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Objective To compare tooth movement rate and histological responses with three different force magnitude designs under osteoperforation in rabbit models. Methodology 48 rabbits were divided into three groups: Group A, Group B, and Group C, with traction force of 50 g, 100 g, 150 g, respectively. Osteoperforation was performed at the mesial of the right mandibular first premolar, the left side was not affected. One mini-screw was inserted into bones between two central incisors. Coil springs were fixed to the first premolars and the mini-screw. Tooth movement distance was calculated, and immunohistochemical staining of PCNA, OCN, VEGF, and TGF-β1 was analyzed. Results The tooth movement distance on the surgical side was larger than the control side in all groups (P0.05). For the control side, tooth movement distance in Group A was significantly smaller than Groups B and C (P0.05). On the tension area of the moving premolar, labeling of PCNA, OCN, VEGF and TGF-β1 were confirmed in alveolar bone and periodontal ligament in all groups. PCNA, OCN, VEGF and TGF-β1 on the surgical side was larger than the control side in all groups (P

Background This is a retrospective study that compares mandibular growth changes in skeletal Class II patients treated by rapid maxillary expansion (RME) and following fixed appliance with those patients treated by Twin-Block (TB) and following fixed appliance. Methods Fourteen patients treated by RME and following fixed appliance were included into the RME group. Fifteen patients treated by Twin-Block and following fixed appliance were included into the TB group. Lateral cephalometric radiographs taken before treatment and immediately after fixed appliance treatment were used to evaluate mandibular growth effects. Results The starting forms of the patients in the two groups were examined to be of good comparability. The mandibular length increased significantly in both groups as measured by Co-Gn, Go-Gn and Ar-Gn, but the TB group didn’t show more mandibular growth than the RME group (P > 0.05). Skeletal changes of the mandible in vertical dimension were different in the two groups. The change in FMA was 0.35° in the RME group, while the change was 2.65° in the TB group (P P Conclusion The investigated Phase I treatment with RME followed by Phase II treatment of fixed appliance achieved the same increases in sagittal mandibular growth and facial profile improvements as the Twin-Block therapy. The treatment with RME followed by fixed appliance was better for vertical control, while the treatment with Twin-Block followed by fixed appliance significantly increased the mandibular plane angle.

Dissertação de mestrado em International Business, In international trade settlement, letters of credit (documentary credit), documentary collections, and remittances are generally accepted international settlement methods. Letters of credit take the leading position, with the characteristics of bank credit and the reciprocal rights and obligations of buyer and seller. It has the function of guaranteeing security to both exporters and importers; therefore, it is relatively safe means of settlement, which guarantees the adequate functioning of international transactions. However, due to their characteristics, letters of credit are not exempt from risks in their practical application. Therefore, the study of the risk and preventive measures of the letter of credit has a strong relevance to the practice of international trade. This dissertation mainly analyzes the risk that the applicant, the bank (issuing bank and negotiating bank) and the beneficiary may face in the process of using the credit, and puts forward the corresponding risk prevention measures. Using a qualitative approach, we found a unique perspective and new findings on the risk and risk prevention measures. The results of this exploratory study suggest that there is a consensus in considering the principle of letter of credit independence as one of its main sources of risk. This consensus suggests that future development of the letter of credit involves reducing their independence, without completely losing its independence essence. The evolution of letters of credit may also include the cooperative development of operations and the use of digital platforms to facilitate the investigation of the credibility of business partners., No comércio internacional, letras de crédito (crédito documentário), cobranças documentárias e remessas são os métodos de pagamento geralmente aceites. A letra de crédito assume a posição de liderança enquanto forma de pagamento no comércio internacional com as características do crédito bancário e os direitos e obrigações recíprocos do comprador e do vendedor. Tem a função de garantir a segurança a importadores e exportadores, sendo uma forma de liquidação relativamente segura, que garante a condução normal das transações internacionais. No entanto, pelas suas características, as letras de crédito não estão isentas de risco na sua aplicação prática. Portanto, o estudo do risco e das medidas preventivas do risco da carta de crédito tem uma forte relevância para a prática comercial internacional. Esta dissertação analisa principalmente o risco que o ordenador (comprador), os bancos (banco emitente e banco negociador) e o beneficiário (vendedor) podem enfrentar no processo de utilização das letras de crédito e discute as correspondentes medidas de prevenção de risco. Com base numa abordagem qualitativa, foi possível obter uma perspetiva prática sobre os riscos e as correspondentes medidas de prevenção de risco. Os resultados deste estudo exploratório sugerem que existe um consenso em considerar o princípio da independência da carta de crédito como uma das suas principais fontes de risco. Esse consenso sugere que o desenvolvimento futuro da letra de crédito deverá passar por reduzir a sua independência, mas sem perder completamente a sua essência de independência. A evolução também deverá incluir o desenvolvimento cooperativo das operações e o uso das plataformas digitais para facilitar a investigação da credibilidade dos parceiros de negócios.

The economically important Luzong ore district, located at the north-eastern margin of the South China Block, developed numerous Fe–Cu–Pb–Zn–U deposits during the Early Cretaceous. The identified uranium deposits are primarily granite-related vein-type deposits distributed in the exposed granites and adjacent Jurassic sediments along the SE edge of the Luzong volcanic basin. Recently, new uranium mineralisation has been discovered by scientific drilling in concealed syenite in the centre of the Luzong basin. In this study, we conducted detailed studies of geological characteristics and determined the geochronology of the uranium mineralisation to constrain the ore-forming process. Luzong scientific drilling (LTZK01) penetrated Quaternary loose surface deposits (0–2 m), Cretaceous volcanic rocks (2–1488.84 m), concealed syenite and monzonite (1488.84–2012.35 m), and uranium mineralisation (1506–1742 m). Uranium mineralisation predominantly occurs as uranothorite in hydrothermal veins along the intragranitic fractures and breccias, which are associated with a pyrite-quartz-albite-tourmaline-phlogopite gangue assemblage. LA-ICPMS U–Pb dating of zircons from syenite and monzonite yields crystallisation ages of 131.4 ± 1.6 (MSWD = 0.45) and 131.7 ± 1.0 Ma (MSWD = 0.87), respectively. Based on the close textural relationship with other hydrothermal minerals, morphology, and trace element features, the zircons from the uraniferous veins are of a hydrothermal origin. In-situ LA-ICPMS U–Pb dating of hydrothermal zircons yielded a weighted mean age of 131.1 ± 1.6 Ma (MSWD = 3.6), which is consistent with the hydrothermal phlogopite 40Ar–39Ar plateau age of 129.25 ± 1.51 Ma (MSWD = 7.70). These ages indicate that uranium mineralisation in LTZK01 is marginally younger than the crystallisation of the host igneous rocks and might be associated with the post-magmatic hydrothermal process. Based on the magmatic and mineralisation ages obtained in this study and previous researches, we propose that the uranium was probably fractionated from the felsic melt into F-rich magmatic fluids to form uraniferous veins in LTZK01 as the pressure and/or temperature decreased.

The Shizishan ore field is the largest gold–copper ore field in the Tongling ore district of Anhui Province, China. Copper and gold deposits in the district are present as one-commodity deposits or as deposits with both commodities. Copper and gold mineralization are either cogenetic or are temporally and spatially distinct. We present the results of systematic geochemical analysis of fluid inclusions from typical Au–Cu deposits in the Shizishan ore field; these data are used to determine the solubility of Cu and Au in the ore-forming fluids and to ascertain the mechanisms and factors that controlled variations in the association and separation of copper and gold mineralization. Our results indicate that copper in the ore-forming fluids was transported as CuCl2− and CuCl0 complexes and that the solubility of copper was controlled by variations in Cl− concentration. In addition, the precipitation of copper was controlled by changes in temperature, pH, fO2, and fO2. In comparison, gold in the ore-forming fluids was transported as Au(HS)2− and Au2S(HS)22− complexes, and the solubility of gold was controlled by variations in total sulfur concentration; the precipitation of gold was controlled by temperature, pH, fO2, and fO2. These differences between the two elements meant that copper and gold in the ore-forming fluids responded in different ways to changes in physicochemical conditions. Copper precipitated under relatively acidic conditions at high temperatures, while gold precipitated under weakly alkaline conditions at relatively low temperatures; this dissociation resulted in the temporal and spatial separation and zonation of copper and gold mineralization in the Shizishan ore field.