scholarly journals Femtosecond-Laser Assisted Surgery of the Eye: Overview and Impact of the Low-Energy Concept

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 122
Author(s):  
Catharina Latz ◽  
Thomas Asshauer ◽  
Christian Rathjen ◽  
Alireza Mirshahi
Keyword(s):  
Surgical Techniques ◽  
Numerical Aperture ◽  
Optical Breakdown ◽  
Pulse Frequency ◽  
Low Energy ◽  
Human Cornea ◽  
Energy Concept ◽  
High Pulse Frequency ◽  
Fs Laser ◽  
High Pulse

This article provides an overview of both established and innovative applications of femtosecond (fs)-laser-assisted surgical techniques in ophthalmology. Fs-laser technology is unique because it allows cutting tissue at very high precision inside the eye. Fs lasers are mainly used for surgery of the human cornea and lens. New areas of application in ophthalmology are on the horizon. The latest improvement is the high pulse frequency, low-energy concept; by enlarging the numerical aperture of the focusing optics, the pulse energy threshold for optical breakdown decreases, and cutting with practically no side effects is enabled.

scholarly journals Femtosecond lasers for eye surgery applications: historical overview and modern low pulse energy concepts

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Thomas Asshauer ◽  
Catharina Latz ◽  
Alireza Mirshahi ◽  
Christian Rathjen
Keyword(s):  
Pulse Energy ◽  
Femtosecond Lasers ◽  
Laser System ◽  
Numerical Aperture ◽  
Optical Breakdown ◽  
Pulse Frequency ◽  
High Pulse Frequency ◽  
Fs Laser ◽  
High Pulse ◽  
Lens Surgery

Abstract This review provides an overview of the historical development and modern applications of femtosecond (fs) lasers in ophthalmology, with a focus on the optical concepts involved. fs-Laser technology is unique because it allows very precise cutting inside the eye through optically transparent tissue, without a need for any mechanical openings. fs-Lasers were historically first used for refractive cornea surgery, later also for therapeutic cornea procedures and lens surgery. Further new areas of ophthalmic application are under development. The latest laser system concept is low pulse energy and high pulse frequency: by using larger numerical aperture focusing optics, the pulse energy required for optical breakdown decreases, and athermal tissue cutting with minimal side effects is enabled.

scholarly journals A New Filter Concept for High Pulse-Frequency 3-Phase AFE Motor Drives

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2814
Author(s):  
Stefan Hoffmann ◽  
Matthias Bock ◽  
Eckart Hoene
Keyword(s):  
Pulse Frequency ◽  
Motor Drives ◽  
Common Mode ◽  
The Public ◽  
Electrical Potentials ◽  
Common Mode Voltage ◽  
High Pulse Frequency ◽  
Power Modules ◽  
High Pulse ◽  
The Difference

The size of back-to-back converters with active front end is significantly determined by the size of the passive filter components. This paper presents a new complete EMC filter concept for this type of converter system that is effective on the input and the output. This involves filtering the main common mode interferences from the grid and motor sides with a single CM choke. Since only the difference of the generated common mode voltage-time areas of both converters is absorbed by this component, the size of the required filter can be greatly reduced compared to conventional filter concepts. The concept is validated on a grid feeding inverter that can be connected to the public distribution network with an output power of 63 kW. The size reduction is demonstrated by means of a design example on a system with the same power and electrical requirements. It is elaborated why, applying the new filter concept, the impedance of the DC link potentials to ground and other electrical potentials should be as high as possible and therefore associated parasitic capacitances should be minimized. From this requirement, rules for the design of the power modules of PFC and motor converters for the application of this filter concept are derived.

Deletion of Gαq/11 or Gαs proteins in gonadotropes differentially affects gonadotropin production and secretion in mice

Endocrinology ◽  
2021 ◽  
Author(s):  
George A Stamatiades ◽  
Chirine Toufaily ◽  
Han Kyeol Kim ◽  
Xiang Zhou ◽  
Iain R Thompson ◽  
...  
Keyword(s):  
Hypogonadotropic Hypogonadism ◽  
Pulse Frequency ◽  
Conditional Knockout ◽  
High Pulse Frequency ◽  
High Pulse ◽  
Males And Females ◽  
G Protein Coupled ◽  
In Vitro Data

Abstract GnRH regulates gonadal function via its stimulatory effects on gonadotropin production by pituitary gonadotrope cells. GnRH is released from the hypothalamus in pulses and GnRH pulse frequency differentially regulates FSH and LH synthesis and secretion. The GnRH receptor (GnRHR) is a G protein-coupled receptor that canonically activates Gαq/11-dependent signaling upon ligand binding. However, the receptor can also couple to Gαs and in vitro data suggest that toggling between different G proteins may contribute to GnRH pulse frequency decoding. For example, as we show here, knockdown of Gαs impairs GnRH-stimulated FSH synthesis at low, but not high pulse frequency in a model gonadotrope-derived cell line. We next used a Cre-lox conditional knockout approach to interrogate the relative roles of Gαq/11 and Gαs proteins in gonadotrope function in mice. Gonadotrope-specific Gαq/11 knockouts exhibit hypogonadotropic hypogonadism and infertility, akin to the phenotypes seen in GnRH- or GnRHR-deficient mice. In contrast, under standard conditions, gonadotrope-specific Gαs knockouts produce gonadotropins at normal levels and are fertile. However, the LH surge amplitude is blunted in Gαs knockout females and post-gonadectomy increases in FSH and LH are reduced in both males and females. These data suggest that GnRH may signal principally via Gαq/11 to stimulate gonadotropin production, but that Gαs plays important roles in gonadotrope function in vivo when GnRH secretion is enhanced.

Development and Study on Transformer Characteristics of A High Repetition Pulse Generator

2013 ◽  
Vol 64 (4) ◽  
Author(s):  
Muhammad Abu Bakar Sidik ◽  
Hamizah Shahroom ◽  
Hussein Ahmad ◽  
Zolkafle Buntat ◽  
Zafar Iqbal ◽  
...  
Keyword(s):  
High Voltage ◽  
Pulse Generator ◽  
Pulse Frequency ◽  
Iron Core ◽  
Fast Switching ◽  
High Repetition ◽  
Simulink Model ◽  
Switching Losses ◽  
High Pulse Frequency ◽  
High Pulse

High repetition pulse/ high frequency generators are of great interest for scientific and technological applications, including high voltage devices. This paper addresses the design and development of a high repetition pulse generator using a PIC microcontroller (PIC 16F877A). The PIC microcontroller generates two PWM pulses to drive the IGBTs through the optocouplers, which can perform fast switching in high voltage devices with low switching losses. The voltage and current supplied by the optocouplers make it perfectly suitable for the driving operations of IGBTs. Experiments were carried out to test its efficiency, and the waveforms of high repetition pulse frequency were observed by oscilloscope. The results of its operation present that the system could be used in the frequency range 2kHz < f < 200kHz. The system was also simulated by a Matlab Simulink model, in which two types of transformer were introduced to predict its validity in real operation with high voltage devices. The simulated results of the designed pulse generator show that the ignition coil transformer is more suitable than other iron core transformers for a high voltage with high pulse frequency. The system could be easily integrated with other high voltage devices to produce high pulsed frequency high voltages.

The 1994 Stevenson Award Lecture. Follicle-stimulating hormone and luteinizing hormone: a tale of two gonadotropins

1995 ◽  
Vol 73 (6) ◽  
pp. 675-684 ◽  
Author(s):  
Neena B. Schwartz
Keyword(s):  
Luteinizing Hormone ◽  
Follicle Stimulating Hormone ◽  
Pulse Frequency ◽  
Gonadotropin Releasing Hormone ◽  
Specific Cell ◽  
Releasing Hormone ◽  
High Pulse Frequency ◽  
High Pulse ◽  
Secretion Rates ◽  
Stimulating Hormone

Although most gonadotropes synthesize both luteinizing hormone and follicle-stimulating hormone, the transcription, content, and secretion rates of the two gonadotropins can be separated. The signals external to the gonadotropic cells that appear to be important in the differential regulation are gonadotropin-releasing hormone pulse frequency (high pulse frequency favors luteinizing hormone), steroid feedback (works on both but induces a more powerful negative feedback on luteinizing hormone), and gonadal peptide feedback (activin increases follicle-stimulating hormone; inhibin and follistatin decrease it). We know very little about the pathways within the gonadotropes that favor one gonadotropin rather than another. It is expected that the cloning of the genes for both gonadotropins and the use of specific cell lines and transfections will lead to elucidation of these pathways.Key words: luteinizing hormone, follicle-stimulating hormone, gonadotropin-releasing hormone, inhibin, anterior pituitary, gonads.

Sign in / Sign up

Export Citation Format

Share Document