Powerful Modulatory Effects Research Articles

Investigating the effect of laser power modulation in transient states during fusion cutting of 10 mm thick AISI304

In fusion laser cutting of intricate geometries, the processing speed often varies significantly from its nominal value due to inherent machine dynamics. These variations can lead to excessive energetic input and drifts from the reference cut quality. To address defect formation during transient conditions, a conventional approach involves power reduction to compensate for speed variations. This help prevent thermal imbalances and material overheating issues, ultimately preserving the final cut’s quality. An alternative solution is based on pulsed wave emission, providing dynamic and precise control over the thermal energy delivered to the workpiece. In this work, pulsed wave emission was employed to ensure process stability during transient conditions for fusion cutting of 10mm AISI304. A 6kW fiber laser was utilized alongside a coaxial camera-based monitoring setup to observe the melt dynamics. Results demonstrate that power modulation effectively reduces defect formation, and process emission images can be exploited to identify successful cuts.

Effects of Laser Power Modulation on Weld Penetration and Pore of AZ31 Magnesium Alloy

Effects of Laser Power Modulation on Weld Penetration and Pore of AZ31 Magnesium Alloy

Effects of laser power modulation on keyhole behavior and energy absorptivity for laser welding of magnesium alloy AZ31

Effects of laser power modulation on keyhole behavior and energy absorptivity for laser welding of magnesium alloy AZ31

Investigations on the Specifics of Laser Power Modulation in Laser Beam Welding of Round Bars

Welding round bars of large diameters in a rotational laser beam welding process corresponds with weld pool bulging and the risk of weld defects. Power modulation is a promising approach for bulge reduction and for keyhole stabilisation to achieve superior weld quality. The following investigations are about the specific effects of power modulation for round bars with a diameter of 30 mm. The welding speed is 0.95 m/min and argon is used as shielding and process gas. Triangle shaped power modulation at 8 kW average laser beam power, 0/2/4/6 kW amplitude power and 2/10/50 Hz modulation frequency is used for the round bar welding of a 1.4301 steel alloy. The welds are evaluated by visual inspection, metallographic cross sections and scanning acoustic microscopy. The amount of weld defects increases at medium and high power modulation, but weld pool bulging is already reduced at low power modulation. Weld pool bulging can be impeded by a low normalised power modulation frequency of 0.05 and a high modulation depth of 0.86. The power modulation’s advantages of weld mixing and degassing do not apply to rotational round bar welding because of the linear welding speed’s gradient from the specimen surface to the centre.

Reduction of Allergic Lung Disease by Mucosal Application of Toxoplasma gondii-Derived Molecules: Possible Role of Carbohydrates.

BackgroundThe hygiene hypothesis suggests a link between parasitic infections and immune disorders, such as allergic diseases. We previously showed that infection with Toxoplasma gondii or systemic application of T. gondii tachyzoites lysate antigen (TLA) in a prophylactic, but not therapeutic protocol, prevented allergic airway inflammation in mice. Here we tested the effect of prophylactic and therapeutic application of TLA via the mucosal route.MethodsMice were intranasally treated with TLA either i) prior to sensitization, ii) during sensitization and challenge, or iii) after sensitization with ovalbumin (OVA). Recruitment of inflammatory cells to the lung, cytokine levels in restimulated lung and spleen cell cultures as well as levels of OVA-specific antibodies in serum were measured. In parallel, the effect of native TLA, heat-inactivated (hiTLA) or deglycosylated TLA (dgTLA) on sensitized splenocytes was evaluated ex vivo.ResultsWhen applied together with OVA i) during systemic sensitization and local challenge or ii) exclusively during local challenge, TLA reduced infiltration of eosinophils into the lung, OVA-specific type 2 cytokines in restimulated lung cell cultures, and partially, type 2 cytokines in restimulated spleen cell cultures in comparison to allergic controls. No beneficial effect was observed when TLA was applied prior to the start of sensitization. Analysis of epitope sugars on TLA indicated a high abundance of mannose, fucose, N-acetylglucosamine, and N-acetylgalactosamine. Deglycosylation of TLA, but not heat-inactivation, abolished the potential of TLA to reduce type 2 responses ex vivo, suggesting a significant role of carbohydrates in immunomodulation.ConclusionWe showed that mucosal application of TLA reduced the development of experimental allergy in mice. The beneficial effects depended on the timing of the application in relation to the time point of sensitization. Not only co-application, but also therapy in sensitized/allergic animals with native TLA reduced local allergic responses. Furthermore, we show that TLA is highly glycosylated and glycoconjugates seem to play a role in anti-allergic effects. In summary, given the powerful modulatory effect that TLA exhibits, understanding its exact mechanisms of action may lead to the development of novel immunomodulators in clinical application.

Taenia larvae possess distinct acetylcholinesterase profiles with implications for host cholinergic signalling.

Larvae of the cestodes Taenia solium and Taenia crassiceps infect the central nervous system of humans. Taenia solium larvae in the brain cause neurocysticercosis, the leading cause of adult-acquired epilepsy worldwide. Relatively little is understood about how cestode-derived products modulate host neural and immune signalling. Acetylcholinesterases, a class of enzyme that breaks down acetylcholine, are produced by a host of parasitic worms to aid their survival in the host. Acetylcholine is an important signalling molecule in both the human nervous and immune systems, with powerful modulatory effects on the excitability of cortical networks. Therefore, it is important to establish whether cestode derived acetylcholinesterases may alter host neuronal cholinergic signalling. Here we make use of multiple techniques to profile acetylcholinesterase activity in different extracts of both Taenia crassiceps and Taenia solium larvae. We find that the larvae of both species contain substantial acetylcholinesterase activity. However, acetylcholinesterase activity is lower in Taenia solium as compared to Taenia crassiceps larvae. Further, whilst we observed acetylcholinesterase activity in all fractions of Taenia crassiceps larvae, including on the membrane surface and in the excreted/secreted extracts, we could not identify acetylcholinesterases on the membrane surface or in the excreted/secreted extracts of Taenia solium larvae. Bioinformatic analysis revealed conservation of the functional protein domains in the Taenia solium acetylcholinesterases, when compared to the homologous human sequence. Finally, using whole-cell patch clamp recordings in rat hippocampal brain slice cultures, we demonstrate that Taenia larval derived acetylcholinesterases can break down acetylcholine at a concentration which induces changes in neuronal signalling. Together, these findings highlight the possibility that Taenia larval acetylcholinesterases can interfere with cholinergic signalling in the host, potentially contributing to pathogenesis in neurocysticercosis.

Protective effect of methylene blue against copper oxide nanoparticle-induced neurobehavioral toxicity

Increasing attention has been paid in the past decade to assessing the toxicological effects of nanoparticles and finding a protectant; thus, the current study aimed to investigate the protective effect of the mitochondria-targeting drug methylene blue (MB) against copper oxide nanoparticle (CuO-NP)-induced neurobehavioral toxicity in rats. For this purpose, twenty rats were allocated to four equal groups (n = 5). The negative control group received distilled water intraperitoneally (IP) and Tween 80 (10 %) orally. The CuO-NP group was given a dose of 100 mg/kg of CuO-NPs, administered orally, and the positive control group was treated with 1 mg/kg MB intraperitoneally (IP). The final group was concurrently exposed to CuO-NPs and MB for 14 consecutive days. At the end of the study, each group was neurobehaviorally blind tested relative to other experimental animals, then brain tissue markers were determined and a histopathological examination was conducted. The results showed that supplementation with CuO-NPs induced neurobehavioral alterations; increased Cu content in the brain; and enhanced lipid peroxidation (malondialdehyde [MDA]), protein peroxidation (protein carbonyl [PC]), and DNA oxidative damage (8-hydroxy-2-deoxyguanosine [8−OH-dG]) compared to other treatments. In addition, a decrease was noted in the mitochondrial dehydrogenases’ (aldehyde dehydrogenase 2 [ALDH2], and glutamate dehydrogenase [GDH]) activity in Cu-exposed rats. The histopathological findings revealed shrunken, pyknotic, and hypereosinophic cortical neurons and increased immune positive brown staining of caspase-3 protein, indicating apoptosis. Co-treatment with methylene blue ameliorated the neurotoxic effects of CuO-NPs; therefore, MB evidently had a powerful modulatory effect against the neurotoxicity of nano-Cu oxide via its antioxidant and mitochondrial protection properties.

Effects of power modulation on behaviours of molten pool and keyhole during laser–arc hybrid welding of pure copper

Modulated laser power hybrid welding (M-HW) of 4 mm-thick T2 pure copper was conducted to improve the welding stability. It was observed that the sinusoidal modulation of laser power in hybrid welding can reduce the incidence of weld defects such as spatters and pores, and decrease the transverse shrinkage of the weld seam. An observation of the evolution of the molten pool and keyhole using high-speed CCD photography reveals the main reason behind this to be the increase in the instantaneous maximum power because of power modulation, which increases the keyhole depth and frequency of formation of penetrated keyholes. The formation of a penetrated keyhole facilitates the escape of excess energy from the aperture at the bottom of the keyhole, thereby preventing the instability of the bottom of the keyhole caused by over concentration of energy thereat. This reduces the energy transfer within the surroundings of the molten pool, as well as the transverse shrinkage of the weld seam. The effects of the amplitude and the frequency of the sinuous waveforms of laser power on the frequency of formation of penetrated keyholes were analysed.

Influences of Antroquinonol and 4-Acetylantroquinonol B on Inflammatory Tumorigenesis in the MCF-7 Breast Cancer Cell Line (P06-039-19)

ObjectivesThe inflammatory microenvironment is currently received substantial attentions in the prevention and treatment of breast cancer (BC), the leading cause of cancer death, ∼15%, among women worldwide. The present study investigated the anti-inflammation and anti-cancer properties of 2 bioactive components from Antrodia Camphorata, a rare medicinal mushroom natively grown in Taiwan and commonly used in Chinese traditional medicine. MethodsIn the MCF BC cell lines with or without TNF-α stimulation, influences of Antroquinonol (AQ) and 4-Acetylantroguinonol B (4AAQB) on inflammatory mediators, aromatase, immune checkpoint and Wnt-signaling downstream genes were examined by quantitative real-time PCR. ResultsAmong 9 inflammatory mediators (IL6, IL10, IL1β, IFNγ, PTGS2, TGFβ1, TNF-α, CCL2 andCSF1) examined, AQ inhibited 2 of them (IL-10 and PTGS2), while 4-AAQB inhibited 3 of them (IL-10, PTGS2 and TNF-α) (p < 0.05). TNF-α stimulated IL6, IL10, IFNγ, PTGS2, and CCL2 whereas AQ and 4-AAQB only inhibited the IL-6 elevation (p < 0.05). Both components inhibited aromatase expression with/without TNF-α stimulation, with 4-AAQB to be more effective (p < 0.05). For the immune checkpoint CD47, both components inhibited CD47expression (p < 0.05), but it did not respond to TNF-α stimulation. For Wnt-signaling target genes (CCND1, C-MYC and AXIN2), both components have significant or marginal inhibitory functions on C-MYC in the condition with or without TNF-α stimulation. ConclusionsOverall, our results suggested that AQ and 4-AAQB possess the function to modulate the expression of factors related to inflammatory tumorigenesis in MCF-7 cells. Comparing these two compounds, 4-AAQB holds a more powerful modulatory effect on the expression of inflammatory mediators, aromatase as well as CD47, whereas AQ may be a more effective inhibitory compound for Wnt-signaling responses. Funding SourcesThis project was supported by USDA/Hatch (MAS00514) and industrial funds.

Mechanism study on the effects of power modulation on energy coupling efficiency in infrared laser welding of highly-reflective materials

High-reflectivity of materials, such as magnesium, copper and aluminum, results in low thermal efficiency of their infrared laser welding processes. AZ31 magnesium alloy was selected to study the effects of power modulation on energy coupling efficiency in laser welding of highly-reflective materials. A model for the relationship between energy coupling efficiency and modulation parameters was obtained. The energy coupling efficiency in optimized modulated-power laser welding was about 1.58 times that in constant-power welding. The mechanism was explored by analyzing keyhole evolution and the resulted pressure distribution along keyhole wall during welding. The keyhole evolutions in laser continuous welding of common material (Q345 steel, reflectivity of 65%) and highly-reflective material (AZ31, reflectivity of 85%) were observed through high-speed imaging by utilizing a half sandwich method. The results indicated that the secret of improving energy coupling efficiency of laser welding process of highly-reflective materials through power modulation was the formation of a deep keyhole and its long life. When instantaneous power decreased from the peak, there was still enough recoil pressure at the bottom of keyhole to resist surface tension and hydrostatic pressure of liquid metal, which was the fundamental reason for the long time existence of keyhole with a large depth.

Influence of spatial power modulation on pore and crack formation in laser beam welding of aluminum

The effect of spatial power modulation (SPM)—also known as wobble—for the welding of aluminum alloys has been investigated in laser beam microwelding. As the superposition of a high frequency circular oscillation movement and a global feed, two new parameters (A—amplitude and f—frequency) are added to the typical process parameters P—power and vw—welding feed rate. Microscopic and metallographic analyses have been used to determine crack appearance and position. With the choice of a sufficient ratio of A, f, and vw, the cooling behavior can be influenced. This also has an impact on the crack formation. Furthermore, the circular movement influences the local speed of the laser beam which in turn can affect the pore formation. The same effect appears on the depth stability as the keyhole formation strongly depends on the speed of the laser beam. The pore formation and weld depth stability have also been analyzed to determine the difference between conventional welding and welding with SPM.

Effects of Power Modulation, Multipass Remelting and Zr Addition Upon Porosity Defects in Laser Seal Welding of End Plug to Thin-Walled Molybdenum Alloy

Aiming to solve the serious porosity defects in laser welded girth joints of thin-walled tube and end plug made of nano-sized Ce2O3 doped Mo alloy (NC-Mo), the influences of laser power modulation, multipass remelting and zirconium (Zr) addition on the number, size and distribution of porosity defects were experimentally studied. By utilizing X-ray computed tomography (XCT), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, transmission electron microscope (TEM) and Raman spectrum (RS), the porosity feature of welded joints achieved under various conditions was analyzed. The results showed that welding cycles had a significant influence on the porosity ratio of fusion zone (FZ) while the amplitude and frequency of laser power waveform slightly influenced the porosity. When the welding cycles increased from 2 to 8, the porosity ratio of FZ decreased from about 1.00% to about 0.48% and the maximum and average pore diameters reduced by about 53% and 27%, respectively. Adding minor Zr in molten pool can further reduce the RP of FZ to about 0.35%. Through analysis, it can be seen that the pores in FZ can be divided into irregularly-shaped keyhole-induced pores and spherical metallurgy-induced pores. The latter was generated possibly because some impurity elements (including O and H) pre-existing in base metal (BM). Increasing welding cycles can promote the gas in molten pool to float and outflow, thus significantly decreasing the porosity. Moreover, Zr added in molten pool can be preferentially reacted with O to generate ZrO2, which can inhibit the precipitation of volatile MoO2 to thus suppress the generation of metallurgy-induced pores.

Fortuitous benefits of activity-based rehabilitation in stem cell-based therapy for spinal cord repair: enhancing graft survival.

Traumatic injuries to spinal cord elicit diverse signaling pathways leading to unselective and complex pathological outcomes: death of multiple classes of neural cells, formation of cystic cavities and glial scars, disruption of axonal connections, and demyelination of spared axons, all of which can contribute more or less to debilitating functional impairments found in patients with spinal cord injury. The multitude of pathobiological processes involved in spinal cord trauma may make it highly challenging to develop a clinically meaningful therapeutic approach targeting only a specific molecule or signaling pathway. A hopeful alternative might be a cell therapy, especially a transplantation approach using neural stem cells (NSC) with a clear potential to differentiate into various neural cell types. Provision of NSCs with capacity to differentiate into mature neural cells can ideally replace lost segmental neurons and dying oligodendrocytes around surviving axons. Furthermore, NSCs secrete various growth factors that provide protective or pro-regenerative effects. It has been also demonstrated that NSCs can exert powerful modulatory effects on immune cells ameliorating secondary degenerative processes.

Spontaneous Network Events Driven by Depolarizing GABA Action in Neonatal Hippocampal Slices are Not Attributable to Deficient Mitochondrial Energy Metabolism

In two recent papers (Rheims et al., 2009; Holmgren et al., 2010), Zilberter and coworkers argue that the well known depolarizing GABA actions that take place at the cellular and network level in the neonatal hippocampus and neocortex in vitro are pathophysiological phenomena, attributable to deficient mitochondrial energy metabolism. In their experiments, supplementing the glucose-containing solution with weak-acid substrates of mitochondrial energy metabolism (such as β-hydroxy-butyrate, lactate, or pyruvate) abolished the spontaneous network events (giant depolarizing potentials; GDPs) and the underlying depolarizing actions of GABA. In this study, we made electrophysiological recordings of GDPs and monitored the mitochondrial membrane potential (Ψm) and intracellular pH (pH(i)) in CA3 neurons in neonatal rat hippocampal slices. Supplementing the standard physiological solution with l-lactate did not produce a change in Ψm, whereas withdrawal of glucose, in the presence or absence of l-lactate, was followed by a pronounced depolarization of Ψm. Furthermore, d-lactate (a poor substrate of mitochondrial metabolism) caused a prompt inhibition in GDP frequency which was similar to the effect of l-lactate. The suppression of GDPs was strictly proportional to the fall in pH(i) caused by weak carboxylic acids (l-lactate, d-lactate, or propionate) or by an elevated CO(2). The main conclusions of our work are that the inhibitory effect of l-lactate on GDPs is not mediated by mitochondrial energy metabolism, and that glucose at its standard 10 mm concentration is an adequate energy substrate for neonatal neurons in vitro. Notably, changes in pH(i) appear to have a very powerful modulatory effect on GDPs.

Effect of power modulation on properties of pulsed capacitively coupled radiofrequency discharges

We describe measurements of plasma properties of pulsed, low pressure, capacitively coupled discharges operated in argon. The study aims to determine the effect of modulating the radiofrequency power during the discharge part of the pulse cycle. Measurements of local electron density and optical emission were made in capacitively coupled rf discharges generated in a Gaseous Electronics Conference (GEC) reference reactor. Gas pressure was in the range 7–70 Pa, rf power in the range 1–100 W and pulse durations in the range 10 µs–100 ms. The results indicate that the ignition and afterglow decay processes in pulsed discharges can be controlled by modulating the shape of applied radiofrequency pulse.

Energy-Efficient Resource Allocation in Wireless Networks

An overview of game-theoretic approaches to energy-efficient resource allocation in wireless networks is presented. Focusing on multiple-access networks, it is demonstrated that game theory can be used as an effective tool to study resource allocation in wireless networks with quality-of-service (QoS) constraints. A family of non-cooperative (distributed) games is presented in which each user seeks to choose a strategy that maximizes its own utility while satisfying its QoS requirements. The utility function considered here measures the number of reliable bits that are transmitted per joule of energy consumed and, hence, is particulary suitable for energy-constrained networks. The actions available to each user in trying to maximize its own utility are at least the choice of the transmit power and, depending on the situation, the user may also be able to choose its transmission rate, modulation, packet size, multiuser receiver, multi-antenna processing algorithm, or carrier allocation strategy. The best-response strategy and Nash equilibrium for each game is presented. Using this game-theoretic framework, the effects of power control, rate control, modulation, temporal and spatial signal processing, carrier allocation strategy and delay QoS constraints on energy efficiency and network capacity are quantified.

Luteal-Phase Accentuation of Acoustic Startle Response in Women with Premenstrual Dysphoric Disorder

Alterations in central nervous system response to menstrual cycle-related fluctuations in neuroactive steroids are thought to underlie the emergence of negative affect in the luteal phase of the menstrual cycle in women with premenstrual dysphoric disorder (PMDD). Such changes in the neuroendocrine milieu may lead to heightened arousal and response to stress in women with PMDD. Using the acoustic startle paradigm, we sought to determine whether women with PMDD have an accentuated physiologic response to a mildly aversive stimulus during the luteal compared to follicular phase. Further, we also examined the impact of visual affective stimuli on acoustic startle response (ASR) magnitude. During the follicular and luteal phases of the menstrual cycle, acoustic stimuli (103 dB) were delivered to 15 women with PMDD and 14 healthy menstruating women of similar age. After obtaining baseline ASR, the procedure was repeated when subjects viewed pleasant, neutral and unpleasant pictures. There was a significant group by menstrual cycle phase interaction for baseline ASR magnitude, which can be attributed to the heightened startle magnitude in women with PMDD compared to healthy women during the luteal relative to the follicular phase. The direction and degree to which picture viewing modulated the startle magnitude did not vary by group or menstrual cycle phase. These data suggest that menstrual cycle phase has a powerful modulatory effect on physiologic reactivity in women with PMDD but not in healthy women. Physiologic response to affective stimuli appears to be intact in women with PMDD across the menstrual cycle.

Control of chaos in laser-induced vapor capillaries

Vapor capillaries associated with deep penetration laser welding (keyholes) are inherently unstable and it is well known that the bounded evolution of unstable modes of nonlinear dynamic systems can lead to complex fluctuations of state and/or output variables. In the case of keyholes, the magnitude of self-induced fluctuations is sometimes large enough to cause occasional closure (“collapse”) and trapping of voids in the solidifying weld metal. Since voids are serious and frequent defects in partial penetration laser welds, methods to improve the stability of the keyhole, and thereby reduce or eliminate their incidence are of considerable practical interest. One technique that is known to simplify the complicated behavior of chaotic systems involves the application of periodic perturbations to accessible system inputs or boundaries. Consequently, this work investigated the effect of power modulation on porosity formation in laser welds. Frozen glycerin was used as the medium for welding since its transparency allowed visualization of the keyhole, facilitating control parameter development. Statistical and spectral analysis of penetration depth signals for the uncontrolled system was performed to characterize the nonlinear keyhole dynamics. In the control studies, it was found that the optimum frequency of power modulation at 400 Hz was very effective for reducing porosity. A 15° leading beam incidence angle was found to provide further improvements. Three-dimensional phase portraits of the keyhole depth for uncontrolled and controlled signals showed that the control did not convert depth fluctuations to a completely predictable limit cycle but that the remaining fluctuations were more predictable than those of the uncontrolled system.

PH-induced changes in calcium: functional consequences and mechanisms of action in guinea pig portal vein.

The effects of changing extracellular (pH(o)) and intracellular pH (pH(i)) on force and the mechanisms involved in the guinea pig portal vein were investigated to better understand the control of tone in this vessel. When pH(o) was altered, the effects on force and calcium were the same irrespective of whether force had been produced spontaneously by high-K depolarization or by norepinephrine; alkalinization increased tone, and acidification reduced it. Because pH(o) changes also lead to changes in pH(i), we determined whether the effects on force could be explained by these induced pH(i) changes. It was found, however, that only with spontaneous activity did intracellular alkalinization increase force. In depolarized preparations, force was decreased, and, with norepinephrine, force was initially decreased and then increased. Thus the effects of pH(o) cannot be explained solely by changes in pH(i). The role of the sarcoplasmic reticulum (SR) and surface membrane Ca(2+)-ATPase on the mechanism were investigated and shown not to be involved. Therefore, it is concluded that both pH(o) and pH(i) can have powerful modulatory effects on portal vein tone, that these effects are not identical, and that they are likely to be due to effects of pH on ion channels rather than the SR or plasma membrane Ca(2+)-ATPase.

Combined effect of nitrogen and pulsed microwave plasma on diamond growth using CH 4–CO 2 gas mixture

Deposition of diamond layers in a CH 4–CO 2 microwave discharge operating in pulsed mode was achieved. The effects of nitrogen addition and microwave power modulation on the plasma reactivity were studied by time resolved optical emission spectroscopy. An enhancement of the molecular dissociation during the early stage of the pulse has been observed. The resulting diamond layers showed less graphite contamination as compared with that obtained in continuous discharge. Furthermore, the addition of nitrogen to the discharge operating in this pulsed mode further decreases the graphite contamination and improves crystallization due to reduction of secondary germination.