Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Evolution of 3D Printing for Martian Habitats

Evolution of 3D printing processes and applications will have significant importance to near term and long term planetary space program initiatives. Long–term Martian missions will require a large amount of supplies to be transported to Mars. In-situ Resource Utilization and 3D Printing will reduce the interplanetary material transportation needs and thereby will contribute to more efficient Mars colonization. The composition of Martian soil enables it to be used as a 3D printing material. Martian atmospheric composition and presence of water allows production of 3D printing binder on the surface. Once 3D printing of habitats is finished, they will be made Human-rated to ensure the habitability of 3D printed domes. Multiple 3D printed domes will serve different functionalities: habitation, science and medical labs and green house.Mechanical Engineering, Department o

Technical pearls and surgical outcome of early transitional period experience in minimally invasive lumbar discectomy: A prospective study

Background: There is growing indications of minimally invasive spine surgery. The inherent attitude and institutive learning curve limit transition from standard open surgery to minimally invasive surgery demanding understanding of new instruments and correlative anatomy. Materials and Methods: In this prospective study, 80 patients operated for lumbar disc prolapse were included in the study (between January 2016 and March 2018). Fifty patients (Group A) operated by various minimally invasive spine surgery (MISS) techniques for herniated disc disease were compared with randomly selected 30 patients (Group B) operated between the same time interval by standard open approach. Surgical outcome with Oswestry Disability Index (ODI) and patient satisfaction score was calculated in pre- and postoperative periods. Results: Mean preoperative ODI score in Group A was 31.52 ± 7.5 standard deviation (SD) (range: 6–46; interquartile range [IQR]: 8; median: 32.11) and postoperative ODI score was 9.20 ± 87.8 SD (range: 0–38; IQR: 11; median: 6.67). Mean preoperative ODI score in Group B was 26.47 ± 4.9 SD (range: 18–38; IQR: 4; median: 25) and postoperative ODI score was 12.27 ± 8.4 SD (range: 3–34; IQR: 12; median: 10.0). None of the patients was unsatisfied in either group. On comparing the patient satisfaction score among two groups, no significant difference (P = 0.27) was found. Discussion: On comparing the change in ODI and preoperative ODI among both groups, we found a significant difference between the groups. It is worth shifting from open to MISS accepting small learning curve. The satisfaction score of MISS in early transition period is similar to open procedure. Conclusion: The MISS is safe and effective procedure even in transition period for the central and paracentral prolapsed lumbar intervertebral disc treatment. The results are comparable, and patient satisfaction and symptomatic relief are not compromised