Subsequent Transition Research Articles

Dates of Holocene environmental changes in Lake Bafa: A hierarchical Bayesian analysis of change points

The timing of the separation of Lake Bafa from the Aegean Sea and its subsequent transition to a lake remains a topic of debate, with considerable uncertainties associated with the proposed dates for these transitions. This study introduces a novel approach, hierarchical Bayesian change point analysis (HBCPA), to identify tipping points in paleoenvironmental time series. The objective is to offer more precise and objectively selected results concerning the previously uncertain transition dates of Lake Bafa’s geological evolution in the Holocene. The method presented in this study is applied to analyze stable oxygen and carbon isotope data from foraminifer and ostracod shells, as well as total organic carbon (TOC) data, obtained from the BAFA09P02 sediment core. Results indicate that the transition from a marine to an isolated lagoon environment occurred around 2060 years BP, with an 89% uncertainty interval ranging from 2250 to 1870 years BP. Additionally, the transition from an isolated lagoon to a brackish lake environment is estimated to have occurred around 595 years BP, with an 89% uncertainty interval ranging from 780 to 425 years BP. The results of this study illustrate that the suggested HBCPA approach holds the capability to identify tipping points in environmental data while quantifying their intrinsic uncertainties.

Sense of Neighbourhood in a South African Urban Locale

ABSTRACT The nature of the unfolding social cohesion in previously racially segregated residential spaces has attracted attention since the collapse of apartheid in South Africa and the subsequent transition to democracy in 1994. This paper uses sense of neighbourhood to investigate the emerging social interactions in Cambridge, a former whites-only residential suburb in East London, South Africa. Fitting a binary logistic regression on survey data from a sample of residents of Cambridge, the paper tests the likelihood of race and gender influencing three indicators of the sense of neighbourhood: the sense of safety, trust and norms of reciprocity. The results show that relational dimensions of the sense of neighbourhood differed along racial lines, with low levels of interracial trust mirroring studies elsewhere in the country, and the national-level South African Reconciliation Barometer survey reports. Due to the voluntaristic nature of relational ties, social integration will remain elusive, and regardless of the extent of racial changes, variations in the sense of neighbourhood will characterise the urban residential spaces.

Functional differences in human aortic valve interstitial cells from patients with varying calcific aortic valve disease.

Calcific aortic valve disease (CAVD) is characterized by progressive stiffening of aortic valve (AV) tissues, inducing stenosis and insufficiency. Bicuspid aortic valve (BAV) is a common congenital defect in which the AV has two leaflets rather than three, with BAV patients developing CAVD decades years earlier than in the general population. Current treatment for CAVD remains surgical replacement with its continued durability problems, as there are no pharmaceutical therapies or other alternative treatments available. Before such therapeutic approaches can be developed, a deeper understanding of CAVD disease mechanisms is clearly required. It is known that AV interstitial cells (AVICs) maintain the AV extracellular matrix and are typically quiescent in the normal state, transitioning into an activated, myofibroblast-like state during periods of growth or disease. One proposed mechanism of CAVD is the subsequent transition of AVICs into an osteoblast-like phenotype. A sensitive indicator of AVIC phenotypic state is enhanced basal contractility (tonus), so that AVICs from diseased AV will exhibit a higher basal tonus level. The goals of the present study were thus to assess the hypothesis that different human CAVD states lead to different biophysical AVIC states. To accomplish this, we characterized AVIC basal tonus behaviors from diseased human AV tissues embedded in 3D hydrogels. Established methods were utilized to track AVIC-induced gel displacements and shape changes after the application of Cytochalasin D (an actin polymerization inhibitor) to depolymerize the AVIC stress fibers. Results indicated that human diseased AVICs from the non-calcified region of TAVs were significantly more activated than AVICs from the corresponding calcified region. In addition, AVICs from the raphe region of BAVs were more activated than from the non-raphe region. Interestingly, we observed significantly greater basal tonus levels in females compared to males. Furthermore, the overall AVIC shape changes after Cytochalasin suggested that AVICs from TAVs and BAVs develop different stress fiber architectures. These findings are the first evidence of sex-specific differences in basal tonus state in human AVICs in varying disease states. Future studies are underway to quantify stress fiber mechanical behaviors to further elucidate CAVD disease mechanisms.

The formation of hydride and its influence on Ti–6Al–4V alloy fracture behavior

The fracture mechanism of hydrogen charged Ti–6Al–4V has been investigated through a multianalytical approach. The difference in hydrogen solubility between β phase (high solubility) and α phase (low) governs the formation and growth pattern of titanium hydrides, and determine the fracture mode of Ti–6Al–4V. Depending on the hydrogen charging extent, the penetration of hydrogen and distribution of hydrides can be divided into three stages. In the initial stage hydrogen diffuses mainly into the β phase, as judged from its increase in Volta potential, and with no hydrides formed. Failure analysis after tensile tests exhibits plastic behavior and a fracture surface with mainly dimples. In the subsequent transition stage, hydrides are formed at the α/β interfaces and along α grain boundaries. More initial cracks occur in the brittle hydrides and the fracture surface transforms from dimple to quasi-cleavage. In the final stage a layer of uniformly distributed hydride is produced on the surface and within the α phase. Supported by nanoindentation measurements, the plasticity of the charged sample diminishes with hydrogen charging time, and an intergranular-transgranular mixed fracture is observed. Overall, the study forms clear evidence that the distribution and cracks of hydrides influence the fracture mode of the Ti-6A-4V alloy.

Chiral Nelson-Barr models: Quality and cosmology

It was recently shown that domain walls from the spontaneous breaking of CP symmetry are exactly stable, and must be inflated away to recover a viable cosmology. We investigate the phenomenological implications of this result in Nelson--Barr solutions of the strong CP problem. Combined with the upper bound on the scale of spontaneous CP breaking necessary to suppress contributions from dangerous, nonrenormalizable operators to $\bar{\theta}$, this puts an upper bound on the scale of inflation and the reheating temperature after inflation. Minimal Nelson--Barr models are therefore in tension with thermal leptogenesis, models of large-field inflation, or potential future observations of signals from topological remnants of an unrelated, subsequent phase transition. We study how extending Nelson--Barr models with a new, continuous chiral gauge symmetry can ameliorate this tension by forbidding the dangerous dimension-five operators. In particular, we show that gauging a linear combination of baryon number and hypercharge allows for an economic, anomaly-free extension of the minimal Nelson--Barr model, and discuss the phenomenological implications.

Field induced phase transition and magnetic phase diagram of multiferroic Ca2CoSi2O7

Magnetic phase transitions are important for the application of individual materials toward modern spintronics and sensing. Using high-resolution sound velocity and pyrocurrent measurements, we have obtained a detailed magnetic phase diagram of multiferroic Ca2CoSi2O7 for magnetic fields applied along the crystallographic [100]- and [001]-directions. The magneto-acoustic measurements were conducted for both longitudinal and transverse modes in both static and pulsed magnetic fields up to 17 and 68 T, respectively. Distinct anomalies with significant changes in sound velocity and sound attenuation were observed at the onset of the structural and magnetic phase transitions. Interestingly, results obtained for fields parallel to the [100]-direction reveal a hysteresis and step-like decrements in ultrasound indicating a transition into a different metastable structural distortion below TN and at magnetic fields between 4 and 10 T that has not been previously reported. We believe that this field-induced distorted structure phase may be the cause of the subsequent phase transition at 11 T. At low temperatures, a softening of the lattice within the ordered phases is also observed, which may be due to residual spin fluctuations.

Curricular Experiences Leading to the ABET Accreditation in the Electrical and Electronics Engineering Programs

Accreditation processes not only recognize the high quality of curricular programs; they also guarantee their continuous self-improvement. This paper aims to socialize the curricular experiences in the Electrical and Electronics Engineering programs of Universidad Nacional de Colombia (Bogotá Campus) within the decade-long efforts to achieve international ABET accreditation in 2021. This work thoroughly describes the implementation of the CDIO curriculum design methodology and its subsequent transition towards a curricular assessment based on learning outcomes. The results of some qualitative studies regarding the perceptions of faculty and alumni are presented, as well as a detailed proposal of the skills to be developed in each year of the syllabus, establishing their level of implementation. Moreover, a detailed description is provided regarding the methodology adopted for measuring performance indices during four semesters and the main results of the assessment of each learning outcome. Finally, the main curricular challenges to be addressed over the following years within the Electrical and Electronics Engineering programs are described.

PD-1 Carried on Small Extracellular Vesicles Leads to OSCC Metastasis

Immune checkpoint molecule PD-1, expressed on the cell surface, impairs antigen-driven activation of T cells and thus plays a critical role in tumorigenesis, progression, and the poor prognosis of oral squamous cell carcinoma (OSCC). In addition, increasing evidence indicates that PD-1 carried on small extracellular vesicles (sEVs) also mediates tumor immunity, although their contributions to OSCC are yet unclear. Here, we investigated the biological functions of sEV PD-1 in patients with OSCC. The cell cycle, proliferation, apoptosis, migration, and invasion of CAL27 cell lines treated with or without sEV PD-1 were examined in vitro. We performed mass spectrometry to investigate the underlying biological process, combined with an immunohistochemical study of SCC7-bearing mice models and OSCC patient samples. In vitro data demonstrated that sEV PD-1 induced senescence and subsequent epithelial-mesenchymal transition (EMT) in CAL27 cells by ligating with tumor cell surface PD-L1 and activating the p38 mitogen-activated protein kinase (MAPK) pathway. Comprehensive immunohistochemical analysis of the xenograft mice models and OSCC patient samples revealed a very close correlation between the level of circulating sEV PD-1 and lymph node metastasis. These results demonstrate that circulating sEV PD-1 triggers senescence-initiated EMT in a PD-L1-p38 MAPK-dependent manner, contributing to tumor metastasis. It also suggests that the inhibition of sEV PD-1 may be a promising therapeutic target for the treatment of OSCC.

Coacervation-Mediated Cytocompatible Formation of Supramolecular Hydrogels with Self-Evolving Macropores for 3D Multicellular Spheroid Culture.

Coacervation driven liquid-liquid phase separation of biopolymers has aroused considerable attention for diverse applications, especially for the construction of microstructured polymeric materials. Herein, a coacervate-to-hydrogel transition strategy is developed to create macroporous hydrogels (MPH), whichare formed via the coacervation process of supramolecular assemblies (SA) built by the host-guest complexation between γ-cyclodextrin and anthracene dimer. The weak and reversible supramolecular crosslinks endow the SA with liquid-like rheological properties, which facilitate the formation of SA-derived macroporous coacervates and the subsequent transition to MPH (pore size ≈ 100µm). The excellent structural dynamics (derived from SA) and the cytocompatible void-forming process of MPH can better accommodate the dramatic volumetric expansion associated with colony growth of encapsulated multicellular spheroids compared with the non-porous static hydrogel with similar initial mechanical properties. The findings of this work not only provide valuable guidance to the design of biomaterials with self-evolving structures but also present a promising strategy for 3D multicellular spheroid culture and other diverse biomedical applications.

The representation of the 1989 regime change in contemporary Hungarian prose texts

AbstractA fundamental segment of contemporary Hungarian prose literature has attempted to represent and textually portray the change in political regimes which took place in 1989. The dictatorship, the totalitarian system and the subsequent transition period proved to be excellent raw material; resulting in a very different kind of prose which, when compared to previous representations of Transylvania, elicits attention on the one hand by being distinctly separate from the assumption of an ideological role, and on the other hand by creating the given linguistic and fictional space through continuous transition(s), (inter-ethnic) in-betweenness and the relevance of otherness.

Observational study of pimecrolimus 1% cream for prevention of transcutaneous sensitization in children with atopic dermatitis during their first year of life.

Epidermal barrier dysfunction in children with atopic dermatitis can cause transcutaneous sensitization to allergens and allergic diseases. We evaluated the effectiveness of an early-intervention algorithm for atopic dermatitis treatment, utilizing pimecrolimus for long-term maintenance therapy, in reducing transcutaneous sensitization in infants. This was a single-center cohort observational study that enrolled children aged 1-4 months with family history of allergic diseases, moderate-to-severe atopic dermatitis, and sensitization to ≥ 1 of the investigated allergens. Patients who sought medical attention at atopic dermatitis onset (within 10 days) were group 1 "baseline therapy with topical glucocorticoids with subsequent transition to pimecrolimus as maintenance therapy"; patients who sought medical attention later were group 2 "baseline and maintenance therapy with topical glucocorticoids, without subsequent use of pimecrolimus". Sensitization class and level of allergen-specific immunoglobulin E were determined at baseline, and 6 and 12 months of age. Atopic dermatitis severity was evaluated using the Eczema Area and Severity Index score at baseline and 6, 9 and 12 months of age. Fifty-six and 52 patients were enrolled in groups 1 and 2, respectively. Compared with group 2, group 1 demonstrated a lower level of sensitization to cow's milk protein, egg white and house dust mite allergen at 6 and 12 months of age, and a more pronounced decrease in atopic dermatitis severity at 6, 9 and 12 months of age. No adverse events occurred. The pimecrolimus-containing algorithm was effective in treating atopic dermatitis and prophylaxis of early forms of allergic diseases in infants. https://clinicaltrials.gov/ NCT04900948, retrospectively registered, 25 May 2021.

Modulating Liquid-Liquid Transitions and Glass Formation in Zeolitic Imidazolate Frameworks by Decoration with Electron-Withdrawing Cyano Groups.

The liquid phase of metal-organic frameworks (MOFs) is key for the preparation of melt-quenched bulk glasses as well as the shaping of these materials for various applications; however, only very few MOFs can be melted and transformed into stable glasses. Here, the solvothermal and mechanochemical preparation of a new series of functionalized derivatives of ZIF-4 (Zn(im)2, where im- = imidazolate and ZIF = zeolitic imidazolate framework) containing the cyano-functionalized imidazolate linkers CNim- (4-cynanoimidazolate) and dCNim- (4,5-dicyanoimidazolate) is reported. The strongly electron-withdrawing nature of the CN groups facilitates low-temperature melting of the materials (below 310 °C for some derivatives) and the formation of microporous ZIF glasses with remarkably low glass-transition temperatures (down to only about 250 °C) and strong resistance against recrystallization. Besides conventional ZIF-4, the CN-functionalized ZIFs are so far the only MOFs to show an exothermic framework collapse to a low-density liquid phase and a subsequent transition to a high-density liquid phase. By systematic adjustment of the fraction of cyano-functionalized linkers in the ZIFs, we derive fundamental insights into the thermodynamics of the unique polyamorphic nature of these glass formers as well as further design rules for the porosity of the ZIF glasses and the viscosity of their corresponding liquids. The results provide new insights into the unusual phenomenon of liquid-liquid transitions as well as a guide for the chemical diversification of meltable MOFs, likely with implications beyond the archetypal ZIF glass formers.

Quantifying the Predictability of ENSO Complexity Using a Statistically Accurate Multiscale Stochastic Model and Information Theory

Abstract An information theory–based framework is developed to assess the predictability and quantify the forecast uncertainty of ENSO complexity, which includes different types of ENSO events with diverse characteristics. With the assistance of a recently developed multiscale stochastic conceptual model that successfully captures both the large-scale dynamics and many crucial statistical properties of the observed ENSO complexity, it is shown that different ENSO events possess distinct predictability limits. Beyond the ensemble mean value, the spread of the ensemble members also contains valuable information about predictability. First, La Niña events are most predictable at long lead times, especially as a subsequent transition after eastern Pacific (EP) El Niño events or during multiyear La Niña phases. Second, EP El Niños tend to be more predictable than the central Pacific (CP) El Niño events up to one year ahead due to a more favorable signal-to-noise ratio, even though their onset remains hard to predict. Third, 4 out of 6 CP El Niño events seem to be predictable up to 24 months ahead, where such strong predictability is often converted to skillful forecast. Fourth, strengthening/weakening the Walker circulation intensity increases/decreases CP predictability at long leads. Fifth, accounting for intraseasonal wind events in the initial condition strongly contributes to EP predictability at lead times of less than one year. Finally, it is shown that a Gaussian approximation of the information gain computation is accurate, making the information theory approach tractable for studying the predictability of more sophisticated models.

Electrostatics-Induced Nucleated Conformational Transition of Protein Aggregation.

Despite the wide existence of protein aggregation in nature and its intimate connection to many human diseases, the underlying mechanism remains unclear. Here, we develop a molecular theory by systematically incorporating the self-consistent field theory for charged macromolecules into the dilute solution thermodynamics. The kinetic pathway is tracked without any restriction on the morphology of the aggregates. We find that protein aggregation at low salt concentrations is via a two-step nucleated process involving a conformational transition from metastable spherical oligomer to elongated fibril. The scaling analysis elucidates the electrostatic origin of the conformational transition: the fibril enters the screening region much earlier than the spherical aggregate. As salt concentration increases, the classical mode of one-step nucleation corresponding to macroscopic liquid-liquid phase separation is recovered. Our results reveal that the screened electrostatic interaction is essential for the existence of the metastable oligomer and its subsequent conformational transition to fibril. The theoretical predictions of the kinetic pathway and the morphology of the aggregates are in good agreement with the experimental observations of real proteins.

Evaluation of the Anti-Infectious Activity of the Complex Based on Quantum Dots InP / ZnSe / ZnS 650 and Tobramycin Against <i>Pseudomonas Aeruginosa</i> Infection of the Cornea. Experimental Research

Microbial keratitis (MK) is a homogeneous group of diseases accompanied by loss of the corneal epithelium, stromal leukocyte infiltration and/or destructive tissue breakdown, occurring when the protective mechanisms of the ocular surface are disturbed, which require an immediate set of therapeutic measures, including, first of all, massive etiotropic therapy, which is represented, as a rule, by broad-spectrum antibiotics (AB) and anti-inflammatory drugs. One of the most threatening MK pathogens is P. aeruginosa (PA) (Pseudomonas aeruginosa). Multiple drug resistance, the highest pathogenicity, numerous RA virulence factors dictate the need to search for new highly effective methods to combat MC, in the etiological structure of which RA dominates. The most promising direction in this area is the use of artificial fluorophores, in particular quantum dots (QDs). The objective of this study was to evaluate the anti-infectious activity of the complex based on InP/ZnSe/ZnS 650 quantum dots and Tobramycin against Pseudomonas aeruginosa infection of the cornea. As an object of study, laboratory New Zealand rabbits (No. 6) were studied — 2 females, 4 males, which were induced bacterial keratitis by introducing a nosocomial Ps strain. aeruginosa in the structure of the cornea. The following antimicrobial agents were used: Tobramycin solution 5 ml for epibulbar application and a bioconjugate based on QD InP/ZnSe/ZnS 650 and tobramycin. Laboratory animals were divided into 2 groups. Rabbits of the 1st group, after the manifestation of the clinical picture of microbial keratitis, received instillations of tobramycin drops into the conjunctival sac every 2 hours for 3 days with a complete absence of positive clinical dynamics and a subsequent transition from day 4 in order to anatomically preserve the eyeball to instillations of the CT InP/ZnSe/ZnS complex 650 + Tobramycin. Rabbits of the 2nd group received instillations of the CT + Tobramycin complex and showed positive dynamics in relation to the regression of symptoms from the 2nd day of therapy. As methods of dynamic observation, photoregistration of the anterior segment with fluorescein staining and optical coherence tomography of the anterior segment were used. A clinical experiment has demonstrated the highest efficiency of the InP/ZnSe/ZnS 650 + Tobramycin complex in relation to Pseudomonas aeruginosa strain resistant to Tobramycin monotherapy.

Secreted Colostrum Volume, Transition and Mature Milk Outputs After Calving in Holstein Friesian Cows

Colostrum volume after calving, transition and mature milk outputs in the time from 1^st to 10^th milkings were evaluated at 30 primiparous and 30 multiparous cows milked twice daily. Colostrum volume at the first milking after calving varied from 1.5 to 19.2 kg (mean 9.44 ±5.6 kg SD) in multiparous and from 1.2 to 9.8 kg (mean 5.65 ± 2.3 kg SD) in primiparous cows. Timing of the first milking did not negatively influence colostrum volume. Colostrum volume of the second milking decreased over all multiparous and primiparous cows because the period of time between first and second milking was shorter (10.5 hours). The hourly milk outputs increased sharply from the second to the fourth milking in multiparous and primiparous Holstein Friesian cows. Applying a linear regression model we observed a significant large positive relationship between volume of colostrum at first milking and subsequent transition and mature milk outputs from 2^nd to 10^th milkings. A low colostrum volume secreted was identified in multiparous cows, as a results of sorter dry period and in primiparous cows, probably as a result of low secretory capacity of mammary gland. Extended feeding with transition milk can be real health benefits for the newborn calf.

Peculiarities of the course of genital endometriosis and its recurrence in women of reproductive age

Endometriosis remains one of the most studied pathologies in modern gynecology, as it is accompanied by such complications as constant pelvic pain, menstrual cycle disorders, and infertility. These complications not only prevent the implementation of a woman’s reproductive function, but also worsen the normal life of a woman in general. The early diagnosis and the right choice of treatment is the basis of prevention of disease recurrence. Therefore, most of the efforts of scientists are directed to this.The objective: to reduce the frequency of genital endometriosis recurrence and improve the implementation of reproductive functions based on the improved approaches to its diagnosis and treatment.Materials and methods. The study included two groups of patients. The 1st group included 60 women with a diagnosis of ovarian endometriosis, whose data were analyzed retrospectively based on the results of medical histories. The 2nd group was studied prospectively and included 60 women with a diagnosis of ovarian endometriosis.All patients had general clinical and laboratory examinations, specific laboratory and ultrasound examinations. In patients of the 2nd group tumor markers were additionally determined, in particular CA-125, HE4, CA 19-9, CA 72-4, CA 15-3, REA, and the level of anti-Müllerian hormone, magnetic resonance imaging was performed. Patients of both groups were operated and histological examination of the material obtained during the operation was performed.The difference in the management of the postoperative period in the 2nd group was that, in addition to anti-inflammatory therapy all women received hormonal therapy (gonadotropin-releasing hormone agonist (GnRH agonist) with subsequent use of combined oral contraceptives (COCs) or simultaneous use of GnRH agonist and COCs with subsequent transition in both variants for dienogest for 6 months continuously). Recurrence of the pathology was detected after 3 and 6 months on the basis of a repeated diagnosis of ovarian endometriosis.Results. The obtained data showed that in the postoperative period, 3 months after treatment 5 (8.3 %) women in the 1st group had a recurrence of ovarian endometriosis and 4 (6.7 %) patients – pelvic adhesions. Whereas in the 2nd group, there were no cases of recurrence and adhesions.In 6 months after treatment in the 1st group 11 (18.3 %) patients were diagnosed with ovarian endometriosis recurrence, and 6 (10.0 %) women were diagnosed with pelvic adhesions. In the 2nd group recurrence of ovarian endometriosis was found only in 1 (1.7 %) woman, pelvic adhesions were not detected (p<0.05). During the year after treatment the number of pregnant women among persons who wished to become pregnant and had a history of infertility was statistically higher in the 2nd group compared to the 1st group, in particular, 10 (16.7 %) and 2 (3.3 %) women, respectively (p<0.05).Conclusions. The proposed algorithm for the diagnosis and treatment of genital endometriosis minimizes the risk of its recurrence and improves reproductive function.

Comprehensive structural changes in nanoscale-deformed silicon modelled with an integrated atomic potential

In spite of remarkable developments in the field of advanced materials, silicon remains one of the foremost semiconductors of the day. Of enduring relevance to science and technology is silicon's nanomechanical behaviour including phase transformation, amorphization and dislocations generation, particularly in the context of molecular dynamics and materials research. So far, comprehensive modelling of the whole cycle of events in silicon during nanoscale deformation has not been possible, however, due to the limitations inherent in the existing interatomic potentials. This paper examines how well an unconventional combination of two well-known potentials - the Tersoff and Stillinger-Weber - can perform in simulating that complexity. Our model indicates that an irreversible deformation of silicon (Si-I) is set in motion by a transformation to a non-diamond structure (Si-nd), and followed by a subsequent transition to the Si-II and Si-XII phases (Si-1→Si-nd→Si-II→Si-XII). This leads to the generation of dislocations spreading outwards from the incubation zone. In effect, our simulations parallel the structural changes detected experimentally in the deformed material. This includes both the experimentally observed sequence of phase transitions and dislocation activity, which - taken together - neither the Tersoff nor Stillinger-Weber, or indeed any other available Si interatomic potential, is able to achieve in its own right. Notably, the Si-XII phase was not discerned by any of the previous computational models, which points towards the effectiveness of our integrated approach to forecasting novel phenomena discovered by advanced structure examinations. Last not least, our method satisfies the demand for a quick means to construct potentials by opening up the huge library of existing models to new applications in various branches of materials science.

Diffusion controlled early-stage L12-D023 transitions within Al3Zr

Antiphase boundary (APB) in Al3Zr was regarded to play an important role in the L12-D023 phase transition, the formation of which has long been explained through the shearing/slipping mechanism. Herein, the detailed atomic structures of conservative {100} APBs within L12-Al3Zr particles forming at the early-stage of L12-D023 transition in an Al-Zr alloy were systematically studied by high angle annual dark-field scanning transmission electron microscope (HAADF-STEM). As a strong evidence of diffusion-limited phase transformation process, significant de-ordering of atoms in APBs and the neighboring atomic planes have been found. By analyzing the two possible pathways, it is suggested that L12-D023 phase transition has been achieved through a diffusion mechanism, instead of shearing mechanism while the formation of APB is an intermediate stage of the phase transition process. First principles density functional theory (DFT) reveals that the formation of APBs and subsequent phase transition are energetically favorable, which provide the driving force for diffusion.

The Miocene Climatic Optimum at the interface of epicontinental sea and large continent: A case study from the Middle Miocene of the Eastern Paratethys

The Miocene Climate Optimum (MCO) and the subsequent Miocene Climate Transition (MCT) are important biotic, environmental and geologic events. Here we address whether this holds true for the epicontinental Eastern Paratethys Sea (today's Black – Caspian Sea region). Two Tarkhanian – lower Chokrakian sequences of Middle Miocene age in the Kerch Peninsula were investigated using foraminifera, calcareous nannofossils, molluscs, fish otoliths, spores and pollen, oxygen and carbon stable isotopes and strontium isotope stratigraphy (SIS). Our results show that the marine environment during the Tarkhanian to early Chokrakian in the study area was characterized by open shelf conditions (near upper part of lower sublittoral zone), variable water column stratification and bottom water oxygen levels. Biostratigraphy and new SIS data suggest an age of >15.5 (∼16.0?) – 14.75 Ma for the Tarkhanian, which implies a considerably longer duration (> 0.75 Ma vs. 0.1 Ma) than was previously suggested. The maximum transgression seen in the middle Tarkhanian could be dated to ∼15.5–15.1 Ma and correlates with the highstand of sequence Bur 5/Lan 1 (15.2 Ma) and terminal phase of the MCO. The vegetation indicates a gradual change from subtropical humid (early Tarkhanian) to arid (early Chokrakian) conditions, which reflect the MCT. The climate change in the Eastern Paratethys occurred slightly earlier than in the Central Paratethys, possibly related to the existence of the large flat Eurasian continent.