Slow magnetization relaxation in Ni(II)Dy(III)Fe(III) molecular cycles.

Two cyano- and phenoxo-bridged hexanuclear Ni(II)2Dy(III)2Fe(III)2 (1) and octanuclear Ni(II)4Dy(III)2Fe(III)2 (2) trimetallic cyclic complexes have been obtained. They are the first trimetallic metallocycles. Magnetic studies reveal that 1 and 2 exhibit single-molecule-magnet behavior with an energy barrier of 17.9 K for complex 1 in a 2000 Oe static field and 25.0 K for complex 2 in a zero static field.

Toward higher nuclearity: tetranuclear cobalt(II) metallogrid exhibiting spin crossover.

Supramolecular strategy was employed to achieve the highest nuclearity Co(II) cluster exhibiting spin-crossover (SCO) behavior. Magnetic susceptibility characterization of the Co4(II) complex shows that two different spin-transition processes occur. The SCO behavior is directed by the partially deprotonated polydentate ligand, which favors the structural distortion required by the spin transition.

Spin transitions in Fe(II) metallogrids modulated by substituents, counteranions, and solvents.

Two bis(tridentate) Schiff base ligands H2L(x) were used to construct three 2×2 grid-type tetranuclear Fe(II) complexes 1-3 to obtain polynuclear spin-crossover materials. Magnetic susceptibility measurements show that the spin states of the complexes are related to the substituents of H2L(x), and that spin transition occurs only in complexes 1 and 2, which are derived from a bulky ligand, whereas complex 3 is diamagnetic. The transition temperatures of complexes 1 and 2 are close to room temperature and are dependent on counteranions. The spin transition of complex 1 can be reversibly tuned by the dehydration and hydration process.

Etiological and epidemiological features of acute meningitis or encephalitis in China: a nationwide active surveillance study.

BACKGROUND: Acute meningitis or encephalitis (AME) results from a neurological infection causing high case fatality and severe sequelae. AME lacked comprehensive surveillance in China. METHODS: Nation-wide surveillance of all-age patients with AME syndromes was conducted in 144 sentinel hospitals of 29 provinces in China. Eleven AME-causative viral and bacterial pathogens were tested with multiple diagnostic methods. FINDINGS: Between 2009 and 2018, 20,454 AME patients were recruited for tests. Based on 9,079 patients with all-four-virus tested, 28.43% (95% CI: 27.50%‒29.36%) of them had at least one virus-positive detection. Enterovirus was the most frequently determined virus in children <18 years, herpes simplex virus and Japanese encephalitis virus were the most frequently determined in 18-59 and ≥60 years age groups, respectively. Based on 6,802 patients with all-seven-bacteria tested, 4.43% (95% CI: 3.94%‒4.91%) had at least one bacteria-positive detection, Streptococcus pneumoniae and Neisseria meningitidis were the leading bacterium in children aged <5 years and 5-17 years, respectively. Staphylococcus aureus was the most frequently detected in adults aged 18-59 and ≥60 years. The pathogen spectrum also differed statistically significantly between northern and southern China. Joinpoint analysis revealed age-specific positive rates, with enterovirus, herpes simplex virus and mumps virus peaking at 3-6 years old, while Japanese encephalitis virus peaked in the ≥60 years old. As age increased, the positive rate for Streptococcus pneumoniae and Escherichia coli statistically significantly decreased, while for Staphylococcus aureus and Streptococcus suis it increased. INTERPRETATION: The current findings allow enhanced identification of the predominant AME-related pathogen candidates for diagnosis in clinical practice and more targeted application of prevention and control measures in China, and a possible reassessment of vaccination strategy. FUNDING: China Mega-Project on Infectious Disease Prevention and the National Natural Science Funds.

Pyrazine-2-amidoxime Ni(II) complexes: from ferromagnetic cluster to antiferromagnetic layer.

Tetranuclear [Ni(4)(Hpzaox)(2)(pzaox)(2)(py)(4)](ClO(4))(2)·2py (1), [Ni(4)(Hpzaox)(2)(pzaox)(2)(py)(4)](NO(3))(2)·4py (2), and two-dimensional (2D) [Ni(4)(Hpzaox)(2)(pzaox)(2)(H(2)O)(2)](NO(3))(2)·2H(2)O (3) are prepared via the reaction of NiX(2)·6H(2)O and pyrazine-2-amidoxime (H(2)pzaox). All compounds contain [Ni(4)(Hpzaox)(2)(pzaox)(2)](2+) fragments, which assemble to form a tetranuclear or polymeric network. Magnetic studies show that the tetranuclear compounds display usual ferromagnetic coupling via the oxime N-O bridges, and the 2D compound displays unusual antiferromagnetic behavior.

Etiological and epidemiological features of acute respiratory infections in China.

Nationwide prospective surveillance of all-age patients with acute respiratory infections was conducted in China between 2009‒2019. Here we report the etiological and epidemiological features of the 231,107 eligible patients enrolled in this analysis. Children <5 years old and school-age children have the highest viral positivity rate (46.9%) and bacterial positivity rate (30.9%). Influenza virus, respiratory syncytial virus and human rhinovirus are the three leading viral pathogens with proportions of 28.5%, 16.8% and 16.7%, and Streptococcus pneumoniae, Mycoplasma pneumoniae and Klebsiella pneumoniae are the three leading bacterial pathogens (29.9%, 18.6% and 15.8%). Negative interactions between viruses and positive interactions between viral and bacterial pathogens are common. A Join-Point analysis reveals the age-specific positivity rate and how this varied for individual pathogens. These data indicate that differential priorities for diagnosis, prevention and control should be highlighted in terms of acute respiratory tract infection patients' demography, geographic locations and season of illness in China.

Etiological, epidemiological, and clinical features of acute diarrhea in China.

National-based prospective surveillance of all-age patients with acute diarrhea was conducted in China between 2009‒2018. Here we report the etiological, epidemiological, and clinical features of the 152,792 eligible patients enrolled in this analysis. Rotavirus A and norovirus are the two leading viral pathogens detected in the patients, followed by adenovirus and astrovirus. Diarrheagenic Escherichia coli and nontyphoidal Salmonella are the two leading bacterial pathogens, followed by Shigella and Vibrio parahaemolyticus. Patients aged <5 years had higher overall positive rate of viral pathogens, while bacterial pathogens were more common in patients aged 18‒45 years. A joinpoint analysis revealed the age-specific positivity rate and how this varied for individual pathogens. Our findings fill crucial gaps of how the distributions of enteropathogens change across China in patients with diarrhea. This allows enhanced identification of the predominant diarrheal pathogen candidates for diagnosis in clinical practice and more targeted application of prevention and control measures.

Human bocavirus in children suffering from acute lower respiratory tract infection in Beijing Children's Hospital.

BACKGROUND: Human bocavirus (HBoV) is a parvovirus recently found to possibly cause respiratory tract disease in children and adults. This study investigated HBoV infection and its clinical characteristics in children younger than five years of age suffering from acute lower respiratory tract infection in Beijing Children's Hospital. METHODS: Nasopharyngeal aspirates were collected from children suffering from acute lower respiratory tract infection during the winters of 2004 to 2006 (from November through the following February). HBoV was detected by polymerase chain reaction amplification and virus isolation and the amplification products were sequenced for identification. RESULTS: HBoV infection was detected in 16 of 333 study subjects. Coinfections with respiratory syncytial virus were detected in 3 of 16 HBoV positive patients with acute lower respiratory tract infection. The median age for HBoV positive children was 8 months (mean age, 17 months; range, 3 to 57 months). Among the HBoV positive children, 14 were younger than 3 years old, 9 were younger than 1 year old and 7 were younger than 6 months. These 16 positive HBoV children exhibited coughing and abnormal chest radiography findings and more than 60% of these children had wheezing and fever. Ten children were clinically diagnosed with pneumonia, 2 bronchiolitis, 2 acute bronchitis and 2 asthma. One child died. CONCLUSIONS: HBoV was detected in about 5% of children with acute lower respiratory infection seen in Beijing Children's Hospital. Further investigations regarding clinical and epidemiologic characteristics of HBoV infection are needed.

Poly[mu2-(N-hydroxypyridine-2-carboxamidine)-mu2-nitrato-silver(I)].

In the title complex, [Ag(NO3)(C6H7N3O)]n or [Ag(NO3)(pyaoxH2)] (pyaoxH2 is N-hydroxypyridine-2-carboxamidine), the Ag+ ion is bridged by the pyaoxH2 ligands and nitrate anions, giving rise to a two-dimensional molecular structure. Each pyaoxH2 ligand coordinates to two Ag+ ions using its pyridyl and carboxamidine N atoms, and the OH and the NH2 groups are uncoordinated. Each nitrate anion uses two O atoms to coordinate to two Ag+ ions. The Ag...Ag separation via the pyaoxH2 bridge is 2.869 (1) A, markedly shorter than that of 6.452 (1) A via the nitrate bridge. The two-dimensional structure is fishscale-like, and can be described as pyaoxH2-bridged Ag2 nodes that are further linked by nitrate anions. Hydrogen bonding between the amidine groups and the nitrate O atoms connects adjacent layers into a three-dimensional network.

Metallocyclic Ni4Ln2M2 single-molecule magnets.

We herein report the synthesis, crystal structure and magnetic properties of nine new heterotrimetallic complexes. [Ni(Me2valpn)] (H2Me2valpn = N,N'-bis(3-methoxysalicylidene)-2,2-dimethyl-1,3-diaminopropane) was used as the precursor to construct phenoxo-bridged [Ni2Ln]3+ (Ln3+ = Dy, Tb, Gd and Y) species that were respectively connected by two [M(CN)6]3- (M = Cr, Fe or Co) anions to form octanuclear cyclic complexes, i.e. {[Ni(Me2valpn)]2Ln(H2O)M(CN)6}2 in which Ln = Y, Gd, Tb and Dy and M = Cr, Fe or Co (1-9). Each of the complexes contains many lattice-bound molecules of solvation. The Ni(ii) ions are penta-coordinate, while the Ln(iii) ions are nine coordinated with a muffin geometry. The fitting to the χmT vs. T curves of complexes 6-9 gave the parameters of JNiCr = 11.82 cm-1, JNiGd = 0.94 cm-1 and g = 2.04 for complex 6, JNiFe = 10.58 cm-1, JNiGd = 1.24 cm-1 and g = 2.03 for complex 7, JNiCr = 9.4(1) cm-1, zJ' = -0.050(2) cm-1 and g = 2.06(1) for complex 8 and JNiFe = 4.9(7) cm-1, zJ' = -0.35(2) cm-1 and g = 2.24(1) for complex 9, respectively. The dynamic magnetic investigations demonstrate that complexes 1-5 display single-molecule magnet properties with an effective energy barrier (Ueff) of 38.9 K (1, M1 = Dy, M2 = Cr), 37.2 K (2, M1 = Dy, M2 = Cr), 24.4 K (3, M1 = Dy, M2 = Co), 21.9 K (4, M1 = Tb, M2 = Cr) and 29.6 K (5, M1 = Tb, M2 = Fe), respectively. Complex 1 shows the highest energy barrier among the octanuclear [Ni4LnM2] (Ln = Dy or Tb, M = Fe, Cr, Co or W) system. Although the [Ni4Dy2Cr2] complexes have Ueff higher than that of [Ni4Dy2Fe2], complex [Ni4TbCr2] shows lower Ueff than that of [Ni4TbFe2]. The results indicate that besides the M-C[triple bond, length as m-dash]N-Ni magnetic coupling the lanthanide ions can significantly affect the magnetic performances of heterotrimetallic SMMs as well. Moreover, the SMMs are achieved when diamagnetic Co(iii) was substituted by paramagnetic Cr(iii) or Fe(iii) in the [Ni4Tb2 M2] system, suggesting that the trimetallic strategy is effective in the construction of new 3d-4f SMMs.

A trimetallic strategy towards ZnDyCr and ZnDyCo single-ion magnets.

Two cyano- and phenoxo-bridged octanuclear complexes ZnDyCo (complex ) and ZnDyCr (complex ) with diamagnetic Zn(ii) and Co(iii) are reported. Dy(iii) is surrounded by nine oxygen atoms of two [Zn(Me2valpn)] (Me2valpn(2-) = dianion of N,N'-2,2-dimethylpropylenebis(3-methoxysalicylideneimine)) and one water molecule. Magnetic studies reveal that both exhibit single-ion magnet (SIM) behavior with the energy barrier of 85.9 K for complex and 100.9 K for complex .

DNA sequences of Paragonimus skrjabini populations from five provinces in China.

BACKGROUND: To study differences among Paragonimus skrjabini (P. skrjabini) populations from five provinces in China (Guangdong, Fujian, Yunnan, Hubei, and Sichuan) and Paragonimus szechuanensis. METHODS: DNA sequences were obtained from the ITS2 and CO1 genes and phylogenetic trees were constructed from the results. Sequences were also obtained from several other species of Paragonimus for comparative purposes. RESULTS: Although differences existed in the DNA sequence among P. skrjabini populations from five provinces, the differences were very small. There was also some resemblance between P. miyazakii from Japan and Fujian strains of P. skrjabini. CONCLUSION: All studied populations can be regarded as different strains of P. skrjabini; P. szechuanensis is not a separate species but may be a geographical strain of P. skrjabini. We also found that P. miyazakii may be synonymous with P. skrjabini.

[Taxonomic status in DNA sequences of five species of genus Paragonimus].

OBJECTIVE: To analyze the taxonomic status of Paragonimus hokuoensis, P. paishuihoensis, P. menglaensis, P. bangkokensis and P. xiangshanensis in Genus Paragonimus Braun, 1899. METHODS: DNA sequences were obtained from the ITS2 and CO I genes and phylogenetic trees were built from these. RESULTS: There are some DNA sequence differences among P. paishuihoensis, P. menglaensis, P. bangkokensis and P. xiangshanensis, but the differences are small. P. hokuoensis and P. skrjabini are similar in DNA sequence. CONCLUSION: P. paishuihoensis, P. menglaensis, P. bangkokensis and P. xiangshanensis are closer in the genetic relationship. Their taxonomic status lies between P. skrjabini and P. westermani. The genetic relationship between P. hokuoensis and P. skrjabini is very close.

[Study on DNA sequences of Paragonimus skrjabini populations from five provinces in China].

OBJECTIVE: To study differences among Paragonimus skrjabini populations from five provinces (Guangdong, Fujian, Yunnan, Hubei, Sichuan) and Paragonimus szechuanensis and to analyze the taxonomic status of P. heterotremus and P. veocularis in the Genus Paragonimus Braun, 1899. METHODS: DNA sequences were obtained from the ITS2 and CO1 genes and phylogenetic trees were built. RESULTS: Difference of the DNA sequences among P. skrjabini populations from five provinces were minor. P. veocularis and P. skrjabini were similar in DNA sequences. There were also some resemblances between P. miyazakii from Japan and the Fujian isolates of P. skrjabin. In addition, P. heterotremus was found to be closer to P. skrjabini and quite a distance from P. westermani in the phylogenetic tree. CONCLUSION: All studied populations can be regarded as different strains of P. skrjabini; P. szechuanensis is not a separate species, but possibly a geographical strain of P. skrjabini. Also found was that P. veocularis and P. miyazakii may be the synonyms of P. skrjabini. As a separate species, P. heterotremus was found to be closer to P. skrjabini and quite a distance from P. westermani in the genetic relationship.

In Situ Formation of Semichelating Ligands: A Strategy for Tuning the Magnetic Coupling in Azide-Bridged Copper(II) Complexes.

Five CuII complexes of trinuclear [Cu3 (L1 )2 (N3 )6 ] (1), one-dimensional chain [Cu5 (L2 )2 (N3 )10 ]n  (2), trinuclear [Cu3 (L3 )2 (N3 )6 ] (3) and dinuclear [Cu2 (L4 )2 (N3 )2 Cl2 ] (4) and [Cu2 (L5 )2 (N3 )2 Cl2 ] (5) (L1-5 =RCH2 OR', R=substituted pyrazole or imidazole, R'=Me, Et or nPr) were synthesized by the reaction of CuCl2 ⋅2 H2 O, sodium azide with RCH2 Cl in CH3 OH, C2 H5 OH or n-C3 H7 OH. The ether ligands L1 and L2 can be alternatively prepared by the alcoholysis of RCH2 Cl in the presence of sodium azide, whereas the ligands L3-5 form in corresponding alcohols without azide. For complexes 1-5, the oxygen atom of the ether ligands is located at the Jahn-Teller axis of CuII with the long CuO separations of 2.377(3)-2.830(3) Å. The nitrogen atoms of bridging azides are located in the equatorial or basal planes of CuII ions, favoring strong magnetic coupling. The Cu-Nazido -Cu bridging angles in complexes 1-3 are 98.8(2)°-101.6(1)°, leading to ferromagnetic coupling, whereas the Cu-Nazido -Cu angles in complexes 4 and 5 are close to 103°, leading to antiferromagnetic coupling.

A cyano-bridged single-chain magnet featuring alternate high- and low-spin manganese(III) porphyrins.

The chains in complex [Mn(TPP)][Mn(TPP)(CN)2] (H2TPP = meso-tetra(4-phenyl)-porphyrin) demonstrate perfect linearity, and are well isolated with the nearest interchain Mn-Mn separation of 12.95 Å. Ferromagnetic coupling is present among adjacent Mn(III) ions, and single-chain magnet (SCM) behaviour is verified.

Heterodinuclear M(II)-Ln(III) single molecule magnets constructed from exchange-coupled single ion magnets.

The synthesis and characterization of four dinuclear 3d-4f complexes [M(II)Ln(III)(L)(DBM)3] (ZnDy = 1, CoY = 2, CoDy = 3·3.5CH3CN, CoGd = 4·3.5CH3CN) are reported (H2L = N,N'-dimethyl-N,N'-(2-hydroxy-3-methoxy-5-methyl-benzyl)ethylenediamine, DBM(-) = anion of 1,3-diphenyl-propane-1,3-dione). In each of the four complexes, the M(II) ion occupies the internal N2O2 site whereas the Ln(III) ion occupies the external O4 site. There are diphenoxo bridges between the M(II) and Ln(III) ions in these complexes. The remaining coordination sites are occupied by three DBM(-) anions. Direct current (dc) magnetic susceptibility measurements indicate the presence of intramolecular ferromagnetic interactions in complexes 3 and 4. The magnetic coupling constant, JCoGd, of complex 4 is estimated to be 0.26 cm(-1) (H = -2JCoGdSCoSGd). Alternating current (ac) magnetic susceptibility studies reveal that complexes 1 and 2 show field-induced single molecule magnet behavior, with ΔE values of 36.5 K and 8.56 K, respectively. Complex 3 shows frequency dependent out-of-phase signals, indicating the presence of a slow relaxation of the magnetization, whereas complex 4 does not display slow magnetization relaxation.

[Development of A synthetic positive control for the nucleic acid detection of mumps virus].

To rapidly identify the cross-contamination problems caused by the positive control in the process of mumps virus nucleic acid detection, a new mumps virus RNA positive control was developed in this study. Using the same primers and reaction conditions, the cross-contamination problems caused by the positive control could be readily identified by comparing the fragments lengths of the PCR products between the positive control and the samples. This new RNA positive control of mumps virus can be widely used in the diagnosis and genotyping of mumps virus as a better laboratory quality control.

[Genetic analysis of a genotype F mumps virus based on its complete genome sequence].

Mumps virus strains of genotype F have been circulating in China for decades. To identify genetic variation of mumps virus based on the complete genome sequence of a mumps isolate of genotype F, the complete genome of the genotype F reference strain, MuVi/Shandong. CHN/4.05 [F] was sequenced. Genetic characteristics of this virus were analyzed and compared with the complete genome sequences of others genotypes available in GenBank. The genetic differences in antigenic sites were also compared between the genotype F strain and the vaccine strains. The nucleotide differences between MuVi/Shandong. CHN/4.05 [F] and other genotypes of mumps virus based on the whole genome ranged between 3.8% and 6.5%. The maximum and minimum difference was found between MuVi/Shandong. CHN/4.05 [F] and genotype A (the vaccine strains), and genotype B-N strains, respectively. There were 26 N-glycosylation sites in the strain MuVi/Shandong. CHN/4.05 [F] and all other genotypes of mumps virus, however, one N-glycosylation site was absent from the vaccine strains, which was at the aa position 464-466 of the HN gene. Variation was detected at some of the known antigenic sites of mumps virus strain MuVi/Shandong. CHN/4.05 [F] and the vaccine strains. Genetic variations were detected in the epidemic mumps virus strain in China as well as in other genotypes of mumps virus strains and the vaccine strains across the complete genome. These results indicate the need to further strengthen the surveillance of genetic variation of wild type mumps virus.

Syntheses, structure, and magnetic properties of heteronuclear Cu(II)4Fe(III)4 cluster and Cu(II)8 bimetallacycles.

The compartmental Schiff base ligands N,N'-ethylenebis(3-hydroxysalicylidene) (H(4)L) and N,N'-propylenebis(3-hydroxysalicylidene) (H(4)L') have been employed in the synthesis of a cyclic tetranuclear Cu(II) complex [Cu(4)(L')(2)(MeOH)(3)(H(2)O)]·[Cu(4)(L')(2)(MeOH)(3)] (1), a novel octanuclear Cu(II) complex [Cu(8)(L-L)(2)(H(2)O)(4)(µ(2)-H(2)O)]·3DMF·3H(2)O (2) and a hetero-octanuclear Cu(II)-Fe(III) complex [Cu(4)Fe(4)(L)(4)(H(2)O)(3)(µ(3)-O)(2)]·3DMF·3H(2)O (3). During the formation of the Cu(8) complex (2), a new bis-Schiff base ligand (L-L)(8-) forms via the ortho-para C-C coupling of two H(4)L ligands. The bicyclic complex (2) is comprised of two cyclic Cu(4) units that are similar to that of complex 1. In the Cu(4) unit, the alternate Cu(II) ions are singly bridged by phenoxo groups. The three complexes display overall antiferromagnetic coupling, and the Cu(II)-Cu(II) magnetic coupling constant falls in the range -117.2 to -473.6 cm(-1) for complexes 1 and 2 corresponding to the bridging Cu-O(phenoxide)-Cu bond angles of 124.3-131.0°.