Dow Chemical (India)

Manifesto escrito por Karl Marx e Friedrich Engels sob encomenda da Liga dos Comunistas que virá a se constituir no documento político mais importante da era moderna. Escrito em 1848, o documento está completando em 2010 162 anos.

We report a catalytic system that produces olefin block copolymers with alternating semicrystalline and amorphous segments, achieved by varying the ratio of alpha-olefin to ethylene in the two types of blocks. The system uses a chain shuttling agent to transfer growing chains between two distinct catalysts with different monomer selectivities in a single polymerization reactor. The block copolymers simultaneously have high melting temperatures and low glass transition temperatures, and therefore they maintain excellent elastomeric properties at high temperatures. Furthermore, the materials are effectively produced in economically favorable, continuous polymerization processes.

ADVERTISEMENT RETURN TO ISSUEPREVArticleDendritic macromolecules: synthesis of starburst dendrimersDonald A. Tomalia, H. Baker, J. Dewald, M. Hall, G. Kallos, S. Martin, J. Roeck, J. Ryder, and P. SmithCite this: Macromolecules 1986, 19, 9, 2466–2468Publication Date (Print):September 1, 1986Publication History Published online1 May 2002Published inissue 1 September 1986https://pubs.acs.org/doi/10.1021/ma00163a029https://doi.org/10.1021/ma00163a029research-articleACS PublicationsRequest reuse permissionsArticle Views4596Altmetric-Citations753LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Nanomaterials are used in practically every aspect of modern life, including agriculture. The aim of this study was to evaluate the effectiveness of iron oxide nanoparticles (Fe2O3 NPs) as a fertilizer to replace traditional Fe fertilizers, which have various shortcomings. The effects of the Fe2O3 NPs and a chelated-Fe fertilizer (ethylenediaminetetraacetic acid-Fe; EDTA-Fe) fertilizer on the growth and development of peanut (Arachis hypogaea), a crop that is very sensitive to Fe deficiency, were studied in a pot experiment. The results showed that Fe2O3 NPs increased root length, plant height, biomass, and SPAD values of peanut plants. The Fe2O3 NPs promoted the growth of peanut by regulating phytohormone contents and antioxidant enzyme activity. The Fe contents in peanut plants with Fe2O3 NPs and EDTA-Fe treatments were higher than the control group. We used energy dispersive X-ray spectroscopy (EDS) to quantitatively analyze Fe in the soil. Peanut is usually cultivated in sandy soil, which is readily leached of fertilizers. However, the Fe2O3 NPs adsorbed onto sandy soil and improved the availability of Fe to the plants. Together, these results show that Fe2O3 NPs can replace traditional Fe fertilizers in the cultivation of peanut plants. To the best of our knowledge, this is the first research on the Fe2O3 NPs as the iron fertilizer.

This review gives an overview of techniques used for high-resolution jet printing that rely on electrohydrodynamically induced flows. Such methods enable the direct, additive patterning of materials with a resolution that can extend below 100 nm to provide unique opportunities not only in scientific studies but also in a range of applications that includes printed electronics, tissue engineering, and photonic and plasmonic devices. Following a brief historical perspective, this review presents descriptions of the underlying processes involved in the formation of liquid cones and jets to establish critical factors in the printing process. Different printing systems that share similar principles are then described, along with key advances that have been made in the last decade. Capabilities in terms of printable materials and levels of resolution are reviewed, with a strong emphasis on areas of potential application.

Simulation optimization (SO) refers to the optimization of an objective function subject to constraints, both of which can be evaluated through a stochastic simulation. To address specific features of a particular simulation-discrete or continuous decisions, expensive or cheap simulations, single or multiple outputs, homogeneous or heterogeneous noise-various algorithms have been proposed in the literature. As one can imagine, there exist several competing algorithms for each of these classes of problems. This document emphasizes the difficulties in SO as compared to algebraic model-based mathematical programming, makes reference to state-of-the-art algorithms in the field, examines and contrasts the different approaches used, reviews some of the diverse applications that have been tackled by these methods, and speculates on future directions in the field.

We show that small diameter, single-walled carbon nanotubes can serve as templates for performing polymer imprint lithography with feature sizes as small as 2 nm − comparable to the size of an individual molecule. The angstrom level uniformity in the critical dimensions of the features provided by this unusual type of template provides a unique ability to investigate systematically the resolution of imprint lithography at this molecular scale. Collective results of experiments with several polymer formulations for the molds and the molded materials suggest that the density of cross-links is an important molecular parameter that influences the ultimate resolution in this process. Optimized materials enable reliable, repetitive patterning in this single nanometer range.

New nanocomposites are currently being developed that have real industrial potential—loading a polymer with a small (ca. 5 %) amount of inorganic nanoparticles (the Figure shows a polypropylene–clay hybrid composite) is expected to give rise to significant improvement to the materials properties with only a minor increase in cost. Recent developments in this area are summarized here.

Abstract Considerable progress has been made in the past 20 years in the synthesis, characterization and fabrication of plastics. Previous SPE Award winners, such as Mark, Natta, and Marvel dealt largely with synthesis; Flory with characterization; Alfrey and Du Bois with fabrication. One of the still unsolved problems lies in the realm of relating mechanical properties, such as impact strenght and creep to molecular structure. The design enginner who wishes to use a plastic part is concerned primarily with how some property such as impact strenght varies with temperature, speed of test, test method, etc. The polymer scientist must know why. Through knowing why, he may be able to design better plastics. This paper attempts to survey some of the world‐wide progress made in this area in the past 10 years. The ultimate goal is to understand these mechanical properties in terms of internal molecular motions which occur in solid polymers. Internal motion can be detected by electrical, electromagnetic and dynamic mechanical measurements. When these three methods are applied on a given polymer over a range of temperatures, insights can be gained as to the variation of impact strength and other properties with temperature and frequency for that same polymer. These three fundamental methods, which require very small samples (less than 50 grams), can provide insight into the practical behavior of plastic materials over the wide range of temperatures and frequencies encountered in the real world.

Communication: The efficiency of electroluminescent devices is strongly affected by charge carrier mobilities, in that electrons and holes must be able to be quickly transported for high quantum efficiency. Hole mobility data are reported here for a new family of five conjugated copolymers consisting of triarylamines—which are known to possess high time-of-flight (TOF) hole mobilities—combined with fluorenes via a Suzuki coupling reaction. All five display high room-temperature TOF hole mobilities, while one, “TFB“, has the highest yet reported for a π-conjugated polymer.

Dietary bisphenol A (BPA) was evaluated in a mouse two-generation study at 0, 0.018, 0.18, 1.8, 30, 300, or 3500 ppm (0, 0.003, 0.03, 0.3, 5, 50, or 600 mg BPA/kg/day, 28 per sex per group). A concurrent positive control group of dietary 17beta-estradiol (0.5 ppm; 28 per sex) confirmed the sensitivity of CD-1 mice to an endogenous estrogen. There were no BPA-related effects on adult mating, fertility or gestational indices, ovarian primordial follicle counts, estrous cyclicity, precoital interval, offspring sex ratios or postnatal survival, sperm parameters or reproductive organ weights or histopathology (including the testes and prostate). Adult systemic effects: at 300 ppm, only centrilobular hepatocyte hypertrophy; at 3500 ppm, reduced body weight, increased kidney and liver weights, centrilobular hepatocyte hypertrophy, and renal nephropathy in males. At 3500 ppm, BPA also reduced F1/F2 weanling body weight, reduced weanling spleen and testes weights (with seminiferous tubule hypoplasia), slightly delayed preputial separation (PPS), and apparently increased the incidence of treatment-related, undescended testes only in weanlings, which did not result in adverse effects on adult reproductive structures or functions; this last finding is considered a developmental delay in the normal process of testes descent. It is likely that these transient effects were secondary to (and caused by) systemic toxicity. Gestational length was increased by 0.3 days in F1/F2 generations; the toxicological significance, if any, of this marginal difference is unknown. At lower doses (0.018-30 ppm), there were no treatment-related effects and no evidence of nonmonotonic dose-response curves for any parameter. The systemic no observable effect level (NOEL) was 30 ppm BPA (approximately 5 mg/kg/day); the reproductive/developmental NOEL was 300 ppm (approximately 50 mg/kg/day). Therefore, BPA is not considered a selective reproductive or developmental toxicant in mice.

Abstract A survey of alumni from the College of Engineering at the University of Delaware was conducted to assess the impact of the undergraduate research experience. Students who had participated in undergraduate research were matched with a comparable group of alumni who had no research experience. Alumni were unaware that their responses would be used to assess the impact of undergraduate research. Respondents who had participated in research indicated that this experience was “very” or “extremely” important, with a greater perceived benefit for students who had participated in research for a longer time. Alumni with research experience were more likely to pursue graduate degrees, and they reported greater enhancement of important cognitive and personal skills. In addition, respondents who had been involved in research were much more likely to have reported that they had a faculty member play an important role in their career choice.

This work presents a novel approach to fine-tuning the size, shape, and interparticle spacing of nanoparticles fabricated by nanosphere lithography (NSL). This approach, termed angle-resolved nanosphere lithography (AR NSL), is a variant of NSL that yields vastly different, and increasingly flexible, nanostructures. This is accomplished by controlling the angle, θ, between the surface normal of the sample assembly and the propagation vector of the material deposition beam. Comparison of experimental results to simulated nanoparticle array geometries generated using an analytical model show excellent qualitative agreement. Using AR NSL, we have demonstrated that it is possible to reduce in-plane nanoparticle dimensions by a factor of 4. This important result shows that it will be possible to achieve fabrication of nanoparticles with precision control of their dimensions in a size regime comparable with the industry standard electron beam lithography. AR NSL provides a massively parallel, rather than serial, nanoparticle fabrication method. One limitation of the AR NSL technique is the inability to pattern an entire substrate with a single nanoparticle geometry without control of the mask domain orientation. While the presence of multiple domains in any given colloidal crystal mask complicates the fabrication of large-area homogeneous nanoparticle arrays, this quality is, in fact, useful in laboratory scale experiments requiring a diverse set of nanostructure features on a single sample. The precision tuning of nanoparticle size, shape, and spacing that can be achieved in a massively parallel, materials/substrate general, and inexpensive fashion using AR NSL is likely to have significant impact on the fields of surface-enhanced spectroscopy, near field optical microscopy, nanoscopic object manipulation, and chemical/biological sensing.

Click to increase image sizeClick to decrease image size ACKNOWLEDGMENTS We thank Eric Amis, Clive Bosnyak, Jim Chou, Chris Christenson, Rich Fibiger, Glenn Fredrickson, Ed Garboczi, Juan Garcés, and Dave Moll for helpful discussions. We also thank Giovanni Nisato and Richard Parnas for their helpful comments on our paper. This work was supported in part by the government under Cooperative Agreement No. 70NANB7H3028, awarded by the Department of Commerce, National Institute of Standards and Technology.

The constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are important nuclear receptors involved in the regulation of cellular responses from exposure to many xenobiotics and various physiological processes. Phenobarbital (PB) is a non-genotoxic indirect CAR activator, which induces cytochrome P450 (CYP) and other xenobiotic metabolizing enzymes and is known to produce liver foci/tumors in mice and rats. From literature data, a mode of action (MOA) for PB-induced rodent liver tumor formation was developed. A MOA for PXR activators was not established owing to a lack of suitable data. The key events in the PB-induced liver tumor MOA comprise activation of CAR followed by altered gene expression specific to CAR activation, increased cell proliferation, formation of altered hepatic foci and ultimately the development of liver tumors. Associative events in the MOA include altered epigenetic changes, induction of hepatic CYP2B enzymes, liver hypertrophy and decreased apoptosis; with inhibition of gap junctional intercellular communication being an associative event or modulating factor. The MOA was evaluated using the modified Bradford Hill criteria for causality and other possible MOAs were excluded. While PB produces liver tumors in rodents, important species differences were identified including a lack of cell proliferation in cultured human hepatocytes. The MOA for PB-induced rodent liver tumor formation was considered to be qualitatively not plausible for humans. This conclusion is supported by data from a number of epidemiological studies conducted in human populations chronically exposed to PB in which there is no clear evidence for increased liver tumor risk.

In this report, we investigated BRAF/NRAS mutations in samples from a case-control study of melanoma and a series of benign melanocytic nevi. We evaluated potential associations between BRAF mutations and histopathologic and pigmentary characteristics of melanoma. Mutations in BRAF and NRAS were detected by sequencing microdissected/laser-captured DNA from 18 in-situ melanomas, 64 primary melanomas, and 51 nevi. Nevi showed the highest frequency of BRAF mutations (82%). BRAF mutations were identified in 29% of invasive melanomas and in only 5.6% of in-situ melanomas. Mutations in NRAS were found in 5.2% of primary melanomas, 5.9% of nevi and no NRAS mutations were seen in in-situ melanomas. A majority of the BRAF mutations observed in primary invasive melanoma were seen in superficial spreading melanoma (15/17), and melanomas with BRAF mutations were also more likely to be found on a body site that was likely to be exposed to intermittent sun exposure compared with chronic or no sun exposure (P=0.02). Tumors with BRAF mutations were also significantly more likely to occur in association with a contiguous nevus (odds ratio 3.49, 95% confidence interval 1.06-11.46), although a contiguous nevus was not found in all melanomas with a BRAF mutation. Our data support the evidence that the mitogen-activated protein kinase pathway is upregulated in a large percentage of melanocytic lesions, but these mutations are not sufficient for malignant transformation. We suggest that BRAF mutations contribute to benign melanocytic hyperplasia, but are likely to contribute to invasive melanoma only in conjunction with other mutations.

Synthetic polymers are vital to our society, affecting practically every aspect of modern life. The ubiquitous nature of these materials is a result of years of collaboration between basic and applied researchers across many disciplines, resulting in economic routes to materials that meet customer needs. These considerations are exemplified by recent developments in the synthesis of block copolymers from simple olefins. The practical application of creative chemistry has produced materials with a favorable balance of desirable polymer properties and process economics.

A facile approach to unique 3D, patterned polymer brushes is based on visible-light-mediated controlled radical polymerization. The temporal and spatial control of the polymerization allows the patterning of polymer brushes from a uniform initiating layer using a simple photomask (see picture). Furthermore, gradient polymer brushes, patterned block copolymers, and complex 3D structures can be obtained by modulating light intensity. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Styrene is an extremely important commodity chemical used extensively in the manufacture of numerous polymers and copolymers, including polystyrene, acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), styrene-butadiene latex, and styrene-butadiene rubber. Styrene is a component of cigarette smoke and automobile exhaust, and it may occur naturally at low levels in various types of foods. The highest potential human exposures to styrene occur in occupational settings, particularly those involving the production of large glass-reinforced polyester products such as boats, which require manual lay-up and spray-up operations. Substantially lower occupational exposures occur in styrene monomer and polymer production facilities. The general public is exposed to very low concentrations of styrene in ambient air, indoor air, food, and drinking water.

Abstract In this article, we consider the risk management for mid‐term planning of a global multi‐product chemical supply chain under demand and freight rate uncertainty. A two‐stage stochastic linear programming approach is proposed within a multi‐period planning model that takes into account the production and inventory levels, transportation modes, times of shipments, and customer service levels. To investigate the potential improvement by using stochastic programming, we describe a simulation framework that relies on a rolling horizon approach. The studies suggest that at least 5% savings in the total real cost can be achieved compared with the deterministic case. In addition, an algorithm based on the multi‐cut L‐shaped method is proposed to effectively solve the resulting large scale industrial size problems. We also introduce risk management models by incorporating risk measures into the stochastic programming model, and multi‐objective optimization schemes are implemented to establish the tradeoffs between cost and risk. To demonstrate the effectiveness of the proposed stochastic models and decomposition algorithms, a case study of a realistic global chemical supply chain problem is presented. © 2009 American Institute of Chemical Engineers AIChE J, 2009