FP(µ-N)2 S: A Sulfur-Pnictogen Four-Membered Ring with 6π Electrons.

The new 6π-electron four-membered ring compound 3-fluoro-1λ2 ,2,4,3λ3 -thiadiazaphosphetidine, FP(µ-N)2 S, has been generated in the gas phase through high-vacuum flash pyrolysis (HVFP) of thiophosphoryl diazide, FP(S)(N3 )2 , at 1000 K. Subsequent isolation of FP(µ-N)2 S in cryogenic matrices (Ar, Ne, and N2 ) allows its characterization with matrix-isolation IR and UV-vis spectroscopy by combination with 15 N-isotope labeling and computations at the CCSD(T)-F12a/VTZ-F12 level of theory. Upon visible-light irradiation at 550 nm, this cyclic compound undergoes ring-opening to the thiazyl isomer FPNSN, followed by dissociation to FP and SN2 under subsequent UV-irradiation at 365 nm. In sharp contrast to the square planar structure for the isolobal four-membered ring S2 N2 , a puckered structure with significant biradical character has been found for FP(µ-N)2 S.

3-Fluoro-2H-azirine: Generation, Characterization, and Photochemistry.

The elusive 3-fluoro-2H-azirine, cyclic NCH2CF, has been generated through the stepwise decomposition of the acryloyl azide CH2CFC(O)N3 in an N2-matrix at 10 K. The characterization of cyclic NCH2CF with matrix-isolation IR spectroscopy is supported by 15N isotope labeling and the calculations with density functional theory (DFT) at the B3LYP/6-311++G(3df,3pd) level of theory. Upon irradiation at 193 nm, cyclic NCH2CF undergoes ring opening by forming the more stable nitrile isomer CH2FCN. In contrast to the photodecomposition reactions, the high-vacuum flash pyrolysis of CH2CFC(O)N3 in the gas phase at 500 °C yields the Curtius rearrangement product CH2CFNCO along with secondary fragmentation to the atmospherically relevant fluorocarbonyl radical (FCO) and cyanomethyl radical (CH2CN). Calculations on the potential energy profile for the decomposition reactions of CH2CFC(O)N3 demonstrate that the excessive energy, arising from the highly exothermic Curtius rearrangement of the azide, plays a key role in driving further dissociation reactions of CH2CFNCO by overcoming the formidable barriers (>50 kcal mol-1) under the pyrolysis conditions.

Fluoromethylsulfinyl radicals: spectroscopic characterization and photoisomerization via intramolecular hydrogen shift.

Two new sulfinyl radicals, CHF2SO˙ and CH2FSO˙, have been generated in the gas phase through homolytic cleavage of the weak S-S bonds in disulfane oxides CHF2S(O)SCF3 and CH2FS(O)SCF3 by high-vacuum flash pyrolysis (HVFP) at ca. 500 °C. The IR spectroscopy characterization of the two fluoromethylsulfinyl radicals in solid N2 (10 K), Ar (10 K), and Ne (3 K) matrices reveals the presence of two conformers for CHF2SO˙ (gauche and cis) and one conformer for CH2FSO˙ (gauche). Upon 266 nm laser irradiation, these radicals undergo both isomerization and decomposition in the matrices. In addition to the dominant formation of the elusive oxathiyl radicals CHF2OS˙ (gauche and cis) and CH2FOS˙ (gauche) via 1,2-alkyl migration, two higher-energy carbon-centered radicals ˙CF2SOH and ˙CHFSOH bearing similar molecular structures to hydroperoxyalkyl radicals (˙QOOH) form via intramolecular 1,3-hydrogen shift in the two sulfinyl radicals. Additionally, the involvement of 1,3-hydrogen shift in CHF2OS˙ and CH2FOS˙ is also indicated by the observation of the fragmentation species. The identification of these radicals by matrix-isolation IR and UV-vis spectroscopy is aided by the quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) level of theory. The stability of the isomers of the two sulfinyl radicals CHF2SO˙ and CH2FSO˙ has been discussed according to the experimental observations and also based on the CCSD(T)-F12a/aug-cc-pVTZ//B3LYP/6-311++G(3df,3pd) calculated energy profiles.

Photochemistry of phosphenic chloride (ClPO2): isomerization with chlorine metaphosphite (ClOPO) and reduction by carbon monoxide.

Phosphenic chloride (ClPO2) is an elusive congener of nitryl chloride (ClNO2). By high-vacuum flash pyrolysis of 2-chloro-1,3,2-dioxaphospholane in the gas phase, ClPO2 has been efficiently generated and subsequently isolated in cryogenic N2, Ar, and CO matrices (10 K) for a first time study on its photochemistry. Upon 193 nm laser irradiation, ClPO2 isomerizes to the novel chlorine metaphosphite (ClOPO) by initial cleavage of the Cl-P bond (→ ˙Cl + ˙PO2) with subsequent Cl-O bond formation inside the N2 and Ar matrix cages. The reverse transformation becomes feasible under further irradiation at 266 nm. This photochemistry is consistent with the observed absorptions of ClPO2 and ClOPO at 207 and 250 nm, respectively. When the photolysis was performed in solid CO ice, no isomerization occurs due to CO-trapping of the initially generated ˙Cl atoms by forming caged radical pair ClCO˙⋯˙PO2. Concomitantly, photolytic reduction of ClPO2 to ClPO by CO has been observed, yielding a weakly bonded molecular complex consisting of ClPO and CO2 bonded through short intermolecular C⋯O contact (2.910 Å). The characterization of ClPO, ClPO2, ClOPO, and the molecular complexes of ClPO2-CO and ClPO-CO2 using matrix-isolation IR and UV-vis spectroscopy is supported by the theoretical calculations at the B3LYP/6-311 + G(3df) level, and the photochemistry of ClPO2 is also compared with the revisited photochemistry of ClNO2 in the N2-matrix.

Low-dose fractionated irradiation promotes axonal regeneration beyond reactive gliosis and facilitates locomotor function recovery after spinal cord injury in beagle dogs.

Injury to the adult central nervous system (CNS) results in the formation of glial scar tissues. Glial scar-induced failure of regenerative axon pathfinding may limit axon regrowth beyond the lesion site and cause incorrect reinnervation and dystrophic appearance of stalled growth after CNS trauma. Glial scars also upregulate chondroitin sulphate proteoglycans (CSPGs) and expression of proinflammatory factor(s) that form a barrier to axonal regeneration. Therefore, interventions for glial scarring are an attractive strategy for augmenting axonal sprouting and regeneration and overcoming the physical and molecular barriers impeding functional repair. The glial reaction occurs shortly after spinal cord injury (SCI) and can persist for days or weeks with upregulation of cell cycle proteins. In this study, we utilised Beagle dogs to establish a preclinical SCI model and examine the efficacy of low-dose fractionated irradiation (LDI) treatment, which was performed once a day for 14 days (2 Gy per dose, 28 Gy in total). Low-dose fractionated irradiation is a stable method for suppressing cell activation and proliferation through interference in the cell cycle. Our results demonstrated that LDI could reduce astrocyte and microglia activation/proliferation and attenuate CSPGs and IL-1ß expression. Low-dose fractionated irradiation also promoted and provided a pathway for long-distance axon regeneration beyond the lesion site, induced reinnervation of axonal targets and restored locomotor function after SCI in Beagle dogs. Taken together, our findings suggest that LDI would be a promising therapeutic strategy for targeting glial scarring, promoting axon regeneration and facilitating reconstruction of functional circuits after SCI.

Gas-Phase Generation and Decomposition of a Sulfinylnitrene into the Iminyl Radical OSN.

The dipolar oxathiazyne-like sulfinylnitrene RS(O)N, a highly reactive α-oxo nitrene, has been rarely investigated. Upon flash vacuum pyrolysis of sulfinyl azide CF3S(O)N3 at 350 °C, an elusive sulfinylnitrene CF3S(O)N was generated in the gas phase in its singlet ground state and was characterized by matrix-isolation IR spectroscopy. Further fragmentation of CF3S(O)N at 600 °C produced CF3 and a novel iminyl radical OSN, an SO2 analogue, which were unambiguously identified by IR spectroscopy. Consistent with the experimental observations, DFT calculations clearly support a stepwise decomposition mechanism of CF3S(O)N3.

Thermally persistent carbonyl nitrene: FC(O)N.

Transient carbonyl nitrenes RC(O)N, formed during thermal- or photoinduced decomposition of carbonyl azides RC(O)N3, are highly liable to the Curtius rearrangement, producing isocyanates RNCO in almost quantitative yield. Contrary to common belief, we found a thermally persistent triplet carbonyl nitrene, FC(O)N, that can be produced by flash pyrolysis of FC(O)N3 in 49% yield. The computed CBS-QB3 activation barrier for the thermal decomposition of FC(O)N3 to FC(O)N is 29 kJ mol(-1) lower than that for a concerted pathway producing FNCO.

Decomposition of fluorophosphoryl diazide: a joint experimental and theoretical study.

The photolytic and thermal decomposition of fluorophosphoryl diazide, FP(O)(N3)2, was studied using matrix isolation spectroscopy. Upon ArF laser photolysis (λ = 193 nm), FPO and a new geminal azido nitrene FP(O)(N3)N were identified using matrix IR spectroscopy. The nitrene shows a triplet ground state with the zero-field parameters |D/hc| = 1.566 cm(-1) and |E/hc| = 0.005 cm(-1). Further decomposition of the nitrene into FPO was observed under an irradiation of λ > 335 nm. In contrast, no nitrene but only FPO was identified after flash vacuum pyrolysis of the diazide. To reveal the decomposition mechanism, quantum chemical calculations on the potential energy surface (PES) of the diazide using DFT methods were performed. On the singlet PES four conformers of the nitrene were predicted. The two conformers (syn and anti) showing intramolecular Nnitrene···Nα,azide interactions are much lower in energy (ca. 40 kJ mol(-1), B3LYP/6-311+G(3df)) than the other two exhibiting Nnitrene···O interactions. syn/anti refers to the relative orientation of the P[double bond, length as m-dash]O bond and the N3 group. The interconversion of these species and the decomposition into FPO via a novel three-membered ring diazo intermediate cyclo-FP(O)N2 were computationally explored. The calculated low dissociation barrier of 45 kJ mol(-1) (B3LYP/6-311+G(3df)) of this cyclic intermediate rationalizes why it could not be detected in our experiments.

Conformational composition, molecular structure and decomposition of difluorophosphoryl azide in the gas phase.

The conformational composition, molecular structure and decomposition of difluorophosphoryl azide F2P(O)N3 in the gas phase were studied using gas electron diffraction (GED), matrix isolation IR spectroscopy, and quantum-chemical calculations, respectively. While computational methods predict only minor differences in the total energy between the two possible conformers (syn and anti), the analysis of electron diffraction data reveals the dominating abundance of the syn conformer in the gas phase at room temperature. Ab initio frequency analyses suggest that a low-frequency large-amplitude motion of the N3 group with respect to the P-N-N-N torsion is to be expected for the syn conformer. The large amplitude motion was included explicitly into the GED structure refinement procedure. It presumably contributes to a thermodynamic stabilization of the syn-conformer with respect to the anti-conformer in the gas phase at ambient temperature. Upon flash vacuum pyrolysis, this syn conformer undergoes a stepwise decomposition via the difluorophosphoryl nitrene, F2P(O)N, which features as the first experimentally observed phosphoryl nitrene that can be thermally produced in the gas phase. To reveal the reaction mechanism, quantum-chemical calculations on the potential energy surface (PES) of F2P(O)N3 were performed. Both B3LYP/6-311+G(3df) and CBS-QB3 calculation results strongly support a stepwise decomposition into the singlet F2P(O)N, which prefers intersystem crossing to the thermally persistent triplet ground state instead of a Curtius rearrangement into FP(O)NF.

The Methylsulfonyloxyl Radical, CH3SO3.

The methylsulfonyloxyl radical, CH3SO3, one of the key intermediates in the atmospheric oxidation of dimethyl sulfide (DMS), was generated by flash pyrolysis of CH3SO2OOSO2CH3 and subsequently isolated in solid noble-gas matrices. The radical has been characterized by UV/Vis and IR spectroscopy and its tautomerization to CH2SO3H observed upon irradiation with light of λ≥360 nm.

Mapping carbon reduction: A cross-continental study of alliance strategies.

Addressing the equitable distribution of global carbon emission rights is critical for sustainable development. Our research develops a detailed framework for a Global Carbon Reduction Alliance based on regional cooperation strategies, identifying key modes of intracontinental proximity and intercontinental distance collaboration. It emphasizes alliances formed among high carbon emission right countries and leadership-driven models propelling low carbon emission right countries, offering insights for optimizing emission reduction efforts. The analysis highlights the strategic role of developing nations in Africa and Asia, as well as developed regions in Europe and North America, advocating for the adoption of clean energy, enhancement of forest economic value, acceleration of urbanization, and an increased contribution of the service sector to the economy as essential pathways to achieving net-zero emissions. Our approach advocates for a comprehensive model of global carbon reduction cooperation, aiming at the equitable distribution of carbon emission rights and supporting the sustainable development goals.

Gut Bacterial Diversity of Insecticide-Susceptible and Insecticide-Resistant Megalurothrips usitatus (Thysanoptera: Thripidae) and Elucidation of Their Putative Functional Roles.

The gut bacterial microbiota of insects plays a crucial role in physiological, metabolic, and innate immune processes. In the current study, the gut bacterial communities of an insecticide-susceptible (IS), and a resistant (IR) population of a major legume pest, Megalurothrips usitatus (Bagnall), were evaluated. The 16S rDNA V3 + V4 regions of M. usitatus infected with Beauveria brongniartii along with the intestinal flora of both populations were sequenced based on a High-throughput sequencing platform. Toxicological bioassays revealed that the IR population exhibited resistance to acetamiprid and B. brongniartii isolate SB010 at levels of 138.0-fold and 55.6-fold higher, respectively, compared to the IS population. Through 16S High-throughput sequencing, the results indicate that both resistant populations, as well as B. brongniartii infestation, reduce the number of species of M. usitatus gut microbes. Using KEGG function prediction, it was found that most intestinal bacteria were involved in various metabolic activities, and the abundance of resistant populations was higher than that of sensitive populations. The bacteria in the gut of M. usitatus are mainly involved in various metabolic activities to achieve the degradation of B. brongniartii. This study provides valuable insights into the interaction between gut bacteria, insecticide resistance, and Beauveria. brongniartii infection in Megalurothrips usitatus, which can help inform future pest control strategies.

Assessment of Four Serum Biochemical Markers in Elderly Patients with Vascular Dementia after Cerebral Infarction and Their Response to Donepezil and Idebenone.

Objective Our study aimed to explore four serum levels of biochemical markers, including brain-derived neurotrophic factor (BDNF), homocysteine (Hcy), nitric oxide (NO), and γ-interferon (IFN-γ), in elderly patients with vascular dementia (VD) after the cerebral infarction and to elucidate possible connections between them. Method The elderly patients with VD after cerebral infarction admitted in our hospital, and the elderly persons for physical examination from November 2020 to December 2021 were included in this study. The serum levels of BDNF, Hcy, NO, and IFN-γ were compared between the study group and the control group. Results In the study group, the serum levels of Hcy and IFN-γ were significantly higher than that in the control group, whereas significantly lower serum levels of BDNF and NO were found in the study group compared with the control group. After receiving the intervention of donepezil and/or idebenone, the serum levels of Hcy and IFN-γ in group B were significantly lower than that in group A, while the serum levels of BDNF and NO in group B were significantly higher than that in Group A. Conclusion The results of our study showed abnormally expressed serum levels of Hcy, IFN-γ, BDNF, and NO in elderly patients with VD after cerebral infarction which might strongly reflect the severity of VD. Moreover, after intervention of donepezil alone or combined with idebenone, the changes of serum levels of Hcy, IFN-γ, BDNF, and NO may reflect the curative effect of the disease.

Hydrogen-Bonded π Complexes between Phosphaethyne and Hydrogen Chloride.

The highly labile complexes between phosphaethyne (HCP) and hydrogen chloride (HCl) with 1:1 and 1:2 stoichiometries have been generated in Ar and N2 matrices at 10 K through laser photolysis of the molecular precursors 1-chlorophosphaethene (CH2PCl) and dichloromethylphosphine (CH3PCl2), respectively. The IR spectrum of the 1:1 complex suggests the preference of a single "T-shaped" structure in which HCl acts as the hydrogen donor that interacts with the electron-rich C≡P triple bond. In contrast, three isomeric structures for the 1:2 complex bearing a core structure of the "T-shaped" 1:1 complex are present in the matrix. The spectroscopic identification of these rare HCP π-electron complexes is supported by D-isotope labeling and the quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level of theory.

Factors driving the implementation of the 'Local New Year' policy to prevent COVID-19 in China.

This study examines the contradiction caused by the 'local new year' policy, that is, the conflict between the pandemic prevention policies and people's emotional demands during the Spring Festival, based on the normalisation of pandemic prevention and control. It focuses on the scientific logical relationship with the contradiction that people voluntarily support 'local new year', to explore the primary driving factors of their willingness. By evaluating the migrant workers in large cities, the primary influencing factors were screened, and the primary dynamic factors and their relationship were obtained using the Logit logical selection model and maximum-likelihood estimation. The study identified, 'whether social and entertainment activities are planned in migrant cities', as the primary driving factor, followed by 'whether there are relatives (elderly /children) at home', and 'contracting the infection during travel'. In view of this conclusion, this study further proposes corresponding policy suggestions: Relevant measures should be adopted according to different regions and the current situation of the pandemic in combination with the characteristics of the episodic and local nature of the pandemic. 'Local new year' is encouraged from the perspective of enriching people's emotional needs for spiritual entertainment and care. This study provides a new perspective and theoretical basis for the research and formulation of policies related to the normalisation of pandemic prevention and control in China and worldwide, and has a certain practical reference value.

Contrast agent retention sign in angiography predicts acute internal carotid artery embolic occlusion.

BACKGROUND: Identification of acute internal carotid artery embolism (ICAE) and internal carotid artery atherosclerotic stenosis (ICAAS) in acute ischemic stroke patients is important for selection of treatment. The presence of contrast agent retention on pre-procedural angiographic images is more common in patients with ICA occlusion caused by embolism compared to patients with ICA atherosclerotic stenosis. This study aimed to evaluate effectiveness of contrast agent retention sign for predicting ICAE. METHODS: Sixty-five patients with ICA occlusion who underwent emergency endovascular treatment from September 2014 to September 2020 were included in this retrospective analysis. Patients were divided into ICAE (n = 46) and ICAAS (n = 19) groups. Clinical characteristics, imaging data and ICA contrast agent retention signs of patients were collected. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnosis accuracy of contrast agent retention sign were conducted. RESULTS: The positive ICA contrast agent retention sign was significantly more common in patients with ICAE (60.87% vs 0.00%, P < 0.001) than that of patients with ICAAS, but significantly lower in male patients (53.57% vs 81.08%, P = 0.017). There were significantly more patients with positive sign had occlusion in C6 segment (64.29% vs 13.51%, P < 0.001) and no outflow tract (85.71% vs 5.41%, P < 0.001) compared with negative sign group. There were significantly fewer patients with postive sign had occlusion in C1 segment (0.00% vs 40.54%, P < 0.001) compared with negative sign group. The sensitivity, specificity, PPV, NPV and diagnosis accuracy of contrast agent retention sign for predicting ICAE occlusion were 60.87%, 100%, 100%, 51.35% and 72.31%, respectively. CONCLUSION: The ICA contrast agent retention sign has very high specificity and moderate sensitivity for detection of acute ICAE.

Manipulation of Elastic Instability of Viscoelastic Fluid in a Rhombus Cross Microchannel.

This paper reports the manipulation of elastic instability of the viscoelastic fluid in a rhombus cross microchannel (RCM) structure. The bistable instability and unsteady instability of the flow is firstly demonstrated in a standard cross microchannel (SCM) for reference. We then keep the bi-stable instability over a much wider injection rate range in the RCM, which is attributed to the stabilizing effect of the rhombus structure. A semi-bistable instability was also established in the RCM at a high enough injection rate. In addition, the unsteady elastic instability is realized in the RCM through an asymmetric injection rate condition.

Phosphenic isocyanate (O2PNCO): gas-phase generation, characterization, and photodecomposition reactions.

Phosphenic isocyanate (O2PNCO), a novel phosphorus-containing small molecule has been generated by thermolysis of a dioxaphospholane-based precursor. The characterization of O2PNCO with IR and UV-vis spectroscopy in solid N2 and Ar matrices at 10 K is supported by the calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level of theory. Upon irradiation at 193 nm, O2PNCO decomposes yielding CO2, OPN, CO, ˙NO, and ˙PO, in which the possible formation of two exotic intermediates O2PN and OPNO in the triplet ground state has been proposed.

Spectroscopic characterization of two peroxyl radicals during the O2-oxidation of the methylthio radical.

The atmospheric oxidation of dimethyl sulfide (DMS) yields sulfuric acid and methane sulfonic acid (MSA), which are key precursors to new particles formed via homogeneous nucleation and further cluster growth in air masses. Comprehensive experimental and theoretical studies have suggested that the oxidation of DMS involves the formation of the methylthio radical (CH3S•), followed by its O2-oxidation reaction via the intermediacy of free radicals CH3SOx• (x = 1-4). Therefore, capturing these transient radicals and disclosing their reactivity are of vital importance in understanding the complex mechanism. Here, we report an optimized method for efficient gas-phase generation of CH3S• through flash pyrolysis of S-nitrosothiol CH3SNO, enabling us to study the O2-oxidation of CH3S• by combining matrix-isolation spectroscopy (IR and UV-vis) with quantum chemical computations at the CCSD(T)/aug-cc-pV(X + d)Z (X = D and T) level of theory. As the key intermediate for the initial oxidation of CH3S•, the peroxyl radical CH3SOO• forms by reacting with O2. Upon irradiation at 830 nm, CH3SOO• undergoes isomerization to the sulfonyl radical CH3SO2• in cryogenic matrixes (Ar, Ne, and N2), and the latter can further combine with O2 to yield another peroxyl radical CH3S(O)2OO• upon further irradiation at 440 nm. Subsequent UV-light irradiation (266 nm) causes dissociation of CH3S(O)2OO• to CH3SO2•, CH2O, SO2, and SO3. The IR spectroscopic identification of the two peroxyl radicals CH3SOO• and CH3S(O)2OO• is also supported by 18O- and 13C-isotope labeling experiments.

Unraveling sulfur chemistry in interstellar carbon oxide ices.

Formyl radical (HCO•) and hydroxycarbonyl radical (HOCO•) are versatile building blocks in the formation of biorelevant complex organic molecules (COMs) in interstellar medium. Understanding the chemical pathways for the formation of HCO• and HOCO• starting with primordial substances (e.g., CO and CO2) is of vital importance in building the complex network of prebiotic chemistry. Here, we report the efficient formation of HCO• and HOCO• in the photochemistry of hydroxidooxidosulfur radical (HOSO•)-a key intermediate in SO2 photochemistry-in interstellar analogous ices of CO and CO2 at 16 K through hydrogen atom transfer (HAT) reactions. Specifically, 266 nm laser photolysis of HOSO• embedded in solid CO ice yields the elusive hydrogen­bonded complexes HCO•···SO2 and HOCO•···SO, and the latter undergoes subsequent HAT to furnish CO2···HOS• under the irradiation conditions. Similar photo-induced HAT of HOSO• in solid CO2 ice leads to the formation of HOCO•···SO2. The HAT reactions of HOSO• in astronomical CO and CO2 ices by forming reactive acyl radicals may contribute to understanding the interplay between the sulfur and carbon ice-grain chemistry in cold molecular clouds and also in the planetary atmospheric chemistry.