Selective spin coupling through a single exciton

We present a novel scheme for performing a conditional phase gate between two spin qubits in adjacent semiconductor quantum dots through delocalized single exciton states, formed through the interdot F?rster interaction. We consider two resonant quantum dots, each containing a single excess conduction band electron whose spin embodies the qubit. We demonstrate that both the two-qubit gate and arbitrary single-qubit rotations may be realized to a high fidelity with current semiconductor and laser technology.     

Thermodynamic aspect: kinetics of the reduction of dicyanobis(phen)iron(III) by acetylferrocene and methylferrocenemethanol

Protonation plays an important role in the redox reactions. We observed this leading role during the reduction of [Fe^III(phen)₂(CN)₂]⁺ by FcCOMe and FcCHOHMe. The kinetic data showed that the reaction(s) followed a complex kinetics due to the formation of protonated acetylferrocene (FcC⁺OHMe), and or, protonated α-methylferrocenemethanol (FcCHO⁺H₂Me) in aqueous dioxane (80% v/v). Our results helped us to conclude that the reactions were completed in three phases. An overall zeroth order was observed in the first phase of the reactions. In the second phase, the kinetic data showed an overall second order reaction. The third phase was a complex phase where the rate of redox reactions and the insolubility of the neutral product ([Fe^II(phen)₂(CN)₂]) competed with each other. We studied the effect of different factors to identify the reacting entities, which take part in the rate-determining step of each reaction in the second phase. Consequently, we determined the effects of selected factors upon the observed pseudo-first order rate constant(s) (k′ _obs) of each reaction. The value of k′ _obs increased upon addition of protons in the reaction mixture in case of FcCOMe, and it decreased during the oxidation of FcCHOHMe. Meanwhile, upon enhancing the ionic strength, we observed an increase in k′ _obs for FcCOMe, and no change in the value of k′ _obs during the reaction of FcCHOHMe. However, a decrease in k′ _obs was noticed upon increasing the dielectric constant of the reaction mixture when the reductant was FcCOMe, and no effect was observed in case of FcCHOHMe. Together, these results suggested oxidation of FcC⁺OHMe and FcCHOHMe in the slow-step, and FcCOMe and FcCHO⁺H₂Me during the fast-step. We refined our results by estimating the thermodynamic parameters of activation. The low values of activation energy and enthalpy of activation confirmed that the reduction of [Fe^III(phen)₂(CN)₂]⁺ hardly depends upon temperature when the reducing agent is FcCOMe. The outcomes justified that the rate of reaction depends upon the unsaturated FcC⁺OHMe. This intermediate species contain a ‘carbonium ion’, which is very reactive and energetic. We obtained comparatively high values of the activation energy and enthalpy of activation for the reaction between [Fe^III(phen)₂(CN)₂]⁺ and FcCHOHMe. The results show that FcCHOHMe is a saturated and stable compound that leads the slow-step and controls the rate of reaction.     

Comparative Assessment of Phytoconstituents,Antioxidant Activity and Chemical Analysis of Different Parts of Milk Thistle Silybum marianum L.

Silybum marianum L. is a therapeutic plant belonging to the family Asteraceae, which has exhibited silymarin, a principal component used to cure various physiochemical disorders. The study appraised the phytochemical analysis, antioxidant activity and chemical analysis of an extract from the seed, stem and leaves. Qualitative and quantitative phytochemical analysis was evaluated by the Folin–Ciocalteu reagent method and aluminum chloride colorimetric method, respectively. While the antioxidant activity was determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and acetate buffer in ferric chloride (FRAP) assay, respectively, the chemical profile was evaluated by Gas Chromatography-Mass Spectrometry (GC-MS) assay. The study outcomes identified that alkaloids, glycosides, flavonoids, terpenoids, steroids and catcholic tannins were present in seed, stem and leaves extracts except for saponins and Gallic tannins. Whereas, phenols were absent only in seed extract. Quantitative analysis revealed the presence of phenols and flavonoids in appreciable amounts of 21.79 (GAE/g), 129.66 (QE/g) and 17.29 (GAE/g), 114.29 (QE/g) from the leaves and stem extract, respectively. Similarly, all extracts expressed reasonable DPPH inhibition (IC₅₀) and FRAP reducing power such as 75.98, 72.39 and 63.21% and 46.60, 51.40 and 41.30 mmol/g from the seeds, stem and leaves extract, respectively. Additionally, chemical analysis revealed the existence of 6, 8 and 9 chemical compounds from the seeds, stem and leaves extract, respectively, corresponding to 99.95, 99.96 and 98.89% of the whole extract. The chemical compound, Dibutyl phthalate was reported from all extracts while, Hexadecanoic acid, methyl ester and Silane, (1,1-dimethylethyl), dimethyl (phenylmethoxy) were reported only from the seed and leaves extract. Moreover, Methyl stearate was also a major compound reported from all extracts except for seed extract. It is demonstrable that extracts from different parts of S. marianum possess significant antioxidant activity, as well as valuable chemical compounds accountable for therapeutic effects that might be incorporated as an alternative to synthetic chemical agents.     

Dietary Polyphenols: Extraction,Identification, Bioavailability,and Role for Prevention and Treatment of Colorectal and Prostate Cancers

Fruits, vegetables, and other edible plants in our diet have numerous health benefits, due to the bioactive compounds in these food items, including polyphenols. These plants are a rich and promising source of natural products and phytochemicals that can be used to treat and prevent numerous diseases and prevent the progression of cancer. Dietary polyphenols exhibit chemo-preventive and therapeutic effects against various ailments, including several types of cancer. The current study focuses on polyphenol’s traditional and advanced extraction methods, with supercritical extraction as a novel approach. It also deals with their identification, bioavailability, and role in preventing and treating colorectal and prostate cancers. Additionally, the article covers the literature that deals with the anticancer activities of polyphenols, as well as their potential use as anticancer agents.     

A monotropic liquid crystal polyester with a biphasic nematic-smectic phase

The polyesters made from the condensation of isophthalic acid (IA) or terephthalic acid (TA) with the mesogenic diol 4,4′-bis (6-hydroxy hexoxy)biphenyl (BHHBP) are both reported to show a smectic mesophase. However, in our previous work, we found evidence for a mesophase in the polyester containing BHHBP and IA, but not in the one with BHHBP and TA. For the BHHBP-IA polyester, we thought the phase sequence on cooling was I → S_A → K, while on heating the situation was unresolved; there was some indication that on heating, a K → I transition occurs without any intervening mesophase. In other words, it was suspected that the mesophase in the IA polyester was monotropic. In this work, we have now obtained firm evidence that the mesophase behavior of the BHHBP-IA polyester is indeed monotropic. Further, an additional complexity has been found: on cooling, there is in fact a nematic phase, besides a smectic A, and a crystal phase. However, the mesophase appears to be complex. As the nematic and smectic textures occurred simultaneously, it seems that the mesophase is a nematic-smectic biphase. © 1996 John Wiley & Sons, Inc.     

Dirac R-matrix calculations of photoionization cross sections of Ni XII and atomic structure data of Ni XIII

We performed R-matrix calculations for photoionization cross sections of the two ground state configuration 3s²3p⁵ (²P^o_3/2,1/2) levels and 12 excited states of Ni XII using relativistic Dirac Atomic R-matrix Codes (DARC) across the photon energy range between the ionizations thresholds of the corresponding states and well above the thresholds of the last level of the Ni XIII target ion. Generally, a good agreement is obtained between our results and the earlier theoretical photoionization cross sections. Moreover, we have used two independent fully relativistic GRASP and FAC codes to calculate fine-structure energy levels, wavelengths, oscillator strengths, transitions rates among the lowest 48 levels belonging to the configuration (3s²3p⁴, 3s3p⁵, 3p⁶, 3s²3p³3d) in Ni XIII. Additionally, radiative lifetimes of all the excited states of Ni XIII are presented. Our results of the atomic structure of Ni XIII show good agreement with other theoretical and experimental results available in the literature. A good agreement is found between our calculated lifetimes and the experimental ones. Our present results are useful for plasma diagnostic of fusion and astrophysical plasmas.     

Anabasis articulata (Forssk.) Moq: A Good Source of Phytochemicals with Antibacterial,Antioxidant, and Antidiabetic Potential

Anabasis articulata is medicinally used to treat various diseases. In this study, A. articulata was initially subjected to extraction, and the resultant extracts were then evaluated for their antimicrobial, antioxidant, and antidiabetic potentials. After obtaining the methanolic extract, it was subjected to a silica gel column for separation, and fractions were collected at equal intervals. Out of the obtained fractions (most rich in bioactive compounds confirmed through HPLC), designated as A, B, C, and D as well hexane fraction, were subjected to GC-MS analysis, and a number of valuable bioactive compounds were identified from the chromatograms. The preliminary phytochemical tests were positive for the extracts where fraction A exhibited the highest total phenolic and flavonoid contents. The hexane fraction as antimicrobial agent was the most potent, followed by the crude extract, fraction A, and fraction D. DPPH and ABTS assays were used to estimate the free radical scavenging potential of the extracts. Fraction C was found to contain potent inhibitors of both the tested radicals, followed by fraction D. The potential antidiabetic extracts were determined using α-glucosidase and amylase as probe enzymes. The former was inhibited by crude extract, hexane, and A, B, C and D fractions to the extent of 85.32 ± 0.20, 61.14 ± 0.49, 62.15 ± 0.84, 78.51 ± 0.45, 72.57 ± 0.92 and 70.61 ± 0.91%, respectively, at the highest tested concentration of 1000 µg/mL with their IC₅₀ values 32, 180, 200, 60, 120 and 140 µg/mL correspondingly, whereas α-amylase was inhibited to the extent of 83.98 ± 0.21, 58.14 ± 0.75, 59.34 ± 0.89, 81.32 ± 0.09, 74.52 ± 0.13 and 72.51 ± 0.02% (IC₅₀ values; 34, 220, 240, 58, 180, and 200 µg/mL, respectively). The observed biological potentials might be due to high phenolic and flavonoid content as detected in the extracts. The A. articulata might thus be considered an efficient therapeutic candidate and could further be investigated for other biological potentials along with the isolation of pure responsible ingredients.     

Interface,morphology, and the rheological properties of polymethylmethacrylate/impact modifier blends

Impact modifiers with grafted PMMA shell are used to modify polymethylmethacrylate matrix. The composition of the shell is chosen to enhance the interactions at the modifier/matrix interface and to obtain good dispersion of the impact modifier in order to optimize impact strength of the blend. The degree of interactions at the interface is characterized by the interfacial region where the chains of the matrix mix with those of the shell of the modifier. The deviation of the measured viscoelastic behavior of these blends from that predicted by the emulsion models has been attributed to the formation of the network structure due to the association of matrix chains with the shell of the modifier. It is expected that the network structure will decrease with increasing frequency and, as such, the effective volume of the particle is frequency dependent. This study uses the emulsion models to estimate the larger effective volume of the particle and, therefore, the extent of interaction at the interface. In the blends of this study it can be shown that at low modifier levels the solvent swelling of the modifier shell results in stronger interactions with the matrix; this effect is negated by the aggregation of particles at higher modifier loadings. The interaction of core modifier with the PMMA matrix seems to be similar to that of the core-shell modifier. This would not be expected from the calculated interfacial thickness of approximately 4 nm. It is, therefore, proposed that during melt-processing the core modifier surface was altered due to grafting of the matrix PMMA chains during melt-blending to (BA/St) copolymer of the core modifier thus reducing the interfacial tension. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2623–2634, 1998