Synthesis, structure and dispersion interactions in bis(1,8-naphthalendiyl)distibine.

Naph2Sb21 was synthesized by a reaction of 1,8-dilithionaphthalene NaphLi2 with SbCl3 and its solid state structure is reported on. 1 shows intermolecular interactions in the solid state, which were studied by quantum chemical calculations with dispersion corrected density functional theory, supermolecular ab initio approaches and symmetry adapted perturbation theory. The same methods were employed to compare the solid state interactions in the crystal of 1 to those in real (for E = P) and hypothetical (for E = As and Bi) crystal structures of Naph2E2. Dispersion interactions were found to provide the most important stabilising contribution in all cases, seconded by electrostatic attraction between pnictogen atoms and π-systems of neighbouring naphthyl groups.

Synthesis of Bi2Te3 and (BixSb1-x)2Te3 nanoparticles using the novel IL [C4mim]3[Bi3I12].

The novel Bi-containing reactive ionic liquid [C4mim]3[Bi3I12], which was synthesized in quantitative yield by equimolar reaction of BiI3 and [C4mim]I, was used as a novel Bi-source for the ionothermal synthesis of Bi2Te3 nanoparticles by reaction with (Et3Si)2Te in the ionic liquid [C4mim]I. The solid state structure of [C4mim]3[Bi3I12] was determined by single crystal X-ray diffraction. In addition, the ionothermal synthesis of the single source precursor (Et2Sb)2Te and [C4mim]3[Bi3I12] yielded the ternary (BixSb1-x)2Te3 (x = 0.25, 0.5, 0.75) nanoparticles. The chemical composition and phase purity of the tetradymite-type materials were determined by EDX and XRD and the surface composition of the nanoparticles was further investigated by IR and XPS. In addition, the morphology of the nanoparticles was investigated by SEM and TEM.

Synthesis and solid state structure of a metalloid tin cluster [Sn10(trip8)].

(trip2Sn)2 (trip = 2,4,6-i-Pr3C6H2) reacts with Mg(i) reductants (LMg)2 (L = HC[C(Me)N(dipp)]2) and (L'Mg)2 (L' = HC[C(Me)N(mes)]2) with Sn-C bond cleavage and formation of the novel metalloid tin cluster Sn10trip8 1 or elemental tin. 1, which contains Sn atoms in the formal oxidation states 0, +I and +II, and the side products LMgtrip (2) and L'Mgtrip (3) were characterized spectroscopically and by single crystal X-ray diffraction.

Lewis acid-base adducts of group 13 elements: synthesis, structure and reactivity toward benzaldehyde.

Lewis acid-base adducts [LGa-M(C6F5)3] (M = B 1, Al 2, Ga 3) were prepared by the reaction of gallanediyl LGa {L = HC[C(Me)N(2,6-i-Pr2C6H3)]2} with the Lewis acids M(C6F5)3 (M = B, Al, Ga). Benzaldehyde reacts with [LGa-M(C6F5)3] (M = B 1, Al 2) at room temperature with the insertion and formation of [LGa(C6F5){CH(Ph)(OB(C6F5)2)}] (4) and the zwitterionic species [LGa(C6F5){CH(Ph)(OAl(C6F5)2)}] (5), respectively, which was found to decompose at 80 °C with the formation of {(C6F5)2Al(OCH2Ph)}2 (6). Any attempts to isolate the insertion complex of [LGa-Ga(C6F5)3] with benzaldehyde failed and only {(C6F5)2Ga(OCH2Ph)}2 (7) was isolated at elevated temperatures. 2-5 and 7 were structurally characterized by heteronuclear NMR spectroscopy and single crystal X-ray diffraction.

(Me)L2Zn2(µ-1,6-Ph2-N6) - a building block for new hexazene complexes.

The zinc hexazene complex (Me)L2Zn2(µ-1,6-Ph2-N6) 1 ((Me)L = HC[C(Me)N(2,4,6-Me3C6H2)]2) is a suitable hexazene transfer reagent in reactions with main group metal and transition metal complexes containing M-Me units. The reactions proceed with elimination of (Me)LZnMe and the resulting complexes were characterized by NMR and IR spectroscopy and single crystal X-ray diffraction (5, 8). Quantum chemical calculations were performed to investigate the electronic structure of 5' and 8' in more detail and to identify the absorption bands of the hexazene unit.

Bonding situation in Be[N(SiMe3)2]2 ­ an experimental and computational study.

The solid state structure of Be[N(SiMe3)2]2 (1) was determined by in situ crystallisation and the bonding situation investigated by quantum chemical calculations. The Be-N bond is predominantly ionic, but some evidence for the presence of a partial Be-N double bond character was found.

Germane vs. digermane formation.

Oxidative addition reactions of dialkylchalcogenanes R2E2 and [Me2Si(Nt-Bu)2]Ge 1 yielded bis(alkylchalcogeno)germanes Me2Si(Nt-Bu)2Ge(ER)2 (R = Et, E = S 2, Se 3; R = Me, E = Se 4) and digermanes [Me2Si(Nt-Bu)2Ge(EEt)]2 (E = S 5, Se 6). The reaction of 1 with Et2Te2 proceeds with formation of Me2Si(Nt-Bu)2Ge(TeEt)27, which slowly converts into the Te-bridged complex [Me2Si(Nt-Bu)2GeTe]28. 1-6 and 8 were characterized by single crystal X-ray diffraction.

Sequential Bi-C bond activation reactions of BiEt3 via insertion reactions of RE {R = HC[C(Me)N(2,6-i-Pr2C6H3)]2; E = Al, Ga, In}.

Two of the Bi-C bonds of BiEt3 are sequentially activated by mono-valent RM {R = HC[C(Me)N(2,6-i-Pr2C6H3)]2; M = Al, Ga, In}. The first Bi-C bond activation leads to the formation of insertion complexes, [RMEt(BiEt2)] (M = Al 1; Ga 2; In 3), whereas the consecutive second activation proceeds through a reductive elimination of RMEt2 (M = Al 4, Ga 5), elemental Bi and BiEt3.

Reactions of a Zn(I) complex with group 14 azides--formation of zinc azide and zinc hexazene complexes.

Two zinc hexazene complexes L2Zn2(l-1,6-R2-N6) (L = HC[C(Me)N-(2,4,6-Me3C6H2)]2; R = Ph (3), Dipp = 2,6-i-Pr2C6H3 (4)), were synthesized by reaction of the Zn(I) complex L2Zn2 (1) with phenyl azide and 2,6-diisopropylphenyl azide, respectively. 3 represents the second structurally characterized transition metal hexazene complex. In contrast, reactions of 1 with Me3MN3 (M = Si, Sn) yielded the azido complex [LZn(l-N3)]2 (2) and Me3M-MMe3.

Reaction of L2Zn2 with Ph2E2--synthesis of LZnEPh and reactions with oxygen and H-acidic substrates.

L2Zn2 (L = HC[C(Me)N(2,4,6-Me3C6H2)]2) and Ph2E2 (E = Se, Te) react to form LZnSePh (1) and LZnTePh (2).1 and 2 further react with H2O and EtOH to form LZnOH (3) and LZnOEt (4), respectively, whereas the reaction of 2 with oxygen yielded [LZnOTe(O)Ph]2 (5). 1, 4 and 5 were characterized by single crystal X-ray diffraction.

Electroretinographic detection of human brain dopamine response to oral food stimulation.

OBJECTIVE: The activity of dopamine-dependent retinal signaling can be assessed using electroretinography. Response of this system to oral food stimulation might provide accessible insight into the brain dopamine response to oral stimuli as retinal dopamine concentration is dependent upon mid brain dopamine concentration was postulated. DESIGN AND METHODS: Nine individuals had cone ERG (b wave) response to oral food stimulation and oral methylphenidate (MPH) administration measured on separate days, and completed self reported eating behavior questionnaires. RESULTS: Significant and similar increases in b wave response to both stimuli (P = 0.012 and P = 0.042, MPH and food, respectively) and significant correlations of the food stimulated b wave amplitude with binge eating related behavior as measured by the Gormally Binge Eating Scale (r = 0.68, P = 0.044) and self-reported trait hunger as measured by the Stunkard and Messick Three Factor Eating Questionnaire (r = 0.67, P = 0.048) were found. CONCLUSION: The significant increase in food stimulated dopamine dependent b wave amplitude and correlation with methylphenidate stimulated b wave amplitude suggest that ERG may offer a relatively inexpensive and accessible methodology for potentially assess dopaminergic responses to food and other externally applied stimuli that have been implicated in the pathogenesis of a number of human diseases.

Comparison of calcium supplementation or low-fat dairy foods on epithelial cell proliferation and differentiation.

Epidemiological evidence suggests that dietary calcium and vitamin D intake are inversely related to incidence of colon cancer. Previous studies have demonstrated that supplementation of the diet with calcium in the form of calcium tablets or low-fat dairy foods alters colonic epithelial cell proliferation from a higher- to a lower-risk pattern. The present study compared relative effects of administration of calcium carbonate at approximately 900 mg/day (calcium) with those of a low-fat dairy food diet providing about the same amount of calcium (dairy) in a cross-over "head-to-head" study of 40 subjects at risk for colonic neoplasia. Dietary intake of macronutrients was similar in the two study periods, except for a slight increase in protein intake during dairy calcium supplementation. Rectal epithelial cell proliferation was studied in flat endoscopically normal-appearing mucosa at baseline and at the end of each of the two study periods and showed a significant reduction in epithelial crypt cell labeling index from 12.5% to 9.1% (calcium) or 9.3% (dairy) as well as in proliferating cells in the upper 40% of the crypt from 0.09 to 0.03 in the calcium- and low-fat dairy-supplemented intervention groups. No significant changes in two epithelial cell differentiation markers, cytokeratin AE1 and acidic mucins, were found. Furthermore, there were no differences in epithelial cell apoptosis or expression of the proapoptotic gene product BAK. These data indicate that increased dietary calcium given as supplements or in the diet in low-fat dairy foods lowers epithelial cell proliferation indexes from a higher- to a lower-risk pattern. Because supplemental calcium has been shown to reduce the recurrence of colonic adenomatous polyps in patients at increased risk for colonic neoplasia, our data suggest that supplemental low-fat dairy foods may also be effective.

The calorie: myth, measurement, and reality.

Few dietary components are surrounded by more misinformation and myths than the calorie. This confusion can be attributed in part to a lack of accurate and practical methods for assessing energy intake and thus requirements in humans over periods extending beyond several days. The availability of modern respiratory-chamber indirect calorimetry systems and results from human studies with doubly labeled water are now helping to clarify uncertainties surrounding energy requirements. We describe studies of patients with endogenous obesity as an example of how these research methods are resolving long-standing questions regarding energy requirements. The results of these investigations reveal some of the flaws in estimating energy requirements by self-report methods. Advances in accurately measuring energy expenditure are making important contributions to the study of human energy requirements and are providing new and important research opportunities.

Menopausal changes in body composition and energy expenditure.

Adult American women as a group tend to gain weight with age, and many women report that their weight gain started around the time of their menopause. Moreover, as women age, there are changes in body composition that include losses in bone mineral and body cell mass, and increases in total body fat, visceral fat, and extracellular fluid. It appears as if these body composition changes begin or accelerate during the menopausal years. The importance of weight gain and changes in body composition are their associations with an increased risk of developing some malignancies, cardiovascular disease, osteoporosis, and several other clinical conditions. This overview describes selected studies of menopause and aging-associated weight gain, changes in body composition, and alterations of energy expenditure in women. Gaps in the present understanding of these changes are highlighted, and an emphasis is placed on new research methodologies for investigating body composition and energy expenditure in vivo. A concluding section of the report summarizes areas in need of future investigation.