Emergence of Periodic Structure from Maximizing the Lifetime of a Bound State Coupled to Radiation

Consider a system governed by the time-dependent Schr\"odinger equation in its ground state. When subjected to weak (size $\epsilon$) parametric forcing by an "ionizing field" (time-varying), the state decays with advancing time due to coupling of the bound state to radiation modes. The decay-rate of this metastable state is governed by {\it Fermi's Golden Rule}, $\Gamma[V]$, which depends on the potential $V$ and the details of the forcing. We pose the potential design problem: find $V_{opt}$ which minimizes $\Gamma[V]$ (maximizes the lifetime of the state) over an admissible class of potentials with fixed spatial support. We formulate this problem as a constrained optimization problem and prove that an admissible optimal solution exists. Then, using quasi-Newton methods, we compute locally optimal potentials. These have the structure of a truncated periodic potential with a localized defect. In contrast to optimal structures for other spectral optimization problems, our optimizing potentials appear to be interior points of the constraint set and to be smooth. The multi-scale structures that emerge incorporate the physical mechanisms of energy confinement via material contrast and interference effects. An analysis of locally optimal potentials reveals local optimality is attained via two mechanisms: (i) decreasing the density of states near a resonant frequency in the continuum and (ii) tuning the oscillations of extended states to make $\Gamma[V]$, an oscillatory integral, small. Our approach achieves lifetimes, $\sim (\epsilon^2\Gamma[V])^{-1}$, for locally optimal potentials with $\Gamma^{-1}\sim\mathcal{O}(10^{9})$ as compared with $\Gamma^{-1}\sim \mathcal{O}(10^{2})$ for a typical potential. Finally, we explore the performance of optimal potentials via simulations of the time-evolution.Comment: 33 pages, 6 figure

An Alternative to Stride-Based RNG for Monte Carlo Transport

The techniques used to generate pseudo-random numbers for Monte Carlo (MC) applications bear many implications on the quality and speed of that programs work. As a random number generator (RNG) slows, the production of random numbers begins to dominate runtime. As RNG output grows in correlation, the final product becomes less reliable. These difficulties are further compounded by the need for reproducibility and parallelism. For reproducibility, the numbers generated to determine any outcome must be the same each time a simulation is run. However, the concurrency that comes with most parallelism introduces race conditions. To have both reproducibility and concurrency, separate RNG states must be tracked for each independently schedulable unit of simulation, forming independent random number streams. We propose an alternative to the stride-based parallel LCG seeding approach that scales more practically with increased concurrency and workload by generating seeds through hashing and allowing for repeated outputs. Data gathered from normality tests of tally results from simple MC transport benchmark calculations indicates that the proposed hash-based RNG does not significantly affect the tally result normality property as compared to the conventional stride-based RNG.Comment: 4 Pages, 3 Figures, Submitted to 2024 ANS Annual Conferenc

Diffraction on the Two-Dimensional Square Lattice

We solve the thin-slit diffraction problem for two-dimensional lattice waves. More precisely, for the discrete Helmholtz equation on the semi-infinite square lattice with data prescribed on the left boundary (the aperture), we use lattice Green's functions and a discrete Sommerfeld outgoing radiation condition to derive the exact solution everywhere in the lattice. The solution is a discrete convolution that can be evaluated in closed form for the wave number $k=2$. For other wave numbers, we give a recursive algorithm for computing the convolution kernel

Accessory to dissipate heat from transcranial magnetic stimulation coils

Background: Transcranial magnetic stimulation (TMS) produces magnetic pulses by passing a strong electrical current through coils of wire. Repeated stimulation accumulates heat, which places practical constraints on experimental design. New Method: We designed a condensation-free pre-chilled heat sink to extend the operational duration of transcranial magnetic stimulation coils. Results: The application of a pre-chilled heat sink reduced the rate of heating across all tests and extended the duration of stimulation before coil overheating, particularly in conditions where heat management was problematic. Comparison with Existing Method: Applying an external heat sink had the practical effect of extending the operational time of TMS coils by 5.8 to 19.3 minutes compared to standard operating procedures. Conclusion: Applying an external heat sink increases the quantity of data that can be collected within a single experimental session

Identifying Inviolable Behavioral Norms of Campus Housing and Residence Life Professionals

Housing and residence life (HRL) administrators who lack knowledge about accepted professional behaviors risk violating normative boundaries, likely jeopardizing themselves or their clients (e.g., students, parents, colleagues). The purpose of this survey study was to understand if a normative structure exists for the administrative role performance of HRL professionals. Findings revealed six inviolable norms, some of which differ by personal and professional characteristics of HRL professionals. The authors offer recommendations to guide practice and research

The Effect of γ-Guanidinobutyric Acid on the Clotting Time of Normal Plasma and on the Euglobulin Lysis Time of Fibrinolytically Active Plasma

It has been established that ε-aminocaproic acid (EACA) inhibits the activation of human plasminogen (Ablondi et al., 1959; Alkjaersig, Fletcher, and Sherry, 1959). Because of this observation, this compound has been used extensively to inhibit the pathologically occurring fibrinolytic system in patients. Recently Roberts (1965) reported that another compound, γ-guanidinobutyric acid (GGBA), like EACA, inhibits the lysis of human blood clots. Furthermore, GGBA, unlike EACA, retards the formation of these clots. The present investigation was undertaken to determine whether GGBA inhibits clot formation in the one-stage prothrombin and in the partial thromboplastin time tests. In addition, the ability of GGBA to inhibit clot lysis was tested using blood from a patient showing active fibrinolysis

Two dimensional bulge disk decomposition

We propose a two dimensional galaxy fitting algorithm to extract parameters of the bulge, disk, and a central point source from broad band images of galaxies. We use a set of realistic galaxy parameters to construct a large number of model galaxy images which we then use as input to our galaxy fitting program to test it. We find that our approach recovers all structural parameters to a fair degree of accuracy. We elucidate our procedures by extracting parameters for 3 real galaxies -- NGC 661, NGC 1381, and NGC 1427.Comment: 23 pages, LaTeX, AASTEX macros used, 7 Postscript figures, submitted to Ap

Behaviors Viewed as Deplorable by Peers: A Different Approach to Programming to Curb Unacceptable Behaviors in Fraternities and Sororities

This article posits a different approach to social norm programming by presenting a targeted approach that centers attention on the degree to which members of a fraternity or sorority disdain excessive alcohol use, drug use, sexual assault, racism, and homophobia rather than a focus on the frequency of such behaviors of their peers. An appendix to this article provides a survey instrument for fraternity/sorority advisors to gauge the social norms of their chapters in regards to a handful of specific illicit behaviors – homophobia, racism, sexual assault, drug use, and alcohol use. While social norms interventions have met with limited success historically with fraternity and sorority members, this instrument and its proposed implementation are designed to evade the pitfalls of past fraternity/sororityfocused programs

Delivering a “Dose of Hope”: A Faith-Based Program to Increase Older African Americans’ Participation in Clinical Trials

Background: Underrepresentation of older-age racial and ethnic minorities in clinical research is a significant barrier to health in the United States, as it impedes medical research advancement of effective preventive and therapeutic strategies. Objective: The objective of the study was to develop and test the feasibility of a community-developed faith-based intervention and evaluate its potential to increase the number of older African Americans in clinical research. Methods: Using a cluster-randomized design, we worked with six matched churches to enroll at least 210 persons. We provided those in the intervention group churches with three educational sessions on the role of clinical trials in addressing health disparity topics, and those in the comparison group completed surveys at the same timepoints. All persons enrolled in the study received ongoing information via newsletters and direct outreach on an array of clinical studies seeking participants. We evaluated the short-, mid-, and longer-term effects of the interventional program on clinical trial-related outcomes (ie, screening and enrollment)