Uniform energy decay for wave equations with unbounded damping coefficients

We consider the Cauchy problem for wave equations with unbounded damping coefficients in the whole space. For a general class of unbounded damping coefficients, we derive uniform total energy decay estimates together with a unique existence result of a weak solution. In this case we never impose strong assumptions such as compactness of the support of the initial data. This means that we never rely on the finite propagation speed property of the solution, and we try to deal with an essential unbounded coefficient case.Comment: 15 page

On the pairing of Antarctic ureilites with refernce to their parent body

In spite of their apparent igneous textures, ureilites preserve significant records of primitive nature including oxygen isotope anomaly and high planetary-type noble gas contents in the carbonaceous matrices. Mineralogical studies of new Antarctic ureilites revealed that pairing of the small ureilite specimens may be only minor (two out of twenty-two) in comparison with the polymict eucrites. However, we noticed two groupings, which are almost paired but are distinct in pyroxene assemblages and reduction textures. The magnesian and calcic groups have been recognized only in the Antarctic collections. The individual specimens within the group may have evolved in the vicinity within a parent body. A model in conformity with this evolution has been proposed in the context of the ureilite-carbonaceous chondrite connection. However, the carbon-containing chondrite-like materials do not imply the actual chemistry of the known chondrites, because the preferential sedimentation of mafic silicates in the solar nebula may produce source materials much closer to ureilites

Early expression of Ig μ chain from a transgene significantly reduces the duration of the pro-B stage but does not affect the small pre-B stage

During B cell development, V-J rearrangements at the Ig heavy μ chain (IgH μ chain) locus occur in early cycling precursors (pro-B stage). Subsequently, rearrangements at the Ig light (IgL) chain locus occur in late resting precursors (small pre-B stage). To study the effects of μ chain expression on the rate of B cell development, purified hematopoletic stem cells (HSC) bearing a μ chain transgene or wild-type HSC were transferred Into Immunodeficlent RAG-2-/-mice and B cell development was followed over time. In addition, cycling B cell precursors were pulse-labeled by the Injection of BrdU into transgenlc and wild-type mice, and the production of BrdU-labeled k+ and λ+ B cells was followed over time. These experiments suggested that early expression of the μ chain from the transgene significantly shortened the duration of the pro-B stage and Immediately drove the precursors to differentiate into small pre-B cells. By contrast, the presence of the transgene did not affect the small pre-B stage, where IgL rearrangements occur. Thus, k and λ rearrangements occurred only after the arrest of cell cycling as previously shown in wild-type mice, even when the μ chain is artificially expressed earlier in B cell developmen

Mineralogical study of some Antarctic monomict eucrites including Yamato-74356: A unique rock containing recrystallized clastic matrix

We studied the thermal and impact history of four Yamato Antarctic monomict eucrites, Yamato (Y)-74356,Y-791186,Y-792510,and Y-82037,by mineralogical techniques. Although the mineral chemistry of Y-74356 is typical of monomict eucrites, it contains a recrystallized clastic matrix similar to that of some lunar granulitic breccias. Y-74356 experienced shock brecciation during a major thermal event. In contrast, Y-791186 and Y-792510 have pyroxenes of the highest metamorphic degree but the clastic matrices are weakly recrystallized, i. e., these two rocks were not extensively metamorphosed after breccia assembly. This indicates that the process that caused brecciation is distinct from the major thermal event. Y-82037 is a coarse-grained, unbrecciated ordinary eucrite, indicating that it was not affected by the brecciation event, except for the presence of a granoblastic portion in part of the pyroxene crystals. We deduce that the thermal metamorphism that formed ordinary eucrites took place on a longer time scale and at a lower temperature than that which formed some lunar granulitic breccias. The precursors of these ordinary eucrites have suffered from smaller scale brecciation events than those of the lunar granulitic breccias (metamorphic polymict breccias). It is unlikely that there were comparably large cratering events on the small HED parent body to cause the strong thermal metamorphism. The thermal events may have taken place at a very early stage of the evolution of the primary crust of the HED parent body

Mineralogy of five new Antarctic ureilites, LEW86216, LEW85328, Y-791839, Y-75154, Y-8448, and the origin of their chemical variations of pyroxene

Mineralogical studies of mafic silicates in heavily shocked ureilites, LEW86216,Y-75154,Y-791839,and moderately shocked ureilite LEW85328 were performed to reveal the chemical variations and textures produced by shock events on the ureilite parent body. Y-8448 is one of common ureilites, but such ureilites are found in relatively small numbers in Antarctica. Olivines in Y-75154 and LEW86216 show granoblastic textures and the carbonaceous veins are disrupted. Their pyroxenes show chemical variations toward enstatite. They are among the most heavily shocked ureilites. Grain rims of Y-791839 and LEW85328 show chemical variations due to shock. The chemical trends of all these heavily shocked ureilites cover the entire range of known individual ureilites. Shock effects of these ureilites are interpreted to have been produced during the break-up of their parent body. Their chemical variations may be applied to study of the chemical differentiation by the planetesimal-scale collision in the earliest stage of ureilite formation

Mineralogical study of some brecciated Antarctic eucrites

In order to obtain better understanding of the entire range of Antarctic brecciated eucrites and impact and thermal history of the HED-parent body, we studied brecciated Antarctic eucrites : Y-82202,Y-82210,Y-793548,and Y-793570 mineralogically and petrographically. Y-793548,Y-82210,and Y-793570 are nearly monomict breccias with clasts components of rapidly cooled materials and minor slowly cooled pyroxenes (e. g., Juvinastype). Y-82202 is a monomict breccia penetrated by glassy shock melt veins. We suggest that the polished thin sections of the five eucrites presently available belong to a single suite which contains mostly quickly cooled varieties of eucrites similar to those in Pasamonte or in the Y-74159-type polymict eucrites, but more slowly cooled varieties such as ordinary eucrites or cumulate eucrites are scarce in these sections. On the basis of geological setting of HED parent body, we envision that these eucrites may have been located in the shallow ejecta blanket of the HED-parent body, judging from the high mixing ratio of unequilibrated clasts and low degree of equilibration of pyroxene