Free Pair Research Articles

Benzofurazan-based fluorophore for the selective determination of flupentixol dihydrochloride: Application to content uniformity testing.

One of the most commonly used drugs in treatment of schizophrenia is flupentixol dihydrochloride, therefore it is important to develop a simple, low cost and sensitive spectrofluorimetric method for the estimation of flupentixol dihydrochloride. The yellow fluorescent product that is generated from the nucleophilic substitution reaction of the free lone pair of the alcoholic hydroxyl group of the drug and 4-chloro-7-nitrobenzofurazan (NBD-Cl) in Mcllvaine buffer pH7.0 was estimated at 510nm (λex 460nm). The variables that affect the development of the reaction product were explored and optimized. The linear range of this method was 0.5-2.5μgml-1 with a limit of quantitation equal to 0.29μgml-1 . Our method was successfully applied for the assurance of flupentixol in tablet form with average percentage recovery of 99.08±1.01% without obstruction from the basic excipients exhibits. Furthermore, our strategy was extended to study the content uniformity testing of flupentixol in Fluaxnol® tablets.

Oxidation of cyanobacterial neurotoxin beta-N-methylamino-L-alanine (BMAA) with chlorine, permanganate, ozone, hydrogen peroxide and hydroxyl radical

Beta-N-methylamino-L-alanine (BMAA), a new cyanobacterial neurotoxin produced by more than 20 genera of cyanobacteria, has been associated with amyotrophic lateral sclerosis/parkinsonism–dementia complex (ALS/PDC) or Alzheimer's disease. Although BMAA has been shown to be removed in drinking water treatment plants (DWTPs), studies regarding the reactions between BMAA and the commonly used oxidants in DWTPs are limited to chlorine under specific conditions. In this study, the reaction kinetics between BMAA and five oxidants commonly used in DWTPs, including chlorine, potassium permanganate, ozone, hydrogen peroxide and hydroxyl radical were investigated. The oxidation of BMAA by chlorine, ozone or OH radical followed the second order reaction rate law, and the reaction rate was in the order of OH radicals > ozone >> chlorine. The rate constants increased by 20 times from 2 × 103 M−1s−1 at pH 5.8 to 4.93 × 104 M−1s−1 at pH 7, and kept in a relatively stable level at pH 7–9.5; rate constants of OH radicals were 1.11 × 108 M−1s−1 at pH 6.5 and 5.51 × 109- 1.35 × 1010 M−1s−1 at pH > 6.5. For both permanganate and H2O2 only, the removal of BMAA was negligible. The pH dependency of chlorine and the OH radical may be attributed to the neutral form of BMAA with free lone pair electrons readily to be attacked by oxidants. However, for ozonation of BMAA, the rate constants were 1.88 × 106–3.72 × 1010 M−1s−1, with a linear dependency on pH, implying that the hydroxide concentration governs the reaction. In addition, the rate of BMAA degradation was found to be slower in natural water if compared with that in deionized water.

Health Seeking Behavior among Rural Left-Behind Children: Evidence from Shaanxi and Gansu Provinces in China.

More than 60 million children in rural China are “left-behind”—both parents live and work far from their rural homes and leave their children behind. This paper explores differences in how left-behind and non-left-behind children seek health remediation in China’s vast but understudied rural areas. This study examines this question in the context of a program to provide vision health care to myopic rural students. The data come from a randomized controlled trial of 13,100 students in Gansu and Shaanxi provinces in China. The results show that without a subsidy, uptake of health care services is low, even if individuals are provided with evidence of a potential problem (an eyeglasses prescription). Uptake rises two to three times when this information is paired with a subsidy voucher redeemable for a free pair of prescription eyeglasses. In fact, left-behind children who receive an eyeglasses voucher are not only more likely to redeem it, but also more likely to use the eyeglasses both in the short term and long term. In other words, in terms of uptake of care and compliance with treatment, the voucher program benefitted left-behind students more than non-left-behind students. The results provide a scientific understanding of differential impacts for guiding effective implementation of health policy to all groups in need in developing countries.

Rational Surface Modification of Two-Dimensional Layered Black Phosphorus: Insights from First-Principles Calculations.

Surface modification of atomically thin semiconductors enables their electronic, optical, chemical, and mechanical properties to be tailored and allows these nanosheets to be processed in solutions. Here, we report first-principles density functional theory calculations, through which we show chemical functionalization of black phosphorus using phenyl, phenolate, and nitrene species, which were widely investigated for carbon-based materials. We find that covalent functionalization using nitrene-derived species introduces a strong P–N dative bond at the interface without perturbing its intrinsic electronic structure. The Lewis basic and nucleophilic P atom attacks, through a free pair of electrons, the Lewis acidic nitrene species. These results are further compared to other nitrene-derived functional groups on black phosphorus, including N-methylbenzene, N-aminobenzene, and N-nitrobenzene. We find that by tuning the charge redistribution at the interface, the work function of black phosphorus can be tuned by more than 2 eV. These results suggest valuable tunability of the electronic properties of two-dimensional layered black phosphorus by covalent functionalization for future device applications.

Carbodicarbenes and their Captodative Behavior in Catalysis

AbstractThat of carbones is a new family member in the class of low‐valent carbon compounds. Unlike its cousin, the conventional carbene, the carbone possesses two free electron lone pairs. In combination with their unique allene‐type structure, they possess stronger σ‐donating ability than conventional carbenes such as NHCs or CAACs. Because of this property, they have a huge potential to become a new class of ligands in organometallic chemistry and catalysis. Although carbodiphosphoranes (CDP) were initially discovered in 1961, nearly 50 years were needed to attract the attention of the chemical community with the synthesis of the carbodicarbene (CDC). This Concept paper summarizes developments over the last 10 years and future outlooks for this new class of σ‐donors, particularly carbodicarbenes.

Egg-shell derived carbon dots for base pair selective DNA binding and recognition.

The development of base pair selective fluorescent binding probes and their interaction mode with nucleic acids have created great interest for sensing and biomedical applications. Herein, we have used chicken egg shell membrane (ESM) as a cost effective easily available protein source for the synthesis of highly fluorescent carbon dots. The detailed characterizations have confirmed the in situ formation of heteroatom doped graphitic carbon nanodots (CDs) from ESM. The intrinsic fluorescence property of the material has been utilized for the label free binding of duplex deoxyribonucleic acid (DNA). The interaction of different natural and synthetic DNAs with carbon dots resulted in the enhancement of fluorescence characteristics of the latter. Analysis of the binding data obtained from steady state fluorescence studies revealed a selective and stronger affinity of CDs to the adenine-thymine (AT) base pair rich double stranded DNA (ds DNA) than that of the guanine-cytosine (GC) pair rich ds DNA. Base pair specific binding was further validated from isothermal titration calorimetry (ITC) and melting temperature data. The thermodynamic profile revealed endothermic binding that was driven by the hydrophobic interaction at the nano-bio interfaces. The results reveal the potential of carbon dots as a new and promising fluorescent probe for base pair selective and sequence specific DNA recognition.

Mate choice in red-legged partridges (Alectoris rufa L.) kept in commercial laying cages; does it affect laying output?

In some gamebirds reared for shooting purposes, it has been demonstrated that free pairing and enriched environment may improve welfare. However, the effects of free pairing on the laying output of birds kept in commercial laying cages are poorly understood. Thus, the effects of free pairing on egg production were assessed in red-legged partridges (Alectoris rufa) kept in commercial laying cages (area of 0.45m2 and volume of 0.18m3). Between 2006 and 2007, we evaluated the laying output in two types of pairs: forced (n=24), where one male and one female were randomly chosen, and free (n=21), where the female chose between four males. Compared to forced pairs, free pairs laid the first egg 22days earlier and 50% of the clutch was laid 11.6days earlier. However, no significant differences in the quality of eggs or laying were found between forced and free pairs, resulting in length of laying of 76.5 days, clutch size of 39.5 eggs, 95.8% of fertility and 61.0% of hatchability of fertile eggs. Also, testosterone levels in eggs were not affected by the type of pair. We therefore recommend incorporating free pairing methods in commercial laying cages, as allowing natural reproductive behaviour has no negative effects on laying output and improves partridge welfare.

Topological defects in an unconfined nematic fluid induced by single and double spherical colloidal particles.

We present numerical solutions to the Landau-de Gennes free-energy model under the one-constant approximation for systems of single and double spherical colloidal particles immersed in an otherwise uniformly aligned nematic liquid crystal. A perfect homeotropic surface anchoring of liquid-crystal molecules on the spherical surface is considered. A large parameter space is carefully examined, including those in the free-energy model and those describing the dimer configurations and the background liquid-crystal orientation. The stability of the resulting liquid-crystal defects appearing in the neighborhood of the colloidal dimer pair is analyzed in light of the numerical results for their free energies. A number of scenarios are considered: a free dimer pair in a nematic fluid where the free-energy ground states are described in terms of a phase diagram, and a constrained dimer pair where the interparticle distance and the relative orientation of the distance vector to the nematic director can be manipulated. We pay particular attention to the nonsymmetric solutions, which yield several metastable defect states that can be observed in real systems. The high-precision numerical calculations are based on a spectral method, which is an enabling factor that allows us to compare the subtle difference in the free energies of different defect structures.

Characterization of newly synthesized pyrimidine derivatives for corrosion inhibition as inferred from computational chemical analysis

Corrosion of metallic constructions is a serious problem in most industries worldwide that can be controlled via addition of special chemicals having adsorption capability on metal surfaces and hence isolating it from the aggressive environment. These chemicals are characterized by being rich in functional groups containing free lone pairs of electrons and/or π-electrons. In the present study four newly imidazole-pyrimidine based ionic derivatives have been synthesized and their structures were characterized by means of elemental analysis and different spectroscopic techniques. Quantum chemical calculations were carried out to give insights into the structural and electronic characteristics of these fabricated compounds. Monte Carlo simulation was also applied to shed the light on our prepared corrosion inhibitor molecules by examining their aptitude to adsorb on iron surface. Our ultimate goal is to help industries in fighting corrosion by providing them with a cheap and efficient anti-corrosion molecules.

Intramedullary Cortical Button Fixation Of Distal Biceps Tendon Rupture: Long-term Patient Outcomes

Objectives:No consensus currently exists for optimal distal biceps rupture fixation. Dorsal cortical button (DCB) and dual incision transosseous (DITO) provide the greatest biomechanical load-to-failure, permitting earlier mobilization to prevent arthrofibrosis. Both methods have associated complications, restricted range of motion (ROM) from heterotopic ossification and proximal radioulnar synostosis for DITO while DCB has increased incidence of cutaneous and posterior interosseous nerve (PIN) injuries despite different techniques to reduce their frequency. The intramedullary cortical button (ICB) fixation technique aims to decrease PIN palsy risk, decrease implant costs and provide strong tendon-bone fixation allow for early ROM. We set out to determine the long-term efficacy of this technique and any difference in complication rates including re-rupture.Methods:31 patients underwent ICB fixation of chronic and acute distal biceps tendon ruptures without allograft with more than 1 year follow up. 21 patients completed a questionnaire and Disabilities of the Arm, Shoulder and Hand (DASH) survey. Elbow and forearm ROM, cosmesis, pain, strength, motor nerve neuropraxia, cutaneous sensory changes and other complications were obtained from the chart and questionnaire. The ICB technique utilizes a 4cm transverse anterior incision 2cm distal to the distal antecubital flexion crease. The tuberosity is prepared, creating a clean, bleeding bony surface. A #2 high-strength braided suture is passed through the toggle hole at both ends of a Smith and Nephew Endobutton. A needle passes one suture pair in the 4.7mm hole and out the 2mm hole drilled with mild convergence in the distal and proximal tuberosity footprint with a 1.5cm bony bridge. This suture pair shuttles the Endobutton into the intramedullary canal, both limbs of each suture exits their respective hole. One limb from each suture is whipstitched proximally and back distally. Tensioning the free suture limb exiting the 2mm hole and tying to its free suture pair compresses the biceps stump against the radial tuberosity and secures the Endobutton against the intramedullary cortex at the 2mm hole. Finally the free suture limb exiting the 4.7mm hole is tensioned and tied to its suture pair limb, distributing tendon compression over the entire tuberosity footprint.Results:At an average of 4 (1.3-7.4) years postoperatively, 81% were extremely and 10% very satisfied with their overall outcome. 81% reported no strength or ROM limitations, 76% had pain-free activity, 86% and 81% were extremely satisfied with postoperative elbow ROM and forearm ROM respectively. The mean DASH and sports DASH score were 3.52 and 2.5. Transient sensory changes were noted in the lateral antebrachial cutaneous nerve and superficial radial nerve distributions in 38% and 19% of patients respectively. Excluding workers compensation patients improved the percent of extremely satisfied patients to 93% and the average DASH score to 0.93. No biceps re-ruptures or PIN palsies were observed.Conclusion:The ICB technique provides secure distal biceps tendon fixation with excellent long-term patient satisfaction and comparable functional outcomes to existing fixation techniques with restoration of normative DASH scores. The ICB technique has a cutaneous nerve complication rate comparable to other single incision studies and no observed PIN palsies or wound complications were noted while decreasing the implant costs.

Solvation of Sodium Salts in Glymes

Sodium ion batteries are promising candidates to replace high cost lithium ion batteries due to the high natural abundance of sodium. However, conventional graphite anodes cannot be used in sodium ion batteries due to difficulties in intercalating sodium ions into graphite. Previous studies have shown that ether based electrolytes, such as glymes, are promising candidates since they do not present the problem of intercalation of sodium ions into graphite. Interestingly, the solvation of sodium ions in glymes has not been fully characterized. Here, we studied the solvation of sodium ions in glymes of different lengths, from two to four units, via two dimensional infrared spectroscopy, 2D-IR, and FTIR spectroscopy. Our studies show that the solvent molecules and counter ion play a significant role in the solvation of the sodium ion. For example, the sodium ion is mainly associated to its thiocyanate counter ion through the sulfur atom irrespective of the glyme length. Moreover, the ratio between free ions and ion pairs changes with the type of glyme. In addition, 2D-IR spectroscopic studies reveal the presence of two distinct motions in the molecular environment of the thiocyanate ion with the picosecond time scales that increase their characteristic times with the length of the glyme. In contrast, studies on sodium bis(trifluoromethane)sulfonimide (TFSI) in different glymes show a contrasting picture in which most of the counter ions do not form ion pairs with the sulfonate groups of the anion. Moreover, the TFSI ions do not seem to observe any changes in their dynamics in glymes of different lengths. Our results indicate that the molecular solvation of the sodium ion is strongly influenced by the effectiveness of the glyme to solvate the cation. However, the delocalization of the charge in the counter ion seems to be key for explaining the tendency of ion pair formation in glyme-based sodium ion electrolytes.

Free pairs of symmetric and unitary units in normal subgroups of a division ring

Let [Formula: see text] be the field of fractions of the group algebra [Formula: see text] of the Heisenberg group [Formula: see text], over the field [Formula: see text] of characteristic [Formula: see text]. We show that for some involutions of [Formula: see text] that are not induced from involutions of [Formula: see text], [Formula: see text] contains free symmetric and unitary pairs. We also give a general condition for a normal unitary subgroup of a division ring to contain a free group, and prove a generalization of Lewin’s Conjecture.

Production of dimeson atoms in high-energy collisions

The production of two-meson electromagnetic bound states and free meson pairs \( \pi^+\pi^-\) , \( K^+K^-\) , \( \pi^+K^{\mp}\) in relativistic collisions has been considered. It is shown that using of exact Coulomb wave functions for dimeson atom (DMA) allows one to calculate the yield of discrete states with the desired accuracy. The relative probabilities of production of DMA and meson pairs in the free state are estimated. The amplitude of DMA transition from 1S to 2P state, which is essential for the pionium Lamb shift measurements, has been obtained.

Hybridized estimations of support vector machine free parameters C and γ using a fuzzy learning strategy for microphone array-based speaker recognition in a Kinect sensor-deployed environment

The support vector machine (SVM) is a popular classification model for speaker verification. However, although SVM is suitable for classifying speakers, the uncertain values of the free parameters C and γ of the SVM model have been a challenging technique problem. An improper value set provided for the free parameter pair (C, γ) can cause dissatisfactory performance in the recognition accuracy of speaker verification. Moreover, the sound source localization information of the collected acoustic data has a large effect on the recognition performance of SVM speaker verification. In response, this study developed a sound source localization-driven fuzzy scheme to help determine the optimal value set of (C, γ) for the establishment of an SVM model. Specifically, this scheme adopts the estimated information of time difference of arrival (TDOA) derived from the Kinect microphone array (containing both the angle and distance information of the acoustic data of the speaker), to optimally calculate the value set of the SVM free parameters C and γ. It was demonstrated that speaker verification using the SVM with a properly estimated parameter pair (C, γ) is more accurate than that with only an arbitrarily given value set for the parameter pair (C, γ) on recognition rate.

Spin and valley control of free carriers in single-layer WS2

The semiconducting single-layer transition metal dichalcogenides have been identified as ideal materials for accessing and manipulating spin- and valley-quantum numbers due to a set of favorable optical selection rules in these materials. Here, we apply time- and angle-resolved photoemission spectroscopy to directly probe optically excited free carriers in the electronic band structure of a high quality single layer of WS$_2$. We observe that the optically generated free hole density in a single valley can be increased by a factor of 2 using a circularly polarized optical excitation. Moreover, we find that by varying the photon energy of the excitation we can tune the free carrier density in a given spin-split state around the valence band maximum of the material. The control of the photon energy and polarization of the excitation thus permits us to selectively excite free electron-hole pairs with a given spin and within a single valley.

Vibrational and impedance spectroscopic analyses of semi-interpenetrating polymer networks as solid polymer electrolytes.

Semi-interpenetrating polymer networks (semi-IPNs) with significant ionic conductivity (10-4 S cm-1 at ambient temperature) were studied by vibrational and impedance spectroscopies coupled with advanced analysis procedures. Vibrational spectroscopy recognized the numbers of free ions, ion pairs, ion-polymers and hydrogen bonds within the solid polymer electrolyte matrices (SPE). Electrochemical impedance spectroscopy (EIS) was used to quantify the bulk resistance and bulk relaxation time. The analyses used discrepancy-complexity plots to assess the number of free parameters properly, and EIS was further analyzed using impedance spectroscopy genetic programming (ISGP). Four compositions of PEO-polyurethane/poly(ethylene glycol) dimethyl ether (PEO-PU/PEGDME) were examined with LiClO4 salt. The polymer electrolyte composition of 30/70 PEO-PU/PEGDME resulted in the lowest relaxation times and the highest ionic conductivity. The best salt concentration was observed at an EO/Li ratio of 30 for the PEO-PU/PEGDME : LiClO4 (30/70) semi-IPN matrix. Several lithium salts of different anions were examined at an EO/Li ratio of 10, and the ionic conductivity achieved varied in the order -N(CF3SO2)2- > -ClO4- > -(CF3SO3)- > -I-/I3-.

On the numbers of prime factors of square free amicable pairs

On the numbers of prime factors of square free amicable pairs

Candida albicans Carriage in Children with Severe Early Childhood Caries (S-ECC) and Maternal Relatedness.

IntroductionCandida albicans has been detected together with Streptococcus mutans in high numbers in plaque-biofilm from children with early childhood caries (ECC). The goal of this study was to examine the C. albicans carriage in children with severe early childhood caries (S-ECC) and the maternal relatedness.MethodsSubjects in this pilot cross-sectional study were recruited based on a convenient sample. DMFT(S)/dmft(s) caries and plaque scores were assessed during a comprehensive oral exam. Social-demographic and related background information was collected through a questionnaire. Saliva and plaque sample from all children and mother subjects were collected. C. albicans were isolated by BBL™ CHROMagar™ and also identified using germ tube test. S. mutans was isolated using Mitis Salivarius with Bacitracin selective medium and identified by colony morphology. Genetic relatedness was examined using restriction endonuclease analysis of the C. albicans genome using BssHII (REAG-B). Multilocus sequence typing was used to examine the clustering information of isolated C. albicans. Spot assay was performed to examine the C. albicans Caspofungin susceptibility between S-ECC children and their mothers. All statistical analyses (power analysis for sample size, Spearman’s correlation coefficient and multiple regression analyses) were implemented with SAS 9.4ResultsA total of 18 S-ECC child-mother pairs and 17 caries free child-mother pairs were enrolled in the study. Results indicated high C. albicans carriage rate in the oral cavity (saliva and plaque) of both S-ECC children and their mothers (>80%). Spearman’s correlation coefficient also indicated a significant correlation between salivary and plaque C. albicans and S. mutans carriage (p<0.01) and caries severity (p<0.05). The levels of C. albicans in the prepared saliva and plaque sample (1ml resuspension) of S-ECC children were 1.3 ± 4.5 x104 cfu/ml and 1.2 ± 3.5 x104 cfu/ml (~3-log higher vs. caries-free children). Among 18 child-mother pairs, >60% of them demonstrated identical C. albicans REAG-B pattern. C. albicans isolated from >65% of child-mother pairs demonstrated similar susceptibility to caspofungin in spot assay, while no caspofungin resistant strains were seen when compared with C. albicans wild-type strain SC5314. Interestingly, the regression analysis showed that factors such as antibiotic usage, birth weight, inhaler use, brushing frequency, and daycare attendance had no significant effect on the oral carriage of C. albicans in the S-ECC children.ConclusionsOur results reveal that both the child with S-ECC and the mother were highly infected with C. albicans, while most of the strains were genetically related, suggesting that the mother might be a source for C. albicans acquisition in the oral cavity of children affected by the disease.

Characteristics of novel plastic crystal gel polymer electrolytes based on PVdC-co-AN

A new gel polymer electrolytes composed of poly(vinylidene chloride-co-acrylonitrile) (PVdC-co-AN) co-polymer and plastic crystal succinonitrile (SN) were prepared to form plastic crystal gel polymer electrolytes (PGPEs) with the variation of magnesium triflate (MgTf2) salt from 5 to 30 wt.%. The room temperature and temperature dependence studies of the PGPE films were determined by using AC impedance spectroscopy. The conductivity versus reciprocal temperature plot has shown a nonlinear behavior. The ionic and cationic transport numbers were evaluated by DC polarization method and the combination of DC polarization and AC impedance methods, respectively to determine the charge carrier species in the PGPE films. To study the interactions among the constituents in the PGPEs as well as to confirm the complexation between them, Fourier transform infrared spectroscopy (FTIR) was carried out. The analysis of FTIR spectra was further investigated by deconvolution of the FTIR spectra to prove the dependability of ionic conductivity and transport number with the presence of free ions, ion pairs, and ion aggregates in the PGPEs.

Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate

In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and ethylene carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.