Basic Science

New Phenomenon Discovered in Low Energy Nuclear Astrophysics

Researchers of the Experimental Physics Research Center of the CAS Institute of Modern Physics achieved direct measurement of 6Li (p, γ) 7Be, the nuclear reaction cross section using a high-pressure ion experimental platform, and a new experimental phenomenon was discovered. In the experiment, researchers built a measuring apparatus of low-background featured low-energy nuclear astrophysics on the 320kV high-pressure ion experimental platform, using the 30μA high intensity proton beam to bombard the target of 6Li2O with thickness of 35μg/cm2, and a measurement was made for the cross section of 6Li(p, γ)7Be in the high-pressure zone with 70kV-300kV. The directly captured γ ray was measured by the high purity germanium (HPGe) γ-ray detector. The astrophysical S factor, which is obtained during the nuclear reaction of 6Li (p, γ) 7Be becomes smaller along with the decrease of energy in the low energy zone (lower than 200keV, does not conform to any theoretical prophecy and no exact explanation can be found. The new phenomenon might be explained assuming that there is a resonance with spin-parity of J▲=1/2+ or 3/2+ near the 200keV. But the existence of positive parity level remains as a controversial issue for a long time. To verify whether the positive parity exists or not, further experimental evidences are still required, which reminds us just simple theoretical extrapolation in the low-energy zone is not reliable, and meticulous experimental study for this energy zone is needed, and experimental data by direct measurement should be obtained.

Molecular Mechanisms of Depression is discovered

The lateral habenula (LHb), a brain region that interconnects the forebrain limbic system and the midbrain monoamine center, has recently emerged as a key region in the pathophysiology and treatment of depression. Neuroimaging studies have identified heightened habenula activity in the depressed state. However, what molecular mechanisms underlie these aberrant cellular processes in LHb and how depression-inducing stimuli lead to these changes were largely unknown. To address this problem, Li Kun and Zhou Tao from Hu Hailan’s lab at the Institute of Neuroscience, in collaboration with Lujian Liao and Catherine Wong in John R. Yates’s laboratory at Scripps Institute, took an unbiased, mass spectrometry-based, quantitative proteomic screening, to compare the protein content of LHb in the normal and congenital depressed rats (cLH rats, provided by Dr. Fritz Henn at Cold Spring Harbor Laboratory). They discovered that a member of the calcium/calmodulin-dependent protein kinase type II family, βCaMKII, was significantly up-regulated in the habenular of cLH rats, a change that can be reversed by antidepressant treatment. Using viral vector-based and brain-region-specific gene manipulations, they found that over expression of βCaMKII in the LHb of unstressed animals caused core symptoms of depression, including anhedonia (inability to feel pleasure) and behavioral despair. In contrast, down-regulation of βCaMKII using RNAi in LHb reversed depression-like symptoms. These results uncovered new molecular mechanisms underlying the hyperactivity of habenula in depression and identified new molecular targets for therapy. Such findings were published in Science on Aug. 30, 2013, entitled βCaMKII in lateral habenula mediates core symptoms of depression.