Values Of Dd Research Articles

Applied Insulating Coatings for Gas Distribution Pipelines in the Republic of Belarus and Their Characteristics

Gas distribution system is a production complex, which is part of the gas supply system and consists of organizational and economically interconnected facilities designed to organize the supply of gas directly to consumers. On the national basis of the gas distribution system is formed by about 67.0 thousand km of external distribution gas pipelines, 28.0 thousand km of which are underground steel pipelines. As potentially hazardous objects, steel underground distribution pipelines are subject to higher requirements for corrosion protection. As a rule, they are provided with complex anticorrosion protection, an obligatory component of which is insulation coatings. Taking into account the above mentioned, the definition of general indicators characterizing condition of insulation, the degree of its wear is an actual task. To solve it, for the first time, we have analyzed an array of long-term statistical data on defects of protective coatings of distribution gas pipelines, detected by instrumental method. The values of specific defect density Dd and damageability Ad have been determined for all types of applied protective coatings. The best values have been found for insulation on the basis of heat-shrinkable tapes. The characteristic damage of the protective coating on the basis of bituminous mastics (microcracks), which can be used as an indicator of aging of this type of insulation, has been determined. It has been shown that defect formation in the insulation coatings of gas pipelines up to the present time is, as a rule, a low-intensive process, which has been confirmed, among other things, for gas pipelines operated for a long time. The obtained results were included into the justification of abolition of the previously used 40-year normative service life of steel gas pipelines in the new edition of the Rules of Technical Safety in the Field of Gas Supply of the Republic of Belarus.

Analyzing drainage basin orientation and its relationship to active fold growth (Handun anticline, Zagros, Iran)

Combinations of tectonic geomorphological criteria are frequently used to detect vertical and lateral growth of fold structures in tectonically active settings due to their low cost and relative ease of application. The purpose of this study is to analyze the morphometric properties of drainage basins developed into the flanks of a growing anticline to explore the active tectonic growth patterns of the fold. We target the Handun anticline in the Zagros Simply Folded Belt due to it being an actively growing fold structure with a high variability of drainage basin morphologies across different parts of the fold.57 drainage basins were characterized in terms of their orientation using a newly defined drainage basin orientation (DBO) index, in combination with a set of standard tectonic geomorphological metrics (drainage basin area [Ba], slope [S], asymmetry factor [AF], hypsometric integral [HI], basin shape [Bs], crescentness index [CI], sinuosity of the main drainage [Smd], drainage density [Dd], drainage density of 1st-order streams [Dd1], drainage frequency [Df] and sinuosity of anticline divide [Sad]). Indices were synthesized for spatial comparison between western, central and eastern zones of the growing fold.Results show that the DBO is strongly correlated with its CI, Smd, and Ba. In terms of spatial distribution, the central zone is characterized by higher values of DBO, Ba, S, CI, Smd, and Sad. These contrast with the western and eastern zones (fold plunge regions), which are characterized by higher values of Dd, Dd1, and Df. Of note is the southern limb of the anticline, which is characterized by larger drainage basins, and higher values of AF, CI, and Smd. This suggests higher lateral erosion on the southern fold flank. In contrast, drainage basins with steeper S, and greater DBO and elongation are found on the northern limb, suggesting dominance of vertical erosion. This contrasting south-north erosion pattern suggests that the northern fold flank is actively steepening, and presenting a more youthful topography, with lower and spatially focused erosion that is increasing with time. Overall, high values of the newly proposed DBO metric relate to the presence of a curved and/or an asymmetric forked drainage pattern, and also to the trend of faults and fractures across the fold. These structures are typically oriented oblique to the fold axis, with further modification into a semi-annular drainage pattern developed around a salt diapir.

ℚ-Curves, Hecke characters and some Diophantine equations

In this article we study the equations x 4 + d y 2 = z p x^4+dy^2=z^p and x 2 + d y 6 = z p x^2+dy^6=z^p for positive square-free values of d d . A Frey curve over Q ( − d ) \mathbb {Q}(\sqrt {-d}) is attached to each primitive solution, which happens to be a Q \mathbb {Q} -curve. Our main result is the construction of a Hecke character χ \chi satisfying that the Frey elliptic curve representation twisted by χ \chi extends to G a l Q Gal_\mathbb {Q} , therefore (by Serre’s conjectures) corresponds to a newform in S 2 ( Γ 0 ( n ) , ε ) S_2(\Gamma _0(n),\varepsilon ) for explicit values of n n and ε \varepsilon . Following some well known results and elimination techniques (together with some improvements) our result provides a systematic procedure to study solutions of the above equations and allows us to prove non-existence of non-trivial primitive solutions for large values of p p of both equations for new values of d d .

Evolving a total-evaluation map of flash flood hazard for hydro-prioritization based on geohydromorphometric parameters and GIS–RS manner in Al-Hussain river basin, Tartous, Syria

Floods are one of the most severe hydrological hazards that cause an excessive threat to landscape stability, population welfare, infrastructure and spatial development in the Syrian coastal region. Al-Hussain river basin, like other Syrian coastal basins, is prone to a hazardous, frequent-flooding threat. However, investigating the probable areas of flooding risk is a difficult challenge that results from the almost complete absence of spatially distributed geo-hydrological measurements in Al-Hussain river basin. In this regard, geohydromorphometric parameters (Stream number Nu, Stream length Lu, Bifurcation ratio Rb, Form factor F, Elongation ratio Eb, Drainage density Dd, Stream frequency Fs, Drainage texture Td, Lemniscate ratio K, Compactness index C, Circulatory ratio Rc, Ruggedness number Rn, Basin relief Hr, and Relief ratio Rr) derived from remote sensing data in the GIS environment can provide a comprehensive and objective approach that can be utilized to map the spatial distribution of flood hazards at the level of delineated sub-basins. This being the case, the present research focuses on exploring the spatial distribution of flood risk in ten sub-basins belonging to Al-Hussain river basin by using spatial techniques tools in order to overall determine the hydro-prioritization of conservation. The geo-visualization map of generated flash flood susceptibility evaluates five degrees of the flood risk: very low, low, moderate, high, and very high. The flood risk map indicates that Qalea, and Talaa sub-basins have massive hydrodynamic risk, which, in turn, indicates the urgent need of soil and water maintaining measures. This hydrological dynamic in these sub-basins is explained by high values of Dd, F, Rr, Rn, Rc, and K, respectively. Overall, the spatial outcomes of the current work successfully proved the efficiency of extracted geohydromorphometric layers from RS data in the context of the spatial assessment of flash flood hazard; they also ensure ecological sustainability and productivity of the study basin.

Synthesis and Evaluation of Herbal Chitosan from Ganoderma Lucidum Spore Powder for Biomedical Applications

Chitosan is an extremely valuable biopolymer and is usually obtained as a byproduct from the shells of crustaceans. In the current work, chitosan is obtained from an herbal source (Ganoderma lucidum spore powder (GLSP)) for the first time. To show this, both standard (thermochemical deacetylation, (TCD)) and emerging (ultrasound-assisted deacetylation (USAD)) methods of chitosan preparation were used. The obtained chitosan was characterized by elemental analysis, XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy) and thermogravimetric measurements. The process resulted in chitosan possessing comparable values of DD, [η] and ,overline{{rm{Mv}}} to the commercial product. Chitosan obtained via both processes (TCD and USAD) displayed excellent biocompatibility; although the USAD prepared biopolymer exhibited significantly improved fibroblast (L929 cell) viability and enhanced antibacterial zones for both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The findings of new herbal chitosan mark key developments of natural biomaterials; marking a potential shift from conventional sea-based organisms.

Tectonic Geomorphology of Upper Cimanuk Drainage Basin, West Java, Indonesia

The upper Cimanuk drainage basin is an inter-mountain basin. It is surrounded by volcanoes such as Mt. Tampomas, Mt. Guntur, Mt. Dano, Mt. Kamasan, Mt. Papandayan, and Mt. Cikuray. The objective of this research is to identify the degree of tectonic activity based on quantitative geomorphology analysis. Data are obtained from a topographic map, Digital Elevation Model, geological map, and field observation. Various morphometric variables are bifurcation ratio (Rb), drainage density (Dd), and mountain front sinuosity (Smf) index. The integrated analysis of morphometric and field data provides evidence of tectonic activity in Cimanuk drainage basin. Their streams have 1st until seventh order. The research area is proved to be an active tectonic area. This is confirmed by values of Rb, Dd, and Smf showing that some area in Cimanuk drainage basin has been affected by the tectonic activity. Rb values are ranging from 0.74 to 3.99, Dd values are ranging from 0.53 to 7.20, and Smf index area ranged from 1.2 to 1.6. These values can be classified into a medium class of tectonic activity level. The geological structure can be found in the middle to downstream of Cimanuk drainage basin and showed by primarily northwest-southeast trends. On the other hand, drainage pattern such as rectangular and trellis can reflect geological structures. Rectangular control is by joint and fault structure whereas trellis by dipping or folded sedimentary rocks. The Jatigede Reservoir is located in a strongly deformed area, so monitoring is necessary to reduce the impact of the disaster if some of the faults in the area are active again.

Morphometric Analysis and Flash Floods Assessment for Drainage Basins of the Ras En Naqb Area, South Jordan Using GIS

Morphometric analysis and flash floods assessment were conducted for the watersheds of Ras En Naqb escarpment, south Jordan. The study area comprises of twelve small watersheds occupying the faulted-erosional slopes, and the dip slopes. The drainage network shows that dendritic and sub-dendritic patterns dominated the dip slopes, whereas trellis pattern characterized the faulted-erosional slopes. Stream orders range from fourth to sixth order. The mean bifurcation ratios vary between 4.2 and 5.38 for the dip slope basins, and between 3.5 and 5.0 for the faulted-erosional slope watersheds, indicating a noticeable influence of structural disturbances (i.e., faulting and uplifting), and rejuvenation of drainage networks. All watersheds have short basin lengths, ranging from 23.8 km to 42.2 km for the dip slope basins, and between 15.3 km and 45.4 km for the faulted-erosional slope catchments. This is indicative of high flooding susceptibility associated with heavy rainstorms of short duration. The circularity ratios range from 0.177 to 0.704 which denote that the catchments are moderately circular on the faulted-erosional slopes, and to some extent elongated on the dip slopes. The length of overland flow values ranges from 0.854 to 0.924 for the dip slope catchments, whereas LO values for the faulted-erosional slopes vary from 0.793 to 0.945 denoting steep slopes and shorter paths on both dip slope and faulted-erosional slope watersheds. Values of stream frequency range from 1.509 to 1.692 for the dip slope, and from 1.688 to 2.0 for the faulted-erosional slope catchments. FS values are also indicative of slope steepness, low infiltration rate, and high flooding potential. The watersheds of the dip slopes show lower values of form factor varying from 0.079 to 0.364, indicating elongated shape and suggesting a relatively flat hydrograph peak for longer duration. Similarly, values of Dd are high for catchments on the dip slope basins (1.709 - 1.85) and the faulted-erosional slope watersheds (1.587 - 2.0) indicating highly dissected topography, high surface runoff, low infiltration rate, and consequently high flooding potential. Furthermore, high relief values exist, ranging from 388 m to 714 m for the dip slope basins, and from 421 m to 846 m for the faulted-erosional slope catchments indicting high relief and steep slopes. Morphometric analysis, and flash flood assessment suggest that ten watersheds (83.3%) are categorized under high and intermediate flooding susceptibility, and the faulted-erosional slope catchments are more hazardous in terms of flooding. Thus the protection of Ma’an, El Jafr rural Bedouin settlements, and Amman-Aqaba highway from recurrent flooding is essential to ensure sustainable future development in Ras En Naqb-Ma’an area.

Effects of active folding and reverse faulting on stream channel evolution, Santa Barbara Fold Belt, California

The Santa Barbara Fold Belt (SBFB) is an area of active crustal shortening comprising younger east–west and older southeast-northwest oriented reverse faults and folds. Changes in channel position and stream incision are the result of active fold growth and uplift. Rates of incision range from 0.4±0.1m/ka to 1.2±0.04m/ka. Lateral stream diversion from fold and fault growth varies from 6.7 to 0.4km. Minimum uplift of western Mission Ridge anticline is 0.8±0.1m/ka and minimum uplift on the Mesa fault is 0.3–0.4m/ka. The hypothesis that east-to-west folds are younger is suggested by a cross-cutting relationship and is tested using geomorphic indices of active tectonics including: valley width to height ratios (Vf), mountain front sinuosity (Smf) and drainage densities (Dd). East-to-west trending structures have mean values of Vf, Smf, and Dd of 2.7, 1.2, and 2.2km/km2, respectively, while southeast-to-northwest trending structures have mean values of 5.0, 1.5, and 3.7km/km2, respectively. We present a new geomorphic tool, the stream diversion index, which uses diversion timing and distance to assess relative tectonic activity; these values range from 6 to 260m/ka. All of these values support the hypothesis that the east-to-west folds are younger and more active. Clockwise rotation of the Western Transverse Ranges is probably the process that produced the two sets of structures. With rotation the older set that started out east-to-west eventually became northwest-to-southeast, and more difficult to maintain with the north-to-south contractional (shortening) associated with the Big Bend of the San Andreas fault 80km to the north. The second set of younger structures formed with a more favorable (east-to-west) orientation to the shortening.

Morphometric Analysis and Micro-watershed Prioritization of Peruvanthanam Sub-watershed, the Manimala River Basin, Kerala, South India

Morphometric analysis is important in any hydrological investigation and it is inevitable in development and management of drainage basin. A critical evaluation and assessment of morphometric parameters and prioritization of micro-watersheds based on water holding capacity of Peruvanthanam sub-watershed have been achieved through measurement of linear, aerial and relief aspects of basins by using remote sensing and GIS techniques, and it necessitates preparation of a detailed drainage map. For prioritization, 9 micro-watersheds are delineated and parameters such as Rb, Dd, Fs,T, Lof and C are calculated separately and prioritization has been done by using the Raster calculator option of Spatial analyst. The analysis reveals that the stream order varies from 1 to 6 and the total number of stream segments of all orders counted as 347, out of which the maximum area (69.16%) is covered by 1 st order streams and the minimum (0.29%) by 6 th order. Lower values of Rb (linear parameters) in each order, higher values of Bh (0.90), Rh (0.07) and Rn (3.02) (relief parameters), high values of Dd (3.36), Fs (6.15), T (6.82), low values of Lof (0.14) and C (0.30) (aerial parameters) all together reveal that the sub-watershed has a complex structure, mountainous relief, high runoff and low infiltration. The maximum area is covered by high to medium prioritized zones (19.07km 2 ) followed by low to very low (17.75km 2 ) while a very high to high zone is only 4.72km 2 .

Interaction of microcrystalline chitosan (MCCh) with Mo(VI) in aqueous solution

AbstractThe molybdenum(VI) complex formation equilibria of microcrystalline chitosan (MCCh) with three different degrees of deacetylation (DD = 0.750, 0.812, and 0.948) were studied by pH‐potentiometric and UV‐spectrophotometric methods. The hydrolysis constants of Mo(VI) were evaluated under exactly the same conditions as during the experiments in presence of chitosan. It has been shown that the complexation model depends on DD. Besides the formation of a ligand to metal 2 : 1 MoO2B22+ complex (“bridge model”) with A = MoO42−, B = MCCh, H = proton, the 1 : 1 MoO3B species (“pendant model”) has been confirmed as well for the two lower values of DD and moderate excess of ligand. At the highest DD, the results indicate only the occurrence of 2 : 1 species. When taking into account the number of protons in reaction as the third index, the corresponding average overall stability constants log βabh of MoO3B and MoO2B22+ reach log β112 = 13.8 and log β124 = 27.9, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Theoretical determination of H2 ground-state spectroscopic properties

Dunham coefficients aa are here determined for the H2 ground-state potential calculated by Kolos and Wolniewicz. From these aa Born-Oppenheimer spectroscopic constants YY are found. Adiabatically corrected YY are also calculated. An inaccuracy in a virial theorem result is described. From Kotos-Wolnie-wicz eigenenergies theoretical values of BB, DD, and HH are determined. The theoretical YY, BB, DD, and HH are compared with experimental values.

Análise direcional do crescimento urbano da região metropolitana de São Paulo entre 1905 e 2001, utilizando-se a dimensão fractal

The objective of this study is to analyze the growing process of São Paulo metropolitan area urban agglomeration, from 1905 to 2001. Fractal analysis was used to identify factors that influenced the urban shape, spatial distribution of structures and the density of the occupation in the urbanized areas. This study was accomplished to thematic maps and orbital images. Using the association between concentric circles and cell count methods, the fractal dimension was measured to yield occupational density (Dd) of the urban areas. Urban agglomeration showed means values of Dd = 1.755 - which reflect a non-homogeneity in the filling pattern of the density from central to peripheral circle of urban space. Mean fractal dimension of urban radial growing was calculated to eight urban radial sectors as following: (I) Cantareira=1.829; (II) East Zone=1.898; (III) Mauá=1.848; (IV) Ipiranga=1.852; (V) Billings=1.858; (VI) Santo Amaro/Interlagos=1.848; (VII) Castelo Branco/Anhangüera=1.859; and (VIII) Anhangüera/Bandeirantes=1.863. Among determinants factors on fractal behavior of the sectors I, III, IV, V, VI e VIII, the topographical, hydrographical and environment-legal constraints did influence on fragmented occupation; and for sectors II, III, IV, VI e VII the high density of the occupation was supported by the public incentives on industrial, business and road development.

A drainage morphological approach for water resources development of the sur catchment, Vidarbha region

Drainage channels as represented over the topographical maps of the Survey of India on scale 1:50,000 and depicted over the IRS-IB imageries (May 1993) and limited photographs are characterized in view of its areal, linear and abstract properties associated with the Archean gneissic plate of the Sur catchment spread over 983 km2. Morphological characteristics of the drainage lines as appear in shape, size, number and order, length, Dd, Sf, Rb, Is, II, Re, It and infiltration number are derived to trace its usefulness for surface water development. Chiefly dendritic, sub-dendritic and sub-parallel drainage patterns evolved out of the dissected hills, undulating plateau, pediplain and the gently sloping plain persisting under dry sub-humid climatic conditions at an elevation ranging from 246 to 580 m above MSL have given rise to situations suitable for good bunding sites mostly occurring at 3rd and 4th orders of streams for water resource development. Detailed analysis of dominant V order segments (Total 7) suggests high intensity of flood occurrence at a time at the outlet point of the streams indicated along the increased values of Dd, Sf, Rb and Re thereby cautioning proper bunding structure at sites marked on the map for irrigation of crops beyond rainy season.

Features of Conventional Static and New Dynamic Drape Coefficients of Woven Silk Fabrics

Conventional static and new dynamic drape coefficients of silk woven fabrics are examined precisely to distinguish those features of each classified fabric by its yarn structure using our regression equations. We find that Shantung has large values of static drape coefficient D, and small node number n, revolving drape increase coefficient D,., and dynamic drape coefficient with swinging motion Dd. Chirimen is characterized by large values of Dr and Dd. Georgette has small values of revolving drape coefficient at 200 rpm, D200. Habutae has relatively large values of Ds and small n, and Dechine has relatively large values of Dr and Dd, but Fujiginu has no peculiar features. The differences between Fujiginu, Dechine, and Georgette become clear from the discriminant analysis, using the five drape parameters as variables. New dynamic drape coefficients are more useful for characterizing each classified silk fabric.

Polyester "Shingosen" Fabrics Characterized by Dynamic Drape Coefficient with Swinging Motion

The static and dynamic drape behavior of polyester Shingosen fabrics is investigated using the new mechanical parameter of dynamic drapability, that is, the dynamic drape coefficient with swinging motion Dd. The Dd of the Peach Face fabric is small and that of the New Worsted fabric is large. On the other hand, there are almost no differences between each group of Shingosen fabrics in node numbers and conventional static drape coefficients. In classifying production characteristics, yam-processing fabrics show larger values of Dd than other fiber-production and fabric-finishing samples. In classifying fiber characteristics contractile fiber and ultra-fine fiber Shingosen fabrics show smaller values of Dd than irregular fiber fabrics.

Distribution and diffusion coefficients of NaCl in polyamide (nylon-6,6 and polyxylyleneadipamide) membranes

Thin membranes of an aliphatic polyamide (nylon-6,6) and an aromatic polyamide (polyxylyleneadipamide) (PXAP) were prepared, and their distribution (K) and overall diffusion (D) coefficients of sodium chloride were measured with the unsteady-state and steady-state dialysis method. The overall diffusion coefficients at a zero concentration [D(0)] of sodium chloride for nylon-6,6 and PXAP were 1.3–0.8 μm2/s (from 2 min of interfacial polymerization to 4 min) and 0.078, respectively. D(0) for PXAP was about 3 times greater than that of a cellulose acetate (CA) membrane (0.024 μm2/s). The K values for nylon-6,6 and PXAP were 0.7–0.5 from 2 to 4 min and 0.05, respectively. K for PXAP was almost the same as K for CA (0.06). A two-part (dense and porous) model of the membrane structure was applied to obtain Dd (the diffusion coefficient in the dense part of the membrane) and Dp (the diffusion coefficient in the porous part of the membrane) for CA, PXAP, and nylon-6,6 thin membranes. The values of Dd were almost the same for both nylon-6,6 and PXAP (0.05–0.061 μm2/s) and about 10 times greater than the value for the CA membrane (5.6 × 10−3 μm2/s). Dp for PXAP was almost the same as Dp for CA. However, Dp for the nylon-6,6 membrane was 10–16 times greater than Dp for the PXAP membrane. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2605–2612, 2002

Use of Hydrogen and Carbon Stable Isotopes Characterizing Oils from the Potiguar Basin (Onshore), Northeastern Brazil

Hydrogen and carbon isotopic abundances were measured in representative samples of marine- evaporitic, lacustrine, and mixed oils from the onshore Potiguar basin. The isotopic data, together with chemical compositions and geological information, were used to investigate relationships among dDoil and d13Coil and source, thermal maturity, biodegradation, mixing, and the distance of secondary migration of these oils. The marine-evaporitic oils are depleted in deuterium (-135 to -114‰), and the lacustrine oils are enriched (-101 to -88‰). Values of dD for mixed oils are intermediate (-113 to -104‰) between those of marine-evaporitic and lacustrine oils, showing that dDoil is a reliable tool to identify oils that differ genetically. Values of dDoil were not directly related to thermal maturation, biodegradation, or distance of the secondary migration. Hydrogen isotopic compositions of the oils can be related mainly to the dDwater in the paleoenvironments in which the primary producers lived; therefore, dDoil values can provide rough estimates of dDwater in the depositional environments of the source rocks, and consequently may provide evidence about paleoclimatic conditions at the site. Marine-evaporitic oils are enriched in 13C (-26.5 to -25.7‰), and lacustrine oils are depleted (-33.6 to -30.2‰) in 13C. Relative contributions of marine-evaporitic and lacustrine sources to mixed oils thus can be calculated independently from carbon or hydrogen isotopic mixing models. When these calculations are done independently, the mixed oils separate into two families, and a previously unrecognized component possibly associated with environments that formed during the lacustrine-to-marine transition is revealed. The investigation thus demonstrates the superior resolving power of two-element mixing systematics.

Comparison of the effects of halothane, isoflurane and methoxyflurane on the electroencephalogram of the horse

We have investigated in eight ponies the effects of three different end-tidal concentrations of halothane, isoflurane and methoxyflurane on median (F50) and 95% spectral edge (F95) frequencies of the EEG and the second differential (DD) of the middle latency auditory evoked potential (MLAEP). The three concentrations of each agent were chosen to represent approximately the minimum alveolar concentration (MAC), 1.25 MAC and 1.5 MAC for each agent. During halothane anaesthesia, F95 decreased progressively as halothane concentration increased, from mean 13.9 (SD 2.6) at 0.8% to 11.9 (1.1) at 1.2%. DD was lower during anaesthesia with the highest concentration (21 (6.5)) compared with the lowest (27.6 (11.4)). There were no significant changes in F50. During isoflurane anaesthesia, there was a small, but significant increase in F95 between the intermediate and highest concentrations (10.2 (1.5) to 10.8 (1.6)). There were no changes in F50 and DD. Values of F95, F50 and DD at all isoflurane concentrations were similar to those of halothane at the highest concentration. During methoxyflurane anaesthesia, F95 and F50 decreased progressively as methoxyflurane concentration was increased, from 21.3 (0.7) and 6.5 (1), respectively, at 0.26%, to 20.1 (0.6) and 5.6 (0.8), respectively, at 0.39%. DD was lower during anaesthesia with the highest concentration of methoxyflurane (25.7 (7.8)) compared with the lowest (39.7 (20.6)). Values of F95, F50 and DD at all methoxyflurane concentrations were higher than those seen with halothane at the lowest concentration. The different relative positions of the dose-response curves for EEG and MLAEP changes compared with antinociception (MAC) changes suggest differences in the mechanisms of action of these three agents. These differences may explain the incomplete adherence to the Meyer-Overton rule.

Dynamic mechanical analysis and water sorption of some experimental elastomeric soft lining materials

This research was undertaken to develop a better understanding of the relationships among the compositions, structures and properties of denture soft liners. Five butadiene-styrene-acrylic elastomers were prepared. They were prepared using 50% of powdered prepolymerized butadiene-styrene polymer combined with 50% of a methacrylate monomer (HMA or EHMA) plus varying amounts of initiator and crosslinker. The mixtures were gelled and processed conventionally. Specimens were then committed to dynamic mechanical analysis and water sorption. Dynamic mechanical analysis was performed over the temperature range 5–95°C at the rate of 2.5°C/min using a Perkin Elmer DMA-7 with 3 mm flat tip probe at 1 Hz. Wet and dry values for storage modulus (E') and damping factor (tan δ) were determined at 37°C. Water sorption of these butadiene styrene elastomer-acrylic systems from solutions of varying concentrations was measured in order to establish the role of osmotic pressure. Diffusion coefficient (D d) was determined from the desorption values. The relatively lower values of D d observed in most highly concentrated solutions particularly 1 m sodium chloride and glucose may be interpreted as related to reduced water sorption from these solutions. Increasing crosslinking increased the modulus and decreased water sorption. Using hydrophobic EHMA instead of HMA reduced water uptake, reduced dry modulus and reduced the decrease in modulus caused by water sorption. Dynamic moduli and water sorption generally exceeded those of the commercial materials studied. For all experimental materials, water uptake from saline and glucose solutions confirmed that the diffusion process is osmotically driven.

Projection of cat jaw muscle spindle afferents related to intrafusal fibre influence.

1. A method of classification of muscle spindle afferents using succinylcholine (SCh) and ramp stretches has recently been described, which appears to estimate separately the strength of influence of bag1 (b1) and of bag2 (b2) intrafusal fibres. Increase in dynamic difference (delta DD) indicates b1 influence whilst increase in initial frequency (delta IF) indicates b2 influence. The significance of this classification has now been examined by correlation with the strength of synaptic projection of jaw muscle spindle afferents to the fifth motor nucleus (MotV) and the supratrigeminal region (STR) in anaesthetized cats. 2. Projection strength was estimated by computing the extracellular focal synaptic potential (FSP) from spike-triggered averages of 1024 sweeps at 100 microns intervals along tracks through STR and MotV. Trigger pulses were derived from spindle afferent cell bodies of the jaw-closer muscles recorded in the mesencephalic trigeminal nucleus, and characterized by the effect of SCh on their responses to ramp-and-hold stretches. 3. The maximum size of FSPs in tracks traversing STR and MotV ranged from 2.08 to 36.99 microV with a mean of 7.55 microV. The amplitudes were bimodally distributed into roughly equal-sized groups with high and low amplitude FSPs. 4. Mean values of delta IF were significantly greater for the group with large FSPs than for those with small FSPs. There were no significant differences in delta DD. FSP amplitude was significantly positively correlated with delta IF, but not with delta DD. 5. Spindle afferents with high values of FSP amplitude in MotV had a wide range of values of delta DD (b1b2c and b2c groups), while units with large FSPs in STR were all in the b2c category. Some evidence is presented to indicate that this reflects a preferential projection of secondary afferents to the STR. 6. For those units with projection to both STR and to MotV, there was a significant positive correlation between FSP amplitude in the two nuclei. 7. These results indicate that the extent of the b2 influence on spindle afferents predicts the central projection strength better than does the b1 influence. This finding is discussed from the viewpoint of possible developmental and functional issues.