Multiple Forks Research Articles

Flexible Example-Based Program Synthesis on Tree-Structured Function Compositions

We introduce a flexible program synthesis system whose task is to predict function compositions that transform given inputs to their corresponding given outputs. We process input lists in a sequential manner, allowing the system to generalize to a wide range of input lengths. We separate the operator and the operand in the lambda functions of the used higher order functions to achieve significantly wider numeric parameter ranges compared to the previous works. The evaluations show that this approach is competitive with state-of-the-art systems, while it is much more flexible in terms of the input length, the parameters of the lambda functions, and the integer range of the inputs and outputs. We extend the system to handle tree-structured function compositions by introducing two additional functions (zip_with, copy) and the ability to represent unfinished function compositions during the synthesis process. The extended system achieves state-of-the-art results while synthesizing complex function compositions with multiple forks. We believe that flexibility in these aspects is an important step towards solving real-world problems with example-based program synthesis.

Replication fork collisions cause pathological chromosomal amplification in cells lacking RecG DNA translocase

Duplication and transmission of chromosomes require precise control of chromosome replication and segregation. Here we present evidence that RecG is a major factor influencing these processes in bacteria. We show that the extensive DnaA-independent stable DNA replication observed without RecG can lead to replication of any area of the chromosome. This replication is further elevated following irradiation with UV light and appears to be perpetuated by secondary events that continue long after the elimination of UV lesions. The resulting pathological cascade is associated with an increased number of replication forks traversing the chromosome, sometimes with extensive regional amplification of the chromosome, and with the accumulation of highly branched DNA intermediates containing few Holliday junctions. We propose that the cascade is triggered by replication fork collisions that generate 3′ single-strand DNA flaps, providing sites for PriA to initiate re-replication of the DNA and thus to generate linear duplexes that provoke recombination, allowing priming of even further replication. Our results shed light on why termination of replication in bacteria is normally limited to a single encounter of two forks and carefully orchestrated within a restricted area, and explain how a system of multiple forks and random termination can operate in eukaryotes.

Bald eagle nest site and nest tree characteristics in select biogeoclimatic zones of the 100 Mile House Forest District, British Columbia

Bald eagle (Haliaeetus leucocephalus) nest site and nest tree characteristics were studied in the Sub-Boreal Spruce (SBS), Interior Cedar–Hemlock (ICH), Sub-Boreal Pine–Spruce (SBPS), and interior Douglas-fir (IDF) biogeoclimatic zones in the 100 Mile House Forest District, British Columbia. Dominant or codominant Douglas-fir (Pseudotsuga menziesii) containing large trunk forks or multiple forks of the trunk comprised 85% of 121 bald eagle nest trees. Black cottonwood (Populus trichocarpa) comprised 11% of known nest trees, and trembling aspen (Populus tremuloides), lodgepole pine (Pinus contorta), Ponderosa pine (Pinus ponderosa), and hybrid white spruce (Picea glauca x engelmannii) each contained 1% of known bald eagle nests. Tree height and diameter at breast height (DBH), nest height, and distance of nest to fish-bearing water were less for island nests compared to non-island nests. The mean distance of nests to fish-bearing water, by biogeoclimatic zone, was 78 m in the SBS, 104 m in the ICH, 241 m in the SBPS, and 368 m in the IDF. Ground slope and aspect were not factors in nest site location. The bald eagle nest trees studied were generally of low economic value to the forest industry as they contained less recoverable lumber than similar-sized trees with better form. To maintain bald eagle nesting habitat, large diameter, dominant or codominant trees containing large trunk forks, or multiple forks or leaders of the trunk and (or) large limbs should be identified and retained in groups, patches, or forest stands.

The optical illusion of sound

The graphic depiction of sound is not a straightforward matter. Stationary representations using lines, waves, or circles leave the notion of movement (either particle or energy) and pressure fluctuations within the wave to the reader's imagination. The common sinuous wave shape evident in most all sources of study originates from Lissajous, and resulted from his transfer of tuning fork motions into a point of reflected light that traversed a screen. Lissajous performed his experiments with finely focused electric lamp light, tuning forks, and mirrors. Similar experiments can be replicated today using laser light and audio speakers. Thus one can more readily gain an appreciation for the familiar wave pattern representing sound, and see by the simple instruments used to create it, how this waveform is not a true depiction of the shape of sound waves in a medium. It is in reality a displacement versus time graph. By using multiple forks or speakers in opposing planes and tuned to various frequencies, the creation of the single- and multiple-ellipse Lissajous patterns that are often produced on an oscilloscope screen can also be accomplished.

Replication of Deoxyribonucleic Acid During the Division Cycle of Salmonella typhimurium

The rate of thymidine incorporation into cells of Salmonella typhimurium growing in different media has been measured. In glucose-minimal medium, deoxyribonucleic acid (DNA) replication occurs during the first two-thirds of the division cycle; the final one-third of the division cycle was devoid of DNA replication. The measured doubling time of S. typhimurium in this medium is approximately 48 min, indicating that C (the time for a round of replication) and D (the time between termination and cell division) are approximately 32 and 16 min, respectively. At slower growth rates the pattern of replication is the same as glucose minimal medium. At faster growth rates the "gap" in DNA synthesis disappears. At rapid growth rates evidence for multiple forks is obtained.