Transformation Mechanism of Magnesium and Aluminum Precursor Solution into Crystallites of Layered Double Hydroxide

Layered double hydroxides (LDHs), members of a family of two-dimensional anionic clay with flexibility in composition, have found a wide variety of applications in industry, including as additives in polymers, as precursors to magnetic materials, in biology and medicine, in catalysis, and in environmental remediation. A detailed understanding of the mechanism of the LDH formation should gain deep insight on the synthetic methodologies of the material and further allow the properties of the resulting LDH to be tailored to specific applications. Herein, we report a systematic investigation of the formation mechanism of the typical MgAl-LDH by urea precipitation method from a magnesium and aluminum precursor salt solution. It is revealed that, at the first stage of the synthesis, amorphous colloidal hydroxide aluminum is formed from the aluminum precursor salt solution. Then, the amorphous hydroxides are transformed into the crystallites of oxide-hydroxide aluminum boehmite γ-AlOOH, accompanying the continuous incorporation of surrounding Mg²⁺ into the sheet of the lamellar γ-AlOOH, leading to the charge imbalance of the sheet, which destroys the hydrogen bonds existing between the sheets. Subsequently, the carbonate ions in the solution are intercalated into the interlayer galleries by an electrostatic interaction for balancing the sheet charge, resulting in an initial LDH phase with alveolate-like structure. Finally, the main layers stack to build a three-dimensional network with the positive charge being balanced by the carbonate ions arranged in the hydrated interlayer galleries, and the integrated plate-like structure of LDH is formed. Throughout the above-mentioned processes, the incorporation of magnesium ions into the sheet of the lamellar boehmite can play a primary role for the formation of LDH crystallites

Plasma fibrin D-dimer and the risk of left atrial thrombus: A systematic review and meta-analysis

<div><p>Background</p><p>Plasma fibrin d-dimer has been taken as a marker for thrombus. The aim of this study was to evaluate the relationship between d-dimer (DD) levels and left atrial spontaneous echo contrast (SEC)/left atrial thrombus (LAT).</p><p>Methods</p><p>We identified clinical studies by systematic search of MEDLINE and EMBASE databases up to Feb 2016. All observational studies that considered DD as a study factor and trans-esophageal echocardiography (TEE) identified SEC/LAT as an outcome were included. Two reviewers independently selected the studies and extracted the data.</p><p>Results</p><p>Of the 21 included studies, 16 studies (2652 patients) have compared the mean DD differences between patients with and without an evidence of the presence of SEC/LAT, 9 studies (1667 patients) have estimated the diagnostic value of DD in the presence of LAT, and 11 studies (1856 patients) have available information to calculate a ratio of the presence of LAT among individuals in the top and the bottom third of DD levels. The pooled standardized mean difference (SMD) of DD between patients with and without left atrial SEC and/or LAT was 1.29 [95%CI: 0.51, 2.08], with SMDs of 0.42 [95% CI: 0.08, 0.77] and 2.34 [95% CI: 1.01, 3.68] in SEC/LAT and LAT subgroups, respectively. The combined risk ratio of the presence of LAT among individuals between the top of the distribution of DD levels and that in the bottom third was 3.84 [95% CI: 2.35, 6.28], associating with a mean difference of 0.78 ug/ml (1.10 vs 0.32 ug/ml). The pooled sensitivity, specificity and positive likelihood ratio of DD for LAT were 0.75 [95% CI: 0.65, 0.83], 0.81 [95% CI: 0.59, 0.93] and 4.0 [95% CI: 1.7, 9.9], respectively.</p><p>Conclusions</p><p>High plasma fibrin DD was associated with left atrial SEC/LAT, particularly among patients with LAT. DD levels have moderate sensitivity and specificity for diagnosing LAT.</p></div

Additional file 1 of Association of dietary inflammatory index and the SARS-CoV-2 infection incidence, severity and mortality of COVID-19: a systematic review and dose-response meta-analysis

Supplementary Material

Characteristics of eligible studies.

<p>Characteristics of eligible studies.</p

Risk of bias assessment of 9 diagnostic tests by QUADAS-2.

<p>Risk of bias assessment of 9 diagnostic tests by QUADAS-2.</p

Risk ratios for the presence of LAT comparing the top third with the bottom third based on d-dimer distributions.

<p>Risk ratios for the presence of LAT comparing the top third with the bottom third based on d-dimer distributions.</p

Egger’s test for the assessment of publication bias of 16 observational studies.

<p>SND, standard normal deviate.</p

Flow diagram illustrating the systemic literature and study selection process.

<p>Flow diagram illustrating the systemic literature and study selection process.</p

Egger’s test for the assessment of publication bias of 11 studies.

<p>SND, standard normal deviate.</p

Forest plot of the standard mean difference in d-dimer levels between patients with and without left atrial spontaneous echo contrast/left atrial thrombus.

<p>Forest plot of the standard mean difference in d-dimer levels between patients with and without left atrial spontaneous echo contrast/left atrial thrombus.</p