9,341 research outputs found
Two-Dimensional Geometric Theory for Maximizing Lumber Yield From Logs
A two-dimensional geometric theory for maximizing lumber yield from logs was developed. Centered cant sawing solutions for both circular and elliptical shaped logs were derived. Sawline placement for maximum yield is dependent upon the diameter of round logs or upon the cross-sectional axis of elliptical logs. The width of the face of the cant is equal to 0.707 times the diameter or parallel-axis of the log. Slab thickness is equal to 0.147 times the diameter or perpendicular-axis of the log. It assumes circular and elliptical log shapes and provides a method that may substantially reduce computation time when applied to computerized log breakdown decisions
The Blind Watchmaker Network: Scale-freeness and Evolution
It is suggested that the degree distribution for networks of the
cell-metabolism for simple organisms reflects an ubiquitous randomness. This
implies that natural selection has exerted no or very little pressure on the
network degree distribution during evolution. The corresponding random network,
here termed the blind watchmaker network has a power-law degree distribution
with an exponent gamma >= 2. It is random with respect to a complete set of
network states characterized by a description of which links are attached to a
node as well as a time-ordering of these links. No a priory assumption of any
growth mechanism or evolution process is made. It is found that the degree
distribution of the blind watchmaker network agrees very precisely with that of
the metabolic networks. This implies that the evolutionary pathway of the
cell-metabolism, when projected onto a metabolic network representation, has
remained statistically random with respect to a complete set of network states.
This suggests that even a biological system, which due to natural selection has
developed an enormous specificity like the cellular metabolism, nevertheless
can, at the same time, display well defined characteristics emanating from the
ubiquitous inherent random element of Darwinian evolution. The fact that also
completely random networks may have scale-free node distributions gives a new
perspective on the origin of scale-free networks in general.Comment: 5 pages, 3 figure
Overall survival benefits of cancer drugs approved in China from 2005 to 2020
Importance: Of approximately 9 million patients with cancer in China in 2020, more than half were diagnosed with late-stage cancers. Recent regulatory reforms in China have focused on improving the availability of new cancer drugs. However, evidence on the clinical benefits of new cancer therapies authorized in China is not available. Objective: To characterize the clinical benefits of cancer drugs approved in China, as defined by the availability and magnitude of statistically significant overall survival (OS) results. Design, Setting, and Participants: This mixed-methods study comprising a systematic review and cross-sectional analysis identified antineoplastic agents approved in China between January 1, 2005, and December 31, 2020, using publicly available data and regulatory review documents issued by the National Medical Products Administration. The literature published up to June 30, 2021, was reviewed to collect results on end points used in pivotal trials supporting cancer drug approvals. Main Outcomes and Measures: The primary outcome measure was a documented statistically significant positive OS difference between a new cancer therapy and a comparator treatment. Secondary outcome measures were the magnitude of OS benefit and other primary efficacy measures in pivotal trials. Results: Between 2005 and 2020, 78 cancer drugs corresponding to 141 indications were authorized in China, including 20 drugs (25.6%) (for 30 indications) approved in China only. Of all indications, 26 (18.4%) were evaluated in single-arm or dose-optimization trials, most of which were authorized after 2017. By June 30, 2021, 34 drug indications (24.1%) had a documented lack of OS gain. For 68 indications (48.2%) that had documented evidence of OS benefit, the median magnitude of OS improvement was 4.1 (range, 1.0-35.0) months. After a median follow-up of 1.9 (range, 1.0-11.1) years from approval, OS data for 13 indications (9.2%) were either not reported or were still not mature. Fewer than one-third of cancer drug indications approved in China only had documented evidence of OS benefits (9 of 30 [30.0%]), whereas more than one-half of the cancer drug indications also available in the US or Europe had OS benefits (59 of 111 [53.1%]). Conclusions and Relevance: In this study, almost half of cancer drug indications approved in China had demonstrated OS gain. With the increase of cancer drug approvals based on single-arm trials or immature survival data in recent years, these findings highlight the need to routinely monitor the clinical benefits of new cancer therapies in Chin
Phase transitions in MgSiO3 post-perovskite in super-Earth mantles
The highest pressure form of the major Earth-forming mantle silicate is
MgSiO3 post-perovskite (PPv). Understanding the fate of PPv at TPa pressures is
the first step for understanding the mineralogy of super-Earths-type
exoplanets, arguably the most interesting for their similarities with Earth.
Modeling their internal structure requires knowledge of stable mineral phases,
their properties under compression, and major element abundances. Several
studies of PPv under extreme pressures support the notion that a sequence of
pressure induced dissociation transitions produce the elementary oxides SiO2
and MgO as the ultimate aggregation form at ~3 TPa. However, none of these
studies have addressed the problem of mantle composition, particularly major
element abundances usually expressed in terms of three main variables, the
Mg/Si and Fe/Si ratios and the Mg#, as in the Earth. Here we show that the
critical compositional parameter, the Mg/Si ratio, whose value in the Earth's
mantle is still debated, is a vital ingredient for modeling phase transitions
and internal structure of super-Earth mantles. Specifically, we have identified
new sequences of phase transformations, including new recombination reactions
that depend decisively on this ratio. This is a new level of complexity that
has not been previously addressed, but proves essential for modeling the nature
and number of internal layers in these rocky mantles.Comment: Submitted to Earth Planet. Sci. Lett., 28 pages, 6 figure
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Expansion of Thaumarchaeota habitat range is correlated with horizontal transfer of ATPase operons.
Thaumarchaeota are responsible for a significant fraction of ammonia oxidation in the oceans and in soils that range from alkaline to acidic. However, the adaptive mechanisms underpinning their habitat expansion remain poorly understood. Here we show that expansion into acidic soils and the high pressures of the hadopelagic zone of the oceans is tightly linked to the acquisition of a variant of the energy-yielding ATPases via horizontal transfer. Whereas the ATPase genealogy of neutrophilic Thaumarchaeota is congruent with their organismal genealogy inferred from concatenated conserved proteins, a common clade of V-type ATPases unites phylogenetically distinct clades of acidophilic/acid-tolerant and piezophilic/piezotolerant species. A presumptive function of pumping cytoplasmic protons at low pH is consistent with the experimentally observed increased expression of the V-ATPase in an acid-tolerant thaumarchaeote at low pH. Consistently, heterologous expression of the thaumarchaeotal V-ATPase significantly increased the growth rate of E. coli at low pH. Its adaptive significance to growth in ocean trenches may relate to pressure-related changes in membrane structure in which this complex molecular machine must function. Together, our findings reveal that the habitat expansion of Thaumarchaeota is tightly correlated with extensive horizontal transfer of atp operons
Successful Salvage Unrelated Umbilical Cord Blood Transplantation with Two Units After Engraftment Failure with Single Unit in Severe Aplastic Anemia
Severe aplastic anemia (SAA) patients without an HLA-matched sibling donor need alternative treatment options. Umbilical cord blood transplantation (UCBT) has become an alternative means for treating various diseases, but it has not been proved to be a satisfactory method to treat SAA. Here, we report the case of a girl who underwent successful two-unit UCBT after engraftment failure with a single unit. Two-unit UCBT is proposed to have better engraftment potential and to offer a better chance of survival, according to some reports. Increased cell dose and graft-versus-graft reaction could contribute to these advantages. With this promising result, two-unit UCBT could be an alternative treatment option for patients with SAA without an HLA-matched donor
Preferential attachment renders an evolving network of populations robust against crashes
We study a model for the evolution of chemical species under a combination of
population dynamics on a short time scale and a selection mechanism on a longer
time scale. Least fit nodes are replaced by new nodes whose links are attached
to the nodes of the given network via preferential attachment. In contrast to a
random attachment of newly incoming nodes that was used in previous work, this
preferential attachment mechanism accelerates the generation of a so-called
autocatalytic set after a start from a random geometry and the growth of this
structure until it saturates in a stationary phase in which the whole system is
an autocatalytic set. Moreover, the system in the stationary phase becomes much
more stable against crashes in the population size as compared to random
attachment. We explain in detail in terms of graph theoretical notions which
structure of the resulting network is responsible for this stability.
Essentially it is a very dense core with many loops and less nodes playing the
role of a keystone that prevents the system against crashes almost completely.Comment: 12 pages, 9 figures, 2 table
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