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  • 1
    Electronic Resource
    Electronic Resource
    High-pressure light scattering apparatus to study pressure-induced phase separation in polymer solutions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1463-1471 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new high-pressure time- and angle-resolved light scattering apparatus has been developed to study the kinetics of phase separation in polymer solutions and other fluid mixtures under pressure at near- and supercritical conditions. The system consists of a high-pressure polymer loading chamber, a solvent charge line, a variable-volume scattering cell (with a built-in movable piston connected to a pressure generator, and an expansion rod driven by an air-actuated diaphragm), and a recirculation pump which are all housed in a temperature-controlled oven. The system is operable at pressures up to 70 MPa, and temperatures up to 473 K. The scattering cell is a short path-length cell made of two flat sapphire windows that are separated by 250 μm. It is designed to permit measurements of transmitted and scattered light intensities over an angle range from 0° to 30°. A linear image sensor with 256 elements is used to monitor the time evolution of the scattered light intensities at different angles. With this sensor, the angle range from 2° to 13° is scanned at a sampling rate of 3.2 ms/scan. The pressure quenches are achieved by movement of the air-actuated movable expansion rod, or by the movement of the piston with the aid of the pressure generator to bring about either rapid (at rates approaching 2000 MPa/s) or slow pressure changes in the system. Quench depth is also adjustable, and very deep (70 MPa) or very shallow (as low as 0.1 MPa) pressure quenches are readily achievable. The temperature and the pressure of the solution in the scattering cell, and the transmitted and scattered light intensities at different angles are recorded in real time through a computerized data acquisition system before and during phase separation. The experimental system is especially suited to follow the kinetics of phase separation in polymer solutions and to assess the metastable and unstable regions where phase separation proceeds by the nucleation and growth, and the spinodal decomposition mechanisms, respectively. The capability of the instrument is demonstrated for polystyrene/methylcyclohexane solutions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148782
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of virulence determinants in vitro and in vivo in Staphylococcus aureus (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 40 (2004), S. 0 
    Details
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Staphylococcus aureus is an opportunistic pathogen. In response to changing host environments, this bacterium has the capability to switch on selective sets of genes to enhance its chances for survival. This switching process is precisely controlled by global regulatory elements. There are two major groups of global regulatory elements in S. aureus, including two-component regulatory systems (TCRSs) and the SarA protein family. Presumably, the sensor proteins of the 16 TCRSs in S. aureus provide external sensing, while the response regulators, in conjunction with alternative transcription factors and the SarA protein family, function as effectors within the intricate regulatory network to respond to environmental stimuli. Sequence alignment and structural data indicate that the SarA protein family could be subdivided into three subfamilies: (1) single-domain proteins; (2) double-domain proteins; and (3) proteins homologous to the MarR protein family. Recent data using reporter gene fusions in animal models, have confirmed distinct expression profiles of selected regulatory and target genes in vitro vs. in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0928-8244(03)00309-2
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  • 3
    Electronic Resource
    Electronic Resource
    Densification of Aluminum Nitride Ceramics with CaF〈sub〉2〈/sub〉 Additive (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 368-372 (Feb. 2008), p. 970-972 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Effect of adding up to 5wt% CaF2 on the densification and microstructural development of hotpressed aluminum nitride (AlN) was investigated. SEM investigation showed that the grain size of thesintered sample decreases with the increasing content of CaF2. Secondary-phase evolution paths convergefrom CA6 to CA phase above 1650°C. TEM micrographs showed that formed secondary phases couldevaporate from sintered bodies at higher temperatures in the carbon-containing nitrogen atmosphere andthe residuals were mainly distributed at triple grain junctions, keeping direct connections of AlN grains.Translucnet AlN ceramics were prepared using CaF2 additive sintered at 1850°C for 5 h
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/56/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.368-372.970.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Solid-state reactivity of iron molybdate artificially contaminated by antimony ions and its relation with catalytic activity in the selective oxidation of isobutene to methacrolein (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 167-180 
    Details
    ISSN: 1572-9028
    Keywords: iron–molybdenum–antimony catalysts ; solid-state reactions in catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Catalysts were prepared by impregnation of Fe2(MoO4)3 with different quantities of antimony butoxide. BET surface area measurement, XRD, Mössbauer spectroscopy, CTEM-AEM, XPS and ISS were used to characterize phase and surface architectures and their changes after calcination and catalytic reaction. Before calcination, antimony was present as pure oxide or hydroxide, partly as particles and partly as an incomplete monolayer on the surface of Fe2(MoO4)3. After calcination at 400°C, antimony got detached from the Fe2(MoO4)3 surface and aggregated very intensively, partly as Sb2O4 and partly, through reaction with the iron molybdate, as a mixture of distorted FeSbO4 and MoO3. After reaction or calcination at 500°C, more distorted FeSbO4 and MoO3 are formed, separated from Fe2(MoO4)3. Selective oxidation of isobutene to methacrolein was carried out on the calcined material. Impregnated catalysts show considerably improved catalytic performances compared to the pure Fe2(MoO4)3 phase or mechanical mixtures of it with α-Sb2O4. The catalytic performances are explained by several catalytic cooperations via spillover oxygen. These cooperative effects involve all the oxide phases present in the material having worked as catalyst: Fe2(MoO4)3 (pure or possibly contaminated by small amounts of antimony oxide), FeSbO4, MoO3 and SbyOx.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1027287528394
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of Sanchez-Lacombe and SAFT model in predicting solubility of polyethylene in high-pressure fluids (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 1805-1818 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Sanchez-Lacombe and SAFT (statistical associating fluid theory) models are used to describe phase behavior of polyethylene solutions (Mw = 2,150, 16,400, 108,000, and 420,000, and MwMn = 1.14, 1.16, 1.32, and 2.66, respectively) in n-pentane and in n-butane at high pressures. In order to test the predictive capability of the two models, all the predictions were conducted without any adjustment of the binary interaction parameter. Even though both models correctly predict the general trends of the phase envelopes and the LCST (lower critical solution temperature) nature of the systems, SAFT gives predictions that are much closer to the experimental data than the Sanchez-Lacombe model. © 1995 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070551311
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  • 6
    Electronic Resource
    Electronic Resource
    High-pressure phase behavior in polyethylene/n-butane binary and polyethylene/n-butane/CO2 ternary systems (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 1179-1190 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Solubility of polyethylene molecular weight standards (Mw = 2150, 16,400, 108,000, and 420,000 and Mw/Mn = 1.14, 1.16, 1.32, and 2.66, respectively) has been studied in near- and supercritical n-butane and n-butane/CO2 mixtures at pressures up to 70 MPa. For each polyethylene/solvent system at selected compositions, demixing pressures have been determined using a high-pressure variable-volume view-cell at temperatures up to 200°C. Solutions in pure n-butane are found to display LCST (lower critical solution temperature)-type behavior. The behavior of the solutions in n-butane/CO2 mixtures are observed to change from the LCST to the UCST (upper critical solution temperature) with increasing CO2 content in the binary solvent. Sanchez-Lacombe theory has been used to model these systems. The predictions correctly describe the nature of the phase diagrams for both binary and ternary systems and the calculations are in reasonable agreement with experimental data. © 1994 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530905
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  • 7
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    Noncanonical auxin signaling regulates cell division pattern during lateral root development (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-09-30
    Description: In both plants and animals, multiple cellular processes must be orchestrated to ensure proper organogenesis. The cell division patterns control the shape of growing organs, yet how they are precisely determined and coordinated is poorly understood. In plants, the distribution of the phytohormone auxin is tightly linked to organogenesis, including lateral root (LR) development. Nevertheless, how auxin regulates cell division pattern during lateral root development remains elusive. Here, we report that auxin activates Mitogen-Activated Protein Kinase (MAPK) signaling via transmembrane kinases (TMKs) to control cell division pattern during lateral root development. Both TMK1/4 and MKK4/5-MPK3/6 pathways are required to properly orient cell divisions, which ultimately determine lateral root development in response to auxin. We show that TMKs directly and specifically interact with and phosphorylate MKK4/5, which is required for auxin to activate MKK4/5-MPK3/6 signaling. Our data suggest that TMK-mediated noncanonical auxin signaling is required to regulate cell division pattern and connect auxin signaling to MAPK signaling, which are both essential for plant development.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    TOR and RPS6 transmit light signals to enhance protein translation in deetiolating Arabidopsis seedlings (2018)
    National Academy of Sciences
    Details
    Publication Date: 2018-11-27
    Description: Deetiolation is an essential developmental process transforming young plant seedlings into the vegetative phase with photosynthetic activities. Light signals initiate this important developmental process by triggering massive reprogramming of the transcriptome and translatome. Compared with the wealth of knowledge of transcriptional regulation, the molecular mechanism underlying this light-triggered translational enhancement remains unclear. Here we show that light-enhanced translation is orchestrated by a light perception and signaling pathway composed of photoreceptors, CONSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1), the phytohormone auxin, target of rapamycin (TOR), and ribosomal protein S6 (RPS6). In deetiolating Arabidopsis seedlings, photoreceptors, including phytochrome A and cryptochromes, perceive far-red and blue light to inactivate the negative regulator COP1, which leads to activation of the auxin pathway for TOR-dependent phosphorylation of RPS6. Arabidopsis mutants defective in TOR, RPS6A, or RPS6B exhibited delayed cotyledon opening, a characteristic of the deetiolating process to ensure timely vegetative development of a young seedling. This study provides a mechanistic view of light-triggered translational enhancement in deetiolating Arabidopsis.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Metabolite-mediated TOR signaling regulates the circadian clock inArabidopsis (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-12-02
    Description: Circadian clocks usually run with a period close to 24 h, but are also plastic and can be entrained by external environmental conditions and internal physiological cues. Two key nutrient metabolites, glucose and vitamin B3 (nicotinamide), can influence the circadian period in both mammals and plants; however, the underlying molecular mechanism is still largely unclear. We reveal that the target of rapamycin (TOR) kinase, a conserved central growth regulator, is essential for glucose- and nicotinamide-mediated control of the circadian period inArabidopsis. Nicotinamide affects the cytosolic adenosine triphosphate concentration, and blocks the effect of glucose-TOR energy signaling on period length adjustment, meristem activation, and root growth. Together, our results uncover a missing link between cellular metabolites, energy status, and circadian period adjustment, and identify TOR kinase as an essential energy sensor to coordinate circadian clock and plant growth.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Abnormal glycogen storage in tuberous sclerosis complex caused by impairment of mTORC1-dependent and -independent signaling pathways (2019)
    National Academy of Sciences
    Details
    Publication Date: 2019-02-06
    Description: Tuberous sclerosis complex (TSC) is an autosomal dominant syndrome that causes tumor formation in multiple organs. TSC is caused by inactivating mutations in the genes encoding TSC1/2, negative regulators of the mammalian target of rapamycin complex 1 (mTORC1). Diminished TSC function is associated with excess glycogen storage, but the causative mechanism is unknown. By studying human and mouse cells with defective or absent TSC2, we show that complete loss of TSC2 causes an increase in glycogen synthesis through mTORC1 hyperactivation and subsequent inactivation of glycogen synthase kinase 3β (GSK3β), a negative regulator of glycogen synthesis. Specific TSC2 pathogenic mutations, however, result in elevated glycogen levels with no changes in mTORC1 or GSK3β activities. We identify mTORC1-independent lysosomal depletion and impairment of autophagy as the driving causes underlying abnormal glycogen storage in TSC irrespective of the underlying mutation. The defective autophagic degradation of glycogen is associated with abnormal ubiquitination and degradation of essential proteins of the autophagy-lysosome pathway, such as LC3 and lysosomal associated membrane protein 1 and 2 (LAMP1/2) and is restored by the combined use of mTORC1 and Akt pharmacological inhibitors. In complementation to current models that place mTORC1 as the central therapeutic target for TSC pathogenesis, our findings identify mTORC1-independent pathways that are dysregulated in TSC and that should therefore be taken into account in the development of a therapeutic treatment.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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