Irreversible Breakdown Research Articles

Effects of High Pressure on Azobenzene and Hydrazobenzene Probed by Raman Spectroscopy

In this study, two hydrazine derivatives, azobenzene and hydrazobenzene, were compressed in a diamond anvil cell at room temperature up to 28 GPa followed by decompression. In situ Raman spectroscopy was employed to monitor the pressure-induced structural evolutions. Azobenzene was found to undergo a phase transition at ~10 GPa. Further compression to 18 GPa resulted in an irreversible breakdown of the molecular structure. Although hydrazobenzene exhibited a structural transition at a similar pressure of 10 GPa, it was found to sustain a compression pressure as high as 28 GPa without chemical reactions. The transition sequence of hydrazobenzene upon compression and decompression was thus entirely reversible in the pressure region studied, in strong contrast to that of azobenzene. The high-pressure structures of these two molecules were examined based on the spectroscopic data, and their drastically different high-pressure behaviors were analyzed and interpreted with the aid of ab initio molecular orbital calculations.

Opto-electronic characterization of electron traps upon forming polymer oxide memory diodes

Metal-insulator-polymer diodes where the insulator is a thin oxide (Al2O3) layer are electroformed by applying a high bias. The initial stage is reversible and involves trapping of electrons near the oxide/polymer interface. The rate of charge trapping is limited by electron transport through the polymer. Detrapping of charge stored can be accomplished by illuminating with light under short-circuit conditions. The amount of stored charge is determined from the optically induced discharging current transient as a function of applied voltage and oxide thickness. When the charge density exceeds 8 × 1017/m2, an irreversible soft breakdown transition occurs to a non-volatile memory diode.

A review and appraisal of the DNA damage theory of ageing

Given the central role of DNA in life, and how ageing can be seen as the gradual and irreversible breakdown of living systems, the idea that damage to the DNA is the crucial cause of ageing remains a powerful one. DNA damage and mutations of different types clearly accumulate with age in mammalian tissues. Human progeroid syndromes resulting in what appears to be accelerated ageing have been linked to defects in DNA repair or processing, suggesting that elevated levels of DNA damage can accelerate physiological decline and the development of age-related diseases not limited to cancer. Higher DNA damage may trigger cellular signalling pathways, such as apoptosis, that result in a faster depletion of stem cells, which in turn contributes to accelerated ageing. Genetic manipulations of DNA repair pathways in mice further strengthen this view and also indicate that disruption of specific pathways, such as nucleotide excision repair and non-homologous end joining, is more strongly associated with premature ageing phenotypes. Delaying ageing in mice by decreasing levels of DNA damage, however, has not been achieved yet, perhaps due to the complexity inherent to DNA repair and DNA damage response pathways. Another open question is whether DNA repair optimization is involved in the evolution of species longevity, and we suggest that the way cells from different organisms respond to DNA damage may be crucial in species differences in ageing. Taken together, the data suggest a major role of DNA damage in the modulation of longevity, possibly through effects on cell dysfunction and loss, although understanding how to modify DNA damage repair and response systems to delay ageing remains a crucial challenge.

The Sphingosine-1 Phosphate receptor agonist FTY720 dose dependently affected endothelial integrity in vitro and aggravated ventilator-induced lung injury in mice

Lung barrier protection by Sphingosine-1 Phosphate (S1P) has been demonstrated experimentally, but recent evidence suggests barrier disruptive properties of high systemic S1P concentrations. The S1P analog FTY720 recently gained an FDA approval for treatment of multiple sclerosis. In case of FTY720 treated patients experiencing multiple organ dysfunction syndrome the drug may accumulate due to liver failure, and the patients may receive ventilator therapy. Whereas low doses of FTY720 enhanced endothelial barrier function, data on effects of increased FTY720 concentrations are lacking. We measured transcellular electrical resistance (TER) of human umbilical vein endothelial cell (HUVEC) monolayers, performed morphologic analysis and measured apoptosis by TUNEL staining and procaspase-3 degradation in HUVECs stimulated with FTY720 (0.01–100 μM). Healthy C57BL/6 mice and mice ventilated with 17 ml/kg tidal volume and 100% oxygen for 2 h were treated with 0.1 or 2 mg/kg FTY720 or solvent, and lung permeability, oxygenation and leukocyte counts in BAL and blood were quantified. Further, electron microscopic analysis of lung tissue was performed. We observed barrier protective effects of FTY720 on HUVEC cell layers at concentrations up to 1 μM while higher concentrations induced irreversible barrier breakdown accompanied by induction of apoptosis. Low FTY720 concentrations (0.1 mg/kg) reduced lung permeability in mechanically ventilated mice, but 2 mg/kg FTY720 increased pulmonary vascular permeability in ventilated mice accompanied by endothelial apoptosis, while not affecting permeability in non-ventilated mice. Moreover, hyperoxic mechanical ventilation sensitized the pulmonary vasculature to a barrier disrupting effect of FTY720, resulting in worsening of ventilator induced lung injury. In conclusion, the current data suggest FTY720 induced endothelial barrier dysfunction, which was probably caused by proapoptotic effects and enhanced by mechanical ventilation.

Equilibrium responses of cliffed coasts to changes in the rate of sea level rise

Basic formulae have long been used to predict the effects of sea-level rise on coastal recession; for instance, the geometric ‘Bruun rule’ (and its modifications) has often been applied to sandy coasts, both low-lying and steep. However, the behavior of rocky coasts, whether strongly or poorly lithified, should be significantly different than that of sandy coasts given that rocky coast evolution depends upon the irreversible breakdown of rock, whereas sandy and depositional systems are controlled by the transport (and related transport gradients) of mobile sediment. Here, we investigate the basis of a modeled relationship which suggests (with a number of caveats) that the equilibrium soft-rock cliff recession rate can be estimated by the square root of the relative change in sea-level rise rate. Although this relationship was derived using the numerical model SCAPE (Soft Cliff And Platform Erosion), which simulates a broad soft-rock cliffed coastal system driven by stochastic environmental forces, here we show that a simplified modeling approach also reproduces the relationship. We then extend this approach to develop a general theoretical framework within which it is possible to consider the potential responses of the different types of cliffed coasts to changes in the rate of sea level rise. Although a wide variety of processes affect different coastal settings, this framework demonstrates how the strength and the nature of feedbacks within cliffed system control their response to sea-level rise. This suggests that cliffed environments controlled by different processes can still respond in similar ways to changes in the rate of sea-level rise. Most rocky coasts would be expected to respond as a damped, or ‘negative feedback’ system between the extremes of a ‘no feedback’ system that is unresponsive to sea-level rise rate and an ‘instant response’ system characterized by a linear response similar to the Bruun rule. This framework suggests that a potential ‘inverse feedback’ case could also exist, in which increased rates of sea-level rise reduce the rate of coastal recession. In almost all cases, it is apparent that cliffed coast response to sea-level rise depends not only upon the total elevation change of sea level, but on the rate of the sea-level rise. These theoretical investigations and the classifications presented provide a framework to understand the behavior of systems affected by a wide array of processes, and provide expectations that can be tested using more complex models of cliffed coast evolution in a variety of environments, whether sandy or rocky, hard or soft.

Effects of a Pulse Electric Field on Electrofusion of Giant Unilamellar Vesicle (GUV) -Jurkat Cell (Measurement of Fusion Ratio and Electric Field Analysis of Pulsed GUV-Jurkat Cell)

Electrofusion of Giant Unilamellar Vesicle (GUV) and living cell is a gentle method to deliver membrane impermeable cryo-/lyo-protective molecules into living cell for cryo-/lyopreservation. In this method, cellular fusion is believed to be triggered by the irreversible electical breakdown of the membrane at contact region. Nevertheless, as the time change of the membrane potential distribution during an electric pulse is still not clear, the length and strength of electric pulse are hardly designed. In this study, the GUV-Jurkat electrofusion ratios under various pulse strength and length were measured. In addition, we calculated the time change of membrane potential distribution of a deformed GUV-Jurkat pair during the electric field application by a finite element method (FEM)-electric field analysis. The measured cellular and GUV's electric properties and a GUV-Jurkat profile were used for the analysis to validate the quantitative calculation results. Both results of experiment and calculation suggested that; 1) GUV-Jurkat should be stretched for the electrofusion, 2) whole contact region of membrane should breakdown at the same time to process electrofusion, 3) after applying an electric field for around 1μsec, membrane potential in contact region becomes homogeneous, 4) after applying an electric field for around 10μsec, membrane potential is relaxed, 5) the irreversible electric breakdown is around 3V.

Allopurinol and xanthine oxidase inhibition in liver ischemia reperfusion

Allopurinol was first introduced, in 1963, as a xanthine oxidase inhibitor when it was investigated for concomitant use with cancer chemotherapy drugs. Today it is used in gout and hyperuricemia. Due to its additive benefit in preventing oxidative damage, attention has shifted towards the use of allopurinol in organ ischemia and reperfusion. Currently, the mechanism by which allopurinol exerts a protective benefit in ischemia reperfusion related events is not fully understood. There are various theories: it may act by inhibiting the irreversible breakdown of purine substrates, and/or by inhibiting the formation of reactive oxygen species, and/or by protecting against damage to the mitochondrial membrane. This work focuses on liver ischemia and reperfusion injury in an effort to better understand the mechanisms associated with allopurinol and with this pathological entity. The current research, mainly in animal models, points to allopurinol having a protective benefit, particularly if used pre-ischemically in liver ischemia reperfusion injury. Furthermore, after reviewing allopurinol dosing and administration, it was found that 50 mg/kg is statistically the most effective dose in attenuating liver ischemia reperfusion injury. Owing to the limited number of samples, the time of administration did not show statistical difference, but allopurinol was often beneficial when given around 1 h before ischemia. In conclusion, allopurinol, through its known xanthine oxidase inhibitory effect, as only one of the potential mechanisms, has demonstrated its potential application in protecting the liver during ischemia and reperfusion.

Electrochemical Redox Behaviour of Temozolomide Using a Glassy Carbon Electrode

AbstractThe electrochemical behaviour of temozolomide on a glassy carbon electrode has been investigated. The reduction of temozolomide is an irreversible process, pH dependent, and the mechanism involves the addition of one electron and one proton to C5 to form an anion radical, causing the irreversible breakdown of the tetrazinone ring. The oxidation mechanism of temozolomide is an irreversible, adsorption‐controlled process, pH dependent up to value close to the pKa and occurs in two consecutive charge transfer reactions, with the formation of the hydroxylated product. The electroanalytical determination of TMZ led to a detection limit of 1.1 µM.

ChemInform Abstract: Reversibility of the Electrochemical Lithium Insertion in “Cr3O8” - Comparison with LiCr3O8.

Abstract Electrochemical lithium insertion in Cr3O8 at room temperature and at 125°C is compared to that of LiCr3O8. The capacity is ca 1.4 Li/Cr in Cr8O21 at both temperatures by discharge to 2 V vs Li. During recharge a structural change takes place. By discharge to 1.5 V, additional 0.4 Li/Cr (1.8 in total) is accepted by the oxide. At high temperature, it is difficult to extract the inserted lithium. Only 2–3 cycles are obtained. At room temperature the system appears to be fairly insensitive to overdischarge. By discharge of the system Li/LiCr3O8, ca 1.7 Li/Cr is accepted by both temperatures and at potentials above 1.5 V vs Li. The reaction involves major structural changes as insertion of even small amounts of lithium leads to irreversible structural breakdown. Comparison of the lithium insertion of the two compounds, indicates that the reaction products of the insertion reactions are similar in nature after a number of cycles.

On the Ordinary Concept of Death

abstractWhat is death? The question is of wide‐ranging practical importance because we need to be able to distinguish the living from the dead in order to treat both appropriately; specifically, the permissibility of retrieving vital organs for transplantation depends upon the potential donor's ontological status. There is a well‐established and influential biological definition of death as irreversible breakdown in the functioning of the organism as a whole, but it continues to elicit disquiet and rejoinders. The central claims of this paper are that the best way to address the question as to what death is, is to attend closely to our ordinary concept of death; doing so reveals that, whilst our ordinary understanding accommodates the biological definition, it also includes the thought that, for someone who has died, there will never again be anything it is like to be that person. Support for these claims is provided, and their academic and practical implications traced. The important practical implication is that we are left in quandary as to whether certain potential organ donors — for example, anencephalic babies and the permanently vegetative — are dead, a quandary that has serious implications for the relevance of the dead donor rule in transplant ethics.

Synthesis and hydrogen storage properties of mechanically ball-milled SiC/MgH 2 nanocomposites

The hydrogen storage characteristics of SiC/MgH 2 nanocomposites which are prepared by mechanical ball milling of MgH 2 and SiC with cyclohexane have been studied. MgH 2 as a starting material exhibited a desorption peak of hydrogen at 705 K in thermal desorption spectrometry (TDS), while the ball-milled SiC/MgH 2 nanocomposites showed much lower desorption temperatures near 437 K. The hydrogen storage properties of SiC/MgH 2 were significantly improved as a result of nanocomposite formation. In addition, the nanocomposites were characterized by X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimeter (DSC) and pressure–composition isotherm (PCT) measurements. For the SiC/MgH 2 nanocomposites, the reversibility of hydrogen absorption/desorption was observed, but heating above 573 K led to the irreversible breakdown of nanocomposites into MgH 2 and SiC.

White matter diffusion is higher in Binswanger disease than in idiopathic normal pressure hydrocephalus

To explore diagnostic differences in periventricular white matter (PWM) and deep white matter (DWM) diffusion patterns in patients diagnosed with Binswanger disease (BD) and in patients diagnosed with probable idiopathic normal pressure hydrocephalus (INPH) using diffusion-weighted imaging (DWI). Apparent diffusion coefficient (ADC) values were calculated in the PWM and DWM in patients with INPH (n = 14) and BD (n = 9) and in controls (n = 10) using an spin echo echo planar imaging single-shot diffusion sequence and region of interest (ROI) analysis. Patients with BD had higher ADC values than patients with INPH in the PWM and DWM in the frontal and occipital regions (P < 0.05) and higher values than controls in the frontal PWM and DWM (P < 0.01). After shunt surgery, ADC values were reduced in the frontal PWM in patients with INPH (P < 0.05). Increased diffusion in the PWM and DWM in patients with BD may reflect irreversible breakdown of axonal integrity caused by the subcortical ischaemic vascular disease. By contrast, the normal white matter diffusion in patients with INPH indicates structurally intact axons, compatible with the reversibility of this disorder. DWI may be an important non-invasive diagnostic tool for differentiating between INPH and BD and identifying shunt responders and reversible brain damage in patients with INPH. However, the overlap between patients with INPH and BD in this study restricts the predictive value of the method.

Mechanisms and application of irreversible electrical breakdown of steep pulse in tumor therapy

Irreversible electrical breakdown (IREB) of steep pulse is a new physical method for tumor therapy. Because of the distinct mechanism, it can destroy tumor tissue effectively with non- thermal effect, and high safety. IREB can be performed easily and quickly, and may be a promising additional method for com-bined therapy of tumor. Key words: Electroporation; Neoplasms; Therapy

Changes in Bacterial Communities Accompanied by Aggregation in a Fed-Batch Composting Reactor

The contents of fed-batch composting (FBC) reactors often aggregate after prolonged operation. This process leads to irreversible breakdown of the decomposition reaction and possible alteration of the bacterial communities. We compared the structures of bacterial communities in reactors under aggregate and optimal conditions. The results of 16S rRNA gene clone analysis showed that populations of the family Bacillaceae (such as Bacillus spp., Cerasibacillus spp., Gracilibacillus spp.), which dominate (98%) under optimal condition, were significantly decreased under aggregate condition. In contrast, populations of the family Staphylococcaceae considerably increased after aggregation and accounted for 53% of the total. Phylogenetic analysis also showed that anaerobes or facultative anaerobes related to Tetragenococcus halophilus, Atopostipes suicloacalis, Jeotgalicoccus pinnipedialis, and Staphylococcus spp. were dominant in the aggregates. These results suggested that aerobic Gram-positive bacteria mainly contributed to organic degradation and that aggregation created some anaerobic environment, which promoted the growth of bacterial communities usually not found in well-functioning FBC reactors.

Spatial dynamics of thermal overload in silicon diodes and dynistors

A modified model of injection and thermal processes is proposed for the description of spatial dynamics of pulsed current overload in ultra-high-power silicon switches. The results of numerical analysis demonstrate an unusual phenomenon of dynamic depletion of plasma density in a narrow layer of the injection channel with anomalously high electric field and heat evolution. This layer is observed when the current density increases above several kA/cm2 and temperature gradients on the order of ∼5 × 105 K/cm develop. The moment of absolute minimum in the plasma density coincides with the appearance of a sharp peak on the transient voltage characteristics, which is a precursor of irreversible thermal breakdown.

Biomechanical responses of human temporomandibular joint disc under tension and compression

The purpose of this study was to observe the microscopic changes in the temporomandibular joint (TMJ) disc in response to tension and compression, and to study the mechanism of disc failure when subjected to mechanical stresses. The scanning electron microscope was used to observe topographic characteristics of TMJ disc samples obtained from 13 cadavers before and during biomechanical experiments. The stress relaxation experiments were conducted at different strain levels (2, 3, 4 and 6%). The uniaxial tensile experiments were carried out at a constant strain rate (0.05 mm/s). The confined compression tests were performed with 3 different indenters (2, 3 and 4 mm in diameter) for 150 s and 3 h. The maximal tensile strain of the disc was 5% (nearly equal to 0.22 MPa of tensile stress) in the mediolaterally tensile direction. Typical wavelike structure of the collagen fibrils of the disc was present at 2–4% strain ranges. Tensile and shear damage to local collagen fibrils was observed in specimens of the intermediate zone and the posterior band at 6% strain level. Changes in the collagen network from a wavelike structure to distortion observed on the surface of the testing samples were reversible in the 150-s indentation, but severe, irreversible breakdown and deformation of the collagen–proteoglycan network occurred in those specimens that had been compressed for 3 h. Persistent and prolonged compression inevitably resulted in irrecoverable disc failure. Mechanical stress is a crucial factor in breakdown of the TMJ disc.

Protoplast electrofusion between common wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) and regeneration of mature cybrids

This study describes the development of electrofusion techniques using the ‘donor-recipient’ model for the production of cybrids between common cultivated winter wheat (Triticum aestivum L.) cv. Jinghua No. 1 and a phylogenetically remote, sexually incompatible grass species, Italian ryegrass (Lolium multiflorum Lam.), which belong to two different subtribes: Triticinae and Loliinae. Wheat protoplasts were metabolically inactivated by iodoacetamide before fusion, while protoplasts of Italian ryegrass were X-ray irradiated before protoplast isolation. The suspension cells were directly used to optizmize the inactivation parameters. By exploring the minimum irreversible membrane breakdown strength, the electrofusion parameters were optimized just a few minutes before electrofusion began. A total of 108 green plantlets were obtained, and about half of the green plants uncontrollably necrotized. Among all green plants, 14 were rooted normally and transplanted in growth chamber or field and developed to maturity. All these transplanted plants were male sterile with smaller and off-white anthers. Seeds were obtained by crossing with Jinghua No. 1. Three transplanted regenerants possessed the characteristics of glume facing the rachis, which was the taxonomic characteristic distinguishing the two subtribes of Triticinae and Lolliinae. Although Southern blot hybridization analysis of 33 randomly selected regenerants using a wheat ribosomal DNA probe (pHA71) did not find any differences to wheat, analysis using two mitochondrial probes B342 (cox l), 490 (Pro II) and one chloroplastidic probe pHve H5 revealed that 31 plants were ‘true cybrids’ by showing ryegrass-specific band(s) or new band(s). It also showed that the mitochondria and chloroplasts were not coexistent as the restriction fragment length polymorphism band of Italian ryegrass was not detected by the mitochondrial probes 7 (26s), B342 (cox I), pHJ2-7-1 (cox II), B30 (atp9), and the chloroplast probe pHvc P5. To regenerate the cybrids, the regeneration capacity of the recipient (wheat) was crucial in this study.

Photodestructible Vesicles

Stable vesicles are formed in a 1.4 wt % solution comprising a 1:3 mixture of the anionic photodestructible surfactant sodium 4-hexylphenylazosulfonate (C6PAS) and inert cationic cetyltrimethylamonium bromide (CTAB). UV irradiation drives an irreversible breakdown of the mixed C6PAS/CATB vesicles, owing to the selective degradation of C6PAS. A light-induced transition from small spherical-like polydisperse vesicles to long needle-like aggregation is observed.

Effect of voltage on the conduction of a high-density polyethylene/carbon black composite at the NTC region

The time dependences of current and Joule heating under various voltages are studied to high-density polyethylene (HDPE) filled with carbon black (CB) of 0.082 in volume at an ambient temperature of 158 °C located at the region of negative temperature coefficient (NTC) of resistivity. The composite shows either a transition from the intrinsic to the steady conductions or an irreversible electrical breakdown depending on the applied voltage. The intrinsic conduction in the absence of Joule heating is explained combining two electron tunneling processes while the electric field induced NTC effect is related to the production of additional conducting pathways resulted from cold-emission.

Observation of structural changes in carbon films under external influences

Carbon films obtained by the plasma chemical deposition method from the multicomponent stream of ionized particles on the various substrates are investigated. Structural formations with parallel lines were observed under the microscope on the film surface. Apparently, charge accumulation takes place along these lines. When the film locally is heated then micro tube-like structure peculiarities are formed along these lines. Observed peculiarities are periodic in nature with well-established formation phases. Possibly, the charge accumulation lines coincide with the micro tube-like formations as our observations revealed. It is important to stress that the parameters of micro tube-like formations, i.e., the period of sinus-like formations and their linear dimensions are dependent on the technological parameters. Metal–carbon film-Si sandwich-like system's volt–ampere characteristics show irreversible breakdown due to structural changes taking place in system and being observed microscopically. Obviously, this is due to applied strong electric fields (∼10 5–10 6 V/cm). Thus, origination of micro- and nano-formations both on the surface and in the bulk of carbon films under strictly controlled conditions is possible to obtain from multicomponent ion streams.