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1.
J Nanosci Nanotechnol ; 20(2): 709-718, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31383066

RESUMO

We report the preparation and characterization of a new heterostructured Ag-TiO2/ZnFe2O4 (ATZ) nanocomposite. X-ray diffraction (XRD) reveals the presence of spinel type ZnFe2O4 and anatase TiO2. Scanning electron microscope (SEM) images of ATZ nanocomposites show that Ag nanoparticles are successfully loaded on the composite Ag-TiO2 and is uniformly distributed on surface of ZnFe2O4 forming a nanocomposite with an approximate particle size of 44.8 nm. High-resolution transmission electron microscope (HR-TEM) analysis clearly indicates the particles with spherical and hexagonal structure and sizes of most of the particles are below 50 nm. Ultra violet-visible diffuse reflectance spectra (UV-vis-DRS) show that Ag-TiO2/ZnFe2O4 has increased visible absorption than TiO2. Photoluminescence (PL) spectra shows that the intensity of ATZ is low relative to prepared TiO2. The photocatalytic degradation of Reactive Yellow 86 (RY 86) dye was studied. Based on the band gap energies of TiO2 and ZnFe2O4, a mechanism of degradation is given. Photocatalytic activity results suggest that as-prepared ATZ shows higher photodegradation efficiency than pure TiO2. The main reactive oxidative species involved in the degradation and stability of photocatalyst were also investigated. ATZ shows higher electrocatalytic activity than TiO2 for methanol electrooxidation. The cytotoxicity of ATZ was analysed. Multifunctionality of ATZ makes it useful for environmental and biomedical applications.

2.
J Nanosci Nanotechnol ; 19(12): 8163-8171, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31196340

RESUMO

A simple and efficient one pot synthesis of 1,2,4,5-tetra substituted imidazoles is achieved by condensation-cyclization reaction of benzil, aromatic aldehyde, 2-amino ethyl pyrrolidine, ammonium acetate using fly ash loaded Bi2O3-ZnO. Different substituted aldehydes have been used in this reaction. The process is operationally simple, environmentally safe and has magnificent yield. Furthermore this catalyst can be recycled at least four times without any loss of activity.

3.
Rev Sci Instrum ; 90(4): 044702, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31042982

RESUMO

Atomic physics experiments commonly use millitesla-scale magnetic fields to provide a quantization axis. As atomic transition frequencies depend on the magnitude of this field, many experiments require a stable absolute field. Most setups use electromagnets, which require a power supply stability not usually met by commercially available units. We demonstrate the stabilization of a field of 14.6 mT to 4.3 nT rms noise (0.29 ppm), compared to noise of >100 nT without any stabilization. The rms noise is measured using a field-dependent hyperfine transition in a single 43Ca+ ion held in a Paul trap at the center of the magnetic field coils. For the 43Ca+ "atomic clock" qubit transition at 14.6 mT, which depends on the field only in second order, this would yield a projected coherence time of many hours. Our system consists of a feedback loop and a feedforward circuit that control the current through the field coils and could easily be adapted to other field amplitudes, making it suitable for other applications such as neutral atom traps.

4.
J Nanosci Nanotechnol ; 19(8): 5089-5099, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30913824

RESUMO

The Activated Charcoal supported Bi2O3-ZnO (AC-BZ) nanocomposite is successfully synthesized by simple and efficient hydrothermal followed by thermal decomposition method. The addition of Activated charcoal into the Bi2O3-ZnO matrices increases the active sites and shows efficient catalytic activity upon the degradation of azo dyes, Rhodamine-B (Rh-B) and Trypan Blue (TB). Prepared photocatalysts further prove its ability by the way of structure and absorption capacity. For understanding the efficiency of photocatalyst, it was characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Field Emission Transmission Electron Microscopy (FE-TEM), High Resolution Transmission Electron Microscopy (HR-TEM), Diffused Reflectance Spectroscopy (UV-DRS), Photo Luminescense spectroscopy (PL) and N2 adsorption- desorption isotherms (BET). The FESEM images of the activated charcoal supported Bi2O3-ZnO show a nanocomposite structure and reveal that most of particles have hexagonal and spherical type in nano range. Absorption range and band gap energy were examined by UV-DRS techniques, which indicate the photogenerated electrons and holes are responsible for better photocatalytic activity. The prepared AC-BZ nanocomposite has maximum efficiency at pH 7, and it shows enhanced degradation efficiency up to four cycles which proves reusability of the catalyst. The obtained catalyst shows higher efficiency in self cleaning property by forming maximum degree of contact angle when compared with pure ZnO and Bi2O3-ZnO. This work may provide new strategy for eco-friendly and cost effective photocatalysts for various applications.

5.
Nature ; 555(7694): 75-78, 2018 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-29493595

RESUMO

Quantum bits (qubits) based on individual trapped atomic ions are a promising technology for building a quantum computer. The elementary operations necessary to do so have been achieved with the required precision for some error-correction schemes. However, the essential two-qubit logic gate that is used to generate quantum entanglement has hitherto always been performed in an adiabatic regime (in which the gate is slow compared with the characteristic motional frequencies of the ions in the trap), resulting in logic speeds of the order of 10 kilohertz. There have been numerous proposals of methods for performing gates faster than this natural 'speed limit' of the trap. Here we implement one such method, which uses amplitude-shaped laser pulses to drive the motion of the ions along trajectories designed so that the gate operation is insensitive to the optical phase of the pulses. This enables fast (megahertz-rate) quantum logic that is robust to fluctuations in the optical phase, which would otherwise be an important source of experimental error. We demonstrate entanglement generation for gate times as short as 480 nanoseconds-less than a single oscillation period of an ion in the trap and eight orders of magnitude shorter than the memory coherence time measured in similar calcium-43 hyperfine qubits. The power of the method is most evident at intermediate timescales, at which it yields a gate error more than ten times lower than can be attained using conventional techniques; for example, we achieve a 1.6-microsecond-duration gate with a fidelity of 99.8 per cent. Faster and higher-fidelity gates are possible at the cost of greater laser intensity. The method requires only a single amplitude-shaped pulse and one pair of beams derived from a continuous-wave laser. It offers the prospect of combining the unrivalled coherence properties, operation fidelities and optical connectivity of trapped-ion qubits with the submicrosecond logic speeds that are usually associated with solid-state devices.

6.
Immunity ; 12(5): 581-90, 2000 May.
Artigo em Inglês | MEDLINE | ID: mdl-10843390

RESUMO

Caspases are intracellular proteases that mediate mammalian cell apoptosis. Caspase-1 (Casp-1) is a unique caspase because it activates the proinflammatory cytokines interleukin (IL)-1beta and IL-18. Shigella flexneri, the etiological agent of bacillary dysentery, induces macrophage apoptosis, which requires Casp-1 and results in the release of mature IL-1beta and IL-18. Here we show that casp-1(-/-) mice infected with S. flexneri do not develop the acute inflammation characteristic of shigellosis and are unable to resolve the bacterial infection. Using casp-1(-/-) mice supplemented with recombinant cytokines and experiments with IL-1beta(-/-) and IL-18(-/-) mice, we show that IL-1beta and IL-18 are both required to mediate inflammation in S. flexneri infections. Together, these data demonstrate the importance of Casp-1 in acute inflammation and show the different roles of its substrates, IL-1beta and IL-18, in this response.


Assuntos
Caspase 1/imunologia , Disenteria Bacilar/imunologia , Interleucina-18/imunologia , Interleucina-1/imunologia , Shigella flexneri , Animais , Disenteria Bacilar/metabolismo , Imuno-Histoquímica , Inflamação/imunologia , Camundongos , Especificidade por Substrato/imunologia
7.
Infect Immun ; 65(12): 5165-70, 1997 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9393811

RESUMO

Shigella, the etiological agent of bacillary dysentery, rapidly kills human monocyte-derived macrophages in vitro. Wild-type Shigella flexneri, but not a nonvirulent derivative, induced human macrophage apoptosis as determined by morphology and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL). Shigella-mediated macrophage cell death was blocked by the peptide inhibitors of caspases, acetyl-Tyr-Val-Ala-Asp-aldehyde (acetyl-YVAD-CHO) and acetyl-Tyr-Val-Ala-Asp-chloromethylketone (acetyl-YVAD-CMK). Protection from apoptosis by YVAD was observed in monocytes matured in the presence or absence of colony-stimulating factors (CSF) like macrophage-CSF or granulocyte-macrophage-CSF. Furthermore, lipopolysaccharide (LPS) or gamma interferon (IFN-gamma) rendered human macrophages partially resistant to Shigella cytotoxicity. Macrophages stimulated with either LPS or IFN-gamma were also protected by YVAD from Shigella-induced cell death. During Shigella infections of human macrophages, interleukin-1beta (IL-1beta) was cleaved to the mature form. IL-1beta maturation was severely retarded by YVAD, indicating that IL-1beta-converting enzyme (ICE; caspase 1) is activated in Shigella-induced apoptosis. The finding that Shigella induces apoptosis in human macrophages by activating ICE supports the hypothesis that the acute inflammation characteristic of shigellosis is initially triggered by apoptotic macrophages which release mature IL-1beta during programmed cell death.


Assuntos
Apoptose , Cisteína Endopeptidases/metabolismo , Disenteria Bacilar/enzimologia , Disenteria Bacilar/patologia , Macrófagos/microbiologia , Shigella flexneri , Caspase 1 , Células Cultivadas , Humanos , Interleucina-1/metabolismo , Macrófagos/enzimologia , Macrófagos/patologia , Monócitos
8.
Infect Immun ; 65(2): 787-93, 1997 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9009343

RESUMO

Shigellae are the most prevalent etiological agents of dysentery. A crucial step in shigella pathogenesis is the induction of macrophage apoptosis. The invasion plasmid antigen B (IpaB) is necessary and sufficient to induce macrophage programmed cell death. IpaB activates apoptosis by binding to interleukin-1 beta (IL-1 beta)-converting enzyme (ICE) or a highly homologous protease. Here, we show that IpaB is disseminated throughout the cytoplasm of shigella-infected macrophages as detected by both immunofluorescence and immunoelectron microscopy. The cytoplasmic distribution of IpaB requires phagosome escape, and it is specific to IpaB, since lipopolysaccharide, used here as a bacterial marker, remains closely associated with the bacteria. In double-labeling experiments, we show that IpaB and ICE colocalize in the cytoplasm of the macrophage, suggesting that soon after secretion, IpaB binds to ICE to initiate apoptosis and to promote the cleavage of IL-1 beta.


Assuntos
Adesinas Bacterianas , Proteínas de Bactérias/metabolismo , Cisteína Endopeptidases/metabolismo , Citoplasma/enzimologia , Citoplasma/metabolismo , Interleucina-1/metabolismo , Macrófagos/metabolismo , Shigella flexneri/metabolismo , Animais , Proteínas de Bactérias/ultraestrutura , Caspase 1 , Humanos , Macrófagos/enzimologia , Macrófagos/ultraestrutura , Microscopia Imunoeletrônica , Shigella flexneri/patogenicidade , Shigella flexneri/ultraestrutura , Frações Subcelulares/metabolismo
9.
Infect Immun ; 64(12): 5357-65, 1996 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-8945588

RESUMO

Shigella flexneri, an etiological agent of bacillary dysentery, causes apoptosis in vitro. Here we show that it also induces apoptosis in vivo. We were able to quantify the number of apoptotic cells in rabbit Peyer's patches infected with S. flexneri by detecting cells with fragmented DNA. Infection with virulent S. flexneri results in massive numbers of apoptotic cells within the lymphoid follicles. In contrast, neither an avirulent strain nor an avirulent strain capable of colonizing Peyer's patches increases the background level of apoptotic cells. Macrophages, T cells, and B cells are shown to undergo apoptosis in vivo. These results indicate that apoptosis may play a crucial role in the pathogenesis of shigellosis.


Assuntos
Apoptose , Disenteria Bacilar/patologia , Nódulos Linfáticos Agregados/patologia , Shigella flexneri , Animais , Disenteria Bacilar/microbiologia , Microscopia Eletrônica , Nódulos Linfáticos Agregados/microbiologia , Nódulos Linfáticos Agregados/ultraestrutura , Coelhos
10.
EMBO J ; 15(15): 3853-60, 1996 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-8670890

RESUMO

Shigella, the etiological agent of dysentery, kills macrophages by inducing apoptosis. Deletion mutants in the invasion invasion plasmid antigen B (ipaB) of Shigella flexneri are not cytotoxic. Here, we localized IpaB to the cytoplasm of macrophages infected with S. flexneri. Purified IpaB induced apoptosis when microinjected into macrophages, indicating that IpaB is sufficient to induce apoptosis. Using a GST-IpaB fusion protein as a ligand in affinity purification, we isolated four IpaB binding proteins from macrophages which were identified as the precursor and the mature polypeptides of interleukin-1beta converting enzyme (ICE) or a highly homologous protease. We found that IpaB binds directly to ICE and this enzyme is activated during S. flexneri infection. Furthermore, specific inhibitors of ICE prevented Shigella-induced apoptosis.


Assuntos
Adesinas Bacterianas , Apoptose , Proteínas de Bactérias/metabolismo , Cisteína Endopeptidases/metabolismo , Macrófagos/citologia , Shigella flexneri/patogenicidade , Western Blotting , Caspase 1 , Cromatografia de Afinidade , Técnica Direta de Fluorescência para Anticorpo , Glutationa Transferase/metabolismo , Células HeLa , Humanos , Interleucina-1/metabolismo , Ligação Proteica
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