True Space Research Articles

Take the edge off: A hybrid geographic food access measure

Measures of geographic food access overlook an important source of statistical biases, termed the edge effect. The edge effect refers to the fallacy that events contributing to the spatial pattern of an analysis unit may be outside of that unit; thus merely summarizing events within the unit may lead to distortion of the estimation. Food procurement activities can happen beyond existing administrative boundaries. Delineating food access using unit-based metrics may misrepresent the true space within which food stores are accessible. To overcome this problem, this paper proposes a gravity-based accessibility measure to improve unit-based statistical approaches in food access research. In addition, this method accounts for the spatial interaction between food supply (e.g., food items in stock) and demand (e.g., population) as well as how this interaction is mediated by the spatiotemporal separation (e.g., travel time, modality). The method is applied to the case of Franklin County, OH and has revealed the food access inequity for African Americans by modes of transport, including walking, biking, and driving. The analysis of the correlation between mode-specific food access and socioeconomic status (SES) variables reveals that using a single modality in food access research may not fully capture the travel behavior and its relationship with local food environments. With modifications, the proposed method can help evaluate food access for a target population group, such as Supplemental Nutrition Assistance Program (SNAP) users or selected ethnic minorities who may face acute difficulties in procuring economically affordable and culturally appropriate foods.

Optimized clustering estimators for BAO measurements accounting for significant redshift uncertainty

We determine an optimized clustering statistic to be used for galaxy samples with significant redshift uncertainty, such as those that rely on photometric redshifts. To do so, we study the baryon acoustic oscillation (BAO) information content as a function of the orientation of galaxy clustering modes with respect to their angle to the line-of-sight (LOS). The clustering along the LOS, as observed in a redshift-space with significant redshift uncertainty, has contributions from clustering modes with a range of orientations with respect to the true LOS. For redshift uncertainty $\sigma_z \geq 0.02(1+z)$ we find that while the BAO information is confined to transverse clustering modes in the true space, it is spread nearly evenly in the observed space. Thus, measuring clustering in terms of the projected separation (regardless of the LOS) is an efficient and nearly lossless compression of the signal for $\sigma_z \geq 0.02(1+z)$. For reduced redshift uncertainty, a more careful consideration is required. We then use more than 1700 realizations (combining two separate sets) of galaxy simulations mimicking the Dark Energy Survey Year 1 sample to validate our analytic results and optimized analysis procedure. We find that using the correlation function binned in projected separation, we can achieve uncertainties that are within 10 per cent of those predicted by Fisher matrix forecasts. We predict that DES Y1 should achieve a 5 per cent distance measurement using our optimized methods. We expect the results presented here to be important for any future BAO measurements made using photometric redshift data.

More quantum centrifugal effect in rotating frame

The behaviour of quantum systems in non-inertial frames is revisited from the point of view of affine coherent state (ACS) quantization. We restrict our approach to the one-particle dynamics confined in a rotating plane about a fixed axis. This plane is considered as punctured due to the existence of the rotation center, which is viewed as a singularity. The corresponding phase space is the affine group of the plane and the ACS quantization enables us to quantize the system by respecting the affine symmetry of the true phase space. Our formulation predicts the appearance of an additional quantum centrifugal term, besides the usual angular-momentum one, which prevents the particle to reach the singular rotation center. Moreover it helps us to understand why two different non-inertial Schrödinger equations are obtained in previous works. The validity of our equation can be confirmed experimentally by observing the harmonic oscillator bound states and the critical angular velocity for their existence.

Interplay of space radiation and microgravity in DNA damage and DNA damage response

In space, multiple unique environmental factors, particularly microgravity and space radiation, pose constant threat to the DNA integrity of living organisms. Specifically, space radiation can cause damage to DNA directly, through the interaction of charged particles with the DNA molecules themselves, or indirectly through the production of free radicals. Although organisms have evolved strategies on Earth to confront such damage, space environmental conditions, especially microgravity, can impact DNA repair resulting in accumulation of severe DNA lesions. Ultimately these lesions, namely double strand breaks, chromosome aberrations, micronucleus formation, or mutations, can increase the risk for adverse health effects, such as cancer. How spaceflight factors affect DNA damage and the DNA damage response has been investigated since the early days of the human space program. Over the years, these experiments have been conducted either in space or using ground-based analogs. This review summarizes the evidence for DNA damage induction by space radiation and/or microgravity as well as spaceflight-related impacts on the DNA damage response. The review also discusses the conflicting results from studies aimed at addressing the question of potential synergies between microgravity and radiation with regard to DNA damage and cellular repair processes. We conclude that further experiments need to be performed in the true space environment in order to address this critical question.

Pleural Effusions and Pneumothoraces.

1. Katherine Cashen, DO* 2. Tara L. Petersen, MD† 1. *Department of Pediatrics, Children's Hospital of Michigan/Wayne State University School of Medicine, Detroit, MI 2. †Division of Critical Care, Department of Pediatrics, The Children’s Hospital of Wisconsin/The Medical College of Wisconsin, Milwaukee, WI * Abbreviations: BTS: : British Thoracic Society CHF: : congestive heart failure CT: : computed tomography VATS: : video-assisted thoracoscopic surgery 1. Clinicians should be aware of the causes and clinical presentation of pleural effusions and pneumothoraces. 2. Clinicians should understand the current role of diagnostic tests, imaging modalities, and timing of minimally invasive treatments. After completing this article, readers should be able to: 1. Describe the pathogenesis of pleural fluid accumulation. 2. Identify the most likely causes of pleural effusion and pneumothorax. 3. Understand the basic clinical presentation, diagnostic tests, and management of pleural effusions and pneumothoraces. 4. Differentiate between transudative and exudative pleural effusions. 5. Understand the natural history of spontaneous pneumothorax. The pleural space is created by the parietal and visceral pleura that line the chest wall and the lung surface, respectively. Normally, only a small amount (0.3 mL/kg) of hypotonic fluid is present within the pleural space due to homeostatic balances in physiologic fluid production and absorption. Various infectious and noninfectious processes can lead to pathologic filling of the pleural space with fluid (effusion) or air (pneumothorax). Such pathologic changes create a true space that can interfere with normal lung mechanics and, in severe cases, cardiac function. Although much less common in pediatric than adult populations, pleural effusions and pneumothoraces in both groups can lead to substantial complications, resulting in significant morbidity and mortality if unrecognized or untreated. Overall, the cause of pleural effusions and pneumothoraces differs in children compared to adults. In adults, congestive heart failure (CHF) and malignancy account for a substantial number of pleural effusions, but these are uncommon causes in children. Infectious pleural effusions in the setting of pneumonia (parapneumonic effusions) remain the most common cause of effusions in both children and adults. Unlike the adult population, children experience spontaneous …

The assessment of knowledge and learning in competence spaces: The gain-loss model for dependent skills.

The gain-loss model (GaLoM) is a formal model for assessing knowledge and learning. In its original formulation, the GaLoM assumes independence among the skills. Such an assumption is not reasonable in several domains, in which some preliminary knowledge is the foundation for other knowledge. This paper presents an extension of the GaLoM to the case in which the skills are not independent, and the dependence relation among them is described by a well-graded competence space. The probability of mastering skill s at the pretest is conditional on the presence of all skills on which s depends. The probabilities of gaining or losing skill s when moving from pretest to posttest are conditional on the mastery of s at the pretest, and on the presence at the posttest of all skills on which s depends. Two formulations of the model are presented, in which the learning path is allowed to change from pretest to posttest or not. A simulation study shows that models based on the true competence space obtain a better fit than models based on false competence spaces, and are also characterized by a higher assessment accuracy. An empirical application shows that models based on pedagogically sound assumptions about the dependencies among the skills obtain a better fit than models assuming independence among the skills.

Experimental tests for quality validation of computationally predicted crystal structures – a case of a conformationally flexible procyanidin A-2 dihydrate

Crystal structure prediction (CSP) of large, flexible, multi-component crystals is currently one of the most challenging computational tasks. In this work, we present a new approach to the CSP procedure, in which computationally generated crystal structures are evaluated not only on the basis of lattice energy, but also by the similarity of their theoretical NMR parameters and PXRD diffractograms with the experimental results. We employ procyanidin A-2 dihydrate as a model structure, and prove that even for such large and flexible systems with multiple possibilities of hydrogen bond formation it is possible to obtain a true crystal structure without single crystal diffraction experiments, on the condition that all three measures, i.e. lattice energy, NMR and PXRD similarity, are accounted for in an appropriate manner, so that they can guide us through a labyrinth of CSP-generated structures. The similarity of NMR parameters allows for unambiguous identification of the conformation of a molecule inside the crystal, whereas the PXRD data plainly indicates the true space group and, when combined with the crystal lattice energy, also the correct packing arrangement. Such an approach allows for faster elimination of incorrect structures, which in particular cases may be the only chance to obtain the true crystal structure within reasonable time and effort.

Bone‐marrow densitometry: Assessment of marrow space of human vertebrae by single energy high resolution‐quantitative computed tomography

Accurate noninvasive assessment of vertebral bone marrow fat fraction is important for diagnostic assessment of a variety of disorders and therapies known to affect marrow composition. Moreover, it provides a means to correct fat-induced bias of single energy quantitative computed tomography (QCT) based bone mineral density (BMD) measurements. The authors developed new segmentation and calibration methods to obtain quantitative surrogate measures of marrow-fat density in the axial skeleton. The authors developed and tested two high resolution-QCT (HR-QCT) based methods which permit segmentation of bone voids in between trabeculae hypothesizing that they are representative of bone marrow space. The methods permit calculation of marrow content in units of mineral equivalent marrow density (MeMD). The first method is based on global thresholding and peeling (GTP) to define a volume of interest away from the transition between trabecular bone and marrow. The second method, morphological filtering (MF), uses spherical elements of different radii (0.1-1.2 mm) and automatically places them in between trabeculae to identify regions with large trabecular interspace, the bone-void space. To determine their performance, data were compared ex vivo to high-resolution peripheral CT (HR-pQCT) images as the gold-standard. The performance of the methods was tested on a set of excised human vertebrae with intact bone marrow tissue representative of an elderly population with low BMD. 86% (GTP) and 87% (MF) of the voxels identified as true marrow space on HR-pQCT images were correctly identified on HR-QCT images and thus these volumes of interest can be considered to be representative of true marrow space. Within this volume, MeMD was estimated with residual errors of 4.8 mg/cm(3) corresponding to accuracy errors in fat fraction on the order of 5% both for GTP and MF methods. The GTP and MF methods on HR-QCT images permit noninvasive localization and densitometric assessment of marrow fat with residual accuracy errors sufficient to study disorders and therapies known to affect bone marrow composition. Additionally, the methods can be used to correct BMD for fat induced bias. Application and testing in vivo and in longitudinal studies are warranted to determine the clinical performance and value of these methods.

Twinning in chemical crystallography – a practical guide

Abstract A non-negliglible percentage of crystal structures in chemical crystallography are derived from twinned crystals. The treatment of these data is dependent on the type of twinning. Twins by strict, pseudo or reticular merohedry may hamper space group determination and structure solution, while non-merohedral twins mainly hinder the data integration process. One structure determination of each type is described in detail. CsCp*Py (1) crystallizes in space group P65, mimicking 6/mmm symmetry by merohedral twinning. The data of IPr · AlI3 (2) (IPr=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) simulate mmm symmetry although the true space group is P21/n. The crystals of K[Au(CN)2] (3) are obverse/reverse twins. [Cu3(dppaO2)2((OSiMe2)2O)2(thf)2] (4) (ddpaO2=bis(diphenylphosphoryl)amine) crystallizes in space group P21/n and is an example of a non-merohedral twin.

Assessment of dead-space ventilation in patients with acute respiratory distress syndrome: a prospective observational study.

BackgroundPhysiological dead space (VD/VT) represents the fraction of ventilation not participating in gas exchange. In patients with acute respiratory distress syndrome (ARDS), VD/VT has prognostic value and can be used to guide ventilator settings. However, VD/VT is rarely calculated in clinical practice, because its measurement is perceived as challenging. Recently, a novel technique to calculate partial pressure of carbon dioxide in alveolar air (PACO2) using volumetric capnography (VCap) was validated. The purpose of the present study was to evaluate how VCap and other available techniques to measure PACO2 and partial pressure of carbon dioxide in mixed expired air (PeCO2) affect calculated VD/VT.MethodsIn a prospective, observational study, 15 post-cardiac surgery patients and 15 patients with ARDS were included. PACO2 was measured using VCap to calculate Bohr dead space or substituted with partial pressure of carbon dioxide in arterial blood (PaCO2) to calculate the Enghoff modification. PeCO2 was measured in expired air using three techniques: Douglas bag (DBag), indirect calorimetry (InCal), and VCap. Subsequently, VD/VT was calculated using four methods: Enghoff-DBag, Enghoff-InCal, Enghoff-VCap, and Bohr-VCap.ResultsPaCO2 was higher than PACO2, particularly in patients with ARDS (post-cardiac surgery PACO2 = 4.3 ± 0.6 kPa vs. PaCO2 = 5.2 ± 0.5 kPa, P < 0.05; ARDS PACO2 = 3.9 ± 0.8 kPa vs. PaCO2 = 6.9 ± 1.7 kPa, P < 0.05). There was good agreement in PeCO2 calculated with DBag vs. VCap (post-cardiac surgery bias = 0.04 ± 0.19 kPa; ARDS bias = 0.03 ± 0.27 kPa) and relatively low agreement with DBag vs. InCal (post-cardiac surgery bias = −1.17 ± 0.50 kPa; ARDS mean bias = −0.15 ± 0.53 kPa). These differences strongly affected calculated VD/VT. For example, in patients with ARDS, VD/VTcalculated with Enghoff-InCal was much higher than Bohr-VCap (VD/VTEnghoff-InCal = 66 ± 10 % vs. VD/VTBohr-VCap = 45 ± 7 %; P < 0.05).ConclusionsDifferent techniques to measure PACO2 and PeCO2 result in clinically relevant mean and individual differences in calculated VD/VT, particularly in patients with ARDS. Volumetric capnography is a promising technique to calculate true Bohr dead space. Our results demonstrate the challenges clinicians face in interpreting an apparently simple measurement such as VD/VT.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-016-1311-8) contains supplementary material, which is available to authorized users.

A Self-Organized Internal Models Architecture for Coding Sensory–Motor Schemes

Cognitive robotics research draws inspiration from theories and models on cognition, as conceived by neuroscience or cognitive psychology, to investigate biologically plausible computational models in artificial agents. In this field, the theoretical framework of Grounded Cognition provides epistemological and methodological grounds for the computational modeling of cognition. It has been stressed in the literature that \textit{simulation}, \textit{prediction}, and \textit{multi-modal integration} are key aspects of cognition and that computational architectures capable of putting them into play in a biologically plausible way are a necessity. Research in this direction has brought extensive empirical evidence suggesting that \textit{Internal Models} are suitable mechanisms for sensory-motor integration. However, current Internal Models architectures show several drawbacks, mainly due to the lack of a unified substrate allowing for a true sensory-motor integration space, enabling flexible and scalable ways to model cognition under the embodiment hypothesis constraints. We propose the Self-Organized Internal Models Architecture (SOIMA), a computational cognitive architecture coded by means of a network of self-organized maps, implementing coupled internal models that allow modeling multi-modal sensory-motor schemes. Our approach addresses integrally the issues of current implementations of Internal Models. We discuss the design and features of the architecture, and provide empirical results on a humanoid robot that demonstrate the benefits and potentialities of the SOIMA concept for studying cognition in artificial agents.

Reason for T2K to run in dominant neutrino mode for detectingCPviolation

The long-baseline experiment T2K in Japan has collected data in the neutrino mode corresponding to an exposure of $6.57 \times 10^{20}$ POT (Protons on Target) and currently it is running in the antineutrino mode. The main aim of the antineutrino run is to measure the leptonic phase $\delta_{CP}$ which may help to understand the matter-antimatter asymmetry of the universe. In this work we show that in T2K, antineutrinos are required only for removing the wrong octant solutions which in turn improves the CP sensitivity. If however the octant is known then pure neutrino run is capable of giving the maximum CP sensitivity. If we divide the total true parameter space into eight sets, then we find that T2K antineutrino run helps in improving the CP sensitivity for only two sets while for the remaining six combinations pure neutrino run gives the best CP sensitivity. Thus if the neutrino run is replaced by the antineutrino run then it causes a reduction in the CP sensitivity in 75$\%$ of the true parameter space due to lesser statistics. Thus it is worthwhile to study if the T2K antineutrino run can be reduced by the antineutrino runs of the other experiments, so that T2K can run in dominant neutrino mode to extract the best CP sensitivity. In this work we explore the possibility of the antineutrino component of NO$\nu$A and the atmospheric neutrino experiment ICAL@INO for compensating the antineutrino run of T2K.

New look at the degeneracies in the neutrino oscillation parameters, and their resolution by T2K,NOνAand ICAL

At present the three major unknowns in neutrino oscillation parameters are the mass hierarchy, the octant of $\theta_{23}$ and the CP phase $\delta_{CP}$. It is well known that the presence of hierarchy$-\delta_{CP}$ and octant degeneracies affects the unambiguous determination of these parameters. In this paper we show that a comprehensive way to study the remaining parameter degeneracies is in the form of a generalized hierarchy-$\theta_{23}$ - $\delta_{CP}$ degeneracy. We show that the wrong-hierarchy and/or wrong-octant solutions can be further classified into eight different solutions depending on whether they occur with the wrong or right value of $\delta_{CP}$. These eight solutions are different from the original eightfold degenerate solutions and can exist, in principle, even if $\theta_{13}$ is known. These multiple solutions, apart from affecting the determination of the true hierarchy and octant, also affect the accurate estimation of $\delta_{CP}$. We identify which of these eight different degenerate solutions can occur in the test ($\theta_{23} - \delta_{CP}$) parameter space, taking the long-baseline experiment NO$\nu$A running in the neutrino mode as an example. The inclusion of the NO$\nu$A antineutrino run removes the wrong-octant solutions appearing with both right and wrong hierarchy. Adding T2K data to this resolves the wrong hierarchy -- right octant solutions to a large extent. The remaining wrong hierarchy solutions can be removed by combining NO$\nu$A + T2K with atmospheric neutrino data. We demonstrate this using ICAL@INO as the prototype atmospheric neutrino detector. We find that the degeneracies can be resolved at the $2\sigma$ level by the combined data set, for the true parameter space considered in the study.

Anatomic Considerations of Intervertebral Disc Perspective in Lumbar Posterolateral Approach via Kambin's Triangle: Cadaveric Study

Study DesignAnatomical study.PurposeTo evaluate the anatomy of intervertebral disc (IVD) area in the triangular working zone of the lumbar spine based on cadaveric measurements.Overview of LiteratureThe posterolateral percutaneous approach to the lumbar spine has been widely used as a minimally invasive spinal surgery. However, to our knowledge, the actual perspective of disc boundaries and areas through posterolateral endoscopic approach are not well defined.MethodsNinety-six measurements for areas and dimensions of IVD in Kambin's triangle on bilateral sides of L1–S1 in 5 fresh human cadavers were studied.ResultsThe trapezoidal IVD area (mean±standard deviation) for true working space was 63.65±14.70 mm2 at L1–2, 70.79±21.88 mm2 at L2–3, 99.03±15.83 mm2 at L3–4, 116.22±20.93 mm2 at L4–5, and 92.18±23.63 mm2 at L5–S1. The average dimension of calculated largest ellipsoidal cannula that could be placed in IVD area was 5.83×11.02 mm at L1–2, 6.97×10.78 mm at L2–3, 9.30×10.67 mm at L3–4, 8.84×13.15 mm at L4–5, and 6.61×14.07 mm at L5–S1.ConclusionsThe trapezoidal perspective of working zone of IVD in Kambin's triangle is important and limited. This should be taken into consideration when developing the tools and instruments for posterolateral endoscopic lumbar spine surgery.

Computing the Degenerate Ground Space of Gapped Spin Chains in Polynomial Time

Given a gapped Hamiltonian of a spin chain, we give a polynomial-time algorithm for finding the degenerate ground space projector. The output is an orthonormal set of matrix product states that approximate the true ground space projector up to an inverse polynomial error in any Schatten norm, with a runtime exponential in the degeneracy. Our algorithm is an extension of the recent algorithm of Landau, Vazirani, and Vidick for the nondegenerate case, and it includes the recent improvements due to Huang. The main new idea is to incorporate the local distinguishability of ground states on the half-chain to ensure that the algorithm returns a complete set of global ground states.

A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay (BRAVA-RR), which has the unusual radial velocity of -372 +- 8 km/s and true space velocity of -482 +- 22 km/s relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l,b)=(3,-2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.

On the structure of polyharmonic Bergman-type spaces over the unit disk

Let be a pair of nonnegative integers. We deduce explicit representations for the projections onto spaces of square integrable -polyanalytic functions in terms of the two-sided compression of the Beurling–Ahlfors transform to the unit disk. We show that the space of square integrable -polyanalytic functions is a reproducing kernel Hilbert space and we deduce representations for one-to-one bounded operators from the Bergman space onto the true poly-Bergman spaces and from the harmonic Bergman space onto the true polyharmonic Bergman spaces. Moreover, we prove a decomposition theorem for polyharmonic functions in terms of their harmonic components. Finally, for positive integers we establish an isometry between a subspace of the true polyharmonic Bergman space of order with codimension and the true polyharmonic Bergman space of order .

Extension of concurrent subspace optimization to structural optimization of product families

This paper discusses the problem of structural optimization of product families with predefined platforms. The main challenge lies in the increased design variables and constraints, and providing an optimal tradeoff for individual products performance in the family which are competitive with each other. The Concurrent Subspace Optimization for multidisciplinary problem is extended to product family design with predefined platforms. The main advantage of the proposed approach is that the system level owns the ability to catch the global tendency of the true design space and the number of evaluations required is reduced by using surrogate models. Each subspace optimization problem has the freedom to specify the unique variables for one family member, and the system level optimizes the product platform using the surrogate models created based on subspace optimizations. The process is solved in an iterative way, and the improving surrogate models guide the optimization to the global optimal design. Results from a truss family example with small design space confirm the ability and efficiency of the extended Concurrent Subspace Optimization to address product family problem by compared with ATC approach. Then the proposed method is successfully applied to a family of unmanned aircraft wing structures, which is more complicated and related to practical implementation issues.

Regulation of signal transduction by spatial parameters: a case in NF-κB oscillation.

NF-κB is a transcription factor regulating expression of more than 500 genes, and its dysfunction leads to the autoimmune and inflammatory diseases. In malignant cancer cells, NF-κB is constitutively activated. Thus the elucidation of mechanisms for NF-κB regulation is important for the establishment of therapeutic treatment caused by incorrect NF-κB responses. Cytoplasmic NF-κB translocates to the nucleus by the application of extracellular stimuli such as cytokines. Nuclear NF-κB is known to oscillate with the cycle of 1.5-4.5 h, and it is thought that the oscillation pattern regulates the expression profiles of genes. In this review, first we briefly describe regulation mechanisms of NF-κB. Next, published computational simulations on the oscillation of NF-κB are summarised. There are at least 60 reports on the computational simulation and analysis of NF-κB oscillation. Third, the importance of a 'space' for the regulation of oscillation pattern of NF-κB is discussed, showing altered oscillation pattern by the change in spatial parameters such as diffusion coefficient, nuclear to cytoplasmic volume ratio (N/C ratio), and transport through nuclear membrane. Finally, simulations in a true intracellular space (TiCS), which is an intracellular 3D space reconstructed in a computer with organelles such as nucleus and mitochondria are discussed.

Interpreting Quantum Theories

Laura Ruetsche, Interpreting Quantum Theories. Oxford: Oxford University Press. Pp. xvii, 377. Most philosophical work on quantum physics has concerned simple systems. And for good reason. Even one or two particle systems can exhibit the striking features we have come to associate with quantum physics—features such as entanglement, interference, and non-locality. But as far as physics goes, such systems barely scrape the surface. In particular, they have only a finite number of degrees of freedom, which means their states are characterized by a finite number of independent parameters. The systems studied in fields such as high energy particle physics and many-body physics, meanwhile, have uncountably many degrees of freedom. They are far more complicated than the usual philosophical fare. This is untroubling as long as the conceptual heart of quantum physics can be effectively condensed down. But what if philosophers’ toy systems are fundamentally different from realistic ones? That would be a problem. And indeed, as Laura Ruetsche convincingly argues in Interpreting Quantum Theories, systems with uncountable degrees of freedom—what Ruetsche collectively calls QM ∞ —are fundamentally different from the systems that have become the stock and trade of philosophy of physics, in ways that change the interpretational project. Ruetsche’s book does two things exceedingly well. The first is to provides a (comparatively) accessible and philosophically-oriented introduction to the algebraic approach to quantum physics, which is essential for understanding QM ∞ . This is a valuable contribution. The algebraic approach is the setting for much recent philosophical work. And yet learning it is notoriously difficult, as even pedagogical texts are aimed at research-level mathematicians. Ruetsche’s book is technically demanding, but it works to bring non-mathematicians along. It is, without a doubt, the best place to enter this literature. Second, the book sets the agenda for future work on QM ∞ , by effectively and judiciously drawing important foundational questions out of a sprawling and difficult physics literature. In this regard, it is a close cousin to John Earman’s excellent Bangs, Crunches, Whimpers, and Shrieks, which has had a significant influence on subsequent philosophy of spacetime physics. 1 Philosophers of physics will be addressing the questions Ruetsche has raised, in many cases for the first time, for years to come. Interpreting Quantum Theories centers on what might be called the problem of inequivalent representations. The quantum theories that philosophers are accustomed to are set in a mathematical structure known as a (separable) Hilbert space, which is an at-most countably infinite dimensional complex vector space. Rays in a Hilbert space represent possible states of a physical system, and self- adjoint operators on that Hilbert space correspond to properties of the system. 1 John Earman, Bangs, Crunches, Whimpers, and Shrieks (Oxford: Oxford University Press, 1995).