Magnetic Carbonate Research Articles

Unmixing of Magnetic Hysteresis Loops Through a Modified Gamma‐Cauchy Exponential Model

AbstractQuantifying the contributions of distinct mineral populations in bulk magnetic experiments greatly enhances the analysis of environmental and rock magnetism studies. Here, we develop a new method of parametric unmixing of susceptibility components in hysteresis loops. Our approach is based on a modified Gamma‐Cauchy exponential model that accounts for variable skewness and kurtosis. The robustness of the model is tested with synthetic curves that examine the effects of noise, sampling, and proximity (similar coercivities) of susceptibility components. We provide a Python‐based script, the Hist‐unmix, which allows the user to adjust a forward model of up to three ferromagnetic components as well as a dia/paramagnetic contribution. Optimization of all the parameters is achieved through least squares fitting (Levenberg‐Marquardt method), with uncertainties of each inverted parameter calculated through a Monte Carlo error propagation approach. For each ferromagnetic component, it is possible to estimate the saturation magnetization (Ms), saturation remanent magnetization (Mrs) and the mean coercivity (). Finally, Hist‐unmix was applied to a set of weakly magnetic carbonate rocks from Brazil, which typically show distorted hysteresis loops (wasp‐waisted and potbellied). For these samples, we resolved two components with distinct coercivities. These results are corroborated by previous experimental data, showing that the lower branch of magnetic hysteresis can be modeled by the presented approach and might offer important mineralogical information for rock magnetic and paleomagnetic studies.

Interception of phosphorus release from sediment by magnetite/lanthanum carbonate co modified activated attapulgite composite: Performance and mechanism

The release of phosphorus from sediment and the high concentration of phosphorus in the water environment make the water body continuously eutrophic, so it is very important to develop new phosphorus removal materials to reverse the eutrophication of river and lake. In this study, the effect and mechanism of magnetic lanthanum carbonate modified attapulgite (MT-LCMT) prepared by co-precipitation in fixed water and prime phosphorus were studied. The results showed that MT-LCMT had excellent magnetic hysteresis performance and its maximum model adsorption of phosphate could reach 51.69 mg/g. The phosphate adsorption process mainly followed the co-kinetics of intraparticle diffusion and membrane diffusion and conformed to the Redlich-Peterson model and Sips model. After five adsorption-desorption cycle experiments, MT-LCMT exhibited stable adsorption and regeneration properties, which may also be used for the removal of phosphate from actual water bodies. The experiment of exploring the factors affecting the adsorption of phosphate by MT-LCMT shows that the adsorption capacity of phosphate is the highest when the pH is between 3 and 8, and the existence of HCO3-, CO32- and humic acid reduce the adsorption capacity of phosphate. The binding mechanism of MT-LCMT to orthophosphate involves coordination exchange, precipitation and electrostatic attraction. MT-LCMT capping can significantly reduce the risk of sediment releasing mobile phosphorus (Mobile-P), bioavailable phosphorus (BAP), overlying water dissolve reactive phosphorus (DRP) and available phosphorus with medium diffusion gradient in thin film (DGT-P) to the overlying water, and the unstable phosphorus (NH4Cl-P and BD-P) of surface sediment are converted into stable phosphorus (HCl-P and NaOH85-P). The above results indicated that MT-LCMT had a high potential to be used as an active capping material for managing phosphorus loads inside surface water bodies and substrates.

Preparation of hydrophobic magnetic calcium carbonate and its oil removal properties

Preparation of hydrophobic magnetic calcium carbonate and its oil removal properties

The preparation of layered hierarchical and cube-shaped magnetic Fe3O4/CaCO3 for efficient enrichment of Pb(Ⅱ) from aqueous solutions

In this study, magnetic layered hierarchical calcium carbonate (MLH-CaCO3) and magnetic cube-shaped calcium carbonate (MCS-CaCO3) materials were prepared using a simple coprecipitation method for the removal of Pb(Ⅱ). In addition, the formation processes of the different morphologies of calcium carbonate were reasonably explained. The adsorption properties and adsorption mechanism of magnetic CaCO3 toward Pb(Ⅱ) were revealed through characterization with IR, XRD, SEM, EDS, XPS, and control experiments. The adsorption performance of MLH-CaCO3, which was used to remove heavy metal ions from simulated wastewater was better than that of MCS-CaCO3. The experimental data showed that the Pb(Ⅱ) adsorption capacity of MLH-CaCO3 is higher than that of the MCS-CaCO3 adsorbent by 45.1%. The isotherm study indicated that the maximum adsorption capacity of up to 1201.15 mg/g Pb(Ⅱ) with MLH-CaCO3 well fits the Langmuir adsorption model. Also, at pH = 5, the highest removal rate of 100 mg/L Pb(II) using magnetic calcium carbonate was 99.9%. Furthermore, except Cu(II) ions, the coexistence of many heavy metals or salt ions has little effect on the removal of Pb(II) ions by magnetic CaCO3 adsorbents. BET analysis results showed that the MLH-CaCO3 adsorbent (16.728 m2/g) has larger specific surface areas and more gaps than the MCS-CaCO3 adsorbent (14.204 m2/g). Therefore, it not only provides numerous adsorption sites but also promotes the permeation of Pb(Ⅱ) into the inner structure of CaCO3. Moreover, a magnetic calcium carbonate adsorbent containing Pb could be easily separated using external magnets to avoid secondary environmental pollution and facilitate the recovery of subsequent resources.

The Požarevac loess–paleosol sequence: a record of increased aridity in the south‐eastern margin of the Carpathian Basin during the last 350 ka

ABSTRACTThe loess sequence preserved in the Požarevac brickyard in north‐eastern Serbia comprises eight loess units separated by seven paleosols. Geochronological investigation using amino acid racemization and luminescence dating support stratigraphic correlations of loess units L3, S2LL1 and L1 at the Požarevac section with loess of glacial cycles E [Marine Isotope Stage (MIS) 10], D (MIS 9–8), C (MIS 7–6) and B (MIS 5–2) across central Europe. Correlation with the marine oxygen‐isotope stratigraphy and associated paleoclimatic inferences are further supported by magnetic susceptibility, particle size and carbonate content measured in Požarevac sediments. Malacological investigations at the Požarevac section reveal the continuous presence of the Chondrula tridens and Helicopsis striata faunal assemblages throughout the last 350 ka. The loess malacological fauna, which is characterized by the complete absence of cold‐resistant and cold‐preferring species, suggests a stable, dry and relatively warm glacial and interglacial climate, compared with other central European loess localities. Together these data suggest that the south‐eastern part of the Carpathian (Pannonian, Middle Danube) Basin was a refugium for warm‐preferring and xerophilous land‐snails during the generally unfavorable glacial climates of the late Middle and Late Pleistocene.

Linking the Variation of Sediment Accumulation Rate to Short Term Sea-Level Change Using Cyclostratigraphy: Case Study of the Lower Berriasian Hemipelagic Sediments in Central Tunisia (Southern Tethys)

High-resolution magnetic susceptibility and % CaCO3 records (5 to 10 cm sampling interval) are used to track astronomical cycles from a Lower Berriasian record from central Tunisia. Six hundred and twenty two samples were measured for magnetic susceptibility and carbonate content as paleoclimate proxies for the detection of potential Milankovitch cycles. Elemental data using X-Ray fluorescence analyses was acquired from 19 samples to prove the reliability of the MS signal on recording the past paleoclimatic changes. We performed multiple spectral analyses and statistical techniques on the magnetic susceptibility signal, such as Multi-taper Method, Evolutive Harmonic Analysis, Correlation Coefficient, Time-optimization, and Average Spectral Misfit to obtain an optimal astronomical model. The application of these spectral analysis techniques revealed a pervasive dominance of E405-kyr and e100-kyr cycles showing that the climate turnover across the early Berriasian—middle Berriasian seems to had been governed by the long and short orbital eccentricity cycles. The identification of Milankovitch cycles in the record also allowed to propose a floating astronomical timescale of the studied section, with ~4 long eccentricity cycles (E405) extracted, which points to a duration estimate of ~1.6 Myr with an average sediment accumulation rate (SAR, after compaction) of 2.77 cm/kyr. The inferred floating ATS was tuned to the La2004 astronomical solution. In addition, we applied the DYNOT and ρ1 methods for seal-level change modeling to reconstruct a local eustatic profile which matches the previously published local and global eustatic charts.

Pleistocene dynamics of dust accumulation and soil formation in the southern Caspian Lowlands - New insights from the loess-paleosol sequence at Neka-Abelou, northern Iran

The southern Caspian Lowland sensitively reacted to Pleistocene climate change and is a key area for reconstructing climate dynamics and landscape evolution in Southern Eurasia. Loess-paleosol sequences (LPS) of the northern foothills of Alborz Mountains provide detailed records of climate-induced changes of dust accumulation and soil formation correlating with relatively dry or moist conditions of the past. The LPS at Neka-Abelou (NA) was studied in detail in order to understand these dynamics and provide a base for regional pedostratigraphic correlation. We have carried out high-resolution analyses of grain-size, sediment color, mass specific and frequency-dependent magnetic susceptibility and carbonate content and established a temporal framework as based on luminescence dating using a post-IR infrared stimulated luminescence (pIRIR) protocol and fading corrections. The LPS of NA is composed of finely textured loess, which is subdivided by at least eleven paleosols. Moreover, it contains a thin loess layer with lenses of trachytic tephra which most likely originated from the Damavand volcano and was deposited during Marine Isotope Stage (MIS) 4. The lower part of the LPS at NA consists of four strongly-developed reddish-brown paleosols (Bt, Btg horizons) separated by thin layers of pedogenically-altered loess indicating moist climate conditions and low dust accumulation rates during the Middle Pleistocene or earlier. The central part contains a pedocomplex of clay-rich paleosols composed of well developed Bt, ABk and Bw horizons formed under strongly reduced dust accumulation rates and intercalated by loess layers. Pedostratigraphic reasoning suggests that this pedocomplex formed during MIS 5, which is corroborated by luminescence dating. The pedocomplex reflects precession time scale climate change and represents an excellent pedostratigraphic marker recognized in numerous exposures along the northern foothills of the Alborz Mountains. The upper part of the LPS accumulated during the Last Pleniglacial and contains probably six weakly developed synsedimentary paleosols (CBk horizons) as well as the modern soil (Bt horizon). Magnetic susceptibility records show very close similarity with the pleniglacial sequence of the LPS at Toshan located about 100 km farther to the east of the Caspian Lowlands suggesting that the weak paleosols at both locations have formed synchronously, which is supported by luminescence dating. Their presence thus reflects at least a regional-scale climate change between dry phases and those of slightly increased edaphic moisture with ongoing dust supply. The LPS of the Caspian Lowlands document a multitude of changes between dominance of dust accumulation or pedogenesis controlled by moisture availability in the context of Pleistocene climate change. The proposed regional pedostratigraphy for the Late Quaternary provides a scheme for large-scale stratigraphic correlation and reconstruction of climate change in Southern Eurasia.

A multi-proxy quantitative record of Holocene hydrological regime on the Heixiazi Island (NE China): indications for the evolution of East Asian summer monsoon

The Holocene hydrological regime on the Heixiazi Island is critical for understanding the evolution of the East Asian summer monsoon (EASM) for the island’s climate-sensitive location on the northern fringe of the EASM domain. In this paper, a marsh depression on the central island was selected to reconstruct the locally hydrological variation and to discuss its indications for the Holocene EASM evolution. This work is based on multi-proxy (magnetic susceptibility, grain size, loss-on-ignition, and carbonate content) analyses of 22 modern sedimentary samples with a water-level gradient of 0–66 cm and 100 cored sedimentary samples covering last ~ 9.0 ka BP. The proxies’ hydrological significance was previously interpreted by the 22 modern samples using linear regression equations to construct their relationships to water-level changes. Among these proxies, the magnetic susceptibility, carbonate content, as well as the Md and sand fraction of grain size exhibit high-level relationships against the water-level changes with R2 > 0.6. Thus, these four proxies’ linear-regression equations were selected and used on the 100 cored samples, and the Holocene water-level changes in the studied depression were quantitatively reconstructed. It shows that two relatively high water-level stages with strengthened EASM occurred during 8.0–4.5 ka BP and 3.0–1.4 ka BP, which were alternated by three low water-level stages with declined EASM during ~ 9.0–8.0 ka BP, 4.5–3.0 ka BP, and 1.4–0 ka BP, respectively. Among these fluctuations, the highest water-level stage with most strengthened EASM which is defined as the Holocene Monsoon Maximum occurred during 6.4–4.5 ka BP. Such a new evolution pattern of the EASM can be further supported by a large variety of records from monsoon-margin regions. We suggest the Holocene EASM evolution was generally associated with the thermal conditions in both the inner Eurasia landmass and the West Pacific Ocean, with an exception of the weak EASM before 8.0 ka BP due to the enhanced Siberia High with the dominance of the Eurasia ice sheet in the early Holocene.

Sandy Loess Records of Precipitation Changes and Monsoon Migrations in the Hunshandake Sandy Land Since the Last Glacial Maximum

AbstractThe Hunshandake Sandy Land (Hunshandake) in central Inner Mongolia, China, is located within the fringe of the East Asian summer monsoon (EASM) domains. Precipitation records in Hunshandake are essential to studying the migrations of the EASM. This work reproduced the precipitation changes since the Last Glacial Maximum (LGM) by measuring the magnetic susceptibility and carbonate content through optically stimulated luminescence dating of two sandy loess profiles within the sandy land to obtain a high‐resolution sedimentary chronological sequence. In addition, eolian topsoil samples were collected along the modern precipitation gradient and their magnetic susceptibility values were compared among the monsoon region, the monsoon marginal region, and the nonmonsoon region. The results demonstrate the following: (1) from 25 to 15 ka, precipitation was low in Hunshandake and exhibited no substantial variability or trend; from 15 to 6 ka, precipitation increased gradually and reached its maximum at approximately 6 ka; and after 6 ka, precipitation decreased again; (2) precipitation changes in Hunshandake since the LGM were mainly determined by the migration of the EASM; and (3) changes in the monsoon migrations in Hunshandake since the LGM are primarily driven by the changes in global ice volume and subordinately by solar radiation.

High‐resolution paleoclimatic records spanning the past 30 cal ka BP inferred from Qionghai Lake sediments in south‐west China: Insights from geochemical investigations and grain‐size characteristics

There have been few high‐resolution investigations covering the last glacial and Holocene from Sichuan, Yunnan, or south Asia area in the south‐west monsoon domain region. High‐resolution analyses of lake sediments retrieved from Qionghai Lake, Sichuan Province, were conducted using a combination of variables including total organic carbon (TOC) and total nitrogen (TN) concentration, low frequency magnetic susceptibility (χLF), particle size, carbonate content, and δ13C value of organic matter (δ13Corg), to provide a new perspective on the detailed paleoclimate history of south‐west China spanning the past 30 cal ka BP. Our findings suggest that organic matter in the Qionghai Lake was mainly derived from microorganisms, aquatic macrophytes, and terrestrial C3 plants. From 29.1 to 23.2 cal ka BP, low carbonate contents, high median grain size (Md values), and χLF values indicated a warm and wet climate. During the period 23.2 to 15.4 cal ka BP, low χLF, Md values, and high carbonate contents suggested a decrease in temperature and humidity. The cold and dry Last Glacial Maximum (LGM) and Heinrich 1 event (H1) were captured between 21.6 and 19.4 cal ka BP and 17.6 and 15.8 cal ka BP, respectively. During the interval 15.4 to 9.7 cal ka BP, low level of χLF values and Md values, together with relatively high carbonates, demonstrated that a dry climate prevailed in this period. Since 9.7 cal ka BP, the climate was warm and humid in the early to mid‐Holocene and shifted towards cold and dry condition in the late Holocene. A cold and dry period at 8.5 to 8.1 cal ka BP and warm and wet interval at 6.6 to 4.6 cal ka BP were identified, corresponding to the 8.2‐ka cold event and Holocene climatic optimum (HCO), respectively. These climate changes may reflect variations of the intensity of the south‐west summer monsoon, primarily in response to the Northern Hemisphere solar insolation on a millennial scale induced by orbital forcing. The position of the Intertropical Convergence Zone (ITCZ) may add a complementary effect on the evolution of the monsoon strength in the Holocene.

Chronostratigraphy of a loess-palaeosol sequence in Biały Kościół, Poland using OSL and radiocarbon dating

Optically stimulated luminescence (OSL) is particularly suitable for providing a numerical timescale necessary for loess to be useful in climatic reconstructions. It is widely accepted that quartz OSL dating using the single-aliquot regenerative dose (SAR) procedure usually yields reliable ages. The current work presents OSL ages derived from coarse (90–125 μm) and medium (45–63 μm) quartz grain size fractions, and post-IR IR290 for polymineral fine grains (4–11 μm). In addition to dating, analyses of the magnetic susceptibility, grain-size distribution, carbonate and organic carbon content were conducted. Previously the profile was dated using single aliquot optically stimulated luminescence (OSL) applied to coarse grained quartz fraction (90–125 μm) only, using the central age model. This analysis yielded unexpectedly young ages for the deepest part of the Biały Kościół loess profile. In the current study, we investigate the differences between the previously obtained results and new results obtained for medium grained quartz and polymineral fine grain fractions. Ages obtained for coarse and medium fractions show no differences up to the equivalent dose of about 150 Gy. In contrast to the younger samples, for the five oldest samples we observe that the results obtained for coarse grained quartz yield ages lower that the medium grained quartz. Those differences reach 25% for the two oldest samples. In addition, the polymineral fine grain fraction yields results very similar to the previously obtained coarse grained quartz ages with the exception of the two oldest samples where the polymineral fraction gives much older results. Those differences between the ages of the two grain size fractions can arise from post-depositional (grain size dependent) sediment translocation processes due to pedo- and bio-turbation and a different efficiency of bleaching of the post-IR signal. Those results, obtained for lithostratigraphic units II and I correspond to MOIS 4 and 5, respectively, confirming the earlier established MOIS chronology and strengthen the chronological correlation of the loess profile at Biały Kościół with other loess profiles in Europe.

Deep-brain magnetic stimulation as add-on treatment to lithium carbonate in the treatment of bipolar depression: study protocol for a randomized, double-blind, sham-controlled trial

Background and objectives: Bipolar disorder is a highly prevalent mental disorder. In clinical practice, mood stabilizers such as lithium carbonate are the conventional treatment for bipolar disorder. However, these drugs have slow onset of action and are not sufficiently effective in the acute phase. Deep-brain magnetic stimulation was hypothesized to have significant therapeutic effects in patients with major depressive disorder by entrainment of neural oscillations. In previous clinical trials, deep-brain magnetic stimulation showed good outcomes in the treatment of unipolar depression. However, randomized controlled trials that verify these results are lacking. Therefore, the current proposal intends to address this issue. Design: A single-center, randomized, double-blind, sham-controlled trial. Methods: Sixty patients aged 18–60 years who have been diagnosed with bipolar disorder at Beijing Anding Hospital, Capital Medical University of China, will be included and randomly divided into experimental and control groups (n = 30 per group). Patients in the experimental group will be treated with deep-brain magnetic stimulation plus lithium carbonate for 2 weeks followed by subsequent treatment with only lithium carbonate for 4 weeks. Patients in the control group will be treated with the same protocol, except they will receive sham stimulation. Outcome measures: The primary outcome measure is the change in score on the 17-Item Hamilton Rating Scale for Depression at weeks 2 and 6. The secondary outcome measures include response rate, complete remission rate (clinical cure rate), and changes in scores on the Hamilton Anxiety Rating Scale, 16-Item Quick Inventory of Depressive Symptomatology Self-Report, Generalized Anxiety Disorder-7, 9-Item Patient Health Questionnaire, Young Mania Rating Scale, Clinical Global Impression-Bipolar Disorder, and Montreal Cognitive Assessment at visit points relative to baseline scores. The safety evaluation indicators are the incidence of adverse events and the rate of manic switch. Discussion: The trial will verify the effectiveness of deep-brain magnetic stimulation with lithium carbonate in the treatment of bipolar disorder, providing evidence as to whether this combined therapy has the potential to be new alternative treatment for bipolar disorder. Ethics and dissemination: The trial was approved by the Ethics Committee of Beijing Anding Hospital, Capital Medical University in China (approval No. 201777FS-2) on October 27, 2017. Design of the trial was completed on June 28, 2017, and the trial registration was completed at the Chinese Clinical Trial Registry on November 10, 2017. Recruitment was initiated in January 2018 and it is expected to be completed in December 2018. Follow-up visit will end in June, 2019. Data analysis will be completed in December 2019. The results of the study will be disseminated through presentations at scientific meetings and/or in peer-reviewed publications. Anonymized trial data will be available indefinitely at www.figshare.com . Trial registration: The trial has been registered with the Chinese Clinical Trial Registry (Registration No. ChiCTR-INR-17013338) and the version number is 2.1.

Sea level and climatic-induced facies variations in the Middle Cambrian House Range Embayment, western Laurentia

The Middle Cambrian House Range Embayment (HRE) represents a deep-water incursion into an extensive carbonate platform along the passive margin of western Laurentia. The distribution and source of HRE mixed siliciclastic-carbonate sediments are poorly understood because many key elements were missed during past field observations or coarse correlation. This study describes the HRE complex lithological variations, and improves current understanding concerning the global climatic and sea level fluctuations that drove these variations. Magnetic susceptibility (χ), gamma radiation (GR) and carbonate content (CaCO3%) are used to construct high-resolution correlation among three overlapping Middle Cambrian marine sedimentary sections: 1) the Drumian Global boundary Stratotype Section and Point (GSSP) in the Drum Mountains, western Utah, 2) the Marjum Pass section in the House Range, western Utah, and 3) the Packrat section Great Basin National Park in the Snake Range, eastern Nevada. Middle Cambrian HRE lithological variations followed broad facies patterns. Carbonate sediments dominated the HRE edges and decreased inward, while shale, dominated the HRE trough and decreased outward. The carbonate/detrital ratio varied along the area between the HRE Edge and trough due to; 1) sea level fluctuations, (2) the depositional setting at each section, and 3) the allocyclic, climatic variations that acted on the carbonate platform of western Laurentia. Sea level and climatic fluctuations drove temporal facies variations that are well correlated among the three sections, while the depositional setting for each section drove spatial facies variations that account for carbonate and detrital sediment sources and their trajectories into the HRE. The GSSP is a shallow trough section; Marjum Pass is a lower slope section of the northern HRE ramp; and the Packrat is a lower slope section situated along the southern HRE ramp. Sea level and climatic cycles during the Middle Cambrian Drumian Stage, induced long-term and short-term facies variations, respectively, that were superimposed on each other.

Atlantic forcing of Western Mediterranean winter rain minima during the last 12,000 years

Abstract The limited availability of high-resolution continuous archives, insufficient chronological control, and complex hydro-climatic forcing mechanisms lead to many uncertainties in palaeo-hydrological reconstructions for the Western Mediterranean. In this study we present a newly recovered 19.63 m long core from Lake Sidi Ali in the North African Middle Atlas, a transition zone of Atlantic, Western Mediterranean and Saharan air mass trajectories. With a multi-proxy approach based on magnetic susceptibility, carbonate and total organic C content, core-scanning and quantitative XRF, stable isotopes of ostracod shells, charcoal counts, Cedrus pollen abundance, and a first set of diatom data, we reconstruct Western Mediterranean hydro-climatic variability, seasonality and forcing mechanisms during the last 12,000 yr. A robust chronological model based on AMS 14 C dated pollen concentrates supports our high-resolution multi-proxy study. Long-term trends reveal low lake levels at the end of the Younger Dryas, during the mid-Holocene interval 6.6 to 5.4 cal ka BP, and during the last 3000 years. In contrast, lake levels are mostly high during the Early and Mid-Holocene. The record also shows sub-millennial- to centennial-scale decreases in Western Mediterranean winter rain at 11.4, 10.3, 9.2, 8.2, 7.2, 6.6, 6.0, 5.4, 5.0, 4.4, 3.5, 2.9, 2.2, 1.9, 1.7, 1.5, 1.0, 0.7, and 0.2 cal ka BP. Early Holocene winter rain minima are in phase with cooling events and millennial-scale meltwater discharges in the sub-polar North Atlantic. Our proxy parameters do not show so far a clear impact of Saharan air masses on Mediterranean hydro-climate in North Africa. However, a significant hydro-climatic shift at the end of the African Humid Period (∼5 ka) indicates a change in climate forcing mechanisms. The Late Holocene climate variability in the Middle Atlas features a multi-centennial-scale NAO-type pattern, with Atlantic cooling and Western Mediterranean winter rain maxima generally associated with solar minima.

Spectral Analysis of a Core from the Sebkha of Sidi Mansour, Southern Tunisia: The Holocene Cyclostratigraphy

The Milancovitch Theory explaining the ancient cyclostratigraphy does not file a case for the Holocene cyclostratigraphy. Instead, other astronomical and oceanographic mechanisms control the cyclicity within Holocene sediment. This work aimed to find out the climatic cyclicity along a core from the sebkha of Sidi Mansour located along the Mediterranean coast in Tunisia, through using different proxies: the magnetic susceptibility, carbonate percentages and chemical elements (Ca, Na, and K). Based on previous radiocarbon and tephrochrnological dating in the study area, the core was estimated to cover the two last millennia with a sedimentation rate of 0.35 mm/yr. This rate allows the elaboration of a depth-age model to carry the spectral analysis. Not all the proxies visualize the same climatic cycles. For instance, the spectral analysis of the magnetic susceptibility and Sodium data visualized a 1000 yr cycle. The spectral analysis of Potassium data did not visualize significant cycles. The spectral analysis of the carbonate percentages and calcium data visualized dual cycles of 1700-700 yr and 493-329 yr respectively. The about 500 yr and 1000 yr cycles are related to Sun activity. Other oceanographic and atmospheric factors could generate other cycles of 1700 yr, 700 yr, 493 yr, and 329 yr. The majority of these cycles were worldwide recorded as interplay between the oceanography and the solar forcing. Contrary to the earth-driven cyclostratigraphy related to orbital parameters and geographical positions, the Holocene cyclostratigraphy is sun-driven.

Preparation and Characterization of Magnetic Carbonate Apatite/Chitosan/Alginate Composite Scaffold

Treatment for bone cancer has begun to be experimented with ferrimagnetic for magnetic induction hyperthermia. On the other hand, composites of bioceramics and biopolymer have been studied for scaffold as these materials resemble the structure of bone. The current study investigated the magnetization of calcium aluminum ferrite magnetic (CaAl4Fe8O19) incorporated in carbonate apatite, alginate and chitosan, that serves as a scaffold. CaAl4Fe8O19 powder were synthesized using calcium nitrate, aluminium nitrate and ferrous chloride using the sol-gel method. Combining the carbonate apatite/chitosan/alginate compoiste and CaAl4Fe8O19using the freeze-dry method has produced carbonate apatite/alginate/chitosan/CaAl4Fe8O19 composite scaffolds. The CaAl4Fe8O19powder and the scaffolds were observed using SEM (scanning electrone microscope) and their magnetization were measured using VSM (vibrating sample magnetometer). It was shown that the scaffold is a composite structure of CaAl4Fe8O19 particles, having diameter ranging from 0.5 to 2 µm, embedded in the pore walls of the carbonate apatite/alginate/chitosan matrix. The saturation magnetization Ms and remanence magnetization Mr of the CaAl4Fe8O19particles were 20 and 2.0 emu/g, whereas, those of the magnetic scaffold were 4.3 and 2.0 emu/gr. The addition of the carbonate apatite/alginate/chitosan composite into CaAl4Fe8O19 decreased the fraction and/or magnetic of the CaAl4Fe8O19 particles.

OSL chronostratigraphy of a loess-palaeosol sequence in Złota using quartz and polymineral fine grains

Loess deposits are one of the most important sources of information about palaeoclimatic changes for the whole Quaternary. In general, loess is typical for cold and dry, periglacial climate and environment. The intercalated palaeosols are indicators of warmer and more humid climate representing interstadials or interglacials. In Poland, loess and loess-like formations occur in the southern part of the country, mostly in the south Polish uplands, i.e. in the Lublin, Sandomierz, and Cracow Uplands. In addition, such deposits are found in the forelands and foothills of the Carpathians and Sudetes. Luminescence dating is one of the leading techniques to establish chronologies for loess-palaeosol sequences and has been successfully applied to different minerals and grain size fractions by several research groups. OSL chronostratigraphy over the last two decades became very popular especially for loess deposits around the world, meaning that there are hundreds of new luminescence dates associated with those deposits. Our investigation is focused on the determination of chronostratigraphy for Polish loess deposits from the last glacial cycle in SE Poland up to about 130 ka. Twenty-one samples from the loess profile in Złota (21°39′E, 50°39′N) were collected for luminescence dating and six for 14C dating. Two different fractions were investigated, the polymineral fine grains (4–11 μm) and silt-sized quartz grains (45–63 μm). In addition, analyses of the magnetic susceptibility, grain-size distribution, carbonate and organic carbon content were conducted. Although further investigations are needed, our results show the suitability of the Polish loess for OSL dating and very good agreement between obtained luminescence and 14C dating results.

Mechanism of Pb(ii) and methylene blue adsorption onto magnetic carbonate hydroxyapatite/graphene oxide

Magnetic carbonate hydroxyapatite was loaded onto GO sheets to obtain a novel adsorbent for the removal of heavy metals and dyes.

Hydrothermal fabrication of magnetic mesoporous carbonated hydroxyapatite microspheres: biocompatibility, osteoinductivity, drug delivery property and bactericidal property.

Implant-associated infection is a serious problem in orthopaedic surgery. Ideal bone filling materials should not only possess excellent biocompatibility, but also have good anti-infection property and osteoinductivity. Herein, magnetic mesoporous carbonated hydroxyapatite microspheres (MHMs) have been fabricated according to the following stages: (i) preparation of CaCO3/Fe3O4 microspheres; and (ii) hydrothermal transformation of magnetic calcium carbonate microspheres into MHMs. MHMs possess well-defined 3D nanostructures constructed by nanoplates as building blocks. The mesopores and macropores exist in and among the nanoplates, respectively. The porous structure makes the MHMs possess a great drug loading efficiency of 73-82%. Gentamicin-loaded MHMs display a sustained drug release property, and the controlled release of gentamicin can prevent biofilm formation against S. epidermidis. Moreover, the MHMs possess a magnetic property with a saturation magnetization strength of 3.98 emu g-1 because Fe3O4 nanoparticles are dispersed in the microspheres. The in vitro cell tests indicate that the magnetic nanoparticles in the MHMs not only promote the cell adhesion and proliferation of human bone marrow stromal cells (hBMSCs), but also stimulate the osteogenic differentiation. MHMs exhibit excellent biocompatibility, osteoinductivity, drug delivery property and bactericidal property, so they have great application potential for the treatment of complicated bone defects.

Geoarchaeological context of the later phases of Mousterian occupation (80–115 ka) at Nesher Ramla, Israel: Soil erosion, deposition and pedogenic processes

A new open-air Mousterian site was found in karst depression on hilly limestone terrain of central Israel at Nesher Ramla. The paper highlights the complex history of depositional, post-depositional and pedogenic processes that took place at the later phases of Mousterian site formation during the OSL age interval between ∼80 and ∼115 ka. The Upper sequence is divided into Unit I and Unit II, both comprising rather uniform calcareous, gravel-rich, silty clay deposits. Gravel largely consists of calcrete (Nari) and possibly some chalky limestone. Unit I is darker, partially decarbonated, magnetically enhanced, and shows microscopic features of shrink–swell process analogous to Vertisols. Mousterian artifacts, chunks of ochre and animal bones are scarce in this unit. Unit II has increased gravel, magnetic susceptibility values drop, and humus and carbonate content both increase. Mousterian artifact density significantly increases in the middle part of Unit II. Lithologic characteristics, thin sections and SEM/EDS all indicate that the Upper sequence originated from periodic erosion of loess-derived soils developed upon chalky hillslopes intermittent with more stable periods when hominins occupied the site. The proposed model relates the Upper sequence to heterogeneous anthropogenic pedosediments with high proportions of eroded soil materials and signs of in situ pedogenesis. Apart from singular mm-sized pyrogenic features, remnants of bedded combustion features in the Upper sequence are lacking, probably because of pedogenic and diagenetic alterations on the site.