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Neutron Diffraction Study on the Magnetic Structure of the Promised Multiferroic Hybrid Perovskite C(ND2)(3)]Cu(DCOO)(3) and Its Centrosymmetric Analogues
No full textThis report presents with one of the rare experimental studies on the magnetic structure of hybrid framework materials, C(ND2)(3)]Me2+(DCOO)(3) (Me = Cu, Mn, and Co), by using neutron powder diffraction. Copper guanidinium formate (CuGF) having a polar structure is a promised multiferroic member of the hybrid perovskite metal guanidinium formates and its Mn/Co analogues possessing a centrosymmetric structure. Previous investigations based on ab initio calculations have suggested that CuGF is a multiferroic whose magnetic space groups are assignable either to Pn'a'2(1) or Pna'2(1)'. Our neutron experiments concurrently reject the Pna'2(1)' possibility and suggest the magnetic structure of CuGF as either Pna2(1) or Pn'a'2(1), with both exhibiting ``Type-A'' magnetic ordering, free from ferromagnetic ordering along the polar-axis, with spins lying in the ab plane. In contrast to CuGF, its centrosymmetric analogues Mn/CoGF are found to display ``Type-G'' magnetic ordering, with their spins aligned along the b and c axis, respectively. The in-depth evaluation of magnetic structure of the metal guanidinium formate frameworks could be helpful in the understanding and designing of the magnetic functionalities of multiferroic hybrid perovskites and could provide an encouraging platform for the improvement of ab initio studies
On the numerical index of polyhedral Banach spaces
No full textThe computation of the numerical index of a Banach space is an intriguing problem, even in case of two-dimensional real polyhedral Banach spaces. In this article we present a general method to estimate the numerical index of any finite dimensional real polyhedral Banach space, by considering the action of only finitely many functionals, on the unit sphere of the space. We further obtain the exact numerical index of a family of 3-dimensional polyhedral Banach spaces for the first time, in order to illustrate the applicability of our method
Tissue mimetic 3D scaffold for breast tumor-derived organoid culture toward personalized chemotherapy
No full textBreast cancer cell lines lose the inherent gene expression profiles of their source tumor and when cultured as monolayers (two-dimensional) are unable to represent patient tumors. Thus, we engineered a biochemico- and mechano-mimetic three-dimensional (3D) culture platform for primary breast cancer cells by decellularizing cancer-associated fibroblasts (CAFs) cultured on 3D macroporous polymer scaffolds to recapitulate tumor behavior and drug response more realistically. The presence of the CAF-derived extracellular matrix deposited on the polycaprolactone scaffold promoted cell attachment and viability, which is ascribed to higher levels of phosphorylated Focal Adhesion Kinase that mediates cell attachment via integrins. Single cells from primary breast cancers self-organized into tumoroids on prolonged culture. Response of the tumoroids to two chemotherapeutic drugs, doxorubicin and mitoxanthrone, varied significantly across patient samples. This model could be used as an ex vivo platform to culture primary cells toward developing effective and personalized chemotherapy regimens
A Single Atom Change Facilitates the Membrane Transport of Green Fluorescent Proteins in Mammalian Cells
No full textDirect delivery of proteins into mammalian cells is a challenging problem in biological and biomedical applications. The most common strategies for the delivery of proteins into the cells include the use of cell-penetrating peptides or supercharged proteins. Herein, we show for the first time that a single atom change, hydrogen to halogen, at one of the tyrosine residues can increase the cellular entry of similar to 28kDa green fluorescent protein (GFP) in mammalian cells. The protein uptake is facilitated by a receptor-mediated endocytosis and the cargo can be released effectively into cytosol by co-treatment with the endosomolytic peptide ppTG21
Conductivity noise across temperature-driven transitions of rare-earth nickelate heterostructures
No full textThe metal-insulator transition (MIT) of bulk rare-earth nickelates is accompanied by a simultaneous charge ordering (CO) transition. We have investigated low-frequency resistance fluctuations (noise) across the MIT and magnetic transition of EuNiO3/LaNiO3] superlattices, where selective suppression of charge ordering has been achieved by mismatching the superlattice periodicity with the periodicity of charge ordering. We have observed that irrespective of the presence or absence of long-range CO, the noise magnitude is enhanced by several orders with a strong non-1/f (f = frequency) component when the system undergoes a MIT and magnetic transition. The higher-order statistics of resistance fluctuations reveal the presence of strong non-Gaussian components in both cases, further indicating inhomogeneous electrical transport arising from the electronic phase separation. Specifically, we find almost three orders of magnitude smaller noise in the insulating phase of the sample without long-range CO compared to the sample with CO. These findings suggest that digital synthesis can be a potential route to implement electronic transitions of complex oxides for device application
Sugar Vinyl Sulfoxide Glycoconjugation of Peptides and Lysozynne: Abrogation of Proteolysis at the Lysine Sites
No full textWe describe a glycoconjugation strategy in which a sugar vinyl sulfoxide, acting as Michael donor, reacts efficiently with amine nucleophiles arising from the lysine side chain in peptides and proteins, at physiological pH and temperature. The method permits glycoconjugation of the lysine residues present in lysozyme with the sugar vinyl sulfoxide. The glycoconjugation of the protein abrogates the trypsin-mediated proteolysis at the lysine sites. The modified protein catalyzes digestion of the Gram-negative Escherichia coli cell wall and retains the same antimicrobial property as the native lysozyme
Directing Traffic: Halogen-Bond-Mediated Membrane Transport
No full textThe plasma membrane regulates the transport of molecules into the cell. Small hydrophobic molecules can diffuse directly across the lipid bilayer. However, larger molecules require specific transporters for their entry into the cell. Regulating the cellular entry of small molecules and proteins is a challenging task. The introduction of halogen, particularly iodine, to small molecules and proteins is emerging to be a promising strategy to improve the cellular uptake. Recent studies reveal that a simple substitution of hydrogen atom with iodine not only increases the cellular uptake, but also regulates the membrane transport. The strong halogen-bond-forming ability of iodine atoms plays a crucial role in the transport and the introduction of iodine may provide an efficient strategy for studying membrane activity and cellular functions and improving the delivery of therapeutic agents. This Concept article does not provide a comprehensive picture of membrane transport but highlights halogen-substitution as a novel strategy for understanding and regulating the cell-membrane traffic
Extraction of Trench Capacitance and Reverse Recovery Time of InGaAs Self-Switching Diode
No full textIn this paper, we have presented the transient analysis of an InGaAs based novel nano diode called self-switching device utilizing Silvaco TCAD simulator. The device exhibits current-voltage (I-V) characteristics analogous to a conventional diode without requiring any p-n junction. The cut-in voltage and the output current of the device can be tuned by varying channel width and length, respectively. The charging/discharging time (RC time constants) have been extracted from the I-V characteristics of the device demonstrating almost very small reverse recovery time of the order of 10(-9) s, which significantly affects the device on-off switching. Furthermore, results are validated by implementing the conformal mapping technique to extract device capacitance, which in turn predicts device charging and discharging, and hence, reverse recovery time to enable high frequency operation. Additionally, it is demonstrated that small reverse recovery time enables SSDs to rectify the input signal without requiring additional filter circuitry
Microstructure and texture development in Ti-15V-3Cr-3Sn-3A1 alloy-Possible role of strain path
No full textIn the present investigation, evolution of microstructure and texture was studied for a beta titanium alloy during cold rolling (unidirectional rolling (UDR) and cross rolling (multi-step cross rolling (MSCR) and two step cross rolling). For both UDR and MSCR of initially hot rolled alloy consisting of elongated and equiaxed grain structure, the occurrence of shear bands inside the grains was the main feature of the microstructure. The density of these shear bands was dependent on the cold rolling reduction and strain path and was found to be orientation dependent. Shear bands preferentially occurred in gamma-fiber (normal direction (ND)//< 111 >) oriented grains. The regions with shear bands had higher hardness than the regions without shear bands, and {111}< 112 > component of the gamma-fiber was found to be more susceptible to formation of shear bands. The orientation dependence of these shear bands was analyzed within the framework of Dillamore's plastic instability criterion. During UDR, strong alpha and gamma-fibers were observed after highest strain (epsilon = 1.6), while strong rotated cube ({100}< 110 >) texture developed after MSCR at highest strain (epsilon = 1.6). The volume fraction of both alpha and gamma fibers gradually increased with the increase in cold rolling reduction during UDR. For MSCR, the rotated cube component gradually increased with increase in cold rolling reduction. In solution annealed beta-Ti alloy with equiaxed grain structure, alpha and gamma fibers were formed after highest strain (epsilon = 1.6) during UDR. However, due to large grain size, both alpha and gamma fibers were discontinuous. The texture development was found to be more strongly dependent on the strain path than the initial microstructure during cold rolling
Alluaudite NaCoFe2(PO4)(3) as a 2.9 V Cathode for Sodium-Ion Batteries Exhibiting Bifunctional Electrocatalytic Activity
No full textDeveloping novel earth-abundant and high energy density cathode materials is pivotal to realize the enduring energy storage revolution. Alluaudites NaxMy(XO4)(3) (M = Mn, Fe, Co, Ni; X = Mo, W, P, As, S), as a competent series of sodium insertion cathode contenders, have attracted wide scientific attention in recent years due to their unique open framework geometry, structural flexibility, scalable synthesis, and desirable electro- chemical performance. Exploring the alluaudite family of sodium insertion systems, we herein present a hitherto unknown NaCoFe2(PO4)(3) alluaudite prepared by an economic solution combustion technique. Rietveld analysis of powder X-ray diffraction pattern identified the formation of alluaudite-type monoclinic C-2/c phase with a = 11.750(3) angstrom, b = 12.459(1) angstrom, c = 6.383(3) angstrom, and unique angle beta = 113.711(7)degrees. As confirmed by bond valence site energy calculations, the structure renders two distinct tunnels: Na(1) and Na(2), for the one-dimensional migration of Nat ions along the c-direction. Computational modeling revealed a migration barrier of E-a similar to 0.31 eV for Na(2), which is one of the lowest values for Na+- conducting materials. Preliminary electrochemical study on the as-synthesized NaCoFe2 (PO4)(3) alluaudite exhibited reversible sodium intercalation involving a 2.9 V Fe3+/Fe2+ redox activity delivering capacity similar to 70 mAh/g with good cyclability over 100 cycles. Taking advantage of transition metal active centers and PO4 linkage, NaCoFe2(PO4)(3) further showed efficient bifunctional electrocatalytic activity with near four electron transfer reaction. With favorable diffusional and electrochemical performance, the discovery of alluaudite NaCoFe2(PO4)(3) introduces a novel 3 V class of cathode for sodium-ion batteries. It not only enriches the materials database of sodium insertion compounds, but also enables its possible application in metal-air batteries and water splitting