Catastrophic Break Research Articles

Flood vulnerability indices and emergency management planning in the Yazoo Basin, Mississippi

The alluvial plain of the Yazoo Basin lies in part of the Lower Mississippi River Valley in the south-central United States. The Great Flood of 1927 inundated a large part of the Yazoo Basin and was, until Hurricane Katrina struck the Gulf Coast in 2005, the worst natural disaster economically to have occurred in the United States. It would be naïve to believe that a major flood could not recur in this area in the future and emergency planning and mitigation are of critical importance. This study does not evaluate the overall risk of flooding, but rather the vulnerability of any location within the Yazoo Basin to flooding should it occur. A method is presented in which indicators are used to categorize the vulnerability to catastrophic flooding by considering physical, social, economic, and environmental components of susceptibility. Ordinal vulnerability indices are derived for each of these components individually and then combined into a single three-level (low-moderate-high) Flood Vulnerability Index (FVI) using a weighted sum of component vulnerabilities. The results of the indexing method were mapped using Geographic Information System (GIS) tools and validated by simulating a series of floods which modeled catastrophic breaks at 28 different locations along the mainline levee system. The inundation patterns generated by the simulations agree with predictions from the physical vulnerability indicator, and permit evaluation of total impact via the FVI. Mitigation and emergency response planning in the Yazoo Basin are aided by considering the different characteristics of flooding in different parts of the basin.

Compressive failure of spruce wood rings reinforced with glass epoxy composite

We experimentally tested under radial compressive loads and statistically analyzed rings constructed from spruce wood and reinforced with glass fiber. We used the Weibull distribution in statistical analysis, and tested five types of rings including unreinforced and composite reinforced (CR) as wound around the ring, oriented as two layers at angles of 45°, 60°, 75° and 90° to the column axis. We calculated 95 % reliability of load carrying capacity of the rings by Weibull distribution. The highest load carrying capacity was obtained with CR rings at 60° to the axial axis of the ring. Load carrying capacities of rings at CR90, CR75, CR60 and CR45 were 137, 192, 215 and 126 % greater, respectively, than unreinforced rings. For unreinforced rings, failures resulted from catastrophic breaking of wood materials. None of the reinforced rings failed catastrophically because the outer surface of the rings was reinforced with glass–epoxy composite fiber. Cracks began at the core of the materials under the composite layer for all specimens and resulted in failure of the rings.

Ultrafast feedback-controlled electromigration using a field-programmable gate array

Feedback-controlled electromigration (FCE) has been a useful technique for creating nanoscale gaps between metal electrodes. In general, it is considered that the fabrication of nanogaps by the conventional FCE method using a microprocessor-based control system is a very time consuming and slow process. Here, the authors propose an ultrafast FCE method using a field-programmable gate array (FPGA) to immediately and precisely control the channel resistance of metal nanowires at room temperature. Using the ultrafast FCE method based on an FPGA, the channel resistance of Au micrometer wires was precisely controlled from 102 to 104 Ω within 1 s at room temperature, and without catastrophic breaks of the Au micrometer wires. Furthermore, the total process time of the FPGA-based ultrafast FCE procedure was considerably shortened without degradation of the controllability of the channel resistance of the Au micrometer wires, and is 103 to 104 times shorter than that of conventional FCE. These results imply that ultrafast FCE using an FPGA can precisely and stably control the channel resistance of Au micrometer wires with a shortened process time.

Naked Replication Forks Break apRPArt

Stalled replication forks occasionally collapse, leading to potentially catastrophic DNA double-strand breaks. Now, Toledo etal. (2013) reveal that fork breakage occurs when the pool of the single-strand DNA-binding protein RPA becomes exhausted. This study has important implications for the origin and treatment of cancers with high levels of replicative stress.

LIM Domains Target Actin Regulators Paxillin and Zyxin to Sites of Stress Fiber Strain

Contractile actomyosin stress fibers are critical for maintaining the force balance between the interior of the cell and its environment. Consequently, the actin cytoskeleton undergoes dynamic mechanical loading. This results in spontaneous, stochastic, highly localized strain events, characterized by thinning and elongation within a discrete region of stress fiber. Previous work showed the LIM-domain adaptor protein, zyxin, is essential for repair and stabilization of these sites. Using live imaging, we show paxillin, another LIM-domain adaptor protein, is also recruited to stress fiber strain sites. Paxillin recruitment to stress fiber strain sites precedes zyxin recruitment. Zyxin and paxillin are each recruited independently of the other. In cells lacking paxillin, actin recovery is abrogated, resulting in slowed actin recovery and increased incidence of catastrophic stress fiber breaks. For both paxillin and zyxin, the LIM domains are necessary and sufficient for recruitment. This work provides further evidence of the critical role of LIM-domain proteins in responding to mechanical stress in the actin cytoskeleton.

The application of leak before break concept to W7-X target module

Fusion is the energy production technology, which could potentially solve problems with growing energy demand of population in the future. Wendelstein 7-X (W7-X) is an experimental stellarator of the helias type fusion reactor currently being built in Greifswald, Germany. This experimental stellarator is a complex structure, such as nuclear power plants and high level of safety requirements should be used for structural integrity analysis. It is thus not possible to obtain simple solutions for general cases, therefore sophisticated methods are necessary for the analysis. Inside the Plasma Vessel (PV) of W7-X there is a number of different components such as pipes, divertors, baffles and targets. A guillotine failure of one component is very dangerous for structural integrity of surrounding components located in PV. For this reason it is very important to evaluate possibility to apply “leak before break” (LBB) concept for W7-X. The LBB concept is widely used in the nuclear industry to describe the idea that in the piping carrying the coolant of a power reactor a leak will occur before a catastrophic break will occurred. LBB allows to conduct the structural design without considering the loads due to postulated line breaks.The LBB analysis was made for the case when plasma vessel is operating in “baking” mode. “Baking” is the mode, when the cooling system is working as a warming system and it heats the plasma vessel structures up to 160°C in order to release the absorbed gases from the surfaces and to pump them out of the plasma vessel before plasma operation.The LBB analysis was performed for most loaded component of target module. According to the results of the analysis it is possible to conclude that target module 1H fulfils the LBB requirements.

Molecular Pathways: Targeted α-Particle Radiation Therapy

An α-particle, a (4)He nucleus, is exquisitely cytotoxic and indifferent to many limitations associated with conventional chemo- and radiotherapy. The exquisite cytotoxicity of α-radiation, the result of its high mean energy deposition [high linear energy transfer (LET)] and limited range in tissue, provides for a highly controlled therapeutic modality that can be targeted to selected malignant cells [targeted α-therapy (TAT)] with minimal normal tissue effects. A burgeoning interest in the development of TAT is buoyed by the increasing number of ongoing clinical trials worldwide. The short path length renders α-emitters suitable for treatment and management of minimal disease such as micrometastases or residual tumor after surgical debulking, hematologic cancers, infections, and compartmental cancers such as ovarian cancer or neoplastic meningitis. Yet, despite decades of study of high LET radiation, the mechanistic pathways of the effects of this modality remain not well defined. The modality is effectively presumed to follow a simple therapeutic mechanism centered on catastrophic double-strand DNA breaks without full examination of the actual molecular pathways and targets that are activated that directly affect cell survival or death. This Molecular Pathways article provides an overview of the mechanisms and pathways that are involved in the response to and repair of TAT-induced DNA damage as currently understood. Finally, this article highlights the current state of clinical translation of TAT as well as other high-LET radionuclide radiation therapy using α-emitters such as (225)Ac, (211)At, (213)Bi, (212)Pb, and (223)Ra.

Removal of uracil by uracil DNA glycosylase limits pemetrexed cytotoxicity: overriding the limit with methoxyamine to inhibit base excision repair.

Uracil DNA glycosylase (UDG) specifically removes uracil bases from DNA, and its repair activity determines the sensitivity of the cell to anticancer agents that are capable of introducing uracil into DNA. In the present study, the participation of UDG in the response to pemetrexed-induced incorporation of uracil into DNA was studied using isogenic human tumor cell lines with or without UDG (UDG+/+/UDG−/−). UDG−/− cells were very sensitive to pemetrexed. Cell killing by pemetrexed was associated with genomic uracil accumulation, stalled DNA replication, and catastrophic DNA strand breaks. By contrast, UDG+/+ cells were >10 times more resistant to pemetrexed due to the rapid removal of uracil from DNA by UDG and subsequent repair of the resultant AP sites (abasic sites) via the base excision repair (BER). The resistance to pemetrexed in UDG+/+ cells could be reversed by the addition of methoxyamine (MX), which binds to AP sites and interrupts BER pathway. Furthermore, MX-bound AP sites induced cell death was related to their cytotoxic effect of dual inactivation of UDG and topoisomerase IIα, two genes that are highly expressed in lung cancer cells in comparison with normal cells. Thus, targeting BER-based therapy exhibits more selective cytotoxicity on cancer cells through a synthetic lethal mechanism.

Abstract A104: Removal of uracil by uracil DNA glycosylase limits pemetrexed cytotoxicity: Overriding the limit with methoxyamine (TRC102) to inhibit base excision repair.

Abstract Uracil DNA glycosylase (UDG) is a conserved DNA repair protein existing in all types of human cells. Since UDG specifically removes uracil bases from DNA, its repair activity determines cell sensitivity to anticancer agents that are capable of introducing uracil into DNA. We studied the participation of UDG in response to pemetrexed-induced incorporation of uracil into DNA using isogenic human tumor cell lines with or without UDG (UDG+/+/UDG−/−). Results revealed that UDG−/− cells were very sensitive to pemetrexed. Cell killing by pemetrexed was associated with genomic uracil accumulation, stalled DNA replication, and catastrophic DNA strand breaks. In contrast, UDG+/+ cells were >10 times more resistant to pemetrexed due to a rapid removal of uracil from DNA, generating abasic sites (AP sites). Resultant AP sites were efficiently repaired by base excision repair (BER) so that they contributed little to cell death. However, addition of the BER inhibitor methoxyamine (TRC102) synergistically enhanced the cytotoxicity of pemetrexed in UDG proficient cells. MX bound covalently to AP sites to form unrepairable MX-bound AP sites, thereby inhibiting the BER pathway. Importantly, we identified that MX-bound AP sites induced cell death by inactivating UDG and poisoning topoisomerase II. These two genes are highly expressed in lung cancer cells in comparison with normal bone marrow cells. Thus, targeting UDG/BER to enhance pemetrexed cytotoxic effects is a target-based strategy that selectively mediates cytotoxicity on cancer cells through a synthetic lethal mechanism. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A104.

Influence of Feedback Parameters on Resistance Control of Metal Nanowires by Stepwise Feedback-Controlled Electromigration

We propose a stepwise feedback-controlled electromigration (SFCE) approach to control the channel resistance of metal nanowires at room temperature. SFCE procedure finely divides a conventional feedback-controlled electromigration (FCE) scheme into several FCE cycles. This approach effectively removes thermal instability caused by large current passing through a metal nanowire, because process time of each FCE cycle can be successfully reduced. Using the SFCE approach, a wide-range control of the channel resistance of Ni nanowires was achieved ranging from the order of 10(2) omega to 10(5) omega at room temperature, without catastrophic breaks of the nanowires. Furthermore, total process time of the SFCE procedure was considerably shortened without degradation of the controllability of the resistance of the nanowires. The channel resistance of a Ni nanowire was precisely controlled from 0.2 to 600 k(omega) for 20 min at room temperature, which is 3000 times larger than the initial resistance of the channel. These results clearly indicate that a wide-range control of the channel resistance of metal nanowires can be achieved with a shortened process time using SFCE scheme.

A preliminary investigation of rapid depressurization phenomena following a sudden DLOFC in a VHTR

Air ingress has been identified as a potential threat for Very High Temperature gas-cooled Reactors (VHTR). Reactor components constructed of graphite will, at high temperatures, produce exothermic reactions in the presence of oxygen. The danger lies in the possibility of fuel element damage and core structural failure. Previous investigations of air ingress mechanisms have focused on thermal and molecular diffusion, density-driven stratified flow due to hydrodynamic instability, and natural convection. Not yet investigated is the possibility of a rapid flow reversal of helium coolant due to a Taylor (rarefaction) wave expansion after a hypothetical sudden Depressurized Loss of Forced Cooling (DLOFC) scenario in a VHTR. Conceivably, flow reversal of the helium coolant could entrain significant quantities of air into the reactor vessel. Our goal here is to simply demonstrate this natural phenomena of compressible flow that could possibly result in rapid air ingress into a VHTR. We start with a one-dimensional shock tube simulation to simply illustrate the development of a Taylor wave. The simulation is carried out far enough in time to allow the resulting reentrant flow to occur. Then, a simulation is performed of an idealized two-dimensional axisymmetric representation of the lower plenum of General Atomics GT-MHR subjected to a hypothetical catastrophic break of the hot duct. Results show the potential for significant and rapid air ingress into the reactor vessel in the case of a large break in the cooling system.

The outburst of the κ Cygnids in 2007: clues about the catastrophic break up of a comet to produce an Earth-crossing meteoroid stream

Using high-resolution, low-scan-rate, all-sky CCD cameras and high-level CCD video cameras, the SPanish Meteor and fireball Network (SPMN) recorded the 2007 κ Cygnid fireball outburst from several observing stations. Here, accurate trajectory, radiant and orbital data obtained for the κ Cygnid meteor are presented. The typical astrometric uncertainty is 1–2 arcmin, while velocity determination errors are of the order of 0.3–0.6 km s −1 , though this depends on the distance of each event to the station and its particular viewing geometry. The observed orbital differences among 1993 and 2007 outbursts support the hypothesis that the formation of this meteoroid stream is a consequence of the fragmentation of a comet nucleus. Such disruptive process proceed as a cascade, where the break up of the progenitor body leads to produce small remnants, some fully disintegrate into different clumps of particles and other remaining as dormant objects such as 2008ED69, 2001MG1 and 2004LA12 which are now observed as near-Earth asteroids. In addition to the orbital data, we present a unique spectrum of a bright κ Cygnid fireball revealing that the main rocky components have chondritic abundances, and estimations of the tensile strength of those fireballs that exhibited a catastrophic disruption behaviour. All this evidence of the structure and composition of the κ Cygnid meteoroids is consistent with being composed by fine-grained materials typically released from comets.

Thermography as a routine diagnostic for mechanical testing of composites

Active and passive infrared thermographies, techniques extensively used in NDE, can also be used to monitor mechanical tests of composite materials. These techniques permit a better understanding of the damage and ruin mechanisms. This is illustrated by the application of thermography to the tensile loading experiments of two sandwich coupons (carbon/epoxy skins and aluminum honeycomb core). Active thermography permits the detection and characterization of delaminations in the skins at various stages of the loading and passive thermography allows the localization of the initiation of the catastrophic breaking.

Hydraulic System Protection against Catastrophic Line Failure using Newly Developed Safety Valve

AbstractHydraulic hose and line failures in the field cause an extreme hazard to operators, work crews, and the environment. This happens more than is reported on a daily basis. Hydraulic line breaks are a good reason for the increased fluid replacement bills of nearly all industrial and mobile hydraulic equipments. Sadly, we can fairly say up to now, there has been no cost effective solution introduced to the industry to resolve this hazard effectively until now. In this paper, a patent pending device is proposed as a realistic and feasible solution to offer protection when catastrophic accidental line breaks occur. The device consists of a modified spool design, found in velocity fuses with an optimized dynamic surge chamber. A mathematical model to describe the valve's dynamic response has been developed. This mathematical model has been used to assure the feasibility of the idea by simulating the valve's response over a wide range of working pressures. The agreement between the simulation results and ...

Hybrid and module designs for ATLAS silicon tracker upgrade for super LHC

Based on the ATLAS SCT experience, hybrid and module designs of a short strip silicon detector for an upgraded ATLAS inner tracker for the super LHC have been pursued. At the super LHC, which provides 10 times more intense beam collisions than the LHC, the detectors envisage a very high rate operation in a much harsher radiation environment. Immediate concern is an increase of leakage current due to a radiation damage, which may induce a catastrophic break down of a thermal runaway. We have deduced a simple model for the thermal runaway, which can be conveniently utilized for the module designs. The thermal runaway model was verified by comparing with the corresponding FEM thermal analyses. The upgraded module is structurally similar to the present SCT barrel module. Two rectangular sensors, each of 12.5 × 6.4 cm 2 , are sandwiched along with a thermo-mechanical baseboard to provide two-dimensional space points. A one-piece wrap-around hybrid bridged over the sensors serves both the top and bottom sensors. Mounting and cooling schemes also follow the present barrel SCT designs with necessary modifications and improvements.

Entropic Stabilization and Equilibrium Size of Lipid Vesicles

We have studied the phase behavior of zwitterionic phospholipid dioleoylphosphatidylcholine (DOPC) vesicles (membranes) and interpreted our results using scaling arguments in combination with molecular realistic self-consistent field (SCF) calculations. DOPC membranes acquire a partial negative charge per lipid molecule at intermediate NaBr concentrations. As a result of this, dilute DOPC solutions form stable unilamellar vesicles. Both at low and high salt concentrations phase separation into a lamellar and a vesicular phase is observed. The vesicle radius decreases as a power law with decreasing lipid concentration. This power-law concentration dependence indicates that the vesicle phase is entropically stabilized; the size of the DOPC vesicles result from a competition between the bending energy and translation and undulation entropy. This scaling behavior breaks down for very small vesicles. This appears to be consistent with SCF predictions that point to the fact that in this regime the mean bending modulus kc increases with curvature. The SCF theory predicts that, at low ionic strength, the membrane stability improves when there is more charge on the lipids. Upon a decrease of the ionic strength, lipids with a full negative charge form vesicles that grow exponentially in size because the mean bending modulus increases with decreasing ionic strength. At the same time the Gaussian bending modulus becomes increasingly negative such that the overall bending energy tends to zero. This indicates that small micelles become the dominant species. The SCF theory thus predicts a catastrophic break down of giant vesicles in favor of small micelles at sufficiently low ionic strength and high charge density on the lipids.

Modernism and tradition and the traditions of modernism

Conventionally, the story of musical modernism has been told in terms of a catastrophic break with the (tonal) past and the search for entirely new techniques and modes of expression suitable to a new age. The resulting notion of a single, linear, modernist mainstream (predicated on the basis of a Schoenbergian model of musical progress) has served to conceal a more subtle relationship between past and present. Increasingly, it is being recognized that there exist many modernisms and their various identities are forged from a continual renegotiation between past and present, between tradition(s) and the avant-garde. This is especially relevant when attempting to discuss the reception of modernism outside central Europe, where the adoption of (Germanic) avant-garde attitudes was often interpreted as being "unpatriotic". The case of Great Britain is examined in detail: Harrison Birtwistle?s opera The Mask of Orpheus (1973?83) forms the focus for a wider discussion of modernism within the context of late/post-modern thought.

Influences of the dynamic strain aging on the J– R fracture characteristics of the ferritic steels for reactor coolant piping system

The leak-before-break (LBB) design of the piping system for nuclear power plants has been based on the premise that the leakage due to the through-wall crack can be detected by using leak detection systems before a catastrophic break. The piping materials are required to have excellent J– R fracture characteristics. However, where ferritic steels for reactor coolant piping systems operate at the temperatures where dynamic strain aging (DSA) could occur, the fracture resistance could be reduced with the influence of DSA under dynamic loading. Therefore, in order to apply the LBB design concept to the piping system under seismic loading, both static and dynamic J– R characteristics must be evaluated. Materials used in this study are SA516 Gr.70 for the elbow pipe and SA508 Cl.1a for the main pipe and their welding joints. The crack extension during the dynamic and the static J– R tests was measured by the direct current potential drop (DCPD) and the compliance method, respectively. This paper describes the influences of the dynamic strain aging on the J– R fracture characteristics with the loading rate of the pipe materials and their welding joints.

Leak rates through cracks and slits in PHT pipes for LBB

The Leak Before Break (LBB) concept is widely used in the nuclear industry to eliminate the consideration of postulated double ended guillotine ruptures. This is based on the premise that a detectable leak will develop before a catastrophic break occurs. A ‘throughwall flaw’ is postulated at critical sections so that any leakage from the postulated flaw is sure to be detected. The main purpose of the present study is to develop computer codes to estimate the leakage critical flow through a postulated crack. Flow through a crack may not always attain thermodynamic equilibrium; therefore Henry's Homogeneous Non-equilibrium Model (HHNM) and a Homogeneous Frozen Model (HFM) have been adopted for the present study. Here HFM has been modified taking into account the contribution of change in liquid phase kinetic energy. According to these models, critical mass flow is expressed in terms of inlet quality and exit pressure and quality. The exit pressure is related to the inlet pressure through the cumulative effect of various pressure losses, e.g. entrance loss, friction loss and loss due to flashing. A hybrid correlation for frictional pressure drop due to surface roughness has been incorporated in the present method. Computer codes have been developed based on these models. The results obtained have been verified against published data and are found to be in good agreement. Parametric studies have been carried out to examine the effects of different physical and thermal–hydraulic parameters and to assess the extent of leakage.

The July 29, 1998, debris flow and landslide dam at Capricorn Creek, Mount Meager Volcanic Complex, southern Coast Mountains, British Columbia

A very large debris flow was triggered during a period of record-breaking high temperatures in upper Capricorn Creek, within the Mount Meager Volcanic Complex, a part of the Garibaldi Volcanic Belt of the southern Coast Mountains. The debris flow deposit impounded Meager Creek, creating an 800 m long landslide-dammed lake. The total event volume was 1.2 × 106 m3. The debris flow was followed by three days of almost continuous hyperconcentrated flow surges, which caused significant fluvial aggradation in the Meager Creek flood plain below the Capricorn Creek confluence. Within a few days of the formation of the landslide dam, a spillway notch had been cut through the deposit, thereby preventing the occurrence of a catastrophic dam break. The landslide, which triggered the debris flow, originated in deep volcanic colluvium having a previous history of progressive slope deformation, a consequence of glacial downwasting since the Neoglacial maximum. This paper highlights an important landslide response to recent glacial retreat and suggests that similar events could reoccur within Capricorn Creek, as well as at other sites where steep colluvial and weak bedrock slopes have been glacially debuttressed.