Most Popular Books by David Christian

This a companion reader for the website World History for Us All, a site with free online lesson plans. http://worldhistoryforusall.sdsu.edu This reader is edited for language accessible to grades 6–9 and contains Big Eras One–Seven.

"Multiple-unit activity (MUA) and average evoked potentials (AEP) were simultaneously recorded from rats performing in a "go, no-go" auditory discrimination task. Average MUA was generally less variable and better related to the animal''s response than was the AEP. The lateral septal area was the only structure where the poststimulus pattern of MUA was consistently related to whether or not the animal bar pressed. Medial septal prestimulus MUA levels were highest when the animal did not subsequently bar press, while poststimulus MUA levels were always sharply reduced from the prestimulus range, regardless of stimulus or response conditions. These results were frequently independent of whether the response was correct or incorrect. The poststimulus latencies of AEP and average MUA peaks were closely related in the dorsal hippocampus and medial geniculate but were not clearly related in either septal area."--

"The formation of patterns of functionally appropriate chemical synapses is one of the key aspects of nervous system development. I have investigated the cellular interactions that culminate in the formation of an inhibitory synapse between the R and P neurons of the leech. These neurons may be isolated and maintained in culture, where they reform synaptic connections under easily manipulable conditions. An early event in the formation of this synapse is the loss from sites of contact in the postsynaptic P cell of an excitatory response to the transmitter serotonin. The loss of this response was triggered specifically by contact with the presynaptic R neuron, and not by contact with other leech neurons, including other serotonergic neurons. Furthermore, contact with the R neurons of the reproductive ganglia, which do not innervate P cells, was also ineffective in causing the loss of response. This highly specific cellular interaction was prevented by treatment of the R cell surface with the proteolytic enzyme trypsin or with the lectin wheat germ agglutinin (WGA), suggesting involvement of an R cell surface glycoprotein. WGA blocked not only the loss of the excitatory response, but also prevented the formation of the R-P synapse. An antibody library against the R cell generated using a novel phage-display system produced antibodies which bound to subsets of leech neurons, including the R neurons, but none of these was specific for the R cells. I conclude that an early event in the formation of the R-P synapse is the recognition by the P cell of its correct synaptic partner through an R cell-specific surface molecule." --

Because concurrent programming as a field is still maturing, and access to massively parallel machines is restricted to large businesses and universities, there is a dearth of debuggers for concurrent programs. Those that do exist are usually difficult to obtain. This project helps alleviate these problems by creating a freely available debugger for concurrent programs written using the MPI (Message Passing Interface) protocol. A survey of the current field of debuggers was completed, out of which a design focused on user interface issues and replay capability developed. Testing shows the debugger to be an effective tool.

Images of nearby starburst galaxies taken with the Chandra X-ray Observatory (CXO) reveal bright X-ray sources, many of which are believed to be high mass X-ray binaries (HMXBs), formed during recent star formation. A HMXB is a star system that emits strong in the X-ray, usually a massive star and a compact object like a BH or NS. We found 49 HMXB candidates in six nearby starburst galaxies, based on 14 observations from the CXO. While the individual analyses from such galaxies lack statistical significance to produce unambiguous results on the nature and origin of HMXBs, combining the data from multiple starburst galaxies allows us to draw more solid conclusions about the HMXB population in galaxies of this type. For all X-ray sources, we determined their X-ray properties such as luminosity, X-ray counts, and hardness ratios. We utilized data from the Hubble Space Telescope to investigate the nature of these X-ray sources. We identified ~33 candidate donor stars to the HMXBs in the age range of 10-100 Myr. Six out of 49 XRBs are spatially coincident with young star clusters, and hence likely host BHs. Nearly half of the sources are located further than 100 pc from a cluster. Dynamical arguments and the results of N-body simulations suggest that these are likely NS-XRBs. The remaining sources are located less than 100 pc away from a cluster, and it is harder to assess if these are BH- or NS-binaries.