254 research outputs found

    Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi: I. Early X-ray emission from the shocked ejecta and red giant wind

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    RS Ophiuchi began its latest outburst on 2006 February 12. Previous outbursts have indicated that high velocity ejecta interact with a pre-existing red giant wind, setting up shock systems analogous to those seen in Supernova Remnants. However, in the previous outburst in 1985, X-ray observations did not commence until 55 days after the initial explosion. Here we report on Swift observations covering the first month of the 2006 outburst with the Burst Alert (BAT) and X-ray Telescope (XRT) instruments. RS Oph was clearly detected in the BAT 14-25 keV band from t=0 to t6t\sim6 days. XRT observationsfrom 0.3-10 keV, started at 3.17 days after outburst. The rapidly evolving XRT spectra clearly show the presence of both line and continuum emission which can be fitted by thermal emission from hot gas whose characteristic temperature, overlying absorbing column, [NH]W[N_H]_W, and resulting unabsorbed total flux decline monotonically after the first few days. Derived shock velocities are in good agreement with those found from observations at other wavelengths. Similarly, [NH]W[N_H]_W is in accord with that expected from the red giant wind ahead of the forward shock. We confirm the basic models of the 1985 outburst and conclude that standard Phase I remnant evolution terminated by t10t\sim10 days and the remnant then rapidly evolved to display behaviour characteristic of Phase III. Around t=26 days however, a new, luminous and highly variable soft X-ray source began to appear whose origin will be explored in a subsequent paper.Comment: 20 pages, 4 figures (2 updated), accepted by Ap

    Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts

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    NASA's Dawn spacecraft observations of asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75 {\mu}m filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater walls and rims); as flow-like deposits or rays commonly associated with topographic highs; and as dark spots (likely secondary impacts) nearby impact craters. This DM could be a relic of ancient volcanic activity or exogenic in origin. We report that the majority of the spectra of DM are similar to carbonaceous chondrite meteorites mixed with materials indigenous to Vesta. Using high-resolution seven color images we compared DM color properties (albedo, band depth) with laboratory measurements of possible analog materials. Band depth and albedo of DM are identical to those of carbonaceous chondrite xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance in DM (1-6 vol%) is consistent with howardite meteorites. We find no evidence for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of DM. Our modeling efforts using impact crater scaling laws and numerical models of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta during the formation of the ~400 km Veneneia basin by a low-velocity (<2 km/sec) carbonaceous impactor. This discovery is important because it strengthens the long-held idea that primitive bodies are the source of carbon and probably volatiles in the early Solar System.Comment: Icarus (Accepted) Pages: 58 Figures: 15 Tables:

    Flux Rope Modeling of the 2022 September 5 Coronal Mass Ejection Observed by Parker Solar Probe and Solar Orbiter from 0.07 to 0.69 au

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    As both Parker Solar Probe (PSP) and Solar Orbiter (SolO) reach heliocentric distances closer to the Sun, they present an exciting opportunity to study the structure of coronal mass ejections (CMEs) in the inner heliosphere. We present an analysis of the global flux rope structure of the 2022 September 5 CME event that impacted PSP at a heliocentric distance of only 0.07 au and SolO at 0.69 au. We compare in situ measurements at PSP and SolO to determine global and local expansion measures, finding a good agreement between magnetic field relationships with heliocentric distance, but significant differences with respect to flux rope size. We use PSP/Wide-Field Imager for Solar Probe images as input to the ELlipse Evolution model based on Heliospheric Imager data (or ELEvoHI), providing a direct link between remote and in situ observations; we find a large discrepancy between the resulting modeled arrival times, suggesting that the underlying model assumptions may not be suitable when using data obtained close to the Sun, where the drag regime is markedly different in comparison to larger heliocentric distances. Finally, we fit the SolO's magnetometer and PSP's FIELDS data independently with the 3D Coronal ROpe Ejection (or 3DCORE) model, and find that many parameters are consistent between spacecraft. However, challenges are apparent when reconstructing a global 3D structure that aligns with arrival times at PSP and SolO, likely due to the large radial and longitudinal separations between spacecraft. From our model results, it is clear the solar wind background speed and drag regime strongly affect the modeled expansion and propagation of CMEs and need to be taken into consideration

    Cancer drug-tolerant Persister cells: from biological questions to clinical opportunities

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    The emergence of drug resistance is the most substantial challenge to the effectiveness of anticancer therapies. Orthogonal approaches have revealed that a subset of cells, known as drug-tolerant ‘persister’ (DTP) cells, play a prominent role in drug resistance. While long recognized in bacterial populations which have acquired resistance to antibiotics, the presence of DTPs in various cancer types has come to light only in the last two decades, yet several aspects of their biology remain enigmatic. Here we delve into the biological characteristics of DTPs and explore potential strategies for tracking and targeting them. Recent findings suggest that DTPs exhibit remarkable plasticity, being capable of transitioning between different cellular states, resulting in distinct DTP phenotypes within a single tumor. However, defining the biological features of DTPs has been challenging, partly due to the complex interplay between clonal dynamics and tissue-specific factors influencing their phenotype. Moreover, the interactions between DTPs and the tumor microenvironment, including their potential to evade immune surveillance, remain to be discovered. Lastly, the mechanisms underlying DTP-derived drug resistance and their correlation with clinical outcomes remain poorly understood. This Roadmap aims to provide a comprehensive overview of the field of DTPs, encompassing past achievements and current endeavors in elucidating their biology. We also discuss the prospect of future advancements in technologies in helping to unveil the features of DTPs and propose novel therapeutic strategies that could lead to their eradication

    Separation versus affiliation with partial vertical ownership in network industries

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    The separation of integrated monopolies and new market entrants have changed vertical interactions between suppliers and dealers. Firms have substituted full integration with vertical restraints leading to collusive behaviour harmful to competition. We examine how a partial vertical ownership (an affiliation) of one of the competing downstream retailers by the upstream monopoly could help internalise the production decision after a complete divestiture. Our results in a Cournot framework confirm the positive role of partial integration on firms' profits and consumer surplus in increasing social welfare. These results are consistent with empirical studies of economies after vertical separation in network industries

    Update of the ICUD-SIU consultation on upper tract urothelial carcinoma 2016: treatment of low-risk upper tract urothelial carcinoma

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    Introduction The conservative management of upper tract urothelial carcinoma (UTUC) has historically been offered to patients with imperative indications. The recent International Consultation on Urologic Diseases (ICUD) publication on UTUC stratified treatment allocations based on high- and low-risk groups. This report updates the conservative management of the low-risk group. Methods The ICUD for low-risk UTUC working group performed a thorough review of the literature with an assessment of the level of evidence and grade of recommendation for a variety of published studies in this disease space. We update these publications and provide a summary of that original report. Results There are no prospective randomized controlled studies to support surgical management guidelines. A risk-stratified approach based on clinical, endoscopic, and biopsy assessment allows selection of patients who could benefit from kidney-preserving procedures with oncological outcomes potentially similar to radical nephroureterectomy with bladder cuff excision, with the added benefit of renal function preservation. These treatments are aided by the development of high-definition flexible digital URS, multi-biopsies with the aid of access sheaths and other tools, and promising developments in the use of adjuvant topical therapy. Conclusions Recent developments in imaging, minimally invasive techniques, multimodality approaches, and adjuvant topical regimens and bladder cancer prevention raise the hope for improved risk stratification and may greatly improve the endoscopic treatment for low-risk UTUC

    The global distribution and diversity of protein vaccine candidate antigens in the highly virulent Streptococcus pnuemoniae serotype 1

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    Serotype 1 is one of the most common causes of pneumococcal disease worldwide. Pneumococcal protein vaccines are currently being developed as an alternate intervention strategy to pneumococcal conjugate vaccines. Pre-requisites for an efficacious pneumococcal protein vaccine are universal presence and minimal variation of the target antigen in the pneumococcal population, and the capability to induce a robust human immune response. We used in silico analysis to assess the prevalence of seven protein vaccine candidates (CbpA, PcpA, PhtD, PspA, SP0148, SP1912, SP2108) among 445 serotype 1 pneumococci from 26 different countries, across four continents. CbpA (76%), PspA (68%), PhtD (28%), PcpA (11%) were not universally encoded in the study population, and would not provide full coverage against serotype 1. PcpA was widely present in the European (82%), but not in the African (2%) population. A multi-valent vaccine incorporating CbpA, PcpA, PhtD and PspA was predicted to provide coverage against 86% of the global population. SP0148, SP1912 and SP2108 were universally encoded and we further assessed their predicted amino acid, antigenic and structural variation. Multiple allelic variants of these proteins were identified, different allelic variants dominated in different continents; the observed variation was predicted to impact the antigenicity and structure of two SP0148 variants, one SP1912 variant and four SP2108 variants, however these variants were each only present in a small fraction of the global population (<2%). The vast majority of the observed variation was predicted to have no impact on the efficaciousness of a protein vaccine incorporating a single variant of SP0148, SP1912 and/or SP2108 from S. pneumoniae TIGR4. Our findings emphasise the importance of taking geographic differences into account when designing global vaccine interventions and support the continued development of SP0148, SP1912 and SP2108 as protein vaccine candidates against this important pneumococcal serotype

    Polygenic resilience scores capture protective genetic effects for Alzheimer’s disease

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    Polygenic risk scores (PRSs) can boost risk prediction in late-onset Alzheimer’s disease (LOAD) beyond apolipoprotein E (APOE) but have not been leveraged to identify genetic resilience factors. Here, we sought to identify resilience-conferring common genetic variants in (1) unaffected individuals having high PRSs for LOAD, and (2) unaffected APOE-ε4 carriers also having high PRSs for LOAD. We used genome-wide association study (GWAS) to contrast “resilient” unaffected individuals at the highest genetic risk for LOAD with LOAD cases at comparable risk. From GWAS results, we constructed polygenic resilience scores to aggregate the addictive contributions of risk-orthogonal common variants that promote resilience to LOAD. Replication of resilience scores was undertaken in eight independent studies. We successfully replicated two polygenic resilience scores that reduce genetic risk penetrance for LOAD. We also showed that polygenic resilience scores positively correlate with polygenic risk scores in unaffected individuals, perhaps aiding in staving off disease. Our findings align with the hypothesis that a combination of risk-independent common variants mediates resilience to LOAD by moderating genetic disease risk

    A Phase 2 Study of Coltuximab Ravtansine (SAR3419) Monotherapy in Patients with Relapsed or Refractory Acute Lymphoblastic Leukemia (ALL)

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    International audienceBackground Long-term disease-free survival in adult patients with acute lymphoblastic leukemia (ALL) remains unsatisfactory, and treatment options are limited for those patients who relapse or fail to respond following initial therapy. We conducted a dose-escalation/expansion phase 2, multicenter, single-arm study to determine the optimal dose of coltuximab ravtansine (SAR3419), an anti-CD19 antibody-drug conjugate, in this setting. Patients and Methods The dose-escalation part of the study determined the selected dose of coltuximab ravtansine for evaluation of efficacy and safety in the dose-expansion phase. Patients received coltuximab ravtansine induction therapy (up to 8 weekly doses); responding patients were eligible for maintenance therapy (biweekly administrations for up to 24 weeks). Three dose levels of coltuximab ravtansine were examined: 55, 70, and 90 mg/m2. The primary endpoint was objective response rate (ORR). Secondary endpoints included duration of response (DOR) and safety. Results A total of 36 patients were treated: 19 during dose escalation; 17 during dose expansion. One dose-limiting toxicity was observed at 90 mg/m2 (grade 3 peripheral motor neuropathy), and therefore 70 mg/m2 was selected for the dose-expansion phase. Five patients discontinued therapy due to adverse events (AEs). The most common AEs were pyrexia, diarrhea, and nausea. Of 17 evaluable patients treated at the selected dose, 4 responded (estimated ORR using Bayesian methodology: 25.47% [80% confidence interval: 14.18-39.6%]); DOR was 1.94 (range: 1-5.6) months. Based on these results, the study was prematurely discontinued. Conclusions Coltuximab ravtansine is well tolerated but is associated with a low clinical response rate in patients with relapsed/refractory AL
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