Characterization of the train-average time-frequency parameters inherent in the low-power picosecond optical pulses generated by the actively mode-locked semiconductor laser with an external single-mode fiber cavity

The specific approach to characterizing the train-average parameters of low-power picosecond optical pulses with the frequency chirp, arranged in high-repetition-frequency trains, in both time and frequency domains is elaborated for the important case when the semiconductor laser is matched by an external single-mode fiber cavity and operates in the active mode-locking regime. This approach involves the joint Wigner time-frequency distributions, which can be created for those pulses due to exploitation of a novel interferometric technique. Practically, the InGaAsP/InP-heterolaser generating at the wavelength 1320 nm was used during the experiments carried out and an opportunity of reconstructing the corresponding joint Wigner time-frequency distributions was successfully demonstrated.     

Kinetics and mechanisms of the permanganate oxidation of L-valine in neutral aqueous solutions

The permanganate oxidation of L-valine has been studied by visible spectrophotometry in neutral aqueous solutions. Under these conditions, both the zwitterionic and anionic forms of the amino acid are oxidized, the reaction being autocatalyzed by soluble colloidal manganese dioxide. Kinetic data for both the uncatalyzed and autocatalytic reaction pathways have been obtained, and reaction sequences consistent with the experimental findings are proposed.     

Using Process Control Chart Techniques to Analyse Crime Rates in Houston,Texas

In this paper we use ARIMA time series models and statistical process control techniques to determine if changes occurred in the process that generated a series of observations. The procedure is applied to eight crime time series for the city of Houston, Texas: total crime, murder, rape, robbery, aggravated assault, burglary, theft, and motor vehicle theft. The objective of our analysis is to determine if, after the institution of an overtime programme by the Houston Police Department, the different series show some statistical evidence of a change. Our results show that the categories of total crime, robbery, burglary, theft, and motor vehicle theft decreased significantly. Murder and rape remained statistically unchanged, while aggravated assault continued to increase.     

Magnesium monoperoxyphtalate: A new reagent for the oxidative ring opening of furans to cis-enediones

Ring opening of furans can be accomplished with the title reagent to afford cis-enediones stereospecifically, with great advantages over the hazardous MCPBA.     

Structure and bonding in binuclear metal carbonyls from the analysis of domain averaged Fermi holes. I. Fe2(CO)9 and Co2(CO)8

The nature of the bonding in the above carbonyls was studied using the analysis of domain averaged Fermi holes (DAFH). The results straightforwardly confirm the conclusions of earlier theoretical studies in which the existence of direct metal-metal bond, anticipated for the above carbonyls on the basis of 18-electron rule, was questioned. In addition to indicating the lack of direct metal-metal bond, the DAFH analysis also allowed to characterize the nature of the electron pairs involved in the bonding of the bridging ligands. The analysis has shown that because the number of available electron pairs is not sufficient for the formation of ordinary localized 2c-2e bonds between terminal M(CO)(3) fragments and the bridging ligands, the bonding in both carbonyls exhibits typical features of electron deficiency and one bonding electron pair is effectively involved in multicenter 3c-2e bonding. Because of the symmetry of the complexes the bridging ligands are not distinguishable and all M-C-M bridges have a partial 3c-2e nature via resonance of the localized structures.     

Fabrication and gas separation properties of polybenzimidazole (PBI)/nanoporous silicates hybrid membranes

Composites of polybenzimidazole (PBI) with proton-exchanged AMH-3 and swollen AMH-3 were prepared, characterized by electron microscopy and X-ray scattering and tested for hydrogen/carbon dioxide ideal selectivity. Proton-exchanged AMH-3 was prepared under mild conditions by the ion exchange of Sr and Na cations in the original AMH-3 using aqueous solution of dl-histidine. Swollen AMH-3 was prepared by sequential intercalation of dodecylamine following the ion exchange in the presence of dl-histidine. Both silicate materials were introduced into a continuous phase of PBI as a selective phase. Mixed matrix nanocomposite membranes, prepared under certain casting conditions, with only 3 wt% of swollen AMH-3 present substantial increase of hydrogen/carbon dioxide ideal selectivity at 35 °C, i.e., more than by a factor of 2 compared to pure PBI membranes (40 vs. 15). Similar ideal selectivity was observed using higher loadings (e.g., 14%) of proton-exchanged AMH-3 particles suggesting that transport of hydrogen is faster than carbon dioxide in AMH-3-derived silicates. However, the ideal selectivity of mixed matrix membranes approaches that of pure polymer as the operating temperature increases to 100 °C and 200 °C. The composite membranes with AMH-3-derived materials were compared with MCM-22/PBI membranes. Composite membranes incorporating MCM-22 plate-like crystals show no selectivity enhancements possibly due to the presence of larger pores in MCM-22.     

(infinity)(2)[Cu2(mu5-btb)(mu-OH)(mu-H2O)]: a two-dimensional coordination polymer built from ferromagnetically coupled Cu2 units (btb = benzene-1,2,3-tricarboxylate)

Hydrothermal reaction of Cu(NO(3))(2).3H(2)O, Cd(OH)(2) or Zn(OH)(2) with benzene-1,2,3-tricarboxylic acid (H(3)btb, hemimellitic acid) produced the 2D coordination polymer (MOF) [Cu(2)(mu(5)-btb)(mu-OH)(mu-H(2)O)] () and the 2D hydrogen-bonded complexes [Cd(H(2)btb)(2)(H(2)O)(4)].2H(2)O () and [Zn(H(2)O)(6)](H(2)btb)(2).4H(2)O () which are characterized by single-crystal X-ray diffraction, X-ray powder diffraction and thermoanalysis. Magnetic susceptibility measurements between 1.9-300 K for revealed three magnetic active exchange pathways that link the copper(ii) ions through a long mu-aqua bridge, an anti-syn carboxylate bridge [j(2) = 0.161(1) cm(-1)], and through a mixed mu-hydroxo + syn-syn carboxylate bridge [J = 83(1) cm(-1)]. At temperatures higher than 30 K the system behaves as isolated Cu(2) units with strong ferromagnetic Cu-Cu coupling through the mu-hydroxo and syn-syn carboxylate bridge. The strong ferromagnetic coupling is explained with Hoffmann's approach by means of the concept of counter-complementarity introduced by Nishida et al.[Chem. Lett., 1983, 1815-1818].     

Cored anion-exchange chromatography media for antibody flow-through purification

Agarose-based anion-exchangers (e.g. quaternary amine, Q) have been widely used in monoclonal antibody flow-through purification to remove trace levels of impurities. Such media are often packed in a large column and the operation is usually robust but with limited throughput due to the compressibility of agarose and consequentially low bed permeability. In order to address this limitation, cored Q beads consisting of a rigid core and a thin agarose gel coating were developed and evaluated for protein flow-through chromatography. Using laboratory-scale columns it was found that, the cored beads indeed provide significantly enhanced rigidity and flow permeability relative to conventional homogeneous agarose resins. Depending on the structure and size of the cored beads, the permeability was 2-4-fold higher than that of a commonly used commercial agarose resin. Good virus and host cell protein clearance was achieved with the cored Q beads even at increased flow velocities. In addition, the impermeable core allows for more efficient use of buffers without loss of useful capacity in polishing applications. Process analyses based upon the experimental data demonstrated that the enhanced permeability achieved with the cored beads can significantly improve process throughput and economics.     

A Bibliometric Evaluation of the Top 100 Cited Dimethyl Fumarate Articles

Dimethyl fumarate is a cytoprotective and immunomodulatory drug used in the treatment of multiple sclerosis. We performed a bibliometric study examining the characteristics and trends of the top 100 cited articles that include dimethyl fumarate in the title. On 21 September 2020 we carried out an electronic search in the Web of Science (WOS), seeking articles that include the following terms within the title: dimethyl fumarate, BG-12, or Tecfidera. To focus our investigation on original research, we refined the search to include only articles, early access, others, case report, and clinical trials. We obtained a total of 1115 items, which were cited 7169 times, had a citation density of 6.43 citations/item, and an h-index of 40. Around 2010, there was a jump in the number of published articles per year, rising from 5 articles/year up to 12 articles/year. We sorted all the items by the number of citations and selected the top 100 most cited (T100). The T100 had 4164 citations, with a density of 37 citations/year and contained 16 classic research articles. They were published between 1961 and 2018; the years 2010–2018 amassed nearly 80% of the T100. We noted 17 research areas with articles in the T100. Of these, the number one ranking went to neurosciences/neurology with 39 articles, and chemistry ranked second on the T100 list with 14 items. We noticed that the percentage of articles belonging to different journals changed depending on the time period. Chemistry held the highest number of papers during 1961–2000, while pharmacology andneurosciences/neurology led the 2001–2018 interval. A total of 478 authors from 145 institutions and 25 countries were included in the T100 ranking. The paper by Gold R et al. was the most successful with 14 articles, 1.823 citations and a density of 140.23 citations/year. The biotechnological company Biogen led the T100 list with 20 articles. With 59 published articles, the USA was the leading country in publications. We concluded that this study analyzed the use of and research on dimethyl fumarate from a different perspective, which will allow the readership (expert or not) to understand the relevance of classic and recent literature on this topic.