A single-electron inverter

A single-electron inverter was fabricated that switches from a high output to a low output when a fraction of an electron is added to the input. For the proper operation of the inverter, the two single-electron transistors that make up the inverter must exhibit voltage gain. Voltage gain was achieved by fabricating a combination of parallel-plate gate capacitors and small tunnel junctions in a two-layer circuit. Voltage gain of 2.6 was attained at 25 mK and remained larger than one for temperatures up to 140 mK. The temperature dependence of the gain agrees with the orthodox theory of single-electron tunneling.Comment: 3 pages, 4 figures (1 color), to be published in Appl. Phys. Let

Negative differential resistance due to single-electron switching

We present the multilevel fabrication and measurement of a Coulomb-blockade device displaying tunable negative differential resistance (NDR). Applications for devices displaying NDR include amplification, logic, and memory circuits. Our device consists of two Al/Al$_{x}$O$_{y}$ islands that are strongly coupled by an overlap capacitor. Our measurements agree excellently with a model based on the orthodox theory of single-electron transport.Comment: 3 pages, 3 figures; submitted to AP

Featured Piece

This year the General Editors continued the tradition started last year by creating a feature piece to show our appreciation for the History Department. We selected four professors from the faculty to answer a question about history: what figure/event/idea inspires your interest in history? Reading their responses helped give us insight into the thoughts of these brilliant minds and further help us understand their passion for the subject we all share a common love and interest in. We hope that you enjoy reading their responses as much as we did. The four members of the faculty we spoke with are Dr. Abou Bamba, Dr. William Bowman, Dr. David Hadley, and Magdalena Sánchez

Alien Registration- Grant, Hadley P. (Presque Isle, Aroostook County)

https://digitalmaine.com/alien_docs/33637/thumbnail.jp

Factors involved in the initial employment of African-American graduating seniors at a predominantly white university.

This study was designed to investigate factors involved in the initial employment of African-American graduating seniors at a predominantly white university. More specifically, this study focused on examining the job activities which contributed to African-American seniors securing entry-level professional positions and the role played by the Mather Career Center in the job search of graduating seniors. Questionnaires were sent to the graduating seniors of the Class of 1992. From the ninety seven respondents, a subset of twenty four were selected for indepth interviews. Theses interviews provided the primary data for the study. Data was obtained by the use of two instruments. A survey was constructed using a Likert-type scale combined with open and closed form questions to assess how many job-seeking activities the seniors participated in at the Mather Career Center. One thousand questionnaires were distributed; ninety-seven were returned completed. The questionnaire included four categories: Self-Development and Marketing Skills, Networking System, Career Planning and Placement, and Post-Placement Information. Sixteen questions focusing on the individual experiences of twenty four African-American and white graduating seniors were used to determine those factors that may have been involved in securing an entry-level professional position. The findings of this study revealed that several factors are a consideration for sampled African-American graduating seniors in their job search activities: networking with relatives and other support systems, lack of support from faculty, focus on race and ethnicity, heavy course and workloads, and spirituality. A significant difference was found between African-American participants and white participants in the amount of hours worked during their college careers. One important finding is that, while 66.6% of the African-American graduating seniors of this study did take advantage of the Mather Career Center, most relied upon external resources outside of the University, such as their support systems to assist with actual employment. The study suggests that there must be a collaborative effort among faculty, administrators, students, parents and the private and public sectors to facilitate a smoother transition for graduates in becoming future professionals

Boundary effects to the entanglement entropy and two-site entanglement of the spin-1 valence-bond solid

We investigate the von Neumann entropy of a block of subsystem for the valence-bond solid (VBS) state with general open boundary conditions. We show that the effect of the boundary on the von Neumann entropy decays exponentially fast in the distance between the subsystem considered and the boundary sites. Further, we show that as the size of the subsystem increases, its von Neumann entropy exponentially approaches the summation of the von Neumann entropies of the two ends, the exponent being related to the size. In contrast to critical systems, where boundary effects to the von Neumann entropy decay slowly, the boundary effects in a VBS, a non-critical system, decay very quickly. We also study the entanglement between two spins. Curiously, while the boundary operators decrease the von Neumann entropy of L spins, they increase the entanglement between two spins.Comment: 4 pages, 2 figures. Physical Review B (in press

Two Types of K⁺ Channel Subunit, Erg1 and KCNQ2/3, Contribute to the M-Like Current in a Mammalian Neuronal Cell

The potassium M current was originally identified in sympathetic ganglion cells, and analogous currents have been reported in some central neurons and also in some neural cell lines. It has recently been suggested that the M channel in sympathetic neurons comprises a heteromultimer of KCNQ2 and KCNQ3 (Wang et al., 1998) but it is unclear whether all other M-like currents are generated by these channels. Here we report that the M-like current previously described in NG108–15 mouse neuroblastoma x rat glioma cells has two components, “fast” and “slow”, that may be differentiated kinetically and pharmacologically. We provide evidence from PCR analysis and expression studies to indicate that these two components are mediated by two distinct molecular species of K+ channel: the fast component resembles that in sympathetic ganglia and is probably carried byKCNQ2/3 channels, whereas the slow component appears to be carried by merg1a channels. Thus, the channels generating M-like currents in different cells may be heterogeneous in molecular composition