Strategies for reducing fumigant loss to the atmosphere

A model is developed to describe transport and loss of methyl bromide (MeBr) in soil following application as a soil fumigant. The model is used to investigate the effect of soil and management factors on MeBr volatilization. Factors studied include depth of injection, soil water content, presence or absence of tarp, depth to downward barrier, and irrigation after injection. Of these factors, the most important was irrigation after injection followed by covering with the tarp, which increased the diffusive resistance of the soil and prevented early loss of MeBr. The model offers an explanation for the apparently contradictory observations of earlier field studies of MeBr volatilization from soils under different conditions. The model was also used to calculate the concentration-time index for various management alternatives, showing that the irrigation application did not make the surface soil more difficult to fumigate, except at very early times. Therefore, irrigation shows promise for reducing fumigant loss while at the same time permitting control of target organisms during fumigation.

Regulation of Spec genes in aboral ectoderm cells of sea urchin {\it Strongylocentrotus purpuratus}

The Spec genes of the sea urchin Stronylocentrotus purpuratus serves as an excellent model for studying cell type-specific gene expression during early embryogenesis. The Spec1/Spec2 genes encode cytosolic calcium-binding proteins related to the calmodulin/troponin C/myosin light chain superfamily. Members of the Spec gene family are activated shortly after the sixth cleavage as the lineage-specific founder cells giving rise to aboral ectoderm are established, and the accumulation of the Spec mRNAs is limited exclusively to aboral ectoderm cell lineages. In this dissertation, the transcriptional regulation of the Spec genes was studied. Sequence comparisons of the Spec gene 5$\sp\prime$ flanking regions showed that a DNA block of approximately 800 bp from the 3$\sp\prime$ end of the first exon to the 5$\sp\prime$ end of a repetitive DNA element, termed RSR, was highly conserved. In Spec2a, the conserved region was a continuous stretch of DNA, but in Spec1 and Spec2c, DNA insertions interrupt the conserved sequence block and alter the relative placement of the RSR element and other 5$\sp\prime$ flanking DNA. Thus, drastic rearrangements have occurred within the putative control regions of the Spec genes. In vivo expression experiments using the sea urchin embryo gene-transfer system showed that while the 5$\sp\prime$ flanking regions of all three Spec genes conferred proper temporal activation to the reporter CAT gene, only the Spec2a 5$\sp\prime$ flanking region could restrict lacZ gene expression to aboral ectoderm cells. However, the Spec2a conserved region alone was not sufficient to confer proper spatial expression, suggesting that negative spatial elements are also associated with the proper activation of Spec2a. A major positive regulatory region, defined as the RSR enhancer, was identified between base pairs $-$631 and $-$443 on Spec2a. The RSR enhancer was essential for maximal activity and conferred preferential aboral ectoderm expression to a lacZ reporter gene. DNaseI footprinting and band-shift analysis of the RSR enhancer revealed multiple DNA-elements. One of the elements, an A/T-rich sequence called the A/T palindrome was studied in detail. This element binds a single 45-kDa nuclear protein, the A/T palindrome binding protein (A/TBP), whose DNA-binding specificity suggests a possible relationship with the bicoid-class homeodomain proteins. Mutated A/T palindromes are incapable of binding the 45-kDa protein and lower promoter activity by 8-fold. DNA-binding activity for A/TBP is low in unfertilized eggs, increases by the 16-cell stage and continues rising in blastulae. These data suggest that A/TBP plays a major role in the activation of the Spec2a gene in aboral ectoderm cells. ^

Prescriptions of Chinese medicinal herbs in Switzerland: the example of suan zao ren (Ziziphi Spinosae Semen)

Introduction According to the Swiss Health Survey 2007, 1.7% of the adult population use traditional Chinese medicine (including Chinese herbal medicine, but excluding acupuncture). In contrast to conventional drugs, that contain single chemically defined substances, prescriptions of Chinese herbs are mixtures of up to 40 ingredients (parts of plants, fungi, animal substances and minerals). Originally they were taken in the form of decoctions, but nowadays granules are more popular. Medium daily dosages of granules range between 8 to 12g. In a recent work we identified the most commonly used Chinese herbs (all ingredients are referred to as herbs for reasons of simplicity) and classical formulas (mixtures). Here we present a short overview and the example of suan zao ren (Ziziphi Spinosae Semen), which is used in the treatment of insomnia and anxiety and contains saponins that have been shown to increase sleep in animal studies. Material and Methods A random sample of 1,053 prescriptions was drawn from the database of Lian Chinaherb AG, Switzerland, and analysed according to the most frequently used individual herbs and classical formulas. Cluster analysis (Jaccard similarity coefficient, complete linkage method) was applied to identify common combinations of herbs. Results The most frequently used herbs were dang gui (Angelicae Sinensis Radix), fu ling (Poria), bai shao (Paeoniae Radix Alba), and gan cao (Glycyrrhizae Radix et Rhizoma); the most frequently used classical formulas were gui pi tang (Restore the Spleen Decoction) and xiao yao san (Rambling Powder). The average number of herbs per prescription was 12.0, and the average daily dosage of granules was 8.7g. 74.3% of the prescriptions were for female, 24.8% for male patients. Suan zao ren was present in 14.2% of all prescriptions. These prescriptions contained on average 13.7 herbs, and the daily dosage of granules was 8.9g. Suan zao ren was more frequently prescribed by practitioners of non-Asian than of Asian origin but equally often for female and male patients. Cluster analysis grouped suan zao ren with yuan zhi (Polygalae Radix), bai zi ren (Platycladi Semen), sheng di huang (Rehmanniae Radix) and dan shen (Salviae Miltiorrhizae Radix et Rhizoma). Discussion Prescriptions including suan zao ren contained on average slightly more herbs than other prescriptions. This might be due to the fact that two of the three most popular classical formulas with suan zao ren are composed of 13 and 12 herbs with the possibility of adding more ingredients when necessary. Cluster analysis resulted in the clustering of suan zao ren with other herbs of the classical formula tian wang bu xin dan (Emperor of Heaven’s Special Pill to Tonify the Heart), indicating the use of suan zao ren for the treatment of insomnia and irritability. Unfortunately, the diagnoses of the patients were unavailable and thus correlations between use of suan zao ren and diseases could not be analysed.

From supramolecular sheets to fibers and back: establishing the critical parameters that govern the morphology of pyrene-based self-assembled materials

The precise arraying of functional entities in morphologically well-defined shapes remains one of the key challenges in the processing of organic molecules1. Among various π-conjugated species, pyrene exhibits a set of unique properties, which make it an attractive compound for the utilization in materials science2. In this contribution we report on properties of self-assembled structures prepared from amphiphilic pyrene trimers (Py3) consisting of phosphodiester-linked pyrenes. Depending on the geometry of a pyrene core substitution (1.6-, 1.8-, or 2.7- type, see Scheme), the thermally-controlled self-assembly allows the preparation of supramolecular architectures of different morphologies in a bottom-up approach: two-dimensional (2D) nanosheets3 are formed in case of 1.6- and 2.7-substitution4 whereas one-dimensional (1D) fibers are built from 1.8- substituted isomers. The morphologies of the assemblies are established by AFM and TEM, and the results are further correlated with spectroscopic and scattering data. Two-dimensional assemblies consist of an inner layer of hydrophobic pyrenes, sandwiched between a net of phosphates. Due to the repulsion of the negative charges, the 2D assemblies exist mostly as free-standing sheets. An internal alignment of pyrenes leads to strong exciton coupling with an unprecedented observation (simultaneous development of J- and H-bands from two different electronic transitions). Despite the similarity in spectroscopic properties, the structural parameters of the 2D aggregates drastically depend on the preparation procedure. Under certain conditions extra-large sheets (thickness of 2 nm, aspect ratio area/thickness ~107) in aqueous solution are formed4B. Finally, one-dimensional assemblies are formed as micrometer-long and nanometer-thick fibers. Both, planar and linear structures are intriguing objects for the creation of conductive nanowires that may find interest for applications in supramolecular electronics.

From supramolecular sheets to fibers and back: establishing the critical parameters that govern the morphology of pyrene-based self-assembled materials

The precise arraying of functional entities in morphologically well-defined shapes remains one of the key challenges in the processing of organic molecules1. Among various π-conjugated species, pyrene exhibits a set of unique properties, which make it an attractive compound for the utilization in materials science2. In this contribution we report on properties of self-assembled structures prepared from amphiphilic pyrene trimers (Py3) consisting of phosphodiester-linked pyrenes. Depending on the geometry of a pyrene core substitution (1.6-, 1.8-, or 2.7- type, see Scheme), the thermally-controlled self-assembly allows the preparation of supramolecular architectures of different morphologies in a bottom-up approach: two-dimensional (2D) nanosheets3 are formed in case of 1.6- and 2.7-substitution4 whereas one-dimensional (1D) fibers are built from 1.8- substituted isomers. The morphologies of the assemblies are established by AFM and TEM, and the results are further correlated with spectroscopic and scattering data. Two-dimensional assemblies consist of an inner layer of hydrophobic pyrenes, sandwiched between a net of phosphates. Due to the repulsion of the negative charges, the 2D assemblies exist mostly as free-standing sheets. An internal alignment of pyrenes leads to strong exciton coupling with an unprecedented observation (simultaneous development of J- and H-bands from two different electronic transitions). Despite the similarity in spectroscopic properties, the structural parameters of the 2D aggregates drastically depend on the preparation procedure. Under certain conditions extra-large sheets (thickness of 2 nm, aspect ratio area/thickness ~107) in aqueous solution are formed4B. Finally, one-dimensional assemblies are formed as micrometer-long and nanometer-thick fibers. Both, planar and linear structures are intriguing objects for the creation of conductive nanowires that may find interest for applications in supramolecular electronics.

La educación especial y sus protagonistas : desde la recuperación democrática hasta nuestros días. La ética en la agenda

La recuperación de la democracia en diciembre de 1983, fue el inicio de una nueva etapa en la vida de la República Argentina. Sin embargo, ciclos repetidos de ilusiones y desilusiones, de incertidumbres y esperanzas, de encuentros y desencuentros, de proyectos y frustraciones, marcaron fuertemente a toda la población y a las instituciones que la representan. La educación, las escuelas y sus protagonistas no quedaron fuera de esta realidad, lo que limitó su posibilidad de mejorar la oferta educativa. Sin embargo, las fuertes experiencias cotidianas, marcaron a cada uno y a las relaciones con el otro, con los otros, con las organizaciones sociales. Se ganó algo muy importante: La vida en democracia. Pero se trastocaron valores y muchos principios éticos quedaron fuertemente mancillados. Esta es la reflexión que nos proponemos.