Active set algorithms for isotonic regression; A unifying framework

In this and subsequent papers we will show that several algorithms for the isotonic regression problem may be viewed as active set methods. The active set approach provides a unifying framework for studying algorithms for isotonic regression, simplifies the exposition of existing algorithms and leads to several new efficient algorithms. We also investigate the computational complexity of several algorithms.In this paper we consider the isotonic regression problem with respect to a complete order where eachw _i is strictly positive and eachy _i is an arbitrary real number. We show that the Pool Adjacent Violators algorithm (due to Ayer et al., 1955; Miles, 1959; Kruskal, 1964), is a dual feasible active set method and that the Minimum Lower Set algorithm (due to Brunk et al., 1957) is a primal feasible active set method of computational complexity O(n ²). We present a new O(n) primal feasible active set algorithm. Finally we discuss Van Eeden's method and show that it is of worst-case exponential time complexity.This work was supported by the National Science and Engineering Research Council of Canada under Research Grant A8189 and an Ontario Graduate Scholarship.     

Surface functionalized silver nanoparticle conjugates: demonstration of uptake and release of a phototherapeutic porphyrin dye

A facile supramolecular approach to prepare surface functionalized silver nanoparticle conjugates has been established and their enhanced molecular recognition features have been explored to demonstrate the uptake and stimulus responsive release of a phototherapeutic porphyrin dye, the TMPyP.     

Translational diffusion of polystyrene in 1,4-dioxane at infinite dilution determined with the extended Taylor dispersion method

The extended Taylor dispersion method was used to determine the translational diffusion coefficients of a series of polystyrene standards in 1,4-dioxane at infinite dilution at temperatures from 323.2 to 378.2 K. The experimental data suggest that in the context of Kirkwood's theory the Monte Carlo chain represents real polystyrene molecules better than does the Guassian chain with physically reasonable values for the hydrodynamic interaction parameter h^*. The feasibility and accuracy of the simultaneous determination of the diffusivities of several polystyrene standards from a single dispersion measurement were also analyzed using a binary mixture of polystyrenes with molecular weights of 2000 and 100,000 as an example.     

Translational diffusion of polystyrene in cyclohexane at infinite dilution from 283 to 348 K

The translational diffusion coefficients are reported for polystyrenes with molecular weights 2000, 4000, and 9000 in cyclohexane at infinite dilution from 283.2 to 348.2 K. The results suggest that the hydrodynamic radii stay constant to within ±3% and that the real chain for molecular weight 9000 at 308.2 K is well represented by a Gaussian or Monte Carlo model involving the idea of statistical steps. Furthermore, the success of Hildebrand's free-volume empiricism has led to a correlation between Dμ₀/T and M which represents the observed diffusivities to within ±2%.     

Redox-mediated Negative Differential Resistance (NDR) Behavior in Perylenediimide Derivative: A Supramolecular Approach

Deaggregated perylenediimide (PDI) derivatives exhibit exceptionally high quantum yields, photostability and appropriate molecular features for organic electronics. This work demonstrates a metal–dye–metal framework with a large and stable negative differential resistance (NDR) at ambient conditions, built using a supramolecular strategy. The deaggregation achieved through the encapsulation of the bay-substituted phenyl groups of aggregated (l/d )-Phe-PDI dyes by the β-CD macrocyclic host is validated through detailed spectroscopic and imaging techniques. The host–guest interaction resulted in a dramatic enhancement in the emission yield from 0.28 to 0.90. In the thin film deposits, the β-CD/(l/d )-Phe-PDI complex displayed well-connected sheet-like morphology, whereas the uncomplexed (l/d )-Phe-PDI dye remained as scattered lumps. The large and reversible I–V characteristics displaying strong NDR behavior is attributed to the oxidation/reduction processes involving the rigid π-rich PDI core and is stable at least for about six months at ambient conditions, a promising system for organic electronics applications.     

Structural variations in self-assembled cadmium benzoate complexes

A series of mixed ligand cadmium(II) complexes having 3,5-dimethylpyrazole and aromatic carboxylate are structurally characterized. The effect of substituent on aromatic ring and also the effect of composition on co-ordination behavior of these complexes are ascertained. Hydrogen bonded self-assembled mononuclear complexes are obtained from composition [Cd(L)₂(L_a)₂] where L_a = 3,5-dimethylpyrazole L = R–C₆H₄COO– [R = H (1), 2-Cl (2), 4-OH (3), 2-OH (4)]. The cadmium complex (5) having composition [Cd(L)₂(L_a)(H₂O)] (L = 2-NO₂–C₆H₄COO–) is tetra-nuclear. The complex has eight and six co-ordination around cadmium and self-assembles through hydrogen bonding leading to form extended chain structure. The four complexes (1–4) have six co-ordinated trigonal prismatic geometry around cadmium ions. Cadmium complexes having composition [Cd(L)₂(L_a)] such as R = 4-NO₂ (6), 4-Cl (7), and 1-naphthoate complex (8) are co-ordination polymers with seven co-ordination geometry around cadmium. In these co-ordination polymers different Cd–Cd distances are observed for alternate pair of cadmium ions. For example in the case of the co-ordination polymer of 4-nitro-benzoate complex the Cd–Cd distance between alternate pairs are 4.138 Å, and 3.748 Å. The 1-naphthoate complex having pyridine has composition [Cd(L)₂(L_b)₂](H₂O)] (9) where L_b = pyridine and L = 1-naphthoate has seven co-ordination with a distorted pentagonal bipyramid geometry.     

Identification of Putative Vaccine and Drug Targets against the Methicillin-Resistant Staphylococcus aureus by Reverse Vaccinology and Subtractive Genomics Approaches

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen and responsible for causing life-threatening infections. The emergence of hypervirulent and multidrug-resistant (MDR) S. aureus strains led to challenging issues in antibiotic therapy. Consequently, the morbidity and mortality rates caused by S. aureus infections have a substantial impact on health concerns. The current worldwide prevalence of MRSA infections highlights the need for long-lasting preventive measures and strategies. Unfortunately, effective measures are limited. In this study, we focus on the identification of vaccine candidates and drug target proteins against the 16 strains of MRSA using reverse vaccinology and subtractive genomics approaches. Using the reverse vaccinology approach, 4 putative antigenic proteins were identified; among these, PrsA and EssA proteins were found to be more promising vaccine candidates. We applied a molecular docking approach of selected 8 drug target proteins with the drug-like molecules, revealing that the ZINC4235426 as potential drug molecule with favorable interactions with the target active site residues of 5 drug target proteins viz., biotin protein ligase, HPr kinase/phosphorylase, thymidylate kinase, UDP-N-acetylmuramoyl-L-alanyl-D-glutamate-L-lysine ligase, and pantothenate synthetase. Thus, the identified proteins can be used for further rational drug or vaccine design to identify novel therapeutic agents for the treatment of multidrug-resistant staphylococcal infection.     

Crystal Structure of a Metallohybrid Acid of 1,3,5-Benzenetricarboxylic Acid of Copper(II)

Abstract The crystal structure of a metallohybrid carboxylic acid obtained from the reaction of 1,3,5-benzenetricarboxylic acid (TCAH3) with copper(II)acetate monohydrate in the presence of pyridine (py) having composition Cu(py)₂(TCAH2)₂(H₂O)₂ [1] is reported. It crystallizes in triclinic space group P-1 and with a = 7.0110(3)?, b = 8.9523(5)?, c = 11.5370(5) ?, α = 79.776(3) °, β = 82.881(3)°, γ = 83.628(3)°, and V = 704.18(6)?³. The hydrogen bond in 1 is compared with the hydrogen bond pattern in the structure of 1,3-dicarbomethoxy 4,6-benzenedicarboxylic acid, which crystallizes in mononclinic space group P21/c and has unit cell parameters of a = 6.9549(16)?, b = 8.7676(15)?, c = 20.111(4)?; β = 92.585(17) ° and V = 1225.1(4) ?³. Index Abstract Crystal structure of a metallohybrid carboxylic acid obtained from the reaction of 1,3,5-benzenetricarboxylic acid with copper(II)acetate monohydrate in the presence of pyridine is determined and compared with hydrogen bond pattern present in the structure of 1,3-dicarbomethoxy 4,6-benzenedicarboxylic acid. Crystal structure of a metallohybrid acid of 1,3,5-benzenetricarboxylic acid of copper(II). Kusum Bania, Nilotpal Barooah, Rupam Sarma, Jubaraj B. Baruah     

Supramolecular assembly of Hoechst-33258 with cucurbit[7]uril macrocycle

Molecular assemblies of potential guest molecules through non-covalent host-guest interactions have found immense use in many applied areas. In this study supramolecular interaction of a biologically important dye Hoechst-33258 (H33258) has been investigated in aqueous solutions at different pHs, in the presence of a macrocyclic host, namely, cucurbit[7]uril (CB7). The pH dependent emission behaviour of H33258 is inherently connected with its protolytic equilibria which allow the dye in different geometrical conformations. This pH dependent structural orientation is greatly affected by the complexation with CB7. The significant structural changes in the monocationic H33258 brought out by CB7 at pH 7 have been documented in the fluorescence emission and lifetime data, which are comparatively less affected in case of the dicationic form, which is prominent in dye solutions at pH 4.5. The strong ion-dipole interactions provided by the carbonyl portals of the CB7 host adequately stabilize the CB7-H33258 complex, both in 1:1 and 2:1 stoichiometries at both the pH conditions. The Job's plot method, fluorescence anisotropy, NMR measurements and geometry optimization calculations confirm the stoichiometric arrangement and are found to be tunable with the addition of metal ions. The non-covalently stabilized assembly brings out large enhancement in the fluorescence emission due to the unique structural orientation attained by H33258, which reduces the non-radiative relaxation pathways. Comparison of the spectral data of the dye at different pH conditions in the absence and presence of CB7 proposes a large upward pK(a) shift due to CB7 encapsulation, thus providing a handy tool to modulate the photophysical characteristics of the guest molecules.     

Calculation of gluon cut vertices occurring in sterman-weinberg jet cross sections

A complete calculation to order g² in the QCD coupling of gluon cut vertices occurring in the factorization of single-jet cross sections in e⁺e^? collisions is given. This completes the calculations initiated by Duncan, Gupta and Mueller.