Influence of chitosan characteristics on the coagulation and the flocculation of bentonite suspensions

Ten chitosan preparations with different molecular weights (MW) and degrees of deacetylation (DD) were tested for coagulation of 5 g L(-1) bentonite suspensions at pH 5 and 7 in demineralized water (DW) and in tap water (TW). Coagulation was better in TW than in DW for every condition and lower doses of chitosan were required at pH 5 than at pH 7. More than 95% of residual turbidity (after sedimentation in the absence of chitosan) was removed using less than 0.10 mg L(-1) chitosan in either TW or DW at pH 5 or in TW at pH 7. Higher doses were required for removal of turbidity in DW at pH 7, but in all cases the effective concentrations of chitosan were much lower than required for complete neutralization of the negative charge on the bentonite particles. Removal of turbidity was best for the higher MW chitosans in either the B series (89.5% DD) or the C series (95% DD) of chitosans. Overall, the results were consistent with destabilization of bentonite by the combined mechanisms of electrostatic patch and bridging. The improved performance of chitosan in TW could have been due to improved attachment to bentonite due to the presence of sulfate and other counter-ions in TW.     

Studies of thermal-hydraulic phenomena in EBR-II

An experimental and theoretical program has been undertaken during the past several years with the objective of developing a well-documented understanding of steady-state and transient thermal-hydraulic behavior in EBR-II. The results of this effort have provided reactor designers and system modelers with needed integral-type demonstrations of important phenomena. This paper will discuss the particular problems of steady-state and transient hot channel peaking factors and plant operational characteristics impact upon natural circulation dynamics. Direct in-core experimental measurements have demonstrated that factors used for the prediction of peak coolant temperature rises at normal rated plant conditions may not be conservative due to pin-bundle distortions or inlet flow maldistributions, while those applied during loss-of-flow transients are most likely overconservative due to inter- and intrasubassembly phenomena. The importance of somewhat controllable parameters such as the sequence of primary and secondary pump trips and reactor scram, primary pump rundown times, and nominal operational power-to-flow ratio upon the dynamics of the transition from forced to natural convective flow are also presented.     

Heat-flow near a North Atlantic fracture zone

Fifteen new heat-flow measurements are reported, fourteen of which are located in or near a fracture zone near 43°N on the mid-Atlantic Ridge. These data, combined with earlier nearby measurements, show the fracture zone to have an observable, positive effect on the regional heat-flow field. A good correlation is observed between large near-bottom water potential temperature gradients and the occurrence of significant variations with depth in the measured rate of heat-flow. One measurement was taken in the Horseshoe abyssal plain west of Gibraltar and gave a value of 1.38 μcal/cm²s.     

Psychopathy and punishment.

An experiment to test the hypothesis that psychopathy is associated with deficient passive avoidance learning under punishment. 75 High Pd and 75 Low Pd female undergraduates, equated for intelligence, learned a list of 10 nonsense syllables under 1 of 3 conditions of reinforcement: verbal reward, verbal punishment, and absence of comment by E. Punishment significantly retarded the learning of Low Pd Ss, but not that of High Pd Ss. No significant differences occurred under reward or neutral conditions. The hypothesis was considered confirmed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fantasy need achievement as a motivational construct.

The McClelland-Atkinson theory that arousal of achievement fantasy depends upon arousal of the achievement motive is examined critically in light of accrued empirical evidence. The effects of achievement-arousal conditions on fantasy n Ach are shown to be probably nonmotivational. n Ach scores are shown to be correlated with performance measures in about ? of the studies reported, but the pattern of hypothesis confirmation presents the theory with difficulties. The addition of perceptual and cognitive situational and developmental variables appears to render the empirical evidence theoretically more tractable. It is argued that motivation influences fantasy by processes more complex and less direct than originally thought. (3 p. ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polychlorinated biphenyl,DDT and dieldrin residues in grey seal (Halichoerus grypus) males,females and mother-foetus pairs sampled at the Farne Islands,England, during the breeding season

PCB, DDT, DDE, dieldrin and total non-polar organohalogen residues have been determined in the blubber-lipid of grey seals (Halichoerus grypus) sampled during the 1972 breeding season (November) at the Farne Islands off the north eastern coast of England. PCBs were analysed by gas-liquid chromatography linked to a chlorine- and carbon-selective microwave plasma detector and total organohalogen residues were determined by microcoulometry.Total organohalogen residues were negatively correlated with blubber thickness and positively correlated with age in males (aged 1 to 24 y) and females (aged 5 to 38 y). However, the correlation of blubber-lipid residue with age in males depended upon the inclusion of immature (aged < 6 y) animals, and in females reflected only a small residue increment. The mean blubber organohalogen concentration of the males was significantly greater than that of the females. PCB and DDT group residue concentrations were significantly correlated.PCB, DDT, DDE and dieldrin were detected in the liver of mother/foetus pairs demonstrating transplacental movement of these residues.The possibility of the condition of the seals at breeding time influencing residue levels and of these residues influencing the health of the population is discussed.     

The internal consistency of measures of cognitive structure.

The distribution of judgments between alternative poles of a construct, derived from the grid form of the Role Construct Repertory Test, influences the interpretation of measures of cognitive structure. Investigations of the reliability of these measures have excluded the possibility that differentiation on the basis of similarity is distinct from differentiation on the basis of contrast. In the present study with 107 business school students, judgments of similarity were assumed to be different from those of contrast. The present evaluation of internal consistency, temporal stability, and construct validity for 10 measures of cognitive structure indicates that only 1 measure satisfies criteria on these 3 attributes. (French abstract) (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contribution to the study of the surface groups on carbons—II: Spectroscopic methods

Electron spectroscopy was applied to the study of a colour black (Carbolac 1) and of graphitic oxide, modified by esterification of the acidic surface groups. The deconvolution of the O_ls spectra indicates that in the case of carbon black irreversible transformations of the surface structure occur. On the contrary, for the methylated graphite oxide, a subsequent hydrolysis of the ester groups restores the original structure. IR Spectroscopy (transmission and internal reflection spectroscopies) confirms this observation: the irreversible transformation intervenes during the hydrolysis step of the methylated black.Use of a tracer technique gives direct support to the hypothesis of an enol structure which appears to become partially blocked. Possibly, the labile hydrogen involved in the keto-enol equilibrium is substituted by an alkyl group. The differences in behaviour of the surface groups of carbon black and graphite oxide can be explained on the basis of their location on solid supports having different electronic properties.     

NEIGHBORHOOD EMPOWERMENT AND URBAN MANAGEMENT IN THE 1980s

A variety of forms of neighborhood empowerment have continued to evolve during the 1970s and 1980s. At the most basic level, neighborhood organizations have shown the capability to articulate successfully community interests to both the private and public sectors. Furthermore, these organizations have also shown the capacity to administer neighborhood services and have begun to take on more comprehensive policy making functions. Recent experiences indicate that these efforts have enhanced neighborhood participation, improved the delivery of neighborhood services, and helped resolve conflicts. While the current urban fiscal crisis provides some political opportunities for extending these neighborhood efforts, neighborhood groups will have to avoid vigilantly the economic and political entrapments present in the current situation.