Search results for "MOLA"
showing 10 items of 1216 documents
Convenient Access to α‐Amino‐ω‐Hydroxyl Heterobifunctional PEG and PPO via a Sacrificial Hexahydro‐Triazine Star Strategy
2019
The anionic ring opening polymerizations of ethylene oxide (EO) and propylene oxide (PO) are performed by using 1,3,5-triethanol hexahydro-1,3,5-triazine (TrAz) as a "sacrificial" trifunctional initiator. Well-defined three-arm star polymers are obtained with a narrow molecular weight distribution (M w /M n < 1.1). Molecular weights range from 3-15 kg mol-1 . Since these star polymers possess an acid-labile hexahydro-triazine core, acidic hydrolysis leads to cleavage of the arms. This gives access to well-defined α-amino-ω-hydroxyl heterobifunctional poly(ethylene glycol) (PEG) and poly(propylene oxide) (PPO) in the molecular weight range of 1-5 kg mol-1 and low dispersity M w /M n < 1.1. T…
Characterization of ethylene oxide/tert-octylphenol condensates by ultraviolet and infrared spectrometry
1986
Abstract The average degree of condensation of ethylene oxide/tert-octylphenol condensate surfactants can be estimated rapidly by u.v. and i.r. spectrometry. The u.v. method is based on evaluating the specific absorptivity, a , at 275 nm in aqueous ethanol (60:40 v/v), and inserting this value in equations obtained from previously characterized samples, relating a to the average properties to be determined. Infrared spectrometry is applied similarly; the average properties to be determined are related to the ratio between the band heights at 960 and 840 cm −1 . The relative standard deviations ( n = 10) obtained for a sample of Triton X-100 were 2% by u.v. spectrometry, and 3% by i.r. spect…
Secondary structure of peptides. 4:13C-Nmr CP/MAS investigation of solid oligo- and poly(L-alanines)
1983
Primary and tertiary amine-initiated polymerizations of L-alanine-N-carboxyanhydride (L-Ala-NCA) were conducted at 20 or 100°C in a variety of solvents. The 75.5-MHz 13C-nmr CP/MAS spectra of the resulting poly(L-alanines) revealed that all samples contain both α-helix and pleated-sheet structures. Depending on the reaction conditions the α-helix content varied between ca. 1 and 99%. Reprecipitation from aprotic nonsolvents does not change the α-helix/β-sheet ratio, indicating that this ratio is thermodynamically controlled. Since relatively large amounts of oligopeptides of degree of polymerization (DP) 4–6 can be extracted by means of acetic acid, it is concluded that (a) most poly(L-alan…
The role of crystalline, mobile amorphous and rigid amorphous fractions in the performance of recycled poly (ethylene terephthalate) (PET)
2012
[EN] The action of thermo-mechanical degradation induced by mechanical recycling of poly(ethylene terephthalate) was simulated by successive injection moulding cycles. Degradation reactions provoked chain scissions and a reduction in molar mass mainly driven by the reduction of diethyleneglycol to ethylene glycol units in the flexible domain of the PET backbone, and the formation of -OH terminated species with shorter chain length. The consequent microstructural changes were quantified taking into account a three-fraction model involving crystalline, mobile amorphous (MAF) and rigid amorphous fractions (RAF). A remarkable increase of RAF, to a detriment of MAF was observed, while the percen…
Sulfur-free pulping of hot-water-extracted spruce sawdust
2016
Softwood (Picea abies) sawdust was hot-water-extracted with two multi-phase processes (160-180°C, 100-280 min, and liquor-to-wood ratio 5 l/kg) corresponding to P-factors of ~780 (yield 80.0%) and ~4580 (yield 72.4%). The pre-treated materials were then pulped with the soda-AQ cooking (170°C, NaOH charge 20%, AQ charge 0.1%, 30-150 min, and liquor-to-wood ratio 5 l/kg), resulting in a yield range of 36.1-61.4% (for reference cooks without pre-extraction 47.9-60.0%). It was observed that the pre-extraction under moderate conditions enhanced the dissolution especially of large-molar-mass lignin during cooking, and the total amount of the dissolved lignin was also higher than that removed from…
Saying Hello World with MOLA - A Solution to the TTC 2011 Instructive Case
2011
This paper describes the solution of Hello World transformations in MOLA transformation language. Transformations implementing the task are relatively straightforward and easily inferable from the task specification. The required additional steps related to model import and export are also described.
Latvijas zvanu centru SIA Transcom Worldwide Latvia un SIA Sonido sociālā tīkla Facebook komunikācijas analīze 2021. gadā
2022
Bakalaura darba “Latvijas zvanu centru SIA Transcom Worldwide Latvia un SIA Sonido sociālā tīkla Facebook komunikācijas analīze 2021. gadā” mērķis ir izpētīt minēto uzņēmumu Facebook komunikāciju un sniegt tās vērtējumu. Mērķa īstenošanai tika izmantotas trīs pētījuma metodes - kontentanalīze, intervija un aptauja. Teorētiskajā daļā tika aplūkotas teorētiskās nostādnes, kā sociālo tīklu sabiedrība, sociālo tīklu komunikācija, sociālo tīklu komunikācijas stratēģijas, organizāciju ārējā komunikācija, zīmola tēls un sociālo tīklu auditorijas piesaistes metodes. Empīriskajā daļā tika noskaidrots, ka uzņēmumu nepieciešamie uzlabojumi komunikācijā, korelē ar publicētā satura kontentanalīzes datie…
Ultrafast ionization and rotational dynamics of molecules in strong laser fields
2021
The investigation of ultrafast molecular dynamics is of great importance towards the understanding of a variety of natural phenomena in physical and chemical sciences. With the rapid development of femtosecond laser systems and precision detection technologies, it is possible now to visualize and steer the motion of molecules in matter as well as the ultrafast dynamics of electrons and nuclei in molecules on a microscopic timescale. When a molecule is exposed to a strong laser field, its electrons can be freed or excited, which often triggers a rapid dissociation of the system, in which the released electrons and nuclei exhibit a strong correlation, while the electronic motion on attosecond…
Shape transitions of giant liposomes induced by an anisotropic spontaneous curvature
2000
International audience; We explore how a magnetic field breaks the symmetry of an initially spherical giant liposome filled with a magnetic colloid. The condition of rotational symmetry along the field axis leads either to a prolate or to an oblate ellipsoid. We demonstrate that an electrostatic interaction between the nanoparticles and the membrane triggers the shape transition. PACS numbers: 75.
The effect of composite resin preheating on marginal adaptation of class II restorations
2020
Background One of the problems with a high filler content composite resins is gap formation at restorative material-tooth interface. The present study investigated the effect of preheating composite resins on the formation of marginal gap in Cl II restorations. Material and Methods In this in vitro study Sixty Cl II cavities were prepared on the mesial and distal surfaces of 30 extracted premolar teeth. The gingival floor of cavities was placed 1 m below the CEJ. The samples were randomly allocated to 4 groups for restoration placement: group 1, Filtek P60 composite resin at room temperature; group 2, Filtek P60 composite resin at 68°C; group 3, X-tra fil composite resin at room temperature…