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1.
Org Biomol Chem ; 17(37): 8628-8635, 2019 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-31528943

RESUMO

Nucleophilic ring opening of cyclohexene oxides is known to proceed preferentially through the trans-diaxial pathway (the Fürst-Plattner rule). This preference, however, is not absolute, and can be affected by substituents on the cyclohexene oxide ring, as illustrated by LiAlH4 ring-opening of the cis- and trans-isomers of 4-t-butyl- and 3-methylcyclohexene oxide (cis- and trans-1, cis- and trans-2). We performed B3LYP/6-31+G*(PCM) geometry optimizations to locate the chair-like and twist-boat-like transition structures for the hydride attacks on the pseudoaxial and pseudoequatorial conformers of these epoxides. Our calculations are consistent with the experimental observation of effective Fürst-Plattner control of AlH4--opening of cis-1, trans-1, and cis-2, but low selectivity in ring-opening of trans-2. Our data at B3LYP/6-31+G*(PCM) suggests this reduction in selectivity is due to a diminished pseudoequatorial preference of the 3-methyl group in trans-2 relative to that in cis-2. The two calculated chair-like transition structures for hydride opening of trans-2 differ in activation energy free energy (ΔΔG‡) by only 0.4 kcal mol-1. Thus, these calculations account for the reduced regioselectivity of ring opening seen for trans-2 by AlH4- and other nucleophiles.


Assuntos
Compostos de Alumínio/química , Cicloexenos/química , Teoria da Densidade Funcional , Compostos de Lítio/química , Óxidos/química , Conformação Molecular , Estereoisomerismo
2.
Nanoscale ; 11(32): 15347-15358, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31386746

RESUMO

A serious decline in mechanical properties of polysaccharide hydrogels caused by swelling has always been a difficult problem which greatly limited their application especially in the medical field. Herein, nonswelling high-strength natural hydrogels based on self-reinforced double-crosslinked bacterial cellulose (SDBC) were prepared. Inspired by the concept of homogeneous composite materials, by regulating the ratio of LiOH/urea alkaline solvent, the aggregation structure and nanostructure of SDBC hydrogels can be controlled, thereby a unique nanofiber-network-self-reinforced (FNSR) structure was constructed and a new self-reinforcing mechanism is proposed. The prepared SDBC hydrogels have excellent mechanical properties at a high water content (>91%) for the combination of double-crosslinking and a unique FNSR structure, which can effectively prevent crack propagation and dissipate a large amount of energy. In particular, the compressive strength can reach 3.17 MPa which is 56 times that of native bacterial cellulose (BC). It is worth mentioning that no swelling occurs for the hydrogel, and the mechanical strength still remains in excess of 90% for 15 days in water, which is favorable for promising application in underwater equipment, implantable ionic devices, and tissue engineering scaffolds. This study also opens up a new horizon for the preparation of self-reinforced hydrogels.


Assuntos
Celulose/química , Hidrogéis/química , Nanoestruturas/química , Animais , Bactérias/metabolismo , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Celulose/farmacologia , Força Compressiva , Hidrogéis/farmacologia , Compostos de Lítio/química , Camundongos , Ureia/química , Água/química
3.
Molecules ; 24(14)2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31340539

RESUMO

First-principles calculations based on the density functional theory (DFT) were carried out to study the atomic structure and electronic structure of LiAl2(OH)6Cl, the only material in the layered double hydroxide family in which delithiation was found to occur. Ab initio molecular dynamics (AIMD) simulations were used to explore the evolution of the structure of LiAl2(OH)6Cl during a thermally induced delithiation process. The simulations show that this process occurs due to the drastic dynamics of Li+ at temperatures higher than ~450 K, in which the [Al2(OH)6] host layers remain stable up to 1100 K. The calculated large value of the Li+ diffusion coefficient D, ~ 3.13 × 10 - 5 c m 2 / s , at 500 K and the high stability of the [Al2(OH)6] framework suggest a potential technical application of the partially-delithiated Li1-xAl2(OH)6Cl1-x (0 < x < 1) as a superionic conductor at high temperatures.


Assuntos
Compostos de Alumínio/química , Hidróxidos/química , Compostos de Lítio/química , Cristalização , Difusão , Simulação de Dinâmica Molecular , Teoria Quântica , Temperatura , Água/química
4.
Carbohydr Polym ; 215: 90-98, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30981375

RESUMO

A series of hydroxybutyl chitosans (HBCSs) with a degree of substitution (DS) ranging from 0.38 to 1.54 were homogeneously synthesized in KOH/LiOH/urea aqueous solutions under ambient conditions. The structure and solution properties of HBCSs were characterized by FT-IR, NMR, SEC-LLS, UV-vis, rheological and DLS measurements. The amino groups at C2 and hydroxyl groups at C3 and C6 participated in the reaction, although substitution mainly occurred at the hydroxyl groups at C6. The HBCSs exhibited good solubility in aqueous solutions, and those with a DS above 1.25 displayed phase separation behavior and precipitated out from solution when heated to a critical temperature. All results confirmed the hypothesis that the homogeneous KOH/LiOH/urea aqueous solution is a stable, mild, and energy-saving reaction medium for preparing HBCSs. Moreover, the HBCSs exhibited excellent biocompatibility, and even promoted the proliferation of normal cells. They also displayed antibacterial activities against Staphylococcus aureus and Escherichia coli, thus being suitable for biomedical applications.


Assuntos
Antibacterianos , Quitosana/análogos & derivados , Citotoxinas , Antibacterianos/síntese química , Antibacterianos/química , Antibacterianos/farmacologia , Proliferação de Células/efeitos dos fármacos , Quitosana/síntese química , Quitosana/química , Quitosana/farmacologia , Citotoxinas/síntese química , Citotoxinas/química , Citotoxinas/farmacologia , Escherichia coli/efeitos dos fármacos , Células HEK293 , Células HeLa , Humanos , Hidróxidos/química , Compostos de Lítio/química , Compostos de Potássio/química , Solubilidade , Staphylococcus aureus/efeitos dos fármacos , Temperatura , Ureia/química
5.
Org Lett ; 21(9): 3295-3298, 2019 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-31013112

RESUMO

This work characterizes a previously undetected epimerization in the preparation of alkynyl diols from pentose precursors utilizing the Ohira-Bestmann reagent. Lithium trimethylsilyldiazomethane (Colvin reagent) additions to the d-ribose and d-lyxose-derived benzylidene acetals provide the respective alkynyl diol stereoisomers, without epimerization. Regioselective tungsten-catalyzed cycloisomerizations of the d-ribose- and d-lyxose-derived alkynyl diols yield rigid bicyclic pyranose glycals, confirming the stereochemical fidelity of the Colvin alkynylation process.


Assuntos
Alquinos/química , Éteres Cíclicos/síntese química , Pentoses/química , Acetais/química , Álcoois/química , Catálise , Compostos de Lítio/química , Estrutura Molecular , Ribose/química , Estereoisomerismo , Tungstênio/química
6.
Molecules ; 24(3)2019 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-30759856

RESUMO

The paper analyses influences of the temperature and hydrophilic groups on micellar properties of ionic surfactants with 12-carbonic hydrophobic chains. The aim is to assess the impact of hydrophilic groups and temperature on thermodynamic parameters and micellization. This knowledge is indispensable for the formulation of new dosage forms. The method uses conductometric measurements. The following hydrophilic groups are analyzed: trimethylammonium bromide, trimethylammonium chloride, ethyldimethylammonium bromide, didodecyldimethylammonium bromide, pyridinium chloride, benzyldimethyl-ammonium chloride, methylephedrinium bromide, cis and trans-[(2-benzyloxy)-cyclohexyl-methyl]-N, N-dimethylammonium bromide, sodium sulphate and lithium sulphate. Except for a few cases, there is a good agreement between values of critical micellar concentrations (CMC) and critical vesicle concentration (CVC) obtained here and those which were obtained by other authors and/or by other physicochemical methods. Values of the CMC are compared with respect to the molar masses of hydrophilic groups. It was found that CMC values increased non-linearly with increasing system temperature. The degrees of counterion binding and thermodynamic parameters, like the standard molar Gibbs energy, enthalpy and entropy of micellization are determined and discussed in detail. The results obtained will be incorporated into in silico processes of modeling and design of optimal dosage forms, a current interdisciplinary research focus of the team.


Assuntos
Íons/química , Tensoativos/química , Brometos/química , Simulação por Computador , Interações Hidrofóbicas e Hidrofílicas , Compostos de Lítio/química , Micelas , Modelos Químicos , Compostos de Amônio Quaternário/química , Sulfatos/química , Temperatura , Termodinâmica
7.
Luminescence ; 34(3): 382-386, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30784183

RESUMO

An energy transfer process from Ce3+ to Tb3+ ions was successfully achieved in a Li2 SO4 -Al2 (SO4 )3 mixed-sulphate system. A wet-chemical synthesis was employed to prepare the Li2 SO4 -Al2 (SO4 )3 system by doping Ce3+ and Tb3+ ions individually as well as collectively. The phases were identified using X-ray diffraction studies. The as-prepared samples were characterized by FT-IR and photoluminescence measurements. Green-light emission was exhibited by Ce3+ , Tb3+ co-doped Li2 SO4 -Al2 (SO4 )3 system, thus, indicating its potential as a material for display devices or in the lamp industry.


Assuntos
Compostos de Alúmen/química , Cério/química , Compostos de Lítio/química , Sulfatos/química , Térbio/química , Transferência de Energia , Luz , Luminescência , Espectroscopia de Infravermelho com Transformada de Fourier
8.
Radiat Res ; 191(2): 154-161, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30499384

RESUMO

The harmful effects of space radiation pose a serious health risk to astronauts participating in future long-term missions. Such radiation effects must be considered in the design phase of space vessels as well as in mission planning. Crew radioprotection during long periods in deep space (e.g., transit to Mars) represents a major challenge, especially because of the strong restrictions on the passive shielding load allowed on-board the vessel. Novel materials with better shielding performance compared to the "gold standard" high-density polyethylene are therefore greatly needed. Because of the high hydrogen content of hydrides, lithium hydride has been selected as a starting point for further studies of promising candidates to be used as passive shielding materials. In the current experimental campaign, the shielding performance of lithium hydride was assessed by measuring normalized dose, primary beam attenuation and neutron ambient dose equivalent using 430 MeV/u 12C, 600 MeV/u 12C and 228 MeV proton beams. The experimental data were then compared to predictions from the Monte Carlo transport codes PHITS and GRAS. The experimental results show an increased shielding effectiveness of lithium hydride compared to reference materials like polyethylene. For instance, the attenuation length for 600 MeV/u 12C primary particles in lithium hydride is approximately 20% shorter compared to polyethylene. Furthermore, the comparison results between both transport codes indicates that the standard Tripathi-based total reaction cross-section model of PHITS cannot accurately reproduce the presented experimental data, whereas GRAS shows reasonable agreement.


Assuntos
Radiação Cósmica , Compostos de Lítio/química , Proteção Radiológica/métodos , Hidrogênio/análise , Método de Monte Carlo , Doses de Radiação
9.
Radiat Prot Dosimetry ; 184(2): 248-255, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30508125

RESUMO

Many dosimetric applications and especially those involved in clinical dosimetry are hampered by the supralinearity of TLD-100 which begins at a level of dose of 1 Gy. This research investigates the effect of optical excitation following irradiation on the dose-response. It is expected that this will lead to a more linear dose-response, however, irrespective of the hoped-for linearity, the theoretical/kinetic simulations of the effect of optical excitation will further enhance our understanding of the thermoluminescence mechanisms, especially the role of spatially correlated trapping and luminescent centers. In the following, the various stages carried out in these investigations are discussed and preliminary results presented.


Assuntos
Fluoretos/química , Compostos de Lítio/química , Magnésio/química , Dosimetria Termoluminescente/instrumentação , Dosimetria Termoluminescente/métodos , Titânio/química , Desenho de Equipamento , Fluoretos/efeitos da radiação , Humanos , Compostos de Lítio/efeitos da radiação , Magnésio/efeitos da radiação , Doses de Radiação , Titânio/efeitos da radiação
10.
Fortschr Neurol Psychiatr ; 87(9): 483-491, 2019 Sep.
Artigo em Alemão | MEDLINE | ID: mdl-30453335

RESUMO

For avoiding affective episodes, patients with bipolar disorders are treated with mood stabilizers. Under that term, the substances lithium, valproic acid, lamotrigine and carbamazepine are included. In the light of upcoming new psychiatric concepts, the use of second generation antipsychotics is also taken into consideration in pharmacological treatment. In this review, the relation between brain structure and the use of lithium in bipolar disorders is examined. Therefore, results from MRI-, DTI-, SPECT-studies assessing this relation, were included.Most of the studies are cross-sectional and examined the effects of lithium. The latter is associated with increased cortical and sub-cortical gray matter volume and ameliorative white matter microstructure. 7-lithium spectroscopy showed a significant difference in brain-lithium concentrations between remitted and non-remitted patients.There are preclinical studies reporting induction of promitotic and antiapoptotic effects by lithium. This literature underpins the hypothesis of lithium-induced neurogenesis. However, osmotic and physical effects of lithium could also explain the demonstrated volume gain in bipolar human brain.Cross-sectional design and small patient groups are typical limitations of numerous studies included in this review.Notably, with the 7-lithium spectroscopy of the central nervous system, new perspectives in clinical research to clarify pharmacokinetic differences between remitted and non-remitted bipolar patients can be established in future.


Assuntos
Transtorno Bipolar/tratamento farmacológico , Transtorno Bipolar/patologia , Compostos de Lítio/uso terapêutico , Indução de Remissão , Antimaníacos/análise , Antimaníacos/química , Antimaníacos/uso terapêutico , Antipsicóticos/análise , Antipsicóticos/química , Antipsicóticos/uso terapêutico , Transtorno Bipolar/psicologia , Estudos Transversais , Humanos , Compostos de Lítio/análise , Compostos de Lítio/química
11.
J Prosthet Dent ; 121(1): 22-25, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29961631

RESUMO

Discolored substrates constitute a challenge to the esthetics of the definitive restoration. Because of technique sensitivity, the generally prolonged treatment time is a drawback to both the patient and the dentist. The technique described presents the replacement of ceramic maxillary incisors crowns over discolored substrates in a single visit by using a milling machine. Translucent blocks of a lithium silicate ceramic reinforced with zirconium dioxide particles were used. Intraoral scans of the trial restorations and of the tooth preparations were performed. The crown parameters were defined in the software. Ceramic blocks were milled in the presintered phase and characterized. The crowns were cemented at the end of the appointment with excellent esthetics.


Assuntos
Cerâmica/química , Cor , Desenho Assistido por Computador , Coroas , Incisivo , Compostos de Lítio/química , Maxila , Silicatos/química , Dente Suporte , Adaptação Marginal Dentária , Materiais Dentários/química , Porcelana Dentária/química , Planejamento de Prótese Dentária , Estética Dentária , Retração Gengival , Humanos , Polivinil/química , Pigmentação em Prótese , Siloxanas/química , Preparo do Dente/métodos , Zircônio/química
12.
Molecules ; 24(1)2018 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-30577631

RESUMO

We built a full-dimensional analytical potential energy surface of the ground electronic state of Li2H from ca. 20,000 ab initio multi-reference configuration interaction calculations, including core⁻valence correlation effects. The surface is flexible enough to accurately describe the three dissociation channels: Li (2s ²S) + LiH (¹Σ⁺), Li2 (¹Σg⁺) + H (1s ²S) and 2Li (2s ²S) + H (1s ²S). Using a local fit of this surface, we calculated pure (J = 0) vibrational states of Li2H up to the barrier to linearity (ca. 3400 cm-1 above the global minimum) using a vibrational self-consistent field/virtual state configuration interaction method. We found 18 vibrational states below this barrier, with a maximum of 6 quanta in the bending mode, which indicates that Li2H could be spectroscopically observable. Moreover, we show that some of these vibrational states are highly correlated already ca. 1000 cm-1 below the height of the barrier. We hope these calculations can help the assignment of experimental spectra. In addition, the first low-lying excited states of each B1, B2 and A2 symmetry of Li2H were characterized.


Assuntos
Hidrogênio/análise , Hidrogênio/química , Compostos de Lítio/análise , Compostos de Lítio/química , Modelos Químicos , Algoritmos
13.
Nat Commun ; 9(1): 5297, 2018 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-30546065

RESUMO

Polypeptides have broad applications and can be prepared via ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs). Conventional initiators, such as primary amines, give slow NCA polymerization, which requires multiple days to reach completion and can result in substantial side reactions, especially for very reactive NCAs. Moreover, current NCA polymerizations are very sensitive to moisture and must typically be conducted in a glove box. Here we show that lithium hexamethyldisilazide (LiHMDS) initiates an extremely rapid NCA polymerization process that is completed within minutes or hours and can be conducted in an open vessel. Polypeptides with variable chain length (DP = 20-1294) and narrow molecular weight distribution (Mw/Mn = 1.08-1.28) were readily prepared with this approach. Mechanistic studies support an anionic ring opening polymerization mechanism. This living NCA polymerization method allowed rapid synthesis of polypeptide libraries for high-throughput functional screening.


Assuntos
Antibacterianos , Compostos de Lítio/química , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Peptídeos , Pseudomonas aeruginosa/efeitos dos fármacos , Silanos/química , Aminas/química , Aminoácidos/química , Anidridos/química , Antibacterianos/síntese química , Antibacterianos/química , Antibacterianos/farmacologia , Farmacorresistência Bacteriana Múltipla , Compostos de Organossilício/química , Peptídeos/síntese química , Peptídeos/química , Peptídeos/farmacologia , Polimerização
14.
J Am Chem Soc ; 140(49): 17197-17202, 2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30419749

RESUMO

A methyl group on an arene, despite its small size, can have a profound influence on biologically active molecules. Typical methods to form a methylarene involve strong nucleophiles or strong and often toxic electrophiles. We report a strategy for a new, highly efficient, copper and iodide co-catalyzed methylation of aryl- and heteroarylboronic esters with the mild, nontoxic reagent trimethylphosphate, which has not been used previously in coupling reactions. We show that it reacts in all cases tested in yields that are higher than those of analogous copper-catalyzed reactions of MeOTs or MeI. The combination of C-H borylation and this methylation with trimethylphosphate provides a new approach to the functionalization of inert C-H bonds and is illustrated by late-stage methylation of four medicinally active compounds. In addition, reaction on a 200 mmol scale demonstrates reliability of this method. Mechanistic studies show that the reaction occurs by a slow release of methyl iodide by reaction of PO(OMe)3 with iodide catalyst, rather than the typical direct oxidative addition to a metal center. The low concentration of the reactive electrophile enables selective reaction with an arylcopper intermediate, rather than nucleophilic groups on the arylboronate, and binding of tert-butoxide to the boronate inhibits reaction of the electrophile with the tert-butoxide activator to form methyl ether.


Assuntos
Ácidos Borônicos/química , Ésteres/química , Organofosfatos/química , Catálise , Cobre/química , Iodetos/química , Cinética , Compostos de Lítio/química , Metilação , Modelos Químicos
15.
Luminescence ; 33(8): 1358-1364, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30288909

RESUMO

The classical initial rise method is limited to evaluate the activation energy for signal levels that do not exceed 10-15% of the maximum intensity. When it becomes necessary to include higher signal levels the associated error in the activation energy increases. In the present work we introduced a new correction factor for the activation energy obtained by the initial rise method in terms of the percentage of maximum intensity and the geometrical factor of the glow peak. The new expression reflects the dependence of the correction factor on the order of kinetics through the geometrical factor, especially when high signal levels are involved in the analysis. With this correction, the initial rise method can be applied to signal levels up to 70% of the maximum intensity with errors lower than those encountered in applying the classical method at low intensity levels (~10% of the maximum intensity). In addition, the order of kinetics was evaluated based on the difference between the corrected value of E and the one obtained by the initial rise method. The present procedure was applied to the glow curve of Li2 B4 O7 :Mn single crystal. The obtained parameters show very good agreement with curve fitting, peak shape methods and the published data on this material which supports the validity and reliability of the present approach.


Assuntos
Boratos/química , Compostos de Lítio/química , Manganês/química , Cinética , Medições Luminescentes , Dosimetria Termoluminescente
16.
Adv Mater ; 30(43): e1804046, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30260520

RESUMO

Peroxynitrite (ONOO- ), the reaction product derived from nitric oxide (NO) and superoxide (O2 -• ), is a potent oxidizing and nitrating agent that modulates complex biological processes and promotes cell death. Therefore, it can be expected that the overproduction of ONOO- in tumors can be an efficient approach in cancer therapy. Herein, a multifunctional X-ray-controlled ONOO- generation platform based on scintillating nanoparticles (SCNPs) and UV-responsive NO donors Roussin's black salt is reported, and consequently the mechanism of their application in enhanced therapeutic efficacy of radiotherapy is illustrated. Attributed to the radioluminescence and high X-ray-absorbing property of SCNPs, the nanocomposite can produce NO and O2 -• simultaneously when excited by X-ray irradiation. Such simultaneous release of NO and O2 -• ensures the efficient X-ray-controlled generation of ONOO- in tumors. Meanwhile, the application of X-rays as the excitation source can achieve better penetration depth and induce radiotherapy in this nanotherapeutic platform. It is found that the X-ray-controlled ONOO- -generation platform can efficiently improve the radiotherapy efficiency via directly damaging DNA, downregulating the expression of the DNA-repair enzyme, and overcoming the hypoxia-associated resistance in radiotherapy. Therefore, this SCNP-based platform may provide a new combinatorial strategy of ONOO- and radiotherapy to improve cancer treatment.


Assuntos
Compostos de Lítio/farmacologia , Nanocompostos/química , Neoplasias/radioterapia , Ácido Peroxinitroso/química , Radiossensibilizantes/farmacologia , Raios X , Células A549 , Animais , Humanos , Compostos de Ferro/química , Compostos de Ferro/farmacologia , Compostos de Lítio/química , Camundongos Nus , Transplante de Neoplasias , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Neoplasias/patologia , Compostos Nitrosos/química , Compostos Nitrosos/farmacologia , Ácido Peroxinitroso/metabolismo , Radiossensibilizantes/química
17.
Chemistry ; 24(68): 17902-17905, 2018 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-30216580

RESUMO

Azanucleosides, the sugar-modified nucleoside analogues, have various biological activities, while their efficient synthetic strategy is still under development. Herein, a novel method for the synthesis of pharmaceutically relevant azanucleosides, ß-anomers of ribo-azanucleosides, by means of site-specific anodic C-H activation by using a nitroalkane-lithium perchlorate medium is reported. A mechanistic study of the electrochemical reaction and the armed/disarmed concept from traditional glycochemistry revealed that the 2'-substituent has a significant effect on the reactivity of prolinol derivative, and suitable carboxylic acid additives can control the reactivity of the intermediate species, an iminium cation equivalent. Finally, this method was demonstrated to be applicable for the synthesis of ß-anomers of ribo-azanucleosides with all four nucleobases in a stereoselective manner.


Assuntos
Compostos Aza/síntese química , Técnicas de Química Sintética/métodos , Nucleosídeos/síntese química , Compostos Aza/química , Eletrodos , Compostos de Lítio/química , Nucleosídeos/química , Oxirredução , Percloratos/química , Pirrolidinas/síntese química , Pirrolidinas/química , Estereoisomerismo
18.
J Colloid Interface Sci ; 530: 137-145, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29966846

RESUMO

Lithium-Sulfur (Li-S) batteries are mostly known for their high energy density and cost-effectiveness. However, their intrinsic problems hinder their implementation into the marketplace. The most pronounced problems are the parasitic reactions which occur between lithium polysulfides species and lithium metal anode, the volume expansion of sulfur (80%) at the end of discharge and the safety issues which are linked with the use of lithium metal. Herein this work, two approaches are applied to prevent these effects; one approach is the use of Li2S as cathode material, instead of starting from sulfur powder, both to circumvent the volume expansion of sulfur taking place during discharge and to enable lithium-free anodes cell assembling (i.e. Si-Li2S or Sn-Li2S cell configurations). Second approach deals with the lithium anode protection by SnO2 containing freestanding pyrolyzed bacterial cellulose interlayers located between anode and cathode electrodes. Since bacterial celluloses are formed in the presence of SnO2 nanoparticles, the resulting structure enables intimate contact between carbon and SnO2 nanoparticles. By employing Li2S cathode and freestanding interlayer concurrently, 468 mAh g-1 discharge capacity is obtained at C/10 current density over 100 cycles.


Assuntos
Carbono/química , Celulose/química , Fontes de Energia Elétrica , Compostos de Lítio/química , Nanofibras/química , Nanopartículas/química , Sulfetos/química , Compostos de Estanho/química , Bactérias/química , Nanofibras/ultraestrutura , Nanopartículas/ultraestrutura , Polissacarídeos Bacterianos/química , Enxofre/química
19.
Nano Lett ; 18(9): 5768-5774, 2018 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-30052464

RESUMO

X-ray-induced photodynamic therapy (X-PDT) has high depth of penetration and has considerable potential for applications in cancer therapy. Scintillators and heavy metals have been adopted to absorb X-rays and transmit the energy to photosensitizers. However, the low efficiency of converting X-rays to reactive oxygen species (ROS) presents a challenge for the use of X-PDT to cure cancer. In this study, a new method based on LiLuF4:Ce@SiO2@Ag3PO4@Pt(IV) nanoparticles (LAPNP) is presented that could be used to enhance the curative effects of X-PDT. To make full use of the fluorescence produced by nanoscintillators (LiLuF4:Ce), a cisplatin prodrug Pt(IV) was utilized as a sacrificial electron acceptor to increase the yield of hydroxyl radicals (·OH) by increasing the separation of electrons and holes in photosensitizers (Ag3PO4). Additionally, cisplatin is produced upon the acceptance of electrons by Pt(IV) and further enhances the damage caused by ·OH. Via two-step amplification, the potential of LAPNP to enhance the effects of X-PDT has been demonstrated.


Assuntos
Antineoplásicos/uso terapêutico , Cisplatino/uso terapêutico , Neoplasias/tratamento farmacológico , Fosfatos/uso terapêutico , Fotoquimioterapia/métodos , Fármacos Fotossensibilizantes/uso terapêutico , Pró-Fármacos/uso terapêutico , Compostos de Prata/uso terapêutico , Animais , Antineoplásicos/química , Antineoplásicos/farmacologia , Cério/química , Cisplatino/administração & dosagem , Cisplatino/farmacologia , Elétrons , Fluorescência , Células HeLa , Humanos , Compostos de Lítio/química , Camundongos , Nanopartículas/química , Nanopartículas/ultraestrutura , Neoplasias/metabolismo , Neoplasias/patologia , Fosfatos/administração & dosagem , Fosfatos/farmacologia , Fármacos Fotossensibilizantes/administração & dosagem , Fármacos Fotossensibilizantes/farmacologia , Pró-Fármacos/administração & dosagem , Pró-Fármacos/farmacologia , Espécies Reativas de Oxigênio/metabolismo , Dióxido de Silício/química , Compostos de Prata/administração & dosagem , Compostos de Prata/farmacologia , Raios X
20.
J Vis Exp ; (135)2018 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-29806840

RESUMO

The occurrence of lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH) is a common problem with a high incidence in the aging male population. Although it is not a life-threatening disease, BPH causes problems that seriously impact the quality of life. Here, we introduce a new technique called photoselective vaporesection of the prostate (PVRP) in treating BPH, which can be seen as a variation of photoselective vaporization of the prostate (PVP). This procedure presents several advantages compared to the PVP technique including less laser energy loss, less intraoperative complications as well as more tissue resection rate.


Assuntos
Boratos/química , Terapia a Laser/métodos , Compostos de Lítio/química , Próstata/patologia , Hiperplasia Prostática/diagnóstico por imagem , Idoso , Humanos , Masculino , Resultado do Tratamento
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