Sharp Component Research Articles

Comparative calorimetric and spectroscopic studies of the effects of cholesterol and epicholesterol on the thermotropic phase behaviour of dipalmitoylphosphatidylcholine bilayer membranes

We carried out comparative differential scanning calorimetric and Fourier transform infrared spectroscopic studies of the effects of cholesterol (Chol) and epicholesterol (EChol) on the thermotropic phase behaviour and organization of dipalmitoylphosphatidylcholine (DPPC) bilayers. EChol is an epimer of Chol in which the axially oriented hydroxyl group of C3 of Chol is replaced by an equatorially oriented hydroxyl group, resulting in a different orientation of the hydroxyl group relative to sterol fused ring system. Our calorimetric studies indicate that the incorporation of EChol is more effective than Chol is in reducing the enthalpy of the pretransition of DPPC. EChol is also initially more effective than Chol in reducing the enthalpies of both the sharp and broad components of the main phase transition of DPPC. However, at higher EChol concentrations (~ 30–50 mol%), EChol becomes less effective than Chol in reducing the enthalpy and cooperativity of the main phase transition, such that at sterol concentrations of 50 mol%, EChol does not completely abolish the cooperative hydrocarbon chain-melting phase transition of DPPC, while Chol does. However, EChol does not appear to form a calorimetrically detectable crystallite phase at higher sterol concentrations, suggesting that EChol, unlike Chol, may form dimers or lower order aggregates at higher sterol concentrations. Our spectroscopic studies demonstrate that EChol incorporation produces more ordered gel and comparably ordered liquid-crystalline bilayers compared to Chol, which are characterized by increased hydrogen bonding in the glycerol backbone region of the DPPC bilayer. These and other results indicate that monomeric EChol is less miscible in DPPC bilayers than is Chol at higher sterol concentrations, but perturbs their organization to a greater extent at lower sterol concentrations, probably due primarily to the larger effective cross-sectional area of the EChol molecule. Nevertheless, EChol does appear to produce a lamellar liquid-ordered phase in DPPC bilayers.

Care and Handling of Basic Surgical Instruments

A well-made, properly cared-for instrument can be expected to last 10 years. The most important considerations in extending the life of an instrument are appropriate use, careful handling, and proper cleaning and sterilization. Every instrument is designed for a specific purpose. Using it for an unintended purpose is a sure method of damaging an instrument. Examples of misuse include securing surgical drapes or opening a medicine vial with an instrument designed to grasp tissue. The proper cleaning of instruments during and after surgery can help to prevent stiff joints, malfunctions, and deterioration of the instruments’ material, including stainless steel. During surgery, instruments contaminated by blood or tissue should be properly wiped and rinsed in the sterile distilled water in the sterile field. Thorough rinsing is important to ensure removal of blood and other contaminants from hinges, joints, and crevices. Blood and foreign matter that are not removed or are allowed to dry and harden may become trapped in jaw serrations, between scissor blades, or in box locks, making final cleaning more difficult and the sterilization or disinfection process ineffective. It can cause instruments to become stiff and eventually break. Channels, or lumens, within instruments such as suction tips should be irrigated periodically to prevent blood from drying and adhering to the inside of the lumen. Neglecting this action can cause blood and other debris to remain in lumens throughout the postoperative cleaning, decontamination, and sterilization processes. A syringe should be present in the sterile field for the purpose of flushing lumens with water throughout the procedure. Flushing the lumen should be done below the surface of the water to prevent the aerosolization of debris. Instruments should be rinsed in distilled water. Saline should not be used for this purpose. Prolonged exposure to saline can result in corrosion and can eventually lead to the pitting of stainless steel. Pitting can permit entrapment of debris, interfere with sterilization, and result in the destruction of an instrument. Instruments should be handled carefully and gently, either individually or in small lots, to avoid possible damage caused by their becoming tangled, dented, and misaligned. During and after surgery they should be placed, not tossed, into the basin. Heavy instruments should be on the bottom, with the lighter, more delicate and fragile ones on top. Rigid endoscopes and fiberoptic cables should also be placed on top or separated. Fiberoptic cables should be loosely coiled, never wound tightly. When the procedure is complete, instruments that can be immersed are disassembled and all box locks are opened. Care should be taken to ensure that they are not tangled or piled high. Instruments should be returned to their respective containers or baskets to prevent sets from becoming incomplete, and they should be covered for transport to the decontamination area. All disposable blades and sharps should be removed and placed in a designated sharps container. Delicate instruments, endoscopes, and other specialty instruments may have to be separated and transported to the decontamination area in containers specifically designed to prevent damage to these devices. Instruments with cutting edges, pointed tips, or other sharp components should be placed in such a manner that sharp edges are protected and personnel responsible for cleaning and decontamination are not injured when reaching into the container.

Processing and properties of ultra-high temperature ceramics for space applications

The processing and the properties of two ultra-high temperature ceramics (UHTCs) designed for the manufacturing of aerospace sharp-shaped hot-structures are presented, along with the results obtained in the electrical discharge machining (EDM) of these UHTCs into sharp hot-structure components. The powder mixtures in the (ZrB 2–SiC)-based systems were brought to full density by hot-pressing. The hot-pressed bodies were characterized by fine and uniform microstructures (typical grain size < 5 μm), along with controlled thermo-mechanical properties. Average flexure strength and fracture toughness at room temperature (RT) up to about 900 MPa and 4.1 MPa√m, respectively, were measured. Elastic moduli at RT approaching 500 GPa were also measured. At 1500 °C in air, flexure strength decreased to 250 MPa. Beyond basic mechanical properties, the machinability of UHTC blocks into a more complex shape by means of the EDM was also assessed. Sharp-shaped hot-structures in the form of a nose-cone were produced from 12 cm × 10 cm hot-pressed cylindrical blocks. The machined surfaces showed limited roughness Ra < 1 μm. With the exception of the typical size of critical flaws induced by EDM seeming slightly larger than those of specimens machined with conventional diamond-loaded tools, the EDM technique proved to be as effective in machining UHTC sintered pieces into more complex components.

Usefulness of the eeg investigation to diagnose TIC disorders in children and adolescents.

The convulsant action of 3-mercaptopropionic acid (3-MPA), a known inhibitor of glutamate decarboxylase activity, was studied in 7-, 12-, 18- and 25-day-old rats and in adult animals. 3-MPA elicited predominantly clonic, minimal seizures as well as generalized tonicclonic (major) seizures at all developmental stages studied. The CD50 for major seizures did not change during development; CD50 for minimal seizures was significantly lower in 18-day-old rats than in older animals. Latency to the onset of seizures was shortest in 18-dayold rats and extremely long in 12- and, especially, in 7-day-old rats. This long latency might signify either changing molecular properties of glutamate decarboxylase during development or slow turnover of GABA at early postnatal stages. Electrocorticographic recordings demonstrated sharp EEG components in the frontal region as a first sign of 3-MPA action, and seizure patterns exhibited similar developmental changes as found with other seizure models (a decrease in duration of individual graphoelements and an increase in synchronization among various cortical regions). This indicates the primary importance of brain maturation in the expression of epileptic EEG phenomena. The correlation between EEG and motor phenomena was poor in the youngest animals and it ameliorated with age, but it never became perfectly coincidental.

Side Chain-dependent Stacking Modulates Tau Filament Structure

The misfolding of proteins into highly ordered fibrils with similar physical properties is a hallmark of many degenerative diseases. Here, we use the microtubule associated protein tau as a model system to investigate the role of amino acid side chains in the formation of such fibrils. We identify a region (positions 272-289) in the tau protein that, in the fibrillar state, either forms part of a core of parallel, in-register, beta-strands, or remains unfolded. Single point mutations are sufficient to control this conformational switch with disease mutants G272V and DeltaK280 (found in familial forms of dementia) inducing a folded state. Through systematic mutagenesis we derive a propensity scale for individual amino acids to form fibrils with parallel, in-register, beta-strands. This scale should not only apply to tau fibrils but generally to all fibrils with same strand arrangement.

Electrolytes Disturbances and Seizures

Electrolytes Disturbances and Seizures

Comparative Calorimetric and Spectroscopic Studies of the Effects of Lanosterol and Cholesterol on the Thermotropic Phase Behavior and Organization of Dipalmitoylphosphatidylcholine Bilayer Membranes

We carried out comparative DSC and Fourier transform infrared spectroscopic studies of the effects of cholesterol and lanosterol on the thermotropic phase behavior and organization of DPPC bilayers. Lanosterol is the biosynthetic precursor of cholesterol and differs in having three rather than two axial methyl groups projecting from the β-face of the planar steroid ring system and one axial methyl group projecting from the α-face, whereas cholesterol has none. Our DSC studies indicate that the incorporation of lanosterol is more effective than cholesterol is in reducing the enthalpy of the pretransition. Lanosterol is also initially more effective than cholesterol in reducing the enthalpies of both the sharp and broad components of the main phase transition. However, at sterol concentrations of 50 mol %, lanosterol does not abolish the cooperative hydrocarbon chain-melting phase transition as does cholesterol. Moreover, at higher lanosterol concentrations (∼30–50 mol %), both sharp and broad low-temperature endotherms appear in the DSC heating scans, suggestive of the formation of lanosterol crystallites, and of the lateral phase separation of lanosterol-enriched phospholipid domains, respectively, at low temperatures, whereas such behavior is not observed with cholesterol at comparable concentrations. Our Fourier transform infrared spectroscopic studies demonstrate that lanosterol incorporation produces a less tightly packed bilayer than does cholesterol, which is characterized by increased hydration in the glycerol backbone region of the DPPC bilayer. These and other results indicate that lanosterol is less miscible in DPPC bilayers than is cholesterol, but perturbs their organization to a greater extent, probably due primarily to the rougher faces and larger cross-sectional area of the lanosterol molecule and perhaps secondarily to its decreased ability to form hydrogen bonds with adjacent DPPC molecules. Nevertheless, lanosterol does appear to produce a lamellar liquid-ordered phase in DPPC bilayers, although this phase is not as tightly packed as comparable cholesterol/DPPC mixtures.

Rationale for a new loudness standard

In 2005, a new loudness standard was approved by ANSI for calculating the loudness of steady sounds. The new standard is based on a recent loudness model [Moore et al., J. Audio Eng. Soc. 45, 224–240 (1997)] derived from an earlier model devised by Zwicker [Acustica 8, 237–258 (1958)]. It replaces and supersedes the more limited computational procedure used in the old ANSI S3.4-1980 standard that had its origins in the protocol developed by S.S. Stevens [J. Acoust. Soc. Am. 33, 1577–1585 (1961)]. Unlike the old ANSI S3.4-1980 procedure, the newly adopted ANSI standard can be applied to sounds with sharp line spectral components as well as to broadband spectra. The new standard also extends the dynamic range for loudness calculations to loudness levels below 40 phons. Hence, it can be used to estimate loudness, or loudness level, with reasonable accuracy at levels close to threshold. Moreover, in accord with the revision of ISO 226 [International Organization for Standardization, Geneva (2003)], it enables the loudness of complex sounds containing spectral energy below 500 Hz to be determined. Empirical examples that illustrate the broader and more accurate scope of the new loudness standard are presented.

Mechanism of cube grain nucleation during recrystallization of deformed commercial purity aluminium

Cube texture is a sharp recrystallization texture component infcc metals like aluminium, copper, etc. It is described by an ideal orientation i.e. (100) (100). The subject of cube texture nucleation i.e. cube grain nucleation, from the deformed state of aluminium and copper is of scientific curiosity with concurrent technological implications. There are essentially two models currently in dispute over the mechanism of cube grain nucleation i.e. the differential stored energy model founded on the hypothesis proposed by Ridha and Hutchinson and the micro-growth selection model of Dugganet al. In this paper, calculations are made on the proposal of Ridha and Hutchinson model and the results are obtained in favour of the differential stored energy model. It is also shown that there is no need for the micro-growth model.

Effects of Single-Crystalline GaN Target on GaN Thin Films in Pulsed Laser Deposition Process

The effects of a GaN single-crystal target (SC-GaN) of laser-ablated GaN thin films on sapphire were investigated. GaN thin films were grown on a single-crystalline c-plane sapphire substrate using the SC-GaN. Unlike the usual growth behavior in laser ablation of a sintered ceramics GaN target (CR-GaN), the rocking curves of the obtained GaN films were superimposed patterns composed of sharp and broad components. The interface between the GaN film and sapphire substrate was atomically flat and sharp. To investigate the effects of the target on the plume of a pulsed laser deposition process in detail, the plume was analyzed by Langmuir probe methods and optical emission spectroscopy (OES). The Langmuir probe results showed that the electron temperature for the plume of an SC-GaN was nearly one third of that of a CR-GaN, although the ion density in the plume of the SC-GaN was found to be greater than the ion density in that of the CR-GaN. OES data showed a significant fraction of the oxygen species in the plume of the CR-GaN. These are thought to be the primary cause of damage and/or impurity to growing films in the plume of the CR-GaN.

Structures, physicochemical properties and oxygen reduction activities of carbons derived from ferrocene-poly(furfuryl alcohol) mixtures

The structure, physicochemical properties and oxygen reduction abilities of carbons prepared by the carbonization of mixtures of ferrocene and poly(furfuryl alcohol) were studied. X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) studies revealed that the carbons thus prepared consisted of two components; amorphous and turbostratic shell-like components. The fraction, f sharp, obtained by the analysis of the (002) peak in XRD was found to be a parameter that represented the degree of formation of the shell-like components. The formation of the shell-like components induced an increase in the mesopore volumes. Electrical conductivity increased exponentially with f sharp, which indicated that the conduction process was governed by a percolation process of the conductive shell-like components. The amount of CO-desorption by O2-TPD technique showed a maximum desorption at f sharp=0.3, and the further development in the sharp component led to a decrease in the CO-desorption. Mossbauer spectroscopy technique revealed the presence of α-Fe, γ-Fe, Fe1-x O and Fe3C in the prepared carbons, which were soluble species to acids. The oxygen reduction activity was studied in a oxygen saturated sulfuric acid solution by rotating disk electrode voltammetry. The oxygen reduction potential varied with f sharp; initially it increased by f sharp=0.3 and then it decreased at higher f sharp values. This behavior was similar to that of CO-desorption, which meant the presence of an adequate degree of the development of the shell-like structure for maximizing oxygen adsorption. Removal of the surface metal component from the carbons by acid-washing resulted in no decrease in the oxygen reduction activities of the carbons. The nature of the active sites on the carbon materials is discussed.

Cube Texture Formation in P/M Ni, Ni-W and Ni-Mo Alloy Tapes for Coated Superconductor Applications

Pure Ni, Ni-5at.%Mo and Ni-5at.%W prepared through P/M route have been severely cold deformed (~95%) and given different heat treatments to develop sharp cube component ({001}&lt;100&gt;) for coated superconductor applications. It was found that amongst the three materials studied, Ni-5at%W develops the most sharp cube texture. This is in contrary to the observation in similar materials produced by the melting and casting route.

Theoretical aspects of photoemission spectroscopy on strongly correlated electron systems

We will clarify, from the theoretical viewpoint, how electron correlations affect the density of states (DOS) and the angle-resolved photoemission spectra (ARPES). The two-dimensional half-filled Hubbard model is employed as a prototype of the interacting electron system. In the weak interaction regime, the DOS has a multi-peak structure, which consists of a sharp one-body coherent component and a broad many-body incoherent component. Accordingly, the ARPES has a sharp coherent peak near the Fermi level. We will show that a short-range spin correlation causes the multi-peak structure in the DOS. On the other hand, as the electronic interaction increases, the DOS and APRES are dominated by the many-body incoherent component even near the Fermi level. It will be shown that the strong coupling between the collective spin excitations and photo-generated hole causes the incoherent component.

Topographic distribution of direct and hippocampus- mediated entorhinal cortex activity evoked by olfactory tract stimulation.

Olfactory information is central for memory-related functions, such as recognition and spatial orientation. To understand the role of olfaction in learning and memory, the distribution and propagation of olfactory tract-driven activity in the parahippocampal region needs to be characterized. We recently demonstrated that repetitive stimulation of the olfactory tract in the isolated guinea pig brain preparation induces an early direct activation of the rostrolateral entorhinal region followed by a delayed response in the medial entorhinal cortex (EC), preceded by the interposed activation of the hippocampus. In the present study we performed a detailed topographic analysis of both the early and the delayed entorhinal responses induced by patterned stimulation of the lateral olfactory tract in the isolated guinea pig brain. Bi-dimensional maps of EC activity recorded at 128 recording sites with 4 x 4 matrix electrodes (410 microm interlead separation) sequentially placed in eight different positions, showed (i) an early (onset at 16.09 +/- 1.2 ms) low amplitude potential mediated by the monosynaptic LOT input, followed by (ii) an associative potential in the rostral EC which originates from the piriform cortex (onset at 33.2 +/- 2.3 ms), and (iii) a delayed potential dependent on the previous activation of the hippocampus. The sharp component of the delayed response had an onset latency between 52 and 63 ms and was followed by a slow wave. Laminar profile analysis demonstrated that in the caudomedial EC the delayed response was associated with two distinct current sinks located in deep and in superficial layers, whereas in the rostrolateral EC a small-amplitude sink could be detected in the superficial layers exclusively. The present report demonstrates that the output generated by the hippocampal activation is unevenly distributed across different EC subregions and indicates that exclusively the medial and caudal divisions receive a deep-layer input from the hippocampus. In the rostrolateral EC, specific network interactions may be generated by the convergence of the direct olfactory input and the olfaction-driven hippocampal output.

Simulations of spectral lines from an eccentric precessing accretion disc

Two-dimensional smoothed particle hydrodynamics (SPH) simulations of a precessing accretion disc in a q= 0.1 binary system (such as XTE J1118+480) reveal complex and continuously varying shape, kinematics and dissipation. The stream–disc impact region and disc spiral density waves are prominent sources of energy dissipation. The dissipated energy is modulated on the period Psh= (P−1orb−P−1prec)−1 with which the orientation of the disc relative to the mass donor repeats. This superhump modulation in dissipation energy has a variation in amplitude of ∼10 per cent relative to the total dissipation energy and evolves, repeating exactly only after a full disc precession cycle. A sharp component in the light curve is associated with centrifugally expelled material falling back and impacting the disc. Synthetic trailed spectrograms reveal two distinct ‘S-wave’ features, produced respectively by the stream gas and the disc gas at the stream–disc impact shock. These S-waves are non-sinusoidal, and evolve with disc precession phase. We identify the spiral density wave emission in the trailed spectrogram. Instantaneous Doppler maps show how the stream impact moves in velocity space during an orbit. In our maximum entropy Doppler tomogram, the stream impact region emission is distorted, and the spiral density wave emission is suppressed. A significant radial velocity modulation of the whole line profile occurs on the disc precession period. We compare our SPH simulation with a simple three-dimensional model; the former is appropriate for comparison with emission lines, while the latter is preferable for skewed absorption lines from precessing discs.

The recrystallization of copper single crystals deformed at 4.2 K

The deformation of copper single crystals at 4.2 K occurs by a sequence of slip, twinning and slip in the twinned structure. Subsequent annealing of the deformed structures obtained at various points at this sequence of deformation permits the detailed nature of the deformed and recrystallized states to be related in a unique fashion. Material recrystallized from structures obtained prior to the occurrence of twinning yields randomly oriented grains. However, the recrystallization textures obtained from the twinned material show two sharp components both of which are obtained from a 40° rotation around the normal to the twinning plane. The two components grow along the original matrix–twin interfaces resulting in a new layered structure, which is coarser than that formed by plastic deformation. The origin of the two recrystallization texture components is interpreted in terms of the enhanced mobility of the 40° 〈1 1 1〉 tilt grain boundaries, which in the present layered twin–matrix structure lies parallel to the twin–matrix lamellae.

A fracture criterion for sharp V-notched samples

The objective of this paper is to show the advantages of the cohesivecrack model for predicting fracture of V-notched components. Criticalvalues of the generalized stress intensity factor can be obtained fromthe knowledge of the material softening function and the elastic parameters,avoiding a cumbersome experimental work. The results were checked successfullyagainst experimental ones, from other authors, in different materials: steel,aluminium, PMMA and PVC. A non dimensional formulation of the fracturecriterion for sharp V-notched components was obtained and a simpleapproximate expression derived for easy appication.

Dynamical Evidence for a Black Hole in GX 339−4

We present outburst spectroscopy of GX 339-4 that may reveal the motion of its elusive companion star. N III lines exhibit sharp emission components moving over ~300 km s-1 in a single night. The most plausible interpretation of these components is that they are formed by irradiation of the companion star and the velocities indicate its orbital motion. We also detect motion of the wings of the He II 4686 A line and changes in its morphology. No previously proposed period is consistent with periodic behavior of all of these measures. However, consistent and sensible solutions are obtained for periods around 1.7 days. For the best period, 1.7557 days, we estimate a mass function of 5.8 ± 0.5 M☉. Even allowing for aliases, the 95% confidence lower limit on the mass function is 2.0 M☉. GX 339-4 can therefore be added to the list of dynamical black hole candidates. This is supported by the small motion in the wings of the He II line; if the compact object velocity is not larger than the observed motion, then the mass ratio is q 0.08, similar to other systems harboring black holes. Finally, we note that the sharp components are not always present but do seem to occur within a repeating phase range. This appears to migrate between our epochs of observation and may indicate shielding of the companion star by a variable accretion geometry such as a warp.

Ergonomic Study on the Manual Component Insertion Lines for Occupational Health and Safety Improvements

The study aimed at reducing the occupational health and safety problems faced by the manual component insertion operators. Subjective and objective assessments, and direct observations were made in the printed circuit assembly factory. Simple and low-cost ergonomic interventions were implemented, that is, repairing chairs, reducing high workloads, assigning operators to a maximum of 2 workstations, confining machines that emitted bad smell and much noise, and providing finger work aids. The results of the interventions were reductions in operators’ work discomforts, that is, chair discomfort (by 90%), high work stress, and discomfort due to frequent change of their workstations. Their health hazards were also eliminated, that is, inhalation of toxic fumes, exposure to too much noise, and pain due to pressing sharp components.

Robustness in the suppression of bidirectional chaotic escape from a potential well by weak parametric excitations

This Letter studies the robustness of the inhibition of bidirectional chaotic escape of a harmonically driven oscillator from a quartic potential well by the application of weak parametric excitations. We show that Melnikov-method-based theoretical predictions for harmonic escape-inducing excitations also work in the presence of external noise, and for chaotic-escape-inducing excitations having a sharp Fourier component with a sufficiently high power.