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The shear experiments revealed two different types of the shear stressdisplacement relations of food powders: smooth curve in the case of wheat flour and groats and a considerable shear stress vibration in the case of fine milk, agglomerated milk and potato starch. The most probable reason of the vibrations is dilation and hardening of the material during slow deformation. The frequency of these vibrations were found to decrease as normal stress increased. Two components of the total strength were suggested: the physical friction strength and the extra component of strength caused by dilation. REFERENCES 1. Bolton M.D. The strength and dilatancy of sands. Géotechnique, 36(1), pp. 65-78, 1986. 2. Dunstan T., Arthur J.R.F., Dalili A., Ogunbekun O.O., Wong R.K.S. Limiting mechanisms of slow dilatant plastic shear deformation of granular media. Nature, 336, pp. 52- 54, 1988. 3. Eurocode 1. Basis of design and actions on structures. Part 4. Actions in silos and tanks. European Committee for Sandarization. Rue de Stassart 36, B-1050 Brussels, 1996. 4. Gephard H. Scherversuche an leicht verdichteten Schüttgütern unter besonderer Berücksichtigung des Verformungsverhaltens. Verein Deutscher Ingenieure, VDI-Verlag GmbH Düsseldorf 3, 68, 1982. 5. Jenike A.W. Storage and flow of solids. Bull. 123, Eng. Expt. Station, Utah State Univ., 1964. 6. Lubert M., de Ryck A., Dodds J.A. Evaluation of the mechanical properties of powder for storage. The Third Israeli Conference for Conveying and Handling of Particulate Solids, Israel, pp. 3.93-3.98, 2000. 7. Maksimovic M. A family of nonlinear failure envelopes for non-cemented soils and rock discontinuities. The Electronic Journal of Geotechnical Engineering, 1, pp. 1-15, 1996 (http://geotech.civen.okstate.edu/ejge/ppr9607). 8. Molerus M. Theory of yield of cohesive powders. Powder Technology, 12, pp. 259-275, 1975. 62
SURFACE CHARGE OF SOILS AND PLANT ROOTS Józefaciuk G. Electric charge of natural materials may be divided onto two general types: permanent charge and variable charge. The permanent charge results from a substitution of higher valence cations by lower valence cations in the atomic (macromolecular or crystal lattice) structure, and a variable charge resulting from dissociation and/or association of protons by surface acidic groups (Van Olphen, 1993). Prevalence of permanent charge exposed on basal planes of the particles is a common feature of most clay minerals. Variable charge occurs on surfaces of most soil solid phase constituents: organic matter, aluminum, iron and silicon oxides, edges of clay minerals and on plant roots surfaces, as well. Variable charge dominates also on kaolinites that is located both on the edges and on the basal Al and Si sites of the mineral (Ward and Brady, 1998). Contrary to the permanent charge, the magnitude of the variable charge depends on the composition of the soil solution (pH, concentration, ionic composition). The variable charge origins from dissociation and association of hydrogen ions (protons) from/to surface functional groups of acidic, basic or amphoteric character. MINERAL SOIL CONSTITUENTS The permanent charge of clay minerals origins from that higher valence cations in the crystal lattice (for example silicon in the silica layers) are substituted by lower valence cations (for example by aluminum) during the genetic processes. This results in the “unsaturation” of oxygen bonds and excess of the negative charge. The substituting cation should be of similar size to this being replaced, therefore this process is called isomorphic substitution. Frequently the summarical amount of the charge resulting from the isomorphic substitution is not equal to the permanent charge of the mineral. For example a part of the lattice charge may be neutralized by specifically bound cations inside the mineral particle structure (i.e. in the interlayers), as this frequently occurs in illites (binding of potassium cations) or may be blocked by multivalent polycations adsorption (Keren, 1986). The amount of permanent charge is characteristic for the mineral and conditions of its genesis. For most frequently occurring clay minerals this charge amounts from a few (kaolin group) by few tens (mica group – illites) to hundreds (smectites, zeolites) of centimoles per kilogram of the mineral. Permanent charge minerals dominate in mineral soils of the temperate climatic zone, therefore soils of these regions are called permanent charge soils. 63
Page 2 and 3:
PHYSICS, CHEMISTRY AND BIOGEOCHEMIS
Page 4 and 5:
IN MEMORIAM Dr Ludmila Petrovna Kor
Page 6 and 7: magnetic (ferrimagnetic) oxides, ma
Page 8 and 9: educed water activity, would favour
Page 10 and 11: In this paper AT sorption by surfac
Page 12 and 13: were obtained with clay content, pH
Page 14 and 15: In present investigation the quartz
Page 16 and 17: Hence, the micromorphology suggests
Page 18 and 19: As the indicators of soil aeration
Page 20 and 21: Stomatal diffusive resistance of th
Page 22 and 23: indicators of soil aeration conditi
Page 24 and 25: REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.
Page 26 and 27: Table 1. Breakdown of numbers and t
Page 28 and 29: MORPHOLOGICAL AND PHYSICOCHEMICAL P
Page 30 and 31: conditions, existing at the first p
Page 32 and 33: INFLUENCE OF TEMPERATURE ON WATER P
Page 34 and 35: moisture % 100 90 80 70 60 50 40 so
Page 36 and 37: STATE OF MICROBIAL COMMUNITIES IN M
Page 38 and 39: million cells/g soil 25 20 15 10 5
Page 40 and 41: THE INFLUENCE OF COMPOSITION AND PR
Page 42 and 43: days grew faster than on substrate
Page 44 and 45: SOIL SALINITY AND CLIMATE CHANGES I
Page 46 and 47: POROUS STRUCTURE OF NATURAL BODIES
Page 48 and 49: These nonuniform classification sys
Page 50 and 51: Mercury intrusion data are plotted
Page 52 and 53: METHOD AND MATERIALS The shear stre
Page 54 and 55: wheat flour NaCl salt fine milk Fig
Page 58 and 59: Variable charge of mineral surfaces
Page 60 and 61: 3. Huffaker RC and Wallace A 1958 P
Page 62 and 63: Q V (pH)/N t = α(pH) = n ∑ i= 1
Page 64 and 65: REFERENCES 1. De Wit, J.C.M, Van Ri
Page 66 and 67: BM - biomass; NM - necromass; MM -
Page 68 and 69: thousand times at the absence of co
Page 70 and 71: . m 131.5 131.0 I Height above sea
Page 72 and 73: SEASONAL VARIABILITY OF SOIL WATER
Page 74 and 75: The mean difference (MD) and the ro
Page 76 and 77: Acknowledgement This paper presents
Page 78 and 79: 1992; Selim 1999). The relative imp
Page 80 and 81: 1.0 C rel 0.5 0.0 v=0.7 D=3.28 v=0.
Page 82 and 83: 1.0 a b C rel 0.5 0.0 0 1 2 3 0 1 2
Page 84 and 85: Comparison of before- and after-pul
Page 86 and 87: provides the accessibility of catio
Page 88 and 89: MODEL RESEARCH ON FORMATION OF SYNT
Page 90 and 91: The analysis of the specific surfac
Page 92 and 93: PHOSPHATE-INDUCED CHANGES IN THE SP
Page 94 and 95: According to the data of Table 1, t
Page 96 and 97: MINERAL-ORGANIC COMPOUND OF SOILS:
Page 98 and 99: RESULTS AND DISCUSSION An analysis
Page 100 and 101: INTRODUCTION CHEMICAL DEGRADATION O
Page 102 and 103: of organic particles and their elec
Page 104 and 105: HNO 3 -extractable form is very clo
Page 106 and 107:
Results demonstrated that Pb and Cd
Page 108 and 109:
tion was measured using the Tjurina
Page 110 and 111:
OUTPUT FLUXES OF LEAD IN FOREST ECO
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Regional data on Pb concentrations
Page 114 and 115:
DEVICE FOR EVALUATION OF THE RAPE P
Page 116 and 117:
SPECTROSCOPIC COMPARISON OF HUMIC A
Page 118 and 119:
ehavior of sequentially extracted H
Page 120 and 121:
MODERN MONITORING SYSTEMS FOR THE M
Page 122 and 123:
The control of the measurement syst
Page 124 and 125:
ASORPTION AND SURFACE AREA OF SOILS
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Nm xCBET N = ( 1− x BET − )[ 1+
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According to this, when x/N (1-x) i
Page 130 and 131:
POTENTIAL OF AZOLLA CAROLINIANA TO
Page 132 and 133:
The decrease of Pb(II) and of Cd(II
Page 134 and 135:
12. 13. 14. 15. 16. Piechalak, A.,
Page 136 and 137:
Kloc, 2001]. Nitrogen adsorption is
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This is worth noting that the lower
Page 140 and 141:
N ( h) 1 2 γ ( h) = [ ( ) ( )] ( )
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Exemplary spatial distributions (sa
Page 144 and 145:
This is worth noting that significa
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adsorbed chemicals to microorganism
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were detected in the untreated soil
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0.4 1000 Moisture [Vol.] 0.3 0.2 0.
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NITROUS OXIDE EMISSION FROM SOILS W
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N2O-N [mg kg -1 ] 100 80 60 40 20 0
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LITERATURE 1. 2. 3. 4. 5. 6. 7. 8.
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where v(t) - CO 2 production rate;
Page 160 and 161:
carbon was involved mainly into mic
Page 162 and 163:
Demkin Vitaliiy DrSc Dmitrakov Leon
Page 164 and 165:
Priputina Irina PhD Rudko Tadeusz P
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