skip to main content


Search for: All records

Creators/Authors contains: "Christopher, G."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. Plasma protein therapies are used by millions of people across the globe to treat a litany of diseases and serious medical conditions. One challenge in the manufacture of plasma protein therapies is the removal of salt ions (e.g., sodium, phosphate, and chloride) from the protein solution. The conventional approach to remove salt ions is the use of diafiltration membranes (e.g., tangential flow filtration) and ion-exchange chromatography. However, the ion-exchange resins within the chromatographic column as well as filtration membranes are subject to fouling by the plasma protein. In this work, we investigate the membrane capacitive deionization (MCDI) as an alternative separation platform for removing ions from plasma protein solutions with negligible protein loss. MCDI has been previously deployed for brackish water desalination, nutrient recovery, mineral recovery, and removal of pollutants from water. However, this is the first time this technique has been applied for removing 28% of ions (sodium, chloride, and phosphate) from human serum albumin solutions with less than 3% protein loss from the process stream. Furthermore, the MCDI experiments utilized highly conductive poly(phenylene alkylene)- based ion exchange membranes (IEMs). These IEMs combined with ionomer-coated nylon meshes in the spacer channel ameliorate Ohmic resistances in MCDI improving the energy efficiency. Overall, we envision MCDI as an effective separation platform in biopharmaceutical manufacturing for deionizing plasma protein solutions and other pharmaceutical formulations without a loss of active pharmaceutical ingredients. 
    more » « less
    Free, publicly-accessible full text available February 23, 2025
  2. Abstract

    The human brain utilizes ∼20% of all of the body's metabolic resources, while chimpanzee brains use <10%. Although previous work shows significant differences in metabolic gene expression between the brains of primates, we have yet to fully resolve the contribution of distinct brain cell types. To investigate cell type–specific interspecies differences in brain gene expression, we conducted RNA-seq on neural progenitor cells, neurons, and astrocytes generated from induced pluripotent stem cells from humans and chimpanzees. Interspecies differential expression analyses revealed that twice as many genes exhibit differential expression in astrocytes (12.2% of all genes expressed) than neurons (5.8%). Pathway enrichment analyses determined that astrocytes, rather than neurons, diverged in expression of glucose and lactate transmembrane transport, as well as pyruvate processing and oxidative phosphorylation. These findings suggest that astrocytes may have contributed significantly to the evolution of greater brain glucose metabolism with proximity to humans.

     
    more » « less
  3. Free, publicly-accessible full text available November 28, 2024
  4. The capstone chemical engineering senior process design course at Penn State in spring 2023 tasked students with designing a caustic soda process to partially meet the global demand for commoditized sodium hydroxide. This article disseminates our experience teaching senior chemical engineering students the core tenets of electrochemical engineering in a single class period for designing an electrolytic caustic soda process. In this E-Chem Education article, we relate key concepts found in chemical engineering (such as sizing up a reactor volume), which chemical engineering seniors are adept with, to electrochemical engineering principles (e.g., current density, voltage, and membrane electrode assembly area) for sizing up and costing out a chlor-alkali electrolyzer. Furthermore, we also discuss alternative electrolyzer designs outside the traditional chlor-alkali process, such as oxygen depolarized cathode (ODC) chlor-alkali and bipolar membrane electrodialysis (BPMED), for caustic soda production and the pros and cons of the alternative process designs.

     
    more » « less
    Free, publicly-accessible full text available September 1, 2024
  5. Free, publicly-accessible full text available August 1, 2024
  6. Free, publicly-accessible full text available September 1, 2024
  7. Free, publicly-accessible full text available November 1, 2024
  8. Free, publicly-accessible full text available July 1, 2024
  9. Free, publicly-accessible full text available June 25, 2024
  10. Abstract

    The Gulf Stream is a vital limb of the North Atlantic circulation that influences regional climate, sea level, and hurricane activity. Given the Gulf Stream's relevance to weather and climate, many studies have attempted to estimate trends in its volumetric transport from various data sets, but results have been inconclusive, and no consensus has emerged whether it is weakening with climate change. Here we use Bayesian analysis to jointly assimilate multiple observational data sets from the Florida Straits to quantify uncertainty and change in Gulf Stream volume transport since 1982. We find with virtual certainty (probabilityP > 99%) that Gulf Stream volume transport through the Florida Straits declined by 1.2 ± 1.0 Sv in the past 40 years (95% credible interval). This significant trend has emerged from the data set only over the past ten years, the first unequivocal evidence for a recent multidecadal decline in this climate‐relevant component of ocean circulation.

     
    more » « less