Evolution of optical gain properties through three generations of electroluminescent fluorene-based polymers

Conjugated polymer semiconductors combine the processing and mechanical characteristics of plastics with the desirable optical and electronic properties of semiconductors. The aim of the research reported in this thesis was to investigate the evolution of the optical gain properties through three generations of electroluminescent fluorene-based polymers. Detailed optical, optoelectrical and gain characterisations were carried out on a range of different electroluminescent polyfluorene-based polymers. It was discovered that not all of the polymers were gain media as some were unable to give ASE. SC006 was found to be the most intriguing material among the rest of the tested polymers; this third generation polymer was found to be a non ASE material while achieving a high PLQE of 96% with 1.3ns-long excited state lifetime. Therefore it was evident that optimised highly efficient light emitting conjugate polymers for PLEDs are not necessarily effective optical gain media, and high steady state PLQE and long excited state lifetime are insufficient for good optical gain properties. Furthermore, in order to investigate the ASE quenching mechanism in SC006, a series of solvatochromism studies were carried out on this polymer. The time-resolved PL characteristics were compared between polymers of second and third generations. The combination of intermolecular and intramolecular energy transfer process was found to be responsible for the ASE quenching. Moreover, the effects of the differences in Yamamoto and Suzuki synthesis routes on optical gain properties of the first generation statistical and alternating copolymers were investigated and were found to be insignificant. Finally, the application of the gain quenching mechanism was demonstrated by an optical switching process performed on a polymer DFB laser. This enabled complete control over the laser emission from the polymer laser, thus achieving a minimum of a thirty fold reduction in the visible light output in the presence of a control pulse

General Pershing : Lafayette, We Are Here

https://digitalcommons.library.umaine.edu/mmb-vp/5905/thumbnail.jp

Interactions Between Stress, Ethanol, and THC Exposure and Effects on Prefrontal Reliant Signaling and Behavior

Post-traumatic stress disorder (PTSD) and substance use disorder (SUD) are two highly prevalent and highly debilitating psychological conditions that often occur comorbidly. In accordance with the self-medication hypothesis, drugs like alcohol and cannabis are used following exposure to a traumatic event to acutely reduce anxiety, but, in the long term, these substances cause impairments in learning and memory processes in the prefrontal cortex and reduce the effectiveness of therapeutic treatments for these disorders. As such, the overarching hypothesis of this dissertation is that exposure to stress, alcohol, and cannabis lead to alterations in learning and memory due to modifications in prefrontal cortex signaling, and it is further hypothesized that these impairments can be reversed by normalizing glutamatergic function in this region. These experiments were divided into three main branches of study using behavioral pharmacology as well as optogenetics and fiber photometry to investigate the deleterious effects of stress, cannabis, and alcohol exposure on cognitive functioning and glutamate signaling in the prefrontal cortex. In the first set of studies, restraint stress was followed by set-shifting and alcohol self-administration behavioral tasks to examine stress-induced changes in cognitive flexibility and drug seeking behavior respectively. These experiments established stress induced increases in ethanol seeking and relapse like behavior as well as impairments in cognitive flexibility. The second set of studies established the detrimental effects of alcohol exposure on fear learning during extinction training. Further, this effect was shown to be dependent on glutamatergic activity in the prefrontal cortex using microinjection and optogenetic studies. In the third set of studies, THC vapor and chronic ethanol administration led to deficits in prefrontal cortex reliant behaviors including cognitive flexibility, ethanol seeking, and responses to fear stimuli, and fiber photometry was used to measure effects of these drugs on prefrontal cortex glutamate signaling. Additionally, the pharmaceutical compounds CDPPB and N-acetylcysteine (NAC) were used to pharmacologically reverse the behavioral and signaling impairments that occur as a result of alcohol and cannabis exposure respectively. Taken together, the data presented within this dissertation highlight the effects of alcohol and cannabis on prefrontal cortex-reliant signaling and behavior and use clinically available therapeutics to treat these deficits in a model of PTSD/SUD comorbidity

General Pershing : Lafayette, We Are Here

https://digitalcommons.library.umaine.edu/mmb-ps/1795/thumbnail.jp

Demokrasi Dan Sistem Pemerintahan

Democracy provides an understanding that the source of power is the people with an understanding that people will give birth to a rule that will benefit and protect their rights. In order for that to happen, a rule is needed to support the idea and serves as the foundation in the life of the state to guarantee and protect the rights of the people. Such rule is called The Constitution.The understanding on the highest power itself does not need to be understood in the sense of absolute monistic and unlimited, because it is in itself that the supreme power which is in the hands of the people is limited by the agreement they set forth together as outlined in the formulation of the constitution they made and promulgated especially on the founding of the state. This is what is called the social contract between citizens as reflected in the constitution. It is that constitution which limits and regulates how the sovereignty of the people is channeled, executed and maintained in state activities and day-to- day running of the government. In essence, within the idea of popular sovereignty, it remains to be guaranteed that the people are the true owners of the State with all its authority to carry out all the functions of state power, both in the field of legislative, executive, and judiciary. It is the people who have the authority to plan, organize, implement, and conduct monitoring and assessment of the implementation of the power functions. Even further, it is for the benefit of the people that every activities aimed at. It is for the people that all the benefits gained from the functioning and the organization of the state are intended. This is the idea of popular sovereignty or democracy that is totally of the people, for the people, by the people, and with people

Initial overview of disconnection events in Halley's Comet 1986

We present an initial overview of the disconnection events (DE's) in Comet Halley in 1986. Although disconnection events are arguably the most spectacular of all dynamic comet phenomena, the mechanisms by which they occur are not fully understood. It is generally believed that the solar wind plays a major role in determining when disconnection events occur, but the details of the solar wind/cometary interactions responsible for initiating the tail disconnection are still under debate. The three most widely accepted models are: (1) high speed streams in the solar wind cause the tail to disconnect due to pressure effects; (2) decreased production of cometary ions in a high speed stream allows magnetic field to slip away from the comet; and (3) the tail disconnects after frontside reconnection of the interplanetary magnetic field (IMF) as the comet crosses a magnetic field sector boundary. We find that the front-side magnetic reconnection model is the best explanation for the DE's we have considered

The Position of Woman in America by Cora Smith, First UND Commencement: June 13, 1889

Report of the speech delivered by Cora Smith, a member of the first graduating class, at the first UND Commencement on June 13, 1889. Smith entitled her remarks: The Position of Woman in America. (Text reprinted from the Grand Forks Daily Herald (evening edition), June 13, 1889.

Records of experiments in catering and dietary studies

Citation: Campbell, Stella and McNutt, Cora E. Records of experiments in catering and dietary studies. Senior thesis, Kansas State Agricultural College, 1906.Morse Department of Special CollectionsIntroduction: The following experiments were conducted between November 30th, 1905 and April 4th, 1906, for the purpose of ascertaining the amount of materials used, their composition, cost, fuel value expressed in calories, and nutritive ratios; also the amount of labor and time required in catering. The record is of six experiments: Number I. Football banquet given November 30th, 1905 to fifty persons. This was the first meal for the team after being for several weeks on rigid training diet. The materials were in season, therefore the prices were r reasonable. The work of preparation was done entirely by two women assisted in serving by seven others. Hours required for preparation 13-1/2, Hours required for serving 1-1/2, Total 15. Number II. A wedding luncheon given December 18th, 1905 to thirty-five persons. The prices of materials were reasonable taking into consideration that it was the beginning of the winter season. The work of preparation was done by two assisted in serving by six. Hours required for preparation 7, Hours required for serving 1, Total 8. Number III. A wedding dinner given January 17th, 1906 to twelve persons. Some materials being out of season made the cost greater than it would otherwise have been. Two prepared this dinner and one assisted in serving. Hours required for preparation 14, Hours required for serving 2, Total 16

Magnetic defects promote ferromagnetism in Zn1-xCoxO

Experimental studies of Zn1-xCoxO as thin films or nanocrystals have found ferromagnetism and Curie temperatures above room temperature and that p- or n-type doping of Zn1-xCoxO can change its magnetic state. Bulk Zn1-xCoxO with a low defect density and x in the range used in experimental thin film studies exhibits ferromagnetism only at very low temperatures. Therefore defects in thin film samples or nanocrystals may play an important role in promoting magnetic interactions between Co ions in Zn1-xCoxO. The electronic structures of Co substituted for Zn in ZnO, Zn and O vacancies, substituted N and interstitial Zn in ZnO were calculated using the B3LYP hybrid density functional in a supercell. The B3LYP functional predicts a band gap of 3.34 eV for bulk ZnO, close to the experimental value of 3.47 eV. Occupied minority spin Co 3d levels are at the top of the valence band and unoccupied levels lie above the conduction band minimum. Majority spin Co 3d levels hybridize strongly with bulk ZnO states. The neutral O vacancy and interstitial Zn are deep and shallow donors, respectively. The Zn vacancy is a deep acceptor and the acceptor level for substituted N is at mid gap. The possibility that p- or n-type dopants promote exchange coupling of Co ions was investigated by computing total energies of magnetic states of ZnO supercells containing two Co ions and an oxygen vacancy, substituted N or interstitial Zn in various charge states. The neutral N defect and the singly-positively charged O vacancy are the only defects which strongly promote ferromagnetic exchange coupling of Co ions at intermediate range.Comment: 9 pages, 11 figure

Atmospheric oxidation chemistry and ozone production: Results from SHARP 2009 in Houston, Texas

This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event (SPE)-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies