Design and specification of iterators using the swapping paradigm

How should iterators be abstracted and encapsulated in modern imperative languages? We consider the combined impact of several factors on this question: the need for a common interface model for user defined iterator abstractions, the importance of formal methods in specifying such a model, and problems involved in modular correctness proofs of iterator implementations and clients. A series of iterator designs illustrates the advantages of the swapping paradigm over the traditional copying paradigm. Specifically, swapping based designs admit more efficient implementations while offering relatively straightforward formal specifications and the potential for modular reasoning about program behavior. The final proposed design schema is a common interface model for an iterator for any generic collection     

Research methodology: Part II, Essentials of factor analysis

This article is part two of our four part series on basic statistical analytical methods. Using a case method presentation, the basic essentials of factor analysis is described.     

Hepatic nucleotide triphosphate regeneration after hypothermic reperfusion in the pig model: an in vitro P-NMR study

The aim of this study was to assess the possibility of regenerating nucleotide triphosphates (NTP) in the pig liver following its harvest and subsequent storage on ice. This study has used a pig model that allowed human donor liver retrieval techniques and methods of storage to be utilized. In vitro phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy was used to evaluate the changes associated with phosphorus containing metabolites such as NTP, phosphomonoesters (PME), phosphodiesters (PDE), and inorganic phosphate (Po). During 4 hr storage NTP levels were reduced to undetectable levels but its regeneration was possible over a period of 2 hr of oxygenated hypothermic reperfusion. Resynthesized NTP reached values that were only 30% reduced from pre-harvest values. There was a corresponding reduction in Pi over the same period. Glycolytic intermediates, 3-phosphoglycerate and 2,3 diphosphoglycerate, both increased significantly during the period of storage and subsequently declined following hypothermic reperfusion. Cellular damage, indicated by the concentrations of glycerophosphorylcholine (GPC) and glycerophosphorylethanolamine (GPE) was minimal during cold storage. However upon hypothermic reperfusion, concentrations of GPC and GPE reduced, indicating a degree of cellular damage caused by reperfusion. This study has shown for the first time that is possible to regenerate high energy phosphate nucleotides following a period of hypothermic reperfusion in a large, clinically related animal model. This technique warrants investigation clinically to improve the outcome of orthotopic liver transplantation. It also provides a method to study the effects of different preservation fluids and methods of storage and organ reperfusion.     

Reconstitution of the response to leukemia inhibitory factor, oncostatin M, and ciliary neurotrophic factor in hepatoma cells

Ciliary neurotrophic factor (CNTF) has been described as a neuro-active cytokine that shares functional similarities with the leukemia inhibitory factor (LIF). We demonstrate here that, like LIF, CNTF stimulates expression of acute phase plasma proteins in rat H-35 hepatoma cells. Transfection of the LIF receptor into Hep3B hepatoma cells reconstituted LIF and oncostatin M regulation of acute phase plasma protein genes. Co-expression of the LIF receptor and the CNTF receptor, but not expression of either subunit alone, generated CNTF responsiveness in Hep3B cells, suggesting cooperativity of these receptor subunits. Evidence is presented for direct interaction of the LIF receptor with the intracellular signal transduction machinery.     

Massive osteolysis

Massive osteolysis is rare, peculiar, and enigmatic. The clinical, radiographic, and histologic features were reviewed in 11 cases. The patients were generally young (mean age, 20.7 years), and males outnumbered females. More than half the patients had involvement of either the femur or the ribs alone or including the vertebrae. On the basis of radiographic studies, the disease process is capable of originating either in bone or adjacent soft tissues. Histologically, the authors were unable to identify pathognomonic features. Other than excision of all involved tissue, surgical treatment was generally ineffective. Radiation therapy may be successful in eradicating the disease in selected cases.     

Induced hypothermia in the postoperative management of refractory cardiac failure following paediatric cardiac surgery

Postoperative low cardiac output states are a major cause of postoperative mortality in infants and children following corrective cardiac surgery for congenital heart defects. In this unit, whole body hypothermia has been used since 1979 in the management of these low output states when they are refractory to conventional modes of therapy. Twenty cases treated in this way between July 1986 and June 1990 were reviewed in 1992. The current report reviews the 50 further cases treated with moderate hypothermia between July 1990 and December 1995. The median (range) age of patients was 8 months (0 days-16 years) with a median weight of 4.1 kg (2.5-33 kg). Following cooling, there was a decrease in heart rate (p < 0.001), an increase in mean arterial pressure (p < 0.001) and a decrease in mean atrial pressure (p < 0.001). Significant increases in pH and urine output were also noticed, the increase in urine output being greater in the surviving group (p = 0.02). A decrease in platelet count occurred (p < 0.001) but white blood cell count remained unchanged (p = 0.18). Twenty-five of the 50 patients survived to leave hospital. Induced hypothermia does not appear to be associated with any complications and after the failure of all conventional treatment, it seems likely that the technique may have been beneficial to outcome in some patients.     

Fda Inspections of Systems in a Pharmaceutical Manufacturing Establishment

Since the late 1960_s, and increasingly as the years have passed, FDA has been using the systems approach to establishment inspections. FDA's Compliance Programs for drug process inspections state, in effect, that if one system is out of control the entire process may be deemed to be out of control. When is a system out of control? There seem to be no two FDA Investigators who do inspections precisely the same way, but they all must follow certain defined policy during inspections. Systems inspections will be presented from the vantage point of an experienced FDA Investigator.     

Performance evaluation of S-ALOHA over non-stationary wirelessinfrared channels

The authors present the throughput analysis of a slotted ALOHA protocol over non-stationary wireless infrared channels. The protocol operation is modelled as a four-dimensional Markov chain and equilibrium point analysis is employed to carry out the performance evaluation. Theoretical predictions are in good agreement with simulation results