Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model

The introduction of two-photon polymerization (TPP) into the area of Carbon Micro Electromechanical Systems (CMEMS) has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography. Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy. In this work, we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900 °C. Through this process, photoresist microwires thermally decompose and shrink by as much as 75%, resulting in glassy carbon nanowires with linewidths between 300 and 550 nm. Even after the thermal decomposition induced by the pyrolysis step, the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters. We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires, but also in buckling in the case of slender carbon nanowires (for aspect ratios greater than 30). Furthermore, we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires, a trend that is consistent with several works found in the literature. This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures, serving as a simple guideline for shrinkage evaluation in other designs

Low grade urothelial carcinoma mimicking basal cell hyperplasia and transitional metaplasia in needle prostate biopsy

ABSTRACT Purpose The vast majority of urothelial carcinomas infiltrating the bladder are consistent with high-grade tumors that can be easily recognized as malignant in needle prostatic biopsies. In contrast, the histological changes of low-grade urothelial carcinomas in this kind of biopsy have not been studied. Materials and Methods We describe the clinicopathologic features of two patients with low-grade bladder carcinomas infiltrating the prostate. They reported dysuria and hematuria. Both had a slight elevation of the prostate specific antigen and induration of the prostatic lobes. Needle biopsies were performed. At endoscopy bladder tumors were found in both cases. Results Both biopsies showed nests of basophilic cells and cells with perinuclear clearing and slight atypia infiltrating acini and small prostatic ducts. The stroma exhibited extensive desmoplasia and chronic inflammation. The original diagnosis was basal cell hyperplasia and transitional metaplasia. The bladder tumors also showed low-grade urothelial carcinoma. In one case, the neoplasm infiltrated the lamina propria, and in another, the muscle layer. In both, a transurethral resection was performed for obstructive urinary symptoms. The neoplasms were positive for high molecular weight keratin (34BetaE12) and thrombomodulin. No metastases were found in either of the patients, and one of them has survived for five years. Conclusions The diagnosis of low-grade urothelial carcinoma in prostate needle biopsies is difficult and may simulate benign prostate lesions including basal cell hyperplasia and urothelial metaplasia. It is crucial to recognize low-grade urothelial carcinoma in needle biopsies because only an early diagnosis and aggressive treatment can improve the prognosis for these patients

Is iron overload associated with worse outcomes in patients with chronic liver disease undergoing liver transplantation?

Background: Iron overload is frequent in patients with chronic liver disease, associated with shorter survival after liver transplantation in patients with hereditary hemochromatosis. Its effect on patients without hereditary hemochromatosis is unclear. The aim of the study was to study the clinical impact of iron overload in patients who underwent liver transplantation at an academic tertiary referral center. Methods: We performed a retrospective cohort study including all patients without hereditary hemochromatosis who underwent liver transplantation from 2015 to 2017 at an academic tertiary referral center in Mexico City. Explant liver biopsies were reprocessed to obtain the histochemical hepatic iron index, considering a score >- 0.15 as iron overload. Baseline characteristics were compared between patients with and without iron overload. Survival was estimated using the Kaplan-Meier method, compared with the log-rank test and the Cox proportional hazards model. Results: Of 105 patients included, 45% had iron overload. Viral and metabolic etiologies, alcohol consumption, and obesity were more frequent in patients with iron overload than in those without iron overload (43% vs. 21%, 32% vs. 22%, p = 0.011; 34% vs. 9%, p = 0.001; and 32% vs. 12%, p = 0.013, respectively). Eight patients died within 90 days after liver transplantation (one with iron overload). Complication rate was higher in patients with iron overload versus those without iron overload (223 vs. 93 events/100 personmonths; median time to any complication of 2 vs. 3 days, p = 0.043), without differences in complication type. Fatality rate was lower in patients with iron overload versus those without iron overload (0.7 vs. 4.5 deaths/100 person-months, p = 0.055). Conclusion: Detecting iron overload might identify patients at risk of early complications after liver transplantation. Further studies are required to understand the role of iron overload in survival

Pyrolysis-induced shrinking of three-dimensional structures fabricated by two-photon polymerization: experiment and theoretical model.

The introduction of two-photon polymerization (TPP) into the area of Carbon Micro Electromechanical Systems (C-MEMS) has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography. Pyrolysis of TPP structures conveys a characteristic reduction of feature size-one that should be properly estimated in order to produce carbon microdevices with accuracy. In this work, we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900 °C. Through this process, photoresist microwires thermally decompose and shrink by as much as 75%, resulting in glassy carbon nanowires with linewidths between 300 and 550 nm. Even after the thermal decomposition induced by the pyrolysis step, the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters. We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires, but also in buckling in the case of slender carbon nanowires (for aspect ratios greater than 30). Furthermore, we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires, a trend that is consistent with several works found in the literature. This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures, serving as a simple guideline for shrinkage evaluation in other designs

Association of PTP1B with Outcomes of Breast Cancer Patients who Underwent Neoadjuvant Chemotherapy

PTP1B is involved in the oncogenesis of breast cancer. In addition, neoadjuvant therapy has been widely used in breast cancer; thus, a measurement to assess survival improvement could be pathological complete response (pCR). Our objective was to associate PTP1B overexpression with outcomes of breast cancer patients who underwent neoadjuvant chemotherapy. Forty-six specimens were included. Diagnostic biopsies were immunostained using anti-PTP1B antibody. Expression was categorized as negative (<5%) and overexpression (≥5%). Patients' responses were graded according to the Miller-Payne system. Sixty-three percent of patients overexpressed PTP1B. There was no significant association between PTP1B overexpression and pCR (P = 0.2). However, when associated with intrinsic subtypes, overexpression was higher in human epidermal growth factor receptor 2-positive-enriched specimens (P = 0.02). Ten-year progression-free survival showed no differences. Our preliminary results do not show an association between PTP1B overexpression and pCR; however, given the limited sample and heterogeneous treatment in our cohort, this hypothesis cannot be excluded

Simple Approach to Reducing Particle Trapping Voltage in Insulator-Based Dielectrophoretic Systems

Insulator-based dielectrophoresis (iDEP) is a microfluidic technique used for particle analysis in a wide array of applications. Significant efforts are dedicated to improve iDEP systems by reducing voltage requirements. This study assesses how the performance of an iDEP system, in terms of particle trapping, depends on the number of insulating obstacles longitudinally present in the microchannel. In analogy with Kirchhoff’s loop rule, iDEP systems were analyzed as a series combination of electrical resistances, where the equivalent resistance of the post array is composed by a number of individual resistors (columns of insulating posts). It was predicted by the COMSOL model, and later confirmed by experimental results, that reducing the number of columns of insulating posts significantly affects the electric field distribution, decreasing the required voltage to dielectrophoretically trap particles within the post array. As an application, it was demonstrated that decreasing the number of columns in the post array allows for the dielectrophoretic trapping of nanometer-scale particles at voltages well below those reported in previous similar iDEP systems. These findings illustrate how the iDEP channel configuration can be customized for specific applications