Changes In Local Composition Research Articles

Modulation of Mast Cell Reactivity by Lipids: The Neglected Side of Allergic Diseases.

Mast cells (MCs) have long been mainly regarded as effector cells in IgE-associated allergic disorders with potential immunoregulatory roles. Located close to the allergen entry sites in the skin and mucosa, MCs can capture foreign substances such as allergens, toxins, or noxious substances and are exposed to the danger signals produced by epithelial cells. MC reactivity shaped by tissue-specific factors is crucial for allergic responses ranging from local skin reactions to anaphylactic shock. Development of Th2 response leading to allergen-specific IgE production is a prerequisite for MC sensitization and induction of FcεRI-mediated MC degranulation. Up to now, IgE production has been mainly associated with proteins, whereas lipids present in plant pollen grains, mite fecal particles, insect venoms, or food have been largely overlooked regarding their immunostimulatory and immunomodulatory properties. Recent studies, however, have now demonstrated that lipids affect the sensitization process by modulating innate immune responses of epithelial cells, dendritic cells, and NK-T cells and thus crucially contribute to the outcome of sensitization. Whether and how lipids affect also MC effector functions in allergic reactions has not yet been fully clarified. Here, we discuss how lipids can affect MC responses in the context of allergic inflammation. Direct effects of immunomodulatory lipids on MC degranulation, changes in local lipid composition induced by allergens themselves and changes in lipid transport affecting MC reactivity are possible mechanisms by which the function of MC might be modulated.

A century of local changes in bumblebee communities and landscape composition in Belgium

Bumblebees (Bombus spp.) are declining in most parts of Western Europe. Many studies have highlighted the role of agricultural intensification and urbanisation in this decline, and some have also shown the influence of landscape composition on bumblebee populations. However, very few studies have explored bumblebee communities prior to the onset of these major land use changes, and those studies that do are mostly based on low-resolution spatial data. Here, we perform a comparative analysis based on detailed landscape composition and bumblebee occurrence records between the early twentieth century (1910–1930) and the contemporary period (2013–2015) in four localities representative of Belgium. We show that bumblebee assemblages changed drastically over this period, and that the decline in richness was strongest in areas with the greatest increase in urbanization and agricultural intensification. The one locality still retaining a high proportion of grasslands, orchards and woodlands with the smallest overall change in landscape composition still hosts a rich bumblebee fauna, very similar than in the past. We provide recommendations for land use management based on these findings. We also warn about the importance of other factors such as land use intensity, climatic conditions and altitude, which should be included in any future study addressing changes in bumblebee populations related to land use changes.

Effect of Electrolyte Composition on Performance and Stability of Lithium-Sulfur Batteries

Rechargeable lithium-ion batteries are necessary for our life to use as a mobile phone, electric vehicle and so on. However, there is a limit to the capacity of lithium-ion batteries. Therefore it is necessary to develop batteries which has large capacity. Lithium-sulfur (Li-S) battery is expected for next generation rechargeable battery owing to have high capacity (1,645 mAh/g) compared with conventional Li-ion batteries. However, Li-S battery has serious problem that lithium polysulfide (Li2S x ) which is an intermediate product dissolves into electrolyte. If we can suppress the dissolution of Li2S x , the battery life should be extended. To suppress the dissolution of Li2S x , we use solvate ionic liquid (SIL) electrolytes. SIL is mixture of 1:1 complex from low-molecular weight ether and Li salt, which have high thermal / electrochemical stabilities owing to strong interaction of between ether oxygen and Li cation. SIL electrolytes have low solubility of Li2S x owing to their low Lewis acidity / basicity and suppress dissolution of Li2S x into electrolyte. Recently, it was found that high Li salt concentration more than 1:1 SIL electrolyte is effective for high performance lithium-ion batteries and Li-S batteries. Fig. 1 shows cycle performance of LiNi1/3Mn1/3Co1/3O2 | [Li(G3) x ]TFSA | Li cell. Excess Li salts achieved high cycle performances and stable charge-discharge operations. Li salt excess SIL electrolyte contributes to extension of cycle life for Li-ion batteries. According to these previous researches, it is shows that local composition changes of SIL electrolytes of glyme and Li salt near the electrode during the charge and discharge process. Li2S x should be dissolved in the released free glyme. Therefore, we considered that Li salt excess SIL electrolyte can suppress the formation of temporary free glyme. Therefore, the purpose of this study is to clarify the influence of the composition of SIL electrolyte on the solubility of Li2S x and the performance of Li-S batteries. All preparations and measurements were carried out in an inert atmosphere Ar-filled glove box and a sealed cell. SILs, [Li(G3)1.25]TFSA, [Li(G3)1.11]TFSA, [Li(G3)]TFSA, [Li(G3)0.9]TFSA and [Li(G3)0.8]TFSA (composition ratio of triglyme (G3) and LiTFSA is 10:8, 10:9, 10:10, 10:9 and 10:8), were prepared, respectively. Viscosity, density and thermal stability of SIL electrolyte samples were measured. Then, dissolution tests of Li2S x were carried out. Lithium polysulfide is an unstable substance, so S8 and Li2S were mixed with S8 and Li2S=7:8, we defined as Li2S8 were prepared. Prepared SIL electrolyte and Li2S8 were mixed for saturation. SILs were each diluted 50 times (molar ratio) with SIL electrolyte, and the absorbance was measured by UV-vis spectrometer. Fig. 2 shows appearances of five SIL electrolytes with saturated Li2S8. It was visually observed that the amount of free glyme decreased in the Li excess SIL electrolyte and the dissolution of Li2S x into SIL electrolyte was suppressed with LiTFSA concentration. From this result, improvement of Li-S battery performances were expected by using Li salt excess SIL electrolytes. Charge and discharge tests were carried out using [S|[Li(G3) x ]TFSA|Li] cells, and cycle performances were shown (Fig. 3) . All initial capacities were more than 800 mAh/g. The figure is the normalized cycle characteristics as deterioration rate with the initial capacity set to 100%. At 25 cycles [Li(G3) x ]TFSA x=0.8 (Li salt excess SIL electrolyte) showed a sufficient capacity retention about 10% higher than x=1 (equimolar). From the above results, the Li salt excess SIL electrolyte can conclude as effective electrolyte design for Li-S batteries. In the presentation, we will comprehensively report the thermal and transport properties of each SIL and the results of UV-vis measurement results. Figure 1

Electron energy-loss spectroscopy (EELS) with a cold-field emission scanning electron microscope at low accelerating voltage in transmission mode

A commercial electron energy-loss spectrometer (EELS) attached to a high-resolution cold-field emission scanning electron microscope in transmission mode (STEM) is evaluated and its potential for characterizing materials science thin specimens at low accelerating voltage is reviewed. Despite the increased beam radiation damage at SEM voltages on sensitive compounds, we describe some potential applications which benefit from lowering the primary electrons voltage on less-sensitive specimens. We report bandgap measurements on several dielectrics which were facilitated by the lack of Cherenkov radiation losses at 30 kV. The possibility of volume plasmon imaging to probe local composition changes in complex materials was demonstrated using energy-filtered STEM, either via spectrum imaging or elemental mapping using the “three-windows” method. As plasmonic materials are increasing used for energy, electronics or biomedical applications, the ability of reliably evaluate their properties at low accelerating voltage in a SEM is very appealing and is demonstrated. The energy resolution of the spectrometer, taken as the full width at half maximum of the zero-loss peak, was routinely measured at around 0.55 eV and it is demonstrated that t/λ ratios up to 1.5 allowed practical EEL spectroscopy at 30 kV.

Chemical differentiation, cold storage and remobilization of magma in the Earth's crust.

The formation, storage and chemical differentiation of magma in the Earth's crust is of fundamental importance in igneous geology and volcanology. Recent data are challenging the high-melt-fraction 'magma chamber' paradigm that has underpinned models of crustal magmatism for over a century, suggesting instead that magma is normally stored in low-melt-fraction 'mush reservoirs'1-9. A mush reservoir comprises a porous and permeable framework of closely packed crystals with melt present in the pore space1,10. However, many common features of crustal magmatism have not yet been explained by either the 'chamber' or 'mush reservoir' concepts1,11. Here we show that reactive melt flow is a critical, but hitherto neglected, process in crustal mush reservoirs, caused by buoyant melt percolating upwards through, and reacting with, the crystals10. Reactive melt flow in mush reservoirs produces the low-crystallinity, chemically differentiated (silicic) magmas that ascend to form shallower intrusions or erupt to the surface11-13. These magmas can host much older crystals, stored at low and even sub-solidus temperatures, consistent with crystal chemistry data6-9. Changes in local bulk composition caused by reactive melt flow, rather than large increases in temperature, produce the rapid increase in melt fraction that remobilizes these cool- or cold-stored crystals. Reactive flow can also produce bimodality in magma compositions sourced from mid- to lower-crustal reservoirs14,15. Trace-element profiles generated by reactive flow are similar to those observed in a well studied reservoir now exposed at the surface16. We propose that magma storage and differentiation primarily occurs by reactive melt flow in long-lived mush reservoirs, rather than by the commonly invoked process of fractional crystallization in magma chambers14.

Fabrication and Thermoelectric Characterization of Transition Metal Silicide-Based Composite Thermocouples.

Metal silicide-based thermocouples were fabricated by screen printing thick films of the powder compositions onto alumina tapes followed by lamination and sintering processes. The legs of the embedded thermocouples were composed of composite compositions consisting of MoSi2, WSi2, ZrSi2, or TaSi2 with an additional 10 vol % Al2O3 to form a silicide–oxide composite. The structural and high-temperature thermoelectric properties of the composite thermocouples were examined using X-ray diffraction, scanning electron microscopy and a typical hot–cold junction measurement technique. MoSi2-Al2O3 and WSi2-Al2O3 composites exhibited higher intrinsic Seebeck coefficients (22.2–30.0 µV/K) at high-temperature gradients, which were calculated from the thermoelectric data of composite//Pt thermocouples. The composite thermocouples generated a thermoelectric voltage up to 16.0 mV at high-temperature gradients. The MoSi2-Al2O3//TaSi2-Al2O3 thermocouple displayed a better performance at high temperatures. The Seebeck coefficients of composite thermocouples were found to range between 20.9 and 73.0 µV/K at a temperature gradient of 1000 °C. There was a significant difference between the calculated and measured Seebeck coefficients of these thermocouples, which indicated the significant influence of secondary silicide phases (e.g., Mo5Si3, Ta5Si3) and possible local compositional changes on the overall thermoelectric response. The thermoelectric performance, high sensitivity, and cost efficiency of metal silicide–alumina ceramic composite thermocouples showed promise for high-temperature and harsh-environment sensing applications.

Особенности питания керчака-яока Myoxocephalus jaok (Cuvier, 1829) (Cottidae) и его место в трофической системе прикамчатских вод

По материалам 1978–2008 гг. (975 желудков обработано количественно-весовым методом, около 2 тыс. желудков вскрыто и проанализировано в полевых условиях) рассмотрены особенности питания керчака-яока Myoxocephalus jaok в прикамчатских водах Охотского, Берингова морей и Тихого океана и предпринята попытка выяснить место этого вида рогатковых в трофической системе данного района. Показано, что керчак-яок характеризуется широким спектром питания (свыше 100 кормовых объектов), однако наибольшее значение в его рационе имеют рыбы (в среднем 64,1 % массы пищи) и десятиногие раки (32,2 %). Основу первых составляют камбалы Pleuronectidae (24,3 % массы пищи), минтай Theragra chalcogramma (14,4 %), тихоокеанская песчанка Ammodytes hexapterus (9,5 %) и рогатковые Cottidae (5,6 %); вторых ― крабы семейства Majidae (22,4 %) (главным образом краб-стригун Chionoecetes opilio (14,2 %) и краб-паук Hyas coarctatus (8,1 %)), а также крабы семейства Atelecyclidae (4,7 %) (преимущественно пятиугольный волосатый краб Telmessus cheiragonus (4,5 %)) и креветки семейства Crangonidae (3,1 %). Рассмотрены сезонные, локальные, межгодовые и возрастные изменения состава пищи керчака-яока. Установлено, что этот вид является факультативным хищником-засадчиком; ему свойственна высокая пластичность питания, дающая возможность использовать значительный набор пищевых компонентов. В трофической системе прикамчатских вод выделены звенья, формирующие биомассу керчака-яока.

Examining the influence of PTH(1-34) on tissue strength and composition.

The lacunar-canaliculi system is a network of channels that is created and maintained by osteocytes as they are embedded throughout cortical bone. As osteocytes modify their lacuna space, the local tissue composition and tissue strength are subject to change. Although continual exposure to parathyroid hormone (PTH) can induce adaptation at the lacunar wall, the impact of intermittent PTH treatment on perilacunar adaptation remains unclear. Therefore, the primary objective of this study was to establish how intermittent PTH(1-34) treatment influences perilacunar adaptation with respect to changes in tissue composition. We hypothesized that local changes in tissue composition following PTH(1-34) are associated with corresponding gains in tissue strength and resistance to microdamage at the whole bone level. Adult male C57BL/6J mice were treated daily with PTH(1-34) or vehicle for 3 weeks. In response to PTH(1-34), Raman spectroscopy revealed a significant decrease in the carbonate-to-phosphate ratio and crystallinity across the entire tissue, while the mineral-to-matrix ratio demonstrated a significant decrease in just the perilacunar region. The shift in perilacunar composition largely explained the corresponding increase in tissue strength, while the degree of new tissue added at the endosteum and periosteum did not produce any significant changes in cortical area or moment of inertia that would explain the increase in tissue strength. Furthermore, fatigue testing revealed a greater resistance to crack formation within the existing tissue following PTH(1-34) treatment. As a result, the shift in perilacunar composition presents a unique mechanism by which PTH(1-34) produces localized differences in tissue quality that allow more energy to be dissipated under loading, thereby increasing tissue strength and resistance to microdamage. In addition, our findings demonstrate the potential for PTH(1-34) to amplify osteocytes' mechanotransduction by producing a more compliant tissue. Overall, the present study demonstrates that changes in tissue composition localized at the lacuna wall contribute to the strength and fatigue resistance of cortical bone gained in response to intermittent PTH(1-34) treatment.

Atomic Ordering and Disordering of Amorphous CoNiP Alloy

The structure of electrolytically deposited nanocrystalline alloys of the CoP-CoNiP systems under low-temperature heating was investigated by means of high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM), and analytical methods such as energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Structural relaxation and crystallization were investigated at temperatures from 150°C to 300°C. Structural and compositional inhomogeneities were found in the CoP-CoNiP alloys, while the local changes in composition were found to reach 15 at.%. Nanocrystals in the alloys grew most intensely in the presence of a free surface. It was determined that the local diffusion coefficient ranged from 1.2 to 2.4 10−18 m2/s, which could be explained by the surface diffusion prevalence. The data gathered in these investigations can be further used to predict the thermal stability of CoP-CoNiP alloys.

Influence of the Microstructure on Magnetic Stray Fields of Low-Carbon Steel Welds

This study examines the relationship between the magnetic mesostructure with the microstructure of low carbon steel tungsten inert gas welds. Optical microscopy revealed variation in the microstructure of the parent material, in the heat affected and fusion zones, correlating with distinctive changes in the local magnetic stray fields measured with high spatial resolution giant magneto resistance sensors. In the vicinity of the heat affected zone high residual stresses were found using neutron diffraction. Notably, the gradients of von Mises stress and triaxial magnetic stray field modulus follow the same tendency transverse to the weld. In contrast, micro-X-ray fluorescence characterization indicated that local changes in element composition had no independent effect on magnetic stray fields.

Formation and characteristic corrosion behavior of alternately lamellar arranged α and β in as-cast AZ91 Mg alloy

Formation and characteristic corrosion resistance of alternately lamellar arranged α and β in as-cast AZ91 Mg alloy were investigated as an independent micro-constituent identity. As-cast AZ91 presented three microstructural entities, i.e. α-Mg grain, (α+β) lamellae and coarse β particle, and each had its own Al content and microstructural morphology. The lamellae occurrence was due to the precipitation of β particle from the divorced eutectic Al-rich-α phase during solidification, because the Al composition can not exceed its maximum solubility. The evidences that were obtained from electrochemical tests, micro-corrosion morphology and hydrogen evolution rate certified that the (α+β) lamellae was beneficial to corrosion resistance, which was different from the reported deleterious influence for its original eutectic Al-rich-α phase. This different corrosion behavior was explained to be ascribed to the changes in fine structure and local composition that resulted in combined electrochemical effects of the changes in α and β phases on the corrosion.

(Invited) Magnetic Gradient-Assisted Physical and Chemical Structuring of Electrodeposits

Magnetic thin films, micro and nano structures are key features in magnetic sensors and for data storage in hard drives. To date often physical deposition methods are more frequently employed than electrodeposition to produce these magnetic structures. This is due to the fact that the usually inexpensive alternative production by electrodeposition requires sophisticated masking or templating if structured deposits are desired. Magnetic-field assisted electrodeposition has been demonstrated as a method to produce structured deposits by employing reusable magnetic gradient templates. [1] The working principle is based on a locally enhanced mass transports thanks to a magnetic gradient force induced local convection in the electrolyte during electrodeposition. In regions of high magnetic gradients, typically film thickness and roughness are increased for paramagnetic ions like Cu2+, Co2+ or Fe2+. Here, we demonstrate that not only single component metals, but also bimetallic alloy electrodeposits can be deposited in a desired structure by this approach. By suitably selecting the electrolyte composition and deposition parameters, we demonstrate that the current efficiency can be increased for the electrodeposition of transition metal-based alloys. This is evidenced by electrochemical quartz crystal microbalance studies during electrodeposition of CoFe in the presence of varied magnetic gradients. [2] In addition, we show that also chemical structuring of bimetallic deposits can be achieved by means of magnetic gradient-assisted electrodeposition, which is shown or CuNi electrodeposits. For both systems the observed local morphological and compositional changes are characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. The experimental findings are then discussed in terms of magneto-hydrodynamic effects, which are attributed to the magnetic field gradient force. Thus, magnetic-gradient assisted electrodeposition is suggested as a new route to magnetic patterning of surfaces. [1] Tschulik, Kristina; Koza, Jakub Adam; Uhlemann, Margitta; Gebert, Annett; Schultz, Ludwig Electrochemistry Communications, 2009, 11(11), 2241–2244 [2] Karnbach, F.; Uhlemann, M.; Gebert, A.; Eckert, J.; Tschulik, K. Electrochimica Acta, 2014, 123, 477–484

Unveiling the science behind the tea bowls from the Jizhou kiln. Part II. Microstructures and the coloring mechanism

In this part of the study, optical microscope, field emission scanning electron microscope-energy dispersive spectrometer, transmission electron microscope-selected area diffraction-energy dispersive spectrometer, micro-Raman and reflectance spectrum were applied to further study the microstructures of the characteristic areas of the glazes and illustrate the coloring mechanism of the “hare's fur” tea bowls with blue or bluish violet patterns. The results show that due to the diffusion between the cover glaze and ground glaze caused by compositional difference, as well as the “boiling effect” of the ground glaze, local chemical composition changes to form the different microstructures in different regions. Large sized interconnected phase separation structure with approximately 350 nm characteristic size forms in the unreacted portion of the cover glaze, leading to the scattering of all wavelengths of the incident visible light. With the contribution of the ground glaze which has low immiscibility tendency, small sized interconnected phase separation structure with approximately 170 nm characteristic size forms at the edge of the white region, leading to the scattering of the blue light range of the incident visible light. The fluctuation of thermal history gives various appearance to the Jizhou “hare's fur” tea bowls, although they share the same coloring mechanism. In general, chemical composition, microstructure and firing schedule cooperate with each other to create the changeful appearance of the Jizhou tea bowls.

Cellular Mechanotransduction: From Tension to Function.

Living cells are constantly exposed to mechanical stimuli arising from the surrounding extracellular matrix (ECM) or from neighboring cells. The intracellular molecular processes through which such physical cues are transformed into a biological response are collectively dubbed as mechanotransduction and are of fundamental importance to help the cell timely adapt to the continuous dynamic modifications of the microenvironment. Local changes in ECM composition and mechanics are driven by a feed forward interplay between the cell and the matrix itself, with the first depositing ECM proteins that in turn will impact on the surrounding cells. As such, these changes occur regularly during tissue development and are a hallmark of the pathologies of aging. Only lately, though, the importance of mechanical cues in controlling cell function (e.g., proliferation, differentiation, migration) has been acknowledged. Here we provide a critical review of the recent insights into the molecular basis of cellular mechanotransduction, by analyzing how mechanical stimuli get transformed into a given biological response through the activation of a peculiar genetic program. Specifically, by recapitulating the processes involved in the interpretation of ECM remodeling by Focal Adhesions at cell-matrix interphase, we revise the role of cytoskeleton tension as the second messenger of the mechanotransduction process and the action of mechano-responsive shuttling proteins converging on stage and cell-specific transcription factors. Finally, we give few paradigmatic examples highlighting the emerging role of malfunctions in cell mechanosensing apparatus in the onset and progression of pathologies.

Delayed adaptation in stochastic metapopulation models(a)(a)Contribution to the Focus Issue Evolutionary Modeling and Experimental Evolution edited by José Cuesta, Joachim Krug and Susanna Manrubia.

How does delayed fitnesses adaptation after local habitat changes affect survival of species metapopulation? We study this question in a two-species model system, where the species composition of a local patch determines the reference fitness of all its individuals. When individuals move, this local species composition changes. As the local environment on the patch might adapt slowly to this change, we assume that individuals in turn adapt their fitness with a stochastic delay. We show that the combination of delay and spatial substructure can yield significantly different phase diagrams for the survival of these species with respect to models with immediate response. We investigate this exemplarily for the case where the two species interact via an exoproduct: thus, our population consists of a slow-growing producer species and a fast-growing dominant species. We provide a conceptual understanding of the role of delay by presenting analytic results in the well-mixed and low-mobility limit. By studying intermediate mobilities numerically, we ensure that our results are robust, and may be relevant to different ecological situations as well as microbial metapopulation experiments.

Invasive Species May Disrupt Protected Area Networks: Insights from the Pine Wood Nematode Spread in Portugal

The expansion of invasive alien species is considered a major threat to forest ecosystems and biodiversity. Their potential impacts range from local changes in species composition to wider-scale effects on forest habitat and landscape functioning, although the latter has been relatively little explored in the literature. Here, we assessed the impact of an invasive forest pest, the pine wood nematode (PWN), in the Natura 2000 network of protected areas (PAs) in Portugal, the first European country in which PWN was reported. We considered the impacts of the pest’s spread (up to 2016) on individual PAs, in terms of the fraction of their coniferous forest infected, and on the corridors between PAs, which were mapped and prioritized through least-cost path modelling, geographic information system analysis, and the graph-based probability of connectivity metric. We found that PWN by 2016 had spread into 49% of the Portuguese Natura 2000 coniferous forest habitat, while it had invaded 68% of the coniferous forests that form the priority corridors between the PAs. These impacts are likely to be aggravated in the next years, given the pace of PWN expansion and the predicted rates of natural spread to new areas in Portugal and, increasingly likely, in Spain. Our results suggest that the connectivity of PA systems may be significantly disrupted by alien species, and that spatially prioritized control measures can help mitigate the impacts of invasive species on the coherence and functionality of protected area networks such as Natura 2000.

Effects of laser processing on the transformation characteristics of NiTi: A contribute to additive manufacturing

Laser additive manufacturing of NiTi generates complex microstructural features not fully understood yet. Thermal similarities between laser microjoining and laser additive manufacturing, enables correlating the effect of the laser on the material in both processes. To clarify them, a simplified yet accurate approach was employed: in-situ X-ray diffraction was used to determine the local transformation temperatures along the thermally affected regions in a laser processed NiTi thin sheet. The observed gradient of transformation temperatures is related to local chemical compositional changes through Ni depletion and residual stresses, explaining the peculiar microstructural and mechanical features observed in additive manufacturing of NiTi.

Can paid sick leave mandates reduce leave-taking?

Since 2006, several cities and states have implemented paid sick leave mandates. We examine the effects of paid sick leave mandates in Washington, D.C. (2008) and Connecticut (2011) on leave-taking behavior. After these policies are implemented, there are significant decreases in the aggregate rate of illness-related leave taking, relative to control groups, for both those directly affected and those not directly affected by the policy. The estimates are strong for Connecticut, but are more sensitive to the specification and weaken over time for D.C. We also find decreases in leave-taking when exploiting exogenous variation in access to paid sick leave through changes in local industry composition over time. Our results suggest that mandated sick leave policies can provide large positive public health externalities by allowing sick workers to stay home rather than coming to work and spreading their illness to customers and coworkers.

AC electric field‐induced softening of alkali silicate glasses

AbstractElectric field‐induced softening (EFIS) is a recently discovered phenomenon leading to significant reduction in the furnace temperature at which glass softens under the application of DC voltage. Unfortunately, it is accompanied by local compositional changes due to migration of ions that could limit its usefulness. To overcome this drawback, we have investigated the same phenomenon using AC voltage, that is, AC‐EFIS on a sodium disilicate glass and a 50/50 mixed lithium‐sodium disilicate glass of very different ionic resistivity yet similar network structure. The results show that the magnitude of EFIS temperature reduction is significantly greater for AC compared to DC for both glass compositions. The enhancement of EFIS under AC voltage appears to be due to a more uniform power dissipation and self‐healing of changes than under DC voltage. This uniformity allows for the overall sample temperature to increase throughout the bulk and provides a better technique for practical applications than the DC case which produces potentially undesirable changes, especially in the anode region.

A 12,000 year record of changes in herbivore niche separation and palaeoclimate (Wonderwerk Cave, South Africa)

The large mammalian fauna of southern Africa is characterised by strong niche separation into grazer and browser species, with few falling into the intermediate mixed-feeder niche. Moreover, the modern fauna is reduced in species diversity compared to the Pleistocene, following the extinction of several specialized grazers in the late Pleistocene and early Holocene. How did this state develop, and how might it be connected to climatic change during the Holocene? To better understand this development, we obtained extensive carbon and oxygen stable light isotope data from herbivore tooth enamel samples from Wonderwerk Cave, South Africa, spanning about 12,000–500 cal. BP. This is a unique dataset since it is the only site in the southern Kalahari with a robust chronometric record and well-preserved faunal remains for the last 12,000 years without significant gaps. Combining the stable isotopes with pollen and micromammal data from Wonderwerk Cave, we have explored shifts in the proportions of C3 and C4 plants and moisture availability. Although climate remained generally semi-arid for much of this period, the results show significant hydrological and vegetation shifts in the sequence, particularly with the strengthening of summer rainfall in the mid-Holocene. The results for the sixteen herbivore species reveal a reinforcement of the grazer-browser niche partitioning through the Holocene and shows how niche specialization follows changes in local vegetation composition. In the light of this reconstruction of the local ecology we discuss grazer extinctions, human adaptations, and the drivers behind climatic changes in the summer rainfall zone of southern Africa.