Antiferromagnetic exchange interactions from hybrid density functional theory

A hybrid theory which combines the full nonlocal ¿exact¿ exchange interaction with the local spin-density approximation of density-functional theory is shown to lead to marked improvement in the description of antiferromagnetically coupled systems. Semiquantitative agreement with experiment is found for the magnitude of the coupling constant in La2CuO4, KNiF3, and K2NiF4. The magnitude of the unpaired spin population on the metal site is in excellent agreement with experiment for La2CuO4.

Reception of Walras' theory of exchange and theory of production in Russia

This paper evaluates the reception of Léon Walras' ideas in Russia before 1920. Despite an unfavourable institutional context, Walras was read by Russian economists. On the one hand, Bortkiewicz and Winiarski, who lived outside Russia and had the opportunity to meet and correspond with Walras, were first class readers and very good ambassadors for Walras' ideas, while on the other, the economists living in Russia were more selective in their readings. They restricted themselves to Walras' Elements of Pure Economics, in particular, its theory of exchange, while ignoring its theory of production. We introduce a cultural argument to explain their selective reading. JEL classification numbers: B 13, B 19.

Early blood exchange transfusion in malignant pertussis: A case report.

OBJECTIVE:: To report early blood exchange transfusion in malignant pertussis and a favorable clinical outcome. SETTING:: A pediatric intensive care unit in a tertiary hospital in Geneva, Switzerland. DESIGN:: A descriptive case report. PATIENT:: An 8-wk-old girl was diagnosed with malignant pertussis (extreme leukocytosis, seizures, pneumonia, and secondary severe hypoxic respiratory failure associated with pulmonary hypertension). After administration of a one-volume blood exchange transfusion, a rapid decrease in white blood cell count (from 119,000/mm to 36,500/mm) was observed and followed by clinical improvement and favorable outcome despite the initial presence of all described risk factors associated with a high mortality. CONCLUSION:: The use of exchange blood transfusion early in the course of the disease might help to prevent a fatal outcome of malignant pertussis.

Physiological responses of two tropical weeds to shade: II. Leaf gas exchange and nitrogen content

Ipomoea asarifolia (Desr.) Roem. & Schultz (Convolvulaceae) and Stachytarpheta cayennensis (Rich) Vahl. (Verbenaceae), two weeds found in pastures and crop areas in the Brazilian Amazonia, Brazil, were grown in controlled environment cabinets under high (800-1000 µmol m-² s-¹) and low (200-350 µmol m-² s-¹) light regimes during a 40-day period. The objective was to determine the effect of shade on photosynthetic features and leaf nitrogen content of I. asarifolia and S. cayennensis. High-irradiance grown I. asarifolia leaves had significantly higher dark respiration and light saturated rates of photosynthesis than low-irradiance leaves. No significant differences for these traits, between treatments, were observed in S. cayennensis. Low-irradiance leaves of both species displayed higher CO2 assimilation rates under low irradiance. High-irradiance grown leaves of both species had less nitrogen per unit of weight. Low-irradiance S. cayennensis had more nitrogen per unit of leaf area than high-irradiance plants; however, I. asarifolia showed no consistent pattern for this variable through time. For S. cayennensis, leaf nitrogen content and CO2 assimilation were inversely correlated to the amount of biomass allocated to developing reproductive structures. These results are discussed in relation to their ecological and weed management implications.

Tagging reveals limited exchange of immature loggerhead sea turtles (Caretta caretta) between regions in the western Mediterranean.

Exchange of immature loggerhead sea turtles (Caretta caretta) between the northern and southern regions of the western Mediterranean was investigated using data obtained from several Spanish tagging programmes. Tagged turtles ranged in straight carapace length from 23.0 to 74.0 cm. Thirty-six turtles were recaptured after an average interval of 390.5±462.6 days (SD). As the mean dispersal distance (MDD) of a turtle population that spreads over the western Mediterranean would stabilize after 117 days (CI 95%: 98 to 149), two analyses were conducted that included data from turtles recaptured after 98 and 149 days respectively. In both analyses, turtles were recaptured more often than expected in the same region where they had been tagged. No difference was found in either of the two regions between the average distance between the capture and recapture locations and the expected MDD if the turtles were to remain in the region where they were first captured. Turtles recaptured after 15 and 25 days respectively were excluded from the analysis to ensure data independence. The overall evidence indicates that immature turtles exhibit strong site fidelity to certain areas and that there is a strong barrier to dispersal between the northern and southern parts of the western Mediterranean. Therefore, loggerhead turtles in the western Mediterranean should be split into at least two management units.

Exchange rate predictability

The main goal of this article is to provide an answer to the question: "Does anything forecast exchange rates, and if so, which variables?". It is well known thatexchange rate fluctuations are very difficult to predict using economic models, andthat a random walk forecasts exchange rates better than any economic model (theMeese and Rogoff puzzle). However, the recent literature has identified a series of fundamentals/methodologies that claim to have resolved the puzzle. This article providesa critical review of the recent literature on exchange rate forecasting and illustratesthe new methodologies and fundamentals that have been recently proposed in an up-to-date, thorough empirical analysis. Overall, our analysis of the literature and thedata suggests that the answer to the question: "Are exchange rates predictable?" is,"It depends" -on the choice of predictor, forecast horizon, sample period, model, andforecast evaluation method. Predictability is most apparent when one or more of thefollowing hold: the predictors are Taylor rule or net foreign assets, the model is linear, and a small number of parameters are estimated. The toughest benchmark is therandom walk without drift.

Understanding the gains from wage flexibility: The exchange rate connection

We study the gains from increased wage flexibility and their dependence on exchange rate policy, using a small open economy model with staggered price andwage setting. Two results stand out: (i) the impact of wage adjustments on employment is smaller the more the central bank seeks to stabilize the exchange rate,and (ii) an increase in wage flexibility often reduces welfare, and more likely so ineconomies under an exchange rate peg or an exchange rate-focused monetary policy.Our findings call into question the common view that wage flexibility is particularlydesirable in a currency union.

Constraints on effective field theory parameters for the Lambda N -> NN transition

The relation between the low-energy constants appearing in the effective field theory description of the Lambda N -> NN transition potential and the parameters of the one-meson-exchange model previously developed is obtained. We extract the relative importance of the different exchange mechanisms included in the meson picture by means of a comparison to the corresponding operational structures appearing in the effective approach. The ability of this procedure to obtain the weak baryon-baryon-meson couplings for a possible scalar exchange is also discussed.

Constraints on effective field theory parameters for the Lambda N -> NN transition

The relation between the low-energy constants appearing in the effective field theory description of the Lambda N -> NN transition potential and the parameters of the one-meson-exchange model previously developed is obtained. We extract the relative importance of the different exchange mechanisms included in the meson picture by means of a comparison to the corresponding operational structures appearing in the effective approach. The ability of this procedure to obtain the weak baryon-baryon-meson couplings for a possible scalar exchange is also discussed.

Seed viability constants for Eucalyptus grandis

This work aimed to analyse Eucalyptus grandis W.Hill ex Maiden seed behaviour, under controlled deterioration, and to estimate viability equation constants for the species. Seeds were harvested in the growing season of 1999, and the moisture contents were adjusted from 11.3% to a range between 1.2 and 18.1% at 25ºC. The subsamples were sealed into laminate aluminium-foil packets, for storage in incubators at 40, 50 and 65±0.5ºC. The seeds presented orthodox performance, in which the constants for predicting seed longevity of E. grandis were K E = 9.661, C W = 6.467, C H = 0.03498 and C Q = 0.0002330. The usual and inverse relationship between water content and seed longevity was also observed. The lowest moisture content limit for application of the viability equation at 65ºC was 4.9%, estimated under hygroscopic equilibrium with 23% of relative humidity in the storage environment.

A simple halide-to-anion exchange method for heteroaromatic salts and ionic liquids

A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A− form) in non-aqueous media. The anion loading of the AER (OH− form) was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A− form) method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH3OH, CH3CN and the dipolar nonhydroxylic solvent mixture CH3CN:CH2Cl2 (3:7) and the anion exchange was equally successful with both lipophilic cations and anions.

Oxygen consumption of Litopenaeus vannamei juveniles in heterotrophic medium with zero water exchange

This work aimed at determining the dissolved oxygen consumption rate of Litopenaeus vannamei juveniles maintained in a microbial biofloc raceway system at high density with no aeration. Three 4 L bottles were filled for each treatment, sealed hermetically, and placed in an enclosed greenhouse raceway system. Four shrimp (13.2±1.42 g) were assigned to two sets of the bottles, which underwent the following treatments: light conditions with no shrimp; dark conditions with no shrimp; light conditions with shrimp; and dark conditions with shrimp. Dissolved oxygen content was measured every 10 min for 30 min. A quadratic behavior was observed in dissolved oxygen concentration over time. Significant differences for oxigen consumption were observed only at 10 and 20 min between shrimp maintained in the dark and those under light conditions. At 10 min, a higher value was observed in shrimp maintained under light, and at 20 min, in the dark. Significant differences between 10 and 20 min and between 10 and 30 min were observed when oxygen consumption was analyzed over time in the presence of light. Under dark conditions there were significant differences only between 20 and 30 min. Lethal oxygen concentration (0.65 mg L-1) would be reached in less than one hour either under light or dark conditions with no aeration.