Internal Stratification Research Articles

Quadratic Frequency Dispersion in the Oscillations of Intermediate-mass Stars

Asteroseismology, the study of stellar vibration, has met with great success, shedding light on stellar interior structure, rotation, and magnetism. Prominently known as δ Scutis, the intermediate-mass main-sequence oscillators that often exhibit rapid rotation and possess complex internal stratification are important targets of asteroseismic study. δ Scuti pulsations are driven by the κ (opacity) mechanism, resulting in a set of acoustic modes that can be challenging to interpret. Here, we apply machine learning to identify new patterns in the pulsation frequencies of δ Scuti stars, discovering resonances spaced according to quadratic functions of integer mode indices. This unusual connection between mode frequencies and indices suggests that rotational influence may play an important role in determining the frequencies of these acoustic oscillations.

The Hybridization of the Regulatory Framework of Insurance Contract Law: Elements of a New Setting

This article aims to highlight the phenomenon of hybridization of insurance contract law, which started with its emancipation from contract law. The next phase included its internal stratification, stemming from obvious differences between commercial and consumer insurance, and various contractual positions of contracting parties in these different insurance contracts. Two features of insurance contracts regulation are addressed, based on Serbian law as it currently stands, as well as comparative legal analysis. The first feature is that the legislatively envisaged unified regime for insurance contracts is incomplete and inadequate for all manifestations of this contract. The second feature is that regulation of this matter must enable balancing of interests between insurers and insureds, especially consumers. The authors conclude that insurance regulation can only be conducive when simultaneously ensuring protection of the weaker party, protecting insurers from the negligent actions of the insured, while facilitating conduct of insurance business.

22Ne distillation and the cooling sequence of the old metal-rich open cluster NGC 6791

Recent Monte Carlo plasma simulations carried out to study the phase separation of 22Ne in crystallizing carbon-oxygen (CO) white dwarfs (WDs; the most abundant metal after carbon and oxygen) have shown that, under the right conditions, a distillation process that transports 22Ne towards the WD centre is efficient and releases a considerable amount of gravitational energy. This can lead to cooling delays of up to several Gyr. Here we present the first CO WD stellar evolution models that self-consistently include the effect of neon distillation and cover the full range of CO WD masses for a twice-solar progenitor metallicity, which is appropriate for the old open cluster NGC 6791. The old age (about 8.5 Gyr) and high metallicity of this cluster – and hence the high neon content (about 3% by mass) in the cores of its WDs – maximize the effect of neon distillation in the models. We discuss the effect of distillation on the internal chemical stratification and cooling time of the models, confirming that distillation causes cooling delays of up to several Gyr that depend in a non-monotonic way on the mass. We also show how our models produce luminosity functions (LFs) that can match the faint end of the observed WD LF in NGC 6791, for ages consistent with the range determined from a sample of cluster eclipsing binary stars and the main sequence turn-off. Without the inclusion of distillation, the theoretical WD cooling sequences reach magnitudes that are too faint compared to observations. We also propose James Webb Space Telescope observations that would independently demonstrate the efficiency of neon distillation in the interiors of NGC 6791 WDs and help resolve the current uncertainty on the treatment of the electron conduction opacities for the hydrogen-helium envelope of WD models.

Distribution patterns and controlling factors of beach bars in Qinghai Lake, NW China

The significance of beach-bar reservoirs, which are intricately linked to unconventional hydrocarbon reservoirs, has gained increased attention. This study elucidates the complex mechanisms governing the formation, spatial distribution, and morphological characteristics of beach bars in Qinghai Lake, NW China, highlighting the interplay of lake-level fluctuations, wind wave dynamics, sediment provenance, and terrain gradient. Our findings reveal that large-scale lake-level fluctuations primarily dictate the initial formation settings of beach bars, while small-scale fluctuations refine their internal stratification and sedimentary features. Wind wave dynamics play a critical role in defining suitable depth zones for beach bar development, influencing their morphology and resulting in distinct sedimentary characteristics across different lake zones. Furthermore, the study categorizes beach bars into three main systems based on sediment provenance—bedrock, alluvial fan (fan delta), and braided river systems—each exhibiting unique compositional and structural attributes. Terrain gradient around the lake significantly affects beach bar formation, with areas having a gradient less than 0.7° being particularly favorable. This research advances our understanding of lacustrine beach bar dynamics, offering insights into their potential as indicators of past environmental conditions and their implications for hydrocarbon exploration. The comprehensive analysis of controlling factors provides a foundation for predicting beach bar distribution and contributes to the broader field of sedimentary geology by integrating multi-disciplinary approaches to study lacustrine sedimentary processes.

Equilibrium tides and magnetic activity in stars with close-by massive planets. The intriguing case of WASP-18

WASP-18 is an F6V star that hosts a planet with a mass of $ 10$ Jupiter masses and an orbital period of $ 0.94$ days. In spite of its relatively fast rotation and young age, the star remains undetected in X-rays, thus implying a very low level of magnetic activity. To account for such unexpected properties, we propose a mechanism that modifies the internal stratification and the photospheric magnetic activity of a late-type main sequence star with a close-by massive planet based on the action of the equilibrium tide. We speculate that the horizontal flow produced by the equilibrium tide may interact with the convective plumes in the overshoot layer below the stellar outer convective envelope. The interaction is characterised by a very high Reynolds number ($Re $), leading to the development of turbulent boundary layers at the surface of such structures, whereas turbulent wakes extend over most of the overshoot layer that they straddle. We propose that such a tidally induced turbulence can lead to a reduction of the filling factor of the downdrafts in the overshoot layer. As a consequence, the absolute value of the sub-adiabatic gradient increases in that layer hindering the emergence of magnetic flux tubes responsible for the formation of photospheric starspots. We conjecture that this process is occurring in WASP-18, thus providing a possible mechanism to account for the very low level of magnetic activity observed for such a planet host.

A state-space heating and cooling model for thermal stratification in horizontally configured electric hot water storage cylinders

Domestic water heating significantly impacts global energy demand, with electric hot water storage devices notably contributing to grid load. Efficient management of these widespread devices is contingent on a deep understanding of the internal thermal stratification occurring naturally during heating and cooling phases. While extensive research exists for vertical water heaters, horizontal heaters, more challenging to model, have been comparatively overlooked in scholarly research. This paper introduces a state-space model developed using measured datasets, aimed at accurately describing temperature distributions inside a horizontally-configured electric hot water storage cylinder during heating, thermal diffusion, and cooling stages. The model’s effectiveness was validated through various evaluation metrics and separate, unseen evaluation datasets. It achieved an accuracy of 90.6% for the dimensionless stratification factor, 94.6% for the dimensionless exergy number, and reported Root Mean Square Errors (RMSEs) of 150kJ for energy, 11kJ for exergy, and 0.8°C for temperature.

Civilisational ‘ideas’, state power, and globalising ‘realities’: structuring mechanisms shaping contemporary higher education outcomes in China

ABSTRACT In this paper we ask: what does ‘the idea’ of the Chinese university mean at the current time, especially when the sector has been shaped by endogenous and exogenous globalising dynamics? We explore this question, drawing on cultural political economy as a heuristic to make visible the links between culture, economy and politics. We identify three key dynamics: the constitutive powers of civilisational ideas; the power of the Chinese state; and the ongoing integration of Chinese higher education into knowledge production and its circulation nationally and globally. We show these dynamics have the unintended consequence of accelerating global processes including: (i) outward and inward academic and student mobility; (ii) internal social stratification, education inequalities and injustice; and (iii) the instrumentalism of knowledge production and its circulation that emulates the neoliberal academy in the West. Despite invocations from President Xi to nurture the red gene, higher education in China is deeply entangled in global dynamics as well as a shaper of its trajectories.

Racial challenges and finding meaning in ethnic identity: ethnic-racial socialization experiences of indigenous college students in Taiwan’s higher education

ABSTRACT The culturally diverse higher education settings is conceptualized to facilitate indigenous university students in Taiwan to establish a deeper connection with and understand the meaning of their ethnic identity. Guided by the ethnic identity development theory and school ethnic-racial socialization framework, we asked two research questions: (1) What racial challenges did indigenous students in Taiwan experience at their colleges? (2) How did students utilize college resources to overcome racial challenges and develop a meaningful sense of ethnic identity? A participatory research approach using narrative inquiry was employed (N = 20). Convenience sampling and thematic analysis were adopted. Six themes emerged. Racial challenges were: (1) intergroup discrimination; (2) internal stratification; (3) ethnic identity confusion. Social resources in higher education were: (4) confronting discrimination together; (5) peer appraisal support and encouragement; (6) multicultural social interactions. Research, practice, and policy implications were discussed.

Los Santos Formation in the Platanalito section: A fluvial and transgressive river-mouth estuary deposit of the Eastern Cordillera of Colombia

This study provides a new perspective in relation to the Los Santos Formation in the Mesas area, Eastern Cordillera of Colombia. The deposition at the base of the Los Santos Formation, referred to as Segment A, forms a coarsening-upward succession consisting of smaller entities of fining-upward type. This suggests a fluvial bay-head delta below the overlying Segment B, which is characterized by predominantly muddy succession. This lutitic domain of Segment B shows intercalated thin-bedded, very-fine-grained sandstones with double mud drapes, occasional plant remains, and the local appearance of Kinneyia. It has been interpreted as the deposit in the central part of an estuary. The presence of a tabular body of quartz sandstones, several meters thick (Segment C), observable at a distance in the landscape of the Mesas area, which develops a remarkable ravinement surface or some gullying features over the underlying lithologies at the bottomset. Segment C is mainly constituted by compound dune fields, where reactivation surfaces are oriented in the same direction as the internal stratification. These sedimentological features allow us to deduce its genesis from sediments coming from a source area located westward or southwestward, deposited obliquely or almost perpendicular to the fluvial deposit in Segment A. Segment C is interpreted as a transgressive sandy deposit at the mouth of the consolidating estuary. Subsequent minor tectonic activity reintroduces subaerial and muddy fluvial facies followed by scattered intertidal bars and channels in the fine-grained deposits of the coastal plain (Segment D). This reflects base-level fluctuations prior to the emergence of fossil-contained, tidal-influenced facies in the Cumbre Formation.

Forcing of slow density waves in the C ring by Saturn's quasi-toroidal normal modes

We calculate Saturn's quasi-toroidal normal modes of azimuthal order three for several candidate models for the interior stratification. We propose that these oscillations are responsible for exciting a class of slowly propagating spiral density waves observed in the C ring, possessing the same azimuthal symmetry and pattern speeds, that cluster near the rotation rate of the planet. Both prograde and retrograde propagation relative to the planetary rotation are observed. We find that we can construct interior models for which the pattern speeds of the normal modes align with those of a majority of the slow density waves. Excitation of the retrograde density waves requires retrograde toroidal modes with matching pattern speeds. We find that in order to support such modes, the interior model must include a layer of positive static stability in the molecular hydrogen envelope. The model that performs best places the peak of the static stability at a fractional radius of 0.85, near the radius of the semi-conductive layer where Saturn's zonal jets are inferred to decay. The properties of the toroidal modes are less sensitive to the stratification in the deep interior, hence our results neither confirm nor contradict the presence of a dilute core. When differential rotation is included in the form of zonal winds based on analysis of Cassini gravity and magnetic field data, we find that several toroidal modes become inertially unstable, raising the possibility that this instability is the principal mechanism for their excitation. However, while we are able to construct interior models that align the pattern speeds of a few unstable retrograde modes with those of prominent density waves in the ring, the same models fail with respect to the unstable prograde modes. Consequently, the significance of the instability mechanism remains an open question. Our results suggest that the interaction of Saturn's quasi-toroidal modes with the C ring provides an important source of new, complementary constraints on the planet's internal stratification and that further study of these modes is warranted.

Tidal Dissipation in Stratified and Semi-convective Regions of Giant Planets

We study how stably stratified or semi-convective layers alter the tidal dissipation rates associated with the generation of internal waves in planetary interiors. We consider if these layers could contribute to the high rates of tidal dissipation observed for Jupiter and Saturn in our solar system. We use an idealized global spherical Boussinesq model to study the influence of stable stratification and semi-convective layers on tidal dissipation rates. We carry out analytical and numerical calculations considering realistic tidal forcing and measure how the viscous and thermal dissipation rates depend on the parameters relating to the internal stratification profile. We find that the strongly frequency-dependent tidal dissipation rate is highly dependent on the parameters relating to the stable stratification, with strong resonant peaks that align with the internal modes of the system. The locations and sizes of these resonances depend on the form and parameters of the stratification, which we explore both analytically and numerically. Our results suggest that stable stratification can significantly enhance the tidal dissipation in particular frequency ranges. Analytical calculations in the low-frequency regime give us scaling laws for the key parameters, including the tidal quality factor due to internal gravity waves. Stably stratified layers can significantly contribute to tidal dissipation in solar and extrasolar giant planets, and we estimate substantial tidal evolution for hot Neptunes. Further investigation is needed to robustly quantify the significance of the contribution in realistic interior models, and to consider the contribution of inertial waves.

A Seawater Salinity Sensor Based on Optimized Long Period Fiber Grating in the Dispersion Turning Point.

Variations of seawater salinity often cause ocean internal waves, water masses and stratification, which affect the stability of the ocean environment. Therefore, the study of seawater salinity is significant for the prediction of changes in the ocean environment. However, existing methods for measuring seawater salinity generally have the disadvantages of low sensitivity and low accuracy. In this work, we proposed a seawater salinity sensor based on long period fiber grating (LPFG) in the dispersion turning point (DTP), which has demonstrated the possibility to fabricate LPFG with a shorter grating period by CO2 laser in a thin single mode fiber (SMF) of 80 μm cladding diameter without etching. For obtaining higher sensitivity that could meet the measurement requirement in practice, the proposed sensor was optimized by combining etching cladding and DTP. After the LPFG working near DTP was fabricated by a CO2 laser, the cladding diameter was reduced to 57.14 μm for making cladding mode LP1,7 work near DTP by hydrofluoric acid (HF) solutions. The experimental results have demonstrated that a sensitivity of 0.571 nm/‱ can be achieved when the salinity increases from 5.001‱ to 39.996‱, and the sensor shows good repeatability and stability. Based on its excellent performance, the optimized LPFG is a prospective sensor to monitor seawater salinity in real time. Meanwhile, a low-cost way was provided to make LPFG work near DTP instead of ultraviolet exposure and femtosecond laser writing.

Controlling self-assembling co-polymer coatings of hydrophilic polysaccharide substrates via co-polymer block length ratio

HypothesisThe degree of polymerization of amphiphilic di-block co-polymers, which can be varied with ease in computer simulations, provides a means to control self-assembling di-block co-polymer coatings on hydrophilic substrates. SimulationsWe examine self-assembly of linear amphiphilic di-block co-polymers on hydrophilic surface via dissipative particle dynamics simulations. The system models a glucose based polysaccharide surface on which random co-polymers of styrene and n-butyl acrylate, as the hydrophobic block, and starch, as the hydrophilic block, forms a film. Such setups are common in e.g. hygiene, pharmaceutical, and paper product applications. FindingsVariation of the block length ratio (35 monomers in total) reveals that all examined compositions readily coat the substrate. However, strongly asymmetric block co-polymers with short hydrophobic segments are best in wetting the surface, whereas approximately symmetric composition leads to most stable films with highest internal order and well-defined internal stratification. At intermediate asymmetries, isolated hydrophobic domains form. We map the sensitivity and stability of the assembly response for a large variety of interaction parameters. The reported response persists for a wide polymer mixing interactions range, providing general means to tune surface coating films and their internal structure, including compartmentalization.

Адыгская социальная терминология по материалам этнографической экспедиции Е.Н. Сту-денецкой в Кабардинскую АССР (1947 г.)

The publication continues the introduction into scientific circulation of the report on the field eth-nographic work in Kabarda by E.N. Studenetskaya. When considering the report fragment, prima-ry attention was paid to the social structure of Kabardian society issue, which was one of its key topics. In his report, the author describes thoroughly the social roles of representatives of all clas-ses, gives information about the rights and duties of the privileged and dependent estates. Signifi-cant attention is paid to the forms of capture and the fate of the prisoners, since one of the depend-ent estates was also formed from them. The field material is oral histories, which in the middle of the XX century continued to be preserved in the memory of old-timers. An important circum-stance that influenced the nature and structure of the collected material was that the informants of E.N. Studenetskaya belonged to the descendants of dependent groups of the local population. The report’s publishers pay the most important attention to native social terminology used in it, since the fixation of the material was complicated by the periodic absence of an interpreter, ignorance of the language by the researcher, as well as the conditions for translating the collected material into printed form, which was carried out by a typist who also does not speak Kabardian. The need to clarify the details related to social terminology is because there is still no complete clarity on the internal social stratification of traditional Kabardian society.

Complex Activity & Selective Associativity: the Effectiveness of Elite University Association

In the article, based on data from the Shanghai Ranking (ARWU) 2003-2022, ranking achievements of elite associations of top universities in the USA (AAU), the United Kingdom (Russell Group), Canada (U15 Group), Japan (RU11), China (C9 League), Australia (Group of Eight), Germany (U15), taking into account the political and economic context of their functioning, the factors of the effectiveness of such associations are determined to ensure the leadership of member universities. It has been found that the greatest synergistic effect of association is achieved in small associations or their parts (with the number of up to 10-20 institutions), which include institutions close in terms of ratings, which are characterized by significant (resonant) intragroup interaction and which are provided with strong national support. Activities at the same level of complexity of educational programs and research and development, selective significant cooperation on the principle of "equal to equal" (thus achieving the effect of resonant interaction) serve as a guarantee of successful collective advancement to the top levels of excellence of all participants of the interaction. Otherwise, the formal association either declines or undergoes informal internal stratification (differentiation) into groups more homogeneous in complexity of activity, not all of which can withstand the competitive struggle for leadership and the ability to fully use the advantages of formally open science due to its actual closedness in part complex knowledge for insufficiently capable universities. An alternative to the selective associative union of universities withing the country can be their direct organizational consolidation with systematic state support to transform into powerful university centers, as is done in France, or a strong national policy for the development of flagship universities, as in Switzerland. Scientifically based practical recommendations on the creation of a domestic elite Association of Ukrainian Universities (AUU) and the strategy of their consolidation are formulated in order to overcome the growing global backwardness of higher education of Ukraine, which is especially relevant in the conditions of the specifics of open science and the post-war recovery of the country on an innovative, high-intellectual, and high-tech basis.

Computational model development for heat production of Al-CaO flameless ration heaters (FRHs): The effect of temperature, pressure, and pH on the exothermic characteristics

The principle of the Al-CaO flameless ration heaters (FRHs), as a kind of portable chemical energy device for self-heating food packaging, is to release a large amount of heat mainly through the complex chemical reactions of the mixture of aluminium powder, calcium oxide, and water for reheating food. The effect of temperature (20–130 °C), pressure (101.325–607.95 kPa), and pH (12.70–13.40) on the heat production of the thermogenic agent were investigated. A computational model for FRHs' actual heat production was established based on the internal stratification phenomenon and then verified with five ratios of Al to CaO (45:55, 50:50, 55:45, 60:40, 65:35). Results showed that temperatures greater than 120 °C would promote the increase in solids content and decrease in liquid water of the reaction products. It mainly caused the insufficient reaction response of the thermogenic agent in the inner layer of the heater. The increasing pH could vastly increase the reaction rate and shorten the response time. The pressure has no apparent effect on the chemical reaction of the mixture. The computation method proposed in this study enables stable and precise calculation of the actual heat production by Al-CaO FRHs. The results of this study provide a deep understanding and insight into Al-CaO FRHs and are helpful for designing and optimizing food self-heating units.

Fine Grained Braided River Sedimentation in Brahmaputra River, Majuli, Assam, India

Abstract The Brahmaputra River in Assam exhibits a typical braided pattern and is characterized by a sediment load comprising of sand and mud. The river contains channel-bars of varied types and dimensions and embraces the world’s largest river island – Majuli, which at present is under the effect of severe bank-erosion along its southern margin. The objective of this study is to examine the characteristics of fluvial sedimentation prevailing along the southern margin of the Majuli landmass. Both channel as well as bank sediments were analyzed to understand the mechanism of transportation, depositional process and hydrodynamic behavior. Both channel and bank sediments consist of very fine to medium sand with subordinate amount of silt and mud. Majority of the sediments exhibit well to very well sorting and positive skewness. The Probability curves of grain size distribution indicate transportation of sediments dominantly by saltation mode with minor amount by suspension and surface-creep mode. CM plot suggest transportation by graded suspension (saltation) with subordinate rolling and uniform suspension process by means of tractive current. The internal stratifications are dominated by planar cross stratifications followed by horizontal stratifications, trough cross stratifications, ripple laminated layers and massive sand. The bank sediments in few locations exhibit a general fining upward sequence which ends up with the deposition of a mud layer.The lithofacies sequences of the study area show prevalence of both lower as well as upper flow regime energy conditions indicating fluctuations of energy conditions during their respective sedimentation.

Experimental study on gravity currents with internal stratification in semicircular channels

We present an experimental study of gravity currents (GCs) with internal stratification in a semicircular channel in the inertial–buoyancy and Boussinesq regime. Forty tests were performed with a denser volume of fluid (brine advancing in a fresh water ambient fluid) in lock-release. The lock contains an internal stratification, with a layer of density ρL overlain by a layer of density ρU, where ρa<ρU<ρL and ρa is the density of the ambient fluid. The experiments cover both a full depth and a partial depth configurations. The measurements consist of marking the front position of the currents as a function of the time from release, t. Two lateral video-cameras were used to detect the flow profile. Also local instantaneous density and velocity profiles data were collected in a fixed section downstream of the gate, in order to give further details and a better description of the physical phenomenon. The data of front speed and current thickness were compared to a theoretical model (Zemach and Ungarish, 2021) based on (i) a Boussinesq flow; (ii) large Reynolds number; (iii) current advancing in shallow water conditions; and (iv) negligible ambient fluid dynamics. The system of equations and boundary conditions allow the prediction of the motion of the GC, in particular the position and speed of the nose xNt and uNt. The agreement of theory and experiments is fairly good, especially for the full depth configuration. The partial depth configuration experiments are less accurately reproduced by the theory, and require a correction coefficient of the Froude number at the front, that accounts for the deviations of the realistic system from the free-slip and sharp non-entraining interface in the control volume about the head.

Melting curve and transport properties of ammonia ice up to the deep mantle conditions of Uranus and Neptune

Motivated by the poor knowledge of the implication of planetary ice on the internal convection and anomalous magnetic field of ice giants, we perform extensive first-principles molecular dynamics simulation on ammonia ice to investigate its thermophysical behaviors at high temperature ($T$) and pressure ($P$) conditions relevant to the deep mantle of Neptune and Uranus. The melting curve, transport properties, and sound velocity of ammonia up to 350 GPa and 5500 K, spanning from fluid mixtures to a highly compressed superionic regime, are determined. A first-order phase transition of ammonia from the plastic state to the superionic state is observed explicitly, which is associated with the reduction of entropy. In contrast to previous predictions, the melting curve elucidates the existence of superionic ammonia in deep planetary interiors. Inspection of the reduction for transport properties and sound velocity along the isentrope of ice giants further evidences that superionic ammonia can sufficiently sustain the planetary dynamo mechanism and may contribute to the internal stratification which is responsible for the generation of the multipolar magnetic field. Finally, a comprehensive phase diagram of ammonia extended to a higher T-P regime is constructed, which provides a clear picture for studying the fundamental behavior and phase transition of ammonia in deep planets, and enhances our understanding of the interior structure and thermal convection of these planetary systems.

An Erosional Unconformity At The Top Of The Nyalau Formation Near Bintulu, Central Sarawak (Malaysia): Its Regional Context And Significance

This article documents an erosional unconformity at the top of the Nyalau Formation (Oligocene-Early Miocene) exposed in a road-cut northeast of Bintulu in central Sarawak. The outcrop succession essentially comprises a lower unit of thickly-bedded sandstones representing wave-dominated shoreface facies overlain by fluvio-tidal channel deposits that were deposited following a base-level lowering. This gently tilting sand-rich unit is cut by an irregular concave-up erosional surface, overlain by mudstones and thinly interbedded heterolithics that show large-scale internal stratification indicative of multiple scour-and-fill structures, progradation and/or lateral accretion. The erosional surface separating the two units not only marks a significant shift in sedimentary facies but the fact that it cuts into deformed and tilted strata (Upper Nyalau) suggests that it is an erosional unconformity caused by a tectonic deformational event. Based on regional structural synthesis and stratigraphic evidences, the unconformity probably represents the eroded top of the Nyalau Formation, overlain by a relatively undeformed succession tentatively correlated with the Early-Middle Miocene post-Nyalau formations in the Mukah-Balingian region.