Phase and amplitude dynamics of nonlinearly coupled oscillators.

This paper addresses the amplitude and phase dynamics of a large system of nonlinearly coupled, non-identical damped harmonic oscillators, which is based on recent research in coupled oscillation in optomechanics. Our goal is to investigate the existence and stability of collective behaviour which occurs due to a play-off between the distribution of individual oscillator frequency and the type of nonlinear coupling. We show that this system exhibits synchronisation, where all oscillators are rotating at the same rate, and that in the synchronised state the system has a regular structure related to the distribution of the frequencies of the individual oscillators. Using a geometric description, we show how changes in the non-linear coupling function can cause pitchfork and saddle-node bifurcations which create or destroy stable and unstable synchronised solutions. We apply these results to show how in-phase and anti-phase solutions are created in a system with a bi-modal distribution of frequencies.

The slow death of psychiatric nursing: what next?

Nursing has always struggled for recognition and status, and there has always been exploitation and shortages, and no more so than in psychiatric settings. Today, however, nursing is in truly dire straits and, as a consequence, psychiatric nursing is more precariously positioned than ever. In order to think constructively about psychiatric nursing's future, it is crucial that this wider context in which it operates is fully appreciated, and this paper begins by summarizing the key features of this context from an international perspective. It is argued that dramatic changes occurring in 'Western' societies call for radical changes in public and professional thinking, and in their vision for health care in the future. Beginning with the general nursing context, this paper depicts the perilous state of psychiatric nursing and mental health care in Australia and elsewhere, and suggests some of the causal factors. It concludes by arguing that the future mental health workforce should be a graduate specialist who stands outside existing disciplinary identities.

Lipoxygenase inhibitors as potential cancer chemopreventives.

Mounting evidence suggests that lipoxygenase (LO)-catalyzed products have a profound influence on the development and progression of human cancers. Compared with normal tissues, significantly elevated levels of LO metabolites have been found in lung, prostate, breast, colon, and skin cancer cells, as well as in cells from patients with both acute and chronic leukemias. LO-mediated products elicit diverse biological activities needed for neoplastic cell growth, influencing growth factor and transcription factor activation, oncogene induction, stimulation of tumor cell adhesion, and regulation of apoptotic cell death. Agents that block LO-catalyzed activity may be effective in preventing cancer by interfering with signaling events needed for tumor growth. In fact, in a few studies, LO inhibitors have prevented carcinogen-induced lung adenomas and rat mammary gland cancers. During the past 10 years, pharmacological agents that specifically inhibit the LO-mediated signaling pathways are now commercially available to treat inflammatory diseases such as asthma, arthritis, and psoriasis. These well-characterized agents, representing two general drug effect mechanisms, are considered good candidates for clinical chemoprevention studies. One mechanism is inhibition of LO activity (5-LO and associated enzymes, or 12-LO); the second is leukotriene receptor antagonism. Although the receptor antagonists have high potential in treating asthma and other diseases where drug effects are clearly mediated by the leukotriene receptors, enzyme activity inhibitors may be better candidates for chemopreventive intervention, because inhibition of these enzymes directly reduces fatty acid metabolite production, with concomitant damping of the associated inflammatory, proliferative, and metastatic activities that contribute to carcinogenesis. However, because receptor antagonists have aerosol formulations and possible antiproliferative activity, they may also have potential, particularly in the lung, where topical application of such formulations is feasible.

Potential use of lipoxygenase inhibitors for cancer chemoprevention.

Increasing evidence suggests that lipoxygenase (LO)-catalysed metabolites have a profound influence on the development and progression of human cancers. Compared with normal tissues, significantly elevated levels of LO products have been found in breast tumours, colon cancers, lung, skin and prostate cancers, as well as in cells from patients with both acute and chronic leukaemias. LO-mediated products elicit diverse biological activities needed for neoplastic cell growth, influencing growth factor and transcription factor activation, oncogene induction, stimulation of tumour cell adhesion and regulation of apoptotic cell death. Agents that block LO catalytic activity may be effective in preventing cancer by interfering with signalling events needed for tumour growth. In the past ten years, pharmaceuticals agents that specifically inhibit the 5-LO metabolic pathway have been developed to treat inflammatory diseases such as asthma, arthritis and psoriasis. Some of these compounds possess anti-oxidant properties and may be effective in preventing cancer by blocking free radical-induced genetic damage or by preventing the metabolic activation of carcinogens. Other compounds may work by negatively modulating DNA synthesis. Pharmacological profiles of potential chemopreventive agents are compiled from enzyme assays, in vitro testing (e.g., cell proliferation inhibition in human cancer cells) and in vivo animal carcinogenesis models (e.g., N-methyl-N-nitrosourea-induced rat mammary cancer, benzo(a)pyrene-induced lung tumours in strain A/J mice and hormone-induced prostate tumours in rats). In this way, compounds are identified for chemoprevention trials in human subjects. Based on currently available data, it is expected that the prevention of lung and prostate cancer will be initially studied in human trials of LO inhibitors.

Preclinical drug development paradigms for chemopreventives.

Preclinical screening studies and animal efficacy testing models currently are used by the National Cancer Institute's chemoprevention drug discovery program to assess and identify chemical agents and natural products that may have the potential to prevent human cancer. Identification of potential cancer preventing agents begins by subjecting each compound to a sequential series of short-term, in vitro prescreens of mechanistic, biochemical assays to provide quantitative data to help establish an early indication of chemopreventive efficacy and to assist in prioritizing agents for further evaluation in longer-term, in vitro transformation bioassays and whole animal models. Promising chemical agents or combinations of agents that work through different inhibitory mechanisms subsequently are tested in well-established, chemically induced, animal tumor models, which include models of the lung, bladder, mammaries, prostate, and skin. These preclinical bioassays afford a strategic framework for evaluating agents according to defined criteria, and not only provide evidence of agent efficacy, but also serve to generate valuable dose-response, toxicity, and pharmacokinetic data required prior to phase I clinical safety testing. Based on preclinical efficacy and toxicity screening studies, only the most successful agents considered to have potential as human chemopreventives progress into clinical chemoprevention trials.

Biomechanics of pin and screw fixation of femoral neck fractures.

Using an in vitro cadaveric femoral neck osteotomy model and a paired experimental design, we compared fixation stiffness and yield load for three- and four-pin configurations for both Knowles pins and Asnis screws and for three Asnis screws versus an AO-ASIF sliding hip screw. Repeat measure analyses of variance indicated a significant increase in stiffness (p < 0.05) with the use of three versus four pins; the yield load did not depend significantly on the number of pins. Fixation was significantly stiffer (p < 0.01) and stronger (p = 0.02) for Knowles pins if the osteotomy was oblique rather than transverse to the femoral neck; the opposite was found for Asnis screws. Femoral fixed with hip screws were significantly stiffer (p < 0.01) than the contralateral side fixed with three Asnis screws. No significant difference in yield load was observed, however. Clinically, it appears from these findings that the use of three Asnis screws or three Knowles pins provides modest increases (averaging 4%) in fixation stiffness with no degradation in strength when compared with four screws or pins. Parallel placement of Asnis screws also provides advantages over nonparallel Knowles pins by allowing controlled impaction of the femoral head. While three Asnis screws provide fixation stiffness approximately 40% less than that found with a sliding hip screw, there is no compromise in fixation strength.

Weight, water, and cation losses in horses competing in a three-day event.

Body weight of 48 horses competing in a 3-day event was measured the day before the event (baseline), following the dressage phase of the event (day 1), after the endurance phases of the event (day 2), and 18 to 24 hours after the endurance phases (day 3). Plasma sodium and potassium concentrations were measured the evening before, immediately after, and 10 minutes after the endurance phases. Total body water, water loss, and net exchangeable cation loss were then calculated. Body weight and total body water were significantly decreased, compared with baseline values, at all times during the event, and significant water loss was detected. The largest changes were recorded after the endurance phases of the event. Water deficits were still detected 18 to 24 hours after the endurance phases of the event. Mean plasma sodium concentration was significantly increased immediately after the endurance phases of the event, compared with concentration measured the evening before, and remained increased after the 10-minute recovery period, presumably because of dehydration. Mean plasma potassium concentration was significantly increased immediately after the endurance phases of the event, compared with concentration measured the evening before, but was not increased after the 10-minute recovery period.

Some implications of postmodernism for nursing theory, research, and practice.

This paper explores ways in which some aspects of postmodernist thought impact upon nursing theory and research. The focus is on postmodernist accounts of epistemology and language, in particular notions such as multiple truths, uncertain and provisional knowledge, and claims as to the purposes of knowledge development. Common themes of postmodernism are articulated, including antifoundationalism, the dissonance between competing discourses, and the rejection of "grand theories." The paper concludes with a short set of suggestions for a postmodern approach to nursing practice.

Arthroscopic surgery of the knee on the U.S. Naval Hospital Ships during Operation Desert Shield.

Between September 1990 and January 1991, while deployed to the Persian Gulf for Operation Desert Shield, 118 patients underwent arthroscopic surgery of the knee on the U.S. Naval Hospital Ships USNS Mercy and USNS Comfort. There were 113 men and 5 women, with an average age of 28 years (range, 19-59 years). The most common findings at the time of arthroscopy were meniscus tears (53%), anterior cruciate ligament tears (29%), and normal arthroscopic examinations (9%). There were three complications, two hemarthroses and one superficial portal site infection. Seventy patients (59%) were able to be returned to duty at an average of 6 days post-operatively, obviating the need to evacuate these patients out of the Middle East theater to Europe or the United States, thus avoiding additional delay, expense, and loss of the service member to his military unit.

Alternatives to natural science foundations for nursing.

The underlying philosophical assumptions associated with the current vogue for humanistic and holistic approaches to nursing have not been subjected to systematic scrutiny, laying nursing open to the charge of being anti-scientific and even irrational. This paper outlines some of these assumptions and their origins, and proceeds to a brief survey of their impact on nursing theory, education and practice. It concludes with a call for the elucidation and consolidation of nursing practice which reflects phenomenological and humanistic alternatives to the natural science principles which have characterized traditional medical practice. In this connection I have used the term 'positivism' to refer to a general orientation according to which the world can only be known through observable entities, and regularities may be demonstrated and general laws verified through their measurement and quantification.

AIDS education for the podiatric physician. Evaluating program impact.

An important component in the development of any educational program is the evaluation of its effectiveness. The program described in this article was designed in such a way that its impact on practitioners' knowledge, attitudes, and clinical practices regarding human immunodeficiency virus (HIV) could be evaluated. One hundred ten participants were asked to complete pre-conference and post-conference tests in order to measure improvement that resulted from program attendance. The author presents both a description of the conference and a summary of the evaluation results, along with suggestions for improving future educational programs.

Educating podiatric medical assistants about AIDS and HIV infection.

In order to assess the need for acquired immunodeficiency syndrome education among podiatric assistants, comprehensive questionnaires on human immunodeficiency virus infection were distributed in February and March 1989. The findings presented here are based upon questionnaires completed and returned by 300 assistants. The purpose of the needs assessment was three-fold: to find out how much the surveyed assistants know about AIDS and HIV infection, how they feel about working with HIV-infected patients, and to what extent they understand and follow recommended infection control practices. The results of the survey reveal that many of the assistants in the sample in this study are ill-informed about HIV infection, that they have numerous concerns and fears about working with HIV-infected patients, and that they are not following recommended infection control guidelines.

Legal and ethical aspects of seclusion: an Australian perspective.

The debate about the appropriateness of seclusion as a nursing practice in inpatient settings in the 21st century continues, with powerful and often emotive arguments from those who view it as an anachronistic and punitive form of ward management, and from others who see it as a useful emergency measure to protect individuals from imminent harm. This is the first paper, however, to focus on legal and ethical issues in relation to the use of seclusion, with policies and practices in Australian psychiatric institutions viewed within the context of worldwide trends. The interplay of ethical principles and international mental health law has encouraged a move towards the provision of care and treatment of the disturbed psychiatric patient within the least restrictive environment, supposedly reducing the potential for the inappropriate use of control mechanisms. Nevertheless, current legislation can be seen to preserve the status quo because it legitimizes seclusion as an acceptable nursing practice, albeit within given parameters, thereby defusing the imperative to promote the reduction and abolition of psychiatric control mechanisms and seek new possibilities in mental health care.

QALYs (Quality Adjusted Life Years): a nurse's view.

Examines the political and ideological significance of measures of quality of life, specifically Quality Adjusted Life Years (QALYs). Briefly reviews recent developments in the debate surrounding the economic and political functions of quality of life measures. The dialectic between conceptions of the quality of life and the implicit realpolitik of socio-economic pressures, ecological conditions, political ethos and cultural norms and expectations, is conceived as a powerful means for the critique of our aspirations concerning health. Argues that existing approaches to assessing quality of life, in denying this dialectic, have jeopardized their potential contribution to the planning, implementation and evaluation of health are policy. Resource allocation challenges us to develop openly ideological strategies and measures.

Human immunodeficiency virus transmission in health care settings. Risks to health care workers.

Taken together, studies of seroconversion, exposure incidents, and compliance with Universal Precautions Policy help researchers understand the risks to health care workers of occupationally acquired HIV infection. The seroconversion studies show that the risk of infection is low (1 in 250) even when the incident is a percutaneous exposure to blood from a known HIV-positive patient. When the exposure is to blood from a patient whose HIV-status is unknown, or if the exposure is not through the skin, or if the exposure is to a body substance other than blood, the risk is considerably lower. The studies of exposure incidents show that for most health care workers, percutaneous exposures to blood are infrequent. Studies of compliance with Universal Precautions Policy show that exposure incidents that do occur can be prevented nearly half the time. The risk of patient-to-provider transmission of HIV is small but not completely negligible. This small risk can be made even smaller by adhering to recommended infection control guidelines, but it cannot be eliminated completely. Although most health care workers enter the medical field accepting that their work may expose them to infectious agents, there is still a desire for risk-free practice. Achieving an entirely risk-free practice is probably impossible; it is certainly not within reach today. For the foreseeable future, the only reasonable course is to fully understand the risks, to enter into practice psychologically prepared to accept these risks, and to practice in a way that minimizes exposures without compromising patient care.

Synchronization in a mechanical resonator array coupled quadratically to a common electromagnetic field mode.

Optomechanical systems are based on the nonlinear coupling between the electromagnetic (EM) field in a resonator and one or more bulk mechanical resonators such that the frequency of the EM field resonator depends on the displacement coordinates of each of the mechanical resonators. In this paper we consider the case of multiple mechanical resonators interacting with a common field for which the frequency of the EM resonance is tuned to depend quadratically (to lowest order) on the displacement of the resonators. By using the method of amplitude equations around a critical point, it is shown that groups of near-identical bulk mechanical resonators with low driving fail to synchronize unless their natural frequencies are identical, in which case the resulting system can exhibit multistability.

Synchronization of many nanomechanical resonators coupled via a common cavity field.

Using amplitude equations, we show that groups of identical nanomechanical resonators, interacting with a common mode of a cavity microwave field, synchronize to form a single mechanical mode which couples to the cavity with a strength dependent on the squared sum of the individual mechanical-microwave couplings. Classically this system is dominated by periodic behavior which, when analyzed using amplitude equations, can be shown to exhibit multistability. In contrast, groups of sufficiently dissimilar nanomechanical oscillators may lose synchronization and oscillate out of phase at significantly higher amplitudes. Further, the method by which synchronization is lost resembles that for large amplitude forcing which is not of the Kuramoto form.

Critical fluctuations in cortical models near instability.

Computational studies often proceed from the premise that cortical dynamics operate in a linearly stable domain, where fluctuations dissipate quickly and show only short memory. Studies of human electroencephalography (EEG), however, have shown significant autocorrelation at time lags on the scale of minutes, indicating the need to consider regimes where non-linearities influence the dynamics. Statistical properties such as increased autocorrelation length, increased variance, power law scaling, and bistable switching have been suggested as generic indicators of the approach to bifurcation in non-linear dynamical systems. We study temporal fluctuations in a widely-employed computational model (the Jansen-Rit model) of cortical activity, examining the statistical signatures that accompany bifurcations. Approaching supercritical Hopf bifurcations through tuning of the background excitatory input, we find a dramatic increase in the autocorrelation length that depends sensitively on the direction in phase space of the input fluctuations and hence on which neuronal subpopulation is stochastically perturbed. Similar dependence on the input direction is found in the distribution of fluctuation size and duration, which show power law scaling that extends over four orders of magnitude at the Hopf bifurcation. We conjecture that the alignment in phase space between the input noise vector and the center manifold of the Hopf bifurcation is directly linked to these changes. These results are consistent with the possibility of statistical indicators of linear instability being detectable in real EEG time series. However, even in a simple cortical model, we find that these indicators may not necessarily be visible even when bifurcations are present because their expression can depend sensitively on the neuronal pathway of incoming fluctuations.