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Over the last 12 years, technology in the drilling and completions space has reduced cycle time and dramatically lowered costs for operators. With the adoption of re-stimulations, additional production is being gained from existing wells at a cost that is less than the cost of drilling new wells. However, there has been limited development of low-cost intervention techniques to restore lost production or to extend the life of existing wells. To address this relatively untapped area of intervention, new tools and techniques are needed to revitalize older wells in unconventional reservoirs that are more cost effective than traditional intervention techniques. The economics of a workover are challenged by the uncertainties of successfully removing the existing production tubing and replacing it with a newly designed completion. In response a tool and cleanout technique has been developed that improves the ability of 1.25 in. coiled tubing to clean out the 5.5 in. casing through the 2.375 in. tubing string, thereby eliminating the need to pull and replace the upper completion. A recent application of this new technique in an unconventional well demonstrated that a modified jetting tool (Reverse Nozzle Bit Sub or RNBS), along with a regimented cleanout schedule, can clean out most of the lateral length and restore lost production at a greatly reduced time and cost compared to jointed pipe workovers. Additionally, using coiled tubing to spot acid along the length of the lateral in a uniform matter can remove scale buildup and clean up perforations for improved performance. This paper will review the design, testing and field application of the new tool and technique as well as show early results.

A new software package, the Fission Induced Electromagnetic Response (FIER) code, has been developed to analytically predict delayed $\gamma$-ray spectra following fission. FIER uses evaluated nuclear data and solutions to the Bateman equations to calculate the time-dependent populations of fission products and their decay daughters resulting from irradiation of a fissionable isotope. These populations are then used in the calculation of $\gamma$-ray emission rates to obtain the corresponding delayed $\gamma$-ray spectra. FIER output was compared to experimental data obtained by irradiation of a $^{235}$U sample in the Godiva critical assembly. This investigation illuminated discrepancies in the input nuclear data libraries, showcasing the usefulness of FIER as a tool to address nuclear data deficiencies through comparison with experimental data. FIER provides traceability between $\gamma$-ray emissions and their contributing nuclear species, decay chains, and parent fission fragments, yielding a new capability for the nuclear science community., Comment: 11 pages, 10 figures

The objectives of this study were to 1) assess the performance Entrustable Professional Activities (EPAs) when integrated into the summative assessment of third-year medical students on the surgery clerkship and 2) to compare EPAs to traditional clinical performance assessment tools.EPA assessments were collected prospectively from a minimum of 4 evaluators at the completion of each surgical clerkship rotation from November 2019 to June 2019. Overall EPA-based clinical performance scores were calculated as the sum of the mean EPA score from each evaluator. A rating of overall clinical performance called the clinical performance appraisal (CPA) was also collected. EPA ratings were compared to the CPA score, National Board of Medical Examiners exam score, objective structured clinical exam scores, and final clerkship grade.Northwestern Memorial Hospital, a tertiary care teaching institution in Chicago, IL.Overall, 446 evaluations (111 students) were included in the analysis. The aggregate EPA scores ranged from 11.6-24.0 (mean 19.9 ± 2.0), and the CPA scores ranged from 4.4-9.0 (mean 7.6 ± 0.7). The variance among learners in EPA scores was significantly higher than CPA scores (p0.001). The aggregate EPA scores correlated well with CPA scores (Spearman's rho 0.803) but had lesser, positive correlations with the objective structured clinical exam (rho 0.153) and National Board of Medical Examiners (rho 0.265) scores. When all EPA scores were included in ordinal logistic regression, only EPA 6, oral presentation of patients, was independently associated with students' final grades (OR: 10.05, 95%CI 1.41-71.80; p = 0.02).Integration of EPAs for use in clinical performance assessment of medical students is feasible within a surgery clerkship. Compared to a global clinical performance assessment, EPA-based assessment provided better discrimination of clinical performance among learners. Use of EPAs may better identify advanced learners and those that need additional time.

The desire to build nuclear clocks with an unprecedented accuracy of 1 part in $$10^{19}$$ is currently driving the interest in accurate measurements of the first excited nuclear state in $$^{229}$$ Th. We have used superconducting tunnel junction (STJ) radiation detectors to search for the associated decay of $$^{229m}$$ Th and measure its energy accurately. In this experiment, recoiling $$^{229m}$$ Th ions from the alpha decay of $$^{233}$$ U are embedded in the STJ detectors, and their subsequent decay into the ground state is expected to produce a signal at an energy of $$7.8\pm 0.5$$ eV. This approach is particularly promising, because all decay products are captured inside the STJ so that the measured energy does not depend on the decay mode or on chemical effects. Although this approach works well to characterize the decay of metastable $$^{235m}$$ U, no signal from $$^{229m}$$ Th has been observed. This negative result can be explained by recent measurements of the $$^{229m}$$ Th half-life of only $$7\pm 1\,\upmu \mathrm{s}$$ . We discuss our experiments and the modifications required to measure the energy of metastable $$^{229m}$$ Th with an accuracy of order ± 10 meV.

NeutronSTARS ( Neutron - S ilicon T elescope A rray for R eaction S tudies) consists of 2.2-tons of gadolinium-doped liquid scintillator for neutron detection and large area silicon detectors for charged particle identification. This detector array is intended for low-energy-nuclear-reaction measurements that result in the emission of neutrons such as ( n , x n ) and fission. This paper describes the NeutronSTARS experimental setup, calibration, and the array’s response to neutral and charged particles.

Hyperion is a new high-efficiency charged-particle γ -ray detector array which consists of a segmented silicon telescope for charged-particle detection and up to fourteen high-purity germanium clover detectors for the detection of coincident γ rays. The array will be used in nuclear physics measurements and Stockpile Stewardship studies and replaces the STARLiTeR array. This article discusses the features of the array and presents data collected with the array in the commissioning experiment.

Fission neutron multiplicity data are imperative for nuclear models that support criticality safety, nuclear nonproliferation, and stockpile stewardship. This work presents the first experimental measurement to determine the average neutron multiplicity ($\overline{\ensuremath{\nu}}$) and the neutron multiplicity distribution using a surrogate reaction. $^{241}\mathrm{Pu}$ has a short half-life of 14.3 yr. To circumvent experimental difficulties, inelastic scattering of 53.96-MeV $\ensuremath{\alpha}$ particles on $^{242}\mathrm{Pu}$ served as a surrogate for $^{241}\mathrm{Pu}(n,f)$. The present text reports and discusses the average neutron multiplicity, in addition to the neutron multiplicity moments and distribution for equivalent neutron energies up to 20 MeV. The $\overline{\ensuremath{\nu}}$ measured in this experiment agrees with previous measurements until 12 MeV, where discrepancies arise due to preequilibrium neutron emission.

The neutron-capture reaction plays a critical role in the synthesis of the elements in stars and is important for societal applications including nuclear power generation and stockpile-stewardship science. However, it is difficult---if not impossible---to directly measure neutron capture cross sections for the exotic, short-lived nuclei that participate in these processes. In this Letter we demonstrate a new technique which can be used to indirectly determine neutron-capture cross sections for exotic systems. This technique makes use of the $(d,p)$ transfer reaction, which has long been used as a tool to study the structure of nuclei. Recent advances in reaction theory, together with data collected using this reaction, enable the determination of neutron-capture cross sections for short-lived nuclei. A benchmark study of the $^{95}\mathrm{Mo}(d,p)$ reaction is presented, which illustrates the approach and provides guidance for future applications of the method with short-lived isotopes produced at rare isotope accelerators.

The $\ensuremath{\gamma}$-strength functions and level densities in the quasicontinuum of $^{147,149}\mathrm{Sm}$ isotopes have been extracted from particle-$\ensuremath{\gamma}$ coincidences using the Oslo method. The nuclei of interest were populated via $(p,d)$ reactions on pure $^{148,150}\mathrm{Sm}$ targets and the reaction products were recorded by the Hyperion array. An upbend in the low-energy region of the $\ensuremath{\gamma}\mathrm{SF}$ has been observed. The systematic analysis of the $\ensuremath{\gamma}\mathrm{SF}$ for a range of Sm isotopes highlights the interplay between scissors mode and the upbend. Shell-model calculations show reasonable agreement with the experimental $\ensuremath{\gamma}\mathrm{SFs}$ and confirm the correspondence between the upbend and scissors mode.

The spin distribution populated in the $^{150}\mathrm{Sm}(p,t)$ reaction with 25 MeV protons has been investigated using the silicon telescope and high-purity germanium array Hyperion. Angular distributions of outgoing tritons and relative intensities of $\ensuremath{\gamma}$ rays from low-lying levels are used to deduce the initial spin distribution using statistical calculations and are compared with a semiclassical model of the $(p,t)$ reaction. Experimental and theoretical results suggest a peak strength near $4\ensuremath{\hbar}$ when gated on outgoing tritons detected in Hyperion, while the full $4\ensuremath{\pi}$ distribution may peak near $2\ensuremath{\hbar}$. Additionally, the average $\ensuremath{\gamma}$-neutron branching ratio is determined from the data with the aid of one of two new codes presented in this work. The analysis is extended to other recent studies of $^{152,154}\mathrm{Sm}(p,t)$ to form systematics of the spin-dependence of the surrogate method applied to heavy nuclei in the transitional to deformed region.

We have used superconducting high-resolution radiation detectors to measure the energy level of metastable $^{235m}\mathrm{U}$ as 76.737 \ifmmode\pm\else\textpm\fi{} 0.018 eV. The $^{235m}\mathrm{U}$ isomer is created from the \ensuremath{\alpha} decay of $^{239}\mathrm{Pu}$ and embedded directly into the detector. When the $^{235m}\mathrm{U}$ subsequently decays, the energy is fully contained within the detector and is independent of the decay mode or the chemical state of the uranium. The detector is calibrated using an energy comb from a pulsed UV laser. A comparable measurement of the metastable $^{229m}\mathrm{Th}$ nucleus would enable a laser search for the exact transition energy in $^{229}\mathrm{Th}\ensuremath{-}^{229m}\mathrm{Th}$ as a step towards developing the first ever nuclear (baryonic) clock.

Uncertainties associated with short lived (half-lives less than 1 day) fission product yields listed in databases such as the National Nuclear Data Center’s ENDF/B-VII are large enough for certain isotopes to provide an opportunity for new precision measurements to offer significant uncertainty reductions. A series of experiments has begun where small samples of 235U are irradiated with a pulsed, fission neutron spectrum at the Nevada National Security Site and placed between two broad-energy germanium detectors. The amount of various isotopes present immediately following the irradiation can be determined given the total counts and the calibrated properties of the detector system. The uncertainty on the fission yields for multiple isotopes has been reduced by nearly an order of magnitude.

Obtaining reliable data for nuclear reactions on unstable isotopes remains an extremely important task and a formidable challenge. Neutron capture cross sections---crucial ingredients for models of astrophysical processes, national security applications, and simulations of nuclear energy generation---are particularly elusive, as both projectile and target in the reaction are unstable. We demonstrate a new method for determining cross sections for neutron capture on unstable isotopes, using $^{87}\mathrm{Y}(n,\ensuremath{\gamma})$ as a prototype. To validate the method, a benchmark experiment is carried out to obtain the known $^{90}\mathrm{Zr}(n,\ensuremath{\gamma})$ cross section analogously. Our approach, which employs an indirect (``surrogate'') measurement combined with theory, can be generalized to a larger class of nuclear reactions. It can be used both with traditional stable-beam experiments and in inverse kinematics at rare-isotope facilities.

Cumulative fast fission product yields for 235 U and 238 U were measured at Godiva-IV in burst mode. Data was collected starting 45 minutes after the prompt irradiation. Data analysis codes were developed to analyze gammarays and calculate fission product yields with their respective uncertainties. Due to uncertainties in the branching ratios, different γ-rays from the same isotope led to different fission yield. This led to an effort at Oregon State University (OSU) to utilize the Rabbit facility at their 1 MegaWatt Training, Research, Isotopes, General Atomics (TRIGA) nuclear research reactor. The new experimental setup will allow us to measure branching ratio data and short-lived fission product yields starting seconds after a prompt irradiation.

Author(s): Munson, JM; Norman, EB; Burke, JT; Casperson, RJ; Phair, LW; McCleskey, E; McCleskey, M; Lee, D; Hughes, RO; Ota, S; Czeszumska, A; Chodash, PA; Saastamoinen, AJ; Austin, RAE; Spiridon, AE; Dag, M; Chyzh, R; Basunia, MS; Ressler, JJ; Ross, TJ | Abstract: The nuclear reactions C12(C12,α)Ne20, C12(C12,p)Na23, and C12(C12,n)Mg23 are the primary reactions in carbon burning, which occurs as part of several stellar processes. The Gamow window, which describes the energy range where most of these reactions take place, is typically around 1.5 MeV in the center-of-mass frame. Direct measurements of the cross sections at this energy are difficult due to the large Coulomb barrier present between the carbon nuclei; however, a successful surrogate measurement can provide the branching ratios between these reactions while avoiding the C12+C12 Coulomb barrier. An experiment was performed using inelastic scattering of 40 MeV α particles on Mg24 as a possible surrogate for the C12+C12 compound nucleus.

New levels and $\ensuremath{\gamma}$-ray transitions were identified in $^{150,152}\mathrm{Sm}$ utilizing the $(p,t)$ reaction and particle-$\ensuremath{\gamma}$ coincidence data. A large, peak-like structure observed between 2.3--3.0 MeV in excitation energy in the triton energy spectra was also investigated. The orbital angular-momentum transfer was probed by comparing the experimental angular distributions of the outgoing tritons to calculated distorted wave Born approximation curves. The angular distributions of the outgoing tritons populating the peak-like structure are remarkably similar in the two reactions and are significantly different from the angular distributions associated with the nearby continuum region. Relative partial cross sections for the observed levels, angle averaged between 34 and 58 degrees, were measured. In $^{150}\mathrm{Sm}$, 39(4)% of the strength of the peak-like structure could be accounted for by the observed discrete states. This compares with a value of 93(15)% for $^{152}\mathrm{Sm}$.

This study focuses on the comparative evaluation of star (branched) and linear poly(L,D-lactic acid) (PDLLA) as degradable materials employed in controlled release. The polymers were prepared via ring-opening polymerization initiated by decanol (linear), pentaerythritol (4-armed star) and dipentaerythritol (6-armed star), and processed both in the form of films and nanoparticles. Independently on the length or number of their arms, star polymers degrade slower than linear polymers, possibly through a surface (vs. bulk) mechanism Further, the release of a model drug (atorvastatin) followed a zero-order-like kinetics for the branched polymers, and a first order kinetics for linear PDLLA. Using NHOst osteoblastic cells, both linear and star polymers were devoid of any significant toxicity and released atorvastatin in a bioavailable form; cell adhesion was considerably lower on star polymer films, and the slower release from theirnanoparticles appeared to be beneficial to avoid atorvastatin overdosing.

Here, nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that can occur in isotopes containing a low-lying nuclear excited state. Over the past 40 yr, several experiments have attempted to measure NEET of 235U and those experiments have yielded conflicting results.

The $\ensuremath{\gamma}$-ray strength function and level density in the quasi-continuum of $^{151,153}\mathrm{Sm}$ have been measured using bismuth germanate shielded Ge clover detectors of the STARLiTeR system. The Compton shields allow an extraction of the $\ensuremath{\gamma}$ strength down to unprecedentedly low $\ensuremath{\gamma}$ energies of $\ensuremath{\approx}500$ keV. For the first time an enhanced low-energy $\ensuremath{\gamma}$-ray strength has been observed in the rare-earth region. In addition, for the first time both the upbend and the well-known scissors resonance have been observed simultaneously for the same nucleus. Hauser-Feshbach calculations show that this strength enhancement at low $\ensuremath{\gamma}$ energies could have an impact of 2--3 orders of magnitude on the ($n,\ensuremath{\gamma}$) reaction rates for $r$-process nucleosynthesis.

We studied the low-spin structure of odd-odd 88Y via (p,dγ) reactions on an 89Y target. The K150 Cyclotron at the Texas A&M University Cyclotron Institute was employed to provide a 28.5-MeV proton beam, and particle-γ and particle-γ-γ coincidence data were collected with the STARLiTeR array. Moreover, a number of new levels and γ rays have been observed below 2.5 MeV, while level and γ-ray energies as well as spin-parity assignments have been re-evaluated.

The emission of γ rays from neutron-bound and neutron-unbound states in Mo95, populated in the Mo94(d,p) reaction, has been investigated. Charged particles and γ radiation were detected with arrays of annular silicon and Clover-type high-purity Germanium detectors, respectively. Utilizing p-γ and p-γ-γ coincidences, the Mo95 level scheme was greatly enhanced with 102 new transitions and 43 new states. It agrees well with shell model calculations for excitation energies below ≈2 MeV. From p-γ coincidence data, a new method for the determination of spins of discrete levels is proposed. The method exploits the suppression of high-angular momentum neutron emission from levels with high spins populated in the (d,p) reaction above the neutron separation energy. Spins for almost all Mo95 levels below 2 MeV (and for a few levels above) have been determined with this method.

Nuclear reaction cross sections are important for a variety of applications in the areas of astrophysics, nuclear energy, and national security. When these cross sections cannot be measured directly or predicted reliably, it becomes necessary to develop indirect methods for determining the relevant reaction rates. The surrogate nuclear reactions approach is such an indirect method. First used in the 1970s for estimating ðn; fÞ cross sections, the method has recently been recognized as a potentially powerful tool for a wide range of applications that involve compound-nuclear reactions. The method is expected to become an important focus of inverse-kinematics experiments at rareisotope facilities. The present paper reviews the current status of the surrogate approach. Experimental techniques employed and theoretical descriptions of the reaction mechanisms involved are presented and representative cross section measurements are discussed.