DUJS Science News

Physics and Astronomy

In the future, quantum computing may be incredibly fast and powerful. But for now, the individual units, known as quantum gates, are highly prone to errors compared to their modern counterparts, the binary 1s and 0s.

Viola and Khodjasteh exploited relationships between erroneous gates to dynamically compensate for errors, thus bringing quantum computers closer to reality. (1)

One characteristic of life is homochirality. Certain types of molecules can exist in two distinct mirror-image configurations, but in living organisms they are either all “right-handed” or all “left-handed,” instead of a random combination of the two. Gleiser and Walker modeled the development of homochirality under conditions similar to evaporating tides and pools where life is believed to have originated. Regions of high homochirality form protocellular structures, bridging the gap in previous research between pre-biotic chemistry and the first cellular structures. (2)

Earth Sciences

Osmium concentrations rise globally, catalytic converters may be to blame

The concentration of the rare element osmium is rising globally, according to a study led by earth sciences professor Mukul Sharma, published in the Proceedings of the National Academy of Sciences. The increase is thought to be due to the refinement process of platinum for catalytic converters.

Platinum-coated catalytic converters became widely used in the ’70s to remove smog from car exhaust, when lead became unpopular in gasoline due to its environmental dangers. Luckily, unlike lead, osmium is found in such low concentrations as to pose no risk. Still, tracking the rise of osmium concentration may signal the need for future regulation of platinum refinement. (3)

Chronic exposure to steroid cocktail affects forebrain of female mice

Commonly abused steroids affect the brain, but the specifics are not clear. A new key mechanism, reported by DMS professor Leslie Henderson and colleagues in Neuroscience, reveals how chronic anabolic-androgenic steroid (AAS) use alters neural signaling involved in the expression of social behaviors in female mice. 

The brain region studied, known as the MPN, is critical for the expression of social behaviors like sexual/reproductive behaviors, aggression, and anxiety, which are known to be altered in AAS abuse. AAS are now mostly illicitly self-administered for enhancement of performance and body image.

The researchers found that chronic exposure to AAS, in a manner imitating the multi-drug regime self-administered by human abusers, resulted in reduced action potential frequency and altered synaptic currents in the MPN. This may help explain the observed behavioral changes in humans due to AAS abuse. (4)

An MRI of the brain, courtesy of the NIH.

Early life seizures impair hippocampal map

It is known that children who experience seizures early in life are at risk for long-term cognitive damage, but the exact mechanisms are not clear. A recent paper by Dartmouth alumnus Havisha Karnam and DMS professor Gregory Holmes in Experimental Neurology suggests that seizures cause impairment in spatial learning.

Seizures in rats during early development caused abnormal place cell firing patterns, and long-term damage in learning and spatial performance. The poor performance of rats with abnormal place cell firing in water maze tasks relates to their impaired spatial ability, as demonstrated.

“This is quite remarkable that we can now use single cell action potentials as a biomarker for cognition….While knowing that the hippocampal map is permanently altered following seizures during early development is important, even more important is determining why this occurs,” Holmes explained. (5)

Orthopedicians research demographics of child abuse

Recently, researchers led by Daniel Bullock at DHMC pinpointed three main characteristics used to identify child abuse cases in hospitals. The findings were published recently in the Journal of Pediatric Orthopaedics.

Based on the study, the researchers were able to pinpoint three main characteristics of abused children, who tended to be younger than two years old. Usually, evidence of abuse is seen on the ribs, sternum, and scapulae. Child abuse occurred more frequently in the winter months and on weekdays. Finally, those families that relied on Medicaid made up a large portion of the demographic of child abusers.

This study is very important to orthopedic doctors because, historically, around 28 percent of the cases of child abuse have required medical attention from orthopedic management. Therefore, the research conducted will help those in orthopedics to distinguish between cases that are accidental versus intentional. (6)

Researchers uncover mechanism in mother-to-child HIV transmission

Immune factors in human breast milk may inhibit mother-to-child transmission of HIV-1 virus, according to research conducted by DMS student Magdalena Lyimo under professors Ruth Connor and Alexandra Howell.

Lyimo’s research, published in the Journal of Acquired Immune Deficiency Syndromes, demonstrated that immune factors in human breast milk inhibited infection due to the cell-free HIV-1 in vitro, but did not reduce infection due to cell-associated HIV-1.

This marks the first demonstrated inhibitory mechanism involved in breast-feeding HIV transmission. Lyimo’s work also may have implications for improved drug treatments, because current antiretroviral drugs decrease the levels of cell-free virus in breast milk, but have little effect on the amount of cell-associated virus.

Lyimo, who is originally from Tanzania, felt a personal connection to her research.

“Breast milk transmission of HIV is something I thought was very interesting. It’s something that’s going on back home,” she said. “We’re trying to add a better understanding of what’s going on so that we can preserve the goodness of breast feeding but at the same time reduce transmission of HIV, especially in settings where women really don’t have the option of not breastfeeding.” (7)

Biology

Dartmouth prof. tracks mercury in aquatic ecosystems

Mercury concentration in fish is not solely determined by the amount of mercury in the water, according to biology professor Celia Chen and colleagues. The study, published in Environmental Science & Technology, revealed that organic carbon concentration and specific feeding pathways must also be considered.

Mercury (Hg), released by coal plants, becomes methylated (MeHg) in aquatic ecosystems and is then biomagnified as it moves up the food web. MeHg is readily absorbed by the human digestive tract and is believed to be a neurotoxin.

Based on four sample areas in the Gulf of Maine, the researchers found that while highly polluted areas had over 100 fold higher concentrations of Hg in the sediment, bioaccumulation of Hg only ranged by 2-4 fold and was not always explained by sediment concentration. In contaminated sites, high organic carbon content are thought to have decreased bioaccumulation.

Additionally, organisms feeding in the open water column had higher MeHg content than bottom feeders. Also, a greater proportion of total mercury was methylated in species higher in the food web. These distinctions help reveal the pathway mercury takes from coal plants to our table. (8)

References

1. K. Khodjasteh, L. Viola, Physical Review Letters (2009).
2. M. Gleiser, S. I. Walker, Orig Life Evol Biosph Epub ahead of print (2009).
3. C. Chen, P. N. Sedwick, M. Sharma, PNAS Epub ahead of print (2009).
4. Penatti CA, Costine BA, Porter DM, Henderson LP., Neuroscience Epub ahead of print (2009).
5. Karnam HB, Zhou JL, Huang LT, Zhao Q, Shatskikh T, Holmes GL., Exp Neurol Epub ahead of print (2009).
6. D. B. P. Bullock, K. J. Koval, K. Y. Moen, B. Carney, K. F. Spratt, Journal of Pediatric Orthopaedics 29, 231 (2009).
7. M. Lyimo, A. Howell, E. Balandya, S. Eszterhas, R. Connor, J Acquir Immune Defic Syndr. Epub ahead of print (2009).
8. Chen CY, Dionne M, Mayes BM, Ward DM, Sturup S, Jackson BP., Environ Sci Technol 43, 1804 (2009).