The Unprecedented Role of 3D Printing Technology in Fighting the COVID-19 Pandemic: A Comprehensive Review.

The coronavirus disease 2019 (COVID-19) rapidly spread to over 180 countries and abruptly disrupted production rates and supply chains worldwide. Since then, 3D printing, also recognized as additive manufacturing (AM) and known to be a novel technique that uses layer-by-layer deposition of material to produce intricate 3D geometry, has been engaged in reducing the distress caused by the outbreak. During the early stages of this pandemic, shortages of personal protective equipment (PPE), including facemasks, shields, respirators, and other medical gear, were significantly answered by remotely 3D printing them. Amidst the growing testing requirements, 3D printing emerged as a potential and fast solution as a manufacturing process to meet production needs due to its flexibility, reliability, and rapid response capabilities. In the recent past, some other medical applications that have gained prominence in the scientific community include 3D-printed ventilator splitters, device components, and patient-specific products. Regarding non-medical applications, researchers have successfully developed contact-free devices to address the sanitary crisis in public places. This work aims to systematically review the applications of 3D printing or AM techniques that have been involved in producing various critical products essential to limit this deadly pandemic's progression.

Effect of through thickness separation of fiber orientation on low velocity impact response of thin composite laminates.

The effect of separation of fiber orientation through the thickness of thin composites on their low velocity impact response is studied. The composites are prepared using unidirectional glass fiber reinforced epoxy through hand layup followed by vacuum bagging. The two dissimilar layups of composites considered have separation of composite layers with fibers having the same and different orientations through the thickness. The composites are subjected to low velocity impact using a drop-weight testing machine. The composites are evaluated using different performance parameters such as damage degree, first damage and maximum forces, first cracking energy, bending stiffness, elastic strain energy, elastic, residual and maximum displacements, permanent deformation, square-root delaminated area, delamination length and width, and contact duration. Among the two composites, it is observed that [90/-45/45/0] composite in which two layers with fibers having 90° and 0° orientations separating by two layers with fibers having -45° and 45° orientations, levels of deformation are lower and recorded force and square-root delaminated area are higher and lower, respectively for the same level of impact energy. Whereas, in case of [0/90/90/0] composite in which two layers with fibers having 0° orientations separating by two layers with fibers having 90° orientations, recorded force is lower and deformation and square-root delaminated area are higher. The [0/90/90/0] composite is having a comparatively more lateral spread of delamination and inter-layer opening than that of [90/-45/45/0] composite considering extensional and bending stiffnesses along longitudinal (A11, D11) and transverse (A22, D22) directions. This facilitates that lateral spread of damage within composite can be decreased by separating two layers of composite with 90° and 0° fiber orientations by two layers with -45° and 45° fiber orientations, i.e., [90/-45/45/0] composite.

2-(6-Chloro-2,3,4,9-tetra-hydro-1H-carbazol-1-yl-idene)propane-dinitrile.

The mol-ecular conformation of the title compound, C(15)H(10)ClN(3), is stabilized by an intra-molecular N-H⋯N hydrogen bond with an S(7) ring motif. The crystal packing is controlled by N-H⋯N and C-H⋯N inter-molecular inter-actions. One of the methyl-ene groups of the cyclo-hexene ring is disordered over two positions with refined occupancies of 0.457 (12) and 0.543 (12).

6-Bromo-2-(3-phenyl-allyl-idene)-2,3,4,9-tetra-hydro-1H-carbazol-1-one.

Mol-ecules of the title compound, C(21)H(16)BrNO, are linked through pairs of N-H⋯O inter-molecular hydrogen bonds into centrosymmetric R(2) (2)(10) dimers. One of the C atoms of the cyclohex-2-enone ring is disordered with refined occupancies of 0.61 (2) and 0.39 (2).

2-(6-Methyl-2,3,4,9-tetra-hydro-1H-carbazol-1-yl-idene)propane-dinitrile.

In the title compound, C(16)H(13)N(3), the cyclo-hexene ring adopts a sofa conformation. An intra-molecular N-H⋯N hydrogen bond generates an S(7) ring motif. In the crystal, the mol-ecules are linked by pairs of N-H⋯N inter-actions, forming centrosymmetric dimers with an R(2) (2)(14) motif.

6-Bromo-2-[(E)-thio-phen-2-yl-methyl-idene]-2,3,4,9-tetra-hydro-1H-carbazol-1-one.

In the title compound, C(17)H(12)BrNOS, the cyclo-hexene ring deviates only slightly from planarity (r.m.s. deviation for non-H atoms = 0.047 Å). In the crystal, the mol-ecules are linked into centro-symmetric R(2) (2)(10) dimers via pairs of N-H⋯O hydrogen bonds. The thio-phene ring is disordered over two positions rotated by 180° and with a site-occupation factor of 0.843 (4) for the major occupied site.

Multi criteria decision making to select the suitable method for the preparation of nanoparticles using an analytical hierarchy process.

Selecting the right method for the preparation of nanoparticles is a crucial decision. A wrong decision can result in the product having to be formulated and developed again. One tool that can be useful in determining the most appropriate method is the Analytical Hierarchy Process (AHP). AHP has been employed in almost all areas related to decision-making problems. In this paper, the results of a case study illustrate that the AHP concept can assist designers in the effective evaluation of various methods available for the preparation of nanoparticles. This paper presents the methodology of selecting the most suitable method for preparing nanoparticles using the analytical hierarchy process.

Direct electrochemistry and electrocatalysis of reduced glutathione on CNFs-PDDA/PB nanocomposite film modified ITO electrode for biosensors.

The electrochemical oxidation of reduced glutathione (GSH) catalyzed by electro generated Berlin green at carbon nanofibers-poly(diallyldimethylammonium chloride)/Prussian blue (CNFs-PDDA/PB) nanocomposite film modified ITO electrode has been studied. The CNFs-PDDA/PB nanocomposite film were fabricated by casting the composite CNFs enfolded PDDA on ITO electrode followed by electrochemical deposition of PB on the CNFs-PDDA matrix using cyclic voltammetry (CV). Electron microscopy (TEM, AFM), and Fourier transform infrared spectroscopy (FT-IR) studies were used to characterize the morphology and structure of the nanocomposite. The fabricated CNFs-PDDA/PB/ITO nanocomposite film electrode shows significant improvement of redox activity of PB due to the excellent electron transfer ability of CNFs. It was also found to possess prominent electrocatalytic activity toward the oxidation of glutathione with high sensitivity as high as 2.07 µA dm(3) mol(-1) cm(-2). A nontoxic, stable and convenient method for the detection of GSH in the concentration range of 6.0×10(-6) to 1.74×10(-5) M has been developed and it showed improved sensor performance compared to the unmodified PB electrode. The high sensitivity, wider linear range, good reproducibility, and the minimal surface fouling make this CNFs/PDDA/PB nanocomposite film a promising candidate for GSH sensors.

Benzamide-picric acid (1/1).

In the title compound, C(7)H(7)NO·C(6)H(3)N(3)O(7), one of the nitro groups of the picric acid mol-ecule lies in the plane of the attached benzene ring [dihedral angle = 1.4 (1)°] while the other two are twisted away by 9.9 (1) and 30.3 (1)°. In the benzamide mol-ecule, the amide group is almost coplanar with the benzene ring [dihedral angle = 4.4 (1)°]. An intra-molecular O-H⋯O hydrogen bond generates an S6 ring motif. In the crystal, mol-ecules are linked into a ribbon-like structure along the b axis by O-H⋯O and N-H⋯O inter-molecular hydrogen bonds. In addition, C-H⋯O hydrogen bonds and short O⋯O contacts [2.828 (2) Å] are observed.

2-Amino-pyridinium picrate.

In the title compound, C(5)H(7)N(2) (+)·C(6)H(2)N(3)O(7) (-), there are two crystallographically independent cations and anions (A and B) in the asymmetric unit. In both picrate anions, one of the nitro groups lies in the plane of the benzene ring [r.m.s. deviations = 0.014 (2) and 0.014 (2) Šfor anions A and B, respectively] and the other two are twisted away by 39.0 (2) and 18.8 (2)° in A, and 18.2 (1) and 2.5 (2)° in B. In the crystal, the cations and anions are linked by inter-molecular N-H⋯O and C-H⋯O hydrogen bonds, forming a two-dimensional network.

2-(1,2,3,4-Tetra-hydro-9H-carbazol-1-yl-idene)propane-dinitrile.

In the title compound, C(15)H(11)N(3), the cyclo-hexene ring adopts a sofa conformation. An intra-molecular N-H⋯N hydrogen bond generates an S(7) ring motif. In the crystal, mol-ecules are linked by inter-molecular N-H⋯N, C-H⋯N and C-H⋯π inter-actions into a three-dimensional network.

Photocatalytic activity of surface fluorinated TiO2-P25 in the degradation of Reactive Orange 4.

Photocatalytic activity of surface fluorinated TiO(2)-P25 (F-TiO(2)-P25) in the degradation of a chlorotriazine azo dye Reactive Orange 4 (RO 4) under ambient conditions was investigated in this study. Characterization of F-TiO(2)-P25 reveals that the catalyst has a strong absorption in the UV range and the presence of F atom in the catalyst. The degradation rate of RO 4 with surface fluorinated TiO(2)-P25 is three times faster than bare TiO(2)-P25. The quantum yield of UV/TiO(2)-P25 process is largely decreased by the increase of initial dye concentration, whereas in UV/F-TiO(2)-P25 process, the influence of initial dye concentration is less. Surface fluorination of TiO(2)-P25 enhanced the adsorption of RO 4 dye, while improving overall degradation rate. The optimum operating conditions of UV/F-TiO(2)-P25 process for efficient degradation are reported.

Novel substituted methylenedioxy lignan suppresses proliferation of cancer cells by inhibiting telomerase and activation of c-myc and caspases leading to apoptosis.

Conventional solvent fractionation and bioactivity based target assays were used to identify a new anti-cancer molecule from Phyllanthus urinaria, a herbal medicinal plant used in South India. At each step of the purification process the different fractions that were isolated were tested for specific anti-proliferative activity by assays measuring the inhibition of [(3)H]thymidine incorporation, and trypan blue drug exclusion. The ethyl acetate fraction that contained the bioactivity was further purified and resolved by HPLC on a preparative column. The purity of each of the fractions and their bioactivity were checked. Fraction 3 demonstrated a single spot on TLC and showed maximum anti-proliferative activity. This fraction was further purified and the structure was defined as 7'-hydroxy-3',4',5,9,9'-pentamethoxy-3,4-methylene dioxy lignan using NMR and mass spectrometry analysis. The pure compound and the crude ethyl acetate fraction which showed anti-proliferative activities were examined for ability to target specific markers of apoptosis like bcl2, c-myc and caspases and for effects on telomerase. Four specific cancer cell lines HEp2, EL-1 monocytes, HeLa and MCP7 were used in this study. The results indicate that 7'-hydroxy-3',4',5,9,9'-pentamethoxy-3,4-methylene dioxy lignan was capable of inhibiting telomerase activity and also could inhibit bcl2 and activate caspase 3 and caspase 8 whose significance in the induction of apoptosis is well known. We believe that this compound could serve as a valuable chemotherapeutic drug after further evaluations.