79 research outputs found
Spatially explicit approach to estimation of total population abundance in field surveys.
Population abundance is fundamental in ecology and conservation biology, and provides essential information for predicting population dynamics and implementing conservation actions. While a range of approaches have been proposed to estimate population abundance based on existing data, data deficiency is ubiquitous. When information is deficient, a population estimation will rely on labor intensive field surveys. Typically, time is one of the critical constraints in conservation, and management decisions must often be made quickly under a data deficient situation. Hence, it is important to acquire a theoretical justification for survey methods to meet a required estimation precision. There is no such theory available in a spatially explicit context, while spatial considerations are critical to any field survey. Here, we develop a spatially explicit theory for population estimation that allows us to examine the estimation precision under different survey designs and individual distribution patterns (e.g. random/clustered sampling and individual distribution). We demonstrate that clustered sampling decreases the estimation precision when individuals form clusters, while sampling designs do not affect the estimation accuracy when individuals are distributed randomly. Regardless of individual distribution, the estimation precision becomes higher with increasing total population abundance and the sampled fraction. These insights provide theoretical bases for efficient field survey designs in information deficiency situations
Enhanced collectivity in 74Ni
The neutron-rich nucleus 74Ni was studied with inverse-kinematics inelastic
proton scattering using a 74Ni radioactive beam incident on a liquid hydrogen
targetat a center-of-mass energy of 80 MeV. From the measured de-excitation
gamma-rays, the population of the first 2+ state was quantified. The
angle-integrated excitation cross section was determined to be 14(4) mb. A
deformation length of delta = 1.04(16) fm was extracted in comparison with
distorted wave theory, which suggests that the enhancement of collectivity
established for 70Ni continues up to 74Ni. A comparison with results of shell
model and quasi-particle random phase approximation calculations indicates that
the magic character of Z = 28 or N = 50 is weakened in 74Ni
Metal-Insulator oscillations in a Two-dimensional Electron-Hole system
The electrical transport properties of a bipolar InAs/GaSb system have been
studied in magnetic field. The resistivity oscillates between insulating and
metallic behaviour while the quantum Hall effect shows a digital character
oscillating from 0 to 1 conducatance quantum e^2/h. The insulating behaviour is
attributed to the formation of a total energy gap in the system. A novel looped
edge state picture is proposed associated with the appearance of a voltage
between Hall probes which is symmetric on magnetic field reversal.Comment: 4 pages, 5 Postscript figures: revised versio
Nuclear Alpha-Particle Condensates
The -particle condensate in nuclei is a novel state described by a
product state of 's, all with their c.o.m. in the lowest 0S orbit. We
demonstrate that a typical -particle condensate is the Hoyle state
( MeV, state in C), which plays a crucial role for
the synthesis of C in the universe. The influence of antisymmentrization
in the Hoyle state on the bosonic character of the particle is
discussed in detail. It is shown to be weak. The bosonic aspects in the Hoyle
state, therefore, are predominant. It is conjectured that -particle
condensate states also exist in heavier nuclei, like O,
Ne, etc. For instance the state of O at MeV
is identified from a theoretical analysis as being a strong candidate of a
condensate. The calculated small width (34 keV) of ,
consistent with data, lends credit to the existence of heavier Hoyle-analogue
states. In non-self-conjugated nuclei such as B and C, we discuss
candidates for the product states of clusters, composed of 's,
triton's, and neutrons etc. The relationship of -particle condensation
in finite nuclei to quartetting in symmetric nuclear matter is investigated
with the help of an in-medium modified four-nucleon equation. A nonlinear order
parameter equation for quartet condensation is derived and solved for
particle condensation in infinite nuclear matter. The strong qualitative
difference with the pairing case is pointed out.Comment: 71 pages, 41 figures, review article, to be published in "Cluster in
Nuclei (Lecture Notes in Physics) - Vol.2 -", ed. by C. Beck,
(Springer-Verlag, Berlin, 2011
A theory for ecological survey methods to map individual distributions
Spatially explicit approaches are widely recommended for ecosystem management. The quality of the data, such as presence/absence or habitat maps, affects the management actions recommended and is, therefore, key to management success. However, available data are often biased and incomplete. Previous studies have advanced ways to resolve data bias and missing data, but questions remain about how we design ecological surveys to develop a dataset through field surveys. Ecological surveys may have multiple spatial scales, including the spatial extent of the target ecosystem (observation window), the resolution for mapping individual distributions (mapping unit), and the survey area within each mapping unit (sampling unit). We developed an ecological survey method for mapping individual distributions by applying spatially explicit stochastic models. We used spatial point processes to describe individual spatial placements using either random or clustering processes. We then designed ecological surveys with different spatial scales and individual detectability. We found that the choice of mapping unit affected the presence mapped fraction, and the fraction of the total individuals covered by the presence mapped patches. Tradeoffs were found between these quantities and the map resolution, associated with equivalent asymptotic behaviors for both metrics at sufficiently small and large mapping unit scales. Our approach enabled consideration of the effect of multiple spatial scales in surveys, and estimation of the survey outcomes such as the presence mapped fraction and the number of individuals situated in the presence detected units. The developed theory may facilitate management decision-making and inform the design of monitoring and data gathering
Gradient Descent Optimization in Gene Regulatory Pathways
BACKGROUND: Gene Regulatory Networks (GRNs) have become a major focus of interest in recent years. Elucidating the architecture and dynamics of large scale gene regulatory networks is an important goal in systems biology. The knowledge of the gene regulatory networks further gives insights about gene regulatory pathways. This information leads to many potential applications in medicine and molecular biology, examples of which are identification of metabolic pathways, complex genetic diseases, drug discovery and toxicology analysis. High-throughput technologies allow studying various aspects of gene regulatory networks on a genome-wide scale and we will discuss recent advances as well as limitations and future challenges for gene network modeling. Novel approaches are needed to both infer the causal genes and generate hypothesis on the underlying regulatory mechanisms. METHODOLOGY: In the present article, we introduce a new method for identifying a set of optimal gene regulatory pathways by using structural equations as a tool for modeling gene regulatory networks. The method, first of all, generates data on reaction flows in a pathway. A set of constraints is formulated incorporating weighting coefficients. Finally the gene regulatory pathways are obtained through optimization of an objective function with respect to these weighting coefficients. The effectiveness of the present method is successfully tested on ten gene regulatory networks existing in the literature. A comparative study with the existing extreme pathway analysis also forms a part of this investigation. The results compare favorably with earlier experimental results. The validated pathways point to a combination of previously documented and novel findings. CONCLUSIONS: We show that our method can correctly identify the causal genes and effectively output experimentally verified pathways. The present method has been successful in deriving the optimal regulatory pathways for all the regulatory networks considered. The biological significance and applicability of the optimal pathways has also been discussed. Finally the usefulness of the present method on genetic engineering is depicted with an example
Cultural Adaptation of the Actionable Health App Evaluation in Japan: Protocol for a Web-Based Modified Delphi Expert Consensus Study
BackgroundWith an increase in both the number of mental health disorders people are experiencing and the difficulty in accessing mental health care, the demand for accessible mental health care services has increased. The use of mobile devices has allowed people to receive care in their daily lives without restrictions on time or location. However, the majority of publicly available mobile health apps are not evidence-based, and the top-rated apps are not always safe or user-friendly and may not offer clinically beneficial results.
ObjectiveThis study aims to create a cultural adaptation of the American Psychiatric Association’s comprehensive app evaluation framework in Japan using a web-based modified Delphi expert consensus.
MethodsA web-based modified Delphi study includes developing the Japanese version of the comprehensive app evaluation framework and 3 Delphi rounds. In the first round, our working group sends a questionnaire to the panelists, who then complete it. In the second and third rounds, the working group sends a questionnaire and a summary of the panelists’ answers based on each of the previous rounds. The panelists answer the questionnaires based on this summary. The summarization procedure is automated to help reduce the biases that can be generated when panelists’ answers are summarized and when the panelists receive them. The working group sends only the result of the summarization with the next round’s questionnaire. All interactions between the working group and the panelists will be conducted on Qualtrics (Qualtrics Japan LLC), a questionnaire platform. To culturally validate the comprehensive mental health app evaluation framework, participants from the following three categories will be recruited in Japan: (1) researchers, (2) practitioners, and (3) app developers.
ResultsThis study received funding from a crowdfunding campaign in Japan (April 2023). The Delphi study began in January 2023 and will be completed in December 2023. We had already completed the translation of the 105 original app evaluation item questions by December 2022.
ConclusionsWhile the need for treatment using mental health apps is increasing, no framework that can be used to develop a centralized database for health apps is available or accessible, and no consensus has been reached among stakeholders in Japan about an appropriate framework. The results of the web-based modified Delphi method presented in this paper may provide direction for the development and use of mental health apps in the future among the relevant stakeholders. Furthermore, this study will enhance recognition of the framework among researchers, clinicians, mental health app developers, and users, in addition to devising new instruments to help users or practitioners efficiently choose the right app for their situations.
International Registered Report Identifier (IRRID)PRR1-10.2196/4446
Species‐range‐size distributions: Integrating the effects of speciation, transformation, and extinction
The species-range size distribution is a product of speciation, transformation of range-sizes, and extinction. Previous empirical studies showed that it has a left-skewed lognormal-like distribution. We developed a new mathematical framework to study species-range-size distributions, one in which allopatric speciation, transformation of range size, and the extinction process are explicitly integrated. The approach, which we call the gain-loss-allopatric speciation model, allows us to explore the effects of various speciation scenarios. Our model captures key dynamics thought to lead to known range-size distributions. We also fitted the model to empirical range-size distributions of birds, mammals, and beetles. Since geographic range dynamics are linked to speciation and extinction, our model provides predictions for the dynamics of species richness. When a species-range-size distribution initially evolves away from the range sizes at which the likelihood of speciation is low, it tends to cause diversification slowdown even in the absence of (bio)diversity dependence in speciation rate. Using the mathematical model developed here, we give a potential explanation for how observed range-size distributions emerge from range-size dynamics. Although the framework presented is minimalistic, it provides a starting point for examining hypotheses based on more complex mechanisms
Observation of magnetophotoluminescence from a GaN/Al<sub>x</sub>Ga<sub>1-x</sub>N heterojunction
Magnetophotoluminescence has been studied from a single undoped GaN/AlxGa1-xN heterojunction with a linewidth of 2.5 meV. The peak originates from the recombination of a photoexcited hole with an electron in the two-dimensional electron gas (2DEG) formed as a result of spontaneous and piezoelectric polarizations at the interface. The photoluminescence intensity is strongly enhanced at filling factors corresponding to filled Landau levels as a result of the reduced screening of the Coulomb interaction by the 2DEG. This prevents the rapid diffusion of photoexcited holes away from the heterojunction. The energy of the magnetoexcitonic recombination indicates a very low value for the hole mass of 0.3m(0) close to the band edge in agreement with theory
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