that of deformation potential constant and elastic modulus. Parameters were collected for various anisotropic 2D materials (black phosphorus, Hittorf's phosphorus, BC$_2$N, MXene, TiS$_3$, GeCH$_3$) to calculate their mobility anisotropy. It was revealed that the anisotropic ratio was overestimated in the past.
Two-dimensional quantum repeaters
Wallnöfer, J.; Zwerger, M.; Muschik, C.; Sangouard, N.; Dür, W.
2016-11-01
The endeavor to develop quantum networks gave rise to a rapidly developing field with far-reaching applications such as secure communication and the realization of distributed computing tasks. This ultimately calls for the creation of flexible multiuser structures that allow for quantum communication between arbitrary pairs of parties in the network and facilitate also multiuser applications. To address this challenge, we propose a two-dimensional quantum repeater architecture to establish long-distance entanglement shared between multiple communication partners in the presence of channel noise and imperfect local control operations. The scheme is based on the creation of self-similar multiqubit entanglement structures at growing scale, where variants of entanglement swapping and multiparty entanglement purification are combined to create high-fidelity entangled states. We show how such networks can be implemented using trapped ions in cavities.
Two-dimensional capillary origami
Brubaker, N. D.; Lega, J.
2016-01-01
We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid.
Two-dimensional cubic convolution.
Reichenbach, Stephen E; Geng, Frank
2003-01-01
The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.
Classifying Two-dimensional Hyporeductive Triple Algebras
Issa, A Nourou
2010-01-01
Two-dimensional real hyporeductive triple algebras (h.t.a.) are investigated. A classification of such algebras is presented. As a consequence, a classification of two-dimensional real Lie triple algebras (i.e. generalized Lie triple systems) and two-dimensional real Bol algebras is given.
Two-dimensional echocardiographic assessment of dextrocardia: a segmental approach.
Huhta, J C; Hagler, D J; Seward, J B; Tajik, A J; Julsrud, P R; Ritter, D G
1982-12-01
Two-dimensional echocardiography was used in the prospective evaluation of 40 patients with the clinical diagnosis of dextrocardia. A segmental analysis of the situs, connections, ventricular anatomy, and chamber positions was utilized for a complete diagnostic assessment. An adequate examination was possible in 33 of these patients; the findings were confirmed by cardiac catheterization and angiography in 31 patients and at operation in 26. Use of the location of the liver and the drainage of the hepatic veins and inferior vena cava allowed atrial visceral situs to be defined in 33 patients (solitus 21, inversus 9, and ambiguous 3). Pulmonary venous connections were correctly identified in 27. In 33 patients, atrioventricular (AV) and ventriculoarterial connections and ventricular anatomy were correctly predicted. Twenty patients had 2 separate well-developed ventricles. Ventriculoarterial connections were determined correctly in all 20 patients: concordant in 5, discordant in 6, double-outlet right ventricle in 5, and single-outlet right ventricle (pulmonary atresia) in 4. In 16 patients a ventricular septal defect was correctly identified. In the remainder the ventricular septum was intact. Thirteen patients had univentricular heart: 8 had 2 AV valves (double-inlet ventricle) 3 had common AV inlet, and 2 had atresia of 1 AV connection. Two-dimensional echocardiography allowed the accurate assessment of complex congenital heart defects associated with dextrocardia. Utilizing a segmental approach, one can correctly predict atrial-visceral situs, ventricular morphology and situs, and AV and ventriculoarterial connections.
Two-dimensional function photonic crystals
Wu, Xiang-Yao; Liu, Xiao-Jing; Liang, Yu
2016-01-01
In this paper, we have firstly proposed two-dimensional function photonic crystals, which the dielectric constants of medium columns are the functions of space coordinates $\\vec{r}$, it is different from the two-dimensional conventional photonic crystals constituting by the medium columns of dielectric constants are constants. We find the band gaps of two-dimensional function photonic crystals are different from the two-dimensional conventional photonic crystals, and when the functions form of dielectric constants are different, the band gaps structure should be changed, which can be designed into the appropriate band gaps structures by the two-dimensional function photonic crystals.
Double mitral valve orifice. Two-dimensional and Doppler echocardiographic diagnosis.
Solorio, S; Badui, E; Yáñez, M; Enciso, R; Rodríguez, L; Quintero, L R
1996-01-01
The purpose of this study was to demonstrate the usefulness of two-dimensional and Doppler echocardiography for diagnosing double mitral valve orifices (DMVO) in addition to identifying associated pathologies. We report five cases, three male and two female with an age ranging from 4 to 44 years old (mean age: 17 years), with the diagnosis of DMVO according to the following characteristics: using two-dimensional echocardiography on the short parasternal axis, both orifices were observed; apical in which the "seagull sign" was identified in both chambers, in addition to identifying the flows of each orifice by pulsed and codified color Doppler obtaining the corresponding gradients. With respect to the associated pathologies, all patients presented some type of malformation, such as subaortic ring, patent ductus arteriosus, coarctation of the aorta, bicuspid aorta and pulmonary stenosis. Using the color Doppler echocardiography allows an adequate anatomical and functional definition of DMVO.
Automated analysis of three-dimensional stress echocardiography
K.Y.E. Leung (Esther); M. van Stralen (Marijn); M.G. Danilouchkine (Mikhail); G. van Burken (Gerard); M.L. Geleijnse (Marcel); J.H.C. Reiber (Johan); N. de Jong (Nico); A.F.W. van der Steen (Ton); J.G. Bosch (Johan)
2011-01-01
textabstractReal-time three-dimensional (3D) ultrasound imaging has been proposed as an alternative for two-dimensional stress echocardiography for assessing myocardial dysfunction and underlying coronary artery disease. Analysis of 3D stress echocardiography is no simple task and requires considera
A. Salustri (Alessandro)
1993-01-01
textabstractIn the studies reported in this thesis, stress echocardiography (either with exercise or with pharmacological agents) and myocardial perfusion scintigraphy have been performed in different groups of patients and in different clinical conditions. Some practical aspects on the protocols of
A. Salustri (Alessandro)
1993-01-01
textabstractIn the studies reported in this thesis, stress echocardiography (either with exercise or with pharmacological agents) and myocardial perfusion scintigraphy have been performed in different groups of patients and in different clinical conditions. Some practical aspects on the protocols
Janus Spectra in Two-Dimensional Flows
Liu, Chien-Chia; Cerbus, Rory T.; Chakraborty, Pinaki
2016-09-01
In large-scale atmospheric flows, soap-film flows, and other two-dimensional flows, the exponent of the turbulent energy spectra, α , may theoretically take either of two distinct values, 3 or 5 /3 , but measurements downstream of obstacles have invariably revealed α =3 . Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which α transitions from 3 to 5 /3 for the streamwise fluctuations but remains equal to 3 for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows.
Hadamard States and Two-dimensional Gravity
Salehi, H
2001-01-01
We have used a two-dimensional analog of the Hadamard state-condition to study the local constraints on the two-point function of a linear quantum field conformally coupled to a two-dimensional gravitational background. We develop a dynamical model in which the determination of the state of the quantum field is essentially related to the determination of a conformal frame. A particular conformal frame is then introduced in which a two-dimensional gravitational equation is established.
Topological defects in two-dimensional crystals
Chen, Yong; Qi, Wei-Kai
2008-01-01
By using topological current theory, we study the inner topological structure of the topological defects in two-dimensional (2D) crystal. We find that there are two elementary point defects topological current in two-dimensional crystal, one for dislocations and the other for disclinations. The topological quantization and evolution of topological defects in two-dimensional crystals are discussed. Finally, We compare our theory with Brownian-dynamics simulations in 2D Yukawa systems.
Strongly interacting two-dimensional Dirac fermions
Lim, L.K.; Lazarides, A.; Hemmerich, Andreas; de Morais Smith, C.
2009-01-01
We show how strongly interacting two-dimensional Dirac fermions can be realized with ultracold atoms in a two-dimensional optical square lattice with an experimentally realistic, inherent gauge field, which breaks time reversal and inversion symmetries. We find remarkable phenomena in a temperature
Topology optimization of two-dimensional waveguides
DEFF Research Database (Denmark)
Jensen, Jakob Søndergaard; Sigmund, Ole
2003-01-01
In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....
Waiting Time Dynamics in Two-Dimensional Infrared Spectroscopy
Jansen, Thomas L. C.; Knoester, Jasper
We review recent work on the waiting time dynamics of coherent two-dimensional infrared (2DIR) spectroscopy. This dynamics can reveal chemical and physical processes that take place on the femto- and picosecond time scale, which is faster than the time scale that may be probed by, for example,
Two-Dimensional Electronic Spectroscopy Using Incoherent Light: Theoretical Analysis
Turner, Daniel B; Sutor, Erika J; Hendrickson, Rebecca A; Gealy, M W; Ulness, Darin J
2012-01-01
Electronic energy transfer in photosynthesis occurs over a range of time scales and under a variety of intermolecular coupling conditions. Recent work has shown that electronic coupling between chromophores can lead to coherent oscillations in two-dimensional electronic spectroscopy measurements of pigment-protein complexes measured with femtosecond laser pulses. A persistent issue in the field is to reconcile the results of measurements performed using femtosecond laser pulses with physiological illumination conditions. Noisy-light spectroscopy can begin to address this question. In this work we present the theoretical analysis of incoherent two-dimensional electronic spectroscopy, I(4) 2D ES. Simulations reveal diagonal peaks, cross peaks, and coherent oscillations similar to those observed in femtosecond two-dimensional electronic spectroscopy experiments. The results also expose fundamental differences between the femtosecond-pulse and noisy-light techniques; the differences lead to new challenges and opp...
Perspective: Two-dimensional resonance Raman spectroscopy
Molesky, Brian P.; Guo, Zhenkun; Cheshire, Thomas P.; Moran, Andrew M.
2016-11-01
Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in complex systems. The 2DRR method can leverage electronic resonance enhancement to selectively probe chromophores embedded in complex environments (e.g., a cofactor in a protein). In addition, correlations between the two dimensions of the 2DRR spectrum reveal information that is not available in traditional Raman techniques. For example, distributions of reactant and product geometries can be correlated in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this perspective article, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide and myoglobin. We also address key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopies. Most notably, it has been shown that these two techniques are subject to a tradeoff between sensitivity to anharmonicity and susceptibility to artifacts. Overall, recent experimental developments and applications of the 2DRR method suggest great potential for the future of the technique.
Janus spectra in two-dimensional flows
Liu, Chien-Chia; Chakraborty, Pinaki
2016-01-01
In theory, large-scale atmospheric flows, soap-film flows and other two-dimensional flows may host two distinct types of turbulent energy spectra---in one, $\\alpha$, the spectral exponent of velocity fluctuations, equals $3$ and the fluctuations are dissipated at the small scales, and in the other, $\\alpha=5/3$ and the fluctuations are dissipated at the large scales---but measurements downstream of obstacles have invariably revealed $\\alpha = 3$. Here we report experiments on soap-film flows where downstream of obstacles there exists a sizable interval in which $\\alpha$ has transitioned from $3$ to $5/3$ for the streamwise fluctuations but remains equal to $3$ for the transverse fluctuations, as if two mutually independent turbulent fields of disparate dynamics were concurrently active within the flow. This species of turbulent energy spectra, which we term the Janus spectra, has never been observed or predicted theoretically. Our results may open up new vistas in the study of turbulence and geophysical flows...
Predicting Two-Dimensional Silicon Carbide Monolayers.
Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I
2015-10-27
Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.
Two Dimensional Plasmonic Cavities on Moire Surfaces
Balci, Sinan; Kocabas, Askin; Karabiyik, Mustafa; Kocabas, Coskun; Aydinli, Atilla
2010-03-01
We investigate surface plasmon polariton (SPP) cavitiy modes on two dimensional Moire surfaces in the visible spectrum. Two dimensional hexagonal Moire surface can be recorded on a photoresist layer using Interference lithography (IL). Two sequential exposures at slightly different angles in IL generate one dimensional Moire surfaces. Further sequential exposure for the same sample at slightly different angles after turning the sample 60 degrees around its own axis generates two dimensional hexagonal Moire cavity. Spectroscopic reflection measurements have shown plasmonic band gaps and cavity states at all the azimuthal angles (omnidirectional cavity and band gap formation) investigated. The plasmonic band gap edge and the cavity states energies show six fold symmetry on the two dimensional Moire surface as measured in reflection measurements.
Two-dimensional function photonic crystals
Liu, Xiao-Jing; Liang, Yu; Ma, Ji; Zhang, Si-Qi; Li, Hong; Wu, Xiang-Yao; Wu, Yi-Heng
2017-01-01
In this paper, we have studied two-dimensional function photonic crystals, in which the dielectric constants of medium columns are the functions of space coordinates , that can become true easily by electro-optical effect and optical kerr effect. We calculated the band gap structures of TE and TM waves, and found the TE (TM) wave band gaps of function photonic crystals are wider (narrower) than the conventional photonic crystals. For the two-dimensional function photonic crystals, when the dielectric constant functions change, the band gaps numbers, width and position should be changed, and the band gap structures of two-dimensional function photonic crystals can be adjusted flexibly, the needed band gap structures can be designed by the two-dimensional function photonic crystals, and it can be of help to design optical devices.
Two-Dimensional Planetary Surface Lander
Hemmati, H.; Sengupta, A.; Castillo, J.; McElrath, T.; Roberts, T.; Willis, P.
2014-06-01
A systems engineering study was conducted to leverage a new two-dimensional (2D) lander concept with a low per unit cost to enable scientific study at multiple locations with a single entry system as the delivery vehicle.
Institute of Scientific and Technical Information of China (English)
王银荣
2012-01-01
二维斑点追踪超声心动图(STE)是近年发展起来的一种超声新技术,是应变/应变率成像的一种方法.这种非侵入性诊断方法能够区分节段心肌的主动和被动运动,量化心肌内的收缩不同步,评估局部心肌功能,具有广阔的应用前景.现简要阐述STE的基本概念及其在定量评价扩张型心肌病的临床应用,并讨论该技术的局限性和发展前景.%Two-dimentional speckle tracking echocardiography( STE )is a new ultrasound method developed in recent years,which is a method of strain/strain rate imaging. This noninvasive diagnostic method can distinguish active myocardial movement from passive movement, quantify myocardial dyssynchrony, and assess partial myocardial function,which has promising application field. Here is to elaborate the basic concept of STE and its clinical application in evaluating dilated cardiomyopathy quantitatively, and discuss the limitations and development prospects of the technology.
Estimation of circumferential fiber shortening velocity by echocardiography.
Ruschhaupt, D G; Sodt, P C; Hutcheon, N A; Arcilla, R A
1983-07-01
The M-mode and two-dimensional echocardiograms of 40 young patients were analyzed to compare the mean circumferential fiber shortening velocity (Vcf) of the left ventricle calculated separately by two methods. The mean circumferential fiber shortening velocity was derived from the M-mode echocardiogram as minor axis shortening/ejection time and derived from the two-dimensional echocardiogram as actual circumference change/ejection time. With computer assistance, circumference was determined from the short-axis two-dimensional echocardiographic images during end-diastole and end-systole. Good correlations were obtained between the left ventricular diameter derived by M-mode echocardiography and the vertical axis during end-diastole (r = 0.79) and end-systole (r = 0.88) derived by two-dimensional echocardiography. Likewise, high correlations were noted between diameter and circumference in end-diastole (r = 0.89) and end-systole (r = 0.88). However, comparison of Vcf obtained by M-mode echocardiography with that obtained by two-dimensional echocardiography showed only fair correlation (r = 0.68). Moreover, the diameter/circumference ratio determined in end-diastole and end-systole differed significantly (p less than 0.001), possibly owing to the change in geometry of the ventricular sector image during systole. Although Vcf derived by M-mode echocardiography is a useful index of left ventricular performance, it does not truly reflect the circumference change during systole.
Two-dimensional speckle tracking cardiac mechanics and constrictive pericarditis: systematic review.
Madeira, Marta; Teixeira, Rogério; Costa, Marco; Gonçalves, Lino; Klein, Allan L
2016-10-01
Transthoracic echocardiography has a pivotal role in the diagnosis of constrictive pericarditis (CP). In addition to the classic M-mode, two-dimensional and Doppler indices, newer methodologies designed to evaluate myocardial mechanics, such as two-dimensional speckle tracking echocardiography (2DSTE), provide additional diagnostic and clinical information in the context of CP. Research has demonstrated that cardiac mechanics can improve echocardiographic diagnostic accuracy of CP and aid in differentiating between constrictive and restrictive ventricular physiology. 2DSTE can also be used to assess the success of pericardiectomy and its impact on atrial and ventricular mechanics. In the course of this review, we describe cardiac mechanics in patients with CP and summarize the influence of pericardiectomy on atrial and ventricular mechanics assessed using 2DSTE.
Institute of Scientific and Technical Information of China (English)
钱建芬; 汤裕华; 林银康
2012-01-01
目的 应用实时心肌超声造影(RT-MCE)结合二维应变(2DS)、左心室射血分数(LVEF)评价急性心肌梗死经皮冠状动脉介入术(PCI)后心肌灌注情况与收缩功能的变化.方法对45例急性心肌梗死患者PCI术后1周内行RT-MCE,按照目测定性和半定量法将所有患者分成再灌注良好组、无灌注组和再灌注减弱组,采用Qlab软件计算出各组心肌的充盈速度和心肌的血容量.3组术后3个月复查常规超声心动图测量LVEF及应用2DS软件测量各个节段的收缩期纵向峰值应变(SRs),并将3组LVEF和SRs进行比较.结果 心肌再灌注良好组术后3个月LVEF为(0.60±0.06)%,较术后1周LVEF(0.54±0.05)%增大,差异有统计学意义( t=3.402,P＜0.01).术后3个月时,心肌灌注良好组LVEF、左心室心肌SRs分别为(0.60±0.06)%、(-0.96±0.35)s-1,无灌注组分别为(0.41±0.08)%、(-0.43±0.14)s-1,两组比较差异有统计学意义(t= 2.819、3.214,P均＜0.01);心肌灌注减弱组LVEF、左心室心肌SRs分别为(0.53±0.05 )%、(-0.59±0.31)s-1,与无灌注组比较差异有统计学意义(t= 2.209、2.418,P＜0.05).结论 PCI术后心肌灌注改善与否可以反映心肌功能恢复的趋势,而2DS可较好地定量评价局部心肌收缩功能.%Objective To assess the changes of myocardial perfusion and systolic function in patients with acute myocardial infarction after revascularization by real -time intravenous myocardial contrast echocardiography ( RT-MCE) combined with 2D-3train(2DS). Methods Forty-five patients were examined by RT-MCE within one week after percutaneous coronary intervention (PCI). These patients were divided into groups according to qualitation and demi-quantitation method. The myocardial filling speed and blood volume were calculated by Qlab software. Three months later, the echocardiography was rechecked again to measure the left ventricular ejection fraction (LVEF) and 2DS was used to measure the SRs of every segment of left
Institute of Scientific and Technical Information of China (English)
张弘飞; 夏稻子
2011-01-01
目的 应用斑点追踪技术研究高血压患者左室心肌径向应变与扭转变化规律,探讨左室扭转对心脏收缩功能的影响.方法 32例原发性3级高血压患者和35例正常人,经胸采集左室短轴二尖瓣水平、乳头肌水平和心尖水平二维图像,利用斑点追踪显像技术测算心肌径向收缩期峰值应变、心尖水平旋转角度峰值、心底水平旋转角度峰值及左室扭转角度峰值.结果 原发性3级高血压患者心肌径向峰值应变较正常组相应节段减低(P<0.05),左室旋转及扭转角峰值均较正常组增高(P<0.05).高血压组EF%及FS%值与正常组比较均无统计学差异.结论 高血压患者左室射血分数正常时,心肌收缩功能已经受损.左室扭转角度的增加在维持心脏整体收缩功能的正常起到重要的作用.%Objective To probe into the influence of left ventricular(LV)twist on cardiac systolic function by discussing systolic peak radial strain and LV rotation in essential hypertention(EH) patients using two-dimensional speckle tracking imaging(2D-STI). Methods We studied 32 patients with staging Ⅲ essential hypertention and 35 healthy control subjects. Two dimensional images were recorded from the LV short-axis view at the levels of mitral annulus,papillary muscle and apical levels. The peak systolic radial strain and rotation were measured using 2D-STI. Results In the staging Ⅲ EH,the peak systolic radial strain were lower than those in the control group(P＜0. 05). LV systolic peak rotation and twist increased in EH group(P＜0. 05). There was no significant difference for ejection fraction EF and FS among EH patients and control group. Conclusions When the EF is normal in patients with EH, the myocardial systolic function have been damaged. The increased LV twist help to LV ejection function.
Interpolation by two-dimensional cubic convolution
Shi, Jiazheng; Reichenbach, Stephen E.
2003-08-01
This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.
D'Andrea, Antonello; D'Alto, Michele; Di Maio, Marco; Vettori, Serena; Benjamin, Nicola; Cocchia, Rosangela; Argiento, Paola; Romeo, Emanuele; Di Marco, Giovanni; Russo, Maria Giovanna; Valentini, Gabriele; Calabrò, Raffaele; Bossone, Eduardo; Grünig, Ekkehard
2016-07-01
Enlargement and dysfunction of the right atrium might be an early sign for pulmonary hypertension in systemic sclerosis (SSc). This is the first study to analyse right atrial morphology and function in SSc patients compared to healthy controls by speckle-tracking two-dimensional strain echocardiography (2DSE) at rest and during exercise. Furthermore, right atrial function was correlated with further clinical findings. Adult patients with SSc for >3 years (n = 90) and 55 age- and gender-matched healthy controls underwent a panel of non-invasive assessments including transthoracic echocardiography, pulsed Doppler myocardial imaging and 2DSE at rest and during exercise. Furthermore, serological tests and high-resolution chest computed tomography were performed. SSc patients showed significant impairment of right atrial function and the right atrial enlargement, measured by 2DSE at rest and during exercise compared to controls (both p right atrial lateral strain was significantly associated with PAPs during effort, right atrial area, left ventricle stroke volume and inferior vena cava diameter using multivariable analysis. The findings of this study suggest that a high proportion of SSc patients reveal right atrial dysfunction even without manifest pulmonary hypertension. Impaired right atrial function occurred mostly in patients with pulmonary fibrosis and/or elevated PAPs during exercise, was independently associated with prognostic factors and may therefore be useful for risk stratification. Further studies are needed to analyse if right atrial dysfunction assessed by 2DSE may help to improve early diagnosis of pulmonary hypertension.
TWO-DIMENSIONAL TOPOLOGY OF COSMOLOGICAL REIONIZATION
Energy Technology Data Exchange (ETDEWEB)
Wang, Yougang; Xu, Yidong; Chen, Xuelei [Key Laboratory of Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 China (China); Park, Changbom [School of Physics, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Kim, Juhan, E-mail: wangyg@bao.ac.cn, E-mail: cbp@kias.re.kr [Center for Advanced Computation, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of)
2015-11-20
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two-dimensional genus curve for the early, middle, and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometre Array.
Two dimensional topology of cosmological reionization
Wang, Yougang; Xu, Yidong; Chen, Xuelei; Kim, Juhan
2015-01-01
We study the two-dimensional topology of the 21-cm differential brightness temperature for two hydrodynamic radiative transfer simulations and two semi-numerical models. In each model, we calculate the two dimensional genus curve for the early, middle and late epochs of reionization. It is found that the genus curve depends strongly on the ionized fraction of hydrogen in each model. The genus curves are significantly different for different reionization scenarios even when the ionized faction is the same. We find that the two-dimensional topology analysis method is a useful tool to constrain the reionization models. Our method can be applied to the future observations such as those of the Square Kilometer Array.
Intracardiac echocardiography.
Bruce, C J; Friedman, P A
2002-10-01
This article describes currently available intracardiac ultrasound (ICE) technology contrasting it with intravascular ultrasound (IVUS) highlighting their differences. Clinical applications in the electrophysiologic and cardiac catheterization laboratory are discussed and current limitations addressed. Intracardiac echocardiography (ICE) is possible because lower frequency transducers (in contrast to higher frequency IVUS devices) have been miniaturized and mounted onto catheters capable of percutaneous insertion into the heart. These lower frequency transducers are capable of enhanced tissue penetration, permitting high-resolution 2D "whole heart" imaging. Also, with the introduction of the newest phased array transducer, Doppler hemodynamic data in addition to high resolution imaging can also be obtained. ICE facilitates electrophysiologic procedures by guiding transseptal catheterization, enabling endocardial anatomy visualization and targeting of arrhythmogenic substrate, ensuring optimal ablation electrode/tissue contact and promptly diagnosing procedural complications. Promising non-electrophysiologic applications include guidance of percutaneous closure of septal defects, percutaneous mitral balloon valvuloplasty and complex cardiac biopsy. Current limitations include monoplanar imaging, narrow field of view, and relatively large size of the catheter. Intra-cardiac imaging is now a clinical tool and has the potential to play an important role in diagnostic and therapeutic interventional procedures. Further refinement and miniaturization of these transducers, through continued technological progress, will make way for primary operator controlled, integrated ultrasound-guided interventional devices.
Two-dimensional x-ray diffraction
He, Bob B
2009-01-01
Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea
Matching Two-dimensional Gel Electrophoresis' Spots
DEFF Research Database (Denmark)
Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza
2012-01-01
This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar......This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches...
Towards two-dimensional search engines
Ermann, Leonardo; Chepelianskii, Alexei D.; Shepelyansky, Dima L.
2011-01-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Statistical properties of inf...
Artifacts in three-dimensional transesophageal echocardiography.
Faletra, Francesco Fulvio; Ramamurthi, Alamelu; Dequarti, Maria Cristina; Leo, Laura Anna; Moccetti, Tiziano; Pandian, Natesa
2014-05-01
Three-dimensional (3D) transesophageal echocardiography (TEE) is subject to the same types of artifacts encountered on two-dimensional TEE. However, when displayed in a 3D format, some of the artifacts appear more "realistic," whereas others are unique to image acquisition and postprocessing. Three-dimensional TEE is increasingly used in the setting of percutaneous catheter-based interventions and ablation procedures, and 3D artifacts caused by the metallic components of catheters and devices are particularly frequent. Knowledge of these artifacts is of paramount relevance to avoid misinterpretation of 3D images. Although artifacts and pitfalls on two-dimensional echocardiography are well described and classified, a systematic description of artifacts in 3D transesophageal echocardiographic images and how they affect 3D imaging is still absent. The aim of this review is to describe the most relevant artifacts on 3D TEE, with particular emphasis on those occurring during percutaneous interventions for structural heart disease and ablation procedures.
Trans-esophageal echocardiography for tricuspid and pulmonary valves
Directory of Open Access Journals (Sweden)
Prabhu Mahesh
2009-01-01
Full Text Available Transesophageal echocardiography has been shown to provide unique information about cardiac anatomy, function, hemodynamics and blood flow and is relatively easy to perform with a low risk of complications. Echocardiographic evaluation of the tricuspid and pulmonary valves can be achieved with two-dimensional and Doppler imaging. Transesophageal echocardiography of these valves is more challenging because of their complex structure and their relative distance from the esophagus. Two-dimensional echocardiography allows an accurate visualization of the cardiac chambers and valves and their motion during the cardiac cycle. Doppler echocardiography is the most commonly used diagnostic technique for detecting and evaluating valvular regurgitation. The lack of good quality evidence makes it difficult to recommend a validated quantitative approach but expert consensus recommends a clinically useful qualitative approach. This review ennumerates probe placement, recommended cross-sectional views, flow patterns, quantitative equations including the clinical approach to the noninvasive quantification of both stenotic and regurgitant lesions.
DEFF Research Database (Denmark)
Hoffmann, Soren; Mogelvang, Rasmus; Olsen, Niels Thue
2010-01-01
Aim To determine how the left ventricular wall motion assessed by echocardiographic Tissue Doppler Imaging (TDI) is affected by increasing severity of coronary artery disease (CAD) among patients with stable angina pectoris and preserved ejection fraction. METHODS AND RESULTS: This study comprises.......86 +/- 0.24 vs. 1.00 +/- 0.28, P preserved ejection fraction reveals both diastolic and systolic dysfunction and the nature...
Institute of Scientific and Technical Information of China (English)
刘红臻; 钟敬泉; 孟祥林; 陶文; 张运
2010-01-01
Objective To compare the effect of active compression-decompression cardiopulmonary resuscitation(ACD-CPR) with standard- cardiopulmonary resuscitation(S-CPR) on ventricular function in a canine ventricular fibrillation model. Methods Ventricular fibrillation was induced in anesthetized and instrumented canine. Twenty-four dogs were randomly assigned to either ACD-CPR group or S-CPR group.After 4 minutes of untreated VF,two-dimension echocardiography was used to evaluate the left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV) and left ventricular ejection fraction (LVEF) of every canine of the two groups when they were undergoing cardiopulmonary resuscitation. Results During ventricular fibrillation, both ACD-CPR group and S-CPR group showed decreased LVEDV compared with pre-ventricular fibrillation, but not statistically significant( P ＞0.05).LVEDV was increased in ACD-CPR group compared with S-CPR group, but not statistically significant (P＞ 0. 05). Both ACD-CPR group and S-CPR group showed significantly increased LVESV compared with pre-ventricular fibrillation,of which the difference was statistically significant ( P ＜0. 001). Both ACD-CPRgroup and S-CPR group showed significantly decreased LVEF compared with pre-ventricular fibrillation,of which the difference was statistically significant (P ＜0. 001). LVEF was increased in ACD-CPR group compared with S-CPR group,of which the difference was statistically significant ( P = 0.019). Conclusions Compared with S-CPR,ACD-CPR resulted in higher LVEF.%目的 探讨主动性心肺复苏对犬心室颤动(室颤)时心功能的影响.方法 应用经胸二维超声心动图分别测量犬室颤时主动性心肺复苏组(ACD-CPR组,12只)和标准心肺复苏组(S-CPR组,12只)左心室舒张末期容积、左心室收缩末期容积,计算左心室射血分数(LVEF),比较两组间各项测量结果.结果 室颤时,两组左心室舒张末期容积较室颤前均有下降,
Imperfect two-dimensional topological insulator field-effect transistors
Vandenberghe, William G.; Fischetti, Massimo V.
2017-01-01
To overcome the challenge of using two-dimensional materials for nanoelectronic devices, we propose two-dimensional topological insulator field-effect transistors that switch based on the modulation of scattering. We model transistors made of two-dimensional topological insulator ribbons accounting for scattering with phonons and imperfections. In the on-state, the Fermi level lies in the bulk bandgap and the electrons travel ballistically through the topologically protected edge states even in the presence of imperfections. In the off-state the Fermi level moves into the bandgap and electrons suffer from severe back-scattering. An off-current more than two-orders below the on-current is demonstrated and a high on-current is maintained even in the presence of imperfections. At low drain-source bias, the output characteristics are like those of conventional field-effect transistors, at large drain-source bias negative differential resistance is revealed. Complementary n- and p-type devices can be made enabling high-performance and low-power electronic circuits using imperfect two-dimensional topological insulators. PMID:28106059
Piezoelectricity in Two-Dimensional Materials
Wu, Tao
2015-02-25
Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.
Kronecker Product of Two-dimensional Arrays
Institute of Scientific and Technical Information of China (English)
Lei Hu
2006-01-01
Kronecker sequences constructed from short sequences are good sequences for spread spectrum communication systems. In this paper we study a similar problem for two-dimensional arrays, and we determine the linear complexity of the Kronecker product of two arrays. Our result shows that similar good property on linear complexity holds for Kronecker product of arrays.
Two-Dimensional Toda-Heisenberg Lattice
Directory of Open Access Journals (Sweden)
Vadim E. Vekslerchik
2013-06-01
Full Text Available We consider a nonlinear model that is a combination of the anisotropic two-dimensional classical Heisenberg and Toda-like lattices. In the framework of the Hirota direct approach, we present the field equations of this model as a bilinear system, which is closely related to the Ablowitz-Ladik hierarchy, and derive its N-soliton solutions.
A novel two dimensional particle velocity sensor
Pjetri, Olti; Wiegerink, Remco J.; Lammerink, Theo S.; Krijnen, Gijs J.
2013-01-01
In this paper we present a two wire, two-dimensional particle velocity sensor. The miniature sensor of size 1.0x2.5x0.525 mm, consisting of only two crossed wires, shows excellent directional sensitivity in both directions, thus requiring no directivity calibration, and is relatively easy to fabrica
Two-dimensional microstrip detector for neutrons
Energy Technology Data Exchange (ETDEWEB)
Oed, A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)
1997-04-01
Because of their robust design, gas microstrip detectors, which were developed at ILL, can be assembled relatively quickly, provided the prefabricated components are available. At the beginning of 1996, orders were received for the construction of three two-dimensional neutron detectors. These detectors have been completed. The detectors are outlined below. (author). 2 refs.
Two-dimensional subwavelength plasmonic lattice solitons
Ye, F; Hu, B; Panoiu, N C
2010-01-01
We present a theoretical study of plasmonic lattice solitons (PLSs) formed in two-dimensional (2D) arrays of metallic nanowires embedded into a nonlinear medium with Kerr nonlinearity. We analyze two classes of 2D PLSs families, namely, fundamental and vortical PLSs in both focusing and defocusing media. Their existence, stability, and subwavelength spatial confinement are studied in detai
A two-dimensional Dirac fermion microscope
DEFF Research Database (Denmark)
Bøggild, Peter; Caridad, Jose; Stampfer, Christoph
2017-01-01
in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2...
Institute of Scientific and Technical Information of China (English)
王健; 康春松; 董建红; 薛继平
2009-01-01
目的 探讨冠心病心肌缺血改善前后不同时间点的应变、应变率特点,评价二维应变成像在冠心病患者疗效评价中的价值.方法 24例血运重建治疗的冠心病患者,应用二维应变检测病变节段血运重建前,重建后1周、1月、3月的应变和应变率参数的变化.结果 病变节段治疗前应变-时间曲线、应变率-时间曲线整个心动周期轮廓杂乱,峰值应变(S)、收缩期峰值应变率(SRS)与舒张早期峰值应变率(SRE)波峰低平,部分节段S波峰倒置.治疗后1周,病变节段S、SRS、SRE及舒张晚期峰值应变率(SRA)各峰值指标有所上升,与治疗前比较差异无统计学意义(P>0.05).治疗后1月,病变节段S、SRE与治疗前比较明显上升(P<0.01).治疗后3月应变-时间曲线、应变率-时间曲线轮廓趋于整齐,S、SRS、SRE及SRA峰值明显上升,与治疗前比较差异有统计学意义(P<0.01),S、SRS、SRA与治疗后1周、1月比较差异有统计学意义(P<0.01).结论 二维应变可无创定量评价冠心病血运重建后不同时间的应变及应变率,评价局部心肌收缩、舒张功能.%Objective To probe into the characteristics of strain and strain rate in different time points of coronary artery disease (CAD) patients before and after the improvement of myocardial ischemia, to evaluate the value of two-dimensional strain (2DS) imaging in assessing curative effect of CAD patients. Methods The changes of strain and strain rate in local lesion segments before revascularization,and one week,one month and three months after revascularization of 24 CAD patients accepting revascularization therapy were detected by 2DS. Results Before revascularization treatment,the outlines of strain-time curves and strain-rate-time curves of lesion segments of CAD patients in whole cardiac circle were cluttered. The peak strain (S),the peak systolic strain rate (SRS) and the peak early diastolic strain rate (SRE) were low and calm. The
Molecular assembly on two-dimensional materials
Kumar, Avijit; Banerjee, Kaustuv; Liljeroth, Peter
2017-02-01
Molecular self-assembly is a well-known technique to create highly functional nanostructures on surfaces. Self-assembly on two-dimensional (2D) materials is a developing field driven by the interest in functionalization of 2D materials in order to tune their electronic properties. This has resulted in the discovery of several rich and interesting phenomena. Here, we review this progress with an emphasis on the electronic properties of the adsorbates and the substrate in well-defined systems, as unveiled by scanning tunneling microscopy. The review covers three aspects of the self-assembly. The first one focuses on non-covalent self-assembly dealing with site-selectivity due to inherent moiré pattern present on 2D materials grown on substrates. We also see that modification of intermolecular interactions and molecule–substrate interactions influences the assembly drastically and that 2D materials can also be used as a platform to carry out covalent and metal-coordinated assembly. The second part deals with the electronic properties of molecules adsorbed on 2D materials. By virtue of being inert and possessing low density of states near the Fermi level, 2D materials decouple molecules electronically from the underlying metal substrate and allow high-resolution spectroscopy and imaging of molecular orbitals. The moiré pattern on the 2D materials causes site-selective gating and charging of molecules in some cases. The last section covers the effects of self-assembled, acceptor and donor type, organic molecules on the electronic properties of graphene as revealed by spectroscopy and electrical transport measurements. Non-covalent functionalization of 2D materials has already been applied for their application as catalysts and sensors. With the current surge of activity on building van der Waals heterostructures from atomically thin crystals, molecular self-assembly has the potential to add an extra level of flexibility and functionality for applications ranging
Electronics based on two-dimensional materials.
Fiori, Gianluca; Bonaccorso, Francesco; Iannaccone, Giuseppe; Palacios, Tomás; Neumaier, Daniel; Seabaugh, Alan; Banerjee, Sanjay K; Colombo, Luigi
2014-10-01
The compelling demand for higher performance and lower power consumption in electronic systems is the main driving force of the electronics industry's quest for devices and/or architectures based on new materials. Here, we provide a review of electronic devices based on two-dimensional materials, outlining their potential as a technological option beyond scaled complementary metal-oxide-semiconductor switches. We focus on the performance limits and advantages of these materials and associated technologies, when exploited for both digital and analog applications, focusing on the main figures of merit needed to meet industry requirements. We also discuss the use of two-dimensional materials as an enabling factor for flexible electronics and provide our perspectives on future developments.
Two-dimensional ranking of Wikipedia articles
Zhirov, A. O.; Zhirov, O. V.; Shepelyansky, D. L.
2010-10-01
The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists ab aeterno. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. While PageRank highlights very well known nodes with many ingoing links, CheiRank highlights very communicative nodes with many outgoing links. In this way the ranking becomes two-dimensional. Using CheiRank and PageRank we analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.
Two-Dimensional NMR Lineshape Analysis
Waudby, Christopher A.; Ramos, Andres; Cabrita, Lisa D.; Christodoulou, John
2016-04-01
NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions.
Towards two-dimensional search engines
Ermann, Leonardo; Shepelyansky, Dima L
2011-01-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way the ranking of nodes becomes two-dimensional that paves the way for development of two-dimensional search engines of new type. Information flow properties on PageRank-CheiRank plane are analyzed for networks of British, French and Italian Universities, Wikipedia, Linux Kernel, gene regulation and other networks. Methods of spam links control are also analyzed.
Toward two-dimensional search engines
Ermann, L.; Chepelianskii, A. D.; Shepelyansky, D. L.
2012-07-01
We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank-CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed.
A two-dimensional Dirac fermion microscope
Bøggild, Peter; Caridad, José M.; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads
2017-06-01
The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.
A two-dimensional Dirac fermion microscope.
Bøggild, Peter; Caridad, José M; Stampfer, Christoph; Calogero, Gaetano; Papior, Nick Rübner; Brandbyge, Mads
2017-06-09
The electron microscope has been a powerful, highly versatile workhorse in the fields of material and surface science, micro and nanotechnology, biology and geology, for nearly 80 years. The advent of two-dimensional materials opens new possibilities for realizing an analogy to electron microscopy in the solid state. Here we provide a perspective view on how a two-dimensional (2D) Dirac fermion-based microscope can be realistically implemented and operated, using graphene as a vacuum chamber for ballistic electrons. We use semiclassical simulations to propose concrete architectures and design rules of 2D electron guns, deflectors, tunable lenses and various detectors. The simulations show how simple objects can be imaged with well-controlled and collimated in-plane beams consisting of relativistic charge carriers. Finally, we discuss the potential of such microscopes for investigating edges, terminations and defects, as well as interfaces, including external nanoscale structures such as adsorbed molecules, nanoparticles or quantum dots.
Two-Dimensional Scheduling: A Review
Directory of Open Access Journals (Sweden)
Zhuolei Xiao
2013-07-01
Full Text Available In this study, we present a literature review, classification schemes and analysis of methodology for scheduling problems on Batch Processing machine (BP with both processing time and job size constraints which is also regarded as Two-Dimensional (TD scheduling. Special attention is given to scheduling problems with non-identical job sizes and processing times, with details of the basic algorithms and other significant results.
Two dimensional fermions in four dimensional YM
Narayanan, R
2009-01-01
Dirac fermions in the fundamental representation of SU(N) live on a two dimensional torus flatly embedded in $R^4$. They interact with a four dimensional SU(N) Yang Mills vector potential preserving a global chiral symmetry at finite $N$. As the size of the torus in units of $\\frac{1}{\\Lambda_{SU(N)}}$ is varied from small to large, the chiral symmetry gets spontaneously broken in the infinite $N$ limit.
Two-dimensional Kagome photonic bandgap waveguide
DEFF Research Database (Denmark)
Nielsen, Jens Bo; Søndergaard, Thomas; Libori, Stig E. Barkou;
2000-01-01
The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes...... is investigated with respect to the width of the 2-D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out....
String breaking in two-dimensional QCD
Hornbostel, K J
1999-01-01
I present results of a numerical calculation of the effects of light quark-antiquark pairs on the linear heavy-quark potential in light-cone quantized two-dimensional QCD. I extract the potential from the Q-Qbar component of the ground-state wavefunction, and observe string breaking at the heavy-light meson pair threshold. I briefly comment on the states responsible for the breaking.
Two-dimensional supramolecular electron spin arrays.
Wäckerlin, Christian; Nowakowski, Jan; Liu, Shi-Xia; Jaggi, Michael; Siewert, Dorota; Girovsky, Jan; Shchyrba, Aneliia; Hählen, Tatjana; Kleibert, Armin; Oppeneer, Peter M; Nolting, Frithjof; Decurtins, Silvio; Jung, Thomas A; Ballav, Nirmalya
2013-05-07
A bottom-up approach is introduced to fabricate two-dimensional self-assembled layers of molecular spin-systems containing Mn and Fe ions arranged in a chessboard lattice. We demonstrate that the Mn and Fe spin states can be reversibly operated by their selective response to coordination/decoordination of volatile ligands like ammonia (NH3). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Two-dimensional localized structures in harmonically forced oscillatory systems
Ma, Y.-P.; Knobloch, E.
2016-12-01
Two-dimensional spatially localized structures in the complex Ginzburg-Landau equation with 1:1 resonance are studied near the simultaneous presence of a steady front between two spatially homogeneous equilibria and a supercritical Turing bifurcation on one of them. The bifurcation structures of steady circular fronts and localized target patterns are computed in the Turing-stable and Turing-unstable regimes. In particular, localized target patterns grow along the solution branch via ring insertion at the core in a process reminiscent of defect-mediated snaking in one spatial dimension. Stability of axisymmetric solutions on these branches with respect to axisymmetric and nonaxisymmetric perturbations is determined, and parameter regimes with stable axisymmetric oscillons are identified. Direct numerical simulations reveal novel depinning dynamics of localized target patterns in the radial direction, and of circular and planar localized hexagonal patterns in the fully two-dimensional system.
American Society of Echocardiography
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Pacing stress echocardiography
Directory of Open Access Journals (Sweden)
Agrusta Marco
2005-12-01
Full Text Available Abstract Background High-rate pacing is a valid stress test to be used in conjunction with echocardiography; it is independent of physical exercise and does not require drug administration. There are two main applications of pacing stress in the echo lab: the noninvasive detection of coronary artery disease through induction of a regional transient dysfunction; and the assessment of contractile reserve through peak systolic pressure/ end-systolic volume relationship at increasing heart rates to assess global left ventricular contractility. Methods The pathophysiologic rationale of pacing stress for noninvasive detection of coronary artery disease is obvious, with the stress determined by a controlled increase in heart rate, which is a major determinant of myocardial oxygen demand, and thereby tachycardia may exceed a fixed coronary flow reserve in the presence of hemodynamically significant coronary artery disease. The use of pacing stress echo to assess left ventricular contractile reserve is less established, but promising. Positive inotropic interventions are mirrored by smaller end-systolic volumes and higher end-systolic pressures. An increased heart rate progressively increases the force of ventricular contraction (Bowditch treppe or staircase phenomenon. To build the force-frequency relationship, the force is determined at different heart rate steps as the ratio of the systolic pressure (cuff sphygmomanometer/end-systolic volume index (biplane Simpson rule. The heart rate is determined from ECG. Conclusion Two-dimensional echocardiography during pacing is a useful tool in the detection of coronary artery disease. Because of its safety and ease of repeatability noninvasive pacing stress echo can be the first-line stress test in patients with permanent pacemaker. The force-frequency can be defined as up- sloping (normal when the peak stress pacing systolic pressure/end-systolic volume index is higher than baseline and intermediate stress
Strongly correlated two-dimensional plasma explored from entropy measurements.
Kuntsevich, A Y; Tupikov, Y V; Pudalov, V M; Burmistrov, I S
2015-06-23
Charged plasma and Fermi liquid are two distinct states of electronic matter intrinsic to dilute two-dimensional electron systems at elevated and low temperatures, respectively. Probing their thermodynamics represents challenge because of lack of an adequate technique. Here, we report a thermodynamic method to measure the entropy per electron in gated structures. Our technique appears to be three orders of magnitude superior in sensitivity to a.c. calorimetry, allowing entropy measurements with only 10(8) electrons. This enables us to investigate the correlated plasma regime, previously inaccessible experimentally in two-dimensional electron systems in semiconductors. In experiments with clean two-dimensional electron system in silicon-based structures, we traced entropy evolution from the plasma to Fermi liquid regime by varying electron density. We reveal that the correlated plasma regime can be mapped onto the ordinary non-degenerate Fermi gas with an interaction-enhanced temperature-dependent effective mass. Our method opens up new horizons in studies of low-dimensional electron systems.
Weakly disordered two-dimensional Frenkel excitons
Boukahil, A.; Zettili, Nouredine
2004-03-01
We report the results of studies of the optical properties of weakly disordered two- dimensional Frenkel excitons in the Coherent Potential Approximation (CPA). An approximate complex Green's function for a square lattice with nearest neighbor interactions is used in the self-consistent equation to determine the coherent potential. It is shown that the Density of States is very much affected by the logarithmic singularities in the Green's function. Our CPA results are in excellent agreement with previous investigations by Schreiber and Toyozawa using the Monte Carlo simulation.
Two-dimensional photonic crystal surfactant detection.
Zhang, Jian-Tao; Smith, Natasha; Asher, Sanford A
2012-08-07
We developed a novel two-dimensional (2-D) crystalline colloidal array photonic crystal sensing material for the visual detection of amphiphilic molecules in water. A close-packed polystyrene 2-D array monolayer was embedded in a poly(N-isopropylacrylamide) (PNIPAAm)-based hydrogel film. These 2-D photonic crystals placed on a mirror show intense diffraction that enables them to be used for visual determination of analytes. Binding of surfactant molecules attaches ions to the sensor that swells the PNIPAAm-based hydrogel. The resulting increase in particle spacing red shifts the 2-D diffracted light. Incorporation of more hydrophobic monomers increases the sensitivity to surfactants.
Theory of two-dimensional transformations
Kanayama, Yutaka J.; Krahn, Gary W.
1998-01-01
The article of record may be found at http://dx.doi.org/10.1109/70.720359 Robotics and Automation, IEEE Transactions on This paper proposes a new "heterogeneous" two-dimensional (2D) transformation group ___ to solve motion analysis/planning problems in robotics. In this theory, we use a 3×1 matrix to represent a transformation as opposed to a 3×3 matrix in the homogeneous formulation. First, this theory is as capable as the homogeneous theory, Because of the minimal size, its implement...
Two-dimensional ranking of Wikipedia articles
Zhirov, A O; Shepelyansky, D L
2010-01-01
The Library of Babel, described by Jorge Luis Borges, stores an enormous amount of information. The Library exists {\\it ab aeterno}. Wikipedia, a free online encyclopaedia, becomes a modern analogue of such a Library. Information retrieval and ranking of Wikipedia articles become the challenge of modern society. We analyze the properties of two-dimensional ranking of all Wikipedia English articles and show that it gives their reliable classification with rich and nontrivial features. Detailed studies are done for countries, universities, personalities, physicists, chess players, Dow-Jones companies and other categories.
Sums of two-dimensional spectral triples
DEFF Research Database (Denmark)
Christensen, Erik; Ivan, Cristina
2007-01-01
construct a sum of two dimensional modules which reflects some aspects of the topological dimensions of the compact metric space, but this will only give the metric back approximately. At the end we make an explicit computation of the last module for the unit interval in. The metric is recovered exactly......, the Dixmier trace induces a multiple of the Lebesgue integral but the growth of the number of eigenvalues is different from the one found for the standard differential operator on the unit interval....
Binding energy of two-dimensional biexcitons
DEFF Research Database (Denmark)
Singh, Jai; Birkedal, Dan; Vadim, Lyssenko;
1996-01-01
Using a model structure for a two-dimensional (2D) biexciton confined in a quantum well, it is shown that the form of the Hamiltonian of the 2D biexciton reduces into that of an exciton. The binding energies and Bohr radii of a 2D biexciton in its various internal energy states are derived...... analytically using the fractional dimension approach. The ratio of the binding energy of a 2D biexciton to that of a 2D exciton is found to be 0.228, which agrees very well with the recent experimental value. The results of our approach are compared with those of earlier theories....
Dynamics of film. [two dimensional continua theory
Zak, M.
1979-01-01
The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets. The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles. The theory is illustrated by examples.
Two-dimensional gauge theoretic supergravities
Cangemi, D.; Leblanc, M.
1994-05-01
We investigate two-dimensional supergravity theories, which can be built from a topological and gauge invariant action defined on an ordinary surface. One is the N = 1 supersymmetric extension of the Jackiw-Teitelboim model presented by Chamseddine in a superspace formalism. We complement the proof of Montano, Aoaki and Sonnenschein that this extension is topological and gauge invariant, based on the graded de Sitter algebra. Not only do the equations of motion correspond to the supergravity ones and do gauge transformations encompass local supersymmetries, but we also identify the ∫-theory with the superfield formalism action written by Chamseddine. Next, we show that the N = 1 supersymmetric extension of string-inspired two-dimensional dilaton gravity put forward by Park and Strominger cannot be written as a ∫-theory. As an alternative, we propose two topological and gauge theories that are based on a graded extension of the extended Poincaré algebra and satisfy a vanishing-curvature condition. Both models are supersymmetric extensions of the string-inspired dilaton gravity.
Two-Dimensional Theory of Scientific Representation
Directory of Open Access Journals (Sweden)
A Yaghmaie
2013-03-01
Full Text Available Scientific representation is an interesting topic for philosophers of science, many of whom have recently explored it from different points of view. There are currently two competing approaches to the issue: cognitive and non-cognitive, and each of them claims its own merits over the other. This article tries to provide a hybrid theory of scientific representation, called Two-Dimensional Theory of Scientific Representation, which has the merits of the two accounts and is free of their shortcomings. To do this, we will argue that although scientific representation needs to use the notion of intentionality, such a notion is defined and realized in a simply structural form contrary to what cognitive approach says about intentionality. After a short introduction, the second part of the paper is devoted to introducing theories of scientific representation briefly. In the third part, the structural accounts of representation will be criticized. The next step is to introduce the two-dimensional theory which involves two key components: fixing and structural fitness. It will be argued that fitness is an objective and non-intentional relation, while fixing is intentional.
Two-dimensional shape memory graphene oxide
Chang, Zhenyue; Deng, Junkai; Chandrakumara, Ganaka G.; Yan, Wenyi; Liu, Jefferson Zhe
2016-06-01
Driven by the increasing demand for micro-/nano-technologies, stimuli-responsive shape memory materials at nanoscale have recently attracted great research interests. However, by reducing the size of conventional shape memory materials down to approximately nanometre range, the shape memory effect diminishes. Here, using density functional theory calculations, we report the discovery of a shape memory effect in a two-dimensional atomically thin graphene oxide crystal with ordered epoxy groups, namely C8O. A maximum recoverable strain of 14.5% is achieved as a result of reversible phase transition between two intrinsically stable phases. Our calculations conclude co-existence of the two stable phases in a coherent crystal lattice, giving rise to the possibility of constructing multiple temporary shapes in a single material, thus, enabling highly desirable programmability. With an atomic thickness, excellent shape memory mechanical properties and electric field stimulus, the discovery of a two-dimensional shape memory graphene oxide opens a path for the development of exceptional micro-/nano-electromechanical devices.
Predicting clinically unrecognized coronary artery disease: use of two- dimensional echocardiography
Directory of Open Access Journals (Sweden)
Nagueh Sherif F
2009-03-01
Full Text Available Abstract Background 2-D Echo is often performed in patients without history of coronary artery disease (CAD. We sought to determine echo features predictive of CAD. Methods 2-D Echo of 328 patients without known CAD performed within one year prior to stress myocardial SPECT and angiography were reviewed. Echo features examined were left ventricular and atrial enlargement, LV hypertrophy, wall motion abnormality (WMA, LV ejection fraction (EF 15% LV perfusion defect or multivessel distribution. Severe coronary artery stenosis (CAS was defined as left main, 3 VD or 2VD involving proximal LAD. Results The mean age was 62 ± 13 years, 59% men, 29% diabetic (DM and 148 (45% had > 2 risk factors. Pharmacologic stress was performed in 109 patients (33%. MPA was present in 200 pts (60% of which, 137 were high risk. CAS was present in 166 pts (51%, 75 were severe. Of 87 patients with WMA, 83% had MPA and 78% had CAS. Multivariate analysis identified age >65, male, inability to exercise, DM, WMA, MAC and AS as independent predictors of MPA and CAS. Independent predictors of high risk MPA and severe CAS were age, DM, inability to exercise and WMA. 2-D echo findings offered incremental value over clinical information in predicting CAD by angiography. (Chi square: 360 vs. 320 p = 0.02. Conclusion 2-D Echo was valuable in predicting presence of physiological and anatomical CAD in addition to clinical information.
Directory of Open Access Journals (Sweden)
Felix Heggemann
Full Text Available AIMS: This study sought to characterize global and regional right ventricular (RV myocardial function in patients with Takotsubo cardiomyopathy (TC using 2D strain imaging. METHODS: We compared various parameters of RV and left ventricular (LV systolic function between 2 groups of consecutive patients with TC at initial presentation and upon follow-up. Group 1 had RV involvement and group 2 did not have RV involvement. RESULTS: At initial presentation, RV peak systolic longitudinal strain (RVPSS and RV fractional area change (RVFAC were significantly lower in group 1 (-13.2±8.6% vs. -21.8±5.4%, p = 0.001; 30.7±9.3% vs. 43.5±6.3%, p = 0.001 and improved significantly upon follow-up. Tricuspid annular plane systolic excursion (TAPSE did not differ significantly at initial presentation between both groups (14.8±4.1 mm vs. 17.9±3.5 mm, p = 0.050. Differences in regional systolic RV strain were only observed in the mid and apical segments. LV ejection fraction (LVEF and LV global strain were significantly lower in group 1 (36±8% vs. 46±10%, p = 0.006 and -5.5±4.8% vs. -10.2±6.2%, p = 0.040 at initial presentation. None of the parameters were significantly different between the 2 groups upon follow-up. A RVPSS cut-off value of >-19.1% had a sensitivity of 85% and a specificity of 71% to discriminate between the 2 groups. CONCLUSION: In TC, RVFAC, RVPSS, LVEF and LV global strain differed significantly between patients with and without RV dysfunction, whereas TAPSE did not. 2 D strain imaging was feasible for the assessment of RV dysfunction in TC and could discriminate between patients with and without RV involvement in a clinically meaningful way.
Marcus, K.A.; Korte, C.L. de; Feuth, T.; Thijssen, J.M.; Kapusta, L.
2012-01-01
PURPOSE: Congenital valvar aortic stenosis (VAS) causes a pressure overload to the left ventricle. In the clinical setting, the severity of stenosis is graded by the pressure drop over the stenotic valve (pressure gradient). This parameter is dependent on the hemodynamic status and does not provide
Institute of Scientific and Technical Information of China (English)
XU Quan; TIAN Qiang
2007-01-01
Two-dimensional compact-like discrete breathers in discrete two-dimensional monatomic square lattices are investigated by discussing a generafized discrete two-dimensional monatomic model.It is proven that the twodimensional compact-like discrete breathers exist not only in two-dimensional soft Ф4 potentials but also in hard two-dimensional Ф4 potentials and pure two-dimensional K4 lattices.The measurements of the two-dimensional compact-like discrete breather cores in soft and hard two-dimensional Ф4 potential are determined by coupling parameter K4,while those in pure two-dimensional K4 lattices have no coupling with parameter K4.The stabilities of the two-dimensional compact-like discrete breathers correlate closely to the coupling parameter K4 and the boundary condition of lattices.
Magnetic reconnection in two-dimensional magnetohydrodynamic turbulence.
Servidio, S; Matthaeus, W H; Shay, M A; Cassak, P A; Dmitruk, P
2009-03-20
Systematic analysis of numerical simulations of two-dimensional magnetohydrodynamic turbulence reveals the presence of a large number of X-type neutral points where magnetic reconnection occurs. We examine the statistical properties of this ensemble of reconnection events that are spontaneously generated by turbulence. The associated reconnection rates are distributed over a wide range of values and scales with the geometry of the diffusion region. Locally, these events can be described through a variant of the Sweet-Parker model, in which the parameters are externally controlled by turbulence. This new perspective on reconnection is relevant in space and astrophysical contexts, where plasma is generally in a fully turbulent regime.
Optimum high temperature strength of two-dimensional nanocomposites
Energy Technology Data Exchange (ETDEWEB)
Monclús, M. A.; Molina-Aldareguía, J. M., E-mail: jon.molina@imdea.org [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Zheng, S. J.; Mayeur, J. R.; Beyerlein, I. J.; Mara, N. A. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Polcar, T. [Czech Technical University in Prague, Technická 2, Prague 6 (Czech Republic); Llorca, J. [IMDEA Materials Institute, C/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science, Polytechnic University of Madrid, E. T. S. de Ingenieros de Caminos, 28040 Madrid (Spain)
2013-11-01
High-temperature nanoindentation was used to reveal nano-layer size effects on the hardness of two-dimensional metallic nanocomposites. We report the existence of a critical layer thickness at which strength achieves optimal thermal stability. Transmission electron microscopy and theoretical bicrystal calculations show that this optimum arises due to a transition from thermally activated glide within the layers to dislocation transmission across the layers. We demonstrate experimentally that the atomic-scale properties of the interfaces profoundly affect this critical transition. The strong implications are that interfaces can be tuned to achieve an optimum in high temperature strength in layered nanocomposite structures.
Optimum high temperature strength of two-dimensional nanocomposites
Directory of Open Access Journals (Sweden)
M. A. Monclús
2013-11-01
Full Text Available High-temperature nanoindentation was used to reveal nano-layer size effects on the hardness of two-dimensional metallic nanocomposites. We report the existence of a critical layer thickness at which strength achieves optimal thermal stability. Transmission electron microscopy and theoretical bicrystal calculations show that this optimum arises due to a transition from thermally activated glide within the layers to dislocation transmission across the layers. We demonstrate experimentally that the atomic-scale properties of the interfaces profoundly affect this critical transition. The strong implications are that interfaces can be tuned to achieve an optimum in high temperature strength in layered nanocomposite structures.
Optimal excitation of two dimensional Holmboe instabilities
Constantinou, Navid C
2010-01-01
Highly stratified shear layers are rendered unstable even at high stratifications by Holmboe instabilities when the density stratification is concentrated in a small region of the shear layer. These instabilities may cause mixing in highly stratified environments. However these instabilities occur in tongues for a limited range of parameters. We perform Generalized Stability analysis of the two dimensional perturbation dynamics of an inviscid Boussinesq stratified shear layer and show that Holmboe instabilities at high Richardson numbers can be excited by their adjoints at amplitudes that are orders of magnitude larger than by introducing initially the unstable mode itself. We also determine the optimal growth that obtains for parameters for which there is no instability. We find that there is potential for large transient growth regardless of whether the background flow is exponentially stable or not and that the characteristic structure of the Holmboe instability asymptotically emerges for parameter values ...
Phonon hydrodynamics in two-dimensional materials.
Cepellotti, Andrea; Fugallo, Giorgia; Paulatto, Lorenzo; Lazzeri, Michele; Mauri, Francesco; Marzari, Nicola
2015-03-06
The conduction of heat in two dimensions displays a wealth of fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene and related materials. Here, we use density-functional perturbation theory and an exact, variational solution of the Boltzmann transport equation to study fully from first-principles phonon transport and heat conductivity in graphene, boron nitride, molybdenum disulphide and the functionalized derivatives graphane and fluorographene. In all these materials, and at variance with typical three-dimensional solids, normal processes keep dominating over Umklapp scattering well-above cryogenic conditions, extending to room temperature and more. As a result, novel regimes emerge, with Poiseuille and Ziman hydrodynamics, hitherto typically confined to ultra-low temperatures, characterizing transport at ordinary conditions. Most remarkably, several of these two-dimensional materials admit wave-like heat diffusion, with second sound present at room temperature and above in graphene, boron nitride and graphane.
Probabilistic Universality in two-dimensional Dynamics
Lyubich, Mikhail
2011-01-01
In this paper we continue to explore infinitely renormalizable H\\'enon maps with small Jacobian. It was shown in [CLM] that contrary to the one-dimensional intuition, the Cantor attractor of such a map is non-rigid and the conjugacy with the one-dimensional Cantor attractor is at most 1/2-H\\"older. Another formulation of this phenomenon is that the scaling structure of the H\\'enon Cantor attractor differs from its one-dimensional counterpart. However, in this paper we prove that the weight assigned by the canonical invariant measure to these bad spots tends to zero on microscopic scales. This phenomenon is called {\\it Probabilistic Universality}. It implies, in particular, that the Hausdorff dimension of the canonical measure is universal. In this way, universality and rigidity phenomena of one-dimensional dynamics assume a probabilistic nature in the two-dimensional world.
Two-dimensional position sensitive neutron detector
Indian Academy of Sciences (India)
A M Shaikh; S S Desai; A K Patra
2004-08-01
A two-dimensional position sensitive neutron detector has been developed. The detector is a 3He + Kr filled multiwire proportional counter with charge division position readout and has a sensitive area of 345 mm × 345 mm, pixel size 5 mm × 5 mm, active depth 25 mm and is designed for efficiency of 70% for 4 Å neutrons. The detector is tested with 0.5 bar 3He + 1.5 bar krypton gas mixture in active chamber and 2 bar 4He in compensating chamber. The pulse height spectrum recorded at an anode potential of 2000 V shows energy resolution of ∼ 25% for the 764 keV peak. A spatial resolution of 8 mm × 6 mm is achieved. The detector is suitable for SANS studies in the range of 0.02–0.25 Å-1.
Two-dimensional heterostructures for energy storage
Pomerantseva, Ekaterina; Gogotsi, Yury
2017-07-01
Two-dimensional (2D) materials provide slit-shaped ion diffusion channels that enable fast movement of lithium and other ions. However, electronic conductivity, the number of intercalation sites, and stability during extended cycling are also crucial for building high-performance energy storage devices. While individual 2D materials, such as graphene, show some of the required properties, none of them can offer all properties needed to maximize energy density, power density, and cycle life. Here we argue that stacking different 2D materials into heterostructured architectures opens an opportunity to construct electrodes that would combine the advantages of the individual building blocks while eliminating the associated shortcomings. We discuss characteristics of common 2D materials and provide examples of 2D heterostructured electrodes that showed new phenomena leading to superior electrochemical performance. We also consider electrode fabrication approaches and finally outline future steps to create 2D heterostructured electrodes that could greatly expand current energy storage technologies.
Rationally synthesized two-dimensional polymers.
Colson, John W; Dichtel, William R
2013-06-01
Synthetic polymers exhibit diverse and useful properties and influence most aspects of modern life. Many polymerization methods provide linear or branched macromolecules, frequently with outstanding functional-group tolerance and molecular weight control. In contrast, extending polymerization strategies to two-dimensional periodic structures is in its infancy, and successful examples have emerged only recently through molecular framework, surface science and crystal engineering approaches. In this Review, we describe successful 2D polymerization strategies, as well as seminal research that inspired their development. These methods include the synthesis of 2D covalent organic frameworks as layered crystals and thin films, surface-mediated polymerization of polyfunctional monomers, and solid-state topochemical polymerizations. Early application targets of 2D polymers include gas separation and storage, optoelectronic devices and membranes, each of which might benefit from predictable long-range molecular organization inherent to this macromolecular architecture.
Local doping of two-dimensional materials
Wong, Dillon; Velasco, Jr, Jairo; Ju, Long; Kahn, Salman; Lee, Juwon; Germany, Chad E.; Zettl, Alexander K.; Wang, Feng; Crommie, Michael F.
2016-09-20
This disclosure provides systems, methods, and apparatus related to locally doping two-dimensional (2D) materials. In one aspect, an assembly including a substrate, a first insulator disposed on the substrate, a second insulator disposed on the first insulator, and a 2D material disposed on the second insulator is formed. A first voltage is applied between the 2D material and the substrate. With the first voltage applied between the 2D material and the substrate, a second voltage is applied between the 2D material and a probe positioned proximate the 2D material. The second voltage between the 2D material and the probe is removed. The first voltage between the 2D material and the substrate is removed. A portion of the 2D material proximate the probe when the second voltage was applied has a different electron density compared to a remainder of the 2D material.
Two-dimensional fourier transform spectrometer
Energy Technology Data Exchange (ETDEWEB)
DeFlores, Lauren; Tokmakoff, Andrei
2016-10-25
The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.
Two-dimensional fourier transform spectrometer
DeFlores, Lauren; Tokmakoff, Andrei
2013-09-03
The present invention relates to a system and methods for acquiring two-dimensional Fourier transform (2D FT) spectra. Overlap of a collinear pulse pair and probe induce a molecular response which is collected by spectral dispersion of the signal modulated probe beam. Simultaneous collection of the molecular response, pulse timing and characteristics permit real time phasing and rapid acquisition of spectra. Full spectra are acquired as a function of pulse pair timings and numerically transformed to achieve the full frequency-frequency spectrum. This method demonstrates the ability to acquire information on molecular dynamics, couplings and structure in a simple apparatus. Multi-dimensional methods can be used for diagnostic and analytical measurements in the biological, biomedical, and chemical fields.
FACE RECOGNITION USING TWO DIMENSIONAL LAPLACIAN EIGENMAP
Institute of Scientific and Technical Information of China (English)
Chen Jiangfeng; Yuan Baozong; Pei Bingnan
2008-01-01
Recently,some research efforts have shown that face images possibly reside on a nonlinear sub-manifold. Though Laplacianfaces method considered the manifold structures of the face images,it has limits to solve face recognition problem. This paper proposes a new feature extraction method,Two Dimensional Laplacian EigenMap (2DLEM),which especially considers the manifold structures of the face images,and extracts the proper features from face image matrix directly by using a linear transformation. As opposed to Laplacianfaces,2DLEM extracts features directly from 2D images without a vectorization preprocessing. To test 2DLEM and evaluate its performance,a series of ex-periments are performed on the ORL database and the Yale database. Moreover,several experiments are performed to compare the performance of three 2D methods. The experiments show that 2DLEM achieves the best performance.
Equivalency of two-dimensional algebras
Energy Technology Data Exchange (ETDEWEB)
Santos, Gildemar Carneiro dos; Pomponet Filho, Balbino Jose S. [Universidade Federal da Bahia (UFBA), BA (Brazil). Inst. de Fisica
2011-07-01
Full text: Let us consider a vector z = xi + yj over the field of real numbers, whose basis (i,j) satisfy a given algebra. Any property of this algebra will be reflected in any function of z, so we can state that the knowledge of the properties of an algebra leads to more general conclusions than the knowledge of the properties of a function. However structural properties of an algebra do not change when this algebra suffers a linear transformation, though the structural constants defining this algebra do change. We say that two algebras are equivalent to each other whenever they are related by a linear transformation. In this case, we have found that some relations between the structural constants are sufficient to recognize whether or not an algebra is equivalent to another. In spite that the basis transform linearly, the structural constants change like a third order tensor, but some combinations of these tensors result in a linear transformation, allowing to write the entries of the transformation matrix as function of the structural constants. Eventually, a systematic way to find the transformation matrix between these equivalent algebras is obtained. In this sense, we have performed the thorough classification of associative commutative two-dimensional algebras, and find that even non-division algebra may be helpful in solving non-linear dynamic systems. The Mandelbrot set was used to have a pictorial view of each algebra, since equivalent algebras result in the same pattern. Presently we have succeeded in classifying some non-associative two-dimensional algebras, a task more difficult than for associative one. (author)
On numerical evaluation of two-dimensional phase integrals
DEFF Research Database (Denmark)
Lessow, H.; Rusch, W.; Schjær-Jacobsen, Hans
1975-01-01
The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated.......The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated....
Comparative Two-Dimensional Fluorescence Gel Electrophoresis.
Ackermann, Doreen; König, Simone
2018-01-01
Two-dimensional comparative fluorescence gel electrophoresis (CoFGE) uses an internal standard to increase the reproducibility of coordinate assignment for protein spots visualized on 2D polyacrylamide gels. This is particularly important for samples, which need to be compared without the availability of replicates and thus cannot be studied using differential gel electrophoresis (DIGE). CoFGE corrects for gel-to-gel variability by co-running with the sample proteome a standardized marker grid of 80-100 nodes, which is formed by a set of purified proteins. Differentiation of reference and analyte is possible by the use of two fluorescent dyes. Variations in the y-dimension (molecular weight) are corrected by the marker grid. For the optional control of the x-dimension (pI), azo dyes can be used. Experiments are possible in both vertical and horizontal (h) electrophoresis devices, but hCoFGE is much easier to perform. For data analysis, commercial software capable of warping can be adapted.
Two-dimensional hexagonal semiconductors beyond graphene
Nguyen, Bich Ha; Hieu Nguyen, Van
2016-12-01
The rapid and successful development of the research on graphene and graphene-based nanostructures has been substantially enlarged to include many other two-dimensional hexagonal semiconductors (THS): phosphorene, silicene, germanene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs) such as MoS2, MoSe2, WS2, WSe2 as well as the van der Waals heterostructures of various THSs (including graphene). The present article is a review of recent works on THSs beyond graphene and van der Waals heterostructures composed of different pairs of all THSs. One among the priorities of new THSs compared to graphene is the presence of a non-vanishing energy bandgap which opened up the ability to fabricate a large number of electronic, optoelectronic and photonic devices on the basis of these new materials and their van der Waals heterostructures. Moreover, a significant progress in the research on TMDCs was the discovery of valley degree of freedom. The results of research on valley degree of freedom and the development of a new technology based on valley degree of freedom-valleytronics are also presented. Thus the scientific contents of the basic research and practical applications os THSs are very rich and extremely promising.
Two-Dimensional Phononic Crystals: Disorder Matters.
Wagner, Markus R; Graczykowski, Bartlomiej; Reparaz, Juan Sebastian; El Sachat, Alexandros; Sledzinska, Marianna; Alzina, Francesc; Sotomayor Torres, Clivia M
2016-09-14
The design and fabrication of phononic crystals (PnCs) hold the key to control the propagation of heat and sound at the nanoscale. However, there is a lack of experimental studies addressing the impact of order/disorder on the phononic properties of PnCs. Here, we present a comparative investigation of the influence of disorder on the hypersonic and thermal properties of two-dimensional PnCs. PnCs of ordered and disordered lattices are fabricated of circular holes with equal filling fractions in free-standing Si membranes. Ultrafast pump and probe spectroscopy (asynchronous optical sampling) and Raman thermometry based on a novel two-laser approach are used to study the phononic properties in the gigahertz (GHz) and terahertz (THz) regime, respectively. Finite element method simulations of the phonon dispersion relation and three-dimensional displacement fields furthermore enable the unique identification of the different hypersonic vibrations. The increase of surface roughness and the introduction of short-range disorder are shown to modify the phonon dispersion and phonon coherence in the hypersonic (GHz) range without affecting the room-temperature thermal conductivity. On the basis of these findings, we suggest a criteria for predicting phonon coherence as a function of roughness and disorder.
Two-dimensional topological photonic systems
Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng
2017-09-01
The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.
Radiation effects on two-dimensional materials
Energy Technology Data Exchange (ETDEWEB)
Walker, R.C. II; Robinson, J.A. [Department of Materials Science, Penn State, University Park, PA (United States); Center for Two-Dimensional Layered Materials, Penn State, University Park, PA (United States); Shi, T. [Department of Mechanical and Nuclear Engineering, Penn State, University Park, PA (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States); Silva, E.C. [GlobalFoundries, Malta, NY (United States); Jovanovic, I. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI (United States)
2016-12-15
The effects of electromagnetic and particle irradiation on two-dimensional materials (2DMs) are discussed in this review. Radiation creates defects that impact the structure and electronic performance of materials. Determining the impact of these defects is important for developing 2DM-based devices for use in high-radiation environments, such as space or nuclear reactors. As such, most experimental studies have been focused on determining total ionizing dose damage to 2DMs and devices. Total dose experiments using X-rays, gamma rays, electrons, protons, and heavy ions are summarized in this review. We briefly discuss the possibility of investigating single event effects in 2DMs based on initial ion beam irradiation experiments and the development of 2DM-based integrated circuits. Additionally, beneficial uses of irradiation such as ion implantation to dope materials or electron-beam and helium-beam etching to shape materials have begun to be used on 2DMs and are reviewed as well. For non-ionizing radiation, such as low-energy photons, we review the literature on 2DM-based photo-detection from terahertz to UV. The majority of photo-detecting devices operate in the visible and UV range, and for this reason they are the focus of this review. However, we review the progress in developing 2DMs for detecting infrared and terahertz radiation. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Photodetectors based on two dimensional materials
Zheng, Lou; Zhongzhu, Liang; Guozhen, Shen
2016-09-01
Two-dimensional (2D) materials with unique properties have received a great deal of attention in recent years. This family of materials has rapidly established themselves as intriguing building blocks for versatile nanoelectronic devices that offer promising potential for use in next generation optoelectronics, such as photodetectors. Furthermore, their optoelectronic performance can be adjusted by varying the number of layers. They have demonstrated excellent light absorption, enabling ultrafast and ultrasensitive detection of light in photodetectors, especially in their single-layer structure. Moreover, due to their atomic thickness, outstanding mechanical flexibility, and large breaking strength, these materials have been of great interest for use in flexible devices and strain engineering. Toward that end, several kinds of photodetectors based on 2D materials have been reported. Here, we present a review of the state-of-the-art in photodetectors based on graphene and other 2D materials, such as the graphene, transition metal dichalcogenides, and so on. Project supported by the National Natural Science Foundation of China (Nos. 61377033, 61574132, 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.
Asymptotics for Two-dimensional Atoms
DEFF Research Database (Denmark)
Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip
2012-01-01
We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....
Ultrabroadband two-quantum two-dimensional electronic spectroscopy
Gellen, Tobias A.; Bizimana, Laurie A.; Carbery, William P.; Breen, Ilana; Turner, Daniel B.
2016-08-01
A recent theoretical study proposed that two-quantum (2Q) two-dimensional (2D) electronic spectroscopy should be a background-free probe of post-Hartree-Fock electronic correlations. Testing this theoretical prediction requires an instrument capable of not only detecting multiple transitions among molecular excited states but also distinguishing molecular 2Q signals from nonresonant response. Herein we describe a 2Q 2D spectrometer with a spectral range of 300 nm that is passively phase stable and uses only beamsplitters and mirrors. We developed and implemented a dual-chopping balanced-detection method to resolve the weak molecular 2Q signals. Experiments performed on cresyl violet perchlorate and rhodamine 6G revealed distinct 2Q signals convolved with nonresonant response. Density functional theory computations helped reveal the molecular origin of these signals. The experimental and computational results demonstrate that 2Q electronic spectra can provide a singular probe of highly excited electronic states.
Quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi$_2$
Wang, Kefeng; Graf, D.; Petrovic, C.
2016-01-01
We report quasi-two-dimensional Dirac fermions and quantum magnetoresistance in LaAgBi$_2$. The band structure shows several narrow bands with nearly linear energy dispersion and Dirac-cone-like points at the Fermi level. The quantum oscillation experiments revealed one quasi-two-dimensional Fermi pocket and another complex pocket with small cyclotron resonant mass. The in-plane transverse magnetoresistance exhibits a crossover at a critical field $B^*$ from semiclassical weak-field $B^2$ dep...
Electronic structure of boron based single and multi-layer two dimensional materials
Miyazato, Itsuki; Takahashi, Keisuke
2017-09-01
Two dimensional nanosheets based on boron and Group VA elements are designed and characterized using first principles calculations. B-N, B-P, B-As, B-Sb, and B-Bi are found to possess honeycomb structures where formation energies indicate exothermic reactions. Contrary to B-N, the cases of B-P, B-As, B-Sb, and B-Bi nanosheets are calculated to possess narrow band gaps. In addition, calculations reveal that the electronegativity difference between B and Group VA elements in the designed materials is a good indicator to predict the charge transfer and band gap of the two dimensional materials. Hydrogen adsorption over defect-free B-Sb and B-Bi results in exothermic reactions, while defect-free B-N, B-P, and B-As result in endothermic reactions. The layerability of the designed two dimensional materials is also investigated where the electronic structure of two-layered two dimensional materials is strongly coupled with how the two dimensional materials are layered. Thus, one can consider that the properties of two dimensional materials can be controlled by the composition of two dimensional materials and the structure of layers.
Two-dimensional gas of massless Dirac fermions in graphene.
Novoselov, K S; Geim, A K; Morozov, S V; Jiang, D; Katsnelson, M I; Grigorieva, I V; Dubonos, S V; Firsov, A A
2005-11-10
Quantum electrodynamics (resulting from the merger of quantum mechanics and relativity theory) has provided a clear understanding of phenomena ranging from particle physics to cosmology and from astrophysics to quantum chemistry. The ideas underlying quantum electrodynamics also influence the theory of condensed matter, but quantum relativistic effects are usually minute in the known experimental systems that can be described accurately by the non-relativistic Schrödinger equation. Here we report an experimental study of a condensed-matter system (graphene, a single atomic layer of carbon) in which electron transport is essentially governed by Dirac's (relativistic) equation. The charge carriers in graphene mimic relativistic particles with zero rest mass and have an effective 'speed of light' c* approximately 10(6) m s(-1). Our study reveals a variety of unusual phenomena that are characteristic of two-dimensional Dirac fermions. In particular we have observed the following: first, graphene's conductivity never falls below a minimum value corresponding to the quantum unit of conductance, even when concentrations of charge carriers tend to zero; second, the integer quantum Hall effect in graphene is anomalous in that it occurs at half-integer filling factors; and third, the cyclotron mass m(c) of massless carriers in graphene is described by E = m(c)c*2. This two-dimensional system is not only interesting in itself but also allows access to the subtle and rich physics of quantum electrodynamics in a bench-top experiment.
Comprehensive two-dimensional liquid chromatographic analysis of poloxamers.
Malik, Muhammad Imran; Lee, Sanghoon; Chang, Taihyun
2016-04-15
Poloxamers are low molar mass triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), having number of applications as non-ionic surfactants. Comprehensive one and two-dimensional liquid chromatographic (LC) analysis of these materials is proposed in this study. The separation of oligomers of both types (PEO and PPO) is demonstrated for several commercial poloxamers. This is accomplished at the critical conditions for one of the block while interaction for the other block. Reversed phase LC at CAP of PEO allowed for oligomeric separation of triblock copolymers with regard to PPO block whereas normal phase LC at CAP of PPO renders oligomeric separation with respect to PEO block. The oligomeric separation with regard to PEO and PPO are coupled online (comprehensive 2D-LC) to reveal two-dimensional contour plots by unconventional 2D IC×IC (interaction chromatography) coupling. The study provides chemical composition mapping of both PEO and PPO, equivalent to combined molar mass and chemical composition mapping for several commercial poloxamers.
Interaction of two-dimensional magnetoexcitons
Dumanov, E. V.; Podlesny, I. V.; Moskalenko, S. A.; Liberman, M. A.
2017-04-01
We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector k→∥ = 0 , taking into account the influence of the excited Landau levels (ELLs) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field. It is shown that the account of the ELLs gives rise to the repulsion between the spinless magnetoexcitons with k→∥ = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g (0) ∼ 1 / B) . In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 2D magnetoexcitons with k→∥ = 0 . The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g (0) 1 /√{ B} .
Two-dimensional materials and their prospects in transistor electronics.
Schwierz, F; Pezoldt, J; Granzner, R
2015-05-14
During the past decade, two-dimensional materials have attracted incredible interest from the electronic device community. The first two-dimensional material studied in detail was graphene and, since 2007, it has intensively been explored as a material for electronic devices, in particular, transistors. While graphene transistors are still on the agenda, researchers have extended their work to two-dimensional materials beyond graphene and the number of two-dimensional materials under examination has literally exploded recently. Meanwhile several hundreds of different two-dimensional materials are known, a substantial part of them is considered useful for transistors, and experimental transistors with channels of different two-dimensional materials have been demonstrated. In spite of the rapid progress in the field, the prospects of two-dimensional transistors still remain vague and optimistic opinions face rather reserved assessments. The intention of the present paper is to shed more light on the merits and drawbacks of two-dimensional materials for transistor electronics and to add a few more facets to the ongoing discussion on the prospects of two-dimensional transistors. To this end, we compose a wish list of properties for a good transistor channel material and examine to what extent the two-dimensional materials fulfill the criteria of the list. The state-of-the-art two-dimensional transistors are reviewed and a balanced view of both the pros and cons of these devices is provided.
Ultrafast two dimensional infrared chemical exchange spectroscopy
Fayer, Michael
2011-03-01
The method of ultrafast two dimensional infrared (2D IR) vibrational echo spectroscopy is described. Three ultrashort IR pulses tuned to the frequencies of the vibrational transitions of interest are directed into the sample. The interaction of these pulses with the molecular vibrational oscillators produces a polarization that gives rise to a fourth pulse, the vibrational echo. The vibrational echo pulse is combined with another pulse, the local oscillator, for heterodyne detection of the signal. For fixed time between the second and third pulses, the waiting time, the first pulse is scanned. Two Fourier transforms of the data yield a 2D IR spectrum. The waiting time is increased, and another spectrum is obtained. The change in the 2D IR spectra with increased waiting time provides information on the time evolution of the structure of the molecular system under observation. In a 2D IR chemical exchange experiment, two species A and B, are undergoing chemical exchange. A's are turning into B's, and B's are turning into A's, but the overall concentrations of the species are not changing. The kinetics of the chemical exchange on the ground electronic state under thermal equilibrium conditions can be obtained 2D IR spectroscopy. A vibration that has a different frequency for the two species is monitored. At very short time, there will be two peaks on the diagonal of the 2D IR spectrum, one for A and one for B. As the waiting time is increased, chemical exchange causes off-diagonal peaks to grow in. The time dependence of the growth of these off-diagonal peaks gives the chemical exchange rate. The method is applied to organic solute-solvent complex formation, orientational isomerization about a carbon-carbon single bond, migration of a hydrogen bond from one position on a molecule to another, protein structural substate interconversion, and water hydrogen bond switching between ions and water molecules. This work was supported by the Air Force Office of Scientific
Symmetry breaking of solitons in two-dimensional complex potentials
Yang, Jianke
2014-01-01
Symmetry breaking is reported for continuous families of solitons in the nonlinear Schr\\"odinger equation with a two-dimensional complex potential. This symmetry-breaking bifurcation is forbidden in generic complex potentials. However, for a special class of partially parity-time-symmetric potentials, such symmetry breaking is allowed. At the bifurcation point, two branches of asymmetric solitons bifurcate out from the base branch of symmetry-unbroken solitons. Stability of these solitons near the bifurcation point are also studied, and two novel stability properties for the bifurcated asymmetric solitons are revealed. One is that at the bifurcation point, zero and simple imaginary linear-stability eigenvalues of asymmetric solitons can move directly into the complex plane and create oscillatory instability. The other is that the two bifurcated asymmetric solitons, even though having identical powers and being related to each other by spatial mirror reflection, can possess different types of unstable eigenval...
Thermal conductivity of disordered two-dimensional binary alloys.
Zhou, Yang; Guo, Zhi-Xin; Cao, Hai-Yuan; Chen, Shi-You; Xiang, Hong-Jun; Gong, Xin-Gao
2016-10-20
Using non-equilibrium molecular dynamics simulations, we have studied the effect of disorder on the thermal conductivity of two-dimensional (2D) C1-xNx alloys. We find that the thermal conductivity not only depends on the substitution concentration of nitrogen, but also strongly depends on the disorder distribution. A general linear relationship is revealed between the thermal conductivity and the participation ratio of phonons in 2D alloys. Localization mode analysis further indicates that the thermal conductivity variation in the ordered alloys can be attributed to the number of inequivalent atoms. As for the disordered alloys, we find that the thermal conductivity variation can be described by a simple linear formula with the disorder degree and the substitution concentration. The present study suggests some general guidance for phonon manipulation and thermal engineering in low dimensional alloys.
Coherent two-dimensional spectroscopy of a Fano model
Poulsen, Felipe; Pullerits, Tõnu; Hansen, Thorsten
2016-01-01
The Fano lineshape arises from the interference of two excitation pathways to reach a continuum. Its generality has resulted in a tremendous success in explaining the lineshapes of many one-dimensional spectroscopies - absorption, emission, scattering, conductance, photofragmentation - applied to very varied systems - atoms, molecules, semiconductors and metals. Unravelling a spectroscopy into a second dimension reveals the relationship between states in addition to decongesting the spectra. Femtosecond-resolved two-dimensional electronic spectroscopy (2DES) is a four-wave mixing technique that measures the time-evolution of the populations, and coherences of excited states. It has been applied extensively to the dynamics of photosynthetic units, and more recently to materials with extended band-structures. In this letter, we solve the full time-dependent third-order response, measured in 2DES, of a Fano model and give the new system parameters that become accessible.
Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs
Mannix, Andrew J.; Zhou, Xiang-Feng; Kiraly, Brian; Wood, Joshua D.; Alducin, Diego; Myers, Benjamin D.; Liu, Xiaolong; Fisher, Brandon L.; Santiago, Ulises; Guest, Jeffrey R.; Yacaman, Miguel Jose; Ponce, Arturo; Oganov, Artem R.; Hersam, Mark C.; Guisinger, Nathan P.
2016-01-01
At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes.Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal. PMID:26680195
Many body localization in two dimensional square and triangular lattices
Gonzalez-Garcia, L; Paredes, R
2016-01-01
Ultracold interacting Bose atoms placed in disordered two dimensional optical lattices with square and triangular symmetries are found to be localized above a certain disorder strength amplitude. From a Gross-Pitaevskii mean analysis we determine the localization length as a function of the disorder strength and investigate the energy spectrum in terms of the disorder magnitude. We found that the localization length is observed to decrease faster in triangular geometries than in square ones. In the presence of a harmonic confinement localization is observed at the center of the trap. The analysis of the energy spectrum reveals that discrete energy levels acquire a finite width that is always smaller than the distance among energy levels.
Irreversibility of the two-dimensional enstrophy cascade
Piretto,; Boffetta, G
2016-01-01
We study the time irreversibility of the direct cascade in two-dimensional turbulence by looking at the time derivative of the square vorticity along Lagrangian trajectories, a quantity which we call metenstrophy. By means of extensive numerical simulations we measure the time irreversibility from the asymmetry of the PDF of the metenstrophy and we find that it increases with the Reynolds number of the cascade, similarly to what found in three-dimensional turbulence. A detailed analysis of the different contributions to the enstrophy budget reveals a remarkable difference with respect to what observed for the direct cascade, in particular the role of the statistics of the forcing to determine the degree of irreversibility.
Polarons and molecules in a two-dimensional Fermi gas
DEFF Research Database (Denmark)
Zöllner, Sascha; Bruun, Georg Morten; Pethick, C. J.
2011-01-01
We study an impurity atom in a two-dimensional Fermi gas using variational wave functions for (i) an impurity dressed by particle-hole excitations (polaron) and (ii) a dimer consisting of the impurity and a majority atom. In contrast to three dimensions, where similar calculations predict a sharp...... transition to a dimer state with increasing interspecies attraction, we show that the polaron Ansatz always gives a lower energy. However, the exact solution for a heavy impurity reveals that both a two-body bound state and distortions of the Fermi sea are crucial. This reflects the importance of particle......-hole pairs in lower dimensions and makes simple variational calculations unreliable. We show that the energy of an impurity gives important information about its dressing cloud, for which both Ansätze give inaccurate results....
Quasi-Two-Dimensional Magnetism in Co-Based Shandites
Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki
2016-06-01
We report quasi-two-dimensional (Q2D) itinerant electron magnetism in the layered Co-based shandites. Comprehensive magnetization measurements were performed using single crystals of Co3Sn2-xInxS2 (0 ≤ x ≤ 2) and Co3-yFeySn2S2 (0 ≤ y ≤ 0.5). The magnetic parameters of both systems; the Curie temperature TC, effective moment peff and spontaneous moment ps; exhibit almost identical variations against the In- and Fe-concentrations, indicating significance of the electron count on the magnetism in the Co-based shandite. The ferromagnetic-nonmagnetic quantum phase transition is found around xc ˜ 0.8. Analysis based on the extended Q2D spin fluctuation theory clearly reveals the highly Q2D itinerant electron character of the ferromagnetism in the Co-based shandites.
The convolution theorem for two-dimensional continuous wavelet transform
Institute of Scientific and Technical Information of China (English)
ZHANG CHI
2013-01-01
In this paper , application of two -dimensional continuous wavelet transform to image processes is studied. We first show that the convolution and correlation of two continuous wavelets satisfy the required admissibility and regularity conditions ,and then we derive the convolution and correlation theorem for two-dimensional continuous wavelet transform. Finally, we present numerical example showing the usefulness of applying the convolution theorem for two -dimensional continuous wavelet transform to perform image restoration in the presence of additive noise.
Optical Spectroscopy of Two Dimensional Graphene and Boron Nitride
Ju, Long
This dissertation describes the use of optical spectroscopy in studying the physical properties of two dimensional nano materials like graphene and hexagonal boron nitride. Compared to bulk materials, atomically thin two dimensional materials have a unique character that is the strong dependence of physical properties on external control. Both electronic band structure and chemical potential can be tuned in situ by electric field-which is a powerful knob in experiment. Therefore the optical study at atomic thickness scale can greatly benefit from modern micro-fabrication technique and electric control of the material properties. As will be shown in this dissertation, such control of both gemometric and physical properties enables new possibilities of optical spectroscopic measurement as well as opto-electronic studies. Other experimental techniques like electric transport and scanning tunneling microscopy and spectroscopy are also combined with optical spectroscopy to reveal the physics that is beyond the reach of each individual technique. There are three major themes in the dissertation. The first one is focused on the study of plasmon excitation of Dirac electrons in monolayer graphene. Unlike plasmons in ordinary two dimensional electron gas, plasmons of 2D electrons as in graphene obey unusual scaling laws. We fabricate graphene micro-ribbon arrays with photolithography technique and use optical absorption spectroscopy to study its absorption spectrum. The experimental result demonstrates the extraordinarily strong light-plasmon coupling and its novel dependence on both charge doping and geometric dimensions. This work provides a first glance at the fundamental properties of graphene plasmons and forms the basis of an emerging subfield of graphene research and applications such as graphene terahertz metamaterials. The second part describes the opto-electronic response of heterostructures composed of graphene and hexagonal boron nitride. We found that there is
Exercise echocardiography in asymptomatic survivors of childhood cancer treated with anthracyclines
DEFF Research Database (Denmark)
Sieswerda, Elske; Kremer, Leontien C M; Vidmar, Suzanna
2010-01-01
BACKGROUND: Exercise echocardiography reveals abnormalities in asymptomatic childhood cancer survivors who previously have been treated with anthracyclines. We determined the added value of monitoring childhood cancer survivors with exercise echocardiography compared to monitoring with resting ec...
Three-dimensional echocardiography
Energy Technology Data Exchange (ETDEWEB)
Buck, Thomas [University Hospital Essen (Germany). West German Heart Center; Franke, Andreas [Klinikum Region Hannover - Klinikum Siloah, Hannover (Germany). Dept. of Cardiology, Angiology and Intensive Care Medicine; Monaghan, Mark J. (eds.) [King' s College Hospital, London (United Kingdom)
2011-07-01
Presents tips and tricks for beginners and experts Provides educational material for 3D training courses Features comprehensively illustrated cases Includes an accompanying DVD with video clips of all sample cases Three-dimensional echocardiography is the most recent fundamental advancement in echocardiography. Since real-time 3D echocardiography became commercially available in 2002, it has rapidly been accepted in echo labs worldwide. This book covers all clinically relevant aspects of this fascinating new technology, including a comprehensive explanation of its basic principles, practical aspects of clinical application, and detailed descriptions of specific uses in the broad spectrum of clinically important heart disease. The book was written by a group of well-recognized international experts in the field, who have not only been involved in the scientific and clinical evolution of 3D echocardiography since its inception but are also intensively involved in expert training courses. As a result, the clear focus of this book is on the practical application of 3D echocardiography in daily clinical routine with tips and tricks for both beginners and experts, accompanied by more than 150 case examples comprehensively illustrated in more than 800 images and more than 500 videos provided on a DVD. In addition to an in-depth review of the most recent literature on real-time 3D echocardiography, this book represents an invaluable reference work for beginners and expert users of 3D echocardiography. - Tips and tricks for beginners and experts - Educational material for 3D training courses - Comprehensively illustrated cases - DVD with video clips of all sample cases.
The Chandrasekhar's Equation for Two-Dimensional Hypothetical White Dwarfs
De, Sanchari
2014-01-01
In this article we have extended the original work of Chandrasekhar on the structure of white dwarfs to the two-dimensional case. Although such two-dimensional stellar objects are hypothetical in nature, we strongly believe that the work presented in this article may be prescribed as Master of Science level class problem for the students in physics.
Beginning Introductory Physics with Two-Dimensional Motion
Huggins, Elisha
2009-01-01
During the session on "Introductory College Physics Textbooks" at the 2007 Summer Meeting of the AAPT, there was a brief discussion about whether introductory physics should begin with one-dimensional motion or two-dimensional motion. Here we present the case that by starting with two-dimensional motion, we are able to introduce a considerable…
Spatiotemporal surface solitons in two-dimensional photonic lattices.
Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S
2007-11-01
We analyze spatiotemporal light localization in truncated two-dimensional photonic lattices and demonstrate the existence of two-dimensional surface light bullets localized in the lattice corners or the edges. We study the families of the spatiotemporal surface solitons and their properties such as bistability and compare them with the modes located deep inside the photonic lattice.
Explorative data analysis of two-dimensional electrophoresis gels
DEFF Research Database (Denmark)
Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine;
2004-01-01
Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...
Mechanics of Apparent Horizon in Two Dimensional Dilaton Gravity
Cai, Rong-Gen
2016-01-01
In this article, we give a definition of apparent horizon in a two dimensional general dilaton gravity theory. With this definition, we construct the mechanics of the apparent horizon by introducing a quasi-local energy of the theory. Our discussion generalizes the apparent horizons mechanics in general spherically symmetric spactimes in four or higher dimensions to the two dimensional dilaton gravity case.
Topological aspect of disclinations in two-dimensional crystals
Institute of Scientific and Technical Information of China (English)
Qi Wei-Kai; Zhu Tao; Chen Yong; Ren Ji-Rong
2009-01-01
By using topological current theory, this paper studies the inner topological structure of disclinations during the melting of two-dimensional systems. From two-dimensional elasticity theory, it finds that there are topological currents for topological defects in homogeneous equation. The evolution of disclinations is studied, and the branch conditions for generating, annihilating, crossing, splitting and merging of disclinations are given.
Invariant Subspaces of the Two-Dimensional Nonlinear Evolution Equations
Directory of Open Access Journals (Sweden)
Chunrong Zhu
2016-11-01
Full Text Available In this paper, we develop the symmetry-related methods to study invariant subspaces of the two-dimensional nonlinear differential operators. The conditional Lie–Bäcklund symmetry and Lie point symmetry methods are used to construct invariant subspaces of two-dimensional differential operators. We first apply the multiple conditional Lie–Bäcklund symmetries to derive invariant subspaces of the two-dimensional operators. As an application, the invariant subspaces for a class of two-dimensional nonlinear quadratic operators are provided. Furthermore, the invariant subspace method in one-dimensional space combined with the Lie symmetry reduction method and the change of variables is used to obtain invariant subspaces of the two-dimensional nonlinear operators.
Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase
Lu, Jian; Hwang, Harold Y; Ofori-Okai, Benjamin K; Fleischer, Sharly; Nelson, Keith A
2016-01-01
Ultrafast two-dimensional spectroscopy utilizes correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum. Its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. Here we report ultrafast two-dimensional terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by three terahertz field-dipole interactions. The nonlinear time-domain orientation signals are mapped into the frequency domain in two-dimensional rotational spectra which reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.
Ionic solutions of two-dimensional materials
Cullen, Patrick L.; Cox, Kathleen M.; Bin Subhan, Mohammed K.; Picco, Loren; Payton, Oliver D.; Buckley, David J.; Miller, Thomas S.; Hodge, Stephen A.; Skipper, Neal T.; Tileli, Vasiliki; Howard, Christopher A.
2016-11-01
Strategies for forming liquid dispersions of nanomaterials typically focus on retarding reaggregation, for example via surface modification, as opposed to promoting the thermodynamically driven dissolution common for molecule-sized species. Here we demonstrate the true dissolution of a wide range of important 2D nanomaterials by forming layered material salts that spontaneously dissolve in polar solvents yielding ionic solutions. The benign dissolution advantageously maintains the morphology of the starting material, is stable against reaggregation and can achieve solutions containing exclusively individualized monolayers. Importantly, the charge on the anionic nanosheet solutes is reversible, enables targeted deposition over large areas via electroplating and can initiate novel self-assembly upon drying. Our findings thus reveal a unique solution-like behaviour for 2D materials that enables their scalable production and controlled manipulation.
Two-dimensional discrete gap breathers in a two-dimensional discrete diatomic Klein-Gordon lattice
Institute of Scientific and Technical Information of China (English)
XU Quan; QIANG Tian
2009-01-01
We study the existence and stability of two-dimensional discrete breathers in a two-dimensional discrete diatomic Klein-Gordon lattice consisting of alternating light and heavy atoms, with nearest-neighbor harmonic coupling.Localized solutions to the corresponding nonlinear differential equations with frequencies inside the gap of the linear wave spectrum, i.e. two-dimensional gap breathers, are investigated numerically. The numerical results of the corresponding algebraic equations demonstrate the possibility of the existence of two-dimensional gap breathers with three types of symmetries, i.e., symmetric, twin-antisymmetric and single-antisymmetric. Their stability depends on the nonlinear on-site potential (soft or hard), the interaction potential (attractive or repulsive)and the center of the two-dimensional gap breather (on a light or a heavy atom).
Hernandez, Carlos M; Arisha, Mohammed J; Ahmad, Amier; Oates, Ethan; Nanda, Navin C; Nanda, Anil; Wasan, Anita; Caleti, Beda E; Bernal, Cinthia L P; Gallardo, Sergio M
2017-07-01
Loeffler endocarditis is a complication of hypereosinophilic syndrome resulting from eosinophilic infiltration of heart tissue. We report a case of Loeffler endocarditis in which three-dimensional transthoracic and transesophageal echocardiography provided additional information to what was found by two-dimensional transthoracic echocardiography alone. Our case illustrates the usefulness of combined two- and three-dimensional echocardiography in the assessment of Loeffler endocarditis. In addition, a summary of the features of hypereosinophilic syndrome and Loeffler endocarditis is provided in tabular form. © 2017, Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
Hsu YL
2016-03-01
Full Text Available Yueh-Lun Hsu, Hui-Pi Huang Institute of Veterinary Clinical Science, Veterinary School, National Taiwan University, Taipei, Taiwan Abstract: Ventricular heterogeneity and synchrony are associated with hypertrophic cardiomyopathy in humans. Hypertrophic cardiomyopathy is commonly observed in cats. The aim of this study was to determine the presence and normal range of left ventricular mechanical heterogeneity and synchrony in clinically healthy cats using two-dimensional speckle-tracking echocardiography. Thirty-four clinically healthy cats were included in this prospective study. Two-dimensional echocardiography and two-dimensional speckle-tracking echocardiography were performed on all cats. Echocardiographic parameters, including circumferential, radial, and longitudinal strain and strain rate, heterogeneity, and synchrony, were measured. Segmental heterogeneity values in the circumferential, radial, and longitudinal directions were 13.1%±5.9%, 19.1%±10.3%, and 15.4%±6.8%, respectively. Transmural heterogeneity was -14.3%±4.6% in the circumferential direction. Left ventricular synchrony values in the circumferential, radial, and longitudinal directions were 11.7±4.2, 16.5±13.4, and 19.4±8.5 ms, respectively. Interventricular synchrony was -3.9±13.2 ms. Left ventricular heterogeneity and synchrony were noted in clinically healthy cats; segmental heterogeneity, which is characterized as longitudinal, progressively increased from the apical to the basal segments, while transmural heterogeneity, which is characterized as circumferential, progressively decreased from the endocardium to the epicardium. Keywords: feline, ventricular heterogeneity, synchrony
Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway
2012-09-01
ER D C/ CH L TR -1 2 -2 0 Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway C oa st al a n d H yd ra u lic s La b or at...distribution is unlimited. ERDC/CHL TR-12-20 September 2012 Two Dimensional Hydrodynamic Analysis of the Moose Creek Floodway Stephen H. Scott, Jeremy A...A two-dimensional Adaptive Hydraulics (AdH) hydrodynamic model was developed to simulate the Moose Creek Floodway. The Floodway is located
RESEARCH ON TWO-DIMENSIONAL LDA FOR FACE RECOGNITION
Institute of Scientific and Technical Information of China (English)
Han Ke; Zhu Xiuchang
2006-01-01
The letter presents an improved two-dimensional linear discriminant analysis method for feature extraction. Compared with the current two-dimensional methods for feature extraction, the improved two-dimensional linear discriminant analysis method makes full use of not only the row and the column direction information of face images but also the discriminant information among different classes. The method is evaluated using the Nanjing University of Science and Technology (NUST) 603 face database and the Aleix Martinez and Robert Benavente (AR) face database. Experimental results show that the method in the letter is feasible and effective.
ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES
Directory of Open Access Journals (Sweden)
Nikola Stefanović
2007-06-01
Full Text Available In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic leadership style, leadership theory researchers use two dimensional matrices. The two-dimensional matrices define leadership styles on the basis of different parameters. By using these parameters, one can identify two-dimensional styles.
Advanced Three-Dimensional Echocardiography
B. Ren (Ben)
2014-01-01
markdownabstract__Abstract__ During the development of echocardiography, 3D echocardiography imaging represents a major innovation in cardiovascular ultrasound (Figure 1). Advancements in computer and transducer technologies permit real-time 3D acquisition and presentation of cardiac
Short-range magnetic order in two-dimensional cobalt-ferrite nanoparticle assemblies
Georgescu, M; Viota, J.L.; Klokkenburg, M.; Erne, B.H.; Vanmaekelbergh, D.; Zeijlmans Van Emmichoven, P.A.
2008-01-01
Magnetic order in two-dimensional islands of spherical 21 nm cobalt-ferrite (CoFe2O4) nanoparticles is studied by magnetic force microscopy and spectroscopy. Images obtained at a temperature of 105 K clearly reveal the presence of repulsive and attractive areas on top of the islands. Monte Carlo
Silverman, S; Sanchez-Migallon Guzman, D; Stern, J; Gustavsen, K A; Griffiths, L G
2016-06-01
To objectively and subjectively describe the normal spectrum of two-dimensional echocardiographic findings in the central bearded dragon (Pogona vitticeps). Sixteen central bearded dragons. Central bearded dragons were prospectively evaluated under manual restraint in right and left lateral recumbency to identify imaging planes for reproducible measurements of cardiac chambers, subjective two-dimensional analysis and color Doppler assessment. Echocardiography can be performed through windows in the left and right axillae. The window in the left axilla allows for a subjective and objective assessment of cardiac structure and function. The right axillary window allows for evaluation of pulmonary artery flow. Both views provide data for the presence of pericardial effusion or valvular insufficiency. With optimized imaging planes, cardiac chambers and fractional area change along with fractional shortening in the longitudinal and transverse planes can be calculated. Body weight and cardiac chamber dimensions of males were significantly larger than females. Ventricular fractional area change was the most consistent functional assessment. The majority of animals were found to have no evidence of valvular insufficiency, while approximately half had evidence of pericardial fluid. Pulmonary artery flow was assessed in all patients. Left and right aortic velocities cannot be reliably obtained. This study is the first to generate reference values for cardiac structure and function in clinically healthy central bearded dragons. Valvular insufficiency is not a normal finding in central bearded dragons, while mild pericardial effusion may be. Copyright © 2015 Elsevier B.V. All rights reserved.
Ellis, S.; Giometti, C. S.; Riley, D. A.
1985-01-01
Using 320 g rats, a two-dimensional electrophoretic analysis of muscle proteins in the soleus and EDL muscles from hindlimbs maintained load-free for 10 days is performed. Statistical analysis of the two-dimensional patterns of control and suspended groups reveals more protein alteration in the soleus muscle, with 25 protein differences, than the EDL muscle, with 9 protein differences, as a result of atrophy. Most of the soleus differences reside in minor components. It is suggested that the EDL may also show alteration in its two-dimensional protein map, even though no significant atrophy occurred in muscle wet weight. It is cautioned that strict interpretation of data must take into account possible endocrine perturbations.
Two-dimensional networks of lanthanide cubane-shaped dumbbells.
Savard, Didier; Lin, Po-Heng; Burchell, Tara J; Korobkov, Ilia; Wernsdorfer, Wolfgang; Clérac, Rodolphe; Murugesu, Muralee
2009-12-21
The syntheses, structures, and magnetic properties are reported for three new lanthanide complexes, [Ln(III)(4)(mu(3)-OH)(2)(mu(3)-O)(2)(cpt)(6)(MeOH)(6)(H(2)O)](2) (Ln = Dy (1.15MeOH), Ho (2.14MeOH), and Tb (3.18MeOH)), based on 4-(4-carboxyphenyl)-1,2,4-triazole ligand (Hcpt). The three complexes were confirmed to be isomorphous by infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure of 1 reveals that the eight-coordinate metal centers are organized in two cubane-shaped moieties composed of four Dy(III) ions each. All metal centers in the cubane core are bridged by two mu(3)-oxide and two mu(3)-hydroxide asymmetrical units. Moreover, each cubane is linked to its neighbor by two externally coordinating ligands, forming the dumbbell {Dy(III)(4)}(2) moiety. Electrostatic interactions between the ligands of the triazole-bridged dimers form an extended supramolecular two-dimensional arrangement analogous to a metal-organic framework with quadrilateral spaces occupied by ligands from axial sheets and by four solvent molecules. The magnetic properties of the three compounds have been investigated using dc and ac susceptibility measurements. For 1, the static and dynamic data corroborate the fact that the {Dy(III)(4)} cubane-shaped core exhibits slow relaxation of its magnetization below 5 K associated with a single-molecule magnet behavior.
Two-dimensional Fourier transform ESR correlation spectroscopy
Gorcester, Jeff; Freed, Jack H.
1988-04-01
We describe our pulsed two-dimensional Fourier transform ESR experiment and demonstrate its applicabilty for the double resonance of motionally narrowed nitroxides. Multiple pulse irradiation of the entire nitroxide spectrum enables the correlation of two precessional periods, allowing observation of cross correlations between hyperfine lines introduced by magnetization transfer in the case of a three-pulse experiment (2D ELDOR), or coherence transfer in the case of a two-pulse experiment (COSY). Cross correlations are revealed by the presence of cross peaks which connect the autocorrelation lines appearing along the diagonal ω1=ω2. The amplitudes of these cross peaks are determined by the rates of magnetization transfer in the 2D ELDOR experiment. The density operator theory for the experiment is outlined and applied to the determination of Heisenberg exchange (HE) rates in 2,2,6,6-tetramethyl-4-piperidone-N-oxyl-d15 (PD-tempone) dissolved in toluene-d8. The quantitative accuracy of this experiment is established by comparison with the HE rate measured from the dependence of the spin echo T2 on nitroxide concentration.
Two-dimensional screening of the Wageningen chicken BAC library.
Crooijmans, R P; Vrebalov, J; Dijkhof, R J; van der Poel, J J; Groenen, M A
2000-05-01
We have constructed a Bacterial Artificial Chromosome (BAC) library that provides 5.5-fold redundant coverage of the chicken genome. The library was made by cloning partial HindIII-digested high-molecular-weight (HMW) DNA of a female White Leghorn chicken into the HindIII site of the vector pECBAC1. Several modifications of standard protocols were necessary to clone efficiently large partial HindIII DNA fragments. The library consists of 49,920 clones arranged in 130 384-well plates. An average insert size of 134 kb was estimated from the analysis of 152 randomly selected BAC clones. The average number of NotI restriction sites per clone was 0.77. After individual growth, DNA was isolated of the pooled clones of each 384-well plate, and subsequently DNA of each plate was isolated from the individual row and column pools. Screening of the Wageningen chicken BAC library was performed by two-dimensional PCR with 125 microsatellite markers. For 124 markers at least one BAC clone was obtained. FISH experiments of 108 BAC clones revealed chimerism in less than 1%. The number of different BAC clones per marker present in the BAC library was examined for 35 markers which resulted in a total of 167 different BAC clones. Per marker the number of BAC clones varied from 1 to 11, with an average of 4.77. The chicken BAC library constitutes an invaluable tool for positional cloning and for comparative mapping studies.
A study of two-dimensional magnetic polaron
Institute of Scientific and Technical Information of China (English)
LIU; Tao; ZHANG; Huaihong; FENG; Mang; WANG; Kelin
2006-01-01
By using the variational method and anneal simulation, we study in this paper the self-trapped magnetic polaron (STMP) in two-dimensional anti-ferromagnetic material and the bound magnetic polaron (BMP) in ferromagnetic material. Schwinger angular momentum theory is applied to changing the problem into a coupling problem of carriers and two types of Bosons. Our calculation shows that there are single-peak and multi-peak structures in the two-dimensional STMP. For the ferromagnetic material, the properties of the two-dimensional BMP are almost the same as that in one-dimensional case; but for the anti-ferromagnetic material, the two-dimensional STMP structure is much richer than the one-dimensional case.
UPWIND DISCONTINUOUS GALERKIN METHODS FOR TWO DIMENSIONAL NEUTRON TRANSPORT EQUATIONS
Institute of Scientific and Technical Information of China (English)
袁光伟; 沈智军; 闫伟
2003-01-01
In this paper the upwind discontinuous Galerkin methods with triangle meshes for two dimensional neutron transport equations will be studied.The stability for both of the semi-discrete and full-discrete method will be proved.
Two-Dimensionally-Modulated, Magnetic Structure of Neodymium Metal
DEFF Research Database (Denmark)
Lebech, Bente; Bak, P.
1979-01-01
The incipient magnetic order of dhcp Nd is described by a two-dimensional, incommensurably modulated structure ("triple-q" structure). The ordering is accompanied by a lattice distortion that forms a similar pattern....
Entanglement Entropy for time dependent two dimensional holographic superconductor
Mazhari, N S; Myrzakulov, Kairat; Myrzakulov, R
2016-01-01
We studied entanglement entropy for a time dependent two dimensional holographic superconductor. We showed that the conserved charge of the system plays the role of the critical parameter to have condensation.
Decoherence in a Landau Quantized Two Dimensional Electron Gas
Directory of Open Access Journals (Sweden)
McGill Stephen A.
2013-03-01
Full Text Available We have studied the dynamics of a high mobility two-dimensional electron gas as a function of temperature. The presence of satellite reflections in the sample and magnet can be modeled in the time-domain.
Quantization of Two-Dimensional Gravity with Dynamical Torsion
Lavrov, P M
1999-01-01
We consider two-dimensional gravity with dynamical torsion in the Batalin - Vilkovisky and Batalin - Lavrov - Tyutin formalisms of gauge theories quantization as well as in the background field method.
Spatiotemporal dissipative solitons in two-dimensional photonic lattices.
Mihalache, Dumitru; Mazilu, Dumitru; Lederer, Falk; Kivshar, Yuri S
2008-11-01
We analyze spatiotemporal dissipative solitons in two-dimensional photonic lattices in the presence of gain and loss. In the framework of the continuous-discrete cubic-quintic Ginzburg-Landau model, we demonstrate the existence of novel classes of two-dimensional spatiotemporal dissipative lattice solitons, which also include surface solitons located in the corners or at the edges of the truncated two-dimensional photonic lattice. We find the domains of existence and stability of such spatiotemporal dissipative solitons in the relevant parameter space, for both on-site and intersite lattice solitons. We show that the on-site solitons are stable in the whole domain of their existence, whereas most of the intersite solitons are unstable. We describe the scenarios of the instability-induced dynamics of dissipative solitons in two-dimensional lattices.
Bound states of two-dimensional relativistic harmonic oscillators
Institute of Scientific and Technical Information of China (English)
Qiang Wen-Chao
2004-01-01
We give the exact normalized bound state wavefunctions and energy expressions of the Klein-Gordon and Dirac equations with equal scalar and vector harmonic oscillator potentials in the two-dimensional space.
A two-dimensional polymer prepared by organic synthesis.
Kissel, Patrick; Erni, Rolf; Schweizer, W Bernd; Rossell, Marta D; King, Benjamin T; Bauer, Thomas; Götzinger, Stephan; Schlüter, A Dieter; Sakamoto, Junji
2012-02-05
Synthetic polymers are widely used materials, as attested by a production of more than 200 millions of tons per year, and are typically composed of linear repeat units. They may also be branched or irregularly crosslinked. Here, we introduce a two-dimensional polymer with internal periodicity composed of areal repeat units. This is an extension of Staudinger's polymerization concept (to form macromolecules by covalently linking repeat units together), but in two dimensions. A well-known example of such a two-dimensional polymer is graphene, but its thermolytic synthesis precludes molecular design on demand. Here, we have rationally synthesized an ordered, non-equilibrium two-dimensional polymer far beyond molecular dimensions. The procedure includes the crystallization of a specifically designed photoreactive monomer into a layered structure, a photo-polymerization step within the crystal and a solvent-induced delamination step that isolates individual two-dimensional polymers as free-standing, monolayered molecular sheets.
Second invariant for two-dimensional classical super systems
Indian Academy of Sciences (India)
S C Mishra; Roshan Lal; Veena Mishra
2003-10-01
Construction of superpotentials for two-dimensional classical super systems (for ≥ 2) is carried out. Some interesting potentials have been studied in their super form and also their integrability.
Measured Two-Dimensional Ice-Wedge Polygon Thermal Dynamics
Cable, William; Romanovsky, Vladimir; Busey, Robert
2016-04-01
necessarily found in areas of higher MAGT. Active layer thickness does not appear to be correlated to mean annual air temperature but rather is a function of summer air temperature or thawing degree-days. While the refreezing of the active layer initiated at nearly the same time for all locations and polygons, we find differences in the proportion of top-down versus bottom-up freezing and the length of time required to complete the refreezing process. Examination of the daily temperature dynamics using interpolated two-dimensional temperature fields reveal that during the summer, the predominate temperature gradient is vertical while the isotherms tend to follow the topography. However, as the active layer begins to refreeze and snow accumulates, the thermal regime diverges. The fall shows an increased temperature gradient horizontally with landscape positions containing higher soil moisture and/or snow depth (low centers and troughs) cooling more slowly than the adjacent ground (rims and high centers). This two-dimensional effect is greatest as the active layer refreezes and persists until mid-winter, by which time the temperature gradients are again mostly vertical and the isotherms follow the topography. Our findings demonstrate the complexity and two-dimensionality of the temperature dynamics in these landscapes.
Extreme paths in oriented two-dimensional percolation
Andjel, E. D.; Gray, L. F.
2016-01-01
International audience; A useful result about leftmost and rightmost paths in two dimensional bond percolation is proved. This result was introduced without proof in \\cite{G} in the context of the contact process in continuous time. As discussed here, it also holds for several related models, including the discrete time contact process and two dimensional site percolation. Among the consequences are a natural monotonicity in the probability of percolation between different sites and a somewha...
Two Dimensional Nucleation Process by Monte Carlo Simulation
T., Irisawa; K., Matsumoto; Y., Arima; T., Kan; Computer Center, Gakushuin University; Department of Physics, Gakushuin University
1997-01-01
Two dimensional nucleation process on substrate is investigated by Monte Carlo simulation, and the critical nucleus size and its waiting time are measured with a high accuracy. In order to measure the critical nucleus with a high accuracy, we calculate the attachment and the detachment rate to the nucleus directly, and define the critical nucleus size when both rate are equal. Using the kinematical nucleation theory by Nishioka, it is found that, our obtained kinematical two dimensional criti...
Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers
2016-06-15
polymers . 2. Introduction . Research objectives: This research aims to study the physical (van der Waals forces: crystal epitaxy and π-π...AFRL-AFOSR-JP-TR-2016-0071 Controlled Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers Cheolmin Park YONSEI UNIVERSITY...Interactions between Two Dimensional Layered Inorganic Nanosheets and Polymers 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA2386-14-1-4054 5c. PROGRAM ELEMENT
Two-Dimensional Weak Pseudomanifolds on Eight Vertices
Indian Academy of Sciences (India)
Basudeb Datta; Nandini Nilakantan
2002-05-01
We explicitly determine all the two-dimensional weak pseudomanifolds on 8 vertices. We prove that there are (up to isomorphism) exactly 95 such weak pseudomanifolds, 44 of which are combinatorial 2-manifolds. These 95 weak pseudomanifolds triangulate 16 topological spaces. As a consequence, we prove that there are exactly three 8-vertex two-dimensional orientable pseudomanifolds which allow degree three maps to the 4-vertex 2-sphere.
Two-Dimensional Materials for Sensing: Graphene and Beyond
Directory of Open Access Journals (Sweden)
Seba Sara Varghese
2015-09-01
Full Text Available Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications.
Transesophageal echocardiography: Instrumentation and system controls
Directory of Open Access Journals (Sweden)
Mahesh Prabhu
2012-01-01
Full Text Available Transesophageal echocardiography (TEE is a semi-invasive, monitoring and diagnostic tool, which is used in the perioperative management of cardiac surgical and hemodynamically unstable patients. The low degree of invasiveness and the capacity to visualize and assimilate dynamic information that can change the course of the patient management is an important advantage of TEE. Although TEE is reliable, comprehensive, credible, and cost-effective, it must be performed by a trained echocardiographer who understands the indications and the potential complications of the procedure, and has the ability to achieve proper acquisition and interpretation of the echocardiographic data. Adequate knowledge of the physics of ultrasound and the TEE machine controls is imperative to optimize image quality, reduce artifacts, and prevent misinterpretation of diagnosis. Two-dimensional (2D and Motion (M mode imaging are used for obtaining anatomical information, while Doppler and Color Flow imaging are used for information on blood flow. 3D technology enables us to view the cardiac structures from different perspectives. Despite the recent advances of 3D TEE, a sharp, optimized 2D image is pivotal for the reconstruction. This article describes the relevant underlying physical principles of ultrasound and focuses on a systematic approach to instrumentation and use of controls in the practical use of transesophageal echocardiography.
Barbosa, Marcia M; Vasconcelos, Maria Carmen M; Ferrari, Teresa Cristina A; Fernandes, Bárbara Martins; Passaglia, Luiz Guilherme; Silva, Célia Maria; Nunes, Maria Carmo P
2014-11-01
Sickle cell disease (SCD) is a hemoglobinopathy that is common worldwide. It usually presents with cardiac involvement, although data on systolic function are somewhat controversial. The aim of this study was to investigate the value of speckle-tracking strain, a deformation index, in detecting ventricular dysfunction in SCD. Ninety adult patients with SCD were compared with 20 healthy controls. Doppler echocardiography with Doppler tissue imaging was performed in all, and the left and right ventricles were analyzed by the use of two-dimensional speckle-tracking strain. The mean age of the patients with SCD was 26 years, and 43% were men. Left ventricular (LV) dimensions and mass were higher in patients with SCD, whereas LV ejection fraction did not differ from the controls. E and A waves, as well as E/e' ratio, were also higher in patients with SCD. Two-dimensional speckle-tracking strain of both ventricles in the patients with SCD was not different from that of controls. The factors independently associated with LV longitudinal strain were age (P = .009), oximetry (P = .001), lactate dehydrogenase (P = .014), LV ejection fraction (P speckle-tracking strain of both ventricles was similar in patients and controls, suggesting normal myocardial contractility in patients with SCD. LV global longitudinal strain was associated with age, intensity of hemolysis, and ventricular function. Copyright © 2014 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.
Tracking dynamics of two-dimensional continuous attractor neural networks
Fung, C. C. Alan; Wong, K. Y. Michael; Wu, Si
2009-12-01
We introduce an analytically solvable model of two-dimensional continuous attractor neural networks (CANNs). The synaptic input and the neuronal response form Gaussian bumps in the absence of external stimuli, and enable the network to track external stimuli by its translational displacement in the two-dimensional space. Basis functions of the two-dimensional quantum harmonic oscillator in polar coordinates are introduced to describe the distortion modes of the Gaussian bump. The perturbative method is applied to analyze its dynamics. Testing the method by considering the network behavior when the external stimulus abruptly changes its position, we obtain results of the reaction time and the amplitudes of various distortion modes, with excellent agreement with simulation results.
Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.
Wang, Qing Hua; Kalantar-Zadeh, Kourosh; Kis, Andras; Coleman, Jonathan N; Strano, Michael S
2012-11-01
The remarkable properties of graphene have renewed interest in inorganic, two-dimensional materials with unique electronic and optical attributes. Transition metal dichalcogenides (TMDCs) are layered materials with strong in-plane bonding and weak out-of-plane interactions enabling exfoliation into two-dimensional layers of single unit cell thickness. Although TMDCs have been studied for decades, recent advances in nanoscale materials characterization and device fabrication have opened up new opportunities for two-dimensional layers of thin TMDCs in nanoelectronics and optoelectronics. TMDCs such as MoS(2), MoSe(2), WS(2) and WSe(2) have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as transistors, photodetectors and electroluminescent devices. We review the historical development of TMDCs, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Hamiltonian formalism of two-dimensional Vlasov kinetic equation.
Pavlov, Maxim V
2014-12-08
In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.
Control Operator for the Two-Dimensional Energized Wave Equation
Directory of Open Access Journals (Sweden)
Sunday Augustus REJU
2006-07-01
Full Text Available This paper studies the analytical model for the construction of the two-dimensional Energized wave equation. The control operator is given in term of space and time t independent variables. The integral quadratic objective cost functional is subject to the constraint of two-dimensional Energized diffusion, Heat and a source. The operator that shall be obtained extends the Conjugate Gradient method (ECGM as developed by Hestenes et al (1952, [1]. The new operator enables the computation of the penalty cost, optimal controls and state trajectories of the two-dimensional energized wave equation when apply to the Conjugate Gradient methods in (Waziri & Reju, LEJPT & LJS, Issues 9, 2006, [2-4] to appear in this series.
A two-dimensional spin liquid in quantum kagome ice.
Carrasquilla, Juan; Hao, Zhihao; Melko, Roger G
2015-06-22
Actively sought since the turn of the century, two-dimensional quantum spin liquids (QSLs) are exotic phases of matter where magnetic moments remain disordered even at zero temperature. Despite ongoing searches, QSLs remain elusive, due to a lack of concrete knowledge of the microscopic mechanisms that inhibit magnetic order in materials. Here we study a model for a broad class of frustrated magnetic rare-earth pyrochlore materials called quantum spin ices. When subject to an external magnetic field along the [111] crystallographic direction, the resulting interactions contain a mix of geometric frustration and quantum fluctuations in decoupled two-dimensional kagome planes. Using quantum Monte Carlo simulations, we identify a set of interactions sufficient to promote a groundstate with no magnetic long-range order, and a gap to excitations, consistent with a Z2 spin liquid phase. This suggests an experimental procedure to search for two-dimensional QSLs within a class of pyrochlore quantum spin ice materials.
Spectral Radiative Properties of Two-Dimensional Rough Surfaces
Xuan, Yimin; Han, Yuge; Zhou, Yue
2012-12-01
Spectral radiative properties of two-dimensional rough surfaces are important for both academic research and practical applications. Besides material properties, surface structures have impact on the spectral radiative properties of rough surfaces. Based on the finite difference time domain algorithm, this paper studies the spectral energy propagation process on a two-dimensional rough surface and analyzes the effect of different factors such as the surface structure, angle, and polarization state of the incident wave on the spectral radiative properties of the two-dimensional rough surface. To quantitatively investigate the spatial distribution of energy reflected from the rough surface, the concept of the bidirectional reflectance distribution function is introduced. Correlation analysis between the reflectance and different impact factors is conducted to evaluate the influence degree. Comparison between the theoretical and experimental data is given to elucidate the accuracy of the computational code. This study is beneficial to optimizing the surface structures of optoelectronic devices such as solar cells.
Two dimensional convolute integers for machine vision and image recognition
Edwards, Thomas R.
1988-01-01
Machine vision and image recognition require sophisticated image processing prior to the application of Artificial Intelligence. Two Dimensional Convolute Integer Technology is an innovative mathematical approach for addressing machine vision and image recognition. This new technology generates a family of digital operators for addressing optical images and related two dimensional data sets. The operators are regression generated, integer valued, zero phase shifting, convoluting, frequency sensitive, two dimensional low pass, high pass and band pass filters that are mathematically equivalent to surface fitted partial derivatives. These operators are applied non-recursively either as classical convolutions (replacement point values), interstitial point generators (bandwidth broadening or resolution enhancement), or as missing value calculators (compensation for dead array element values). These operators show frequency sensitive feature selection scale invariant properties. Such tasks as boundary/edge enhancement and noise or small size pixel disturbance removal can readily be accomplished. For feature selection tight band pass operators are essential. Results from test cases are given.
Optical modulators with two-dimensional layered materials
Sun, Zhipei; Wang, Feng
2016-01-01
Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that two-dimensional layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this review, we cover the state-of-the-art of optical modulators based on two-dimensional layered materials including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as two-dimensional heterostructures, plasmonic structures, and silicon/fibre integrated structures. We also take a look at future perspectives and discuss the potential of yet relatively unexplored mechanisms such as magneto-optic and acousto-optic modulation.
Two-dimensional superconductors with atomic-scale thickness
Uchihashi, Takashi
2017-01-01
Recent progress in two-dimensional superconductors with atomic-scale thickness is reviewed mainly from the experimental point of view. The superconducting systems treated here involve a variety of materials and forms: elemental metal ultrathin films and atomic layers on semiconductor surfaces; interfaces and superlattices of heterostructures made of cuprates, perovskite oxides, and rare-earth metal heavy-fermion compounds; interfaces of electric-double-layer transistors; graphene and atomic sheets of transition metal dichalcogenide; iron selenide and organic conductors on oxide and metal surfaces, respectively. Unique phenomena arising from the ultimate two dimensionality of the system and the physics behind them are discussed.
TreePM Method for Two-Dimensional Cosmological Simulations
Indian Academy of Sciences (India)
Suryadeep Ray
2004-09-01
We describe the two-dimensional TreePM method in this paper. The 2d TreePM code is an accurate and efficient technique to carry out large two-dimensional N-body simulations in cosmology. This hybrid code combines the 2d Barnes and Hut Tree method and the 2d Particle–Mesh method. We describe the splitting of force between the PM and the Tree parts. We also estimate error in force for a realistic configuration. Finally, we discuss some tests of the code.
Singular analysis of two-dimensional bifurcation system
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Bifurcation properties of two-dimensional bifurcation system are studied in this paper.Universal unfolding and transition sets of the bifurcation equations are obtained.The whole parametric plane is divided into several different persistent regions according to the type of motion,and the different qualitative bifurcation diagrams in different persistent regions are given.The bifurcation properties of the two-dimensional bifurcation system are compared with its reduced one-dimensional system.It is found that the system which is reduced to one dimension has lost many bifurcation properties.
Critical Behaviour of a Two-Dimensional Random Antiferromagnet
DEFF Research Database (Denmark)
Als-Nielsen, Jens Aage; Birgeneau, R. J.; Guggenheim, H. J.
1976-01-01
A neutron scattering study of the order parameter, correlation length and staggered susceptibility of the two-dimensional random antiferromagnet Rb2Mn0.5Ni0.5F4 is reported. The system is found to exhibit a well-defined phase transition with critical exponents identical to those of the isomorphou...... pure materials K2NiF4 and K2MnF4. Thus, in these systems, which have the asymptotic critical behaviour of the two-dimensional Ising model, randomness has no measurable effect on the phase-transition behaviour....
Nonlinear excitations in two-dimensional molecular structures with impurities
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Rasmussen, Kim; Christiansen, Peter Leth
1995-01-01
We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence of the imp......We study the nonlinear dynamics of electronic excitations interacting with acoustic phonons in two-dimensional molecular structures with impurities. We show that the problem is reduced to the nonlinear Schrodinger equation with a varying coefficient. The latter represents the influence...... excitations. Analytical results are in good agreement with numerical simulations of the nonlinear Schrodinger equation....
Vortices in the Two-Dimensional Simple Exclusion Process
Bodineau, T.; Derrida, B.; Lebowitz, Joel L.
2008-06-01
We show that the fluctuations of the partial current in two dimensional diffusive systems are dominated by vortices leading to a different scaling from the one predicted by the hydrodynamic large deviation theory. This is supported by exact computations of the variance of partial current fluctuations for the symmetric simple exclusion process on general graphs. On a two-dimensional torus, our exact expressions are compared to the results of numerical simulations. They confirm the logarithmic dependence on the system size of the fluctuations of the partial flux. The impact of the vortices on the validity of the fluctuation relation for partial currents is also discussed in an Appendix.
Two-dimensional hazard estimation for longevity analysis
DEFF Research Database (Denmark)
Fledelius, Peter; Guillen, M.; Nielsen, J.P.
2004-01-01
the two-dimensional mortality surface. Furthermore we look at aggregated synthetic population metrics as 'population life expectancy' and 'population survival probability'. For Danish women these metrics indicate decreasing mortality with respect to chronological time. The metrics can not directly be used......We investigate developments in Danish mortality based on data from 1974-1998 working in a two-dimensional model with chronological time and age as the two dimensions. The analyses are done with non-parametric kernel hazard estimation techniques. The only assumption is that the mortality surface...... for analysis of economic implications arising from mortality changes....
Field analysis of two-dimensional focusing grating couplers
Borsboom, P.-P.; Frankena, H. J.
1995-05-01
A different technique was developed by which several two-dimensional dielectric optical gratings, consisting 100 or more corrugations, were treated in a numerical reliable approach. The numerical examples that were presented were restricted to gratings made up of sequences of waveguide sections symmetric about the x = 0 plane. The newly developed method was effectively used to investigate the field produced by a two-dimensional focusing grating coupler. Focal-region fields were determined for three symmetrical gratings with 19, 50, and 124 corrugations. For focusing grating coupler with limited length, high-frequency intensity variations were noted in the focal region.
Self-assembly of two-dimensional DNA crystals
Institute of Scientific and Technical Information of China (English)
SONG Cheng; CHEN Yaqing; WEI Shuai; YOU Xiaozeng; XIAO Shoujun
2004-01-01
Self-assembly of synthetic oligonucleotides into two-dimensional lattices presents a 'bottom-up' approach to the fabrication of devices on nanometer scale. We report the design and observation of two-dimensional crystalline forms of DNAs that are composed of twenty-one plane oligonucleotides and one phosphate-modified oligonucleotide. These synthetic sequences are designed to self-assemble into four double-crossover (DX) DNA tiles. The 'sticky ends' of these tiles that associate according to Watson-Crick's base pairing are programmed to build up specific periodic patterns upto tens of microns. The patterned crystals are visualized by the transmission electron microscopy.
Dynamics of vortex interactions in two-dimensional flows
DEFF Research Database (Denmark)
Juul Rasmussen, J.; Nielsen, A.H.; Naulin, V.
2002-01-01
a critical value, a(c). Using the Weiss-field, a(c) is estimated for vortex patches. Introducing an effective radius for vortices with distributed vorticity, we find that 3.3 a(c) ...The dynamics and interaction of like-signed vortex structures in two dimensional flows are investigated by means of direct numerical solutions of the two-dimensional Navier-Stokes equations. Two vortices with distributed vorticity merge when their distance relative to their radius, d/R-0l. is below...
Two-dimensional assignment with merged measurements using Langrangrian relaxation
Briers, Mark; Maskell, Simon; Philpott, Mark
2004-01-01
Closely spaced targets can result in merged measurements, which complicate data association. Such merged measurements violate any assumption that each measurement relates to a single target. As a result, it is not possible to use the auction algorithm in its simplest form (or other two-dimensional assignment algorithms) to solve the two-dimensional target-to-measurement assignment problem. We propose an approach that uses the auction algorithm together with Lagrangian relaxation to incorporate the additional constraints resulting from the presence of merged measurements. We conclude with some simulated results displaying the concepts introduced, and discuss the application of this research within a particle filter context.
Two-dimensional lattice Boltzmann model for magnetohydrodynamics.
Schaffenberger, Werner; Hanslmeier, Arnold
2002-10-01
We present a lattice Boltzmann model for the simulation of two-dimensional magnetohydro dynamic (MHD) flows. The model is an extension of a hydrodynamic lattice Boltzman model with 9 velocities on a square lattice resulting in a model with 17 velocities. Earlier lattice Boltzmann models for two-dimensional MHD used a bidirectional streaming rule. However, the use of such a bidirectional streaming rule is not necessary. In our model, the standard streaming rule is used, allowing smaller viscosities. To control the viscosity and the resistivity independently, a matrix collision operator is used. The model is then applied to the Hartmann flow, giving reasonable results.
Quasinormal frequencies of asymptotically flat two-dimensional black holes
Lopez-Ortega, A
2011-01-01
We discuss whether the minimally coupled massless Klein-Gordon and Dirac fields have well defined quasinormal modes in single horizon, asymptotically flat two-dimensional black holes. To get the result we solve the equations of motion in the massless limit and we also calculate the effective potentials of Schrodinger type equations. Furthermore we calculate exactly the quasinormal frequencies of the Dirac field propagating in the two-dimensional uncharged Witten black hole. We compare our results on its quasinormal frequencies with other already published.
Spin dynamics in a two-dimensional quantum gas
DEFF Research Database (Denmark)
Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank
2014-01-01
We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...
Institute of Scientific and Technical Information of China (English)
Xu Quan; Tian Qiang
2009-01-01
This paper discusses the two-dimensional discrete monatomic Fermi-Pasta-Ulam lattice, by using the method of multiple-scale and the quasi-discreteness approach. By taking into account the interaction between the atoms in the lattice and their nearest neighbours, it obtains some classes of two-dimensional local models as follows: two-dimensional bright and dark discrete soliton trains, two-dimensional bright and dark line discrete breathers, and two-dimensional bright and dark discrete breather.
Yang, Ren-jie; Yang, Yan-rong; Dong, Gui-mei; Du, Yan-hong; Shan, Hui-yong; Zhang, Wei-yu
2014-08-01
Based on Euclidian distances between synchronous two-dimensional infrared correlation spectra, in terms of the average Euclidian distances between unknown samples and "extreme samples", and average intra- and inter-Euclidian distances of samples in the calibration set, a new method for the discrimination of adulterated milk was proposed. Sixteen pure milk samples were collected and 16 adulterated milk samples with urea (0.01-0.3 g x L(-1)), and 16 adulterated milk samples with melamine (0.01-0.3 g x L(-1)) samples were prepared, respectively. The IR absorption spectra of all samples were measured at room temperature. The synchronous two-dimensional correlation spectra were generated from concentration-dependent spectral variation of adulterant in milk. The Euclidian distances were calculated between synchronous two-dimensional infrared correlation spectra of all samples. Then, the classification models were built respectively for adulterated milk with urea, and adiulterated milk with melamine. The "extreme samples", average intra- and inter-Euclidian distances were determined. Finally, the unknown samples in prediction set were predicted using constructed models in terms of classification rules of adulterated milk. The classification accuracy rates for pure milk and adulterated milk were 100%. The effectiveness of the proposed method was verified. The results obtained in this study revealed that synchronous two-dimensional infrared correlation spectra in combination with Euclidian distance has a feasible potential to discriminate adulterated milk and pure milk.
Mapping two-dimensional polar active fluids to two-dimensional soap and one-dimensional sandblasting
Chen, Leiming; Lee, Chiu Fan; Toner, John
2016-07-01
Active fluids and growing interfaces are two well-studied but very different non-equilibrium systems. Each exhibits non-equilibrium behaviour distinct from that of their equilibrium counterparts. Here we demonstrate a surprising connection between these two: the ordered phase of incompressible polar active fluids in two spatial dimensions without momentum conservation, and growing one-dimensional interfaces (that is, the 1+1-dimensional Kardar-Parisi-Zhang equation), in fact belong to the same universality class. This universality class also includes two equilibrium systems: two-dimensional smectic liquid crystals, and a peculiar kind of constrained two-dimensional ferromagnet. We use these connections to show that two-dimensional incompressible flocks are robust against fluctuations, and exhibit universal long-ranged, anisotropic spatio-temporal correlations of those fluctuations. We also thereby determine the exact values of the anisotropy exponent ζ and the roughness exponents χx,y that characterize these correlations.
The partition function of two-dimensional string theory
Dijkgraaf, Robbert; Moore, Gregory; Plesser, Ronen
1993-04-01
We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in two-dimensional string theory. This expression makes manifest relations of the c = 1 system to KP flow nd W 1 + ∞ constraints. Moreover we derive a Kontsevich-Penner integral representation of this generating functional.
The partition function of two-dimensional string theory
Energy Technology Data Exchange (ETDEWEB)
Dijkgraaf, R. (School of Natural Sciences, Inst. for Advanced Study, Princeton, NJ (United States) Dept. of Mathematics, Univ. Amsterdam (Netherlands)); Moore, G.; Plesser, R. (Dept. of Physics, Yale Univ., New Haven, CT (United States))
1993-04-12
We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in two-dimensional string theory. This expression makes manifest relations of the c=1 system to KP flow and W[sub 1+[infinity
Two-Dimensional Electronic Spectroscopy of a Model Dimer System
Directory of Open Access Journals (Sweden)
Prokhorenko V.I.
2013-03-01
Full Text Available Two-dimensional spectra of a dimer were measured to determine the timescale for electronic decoherence at room temperature. Anti-correlated beats in the crosspeaks were observed only during the period corresponding to the measured homogeneous lifetime.
Torque magnetometry studies of two-dimensional electron systems
Schaapman, Maaike Ruth
2004-01-01
This thesis describes a study of the magnetization two-dimensional electron gases (2DEGs). To detect the typically small magnetization, a sensitive magnetometer with optical angular detection was developed. The magnetometer uses a quadrant detector to measure the rotation of the sample. By mounting
Low-frequency scattering from two-dimensional perfect conductors
DEFF Research Database (Denmark)
Hansen, Thorkild; Yaghjian, A.D
1991-01-01
Exact expressions have been obtained for the leading terms in the low-frequency expansions of the far fields scattered from three different types of two-dimensional perfect conductors: a cylinder with finite cross section, a cylindrical bump on an infinite ground plane, and a cylindrical dent...
Two-Dimensional Mesoscale-Ordered Conducting Polymers
Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang
2016-01-01
Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of assem
Piezoelectricity and Piezomagnetism: Duality in two-dimensional checkerboards
Fel, Leonid G.
2002-05-01
The duality approach in two-dimensional two-component regular checkerboards is extended to piezoelectricity and piezomagnetism. The relation between the effective piezoelectric and piezomagnetic moduli is found for a checkerboard with the p6'mm'-plane symmetry group (dichromatic triangle).
Specification of a Two-Dimensional Test Case
DEFF Research Database (Denmark)
Nielsen, Peter Vilhelm
This paper describes the geometry and other boundary conditions for a test case which can be used to test different two-dimensional CFD codes in the lEA Annex 20 work. The given supply opening is large compared with practical openings. Therefore, this geometry will reduce the need for a high number...... of grid points in the wall jet region....
Operator splitting for two-dimensional incompressible fluid equations
Holden, Helge; Karper, Trygve K
2011-01-01
We analyze splitting algorithms for a class of two-dimensional fluid equations, which includes the incompressible Navier-Stokes equations and the surface quasi-geostrophic equation. Our main result is that the Godunov and Strang splitting methods converge with the expected rates provided the initial data are sufficiently regular.
Chaotic dynamics for two-dimensional tent maps
Pumariño, Antonio; Ángel Rodríguez, José; Carles Tatjer, Joan; Vigil, Enrique
2015-02-01
For a two-dimensional extension of the classical one-dimensional family of tent maps, we prove the existence of an open set of parameters for which the respective transformation presents a strange attractor with two positive Lyapounov exponents. Moreover, periodic orbits are dense on this attractor and the attractor supports a unique ergodic invariant probability measure.
Divorticity and dihelicity in two-dimensional hydrodynamics
DEFF Research Database (Denmark)
Shivamoggi, B.K.; van Heijst, G.J.F.; Juul Rasmussen, Jens
2010-01-01
A framework is developed based on the concepts of divorticity B (≡×ω, ω being the vorticity) and dihelicity g (≡vB) for discussing the theoretical structure underlying two-dimensional (2D) hydrodynamics. This formulation leads to the global and Lagrange invariants that could impose significant...
Spin-orbit torques in two-dimensional Rashba ferromagnets
Qaiumzadeh, A.; Duine, R. A.|info:eu-repo/dai/nl/304830127; Titov, M.
2015-01-01
Magnetization dynamics in single-domain ferromagnets can be triggered by a charge current if the spin-orbit coupling is sufficiently strong. We apply functional Keldysh theory to investigate spin-orbit torques in metallic two-dimensional Rashba ferromagnets in the presence of spin-dependent
Numerical blowup in two-dimensional Boussinesq equations
Yin, Zhaohua
2009-01-01
In this paper, we perform a three-stage numerical relay to investigate the finite time singularity in the two-dimensional Boussinesq approximation equations. The initial asymmetric condition is the middle-stage output of a $2048^2$ run, the highest resolution in our study is $40960^2$, and some signals of numerical blowup are observed.
Exact two-dimensional superconformal R symmetry and c extremization.
Benini, Francesco; Bobev, Nikolay
2013-02-08
We uncover a general principle dubbed c extremization, which determines the exact R symmetry of a two-dimensional unitary superconformal field theory with N=(0,2) supersymmetry. To illustrate its utility, we study superconformal theories obtained by twisted compactifications of four-dimensional N=4 super-Yang-Mills theory on Riemann surfaces and construct their gravity duals.
Zero sound in a two-dimensional dipolar Fermi gas
Lu, Z.K.; Matveenko, S.I.; Shlyapnikov, G.V.
2013-01-01
We study zero sound in a weakly interacting two-dimensional (2D) gas of single-component fermionic dipoles (polar molecules or atoms with a large magnetic moment) tilted with respect to the plane of their translational motion. It is shown that the propagation of zero sound is provided by both mean-f
Topology optimization of two-dimensional elastic wave barriers
DEFF Research Database (Denmark)
Van Hoorickx, C.; Sigmund, Ole; Schevenels, M.
2016-01-01
Topology optimization is a method that optimally distributes material in a given design domain. In this paper, topology optimization is used to design two-dimensional wave barriers embedded in an elastic halfspace. First, harmonic vibration sources are considered, and stiffened material is insert...
Non perturbative methods in two dimensional quantum field theory
Abdalla, Elcio; Rothe, Klaus D
1991-01-01
This book is a survey of methods used in the study of two-dimensional models in quantum field theory as well as applications of these theories in physics. It covers the subject since the first model, studied in the fifties, up to modern developments in string theories, and includes exact solutions, non-perturbative methods of study, and nonlinear sigma models.
Thermodynamics of Two-Dimensional Black-Holes
Nappi, Chiara R.; Pasquinucci, Andrea
1992-01-01
We explore the thermodynamics of a general class of two dimensional dilatonic black-holes. A simple prescription is given that allows us to compute the mass, entropy and thermodynamic potentials, with results in agreement with those obtained by other methods, when available.
Influence of index contrast in two dimensional photonic crystal lasers
DEFF Research Database (Denmark)
Jørgensen, Mette Marie; Petersen, Sidsel Rübner; Christiansen, Mads Brøkner;
2010-01-01
The influence of index contrast variations for obtaining single-mode operation and low threshold in dye doped polymer two dimensional photonic crystal (PhC) lasers is investigated. We consider lasers made from Pyrromethene 597 doped Ormocore imprinted with a rectangular lattice PhC having a cavit...
Magnetic order in two-dimensional nanoparticle assemblies
Georgescu, M
2008-01-01
This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the
Dynamical phase transitions in the two-dimensional ANNNI model
Energy Technology Data Exchange (ETDEWEB)
Barber, M.N.; Derrida, B.
1988-06-01
We study the phase diagram of the two-dimensional anisotropic next-nearest neighbor Ising (ANNNI) model by comparing the time evolution of two distinct spin configurations submitted to the same thermal noise. We clearly se several dynamical transitions between ferromagnetic, paramagnetic, antiphase, and floating phases. These dynamical transitions seem to occur rather close to the transition lines determined previously in the literature.
Two-dimensional static black holes with pointlike sources
Melis, M
2004-01-01
We study the static black hole solutions of generalized two-dimensional dilaton-gravity theories generated by pointlike mass sources, in the hypothesis that the matter is conformally coupled. We also discuss the motion of test particles. Due to conformal coupling, these follow the geodesics of a metric obtained by rescaling the canonical metric with the dilaton.
Magnetic order in two-dimensional nanoparticle assemblies
Georgescu, M
2008-01-01
This thesis involves a fundamental study of two-dimensional arrays of magnetic nanoparticles using non-contact Atomic Force Microscopy, Magnetic Force Microscopy, and Atomic Force Spectroscopy. The goal is to acquire a better understanding of the interactions between magnetic nanoparticles and the r
Two-Dimensional Chirality in Three-Dimensional Chemistry.
Wintner, Claude E.
1983-01-01
The concept of two-dimensional chirality is used to enhance students' understanding of three-dimensional stereochemistry. This chirality is used as a key to teaching/understanding such concepts as enaniotropism, diastereotopism, pseudoasymmetry, retention/inversion of configuration, and stereochemical results of addition to double bonds. (JN)
Field analysis of two-dimensional focusing grating
Borsboom, P.P.; Frankena, H.J.
1995-01-01
The method that we have developed [P-P. Borsboom, Ph.D. dissertation (Delft University of Technology, Delft, The Netherlands); P-P. Borsboom and H. J. Frankena, J. Opt. Soc. Am. A 12, 1134–1141 (1995)] is successfully applied to a two-dimensional focusing grating coupler. The field in the focal regi
Torque magnetometry studies of two-dimensional electron systems
Schaapman, Maaike Ruth
2004-01-01
This thesis describes a study of the magnetization two-dimensional electron gases (2DEGs). To detect the typically small magnetization, a sensitive magnetometer with optical angular detection was developed. The magnetometer uses a quadrant detector to measure the rotation of the sample. By mounting
Two-Dimensional Mesoscale-Ordered Conducting Polymers
Liu, Shaohua; Zhang, Jian; Dong, Renhao; Gordiichuk, Pavlo; Zhang, Tao; Zhuang, Xiaodong; Mai, Yiyong; Liu, Feng; Herrmann, Andreas; Feng, Xinliang
2016-01-01
Despite the availability of numerous two-dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale-ordered superstructures within a 2D monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of
Vibrations of Thin Piezoelectric Shallow Shells: Two-Dimensional Approximation
Indian Academy of Sciences (India)
N Sabu
2003-08-01
In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two-dimensional eigenvalue problem.
Two-dimensional effects in nonlinear Kronig-Penney models
DEFF Research Database (Denmark)
Gaididei, Yuri Borisovich; Christiansen, Peter Leth; Rasmussen, Kim
1997-01-01
An analysis of two-dimensional (2D) effects in the nonlinear Kronig-Penney model is presented. We establish an effective one-dimensional description of the 2D effects, resulting in a set of pseudodifferential equations. The stationary states of the 2D system and their stability is studied...
Forensic potential of comprehensive two-dimensional gas chromatography
Sampat, A.; Lopatka, M.; Sjerps, M.; Vivo-Truyols, G.; Schoenmakers, P.; van Asten, A.
2016-01-01
In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC-MS) have been studied in detail, not o
Easy interpretation of optical two-dimensional correlation spectra
Lazonder, K.; Pshenichnikov, M.S.; Wiersma, D.A.
2006-01-01
We demonstrate that the value of the underlying frequency-frequency correlation function can be retrieved from a two-dimensional optical correlation spectrum through a simple relationship. The proposed method yields both intuitive clues and a quantitative measure of the dynamics of the system. The t
Two Dimensional F(R) Horava-Lifshitz Gravity
Kluson, J
2016-01-01
We study two-dimensional F(R) Horava-Lifshitz gravity from the Hamiltonian point of view. We determine constraints structure with emphasis on the careful separation of the second class constraints and global first class constraints. We determine number of physical degrees of freedom and also discuss gauge fixing of the global first class constraints.
Localization of Tight Closure in Two-Dimensional Rings
Indian Academy of Sciences (India)
Kamran Divaani-Aazar; Massoud Tousi
2005-02-01
It is shown that tight closure commutes with localization in any two-dimensional ring of prime characteristic if either is a Nagata ring or possesses a weak test element. Moreover, it is proved that tight closure commutes with localization at height one prime ideals in any ring of prime characteristic.
Cryptanalysis of the Two-Dimensional Circulation Encryption Algorithm
Directory of Open Access Journals (Sweden)
Bart Preneel
2005-07-01
Full Text Available We analyze the security of the two-dimensional circulation encryption algorithm (TDCEA, recently published by Chen et al. in this journal. We show that there are several flaws in the algorithm and describe some attacks. We also address performance issues in current cryptographic designs.
New directions in science and technology: two-dimensional crystals
Energy Technology Data Exchange (ETDEWEB)
Neto, A H Castro [Graphene Research Centre, National University of Singapore, 2 Science Drive 3, Singapore 117542 (Singapore); Novoselov, K, E-mail: phycastr@nus.edu.sg, E-mail: konstantin.novoselov@manchester.ac.uk [School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester, M13 9PL (United Kingdom)
2011-08-15
Graphene is possibly one of the largest and fastest growing fields in condensed matter research. However, graphene is only one example in a large class of two-dimensional crystals with unusual properties. In this paper we briefly review the properties of graphene and look at the exciting possibilities that lie ahead.
Boundary-value problems for two-dimensional canonical systems
Hassi, Seppo; De Snoo, H; Winkler, Henrik
2000-01-01
The two-dimensional canonical system Jy' = -lHy where the nonnegative Hamiltonian matrix function H(x) is trace-normed on (0,∞) has been studied in a function-theoretic way by L. de Branges. We show that the Hamiltonian system induces a closed symmetric relation which can be reduced to a, not necess
On the continua in two-dimensional nonadiabatic magnetohydrodynamic spectra
De Ploey, A.; Van der Linden, R. A. M.; Belien, A. J. C.
2000-01-01
The equations for the continuous subspectra of the linear magnetohydrodynamic (MHD) normal modes spectrum of two-dimensional (2D) plasmas are derived in general curvilinear coordinates, taking nonadiabatic effects in the energy equation into account. Previously published derivations of continuous sp
Dislocation climb in two-dimensional discrete dislocation dynamics
Davoudi, K.M.; Nicola, L.; Vlassak, J.J.
2012-01-01
In this paper, dislocation climb is incorporated in a two-dimensional discrete dislocation dynamics model. Calculations are carried out for polycrystalline thin films, passivated on one or both surfaces. Climb allows dislocations to escape from dislocation pile-ups and reduces the strain-hardening r
SAR Processing Based On Two-Dimensional Transfer Function
Chang, Chi-Yung; Jin, Michael Y.; Curlander, John C.
1994-01-01
Exact transfer function, ETF, is two-dimensional transfer function that constitutes basis of improved frequency-domain-convolution algorithm for processing synthetic-aperture-radar, SAR data. ETF incorporates terms that account for Doppler effect of motion of radar relative to scanned ground area and for antenna squint angle. Algorithm based on ETF outperforms others.
Sound waves in two-dimensional ducts with sinusoidal walls
Nayfeh, A. H.
1974-01-01
The method of multiple scales is used to analyze the wave propagation in two-dimensional hard-walled ducts with sinusoidal walls. For traveling waves, resonance occurs whenever the wall wavenumber is equal to the difference of the wavenumbers of any two duct acoustic modes. The results show that neither of these resonating modes could occur without strongly generating the other.
Confined two-dimensional fermions at finite density
De Francia, M; Loewe, M; Santangelo, E M; De Francia, M; Falomir, H; Loewe, M; Santangelo, E M
1995-01-01
We introduce the chemical potential in a system of two-dimensional massless fermions, confined to a finite region, by imposing twisted boundary conditions in the Euclidean time direction. We explore in this simple model the application of functional techniques which could be used in more complicated situations.
Bounds on the capacity of constrained two-dimensional codes
DEFF Research Database (Denmark)
Forchhammer, Søren; Justesen, Jørn
2000-01-01
Bounds on the capacity of constrained two-dimensional (2-D) codes are presented. The bounds of Calkin and Wilf apply to first-order symmetric constraints. The bounds are generalized in a weaker form to higher order and nonsymmetric constraints. Results are given for constraints specified by run...
Miniature sensor for two-dimensional magnetic field distributions
Fluitman, J.H.J.; Krabbe, H.W.
1972-01-01
Describes a simple method of production of a sensor for two-dimensional magnetic field distributions. The sensor consists of a strip of Ni-Fe(81-19), of which the magnetoresistance is utilized. Typical dimensions of the strip, placed at the edge of a glass substrate, are: length 100 mu m, width 2 or
Forensic potential of comprehensive two-dimensional gas chromatography
Sampat, A.; Lopatka, M.; Sjerps, M.; Vivo-Truyols, G.; Schoenmakers, P.; van Asten, A.
2016-01-01
In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC-MS) have been studied in detail, not o
Spontaneous emission in two-dimensional photonic crystal microcavities
DEFF Research Database (Denmark)
Søndergaard, Thomas
2000-01-01
The properties of the radiation field in a two-dimensional photonic crystal with and without a microcavity introduced are investigated through the concept of the position-dependent photon density of states. The position-dependent rate of spontaneous radiative decay for a two-level atom with random...
Linkage analysis by two-dimensional DNA typing
te Meerman, G J; Mullaart, E; van der Meulen, M A; den Daas, J H; Morolli, B; Uitterlinden, A G; Vijg, J
1993-01-01
In two-dimensional (2-D) DNA typing, genomic DNA fragments are separated, first according to size by electrophoresis in a neutral polyacrylamide gel and second according to sequence by denaturing gradient gel electrophoresis, followed by hybridization analysis using micro- and minisatellite core pro
Phase conjugated Andreev backscattering in two-dimensional ballistic cavities
Morpurgo, A.F.; Holl, S.; Wees, B.J.van; Klapwijk, T.M; Borghs, G.
1997-01-01
We have experimentally investigated transport in two-dimensional ballistic cavities connected to a point contact and to two superconducting electrodes with a tunable macroscopic phase difference. The point contact resistance oscillates as a function of the phase difference in a way which reflects
Two-dimensional manifold with point-like defects
Gani, Vakhid A; Rubin, Sergei G
2014-01-01
We study a class of two-dimensional extra spaces isomorphic to the $S^2$ sphere in the framework of the multidimensional gravitation. We show that there exists a family of stationary metrics that depend on the initial (boundary) conditions. All these geometries have a singular point. We also discuss the possibility for these deformed extra spaces to be considered as dark matter candidates.
Instability of two-dimensional heterotic stringy black holes
Azreg-Ainou, M
1999-01-01
We solve the eigenvalue problem of general relativity for the case of charged black holes in two-dimensional heterotic string theory, derived by McGuigan et al. For the case of $m^{2}>q^{2}$, we find a physically acceptable time-dependent growing mode; thus the black hole is unstable. The extremal case $m^{2}=q^{2}$ is stable.
Institute of Scientific and Technical Information of China (English)
XIONG Lei; LI haijiao; ZHANG Lewen
2008-01-01
The fourth-order B spline wavelet scaling functions are used to solve the two-dimensional unsteady diffusion equation. The calculations from a case history indicate that the method provides high accuracy and the computational efficiency is enhanced due to the small matrix derived from this method.The respective features of 3-spline wavelet scaling functions, 4-spline wavelet scaling functions and quasi-wavelet used to solve the two-dimensional unsteady diffusion equation are compared. The proposed method has potential applications in many fields including marine science.
Addressing asymmetry of the charge and strain in a two-dimensional fullerene peapod
Valeš, V.; Verhagen, T.; Vejpravová, J.; Frank, O.; Kalbáč, M.
2015-12-01
We prepared a two-dimensional C70 fullerene peapod by the sequential assembly of 12C graphene, C70 fullerenes and 13C graphene. The local changes in the strain and doping were correlated with local roughness revealing asymmetry in the strain and doping with respect to the top and bottom graphene layers of the peapod.We prepared a two-dimensional C70 fullerene peapod by the sequential assembly of 12C graphene, C70 fullerenes and 13C graphene. The local changes in the strain and doping were correlated with local roughness revealing asymmetry in the strain and doping with respect to the top and bottom graphene layers of the peapod. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06271c
van der Waals epitaxy and photoresponse of two-dimensional CdSe plates
Zhu, Dan-Dan; Xia, Jing; Wang, Lei; Li, Xuan-Ze; Tian, Li-Feng; Meng, Xiang-Min
2016-06-01
Here we demonstrate the first growth of two-dimensional (2D) single-crystalline CdSe plates on mica substrates via van der Waals epitaxy. The as-synthesized 2D plates exhibit hexagonal, truncated triangular and triangular shapes with the lateral size around several microns. Photodetectors based on 2D CdSe plates present a fast response time of 24 ms, revealing that 2D CdSe is a promising building block for ultrathin optoelectronic devices.
Kulikovsky, A. A.; Divisek, J.; Kornyshev, Yu. M.
2000-01-01
A two-dimensional numerical model of the direct methanol fuel cell with gas fuel is developed. Simulation of the cell with current collectors of conventional geometry reveal the formation of fuel-depleted, "shaded" regions in the cathode and anode catalyst layers. These regions are positioned in front of current collectors, farther from the gas channel windows. Another disadvantage of the conventional geometry is the concentration of electron current at the edges of current collectors. Based ...
Soliton solutions of the two-dimensional KdV-Burgers equation by homotopy perturbation method
Energy Technology Data Exchange (ETDEWEB)
Molabahrami, A. [Department of Mathematics, Ilam University, PO Box 69315516, Ilam (Iran, Islamic Republic of)], E-mail: a_m_bahrami@yahoo.com; Khani, F. [Department of Mathematics, Ilam University, PO Box 69315516, Ilam (Iran, Islamic Republic of); Bakhtar Institute of Higher Education, PO Box 696, Ilam (Iran, Islamic Republic of)], E-mail: farzad_khani59@yahoo.com; Hamedi-Nezhad, S. [Bakhtar Institute of Higher Education, PO Box 696, Ilam (Iran, Islamic Republic of)
2007-10-29
In this Letter, the He's homotopy perturbation method (HPM) to finding the soliton solutions of the two-dimensional Korteweg-de Vries Burgers' equation (tdKdVB) for the initial conditions was applied. Numerical solutions of the equation were obtained. The obtained solutions, in comparison with the exact solutions admit a remarkable accuracy. The results reveal that the HPM is very effective and simple.
Coexistence of Incommensurate Magnetism and Superconductivity in the Two-Dimensional Hubbard Model.
Yamase, Hiroyuki; Eberlein, Andreas; Metzner, Walter
2016-03-04
We analyze the competition of magnetism and superconductivity in the two-dimensional Hubbard model with a moderate interaction strength, including the possibility of incommensurate spiral magnetic order. Using an unbiased renormalization group approach, we compute magnetic and superconducting order parameters in the ground state. In addition to previously established regions of Néel order coexisting with d-wave superconductivity, the calculations reveal further coexistence regions where superconductivity is accompanied by incommensurate magnetic order.
Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals
Gong, Cheng; Li, Lin; Li, Zhenglu; Ji, Huiwen; Stern, Alex; Xia, Yang; Cao, Ting; Bao, Wei; Wang, Chenzhe; Wang, Yuan; Qiu, Z. Q.; Cava, R. J.; Louie, Steven G.; Xia, Jing; Zhang, Xiang
2017-06-01
The realization of long-range ferromagnetic order in two-dimensional van der Waals crystals, combined with their rich electronic and optical properties, could lead to new magnetic, magnetoelectric and magneto-optic applications. In two-dimensional systems, the long-range magnetic order is strongly suppressed by thermal fluctuations, according to the Mermin-Wagner theorem; however, these thermal fluctuations can be counteracted by magnetic anisotropy. Previous efforts, based on defect and composition engineering, or the proximity effect, introduced magnetic responses only locally or extrinsically. Here we report intrinsic long-range ferromagnetic order in pristine Cr2Ge2Te6 atomic layers, as revealed by scanning magneto-optic Kerr microscopy. In this magnetically soft, two-dimensional van der Waals ferromagnet, we achieve unprecedented control of the transition temperature (between ferromagnetic and paramagnetic states) using very small fields (smaller than 0.3 tesla). This result is in contrast to the insensitivity of the transition temperature to magnetic fields in the three-dimensional regime. We found that the small applied field leads to an effective anisotropy that is much greater than the near-zero magnetocrystalline anisotropy, opening up a large spin-wave excitation gap. We explain the observed phenomenon using renormalized spin-wave theory and conclude that the unusual field dependence of the transition temperature is a hallmark of soft, two-dimensional ferromagnetic van der Waals crystals. Cr2Ge2Te6 is a nearly ideal two-dimensional Heisenberg ferromagnet and so will be useful for studying fundamental spin behaviours, opening the door to exploring new applications such as ultra-compact spintronics.
Growth and electronic properties of two-dimensional systems on (110) oriented GaAs
Energy Technology Data Exchange (ETDEWEB)
Fischer, F.
2005-07-01
As the only non-polar plane the (110) surface has a unique role in GaAs. Together with Silicon as a dopant it is an important substrate orientation for the growth of n-type or p-type heterostructures. As a consequence, this thesis will concentrate on growth and research on that surface. In the course of this work we were able to realize two-dimensional electron systems with the highest mobilities reported so far on this orientation. Therefore, we review the necessary growth conditions and the accompanying molecular process. The two-dimensional electron systems allowed the study of a new, intriguing transport anisotropy not explained by current theory. Moreover, we were the first growing a two-dimensional hole gas on (110) GaAs with Si as dopant. For this purpose we invented a new growth modulation technique necessary to retrieve high mobility systems. In addition, we discovered and studied the metal-insulator transition in thin bulk p-type layers on (110) GaAs. Besides we investigated the activation process related to the conduction in the valence band and a parallelly conducting hopping band. The new two-dimensional hole gases revealed interesting physics. We studied the zero B-field spin splitting in these systems and compared it with the known theory. Furthermore, we investigated the anisotropy of the mobility. As opposed to the expectations we observed a strong persistent photoconductivity in our samples. Landau levels for two dimensional hole systems are non-linear and can show anticrossings. For the first time we were able to resolve anticrossings in a transport experiment and study the corresponding activation process. Finally, we compared these striking results with theoretical calculations. (orig.)
Deng, Yan; Peng, Long; Liu, Yuan-Yuan; Yin, Li-Xue; Li, Chun-Mei; Wang, Yi; Rao, Li
2017-07-28
The aim of this prospective study was to assess the diagnosis value of four-dimensional echocardiography area strain (AS) combined with exercise stress echocardiography to evaluate left ventricular regional systolic function in patients with mild single vessel coronary artery stenosis. Based on treadmill exercise load status, two-dimensional conventional echocardiography and four-dimensional echocardiography area strain were performed on patients suspected coronary artery disease before coronary angiogram. Thirty patients (case group) with mild left anterior descending coronary artery stenosis (stenosis coronary artery stenosis according to the coronary angiogram results were prospectively enrolled. All the patients had no left ventricular regional wall motion abnormality in two-dimensional echocardiography at rest and exercise stress. There was no significant difference in the 16 segmental systolic peak AS at rest between two groups. After exercise stress, the peak systolic ASrest-stress at mid anterior wall (-7.00%±10.90% vs 2.80%±23.69%) and mid anterolateral wall (-4.40%±18.81% vs 8.80%±19.16%) were decreased, while increased at basal inferolateral wall (14.00%±19.27% vs -5.60%±15.94%) in case group compared with control group (Pcoronary artery stenosis, the area strain was decreased at involved segments, while compensatory increased at noninvolved segments after exercise stress. Four-dimensional echocardiography area strain combined with exercise stress echocardiography could sensitively find left ventricular regional systolic function abnormality in patients with mild single vessel coronary artery stenosis, and locate stenosis coronary artery accordingly. © 2017, Wiley Periodicals, Inc.
Waiting time dynamics in two-dimensional infrared spectroscopy.
Jansen, Thomas L C; Knoester, Jasper
2009-09-15
We review recent work on the waiting time dynamics of coherent two-dimensional infrared (2DIR) spectroscopy. This dynamics can reveal chemical and physical processes that take place on the femto- and picosecond time scale, which is faster than the time scale that may be probed by, for example, nuclear magnetic resonance spectroscopy. A large number of chemically relevant processes take place on this time scale. Such processes range from forming and breaking hydrogen bonds and proton transfer to solvent exchange and vibrational population transfer. In typical 2DIR spectra, multiple processes contribute to the waiting time dynamics and the spectra are often congested. This makes the spectra challenging to interpret, and the aid of theoretical models and simulations is often needed. To be useful, such models need to account for all dynamical processes in the sample simultaneously. The numerical integration of the Schrodinger equation (NISE) method has proven to allow for a very general treatment of the dynamical processes. It accounts for both the motional narrowing resulting from solvent-induced frequency fluctuations and population transfer between coupled vibrations. At the same time, frequency shifts arising from chemical-exchange reactions and changes of the transition dipoles because of either non-Condon effects or molecular reorientation are included in the treatment. This method therefore allows for the disentanglement of all of these processes. The NISE method has thus far been successfully applied to study chemical-exchange processes. It was demonstrated that 2DIR is not only sensitive to reaction kinetics but also to the more detailed reaction dynamics. NISE has also been applied to the study of population transfer within the amide I band (CO stretch) and between the amide I and amide II bands (CN stretch and NH bend) in polypeptides. From the amide I studies, it was found that the population transfer can be used to enhance cross-peaks that act as
Speckle tracking echocardiography in mature Irish Wolfhound dogs
DEFF Research Database (Denmark)
Westrup, Ulrik; McEvoy, Fintan
2013-01-01
Two-dimensional strain measurements obtained by speckle tracking echocardiography (STE) have been reported in both humans and dogs. Incorporation of this technique into canine clinical practice requires the availability of measurements from clinically normal dogs, ideally of the same breed, taken...... under normal clinical conditions.The aims of this prospective study were to assess if it is possible to obtain STE data during a routine echocardiographic examination in Irish Wolfhound dogs and that these data will provide reference values and an estimation of measurement error....
Directory of Open Access Journals (Sweden)
Mr. Agbo Julius Amaechi
2008-07-01
Full Text Available This study was conducted with the objective to establish a nomogram for some left ventricular structures and their alterations in hypertension. Correlations between left ventricular structures and anthropometric variables in hypertension were also established. A sample of 320 normotensive and 80 hypertensive subjects were studied. Echocardiograhic end diastolic diameter, posterior wall thickness and septal wall thickness were obtained. Subject height, weight, age and blood pressures were obtained. Blood pressures were measured in sitting position. The values of left ventricular mass (LVM, left ventricular mass index (LVMI and left relative wall thickness (RWT were computed. Parametric tests were conducted. Tests were two tailed with P < 0.05 indicating statistical significance. Normal values of left ventricular structures were established; LVM: 63.72g – 336.18g, LVMI: 38.16g/m – 222.64g/m, and RWT: 0.25 – 0.52. Significant differences (P < 0.05 were established in LVM, LVMI and RWT between normotensive and hypertensive subjects. Positive and significant correlations were noted between these variables and systolic blood pressure in hypertensive subjects. A simple linear regression of RWT on Body surface area gives RWT = - 0.058 BSA + 0.475 in normotensive subjects. Normal values of left ventricular structures and a linear regression model have been established which could be used in the assessment of morbidity in hypertension.
Directory of Open Access Journals (Sweden)
P Chiaramonte
2010-12-01
Full Text Available Los autores describen las posiciones de las ventanas ecocardiográficas paraesternal derecha e izquierda, subxifoidea y subcostal izquierda, los aspectos anatómicos de los ecotomogramas de referencia en cada una de las ventanas estudiadas y presentan los valores medios obtenidos de los distintos accidentes e índices ecocardiográficos medidos en 38 conejos neozelandeses blancos. Los valores promedios obtenidos fueron los siguientes: espesor del septum interventricular en sístole (ESIVs: 2,9 mm ± 0,53 mm; espesor del septum interventricular en diástole (ESIVd: 4,41 mm ± 1,12 mm; diámetro sistólico del ventrículo izquierdo (DSVI: 15,76 mm ± 1,77 mm; diámetro diastólico del ventrículo izquierdo (DDVI:11,14 mm ± 1,73 mm; espesor de la pared libre del ventrículo izquierdo en sístole (EPLVId: 3,59 mm ± 0,54 mm; espesor de la pared libre del ventrículo izquierdo en diástole (EPLVIs: 4,53 mm ± 0,71 mm; fracción de acortamiento (FA%: 29,72 % ± 5,79 %; fracción de eyección (FE%: 64,09 % ± 8,61 %; diámetro aórtico a nivel de la base cardíaca (DAo: 8,87 mm ± 1,21 mm; diámetro del atrio izquierdo a nivel de la base cardíaca (DAi: 10,61 mm ± 1,28 mm; Relación atrio izquierdo y aorta en la base cardíaca (Ai:Ao: 1,21± 0,21; separación septal del punto E (SSPE: 2,18 mm ± 0,6 mm y excursión del anillo mitral (EAM: 5,61 mm ± 0,83 mm.Authors describe the position of the right and left parasternal, subxifoid and left subcostal echocardiographic windows, the anatomical aspects of the reference echotomograms of the studied windows, and present the obtained mean values of the different echocardiographic accidents and indexes in 38 New Zealand rabbits. The obtained means values were: interventricular septal thickness in systole (IVSTs: 2.95 mm ± 0.53 mm; interventricular septal thickness in diastole (IVSTd: 4.41 mm ± 1.12 mm; left ventricular systolic diameter (LVSD: 15.76 mm ± 1.77 mm; left ventricular diastolic diameter (LVDD: 11.14 mm ± 1.73 mm; left ventricular posterior wall thickness in diastole (LVPWTd: 3.59 mm ± 0.54 mm; left ventricular posterior wall thickness in systole (LVPWTs: 4.53 mm ± 0.71 mm; fractional shortening (FS%: 29.72 % ± 5.79 %; ejection fraction (EF%: 64.09 % ± 8.61 %; aortic diameter (AoD: 8.87 mm ± 1.21 mm; left atrium diameter (LAD: 10.61 mm ± 1.28 mm; left atrium and aortic diameter ratio (LA:AO: 1.21 ± 0.21; E-point septal separation (EPSS: 2.18 mm ± 0,6 mm and mitral annulus excursion (MAE: 5.61 mm ± 0,83 mm.
Friedman, B J; Waters, J; Kwan, O L; DeMaria, A N
1985-06-01
No data exist regarding the ability of magnetic resonance imaging to assess cardiac size and performance in human beings. Therefore, measurements of cardiac dimensions by magnetic resonance imaging were compared with those obtained by two-dimensional echocardiography in 21 normal subjects. Magnetic resonance transverse cardiac sections were obtained during electrocardiographic gating using a spin echo pulse sequence. In normal subjects, magnetic resonance imaging yielded a range of values for cardiac dimensions having a similar standard deviation as that of two-dimensional echocardiography. Diastolic measurements of the aorta, left atrium, left ventricle and septum obtained by magnetic resonance imaging correlated well with those obtained by two-dimensional echocardiography (r = 0.82, 0.78, 0.81 and 0.75, respectively). The correlation coefficient of r = 0.35 observed for the posterior wall thickness was not surprising in view of the narrow range of normal values. Only a general correlation (r = 0.53) existed for the right ventricular diastolic dimension; this was probably related to the difficulty in obtaining representative measurements due to the complex geometry of this chamber. Failure of systolic dimension measurements by magnetic resonance imaging to correlate with those obtained by echocardiography is probably related to limitations of electrocardiographic gating, especially of determining the exact end-systolic frame. Although technically complex at present, magnetic resonance imaging does provide an additional noninvasive technique for measurement of cardiac size.
Stress Wave Propagation in Two-dimensional Buckyball Lattice
Xu, Jun; Zheng, Bowen
2016-11-01
Orderly arrayed granular crystals exhibit extraordinary capability to tune stress wave propagation. Granular system of higher dimension renders many more stress wave patterns, showing its great potential for physical and engineering applications. At nanoscale, one-dimensionally arranged buckyball (C60) system has shown the ability to support solitary wave. In this paper, stress wave behaviors of two-dimensional buckyball (C60) lattice are investigated based on square close packing and hexagonal close packing. We show that the square close packed system supports highly directional Nesterenko solitary waves along initially excited chains and hexagonal close packed system tends to distribute the impulse and dissipates impact exponentially. Results of numerical calculations based on a two-dimensional nonlinear spring model are in a good agreement with the results of molecular dynamics simulations. This work enhances the understanding of wave properties and allows manipulations of nanoscale lattice and novel design of shock mitigation and nanoscale energy harvesting devices.
The separation of whale myoglobins with two-dimensional electrophoresis.
Spicer, G S
1988-10-01
Five myoglobins (sperm whale, Sei whale, Hubbs' beaked whale, pilot whale, and Amazon River dolphin) were examined using two-dimensional electrophoresis. Previous reports indicated that none of these proteins could be separated by using denaturing (in the presence of 8-9 M urea) isoelectric focusing. This result is confirmed in the present study. However, all the proteins could be separated by using denaturing nonequilibrium pH-gradient electrophoresis in the first dimension. Additionally, all the myoglobins have characteristic mobilities in the second dimension (sodium dodecyl sulfate), but these mobilities do not correspond to the molecular weights of the proteins. We conclude that two-dimensional electrophoresis can be more sensitive to differences in primary protein structure than previous studies indicate and that the assessment seems to be incorrect that this technique can separate only proteins that have a unit charge difference.
Entanglement Entropy in Two-Dimensional String Theory.
Hartnoll, Sean A; Mazenc, Edward A
2015-09-18
To understand an emergent spacetime is to understand the emergence of locality. Entanglement entropy is a powerful diagnostic of locality, because locality leads to a large amount of short distance entanglement. Two-dimensional string theory is among the very simplest instances of an emergent spatial dimension. We compute the entanglement entropy in the large-N matrix quantum mechanics dual to two-dimensional string theory in the semiclassical limit of weak string coupling. We isolate a logarithmically large, but finite, contribution that corresponds to the short distance entanglement of the tachyon field in the emergent spacetime. From the spacetime point of view, the entanglement is regulated by a nonperturbative "graininess" of space.
Topological defect motifs in two-dimensional Coulomb clusters
Radzvilavičius, A; 10.1088/0953-8984/23/38/385301
2012-01-01
The most energetically favourable arrangement of low-density electrons in an infinite two-dimensional plane is the ordered triangular Wigner lattice. However, in most instances of contemporary interest one deals instead with finite clusters of strongly interacting particles localized in potential traps, for example, in complex plasmas. In the current contribution we study distribution of topological defects in two-dimensional Coulomb clusters with parabolic lateral confinement. The minima hopping algorithm based on molecular dynamics is used to efficiently locate the ground- and low-energy metastable states, and their structure is analyzed by means of the Delaunay triangulation. The size, structure and distribution of geometry-induced lattice imperfections strongly depends on the system size and the energetic state. Besides isolated disclinations and dislocations, classification of defect motifs includes defect compounds --- grain boundaries, rosette defects, vacancies and interstitial particles. Proliferatio...
The Persistence Problem in Two-Dimensional Fluid Turbulence
Perlekar, Prasad; Mitra, Dhrubaditya; Pandit, Rahul
2010-01-01
We present a natural framework for studying the persistence problem in two-dimensional fluid turbulence by using the Okubo-Weiss parameter {\\Lambda} to distinguish between vortical and extensional regions. We then use a direct numerical simulation (DNS) of the two-dimensional, incompressible Navier-Stokes equation with Ekman friction to study probability distribution functions (PDFs) of the persistence times of vortical and extensional regions by employing both Eulerian and Lagrangian measurements. We find that, in the Eulerian case, the persistence-time PDFs have exponential tails; by contrast, this PDF for Lagrangian particles, in vortical regions, has a power-law tail with a universal exponent {\\theta} = 3.1 \\pm 0.2.
On Dirichlet eigenvectors for neutral two-dimensional Markov chains
Champagnat, Nicolas; Miclo, Laurent
2012-01-01
We consider a general class of discrete, two-dimensional Markov chains modeling the dynamics of a population with two types, without mutation or immigration, and neutral in the sense that type has no influence on each individual's birth or death parameters. We prove that all the eigenvectors of the corresponding transition matrix or infinitesimal generator \\Pi\\ can be expressed as the product of "universal" polynomials of two variables, depending on each type's size but not on the specific transitions of the dynamics, and functions depending only on the total population size. These eigenvectors appear to be Dirichlet eigenvectors for \\Pi\\ on the complement of triangular subdomains, and as a consequence the corresponding eigenvalues are ordered in a specific way. As an application, we study the quasistationary behavior of finite, nearly neutral, two-dimensional Markov chains, absorbed in the sense that 0 is an absorbing state for each component of the process.
Statistical mechanics of two-dimensional and geophysical flows
Bouchet, Freddy
2011-01-01
The theoretical study of the self-organization of two-dimensional and geophysical turbulent flows is addressed based on statistical mechanics methods. This review is a self-contained presentation of classical and recent works on this subject; from the statistical mechanics basis of the theory up to applications to Jupiter's troposphere and ocean vortices and jets. Emphasize has been placed on examples with available analytical treatment in order to favor better understanding of the physics and dynamics. The equilibrium microcanonical measure is built from the Liouville theorem. On this theoretical basis, we predict the output of the long time evolution of complex turbulent flows as statistical equilibria. This is applied to make quantitative models of two-dimensional turbulence, the Great Red Spot and other Jovian vortices, ocean jets like the Gulf-Stream, and ocean vortices. We also present recent results for non-equilibrium situations, for the studies of either the relaxation towards equilibrium or non-equi...
Two-dimensional hazard estimation for longevity analysis
DEFF Research Database (Denmark)
Fledelius, Peter; Guillen, M.; Nielsen, J.P.
2004-01-01
We investigate developments in Danish mortality based on data from 1974-1998 working in a two-dimensional model with chronological time and age as the two dimensions. The analyses are done with non-parametric kernel hazard estimation techniques. The only assumption is that the mortality surface...... the two-dimensional mortality surface. Furthermore we look at aggregated synthetic population metrics as 'population life expectancy' and 'population survival probability'. For Danish women these metrics indicate decreasing mortality with respect to chronological time. The metrics can not directly be used...... for prediction purposes. However, we suggest that life insurance companies use the estimation technique and the cross-validation for bandwidth selection when analyzing their portfolio mortality. The non-parametric approach may give valuable information prior to developing more sophisticated prediction models...
Analysis of one dimensional and two dimensional fuzzy controllers
Institute of Scientific and Technical Information of China (English)
Ban Xiaojun; Gao Xiaozhi; Huang Xianlin; Wu Tianbao
2006-01-01
The analytical structures and the corresponding mathematical properties of the one dimensional and two dimensional fuzzy controllers are first investigated in detail.The nature of these two kinds of fuzzy controllers is next probed from the perspective of control engineering. For the one dimensional fuzzy controller, it is concluded that this controller is a combination of a saturation element and a nonlinear proportional controller, and the system that employs the one dimensional fuzzy controller is the combination of an open-loop control system and a closedloop control system. For the latter case, it is concluded that it is a hybrid controller, which comprises the saturation part, zero-output part, nonlinear derivative part, nonlinear proportional part, as well as nonlinear proportional-derivative part, and the two dimensional fuzzy controller-based control system is a loop-varying system with varying number of control loops.
Extension of modified power method to two-dimensional problems
Zhang, Peng; Lee, Hyunsuk; Lee, Deokjung
2016-09-01
In this study, the generalized modified power method was extended to two-dimensional problems. A direct application of the method to two-dimensional problems was shown to be unstable when the number of requested eigenmodes is larger than a certain problem dependent number. The root cause of this instability has been identified as the degeneracy of the transfer matrix. In order to resolve this instability, the number of sub-regions for the transfer matrix was increased to be larger than the number of requested eigenmodes; and a new transfer matrix was introduced accordingly which can be calculated by the least square method. The stability of the new method has been successfully demonstrated with a neutron diffusion eigenvalue problem and the 2D C5G7 benchmark problem.
Two Dimensional Lattice Boltzmann Method for Cavity Flow Simulation
Directory of Open Access Journals (Sweden)
Panjit MUSIK
2004-01-01
Full Text Available This paper presents a simulation of incompressible viscous flow within a two-dimensional square cavity. The objective is to develop a method originated from Lattice Gas (cellular Automata (LGA, which utilises discrete lattice as well as discrete time and can be parallelised easily. Lattice Boltzmann Method (LBM, known as discrete Lattice kinetics which provide an alternative for solving the Navier–Stokes equations and are generally used for fluid simulation, is chosen for the study. A specific two-dimensional nine-velocity square Lattice model (D2Q9 Model is used in the simulation with the velocity at the top of the cavity kept fixed. LBM is an efficient method for reproducing the dynamics of cavity flow and the results which are comparable to those of previous work.
Transport behavior of water molecules through two-dimensional nanopores
Energy Technology Data Exchange (ETDEWEB)
Zhu, Chongqin; Li, Hui; Meng, Sheng, E-mail: smeng@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)
2014-11-14
Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.
Transport behavior of water molecules through two-dimensional nanopores
Zhu, Chongqin; Li, Hui; Meng, Sheng
2014-11-01
Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules.
Thermodynamics of two-dimensional Yukawa systems across coupling regimes
Kryuchkov, Nikita P.; Khrapak, Sergey A.; Yurchenko, Stanislav O.
2017-04-01
Thermodynamics of two-dimensional Yukawa (screened Coulomb or Debye-Hückel) systems is studied systematically using molecular dynamics (MD) simulations. Simulations cover very broad parameter range spanning from weakly coupled gaseous states to strongly coupled fluid and crystalline states. Important thermodynamic quantities, such as internal energy and pressure, are obtained and accurate physically motivated fits are proposed. This allows us to put forward simple practical expressions to describe thermodynamic properties of two-dimensional Yukawa systems. For crystals, in addition to numerical simulations, the recently developed shortest-graph interpolation method is applied to describe pair correlations and hence thermodynamic properties. It is shown that the finite-temperature effects can be accounted for by using simple correction of peaks in the pair correlation function. The corresponding correction coefficients are evaluated using MD simulation. The relevance of the obtained results in the context of colloidal systems, complex (dusty) plasmas, and ions absorbed to interfaces in electrolytes is pointed out.
Topological states in two-dimensional hexagon lattice bilayers
Zhang, Ming-Ming; Xu, Lei; Zhang, Jun
2016-10-01
We investigate the topological states of the two-dimensional hexagon lattice bilayer. The system exhibits a quantum valley Hall (QVH) state when the interlayer interaction t⊥ is smaller than the nearest neighbor hopping energy t, and then translates to a trivial band insulator state when t⊥ / t > 1. Interestingly, the system is found to be a single-edge QVH state with t⊥ / t = 1. The topological phase transition also can be presented via changing bias voltage and sublattice potential in the system. The QVH states have different edge modes carrying valley current but no net charge current. The bias voltage and external electric field can be tuned easily in experiments, so the present results will provide potential application in valleytronics based on the two-dimensional hexagon lattice.
CORPORATE VALUATION USING TWO-DIMENSIONAL MONTE CARLO SIMULATION
Directory of Open Access Journals (Sweden)
Toth Reka
2010-12-01
Full Text Available In this paper, we have presented a corporate valuation model. The model combine several valuation methods in order to get more accurate results. To determine the corporate asset value we have used the Gordon-like two-stage asset valuation model based on the calculation of the free cash flow to the firm. We have used the free cash flow to the firm to determine the corporate market value, which was calculated with use of the Black-Scholes option pricing model in frame of the two-dimensional Monte Carlo simulation method. The combined model and the use of the two-dimensional simulation model provides a better opportunity for the corporate value estimation.
Two-dimensional magnetostriction under vector magnetic characteristic
Wakabayashi, D.; Enokizono, M.
2015-05-01
This paper presents two-dimensional magnetostriction of electrical steel sheet under vector magnetic characteristic. In conventional measurement method using Single Sheet Tester, the magnetic flux density, the magnetic field strength, and the magnetostriction have been measured in one direction. However, an angle between the magnetic flux density vector and the magnetic field strength vector exists because the magnetic property is vector quantity. An angle between the magnetic flux density vector and the direction of maximum magnetostriction also exists. We developed a new measurement method, which enables measurement of these angles. The vector magnetic characteristic and the two-dimensional magnetostriction have been measured using the new measurement method. The BH and Bλ curves considering the angles are shown in this paper. The analyzed results considering the angles are also made clear.
Phase separation under two-dimensional Poiseuille flow.
Kiwata, H
2001-05-01
The spinodal decomposition of a two-dimensional binary fluid under Poiseuille flow is studied by numerical simulation. We investigated time dependence of domain sizes in directions parallel and perpendicular to the flow. In an effective region of the flow, the power-law growth of a characteristic length in the direction parallel to the flow changes from the diffusive regime with the growth exponent alpha=1/3 to a new regime. The scaling invariance of the growth in the perpendicular direction is destroyed after the diffusive regime. A recurrent prevalence of thick and thin domains which determines log-time periodic oscillations has not been observed in our model. The growth exponents in the infinite system under two-dimensional Poiseuille flow are obtained by the renormalization group.
Enstrophy inertial range dynamics in generalized two-dimensional turbulence
Iwayama, Takahiro; Watanabe, Takeshi
2016-07-01
We show that the transition to a k-1 spectrum in the enstrophy inertial range of generalized two-dimensional turbulence can be derived analytically using the eddy damped quasinormal Markovianized (EDQNM) closure. The governing equation for the generalized two-dimensional fluid system includes a nonlinear term with a real parameter α . This parameter controls the relationship between the stream function and generalized vorticity and the nonlocality of the dynamics. An asymptotic analysis accounting for the overwhelming dominance of nonlocal triads allows the k-1 spectrum to be derived based upon a scaling analysis. We thereby provide a detailed analytical explanation for the scaling transition that occurs in the enstrophy inertial range at α =2 in terms of the spectral dynamics of the EDQNM closure, which extends and enhances the usual phenomenological explanations.
Folding two dimensional crystals by swift heavy ion irradiation
Energy Technology Data Exchange (ETDEWEB)
Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)
2014-12-01
Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.
Explorative data analysis of two-dimensional electrophoresis gels
DEFF Research Database (Denmark)
Schultz, J.; Gottlieb, D.M.; Petersen, Marianne Kjerstine
2004-01-01
Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening...... of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine...... if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots...
Two-dimensional model of elastically coupled molecular motors
Institute of Scientific and Technical Information of China (English)
Zhang Hong-Wei; Wen Shu-Tang; Chen Gai-Rong; Li Yu-Xiao; Cao Zhong-Xing; Li Wei
2012-01-01
A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins.Extensive Langevin simulations of the model are performed.We discuss the dependences of motion and efficiency on the model parameters,including the external force and the temperature.A good qualitative agreement with the expected behavior is observed.
Conductivity of a two-dimensional guiding center plasma.
Montgomery, D.; Tappert, F.
1972-01-01
The Kubo method is used to calculate the electrical conductivity of a two-dimensional, strongly magnetized plasma. The particles interact through (logarithmic) electrostatic potentials and move with their guiding center drift velocities (Taylor-McNamara model). The thermal equilibrium dc conductivity can be evaluated analytically, but the ac conductivity involves numerical solution of a differential equation. Both conductivities fall off as the inverse first power of the magnetic field strength.
Minor magnetization loops in two-dimensional dipolar Ising model
Energy Technology Data Exchange (ETDEWEB)
Sarjala, M. [Aalto University, Department of Applied Physics, P.O. Box 14100, FI-00076 Aalto (Finland); Seppaelae, E.T., E-mail: eira.seppala@nokia.co [Nokia Research Center, Itaemerenkatu 11-13, FI-00180 Helsinki (Finland); Alava, M.J., E-mail: mikko.alava@tkk.f [Aalto University, Department of Applied Physics, P.O. Box 14100, FI-00076 Aalto (Finland)
2011-05-15
The two-dimensional dipolar Ising model is investigated for the relaxation and dynamics of minor magnetization loops. Monte Carlo simulations show that in a stripe phase an exponential decrease can be found for the magnetization maxima of the loops, M{approx}exp(-{alpha}N{sub l}) where N{sub l} is the number of loops. We discuss the limits of this behavior and its relation to the equilibrium phase diagram of the model.
Cryptography Using Multiple Two-Dimensional Chaotic Maps
Directory of Open Access Journals (Sweden)
Ibrahim S. I. Abuhaiba
2012-08-01
Full Text Available In this paper, a symmetric key block cipher cryptosystem is proposed, involving multiple two-dimensional chaotic maps and using 128-bits external secret key. Computer simulations indicate that the cipher has good diffusion and confusion properties with respect to the plaintext and the key. Moreover, it produces ciphertext with random distribution. The computation time is much less than previous related works. Theoretic analysis verifies its superiority to previous cryptosystems against different types of attacks.
A UNIVERSAL VARIATIONAL FORMULATION FOR TWO DIMENSIONAL FLUID MECHANICS
Institute of Scientific and Technical Information of China (English)
何吉欢
2001-01-01
A universal variational formulation for two dimensional fluid mechanics is obtained, which is subject to the so-called parameter-constrained equations (the relationship between parameters in two governing equations). By eliminating the constraints, the generalized variational principle (GVPs) can be readily derived from the formulation. The formulation can be applied to any conditions in case the governing equations can be converted into conservative forms. Some illustrative examples are given to testify the effectiveness and simplicity of the method.
Nonlocal bottleneck effect in two-dimensional turbulence
Biskamp, D; Schwarz, E
1998-01-01
The bottleneck pileup in the energy spectrum is investigated for several two-dimensional (2D) turbulence systems by numerical simulation using high-order diffusion terms to amplify the effect, which is weak for normal diffusion. For 2D magnetohydrodynamic (MHD) turbulence, 2D electron MHD (EMHD) turbulence and 2D thermal convection, which all exhibit direct energy cascades, a nonlocal behavior is found resulting in a logarithmic enhancement of the spectrum.
Level crossings in complex two-dimensional potentials
Indian Academy of Sciences (India)
Qing-Hai Wang
2009-08-01
Two-dimensional $\\mathcal{PT}$-symmetric quantum-mechanical systems with the complex cubic potential 12 = 2 + 2 + 2 and the complex Hénon–Heiles potential HH = 2 + 2 + (2 − 3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the $\\mathcal{PT}$ symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates.
Extraction of plant proteins for two-dimensional electrophoresis
Granier, Fabienne
1988-01-01
Three different extraction procedures for two-dimensional electrophoresis of plant proteins are compared: (i) extraction of soluble proteins with a nondenaturing Tris-buffer, (ii) denaturing extraction in presence of sodium dodecyl sulfate at elevated temperature allowing the solubilization of membrane proteins in addition to a recovery of soluble proteins, and (iii) a trichloroacetic acid-acetone procedure allowing the direct precipitation of total proteins.
Lyapunov Computational Method for Two-Dimensional Boussinesq Equation
Mabrouk, Anouar Ben
2010-01-01
A numerical method is developed leading to Lyapunov operators to approximate the solution of two-dimensional Boussinesq equation. It consists of an order reduction method and a finite difference discretization. It is proved to be uniquely solvable and analyzed for local truncation error for consistency. The stability is checked by using Lyapunov criterion and the convergence is studied. Some numerical implementations are provided at the end of the paper to validate the theoretical results.
Complex dynamical invariants for two-dimensional complex potentials
Indian Academy of Sciences (India)
J S Virdi; F Chand; C N Kumar; S C Mishra
2012-08-01
Complex dynamical invariants are searched out for two-dimensional complex potentials using rationalization method within the framework of an extended complex phase space characterized by $x = x_{1} + ip_{3}. y = x_{2} + ip_{4}, p_{x} = p_{1} + ix_{3}, p_{y} = p_{2} + ix_{4}$. It is found that the cubic oscillator and shifted harmonic oscillator admit quadratic complex invariants. THe obtained invariants may be useful for studying non-Hermitian Hamiltonian systems.
Two-dimensional hydrogen negative ion in a magnetic field
Institute of Scientific and Technical Information of China (English)
Xie Wen-Fang
2004-01-01
Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional hydrogen negative ion H- in a magnetic field. The results show that the ground and low-excited states of H- in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states.
А heuristic algorithm for two-dimensional strip packing problem
Dayong, Cao; Kotov, V.M.
2011-01-01
In this paper, we construct an improved best-fit heuristic algorithm for two-dimensional rectangular strip packing problem (2D-RSPP), and compare it with some heuristic and metaheuristic algorithms from literatures. The experimental results show that BFBCC could produce satisfied packing layouts than these methods, especially for the large problem of 50 items or more, BFBCC could get better results in shorter time.
Chronology Protection in Two-Dimensional Dilaton Gravity
Mishima, T; Mishima, Takashi; Nakamichi, Akika
1994-01-01
The global structure of 1 + 1 dimensional compact Universe is studied in two-dimensional model of dilaton gravity. First we give a classical solution corresponding to the spacetime in which a closed time-like curve appears, and show the instability of this spacetime due to the existence of matters. We also observe quantum version of such a spacetime having closed timelike curves never reappear unless the parameters are fine-tuned.
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M
1993-01-01
Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175
2009-01-01
We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
SU(1,2) invariance in two-dimensional oscillator
Krivonos, Sergey
2016-01-01
Performing the Hamiltonian analysis we explicitly established the canonical equivalence of the deformed oscillator, constructed in arXiv:1607.03756[hep-th], with the ordinary one. As an immediate consequence, we proved that the SU(1,2) symmetry is the dynamical symmetry of the ordinary two-dimensional oscillator. The characteristic feature of this SU(1,2) symmetry is a non-polynomial structure of its generators written it terms of the oscillator variables.
Multiple Potts Models Coupled to Two-Dimensional Quantum Gravity
Baillie, C F
1992-01-01
We perform Monte Carlo simulations using the Wolff cluster algorithm of {\\it multiple} $q=2,3,4$ state Potts models on dynamical phi-cubed graphs of spherical topology in order to investigate the $c>1$ region of two-dimensional quantum gravity. Contrary to naive expectation we find no obvious signs of pathological behaviour for $c>1$. We discuss the results in the light of suggestions that have been made for a modified DDK ansatz for $c>1$.
Multiple Potts models coupled to two-dimensional quantum gravity
Baillie, C. F.; Johnston, D. A.
1992-07-01
We perform Monte Carlo simulations using the Wolff cluster algorithm of multiple q=2, 3, 4 state Potts models on dynamical phi-cubed graphs of spherical topology in order to investigate the c>1 region of two-dimensional quantum gravity. Contrary to naive expectation we find no obvious signs of pathological behaviour for c>1. We discuss the results in the light of suggestions that have been made for a modified DDK ansatz for c>1.
Colloidal interactions in two-dimensional nematic emulsions
Indian Academy of Sciences (India)
N M Silvestre; P Patrício; M M Telo Da Gama
2005-06-01
We review theoretical and experimental work on colloidal interactions in two-dimensional (2D) nematic emulsions. We pay particular attention to the effects of (i) the nematic elastic constants, (ii) the size of the colloids, and (iii) the boundary conditions at the particles and the container. We consider the interactions between colloids and fluid (deformable) interfaces and the shape of fluid colloids in smectic-C films.
Thermal diode from two-dimensional asymmetrical Ising lattices.
Wang, Lei; Li, Baowen
2011-06-01
Two-dimensional asymmetrical Ising models consisting of two weakly coupled dissimilar segments, coupled to heat baths with different temperatures at the two ends, are studied by Monte Carlo simulations. The heat rectifying effect, namely asymmetric heat conduction, is clearly observed. The underlying mechanisms are the different temperature dependencies of thermal conductivity κ at two dissimilar segments and the match (mismatch) of flipping frequencies of the interface spins.
Numerical Study of Two-Dimensional Viscous Flow over Dams
Institute of Scientific and Technical Information of China (English)
王利兵; 刘宇陆; 涂敏杰
2003-01-01
In this paper, the characteristics of two-dimensional viscous flow over two dams were numerically investigated. The results show that the behavior of the vortices is closely related to the space between two dams, water depth, Fr number and Reynolds number. In addition, the flow properties behind each dam are different, and the changes over two dams are more complex than over one dam. Finally, the relevant turbulent characteristics were analyzed.
Spirals and Skyrmions in two dimensional oxide heterostructures.
Li, Xiaopeng; Liu, W Vincent; Balents, Leon
2014-02-14
We construct the general free energy governing long-wavelength magnetism in two dimensional oxide heterostructures, which applies irrespective of the microscopic mechanism for magnetism. This leads, in the relevant regime of weak but non-negligible spin-orbit coupling, to a rich phase diagram containing in-plane ferromagnetic, spiral, cone, and Skyrmion lattice phases, as well as a nematic state stabilized by thermal fluctuations.
Acoustic Bloch oscillations in a two-dimensional phononic crystal.
He, Zhaojian; Peng, Shasha; Cai, Feiyan; Ke, Manzhu; Liu, Zhengyou
2007-11-01
We report the observation of acoustic Bloch oscillations at megahertz frequency in a two-dimensional phononic crystal. By creating periodically arrayed cavities with a decreasing gradient in width along one direction in the phononic crystal, acoustic Wannier-Stark ladders are created in the frequency domain. The oscillatory motion of an incident Gaussian pulse inside the sample is demonstrated by both simulation and experiment.
Exact analytic flux distributions for two-dimensional solar concentrators.
Fraidenraich, Naum; Henrique de Oliveira Pedrosa Filho, Manoel; Vilela, Olga C; Gordon, Jeffrey M
2013-07-01
A new approach for representing and evaluating the flux density distribution on the absorbers of two-dimensional imaging solar concentrators is presented. The formalism accommodates any realistic solar radiance and concentrator optical error distribution. The solutions obviate the need for raytracing, and are physically transparent. Examples illustrating the method's versatility are presented for parabolic trough mirrors with both planar and tubular absorbers, Fresnel reflectors with tubular absorbers, and V-trough mirrors with planar absorbers.
Tricritical behavior in a two-dimensional field theory
Hamber, Herbert
1980-05-01
The critical behavior of a two-dimensional scalar Euclidean field theory with a potential term that allows for three minima is analyzed using an approximate position-space renormalization-group transformation on the equivalent quantum spin Hamiltonian. The global phase diagram shows a tricritical point separating a critical line from a line of first-order transitions. Other critical properties are examined, and good agreement is found with results on classical spin models belonging to the same universality class.
Quantum entanglement in a two-dimensional ion trap
Institute of Scientific and Technical Information of China (English)
王成志; 方卯发
2003-01-01
In this paper, we investigate the quantum entanglement in a two-dimensional ion trap system. We discuss the quantum entanglement between the ion and phonons by using reduced entropy, and that between two degrees of freedom of the vibrational motion along x and y directions by using quantum relative entropy. We discuss also the influence of initial state of the system on the quantum entanglement and the relation between two entanglements in the trapped ion system.
Coll Positioning systems: a two-dimensional approach
Ferrando, J J
2006-01-01
The basic elements of Coll positioning systems (n clocks broadcasting electromagnetic signals in a n-dimensional space-time) are presented in the two-dimensional case. This simplified approach allows us to explain and to analyze the properties and interest of these relativistic positioning systems. The positioning system defined in flat metric by two geodesic clocks is analyzed. The interest of the Coll systems in gravimetry is pointed out.
Two-dimensional correlation spectroscopy in polymer study
Park, Yeonju; Noda, Isao; Jung, Young Mee
2015-01-01
This review outlines the recent works of two-dimensional correlation spectroscopy (2DCOS) in polymer study. 2DCOS is a powerful technique applicable to the in-depth analysis of various spectral data of polymers obtained under some type of perturbation. The powerful utility of 2DCOS combined with various analytical techniques in polymer studies and noteworthy developments of 2DCOS used in this field are also highlighted. PMID:25815286
Interior design of a two-dimensional semiclassic black hole
Levanony, Dana; 10.1103/PhysRevD.80.084008
2009-01-01
We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. The field equations admit two types of singularities, and their local asymptotic structure is investigated. One of these singularities is found to develop, as a spacelike singularity, inside the black hole. We then study the internal structure of the evaporating black hole from the horizon to the singularity.
Towards a two dimensional model of surface piezoelectricity
Monge Víllora, Oscar
2016-01-01
We want to understand the behaviour of flexoelectricity and surface piezoelectricity and distinguish them in order to go deep into the controversies of the filed. This motivate the construction of a model of continuum flexoelectric theory. The model proposed is a two-dimensional model that integrates the electromechanical equations that include the elastic, dielectric, piezoelectric and flexoelectric effect on a rectangular sample. As the flexoelectric and the surface piezoelectric effects ap...
Velocity Statistics in the Two-Dimensional Granular Turbulence
Isobe, Masaharu
2003-01-01
We studied the macroscopic statistical properties on the freely evolving quasi-elastic hard disk (granular) system by performing a large-scale (up to a few million particles) event-driven molecular dynamics systematically and found that remarkably analogous to an enstrophy cascade process in the decaying two-dimensional fluid turbulence. There are four typical stages in the freely evolving inelastic hard disk system, which are homogeneous, shearing (vortex), clustering and final state. In the...
Statistical study of approximations to two dimensional inviscid turbulence
Energy Technology Data Exchange (ETDEWEB)
Glaz, H.M.
1977-09-01
A numerical technique is developed for studying the ergodic and mixing hypotheses for the dynamical systems arising from the truncated Fourier transformed two-dimensional inviscid Navier-Stokes equations. This method has the advantage of exactly conserving energy and entropy (i.e., total vorticity) in the inviscid case except for numerical error in solving the ordinary differential equations. The development of the mathematical model as an approximation to a real physical (turbulent) flow and the numerical results obtained are discussed.
Static Structure of Two-Dimensional Granular Chain
Institute of Scientific and Technical Information of China (English)
WEN Ping-Ping; LI Liang-Sheng; ZHENG Ning; SHI Qing-Fan
2010-01-01
@@ Static packing structures of two-dimensional granular chains are investigated experimentally.It is shown that the packing density approximates the saturation with the exponential law as the length of chain increases.The packing structures are globally disordered,while the local square crystallization is found by using the radial distribution function.This characteristic phase of chain packing is similar to a liquid crystal state,and has properties between a conventional liquid and solid crystal.
THE DEGENERACY PROBLEM OF TWO-DIMENSIONAL LINEAR RECURRING ARRAYS
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The degeneracy degree and degeneracy position sets of a wo-dimensional linear recurrence relation set are characterized. The fact that a linear recurring array is essentially a doubly periodic array is shown. By using the Grbner base theory, a calculation formula for degeneracy degree is given and the existence of a special degeneracy position set is proved. In the present paper, the degeneracy problem of the two-dimensional linear recurring arrays is completely solved.
Two-Dimensional Identification of Fetal Tooth Germs.
Seabra, Mariana; Vaz, Paula; Valente, Francisco; Braga, Ana; Felino, António
2017-03-01
To demonstrate the efficiency and applicability of two-dimensional ultrasonography in the identification of tooth germs and in the assessment of potential pathology. Observational, descriptive, cross-sectional study. Prenatal Diagnosis Unit of Centro Hospitalar de Vila Nova de Gaia / Espinho-Empresa Pública in Portugal. A total of 157 white pregnant women (median age, 32 years; range, 14 to 47 years) undergoing routine ultrasound exams. Description of the fetal tooth germs, as visualized by two-dimensional ultrasonography, including results from prior fetal biometry and detailed screening for malformations. In the first trimester group, ultrasonography identified 10 tooth germs in the maxilla and 10 tooth germs in the mandible in all fetuses except for one who presented eight maxillary tooth germs. This case was associated with a chromosomal abnormality (trisomy 13) with a bilateral cleft palate. In the second and third trimesters group, ultrasonography identified a larger range of tooth germs: 81.2% of fetuses showed 10 tooth germs in the maxilla and 85.0% of fetuses had 10 tooth germs in the mandible. Hypodontia was more prevalent in the maxilla than in the mandible, which led us to use qualitative two-dimensional ultrasonography to analyze the possible association between hypodontia and other variables such as fetal pathology, markers, head, nuchal, face, and spine. We recommend using this method as the first exam to evaluate fetal morphology and also to help establish accurate diagnosis of abnormalities in pregnancy.
Electromagnetically induced two-dimensional grating assisted by incoherent pump
Energy Technology Data Exchange (ETDEWEB)
Chen, Yu-Yuan; Liu, Zhuan-Zhuan; Wan, Ren-Gang, E-mail: wrg@snnu.edu.cn
2017-04-25
We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication. - Highlights: • Two-dimensional grating is coherently induced in four-level atoms. • Phase and gain-phase gratings are obtained assisted by incoherent pump. • The diffraction power is improved due to the enhanced refraction modulation. • The gratings can be utilized as multi-channel all-optical splitter and router.
a First Cryptosystem for Security of Two-Dimensional Data
Mishra, D. C.; Sharma, Himani; Sharma, R. K.; Kumar, Naveen
In this paper, we present a novel technique for security of two-dimensional data with the help of cryptography and steganography. The presented approach provides multilayered security of two-dimensional data. First layer security was developed by cryptography and second layer by steganography. The advantage of steganography is that the intended secret message does not attract attention to itself as an object of scrutiny. This paper proposes a novel approach for encryption and decryption of information in the form of Word Data (.doc file), PDF document (.pdf file), Text document, Gray-scale images, and RGB images, etc. by using Vigenere Cipher (VC) associated with Discrete Fourier Transform (DFT) and then hiding the data behind the RGB image (i.e. steganography). Earlier developed techniques provide security of either PDF data, doc data, text data or image data, but not for all types of two-dimensional data and existing techniques used either cryptography or steganography for security. But proposed approach is suitable for all types of data and designed for security of information by cryptography and steganography. The experimental results for Word Data, PDF document, Text document, Gray-scale images and RGB images support the robustness and appropriateness for secure transmission of these data. The security analysis shows that the presented technique is immune from cryptanalytic. This technique further provides security while decryption as a check on behind which RGB color the information is hidden.
Two-dimensional capillary electrophoresis using tangentially connected capillaries.
Sahlin, Eskil
2007-06-22
A novel type of fused silica capillary system is described where channels with circular cross-sections are tangentially in contact with each other and connected through a small opening at the contact area. Since the channels are not crossing each other in the same plane, the capillaries can easily be filled with different solutions, i.e. different solutions will be in contact with each other at the contact point. The system has been used to perform different types of two-dimensional separations and the complete system is fully automated where a high voltage switch is used to control the location of the high voltage in the system. Using two model compounds it is demonstrated that a type of two-dimensional separation can be performed using capillary zone electrophoresis at two different pH values. It is also shown that a compound with acid/base properties can be concentrated using a dynamic pH junction mechanism when transferred from the first separation to the second separation. In addition, the system has been used to perform a comprehensive two-dimensional capillary electrophoresis separation of tryptic digest of bovine serum albumin using capillary zone electrophoresis followed by micellar electrokinetic chromatography.
A Two-dimensional Magnetohydrodynamics Scheme for General Unstructured Grids
Livne, Eli; Dessart, Luc; Burrows, Adam; Meakin, Casey A.
2007-05-01
We report a new finite-difference scheme for two-dimensional magnetohydrodynamics (MHD) simulations, with and without rotation, in unstructured grids with quadrilateral cells. The new scheme is implemented within the code VULCAN/2D, which already includes radiation hydrodynamics in various approximations and can be used with arbitrarily moving meshes (ALEs). The MHD scheme, which consists of cell-centered magnetic field variables, preserves the nodal finite difference representation of divB by construction, and therefore any initially divergence-free field remains divergence-free through the simulation. In this paper, we describe the new scheme in detail and present comparisons of VULCAN/2D results with those of the code ZEUS/2D for several one-dimensional and two-dimensional test problems. The code now enables two-dimensional simulations of the collapse and explosion of the rotating, magnetic cores of massive stars. Moreover, it can be used to simulate the very wide variety of astrophysical problems for which multidimensional radiation magnetohydrodynamics (RMHD) is relevant.
Procedures for two-dimensional electrophoresis of proteins
Energy Technology Data Exchange (ETDEWEB)
Tollaksen, S.L.; Giometti, C.S.
1996-10-01
High-resolution two-dimensional gel electrophoresis (2DE) of proteins, using isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) in the second, was first described in 1975. In the 20 years since those publications, numerous modifications of the original method have evolved. The ISO-DALT system of 2DE is a high-throughput approach that has stood the test of time. The problem of casting many isoelectric focusing gels and SDS-PAGE slab gels (up to 20) in a reproducible manner has been solved by the use of the techniques and equipment described in this manual. The ISO-DALT system of two-dimensional gel electrophoresis originated in the late 1970s and has been modified many times to improve its high-resolution, high-throughput capabilities. This report provides the detailed procedures used with the current ISO-DALT system to prepare, run, stain, and photograph two-dimensional gels for protein analysis.
A two-dimensional analytical model of petroleum vapor intrusion
Yao, Yijun; Verginelli, Iason; Suuberg, Eric M.
2016-02-01
In this study we present an analytical solution of a two-dimensional petroleum vapor intrusion model, which incorporates a steady-state diffusion-dominated vapor transport in a homogeneous soil and piecewise first-order aerobic biodegradation limited by oxygen availability. This new model can help practitioners to easily generate two-dimensional soil gas concentration profiles for both hydrocarbons and oxygen and estimate hydrocarbon indoor air concentrations as a function of site-specific conditions such as source strength and depth, reaction rate constant, soil characteristics and building features. The soil gas concentration profiles generated by this new model are shown in good agreement with three-dimensional numerical simulations and two-dimensional measured soil gas data from a field study. This implies that for cases involving diffusion dominated soil gas transport, steady state conditions and homogenous source and soil, this analytical model can be used as a fast and easy-to-use risk screening tool by replicating the results of 3-D numerical simulations but with much less computational effort.
Experimental realization of two-dimensional boron sheets.
Feng, Baojie; Zhang, Jin; Zhong, Qing; Li, Wenbin; Li, Shuai; Li, Hui; Cheng, Peng; Meng, Sheng; Chen, Lan; Wu, Kehui
2016-06-01
A variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. Boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp(2) hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. Here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a Ag(111) substrate. Two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. Density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. The boron sheets are quite inert to oxidization and interact only weakly with their substrate. We envisage that such boron sheets may find applications in electronic devices in the future.
Two-dimensional oxides: multifunctional materials for advanced technologies.
Pacchioni, Gianfranco
2012-08-13
The last decade has seen spectacular progress in the design, preparation, and characterization down to the atomic scale of oxide ultrathin films of few nanometers thickness grown on a different material. This has paved the way towards several sophisticated applications in advanced technologies. By playing around with the low-dimensionality of the oxide layer, which sometimes leads to truly two-dimensional systems, one can exploit new properties and functionalities that are not present in the corresponding bulk materials or thick films. In this review we provide some clues about the most recent advances in the design of these systems based on modern electronic structure theory and on their preparation and characterization with specifically developed growth techniques and analytical methods. We show how two-dimensional oxides can be used in mature technologies by providing added value to existing materials, or in new technologies based on completely new paradigms. The fields in which two-dimensional oxides are used are classified based on the properties that are exploited, chemical or physical. With respect to chemical properties we discuss use of oxide ultrathin films in catalysis, solid oxide fuel cells, gas sensors, corrosion protection, and biocompatible materials; regarding the physical properties we discuss metal-oxide field effect transistors and memristors, spintronic devices, ferroelectrics and thermoelectrics, and solar energy materials. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Thuny, Franck; Jacquier, Alexis; Jop, Bertrand; Giorgi, Roch; Gaubert, Jean-Yves; Bartoli, Jean-Michel; Moulin, Guy; Habib, Gilbert
2010-03-01
Two-dimensional echocardiography images obtained at end-diastole and end-systole and cardiac magnetic resonance (CMR) images obtained at end-diastole represent the three imaging methodologies validated for diagnosis of left ventricular non-compaction (LVNC). No study has compared these methodologies in assessing the magnitude of non-compaction. To compare two-dimensional echocardiography with CMR in the evaluation of patients with suspected LVNC. Sixteen patients (48+/-17 years) with LVNC underwent echocardiography and CMR within the same week. Echocardiography images obtained at end-diastole and end-systole were compared in a blinded fashion with those obtained by CMR at end-diastole to assess non-compaction in 17 anatomical segments. All segments could be analysed by CMR, whereas only 238 (87.5%) and 237 (87.1%) could be analysed by echocardiography at end-diastole and end-systole, respectively (p=0.002). Among the analysable segments, a two-layered structure was observed in 54.0% by CMR, 42.9% by echocardiography at end-diastole and 41.4% by echocardiography at end-systole (p=0.006). Similar distribution patterns were observed with the two echocardiographic methodologies. However, compared with echocardiography, CMR identified a higher rate of two-layered structures in the anterior, anterolateral, inferolateral and inferior segments. Echocardiography at end-systole underestimated the NC/C maximum ratio compared with CMR (p=0.04) and echocardiography at end-diastole (p=0.003). No significant difference was observed between CMR and echocardiography at end-diastole (p=0.83). Interobserver reproducibility of the NC/C maximum ratio was similar for the three methodologies. CMR appears superior to standard echocardiography in assessing the extent of non-compaction and provides supplemental morphological information beyond that obtained with conventional echocardiography.
Numerical Study of Two-Dimensional Volterra Integral Equations by RDTM and Comparison with DTM
Directory of Open Access Journals (Sweden)
Reza Abazari
2013-01-01
Full Text Available The two-dimensional Volterra integral equations are solved using more recent semianalytic method, the reduced differential transform method (the so-called RDTM, and compared with the differential transform method (DTM. The concepts of DTM and RDTM are briefly explained, and their application to the two-dimensional Volterra integral equations is studied. The results obtained by DTM and RDTM together are compared with exact solution. As an important result, it is depicted that the RDTM results are more accurate in comparison with those obtained by DTM applied to the same Volterra integral equations. The numerical results reveal that the RDTM is very effective, convenient, and quite accurate compared to the other kind of nonlinear integral equations. It is predicted that the RDTM can be found widely applicable in engineering sciences.
Terahertz magneto-optical spectroscopy of a two-dimensional hole gas
Energy Technology Data Exchange (ETDEWEB)
Kamaraju, N., E-mail: nkamaraju@lanl.gov; Taylor, A. J.; Prasankumar, R. P., E-mail: rpprasan@lanl.gov [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Pan, W.; Reno, J. [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Ekenberg, U. [Semiconsultants, Brunnsgrnd 12, SE-18773 Täby (Sweden); Gvozdić, D. M. [School of Electrical Engineering, University of Belgrade, Belgrade 11120 (Serbia); Boubanga-Tombet, S. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-Ku, Sendai (Japan); Upadhya, P. C. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Laboratory for Electro-Optics Systems, Indian Space Research Organization, Bangalore 560058 (India)
2015-01-19
Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also find that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.
Two-Dimensional Rotating Stall Analysis in a Wide Vaneless Diffuser
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available We report a numerical study on the vaneless diffuser core flow instability in centrifugal compressors. The analysis is performed for the purpose of better understanding of the rotating stall flow mechanism in radial vaneless diffusers. Since the analysis is restricted to the two-dimensional core flow, the effect of the wall boundary layers is neglected. A commercial code with the standard incompressible viscous flow solver is applied to model the vaneless diffuser core flow in the plane parallel to the diffuser walls. At the diffuser inlet, rotating jet-wake velocity pattern is prescribed and at the diffuser outlet constant static pressure is assumed. Under these circumstances, two-dimensional rotating flow instability similar to rotating stall is found to exist. Performed parameter analysis reveals that this instability is strongly influenced by the diffuser geometry and the inlet and outlet flow conditions.
Two-Dimensional IIR Filter Design Using Simulated Annealing Based Particle Swarm Optimization
Directory of Open Access Journals (Sweden)
Supriya Dhabal
2014-01-01
Full Text Available We present a novel hybrid algorithm based on particle swarm optimization (PSO and simulated annealing (SA for the design of two-dimensional recursive digital filters. The proposed method, known as SA-PSO, integrates the global search ability of PSO with the local search ability of SA and offsets the weakness of each other. The acceptance criterion of Metropolis is included in the basic algorithm of PSO to increase the swarm’s diversity by accepting sometimes weaker solutions also. The experimental results reveal that the performance of the optimal filter designed by the proposed SA-PSO method is improved. Further, the convergence behavior as well as optimization accuracy of proposed method has been improved significantly and computational time is also reduced. In addition, the proposed SA-PSO method also produces the best optimal solution with lower mean and variance which indicates that the algorithm can be used more efficiently in realizing two-dimensional digital filters.
Directory of Open Access Journals (Sweden)
D. A. Fetisov
2015-01-01
Full Text Available The controllability conditions are well known if we speak about linear stationary systems: a linear stationary system is controllable if and only if the dimension of the state vector is equal to the rank of the controllability matrix. The concept of the controllability matrix is extended to affine systems, but relations between affine systems controllability and properties of this matrix are more complicated. Various controllability conditions are set for affine systems, but they deal as usual either with systems of some special form or with controllability in some small neighborhood of the concerned point. An affine system is known to be controllable if the system is equivalent to a system of a canonical form, which is defined and regular in the whole space of states. In this case, the system is said to be feedback linearizable in the space of states. However there are examples, which illustrate that a system can be controllable even if it is not feedback linearizable in any open subset in the space of states. In this article we deal with such systems.Affine systems with two-dimensional control are considered. The system in question is assumed to be equivalent to a system of a quasicanonical form with two-dimensional zero dynamics which is defined and regular in the whole space of states. Therefore the controllability of the original system is equivalent to the controllability of the received system of a quasicanonical form. In this article the sufficient condition for an available solution of the terminal problem is proven for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. The condition is valid in the case of an arbitrary time interval and arbitrary initial and finite states of the system. Therefore the controllability condition is set for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. An example is given which illustrates how the proved
Institute of Scientific and Technical Information of China (English)
XU Quan; TIAN Qiang
2009-01-01
We restrict our attention to the discrete two-dimensional monatomic β-FPU lattice. We look for twodimensional breather lattice solutions and two-dimensional compact-like discrete breathers by using trying method and analyze their stability by using Aubry's linearly stable theory. We obtain the conditions of existence and stability of two-dimensional breather lattice solutions and two-dimensional compact-like discrete breathers in the discrete twodimensional monatomic β-FPU lattice.
[Stress echocardiography: development and significance].
Attenhofer, C; Ritter, M; Jenni, R
1994-08-27
Exercise electrocardiography is still the primary method used in the non-invasive assessment of coronary artery disease. Stress echocardiography is now being increasingly used as a more sensitive adjunct technique to assess ischemia. Ischemia provoked by stress can induce reversible wall motion abnormalities which are disclosed by cross-sectional 2-dimensional echocardiography and standard projections. The types of stress used are physical exercise (bicycle, treadmill), atrial pacing or pharmacologic stimulation. In the latter, the catecholamine dobutamine has emerged as preferable to the vasodilators dipyridamole and adenosine. The diagnostic accuracy of dobutamine stress echocardiography is comparable to that of bicycle or treadmill exercise echocardiography, but dobutamine stress echocardiography is technically simpler and can be performed in patients unable to exercise. Its sensitivity in diagnosing ischemic or viable myocardium is comparable to that of nuclear methods, MRI or PET. In contrast to nuclear methods, stress echocardiography is however free of radiation. In the assessment of patients with coronary artery disease, stress echocardiography has been shown to be valuable for diagnosis, preoperative risk stratification and determination of prognosis. Furthermore, low dose dobutamine echocardiography can be used to detect viable myocardium. Despite these very promising aspects of the method, there are recognized disadvantages and limitations: stress echocardiography is very time-consuming and operator-dependent; its sensitivity correlates strongly with the number of studies performed; analysis of wall motion is performed qualitatively on a purely subjective level, and hence lacks the objectivity of a quantitative approach. These factors emphasize the need for intensive research to render stress echocardiographic analysis more objective. Automatic boundary detection of left ventricular endocardium, color-Doppler-based tissue imaging and three
Directory of Open Access Journals (Sweden)
Taner Yavuz
2011-12-01
Full Text Available Objective: The aim of this study was to evaluate ventricular performance before and after exercise in children who had surgically repaired coarctation of aorta (CoA by using two dimensional, M- mode and Doppler echocardiography and to determine whether this method can be used for identifying recoarctation in comparison to Magnetic Resonance Imaging (MRI. Design: We studied on 24 patients who were operated for CoA previously and compared with 24 healthy controls. Blood pressure monitoring, echocardiographies at rest and after exercise and MRI of aortic arc were performed. Patients having had ≥ 30 % of isthmic stenosis on MRI was diagnosed as recoarctation. The patient group were divided as Group A (patient without recoarctation and Group B (patients with recoarctation and were compared. Results: We found that 8 of 24 patients had recoarctation on MRI. Physical examination and echocardiographic evaluation revealed that hypertension on the right arm at rest, systolic and diastolic hypotension on the left leg after exercise, increased values of ejection fraction, fractioned shortening and aortic gradient on exercise may predict more than 30 % narrowing of the aortic isthmus. Conclusion: These findings can be useful as predictors for recoarctation.
The characters of nonlinear vibration in the two-dimensional discrete monoatomic lattice
Institute of Scientific and Technical Information of China (English)
XU Quan; TIAN Qiang
2005-01-01
The two-dimensional discrete monoatomic lattice is analyzed. Taking nearest-neighbor interaction into account, the characters of the nonlinear vibration in two-dimensional discrete monoatomic lattice are described by the two-dimensional cubic nonlinear Schrodinger equation. Considering the quartic nonlinear potential, the two-dimensional discrete-soliton trains and the solutions perturbed by the neck mode are presented.
Nazarov, V. U.
2015-10-01
We investigate the wave vector and frequency-dependent screening of the electric field in atomically thin (quasi-two-dimensional) crystals. For graphene and hexagonal boron nitride we find that, above a critical wave vector qc, the static permittivity ɛ (q >qc,ω =0 ) becomes negative and the Kramers-Kronig relations do not hold for ɛ (q >qc,ω ) . Thus, in quasi-two-dimensional crystals, we reveal the physical confirmation of a proposition put forward decades ago [D. A. Kirzhnits, Sov. Phys. Usp. 19, 530 (1976), 10.1070/PU1976v019n06ABEH005268], allowing for the breakdown of Kramers-Kronig relations and for negative static permittivity. In the vicinity of the critical wave vector, we find a giant growth of the permittivity. Our results, obtained in the ab initio calculations using both the random-phase approximation and the adiabatic time-dependent local-density approximation, and further confirmed with a simple slab model, allow us to argue that the above properties, being exceptional in the three-dimensional case, are common to quasi-two-dimensional systems.
Nonlinear acoustic propagation in two-dimensional ducts
Nayfeh, A. H.; Tsai, M.-S.
1974-01-01
The method of multiple scales is used to obtain a second-order uniformly valid expansion for the nonlinear acoustic wave propagation in a two-dimensional duct whose walls are treated with a nonlinear acoustic material. The wave propagation in the duct is characterized by the unsteady nonlinear Euler equations. The results show that nonlinear effects tend to flatten and broaden the absorption versus frequency curve, in qualitative agreement with the experimental observations. Moreover, the effect of the gas nonlinearity increases with increasing sound frequency, whereas the effect of the material nonlinearity decreases with increasing sound frequency.
Two-dimensional dispersive shock waves in dissipative optical media
Kartashov, Yaroslav V
2013-01-01
We study generation of two-dimensional dispersive shock waves and oblique dark solitons upon interaction of tilted plane waves with negative refractive index defects embedded into defocusing material with linear gain and two-photon absorption. Different evolution regimes are encountered including the formation of well-localized disturbances for input tilts below critical one, and generation of extended shock waves containing multiple intensity oscillations in the "upstream" region and gradually vanishing oblique dark solitons in "downstream" region for input tilts exceeding critical one. The generation of stable dispersive shock waves is possible only below certain critical defect strength.
Three-dimensional versus two-dimensional vision in laparoscopy
DEFF Research Database (Denmark)
Sørensen, Stine Maya Dreier; Savran, Mona M; Konge, Lars;
2016-01-01
BACKGROUND: Laparoscopic surgery is widely used, and results in accelerated patient recovery time and hospital stay were compared with laparotomy. However, laparoscopic surgery is more challenging compared with open surgery, in part because surgeons must operate in a three-dimensional (3D) space...... through a two-dimensional (2D) projection on a monitor, which results in loss of depth perception. To counter this problem, 3D imaging for laparoscopy was developed. A systematic review of the literature was performed to assess the effect of 3D laparoscopy. METHODS: A systematic search of the literature...
The Rare Two-Dimensional Materials with Dirac Cones
Wang, Jinying; Deng, Shibin; Liu, Zhongfan; Liu, Zhirong
2014-01-01
Inspired by the great development of graphene, more and more works have been conducted to seek new two-dimensional (2D) materials with Dirac cones. Although 2D Dirac materials possess many novel properties and physics, they are rare compared with the numerous 2D materials. To provide explanation for the rarity of 2D Dirac materials as well as clues in searching for new Dirac systems, here we review the recent theoretical aspects of various 2D Dirac materials, including graphene, silicene, ger...
Logarithmic divergent thermal conductivity in two-dimensional nonlinear lattices.
Wang, Lei; Hu, Bambi; Li, Baowen
2012-10-01
Heat conduction in three two-dimensional (2D) momentum-conserving nonlinear lattices are numerically calculated via both nonequilibrium heat-bath and equilibrium Green-Kubo algorithms. It is expected by mainstream theories that heat conduction in such 2D lattices is divergent and the thermal conductivity κ increases with lattice length N logarithmically. Our simulations for the purely quartic lattice firmly confirm it. However, very robust finite-size effects are observed in the calculations for the other two lattices, which well explain some existing studies and imply the extreme difficulties in observing their true asymptotic behaviors with affordable computation resources.
Two-dimensionally confined topological edge states in photonic crystals
Barik, Sabyasachi; Miyake, Hirokazu; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad
2016-11-01
We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three-dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters.
Two-Dimensionally Confined Topological Edge States in Photonic Crystals
Barik, Sabyasachi; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad
2016-01-01
We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters.
Theories on Frustrated Electrons in Two-Dimensional Organic Solids
Directory of Open Access Journals (Sweden)
Chisa Hotta
2012-08-01
Full Text Available Two-dimensional quarter-filled organic solids are a promising class of materials to realize the strongly correlated insulating states called dimer Mott insulator and charge order. In their conducting layer, the molecules form anisotropic triangular lattices, harboring geometrical frustration effect, which could give rise to many interesting states of matter in the two insulators and in the metals adjacent to them. This review is concerned with the theoretical studies on such issue over the past ten years, and provides the systematic understanding on exotic metals, dielectrics, and spin liquids, which are the consequences of the competing correlation and fluctuation under frustration.
Wake-induced bending of two-dimensional plasma crystals
Energy Technology Data Exchange (ETDEWEB)
Röcker, T. B., E-mail: tbr@mpe.mpg.de; Ivlev, A. V., E-mail: ivlev@mpe.mpg.de; Zhdanov, S. K.; Morfill, G. E. [Max Planck Institute for Extraterrestrial Physics, 85741 Garching (Germany); Couëdel, L. [CNRS, Aix-Marseille-Université, Laboratoire de Physique des Interactions Ioniques et Moléculaires, UMR 7345, 13397 Marseille Cedex 20 (France)
2014-07-15
It is shown that the wake-mediated interactions between microparticles in a two-dimensional plasma crystal affect the shape of the monolayer, making it non-flat. The equilibrium shape is calculated for various distributions of the particle number density in the monolayer. For typical experimental conditions, the levitation height of particles in the center of the crystal can be noticeably smaller than at the periphery. It is suggested that the effect of wake-induced bending can be utilized in experiments, to deduce important characteristics of the interparticle interaction.
Wake-induced bending of two-dimensional plasma crystals
Röcker, T B; Zhdanov, S K; Couëdel, L; Morfill, G E
2014-01-01
It is shown that the wake-mediated interactions between microparticles in a two-dimensional plasma crystal affect the shape of the monolayer, making it non-flat. The equilibrium shape is calculated for various distributions of the particle number density in the monolayer. For typical experimental conditions, the levitation height of particles in the center of the crystal can be noticeably smaller than at the periphery. It is suggested that the effect of wake-induced bending can be utilized in experiments, to deduce important characteristics of the interparticle interaction.
Corner wetting transition in the two-dimensional Ising model
Lipowski, Adam
1998-07-01
We study the interfacial behavior of the two-dimensional Ising model at the corner of weakened bonds. Monte Carlo simulations results show that the interface is pinned to the corner at a lower temperature than a certain temperature Tcw at which it undergoes a corner wetting transition. The temperature Tcw is substantially lower than the temperature of the ordinary wetting transition with a line of weakened bonds. A solid-on-solid-like model is proposed, which provides a supplementary description of the corner wetting transition.
Dynamic Multiscaling in Two-dimensional Fluid Turbulence
Ray, Samriddhi Sankar; Perlekar, Prasad; Pandit, Rahul
2011-01-01
We obtain, by extensive direct numerical simulations, time-dependent and equal-time structure functions for the vorticity, in both quasi-Lagrangian and Eulerian frames, for the direct-cascade regime in two-dimensional fluid turbulence with air-drag-induced friction. We show that different ways of extracting time scales from these time-dependent structure functions lead to different dynamic-multiscaling exponents, which are related to equal-time multiscaling exponents by different classes of bridge relations; for a representative value of the friction we verify that, given our error bars, these bridge relations hold.
Absolute band gaps in two-dimensional graphite photonic crystal
Institute of Scientific and Technical Information of China (English)
Gaoxin Qiu(仇高新); Fanglei Lin(林芳蕾); Hua Wang(王华); Yongping Li(李永平)
2003-01-01
The off-plane propagation of electromagnetic (EM) waves in a two-dimensional (2D) graphite photoniccrystal structure was studied using transfer matrix method. Transmission spectra calculations indicatethat such a 2D structure has a common band gap from 0.202 to 0.2035 c/a for both H and E polarizationsand for all off-plane angles form 0° up to 90°. The presence of such an absolute band gap implies that 2Dgraphite photonic crystal, which is much easier and more feasible to fabricate, can exhibit some propertiesof a three-dimensional (3D) photonic crystal.
Kinetic analysis of two dimensional metallic grating Cerenkov maser
Energy Technology Data Exchange (ETDEWEB)
Zhao Ding [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)
2011-08-15
The dispersion relation of two dimensional metallic grating Cerenkov maser has been given by using kinetic analysis, in which the influence of electron movement is directly considered without using an equivalent dielectric medium assumption. The effects of structural parameters and beam state on the interaction gain and synchronous frequency have also been investigated in detail by numerical calculations. To an illustrative case, the quantitative relations produced from varying the gap distance between electron beam and metallic grating, beam current, electron transverse to axial velocity ratio, and electron axial velocity spread have been obtained. The developed method can be used to predict the real interaction system performances.
Mean flow generation in rotating anelastic two-dimensional convection
Currie, Laura K
2016-01-01
We investigate the processes that lead to the generation of mean flows in two-dimensional anelastic convection. The simple model consists of a plane layer that is rotating about an axis inclined to gravity. The results are two-fold: firstly we numerically investigate the onset of convection in three-dimensions, paying particular attention to the role of stratification and highlight a curious symmetry. Secondly, we investigate the mechanisms that drive both zonal and meridional flows in two dimensions. We find that, in general, non-trivial Reynolds stresses can lead to systematic flows and, using statistical measures, we quantify the role of stratification in modifying the coherence of these flows.
Duality, Monodromy and Integrability of Two Dimensional String Effective Action
Das, A; Melikyan, A; Das, Ashok
2002-01-01
The monodromy matrix, ${\\hat{\\cal M}}$, is constructed for two dimensional tree level string effective action. The pole structure of ${\\hat{\\cal M}}$ is derived using its factorizability property. It is found that the monodromy matrix transforms non-trivially under the non-compact T-duality group, which leaves the effective action invariant and this can be used to construct the monodromy matrix for more complicated backgrounds starting from simpler ones. We construct, explicitly, ${\\hat{\\cal M}}$ for the exactly solvable Nappi-Witten model, both when B=0 and $B\
Homogenization of Two-Dimensional Phononic Crystals at Low Frequencies
Institute of Scientific and Technical Information of China (English)
NI Qing; CHENG Jian-Chun
2005-01-01
@@ Effective velocities of elastic waves propagating in two-dimensional phononic crystal at low frequencies are analysed theoretically, and exact analytical formulas for effective velocities of elastic waves are derived according to the method presented by Krokhin et al. [Phys. Rev. Lett. 91 (2003) 264302]. Numerical calculations for phononic crystals consisted of array of Pb cylinders embedded in epoxy show that the composites have distinct anisotropy at low filling fraction. The anisotropy increases as the filling fraction increases, while as the filling fraction closes to the limitation, the anisotropy decreases.
Electronic Transmission Properties of Two-Dimensional Quasi-Lattice
Institute of Scientific and Technical Information of China (English)
侯志林; 傅秀军; 刘有延
2002-01-01
In the framework of the tight binding model, the electronic transmission properties of two-dimensional Penrose lattices with free boundary conditions are studied using the generalized eigenfunction method (Phys. Rev. B 60(1999)13444). The electronic transmission coefficients for Penrose lattices with different sizes and widths are calculated, and the result shows strong energy dependence because of the quasiperiodic structure and quantum coherent effect. Around the Fermi level E = 0, there is an energy region with zero transmission amplitudes,which suggests that the studied systems are insulating. The spatial distributions of several typical electronic states with different transmission coefficients are plotted to display the propagation process.
Two-dimensional conformal field theory and the butterfly effect
Roberts, Daniel A
2014-01-01
We study chaotic dynamics in two-dimensional conformal field theory through out-of-time order thermal correlators of the form $\\langle W(t)VW(t)V\\rangle$. We reproduce bulk calculations similar to those of [1], by studying the large $c$ Virasoro identity block. The contribution of this block to the above correlation function begins to decrease exponentially after a delay of $\\sim t_* - \\frac{\\beta}{2\\pi}\\log \\beta^2E_w E_v$, where $t_*$ is the scrambling time $\\frac{\\beta}{2\\pi}\\log c$, and $E_w,E_v$ are the energy scales of the $W,V$ operators.
Two-Dimensional Gel Electrophoresis: A Reference Protocol.
Saia-Cereda, Veronica M; Aquino, Adriano; Guest, Paul C; Martins-de-Souza, Daniel
2017-01-01
Two-dimensional gel electrophoresis (2DE) has been a mainstay of proteomic techniques for more than four decades. It was even in use for several years before the term proteomics was actually coined in the early 1990s. Over this time, it has been used in the study of many diseases including cancer, diabetes, heart disease, and psychiatric disorders through the proteomic analysis of body fluids and tissues. This chapter presents a general protocol which can be applied in the study of biological samples such as blood serum or plasma and multiple tissues including the brain.
Basics and recent advances of two dimensional- polyacrylamide gel electrophoresis
2014-01-01
Gel- based proteomics is one of the most versatile methods for fractionating protein complexes. Among these methods, two dimensional- polyacrylamide gel electrophoresis (2-DE) represents a mainstay orthogonal approach, which is popularly used to simultaneously fractionate, identify, and quantify proteins when coupled with mass spectrometric identification or other immunological tests. Although 2-DE was first introduced more than three decades ago, several challenges and limitations to its utility still exist. This review discusses the principles of 2-DE as well as both recent methodological advances and new applications. PMID:24735559
Size-dispersity effects in two-dimensional melting.
Watanabe, Hiroshi; Yukawa, Satoshi; Ito, Nobuyasu
2005-01-01
In order to investigate the effect of size dispersity on two-dimensional melting transitions, hard-disk systems with equimolar bidispersity are studied by means of particle dynamics simulations. From the nonequilibrium relaxation behaviors of bond-orientational order parameters, we find that (i) there is a critical dispersity at which the melting transition of the hexagonal solid vanishes and (ii) the quadratic structure is metastable in a certain region of the dispersity-density parameter space. These results suggest that the dispersity not only destroys order but produces new structures under certain specific conditions.
Human muscle proteins: analysis by two-dimensional electrophoresis
Energy Technology Data Exchange (ETDEWEB)
Giometti, C.S.; Danon, M.J.; Anderson, N.G.
1983-09-01
Proteins from single frozen sections of human muscle were separated by two-dimensional gel electrophoresis and detected by fluorography or Coomassie Blue staining. The major proteins were identical in different normal muscles obtained from either sex at different ages, and in Duchenne and myotonic dystrophy samples. Congenital myopathy denervation atrophy, polymyositis, and Becker's muscular dystrophy samples, however, showed abnormal myosin light chain compositions, some with a decrease of fast-fiber myosin light chains and others with a decrease of slow-fiber light chains. These protein alterations did not correlate with any specific disease, and may be cause by generalized muscle-fiber damage.
The XY model coupled to two-dimensional quantum gravity
Baillie, C. F.; Johnston, D. A.
1992-09-01
We perform Monte Carlo simulations using the Wolff cluster algorithm of the XY model on both fixed and dynamical phi-cubed graphs (i.e. without and with coupling to two-dimensional quantum gravity). We compare the numerical results with the theoretical expectation that the phase transition remains of KT type when the XY model is coupled to gravity. We also examine whether the universality we discovered in our earlier work on various Potts models with the same value of the central charge, c, carries over to the XY model, which has c=1.
Two-dimensional chiral topological superconductivity in Shiba lattices
Li, Jian; Neupert, Titus; Wang, Zhijun; MacDonald, A. H.; Yazdani, A.; Bernevig, B. Andrei
2016-07-01
The chiral p-wave superconductor is the archetypal example of a state of matter that supports non-Abelian anyons, a highly desired type of exotic quasiparticle. With this, it is foundational for the distant goal of building a topological quantum computer. While some candidate materials for bulk chiral superconductors exist, they are subject of an ongoing debate about their actual paring state. Here we propose an alternative route to chiral superconductivity, consisting of the surface of an ordinary superconductor decorated with a two-dimensional lattice of magnetic impurities. We furthermore identify a promising experimental platform to realize this proposal.
Field analysis of two-dimensional focusing grating
Borsboom, P.P.; Frankena, H.J.
1995-01-01
The method that we have developed [P-P. Borsboom, Ph.D. dissertation (Delft University of Technology, Delft, The Netherlands); P-P. Borsboom and H. J. Frankena, J. Opt. Soc. Am. A 12, 1134–1141 (1995)] is successfully applied to a two-dimensional focusing grating coupler. The field in the focal region has been determined for symmetrical chirped gratings consisting of as many as 124 corrugations. The intensity distribution in the focal region agrees well with the approximate predictions of geo...
Field analysis of two-dimensional integrated optical gratings
Borsboom, P.-P.; Frankena, H. J.
1995-05-01
A rigorous technique to determine the field scattered by a two-dimensional rectangular grating made up of many corrugations was developed. In this method, the grating was deemed as a sequence of two types of waveguide sections, alternatingly connected by step discontinuities. A matrix was derived that described the entire rectangular grating by integrating the separate steps and waveguide sections. With the proposed technique, several configuration were analyzed. The obtained results showed good consistency with the consequences of previous studies. Furthermore, to examine the numerical stability of the proposed method, the length of the grating was increased and obtained results for a grating with 100 periods.
Numerical Simulation of Two-dimensional Nonlinear Sloshing Problems
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Numerical simulation of a two-dimensional nonlinearsloshing problem is preceded by the finite element method. Two theories are used. One is fully nonlinear theory; the other is time domain second order theory. A liquid sloshing in a rectangular container subjected to a horizontal excitation is simulated using these two theories. Numerical results are obtained and comparisons are made. It is found that a good agreement is obtained for the case of small amplitude oscillation. For the situation of large amplitude excitation, although the differences between using the two theories are obvious the second order solution can still exhibit typical nonlinear features of nonlinear wave.
Finite Element Analysis to Two-Dimensional Nonlinear Sloshing Problems
Institute of Scientific and Technical Information of China (English)
严承华; 王赤忠; 程尔升
2001-01-01
A two-dimensional nonlinear sloshing problem is analyzed by means of the fully nonlinear theory and time domainsecond order theory of water waves. Liquid sloshing in a rectangular container subjected to a horizontal excitation is sim-ulated by the finite element method. Comparisons between the two theories are made based on their numerical results. Itis found that good agreement is obtained for the case of small amplitude oscillation and obvious differences occur forlarge amplitude excitation. Even though, the second order solution can still exhibit typical nonlinear features ofnonlinear wave and can be used instead of the fully nonlinear theory.
Graphene and Two-Dimensional Materials for Optoelectronic Applications
Directory of Open Access Journals (Sweden)
Andreas Bablich
2016-03-01
Full Text Available This article reviews optoelectronic devices based on graphene and related two-dimensional (2D materials. The review includes basic considerations of process technology, including demonstrations of 2D heterostructure growth, and comments on the scalability and manufacturability of the growth methods. We then assess the potential of graphene-based transparent conducting electrodes. A major part of the review describes photodetectors based on lateral graphene p-n junctions and Schottky diodes. Finally, the progress in vertical devices made from 2D/3D heterojunctions, as well as all-2D heterostructures is discussed.
Two-dimensional carbon fundamental properties, synthesis, characterization, and applications
Yihong, Wu; Ting, Yu
2013-01-01
After a brief introduction to the fundamental properties of graphene, this book focuses on synthesis, characterization and application of various types of two-dimensional (2D) nanocarbons ranging from single/few layer graphene to carbon nanowalls and graphene oxides. Three major synthesis techniques are covered: epitaxial growth of graphene on SiC, chemical synthesis of graphene on metal, and chemical vapor deposition of vertically aligned carbon nanosheets or nanowalls. One chapter is dedicated to characterization of 2D nanocarbon using Raman spectroscopy. It provides extensive coverage for a
AN APPROACH IN MODELING TWO-DIMENSIONAL PARTIALLY CAVITATING FLOW
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
An approach of modeling viscosity, unsteady partially cavitating flows around lifting bodies is presented. By employing an one-fluid Navier-Stokers solver, the algorithm is proved to be able to handle two-dimensional laminar cavitating flows at moderate Reynolds number. Based on the state equation of water-vapor mixture, the constructive relations of densities and pressures are established. To numerically simulate the cavity wall, different pseudo transition of density models are presumed. The finite-volume method is adopted and the algorithm can be extended to three-dimensional cavitating flows.
The problem of friction in two-dimensional relative motion
Grech, D K; Grech, Dariusz; Mazur, Zygmunt
2000-01-01
We analyse a mechanical system in two-dimensional relative motion with friction. Although the system is simple, the peculiar interplay between two kinetic friction forces and gravity leads to the wide range of admissible solutions exceeding most intuitive expectations. In particular, the strong qualitative dependence between behaviour of the system, boundary conditions and parameters involved in its description is emphasised. The problem is intended to be discussed in theoretical framework and might be of interest for physics and mechanics students as well as for physics teachers.
Quantum computation with two-dimensional graphene quantum dots
Institute of Scientific and Technical Information of China (English)
Li Jie-Sen; Li Zhi-Bing; Yao Dao-Xin
2012-01-01
We study an array of graphene nano sheets that form a two-dimensional S =1/2 Kagome spin lattice used for quantum computation.The edge states of the graphene nano sheets axe used to form quantum dots to confine electrons and perform the computation.We propose two schemes of bang-bang control to combat decoherence and realize gate operations on this array of quantum dots.It is shown that both schemes contain a great amount of information for quantum computation.The corresponding gate operations are also proposed.
Complex Saddles in Two-dimensional Gauge Theory
Buividovich, P V; Valgushev, S N
2015-01-01
We study numerically the saddle point structure of two-dimensional (2D) lattice gauge theory, represented by the Gross-Witten-Wadia unitary matrix model. The saddle points are in general complex-valued, even though the original integration variables and action are real. We confirm the trans-series/instanton gas structure in the weak-coupling phase, and identify a new complex-saddle interpretation of non-perturbative effects in the strong-coupling phase. In both phases, eigenvalue tunneling refers to eigenvalues moving off the real interval, into the complex plane, and the weak-to-strong coupling phase transition is driven by saddle condensation.
Band alignment of two-dimensional lateral heterostructures
Zhang, Junfeng; Xie, Weiyu; Zhang, S B
2016-01-01
Band alignment in two-dimensional (2D) lateral heterostructures is fundamentally different from three-dimensional (3D), as Schottky barrier height is at the Schottky-Mott limit and band offset is at the Anderson limit, regardless interfacial conditions. This robustness arises because, in the asymptotic limit, effect of interfacial dipole vanishes. First-principles calculations of graphene/h-BN and MoS2/WS2 show that 2D junction width W is typically an order of magnitude longer than 3D. Therefore, heterostructures with dimension less than W can also be made, leading to tunable band alignment.
Topological Quantum Optics in Two-Dimensional Atomic Arrays
Perczel, J.; Borregaard, J.; Chang, D. E.; Pichler, H.; Yelin, S. F.; Zoller, P.; Lukin, M. D.
2017-07-01
We demonstrate that two-dimensional atomic emitter arrays with subwavelength spacing constitute topologically protected quantum optical systems where the photon propagation is robust against large imperfections while losses associated with free space emission are strongly suppressed. Breaking time-reversal symmetry with a magnetic field results in gapped photonic bands with nontrivial Chern numbers and topologically protected, long-lived edge states. Due to the inherent nonlinearity of constituent emitters, such systems provide a platform for exploring quantum optical analogs of interacting topological systems.
Elastic models of defects in two-dimensional crystals
Kolesnikova, A. L.; Orlova, T. S.; Hussainova, I.; Romanov, A. E.
2014-12-01
Elastic models of defects in two-dimensional (2D) crystals are presented in terms of continuum mechanics. The models are based on the classification of defects, which is founded on the dimensionality of the specification region of their self-distortions, i.e., lattice distortions associated with the formation of defects. The elastic field of an infinitesimal dislocation loop in a film is calculated for the first time. The fields of the center of dilatation, dislocation, disclination, and circular inclusion in planar 2D elastic media, namely, nanofilms and graphenes, are considered. Elastic fields of defects in 2D and 3D crystals are compared.
On two-dimensional magnetic reconnection with nonuniform resistivity
Malyshkin, Leonid M.; Kulsrud, Russell M.
2010-12-01
In this paper, two theoretical approaches for the calculation of the rate of quasi-stationary, two-dimensional magnetic reconnection with nonuniform anomalous resistivity are considered in the framework of incompressible magnetohydrodynamics (MHD). In the first, 'global' equations approach, the MHD equations are approximately solved for a whole reconnection layer, including the upstream and downstream regions and the layer center. In the second, 'local' equations approach, the equations are solved across the reconnection layer, including only the upstream region and the layer center. Both approaches give the same approximate answer for the reconnection rate. Our theoretical model is in agreement with the results of recent simulations of reconnection with spatially nonuniform resistivity.
Quantum skyrmions in two-dimensional chiral magnets
Takashima, Rina; Ishizuka, Hiroaki; Balents, Leon
2016-10-01
We study the quantum mechanics of magnetic skyrmions in the vicinity of the skyrmion-crystal to ferromagnet phase boundary in two-dimensional magnets. We show that the skyrmion excitation has an energy dispersion that splits into multiple bands due to the combination of magnus force and the underlying lattice. Condensation of the skyrmions can give rise to an intermediate phase between the skyrmion crystal and ferromagnet: a quantum liquid, in which skyrmions are not spatially localized. We show that the critical behavior depends on the spin size S and the topological number of the skyrmion. Experimental signatures of quantum skyrmions in inelastic neutron-scattering measurements are also discussed.
Local kinetic effects in two-dimensional plasma turbulence.
Servidio, S; Valentini, F; Califano, F; Veltri, P
2012-01-27
Using direct numerical simulations of a hybrid Vlasov-Maxwell model, kinetic processes are investigated in a two-dimensional turbulent plasma. In the turbulent regime, kinetic effects manifest through a deformation of the ion distribution function. These patterns of non-Maxwellian features are concentrated in space nearby regions of strong magnetic activity: the distribution function is modulated by the magnetic topology, and can elongate along or across the local magnetic field. These results open a new path on the study of kinetic processes such as heating, particle acceleration, and temperature anisotropy, commonly observed in astrophysical and laboratory plasmas.
Drift modes of a quasi-two-dimensional current sheet
Energy Technology Data Exchange (ETDEWEB)
Artemyev, A. V.; Malova, Kh. V.; Popov, V. Yu.; Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)
2012-03-15
Stability of a plasma configuration consisting of a thin one-dimensional current sheet embedded into a two-dimensional background current sheet is studied. Drift modes developing in plasma as unstable waves along the current direction are considered. Dispersion relations for kink and sausage perturbation modes are obtained depending on the ratio of parameters of thin and background current sheets. It is shown that the existence of the background sheet results in a decrease in the instability growth rates and a significant increase in the perturbation wavelengths. The role of drift modes in the excitation of oscillations observed in the current sheet of the Earth's magnetotail is discussed.
Synthesis of two-dimensional materials for beyond graphene devices
Zhang, Kehao; Eichfeld, Sarah; Leach, Jacob; Metzger, Bob; Lin, Yu-Chuan; Evans, Keith; Robinson, Joshua A.
2015-05-01
In this paper, we present an overview of the currently employed techniques to synthesize two-dimensional materials, focusing on MoS2 and WSe2, and summarize the progress reported to-date. Here we discuss the importance of controlling reactor geometries to improve film uniformity and quality for MoS2 through a combination of modeling and experimental design. In addition, development of processes scalable to provide wafer scale uniformity is explored using synthesis of WSe2 via metal-organic chemical vapor deposition. Finally, we discuss the impact of each of these processes for TMD synthesis on epitaxial graphene.
Magnetic quantum dot in two-dimensional topological insulators
Li, Guo; Zhu, Jia-Lin; Yang, Ning
2017-03-01
Magnetic quantum dots in two-dimensional band and topological insulators are studied by solving the modified Dirac model under nonuniform magnetic fields. The Landau levels split into discrete states with certain angular momentum. The states splitting from the zero Landau levels lie in the energy gap for topological insulators but are out of the gap for band insulators. It is found that the ground states oscillate between the spin-up and spin-down states when the magnetic field or the dot size changes. The oscillation manifests itself as changes of sign and strength of charge currents near the dot's edge.
Mass/Count Variation: A Mereological, Two-Dimensional Semantics
Directory of Open Access Journals (Sweden)
Peter R Sutton
2016-12-01
Full Text Available We argue that two types of context are central to grounding the semantics for the mass/count distinction. We combine and develop the accounts of Rothstein (2010 and Landman (2011, which emphasize (non-overlap at a context. We also adopt some parts of Chierchia’s (2010 account which uses precisifying contexts. We unite these strands in a two-dimensional semantics that covers a wide range of the puzzling variation data in mass/count lexicalization. Most importantly, it predicts where we should expect to find such variation for some classes of nouns but not for others, and also explains why.
A two-dimensional approach to relativistic positioning systems
Coll, B; Morales, J A; Coll, Bartolom\\'{e}; Ferrando, Joan Josep; Morales, Juan Antonio
2006-01-01
A relativistic positioning system is a physical realization of a coordinate system consisting in four clocks in arbitrary motion broadcasting their proper times. The basic elements of the relativistic positioning systems are presented in the two-dimensional case. This simplified approach allow to explain and to analyze the properties and interest of these new systems. The positioning system defined by geodesic emitters in flat metric is developed in detail. The information that the data generated by a relativistic positioning system give on the space-time metric interval is analyzed, and the interest of these results in gravimetry is pointed out.
Dynamical matrix of two-dimensional electron crystals
Côté, R.; Lemonde, M.-A.; Doiron, C. B.; Ettouhami, A. M.
2008-03-01
In a quantizing magnetic field, the two-dimensional electron gas has a rich phase diagram with broken translational symmetry phases such as Wigner, bubble, and stripe crystals. In this paper, we derive a method to obtain the dynamical matrix of these crystals from a calculation of the density response function performed in the generalized random-phase approximation (GRPA). We discuss the validity of our method by comparing the dynamical matrix calculated from the GRPA with that obtained from standard elasticity theory with the elastic coefficients obtained from a calculation of the deformation energy of the crystal.
Two-dimensional transport study of scrape off layer plasmas
Energy Technology Data Exchange (ETDEWEB)
Yamamoto, Nobuyuki [Interdisciplinary Graduate School of Advanced Energy Engineering Sciences, Kyushu University, Fukuoka (Japan); Yagi, Masatoshi; Itoh, Sanae-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics
1999-09-01
Two-dimensional transport code is developed to analyzed the heat pulse propagation in the scrape-off layer plasma. The classical and anomalous transport models are considered as a thermal diffusivity perpendicular to the magnetic field. On the other hand, the classical transport model is chosen as a thermal diffusivity parallel to the magnetic field. The heat deposition profiles are evaluated for various kinds of transport models. It is found that the heat pulse which arrives at the divertor plate due to the classical transport is largest compared with other models. The steady state temperate profiles of the electron and ion are also discussed. (author)
Consistent theory of turbulent transport in two-dimensional magnetohydrodynamics.
Kim, Eun-jin
2006-03-03
A theory of turbulent transport is presented in two-dimensional magnetohydrodynamics with background shear and magnetic fields. We provide theoretical predictions for the transport of magnetic flux, momentum, and particles and turbulent intensities, which show stronger reduction compared with the hydrodynamic case, with different dependences on shearing rate, magnetic field, and values of viscosity, Ohmic diffusion, and particle diffusivity. In particular, particle transport is more severely suppressed than momentum transport, effectively leading to a more efficient momentum transport. The role of magnetic fields in quenching transport without altering the amplitude of flow velocity and in inhibiting the generation of shear flows is elucidated. Implications of the results are discussed.
Deformable two-dimensional photonic crystal slab for cavity optomechanics
Antoni, T; Briant, T; Cohadon, P -F; Heidmann, A; Braive, R; Beveratos, A; Abram, I; Gatiet, L Le; Sagnes, I; Robert-Philip, I
2011-01-01
We have designed photonic crystal suspended membranes with optimized optical and mechanical properties for cavity optomechanics. Such resonators sustain vibration modes in the megahertz range with quality factors of a few thousand. Thanks to a two-dimensional square lattice of holes, their reflectivity at normal incidence at 1064 nm reaches values as high as 95%. These two features, combined with the very low mass of the membrane, open the way to the use of such periodic structures as deformable end-mirrors in Fabry-Perot cavities for the investigation of cavity optomechanical effects
Magnetization of two-dimensional superconductors with defects
Kashurnikov, V A; Zyubin, M V
2002-01-01
The new method for modeling the layered high-temperature superconductors magnetization with defects, based on the Monte-Carlo algorithm, is developed. Minimization of the free energy functional of the vortex two-dimensional system made it possible to obtain the equilibrium vortex density configurations and calculate the magnetization of the superconductor with the arbitrary defects distribution in the wide range of temperatures. The magnetic induction profiles and magnetic flux distribution inside the superconductor, proving the applicability of the Bean model, are calculated
The XY Model Coupled to Two-Dimensional Quantum Gravity
Baillie, C F; 10.1016/0370-2693(92)91037-A
2009-01-01
We perform Monte Carlo simulations using the Wolff cluster algorithm of the XY model on both fixed and dynamical phi-cubed graphs (i.e. without and with coupling to two-dimensional quantum gravity). We compare the numerical results with the theoretical expectation that the phase transition remains of KT type when the XY model is coupled to gravity. We also examine whether the universality we discovered in our earlier work on various Potts models with the same value of the central charge, $c$, carries over to the XY model, which has $c=1$.
Smoothed Particle Hydrodynamics Method for Two-dimensional Stefan Problem
Tarwidi, Dede
2016-01-01
Smoothed particle hydrodynamics (SPH) is developed for modelling of melting and solidification. Enthalpy method is used to solve heat conduction equations which involved moving interface between phases. At first, we study the melting of floating ice in the water for two-dimensional system. The ice objects are assumed as solid particles floating in fluid particles. The fluid and solid motion are governed by Navier-Stokes equation and basic rigid dynamics equation, respectively. We also propose a strategy to separate solid particles due to melting and solidification. Numerical results are obtained and plotted for several initial conditions.
A Direct Two-Dimensional Pressure Formulation in Molecular Dynamics
YD, Sumith
2016-01-01
Two-dimensional (2D) pressure field estimation in molecular dynamics (MD) simulations has been done using three-dimensional (3D) pressure field calculations followed by averaging, which is computationally expensive due to 3D convolutions. In this work, we develop a direct 2D pressure field estimation method which is much faster than 3D methods without losing accuracy. The method is validated with MD simulations on two systems: a liquid film and a cylindrical drop of argon suspended in surrounding vapor.
Two-Dimensional Change Detection Methods Remote Sensing Applications
Ilsever, Murat
2012-01-01
Change detection using remotely sensed images has many applications, such as urban monitoring, land-cover change analysis, and disaster management. This work investigates two-dimensional change detection methods. The existing methods in the literature are grouped into four categories: pixel-based, transformation-based, texture analysis-based, and structure-based. In addition to testing existing methods, four new change detection methods are introduced: fuzzy logic-based, shadow detection-based, local feature-based, and bipartite graph matching-based. The latter two methods form the basis for a
Cioffi, Giovanni; Viapiana, Ombretta; Ognibeni, Federica; Dalbeni, Andrea; Giollo, Alessandro; Gatti, Davide; Idolazzi, Luca; Faganello, Giorgio; Di Lenarda, Andrea; Rossini, Maurizio
2017-06-01
Speckle-tracking echocardiography allows early detection of subclinical left ventricular systolic dysfunction (LVSD) in patients with rheumatoid arthritis (RA). In this prospective study, we assessed the prevalence and the prognostic role of subclinical LVSD detected by speckle-tracking echocardiography in RA patients. Two-dimensional global longitudinal strain (GLS) and global circumferential strain (GCS) were measured in 209 RA patients without overt cardiac disease. LVSD was defined as low GLS (> -16.0%), low GCS (> -17.8%), or both. The primary end point was all-causes hospitalization; the coprimary end point was hospitalization for cardiovascular causes. The study population had a mean age of 58 ± 11 years; 67% were female, 52% had hypertension, and the RA duration was 14 ± 10 years. Low GLS was detected in 51 patients (24%), low GCS in 42 patients (20%), and combined low GLS and GCS in 18 patients (9%). During a median follow-up time of 16 months (range, 10-21 months), a primary end point occurred in 50 patients (24%), and 25 patients were hospitalized for a cardiovascular event. Multiple Cox regression analyses revealed that combined low GLS and GCS was independently associated with the end point defined as all-causes hospitalization together with higher aortic stiffness. Examined individually, neither low GCS nor low GLS showed an independent association with this typology of clinical outcome. Conversely, both low GCS and low GLS (examined individually or as combined low GLS and GCS) emerged as strong independent prognosticators of cardiovascular events. Subclinical LVSD defined as low GLS, GCS, or both is common in RA patients without overt cardiac disease and provides additional prognostic information in these individuals. Copyright © 2017 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.
Comparative Skeletal Muscle Proteomics Using Two-Dimensional Gel Electrophoresis.
Murphy, Sandra; Dowling, Paul; Ohlendieck, Kay
2016-09-09
The pioneering work by Patrick H. O'Farrell established two-dimensional gel electrophoresis as one of the most important high-resolution protein separation techniques of modern biochemistry (Journal of Biological Chemistry1975, 250, 4007-4021). The application of two-dimensional gel electrophoresis has played a key role in the systematic identification and detailed characterization of the protein constituents of skeletal muscles. Protein changes during myogenesis, muscle maturation, fibre type specification, physiological muscle adaptations and natural muscle aging were studied in depth by the original O'Farrell method or slightly modified gel electrophoretic techniques. Over the last 40 years, the combined usage of isoelectric focusing in the first dimension and sodium dodecyl sulfate polyacrylamide slab gel electrophoresis in the second dimension has been successfully employed in several hundred published studies on gel-based skeletal muscle biochemistry. This review focuses on normal and physiologically challenged skeletal muscle tissues and outlines key findings from mass spectrometry-based muscle proteomics, which was instrumental in the identification of several thousand individual protein isoforms following gel electrophoretic separation. These muscle-associated protein species belong to the diverse group of regulatory and contractile proteins of the acto-myosin apparatus that forms the sarcomere, cytoskeletal proteins, metabolic enzymes and transporters, signaling proteins, ion-handling proteins, molecular chaperones and extracellular matrix proteins.
Confinement and dynamical regulation in two-dimensional convective turbulence
DEFF Research Database (Denmark)
Bian, N.H.; Garcia, O.E.
2003-01-01
In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low-frequency bur......In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...... to the mean component of the flow. Bursting can also result from the quasi-linear modification of the linear instability drive which is the mean pressure gradient. For each bursting process the relevant zero-dimensional model equations are given. These are finally coupled in a minimal model of convection...
The two dimensional fold test in paleomagnetism using ipython notebook
Setiabudidaya, Dedi; Piper, John D. A.
2016-01-01
One aspect of paleomagnetic analysis prone to controversy is the result of the fold test used to evaluate the age of a magnetisation component relative to the age of a structural event. Initially, the fold test was conducted by comparing the Fisherian precision parameter (k) to results from different limbs of a fold structure before and after tilt adjustment. To accommodate synfolding magnetisation, the tilt correction can be performed in stepwise fashion to both limbs simultaneously, here called one dimensional (1D) fold test. The two dimensional (2D) fold test described in this paper is carried out by applying stepwise tilt adjustment to each limb of the fold separately. The rationale for this is that tilts observed on contrasting limbs of deformed structure may not be synchronous or even belong to the same episode of deformation. A program for the procedure is presented here which generates two dimensional values of the k-parameter visually presented in contoured form. The use of ipython notebook enables this 2D fold test to be performed interactively and yield a more precise evaluation than the primitive 1D fold test.
Quantum creep in a highly crystalline two-dimensional superconductor
Saito, Yu; Kasahara, Yuichi; Ye, Jianting; Iwasa, Yoshihiro; Nojima, Tsutomu
Conventional studies on quantum phase transitions, especially on superconductor-insulator or superconductor-metal-insulator transitions have been performed in deposited metallic thin films such as Bismuth or MoGe. Although the techniques of thin films deposition have been considerably improved, unintentional disorder such as impurities and deficiencies, generating the pinning centers, seems to still exist in such systems. The mechanical exfoliated highly crystalline two-dimensional material can be a good candidate to realize a less-disordered 2D superconductor with extremely weak pinning, combined with transfer method or ionic-liquid gating. We report on the quantum metal, namely, magnetic-field-induced metallic state observed in an ion-gated two-dimensional superconductor based on an ultra-highly crystalline layered band insulator, ZrNCl. We found that the superconducting state is extremely fragile against external magnetic fields; that is, zero resistance state immediately disappears, once an external magnetic field switches on. This is because the present system is relatively clean and the pinning potential is extremely weak, which cause quantum tunneling and flux flow of vortices, resulting in metallic ground state.
Two-dimensional nuclear magnetic resonance of quadrupolar systems
Energy Technology Data Exchange (ETDEWEB)
Wang, Shuanhu
1997-09-17
This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combining the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.
Unpacking of a Crumpled Wire from Two-Dimensional Cavities.
Directory of Open Access Journals (Sweden)
Thiago A Sobral
Full Text Available The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates in the jammed limit a series of closed structures that we call loops. In this work we study the extraction of a crumpled tightly packed wire from a circular cavity aiming to remove loops individually. The size of each removed loop, the maximum value of the force needed to unpack each loop, and the total length of the extracted wire were measured and related to an exponential growth and a mean field model consistent with the literature of crumpled wires. Scaling laws for this process are reported and the relationship between the processes of packing and unpacking of wire is commented upon.
Two-Dimensional Gel Electrophoresis and 2D-DIGE.
Meleady, Paula
2018-01-01
Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) continues to be one of the most versatile and widely used techniques to study the proteome of a biological system. In particular, a modified version of 2D-PAGE, two-dimensional difference gel electrophoresis (2D-DIGE), which uses differential labeling of protein samples with up to three fluorescent tags, offers greater sensitivity and reproducibility over conventional 2D-PAGE gels for differential quantitative analysis of protein expression between experimental groups. Both these methods have distinct advantages in the separation and identification of thousands of individual proteins species including protein isoforms and post-translational modifications. This review will discuss the principles of 2D-PAGE and 2D-DIGE including limitations to the methods. 2D-PAGE and 2D-DIGE continue to be popular methods in bioprocessing-related research (particularly on recombinant Chinese hamster ovary cells), which will also be discussed in the review chapter.
Commensurability oscillations in a two-dimensional lateral superlattice
Davies, John; Long, Andrew; Grant, David; Chowdhury, Suja
2000-03-01
We have calculated and measured conduction in a two-dimensional electron gas subject to a weak two-dimensional periodic potential and a normal magnetic field. Simulations with a potential Vx \\cos(2π x/a) + Vy \\cos(2π y/a) show the usual commensurability oscillations in ρ_xx(B) with Vx alone. The introduction of Vy suppresses these oscillations, rather than introducing the additional oscillations in ρ_yy(B) expected from previous perturbation theories. We explain this in terms of drift of the guiding center of cyclotron motion along contours of an effective potential: open orbits of the guiding center contribute to conduction but closed orbits do not. All orbits are closed in a symmetric superlattice with |V_x| = |V_y| and commensurability oscillations are therefore quenched. Experiments on etched superlattices confirm this picture. Conventional lattice-matched samples give a symmetric potential and weak oscillations; the symmetry is broken by the piezoelectric effect in stressed samples, leading to strong oscillations. Periodic modulation of the magnetic field can be treated in the same way, which explains previous experimental results.
Nonclassical Symmetry Analysis of Heated Two-Dimensional Flow Problems
Naeem, Imran; Naz, Rehana; Khan, Muhammad Danish
2015-12-01
This article analyses the nonclassical symmetries and group invariant solution of boundary layer equations for two-dimensional heated flows. First, we derive the nonclassical symmetry determining equations with the aid of the computer package SADE. We solve these equations directly to obtain nonclassical symmetries. We follow standard procedure of computing nonclassical symmetries and consider two different scenarios, ξ1≠0 and ξ1=0, ξ2≠0. Several nonclassical symmetries are reported for both scenarios. Furthermore, numerous group invariant solutions for nonclassical symmetries are derived. The similarity variables associated with each nonclassical symmetry are computed. The similarity variables reduce the system of partial differential equations (PDEs) to a system of ordinary differential equations (ODEs) in terms of similarity variables. The reduced system of ODEs are solved to obtain group invariant solution for governing boundary layer equations for two-dimensional heated flow problems. We successfully formulate a physical problem of heat transfer analysis for fluid flow over a linearly stretching porous plat and, with suitable boundary conditions, we solve this problem.