We consider the motion at large Reynolds number of an incompressible fluid around a thin circular disk of finite radius rotating in its plane. The disk is placed in a large tank filled with an ...initially stagnant fluid. Then it is brought into rotation about its centre with constant angular velocity. Due to viscosity, a layer of fluid adjacent to the disk gets involved in the circumferential motion. This activates centrifugal forces; the fluid particles start to deviate in the radial direction. When they cross the edge of the disk, a thin jet is formed. Firstly, we solve the classical boundary-layer equations for the flow in the boundary layer in the direct neighbourhood of the disk surface and in the jet. The solution is found to develop a discontinuity at the ‘head’ of the jet where the radial and circumferential velocity components experience a jump. This type of discontinuity, called a pseudo-shock, was previously observed by Ruban & Vonatsos (J. Fluid Mech., vol. 614, 2008, pp. 407–424). Then, we investigate the internal structure of the pseudo-shock. We find that the fluid motion is described by the Euler equations in the leading-order approximation. Their solution shows that, as the jet penetrates the stagnant fluid, it ejects the fluid from the boundary layer into the surrounding area. Analysis of the inviscid region outside the boundary layer reveals that the ejected fluid returns back to the boundary layer through the ‘entrainment process’. Finally, we conclude this paper with the study of the wake in the vicinity of the disk rim.
Biosensing demands the development of reliable, eco-friendly, and real-time detection techniques for the early diagnosis and eradication of diseases from our vicinity. Among the variety of sensing ...techniques, surface plasmon resonance (SPR) sensors have gotten considerable attention due to their low time consumption and low cost. Through this review, we have figured out various schemes for the detection of bio species using SPR sensors, and the role of 2D materials in enhancing the performance of the sensor is also conveyed. We started with a brief explanation of different types of 2D nanomaterials and discussed the mechanical, chemical, electrical, optical, thermal, and magnetic properties of 2D materials. We have carefully studied the recent developments in the field of biosensing with different 2D materials such as; carbon-related compounds, MoS2, WS2, MXene, black phosphorus, and their composites. We have further studied the role of each plasmonic metal in the enhancement process.
•The concepts of SPR sensors centered on Kretschmann principle are framed by pictorial illustrations.•The impact of Graphene and MoS2 on the performance of SPR sensor are consolidated.•Dissected the outcome of other 2-D nanomaterials on the augmentation of SPR activity.•Inspected contemporary inclinations on detection of biomolecule and the scopes of future investigation.
Studying palaeotsunamis is important to the comprehensive understanding of these events and their role in the geological evolution of the coasts of oceans and seas. The present work aims at ...summarizing the published information on Triassic tsunamis to document their spatiotemporal distribution and the related knowledge gaps and biases. A bibliographical survey was undertaken to collect the literature sources, and their content was examined to extract the principal information about palaeotsunamis. The certainty of the literary evidence for particular localities and regions is addressed by checking the consistency of the published interpretations. It is found that tsunamis were discussed commonly in different parts of the world for the Permian–Triassic transition and the end-Triassic. However, the certainty of the literary evidence is questionable in both cases. Some interpretations of palaeotsunamis were disputed, and storm versus tsunami interpretations were offered in several cases. A few tsunamis were also reported from the Olenekian–Carnian interval but with the same quality of literary evidence. Taking into account the frequency of tsunamis in the historical times and the Holocene, as well as the presence of their possible triggers in the Triassic, it is proposed that the analyzed literary evidence is significantly incomplete, and, thus, our knowledge about Triassic tsunamis is imperfect. Further research should aim at studying them in a bigger number of localities, paying attention to the Olenekian–Norian interval and trying to relate them to different triggers.
Under conditions of excess sunlight the efficient light-harvesting antenna1 found in the chloroplast membranes of plants is rapidly and reversibly switched into a photoprotected quenched state in ...which potentially harmful absorbed energy is dissipated as heat, a process measured as the non-photochemical quenching of chlorophyll fluorescence or qE. Although the biological significance of qE is established, the molecular mechanisms involved are not. LHCII, the main light-harvesting complex, has an inbuilt capability to undergo transformation into a dissipative state by conformational change and it was suggested that this provides a molecular basis for qE, but it is not known if such events occur in vivo or how energy is dissipated in this state. The transition into the dissipative state is associated with a twist in the configuration of the LHCII-bound carotenoid neoxanthin, identified using resonance Raman spectroscopy. Applying this technique to study isolated chloroplasts and whole leaves, we show here that the same change in neoxanthin configuration occurs in vivo, to an extent consistent with the magnitude of energy dissipation. Femtosecond transient absorption spectroscopy, performed on purified LHCII in the dissipative state, shows that energy is transferred from chlorophyll a to a low-lying carotenoid excited state, identified as one of the two luteins (lutein 1) in LHCII. Hence, it is experimentally demonstrated that a change in conformation of LHCII occurs in vivo, which opens a channel for energy dissipation by transfer to a bound carotenoid. We suggest that this is the principal mechanism of photoprotection.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Purpose
To present the results of the treatment of traumatic macular holes.
Methods
This study is a retrospective consecutive case series of 7 patients who underwent a 25G PPV with the displacement ...of macular retina after subretinal balanced salt solution injection to treat traumatic full thickness macular holes (TFMH). The efficiency was evaluated by the anatomical macular hole closure rate and best‐corrected visual acuity (BCVA) during follow‐up visits. The degree of retinal displacement was accessed by comparing the preoperative and postoperative fundus photographies.
Results
Complete closure of macular hole was achieved in 85,7% and 14,3% had partial closure. Average macular hole diameter was (825 μm). Visual acuity after surgery in the total group was significantly increased. All patients revealed a negative correlation between postoperative visual acuity and the time elapsed from the moment of the trauma, and a strong positive correlation between the macular hole size and elapsed time from the injury. There were no intraoperative or postoperative complications.
Conclusion
Vitrectomy with the «retinal displacement» technique may be an effective addition to surgical options for treating traumatic macular holes.
Photoinhibition is the light‐induced reduction in photosynthetic efficiency and is usually associated with damage to the D1 photosystem II (PSII) reaction centre protein. This damage must either be ...repaired, through the PSII repair cycle, or prevented in the first place by nonphotochemical quenching (NPQ). Both NPQ and D1 repair contribute to light tolerance because they ensure the long‐term maintenance of the highest quantum yield of PSII. However, the relative contribution of each of these processes is yet to be elucidated. The application of a pulse amplitude modulation fluorescence methodology, called protective NPQ, enabled us to evaluate of the protective effectiveness of the processes. Within this study, the contribution of NPQ and D1 repair to the photoprotective capacity of Arabidopsis thaliana was elucidated by using inhibitors and mutants known to affect each process. We conclude that NPQ contributes a greater amount to the maintenance of a high PSII yield than D1 repair under short periods of illumination. This research further supports the role of protective components of NPQ during light fluctuations and the value of protective NPQ and qPd as unambiguous fluorescence parameters, as opposed to qI and Fv/Fm, for quantifying photoinactivation of reaction centre II and light tolerance of photosynthetic organisms.
Protective nonphotochemical quenching (NPQ) of chlorophyll fluorescence as well as photosystem II reaction centre repair processes contributes to light tolerance of plants. However, the relative contribution of each of these processes is not known for short‐term illumination. Here, we applied the novel fluorescence methodology, called protective NPQ, that enabled evaluation of the contribution of these processes to light tolerance of the photosynthetic membrane and found that NPQ contributes a greater amount than D1 repair, but this contribution depends upon the light treatment and the NPQ capacity of the plant.
Magnetic and atomic ordering in equiatomic FeNi alloy is studied by different ab initio techniques and methods based on density functional theory in order to clarify the main driving forces and their ...interplay behind these transitions and possibility of their accurate description within standard density functional theory calculations. The Curie temperature is obtained in Monte Carlo simulations using magnetic exchange interactions obtained by applying the magnetic force theorem within multiple scattering theory for different magnetic and atomic configurational states, including account for the thermal atomic displacements and exchange-correlation potential. The calculations show a very strong sensitivity of the results upon exchange-correlation potential, atomic order, and thermal atomic displacements. The calculated Curie temperature of a completely random alloy with the account of thermal lattice displacement is at least about 200 K below the known experimental data (780-800 K) depending on the above mentioned factors. The atomic order-disorder transition temperature is determined from effective chemical interactions, which apart from the chemical contribution (on the ideal fcc lattice) include contributions from lattice thermal vibrations and local lattice relaxations. The effective chemical interactions are strongly affected by the magnetic state, so the order-disorder transition temperature changes between 1000 and 140 K in the fully ordered ferromagnetic and paramagnetic states, respectively. For the reduced magnetization 0.7 (close to the experimental order-disorder transition temperature at 600 K), the order-disorder transition temperature varies between 550 and 700 K depending mostly on the exchange-correlation potential. The latter effect is the uncertainty in the choice of the exchange-correlation approximation in density functional theory calculations.
The strontium aluminium hexaferrite was substituted with the divalent ions (Ba/Ca) with the chemical formula of Sr1-xMxAl2Fe10O19 (M = Ba, Ca; x = 0.1, 0.2), and all the samples were synthesized via ...sol-gel auto combustion method. The particles are shaped in a hexagonal structure with space group P63/mmc. The field-emission scanning microscopy revealed the platelet-like morphology of the particles. The magnetic studies disclosed the single-domain arrangement of particles and decent energy product value for all the samples (0.36–0.38 MG Oe), implying their potential application in permanent magnets. The declined value of the Dielectric constant at mega-range frequency suggests that the samples could be useful for microwave application.
•Conventional and economical sol-gel auto-combustion method was adopted for the synthesis procedure.•Double site substitution was performed to investigate the effect on magnetic and.dielectric properties.•Notable energy product value (BHmax) of 3.02 kJ/m3 was achieved without any rare- earth element being present in the samples.•High dielectric constant values at lower frequencies suggests that the samples have potential application in microwave frequency range.
Ancient carbonate reefs, which represent specific palaeoecosystems, are promising as geological heritage sites (geosites). The bibliographical survey allows to identify 30 palaeoreef localities ...already interpreted in the terms of geoheritage. These were described in 18 countries from the different parts of the world; many palaeoreefs were reported from Europe and North Africa. The ages of the considered palaeoreefs differ, and they tend to concentrate in the Early–Middle Paleozoic, the Late Triassic–Jurassic, and the Late Cretaceous–Neogene intervals. The correspondence between the global dynamics of the reef growth in the Phanerozoic and the stratigraphical distribution of the palaeoreef-related geosites is uncertain. As a case example, three palaeoreefs from the Western Caucasus are taken into account. These are the Raskol (latest Permian), Tkhach–Sakhray (Late Triassic), and Oshten (Late Jurassic) palaeoreefs, which can be brought in correspondence to the global reef booms. They are important for geological research, education, and tourism. Generally, the present knowledge of the ancient carbonate reefs as geoheritage remains incomplete. The related research is perspective, and it requires cross-disciplinary cooperation of specialists.
This work is concerned with the laminar–turbulent transition in the boundary layer on an aircraft wing covered by a water film. We consider the initial stage of the transition process known as the ...receptivity of the boundary layer, namely, we study the generation of the interfacial instability waves by the unsteady free-stream acoustic noise interacting with a small roughness on the wing surface. For effective receptivity, the ‘forcing’ should obey the so-called ‘double-resonance’ principle. According to this principle, both the frequency and the wavenumber of the external perturbations should be in tune with the natural instability modes of the flow. Correspondingly, we choose the frequency of the acoustic wave to coincide with that of the interfacial instability wave. However, this makes the wavelength of the acoustic wave significantly larger than wavelength of the instability wave. Thus, the second resonance condition is not satisfied, which means that the acoustic wave alone cannot produce the instability waves in the boundary layer. Instead, the Stokes layer is created in the boundary layer just above the liquid film. As far as the film is concerned, it also experiences wave-like motion caused by the varying shear stress on the interface. The generation of the interfacial instability waves takes place when the Stokes layer encounters a wall roughness that is short enough for an appropriate scale conversion to take place. To describe the flow in the vicinity of the roughness, a suitably modified triple-deck theory is used.
PDF
