Concentration Dependence Of Parameters Research Articles

Machine Learning Allowed Interpreting Toxicity of a Fe-Doped CuO NM Library Large Data Set─An Environmental In Vivo Case Study.

The wide variation of nanomaterial (NM) characters (size, shape, and properties) and the related impacts on living organisms make it virtually impossible to assess their safety; the need for modeling has been urged for long. We here investigate the custom-designed 1-10% Fe-doped CuO NM library. Effects were assessed using the soil ecotoxicology model Enchytraeus crypticus (Oligochaeta) in the standard 21 days plus its extension (49 days). Results showed that 10%Fe-CuO was the most toxic (21 days reproduction EC50 = 650 mg NM/kg soil) and Fe3O4 NM was the least toxic (no effects up to 3200 mg NM/kg soil). All other NMs caused similar effects to E. crypticus (21 days reproduction EC50 ranging from 875 to 1923 mg NM/kg soil, with overlapping confidence intervals). Aiming to identify the key NM characteristics responsible for the toxicity, machine learning (ML) modeling was used to analyze the large data set [9 NMs, 68 descriptors, 6 concentrations, 2 exposure times (21 and 49 days), 2 endpoints (survival and reproduction)]. ML allowed us to separate experimental related parameters (e.g., zeta potential) from particle-specific descriptors (e.g., force vectors) for the best identification of important descriptors. We observed that concentration-dependent descriptors (environmental parameters, e.g., zeta potential) were the most important under standard test duration (21 day) but not for longer exposure (closer representation of real-world conditions). In the longer exposure (49 days), the particle-specific descriptors were more important than the concentration-dependent parameters. The longer-term exposure showed that the steepness of the concentration-response decreased with an increased Fe content in the NMs. Longer-term exposure should be a requirement in the hazard assessment of NMs in addition to the standard in OECD guidelines for chemicals. The progress toward ML analysis is desirable given its need for such large data sets and significant power to link NM descriptors to effects in animals. This is beyond the current univariate and concentration-response modeling analysis.

A high-resolution record of Mid- to Late-Holocene environmental changes from a land-locked lake in Schirmacher Oasis, East Antarctica

We present a high-resolution record of environmental changes during the Mid-Late Holocene obtained from a lake sediment core covering the past 4.87 cal kyr BP in the Schirmacher Oasis, East Antarctica. The magnetic signal of Lake L6 was found to be primarily controlled by catchment-derived ferrimagnetic minerals. The period between 4.87 and 3.35 cal kyr BP is marked by several episodes of cold and warm conditions. Warm and wet conditions prevailed in the region from 3.35 to 2.43 cal kyr BP. Magnetic susceptibility values remained generally low indicating the pedogenic formation of fine magnetic grains. The high values of the chemical weathering indices reflected the warm and wet conditions conducive to chemical weathering. A transition to cold and dry conditions was observed at around 2.43 cal kyr BP, representing the Neoglacial cooling, with high values of magnetic concentration-dependent parameters. Following the Neoglacial period, a return to warm and wet conditions was observed at 1.63 cal kyr BP, coeval with the Medieval Climate Anomaly. Our record shows a Late-Holocene cooling marked by a sudden increase in magnetic susceptibility values, which could represent the Little Ice Age, followed by a shift to warmer conditions near the core top.

Modeling and Analysis of Temperature-Dependent Capacity Degradation in Large Format Lithium-Ion Batteries

The large-format lithium-ion batteries, widely used for electric vehicle applications, are generally characterized by spatial non-uniformities in temperature. The presence of thermal gradients and temperature-dependence of cell parameters are responsible for non-uniform degradation within the battery that leads to poor performance of the battery packs and also poses safety risks. In this work, we aim to develop a detailed physics-based simulation framework to model non-uniform, temperature-dependent capacity degradation within these large format batteries based on the classical pseudo two-dimensional (p2D) battery model. The electrochemical model will be coupled with degradation mechanisms to capture solid-electrolyte interface layer growth, reversible lithium plating, structural disintegration, and volume change within the electrodes on the cell level signatures and usable capacity over charge/discharge cycles. The effects of temperature inhomogeneities will be accounted in the multi-cell simulations at different operating temperatures for individual cells with dynamic currents and temperature and concentration dependent battery parameters as the model inputs.Overall, the primary focus of this study is to capture the effect of spatial temperature variation on battery capacity over cycles and help identify an improved design for the battery module. The model is implemented in an efficient equation-based form for the p2D model and degradation mechanisms with dynamic cell inputs using the mathematical modules in the finite element based solver, COMSOL Multiphysics. This approach enables an easier model development and analysis of the detailed physics and allows an easier implementation of any additional side reaction. The relative contributions of various fade modes have also been compared to understand their competitive interplay over cell cycles. The model predictions are validated with the available experimental data and in-house codes for each case. We believe that this simple yet detailed model can be further developed to be computationally feasible for adoption and implementation in a battery thermal management system.

Rock Magnetic and Mineralogical Properties of Lateritic Soil Profiles Developed on Two Different Parent Rocks in Northern Kerala, South-Western India

The rock magnetic and mineralogical properties of two lateritic soil profiles developed on two different parent rocks (khondalite and granite) in northern Kerala, south-western India were investigated to better understand pedogenic processes under tropical climate. Field investigations reveal the presence of various horizons in the lateritic profiles, such as saprolite, mottled zone, pebble horizon and top soil. The particle size, rock magnetic, Vibrating Sample Magnetometer (VSM), Scanning Electron Microscopy (SEM)-Energy-Dispersive X-ray Spectrometer (EDS) and X-Ray Diffraction (XRD) analyses were performed on samples collected from different horizons of the two profiles. Magnetic susceptibility (χlf) values of the lateritic profiles vary from 9.97 to 1717.04 x 10-8 m3 kg-1, with the granitic profile exhibiting overall higher values. The percentage frequency-dependent susceptibility (χ %) ranges between 0 % and 13.9 %. The XRD data reveal the presence of kaolinite, gibbsite (except for top soil layer) and quartz along with magnetic minerals like magnetite, hematite and goethite. The upper horizons (top-soil and pebble horizon) exhibit high values for concentration dependent magnetic parameters like χlf and χfd%, whereas, the lower horizons (saprock, saprolite, pallid zone horizons) exhibit low values. The tropical soils in the region have undergone a higher degree of pedogenesis with increased magnetic mineral concentration compared to temperate soils. The magnetic enhancement in the topsoil may be due to the neoformation of ultra fine-grained SP magnetite/maghemite (with minor anti-ferro magnetic component), aided by sufficient Fe supply, alternate wetting and drying cycles, dehydration, oxidation and redox conditions. Keywords: Lateritic Soils; Soil Magnetism; XRD; SEM; Magnetic Enhancement; Pedogenesis; Southern India

Investigation on high-energy Si anode mechanical-electrochemical-thermal characteristic under wide temperature range

Studying the cyclic evolution of high-energy Si anode, including the mechanical deformation, voltage hysteresis, heat generation and temperature response, is of great significance for its performance and safety. In this paper, a novel coupled semi-analytical model is developed to investigate the mechanical-electrochemical-thermal characteristic of Si particle anode. This model is adopted a series of temperature and concentration dependent parameters related to electrochemical reaction and Li+ diffusion. The results show that Li+ diffusion process will be limited at a lower initial temperature, which may increase the elastic–plastic stress. Thus, the stress-induced voltage hysteresis is more evident, resulting in the capacity loss and polarization heat increase. In the aspect of thermal behavior, the heat generation during lithiation is more than that during delithiation at each initial temperature, and the total heat accumulation after one cycle is greater at a higher initial temperature. Besides, the asymmetrical elastic–plastic deformation and heat accumulation during cyclic lithiation/delithiation may lead to ratcheting deformation of the Si particle electrode. The ratcheting deformation will be aggravated at a lower temperature. Additionally, the effects of charging rates (0.2C, 0.5C and 1C) are also discussed. The increased charging rate leads to a steeper concentration gradient, the more obvious asymmetrical elastic–plastic deformation, and earlier reaching the cut-off voltage. The electrode will produce more heat in a short time in the case of fast charging, and the resulting self-heating accumulation will affect its thermal stability. Based on this, ratcheting deformation at a fast charging rate is more severe, which will further decrease the mechanical stability of the Si electrode. The theoretical results are verified by the experiments. This study provides a theoretical and experimental basis for understanding the comprehensive performance of high-energy lithium-ion batteries, as well as design and management guidance.

Dynamics of post-occlusion water diffusion in stratum corneum

Diffusion of water through membranes presents a considerable challenge, as the diffusivity often depends on the local concentration of water. One particular example with strong biological relevance is the stratum corneum (SC) as the primary permeability barrier for the skin. A simple alternative for the constant diffusivity model is provided by the Fujita’s two-parameter rational approximation, which captures the experimentally observed fact that the SC diffusion constant for water increases with increasing the water concentration. Based on Fick’s law of diffusion, a one-dimensional concentration-dependent diffusion model is developed and applied for the analysis of both the steady-state transepidermal water loss (TEWL) and the non-steady-state so-called skin surface water loss (SSWL) occurred after removal of an occlusion patch from the SC surface. It is shown that some of the age-related changes in the SSWL can be qualitatively explained by the variation of the dimensionless Fujita concentration-dependence parameter.

Bursera fagaroides bark as a bioindicator for air particle pollution using magnetic properties

Shrub barks can accumulate airborne particles and seem to be suitable biological monitors for assessing air pollution. We studied the bark of the species Bursera fagaroides as a biomonitor of air pollution in an urban area of Mexico. Samples were collected in dry and rainy seasons during 2011 and 2012, in 28 sites which are exposed to magnetic pollutants emitted by different human activities (industrial point-sources and vehicular emissions). Environmental magnetism studies allow determining mineralogy, concentration and grain size of magnetic particles accumulated in barks, providing information on the sources and characteristics of their emitted particles. Magnetic properties of all samples were determined by environmental magnetism method. The highest values of magnetic concentration dependent parameters were observed in industrial and vehicular traffic sites. The mean values of saturation of isothermal remanent magnetization SIRM for dry seasons are two to threefold (SIRM = 0.8–1.2 × 10−3Am2kg−1) the mean value for rainy season (SIRM = 0.4 × 10−3Am2kg−1). The integrated magnetic analysis indicates the presence of ferrimagnetic minerals, mostly magnetite-like (remanent coercivity Hcr = 31.6–38.7 mT) particles of small sizes (1 – < 0.1 μm). Selected samples were observed by scanning electron microscopy, revealing the presence of such iron-rich particles hosted in species’ lenticels. These results demonstrate the usefulness of the species' cortex as a biomonitor of air pollution, with an affordable and immediate application, and raise new questions about what type of physiological mechanism is involved for trapping magnetic particles.

Magnetic properties of surface sediments in Schirmacher Oasis, East Antarctica: spatial distribution and controlling factors

PurposeWe investigated the magnetic properties (abundance, grain size, and mineralogy) of iron oxides present in Lake L-55 sediments, Schirmacher Oasis, East Antarctica, with an aim to understand their spatial distribution and the underlying mechanisms that control their formation and distribution.MethodsTwenty-five surficial sediments retrieved from different parts of Lake L-55 were subjected to the entire range of environmental magnetic (magnetic susceptibility, anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM)) measurements (at different field strengths). Inter-parametric ratios (χARM/SIRM, χARM/χlf, χARM/χfd, IRM20 mT/SIRM, IRM20 mT/ARM, S-ratio, L-ratio) provided insights into the magnetic properties (abundance, grain size, and mineralogy of iron oxides). Scanning electron microscopic-energy dispersive X-ray spectroscopic (SEM-EDS) analysis was performed on magnetic extracts from a few sediments. Besides, organic matter (%) was also calculated for the sediment samples. Principal component analysis was performed to gain information on the presence of different components and their relative dominance.ResultsThe iron oxides are strongly magnetic (high values of concentration-dependent parameters). The principal iron oxide is magnetite (S-ratio > 0.90) which is coarse-grained (multi-domain (MD) and stable single-domain (SSD) grains), and there is no influence of authigenic greigite, bacterial magnetite, and anthropogenic magnetite. The mineralogy is confirmed by SEM-EDS data. The iron oxides are of different grain sizes, and their contribution is in the order of MD > SSD > SP as shown by the principal component analysis. Pedogenic iron oxide minerals seem to be present in the samples whose formation is due to the oxidation of magnetite into hematite. However, they are of SSD size and not SP, suggesting that the intensity of pedogenesis is not sufficient to form SP grains.ConclusionThe iron oxide minerals are mainly terrigenous, and the biogenic activity within the lake is not sufficient to modify the ferrimagnetic minerals. Spatial distribution patterns suggest the non-uniform distribution of magnetite/titanomagnetite of varying sizes in the lake basin which is transported by both melt water streams and winds.

Authigenic Ferrimagnetic Iron Sulfide Preservation Due to Nonsteady State Diagenesis: A Perspective From Perseverance Drift, Northwestern Weddell Sea

AbstractWe document magnetic mineral diagenesis with high‐resolution magnetic susceptibility, hysteresis, isothermal remanent magnetization, and other rock magnetic measurements through a shallow sulfate‐methane transition (SMT) at Perseverance Drift—a high‐accumulation rate Holocene biosiliceous Antarctic marine sediment deposit. The structure of the SMT is defined with porewater measurements from the same core, allowing direct comparison. Dissolution of the detrital (titano)magnetite assemblage, with preferential dissolution of stochiometric magnetite, occurs in the upper SMT. Higher coercivity magnetic minerals dissolve more slowly, continuing to dissolve through the entire SMT and could be a source of ferric iron for microbial respiration following exhaustion of porewater sulfate, as suggested by accumulation of porewater ferrous iron below the SMT. Superparamagnetic ferrimagnetic mineral enrichment/depletion occurs in three phases through the SMT and is coupled tightly to the availability of dissolved ferrous iron relative to dissolved sulfide. High concentrations of authigenic remanence‐bearing iron sulfides, including greigite and hexagonal 3C pyrrhotite, which can be detected using remanence parameters but not in‐field concentration dependent parameters, accumulate in a transient horizon at the base of the SMT during this early diagenesis, where sulfide is present but limited relative to dissolved ferrous iron. Formation of this remanence‐bearing iron sulfide horizon is likely facilitated by continued iron reduction through the SMT. Nonsteady state perturbations that shift the porewater profile, such as changes in carbon flux or sedimentation rate, can lead to preservation of these transient horizons, much like well documented preservation of manganese oxide layers in marine sediments following similar shifts to porewater profiles.

Closed-system transposon-mediated manufacture of GMP grade CAR T-cells via the Lonza Nucleofector LV XL

Background & Aim A method for the non-viral transposon based manufacture of CAR19.41BBz T-cells for the Phase I CARTELL (UTN: U1111-1204-6974) and AUTOCAR19 (U1111-1226-8682) clinical trials has previously been described. The original method was non-Good Manufacturing Practice (GMP) standard, and used a traditional open-container electroporation system. The method presented here is a modification of the original method to GMP standard to incorporate the fully enclosed Lonza 4-D Nucleofector LV Unit XL cartridge system and eliminate open-container cell handling and processing. For GMP applications, closed electroporation systems are preferable to open-container systems, such as the older 4-D X-unit nucleocuvettes offered by Lonza, as they reduce the risk of product contamination. Methods, Results & Conclusion Buffy coats were extracted from whole blood via Sepax 2 and the CD4+/CD8+ T-cell fraction obtained via immunomagnetic cell selection (Miltenyi). The T-cells were washed, resuspended in P3 Nucleofector Solution and sequentially nucleofected with CAR19.41BBz transposon plasmid DNA in Nucleofector LV XL cartridges. The cells were directly ejected immediately post-nucleofection into AIM V conditioned media for subsequent stimulation with gamma-irradiated antigen presenting cells and G-Rex culture expansion up to 15 days. Both the piggyBac and piggyBat transposon/transposase systems were tested. Transposase delivery via either DNA plasmid or mRNA was also tested. While some aspects of nucleofection protocols previously established on Lonza's 4-D Nucleofector X-Unit nucleocuvettes were directly transferrable to the LV Unit's XL cartridge-based consumables, other parameters must be modified and re-optimized to adapt to the demands of the LV's liquid handling system. In particular, while the X-cuvettes are capable of successfully nucleofecting cell suspensions of relatively high concentration (2 × 108/ml), the LV XL demands more dilute cell suspensions to decrease the risk of blockages within the tubing and minimize cell product retention within the cartridge electrodes. Staged addition of mRNA volumes via the secondary input line must also be taken into consideration, and other concentration-dependent parameters must be re-optimized accordingly. This modular method is flexible, efficient, and robust. It allows cost-effective manufacture of non-viral genetically-modified T-cell products at clinical point-of-care.

Vapor pressures and activity coefficients of 2,2,2-trifluoroethanol in binary mixtures with 1,3-dimethyl-2-imidazolidinone and 2-pyrrolidone

The vapor pressures of two binary mixtures containing 2-trifluoroethanol (TFE) + 1,3-dimethyl-2-imidazolidinone (DMI) and TFE + 2-pyrrolidone (PYR), were investigated at temperatures T = (274.15 to 423.15) K using two different static method installations. Both combinations were modelled using an extended Clausius-Clapeyron equation with concentration dependent parameters and the NRTL equation with temperature dependent parameters. The best fit was obtained using the NRTL equation. • Two high-accuracy static experimental set ups were used. • An extended Clausius–Clapeyron type equation has been developed. • The NRTL activity coefficient model was developed.

Investigations of rare earth doped CdTe QDs as sensitizers for quantum dots sensitized solar cells

Gd doped CdTe (Gd:CdTe) QDs sensitized working electrodes were fabricated for QDSSC applications. In this fabrication process, mercapto succinic acid capped Gd:CdTe QDs were synthesized by colloidal method and used as the sensitizer. Improved optical properties of the prepared QDs were examined by optical absorption and emission spectral analysis. Fluorescence quantum yield measurement reveals that 10% Gd:CdTe QDs shows the highest quantum yield of 67%. XRD analysis confirms the cubic zinc blende crystalline structure of the prepared QDs and the dopant concentration dependent cell parameters and crystallite sizes were revealed. Performance of capping molecules over the prepared QDs was analyzed by FT-IR studies. Enhanced photovoltaic performance of prepared pure and doped QDs was analyzed through J-V characteristic curves, which show better photovoltaic response with an efficiency of 2.24% for 10% Gd:CdTe QDs.

Magnetic parameters as proxies for anthropogenic pollution in water reservoir sediments from Mexico: An interdisciplinary approach

We assess the element pollution level of water reservoir sediments using environmental magnetism techniques as a novel approach. Although “La Purísima” Water Reservoir is an important source for multiple activities (e.g. recreational, fishing and agricultural) in Guanajuato state, it has been receiving for the last centuries a high load of pollutants by mining extraction, urbanization and land-use change from the Guanajuato Hydrological Basin. The analyses of environmental magnetism, geochemistry, X-ray energy dispersive spectroscopy, scanning electron microscopy and multivariate methods were applied to study sediments from the reservoir and basin. Accordingly, they indicate the presence of iron oxides (magnetite and hematite) and iron sulfides (pyrite and greigite), which evidences relevant differences in particle size and concentration within the water reservoir (median mass-specific magnetic susceptibility χ = 23.2 × 10−8 m3/kg), as well as with respect to the river basin sediments (median χ = 88.8 × 10−8 m3/kg). The highest enrichment factor EF values (median values of EF = 2–10 for As, Co, Ba, Cu, Cd, Ni and EF > 20 for S) are mainly associated with historical mining activities that have led to an enrichment of potentially toxic elements on these water reservoir sediments. We propose the use of concentration and grain size dependent magnetic parameters, i.e. χ, remanent magnetizations and anhysteretic ratios ARM/SIRM and χARM/χ, as proxies for Ba, Co, Cr, Ni, P and Pb pollution in these river and water reservoir sediments. Such parameters allow to evaluate this sedimentary environment, and similar ones, through useful and convenient proxies.

Rock magnetic signature of a Miocene playa cycle in Central Asia and environmental implications

The increased aridification of Central Asia during the Miocene coincides in time with lake formations and the evolution of playa environments in the region. However, Miocene continental climate dynamics and the forcing of aridification are still not well constrained. Neogene lacustrine mudflat deposits in the Ili Basin in southeast Kazakhstan provide a well-exposed paleoclimate archive. Here, we present a detailed rock magnetic study of a middle Miocene playa cycle deposited in a closed basin. We use high-resolution rock magnetic parameters, lithological studies and geochemistry to reconstruct the playa environment and the depositional conditions. The rock magnetic mineralogy of the playa cycle is controlled by hematite and two fine-grained magnetite phases. Increased magnetic concentrations occur during dry mudflat conditions, with a lower groundwater table and increased aridity. The underlying processes controlling the observed variation in magnetic concentrations are a complex interplay of diagenetic processes during and after deposition. The data support an authigenic origin of both magnetite phases, one formed before and the other after sediment consolidation. Early diagenetic formation of fine-grained magnetite by microbial activity is followed by post-depositional formation of a secondary fine-grained magnetite phase. The rock magnetic results such as magnetic concentration-dependent parameters, ARM/SIRM and s-ratio indicate a sensitive record of (ground) water availability and aridity changes in the Ili Basin. We suggest that they can serve as an effective proxy for detailed paleo-environment reconstruction of playa evolution, not only in the middle Miocene Ili Basin but also in comparable floodplain/playa lake settings.

Magnetic properties and correlation with heavy metals in mangrove sediments, the case study on the coast of Fujian, China

To characterize the magnetic signature of sediment heavy metal contamination and identify sources of heavy metals in mangroves, 83 sediment specimens were collected from three mangroves in Fujian, China; various magnetic parameters and heavy metal concentrations were then determined. Variation in magnetic magnetization among specimens was linked to changes in pseudo-single-domain magnetite. Average values of Co, Cu, Ni, and Zn (but not Cr or Pb) were slightly lower than background levels. Geochemical evidence suggested that Co, Cr, Ni, Ti, and V were associated with lithogenic minerals in the sediment, while Cu, Pb, and Zn were associated with terrigenous minerals. A strong positive correlation was seen between magnetic concentration-dependent parameters and metal concentrations (Cu, Pb, and Zn), suggesting enrichment of metal-containing magnetic minerals with heavy metal pollution. The combined assessment of both sediment magnetic properties and heavy metal concentrations thus provides insight into the pollution status of mangrove sediments under complex conditions.

Combined magnetic, chemical and morphoscopic analyses on lichens from a complex anthropic context in Rome, Italy

Native and transplanted lichens were analyzed as bioaccumulators of airborne particulate matter (PM) in an eastern district of Rome, Italy, where frequent fraudulent fires are set to recover metals, mostly copper, from waste electrical and electronic equipment (WEEE). The presence of native lichens was scarce, due to the drought of spring-summer 2017, thus, sampling was extended to a neighboring area for toughening the dataset to a similar context. The magnetic analyses revealed intense properties connected to the anthropic complexity of the zone, where industrial, traffic and arson-related dusts are emitted and bio-accumulated. Magnetic and chemical analyses were compared, leading to significant linear correlations between the concentration dependent magnetic parameters (susceptibility, saturation magnetization and saturation remanence) and the concentration of heavy metals, among which copper, chrome, lead and zinc. Moreover, selected magnetic particles were chemically and morphologically characterized by Scanning Electron Microscope and Energy Dispersion System microanalyses. Magnetic particles resulted incorporated into the lichens' tissues and their composition, morphology and grain size strongly supported their anthropogenic, mostly combustion-related, origin. Even if, given the complexity of the area, it was not feasible to fully discriminate the multiple anthropogenic sources, magnetic biomonitoring of lichens, especially when combined with microtextural and compositional analyses, confirmed to be an excellent methodology for a rapid characterization of environmental pollution.

Abstract 3890: Pharmacodynamic and proteomic analysis of combined gemcitabine/nab-paclitaxel in patient-derived pancreatic cancer xenograft models

Abstract Gemcitabine (GEM) combined with albumin-bound paclitaxel nanoparticles (nab-PTX) is the first-line therapy for patients with metastatic pancreatic adenocarcinoma (PDAC). However, the in vivo mechanisms of drug action and interaction have not been investigated quantitatively for this combination. We evaluated the effects of GEM (100 mg/kg iv weekly) and nab-PTX (equivalent to 30 mg/kg PTX iv weekly), alone or combined, on tumor volume progression in 3 patient-derived xenograft (PDX) PDAC models in SCID mice. The MS1-based quantitative proteomic analysis (IonStar), which offers highly reproducible and accurate quantification with extremely low missing data (&amp;lt;0.5%), was conducted on Days 1, 4, and 8 after dosing to evaluate tumor pharmacodynamic responses in protein expression. Proteins were quantified based on species-specific peptides in order to identify responses of the PDAC cells (human) and tumor-associated stromal cells (murine). A population pharmacokinetic/pharmacodynamic model was developed to quantify tumor growth inhibition by the individual and combined drugs. Tumor growth kinetics were described by a composite function of exponential growth transitioning to linear growth. Treatment effects were represented by a 2nd-order, concentration-dependent parameter k that leads to cell death following delays arising from signal transduction. All 3 PDX models responded to the combination therapy, but with different sensitivities. PDX#14312 showed the least inhibition by the drugs alone (k[GEM]=13.6, k[PTX]=37.0 /day/mM), compared to the other PDXs (#18254: k[GEM]=68.1, k[PTX]=125; 18269: k[GEM]=112, k[PTX]=51.2 /day/mM). Compared to the more potent single-drug treatment for each PDX, the combination resulted in 1.33-fold greater cell death in #14312, 1.39 fold in #18269 and 1.19 fold in #18254. Model simulations showed distinct temporal profiles of cytotoxic signals in the 3 PDXs. Pathway analysis showed that the top changes mediated by the drug combination in PDX#14312 PDAC cells included extracellular matrix organization (FDR-corrected p-value = 7E-5), synthesis of nucleotide di- and triphosphates (p = 0.012), and interferon signaling (p = 0.04), whereas top changes in stroma included increased platelet activation (p = 3.8E-4) and extracellular matrix organization (p = 0.046). These processes represent potential contributors to the resistance of PDX#14312 to the drug combination. Top changes in #18269 and #18254, which were sensitive to the combination, included increased glycolysis (p = 0.038), decreased fatty acid beta-oxidation (p = 3E-5) and DNA replication (p = 0.0058) in PDAC cells, and increased complement activation (p &amp;lt; 1E-5) in stroma. Overall, inter-patient variability in PDAC responsiveness to GEM/nab-PTX therapy may be associated with tumor stress responses partially resembling wound healing processes. Citation Format: Jin Niu, Xue Wang, Shichen Shen, Ju Qu, Donald Mager, Robert M. Straubinger. Pharmacodynamic and proteomic analysis of combined gemcitabine/nab-paclitaxel in patient-derived pancreatic cancer xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3890.

Environmental magnetic record of a ~ 3000-years subalpine peat core from the western Nanling Mountains, South China

A 95-cm subalpine peat core from the Daping Swamp, located in the transition zone between the middle and southern subtropical regions of China, provides an environmental mineral magnetism record over the past ~ 3000 years. Magnetic concentration-dependent parameters [i.e. magnetic susceptibility (χlf), anhysteretic susceptibility (χARM), and saturation isothermal remanent magnetization (SIRM)] and grain size-dependent parameters [i.e. percentage frequency-dependent susceptibility (χfd%), SIRM/χlf, and χARM/χlf] of core and catchment sediments were measured to characterize provenance and catchment processes. Multi-magnetic parameters revealed that the primary magnetic minerals in the peat samples were mainly detrital magnetic minerals, which originated from catchment surface soil erosion. Changes in vegetation coverage as well as pedogenesis induced by rainfall variation play an important role in controlling the input of magnetic materials. Therefore, we infer that variations of magnetic features in the core bear potential to elucidate the history of environmental changes in the past ~ 3000 years, which are closely related to Asian summer monsoon evolution. Multiple parameters revealed that in three periods (i.e. 2700–2500, 1600–1000, and 500–300 cal year BP), decreased pedogenesis intensity and increased erosion induced by decline in vegetation coverage under dry conditions led to increased input of magnetic minerals, especially the coarser minerals in peat samples. However, in the two periods (i.e. 2500–1600, and 1000–500 cal year BP), multi-magnetic proxies indicate increased pedogenesis and decreased input of magnetic minerals dominated by fine-grained magnetic minerals caused by increased vegetation coverage under relatively wet and warm conditions. These climatic periods are of broad regional consistence across the world. The general trend of the late Holocene climate revealed by magnetic parameters confirms the sensitivity of environmental magnetism in this peat succession from the subalpine western Nanling Mountains to the climatic/environmental variability in the Asian summer monsoon region.

Miocene Glacial Dynamics Recorded by Variations in Magnetic Properties in the ANDRILL‐2A Drill Core

AbstractDuring the 2007 ANtarctic geological DRILLing (ANDRILL) campaign in the Ross Sea, Antarctica, the AND‐2A core was recovered through a stratigraphic succession spanning 1,138.54 m of Neogene sedimentary rocks that include an expanded early to middle Miocene sequence. The study reported here focuses on the magnetic properties of the interval from 778.63 m below sea floor (mbsf) to 1,138.54 mbsf, which comprises a time interval spanning 1.5 Myr, from ~18.7 to ~20.2 Ma. We recognize three main pulses of increased input of magnetic materials to the drill site between 778.34–903.06, 950.55–995.78, and 1,040–1,103.96 mbsf. Trends in the magnetic mineral concentration dependent parameters mirror changes in the proportion of sediments derived from McMurdo Volcanic Group rocks. We suggest that these pulses in magnetic mineral concentration reflect changes in sediment transport processes associated with changing glacial conditions at the drill site that included (1) subglacial and grounding zone proximal settings, (2) hemipelagic and neritic conditions with abundant sediment‐rich icebergs, and (3) grounding zone‐distal environment that was covered by land‐fast multiyear sea ice or a fringing ice shelf. The magnetic minerals record preserved in the AND‐2A core supports other data that indicate a highly dynamic and variable coastal environment during the early Miocene, where glaciers retreated inland under warm climatic conditions and advanced beyond the drill site across the continental shelf when cold climate prevailed.

Rock-magnetic and paleomagnetic study on a 27-m-long core from Lake Chapala, western Mexico: Paleoenvironmental implications for the last 10 ka

We report detailed rock-magnetic and paleomagnetic results from a 27-m-long sedimentary core collected at depocenter of Lake Chapala, western Trans-Mexican Volcanic Belt. Rock-magnetic parameters point to PSD grain-size titanomagnetites as the dominant magnetic mineralogy. Observed variations, in both concentration and grain-size dependent magnetic parameters, reflect changes in the sediment supply through the studied depth, but mainly during the last half century. Stable characteristic remanent magnetization, representative of secular variation of the geomagnetic field, was retrieved after alternating field demagnetization of the natural remanent magnetization (NRM). The comparison of the obtained magnetic inclination and declination logs against the corresponding curves predicted by the Global Geomagnetic Field Model SHA.DIF.14k enables to establish an alternative sedimentation-rate independent age-depth model for the whole core, in reasonably good agreement with the one calculated using conventional radiocarbon dating. This approach works not only for Lake Chapala, but also for Lake Chalco. The correlation established between rock-magnetic parameters and paleoenvironments, based on diatom identification of representative samples within specific zones, can be considered as a novel proxy methodology. This approach opens a new perspective for new, more detailed rock-magnetic, paleomagnetic and paleoenvironmental investigations for better paleoclimatic reconstructions.