Quantum-state tomography for spin-l systems

We show that the density matrix of a spin-l system can be described entirely in terms of the measurement statistics of projective spin measurements along a minimum of 4l+1 different spin directions. It is thus possible to represent the complete quantum statistics of any N-level system within the spherically symmetric three dimensional space defined by the spin vector. An explicit method for reconstructing the density matrix of a spin-1 system from the measurement statistics of five non-orthogonal spin directions is presented and the generalization to spin-l systems is discussed.Comment: 10 pages, including 2 tables, minor modifications in section II, final version for publication in Phys. Rev.

Fourier's Law from Schroedinger Dynamics

We consider a class of one-dimensional chains of weakly coupled many level systems. We present a theory which predicts energy diffusion within these chains for almost all initial states, if some concrete conditions on their Hamiltonians are met. By numerically solving the time dependent Schroedinger equation, we verify this prediction. Close to equilibrium we analyze this behavior in terms of heat conduction and compute the respective coefficient directly from the theory.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev. Let

Results of the Evaluation Study DeAL Decentralized Facade Integrated Ventilation Systems

Report and PowerPoint PresentationMost office buildings in Germany have either no mechanical ventilation system or a centralized ventilation system with fresh and exhaust air supply. Within the last 10 years some projects using decentralized ventilation systems (DVS) came up. Common for this type of decentralized systems is that they take fresh air directly from outside through the facade via the DVS into the room. Within the DVS-component air conditioning (at least heating) takes place. Since the year 2000 more than six companies provide this type of ventilation systems for office buildings and about 50 buildings have been realized in Western Europe. Within a two year research project the evaluation study DeAL investigated 10 of these buildings in respect of: • How do the DVS operate in reality (reliability, energy consumption, noise etc.)? • Are the users and operational staff satisfied with DVS? • Are there advantages that can be quantified within the evaluation buildings? • What is the thermal comfort in these buildings? • Is maintenance a problem with decentralized systems? • Does the necessary "wholes" in the façade influence the building performance (wind, sound protection, water tightness...)? The investigation included detailed monitoring of the DVS for a period of at least one year. The study was finished by August 2008

The experience of early childhood educators on working with children who have attachment impairments

The following thesis investigates the work done by early childhood educators for attachment-impaired children in the classroom setting. The experiences shared by the educators in this open study may guide and inspire other helping professionals as they develop strategies for working with children for whom it is difficult to build relationships. This study employed open-ended interview questions to gather narrative data from twelve experts who work or have worked in preschool programs. Through direct interviews with the relevant professionals this study examined their efforts to service this challenging population. The overarching request made of participants was to describe [a] case of a child presenting attachment limitations with whom it was particularly difficult to build a relationship. Participants were asked to maintain confidentiality in their answers. The research found that the teachers were significantly affected by their experiences. Those who had been in the field longer demonstrated a calmness that was useful when working with this population. Unique and remarkable techniques were utilized to try to engage the children and when the methods were actively reparative in approach the child more often responded positively and developed a more secure attachment. The participants also described learning how important it is for relationship-building to be a priority in the classroom. Lastly it is clear that educators and clinicians must continue to seek out support in one another\u27s professional experiences

On conjectures and problems of Ruzsa concerning difference graphs of S-units

Given a finite nonempty set of primes S, we build a graph $\mathcal{G}$ with vertex set $\mathbb{Q}$ by connecting x and y if the prime divisors of both the numerator and denominator of x-y are from S. In this paper we resolve two conjectures posed by Ruzsa concerning the possible sizes of induced nondegenerate cycles of $\mathcal{G}$, and also a problem of Ruzsa concerning the existence of subgraphs of $\mathcal{G}$ which are not induced subgraphs.Comment: 15 page

Local effective dynamics of quantum systems: A generalized approach to work and heat

By computing the local energy expectation values with respect to some local measurement basis we show that for any quantum system there are two fundamentally different contributions: changes in energy that do not alter the local von Neumann entropy and changes that do. We identify the former as work and the latter as heat. Since our derivation makes no assumptions on the system Hamiltonian or its state, the result is valid even for states arbitrarily far from equilibrium. Examples are discussed ranging from the classical limit to purely quantum mechanical scenarios, i.e. where the Hamiltonian and the density operator do not commute.Comment: 5 pages, 1 figure, published versio

Local Versus Global Thermal States: Correlations and the Existence of Local Temperatures

We consider a quantum system consisting of a regular chain of elementary subsystems with nearest neighbor interactions and assume that the total system is in a canonical state with temperature $T$. We analyze under what condition the state factors into a product of canonical density matrices with respect to groups of $n$ subsystems each, and when these groups have the same temperature $T$. While in classical mechanics the validity of this procedure only depends on the size of the groups $n$, in quantum mechanics the minimum group size $n_{min}$ also depends on the temperature $T$! As examples, we apply our analysis to a harmonic chain and different types of Ising spin chains. We discuss various features that show up due to the characteristics of the models considered. For the harmonic chain, which successfully describes thermal properties of insulating solids, our approach gives a first quantitative estimate of the minimal length scale on which temperature can exist: This length scale is found to be constant for temperatures above the Debye temperature and proportional to $T^{-3}$ below.Comment: 12 pages, 5 figures, discussion of results extended, accepted for publication in Phys. Rev.

Differences in College Readiness Rates in Two School Years for Students in Special Education

Examined in this study were the college readiness rates i e reading mathematics and both subjects of students who received special education services in the 2012-2013 and 2013-2014 school years Data from the 2012-2013 and 2013-2014 Texas Academic Progress Reports were obtained and analyzed Students who received special education services had a statistically significantly higher reading college readiness rate in the 2013-2014 school year than in the 2012-2013 school year Mathematics college readiness rates were statistically significantly lower in the 2013-2014 school year than the 2012-2013 school year The college readiness rates for both subjects approached statistical significance and college readiness rates were lower in the 2013-2014 school year Of importance were the very very low college readiness rates of students who were enrolled in special education Implications of these findings and recommendations for future research are discusse

University student perceptions of the current and future role of non-carbon emitting energy sources in the world

This article documents university student perceptions of the role and viability of non-carbon emitting energy sources in the short term (1 to 3 years) and medium term (10 to 30 years) for Earth. Consequently, the perceptions of 7,980 students at the University of Idaho (Moscow, ID, USA) about the future of geothermal energy (G), hydropower energy (H), nuclear power (NP), ocean thermal energy conversion (OTEC), solar energy (S) and wind energy (W) were measured between 1993 and 2016. All students were enrolled in the introductory environmental science class. Two survey instruments were used to gather this data. The first survey instrument evaluated six energy sources in 1994, 1998, 2002, 2006, 2010 and 2014. The second instrument focused on questions about nuclear energy. In the first survey a significant portion of the students considered solar, wind and nuclear power to be viable nonemitting carbon energy sources in the medium-term (10 to 30 years) future. Also, students taking the survey in later years (2006, 2010, 2014) were much more likely to consider non-carbon energy sources viable in the near and mid-term than students taking the survey in 1994, 1998 and 2002. In general, 46.7% of students considered nuclear power a serious problem at the beginning of the course; however, at the end of the term less than 36% of students still held their initial negative opinion. In addition, a significant majority of the students changed from indicating that fossil fuels were preferable to nuclear energy, an opinion they held at the beginning of the course, to favoring or at least saying that nuclear power was no worse than fossil fuels at the conclusion of the term. The significant findings of this study were: (1) students considered both solar and wind energy viable alternatives that have the potential to be significant on a world-wide basis within 30 years; (2) students saw only a limited expansion of hydropower and geothermal energy in the next 30 years; and (3) once students were educated in an unbiased way – including both the pros and cons of using nuclear energy – they were more receptive to view the nuclear power option favorably