29 research outputs found
(R)-(1-Ammoniopropyl)phosphonate
The title compound, C3H10NO3P, crystallizes in its zwitterionic form, H3N+CH(C2H5)PO(O−)(OH), with the asymmetric unit being composed by two of such entities (Z′ = 2). The crystal packing leads to a sequence of hydrophobic and hydrophilic layers. While the hydrophobic layer comprises the aliphatic substituent groups, the hydrophilic one is held together by a series of strong and rather directional N+—H⋯O and O—H⋯O hydrogen bonds
Methyl 2-(4,6-dichloro-1,3,5-triazin-2-ylamino)acetate
The title compound, C6H6Cl2N4O2, was prepared by the nucleophilic substitution of 2,4,6-trichloro-1,3,5-triazine by glycine methyl ester hydrochloride, and was isolated from the reaction by using flash chromatography. The crystal structure at 150 K reveals the presence two crystallographically independent molecules in the asymmetric unit which differ in the orientation of the pendant methoxycarbonyl group. Each molecular unit is engaged in strong and highly directional N—H⋯N hydrogen-bonding interactions with a symmetry-related molecule, forming supramolecular dimers which act as the synthons in the crystal packing
Di-ureasil hybrids doped with LiBF4: attractive candidates as electrolytes for "Smart Windows"
The sol-gel process has been used to prepare hybrid electrolytes composed of a poly(oxyethylene) (POE)/siloxane hybrid network doped with lithium tetrafluoroborate (LiBF4) with compositions of n between ∞ and 2.5. In this context the lithium salt concentration is expressed in terms of the number of oxyethylene units in the organic component of the network per Li+ ion. Electrolyte samples with n ≥ 20 are thermally stable up to approximately 250 ºC. All the materials synthesized are semi-crystalline: in the composition range n ≥ 15 free crystalline POE exists and at 60 ≥ n ≥ 2.5 evidence of the presence of a crystalline POE/LiBF4 compound has been found. At n = 2.5 this latter crystalline phase coexists with free salt. The room temperature conductivity maximum of this electrolyte system is located at n = 10 (1.5x10-5 S cm-1 at 22 ºC). The electrochemical stability domain of the sample with n = 15 spans about 5.5 V versus Li/Li+. This new series of materials represents a promising alternative to the LiTFSI- and LiClO4-doped POE and POE/siloxane analogues. Preliminary tests performed with a prototype electrochromic device (ECD) comprising the sample with n = 8 as electrolyte and WO3 as cathodically coloring layer are extremely encouraging. The device exhibits switching time around 50 s, an optical density change of 0.13, open circuit memory of about 4 months and high coloration efficiency (106 cm2C-1 in the 3rd cycle).Fundação para a Ciência e a Tecnologi
Glycine methyl ester hydrochloride
The title compound [systematic name: (methoxycarbonylmethyl)ammonium chloride], crystallizes as a salt, C3H8NO2
+·Cl−, with the charged species interacting mutually via strong and highly directional N+—H⋯Cl− hydrogen bonds which lead to the formation of a supramolecular tape running parallel to the c axis. Tapes close pack in the solid state mediated by multipoint recognition synthons based on weak C—H⋯O interactions and van der Waals contacts between adjacent methyl groups
Multifunctionality in an Ion-Exchanged Porous Metal-Organic Framework
Porous robust materials are typically the primary selection of several industrial processes. Many of these compounds are, however, not robust enough to be used as multifunctional materials. This is typically the case of Metal-Organic Frameworks (MOFs) which rarely combine several different excellent functionalities into the same material. In this report we describe the simple acid-base postsynthetic modification of isotypical porous rare-earth-phosphonate MOFs into a truly multifunctional system, maintaining the original porosity features: [Ln(H3pptd)]·xSolvent [where Ln3+ = Y3+ (1) and (Y0.95Eu0.05)3+ (1_Eu)] are converted into [K3Ln(pptd)]·zSolvent [where Ln3+ = Y3+ (1K) and (Y0.95Eu0.05)3+ (1K_Eu)] by immersing the powder of 1 and 1_Eu into an ethanolic solution of KOH for 48 h. The K+-exchanged Eu3+-based material exhibits a considerable boost in CO2 adsorption, capable of being reused for several consecutive cycles. It can further separate C2H2 from CO2 from a complex ternary gas mixture composed of CH4, CO2, and C2H2. This high adsorption selectivity is, additionally, observed for other gaseous mixtures, such as C3H6 and C3H8, with all these results being supported by detailed theoretical calculations. The incorporation of K+ ions notably increases the electrical conductivity by 4 orders of magnitude in high relative humidity conditions. The conductivity is assumed to be predominantly protonic in nature, rendering this material as one of the best conducting MOFs reported to date.publishe
(R)-(1-Ammonioethyl)phosphonate
The title compound, C2H8NO3P, crystallizes in its zwitterionic form H3N+CH(CH3)PO(O−)(OH). In the crystal, the molecules are linked by N—H⋯O and O—H⋯O hydrogen bonds
Estádio de maturação dos frutos e fatores relacionados aos aspectos nutritivos e de textura da polpa de pequi (Caryocar brasiliense Camb.)
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4
While the increasing availability of global databases on ecological communities has advanced our knowledge
of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In
the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of
Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus
crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced
environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian
Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by
2050. This means that unless we take immediate action, we will not be able to establish their current status,
much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio