Showing papers by "University of Ljubljana published in 1974"

Cathepsin D: Rapid Isolation by Affinity Chromatography on Haemoglobin-Agarose Resin

Abstract: The intracellular proteinase, cathepsin D, has been isolated from bovine spleen and thymus, in times as short as several hours, by affinity chromatography of partially purified and unpurified tissue extracts on haemoglobin-agarose resin. After subsequent separation from an inactive higher-molecular-weight protein by gel permeation chromatography, the enzyme from both tissues shows three dominant proteolytically active bands on gel electrophoresis at pH 4.3 and 9.5: this proteolytic activity is completely inhibited by the acid-proteinase inhibitor, pepstatin. These enzyme electrophoretic patterns were approximately constant with variation in isolation time and with various preliminary purification procedures. The enzyme shows only traces of polypeptides other than that with an apparent molecular weight of 42000 on dodecylsulphate electrophoresis, in contrast to the enzyme prepared by conventional methods, which contains considerable amounts of smaller polypeptides. This difference in polypeptide composition is shown to be the result of degradation of the enzyme in vitro during isolation by the previously published methods.

External inversion, internal inversion, and reflection invariance

Abstract: Having in mind that physical systems have different levels of structure we develop the concept of external, internal and total improper Lorentz transformation (space inversion and time reversal). A particle obtained from the ordinary one by the application of internal space inversion or time reversal is generally a different particle. From this point of view the intrinsic parity of a nuclear particle (‘elementary particle’) is in fact the external intrinsic parity, if we take into account the internal structure of a particle. We show that non-conservation of the external parity does not necessarily imply noninvariance of nature under space inversion. The conventional theory of beta-decay can be corrected by including the internal degrees of freedom to become invariant under total space inversion, though not under the external one.

Closed-Loop Positioning of Hemiplegic Patient's Joint by Means of Functional Electrical Stimulation

Abstract: We report about the results on positioning of the ankle joint of a hemiplegic patient and of normal experimental subjects, using functional electrical stimulation (FES) of antagonistic muscle groups and position feedback. Such a controller is intended to be used as the execution level of a multilevel orthotic system. The synthesis of the controller has been made with the aid of the components of an analog hybrid computer. Experimental results show that the static and dynamic properties of regulated movements are not essentially inferior to the properties of voluntary movements. There are stated technological problems that will have to be solved before the controller can be clinically applied for rehabilitation purposes. At the present state of the art, the poor technology of FES, the unsolved problem of fatigue with FES muscles, size, price, and bad cosmetic effect prevent the position controller from being clinically applicable.

Substrate-borne sound communication in cydnidae (Heteroptera)

Abstract: 1. Propagation and reception of communicative sound signals were studied ethologically in two species of Cydnidae (Tritomegas bicolor L.,Canthophorus dubius Scop.). The rivalry alternation or rival song evocation was chosen as criterion for successful communication. 2. Sexually mature males in the presence of a female begin rivalry alternation within 2 min after a short courtship. Amputation of abdominal trichobothria does not essentially change the acoustical communication ability. 3. Two males in separate cages do not emit coordinated sounds (heterophonic rival song) unless the frames of the cages are in direct contact (T. b.)(Fig. 3) or signal transmission is secured through plant stems or similar material (C. d.). 4. Single males, stimulated with tape-recorded courtship (M-2) and rivalry (M-E) signals through a piezoelectric transducer, answered with M-R sounds only if the crystal was in contact with the frame of a cage. An air gap of a few millimeters between transducer and cage suffices to prevent the normal acoustical reaction (Figs. 4, 5). 5. Animals (T. b.) without trichobothria or tarsi do not show any difference to the control animals in this experiment (Fig. 4a-c). Only animals without legs did not answer (Fig. 4d). 6. From these experiments the following conclusions are drawn: a) The bugs of the fam. Cydnidae communicate acoustically primarily or exclusively by substrate-borne signals. b) The abdominal trichobothria are not the main mechanoreceptors in their acoustical communication system. c) The critical receptors are probably located in the legs at a site other than the tarsi.

Mass spectra of monosubstituted trans‐stilbenes

Abstract: The mass spectra of twenty-eight monosubstituted trans-stilbenes in ortho, meta, para and alpha positions with N(CH3)2, NH2, OCH3, OH, Br, Cl, F, CH3, COOH, CN and NO2 groups as substituents have been studied. A detailed fragmentation pathway is given for stilbene. This fragmentation, characteristic for most of the substituted stilbenes, takes place either from the molecular or from the [M - Substituent] ion. In o-nitro-, o-methoxy-,α-carboxyl- and α-methylstilbene, however, rearrangement reactions prior to fragmentation influence the fragmentation pattern.

Proton spin-lattice relaxation by critical polarization fluctuations in KH2PO4

Abstract: The observed anomalous decrease in the proton spin-lattice relaxation timeT1 on approaching the Curie point in a rather pure KH2PO4 single crystal is explained by magnetic dipolar coupling to the ferroelectric mode. The isolated “non-interacting” O−H...O proton flipping time is estimated from theT1 data as τ=0.66·10−12 sec for the paraelectric phase and τ=2.24·10−12 sec for the ferroelectric phase, in good agreement with the results obtained from other methods.

Study of the isothermal bulk polymerization of methyl methacrylate by differential scanning calorimetry

Abstract: Course and kinetics of the isothermal bulk polymerization of methyl methacrylate were studied by differential scanning calorimetry. The initiator used was 2,2′-azoisobutyronitrile. The polymerization was investigated at temperatures between 70 and 90°C at constant initiator concentration, 5,2.10−2 mol dm−3. The heat of polymerization at 70°C is −52,3 kJ/mol (−12,5 kcal/mol) and decreases, i.e. becomes more negative, with increasing temperature. Initial rate constants for the polymerization were also determined and from them the overall activation energy, 77 kJ/mol (18,4 kcal/mol), which is in good agreement with the literature value. Another series of polymerization experiments were performed at 80°C with variable amounts of the initiator. The heat of polymerization found is −52,8 kJ/mol (−12,6 kcal/mol) and depends only slightly on the initiator concentration. The overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration. These findings thus corroborate the conclusion reached by other authors that differential scanning calorimetry is a useful method for studying the kinetics of polymerization. Mit Hilfe der Differential-Scanning-Kalorimetrie (DSC) wurden der Verlauf und die Kinetik der isothermen Polymerisation des Methylmethacrylates in Substanz untersucht. Als Initiator wurde 2,2′-Azoisobutyronitril verwendet. Die Polymerisation wurde bei Temperaturen zwischen 70 und 90°C mit konstanter Initiatorkonzentration, 5,2.10−2 mol/dm3, ausgefuhrt. Die Polymerisationswarme betragt bei 70°C −52,3 kJ/mol (−12,5 kcal/mol) und nimmt mit steigender Temperatur ab (sie wird negativer). Es wurden auch Geschwindigkeitskonstanten der Polymerisation im stationaren Zustand und aus ihnen die Bruttoaktivierungs energie 77 kJ/mol (18,4 kcal/mol) bestimmt, die gut mit Literaturangaben ubereinstimmt. Eine andere Reihe von Experimenten wurde bei 80°C mit verschiedenen Initiatormengen durchgefuhrt. Der dabei gefundene Wert der Polymerisationswarme −52,8 kJ/mol (−12,6 kcal/mol) ist von der Initiatormenge nur wenig abhangig. Die Bruttogeschwindigkeit der Polymerisation bei kleinen Umsatzen ist der Wurzel aus der Initiatorkonzentration proportional. Diese Ergebnisse zeigen in Ubereinstimmung mit den Befunden anderer Autoren, das die Scanning-Kalorimetrie eine brauchbare Methode zum Studium der Kinetik der Polymerisation ist.

The crystal and molecular Structure of Trans‐MoCl3(C5H5N)3

Abstract: Trans-MoCl3Py3 (Py 7mdash; pyridine) crystallizes in the monoclinic space group P21/c with four molecules in the unit cell. The cell dimensions are: a = 9.229(3), b = 12.555(3), c = 17.920(4) A and β = 119.33(2)°. Calculated density for Z = 4 is 1.61 gcm−3 and measured 1.61 ± 0.02 gcm−3. Structure has been solved from 1594 independent film data and refined to the conventional R factor 9.1%. Three chlorine atoms and three nitrogen atoms of the pyridine molecules form an octahedral coordination about molybdenum in the 1, 2,6 or trans configuration. Distances within octahedron are: MoCl 2.437(5), 2.424(5), 2.423(5) A, and MoN(pyridine) 2.189(13), 2.163(15), 2.223(15) A. CrCl3Py3, CrBr3Py3 and MoBr3Py3 crystallize in the same space group with comparable cell dimensions and are probably isostructural with trans-MoCl3Py3. Kristall-und Molekulstruktur von Trans-MoCI3(C5H5N)3 Trans-MoCl3Py3 (Py = Pyridin) kristallisiert monoklinisch in der Raumgruppe P21/c mit a = 9,229(3), b = 12,555(3), c = 17,920(4) A, β = 119,33(2)°. Die gemessene Dichte betragt 1,61(2) g/cm3, damit ergibt sich Z = 4 und drontg. = 1,61 g/cm3. Die Struktur war mittels 1594 unabhangigen Filmdaten aufgeklart und zu einem konventionellem R-Wert von 9,1% verfeinert. Das Molybdan ist von drei Chloratomen und drei Stickstoffatomen der Pyridinmolekeln oktaedrisch umgeben in einer 1, 2, 6 oder Transkonfiguration. Die Abstande innerhalb des Oktaeders sind: MoCl 2,437(5), 2,424(5), 2,423(5) A, und MoN(Pyridin) 2,189(13), 2,163(15), 2,223(15) A. CrCl3Py3, CrBr3Py3 und MoBr3Py3 kristallisieren in der gleichen Raumgruppe mit ahnlichen Gitterkonstanten und sind mit MoCl3Py3 moglicherweise isostrukturell.

Variability of electrically evoked muscle contractions with special regard to closed-loop controlled orthosis

Abstract: One of the essential deficiencies of functional electrical stimulation (FES) as a method of rehabilitation of hemiplegic patients is the great variability of responses. This paper treats quantitatively the variability of isometric responses. The parameters chosen for the evaluation of variability were the dynamics of isometric moment and the static value of the moment during maintained stimulation. Experiments were performed to evaluate both surface and implanted stimulation, as both of these methods have reached the stage of clinical application. It was established that the variability is quite large, relative dispersion being ν≐0.35. Using a closed-loop controller of FES of muscles it was shown that such an actuator is too variable to be used as an efficient orthosis. No significant difference was found between surface and implanted FES. The comparison of data obtained without electrode shifting and with readjustment of the electrodes to the same premarked position has convinced us that one of the main causes for the variability is the unpredictable displacement of different tissues between the electrodes and the stimulated nerve. The influence of reflex action and supraspinal centers was studied on a patient with compression of the peroneal nerve. It was found that this influence is strongly subjective. In some hemiplegics this influence was detectable, though on the average less important than the technological-anatomical properties of the contact between the electrodes and the nerve. Better reproducibility is expected with the introduction of improved electrode technology.

Thermodynamic Properties of Polyelectrolyte Solutions

Abstract: During the last two decades the thermodynamic properties of numerous polyelectrolytes in aqueous solution have been investigated. Some research workers were more interested in natural, others again in synthetic polyelectrolytes with a variety of counter-ions. The thermodynamic behaviour of pure polyelectrolyte solutions and of their mixtures with simple electrolytes, was studied. It is impossible to give in one lecture a full account of the efforts in this direction. I shall, therefore, confine myself mainly to the work which has been done at this Department.

A highly selective diethyldithiocarbamate extraction system in activation analysis of copper, indium, manganese and zinc

Abstract: A versatile separation system based on the extraction of dithiocarbamates and applicable to the determination of copper, managanese, zinc and indium in a wide selection of materials by activation analysis is described. After the dissolution of the sample and a few simple operations which eliminate specific interferences, depending upon the material (e. g. sodium and gold in the NBS Standard Reference Glasses), carbamates are extracted under specific conditions by addition of appropriate complexing agents and selective stripping. Extreme separation factors permit interference-free counting using a sodium iodide detector. For example, indium is separated from a hundred thousand fold excess of manganese in the determination of the two elements in Orchard Leaves. Results are also presented for all four elements in Bowen's Kale, NBS Bovine Liver, and for Cu, In and Mn in the 0.02 ppm and 1 ppm SRM glasses.

On the rearrangement and scrambling of hydrogen in the benzophenone oxime molecular ion

Abstract: The losses of CO, hydrogen and CO, OH and HNOH radicals from the benzophenone oxime molecular ion have been studied by means of deuterium labelled compounds. Hydrogen scrambling and/or exchange and rearrangement reactions of interest, taking place prior to fragmentation, were observed.

The extraction of uranium (IV) from sulphuric acid by tri-octylamine in benzene

Abstract: The extraction of U(IV) from aqueous sulphuric acid media by TOA in benzene has been studied as a function of the sulphuric acid concentration and the concentration of TOA in the organic phase. The extraction may be represented by an equation such as H2U(SO4)3+(R3NH)2SO4=(R3NH)2U(SO4)3+H2SO4 The results for extraction from mixtures of U(VI) and U(IV) suggest that U(VI) forms a much more stable complex with TOA. Osmometric measurements on solutions of the U(IV)-complex in the organic phase indicate a tendency of this complex to aggregate.

Osmotic coefficients of aqueous polyelectrolyte solutions at low concentrations, 1. Polystyrenesulfonates with mono‐ and bivalent counterions

Abstract: With the aid of a membrane osmometer, the osmotic coefficients, Φ, of aqueous solutions of polystyrenesulfonic acid and its salts with mono- and bivalent counterions were measured at molalities from 1 · 10−2 to less than 1·10−3 mol/kg. The results were inconsistent with published “limiting laws” and a dependence of Φ on the nominal molecular weight of the macroions was observed. The obtained Φ-values were compared with the data compiled from other studies. The Φ-values for solutions containing H and Ca counterions were compared with the corresponding Φ-values obtained cryoscopically to establish the validity of the method used. Mit einem Membranosmometer wurden die osmotischen Koeffizienten (Φ) wasriger Losungen von Polystyrolsulfonsaure und ihrer Salze mit mono- und divalenten Gegenionen im Konzentrationsbereich von 1.10−2 bis 1.10−3 mol/kg und niedriger gemessen. Es wurde keine ubereinstimmung der Resultate mit ‘limiting laws’ aus der Literatur gefunden, und es wurde eine Abhangigkeit der osmotischen Koeffizienten von den nominalen Molekulargewichten der Makroionen beobachtet. Die erhaltenen Φ-Werte wurden mit den aus anderen Arbeiten entnommenen Ergebnissen verglichen. Die Φ-Werte von Losungen, die H und Ca Gegenionen enthielten, wurden mit den entsprechenden Φ-Werten aus kryoskopischen Messungen verglichen, um die Gultigkeit der benutzten Methode zu bestatigen.

Statics in special relativity

Abstract: A general treatment for relativistic statics is given in the framework of the asynchronous formulation of Cavalleri and Salgarelli. In particular, pivot events are introduced and the motion of the pivot point is treated in the same way as the motion of a particle. The new definition allows the development of relativistic statics in a form similar to that of its classical counterpart.