To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Almost all hospitals are equipped with air-conditioning systems to provide a comfortable environment for patients and staff. However, the accumulation of dust and moisture within these systems increases the risk of transmission of microbes and have on occasion been associated with outbreaks of infection. Nevertheless, the impact of air-conditioning on the transmission of microorganisms leading to infection remains largely uncertain. We conducted a scoping review to screen systematically the evidence for such an association in the face of the coronavirus disease 2019 epidemic. PubMed, Embase and Web of Science databases were explored for relevant studies addressing microbial contamination of the air, their transmission and association with infectious diseases. The review process yielded 21 publications, 17 of which were cross-sectional studies, three were cohort studies and one case−control study. Our analysis showed that, compared with naturally ventilated areas, microbial loads were significantly lower in air-conditioned areas, but the incidence of infections increased if not properly managed. The use of high-efficiency particulate air (HEPA) filtration not only decreased transmission of airborne bioaerosols and various microorganisms, but also reduced the risk of infections. By contrast, contaminated air-conditioning systems in hospital rooms were associated with a higher risk of patient infection. Cleaning and maintenance of such systems to recommended standards should be performed regularly and where appropriate, the installation of HEPA filters can effectively mitigate microbial contamination in the public areas of hospitals.
The impact of diet on the metabolic syndrome (MetS) and CVD has been investigated widely, but few studies have investigated the association between dietary patterns (DP) and the predicted CVD, derived from reduced rank regression (RRR). The objectives of this study were to derive DP using RRR and principal component analysis (PCA) and investigate their associations with the MetS and estimated 10-year atherosclerotic CVD (ASCVD). We used the baseline dataset from the Xinjiang multi-ethnic cohort study in China, collected from June 2018 to May 2019. A total of 14 982 subjects aged 35–74 years from Urumqi, Huo Cheng and Mo Yu were included in the analysis. The 10-year ASCVD risk was estimated using the Chinese ASCVD risk equations. The associations of DP with the MetS and 10-year ASCVD were determined using multivariable logistic regression models. In Urumqi and Mo Yu, the increased RRR DP score was associated with a higher OR of having the MetS and with a higher OR of elevated 10-year ASCVD risk. However, only the first DP determined by PCA in Urumqi was inversely associated with the MetS and elevated 10-year ASCVD risk. The prevalence of the MetS and elevated ASCVD risk in urban population is higher than that in rural areas. Our results may help nutritionists develop more targeted dietary strategies to prevent the MetS and ASCVD in different regions in China.
Drug use disorders are an important issue worldwide. Systematic attempts to estimate the global incidence of drug use disorders are rare. We aimed to determine the incidence of drug use disorders and their trends.
We obtained the annual incident cases and age-standardised incidence rate (ASR) of drug use disorders from 1990 to 2017 using the Global Health Data Exchange query tool. The estimated annual percentage changes of the ASR were used to quantify and evaluate the trends in the incidence rate. Gaussian process regression and the Pearson's correlation coefficient were used to assess the relationship between the ASR and socio-demographic index (SDI).
The number of drug use disorders’ cases increased by 33.5% from 1990 to 2017 globally, whereas the ASR exhibited a stable trend. The ASR was higher in men than in women. Most cases (53.1%) of drug use disorders involved opioid. A positive association (ρ=0.35, p < 0.001) was found between ASR and SDI. Teenagers aged 15–19 years had the highest incidence rate.
The incident cases of drug use disorders were increasing, but the incidence rate did not change significantly from 1990 to 2017. Current preventive measures and policies for drug use disorders might have little effect. The present results suggest that future strategies should focus on men, teenagers and high-risk regions in order to improve the current status of drug use disorders.
Schizophrenia is a complex mental disorder with high heritability and polygenic inheritance. Multimodal neuroimaging studies have also indicated that abnormalities of brain structure and function are a plausible neurobiological characterisation of schizophrenia. However, the polygenic effects of schizophrenia on these imaging endophenotypes have not yet been fully elucidated.
To investigate the effects of polygenic risk for schizophrenia on the brain grey matter volume and functional connectivity, which are disrupted in schizophrenia.
Genomic and neuroimaging data from a large sample of Han Chinese patients with schizophrenia (N = 509) and healthy controls (N = 502) were included in this study. We examined grey matter volume and functional connectivity via structural and functional magnetic resonance imaging, respectively. Using the data from a recent meta-analysis of a genome-wide association study that comprised a large number of Chinese people, we calculated a polygenic risk score (PGRS) for each participant.
The imaging genetic analysis revealed that the individual PGRS showed a significantly negative correlation with the hippocampal grey matter volume and hippocampus–medial prefrontal cortex functional connectivity, both of which were lower in the people with schizophrenia than in the controls. We also found that the observed neuroimaging measures showed weak but similar changes in unaffected first-degree relatives of patients with schizophrenia.
These findings suggested that genetically influenced brain grey matter volume and functional connectivity may provide important clues for understanding the pathological mechanisms of schizophrenia and for the early diagnosis of schizophrenia.
The Chinese Solar and Geophysical Data (CSGD) was first issued at the Beijing Astronomical Observatory, Chinese Academy of Sciences (now the headquarter of the National Astronomical Observatories, Chinese Academy of Sciences) in 1971, when China’s satellite-industry was booming. CSGD covers the observational data (observations of the sunspots, solar flares, solar radio bursts, ionospheric storm and geomagnetic storm) from a couple of domestic observatories and the forecast data. The compiler of CSGD still keeps the data exchange with other institutes worldwide. The type of the dataset includes texts, tables, figures and so on. Up to now, we have electronized all the historic archives, making them easily accessible to people who are interested in them.
In this paper we consider the computation of some eigenpairs with smallest eigenvalues in modulus of large-scale polynomial eigenvalue problem. Recently, a partially orthogonal projection method and its refinement scheme were presented for solving the polynomial eigenvalue problem. The methods preserve the structures and properties of the original polynomial eigenvalue problem. Implicitly updating the starting vector and constructing better projection subspace, we develop an implicitly restarted version of the partially orthogonal projection method. Combining the implicit restarting strategy with the refinement scheme, we present an implicitly restarted refined partially orthogonal projection method. In order to avoid the situation that the converged eigenvalues converge repeatedly in the later iterations, we propose a novel explicit non-equivalence low-rank deflation technique. Finally some numerical experiments show that the implicitly restarted refined partially orthogonal projection method with the explicit non-equivalence low-rank deflation technique is efficient and robust.
Low-temperature stress is an important limiting factor to tobacco growth in early spring of south China. In this study, a low-temperature-resistant agent (LTRA) was employed to examine its ameliorating effect on the inhibition of tobacco growth triggered by low-temperature stress. Results indicated that low-temperature stress of 12 °C for 6 days reduced root number and biomass of tobacco seedling by 27.4% and 24.1%, while treatment with LTRA could recover the inhibitory effect of low-temperature stress on tobacco growth significantly. The content of ascorbic acid and the activities of superoxide dismutase and catalase at low-temperature stress were 65.2%, 53.5% and 32.1% of those at normal temperature condition (26 °C), while the corresponding values with LTRA treatment were 89.2%, 88.9% and 74.2%, suggesting that LTRA treatment could enhance the activity of antioxidant enzyme and the synthesis of antioxidant compounds. Low-temperature stress increased the membrane permeability by 84.8%, while LTRA treatment recovered it by 77.4%. Furthermore, LTRA treatment contributed to increase chlorophyll synthesis and maintain the integrity of tobacco leaf structure. Effective component analysis indicated that the complex of ammonium calcium nitrate and glycine betaine was the main effective component of LTRA in maintaining membrane integrity. Its effective concentration was 1.0 g L−1. The above results suggested that LTRA could enhance the synthesis of chlorophyll, activate the activity of antioxidant enzyme, maintain the integrity of cell membrane, and thus elevate the tolerance of tobacco seedlings to low-temperature stress.
To evaluate the prevalence of vitamin D deficiency and insufficiency, as well as their association with Hb and elevated blood lead levels (BLL) in children in China.
A cross-sectional and 1-year retrospective study.
Department of Laboratory Medicine, West China Second University Hospital, Sichuan University, China.
Children aged from 6 months to 14 years living in south-west China who were taken to physical examinations (January–December 2011).
Of 1218 children included in the study, 25-hydroxyvitamin D (25(OH)D) concentration (mean 33·18 (sd 16·48) ng/ml) was deficient in 21·6 % and insufficient in 27·4 %, which were higher than the prevalence of both anaemia at 8·5 % and elevated BLL (Pb ≥ 10 μg/dl) at 1·8 %, but lower than mildly elevated BLL prevalence (5 μg/dl ≤ Pb < 10 μg/dl) at 56·9 %. There was a negative correlation between 25(OH)D concentration and BLL (r = −0·216, P < 0·001) while no significant relationship was found between 25(OH)D concentration and Hb (r = −0·012, P > 0·05). After multivariable adjustment, the significant predictors of 25(OH)D deficiency and insufficiency were increasing child age especially between 8 and 14 years (OR = 18·29; 95 % CI 10·14, 32·99; P < 0·001) and BLL (OR = 1·01; 95 % CI 1·00, 1·02; P = 0·045).
The prevalence of 25(OH)D deficiency and insufficiency was much higher than that of anaemia or elevated BLL in south-west China, and associated with increasing age and BLL.
Amplified fragment length polymorphism (AFLP) markers linked to the stem nematode resistance gene were developed in sweet potato (Ipomoea batatas (L.) Lam.). Using bulked segregant analysis (BSA), 800 AFLP primer combinations were screened in the resistant and susceptible bulked DNA from the 186 progeny of an F1 single-cross population of Xu781 (resistant parent)×Xushu18 (susceptible parent), and 245 of these AFLP primers showed polymorphic bands between resistant and susceptible DNA. Primer combinations detecting polymorphism between the two bulks were used to screen the parents and eight individuals from each of the bulks. The results showed that E2M23 and E33M20 produced a specific band of about 500 bp and 200 bp in length, respectively, in the resistant plants but not in the susceptible plants, suggesting that the markers named E2M23500 and E33M20200 linked to a gene for stem nematode resistance. Amplified analysis of the 186 F1 individuals indicated that the genetic distance between these two markers and the stem nematode resistance gene was 6.9 cM and 11.1 cM, respectively, measured with Mapmaker 3.0. These two AFLP markers were used to identify ten sweet potato varieties planted widely in China and the results were consistent with those of conventional resistance identification, indicating that the two markers can be used in molecular marker-assisted breeding for stem nematode resistance in the sweet potato.
The present study was designed to evaluate the feasibility of producing pig transgenic blastocysts expressing enhanced green fluorescent protein (GFP) and to examine the effects of shape and preparation methods of donor cells on in vitro developmental ability of pig nuclear transferred embryos (NTEs). In experiment 1, the effect of GFP transfection on development of pig NTEs was evaluated. The cleavage and blastocyst rates showed no significant difference between NTEs derived from transfected and non-transfected donors. In experiment 2, the effect of different nuclear donor preparation methods on in vitro development of NTEs was examined. The cleavage rate showed no statistically significant differences among three preparation methods. The blastocyst rates of donor cells treated once at −4 °C and those of freshly digested cells were similar to each other (26.3% vs 17.9%). The lowest blastocyst rates (5.88%) were observed when cells cryopreserved at −196 °C were used as donors. In experiment 3, the effect of different cell cycle synchronization methods on the in vitro development potential of pig NTEs was evaluated. The cleavage rate of NTEs derived from cycling cells was much better than that of NTEs derived from serum-starved cells (64.4% vs 50.5%, p < 0.05), but no significant difference was observed between the the blastocyst rates of the two groups. In experiment 4, the effect of different shapes of cultured fibroblast cells on the in vitro development of pig NTEs was examined. The fusion rate for couplets derived from rough cells was poorer than that observed in couplets derived from round smooth cells (47.8% vs 76.8%, p < 0.05). However, there were no significant differences observed in the cleavage rate and blastocyst rate. In conclusion, the present study indicated that (i) refrigerated pig GFP-transfected cells could be used as donors in nuclear transfer and these NTEs could be effectively developed to blastocyst stage; (ii) serum starvation of GFP-transfected cells is not required for preimplantation development of pig NTEs; and (iii) a rough surface of GFP-transfected donor cells affects fusion rate negatively but has no influence on the cleavage rate or blastocyst rate of pig NTEs.
This study was designed to examine the effects of extracellular reduced glutathione on development of pig embryos, produced by in vitro maturation (IVM) and in vitro fertilisation (IVF), in a chemically defined North Carolina State University (NCSU) 23 medium or in NCSU 23 medium with bovine serum albumin (BSA). Microfilament distribution, as a marker of embryo quality, was also examined by immunocytochemical staining and confocal microscopy. When the inseminated oocytes were cultured in the defined medium containing 0-0.5 mM glutathione, blastocyst formation as observed only in the media with glutathione (8.5-16.0%). Increased numbers of blastomeres were observed in the blastocysts as the concentration of glutathione was increased (18.8±7.2 to 31.0±8.6). In NCSU 23 medium with 4 mg BSA/ml, addition of glutathione at concentrations of 0.125-0.5 mM significantly increased the proportions of oocytes that developed to blastocysts (39.2-52.5%) compared with the control (29.5%). However, no difference was observed in the average cell number in the blastocysts (41.9±15.6 to 49.1±15.5). There were no significant differences in the microfilament distribution in the embryos produced in the defined medium and in the BSA-containing medium. These results indicate that pig embryos produced by IVM/IVF can develop to the blastocyst stage in a defined medium. BSA and glutathione have a synergistic effect on pig embryo development.
The present study examined the effect of low culture temperature during in vitro maturation (IVM) of pig oocytes on their nuclear maturation, fertilisation and subsequent embryo development. In experiment 1, oocytes were cultured at 35 or 39 °C for 44 h in modified tissue culture medium 199 supplemented with 10 ng/ml epidermal growth factor, 0.57 mM cysteine, 75 μg/ml potassium penicillin G, 50 μg/ml streptomycin sulphate, 0.5 μg/ml LH and 0.5 μg/ml FSH to examine the nuclear maturation status. In experiment 2, oocytes were cultured at 35 °C for 44 or 68 h and nuclear maturation was examined. In experiment 3, oocytes matured for 44 or 68 h at 39 °C and for 68 h at 35 °C were co-incubated with frozen-thawed spermatozoa for 5-6 h. Putative embryos were transferred into North Carolina State University (NCSU) 23 medium containing 0.4% bovine serum albumin. At 12 h after insemination, some oocytes were fixed to examine the fertilisation rate and the remaining embryos were examined at 48 and 144 h for cleavage and blastocyst formation rate, respectively. Compared with 39 °C, culture of oocytes at 35 °C for 44 h significantly (p < 0.05) reduced the metaphase II (M II) rate (79% vs 12%). However, extension of culture time to 68 h at 35 °C significantly increased (p < 0.05) the M II rate (7% vs 58%). In experiment 3, compared with other groups, fewer (p < 0.05) oocytes reached M II when cultured at 35 °C for 68 h (69-81% vs 49%). Extension of culture duration to 68 h at 39 °C stimulated spontaneous activation (28%) of oocytes. No difference in cleavage rates was observed among different groups. Compared with oocytes matured for 44 h at 39 °C (31%), the proportion of blastocysts obtained was low (p < 0.05) for oocytes matured at 35 °C (13%) or 39 °C (3%) for 68 h. The results indicate that lower culture temperature can delay nuclear maturation of pig oocytes. However, extension of culture time can stimulate nuclear maturation and these oocytes are capable of fertilisation and development to the blastocyst stage at moderate rates.
Actin filaments play an important role in cell division. The present study was designed to examine the relationship between actin filament distribution and pig embryo development. When in vivo matured and fertilised pig oocytes were cultured in TCM 199 or NCSU 23, in various proportions, 45–65% of inseminated oocytes developed to the 2- to 4-cell stages but blastocyst development was observed only in NCSU 23 (34%) or NCSU 23 containing 10% TCM 199 (7%). Supplementation of NCSU 23 medium with 20% or more TCM 199 resulted in no blastocyst formation. Examination of actin filaments indicated that microfilaments were distributed in the cortex, at the junction of blastomeres and in the perinuclear area in the embryos cultured in NCSU 23, but perinuclear actin filaments were not observed in embryos cultured in TCM 199. When 2- to 4-cell stage embryos obtained from TCM 199 were transferred to NCSU 23 medium at 36 h after in vivo fertilisation, 57% of the cleaved embryos developed to blastocysts, which was no different from the proportion obtained after culture in NCSU 23 alone (56%). In addition, when 2- to 4-cell stage embryos obtained from TCM 199 were transferred to NCSU 23, most embryos showed perinuclear actin filaments within 6 h. The results indicate that the composition of the culture medium plays an important role in the polymerisation of actin filaments, which in turn influences embryo development. It is possible that pig embryo development was blocked by some components in TCM 199 which prevented actin filament polymerisation.
Based on QR-like decomposition with column pivoting,
a new and efficient numerical method for solving symmetric matrix inverse
eigenvalue problems is proposed, which is suitable for both the distinct and
multiple eigenvalue cases. A locally quadratic convergence analysis is given.
Some numerical experiments are presented to illustrate our results.
The present study examined the effect of different concentrations of cysteine in the presence of a thiol compound, β-mercaptoethanol (BME), during in vitro maturation (IVM) of pig oocytes on cumulus expansion, nuclear maturation, intracellular glutathione (GSH) level and subsequent embryonic development after in vitro fertilisation (IVF). In experiment 1, oocytes were matured in NCSU 23 medium containing 10% porcine follicular fluid, 25 μM BME, 0.5 μg/ml LH, 0.5 μg/ml FSH and 0, 0.1, 0.2 or 0.4 mg/ml cysteine for 20–22 h and then without hormonal supplements for an additional 20–22 h. After culture, cumulus cells were removed and a proportion of oocytes fixed to examine the rate of nuclear maturation. The remaining oocytes were co-incubated with spermatozoa for 5–6 h and putative zygotes were transferred to NCSU 23 medium containing 0.4% bovine serum albumin for 144 h. A proportion of putative zygotes were fixed 12 h after insemination to examine fertilisation parameters. In experiment 2, oocytes were matured as in experiment 1 and the GSH content was measured by a DTNB-GSSG reductase recycling assay. No mean differences among treatments were observed in nuclear maturation (78–89%). The mean differences in penetration rate (69–77%), polyspermy rate (31–40%), male pronuclear formation rate (93–96%) or mean number of sperm per oocyte (1.5-1.8) were not affected by the presence or absence of cysteine during oocyte maturation. Also no difference was observed in cleavage rates 48 h after insemination. However, compared with no addition (19%), the presence of 0.1-0.4 mg/ml cysteine during IVM increased (p < 0.001) the proportion of blastocysts (32–39%) at 144 h. In comparison with controls (5.6 pmol/oocyte), the GSH content of oocytes matured in the presence of cysteine was significantly (p < 0.001) higher (13–15 pmol/oocyte) with no mean differences among different cysteine concentrations. The results indicate that in the presence of a thiol compound, supplementation of IVM medium with cysteine can increase the GSH level and improve the developmental competence of pig oocytes following fertilisation. Further, no effect on either GSH level or embryo development was observed by increasing the levels of cysteine supplementation from 0.1 to 0.4 mg/ml.
Our previous study indicated that thimerosal is one of the most effective artificial activators to mimic sperm-induced increases in the intracellular free calcium concentration ([Ca2+]i) and other activation events in pig oocytes (Macháty et al., 1997). The present study was conducted to examine the temporal relationship between intracellular calcium transients, cortical granule (CG) exocytosis and the zona reaction induced by thimerosal. When pig oocytes matured in vitro were exposed to 200 μM thimerosal the first intracellular calcium transient, with a mean peak ratio of 4.97 ± 1.14, was observed 509.64 ± 122.03 s after addition of thimerosal. The density of CGs fell significantly from 63.3 ± 11.7 CGs/100 μm2 of cortex in control oocytes to 25.7 ± 19.2 CGs/100 μm2 of cortex (59.4% release) at 2 min after the first intracellular calcium transient. At 5 min after the calcium transient the residual CG density had been reduced to 10.7 ± 10.4 CGs/100 μm2 of cortex (83.1% release). This degree of CG exocytosis was the same as that in oocytes penetrated by sperm (9.5 ± 5.1 CGs/100 μm2 of cortex). No further decrease in residual CG density was observed at 10 min (10.3 ± 14.8 CGs/100 μm2 of cortex). Whereas 77.4% (120/155) of control oocytes were penetrated by spermatozoa only 1.4% (2/144) of thimerosal-treated oocytes were penetrated. Further experimental results obtained by in vitro fertilisation of oocytes with preincubated (capacitated) spermatozoa suggested that the zona block to sperm penetration in thimerosal-treated oocytes occurred within 35 min after CG exocytosis and 40 min after the first calcium transient. These results indicate that polyspermic penetration of pig oocytes inseminated in vitro is not due to delayed or incomplete CG exocytosis but more likely to a delayed zona reaction and/or simultaneous sperm penetration.
The generation of undesirable ashes from municipal and hazardous waste incineration, and from coal-fired power plants has become a serious environmental problem. Ash contains heavy metals and/or unburned organics, and the disposal of this material is drawing increased concern from the public and government agencies. Since the leaching of a toxic constituent from a powder is proportional to the surface area of the powder, any method of consolidation is welcome. The interest of such a consolidation process would be greatly increased if, in addition to making this material safe, a commercially useful material could be produced. Conventional methods of heating such as oil-fired furnaces require large flows of air. They are also time and energy consuming because it is relatively difficult to heat up a powder. Microwave processing creates rapid heating and allows for the attainment of uniformly high temperatures; therefor, it is a viable alternative. However, most ashes will not easily absorb microwaves if they do not contain a phase that couples with the microwaves. Transition metal oxides are lossy materials when submitted to microwave radiation. If they are mixed into ashes in a sufficient amount, they will generate heat, cause sintering and reduce the surface area of the powder. In the present work, coal ash-derived bricks and tiles were successfully obtained. Details of processing, mechanical properties and chemical durability of these consolidated ceramics are presented
Email your librarian or administrator to recommend adding this to your organisation's collection.