Detection and Measurement of Air-Borne Radiation at Grinnell, Iowa

A relatively simple method is presented for the detection and measurement of total air-borne radiation. It employs only a scintillation counter, and ordinary laboratory materials. Using this method, a monitoring station was established for the period from the Fall of 1961 through the Spring of 1962. The results from this study, when compared with the results published by the United States Public Health Service, indicate a high degree of reliability in the method used

Errors in the bisulfite conversion of DNA: modulating inappropriate- and failed-conversion frequencies

Bisulfite treatment can be used to ascertain the methylation states of individual cytosines in DNA. Ideally, bisulfite treatment deaminates unmethylated cytosines to uracils, and leaves 5-methylcytosines unchanged. Two types of bisulfite-conversion error occur: inappropriate conversion of 5-methylcytosine to thymine, and failure to convert unmethylated cytosine to uracil. Conventional bisulfite treatment requires hours of exposure to low-molarity, low-temperature bisulfite (‘LowMT’) and, sometimes, thermal denaturation. An alternate, high-molarity, high-temperature (‘HighMT’) protocol has been reported to accelerate conversion and to reduce inappropriate conversion. We used molecular encoding to obtain validated, individual-molecule data on failed- and inappropriate-conversion frequencies for LowMT and HighMT treatments of both single-stranded and hairpin-linked oligonucleotides. After accounting for bisulfite-independent error, we found that: (i) inappropriate-conversion events accrue predominantly on molecules exposed to bisulfite after they have attained complete or near-complete conversion; (ii) the HighMT treatment is preferable because it yields greater homogeneity among sites and among molecules in conversion rates, and thus yields more reliable data; (iii) different durations of bisulfite treatment will yield data appropriate to address different experimental questions; and (iv) conversion errors can be used to assess the validity of methylation data collected without the benefit of molecular encoding

Detection of Streptococcus mutans Genomic DNA in Human DNA Samples Extracted from Saliva and Blood

Caries is a multifactorial disease, and studies aiming to unravel the factors modulating its etiology must consider all known predisposing factors. One major factor is bacterial colonization, and Streptococcus mutans is the main microorganism associated with the initiation of the disease. In our studies, we have access to DNA samples extracted from human saliva and blood. In this report, we tested a real-time PCR assay developed to detect copies of genomic DNA from Streptococcus mutans in 1,424 DNA samples from humans. Our results suggest that we can determine the presence of genomic DNA copies of Streptococcus mutans in both DNA samples from caries-free and caries-affected individuals. However, we were not able to detect the presence of genomic DNA copies of Streptococcus mutans in any DNA samples extracted from peripheral blood, which suggests the assay may not be sensitive enough for this goal. Values of the threshold cycle of the real-time PCR reaction correlate with higher levels of caries experience in children, but this correlation could not be detected for adults

Detection of Streptococcus mutans Genomic DNA in Human DNA Samples Extracted from Saliva and Blood

Caries is a multifactorial disease, and studies aiming to unravel the factors modulating its etiology must consider all known predisposing factors. One major factor is bacterial colonization, and Streptococcus mutans is the main microorganism associated with the initiation of the disease. In our studies, we have access to DNA samples extracted from human saliva and blood. In this report, we tested a real-time PCR assay developed to detect copies of genomic DNA from Streptococcus mutans in 1,424 DNA samples from humans. Our results suggest that we can determine the presence of genomic DNA copies of Streptococcus mutans in both DNA samples from caries-free and caries-affected individuals. However, we were not able to detect the presence of genomic DNA copies of Streptococcus mutans in any DNA samples extracted from peripheral blood, which suggests the assay may not be sensitive enough for this goal. Values of the threshold cycle of the real-time PCR reaction correlate with higher levels of caries experience in children, but this correlation could not be detected for adults

INELASTIC NEUTRON SCATTERING FROM MnF2 IN THE CRITICAL REGION

Les mesures de la diffusion des neutrons ont donné en détail la forme de la fonction de diffusion pour les fluctuations des spins transverses dans la région critique du composé antiferromagnétique uniaxial MnF2. La susceptibilité statique et les temps de la relaxation sont présentés pour les températures au-dessus et au-dessous de la transition de phase. Au-dessous de TN l'intervalle d'énergie varie avec la température comme l'aimantation dans la région critique.Detailed neutron scattering measurements have yielded the behavior of the scattering function for transverse spin fluctuations in the critical region of the uniaxial antiferromagnet MnF2. The static wavevector dependent susceptibility and relaxation rates are presented for temperatures above and below the phase transition. Below TN the spinwave energy gap is found to Vary with temperature like the magnetization in the critical region