浅谈客滚船重量重心控制原则

客滚船是连接陆岛间、岛屿间、海峡间的人车两用交通运输船舶,主要用于装运卡车、小汽车、旅客以及提供船上旅客住宿和娱乐服务,是世界造船领域中高技术含量,高附加值的型船,建造技术难度大。对于客滚船整个研制和建造,重量重心控制极为重要,重量重心控制原则是客滚船建造必不可少的关键技术之一。

Microbially-mediated formation of Ca-Fe carbonates during dissimilatory ferrihydrite reduction:Implications for the origin of sedimentary ankerite

The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to help solving the dolomite problem.The purpose of this study was to probe whether microbial activity can be involved in the formation of ankerite.Bio-carbonation experiments associated with microbial iron reduction were performed in batch systems with various concentrations of Ca^(2+)(0–20 mmol/L),with a marine iron-reducing bacterium Shewanella piezotolerans WP3 as the reaction mediator,and with lactate and ferrihydrite as the respective electron donor and acceptor.Our biomineralization data showed that Ca-amendments expedited microbially-mediated ferrihydrite reduction by enhancing the adhesion between WP3 cells and ferrihydrite particles.After bioreduction,siderite occurred as the principal secondary mineral in the Ca-free systems.Instead,Ca-Fe carbonates were formed when Ca^(2+)ions were present.The CaCO_(3) content of microbially-induced Ca-Fe carbonates was positively correlated with the initial Ca2+concentration.The Ca-Fe carbonate phase produced in the 20 mmol/L Ca-amended biosystems had a chemical formula of Ca_(0.8)Fe_(1.2)(CO_(3))_(2),which is close to the theoretical composition of ankerite.This ankeritelike phase was nanometric in size and spherical,Ca-Fe disordered,and structurally defective.Our simulated diagenesis experiments further demonstrated that the resulting ankerite-like phase could be converted into ordered ankerite under hydrothermal conditions.We introduced the term“proto-ankerite”to define the Ca-Fe phases that possess near-ankerite stoichiometry but disordered cation arrangement.On the basis of the present study,we proposed herein that microbial activity is an important contributor to the genesis of sedimentary ankerite by providing the metastable Ca-Fe carbonate precursors.

Initial COVID-19 severity influenced by SARS-CoV-2-specific T cells imprints T-cell memory and inversely affects reinfection

The immunoprotective components control COVID-19 disease severity,as well as long-term adaptive immunity maintenance and subsequent reinfection risk discrepancies across initial COVID-19 severity,remain unclarified.Here,we longitudinally analyzed SARS-CoV-2-specific immune effectors during the acute infection and convalescent phases of 165 patients with COVID-19 categorized by severity.We found that early and robust SARS-CoV-2-specific CD4^(+)and CD8^(+)T cell responses ameliorate disease progression and shortened hospital stay,while delayed and attenuated virus-specific CD8^(+)T cell responses are prominent severe COVID-19 features.Delayed antiviral antibody generation rather than titer level associates with severe outcomes.Conversely,initial COVID-19 severity imprints the long-term maintenance of SARS-CoV-2-specific adaptive immunity,demonstrating that severe convalescents exhibited more sustained virus-specific antibodies and memory T cell responses compared to mild/moderate counterparts.Moreover,initial COVID-19 severity inversely correlates with SARS-CoV-2 reinfection risk.Overall,our study unravels the complicated interaction between temporal characteristics of virus-specific T cell responses and COVID-19 severity to guide future SARS-CoV-2 wave management.