Communications from the psychological laboratory of Harvard University: Automatic reactions.

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A finite-difference solution of solute transport through a membrane bioreactor

The current paper presents a theoretical analysis of the transport of solutes through a fixed-film membrane bioreactor (MBR), immobilised with an active biocatalyst. The dimensionless convection-diffusion equation with variable coefficients was solved analytically and numerically for concentration profiles of the solutes through the MBR. The analytical solution makes use of regular perturbation and accounts for radial convective flow as well as axial diffusion of the substrate species. The Michaelis-Menten (or Monod) rate equation was assumed for the sink term, and the perturbation was extended up to second-order. In the analytical solution only the first-order limit of the Michaelis-Menten equation was considered; hence the linearized equation was solved. In the numerical solution, however, this restriction was lifted. The solution of the nonlinear, elliptic, partial differential equation was based on an implicit finite-difference method (FDM). An upwind scheme was employed for numerical stability. The resulting algebraic equations were solved simultaneously using the multivariate Newton-Raphson iteration method. The solution allows for the evaluation of the effect on the concentration profiles of (i) the radial and axial convective velocity, (ii) the convective mass transfer rates, (iii) the reaction rates, (iv) the fraction retentate, and (v) the aspect ratio

Electron orbital valves made of multiply connected armchair carbon nanotubes with mirror-reflection symmetry: tight-binding study

Using the tight-binding method and the Landauer-B\"{u}ttiker conductance formalism, we demonstrate that a multiply connected armchair carbon nanotube with a mirror-reflection symmetry can sustain an electron current of the $\pi$-bonding orbital while suppress that of the $\pi$-antibonding orbital over a certain energy range. Accordingly, the system behaves like an electron orbital valve and may be used as a scanning tunneling microscope to probe pairing symmetry in d-wave superconductors or even orbital ordering in solids which is believed to occur in some transition-metal oxides.Comment: 4 figures, 12 page

Projected Utility of the Ready Set Return Application

Introduction: An application (app) that summarizes best practices may promote standardized care among clinicians treating patients during anterior cruciate ligament (ACL) rehabilitation. The purpose of this study was to test the prototype of the Ready Set Return (RSR) app to determine receptiveness for use in clinical practice. Methods: Two mock patient cases were used to familiarize 19 physical therapists and athletic trainers with the RSR app. Then these participants provided feedback about the user experience, features, and content using Likert ratings and free-text fields through an online survey. Results: Most participants (89%-95%) would recommend the RSR app to others and noted that the app would allow them to stay up to date with current practice. Thematic analysis of free-text responses indicated that the app was easy to navigate and that evidence-based progressions and clinical milestones were useful in clinical practice. Users suggested enhancements that included adding patient access and specific treatment options. Discussion: Generalizable findings suggest that clinicians appreciated the details and images of specific tests and measures; automatic test scoring; and standardized benchmarks to progress care. Specific findings suggest the RSR app’s summary of evidence-informed practice may help standardize care, specifically for patients undergoing rehabilitation after ACL reconstruction. Conclusion: This subset of clinicians reacted positively to the prototype and felt that the RSR app would benefit their practice and patients. This feedback will guide the next iteration, advancing from a low-fidelity to high-fidelity prototype

Seizure outcomes and survival in adult low-grade glioma over 11 years: living longer and better

Background: There has been a trend toward earlier and more aggressive resection for low-grade gliomas (LGGs). This study set out to compare seizure control and survival of adults with LGG seen in the same neuro-oncology clinic over 11 years and to determine whether a change in surgical philosophy has led to a corresponding improvement in outcomes. / Methods: We conducted a retrospective analysis using case-note review of 153 adults with histologically verified or radiologically suspected LGG, collecting data on patient, tumor, and seizure characteristics between 2006 and 2017. / Results: We studied 79 patients in 2006 and 74 patients in 2017. There was no significant difference between the 2 groups in age at presentation, tumor location, or integrated pathological diagnosis. The numbers of complete or partial resections increased from 21.5% in 2006 to 60.8% in 2017 (P < .05). Five- and 10-year overall survival increased from 81.8% and 51.7% in 2006 to 100% and 95.8% in 2017 (P < .001); similarly, 5- and 10-year progression-free survival increased from 47.0% and 30.7% in 2006 to 93.1% and 68.7% in 2017. The proportion of patients with intractable epilepsy declined from 72.2% in 2006 to 43.2% in 2017 (P < .05). The neurosurgical morbidity rate was identical in both groups (11.8% in 2006 vs 11.1% in 2017). / Conclusion: Management of LGG over the last 11 years has led to substantial improvements in survival and seizure control. This is most likely thanks to a change in surgical philosophy, with early resection now favored over watchful waiting where possible

Cutting Ties with Pro-Ana: A Narrative Inquiry Concerning the Experiences of Pro-Ana Disengagement from Six Former Site Users.

Websites advocating the benefits of eating disorders (“Pro-Ana”) tend to reinforce and maintain restrictive eating and purging behaviors. Yet remarkably, no study has explored individual accounts of disengagement from these sites and the associated meanings. Using narrative inquiry, this study sought to address this gap. From the interviews of six women, two overarching storylines emerged. The first closely tied disengagement to recovery with varying positions of personal agency claimed: this ranged from enforced and unwelcomed breaks that ignited change, to a personal choice that became viable through the development of alternative social and personal identities. A strong counternarrative to “disengagement as recovery” also emerged. Here, disengagement from Pro-Ana was storied alongside a need to retain an ED lifestyle. With “recovery” being just one reason for withdrawal from Pro-Ana sites, clinicians must remain curious about the meanings individuals ascribe to this act, without assuming it represents a step toward recovery.Peer reviewedFinal Accepted Versio

A Solution to the Graceful Exit Problem in Pre-Big Bang Cosmology

We examine the string cosmology equations with a dilaton potential in the context of the Pre-Big Bang Scenario with the desired scale factor duality, and give a generic algorithm for obtaining solutions with appropriate evolutionary properties. This enables us to find pre-big bang type solutions with suitable dilaton behaviour that are regular at $t=0$, thereby solving the graceful exit problem. However to avoid fine tuning of initial data, an `exotic' equation of state is needed that relates the fluid properties to the dilaton field. We discuss why such an equation of state should be required for reliable dilaton behaviour at late times.Comment: 16 pages LaTeX, 5 figures. To appear in Physical Review

Mycophenolate mofetil and intravenous cyclophosphamide are similar as induction therapy for class V lupus nephritis

Class V lupus nephritis (LN) occurs in one-fifth of biopsy-proven cases of systemic lupus erythematosus. To study the effectiveness of treatments in this group of patients, we pooled analysis of two large randomized controlled multicenter trials of patients with diverse ethnic and racial background who had pure class V disease. These patients received mycophenolate mofetil (MMF) or intravenous cyclophosphamide (IVC) as induction therapy for 24 weeks, with percentage change in proteinuria and serum creatinine as end points. Weighted mean differences, pooled odds ratios, and confidence intervals were calculated by using a random-effects model. A total of 84 patients with class V disease were divided into equal groups, each group had comparable entry variables but one received MMF and one received IVC. Within these groups, 33 patients on MMF and 32 patients on IVC completed 24 weeks of treatment. There were no differences between the groups in mean values for the measured end points. Similarly, no difference was found regarding the number of patients who did not complete the study or who died. In patients with nephrotic syndrome, no difference was noted between those treated with MMF and IVC regarding partial remission or change in urine protein. Hence we found that the response to MMF as induction treatment of patients with class V LN appears to be no different from that to IVC

Caustics of Compensated Spherical Lens Models

We consider compensated spherical lens models and the caustic surfaces they create in the past light cone. Examination of cusp and crossover angles associated with particular source and lens redshifts gives explicit lensing models that confirm previous claims that area distances can differ by substantial factors from angular diameter distances even when averaged over large angular scales. `Shrinking' in apparent sizes occurs, typically by a factor of 3 for a single spherical lens, on the scale of the cusp caused by the lens; summing over many lenses will still leave a residual effect.Comment: 21 pages, 5 ps figures, eps