Accurate Density Prediction of Sesquiterpenoid HEDFs and the Multiproperty Computing Server SesquiterPre.

Accurate and rapid evaluation of density is crucial for evaluating the packing and combustion characteristics of high-energy-density fuels (HEDFs). This parameter is pivotal in the selection of high-performance HEDFs. Our study leveraged a polycyclic compound density data set and quantum chemical (QC) descriptors to establish a correlation with the target properties using the XGBoost algorithm. We utilized a recursive feature elimination method to simplify the model and developed a concise and interpretable density prediction model incorporating only six QC descriptors. The model demonstrated robust performance, achieving coefficients of determination (R 2) of 0.967 and 0.971 for internal and external test sets, respectively, and root-mean-square errors (RMSE) of 0.031 and 0.027 g/cm3, respectively. Compared to the other two mainstream methods, the marginal discrepancy between the predicted and actual molecular densities underscores the model's superior predictive ability and more usefulness for energy density calculation. Furthermore, we developed a web server (SesquiterPre, https://sespre.cmdrg.com/#/) that can simultaneously calculate the density, enthalpy of combustion, and energy density of sesquiterpenoid HEDFs, which greatly facilitates the use of researchers and is of great significance for accelerating the design and screening of novel sesquiterpenoid HEDFs.

Molecular Dynamics Study on the Reaction of RDX Molecule with Si Substrate.

RDX is widely used in various explosion situations, and there are many studies on its detonation performance, safety, preparation, etc. Research on preparation of ß-RDX is mainly conducted by experiments. In recent years, part of the research points to the use of substrate as a medium to produce ß-RDX faster. Based on this guidance, our work aims to theoretically solve the physical and chemical processes that RDX may experience in the production process through numerical simulation. In this work, molecular dynamics simulation is set up for the interaction between RDX and a Si clean surface and a Si hydroxyl saturated surface separately, and a higher precision simulation is set up to verify the reliability of the results. NCI analysis is also used to guess the possible phase transition mechanism in the simulation results. In the simulation process, a 7 × 7 Si clean surface, a 3 × 3 Si clean surface, and a 7 × 7 Si-OH surface are set, and each surface adsorbs one α-RDX. The semiempirical Gfn1-xtb method is used for the 7 × 7 surface, and the DFT method is used for the 3 × 3 surface. The calculation results confirmed by high-precision results show that RDX molecules will react with the dangling bonds on the Si surface. Three conformations of RDX were found on the hydroxyl saturated surface of Si. The isosurface generated by the NCI method is used to analyze the reasons for the formation of these conformations.

Detoxification of aflatoxins on prospective approach: effect on structural, mechanical, and optical properties under pressures.

Aflatoxins are sequential of derivatives of coumarin and dihydrofuran with similar chemical structures and well-known carcinogenic agent. Many studies performed to detoxify aflatoxins, but the result is not ideal. Therefore, we studied structural, infrared spectrum, mechanical, and optical properties of these compounds in the aim of perspective physics. Mulliken charge distributions and infrared spectral analysis performed to understand the structural difference between the basic types of aflatoxins. In addition, the effect of pressure, different polarized, and incident directions on their structural changes was determined. It is found that AFB1 is most stable structure among four basic types aflatoxins (AFB1, AFB2, AFG1, and AFG2), and IR spectra are analyzed to exhibit the difference on structures of them. The mechanical properties of AFB1 indicate that the structure of this toxin can be easily changed by pressure. The real [Formula: see text] and imaginary [Formula: see text] parts of the dielectric function, and the absorption coefficient [Formula: see text] and energy loss spectrum [Formula: see text] were also obtained under different polarized and incident directions. Furthermore, biological experiments needed to support the toxic level of AFB1 using optical technologies.

First-principle study of structural, electronic and magnetic properties of (FeC)n (n = 1-8) and (FeC)8TM (TM = V, Cr, Mn and Co) clusters.

The structural, electronic and magnetic properties of the (FeC)n (n = 1-8) clusters are studied using the unbiased CALYPSO structure search method and density functional theory. A combination of the PBE functional and 6-311 + G* basis set is used for determining global minima on potential energy surfaces of (FeC)n clusters. Relatively stabilities are analyzed via computing their binding energies, second order difference and HOMO-LUMO gaps. In addition, the origin of magnetic properties, spin density and density of states are discussed in detail, respectively. At last, based on the same computational method, the structures, magnetic properties and density of states are systemically investigated for the 3d (V, Cr, Mn and Co) atom doped (FeC)8 cluster.

Insights into the structures and electronic properties of Cun+1µ and CunS µ (n = 1-12; µ = 0, ±1) clusters.

ABSTARCT: The stability and reactivity of clusters are closely related to their valence electronic configuration. Doping is a most efficient method to modify the electronic configuration and properties of a cluster. Considering that Cu and S posses one and six valence electrons, respectively, the S doped Cu clusters with even number of valence electrons are expected to be more stable than those with odd number of electrons. By using the swarm intelligence based CALYPSO method on crystal structural prediction, we have explored the structures of neutral and charged Cun+1 and CunS (n = 1-12) clusters. The electronic properties of the lowest energy structures have been investigated systemically by first-principles calculations with density functional theory. The results showed that the clusters with a valence count of 2, 8 and 12 appear to be magic numbers with enhanced stability. In addition, several geometry-related-properties have been discussed and compared with those results available in the literature.

Efficacy of carbamazepine combined with botulinum toxin a in the treatment of blepharospasm and hemifacial spasm.

PURPOSE: To observe the efficacy of the combined treatment of carbamazepine and botulinum toxin A for blepharospasm and hemifacial spasm. METHODS: Fifty-eight patients with either blepharospasm or hemifacial spasm were randomly divided into treatment and control groups. In the treatment group, 30 patients were administered with local intramuscular injections of botulinum toxin A and oral carbamazepine 100 mg/time, 3 times a day for 60 days. Twenty-eight subjects in the control group underwent local intramuscular injections of botulinum toxin A only. RESULTS: After combined treatment, the complete remission rate was 90%, which was significantly higher than that of the of the control group (67.9%, P<0.05, X2=4.733). However, no statistical significance was noted regarding the duration of therapeutic effects between the treatment group (range 14~40 weeks; 19.2 weeks on average) and control group (range 12~36 weeks; 18 weeks on average). CONCLUSION: The combined therapy of carbamazepine and topical injections of botulinum toxin A had increased efficacy in the treatment of blepharospasm or hemifacial spasm, but had no significant effect in terms of the duration of the therapeutic effect.

[Clinical value of preoperative comprehensive evaluation of cataract surgery in age-related cataract].

OBJECTIVE: To evaluate the clinical results, the selection of time and procedures of surgery and preoperative evaluation of the phacoemulsification or small incision cataract surgery with intraocular lens implantation (PSI) in senile cataract patients with cardiovascular disease. METHODS: The authors performed a retrospective study in 218 senior patients (255 eyes) with cardiovascular disease, which were treated by PSI in the past 5 years. RESULTS: Thirteen cases (14 eyes) did not have PSI due to surgical contraindication or impossible to tolerate the operation or impossible to obtain an improvement of visual acuity after operation. Two hundred and five cases (241 eyes) with cardiovascular disease were treated with PSI. After follow up for 1 - 18 months (mean 6.3 months), 165 cases (193 eyes) had a best corrected visual acuity (BCVA) equal or more than 20/60 (80.5%); 32 cases (39 eyes) had BCVA of 20/400 or less than 20/60 (15.6%); and 8 cases (9 eyes) had BCVA less than 20/400 (3.9%). There were no severe complications during the operation. One case developed inhalation pneumonia postoperatively and was transferred to internal medicine for rescue. CONCLUSIONS: Senile cataract patients with cardiovascular disease must be evaluated before performing PSI. The advantages of general hospital should be utilized to treat patients with cardiovascular disease before, during and after the operation. The use of sedatives, adrenalin and steroids must be individualized; high-risk patients should be monitored by EKG and supplied by constant inhalation of low dose oxygen to minimize the surgical risk. In senile cataract patients with cardiovascular disease and IV grade or more lens nucleus, small incision cataract surgery with intraocular lens implantation is better than phacoemulsification with intraocular lens implantation.