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1.
J Biomol Struct Dyn ; : 1-18, 2024 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-38450736

RESUMEN

5-Methylcytosine methyltransferases (m5C MTases) are known to be involved in the modification of RNA. Although these enzymes have been relatively well characterized in bacteria and eukarya, a complete understanding of the archaeal counterparts is lacking. In this study, the identification and characterization of archaeal RNA m5C MTases were performed. As a case study, a hyperthermophilic archaeon, Pyrococcus horikoshii OT3, which possesses five putative RNA m5C MTases, was chosen. Among the five putative RNA m5C MTases, two proteins (PH0851 and PH1991) have been characterized as homologs of a bacterial rRNA MTase (RsmB) and eukaryal tRNA MTase (NSUN6), respectively. The in-depth characterization of the remaining three putative RNA m5C MTases (PH1078, PH1374, and PH1537) in this study suggests the presence of the signature architecture and catalytic residues plausibly involved in the binding of their cognate RNA substrates. Additionally, the results also suggest the existence of two RsmB-like proteins (PH0851 and PH1078) belonging to the same subfamily IV of m5C RNA MTase. However, the proteins PH1374 and PH1537 belong to the same subfamily V but bind to different substrates, rRNA and tRNA, respectively. The findings further indicate that archaeal RNA m5C MTases link those from bacteria and eukarya.Communicated by Ramaswamy H. Sarma.

2.
Indian J Psychiatry ; 65(8): 862-868, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37736223

RESUMEN

Background and Aims: Despite a large body of research linking caregiver burden and social support in substance dependence, positive aspects of caregiving in these disorders have received very minimal attention. This exploratory observational study aimed to assess the positive aspects of caregiving for opioid dependence and evaluate the association of these positive aspects with caregiver quality of life, burden, and social support. Methods: This cross-sectional study included 199 caregivers of patients with opioid dependence recruited through purposive sampling. Participants were assessed using the Scale for Positive Aspects of Caregiving Experience (SPACE), World Health Organization Quality of Life-BREF version, Family Burden Interview Schedule (FBIS), and Social Support Questionnaire. Results: Of the 199 caregivers recruited, a majority of the caregivers were middle-aged women. About two-thirds of the patients were currently using opioids (n = 135, 67.8%), while the remaining were abstinent. Among the SPACE domain scores, the mean was highest for motivation for the caregiving role (2.07), which was followed by self-esteem and social aspect of caring (2.04), caregiving personal gains (1.76), and caregiver satisfaction (1.65). Caregivers of patients currently abstinent experienced greater positive aspects of caregiving (SPACE mean item score 2.57 versus 1.62, P < 0.001), and lesser burden (FBIS mean score 13.4 versus 29.3, P < 0.001). Conclusion: Positive aspects of caregiving can be potentially utilized for better caregiver engagement in treatment and improved caregiver outcomes.

3.
Dalton Trans ; 52(34): 11922-11933, 2023 Aug 29.
Artículo en Inglés | MEDLINE | ID: mdl-37574905

RESUMEN

A reaction between CoCl2 and L3-(CO2-)2 (2 : 1 stoichiometry) in CH3OH affords a discrete complex [CoII4-{L3-(CO2-)2}2(µ3-OCH3)2(CH3OH)2(H2O)2Cl2] (1) [L3-(CO2-)2 = 3-[N-{2-(pyridin-2-yl)methyl}amino]-bis(propionate)]. The structure of 1 reveals two terminal mononuclear CoII{L3-(CO2-)2}Cl units connected by a dimeric CoII2(µ3-OCH3)2(CH3OH)2(H2O) unit present in the centre through two methoxo (µ3-OCH3)- and two carboxylate (µ-1,1-OCO-) bridges affording a tetranuclear coordination cluster of Co(II) with a defective dicubane topology. In 1, Co1 (terminal) has distorted octahedral CoIIN2O3Cl and the central Co2 has CoIIO6 coordination. Such coordination arrangements afford the observed topology. Variable-temperature magnetic studies reveal anti-ferromagnetic coupling in 1. Three magnetic exchange interactions (one anti-ferromagnetic and two ferromagnetic: J1 = +3.3 cm-1 (Co⋯Co 3.176 Å; µ-1,1-OCO- and µ3-OCH3 bridges), J2 = -2.5 cm-1 (Co⋯Co 3.228 Å; µ-1-OCO- and µ3-OCH3 bridges) and J3 = +10.6 cm-1 (Co⋯Co 3.084 Å; two µ3-OCH3 bridges)) have been identified, with the inclusion of the orbital reduction parameter (α = Aκ = 1.38), spin-orbit coupling (λ = -158 cm-1) and axial distortion (energy gap Δ = -975 cm-1 between singlet and doublet levels), rationalized by density functional theory (DFT) calculations.

4.
ACS Appl Bio Mater ; 6(8): 3278-3290, 2023 08 21.
Artículo en Inglés | MEDLINE | ID: mdl-37565455

RESUMEN

This work delivers a targeted synthesis of four isostructural O-substituted imidazole-based zinc(II) complexes, namely, [Zn2(L1)2(I)2](DMF) (1), [Zn2(L2)2(I)2](DMF) (2), [Zn2(L1)2(Br)2] (3), and [Zn2(L2)2(Br)2] (4), derived from homologous Schiff-base ligands HL1 and HL2 to explore their impact on free radicals, microbes, and dephosphorylation of phosphoesters. The antioxidant activity of all complexes was checked by various radical scavenging assays (ABTS+•, DPPH•, and H2O2 radical quenching). Among them, complex 2 showed superior radical quenching activity, as indicated by its lowest EC50 value and thus maximum antioxidative capability. Again, antibacterial assays against several Gram-positive and Gram-negative bacteria were conducted to evaluate the zone of inhibition. The minimum bactericidal concentration and minimum inhibitory concentration values from the microdilution method for all complexes revealed complex 3 to have maximum potency against Gram-positive bacteria. The P-O bond hydrolysis in the phospholipid chain caused by the hydrolytic phosphoesterase activity of the Zn(II)-complexes plays a crucial role in cell membrane rupture. A model substrate 4-PNPP was used to explain the potency of monomeric Zn(II) complex (3) for cell penetration over dimeric one (2) with a proper mechanism. Furthermore, a heme model substrate, Fe(TPP)Cl, has been introduced with the most potent complex 3 and has spectrophotometric evidence for covalent interaction with imidazole and Fe(III) that can disrupt the nitric oxide dioxygenase function of flavohemoglobin, leading to bacterial cell death. To our knowledge, this is the first case to report a novel mechanism of antimicrobial action where both the metal and the ligand are cooperatively involved in bacterial cell death. The main goal of this work is to invent multifunctional therapeutics as well as the proper chemical rationalization of biological processes using mechanistic approaches, which includes investigating the roles of halides, imidazoles, and solution-phase structural variations of complexes..


Asunto(s)
Antibacterianos , Compuestos Férricos , Antibacterianos/química , Peróxido de Hidrógeno , Bacterias Gramnegativas , Bacterias Grampositivas , Imidazoles/farmacología , Imidazoles/química , Zinc/farmacología , Zinc/química , Antioxidantes/química , Radicales Libres , Bacterias
5.
Waste Manag ; 169: 289-300, 2023 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-37487342

RESUMEN

Plastic waste management is one of the major global challenges at present. Recycling single used plastic waste as partial replacement of natural aggregates in concrete may reduce problems regarding mismanagement of plastic waste and unsustainable utilisation of natural resources as aggregates. This concept has been explored in many studies and positive results are obtained, but it has not been materialized at a large scale due to the uncertainty regarding economic viability. The present study therefore focuses on the economic aspects of using Polyethylene based fine aggregates and Polyethylene Terephthalate based coarse aggregates as partial replacement (10%, 20%, 30% and 40%) of natural fine and coarse aggregates separately and simultaneously, with special emphasis given on environmental and social cost. A material flow diagram using STAN is first developed to calculate plastic waste generation. An industrial survey has been conducted to estimate production cost of plastic aggregates, while social cost as WTP is determined through CVM method. The result shows that the total cost of concrete decreases with increase of replacement percentage and cost reduction varies between 0.65% and 7.58% compare to conventional concrete depending on the percentage and type of replacement without compromising strength. So, alongside being hugely beneficial to environment and society in terms of reduction of leachate and greenhouse gas generation, micro-plastic pollution, requirement of landfill area, mosquito borne diseases, erosion, sedimentation, land loss etc.; the concept of recycling plastic waste as partial replacement of natural aggregates in concrete has been proved to be economically viable and beneficial too.


Asunto(s)
Materiales de Construcción , Administración de Residuos , Plásticos , Residuos Industriales/análisis , Administración de Residuos/métodos , Conservación de los Recursos Naturales , Reciclaje/métodos
6.
Inorg Chem ; 62(8): 3485-3497, 2023 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-36780226

RESUMEN

Photoinduced electricity and proton conductivity led fuel cells have emerged, inter alia, as highly promising systems for unconventional energy harvesting. Notwithstanding their individual presence with widely acclaimed results, an integrating system with mutually inclusive manifestation of both features has hitherto not been reported in the literature. To achieve this objective, our approach was to design a ligand system incorporating prerequisite features of both systems, like extended conjugation instigating photophysical activity and functional groups facilitating ionic conduction. As such, we report herein the design, synthesis, and characterization of a pyridyl-pyrazole-based silver compound that exhibits an excellent photocurrent generation and very high proton conductivity. The X-ray single-crystal structure of the Ag complex fully supports our notion, showing extensive π-π conjugated aromatic rings with a protruding free sulfonic group, facing toward solvent-filled channels with numerous supramolecular interactions. The nanoscopic silver metallogel induces semiconductive features in the system which ultimately result in photoresponse behavior in terms of photocurrent generation with an whopping photocurrent gain (Ion/Ioff) of 21.2. To complete the idea of an integrated system, the proton conductivity values were also measured for both gel and crystalline states, while the former state yields a better result. The maximum proton conductivity value turns out to be 1.03 × 10-2 S cm-1 at 70 °C, which is higher than or comparable to those of well-known systems in the literature for proton conductivity.

7.
Disabil Rehabil Assist Technol ; 18(6): 819-826, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-34043925

RESUMEN

PURPOSE: To design and develop a mobile application for pre-school readiness of children with autism and also to identify their learning pattern. METHODOLOGY: Based on strong foundation of functional academics, we have developed a mobile application for providing an early educational intervention program to the children with autism. Three successive software trials have been conducted among 31 children with autism of age group of three to 10 years. The mobile app has been provided to educators and parents and they have been allowed to supervise the children during their learning phase for eight to 10 weeks. The imprint of learning pattern is recorded and learning progress profile is generated for individual child. RESULTS: Data analysis of learning progress profile shows that 90% of the participants preferred drag and drop or simple touch approach over conventional methods practised during classroom teachings. More than 84% of the children are found to adapt pre-requisite skills for writing like scribbling, tracing, dots joining, copying, etc. after using the app on their tablet who are reluctant to hold pencil and paper otherwise. Twenty-five percent of the participants are reported to reciprocate the greeting etiquettes in class such as greeting teachers and their peers. CONCLUSIONS: The mobile application made a valuable contribution to early intervention program for children with autism by imparting appropriate learning opportunities readily available to them. Performance metrics underlying each activity form a strong base of identification of learning patterns and formulation of revised individualized education plan (IEP).Implications for RehabilitationChildren with autism need the mobile application as an educational intervention program for it is readily available and user friendly.Educators need the mobile application to quantify the performance parameters and there by monitor/evaluate the progress of the child.Overall, the present research has aimed to develop an easy reach app by which educating as well as handling challenging behaviour of the children with autism would be easier.


Asunto(s)
Trastorno Autístico , Aplicaciones Móviles , Preescolar , Humanos , Niño , Proyectos Piloto , Aprendizaje , Padres
8.
Dalton Trans ; 51(4): 1617-1633, 2022 Jan 25.
Artículo en Inglés | MEDLINE | ID: mdl-34994757

RESUMEN

Besides iron, ironically neodymium (Nd) is the most ubiquitously used metal for magnetic purposes, even among the lanthanides, when it comes to the field of molecular magnetism, yet it ranks among the least studied metals. However, strong apathy towards this magnetic lanthanide means that vital information will be missed, which is required for the advancement of the subject. Herein, we have successfully demonstrated the usefulness of a hexanuclear neodymium complex as a magnetic material, and also in electronic device fabrication. A {NdIII6} cage with an aesthetically pleasing butterfly topology was synthesized using a rather non-conventional N-rich pyridyl-pyrazolyl based ligand. The cage shows single molecule magnet (SMM) properties, with an effective energy barrier, Ueff, value of 3.4 K and relaxation time, τ0, of 3.1 × 10-4 s, originating from an unusual occurrence of metal centres with different coordination environments. Furthermore, magnetic studies reveal significant cyrogenic magnetic cooling, with a magnetic entropy change of 8.28 J kg-1 K-1 at 5 T and 3 K. To the best of our knowledge, the titular compound is the only example of a Nd-complex that exhibits concomitant magnetocaloric effect (MCE) and SMM properties. Complete active space self-consistent field (CASSCF) calculations were carried out to shed light on the origin of the magnetic anisotropy and magnetic relaxation of the compound. The same uniqueness is also true for the first electronic investigation carried out on the Nd complex. The maiden electronic device fabricated using the Nd complex shows an interesting intertwining of electronic and optical features, which contribute towards its improved photosensitized optoelectronic data.

9.
Inorg Chem ; 61(4): 2141-2153, 2022 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-35049278

RESUMEN

The present work is part of our ongoing quest for developing functional inorganic complexes using unorthodox pyridyl-pyrazolyl-based ligands. Accordingly, we report herein the synthesis, characterization, and luminescence and magnetic properties of four 3d-4f mixed-metal complexes with a general core of Ln2Zn6 (Ln = Dy, Gd, Tb, and Eu). In stark contrast to the popular wisdom of using a compartmental ligand with separate islands of hard and soft coordinating sites for selective coordination, we have vindicated our approach of using a ligand with overcrowded N-coordinating sites that show equal efficiency with both 4f and 3d metals toward multinuclear cage-cluster formation. The encouraging red and green photolumiscent features of noncytotoxic Eu2Zn6 and Tb2Zn6 complexes along with their existence in nanoscale dimension have been exploited with live-cell confocal microscopy imaging of human breast adenocarcinoma (MCF7) cells. The magnetic features of the Dy2Zn6 complex confirm the single-molecule-magnet behavior with befitting frequency- and temperature-dependent out-of-phase signals along with an Ueff value of ∼5 K and a relaxation time of 8.52 × 10-6 s. The Gd2Zn6 complex, on the other hand, shows cryogenic magnetic refrigeration with an entropy change of 11.25 J kg-1 K-1 at a magnetic field of 7 T and at 2 K. Another important aspect of this work reflects the excellent agreement between the experimental results and theoretical calculations. The theoretical studies carried out using the broken-symmetry density functional theory, ORCA suite of programs, and MOLCAS calculations using the complete-active-space self-consistent-field method show an excellent synergism with the experimentally measured magnetic and spectroscopic data.

10.
Chem Commun (Camb) ; 57(85): 11177-11180, 2021 Oct 26.
Artículo en Inglés | MEDLINE | ID: mdl-34617535

RESUMEN

We report herein three air, thermal and solvent stable interlocked triacontanuclear giant nanocages, generated using a node and spacer concept. Interestingly, the crystal structures of the cages are not only nano-dimensional but also exist in the nano-dimension range, which was corroborated with microscopic images. The combination of microscopic and crystallographic data, in effect, led us to a unique advantageous situation of generating nanomaterials with hard-to-come-by structural information at the molecular level.

11.
Dalton Trans ; 50(10): 3593-3609, 2021 Mar 16.
Artículo en Inglés | MEDLINE | ID: mdl-33624673

RESUMEN

In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+ and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of -23.42 J kg-1 K-1 at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.


Asunto(s)
Complejos de Coordinación/química , Elementos de la Serie de los Lantanoides/química , Imagen Óptica , Fenantrolinas/química , Complejos de Coordinación/síntesis química , Humanos , Ligandos , Células MCF-7 , Fenómenos Magnéticos , Estructura Molecular , Pirazoles , Piridinas
12.
RSC Adv ; 11(17): 10094-10109, 2021 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-35423527

RESUMEN

We report herein the development of a new pyridine-pyrazole based bis-bidentate asymmetric chemosensor that shows excellent turn-on chelation-enhanced Al3+-responsive fluorescence. The presence of two 'hard' phenolic hydroxyl groups plays a pivotal role in switching-on the sensing through coordination to the 'hard' Al3+ ion, while the mechanism can be interpreted by the chelation-enhanced fluorescence (CHEF) process. The X-ray single structure show a planar conjugated structure of the ligand, which was further stabilized by extensive H-bonding and π-π stacking. The photophysical studies related to the sensing behavior of the titular ligand toward aluminum was investigated in detail using various spectroscopic techniques like UV-Vis, photoluminescence, fluorescence and time-correlated single-photon count (TCSPC) and time-resolved NMR. The spectroscopic methods also confirm the selective detection of Al3+ ion in the presence of other metal ions. The theoretical calculations using Density Functional Theory (DFT) and the Time Dependent Density Functional Theory (TD-DFT) provide further insight on the mechanistic aspects of the turn-on sensing behavior including the electronic spectra of both the ligand and the complex. Interestingly, the as-synthesized H2DPC-Al complex can also be utilized as a fluorescence-based sensor for various nitroaromatics including picric acid, for which an INHIBIT logic gate can also be constructed. The as synthesized complex was subsequently used as a fluorescent probe for imaging of human breast adenocarcinoma (MCF7) cells using live cell confocal microscopic techniques.

13.
Dalton Trans ; 49(46): 17005-17016, 2020 Dec 08.
Artículo en Inglés | MEDLINE | ID: mdl-33191411

RESUMEN

The present work reports the fabrication of anion-induced electrical devices with Zn(ii) metal-organic frameworks. The essence of our electronic device fabrication is to utilize the anionic species entrapped inside of the three-dimensional network of the MOFs for charge transportation. The idea is to generate MOFs as a host-guest system with encapsulated anions or anion-solvent clusters as guests and a cationic yet insulating three-dimensional framework as the host. Accordingly, we have synthesized two Zn(ii) MOFs using a neutral bispyrazole-based ligand, which results in a cationic chassis with substantial void space and porous channels inside the network. For both MOFs, the porous channels are occupied by infinitely hydrogen bonded networks of anions and anion-solvent clusters. This provides an excellent platform for anionic species-induced charge transportation and improved electrical conductivity. Indeed, the impedance spectroscopy data and current density-voltage (J-V) characteristics of the fabricated electrical devices further vindicate our idea. The current-voltage measurements clearly indicate the usefulness of modified host-guest-type MOFs for electronic device fabrication with corroborating conductivity values of 8.71 × 10-5 S m-1 and 5.79 × 10-4 S m-1 for compound 1 and compound 2, respectively.

14.
Dalton Trans ; 49(38): 13487-13495, 2020 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-32966459

RESUMEN

A novel Fe(iii)-based gel was synthesized via the self-assembly of Fe(iii) and pyridine 2,6 dicarboxylic acid. The synthesized gel has remarkable mechanical strength as well as self-sustainability. The metallogel also has thixotropic as well as self-healing properties. The metallogel shows amazing colourimetric NH3 sensing with unique gel-to-gel transformation. Magnetic studies on the as-synthesized gel reveal significant cryogenic magnetic cooling behavior. Last but not least, to the best of our knowledge, this would be the first case where MCE is investigated for any reported metallogel.

16.
Inorg Chem ; 58(21): 14568-14576, 2019 Nov 04.
Artículo en Inglés | MEDLINE | ID: mdl-31647230

RESUMEN

Ruthenium compounds with coordinated photolabile molecules that can be selectively released by irradiation with a visible light source are finding increasing applications in photoactivated chemotherapy (PCT) as photocages. Earlier photocages based on mononuclear Ru(II) compounds lack absorption in the therapeutic window (λ > 600 nm). In previous work, we synthesized the first partially solvated tppz bridged (tppz= 2,3,5,6-tetrakis(pyridin-2-yl)pyrazine) dinuclear Ru(II) complex capable of photoinduced ligand exchange at both metal centers. To further explore the effect of the bridging ligand on Ru(II) photocage design, we used quinoxaline-functionalized bridging ligand platforms to prepare [{RuII(NCCH3)4}2(µ-BL)](PF6)4[BL = dpq, 2,3-di(pyridin-2-yl)quinoxaline (1); BL = dpb, 2,3-di(pyridin-2-yl)benzo[g]quinoxaline (2)]. The compounds are capable of absorbing green light with tails extending beyond 650 nm which can be exploited for applications as PCT agents. Experimental results were additionally verified by DFT calculations. The use of two Ru(II) centers equipped with quinoxaline-based bridging ligands is a promising design strategy for the synthesis of a new family of dinuclear Ru(II) photocage prototypes with the ability to absorb low-energy visible light.

17.
Inorg Chem ; 57(20): 12777-12786, 2018 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-30239197

RESUMEN

Ru(II)-polypyridyl complexes exhibit antitumor properties that can be systematically tailored by means of adjusting the ligand environment. In this work, the effect of incorporating π-extended moieties into anionic N∧O- based chelating ligands on the cytotoxic properties of Ru compounds is explored. Four new Ru(II) complexes, [Ru(bpy)2(dphol)][PF6] (1; bpy = 2,2'-bipyridine, dphol = dibenzo[ a, c]phenazin-10-olate), [Ru(phen)2(dphol)][PF6] (2; phen = 1,10-phenanthroline), [Ru(bpy)2(hbtz)][PF6] (3; hbtz = 2-(benzo[ d]thiazol-2-yl)phenolate), and [Ru(phen)2(hbtz)][PF6] (4) were synthesized and thoroughly characterized. In vitro cytotoxicity was investigated in human lung adenocarcinoma (A549) cells, which revealed that 4 is the most cytotoxic compound (IC50 = 0.8 µM) in the series including a control compound [Ru(bpy)2(quo)][PF6] (5; quo = 8-hydroxyquinolinate) and is nearly 8-fold more cytotoxic than cisplatin. An investigation of the mechanism of cell death led to the finding that compounds 1-4 disrupt the mitochondrial transmembrane potential (ΔΨm) in a concentration-dependent fashion, which is an event associated with the intrinsic pathway of apoptosis. Moreover, compound 4 triggers the activity of caspase-3/7, which eventually induces the apoptotic cellular death of A549 cells. Thus, increasing the overall lipophilicity of the Ru compounds by introducing π-extended moieties in the anionic N∧O- ligand is a successful strategy for realizing a new family of pro-apoptotic compounds with a [RuIIN5O]+ coordination environment.


Asunto(s)
Adenocarcinoma/metabolismo , Apoptosis/efectos de los fármacos , Caspasas/metabolismo , Redes y Vías Metabólicas/efectos de los fármacos , Nitrógeno/química , Compuestos de Rutenio/farmacología , Células A549 , Supervivencia Celular/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Humanos , Ligandos , Neoplasias Pulmonares/metabolismo , Modelos Moleculares , Estructura Molecular , Nitrógeno/metabolismo , Compuestos de Rutenio/química
18.
Phys Rev B ; 95(10)2017 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-28752135

RESUMEN

Modern integrated circuits (ICs) employ a myriad of materials organized at nanoscale dimensions, and certain critical tolerances must be met for them to function. To understand departures from intended functionality, it is essential to examine ICs as manufactured so as to adjust design rules, ideally in a non-destructive way so that imaged structures can be correlated with electrical performance. Electron microscopes can do this on thin regions, or on exposed surfaces, but the required processing alters or even destroys functionality. Microscopy with multi-keV x-rays provides an alternative approach with greater penetration, but the spatial resolution of x-ray imaging lenses has not allowed one to see the required detail in the latest generation of ICs. X-ray ptychography provides a way to obtain images of ICs without lens-imposed resolution limits, with past work delivering 20-40 nm resolution on thinned ICs. We describe a simple model for estimating the required exposure, and use it to estimate the future potential for this technique. Here we show for the first time that this approach can be used to image circuit detail through an unprocessed 300 µm thick silicon wafer, with sub-20 nm detail clearly resolved after mechanical polishing to 240 µm thickness was used to eliminate image contrast caused by Si wafer surface scratches. By using continuous x-ray scanning, massively parallel computation, and a new generation of synchrotron light sources, this should enable entire non-etched ICs to be imaged to 10 nm resolution or better while maintaining their ability to function in electrical tests.

19.
Appl Opt ; 53(27): 6140-7, 2014 Sep 20.
Artículo en Inglés | MEDLINE | ID: mdl-25322089

RESUMEN

The optical absorption in 25-µm-thick, single-crystal Si foils fabricated using a novel exfoliation technique for solar cells is studied and improved in this work. Various light-trapping and optical absorption enhancement schemes implemented show that it is possible to substantially narrow the gap in optical absorption loss between the 25 µm Si foils and industry-standard 180-µm-thick Si wafer solar cells. An improvement of absorption by 58% in the near-infrared (740-1200 nm) range is observed for the 25 µm monocrystalline Si substrates with the use of antireflective coating and texturing. The back reflectance of the metal foil that provides mechanical support to the ultrathin Si semiconductor-on-metal foils is extracted to be ∼51.5%, based on the reflectance matching with the simulated escape reflectance in the sub-bandgap region. The back reflectance is enhanced to ∼58% by incorporating an intermediate silicon nitride layer on the back between the Si and the metal. The incorporation of Al as an improved metal reflector on top of the silicon nitride at the backside of the solar cell results in a 5.8 times enhancement in optical path length as a consequence of the improved effective back reflectance of ∼95%. A thin Si foil solar cell with an unoptimized amorphous Si/crystalline Si heterojunction with intrinsic-thin-layer design with implementation of such light-trapping schemes shows an efficiency of 13.28% with a short-circuit current density (JSC) of 35.97 mA/cm2, which approaches the JSC of industrial wafer-based Si solar cells.

20.
Indian J Exp Biol ; 51(10): 828-32, 2013 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-24266107

RESUMEN

Methanolic and ethyl acetate extract of A. galanga showed significant central nervous system (CNS) stimulant activity in mice using actophotometer and rotarod test. CNS stimulation at a dose of 500 mg/kg was comparable with standard drugs caffeine and amphetamine derivative modalart. The extracts did not shown any depressant effect in forced swim or tail suspension tests. It can be concluded that A. galanga rhizome may have stimulant activity in mice and the active constituents responsible for this effect is present both in crude methanolic extract as well as in ethyl acetate fraction of methanolic extract of this plant species.


Asunto(s)
Alpinia , Estimulantes del Sistema Nervioso Central/farmacología , Extractos Vegetales/farmacología , Rizoma , Alpinia/química , Animales , Sistema Nervioso Central/efectos de los fármacos , Locomoción/efectos de los fármacos , Masculino , Ratones , Proyectos Piloto , Desempeño Psicomotor/efectos de los fármacos , Rizoma/química
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