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Objective: To study the clinical and microbiological characteristics of hypervirulent Klebsiella pneumoniae (hvKP) lung abscess, and to compare with the classic Klebsiella pneumoniae (cKP) lung abscess. Methods: A total of 18 patients with Klebsiella pneumoniae lung abscesses admitted to the First Affiliated Hospital of Zhejiang University School of Medicine from January 2017 to September 2020 enrolled. The strains with positive result of string test were defined as hvKP, and the negative strains were defined as cKP. The patients' basic diseases, symptoms, laboratory data and other clinical characteristics were collected. The microbiological characteristics of the strains included as following: VITEK method to determine the in vitro susceptibility of the strains to antibiotics; PCR to detect the capsular serotypes and virulence genes. The differences in clinical characteristics and microbiological characteristics of strains between hvKP group and cKP group were compared. Results: Among the 18 patients with Klebsiella pneumoniae lung abscess, 12 were hvKP infection, mainly male (10 cases), with a median age of 59.0 years; 8 cases in the hvKP group had an onset time of ≤2 weeks, and the median onset time was 10.5 days. There were significantly more diabetes (12 cases) and extrapulmonary abscesses (11 cases) in hvKP group than those in cKP group (both P<0.001). The extrapulmonary abscesses in the hvKP group were mainly liver abscesses (10 cases), and 4 cases were multi-site (≥3) abscesses. The number of indwelling catheters and invasive procedures before infection were higher in cKP group than those in hvKP group (both P=0.025). The imaging of Klebsiella pneumoniae lung abscess was mainly subpleural with the size of less than 10 cm. There were more multiple abscesses cases in hvKP group (9 cases) than cKP group (P=0.009). The median interval time between the detection of a pulmonary abscess and an extrapulmonary abscess was 1.0 day. The resistance rate of common antibiotics was significantly lower in hvKP than cKP. Conclusions: hvKP lung abscesses are more common in patients with diabetes, and the clinical manifestations are nonspecific. The lung imaging manifestations are multiple subpleural abscesses, indicating hematogenous dissemination. Liver abscesses were present in most cases, suggesting the source of infection. The main virulent gene of hypervirulent Klebsiella pneumoniae is aero. For patients with hvKP lung abscess, attention should be paid to finding hidden lesions.
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Infecções por Klebsiella , Abscesso Hepático , Abscesso Pulmonar , Pneumonia , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Humanos , Klebsiella pneumoniae , Masculino , Pessoa de Meia-IdadeRESUMO
To investigate the prevalence of canine and feline hookworms in South China, and to assess the risk of zoonotic hookworms to humans, one pair of primers (HRM-F/HRM-R) was designed to establish a high-resolution melting (HRM) method based on internal transcribed spacer 1 (ITS-1) rDNA for the detection of Ancylostoma ceylanicum, A. caninum and A. tubaeforme infection. The results showed that the HRM for the three hookworms produced different melting-curve profiles, where melting temperature (Tm) values were 84.50°C for A. ceylanicum, 82.25°C for A. caninum and 81.73°C for A. tubaeforme, respectively. The reproducibility of intra- and inter-assay melting curves was almost perfect. The lowest concentration detected was about 5.69 ×10-4 g/µl. The HRM detection results from 18 canine and feline hookworm samples were in complete accordance with their sequencing results. The HRM method was more sensitive than the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique in the detection of 98 clinical samples. It is concluded that the HRM method can differentiate between A. ceylanicum, A. caninum, A. tubaeforme and their mixed infections, which may provide important technical support for the zoonotic risk assessment and molecular epidemiological survey of canine and feline hookworms.
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Ancylostomatoidea/genética , Doenças do Gato/epidemiologia , DNA de Helmintos/genética , Doenças do Cão/epidemiologia , Infecções por Uncinaria/veterinária , Ancylostomatoidea/classificação , Animais , Doenças do Gato/parasitologia , Gatos , China/epidemiologia , Primers do DNA/genética , DNA Ribossômico/genética , Doenças do Cão/parasitologia , Cães , Fezes/parasitologia , Infecções por Uncinaria/epidemiologia , Infecções por Uncinaria/parasitologia , Limite de Detecção , Filogenia , Reação em Cadeia da Polimerase/veterinária , Polimorfismo de Fragmento de Restrição , Prevalência , Reprodutibilidade dos Testes , Temperatura de TransiçãoRESUMO
Objective: To summarize the clinical characteristics of pulmonary actinomycosis and analyze its diagnostic methods. Methods: The clinical symptoms, underlying diseases, imaging characteristics, preliminary diagnosis, diagnostic methods, treatment and prognosis of 30 patients with pulmonary actinomycetes admitted into the First Affiliated Hospital of Zhejiang University School of Medicine during the 10 years (January 2007 to November 2017) were retrospectively analyzed. Results: The 30 patients with pulmonary actinomycetes included were from 47 to 81 years old, with an average age of (59.5±7.8) years, with a course of disease from 5 days to 48 months, and a median course of disease of 1.5 months; 18 patients (60.0%) were complicated with underlying diseases, 10 patients (33.3%) had a history of smoking, 10 patients (33.3%) had a history of alcohol abuse. The main clinical manifestations were cough in 29 cases (96.7%), followed by sputum in 22 cases (73.3%), hemoptysis in 20 cases (66.7%), fever in 12 cases (40.0%), chest pain in 5 cases (16.7%) and shortness of breath in 3 cases (10.0%). Mass, nodules, consolidation, atelectasis can be seen by imaging, there can be a low-density lesion necrosis, formation of voids or vacuoles. Among the 25 patients (83.3%) who underwent bronchoscopy, 14 cases were abnormal, 5 cases showed endotracheal polypoid neoplasms, 9 cases showed endotracheal mucosal inflammatory changes, 2 cases of them showed bronchial foreign body, and 1 case showed broncholithiasis. All cases were diagnosed by pathology. Nine cases (30.0%) were confirmed by bronchoscopic biopsy. Two cases (6.7%) underwent CT-guided percutaneous lung biopsy, 18 cases (60.0%) underwent surgical resection of pathology, and 1 case (3.3%) was diagnosed by puncture of chest wall mass. Sufficient dose and course of penicillin were effective. Surgical excision of the lesion with antibiotics for 2-4 weeks was effective. Conclusion: The clinical manifestation of pulmonary actinomycosis is lack of specificity, obtaining positive pathological specimens is the key to the diagnosis of this disease, the first choice is bronchoscopy and percutaneous lung biopsy.
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Actinomicose , Idoso , Idoso de 80 Anos ou mais , Biópsia por Agulha , Broncoscopia , Humanos , Pulmão , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
Oncogenic Kras with loss of heterozygosity (LOH) is frequently detected in various tumours. However, the exact function and mechanism by which KrasG12D-LOH operates remain unclear. Therefore, the current study investigated the effect of KrasG12D-LOH on the malignant phenotype of pancreatic ductal adenocarcinoma (PDAC) cells. Our investigation revealed that KrasG12D-LOH is associated with increased proliferation, invasion and reduced apoptosis in PDAC cells. The results also exhibited enhanced glycolytic phenotype of KrasG12D-LOH PDAC cells. Hyperactive mTOR plays a significant role in the initiation and maintenance of tumors. To investigate the correlation between KrasG12D-LOH and mTOR, the mTOR signaling pathway was detected by western blot analysis. We found that KrasG12D-LOH up-regulated Akt, AMPK, REDD1 and mTOR in PDAC cells. In summary, our results demonstrated that KrasG12D-LOH promotes oncogenic Kras-induced PDAC by regulating energy metabolism and mTOR signaling pathway. These data may provide novel therapeutic perspectives for PDAC.
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Carcinoma Ductal Pancreático/metabolismo , Perda de Heterozigosidade , Neoplasias Pancreáticas/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/genética , Transdução de Sinais , Serina-Treonina Quinases TOR/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Metabolismo Energético , HumanosRESUMO
Dipetalonema gracile is a common parasite in squirrel monkeys (Saimiri sciureus), which can cause malnutrition and progressive wasting of the host, and lead to death in the case of massive infection. This study aimed to identify a suspected D. gracile worm from a dead squirrel monkey by means of molecular biology, and to amplify its complete mitochondrial genome by polymerase chain reaction (PCR) and sequence analysis. The results identified the worm as D. gracile, and the full length of its complete mitochondrial genome was 13,584 bp, which contained 22 tRNA genes, 12 protein-coding genes, two rRNA genes, one AT-rich region and one small non-coding region. The nucleotide composition included A (16.89%), G (20.19%), T (56.22%) and C (6.70%), among which A + T = 73.11%. The 12 protein-coding genes used TTG and ATT as start codons, and TAG and TAA as stop codons. Among the 22 tRNA genes, only trnS1AGN and trnS2UCN exhibited the TΨC-loop structure, while the other 20 tRNAs showed the TV-loop structure. The rrnL (986 bp) and rrnS (685 bp) genes were single-stranded and conserved in secondary structure. This study has enriched the mitochondrial gene database of Dipetalonema and laid a scientific basis for further study on classification, and genetic and evolutionary relationships of Dipetalonema nematodes.
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Infecções por Dipetalonema/veterinária , Dipetalonema/genética , Genoma Mitocondrial , Doenças dos Macacos/parasitologia , Saimiri/parasitologia , Animais , Composição de Bases , Sequência de Bases , China , Dipetalonema/classificação , Dipetalonema/isolamento & purificação , Infecções por Dipetalonema/parasitologia , Genoma Helmíntico , FilogeniaRESUMO
Ancylostoma tubaeforme may infect canids, felids and humans, and pose a potential risk to public health. Polymerase chain reaction (PCR) techniques were used to amplify the complete mitochondrial (mt) genome sequence of A. tubaeforme from cats and to analyse its sequence characteristics after molecular identification based on the internal transcribed spacer ITS1+ sequence. The results show that the complete mt genome sequence (GenBank accession number KY070315) of A. tubaeforme from cats was 13,730 bp in length, including 12 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, two non-coding regions and an AT-rich region. The nucleotide content of A and T was 77.93%, biased toward A and T. Twelve protein-coding genes used ATT, TTG and GTG as initiation codons, and TAA, TAG, TA and T as termination codons. The length of the 22 tRNA genes ranged from 52 to 62 bp, their predicted secondary structures were D loops and V loops. The lengths of the two rRNAs were 958 and 697 bp. Phylogenetic analyses showed that A. tubaeforme from cats was in the lineage of Ancylostoma, having a close phylogenetic relationship with A. caninum. This study reports for the first time the mt genome of A. tubaeforme from cats in China, which could enhance the mt genome database of Ancylostomatidae nematodes, and it offers the scientific basis for further studies in the genetic diversity of hookworms among different hosts.
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Ancylostoma/genética , Ancilostomíase/veterinária , Doenças do Gato/parasitologia , Genoma Mitocondrial/genética , Ancilostomíase/diagnóstico , Ancilostomíase/epidemiologia , Ancilostomíase/parasitologia , Animais , Doenças do Gato/epidemiologia , Gatos , China/epidemiologia , DNA de Helmintos/genética , DNA Mitocondrial/genética , Filogenia , RNA de Helmintos/genética , RNA Ribossômico/genética , RNA de Transferência/genéticaRESUMO
Objective: To analyze the drug resistance of Escherichia coli (E.coli) from bloodstream infection (BSI) and the predictors of mortality in E. coli bloodstream infection (BSI). Methods: The clinical data of 139 E. coli BSI cases diagnosed from January 2012 to December 2015 in The Second Affiliated Hospital of Zhejiang University School of Medicine, Lanxi Branch (Lanxi People's Hospital), Zhejiang Province, were retrospectively analyzed. The antimicrobial susceptibility testing was performed using Vitek 2 system. Extended-spectrum beta-lactamases (ESBLs) were detected by disk diffusion confirmatory testing. The factors associated with ESBLs-producing strains were identified by univariate analysis. Multivariate analysis was used to identify independent predictors of infection mortality by applying Logistic regression. Results: 42.4% of E. coli isolates were ESBLs-producing. The resistant rate of imipenem was 0.7%. The percent of ESBLs in hospital-acquired infection was higher than that in community-acquired infection but without statistical significance (48.7% versus 40.0%, P=0.350). Univariate analysis suggested that the percent of ESBLs-producing strains in BSI happened on ≥15 d after admission and in BSI of biliary tract infection source was 76.9% and 68.0%, which were much higher than those in BSI happened on <15 d after admission and in BSI of non-biliary tract infection source (34.6% and 36.8%, P=0.013 and 0.004). The overall mortality of E. coli BSI was 13.7%. Multivariate Logistic regression analysis indicated that Sequential Organ Failure Assessment (SOFA ) score (OR=1.393, P<0.001), ceftazidime non-susceptibility (OR=4.444, P=0.018) and liver cirrhosis (OR=13.513, P=0.001) were independent risk factors of mortality. Conclusions: The frequency of ESBLs-producing E. coli was high in primary hospital of Zhejiang Province. SOFA score, ceftazidime non-susceptibility and cirrhosis were predictors of poor outcome in E. coli BSI.
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Bacteriemia , Infecções por Escherichia coli , Antibacterianos , Resistência Microbiana a Medicamentos , Escherichia coli , Humanos , Estudos Retrospectivos , beta-LactamasesRESUMO
Smooth and continuous ZnO films consisting of densely packed ZnO nanorods (NRs), which can be used for electronic device fabrication, were synthesized using a hydro-thermo-chemical solution deposition method. Such devices would have the novelty of high performance, benefiting from the inherited unique properties of the nanomaterials, and can be fabricated on these smooth films using a conventional, low cost planar process. Photoluminescence measurements showed that the NR films have much stronger shallow donor to valence band emissions than those from discrete ZnO NRs, and hence have the potential for the development of ZnO light emission diodes and lasers, etc. The NR films have been used to fabricate large area surface acoustic wave devices by conventional photolithography. These demonstrated two well-defined resonant peaks and their potential for large area device applications. The chemical solution deposition method is simple, reproducible, scalable and economic. These NR films are suitable for large scale production on cost-effective substrates and are promising for various fields such as sensing systems, renewable energy and optoelectronic applications.
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Nanotubos/química , Óxido de Zinco/química , Eletrônica/instrumentação , Desenho de Equipamento , Nanotecnologia , Nanotubos/ultraestruturaRESUMO
Objective: To understand the research progresses of economic evaluation of COVID-19 vaccination strategies both at home and abroad, and provide reference for the economic evaluation of COVID-19 vaccination strategies using real word data in China. Methods: Literature retrieval was conducted for related papers published from January, 2020 to December, 2021 in Chinese and English databases, including the economic evaluation of COVID-19 vaccination, and the results of the related literatures were narratively integrated. Results: A total of 16 English literatures (including 3 reviews) were included, and it was found that the COVID-19 vaccination was cost-effective or cost-saving regardless of the vaccine types, while the cost-effectiveness in different population and under different vaccination dose strategies varied due to vaccine efficacy, vaccine price, duration of natural immunity, duration of vaccination campaign, vaccine supply, and vaccination pace. Conclusions: China lacks suitable evidences of economic evaluation of COVID-19 vaccination strategies based on real-world data in the context of long-term epidemic. Therefore, further researches of suitable strategies of booster COVID-19 vaccination are needed.
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Vacinas contra COVID-19 , COVID-19 , COVID-19/prevenção & controle , China/epidemiologia , Análise Custo-Benefício , Humanos , VacinaçãoRESUMO
Objective: To understand the research progresses of economic evaluation of non-pharmaceutical interventions (NPIs) both at home and abroad, and provide reference for economic evaluation of NPIs using real-world data in China. Methods: The literature retrieval was conducted by searching Chinese and English databases to indude papers about economic evaluation of NPIs and integrated NPIs published from January, 2020 to December, 2021, and the results were analyzed comprehensively. Results: A total of 30 Chinese and English literatures about economic evaluation of NPIs for COVID-19 prevention and control were included; including 7 papers about nucleic acid and testing and screening, 6 papers about individual prevention and protection measures, 12 papers about integrated implementation of individual prevention and protection, social distancing, nucleic acid or antigen testing, community screening and symptom screening, as well as close contact tracing and isolation/quarantine, and 5 papers about contain strategies, such as lockdown. This study found that personal protection, social distancing, and testing-tracing-isolation measures were cost-effective; however, different combinations of NPIs might lead to different results. Moreover, the cost of lockdown was high, which might cause huge economic burden. Conclusions: Most NPIs are cost-effective except lockdown, while the cost-effectiveness of the integrations of NPIs at different levels and in different scenarios needs to be further evaluated. It is necessary to carry out economic evaluation of integrated NPIs and the combination of NPIs with other interventions, such as vaccination and medication, based on real-world settings in China.
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COVID-19 , Ácidos Nucleicos , COVID-19/prevenção & controle , Controle de Doenças Transmissíveis/métodos , Análise Custo-Benefício , Humanos , SARS-CoV-2RESUMO
A novel method is proposed to fabricate micro Diffractive Optical Elements (DOE) using micro cutting tools shaped with focused ion beam (FIB) milling. Micro tools with nanometric cutting edges and complicated shapes are fabricated by controlling the tool facet's orientation relative to the FIB. The tool edge radius of less than 30 nm is achieved for the nano removal of the work materials. Semi-circular micro tools and DOE-shaped micro tools are developed to fabricate micro-DOE and sinusoidal modulation templates. Experiments show that the proposed method can be a high efficient way in fabricating micro-DOE with nanoscale surface finishes.
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The low temperature sintering behaviour of nanocrystalline Ag powder (with an average size of 70 nm) was characterized. Using spark plasma sintering (SPS), the Ag nanopowders can be successfully sintered at low pressure for only 5 min without external heating, and the sintering density increases and porosity decreases significantly with increase in the sintering temperature. Nanoindentation has been used to characterize the SPS sintered Ag samples. The mechanisms of the low sintering temperature behaviour of the nano-Ag powder and the nanoscale mechanical performance have been discussed. Compression tests were also used to characterize the mechanical properties of the sintered Ag sample with a maximum strain up to 15%.
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This study investigated the effects of different acute high ambient temperatures on dysfunction of hepatic mitochondrial respiration, the antioxidative enzyme system, and oxidative injury in broiler chickens. One hundred twenty-eight 6-wk-old broiler chickens were assigned randomly to 4 groups and subsequently exposed to 25 (control), 32, 35, and 38 degrees C (RH, 70 +/- 5%) for 3 h, respectively. The rectal temperatures, activity of antioxidative enzymes (superoxide dismutase, catalase, and glutathione peroxidase), content of malondialdehyde and protein carbonyl, and the activity of mitochondrial respiratory enzymes were determined. The results showed that exposure to high ambient temperature induced a significant elevation of rectal temperature, antioxidative enzyme activity, and formation of malondialdehyde and protein carbonyl, as well as dysfunction of the mitochondrial respiratory chain in comparison with control (P < 0.05). Almost all of the indicators changed in a temperature-dependent manner with the gradual increase of ambient temperature from 32 to 38 degrees C; differences in each parameter (except catalase) among the groups exposed to different high ambient temperatures were also statistically significant (P < 0.05). The results of the present study suggest that, in the broiler chicken model used here, acute exposure to high temperatures may depress the activity of the mitochondrial respiratory chain. This inactivation results subsequently in overproduction of reactive oxygen species, which ultimately results in oxidative injury. However, this hypothesis needs to be evaluated more rigorously in future studies. It has also been shown that, with the gradual increase in temperature, the oxidative injury induced by heat stress in broiler chickens becomes increasingly severe, and this stress response presents in a temperature-dependent manner in the temperature range of 32 to 38 degrees C.
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Antioxidantes/metabolismo , Temperatura Alta , Mitocôndrias Hepáticas/metabolismo , Estresse Oxidativo , Consumo de Oxigênio/fisiologia , Animais , GalinhasRESUMO
A label-free quartz crystal microbalance (QCM) biosensor was developed for the selective and real-time estimation of carcinoembryonic antigen (CEA) through the present study. Graphene oxide-Au nanoparticles (GO-AuNPs) was in situ synthesised on the surface of the QCM electrode and the antibody of CEA (monoclonal anti-CEA from mouse) was covalently immobilized on this layer as the bioreceptor for CEA. Mercaptoacetic acid-EDC-NHS reaction mechanism was used for anti-CEA immobilization. The effect of oxygen plasma treatment of the QCM electrode surface before bioreceptor preparation on the performance of the biosensor was tested and was found promising. CEA solutions with various concentrations were analysed using the bioreceptors to estimate the sensitivity and detection limit of the biosensor. The biosensors selectively recognized and captured CEA biomolecules with a detection limit of 0.06 and 0.09 ng mL-1 of CEA for oxygen plasma-treated (E2) and untreated (E1) bioreceptors, respectively. The sensitivity was estimated at 102 and 79 Hz, respectively, for E2 and E1. Clinical serum samples were analysed and the results were found in good agreement with the ELISA analysis. Long term stability was also found to be excellent. Langmuir adsorption isotherm was also conducted using the experimental results.
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Objective: To explore the reference ranges and influential factors of disturbance coefficient (DC) in children without craniocerebral injury at different ages. Methods: Two hundred children without craniocerebral injury admitted to the Department of Orthopaedics in Children's Hospital of Chongqing Medical University from May 2018 to October 2019 were enrolled in this prospective study. The children were divided into four groups according to age, 0-1 year, >1-3 years, >3-5 years and >5-16 years, each of which included 50 children. Each child had DC measured twice with the non-invasive dynamic cerebral edema monitor, and the average value was used as the terminal DC value. Each measurement lasted 15 minutes, 12 hours apart. The difference of DC values among the four groups and between different genders were compared with ANOVA test and nonparametric test. And the Loess local weighted nonparametric regression analysis was used to explore the change of DC according to the increase of age, weight and head circumference (HC). Results: The reference values of DC for children of 0-1 year,>1-3 years, >3-5 years, and >5-16 years were 60±14, 92±18, 112±18, 135±18, respectively (F=175.690, P<0.01). There was no statistical significance in DC between male and female children either in the whole or in each separate age group (103 (81, 125) vs. 102 (68, 123) , Z=-0.739, P=0.460; 59 (52, 68) vs. 57 (53, 65) , Z=-0.243, P=0.808; 88 (81, 105) vs. 95 (70, 105) , Z=-0.776, P=0.437; 117 (99, 120) vs. 113 (101, 123) , Z=-0.170, P=0.865; 137 (123, 143) vs. 142 (123, 160) , Z=-1.279, P=0.201). When the child's age was younger than 5 years, weight was less than 18 kg or HC was less than 51 cm, the DC increased significantly with the increase of age, weight or HC. However, when the age, weight and HC were over the above values, the DC did not show obvious increase, but approaching to stable values of 135, 130, and 130, respectively. Conclusions: For children without craniocerebral injury, the reference values of DC are obviously different at different ages. DC is positively related to age, weight and HC, but not related to gender.
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Cefalometria , Adolescente , Criança , Pré-Escolar , Traumatismos Craniocerebrais , Edema/diagnóstico , Feminino , Cabeça/anatomia & histologia , Hospitalização , Hospitais Pediátricos , Humanos , Lactente , Recém-Nascido , Masculino , Estudos ProspectivosRESUMO
Surface acoustic wave (SAW)-based formaldehyde gas sensor using bi-layer nanofilms of bacterial cellulose (BC) and polyethyleneimine (PEI) was developed on an ST-cut quartz substrate using sol-gel and spin coating processes. BC nanofilms significantly improve the sensitivity of PEI films to formaldehyde gas, and reduces response and recovery times. The BC films have superfine filamentary and fibrous network structures, which provide a large number of attachment sites for the PEI particles. Measurement results obtained using in situ diffuse reflectance Fourier transform infrared spectroscopy showed that the primary amino groups of PEI strongly adsorb formaldehyde molecules through nucleophilic reactions, thus resulting in a negative frequency shift of the SAW sensor due to the mass loading effect. In addition, experimental results showed that the frequency shifts of the SAW devices are determined by thickness of PEI film, concentration of formaldehyde and relative humidity. The PEI/BC sensor coated with three layers of PEI as the sensing layer showed the optimal sensing performance, which had a frequency shift of 35.6 kHz for 10 ppm formaldehyde gas, measured at room temperature and 30 % RH. The sensor also showed good selectivity and stability, with a low limit of detection down to 100 ppb.
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Poluentes Atmosféricos/análise , Celulose/química , Monitoramento Ambiental/instrumentação , Formaldeído/análise , Polietilenoimina/química , Quartzo/química , Som , Adsorção , Monitoramento Ambiental/métodos , Desenho de Equipamento , Modelos Teóricos , Nanoestruturas/química , Sensibilidade e EspecificidadeRESUMO
Nanocrystalline Si films were prepared with a RF-PECVD system using different SiH4/H2 ratios, plasma powers, substrate temperatures and annealing conditions. The film's intrinsic stress was characterized in relation to the crystallization fraction. Results show that an increasing H2 gas ratio, plasma power or substrate temperature can shift the growth mechanism across a transition point, past which nanocrystalline Si is dominant in the film structure. The film's intrinsic stress normally peaks during this transition region. Different mechanisms of stress formation and relaxation during film growth were discussed, including ion bombardment effects, hydrogen induced bond-reconstruction and nanocomposite effects (nanocrystals embedded in an amorphous Si matrix). A three-parameter schematic plot has been proposed which is based on the results obtained. The film structure and stress are presented in relation to SiH4 gas ratio, plasma power and temperature.
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Significant surface morphology evolution between relief and wrinkling was observed on a 3.5 microm thick TiNiCu film sputter-deposited on a silicon substrate. At room temperature, variation in surface relief morphology (from separated martensite crystals embedded in amorphous matrix to fully interweaved martensite plates) was observed with slight change in film composition. The phenomenon was attributed to variations in crystallization temperatures of as-deposited amorphous films during annealing because of the compositional difference. During thermal cycling between room temperature and 100 degrees C, reversible surface morphology changes can be observed between surface relief and wrinkling patterns. The formation of the surface wrinkling is attributed to the large compressive stress in the film during high temperature post-annealing and crystallization, whereas surface relief is caused by the martensitic transformation to relieve the large tensile stress in the film. Compositional effect on this surface morphology evolution is discussed. Results also indicate that there is a critical dimension for the wrinkling to occur, and a small circular island can only relax by in-plane expansion.
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A fundamental challenge for surface acoustic wave (SAW) temperature sensors is the detection of small temperature changes on non-planar, often curved, surfaces. In this work, we present a new design methodology for SAW devices based on flexible substrate and bimorph material/structures, which can maximize the temperature coefficient of frequency (TCF). We performed finite element analysis simulations and obtained theoretical TCF values for SAW sensors made of ZnO thin films (~5 µm thick) coated aluminum (Al) foil and Al plate substrates with thicknesses varied from 1 to 1600 µm. Based on the simulation results, SAW devices with selected Al foil or plate thicknesses were fabricated. The experimentally measured TCF values were in excellent agreements with the simulation results. A normalized wavelength parameter (e.g., the ratio between wavelength and sample thickness, λ/h) was applied to successfully describe changes in the TCF values, and the TCF readings of the ZnO/Al SAW devices showed dramatic increases when the normalized wavelength λ/h was larger than 1. Using this design approach, we obtained the highest reported TCF value of -760 ppm/K for a SAW device made of ZnO thin film coated on Al foils (50 µm thick), thereby enabling low cost temperature sensor applications to be realized on flexible substrates.
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Various studies on ancient DNA have attempted to reconstruct population movement in Asia, with much interest focused on determining the arrival of European lineages in ancient East Asia. Here, we discuss our analysis of the mitochondrial DNA of human remains excavated from the Yu Hong tomb in Taiyuan, China, dated 1400 years ago. The burial style of this tomb is characteristic of Central Asia at that time. Our analysis shows that Yu Hong belonged to the haplogroup U5, one of the oldest western Eurasian-specific haplogroups, while his wife can be classified as haplogroup G, the type prevalent in East Asia. Our findings show that this man with European lineage arrived in Taiyuan approximately 1400 years ago, and most probably married a local woman. Haplogroup U5 was the first west Eurasian-specific lineage to be found in the central part of ancient China, and Taiyuan may be the easternmost location of the discovered remains of European lineage in ancient China.