Showing papers by "University of Turin published in 1982"

An Efficient Unification Algorithm

Abstract: The unification problem in f'mst-order predicate calculus is described in general terms as the solution of a system of equations, and a nondeterministic algorithm is given. A new unification algorithm, characterized by having the acyclicity test efficiently embedded into it, is derived from the nondeterministic one, and a PASCAL implementation is given. A comparison with other well-known unification algorithms shows that the algorithm described here performs well in all cases.

Visible Light Induced Generation of Hydrogen from H2S in CdS‐Dispersions, Hole Transfer Catalysis by RuO2

Abstract: Illumination of US-dispersions by visible light in solutions containing H2S or sulfide ions leads to efficient generation of hydrogen and sulfur. Very small quantities of RuO2 deposited on the CdS-particles improve markedly the quantum yield of H2-formation for which the optimum value obtained so far is ϕ = 0.35 ± 0.1. The effect of RuO2 is attributed to catalysis of hole transfer from the valence band of CdS to H2S or sulfide in solution.

Cell surface molecules and fibronectin-mediated cell adhesion: effect of proteolytic digestion of membrane proteins.

Abstract: Proteases have been used as a tool to investigate the role of surface molecules in fibronectin-mediated cell adhesion. Proteolytic digestion of membrane-proteins by pronase (1 mg/ml for 20 min at 37 degrees C) completely inhibited adhesion of baby hamster kidney (BHK) fibroblasts on fibronectin-coated plastic dishes. Various degrees of inhibition were also obtained after treatment with proteinase K, chymotrypsin, papain, subtilopeptidase A, and thermolysin. Protein synthesis was required to restore the adhesive properties of pronase-treated cells, showing the protein nature of the molecules involved in adhesion to fibronectin. A peculiar feature of these proteins was their resistance to cleavage by trypsin. After prolonged trypsin treatment (1 mg/ml for 20 min at 37 degrees C), cells adhered and spread on fibronectin-coated dishes, even when protein synthesis was inhibited by 4 microM cycloheximide. Under these conditions only three glycoproteins (gp) of molecular weight 130,000, 120,000, and 80,000 were left on the cell surface. These were precipitated by a rabbit antiserum against BHK cells that also inhibited adhesion of trypsin-treated cells. gp120 and gp80 were left at the cell surface after mild pronase digestion (0.2 mg/ml for 20 min at 37 degrees C), under conditions not affecting adhesion. These data suggest that these glycoproteins may be involved in fibronectin-mediated cell adhesion in some yet unknown way.

The use of β-galactosidase as a tracer in immunocytochemistry

Abstract: A new immunocytochemical method using β-galactosidase as a tracer is described. The positive staining appears blue on an unstained background. The present method has the high sensitivity and specificity of the immunoperoxidase method and appears to be a practical alternative. The substrate has no carcinogenic activity. Staining is permanent and the sections can be dehydrated and mounted in synthetic media. Enzyme and substrate solutions are stable for several months.

Ultrastructural aspects of endomycorrhiza in the ericaceae

Abstract: Summary The ultrastructural features of the dissociated mycorrhizal symbionts Pezizella ericae Read and Calluna vulgaris L. Hull, grown in pure culture, and of the modifications occurring in both fungus and root cells during their reassociation in axenic culture have been studied in detail. Growing (apical/subapical and vacuolated zones) and non-growing (ageing zone) regions can be distinguished in colony margins of Pezizella ericae in pure culture. In axenic mycorrhiza cultures the general morphology of the fungus remains the same with living hyphae closely resembling those in the active growing region. However, the external hyphae around roots develop an abundant fibrillar sheath which has a polysaccharide-protein composition and the possibility that this may play a role in recognition and adhesion phenomena in ericoid mycorrhizae is discussed. Metachromatic vacuolar granules, which are very common in pure cultures of Pezizella ericae, are often present in external hyphae around axenic mycorrhizal roots but are very rarely observed in intracellular fungal hyphae. The general ultrastructural organization of these axenically produced ericoid mycorrhizae is compared to that reported for natural infections in several ericaceous species.

Perinatal transmission of the hepatitis b virus and of the hbv‐associated delta agent from mothers to offspring in northern italy

Abstract: We report a prospective study on infants born to hepatitis B surface antigen (HBsAg) carrier mothers to estimate the incidence of perinatal transmission of HBV and HBV-associated delta agent in Northern Italy. The risk of infection to the infant was related to the presence of the HBe antigen-antibody system, HBV-specific DNA polymerase activity and antibody to delta in maternal sera, and to the titer of anti-HBe in babies at birth. The data of this study indicate: 1. Babies born to HBsAg carrier mothers with HBeAg in serum are at extremely high risk of acquiring HBV infection and of developing a chronic carrier state, whereas those born to anti-HBe-positive mothers are at a lower (P less than .01) yet consistent risk of infection. 2. HBs antigenemia is usually prolonged and symptomatic in babies born to HBeAg-positive mothers while being self-limited and asymptomatic in babies born to anti-HBe-positive mothers. 3. DNA polymerase activity in maternal serum appears to be the most sensitive marker predicting HBV transmission to the infant since it was detected in all the HBeAg-positive mothers and also in two anti-HBe-positive mothers and in one HBeAg/anti-HBe-negative mother who transmitted infection to their babies. 4. High titers of anti-HBe (up to 1:103) do not prevent HBV infection. 5. Vertical transmission of delta infection seems to occur only in circumstances that permit perinatal transmission of HBV infection.

Unified geometric theory of electromagnetic and gravitational interactions

Abstract: A geometric unification of the electromagnetic and gravitational fields is presented. The unified field is described by a linear connection Γ on the space-time. Field equations for the unified field Γ are equivalent to Einstein-Maxwell equations. Field equations for matter interacting with the unified field are the usual ones. The interaction of the unified field with a charged scalar field is studied in detail.

On the equivalence of the relativistic theories of gravitation

Abstract: Einstein's equations are rewritten in terms of a certain torsionless linear connection Γαβμ which differs, in general, from the Levi-Civita metric connection γαβμ. The torsionless connection Γαβμ appears in a natural way as the canonical momentum of the gravitational field gμν. Einstein's equations have a simple interpretation in terms of the connection Γαβμ. The equivalence of the so-calledpurely metric, purely affine, andmetricaffine theories of gravitation is proved.

Effects of Visual Angle on Perspective Reversal for Ambiguous Patterns

Abstract: Reversal rates of an ambiguous figure (the Necker cube) were studied for different pattern sizes covering a range of visual angles theta from approximately 1 to 62 deg. A large number of reversals was obtained for each observer and each pattern in order to examine the statistical distributions of reversal times. A pronounced flattening of the statistical distributions (represented throughout by a gamma distribution) and a growth of the mean duration of each percept, with increasing pattern size was found. A plateau in the range of theta between 5 and 20-30 deg was observed. For larger values of theta two kinds of observers have been identified: for 'fast' observers the inversion rate is little affected by theta, whilst for 'slow' observers, the mean reversal time increases strongly with theta. A tentative model, based on three different contributions to the duration of the alternation process, is proposed: a constant term, independent of theta, and two terms dependent on theta--a retinal term, and a cortical one. The last term is interpreted as due to the spreading of excitation with the characteristic of a filling-in process.

Crystal structures of Ca-rich clinopyroxenes on the CaMgSi2O6-Mg2Si2O6 join

Abstract: The structural changes occurring in the clinopyroxenes with composition Di100, Di90En10 and Di80En20, due to the Ca-Mg substitution in the M2 site, have been studied. Evidence is given that with increasing Mg content a small percentage of the atoms converts from the M2 position to a new M2′ position which is solely occupied by Mg. The maximum conversion of M2 to M2′ found in this study is 7%. The closest parallel to the M2′ geometry is found in the ZnSiO3 pyroxene (C2/c). The presence of this new site causes significant changes in the tetrahedral configuration, because the M2′ atoms are not bonded to 03. The intermediate compositions, Di90En10 and Di80En20, may be thought of as the coexistence of two structural models: diopside and ZnSiO3 pyroxene (C2/c).

Histological observations on the regrowth of malignant gliomas after radiotherapy and chemotherapy.

Abstract: The reproliferation of glioblastomas after radiation and chemotherapy has been studied in 25 tumors by means of whole mount histological preparations. The tumors have been subdivided into four groups according to the radiation dose and the distance from the end of radiation. After 4,000 rad vessel proliferations and mitoses stop, while vessel degenerations and astrocytes with deformed nuclei appear. Six months after 6,000 rad have been delivered, repopulation phenomena are clearly evident and are mainly represented by mitoses both in parenchyma and in the vessel walls, circumscribed necroses with pseudopalisadings, proliferations of formerly degenerated vessels, etc. The brain adjacent to tumor (BAT) has a great importance since it is one of the reproliferating sites, even though it may be unrecognizable for the occurrence of radiation damages.

Autonomic innervation of the ocular choroid membrane in the chicken: a fluorescence-histochemical and electron-microscopic study.

Abstract: The distribution pattern of adrenergic fibres innervating the ocular choroid membrane of the chicken was studied by means of fluorescence and electron microscopy. In addition, the origin of these fibres was investigated after superior cervical ganglionectomy. Adrenergic axons reach the choroid, partly forming the perivascular plexuses and partly running in the choroid nerves and the choroidal branches of the ciliary nerves. The axon terminals distribute to the smooth muscle cells of the arterial wall and to the extensive system of smooth muscle cells of the intervascular stroma. After unilateral ganglionectomy, fluorescent fibres almost completely disappeared, and degenerative changes could be observed in the terminal varicosities on both smooth muscle cell populations. These findings suggest that the adrenergic axons either originate from neurones within the ipsilateral superior cervical ganglion, or pass through this ganglion. The persistence of normal terminals in short- and long-term ganglionectomised animals shows that the vasal and intervascular muscle cells of the choroid membrane are provided with both an adrenergic and a cholinergic innervation.

Solitonic gravitational waves in Bianchi II cosmologies. 1. The general framework

Abstract: The inverse scattering method is applied to a class of space-times belonging to the Bianchi types I–VII. Solitonic perturbations corresponding to one or two poles on an arbitrary cosmological background are described in detail. The fundamental matrixψ 0 is explicitly calculated for a Bianchi II background, thus providing the first known example of a non-diagonal case.

Photocoagulation of cerebral arteriovenous malformations and arterial aneurysms with the neodymium: yttrium-aluminum-garnet or argon laser: preliminary results in twelve patients.

Abstract: Six arteriovenous malformations (AVMs) and five arterial aneurysms (AAs) were treated with either argon or neodymium:yttrium-aluminum-garnet laser irradiation; one AVM was treated with both. All AVMs were occluded completely, leaving adjacent tissue untouched and preserving the regional vascularization. Photocoagulation produced varying effects on AAs: in one case an intraoperative rupture was sealed, in two cases the volume of an ectasia was reduced when the bleeding and thinner areas were coagulated, and in one case a saccular aneurysm was progressively and completely obliterated while the patency of the parent artery was preserved. These preliminary results are satisfactory; more experience will indicate how and when these new techniques can replace traditional ones or be used in combination with them.

A clinical study of graphic registration of the condylar path inclination.

Abstract: The angular values of the CSP registered from 390 patients and obtained by tracing a tangent to the graph with the GR were analyzed. The data subjected to statistical analysis gave a median angular value of the CSP equal to 33 degrees and showed a great median value dispersion. A low error index was obtained in tracing the tangent to the CSP tracing with the GR method. The angular values of the CSP were repeatable over time since the variations found were less than 5 degrees. Variations of the CSP greater than 5 degrees were noted after repeated registrations in patients with TMJ disturbances as well as in patients treated with complete dentures. These data show the necessity for an individual measurement of the CSP value, especially in patients who need extensive readjustments of the prosthesis.

Bedside evaluation of atrioventricular block with narrow QRS complexes: Usefulness of carotid sinus massage and atropine administration

Abstract: Second-degree intra-His bundle block is frequently of type I (Wenckebach periods) or 2:1. In this situation, the surface electrocardiogram does not permit distinction between intranodal (atrioventricular [A-V] and subnodal (intra-His) block. This study examined the value of bedside carotid sinus massage and atropine administration in diagnosing the site of block from the standard electrocardiogram in subjects with chronic A-V block and narrow QRS complexes. Fifteen patients had intra-His bundle block and 10 had intranodal block. The combination of two tests correctly located the site of block in 22 subjects, and was noncontributory in 3. Thirteen of the 15 intra-His bundle blocks and 9 of the 10 intranodal blocks were properly identified; in three cases the results were nondiagnostic, but no wrong diagnoses were made. The noninvasive bedside method of carotid sinus massage and the use of atropine permit both the localization and the determination of the type of block in the majority of cases of second degree A-V block and narrow QRS complexes. In a proper clinical context they can obviate the need for invasive electrophysiologic studies.

Juvenile milk protein secreting carcinoma

Abstract: A case of juvenile secretory carcinoma of the breast is reported. The tumor occured in a 19 yr-old nulliparous woman and was treated by local resection; it recurred 7 years later. Slight infiltration of the pectoral muscle, metastatic involvement of one lymph node and multifocal areas of carcinoma were found at radical mastectomy. No further recurrence has been detected after 1 year. This case confirms the slow evolution of this neoplasm but stresses that its behaviour is not always as indolent as previously believed. We have used histochemical techniques for mucins (PAS, Alcian Blue) and immunoperoxidase methods for milk proteins (MFGM, β-Casein, α-lactalbumin), for myoepithelial cells (actin) and for oncofetal antigens (CEA). Our results suggest that: Immunoperoxidase methods for milk proteins are a more specific and reliable marker than PAS staining in characterizing the secretory activity of juvenile carcinoma. The absence of myoepithelial cells in infiltrative areas detected by immunoperoxidase methods for actin confirms the low degree of organization in this well differentiated carcinoma of limited aggressiveness which secretes milk proteins.