Fast and pervasive diagenetic isotope exchange in foraminifera tests is species-dependent

Oxygen isotope compositions of fossil foraminifera tests are commonly used proxies for ocean paleotemperatures, with reconstructions spanning the last 112 million years. However, the isotopic composition of these calcitic tests can be substantially altered during diagenesis without discernible textural changes. Here, we investigate fluid-mediated isotopic exchange in pristine tests of three modern benthic foraminifera species (Ammonia sp., Haynesina germanica, and Amphistegina lessonii) following immersion into an 18O-enriched artificial seawater at 90 °C for hours to days. Reacted tests remain texturally pristine but their bulk oxygen isotope compositions reveal rapid and species-dependent isotopic exchange with the water. NanoSIMS imaging reveals the 3-dimensional intra-test distributions of 18O-enrichment that correlates with test ultra-structure and associated organic matter. Image analysis is used to quantify species level differences in test ultrastructure, which explains the observed species-dependent rates of isotopic exchange. Consequently, even tests considered texturally pristine for paleo-climatic reconstruction purposes may have experienced substantial isotopic exchange; critical paleo-temperature record re-examination is warranted.

Composite microbialites: Thrombolite, dendrolite, and stromatolite associations in a modern environment, Pozo Bravo lake, Salar de Antofalla, Catamarca Puna, Argentina

ABSTRACT Pozo Bravo is a high-altitude Andean lake that harbors modern microbialites thriving in hypersaline conditions in the Salar de Antofalla, one of the driest sites on Earth and located in the Puna region of Catamarca, northwest Argentine. Due to the lake physiography, microbialites are restricted to a narrow belt following Pozo Bravo lake variations. Microbialites exhibit a wide range of external morphologies including domal, discoidal, tabular, and horseshoe-like bioherms which vary considerably in size, as well as large biostromal terraces. As documented by other studies on modern microbialites, external morphology appears to be mainly the product of the environmental setting. In Pozo Bravo lake, high evaporation rates and hypersalinity (driven by high temperature and strong winds), water-level fluctuations, and lake-bottom topography are major controlling factors. The distinctive feature of Pozo Bravo microbialites is their internal structure, showing a gradual transition from a thrombolitic core to dendrolitic structures and to a sharply overlying stromatolitic layer within a single microbialite. We suggest that these various microbialite textures represent a gradual change within an environmental gradient based on lake-level variations, and the influence of these environmental factors on biological activity, mainly by cyanobacteria and diatoms. The study of this site is particularly relevant given that it represents an active system where progressive changes in microbialite type (from thrombolites to dendrolites and stromatolites) are recorded, providing an excellent natural laboratory to study these textural changes from a mechanistic perspective, and it may provide insights for better understanding of the microbialite geological record. In addition, given that these systems are threatened by human activities (mining of lithium-rich brines), its study and preservation are necessary.

Hardness and Texture of Electrolytic Copper Processed by ECAP at Ambient and Warm Temperature

Among several severe plastic deformation (SPD) methods, the Equal Channel Angular Pressing (ECAP) process is one of the most popular. This process's main characteristic is producing materials with ultra-fine or nanometric grains. Due to these microstructural changes, it is possible to improve mechanical properties such as strength and ductility. In this perspective, the aim of the present work was to evaluate the variations of the mechanical hardness property associated with microstructural and textural changes of pure copper as a function of its processing by SPD via ECAP. For this, the material was submitted to four passes through routes A (the sample is repetitively pressed without any rotation between each pass) and Bc (the sample is rotated in the same sense by 90° between each pass) at cold and warm temperatures. Through the obtained result, it was verified that the ambient temperature of the Bc route was the one that promoted greater homogeneity in the microstructure and weakening of the texture after the fourth pass. On the other hand, warm processing of copper by ECAP promoted a softening of the samples and a homogeneous distribution of hardness in both routes.

Preliminary Results for Improving the Colloidal Stability of Sunflower Tahini and Halva Products by Wax Based Oleogelation Mechanism

Halva is a confectionery product based on nougat and different oilseeds paste called tahini. The oil separation during storage has been considered a normal and natural phenomenon, but current trends consider this process a defect that gives a depreciated commercial appearance. Thus, the aim of this work was to assess the influence of edible waxes addition on the stability, textural changes, and sensorial acceptance of sunflower halva. Firstly, tahini samples containing several waxes (sunflower, carnauba, rice bran and beeswax) in different concentrations (1%, 2%, 3%) were prepared and their textural parameters and colloidal stability (CS) during storage was determined. The samples (excepting the 1% containing beeswax) demonstrated higher CS (p<0.05) as compared to the reference prepared without wax. The main effects: wax type and storage time, accounted 51.64%, and 18.58%, respectively of the tahini CS variability. When it comes for the halva, the CS of all samples containing different waxes (excepting the sample with 1% beeswax) showed statistically significant (p<0.05) higher values in comparison to the reference which registered the lowest CS (94.06%).

Automated differentiation of Alzheimer’s condition using Kernel Density Estimation based texture analysis of single slice brain MR images

Computer-assisted tools can aid in the detection of Alzheimer disease (AD) which is a progressive neurodegenerative disorder that can lead to cognitive impairments and eventually death. The accumulated effects due to AD can cause changes in the appearance of grey matter, white matter and cerebrospinal fluid in brain Magnetic Resonance (MR) images. This study aims to use Kernel Density Estimation (KDE) technique to analyse the textural changes from single slice brain MR images for the detection of AD. The preprocessed, skull stripped T1-weighted MR brain images are obtained from the publicly available OASIS database. A single axial slice per subject is chosen from a volumetric image for further processing to reduce the computational load. Multivariate KDE technique is applied to each pixel, by considering the changes in the neighbourhood based on selected bandwidth to obtain corresponding density estimates. Statistical features quantifying the distribution of density estimates are extracted to characterise textural variations in images. Linear discriminant analysis (LDA) classifier is implemented with ten-fold cross-validation for detecting AD. An optimum bandwidth of 18 for the KDE technique is selected based on the classification performance. Out of seven extracted texture features, three are found to be statistically significant in distinguishing AD. The classification with LDA yields an accuracy of 72.3% with a sensitivity of 80.6% for identifying AD from healthy subjects. The proposed method is efficient in detecting AD by revealing the textural changes within the brain slice without the involvement of any segmentation technique. Thus, the novel KDE-based texture analysis proves to be an effective tool for the automated diagnosis of AD from single slice brain MR images.

Development of Freeze-Thaw Stable Starch through Enzymatic Modification

The use of unmodified starch in frozen foods can cause extremely undesirable textural changes after the freeze-thaw process. In this study, using cyclodextrin glucanotransferase (CGTase) and branching enzymes, an amylopectin cluster with high freeze-thaw stability was produced, and was named CBAC. It was found to have a water solubility seven times higher, and a molecular weight 77 times lower, than corn starch. According to the results of a differential scanning calorimetry (DSC) analysis, dough containing 5% CBAC lost 19% less water than a control dough after three freeze-thaw cycles. During storage for 7 days at 4 °C, bread produced using CBAC-treated dough exhibited a 14% smaller retrogradation peak and 37% less hardness than a control dough, suggesting that CBAC could be a potential candidate for clean label starch, providing high-level food stability under repeated freeze-thaw conditions.

Determination of the Best Method of Dehydration of Tropical Fruits to be Incorporated in Gelatin-based Dessert with Unaltered Sensory Qualities

Background: Jelly based desserts are very popular among millions of people worldwide. The main gel forming ingredient used in these products is ‘Gelatin’, which is a complex polysaccharide in their chemical structure. This research study focusses on incorporation of fruit pieces in to the dessert jelly in order to give a novel experience to the consumers. Methods: To determine the best way of incorporating fruit pieces in a commercially available jelly mixture (which is made up of fruit flavour, acid, water, sugar and pectin as the jelling agent), fruit pieces were treated in two ways and compared for the best textural and sensory qualities. First sample constituted unblanched, oven dried fruit pieces in a commercially available jelly mixture and its was compared with a jelly sample with blanched (fruit pieces were pretreated to minimize any possible discolorations and textural changes), osmo air dehydrated and oven dried fruit pieces. Sensory qualities such as texture, mouth feel and flavour of two different samples were gauged through a sensory test. Result: From a sensory test carries out by a panel of 09 sensory panelists it was found that the jelly mixture when incorporated with osmo air dehydrate fruit pieces it did not degrade the texture of the final product as opposed to unblanched dried fruit pieces does. The osmo air dehydrated fruit pieces in the prepared jelly has a texture and an acceptable mouth feel which is closer in texturally to the natural mouth feel and the taste, when they are reconstituted inside the jelly mixture by absorbing the water from the mixture.

Thermochronology of Alkali Feldspar and Muscovite at T > 150 °C Using the 40Ar/39Ar Method: A Review

The 40Ar/39Ar method applied to K-feldspars and muscovite has been often used to construct continuous thermal history paths between ~150–600 °C, which are usually applied to structural and tectonic questions in many varied geological settings. However, other authors contest the use of 40Ar/39Ar thermochronology because they argue that the assumptions are rarely valid. Here we review and evaluate the key assumptions, which are that (i) 40Ar is dominantly redistributed in K-feldspars and muscovite by thermally-driven volume diffusion, and (ii) laboratory experiments (high temperatures and short time scales) can accurately recover intrinsic diffusion parameters that apply to geological settings (lower temperatures over longer time scales). Studies do not entirely negate the application of diffusion theory to recover thermal histories, although they reveal the paramount importance of first accounting for fluid interaction and secondary reaction products via a detailed textural study of single crystals. Furthermore, an expanding database of experimental evidence shows that laboratory step-heating can induce structural and textural changes, and thus extreme caution must be made when extrapolating laboratory derived rate loss constants to the geological past. We conclude with a set of recommendations that include minimum sample characterisation prior to degassing, an assessment of mineralogical transformations during degassing and the use of in situ dating.

Zonal anatomy of the prostate using magnetic resonance imaging, morphometrics, and radiomic features: impact of age-related changes

Objective: To evaluate the impact of age on the zonal anatomy of the prostate by MRI using morphometric and textural analysis. Methods: A total of 154 men (mean age: 63 years) who underwent MRI due to a high prostate-specific antigen (PSA) level were included retrospectively. At each MRI examination the following variables were measured: overall dimensions of the prostate (whole gland (WG), transitional zone (TZ), and peripheral zone (PZ)), and thickness of the anterior fibromuscular stroma (AFMS) and the periprostatic venous plexus (PPVP) on T2 weighted images. Identical regions of interest (ROIs) were delineated on the apparent diffusion coefficient (ADC) map on the anterior (horn) and posterior part of the PZ. Textural (TexRAD®) parameter differences between TZ and PZ ROIs on T2 weighted images were analyzed by linear regression. Results were correlated with age (distributed into five decades from 22 to 89 years). Results: Age was positively correlated with PSA level and glandular volumes (WG, TZ, and TZ/WG ratio; p < 0.0001) and was negatively correlated with AFSM and PPVP thickness (p < 0.0001). There was a positive correlation between ADC values of the PZ and age (p = 0.003) and between entropy of the TZ and PZ and age (p < 0.001). Conclusion: Gradual variations in morphologic and textural features of the prostate were observed with age, mainly due to the increase in TZ volume while PZ volume tended to decrease. These modifications resulted in textural changes mainly at the expense of entropy. Advances in knowledge: Entropy could be relevant for studying the process of aging of the prostate.