Molecular Biology and Biochemistry
A mere 2% of the US population is on the national bone marrow registry and at least 3,000 patients die each year because they cannot find a match for a bone marrow transplant. A way to circumvent the need to find a donor is to make patient specific hematopoietic stem cells (HSCs), the cell type important for bone marrow transplantation. However, this has not been reliably achieved. What remains unknown are the factors necessary for their generation. Thus, there is a critical need to determine where HSCs arise during embryogenesis to understand the signals necessary for their creation. We hypothesize that some HSCs come from the yolk sac, a thin membrane that surrounds the embryo. We have a lineage tracing system that allows us to label and track yolk sac derived cells. Our preliminary data shows that yolk sac derived HSCs persist to adulthood in mice. Once we have identified the contribution of the yolk sac to the HSC pool, we can then identify the factors necessary for the creation of HSCs with hopes of improving bone marrow transplantation to make it a more effective and efficient procedure that is readily available to patients regardless of their ability to find a matching donor.
Ecology and Evolutionary Biology
In flowering plants, chemical communication often facilitates pollinator specificity, which may affect whether populations diverge or hybridize. Species possessing divergent floral scents may attract distinct pollinators, limiting interspecific pollen transfer. Conversely, shared scents that attract the same pollinator could reduce isolation. Furthermore, ability of pollinators to recognize hybrid scent could mediate gene flow between hybrids and parental species. Hybrids may produce novel scent compounds or reduced emissions. Alternatively, overlap between hybrid and parental scent could enhance uni- or bi-directional gene flow. We investigated the floral scent of two species produced by an island radiation and their artificial hybrids. Despite their geographic overlap, visitation by the same pollinator species, and their ability to artificially hybridize, we have no evidence of natural hybridization or historic genetic exchange. We found that parental species differed in floral volatile composition, and hybrids were intermediate in their scent composition, prompting further investigation into the chemical mechanisms of attraction and species barriers.
Approaches to coping with chronic pain, like medication or healthcare, can require financial resources. I examined whether income may affect patients’ belief in their ability to cope with pain.
I analyzed survey data from 1394 patients from 125 chiropractic clinics in the US. I used linear regression to explore the relationship between annual household income (divided into tertiles at $50,000 and $100,000) and Chronic Pain Self-Efficacy Scale scores.
I found that patients in the high and middle income tertiles had significantly higher self-efficacy than the lowest income group. Income was still significantly related to self-efficacy when I controlled for gender, age, race/ethnicity, location and health insurance. When I added pain intensity to the model, the relationship remained significant when comparing the highest income tertile to the lowest.
Thus, while income is positively associated with self-efficacy, pain intensity is also an important predictor, and it is negatively associated with self-efficacy. It is important for practitioners to consider how patients’ resources as well as the intensity of their pain can limit their coping self-efficacy.
Ecology and Evolutionary Biology
The field of animal locomotion has its roots in the work of photographer Eadward Muybridge. He developed a technology that allowed scientists to study rapid motion, such as a horse’s gallop, in great detail. This lead to the widespread use of photographs as scientific data. Over 100 years later, we still employ similar techniques to study animal locomotion. In my research, I use high-speed video to understand how predatory zebrafish move when hunting prey. I found that the angular deviation between the predator’s heading and the prey’s position is predictive of the subsequent maneuver. The predator adjusts course by making turns that align its heading with the position of the prey. Further, the predator’s caudal fin trajectory during a tail beat drives these changes in swimming direction and speed. Ongoing work is focused on developing mathematical models of fish swimming. This work will lead to a greater understanding of how the motion of fins affects swimming trajectories, which can inform the design of underwater vehicles.
Microbiology & Molecular Genetics
Multiple sclerosis (MS) is an autoimmune disease in which the body’s own immune system attacks the neurons of the central nervous system (brain and spinal cord). This leaves people affected with MS with any number of disabilities such as impaired speech and mobility. There is no cure, and current treatments often have toxic side effects. My research focuses on (1) how a molecular network called the galectin-glycoprotein lattice controls the functions of immune cells, (2) how a compromised lattice on specific immune cells cause them to promote MS, and (3) how one special sugar can fix a damaged lattice and become a potential, safe treatment for MS.
Molecular Biology and Biochemistry
Cancer treatment currently takes a one-size-fits-all, carpet-bomb approach that exposes the patient to drugs that often have severe side effects and no guarantee of success. Personalized, precision treatments are needed, but unfortunately, there’s currently no way to test a drug’s effectiveness on a particular patient’s cancer in conditions that mimic those of their own body. In the Hughes lab at UC Irvine we have addressed this need by designing and fabricating an advanced microfluidics device to quickly test a variety of drugs on a patient’s actual tumor cells. Our platform is the only one of its kind to incorporate a living vasculature that feeds the tumor just as it occurs inside the human body. Most importantly, the biological conditions required for drug testing form within days, require very few cells for establishment, allow for rapid testing of anti-cancer drugs and real-time analysis of response. Using this truly personal drug screening methodology, cancer treatments could be tested for effectiveness in the lab, using the patients own cells, and the most effective drug would then be given in the clinic, increasing the chances of successful outcomes and saving lives.
Single cell analysis methods are becoming increasingly important since understanding how individual cells process information and respond to stimuli could lead to greater insight into cell heterogeneity and population behavior. One area that has only received limited attention is the detection of secreted products from single cells. Previous studies have been done where single cell arrays have isolated single cells in microwells. The wells are then covered with a glass slide containing immobilized antibodies to capture proteins secreted by individual cells, followed by removal of the glass slide and quantification by immunofluorescence. A major current limitation is that detection sensitivity is only in the ng/ml range. We have developed a powerful method to amplify nanoparticle binding that utilizes bioorthogonal cycloaddition chemistry between tetrazine (Tz) and trans-cyclooctene (TCO). The Tz/TCO chemistry was utilized to couple fluorescent quantum dots (QD) to the detection antibody used to probe the captured analytes on the glass substrates. In this study, soluble TNF-α detection can be achieved at concentrations as low as 0.1 fg/ml using chemical amplification.
Rachel Leigh Greenspan
Psychology and Social Behavior
Eyewitness testimony is the single leading cause of wrongful conviction in the United States. Although laypeople believe in the accuracy of eyewitnesses and jurors put significant weight on this form of evidence, laboratory based psychological research has shown the fallibility of human memory. Recently, the National Academy of Sciences published a report recommending best practices for law enforcement on how to improve eyewitness identification evidence. In this talk, I will summarize both the existing research on factors that affect the reliability of an eyewitness identification and research on proposed reforms on how to improve eyewitness evidence. Finally, I will present data from a large, national survey of police agencies that identifies how often best practices regarding eyewitness identification are being used in the field. This project informs policy makers about where additional training or resources may be most needed as well as spurring interesting new research questions driven by specific challenges faced by law enforcement in the field.
Criminology, Law and Society
Following the social media release of a photo of two armed police officers smiling at a Christmas market in the United Kingdom, much discussion surrounding the effects of smiling in the context of policing has emerged. Despite immense interest, however, little research has empirically examined the effects of facial expressions on perceptions of the police. Using novel data from my experiment, the Police Officer Perception Project (POPP), I investigate the effects of smiling on participants’ perceptions of police officers as (1) aggressive versus not aggressive, (2) approachable versus not approachable, (3) friendly versus not friendly, (4) respectful versus not respectful, and (5) accountable versus not accountable. My results reveal a number of significant findings. I discuss these findings with respect to public-police relations.
Criminology, Law & Society
In cities across the United States, police and prosecutors are using rap lyrics as autobiographical confessions, rather than treat the lyrics as a form of entertainment, a process virtually unheard of for other genres. Notably, the vast majority of these cases involve aspiring rappers—most of whom are young black men from inner-city communities. One concern articulated by scholars and attorneys is that introducing rap lyrics as evidence potentially introduces stereotypes into the courtroom, which might shape how jurors interpret the lyrics and ultimately evaluate the case. The current study uses four experiments to test the impact of genre-specific stereotypes on the evaluation of violent song lyrics, and those who write them, by manipulating the musical genre (e.g. rap, country, etc), but holding constant the actual lyrics. Results indicate that lyrics were uniquely viewed as threatening and the writer as criminal, across a number of dimensions, when the lyrics were categorized as rap compared to other genres. These findings highlight the possibility that rap lyrics could inappropriately impact jurors when admitted as evidence to prove guilt.
Department of Economics
Road pricing and emission taxes are economically eﬃcient policies to deal with the two major urban transportation externalities plaguing most metropolitan cities: congestion and pollution. However, policymakers, particularly in developing countries, often tend to resort to non-price alternatives like road space rationing to solve these externalities. This paper analyzes the welfare cost of the road space rationing policy in comparison to two tax-based policies: a vehicle mile tax and a cordon charge. In the absence of a revenue redistribution system, for the same reduction in total car trips, the consumer surplus loss for commuters in all income groups is higher under a tax scheme compared to road space rationing. Revenue recycling reduces the welfare loss, but the mechanism may not exist in developing countries.
As traffic externalities increase with rising motorization rates, policymakers are examining these policy options and their constraints. The ﬁndings of this study oﬀer evidence of the dilemma policymakers often face between choosing an economically eﬃcient policy and one that suits the voters using Santiago, Chile as a case study.
Achen and Bartels deliver a long-overdue attack upon apologetics for the US political system. They argue that the normatively-desirable “folk theory of democracy” (also known as democracy) is not an accurate description of the really-existing system of government in place in the US. Without a greater degree of economic and social equality, democracy will remain an unattainable ideal – no matter what sort of mathematical and rhetorical gymnastics apologists for the present system use. But their account of the gap between ideal and actual relies too heavily on the innate cognitive limitations of our psychology. Evolutionary and political epistemology, along with the conclusions of media research, provide a supplement resulting in a more complete and realistic account.
Earth System Science
On Earth there are gases in the atmosphere, called greenhouse gases, that absorb heat and cause the planet to warm up. This causes what we know as climate change. One important effect is that when the planet gets warmer this actually ends up increasing the amount of the amount of greenhouse gases in the atmosphere as a direct result. Because these gases then cause even more warming, this creates a self-reinforcing loop. What we would like to know is how much additional warming is this self-reinforcing effect going to be responsible for? To answer this, we need to understand all the different pieces that contribute to this effect. Some happen in the ocean and the land, and these are pretty well-understood. However there is an entirely different set of these effects in the human economy, and these are not yet included in the models that scientists use to predict future climate change. In my work I use a computer model to figure out how big these effects are and how much warming they could be responsible for, compared to the effects in the ocean and the land. As it turns out, they actually help cool the planet off a bit instead, but this apparent benefit comes at a pretty high cost.
Program in Public Health
Mosquitoes transmit diseases including malaria, dengue, and Zika, and are responsible for over one million annual deaths across the globe. These insects are home to diverse bacterial communities, also known as the mosquito microbiota. Stable tracking of bacteria dynamics in mosquitoes is an effective way to determine bacterial functions. Our study aims to test quantum dot and fluorescent protein approaches for labelling bacteria within mosquitoes. We successfully synthesized mannose-modified carbon quantum dots (Man-CQDs), tiny particles with unique fluorescent properties that make them ideal candidates for labelling and cell imaging. Once labeled with Man-CQDs and green fluorescent protein (GFP), Escherichia coli (E. coli) bacteria were then fed to a group of Aedes aegypti mosquito larvae. Larvae fed with Man-CQD-labeled bacteria showed a constant blue fluorescence, while those fed with GFP-labeled bacteria showed a relative short-term green fluorescence. These techniques can be applied in future research aimed to study mosquito behaviors and to explore the function of bacteria in mosquitoes.
Nearly 2 million U.S. troops have served in Afghanistan and Iraq. As fewer troops have died in combat, the military suicide rate has exceeded the combat death rate. Even though we know grief is linked to suicidal ideation and poor physical health, military psychological research has primarily focused on PTSD, depression, and substance use associated with combat trauma, with little focus on grief over a comrade’s death. This study sought to understand how veterans experience their comrades’ combat and suicide deaths. 22 veterans that lost comrades to both combat and suicide participated in semi-structured interviews. Analysis identified seven themes that suggest what factors may influence a veteran’s grief response: 1) Combat death as expected can ease acceptance of death; 2) Suicide as unexpected can make acceptance harder; 3) Combat death as heroic can ease acceptance; 4)Bonds forged in combat intensify a response, even if the deceased was not a friend; 5) Guilt over failure to prevent a death makes acceptance harder; 6) Attributing blame for a death creates anger; and 7) Detachment from civilians may make coping harder. This study further delineates adverse outcomes in veterans.
Earth System Science
The Southeast Asian Monsoon (SEAM) directly impacts the livelihood of millions of people in Southeast Asia by providing the essential water resources for food production. As a result, variability in SEAM has direct societal and economic implications. Future projections of SEAM variability have large uncertainties since instrumental records only extend back 150 years. Paleoclimate records obtained from stalagmites (mineral cave deposits) are beneficial in investigating monsoon changes. The last 2,000 years represent the natural baseline on which man-made climate change is superimposed. For that reason, the development of high-resolution and precisely dated stalagmite records from Southeast Asia is crucial to improve future projections of SEAM variability.
We utilize stalagmites from Laos to examine how monsoon changes have altered the climate in Southeast Asia over the last 2,000 years. Certain elements within the layers of stalagmites respond to seasonal cycles of wet and dry and allow us to reconstruct past precipitation patterns over annual to millennial resolutions. In addition, we focus on persistent and severe droughts (mega-droughts) over the last 800 years.
Earth System Science
Valley fever is a fungal disease endemic to the deserts of the southwestern US. People contract valley fever when they breathe in Coccidioides spp. fungal spores, which grow in the desert soil. Symptoms range from short term, flu-like illness to long term morbidity and even death.
The amount of valley fever cases fluctuates by year and is increasing for unknown reasons. However, since the fungi live within the soil, it is thought that climate conditions may control how much the fungus grows and when it is lofted into the air. These relationships have been historically difficult to study due to the lack of a regional valley fever incidence database.
Psychology & Social Behavior
This study tests whether smartphone presence alters psychological and physiological responses to a social exclusion stressor. Participants (N=148) were randomized to one of three conditions: (1) phone present with use encouraged, (2) phone present with use restricted, or (3) no phone access. Saliva samples and self-report data were collected throughout the study to assess salivary alpha amylase (sAA) and feelings of exclusion. Those in both phone-present conditions reported lower feelings of exclusion compared to individuals who had no access to their phone, p=.005. Multi-level modeling of sAA responses revealed that the those in the restricted phone condition had a significantly different trajectory compared to the phone use condition (p=.032) and no phone condition (p=.008). Specifically, those in the restricted phone condition showed a decrease in sAA following exclusion, those in the no phone condition showed a gradual increase, and phone users exhibited little change. Taken together, these results suggest that the mere presence of a phone (not necessarily phone use) can buffer stress and serve purposes akin to a digital security blanket.
While carbon dioxide is the most prevalent greenhouse gas emitted, methane, another greenhouse gas, needs to be considered as well as it can absorb 86 times more heat per molecule over a 20 year period. Methane emissions are not as well quantified as carbon dioxide as they stem from many aspects of urban life such as landfills, dairies, and combustion sources. In order to continue to cut methane emissions, it is important to have an inventory of where it is coming from.
We collected over 500 air samples over two years from a site downwind of the Los Angeles megacity. These samples were analyzed for many volatile organic compounds that are emitted from both human and natural sources. The concentrations of these gases were analyzed via a mathematical program that separates out the varying emissions sources and determine a signature for each. We calculated that roughly two thirds of all methane from Southern California is from the leakage of pipeline natural gas. This is a higher percentage than other estimates and this difference could be due to inventories not accounting for leakage from homes and kitchens after the gas meter.