Subsequent Rejuvenation Research Articles

Boardroom characteristics and forward-looking information disclosure: evidence from Ghana

PurposeAmid growing stakeholder needs, this study aims to assess the effect of boardroom characteristics on the disclosure of forward-looking information by listed firms on the Ghana stock exchange (GSE). Further, it investigates the mediating role of firm size in the relationship between boardroom characteristics and forward-looking information disclosure (FLID).Design/methodology/approachUsing data from the annual reports of a sample of firms on the GSE in 2019 and multiple regression analysis, the effect of boardroom characteristics on the disclosure of forward-looking information is ascertained.FindingsThe results depict that board gender diversity, i.e. female representation on the board, is positive and significantly related to firms’ disclosure levels on the GSE. Similarly, board independence and auditor type have a positive and significant relationship with FLID, whereas profitability and financial leverage do not affect disclosure levels. The further analysis depicts that the relationship between board size and FLID is mediated by firm size.Practical implicationsThis study’s findings would aid management, market regulators and investors in Ghana and other developing contexts assess mechanisms that would increase FLID among firms to satisfy stakeholders.Originality/valueThis paper focuses on the extent of FLID after the setbacks and subsequent rejuvenation of Ghana’s financial and nonfinancial system. Specifically, this paper adds to the few studies on the African continent that examined the influence of boardroom characteristics on FLID.

Stratigraphy of volcanic rock successions of the North Atlantic rifted margin: the offshore record of the Faroe–Shetland and Rockall basins

ABSTRACTThe integration of biostratigraphical, wireline log, geophysical and available geochronological ages has identified two principal periods of volcanism in the Faroe–Shetland and Rockall basins. The first is pre-breakup, upper Danian to lower Thanetian: in the Rockall and Faroe–Shetland basins, isolated volcanic activity from 62 Ma to 58.7 Ma is identified in areas closely linked to the SSW–NNE structural fabric of the continental margin. Volcanic activity was concentrated at basin flank fissures and localised point sources. This rift-flank volcanism led to widespread volcanic ash deposition, localised lava flow fields and the formation of igneous centres. Some of the Hebridean and onshore central complexes (e.g., Rum) were uplifted and rapidly eroded during the later pre-breakup period, while additional accommodation space was developed in the adjacent offshore basins. Onset and termination of pre-breakup volcanism is correlated to intra-plate stress regimes in Europe, following the cessation of convergence of Africa and Europe in the Danian. The second is syn-breakup, upper Thanetian to Ypresian, initiated at ca.57 Ma in the Rockall and Faroe–Shetland basins. Initial high-volume extrusive igneous successions were focussed to the W in the Faroe–Shetland Basin. In the centre and E of the Faroe–Shetland and Rockall basins, separate eruption loci developed along pre-existing lineaments either as fissure or point-sourced lava fields. Short-term cessation of eruption at ~55.8 Ma was followed by resumption of flood basalt eruptions and a shift in focus to the NW. Fluctuations in the syn-breakup eruption tempo are reflected in the formation and subsequent rejuvenation of prominent unconformities, only previously recognised as a single erosive event. The W and northward shift of eruption focus, and the eruption of mid ocean ridge basalt-type lavas in the syn-breakup period reflect the onset of lithospheric thinning in the nascent North Atlantic Rift prior to flooding of the rift and eruption of the widespread lower Ypresian Balder Formation tephras.

Evaluation of strength properties of oil-contaminated sands upon stabilisation with laterite soil

ABSTRACT Commercial decontamination procedures of oil contaminated sands can be costly. In this study, the inexpensive laterite soil was used as the stabilization additive, which brought notable results in geotechnical strengths, permeability, penetrability by a standard plunger, and surface morphology. To simulate contamination, clean sands were blended with motor oil where loses in geotechnical strength and permeability decreases were observed.Subsequent stabilization by the laterite soil recovered the strengths where maximum dry unit weights, friction angles cohesions and California bearing ratios (CBR) were enhanced; the permeability however decreased further. Adding 15% laterite soil to sands with 3 to 10% oil contents increased friction angles by 9.5 to 14.4%. For sands with 5% oil, treatment with 15 and 20% laterite soils increased CBR by 27 and 36% respectively; the latter figure indicates strength even better than that of the uncontaminated.The scanning electron microscopy (SEM) showed morphologies of soil grains drenched in oil and the subsequent rejuvenation brought by the stabilization. Rather than neglected, oil-contaminated sands, after stabilisation by laterite soil, are now feasible for use as subgrade or subbase material, or the fine aggregate of hot-mixed asphalts.

Role of elastostatic loading and cyclic cryogenic treatment on relaxation behavior of Ce-based amorphous alloy

In this work, Ce65Cu15Al10Ni8Co2 bulk metallic glass was annealed at sub-Tg and then elastostatically and cryogenically was loaded and treated, respectively. X-ray Diffraction (XRD) analysis was carried out to show amorphousness of treated alloys, and enthalpy variations and specific heat capacity were evaluated using differential scanning calorimetry (DSC). The results showed that the designed treatment procedure leads to the recovery of relaxation, i.e. rejuvenation, from the relaxed state to the as-cast condition. It is suggested that the generation of free volume and the structural rearrangements, appeared in the abnormal behavior of DSC curves, are responsible for recovery of relaxation. It is also found that the primary elastostatic loading facilitates the subsequent rejuvenation evolution caused by the cryogenic cycling process.

Predicting plasticity‐controlled failure of glassy polymers: Influence of stress‐accelerated progressive physical aging

ABSTRACTThis study focuses on the prediction of long‐term failure of glassy polymers under static or cyclic loading conditions, including the role of stress‐accelerated progressive aging. Progressive physical aging plays a dominant role in a polymer's performance under prolonged loading conditions, and to obtain accurate predictions of failure, its effect has to be considered. First, the aging kinetics, as influenced by temperature and stress history, are studied extensively. Similar to an elevated temperature, the application of a stress (below the yield stress) activates the aging process, and as a result, the yield stress will evolve faster in time. The activation by stress appears to be limited; at some stress level, the activation stagnates and is followed by rejuvenation. This evolution is captured in a model by introducing a state parameter, which describes the thermodynamic state of the material and is directly linked to the yield stress. With the aging kinetics included in the model, an accurate prediction of the failure time for cyclic loading conditions is obtained. For static loading conditions, however, the effect of physical aging is overestimated because of the stagnation of the activation by stress. It appears that there are marked differences in the stress level where stagnation and subsequent rejuvenation occur for a cyclic or static load. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1300–1314

Cation‐/Anion‐Based Electrochemical Degradation and Rejuvenation of Electrochromic Nickel Oxide Thin Films

AbstractNi oxide thin films are widely used in electrochromic (EC) devices with variable throughput of visible light and solar energy. However, the mechanisms underlying the optical modulation – and its degradation under extended operation and subsequent rejuvenation – are poorly understood especially for Li+‐conducting electrolytes. Here, we report a comprehensive study of the EC properties of sputter‐deposited Ni oxide films immersed in an electrolyte of LiClO4 in propylene carbonate. Cyclic voltammetry and optical transmittance measurements were used to document degradation and subsequent potentiostatic rejuvenation. X‐ray diffraction did not show evidence for accompanying changes in crystallinity, whereas vibrational spectroscopy indicated that degraded films had carbonaceous surface layers. Time‐of‐flight elastic recoil detection analysis demonstrated that both Li+ and Cl‐based ions participate in the electrochromism and its degradation and rejuvenation. A major result was that degradation is associated with a reduced difference in the concentrations of Li+ and Cl‐based ions in the nickel oxide during extended electrochemical cycling, and rejuvenation of degraded films is achieved by removal of Li+ ions and accumulation of Cl‐based anions to regain their initial concentration difference. Our work provides new insights into the use of ion‐exchange‐based devices incorporating nickel oxide.

Microstructural and Chemical Rejuvenation of a Ni-Based Superalloy

Abstract The microstructural evolution of the Ni-based superalloy CMSX-4 including the change in gamma prime morphology, size, and distribution after high-temperature degradation and subsequent rejuvenation heat treatments has been examined using field emission gun scanning electron microscopy and transmission electron microscopy. In this paper, it is shown that there are significant differences in the size of the ‘channels’ between gamma prime particles, the degree of rafting, and the size of tertiary gamma prime particles in each of the different microstructural conditions studied. Chemical analysis has been carried out to compare rejuvenated and pre-service samples after the same subsequent degradation procedure. The results indicate that although the microstructures of pre-service and rejuvenated samples are similar, chemical differences are more pronounced in the rejuvenated samples, suggesting that chemical segregation from partitioning of the elements was not completely eliminated through the applied rejuvenation heat treatment. A number of modified rejuvenation heat treatment trials were carried out to reduce the chemical segregation prior to creep testing. The creep test results suggest that chemical segregation has an immeasurable influence on the short-term mechanical properties under the test conditions used here, indicating that further work is required to fully understand the suitability of specific rejuvenation heat treatments and their role in the extension of component life in power plant applications.

Sequence architecture of a Jurassic ramp succession from Gebel Maghara (North Sinai, Egypt): Implications for eustasy

The Jurassic succession at Gebel Maghara, North Sinai, Egypt, represents a mixed carbonate–siliciclastic sequence. Combining information from both fossils and rocks allowed a plausible reconstruction of the depositional environments and of the basin evolution. The Jurassic succession of Gebel Maghara was deposited on a ramp, and the architecture of the ramp facies was strongly controlled not only by sea–level changes but also by extensional tectonics in connection with rifting of the Tethys, North Gondwana. Seven tectonically modified thirdorder sequences (DS 1–DS 7) have been recognized. The first three sequences (DS 1–DS 3), ranging from the Toarcian to the Bajocian, record sea invasion (intertidal to shallow subtidal conditions) across an intracratonic area as a result of eustatic sea–level changes during a quiescent rift stage. The remaining sequences (DS 4–DS 7) reflect open marine mid to outer ramp settings. Non–marine conditions around the Bajocian–Bathonian boundary, documented by caliche, represent the maximum regression of the sea. During an active extensional stage, horsts, which formerly acted as barriers separating the Maghara sub–basin from the main ocean, subsided. Subsequent rejuvenation and reactivation of faults shifted the homoclinal physiography of the ramp to a distally steepened ramp during the early Bathonian, creating a 200–m–thick deltaic wedge. Similar processes during the early Kimmeridgian created a calcirudite–calcarenite succession of slope origin. The diversity and the epifaunal/infaunal percentage of the macrofauna display a cyclic pattern which coincides more or less with the sequence stratigraphic architecture.

Study of GTD-111 Superalloy Microstructural Evolution During High-Temperature Aging and After Rejuvenation Treatments

Nickel-based superalloys are normally present in mechanical components requiring resistance to high temperatures and extreme mechanical stresses, e.g., gas turbine blades. The large amount of γ′-precipitates coherent with the γ-matrix in these superalloys ensures excellent properties at high operating temperatures. Nevertheless, after long service periods, the γ′-precipitates grow and lose coherence with the matrix. Intermediate thermal treatments are a potential solution to recover the microstructure, extending the component lifetime. Thermal cycles for γ′-dissolution and reprecipitation define the efficiency of such thermal treatments. The objectives of this work are to analyze the aging kinetics of the nickel-based superalloy GTD-111 (used in gas turbine blades for thermoelectric energy generation) and to study the effects of solution and preprecipitation treatment temperatures on the microstructure and hardness obtained by rejuvenation thermal treatment. For the experiments, samples were previously aged under laboratory conditions during 2,000 h at 1,000 °C. The subsequent rejuvenation thermal treatments consisted of four steps: solution (at 1,150, 1,175, and 1,190 °C), preprecipitation (at 1,055 and 1,120 °C), and reprecipitation (at 845 °C). The resulting microstructures were analyzed using scanning electron microscopy and Vickers hardness measurements. During the aging treatment, the average size of γ′-particles changed from 0.20 µm2, as found in virgin material, to 0.99 µm2 after 2,000 h of aging; the hardness changed from 417 to 320 HV, respectively. For solution treatment at 1,150 °C, total dissolution of γ′-particles did not occur and they presented a bimodal size distribution of coarse and fine particles. For solution treatment at 1,175 and 1,190 °C, the γ′-particles were fine and homogeneous, and the maximum hardness obtained after reprecipitation was 460 HV for 1,190 °C solution treatment and 1,120 °C preprecipitation.

The long-term topographic response of a continent adjacent to a hyperextended margin: A case study from Scandinavia

We present data that link Scandinavia’s passive-margin domains under a unified system invoking isostatically driven, postextension phase vertical adjustments to severe crustal thinning. Topographic and geological data indicate that the relative location of the first landward occurrence of total crustal embrittlement or deformation coupling—the Taper Break—controlled and continues to control Scandinavia’s post-thinning geomorphic evolution. Formed during Late Jurassic or Early Cretaceous thinning, yet marked today by seismicity, the Taper Break closely approximates the boundary between (1) less-stretched lithosphere that increases in rigidity both toward land and through postrift time, and (2) the highly attenuated, pervasively faulted, permanently weakened lithosphere of the distal margin. Following the stretching, thinning, and exhumation phases proposed by other workers, an accommodation phase is warranted. Commencing during “sag” basin time and continuing today, it is probably driven by thermal cooling and mass transfer from the escarpment to the basins offshore. The accommodation phase does not entirely coincide with the traditional postrift phase as the former may contain the latter. During accommodation, the original synrift escarpments can be eroded to very low base levels. Sharply tapered margin segments can undergo subsequent rejuvenation by out-of-sequence normal faulting and footwall uplift, probably in response to tensile bending stresses engendered by lithospheric-scale flexure. Accommodation-phase uplift at passive margins is the inexorable and penultimate phase of hyperextension, and may perhaps be followed by the onset of subduction localized by the weakened lithosphere of the distal margin and the ocean-continent transition.

Changes in endogenous cytokinin levels in cotyledons of Cucurbita pepo (zucchini) during natural and dark‐induced senescence

Cytokinin (CK) levels in cotyledons of Cucurbita pepo L. (zucchini) were investigated through the processes of post‐germination, greening, natural senescence and subsequent rejuvenation. The concentrations of the physiologically active CK bases, ribosides and nucleotides, as well as the cis‐isomers of zeatin derivatives, decreased between the first and fifth weeks of cultivation under controlled light conditions. At the same time, the levels of storage CK O‐glucosides and physiologically inactive CK 7‐ and 9‐glucosides increased with senescence. With plant decapitation and subsequent cotyledon rejuvenation, not only the chlorophyll content but also the levels of physiologically active CKs, nucleotides and cis‐zeatin derivatives increased. The levels of O‐glucosides, however, decreased. When 1‐week‐old seedlings were transferred to the dark, there was a progressive reduction in cotyledon chlorophyll content, deterioration of chloroplast ultrastructure and a decrease in physiologically active CKs and their nucleotides. In contrast with natural senescence, the storage CK O‐glucosides decreased under dark conditions, suggesting different metabolic regulation of endogenous CK levels during natural and dark‐induced senescence of zucchini cotyledons. The chlorophyll loss of dark‐treated cotyledons could be partially reversed, even after 5 days, with return to light conditions. During this recovery, physiologically active CKs and their nucleotides again increased, whereas the storage CK O‐glucosides and cis‐zeatins decreased. The present results suggest that dark‐induced destruction and subsequent restoration of chloroplasts during light shifts are controlled by changes in the levels of physiologically active CKs and their nucleotides.

Carbon and Strontium Isotopes of Late Palaeozoic Marine Carbonates in the Upper Yangtze Platform, Southwest China

Abstract238 marine carbonate samples were collected from seven sedimentary sections of the entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Platform, southwest China. Based on the absence of cathodoluminescence and very low Mn (generally < 50 ppm) contents of the samples, it is thought that they contain information on the original sea water geochemistry. The results of isotopic analyses of these samples are presented in terms of δ13C and 87Sr/86Sr ratios versus geological time. The strontium data, consistent with other similar data based on samples from North America, Europe, Africa and other areas in Asia, support the notion of a global consistency in strontium isotope composition of marine carbonates. The strontium data exhibit three intervals of relatively low 87Sr/86Sr ratios in the late Middle Devonian to early Late Devonian, Early Carboniferous and Early Permian, corresponding to global eustatic high sea level stands. The lowest 87Sr/86Sr ratio recorded in the Late Permian was probably caused by substantial basalt eruptions in the Upper Yangtze Platform at the time. Three corresponding periods of relatively high δ13C values at roughly the same time intervals were caused by a relatively high rate of accumulation of organic carbon during sea level rises at these times. The deposition of coal was probably responsible for the increase of sea water δ13C at other times. The δ13C values drop dramatically near the Devonian/Carboniferous, Carboniferous/Permian and Permian/Triassic boundaries, consistent with other similar data, which further support the notion that geological time boundaries are associated with mass extinction and subsequent rejuvenation.

Performance of field hedge and stoolbed plants of micropropagated dwarfing apple rootstock clones with different degrees of apparent rejuvenation

M. 9 and Ottawa 3 apple rootstocks from micropropagation were evaluated in the field as hedge or stoolbed plants for three or eight years, respectively. The study involved clones of M.9 from in vitro shoot culture lines which had undergone different durations of subculture in an attempt to influence the dgree of subsequent rejuvenation of the micropropagated plants. Subculture of shoots in vitro for up to nine years did not appear to lead to genetic change since the micropropagated plants of both rootstocks were similar to the conventional counterparts with respect to leaf and bark characteristics. Nevertheless, micropropagated hedge plants of both rootstocks had increased production of suckers and in the case of M.9, increased production of burrknots also. Micropropagated hedge plants of both rootstocks also produced summer and winter shoot cuttings with superior rooting performances whilst stoolbeds of micropropagated M.9 gave increased production of shoots and plants compared with their conventionally propagated counterparts. In general, sucker and burr knot production and rooting of cuttings produced from the various micropropagated M.9 stocks increased with increasing durations of subculture of shoots in vitro.

Tectonic evolution of the easternmost Panama basin: Some new data and inferences

A scheme for the evolution of the easternmost Panama Basin is desbribed, based largely on the interpretation of magnetic data from the area, the most recent of which was collected aboard RRS Charles Darwin in July 1989. A previously unknown extinct oceanic spreading center the “Buenaventura” rift, with an extinction date of about 12 Ma, has been identified passing beneath the Colombian accretionary complex at 3°40′N. The extinction of this rift is attributed to the attempted subduction of a scarp in the oceanic basement, marking the northern boundary of the Galapagos gore, beneath what is today Panama. Transtensional sections along the sinuous Cocos-Nazca plate boundary, which existed between 12 and 8 Ma, are invoked to explain the formation of the Yaquina graben. It is further proposed that transpressive sections along the same boundary may have been partly responsible for the “locking up” of the transform, ultimately contributing to the cessation of spreading along the Malpelo rift at 8 Ma. The southern boundary of a possible “Coiba” microplate is tentatively linked with a line of abandoned rifting at 5°N. A rift jump at 16–17 Ma led to initial abandonment, but subsequent rejuvenation of spreading activity, caused by divergent slab pull forces at the trench, may have led to the formation of a roughly V-shaped rifted zone.

Tectonothermal evolution of contrasting metamorphic complexes in northwest Spitsbergen (Biskayerhalvøya): Evidence from 40Ar/39Ar and Rb-Sr mineral ages

Contrasting metamorphic sequences are exposed within a fault-bounded horst on Biskayerhalvoya, northwestern Spitsbergen. The Biskayerfonna Group is composed of variably pelitic metasedimentary rocks together with interlayered amphibolite. Amphibole within this sequence records 40 Ar/ 39 Ar isotope correlation ages of 429 and 437 m.y., which are interpreted to date cooling through appropriate argon closure temperatures following a late Caledonian amphibolite-facies metamorphism. Muscovite and biotite record slightly younger 4O Ar/ 39 Ar and Rb-Sr ages (400-430 m.y.), which are interpreted to date cooling through lower closure temperatures. The Biskayerfonna Group is tectonically imbricated with an older metamorphic complex (Richarddalen Group) composed of variably retrogressed eclogite, metagranite, foliated amphibolite, and various metasedimentary rocks. Amphibole within massive retrogressive assemblages derived from eclogite and wihin foliated amphibolite records 4O Ar/ 39 Ar isotope correlation ages between 500 and 542 m.y. These are interpreted to date cooling through appropriate closure temperatures following the initial high-pressure metamorphism. Rb-Sr ages recorded by muscovite and most biotite within the Richarddalen Group are markedly younger, ranging between 410 and 430 m.y. These ages likely record cooling following a late Caledonian metamorphic overprint that occurred at approximately the same time as initial prograde metamorphism of the Biskayerfonna Group; however, maximum overprint temperatures in the Richarddalen Group must have been less than prograde conditions in the Biskayerfonna Group because amphibole in the former shows no evidence of any isotopic rejuvenation. These relationships suggest that structural imbrication of the contrasting metamorphic sequences must have occurred during or immediately following late Caledonian metamorphism at ca. 429-437 Ma but prior to regional cooling between ca. 402 and 430 Ma. Phengitic muscovite within the Richard-dalen Group records 4O Ar/ 39 Ar plateau ages between 440 and 480 m.y. and displays no spectral evidence of subsequent rejuvenation. This suggests that the late Caledonian metamorphism must have been of variable intensity within the Richarddalen Group.

Osteosclerosis (traumatic) of carpal bones: A suggestion as to treatment

An operative procedure is suggested for the re-establishment of a circulation in traumatic osteosclerosis of the carpal bones with subsequent rejuvenation and retrabeculation of the affected bone with restoration of its normal appearance. Whether the drilling in itself is adequate, I am not prepared to say. The bone grafts across the joint spaces seem to be absorbed. The functional result with this method seems to be better than the 8 cases of excision of the affected carpal bone, no doubt because the anatomical relationship of the carpal bones has not been destroyed.