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

A CHARACTERIZATION OF KEY RESIDUES IN CLASS I VIRAL FUSION PROTEINS IMPORTANT FOR FUSOGENIC ACTIVITY

Viral fusion proteins are critical for viral entry and subsequent infection. Class I fusion proteins are characterized by synthesis as an inactive precursor requiring cleavage by a host cell protease to become fusion competent. Though vaccine and antiviral therapeutic developments often target the fusion protein, questions surrounding cleavage dynamics and protein stability remain. The work presented in this dissertation investigates specific regions of three class I viral fusion proteins in an effort to identify key residues involved in proteolytic processing and membrane fusion. The trimeric severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein (S) mediates receptor binding, facilitates fusion needed for viral entry, and drives cell–cell fusion. We demonstrate that S must be proteolytically processed at the S1/S2 border and within the S2 subunit in order to become fusion competent. We also identify residues within the internal fusion peptide and the cytoplasmic tail that modulate S-mediated cell–cell fusion. The transmembrane (TM) region of the HeV hendra virus fusion protein (F) has been shown to play a role in F protein stability and the overall trimeric association of F. Previous work classified β-branched residues within the C-terminal TM domain as important for F protein endocytosis, proteolytic processing, and protein stability. The work presented here completes the analysis of the HeV F TM and identifies specific residues that alter F protein function, suggesting a role for these residues in the fusion process. The respiratory syncytial virus (RSV) fusion protein (F) requires cleavage at two sites, separated by 27 amino acids. Cleavage at both sites results in a 27 amino acid fragment, termed Pep27. Previous work has provided conflicting results on the relative timing of when the two cleavage events occur. In addition, the fate of Pep27 is unclear. Examination of F cleavage kinetics in both infected and transfected systems over time determined that cleavage of both sites occurs within the secretory pathway as F is transported to the cell surface. We found that the deletion of Pep27 does not alter F function, but the mutation of N-linked glycosylation sites within Pep27 reduces both F surface expression and cell-cell fusion activity. This work clarifies the timing of RSV F proteolytic cleavage and offers insight into the crucial role the N-linked glycosylation sites within the Pep27 play in the biological function of F. The work presented in this dissertation identifies residues within distinct regions of class I viral fusion proteins critical for fusion protein cleavage and stability, therefore impacting infection

Stress Fractures of the Elbow in the Throwing Athlete: A Systematic Review.

Background: Stress fractures of the elbow are rare in throwing athletes and present a challenge from both a management and rehabilitation perspective. Although the incidence of stress fractures of the elbow is increasing, there is a lack of data in the literature focused on throwers. Purpose: To evaluate studies regarding the management and outcomes of stress fractures of the elbow in throwing athletes. Study Design: Systematic review; Level of evidence, 4. Methods: A systematic review was conducted by searching the Scopus, PubMed, and Cochrane Library electronic databases to identify studies reporting on the management and outcomes of stress fractures in overhead-throwing athletes. Management data included nonoperative and operative modalities, and outcome data included return to play, encompassing the timing and level of activity. Studies were excluded if the stress fracture of the elbow was not a result of a sport injury attributed to throwing or if the study failed to report whether an athlete returned to play. Results: Fourteen studies met the inclusion criteria and were included in this analysis. There were 52 patients in total (50 male, 2 female) with a mean age of 19.7 years (range, 13-29.1 years). The olecranon was the most common location of the stress fracture (51 patients; 98.1%), followed by the distal humerus (1 patient; 1.9%). The majority of patients (n = 40; 76.9%) were treated operatively. Of the 40 patients who were treated surgically, 14 (35.0%) underwent a period of conservative treatment preoperatively that ultimately failed because of persistent nonunion or continued elbow pain. A total of 50 patients (96.2%) returned to sport either at or above their preinjury level. Of the 2 patients (3.8%) who did not return to sport, 1 did not return because of continued elbow pain postoperatively, and the other was lost to follow-up. Complications occurred in 9 patients (17.3%), all of whom were treated surgically. Conclusion: On the basis of this systematic review, the majority of elbow stress fractures were treated operatively and approximately one-third after a period of failed nonoperative management. The return-to-sport rate was high. Further, higher level studies are needed to optimize management and return-to-sport rates in this population

Multi-level, multi-party singlets as ground states and their role in entanglement distribution

We show that a singlet of many multi-level quantum systems arises naturally as the ground state of a physically-motivated Hamiltonian. The Hamiltonian simply exchanges the states of nearest-neighbours in some network of qudits (d-level systems); the results are independent of the strength of the couplings or the network's topology. We show that local measurements on some of these qudits project the unmeasured qudits onto a smaller singlet, regardless of the choice of measurement basis at each measurement. It follows that the entanglement is highly persistent, and that through local measurements, a large amount of entanglement may be established between spatially-separated parties for subsequent use in distributed quantum computation.Comment: Corrected method for physical preparatio