1,255 research outputs found
A comparison of the reactivity of different synthetic calcium carbonate minerals with arsenic oxyanions
This study was conducted to determine how the structure and surface chemistry of bulk CaCO3 differs from that of nanometer-sized CaCO3 and then to determine rate, extent and mechanisms of As adsorption on various synthetic CaCO3 materials. Additionally, we sought to devise a chemical CaCO3 precipitate that approximates biogenic CaCO3. The bulk CaCO3 precipitation was performed by using a solution that was highly oversaturated so that large CaCO3 precipitates rapidly form. Two different methods were employed for the synthesis of nanometer size CaCO3 i) an in situ deposition technique and ii) an interfacial reaction (water in oil emulsion). Mineral characterization of all CaCO3 precipitates was done with Nitrogen Porosimetry (Brunauer Emmett Teller method), particle size analysis, X-ray diffraction and Fourier Transform Infrared/ Fourier Transform Raman spectroscopy. The principal objective of the research was to assess the overall reactivity of As(III) and As(V) with different synthetic CaCO3 minerals. This was accomplished by i) running adsorption isotherms (varying As concentration), ii) measuring pH envelopes (varying pH at a fixed concentration) and iii) kinetic experiments (varying reaction time). Also, electrophoretic mobility experiments were performed in the presence of As(III) and As(V), and these studies revealed that As(III) forms stronger inner-sphere complexes with CaCO3 than As(V). Also, it was found that nanometer-sized CaCO3 prepared via deposition formed stronger inner-sphere complexes with As oxyanions (q = 5.26 µmol/m2) compared to either nano-sized CaCO3 from interfacial reactions (q = 4.51 µmol/m2) or bulk CaCO3 (q = 4.39 µmol/m2).
The PEG-based nano CaCO3 prepared by an in-situ deposition technique presents a novel and readily available synthesis route that can be used as proxy for the biogenic CaCO3 known to be present in many different environmental conditions. The results of this study suggest that CaCO3 can be used as a sorbent for As in groundwater
On Lie algebroid over algebraic spaces
We consider Lie algebroids over algebraic spaces (in short we call it as
-spaces) by considering the sheaf of Lie-Rinehart algebras. We discuss about
properties of universal enveloping algebroid
of a Lie algebroid over
an -space . This is done by sheafification of the
presheaf of universal enveloping algebras of Lie-Rinehart algebras. We review
the extent to which the structure of the universal enveloping algebroid of Lie
algebroids (over special -spaces) resembles a bialgebroid structure, and
present a version of Poincare-Birkhoff-Witt theorem and Cartier-Milnor-Moore
theorem for this type of structure.Comment: Some minor changes done. Mainly, we shorten it and kept main idea
Retrospect, resurgence and prospects of micelles
Recent studies on micellar systems were systematically overviewed, paying special attention to Gemini surfactants, mixed micelles, clouding phenomena and microemulsions. Gemini surfactants are surfactants that have two hydrophilic groups and two hydrophobic groups per amphiphilic molecule, rather than the single hydrophilic and single hydrophobic group of conventional surfactants. The greater efficiency and effectiveness of geminis over comparable conventional surfactants make them more cost effective as well as environmentally desirable. Mixed micelles have received wide attention for several decades, both in theoretical studies and in practical applications, because of their distinctive behaviour in comparison with normal micellar systems. Clouding (cloud point, CP) is a well known phenomenon observed in non-ionic surfactants. For charged micelles (i.e., ionic surfactants), the phenomenon rarely occurs, however, under special conditions, the CP in ionic surfactant solutions is observed. Some amphiphilic drugs, like ionic surfactants, also undergo pH-, concentration-, and temperature- dependent phase separation. It was observed that their CP can vary with additives. Due to their unique properties, namely, thermodynamic stability, ultralow interfacial tension, large interfacial area and the ability to solubilize otherwise immiscible liquids, microemulsions have attained increasing significance both in basic research and in industry. The uses and applications of microemulsions have been numerous. Several reviews on micellar systems and their applications have been published. However, this topic is developing quite rapidly and it is hoped that this review will help newcomers in the field as well as those already involved in this field
Biased Attention: Do Vision Transformers Amplify Gender Bias More than Convolutional Neural Networks?
Deep neural networks used in computer vision have been shown to exhibit many
social biases such as gender bias. Vision Transformers (ViTs) have become
increasingly popular in computer vision applications, outperforming
Convolutional Neural Networks (CNNs) in many tasks such as image
classification. However, given that research on mitigating bias in computer
vision has primarily focused on CNNs, it is important to evaluate the effect of
a different network architecture on the potential for bias amplification. In
this paper we therefore introduce a novel metric to measure bias in
architectures, Accuracy Difference. We examine bias amplification when models
belonging to these two architectures are used as a part of large multimodal
models, evaluating the different image encoders of Contrastive Language Image
Pretraining which is an important model used in many generative models such as
DALL-E and Stable Diffusion. Our experiments demonstrate that architecture can
play a role in amplifying social biases due to the different techniques
employed by the models for feature extraction and embedding as well as their
different learning properties. This research found that ViTs amplified gender
bias to a greater extent than CNN
Gender Bias in Multimodal Models: A Transnational Feminist Approach Considering Geographical Region and Culture
Deep learning based visual-linguistic multimodal models such as Contrastive
Language Image Pre-training (CLIP) have become increasingly popular recently
and are used within text-to-image generative models such as DALL-E and Stable
Diffusion. However, gender and other social biases have been uncovered in these
models, and this has the potential to be amplified and perpetuated through AI
systems. In this paper, we present a methodology for auditing multimodal models
that consider gender, informed by concepts from transnational feminism,
including regional and cultural dimensions. Focusing on CLIP, we found evidence
of significant gender bias with varying patterns across global regions. Harmful
stereotypical associations were also uncovered related to visual cultural cues
and labels such as terrorism. Levels of gender bias uncovered within CLIP for
different regions aligned with global indices of societal gender equality, with
those from the Global South reflecting the highest levels of gender bias.Comment: Selected for publication at the Aequitas 2023: Workshop on Fairness
and Bias in AI | co-located with ECAI 2023, Krak\'ow, Polan
INVESTIGATIONS OF THE STRUCTURAL CHANGES IN PROAPOPTOTIC PEROXIDASE-ACTIVE CARDIOLIPIN-BOUND CYTOCHROME C AND LIQUID- GEL PHASE TRANSITIONS IN LIPOSOMES USING SOLID STATE NMR SPECTROSCOPY
Mitochondrial cytochrome c (cyt-c) plays a key role in the activation of intrinsic apoptosis. Cyt-c gains a new function under apoptotic conditions; the peroxidation of mitochondrial lipid cardiolipin (CL) by cyt-c is a required step in the intrinsic apoptosis pathway. Understanding the mechanism of this alternate functionality in cyt-c has implications for treatment of neurological diseases like Huntington’s disease and in cancer. In order to gain insights into this mechanism, structural and dynamical information on the membrane bound protein is required. Solid-state nuclear magnetic resonance (ssNMR) provides an array of tools to study this system and extract necessary structural and dynamical information on the protein as well as the membranes. In this thesis, magic-angle-spinning (MAS) NMR and static ssNMR are used in conjunction with various other biophysical tools to gain insights into the mechanism of cyt-c’s peroxidase activity.
The effect of lipid peroxidation by cyt-c during apoptosis has also been implicated in modulating the structure, dynamics and behaviour of mitochondrial membranes, including facilitating pore formation in cyt-c-bound liposomes [1-3]. An understanding of lipid structure and phase behaviour has tremendous bearing on the study of lipids, membrane proteins and cryoprotection in general and cyt-c’s role in apoptosis in particular. MAS NMR is used here to investigate the link between the freezing point depression of water and the lowering of the lipid transition temperature.
One of the requirements to performing MAS NMR is a method of sample preparation that provides highly concentrated samples in tiny microliter sized MAS sample rotors. Additionally, for biological samples, as the ones under study here, it is very important to maintain hydration of the sample at all times in order to preserve function of the protein and the membranes, prevent damage to the sample, obtain better quality NMR spectra and most importantly, maintain biological relevance. Thus, the design and use of an ultracentrifuge based packing tool, that fulfills the requirements listed above, is discussed and illustrated here
Observational constraints and some toy models in gravity with bulk viscous fluid
The standard formulation of general relativity fails to describe some recent
interests in the universe. It impels us to go beyond the standard formulation
of gravity. The gravity theory is an interesting modified theory of
gravity, where the gravitational interaction is driven by the nonmetricity .
This study aims to examine the cosmological models with the presence of bulk
viscosity effect in the cosmological fluid within the framework of
gravity. We construct three bulk viscous fluid models, i.e. (i) for the first
model, we assuming the Lagrangian as linear dependence on , (ii) for
the second model the Lagrangian as a polynomial functional form, and
(iii) the Lagrangian as a logarithmic dependence on . Furthermore, we
use 57 points of Hubble data and 1048 Pantheon dataset to constraint the model
parameters. Then, we discuss all the energy conditions for each model, which
helps us to test the self-consistency of our models. Finally, we present the
profiles of the equation of state parameters to test the models' present
status.Comment: 13 pages,9 figures. Comments are Welcom
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