24,389 research outputs found
Development of a cold end filament feeder for a hanging 3D printer
No full textHitrost tiskanja 3D tiskalnikov, ki uporabljajo tehnologijo ekstrudiranja polimerne niti (FFF) je v veliki meri odvisna od hitrosti podajalnika polimerne niti. V zaključni nalogi obravnavamo razvoj podajalnika polimerne niti za viseč 3D tiskalnik, ki bo zmogel večjo podajalno hitrost kot obstoječi podajalniki. Predstavljen je postopek od zastavljanja konstrukcijskih zahtev, preko preučevanja delnih funkcij podajalnika, do ocenjevanja prototipov. Na osnovi ocen delnih rešitev smo prišli do končnega prototipa podajalnika.The speed of 3D printers using fused filament fabrication (FFF) technology depends mostly on the speed of the extruder. In this document we discuss the development of a cold end of extruder for a large-scale 3D printer. A presented process starts from the setting of construction requirements, go through the study of the partial functions of the cold end and finish with the evaluation of prototypes. Based on the estimates of partial solutions we create final prototype of cold end of extruder
PRODAN dual emission feature to monitor BHDC interfacial properties changes with the external organic solvent composition
No full textWe have investigated the water/benzyl-n-hexadecyldimethylammonium chloride (BHDC)/n-heptane:benzene reverse micelles (RMs) interfaces properties using 6-propionyl- 2-(N,N-dimethyl)aminonaphthalene, PRODAN, as molecular probe. We have used absorption and emission (steady-state and time-resolved) spectroscopy of PRODAN to monitor the changes in the RMs interface functionalities upon changing the external organic solvent blend. We demonstrate that PRODAN is a useful probe to investigate how the external solvent composition affects the micelle interface properties. Our results show that changes in the organic solvent composition in water/BHDC/n-heptane:benzene RMs have a dramatic effect on the photophysics of PRODAN. Thus, increasing the aliphatic solvent content over the aromatic one produces PRODAN partition and PRODAN intramolecular electron transfer (ICT) processes. Additionally, the water presence in these RMs makes the PRODAN ICT process favored with the consequent decreases in the LE emission intensity and a better definition of the charge transfer (CT) band. All this evidence suggests that the benzene molecules are expelled out of the interface, and the water−BHDC interactions are stronger with more presence of water molecules in the polar part of the interface. Thus, we demonstrate that a simple change in the composition of the external phase promotes remarkable changes in the RMs interface. Finally, the results obtained with PRODAN together with those reported in a previous work in our lab reveal that the external phase is important when trying to control the properties of RMs interface. It should be noted that the external phase itself, besides the surfactant and the polar solvent sequestrated, is a very important control variable that can play a key role if we consider smart application of these RMs systems.Fil: Agazzi, Federico Martin. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodriguez, Javier. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Falcone, Ruben Dario. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chessa, Juana Josefa. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Correa, Nestor Mariano. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Solvent-Dependent Excited-State Evolution of Prodan Dyes
No full textExcited-state
character and dynamics of two 6-(dimethylamino)-2-acylnaphthalene
dyes (Prodan and Badan-SCH2CH2OH) were studied
by picosecond time-resolved IR spectroscopy (TRIR) in solvents of
different polarity and relaxation times: hexane, CD3OD,
and glycerol-d8. In all these solvents,
near-UV excitation initially produced the same S1(ππ*)
excited state characterized by a broad TRIR signal. A very fast decay
(3, ∼100 ps) followed in hexane, whereas conversion to a distinct
IR spectrum with a ν(CO) band downshifted by 76 cm–1 occurred in polar/H-bonding solvents, slowing down
on going from CD3OD (1, 23 ps) to glycerol-d8 (5.5, 51, 330 ps). The final relaxed excited state was
assigned as planar Me2N → CO intramolecular
charge transfer S1(ICT) by comparing experimental and TDDFT-calculated
spectra. TRIR conversion kinetics are comparable to those of early
stages of multiexponential fluorescence decay and dynamic fluorescence
red-shift. This work presents a strong evidence that Prodan-type dyes
undergo solvation-driven charge separation in their S1 state,
which is responsible for the dynamic fluorescence Stokes shift observed
in polar/H-bonding solvents. The time evolution of the optically prepared
S1(ππ*) state to the S1(ICT) final
state reflects environment relaxation and solvation dynamics. This
finding rationalizes the widespread use of Prodan-type dyes as probes
of environment dynamics and polarity
Fluorescence Quenching of (Dimethylamino)naphthalene Dyes Badan and Prodan by Tryptophan in Cytochromes P450 and Micelles
No full textFluorescence
of 2-(<i>N</i>,<i>N</i>-dimethylamino)-6-propionylnaphthalene
dyes Badan and Prodan is quenched by tryptophan in Brij 58 micelles
as well as in two cytochrome P450 proteins (CYP102, CYP119) with Badan
covalently attached to a cysteine residue. Formation of nonemissive
complexes between a dye molecule and tryptophan accounts for about
76% of the fluorescence intensity quenching in micelles, the rest
is due to diffusive encounters. In the absence of tryptophan, fluorescence
of Badan-labeled cytochromes decays with triexponential kinetics characterized
by lifetimes of about 100 ps, 700–800 ps, and 3 ns. Site mutation
of a histidine residue in the vicinity of the Badan label by tryptophan
results in shortening of all three decay lifetimes. The relative amplitude
of the fastest component increases at the expense of the two slower
ones. The average quenching rate constants are 4.5 × 10<sup>8</sup> s<sup>–1</sup> (CYP102) and 3.7 × 10<sup>8</sup> s<sup>–1</sup> (CYP119), at 288 K. Cyclic voltammetry of Prodan
in MeCN shows a reversible reduction peak at −1.85 V vs NHE
that becomes chemically irreversible and shifts positively upon addition
of water. A quasireversible reduction at −0.88 V was observed
in an aqueous buffer (pH 7.3). The excited-state reduction potential
of Prodan (and Badan) is estimated to vary from about +0.6 V (vs NHE)
in polar aprotic media (MeCN) to approximately +1.6 V in water. Tryptophan
quenching of Badan/Prodan fluorescence in CYPs and Brij 58 micelles
is exergonic by ≤0.5 V and involves tryptophan oxidation by
excited Badan/Prodan, coupled with a fast reaction between the reduced
dye and water. Photoreduction is a new quenching mechanism for 2-(<i>N</i>,<i>N</i>-dimethylamino)-6-propionylnaphthalene
dyes that are often used as solvatochromic polarity probes, FRET donors
and acceptors, as well as reporters of solvation dynamics
Jack Alive / Martin Dead : The Location of the "Author" in Jack London\u27s Martin Eden
No full textThis essay is an attempt to read Martin Eden, Jack Londonʼs autobiographical novel, in terms of the inextricable relationship between the author and the protagonist. Critics have often taken the unbalanced plot and the lack of ironic distance between narrator and character in Martin Eden as the technical weakness of London, but this paper argues that the achievement of this novel owes a great deal to the attachment of London to Martin. The unbalanced structure is a necessary product of the severe struggle of the author to kill his romantic alter ego. // Martin, who aspires to win Ruth Morse, tries to cross class boundaries by making a career of a writer. Even after realizing the emptiness of Ruth, who turns out to be nothing but a typical figure of the bourgeoisie, he somehow persists in loving her. The notion underlying here is that, for Martin, love, career and art are fundamentally inseparable. He objects to the aestheteʼs view of Brissenden on account of his separation of art from career. Martinʼs identity and life consist only in the triunity of love/career/art; the alternative is the repudiation of life. Thus, the unnatural delay of his disappointment in love can be regarded as Londonʼs strategy to set the suicide of Martin as the necessary consequence of the story. // By finishing the story and killing Martin, London finally detaches himself from Martin, reconstructs his self, and, unlike Martin, survives as a professional writer. In this sense, Martin Eden is a story about “writerʼs self-reconstruction.
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Letter from Martin Chizzick
No full textCongratulations to Duane Pearsall for receiving the Enterpreneur of the Year award; note on the letter was written by Pearsall and it mentions that Martin, the author of the letter, died in a airplane accident
Robert Martin Tiffin's Mystery Man Newspaper Articles
No full textAdvertiser-Tribune newspaper clippings featuring a story about Robert Martin (written by Nancy Kleinhenz), a local author from Tiffin (Ohio) who wrote under the pseudonym of Lee Roberts, and two of his short stories. Martin wrote mystery novels in his spare time, creating more than 22 mystery novels. For more information about Robert Martin and a list of books go to http://www.mysteryfile.com/RMartin/JBennett.html
Absorption and Fluorescence of PRODAN in Phospholipid Bilayers: A Combined Quantum Mechanics and Classical Molecular Dynamics Study
No full textAbsorption and fluorescence spectra of PRODAN (6-propionyl-2-dimethylaminonaphthalene) were studied by means of the time-dependent density functional theory and the algebraic diagrammatic construction method. The influence of environment, a phosphatidylcholine lipid bilayer and water, was taken into account employing a combination of quantum chemical calculations with empirical force-field molecular dynamics simulations. Additionally, experimental absorption and emission spectra of PRODAN were measured in cyclohexane, water, and lipid vesicles. Both planar and twisted configurations of the first excited state of PRODAN were taken into account. The twisted structure is stabilized in both water and a lipid bilayer, and should be considered as an emitting state in polar environments. Orientation of the excited dye in the lipid bilayer significantly depends on configuration. In the bilayer, the fluorescence spectrum can be regarded as a combination of emission from both planar and twisted structures
Experiences Using Large Scale Video Walls for Distance Education
No full textWe describe our experiences building and using the Rutgers Videowall, a low-cost telepresence system that has been used teaching 15 courses and colloquia. By relaxing typical spatial telepresence features, such as background continuity, we greatly reduced costs and gained flexibility in the rooms it could be deployed in. The lower costs and room flexibility enabled academic departments to use the wall, in contrast to traditional telepresence systems which remained inaccessible. We found that the Videowall’s spatial distortions did not have a significant impact on useability, as our initial survey results show that students had an overall positive experience.Technical report DCS-tr-72
Hans Martin Schwarz Collection 1934 - 1938
No full textThis collection contains clippings of articles by Hans Martin Schwarz (1917, Hamburg – 2006, New York, better known as Martin Ebon), published between 1934 and 1938 in German-Jewish newspapers on a wide variety of subjects such as sports, emigration, the political situation in Germany, and religious attitudes of the young. It also contains reviews of his books "Einer wie Du und Ich" and "Heiteres, Besinnliches, Nachdenkliches."digitizedHans Martin Schwarz (1917, Hamburg – 2006, New York, better known as Martin Ebon), was a journalist and author. In Germany during the 1930s, he published in a variety of German-Jewish periodicals, primarily the Israelitisches Familienblatt. After immigrating to the United States in 1938, he changed his name to Martin Ebon, and published dozens of books in the areas of world affairs and parapsychology.Processe
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