Search results for "Urea"
showing 10 items of 888 documents
Two dimensional self-assembly of bis-acylureas having various functional end groups.
2011
We present the synthesis and morphology study of thirteen bis-acylurea molecules with various functional end groups. The bis-acylureas have two acylurea groups, -NH-CO-NH-CO-, divided by a pentamethylene spacer, -(CH(2))(5)-, and two symmetric functional end groups, such as, aliphatic, benzyl, mono- and bi-thiophenyl, sulfur-containing, and propargyl (HC[triple bond]CCH(2)-) moieties. The bis-acylureas were synthesized by the coupling reactions of ureas with pimeloyl chloride or pimelic acid. Upon cooling from hot isotropic solutions, the bis-acylureas spontaneously form supermolecules. In the cases of aliphatic, benzyl, mono- and bi-thiophenyl functional groups, two dimensional supramolecu…
A Self-Sorting Scheme Based on Tetra-Urea Calix[4]arenes
2009
Size and shape do matter: When dimerized in nonpolar solvents, an equimolar mixture of eleven tetra-urea calix[4]arenes with different wide-rim substituents self-sorts into only six out of 35 different homo- and heterodimers (see picture). Since the calixarene scaffold and the four urea units are the same in all cases, the self-sorting process is driven only by the cooperative action of steric requirements and stoichiometry.
Vox Naturae: The Myth of Animal Nature in the Latin Roman Republic
2016
The paper examines the representation of animals as embodiment of nature in the culture of the late Roman republic. By discussing a selection of passages from Sallust, Cicero and Lucretius in conjunction with other Greek and Latin sources, the paper shows that the typically Western myth of 'animal nature' - the cultural belief that animal mirror a perennial state of nature, as opposed to human society - played a very important role in the ethical debate of the first century BC and took in this period a form which was bound to influence the centuries to come.
Stress management strategies and quality of life in undergraduate nursing and midwifery students in Poland: A pilot study
2022
Abstract Aim To establish the level of the quality of life (QOL) and its determinants in nursing and midwifery students, evaluate stress management strategies and find the correlation between the frequency of specific strategies and the QOL. Design Diagnostic survey. Methods The study was conducted in June 2019. Two hundred thirty‐four undergraduate students were examined with the use of Mini‐Cope Inventory of Stress Management Measurement (Mini‐Cope) and World Health Organization Quality of Life Instrument Brief Form. Results The average QOL of the respondents was found as good (4.06 ± 0.73). The students graded their QOL in the social relationship domain the highest (15.98 ± 2.97) and the…
Overload of Medical Documentation: A Disincentive for Healthcare Professionals
2020
This review addresses the theories concerning the development and functioning of medical bureaucracy creating an excess of the patient records. An ever-growing number of medical files comply with the typical development of the bureaucratic management of an entrepreneurial organization, an essential feature of which is the life cycle of documentation. When the life cycle ends, an update is created with a multiplication of forms and items to be filled out, resembling that of what happens with the outdated computer program. Yet medical records should have a logical and well-functioning structure using the language of computer science in the form of a cascade or evolutionary model. Further, we …
Dynamics in the Field of Museums: Contemporary Challenges for Polish Museologists
2018
The aim of this text is to present and analyze the attitudes of Polish museologists towards the changes currently taking place in the field of museums. More specifically, it will focus on their opinions regarding the evolution of museums—from the traditional model, based on symbolic violence, to the contemporary model, which accents the subjectivity of the audience. Its conclusions, based on analyses of 26 qualitative interviews with employees of Polish museums, are as follows: the organizational changes taking place in Polish museums do not relieve museologists from bureaucratic work; the collections in museums distinguish them from other institutions of culture; there is a struggle …
Improvement of Resveratrol Permeation through Sublingual Mucosa: Chemical Permeation Enhancers versus Spray Drying Technique to Obtain Fast-Disintegr…
2021
Resveratrol (RSV) is a natural polyphenol with several interesting broad-spectrum pharmacological properties. However, it is characterized by poor oral bioavailability, extensive first-pass effect metabolism and low stability. Indeed, RSV could benefit from the advantage of the sublingual route of administration. In this view, RSV attitudes to crossing the porcine sublingual mucosa were evaluated and promoted both by six different chemical permeation enhancers (CPEs) as well as by preparing four innovative fast-disintegrating sublingual mini-tablets by spray drying followed by direct compression. Since RSV by itself exhibits a low permeation aptitude, this could be significantly enhanced by…
Acid- and Base-Catalysis in the Mononuclear Rearrangement of Some (Z)-arylhydrazones of 5-Amino-3-benzoyl-1,2,4-oxadiazole in Toluene: Effect of Subs…
2011
The reaction rates for the rearrangement of eleven (Z)-arylhydrazones of 5-amino-3-benzoyl-1,2,4-oxadiazole 3a-k into the relevant (2-aryl-5-phenyl-2H-1, 2,3-triazol-4-yl)ureas 4a-k in the presence of trichloroacetic acid or of piperidine have been determined in toluene at 313.1 K. The results have been related to the effect of the aryl substituent by using Hammett and/or Ingold-Yukawa-Tsuno correlations and have been compared with those previously collected in a protic polar solvent (dioxane/water) as well as with those on the analogous rearrangement of the corresponding (Z)-arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole 1a-k in benzene. Some light can thus be shed on the general di…
A novel and simple method for the purification of extracellular levansucrase from Zymomonas mobilis.
2003
A new and simple method for the purification of extracellular levansucrase from Zymomonas mobilis from highly viscous fermentation broth was developed. After incubation of the fermentation broth with a fructose-polymer cleaving enzyme preparation (Fructozyme, Novozymes, DK) for 48 h, levansucrase precipitated as aggregates and was redissolved in a 3 M urea solution. By ongoing size-exclusion chromatography on Sephacryl S-300 the final levansucrase preparation was purified 100-fold and exhibited a specific activity of 25-35 U/mg(protein). The levansucrase was stable in 3 M urea solution for at least four months without inactivation. To maximize the enzyme yield the dynamic changes of extrace…
Supercritical fluid crystallization of adipic acid using urea as habit modifier
2008
The crystal morphology of adipic acid mediated by the action of urea as additive has been investigated using the supercritical antisolvent precipitation (SAS). The process was performed using acetone and carbon dioxide as solvent and antisolvent, respectively. The effect of urea concentration in the liquid solution and of precipitation pressure on the crystal habit was investigated; the products were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and infrared spectrometry (FT-IR). Urea was found to be very effective in modifying the crystal habit of adipic acid from needle-like shape with a length of several hun…