The Single Precipitation of Calcium Oxalate in the Presence of Magnesium

It has been known for a long time that when calcium is precipitated as the oxalate in the presence of magnesium some magnesium is likely to be found in the precipitate. Therefore, it is customary to perform a double precipitation whenever the content of magnesium amounts to more than a few milligrams. With a view toward eliminating the time-consuming second precipitation whenever possible, it is the purpose of the present work to determine to what extent reliable results may be obtained for calcium using merely a single precipitation

An Experiment in Gravitation

In this work an attempt is made to repeat in somewhat altered form, an experiment of the late Charles F. Brush, in which he believed he had observed a considerable deviation from the accepted relationship that the inertia of an object is proportional to its weight

Question Box

Question: Wood is opaque to light but is easily penetrated by X rays. The latter, however, are stopped by some kinds of clear glass. Does this not show that light and X rays are of different nature? Is it desirable to study the theory of evolution in connection with a high school course in Botany? If so, to what extent? What is the purpose of crop rotation

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How can breakage fees be best handled in connection with the high school laboratory sciences? Will you describe the method followed by the weather bureau in weather forecasting? When you blow burns the better. or fan a camp fire it When you blow a candle it goes out. What is the reason for the difference? Should static electricity be continued as a part of the high school physics course

A Weakened Transcriptional Enhancer Yields Variegated Gene Expression

Identical genes in the same cellular environment are sometimes expressed differently. In some cases, including the immunoglobulin heavy chain (IgH) locus, this type of differential gene expression has been related to the absence of a transcriptional enhancer. To gain additional information on the role of the IgH enhancer, we examined expression driven by enhancers that were merely weakened, rather than fully deleted, using both mutations and insulators to impair enhancer activity. For this purpose we used a LoxP/Cre system to place a reporter gene at the same genomic site of a stable cell line. Whereas expression of the reporter gene was uniformly high in the presence of the normal, uninsulated enhancer and undetectable in its absence, weakened enhancers yielded variegated expression of the reporter gene; i.e., the average level of expression of the same gene differed in different clones, and expression varied significantly among cells within individual clones. These results indicate that the weakened enhancer allows the reporter gene to exist in at least two states. Subtle aspects of the variegation suggest that the IgH enhancer decreases the average duration (half-life) of the silent state. This analysis has also tested the conventional wisdom that enhancer activity is independent of distance and orientation. Thus, our analysis of mutant (truncated) forms of the IgH enhancer revealed that the 250 bp core enhancer was active in its normal position, ∼1.4 kb 3′ of the promoter, but inactive ∼6 kb 3′, indicating that the activity of the core enhancer was distance-dependent. A longer segment – the core enhancer plus ∼1 kb of 3′ flanking material, including the 3′ matrix attachment region – was active, and the activity of this longer segment was orientation-dependent. Our data suggest that this 3′ flank includes binding sites for at least two activators

Unphosphorylated SR-Like Protein Npl3 Stimulates RNA Polymerase II Elongation

The production of a functional mRNA is regulated at every step of transcription. An area not well-understood is the transition of RNA polymerase II from elongation to termination. The S. cerevisiae SR-like protein Npl3 functions to negatively regulate transcription termination by antagonizing the binding of polyA/termination proteins to the mRNA. In this study, Npl3 is shown to interact with the CTD and have a direct stimulatory effect on the elongation activity of the polymerase. The interaction is inhibited by phosphorylation of Npl3. In addition, Casein Kinase 2 was found to be required for the phosphorylation of Npl3 and affect its ability to compete against Rna15 (Cleavage Factor I) for binding to polyA signals. Our results suggest that phosphorylation of Npl3 promotes its dissociation from the mRNA/RNAP II, and contributes to the association of the polyA/termination factor Rna15. This work defines a novel role for Npl3 in elongation and its regulation by phosphorylation

Système spectrométrique interférentiel proposé pour l'Université de Wisconsin

The proposed device may include any number of gratings and Fabry-Perot etalons. The spectrum is scanned by varying the pressure. Perfect synchronism in the scanning of each element (grating or Fabry-Perot) is obtained simply by putting them all together in the same variable pressure chamber.Le dispositif proposé peut comprendre un ou plusieurs réseaux et un ou plusieurs Fabry-Perot. L'exploration du spectre est obtenue par variation de pression. Un synchronisme rigoureux entre les explorations pour les différents éléments (réseaux ou Fabry-Perot) est assuré simplement en les enfermant dans la même enceinte où l'on effectue la variation de pression