Fabrication of large UV transmission blazed gratings for slitless spectral sky survey

Slitless spectral sky survey is a critical direction of international astronomical research. Compared with ground-based sky survey, space-based sky survey can achieve full-band observation, and its imaging quality and resolution capability are restricted by the efficiency and size of dispersive elements. Transmission blazed gratings are often used as the dispersive elements in the UV band. Holographic interference lithography produces the photoresist mask of a grating, and the ion beam etching vertically transfers the pattern to the substrate to form the SiO2 mask of a grating. To reduce the effect of ion beam divergence on the uniformity of the groove shape, the grating mask is etched tilted by the ion beam passing through a narrow slit to obtain a blazed grating with consistent structural parameters. Moreover, two-dimensional scanning of the sample stage enables the etching of large-size samples. A UV transmission blazed grating with a linear density of 333 lines mm−1, a blazing angle of 11.8°, and a dimension of 99.2mm × 60.0mm × 6.0mm was successfully fabricated with an average diffraction efficiency of 66%, a PV diffraction wavefront of 0.169λ (λ = 632.8 nm) and low stray light.

Structural and Dynamical Behaviour of Colloids with Competing Interactions Confined in Slit Pores

Systems with short-range attractive and long-range repulsive interactions can form periodic modulated phases at low temperatures, such as cluster-crystal, hexagonal, lamellar and bicontinuous gyroid phases. These periodic microphases should be stable regardless of the physical origin of the interactions. However, they have not yet been experimentally observed in colloidal systems, where, in principle, the interactions can be tuned by modifying the colloidal solution. Our goal is to investigate whether the formation of some of these periodic microphases can be promoted by confinement in narrow slit pores. By performing simulations of a simple model with competing interactions, we find that both the cluster-crystal and lamellar phases can be stable up to higher temperatures than in the bulk system, whereas the hexagonal phase is destabilised at temperatures somewhat lower than in bulk. Besides, we observed that the internal ordering of the lamellar phase can be modified by changing the pore width. Interestingly, for sufficiently wide pores to host three lamellae, there is a range of temperatures for which the two lamellae close to the walls are internally ordered, whereas the one at the centre of the pore remains internally disordered. We also find that particle diffusion under confinement exhibits a complex dependence with the pore width and with the density, obtaining larger and smaller values of the diffusion coefficient than in the corresponding bulk system.

Surgical mask designed for endoscopic procedures to prevent the diffusion of droplets

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2) has become a global pandemic. The human-tohuman transmission of SARS-CoV-2 occurs primarily through droplets, aerosols, and direct contact. Endoscopy is performed at a short physical distance between an endoscopist and patient, which increases the risk of SARS-CoV-2 transmission to the endoscopist through contact with body fluids and exposure to droplets due to vomiting, retching, and coughing during endoscopic procedures (1). Gastrointestinal endoscopic procedures generate aerosols, which mandates the use of appropriate personal protective equipment (PPE) (1,2). To further reduce the risk of viral infection during endoscopy, additional infection protection is needed to assist PPE from not only the side of endoscopists but also the side of patients (3). Various infection prevention devices, such as a reusable plastic cube barrier, have been reported (3); however, we focused on a surgical mask as a simple and inexpensive method (4). Previous studies proposed modified surgical masks with an endoscopic insertion port, which were handmade with an incision for endoscope insertion into commercially available surgical masks (2,4). Although these “handmade” masks may be easily modified, their preparation is burdensome and not sterile. We developed a novel disposal surgical mask with a mask manufacturer that is specifically designed as a droplet prevention device for endoscopic procedures that may be massproduced with uniform quality and easily introduced into endoscopy units. This novel surgical mask has a 10-mm slit in the center for the insertion of an endoscope and two small 6-mm slits for suction on the left and right. The width of the pleats in the center have been widened to easily cut the slits, which allows for cost-effective mass production. Despite its close fit, the narrow slit allows for the easy passage of an endoscope and smooth endoscopic manipulation. Furthermore, the leakage of droplets and aerosols through the slit in the surgical mask is minimized (Fig. 1A-D).

Efficient multiscale calculation results for microchannel mass transfer

When the channel height is reduced to a small value such as on the scales of 10 nm or 100 nm, the physical adsorbed layers on the channel walls will participate in the flow, although intermediate between them is a continuum fluid flow. The multiscale simulation results are presented for this multiscale mass transfer in a narrow slit pore based on the derived flow equations. The results are respectively compared with those calculated from conventional continuum flow theory and from the theory based on the solid layer assumption, when the fluid-wall interaction is respectively weak, medium and strong. The total mass flow rate of the two adsorbed layers is also compared with the mass flow rate of the intermediate continuum fluid. The obtained results show the importance of the incorporation of the adsorbed layer flow by the multiscale scheme when calculating the transferred mass in a microchannel.

Notes on lichenicolous species of Opegrapha s. lat. (Arthoniales) on Arthoniaceae and Verrucariaceae, with a key to British and Irish lichenicolous Opegraphaceae

Three species of lichenicolous Opegrapha s. lat. are newly described, all apparently host-specific at genus level. Opegrapha arthoniicola Coppins & S. Y. Kondr. is described from western Britain and Ireland, where it grows on the thallus of Arthonia radiata on Corylus bark; it has small clustered ascomata, asci that are usually 6-spored and rather small ascospores (10.5–)12.5–14.5 μm in length. Opegrapha sawyeriana Coppins occurs on the thallus of Coniocarpon cinnabarinum, also on Corylus bark, from oceanic western parts of Scotland, Ireland and southern England; in comparison to O. arthoniicola it has smaller, often scattered ascomata with a pigmented basal layer, 8-spored asci and slightly larger ascospores 13–14.5(–16) μm in length. Opegrapha hochstetteri Coppins has been found on thalli of Verrucaria hochstetteri and V. muralis on calcareous rocks and stonework in southern England and Luxembourg; collections were formerly identified as Opegrapha rupestris Pers. but it differs from this species by narrower ascomata with a persistent narrow slit, normally 6- rather than 8-spored asci and ascospores with pigmentation in the spore wall rather than the perispore. Lifted from synonymy is Opegrapha opaca Nyl., which inhabits the thallus of Verrucaria nigrescens and V. viridula on calcareous rocks and stonework, and is so far recorded from southern England, Luxembourg, France, northern Spain and Israel. The hosts of the European species of lichenicolous Opegrapha on Verrucaria s. lat. on calcareous rocks (O. hochstetteri, O. opaca and O. rupestris) belong to different phylogenetic lineages within the Verrucariaceae. A key is also provided to the lichenicolous species of Opegraphaceae currently known from Great Britain and Ireland.

Dual-Core Fiber-Based Interferometer for Detection of Gas Refractive Index

We demonstrate a dual-core fiber-based Mach–Zehnder interferometer that could be used for precise detection of variations in refractive indices of gaseous samples. The fiber used here have a solid germanium-doped silica core and an air core that allows gases to flow through. Coherent laser beams are coupled to the two cores, respectively, and thus excite guiding modes thereby. Interferogram would be produced as the light transmitted from the dual cores interferes. Variations in refractive index of the hollow core lead to variations in phase difference between the modes in the two cores, thus shifting the interference fringes. The fringe shifts can be then interrogated by a photodiode together with a narrow slit in front. The resolution of the sensor was found to be ~1 × 10−8 RIU, that is comparable to the highest resolution obtained by other fiber sensors reported in previous literatures. Other advantages of our sensor include very low cost, high sensitivity, straightforward sensing mechanism, and ease of fabrication.

Evidence of a second nursery area of the sandbar shar, Carcharhinus plumbeus (Nardo, 1827) in the Eastern Mediterranean Sea

The sandbar shark (Carcharhinus plumbeus) is a large coastal species with a cosmopolitan distribution that has been listed as Endangered in the Mediterranean Sea and as Vulnerable for the rest of the world on the IUCN Red List of threatened species. The Gökova's Boncuk Cove in south-western Turkey and the Gulf of Gabès in southern Tunisia are the only known nursery area for the Mediterranean population. On 24 – 27 July 2017, eight specimens, four males and four females, of sandbar sharks were accidentally caught at a depth of 7 to 9 m by a pelagic bluefish longline off the coast of Yumurtalik Bight in the Gulf of Iskenderun. The total length and weight of males and females were 54.5 – 61.0 cm, 930 – 1,484 g and 49.6 – 62.4 cm, 918 – 1,568 g, respectively. They all had unhealed umbilical scars that were still open as a narrow slit, measuring 4.35 and 5.39 mm in lengths. This study thus provides the records of the neonate sandbar sharks from the Yumurtalik Bight. Consequently, this occurrence represents that this area of the north-eastern Mediterranean Sea can be the second breeding and nursery grounds for this species after the Boncuk Cove in Gökova Bay in Turkey.

Study of Creeping Flow of Jeffrey Fluid Through a Narrow Permeable Slit With Uniform Reabsorption

This research explores the creeping flow of a Jeffrey fluid through a narrow permeable slit with an application of blood flow through a planer hemodialyzer. The fluid motion of Jeffrey fluid in a two-dimensional conduit with nonhomogeneous boundary conditions due to constant reabsorption on the wall is a complicated problem. The viscous effect of Jeffrey fluid in a cross-sectional area of a narrow slit is computed with the help of continuity and momentum equation. The stress component, velocity profile, stream function, and pressure gradient show the behavior of creeping flow of Jeffrey fluid in a narrow slit. To find the explicit expression of velocity, pressure, stream function, and flux, recursive (Langlois) approach is adopted. Maximum velocity, shear stress, leakage flux, and fractional absorption on the wall are also calculated in this research. The mathematical results of this research are very helpful to study the blood flow through planer hemodialyzer; therefore, this theoretical model has significant importance in the field of renal physiology.

Modeling and Simulation of Subcooled Coolant Loss Through Circumferential Pipe Leakage

The present work demonstrates the leak flow behavior of subcooled water at high pressure and high temperature through a narrow slit analogous to a pipe crack. The modeling and simulations are based on the loss of coolant accident in the primary loop piping of pressurized water-cooled reactors where a subcooled liquid is subjected to a rapid depressurization. Prediction of critical leak flow pattern is crucial in the design methodology of costly high energy pipelines in the perspective of leak before break consideration. Computational techniques have been used to replace costly experiments required for simulating leak flow conditions. For a variety of entry and exit conditions, the interphase mass transfer was studied with a change of boundary conditions. Presence of thermodynamic nonequilibrium has been detected on several occasions due to high transit velocities. A comparison with experimental findings indicates the validity of the flashing model for safety analysis of similar high energy thermal systems.