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Background: Patients with chronic obstructive pulmonary disease (COPD) complicated by pulmonary hypertension (PH) represent a high-risk population with limited evidence regarding early ICU fluid management. We investigated whether persistent positive fluid balance during the first 48 hours after ICU admission was associated with in-hospital mortality. Methods: We performed a retrospective multicenter cohort study using MIMIC-IV as the discovery cohort and eICU as the external validation cohort. Adult ICU patients with diagnosis-coded COPD complicated by PH were included. The main exposure was persistent positive fluid balance, defined as positive net fluid balance on both day 1 and day 2 after ICU admission. The primary outcome was in- hospital mortality. Multivariable logistic regression with multiple imputation was used as the primary analysis. Propensity score overlap weighting, stabilized inverse probability of treatment weighting (IPTW), complete-case analysis, nonlinear spline analysis, and clinically relevant subgroup analyses were performed. Results: The analysis included 1,891 ICU stays (1,493 from MIMIC-IV and 398 from eICU), with 348 in- hospital deaths. Persistent positive 48-hour fluid balance occurred in 484 patients (25.6%). Crude mortality was higher in the persistent positive group than in the non-persistent positive group (30.0% vs 14.4%). In the main multiply imputed multivariable model, persistent positive fluid balance was associated with higher in-hospital mortality in MIMIC-IV (OR 1.45, 95% CI 1.01-2.07; P=0.043) and in eICU (OR 1.88, 95% CI 1.06-3.32; P=0.030), with a fixed-effect pooled OR of 1.56 (95% CI 1.15-2.11; P=0.004). The association remained robust after overlap weighting, stabilized IPTW, and complete- case analysis. Subgroup analyses showed directionally consistent associations across all examined strata. Conclusions: Among ICU patients with diagnosis-coded COPD complicated by PH, persistent positive fluid balance during the first 48 hours was independently associated with higher in-hospital mortality and externally validated in eICU. Persistent early positive fluid balance may represent a high-risk dynamic fluid phenotype rather than a causal treatment effect. Keywords: COPD; pulmonary hypertension; fluid balance; intensive care unit; MIMIC-IV; eICU; mortality; multiple imputation

思想实验：纯净版循环宇宙——从 $$R \equiv 0$$ 到完整宇宙学模型的顺叙推导 本文为独立纯思想实验推导，核心基于公理性假设「时空标量曲率恒为零 $$R \equiv 0$$」，以无宇宙常数的标准爱因斯坦场方程为基础框架，补充均匀各向同性、尘埃近似、弱场极限匹配等约束条件，完成全程顺向推导。 本文推导过程仅在上述设定的框架内展开，不引入宇宙学常数、暗物质、暗能量、暴胀场等ΛCDM标准宇宙学框架下的特设概念。在本文给定的约束条件与推导逻辑内，上述ΛCDM特设概念无引入必要；若在本文框架内强行加入上述特设概念，将破坏本文特定解的自洽闭环，造成对应推导逻辑的不一致与计算结果的偏差。 $$R \equiv 0$$ 作为基础几何约束公理，其本身可适配不同的补充约束与宇宙学模型；本文仅给出该公理框架下，满足给定约束条件的一个自洽特解与对应的物理机制。

本⽂基于「时空标量曲率在任意时空点严格恒为零（R ≡ 0）」的基本假设，结合广义相对论场方程的迹关系，完成了对应宇宙学模型的完整理论推导。本⽂给出了该框架下的协变场方程、约束下的FLRW时空演化方程与完整的宇宙演化序列。本⽂为纯理论公理化思想实验⼯作，全⽂正确性仅由内部逻辑⾃洽性与数学推导严谨性定义。

本文基于「时空标量曲率在任意时空点严格恒为零（$$R \equiv 0$$）」的基本假设，结合广义相对论场方程的迹关系，完成了对应宇宙学模型的完整理论推导。本文给出了该框架下的协变场方程、约束下的FLRW时空演化方程与完整的宇宙演化序列。 --- 本文为纯理论公理化思想实验工作，全文正确性仅由内部逻辑自洽性与数学推导严谨性定义。

标准ΛCDM模型在解释宇宙加速膨胀、大尺度结构形成等观测现象时，必须引入暗能量、暗物质、暴胀场等多个未被直接探测的假设实体，且面临哈勃张力、暗能量演化、膨胀速率精细微调等难以解决的理论困难。本文提出一个基于空间-物质引力二元独立守恒的替代宇宙学模型，该模型仅基于一个核心公理：宇宙中存在两种完全独立、总量固定且永远相等的基本力——物质引力与空间引力。物质引力随物质聚集度增强，并对空间引力具有屏蔽效应；空间引力随宇宙体积增大而衰减，并天然倾向于物质稀少的宇宙空洞富集。 本模型无需引入任何未被探测的假设实体，即可自然解释： - 宇宙加速膨胀（空间引力主导） - 星系旋转曲线异常（屏蔽效应产生的等效引力） - 哈勃张力（空间引力分布不均匀） - DESI观测的暗能量演化（空间引力随体积衰减） - 黑暗流与巨引源现象（空洞膨胀的推力效应） 特别重要的是，本模型彻底解决了标准模型中最棘手的膨胀速率精细微调问题：由于两种引力总量严格相等，宇宙的所有演化参数都由宇宙总质量唯一决定，不存在任何微调空间。模型预言宇宙将经历"暴涨→减速膨胀→加速膨胀→减速膨胀→收缩→闭合"的完整轮回，并提出了一系列可通过未来观测检验的明确预测。

标准ΛCDM宇宙学模型成功解释了宇宙微波背景辐射、轻元素丰度等大量观测现象，是当前宇宙学的主流框架。然而，该模型需要引入暗能量、暗物质、暴胀场等多个未被直接探测的假设实体，同时面临哈勃张力、膨胀速率精细微调等尚未解决的理论困难。 一个自然的问题是，我们是否有可能从一个不同的角度，来理解这些观测现象？本文尝试从一个简单的思想实验出发，基于爱因斯坦广义相对论的引力几何化核心思想，提出一个基于空间与物质二元曲率守恒的宇宙学探索性构想。 该构想仅基于一个已被观测证实的基本事实：当前可观测宇宙的总曲率近似为零（Planck 2018结果给出 $$\Omega_K = 0.0007 \pm 0.0019$$，与零在1σ置信度内一致）。我们发现，这个构想可为宇宙加速膨胀、星系旋转曲线异常、哈勃张力等关键观测现象，提供一种不依赖于暗能量和暗物质的潜在定性解释路径。 本文给出了该构想的基本框架和定性描述，并提出了若干可量化、可证伪的观测线索，以便与标准模型进行区分和检验。本文仅提出该构想的基本思想和定性框架，完整的数学化推导和定量观测验证留待后续合作研究完成。 关键词：空间曲率；物质曲率；二元曲率守恒；宇宙加速膨胀；星系动力学；宇宙学替代模型