617 research outputs found
Interannual differences in the regressions of the polar caps of Mars
Analyses of the behavior of the Martian polar caps in the recent spacecraft and ground based observations seem to reveal the existence of year to year variations on their regressions. In order to investigate the interannual differences in the regressions of the polar caps, the earlier data by Fischbacher et al., were reexamined, which were based on the measurements of the large number of high quality photographic plates and films collected from 1905 to 1965 at the Lowell Observatory. The results are reported and discussed
Protein Kinase C Activity in Mouse Eggs Regulates Gamete Membrane Interaction
Every mammalian life develops from one cell after fertilization of an egg by the sperm. The molecular pathways governing this event are still poorly understood. Numerous reports indicate that mammalian eggs highly express various protein kinase C (PKC) isoforms. Accordingly, we hypothesize that PKC activity in the egg plays an important role during egg-sperm membrane binding and fusion. In this study, we tested our hypothesis in mouse gametes using two types of PKC inhibitors (calphostin c and staurosporine) and the typical PKC activator, phorbol ester 12-tetradecanoylphorbol-13 acetate (PMA). After treatment with the individual drug, eggs were inseminated with sperm. The sperm binding number (SB) and fusion rate (FR) were scored using light and fluorescence microscopy. By applying the Student’s t-test, we confirmed that the FR and SB were significantly decreased after PKC activator or inhibitors treatments. All treatment groups, 1 μM calphostin c, 1 μM staurosporine, or 1 nM PMA showed the significant reduction of FR and SB. Further analysis indicated that the inhibition effects of calphostin c and PMA were dose- and time- dependent. Moreover, under scanning electron microscopy (SEM), we observed that the number and shape of microvilli on the PMA-treated eggs, but not on the calphostin c-treated eggs, was severely changed. Taken together, these results suggest that egg PKC activity plays an important role in the signaling regulation of sperm-egg membrane binding and fusion during fertilization
月の海の進化と陸の成長
京都大学0048新制・論文博士理学博士乙第2980号論理博第523号新制||理||226(附属図書館)4742UT51-61-I212(主査)教授 宮本 正太郎, 教授 川口 市郎, 教授 加藤 正二学位規則第5条第2項該当Kyoto UniversityDA
Felling by a Five-Legged Walking Machine
A 1/11 scale model of a walking machine with five legs was constructed, and its operation as a feller-buncher investigated. As slopes steepen, the machine when positioned straight up the slope becomes more efficient than when positioned parallel to the contour lines, because the downward operational range of the machine decreases with increased slopes. In the experiments, the ground pressure of the legs on the end opposite the boom was nearly zero when the boom holding felled trees was positioned at the side of the body and extended farthest from the body. However, further investigations (including such factors as ground disturbance, the operation of the machine, the degrees and the length of slope, and the fuel consumption) of felling operations are needed. Feller-bunching tends to be less efficient as tree density increases assuming that felling time per tree remains constant as tree diameter changes. To obtain greater productivity with the machine as a feller-buncher, it is essential to achieve faster walking-time and shorter felling-time per tree
Hierarchization of the decision-making process according to the economic sector
The objective is to delineate a hierarchical model of decisions and respective management indicators. In an everyday universe of events that occur, if considers a purpose of the organization can face a hierarchy of decisions, from major strategic to minor ones. Such a finding, if delineated as a model, it can be useful in the study of decision-making process. For this analysis was adopted a multiple case study method applied in commercial, industrial and service organization. Afterwards was maximized with a differentiated sample of managers selection to be interviewed according to the organizational pyramid hierarchical rank as structured bases; meetings with key opinion groups; available preliminary data collection directly from the websites. As a result, a hierarchical decision model was obtained, differentiated according to the acting economic segment
Non-Thermal Continuum toward SGRB2(N-LMH)
An analysis of continuum antenna temperatures observed in the Green Bank
Telescope (GBT) spectrometer bandpasses is presented for observations toward
SgrB2(N-LMH). Since 2004, we have identified four new prebiotic molecules
toward this source by means of rotational transitions between low energy
levels; concurrently, we have observed significant continuum in the GBT
spectrometer bandpasses centered at 85 different frequencies in the range of 1
to 48 GHz. The continuum heavily influences the molecular spectral features
since we have observed far more absorption lines than emission lines for each
of these new molecular species. Hence, it is important to understand the
nature, distribution, and intensity of the underlying continuum in the GBT
bandpasses for the purposes of radiative transfer, i.e. the means by which
reliable molecular abundances are estimated. We find that the GBT spectrometer
bandpass continuum is consistent with optically-thin, non thermal (synchrotron)
emission with a flux density spectral index of -0.7 and a Gaussian source size
of ~143" at 1 GHz that decreases with increasing frequency as nu^(-0.52). Some
support for this model is provided by high frequency Very Large Array (VLA)
observations of SgrB2.Comment: Accepted for Publication in the Astrophysical Journal Letter
Ribosome Rescue and Translation Termination at Non-Standard Stop Codons by ICT1 in Mammalian Mitochondria
Release factors (RFs) govern the termination phase of protein synthesis. Human
mitochondria harbor four different members of the class 1 RF family:
RF1Lmt/mtRF1a, RF1mt, C12orf65 and ICT1. The homolog of the essential ICT1
factor is widely distributed in bacteria and organelles and has the peculiar
feature in human mitochondria to be part of the ribosome as a ribosomal
protein of the large subunit. The factor has been suggested to rescue stalled
ribosomes in a codon-independent manner. The mechanism of action of this
factor was obscure and is addressed here. Using a homologous mitochondria
system of purified components, we demonstrate that the integrated ICT1 has no
rescue activity. Rather, purified ICT1 binds stoichiometrically to
mitochondrial ribosomes in addition to the integrated copy and functions as a
general rescue factor, i.e. it releases the polypeptide from the peptidyl tRNA
from ribosomes stalled at the end or in the middle of an mRNA or even from
non-programmed ribosomes. The data suggest that the unusual termination at a
sense codon (AGA/G) of the oxidative-phosphorylation enzymes CO1 and ND6 is
also performed by ICT1 challenging a previous model, according to which
RF1Lmt/mtRF1a is responsible for the translation termination at non-standard
stop codons. We also demonstrate by mutational analyses that the unique
insertion sequence present in the N-terminal domain of ICT1 is essential for
peptide release rather than for ribosome binding. The function of RF1mt,
another member of the class1 RFs in mammalian mitochondria, was also examined
and is discussed
Learn from history : Lessons from early modern Japanese physics experiment textbooks
The aim of our study is to explore the early history of the education of physics experiments in the Meiji era of Japan (1868 - 1912). In this paper, we examine three Japanese physics experiment textbooks which were published during 1880s. One characteristic feature is that the most of the experiments could be performed using simple handmade apparatuses. We consider what can be learned from the ingenuity of physics education pioneers of the late 19th century
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