Switched Off Research Articles

P-169 Oocyte-to-embryo transition is regulated by availability of exogenous aminoacids in culture medium

Abstract Study question Is de novo protein synthesis during the conversion of oocytes into embryos coupled with aminoacid availability more than with gene transcription? Summary answer The oocyte-to-embryo transition is modulated post-transcriptionally by exogenous aminoacids, including translational reactivation of otherwise transcriptionally silent maternal genes. What is known already Countless studies documented how genes’ mRNAs are regulated up or down during the oocyte-to-embryo transition, with maternal genes being switched off and embryonic genes being switched on. This switching off and on has been poorly explored at the protein level, because it required to administer radioactive or non-canonical aminoacids to embryos in vitro or in the genital tract of the mother, in animal models. However, radioactive aminoacids could not be applied for too long as they harm cells, while non-canonical aminoacids are recognized by cells as unnatural and are metabolized differently. A promising solution is provided by non-radioactive isotopic aminoacids. Study design, size, duration In vivo-fertilized mouse oocytes (zygotes) were cultured to blastocysts in KSOM medium, which was adapted for live-cell proteomic labeling by replacing 2 of the 12 Eagle’s essential aminoacids (EAAs) with isotopic but non-radioactive counterparts (Arginine and Lysine, 13C 15N). The 7 non-essential Eagle’s aminoacids (NEAAs) were left untouched. Labeled blastocysts were sampled at 96 hours of culture in vitro. Controls were cultured in parallel under non-labeling conditions in conventional KSOM. Participants/materials, setting, methods B6C3F1 females were stimulated with eCG+hCG and mated to CD1 males. Zygotes were labeled in vitro by culture in KSOM containing polyvinylpyrrolidone in place of albumin, isotopic Arginine and Lysine in place of non-isotopic counterparts, with or without NEAAs and with or without the remaining 10 EAAs, at 37 °C under 5% CO2. In vitro-labeled blastocysts were transplanted to uterus to ascertain viability, or compared to non-labeled blastocysts by cell counting, mass spectrometry and RNA sequencing. Main results and the role of chance A total of 5426 mouse blastocysts were generated. Isotopically labeled embryos formed blastocysts with total cell numbers and full-term ability similar to unlabeled controls (blastocyst rate ≥68%, p ≥ 0.11; cell count ≥58, p ≥ 0.62; birth rate ≥25%, p ≥ 0.33; Wilcoxon test). When isotopic Arginine and Lysine were present as the sole aminoacids, the blastocyst proteome consisted of 54% unlabeled proteins, 30% semi-labeled proteins and 16% completely labeled proteins. The balance changed to 12%-51%-37% and 6%-56%-38% when NEAAs and NEAAs+EAAs, respectively, were added in culture on top of isotopic Arginine and Lysine (p = 1.9E-09; chi test). This rebalancing did not mirror in the transcriptomes, which were conserved in the three groups (p > 0.08, Wilcoxon test). The proteins of 42 maternal-effect genes (PMID 35047854), which are downregulated during the oocyte-to-embryo transition, were unlabeled when isotopic Arginine and Lysine were present as the sole aminoacids, but became increasingly more labeled (49%, 66%) when NEAAs and NEAAs+EAAs were provided on top of isotopic Arginine and Lysine. Collectively, this information supports that the oocyte-to-embryo transition is not a cell-autonomous process, but features a dynamic post-translational response to the composition of culture medium, including an altered pace of degradation and de novo synthesis of maternal proteins. Limitations, reasons for caution This is an animal study. Mature and fertilized mouse oocytes were collected from oviduct, which is not how human embryos are produced in medically assisted reproduction. The role of autophagy as internal source of aminoacids was not investigated. The oocyte-to-embryo transition takes 2-3 days longer in humans than in mice. Wider implications of the findings As seen in mice, so also in humans the oocyte-to-embryo transition could be modulated by aminoacids, considering that human media are mouse embryo-tested and the requirement of aminoacids for development is conserved across species. To recognize that culture media actively change the embryos, also in medically assisted reproduction, is overdue. Trial registration number not applicable

Integration of a Smart Remote Controlling System with Electrical Appliances in Order to Optimize the Usage and to Develop an Energy Efficient System

Electricity is a powerful tool and must needed recourse of energy of all time in life existence since its invention. Its optimum utilization is a need of the era where various measures are taken on controlling methods by some enforced and imposed ways, we discuss a smart system which works to control unnecessary wastage of resources by keeping a time-to-time check on the system can be collaborated with a smart alert system. The idea is to not to control the usage but to curb the wastage for the optimum and efficient use of the available resources. In this project we proposed a smart system in which a signal will be send to mobile phone first if there is no human presence detected. After getting alert of human absence, electrical appliances can be switched OFF through mobile phone. This Idea is helpful when at the same working time some rooms are in use and some rooms are unused. So, by remote controlled switching of the appliances, electricity can be saved. This control can be done from the 25-20 meters range so in this case no need to approach the room manually to operate the switches. The objective of the project is to model a system to optimize the use of available resources for meeting the energy needs by saving energy while it is not under use. In this way a huge amount of energy can be saved. This will not only reduce the electricity bill but it will promote the optimum utilization of energy sources. Remote controlling of electrical appliances through a smart mobile system also restates the human nature of laziness in switching OFF appliances while they are not in use so it has a wide use in domestic’s field also.

Temporal response of the conductivity of electrolytes

We study the temporal response of the electric current in an electrolyte under a sudden switch on or switch off of an external electric field of arbitrary magnitude. We use Stochastic Density Functional Theory including hydrodynamic interactions to express the current as a function of the ionic correlations. Assuming small density fluctuations, we linearize the field theory to compute the correlations in the transient regime. We first show that the correlations do not follow the same trajectory when the field is switched on or switched off. Accordingly, the behavior of the current differs in the two cases: it decays exponentially when the field is switched off, but it relaxes algebraically to its stationary value when the field is switched on. This difference is a non-linear effect since an exponential relaxation is recovered in both cases in the weak field limit.

Intelligent Control of the Energy Storage System for Reliable Operation of Gas-Fired Reciprocating Engine Plants in Systems of Power Supply to Industrial Facilities

Gas-fired reciprocating engine plants (GREPs) are widely used in power supply systems of industrial facilities, which allows for ensuring the operation of electrical loads in case of accidents in the power system. Operating experience attests to the fact that during islanded operations, GREPs are shut down by process protections or protective relays in the event of severe disturbances. This leads to complete load shedding, which is accompanied by losses and damage to industrial facilities. Severe disturbances include the following ones: large load surges on GREPs due to one of them being switched off, the group starting of electric motors, and load shedding (more than 50%) during short circuits or disconnection of process lines. Energy storage systems (ESS) have the ability to compensate for instantaneous power imbalances to prevent GREPs from switching off. The authors of this study have developed methods for intelligent control of the ESS that allow one to solve two problems: prevention of GREPs shutdowns under short-term frequency and voltage deviations as well as preservation of the calendar and cycling lifetime of battery storage (BS) of the GREP. The first method does not require performing the calculation of adjustments of control actions for active and reactive power on the ESS online but rather determines them by the value of frequency deviations and the voltage sag configuration, which greatly simplifies the system of automatic control of the ESS. The second method, which consists in dividing the steady-state power/frequency characteristic into sections with different droops that are chosen depending on the current load of the ESS and the battery state of charge, and offsetting it according to a specified pattern, allows for preventing the premature loss of power capacity of the ESS BS.

Temperature–responsive coating endowing LiNi0.8Co0.1Mn0.1O2 cathode materials with improved cycling stability and overheating self-protection function

The critical challenges of the commercial application of Ni–rich layered LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode materials for lithium ion batteries are their poor cycling stability and terrible safety. The safety concerns are mainly caused by the thermal runway of the battery started from the battery overheating. Here, we report a temperature–sensitive reversible switching material that is coated on NCM811 cathode materials surface, which simultaneously endows NCM811 cathode materials with improved cycling stability and overheating self-protection function. This coating layer could isolate the bulk cathode materials from the electrolyte, alleviate the structure destroy and suppress the side reactions on the cathode-electrolyte interface, thus enhancing the cyclability of NCM811 cathode materials. Besides, the coating layer endows the every active NCM811 particle with overheating self-protection function, which can block off the electrons transfer between NCM811 and neighboring particles under the overheating conditions and thus switch off battery reactions, preventing the battery from further generating heat and avoiding the occurrence of thermal runaway. Furthermore, NCM811 with this coating layer after switched off is able to resume their normal function. This work attempts to resolve these two critical problems of the application of NCM811 cathode materials, providing a new opportunity for the large-scale commercialization of it.

Remnant radio galaxies discovered in a multi-frequency survey

AbstractThe remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a$8.31$deg$^2$subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1–9 GHz. We present a sample of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an ‘absent radio core’ criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz; at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum ($\alpha<-1.2$) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our sample of radio galaxies, our observations constrain the remnant fraction to$4\%\lesssim f_{\mathrm{rem}} \lesssim 10\%$; the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5–10 Myr at 5.5 GHz after the jets switch of—radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants.

Protecting Quasi-Possession of Electricity Supply with the Mandament van Spolie – Has the Supreme Court of Appeal Switched Off this Possibility? [A Discussion of Eskom Holdings Soc Ltd v Masinda 2019 5 SA 386 (SCA)

In Eskom Holdings SOC Ltd v Masinda 2019 5 SA 386 (SCA) (“Masinda”), the Supreme Court of Appeal had to decide whether the mandament van spolie is available for restoring quasi-possession of electricity supply. The respondent used the mentioned supply, which was sourced in contract, at her home. The court ruled that the spoliation remedy does not protect the quasi-possession of rights sourced in contract. For its quasi-possession to enjoy possessory protection, the right must be in the nature of a servitude, be registered or flow from legislation. This emphasis on the source of the right is problematic for two reasons. First, it contradicts certain common-law authorities which reveal that the quasi-possession of electricity supply sourced in contract does, in fact, enjoy protection under the spoliation remedy. This applies as long as the supply is a gebruiksreg (use right) and the spoliatus performs physical acts associated with the right on immovable property. Secondly, (over)emphasising the source of the right potentially undermines various fundamental rights. When the common law is open to several possible interpretations, as seems to be the case with quasi-possession, the supremacy of the Constitution and the single-system-of-law principle require that courts choose the interpretation that upholds (rather than impairs) constitutional rights. In the Masinda case, the court unfortunately opted for an understanding of quasi-possession which seems to undermine the Constitution. For these reasons, the decision is an unwelcome development.

Анализ динамики лазерной 2D-резки крупногабаритного объекта космического мусора в невесомости

In this paper two independent objects in low-earth orbit are analysed. The first object is a large piece of space debris containing fragments that need to be extracted and re-used. The second object is a space debris collector equipped with a laser powerful enough to destruct any element of the space debris in an infinitely small period of time. It is accepted that the switch on and switch off times of the laser beam are infinitely small. It is supposed that the objects are moving in near orbits and the difference between their velocities is small. The object protects itself by applying attitude jets and turning the structure round. The particle method is used to analyze the dynamics of laser cutting of a piece of space debris under zero gravity. In the 2D formulation, the cutting beam is replaced by a cutting dot. The objective in the work was not ensuring conformity between the calculated model and the real part but rather formulating the cutting conditions (deactivation) of the links between the particles. Aiming is problematic under gravity-free conditions, hence random cutting was used. To ensure integrity of the cut-out debris fragments, they were encircled by virtual circumferences and the circumferences’ positions were tracked. As soon as the cutting point entered the circle, the laser was immediately switched off.

Neuropsychological changes in efavirenz switch regimens.

Efavirenz is associated with side effects involving the central nervous system. However, it remains largely unknown whether switching off EFV improves neuropsychological performance. We utilized data from the Multicenter AIDS Cohort Study (MACS). Participants were categorized by their use of EFV: never on EFV (No EFV), continuously on EFV (No Switch-OFF) and on EFV and then switched off (Switch-OFF). Baseline time points were defined as visits when first neuropsychological data were available. In Analysis 1, we compared neuropsychological and Center for Epidemiological Studies-Depression Scale (CES-D) scores before and after EFV switch in Switch-OFF group, aligning participants at the time of switch. Analysis 2 evaluated trajectory of neuropsychological/CES-D score among the three groups. This analysis included 1989 HIV-seropositive participants with neuropsychological data (1675 in No EFV, 44 in No Switch-OFF, and 270 in Switch-OFF group). At baseline, participants had a median age of 37 years, median CD4 cell count 442 cells/μl, and 22.9% viral suppression rate. In Analysis 1, neuropsychological and CES-D scores did not show clinically significant changes over 2 years prior to and 4 years after switch in Switch-OFF group. In Analysis 2, trends in neuropsychological and CES-D scores in the three different groups did not show significant differences during a median of 3.2 years of follow-up. Discontinuation of EFV is not associated with changes in neuropsychological performance or severity of depression in men. Furthermore, we did not observe differences among participants who were never on EFV, continuously on EFV, and on EFV and then switched off.

Energy Optimization for Large-Scale 3D Manycores in the Dark-Silicon Era

In this paper, we study the impact of the idle/dynamic power consumption ratio on the effectiveness of a multi-Vdd/frequency manycore design. We propose a new tool called LVSiM (a Low-Power and Variation-Aware Manycore Simulator) to carry out the experiments. It is a novel manycore simulator targeted towards low-power optimization methods including within-die process and workload variations. LVSiM provides a holistic platform for multi-Vdd/frequency voltage island analysis, optimization, and design. It provides a tool for the early design exploration stage to analyze large-scale manycores with a given number of cores on 3D-stacked layers, network-on-chip communication busses, technology parameters, voltage and frequency values, and power grid parameters, using a variety of different optimization methods. LVSiM has been calibrated with Sniper/McPAT at a nominal frequency, and then the energy-delay-product (EDP) numbers were compared after frequency scaling. The average error is shown to be 10% after frequency scaling, which is sufficient for our purposes. The experiments in this work are carried out for different Idle/Dynamic ratios considering 1260 benchmarks with task sizes ranging from 4000 to 16 000 executing on 3200 cores. The best configurations are shown to produce on average 20.7% to 24.6% EDP savings compared to the nominal configuration. Traditional scheduling methods are used in the nominal configuration with the unused cores switched off. In addition, we show that, as the Idle/Dynamic ratio increases, the multi-Vdd/frequency approach becomes less effective. In the case of a high Idle/Dynamic ratio, the minimum EDP can be achieved through switching off unused cores as opposed to using a multi-Vdd/frequency approach. This conclusion is important, especially in the dark-silicon era, where switching cores on and/or off as needed is a common practice.

A TLBO-BASED ENERGY EFFICIENT BASE STATION SWITCH OFF AND USER SUBCARRIER ALLOCATION ALGORITHM FOR OFDMA CELLULAR NETWORKS

Downlink of a cellular network with orthogonal frequency-division multiple access (OFDMA) is considered. Joint base station switch OFF and user subcarrier-allocation with guaranteed user quality of service, is shown to be a promising approach for reducing network’s total power consumption. However, solving the aforementioned mix-integer and nonlinear optimization problem requires robust and powerful optimization techniques. In this paper, teaching-learning based optimization algorithm has been adopted to lower cellular network’s total power consumption. The results show that the proposed technique is able to reduce network’s total power consumption by determining a near optimum set of base stations to be switched OFF and near optimum subcarrier-user assignments. It is shown that the proposed scheme is superior to existing base station switch OFF schemes. Robustness of the proposed TLBO-based technique is verified.

Do a robot's social skills and its objection discourage interactants from switching the robot off?

Building on the notion that people respond to media as if they were real, switching off a robot which exhibits lifelike behavior implies an interesting situation. In an experimental lab study with a 2x2 between-subjects-design (N = 85), people were given the choice to switch off a robot with which they had just interacted. The style of the interaction was either social (mimicking human behavior) or functional (displaying machinelike behavior). Additionally, the robot either voiced an objection against being switched off or it remained silent. Results show that participants rather let the robot stay switched on when the robot objected. After the functional interaction, people evaluated the robot as less likeable, which in turn led to a reduced stress experience after the switching off situation. Furthermore, individuals hesitated longest when they had experienced a functional interaction in combination with an objecting robot. This unexpected result might be due to the fact that the impression people had formed based on the task-focused behavior of the robot conflicted with the emotional nature of the objection.

53 Please dont shock me: a qi project on implantable cardioverter defibrillators (icds) at the end of life care & dnar

IntroductionThere is an increase in Implantable Cardioverter Defibrillators (ICDs) and Cardiac Resynchronization Therapy Defibrillators (CRT-Ds) being implanted every year. With patients living longer, the number of patients reaching the end...

Estimation of the lifetime of a trapped vortex in a circular cavern on a semicircular airfoil streamlined at a zero angle of attack after switching off slot suction

The restructuring of the periodic structure of a turbulent streamline for a semicircular airfoil at a zero angle of attack with a system of slot suction from the circular cavern switched off is calculated. Multiblock numerical methods are applied for solution of Reynolds-averaged nonstationary Navier–Stokes equations closed using the modified shear-stress transfer model taking into account flow line curvature. The lifetime of a trapped vortex in a circular cavern is estimated.

A test of the equivalence principle(s) for quantum superpositions

We propose an experimental test of the quantum equivalence principle introduced by Zych and Brukner (arXiv:1502.00971), which generalises the Einstein equivalence principle to superpositions of internal energy states. We consider a harmonically trapped atom in the presence of both gravity and an external magnetic field and show that when the external magnetic field is suddenly switched off, various violations of the equivalence principle would manifest as otherwise forbidden transitions. Performing such an experiment would put bounds on the various phenomenological violating parameters. We further demonstrate that the classical weak equivalence principle can be tested by suddenly putting the apparatus into free fall, effectively ‘switching off’ gravity.

Stochastic Geometric Models for Green Networking

In this paper, we use a stochastic geometric approach in order to study the impact on energy consumption when base stations are switched OFF independently of each other. We present here both the uplink and downlink analysis based on the assumption that the base stations are distributed according to an independent stationary Poisson point process. This type of modeling allows us to make use of the property that the spatial distribution of the base stations after thinning (switching OFF) is still a Poisson process. This implies that the probability distribution of the signal to interference and noise ratio (SINR) can be kept unchanged when switching-OFF base stations provided that we scale up the transmission power of the remaining base stations. We then solve the problem of optimally selecting the switch-OFF probabilities so as to minimize the energy consumptions, while keeping unchanged the SINR probability distribution. We then study the tradeoff in the uplink performance involved in switching-OFF base stations. These include the energy consumption, the coverage and capacity, and the impact on amount of radiation absorbed by the transmitting user.

AMPK - a nutrient and energy sensor with roles in diabetes, cancer and viral infection

The AMP-activated protein kinase (AMPK) is a cellular energy sensor that is conserved throughout the eukaryotic domain. AMPK exists as complexes comprising catalytic α subunits and regulatory β and γ subunits, which are activated >100-fold by phosphorylation of the α subunit at Thr-172 by upstream kinases. Binding of AMP to one site on the Y subunit causes 10-fold allosteric activation by AMP, while binding of either AMP or ADP to a second site promotes phosphorylation and inhibits dephosphorylation of Thr-172. Since both effects are antagonized by ATP, the kinase is activated by falling cellular energy status, when it phosphorylates downstream targets that switch on catabolic pathways generating ATP, while switching off processes consuming ATP. Catabolic processes switched on including uptake and metabolism of glucose and fatty acids, and mitochondrial biogenesis. ATP-consuming processes switched off include biosynthetic pathways for lipids (fatty acids, phospholipids, cholesterol), carbohydrates (gluconeogenesis, glycogen synthesis), proteins and ribosomal RNA, and progress through the cell cycle. By switching on glucose and fatty acid uptake and metabolism and switching off gluconeogenesis, AMPK should reverse the key metabolic defects in insulin resistance and type 2 diabetes. Consistent with this, AMPK is a target, although probably not the only target, for the anti-diabetic drug metformin. Because AMPK activation inhibits most biosynthetic pathways and causes cell cycle arrest, it should also have a cytostatic, tumor suppressor effect. The discovery in 2003 that the major upstream kinase that phosphorylates Thr-172 is the tumor suppressor kinase, LKB1, strengthened this view. The finding also led to retrospective analyses suggesting that metformin protects against the development of cancer. If AMPK is a tumor suppressor, one would expect that it would be down-regulated in many tumors. This indeed occurs through loss-of-function mutations in the upstream kinase LKB1, particularly in non-small cell lung cancer and cervical cancer. The majority of cases of breast cancer also appear to have defects in AMPK activation, although the mechanism is not known. We have found that AMPK is down-regulated in cells infected with hepatitis C virus (HCV). HCV may switch off AMPK to prevent its inhibitory effects on lipid and protein synthesis, required for viral replication. HCV infection activates the PKB/Akt pathway, leading to phosphorylation of the α1 subunit of AMPK on Ser-485, thus inhibiting AMPK activation via phosphorylation at Thr-172. It is possible that this contributes to the elevated risk of hepatocellular carcinoma observed in humans with chronic HCV infection. Finally, we have found that AMPK is directly activated by salicylate, and have evidence that at least some of the metabolic changes induced by the drug in vivo are mediated by AMPK. Salicylate is a natural product of plants whose medicinal use was described in ancient manuscripts. Its use has largely been replaced by derivatives such as salsalate and aspirin, but both are rapidly broken down to salicylate in vivo. It is possible that some of the beneficial effects of salicylate derivatives, including amelioration of insulin resistance and protection against colon cancer, might be mediated by AMPK.

Clowning around sets patients at ease

<h3>Introduction</h3> There is an increase in Implantable Cardioverter Defibrillators (ICDs) and Cardiac Resynchronization Therapy Defibrillators (CRT-Ds) being implanted every year. With patients living longer, the number of patients reaching the end of life with an active ICD or CRT-D is also on the rise. These can be missed or be mistaken for a pacemaker, especially during the end of life care. <h3>Problem</h3> In 2015, at our hospital, 75% of patients with an ICD/CRT-D who died had no deactivation. Some of these patients did receive painful and undesirable shocks from their active ICD/CRT-D upon death; unfortunately witnessed by some of their worried families. The hospital staff were surveyed about the awareness on ICDs/CRT-Ds at the end of life and upon death, which revealed&gt;60% of staff were unaware what to do. <h3>Aims/Methodology</h3> A QI project was established to increase the number of ICD/CRT-D deactivation discussions and switch offs during the end of life care by 50%, over a 6 month period. Since January 2016, there were different interventions every month; including Grand round, departmental teaching, posters (Figure 1), implementing related questions in the palliative pathway and e-messages. <h3>Results</h3> After 4 months, 66% of patients with an active ICD/CRT-D received discussions and switch-offs in advance with good timing before death (Figure 2). In turn, there was a strong impact on patient-centred care, quality and co-ordinated care, efficiency, effectiveness, cost and patient safety. <h3>Conclusions</h3> ICDs/CRT-Ds can save lives. However, patients reaching the end of life should be put at ease and comfort by discussing ICD/CRT-D deactivation at DNAR (’Do Not Attempt Resuscitation’) discussion and have their ICD/CRT-D switched off in advance with good timing.

The use of a segmented transducer for rib sparing in HIFU treatments

The use of focused ultrasound as a minimally invasive treatment for tumours is rapidly expanding. Target organs include the liver and kidneys. Both single element and phased array transducers may be used in the clinic. The presence of the rib cage presents a problem in high intensity focused ultrasound (HIFU) treatment planning, due to its high attenuation of the HIFU beam resulting in a loss of power at the focus as well as an increase in the risk of damage at the rib and to overlying tissues, including the skin. In this paper, a linearly segmented transducer, in which all active elements are driven in phase, has been investigated. The aim of the study was to investigate how a beam with a clinically useful profile could be achieved by removing the contribution of edge segments from one side of the transducer to the field. We have considered the case in which the HIFU beam approaches the rib cage during a treatment and investigated configurations of the transducer for which up to three segments on the edge are switched off. This problem has been studied initially using a linear acoustic field program to model the segmented transducer’s acoustic beam profile. Experimental measurements of the transducer’s acoustic field were performed using an automated beam plotting system. Temperature measurements were made on a rib surface for two transducer configurations using a fine wire thermocouple. A thermochromic liquid crystal material was used to assess qualitatively the heating pattern generated by the ultrasound beam. We show the rib sparing potential of the segmented transducer during HIFU treatment by demonstrating a reduction in the prefocal width of the ultrasound beam when edge segments are switched off. This has been predicted with the acoustic field model and demonstrated experimentally by acoustic field measurements and observations of the heating pattern generated by the ultrasound beam. A significant decrease in the temperature rise on a rib was observed in the case for which three edge segments were switched off compared with when all segments were active. We conclude that a segmented transducer extends the potential for treating liver tumours. In the case where the tumour lies behind, but close to the edge of, the ribs, energy loss at the focus and excessive heating in the rib and overlying tissue can be avoided by switching off edge segments. (E-mail: john.civale@icr.ac.uk)

Unbalanced Switching Effects on Dynamic Performance of an Isolated Three-Phase Self-Excited Generator

This paper presents dynamic performance of an isolated three-phase self-excited reluctance generator (SERG) under sudden disconnection of single-phase loads and excitation capacitors. A novel approach based on three-phase reluctance machine model is employed to derive dynamic equations of a stand-alone SERG under different unbalanced conditions. Experimental results obtained from a laboratory 0.37 kW reluctance machine driven by a DC motor are also performed and compared with the simulated results to validate the effectiveness of the proposed method. It can be concluded from the analyzed results that the stator current unbalanced factor for the loaded SERG under switching off one excitation capacitor is much larger than the one under switching off one or two resistive loads. The voltage unbalanced factors for the loaded SERG under switching off one excitation capacitor or switching off one or two resistive loads are very similar. Moreover, the terminal voltage of a loaded SERG cannot be generated when two excitation capacitors are simultaneously switched off.