Subjective Assessment of Image Compression Artefacts on Stereoscopic Display

Image and video quality are important to depict any pictorial information vividly and correctly. With the advancement of technology, we can produce high-quality images and can display those in advanced high-resolution displays. But as high-quality images continue to increase in size, transmitting these exceeds the limited bandwidth of display links. To cope, we need to compress the images but desire that the user cannot perceive any difference between the compressed and uncompressed images. In my thesis, psychophysical experiments with a flicker paradigm were undertaken to do a subjective assessment of the visibility of compression artefacts of two sets of images with two codecs viewed on a stereoscopic display. For one set of images the result shows that artefacts can be silenced in some stereo images relative to 2D while testing with the other set of images was inconclusive. This thesis documented evidence for silencing of artefacts in 3D displays. Other differences between stereoscopic and 2D presentation can be predicted but were not observed here (perhaps due to floor effects). Further large-scale subjective assessment with challenging images may help to get a concrete conclusion

Effects of Biomolecular Crowding on Protein Stability

The intracellular milieu is complex, heterogeneous and crowded-- an environment vastly different from dilute, buffered solutions where most biophysical studies are performed. The cytoplasm excludes about a third of the volume available to macromolecules in dilute solution. This exclusion arises from the sum of two phenomena: steric repulsions and chemical interactions, often called hard and soft interactions, respectively. Most efforts to understand crowding have focused on steric repulsions. Globular protein stability is the difference in free energy between the compact, biologically functional native state and the ensemble of less compact, nonfunctional denatured state. The hard-core repulsive component of crowding stabilizes globular proteins because the decrease in available volume favors compact species. The effect of soft interactions can be stabilizing or destabilizing. Soft repulsive interactions reinforce the stabilizing influence of hard-core repulsions. However, the equilibrium is shifted towards the denatured state in systems dominated by attractive non-specific interactions, because unfolding exposes more reactive surface. In Chapter 1, I introduce the concepts of hard and soft interactions in more depth and discuss how they are expected to affect the equilibrium thermodynamic stability of globular proteins. In Chapter 2, I describe experiments that test these concepts by using Escherichia coli cell lysates as the crowding agents, chymotrypsin inhibitor 2 (CI2) as the test protein and NMR-detected amide-proton exchange to measure stability. The lysate destabilizes CI2, and the destabilization increases with increasing lysate concentration. This observation shows that the cytoplasm interacts favorably, but non-specifically, with CI2, and these interactions overcome the stabilizing hard-core repulsions. In fact, the effects of the lysate are even stronger than those of homogeneous protein crowders, reinforcing the biological significance of weak, non-specific interactions. In Chapter 3, I test the idea that the net charge on the crowding proteins affects stability. To accomplish this goal, I isolated the anionic proteins from the lysate and used them as the crowding agent. CI2 is an anion under the chosen conditions, and, therefore, I expected the net repulsive interactions between CI2 and the crowders to increase the stability of CI2. Instead, the refined lysate also resulted in destabilization. Thus, even the anionic proteins, which have the same net charge as CI2, significantly interact with CI2's backbone non-specifically to overcome the stabilizing effect of steric repulsion. My in vitro studies show that weak chemical interactions play key roles in the cytosol. It will even be more difficult to identify soft interactions in living cells where reductionist approaches are difficult or impossible to apply. Nevertheless, endeavors aimed at quantifying soft interactions are essential for producing a physiologically relevant understanding of biophysics. Once the details of soft interactions are known, it should be possible to tune them so as to obtain bespoke behavior in test tubes and in cells. In summary, despite their weak and non-specific behavior, biologists of all types need to keep these interactions in mind when designing experiments to correlate in vitro studies with in vivo behavior.Doctor of Philosoph

Early predictors of PIH: serum β-HCG and lipid profile

Background: The objective of the study was to evaluate β-HCG and lipid profile in early second trimester and analyse whether these parameters can be used as predictors of PIH.Methods: 180 antenatal women in second trimester (14-20 weeks) attending antenatal clinic were taken as study population. Serum triglycerides, total cholesterol, LDL, VLDL, HDL, β-hCG was measured. All patients were followed till delivery and observed for development of PIH. Results was evaluated and analysed statistically.Results: Out of 180 cases, 173 cases were evaluated. Among 173 cases, 87.86% were normotensive. 8.09% developed mild PIH and 4.05% developed severe PIH. There was significant increase in values of β-hCG (p<0.001) and total cholesterol, triglycerides, low density lipoproteins and very low density lipoprotein (p<0.001) and significant decrease in values of high density lipoprotein (p<0.001) in those women who developed PIH.Conclusions: Measurement of all these parameters in early second trimester can help in predicting PIH. By proper follow up of these patients, early detection and better management of PIH and its complications is possible which would improve the maternal and fetal outcome

An osmolyte mitigates the destabilizing effect of protein crowding: Crowding & Osmolytes

Most theories predict that macromolecular crowding stabilizes globular proteins, but recent studies show that weak attractive interactions can result in crowding-induced destabilization. Osmolytes are ubiquitous in biology and help protect cells against stress. Given that dehydration stress adds to the crowded nature of the cytoplasm, we speculated that cells might use osmolytes to overcome the destabilization caused by the increased weak interactions that accompany desiccation. We used NMR-detected amide proton exchange experiments to measure the stability of the test protein chymotrypsin inhibitor 2 under physiologically relevant crowded conditions in the presence and absence of the osmolyte glycine betaine. The osmolyte overcame the destabilizing effect of the cytosol. This result provides a physiologically relevant explanation for the accumulation of osmolytes by dehydration-stressed cells

Single Key Recovery Attacks on 9-round Kalyna-128/256 and Kalyna-256/512

The Kalyna block cipher has recently been established as the Ukranian encryption standard in June, 2015. It was selected in a Ukrainian National Public Cryptographic Competition running from 2007 to 2010. Kalyna supports block sizes and key lengths of 128, 256 and 512 bits. Denoting the variants of Kalyna as Kalyna-$b/k$, where $b$ denotes the block size and $k$ denotes the keylength, the design specifies $k \in \{b, 2b\}$. In this work, we re-evaluate the security bound of some reduced round Kalyna variants, specifically Kalyna-$128/256$ and Kalyna-$256/512$ against key recovery attacks in the single key model. We first construct new 6-round distinguishers and then use these distinguishers to demonstrate 9-round attacks on these Kalyna variants. These attacks improve the previous best 7-round attacks on the same.\\ Our 9-round attack on Kalyna-128/256 has data, time and memory complexity of $2^{105}$, $2^{245.83}$ and $2^{226.86}$ respectively. For our 9-round attack on Kalyna-256/512, the data/time/memory complexities are $2^{217}$, $2^{477.83}$ and $2^{443.45}$ respectively. The time and data complexities for Kalyna-256/512 reported in this work improve upon the previous best 7-round attack complexities on the same. The attacks presented in this work are currently the best on Kalyna. We apply multiset attack - a variant of meet-in-the-middle attack to achieve these results

Bicliques with Minimal Data and Time Complexity for AES (Extended Version)

Biclique cryptanalysis is a recent technique that has been successfully applied to AES resulting in key recovery faster than brute force. However, a major hurdle in carrying out biclique cryptanalysis on AES is that it requires very high data complexity. This naturally warrants questions over the practical feasibility of implementing biclique attack in the real world. In Crypto\u2713, Canteaut et al. proposed biclique attack where the data complexity of the attack was reduced to a single plaintext-ciphertext pair. However, no application of the same on AES was suggested. In this paper, we re-evaluate the security-bound of full round AES against biclique attack. Under some reasonable restrictions, we exhaustively analyze the most promising class of biclique cryptanalysis as applied to AES through a computer-assisted search and find optimal attacks towards lowest computational and data complexities: - Among attacks with the minimal data complexity of the unicity distance, the ones with computational complexity 2^126.67 (for AES-128), 2^190.9 (for AES-192) and 2^255 (for AES-256) are the fastest. Each attack just requires 2 (for AES-128 and AES-192) or 3 (for AES-256) known plaintexts for success probability 1. We obtain these results using the improved biclique attack proposed in Crypto\u2713. - Among attacks with data complexity less than the full codebook, for AES-128, the ones of computational complexity 2^126.16 are fastest. Within these, the one with data complexity 2^64 requires the smallest amount of data. Thus, the original attack (with data complexity 2^88) did not have the optimal data complexity for AES-128. Similar findings are observed for AES-192 as well (data complexity 2^48 as against 2^80 in the original attack). For AES-256, we find an attack that has a lower computational complexity of 2^254.31 as compared to the original attack complexity of 2^254.42. - Among all attacks covered, the ones of computational complexity 2^125.56 (for AES-128), 2^189.51 (for AES-192) and 2^253.87 (for AES-256) are fastest, though requiring the full codebook. This can be considered as an indication of the limitations of the independent-biclique attack approach as applied to AES

Collision Attack on 4-branch, Type-2 GFN based Hash Functions using Sliced Biclique Cryptanalysis Technique

In this work, we apply the sliced biclique cryptanalysis technique to show 8-round collision attack on a hash function H based on 4-branch, Type-2 Generalized Feistel Network (Type-2 GFN). This attack is generic and works on 4-branch, Type-2 GFN with any parameters including the block size, type of round function, the number of S-boxes in each round and the number of SP layers inside the round function. We first construct a 8-round distinguisher on 4-branch, Type-2 GFN and then use this distinguisher to launch 8-round collision attack on compression functions based on Matyas-Meyer-Oseas (MMO) and Miyaguchi-Preneel (MP) modes. The complexity of the attack on 128-bit compression function is 2^56. The attack can be directly translated to collision attack on MP and MMO based hash functions and pseudo-collision attack on Davies-Meyer (DM) based hash functions. When the round function F is instantiated with double SP layer, we show the first 8-round collision attack on 4-branch, Type-2 GFN with double SP layer based compression function. The previous best attack on this structure was a 6-round near collision attack shown by Sasaki at Indocrypt\u2712. His attack cannot be used to generate full collisions on 6-rounds and hence our result can be regarded the best so far in literature on this structure

Amide proton exchange of a dynamic loop in cell extracts

Intrinsic rates of exchange are essential parameters for obtaining protein stabilities from amide 1H exchange data. To understand the influence of the intracellular environment on stability, one must know the effect of the cytoplasm on these rates. We probed exchange rates in buffer and in Escherichia coli lysates for the dynamic loop in the small globular protein chymotrypsin inhibitor 2 using a modified form of the nuclear magnetic resonance experiment, SOLEXSY. No significant changes were observed, even in 100 g dry weight L−1 lysate. Our results suggest that intrinsic rates from studies conducted in buffers are applicable to studies conducted under cellular conditions

Prevalence of COVID-19 Vaccine Hesitancy in South Asia: A Systematic Review and Meta-Analysis

Vaccine uptake and coverage in susceptible populations are needed through effective vaccination campaigns to address the COVID-19 pandemic in South Asian countries. We aimed to measure the pooled proportion of COVID-19 vaccine hesitancy in this regard. Research articles published between January 1, 2020, to December 31, 2021, were searched through Medline, PubMed, Cochrane, Google Scholar, and the WHO COVID-19 database. The Joanna Briggs Institute (2014) tool for prevalence studies was used to assess data quality. We performed a meta-regression test and a sensitive analysis among the studies and used the DerSimonian and Laird random-effects model to measure the pooled effect estimates. Subgroup analyses were performed concerning vaccine hesitancy, countries, study population, study level, and the time since the first outbreak of the pandemic. A total of 43 studies out of 598 published articles across the eight countries in South Asia were included. The pooled proportion of COVID-19 vaccine hesitancy was 26.5% (95% CI [22, 31], I2 = 99.59%). Vaccine hesitancy was higher in Afghanistan (37%), Pakistan (33%), and Bangladesh (28.9%); among the general population (29%); at community levels (27.9%); and the duration of time of 1–12 months since the first outbreak in each country (27.5%). Vaccine hesitancy exists in South Asia with different rates among countries, population sub-groups, communities, study- levels, duration of time since the first outbreak, and study population. Therefore, enhancing public awareness of vaccination and vaccine hesitancy is required to prevent future pandemics