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Articles 151 - 174 of 174

Full-Text Articles in Other Chemistry

C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin Feb 2008

C–N Bond Rotation And E–Z Isomerism In Some N-Benzyl-N-Methylcarbamoyl Chlorides: A Dft Study, Michael Horwath, Vladimir Benin

Chemistry Faculty Publications

The current report presents the first theoretical study of the restricted CN bond rotation in carbamoyl chlorides. Several N-benzyl-N-methylcarbamoyl chlorides were investigated, with varying pattern of substitution in the aromatic ring. Optimizations and frequency calculations were conducted employing DFT at the B3LYP/6-31+G(d) level of theory. Each of the studied structures exhibits a pair of rotamers (s-Z and s-E), generated upon rotation around the C(O)N bond. The s-E isomer is the global minimum in every case, but the preference for it is usually less than 1 kcal/mol. Two possible transition state structures were identified …

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Methods In Industrial Biotechnology For Chemical Engineers, Florentin Smarandache, W.B. Vasantha Kandasamy Jan 2008

Methods In Industrial Biotechnology For Chemical Engineers, Florentin Smarandache, W.B. Vasantha Kandasamy

Branch Mathematics and Statistics Faculty and Staff Publications

Industrial Biotechnology is an interdisciplinary topic to which tools of modern biotechnology are applied for finding proper proportion of raw mix of chemicals, determination of set points, finding the flow rates etc., This study is significant as it results in better economy, quality product and control of pollution. The authors in this book have given only methods of industrial biotechnology mainly to help researchers, students and chemical engineers. Since biotechnology concerns practical and diverse applications including production of new drugs, clearing up pollution etc. we have in this book given methods to control pollution in chemical industries as it has …

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Biophysical Characterization Of A Beta-Peptide Bundle: Comparison To Natural Proteins, E. James Petersson, Cody J. Craig, Douglas S. Daniels, Jade X. Qiu, Alanna S. Schepartz Apr 2007

Biophysical Characterization Of A Beta-Peptide Bundle: Comparison To Natural Proteins, E. James Petersson, Cody J. Craig, Douglas S. Daniels, Jade X. Qiu, Alanna S. Schepartz

Chemistry Faculty Publications

We recently described the high-resolution X-ray structure of a helical bundle composed of eight copies of the β-peptide Zwit-1F. Like many proteins in Nature, the Zwit-1F octamer contains parallel and antiparallel helices, extensive inter-helical electrostatic interactions, and a solvent-excluded hydrophobic core. Here we explore the stability of the Zwit-1F octamer using circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AU), differential scanning calorimetry (DSC), and NMR. These studies demonstrate that the thermodynamic and kinetic properties of Zwit-1F closely resemble those of α-helical bundle proteins. Together these studies should provide a model for the design of β-peptide proteins with biological functions.

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High-Resolution Structure Of A Beta-Peptide Bundle, Douglas S. Daniels, E. James Petersson, Jade X. Qiu, Alanna S. Schepartz Jan 2007

High-Resolution Structure Of A Beta-Peptide Bundle, Douglas S. Daniels, E. James Petersson, Jade X. Qiu, Alanna S. Schepartz

Chemistry Faculty Publications

We recently reported that β-peptides can form discrete hetero-oligomers in aqueous solution. Here we describe the structure of such an oligomer as determined by X-ray crystallography. The structure of Zwit-1F reveals a homo-octamer of two cupped “hands” composed of both parallel and antiparallel 314-helices. The core of the assembly is composed entirely of solvent-excluded β3-homoleucine residues. The Zwit-1F assembly shares many of the physical characteristics of natural proteins.

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Silica-Coated Lanthanum-Strontium Manganites For Hyperthermia Treatments, Vuk Uskoković, Aljoša Košak, Miha Drofenik Sep 2006

Silica-Coated Lanthanum-Strontium Manganites For Hyperthermia Treatments, Vuk Uskoković, Aljoša Košak, Miha Drofenik

Pharmacy Faculty Articles and Research

La0.76Sr0.24MnO3 + δ particles, prepared by performing a traditional, solid-state method of synthesis, were coated by uniform layers of silica via initiating hydrolysis and condensation of TEOS in aqueous–alcoholic alkali environment. The eventually obtained samples exhibited Curie temperature at ∼40 °C, and comprised core-shell particles of ∼250 nm in diameter. By varying stoichiometric ratio of cations within manganite cores of the particles, Curie point of the resulting material can be varied too, thus opening a way for the simple design of biocompatible, temperature-self-regulating particles for application in hyperthermia treatments, with Curie point thereof adjusted to …

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Synthesis Of Lanthanum-Strontium Manganites By Oxalate-Precursor Co-Precipitation Methods In Solution And In Reverse Micellar Microemulsion, Vuk Uskoković, Miha Drofenik Aug 2006

Synthesis Of Lanthanum-Strontium Manganites By Oxalate-Precursor Co-Precipitation Methods In Solution And In Reverse Micellar Microemulsion, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

Nanostructured lanthanum–strontium manganites were synthesized using two different co-precipitation approaches, one in bulk solution, and the other in reverse micelles of CTAB/1-hexanol/water microemulsion. In both cases, precursor cations were precipitated by using oxalic acid. The properties of the materials synthesized by using these two methods were compared in order to reveal potential advantages of the microemulsion-assisted approach. The influence of the annealing conditions on the properties of synthesized manganites was investigated by using X-ray diffraction, transmission electron microscopy, differential thermal analysis, thermogravimetric analysis and magnetic measurements.

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Mechanism Of A Solid-State Formation Of La1-Xsrxmno3+Δ (0 < X < 0.5) And Magnetic Characterization Thereof, Vuk Uskoković, Miha Drofenik Jul 2006

Mechanism Of A Solid-State Formation Of La1-Xsrxmno3+Δ (0 < X < 0.5) And Magnetic Characterization Thereof, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

Rich diversity of potential, substantially different micro-structural arrangements - reflecting on the wide potential set of interesting properties, ranging from high electrical conductivity to giant, collossal and/or low-field magnetoresistance to low Curie point - of LaSr-manganite materials opens possibilities for numerous scientific investigations oriented towards revealing correlations on the influence line: procedure of synthesis → inherent properties → measured properties → application of the material. The investigations of the influence of synthesis procedures and LaSr-manganite stoichiometries on the Curie point (and other magnetic characteristics) of the material, being the topic of this work, are attractive since they present a necessary …

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Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin May 2006

Secondary N-Nitrosocarbamate Anions: Structure And Alkylation Reactions. A Dft Study, Vladimir Benin

Chemistry Faculty Publications

The current article reports theoretical studies (DFT: B3LYP/6-31+G(d)) on the structure and alkylation reactions of the anions of some secondary N-nitrosocarbamates, a class of ambident nucleophiles whose chemistry has been little explored. Several anions (1–4), with an increasing size of the carbamate alkyl (aryl) group were investigated, in an attempt to establish the influence of the size of that group on the thermal stability and regioselectivity of alkylation of the title anions. The conclusion is that thermal stability and the mode of reaction are affected significantly only in the presence of very large and branched carbamate groups. The thermal …

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Preparation Of Silica-Coated Lanthanum-Strontium Manganite Particles With Designable Curie Point, For Application In Hyperthermia Treatments, Vuk Uskoković, Aljoša Košak, Miha Drofenik Mar 2006

Preparation Of Silica-Coated Lanthanum-Strontium Manganite Particles With Designable Curie Point, For Application In Hyperthermia Treatments, Vuk Uskoković, Aljoša Košak, Miha Drofenik

Pharmacy Faculty Articles and Research

Silica-coated lanthanum–strontium manganite particles with La0.76Sr0.24MnO3+δ stoichiometric formula, exhibiting Curie temperature at ∼40°C, were prepared by using a traditional solid-state method of synthesis of magnetic ceramic particles, followed by milling and a low-temperature coating procedure in an aqueous alcoholic alkali medium. The properties of the obtained material establish it as a potential candidate for self-regulated power-absorbing and temperature-controlling materials in hyperthermia treatments. Moreover, core-comprising LaSr–manganites with different stoichiometries, ranging from La0.5Sr0.5MnO3+δ to LaMnO3+δ, were synthesized, with magnetic and structural properties examined thereof. Herein reported findings can potentially be …

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Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin Jan 2006

Preparation Of Some Substituted Terephthalic Acids, Susanna Branion, Vladimir Benin

Chemistry Faculty Publications

We report in detail the preparation of two substituted terephthalic acids: 2‐sulfomethylterephthalic acid (1) and 2‐phosphonoterephthalic acid (2). Efficient, short syntheses have been developed for both compounds. They are potentially useful monomers for construction of acid‐pendant polymer chains.

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Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin Jan 2006

Preparation, Characterization And Dft Studies Of Some New N-Nitrosocarbamates And N-Nitrosoureas, Ragavan Narayanan, Helene Hedian, Eric Shamo, Vladimir Benin

Chemistry Faculty Publications

We are presenting the preparation, characterization and density functional theory (DFT) studies {B3LYP/6-31+G(d)) of several reiated classes of N-nitrosocarbamates and N-nitrosoureas. The iong-range goal is the design and preparation of compounds, which would undergo photochemical or hydrolytic decomposition, to yield stabilized cyclic cations that can serve as alkylating agents at various nucleophilic centers, including DNA bases.

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A Mechanism For The Formation Of Nanostructured Nizn Ferrites Via A Microemulsion-Assisted Precipitation Method, Vuk Uskoković, Miha Drofenik Sep 2005

A Mechanism For The Formation Of Nanostructured Nizn Ferrites Via A Microemulsion-Assisted Precipitation Method, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

Nanostructured NiZn ferrites were synthesized using two different techniques: first, a precipitation procedure in the reverse micelles of a CTAB/1-hexanol/H2O microemulsion, and second, precipitation in a bulk aqueous solution. XRD measurements, magnetic measurements, TEM imaging, analytical measurements and thermal analyses were used in an attempt to reveal the chemical pathway that leads to the formation of NiZn ferrite in the microemulsion and in the bulk aqueous solution. It was found that reverse micelles do not act as inert nano-sized reactors that influence only morphological properties of the synthesized powders, but have a decisive influence on the identity of …

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Synthesis Of Lanthanum-Strontium Magnanites By A Hydroxide-Precursor Co-Precipitation Method In Solution And In Reverse Micellar Microemulsion, Vuk Uskoković, Darko Makovec, Miha Drofenik Sep 2005

Synthesis Of Lanthanum-Strontium Magnanites By A Hydroxide-Precursor Co-Precipitation Method In Solution And In Reverse Micellar Microemulsion, Vuk Uskoković, Darko Makovec, Miha Drofenik

Pharmacy Faculty Articles and Research

Nanostructured lanthanum-strontium manganites have been synthesized using two different co-precipitation approaches, one in bulk solution, and the other in reverse micelles of CTAB/1-hexanol/1-butanol/water microemulsion. In both cases, precursor cations were precipitated by alkali precipitating agents. The properties of the material synthesized by using these two methods were compared in order to reveal potential advantages of microemulsion-assisted approach. The influence of the annealing conditions on the properties of synthesized manganites was investigated by using X-ray diffraction, transmission electron microscopy, differential thermal analysis, thermogravimetric analysis and magnetic measurements.

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Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin May 2005

Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin

Chemistry Faculty Publications

The present report describes the preparation and characterization of several N-2-(trimethylsilyl)ethyl-N-nitrosocarbamates, designed as precursors to thermally unstable secondary N-nitrosocarbamate anions via fluoride-assisted cleavage. X-ray structural studies demonstrate that the core N-nitrosocarbamate moiety has a nearly planar geometry, with an s-E orientation at the N–N bond. DFT calculations (B3LYP/6-31+G(d)) reproduce accurately the structural features of the title compounds and detailed conformational analysis at the same level of theory addresses the long-standing issue of preferred geometries for three classes of related structures: N-nitrosocarbamates, N-nitrosoureas and N-nitrosoamides. Desilylation studies demonstrate that both the …

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Synthesis Of Relatively Highly Magnetic Nano-Sized Nizn-Ferrite In Microemulsion At 45 Oc, Vuk Uskoković, Miha Drofenik Feb 2005

Synthesis Of Relatively Highly Magnetic Nano-Sized Nizn-Ferrite In Microemulsion At 45 Oc, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

The procedure for the preparation of NiZn-ferrite powder with average particle size of 10 nm and saturation magnetization of 50 emu/g by using precipitation reaction between acidified sulphate precursor salts and NH4OH as the precipitating agent in the water-in-oil domain of the microemulsion CTAB/1-hexanol/water at 45 oC is presented herein. TEM measurements have revealed relatively uniform morphology of the particles, which are associated in coral-like agglomerates. EDS measurements have been used for qualitative analysis of the sample, whereby FAAS measurement has been performed in order to reveal the proportion of the cations in the sample - Ni : Zn : …

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The Characterization Of Nanosized Nickel-Zinc Ferrites Synthesized Within Reverse Micelles Of Ctab/1-Hexanol/Water Microemulsion, Vuk Uskoković, Miha Drofenik, Irena Ban Dec 2004

The Characterization Of Nanosized Nickel-Zinc Ferrites Synthesized Within Reverse Micelles Of Ctab/1-Hexanol/Water Microemulsion, Vuk Uskoković, Miha Drofenik, Irena Ban

Pharmacy Faculty Articles and Research

Stoichiometric nanocrystalline nickel–zinc ferrites were synthesized by a reverse micelle method following a multi-microemulsion approach. Different pH values were chosen for the alkali precipitating reaction during the synthesis of different powders. Synthesized, as-dried and subsequently calcined powders were characterized in terms of their magnetic properties. XRD analyses and specific-surface area measurements were used to determine the average particle sizes of the synthesized samples. DCS and TGA measurements were performed to reveal the phase transitions within the samples at elevated temperatures, whereas TEM was used to view and record the microstructure of the nanosized ferrite samples. A possible mechanism of the …

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Synthesis Of Nanocrystalline Nickel-Zinc Ferrites Via A Microemulsion Route, Vuk Uskoković, Miha Drofenik May 2004

Synthesis Of Nanocrystalline Nickel-Zinc Ferrites Via A Microemulsion Route, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

Nanostructured NiZn-ferrites were synthesized using a low-temperature co-precipitation method within the reverse micelles of ternary CTAB/1-hexanol/water microemulsions. The influence of pH on the precipitation reaction was investigated. It was found that a higher pH resulted in more crystalline particles. Subsequent oxidation of the ferrous ions precipitate, which leads to the formation of spinel ferrites, is discussed. Diffraction-lines broadening and specific surface area measurements yielded an average particle size of ~ 3 nm. The saturation magnetization of the samples was 20 times smaller than for traditionally synthesized NiZn-ferrites, while the coercivities were 10 - 100 times larger than bulk NiZn-ferrites, which …

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Synthesis And Characterization Of Hydroxyapatite-Collagen Biocomposite Materials, Vuk Uskoković, Nenad Ignjatović, Nadejda Petranović Sep 2002

Synthesis And Characterization Of Hydroxyapatite-Collagen Biocomposite Materials, Vuk Uskoković, Nenad Ignjatović, Nadejda Petranović

Pharmacy Faculty Articles and Research

Hydroxyapatite-collagen composite is a prosperous biomaterial in reconstructive surgery for the reparation of defects within human hard tissue. Within this research, three-dimensional blocks of HAp/collagen composite biomaterial were synthesized by homogenizing the HAp/collagen mixture by cold and hot (T=60oC) pressing (P=49 MPa). The changes in the system were followed by using thermal analysis (DSC & TGA), FT-IR spectroscopy and scanning electron microscopy (SEM). The identification and kinetic analysis of appearing phase transition were done. FT-IR spectrum of the biocomposite shows that neither cold nor hot pressing had significant influence on the individual components of the composite. SEM of the fracture …

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Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels Jan 1998

Mea Culpa: Formal Education And The Dis-Integrated World., Brian P. Coppola, Douglas S. Daniels

Chemistry Faculty Publications

Formal education has removed itself so far from any truly integrated view of the Natural World that fragmentation and certainty are prevailing ethics. Technological progress has resulted in increased specialization within academic disciplines and their concurrent separation from each other. Knowledge is extracted from a fully integrated world, but is examined and defined by the 'dis-integrated' objectives.

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The Role Of Written And Verbal Expression In Improving Communication Skills For Students In An Undergraduate Chemistry Program, Brian P. Coppola, Douglas S. Daniels Aug 1996

The Role Of Written And Verbal Expression In Improving Communication Skills For Students In An Undergraduate Chemistry Program, Brian P. Coppola, Douglas S. Daniels

Chemistry Faculty Publications

Proofreading, editing, and critique, the customary assessment tools scientists use to evaluate professional journal articles, grant applications, and any other writing, can be applied equally well in introductory science instruction. Such feedback is, in fact, crucial to growth and development. When learning anything new, students and faculty alike rely heavily on sources other than themselves (‘external editors’) to assess their understanding as they develop self-assessment skills (or ‘internal editors’). Although they rarely describe it in these terms, faculty nonetheless assume that students have developed and refined their internal skills by the time they take examinations and write term papers. Unfortunately, …

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Nonlinear Optical Properties Of Bacteriorhodopsin: Assignment Of The Third-Order Polarizability Based On Two-Photon Absorption Spectroscopy, Robert R. Birge, Mark Masthay, Jeffery A. Stuart, Jack R. Tallent, Chian-Fan Zhang Jun 1991

Nonlinear Optical Properties Of Bacteriorhodopsin: Assignment Of The Third-Order Polarizability Based On Two-Photon Absorption Spectroscopy, Robert R. Birge, Mark Masthay, Jeffery A. Stuart, Jack R. Tallent, Chian-Fan Zhang

Chemistry Faculty Publications

The third-order (pi) -electron polarizability, (gamma) (pi), of bacteriorhodopsin in the 0.0 - 1.2 eV optical region is assigned based on an analysis of the experimental two-photon properties of the low-lying singlet state manifold. The following selected values of (gamma) (pi) (units of 10-36 esu) are observed: (gamma) (0;0,0,0) equals 2482 +/- 327; (gamma) (-3(omega) ;(omega) ,(omega) ,(omega) ) equals 2976 +/- 385 ((omega) equals 0.25 eV), 5867 +/- 704 ((omega) = 0.5 eV), 14863 +/- 1614 ((omega) = 0.66 eV), 15817 +/- 2314 ((omega) equals 1.0 eV), 10755 +/- 1733 ((omega) equals 1.17 eV). The third-order polarizability of this …

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Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang May 1989

Origins Of The Quantum Efficiency Duality In The Primary Photochemical Event Of Bacteriorhodopsin, Robert R. Birge, Leonore A. Findsen, Albert F. Lawrence, Mark Masthay, Chian-Fan Zhang

Chemistry Faculty Publications

Experimental and theoretical evidence is presented which suggests that two distinct forms of light-adapted bacteriorhodopsin may exist. We propose that these two forms have characteristic photocycles with significantly different primary quantum yields. INDO-PSDCI molecular orbital procedures and semiempirical molecular dynamics simulations predict that one ground state geometry of bR undergoes photochemistry with a primary quantum yield, Φ1, of ~ 0.27, and that a second ground state geometry, with a slightly displaced counterion, yields Φ1 ~ 0.74. This theoretical model is supported by the observation that literature measurements of Φ1 tend to fall into one of two categories- those that observe …

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A Theoretical Investigation Of The One– And Two–Photon Properties Of Porphyrins, Mark Masthay, Leonore A. Findsen, Brian M. Pierce, David F. Bocian, James S. Lindsey, Robert R. Birge Jan 1986

A Theoretical Investigation Of The One– And Two–Photon Properties Of Porphyrins, Mark Masthay, Leonore A. Findsen, Brian M. Pierce, David F. Bocian, James S. Lindsey, Robert R. Birge

Chemistry Faculty Publications

The one‐ and two‐photon properties of free base porphin, free base porphin dianion, and the 2,4‐substituted diformyl and divinyl analogs of these molecules are studied using a semiempirical SCF‐MO formalism (CNDO‐π‐SCF‐MO‐PSDCI) including extensive single and double configuration interaction. Strongly two‐photon allowed states are predicted to lie in the Soret region as well as in the region between the Soret and visible bands. A number of the two‐photon allowed states in the Soret region are predicted to have two‐photon absorptivities exceeding 100×10−50 cm4 s molecule−1 photon−1. The calculations indicate that the visible (Q) states are well characterized by the …

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The Development Of Colloid Chemistry, Oscar A. Bouise Jun 1930

The Development Of Colloid Chemistry, Oscar A. Bouise

Electronic Theses and Dissertations

At first, it was as a blur, that had shrouded a great mystery for ages and ages, until some seventy odd years ago. Then came Thomas Graham, who could not satisfy himself with merely viewing a blur as a blur. Being a scientist, he applied his mind experimentally, which the keen precision of any of the eminent astronomers using a telescope, and viewed more clearly this mist which hovered above the horizon.

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