Photonic molecules and spectral engineering

This chapter reviews the fundamental optical properties and applications of pho-tonic molecules (PMs) - photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and en-hanced by the manipulation of their mutual coupling. Mechanical and optical tunability of PMs not only adds new functionalities to microcavity-based optical components but also paves the way for their use as testbeds for the exploration of novel physical regimes in atomic physics and quantum optics. Theoretical studies carried on for over a decade yielded novel PM designs that make possible lowering thresholds of semiconductor microlasers, producing directional light emission, achieving optically-induced transparency, and enhancing sensitivity of microcavity-based bio-, stress- and rotation-sensors. Recent advances in material science and nano-fabrication techniques make possible the realization of optimally-tuned PMs for cavity quantum electrodynamic experiments, classical and quantum information processing, and sensing.Comment: A review book chapter: 29 pages, 19 figure

Single molecule detection from a large-scale SERS-active Au79Ag21 substrate

Detecting and identifying single molecules are the ultimate goal of analytic sensitivity. Single molecule detection by surface-enhanced Raman scattering (SM-SERS) depends predominantly on SERS-active metal substrates that are usually colloidal silver fractal clusters. However, the high chemical reactivity of silver and the low reproducibility of its complicated synthesis with fractal clusters have been serious obstacles to practical applications of SERS, particularly for probing single biomolecules in extensive physiological environments. Here we report a large-scale, free standing and chemically stable SERS substrate for both resonant and nonresonant single molecule detection. Our robust substrate is made from wrinkled nanoporous Au79Ag21 films that contain a high number of electromagnetic “hot spots” with a local SERS enhancement larger than 109. This biocompatible gold-based SERS substrate with superior reproducibility, excellent chemical stability and facile synthesis promises to be an ideal candidate for a wide range of applications in life science and environment protection

Ab initio calculations of optical properties of silver clusters: cross-over from molecular to nanoscale behavior

Electronic and optical properties of silver clusters were calculated using two different \textit{ab initio} approaches: 1) based on all-electron full-potential linearized-augmented plane-wave method and 2) local basis function pseudopotential approach. Agreement is found between the two methods for small and intermediate sized clusters for which the former method is limited due to its all-electron formulation. The latter, due to non-periodic boundary conditions, is the more natural approach to simulate small clusters. The effect of cluster size is then explored using the local basis function approach. We find that as the cluster size increases, the electronic structure undergoes a transition from molecular behavior to nanoparticle behavior at a cluster size of 140 atoms (diameter $\sim 1.7$\,nm). Above this cluster size the step-like electronic structure, evident as several features in the imaginary part of the polarizability of all clusters smaller than Ag$_\mathrm{147}$, gives way to a dominant plasmon peak localized at wavelengths 350\,nm$\le\lambda\le$ 600\,nm. It is, thus, at this length-scale that the conduction electrons' collective oscillations that are responsible for plasmonic resonances begin to dominate the opto-electronic properties of silver nanoclusters

Results of the clinical evaluation of the low-dose protocols of the digital linear tomography of the chest

High levels of tuberculosis morbidity in the Russian Federation lead to the extensive use of X-ray diagnostics for the tuberculosis screening and assessment of the effectiveness of treatment. Digital radiography and computed tomography are traditionally used for the diagnostics of tuberculosis. These methods are associated with significant drawbacks: low specificity for radiography, high costs per examination, significant patient doses, and limited availability for computed tomography. As an additional method for the assessment of the effectiveness of the tuberculosis treatment it is possible to use linear tomography performed on the digital X-ray units. The aim of the current study was to evaluate the possibility of utilization of the digital linear tomography for the control of the effectiveness of tuberculosis treatment in a dedicated antitubercular medical facility. The study was divided in two stages. The first stage was aimed at the assessment of the diagnostic image quality of the digital linear tomograms obtained using the previously developed low-dose imaging protocols. Image quality assessment was performed using an anthropomorphic chest phantom and dedicated imitators of the lung lesions. Image quality was assessed by the experts (radiologists) based on the developed image quality criteria. Results of the first stage of the study indicate that all low-dose protocols allow obtaining images with at least acceptable image quality. Hence it was possible to propose low-dose protocols for clinical evaluations. The second stage of the study was performed as a prospective cohort survey aimed at the evaluation of the structure of X-ray examinations, patient doses and clinical image quality of the digital linear tomograms in antitubercular early treatment center. The cohort survey included two patient samples, uniform by age and gender composition, anthropometric characteristics and structure of diagnosis. One of the samples was imaged using standard (vendor) digital linear protocols, other – using the proposed low-dose protocols. Dose data collection (measurement of dose-area product and subsequent calculation of effective dose) and expert image quality assessment was performed for each patient. The results of the second stage of the study indicate that the use of the low-dose protocols allow reducing the patient effective doses per examination up to a factor of 6–8 (0.56 – 5.9 mSv for standard protocols; 0.2 – 1.15 mSv for low-dose protocols) due to the reduction in tube current-time product (126 mean mAs and 11 mean mAs, respectively). The dose reduction is accompanied by the reduction in the image quality of the linear tomograms (from “excellent” or “good” for standard protocols to “acceptable” for low-dose protocols). However, that dose not hinder the conclusion decision and identification of pathologies. Results of the study indicate that digital linear tomography can be used for the evaluation of the dynamics of the pathological process in the lungs with the previously defined localization of the pathology. The presented low-dose protocols were implemented into radiological practice of the antitubercular early treatment center. Currently, the proposed low-dose protocols are under evaluation for the large-scale study on the base of general practice hospital

Comparion of two techniques crosslinking for progressive keratectasia

Purpose: to compare surgical approaches, features of the postoperative period and functional results of conventional and opti- mized crosslinking techniques.Methods: We followed 2 groups of patients (10 patients, 10 eyes each), treated in Volgograd branch of the S.N. Fyodorov Eye Microsurgery Clinic for kerotoconus of the II-III degree according to the conventional method (I group) and the optimized technique (II group). the optimized technique consisted of the customized excimer laser corneal deepitalization to the depth of 2/3 of the epithelial layer. Excimer laser ablation with intraoperative «on-line» pachymetry was made by means of Schwind Amaris-500 Hz (Schwind, Germany).Results: Method of the optimized crosslinking with a customized depth of excimer laser ablation required a longer period for satu- ration of the cornea with solution of riboflavin (mean 5-10 minutes). However, it was accompanied with a less severe corneal syndrome, a complete reepithelization and an earlier postoperative recovery of visual functions. Six months postoperatively a 1-2-line improve- ment of BCVA and UCVA was achieved in 19 patients (19 eyes). Decrease of cylindrical component averaged 1.2 D in the group I and 1 D in the group II. Mean refraction change in SE was 2.2 D in the group I and 2.0 D in the group II. Six months postoperatively one patient from the group II had a 1-line regression of BCVA in comparison to the preoperative level accompanied with a 10 μm corneal thinning and corneal curvature steepening by 2 D at the top of keratoconus, which was regarded as an aggravation of initial state.Conclusion: Both approaches have proved their safety and effectiveness. However, incurrence of the above-mentioned case of state deterioration calls for the further comparative studies in order to evaluate clinical effectiveness of these methods

Efficacy of intravitreal injection of Lucentis in the treatment of diffuse diabetic macular edema associated with pan-retinal photocoagulation in proliferative diabetic retinopathy

Purpose. To evaluate the efficacy of intravitreal injection of Lucentis in the treatment of diffuse diabetic macular edema (DME) associated with pan-retinal photocoagulation in the proliferative diabetic retinopathy (DR).Material and methods. A retrospective study (58 eyes) with a high diffuse DME and proliferative DR was performed in 46 patients with insulin-dependent diabetes mellitus aged 45-73 years (mean age: 59.2±0.9 years). All participants underwent i ntravitreal injection (IVI) of Lucentis pars plana. The pan-retinal photocoagulation (PRPC) stage was performed 2 weeks after each Lucentis IVI. The main criteria were the dynamics of best corrected visual acuity (BCVA), the OCT parameters – in the central retinal thickness (1mm) area and volume of the macula. The treatment efficacy was assessed one month after the final PRPC stage.Results and discussion. At the end of treatment an increase in the average BCVA values from 0.32 to 0.45, a decrease in retinal thickness in fovea zone – from 506.9mm to 394.6mm, in the volume of macula from 12.9 to 11.6mm3 were noted. Stabilization or an increase in initial visual acuity was observed in 83.4%. The initial thickness of the retina in the region of 1mm was reduced from 506.9mm to 394.6mm, i.e. decreased by an average of 22%. The stabilization of visual functions was achieved more than in 80% of cases one month after the combi ned treatment.Conclusions. The performed retrospective study showed an efficacy of intravitreal injection of Lucentis to stabilize visual functions, to reduce the height of macular edema during the pan-retinal photocoagulation in patients with proliferative diabetic retinopathy

Результаты клинической апробации низкодозовых протоколов проведения цифровой линейной томографии органов грудной клетки

High levels of tuberculosis morbidity in the Russian Federation lead to the extensive use of X-ray diagnostics for the tuberculosis screening and assessment of the effectiveness of treatment. Digital radiography and computed tomography are traditionally used for the diagnostics of tuberculosis. These methods are associated with significant drawbacks: low specificity for radiography, high costs per examination, significant patient doses, and limited availability for computed tomography. As an additional method for the assessment of the effectiveness of the tuberculosis treatment it is possible to use linear tomography performed on the digital X-ray units. The aim of the current study was to evaluate the possibility of utilization of the digital linear tomography for the control of the effectiveness of tuberculosis treatment in a dedicated antitubercular medical facility. The study was divided in two stages. The first stage was aimed at the assessment of the diagnostic image quality of the digital linear tomograms obtained using the previously developed low-dose imaging protocols. Image quality assessment was performed using an anthropomorphic chest phantom and dedicated imitators of the lung lesions. Image quality was assessed by the experts (radiologists) based on the developed image quality criteria. Results of the first stage of the study indicate that all low-dose protocols allow obtaining images with at least acceptable image quality. Hence it was possible to propose low-dose protocols for clinical evaluations. The second stage of the study was performed as a prospective cohort survey aimed at the evaluation of the structure of X-ray examinations, patient doses and clinical image quality of the digital linear tomograms in antitubercular early treatment center. The cohort survey included two patient samples, uniform by age and gender composition, anthropometric characteristics and structure of diagnosis. One of the samples was imaged using standard (vendor) digital linear protocols, other – using the proposed low-dose protocols. Dose data collection (measurement of dose-area product and subsequent calculation of effective dose) and expert image quality assessment was performed for each patient. The results of the second stage of the study indicate that the use of the low-dose protocols allow reducing the patient effective doses per examination up to a factor of 6–8 (0.56 – 5.9 mSv for standard protocols; 0.2 – 1.15 mSv for low-dose protocols) due to the reduction in tube current-time product (126 mean mAs and 11 mean mAs, respectively). The dose reduction is accompanied by the reduction in the image quality of the linear tomograms (from “excellent” or “good” for standard protocols to “acceptable” for low-dose protocols). However, that dose not hinder the conclusion decision and identification of pathologies. Results of the study indicate that digital linear tomography can be used for the evaluation of the dynamics of the pathological process in the lungs with the previously defined localization of the pathology. The presented low-dose protocols were implemented into radiological practice of the antitubercular early treatment center. Currently, the proposed low-dose protocols are under evaluation for the large-scale study on the base of general practice hospitalsВысокий уровень заболеваемости туберкулезом в Российской Федерации обусловливает широкое применение рентгеновских методов для его диагностики и оценки эффективности проводимого лечения. Традиционно для диагностики туберкулеза используются цифровая рентгенография и компьютерная томография. Оба данных метода обладают своими недостатками: низкая специфичность у рентгенографии; высокая стоимость, значительные дозы облучения пациентов и ограниченная доступность у компьютерной томографии. В качестве дополнительного метода для оценки эффективности лечения туберкулеза была предложена линейная томография, выполняемая на цифровых рентгеновских аппаратах. Целью данного исследования являлась оценка возможности использования цифровой линейной томографии для контроля эффективности лечения туберкулеза в рамках специализированного противотуберкулезного учреждения. Исследование было разделено на два этапа. В рамках первого этапа была выполнена оценка диагностического качества цифровых линейных томограмм, выполненных на перспективных низкодозовых протоколах. Данный этап был выполнен с использованием антропоморфного фантома грудной клетки и разработанных имитаторов легочных очагов. Качество изображения оценивалось экспертами по специально разработанным критериям. Было показано, что на всех низкодозовых протоколах обеспечивается как минимум удовлетворительное качество изображения, что позволило использовать низкодозовые протоколы для клинической апробации на базе противотуберкулезного диспансера. На втором этапе исследования были оценены структура исследований, дозы облучения пациентов и качество линейных томограмм в рамках проспективного когортного исследования. Были отобраны две выборки пациентов, однородные по половозрастному составу, антропометрическим характеристикам и структуре диагнозов. Одна из выборок была диагностирована с использованием стандартных протоколов линейной томографии; вторая – с использованием предложенных никодозовых протоколов. Для каждого пациента были определены дозы за одну линейную томограмму и за все исследование (измерено произведение дозы на площадь, рассчитана эффективная доза); выполнена экспертная оценка качества томограмм. Результаты второго этапа исследования показали, что переход на низкодозовые протоколы позволяет снизить эффективные дозы пациентов за все исследование вплоть до 6–8 раз (0,56–5,9 мЗв на стандартных протоколах; 0,2–1,15 мЗв на низкодозовых протоколах), что главным образом обусловливается использованием низких значений экспозиции (126 мАс и 11 мАс соответственно). При этом достоверно снижается диагностическое качество полученных томограмм (с хорошего/отличного до удовлетворительного), что не сказывается на возможности их описания и выявлении патологий. Результаты исследования показали, что цифровую линейную томографию можно применять для оценки динамики патологического процесса в легких в том случае, когда локализация патологии уже известна. Представленные низкодозовые протоколы внедрены в практику противотуберкулезного диспансера. В настоящее время рассматривается возможность проведения более крупномасштабного исследования на базе нескольких медицинских организаций, в том числе многопрофильных стационаров