Stage Of Synthesis Research Articles

Equipment for removing moisture when manipulating piece food products

The work presents the scientific basis for the recognition of small specific parts and finished products on a thin gas layer. The proposed principle is based on the use of the interlayer as a carrier and recognizing the main element of the pneumatic system. The purpose of the work is to substantiate the possibility of increasing the production of high-quality piece food production through the introduction of modern automated devices. Together with the design features of the working surfaces of the devices, the creation of universal pneumatic equipment is ensured. The developed equipment is able to successfully solve the problems of moisture removal, sorting, rejection, orientation of the subject of production. The description of the recognition principle is given. The synthesis of elements of the pneumatic system of the type "pneumatic chamber-working surface of the device-thin gas layer-product" showed that they are interconnected. At the stage of synthesis of elements of the pneumatic system and their structural classification, it was possible to unite the characteristic specifics of the described pieces of food industry with the design features of the devices and the operations implemented on them. The presented device schemes have versatility, multifunctionality, ability to manipulate specific pieces, when switching from one standard size of parts to another.

Activation energy of phase transformations at high-temperature synthesis of tungsten carbide by electrothermal explosion under pressure

The effect of activation energy on phase transformations (transitions) in the W–C system during the synthesis induced by an external heat source was investigated by electrothermal explosion (ETE) under pressure. The ETE technology combines self-propagating high-temperature synthesis (SHS) with additional sample heating by Joule heat – electric current passing through the synthesized mixture, and it makes it possible to determine the chemical reaction rate that is highly susceptible to external impacts such as pressure, concentration, sample shape, any film present on combustion products, etc. The chemical reaction rate, i.e. external source current, may be controlled by changing the activation energy. The study was conducted in the following conditions: temperature Т = 293÷3700 K; carbon concentration of 49.8–50.2 at.%; quasi-static compression at P = 96 MPa; external source voltage and current density V = 10 V, I = 20 МА/m2, respectively; samples 8 mm in diameter weighing 6 g. The Т–τ thermogram of the W–C system was used to determine the following parameters: four stages of the synthesis process, temperatures of special points of phase transformations, temperature boundaries of phases and process activation energy. Thermograms of intermediate states are presented as isothermal plateaus of phase transformations. The analysis of experimental results and the physical representation of the process make it possible to assert that temperature plateau parameters are the effective value of activation energy for synthesis mode maintenance. Each of the 4 W–C mixture synthesis stages is described. Pre-explosion stage I – sample heating in the temperature range of Т = 293÷563К, endothermic reaction, effective activation energy for synthesis mode maintenance Q = 2.96 kJ, and taking into account 1-mole mass Еа = 111.6 kJ/mol. Low-temperature (563–1190 К) stage II – ignition, Q = 5.46 kJ, Еа = 109.2 kJ/mol. High-temperature stage (III) in the range of Т = 1190÷2695К, order–disorder transformation, Q = 14.25 kJ, Еа = 424 kJ/mol. Finally, Stage IV occurs in the range of Т = 2695÷3695К, Q = 14.31 kJ, Еа = 143.2 kJ/mol. It was shown that the limiting stage with the highest activation energy is the melting process.

Zirconium Containing Periodic Mesoporous Organosilica: The Effect of Zr on CO2 Sorption at Ambient Conditions

Two series of zirconium-incorporated-periodic-mesoporous-organosilica (Zr–PMO) materials were successfully prepared, via a co-condensation strategy, in the presence of Pluronic P123 triblock copolymer. The first series of Zr–PMO was prepared using tris[3-(trimethoxysilyl)propyl]isocyanurate (ICS), tetraethylorthosilicate (TEOS), and zirconyl chloride octahydrate(ZrCO), denoted as Zr-I-PMO, where I refers to ICS. The second series was synthesized using bis(triethoxysilyl)benzene (BTEE), TEOS, and ZrCO as precursors, named as Zr-B-PMO, where B refers to BTEE. Zr–PMO samples exhibit type (IV) adsorption isotherms, with a distinct H2-hysteresis loop and well-developed structural parameters, such as pore volume, pore width, high surface area, and narrow pore-size distribution. Structural properties were studied by varying the Zr:Si ratio, adding TEOS at different time intervals, and changing the amount of block copolymer-Pluronic P123 used as well as the calcination temperature. Surface characteristics were tailored by precisely controlling the Zr:Si ratio, upon varying the amount of TEOS present in the mesostructures. The addition of TEOS at different synthesis stages, notably, enhanced the pore size and surface area of the resulting Zr-I-PMO samples more than the Zr-B-PMO samples. Changing the amount of block copolymer, also, played a significant role in altering the textural and morphological properties of the Zr-I-PMO and Zr-B-PMO samples. Optimizing the amount of Pluronic P123 added is crucial for tailoring the surface properties of Zr–PMOs. The prepared Zr–PMO samples were examined for use in CO2 sorption, at ambient temperature and pressure (25 °C, 1.2 bar pressure). Zr–PMO samples displayed a maximum CO2 uptake of 2.08 mmol/g, at 25 °C and 1.2 bar pressure. However, analogous zirconium samples, without any bridging groups, exhibited a significantly lower CO2 uptake, of 0.72 mmol/g, under the same conditions. The presence of isocyanurate- and benzene-bridging groups in Zr-I-PMO and Zr-B-PMO samples enhances the CO2 sorption. Interestingly, results illustrate that Zr–PMO materials show potential in capturing CO2, at ambient conditions.

Synthesis and Tyrosinase Inhibitory Activity of (E)-5-Benzyl-7- (3-Bromobenzylidene)-3-(3-Bromophenyl)-2-Phenyl-3,3a, 4,5,6,7-Hexahydro-2H-Pyrazolo[4,3-c]Pyridine

The tyrosinase enzyme plays an essential role in the pigmentation of human skin, fruits, and vegetables. It has been tied with several human skin diseases and post-harvest problems. Hence, the tyrosinase enzyme becomes an excellent therapeutic target to overcome these issues. This study aimed to screen tyrosinase inhibitors by synthesizing halogen-substituted pyrazolopyridine derivatives. The pyrazolopyridine compound was obtained through two stages of synthesis. First, the intermediate compound, a derivative of 3,5-bis(arylidene)-4-piperidone, was synthesized through the Cleisen-Schmidt condensation reaction of 4-piperidone and benzaldehyde derivatives. Furthermore, the intermediate compound was reacted with phenylhydrazine through a cyclocondensation reaction to produce the titled compound with an 11% yield. The chemical structure of the target compound was identified through the interpretation of UV, FTIR, NMR, and HRMS spectra. Then an in vitro assay was conducted on the tyrosinase enzyme of the fungus Agaricus bisporus by detecting the presence of dopachrome at a wavelength of 492 nm. As a result, the in vitro assay showed that the titled compound had a weak inhibitory activity, and the IC50 value was > 500 µM. Thus, the synthesized compound is considered inactive.

Synthesis of porous γ-Fe2O3 from scorodite synthesized using ultrasound irradiation and evaluation of its battery performance

The effect of 200 kHz ultrasound on scorodite synthesis at 70 °C and 3 h reaction conditions was investigated using sulfuric acidic solutions of various pH (3.0, 2.0, 1.5, 1.0, and 0.0). In contrast to the case of only O2 gas flow without ultrasound irradiation, oxidizing radicals generated by ultrasound irradiation promote Fe(II) oxidation in solution and precursor, allowing scorodite to synthesize with high crystallinity (>99%), which relates to low solubility, even in strong acid solution at pH 1.0. During synthesis, the particle shape was decided to be polyhedral or spindle type depending on the pH of 0.0–3.0. The spindle-shaped scorodite was probably formed by the reduction in precursor amount produced during the initial stage of synthesis. Furthermore, porous maghemite obtained by alkali treatment of scorodite showed initial discharge capacities of 146 mAh g−1 (polyhedron) and 167 mAh g−1 (spindle), indicating that its potential use as a cathode material for lithium-ion batteries.

Structural Characterization of Silica and Amino-Silica Nanoparticles by Fourier Transform Infrared (FTIR) and Raman Spectroscopy

Mesoporous silica nanoparticles were synthesized via the sol-gel method using hexadecyltrimethylammonium bromide (CTAB) micelles as a template and a similar method was used for amino-silica nanoparticle synthesis. Compositional and structural analysis of materials involved Fourier transform infrared (FTIR) and Raman spectroscopies. A comparative study of the two spectra revealed the distinctive pattern for the samples, such as a strong peak from 1030 to 1050 cm−1 in the FTIR spectra, characteristic of Si–O–Si stretching vibration and the specific pattern of silica between 90 and 500 cm−1 and 2880 and 2980 cm−1 in the Raman spectra. A point of interest in this study was the control of CTAB removal during the second stage of synthesis that was highlighted in the FTIR spectra by decreasing intensity or disappearance of the peaks 2850 and 2930 cm−1 for - CH2 absorption. The presence of – NH2 groups in the amino-silica was evidenced by the changes from 1000 to 1500 cm−1 and the sharp band at 2900 cm−1 in the Raman spectra. The peaks at 1050, 1230, 1421, and 1464 cm−1 are present only in the spectra of the amino-silica as well as the higher and sharp band around 2900 cm−1, unlike the pattern in the spectra of silica without amino groups. The two spectroscopic methods offer valuable information concerning the structure of silica and amino-silica. Moreover, thermogravimetric analyses were confirmed these findings and the stability of silica nanoparticles in solution was investigated.

Evaluation of DHEA level in serum of fertile and infertile women

The sulfation of the adrenal steroid dehydroepiandrosterone (DHEA) is a critical step in the provision of substrates for estrogen biosynthesis by the placenta during pregnancy. Dehydroepinadrosterone (DHEA) supplementation improves pregnancy chances in women with diminished ovarian reserve (DOR), by possibly reducing aneuploidy. Defects in the synthesis of DHEA cause deficiencies in the synthesis of androgens and estrogens. In the first stage, mutations in the StAR gene cause potentially lethal lipoid CAH. Defects in the cholesterol side chain cleavage enzyme, the second step, are rare. Defects in the third stage, 17-hydroxylation lead to hypertension and female sexual infantilism. Defects in the final stage of DHEA synthesis, 17, 20 lyase activity, are due to disorders of electron transfer to P450c17, including mutations in POR

Copper-mediated aromatic fluorination using N-heterocycle-carbene ligand: Free energy profile of the Cu(I)/Cu(III) and Cu(II) radical mechanisms

Addition of fluorine to organic molecules in the late stage of synthesis has been an increased interest in the past decade. Catalytic methods using fluoride salts as reagents could be especially useful, mainly with the use of organometallic catalysis with copper. Recent experimental advances have been reported for copper-mediated fluorination and the development of an efficient catalytic process needs a deep understanding of the reaction mechanism and the free energy profile. In this work, different mechanisms of copper-mediated fluorination of 2-(2-bromophenyl)pyridine using LCuF as reagent (L = N-heterocycle-carbene ligand) were investigated using very high level of theory, DLPNO-CCSD(T) method with up to quadruple-zeta basis set. The Cu(I)/Cu(III) mechanism is the predominant one, taking place via neutral (MS2) or cationic (MS2p) intermediates. Although the oxidative addition step has high barrier, the reductive elimination was found to be the rate-determining step. Three reaction pathways involving the Cu(II) radical mechanism was also investigated. The first one is the single-electron transfer mechanism and the second is the bromine atom transfer in the first step. Both pathways involve high free energy intermediates and are inviable. The third mechanism occurs via singlet-triplet spin crossover with bromine transfer from the oxidative addition intermediate MS2 to the LCuF initial reagent. However, the reductive elimination step from the MS2r doublet Cu(II) complex is much more difficult than the MS2 or MS2p singlets of Cu(III) complexes, leading to a very slow kinetics for this Cu(II) radical mechanism. The kinetics analysis of the theoretical free energy profile results in effective ΔG‡ of 30.6 kcal mol−1, in good agreement with an estimated experimental value and providing an important support for the Cu(I)/Cu(III) mechanism.

Total Synthesis of 12,13‐Dibenzyl‐banistenoside B and Analogs

AbstractBanistenosides A and B possessing a unique “azepino(1,2‐a)tetrahydro‐β‐carboline” carbon framework were isolated from the stem of Banisteriopsis caapi and showed MAO‐A inhibition. Herein, we report the total synthesis of dibenzyl derivative of the untouched natural product in the last two decades, Banistenoside B. The key steps involve construction of 6.5.6.7 tetracyclic core using Pictet−Spengler reaction and intramolecular amide coupling. The stereoselective glycation was achieved through Hotha's protocol using gold catalyst, and silver triflate in the late stage of synthesis. The stereochemistry of most of the essential compounds were confirmed by X‐ray crystallography.

Comparison of Efficacy and Specificity in Cancer‐Targeting Prodrug Conjugates

Current chemotherapy methods are non‐specific, killing cancerous and healthy cells alike. This drug‐related cytotoxicity results in many side effects such as hair loss or lower blood cell count. Prodrug conjugates have been developed with the goal of preferentially targeting diseased cells to minimize interactions with healthy cells, thereby mitigating deleterious off‐target effects. One powerful prodrug strategy exploits higher vitamin receptor expression levels in tumor cells. These abundant receptors drive their rapid, nutrient‐demanding growth rates. As such, a vitamin structural motif may be included in the prodrug conjugate design to target the ever‐growing tumor: a “targeting group” that acts as an appealing disguise for the drug. Biotin, folate, cyclic and acyclic RGD peptides have been found to be effective in targeting tumors over non‐cancerous cells. To systematically compare the selectivity and potency of these targeting groups, we intend to construct fluorogenic prodrug conjugates based on a previously established scaffold. The conjugates include one of the four respective targeting groups, the anticancer drug (camptothecin), a naphthalimide fluorophore component to track drug delivery, and an activatable disulfide linker that cleaves upon entering the reducing cellular environment, activating both the drug and the fluorophore. After these conjugates have been synthesized, comparisons of efficacy and specificity among targeting groups will be made to gain a better understanding of targeted cancer prodrug conjugates. Currently, these conjugates are still in the synthesis stages.

Switching Optimally Balanced Fe–N Interaction Enables Extremely Stable Energy Storage

The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms. To address the notoriously significant volume changes accompanying intercalation or formation of alloy/compounds, we aim to introduce and utilize a weak, reversible Fe–N interaction during the (de)intercalation of ammonium ions (NH4+) within iron(III) hexacyanoferrate (FeHCF), inspired by manipulating the electrostatic adsorption between N and Fe in the early stages of ammonia synthesis (Bosch‐Harber Process, Chemical Engineering) and steel nitriding processes (Metal Industry). Such strategy of switching well‐balanced Fe–N interaction is confirmed in between the nitrogen of ammonium ions and high‐spin Fe in FeHCF, as observed by using X‐ray absorption spectroscopy. The resulting material provided an extremely stable energy storage (58 mAh g−1 after 10 000 cycles at current density of 1 A g−1) as well as high‐rate performance (23.6 mAh g−1 at current density of 10 A g−1).

The quest for magic: recent advances in C(sp3)–H methylation

Abstract Frequently referred to as the “magic methyl” effect, the introduction of a methyl group into a biologically active molecule has the potential to drastically alter its physical and biological properties and significantly increase potency. This effect is most pronounced when the methyl group is added at the α-position of an aliphatic heterocycle or ortho to a large rotatable group on an aromatic ring. Although seminal developments in C–H activation strategies offered solutions to the latter, until recent years there had been no selective and functional-group-tolerant method for C(sp3)–H methylation at late stages of synthesis. For many years, the lack of a generally applicable methylation strategy necessitated arduous de novo synthesis approaches to access methylated drug candidates, and discouraged further investigation and understandings of the magic methyl effect. This review will provide a summary of the most recent advances that enabled non-directed late-stage C(sp3)–H methylation, including through hydride transfer, chemical or anodic oxidation, and photocatalytic hydrogen atom transfer.

An exploratory case study investigating the implementation of a novel knowledge translation strategy in a pandemic: the Pandemic Practice Champion

BackgroundThe clinical Pandemic Practice Champion (PPC) role was created in a large tertiary pediatric hospital as a knowledge translation (KT) strategy for implementing COVID-19 evidence-based knowledge. We aimed to describe the core components of the PPC role, the process of implementing the role, and the factors that hindered or facilitated role implementation.MethodsAn exploratory case study was undertaken. Semi-structured interviews were conducted virtually with stakeholders including PPC, managers, and front-line health care professionals (HCP). A directed approach to qualitative content analysis consistent with the Consolidated Framework for Implementation Research (CFIR) guided the analytic process. Inductive analyses and three stages of thematic synthesis were also conducted.ResultsFour PPC, 3 managers, and 6 HCP were interviewed. The core components of the PPC role consisted of (a) acting as knowledge experts and educators, (b) problem-solving for complex patient care issues, (c) conducting crisis management, and (d) acting as a resource to management, HCP, and families. Facilitators for successful implementation included access to external information, a supportive organizational context and culture, dedicated time and resources, and leadership support. Lack of clarity of role definition, insufficient time, pandemic uncertainty and fatigue, inability to change infrastructure, and access to external information hindered implementation.ConclusionThe PPC role was successfully implemented within a crisis context. Key barriers (role clarity, time, resources) and facilitators (organizational and leadership support) need to be considered when implementing the PPC role in practice. Future studies are needed to determine the intervention effectiveness of the champion role in changing HCP behavior and health outcomes and further examine implementation processes and mechanisms.

Redistribution of elements in the main and secondary phases and its effect on the microstructure of the Mo–Fe–B cermet alloyed with Cr

C-containing cermets based on Mo2FeB2–Fe with various Cr concentration were synthesized. The influence of Cr on the phase composition and microstructure of sintered materials was studied. It was shown that an increase in the Cr content in cermet leads to a growth of its amount in ternary boride Mo2FeB2 and carbide Mo2C. It was found that Cr atoms replace a fraction of Fe atoms in Mo2FeB2. At high Cr content, the formation of a binder based on Cr solid solution and M6C carbide was observed. The last one precipitated from the liquid at the final stage of synthesis. It was shown that high Cr concentration suppresses the abnormal growth of boride particles.

Young People’s Sexual Wellbeing: A Qualitative Evidence Synthesis Protocol

Sexual wellbeing is an integral part of a person’s overall sense of wellbeing. It is closely linked to physical, sexual, and mental health. Despite this, sexual wellbeing remains underexplored, including among young people (aged 16–24). This review aims to gain a greater understanding of young people’s experiences of sexual wellbeing. We will include qualitative research on young people’s lived experiences related to sexual wellbeing. We will search PROSPERO, Medline, CINAHL, PsycINFO, and SocINDEX utilising an iterative search approach. If the volume of eligible studies for inclusion is too large to permit in-depth analysis, the team will purposively sample studies to prioritise heterogeneity and richness. The lead author will assess the eligibility of studies, carry out data extraction, and assess the methodological quality of all studies. The wider research team will independently screen papers’ title and abstract, extract data, and conduct methodological quality assessments of a subset of papers. Two reviewers will independently assess inclusion of all papers at full text. We will draw on the QuART tool to assess the methodological quality of included studies. We will utilise a thematic synthesis approach to synthesise the data and produce analytical statements. We will apply GRADE-CERQual to evaluate our confidence in each of the synthesis’ analytical statements. The team will adopt a reflexive approach throughout all stages of the qualitative evidence synthesis (QES). Research will be written up in line with ENTREQ and PRISMA-S standards. The protocol for this QES was prospectively published in the International Prospective Register of Systematic Reviews (PROPERO) database under registration number CRD42022315593.

Total Synthesis of Suberitines A-D Featuring Tunable Biomimetic Late-Stage Oxidative Dearomatization and Acetalization.

Aaptaminoids are a unique family of marine alkaloids bearing a benzo[de][1,6]-naphthyridine core. This work describes the first total synthesis of suberitines A-D (1-4), four typical dimeric natural aaptaminoids, employing a step-saving bidirectional strategy. Key methods applied in the total synthesis include a cationic cascade to construct the bis-isoquinoline(s) with Hendrickson reagent-mediated Friedel-Crafts-type cyclization and eliminative aromatization, and a Bronsted acid-promoted Vilsmeier cyclization to generate the naphthyridine(s). The conditionally tunable PIDA-mediated oxidative dearomatization and subsequent methanolysis or hydrolysis successfully served as a powerful biomimetic tool to elaborate the essential oxygenated functionalities of suberitines A-D (1-4) in proper solvent-combinations at the final stage of total synthesis. The biomimetic proposal employed in the late-stage redox interchanges of related natural products was eventually supported by the isolation of synthetic intermediate 23 a as a natural product from the same natural source. Biological screening revealed that five of the synthetic samples including two natural suberitines and three full-skeleton natural product-like intermediates exhibited low micromolar inhibitory activities against the growth of cancer cell line K562.

Chemo- and Site-Selective Replacement of N-Terminal Carbamates in Peptides.

In peptide synthesis, it is important to distinguish the terminal amino group and carry out the selective transformation of only the N-terminal protecting group. We describe herein a reaction for the chemo- and site-selective replacement of carbamates with various other carbamates only at the N-terminus of peptides. We demonstrate the scope of carbamates and peptides and the introduction of fluorine into a peptide. This strategy is applicable to the late stage of peptide synthesis.

Measuring mental health recovery: Cross-cultural adaptation of the 15-item Questionnaire about the Process of Recovery in Spain (QPR-15-SP).

Mental health services need reliable and valid instruments to measure mental health recovery outcomes, and the only available one in Spanish is arduous. Adapting an instrument is more efficient than creating a new one as it enables international comparison research. The aim of this study was to conduct a cross‐cultural adaptation of the 15‐item Questionnaire about the Process of Recovery.Fifty‐four participants engaged in a five‐stage systematic and standardized process carried out from November 2019 to November 2020. Professional translators (n = 4) from the Translation Service Center for Foreign Languages of the Universidad de Alcalá participated in the direct translation, synthesis and back translation stages, and mental health professionals (n = 33) and service users (n = 17) from the Hospital Regional Universitario de Málaga and the Hospital Universitario Virgen de la Victoria in Andalucía (Spain), with an average of 19.2 (SD 12.86) years of experience in mental health, participated in the committee of experts and pilot debriefing stages. Additionally, legibility was assessed.Out of the 15‐items of the questionnaire, three (20%) were equal amongst translations, three items (20%) of the back translations matched the original questionnaire and discrepancies identified were adapted accordingly. Seven items (46.7%) were approved online by experts and consensus of alternative translations was reached for the rest. The average time spent completing the questionnaire by service users during the face‐to‐face pilot was 4.12 min (SD 2.25). Internal consistency obtained was ω = 0.95 and α = 0.91. Debriefing findings reported the questionnaire as comprehensible (97.1%), adequate in wording (91.2%), formal in language (55.9%) and adequate in terms of length (100%). The questionnaire scored 65.53, ‘normal’ readability, on the Inflesz scale.The adapted instrument has conceptual, linguistic, cultural and metric equivalence to the original instrument.

Fundamental and recent progress on the strengthening strategies for fabrication of polyacrylonitrile (PAN)-derived electrospun CNFs: Precursors, spinning and collection, and post-treatments

Thus far, polyacrylonitrile (PAN)-derived electrospun CNFs with smooth and uniform cross-sections with various morphologies and structures were massively fabricated. There is no denying the fact that the mechanical strength of CNFs is restricted which has been the main obstacle toward being highly applicable for a broad range of applications. Based on recent fundings, these limitations can be simply overcome over different synthesis stages consisting of the precursor strategy, spinning and collection methods, post-treatment processes such as stretching and aligning, and complex post-thermal procedures like stabilization and carbonization. This paper aims to fundamentally review the mechanical characteristics of CNF nanocomposites and systematically summarize the possible strengthening strategies for further development over every stage of the fabrication procedure.

Synthesis of Sorption Materials from Low Grade Titanium Raw Materials.

In this paper, a universal technology is proposed for processing low-titanium mineral raw material—apatite-nepheline ore waste, including its treatment with sulfuric or hydrochloric acid in a two-stage mode with a sequential increase in the concentration. This technique allowed us to remove nepheline and apatite in the first stage and achieve a titanium mineral content of TiO2 of more than 30%; in the second stage, we were able to convert the titanium into its precursors—titanyl sulfate monohydrate TiOSO4·H2O and a hybrid rutile-silica composition. The key stage in the sorbent synthesis is the reaction of the precursor with a phosphoric acid solution. The preferred sequence of operations begins with the mechanical activation of the precursor, causing morphological changes in it, and subsequent treatment with phosphoric acid at different concentrations under atmospheric conditions and in an autoclave, accompanied by phase transformations. Conditions for the chemical reactions which regulated the composition and structure of the final product and, accordingly, its sorption activity were found. With the help of XFA, the phase compositions of the sorbents were identified, including the individual crystalline phase α-TiP obtained from TS or the crystalline phase αTi(HPO4)2∙H2O, which is in an amorphous silica matrix obtained from a rutile–silica composition.