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ACUTE CHROMIUM (CHROMIUM(+VI)) TOXICITY IN THE ESTUARINE SHRIMP, MYSIDOPSIS BAHIA (CRUSTACEA: MYSIDACEA)Bauman, Stephanie January 1985 (has links)
No description available.
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The planar hall effect in thin foils of Ni-Fe alloy丘健倫, Yau, Kin-lun. January 1968 (has links)
published_or_final_version / Physics / Master / Master of Science
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Ultra-short pulse generation with a Cr'4'+:YAG laserConlon, Patrick Joseph January 1994 (has links)
No description available.
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Mechanistic studies relevant to chromate toxicityWoodbridge, Nesta January 1997 (has links)
No description available.
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Reaction-bonding of Crâ†2Oâ†3 ceramicsLi, Tao January 1996 (has links)
No description available.
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Mineral supplementation of feedlot cattleVan Bibber-Krueger, Cadra January 1900 (has links)
Doctor of Philosophy / Department of Animal Sciences and Industry / James S. Drouillard / Four studies evaluated effects of mineral supplementation on feedlot performance, carcass characteristics and ruminal fermentation of finishing cattle. Study 1 supplemented 0 or 3.3 g/d yeast combined with Cr propionate to steers separated into light and heavy groups. No treatment x weight group interactions were observed for ADG, DMI, final BW, carcass traits, or plasma glucose of lactate concentrations (P ≥ 0.06). A treatment x weight group interaction was observed for G:F (P = 0.03). In study 2, steers were supplemented 60 or 300 mg Zn/kg DM with or without zilpaterol hydrochloride (ZH). No interactions or effects of Zn or ZH were observed for IGF-1, plasma glucose, or lactate concentrations (P > 0.05). Plasma urea nitrogen (PUN) concentration decreased with ZH (P < 0.01). No interactions or effects of Zn or ZH were detected for ADG, DMI, final BW, G:F, and carcass traits were minimally affected (P ≥ 0.05). Study 3 evaluated effects of supplementing 30 or 100 mg Zn/kg DM (30 or 100Zn) with and without ractopamine hydrochloride (RH; 200 mg/d). No interactions or effects of Zn were observed for feedlot performance or PUN (P ≥ 0.07). Final BW, ADG, and HCW increased when heifers were fed RH (P ≤ 0.02). Zinc x RH interactions were observed for LM area and yield grade (P ≤ 0.01), but other carcass traits were not affected (P ≥ 0.08). In study 4, heifers were supplemented 0, 30, 60, or 90 mg Zn/kg DM. Zinc supplementation did not affect final BW, ADG, or DMI (P ≥ 0.07), but G:F increased linearly (P = 0.02). Carcass traits were not affected by Zn supplementation (P ≥ 0.07). Effects of in vitro Zn titration (0, 30, 60, 60, 90, 120, or 150 mg/kg Zn) were evaluated using ground corn and soybean meal as substrate. In vitro fermentation was not affected by added Zn (P ≥ 0.05). These studies suggest Cr and Zn supplementation minimally affected carcass traits, but Zn supplementation up to 60 mg/kg improved feed efficiency with minimal impact on ruminal fermentation. Supplementing increased Zn concentrations may alter fat and muscle deposition when fed with RH.
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An analysis of strategies to optimize the exploitation of South Africa's chrome resources27 August 2014 (has links)
M.Com. (Economics) / Please refer to full text to view abstract
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Reaksies van tione met en in metaalkomplekse01 September 2015 (has links)
D.Sc. / Please refer to full text to view abstract
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Preparation of magnetic nano-composite-beads and their application to remediation of Cr(VI) and U(VI) from acid mine drainageTavengwa, Nikita Tawanda 07 August 2013 (has links)
A dissertation submitted to the Faculty of Science, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of
Master of Science
WITS University, Johannesburg, 2013 / Occurring parallel to the developments in imprinting technology are magnetic
materials which are being applied increasingly in environmental remediation,
medicine, biotechnology and many other fields. Combining the imprinting effects
of the polymer and nano magnetic particles yields composite materials which are
both selective to the template and magneto responsive for easy polymer removal
from aqueous solutions.
In this study, magnetic ion imprinted polymers with high recognition for uranyl
ion (UO2
2+) in the presence of competing ions were synthesized by bulk and
precipitation polymerizations. The uranyl template was removed from the
magnetic polymer matric by 1M HCl and 1M NaHCO3 leachants to form cavities
which were complimentary in shape and size to the template. Full characterization
of the magnetite and magnetic polymers was achieved by use of the following
characterization techniques: Raman spectroscopy (RS), Transmission electron
microscopy (TEM), Energy dispersive spectrometry (EDS), Powder X-ray
diffraction (PXRD) analysis, Brunauer, Emmett and Teller (BET) analysis,
Ultraviolet visible (UV-vis) spectroscopy, Fourier-transform infrared (FTIR),
Thermo-gravimetric analysis (TGA), Carbon, hydrogen, nitrogen and sulphur
(CHNS) analysis, Diffuse reflectance spectroscopy (DRS) and Atomic force
microscopy (AFM). Parameters which were optimized included sample pH, which
gave an optimum value of 4. Magnetic IIP and NIP amounts which gave
maximum adsorption capacities were found to be 50 mg for both of these
adsorbents. The optimum contact time was found to be 45 minutes. The
performance of all magnetic ion imprinted polymers (IIPs) was expectedly
superior to that of the corresponding non imprinted polymers (NIPs) in all
adsorption studies. The first rate constant (k1) and correlation coefficient (R2)
values evaluated for the pseudo first order were found to be between 0.048-0.093
min-1 and 0.602-0.991 min-1, respectively. For the pseudo second order, second
rate constant (k2) and correlation coefficient (R2) were found to be between 0.273-
0.678 and 0.9811-0.9992, respectively. The selectivity order observed was as
follows: UO2
2+ > Fe3+ > Pb2+ > Ni2+ > Mg2+.
The magnetic polymers selective to Cr(VI) were also synthesized and were
leached with HCl to remove the template. The synthesized Cr(VI) magnetic
polymers, the optimum pH obtained was 4 for both the magnetic IIP and the
corresponding NIP. The amount of the adsorbent which gave the maximum
adsorption was determined to be 20 and 65 mg for the magnetic IIP and NIP,
respectively. A Cr(VI) concentration which was adsorbed maximally was from 5
mg L-1 which was therefore taken as the optimum. The maximum adsorption
capacities for the magnetic polymers were 6.20 and 1.87 mg g-1 for the magnetic
IIP and NIP, respectively. The optimum time for the adsorption of the Cr(VI)
analyte was determined as 40 minutes. Investigation of the order of selectivity of
anions followed the trend: Cr2O7
2- SO4
2- F- NO3-
-.
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Alpha-Poly-L-Lysine As A Potential Biosorbent For Removal Of Hexavalent Chromium From Industrial Waste WaterChakraborti, Amrita 01 May 2009 (has links)
Remediation of heavy metals from industrial effluents and ground water sources poses a significant challenge. Hexavalent chromium is one such heavy metal, prevalent in industrial wastewaters, which has been proven to be toxic to humans and other living organisms. Most of the conventional methods available for dealing with chromium are either cost prohibitive or generate secondary effluents which are difficult to deal with. The idea of bioremediation has gained much momentum over the last few decades because of its potential low cost and minimum impact on the environment. This study explored the potential for hexavalent chromium bioremediation using a synthetic cationic biopolymer alpha-poly-l-lysine (alpha-PLL) as a biosorbent. In the present research work, equilibrium batch studies were performed in a specially designed dialysis apparatus to obtain preliminary information about the adsorption capacity of the polymer. Metal uptake by the polymer was found to be maximum when the pH of chromium solution (pH 4.6) and that of poly-lysine (pH 5.7) was not changed at the beginning of the experiment. Applying the Langmuir adsorption isotherm model showed that alpha-PLL has a maximum uptake capacity of 42.2 microgram Cr/mg alpha-PLL, and a binding constant of 1.2 microgram/mL +/- 10%. The metal uptake performance of the polymer was also evaluated in a Polymer Enhanced Diafiltration (PEDF) system. The polymer-metal complex was retained and concentrated by the PEDF set up using a tangential flow filtration membrane, while the clean filtrate flowed through. When 3.4 L of 10 mg/L chromium solution in the Cr2O72- form was processed using 300 mL of 2 gm/L PLL, the concentration of chromium in the permeate reached a maximum of 0.79 mg/L. When 30 mg/L chromium solution was used, 2 L could be processed using 300 mL of 2gm/L PLL, and 7.8 mg/L chromium could be detected in the permeate in the end.
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