On the structure and dehydration of hydrous zirconia and hafnia xerogels

Hydrous zirconia and hafnia xerogels of compositions ZrO2 · 2.5H2O and HfO2 · 2.3H2O are dehydrated in two steps upon heating. First, molecular water is mostly removed from the structures to form phases of compositions ZrO2 · H2O and HfO2 · 0.5H2O. Second, polycondensation of OH groups occurs. Both processes are easier for ZrO2 · 2.5H 2O. Apart from these steps, the interaction of water molecules with zirconium-oxygen bridges was found to occur during dehydration of the zirconium compound. The composition of HfO2 · 0.5H2O should actually read as Hf4O7(H2O)(OH)2. © Pleiades Publishing, Ltd., 2010

Crystal structure of Rb2[GeO2(OH)2] •2H2O

Single crystals of Rb2[GeO2(OH)2] • 2H2O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna21, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R 1 = 0.0506. In [GeO2(OH)2]2- anions, the Ge-O distances (1.71-1.73(1) Å) are shorter than the Ge-OH distances (1.76-1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed. © Nauka/Interperiodica 2006

Structure and dehydration of hydrous tin dioxide xerogel

Hydrous tin dioxide xerogel with the composition SnO2 • 1.75H 2O is built of tin-oxygen-hydroxide fragments. Water molecules (no more than 1 mol) in the grain structure are kept by hydrogen bonds. Xerogel is dehydrated in the range 50-890°C in two stages. Below 123°C, molecular water is removed and the polycondensation of ≡Sn-O(H)-Sn≡ bridge groups occurs. There also takes place the transition of some water molecules from the molecular to hydroxide form as follows: ≡Sn-O-Sn≡ + H 2O → 2≡Sn-O-H. All processes occur within individual grains. Above 123°C, water removal is due to the polycondensation of tin-oxygen groups. As a result, grains are coarsen. After 200°C, their structure is determined as cassiterite coated by tin oxyhydrate. © 2007 Pleiades Publishing, Inc

Crystal structure of Rb2[GeO2(OH)2] •2H2O

Single crystals of Rb2[GeO2(OH)2] • 2H2O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna21, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R 1 = 0.0506. In [GeO2(OH)2]2- anions, the Ge-O distances (1.71-1.73(1) Å) are shorter than the Ge-OH distances (1.76-1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed. © Nauka/Interperiodica 2006

Structure and dehydration of hydrous tin dioxide xerogel

Hydrous tin dioxide xerogel with the composition SnO2 • 1.75H 2O is built of tin-oxygen-hydroxide fragments. Water molecules (no more than 1 mol) in the grain structure are kept by hydrogen bonds. Xerogel is dehydrated in the range 50-890°C in two stages. Below 123°C, molecular water is removed and the polycondensation of ≡Sn-O(H)-Sn≡ bridge groups occurs. There also takes place the transition of some water molecules from the molecular to hydroxide form as follows: ≡Sn-O-Sn≡ + H 2O → 2≡Sn-O-H. All processes occur within individual grains. Above 123°C, water removal is due to the polycondensation of tin-oxygen groups. As a result, grains are coarsen. After 200°C, their structure is determined as cassiterite coated by tin oxyhydrate. © 2007 Pleiades Publishing, Inc

On the structure and dehydration of hydrous zirconia and hafnia xerogels

Hydrous zirconia and hafnia xerogels of compositions ZrO2 · 2.5H2O and HfO2 · 2.3H2O are dehydrated in two steps upon heating. First, molecular water is mostly removed from the structures to form phases of compositions ZrO2 · H2O and HfO2 · 0.5H2O. Second, polycondensation of OH groups occurs. Both processes are easier for ZrO2 · 2.5H 2O. Apart from these steps, the interaction of water molecules with zirconium-oxygen bridges was found to occur during dehydration of the zirconium compound. The composition of HfO2 · 0.5H2O should actually read as Hf4O7(H2O)(OH)2. © Pleiades Publishing, Ltd., 2010

Interaction of components in the NaOH-TiO2 · H 2O-H2O system at 25°C

Solubilities in the NaOH TiO2 · H2O-H 2O system at 25°C were studied. The solubility isotherm was found to have two maxima. The formation of two compounds, Na2Ti 5O11 · 10H2O and Na2Ti 3O7 · 7H2O, was established. © Pleiades Publishing, Ltd., 2011

Vaginal microbiota is an epigenetic factor for early onset of atopy in children of asthmatic mothers

E.A.&nbsp;Boytsova1, T.V.&nbsp;Kosenkova1, N.M.&nbsp;Bogdanova2, V.P.&nbsp;Novikova2,3, M.N.&nbsp;Boldyreva4, O.V.&nbsp;Lavrova3, V.F.&nbsp;Bezhenar’3 1 V.A.&nbsp;Almazov National Medical Research Centre, St. Petersburg, Russian Federation 2 St. Petersburg State Pediatric Medical University, St. Petersburg, Russian Federation 3 Pavlov First St. Petersburg State Medical University, St. Petersburg, Russian Federation 4 NRC Institute of Immunology, Moscow, Russian Federation Background: in recent years, early (i.e., within the first days or weeks of life) onset, severe course, and comorbid nature of allergies are reported in children. The risk of atopic disorder in a child of asthmatic mother is always significantly higher. Sensitization is determined by hereditary load as well as by epigenetic factors. Among them, the course of pregnancy is of crucial importance. Molecular mechanisms of the effect of gestational maternal microbiota (in particular, vaginal microbiocenosis) on the course of pregnancy and delivery as well as their protective role in neonatal health and atopic disorder development are still elusive and require further investigation. Aim: to study vaginal microbiota in pregnant women with asthma, to identify factors affecting vaginal microbiocenosis, and to establish the association between cervical microbiota composition and atopy onset in a child. Patients and Methods: the study included 37 couples, i.e., pregnant w oman with moderate asthma and her child. Pregnant women were enrolled at 36–38 weeks of gestation. Quantitative and qualitative composition of cervical microbiota was studied by polymerase chain reaction. Newborns were observed in maternity hospital and then monthly up to one year; clinical symptoms were assessed. Preeclampsia was diagnosed in 53% and threatened abortion in 47% of pregnant women. Results: in pregnant women with asthma, preeclampsia resulted in reduced levels of Lactobacillus spp. (p=0.29) in cervical mucus while threatened abortion resulted in increased levels of Gardnerella vaginalis (p=0.039). In mothers of children with atopy onset within the first 4 weeks of life, increased levels of Eubacterium spp. (p=0.025) in vaginal microflora were revealed at 38 weeks of gestation. In mothers with hypogalactia, increased levels of Mobiluncus spp. and Corynebacterium spp. (p=0.044) were revealed. Conclusion: threatened abortion and preeclampsia are epigen etic factors which affect cervical microflora composition in pregnant women with asthma and interrupt vertical transfer of microbiota from the mother. The result is the early onset of atopy in the child. Keywords: pregnancy, asthma, vaginal microbiota, children, allergy. For citation: Boytsova E.A., Kosenkova T.V., Bogdanova N.M. et al. Vaginal microbiota is an epigenetic factor for early onset of atopy in children of asthmatic mothers. Russian Journal of Woman and Child Health. 2019;2(3):200–205. <br

Interaction of components in the NaOH-TiO2 · H 2O-H2O system at 25°C

Solubilities in the NaOH TiO2 · H2O-H 2O system at 25°C were studied. The solubility isotherm was found to have two maxima. The formation of two compounds, Na2Ti 5O11 · 10H2O and Na2Ti 3O7 · 7H2O, was established. © Pleiades Publishing, Ltd., 2011

Structural features and acid-base properties of hydrated zirconium, hafnium, tin, and lead dioxides

On the basis of structural and pH-metric titration data for suspensions of hydrated zirconium, hafnium, tin, and lead dioxides, it is demonstrated that the acidic properties become weaker while the basic properties become stronger in the sequence Hf-Zr-Sn-Pb. The dependence of these properties on the temperature of the sample pretreatment was revealed. Copyright © 2005 by Pleiades Publishing, Inc