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1. 3D tomographic phase retrieval and unwrapping

   https://doi.org/10.1088/1361-6420/ad11a9  

   Fannjiang, Albert (December 2023, Inverse Problems)

   Abstract This paper develops uniqueness theory for 3D phase retrieval with finite, discrete measurement data for strong phase objects and weak phase objects, including: (i)Unique determination of (phase) projections from diffraction patterns—General measurement schemes with coded and uncoded apertures are proposed and shown to ensure unique reduction of diffraction patterns to the phase projection for a strong phase object (respectively, the projection for a weak phase object) in each direction separately without the knowledge of relative orientations and locations. (ii)Uniqueness for 3D phase unwrapping—General conditions for unique determination of a 3D strong phase object from its phase projection data are established, including, but not limited to, random tilt schemes densely sampled from a spherical triangle of vertexes in three orthogonal directions and other deterministic tilt schemes. (iii)Uniqueness for projection tomography—Unique 

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2. Cross-sectional refractive-index variations in fiber Bragg gratings measured by quantitative phase imaging

   https://doi.org/10.1364/OL.45.000053  

   Noah, Grayson_M; Bao, Yijun; Gaylord, Thomas_K (December 2019, Optics Letters)

   Unexpected micrometer-scale patterns in the induced refractive index of various commercial fiber Bragg gratings (FBGs) are observed in the cross-sectional fiber directions, which are in addition to the expected periodic variations along the fiber axis. These measurements were made using 3D tomographic deconvolution phase microscopy, a type of quantitative phase imaging. The cross-sectional patterns observed are shown to exhibit a variety of appearances, including fringes normal to the fiber axis and radial blades, the details apparently depending on the FBG writing method. 

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3. The Capacity of Private Information Retrieval from Decentralized Uncoded Caching Databases

   https://doi.org/10.3390/info10120372  

   Wei, Yi-Peng; Arasli, Batuhan; Banawan, Karim; Ulukus, Sennur (December 2019, Information)

   null (Ed.)

   We consider the private information retrieval (PIR) problem from decentralized uncoded caching databases. There are two phases in our problem setting, a caching phase, and a retrieval phase. In the caching phase, a data center containing all the K files, where each file is of size L bits, and several databases with storage size constraint μ K L bits exist in the system. Each database independently chooses μ K L bits out of the total K L bits from the data center to cache through the same probability distribution in a decentralized manner. In the retrieval phase, a user (retriever) accesses N databases in addition to the data center, and wishes to retrieve a desired file privately. We characterize the optimal normalized download cost to be D * = ∑ n = 1 N + 1 N n - 1 μ n - 1 ( 1 - μ ) N + 1 - n 1 + 1 n + ⋯ + 1 n K - 1 . We show that uniform and random caching scheme which is originally proposed for decentralized coded caching by Maddah-Ali and Niesen, along with Sun and Jafar retrieval scheme which is originally proposed for PIR from replicated databases surprisingly results in the lowest normalized download cost. This is the decentralized counterpart of the recent result of Attia, Kumar, and Tandon for the centralized case. The converse proof contains several ingredients such as interference lower bound, induction lemma, replacing queries and answering string random variables with the content of distributed databases, the nature of decentralized uncoded caching databases, and bit marginalization of joint caching distributions. 

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4. Quantifying the Projected Suppression of Cluster Escape Velocity Profiles

   https://doi.org/10.3847/1538-4357/ac4786  

   Halenka, Vitali; Miller, Christopher J.; Vansickle, Paige (February 2022, The Astrophysical Journal)

   Abstract The 3D radial escape-velocity profile of galaxy clusters has been suggested to be a promising and competitive tool for constraining mass profiles and cosmological parameters in an accelerating universe. However, the observed line-of-sight escape profile is known to be suppressed compared to the underlying 3D radial (or tangential) escape profile. Past work has suggested that velocity anisotropy in the phase-space data is the root cause. Instead, we find that the observed suppression is from the statistical undersampling of the phase spaces and that the 3D radial escape edge can be accurately inferred from projected data. We build an analytical model for this suppression that only requires the number of observed galaxiesNin the phase-space data within the sky-projected range 0.3 ≤r_⊥/R_200,critical≤ 1. The radially averaged suppression function is an inverse power law $〈Z_{\mathrm{v}}〉=1+{\left(N_0/N\right)}^{\lambda }$withN₀= 17.818 andλ= 0.362. We test our model withN-body simulations, using dark matter particles, subhalos, and semianalytic galaxies as the phase-space tracers, and find excellent agreement. We also assess the model for systematic biases from cosmology (Ω_Λ,H₀), cluster mass (M_200,critical), and velocity anisotropy (β). We find that varying these parameters over large ranges can impart a maximal additional fractional change in 〈Z_v〉 of 2.7%. These systematics are highly subdominant (by at least a factor of 13.7) to the suppression fromN. 

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5. Optimizing Learning Efficiency: Balancing Spacing and Repetition Under Time Constraints

   Cao, M; Yan, V X; Sana, F; Carvalho, P F (July 2025, Proceedings of the 47th Annual Conference of the Cognitive Science Society; eScholarship Open Access Publications from the University of California)

   Barner, D; Bramley, NR; Ruggeri, A; Walker, CM (Ed.)

   Spaced retrieval practice has been repeatedly demonstrated to improve learning, but its implementation is often constrained by real-world time limitations. This study investigated whether, under fixed study durations, learners should prioritize spacing or repetition. Across two experiments (total N = 1589), participants practiced Indonesian vocabulary under four conditions that varied in spacing and repetition. Item difficulty was also manipulated. Results showed that increasing repetitions at the cost of spacing enhanced immediate test performance, particularly for harder items. These findings suggest that spaced retrieval practice is effective only when learners have sufficient prior repetitions to retrieve information successfully. This study highlights the trade-offs between spacing and repetition under time constraints and offers practice insights for optimizing learning strategies. 

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