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Geoffrey
L. Johnston Ph.D. Student in Sustainable Development School of International and
Public Affairs/Earth Institute |
Email: glj2108 (at) columbia.edu My ré
Current Research Blog Previous Publications
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Introduction:
First, hello and welcome. My name is
Geoff; I am currently a Ph.D. student in the Sustainable
Development program at Columbia University. If you
are interested in the program, you can find more
information here
and here.
A little background: I graduated from the
University of Notre Dame, summa cum laude, in 2005 with a Bachelor
of Science in Honors Mathematics and a Bachelor of Arts in
Philosophy. From there I taught in a Mississippi
high school for two years as a member of Teach for America
and then a further year in a Cleveland charter school (5th
and 6th grade math and science).
In the course of my studies, I researched
various programs designed to promote holistic human
development, eventually discovering the program in which I
am currently enrolled. Now I am here in New York,
researching, studying, and hopefully helping.
Research Interests:
My primary research interest is learning more about
poverty: its causes, its effects, and its cures. I
am also interested in complex systems and their usefulness
in describing natural and human-engineered systems.
In pursuit of this broader agenda, I am
currently working on a few specific projects.
The first project that I am working on is
building mathematical models of malaria
transmission. The purpose of these models is to help
public health agencies better predict where and when
malarial epidemics will arise, as well as provide likely
patterns of drug resistance development. My advisors
on this project are David Fidock, a microbiologist at
Columbia (Fidock
Lab), and David Smith, a malaria modeler at
Resources for the Future (RFF)
as well as the Emerging Pathogens Institute at the
University of Florida (EPI).
This project was the basis for my successful research
proposal for the NSF Graduate Research Fellowship.
I am also working on is quantifying the
effectiveness of a variety of development interventions
currently being employed in the Millennium Village Project
(MVP).
Within
the development community today there is great debate over
the value of foreign aid, with positions ranging from the
belief that aid does more harm than good to the belief
that aid is necessary for development. I hope to
work with the MVP team to rigorously quantify the impact
that various interventions are having and their
cost-effectiveness. More data will provide
macroeconomists and other aid researchers and
practitioners with inputs to support or falsify their
theories.
Current Research:
There are there major projects that I am working on
relating to the modeling of malaria. The first
project utilizes clinical data to model the progression of
malaria within a host. We simulate treating these
hosts with different antimalarial drugs in order to
predict how the drugs' different modes of action will
affect transmission. I am building the code in
MATLAB (+1000 lines and going strong) and we are nearing
completion.
Some of these asexual parasites will go on to further develop into gametocytes, the sexual forms of the parasite. If these gametocytes are taken up by a mosquito bite, they will then mate in the mosquito, form an oocyte and an oocyst, and prepare for emergence when the mosquito next bites a host (thus completing the cycle).
Our model simulates the blood stages of this cycle (the asexual and sexual stages), as well as treatment with an antimalarial drug. The functioning of the model is illustrated in thefigure below.
In this figure, the model was run six times, assuming three individuals went untreated and three were treated with artemether-lumefantrine two days after first fever. Treated individuals are colored red/magenta/orange, untreated are blue/violet/green.
Panel A illustrates the log10 asexual parasitemias of the individuals over time. The inset depicts the first 50 days of infection; vertical bars indicate the day of first fever for each of the individuals. Triangles above indicate the first day of fever. The black line is the level of detectability by microscopy (10 PRBC/μL).
Panel B depicts the daily gametocytemias of the same 6 individuals. The gametocytemias are usually approximately 2 orders of magnitude less than the asexual parasitemias a few days prior. Treated individuals' asexual parasitemias and gametocytemias drop rapidly after treatment.
Panel C provides the estimated probability of human to mosquito transmission given the gametocytemias in B. The x-axis maximum is changed from 700 to 200; none of the 6 individuals were infectious after day 152. The areas under the infectivity curves are 3.3, 5.7, and 3.9 days for treated and 19.3, 25.7, and 23.0 days for untreated, respectively. Drug treatment with an ACT rapidly reduces the probability of onward infection. Although the model predicts the persistence of long-lived low-level and sub-detectable infections (as observed in malaria therapy), Panel C illustrates that these infections are usually not transmissive after the initial period of infection.
The fact that this model is able to reproduce the natural course of an infection, as well as the results of treatment, took some effort. However, now that we have developed this tool, we are performing a variety of experiments with it, examining the effects of different treatments on sensitive and resistant parasites in silico. We are also developing a standalone tool for use by researchers; however, we cannot share this tool as of yet.
The other projects that I am working on include a worldwide map of malaria endemicity (i.e. where malaria is most prevalent) as well as developing statistical tools for analysis of laboratory data using genetically-modified parasites. Papers with results of these studies are forthcoming.
Previous
Publications:
“MPD Thruster Performance Analytic Models,” Gilland,
J. and Johnston, G., AIP Conf. Proc. 654, 516 (2003),
DOI:10.1063/1.1541334. Link
to PDF
The
Sustainable Development Doctoral Society sponsors a series
of lectures throughout the year; you can find a syllabus here.
Forms:
Here is where you will eventually be able to enter
comments, thoughts, etc., and post to the server.
But I just haven't had the time yet! If you would
like to contact me, please feel free to email and I will
reply as soon as possible.
