A review of the works performed at the Institute of Macromolecular Compounds, Russian Academy of Sciences in the field of multiblock copoly(urethane–imide)s, a relatively new subclass of thermally ...stable polymers, is presented. The synthesis of the representative family of copoly(urethane–imide)s different in the chemical structure and ratio of flexible polyester/polyether and rigid urethane–imide blocks is performed. Mixed compounds composed of synthesized copoly(urethane–imide)s and thermoplastic polyimides are obtained. The effect of the chemical structure of the flexible and rigid blocks and their ratio on the glass and melting transitions of the studied polymer systems is investigated. Polymer systems that form stable melts and are suitable for processing to thick-wall products, thermoplastic elastomers, are proposed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To date, the internal limiting membrane (ILM), specifically, the side facing the retina, has never been studied by two parallel, mutually complementary methods. This is an attempt to explain ...favorable results of ILM peeling in various macular pathologies.
By employing scanning (SEM) and transmission electron microscopy (TEM), to identify morphological features of epiretinal samples removed during vitrectomy in patients with lamellar macular hole (LMH) or epiretinal membrane (ERM).
We studied 23 eyes of 23 patients divided into two groups. The first group (13 samples, 11 eyes) consisted of patients with LMH; the second (12 samples, 12 eyes) - with ERM. The surgeries yielded a total of 21 epiretinal samples peeled simultaneously with the ILM and 4 epiretinal samples (2 eyes) peeled in two parts, the second part containing the ILM. One half of the samples was studied by SEM without prior dehydratation, the other - by TEM.
The study revealed a high degree of ultrastructural similarity between the two groups of ILM samples. Judging from SEM findings, two sides of the membrane were clearly identified. Porous coral-like structures (PCS) were discovered on the side facing the retina. TEM in the area of PCS discovered parallel arrangement of multiple Muller cell (MC) bodies and processes separated by wide layers of the intercellular matrix. The vitreal side of all ILM samples was notable for numerous fibroblast-like cells. Many variously shaped petrified structures were found on both sides of the membrane.
During the so called ILM peeling, the surgeon removes a layered structure that includes the basal membrane of MC, cells and fibers attached to its vitreal side, and one more layer comprised by PCS and rather readily torn off from the main massif. The functional significance of this previously unknown structure as well as the effect of its partial removal during surgical manipulations with neurosensory retina in the macular region is yet to be investigated.
Processing datasets on the order of tens of terabytes is an onerous task, faced by production coordinators everywhere. Users solicit data productions and, especially for simulation data, the vast ...amount of parameters (and sometime incomplete requests) point at the need for a tracking, control and archiving all requests made so a coordinated handling could be made by the production team. With the advent of grid computing the parallel processing power has increased but traceability has also become increasing problematic due to the heterogeneous nature of Grids. Any one of a number of components may fail invalidating the job or execution flow in various stages of completion and re-submission of a few of the multitude of jobs (keeping the entire dataset production consistency) a difficult and tedious process. From the definition of the workflow to its execution, there is a strong need for validation, tracking, monitoring and reporting of problems. To ease the process of requesting production workflow, STAR has implemented several components addressing the full workflow consistency. A Web based online submission request module, implemented using Drupal's Content Management System API, enforces ahead that all parameters are described in advance in a uniform fashion. Upon submission, all jobs are independently tracked and (sometime experiment-specific) discrepancies are detected and recorded providing detailed information on where/how/when the job failed. Aggregate information on success and failure are also provided in near real-time.
In the process of this work, an oligoimide FT-BAPB-R-BAPB-FT was synthesized, the particles of which consist of numerous lamellas having a semi-crystalline structure. On the DSC thermogram of ...oligoimide powder, two endo peaks were observed at 281.1°C and 306.4°C. A unique WAXS experiment was performed in-situ by heating the reactor oligoimid powder in a heat chamber. There was no significant difference in the X-ray profiles when the sample was heated. It should be noted that the transformation of the crystalline cell does not occur until the sample melts. It was revealed that the degree of crystallinity decreases during heating. We believe that the low-temperature endopeak is associated with the melting of small crystallites and amorphization of the sample. However, a significant increase in crystal size was found to be a result of recrystallization. Thus, the high-temperature endopic corresponds to the melting of larger crystallites.
Over the lifetime of the STAR Experiment, a large investment of workforce time has gone into a variety of QA efforts, including continuous processing of a portion of the data for automated ...calibration and iterative convergence and quality assurance purposes. A rotating workforce coupled with ever-increasing volumes of information to examine led to sometimes inconsistent or incomplete reporting of issues, eventually leading to additional work. The traditional approach of manually screening a data sample was no longer adequate and doomed to eventual failure with planned future growth in data extents. To prevent this collapse we have developed a new system employing user-defined reference histograms, permitting automated comparisons and nagging of issues. Based on the ROOT framework at its core, the front end is a web based service allowing shift personnel to visualize the results, and to set test parameters and thresholds defining success or failure. The versatile and flexible approach allows for a slew of histograms to be configured and grouped into categories (results and thresholds may depend on experimental triggers and data types) ensuring framework evolution with the years of running to come. Historical information is also saved to track changes and allow for rapid convergence of future tuning. Database storage and processing of data are handled outside the web server for security and fault tolerance.
In recent years, the STAR experiment's database demands have grown in accord not only with simple facility growth, but also with a growing physics program. In addition to the accumulated metadata ...from a decade of operations, refinements to detector calibrations force user analysis to access database information post data production. Users may access any year's data at any point in time, causing a near random access of the metadata queried, contrary to time-organized production cycles. Moreover, complex online event selection algorithms created a query scarcity ("sparsity") scenario for offline production further impacting performance. Fundamental changes in our hardware approach were hence necessary to improve query speed. Initial strategic improvements were focused on developing fault-tolerant, load-balanced access to a multi-slave infrastructure. Beyond that, we explored, tested and quantified the benefits of introducing a Tiered storage architecture composed of conventional drives, solid-state disks, and memory-resident databases as well as leveraging the use of smaller database services fitting in memory. The results of our extensive testing in real life usage are presented.
Multiblock (segmented) copoly(urethane–imides) were prepared using as monomers toluene 2,4-diisocyanate-terminated aliphatic polyether and polyester poly(propylene glycol), ...poly(1,6-hexanediol/neopentylene glycol-alt-adipic acid), aromatic diamines 1,4-bis(4'-aminophenoxy)biphenyl sulfone or 4,4'-bis(4''-aminophenoxy)biphenyl in a mixture with 3,5-diaminobenzoic acid, and 1,3-bis(3',4-dicarboxyphenoxy)benzene dianhydride. Each of the polymers contains two structurally different soft polyether/polyester segments and two identical hard imide segments, into one of which the reactive carboxy group is introduced. The covalent cross-linking of the copolymers was performed by the reactions of the carboxy groups with aromatic diisocyanates (toluene 2,4-diisocyanate, biphenylmethane 4,4'-diisocyanate) and 1,2,5,6-diepoxycyclooctane. The cross-linked polymer systems obtained were studied by thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The kind of cross-linking agent influences the properties of cross-linked copoly(urethane–imides). Variation of the mechanical loss tangent tan δ and width of the temperature interval of the transition from glassy to rubber-elastic state in relation to the chemical structure of copoly(urethane–imides) was analyzed. For the polymers under consideration, the maximal tan δ values exceed 0.3, which indicates that these polymers exhibit the damping ability.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Organic-inorganic composites filled with nanoscale graphene and tungsten disulfide particles using thermoelastoplastic multiblock co-poly(urethane-imide)s as polymer matrices were obtained. The ...matrix polymers were the products of the polycondensation of 1,3-bis-(3′,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(aminophenoxy)diphenyl sulfone, and two aliphatic polyesters terminated by 2,4-toluene diisocyanate, namely, polypropylene glycol (M
n
= 2300) and poly(ethylene adipate) (M
n
= 2700). The weight fraction of aromatic segments in samples of co-poly(urethane-imide)s differed by a factor of two. Obtained composites were investigated by TGA, DSC, and DMA methods.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The molecular mobility of poly(4,4'-bis(4-aminophenoxy)biphenyl)imido-1,3-bis(3,3'-4,4'-dicarboxyphenoxy)benzene) films is studied by the thermally stimulated depolarization current (TSDC) technique ...and dielectric spectroscopy. The existence of two dipolar polarization relaxation regions (β and α) related to the local mobility in the glassy state and the cooperative segmental mobility in the rubbery state, respectively, is revealed. The temperature dependences of the relaxation time for the β-process obey the Arrhenius equation; for the α-process, they obey the Vogel–Tammann–Hesse equation. Emergence of the third peak β
I
is related to relaxation of the space homocharge. The molecular mechanisms of all the observed processes are revealed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
New segmented polyurethaneimides containing poly(ethylene glycol adipate) soft segments and bis(urethaneimide) hard segments are synthesized. Copolymers are obtained on the basis of poly(ethylene ...glycol adipate) (
M
n
= 2.5 × 10
3
) terminated with 2,4-toluene diisocyanate, two aromatic dianhydrides, and six aromatic diamines. The structure of the synthesized polymers is studied by IR and NMR spectroscopy. The thermal properties of the copolymers are characterized by TGA and DSC. Effects of hard segment length and substituent position in the diamine fragment on the thermal and mechanical properties of the polyurethaneimides are investigated.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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