The site of ribonucleic acid synthesis in the isolated nucleus

There is still controversy concerning the primary site of RNA synthesis in the cell.(1) When tissues are radioautographed after administration of radioactive inorganic phosphorus or radioactive RNA(2) precursors such as tritiated uridine or cytidine, it is commonly observed that radioactivity appears in the nucleus first and in the cytoplasm later. It has furthermore been shown that isolated nuclei of both animal(3) and plant(4) material are able to synthesize RNA in vitro but that enucleated cytoplasm is unable to carry on such synthesis.(5) Although the problem of whether or not RNA is synthesized in both nucleus and cytoplasm is not completely understood,(6-8) there is increasing cytological evidence that a substantial portion of the cytoplasmic RNA is synthesized in the nucleus (9-17) and subsequently migrates to the cytoplasm

Incorporation of tritiated cytidine into ribonucleic acid by isolated pea nuclei

A new method for the isolation of the nuclei from plant tissue has been devised. This method consists in passing the plant tissue through a set of spring-loaded, counter-rotating rollers and collecting the liberated nuclei in sucrose solution containing calcium ions. A semi-automatic machine which couples the rollers with a special tissue chopping device has been constructed. It has been shown that nuclei obtained in this way actively incorporate cytidine-H3 into RNA. This incorporation is increased in the presence of nucleoside triphosphates and an energy-regenerating system

Identification of Ambient Molecular Clouds Associated with Galactic Supernova Remnant IC443

The Galactic supernova remnant (SNR) IC443 is one of the most studied core-collapse SNRs for its interaction with molecular clouds. However, the ambient molecular clouds with which IC443 is interacting have not been thoroughly studied and remain poorly understood. Using Five College Radio Astronomy Observatory 14m telescope, we obtained fully sampled maps of ~ 1{\deg} \times 1{\deg} region toward IC443 in the 12CO J=1-0 and HCO+ J=1-0 lines. In addition to the previously known molecular clouds in the velocity range v_lsr = -6 to -1 km/s (-3 km/s clouds), our observations reveal two new ambient molecular cloud components: small (~ 1') bright clouds in v_lsr = -8 to -3 km/s (SCs), and diffuse clouds in v_lsr = +3 to +10 km/s (+5 km/s clouds). Our data also reveal the detailed kinematics of the shocked molecular gas in IC443, however the focus of this paper is the physical relationship between the shocked clumps and the ambient cloud components. We find strong evidence that the SCs are associated with the shocked clumps. This is supported by the positional coincidence of the SCs with shocked clumps and other tracers of shocks. Furthermore, the kinematic features of some shocked clumps suggest that these are the ablated material from the SCs upon the impact of the SNR shock. The SCs are interpreted as dense cores of parental molecular clouds that survived the destruction by the pre-supernova evolution of the progenitor star or its nearby stars. We propose that the expanding SNR shock is now impacting some of the remaining cores and the gas is being ablated and accelerated producing the shocked molecular gas. The morphology of the +5 km/s clouds suggests an association with IC443. On the other hand, the -3 km/s clouds show no evidence for interaction.Comment: Accepted for publication in ApJ. 15 pages (with emulateapj.cls), 17 figures, and 2 table

A Design Space for Intelligent and Interactive Writing Assistants

In our era of rapid technological advancement, the research landscape for writing assistants has become increasingly fragmented across various research communities. We seek to address this challenge by proposing a design space as a structured way to examine and explore the multidimensional space of intelligent and interactive writing assistants. Through a large community collaboration, we explore five aspects of writing assistants: task, user, technology, interaction, and ecosystem. Within each aspect, we define dimensions (i.e., fundamental components of an aspect) and codes (i.e., potential options for each dimension) by systematically reviewing 115 papers. Our design space aims to offer researchers and designers a practical tool to navigate, comprehend, and compare the various possibilities of writing assistants, and aid in the envisioning and design of new writing assistants.Comment: Published as a conference paper at CHI 202

Fluorometric Examination of a Lunar Sample

We have been unable to detect porphyrins in 13 grams of the bulk fine lunar sample from the Sea of Tranquillity under conditions in which less than 10-^(1J) mole per gram of lunar sample could have been detected. By appropriate extraction, however, the lunar sample yields a material which exhibits absorption maxima at 310 and 350 nanometers and a fluorescence maximum at 410 nanometers