Results on principal component filter banks: colored noise suppression and existence issues

We have made explicit the precise connection between the optimization of orthonormal filter banks (FBs) and the principal component property: the principal component filter bank (PCFB) is optimal whenever the minimization objective is a concave function of the subband variances of the FB. This explains PCFB optimality for compression, progressive transmission, and various hitherto unnoticed white-noise, suppression applications such as subband Wiener filtering. The present work examines the nature of the FB optimization problems for such schemes when PCFBs do not exist. Using the geometry of the optimization search spaces, we explain exactly why these problems are usually analytically intractable. We show the relation between compaction filter design (i.e., variance maximization) and optimum FBs. A sequential maximization of subband variances produces a PCFB if one exists, but is otherwise suboptimal for several concave objectives. We then study PCFB optimality for colored noise suppression. Unlike the case when the noise is white, here the minimization objective is a function of both the signal and the noise subband variances. We show that for the transform coder class, if a common signal and noise PCFB (KLT) exists, it is, optimal for a large class of concave objectives. Common PCFBs for general FB classes have a considerably more restricted optimality, as we show using the class of unconstrained orthonormal FBs. For this class, we also show how to find an optimum FB when the signal and noise spectra are both piecewise constant with all discontinuities at rational multiples of π

Filterbank optimization with convex objectives and the optimality of principal component forms

This paper proposes a general framework for the optimization of orthonormal filterbanks (FBs) for given input statistics. This includes as special cases, many previous results on FB optimization for compression. It also solves problems that have not been considered thus far. FB optimization for coding gain maximization (for compression applications) has been well studied before. The optimum FB has been known to satisfy the principal component property, i.e., it minimizes the mean-square error caused by reconstruction after dropping the P weakest (lowest variance) subbands for any P. We point out a much stronger connection between this property and the optimality of the FB. The main result is that a principal component FB (PCFB) is optimum whenever the minimization objective is a concave function of the subband variances produced by the FB. This result has its grounding in majorization and convex function theory and, in particular, explains the optimality of PCFBs for compression. We use the result to show various other optimality properties of PCFBs, especially for noise-suppression applications. Suppose the FB input is a signal corrupted by additive white noise, the desired output is the pure signal, and the subbands of the FB are processed to minimize the output noise. If each subband processor is a zeroth-order Wiener filter for its input, we can show that the expected mean square value of the output noise is a concave function of the subband signal variances. Hence, a PCFB is optimum in the sense of minimizing this mean square error. The above-mentioned concavity of the error and, hence, PCFB optimality, continues to hold even with certain other subband processors such as subband hard thresholds and constant multipliers, although these are not of serious practical interest. We prove that certain extensions of this PCFB optimality result to cases where the input noise is colored, and the FB optimization is over a larger class that includes biorthogonal FBs. We also show that PCFBs do not exist for the classes of DFT and cosine-modulated FBs

Discrete multitone modulation with principal component filter banks

Discrete multitone (DMT) modulation is an attractive method for communication over a nonflat channel with possibly colored noise. The uniform discrete Fourier transform (DFT) filter bank and cosine modulated filter bank have in the past been used in this system because of low complexity. We show in this paper that principal component filter banks (PCFB) which are known to be optimal for data compression and denoising applications, are also optimal for a number of criteria in DMT modulation communication. For example, the PCFB of the effective channel noise power spectrum (noise psd weighted by the inverse of the channel gain) is optimal for DMT modulation in the sense of maximizing bit rate for fixed power and error probabilities. We also establish an optimality property of the PCFB when scalar prefilters and postfilters are used around the channel. The difference between the PCFB and a traditional filter bank such as the brickwall filter bank or DFT filter bank is significant for effective power spectra which depart considerably from monotonicity. The twisted pair channel with its bridged taps, next and fext noises, and AM interference, therefore appears to be a good candidate for the application of a PCFB. This is demonstrated with the help of numerical results for the case of the ADSL channel

Role of principal component filter banks in noise reduction

The purpose of this paper is to demonstrate the optimality properties of principal component filter-banks for various noise reduction schemes. Optimization of filter-banks (FB's) for coding gain maximization has been carried out in the literature, and the optimized solutions have been observed to satisfy the principal component property, which has independently been studied. Here we show a strong connection between the optimality and the principal component property; which allows us to optimize FB's for many other objectives. Thus, we consider the noise-reduction scheme where a noisy signal is analyzed using a FB and the subband signals are processed either using a hard-threshold operation or a zeroth order Wiener filter. For these situations, we show that a principal FB is again optimal in the sense of minimizing the expected mean-square error

Molecular Docking Study on Myricetin Derivates as The Inhibitors of Glucosyl Transferase SI, A Virulence Factor of Streptococcus Mutans in The Causation of Dental Caries

Dental caries is one of the most prevalent infectious diseases in the world. Streptococcus mutans is regarded as a primary microbial agent in the pathogenesis of dental caries. The role of S. mutans in cariogenic activity is its ability to adhere to the initially acquired film, produce acids and synthesize insoluble and soluble glucans that help to maintain plaque by producing glucosyl transferases (Gtfs) which metabolize sucrose into free glucans and fructose. Hence the inhibition of Glucosyl transferases will be an ideal strategy in the prevention of dental caries. The three-dimensional structure of GTF-SI was retrieved from RCSB protein data bank. Its PDB code is 3AIB. A total of 1000 ligands in 2D format were generated from myricetin structure with the help of software ACD chemsketch. Rapid virtual screenings of these compounds were performed in the docking tool iGEMDOCK v2.0. Based on the binding energy a total of four ligands were selected for the further study. The selected four ligands were then analyzed for drug- relevant properties. On the basis of binding affinity and drug like properties, all these four ligands were taken for further molecular docking study. The ligand 4-(5-hydroxy-8-iodo-1,8a- dihydronaphthalen-2-yl) benzene-1,2-diol is found to have excellent drug likeliness score of 2.2 and a drug score of 0.73. Further the ligand also possesses excellent docking free energy. The results clearly indicate that the ligand should have a good inhibitory property for GTF -SI protein and hence can be a potential drug candidate in the prevention of caries caused by S.mutans

Study of Etiological Factors, Mycological Profile and Treatment Outcome of Otomycosis

Otomycosis is a common condition encountered in ENT practice. Though it is not a serious condition it causes a lot of misery to the patient. Though there are many studies on various aspects about this disease, there are not many studies from this part of the country. Materials and Methods: 75 patients attending ENT OPD and diagnosed to have otomycosis were included in the study. Two aural swabs or whenever possible otomycotic debris scooped out using Jobson –Horne probe was obtained. From one swab, wet mount preparation in 10% KOH (potassium hydroxide) solution and smear for Grams stain were prepared. The second swab / otomycotic debris was directly inoculated into SDA (sabourad’s dextrose agar) medium. Results: Mycological analysis of the swab from external auditory canal has shown that Aspergillus species was the most common fungus isolated followed by Candida species. All patients were treated with regular suction clearance and 1% clotrimazole ear drops. Conclusion: Simple measures like avoiding usage of ear buds/ unsterile material will help in prevention of otomycosis. 1% clotrimazole is effective in achieving complete mycological cure in otomycosis. Regular long term follow-up is required to effectively treat otomycosis

Quinic Acid Derivatives as Inhibitors of Glucosyltransferase Si, A Virulence Factor of Streptococcus Mutans in The Pathogenesis of Dental Caries

The important prerequisite for the formation of dental caries is the ability of Streptococcus mutans to form the biofilm. It has been proved that the formation of biofilm is mediated mainly by the enzymatic action of the Glucosyltransferase (GTF) enzymes. These enzymes are considered fundamental for the virulence of S. mutans in the causation of dental caries. In the present study quinic acid derivatives have been developed insilico as the inhibitors of GTF-SI enzyme and a molecular docking study is preformed to find its efficiency as inhibitors. The three-dimensional structure of GTF-SI was retrieved from MMDB database. The possible binding sites of GTF-SI were searched using binding site prediction 3DLIGANDSITE. The structure of quinic acid was obtained from ZINC database. A total of 100 ligands were generated with the help of software ACD chemsketch. Rapid virtual screenings of these compounds were performed in the docking tool iGEMDOCK v2.0. Based on the binding energy a total of five ligands were selected for the further study. The selected five ligands were then analyzed for drug- relevant properties based on “Lipinski’s rule of five” and other drug like properties. The docking of five ligands was performed using AutoDock 4.0 software. From the present study, it has been found that (1R)-1,3,4-trihydroxy-5-methylcyclohexane carboxylic acid, which is a novel compound, a derivative of quinic acid, can act has an inhibitor for the GTF-S

A Study on In Vitro Antibacterial Activity of Ficus Bengalensis Linn. on Dental Caries Pathogens streptococcus Mutans and Actinomyces Viscosus

The aerial roots of Ficus bengalensis Linn. were collected in and around Chennai, Tamilnadu, India They were washed, shade dried and were ground into powder. The powder was extracted with chloroform, petroleum ether, methanol and hexane. The antibacterial screening of the extracts was carried out by determining the zone of inhibition using disc diffusion method. The strains were grown to logarithmic phase in BHI broth and the inoculum was prepared by adjusting the turbidity of bacterial suspension to 0.5 McFarland’s tube. The dried extracts were dissolved in 10% Dimethyl sulphoxide (DMSO) in required concentration. The sterile discs were impregnated with 20 μl of extract. The extract discs were placed on BHI agar plates, which were previously inoculated with test strains and incubated at 37oC for 24 hours. Ampicillin disc (10μg) and 10% DMSO impregnated discs were used as positive and negative controls respectively and the zones of inhibition were recorded. The Minimum inhibitory concentration was determined by agar dilution method. The results of the present study showed that the methanol and chloroform extracts of Ficus bengalensis Linn. have activity against both Streptococcus mutans and Actinomyces viscosus. From the present study it is concluded that Ficus bengalensis Linn. extracts can be used as an effective antibacterial agent against dental caries

Optimizing the capacity of orthogonal and biorthogonal DMT channels

The uniform DFT filter bank has been used routinely in discrete multitone modulation (DMT) systems because of implementation efficiency. It has recently been shown that principal component filter banks (PCFB) which are known to be optimal for data compression and denoising applications, are also optimal for a number of criteria in DMT communication. In this paper we show that such filter banks are optimal even when scalar prefilters and postfilters are used around the channel. We show that the theoretically optimum scalar prefilter is the half-whitening solution, well known in data compression theory. We conclude with the observation that the PCFB continues to be optimal for the maximization of theoretical capacity as well

Catechin Derivatives as Inhibitors of Programmed Cell Death 1 Receptor (Pd –1), a Predominant Factor of Homo Sapiens in the Development of Oral Squamous Cell Cancer

One of several mechanisms of tumour-mediated immune suppression is the expression of co-inhibitory molecules by tumour. Upon engagement to their ligands these molecules can suppress effector lymphocytes in the periphery and in the tumour microenvironment. The PD-1 is one of the central signalling molecules that may inhibit T cell immunity when bound to its ligands (PD-L1 or PD-L2) by inducing T cell apoptosis and anergy. PD- L1 expression reduces the number of T cells in human oral squamous cell carcinoma. Further it has been suggested that the development of a strategy to block the interactions of PD-L1 with PD-1 would be a useful tool for inhibiting tumour growth. The three-dimensional structure of GTF-SI was retrieved from RCSB database. The possible binding sites of PD-1 were searched using binding site prediction 3DLIGANDSITE, an online tool. A total of 500 ligands in 2D format were generated from the basic structure of catechin with the help of software ACD chemsketch. Rapid virtual screenings of these compounds were performed in the docking tool iGEMDOCK v2.0. The molecular docking of ligands was performed using AutoDock 4.0 software. In the present study, (2S, 3R)-2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol has found to have very good inhibitory property based on molecular docking study. Further the compound shows a good ADMET properties based on studies in OSIRIS. Hence it is concluded that (2S,3R)-2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H- chromene-3,5,7-triol is an excellent drug candidate in the control of oral squamous cell carcinoma