913 research outputs found
Detachment Faults in the Southwestern United States: Evidence for a Short and Catastrophic Tertiary Period
Low-angle mid-Tertiary detachment faults (gravity slides) within the southwestern United States are best understood as developing very rapidly (years) within a catastrophic framework. This is supported by the example of modern and ancient gravity slides which occur very rapidly (within seconds, minutes, or days) and are usually initiated by catastrophic events such as earthquakes. Evolutionists believe that detachment faulting and related geologic events occurred over a period of 10 to 20 million years. However, the basic principles of rock mechanics reveal that upper-plate movement is impossible under docile uniformitarian conditions. Movement was assisted by large and frequent earthquakes which provided both lateral and horizontal forces to overcome the restraining forces against movement due to friction and cohesion. Studies indicate that rapid basement warping, extensive dike emplacement, volcanism, and hydrothermal mineralization occurred contemporaneous with detachment faulting due to a high heat flow rate within the earth\u27s crust. Thick deposits of coarse grained sediments and megabreccias also indicate rapid uplift, erosion, and deposition. This reveals that an unparalleled amount of seismic energy was released at this time. The rapid development of detachment terrane indicates that the Tertiary period was similar to the latter stages of Noah\u27s Flood as the mountains rose and valleys sank down and was significantly shorter than the millions of years assigned under the uniformitarian model
Evidences for Rapid Formation and Failure of Pleistocene Lava Dams of the Western Grand Canyon, AZ.
Over 200 isolated outcrops of horizontally stratified, basaltic lava flows within the inner gorge of western Grand Canyon indicate that several natural lava dams blocked the flow of the Colorado River during the Pleistocene, resulting in the formation of several lakes within the canyon. The largest lake was 90 m above the high water level of present-day Lake Powell and backed up a distance of over 480 km to Moab, Utah . Although early studies indicated that three or less dams once blocked the inner gorge, work completed in 1994 indicated that at least 13 distinct lava dams may have blocked the Colorado River. Comparison with modern erosion rates of cliff retreat (Niagara Falls) indicate that the 13 dams would have required a minimum of 250,000 years to erode during the Pleistocene. However, geologic features and relationships not previously considered indicate that the dams formed rapidly (hours, days, or months) and failed catastrophically soon after formation. Excess radiogenic argon is contain within many basalts of Grand Canyon. This initial argon invalidates K-Ar model ages which are assumed by many geologists to require an age of more than one million years for the oldest lava dams. We envision that the entire episode of the lava darns can easily be reconciled within a time-frame of less than two thousand years. Our observations and interpretations reveal serious flaws in the current long-age timescale of the Pleistocene Epoch
On the effect of hydrogen on the elastic moduli and acoustic loss behaviour of Ti-6Al-4V
The elastic moduli and acoustic loss behaviour of Ti-6Al-4V (wt.%) in the temperature range 5â298 K have been studied using Resonant Ultrasound Spectroscopy. A peak in the acoustic dissipation was observed at 160 K within the frequency range 250â1000 kHz. Analysis of the data acquired in this study, coupled with complementary data from the literature, showed that this was consistent with a Snoek-like relaxation process with an associated activation energy of 23
3 kJ mol. However, the loss peak was broader than would be expected for a Snoek-like relaxation, and the underlying process was shown to have a spread of relaxation times. It is suggested that this effect arises as a result of variations in the strain experienced by the phase due to different local microstructural constraint by the bounding secondary phase
Fluoride and oral health
The discovery during the first half of the 20th century of the link between natural fluoride, adjusted fluoride levels in drinking water and reduced dental caries prevalence proved to be a stimulus for worldwide on-going research into the role of fluoride in improving oral health. Epidemiological studies of fluoridation programmes have confirmed their safety and their effectiveness in controlling dental caries. Major advances in our knowledge of how fluoride impacts the caries process have led to the development, assessment of effectiveness and promotion of other fluoride vehicles including salt, milk, tablets, toothpaste, gels and varnishes. In 1993, the World Health Organization convened an Expert Committee to provide authoritative information on the role of fluorides in the promotion of oral health throughout the world (WHO TRS 846, 1994). This present publication is a revision of the original 1994 document, again using the expertise of researchers from the extensive fields of knowledge required to successfully implement complex interventions such as the use of fluorides to improve dental and oral health. Financial support for research into the development of these new fluoride strategies has come from many sources including government health departments as well as international and national grant agencies. In addition, the unique role which industry has played in the development, formulation, assessment of effectiveness and promotion of the various fluoride vehicles and strategies is noteworthy. This updated version of âFluoride and Oral Healthâ has adopted an evidence-based approach to its commentary on the different fluoride vehicles and strategies and also to its recommendations. In this regard, full account is taken of the many recent systematic reviews published in peer reviewed literature
Age-related Differences in Prestimulus Subsequent Memory Effects Assessed with Event-related Potentials
Prestimulus subsequent memory effects (preSMEs)âdifferences in neural activity elicited by a task cue at encoding that are predictive of later memory performanceâare thought to reflect differential engagement of preparatory processes that benefit episodic memory encoding. We investigated age differences in preSMEs indexed by differences in ERP amplitude just before the onset of a study item. Young and older adults incidentally encoded words for a subsequent memory test. Each study word was preceded by a task cue that signaled a judgment to perform on the word. Words were presented for either a short (300 msec) or long (1000 msec) duration with the aim of placing differential benefits on engaging preparatory processes initiated by the task cue. ERPs associated with subsequent successful and unsuccessful recollection, operationalized here by source memory accuracy, were estimated time-locked to the onset of the task cue. In a late time window (1000â2000 msec after onset of the cue), young adults demonstrated frontally distributed preSMEs for both the short and long study durations, albeit with opposite polarities in the two conditions. This finding suggests that preSMEs in young adults are sensitive to perceived task demands. Although older adults showed no evidence of preSMEs in the same late time window, significant preSMEs were observed in an earlier time window (500â1000 msec) that was invariant with study duration. These results are broadly consistent with the proposal that older adults differ from their younger counterparts in how they engage preparatory processes during memory encoding
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CHERIvoke: Characterising pointer revocation using CHERI capabilities for temporal memory safety
A lack of temporal safety in low-level languages has led to an epidemic of use-after-free exploits. These have surpassed in number and severity even the infamous buffer-overflow exploits violating spatial safety. Capability addressing can directly enforce spatial safety for the C language by enforcing bounds on pointers and by rendering pointers unforgeable. Nevertheless, an efficient solution for strong temporal memory safety remains elusive.
CHERI is an architectural extension to provide hardware capability addressing that is seeing significant commercial and open- source interest. We show that CHERI capabilities can be used as a foundation to enable low-cost heap temporal safety by facilitating out-of-date pointer revocation, as capabilities enable precise and efficient identification and invalidation of pointers, even when using unsafe languages such as C. We develop CHERIvoke, a technique for deterministic and fast sweeping revocation to enforce temporal safety on CHERI systems. CHERIvoke quarantines freed data before periodically using a small shadow map to revoke all dangling pointers in a single sweep of memory, and provides a tunable trade-off between performance and heap growth. We evaluate the performance of such a system using high-performance x86 processors, and further analytically examine its primary overheads. When configured with a heap-size overhead of 25%, we find that CHERIvoke achieves an average execution-time overhead of under 5%, far below the overheads associated with traditional garbage collection, revocation, or page-table systems.EP/K026399/1, EP/P020011/1, EP/K008528/
Conversion between Triplet Pair States Is Controlled by Molecular Coupling in Pentadithiophene Thin Films
In singlet fission (SF) the initially formed correlated triplet pair state, 1(TT), may evolve toward independent triplet excitons or higher spin states of the (TT) species. The latter result is often considered undesirable from a light harvesting perspective but may be attractive for quantum information sciences (QIS) applications, as the final exciton pair can be spin-entangled and magnetically active with relatively long room temperature decoherence times. In this study we use ultrafast transient absorption (TA) and time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy to monitor SF and triplet pair evolution in a series of alkyl silyl-functionalized pentadithiophene (PDT) thin films designed with systematically varying pairwise and long-range molecular interactions between PDT chromophores. The lifetime of the (TT) species varies from 40 ns to 1.5 ÎŒs, the latter of which is associated with extremely weak intermolecular coupling, sharp optical spectroscopic features, and complex TR-EPR spectra that are composed of a mixture of triplet and quintet-like features. On the other hand, more tightly coupled films produce broader transient optical spectra but simpler TR-EPR spectra consistent with significant population in 5(TT)0. These distinctions are rationalized through the role of exciton diffusion and predictions of TT state mixing with low exchange coupling J versus pure spin substate population with larger J. The connection between population evolution using electronic and spin spectroscopies enables assignments that provide a more detailed picture of triplet pair evolution than previously presented and provides critical guidance for designing molecular QIS systems based on light-induced spin coherence
How children eat may contribute to rising levels of obesity children's eating behaviours: An intergenerational study of family influences
The term âobesogenic environmentâ is rapidly becoming part of common phraseology. However, the influence of the family and the home environment on children's eating behaviours is little understood. Research that explores the impact of this micro environment and intergenerational influences affecting children's eating behaviours is long overdue. A qualitative, grounded theory approach, incorporating focus groups and semi-structured interviews, was used to investigate the family environment and specifically, the food culture of different generations within families. What emerged was a substantive theory based on âordering of eatingâ that explains differences in eating behaviours within and between families. Whereas at one time family eating was highly ordered and structured, typified by the grandparent generation, nowadays family eating behaviours are more haphazard and less ordered, evidenced by the way the current generation of children eat. Most importantly, in families with an obese child eating is less ordered compared with those families with a normal weight child. Ordering of eating' is a unique concept to emerge. It shows that an understanding of the eating process is crucial to the development and improvement of interventions targeted at addressing childhood obesity within the family context
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