Factors influencing the surveillance of re-emerging intracranial infections in elective neurosurgical patients: A single-center retrospective study.

BACKGROUND: At present, many studies have reported the risk factors for postoperative intracranial reinfection, including age, sex, time to surgery, duration of postoperative catheterization, emergency procedures, type of disease and cerebrospinal fluid leakage, but the academic community has not reached a unified conclusion. AIM: To find factors influencing the surveillance of re-emerging intracranial infections in elective neurosurgical patients. METHODS: Ninety-four patients who underwent elective craniotomy from January 1, 2015 to December 31, 2022 in the Department of Neurosurgery, First Hospital of Jilin University, were included in this study. Of those, 45 patients were enrolled in the infection group, and 49 were enrolled in the control group. The clinical data of the patients were collected and divided into three categories, including preoperative baseline conditions, intraoperative characteristics and postoperative infection prevention. The data were analyzed using SPSS 26.0 software. RESULTS: There were 23 males and 22 females in the infection group with a mean age of 52.8 ± 15.1 years and 17 males and 32 females in the control group with a mean age of 48.9 ± 15.2 years. The univariate analysis showed that the infection group had higher systolic blood pressures and postoperative temperatures, fewer patients who underwent a supratentorial craniotomy, more patients with a history of hypertension and higher initial postoperative white blood cell counts than the control group, with statistically significant differences (P < 0.05). The multifactorial logistic regression analysis showed that a history of hypertension and a high postoperative body temperature were independent risk factors for postoperative infection in neurosurgical patients. CONCLUSION: The results obtained in this study indicated that a history of hypertension and a high postoperative body temperature were independent risk factors for postoperative neurological symptoms.

Interlayer Quasi-Bonding Interactions in 2D Layered Materials: A Classification According to the Occupancy of Involved Energy Bands.

Recent studies have revealed that the interlayer interaction in two-dimensional (2D) layered materials is not simply of van der Waals character but could coexist with quasi-bonding character. Herein, we classify the interlayer quasi-bonding interactions into two main categories (I: homo-occupancy interaction; II: hetero-occupancy interaction) according to the occupancy of the involved energy bands near the Fermi level. We then investigate the quasi-bonding-interaction-induced band structure evolution of several representative 2D materials based on density functional theory calculations. Further calculations confirm that this classification is applicable to generic 2D layered materials and provide a unified understanding of the total strength of interlayer interaction, which is a synergetic effect of the van der Waals attraction and the quasi-bonding interaction. The latter is stabilizing in main category II and destabilizing in main category I. Thus, the total interlayer interaction strength is relatively stronger in category II and weaker in category I.

Strain-driven phase transition and spin polarization of Re-doped transition-metal dichalcogenides.

Two-dimensional transition metal dichalcogenides (TMDCs) are promising in spintronics due to their spin-orbit coupling, but their intrinsic non-magnetic properties limit their further development. Here, we focus on the energy landscapes of TMDC (MX2, M = Mo, W and X = S, Se, Te) monolayers by rhenium (Re) substitution doping under axial strains, which controllably drive 1H ↔ 1Td structural transformations. For both 1H and 1Td phases without strain, Re-doped TMDCs have an n-type character and are non-magnetic, but the tensile strain could effectively induce and modulate the magnetism. Specifically, 1H-Re0.5Mo0.5S2 gets a maximum magnetic moment of 0.69 µB at a 6% uniaxial tensile strain along the armchair direction; along the zigzag direction it exhibits a significant magnetic moment (0.49 µB) at a 2.04% uniaxial tensile strain but then exhibits no magnetism in the range of [5.10%, 7.14%]. By contrast, for 1Td-Re0.5Mo0.5S2 a critical uniaxial tensile strain along the zigzag direction reaches up to ∼9.18%, and a smaller uniaxial tensile strain (∼5.10%) along the zigzag direction is needed to induce the magnetism in 1Td-Re0.5M0.5Te2. The results reveal that the magnetism of Re-doped TMDCs could be effectively induced and modulated by the tensile strain, suggesting that strain engineering could have significant applications in doped TMDCs.

Fluorescence and Optical Activity of Chiral CdTe Quantum Dots in Their Interaction with Amino Acids.

Ligand-induced chirality in semiconducting nanocrystals has been the subject of extensive study in the past few years and shows potential applications in optics and biology. Yet, the origin of the chiroptical effect in semiconductor nanoparticles is still not fully understood. Here, we examine the effect of the interaction with amino acids on both the fluorescence and the optical activity of chiral semiconductor quantum dots (QDs). A significant fluorescence enhancement is observed for l/d-Cys-CdTe QDs upon interaction with all the tested amino acids, indicating suppression of nonradiative pathways as well as the passivation of surface trap sites brought via the interaction of the amino group with the CdTe QDs' surface. Heterochiral amino acids are shown to weaken the circular dichroism (CD) signal, which may be attributed to a different binding configuration of cysteine molecules on the QDs' surface. Furthermore, a red shift of both CD and fluorescence signals in l/d-Cys-CdTe QDs is only observed upon adding cysteine, while other tested amino acids do not exhibit such an effect. We speculate that the thiol group induces orbital hybridization of the highest occupied molecular orbital (HOMOs) of cysteine and the valence band of CdTe QDs, leading to the decrease of the energy band gap and a concomitant red shift of CD and fluorescence spectra. This is further verified by density functional theory calculations. Both the experimental and theoretical findings indicate that the addition of ligands that do not "directly" interact with the valence band (VB) of the QD (noncysteine moieties) changes the QD photophysical properties, as it probably modifies the way cysteine is bound to the surface. Hence, we conclude that it is not only the chemistry of the amino acid ligand that affects both CD and PL but also the exact geometry of binding that modifies these properties. Understanding the relationship between the QD's surface and chiral amino acid thus provides an additional perspective on the fundamental origin of induced chiroptical effects in semiconductor nanoparticles, potentially enabling us to optimize the design of chiral semiconductor QDs for chiroptic applications.

Variations of thermoelectric performance by electric fields in bilayer MX2 (M = W, Mo; X = S, Se).

A gate electrode is usually used to controllably tune the carrier concentrations, further modulating the electrical conductivity and the Seebeck coefficient to obtain the optimum thermoelectric figure of merit (ZT) in two-dimensional materials. On the other hand, it is necessary to investigate how an electric field induced by a gate voltage affects the electronic structures, further determining the thermoelectric properties. Therefore, by using density functional calculations in combination with Boltzmann theory, the thermoelectric properties of bilayer MX2 (M = W, Mo; X = S, Se) with or without a 1 V nm-1 perpendicular electric field are comparatively investigated. First of all, the variations of the electrical conductivity (σ), electron thermal conductivity and Seebeck coefficient (S) with the carrier concentration are studied. Due to the trade-off relationship between S and σ, there is an optimum concentration to obtain the maximum ZT, which increases with the temperature due to the enhancement of the Seebeck coefficient. Moreover, N-type bilayers have larger optimum ZTs than P-type bilayers. In addition, the electric field results in the increase of the Seebeck coefficient in low hole-doped MS2 bilayers and high hole-doped MSe2 bilayers, thus leading to similar variations in ZT. The optimum ZTs are reduced from 2.11 × 10-2, 3.19 × 10-2, 2.47 × 10-2, and 2.58 × 10-2 to 1.57 × 10-2, 1.51 × 10-2, 2.08 × 10-2, and 1.43 × 10-2 for the hole-doped MoS2, MoSe2, and WSe2 bilayers, respectively. For N-type bilayers, the electric field shows a destructive effect, resulting in the obvious reduction of the Seebeck coefficient in the MSe2 layers and the low electron-doped MS2 bilayers. In electron-doped bilayers, the optimum ZTs will decrease from 3.03 × 10-2, 6.64 × 10-2, and 6.69 × 10-2 to 2.81 × 10-2, 3.59 × 10-2, and 4.39 × 10-2 for the MoS2, MoSe2, and WSe2 bilayers, respectively.

Ultrahigh power factors in P-type 1T-ZrX2 (X = S, Se) single layers.

The thermoelectric performances of 1T-ZrX2 (X = S and Se) single layers were investigated using a combination of density functional calculations and semi-classical Boltzmann transport theory. Because of the high hole mobilities at 300 K, ultrahigh power factors (PF=S2σ) were found in the P-type compounds; these values were ∼ 11.95 and ∼13.58 mW K-2 m-1 for 1T-ZrS2 and 1T-ZrSe2 single layers, respectively. However, because of the Lorenz relation between the electrical conductivity (σ) and an electron's thermal conductivity (κel) given by the Wiedemann-Franz law, the electronic figures of merit (ZelT=PF·T/κel) at 300 K were approximately 0.67 and 0.75 for the N- and P-type 1T-ZrSe2, respectively. In addition, the lattice thermal conductivities (κph) were calculated, giving values of ∼1.43 and ∼0.97 W K-1 m-1 for 1T-ZrS2 and 1T-ZrSe2 single layers, respectively. Therefore, because of the lower κph/κel ratio, the P-type 1T-ZrX2 single layers possess higher figure-of-merits (ZT=ZelT/1+κphκel) than their counterparts. This signifies that the P-type samples demonstrate better thermoelectric performance than the N-type ones. The thermoelectric properties of metastable 2H-ZrX2 (X = S and Se) single layers were also investigated.

Thermoelectric properties of fullerene-based junctions: a first-principles study.

This study is built on density functional calculations in combination with the non-equilibrium Green's function, and we probe the thermoelectric transport mechanisms through C60 molecules anchored to Al nano-electrodes in three different ways, such as, the planar, pyramidal, and asymmetric surfaces. When the electrode is switched from the planar and pyramidal surfaces, the electrical conductance (σ) and electron's thermal conductance (κel) decrease almost two orders of magnitude due to the reduction of the molecule-electrode contact coupling, whereas the Seebeck coefficients (S) are reduced by ∼55%. Furthermore, the maximum electron's thermoelectric figure of merit (ZelT = S2σT/κel, assuming a vanishing phonon's thermal conductance) is about 0.12 in the asymmetric junction. In particular, all σ, S, κel, and ZelT increase along with the average temperature (T) in all C60-junctions, although their growth is really quite negligible in the pyramidal junction because the Fermi level is far away from the frontier orbitals. In addition, when the strain increases from the compressive (-1.0 Å) to tensile (1.0 Å) strain, the Seebeck coefficient in the planar junction increases drastically, while the Seebeck coefficients in the asymmetric and pyramidal junctions reach their maximum values at 0.2 Å tensile and -0.4 Å compressive strains, respectively. This is because the Seebeck coefficient is inversely proportional to the magnitudes and proportional to the slopes of the transmission spectrum around the Fermi level. Finally, it is found that the shift of the Fermi level is an effective scheme to obtain the maximum ZelT of any molecular junction, including fullerene-based junctions.

Strain and electric field co-modulation of electronic properties of bilayer boronitrene.

The electronic properties of bilayer strained boronitrenes are investigated under an external electric field using density functional methods. Our result is just the same as the previous conclusion: ie, that the electric field will reduce their band gaps. Except for the decrease of their band gaps, the degeneracy of π valence bands at K points will be lifted and the degenerate gap will increase with the electric field increasing. Moreover, the widths of π valence bands are nearly robust and increase a little. In addition, a simple tight-binding model, where different electrostatic potentials are applied to boronitrene layers, can be sufficient to describe the variations of their band gaps. It is found that the interlayer hopping interaction increases while the intralayer hopping parameter changes little with increasing the electric field. Furthermore, a band gap phase diagram is determined within the in-plane strain [-0.2, 0.2] and the interlayer bias [0, 10] V nm(-1). The strain could make the bottom of conduction bands shift from K to M, then to Γ in the Brillouin zone, while the top of valence bands shifts from K to Γ. Thus, a direct-gap semiconductor at K points is changed into an indirect-gap semiconductor, and then a semiconductor with the direct band gap at Γ points. When bilayer boronitrene is a semiconductor with a direct gap at K points, the electric field and strain are inverse proportional relationships. Particularly, when the compressive strain exceeds -0.194, there is an insulator-metal transition and the system becomes metallic with sizable pocket Fermi surfaces.

Flatbands in 2D boroxine-linked covalent organic frameworks.

Density functional calculations have been performed to analyze the electronic and mechanical properties of a number of 2D boroxine-linked covalent organic frameworks (COFs), which are experimentally fabricated from di-borate aromatic molecules. Furthermore, the band structures are surprising and show flat-band characteristics which are mainly attributed to the delocalized π-conjugated electrons around the phenyl rings and can be better understood within aromaticity theories. Next, the effects of branch sizes and hydrostatic strains on their band structures are systematically considered within generalized gradient approximations. It is found that their band gaps will start to saturate when the branch size reaches 9. For boroxine-linked COFs with only one benzene ring in the branch, the band gap is robust under compressive strain while it decreases with the tensile strain increasing. When the branch size is equal or greater than 2, their band gaps will monotonously increase with the strain increasing in the range of [-1.0, 2.0] Å. All boroxine-linked COFs are semiconductors with controllable band gaps, depending on the branch length and the applied strain. In comparison with other 2D materials, such as graphene, hexagonal boron nitride, and even γ-graphyne, all boroxine-linked COFs are much softer and even more stable. That is, they can maintain the planar features under a larger compressive strain, which means that they are good candidates in flexible electronics.

Superconducting behavior in compressed solid SiH4 with a layered structure.

The electronic and lattice dynamical properties of compressed solid SiH4 have been calculated in the pressure range up to 300 GPa with density functional theory. We find two energetically preferred insulating phases with P2(1)/c and Fdd2 symmetries at low pressures. We demonstrate that the Cmca structure having a layered network is the most likely candidate of the metallic phase of SiH4 over a wide pressure range above 60 GPa. The superconducting transition temperature in this layered metallic phase is found to be in the range of 20-75 K.

[Mechanism and pathway of the ozonation of nonylphenol in aqueous solution].

20 mg/L nonylphenol solution was ozonized. The removal efficiency and the intermediate products were studied during the ozonation of nonylphenol, the possible reaction mechanism of the ozonation of nonylphenol was proposed. The experimental results indicate that there are two kinds of ozonation patterns, the oxidation by molecule O3 alone and by O3/*OH. Both ozonation patterns can remove nonylphenol completely within 18 minutes. However, the combined oxidation can remove 96% of the initial nonylphenol within 4 minutes, and it took 12 minutes in the single O3 molecule oxidation system. The formaldehyde was detected during the ozonation of nonylphenol. The concentration reached stability after 8 minutes during the oxidation by single O3 and gradually increased during the combined oxidation process.