Radiation is an Important Component of Multimodality Therapy for Pediatric Supratentorial Non-Pineal Neuroectodermal Tumors

Purpose: We reviewed a historical cohort of pediatric patients with supratentorial primitive neuroectodermal tumors (sPNET) in order to clarify the role of radiation in the treatment of these tumors. Patients and Methods: Fifteen children \u3c18 years old with non-pineal sPNETs diagnosed between 1992 and 2006 were identified. Initial therapy consisted of surgical resection and chemotherapy (CT) in all patients and up-front radiotherapy (RT) in 5 patients. Five patients had RT at the time of progression and five received no RT whatsoever. Kaplan-Meier estimates of overall-survival (OS) were then calculated. Results: The median follow-up from diagnosis for all patients was 31 months (range 0.5-165) and for surviving patients was 49 months (range 10-165). Of the 5 patients who received up-front RT, all were alive without evidence of disease at a median follow-up of 50 months (range 25-165). Only 5 of the 10 patients who did not receive up-front RT were alive at last follow-up. There was a statistically significant difference in overall survival between the group of patients that received up-front RT and the group that did not (P=0.048). Additionally, we found a trend toward a statistically significant improvement in overall-survival for those patients that received gross total resections (P=0.10). Conclusions: Up-front radiotherapy and gross total resection may confer a survival benefit in patients with sPNET. Local failure was the dominant pattern of recurrence. Efforts should be made to determine patients most likely to have local failure exclusively or as a first recurrence in order to delay or eliminate cranio-spinal irradiation (CSI)

Simple Perturbatively Traversable Wormholes from Bulk Fermions

A new class of traversable wormholes was recently constructed which relies only on local bulk dynamics rather than an explicit coupling between distinct boundaries. Here we begin with a four-dimensional Weyl fermion field of any mass $m$ propagating on a classical background defined by a ${\mathbb Z}_2$ quotient of (rotating) BTZ $\times \, S^1$. This setup allows one to compute the fermion stress-energy tensor exactly. For appropriate boundary conditions around a non-contractible curve, perturbative back-reaction at any $m$ renders the associated wormhole traversable and suggests it can become eternally traversable at the limit where the background becomes extremal. A key technical step is the proper formulation of the method of images for fermions in curved spacetime. We find the stress-energy of spinor fields to have important kinematic differences from that of scalar fields, typically causing the sign of the integrated null stress-energy (and thus in many cases the sign of the time delay/advance) to vary around the throat of the wormhole. Similar effects may arise for higher-spin fields.Comment: 30 pages, 5 figure

Influence of Line Tension on Spherical Colloidal Particles at Liquid-Vapor Interfaces

Atomic force microscopy (AFM) imaging of isolated submicron dodecyltrichlorosilane coated silica spheres, immobilized at the liquid polystyrene- (PS-) air interface at the PS glass transition temperature, Tg , allows for determination of the contact angle θ versus particle radius R . At Tg , all θ versus R measurements are well described by the modified Young’s equation for a line tension τ=0.93  nN . The AFM measurements are also consistent with a minimum contact angle θmin and minimum radius Rmin , below which single isolated silica spheres cannot exist at the PS-air interface

Improved In Situ Spring Constant Calibration for Colloidal Probe Atomic Force Microscopy

In colloidal probe atomic force microscopy (AFM) surface forces cannot be measured without an accurate determination of the cantilever spring constant. The effective spring constant k depends upon the cantilever geometry and therefore should be measured in situ; additionally, k may be coupled to other measurement parameters. For example, colloidal probe AFM is frequently used to measure the slip length b at solid/liquid boundaries by comparing the measured hydrodynamic force with Vinogradova slip theory (V-theory). However, in this measurement k and b are coupled, hence, b cannot be accurately determined without knowing k to high precision. In this paper, a new in situ spring constant calibration method based upon the residuals, namely, the difference between experimental force-distance data and V-theory is presented and contrasted with two other popular spring constant determination methods. In this residuals calibration method, V-theory is fitted to the experimental force-distance data for a range of systematically varied spring constants where the only adjustable parameter in V-theory is the slip length b. The optimal spring constant k is that value where the residuals are symmetrically displaced about zero for all colloidal probe separations. This residual spring constant calibration method is demonstrated by studying three different liquids (n-decanol, n-hexadecane, and n-octane) and two different silane coated colloidal probe-silicon wafer systems (n-hexadecyltrichlorosilane and n-dodecyltrichlorosilane)

Viscosity Dependent Liquid Slip at Molecularly Smooth Hydrophobic Surfaces

Colloidal probe atomic force microscopy is used to study the slip behavior of 18 Newtonian liquids from two homologous series, the n-alkanes and n-alcohols, at molecularly smooth hydrophobic n-hexadecyltrichlorosilane coated surfaces. We find that the slip behavior is governed by the bulk viscosity η of the liquid, specifically, the slip length b∼ηx with x∼0.33. Additionally, the slip length was found to be shear rate independent, validating the use of Vinogradova slip theory in this work

The Epstein-Barr Virus Episome Maneuvers between Nuclear Chromatin Compartments during Reactivation.

The human genome is structurally organized in three-dimensional space to facilitate functional partitioning of transcription. We learned that the latent episome of the human Epstein-Barr virus (EBV) preferentially associates with gene-poor chromosomes and avoids gene-rich chromosomes. Kaposi's sarcoma-associated herpesvirus behaves similarly, but human papillomavirus does not. Contacts on the EBV side localize to OriP, the latent origin of replication. This genetic element and the EBNA1 protein that binds there are sufficient to reconstitute chromosome association preferences of the entire episome. Contacts on the human side localize to gene-poor and AT-rich regions of chromatin distant from transcription start sites. Upon reactivation from latency, however, the episome moves away from repressive heterochromatin and toward active euchromatin. Our work adds three-dimensional relocalization to the molecular events that occur during reactivation. Involvement of myriad interchromosomal associations also suggests a role for this type of long-range association in gene regulation.IMPORTANCE The human genome is structurally organized in three-dimensional space, and this structure functionally affects transcriptional activity. We set out to investigate whether a double-stranded DNA virus, Epstein-Barr virus (EBV), uses mechanisms similar to those of the human genome to regulate transcription. We found that the EBV genome associates with repressive compartments of the nucleus during latency and with active compartments during reactivation. This study advances our knowledge of the EBV life cycle, adding three-dimensional relocalization as a novel component to the molecular events that occur during reactivation. Furthermore, the data add to our understanding of nuclear compartments, showing that disperse interchromosomal interactions may be important for regulating transcription

Ridesourcing and the Taxi Marketplace

Thesis advisor: Joseph QuinnThe creation of ridesourcing firms Uber and Lyft greatly disrupted the taxicab marketplace in the United States over the past four years. By examining the taxicab marketplace, as well as the ridesourcing firm’s aspects of creative destruction, the marketplace’s drastic changes become apparent. Thus, 21st century technology disrupts the marketplace, and creates a real time market based on supply and demand factors. Furthermore, disruption impacts all actors within the previous taxicab marketplace as well as the newly created ridesourcing marketplace; therefore, ridesourcing’s widespread effects are examined in detail.Thesis (BS) — Boston College, 2015.Submitted to: Boston College. College of Arts and Sciences.Discipline: Departmental Honors.Discipline: Economics

Long reach cantilevers for sub-cellular force measurements

Maneuverable, high aspect ratio poly 3-4 ethylene dioxythiophene (PEDOT) fibers are fabricated for use as cellular force probes that can interface with individual pseudopod adhesive contact sites without forming unintentional secondary contacts to the cell. The straight fibers have lengths between 5 and 40 μm and spring constants in the 0.07-23.2 nN μm-1 range. The spring constants of these fibers were measured directly using an atomic force microscope (AFM). These AFM measurements corroborate determinations based on the transverse vibrational resonance frequencies of the fibers, which is a more convenient method. These fibers are employed to characterize the time dependent forces exerted at adhesive contacts between apical pseudopods of highly migratory D. discoideum cells and the PEDOT fibers, finding an average terminal force of 3.1 ± 2.7 nN and lifetime of 23.4 ± 18.5 s to be associated with these contacts

Hydrolysis of p-Nitrophenyl Esters Promoted by Semi-fluorinated Quaternary Ammonium Polymer Latexes and Films

Semifluorinated polymer latexes were prepared by emulsion polymerization of 2.5-25% of a fluoroalkyl methacrylate, 25% chloromethylstyrene, 1% styrylmethyl(trimethyl)ammonium chloride, and the remainder 2-ethylhexyl methacrylate under surfactant-free conditions. The chloromethylstyrene units were converted to quaternary ammonium ions with trimethylamine. In aqueous dispersions at particle concentrations of less than 1 mg mL-1 the quaternary ammonium ion latexes promoted hydrolyses of p-nitrophenyl hexanoate (PNPH) in pH 9.4 borate buffer and of diethyl p-nitrophenyl phosphate (Paraoxon) in 0.1 M NaOH at 30 oC with half-lives of less than 10 minutes. Thin 0.7-2 μm films of the latexes on glass promoted fast hydrolysis of Paraoxon but not of PNPH under the same conditions. Even after annealing the quaternary ammonium ion polymer films at temperatures well above their glass transition temperatures, AFM images of the film surfaces had textures of particles. Contact angle measurements of the annealed films against water and against hexadecane showed that the surfaces were not highly fluorinated

Traversable Wormholes, The Positivity of Negativity, and How to Gauge Your Tensor Network

This thesis reports on aspects of semiclassical gravity with an eye towards holography.Chapter 2 introduces a perturbatively traversable wormhole in a particular four-dimensional quotient spacetime, where traversability is ensured by the Casimir energy of bulk fermions. We compute the fermionic contribution to the integrated null stress-energy tensor and find hints that traversability holds at all times.Chapters 3 and 4 report on computations of entanglement negativity, a multipartite entanglement measure which distinguishes between classical and quantum correlations. We compute holographic entanglement negativity in a toy model of Jackiw-Teitelboim gravity with end-of-the-world branes, finding a rich phase structure which includes replica symmetry breaking in a large region of phase space. We also compute entanglement negativity in a toy model of chaotic eigenstates, finding some qualitative agreement with phase transitions in the holographic model.Chapter 5 describes a modification to random tensor networks to incorporate bulk gauge symmetries which we term the "gauged random tensor network." We find an area operator valued in the center of the gauged random tensor network bulk algebra which more closely resembles the area operator provided by the quantum-corrected Ryu-Takayanagi formula