Time delayed electroluminescence overshoot in single layer polymer light-emitting diodes due to electrode luminescence quenching

Journal ArticleWe investigate the transient response of single layer polymer light-emitting diodes (LEDs) based on poly[2-methoxy, 5-(2'ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). An electroluminescence overshoot is observed between 1 and 2 μs after turning off the voltage pulse, depending on temperature. We attribute the delay between overshoot and voltage turnoff to detrapping of majority charge carriers at the polymer/cathode interface. Due to the luminescence quenching zone of the metal the luminescence is found to decrease rapidly after the voltage is switched off, but then rise again to up to a third of the steady state value. The overshoot is found to be independent of the applied bias, but is strongly influenced by temperature and pulse length, indicating a trapping process in interfacial traps is responsible for the effect. The overshoot area corresponds to the charge located on interfacial traps near the cathode and scales as a power law with the pulse length. Our findings demonstrate the presence of extrinsic traps in MEH-PPV devices and highlight the importance of distinguishing between the effects of extrinsic and intrinsic traps in polymer LEDs. Spatial correlations of electrons and holes due to their mutual Coulombic field also appear to be important

Recombination kinetics in wide gap electroluminescent conjugated polymers with on-chain emissive defects

Journal ArticleWe analyze the experimental dependence of temporally and spectrally resolved electroluminescence (EL) from polyfluorene-based light-emitting diodes on electric field and temperature. The blue band in the EL spectrum is caused by emission from the polymer backbone, while the low-energy green emission results from on-chain keto defects, which act as traps for electrons. Although the time and temperature dependencies of the blue and green emission could be explained by the kinetics of redistribution of trapped holes and electrons in energy and space, the increase of the blue-to-green delayed emission ratio with increasing field strength appears to result from a difference in the nature of recombination. We propose that the formation of blue-emitting singlet excitons from close electron-hole pairs after turn-off is impeded by an energy barrier, in contrast to the formation of green-emitting excitons

The role of sentinel lymph nodes in breast cancer

Introduction. The problem of improving early diagnosis and prognosis of breast cancer remains one of the most actual for current oncological practice. Taking into account a close correlation between the general prevalence of breast neoplasms and mortality from breast cancer, this problem is not only of professional interest, but also has medical-social and socio-economic significance. The purpose of the study is to improve the quality of the sentinel lymph node detection in patients with breast cancer using ICG. Material and methods. At the period 2009–2016, 400 patients with T1-T3N0M0 breast cancer were operated on. All the patients were divided into two groups using two dyes – Patent Blue and ICG. The patients after mastectomy with a sentinel lymph node biopsy had a clinical diagnosis of T2-T3N0M0 breast cancer more often. In group I, 100 patients had the sentinel lymph node biopsy. Lymph node staining was performed using Patent Blue dye. In group II, sentinel lymph nodes biopsy was conducted with the Patent Blue dye and another fluorescent dye — ICG, which was also injected on the affected side of the breast. After ICG dye introduction, in 15 minutes the stained green lymph nodes were detected using special equipment. Criteria for inclusion of patients in the clinical trial: 1) breast cancer patients of any age with T1-3N0M0, I-II AB disease stage; 2) patients with clinically unaffected lymph nodes N0 after examination. Criteria for exclusion of patients from the clinical trial: The exceptions were T3-T4 tumors > 5 cm in diameter, or the skin and chest wall invasion, as well as palpable axillary lymph nodes, 3 or more affected lymph nodes with sentinel lymph node biopsy; 3) patients after radiation therapy. Results. The tumor histology was performed after the node trephine biopsy. The main aims of sentinel nodes detection were staging and improving the breast cancer patients’ life quality after surgical treatment. The post-mastectomy syndrome, the main manifestation of which is swelling of the upper extremity is a big problem for patients because it affects their life quality and disturbs their usual lifestyle. The sentinel lymph node detection, in contrast to axillary lymph node dissection of I-II level, significantly minimizes all the risks of postmastectomy syndrome, in particular, impaired lymphatic drainage in the form of lymphatic edema of the upper extremity, impaired venous outflow in the form of stenoses or the axillary and/or subclavian veins occlusion, rough scars which limit the function of the extremity in the shoulder joint, and brachioplexitis. Conclusions. The study of sentinel lymph nodes significantly improves the results of surgical treatment of breast cancer patients. Based on the clinical-laboratory and histological examinations, new data were obtained concerning the sentinel lymph node detection using two dyes, the choice of the surgical intervention volume and reduction of complications rate at the postoperative period. We found that fluorescent lymphography is highly effective, which allows to recommend it for implementation into the clinical practice. The frequency of sentinel lymph node detection in breast cancer patients is 98% in the control group, 100% – in the main group. On the basis of the obtained results, the sentinel lymph node detection algorithm and the surgical management of patients with breast cancer was developed and implemented into practice, which allowed to reduce the number of complications with using two dyes for the sentinel lymph node detection from 19% to 2% (χ2 =15.37, p<0.001). Recurrence of breast cancer fell from 13% to 8%

Summary of the CMS Discovery Potential for the MSSM SUSY Higgses

This work summarises the present understanding of the expected MSSM SUSY Higgs reach for CMS. Many of the studies presented here result from detailed detector simulations incorporating final CMS detector design and response. With 30 fb-1 the h -> gamma,gamma and h -> bb channels allow to cover most of the MSSM parameter space. For the massive A,H,H+ MSSM Higgs states the channels A,H -> tau,tau and H+ -> tau,nu turn out to be the most profitable ones in terms of mass reach and parameter space coverage. Consequently CMS has made a big effort to trigger efficiently on taus. Provided neutralinos and sleptons are not too heavy, there is an interesting complementarity in the reaches for A,H -> tau,tau and A,H -> chi,chi.Comment: 19 pages, 27 figure

The guard lymph nodes when choosing tactics of operational treatment of colorectal cancer

In this article, we analyzed the studies, that were conducted over the past 10 years to study the role of the "guard lymph node" in colorectal cancer. Researches were studied prospectively as well as retrospectively, in which "guard lymph nodes" were defined and was studied the lesion of lymph nodes 1, 2 and 3 orders. The purpose of this work is to evaluate and compare the results of operations used in collorectal cancer. Results and conclusions are presented on the basis of developed and developing countries

Antisymmetric magnetoresistance in magnetic multilayers with perpendicular anisotropy

While magnetoresistance (MR) has generally been found to be symmetric in applied field in non-magnetic or magnetic metals, we have observed antisymmetric MR in Co/Pt multilayers. Simultaneous domain imaging and transport measurements show that the antisymmetric MR is due to the appearance of domain walls that run perpendicular to both the magnetization and the current, a geometry existing only in materials with perpendicular magnetic anisotropy. As a result, the extraordinary Hall effect (EHE) gives rise to circulating currents in the vicinity of the domain walls that contributes to the MR. The antisymmetric MR and EHE have been quantitatively accounted for by a theoretical model.Comment: 17 pages, 4 figure

Possibilities of performance of nonstandard operative interventions in patients, suffering early gastric cancer

Objective. To study a possibility of performance of nonstandard organ-preserving operations in patients, suffering early gastric cancer, using application of the sentinel lymph nodes visualization procedures and the lymph node dissection procedure. Materials and methods. There were performed operative interventions in 35 patients, suffering early gastric cancer (Stages T1 and T2). For identification of sentinel lymph nodes a procedure of luminescence, using green indocyan, was applied. Results.  In all the patients early gastric cancer was diagnosed (T1,T2). Possibility for performance of organ-preserving operations in early gastric cancer was shown. Miniinvasive interventions in a patient with severe concurrent diseases have appeared sufficiently effective and radical. The patients’ quality of life after laparoscopic pylorus-preserving and organ-preserving operations was significantly better, than quality of life in patients, to whom gastric resection with extended D2 lymph node dissection was done. Conclusion. There was established, that intraoperative lymphography constitutes he informative method, which helps to estimate the disease Stage in gastric cancer and to apply the adequate scheme of combined and complex treatment. More sensitive is a procedure of luminescence, using green indocyan. Determination of the affection degree of «sentinel lymph nodes» in gastric cancer may serve as an argument for change of the selection tactics while changing the tactics for the operative intervention volume choice

Unusual Magnetization Reversal in [Co/Pt]\u3csub\u3e4\u3c/sub\u3e Multilayers with Perpendicular Anisotropy

Unusual magnetization reversal of [Co(4 Å)/Pt(10 Å)]4 multilayers with perpendicular magnetic anisotropy has been revealed macroscopically by magnetometry measurements and microscopically by magneto-optical Kerr effect microscopy and magnetic force microscopy (MFM) imaging. During the first-order reversal process, the magnetization first decreases, then reaches a plateau, and finally rises back to saturation, corresponding to expanding bubble domains, stationary domains, and fading contrast but unchanged boundary domains, respectively. MFM imaging reveals the existence of many submicron-scaled unreversed channels within the boundary of the “bubble” domains. The magnetization reversal behavior can be accounted for by the evolution of the unusual domain structures in different field regimes