Sub-Wavelength Terahertz Spin-Flip Laser Based on a Magnetic Point-Contact Array

We present a novel design for a single-mode, truly sub-wavelength THz disk laser based on a nano-composite gain medium comprising an array of metal/ferromagnetic point contacts embedded in a thin dielectric layer. Stimulated emission of light occurs in the point contacts as a result of spin-flip relaxation of spin-polarized electrons that are injected from the ferromagnetic side of the contacts. Ultra-high electrical current densities in the contacts and a dielectric material with a large refractive index, neither condition being achievable in conventional semiconductor media, allows the thresholds of lasing to be overcome for the lowest-order modes of the disk, hence making single-mode operation possible.Comment: 9 pages,4 figure

Mechanical Stimuli in Prediction of Trabecular Bone Adaptation: Numerical Comparison

Adaptation is the process, with which bone responds to changes in loading environment and modifies its properties and organisation to meet the mechanical demands. Trabecular bone undergoes significant adaptation when subjected to external forces, accomplished through resorption of old and fractured bone and formation of a new bone material. These processes are assumed to be driven by mechanical stimuli of bone-matrix deformation sensed by bone mechanosensory cells. Although numerous in vivo and in vitro experimental evidence of trabecular bone morphology adaptation was obtained, the exact nature of mechanical stimuli triggering biological responses (i.e., osteoclastic resorption and osteoblastic formation) is still debated. This study aims to compare different mechanical stimuli with regard to their ability to initiate the load-induced adaptation in trabecular bone. For this purpose, a 2D model of two trabeculae, connected at their basement, with bone marrow in the intertrabecular space was developed. The finite-element method was implemented for the model loaded in compression to calculate magnitudes of several candidates of the bone-adaptation stimuli. A user material subroutine was developed to relate a magnitude of each candidate to changes in the shape of trabeculae

Coupling of whispering-gallery modes in size-mismatched microdisk photonic molecules

Mechanisms of whispering-gallery (WG) modes coupling in microdisk photonic molecules (PMs) with slight and significant size mismatch are numerically investigated. The results reveal two different scenarios of modes interaction depending on the degree of this mismatch and offer new insight into how PM parameters can be tuned to control and modify WG-modes wavelengths and Q-factors. From a practical point of view, these findings offer a way to fabricate PM microlaser structures that exhibit low thresholds and directional emission, and at the same time are more tolerant to fabrication errors than previously explored coupled-cavity structures composed of identical microresonators.Comment: 3 pages with 5 figures (to appear in Opt. Lett. 2007

Efficiency of investment projects and energy security of economic development

Existing methods for assessing the efficiency of energy saving projects in housing and utility services are often of a local nature, which does not contribute to ensuring energy security. A methodology for the economic justification of the demand for energy carriers at affordable prices in the domestic and foreign markets is needed. The authors propose to solve the problem of rational use of fuel and energy resources in the system of three industries: capital construction, housing and utility services, and fuel and energy complex as interrelated sectors of the economy and economic turnover of fuel and energy resources

Band splitting and Modal Dispersion induced by Symmetry braking in Coupled-Resonator Slow-Light Waveguide Structures

We study the dispersion relations in slow-light waveguide structures consisting of coupled microdisk resonators. A group theoretical analysis of the symmetry properties of the propagating modes reveals an interesting phenomenon: The degeneracy of the CW and CCW rotating modes is removed, giving rise to two distinct transmission bands. This effect induces symmetry-based dispersion which may limit usable bandwidth of such structures. The properties of this band splitting and its impact on CROW performance for optical communications are studied in detail

Microcavity lasers on polymer materials: Boundary integral equation modeling and experiments

We consider the modeling and experiments with polymer dye-doped lasers shaped as thin flat cavities, allowing one to consider them as two-dimensional (2-D) active cavities. We focus our modeling on the H-polarized electromagnetic field in a kite-shaped laser. Assuming that the lasing-mode frequency is real-valued, we look for it together with the corresponding threshold value of material gain. Such electromagnetic-field problem is reduced to the Muller set of the boundary integral equations (MBIE), discretization of which yields determinantal equation. Numerical results reveal various types of modes existing in the kite including the perturbed whispering gallery (WG) modes that have the lowest thresholds. Their far-field emission patterns show good agreement with the measurements. © 2015 IEEE

Parity-time symmetric coupled microresonators with a dispersive gain/loss

The paper reports on the coupling of Parity-Time (PT)-symmetric whispering gallery resonators with realistic material and gain/loss models. Response of the PT system is analyzed for the case of low and high material and gain dispersion, and also for two practical scenarios when the pump frequency is not aligned with the resonant frequency of the desired whispering gallery mode and when there is imbalance in the gain/loss profile. The results show that the presence of dispersion and frequency misalignment causes skewness in frequency bifurcation and significant reduction of the PT breaking point, respectively. Finally, we demonstrate a lasing mode operation which occurs due to an early PT-breaking by increasing loss in a PT system with unbalanced gain and loss

Pharmaceutical faculty students’ attitude to drinking water consumption

The article deals with the actual issue of commitment of medical university students to healthy lifestyle in terms of attitude to water consumption. A sociological survey of 123 pharmaceutical faculty students and data processing by methods of descriptive and nonparametric statistics were conducted. 90,2% of respondents use water as a drink (on average about 1,47±0,06 liters per day). The main reason for drinking water is to satisfy the physiological need for water, a sense of thirst (80,5%). 95,1% of respondents agree that drinking water affects person's health. It is possible to draw a conclusion about the rational behavior of pharmaceutical faculty students regarding to drinking water consumption.В статье рассматривается актуальный вопрос приверженности студентов медицинского университета к здоровому образу жизни в части отношения к употреблению воды. Проведен социологический опрос 123 студентов фармацевтического факультета и обработка данных методами описательной и непараметрической статистики. 90,2% опрошенных употребляют воду как напиток (в среднем около 1,47±0,06 литра в течение дня). Основной причиной употребления воды является удовлетворение физиологической потребности в воде, чувства жажды (80,5%). 95,1% респондентов согласны, что употребление воды влияет на состояние здоровья человека. Можно сделать вывод о рациональном поведении студентов фармацевтического факультета в отношении употребления питьевой воды

The Synthesis of Activated Manganese Dioxide From Recycled Chemical Power Sources

Стаття присвячена проблемі поводження з відпрацьованими побутовими джерелами електричного струму. Запропонована лабораторна методика виділення діоксиду мангану з відпрацьованих манган-цинкових хімічних джерел струму з лужним електролітом шляхом електрохімічного синтезу активованого діоксиду мангану.The article deals with the problem of handling waste household power sources. The laboratory method of the extraction of the manganese dioxide from the manganese-zinc waste of the chemical power sources by the electrochemical synthesis with an alkaline electrolyte is proposed