---
title: 'SANS Dataset: Soft Matter & Fundus Imaging'
url: https://www.emergentmind.com/topics/sans-dataset
type: topic
---

# SANS Dataset: Soft Matter & Fundus Imaging

The SANS dataset refers to two distinct, domain-specific datasets: (1) a Small-Angle Neutron Scattering (SANS) dataset characterizing polyelectrolyte–protein complexes, as reported in Morfin et al. [1210.1084], and (2) a fundus photograph dataset for visual assessment of Spaceflight-Associated Neuro-ocular Syndrome (SANS), as described in Hossain et al. [2308.06332]. Each serves as a prototypical data source in its respective field—soft matter structural biophysics and biomedical image super-resolution—under highly controlled or constrained acquisition protocols.

## 1. SANS Dataset in Soft Matter Biophysics

The SANS dataset of Morfin et al. [1210.1084] comprises absolute-scale neutron scattering measurements of complexes formed by hyaluronan (HA), a polyelectrolyte, and lysozyme, a basic protein, across variable protein concentrations, chain lengths, and ionic conditions. HA was examined in two molecular weight regimes: HA1 (Mw ≈ 6 000 Da, Lc ≈ 15 nm) and HA2 (Mw ≈ 500 000 Da, Lc ≈ 1 250 nm). Lysozyme concentrations ranged from 3.32 to 40 g L⁻¹, with a constant HA concentration of 10 g L⁻¹.

Scattering experiments were conducted at three neutron sources with the configurations detailed in Table 1. The Q-range spanned from 3.5×10⁻³ to 3.5×10⁻¹ Å⁻¹, and the data were corrected for transmission and detector efficiency using water as a standard, with absolute scaling in units of cm⁻¹. Experimental conditions included pH variation (4.7 and 7.4), buffer ionic strength modulation (up to 170 mM with NaCl), and ambient temperature (20 ± 2 °C).

## 2. SANS Dataset in Space Medicine Fundus Imaging

The term SANS also denotes the Spaceflight-Associated Neuro-ocular Syndrome fundus image dataset, employed for super-resolution assessment in Hossain et al. [2308.06332]. This collection comprises 276 color retinal images acquired aboard the International Space Station (ISS) with a non-mydriatic portable fundus camera under operational bandwidth constraints. Image data are divided into an 80/20 train/test split with 5-fold cross-validation on the training set, yielding 220 training and 56 test images.

Images were originally captured at high-resolution (exact pixel dimensions not specified) and then rescaled to 512×512 px via center cropping or padding and bicubic interpolation. Synthetic bicubic degradation was applied to simulate data compression for Earth transmission, downsampling by factors s = 2 and s = 4. Labels comprise a binary designation ("control" or "SANS") in a clinically assessed subset of 56 images; no pixel-wise or demographic metadata are provided. Images are stored as 8-bit/channel RGB PNGs.

## 3. Experimental Design and Preprocessing

**Soft Materials SANS Dataset:** Acquisition utilized the PACE (LLB-Saclay), D11, and D22 (ILL-Grenoble) beamlines (see Table 1). All samples were prepared in D₂O-based buffers at fixed HA concentration. pH and salt content were systematically varied to modulate protein charge and ionic screening. Detector absolute intensities were referenced to water, and Q-resolution (ΔQ/Q) was typically 5–10 %. No explicit error propagation for I(Q) was reported beyond point-to-point variations (~3–5 %).

**Spaceflight Fundus SANS Dataset:** All images underwent uniform pre-processing to 512×512 px for neural network input conformity [2308.06332]. Bicubic convolution and downsampling generated LR images according to
\[
I_{LR} = (I_{HQ} * k) \downarrow_s
\]
where \( k \) is the bicubic kernel and \(\downarrow_s\) denotes subsampling. Images were saved losslessly as PNG; no additional noise was simulated.

## 4. Data Structure, Modeling, and Evaluation

**Soft Materials SANS Dataset:** Scattering curves (I(Q) vs. Q) reveal three regimes corresponding to protein concentration. Low concentration displays q⁻².¹ upturns from concentration inhomogeneity; intermediate regimes show q⁻¹ scaling indicative of rod-like complexes; high concentrations yield q⁻⁴ Porod scattering due to cluster formation, with superposed protein–protein correlation features at q ≈ 0.2 Å⁻¹. The form factor for rod-like particles is modeled as
\[
I(Q) = \Delta\rho^2 V^2 \frac{2}{(Q L)^2}\left[\sin(Q L) - Q L \cos(Q L)\right]^2 P_\text{cross}(Q, R)
\]
with simplifications in the limit \( Q L \ll 1 \). Fit-derived parameters (see Table 2) include rod length \( L_{rod} \), radius \( R_{rod} \), intra-rod protein spacing \( a \approx 8 \pm 1 \) nm, and inner charge neutrality (\((–)/(+)_\text{inner} \approx 1\)). Goodness-of-fit is reported by visual correspondence, not by statistical measure.

**Spaceflight Fundus SANS Dataset:** Evaluation metrics for image super-resolution include Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity Index (SSIM), computed as
\[
\mathrm{PSNR} = 10\log_{10} \left( \frac{\mathrm{MAX}^2}{\mathrm{MSE}} \right), \quad \mathrm{SSIM}(x, y) = \frac{(2\mu_x\mu_y + C_1)(2\sigma_{xy} + C_2)}{(\mu_x^2 + \mu_y^2 + C_1)(\sigma_x^2 + \sigma_y^2 + C_2)}
\]
with results of 45.32 dB PSNR and 0.9793 SSIM for 2× upsampling, outperforming previous architectures on the SANS dataset [2308.06332].

## 5. Structural and Clinical Interpretation

**Soft Materials SANS Dataset:** Structural analysis supports a "necklace" complex model in which lysozyme globules electrostatically and possibly via H-bonds bind at quasi-regular intervals along the HA backbone. Unlike the isolated HA chain, where rod-like scattering persists only up to the intrinsic persistence length (\( L_p \approx 80 nm \)), the complexed system exhibits rod-like correlations at much greater lengths, up to the full contour length for long-chain HA2 (\( \sim 1 250 nm \)), with rod radii corresponding to one or several intertwined HA chains. Salt addition suppresses cluster formation and high-q protein–protein peaks while preserving the q⁻¹ regime, indicating a non-purely electrostatic binding contribution [1210.1084].

**Spaceflight Fundus SANS Dataset:** The image-level binary SANS labeling reflects visible pathology, including optic-disc edema and choroidal folds, although ground-truthing is limited. The 276-image set, though of high photographic quality, is constrained by its small size, private status, lack of hardware metadata, and the reliance on synthetic, bicubic degradation for super-resolution assessment. This suggests limited generalizability beyond the ISS operational context.

## 6. Limitations and Data Access

The soft-matter SANS dataset [1210.1084] is comprehensively documented with high methodological transparency, yet no raw datasets are provided for external use. In contrast, the spaceflight fundus SANS dataset [2308.06332] is retained privately by NASA, with only aggregate results published. Neither dataset includes pixel-level or spatial landmarks (for images) nor provides error estimates or ground-truth labels beyond those reported.

## 7. Tables: Instrument and Dataset Summary

### Table 1. SANS Instrument Configurations (Morfin et al. [1210.1084])

| Instrument     | λ (Å) | Collimation (m) | Sample–Detector (m) | Diaphragm     |
|----------------|-------|-----------------|---------------------|---------------|
| PACE (LLB)     | 2.5   | 4.5             | 4.5                 | 7 mm round    |
| D11 (ILL)      | 4.6   | 5.5             | 1.1, 10.8, 13.5     | 7 × 10 mm²    |
| D22 (ILL)      | ≈6.0  | 4–5 (typical)   | 17.5                | 7 × 10 mm²    |

### Table 2. Best‐Fit Rod Parameters (Morfin et al. [1210.1084])

| System          | L₍rod₎ (nm) | R₍rod₎ (nm) | Protein spacing a (nm) | (–)/(+)₍inner₎ |
|-----------------|-------------|-------------|-----------------------|----------------|
| HA1+lysozyme    | 15 ± 2      | 1.1 ± 0.1   | 8 ± 1                 | ≈1.0           |
| HA2+lysozyme    | >60         | 1.4 ± 0.1   | 8 ± 1                 | ≈1.0           |

### Table 3. Spaceflight SANS Fundus Dataset Summary [2308.06332]

| Total Images | Train/Test Split   | Image Dimensions | Labeling              |
|--------------|-------------------|------------------|-----------------------|
| 276          | 220/56            | 512×512 px, RGB  | Binary (control/SANS) |

## References

- Morfin, I., et al. "Rodlike Complexes of a Polyelectrolyte (Hyaluronan) and a Protein (Lysozyme) observed by SANS" [1210.1084].
- Hossain, M. S., et al. "Revolutionizing Space Health (Swin-FSR): Advancing Super-Resolution of Fundus Images for SANS Visual Assessment Technology" [2308.06332].

Source: https://www.emergentmind.com/topics/sans-dataset