Effect of Copper Donor Material Assisted Friction Stir Welding of AA6061-T6 Alloy On Downward Force, Microstructure, And Mechanical Properties

In this research, Copper (Cu) donor material assisted friction stir welding (FSW) of AA6061-T6 alloy was studied. Cu assisted FSW joints of AA6061-T6 alloy were prepared at a constant tool rotational rate of 1400 rpm and various welding speeds at 1 mm/s and 3 mm/s. The Cu donor material of different thickness (i.e., 20%, 40%, and 60%) with respect to the workpiece thickness was selected to assist the FSW joining at the plunge stage. It is observed that the downward force generated in the FSW process was gradually decreased after introducing Cu donor material with incremental thicknesses with respect to workpiece at the plunge stage. Post-weld analysis was characterized in terms of microstructure, and mechanical properties. The results of microstructure analysis at the stir zone (SZ) show the formation of finer grains due to dynamic recrystallization and plastic deformation. Micro-hardness tests reveal that the hardness decreased from the base metal (BM) to the SZ across the heat affected zone (HAZ) and thermo-mechanically affected zone (TMAZ). The lowest value of hardness appeared in the TMAZ and HAZ where tensile failure occurs. With increasing welding speed, the average hardness in the SZ decreased due to lower heat input and faster cooling rate. Tensile test plots show no significant change in ultimate tensile strength with or without Cu donor material. Fractography of tensile tested samples shows both ductile and brittle like structure for given welding parameters. This proposed work of FSW with Cu donor material is promising to increase tool life due to the decrement of the downforce during plunge and throughout the welding stage. Meanwhile, the inclusion of donor material did not compromise the weld quality in terms of the mechanical properties and micro-hardness.

Outcomes of Application Two-Piece Microkeratome-Assisted Mushroom Keratoplasty

Purpose: to evaluate outcomes and to expose possible specific complications of two-piece mushroom keratoplasty.Patients and methods. A total of 9 patients (9 eyes) with corneal perforations and deep stromal opacities involving the Descemet membrane were undergone surgery. In all cases, preserved hypothermic corneoscleral buttons (in Borzenok– Moroz medium) for up to 5 days were used as donor material. The two-piece mushroom keratoplasty was performed using a microkeratome and vacuum trephines set in the variant proposed by M. Busin.Results. Success survival was obtained in 78 % of patients (7 out of 9 cases). Best spectaclecorrected visual acuity (BSCVA) 1 year after surgery averaged 0.54 ± 0.20. The average of corneal astigmatism was 3.41 ± 1.89 D. Endothelial cell density in 6 months after surgery was on average 2364 ± 236/mm2, and in 1 year — 2082 ± 228/mm2. A false chamber formation between separate parts of the graft as a specific complication was detected in 2 patients on 1 day after surgery. In one case it was eliminated by air re-injecting into the ocular anterior chamber. The second patient underwent conventional PKP due to the lack of graft adaptation. In addition, 1 patient also underwent conventional PKP as a result of postoperative crystalline infectious keratopathy, which is the non-specific complication of mushroom keratoplasty.Conclusion. The two-piece microkeratome-assisted mushroom keratoplasty is an effective method of surgical treatment of corneal perforations and deep stromal opacities involving the Descemet membrane.

An Effective D-π-A Type Donor Material Based on 4-Fluorobenzoylacetonitrile Core Unit for Bulk Heterojunction Organic Solar Cells

In order to develop new and effective donor materials, a planar donor-π-acceptor (D-π-A) type small organic molecule (SOM), 2-(4-fluorobenzoyl)-3-(5″-hexyl-[2,2′:5′,2″-terthiophen]-5-yl) acrylonitrile, named as H3T-4-FOP, was synthesized by the reaction of 4-fluorobenzoylacetonitrile (as acceptor unit) and hexyl terthiophene (as donor unit) derivatives. Promising optical, solubility, electronic and photovoltaic properties were observed for the H3T-4-FOP SOM. Significantly, the presence of 4-fluorobenzoylacetonitrile as an acceptor unit in H3T-4-FOP SOM tuned the optical band gap to ~2.01 eV and procured the reasonable energy levels as highest occupied molecular orbital (HOMO) of −5.27 eV and lowest unoccupied molecular orbital (LUMO) −3.26 eV. The synthesized H3T-4-FOP SOM was applied as a donor material to fabricate solution-processed bulk heterojunction organic solar cells (BHJ-OSCs) with an active layer of H3T-4-FOP: PC61BM (1:2, w/w) and was validated as having a good power conversion efficiency (PCE) of ~4.38%. Our studies clearly inspire for future designing of multifunctional groups containing the 4-fluorobenzoylacetonitrile based SOM for high performance BHJ-OSCs.

Study on Photo-Degradation of Inverted Organic Solar Cells Caused by Generation of Potential Barrier between PEDOT:PSS and PBDB-Ts

We investigated that photo-stability of PBDB-T, which is a good donor material for state-of-the-art high-performance organic solar cells (OSCs), in OSCs under prolonged photo-irradiation. PBDB-T itself did not decompose upon...

The hardware method of biomaterial preparation for fecal transplantation

Background: Nowadays fecal transplantation (FT) is considered as a component of the treatment for a wide range of disorders, including autoimmune diseases (ulcerative colitis, Crohn's disease, type 1 diabetes mellitus and insulin resistance, multiple sclerosis, psoriasis). High-quality preparation of the biomaterial is a necessary procedure that allows for long-time storage of the prepared fecal transplant at ultralow temperature conditions and it use as needed.Aim: To optimize the method of preparation of the biomaterial for fecal transplantation and to evaluate its "survival" at different time points under cryopreservation conditions.Materials and methods: A device for the preparation of donor fecal material for transplantation has been developed and proposed (the Russian Federation patent No. 2659417 from July 2, 2018). Donor fecal material (collected in a sterile container on the same day of preparation in the morning), the solvent, and glycerol are homogenized automatically in the closed loop device and passed through a disposable filter with attached sterile hemocon container. Freezing at ultralow temperature (cryopreservation at -80 °C) allows for long time storage of this fecal graft. We studied the microbial composition of the obtained native substrate and samples that were cryopreserved at different time points (7 to 365 days).Results: The proposed original method makes it possible to prepare the biomaterial for storage at a low temperature mode without any contact, in a closed loop, for subsequent fecal transplantation within 6–12 months. The analysis of the fecal transplant at different time points has shown no qualitative and quantitative differences in the microbial composition between the native donor material and the freshly prepared filtrate. The biomaterial prepared according to the original method is stable for 12 months.Conclusion: The proposed hardware method for preparing the biomaterial for fecal transplantation is easy to use and allows for the preparation of a graft with minimal external microbial contamination, in contrast to the conventional method of donor material preparation by filtering fecal matter through gauze or coffee filters with manual assistance.

Planar D-π-A Configured Dimethoxy Vinylbenzene Based Small Organic Molecule for Solution-Processed Bulk Heterojunction Organic Solar Cells

A new and effective planar D-π-A configured small organic molecule (SOM) of 2-5-(3,5-dimethoxystyryl)thiophen-2-yl)methylene)-1H-indene-1,3(2H)-dione, abbreviated as DVB-T-ID, was synthesized using 1,3-indanedione acceptor and dimethoxy vinylbenzene donor units, connected through a thiophene π-spacer. The presence of a dimethoxy vinylbenzene unit and π-spacer in DVB-T-ID significantly improved the absorption behavior by displaying maximum absorbance at ~515 nm, and the reasonable band gap was estimated as ~2.06 eV. The electronic properties revealed that DVB-T-ID SOMs exhibited promising HOMO (−5.32 eV) and LUMO (−3.26 eV). The synthesized DVB-T-ID SOM was utilized as donor material for fabricating solution-processed bulk heterojunction organic solar cells (BHJ-OSCs) and showed a reasonable power conversion efficiency (PCE) of ~3.1% with DVB-T-ID:PC61BM (1:2, w/w) active layer. The outcome of this work clearly reflects that synthesized DVB-T-ID based on 1,3-indanedione units is a promising absorber (donor) material for BHJ-OSCs.