Spatial solitons in semiconductor microresonators

We describe experiments showing the existence of spatial solitons in semiconductor microresonators. We describe the manipulation of such solitons in view of technical applications: switching solitons on and off by coherent, as well as incoherent light, reducing the light power necessary to sustain and switch a soliton by optical pumping, and the limit in which independent solitons become so strongly bound that they form a coherent hexagonal pattern, marking the maximum information storage density     

Evaluation of Canopy Biophysical Variable Retrieval Performances from the Accumulation of Large Swath Satellite Data

The objective of this study was to compare the retrieval performances of several biophysical variables from the accumulation of large swath satellite data, the VEGETATION/SPOT4 sensor being taken as an example. This included leaf area index (LAI), fraction of photosynthetically active radiation (fAPAR) and chlorophyll content integrated over the canopy (C_ab·LAI), gap fraction in any direction [P₀(θ)], or in particular directions (nadir [P₀(0)], sun direction [P₀(θ_s)], or 58° [P₀(58°)] for which the gap fraction is theoretically independent of the LAI). A database of top of canopy BRDF (bidirectional reflectance distribution function) of homogeneous canopies was built using simulations by the SAIL, PROSPECT, and SOILSPECT radiative transfer models for a large range of input variables (LAI, mean leaf inclination angle, hot spot parameter, leaves and soil optical properties, date and latitude of observations) considering the accumulation of observations during an orbit cycle of 26 days. Walthall's BRDF model was used to estimate nadir (ρ₀) and hemispherical reflectance (ρ_h). Results showed that ρ₀ and ρ_h were estimated with a good accuracy (RMSE=0.02) even when few observations within a sequence were available due to cloud masking. The ρ₀ and ρ_h estimates in the blue (445 nm), the red (645 nm), near-infrared (835 nm), and middle infrared (1665 nm) were then used as inputs to neural networks calibrated for estimation of the canopy biophysical variables using part of the data base. Performances evaluated over the rest of the database showed that variables such as nadir gap fraction (P₀(58°)P₀(θ_s)fAPAR) were accurately estimated by neural networks (relative RMSE<0.05). Results of the estimation of LAI (LAI·Cab) was less satisfactory since the level of reflectance saturates for high values of LAI (relative RMSE<0.08). The estimation of the directional variation of the gap fraction was not accurate because the amount of directional information contained in the input variables of the neural network was not sufficient. We also investigated the problem of mixed pixels due to the low spatial resolution associated with large swath sensors. Results showed that variables such as nadir gap fraction were not as sensitive to high levels of heterogeneity in pixels as variables such as leaf area index.     

True absorption of calcium and phosphorus from corn silage fed to nonlactating, pregnant dairy cows

A crossover design was implemented using four nonlactating dairy cows [mean body weight (BW) = 678 kg] and two rations to measure the true absorption of Ca and P from corn silage. True absorption was calculated after dosing cows intravenously with 45Ca and 32P to measure endogenous fecal losses. Rations consisted mainly of corn silage and were formulated to supply 32 g/d of Ca and 20 g/d of P or 16 g/d of Ca and 12 g/d of P. The percentages of total Ca and P that came from corn silage were 95 and 77%, respectively, for ration 1, and 98 and 79%, respectively, for ration 2. Cows ate more dry matter (10.9 vs. 10.2 kg/d) when consuming the corn silage in ration 1 than when consuming the corn silage in ration 2. Calcium intake was greater for cows fed ration 1 than for cows fed ration 2 (32.6 vs. 16.1 g/d), and P intake was greater for cows fed ration 1 than for cows fed ration 2 (20.1 vs. 11.7 g/d). True absorption of Ca was 34.4 and 43.7% for rations 1 and 2, respectively, and true absorption of P was 84.5 and 93.9% for rations 1 and 2, respectively. True absorption of Ca was about equal to values currently used in the National Research Council (NRC) feeding standards, but true absorption of P was higher than values currently used by the NRC. Fecal endogenous excretion of Ca (mean = 8.23 mg/kg of BW per d) was one-half of the value currently used by the NRC, and fecal endogenous excretion of P (mean = 7.23 mg/kg of BW per d) was only slightly less than NRC values.     

Evaluation of hydroxypropyl methylcellulose phthalate 50 as film forming polymer from aqueous dispersion systems

Hydroxypropyl methylcelluose phthalate 50 (HPMCP 50) was evaluated as a film forming polymer from aqueous dispersion systems. The influence of plasticizer type and level on the elasticity of HPMCP 50 free films prepared by the casting method was studied by measuring Young's modulus using an Instron Material Testing System. The release of a water soluble drug in various dissolution media from pellets coated with HPMCP 50 with 30% plasticizer containing various levels of hydroxypropyl cellulose (HPC) or hydroxypropyl methylcellulose (HPMC) was also studied. The influence of coating level on drug release from pellets was also investigated. Results showed that HPMCP 50 alone without a plasticizer does not form a film. However, when a plasticizer was added HPMCP 50 did form a film. Also, as the concentration of the plasticizer triethyl citrate was increased the elasticity of HPMCP 50 films was increased. Similar results were obtained with the plasticizer diethyl phthalate. For pellets a high coating level was required to achieve adequate protection in 0.06 N HCl. Drug release from coated pellets was found to be dependent upon the type and the level of the water soluble polymer incorporated with HPMCP 50. Drug release was increased as the percentage of HPC was increased. Higher release rates were obtained with HPMC compared to HPC. Coating level significantly influenced drug release in 0.06 N HCl; however, less of an effect was observed at pH 5.5.     

Using empirical analysis to refine expert system knowledge bases

seek is a system which gives interactive advice about rule refinement during the design of an expert system. The advice takes the form of suggestions for possible experiments in generalizing or specializing rules in a model of reasoning rules cited by the expert. Case experience, in the form of stored cases with known conclusions, is used to interactively guide the expert in refining the rules of a model. This approach is most effective when the model of the expert's knowledge is relatively accurate and small changes in the model may improve performance. The system is interactive; we rely on the expert to focus the system on those experiments that appear to be most consistent with his domain knowledge. The design framework of seek consists of a tabular format for expressing expert-modeled rules and a general consultation system for applying a model to specific cases. Examples are given from an expert consultation system being developed for diagnosing rheumatic diseases.     

Attraction in context: Acquisition and blocking of person-directed action.

Two experiments with 72 undergraduates investigated attraction to a stranger, which has been previously shown to depend on the social context within which that directed action is acquired. In both experiments, a confederate stranger agreed with the S 100% of the time. Attraction to the stranger, however, was blocked if the stranger agreed with the S while in the presence of someone the S already found attractive. Based on these findings, the present authors employed N. E. Miller's (1959) "extension of liberalized stimulus–response theory" in developing a reinforcement-context theory to predict acquisition and blocking effects in attraction. Additional novel predictions addressing contextual phenomena are generated from the theory. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrous cycle effects on operant responding for ethanol in female rats

Human females have been reported to be uniquely sensitive to the deleterious effects of ethanol, thus it is important to study the characteristics of and mechanisms underlying alcohol consumption that may be specific to females. Models of ethanol self-administration in female rats that take into consideration the estrous cycle have the potential to provide important information concerning these characteristics and mechanisms. The purpose of this study was to explore the effect of the cycle on ethanol self-administration using a limited access operant paradigm. Female Wistar rats were trained to lever press for 10% ethanol versus water using a saccharin fading procedure. Responses were examined across the four phases of the estrous cycle. No effects of estrous cycle phase were observed when these rats were allowed to cycle freely. Subsequently, estrous phase effects were investigated in females whose cycles had been synchronized. Under this condition, an effect of estrous phase was present, with lower ethanol intake observed in estrus (and in some cases proestrus). Synchronized rats all showed at least one very clear 4-day estrous cycle, whereas free-running rats' cycles ranged from 3 to 5 days. Thus, it is more likely that synchronized rats were tested in the identical portion of each phase, when hormone levels were less variable. These results suggest that ethanol may be more reinforcing during diestrus than proestrus and estrus in female rats.     

In vitro expression and inhibition of procoagulant activity produced by bovine alveolar macrophages and peripheral blood cells

Local and systemic activation of coagulation is frequently associated with bacterial sepsis. The coagulopathy is due, at least in part, to expression of tissue factor (TF) by monocytes and macrophages. The purpose of this study was to evaluate the expression of procoagulant activity by bovine alveolar macrophages, leukocytes and platelets, and to determine the relative potency of three chemical inhibitors of TF expression (pentoxifylline, retinoic acid, and cyclosporin A). Bovine alveolar macrophages were stimulated with lipopolysaccharide (LPS) derived from Pasteurella haemolytica or recombinant bovine tumour nervous factor (TNF) and dose- and time-dependent effects on TF expression were studied. LPS and TNF induced TF expression in alveolar macrophages and LPS treatment of whole blood induced TF expression in mononuclear cells. Neutrophils and platelets also expressed procoagulant activity, but this activity was not inhibited by anti-bovine TF monoclonal antibody. Pentoxifylline (40 mumol/L), retinoic acid (0.01 mmol/L) and cyclosporin A (0.08 mumol/L) inhibited TF expression when added concurrently with LPS or TNF, but not when added 4 h after stimulation. TF mRNA was not detected in unstimulated alveolar macrophages by Northern blot analysis. In contrast, exposure to LPS or TNF for 6 h induced marked expression of TF mRNA, which was inhibited by treatment with pentoxifylline, retinoic acid and cyclosporin A. Expression of TNF by alveolar macrophages stimulated with LPS was also inhibited by these compounds. Our results indicate that procoagulant activity expressed by alveolar macrophages and monocytes is associated with expression of TF, whereas procoagulant activity expressed by neutrophils and platelets is not. The concentrations of pentoxifylline and retinoic acid necessary for inhibition of TF expression in vitro may not be achievable in vivo owing to their toxic effects. However, the in vitro concentration of cyclosporin A that inhibited TF expression did not exceed the plasma concentration observed in humans, and therefore may be useful for inhibition of TF expression in vivo.