Berkeley Scientific Journal

Neutral Density (ND) filters attenuate irradiance uniformly across the visible spectrum while preserving color balance. We present a RAW-

domain workflow to measure ND transmittance T and color shift across stops n = 1–5. Experimental transmission T exp is compared with

the ideal 2−n . Color fidelity is evaluated through channel ratios (R/G, B/G) and ΔE* ab from ColorChecker targets. The optical setup, acquisition

protocol, and data-reduction pipeline are described for reproducibility. We discuss polarization leakage, spectral flatness, illuminant

dependence, and signal-to-noise effects. The tested filter follows 2−n closely and shows only minor, illuminant-dependent drifts near

perceptibility thresholds at 5 stops.

Biofilms and their exopolysaccharide (EPS) matrix help soil rhizobia ride out stress, colonize roots, and ultimately succeed in symbiosis.

We asked whether bacteriophages and common abiotic stressors modulate EPS-linked biofilm traits in Bradyrhizobium S3.9.2GM. Using a

validated crystal violet (CV) microtiter assay for biomass and Congo Red (CR) colony phenotyping for matrix-linked traits, we found that

phage and sublethal stressors (osmotic, oxidative, temperature shock) generally increased biofilm biomass, with the largest effects under

combined phage + stress conditions. One-way ANOVA showed a strong treatment effect on OD570 (biofilm biomass; p < 0.001), while mucoid

score and CR halo intensity trended upward in combined treatments but were not significant at α = 0.05. These patterns are consistent with

literature showing stress-induced EPS in rhizobia and context-dependent phage–biofilm interactions, and they suggest that simultaneous

biotic and abiotic pressures can amplify EPS-associated phenotypes in the rhizosphere.

Sturnira spp. are one of the most common genus in Costa Rica as they are frugivorous bats found in middle to high elevations

(600m-2600m). With fruit variation comes differences in tooth morphology. There are two Sturnira spp. that look quite similar and can be

passed as the same species if not given a field guide, as they carry the same field marks in body and fur. S.mordax and S.hondurensis are small

spirited creatures in the Sturnira genus that are distinguished through their maxillary and mandibular central incisors. Unfortunately, there

aren’t many studies when it comes to comparing more characteristics or the sizes of these incisors. I conducted a study of the differences in

tooth morphology between S.mordax and S.hondurensis in Monteverde and San Gerardo. I anticipated for S.hondurensis to have larger teeth

measurements than S.mordax due to the long narrow skull S.hondurensis has compared to S.mordax. I went to four different sites (Monteverde

Estacion Biologica, LIFE Farm, Monteverde Institute, and the Children’s Eternal Rainforest) and installed three mist-nets for each site. I

collected a total of 36 Sturnira bats and found no significant difference in tooth morphology between S.mordax and S.hondurensis. This could

be due to attrition or hybridization of these two species.