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1
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Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

100%
Zun M., Dwornicka D., Wojciechowska K., Swiader K., Kasperek R., Rzadkowska M., Poleszak E.
Current Issues in Pharmacy and Medical Sciences
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2014
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vol. 27
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issue 4
213-216
EN
In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w) of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w) of urea had the best constancy.
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Conflicting results of non-invasive methods for detection of Helicobacter pylori infection in children with celiac disease - a preliminary study

88%
Józefczuk J., Mądry E., Nowak J., Walkowiak M., Łochocka K., Banasiewicz T., Pławski A., Kwiecień J., Walkowiak J.
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2016
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vol. 63
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issue 1
127-130
EN
Background: There are no data addressing the usefulness of non-invasive tests for the detection of Helicobacter pylori (HP) infection in celiac disease (CD). Aim: The aim of this study was to compare two most sensitive and specific tests - urea breath test (UBT) and fecal antigen test (FAT) in HP diagnosis in CD patients. Materials and Methods: The study comprised of 76 CD patients, 49 healthy subjects (HS) and 35 patients who underwent differential diagnosis due to abdominal pain (AP patients). The presence of HP infection was evaluated using the 13C isotope-labeled UBT and FAT (ELISA). Results: HP infection was diagnosed based on UBT and FAT in 8 (16.3%) and 7 (14.3%) HS, and in 8 (10.5%) CD patients and 12 (34.3%) AP patients, respectively, using both tests. The prevalence of conflicting results in comparison with positive results (obtained with any of the two tests) was distinctly higher (54.5%) in CD group than in other subjects (23.3%); however, due to low HP prevalence, it did not reach the level of significance (p<0.1759). Conclusion: CD may increase the risk of divergent results of non-invasive tests used for the detection of HP infection in children. Since UBT is the most reliable test, we suggest its standard use as a method of choice in pediatric CD - at least until new evidence emerges supporting a different approach.
3
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Inhibitors of bacterial and plants urease. A review

88%
Macegoniuk K.
Acta Universitatis Lodziensis. Folia Biologica et Oecologica
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2013
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vol. 9
9-16
EN
Urease is an important virulence factor for Helicobacter pylori and Proteus mirabilis as well as in environmental transformations of certain nitrogenous compounds. Urea hydrolysis caused by these microorganisms leads to increased pH and ammonia toxicity and enables bacterial colonization of the human gastric mucosa and urinary tract formation of struvite and carbonate-apatite stones. Due to the possibility of medical applications the development of novel, selective and efficient classes of urease inhibitors which satisfy the low toxicity requirement for human health and have low environmental impact is necessary. In this article are described the various urease inhibitors used so far by researchers, especially in the last few years.
4
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Precipitation of Calcium Carbonate in the Presence of Urea at 293 K and 343 K

88%
Białowicz K., Kiełkowska U.
Polish Journal of Chemical Technology
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2014
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vol. 16
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issue 2
95-98
EN
The results of the precipitation of calcium carbonate from a waste post-distillation liquid (DS) and a sodium bicarbonate saturated solution – both from the Solvay method – in the presence of urea are presented. The investigation was carried out at 293 K and 343 K. Reagent dosage times of 1, 5, 10, 20 and 30 min, and urea concentrations of 5, 6 and 10 mol/dm3 were applied. The granulometric composition, the values of bulk and packing densities and the absorptiveness sorption of water and paraffin oil from the obtained calcium carbonate were investigated.
5
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Plant ureases: Roles and regulation.

88%
Sirko A., Brodzik R.
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2000
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vol. 47
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issue 4
1189-1195
EN
Both urea and urease were subjects of early scientific investigations. Urea was the first organic molecule to be synthesized and jack bean urease was the first enzyme ever to be crystallized. About 50 years later it was shown to be the first nickel metalloenzyme. Since then, nickel-dependent ureases have been isolated from many bacteria, fungi and higher plants. They have similar structures and mechanisms of catalysis. A urease apoenzyme needs to be activated. This process requires participation of several accessory proteins that incorporate nickel into the urease forming catalytic site. In this review, ureases from various organisms are briefly described and the similarities of their structures discussed. Moreover, the significance of urea recycling in plants is explained and recent literature data about the function and activation of plant ureases are presented.
6
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Selective catalytic reduction of NO with ammonia at low temperature over Cu-promoted and N-modified activated carbon

75%
Saad M., Białas A., Grzywacz P., Czosnek C., Samojeden B., Motak M., Saad M., Białas A., Grzywacz P., Czosnek C., Samojeden B., Motak M.
Chemical and Process Engineering
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2020
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vol. 41
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issue 1
7
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Preparation methods of calcium sulphate and urea adduct

75%
Malinowski P., Biskupski A., Głowiński J.
Polish Journal of Chemical Technology
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2007
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vol. 9
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issue 4
111-114
EN
The paper presents the results of laboratory studies on the preparation of calcium sulphate and urea adduct by: grinding, compacting and mixing in the presence of physical water. A method for the measurement of urea conversion into the adduct form, which is based on the difference in solubility of free urea and the adduct bound urea CaSO4·4CO(NH2)2 in n-butanol, was developed. Mixing the reagents in the presence of physical water produced the best results. High urea conversion into the adduct form, over 85%, in the prepared samples indicates that this method can be successfully used to get CaSO4·4CO(NH2)2 adduct.
8
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Conformational destabilization of Bacillus licheniformis α-amylase induced by lysine modification and calcium depletion

75%
Tan C. Y., Rahman R. N. Z. B. R. A., Kadir H. A., Tayyab S.
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2011
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vol. 58
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issue 3
405-412
EN
Bacillus licheniformis α-amylase (BLA) was chemically modified using 100-fold molar excess of succinic anhydride over protein or 0.66 M potassium cyanate to obtain 42 % succinylated and 81 % carbamylated BLAs. Size and charge homogeneity of modified preparations was established by Sephacryl S-200 HR gel chromatography and polyacrylamide gel electrophoresis. Conformational alteration in these preparations was evident by the larger Stokes radii (3.40 nm for carbamylated and 3.34 nm for succinylated BLAs) compared to 2.43 nm obtained for native BLA. Urea denaturation results using mean residue ellipticity (MRE) as a probe also showed conformational destabilization based on the early start of transition as well as ΔGDH2O values obtained for both modified derivatives and Ca-depleted BLA. Decrease in ΔGDH2O value from 5,930 cal/mol (for native BLA) to 3,957 cal/mol (for succinylated BLA), 3,336 cal/mol (for carbamylated BLA) and 3,430 cal/mol for Ca-depleted BLA suggested reduced conformational stability upon modification of amino groups of BLA or depletion of calcium. Since both succinylation and carbamylation reactions abolish the positive charge on amino groups (both α- and ε- amino), the decrease in conformational stability can be ascribed to the disruption of salt bridges present in the protein which might have released the intrinsic calcium from its binding site.
9
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The Influence of Urea on the KHCO3and NH4VO3Solubility in the KHCO3+ NH4VO3+ H2O System

75%
Kiełkowska U., Trypuć M., Mazurek K., Drużyński S.
Polish Journal of Chemical Technology
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2007
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vol. 9
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issue 2
23-26
EN
The influence of urea on the vanadium(V) and potassium ion concentrations in the KHCO3 + NH4VO3 + H2O system was determined in the temperature range of 293 K to 303 K. Additionally, the solution density dependence versus the urea concentration was presented. These data are essential for the assessment of optimum operating conditions for the new production process of potassium carbonate.
10
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Distribution of dissolved amino acids, dissolved saccharides and urea in the southern Drake Passage and the Bransfield Strait during BIOMASS-FIBEX, 1981

75%
Mężykowski T., Mężykowski T.
Polish Polar Research
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1982
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vol. 3
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issue 3-4
11
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The influence of urea on the K2CO3and NH4VO3solubility in the K2CO3+ NH4VO3+ H2O system

75%
Kiełkowska U.
Polish Journal of Chemical Technology
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2008
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vol. 10
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issue 4
25-27
EN
The influence of urea on the vanadium(V) and potassium ion concentrations in the K2CO3 + NH4VO3 + H2O system was determined in the temperature range of 293 K to 313 K. Additionally, the solution density dependence versus the urea concentration was presented. These data are essential for the assessment of optimum operating conditions for the new production process of potassium carbonate.
12
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Precipitation of calcium carbonate in the presence of urea at 293K

75%
Białowicz K., Kiełkowska U., Trypuć M.
Polish Journal of Chemical Technology
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2008
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vol. 10
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issue 4
7-10
EN
The results of the precipitation of calcium carbonate from waste distillation liquor (DS) from the Solvay method and sodium bicarbonate saturated solution in the presence of urea were presented. The investigation was carried out at 293K. The influence of the time of reagents dosage to the solution of urea on the physicochemical character of obtaining product was studied. The time of reagents dosage: 1, 5, 10, 20, 30 min and the concentration of the urea applied: 0.5, 1, 2 and 4 mol/dm3. The granulometric composition, the values of bulk and packing densities and the absorptiveness sorption of water and paraffin oil of the obtaining calcium carbonate were investigated.
13
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The concentration of urea in hemolymph as a marker of health in Lissachatina fulica and Cornu aspersum edible snails – a preliminary study

75%
Ziętek J., Guz L., Wójcik A., Winiarczyk S., Adaszek Ł., Ziętek J., Guz L., Wójcik A., Winiarczyk S., Adaszek Ł.
Polish Journal of Veterinary Sciences
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2019
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issue 2
14
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Estimation of the effectiveness of nbpt for limiting ammonia emission from urea based on the field experiments

63%
Marcinkowski T., Wardencki W.
Ecological Chemistry and Engineering S
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2014
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vol. 21
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issue 1
147-153
EN
The effectiveness of the ammonia emission reduction from NBPT-stabilized urea was investigated in 2011 during a field experiment on a grassland plot fertilized with a one-time dose of 60 kg N/ha. The obtained reduction coefficient of ammonia emission equaled 73% and 39-51% relative to urea without the inhibitor and ammonium nitrate, respectively.
PL
W doświadczeniu polowym wykonanym późną wiosną w 2011 roku badano efektywność redukcji emisji amoniaku z mocznika stabilizowanego NBPT, który wykorzystywano do nawożenia użytków zielonych w jednorazowej dawce 60 kg N/ha. Uzyskany współczynnik redukcji emisji amoniaku w stosunku do mocznika bez inhibitora wynosił 73%, zaś w stosunku do saletry amonowej 39-51%.
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