Optical spin hall effect in exciton-polariton condensates in lead halide perovskite microcavities.

An exciton-polariton condensate is a hybrid light-matter state in the quantum fluid phase. The photonic component endows it with characters of spin, as represented by circular polarization. Spin-polarization can form stochastically for quasi-equilibrium exciton-polariton condensates at parallel momentum vector k|| ∼ 0 from bifurcation or deterministically for propagating condensates at k|| > 0 from the optical spin-Hall effect (OSHE). Here, we report deterministic spin-polarization in exciton-polariton condensates at k|| ∼ 0 in microcavities containing methylammonium lead bromide perovskite (CH3NH3PbBr3) single crystals under non-resonant and linearly polarized excitation. We observe two energetically split condensates with opposite circular polarizations and attribute this observation to the presence of strong birefringence, which introduces a large OSHE at k|| ∼ 0 and pins the condensates in a particular spin state. Such spin-polarized exciton-polariton condensates may serve not only as circularly polarized laser sources but also as effective alternatives to ultracold atom Bose-Einstein condensates in quantum simulators of many-body spin-orbit coupling processes.

Racial/ethnic and educational differences in the estimated odds of recent nitrite use among adult household residents in the United States: an illustration of matching and conditional logistic regression.

This article compares estimates of the relative odds of nitrite use obtained from weighted unconditional logistic regression with estimates obtained from conditional logistic regression after post-stratification and matching of cases with controls by neighborhood of residence. We illustrate these methods by comparing the odds associated with nitrite use among adults of four racial/ethnic groups, with and without a high school education. We used aggregated data from the 1994-B through 1996 National Household Survey on Drug Abuse (NHSDA). Difference between the methods and implications for analysis and inference are discussed.

Use and support of multicultural and antiracist education: research-informed interdisciplinary social work practice.

Multicultural education (MCE) and antiracist education (ARE) are the primary curricula through which school educators are combating the effects of racism and bigotry. To assist in the efforts of the educators, social workers need an understanding of MCE and ARE objectives, assumptions, and current research to guide their practice. This article discusses the differences between MCE and ARE and presents the findings of a study conducted in five northwestern United States school districts. It examines curricula, policies, and practices used to address racism and bigotry among elementary, middle, and high school students; attempts to discover underlying barriers to implementing antiracist and antibigotry curricula; and reveals the perspectives of teachers, administrators, counselors, and social workers. Implications for social work practice, policy development, and research are discussed.

Beliefs about substance use among pregnant and parenting adolescents.

PIP: Although substance use among pregnant and parenting adolescents has serious health implications for both mother and infant, few studies have investigated the predictors of such behavior. The present study, based on the Theory of Reasoned Action, tracked substance use behavior, intentions, attitudes, perceived social norms, and beliefs from pregnancy to 12 months postpartum in a cohort of 255 US adolescents (mean age, 16 years). Documented was a pattern in which adolescent mothers engaged in low levels of cigarette, marijuana, and alcohol use during pregnancy, but resumed substance use in the first 6 postpartum months, with rates levelling off by 12 months postpartum. Attitudes and perceived social norms about cigarette, alcohol, and marijuana use became increasingly more favorable from pregnancy to 6 months postpartum, paralleling trends in use rates. Doctors were perceived as most opposed to substance use during and after pregnancy, while friends, boyfriends, and siblings were considered to be least opposed. In general, negative outcomes of substance use were viewed less negatively and as less likely after the baby was born. Consistent with the Theory of Reasoned Action, increases in substance use after delivery were accompanied by similar increases in intentions to use these substances, more favorable attitudes toward use, and less perceived disapproval of use. Adolescents' willingness to curtail substance use during pregnancy indicates a concern for the well-being of their infant. This study's findings suggest a need for educational programs that emphasize the need to avoid substance use after as well as during pregnancy.^ieng

Designing and evaluating strategies to recruit African Americans for AIDS/HIV interventions: targeting the African-American family.

The successful recruitment of African-Americans for AIDS/HIV interventions is essential to reducing HIV transmission and the spread of AIDS among this population. However, many high risk groups in the African-American community are reluctant to participate in AIDS/HIV interventions due to factors such as poverty, and cultural and religious values. This paper discusses the basis of these factors and presents a theoretical framework that holds some promise for designing and evaluating AIDS/HIV intervention recruitment strategies and a pilot study implementing this strategy is presented. The results emphasize the importance of targeting and empowering the African-American family in recruitment strategies, as opposed to specific subgroups of high risk individuals. Recruitment messages, which were channeled through a credible source and which stress the role of participants in contributing to the well-being of their families and communities, were most successful.

Ethylene Production during Development of Mustard (Brassica juncea) and Canola (Brassica napus) Seed.

An open, continuous flow system was used to investigate ethylene production during degreening of maturing seed of mustard (Brassica juncea cv Cutlass and cv Lethbridge 22A) and canola (Brassica napus cv Westar and cv Alto). Isolated mustard seed evolved higher amounts of ethylene than those of canola, and this was particularly evident both early in embryogeny and later during the desiccation phase of seed maturation. The silique walls produced negligible amounts of ethylene in both species. The concentrations of ethylene surrounding seed as they matured within siliques were significantly higher in mustard than in canola, and this interspecies difference was greatest during the seed desiccation phase. In mustard, a 4-fold increase in silique internal ethylene levels was apparent during desiccation. In comparison, only a moderate increase in silique-derived ethylene occurred in canola.

How "the best" companies use MRP (materiel requirements planning) and just-in-time for successful manufacturing.

A study of production planning and control methods used in six leading companies found that a blending strategy is more effective than reliance on a single system. The blending of just-in-time and materiel requirements planning and other approaches allowed companies to select methods that best fit the unique characteristics of their production environments.

Effect of 2,4-Dichlorophenoxyacetic Acid on Endogenous Cyanide, beta-Cyanoalanine Synthase Activity, and Ethylene Evolution in Seedlings of Soybean and Barley.

Treatment of etiolated seedlings of barley (Hordeum vulgare) and soybean (Glycine max) with 1 millimolar 2,4-dichlorophenoxyacetic acid (2,4-D) resulted in a 14-fold and greater than 100-fold increase in ethylene production, respectively. Simultaneous monitoring of endogenous cyanide and beta-cyanoalanine synthase (beta-CAS) (EC 4.4. 1.9) activity was also performed. Endogenous levels of cyanide did not change in barley. In soybean, endogenous cyanide increased within 3 hours, increased again 6 hours after exposure to 2,4-D, and continued to increase throughout the experimental period. The activity of beta-CAS increased in both barley and soybean 9 hours after herbicide treatment. The increase in cyanide preceded the increase in beta-CAS activity by 3 to 6 hours in soybean. The steady-state concentration of endogenous cyanide in soybean was 1 micromolar, based on rates of ethylene production and cyanide metabolism by beta-CAS. This agreed with the determination of endogenous cyanide by both distillation and isotope dilution. Given the apparent compartmentalization of beta-CAS in mitochondria and the localization of ethylene/HCN production at the plasmalemma and/or tonoplast, our results suggest that extra-mitochondrial accumulation of cyanide in the cytoplasm may occur. If so, the activity of cyanide-sensitive cytoplasmic enzymes could be adversely affected, thus possibly contributing to the toxicity of 2,4-D.

Control processes in the induction and relief of thermoinhibition of lettuce seed germination : actions of phytochrome and endogenous ethylene.

Germination of lettuce seeds (Lactuca sativa L. cv Grand Rapids) in the dark was nearly 100% at 20 degrees C but was inhibited at 27 degrees C and higher temperatures (thermoinhibition). A single 5-minute exposure to red light completely overcame the inhibition at temperatures up to 28 degrees C, above which the effectiveness of single light exposures gradually declined to reach a negligible level at 32 degrees C. However, the promotive effect of light could be extended to 34 degrees C by repeated irradiations. At any one temperature, increased frequency of irradiations increased germination percentage, and with each degree increase in temperature, increasingly frequent irradiations were necessary to elicit maximal germination. Loss of the effectiveness of single irradiations with increase in temperature may result either from acceleration of the thermal reversion of the far red-absorbing form of phytochrome or decrease in seed sensitivity toward a given percentage of the far red-absorbing form of phytochrome. Using continuous red light to induce germination, the role of endogenous C(2)H(4) in germination at 32 degrees C was studied. Ethylene evolution from irradiated seeds began to increase 2 hours prior to radicle protrusion, whereas the dark-incubated (nongerminating) seeds produced a low, constant amount of C(2)H(4) throughout the 24 hour incubation period. Inhibition of C(2)H(4) synthesis with 2-aminoethoxyvinyl glycine and/or inhibition of C(2)H(4) action with 2,5-norbornadiene blocked the promotive effect of light. Exogenous C(2)H(4) overcame these blockages. The results showed that participation by endogenous C(2)H(4) was essential for the light-induced relief of thermoinhibition of lettuce seed germination. However, light did not act exclusively via C(2)H(4) since exogenous C(2)H(4) alone in darkness did not promote germination.

A role for ethylene in the metabolism of cyanide by higher plants.

The action of ethylene on the capacity of plant tissues to metabolize cyanide to beta-cyanoalanine was examined. Beta-cyanoalanine synthase (EC 4.4.1.9) catalyzes the reaction between cyanide and cysteine to form beta-cyanoalanine and hydrogen sulfide. Levels of beta-cyanoalanine synthase activity in tissues of 6 day old etiolated pea (Pisum sativum) seedlings were enhanced severalfold by 1 microliter per liter ethylene. The promotive effect of ethylene increased with increasing ethylene concentrations from 0.01 to 100 microliters per liter and with the period of exposure from 3 to 24 hours. Ethylene enhanced beta-cyanoalanine synthase activity in all regions of the seedling (shoots and roots, internodal regions, cotyledons). The promotive effect was eliminated by norbornadiene, a competitive inhibitor of ethylene action. Levels of beta-cyanoalanine synthase in seedlings of four other dicots (Phaseolus aureas, Glycine max, Lactuca sativa, Sinapis arvensis) and two monocots (Hordeum vulgares, Triticum aestivum) were also increased in response to ethylene. Our results suggest an important regulatory role for ethylene in the metabolism of cyanide by higher plants.

Ethylene Production by Attached Leaves or Intact Shoots of Tobacco Cultivars Differing in Their Speed of Yellowing during Curing.

Using an open air flow system, differences in the yellowing rate of leaves during curing were assessed in relation to ethylene production by shoots of intact seedlings or attached mature leaves of 60 day old tobacco (Nicotiana tabacum L.) plants. The rate of ethylene evolution from the leaves of the fast yellowing cultivars was significantly higher than in the slow yellowing ones. The same differences were obtained with shoots of intact seedlings. The findings suggest that it is possible to use ethylene production by seedlings as a selection criterion in screening for genotypic differences in the rate of yellowing. The ability of carbon dioxide (1%) to enhance ethylene production by attached leaves was significant in a slow, but not in a fast yellowing cultivar. However, similar amounts of ethylene were produced on administration of 1-aminocyclopropane-1-carboxylic acid to a slow and a fast yellowing cultivar. Exposure of attached leaves to exogenous ethylene (0.1 microliter per liter) accelerated the loss of chlorophyll and protein. This treatment was effective only for slightly yellow leaves and not for fully expanded green ones. The significance and possible use of ethylene in the flue-curing process are discussed.

Hypochlorite Disinfection Influences the GA(3)-Induced Synthesis of alpha-Amylase Isozymes by Isolated Barley Aleurone Layers.

Aleurone layers isolated from half-seeds of Himalaya barley (Hordeum vulgare cv Himalaya) disinfected in hypochlorite solutions containing 1.0% available chlorine synthesized significantly less alpha-amylase in response to gibberellic acid than layers derived from half-seeds disinfected in 0.1% hypochlorite. This effect of hypochlorite involved neither a differential decrease in the synthesis of group A or B alpha-amylase isozymes nor a general decrease in alpha-amylase synthesis attributable to fewer viable aleurone cells in layers from half-seeds disinfected with 1% hypochlorite. Our results emphasize the need to evaluate the potential effects of routine disinfection procedures used in physiological and biochemical studies.

Uptake and Fate of Ethephon ([2-Chloroethyl]phosphonic Acid) in Dormant Weed Seeds.

Although ethephon ([2-chloroethyl]phosphonic acid) is often used as a form of liquid ethylene in studies of seed germination, it is not known if ethylene evolved from ethephon in the seed is sufficient to elicit the desired response and/or if ethephon has a regulatory action that alone accounts for the response. For these reasons we studied the uptake and fate of [1,2-(14)C]ethephon in dormant seeds of Avena fatua, Sinapis arvensis, Thlaspi arvense, and Chenopodium album. The radioactivity within the seeds was separated into a labile carbon-labeled ethephon/ethylene fraction (64-87%) and, following extraction in methanol-chloroform-water (12:5:3), into fractions associated with insoluble (12-29%) and soluble (3-8%) seed constituents. The radioactivity associated with seed constituents was reduced 5 to 75% by hot alkaline hydrolysis (2.5 n KOH, 70 degrees C for 1 hour). Although a small portion of the ethephon (or metabolite of ethephon/ethylene) taken up by the seeds is tightly bound to the tissues, our results indicate that, at the appropriate external concentrations of ethephon, the amount of ethylene evolved from ethephon within the seeds is sufficient to produce the desired ethylene mediated responses. However, factors affecting the decomposition of ethephon must be considered in the decision as to whether to use ethephon as a liquid supply of ethylene.

Requirement for Ethylene Synthesis and Action during Relief of Thermoinhibition of Lettuce Seed Germination by Combinations of Gibberellic Acid, Kinetin, and Carbon Dioxide.

Application of exogenous ethylene in combination with gibberellic acid (GA(3)), kinetin (KIN), and/or CO(2) has been reported to induce germination of lettuce seeds at supraoptimal temperatures. However, it is not clear whether endogenous ethylene also plays a mediatory role when germination under these conditions is induced by treatment regimes that do not include ethylene. Therefore, possible involvement of endogenous ethylene during the relief of thermoinhibition of lettuce (Lactuca sativa L. cv Grand Rapids) seed germination at 32 degrees C was investigated. Combinations of GA(3) (0.5 millimolar), KIN (0.05 millimolar), and CO(2) (10%) were used to induce germination. Little germination occurred in controls or upon treatment with ethylene, KIN, or CO(2). Neither KIN nor CO(2) affected the rate of ethylene production by seeds. Both germination and ethylene production were slightly promoted by GA(3). Treatments with GA(3)+CO(2), GA(3)+KIN, or GA(3)+CO(2)+KIN resulted in approximately 10-to 40-fold increases in ethylene production and 50 to 100% promotion of germination as compared to controls. Initial ethylene evolution from the treated seeds was greater than from the controls and a major surge in ethylene evolution occurred at the time of visible germination. Application of 1 millimolar 2-aminoethoxyvinyl glycine (AVG), an inhibitor of ethylene synthesis, in combination with any of above three treatments inhibited the ethylene production to below control levels. This was accompanied by a marked decline in germination percentage. Germination was also inhibited by 2,5-norbornadiene (0.25-2 milliliters per liter), a competitive inhibitor of ethylene action. Application of exogenous ethylene (1-100 microliters per liter) overcame the inhibitory effects of AVG and 2,5-norbornadiene on germination. The results demonstrate that endogenous ethylene synthesis and action are essential for the alleviation of thermoinhibition of lettuce seeds by combinations of GA(3), KIN, and CO(2). It also appears that these treatment combinations do not act exclusively via promotion of ethylene evolution as the application of exogenous ethylene alone did not promote germination.

Interactions between Ethylene, CO(2), and ABA on GA(3)-Induced Amylase Synthesis in Barley Aleurone Tissue.

Gibberellic acid-induced synthesis and release of alpha-amylase in barley aleurone tissue was inhibited by abscisic acid. This inhibition was relieved by simultaneous application of ethylene ranging in concentration from 0.1 to 100 microliters per liter. When CO(2) was applied, it eliminated the effect of 0.1 microliter per liter ethylene and reimposed the abscisic acid inhibition. All concentrations of CO(2) tested from 400 to 10(5) microliters per liter counteracted the effect of 0.1 microliter per liter ethylene, but had no observable effect on any higher concentration of ethylene. The results indicate that some processes necessary for embryo growth may be subject to regulation by ethylene and carbon dioxide at naturally occurring concentrations of the gases.

Purification and characterization of barley-aleurone xylanase.

Xylanase (ß-1,4-D-xylan xylanohydrolase; EC 3.2.1.8) from aleurone layers of barley (Hordeum vulgare L. cv. Himalaya) was purified and characterized. Purification was by preparative isoelectric focusing and a Sephadex G-200 column. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the enzyme showed a single protein band with an apparent molecular weight (Mr)=34000 daltons. The isoelectric point of the enzyme was 4.6. The enzyme had maximum activity on xylan at pH 5.5 and at 35° C. It was most stable between pH 5 and 6 and at temperatures between 0 and 4° C. The Km was 0.86 mg xylan·ml(-1).

An evaluation of the role of ethylene in herbicidal injury induced by picloram or clopyralid in rapeseed and sunflower plants.

The role of ethylene in herbicidal injury induced by 4-amino-3,5,6-trichloropicolinic acid (picloram) or 3,6-dichloropicolinic acid (clopyralid) was investigated in sunflower (Helianthus annuus L.) and rapeseed (Brassica napus L. cv Altex). Picloram induces herbicide injury in both species, whereas clopyralid induces injury only in sunflower. Picloram applied to the third leaf of a rapeseed plant increased ethylene evolution several-fold. Clopyralid had no effect on ethylene production in rapeseed. In sunflower, both picloram and clopyralid elevated ethylene production. Ethylene biosynthesis induced by the herbicide treatment was not restricted to treated areas. When clopyralid was applied only to the lower stem and cotyledons of sunflower, the herbicide treatment resulted in an increase in the rate of ethylene production from the true leaves. Increased ethylene production preceded or coincided with the onset of morphological responses induced by a herbicide application to a susceptible species. The contrast in ethylene production by these two plant species cannot be accounted for by differences in absorption and translocation of clopyralid and picloram.Treatment with aminoethoxyvinylglycine (AVG) before picloram or clopyralid application prevented an increase in ethylene production. Pretreatment with AVG also delayed the development of morphological changes induced by picloram or clopyralid. It appears that enhanced ethylene biosynthesis after application of picloram or clopyralid to the susceptible plant species was a factor involved in resulting morphological changes.

Seed Germination in Chenopodium album L: Relationships between Nitrate and the Effects of Plant Hormones.

Effects of ethylene, gibberellins, and kinetin on the germination of two lots of Chenopodium album L. seeds, collected from the field in 1982 and 1983, were studied in relation to the availability of nitrate. The experiments were conducted in darkness and at temperatures ranging from 12 to 32 degrees C. Ethylene induced over 75% germination in the 1983 seed but had little effect on the 1982 seed. Nitrate was only slightly promotive in either of the two seed lots. A combination of ethylene and nitrate, however, acted synergistically on 1982 seed, resulting in as much germination as that induced in 1983 seed by ethylene alone. In 1983 seed, a combination of ethylene and nitrate was only marginally more effective than ethylene. A similar relationship was observed in the effects of gibberellic acid(4+7) (GA(4+7)) and nitrate on seeds from the two lots. The 1982 seed, which responded synergistically to combinations of nitrate with ethylene or GA(4+7) was found to contain an extremely low endogenous level of nitrate as compared to 1983 seed. Thus, high levels of either endogenous or applied nitrate appeared to enhance the germination response to ethylene or GA(4+7).Kinetin had no effect on 1982 seed and only a small promotive effect on 1983 seed. There was no synergism between kinetin and nitrate in either of the seed lots.

Does light inhibit ethylene production in leaves?

The effect of light on the rate of ethylene production was monitored using two different techniques-leaf segments incubated in closed flasks versus intact plants in a flow-through open system. Three different plants were used, viz sunflower (Helianthus annuus), tomato (Lycopersicon esculentum), and soybean (Glycine max). Experiments were conducted both in the presence and absence of 1-aminocyclopropane-1-carboxylic acid (ACC).The results obtained indicate that, in all three species studied, light strongly inhibits ethylene production when cut leaf segments are incubated in the presence of ACC in closed flasks. When ethylene measurements are made with ACC-sprayed intact plants using a continuous flow system, the effect of light on ethylene production is only marginal. In leaf segments of sunflower and soybean incubated only in distilled H(2)O in closed flasks, light promotes ethylene production. In tomato, there is no difference between the rate of ethylene production between light and darkness under such conditions. When measurements are made with intact plants in a continuous flow system, the rate of ethylene production is almost identical in light and darkness, in the three plants studied.It is concluded that the effect of light on cut leaf segments incubated in the presence of ACC in closed flasks can be attributed to the techniques used for these measurements. Light has little effect on ethylene production by intact plants in an open system.

Solubilization and partial purification of n,n'-dicyclohexylcarbodiimide-sensitive ATPase from pea cotyledon mitochondria.

The N,N'-dicyclohexylcarbodiimide (DCCD)-sensitive ATPase of pea (Pisum sativum L.) cotyledon mitochondria was solubilized from submitochondrial particle membranes with sodium cholate and ammonium sulfate. Ammonium sulfate precipitation of the enzyme resulted in an increase in specific activity. At between 38% and 45% saturated ammonium sulfate, 20% of the ATPase activity was precipitated, with a specific activity 4 to 5 times higher than that of the crude enzyme. The precipitate was highly sensitive to DCCD.The properties of the ammonium sulfate preparation were investigated. It contained levels of cytochrome and NADH dehydrogenase contamination comparable to those of the highly purified F(0)F(1) preparations from animal tissue. The high degree of purification was corroborated by sodium dodecyl sulfate electrophoresis.