Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 4 de 4
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Mar Pollut Bull ; 150: 110710, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753567

RESUMO

Existing marine bioregions covering the Pacific Ocean are conceptualised at spatial scales that are too broad for national marine spatial planning. Here, we developed the first combined oceanic and coastal marine bioregionalisation at national scales, delineating 262 deep-water and 103 reef-associated bioregions across the southwest Pacific. The deep-water bioregions were informed by thirty biophysical environmental variables. For reef-associated environments, records for 806 taxa at 7369 sites were used to predict the probability of observing taxa based on environmental variables. Both deep-water and reef-associated bioregions were defined with cluster analysis applied to the environmental variables and predicted species observation probabilities, respectively to classify areas with high taxonomic similarity. Local experts further refined the delineation of the bioregions at national scales for four countries. This work provides marine bioregions that enable the design of ecologically representative national systems of marine protected areas within offshore and inshore environments in the Pacific.


Assuntos
Biodiversidade , Conservação dos Recursos Naturais , Recifes de Corais , Análise por Conglomerados , Oceanos e Mares , Oceano Pacífico
2.
Phys Chem Chem Phys ; 19(41): 28232-28238, 2017 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-29027561

RESUMO

Charge selective asymmetric nanochannels are used for a variety of applications, such as nanofluidic sensing devices and energy conversion applications. In this paper, we numerically investigate the influence of an applied temperature difference over tapered nanochannels on the resulting charge transport and flow behavior. Using a temperature-dependent formulation of the coupled Poisson-Nernst-Planck and Navier-Stokes equations, various nanochannel geometries are investigated. Temperature has a large influence on the total ion transport, as the diffusivity of ions and viscosity of the solution are strongly affected by temperature. We find that the selectivity of the nanochannels is enhanced with increasing asymmetry ratios, while the total current is reduced at higher asymmetry cases. Most interestingly, we find that applying a temperature gradient along the electric field and along the asymmetry direction of the nanochannel enhances the selectivity of the tapered channels even further, while a temperature gradient countering the electric field reduces the selectivity of the nanochannel. Current rectification is enhanced in asymmetric nanochannels if a temperature gradient is applied, independent of the direction of the temperature difference. However, the degree of rectification is dependent on the direction of the temperature gradient with respect to the channel geometry and the electric field direction. The enhanced selectivity of nanochannels due to applied temperature gradients could result in more efficient operation in energy harvesting or desalination applications, motivating experimental investigations.

3.
Biomed Pharmacother ; 58 Suppl 1: S150-87, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15754855

RESUMO

"Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scientific research?" A simple photograph of the planet earth from outer space was one of the greatest contributions of space exploration. It drove home in a glance that human survival depends upon the wobbly dynamics in a thin and fragile skin of water and gas that covers a small globe in a mostly cold and vast universe. This image raised the stakes in understanding our place in that universe, in finding out where we came from and in choosing a path for survival. Since that landmark photograph was taken, new astronomical and biomedical information and growing computer power have been revealing that organic life, including human life, is and has been connected to invisible (non-photic) forces, in that vast universe in some surprising ways. Every cell in our body is bathed in an external and internal environment of fluctuating magnetism. It is becoming clear that the fluctuations are primarily caused by an intimate and systematic interplay between forces within the bowels of the earth--which the great physician and father of magnetism William Gilbert called a 'small magnet'--and the thermonuclear turbulence within the sun, an enormously larger magnet than the earth, acting upon organisms, which are minuscule magnets. It follows and is also increasingly apparent that these external fluctuations in magnetic fields can affect virtually every circuit in the biological machinery to a lesser or greater degree, depending both on the particular biological system and on the particular properties of the magnetic fluctuations. The development of high technology instruments and computer power, already used to visualize the human heart and brain, is furthermore making it obvious that there is a statistically predictable time structure to the fluctuations in the sun's thermonuclear turbulence and thus to its magnetic interactions with the earth's own magnetic field and hence a time structure to the magnetic fields in organisms. Likewise in humans, and in at least those other species that have been studied, computer power has enabled us to discover statistically defined endogenous physiological rhythms and further direct effects that are associated with these invisible geo- and heliomagnetic cycles. Thus, what once might have been dismissed as noise in both magnetic and physiological data does in fact have structure. And we may be at the threshold of understanding the biological and medical meaning and consequences of these patterns and biological-astronomical linkages as well. Structures in time are called chronomes; their mapping in us and around us is called chronomics. The scientific study of chronomes is chronobiology. And the scientific study of all aspects of biology related to the cosmos has been called astrobiology. Hence we may dub the new study of time structures in biology with regard to influences from cosmo- helio- and geomagnetic rhythms chronoastrobiology. It has, of course, been understood for centuries that the movements of the earth in relation to the sun produce seasonal and daily cycles in light energy and that these have had profound effects on the evolution of life. It is now emerging that rhythmic events generated from within the sun itself, as a large turbulent magnet in its own right, can have direct effects upon life on earth. Moreover, comparative studies of diverse species indicate that there have also been ancient evolutionary effects shaping the endogenous chronomic physiological characteristics of life. Thus the rhythms of the sun can affect us not only directly, but also indirectly through the chronomic patterns that solar magnetic rhythms have created within our physiology in the remote past. For example, we can document the direct exogenous effects of given specific solar wind events upon human blood pressure and heart rate. We also have evidence of endogenous internal rhythms in blood pressure and heart rate that are close to but not identical to the period length of rhythms in the solar wind. These were installed genetically by natural selection at some time in the distant geological past. This interpretive model of the data makes the prediction that the internal and external influences on heart rate and blood pressure can reinforce or cancel each other out at different times. A study of extensive clinical and physiological data shows that the interpretive model is robust and that internal and external effects are indeed augmentative at a statistically significant level. Chronoastrobiological studies are contributing to basic science--that is, our understanding is being expanded as we recognize heretofore unelaborated linkages of life to the complex dynamics of the sun, and even to heretofore unelaborated evolutionary phenomena. Once, one might have thought of solar storms as mere transient 'perturbations' to biology, with no lasting importance. Now we are on the brink of understanding that solar turbulences have played a role in shaping endogenous physiological chronomes. There is even documentation for correlations between solar magnetic cycles and psychological swings, eras of belligerence and of certain expressions of sacred or religious feelings. Chronoastrobiology can surely contribute to practical applications as well as to basic science. It can help develop refinements in our ability to live safely in outer space, where for example at the distance of the moon the magnetic influences of the sun will have an effect upon humans unshielded by the earth's native magnetic field. We should be better able to understand these influences as physiological and mechanical challenges, and to improve our estimations of the effects of exposure. Chronoastrobiology moreover holds great promise in broadening our perspectives and powers in medicine and public health right here upon the surface of the earth. Even the potential relevance of chronoastrobiology for practical environmental and agricultural challenges cannot be ruled out at this early stage in our understanding of the apparently ubiquitous effects of magnetism and hence perhaps of solar magnetism on life. The evidence already mentioned that fluctuations in solar magnetism can influence gross clinical phenomena such as rates of strokes and heart attacks, and related cardiovascular variables such as blood pressure and heart rate, should illustrate the point that the door is open to broad studies of clinical implications. The medical value of better understanding magnetic fluctuations as sources of variability in human physiology falls into several categories: 1) The design of improved analytical and experimental controls in medical research. Epidemiological analyses require that the multiple sources causing variability in physiological functions and clinical phenomena be identified and understood as thoroughly as possible, in order to estimate systematic alterations of any one variable. 2) Preventive medicine and the individual patients'care. There are no flat 'baselines', only reference chronomes. Magnetic fluctuations can be shown statistically to exacerbate health problems in some cases. The next step should be to determine whether vulnerable individuals can be identified by individual monitoring. Such vulnerable patients may then discover that they have the option to avoid circumstances associated with anxiety during solar storms, and/or pay special attention to their medication or other treatments. Prehabilitation by self-help can hopefully complement and eventually replace much costly rehabilitation. 3) Basic understanding of human physiological mechanisms. The chronomic organization of physiology implies a much more subtle dynamic integration of functions than is generally appreciated. All three categories of medical value in turn pertain to the challenges for space science of exploring and colonizing the solar system. The earth's native magnetic field acts like an enormous umbrella that offers considerable protection on the surface from harsh solar winds of charged particles and magnetic fluxes. The umbrella becomes weaker with distance from the earth and will offer little protection for humans, other animals, and plants in colonies on the surface of the moon or beyond. Thus it is important before more distant colonization is planned or implemented to better understand those magnetism-related biological- solar interactions that now can be studied conveniently on earth. (ABSTRACT TRUNCATED)


Assuntos
Fenômenos Cronobiológicos/fisiologia , Evolução Molecular , Filogenia , Projetos de Pesquisa , Atividade Solar , Conferências de Consenso como Assunto , Humanos , Tempo
4.
Biomed Pharmacother ; 57 Suppl 1: 58s-76s, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-14572679

RESUMO

Self-experimentation concerns not only scientists, but also each individual for the sake of his/her chronobiologic health and science literacy, eventually to be acquired in primary and secondary education. Public education ensures that everybody who knows how to read or write can dispense with the service of a costly scribe. At all ages, public education can teach equally well how to find out whether one's blood pressure (BP) and heart rate (HR) responds to an increase in sodium intake with a rise, with no change or with a decrease in BP. This task and many others could become a matter of informed self-surveillance. Whenever there are inter-individual, sometimes opposite differences in response, government-sponsored trials on groups that do not consider such differences cannot solve what only the individual can do, at first by help from schools. Eventually special institutions may be designed for chronomics, the monitoring, interpretation and archivization of chronomes (time structures; from chronos = time and nomos = rule) of biological variables, also charged with a demographic analyzing and reporting system. Each individual's properly coded record, to guard confidentiality, becomes part of a promptly accessible database for one's own needs and for society's requirements. What individuals and small groups started as chronobiology, what is immediately available on back burners, as a service by an international project on the biosphere and the cosmos (BIOCOS) (corne001@umn.edu) could become a public system of planned surveillance archivization of one's rhythms from womb to tomb. Alterations of a rhythm's amplitude or acrophase or of a deterministic or other chaotic endpoint, such as a correlation dimension and approximate entropy, or of a standard deviation, among a multitude of other endpoints, can signal (in the otherwise neglected normal range) reversible risk elevations. If these elevated risks are detected and prompt the institution of countermeasures, such prehabilitation can save the cost of rehabilitation or of long-term care after morbid events; suffering also can be prevented such as that by those who are unlucky enough to helplessly survive a massive brain, heart or societal "stroke". As an equally important dividend, science gains in basic and applied terms, as illustrated herein by the demonstration of a trans-year, an approximately 1.3 to 1.6-year, heretofore unknown component of the human BP and HR spectrum, beating with the circannual component and characterizing the same data. Chronomically interpreted self-monitoring is a civic duty for both one's health and everybody's science.


Assuntos
Monitorização Ambulatorial da Pressão Arterial/métodos , Fenômenos Cronobiológicos , Atividade Solar , Vento , Humanos , Autocuidado/métodos , Fatores de Tempo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...