Sncg, Mybpc1, and Parm1 Classify subpopulations of VIP-expressing interneurons in layers 2/3 of the somatosensory cortex.

Neocortical vasoactive intestinal polypeptide-expressing (VIP+) interneurons display highly diverse morpho-electrophysiological and molecular properties. To begin to understand the function of VIP+ interneurons in cortical circuits, they must be clearly and comprehensively classified into distinct subpopulations based on specific molecular markers. Here, we utilized patch-clamp RT-PCR (Patch-PCR) to simultaneously obtain the morpho-electric properties and mRNA profiles of 155 VIP+ interneurons in layers 2 and 3 (L2/3) of the mouse somatosensory cortex. Using an unsupervised clustering method, we identified 3 electrophysiological types (E-types) and 2 morphological types (M-types) of VIP+ interneurons. Joint clustering based on the combined electrophysiological and morphological features resulted in 3 morpho-electric types (ME-types). More importantly, we found these 3 ME-types expressed distinct marker genes: ~94% of Sncg+ cells were ME-type 1, 100% of Mybpc1+ cells were ME-type 2, and ~78% of Parm1+ were ME-type 3. By clarifying the properties of subpopulations of cortical L2/3 VIP+ interneurons, this study establishes a basis for future investigations aiming to elucidate their physiological roles.

Clinical and histological features of patients with chronic hepatitis B virus infection in the grey zone.

Chronic HBV infection patients who do not conform to any of the usual immune states are regarded as 'grey zone' patients. We aimed to investigate the proportion of chronic HBV infection patients in the grey zone, and evaluate the clinical characteristics and liver pathological changes in grey zone patients. Clinical data of 1391 treatment-naive chronic HBV infection patients with liver biopsy were collected. Natural history of HBV infection was determined based on European Association for the Study of the Liver (EASL) 2017, American Association for the Study of Liver Diseases (AASLD) 2018 and Chinese 2019 guidelines for the prevention and treatment of chronic HBV infection. Significant liver histological changes and associated risk factors of normal ALT grey zone patients were analysed. According to EASL, AASLD and Chinese criteria, there were 50.0%, 28% and 37.4% chronic HBV infection patients in the grey zone. Among the 353 grey zone patients with normal ALT, 72.4% had significant liver histological changes. ALT (optimal cut-off value 25 IU/L) and HBV DNA (optimal cut-off value 18,000 IU/mL) were independent risk factors of significant liver histological abnormalities. In conclusion, a substantial proportion of grey zone patients with normal ALT have significant liver histological changes that can be predicted by levels of serum ALT and HBV DNA. These results provide guidance of antiviral treatment in grey zone patients.

A maize triacylglycerol lipase inhibits sugarcane mosaic virus infection.

Triacylglycerol lipase (TGL) plays critical roles in providing energy for seed germination and plant development. However, the role of TGL in regulating plant virus infection is largely unknown. In this study, we adopted affinity purification coupled with mass spectrometry and identified that a maize (Zea mays) pathogenesis-related lipase protein Z. mays TGL (ZmTGL) interacted with helper component-proteinase (HC-Pro) of sugarcane mosaic virus (SCMV). Yeast two-hybrid, luciferase complementation imaging, and bimolecular fluorescence complementation assays confirmed that ZmTGL directly interacted with SCMV HC-Pro in vitro and in vivo. The 101-460 residues of SCMV HC-Pro were important for its interaction with ZmTGL. ZmTGL and SCMV HC-Pro co-localized at the mitochondria. Silencing of ZmTGL facilitated SCMV infection, and over-expression of ZmTGL reduced the RNA silencing suppression activity, most likely through reducing HC-Pro accumulation. Our results provided evidence that the lipase hydrolase activity of ZmTGL was associated with reducing HC-Pro accumulation, activation of salicylic acid (SA)-mediated defense response, and inhibition of SCMV infection. We show that ZmTGL inhibits SCMV infection by reducing HC-Pro accumulation and activating the SA pathway.

An evaluation of the customized nasal clip protocol for bilateral cleft lip and palate presurgical infant orthopaedics.

OBJECTIVES: Nasoalveolar moulding (NAM) has resulted in profound outcomes in the treatment of bilateral cleft lip and palate patients, including non-surgical columellar lengthening and nasal moulding. We examine an innovative alternative that is less invasive, yet provides similar results. In this study, we describe a novel approach using the Customized Nasal Clip Protocol (CNCP™) and compare the treatment outcomes of a small cohort of infants with bilateral cleft lip ± palate with published results of the Grayson nasoalveolar moulding protocol. MATERIALS AND METHODS: A cohort of six bilateral-cleft-affected patients was evaluated for this study. Standardized frontal and worm's eye view photographs were obtained, and clinical measurements were utilized to garner columellar length measurements and nostril height comparisons. The initial and post-surgical results were statistically compared with a student's t-test (p < .05). Inclusion and exclusion criteria were applied to the cohort, which will be described. RESULTS: The resulting columellar length and nostril height increases of the CNCP™ group were comparable to a published cohort of subjects that have undergone nasoalveolar moulding. The nasal changes were found to be significant with a p-value <.01. The CNCP™ cohort also had fewer clinic visits, no complications that led to complete pauses of active treatment, and the benefit of receiving comprehensive treatment that was initiated at their first clinical presentation, in comparison to traditional NAM patients. CONCLUSION: The increase of columellar length and nostril height that resulted from utilizing the CNCP™ in bilateral cleft patients met the treatment goals of presurgical infant orthopaedics, with results on par with published results of NAM. These results, paired with the reduction in patient, family, and provider burden, further support the continued use and development of the CNCP™ for appropriate patient populations.

Genomic answers for children: Dynamic analyses of >1000 pediatric rare disease genomes.

PURPOSE: This study aimed to provide comprehensive diagnostic and candidate analyses in a pediatric rare disease cohort through the Genomic Answers for Kids program. METHODS: Extensive analyses of 960 families with suspected genetic disorders included short-read exome sequencing and short-read genome sequencing (srGS); PacBio HiFi long-read genome sequencing (HiFi-GS); variant calling for single nucleotide variants (SNV), structural variant (SV), and repeat variants; and machine-learning variant prioritization. Structured phenotypes, prioritized variants, and pedigrees were stored in PhenoTips database, with data sharing through controlled access the database of Genotypes and Phenotypes. RESULTS: Diagnostic rates ranged from 11% in patients with prior negative genetic testing to 34.5% in naive patients. Incorporating SVs from genome sequencing added up to 13% of new diagnoses in previously unsolved cases. HiFi-GS yielded increased discovery rate with >4-fold more rare coding SVs compared with srGS. Variants and genes of unknown significance remain the most common finding (58% of nondiagnostic cases). CONCLUSION: Computational prioritization is efficient for diagnostic SNVs. Thorough identification of non-SNVs remains challenging and is partly mitigated using HiFi-GS sequencing. Importantly, community research is supported by sharing real-time data to accelerate gene validation and by providing HiFi variant (SNV/SV) resources from >1000 human alleles to facilitate implementation of new sequencing platforms for rare disease diagnoses.

Comparison of predictive value of risk scores for gastrointestinal bleeding in antiplatelet therapy.

Gastrointestinal bleeding (GIB) is the most common serious bleeding complication of antiplatelet therapy. The bleeding risk score (BRS) of GIB may help to determine the risk of bleeding, and provides a reference for the formulation of antiplatelet therapy regimen in clinical practice, but we found that no specific risk scores are available in East Asian patients. This study analyzed patients who were administered antiplatelet therapy from May 2015 to December 2018 in two medical centers. Patient's baseline data were obtained. We assessed four BRSs (New Score, RIETE Score, Cuschieri Score, de Groot Score) and compared them using the area under the receiver operating characteristic curve (AUC). The 4,052 patients enrolled in this study had an average age of 69.6 ± 10.8 years, and 65.9% of them were male. Among the 4,052 patients included, 171 patients experienced GIB within 6 months of follow-up. In the study population, the AUCs for the New, RIETE, Cuschieri, and de Groot scores were 0.673 (95% confidence interval (CI) 0.616-0.729, P < .001), 0.742 (95% CI 0.690-0.794, P < .001), 0.598 (95% CI 0.537-0.659, P = .002), and 0.875 (95% CI 0.839-0.912, P < .001), respectively. After validation, the de Groot Score has better performance. Among the four scores, the de Groot Score might be more suitable for helping Chinese clinicians to predict the risk of GIB in patients taking antiplatelet drugs, and reduce GIB events.

Initial CT-based radiomics nomogram for predicting in-hospital mortality in patients with traumatic brain injury: a multicenter development and validation study.

OBJECTIVE: To develop and validate a radiomic prediction model using initial noncontrast computed tomography (CT) at admission to predict in-hospital mortality in patients with traumatic brain injury (TBI). METHODS: A total of 379 TBI patients from three cohorts were categorized into training, internal validation, and external validation sets. After filtering the unstable features with the minimum redundancy maximum relevance approach, the CT-based radiomics signature was selected by using the least absolute shrinkage and selection operator (LASSO) approach. A personalized predictive nomogram incorporating the radiomic signature and clinical features was developed using a multivariate logistic model to predict in-hospital mortality in patients with TBI. The calibration, discrimination, and clinical usefulness of the radiomics signature and nomogram were evaluated. RESULTS: The radiomic signature consisting of 12 features had areas under the curve (AUCs) of 0.734, 0.716, and 0.706 in the prediction of in-hospital mortality in the internal and two external validation cohorts. The personalized predictive nomogram integrating the radiomic and clinical features demonstrated significant calibration and discrimination with AUCs of 0.843, 0.811, and 0.834 in the internal and two external validation cohorts. Based on decision curve analysis (DCA), both the radiomic features and nomogram were found to be clinically significant and useful. CONCLUSION: This predictive nomogram incorporating the CT-based radiomic signature and clinical features had maximum accuracy and played an optimized role in the early prediction of in-hospital mortality. The results of this study provide vital insights for the early warning of death in TBI patients.

hsa_circ_0067514 suppresses gastric cancer progression and glycolysis via miR-654-3p/LATS2 axis.

Gastric cancer is the third most frequent cancer with high prevalence and mortality globally. Circular RNAs (circRNAs) play a key role in cancer regulation, including gastric cancer. Nevertheless, only a few circRNAs have been well elucidated in gastric cancer. Hence, we investigated the action of circ_0067514 on gastric cancer and clarified the underlying mechanism. Here, we found that circ_0067514 was decreased in gastric cancer patients and cancer cells. The circ_0067514 expression was correlated with gastric cancer overall survival, lymph node metastasis, tumor, node, metastasis (TNM) stage, and histological differentiation. Overexpression of circ_0067514 blocked proliferation, invasion, and glycolysis of gastric cancer cells. Besides, circ_0067514 regulated large tumor suppressor kinase 2 (LATS2) expression by absorbing microRNA (miR)-654-3p. Furthermore, circ_0067514 modulated gastric cancer aggressive behaviors and glycolysis via miR-654-3p/LATS2 axis. Moreover, circ_0067514 constrained tumor growth in vivo. Together, this study showed that circ_0067514 suppressed gastric cancer aggressive development and glycolysis via miR-654-3p/LATS2 axis, making circ_0067514 a valuable target for preventing gastric cancer progression.

Comparison of clinical performance of four gastrointestinal bleeding risk scores in Chinese patients with atrial fibrillation receiving oral anticoagulants.

Gastrointestinal bleeding is the most common bleeding complication during anticoagulant therapy. A reliable bleeding risk score can help the clinician assess risk of bleeding in individual patients and select the anticoagulant regimen. This study retrospectively analyzed the data of patients with atrial fibrillation who received anticoagulant therapy from July 2015 to December 2018 at two centers-the Fujian Medical University Union Hospital and Fuzhou Second Hospital Affiliated to Xiamen University. Demographic data, clinical findings, and laboratory results were collected from the hospital records. Patients were followed up for 6 months. The performance of four bleeding risk scores (New Score, RIETE Score, Cuschieri et al. Score, de Groot et al. Score) for prediction of gastrointestinal bleeding was assessed using the area under the curve. A total of 3462 patients (mean age, 66.3 ± 11.5 years; 59.6% males; 1055 direct oral anticoagulants users and 2407 warfarin users) were followed up for 6 months. While 99/3462 (2.9%) patients had gastrointestinal bleeding. The area under the curves for the New, RIETE, Cuschieri et al., de Groot et al. scores were 0.652 (95% CI 0.576-0.728), 0.862 (95% CI 0.809-0.914), 0.606 (95% CI 0.527-0.685), and 0.873 (95% CI 0.816-0.929), respectively. Among the four BRSs evaluated, the RIETE score and the de Groot et al. score appear to have the good predictive value, while the NEW score and the Cuschieri et al. score did not sufficiently predict gastrointestinal bleeding risk within the study Chinese population.

Enantioseparation of mandelic acid and substituted derivatives by high-performance liquid chromatography with hydroxypropyl-ß-cyclodextrin as chiral mobile additive and evaluation of inclusion complexes by molecular dynamics.

The enantioseparation and resolution mechanism of mandelic acid (MA), 4-methoxymandelic acid (MMA), and 4-propoxymandelic acid (PMA) were investigated by reversed-phase high-performance liquid chromatography (HPLC) with 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD) as a chiral mobile-phase additive and molecular dynamics simulation. The suitable chromatographic conditions for the enantioseparation of MA, MMA, and PMA were obtained. Under the selected chromatographic conditions, these enantiomers could achieve baseline separation. The results of thermodynamic parameter analysis revealed that the main driven forces for the enantioseparation of MA, MMA, and PMA could be van der Waals forces and hydrogen-bonding interactions and the chromatographic retention of these chiral compounds was an enthalpy-driven process. The results of the molecular simulation revealed that their chiral resolution mechanism on HP-ß-CD was responsible for the formation of inclusion complexes of enantiomers with HP-ß-CD with different conformations and binding energies. And the binding energy of HP-ß-CD with (S)-isomer was larger than that with (R)-isomer, which is consistent with the experimental results of the first elution of (S)-isomer. Additionally, it is also confirmed that the interaction energies included the van der Waals energy (∆Evdw ), electrostatic energy (∆Eelec ), polar solvation energy, and SASA energy (∆Esasa ), and the separation factor (α) was closely connected with the disparity in the binding energies of optical isomers and HP-ß-CD complexes. Meanwhile, from molecular dynamics simulation, it can be found that the ∆(∆Ebinding ), (∆(∆Ebinding ) = ∆Ebinding,R - ∆Ebinding,S ) value was in order of MA-HP-ß-CD complex > MMA-HP-ß-CD complex > PMA-HP-ß-CD complex, which was consistent with the order of Δ(ΔG) values obtained from van't Hoff plot. This indicated that the molecular dynamics simulation has predictive function for chiral resolution.

[Lingze Tablets for BPH with kidney-deficiency, blood stasis and dampness resistance: A phase-â £ open-label single-arm multicenter clinical study and safety evaluation].

OBJECTIVE: To evaluate the efficacy and safety of Lingze Tablets in the treatment of BPH with kidney deficiency, blood stasis and dampness resistance. METHODS: Totally 235 eligible BPH patients, aged 50－80 years and meeting the inclusion criteria, were enrolled and treated with Lingze Tablets orally, 4 tablets per time, tid. Before and after an 8-week course of medication, IPSS, quality of life (QOL) and TCM syndromes scores were obtained from the patients. RESULTS: Of the total number of patients, 211 completed the whole course of treatment. Compared with the baseline, the IPSS was dramatically reduced after 4 and 8 weeks of medication (18.28 ± 5.29 vs 12.82 ± 4.66 and 9.23 ± 4.21, P < 0.01), and so were the QOL scores (6.44 ± 1.99 vs 4.95 ± 1.64 and 3.16 ± 1.53, P < 0.01) and TCM syndromes scores (17.49 ± 5.30 vs 12.45 ± 3.74 and 9.17 ± 3.24, P < 0.01). The incidence rates of adverse events and drug-related adverse reactions were 15.2% and 1.9%, respectively, and no organ function impairment was observed. CONCLUSIONS: Lingze Tablets are definitely effective and safe for the treatment of BPH with kidney deficiency, blood stasis and dampness resistance.

Accurate Determination of Barium Isotopic Compositions in Sequentially Leached Phases from Carbonates by Double Spike-Thermal Ionization Mass Spectrometry (DS-TIMS).

Recent studies have proposed barium isotopes as a novel proxy for studying primary productivity in paleo-oceangraphical studies and elements cycling through the critical zone. Pristine marine carbonates are generally assumed to preserve Ba isotope compositions of ancient seawater. However, Ba incorporated in or adsorbed on detrital minerals such as clays in impure carbonates may limit the accurate application of the Ba isotope proxy for paleo-ocean environmental reconstruction purposes. We present here a sequential extraction procedure and show that a considerable range of Ba concentrations can be associated with the four operationally defined sequential leaching fractions (water-soluble, exchangeable, carbonate, and oxidizable fractions). Chemical separation of Ba from these leachates is achieved with a recovery of >98.6% by our modified ion exchange procedure. Potential instrumental mass bias effects and barium isotope fractionation during the chemical separation are corrected using a carefully optimized 130Ba-135Ba double-spike method. A long-term reproducibility better than ±0.03‰ (2SD) for δ137/134Ba has been achieved by using the double spike-thermal ionization mass spectrometry (DS-TIMS) in this study. We demonstrate that significant variations of δ137/134Ba in the analyzed leachates suggest a considerable Ba isotope fractionation between carbonate mineral phase and noncarbonate phases of marine carbonate rocks. The barium isotope distribution in a set of standard reference materials and natural geological samples under various geological settings has been presented. When utilizing Ba isotopes as a proxy for primary productivity and the biogeochemical cycling of Ba, our new findings from sequential Ba extraction as well as our modified precise DS-TIMS analytical setup should be taken into account.

Tricritical Physics in Two-Dimensional p-Wave Superfluids.

We study effects of quantum fluctuations on two-dimensional p+ip superfluids near resonance. In the standard paradigm, phase transitions between superfluids and zero density vacuum are continuous. When strong quantum fluctuations near resonance are present, the line of continuous phase transitions terminates at two tricritical points near resonance, between which the transitions are expected to be first-order ones. The size of the window where first-order phase transitions occur is shown to be substantial when the coupling is strong. Near first-order transitions, superfluids self-contract due to phase separations between superfluids and vacuum.

A simple two-stage column chromatographic separation scheme for strontium, lead, neodymium and hafnium isotope analyses in geological samples by thermal ionization mass spectrometry or multi-collector inductively coupled plasma mass spectrometry.

Here, a two-stage column separation scheme is developed for the concomitant isolation of Sr, Pb, Nd, and Hf from geological samples. The first column, which consists of three resin layers (AG50W-X8 ion exchange resin + Ln specific resin + Sr specific resin), separates the high field strength element + rare earth element, Sr and Pb from the matrices. Subsequently, Nd and Hf are further separated from the high field strength element + rare earth element fraction on the second column using 1 mL of Ln specific resin. The two-stage column process can be completed within about seven and a half hours for a batch of samples (20-30). The separated Sr fraction was ready for isotope ratio measurements by thermal ionization mass spectrometry. The Pb, Nd, and Hf fractions were converted to nitrate prior to isotopic analyses by multi-collector inductively coupled plasma mass spectrometry. The feasibility of this new procedure is confirmed by the analyses of four international rock standards (BCR-2, AGV-2, BHVO-2, and JB-3), which yielded isotope ratios that were in good agreement with other published data.

A novel nonsense substitution identified in the AMIGO2 gene in an Occulo-Auriculo-Vertebral spectrum patient.

OBJECTIVE: Craniofacial microsmia is the second most common congenital disorder with mostly unilateral defects of ear, temporomandibular joint, mandible, and muscles of facial expression and mastication. The objective of this study was to identify, if there were any, de novo germline or somatic variants in a patient with Occulo-Auriculo-Vertebral Spectrum (OAVS) using whole-exome sequencing. SETTINGS AND SAMPLE POPULATION: Trio/Family-based study of an OAVS proband. MATERIALS AND METHODS: Children's Mercy Hospital Institutional Review Board approved this study and a request-to-rely was procured from the University of Missouri Kansas City IRB. Informed assent/consent was obtained for all family members prior to any research activities. The peripheral blood/affected side tissues from corrective surgery of the proband and peripheral blood samples from unaffected parents were collected. The isolated genomic DNA were enriched for exomes and sequenced on an Illlumina HiSeq 2500 instrument yielding paired-end 125 nucleotide reads (84X coverage). Gapped alignment to reference sequences (GRCh37.p5) was performed with BWA and the GATK and analysis completed using custom-developed software. RESULTS: Analyses revealed that the proband carried a de novo germ line nonsense substitution (c.901C>T) in AMIGO2 gene, and missense substitutions in ZCCHC14 (c.1198C>T), and in SZT2 genes (c.2951C>T). CONCLUSIONS: The nonsense substitution in AMIGO2 gene introduces a premature stop codon possibly rendering the gene non-functional via nonsense-mediated pathway decay-therefore considered a stronger candidate. Further functional studies are required to confirm whether loss-of-function variants in AMIGO2 can cause OAVS.

Improved Accuracy for Trace Element Analysis of Al and Ti in Quartz by Electron Probe Microanalysis.

The trace elements in quartz, Al and Ti, contain considerable information about mineral genesis, and determining their concentrations is of great importance in geology. Electron probe microanalysis has the advantages of non-destructive testing and high spatial resolution; however, it is a challenge to improve the accuracy and precision of trace element detection using this method. The important factors affecting accuracy include the fragility of quartz lattices at high beam currents and the methods used to determine the background. In this paper, the peaks of Al-Kα and Ti-Kα, and their backgrounds, were found to exhibit intensity variations at high beam currents and small beam diameters; therefore, it is necessary to select a large beam diameter (up to 20 µm) to avoid variations in intensity at high currents (500 nA). For background determination of Al, a multipoint background method is proposed to determine the background value, which greatly improves the accuracy of the results. For Ti, the choice of background measurement does not affect the result. In addition, it is verified that the background obtained from other quartz samples can be used as the background of an unknown quartz sample, which reduces the analysis time and minimizes sample damage.

Structural Health Monitoring System Based on FBG Sensing Technique for Chinese Ancient Timber Buildings.

Due to the long-term service, Chinese ancient timber buildings show varying degrees of wear. Thus, structural health monitoring (SHM) for these cultural and historical treasures is desperately needed to evaluate the service status. Although there are some FBG sensing-based SHM systems, they are not suitable for Chinese ancient timber buildings due to the differences in architectural types, structural loads, materials, and environment. Besides, a technical gap in Fiber Bragg grating (FBG) sensing-based column inclination monitoring exists. To overcome these weaknesses, this paper develops an FBG sensing-based structural health monitoring system for Chinese ancient Chuan-dou-type timber buildings that aims at monitoring structural deformation, i.e., beam deflection and column inclination, temperature, humidity, and fire around the building. An in-situ test and simulation analyses were conducted to verify the effectiveness of the developed SHM system. To validate the long-term-operation of the developed SHM system, monitoring data within 15 months were analyzed. The results show good agreement between the developed SHM system in this paper and other methods. In addition, the SHM system operated well in the first year after its deployment. This implies that the developed SHM system is applicable and effective in the health state monitoring of Chinese ancient Chuan-dou-type timber buildings, laying a foundation for damage prognosis of such types of timber buildings.

Cleft Care of Internationally Adopted Children From China.

OBJECTIVE: To quantify a population of international adoptees from China with cleft lip and/or palate to assess presentations and team management practices. DESIGN: Single institution retrospective. PATIENTS: One hundred one patients with cleft lip and/or palate and history of international adoption from China. RESULTS: Forty-nine males and 52 females were adopted from 2001 to 2014. Median age at arrival was 26 months. A total of 88.1% had a combined cleft lip and palate: 59 unilateral, 30 bilateral. Only 4 patients had isolated cleft palate. A total of 85.6% had cleft lip repair before adoption; 41.6% had both cleft lip and palate repairs in China. A total of 14.9% of adoptees had no prior surgery. In China, median age at lip repair was 10 months, and palate repair was 19 months. Once in the United States, lip repair was at 24 months and palate repair at 24 months. Eighty-three revision surgeries were performed. A total of 79.2% of children demonstrated moderate to severe articulation disorders. A total of 36.6% had velopharyngeal insufficiency with hypernasal speech. Forty percent required palatal revision surgery to achieve normal resonance. Fifty seven percent of patients presented with concomitant medical issues but less than 10% with global delays or autism. CONCLUSIONS: Chinese adoptees have more complex presentations and delayed surgical care compared to their domestic counterparts. Engaging prospective families starting before adoption helps to manage expectations. Long-range planning, timely surgery, aggressive therapy, and close careful follow-up can mitigate some of these differences. Speech and language problems including articulation disorders, expressive delays, and hypernasality are frequent and can persist despite interventions.

Silicon Isotope Geochemistry: Fractionation Linked to Silicon Complexations and Its Geological Applications.

The fundamental advances in silicon isotope geochemistry have been systematically demonstrated in this work. Firstly, the continuous modifications in analytical approaches and the silicon isotope variations in major reservoirs and geological processes have been briefly introduced. Secondly, the silicon isotope fractionation linked to silicon complexation/coordination and thermodynamic conditions have been extensively stressed, including silicate minerals with variable structures and chemical compositions, silica precipitation and diagenesis, chemical weathering of crustal surface silicate rocks, biological uptake, global oceanic Si cycle, etc. Finally, the relevant geological implications for meteorites and planetary core formation, ore deposits formation, hydrothermal fluids activities, and silicon cycling in hydrosphere have been summarized. Compared to the thermodynamic isotope fractionation of silicon associated with high-temperature processes, that in low-temperature geological processes is much more significant (e.g., chemical weathering, biogenic/non-biogenic precipitation, biological uptake, adsorption, etc.). The equilibrium silicon isotope fractionation during the mantle-core differentiation resulted in the observed heavy isotope composition of the bulk silicate Earth (BSE). The equilibrium fractionation of silicon isotopes among silicate minerals are sensitive to the Si-O bond length, Si coordination numbers (CN), the polymerization degrees of silicate unites, and the electronegativity of cations in minerals. The preferential enrichment of different speciation of dissoluble Si (DSi) (e.g., silicic acid H4SiO4° (H4) and H3SiO4- (H3)) in silica precipitation and diagenesis, and chemical weathering, lead to predominately positive Si isotope signatures in continental surface waters, in which the dynamic fractionation of silicon isotope could be well described by the Rayleigh fractionation model. The role of complexation in biological fractionations of silicon isotopes is more complicated, likely involving several enzymatic processes and active transport proteins. The integrated understanding greatly strengthens the potential of δ30Si proxy for reconstructing the paleo terrestrial and oceanic environments, and exploring the meteorites and planetary core formation, as well as constraining ore deposits and hydrothermal fluid activity.