Laplacian Flow of Closed G$$_$$-Structures Inducing Nilsolitons

We study the existence of left invariant closed \(G_2\)-structures defining a Ricci soliton metric on simply connected nonabelian nilpotent Lie groups. For each one of these \(G_2\)-structures, we show long time existence and uniqueness of solution for the Laplacian flow on the noncompact manifold. Moreover, considering the Laplacian flow on the associated Lie algebra as a bracket flow on \({\mathbb {R}}^7\) in a similar way as in Lauret (Commun Anal Geom 19(5):831–854, 2011) we prove that the underlying metrics \(g(t)\) of the solution converge smoothly, up to pull-back by time-dependent diffeomorphisms, to a flat metric, uniformly on compact sets in the nilpotent Lie group, as \(t\) goes to infinity.     

On Models of Directed Path Graphs Non Rooted Directed Path Graphs

A directed path graph is the intersection graph of a family of directed subpaths of a directed tree. A rooted directed path graph is the intersection graph of a family of directed subpaths of a rooted tree. Clearly, rooted directed path graphs are directed path graphs. Several characterizations are known for directed path graphs: one by forbidden induced subgraphs and one by forbidden asteroids. It is an open problem to find such characterizations for rooted directed path graphs. With the purpose of proving knowledge in this direction, we show in this paper properties of directed path models that can not be rooted for chordal graphs with any leafage and with leafage four. Therefore, we prove that for leafage four directed path graphs minimally non rooted directed path graphs have a unique asteroidal quadruple, and can be characterized by the presence of certain type of asteroidal quadruples.     

Dissociation enthalpies of synthesized multicomponent gas hydrates with respect to the guest composition and cage occupancy

This study presents the influences of additional guest molecules such as C2H6, C3H8, and CO2 on methane hydrates regarding their thermal behavior. For this purpose, the onset temperatures of decomposition as well as the enthalpies of dissociation were determined for synthesized multicomponent gas hydrates in the range of 173-290 K at atmospheric pressure using a Calvet heat-flow calorimeter. Furthermore, the structures and the compositions of the hydrates were obtained using X-ray diffraction and Raman spectroscopy as well as hydrate prediction program calculations. It is shown that the onset temperature of decomposition of both sI and sII hydrates tends to increase with an increasing number of larger guest molecules than methane occupying the large cavities. The results of the calorimetric measurements also indicate that the molar dissociation enthalpy depends on the guest-to-cavity size ratio and the actual concentration of the guest occupying the large cavities of the hydrate. To our knowledge, this is the first study that observes this behavior using calorimetrical measurements on mixed gas hydrates at these temperature and pressure conditions.     

Polyphenolic Flavonoid Compound Quercetin Effects in the Treatment of Acute Myeloid Leukemia and Myelodysplastic Syndromes

Flavonoids are ubiquitous groups of polyphenolic compounds present in most natural products and plants. These substances have been shown to have promising chemopreventive and chemotherapeutic properties with multiple target interactions and multiple pathway regulations against various human cancers. Polyphenolic flavonoid compounds can block the initiation or reverse the promotion stage of multistep carcinogenesis. Quercetin is one of the most abundant flavonoids found in fruits and vegetables and has been shown to have multiple properties capable of reducing cell growth in cancer cells. Acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) therapy remains a challenge for hematologists worldwide, and the outcomes for patients with both disorders continue to be poor. This scenario indicates the increasing demand for innovative drugs and rational combinative therapies. Herein, we discuss the multitarget effects of the flavonoid quercetin, a naturally occurring flavonol, on AML and MDS.     

Rational approximations of the Arrhenius integral using Jacobi fractions and gaussian quadrature

The aim of this work is to find approaches for the Arrhenius integral by using the n-th convergent of the Jacobi fractions. The n-th convergent is a rational function whose numerator and denominator are polynomials which can be easily computed from three-term recurrence relations. It is noticed that such approaches are equivalent to the one established by the Gauss quadrature formula and it can be seen that the coefficients in the quadrature formula can be given as a function of the coefficients in the recurrence relations. An analysis of the relative error percentages in the approximations is also presented.     

Characterization of O2 (1Δg)-derived oxidation products of tryptophan: A combination of tandem mass spectrometry analyses and isotopic labeling studies

The fragmentation mechanisms of singlet oxygen [O(2) ((1)Delta(g))]-derived oxidation products of tryptophan (W) were analyzed using collision-induced dissociation coupled with (18)O-isotopic labeling experiments and accurate mass measurements. The five identified oxidized products, namely two isomeric alcohols (trans and cis WOH), two isomeric hydroperoxides (trans and cis WOOH), and N-formylkynurenine (FMK), were shown to share some common fragment ions and losses of small neutral molecules. Conversely, each oxidation product has its own fragmentation mechanism and intermediates, which were confirmed by (18)O-labeling studies. Isomeric WOH lost mainly H(2)O + CO, while WOOH showed preferential elimination of C(2)H(5)NO(3) by two distinct mechanisms. Differences in the spatial arrangement of the two isomeric WOHs led to differences in the intensities of the fragment ions. The same behavior was also found for trans and cis WOOH. FMK was shown to dissociate by a diverse range of mechanisms, with the loss of ammonia the most favored route. MS/MS analyses, (18)O-labeling, and H(2)(18)O experiments demonstrated the ability of FMK to exchange its oxygen atoms with water. Moreover, this approach also revealed that the carbonyl group has more pronounced oxygen exchange ability compared with the formyl group. The understanding of fragmentation mechanisms involved in O(2) ((1)Delta(g))-mediated oxidation of W provides a useful step toward the structural characterization of oxidized peptides and proteins.     

Calorimetric and SEM studies of PHB–PET polymeric blends

PHB [poly (3-hydroxybutyrate)], post-consumer soft-drink bottles poly (ethylene terephthalate) PET (herein named PET-R) and PHBPET-R (blends of PHB and PET-R in several compositions) samples were evaluated by differential scanning calorimetry (DSC) and scanning electronic microscopy (SEM) in order to verify their thermal properties and porosity according to amounts of PET-R added the blends. The DSC curve showed that the solvents used to solve the polymer mixture cause changes in the thermal behavior of PET-R films and in PHBPET-R blends. SEM studies of the PHBPET-R blends show that with a gradual mass increase of PET-R, there are gradual increases in the porosity of the films.     

Ring expansion of functionalized octahydroindoles to enantiopure cis-decahydroquinolines

A new synthetic entry to enantiopure cis-decahydroquinolines is reported. Endo and exo derivatives of cis-1-benzyl-2-(hydroxymethyl)octahydroindol-6-one ethylene acetal undergo ring enlargement upon treatment with TFAA and then Et3N (thermodynamic conditions) to give enantiopure 1-benzyl-3-hydroxydecahydroquinolin-7-one derivatives in 77 and 82% yield, respectively. For 2-(1-hydroxyethyl) analogues, the best synthetic result is obtained from the (2S,1'R) endo isomer, which under kinetic reaction conditions (MsCl, THF, -20 degrees C, then AgOAc at rt ) gives the expanded product in 54% yield.     

Sex differences in the relationship between white matter microstructure and impulsivity in adolescents

Rapid maturational brain changes occur during adolescence--a time associated with risk-taking behaviors and improvements in cognition. The present study examined the relationship between white matter (WM) microstructure, impulsive behavior and response inhibition in female and male adolescents. Twenty-one healthy adolescents underwent diffusion tensor imaging using a 3.0-T magnetic resonance imaging system. Impulse control was assessed using the Bar-On Emotional Quotient Inventory, Youth Version. Response inhibition was assessed using the Stroop Color-Word Interference Test. Fractional anisotropy (FA), a measure of WM coherence, and trace, a measure of overall diffusivity, were determined from voxels manually placed in the midline and in the left and right forward-projecting arms of the genu and the splenium of the corpus callosum. Sex-specific differences were observed for the relationship between FA and impulsive behavior in the right anterior callosum for males and in the splenium for females. Males, compared to females, displayed significantly higher FA in the left WM region. Although trace was not associated with impulse control, trace in the genu (for females) and splenium (males and females) was associated with Stroop performance. Regional differences in trace also were evident, with lower values in the splenium observed than in all other regions. Although the latter significantly improved with age, no sex differences in impulse control or in Stroop performance were detected. The present findings provide supporting evidence for sex-related differences in the development of WM microstructure during adolescence. These data further suggest a neurobiological mechanism underlying some of the emotional and cognitive changes commonly observed in males versus females during the adolescent period.     

Enantioselective total synthesis of (S)-bisoranjidiol, an axially chiral bisanthraquinone

The first enantioselective total synthesis of the bisanthraquinone (S)-bisoranjidiol and an unnatural regioisomer has been accomplished. Key features of the synthesis include the asymmetric oxidative biaryl coupling of a hindered 8-substituted 2-naphthol, selective para-quinone formation, and regioselective tandem Diels-Alder/aromatization reactions.