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We consider the dynamic scheduling of a multiclass queueing system with two servers, one dedicated (server 1) and one flexible (server 2), with no arrivals. Server 1 is dedicated to processing type-I jobs while server 2 is primarily responsible for processing type-2 jobs but can also aid server 1 with its work. We address when it is optimal for server 2 to aid server 1 with type-i jobs rather than process type-2 jobs. The objective is to minimize the total holding costs incurred until all jobs in the system are processed and leave the system. We show that the optimal policy can exhibit one of three possible structures: (i) an exhaustive policy for type-2 jobs, (ii) a nonincreasing switching curve in the number of type-i jobs and (iii) a nondecreasing switching curve in the number of type-i jobs. We characterize the necessary and sufficient conditions under which each policy will be optimal. We also explore the use of the optimal policy for the problem with no arrivals as a heuristic for the problem with dynamic arrivals. [ABSTRACT FROM AUTHOR]

Polymer-based triboelectric nanogenerators (TENGs) have held promise due to their excellent interfacial conformity and ease of fabrication. However, the role of surface roughness in triboelectricity requires further study. In this study, we have manipulated the nano-/micro-scale roughness configuration in polydimethylsiloxane (PDMS) over a wide range of extents using various sandpaper-based templates. According to the power spectral density analysis, the spatial frequency of template-free PDMS exhibits several distinct bandwidth regions each with different fractal dimensions significantly higher than 2, despite having the lowest roughness value. In contrast, most template-based PDMS shows an entire spatial frequency region that scales nearly with a single power factor corresponding to a fractal dimension as low as 2, despite slight increases in roughness values. Consequently, the surface temperature gradient and output performance of TENG increased, following the trend of fractal dimension and roughness, but the surface potentials have remained almost invariant. However, excessive increases in the surface roughness cause the spatial frequency to be divided once again into several different bandwidth regions with different cutoffs and higher fractal dimensions. These results suggest that the performance of TENG can be controlled by tuning both surface roughness and self-affine properties over multiple scales. Specifically, adhesive interaction becomes dominant on surfaces with lower fractality, enhancing TENG performance due to the expanded contact area. This study sheds light on the relationship among triboelectricity, thermal dissipation, and topography. [ABSTRACT FROM AUTHOR]

Introduction: Postcoital or postejaculation hematuria without bloody ejaculate is rare and little is known about its pathogenesis, treatment and prognosis. This study was conducted to evaluate the clinical characteristics of patients with postcoital hematuria without bloody ejaculate. Methods: The records of 21 men (mean age 48.6 years, range 27-64 years) with isolated postcoital hematuria without bloody ejaculate were retrospectively reviewed. Patients underwent routine laboratory testing including coagulation studies and urological evaluation which included urinalysis, urine cytology, abdominal and transrectal ultrasonography, and cystourethroscopy. Results: Among total 21 patients, there were no detectable abnormalities in 11 (52.4%) patients. Lesions were found in 10 (47.6%) patients, which included 1 pathologically proven prostatic urethral hemangioma, 5 benign prostatic hyperplasia, 1 bladder neck obstruction, and 3 ultrasonographically identified seminal vesicle dilatation. The symptom subsided within 3 months after treatment or simple observation in 18 (85.7%) patients, and within 1 year in 1 patient. In these patients, the symptom did not recur at the mean follow-up period of 44.9 months (range, 10-120 months). In the remaining two patients, postcoital hematuria has still persisted intermittently for 19 and 74 months, respectively, since the first visit. Conclusions: Thorough evaluations are necessary in the case of postcoital hematuria because treatable lesions such as urethral hemangioma could be identified. The symptom did not recur for a long period after remission in the majority of patients. Therefore, in cases without identifiable causes, the patients could be reassured that the condition is benign and self-limiting. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the accuracy of MRI in predicting the pathological complete response (pCR) and the residual tumor size of breast cancer after neoadjucant chemotherapy (NAC), and to determine the factors affecting the accuarcy., Materials and Methods: Eighty-eight breast cancer patients who underwent surgery after NAC at our center between 2010 and 2017 were included in this study. pCR was defined as the absence of invasive cancer on pathological evaluation. The maximum diameter of the residual tumor on post-NAC MRI was compared with the tumor size of the surgical specimen measured pathologically. Statistical analysis was performed to elucidate the factors affecting pCR and the residual tumor size-discrepancy between the MRI and the pathological measurements., Results: The pCR rate was 10%. The diagnostic accuracy of MRI and the area under the curve for predicting pCR were 90.91% and 0.8017, respectively. The residual tumor sizes obtained using MRI and pathological measurements showed a strong correlation ( r = 0.9, p < 0.001), especially in patients with a single mass lesion ( p = 0.047). The size discrepancy between MRI and the pathological measurements was significantly greater in patients with the luminal type ( p = 0.023) and multifocal tumors/non-mass enhancement on pre-NAC MRI ( p = 0.047)., Conclusion: MRI is an accurate tool for evaluating pCR and residual tumor size in breast cancer patients who receive NAC. Tumor subtype and initial MRI features affect the accuracy of MRI., Competing Interests: Conflicts of Interest: The authors have no potential conflicts of interest to disclose., (Copyrights © 2021 The Korean Society of Radiology.)