The Markov switching ACD model

We propose a new framework for modelling time dependence in duration processes on financial markets. The well known autoregressive conditional duration (ACD) approach introduced by Engle and Russell (1998) will be extended in a way that allows the conditional expectation of the duration process to depend on an unobservable stochastic process, which is modelled via a Markov chain. The Markov switching ACD model (MSACD) is a very flexible tool for description and forecasting of financial duration processes. In addition the introduction of an unobservable, discrete valued regime variable can be justified in the light of recent market microstructure theories. In an empirical application we show, that the MSACD approach is able to capture several specific characteristics of inter trade durations while alternative ACD models fail. Furthermore, we use the MSACD to test implications of a sequential trade model

Name relearning in elderly patients with schizophrenia: episodic and temporary, not semantic and permanent

Original article can be found at: http://www.informaworld.com/smpp/title~content=t713659088--Copyright Informa / Taylor and FrancisIntroduction . Recent reports of lexical-semantic deficits in patients with schizophrenia (Laws, Al-Uzri, & Mortimer, 2000; Laws, McKenna, & Kondel, 1998) suggest that younger patients have problems accessing intact memories and older patients show apparent “loss” of the lexical-semantic memory representations themselves. Methods . Picture naming for everyday items was examined in a unique series of elderly patients with schizophrenia ( n = 10) with a mean illness duration of 45.5 years; and compared with that in patients with probable Alzheimer's disease ( n = 18) and elderly healthy controls ( n = 27). Naming consistency across time was used as an indicator of whether the schizophrenic patients had difficulty accessing representations or a loss of the representations themselves. Finally, we examined the ability of the schizophrenic patients to relearn the names of unnamed items across four weekly retraining sessions and to retain them at a one month follow-up. Results . The elderly schizophrenic patients were as anomic as patients with probable Alzheimer's disease. Consistency analysis revealed that the patients had storage deficits. Analysis of patient error types was consistent with a semantic deficit. Finally, the schizophrenic patients showed significant improvement with relearning, but this was not maintained at follow-up. Conclusions . Elderly patients with schizophrenia show a profound and stable anomia. Although name relearning induced some significant gains in naming, these were short-term and reflect episodic rather than semantic reinstatement of representations. Implications for cognitive remediation are discussed.Peer reviewe

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Block spin transformation on the dual lattice and monopole action

To find a perfect lattice action in terms of monopole action on the dual lattice, we performed simulations of a monopole effective action obtained numerically from vacuum configurations in SU(2) QCD. Although the Polyakov loop behavior near $T_c$ is well reproduced by the action, a small but repulsive term is needed in addition to get the string tension correctly. It is reported also a monopole effective action in $SU(3)$ QCD which is expressed by one kind of monopole currents.Comment: 4pages (4 figures), Latex, Contribution to Lattice 9

Constipation and encopresis in children

Chronic constipation is defined as a decrease in frequency or the painful passage of bowel movements present for several weeks. Retentive encopresis is the term reserved for the involuntary and uncontrollable soiling that occurs in children with chronic constipation. Constipation is a relatively common pediatric complaint accounting for up to 3% of general paediatirc outpatient visits and 25% of visits to a pediatric gastroenterologist. Encopresis is also common, occurring in at least 1.5% of all childrenpeer-reviewe

Extensions of supersymmetric spin systems

A discussion of supersymmetric spin systems is presented extending the results obtained in a recent paper (see ibid., vol.9, p.1497 (1976)). A two-dimensional model is given and gauge invariance is defined; the latter is shown to necessitate the introduction of further spin operators