Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 74
Filtrar
1.
Ann Bot ; 2024 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-39279221

RESUMO

BACKGROUND AND AIMS: The Montgomery-Koyama-Smith (MKS) equation predicts that total leaf area per shoot is proportional to the product of the sum of individual leaf widths and maximum individual leaf length, which has been validated for some herbaceous and woody plants. The equation is also predicted to be valid in describing the relationship between the total stomatal area per micrograph (AT) and the product of the sum of individual stomatal widths (denoted as LKS) and maximum individual stomatal length (denoted by WKS) in any particular micrograph. METHODS: To test the validity of the MKS equation, 69,931 stomata (from 720 stomatal micrographs from 12 Magnoliaceae species) were examined. The area of each stoma was calculated using empirical measurements of stomatal length and width multiplied by a constant. Six equations describing the relationships among AT, LKS, and WKS were compared. The root-mean-square (RMSE) and the Akaike information criterion (AIC) were used to measure the goodness of fit, and the trade-off between the goodness of fit and the structural complexity of each model, respectively. KEY RESULTS: Analyses supported the validity of the MKS equation and the power-law equation AT ∝ (LKS∙WKS)α, where a is a scaling exponent. The estimated values of α at the species level and for the pooled data were all statistically smaller than unity, which did not support the hypothesis that AT ∝ LTS∙WTS. The power-law equation had smaller RMSE and AIC values than the MKS equation for the data from the 12 individual species and the pooled data. CONCLUSIONS: These results indicate that AT tends to allometrically scale with LKS∙WKS, and that increases in AT do not keep pace with increases in LTS∙WTS. In addition, using the product of LKS and WKS is better than using only one of the two variables.

2.
Acta Pharmacol Sin ; 45(3): 465-479, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38017298

RESUMO

Epilepsy is a prevalent and severe neurological disorder and approximately 30% of patients are resistant to existing medications. It is of utmost importance to develop alternative therapies to treat epilepsy. Schisandrin B (SchB) is a major bioactive constituent of Schisandra chinensis (Turcz.) Baill and has multiple neuroprotective effects, sedative and hypnotic activities. In this study, we investigated the antiseizure effect of SchB in various mouse models of seizure and explored the underlying mechanisms. Pentylenetetrazole (PTZ), strychnine (STR), and pilocarpine-induced mouse seizure models were established. We showed that injection of SchB (10, 30, 60 mg/kg, i.p.) dose-dependently delayed the onset of generalized tonic-clonic seizures (GTCS), reduced the incidence of GTCS and mortality in PTZ and STR models. Meanwhile, injection of SchB (30 mg/kg, i.p.) exhibited therapeutic potential in pilocarpine-induced status epilepticus model, which was considered as a drug-resistant model. In whole-cell recording from CHO/HEK-239 cells stably expressing recombinant human GABAA receptors (GABAARs) and glycine receptors (GlyRs) and cultured hippocampal neurons, co-application of SchB dose-dependently enhanced GABA or glycine-induced current with EC50 values at around 5 µM, and application of SchB (10 µM) alone did not activate the channels in the absence of GABA or glycine. Furthermore, SchB (10 µM) eliminated both PTZ-induced inhibition on GABA-induced current (IGABA) and strychnine (STR)-induced inhibition on glycine-induced current (Iglycine). Moreover, SchB (10 µM) efficiently rescued the impaired GABAARs associated with genetic epilepsies. In addition, the homologous mutants in both GlyRs-α1(S267Q) and GABAARs-α1(S297Q)ß2(N289S)γ2L receptors by site-directed mutagenesis tests abolished SchB-induced potentiation of IGABA and Iglycine. In conclusion, we have identified SchB as a natural positive allosteric modulator of GABAARs and GlyRs, supporting its potential as alternative therapies for epilepsy.


Assuntos
Epilepsia , Lignanas , Compostos Policíclicos , Receptores de Glicina , Camundongos , Animais , Humanos , Pilocarpina/efeitos adversos , Estricnina/farmacologia , Estricnina/uso terapêutico , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológico , Receptores de GABA-A , Glicina/farmacologia , Hipnóticos e Sedativos , Ácido gama-Aminobutírico , Ciclo-Octanos
3.
J Environ Manage ; 370: 122836, 2024 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-39383750

RESUMO

Urea is a widely applied fertilizer to enhance crop yields. Ecological risks associated with the excessive application of urea fertilizer threaten the paddy fields' sustainable agriculture and biodiversity preservation. There are no practical thresholds based on proven data on microbial communities. Protozoa are nitrogen-sensitive organisms. For the first time, this study conducted acute and chronic urea toxicity tests on eight species of organisms. The results indicate that Blepharisma sp. is the most sensitive species to urea exposure and is a suitable indicator for determining the safe threshold of urea. This study estimated the predicted no-effect concentration using species sensitivity distribution curves. Subsequently, it established the threshold for urea application in rice fields based on the fields' area and the surface water's height. The short-term safety threshold for urea in the studied paddy field with black soil is 87.7 mg/L, equivalent to 43.85 kg of urea per hectare for a single nitrogen fertilizer application. The long-term safety threshold is 5.02 mg/L, representing the concentration for re-applicating urea. The biodiversity-safeguarding application threshold provides the basis for developing a urea fertilizer reduction protocol to safeguard the paddy fields' biodiversity.

4.
J Gerontol Soc Work ; 67(2): 188-206, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-37477277

RESUMO

This study investigated how older Chinese immigrants in affordable senior housing facilities (ASHs) appraise and cope with anti-Asian discrimination and related stress during the COVID-19 pandemic. Qualitative interviews were conducted with 26 participants aged over 65, analyzing verbatim transcripts and field notes using thematic analysis. Four major domains were identified: (1) discriminatory experience, (2) appraisals of discrimination stress, (3) coping strategies, and (4) rationales behind coping. Among the participants, 11 (42%) reported experiencing discrimination either personally or by someone they know. Participants' appraisals of discrimination stress varied, and most of them opted for disengagement coping strategies (e.g., avoidance, rationalization) attributing them to health concerns, individual characteristics, environmental and societal factors, and low acculturation. The findings suggest the need for more social and community resources to enhance coping capacity and resilience in this vulnerable population.


Assuntos
COVID-19 , Emigrantes e Imigrantes , Idoso , Humanos , Adaptação Psicológica , COVID-19/epidemiologia , Instituição de Longa Permanência para Idosos , Pandemias , China/epidemiologia
5.
Environ Res ; 221: 115302, 2023 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-36642124

RESUMO

OBJECTIVE: Diabetic retinopathy (DR) is a leading cause of vision impairment and blindness among diabetics. We aimed to explore whether long-term exposure to residential greenness was beneficial to DR. RESEARCH DESIGN AND METHODS: We used data from a large-scale, cross-sectional screening survey conducted in 129 cities of 27 provincial regions of China from 2018 to 2021 among patients with diabetes. We measured residential greenness exposure as the 3-year average of annual maximum Normalized Difference Vegetation Index (NDVI) at a spatial resolution of 250 m. DR was assessed by ophthalmologists based on fundus photographs. The primary outcome was DR, and secondary outcome included DR severity status (i.e., nonproliferative and proliferative), hallmarks of retinal lesions and macular oedema. RESULTS: A total of 484,380 adult participants with diabetes were included in the current analysis, and 15.7% of them were diagnosed with DR. NDVI was inversely and linearly associated with DR prevalence, and an increment of 0.1 NDVI was associated with a 10% (9%-10%) decrease in DR prevalence. Significant and inverse associations were further found for nonproliferative and proliferative DR, hallmarks of lesions and macular oedema. The association between greenness and DR was stronger among participants who were older, obese, lived in the south, had longer duration of diabetes or did not take antidiabetic medications. CONCLUSIONS: This large-scale nationwide study provides the first-hand epidemiological evidence on the associations of residential greenness with DR. Our findings highlight the importance of residential greenness in alleviating DR risk especially in an era of aging and urbanization.


Assuntos
Diabetes Mellitus , Retinopatia Diabética , Edema Macular , Adulto , Humanos , Retinopatia Diabética/epidemiologia , Retinopatia Diabética/complicações , Edema Macular/epidemiologia , Edema Macular/etiologia , Edema Macular/diagnóstico , Prevalência , Estudos Transversais , China/epidemiologia , Diabetes Mellitus/epidemiologia
6.
Aging Ment Health ; 27(10): 1956-1964, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37212623

RESUMO

OBJECTIVE: Chinese immigrant older adults who live in affordable housing are at high risk of experiencing social isolation during the COVID-19 pandemic, which can affect their mental health. Using a triangulation mixed-methods approach, this study describes Chinese immigrant older adults' social network, mental health status, and their associations during the pandemic. METHODS: Semi-structured in-depth interviews were conducted with 26 Chinese immigrant older adults from June to August 2021. The structure and characteristics of participants' social networks were assessed with a name-generating approach. Mental health status was self-reported with Geriatric Depression Scale and UCLA loneliness scale. RESULTS: This sample (mean age = 78.12, 69.23% female), on average, had 5.08 social ties in their network, and 58% were family ties. Participants reported decreased social contact, family and friends interaction patterns specific to immigrants, and constantly being in a low mood and bored. Having closer relationships with others and maintaining the same or higher contact frequency after COVID-19 onset was associated with fewer depressive symptoms. Resilience from religious beliefs, neighbors as role models, and wisdom learned from past experiences were reported. CONCLUSION: Knowledge built in this study can inform respondence to future crises like the COVID-19 pandemic in affordable housing settings serving older immigrant populations.


Assuntos
COVID-19 , Emigrantes e Imigrantes , Humanos , Feminino , Idoso , Masculino , COVID-19/epidemiologia , Instituição de Longa Permanência para Idosos , Saúde Mental , Pandemias , População do Leste Asiático , Solidão/psicologia , Isolamento Social/psicologia , Rede Social
7.
Sensors (Basel) ; 23(3)2023 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-36772563

RESUMO

In this paper, we build four-part cone models to explore the coupling effect of seven cone fiber couplers. Moreover, this is the first study of the coupling effect of four layers of biological couplers in animals and other biological lives. We simulate the four layers cone couplers by using the beam propagation method, and we assume the input beam is located at the outer fiber of the central cone. Our simulation results showed that there are two wavelength regions (short and long wavelength regions) with the strongest coupling, where the most power of input optical powers of the central cones will transfer to the six surrounding cones after transmitting through the four layers of cone couplers. However, within a wavelength region of ±75 nm near to the peak wavelengths, located in the yellow-green wavelength range, the splitting ratios at the output of the outer segment of the central cone are always greater than the sum of the splitting ratios of the six surrounding cones. These cone couplers may play an important role in color preprocessing (e.g., doing opponent color processing partially). The cone fiber coupler effect and light absorption of cones are considered separately in our models. By taking account of both the cone fiber coupling effect and absorption of outer segment of L cone, we find the multiplication of the relative optical power of cone couplers, the spectral sensitivity data of the L cone, and a normalized coefficient that matches with the photopic luminous efficiency of the human eye well. This is the attempt to use both the cone fiber coupling effect and the absorption of L cones to explain the photopic luminous efficiency. The splitting ratios of the central cones are greater than 80% at peak wavelengths located in the yellow-green wavelength range, and this can help to explain why the human eye is more sensitive to green light.

8.
Molecules ; 28(13)2023 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-37446706

RESUMO

This study aimed to explore the applicability of DNA barcoding for assessing the authenticity of caviar on the Chinese market. A set of universal COI primers and two sets of designed primers based on COI and D-loop genes were used to identify maternal species of samples from 21 batches of caviar. The results showed that the PCR products from three sets of primers had more than 98% similarity to the sequences in database. The COI gene could not distinguish sturgeons with closed genetic relationships, while D-loop gene could effectively improve the accuracy of DNA barcoding and was more suitable to the identification of interspecific sturgeon than the COI gene. The neighbor-joining dendrogram further confirmed the applicability and accuracy of COI and D-loop genes in identifying maternal relatives of caviar (Acipenser baerii/Acipenser gueldenstaedtii/Acipenser schrenckii/Huso dauricus/Huso huso). Despite the limitations of mitochondrial DNA in identifying hybrid sturgeon species, the presence of counterfeit caviar of non-sturgeon ingredients could be excluded. All the caviar samples were identified successfully as sturgeon species, but the mislabeling rate of species was 33.4%, indicating that there were illegal phenomena such as disorderly labeling, mislabeling, and adulteration on the market.


Assuntos
Código de Barras de DNA Taxonômico , DNA Mitocondrial , Animais , DNA Mitocondrial/genética , Peixes/genética , Reação em Cadeia da Polimerase/métodos , Primers do DNA
9.
J Am Chem Soc ; 144(7): 3192-3199, 2022 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-35157445

RESUMO

Covalent organic frameworks (COFs) have found wide applications due to their crystalline structures. However, it is still challenging to quantify crystalline phases in a COF sample. This is because COFs, especially 2D ones, are usually obtained as mixtures of polycrystalline powders. Therefore, the understanding of the aggregated structures of 2D COFs is of significant importance for their efficient utilization. Here we report the study of the aggregated structures of 2D COFs using 13C solid-state nuclear magnetic resonance (13C SSNMR). We find that 13C SSNMR can distinguish different aggregated structures in a 2D COF because COF layer stacking creates confined spaces that enable intimate interactions between atoms/groups from adjacent layers. Subsequently, the chemical environments of these atoms/groups are changed compared with those of the nonstacking structures. Such a change in the chemical environment is significant enough to be captured by 13C SSNMR. After analyzing four 2D COFs, we find it particularly useful for 13C SSNMR to quantitatively distinguish the AA stacking structure from other aggregated structures. Additionally, 13C SSNMR data suggest the existence of offset stacking structures in 2D COFs. These offset stacking structures are not long-range-ordered and are eluded from X-ray-based detections, and thus they have not been reported before. In addition to the dried state, the aggregated structures of solvated 2D COFs are also studied by 13C SSNMR, showing that 2D COFs have different aggregated structures in dried versus solvated states. These results represent the first quantitative study on the aggregated structures of 2D COFs, deepen our understanding of the structures of 2D COFs, and further their applications.

10.
Am J Bot ; 109(3): 377-392, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34994404

RESUMO

PREMISE: The phenomenon called "diminishing returns" refers to a scaling relationship between lamina mass (M) vs. lamina area (A) in many species, i.e., M ∝ Aα>1 , where α is the scaling exponent exceeding unity. Prior studies have focused on the scaling relationships between lamina dry mass (DM) and A, or between fresh mass (FM) and A. However, the scaling between petiole mass and M and A has seldom been investigated. Here, we examine the scaling relationships among FM, DM, A, and petiole fresh mass (PFM). METHODS: For each of 3268 leaves from nine Lauraceae species, FM, DM, A, and PFM were measured, and their scaling relationships were fitted using reduced major axis regression protocols. The bootstrap percentile method was used to test the significance of the difference in α-values between any two species. RESULTS: The phenomenon of diminishing returns was verified between FM vs. A and DM vs. A. The FM vs. A scaling relationship was statistically more robust than the DM vs. A scaling relationship based on bivariate regression r2 -values. Diminishing returns were also observed for the PFM vs. FM and PFM vs. A scaling relationships. The PFM vs. FM scaling relationship was statistically more robust than the PFM vs. A scaling relationship. CONCLUSIONS: "Diminishing returns" was confirmed among the FM, DM, A, and PFM scaling relationships. The data collectively indicate that the petiole scales mechanically more strongly with lamina mass than with area, suggesting that static (self) loading takes precedence over dynamic (wind) loading.


Assuntos
Lauraceae , Folhas de Planta
11.
Am J Bot ; 109(6): 899-909, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35471633

RESUMO

PREMISE: Across species, main leaf vein density scales inversely with leaf area (A). Yet, minor vein density manifests no clear relationship with respect to A, despite having the potential to provide important insights into the trade-off among the investments in leaf mechanical support, hydraulics, and light interception. METHODS: To examine this phenomenon, the leaves of nine Magnoliaceae leaves were sampled, and the scaling relationships among A and midrib length (ML), total vein length (TVL), total vein area (TVA), total areole area (TAA), and mean areole area (MAA) were determined. The scaling relationships between MAA and areole density (the number of areoles per unit leaf area) and between MAA and A were also analyzed. RESULTS: For five of the nine species, A was proportional to ML2 . For eight of the nine species, TVL and TVA were both proportional to A. The numerical values of the scaling exponents for TAA vs. A were between 1.0 and 1.07 for eight species; i.e., as expected, TAA was isometrically proportional to A. There was no correlation between MAA and A, but MAA scaled inversely with respect to areole density for each species. CONCLUSIONS: The correlation between midrib "density" (i.e., ML/A) and A, and the lack of correlation between total leaf vein density and A result from the A ∝$\propto $ ML2 scaling relationship and the proportional relationship between TVL and A, respectively. Leaves with the same size can have widely varying MAA. Thus, leaf size itself does not directly constrain leaf hydraulic efficiency and redundancy.


Assuntos
Magnoliaceae , Folhas de Planta
12.
Angew Chem Int Ed Engl ; 61(47): e202211808, 2022 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-36180387

RESUMO

The isolation of di-branched alkanes from their isomers is vital in gasoline upgrading to achieve high octane numbers but is significantly challenging and energy-intensive. Here, we report the highly efficient separation of hexane isomers by combing molecular recognition and size-sieving in a bismuth-based MOF, UU-200. The unique auxetic structure with reentrant honeycomb-like pore cavities connected by narrow pore windows endows UU-200 with a complete rejection of di-branched alkanes and high capacities for linear and mono-branched isomers. The molecular sieving effect, unprecedented separation selectivities, and excellent efficiencies are proved via adsorption isotherms and breakthrough experiments with high research octane numbers obtained (>96), indicating a benchmark for alkane separation under ambient conditions. The molecular recognition mechanism was unveiled by theoretical simulation and in situ Fourier-transform infrared spectroscopy.

13.
Angew Chem Int Ed Engl ; 61(29): e202203285, 2022 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-35426226

RESUMO

A family of fully sandwiched arachno-lanthanacarborane complexes formulated as {η6 -[µ-1,2-[o-C6 H4 (CH2 )2 ]-1,2-C2 B10 H10 ]2 Ln}{Li5 (THF)10 } (Ln=Tb, Dy, Ho, Er, Y) is successfully synthesized, where the "carbons-adjacent" carboranyl ligand (arachno-R2 -C2 B10 H10 4- ) bears four negative charges and coordinates to the central lanthanide ions using the hexagonal η6 C2 B4 face. Thus, the central lanthanide cations are pseudo-twelve-coordinate and have an approximate pseudo-D6h symmetry or hexagonal-prismatic geometry. As the crystal field effect imparted by this geometry is still unknown, we thoroughly investigated the magnetic properties of this series of complexes and found that the crystal field imposed by this ligand causes a relation of Tb>Dy>Ho>Er for the energy gaps between the ground and the first excited states, which is of striking resemblance to the ferrocenophane and phthalocyanine ligands although the latter two ligands give disparate local coordination geometries. Moreover, the effective energy barrier to magnetization reversal of 445(10) K, the observable hysteresis loop up to 4 K and the relaxation time of the yttrium-diluted sample reaching 193(17) seconds at 2 K under an optimized field for the Tb analogue of this family of arachno-lanthanacarborane complexes, render a new benchmark for Tb3+ -based single-molecule magnets.

14.
J Med Internet Res ; 23(6): e27632, 2021 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-34061757

RESUMO

BACKGROUND: Monitoring public confidence and hesitancy is crucial for the COVID-19 vaccine rollout. Social media listening (infoveillance) can not only monitor public attitudes on COVID-19 vaccines but also assess the dissemination of and public engagement with these opinions. OBJECTIVE: This study aims to assess global hesitancy, confidence, and public engagement toward COVID-19 vaccination. METHODS: We collected posts mentioning the COVID-19 vaccine between June and July 2020 on Twitter from New York (United States), London (United Kingdom), Mumbai (India), and Sao Paulo (Brazil), and Sina Weibo posts from Beijing (China). In total, we manually coded 12,886 posts from the five global metropolises with high COVID-19 burdens, and after assessment, 7032 posts were included in the analysis. We manually double-coded these posts using a coding framework developed according to the World Health Organization's Confidence, Complacency, and Convenience model of vaccine hesitancy, and conducted engagement analysis to investigate public communication about COVID-19 vaccines on social media. RESULTS: Among social media users, 36.4% (571/1568) in New York, 51.3% (738/1440) in London, 67.3% (144/214) in Sao Paulo, 69.8% (726/1040) in Mumbai, and 76.8% (2128/2770) in Beijing indicated that they intended to accept a COVID-19 vaccination. With a high perceived risk of getting COVID-19, more tweeters in New York and London expressed a lack of confidence in vaccine safety, distrust in governments and experts, and widespread misinformation or rumors. Tweeters from Mumbai, Sao Paulo, and Beijing worried more about vaccine production and supply, whereas tweeters from New York and London had more concerns about vaccine distribution and inequity. Negative tweets expressing lack of vaccine confidence and misinformation or rumors had more followers and attracted more public engagement online. CONCLUSIONS: COVID-19 vaccine hesitancy is prevalent worldwide, and negative tweets attract higher engagement on social media. It is urgent to develop an effective vaccine campaign that boosts public confidence and addresses hesitancy for COVID-19 vaccine rollouts.


Assuntos
Tratamento Farmacológico da COVID-19 , Vacinas contra COVID-19/uso terapêutico , Mídias Sociais/normas , Vacinas contra COVID-19/farmacologia , Humanos , Opinião Pública , SARS-CoV-2
15.
Eur J Clin Microbiol Infect Dis ; 39(2): 339-343, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31901114

RESUMO

The roll-out of molecular diagnostic tools continues to be the most important shift in the tuberculosis diagnostic landscape. The aim of this study was to develop a novel external quality assessment (EQA) panels for molecular TB diagnostics. In addition, we also assessed the performance of the laboratories with the EQA panels in China. Dried Mycobacterium tuberculosis (MTB) DNA in the chelex resin was designed as part of an EQA program. The storage of genomic DNA in the chelex resin layer had no effect on the stability of genomic DNA, even after 12 weeks of storage. Seventy-one laboratories have participated in EQA of molecular diagnostics for TB diagnosis in 2018. GeneXpert (74.6%, 53/71) was the most predominant molecular method, followed by GeneChip (32.3%, 23/71), MeltPro (22.5%, 16/71), and TB-LAMP (7.0%, 5/71). Out of 105 EQA panels, 103 EQA results (98.1%) achieved perfect scores, whereas the other two (1.9%) had satisfactory scores. There were a total of two false-negative results reported from two laboratories with local LAMP, respectively. In conclusion, we firstly develop feasible EQA panels for molecular diagnostics for tuberculosis in China. Our data demonstrate that a majority of participating laboratories are able to produce perfect results with molecular diagnostics in China, giving us important hints for the implementation of molecular diagnostics.


Assuntos
Técnicas de Diagnóstico Molecular/métodos , Mycobacterium tuberculosis/genética , Tuberculose/diagnóstico , Tuberculose/microbiologia , China/epidemiologia , Testes Diagnósticos de Rotina , Humanos , Técnicas de Diagnóstico Molecular/normas , Preservação Biológica/métodos , Controle de Qualidade , Kit de Reagentes para Diagnóstico , Reprodutibilidade dos Testes , Fatores de Risco , Temperatura , Tuberculose/epidemiologia
16.
Angew Chem Int Ed Engl ; 59(24): 9350-9354, 2020 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-32090421

RESUMO

The dicarbollide ion, nido-C2 B9 H11 2- is isoelectronic with cyclopentadienyl. Herein, we make dysprosiacarboranes, namely [(C2 B9 H11 )2 Ln(THF)2 ][Na(THF)5 ] (Ln=Dy, 1Dy) and [(THF)3 (µ-H)3 Li]2 [{η5 -C6 H4 (CH2 )2 C2 B9 H9 }Dy{η2 :η5 -C6 H4 (CH2 )2 C2 B9 H9 }2 Li] 3Dy and show that dicarbollide ligands impose strong magnetic axiality on the central DyIII ion. The effective energy barrier (Ueff ) for the loss of magnetization can be varied by the substitution pattern on the dicarbollide. This finding is demonstrated by comparing complexes of nido-C2 B9 H11 2- and nido-[o-xylylene-C2 B9 H9 ]2- , which show a Ueff of 430(5) K and 804(7) K, respectively. The blocking temperature defined by the open hysteresis temperature of 3Dy reaches 6.8 K. Moreover, the linear complex [Dy(C2 B9 H11 )2 ]- is predicted to have comparable properties with the linear [Dy(CpMe3 )2 ]+ complex. As such, carboranyl ligands and their derivatives may provide a new type of organometallic ligand for high-performance single-molecule magnets.

17.
Eur J Clin Microbiol Infect Dis ; 38(10): 1961-1968, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31342215

RESUMO

Mycobacterial culture remains the gold standard for detection of Mycobacterium tuberculosis (MTB) in clinical samples. However, no external quality assessment (EQA) tools exist to validate results obtained using this sophisticated method. Therefore, we developed EQA panels to assess the quality of mycobacterial culture results produced by designated TB hospitals in China. Artificial sputum containing methylcellulose was used to supplement quantified mycobacterial solutions to simulate culture-negative and culture-positive clinical sputum samples of low or high mycobacterial concentration, respectively. After storage of the quantified simulated EQA panels for 4 weeks at 4 °C, experimental bacterial quantification of the panels was again conducted, with no impact of artificial sputum on mycobacterial culture results observed. Next, 47 tuberculosis (TB) hospitals were recruited for evaluation of the EQA panels. Overall, 29 hospitals (61.7%) produced mycobacterial culture test results matching expected results for the EQA panels, while the remaining 18 (38.3%) hospitals did not. False-negative results for the low mycobacterial concentration panel sample accounted for 33 (73.3%) diagnostic errors. Compared with hospitals using solid culture methods as a control group, hospitals using the liquid culture method were less likely to produce uncertified results (aOR 0.064, 95% CI 0.005-0.770). In conclusion, we first developed then evaluated EQA panels for validation of mycobacterial culture testing in China. Our data demonstrate that approximately one-third of TB hospitals failed to produce results that met criteria for classification as certified mycobacterial culture testing providers, emphasizing the importance of quality control and quality assurance in TB diagnostics.


Assuntos
Técnicas Bacteriológicas/métodos , Testes Diagnósticos de Rotina/métodos , Ensaio de Proficiência Laboratorial/métodos , Mycobacterium tuberculosis/isolamento & purificação , Escarro/microbiologia , Tuberculose/diagnóstico , Técnicas Bacteriológicas/normas , China , Testes Diagnósticos de Rotina/normas , Hospitais , Humanos
20.
Ann Hum Genet ; 81(4): 147-160, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28620992

RESUMO

Genomic imprinting is an epigenetic phenomenon in which the expression of an allele copy depends on its parental origin. This mechanism has been found to play an important role in many complex diseases. Statistical tests for imprinting effects have been developed for more than 15 years, but they are only suitable for autosomes. It was not until recently that the parental-asymmetry test on the X chromosome (XPAT) was proposed to test for imprinting effects. However, this test can only be used for qualitative traits. Therefore, in this article, we propose a class of PAT-type tests to test for imprinting for quantitative traits on the X chromosome in the presence of association, namely, Q-XPAT(c), Q-1-XPAT(c) and Q-C-XPAT(c), where c is a constant. These methods can accommodate complete and incomplete nuclear families with an arbitrary number of daughters. Extensive simulation studies demonstrate that the proposed tests control the size well under the null hypothesis of no imprinting effects and are powerful under various family structures. Moreover, by setting the inbreeding coefficient in females to be nonzero and using the assortative mating pattern in simulations, the proposed tests are shown to be valid under Hardy-Weinberg disequilibrium.


Assuntos
Cromossomos Humanos X/genética , Impressão Genômica , Núcleo Familiar , Locos de Características Quantitativas , Simulação por Computador , Feminino , Estudos de Associação Genética , Humanos , Masculino
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA