Experimental Study on the Aging of Sands

Aging effects in sand, such as increases in cone penetration resistance with time after deposition and/or densification, are known to occur in the field, but the causes of these effects are not fully understood. A laboratory testing program was designed to study mechanisms responsible for aging effects under controlled conditions. The testing program included measurements of the small strain shear modulus, electrical conductivity, pore fluid chemistry, and minicone penetration resistance after different periods of aging. Two different sands were tested, and aging effects were evaluated for different combinations of relative density, temperature, and pore fluid composition. Increases in the small strain shear modulus were observed throughout most of the tests, and chemical analyses suggest that precipitation of carbonate and silica occurred in two tests. Despite these changes, there was no corresponding increase in the minicone penetration resistance with time in any of the tests. It is unlikely that precipitation of carbonate or silica is responsible for aging effects in sands; other possible mechanisms include arching due to dissipation of blast gases and redistribution of stresses through the soil skeleton. An additional possibility is that the boundary conditions imposed by the laboratory tests obscure changes in penetration resistance that would be measured had the volume of sand tested been much larger. The implications of these findings in terms of other published field and laboratory studies are discussed.     

Estimation subject to block censoring

A series system comprises n components arranged in decreasing order of likelihood of failure. The components are grouped into modules and, on system failure, the modules are replaced in sequence until the system is repaired. Thus, it is not known which component has failed, only which module contains the failed component. It is shown how, for a certain class of life-length distributions, prior information on the relative propensities of the components to fail can be incorporated to estimate the parameters of the life-length distributions of the components. The case where each component life-length is exponentially distributed is studied in detail     

Rate-Distortion Coding Simulation for Color Images

We propose a distortion measure for color images, based on a mathematical model of color vision, and supported by subjective image quality evaluations. The visual model is configured after a simplified schematic of the retina's physiology and it transforms the red, green and blue image components into a representation that is consistent with major psychophysical phenomena. The distortion criterion proposed consists of measuring the mean square error in the above representation space. Consistency of the measure with human quality judgment is supported by a subjective ranking experiment, using images distorted in various ways by addition of noise. An optimal coder (in the rate distortion sense) is also simulated, which minimizes the distortion measured as proposed. The resulting image provides a quality standard at the rate distortion bound, against which actual coders can be compared. Finally it is observed that from a statistical point of view, the model's output is a near ideal color image representation for efficient coding.     

Telomerase activity and telomere lengths in various cell lines: changes of telomerase activity can be another method for chemosensitivity evaluation

For the cancer cells which have overcome the second mitotic clock (M2), activated telomerase is essential and used as another marker of immortality. Many trials had been initiated to target telomerase, which is known to be specific to tumors. To determine the best in vitro cell system for testing the efficacy of telomerase inhibitors, we evaluated the telomerase activity of various cancer cell lines and measured their telomere lengths. We also treated some cancer cell lines with adriamycin and measured the changes of telomerase activity. Telomerase activity was evaluated in various cell lines with the TRAP (telomeric repeat amplification protocol) assay. Telomerase activity was calculated and translated into arbitrary units by computer-assisted densitometry with the control of telomerase activity in the 293 control cell line. Also, terminal restriction fragment lengths were measured using Southern blotting. We also measured telomerase activity and telomere lengths in 11 benign breast tumor tissues and 19 paired stomach cancer and normal tissues. Cancer cell lines treated with adriamycin we evaluated for changes of telomerase activity and the cell proliferation by MTT assay and dye exclusion test. Telomerase activity of cell lines was 95.3 24.1 unit with a range of 27.6-129.6 unit, while the telomere lengths of those cell lines were variable from 5.0 to 10.4 kbp with a median of 6 kbp. In 11 cancer cell lines which were not yet firmly established, we could not detect any telomerase activity. Low telomerase activity was detected in only 2 benign tumor tissues of breast with a median telomere length of 8.8 (7-10.5) kbp. Among paired 19 gastric cancer and normal tissues, only 7 cancer tissues showed weak telomerase activity. After adriamycin treatment, telomerase activity in YCC-S-1, YCC-S-3, MCF-7 and MCF-7/ADR was decreased in accordance with the changes of the cell numbers. Telomerase is specific to cancer tissues and is expressed differently from organ to organ. Telomerase activity by TRAP assay could be used as a chemosensitivity assay.     

The association rate constant for heme binding to globin is independent of protein structure

Rate constants for CO-heme binding to 35 different recombinant apomyoglobins and several other apoproteins were measured in an effort to understand the factors governing heme affinity and the velocity of the association reaction. Surprisingly, the rate constant for the binding of monomeric heme is approximately 1 x 10(8) M-1 s-1 regardless of the structure or overall affinity of the apoprotein for iron-porphyrin. Major differences between the proteins are reflected primarily in the rates of dissociation of the prosthetic group. Slow phases observed in the reaction of CO heme with excess apomyoglobin result from formation of nonspecific heme-protein complexes which must dissociate before heme can bind specifically in the heme pocket. Once the specific heme-globin complex is formed, the heme pocket rapidly collapses around the porphyrin, simultaneously forming the bond between the proximal His93 and the heme iron atom. The overall affinity of sperm whale apomyoglobin for hemin is approximately 1 x 10(14) M-1. Nonspecific hydrophobic interactions between the porphyrin and the apolar heme cavity account for a factor of 10(5)-10(7). Covalent bond formation between Fe3+ and His93(F8) provides an additional factor of 10(3)-10(4). Specific interactions with conserved amino acids in the heme pocket contribute the final factor of 10(3)-10(4).     

Working Group Report 2: In situ caries models, saliva, microbiology, and statistical considerations

We present a case of a single coronary artery where the right coronary artery (RCA) arose from its proximal part. This rare anomaly was detected during elective coronary angiography in a patient with suspected coronary artery disease. The single coronary artery originated from the left sinus of valsalva, giving rise to RCA proximally and distally dividing into left anterior descending (LAD), ramus intermedius and left circumflex (LCX) arteries. The anginal symptoms in this patient was attributed to a significant stenosis at the proximal LAD which was subsequently dilated by coronary angioplasty. To the best of our knowledge, this is the first reported case of angioplasty of LAD in an anomalous single coronary artery.     

Monoclonal antibodies recognizing epitopes on the extracellular face and intracellular N-terminus of the human erythrocyte anion transporter (band 3) and their application to the analysis of South East Asian ovalocytes

This report describes the production and characterization of 13 rodent monoclonal antibodies to the human erythrocyte anion transport protein AE1 (syn. band 3). Eleven antibodies (4 murine and 7 rat) recognize epitopes dependent on the integrity of the third extracellular loop of the protein. Two antibodies (1 murine and 1 rat) recognize epitopes on the N-terminal cytoplasmic domain. Quantitative binding studies using radioiodinated IgG and Fab fragments of antibodies to extracellular epitopes on AE1 ranged from 77,000 to 313,000 (IgG) and from 241,000 to 772,000 (Fab) molecules bound at saturation. The results indicate that the epitopes recognized by different antibodies vary in their accessibility and suggest that there is heterogeneity in the organization of individual AE1 molecules in the red blood cell membrane. Quantitative binding studies on South East Asian ovalocytes using several antibodies to AE1 and an anti-Wrb show a marked reduction in the number of antibody molecules bound at saturation. These results are consistent with the existence of highly cooperative interactions between transmembrane domains of AE1 in normal erythrocytes and the disruption of these interactions in the variant AE1 found in South East Asian ovalocytes.