Extensive transcriptome data providing great efficacy in genetic research and adaptive gene discovery: a case study of Elymus sibiricus L. (Poaceae, Triticeae).

Genetic markers play a central role in understanding genetic diversity, speciation, evolutionary processes, and how species respond to environmental stresses. However, conventional molecular markers are less effective when studying polyploid species with large genomes. In this study, we compared gene expression levels in 101 accessions of Elymus sibiricus, a widely distributed allotetraploid forage species across the Eurasian continent. A total of 20,273 high quality transcriptomic SNPs were identified. In addition, 72,344 evolutionary information loci of these accessions of E. sibiricus were identified using genome skimming data in conjunction with the assembled composite genome. The population structure results suggest that transcriptome SNPs were more effective than SNPs derived from genome skimming data in revealing the population structure of E. sibiricus from different locations, and also outperformed gene expression levels. Compared with transcriptome SNPs, the investigation of population-specifically-expressed genes (PSEGs) using expression levels revealed a larger number of locally adapted genes mainly involved in the ion response process in the Sichuan, Inner Mongolia, and Xizang geographical groups. Furthermore, we performed the weighted gene co-expression network analysis (WGCNA) and successfully identified potential regulators of PSEGs. Therefore, for species lacking genomic information, the use of transcriptome SNPs is an efficient approach to perform population structure analysis. In addition, analyzing genes under selection through nucleotide diversity and genetic differentiation index analysis based on transcriptome SNPs, and exploring PSEG through expression levels is an effective method for analyzing locally adaptive genes.

An updated overview of the search for biomarkers of osteoporosis based on human proteomics.

Osteoporosis is a chronic metabolic disease that increases bone fragility and, leads to severe osteoporotic fractures. In recent years, the use of high-throughput omics to explore physiological and pathological biomarkers related to bone metabolism has gained popularity. In this review, we first briefly review the technical approaches of proteomics. Additionally, we summarize the relevant literature in the last decade to provide a comprehensive overview of advances in human proteomics related to osteoporosis. We describe the specific roles of various proteins related to human bone metabolism, highlighting their potential as biomarkers for risk assessment, early diagnosis and disease course monitoring in osteoporosis. Finally, we outline the main challenges currently faced by human proteomics in the field of osteoporosis and offer suggestions to address these challenges, to inspire the search for novel osteoporosis biomarkers and a foundation for their clinical translation. In conclusion, proteomics is a powerful tool for discovering osteoporosis-related biomarkers, which can not only provide risk assessment, early diagnosis and disease course monitoring, but also reveal the underlying mechanisms of disease and provide key information for personalized treatment. The translational potential of this article: This review provides an insightful summary of recent human-based studies on osteoporosis-associated proteomics, which can aid the search for novel osteoporosis biomarkers based on human proteomics and the clinical translation of research results.

Design and Fabrication of a C-Band Patch Antenna with Low Loss BaM4Si5O17 Microwave Dielectric Ceramics.

Single-phase BaM4Si5O17 (M = Yb, Er, Y, Ho) ceramics have been investigated for their crystal structures, microwave dielectric properties, flexural strength, and potential applications in dielectric antennas. Rietveld refinement and TEM analysis revealed that the BaM4Si5O17 ceramics exhibit a monoclinic structure (space groups: P21/m). The εr of the BaM4Si5O17 ceramics was dominated by ionic polarizability and ρrel. The Q × f values were considerably larger at BaM4Si5O17 (M = Yb and Y) ceramics with the high Utotal and low intrinsic dielectric loss. The τf values were controlled by the MO6 octahedron distortion and -VBa. The flexural strength was mainly dominated by pores and average grain size and reached the maximum value (156 MPa) at BaY4Si5O17 ceramic with small average gain sizes and high relative density. Additionally, a patch antenna was fabricated using high-performance BaY4Si5O17 ceramic characterized by a εr value of 9.02, a Q × f value of 60620 at 12.30 GHz, and a τf value of -37.65 ppm/°C. This design achieved a high simulated radiation efficiency of 82.70% and a gain of 5.60 dBi at 6.97 GHz. indicating potential applications of BaY4Si5O17 ceramic because of its low dielectric loss and high flexural strength.

SEMQuant: Extending Sipros-Ensemble with Match-Between-Runs for Comprehensive Quantitative Metaproteomics.

Metaproteomics, utilizing high-throughput LC-MS, offers a profound understanding of microbial communities. Quantitative metaproteomics further enriches this understanding by measuring relative protein abundance and revealing dynamic changes under different conditions. However, the challenge of missing peptide quantification persists in metaproteomics analysis, particularly in data-dependent acquisition mode, where high-intensity precursors for MS2 scans are selected. To tackle this issue, the match-between-runs (MBR) technique is used to transfer peptides between LC-MS runs. Inspired by the benefits of MBR and the need for streamlined metaproteomics data analysis, we developed SEMQuant, an end-to-end software integrating Sipros-Ensemble's robust peptide identifications with IonQuant's MBR function. The experiments show that SEMQuant consistently obtains the highest or second highest number of quantified proteins with notable precision and accuracy. This demonstrates SEMQuant's effectiveness in conducting comprehensive and accurate quantitative metaproteomics analyses across diverse datasets and highlights its potential to propel advancements in microbial community studies. SEMQuant is freely available under the GNU GPL license at https://github.com/Biocomputing-Research-Group/SEMQuant.

Factors contributing to organelle genomes size variation and the intracellular DNA transfer in Polygonaceae.

The use of complete organelle genomes, including chloroplast and mitochondrial genomes, is a powerful molecular method for studying biological evolution and gene transfer. However, in the case of Polygonaceae, an important family with numerous edible, medicinal, and ornamental species, the mitochondrial genomes of only three species have been sequenced and analyzed. In this study, we present the mitochondrial and chloroplast genomes of two important Tibetan medicinal plants, Bistorta viviparum and B. macrophyllum. All the organelle genomes are assembled into a single circular structure and contain a common set of 32 protein-coding genes (PCGs). Some genes such as rps2 and ndhF were found to have high nucleotide polymorphism (Pi) in the chloroplast genomes, while cox1, mttB and rps12 showed pronounced Pi values in the mitochondrial genomes. Furthermore, our analysis revealed that most chloroplast genes and mitochondrial PCGs in Polygonaceae plants are under purifying selection. However, a few genes, including the chloroplast gene psaJ and the mitochondrial genes ccmFc, atp8 and nad4, showed positive selection in certain Polygonaceae plants, as indicated by a Ka/Ks ratio greater than one. Structural variation analysis revealed a wealth of differences between the mitochondrial genomes of five Polygonaceae species, with a particularly notable large-scale inversion observed between Reynoutria japonica and Fallopia aubertii. Furthermore, an analysis of the homologous sequences in the chloroplast and mitochondrial genomes revealed that the rps7 has been transferred from the chloroplast to the mitochondrial genome in all five Polygonaceae species. Finally, ecological niche models were constructed for B. viviparum and B. macrophyllum, indicating that mean annual temperature and altitude are the main climatic factors influencing the distribution of both species. Although the current distribution of B. viviparum is significantly wider than that of B. macrophyllum, projections suggest that the optimal growth ranges of both species will expand in the future, with B. macrophyllum potentially exceeding B. viviparum. This study not only contributes to the plastid genome database for Polygonaceae plants, but also provides theoretical insights into the adaptive evolution of these plants.

Effects of the Fungicide Prothioconazole on Lipid Metabolism in Mice: Whitening Alterations of Brown Adipose Tissue.

With considerable concerns about the associations between metabolic disorders and agricultural biocides, there are scattered data suggesting that the triazole fungicide prothioconazole (PTC) at lower doses than the no observed adverse effect level of 5000 µg/kg/d possibly has the potential to disrupt glycolipid metabolism in mammals. Here, we investigated the effects of 50, 500, and 5000 µg/kg/d of PTC on glycolipid metabolism in mice following 8 weeks of administration via drinking water, with specific attention on brown adipose tissue (BAT) and white adipose tissue (WAT) in addition to the liver. We found that along with the increased serum triglyceride level in the 5000 µg/kg/d group, small fatty vacuoles occurred in livers in all treatment groups, indicating lipid accumulation. No change in WAT was observed, but PTC caused BAT whitening, characterized by adipocyte hypertrophy, more unilocular adipocytes with enlarged lipid droplets, reduced UCP1 levels, and down-regulated Doi2 expression, and even the dose of 50 µg/kg/d was effective. Transcriptomic analysis revealed immune inhibition and circadian rhythm disturbance in BAT from the 5000 µg/kg/d group, which are in agreement with BAT whitening and inactivation. On employing the C3H10T1/2 cells in vitro, we found that PTC treatment concentration-dependently promoted lipid accumulation in brown adipocytes, along with altered expression of thermogenesis-related and circadian genes. Taken together, our study shows that low doses of PTC caused BAT whitening, calling for much attention to the new target by pollutants.

Breaking Symmetry for SHG Response: Lanthanide Acetate Crystals via Water Molecule Regulation Strategy.

In the field of nonlinear optical (NLO) materials research, the design and synthesis of novel materials are crucial for advancing modern scientific and technological development. This study employs an innovative coordination strategy, building upon the existing structure of [Ln2(CH3COO)6(H2O)4]·4H2O (Ln = Tb, Sm), to successfully synthesize a series of acetate rare-earth metal compounds [Ln2(CH3COO)6(H2O)]n [Ln = Tb(1), Er(2), Y(3)] by regulating the number of water molecules. This approach achieved a structural transition from centrosymmetric (CS) to noncentrosymmetric (NCS), endowing these compounds with significant nonlinear optical responses. We discovered that reducing the coordinated water molecules and introducing acetate as a bidentate ligand is an effective method for modulating crystal structure and realizing NLO performance. This finding not only deepens the understanding of the structure of acetate salts but also provides important theoretical and experimental support for the development of materials with potential NLO propeties.

All-Arthroscopic Treatment of Combined Off-Track Hill-Sachs Lesions Using Interference Screw and Shoulder Glenoid Bone Defects Using Bone Grafting With Soft Fixation.

Bony changes such as glenoid bone defects and Hill-Sachs lesions are responsible for recurrent anterior shoulder dislocations. With the development of arthroscopic techniques as well as arthroscopic surgical instruments, arthroscopic repair of bony structures has become an important surgical procedure for the treatment of recurrent shoulder dislocation. In this Technical Note, we used screws to fill Hill-Sachs lesions and autologous iliac bone grafts combined with soft tissue to repair the glenoid bone defects. In the surgical procedures within the shoulder, all operations are done arthroscopically, are minimally invasive, and achieve the goal of repairing composite shoulder injuries.

Severe hypertension in tuberous sclerosis complex caused by renal artery stenosis: A case report.

Tuberous sclerosis complex (TSC) is a rare autosomal dominant neurocutaneous disease. Arterial hypertension is one of its uncommon complications, which is supposed to be caused by renal cysts or angiomyolipomas. Few studies have been reported in the literature on renal artery stenosis (RAS) as the cause of hypertension in TSC. Hence, we reported a boy who presented with uncontrolled hypertension under five anti-hypertension drugs and was diagnosed with TSC complicated with left RAS. His high blood pressure was relieved by percutaneous transluminal renal angioplasty (PTRA). In one and a half years follow-up, his blood pressure was normal whilst he took four anti-hypertensive drugs. In conclusion, children with TCS complicated with hypertension should be carefully screened for RAS, which might be relieved by percutaneous balloon dilatation.

Efficacy of a self-made tracheostomy oxygen delivery device for oxygen therapy during postoperative anesthesia recovery.

BACKGROUND: Patients with tracheotomy are often monitored in the anesthesia recovery room after reoperation. During this period, oxygen therapy is necessary, and the existing tracheostomy oxygen supply device has many defects. OBJECTIVE: To evaluate the efficacy of a self-made tracheostomy oxygen delivery device on oxygen therapy during postoperative anesthesia recovery. METHODS: Patients were randomly divided into two groups, E and C, with 30 patients in each group, and admitted to the post-anesthesia care unit (PACU). Patients in group E received oxygen through a self-made tracheostomy oxygen delivery device, while patients in group C were supplied oxygen through a unilateral nasal cannula. Respiration (R), pulse oximetry (SpO2), and the number of patients on ventilators were recorded at the time of admission (T0) and one hour after admission (T1). Rapid dry blood gas analyses were performed on 0.6 ml samples of arterial blood collected at T0 and T1. RESULTS: Compared to group C, patients in group E had significantly higher arterial partial pressure of oxygen (PaO2), arterial oxygen saturation (SaO2), total carbon dioxide (T-CO2), and actual bicarbonate (AB), while arterial partial pressure of carbon dioxide (PaCO2) was significantly reduced (P< 0.01 or < 0.05). Compared to T0, PaO2 decreased in both groups at T1, PaCO2 decreased in group E, while SaO2, T-CO2, and AB decreased in group C (P< 0.01 or < 0.05). CONCLUSION: We found that using the self-made tracheostomy oxygen delivery device in postoperative anesthesia recovery had advantages such as a secure connection to the tracheostoma, adjustable oxygen concentration, air filtration, and the ability to switch oxygen supply between the ventilator and humidifier.

The efficacy of rituximab in the treatment of IgA vasculitis nephritis.

The utility of Rituximab (RTX) for IgA vasculitis nephritis (IgAVN) is not well established. Up to now, we analysed the largest samples of IgAVN patients treated by RTX with a total of 41 retrieved subjects up to December 29, 2023 in the present systematic review. We assessed the clinical profiles, efficacy, and safety of RTX treatments. The present review showed that the renal function tended to be stabilized (P = 1.000) and urinalysis tended to normalize after RTX treatment with no serious adverse events reported. Moreover, 40% (16/40) of patients was freed use of glucocorticoid after RTX administration (P < 0.001). The remission rate was 92.7% (38/41) and complete remission rate was 46.3% (19/41) in IgAVN patients. Interestingly, 76.9% (10/13) of IgAVN child patients achieved complete remission when compared with 32.1% (9/28) of adult patients (P = 0.017). In summary, our results support the benefit of RTX therapy in IgAVN patients, especially children subjects.

TFCP2L1 drives stemness and enhances their resistance to Sorafenib treatment by modulating the NANOG/STAT3 pathway in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a prevalent and aggressive malignancy associated with high risks of recurrence and metastasis. Liver cancer stem cells (CSCs) are increasingly recognized as pivotal drivers of these processes. In our previous research, we demonstrated the involvement of TFCP2L1 in maintaining the pluripotency of embryonic stem cells. However, its relevance to liver CSCs remains unexplored. In this study, we report an inverse correlation between TFCP2L1 protein levels in HCC tissue and patient outcomes. The knockdown of TFCP2L1 significantly reduced HCC cell proliferation, invasion, metastasis, clonal formation, and sphere-forming capacity, while its overexpression enhanced these functions. In addition, experiments using a nude mouse model confirmed TFCP2L1's essential role in liver CSCs' function and tumorigenic potential. Mechanistically, we showed that TFCP2L1 promotes the stemness of CSCs by upregulating NANOG, which subsequently activates the JAK/STAT3 pathway, thereby contributing to HCC pathogenesis. Importantly, we identified a specific small molecule targeting TFCP2L1's active domain, which, in combination with Sorafenib, sensitizes hepatoma cells to treatment. Together, these findings underscore TFCP2L1's pathological significance in HCC progression, supporting its potential as a prognostic biomarker and therapeutic target in this disease.

The molecular regulatory mechanism of reed canary grass under salt, waterlogging, and combined stress was analyzed by transcriptomic analysis.

BACKGROUND: Reed canary grass has been identified as a suitable species for restoring plateau wetlands and understanding plant adaptation mechanisms in wetland environments. In this study, we subjected a reed canary grass cultivar 'Chuanxi' to waterlogging, salt, and combined stresses to investigate its phenotypic characteristics, physiological indices, and transcriptome changes under these conditions. RESULTS: The results revealed that the growth rate was slower under salt stress than under waterlogging stress. The chlorophyll content and energy capture efficiency of the PS II reaction center decreased with prolonged exposure to each stress. Conversely, while the activities of enzymes associated with respiratory metabolism, as well as MDA, PRO, Na+, and K+-ATPase, increased. The formation of distinct aerenchyma was observed under waterlogging stress and combined stress. Transcriptome sequencing analysis identified 5,379, 4,169, and 14,993 DEGs under CK vs. W, CK vs. S, and CK vs. SW conditions, respectively. The WRKY was found to be the most abundant under waterlogging stress, whereas the MYB predominated under salt stress and combined stress. Glutathione metabolic pathways and Plant hormone signal transduction have also been found to play important roles in stress. CONCLUSION: By integrating phenotypic, physiological, anatomical, and transcriptomic, this research provides valuable insights into how reed canary grass responds to salt, waterlogging, and combined stresses. These findings may inform the ecological application of reed canary grass in high-altitude wetlands and for breeding purposes.

Facilitating integrative and personalized oncology omics analysis with UCSCXenaShiny.

The continuous generation of multi-omics and phenotype data is propelling advancements in precision oncology. UCSCXenaShiny was developed as an interactive tool for exploring thousands of cancer datasets available on UCSC Xena. However, its capacity for comprehensive and personalized pan-cancer data analysis is being challenged by the growing demands. Here, we introduce UCSCXenaShiny v2, a milestone update through a variety of improvements. Firstly, by integrating multidimensional data and implementing adaptable sample settings, we create a suite of robust TPC (TCGA, PCAWG, CCLE) analysis pipelines. These pipelines empower users to conduct in-depth analyses of correlation, comparison, and survival in three modes: Individual, Pan-cancer and Batch screen. Additionally, the tool includes download interfaces that enable users to access diverse data and outcomes, several features also facilitate the joint analysis of drug sensitivity and multi-omics of cancer cell lines. UCSCXenaShiny v2 is an open-source R package and a web application, freely accessible at https://github.com/openbiox/UCSCXenaShiny .

Exploring Evolutionary Pathways and Abiotic Stress Responses through Genome-Wide Identification and Analysis of the Alternative Oxidase (AOX) Gene Family in Common Oat (Avena sativa).

The alternative oxidase (AOX), a common terminal oxidase in the electron transfer chain (ETC) of plants, plays a crucial role in stress resilience and plant growth and development. Oat (Avena sativa), an important crop with high nutritional value, has not been comprehensively studied regarding the AsAOX gene family. Therefore, this study explored the responses and potential functions of the AsAOX gene family to various abiotic stresses and their potential evolutionary pathways. Additionally, we conducted a genome-wide analysis to explore the evolutionary conservation and divergence of AOX gene families among three Avena species (Avena sativa, Avena insularis, Avena longiglumis) and four Poaceae species (Avena sativa, Oryza sativa, Triticum aestivum, and Brachypodium distachyon). We identified 12 AsAOX, 9 AiAOX, and 4 AlAOX gene family members. Phylogenetic, motif, domain, gene structure, and selective pressure analyses revealed that most AsAOXs, AiAOXs, and AlAOXs are evolutionarily conserved. We also identified 16 AsAOX segmental duplication pairs, suggesting that segmental duplication may have contributed to the expansion of the AsAOX gene family, potentially preserving these genes through subfunctionalization. Chromosome polyploidization, gene structural variations, and gene fragment recombination likely contributed to the evolution and expansion of the AsAOX gene family as well. Additionally, we hypothesize that AsAOX2 may have potential function in resisting wounding and heat stresses, while AsAOX4 could be specifically involved in mitigating wounding stress. AsAOX11 might contribute to resistance against chromium and waterlogging stresses. AsAOX8 may have potential fuction in mitigating ABA-mediated stress. AsAOX12 and AsAOX5 are most likely to have potential function in mitigating salt and drought stresses, respectively. This study elucidates the potential evolutionary pathways of the AsAOXs gene family, explores their responses and potential functions to various abiotic stresses, identifies potential candidate genes for future functional studies, and facilitates molecular breeding applications in A. sativa.

High ratio of epi-25-(OH)-vitamin D3 to 25-(OH)-vitamin D3 increases the risk of asthma attack in American asthma adults: a population study.

OBJECTIVE: The relationship between vitamin D3 and asthma remains controversial. However, previous studies have largely overlooked the impact of epi-25-(OH)-vitamin D3. This study aims to investigate the effects of different forms of vitamin D3 on asthma attack in adults. METHODS: In this cross-sectional study, a total of 3,873 eligible adult participants were extracted from the national health and nutrition examination survey (NHANES) database from 2007 to 2018. Based on quartiles method, different levels of vitamin D were divided into four groups (Quartile 1-4). Bivariate correlation analysis was performed for vitamin D and covariates to avoid multicollinearity. Multivariate logistic regression was used to investigate the association between serum levels of vitamin D3 (epi-25-(OH)-vitamin D3 and 25-(OH)-vitamin D3) and asthma attack, adjusting for covariates including age, gender, race, length of time in the U.S., house poverty income ratio (PIR), education level, smoking history, hypertension history, and diabetes history. The ratio of epi-25-(OH)-vitamin D3 to 25-(OH)-vitamin D3 was used for secondary analysis of its association with asthma attack. The outcomes were assessed by odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Among the 3,873 eligible adults American with asthma, 1,508 (38.94%) had experienced at least one acute asthma attack in the past year. There was no significant correlation between vitamin D and covariates. After adjusting for covariates including age, gender, race, length of time in the U.S., house poverty income ratio (PIR), education level, smoking history, hypertension history and diabetes history, we found a positive correlation between the ratio of epi-25-(OH)-vitamin D3 to 25-(OH)-vitamin D3 and asthma attack. Additionally, a high ratio of epi-25-(OH)-vitamin D3 to 25-(OH)-vitamin D3 was more common among elder, male, of normal weight, non-Hispanic American, have a long time stay in the U.S., a high house PIR, and a history of hypertension individuals. CONCLUSION: Our findings suggest that attention should be given to asthma attack associated with a high ratio of epi-25-(OH)-vitamin D3 to 25-(OH)-vitamin D3 in American adults who are elderly, male, of normal weight, non-Hispanic Americans, have long-term residence in the U.S., a high house PIR, and a history of hypertension.

N2H4Zn(HC3N3O3): exceptionally strong second harmonic generation and ultra-long phosphorescence.

The discovery and designed synthesis of multifunctional materials is a leading pursuit in materials science. Herein, we report a novel hydro-isocyanurate, N2H4Zn(HC3N3O3), which combines strong second harmonic generation (SHG) and ultra-long room-temperature phosphorescence (RTP). The SHG intensity is the highest within the cyanurate system (13 × KDP), and RTP lifetime extends up to 448 ms, accompanied by a long-lasting afterglow visible to the naked eye for 1.2 s, surpassing most of the current metal-organic complexes. This advancement holds promise for the development of multifunctional optoelectronic devices, particularly leveraging second-harmonic generation (SHG) processes.

Opportunistic Assessment of Hip Fracture Risk Based on Chest CT.

OBJECTIVE: Hip fracture (HF) has been described as the "last fracture of life" in the elderly, so the assessment of HF risk is extremely important. Currently, few studies have examined the relationship between imaging data from chest computed tomography (CT) and HF. This study demonstrated that pectoral muscle index (PMI) and vertebral body attenuation values could predict HF, aiming to opportunistically assess the risk of HF in patients without bone mineral density (BMD) based on chest CT for other diseases. METHODS: In the retrospective study, 800 participants who had both BMD and chest CT were enrolled from January 2021 to January 2024. After exclusion, 472 patients were finally enrolled, divided into the healthy control (HC) group and the HF group. Clinical data were collected, and differences between the two groups were compared. A predictive model was constructed based on the PMI and CT value of the fourth thoracic vertebra (T4HU) by logistic regression analysis, and the predictive effect of the model was analyzed by using the receiver operating characteristic (ROC) curve. Finally, the clinical utility of the model was analyzed using decision curve analysis (DCA) and clinical impact curves. RESULTS: Both PMI and T4HU were lower in the HF group than in the HC group (p < 0.05); low PMI and low T4HU were risk factors for HF. The predictive model incorporating PMI and T4HU on the basis of age and BMI had excellent diagnostic efficacy with an area under the curve (AUC) of 0.865 (95% confidence interval [CI]: 0.830-0.894, p < 0.01), sensitivity and specificity of 0.820 and 0.754, respectively. The clinical utility of the model was validated using calibration curves and DCA. The AUC of the predictive model incorporating BMD based on age and BMI was 0.865 (95% CI: 0.831-0.895, p < 0.01), with sensitivity and specificity of 0.698 and 0.711, respectively. There was no significant difference in diagnostic efficacy between the two models (p = 0.967). CONCLUSIONS: PMI and T4HU are predictors of HF in patients. In the absence of dual-energy x-ray absorptiometry (DXA), the risk of HF can be assessed by measuring the PMI and T4HU on chest CT examination due to other diseases, and further treatment can be provided in time to reduce the incidence of HF.