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1.
Proc Natl Acad Sci U S A ; 115(20): 5145-5150, 2018 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-29712867

RESUMO

The Levantine Aurignacian is a unique phenomenon in the local Upper Paleolithic sequence, showing greater similarity to the West European classic Aurignacian than to the local Levantine archaeological entities preceding and following it. Herewith we highlight another unique characteristic of this entity, namely, the presence of symbolic objects in the form of notched bones (mostly gazelle scapulae) from the Aurignacian levels of Hayonim Cave, Lower Galilee, Israel. Through both macroscopic and microscopic analyses of the items, we suggest that they are not mere cut marks but rather are intentional (decorative?) human-made markings. The significance of this evidence for symbolic behavior is discussed in its chrono-cultural and geographical contexts. Notched bones are among the oldest symbolic expressions of anatomically modern humans. However, unlike other Paleolithic sites where such findings were reported in single numbers, the number of these items recovered at Hayonim Cave is sufficient to assume they possibly served as an emblem of the Levantine Aurignacian.

2.
Angew Chem Int Ed Engl ; 56(35): 10506-10510, 2017 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-28678439

RESUMO

A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm-2 , representing outstanding catalytic activity and stability because of Fe(OH)2 /FeOOH active sites formed at the surface of FeSe2 . Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.

3.
Chem Commun (Camb) ; 53(57): 8018-8021, 2017 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-28664206

RESUMO

The strikingly high catalytic performance and stability of manganese substituted cobalt oxide spinel (MnxCo3-xO4) over pristine cobalt oxide spinel (Co3O4) for the alkaline electrochemical water oxidation is reported. The different role of cations could be uncovered along with the detection of drastic surface-structural changes during the catalysis using spectroscopic and microscopic methods.

4.
J Colloid Interface Sci ; 505: 692-702, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-28658655

RESUMO

A successful methodology for obtaining hybrid films which allow thermal triggering and continuous, irreversible, control of their hydrophilicity/hydrophobicity nature was developed. Two types of poly(dimethylsiloxane)-silica (PDMS@SiO2) films were prepared for that purpose: A hydrophilic film in which the thermal treatment causes an irreversible gradual increase of hydrophobicity; and a hydrophobic film that turns more hydrophilic upon thermal treatment. The opposite directionality of the change is dictated by the film substrate, on which the same hybrid is deposited. In both cases the thermal treatment induced a phase separation which caused the change in hydrophobicity. The magnitude of change in hydrophilicity/hydrophobicity is continuously controllable in both types of films by either the temperature or heating time. The films were characterized before and after heating by a variety of methods, including contact angle (CA) measurements with the sessile drop and the tilting plate methods, and by X-ray photoelectron spectroscopy (XPS) analysis. A thorough kinetic study was carried out, following the progress of the changes in the wettability property of the surfaces. The kinetics analyses proved that the changes in the wettability in all cases are due to phase separation processes, the directionality of which is determined by the treatment of the substrate on which the films are deposited. By monitoring the change of wettability (ΔCA) at various temperatures, an Arrhenius plot was obtained from which the activation energy and Arrhenius pre-exponential factor for the phase separation were derived, corroborating the proposed mechanism. To the best of our knowledge, this is the first use of phase separation behavior of a hybrid film in order to apply irreversible, thermally controllable change of surface wettability, tailored to proceed in opposite directions, and the first kinetic study of such a process.

5.
ACS Nano ; 11(3): 3247-3253, 2017 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-28234445

RESUMO

Cu2+-functionalized carbon nitride nanoparticles (Cu2+-g-C3N4 NPs), ∼200 nm, and Cu2+-carbon dots (Cu2+-C-dots), ∼8 nm, act as horseradish peroxidase-mimicking catalysts. The nanoparticles catalyze the generation of chemiluminescence in the presence of luminol/H2O2 and catalyze the oxidation of dopamine by H2O2 to form aminochrome. The Cu2+-g-C3N4-driven generation of chemiluminescence is used to develop a H2O2 sensor and is implemented to develop a glucose detection platform and a sensor for probing glucose oxidase. Also, the Cu2+-C-dots are functionalized with the ß-cyclodextrin (ß-CD) receptor units. The concentration of dopamine, at the Cu2+-C-dots' surface, by means of the ß-CD receptor sites, leads to a 4-fold enhancement in the oxidation of dopamine by H2O2 to yield aminochrome compared to that of the unmodified C-dots.

6.
Adv Mater ; 28(24): 4944, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27311096

RESUMO

D. Porath, A. Kotlyar, and co-workers transform DNA to a conducting material by metalization through coating or chemical modifications, as described on page 4839. Specific and reversible metalization of poly(dG)-poly(dC) DNA by migration of atoms from silver nanoparticles to the DNA is demonstrated. As the transformation occurs gradually, novel, truly hybrid molecular structures are obtained, paving the way to their usage as nanowires in programmable molecular electronic devices and circuits.


Assuntos
DNA/química , Prata/química , Nanopartículas Metálicas/química , Nanofios/química
7.
PLoS One ; 11(4): e0151804, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27049960

RESUMO

We describe a new species of gundi (Rodentia: Ctenodactylidae: Ctenodactylinae), Sayimys negevensis, on the basis of cheek teeth from the Early Miocene of the Rotem Basin, southern Israel. The Rotem ctenodactylid differs from all known ctenodactylid species, including Sayimys intermedius, which was first described from the Middle Miocene of Saudi Arabia. Instead, it most resembles Sayimys baskini from the Early Miocene of Pakistan in characters of the m1-2 (e.g., the mesoflexid shorter than the metaflexid, the obliquely orientated hypolophid, and the presence of a strong posterolabial ledge) and the upper molars (e.g., the paraflexus that is longer than the metaflexus). However, morphological (e.g., presence of a well-developed paraflexus on unworn upper molars) and dimensional (regarding, in particular, the DP4 and M1 or M2) differences between the Rotem gundi and Sayimys baskini distinguish them and testify to the novelty and endemicity of the former. In its dental morphology, Sayimys negevensis sp. nov. shows a combination of both the ultimate apparition of key-characters and incipient features that would be maintained and strengthened in latter ctenodactylines. Thus, it is a pivotal species that bridges the gap between an array of primitive ctenodactylines and the most derived, Early Miocene and later, gundis.


Assuntos
Evolução Biológica , Dente Molar/anatomia & histologia , Roedores/classificação , Dente/anatomia & histologia , Animais , Fósseis , Israel , Paquistão , Filogenia , Arábia Saudita
8.
Adv Mater ; 28(24): 4839-44, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27116695

RESUMO

Migration of silver atoms from silver nano-particles selectively to a double-stranded poly(dG)-poly(dC) polymer leads to metallization of the DNA. As a result the DNA molecules become shorter and thicker (higher), as evident from the atomic force microscopy imaging analysis. The metalized molecules can be detected by transmission and scanning electron microscopy in contrast to the initial non-metalized ones.


Assuntos
DNA/síntese química , DNA/ultraestrutura , Prata/química , DNA/química , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Polímeros
9.
Photomed Laser Surg ; 33(3): 129-35, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25719951

RESUMO

OBJECTIVE: The purpose of this study was to compare the efficacy of three irrigation techniques for smear-layer removal with 17% EDTA. BACKGROUND DATA: Cleaning and shaping the root canal system during endodontic treatment produces a smear layer and hard tissue debris. Three irrigation techniques were tested for solution infiltration of this layer: positive-pressure irrigation, passive ultrasonic irrigation, and laser-activated irrigation. MATERIALS AND METHODS: Sixty extracted teeth were divided into six equal groups; 17% EDTA was used for 60 sec irrigation of five of the groups. The groups were as follows: Group 1, treated only with ProTaper™ F3 Ni-Ti files; Group 2, positive-pressure irrigation, with a syringe; Group 3, passive ultrasonic irrigation, inserted 1 mm short of the working length; Group 4, passive ultrasonic irrigation, inserted in the upper coronal third of the root; Group 5, Er:YAG laser-activated irrigation, inserted 1 mm short of the working length; and Group 6, Er:YAG laser-activated irrigation, inserted in the upper coronal third of the root. RESULTS: Scanning electron microscopy showed that the smear layer is removed most efficiently using laser-activated irrigation at low energy with 17% EDTA, inserted either at the working length or only in the coronal upper third of the root. Amounts of Ca, P, and O were not significantly different on all treated dentin surfaces. CONCLUSIONS: Smear-layer removal was most effective when the root canals were irrigated using Er:YAG laser at low energy with 17% EDTA solution. Interestingly, removal of the smear layer along the entire canal was similar when the laser was inserted in the upper coronal third and at 1 mm short of the working length of the root canal. This effect was not observed with the ultrasonic and positive-pressure techniques.


Assuntos
Preparo de Canal Radicular/métodos , Irrigação Terapêutica/métodos , Humanos , Lasers , Pressão , Ultrassom
10.
Chem Commun (Camb) ; 51(24): 5005-8, 2015 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-25705747

RESUMO

Nickel-manganese oxides with variable Ni : Mn ratios, synthesised from heterobimetallic single-source precursors, turned out to be efficient water oxidation catalysts. They were subjected to oxidant-driven, photo- and electro-catalytic water oxidation showing superior activity and remarkable stability. In addition, a structure-activity relation could be established.

11.
Langmuir ; 29(32): 10102-9, 2013 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-23859476

RESUMO

This article describes single-molecule force spectroscopy measurements of the interaction between individual amino acid residues and inorganic surfaces in an aqueous solution. In each measurement, there is an amino acid residue, lysine, glutamate, phenylalanine, leucine, or glutamine, and each represents a class of amino acids (positively or negatively charged, aromatic, nonpolar, and polar). Force-distance curves measured the interaction of the individual amino acid bound to a silicon atomic force microscope (AFM) tip with a silcon substrate, cut from a single-crystal wafer, or mica. Using this method, we were able to measure low adhesion forces (below 300 pN) and could clearly determine the strength of interactions between the individual amino acid residues and the inorganic substrate. In addition, we observed how changes in the pH and ionic strength of the solution affected the adsorption of the residues to the substrates. Our results pinpoint the important role of hydrophobic interactions among the amino acids and the substrate, where hydrophobic phenylalanine exhibited the strongest adhesion to a silicon substrate. Additionally, electrostatic interactions also contributed to the adsorption of amino acid residues to inorganic substrates. A change in the pH or ionic strength values of the buffer altered the strength of interactions among the amino acids and the substrate. We concluded that the interplay between the hydrophobic forces and electrostatic interactions will determine the strength of adsorption among the amino acids and the surface. Overall, these results contribute to our understanding of the interaction at the organic-inorganic interface. These results may have implications for our perception of the specificity of peptide binding to inorganic surfaces. Consequently, it would possibly lead to a better design of composite materials and devices.


Assuntos
Aminoácidos/química , Silício/química , Interações Hidrofóbicas e Hidrofílicas , Microscopia de Força Atômica , Fenilalanina/química , Propriedades de Superfície
12.
Photomed Laser Surg ; 31(7): 334-41, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23763481

RESUMO

UNLABELLED: Abstract Objective: The purpose of this study was to evaluate mineral content and surface morphology of root canals coated with Enterococcus faecalis biofilm after treatment with several endodontic irrigation solutions, with and without Er:YAG laser-activated irrigation (LAI). BACKGROUND DATA: LAI has been introduced as a powerful method for root canal irrigation resulting in smear-layer removal from the root canal wall. METHODS: Distal and palatal roots from 60 freshly extracted human molars were used in this study. The coronal of each tooth was removed. Roots were split longitudinally and placed in an ultrasonic bath to remove the smear layer, creating conditions for the formation of E. faecalis biofilm. After incubation, the two halves were reassembled in impression material to simulate clinical conditions. Specimens were divided into two main groups: roots rinsed with irrigation solutions and roots subjected to laser irradiation combined with irrigation solutions. Solutions tested were 2% chlorhexidine and 17% ethylenediaminetetraacetic acid (EDTA) and saline. RESULTS: Surface morphology: 17% EDTA irrigant solution combined with Er:YAG laser showed the best results for removing bacteria from the root canal walls. Chemical analysis: all samples treated with combined laser irradiation and irrigation solution had low surface levels of Ca compared with samples treated with irrigation alone. The Ca/P ratio was highest in the laser-EDTA group. Overall, mineral changes caused by laser with irrigation solutions were minimal, and statistically nonsignificant. CONCLUSIONS: In vitro irrigation solutions, combined with Er:YAG laser irradiation, were effective in removing E. faecalis biofilm from root canal walls. Irrigation solutions without laser irradiation were less effective, leaving a layer of biofilm on the dentin surface.


Assuntos
Biofilmes , Cavidade Pulpar/microbiologia , Enterococcus faecalis/fisiologia , Lasers de Estado Sólido , Irrigantes do Canal Radicular , Humanos
13.
Langmuir ; 27(19): 11889-98, 2011 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-21863826

RESUMO

The essence of this study is to apply the Langmuir-Blodgett (LB) technique for assembling asymmetric membranes. Accordingly, Langmuir films of a (further) polymerizable polymer, 1,2-polybutadiene (1,2-pbd), were studied and transferred onto different solid supports, such as gold, indium tin oxide (ITO), and silicon. The layers were characterized both at the air/water interface as well as on different substrates using numerous methods including cyclic voltammetry, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, and reflection-absorption Fourier transform infrared spectroscopy. The Langmuir films were stable at the air-water interface as long as they were not exposed to UV irradiation. The LB films formed disorganized layers, which gradually blocked the permeation of different species with increasing the number of deposited layers. The thickness was ca. 4-7 Å per layer. Irradiating the Langmuir films caused their cross-linking at the air-water interface. Furthermore, we took advantage of the reactivity of the double bond of the LB films on the solid supports and graft polymerized acrylic acid on top of the 1,2-pbd layers. This approach is the basis of the formation of an asymmetric membrane that requires different porosity on both of its sides.


Assuntos
Butadienos/química , Butadienos/síntese química , Elastômeros/química , Elastômeros/síntese química , Membranas Artificiais , Ouro/química , Tamanho da Partícula , Silício/química , Propriedades de Superfície , Compostos de Estanho/química
14.
Am J Dent ; 24(2): 119-23, 2011 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21698993

RESUMO

PURPOSES: (1) To determine the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and acidulated phosphate fluoride (APF) on S. mutans viability, (2) to observe their effects on biofilm structure, and (3) to examine the element content of the hydroxyapatite (HA) surfaces after exposure to CPP-ACP and APF. METHODS: HA discs were coated with: CPP-ACP (GC Tooth-Mousse), APF, CPP-ACP+APF (1/1). Uncoated HA discs were used as control. Following application of the materials, the discs were immersed in human saliva and incubated with S. mutans ATCC (27315) for 24 hours. Growth of bacteria on the discs was evaluated by microbial culturing methods. The structure of the biofilm was examined with confocal laser scanning microscope (CLSM). The change in element content of HA surfaces (without biofilm) was evaluated with energy-dispersive x-ray spectroscopy (EDS). The values were statistically analyzed using Kruskal-Wallis and Dunn's test. RESULTS: The total number of bacteria of APF and CPP-ACP+APF applied groups were found significantly lower than the control group (P< 0.05). All specimens showed similar microbial colonization structure. No statistically significant differences were observed in O, F, Na, P, Ca content on HA surfaces after exposure to the tested agents, although fluoride concentration of the APF treated HA surfaces were increased compared to CPP-ACP, CPP-ACP +APF.


Assuntos
Fluoreto de Fosfato Acidulado/farmacologia , Biofilmes/efeitos dos fármacos , Cariostáticos/farmacologia , Caseínas/farmacologia , Placa Dentária/tratamento farmacológico , Streptococcus mutans/efeitos dos fármacos , Fluoreto de Fosfato Acidulado/uso terapêutico , Adulto , Cariostáticos/uso terapêutico , Caseínas/uso terapêutico , Combinação de Medicamentos , Durapatita/química , Humanos , Masculino , Viabilidade Microbiana/efeitos dos fármacos , Microscopia Confocal , Saliva , Espectrometria por Raios X , Estatísticas não Paramétricas , Remineralização Dentária/métodos
15.
Langmuir ; 26(6): 4239-45, 2010 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-20039685

RESUMO

The Langmuir-Blodgett (LB) method was used to deposit multilayers of polyaniline (PANI)- and mercaptoethanesulfonate (MES)-stabilized Au nanoparticles. The electrostatic interaction between the negatively charged nanoparticles in the subphase and the positively charged PANI at the air-water interface assisted the deposition of the nanocomposite film onto a solid support. These PANI/Au-NPs films were characterized using cyclic voltammetry, copper under potential deposition, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. We found that the nanocomposite layers were uniform and reproducible. The density of Au-NPs in the monolayer depended on the acidity of the subphase as well as on the nanoparticles concentration. Moreover, the Au-NPs extrude above the PANI and therefore could be used as nanoelectrodes for the underpotential deposition (UPD) of copper.

16.
Anal Chem ; 81(20): 8396-404, 2009 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-19764703

RESUMO

A methodology for online preconcentration of analytes and their subsequent electrochemically induced delivery to an online electrospray mass spectrometer is introduced. The approach is based on electrodeposition of an active metallic layer, silver deposit in this particular case, subsequent specific accumulation of the target analyte by electrochemical or chemical means onto the active layer, and finally oxidative electrostripping of the conductive layer along with the supported analyte to an online mass spectrometer. We demonstrate the new concept by selective electrochemical deposition of homocysteine and other organothiols directly on the working electrode of a miniature flow cell. The same approach was extended to the conjugation of the target analyte (avidin as a test case) to a thiolated ligand (biotin in this case) that was electrodeposited on the silver coated surface. Electrostripping of the silver dissolves the target species and allows their delivery to an online ESI-MS. Furthermore, the dissolved silver ions promote ionization, and its characteristic isotopic pattern assists in the identification of the target analyte.


Assuntos
Eletroquímica/métodos , Proteínas/análise , Espectrometria de Massas por Ionização por Electrospray/métodos , Avidina/análise , Avidina/química , Quelantes/química , Eletrodos , Humanos , Ligantes , Sistemas On-Line , Espectroscopia Fotoeletrônica , Proteínas/química , Prata/química , Compostos de Sulfidrila/química
17.
ACS Appl Mater Interfaces ; 1(11): 2519-28, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20356122

RESUMO

Drug-eluting stents (DESs) have been associated with adverse clinical effects. Moreover, recent publications have shown that the coating of DESs suffers from defects. The purpose of this contribution is to examine a three-step process for surface modification as a means of improving the durability of DESs. In the first step, 4-(2-bromoethyl)benzenediazonium tetrafluoroborate was electrografted onto a stainless steel (SS) stent. X-ray photoelectron spectroscopy (XPS) of the modified stent confirmed the formation of the organic layer. In the second step, methyl methacrylate was polymerized onto the grafted surface by atom-transfer radical polymerization. XPS, electrochemical impedance spectroscopy, and contact-angle measurements were used to characterize the polymer brushes. The last step involved spray-coating of the stent with a drug-in-polymer matrix [poly(n-butyl methacrylate)/poly(ethylene-co-vinyl acetate) + paclitaxel]. Scanning electron microscopy confirmed the considerably improved durability of the drug-in-polymer matrix. Bare controls showed greater cracking and delamination of the coating than did the two-step modified stents after incubation under physiological (37 degrees C) and accelerated (60 degrees C) conditions. Finally, paclitaxel controlled release from the modified SS DESs was moderate compared with that of nontreated samples. In conclusion, the proposed method significantly improves the durability of drug-in-polymer matrixes on a SS DESs.


Assuntos
Stents Farmacológicos , Paclitaxel/farmacologia , Polimetil Metacrilato/química , Aço Inoxidável/química , Boratos , Ácidos Bóricos/química , Tampões (Química) , Preparações de Ação Retardada/farmacologia , Técnicas Eletroquímicas , Microscopia Eletrônica de Varredura , Peso Molecular , Espectroscopia Fotoeletrônica , Propriedades de Superfície/efeitos dos fármacos , Água/química
19.
Langmuir ; 22(25): 10483-9, 2006 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-17129019

RESUMO

A photoisomerizable thiolated nitrospiropyran SP, (1a), monolayer is assembled on a Au electrode by the primary deposition of thiolated nitromerocyanine isomer 1b as a monolayer on the electrode, followed by the irradiation of the surface with visible light, lambda > 475 nm. The surface coverage of nitrospiropyran units (1a) on the electrode is 2 x 10-10 mole cm-2. Irradiation of the electrode with UV light, 320 nm < lambda < 360 nm, results in the nitromerocyanine, MR, monolayer on the electrode that binds Ag+ ions to the phenolate units. The Ag+ ions associated with the MR monolayer undergo cyclic reduction to surface-confined Ag0 nanoclusters, and reoxidation and dissolution of the Ag0 nanoclusters to Ag+ ions associated with the monolayer are demonstrated. The electron-transfer rate constants for the reduction of Ag+ to Ag0 and for the dissolution of Ag0 were determined by chronoamperometry and correspond to ketred = 12.7 s-1 and ketox = 10.5 s-1, respectively. The nanoclustering rate was characterized by surface plasmon resonance measurements, and it proceeds on a time scale of 10 min. The size of the Ag0 nanoclusters is in the range of 2 to 20 nm. The electrochemically induced reduction of the MR-Ag+ monolayer to the MR-Ag0 surface and the reoxidation of the MR-Ag0 surface control the hydrophilic-hydrophobic properties of the surface. The advancing contact angle of the MR-Ag0-functionalized surface is 59 degrees , and the contact angle of the MR-Ag+-monolayer-functionalized surface is 74 degrees . Photoisomerization of the Ag0-MR surface to the Ag0-SP state, followed by the oxidation of the Ag0 nanoclusters, results in the dissolution of the Ag+ ions into the electrolyte solution.


Assuntos
Ouro/química , Nanotubos/química , Prata/química , Compostos de Sulfidrila/química , Eletroquímica , Eletrodos , Estrutura Molecular , Tamanho da Partícula , Fotoquímica , Solubilidade , Compostos de Sulfidrila/efeitos da radiação , Propriedades de Superfície , Fatores de Tempo , Raios Ultravioleta
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