Effect of disorder on the far-infrared conductivity and on the microwave conductivity of two-band superconductors

We consider the far-infrared and the microwave conductivities of a two-band superconductor with non-magnetic impurities. The strong coupling expressions for the frequency and temperature dependent conductivity of a two-band superconductor are developed assuming isotropic bands and interactions. Our numerical results obtained using realistic interaction parameters for MgB$_{2}$ are compared with experiments on this compound. We find that the available experimental results for the far-infrared conductivity of MgB$_{2}$ are consistent with multi-band superconductivity in the presence of a sufficiently strong interband impurity scattering. On the other hand, our numerical results for the microwave conductivity in the superconducting state indicate that the experimental results obtained on samples with the highest transition temperature $T_{c}$ are consistent with a low interband impurity scattering rate but depend sensitively on the ratio of the total scattering rates in the two bands. For the $\pi$-band scattering rate $\gamma_{\pi}$ not greater than the $\sigma$-band scattering rate $\gamma_{\sigma}$ there is a single, broad, low-temperature (at about 0.5$T_{c}$) coherence peak in the microwave conductivity. For $\gamma_{\pi}/\gamma_{\sigma}$=4--7 a high-temperature (at about 0.9$T_{c}$) coherence peak is dominant, but there is also a low-temperature peak/shoulder resulting from the contribution of the $\pi$-band carriers to the microwave conductivity. For $\gamma_{\pi}/\gamma_{\sigma}\gg$1 only the high-temperature coherence peak should be observable.Comment: 11 pages, 6 figure

Mathematical model of energy efficiency in internal spur gears

The impact of geometric parameters of teeth and lubricating oils to the efficiency of involute internal spur gears, when the transverse contact ratio is 2 lt epsilon(alpha) lt = 3, has been analyzed in this paper. The mathematical model and computer program for determining the current and the effective value of the efficiency have been developed. The influence of the character of load distribution and energy losses due to heating effects during the meshing period is included in the factor of load distribution. The results of computer simulation are given in the form of a diagram of the current values of the efficiency during the meshing period. Also, the values of effective efficiency for the considered cylindrical gear pairs have been calculated

Mathematical model of energy efficiency in internal spur gears

The impact of geometric parameters of teeth and lubricating oils to the efficiency of involute internal spur gears, when the transverse contact ratio is 2 lt epsilon(alpha) lt = 3, has been analyzed in this paper. The mathematical model and computer program for determining the current and the effective value of the efficiency have been developed. The influence of the character of load distribution and energy losses due to heating effects during the meshing period is included in the factor of load distribution. The results of computer simulation are given in the form of a diagram of the current values of the efficiency during the meshing period. Also, the values of effective efficiency for the considered cylindrical gear pairs have been calculated

Efficiency analysis of planetary gears

By kinematic combinations of toothed pairs with external and internal contacts, we can obtain planetary gears with a considerably improved performance than the corresponding ones with fixed axes, as well as planetary gears with notably poor performance regarding the efficiency. In regard to that, the reference literature and papers almost regularly emphasize that planetary gears, under the same technical conditions, have a smaller mass and a higher degree of efficiency than the ones with fixed axes. The main aim of this paper is to examine the above statement and to determine the scope of the gear ratios in which the planetary gears are more suitable than the fixed axes gears

Endometrioza ravnog trbušnog mišića poslije carskog reza - prikaz slučaja

Endometriosis is defined by the presence of functional endometrial tissue outside the uterus, where it is normally located. Endometriosis is one of the most common gynecologic entities affecting 8%-18% of menstrual women. Endometriosis can occur at intra-and extrapelvic localizations. The most common intrapelvic localizations are those involving the ovaries, Douglas\u27 area, pelvic peritoneum, uterus, bladder and rectum. Abdominal endometriosis is the most common localization of extrapelvic endometriosis and usually develops in connective tissue. Extra-pelvic implantation of endometrial tissue may develop in any organ including the skin, lungs, liver, extremities, brain and stomach. Three years after cesarean section, a 35-year-old female was operated on for suspected anterior abdominal hernia at the site of previous section. An egg-sized tumor was removed from the rectus abdominis muscle and referred for histopathologic and immunohistochemical analyses. The results showed endometriosis of the muscle with positive estrogen and progesterone receptors. A year after the procedure, treatment with gonadotropin-releasing hormone analogs was continued due to recurrent pain in the scar area, along with ultrasonography and biochemical marker (carbohydrate antigen 125) follow-up. Clinical diagnosis of scar endometriosis can be made by thorough history and physical, ultrasonography and biochemical examinations. Scar endometriosis should always be considered when the symptoms occur in a cyclic and hormone-dependent pattern, mostly after gynecologic operations, and worsening during menstruation. Definitive diagnosis is based on histopathologic analysis.Endometrioza se definira prisustvom funkcionalnih endometrijalnih žlijezda i strome izvan šupljine maternice, gdje je njihova normalna lokalizacija. Endometrioza je jedan od najčešćih ginekoloških entiteta, prisutna kod 8%-18% menstrualnih žena. Endometrioza može biti intra-i ekstrapelvične lokalizacije. Najčešći slučajevi su intrapelvične lokalizacije koje zahvaćaju ovarijume, zatim Douglasov prostor, pelvični peritoneum, veze maternice, mokraćni mjehur, rektum. Abdominalna endometrioza je najčešća lokalizacija ekstrapelvične endometrioze i obično se razvija na vezivnom tkivu. Ekstrapelvična implantacija endometrijalnog tkiva može biti na bilo kom organu u organizmu uključujući i kožu, epiziotomiju, pluća, jetru, ekstremitete, mozak i trbušni zid. Pacijentica stara 35 godina tri godine poslije carskog reza operirana je zbog pretpostavke da se radi o kili prednjeg trbušnog zida, na mjestu prethodnog reza, kada je odstranjen tumor veličine jajeta na ravnom trbušnom mišiću. Histopatološka i imunohistokemijska analiza tumora pokazala je da se radi o endometriozi dotičnog mišića sa pozitivnim estrogenskim i progesteronskim receptorima. Godinu dana poslije procedure pojavila se bol u predjelu ožiljka, bolesnica je stalno liječena analogom hormona za otpuštanje gonadotropina, uz serijsku kontrolu ultrazvuka i biokemijskog markera, CA 125. Klinička dijagnoza ožiljne endometrioze može se postaviti pažljivom anamnezom i fizikalnim pregledom, ultrasonografskim i biokemijskim ispitivanjem. Na ožiljnu endometriozu treba misliti uvijek kada se simptomi javljaju ciklično, u zavisnosti od hormona, najčešće poslije ginekoloških operacija, a koji se pogoršavaju tijekom menstruacije. Prava dijagnoza postavlja se histopatološkom analizom

Typified machine parts series load capacity analysis from aspect of structural strength

Application of typization in the process of designing mechanical sub-assemblies and assemblies is one of the ways to reduce the cost of production. Therefore, nowadays, not only roller bearings, bolts, wedges, etc. are produced as standard machine elements but, by the usage of typization, a production of a large series of typified subassemblies and assemblies, such as electric motors, pumps, power transmissions, etc., is increasing. Increased application of typified parts, sub-assemblies and assemblies in mechanical systems requires an increase in their safety and reliability during operation. Accordingly, in this paper, the load capacity of the typified machine parts series from the aspect of their structural strength is analyzed. It has been shown that there is a scattering of calculated results of the safety factor of members of the typified series from the aspect of the structural strength. The paper presents a proposal for a calculation methodology by which the mentioned scattering of the results of load capacity of typified machine parts series can be significantly reduced

Solving the Problem of Friction and Wear in Auxiliary Devices of Internal Combustion Engines on the Example of Reciprocating Air Compressor for Vehicles

Using vehicles and other mobile systems to transport passengers and goods, approximately 25% of Europe\u27s greenhouse gases are generated. At the same time, many research papers, published by researchers and students, promote the use of electric vehicles as zero-emission vehicles. Given that, more broadly, the emission of electric vehicles is higher, especially in countries where electricity is obtained by burning coal, the use of internal-combustion engines is still dominant. There are other reasons for using an internal-combustion engine, such as already developed pumping station infrastructure, which is not the case when recharging electric vehicles. Improvements in engine design contribute to meet the regulations relating to the fuel consumption and toxic gas emissions. This refers to the use of alternative fuels, improving the combustion process, and increasing efficiency (efficiency coefficient) by reducing losses. The research is focused on the problem of friction and wear in internal combustion engines and reciprocating air compressors, as auxiliary devices on engines. For that purpose, construction of the reciprocating air compressor in motor vehicles was redesigned. The paper presents the characteristic test results of material used to strengthen liner of the aluminum cylinder. Specifically, a method for testing the performance characteristics of a single-cylinder reciprocating compressor inside of an experimental installation for compressed air supply has also been proposed

On the correct formula for the lifetime broadened superconducting density of states

We argue that the well known Dynes formula [Dynes R C {\it et al.} 1978 {\it Phys. Rev. Lett.} {\bf 41} 1509] for the superconducting quasiparticle density of states, which tries to incorporate the lifetime broadening in an approximate way, cannot be justified microscopically for conventional superconductors. Instead, we propose a new simple formula in which the energy gap has a finite imaginary part $-\Delta_2$ and the quasiparticle energy is real. We prove that in the quasiparticle approximation 2$\Delta_2$ gives the quasiparticle decay rate at the gap edge for conventional superconductors. This conclusion does not depend on the nature of interactions that cause the quasiparticle decay. The new formula is tested on the case of a strong coupling superconductor Pb$_{0.9}$Bi$_{0.1}$ and an excellent agreement with theoretical predictions is obtained. While both the Dynes formula and the one proposed in this work give good fits and fit parameters for Pb$_{0.9}$Bi$_{0.1}$, only the latter formula can be justified microscopically.Comment: 6 pages, 4 figure

Bone Regeneration Potential of Periodontal Ligament Stem Cells in Combination with Cold Atmospheric Plasma-Pretreated Beta-Tricalcium Phosphate: An In Vivo Assessment

In regenerative bone tissue medicine, combining artificial bone substitutes with progenitor cells is a prospective approach. Surface modification via cold atmospheric plasma (CAP) enhances biomaterial–cell interactions, which are crucial for successful bone regeneration. Using a rabbit calvarial critical-size defect model, we assessed the use of CAP-pretreated beta-tricalcium phosphate (β-TCP), alone or with periodontal ligament stem cells (PDLSCs), for bone regeneration. Histological and histomorphometric analyses at two and four weeks revealed significantly improved bone regeneration and reduced inflammation in the CAP-treated β-TCP with PDLSCs compared to β-TCP alone. Immunohistochemical analysis also showed an increase in the bone healing markers, including bone morphogenic proteins 2 and 4, runt-related transcription factor 2, collagen-1, and osteonectin, after two and four weeks in the CAP-treated β-TCP implants with PDLSC. This in vivo study demonstrates for the first time the superior bone regenerative capacity of CAP-pretreated β-TCP seeded with PDLSCs, highlighting the therapeutic potential of this combined approach in osteoregeneration