Zero DC offset active RC filter designs.

A class of RC active filters in which the DC offset of the operational amplifier (op-amp) is completely absent from the filter output [1]. Individual filter configurations (Low Pass, High Pass, Band Pass, Band Stop, All Pass) are discussed and corresponding transfer functions are defined. The effects of op-amp gain bandwidth product on filter responses are accounted for and presented in a table. In order to understand the upper limit of dynamic responses, maximum signal magnitude and corresponding frequency of maximum magnitude are calculated. The effects of noise generating components are defined and included, thus establishing the lower limit of dynamic responses for all filter configurations. Step-by-step design procedures are given for most common filter configurations. Sample filters are designed based on chosen values for critical frequency ù 0 and filter quality factor Q. Filter schematics are captured and their frequency responses are simulated using circuit simulation software. Sample filters are built and their frequency responses are confirmed using a network analyzer. Extension to higher order filters is discussed and demonstrated

Short communication: Teat wall diameter and teat tissue thickness in dairy cows are affected by intramammary pressure and by the mechanical forces of machine milking.

The objective of this study was to validate and apply 2 different methods to record changes in teat tissue related to machine milking. Teat wall diameter was measured via B-mode ultrasound cross sectioning with a 7.5-MHz linear probe. Teat tissue thickness was measured using a cutimeter (spring-loaded caliper, spring constant 6.5 N/cm, 0.5 N at closed jaws). Both methods were applied at the teat barrel, 2 cm above the teat tip. In experiment 1, 24 teats from freshly slaughtered cows were used to perform ultrasound imaging (12 teats) or cutimeter measurements (12 teats) while the teat cisterns were filled with water to increase the intracisternal pressure from 0 to 30 kPa in steps of 1 kPa. Teat tissue thickness did not change at an intracisternal pressure from 0 to 10 kPa but increased with intracisternal pressure at levels >10 kPa. In contrast, teat wall diameter decreased with intracisternal pressure between 0 and 7 kPa but did not significantly change at a pressure ≥7 kPa up to 30 kPa. Significant Pearson correlation coefficients between intracisternal pressure and teat wall diameter were observed from 0 to 7 kPa (r = -0.38), and between intracisternal pressure and teat tissue thickness from 10 to 30 kPa (r = 0.45). In experiment 2, ultrasound and cutimeter measurements were performed in 12 lactating Holstein cows. Measurements before and during milking, immediately after cluster removal, with normal milking or with a 5-min overmilking, were performed and continued at 5-min intervals for 60 min and at 10-min intervals until 120 min. Additionally, with the 5-min overmilking treatment, measurements were continued at 60-min intervals up to 10 h after milking. Teat wall diameter decreased in response to milk ejection, followed by a continuous increase during the course of milking, with highest values after 5 min overmilking. Teat tissue thickness did not change during milking but was significantly increased after overmilking. Teat wall diameter and teat tissue thickness recovered to premilking levels within 35 min after normal milking and within 60 min after overmilking. Until 10 h after overmilking, the teat wall diameter decreased steadily, whereas teat tissue thickness was unfluctuating. In the physiologically relevant range of intramammary pressure, ultrasound measurements of the teat wall were affected by both intramammary pressure and mechanical forces, whereas cutimeter measurements were not affected by the intramammary pressure

Second instrument tip breaks during phacoemulsification

Background: Second instrument tip breaks during phacoemulsification are complications that are anecdotally recalled, yet little information exists on why and how often they occur, whether they are consistently tracked, and how they are managed. They may be an underreported, but potentially serious, complication of phacoemulsification. Methods:We surveyed 114 cataract surgeons in Ontario to determine reported rates of second instrument tip breaks, their management, and presumed etiology.We reviewed 4 Toronto cataract centres for incident reports, instrument sterilization processes, and purchase histories. Using scanning electron microscopy (SEM), we compared the characteristics of a broken Sweeney tip to new and used second instruments. Results: Of the 35 surgeons responding to the survey, 34% had experienced a second instrument tip break during their careers. Approximately 73% (16 cases) of the 22 cases reported were managed successfully during the procedure by the primary surgeon, 14% (3 cases) required imaging by computerized tomography or x-ray, and another 14% (3 cases) required pars plana vitrectomy for tip retrieval. Purchase histories revealed that 1 Sweeney hook was exchanged monthly, equivalent to 100 to 150 surgeries. SEM of new and used second instruments revealed signs of metal fatigue on both new and used second instruments. Interpretation: Although both physicians and hospitals lack a method for ensuring quality control of second instruments, approximately one third of cataract surgeons encounter second instrument tip breaks during the course of their careers. Although most cases are managed intraoperatively, consistent hospital tracking records and standardized instrument inspection by institutions and surgeons are needed to determine how these complications occur and to establish protocols for complication reporting and management.link_to_subscribed_fulltex

Activation of Notch signaling in human colon adenocarcinoma.

Notch and Wnt signaling function together to regulate colonic progenitor cell division and differentiation. Studies in mice have also shown that Notch signaling is required for adenoma formation in response to elevated Wnt-pathway signaling that occurs in the APCMin mouse model of human adenomatous polyposis coli. We therefore used in situ hybridization to analyze expression of Notch ligands, receptors and fringe genes, as well as the Notch target gene, HES1, in human colorectal cancer (CRC). In a small cohort of tumors, JAGGED ligands, NOTCH1, LFNG and HES1 were expressed at levels similar to, or higher than, levels observed in the crypt. To explore the possibility that Notch signaling may play a quantitative role in human CRC we next analyzed HES1 mRNA expression in 130 tumors, each associated with outcome data. The vast majority of these tumors expressed HES1, although at varying levels. Absolute expression levels did not correlate with patient survival. These results establish that JAG ligands and NOTCH1, as well as Notch receptor activation are consistent features of human CRC and support the notion that many of these tumors, like the APCMin mouse, may respond to anti-Notch therapeutic regimes