scholarly journals Unicellular-Multicellular Evolutionary Branching Driven by Resource Limitations

2021 ◽  
Author(s):  
Adriano Bonforti ◽  
Ricard Sole
Keyword(s):  
Life Forms ◽  
Limited Resources ◽  
Evolutionary Branching ◽  
Resource Limitations ◽  
Evolutionary Innovation ◽  
Multicellular Aggregates ◽  
Dividing Cells ◽  
Intermediate Domain ◽  
Critical Resource ◽  
Two Phases

Multicellular life forms have evolved many times in our planet, suggesting that this is a common evolutionary innovation. Multiple advantages have been proposed for multicellularity (MC) to emerge. In this paper we address the problem of how the first precondition for multicellularity, namely "stay together" might have occurred under spatially limited resources exploited by a population of unicellular agents. Using a minimal model of evolved cell-cell adhesion among growing and dividing cells that exploit a localised resource with a given size, we show that a transition occurs at a critical resource size separating a phase of evolved multicellular aggregates from a phase where unicellularity (UC) is favoured. The two phases are separated by an intermediate domain where where both UC and MC can be selected by evolution. This model provides a minimal approach to the early stages that were required to transition from Darwinian individuality to cohesive groups of cells associated with a physical cooperative effect: when resources are present only in a localised portion of the habitat, MC is a desirable property as it helps cells to keep close to the available local nutrients.

Late Quaternary Glaciation of the Tropical Andes

2007 ◽  
Author(s):  
Geoffrey O. Seltzer
Keyword(s):  
South America ◽  
Late Quaternary ◽  
Life Forms ◽  
Mean Annual Temperature ◽  
Tropical Andes ◽  
The Andes ◽  
Significant Depression ◽  
Two Phases ◽  
Patagonian Andes ◽  
Glacial Tills

The effects of climate change are intrinsic features of Earth’s landscapes, and South America is no exception. Abundant evidence bears witness to the changes that have shaped the continent over time—from the glacial tillites inherited from late Paleozoic Gondwana to recent terrigenous sediments and life forms trapped in alluvial, lacustrine, and nearby marine deposits. Preeminent among this evidence are the landforms and sediments derived from the late Cenozoic glaciations of the Andes, which have been the focus of so much recent and ongoing research. Because South America has long been a mainly tropical and subtropical continent, most of it escaped the direct effects of these glaciations. Nevertheless, portions of the continent extend sufficiently far poleward and rise high enough to attract snowfall and promote glaciers today. Glaciers were more emphatically present during Pliocene and Pleistocene cold stages, and it is their legacies that provide information about the changing environments of those times, and more especially of the past 30,000 years. There is evidence for glaciation in the tropical and extratropical Andes as early as Pliocene time (Clapperton, 1993). In southern South America, along the eastern side of the Patagonian Andes, Mercer (1976) dated a series of basalts interbedded with glacial tills that suggest multiple glacial advances after ~3.6 Ma (million years before present). In the La Paz Valley, Bolivia, volcanic ashes dated by K/Ar (potassium/argon) methods are interbedded with glacial tills indicative of at least two phases of glaciation in the late Pliocene, at 3.27 and 2.20 Ma (Clapperton, 1979, 1993). This evidence for early glaciation in disparate parts of the Andes indicates that portions of the cordillera were high enough and climatic variations were great enough in the Pliocene for glaciers to form long before the cold episodes of the Pleistocene. Glacial deposits in Ecuador, Perú, and Bolivia provide evidence for climate variability in tropical South America in the recent geological past. In the late Pleistocene, glacier equilibrium-line altitudes were as much as 1,200 m lower than they are today on the eastern slopes of the Andes, indicative of a significant depression in mean annual temperature in the tropics at maximum glaciation (e.g., Klein et al., 1999).

Joint Transferable Dictionary Learning and View Adaptation for Multi-view Human Action Recognition

2021 ◽  
Vol 15 (2) ◽  
pp. 1-23
Author(s):  
Bin Sun ◽  
Dehui Kong ◽  
Shaofan Wang ◽  
Lichun Wang ◽  
Baocai Yin
Keyword(s):  
Action Recognition ◽  
Dictionary Learning ◽  
Human Action Recognition ◽  
Human Action ◽  
Individual Characteristics ◽  
Locality Preservation ◽  
Balanced Distribution ◽  
Common Domain ◽  
Intermediate Domain ◽  
Two Phases

Multi-view human action recognition remains a challenging problem due to large view changes. In this article, we propose a transfer learning-based framework called transferable dictionary learning and view adaptation (TDVA) model for multi-view human action recognition. In the transferable dictionary learning phase, TDVA learns a set of view-specific transferable dictionaries enabling the same actions from different views to share the same sparse representations, which can transfer features of actions from different views to an intermediate domain. In the view adaptation phase, TDVA comprehensively analyzes global, local, and individual characteristics of samples, and jointly learns balanced distribution adaptation, locality preservation, and discrimination preservation, aiming at transferring sparse features of actions of different views from the intermediate domain to a common domain. In other words, TDVA progressively bridges the distribution gap among actions from various views by these two phases. Experimental results on IXMAS, ACT4 2 , and NUCLA action datasets demonstrate that TDVA outperforms state-of-the-art methods.

scholarly journals Efficiency of pooled surveillance testing in academic labs to detect and inhibit COVID-19 outbreaks

Bioanalysis ◽  
2021 ◽  
Author(s):  
John C Sitko ◽  
James Jordan Steel ◽  
Erin A Almand ◽  
Christopher A Cullenbine ◽  
Joseph W Rohrer ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Processing Time ◽  
Financial Burden ◽  
Limited Resources ◽  
Chain Reaction ◽  
Surveillance Strategy ◽  
Resource Limitations ◽  
Reagent Cost ◽  
Academic Faculty ◽  
Polymerase Chain

Robust surveillance testing is a key strategic plan to prevent COVID-19 outbreaks and slow the spread of the SARS-CoV-2 pandemic; however, limited resources, facilities and time often impair the implementation of a widespread surveillance effort. To mitigate these resource limitations, we employed a strategy of pooling samples, reducing reagent cost and processing time. Through utilizing academic faculty and labs, successful pooled surveillance testing was conducted throughout Fall 2020 semester to detect positive SARS-CoV-2 infections in a population of 4400 students. During the semester, over 25,000 individual COVID status evaluations were made by pooling eight individual samples into one quantitative reverse transcription polymerase chain reaction. This pooled surveillance strategy was highly effective at detecting infection and significantly reduced financial burden and cost by $3.6 million.

scholarly journals Measuring the effectiveness of marketing activities use in relation to company size

2013 ◽  
Vol 61 (2) ◽  
pp. 493-500 ◽  
Author(s):  
Lucie Sychrová
Keyword(s):  
Limited Resources ◽  
Company Size ◽  
Structure Questionnaire ◽  
Primary Research ◽  
Chi Square ◽  
Marketing Effectiveness ◽  
Chi Square Test ◽  
Marketing Activities ◽  
Two Phases ◽  
The Relationship

The aim of this paper is to research the relationship between measurements of effectiveness of marketing activities and company size. An analysis of the economic sources, professional publications, analysis and reports of previous research shows that the concept of measuring of effectiveness is one of the key themes, which economists always pay much attention. It is a criterion that helps to rationally decide on the use limited resources to meet the needs that are not limited. This topic deals with numerous domestic and foreign literatures. The authors are not only different concepts of effectiveness, but also the using terminology. There are multiple definitions of terms “effectiveness” For the same purpose and meaning. The same concept is often defined semantically different. Therefore, every company has a strong interest to be in all their activities more effectively than the competition. Logical response to changes and requirements of nowadays is using a combination of lot of methods to measure marketing effectiveness. Methods used for this article includes two phases. The first it was gained date by primary research, using a structure questionnaire and processed by statistical software SPSS. Research sample consists 115 companies operating in the Czech environment, which was chosen at random. There is investigated the correlation between measuring the effectiveness of marketing activities and company size. The second part investigated the dependence between the choice of metrics used to measure the effectiveness and company size. The results of the research showed that there is no correlation between measuring the effectiveness of marketing activities and company size. The value of Pearson Chi-Square test is greater than 0.05, it is 0.187. We can presume that dependency does not exist or it is small for these. Value of Symmetric measures is 0.432, which means that the intensity tends to be small rather than high.

scholarly journals Surgical intervention on uterine fibromyoma in a country with limited resources: case of the gynaecology-obstetrics department of the Communal Medical Centre of Ratoma Conakry - Guinea

2020 ◽  
Vol 9 (6) ◽  
pp. 2227
Author(s):  
Mamadou H. Diallo ◽  
Ibrahima S. Balde ◽  
Amadou D. Diallo ◽  
Ousmane Balde ◽  
Fatoumata B. Diallo ◽  
...  
Keyword(s):  
Surgical Intervention ◽  
Vaginal Surgery ◽  
Limited Resources ◽  
Physical Sign ◽  
Less Invasive Surgery ◽  
Nulliparous Women ◽  
Large Uterus ◽  
Operative Indications ◽  
Two Phases ◽  
Technical Platform

Background: In developing countries, treatment of uterine fibromyoma is confronted with numerous problems, namely: financial inaccessibility to the proposed treatments, fear of surgery and the weakness of the technical platform. The objectives of the study were to calculate the frequency of uterine fibromyomas, describe the socio-demographic characteristics of patients, identify the main clinical data and to describe the modalities of surgical management.Methods: It was a mixed descriptive study, cumulative over a period of 5 years (60 months) with data collection in two phases: a 4-year retrospective study from January 1, 2015 to December 31, 2018 and a 1-year prospective study from January 1, 2019 to December 31, 2019.Results: Authors collected 135 cases of uterine fibromyomas operated on out of a total of 260 cases of gynaecological pathologies, i.e. a frequency of 51.92%. Nulliparous women were the most concerned (45.18%), and women who attended school (60%) and those who did not attend school (40%). Women at home and housewives accounted for 42.20% and 54.07% respectively. Clinically, the circumstances of discovery were dominated by menometrorrhagia and menorrhagia respectively 77.77% and 68.14%. The large uterus was the most frequent physical sign found in 96.29% of cases. Uterine fibromyomas were recorded in 86.6% of cases in women with genital activity. The operative indications were dominated by the large polymyomatous uterus (64.44%), followed by hemorrhagic fibroma (18.52%) The surgical treatment was conservative in 92.60%. The total hysterectomy was performed in 7.40. Lethality was 1.4%.Conclusions: The surgical management of fibroids contrasts conservative treatment (myomectomy) with radical treatment (hysterectomy) with multiple possible approaches (hysteroscopy, vaginal surgery, laparoscopy or laparotomy). In this context, only laparotomy was possible due to lack of equipment. Laparoscopy and hysteroscopy equipment are necessary for less invasive surgery.

scholarly journals Energy- and Resource-Aware Computation Offloading for Complex Tasks in Edge Environment

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Kai Peng ◽  
Bohai Zhao ◽  
Shengjun Xue ◽  
Qingjia Huang
Keyword(s):  
Mobile Devices ◽  
Mobile Network ◽  
Mobile Terminal ◽  
Computation Offloading ◽  
Limited Resources ◽  
Battery Life ◽  
Complex Tasks ◽  
Resource Limitations ◽  
Resource Aware ◽  
Nondominated Sorting

Mobile users typically have a series of complex tasks consisting of time-constrained workflows and concurrent workflows that need to be processed. However, these tasks cannot be performed directly locally due to resource limitations of the mobile terminal, especially for battery life. Fortunately, mobile edge computing (MEC) has been recognized as a promising technology which brings abundant resource at the edge of mobile network enabling mobile devices to overcome the resource and capacity constraints. However, edge servers, such as cloudlets, are heterogeneous and have limited resources. Thus, it is important to make an appropriate offloading strategy to maximize the utility of each cloudlet. In view of this, the time consumption and energy consumption of mobile devices and resource utilization of cloudlets have been taken into consideration in this study. Firstly, a multiconstraint workflow mode has been established, and then a multiobjective optimization mode is formulated. Technically, an improved optimization algorithm is proposed to address this mode based on Nondominated Sorting Genetic Algorithm II. Both extensive experimental evaluations and detailed theoretical analysis are conducted to show that the proposed method is effective and efficiency.

scholarly journals Consensus in Surgical Practice during the COVID-19 Pandemic: An Appraisal of the Literature

2020 ◽  
Author(s):  
Ravindri Jayasinghe ◽  
Umesh Jayarajah ◽  
Sanjeewa Seneviratne
Keyword(s):  
Disease Transmission ◽  
Surgical Care ◽  
Disease Spread ◽  
Limited Resources ◽  
Surgical Practice ◽  
Resource Limitations ◽  
Aerosol Generation ◽  
Surgical Units ◽  
Operating Theatres ◽  
Risk Of Disease

The coronavirus disease-2019 (COVID-19) pandemic is an ongoing pandemic caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Although COVID-19 pandemic is not a direct surgical problem, its impact on the surgical units has been substantial. Many operations have been cancelled or deferred due to risk of disease spread and staff shortages. Operating theatres are identified as areas of high risk of disease transmission due to aerosol generation during the surgical procedures and prolonged patient contact. Resource limitations, including lack of personal protective equipment (PPE) and limited availability of testing, continue to expose the surgical community to COVID-19. In this review, evidence and consensus guidelines on surgical practice during the COVID-19 pandemic are summarised and described. Immediate action is deemed essential to ensure unhindered provision of surgical care while optimizing the use of limited resources and ensuring staff safety.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

Precipitation of NiHfsi phase in NiAl single crystals containing Hf

1995 ◽  
Vol 53 ◽  
pp. 532-533
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
R. Darolia
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
High Temperature Strength ◽  
Bridgman Technique ◽  
Shell Mold ◽  
Third Phase ◽  
Unknown Phase ◽  
Transmission Electron ◽  
Two Phases ◽  
Nial Matrix

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.

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