99 research outputs found
Micro Virtual Machines: A Solid Foundation for Managed Language Implementation
Today new programming languages proliferate, but many of them
suffer from
poor performance and inscrutable semantics. We assert that the
root of
many of the performance and semantic problems of today's
languages is
that language implementation is extremely difficult. This
thesis
addresses the fundamental challenges of efficiently developing
high-level
managed languages.
Modern high-level languages provide abstractions over execution,
memory
management and concurrency. It requires enormous intellectual
capability
and engineering effort to properly manage these concerns.
Lacking such
resources, developers usually choose naive implementation
approaches
in the early stages of language design, a strategy which too
often has
long-term consequences, hindering the future development of the
language. Existing language development platforms have failed
to
provide the right level of abstraction, and forced implementers
to
reinvent low-level mechanisms in order to obtain performance.
My thesis is that the introduction of micro virtual machines will
allow
the development of higher-quality, high-performance managed
languages.
The first contribution of this thesis is the design of Mu, with
the
specification of Mu as the main outcome. Mu is
the first micro virtual machine, a robust, performant, and
light-weight
abstraction over just three concerns: execution, concurrency and
garbage
collection. Such a foundation attacks three of the most
fundamental and
challenging issues that face existing language designs and
implementations, leaving the language implementers free to focus
on the
higher levels of their language design.
The second contribution is an in-depth analysis of on-stack
replacement
and its efficient implementation. This low-level mechanism
underpins
run-time feedback-directed optimisation, which is key to the
efficient
implementation of dynamic languages.
The third contribution is demonstrating the viability of Mu
through
RPython, a real-world non-trivial language implementation. We
also did
some preliminary research of GHC as a Mu client.
We have created the Mu specification and its reference
implementation,
both of which are open-source. We show that that Mu's on-stack
replacement API can gracefully support dynamic languages such as
JavaScript, and it is implementable on concrete hardware. Our
RPython
client has been able to translate and execute non-trivial
RPython
programs, and can run the RPySOM interpreter and the core of the
PyPy
interpreter.
With micro virtual machines providing a low-level substrate,
language
developers now have the option to build their next language on a
micro
virtual machine. We believe that the quality of programming
languages
will be improved as a result
Atmospheric Deposition History of Trace Metals and Metalloids for the Last 200 Years Recorded by Three Peat Cores in Great Hinggan Mountain, Northeast China
A large number of studies on trace metals and metalloids (TMs) accumulations in peatlands have been reported in Europe and North America. Comparatively little information is available on peat chronological records of atmospheric TMs flux in China. Therefore, the objective of our study was to determine the concentrations and accumulation rates (ARs) of TMs in Motianling peatland from Great Hinggan Mountain, northeast China, and to assess these in relation to establish a historical profile of atmospheric metal emissions from anthropogenic sources. To meet these aims we analyzed 14 TMs (As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sr, Sb, Tl, and Zn) and Pb isotopes (206Pb, 207Pb, 208Pb) using ICP-AES and ICP-MS, respectively, in three peat sections dated by 210Pb and 137Cs techniques (approximately spanning the last 200 years). There is a general agreement in the elemental concentration profiles which suggests that all investigated elements were conserved in the Motianling bog. Three principal components were discriminated by principal componentanalysis (PCA) based on Eigen-values >1 and explaining 85% of the total variance of element concentrations: the first component representing Ba, Co, Cr, Mo, Ni, Sr and Tl reflected the lithogenic source; the second component covering As, Cu and Sb, and Cd is associated with an anthropogenic source from ore mining and processing; the third component (Pb isotope, Pb and Zn) is affected by anthropogenic Pb pollution from industrial manufacturing and fossil-fuel combustion. The pre-industrial background of typical pollution elements was estimated as the average concentrations of TMs in peat samples prior to 1830 AD and with a 207Pb/206Pb ratio close to 1.9. ARs and enrichment factors (EFs) of TMs suggested enhanced metal concentrations near the surface of the peatland (in peat layers dated from the 1980s) linked to an increasing trend since the 2000s. This pollution pattern is also fingerprinted by the Pb isotopic composition, even after the ban of leaded gasoline use in China. Emissions from coal and leaded gasoline combustions in northern China are regarded as one of the major sources of anthropogenic Pb input in this region; meanwhile, the long-distance transportation of Pb-bearing aerosols from Mongolia should be also taken into consideration. The reconstructed history of TMs’ pollution over the past ca. 200 years is in agreement with the industrial development in China and clearly illustrates the influence of human activities on local rural environments. This study shows the utility of taking multi-cores to show the heterogeneity in peat accumulation and applying PCA, EF and Pb isotope methods in multi-proxies analyses for establishing a high resolution geochemical metal record from peatland
Draining the Swamp: Micro Virtual Machines as Solid Foundation for Language Development
Many of today\u27s programming languages are broken. Poor performance, lack of features and hard-to-reason-about semantics can cost dearly in software maintenance and inefficient execution. The problem is only getting worse with programming languages proliferating and hardware becoming more complicated. An important reason for this brokenness is that much of language design is implementation-driven. The difficulties in implementation and insufficient understanding of concepts bake bad designs into the language itself. Concurrency, architectural details and garbage collection are three fundamental concerns that contribute much to the complexities of implementing managed languages.
We propose the micro virtual machine, a thin abstraction designed specifically to relieve implementers of managed languages of the most fundamental implementation challenges that currently impede good design. The micro virtual machine targets abstractions over memory (garbage collection), architecture (compiler backend), and concurrency. We motivate the micro virtual machine and give an account of the design and initial experience of a concrete instance, which we call Mu, built over a two year period. Our goal is to remove an important barrier to performant and semantically sound managed language design and implementation
Ocean acidification increases the accumulation of toxic phenolic compounds across trophic levels
Increasing atmospheric CO2 concentrations are causing ocean acidification (OA), altering carbonate chemistry with consequences for marine organisms. Here we show that OA increases by 46–212% the production of phenolic compounds in phytoplankton grown under the elevated CO2 concentrations projected for the end of this century, compared with the ambient CO2 level. At the same time, mitochondrial respiration rate is enhanced under elevated CO2 concentrations by 130–160% in a single species or mixed phytoplankton assemblage. When fed with phytoplankton cells grown under OA, zooplankton assemblages have significantly higher phenolic compound content, by about 28–48%. The functional consequences of the increased accumulation of toxic phenolic compounds in primary and secondary producers have the potential to have profound consequences for marine ecosystem and seafood quality, with the possibility that fishery industries could be influenced as a result of progressive ocean change
On-stack replacement, distilled
On-stack replacement (OSR) is essential technology for adaptive optimization, allowing changes to code actively executing in a managed runtime. The engineering aspects of OSR are well-known among VM architects, with several implementations available to date. However, OSR is yet to be explored as a general means to transfer execution between related program versions, which can pave the road to unprecedented applications that stretch beyond VMs. We aim at filling this gap with a constructive and provably correct OSR framework, allowing a class of general-purpose transformation functions to yield a special-purpose replacement. We describe and evaluate an implementation of our technique in LLVM. As a novel application of OSR, we present a feasibility study on debugging of optimized code, showing how our techniques can be used to fix variables holding incorrect values at breakpoints due to optimizations
Role of C4 carbon fixation in Ulva prolifera, the macroalga responsible for the world's largest green tides
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Liu, D., Ma, Q., Valiela, I., Anderson, D. M., Keesing, J. K., Gao, K., Zhen, Y., Sun, X., & Wang, Y. Role of C4 carbon fixation in Ulva prolifera, the macroalga responsible for the world's largest green tides. Communications Biology, 3(1), (2020): 494, doi:10.1038/s42003-020-01225-4.Most marine algae preferentially assimilate CO2 via the Calvin-Benson Cycle (C3) and catalyze HCO3− dehydration via carbonic anhydrase (CA) as a CO2-compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C4) to enhance photosynthesis. The occurrence and importance of the C4 pathway remains uncertain, however. Here, we demonstrate that carbon fixation in Ulva prolifera, a species responsible for massive green tides, involves a combination of C3 and C4 pathways, and a CA-supported HCO3− mechanism. Analysis of CA and key C3 and C4 enzymes, and subsequent analysis of δ13C photosynthetic products showed that the species assimilates CO2 predominately via the C3 pathway, uses HCO3− via the CA mechanism at low CO2 levels, and takes advantage of high irradiance using the C4 pathway. This active and multi-faceted carbon acquisition strategy is advantageous for the formation of massive blooms, as thick floating mats are subject to intense surface irradiance and CO2 limitation.This work was supported by the State Key Project of Research and Development Plan, Ministry of Science and Technology of the Peopleʼs Republic of China (2016YFC1402106). Support for D.M.A. provided by the Woods Hole Oceanographic Institution—Ocean University of China Cooperative Research Initiative. We thank Dr. Juntian Xu, Jing Ma, Ying Li, and Chenglong Ji for assisting culture experiments and sample analysis
Fungsi Sosial Cerita Rakyat Batu Bujang Lengong Di Nagari Alahan Panjang Kecamatan Lembah Gumanti Kabupaten Solok
The purpose for describe function social strori people stone bachelor lengong di Nagari Alahan Panjang Kecamatan Lembah Gumanti Kabupaten Solok hasil researeh in is function social ditemukan faef function social yaitu (1),Studi theory which be usea in research, (2) nature folklore nature, (3) function social strory people. Type researeh is researeh qualilative data dianalisis with step measuresDescribe result recording in language writler translate result interesting conclusior and write report.of destination in is function social strory people bachelor lengong foun Nagari Alahan Panjang Kecamatan Lembah Gumanti Kabupaten Solok, (1) Function social entertain, (2) Function social educate, (3) Function social begueath, (4) Function social tradition, (5) Function social identity
Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems
Ocean acidification, a complex phenomenon that lowers seawater pH,
is the net outcome of several contributions. They include the dissolution of
increasing atmospheric CO<sub>2</sub> that adds up with dissolved inorganic
carbon (dissolved CO<sub>2</sub>, H<sub>2</sub>CO<sub>3</sub>, HCO<sub>3</sub><sup>−</sup>, and
CO<sub>3</sub><sup>2−</sup>) generated upon mineralization of primary producers (PP) and
dissolved organic matter (DOM). The aquatic processes leading to inorganic
carbon are substantially affected by increased DOM and nutrients via
terrestrial runoff, acidic rainfall, increased PP and algal blooms,
nitrification, denitrification, sulfate reduction, global warming (GW), and
by atmospheric CO<sub>2</sub> itself through enhanced photosynthesis. They are
consecutively associated with enhanced ocean acidification, hypoxia in
acidified deeper seawater, pathogens, algal toxins, oxidative stress by
reactive oxygen species, and thermal stress caused by longer stratification
periods as an effect of GW. We discuss the mechanistic insights into the
aforementioned processes and pH changes, with particular focus on processes
taking place with different timescales (including the diurnal one) in
surface and subsurface seawater. This review also discusses these collective
influences to assess their potential detrimental effects to marine organisms,
and of ecosystem processes and services. Our review of the effects operating
in synergy with ocean acidification will provide a broad insight into the
potential impact of acidification itself on biological processes. The
foreseen danger to marine organisms by acidification is in fact expected to
be amplified by several concurrent and interacting phenomena
Impaired thymic iNKT cell differentiation at early precursor stage in murine haploidentical bone marrow transplantation with GvHD
IntroductionEarly recovery of donor-derived invariant natural killer T (iNKT) cells are associated with reduced risk of graft-versus-host disease (GvHD) and overall survival. Patients with severe GvHD, however, had much slower iNKT cell reconstitution relative to conventional T cells.MethodsTo characterize the delay of iNKT cell reconstitution and explore its possible causes, we used a haploidentical bone marrow transplantation (haplo-BMT) mouse model with GvHD. We found the delayed recovery of thymic and peripheral iNKT cell numbers with markedly decreased thymic NKT1 subset in GvHD mice. The defective generation of thymic iNKT precursors with egress capability contributed to the reduced peripheral iNKT cells in GvHD mice. We further identified intermediate NK1.1- NKT1 precursor subpopulations under steady-state conditions and found that the differentiation of these subpopulations was impaired in the thymi of GvHD mice. Detailed characterization of iNKT precursors and thymic microenvironment showed a close association of elevated TCR/co-stimulatory signaling provided by double positive thymocytes and macrophages with defective down-regulation of proliferation, metabolism, and NKT2 signature in iNKT precursor cells. Correspondingly, NKT2 but not NKT1 differentiation was favored in GvHD mice.DiscussionThese data underline the important roles of TCR and co-stimulatory signaling in the differentiation of thymic iNKT subsets under transplantation conditions
Single-Cell Transcriptome Analyses Reveal Signals to Activate Dormant Neural Stem Cells
SummaryThe scarcity of tissue-specific stem cells and the complexity of their surrounding environment have made molecular characterization of these cells particularly challenging. Through single-cell transcriptome and weighted gene co-expression network analysis (WGCNA), we uncovered molecular properties of CD133+/GFAP− ependymal (E) cells in the adult mouse forebrain neurogenic zone. Surprisingly, prominent hub genes of the gene network unique to ependymal CD133+/GFAP− quiescent cells were enriched for immune-responsive genes, as well as genes encoding receptors for angiogenic factors. Administration of vascular endothelial growth factor (VEGF) activated CD133+ ependymal neural stem cells (NSCs), lining not only the lateral but also the fourth ventricles and, together with basic fibroblast growth factor (bFGF), elicited subsequent neural lineage differentiation and migration. This study revealed the existence of dormant ependymal NSCs throughout the ventricular surface of the CNS, as well as signals abundant after injury for their activation
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