scholarly journals Accelerated sliding of pollen tube organelles along Characeae actin bundles regulated by Ca2+.

1988 ◽  
Vol 106 (5) ◽  
pp. 1539-1543 ◽  
Author(s):  
T Kohno ◽  
T Shimmen
Keyword(s):  
Heat Treatment ◽  
Pollen Tube ◽  
Cytoplasmic Streaming ◽  
Pollen Tubes ◽  
The Other ◽  
Cell Models ◽  
Organelle Movement ◽  
Actin Bundles ◽  
Other Hand ◽  
Order Of Magnitude

Pollen tubes show active cytoplasmic streaming. We isolated organelles from pollen tubes and tested their ability to slide along actin bundles in characean cell models. Here, we show that sliding of organelles was ATP-dependent and that motility was lost after N-ethylmaleimide or heat treatment of organelles. On the other hand, cytoplasmic streaming in pollen tube was inhibited by either N-ethylmaleimide or heat treatment. These results strongly indicate that cytoplasmic streaming in pollen tubes is supported by the "actomyosin"-ATP system. The velocity of organelle movement along characean actin bundles was much higher than that of the native streaming in pollen tubes. We suggested that pollen tube "myosin" has a capacity to move at a velocity of the same order of magnitude as that of characean myosin. Moreover, the motility was high at Ca2+ concentrations lower than 0.18 microM (pCa 6.8) but was inhibited at concentration higher than 4.5 microM (pCa 5.4). In conclusion, cytoplasmic streaming in pollen tubes is suggested to be regulated by Ca2+ through "myosin" inactivation.

Comparison of the Potency of 8-L-Arginine, 8-D-Arginine and 8-D-Homoarginine Vasopressin Analogs with Substituted Phenylalanine in Position 2

1994 ◽  
Vol 59 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
Miroslava Žertová ◽  
Jiřina Slaninová ◽  
Zdenko Procházka
Keyword(s):  
Amino Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Basic Amino Acid ◽  
The Other ◽  
Side Chain ◽  
Inhibitory Potency ◽  
Phase Synthesis ◽  
Other Hand ◽  
Order Of Magnitude

An analysis of the uterotonic potencies of all analogs having substituted L- or D-tyrosine or -phenylalanine in position 2 and L-arginine, D-arginine or D-homoarginine in position 8 was made. The series of analogs already published was completed by the solid phase synthesis of ten new analogs having L- or D-Phe, L- or D-Phe(2-Et), L- or D-Phe(2,4,6-triMe) or D-Tyr(Me) in position 2 and either L- or D-arginine in position 8. All newly synthesized analogs were found to be uterotonic inhibitors. Deamination increases both the agonistic and antagonistic potency. In the case of phenylalanine analogs the change of configuration from L to D in position 2 enhances the uterotonic inhibition for more than 1 order of magnitude. The L to D change in position 8 enhances the inhibitory potency negligibly. Prolongation of the side chain of the D-basic amino acid in position 8 seems to decrease slightly the inhibitory potency if there is L-substituted amino acid in position 2. On the other hand there is a tendency to the increase of the inhibitory potency if there is D-substituted amino acid in position 2.

Interactions of LO Phonons with Bound Excitons in Homoepitaxial GaN

1997 ◽  
Vol 482 ◽  
Author(s):  
K. P. Koron ◽  
A. Wysmolek ◽  
J. M. Baranowskil ◽  
K. Pakul ◽  
J. P. Bergman ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
The Other ◽  
Direct Influence ◽  
Neutral Donor ◽  
Phonon Replica ◽  
Temperature Range ◽  
Other Hand ◽  
Order Of Magnitude ◽  
Neutral Acceptor

AbstractPhotoluminescence connected with excitons and their phonon replicas in undoped homoepitaxial MOCVD grown GaN layers have been studied in the temperature range 2 - 100 K. It is shown that the coupling between LO phonons and neutral acceptor bound excitons (ABE) is much stronger than the coupling between LO phonons and neutral donor bound excitons (DBE). In spite that emission due the DBE no-phonon is one order of magnitude stronger than the ABE one, the predominant feature of the first LO phonon replica of the excitonic structures is related to the ABE. It is argued that this fact is connected with delocalization of the acceptor wavefunction in the k-space which leads to a higher number of interacting LO phonons in the first replica. On the other hand, the second LO phonon replica of the excitonic structures is predominantly connected with the DBE. In the case of two LO phonons interacting with bound excitons the k - conservation has not so direct influence. In addition, the temperature dependence of LO phonon replicas and their kinetics in ps regime are also reported.

A PDL APPROACH FOR QUALITATIVE VELOCITY

2011 ◽  
Vol 19 (01) ◽  
pp. 11-26 ◽  
Author(s):  
A. BURRIEZA ◽  
E. MUÑOZ-VELASCO ◽  
M. OJEDA-ACIEGO
Keyword(s):  
Programming Languages ◽  
Moving Objects ◽  
Spatial Reasoning ◽  
Axiom System ◽  
Qualitative Reasoning ◽  
The Other ◽  
Other Hand ◽  
Order Of Magnitude ◽  
The One ◽  
Different Levels

We introduce the syntax, semantics, and an axiom system for a PDL-based extension of the logic for order of magnitude qualitative reasoning, developed in order to deal with the concept of qualitative velocity, which together with qualitative distance and orientation, are important notions in order to represent spatial reasoning for moving objects, such as robots. The main advantages of using a PDL-based approach are, on the one hand, all the well-known advantages of using logic in AI, and, on the other hand, the possibility of constructing complex relations from simpler ones, the flexibility for using different levels of granularity, its possible extension by adding other spatial components, and the use of a language close to programming languages.

Effect of Heating Treatment on the Resistivity of Polycrystalline Silicon

2011 ◽  
Vol 675-677 ◽  
pp. 113-116
Author(s):  
Lei Zhang ◽  
Jia Yan Li ◽  
Hao Yang Wang ◽  
Fu Min Xu ◽  
Yi Tan
Keyword(s):  
Heat Treatment ◽  
Polycrystalline Silicon ◽  
Influence Factors ◽  
The Other ◽  
Type Region ◽  
Obvious Change ◽  
Other Hand ◽  
Heating Treatment ◽  
P Type

Effect of heat treatment in atmosphere on the resistivity of polycrystalline silicon has been investigated in this paper. After heat treatment at 1050oC for 10h, there is no obvious change of the resistivity in the N-type region of polycrystalline silicon, which could be contributed to the complicated influence factors, such as more impurities content and defects. On the other hand, an obvious increase of the resistivity was observed in the P-type region which could be contributed the redistribution of Al and B in the Si-SiO2 interface. The resistivity of the P-type region increased from less than 1Ω·cm to several hundreds Ω·cm.

Floral Anatomy and Pollen Tube Growth in the Quandong (Santalum acuminatum (R. Br.) A. DC.)

1982 ◽  
Vol 30 (6) ◽  
pp. 601 ◽  
Author(s):  
M Sedgley
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Floral Anatomy ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
The Other ◽  
Tube Growth ◽  
Scanning Electron

Floral anatomy and pollen tube growth in the quandong were studied using light and scanning electron microscopy. The flowers had four perianth lobes and four stamens whose anthers dehisced by longitudinal slits. The pollen became caught in long unicellular hairs adjacent to the anthers. The central disc secreted nectar through raised stomata. The stigma papilla cells had a cuticle with a rough surface overlying thick PAS-positive walls. The half-inferior ovary normally contained two ovules. The embryo sac extended beyond the ovule at the micropylar end and into the placenta at the chalazal end. Half of the ovaries observed at both anthesis and 4 days following anthesis had no embryo sacs and the other half had one embryo sac. Occasional ovaries had two embryo sacs and some underdeveloped embryo sacs were observed that did not extend beyond the ovule or into the placenta. Pollen tubes had reached the ovary by 1 day following pollination and the stigma was receptive for 8 days following anthesis. Only half of the pistils had pollen tubes in the ovary. Unpollinated flowers had no pollen tube growth in the pistil.

STUDY OF METHYLENE BLUE INTERACTION WITH SYNTHETIC POLYNUCLEOTIDE POLY(rA)-POLY(rU)

2020 ◽  
Vol 54 (2 (252)) ◽  
pp. 112-117
Author(s):  
M.A. Parsadanyan ◽  
M.A. Shahinyan ◽  
A.P. Antonyan
Keyword(s):  
Methylene Blue ◽  
Fluorescence Spectroscopy ◽  
The Other ◽  
Binding Modes ◽  
Other Hand ◽  
Non Linear ◽  
Order Of Magnitude ◽  
Synthetic Polynucleotide ◽  
Specific Ligand

A study of the interaction of methylene blue (MB) with poly(rA)-poly(rU) by the method of fluorescence spectroscopy has been carried out. The data obtained revealed that MB, being a DNA-specific ligand, can bind to double-stranded regions of RNA. In this regard, as in the case of DNA, semi-intercalation was the most preferable mechanism for the binding of this ligand to poly(rA)-poly(rU). On the other hand, non-linear curves of dependence of F0/F on concentration of polynucleotide might result from two binding modes, the second of which was probably of an electrostatic nature. Proceeding from the data obtained, the value of KSV was revealed to be almost an order of magnitude less than for DNA, which may indicate that RNA is a less preferable target for MB.

scholarly journals THE SPECTRAL SEQUENCE OF BLAZARS — STATUS AND PERSPECTIVES

2008 ◽  
Vol 17 (09) ◽  
pp. 1457-1466 ◽  
Author(s):  
L. MARASCHI ◽  
G. GHISELLINI ◽  
F. TAVECCHIO ◽  
L. FOSCHINI ◽  
R. M. SAMBRUNA
Keyword(s):  
Spectral Sequence ◽  
Present Status ◽  
The Other ◽  
Lower Power ◽  
Original Idea ◽  
Other Hand ◽  
New Findings ◽  
Order Of Magnitude ◽  
Γ Rays ◽  
Magnitude Increase

The present status of the blazar spectral sequence is discussed, including new findings about blazars selected with different criteria than the original complete radio-samples. Despite extensive searches of blazars "breaking" the sequence, the original idea proposed 10 years ago still seems to hold. On the other hand, the forthcoming launch of the GLAST satellite will provide a new selection band for blazars and blazar related populations as well as fantastic progress on the spectra and variability behaviour of presently known blazars. The order of magnitude increase in sensitivity of GLAST will allow detection of γ-rays from jets with lower power and/or lower beaming factor, thus sampling a much wider population.

The congruence equation a¯ + b¯ ≡c¯(modp)

2019 ◽  
pp. 1-12
Author(s):  
Tsz Ho Chan
Keyword(s):  
Gauss Sums ◽  
Kloosterman Sums ◽  
The Other ◽  
Number Of Solutions ◽  
Multiplicative Inverse ◽  
Other Hand ◽  
Order Of Magnitude ◽  
Congruence Equation ◽  
First Moment

In this paper, we consider the congruence equation [Formula: see text] with [Formula: see text] where [Formula: see text] denotes the multiplicative inverse of [Formula: see text]. We prove that its number of solutions is asymptotic to [Formula: see text] when [Formula: see text] by estimating a certain average of Kloosterman sums via Gauss sums. On the other hand, when [Formula: see text], the number of solutions has order of magnitude at least [Formula: see text]. It would be interesting to better understand its transition of behavior. By transforming the question slightly, one can relate the problem to a certain first moment of Dirichlet [Formula: see text]-functions at [Formula: see text].

Effect of Sandblasting and Heat Treatment on Biaxial Flexure Strength of the Zirconia/Alumina Nanocomposite

2007 ◽  
Vol 330-332 ◽  
pp. 353-356 ◽  
Author(s):  
Seiji Ban ◽  
Hideo Sato ◽  
Y. Suehiro ◽  
H. Nakanishi ◽  
Masahiro Nawa
Keyword(s):  
Heat Treatment ◽  
Cerium Oxide ◽  
Tetragonal Zirconia ◽  
The Other ◽  
Alumina Powder ◽  
Monoclinic Zro2 ◽  
Flexure Strength ◽  
Other Hand ◽  
Biaxial Flexure

The effect of sandblasting and heat treatment on biaxial flexure strengths of the zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite) was evaluated in comparison to that of yttria stabilized tetragonal zirconia polycrystals (Y-TZP). The disc-shaped specimens of the nanocomposite and Y-TZP were sandblasted with 70)m alumina powder. After sandblasting, half of the specimens were heated at 1000°C for 5 min. The biaxial flexure strengths of Y-TZP were independent on the sandblasting, but decreased with the heat treatment. On the other hand, the biaxial flexure strength of the nanocomposite increased with the sandblasting and significantly decreased with the heat treatment. The content of monoclinic ZrO2 of Y-TZP and the nanocomposite increased with the sandblasting pressure and dramatically decreased with the heat treatment. These results suggest that the stress-induced transformation from tetragonal to monoclinic of the nanocomposite occurs more easily than Y-TZP.

scholarly journals The IAU Nutation Theory and Perspectives of its Change

1995 ◽  
Vol 10 ◽  
pp. 247-248
Author(s):  
D. McCarthy ◽  
V. Dehant
Keyword(s):  
Celestial Mechanics ◽  
Analytical Theory ◽  
The Other ◽  
General Assembly ◽  
Other Hand ◽  
Order Of Magnitude ◽  
Rigid Earth ◽  
The One ◽  
Nutation Series ◽  
Whole Earth

The IAU General Assembly has adopted in 1980 a nutation series, on the one hand, based on rigid Earth’s contributions theorically computed from celestial mechanics, and on the other hand, based on non-rigid Earth’s contributions theoretically computed from Earth deformation equations using geophysical parameters.1.From the previous papers (see Session 1) of this Joint Discussion, we know that there are differences of this adopted theory with respect to the observations of precession and nutations. These differences can reach several mas, which is well above the present accuracy of the observations.2.From previous papers (see Session 2) and from the posters, we also know that there exist new rigid-Earth nutations (Kinoshita-Souchay, Roosbeek, Hartmann) of which the accuracy has increased by one order of magnitude.3.From Session 3 papers, we know that there are some additional geophysical effects that are not yet taken into account in Wahr’s nutation theory adopted in 1980 by the IAU which have a contribution at a level above the present precision of the observations. These additional geophysical aspects can be accounted for either from a semi-analytical theory (like Mathews, Herring, Shapiro and Buffett are doing), or from an integration of deformation equations through the whole Earth (Dehant, Wahr).

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