Yield Contradictory Results Research Articles

Effects of radiofrequency radiation on colorectal cancer cell proliferation and inflammation

Abstract Objectives The aim of this study is to investigate the effects of radiofrequency radiation (RFR) on apoptosis, proliferation, stress response, and inflammation markers in colorectal cancer cells. Methods We tested the effects of intermittent exposure to RFR at different frequencies on two different colorectal cancer cell lines; HCT-116 and DLD-1. Protein levels were subsequently analyzed by ELISA. Results RFR led to a decrease in P53, p-P53, p-P38, and p-IkB levels in HCT-116 cells, while leading to an increase in BAD, p-BAD, p-STAT3,NF-κB levels. Two thousand one hundred Megahertz of RFR altered the P53, BAD, and NF-ΚB expression in HCT-116 cells. P53, p-P53, BAD, p-BAD, NF-κB, p-NF-κB, p-P38, p-SAPK/JNK, p-STAT3, and p-IkB levels increased after exposure to RFR at 900 and 2,100 MHz in DLD-1 cells. Unlike HCT-116 cells, 1,800 MHz of RFR was reported to have no effect on DLD1 cells. Conclusions RFR increased apoptosis and inflammatory response in HCT116 cells, while lowering the active P38 and active P53 levels, which are indicators of poor prognosis in several cancers. Genetic differences, such as P53 mutation (DLD-1), are critical to the cell response to RFR, which explains the reason why scientific studies on the effects of RFR yield contradictory results.

Mobilization of Antibiotic Resistance: Are Current Approaches for Colocalizing Resistomes and Mobilomes Useful?

Antimicrobial resistance (AMR) poses a global human and animal health threat, and predicting AMR persistence and transmission remains an intractable challenge. Shotgun metagenomic sequencing can help overcome this by enabling characterization of AMR genes within all bacterial taxa, most of which are uncultivatable in laboratory settings. Shotgun sequencing, therefore, provides a more comprehensive glance at AMR “potential” within samples, i.e., the “resistome.” However, the risk inherent within a given resistome is predicated on the genomic context of various AMR genes, including their presence within mobile genetic elements (MGEs). Therefore, resistome risk stratification can be advanced if AMR profiles are considered in light of the flanking mobilizable genomic milieu (e.g., plasmids, integrative conjugative elements (ICEs), phages, and other MGEs). Because such mediators of horizontal gene transfer (HGT) are involved in uptake by pathogens, investigators are increasingly interested in characterizing that resistome fraction in genomic proximity to HGT mediators, i.e., the “mobilome”; we term this “colocalization.” We explored the utility of common colocalization approaches using alignment- and assembly-based techniques, on clinical (human) and agricultural (cattle) fecal metagenomes, obtained from antimicrobial use trials. Ordination revealed that tulathromycin-treated cattle experienced a shift in ICE and plasmid composition versus untreated animals, though the resistome was unaffected during the monitoring period. Contrarily, the human resistome and mobilome composition both shifted shortly after antimicrobial administration, though this rebounded to pre-treatment status. Bayesian networks revealed statistical AMR-MGE co-occurrence in 19 and 2% of edges from the cattle and human networks, respectively, suggesting a putatively greater mobility potential of AMR in cattle feces. Conversely, using Mobility Index (MI) and overlap analysis, abundance of de novo-assembled contigs supporting resistomes flanked by MGE increased shortly post-exposure within human metagenomes, though > 40 days after peak dose such contigs were rare (∼2%). MI was not substantially altered by antimicrobial exposure across all cattle metagenomes, ranging 0.5–4.0%. We highlight that current alignment- and assembly-based methods estimating resistome mobility yield contradictory and incomplete results, likely constrained by approach-specific data inputs, and bioinformatic limitations. We discuss recent laboratory and computational advancements that may enhance resistome risk analysis in clinical, regulatory, and commercial applications.

Association between ladybird homeobox 1 gene polymorphisms and adolescent idiopathic scoliosis: A MOOSE-compliant meta-analysis.

The Ladybird Homeobox 1 (LBX1) gene has been implicated in the etiology of adolescent idiopathic scoliosis (AIS). The association between LBX1 gene polymorphisms and AIS has been investigated in several studies. However, these findings have yield contradictory results rather than conclusive evidence.This study is to provide a meta-analysis of the published case-control studies on the association between LBX1 gene polymorphisms and AIS in Asian and Caucasian populations.This meta-analysis conformed to the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines. We conducted a literature research on PubMed, Embase, Web of Science, and Cochrane Library until February 10, 2018. We included all case-control or cohort studies about association between LBX1 gene polymorphisms and AIS. The Risk Of Bias In Non-randomised Studies-of Interventions and Critical Appraisal Skills Programme were used to evaluate the risk of bias and study quality. We assessed the strength of association by pooled odds ratios (ORs) and 95% confidence intervals (CIs) in all genetic models under a fixed-effect model or random-effect model. We further performed subgroup analysis by ethnicity and sex. Sensitivity analysis and publication bias were also undertaken.A total of 10 studies (11,411 cases and 26,609 controls) were included in this meta-analysis. The pooled results showed a statistically significant association between LBX1 gene polymorphisms and AIS (for rs11190870, T vs C, OR = 1.54, 95% CI = 1.48-1.61, P < .00001; for rs625039, G vs A, OR = 1.50, 95% CI: 1.38-1.62; P < .00001; for rs678741, G vs A, OR = 0.74, 95% CI: 0.63-0.86; P < .0001; for rs11598564, G vs A, OR = 1.41, 95% CI: 1.31-1.51; P < .0001). For stratified analyses by ethnicity and sex, robust significant associations were detected in Asian and Caucasian populations, and in women and men under all genetic models.T allele of rs11190870 and G alleles of rs625039 and rs11598564 represent risk factors for AIS, but G allele of rs678741 may play a protective role in the occurrence of AIS. Further research is needed to confirm this finding and to understand its implications.

A universal freeze all strategy: why it is not warranted.

There's some preclinical evidence of an adverse effect of multifollicular growth on endometrial function in assisted reproductive technology cycles. Universal elective frozen embryo transfer (eFET) in an unstimulated cycle is being promoted as a panacea, regardless of patient, and cycle characteristics. We review the clinical evidence on the effectiveness and safety of eFETs. Randomized controlled trials (RCTs) comparing fresh and eFET yield contradictory results in terms of live birth rates. RCTs mainly involve women with an excessive response to ovarian stimulation. Studies including women with a normal or low ovarian response are either patient/physician preference or retrospective studies, prone to bias. Yet, they yield contradictory results as well. Overall, eFET seems to have limited potential to improve effectiveness of assisted reproductive technology, which could be limited to hyper-responders. Other suggested advantages of eFET include better obstetric and perinatal outcome. However, recent studies show that frozen embryo transfers can be associated with serious complications including hypertensive disorders during pregnancy, placenta accreta, or increased perinatal mortality. The evidence behind advantages of eFET is of low quality. As such, switching to a universal eFET strategy does not seem justified. New RCTs including women from different strata of ovarian response are needed.

Are Socio-Demographic Factors Associated to Burnout Syndrome in Police Officers? A Correlational Meta-Analysis

Burnout syndrome is considered a long term stress reaction which is seen primarily among professionals who work face-to-face with other people. Socio-demographic characteristics have been suggested as risk factors in the development of burnout, although empirical studies have yield contradictory results. The objective of the present study is to conduct a meta-analytic review of four socio-demographic factors (age, sex, marital status, and number of children) that may be correlated to burnout in police officers. These professionals have been considered a high-risk occupational group to suffer burnout due to specific characteristics of their job. We collected 43 empirical studies that fulfilled the inclusion criteria: 23 on age, 32 on sex, 9 on marital status, and 4 on number of children. The bivariate correlation coefficient was used as the effect size measure. The results show that all the average effect were small, and the majority of them were not statistically significant. We can conclude that sex and age are factors to discard in the development of the burnout syndrome in police officers. We found that many studies did not report enough statistical information to estimate effect sizes. This systematic lack of information is likely to contribute finding contradictory results. Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";} Burnout syndrome is considered a long term stress reaction which is seen primarily among professionals who work face-to-face with other people. Socio-demographic characteristics have been suggested as risk factors in the development of burnout, although empirical studies have yield contradictory results. The objective of the present study is to conduct a meta-analytic review of four socio-demographic factors (age, sex, marital status, and number of children) that may be correlated to burnout in police officers. These professionals have been considered a high-risk occupational group to suffer burnout due to specific characteristics of their job. We collected 43 empirical studies that fulfilled the inclusion criteria: 23 on age, 32 on sex, 9 on marital status, and 4 on number of children. The bivariate correlation coefficient was used as the effect size measure. The results show that all the average effect were small, and the majority of them were not statistically significant. We can conclude that sex and age are factors to discard in the development of the burnout syndrome in police officers. We found that many studies did not report enough statistical information to estimate effect sizes. This systematic lack of information is likely to contribute finding contradictory results. Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}

A new genus and species of marine catfishes (Siluriformes; Ariidae) from the upper Eocene Birket Qarun Formation, Wadi El-Hitan, Egypt.

Wadi El-Hitan, the UNESCO World Heritage Site, of the Fayum Depression in the northeast part of the Western Desert of Egypt, has produced a remarkable collection of Eocene vertebrates, in particular the fossil whales from which it derives its name. Here we describe a new genus and species of marine catfishes (Siluriformes; Ariidae), Qarmoutus hitanensis, from the base of the upper Eocene Birket Qarun Formation, based on a partial neurocranium including the complete left side, partial right dentary, left suspensorium, two opercles, left pectoral girdle and spine, nuchal plates, first and second dorsal spines, Weberian apparatus and a disassociated series of abdominal vertebrae. All of the elements belong to the same individual and some of them were found articulated. Qarmoutus gen. nov. is the oldest and the most complete of the Paleogene marine catfishes unearthed from the Birket Qarun Formation. The new genus exhibits distinctive features not seen in other African Paleogene taxa, such as different sculpturing on the opercle and pectoral girdle with respect to that on the neurocranium and nuchal plates, denticulate ornamentation on the skull bones arranged in longitudinal rows and forming a radiating pattern on the sphenotic, pterotic, extrascapular and the parieto-supraoccipital, indentations or pitted ornamentation on the nuchal plates as well as the parieto-supraoccipital process, strut-like radiating pattern of ornamentation on the opercle from the proximal articulation to margins, longitudinal, curved, reticulate ridges and tubercular ornamentations on the cleithrum, sinuous articulation between the parieto-supraoccipital process and the anterior nuchal plate, long, narrow, and arrowhead shaped nuchal shield, very small otic capsules restricted to the prootic. Multiple parsimony and Bayesian morphological phylogenetic analyses of Ariidae, run with and without “molecular scaffolds”, yield contradictory results for the placement of Qarmoutus; the genus is either a phylogenetically basal ariid, or it is deeply nested within the ariid clade containing New World species of Sciades.

Meta-analysis of extremely low frequency electromagnetic fields and cancer risk: a pooled analysis of epidemiologic studies

Studies have suggested that extremely low frequency electromagnetic fields (ELF-EMF) may affect physiological functions in animal models. However, epidemiologic studies investigating the association of ELF-EMF with the susceptibility to cancer yield contradictory results. In this comprehensive analysis, we conducted a search for case–control surveys regarding the associations of ELF-EMF and cancer susceptibility in electronic databases. A total of 42 studies involving 13,259 cases and 100,882 controls were retrieved. Overall, increased susceptibility to cancer was identified in the ELF-EMF exposed population (OR=1.08, 95% CI: 1.01, 1.15, P=0.02). In the stratified analyses, increased risk was found in North America (OR=1.10; 95% CI: 1.02, 1.20, P=0.02), especially the United States (OR=1.10; 95% CI: 1.01, 1.20, P=0.03). However, studies from Europe contradict these results. Moreover, a higher risk was found to be statistically significantly associated with the residential exposed population (OR=1.18; 95% CI: 1.02, 1.37, P=0.03). Furthermore, an increased cancer risk was found in interview-based surveys (OR=1.16; 95% CI: 1.00, 1.35, P=0.04). In device measurement-based studies, a slight increased risk was found only in premenopausal breast cancer (OR=1.23; 95% CI: 1.01, 1.49, P=0.04). Our meta-analysis suggests that ELF-EMFs are associated with cancer risk, mainly in the United States and in residential exposed populations. Methodological challenges might explain the differences among studies.

Proton form factors and two-photon exchange in elastic electron-proton scattering

Proton electromagnetic form factors are among the most important sources of information about the internal structure of the proton. Two different methods for measuring these form factors, the method proposed by Rosenbluth and the polarization-transfer method, yield contradictory results. It is assumed that this contradiction can be removed upon taking into account the hard part of the contribution of two-photon exchange to the cross section for elastic electron-proton scattering. This contribution can measured experimentally via a precision comparison of the cross sections for the elastic scattering of positrons and electrons on protons. Such a measurement, performed at the VEPP-3 storage ring in Novosibirsk at the beam energies of 1.6 and 1.0 GeV for positron (electron) scattering angles in the ranges of θe = 15°–25° and 55°–75° in the first case and in the range of θe = 65°–105° in the second case is described in the present article. Preliminary results of this experiment and their comparison with theoretical predictions are described.

Abstract 222: Serum Adiponectin Level and Incident Dementia in Patients with Vascular Risk Factors - Sub-analysis of OSACA2 Follow-up Study

Background and Purpose: Involvement of metabolic factors on dementia development has received much attention. However, several previous studies have yield contradictory results for the involvement of blood adipocytokine levels on cognitive decline and dementia. The aim of this study is to clarify whether serum adiponectin level is related to incident dementia in patients with vascular risk factors. Methods: OSACA2 is a prospective cohort study for cardiovascular events and dementia in which patients with vascular risk factors undergo carotid ultrasound and blood sampling. Between 2001 and 2009, 1106 outpatients were enrolled. Among them, 466 patients who underwent brain MRI and had normal cognitive function were included in this study. High molecular weight adiponectin level was measured with frozen serum. Follow-up data for dementia occurrence were collected in June 2013. Results: Among 466 subjects (mean: 67.8 years), serum adiponectin level was 4.33 + 2.95 μg/mL. Adiponectin level was lower in male than in female, and positively associated with body mass index. During the follow-up period of median 6.9 years, 47 patients had incident dementia (27 AD, 17 vascular dementia, 3 others). Age, baseline MMSE, eGFR and the presence of lacunar infarction were related to incident dementia. No difference in adiponectin level was found between patients with and without incident dementia (4.31+3.07 vs. 4.33+2.94 μg/mL). The survival analyses for dementia-free rate curves, determined with respect to median level of adiponectin, are shown in Figure. Risk of incident dementia in patients with high and low adiponectin levels were almost similar (Log-rank test: p = 0.868). Risk of AD and vascular dementia were also similar between two groups. Conclusion: This study suggested that serum adiponectin level have little association with future dementia. The impact of metabolic factors on dementia would need to be evaluated not by adiponectin level but other biomarkers or parameters.

Topographical Analysis of the Subependymal Zone Neurogenic Niche

The emerging model for the adult subependymal zone (SEZ) cell population indicates that neuronal diversity is not generated from a uniform pool of stem cells but rather from diverse and spatially confined stem cell populations. Hence, when analysing SEZ proliferation, the topography along the anterior-posterior and dorsal-ventral axes must be taken into account. However, to date, no studies have assessed SEZ proliferation according to topographical specificities and, additionally, SEZ studies in animal models of neurological/psychiatric disorders often fail to clearly specify the SEZ coordinates. This may render difficult the comparison between studies and yield contradictory results. More so, by focusing in a single spatial dimension of the SEZ, relevant findings might pass unnoticed. In this study we characterized the neural stem cell/progenitor population and its proliferation rates throughout the rat SEZ anterior-posterior and dorsal-ventral axes. We found that SEZ proliferation decreases along the anterior-posterior axis and that proliferative rates vary considerably according to the position in the dorsal-ventral axis. These were associated with relevant gradients in the neuroblasts and in the neural stem cell populations throughout the dorsal-ventral axis. In addition, we observed spatially dependent differences in BrdU/Ki67 ratios that suggest a high variability in the proliferation rate and cell cycle length throughout the SEZ; in accordance, estimation of the cell cycle length of the neuroblasts revealed shorter cell cycles at the dorsolateral SEZ. These findings highlight the need to establish standardized procedures of SEZ analysis. Herein we propose an anatomical division of the SEZ that should be considered in future studies addressing proliferation in this neural stem cell niche.

Moderation of Religious Parties

Whether religious parties’ inclusion in electoral competition moderates or polarizes their positions remains an enigma as deductive accounts yield contradictory results. This analysis questions the institution- and ideology-centered approaches to party change and shows that dichotomizing religious parties as moderate or extreme and moderation as a monolithic process obscures religious parties’ role in democracy. When scholars view moderation as consisting of behavioral and ideological dimensions and examine it through an inductive analysis of Israel and Turkey’s religious parties, several modes of moderation emerge with different democratic outcomes. While some bolster procedural democracy, others thwart the expansion of liberal democracy.

Determinants of translation efficiency and accuracy

Proper functioning of biological cells requires that the process of protein expression be carried out with high efficiency and fidelity. Given an amino-acid sequence of a protein, multiple degrees of freedom still remain that may allow evolution to tune efficiency and fidelity for each gene under various conditions and cell types. Particularly, the redundancy of the genetic code allows the choice between alternative codons for the same amino acid, which, although 'synonymous,' may exert dramatic effects on the process of translation. Here we review modern developments in genomics and systems biology that have revolutionized our understanding of the multiple means by which translation is regulated. We suggest new means to model the process of translation in a richer framework that will incorporate information about gene sequences, the tRNA pool of the organism and the thermodynamic stability of the mRNA transcripts. A practical demonstration of a better understanding of the process would be a more accurate prediction of the proteome, given the transcriptome at a diversity of biological conditions.

Findings follow framings: navigating the empirical turn

In this paper, I outline several methodological questions that we need to confront. The chief question is how can we identify the nature of technological change and its varied cultural consequences—including social, political, institutional, and economic dimensions—when our different research methods, using distinct ‘levels’ or ‘scales’ of analysis, yield contradictory results. What can we say, in other words, when our findings about technology follow from the framings of our inquiries? In slightly different terms, can we combine insights from the fine-grained “social shaping of technology” as well as from complementary approaches accenting the “technological shaping of society?” As a way forward, I will suggest conducting multi-scale inquiries into the processes of technological and cultural change. This will involve recognizing and conceptualizing the analytical scales or levels on which we conduct inquiry (very roughly, micro, meso, macro) as well as outlining strategies for moving within and between these scales or levels. Of course we want and need diverse methodologies for analyzing technology and culture. I find myself in sympathy with geographer Brenner (New state spaces: urban governance and the rescaling of statehood, 2004, p. 7), who aspires to a “theoretically precise yet also historically specific conceptualization of [technological change] as a key dimension of social, political and economic life.”

On the sexuality of South American Parastacidae (Crustacea, Decapoda)

Summary Ten parastacid species inhabit South American continental waters, grouped in the genera Samastacus, Virilastacus and Parastacus. The sexuality of these species is one of the most unknown and controversial features of their biology. This article gives updated information about these species sexuality. Information is also provided on the geographic distribution, habitat and lifestyle of each of these parastacids. Three patterns of sexuality are distinguished: (1) gonochorism, in the lake populations of S. spinifrons and V. araucanius; (2) permanent intersexuality in P. pugnax, P. varicosus, P. pilimanus, P. defossus and P. saffordi; and (3) partial protandric hermaphroditism in the fluvial populations of S. spinifrons and P. nicoleti. None of these patterns can be assigned to P. laevigatus and P. brasiliensis since no studies of this kind are available for P. laevigatus, and those conducted on P. brasiliensis yield contradictory results.

Editorial: Left ventricular dysfunction after open repair of simple confenital heart defects in infants and children

Editorial: Left ventricular dysfunction after open repair of simple confenital heart defects in infants and children

Long Memory in Inflation Rates: International Evidence

We examine monthly inflation rates of five industrial countries. The application of tests against stationarity as well as tests against a unit root yield contradictory results. Thus fractional integration allowing for long memory is a plausible model. We discuss and apply the periodogram regression to estimate the difference parameters. For all countries we find estimates significantly different from 1 as well as from 0. This is evidence in favor of long memory. Specification tests and maximum likelihood estimates support the fitted models. Finally, we relate our empirical results to the construction of the data.

Comment On: ‘Early Silurian Palaeolatitude of the Springdale Group Redbeds of Central Newfoundland: A Palaeomagnetic Determination With A Remanence Anisotropy Test For Inclination Error’ By J. P. Hodych and K. L. Buchan

Recent palaeomagnetic results from coeval Silurian sedimentary and volcanic rocks of Newfoundland yield contradictory results, with shallow characteristic directions recorded by the redbeds and steeper characteristic directions recorded by the volcanics. In their recent paper on the Springdale Group redbed, Hodych & Buchan (1994a) argue that the redbed magnetization is more reliable based on a fold test, dual-polarity magnetization, conglomerate test and an IRM acquisition experiment specifically designed to test for compaction or inclination error. Accordingly, these authors dismiss the volcanic results as well as the Silurian reference poles for Laurentia, citing possible remagnetization or other complications. However, we argue that the IRM experiments of Hodych & Buchan (1994a) are flawed and do not necessarily resolve the question of inclination error. Moreover, we point out that the conglomerate test is incomplete and that the proposed tectonic reconstruction based solely on the redbed magnetization implies a unique tectonic scenario that is incompatible with out present understanding of Silurian palaeogeography.

Perspectives on the source, segregation and transport of granitoid magmas

ABSTRACTThe pursuit of a comprehensive theory for the origin and evolution of granitoids is hindered by our incomplete understanding of the nature of the source and the mechanisms by which the magma is segregated and transported. This paper is a collection of three largely independent and necessarily incomplete perspectives on these outstanding issues. Lower to mid-crustal regions, which contain the principal source material for granitoid magmas, are highly heterogeneous. Consideration of available transfer mechanisms suggests that (1) this heterogeneity survives all foreseeable lower crustal processes; (2) closure is on very different scales for different chemical systems (e.g. Pb, Nd, Sr and O isotopes); in almost all cases, however, closure scale is much smaller than the scale of magma extraction zones for plutons; and (3) pluton-wide homogenisation of magmas by diffusion is precluded by low diffusivities in felsic melts. Thus, granitoid magmas begin life as aggregates of small, isolated chemical domains; homogenisation occurs only through (and on the scale of) effective stirring by convection. Because of variability in local conditions as well as in bulk composition, crustal regions undergoing anatexis must be patchworks with variable melt fractions and melt compositions. The way in which magma is extracted from and coalesces with this patchwork exerts a critical influence on the nature of granitoid magmas. Decoupling and unusual coupling of compositional parameters and isotopic heterogeneity within plutons are to be expected in crust-derived granitoids and do not require contamination. Granites image their sources, but these sources are ill-defined and do not correspond to simple, easily-recognised materials. Extent and patterns of heterogeneity remaining in crystallised plutons may be effective indicators of the ascent process.The efforts of materials scientists in characterising the nature and evolution of solid-phase interconnectivity in partially-molten materials may offer some insights into crustal magmatic processes. In particular, the rheological properties of partially-molten crustal rocks are probably strongly affected by the contiguity of the solid grains in the system (i.e. the fraction of their surface area that is shared with other grains). Theory and experimental data for simple alloy systems reveal that contiguity depends principally upon melt fraction and upon the characteristic wetting angle (θ) of the system. Measured θ's in granitoids (∼50° on average) imply contiguities as high as ∼0·2 for melt fractions of 0·5 or greater. This value in turn suggests that, at least under static conditions, a continuous skeleton of solid grains is maintained to quite high degrees of melting in the crust. Consequently, regions consisting of 50% or more of melt can, in principle, maintain not only high yield strength, but also high viscosity (provided the strain rate is sufficiently low to avoid disrupting contiguity).Despite the fact that on some time scale the continuous solid skeleton of a partially-molten region resists deformation, it is itself subject to textural evolution that could lead to the upward migration of melt. Occasional detachment of grains from the skeleton and subsequent “microsettling” within the partially-molten column may lead eventually to compaction of the solid (without plastic deformation) and net upward displacement of melt.Proposed granite transport mechanisms are discussed, although several are viewed as having historical interest only. In the absence of tectonic transport, diapirism appears to be the most compelling of these processes. However, considerable diversity exists in the literature regarding a pivotal requirement for this mechanism. Structural studies have tended to conclude that the granite diapir must be highly crystallised in order to ascend, whereas results of physical modelling yield contradictory results. For ascent to occur in these models, the magmas must be sufficiently fluid to allow convective circulation. Indeed, heat loss associated with diapirism is so efficient as to be a significant restriction on overall ascent. The resolution of these contrasting views appears to be that they reflect different phases of the ascent/emplacement continuum. Understanding the emplacement history of a southeastern Australian pluton allows assessment, via the diapir model, of the flow properties of the rock within the deformation aureole. Results suggest rock viscosities about an order of magnitude lower than those predicted by laboratory experiments, perhaps reflecting difficulties in reproducing natural conditions in the laboratory.

Dynamics of a discrete auroral arc

Porcupine Flight 4 data were used to determine the field‐aligned currents associated with a southward moving discrete auroral arc in the postmidnight sector. We use three different methods for determining j∥ which should give identical results if the arcs are quasi‐stationary and no parallel electric field exists between the payload and the dynamo region of the ionosphere. As long as the rocket is above the arc, the three methods agree. The integral of precipitating electron flux, the local magnetic field perturbations, and the divergence of the horizontal Pedersen current all indicate an upward current of 5±3 µA/m². Immediately north of the arc a strong downward current of about 10–20 µA/m² is detected. The magnitude, however, is not well known because the rocket's velocity relative to the arc cannot be clearly established. Further north of the southward moving arc the two methods that can be applied (magnetic field perturbations and divergence of the horizontal Pedersen current) yield contradictory results not only about the magnitude of the current but also about the direction of the current. We suggest that this discrepancy is due to time‐dependent electric fields.

The effect of cooling on supersonic boundary-layer stability

For a number of applications it is important to know the location of the boundary-layer transition from laminar to turbulent. At present it is generally recognized that the onset of turbulence is directly connected with the loss of stability of the initial laminar flow. In the overwhelming majority of cases experimental data on the influence of various factors upon the transition location agree well with the calculated data concerning the influence of these factors on the boundary-layer stability, i.e. the theory of stability may be used successfully to predict various experimental dependencies.The boundary-layer stability and the transition are considerably affected by heat transfer from the surface of the streamlined body. But, in this case, experimental data on the transition do not always correspond to the results of the stability theory. In particular, experimental works concerning the effect of cooling of the model surface on the supersonic boundary layer transition yield contradictory results (see e.g. Gaponov & Maslov 1980; Morkovin 1969). Some of the contradictions were removed by Demetriades (1978) and Lysenko & Maslov (1981), but on the whole the problem cannot be considered solved, primarily owing to the fact that many theoretical results have not yet been experimentally confirmed.In the present paper the experimental study of development of small natural disturbances in the boundary layer of a cooled flat plate for Mach numbers M = 2, 3 and 4 is described. It confirms the main conclusions of the linear theory of hydrodynamic stability concerning the fact that surface cooling: (i) stabilizes the first-mode disturbances; (ii) destabilizes the second-mode disturbances; (iii) may lead to the region of unstable frequencies of the first mode being divided into two; (iv) does not affect the interaction of acoustic waves and the supersonic boundary layer.