184 research outputs found
Nanoparticle-coated microcrystals
Coprecipitation provides a rapid high-yield method for self-assembly of nanoparticles on the surface of flat water-soluble crystalline surfaces and a simple immobilisation technique prior to storage or thermal and chemical modification
TehnoloÅ”ke pretpostavke CDA metode i koncepcije tehniÄkih reÅ”enja
The paper focuses on CDA plant protection method and on the technical solutions for the sprayers to help realize this method. CDA method enables excellent distribution of the chemical to be sprayed, effective active matter utilization and a lower environmental contamination, thereby protecting plants for a much shorter time. It also reduces treatment rate from 300-400 l/ha, thereby increasing working speed by 50% and the machine output, too.U ovom radu su iznete tehnoloÅ”ke pretpostavke CDA metode zaÅ”tite bilja kao i tehniÄka reÅ”enja rasprskivaÄa sa kojima se može realizovati navedena metoda. Primenom CDA metode stiÄu se prednosti koje se sastoje u potpunijem nanoÅ”enju rasprÅ”ene teÄnosti, shodno tome bolje iskoriÅ”Äavanje aktivnih materija i manje zagaÄenje životne sredine. Ovo omoguÄava realizaciju zaÅ”tite bilja u kraÄem vremenskom periodu. Pored toga, primenom CDA metode smanjuje se norma tretiranja sa 300 na 400 l/ha Äime se ostvaruje poveÄanje radne brzine za 50% a time i produktivnost maÅ”ine
Parametri suÅ”enja koÅ”tiÄavog voÄa
The paper presents the study results on technical and technological parameters in the process of low-temperature drying of stone fruit (plum and apricot) under both laboratory conditions and in a multi-purpose prototype dryer intended for plant material drying. The experimental investigations comprised flow and thermal measurements, technological and kinetic drying parameters. Major emphasis was on temperature and relative humidity of the drying agent and moisture and temperature of the dried material, as well as the drying rate. According to the results obtained, the preheating period was 2-3 hours depending on the type of the material and the drying regime i.e. on the condition of the drying agent. Maximum plum drying rate was recorded 2 h after the beginning of the process and amounted to about 1.15 kg w/kg d.b.h. In the case of apricot drying, maximum drying rate was approx. 0.45 kgw/kg d.b.h. and was registered only 4 hours after the beginning of the drying process, which differed from the plum drying rate under approximately equal drying regime. In addition, the apricot drying kinetics curve differed in shape from the plum drying kinetics curve. The obtained quality of both dried fruits under low-temperature drying conditions was found to meet standard requirements to a great extent primarily respecting sugar and acid loss and the fact that there was no odor or contamination of the fruit. The results obtained showed that, in addition to the technical designs of the drying system, the fruit drying process was found to be significantly affected by how the process itself the duration of which could be reduced, was being managed.U radu su prikazani rezultati istraživanja tehniÄko tehnoloÅ”kih parametara procesa niskotemperatuskog suÅ”enja plodova koÅ”tiÄavog voÄa (Å”ljiva i kajsija). Eksperimentalna istraživanja sprovedena na laboratorijskoj instalaciji i na prototipskoj univerzalnoj suÅ”ari namenjenoj za suÅ”enje biljnih materijala, obuhvatila su strujnotermiÄka merenja, parametre kinetike procesa i tehnoloÅ”ke parametre suÅ”enja. Posebno su analizirani temperatura i relativna vlažnost agensa suÅ”enja, vlažnost i temperatura materijala za suÅ”enje kao i brzina suÅ”enja. Rezultati pokazuju da period pregrevanja materijala iznosi od 2-3 h, Å”to je uslovljeno vrstom materijala i režimom suÅ”enja tj. stanjem agensa suÅ”enja. Maksimalna brzina suÅ”enja plodova Å”ljive nastaje nakon 2 h i iznosi oko 1,15 kg w/kg s.m.h. Kod suÅ”enja plodova kajsija maksimalna brzina suÅ”enja iznosi približno 0,45 kgw/kg s.m.h. i pojavljuje se tek nakon 4 Äasa od poÄetka procesa u Äemu se razlikuje od brzine suÅ”enje plodova Å”ljive za približno isti režim suÅ”enja. Pored toga, kriva kinetike suÅ”enja kajsija ima drugaÄiji oblik u odnosu na krivu suÅ”enja Å”ljiva. Ostvaren kvalitet obe vrste osuÅ”enih plodova sa navedenim niskotemperaturskim režimima u velikoj meri odgovara standardima pre svega u pogledu gubitka Å”eÄera i kiselina, kao i odsustva bilo kakvih mirisa i zagaÄenosti plodova. Dobijeni rezultati ukazuju da, pored tehniÄkih reÅ”enja sistema za suÅ”enje, na uspeh procesa znaÄajan uticaj ima i samo voÄenje procesa Äije se trajanje može redukovati
Ultrasonic studies of solid azobenzene decorated polymer thin films
This work investigates the effect of ultrasound on switching of cis azobenzene isomers to their trans counterparts in solid films of methyl methacrylate and methacryloyloxyazobenzene copolymers [P(MMA/MOAB)]. UV/Vis and 1H NMR spectroscopy demonstrates that 46% of the cis isomer converts to the trans form purely by ultrasonic agitation and 46% converts to the trans isomer by localised ultrasound induced heating effects. Comparative studies of isomerisation by ultrasound wave, heat and visible irradiation shows that ultrasound exposure requires a longer time to switch the cis to trans conformation. The estimated activation energy for the cis to trans conversion in the solid polymer films is shown to be comparable to previous values of azobenzene isomerization, indicating that incorporation of the chromophore in a polymeric system affects the kinetics of transition, but not the barriers to conformational change
Uticaj promene naÄina koriÅ”Äenja zemljiÅ”ta na strukturu livadske crnice u zapadnoj Srbiji
Changes in land use can significantly affect aggregate distribution and water stability of structural aggregates. This study was conducted in the Kolubara River Valley, Western Serbia, to determine the effects of land use changes on composition and water stability of aggregates in humus horizons (0-30 cm) of noncarbonated Gleyic Fluvisols. This study was conducted at nine sites, where each site contained two adjacent land uses of natural grassland and arable land which underwent crop rotation for >100 years. Soil samples were taken from depths of 0-10, 10-20 and 20-30 cm for each land use. When the grassland was converted into arable land, the content of the agronomically most valuable aggregates (0.25-10 mm) of cultivated soils for a depth of 0-30 cm was significantly reduced by 22-40%, while the percentage of cloddy aggregates (>10 mm) increased by 41-68%, compared to grassland. In addition, the long-term arable soil had significantly (p lt 0.05) lower aggregate stability, determined by wet sieving, than grassland. The lowest aggregate stability was found in aggregates > 3 mm. Their content is ā 2.3 times lower in arable soil (12.6%) than in grassland (28.6%) at a depth of 0-10 cm. In addition, meanweight diameters of dry and wetstable aggregates and structure coefficient showed significant differences between land use at a depth of 0-30 cm. The results showed that the conversion of natural grassland to arable land in the lowland ecosystems of Western Serbia degraded aggregate distribution and stability.Istraživanja su sprovedena u dolini reke Kolubare da bi se utvrdili efekti promene naÄina koriÅ”Äenja zemljiÅ”ta na agregatni sastav i vodootpornost strukturnih agregata u humusnom horizontu (0-30 cm) beskarbonatne livadske crnice. Izabrano je devet lokacija koje su na bliskom rastojanju imale povrÅ”ine pod prirodnom livadskom vegetacijom i oranice koje su stvorene pre viÅ”e od 100 godina razoravanjem prirodnih livada. Nakon razoravanja prirodnih livada i njihovog pretvaranja u oranice, sadržaj agronomski najpovoljnijih strukturnih agregata (preÄnika 0,25-10 mm) u oranicama na dubini 0-30 cm, znaÄajno je smanjen, za 22-40%, dok je sadržaj grudvastih agregata (>10 mm) poveÄan za 41-68 %, u poreÄenju sa livadom. Pored toga, viÅ”egodiÅ”nje oranice imaju znaÄajno (p lt 0,05) manju vodootpornost strukturnih agregata, odreÄenih mokrim prosejavanjem, od livada. Najmanju vodootpornost pokazali su strukturni agregati preÄnika >3 mm. TakoÄe, proseÄni maseni preÄnici suvih i vodootpornih agregata i koeficijent strukture pokazali su znaÄajne razlike izmeÄu razliÄitih naÄina koriÅ”Äenja zemljiÅ”ta na dubini 0-30 cm. Razoravanje livadskih crnica pod prirodnom livadskom vegetacijom istraženog podruÄja i njihova viÅ”egodiÅ”nja obrada doveli su do znaÄajnih negativnih promena agregatnog sastava i smanjenja vodootpornosti strukturnih agregata
Approximate square-root-time relaxation in glass-forming liquids
We present data for the dielectric relaxation of 43 glass-forming organic
liquids, showing that the primary (alpha) relaxation is often close to
square-root-time relaxation. The better an inverse power-law description of the
high-frequency loss applies, the more accurately is square-root-time relaxation
obeyed. These findings suggest that square-root-time relaxation is generic to
the alpha process, once a common view, but since long believed to be incorrect.
Only liquids with very large dielectric losses deviate from this picture by
having consistently narrower loss peaks. As a further challenge to the
prevailing opinion, we find that liquids with accurate square-root-time
relaxation cover a wide range of fragilities
Cerebrospinal fluid and plasma concentration of soluble intercellular adhesion molecule1, vascular cell adhesion molecule1 and endothelial leukocyte adhesion molecule in patients with acute ischemic b
Background. Leukocyte migration into the ischemic area is a complex process controlled by adhesion molecules (AM) in leukocytes and endothelium, by migratory capacity of leukocytes and the presence of hemotaxic agents in the tissue. In this research it was supposed that in the blood and cerebrospinal fluid (CSF) of patients in the acute phase of ischemic brain disease (IBD) there were relevant changes in the concentration of soluble AM (sICAM-1 sVCAM-1 and sE-selectin), that could have been the indicators of the intensity of damaging processes in central nervous system (CNS). Methods. The study included 45 IBD patients, 15 with transient ischemic attack (TIA) 15 with reversible ischemic attack (RIA), and 15 with brain infarction (BI) of both sexes, mean age 66Ā±7. Control group consisted of 15 patients with radicular lesions of discal origin, subjected to diagnostic radiculography without the signs of interruption in the passage of CSF. Changes of selected biochemical parameters were determined in all patients in frame 72 hours since the occurence of an ischemic episode. Concentrations of soluble AM were determined in plasma and CSF by ELISA. Total number of leukocytes (TNL) in peripheral blood was determined by hematological analyzer. Results. The results showed that during the first 72 hrs of IBD significant increases occured in TNL and that the increase was progressive compared to the severeness of the disease. Significant increase of soluble AM concentration was shown in plasma of IBD patients. The increase was highest in BI somewhat lower in RIA and the lowest in TIA patients compared to the control. In CSF concentrations of sICAM-1, sVCAM-1 and sE-selectin demonstrated similar increasing trend as in plasma. Conclusion. TNL, as well as the soluble AM concentrations in plasma and CSF, were increased during the acute IBD phase and progressive in relation to the severeness of the disease, so that they might have been the indicators of CNS inflammatory reaction intensity. Furthermore, the results indicated their role in IBD pathogenesis and offered the possibility of researching the application of antagonists and/or activity modulators of some of them in IBD therapy
Dehydration mechanism of a small molecular solid: 5-nitrouracil hydrate
Previous studies of the dehydration of 5-nitrouracil (5NU) have resulted in it being classified as a āāchannel
hydrateāā in which dehydration proceeds principally by the exit of the water molecules along channels in
the structure. We have re-examined this proposal and found that in fact there are no continuous channels
in the 5NU structure that would contribute to such a mechanism. Product water molecules would be
immediately trapped in unlinked voids in the crystal structure and would require some additional
mechanism to break loose from the crystal. Through a detailed structural analysis of the macro and micro
structure of the 5NU as it dehydrates, we have developed a model for the dehydration process based on
the observed development of structural defects in the 5NU crystal and the basic crystallography of the
material. The model was tested against standard kinetic measurements and found to present a satisfactory
account of kinetic observations, thus defining the mechanism. Overall, the study shows the necessity of
complementing standard kinetic studies with a parallel macro and micro examination of the dehydrating
material when evaluating the mechanisms of dehydration and decomposition processes
PROLACTIN AND HYPERPROLACTINAEMIA IN FEMALE REPRODUCTIVE ENDOCRINOLOGY ā AN UPDATE
Hyperprolactinaemia is one of the most frequent causes of anovulation, resulting in infertility and hypoestrogenicĀ state with consequences on overall womenās health. Recent investigations on biological actions of prolactin, especially prolactin of extrapituitary origin, expand our knowledgeĀ on prolactin role in the human organism and open new questions connected with female reproductive function and treatment of female infertility. This article represents the review of current knowledge on prolactin physiology, etiopathogenesis, clinical features, assessment , differential diagnosis ,and teatment of hyperprolactinaemia in the female patient
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