Showing papers by "Sapienza University of Rome published in 1974"

Bilinear systems: An appealing class of "nearly linear" systems in theory and applications

Abstract: Recently, attention has been focused on the class of bilinear systems, both for its applicative interest and intrinsic simplicity. In fact, it appears that many important processes, not only in engineering, but also in biology, socio-economics, and ecology, may be modeled by bilinear systems. Moreover, since their nonlinearity is due to products between input and state variables, this class frequently may be studied by techniques similar to those employed for linear systems. This work is intended to motivate the interest of bilinear systems and to present the current state of research in its various aspects. After an introductory section, in which theoretical and applicative aspects of bilinear systems are enlightened, four other sections follow, respectively, devoted to structural properties, mathematical models, identification and optimization. In a final section, some concluding remarks are made on still open problems and possible trends for future research.

Yeast-mycelial conversion induced by N-acetyl-D-glucosamine in Candida albicans

Abstract: DIMORPHISM in fungi is generally defined as a reversible transition from a yeast habit of growth (Y) to a mycelial one (M)1. In Candida albicans Y→M transition can occur rapidly in serum2,3, serum substitutes and other natural4–6 and synthetic media7. In a few hours the yeast cell or blastospore forms a germ tube which grows as a true mycelium6,8,9. Since the cellular form depends on wall construction10, marked modifications in the organisation of wall components are expected to, and in fact do, occur during morphogenesis. Nevertheless, there is chemical11, cytochemical and ultrastructural evidence12,13 that the differences between Y and M walls of C. albicans are essentially quantitative, strongly suggesting that hyphal conversion in this yeast is controlled by the modulation of pre-existing enzymatic activities rather than by any new factors.

Gastrin release by bombesin in the dog

Abstract: 1 The intravenous infusion of bombesin produced in intact dogs and, more strikingly in dogs provided with gastric fistulae a sharp increase in plasma levels of immunoreactive gastrin and at the same time a stimulation of gastric acid secretion. Gastrin response was correlated with the dose of bombesin from approximately 0.1 mug kg(-1) h(-1) (threshold) to 1 mug kg(-1) h(-1) (maximum gastrin release).2 Atropine and metiamide reduced or inhibited gastric acid secretion stimulated by bombesin, but did not affect the rise in gastrin levels.3 Acidification of the whole stomach or of a perfused antral pouch caused a reduced or delayed response to bombesin. However, the inhibitory effect of acidification could be surmounted by prolonging the duration of bombesin infusion.4 Antrectomy greatly reduced the rise in gastrin levels and the increase in acid gastric secretion produced by bombesin, but left unaffected the gastric secretagogue effect of pentagastrin.5 It is concluded that bombesin is a potent releaser of gastrin from the antral mucosa.6 The possible influence of the renal effects evoked by bombesin in the dog on the gastrin response to the polypeptide is discussed.

Evidence of cholecystokinin release by bombesin in the dog

Abstract: 1 The intravenous infusion of bombesin elicited in the dog a contraction of the gall bladder with decreased opening pressure of the choledocho-duodenal junction and stimulation of pancreatic secretion. 2 The pancreatic juice produced under the influence of bombesin was poor in bicarbonate and rich in protein. Threshold doses of the peptide were of the order of 0.25 μg kg-1 h-1 and maximum protein output was obtained with 1 μg kg-1 h-1. The pancreatic protein response to bombesin was very similar, in its onset and duration, to that elicited by intraduodenal infusion of L-tryptophan. Infusions of bombesin repeated at short intervals produced tachyphylaxis. 3 Antrectomy did not affect the stimulant action of bombesin on the pancreas. Atropine however, reduced the pancreatic protein response to bombesin. 4 It is suggested that bombesin acts on the gall bladder and the exocrine pancreas through release of cholecystokinin from the duodenal mucosa. No release of secretion could be demonstrated. It is likely that the releasing activity of bombesin is limited, in the field of gastrointestinal peptides, to those belonging to the gastrin-cholecystokinin family.

Fungal osteoclasia: a model of dead bone resorption

Abstract: A morphological investigation has been carried out on the osteoclastic activity revealed by a fungus of theMucor genus on buried bone. The hallmark of its activity in eroding bone is the finding of resorption pits and boring channels whose walls are sharp and well calcified up to the free edge, suggesting that bone resorption affects crystallites and the organic matrix simultaneously. Unlike normal osteoclastic cells, the fungal membrane in contact with the bone shows no brush border. As the electron microscope reveals no migration of material to the fungal membrane and its protoplasm, the view is expressed that the material which reaches the fungus has been previously solubilized. There is good reason for supposing that a substance capable of solubilizing the inorganic bone fraction spreads freely through bone tissue, decalcifying the matrix, where, but only where, hyphae show the effects of ageing. All the findings are thoroughly discussed and compared with those furnished by the boring channels in fossil bone.

Social Conformity and Psychological Differentiation

Abstract: This study examined the role of socialization experiences in the development of psychological differentiation. In each of three countries (Holland, Italy, Mexico) two villages were selected as presenting a contrasting picture with regard to degree of emphasis on conformity to family, religious and political authority. It was hypothesized that within the pair of villages in each country children from the village which stressed social conformity would tend to be more field dependent and show other signs of less developed differentiation than children from the village in which social conformity was less emphasized. In each of the six villages approximately 100 children (boys and girls, aged 9–11 and 13–15) were studied. Differentiation was assessed by a battery of tests of field-dependence-independence and the figure-drawing test. In every comparison of mean test scores between pairs of villages, in each of the three countries, children from the village in which social conformity was stressed obtain...

Structure of rat liver sinusoids and associated tissue spaces as revealed by scanning electron microscopy.

Abstract: The inner surface of sinusoids and adjacent hepatocytes have been examined by scanning electron microscopy. The endothelial cells lining the sinusoids show large numbers of fenestrations which vary greatly in size and arrangement. Some are very small (0.1 μm) and arranged in clusters; others that are much larger (∼1.0 μm) are subdivided by slender strands of cytoplasm. At sites where the larger fenestrae are present it is evident that the endothelial lining of the sinusoid is double. This may represent a kind of structural assurance against complete breakdown of what seems to be a very thin and fragile endothelial wall. Junctions between adjacent endothelial cells have not been found in these preparations.

The organic-inorganic relationships in bone matrix undergoing osteoclastic resorption.

Abstract: The organic-inorganic relationships in bone matrix undergoing osteoclastic resorption have been studied in rat tibial diaphyses using electron microscope techniques in an attempt to identify the steps of the resorption process Results suggest that bone resorption occurs in two phases: the first, an extracellular phase, leads to bone matrix fragmentation and partial dissolution, and the second, an intracellular phase, to complete digestion of the breakdown products of the bone matrix The first component of the bone matrix to be attacked by the osteoclast is the ground substance This induces the release of the crystals lying between, and on, the collagen fibrils; any crystals lying within fibrils are released later, when the fibrils break up As this stage proceeds, the collagen fibrils retain their normal intrinsic texture, but gradually loose their lateral aggregation, appearing as individual fibrils (some of them uncovered by crystals), mixed with fragments of fibrils and many free crystals The loosened but otherwise structurally normal collagen fibrils, and their fragments, are strongly argyrophilic Complete dissolution of the disaggregated fibrils occurs outside the cell, both in the resorption zone and in the initial portion of the channels of the ruffled border The free crystals present in the resorption zone and those phagocytosed in cytoplasmic vacuoles are organic-inorganic structures, whose organic component (the crystal ghost) is, at least in part, of proteoglycan nature Dissolution of inorganic material occurs within the cytoplasmic vacuoles of the osteoclasts Results are viewed in relation to the process of bone resorption and, as far as crystal ghosts are concerned, to that of bone calcification A tentative summary of the various steps involved in the mechanism of bone resorption is given

The Value of Studying Subjective Evaluations of Probability

Abstract: The evaluation of probabilities, or the art of forecasting (in the judicious sense of weighing the chances of possible outcomes: not as sheer prophecy), is neither a question of taste (descriptive attitude) nor a mathematically determined question (normative attitude). All evaluations are (logically) admissible, provided only that coherence is satisfied; among these, everybody may judge one or the other more or less ‘reasonable’ (that is, in short, more or less in agreement with his own evaluation, or with the most popular one). The major aspect of coherence consists in conforming “learning from experience” to Bayes’ theorem.

Transduodenal sphincteroplasty: its use in the treatment of lithiasis and benign obstruction of the common duct

Abstract: Summary On the basis of the results obtained in 712 patients, an evaluation of the effectiveness of transduodenal sphincteroplasty is presented. This procedure has proved to be appropriate in treating benign obstruction of the common bile duct as well as choledocholithiasis. Mortality was 1.1 per cent and long-term results were satisfactory in 97 per cent of the cases. Only sixteen patients required reoperation for residual or recurrent stones or for stricture of the sphincter of Oddi. Compared with choledochoduodenostomy, sphincteroplasty avoids the hazards of the so-called sump syndrome and of ascending cholangitis by reflux of intestinal contents into the common duct. A high incidence of postoperative pancreatitis in patients who undergo sphincteroplasty has not been observed.

Dynamic Equibalents of Asynchronous Motor Loads in System Stability Studies

Abstract: The dynamic behavior of complex asynchronous motor loads has been investigated by means of a digital computer program based on general equations for induction machines. The paper is devoted to load-voltage relationships. Load-frequency characteristics are not discussed in detail.

Food avoidances during the puerperium and lactation in Tamilnad

Abstract: Over a period of six months, 1200 women of 54 castes and 55 tribal women in Tamilnad (South India) were interviewed about food avoidances during the puerperium and lactation. Avoidances included meat, fish, eggs, buttermilk and curds, certain fruits, gourds, green vegetables, sweet potatoes and groundnuts. All abstentions were primarily conceived in the interest of the baby, to whom harmful influences would be transmitted through the breast milk.

The so-calle "Cloverleaf Skull Syndrome". A report of three cases with a discussion of its relationships with thanatophoric dwarfism and the craniostenoses.

Abstract: Three cases of cloverleaf skull are reported, one in a newborn with generalized bone changes suggesting thanatophoric dwarfism, one in an infant with acrocephalosyndactyly, and the other in an infant with several features of Crouzon's disease. The relationships between cloverleaf skull, on one side, and thanatophoric dwarfism and the severe craniostenoses, on the other, are discussed. The cloverleaf deformity should be considered a purely morphologic feature in common to several diseases, and should no longer be considered a separate “syndrome”.

Scanning electron microscopy demonstration of cilia in rat intrahepatic bile ducts

Abstract: Numerous cilia have been demonstrated by SEM in cells of rat perilobular and portal bile ducts and ductules. Generally these cilia appear as long, cylindrical evaginations of the plasma membrane. Some of them are so long that, curving and twisting at many points, they cross the ductal lumen. It has been suggested that they may be related to a continual mixing up and propulsion of the bile product down the biliary tree.

Wall structure and bud formation inCryptococcus neoformans

Abstract: Cells ofCryptococcus neoformans fixed by the TAPO-acrolein-osmium method show a highly electron-dense capsule with fibrillar and granular structures and a wall organized in two main layers. The outer layer is electrontransparent and contains a variable amount of low to medium-density material, especially abundant in actively growing cells. The inner wall layer shows a lamellar aspect and in the majority of the cells may further be divided into two sub-layers mainly on the basis of lamellar compactness. The wall of the bud, since its early appearance, is also formed by an inner dark lamellar layer and an outer, electron-transparent one. While the former is seen as a direct continuation of the corresponding innermost part of the parent wall, the latter orginates from the inside of the lamellar wall and grows out with the emerging bud through a rupture of the lateral parental wall. Capsular material always covers the wall of the bud even if its amount is very reduced in the early stages of the budding.

The True Subjective Probability Problem

Abstract: Confusion must be avoided between two different meanings given to ‘Subjective Probability’, and the ensuing kind of problems concerning this notion. Subjectivists maintain that every probability is subjective, inasmuch as it is the ‘degree of belief’ of someone facing an uncertain event. Some psychologists call ‘subjective’ a distorted or inaccurate estimation of something that could be meant as (in a sense) ‘true’ probability. The S-P problem is, in the first case, that of properly clarifying the role of subjective weighing of any relevant element for an accurate assessment of any probability feeling; in the second, it concerns, on the other hand, the ‘misleading’ influence of possible ‘subjective’ factors.