We present herein a new class of singularity-free interior solutions to describe realistic anisotropic compact stellar objects with spherically symmetric matter distribution. A specific form of ...anisotropy is assumed to obtain the exact solution for the field equation. Smooth matching of interior solutions thus obtained with the Schwarzschild exterior metric over the bounding surface of a compact star, together with the condition that the radial pressure vanishes at the boundary, is used to obtain the mathematical form for the model parameters. The pulsar 4U1608-52 with its current estimated data (mass
=
1.57
M
⊙
and radius
=
9.8
±
0.8
km; Özel et al. in ApJ 820:28, 2016) is used to study the model graphically.
The molecular origin of the photoluminescence (PL) of carbon dots (CDs) is not fully understood. In this article it is shown that CDs are composed of aggregated 2-pyridone derivatives employing π–π ...stacking and H-bonding, etc. The PL quantum yield of this CD is quite high in aqueous medium (∼75%). Unlike literature reports the PL emission maximum of this CD is excitation wavelength independent, and PL decay follows a single-exponential decay equation. These CDs have a long PL lifetime (from ∼10 to 15 ns), so that solvation is complete before emission. The extent of trap states could be reduced quite significantly. A high PLQY and long and single-exponential PL lifetime and it’s polarity dependence would make this CD a suitable probe for FRET and FLIM. It could be shown that unlike literature reports this CD as a single particle does not blink. Unlike literature reports where CDs are bleached within a few seconds these CDs at the single-particle level are alive for about a few minutes. All these aggregation-induced much improved optical properties will make this CD a suitable optical emitter at the ensemble as well as single-particle level toward bioimaging. As the molecular origin is now known several optical properties can now be tuned.
As community-based ambulatory endoscopy centers (AECs) across the nation are trying to reopen and safely resume outpatient endoscopic procedures after the unprecedented lockdown related to the ...coronavirus disease 2019 (COVID-19) pandemic, guidelines recommend pretesting and screening for COVID-19 along with other mitigation measures for the safety of patients and staff. The impact of such changes in the workflow of AECs on throughput and other performance indicators is largely unknown, although a significant reduction in revenue stream is expected.
A discrete event simulation–based model was developed in the setting of a small to medium community-based single-specialty AEC to quantify the impact of COVID-19–related workflow changes on performance indicators and cost per case compared with the pre–COVID-19 baseline.
In the simulation model, post–COVID-19 recommended workflow changes significantly impacted the operational and productivity metrics and, in turn, adversely affected financial metrics. Overall, there was a significant decrease in staff utilization and consequent increase in total facility time, waiting time for patients, and cost per case because of a bottleneck at the time of preprocedure COVID-19 screening and testing while practicing social distancing. Strategies to minimize this adverse impact on productivity were assessed.
Pretesting and screening for COVID-19 as recommended by current guidelines will significantly impact the productivity and revenue stream of AECs. Urgent measures by payors are needed to adjust the facility reimbursement of endoscopy centers to ensure successful reopening and ramping up outpatient endoscopy services in these facilities already hit hard by the pandemic.
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Carbon dots (CDs) are light-emitting nanoparticles that show great promise for applications in biology and medicine due to the ease of fabrication, biocompatibility, and attractive optical ...properties. Optical chirality, on the other hand, is an intrinsic feature inherent in many objects in nature, and it can play an important role in the formation of artificial complexes based on CDs that are implemented for enantiomer recognition, site-specific bonding, etc. We employed a one-step hydrothermal synthesis to produce chiral CDs from the commonly used precursors citric acid and ethylenediamine together with a set of different chiral precursors, namely, L-isomers of cysteine, glutathione, phenylglycine, and tryptophan. The resulting CDs consisted of O,N-doped (and also S-doped, in some cases) carbonized cores with surfaces rich in amide and hydroxyl groups; they exhibited high photoluminescence quantum yields reaching 57%, chiral optical signals in the UV and visible spectral regions, and two-photon absorption. Chiral signals of CDs were rather complex and originated from a combination of the chiral precursors attached to the CD surface, hybridization of lower-energy levels of chiral chromophores formed within CDs, and intrinsic chirality of the CD cores. Using DFT analysis, we showed how incorporation of the chiral precursors at the optical centers induced a strong response in their circular dichroism spectra. The optical characteristics of these CDs, which can easily be dispersed in solvents of different polarities, remained stable during pH changes in the environment and after UV exposure for more than 400 min, which opens a wide range of bio-applications.
Background and Aims Rates of progression to esophageal adenocarcinoma in subjects with Barrett’s esophagus (BE) are lower than previously estimated. Identification of predictors of progression will ...enable risk stratification of BE subjects, potentially making current surveillance programs more efficient. We aimed to assess the potential of demographic and lifestyle factors, obesity, and medications in predicting progression in BE. Methods BE subjects were identified from the General Practice Research Database using validated diagnostic codes. BE subjects developing esophageal cancer (EC) 12 months after their index BE diagnosis were defined as progressors. Time-to-event analysis was used to assess the overall risk of progression to EC. Cox proportional hazards models and time-varying marginal structural models were used to assess predictors of progression. Results Included in the analysis were 9660 BE patients. The mean age (SD) of the study subjects was 63 (13.5) years; 62.6% were men. One hundred three subjects (1.1%) progressed to EC. The mean (SD) follow-up since initial diagnosis was 4.8 (3.3) years. The incidence of EC was 2.23 per 1000 person-years of follow-up. Increasing age, male gender, and being overweight (body mass index, 25-29.9) were found to be independent predictors of progression. When time-varying models were used, proton pump inhibitor (PPI) and statin use were protective against progression. Conclusions In this large population-based cohort of patients with BE, increasing age, male gender, and being overweight predicted progression to EC, whereas PPI and statin use were protective against EC development. These factors may aid in developing a risk score to predict the risk of progression and chemopreventive strategies in patients with BE.
Stephania hernandifolia
(Nimukho), an ethnomedicinal herb from rural Bengal, has been used traditionally for the management of nerve, skin, urinary, and digestive ailments. Here, we attempted to ...confirm the antiviral potential of aqueous, methanol, and chloroform extracts of
S. hernandifolia
against herpes simplex virus type 1 (HSV-1), the causative agent of orolabial herpes in humans, and decipher its underlying mechanism of action. The bioactive extract was standardized and characterized by gas chromatography-mass spectroscopy, while cytotoxicity and antiviral activity were evaluated by MTT and plaque reduction assay, respectively. Two HSV strains, HSV-1F and the clinical isolate VU-09, were inhibited by the chloroform extract (CE) with a median effective concentration (EC
50
) of 4.32 and 4.50 µg/ml respectively, with a selectivity index (SI) of 11. Time-of-addition assays showed that pre-treatment of virus-infected cells with the CE and its removal before infection reduced the number of plaques without lasting toxicity to the cell, indicating that the CE affected the early stage in the viral life cycle. The number of plaques was also reduced by direct inactivation of virions and by the addition of CE for a short time following attachment of virions. These results together suggest that modification of either the virion surface or the cell surface by the CE inhibits virus entry into the host cell.
Graphic abstract
Translational G proteins, whose release from the ribosome is triggered by GTP hydrolysis, regulate protein synthesis. Concomitantly with binding and dissociation of protein factors, translation is ...accompanied by forward and reverse rotation between ribosomal subunits. Using single-molecule measurements, we explore the ways in which the binding of translational GTPases affects inter-subunit rotation of the ribosome. We demonstrate that the highly conserved translation factor LepA, whose function remains debated, shifts the equilibrium toward the non-rotated conformation of the ribosome. By contrast, the catalyst of ribosome translocation, elongation factor G (EF-G), favors the rotated conformation of the ribosome. Nevertheless, the presence of P-site peptidyl-tRNA and antibiotics, which stabilize the non-rotated conformation of the ribosome, only moderately reduces EF-G binding. These results support the model suggesting that EF-G interacts with both the non-rotated and rotated conformations of the ribosome during mRNA translocation. Our results provide new insights into the molecular mechanisms of LepA and EF-G action and underscore the role of ribosome structural dynamics in translation.
There have been few studies of abdominal imaging screening of individuals at high risk for pancreatic cancer (based on family history or genetic variants). We performed a meta-analysis of prospective ...cohort studies to determine the diagnostic yield and outcomes of abdominal imaging screening for asymptomatic individuals at high risk.
Through a systematic review of multiple electronic databases and conference proceedings through July 2017, we identified prospective cohort studies (>20 patients) of asymptomatic adults determined to be at high-risk of pancreatic cancer (lifetime risk >5%, including specific genetic-associated conditions) who were screened by endoscopic ultrasound (EUS) and/or magnetic resonance imaging (MRI) to detect pancreatic lesions. Our primary outcome was identification of high-risk pancreatic lesions (high-grade pancreatic intraepithelial neoplasia, high-grade dysplasia, or adenocarcinoma) at initial screening, and overall incidence during follow up. Summary estimates were reported as incidence rates per 100 patient-years.
We identified 19 studies comprising 7085 individuals at high risk for pancreatic cancer; of these, 1660 patients were evaluated by EUS and/or MRI. Fifty-nine high-risk lesions were identified (43 adenocarcinomas: 28 during the initial exam and 15 during follow-up surveillance) and 257 patients underwent pancreatic surgery. Based on our meta-analysis, the overall diagnostic yield screening for high-risk pancreatic lesions was 0.74 (95% CI, 0.33-1.14), with moderate heterogeneity among studies. The number needed to screen to identify 1 patient with a high-risk lesion was 135 (95% CI, 88-303). The diagnostic yield was similar for patients with different genetic features that increased risk, and whether patients were screened by EUS or MRI.
Based on meta-analysis, 135 patients at high-risk for pancreatic cancer must be screened to identify 1 patient with a high-risk pancreatic lesion. Further studies are needed to determine whether screening reduces mortality and is cost effectiveness for individuals at high-risk of pancreatic cancer.
This literature review and the recommendations therein were prepared for the AGA Institute Clinical Practice and Economics Committee. The paper was approved by the Committee on March 12, 2007, and by ...the AGA Institute Governing Board on May 19, 2007.
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