Search

To better understand barriers to participation in mail-out bowel cancer screening programs, two survey studies tested the relationship between psychological distress and self-reported bowel cancer screening.First, a nationally representative sample of Australians N = 5421 completed measures of bowel cancer screening and psychological distress (using the Kessler Psychological Distress Scale; K10). Second, N = 479 completed a survey measuring participation in the National Bowel Cancer Screening Program (NBCSP) and psychological distress using the Depression, Anxiety and Stress Scale. In both studies, logistic regressions were conducted to test relationships between psychological distress and self-reported screening participation.Study one found that psychological distress had a significant quadratic effect on having ever screened for bowel cancer, where screening rates were similar for those with low, moderate, or high levels of distress, but were lower for those with very high levels of distress. In study two, depression scores had a negative linear relationship with NBCSP participation (higher depression levels were associated with lower screening participation), and anxiety had a quadratic effect whereby NBCSP participation rates were higher with increasing levels of anxiety except in the severe category, where participation was significantly lower.Findings indicate that psychological distress has a complex relationship with screening, and those with extreme levels of distress consistently show lower participation rates. Special efforts to encourage screening may be required for those experiencing extreme psychological distress and mental health disorders.

To examine the relationships between need for control and self-reliance and barriers to bowel cancer screening to better understand the reasons for lower bowel cancer screening adherence in males and younger individuals.Participants (n = 506) aged between 54 and 75 years old completed an online survey measuring demographic information, the four-factor Barriers to Home Bowel Cancer Screening Scale (BB-CanS) and a measure of Need for Control and Self-Reliance (NCSR). Model fit statistics were compared for seven path models testing the relationships between NCSR and BB-CanS factors and the moderating and mediating effects of age and gender.Models where age and gender were included as moderators showed the best fit. When compared to females and those under 60 years of age, stronger positive associations between NCSR and BB-CanS factors were evident among males (βsubavoidance/sub = 0.539, p lt; 0.001); βsubdisgust/sub = 0.558, p lt; 0.001; βsubdifficulty/sub = 0.489, p lt; 0.001; βsubautonomy/sub = 0.619, p = 0.002) and those over 60 years of age (βsubavoidance/sub = 0.400, p lt; 0.001); βsubdisgust/sub = 0.462, p lt; 0.001; βsubdifficulty/sub = 0.447, p lt; 0.001; βsubautonomy/sub = 0.378, p lt; 0.001.When encouraging males and people aged 60 years and over to participate in bowel cancer screening, public health messages may benefit from conveying preventative health behaviour and cancer screening participation as actions that reflect self-control and self-reliance.

To describe the actions taken by recipients of mail-out faecal occult blood test (FOBT) kits and to identify the points at which progress towards kit completion typically stops. Differences according to gender, age, and screening intention were also examined.1599 people completed an online survey identifying the actions they took upon receiving an FOBT kit. Latent class analysis was conducted to identify latent subgroups of participants that reported similar actions. Differences between gender, age, and intention status were assessed using non-invariance testing.Four latent subgroups of FOBT invitees were identified: those who complete and return their FOBT kit ('completers'); those who bring the kit into their house but go no further ('ignorers'); those who open the package and read the bowel cancer information materials but go no further ('readers'); and those who read the instructions but do not place the kit near the toilet and do not complete their FOBT kit ('leavers'). Non-completers who intended to use the kit were most likely to be in the 'leavers' class, while those who had no intention were most likely to be in the 'readers' class.Distinct subgroups of non-responders exist among bowel cancer screening invitees, suggesting different behaviour change interventions are needed to facilitate participation. Some invitees, especially those with high participatory intention, are likely to benefit from prompts to take the kit into the toilet, while others, with little participatory intention, often read the invitation materials presenting an opportunity to intervene with health messages.

OBJECTIVES: To measure rates of detection via screening, perceived self-imposed delays in seeking medical attention, and support seeking in a sample of regional and remote people with a cancer diagnosis and to test whether an association exists between these behaviours and minimising problems and resignation, a need for self-control and reliance and fatalism. Correlations and binary logistic regressions were conducted to test the associations between demographic characteristics, attitudes and behaviours. RESULTS: Females were more likely to have had their cancer detected via screening (OR = 10.02, CI = 3.49 - 28.78). Younger participants (r = -.103, p =.009) were slightly more likely to seek at least one form of support and online support was sought more often by younger patients (r = -.269, p < .001), females (r = .152 , p

ObjectiveThis study aimed to understand how cancer survivors in rural Queensland seek and receive information, as well as their preferences regarding the content and delivery of health-related information.MethodsThis study explored cancer survivors' experiences in seeking and comprehending health information using a qualitative descriptive approach. Semi-structured interviews were conducted with 24 participants. Data were analysed using reflexive thematic analysis.ResultsTwo major themes and six sub-themes were identified including 1) information content and gaps - a) information about diagnosis and treatment, b) survivorship information gaps and c) practical support needs and 2) delivery and acceptance of information - a) sources of information, b) personalised information needs and c) information seeking or avoidance. Findings suggested that health information provision was inconsistent; survivors' attitudes towards seeking information varied greatly; and survivors' had difficulty processing information due to emotional distress.ConclusionThe role of the health professional is critical in providing information and support to rural cancer survivors. Information provided should be tailored to meet the needs and preferences of individuals taking into consideration demographic factors and attitudes. Implications for public health: The current findings imply that quality information provision after cancer treatment would facilitate improvements in satisfaction among rural cancer survivors.

Objectives: Men with prostate cancer experience a range of physical, psychosocial and psychosexual effects many of which may be long term. The role of health literacy (i.e. people's cognitive and social ability to understand, access, retrieve and use health information and health services) in how men adapt to prostate cancer is as yet unexplored. We assessed the psychometric robustness of the Health Literacy Questionnaire (HLQ) among men with prostate cancer to determine which health literacy components are most important to physical and emotional health status. Methods: A cross‐sectional survey was undertaken with 565 men who were previously treated for prostate cancer and were members of a prostate cancer support network in Queensland (Mage = 71.1, SD = 8.7; Myears since diagnosis = 7.5, SD = 4.7). Measures included the HLQ and the SF‐36. Confirmatory factor analysis was employed to assess the validity of the HLQ in the current prostate cancer sample. The effects of each of the nine health literacy factors on emotional and physical health status were graphed and compared using Fishers exact tests. Results: RMSEA = 0.069 (CI = 0.066–0.072), item loadings and internal consistency (Chronbach alphas > 0.80) for the nine factor model supported the robustness of the HLQ for use in this prostate cancer sample. Health literacy factors reflecting social and health provider support, navigating health systems, finding and understanding health information and active engagement with providers shared small to moderate associations with emotional health status and little to no association with physical health status. Conclusions: The HLQ is a robust measure, with stable constructs of health literacy and has utility predicting health‐related outcomes in a sample of men with prostate cancer. Interventions aimed at improving the emotional health status of men with prostate cancer may benefit from incorporating education around interactions with healthcare providers and systems.

The light microscope is an indispensable tool in the study of living organisms. Most biologists are familiar with microscopes, perhaps being first introduced to the wonders of the world of small things at a very early age. Yet, few fully comprehend the nature of microscopy and the basis of its utility. This review (re)-introduces the concepts of magnification, resolution, and contrast, and explores how they are intimately related and necessary for effective microscopy.

We examined associations between two psychological constructs, analytic cognitive style and the personality facet ‘Openness to Experience’, and several dimensions of religiosity: religious affiliation, strength of faith and spiritual epistemology. In a relatively large (N = 1093), older community sample (M = 55.4 years), analytic cognitive style was associated with a lower probability of affiliating with a religious denomination and a higher probability of possessing strong religious faith. Overall, openness was also associated with a lack of religious affiliation but was positively related to possessing a spiritual epistemology. A path-analytic model revealed that openness had a positive relationship to both faith and religious denomination that was mediated by spiritual epistemology, but negative direct relationships with religiosity after the meditational effects were taken into account. Taken together, these results extend previous findings on the effect of cognitive style on religiosity and provide a new perspective on the complex relationship between cognitive and personality factors and different dimensions of religiosity.

Summary In networked control, there is often an incentive to communicate only what is absolutely necessary to achieve the desired performance goals. This is true to both the downlink (between a control base station and actuators) and the uplink (between the sensors and base station). Here, we present a strategy aimed at this problem based on a singular value decomposition of the Hessian of the quadratic performance index generally considered in Model Predictive Control. The singular vectors are employed to generate an orthonormal basis function expansion of the unconstrained solution to the finite horizon optimal control problem. These are preloaded into each actuator and each sensor. On the downlink, the actuators are informed, in real-time, about which basis functions they should use. On the uplink, after a ‘burn in period’, the sensors need only communicate when their response departs from that pre-calculated for the given basis functions. We show that this strategy facilitates communication in both the downlink and uplink in a cost-effective fashion. We also show that the strategy can be modified so that input constraints are satisfied. We illustrate the proposed results by applying them to a simulation of the cross direction control of a paper machine. Potential extensions and other applications of the proposed strategy are also discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Perceiving that one is rejected is an important correlate of emotional maladjustment. Yet, self-perceptions can substantially differ from classmate-reports of who is rejected. In this study, discrepancies between self- and classmate-reports of rejection were identified in 359 Australian adolescents (age 10-12 years). As expected, adolescents who overestimated rejection reported more rejection sensitivity and felt more victimized by their peers, but were not seen by peers as more victimized. Adolescents who underestimated rejection identified themselves as high in overt aggression, and their peers identified them as high in overt and relational aggression and low in prosocial behavior. Yet, underestimators' feelings of friendship satisfaction did not seem to suffer and they reported low rejection sensitivity. Results suggest that interventions to promote adolescent health should explicitly recognize the different needs of those who do and do not seem to perceive their high rejection, as well as adolescents who overestimate their rejection.

Background Hydrotherapy is frequently indicated for the rehabilitation of patients with rheumatoid arthritis (RA); nevertheless, there has been inadequate appraisal of its effectiveness. The potential benefits of hydrotherapy for patients with RA are to improve and/or maintain functional ability and quality of life. Objectives The aim of this systematic review was to evaluate the effectiveness of hydrotherapy in the management of patients with RA. Method AMED, CINAHL, EMBASE, MEDLINE, PubMed, Science Direct and Web of Science were searched between 1988 and May 2011. Keywords used were rheumatoid arthritis, hydrotherapy, aquatic physiotherapy, aqua therapy and water therapy. Searches were supplemented with hand searches of references of selected articles. Randomized controlled trials were assessed for their methodological quality using the Physiotherapy Evidence Database (PEDro) scale. This scale ranks the methodological quality of a study scoring 7 out of 10 as ‘high quality’, 5–6 as ‘moderate quality’ and less than 4 as ‘poor quality’. Results Initially, 197 studies were identified. Six studies met the inclusion criteria for further analysis. The average methodological quality for all studies was 6.8 using the PEDro scale. Most of the studies reported favourable outcomes for a hydrotherapy intervention compared with no treatment or other interventions for patients with RA. Improvement was particularly noted in reducing pain, joint tenderness, mood and tension symptoms, and increasing grip strength and patient satisfaction with hydrotherapy treatment in the short term. Conclusions There is some evidence to suggest that hydrotherapy has a positive role in reducing pain and improving the health status of patients with RA compared with no or other interventions in the short term. However, the long-term benefit is unknown. Further studies are needed. Copyright © 2012 John Wiley & Sons, Ltd.

SUMMARY Predictive control is one of the major success stories in modern industrial control. It has been successfully used in hundreds of real-world applications, and there is a rich associated theory. The goal of this paper is to provide a historical perspective of predictive control. In view of the breadth of predictive control, we will restrict the discussion to certain specific aspects. In particular, we give emphasis to the seminal work of David Clarke. Copyright © 2012 John Wiley & Sons, Ltd.

We study a source coding method for networked control systems (NCSs) for SISO LTI plant models. To make efficient use of limited communication resources between controller and plant actuator, we develop a non-uniformly sampled subband coding NCS architecture, which we design to minimize a bound on the tracking error variance caused by quantization effects. Our main contribution, in relation to earlier work on subband coding NCSs, lies in that we allow each subband to be equipped with pre- and post-filters. To characterize optimal filters and to solve the subband bit-allocation problem, we model quantization effects via signal-to-noise ratio constraints and explicitly take into account the closed-loop nature of signals. Simulation results verify that the resultant designs perform exceptionally well, even in non-idealized situations. Copyright © 2008 John Wiley & Sons, Ltd.

A novel approach to nonlinear control, called Generalized Feedback Linearization (GFL), is presented. This new strategy overcomes one important drawback of the well known Feedback Linearization strategy, in the sense that it is able to handle a broader class of nonlinear systems, namely those having unstable zero dynamics. It is shown that the use of a nonlinear predictor for the system output is a key feature in the derivation of the control strategy. For certain types of systems this predictor can be found as a nonlinear function of the system input and output, allowing an output feedback control solution. The use of Artificial Neural Networks (ANN) to directly parameterize the predictor of the controlled variable when an explicit model for the system is not available, is investigated via computer simulations. This approach is based on the functional approximation capability of multi layer ANN. KeyWord: Generalized feedback linearization, unstable zero dynamics, generalized predictor, neural networks.

This paper characterises the geometric structure of receding horizon control (RHC) of linear, discrete-time systems, subject to a quadratic performance index and linear constraints. The geometric insights so obtained are exploited to derive a closed-form solution for the case where the total number of constraints is less than or equal to the number of degrees of freedom, represented by the number of control moves. The solution is shown to be a partition of the state space into regions for which an analytic expression is given for the corresponding control law. Both the regions and the control law are characterised in terms of the parameters of the open-loop optimal control problem that underlies RHC and can be computed off line. The solution for the case where the total number of constraints is greater than the number of degrees of freedom is addressed via an algorithm that iteratively uses the off-line solution and avoids on-line optimisation.

The recent discovery of the direct oxidation of spermine via spermine oxidase (SMO) as a mechanism through which specific antitumor polyamine analogues exert their cytotoxic effects has fueled interest in the study of the polyamine catabolic pathway. A major byproduct of spermine oxidation is H2O2, a source of toxic reactive oxygen species. Recent targeted small interfering RNA studies have confirmed that SMO-produced reactive oxygen species are directly responsible for oxidative stress capable of inducing apoptosis and potentially mutagenic DNA damage. In the present study, we describe a second catalytically active splice variant protein of the human spermine oxidase gene, designated SMO5, which exhibits substrate specificities and affinities comparable to those of the originally identified human spermine oxidase-1, SMO/PAOh1, and, as such, is an additional source of H2O2. Importantly, overexpression of either of these SMO isoforms in NCI-H157 human non-small cell lung carcinoma cells resulted in significant localization of SMO protein in the nucleus, as determined by confocal microscopy. Furthermore, cell lines overexpressing either SMO/PAOh1 or SMO5 demonstrated increased spermine oxidation in the nucleus, with accompanying alterations in individual nuclear polyamine concentrations. This increased oxidation of spermine in the nucleus therefore increases the production of highly reactive H2O2 in close proximity to DNA, as well as decreases nuclear spermine levels, thus altering the protective roles of spermine in free radical scavenging and DNA shielding, and resulting in an overall increased potential for oxidative DNA damage in these cells. The results of these studies therefore have considerable significance both with respect to targeting polyamine oxidation as an antineoplastic strategy, and in regard to the potential role of spermine oxidase in inflammation-induced carcinogenesis.

BACKGROUND Inflammation has been strongly implicated in prostate carcinogenesis, but the precise molecular mechanisms linking inflammation and carcinogenic DNA damage are not known. Induction of the polyamine catabolic enzyme, spermine oxidase (SMO) has been linked to increased reactive oxygen species (ROS) and DNA damage in human gastric and lung epithelial cells and suggest direct mechanistic links between inflammation, SMO activity, ROS production, and epithelial carcinogenesis that are likely relevant in prostate cancer. METHODS Tissue microarrays consisting of matched normal and diseased specimens from patients diagnosed with prostate cancer, prostatic intraepithelial neoplasia (PIN), or proliferative inflammatory atrophy (PIA), as well as unaffected individuals, were stained for SMO expression and analyzed using image analysis techniques and TMAJ software tools. RESULTS Average SMO staining was significantly higher in prostate cancer and PIN tissues compared to patient-matched benign tissues. Benign tissues from prostate cancer, PIN, and PIA patients also exhibited significantly higher mean SMO expression versus tissues from prostate disease-free patients. CONCLUSIONS Tissues from patients diagnosed with prostate cancer and PIN exhibit, on average, locally increased SMO expression in regions of prostatic disease and higher overall SMO expression in prostatic epithelial cells compared to healthy individuals. Further studies are warranted to directly examine the role of SMO-produced ROS in prostate carcinogenesis. Prostate 68: 766–772, 2008. © 2008 Wiley-Liss, Inc.

A sub-optimal receding horizon control strategy for input constrained linear systems is presented. The strategy is based on a singular value decomposition (SVD) of the Hessian of the quadratic performance index generally considered in model predictive control (MPC). The singular vectors are employed to generate a basis function expansion of the unconstrained solution to the finite horizon optimal control problem. At each sampling time, a feasible control sequence is determined by selecting a variable subset of the basis representation. No solution to the associated quadratic program is needed. For cases in which the Hessian is poorly conditioned, the proposed strategy can provide a sub-optimal solution with minimal performance degradation. Properties of the singular values of the Hessian are also studied: it is shown that, for sufficiently long prediction horizons, the singular values are arbitrarily close to the magnitude of the energy density spectrum of the system seen by the performance index. Copyright © 2004 John Wiley & Sons, Ltd.

We address the problem of finite horizon optimal control of discrete-time linear systems with input constraints and uncertainty. The uncertainty for the problem analysed is related to incomplete state information (output feedback) and stochastic disturbances. We analyse the complexities associated with finding optimal solutions. We also consider two suboptimal strategies that could be employed for larger optimization horizons.

This contribution addresses the problem of discrete time receding horizon quadratic control for plants whose input is restricted to belong to a finite set. We also study the dynamics of the resulting closed-loop system. Based upon the geometry of the underlying quadratic programme, a finitely parametrized expression for the control law is derived, which makes use of vector quantizers. Alternatively, the control law can be formulated by means of a polyhedral partition of the state space, which is closely connected with the partition induced when considering saturation-like constraints. Exact analytic expressions for the partition can be developed, therefore avoiding the need for on-line optimization. The closed-loop system, comprising controller and plant, exhibits highly nonlinear dynamics, due to the finite set restriction. Asymptotic stability only holds for very special cases. In general, this notion is too strong. Nevertheless, ultimate boundedness of state trajectories is often achieved. Tools for determining positively invariant sets, hence ensuring ultimate boundedness, are presented. Copyright © 2004 John Wiley & Sons, Ltd.

Robust control aims to account for model uncertainty in design. Traditional methods for robust control typically assume knowledge of hard bounds on the system frequency response. However, this does not match well with system identification procedures which typically yield statistical confidence bounds on the estimated model. This paper explores a new procedure for obtaining a better match between robust control and system identification by using stochastic confidence bounds for robust control design. Given a nominal design, we set up an optimization problem which is aimed at reducing the statistical variability, measured in a mean square sense, from the nominal sensitivity. The proposed procedure is straightforward and leads to an easily computable solution for the final robust controller in the case of a stable plant and modest plant uncertainty. An illustrative example is provided which shows the advantages of the method. Copyright © 2002 John Wiley & Sons, Ltd.

Objective: This paper seeks to evaluate the ability to deliver term pregnancies following uterine fibroid embolization, and to identify impediments to pregnancy in the embolization procedure. Study design: Four physicians performed embolization procedures at various facilities. Patients were asked if fertility was an issue prior to embolization. We measured follicle-stimulating hormone levels before and after embolization. Clinical follow-up, six months following embolization was obtained by interview. Patients were questioned regarding attempts to conceive, menstrual history, and subsequent pregnancy. Main outcome measures: Complications were calculated upon the entire patient population, whether or not fertility was identified as a goal. Fertility risks from embolization were identified. We measured radiation exposure in a random consecutive group of 50 women undergoing embolization. All patients who conceived were asked the details of the pregnancy. Results: Four hundred women underwent uterine fibroid embolization between 1996 and 1999. One hundred and thirty nine patients stated a desire for fertility after embolization. Of these, 52 were

A novel hexanuclear Fe(III) complex [Fe6(Hpida)6(?2-O)3Na][NO3]�18H2O (1; H3pida = N-(2-hydroxypropyl)iminodiacetic acid) was prepd. by reaction of equimolar amts. of N-(2-hydroxypropyl)iminodiacetic acid with iron(III) nitrate and was shown by x-ray crystallog. to possess a prismatic structure contg. a Na ion in the core. Magnetic studies showed 1 to have very strong antiferromagnetic character. [on SciFinder(R)]

A full non-linear model including sea-state modelling is used in the design for a ship steering autopilot. This has been done before. However, rather than a conservative design to avoid amplitude and slew rate limit in the rudder, we show how these limits can be accommodated without otherwise compromising the performance. Thus, saturation and slew rate limiting are accepted as inevitable consequence of high performance rather than something to be avoided at all cost. Copyright © 1999 John Wiley & Sons, Ltd.

In time series analysis of data sequences, the estimation of the parameters of an identified autoregressive moving-average (ARMA) model is a well-known and straightforward exercise. However, if the parameters of the model are periodic (i.e. a periodic ARMA (PARMA) model) then the estimation process becomes more difficult. This paper describes an on-line parameter estimation technique, based on methods from automatic control, which is demonstrated to provide consistent estimates of PARMA model parameters.

There has been a recent surge of interest in estimation theory based on very simple noise descriptions; for example, the absolute value of a noise sample is simply bounded. to date, this line of work has not been critically compared with pre-existing work on stochastic estimation theory which uses more complicated noise descriptions. the present paper attempts to redress this by examining the rapprochement between the two schools of work. For example, we show that for many problems a bounded-error estimation approach is precisely equivalent in terms of the final result to the stochastic approach of Bayesian estimation. We also show that in spite of having the advantages of being simple and intuitive, bounded-error estimation theory is demanding on the quantitative accuracy of prior information. In contrast, we discuss how the assumptions underlying stochastic estimation theory are more complex but have the key feature that qualitative assumptions on the nature of a typical disturbance sequence can be made to reduce the importance of quantitative assumptions being correct. We also discuss how stochastic theory can be extended to deal with a problem at present tackled only by bounded-error estimation methods: the quantification of estimation errors arising from the presence of undermodelling.

Networked Control has emerged in recent years as a new and exciting area in systems science. The topic has many potential applications in diverse areas ranging from control of microrobots to biological and economic systems. The supporting theory is very rich and combines aspects of control, signal processing, telecommunications, and information theory. In this paper, we give a partial overview of recent developments in Networked Control with an emphasis on the additive noise model methodology. We also point to several open problems in this emerging area.

This paper describes a simulation study of the relative impact of different operating policies on performance of a hypothetical multistage production system that produces assembled products. The main objective of this study is to examine the impact of operating policy rules on system performance. Several performance criteria, including flow time and earliness and tardiness measures, were used to evaluate system performance. Results show that performance of the production system is significantly influenced by the operating policy rules, although the relative impact of the rules is dependent on the performance measure considered. Interactions between and among policy rules were also found to be important in several cases. Overall, the results indicate that much previous research in non-assembly systems can be generalized to assembly systems. Subject Areas: Scheduling, Material Requirements Planning, and Simulation.

This paper illustrates an integrated indirect adaptive design technique using a case study example. Key features of this approach are the separate optimization of procedures for parameter estimation and control law synthesis as well as a mechanism for integrating robust and adaptive control design.

This paper describes an experimental investigation of adaptive control applied to a coupled tank apparatus. The study is intended to explore several practical considerations which arise in the application of adaptive control to realistic processes. In the experiments, the apparatus was configured so as to have several difficulties found in practical systems, including unmodelled time delay, unmodelled high-frequency lag and unmodelled non-linearities. These features are studied both theoretically and experimentally. The adaptive controller is shown to perform satisfactorily in the presence of these practical difficulties. Also a comparison with other strategies for control system design is given.

Problems and Paradigms is a feature series devoted to discussions of major problems in biology. Past contributions have dealt with the selector gene hypothesis, problems of pattern formation, the phenomenon of paramutation, theories of aging, and the origins of life. In this article, Brian C. Goodwin discusses the problem of morphogenesis, in terms of the idea of the genetic program and in the light of recent findings.

We studied changes in subchondral bone and articular cartilage in an animal model of osteoarthrosis. In this model we applied repetitive impulsive loads to rabbits' knees. Their legs were held in short leg splints so the rabbits were unable to dampen the peak applied load with ankle flexion. After sacrifice, at 1 day to 6 weeks, we studied proximal tibial load-bearing cartilage histologically, biochemically, and with radioactive sulfate uptake. We also studied the subchondral bone under that cartilage histologically, histomorphometrically, with bone scan (99mTc pyrophosphate), and by tetracycline labeling. An increase in 99mTc labeling of the subchondral bone was the first reliable change observed. This was followed by an increase in tetracycline labeling, bone formation, and a decrease in porosity, which has been associated with relative stiffening of bone. Horizontal splitting and deep fibrillation of the overlying articular cartilage followed the early bone changes. All of these changes preceded changes in content and characterization of cartilage proteoglycans or increased chondrocyte activity as manifested by incorporation of radioactive sulfate. In this model the early bone changes preceded changes in the articular cartilage. The deep splitting of articular cartilage occurred prior to metabolic alteration of that tissue.

GOODWIN, DONNA C. (State U. Iowa, Towa City.) Morphogenesis of the sporangium of Comatricha. Amer. Jour. Bot. 48(2): 148-154. Illus. 1961.-Three species of the myxomycete genus, Comatricha, were studied: Comatricha nigra, C. fimbriata, and C. elegans. The sporangia developed on living bark of Ulmus americana in moist chamber. The hypothallus is formed under the homogeneous protoplasmic mass of the sporangial initial. The fibrous threads of the hypothallus hend upward, lengthening at the apices to become the fihers of the stalk and columella. The undifferentiated protoplasm is carried upward as the stalk elongates. When the columella has attained its mature height, threads bend out from the columella and grow toward the periphery of the sporangium. These threads form the capillitium. Simultaneous with the appearance of the capillitial initials, the peridium, a delicate membrane, forms. After the capillitium is mature, the protoplast cleaves into many cells, the future spores. The peridium evanesces early in the stage of spore maturation. Cellulose is present in the stalk, capillitium, and spore walls but is not found in the peridium or hypothallus. The capillitium of these species follows a developmental pattern designated as the "Comatricha-type" by Ross (1957) from a study of Comatricha typhoides. The taxonomic implications of the sporangial developmental pattern are discussed. THE MYXOMYCETE genus, Comatricha, established in 1851 by Preuss, was defined in our present-day concept in 1875 by Rostafinski, Aho noted that in Comatricha the peripheral edge of the capillitial net is characteristically open; that is, the ultimnate branchlets are free and do not anastomose. This absence of a closed surface net distinguishes the members of this genus from Stemonitis, in which the capillitial branchlets fuse to form a complete reticulum at the periphery of the sporangium. Miss Lister (1925), in her discussion of the genus, states that Comatricha is an artificial taxon: that it differs from Lamproderma only by having a fugacious peridium and from Stemonitis only by the absence of a smooth surface net of capillitium and a less clustered habit of the sporan-ia. Macbride and Martin (1934) agree with Lister and describe the distinction between Stemonlitis and Comatricha as " admittedly artificial" and "arbitrary." However, they add that, although the genera come close together, the artificial separation proposed by Rostafinski is convenient enough to justify retaining the 2 groups. Martin (1949) continues to use the presence or aI^sence of the surface net as a basis for distinguishing Cornatricha and Stemonitis. Results obtained from a recent morphological study by Ross (1957) on capillitial formation in 4 species of Stemonitis and in Comatricha typhoides have been 1 Received for publication June 12, 1960. Portion of a thesis submitted to the Graduate College of the State University of Iowa in partial fulfillment of the requirements for the decree of Master of Science. The author gratefully acknowledges the guidance and criticism of Professor C. J. Alexopoulos, and thanks him for taking the photographs which accompany this paper. She also thanks Dr. H. L. Dean who aided in the selection of chemical tests. 2 This research constitutes a part of a program "Experimental Approach to the Taxonomy of Myxomycetes," supported by National Science Foundation Grant G-6382. interpreted by him to indicate that the morphological development of the capillitium of the 2 genera differs. He designates a "Comatricha-type" and a "Stemnonitis-type" of development; in the former, the net originates as lateral extensions of tubes bending out from the columella, and in the latter the capillitium is derived from tubes forming in the peripheral protoplasm; these tubes grow inward from the periphery and outward from the columella and anastomose. In addition to his discussion on capillitium development, Ross describes, in detail, the formation of other sporangial structures of C. typhoides. Prior to Ross' paper, very little had been published on sporangial development in Comatricha or closely related forms. DeBary (1884) writes that the formation of sporangia of Stemonitis and allied forms differs from that of all other known Myxomycetes. He describes the growth of a hollow cylindrical tube in the interior of the protoplasmic mass and states that the primary capillitial branches arise from the outer surface of the columella. From his observations on Stemonitis fusca, Bisby (1914) concludes that hollow capillitial threads are formned by protoplasmic deposition in tubular capillary spaces produced by invaginations of the peridium. Lister (1925) states that the Stemonitaceae are characterized by a solid stalk which develops internally in the young rising sporangium. She mentions that the peridium is evanescent in Comatricha. In an exceedingly complicated discussion, Jahn (1931) notes that in C. nigra the stalk is deposited in the interior of the protoplasm and consists of individual solid fibers which are surrounded by membranes. The threads themselves he believes to originate through the thickening and infolding of membranes. Accompanying the text are a series of excellent photographs which depict the development

The dynamic behaviour of β-galactosidase was studied in chemostat cultures of Escherichia coli B synchronized with respect to cell division by periodic phosphate feeding. Stable oscillations in the enzyme were observed when lactose was present at 0.02%. Perturbation experiments were used to study the stability of these states, and transient high-frequency oscillatory responses were observed. These results show that the lactose control circuit has different dynamic states, which may be due to differences in the degree of damping or in the frequency of autonomous oscillations. The results are interpreted in terms of the interactions between the lactose control circuit and the cyclic physiology of the cell during the growth and division cycle.