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Objective: To examine the effect of surgical treatment in children with pulmonary artery sling and the surgical treatment strategy. Methods: Relevant data of 110 children with pulmonary artery sling admitted to the Department of Cardiac Surgery, Children's Hospital Affiliated to Shandong University from February 2017 to July 2022 were retrospectively analyzed. There were 55 males and 55 females, aging (M(IQR)) 9.0 (10.6) months (range: 1 to 96 months). The weight was 7.8 (3.5) kg (range: 2.5 to 25.0 kg). Of the 110 patients, 108 had different degrees of tracheal stenosis and 2 had normal trachea. Left pulmonary artery transplantation and tracheoplasty were performed in 78 patients. Left pulmonary artery transplantation was performed in 30 patients (11 in our hospital and 19 in other hospitals) due to the lack of an early tracheoplasty technique, in which 24 patients needed stage â ¡ tracheoplasty due to obvious respiratory symptoms and limited activity endurance, and 6 cases did not intervene. Two children with normal trachea only underwent left pulmonary artery transplantation. Results: Among the 78 children who underwent surgery in the same period, 70 cases recovered smoothly after surgery, of whom respiratory symptoms were significantly reduced or disappeared during the 1 to 65 months follow-up, with similar activity endurance to normal children of the same age. Eight cases died, including 4 cases of postoperative multi-drug resistant bacteria infection, died from tracheal anastomotic opening or septic shock, 1 cases with severe congenital heart disease died from postoperative low cardiac output syndrome difficult to correct, 1 case died from blood pressure could not be maintained due to the compressed left pulmonary artery after transplantation, 2 cases of postoperative digestive system diseases (adhesive intestinal obstruction, gastrointestinal bleeding, etc.). The 24 patients in the staging group were followed for 1 to 84 months. All patients needed stage â ¡ tracheoplasty due to respiratory symptoms and decreased endurance to activity. Eight cases of the non-intervention tracheal group were successfully separated from the ventilator, cured and discharged in a short period of time. Conclusions: Most children with pulmonary artery sling have tracheal stenosis. Children with low degree of tracheal stenosis and inconspicuous respiratory symptoms can only undergo left pulmonary artery transplantation by lateral thoracotomy. For patients combined with severe tracheal stenosis or obvious respiratory symptoms, a simultaneous left pulmonary artery transplantat and tracheoplasty is recommended.
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Objective: To examine the treatment strategy of congenital tracheal stenosis associated with non-vascular ring cardiac malformations. Methods: This is a retrospective case series. Clinic data from 24 children with tracheal stenosis who underwent surgical treatment in the Department of Cardiac Surgery, Children's Hospital Affiliated to Shandong University from February 2017 to March 2023 were retrospectively collected. There were 16 males and 8 females, aged (M(IQR)) 6.5 (19.6) months (range: 2.2 to 66.3 months) and weighted 5.95 (4.76) kg (range: 3.2 to 20.0 kg). All patients had obvious respiratory symptoms. Eighteen patients underwent cardiac malformation correction and tracheoplasty at the same time (simultaneous group). Six patients in the staged operation group were treated with cardiac malformation correction in the first stage operation and tracheoplasty in the second stage operation due to missed diagnosis or delayed diagnosis of tracheal stenosis or no condition for tracheoplasty. Slide tracheoplasty was used to correct tracheal stenosis in both groups. The recovery of the children was followed. Wilcoxon sign rank test was used for comparison between the two groups. Results: There was no death during the perioperative period and hospitalization. In the simultaneous group, 1 case with delayed chest closure underwent bedside chest closure after 52 hours, 2 cases were intubated again after operation, and 1 case was implanted with an endotracheal stent. The duration of mechanical ventilation was 40.5 (39.6) hours (range: 19.0 to 438.8 hours). In the staged group, there was 1 case of re-intubation after operation, combined with left vocal cord paralysis and respiratory multidrug-resistant bacterial infection (Acinetobacter baumanii). One patient underwent 3 times of bronchoscopic balloon dilatation of the right middle bronchus, and heart rate returned to normal range. The duration of mechanical ventilation was 19.0 (21.4) hours (range: 17.1 to 96.7 hours). During follow-up, a patient in the simultaneous group was prone to respiratory infection and had good exercise tolerance, 1 patient in the staged group still had sputum stridor in the throat 3 months after the operation, and symptoms improved significantly 6 months after the operation. The other children didn't have obvious respiratory symptoms. Conclusions: The diagnosis of tracheal stenosis may be delayed or missed when tracheal stenosis is complicated by non-vascular ring cardiac malformations. One-stage correction of tracheal stenosis and cardiac malformation can achieve a good outcome.
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Objective: To examine the outcomes of Slide tracheoplasty for the children with severe congenital tracheal stenosis received previous repeated balloon dilatation or metal stent placement under endoscopy. Methods: A retrospective study was conducted in 9 children with congenital tracheal stenosis undergoing previous interventional therapy under tracheoscopy and later received Slide tracheoplasty due to obvious respiratory symptoms at Department of Cardiac Surgery, Qilu Children's Hospital of Shandong University between February 2017 and July 2021. There were 7 males and 2 females with a median age at operation of 72.4 months (range: 13.3 to 98.9 months), and the median weight was 19.0 kg (range: 9.0 to 33.0 kg). Among the 9 patients, 2 patients began to receive repeated balloon dilatation (more than 3 times) 17.8 and 51.8 months ago respectively. One patient received metal stents placement into the trachea for 4 days and the other 6 children for median 56.8 months (range: 21.6 to 74.2 months). Complete tracheal cartilage rings and long segmental stenosis were present. in all 9 children. Operative details and outcome measures, including the need for endoscopic airway intervention and mortality, were collected. Results: Slide tracheoplasty was performed in all cases. Two patients with repeated balloon dilatation had different thickness of tracheal wall, local scar hyperplasia and irregular lumen. Among them, 1 case had obvious local calcification of tracheal wall, which was difficult to suture. The metal stent in one patient with short time of placement was completely removed. However, only part of the metal stents could be removed due to the long placement time in the other 6 cases. There was no operative death in the 9 children. The median postoperative tracheal intubation time was 25.3 hours (range: 17.4 to 74.5 hours). A silicone stent was placed in the trachea of 1 child due to obvious respiratory symptoms. Follow-up of median 11 months (range: 1 to 23 months) showed that no death occurred after discharge and all children had basically normal activity tolerance with no obvious respiratory symptoms. Conclusions: Slide tracheoplasty is feasible for children undergoing prior balloon dilatation or metal stents placement. Previously repeated balloon dilatation or metal stent placement under endoscopy increased the difficulty of slide tracheoplasty, the metal stent could not be completely removed after a long time.
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Procedimentos de Cirurgia Plástica , Estenose Traqueal , Criança , Constrição Patológica , Dilatação , Endoscopia , Feminino , Humanos , Lactente , Masculino , Estudos Retrospectivos , Stents , Traqueia/cirurgia , Estenose Traqueal/congênito , Estenose Traqueal/cirurgia , Resultado do TratamentoRESUMO
OBJECTIVE: While cartilaginous endplate (CEP) avulsion is a common finding in discectomy due to lumbar disc herniation, its roles in residual back and leg pain, associations with Modic changes (MCs) and endplate defects (EPD) remain unknown. DESIGN: Patients with a single-level lumbar disc herniation who underwent endoscopic discectomy were studied. On MR images, the adjacent endplates of the herniated disc were assessed for MCs and EPD. The presence of CEP avulsion was examined under endoscopic and visualized inspection. Back and leg pain were evaluated by a numeric rating scale (NRS) and the Oswestry Disability Index. Associations of CEP avulsion with adjacent MCs, EPD, and residual back and leg pain were examined. In addition, histological features of avulsed CEP were determined using gross staining and immunohistochemical methods. RESULTS: A total of 386 patients were included. CEP avulsion was found in 166 (43%) patients, and adjacent MCs and EPD were observed in 117 (30.3%) and 139 (36%) patients. The presence of CEP avulsion was associated with greater age, adjacent MCs (OR = 2.60, 95%CI [1.61-4.19]) and EPD (OR = 1.63, 95%CI [1.03-2.57]). Among the 187 patients with ≥2 years follow-up, CEP avulsion was associated with residual back pain (OR = 2.49, 95%CI [1.29-4.82]) and leg pain (OR = 2.25, 95%CI [1.04-4.84]). Histologically, the avulsed CEP was characterized by multiple defects, apparent inflammation, and nucleus invasion, as well as the upregulation of IL-1ß, caspase-1, and NLRP3 inflammasome. CONCLUSION: CEP avulsion was associated with MCs, EPD, and residual back and leg pain after discectomy, which may be attributed to NLRP3 inflammasome related inflammations.
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Dor nas Costas/etiologia , Cartilagem/lesões , Discotomia/efeitos adversos , Deslocamento do Disco Intervertebral/cirurgia , Fatores Etários , Cartilagem/diagnóstico por imagem , Cartilagem/metabolismo , Caspase 1/metabolismo , Dor Crônica/etiologia , Avaliação da Deficiência , Feminino , Seguimentos , Humanos , Interleucina-1beta/metabolismo , Vértebras Lombares , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Medição da Dor , Estudos Retrospectivos , Regulação para CimaRESUMO
We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of π^{0}'s produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.
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We report observations of gamma-ray emissions with energies in the 100-TeV energy region from the Cygnus region in our Galaxy. Two sources are significantly detected in the directions of the Cygnus OB1 and OB2 associations. Based on their positional coincidences, we associate one with a pulsar PSR J2032+4127 and the other mainly with a pulsar wind nebula PWN G75.2+0.1, with the pulsar moving away from its original birthplace situated around the centroid of the observed gamma-ray emission. This work would stimulate further studies of particle acceleration mechanisms at these gamma-ray sources.
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Objective: To compare the effect of different supraorbital foramen variations on the clinical efficacy of radiofrequency treatment of primary trigeminal neuralgia V1. Methods: The clinical data of 62 patients with primary trigeminal neuralgia (V1 branch) from February 2011 to August 2017 in the first hospital of Jiaxing were analyzed retrospectively. According to the shape of supraorbital foramen, the patients were divided into foramen group (n=28) and incisional group (n=34). The age, sex, course time, CT scan times of the two groups were recorded, and the mean rank of NRS scores and effective rates (NRS≤1) before operation, 1 day after operation, 6 months after operation, 1 year after operation and 2 years after operation were statistically analyzed, as well as the difference of numbness degree in 1 day and 2 years after operation. The short-term and long-term complications were recorded. Results: There was no significant difference in age, gender, course time, CT scan times, preoperative NRS and postoperative NRS between the two groups (P>0.05). Compared with the preoperative, the mean rank of NRS in the two groups decreased significantly at each postoperative time point, and the difference was statistically significant (all P<0.05). Foramen group of postoperative 1 d â , â ¡, â ¢, â £ numbness rate were 0, 53.6%, 46.4% and 0 respectively, after 2 years were 42.9%, 46.4%, 10.7% and 0 respectively. Incisional group of postoperative 1 d â , â ¡, â ¢, â £ numbness rate were 0, 29.4%, 67.6% and 2.9% respectively, after 2 years were 55.9%, 38.2%, 5.9% and 0 respectively. The degree of numbness 2 years after the operation was reduced in both groups compared with that 1 day after the operation, and the difference was statistically significant (all P<0.05). The effective rates of the foramen group and the incisional group were 78.6% and 52.9%, respectively, with statistically significant differences (χ(2)=4.406, P<0.05) . The patient had no other serious complications in the near and long term except for the swelling of puncture point. Conclusion: The short and long-term effective rates of supraperitoneal foramen in anatomical variants for the radiofrequency treatment of primary trigeminal neuralgia V1 are higher. The supraorbital foramen have higher long-term effective rates, there are no other serious adverse reactions excepting numbness, and the patients have a higher acceptability.
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Tratamento por Radiofrequência Pulsada , Neuralgia do Trigêmeo , Eletrocoagulação , Humanos , Estudos Retrospectivos , Resultado do Tratamento , Neuralgia do Trigêmeo/terapiaRESUMO
We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of a muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies E>100 TeV. As a result, we observed 24 photonlike events with E>100 TeV against 5.5 background events, which corresponds to a 5.6σ statistical significance. This is the first detection of photons with E>100 TeV from an astrophysical source.
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We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disk center in the "away" ("toward") interplanetary magnetic field (IMF) sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IMF strength in the away (toward) sector is 1.54±0.21_{stat}±0.20_{syst} (1.62±0.15_{stat}±0.22_{syst}) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar magnetic field.
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Objective: To investigate the relationship between the level of amniotic fluid inflammatory factor and the pregnancy outcome in patients with cervical incompetence. Methods: A retrospective case-control study was conducted. Totally 110 cases of pregnant women were diagnosed as cervical incompetence for cervical dilation at the medical examination in Sun Yat-sen Memorial Hospital of Sun Yatsen University, from January 1st, 2015 to December 31th, 2016. A total of 32 patients (29.1%, 32/110) were performed cervical cerclage. According to their neonatal outcomes, they were divided into live infant group (23 cases, 72%) and dead infant group (9 cases, 28%) . The demographic and clinical data of two groups were analyzed and compared. Results: The mean peripheral blood leucocyte counts, the median amniotic tumor necrosis factor-α (TNF-α) and the median interleukin-8 (IL-8) level of two groups were (10.5±2.8) ×10(9)/L vs (13.6±3.1) ×10(9)/L, 23.80 ng/L (14.9-85.5 ng/L) vs 379.00 ng/L (70.2-418.5 ng/L) , and 3 354 ng/L (1 020-7 500 ng/L) vs 7 500 ng/L (4 210-7 500 ng/L) respectively. The differences were statistically significant (all P<0.05) . The amniotic fluid IL-1ß, IL-2 receptor, IL-6, IL-10, C-reactive protein and procalcitonin were not significantly different (all P>0.05) between two groups. Conclusions: The peripheral blood leucocyte counts, amniotic fluid TNF-α and IL-8 level are the factors affecting the pregnancy outcome in women with cervical incompetence before cervical cerclage. When IL-8 is higher than 3 580 ng/L and TNF-α is higher than 105 ng/L, the death of perinatal infants could be predicted.
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Cerclagem Cervical , Interleucina-8 , Resultado da Gravidez , Segundo Trimestre da Gravidez/metabolismo , Incompetência do Colo do Útero/sangue , Líquido Amniótico , Proteína C-Reativa , Estudos de Casos e Controles , Feminino , Humanos , Gravidez , Estudos Retrospectivos , Fator de Necrose Tumoral alfa , Incompetência do Colo do Útero/cirurgiaRESUMO
A compact all-in-line graphene-based distributed feedback Bragg-grating fiber laser (GDFB-FL) with narrow linewidth of hundreds kHz is demonstrated and investigated in this study. Performing as an optical saturable absorber, graphene oscillates the initially kHz linewidth DFB-FL, and generates high-quality passively Q-switched pulses. Pumped with a 980 nm continuous-wave laser, the Q-switched GDFB-FL observes ~1 µs pulse durations, with pulse energies up to ~10 nJ and approaching the transform limit. The peak power is ~600 times higher than the original DFB-FL laser. By optimizing the cavity design and the graphene material, it is predicted that fast Q-switched pulses with more than MHz repetition rates and sub-100 ns pulse durations are achievable. Such transform-limited Q-switched GDFB-FLs with narrow linewidth of sub-MHz have long coherence length, good tunability, stability, compactness and robustness, with potential impact in optical coherent communications, metrology and sensing.
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We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the potential field source surface model and the current sheet source surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun's shadow observed in the TeV cosmic-ray flux.
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BACKGROUND: Lateral spinous process deviation (LSPD) is a commonly used morphological parameter in the anatomical study of the cervical spinous process. However, quantitative studies on this issue are still lacking. In this study we aimed to establish reference intervals of C2-C7 LSPD in the adult Chinese population and provide decision-making information for clinical practitioners. MATERIALS AND METHODS: This was a retrospective study of 92 adult patients who received neck computed tomography scans, including 42 females and 50 males meeting the inclusion criteria. Three-dimensional reconstruction and anatomical measurements were performed using Mimics Research 19.0 and 3-Matic Research 11.0. RESULTS: The inter-observer reliability of LSPD measurement in this study was excellent (intraclass correlation coefficient value > 0.93). Only 2 cases of LSPD angles of 90 degrees were found, which means most cervical spinous process exist deviation. The reference interval for the C2-C7 LSPD angle was (85.11, 94.75) degrees. The C2 LSPD showed the different directions to C5 and C7 (p < 0.05). In the C4 vertebrae, the male tends to have greater LSPD angles than the female (T = -2.013, p = 0.047). In the C2 vertebrae, there was a statistically significant but weak correlation between age and LSPD angles (r = 0.24, p = 0.029). There was no statistically significant effect of sex or age on other levels of cervical vertebrae. CONCLUSIONS: Cervical spinous process deviation of less than 5 degrees on either side is a common morphological manifestation in Chinese adults. Thus, LSPD may not be an indicator for clinical care. Moreover, the vertebrae may have opposite directions of LSPD in the upper levels (C2-C4) and lower levels (C5-C7).
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Vértebras Cervicais , População do Leste Asiático , Tomografia Computadorizada por Raios X , Adulto , Feminino , Humanos , Masculino , Vértebras Cervicais/diagnóstico por imagem , Reprodutibilidade dos Testes , Estudos Retrospectivos , Valores de ReferênciaRESUMO
Objective: To investigate the treatment options for multiple myeloma patients with central nervous system involvement (CNS-MM) , as well as their clinical characteristics and prognostic factors. Methods: Between January 2011 and January 2022 our center diagnosed 18 people with CNS-MM. A retrospective analysis was done on the clinical information from the initial diagnosis and central nervous system involvement, and it was compared to 1â¶3 matched newly diagnosed MM from the same period. Analysis was done on the clinical characteristics and survival rates of the two groups. Results: In patients with CNS-MM, the median time of onset was 14.2 (0.9-79.6) months and the median overall survival (OS) was 30.5 months from initial diagnosis and only 3.8 months in patients after CNS involvement. The CNS-MM patients showed more IgD type (P=0.010) , severer anemia (P=0.014) , a higher proportion of bone marrow plasma cells (P=0.013) , more extramedullary lesions (P=0.001) , and increased lactic dehydrogenase (LDH) (P=0.009) when compared to the control group. Lenalidomide or pomalidomide-based combinations had higher rates of hematology and CNS remission than bortezomib or daratumumab-based regimens (75.0% vs 16.7% , P=0.019) . Patients who received IMiD-based regimens and had 2 high-risk factors at initial diagnosis (high LDH and extramedullary lesions) had a significantly lower incidence of CNS-MM (P=0.026) . At the initial diagnosis, LDH (P=0.008, HR=7.319, 95% CI 1.663-32.219) and extramedullary lesions (P=0.006, HR=8.054, 95% CI 1.828-35.486) were independent risk factors for the occurrence of CNS-MM. Conclusion: Patients with CNS-MM had a poor prognosis. Patients with high LDH or extramedullary lesions at the time of the initial diagnosis are more likely to have CNS-MM. The prognosis of this patient may be improved by immunoregulator-based therapy.
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Mieloma Múltiplo , Humanos , Mieloma Múltiplo/tratamento farmacológico , Estudos de Casos e Controles , Estudos Retrospectivos , Lenalidomida/uso terapêutico , Prognóstico , Sistema Nervoso Central/patologia , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêuticoRESUMO
OBJECTIVE: Colon cancer is one of the most common and deadly types of gastrointestinal tumor. Despite progressive treatments, the patient prognosis has not been improved effectively. MATERIALS AND METHODS: Expression of miRNA and mRNA were tested by Realtime PCR. Cell cycle was detected by flow cytometry. Cell viability was evaluated by MTT assay. Cell spheroid formation was determined by colony assay. Wnt signaling pathway activity was evaluated by TOP/FOP ratio. Protein expression was tested using Western blot. ß-catenin binding ability was detected by ChIP assay. miRNA target gene was confirmed by luciferase assay. RESULTS: miR-590-3p was found to be overexpressed in both glioma tissues and cell lines. miR-590-3p is upregulated in colon cancer cells and tissues compared to non-tumorigenic colon cells and normal colon tissues. miR-590-3p positively regulated cell proliferation, spheroid formation, and cell cycle in LS174T cells. Conversely, inhibition of miR-590-3p reduced these effects. We confirmed that WIF1 and DKK1 are targets of miR-590-3p. Overexpression of miR-590-3p promoted TOP flash luciferase activity, enhanced nuclear ß-catenin levels and increased target genes expression of Wnt signaling pathway. The results indicated that miR-590-3p activates the Wnt/ß-catenin signaling pathway. CONCLUSIONS: We demonstrate that miR-590-3p regulates colon cancer progression via WIF1 and DKK1, which suggests that miR-590-3p may be a promising candidate for therapeutic applications in colon cancer treatment.
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Proteínas Adaptadoras de Transdução de Sinal/antagonistas & inibidores , Neoplasias do Colo/genética , Neoplasias do Colo/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , MicroRNAs/genética , Proteínas Repressoras/antagonistas & inibidores , Via de Sinalização Wnt , Ciclo Celular , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular , Neoplasias do Colo/patologia , Regulação para Baixo , Glioma/metabolismo , Humanos , Ensaio Tumoral de Célula-Tronco , Regulação para Cima , beta Catenina/metabolismoRESUMO
In this paper, we develop a methodological approach combining macro-X-ray fluorescence and synchrotron radiation-based techniques (µXRF, full-field XANES and µXRD) to determine the composition and microstructure of underglaze decors of Qinghua porcelains (Ming dynasty). Various transition metal elements (Fe, Mn, Co) are present in the blue decoration of these ceramics and the approach proposed allows for establishing the feature of each. Thus it shows that Fe ions are distributed homogeneously over the whole glaze without any significant difference in blue and white parts. They do not play a significant role in the color. In contrast, Co ions exhibit a heterogeneous distribution with CoAl2O4 particles close to the body/glaze interphase. These particles play a key role in the blue color and, the hue variations seem in greater part to link to their density and repartition. Co dispersed in the glassy matrix is also bivalent and mainly in tetragonal coordination, leading also to a blue color. Mn ion distribution is similar to the one of Co but without presenting local high concentrations associated to Mn based particles. Mn affects the darkness of the color and for the sample without CoAl2O4 particle; it is the main color contribution. The presence of CoAl2O4 crystals was confirmed by µXRD, which revealed, in addition, a variation of cell parameters certainly linking to a Co partial substitution.
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The frequencies of chromosomal aberration (CA) and sister chromatid exchange (SCE) in the peripheral blood lymphocytes of 21 lead-exposed workers from a battery factory were studied, and their blood lead (Pb-B) levels were determined. The results demonstrated that when the mean Pb-B level reached 50 micrograms/dl, the CA percentage increased significantly compared with that of the nonexposed controls. The CA percentage increased as the mean Pb-B level increased, showing a dose-effect relationship. When the mean Pb-B level was as high as 80 micrograms/dl, the rate of SCE in the lymphocyte was also increased significantly, but no correlation was observed between these two parameters. On the basis of such results, lead should be considered an agent harmful to the human chromosome.