92 research outputs found
Development of Dual-Gain SiPM Boards for Extending the Energy Dynamic Range
Astronomical observations with gamma rays in the range of several hundred keV
to hundreds of MeV currently represent the least explored energy range. To
address this so-called MeV gap, we designed and built a prototype CsI:Tl
calorimeter instrument using a commercial off-the-shelf (COTS) SiPMs and
front-ends which may serve as a subsystem for a larger gamma-ray mission
concept. During development, we observed significant non-linearity in the
energy response. Additionally, using the COTS readout, the calorimeter could
not cover the four orders of magnitude in energy range required for the
telescope. We, therefore, developed dual-gain silicon photomultiplier (SiPM)
boards that make use of two SiPM species that are read out separately to
increase the dynamic energy range of the readout. In this work, we investigate
the SiPM's response with regards to active area ( and
) and various microcell sizes (, , and ). We read out CsI:Tl chunks
using dual-gain SiPMs that utilize microcells for both
SiPM species and demonstrate the concept when tested with high-energy gamma-ray
and proton beams. We also studied the response of $17 \times 17 \times 100 \
\mathrm{mm}^30.25-400 \ \mathrm{MeV}2.5-30 \ \mathrm{MeV}$. This development aims to demonstrate
the concept for future scintillator-based high-energy calorimeters with
applications in gamma-ray astrophysics
Development of a CsI Calorimeter for the Compton-Pair (ComPair) Balloon-Borne Gamma-Ray Telescope
There is a growing interest in astrophysics to fill in the observational
gamma-ray MeV gap. We, therefore, developed a CsI:Tl calorimeter prototype as a
subsystem to a balloon-based Compton and Pair-production telescope known as
ComPair. ComPair is a technology demonstrator for a gamma-ray telescope in the
MeV range that is comprised of 4 subsystems: the double-sided silicon detector,
virtual Frisch grid CdZnTe, CsI calorimeter, and a plastic-based
anti-coincidence detector. The prototype CsI calorimeter is composed of thirty
CsI logs, each with a geometry of .
The logs are arranged in a hodoscopic fashion with 6 in a row that alternate
directions in each layer. Each log has a resolution of around
full-width-at-half-maximum (FWHM) at with a dynamic energy
range of around . A array of
SensL J-series SiPMs read out each end of the log to estimate the depth of
interaction and energy deposition with signals read out with an IDEAS ROSSPAD.
We also utilize an Arduino to synchronize with the other ComPair subsystems
that comprise the full telescope. This work presents the development and
performance of the calorimeter, its testing in thermal and vacuum conditions,
and results from irradiation by monoenergetic gamma-ray
beams. The CsI calorimeter will fly onboard ComPair as a balloon experiment in
the summer of 2023
The Advanced Compton Telescope
The Advanced Compton Telescope (ACT), the next major step in gamma-ray astronomy, will probe the fires where chemical elements are formed by enabling high-resolution spectroscopy of nuclear emission from supernova explosions. During the past two years, our collaboration has been undertaking a NASA mission concept study for ACT. This study was designed to (1) transform the key scientific objectives into specific instrument requirements, (2) to identify the most promising technologies to meet those requirements, and (3) to design a viable mission concept for this instrument. We present the results of this study, including scientific goals and expected performance, mission design, and technology recommendations
Magnetoresistance through a single molecule
The use of single molecules to design electronic devices is an extremely
challenging and fundamentally different approach to further downsizing
electronic circuits. Two-terminal molecular devices such as diodes were first
predicted [1] and, more recently, measured experimentally [2]. The addition of
a gate then enabled the study of molecular transistors [3-5]. In general terms,
in order to increase data processing capabilities, one may not only consider
the electron's charge but also its spin [6,7]. This concept has been pioneered
in giant magnetoresistance (GMR) junctions that consist of thin metallic films
[8,9]. Spin transport across molecules, i.e. Molecular Spintronics remains,
however, a challenging endeavor. As an important first step in this field, we
have performed an experimental and theoretical study on spin transport across a
molecular GMR junction consisting of two ferromagnetic electrodes bridged by a
single hydrogen phthalocyanine (H2Pc) molecule. We observe that even though
H2Pc in itself is nonmagnetic, incorporating it into a molecular junction can
enhance the magnetoresistance by one order of magnitude to 52%.Comment: To appear in Nature Nanotechnology. Present version is the first
submission to Nature Nanotechnology, from May 18th, 201
Comment on Spracklandus Hoser, 2009 (Reptilia, Serpentes, ELAPIDAE): request for confirmation of the availability of the generic name and for the nomenclatural validation of the journal in which it was published (Case 3601; see BZN 70: 234β237; 71: 30β38, 133β135, 181β182, 252β253)
How to Choose the Right Inhaler Using a Patient-Centric Approach?
There are many different inhaler devices and medications on the market for the treatment of asthma and chronic obstructive pulmonary disease, with over 230 drug-delivery system combinations available. However, despite the abundance of effective treatment options, the achieved disease control in clinical practice often remains unsatisfactory. In this context, a key determining factor is the match or mismatch of an inhalation device with the characteristics or needs of an individual patient. Indeed, to date, no ideal device exists that fits all patients, and a personalized approach needs to be considered. Several useful choice-guiding algorithms have been developed in the recent years to improve inhaler-patient matching, but a comprehensive tool that translates the multifactorial complexity of inhalation therapy into a user-friendly algorithm is still lacking. To address this, a multidisciplinary expert panel has developed an evidence-based practical treatment tool that allows a straightforward way of choosing the right inhaler for each patient
CyberKnife for hilar lung tumors: report of clinical response and toxicity
<p>Abstract</p> <p>Objective</p> <p>To report clinical efficacy and toxicity of fractionated CyberKnife radiosurgery for the treatment of hilar lung tumors.</p> <p>Methods</p> <p>Patients presenting with primary and metastatic hilar lung tumors, treated using the CyberKnife system with Synchrony fiducial tracking technology, were retrospectively reviewed. Hilar location was defined as abutting or invading a mainstem bronchus. Fiducial markers were implanted by conventional bronchoscopy within or adjacent to tumors to serve as targeting references. A prescribed dose of 30 to 40 Gy to the gross tumor volume (GTV) was delivered in 5 fractions. Clinical examination and PET/CT imaging were performed at 3 to 6-month follow-up intervals.</p> <p>Results</p> <p>Twenty patients were accrued over a 4 year period. Three had primary hilar lung tumors and 17 had hilar lung metastases. The median GTV was 73 cc (range 23-324 cc). The median dose to the GTV was 35 Gy (range, 30 - 40 Gy), delivered in 5 fractions over 5 to 8 days (median, 6 days). The resulting mean maximum point doses delivered to the esophagus and mainstem bronchus were 25 Gy (range, 11 - 39 Gy) and 42 Gy (range, 30 - 49 Gy), respectively. Of the 17 evaluable patients with 3 - 6 month follow-up, 4 patients had a partial response and 13 patients had stable disease. AAT t a median follow-up of 10 months, the 1-year Kaplan-Meier local control and overall survival estimates were 63% and 54%, respectively. Toxicities included one patient experiencing grade II radiation esophagitis and one patient experiencing grade III radiation pneumonitis. One patient with gross endobronchial tumor within the mainstem bronchus developed a bronchial fistula and died after receiving a maximum bronchus dose of 49 Gy.</p> <p>Conclusion</p> <p>CyberKnife radiosurgery is an effective palliative treatment option for hilar lung tumors, but local control is poor at one year. Maximum point doses to critical structures may be used as a guide for limiting toxicities. Preliminary results suggest that dose escalation alone is unlikely to enhance the therapeutic ratio of hilar lung tumors and novel approaches, such as further defining the patient population or employing the use of radiation sensitizers, should be investigated.</p
Radical stereotactic radiosurgery with real-time tumor motion tracking in the treatment of small peripheral lung tumors
<p>Abstract</p> <p>Background</p> <p>Recent developments in radiotherapeutic technology have resulted in a new approach to treating patients with localized lung cancer. We report preliminary clinical outcomes using stereotactic radiosurgery with real-time tumor motion tracking to treat small peripheral lung tumors.</p> <p>Methods</p> <p>Eligible patients were treated over a 24-month period and followed for a minimum of 6 months. Fiducials (3β5) were placed in or near tumors under CT-guidance. Non-isocentric treatment plans with 5-mm margins were generated. Patients received 45β60 Gy in 3 equal fractions delivered in less than 2 weeks. CT imaging and routine pulmonary function tests were completed at 3, 6, 12, 18, 24 and 30 months.</p> <p>Results</p> <p>Twenty-four consecutive patients were treated, 15 with stage I lung cancer and 9 with single lung metastases. Pneumothorax was a complication of fiducial placement in 7 patients, requiring tube thoracostomy in 4. All patients completed radiation treatment with minimal discomfort, few acute side effects and no procedure-related mortalities. Following treatment transient chest wall discomfort, typically lasting several weeks, developed in 7 of 11 patients with lesions within 5 mm of the pleura. Grade III pneumonitis was seen in 2 patients, one with prior conventional thoracic irradiation and the other treated with concurrent Gefitinib. A small statistically significant decline in the mean % predicted DLCO was observed at 6 and 12 months. All tumors responded to treatment at 3 months and local failure was seen in only 2 single metastases. There have been no regional lymph node recurrences. At a median follow-up of 12 months, the crude survival rate is 83%, with 3 deaths due to co-morbidities and 1 secondary to metastatic disease.</p> <p>Conclusion</p> <p>Radical stereotactic radiosurgery with real-time tumor motion tracking is a promising well-tolerated treatment option for small peripheral lung tumors.</p
Global Analysis of Extracytoplasmic Stress Signaling in Escherichia coli
The Bae, Cpx, Psp, Rcs, and ΟE pathways constitute the Escherichia coli signaling systems that detect and respond to alterations of the bacterial envelope. Contributions of these systems to stress response have previously been examined individually; however, the possible interconnections between these pathways are unknown. Here we investigate the dynamics between the five stress response pathways by determining the specificities of each system with respect to signal-inducing conditions, and monitoring global transcriptional changes in response to transient overexpression of each of the effectors. Our studies show that different extracytoplasmic stress conditions elicit a combined response of these pathways. Involvement of the five pathways in the various tested stress conditions is explained by our unexpected finding that transcriptional responses induced by the individual systems show little overlap. The extracytoplasmic stress signaling pathways in E. coli thus regulate mainly complementary functions whose discrete contributions are integrated to mount the full adaptive response
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