Hall Effect in Liquid Copper Alloys

Hall coefficients of liquid copper alloys Cu-Bi, Cu-Sb, Cu-Sn and Cu-In have been measured by means of the double-alternating current method in a wide temperature range from 500° to 950℃. No temperature dependence of the Hall coefficient is observed in the liquid state of these alloys. The observed composition dependence of the Hall coefficient for the liquid Cu-Bi alloy is in good agreement with that calculated under the assumption of random mixing of Cu^ and Bi^ ions and of free electron approximation. In the other copper alloys, however, deviations from the free electron values R_0 calculated under the above simple situation are observed. It is considered that some of the constitutent atoms are randomly distributed and others are associated into clusters consisting of several atoms. Such a cluster is referred to as a pseudo-molecule. A theoretical formula for the Hall coefficients of these liquid alloys is derived as a function of the quantities n_R/N, 2p and αΩ_0 where n_R/N is the concentration of the pseudo-molecules, 2p is the number of localized electrons contributing to the bonding of the pseudo-molecule andαΩ_0 an effective volume of pseudo-molecule seen by conduction electrons. Using experimental values of these parameters obtained from the observation of the heat of mixing, magnetic susceptibility and the electrical resistivity, composition dependence of the Hall coefficients of the liquid Cu-In and Cu-Sn alloys are calculated in good agreement with the observed ones. The temperature dependence of the Hall coefficients estimated from the above formula is found too small to be observed with the present technique of experiment

Reconstruction of ancestral brains: Exploring the evolutionary process of encephalization in amniotes

AbstractThere is huge divergence in the size and complexity of vertebrate brains. Notably, mammals and birds have bigger brains than other vertebrates, largely because these animal groups established larger dorsal telencephali. Fossil evidence suggests that this anatomical trait could have evolved independently. However, recent comparative developmental analyses demonstrate surprising commonalities in neuronal subtypes among species, although this interpretation is highly controversial. In this review, we introduce intriguing evidence regarding brain evolution collected from recent studies in paleontology and developmental biology, and we discuss possible evolutionary changes in the cortical developmental programs that led to the encephalization and structural complexity of amniote brains. New research concepts and approaches will shed light on the origin and evolutionary processes of amniote brains, particularly the mammalian cerebral cortex

Two different classes of co-occurring motif pairs found by a novel visualization method in human promoter regions

<p>Abstract</p> <p>Background</p> <p>It is essential in modern biology to understand how transcriptional regulatory regions are composed of <it>cis</it>-elements, yet we have limited knowledge of, for example, the combinational uses of these elements and their positional distribution.</p> <p>Results</p> <p>We predicted the positions of 228 known binding motifs for transcription factors in phylogenetically conserved regions within -2000 and +1000 bp of transcriptional start sites (TSSs) of human genes and visualized their correlated non-overlapping occurrences. In the 8,454 significantly correlated motif pairs, two major classes were observed: 248 pairs in Class 1 were mainly found around TSSs, whereas 4,020 Class 2 pairs appear at rather arbitrary distances from TSSs. These classes are distinct in a number of aspects. First, the positional distribution of the Class 1 constituent motifs shows a single peak near the TSSs, whereas Class 2 motifs show a relatively broad distribution. Second, genes that harbor the Class 1 pairs are more likely to be CpG-rich and to be expressed ubiquitously than those that harbor Class 2 pairs. Third, the 'hub' motifs, which are used in many different motif pairs, are different between the two classes. In addition, many of the transcription factors that correspond to the Class 2 hub motifs contain domains rich in specific amino acids; these domains may form disordered regions important for protein-protein interaction.</p> <p>Conclusion</p> <p>There exist at least two classes of motif pairs with respect to TSSs in human promoters, possibly reflecting compositional differences between promoters and enhancers. We anticipate that our visualization method may be useful for the further characterisation of promoters.</p

On the Anomalous Physical Properties of Liquid Copper Alloys

Magnetic susceptibilities and electrical resistivities of the liquid copper alloys, Cu-Bi, Cu-Sn and Cu-In have been measured as functions of chemical compositions at temperatures in the neighbourhood of 1000℃. In the liquid Cu-Bi alloy, observed magnetic susceptibility and electrical resistivity are well explained in terms of a model which assumes random distribution of Cu and Bi ions in an free electron gas atmosphere. In the liquid Cu-Sn and Cu-In alloys, anomalous behaviours are observed in their magnetic susceptibility and electrical resistivity. It is shown that the observed deep valleys of diamagnetism in the magnetic susceptibility curves of both liquid alloys correspond to the peaks in the curves of the heat of mixing for the respective alloys observed in our previous report. The observed values of magnetic susceptibility are compared with theoretical curves calculated by taking account of a contribution from n_R pseudo-molecules which are formed by association of Cu ions with Sn or In ion. It is found that about two electrons are localized in a pseudo-molecule for both liquid alloys near 1100℃ and that the observed deep diamagnetism originates from the existence of pseudo-molecules. Electrical resistivities for both kinds of liquid alloys are given as the sum of contributions from scattering of conduction electrons by randomly distributed free ions and by pseudo-molecules. The contribution ρ_1 caused by the former mechanism can be estimated in terms of a hard sphere model for the Ashcroft potential, and the latter contribution ρ_2 can be assumed to be in proportion with the distribution function n_R of the pseudo-molecule in the liquid alloy on the bases of its flexible structure. For both kinds of alloys such a proportional relationship is regarded as a reasonable assumption because the n_R curve behaves similarly to that of ρ_2=ρ-ρ_1 versus alloying compositions, where ρ is the observed total resistivity

Structural basis for rifamycin resistance of bacterial RNA polymerase by the three most clinically important RpoB mutations found in Mycobacterium tuberculosis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136512/1/mmi13606.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136512/2/mmi13606_am.pd

The Pathogenic Factors from Oral Streptococci for Systemic Diseases

The oral cavity is suggested as the reservoir of bacterial infection, and the oral and pharyngeal biofilms formed by oral bacterial flora, which is comprised of over 700 microbial species, have been found to be associated with systemic conditions. Almost all oral microorganisms are non-pathogenic opportunistic commensals to maintain oral health condition and defend against pathogenic microorganisms. However, oral Streptococci, the first microorganisms to colonize oral surfaces and the dominant microorganisms in the human mouth, has recently gained attention as the pathogens of various systemic diseases, such as infective endocarditis, purulent infections, brain hemorrhage, intestinal inflammation, and autoimmune diseases, as well as bacteremia. As pathogenic factors from oral Streptococci, extracellular polymeric substances, toxins, proteins and nucleic acids as well as vesicles, which secrete these components outside of bacterial cells in biofilm, have been reported. Therefore, it is necessary to consider that the relevance of these pathogenic factors to systemic diseases and also vaccine candidates to protect infectious diseases caused by Streptococci. This review article focuses on the mechanistic links among pathogenic factors from oral Streptococci, inflammation, and systemic diseases to provide the current understanding of oral biofilm infections based on biofilm and widespread systemic diseases

A SCINTIGRAPHIC STUDY OF MASS PERISTALSIS IN HUMAN COLON

Although many attempts have been made to study human colonic motility, the colonic transit is still poorly understood. Both spontaneous and neostigmine-induced peristalsis of the colon were studied with scintigraphy. A polythene tube was inserted into the cecum through a colonofiberscope. 37 MBq of ⁹⁹ᵐTc-DTPA and 75 ml of saline were instilled and dynamic scan was begun. Eight healthy volunteers were examined by the method above mentioned. The sampling time was set at fifteen seconds in six persons and three seconds in the rest. 0.5 mg of neostigmine was injected intravenously to stimulate the paristalsis when no peristalsis occurred within thirty minutes after the study was begun. Dynamic scanning was performed for sixty to ninety minutes. This scintigraphic study revealed that the spontaneous and induced peristalsis were almost identical on colonogram. ⁹⁹ᵐTc-DTPA solution was propelled from the cecum and ascending colon to the sigmoid colon or the rectum for about fifteen seconds during mass peristalsis. Colonogram (time-activity curve) enables us to analyze mass peristalsis easily and more objectively than colonoscintigram. The spontaneous and neostigmine-induced peristalsis seemed to be almost identical in all but one of eight subjects