Limit Cycles in Slow-Fast Forest-Pest Models

Some of the most exciting current work in the environmental sciences involves simplified but analytically tractable versions of a few basic equations. IIASA's Environment Program has developed such an approach in its analysis of forest systems. A number of previous papers (WP-87-70 and WP-87-92) have demonstrated the progress that has been made. In this new work some of the ideas contained in those papers have been further developed. In particular a simple aged-structure forest model is considered to prove that a forest can exhibit periodic behavior even in the case the insect pest is adapted only to mature trees. The insect pest assumed to have a very fast dynamics with respect to trees and the analysis is carried out through singular perturbation arguments. The method is based only upon simple geometric characteristics of the equilibrium manifolds of the fast, intermediate and slow variables of the system and allows one to derive explicit conditions on the parameters that guarantee the existence of a limit cycle in the extreme case of very fast-very slow dynamics

Multiple Attractors, Catastrophes and Chaos in Seasonally Perturbed Predator-Prey Communities

The classical predator-prey model is considered in this paper with reference to the case of periodically varying parameters. Six elementary seasonality mechanisms are identified and analyzed in detail by means of a continuation technique producing complete bifurcation diagrams. The results show that each elementary mechanism can give rise to multiple attractors and that catastrophic transitions can occur when suitable parameters are slightly changed. Moreover, the two classical routes to chaos, namely, torus destruction and cascade of period doublings, are numerically detected. Since in the case of constant parameters the model cannot have multiple attractors, catastrophes, and chaos, the results support the conjecture that seasons can very easily give rise to complex population dynamics

Bifurcations and Chaos in a Periodic Predator-Prey Model

The model most often used by ecologists to describe interactions between predator and prey populations is analyzed in this paper with reference to the case of periodically varying parameters. A complete bifurcation diagram for periodic solutions of period one and two is obtained by means of a continuation technique. The results perfectly agree with the local theory of periodically forced Hopf bifurcation. The two classical routes to chaos, i.e., cascade of period doublings and torus destruction, are numerically detected

On the Invertibility of Storage Systems

The invertibility of single-input single output storage systems (network of reservoirs) is considered in this paper. The analysis shows that cascade and feedback connections of invertible subsystems give rise to invertible systems, and that parallel connections are invertible provided that the network is not too diversified topologically and that the reservoirs have comparable dynamics. These results often allow one to ascertain the invertibility of a complex storage system by direct inspection of a graph

George Frankl: an undervalued voice in the history of autism

This paper aims to propose that the psychiatrist George Frankl had more than a marginal role in the early history of autism. Frankl’s conception of autism as characterized by a lack of affective language has influenced both Asperger and Kanner. First, this proposal is historically supported; second it is corroborated by Frankl’s unpublished manuscript on Autism. We found that Frankl’s perspective about autism was, and still can be, considered innovative for multiple reasons. Specifically, Frankl proposed that autism could cover a spectrum of conditions; that it is a state of mind that is not necessarily abnormal; and that it is a neurobiological condition, which primarily needs to be understood by others. Finally, Frankl’s concepts of affective contact and affective language are reconsidered with reference to contemporary neuropsychology from which autism emerges not as a higher-order cognitive deficit, but as a result of an impairment of primordial ability to process low level sensory, motor and perceptual information gained through experiencing other persons

On non-L2L^2 solutions to the Seiberg-Witten equations

We show that a previous paper of Freund describing a solution to the Seiberg-Witten equations has a sign error rendering it a solution to a related but different set of equations. The non-$L^2$ nature of Freund's solution is discussed and clarified and we also construct a whole class of solutions to the Seiberg-Witten equations.Comment: 8 pages, Te

Regulatory T cell defects in adult autoimmune hepatitis

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Decompensated cirrhosis as presentation of LKM1/LC1 positive type 2 autoimmune hepatitis in adulthood. A rare clinical entity of difficult management

Background: Autoimmune hepatitis (AIH) is a chronic and aggressive liver disease that rapidly evolves into cirrhosis and end-stage liver disease if not timely diagnosed and treated with immunosuppressive therapy. AIH is classified into type 1 and type 2 according to the autoantibody pattern, with smooth muscle antibodies and/or antinuclear antibodies as serological markers of AIH-1, while antiliver cytosol antibody type 1 and/or antiliver/kidney microsomal antibody type 1 characterize type 2 AIH, which mainly affects children, including infants, and adolescents. Case Summary: We describe a case of type 2 AIH, clinically onset in a 34-year-old woman with decompensated cirrhosis. Only a thorough analysis of the autoantibody profile allowed for a diagnosis of an AIH-2 evolved into cirrhosis. The patient received a moderate corticosteroid therapy without achieving optimal disease control. We discuss the controversial decision of whether or not to treat the patient with immunosuppressive therapy, which should be balanced with the potential risk of infectious and other complications. A review of the literature on the management of patients with autoimmune cirrhosis is also presented. Conclusions: AIH-2 can be clinically onset in adult patients with cirrhosis and its complications, without being preceded by major clinical signs. Due to the difficult management of cirrhosis with immunosuppressive treatments, a patient-tailored strategy with a case-by-case approach is needed to prevent major complications such as infections, potentially precluding liver transplantation the only curative therapy

Acute liver injury and anorexia nervosa: A case report

Anorexia nervosa is an eating disorder characterized by restriction of energy intake leading to a significant decrease in body weight. While it is primarily a psychiatric disorder, numerous medical complications can occur. In this article we describe a case of a 25-year-old woman with a 12-year history of severe restrictive anorexia nervosa that was referred to the Emergency Service of our Hospital, transferred from a psychiatric institute, for severe weight loss, dehydration, and progressive increase in transaminases. During the hospital stay she developed an acute liver injury with an increase in transaminase level up to 40× the ULN. Infective and immunological causes of acute hepatitis were excluded. In the suspect of severe starvation acute liver injury, we performed a nutritional assessment and started parenteral nutrition. After 15 days of parenteral nutrition, she gained 2.5 kg of body weight and liver tests were drastically reduced and nearly normal