Mutual Strength Research Articles

Complex Adaptive Systems: A Response to Luchins

Luchins (2003, Administration and Policy in Mental Health, 31(2), 183-186) distinguishes the mutual strengths and shortcomings of qualitative and quantitative approaches as applied to the complexities of evaluation psychiatric hospital functioning in particular, and behavioral healthcare practice in general. This brief response offers an examination of the complex interplay of factors within non-linear models in a conceptualization of complex adaptive systems for understanding causal factors in mental health administration as well as calling into question the myth of the relationship between measurement and hence control and understanding and prediction.

Species of plants and associated arbuscular mycorrhizal fungi mediate mycorrhizal responses to CO2 enrichment

AbstractIt has been suggested that enrichment of atmospheric CO2 should alter mycorrhizal function by simultaneously increasing nutrient‐uptake benefits and decreasing net C costs for host plants. However, this hypothesis has not been sufficiently tested. We conducted three experiments to examine the impacts of CO2 enrichment on the function of different combinations of plants and arbuscular mycorrhizal (AM) fungi grown under high and low soil nutrient availability. Across the three experiments, AM function was measured in 14 plant species, including forbs, C3 and C4 grasses, and plant species that are typically nonmycorrhizal. Five different AM fungal communities were used for inoculum, including mixtures of Glomus spp. and mixtures of Gigasporaceae (i.e. Gigaspora and Scutellospora spp.). Our results do not support the hypothesis that CO2 enrichment should consistently increase plant growth benefits from AM fungi, but rather, we found CO2 enrichment frequently reduced AM benefits. Furthermore, we did not find consistent evidence that enrichment of soil nutrients increases plant growth responses to CO2 enrichment and decreases plant growth responses to AM fungi.Our results show that the strength of AM mutualisms vary significantly among fungal and plant taxa, and that CO2 levels further mediate AM function. In general, when CO2 enrichment interacted with AM fungal taxa to affect host plant dry weight, it increased the beneficial effects of Gigasporaceae and reduced the benefits of Glomus spp. Future studies are necessary to assess the importance of temperature, irradiance, and ambient soil fertility in this response. We conclude that the affects of CO2 enrichment on AM function varies with plant and fungal taxa, and when making predictions about mycorrhizal function, it is unwise to generalize findings based on a narrow range of plant hosts, AM fungi, and environmental conditions.

La globalización en la educación superior europea. Pródromos para nuestra educación médica: The precursor of changes in Chilean medical education

At the present time, higher education is a central process shaping the society of knowledge. The mutual strength of society and education influence worldwide changes. Globalization, that mainly embraces politics and commerce, is also promoting changes in professional training, modifying programs, structures and the organization of superior education. The European example is attractive and has a great projection. It will cause a profound impact in culture, development and life of Europeans. Universities in Latin America, in an attempt to achieve the same objectives than their European counterparts, are experiencing premonitory changes, that will have the same effects as in Europe. In the medical area, several changes will occur and we will have to provide initiatives to facilitate these changes in a timely manner. The revision of the model in its inception, is convenient to assimilate changes in our culture.

Management of Plant Invasions: The Conflict of Perspective1

During the past decade, as the issue of plant invasion gained recognition in the public domain, both ecologists and weed scientists voluntarily or by mandate moved to provide their expertise to the management of invasive plants on public lands. Diverse views of nature carried to the table by ecologists and weed scientists have resulted in different priorities and opinions on management strategies. However, both groups share the goal of protecting natural resources for the public good. Efforts to achieve consensus among ecologists and weed scientists should acknowledge and resolve how and why the two groups come to different views of nature. Then, areas of mutual strength need to be identified so that improved management or restoration plans can be developed.Additional index words: Ecosystem management, restoration.

Suppression of chaos using mutual coupling

We demonstrate in this communication the suppression of chaos in a chaotic oscillator by establishing mutual coupling with an another weak periodic oscillator of the same kind. We have chosen specific locations of the state variable for the mutual coupling and the suppression of chaos is observed via period halving route as a result of increase in mutual coupling strength between the oscillators. The technique developed does not require any prior knowledge of the system dynamics and the system parameters are not changed explicitly. The method is expected to be useful for those physical chaotic systems in which direct accessibility of its parameters is either difficult or not possible.

Burst and spike synchronization of coupled neural oscillators

Neural excitability and the bifurcations involved in transitions from quiescence to oscillations largely determine the neuro-computational properties of neurons. Neurons near Hopf bifurcation fire in a small frequency range, respond preferentially to resonant excitation, and are easily synchronized. In the present paper we study the interaction of coupled elliptic bursters with non-resonant spike frequencies. Bursting behaviour arises from recurrent transitions between a quiescent state and repetitive firing, i.e. the rapid oscillatory behaviour is modulated by a slowly varying dynamical process. Bursting is referred to as elliptic bursting when the rest state loses stability via a Hopf bifurcation and the repetitive firing disappears via another Hopf bifurcation or a double limit cycle bifurcation. By studying the fast subsystem of two coupled bursters we obtain a reduced system of equations, allowing the description of synchronized and non-synchronized oscillations depending on frequency detuning and mutual coupling strength. We show that a certain 'overall' coupling constant must exceed a critical value depending on the detuning and the attraction rates in order that burst and spike synchronization can take place. The reduced system allows an analytical study of the bifurcation structure up to codimension-3 revealing a variety of stationary and periodic bifurcations which will be analysed in detail. Finally, the implications of the bifurcation structure for burst and spike synchronization are discussed.

Introduction

In 1994, the Japanese Foundation for AIDS Prevention(JFAP) and the University of California at San Francisco's Center for AIDS Prevention Studies(CAPS) initiated a 2-year collaborative research project with funding from the Center for Global Partnership. The emphasis of the project has been on exploring the ways in which Japan and the United States can benefit from each other's experience in AIDS prevention. Three general questions have guided our research: (a) In what areas do the experiences of Japan and the United States overlap sufficiently for them to pursue similar prevention strategies? (b) Can their different experiences, successes, and failures be mutually educational and beneficial? In which specific ways? (c) How can the United States and Japan work together to develop more effective prevention programs for other nations, particularly those in the Asian-Pacific region? Our first task was to bring together experts in AIDS prevention from Japan and the United States to learn more about the past and present trends of the disease in each country and to discuss current prevention policies, programs, and research. At the outset, there was a need to share basic information about AIDS in both countries. Although there has been more scientific and policy research about the disease in the United States than in Japan, there has been little interchange, and experts in neither country were well informed about AIDS prevention in the other country. [For an overview of AIDS policy in Japan, see Feldman EA, Yonemoto S. Japan: AIDS as a non-issue. In: Kirp DL, Bayer R, eds. AIDS in the industrialized democracies. New Brunswick, NJ: Rutgers University Press, 1992:339-60. ] At the first meeting, a multidisciplinary panel of Japanese and American experts in education, epidemiology, social/behavioral research, government/public health, nongovernmental organizations, law, and health policy identified topics of mutual interest. The participants then wrote papers summarizing a specific aspect of AIDS prevention from their national perspective, which were addressed at a second meeting. The papers that developed from these meetings form the basis of this special issue. Together, they summarize what is currently known about AIDS prevention in each country, its successes and failures, and the specific tasks that must be accomplished to build more effective AIDS prevention programs in the future. Bringing together AIDS prevention and policy experts from Japan and the United States has led to several important outcomes. Most American participants, although expert in their own nation's problems, were uninformed about AIDS in Japan, and the same was true for Japanese understanding of AIDS in the United States. This project has served to expand Japanese and United States perspectives, to stimulate new ideas, and to bring about innovative approaches to research. It has facilitated ongoing professional relationships that will engender further collaboration and intellectual exchange as well as program and policy development. More concretely, we have learned that Japan and the United States have many complementary strengths and weaknesses. In Japan, for example, widespread condom use is a tremendous asset in educating the population about safe sexual behavior. Sexually transmitted diseases are generally well controlled, and the centralized government bureaucracy is able to design and implement national programs. In addition, Japan has been forced from the outset to focus prevention efforts on the heterosexual population. Researchers from the United States have shared with their Japanese colleagues the knowledge gained in more than 10 years of the AIDS epidemic about how to efficiently collect data on HIV and AIDS, how to educate the public and caregivers, and how to target AIDS prevention messages. We have also discovered that our mutual strengths are threatened by similar problems: a lack of openness in both nations in discussing important aspects of AIDS prevention such as sex education, fear and prejudice by some in the medical community about treating AIDS patients, and incomplete epidemiologic information. In the collaborative research process, we have each been enriched by expanding beyond the confines of our own national perspective. We hope that our work will lead not only to greater cooperation and understanding between the United States and Japan in AIDS prevention but also to concrete changes in the way prevention is conceptualized and practiced that will result in behavior change and, ultimately, will save lives. Perhaps the greatest lesson learned has been that the prevention of AIDS in Japan and in the United States cannot be truly effective if the problems of other nations are not also addressed. We hope that the forging of institutional links between JFAP and CAPS will benefit those two nations and, as they work more closely together, will become part of the solution to one of the most serious and tragic problems of our time.

On the Role of the Nonlocal Hartree-Fock (HF) Exchange in Narrow-Band Materials

The influence of the nonlocal Hartree-Fock (HF) exchange in narrow-band materials with finite band gaps is analyzed. The mean-field Hamiltonian in the crystal orbital (CO) basis contains two k-dependent matrix elements responsible for the dispersion of the one-electron levels: the classical tight-binding integrals (kinetic energy of the electrons) that decay exponentially as well as the (non)local exchange. The asymptotic behavior of the two-electron potential is determined by the fall-off of the intercell bond-order matrices; their range exceeds significantly the spatial extension of the k-dependent one-electron integrals. The analytic structure of the HF dispersions of narrow-band systems (weak intercell interactions) is largely influenced by the magnitude of the Fermi-correlation beyond the direct neighbors. The associated ε(k) curves differ strongly from idealized tight-binding relations. The bands are broadened and show enhanced energy gradients in certain domains of k-space. Nonlinearities in the ε(k) relations are a direct consequence of finite neighbor's approximations adopted for the evaluation of the lattice sums. The analytic structures of such HF bands are intermediate between idealized tight-binding relations of covalent solids, on one side, and HF dispersions of metals in (nearly-)free electron-gas approximations, on the other, that show divergent ε(k) gradients at the Fermi level. The exchange influence in insulating narrow-band materials is restricted to the filled one-particle space; this is demonstrated by a perturbational analysis. The crucial importance of reliable numerical integration procedures for the determination of the intercell bond-order matrices is pointed out. Standard techniques may lead to artificial periodicities pretending unphysical decay properties of the electronic exchange. Dispersion patterns of a simple one-orbital model are analyzed as a function of the mutual strength of the kinetic hopping integrals and the HF exchange as well as the spatial extension of the k-dependent two-electron potential. The validity of the theoretical expectations deduced from simple model calculations is studied for two complex polymers. Important one-electron properties of one-dimensional (1 D) porphyrinato nickel(II) derivatives (2 and 3) are investigated by means of semiempirical SCF (self-consistent-field) HF INDO (intermediate neglect of differential overlap) CO calculations. The lattice spacings of 2 and 3 differ by 0.31 Å. This geometrical distinction allows for an inversion of the relative importance of the k-dependent one- and two-electron contributions to the mean-field operator. The exchange influence on the width of the HF dispersion in 3 exceeds the one-electron part by nearly one order of magnitude. It is shown that band structure properties of narrow-band systems are neither properly described by one-electron models of the Wolfsberg-Helmholtz-type nor by bare (unscreened) HF dispersions. The width of a mean-field band calculated within a nonlocal exchange approximation has to be corrected for quasi-particle (QP) interactions beyond the HF scheme (i.e., long-range and short-range correlations and relaxations) as well as for electron (optical) phonon interactions. The phononic coupling leads to a narrowing of the band width via Franck-Condon-like vibrational overlaps; this part is independent of the theoretical details of the electronic structure investigation. Important physical consequences of the exchange-control in narrow-band solids are shortly discussed.

Probability distribution of CW induced currents on randomly oriented subresonant loops and wires

The deterministic prediction of both transient and CW field coupling to large complex electrical systems poses such a formidable problem that other approaches to predicting the coupling may be useful The continuous wave coupling to a complicated electrical system is analyzed in terms of random small dipole interactions in the low-frequency limit (wavelengths \gg system components' sizes). Both random coupling to the incident wave and random interactions among the dipoles are considered. The variables being randomized are the incident direction and polarization, the sizes and orientations of the dipoles, the mutual coupling strengths, and the lumped load impedances. The resulting normalized current distributions are shown to be insensitive to the details of the model except at the extremely low and high percentiles. The magnetic dipole case is investigated in detail. Its resulting induced current distribution roughly resembles, but is not, a log-normal distribution with a standard deviation in the vicinity of \sim6 dB. This result provides insight into some recent measurements obtained for EMP transient field coupling to large systems. An important implication of the results is that for a variety of complicated systems, essentially consisting of many small elements that the coupling is dominated by low-frequency magnetic fields, the central parts of the induced current probability distributions are similar and nearly log-normal. However, conclusions based on the extrapolation of log-normality from measured values near the median to the extreme percentiles may be susceptible to sizeable errors. The electric dipole ease is presented very briefly here, only to the extent of its basic formulations. We refer interested readers to our original report for some basic results for this case and also for the effects caused by an elliptically polarized incident wave versus a linearly polarized one.

Mutual Magnetic Interactions and Oscillator Strengths in the First Spectrum of Oxygen

ABSTRACTThe effects of the spin-other-orbit and spin-spin interactions on the energy levels of the 2p3 3s configuration of oxygen are investigated, and they are found to make an appreciable contribution to the fine structure. The interactions are shown to have a negligible effect on the strengths of all the stronger lines of the 2p4-2p3 3s array, and the more important of the weaker transitions are likewise little affected. The value to be adopted for the radial integral involved in the absolute oscillator strengths is discussed, and numerical values of the oscillator strengths are given.