bluuebunny/crossref_metadata_2025 huggingface dataset:
NORMALIZED DEMAND FOR DRUGS AND OTHER REINFORCERS
Authors: Hursh Steven R. , Winger Gail
Published: March 2006

The concepts of behavioral economics have proven to be useful for understanding the environmental control of overall levels of responding for a variety of commodities, including reinforcement by drug self‐administration. These general concepts have implications for the assessment of abuse liability and drug abuse intervention and the formulation of public policy on drug abuse. An essential requirement is the ability to compare the demand for different drugs directly in order to assess relative abuse liability, and to compare demand for the same drug under different environmental and biological interventions to assess their ability to reduce demand. Until now, such comparisons were hampered by the confounding effect of varying drug doses and potencies that prevent quantitative comparisons of demand elasticity—sensitivity of consumption and responding to the constraint of price (effort). In this paper we describe a procedure to normalize demand‐curve analysis that permits dose‐ and potency‐independent comparisons of demand across drugs. The procedure is shown to be effective for comparing drug demand within and across the drug classes. The technique permits a quantitative ordering of demand that is consistent with the peak levels of responding maintained by the drugs. The same technique is generalized for the comparison of other types of reinforcers under different biological conditions.
BEHAVIORAL ECONOMICS WITHOUT ANOMALIES
Authors: Rachlin Howard
Published: March 2006

Behavioral economics is often conceived as the study of anomalies superimposed on a rational system. As research has progressed, anomalies have multiplied until little is left of rationality. Another conception of behavioral economics is based on the axiom that value is always maximized. It incorporates so‐called anomalies either as conflicts between temporal patterns of behavior and the individual acts comprising those patterns or as outcomes of nonexponential time discounting. This second conception of behavioral economics is both empirically based and internally consistent.
FOOD‐DEPRIVATION EFFECTS ON PUNISHED SCHEDULE‐INDUCED DRINKING IN RATS
Authors: Lamas Esmeralda , Pellón Ricardo
Published: March 2006

Food‐deprived rats (at 80% of their free‐feeding weights) were exposed to a fixed‐time 60‐s schedule of food‐pellet presentation and developed schedule‐induced drinking. Lick‐dependent signaled delays (10 s) to food presentation led to decreased drinking, which recovered when the signaled delays were discontinued. A major effect of this punishment contingency was to increase the proportion of interpellet intervals without any licks. The drinking of yoked control rats, which received food at the same times as those exposed to the signaled delay contingency (masters), was not consistently reduced. When food‐deprivation level was changed to 90%, all master and yoked control rats showed decreases in punished or unpunished schedule‐induced drinking. When the body weights were reduced to 70%, most master rats increased punished behavior to levels similar to those of unpunished drinking. This effect was not observed for yoked controls. Therefore, body‐weight loss increased the resistance of schedule‐induced drinking to reductions by punishment. Food‐deprivation effects on punished schedule‐induced drinking are similar to their effects on food‐maintained lever pressing. This dependency of punishment on food‐deprivation level supports the view that schedule‐induced drinking can be modified by the same variables that affect operant behavior in general.
COCAINE'S EFFECTS ON FOOD‐REINFORCED PECKING IN PIGEONS DEPEND ON FOOD‐DEPRIVATION LEVEL
Authors: Schaal David W. , Miller Mark A. , Odum Amy L.
Published: March 2006

Four pigeons deprived to 80% of their laboratory free‐feeding weights pecked keys under a multiple fixed‐ratio 30 fixed‐interval 5‐min schedule of food presentation. Components alternated strictly with 15‐s timeouts separating them; each was presented six times. When rates of pecking were stable, 2 pigeons' weights were reduced to 70%, and the other 2 pigeons' weights were increased to 82.5% to 85% of free‐feeding levels. Cocaine (1.0, 3.0, 5.6, and 10.0 mg/kg and saline) was administered 5 min prior to sessions. When each dose had been tested twice, pigeons' weights were adjusted to the level that they had not yet experienced, and cocaine was tested again. Cocaine reduced response rates in a dose‐dependent manner under the fixed‐ratio schedule and under the fixed‐interval schedule at high doses, and increased rates under the fixed‐interval schedule at low doses. Reductions in pecking rates occurred at lower doses under both schedules in 3 of 4 pigeons when they were less food deprived compared to when they were more food deprived. Low doses of cocaine increased low baseline rates of pecking in the initial portions of the fixed‐interval schedules by a greater magnitude when pigeons were more food deprived. Thus, food‐deprivation levels altered both the rate‐decreasing and rate‐increasing effects of cocaine. The implications of these results for the mechanisms by which food deprivation increases cocaine self‐administration and for the dependence of cocaine's effects on the baseline strength of operant behavior are discussed.
WITHIN‐SESSION CHANGES IN KEY AND LEVER PRESSING FOR WATER DURING SEVERAL MULTIPLE VARIABLE‐INTERVAL SCHEDULES
Authors: McSweeney Frances K. , Weatherly Jeffrey N. , Swindell Samantha
Published: March 2006

Rats pressed keys or levers for water reinforcers delivered by several multiple variable‐interval schedules. The programmed rate of reinforcement varied from 15 to 240 reinforcers per hour in different conditions. Responding usually increased and then decreased within experimental sessions. As for food reinforcers, the within‐session changes in both lever and key pressing were smaller, peaked later, and were more symmetrical around the middle of the session for lower than for higher rates of reinforcement. When schedules provided high rates of reinforcement, some quantitative differences appeared in the within‐session changes for lever and key pressing and for food and water. These results imply that basically similar factors produce within‐session changes in responding for lever and key pressing and for food and water. The nature of the reinforcer and the choice of response can also influence the quantitative properties of within‐session changes at high rates of reinforcement. Finally, the results show that the application of Herrnstein's (1970) equation to rates of responding averaged over the session requires careful consideration.
WITHIN‐SESSION CHANGES IN THE VI RESPONSE FUNCTION: SEPARATING FOOD DENSITY FROM ELAPSED SESSION TIME
Authors: Campbell Laura S. , Dougan James D.
Published: March 2006

Previous studies examining the relationship between response rate and reinforcement rate on variable‐interval schedules (the variable‐interval response function) have confounded elapsed session time with within‐session changes in food density. The present experiments attempted to manipulate these factors independently and thus isolate their effects on responding. In Experiment 1, 7 rats pressed a bar for food on a series of four variable‐interval schedules (7.5 s, 15 s, 30 s, and 480 s). Elapsed session time was held constant while food density was manipulated via a presession feeding. Changes in food density altered the form of the variable‐interval response function, independently of elapsed session time. In Experiment 2, 8 rats responded on the same series of variable‐interval schedules as in Experiment 1, but food density was held constant and elapsed session time was manipulated via the use of timeout periods. The results revealed no evidence for an effect of elapsed session time independent of food density. The present results extend a recent analysis of the variable‐interval response function by Dougan, Kuh, and Vink (1993) by identifying food density as an important factor determining the form of the function. The present results also help clarify the controversy over the correct empirical form of the variable‐interval response function by further defining the variables responsible for differences in the form of that function.
CLOSED‐ECONOMY MULTIPLE‐SCHEDULE PERFORMANCE: EFFECTS OF DEPRIVATION AND SESSION DURATION
Authors: Elliffe Douglas , Davison Michael
Published: March 2006

Three pigeons responded for food reinforcement on multiple variable‐interval schedules in which the total consumption of food was entirely determined by the subjects' interaction with the schedules (a closed economy). The finding of overmatching, where response allocation between components is more extreme than the distribution of reinforcers, was reconfirmed. Generalized‐matching sensitivity decreased from overmatching to undermatching values typical of conventional multiple schedules when food deprivation was increased by decreasing session duration, but not when deprivation was increased by decreasing overall reinforcer rate. Sensitivity also increased from undermatching to overmatching as session duration increased from 100 min to 24 hr, while deprivation was held constant by decreasing overall reinforcer rate. These results can be understood in terms of increases in the value of extraneous reinforcers relative to food reinforcers as deprivation decreases or as the economy for extraneous reinforcers becomes more closed. However, no published quantitative expression of the effects of extraneous reinforcers is entirely consistent with the results.
BEHAVIORAL VARIABILITY IN SHR AND WKY RATS AS A FUNCTION OF REARING ENVIRONMENT AND REINFORCEMENT CONTINGENCY
Authors: Hunziker M. H. L. , Saldana R. Lisa , Neuringer Allen
Published: March 2006

The spontaneously hypertensive rat (SHR) may model aspects of human attention deficit hyperactivity disorder (ADHD). For example, just as responses by children with ADHD tend to be variable, so too SHRs often respond more variably than do Wistar‐Kyoto (WKY) control rats. The present study asked whether behavioral variability in the SHR strain is influenced by rearing environment, a question related to hypotheses concerning the etiology of human ADHD. Some rats from each strain were reared in an enriched environment (housed socially), and others were reared in an impoverished environment (housed in isolation). Four groups—enriched SHR, impoverished SHR, enriched WKY, and impoverished WKY—were studied under two reinforcement contingencies, one in which reinforcement was independent of response variability and the other in which reinforcement depended upon high variability. The main finding was that rearing environment did not influence response variability (enriched and impoverished subjects responded similarly throughout). However, rearing environment affected body weight (enriched subjects weighed more than impoverished subjects) and response rate (impoverished subjects generally responded faster than enriched subjects). In addition, SHRs tended to respond variably throughout the experiment, whereas WKYs were more sensitive to the variability contingencies. Thus, behavioral variability was affected by genetic strain and by reinforcement contingency but not by the environment in which the subjects were reared.
A COMPUTER TOUCH‐SCREEN APPARATUS FOR TRAINING VISUAL DISCRIMINATIONS IN RATS
Authors: Markham Michael R. , Butt Allen E. , Dougher Michael J.
Published: March 2006

We describe an operant conditioning apparatus that uses computerized touch‐screen technology and is designed for the versatile and highly controlled testing of rats in a potentially wide variety of behavioral paradigms. Although computer‐controlled touch‐screen systems have been developed for use with pigeons, monkeys, and humans, analogous technologies and methods have not yet been developed for rats. The development of a touch‐screen system for rats could enhance the efficiency of behavioral research with rats, and may offer a unique tool for studying animal learning. In the first test of the utility of the apparatus, 3 Sprague‐Dawley rats learned to activate the touch screen only after the touch‐screen panel was made slightly movable. These animals then learned to discriminate visual stimuli presented on the computer monitor, but only after the food magazine and pellet dispenser were moved to the rear of the chamber opposite the stimulus display and response window. In a test of the utility of the modified apparatus, 6 Long‐Evans rats learned to activate the touch screen and learned one of three different simple discriminations using computer‐generated, visually presented stimuli. A basic method for training rats to activate the computer touch screen and for visual discrimination training is described. Results show that rats learned to activate the touch screen and discriminate visual stimuli presented on a computer monitor. Potential applications and advantages of the touch‐screen‐equipped rat operant conditioning chamber are discussed.
ON THE ORIGINS OF NAMING AND OTHER SYMBOLIC BEHAVIOR
Authors: Horne Pauline J. , Lowe C. Fergus
Published: March 2006

We identify naming as the basic unit of verbal behavior, describe the conditions under which it is learned, and outline its crucial role in the development of stimulus classes and, hence, of symbolic behavior. Drawing upon B. F. Skinner's functional analysis and the theoretical work of G. H. Mead and L. S. Vygotsky, we chart how a child, through learning listener behavior and then echoic responding, learns bidirectional relations between classes of objects or events and his or her own speaker‐listener behavior, thus acquiring naming—a higher order behavioral relation. Once established, the bidirectionality incorporated in naming extends across behavior classes such as those identified by Skinner as the mand, tact, and intraverbal so that each becomes a variant of the name relation. We indicate how our account informs the specification of rule‐governed behavior and provides the basis for an experimental analysis of symbolic behavior. Furthermore, because naming is both evoked by, and itself evokes, classes of events it brings about new or emergent behavior such as that reported in studies of stimulus equivalence. This account is supported by data from a wide range of match‐to‐sample studies that also provide evidence that stimulus equivalence in humans is not a unitary phenomenon but the outcome of a number of different types of naming behavior.
EFFECTS OF FOOD‐PELLET SIZE ON RATE, LATENCY, AND TOPOGRAPHY OF AUTOSHAPED KEY PECKS AND GAPES IN PIGEONS
Authors: Ploog Bertram O. , Zeigler H. P.
Published: March 2006

Four pigeons responded under autoshaping contingencies in which different conditional stimuli (red or green keylights) were associated with unconditional stimuli of different magnitudes (large or small food pellets) over successive trials within a session. Both topography (beak opening or gape) and strength (rates and latencies of key pecks and gapes) of responding during the conditional stimuli depended on the magnitude of the correlated unconditional stimulus. Key‐peck and gape rates were higher and latencies were shorter in large‐pellet trials than in small‐pellet trials. Gape amplitudes varied directly with pellet size, although conditional and unconditional gapes were larger than either pellet. These findings were replicated when the key colors were presented either on one or two keys and after reversals of the color‐size correlations. Because the unconditional stimulus was varied through pellet size, magnitude was not confounded with food‐access duration or quality. These results demonstrate the effects of the magnitude of the unconditional stimulus, in that rates and latencies of both key pecks (which are directed movements toward the key) and gapes (which are independent of the bird's position and key properties) varied with pellet size. Gape measures were unique in that two dimensions (response strength and topography) of a single response class varied simultaneously with magnitude.
CONCURRENT SCHEDULES: QUANTIFYING THE AVERSIVENESS OF NOISE
Authors: McAdie Tina M. , Foster T. Mary , Temple William
Published: March 2006

Four hens worked under independent multiple concurrent variable‐interval schedules with an overlaid aversive stimulus (sound of hens in a poultry shed at 100dBA) activated by the first peck on a key. The sound remained on until a response was made on the other key. The key that activated the sound in each component was varied over a series of conditions. When the sound was activated by the left (or right) key in one component, it was activated by the right (or left) key in the other component. Bias was examined under a range of different variable‐interval schedules, and the applicability of the generalized matching law was examined. It was found that the hens' behavior was biased away from the sound independently of the schedule in effect and that this bias could be quantified using a modified version of the generalized matching law. Behavior during the changeover delays was not affected by the presence of the noise or by changes in reinforcement rate, even though the total response measures were. Insensitivity shown during the delay suggests that behavior after the changeover delay may be more appropriate as a measure of preference (or aversiveness) of stimuli than are overall behavior measures.
RESIDENCE TIME AND CHOICE IN CONCURRENT FORAGING SCHEDULES
Authors: Jones B. Maxwell , Davison Michael
Published: March 2006

Five pigeons were trained on a concurrent‐schedule analogue of the “some patches are empty” procedure. Two concurrently available alternatives were arranged on a single response key and were signaled by red and green keylights. A subject could travel between these alternatives by responding on a second yellow “switching” key. Following a changeover to a patch, there was a probability (p) that a single reinforcer would be available on that alternative for a response after a time determined by the value of λ, a probability of reinforcement per second. The overall scheduling of reinforcers on the two alternatives was arranged nonindependently, and the available alternative was switched after each reinforcer. In Part 1 of the experiment, the probabilities of reinforcement, pred and pgreen, were equal on the two alternatives, and the arranged arrival rates of reinforcers, λred and λgreen, were varied across conditions. In Part 2, the reinforcer arrival times were arranged to be equal, and the reinforcer probabilities were varied across conditions. In Part 3, both parameters were varied. The results replicated those seen in studies that have investigated time allocation in a single patch: Both response and time allocation to an alternative increased with decreasing values of λ and with increasing values of p, and residence times were consistently greater than those that would maximize obtained reinforcer rates. Furthermore, both response‐ and time‐allocation ratios undermatched mean reinforcer‐arrival time and reinforcer‐frequency ratios.
EFFECTS OF SPATIAL REARRANGEMENT OF OBJECT COMPONENTS ON PICTURE RECOGNITION IN PIGEONS
Authors: Kirkpatrick‐Steger Kim , Wasserman Edward A. , Biederman Irving
Published: March 2006

Five pigeons were first trained to discriminate among line drawings of four objects: a watering can, an iron, a desk lamp, and a sailboat The birds were then tested with eight versions of each object, in which the object's components were vertically and horizontally rearranged. The pigeons displayed different degrees of generalization decrement to the different scrambled versions of the objects. Two analyses helped to clarify the nature of the varied accuracy scores. First, cluster analyses disclosed subsets of components that were related to test performance. Second, although the clusters varied somewhat across birds for a given object, there was reliable concordance among the subjects in their rankings of the individual scramblings, suggesting that the pigeons may have attended to common aspects of the drawings.
DRUG DISCRIMINATION UNDER A CONCURRENT SCHEDULE
Authors: Snodgrass Samuel H. , McMillan D. E.
Published: March 2006

Three pigeons were trained to discriminate a 5.0 mg/kg dose of pentobarbital from saline under a two‐key concurrent schedule with responding on the key associated with the presession injection, under both stimulus conditions, producing four times as many reinforcers as responding on the other key. This concurrent schedule resulted in approximately 70% responding to the higher reinforcement key under the pentobarbital stimulus and approximately 30% responding to that key under the saline stimulus. During testing, then, the pigeons were able to dose‐dependently emit higher (>70%) or lower (<30%) values than were established under the control conditions. Dose—response curves were determined for pentobarbital (twice), methamphetamine, phencyclidine, chlordiazepoxide, and the combination of pentobarbital and the barbiturate antagonist bemegride. The results obtained with pentobarbital and chlordiazepoxide showed that, as the dose increased, pentobarbital‐appropriate responding also increased. Methamphetamine produced relatively flat dose—response curves, whereas phencyclidine administration produced inconsistent effects on responding. The combination of the training dose of pentobarbital with increasing doses of bemegride produced a decrease in pentobarbital‐appropriate responding. The results also showed that the dose—response curves for pentobarbital and chlordiazepoxide, instead of being all or none, were graded functions of the drug dose.
HUMANS' CHOICES IN SITUATIONS OF TIME‐BASED DIMINISHING RETURNS: EFFECTS OF FIXED‐INTERVAL DURATION AND PROGRESSIVE‐INTERVAL STEP SIZE
Authors: Jacobs Eric A. , Hackenberg Timothy D.
Published: March 2006

Four adult humans made repeated choices between two time‐based schedules of points exchangeable for money: a fixed‐interval schedule and a progressive‐interval schedule that began at 0 s and increased in fixed increments following each point delivered by that schedule. Under reset conditions, selection of the fixed schedule not only produced a point but also reset the progressive interval to 0 s. Reset conditions alternated with no‐reset conditions, in which the progressive‐interval duration was independent of fixed‐interval choices. Fixed‐interval duration and progressive‐interval step size were varied independently across conditions. Subjects were exposed to all step sizes in ascending order at a given fixed‐interval value before the value was changed. Switching from the progressive‐interval schedule to the fixed‐interval schedule was systematically related to fixed‐interval duration, particularly under no‐reset conditions. Switching occurred more frequently and earlier in the progressive‐schedule sequence under reset conditions than under no‐reset conditions. Overall, the switching patterns conformed closely to predictions of an optimization account based upon maximization of overall reinforcement density, and did not appear to depend on schedule‐controlled response patterns or on verbal descriptions of the contingencies.
TYPES OF RESPONDING IN A SIGNAL‐DETECTION TASK
Authors: Alsop Brent , Rowley Rachael
Published: March 2006

Four pigeons were trained to discriminate between two line orientations in a two‐alternative forced‐choice procedure. The distribution of reinforcers for the two types of correct response was varied across conditions. Performance on each trial was recorded separately, including the time taken to make a choice response. Discriminability and response‐bias measures were calculated for overall performance, and, following a median split of the data from each condition, for faster and slower choice responses in each condition. Discriminability between the stimuli did not vary systematically as a function of choice latency. Variations of the reinforcer distributions produced larger response biases for the faster responses than for the slower responses. Responses on trials following reinforcers were faster and showed a greater effect of the reinforcer distribution than did other responses. Behavioral models of signal detection should consider the speed of the choice response as a factor modulating the effects of reinforcer distributions.
Interactive Effects of Elevated Carbon Dioxide and Drought on Wheat
Authors: Wall G. W. , Garcia R. L. , Kimball B. A. , Hunsaker D. J. , Pinter P. J. , Long S. P. , Osborne C. P. , Hendrix D. L. , Wechsung F. , Wechsung G. , Leavitt S. W. , LaMorte R. L. , Idso S. B.
Published: March 2006

Atmospheric CO2 concentration (Ca) continues to rise. An imperative exists, therefore, to elucidate the interactive effects of elevated Ca and drought on plant water relations of wheat (Triticum aestivum L.). A spring wheat (cv. Yecora Rojo) crop was exposed to ambient (Control: 370 μmol mol−1) and free‐air CO2 enrichment (FACE: ambient + 180 μmol mol−1) under ample (Wet), and reduced (Dry), water supplies (100 and 50% replacement of evapotranspiration, respectively) over a 2‐yr study. Our objective was to characterize and quantify the responses of 26 edaphic, gas exchange, water relations, carbohydrate pool dynamics, growth, and development parameters to rising Ca and drought. Increasing Ca minimized the deleterious effects of soil–water depletion by increasing drought avoidance (i.e., lower stomatal conductance and transpiration rate, and growth and development of a more robust root system) and drought tolerance (i.e., enhanced osmoregulation and adaptation of tissue) mechanisms, resulting in a 30% reduction in water stress–induced midafternoon depressions in net assimilation rate. An elevated Ca–based increase in daily and seasonal carbon gain resulted in a positive feedback between source capacity (shoots) and sink demand (roots). Devoid of a concomitant rise in global temperature resulting from the rise in Ca, improved water relations for a herbaceous, cool‐season, annual, C3 cereal monocot grass (i.e., wheat) are anticipated in a future high‐CO2 world. These findings are applicable to other graminaceous species of a similar function‐type as wheat common to temperate zone grassland prairies and savannas, especially under dryland conditions.
Above‐ and Belowground Productivity and Soil Carbon Dynamics of Pasture Mixtures
Authors: Skinner R. Howard , Sanderson Matt A. , Tracy Benjamin F. , Dell Curtis J.
Published: March 2006

Increasing plant species diversity could enhance forage yield, resistance to weed invasion, and soil C accumulation in grazed pastures. Three forage mixtures (2, 3, or 11 species) were established on a farm in eastern Pennsylvania and grazed by dairy heifers or managed under a three‐cut hay system from 1999 to 2002. Net canopy photosynthesis was measured from early April to early October 2000 to 2002. Root distribution to a depth of 60 cm was measured in mid‐September each year, and soil C and N concentrations to a 15‐cm depth were determined in May 1999 and September 2002. The 11‐species mixture yielded 43% more forage dry matter than the two‐species mixture. This difference was mainly due to the inclusion of a few highly productive forage species in the 11‐species mixture. Canopy photosynthesis did not differ among mixtures in the spring, but in the summer was 50% greater in the 3‐ and 11‐species mixtures than the two‐species mixture. The 11‐species mixture also had 30 to 62% greater root biomass than the other two mixtures and a greater proportion of roots in deeper soil layers. Soil C either remained unchanged or decreased, depending on species composition, with the greatest decrease occurring in the 11‐species mixture. No relationship existed between changes in soil C concentration and either canopy photosynthesis or above‐ and belowground productivity. Deeper rooting could reduce drought stress by increasing access to deep soil moisture. Selecting forage mixtures to include specific desirable traits, such as greater rooting depth, could result in improved pasture performance.
Nitrogen Fertilization Affects Bahiagrass Responses to Elevated Atmospheric Carbon Dioxide
Authors: Newman Yoana C. , Sollenberger Lynn E. , Boote Kenneth J. , Allen L. Hartwell , Thomas Jean M. , Littell Ramon C.
Published: March 2006

Increased atmospheric CO2 and temperature typically lead to greater DM (dry matter) production of grassland plants; however, limited plant N may reduce this response. A 2‐yr study (1998–1999) was conducted to evaluate the effects and interactions among atmospheric CO2, temperature, and N fertilization rate on yield and nutritive value of ‘Pensacola’ bahiagrass (Paspalum notatum Flügge). Bahiagrass was field grown in Millhopper fine sand (loamy, siliceous Grossarenic Paleudult) under greenhouses with controlled atmospheric CO2 and temperature. Atmospheric CO2 levels were 360 and 700 μmol mol−1, and temperatures were B (baseline, corresponding to ambient in the greenhouse), B + 1.5°C, B + 3.0°C, and B + 4.5°C. Bahiagrass was fertilized at 80 kg N ha−1 (BG‐80) or 320 kg N ha−1 (BG‐320). Dry matter yield for BG‐80 remained the same regardless of CO2 level (7.5 and 6.3 Mg ha−1 in Years 1 and 2), but BG‐320 DM yield increased with increasing CO2 concentration in three of four harvests in Year 1 and from 14.8 to 17.3 Mg ha−1 in Year 2. Total N harvested response followed a similar trend as DM yield. Increasing temperature from B to B + 4.5°C had a positive effect on DM yield of BG‐80 (23%) and a lesser positive effect on BG‐320 (9% increase). Bahiagrass nutritive value increased due to greater N fertilization, but elevated CO2 concentration and temperature had no effect. Nitrogen fertilization affected bahiagrass DM yield response to CO2, but not the nutritive value response to elevated atmospheric CO2 or temperature.
Maize Yield Response and Nutrient Uptake after Micronutrient Application on a Volcanic Soil
Authors: Lisuma Jacob B. , Semoka J. M. R. , Semu E.
Published: March 2006

Micronutrients, which are often deficient in volcanic soils, together with macronutrients may lead to higher yields in these soils. A study was conducted under pot and field conditions to identify and correct some micronutrient constraints in a volcanic soil at Mpangala, Tanzania, for optimization of maize (Zea mays L.) yields. Dry matter (DM) yields, plant B, Cu, and Zn concentrations, plant B, Cu, and Zn uptake, and grain yields were used to assess the effects of micronutrient treatments. In pots, B, Cu, and Zn fertilizers were applied separately to the soil at two levels, 0 and 2 mg B kg−1, 0 and 5 mg Cu kg−1, and 0 and 10 mg Zn kg−1, in combination with constant rates of 240 mg N kg−1 or 160 mg P kg−1 fertilizers. A higher rate of 320 mg P kg−1 was also included to assess the adequacy of the basal P rate used. A second pot study attempted to establish an optimum rate of Cu under glasshouse conditions; rates ranging from 0 to 20 mg kg−1. Cu were tested. Copper significantly (P = 0.05) increased both maize DM and grain yields; the estimated optimum rate was 20 mg Cu kg−1 under glasshouse conditions. This high rate is thought to be due to the high Cu‐fixation capacity of volcanic soils. Boron and Zn were sufficient for normal plant growth. We conclude that maize production can be increased considerably in Mpangala and other similar soils in the same agroecological zone by applying N, P, and Cu at rates of 120, 80, and 10 kg ha−1, respectively.
Actinides: Inorganic & Coordination ChemistryBased in part on the article Actinides: Inorganic & Coordination Chemistry by Grigorii L. Soloveichik which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Keogh D. Webster
Published: March 2006

The Inorganic and Coordination Chemistry of the 5f elements (Actinides) is intermediate between that of the transition metals and the 4f elements (Lanthanides). The first four members of the actinide series, Ac, Th, Pa, and U, are all naturally occurring but have unstable nuclei, making them radioactive. The other elements in the actinide series (transuranium elements or transuranics) are also radioactive and have been made by man through a variety of nuclear transformation processes, for example, neutron irradiation, atom bombardment, and radioactive decay. The actinide series may be broken into two separate groups, the light or early actinides (Ac–Am) and the heavy or late actinides (Cm–Lr). The chemical behaviors of these two groups are distinct. The light actinides are capable of being stabilized in a variety of oxidation states, for example, II to VII, and have been found to exhibit a significant degree of covalency in binding ligands. The heavy actinides are more reminiscent of the lanthanides in that the most persistent oxidation state is the trivalent and the bonding predominately occurs through ionic interactions. This difference has led to a substantial number of studies into the role of the 5f orbitals in structure and bonding of the actinides. One of the ions that has received a great deal of attention is the ubiquitous actinyl ion, AnO22+/+. This ion is the stable form for all aqueous complexes of the pentavalent and hexavalent light actinides. The oxo ligands are always found in a trans geometry and are strongly bound (triple bond) through a combination of σ‐ and π‐bonds with the 5f and 6d orbitals of the actinide metal center. While these strong covalent interactions exist with the axial oxo ligands, the bonding within the equatorial plane is primarily based on ionic interactions.

The ability of the light actinides to access multiple oxidation states leads to rich and, sometimes, complex electrochemistry. For example, under acidic conditions the reduction potentials for PuO
2
2+
, PuO
2
+
, Pu
4+
, and Pu
3+
are all close to 1 V. The physical manifestation of these close reduction potentials is an aqueous solution in which the plutonium can exist in four different oxidation states simultaneously. By careful control of the conditions, oxidation state pure solutions can be obtained for quantitative and qualitative studies. The binding affinities of the actinide ions to ligands follow the general trend An
4+
 > An
3+
 ∼ AnO
2
2+
 ≫ AnO
2
+
. Since the actinides are strong acids, the ions preferentially bond strong bases, for example, halides, oxygen donors, and so on. Owing to the greater degree of covalency in actinide complexes compared to the lanthanides, complexes with ligands having nitrogen, phosphorus, sulfur, and selenium donors are also found.
Actinides: Organometallic Chemistry
Authors: Burns Carol J. , Clark David L. , Sattelberger Alfred P.
Published: March 2006

An actinide organometallic complex is one containing an actinide‐carbon π‐bond, an actinide‐carbon σ‐bond, or a combination of both. Actinide organometallic complexes are known for the actinide (An) elements from thorium through californium; the vast majority of the reports on organoactinide compounds, however, deal with thorium and uranium. The latter elements have isotopes, for example, thorium‐232 (t1/2 = 1.41 × 1010years) and uranium‐238 (t1/2 = 4.468 × 109years), with extremely long half‐lives. Modern organoactinide chemistry is characterized by the existence not only of actinide analogs to many classes of d transition metal complexes, but increasingly common reports of compounds and types of reactions unique to the actinide series.
Alkali Metals: Inorganic ChemistryBased in part on the article Alkali Metals: Inorganic Chemistry by Francis S. Mair & Ronald Snaith which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Leung Wing‐Por , Wai‐Yan Ip Queenie
Published: March 2006

This article is updated to cover the literature in the area of inorganic chemistry of alkali metals since 1993. The advancement in instrumentation and spectroscopic techniques in the past decade has provided the researchers with more powerful tools for structure determination of compounds. In this respect, alkalides containing mixed‐sandwich complexes of alkali metal cations, complexes with dimers or chains of alkali metal anions, electrides with alkali metal ions intercalating in zeolite, and interstitial hydride enclosed by an unusual (Li+)8cubic cage have been found or studied by NMR. With the successful preparation of Na3N recently, its correct structure has been revealed. The exact composition of ‘NaB6’ has also been determined. The role of alkali metals in trielide clusters of traditional Zintl polyanions has been demonstrated. Trimetallic Li‐Na‐K amides, alkoxide compounds, and highly aggregated cage structures of lithium‐heavier alkali metal alkoxides have been reported.
Alloys
Authors: Giessen Bill C. , Hidalgo Rafael
Published: March 2006

This article treats the current state of fundamental understanding, development, and applications of alloys, with emphasis on alloy chemistry rather than physical metallurgy. First, alloy phases and phase diagrams are treated from a computational viewpoint. Next, technical alloys, including steels, aluminum alloys, superalloys, and titanium alloys, are reviewed; structural intermetallics are treated as a paradigm for theoretical predictive methods. A review of important specialty alloys follows, including hard and soft magnetic alloys, superconductors, shape memory, and magnetostrictive alloys, hydrogen storage alloys, solders, and alloy coatings. A brief survey of current advanced alloy preparation and characterization methods concludes the article.
Aluminum: Inorganic Chemistry
Authors: Apblett Allen W.
Published: March 2006

Aluminum is the most abundant metal to be found in the earth's crust (8.1%). It is component of gemstones and many common minerals such as granite and clays. Aluminum is a very reactive metal and is not found in an uncombined form in nature. However, the use of its compounds has a very long history. For example, the ancient Greeks and Romans used alum as an astringent and as a mordant in dyeing. The pure metal was isolated first by Wohler in 1827. The modern method for obtaining aluminum metal is the electrolysis of alumina dissolved in cryolite. Aluminum can also be produced from clay, but the process is not economically feasible at present.

Pure aluminum, a silvery‐white metal, possesses many desirable characteristics. It is light, nonmagnetic, and nonsparking, and is second amongst all metals in the scale of malleability, and sixth in ductility. It is extensively used for kitchen utensils, outside building materials, airplanes, and in thousands of industrial applications where a strong, light, easily constructed material is needed. Pure aluminum is soft and lacks strength, but when it is alloyed with small amounts of copper, silicon, magnesium, manganese, or other elements these shortcomings can be circumvented. The aluminum compounds of greatest importance are aluminum oxide, aluminum sulfate, aluminum potassium sulfate (alum), and aluminum halides. The oxide, alumina, occurs naturally as ruby (Al2O3), sapphire, corundum, and emery, and is used in glassmaking and refractory ceramic materials. Synthetic ruby and sapphire are used in lasers for producing coherent light. Aluminum nitride, phosphide, and antimonide are important materials for the semiconductor industry. Aluminum halides and oxides are also very important catalyst supports.
Aluminum: Organometallic ChemistryBased in part on the article Aluminum: Organometallic Chemistry by Gregory H. Robinson which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Mason Mark R.
Published: March 2006

The synthesis, reactivity, structures, and applications of the organometallic compounds of aluminum are reviewed. The chapter starts with a discussion of traditional synthetic approaches to aluminum alkyls, aryls, hydrides, and halides and continues with a discussion of their structures and reactivity. The following section focuses on the emerging organometallic chemistry of Al(0), Al(I), and Al(II) and specifically highlights recent developments in aluminum–aluminum bonding, insertions of small molecules and elements into AlAl bonds, and the isolation of large metalloid clusters such as

$\hbox{Al}_{50}\hbox{Cp}^{*}_{12}$

. Organoaluminum heterocycles and cage compounds are the subjects of the next section. This section briefly describes common structural motifs and has separate subsections devoted to cage iminoalanes, alkylaluminoxanes, and alkylaluminophosphinates, ‐phosphates, ‐phosphonates, and ‐arsonates. Structural relationships amongst these groups of compounds and comparisons to secondary building units in aluminophosphate molecular sieves are presented. The importance of alkylaluminoxanes to catalytic activity is also discussed. This chapter includes an independent section on cationic organoaluminum complexes. Although this includes more traditional cationic complexes ligated by crown ether and neutral nitrogen‐donor ligands, the section emphasizes recent developments in generating two‐ and three‐coordinate cationic complexes. Alkide and hydride abstractions by trityl salts of weakly coordinating anions and tris(pentafluorophenyl)borane are described. Common anion decomposition pathways and successful cationic systems for oligomerizing and polymerizing alkenes are discussed. Two additional sections describe the applications of organoaluminum compounds to organic synthesis and applications in industry. Readers are referred to leading works that more adequately describe the extensive use of organoaluminum reagents in organic synthesis. Current and past applications of organoaluminum compounds for the production of long‐chain alkenes and alcohols, as cocatalysts for Ziegler–Natta and metallocene‐catalyzed polymerization of alkenes and dienes, and catalysts for propene dimerization and epoxide polymerization are summarized. Safety issues regarding the handling and disposal of pyrophoric organoaluminum reagents and waste are also discussed. One hundred and twenty‐six reviews and original works are cited.
Ammonia &N‐Donor Ligands
Authors: House Donald A.
Published: March 2006

The coordination chemistry of nonmacrocyclic ligands containing only N, C, and H atoms is surveyed. Such ligands include ammonia and linear polyamines as well as heterocyclic N‐compounds and catenated N‐systems. Among the topics discussed are N‐ligand synthesis, metal–N bond formation, reactions of coordinated N‐donor ligands, and the utilization of metal–N complexes. Structural and theoretical aspects include the consideration of metal–N stability constants, hard‐acid soft‐base concepts, inorganic reaction mechanisms, molecular mechanics, chelate ring stereochemistry, chirality, and supramolecular chemistry.
Antimony: Inorganic ChemistryBased in part on the article Antimony: Inorganic Chemistry by R. Bruce King which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Breunig Hans Joachim
Published: March 2006

An overview of the inorganic chemistry of the element antimony is given in this article, which includes information on the occurrence, production, use, and properties of the element and of compounds with bonds between antimony and main group elements (except carbon) and transition metals.
Antimony: Organometallic ChemistryBased in part on the article Antimony: Organometallic Chemistry by Alan Berry which appeared in theEncyclopedia of Inorganic Chemistry, First Edition.
Authors: Breunig Hans Joachim
Published: March 2006

This article presents a concise overview on the chemistry of organoantimony compounds containing one or more Sb–C bonds. It deals with homoleptic molecules where Sb is bonded exclusively to organic groups R, for example tri‐ or pentorganyls of antimony, and with heteroleptic derivatives where RnSb groups (n = 1, 2, 4) are bonded to other elements. Not only compounds with single bonds between Sb and C but also molecules with double bond character are considered.
Arsenic: Inorganic ChemistryBased in part on the article Arsenic: Inorganic Chemistry by Ralph A. Zingaro which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Muñoz‐Hernández Miguel‐Ángel
Published: March 2006

This article reflects the importance and development of the chemistry of inorganic arsenic compounds. Throughout the text the reader will be taken from the chemistry of simple arsenic species found in minerals to such as those arsenic species that reflect the breath of modern inorganic chemistry. Efforts have been made to show developments in fundamental chemistry, materials science, and aspects of arsenic in the environment. Accordingly, Section 2 covers aspects of the preparation of simple arsenic species like the chalcogenides and halogenides. In Section 3 the important arsenic intermetallic and Zintl phases are discussed emphasizing important technological aspects. The chemistry of inorganic arsenic hydrides and halides is presented in Sections 4 and 5 with many important fundamental issues that are difficult to find in one single textbook. Inorganic simple arsenic compounds that bear pnictogen and/or chalcogen atoms are discussed in Sections 6 and 8. In these two sections the chemistry is presented starting from species that are found in minerals to complexes that have arsenic as the central atom introducing exciting discrete arsenic molecules and aspects of supramolecular chemistry. The chemistry of arsenic–carbon species where the carbon atom is strictly inorganic is shown in Section 7. Finally, Section 9 intends to give a brief introduction of the impact of arsenic in the environment, especially focusing on issues related to living organisms.
Arsenic: Organoarsenic Chemistry
Authors: Krannich Larry K. , Watkins Charles L.
Published: March 2006

This review surveys the chemistry, reactivity, spectroscopic, and structural aspects of several major classes of organometallic arsenic compounds over the time period of 1760 through 2003. These compounds are the core of the field and represent the major areas of research thrusts during this period. We draw heavily from several books, monographs, and review articles to review the primary synthetic routes and reactivity. The primary literature is referenced for all developments that have occurred since the last published review articles. After an extensive review of the fully substituted and AsH bond containing organoarsenic compounds, the focus is on compounds containing AsHalogen, As group 13, As group 14, As group 15, and AsO bonds. Because of the efforts to synthesize As group 13 bonded compounds of the heavier group 13 elements, tables listing the known compounds synthesized after 1985 and their method of preparation are provided.
BiomineralizationBased in part on the article Biomineralization by Richard B. Frankel which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Dauphin Yannicke
Published: March 2006

Three main categories are involved in biominerals: silica, calcium carbonates, and calcium phosphates. The calcium biominerals are usually crystalline, but amorphous types are also known. Within these categories, the shapes and chemical contents of structural units are variable. Moreover, the chemical and physical properties of biominerals are very different from the crystal habits produced inorganically: they depend on the producing plants and animals and the environmental conditions. Biomineral development is permanently controlled by specifically produced organic molecules that remain entrapped within the mineral units. Although biomineralization has been widely studied in the past, the growth mechanisms are still poorly understood, and the most elaborated model is based on the nacreous layer of mollusk shells. Studies on biominerals and biomineralization have various applications, from biology and geology to biomimetics.