Relationship Between Electrical Conductivity and Water Activity of Starch-Water Composites

The aim of study was to characterize 52 samples of Slovak honeys of six types (multifloral, acacia, rape, honeydew, forest and mixed). Physico-chemical analysis of honey included the water content, free acidity, pH, water activity, electrical conductivity, and hydroxymethylfurfural (HMF) content. In addition, the colour of honeys was measured using spectrophotometer and Commission Internationale de I`Eclairage method (CIE L*a*b*); four types of honey were used for identification: multifloral, acacia, rape, and honeydew. Mean values of physico-chemical indicators were as follows: water content 16–21%, acidity 6–42 mekv·kg-1, pH 3.68–5.15, water activity 0.505–0.667, electrical conductivity 0.155–1.585 mS·cm-1 and HMF content 0.17–78.5 mg·kg-1. The highest HMF content was found in forest honey with one sample above the limit established by Council Directive 2001/110/EC. The colour of Slovak honeys analysed in this study was very variable and ranged from pale yellow to dark brown. Differences of physico-chemical indicators and colour of honey samples were found to be significant (P < 0.05). The CIE L*a*b* methods can be used for identification of selected honey samples. This is the first similar study on Slovak honey.

Download Full-text

Physico-chemical Parameters of Honey From Melipona mondury Smith, 1863 (Hymenoptera: Apidae: Meliponini)

Journal of Agricultural Science ◽

10.5539/jas.v10n7p196 ◽

2018 ◽

Vol 10 (7) ◽

pp. 196 ◽

Cited By ~ 1

Author(s):

Rogério Marcos de Oliveira Alves ◽

Jacqueline Lemos Viana ◽

Henrique de Abreu Cerqueira Sousa ◽

Ana Maria Waldschmidt

Keyword(s):

Electrical Conductivity ◽

Water Activity ◽

Reducing Sugars ◽

Chemical Properties ◽

Northeastern Brazil ◽

Chemical Parameters ◽

Technical Regulation ◽

Mean Values ◽

Physico Chemical

The physico-chemical properties of honey produced by the stingless bee Melipona mondury from Atlantic Forest in the state of Bahia, northeastern Brazil were evaluated. The evaluated characteristics included: water content, electrical conductivity, pH, acidity, water activity, ashes, diastase, hydroxymethylfurfural (HMF), reducing sugars and saccharose values. The honey samples showed mean values of 29.18% for moisture; 391.5 μS for electrical conductivity; pH of 4.06; 34.3 meq kg-1 for acidity; 0.73 for water activity; 0.18% for ashes; 4.05 (Goethe unit) for diastase; 1.60% for HMF; 65.42% for reducing sugars; and 2.14% of saccharose. Only the diastase activity was above the limits accepted by the Technical Regulation for Identity and Quality of Honey (Brazilian Ministry of Agriculture and Supplies). Most parameters are according to those reported in honeys from other species of stingless bees in Brazil.

Download Full-text

Removing Substrate Background in TEM Microanalysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052857 ◽

1974 ◽

Vol 32 ◽

pp. 568-569

Author(s):

John C. Russ ◽

Nicholas C. Barbi

Keyword(s):

Electrical Conductivity ◽

Rapid Growth ◽

Organic Film ◽

Absolute Concentration ◽

Background Signal ◽

X Ray ◽

Elemental Concentrations ◽

Transmission Electron ◽

Electron Microscopes ◽

The Continuum

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.

Download Full-text

Macromolecular structures of biological specimens are not obscured by controlled osmium impregnation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076639 ◽

1983 ◽

Vol 41 ◽

pp. 606-607

Author(s):

Klaus-Ruediger Peters ◽

Samuel A. Green

Keyword(s):

Thin Films ◽

Electrical Conductivity ◽

Critical Point ◽

Metal Films ◽

High Magnification ◽

Osmium Impregnation ◽

Instrumental Resolution ◽

20 Nm ◽

Continuous Metal

High magnification imaging of macromolecules on metal coated biological specimens is limited only by wet preparation procedures since recently obtained instrumental resolution allows visualization of topographic structures as smal l as 1-2 nm. Details of such dimensions may be visualized if continuous metal films with a thickness of 2 nm or less are applied. Such thin films give sufficient contrast in TEM as well as in SEM (SE-I image mode). The requisite increase in electrical conductivity for SEM of biological specimens is achieved through the use of ligand mediated wet osmiuum impregnation of the specimen before critical point (CP) drying. A commonly used ligand is thiocarbohvdrazide (TCH), first introduced to TEM for en block staining of lipids and glvcomacromolecules with osmium black. Now TCH is also used for SEM. However, after ligand mediated osinification nonspecific osmium black precipitates were often found obscuring surface details with large diffuse aggregates or with dense particular deposits, 2-20 nm in size. Thus, only low magnification work was considered possible after TCH appl ication.

Download Full-text

Total Body Electrical Conductivity Measurements in the Neonate

Clinics in Perinatology ◽

10.1016/s0095-5108(18)30515-3 ◽

1991 ◽

Vol 18 (3) ◽

pp. 611-627 ◽

Cited By ~ 15

Author(s):

Marta L. Fiorotto ◽

William J. Klish

Keyword(s):

Electrical Conductivity ◽

Conductivity Measurements ◽

Total Body

Download Full-text

Electrical Conductivity Imparted to Liquid Air by Alpha Rays

Scientific American ◽

10.1038/scientificamerican03201915-191bsupp ◽

1915 ◽

Vol 79 (2046supp) ◽

pp. 191-191

Keyword(s):

Electrical Conductivity

Download Full-text

Effect of MCl (M = Na, K) addition on microstructure and electrical conductivity of forsterite

The European Physical Journal Applied Physics ◽

10.1051/epjap/2020200161 ◽

2020 ◽

Vol 92 (1) ◽

pp. 10901

Author(s):

Saloua El Asri ◽

Hamid Ahamdane ◽

Lahoucine Hajji ◽

Mohamed El Hadri ◽

Moulay Ahmed El Idrissi Raghni ◽

...

Keyword(s):

Heat Treatment ◽

Electrical Conductivity ◽

Single Phase ◽

Sol Gel ◽

Complex Impedance ◽

Transmission Spectra ◽

Electrical Measurements ◽

Cation Type ◽

Edx Analyses ◽

The Fourier Transform

Forsterite single phase powder Mg2SiO4 was synthesized by sol–gel method alongside with heat treatment, using two different cation alkaline salts MCl as mineralizers (M = Na, K) with various mass percentages (2.5, 5, 7.5, and 10 wt.%). In this work, we report on the effect of the cation type and the added amount of used mineralizer on microstructure and electrical conductivity of Mg2SiO4. The formation of forsterite started at 680–740 °C and at 630–700 °C with KCl and NaCl respectively, as shown by TG-DTA and confirmed by XRD. Furthermore, the Fourier transform infrared (FTIR) transmission spectra indicated bands corresponding to vibrations of forsterite structure. The morphology and elemental composition of sintered ceramics were examined by SEM-EDX analyses, while their densities, which were measured by Archimedes method, increased with addition of both alkaline salts. The electrical measurements were performed by Complex Impedance Spectroscopy. The results showed that electrical conductivity increased with the addition of both mineralizers, which was higher for samples prepared with NaCl than those prepared with KCl.

Download Full-text