Relaxations of the satisfiability problem using semidefinite programming

We derive a semidefinite relaxation of the satisfiability (SAT) problem and discuss its strength. We give both the primal and dual formulation of the relaxation. The primal formulation is an eigenvalue optimization problem, while the dual formulation is a semidefinite feasibility problem. It is shown that using the relaxation, the notorious pigeon hole and mutilated chessboard problems are solved in polynomial time. As a byproduct we find a new `sandwich' theorem that is similar to Lov'asz' famous $vartheta$-function. Furthermore, using the semidefinite relaxation 2SAT problems are solved. By adding an objective function to the dual formulation, a specific class of polynomially solvable 3SAT instances can be identified. We conclude with discussing how the relaxation can be used to solve more general SAT problems and some empirical observations

Novel Magnetic and Thermodynamic Properties of Thiospinel Compound CuCrZrS4_{4}

We have carried out dc magnetic susceptibility, magnetization and specific heat measurements on thiospinel CuCrZrS$_{4}$. Below $T_{\rm C}^{*} =$ 58 K, dc magnetic susceptibility and magnetization data show ferromagnetic behavior with a small spontaneous magnetization 0.27 $\mu_{\rm B}/$f. u.. In dc magnetic susceptibility, large and weak irreversibilities are observed below $T_{\rm f} =$ 6 K and in the range $T_{\rm f}< T < T_{\rm C}^{*}$ respectively. We found that there is no anomaly as a peak or step in the specific heat at $T_{\rm C}^{*}$.Comment: 11 pages, 4 figure

A systematic study of water models for molecular simulation:Derivation of water models optimized for use with a reaction field

We have performed long molecular dynamics simulations of water using four popular water models, namely simple point charge (SPC), extended simple point charge (SPC/E), and the three point (TIP3P) and four point (TIP4P) transferable intermolecular potentials. System sizes of 216 and 820 molecules were used to study the dependence of properties on the system size. All systems were simulated at 300 K with and without reaction fields and with two different cutoff radii, in order to study the impact of the cutoff treatment on density, energy, dynamic, and dielectric properties. Furthermore we generated two special-purpose water models based on the SPC and TIP4P models, for use with a reaction field. The atomic charges and the Lennard-Jone

Tuning the Charge Density Wave and Superconductivity in CuxTaS2

We report the characterization of layered, 2H-type CuxTaS2, for x between 0 and 0.12. The charge density wave (CDW), at 70 K for TaS2, is destabilized with Cu doping. The sub-1K superconducting transition in undoped 2H-TaS2 jumps quickly to 2.5 K at low x, increases to 4.5 K at the optimal composition Cu0.04TaS2, and then decreases at higher x. The electronic contribution to the specific heat, first increasing and then decreasing as a function of Cu content, is 12 mJ mol-1 K-2 at Cu0.04TaS2. Electron diffraction studies show that the CDW remains present at the optimal superconducting composition, but with both a changed q vector and decreased coherence length. We present an electronic phase diagram for the system.Comment: 7 pages, 9 figures. To be published in Physical Review

Implementation of ultra-hypofractionated radiotherapy schedules for breast cancer during the COVID-19 pandemic in the Netherlands

Background and purpose: The COVID-19 pandemic resulted in an accelerated recommendation to use five-fraction radiotherapy schedules, according to the FAST- and FAST-Forward trial. In this study, trends in the use of different radiotherapy schedules in the Netherlands were studied, as well as the likelihood of receiving five fractions. Materials and methods: Data from the NABON Breast Cancer Audit-Radiotherapy and Netherlands Cancer Registry was used. Women receiving radiotherapy for their primary invasive breast cancer or DCIS between 01–01-2020 and 31–12-2021 were included. Logistic regression was used to investigate the association between patient-, tumour-, treatment-, and radiotherapy institution-related characteristics and the likelihood of receiving five fractions in tumours meeting the FAST and FAST-Forward criteria. Results: Detailed information about radiotherapy treatment was available for 9,392 tumours. Shortly after the start of the COVID-19 pandemic, i.e. April 2020, 19% of the tumours being treated with radiotherapy received five fractions of 5.2 or 5.7 Gray (Gy). While only 3% of the tumours received five fractions in March 2020. The usage of five fractions increased to 26% in December 2021. Partial breast irradiation, compared to whole breast irradiation, was significantly associated with the administration of five fractions, as well as radiotherapy delivered in an academic radiotherapy institution compared to an independent institution. Conclusion: The start of the COVID-19 pandemic was associated with the early use of ultra-hypofractionated radiotherapy schedules. After publication of the trials, and mainly after the recommendation by the national radiotherapy society, the implementation further increased. These schedules were not yet used in all patients meeting the eligibility criteria for the FAST- or FAST-Forward trial.</p

The Impact of Social Desirability Pressures on Whites’ Endorsement of Racial Stereotypes: A Comparison Between Oral and ACASI Reports in a National Survey

In the last 60 years, the proportion of white Americans expressing anti-black prejudice in face-to-face survey interviews has declined dramatically. To test whether social desirability pressures affect the expression of anti-black prejudice, we analyzed a within-subjects experiment in the 2008 American National Election Study in which white respondents first reported their endorsement of stereotypes of blacks confidentially via audio computer-assisted self-interviewing (ACASI) and weeks or months later orally during second interviews. Shifting to ACASI led to a small but significant increase in negative views of blacks. Unexpectedly, shifting to ACASI also led to a similarly large increase in negative views of whites. Furthermore, the ACASI reports had no more predictive validity than did the oral reports. This evidence suggests that social desirability pressures do not seriously compromise oral reports of racial stereotypes in face-to-face interviews