7 research outputs found
Does Serum Vitamin D Level Affect COVID-19 Infection and Its Severity?-A Case-Control Study
Background: As effective medication to treat COVID-19 is currently unavailable, preventive remedies may be particularly important. Objective: To examine the relationship between serum 25-hydroxy vitamin D (25(OH)D) level and COVID-19 infection, its severity, and its clinical case characteristics. Methods: This case-control study compared serum 25(OH)D levels and rates of vitamin D deficiency (VDD) between 80 healthy controls and 62 patients diagnosed with COVID-19 and admitted to Guangxi People’s Hospital, China, 2/16/2020–3/16/2020. Cases were categorized into asymptomatic, mild/moderate, and severe/critical disease. Logistic regression analysis was conducted to examine the associations between 25(OH)D level, or VDD, and case status/severity of COVID-19 while controlling for demographics and comorbidities. A threshold level of vitamin D for conveying COVID-19 risk was estimated. Results: Severe/critical COVID-19 cases were significantly older and had higher percentages of comorbidity (renal failure) compared to mild cases. The serum 25(OH)D concentration in COVID-19 patient was much lower than that in healthy control. And 25(OH)D level was the lowest in severe/ critical cases, compared with mild cases. In further, significantly higher rates of VDD were found in COVID-19 cases (41.9%) compared to healthy controls (11.1%). And VDD was the greatest in severe/critical cases (80%), compared with mild cases (36%). These statistically significant associations remained even after controlling for demographics and comorbidities. A potential threshold of 25(OH)D (41.19nmol/L) to protect against COVID-19 was identified. Conclusion: Elderly and people with comorbidities were susceptible to severe COVID-19 infection. VDD was a risk factor for COVID-19, especially for severe/critical cases. While further confirmation is needed, vitamin D supplementation may have prevention or treatment potential for COVID- 19 disease
Root Traits and Soil Bacterial Composition Explain the Rhizosphere Effects along a Chronosequence of Rubber Plantations
Rubber tree plantations (Hevea brasiliensis) are expanding into the tropical regions of southwest China to ensure production to meet the growing demand for latex. The effects of long-term plantations on soil carbon processes are still unclear. Also, the effects of the plant’s rhizosphere on the decomposition of soil organic matter (SOM) play a crucial role in predicting soil carbon dynamics. The rhizosphere and soils corresponding to a chronosequence of ages (4, 15 and 30 years) of rubber plantations were collected and incubated to determine the effect of the rhizosphere (RE) on SOM decomposition. We also examined the soil physicochemical properties; bacterial community structure; and root morphological, chemical, and physiological traits to further explore the underlying mechanisms of the RE on SOM decomposition. The REs on SOM decomposition varied significantly in the different age classes of the rubber plantations, and the higher the REs on SOM decomposition in an older plantation might limit the accumulation of organic carbon in the soil. Root traits, including the specific root length, root nitrogen content, and root carbon/nitrogen ratio, varied significantly in response to the plantation age and explained more of the variance in the RE on SOM decomposition than the soil and microbial properties. Due to the changing root morphological and chemical traits along the age chronosequence, the rhizosphere bacterial community composition tended to shift the carbon utilisation strategy and the bulk soil nitrogen content decreased. These variations also affected the RE on SOM decomposition. Our results indicate that the development of rubber plantations would prevent soil carbon accumulation, especially in the rhizosphere, by increasing the RE on SOM decomposition, which would be predicated by root morphological and chemical traits
Polymorphic Self-Assemblies of 2,7-Bis(decyloxy)-9-fluorenone at the Solid/Gas Interface: Role of C–H···OC Hydrogen Bond
The self-assembly
of 2,7-bisÂ(decyloxy)-9-fluorenone on highly oriented pyrolytic graphite
is investigated at the solid/gas interface by scanning tunneling microscopy,
which allows us to determine the effect of its molecular structure
on the formation of monolayer morphology. By varying the solution
concentration in dichloromethane, seven types of supramolecular assemblies
can be obtained. The concentration-dependent structural polymorphism
is discussed in terms of thermodynamics. In particular, these different
patterns are identified to be bound with weak intermolecular CÂ(sp2)–H···Oî—»C
hydrogen bonds. As discerned by its position in the fluorenone moiety,
the CÂ(sp2)–H group with larger chemical shift value and stronger
acidity displays a higher priority when involving in the formation
of a CÂ(sp2)–H···O hydrogen bond. Owing to the
high density of CÂ(sp<sup>2</sup>)–H donors, various hydrogen-bonding
configurations arise, further leading to the occurrence of structural
polymorphism. Besides, intermolecular van der Waals interactions as
well as the dipole–dipole interactions act as the complementary
roles to stabilize the whole monolayer. The underlying mechanism is
further confirmed by the density functional theory calculations
Controllable Orientation of Ester-Group-Induced Intermolecular Halogen Bonding in a 2D Self-Assembly
Halogen
bonding with high specificity and directionality in the
geometry has proven to be an important type of noncovalent interaction
to fabricate and control 2D molecular architectures on surfaces. Herein,
we first report how the orientation of the ester substituent for thienophenanthrene
derivatives (5,10-DBTD and 5,10-DITD) affects positive charge distribution
of halogens by density functional theory, thus determining the formation
of an intermolecular halogen bond and different self-assembled patterns
by scanning tunneling microscopy. The system presented here mainly
includes heterohalogen X···OC and X···S
halogen bonds, H···Br and H···O hydrogen
bonds, and I···I interaction, where the directionality
and strength of such weak bonds determine the molecular arrangement
by varying the halogen substituent. This study provides a detailed
understanding of the role of ester orientation, concentration, and
solvent effects on the formation of halogen bonds and proves relevant
for identification of multiple halogen bonding in supramolecular chemistry