559 research outputs found
Operating manual for the RRL 8 channel data logger
A data collection device which takes measurements from external sensors at user specified time intervals is described. Three sensor ports are dedicated to temperature, air pressure, and dew point. Five general purpose sensor ports are provided. The user specifies when the measurements are recorded as well as when the information is read or stored in a minicomputer or a paper tape
The role and regulation of blebs in cell migration.
Blebs are cellular protrusions that have been shown to be instrumental for cell migration in development and disease. Bleb expansion is driven by hydrostatic pressure generated in the cytoplasm by the contractile actomyosin cortex. The mechanisms of bleb formation thus fundamentally differ from the actin polymerization-based mechanisms responsible for lamellipodia expansion. In this review, we summarize recent findings relevant for the mechanics of bleb formation and the underlying molecular pathways. We then review the processes involved in determining the type of protrusion formed by migrating cells, in particular in vivo, in the context of embryonic development. Finally, we discuss how cells utilize blebs for their forward movement in the presence or absence of strong substrate attachment
Rank Maximal Matchings -- Structure and Algorithms
Let G = (A U P, E) be a bipartite graph where A denotes a set of agents, P
denotes a set of posts and ranks on the edges denote preferences of the agents
over posts. A matching M in G is rank-maximal if it matches the maximum number
of applicants to their top-rank post, subject to this, the maximum number of
applicants to their second rank post and so on.
In this paper, we develop a switching graph characterization of rank-maximal
matchings, which is a useful tool that encodes all rank-maximal matchings in an
instance. The characterization leads to simple and efficient algorithms for
several interesting problems. In particular, we give an efficient algorithm to
compute the set of rank-maximal pairs in an instance. We show that the problem
of counting the number of rank-maximal matchings is #P-Complete and also give
an FPRAS for the problem. Finally, we consider the problem of deciding whether
a rank-maximal matching is popular among all the rank-maximal matchings in a
given instance, and give an efficient algorithm for the problem
Dielectric spectroscopy studies of 4-cyano-3-fluorophenyl 4-butylbenzoate liquid crystal at high pressure
For 4-cyano-3- uorophenyl 4-butylbenzoate, nematic glassformer at ambient pressure, dielectric relaxation
studies were performed under elevated pressure. In the isobaric experiment, on cooling the nematic phase two
superarrhenius -relaxations, ascribed to the reorientations of molecules around short axes and precession of long molecular axes were found and the Arrhenius -relaxation related to intramolecular motions. Complexity of dynamics at elevated and ambient pressure is similar. Shift towards lower frequencies was found for both-relaxations
Unexpected Crossover in the kinetics of mutarotation in the supercooled region : the role of H-bonds
Intra- and intermolecular studies on the molten L-sorbose have been carried out at variable temperature
conditions to determine the crosover temperature (Tc). In addition, isothermal time-dependent
FTIR and Raman measurements were performed to probe the pace of mutarotation and activation
energy of this reaction in the studied saccharide, which varied from 53–62 kJ/mol up to 177–192 kJ/mol
below and above Tc, respectively. To explain the change in activation barrier for the mutarotation a
complementary analysis using difference FTIR spectra collected around Tc = 365 K in the hydroxyl region
has been done. It was found that the alteration of kinetic parameters and molecular dynamics around Tc
are strictly related to the variation in the strength of H-bonds which above Tc are significantly weaken,
increasing the freedom of rotation of functional groups and movement of individual molecules. That
phenomenon most likely affects the proton transfer, underlying molecular mechanism of mutarotation,
which may lead to the significant increase in activation barrier. The new insight into a molecular aspect
of the mutarotation around Tc has created an opportunity to better understanding the relationship
between physics of condensed matter and the potential role of H-bonds dynamics on the progress of
the chemical reaction in highly viscous systems
Solid-state characterization of novel active pharmaceutical ingredients: Cocrystal of a salbutamol hemiadipate salt with adipic acid (2:1:1) and salbutamol hemisuccinate salt.
The production of salt or cocrystalline forms is a common approach to alter the physicochemical properties of pharmaceutical compounds. The goal of this work was to evaluate the impact of anion choice (succinate, adipate, and sulfate) on the physicochemical characteristics of salbutamol forms. Novel crystals of salbutamol were produced by solvent evaporation: a cocrystal of salbutamol hemiadipate with adipic acid (salbutamol adipate, SA), salbutamol hemisuccinate tetramethanolate (SSU.MeOH), and its desolvated form (SSU). The crystalline materials obtained were characterized using thermal, X-ray, nuclear magnetic resonance, Fourier transform infrared spectroscopy, dynamic vapor sorption (DVS), and elemental analysis. The crystal forms of SA and SSU.MeOH were determined to be triclinic, (Pī), and monoclinic, (P21/n), respectively. DVS analysis confirmed that SSU and SA do not undergo hydration under increased relative humidity. Both thermal and elemental analyses confirmed the stoichiometry of the salt forms. The aqueous solubilities of SA and SSU were measured to be 82 ± 2 mg/mL (pH 4.5 ± 0.1) and 334 ± 13 mg/mL (pH 6.6 ± 0.1), respectively. Measured values corresponded well with the calculated pH solubility profiles. The intrinsic dissolution rate of cocrystallized SA was approximately four times lower than that of SSU, suggesting its use as an alternative to more rapidly dissolving salbutamol sulfate
Impact of alternative solid state forms and specific surface area of high-dose, hydrophilic active pharmaceutical ingredients on tabletability
YesIn order to investigate the effect of using different
solid state forms and specific surface area (TBET) of active
pharmaceutical ingredients on tabletability and dissolution
performance, the mono- and dihydrated crystalline forms of
chlorothiazide sodium and chlorothiazide potassium (CTZK)
salts were compared to alternative anhydrous and amorphous
forms, as well as to amorphous microparticles of chlorothiazide
sodium and potassium which were produced by spray drying and
had a large specific surface area. The tablet hardness and tensile
strength, porosity, and specific surface area of single-component,
convex tablets prepared at different compression pressures were characterized. Results confirmed the complexity of the
compressibility mechanisms. In general it may be concluded that factors such as solid-state form (crystalline vs amorphous), type
of hydration (presence of interstitial molecules of water, dehydrates), or specific surface area of the material have a direct impact
on the tabletability of the powder. It was observed that, for powders of the same solid state form, those with a larger specific
surface area compacted well, and better than powders of a lower surface area, even at relatively low compression pressures.
Compacts prepared at lower compression pressures from high surface area porous microparticles presented the shortest times to
dissolve, when compared with compacts made of equivalent materials, which had to be compressed at higher compression
pressures in order to obtain satisfactory compacts. Therefore, materials composed of nanoparticulate microparticles (NPMPs)
may be considered as suitable for direct compaction and possibly for inclusion in tablet formulations as bulking agents, APIs,
carriers, or binders due to their good compactibility performanceSolid State Pharmaceutical Cluster (SSPC), supported by Science Foundation Ireland under Grant No. 07/SRC/B1158
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