Incremental Clustering and Expansion for Faster Optimal Planning in Dec-POMDPs

This article presents the state-of-the-art in optimal solution methods for decentralized partially observable Markov decision processes (Dec-POMDPs), which are general models for collaborative multiagent planning under uncertainty. Building off the generalized multiagent A* (GMAA*) algorithm, which reduces the problem to a tree of one-shot collaborative Bayesian games (CBGs), we describe several advances that greatly expand the range of Dec-POMDPs that can be solved optimally. First, we introduce lossless incremental clustering of the CBGs solved by GMAA*, which achieves exponential speedups without sacrificing optimality. Second, we introduce incremental expansion of nodes in the GMAA* search tree, which avoids the need to expand all children, the number of which is in the worst case doubly exponential in the node's depth. This is particularly beneficial when little clustering is possible. In addition, we introduce new hybrid heuristic representations that are more compact and thereby enable the solution of larger Dec-POMDPs. We provide theoretical guarantees that, when a suitable heuristic is used, both incremental clustering and incremental expansion yield algorithms that are both complete and search equivalent. Finally, we present extensive empirical results demonstrating that GMAA*-ICE, an algorithm that synthesizes these advances, can optimally solve Dec-POMDPs of unprecedented size.

Transient Brain Lesions in Neuro-Behçet's Disease without Systemic Involvement

In neuro-Behçet's disease nervous involvement may occasionally precede somatic manifestations, making the diagnosis challenging. The reported case showed only a neurologic onset with relapsing-remitting form, transient brain MRI abnormalities and late appearance of typical muco-cutaneous lesions, thereby delaying the correct diagnosis and appropriate treatment. MRI revealed cerebral alterations mimicking demyelinating disease, but lesions rapidly disappeared on close follow-up scans indicating vasogenic edema. Being aware of this atypical presentation and recognizing these transient abnormalities may be useful for a prompt diagnosis.

Variations of plasma leptin in show horses during a work season

Leptin is an adipocytokine mainly expressed by adipose tissue. Secretion of leptin in healthy animals is closely related to fat mass and metabolic activity. The aim of this study was to investigate plasma leptin variations, in relation to nutritional and exercise parameters in adult show horses during a work season. EDTA-blood samples were taken at rest from 37 Iberian horses. Body weight, body condition score and fat percentage determined by ultrasonic measurement of rump fat thickness were measured. Plasma leptin was determined with a multi-species RIA kit. Linear mixed effects model was used to assess relationship between plasma leptin and other biological parameters. Plasma leptin concentration was <12.6 ng/ml (mean = 2.8 ± 1.6 ng/ml) and was significantly higher during training periods (p < 0.0001) (4.5 ± 1.7 ng/ml) than in show periods (2.0 ± 1.1 ng/ml), despite a significant increase (p < 0.0001) in energy intake. The body weight remained almost constant. The plasma leptin concentrations were significantly affected by exercise (p < 0.0001), body weight (p = 0.04) and BCS (p < 0.0001), but were not affected by percentage of fat. In conclusion, the marked decrease in leptin values observed during a period of intense (i.e. excessive) exercise could result from an adaptation to cumulative alterations in energy balance, to exercise per se or to a combination of both.

Posterior fossa abnormalities in hereditary spastic paraparesis with spastin mutations

BACKGROUND

Hereditary spastic paraparesis (HPS) linked to mutations in the spastin gene (SPG4) is considered to be a pure form of spastic hereditary paraparesis. However, in this disease also other signs of central nervous system involvement are frequently found.

METHODS

Clinical, genetical and neuroradiological investigations were carried out in a large family with autosomal dominant spastic paraparesis and in a sporadic case with spastic paraparesis.

RESULTS

Additional clinical and molecular data are provided, studying other members of the same pedigree, as already described, with a five-base deletion in exon 9 of the SPG4 gene (1215-1219delTATAA) whose members show MRI anomalies that fall within the Dandy-Walker continuum. Furthermore, an unrelated female patient with hypoplasia of the cerebellar vermis is indicated, carrying a de novo previously reported mutation of the SPG4 gene (c.1741C>T p.R581X).

CONCLUSIONS

Spastin may play an important role in the development of the central nervous system and in particular in the development of the structures of posterior fossa.

Policy Iteration for Decentralized Control of Markov Decision Processes

Coordination of distributed agents is required for problems arising in many areas, including multi-robot systems, networking and e-commerce. As a formal framework for such problems, we use the decentralized partially observable Markov decision process (DEC-POMDP). Though much work has been done on optimal dynamic programming algorithms for the single-agent version of the problem, optimal algorithms for the multiagent case have been elusive. The main contribution of this paper is an optimal policy iteration algorithm for solving DEC-POMDPs. The algorithm uses stochastic finite-state controllers to represent policies. The solution can include a correlation device, which allows agents to correlate their actions without communicating. This approach alternates between expanding the controller and performing value-preserving transformations, which modify the controller without sacrificing value. We present two efficient value-preserving transformations: one can reduce the size of the controller and the other can improve its value while keeping the size fixed. Empirical results demonstrate the usefulness of value-preserving transformations in increasing value while keeping controller size to a minimum. To broaden the applicability of the approach, we also present a heuristic version of the policy iteration algorithm, which sacrifices convergence to optimality. This algorithm further reduces the size of the controllers at each step by assuming that probability distributions over the other agents' actions are known. While this assumption may not hold in general, it helps produce higher quality solutions in our test problems.

Nail aplasia, microcephaly, severe mental retardation and MRI abnormalities: report of two unrelated cases

We present the clinical and laboratory features of two unrelated mentally retarded females with sporadic bilateral periventricular nodular heterotopia (BPNH), hypoplastic/absent nails and other malformative features. Clinical examination, MRI scanning, EEG recording, karyotyping and neuropsychological testing were performed. From a molecular genetic point of view, direct sequencing analysis, X-inactivation assay and telomere analysis were carried out in one patient. The two patients showed convincing similarities from clinical and neuroradiological points of view with BPNH, mental retardation, microcephaly and hypoplastic/absent nails of fingers and toes. Our two unrelated mentally retarded females may be affected by complex malformative syndromes sharing some common features such as BPNH, mental retardation and hypoplastic/absent nails. Further genetic studies are needed to better understand the pathogenetic bases of this neurological disease. These two cases widen the spectrum of BPNH-associated syndromes.

Iloprost treatment in patients with Raynaud's phenomenon secondary to systemic sclerosis and the quality of life: a new therapeutic protocol

OBJECTIVES

To evaluate the clinical efficacy and the effects on the quality of life of iloprost, a prostacyclin analogue, used according to a new protocol in patients with Raynaud's phenomenon secondary to systemic sclerosis.

METHODS

In this randomized study, we treated 30 patients with iloprost, given by intravenous infusion, at progressively increasing doses (from 0.5 to 2 ng/kg/min) over a period of 6 h each day for 10 days in two consecutive weeks, with repeated cycles at regular intervals of 3 months for 18 months. The results were compared with those obtained in 30 other patients who received the same drug but with different dosing schemes.

RESULTS

The total average daily duration of the attacks, the average duration of a single attack and the average daily frequency of the attacks were reduced significantly in all treatment groups, but the comparison between the groups demonstrated significant differences between patients treated with the new protocol and the others at later times (12 and 18 months). The effects on the quality of life in the group treated with the new protocol, evaluated with the Short Form-36, demonstrated a marked improvement regarding both the scale relating to the physical aspect of the illness and, especially, the scale relating to the mental aspect.

CONCLUSIONS

In patients with systemic sclerosis, cyclic intravenous iloprost infusion is efficacious in the treatment of Raynaud's phenomenon. The protocol that we used, compared with others, not only has favourable clinical effects but also leads to a marked improvement in the quality of life.

EuCliD--a medical registry

OBJECTIVES

The European Clinical Database EuCliD small star, filled has been developed as a tool for supervising selected quality indicators of about 200 European dialysis centers. Major efforts had to be made to comply with local and European laws regarding data security.

METHOD

EuCliD is a Lotus Notes based flat-file database currently containing medical data of more than 14,000 dialysis patients from 10 European countries. Another 15,000 patients from 150 centers in 4 South-American countries will be added soon. Data are entered either manually or by means of interfaces to existing local data managing systems. This information is transferred to a central Lotus Notes Server. Data evaluation was performed with statistical tools like SPSS.

RESULTS

EuCliD is used as a part of the CQI (Continuous Quality Improvement) management system of Fresenius Medical Care (FMC) dialysis units. Each participating dialysis center receives (currently every half year) benchmarking reports at a regular interval. The benchmark for all quality parameters is the weighted mean of the corresponding data of all centers.

CONCLUSIONS

An obvious impact of data sampling and data evaluation on the quality of the treatments could be observed within the first one and a half years of working with EuCliD. This also concerns important outcome predictors like Kt/V and hemoglobin concentration as the outcome itself expressed in hospitalization days and survival rates. With the help of EuCliD the user is able to sample clinical data, identify problems, search for solutions with the aim of improving the dialysis treatment quality and guarantee a high-class treatment quality for all patients.

Metabolic syndrome and breast cancer risk

States of hyperinsulinemia with insulin resistance are frequently associated with proliferative tissue abnormalities, via stimulation of DNA synthesis and cell proliferation through the IGF-1 receptor. Such elements of metabolic syndrome (hyperinsulinemia/insulin-resistance, obesity, type 2 diabetes mellitus, hypertension, dyslipidemia) are explored in a population of 125 women (n. 50 with histologically confirmed diagnosis of breast cancer, Group A; n. 50 with benign breast pathology, Group B; n. 25 with no breast pathology, Group C, controls), affering to a Center for the prevention of breast cancer, in order to investigate for an eventual relationship between these pathologies. The prevalence of type 2 diabetes mellitus, hypertension, dyslipidemia, was higher in group of women affected by breast cancer vs. benign breast pathology and controls. This finding is in agreement with the hypothesis of the interrelationship of hyperinsulinism/insulin resistance with the growth-related abnormalities of breast cancer.

EuCliD (European Clinical Database): a database comparing different realities

Quality and variability of dialysis practice are generally gaining more and more importance. Fresenius Medical Care (FMC), as provider of dialysis, has the duty to continuously monitor and guarantee the quality of care delivered to patients treated in its European dialysis units. Accordingly, a new clinical database called EuCliD has been developed. It is a multilingual and fully codified database, using as far as possible international standard coding tables. EuCliD collects and handles sensitive medical patient data, fully assuring confidentiality. The Infrastructure: a Domino server is installed in each country connected to EuCliD. All the centres belonging to a country are connected via modem to the country server. All the Domino Servers are connected via Wide Area Network to the Head Quarter Server in Bad Homburg (Germany). Inside each country server only anonymous data related to that particular country are available. The only place where all the anonymous data are available is the Head Quarter Server. The data collection is strongly supported in each country by "key-persons" with solid relationships to their respective national dialysis units. The quality of the data in EuCliD is ensured at different levels. At the end of January 2001, more than 11,000 patients treated in 135 centres located in 7 countries are already included in the system. FMC has put the patient care at the centre of its activities for many years and now is able to provide transparency to the community (Authorities, Nephrologists, Patients.....) thus demonstrating the quality of the service.

Transient MRI abnormalities associated with partial status epilepticus: a case report

We report the case of an 18-year-old woman who presented a long-lasting cluster of partial seizures, and MRI cortical abnormalities localized in the left parietal lobe. The MRI changes correlated with the site of the epileptogenic focus, and disappeared within 2 weeks. The recognition of these reversible MRI abnormalities, which are presumably due to a temporary alteration of blood-brain barrier in the epileptogenic zone with subsequent edema, and are not associated with any underlying organic conditions, is extremely useful in the medical management of the patient and allows to avoid other invasive diagnostic procedures.

Surveillance of acute flaccid paralysis in Italy: 1996-1997. AFP Study Group. Acute flaccid paralysis

The last case of poliomyelitis due to transmission of indigenous wild poliovirus occurred in Italy in 1982. To achieve the certification of the eradication of poliomyelitis in Italy, an active surveillance of acute flaccid paralysis (AFP) in the population aged less than 15 years was set up following the World Health Organization (WHO) guidelines. The survey started in 1996 with a pilot study involving 4 out of 21 regions, and was gradually extended to a national level in 1997. The two-year survey identified five patients with diagnosis of vaccine associated paralytic poliomyelitis (VAPP). Polioviruses type 2 and 3 Sabin-like were isolated and characterized in three of them. In the remaining two cases, samples were collected late after the onset of symptoms, and poliovirus could not be isolated. No wild polioviruses were detected during the survey. The rate of non-polio AFP found in Italy in 1997 was 0.61 cases per 100,000, which is lower than the level of 1.0 case per 100,000 considered as acceptable by the WHO. This was mainly due to the delay in organizing the hospital network and starting the active search of AFP cases in the largest and most densely populated regions. Therefore, the overall rate of AFP found in Italy underestimates the global effectiveness of the program, which however will be better evaluated in the next few years. This study is the first systematic attempt to determine the rate of AFP in Italy.

[The use of stereotaxic cytology in the diagnosis of nonpalpable breast lesions. Our experience]

BACKGROUND AND AIMS

The increasingly frequent use of mammography for the early diagnosis of breast cancer and the consequent identification of mammary lesions at a preclinical stage raises the fundamental problem of the differential diagnosis between non-suspected non-palpable lesions (NPL) which can therefore be monitored over time and suspected NPL or definite carcinoma requiring histological confirmation and surgical biopsy. The diagnostic accuracy of mammography alone is not sufficiently high to differentiate benign lesions from malignant or strongly suspected ones. The use of surgical biopsy in the event of suspected NPL could be significantly reduced by the use of stereotaxic cytology which would improve the diagnostic accuracy of mammography.

METHODS

The study refers to 72 suspected NPL undergoing surgical biopsy after having performed stereotaxic cytology on a sample taken with a dedicated mammographic device (Mammotest-TRC).

RESULTS

The rate of inadequate samples for correct cytological evaluation was 16.1%. Of the 72 NPL undergoing surgical biopsy, 40 (55.5%) were found to be carcinomas and 32 (44.5%) were benign lesions. The sensitivities of mammography alone and cytology alone in identifying infraclinical breast carcinoma were respectively 0.85 and 0.95. If the results of the two methods were evaluated together, the level of sensitivity was 0.98.

CONCLUSIONS

The use of stereotaxic cytology enables a marked improvement to be achieved in the diagnostic accuracy of mammography for the identification of suspected NPL to undergo surgical biopsy, notably reducing the cost of biopsy (number of benign lesions for each carcinoma diagnosed) and consequent discomfort for patients.

Antigenic and molecular characterization of wild type 1 poliovirus causing outbreaks of poliomyelitis in Albania and neighboring countries in 1996

Mass vaccination has led poliomyelitis to become a rare disease in a large part of the world, including Western Europe. However, in the past 20 years wild polioviruses imported from countries where polio is endemic have been responsible for outbreaks in otherwise polio-free European countries. We report on the characterization of poliovirus isolates from a large outbreak of poliomyelitis that occurred in Albania in 1996 and that also spread to the neighboring countries of Yugoslavia and Greece. The epidemics involved 145 subjects, mostly young adults, and caused persisting paralysis in 87 individuals and 16 deaths. The agent responsible for the outbreak was isolated from 74 patients and was identified as wild type 1 poliovirus by both immunological and molecular methods. Sequence analysis of the genome demonstrated the involvement of a single virus strain throughout the epidemics, and genotyping analysis showed 95% homology of the strain with a wild type 1 poliovirus strain isolated in Pakistan in 1995. Neutralization assays with both human sera and monoclonal antibodies were performed to analyze the antigenic structure of the epidemic strain, suggesting its peculiar antigenic characteristics. The presented data underline the current risks of outbreaks due to imported wild poliovirus and emphasize the need to improve vaccination efforts and also the need to implement surveillance in countries free of indigenous wild poliovirus.

[Hypertension and peripheral arterial hemodynamics]

Sixty uncomplicated hypertensive patients (40 stable and 20 borderline) were studied, by strain gauge plethysmography, in comparison with 25 normotensive subjects, in order to evaluate the arterial hemodynamics of the lower limbs in essential hypertension and to verify the different pattern in borderline and in stable hypertensives. Resting blood flow, even if lightly decreased in hypertensive groups, didn't show significant differences in its mean values; Peak Flow, instead, was reduced proportionally to the severity of hypertension in all the hypertensive patients, but only in the stable hypertensives did it prove statistically significant. Minimal Vascular Resistances showed a similar behaviour; they were significantly increased only in the stable hypertensives, whereas Basal Vascular Resistances, were raised in all hypertensive patients, in the borderline group too. Finally, half time and total hyperemic time, which indicate vascular reactivity, were significantly decreased in all hypertensives. These results suggest that the stable hypertensive patients principally develop arterial structural changes, while the borderline hypertensive patients have only functional modifications, such as a reduced compliance and a hyperdynamic condition.

[A seroepidemiological study on the level of immunological coverage in a nomadic population in Rome]

Immunization status to the three types of poliovirus, to tetanus, diphtheria and measles was evaluated in a Gypsy population living at a Roman camp. Information about demographic data and history of immunization was collected from 149 subjects and a blood sample was obtained from 86 individuals to determine antibody titres to the above mentioned infectious agents. Among the responders, only 20.8% had received at least one dose of oral polio vaccine (OPV), tetanus and diphtheria vaccine, while none was vaccinated against measles. In spite of a low immunization coverage, serological data showed high prevalence of antibodies to the three types of poliovirus (81.4% to polio type 1:94.2% to polio type 2:62.8% to polio type 3) and to measles (76.7%), while antibodies to tetanus and to diphtheria were detected respectively only in 3.5% and 0% of the individuals tested. High levels of antibodies to polio were found also among unvaccinated subjects. For these, a statistically significant positive correlation between age and number of "contact doses" from vaccinated family members was observed (r = 0.70; CI 95%: 0.27-0.90). In conclusion, this study uncovers very low levels of immunization to poliovirus, tetanus, diphtheria and measles in the study Gypsy population, and shows the effects of the secondary spread of the OPV, which probably contributed to reduce the risk of contracting the disease in unvaccinated individuals.