Impact Of Different Frequencies Research Articles

Effects of vehicle vibration on driver alertness: a pilot study

Road accidents resulting from the loss of driving alertness cause significant social and economic damage. In recent years, studies have revealed that whole-body vibration affects driver drowsiness directly. However, the impact of different frequency ranges of vibration on driver alertness has not been extensively explored. This driving simulator study aimed to investigate the impact of low frequency (1-4 Hz) and high frequency (16-32 Hz) whole-body vibration on a driver's reaction time during a monotonous highway driving task. Nine participants completed the task for one hour, with reaction tasks presented every 8-12 seconds. After 25 minutes of exposure to whole-body vibration, participants exhibited significantly longer reaction times for both low and high frequency ranges when compared to the control condition. The low frequency range had a stronger effect on driver vigilance, with reaction times increasing by as much as 135 ms within 35 minutes. Subjective evaluations using the Karolinska Sleepiness Scale (KSS) were consistent with the reaction time results. Overall, this study confirms that both low and high frequency vibration can reduce driver alertness, with the effect of low frequency vibration being more pronounced. Further research is suggested with larger sample sizes and wider frequency ranges.

Impact of different frequencies of controlled breath and pressure-support levels during biphasic positive airway pressure ventilation on the lung and diaphragm in experimental mild acute respiratory distress syndrome.

We hypothesized that a decrease in frequency of controlled breaths during biphasic positive airway pressure (BIVENT), associated with an increase in spontaneous breaths, whether pressure support (PSV)-assisted or not, would mitigate lung and diaphragm damage in mild experimental acute respiratory distress syndrome (ARDS). Wistar rats received Escherichia coli lipopolysaccharide intratracheally. After 24 hours, animals were randomly assigned to: 1) BIVENT-100+PSV0%: airway pressure (Phigh) adjusted to VT = 6 mL/kg and frequency of controlled breaths (f) = 100 bpm; 2) BIVENT-50+PSV0%: Phigh adjusted to VT = 6 mL/kg and f = 50 bpm; 3) BIVENT-50+PSV50% (PSV set to half the Phigh reference value, i.e., PSV50%); or 4) BIVENT-50+PSV100% (PSV equal to Phigh reference value, i.e., PSV100%). Positive end-expiratory pressure (Plow) was equal to 5 cmH2O. Nonventilated animals were used for lung and diaphragm histology and molecular biology analysis. BIVENT-50+PSV0%, compared to BIVENT-100+PSV0%, reduced the diffuse alveolar damage (DAD) score, the expression of amphiregulin (marker of alveolar stretch) and muscle atrophy F-box (marker of diaphragm atrophy). In BIVENT-50 groups, the increase in PSV (BIVENT-50+PSV50% versus BIVENT-50+PSV100%) yielded better lung mechanics and less alveolar collapse, interstitial edema, cumulative DAD score, as well as gene expressions associated with lung inflammation, epithelial and endothelial cell damage in lung tissue, and muscle ring finger protein 1 (marker of muscle proteolysis) in diaphragm. Transpulmonary peak pressure (Ppeak,L) and pressure-time product per minute (PTPmin) at Phigh were associated with lung damage, while increased spontaneous breathing at Plow did not promote lung injury. In the ARDS model used herein, during BIVENT, the level of PSV and the phase of the respiratory cycle in which the inspiratory effort occurs affected lung and diaphragm damage. Partitioning of inspiratory effort and transpulmonary pressure in spontaneous breaths at Plow and Phigh is required to minimize VILI.

Assessment of Changes in Laryngeal Configuration and Voice Parameters Among Different Frequencies of Neuromuscular Electrical Stimulation (NMES) and Cumulative Effects of NMES in a Normophonic Subject: A Pilot Study

Neuromuscular electrical stimulation (NMES) is a complementary resource to voice therapy that can be used for the treatment of hypofunctional voice disorders. Although positive clinical studies have been reported, neutral and even potentially harmful effects of NMES are also described in the literature. Furthermore, in the studies examined by the authors, the use of different methods of NMES have been identified, which further contributes to the inconsistent results found among studies. Moreover, limited rationale is provided for the chosen NMES parameters such as electrode placement, frequency of NMES and length of treatment. The aims of this pilot study were to investigate the a) impact of different frequencies of NMES on glottal configuration and vocal fold vibration patterns and b) changes in laryngeal configuration and vocal output across 12 minutes of NMES. Three experiments were carried out looking at changes in laryngeal configuration and voice output using different imaging techniques (fibreoptic nasolaryngoscopy and high-speed video), acoustical analysis (F0, formant analysis, SPL, CPPS and LHSR values), electroglottography (EGG) and Relative Fundamental Frequency (RFF) analyses. Glottal parameters and acoustical measures were recorded before, during, and after stimulation. Data was collected at rest and during phonation. Overall the results showed global changes in laryngeal configuration from normal to hyperfunctional (ie, increased RFF, SPL, CQ, and stiffness). Changes were more pronounced for lower frequencies of NMES and were significant within less than three minutes of application. NMES is an effective resource for the activation of intrinsic laryngeal muscles producing significant levels of adduction within few minutes of application. Lower NMES frequencies produced greater muscle activation when compared to higher frequencies.

Velocity Performance Feedback During Ballistic Training: Which Is the Optimal Frequency of Feedback Administration?

This study explored the impact of different frequencies of knowledge of results (KR) on velocity performance during ballistic training. Fifteen males completed four identical sessions (three sets of six repetitions at 30% one-repetition maximum during the countermovement jump and bench press throw) with the only difference of the KR condition provided: no feedback, velocity feedback after the first half of repetitions of each set (HalfKR), velocity feedback immediately after each repetition (ImKR), and feedback of the average velocity of each set (AvgKR). When compared with the control condition, the ImKR reported the highest velocity performance (1.9-5.3%), followed by the HalfKR (1.3-3.6%) and AvgKR (0.7-4.3%). These results support the verbal provision of velocity performance feedback after every repetition to induce acute improvements in velocity performance.

Sensitivity Analysis of the Impact of the Sub- Hourly Stochastic Unit Commitment on Power System Dynamics

Subhourly modeling of power systems and the use of the stochastic optimization are two relevant solutions proposed in the literature to address the integration of stochastic renewable energy sources. With this aim, this paper deals with the effect of different formulations of the subhourly stochastic unit commitment (SUC) problem on power system dynamics. Different SUC models are presented and embedded into time domain simulations (TDS) through a cosimulation platform. The objective of the paper is to study the combined impact of different frequency control/machine parameters and different SUC formulations on the long-term dynamic behaviour of power systems. The analysis is based on extensive Monte Carlo TDS (MC-TDS) and a variety of scenarios based on the New England 39-bus system.

Do Fire Regime Attributes Affect Soil Biochemical Properties in the Same Way under Different Environmental Conditions?

Global change is altering fire frequency and severity in many regions across the world. In this work, we studied the impact of different frequency and severity regimes on the soil biochemical properties in burned areas with different environmental conditions. We selected three sites dominated by pine ecosystems along a Mediterranean-Transition-Oceanic climatic gradient, where we determined the fire frequency, and severity of the last wildfire. Four years after the last wildfire, we established 184 4 m2 plots. In each plot, we collected a composed soil sample from a 3 cm depth, and measured several ecological variables potentially affected by the fire frequency and severity (cover of bare soil, cover of fine and coarse plant debris, cover of vegetation, and vegetation height). From each soil sample, we analyzed the enzymatic activities corresponding to the biogeochemical cycles of carbon, nitrogen, and phosphorus (β-glucosidase, urease, and acid-phosphatase, respectively), and the microbial biomass carbon. The results indicated that fire frequency only played a significant role in soil biochemical properties at the Mediterranean and Transition sites. Specifically, we found that increases in frequency contributed to increased urease and phosphatase activities (at the Transition site), as well as microbial biomass carbon (at the Mediterranean and Transition sites). In relation to burn severity, we found opposite patterns when comparing the Mediterranean and Oceanic sites. Specifically, increased severity significantly decreased β-glucosidase, urease, and microbial biomass carbon at the Mediterranean site, whereas at the Oceanic one, severity significantly increased them. Burn severity also decreased microbial biomass carbon at the Transition site. Our results also indicated that, overall, fire frequency determined the studied ecological variables at the Mediterranean and Transition sites, but clear indirect effects on biochemical properties due to changes in ecological variables were not found. This study adds to the knowledge on the impact of shifts in fire regimes on soils in the current context of change.

A Phantom Investigation to Quantify Huygens Principle Based Microwave Imaging for Bone Lesion Detection

This paper demonstrates the outcomes of a feasibility study of a microwave imaging procedure based on the Huygens principle for bone lesion detection. This study has been performed using a dedicated phantom and validated through measurements in the frequency range of 1–3 GHz using one receiving and one transmitting antenna in free space. Specifically, a multilayered bone phantom, which is comprised of cortical bone and bone marrow layers, was fabricated. The identification of the lesion’s presence in different bone layers was performed on images that were derived after processing through Huygens’ principle, the S21 signals measured inside an anechoic chamber in multi-bistatic fashion. The quantification of the obtained images was carried out by introducing parameters such as the resolution and signal-to-clutter ratio (SCR). The impact of different frequencies and bandwidths (in the 1–3 GHz range) in lesion detection was investigated. The findings showed that the frequency range of 1.5–2.5 GHz offered the best resolution (1.1 cm) and SCR (2.22 on a linear scale). Subtraction between S21 obtained using two slightly displaced transmitting positions was employed to remove the artefacts; the best artefact removal was obtained when the spatial displacement was approximately of the same magnitude as the dimension of the lesion.

Evaluating the impact of self-monitoring of blood glucose frequencies on glucose control in patients with type 2 diabetes who do not use insulin: A systematic review and meta-analysis.

International diabetes guidelines have not established the frequencies of self-monitoring of blood glucose in patients with type 2 diabetes (T2D) who do not use insulin. The present study aimed to assess the impact of self-monitoring of blood glucose (SMBG) frequencies on the glucose control and other outcomes in non-insulin-treated patients with T2D. A literature search was performed in four databases. Randomised controlled trials with ≥6-month follow-up duration that compared the impact of different frequencies of SMBG on glycated haemoglobin A1c (HbA1c) were included. Studies with abstract only or reported effects of SMBG as a secondary outcome were excluded. Of the 1557 studies identified, 12 RCTs with a total of 3350 patients were analysed. Overall, performing SMBG for 8 to 14 times per week was correlated with a better HbA1c control at 6months (MD -0.46%, 95% CI -0.54 to -0.39) and 12months (MD -0.20%, 95% CI -0.29 to -0.11). However, up to seven measurements of SMBG per week did not significantly affect glycaemic control. In addition, performing SMBG between 8 and 14 times per week was also associated with improved BMI (MD -0.46, 95% CI -0.84 to -0.08). When the results of SMBG were applied to adjust diabetes medication, a significant reduction in HbA1c levels was observed in the intervention arm compared to the control arm. Eight to 14 measurements of SMBG per week were associated with an improved glycaemic control and a reduced BMI in patients with T2D not using insulin.

Timing of Landlocked Fall Chinook Salmon Spawning and Egg Survival

Landlocked fall Chinook salmon (Oncorhynchus tshawytscha) in Lake Oahe, South Dakota, USA return to a remote spawning station either already having ovulated (ripe) or with the eggs still retained in the ovary (green).

Impact of Abrostola asclepiadis combined with other stressors on invasive swallow-worts (Vincetoxicum species)

The moth Abrostola asclepiadis (Lepidoptera: Noctuidae) is being investigated for biological control of pale and black swallow-wort (Vincetoxicum rossicum and V. nigrum, respectively; Apocynaceae), European vines introduced into North America. Limited information existed on its potential impact on swallow-worts, and the combination of defoliation damage by A. asclepiadis and other stresses to the plants had not been studied. We conducted greenhouse studies of the impact of different frequencies (once or twice) and degrees of defoliation (50 or 100%-seedlings; one or two larvae per stem-mature plants) by larvae on seedlings and mature (flowering) plants of black and pale swallow-wort. Defoliation was combined with varying light levels (shaded or not) or competition with quackgrass (Elymus repens). Significant reductions in aboveground dry mass and seeds generally only occurred when plants were completely defoliated twice. Grass competition and, to a greater extent, shading reduced growth and reproduction of swallow-wort plants. However, no interactions between defoliation and the other stressors occurred, suggesting they would have an additive effect. Because A. asclepiadis is likely to be univoltine if released in North America, its impact appears to be limited even if severe defoliation is achieved. Therefore, A. asclepiadis should be given a lower priority for release.

A method for compensating platform attitude fluctuation for helicopter-borne LiDAR: Performance and effectiveness

Attitude fluctuation of helicopter-borne platform is an important factor influencing the quality of point cloud products from airborne LiDAR, especially the roll and pitch parts. Therefore, we proposed a method to compensate the attitude fluctuation for helicopter-borne laser scanning; an attitude compensation prototype was designed, to eliminate the impact of both the roll and pitch fluctuations on point cloud products. The mechanical structure and control system of the prototype were designed. In order to test the dynamic compensation effectiveness of the prototype for airborne LiDAR, we established a semi-physical simulation system. In the experiment setup, the prototype, a laser rangefinder as well as a position and orientation system (POS) were all mounted on the platform of a three-axis turntable. The inner and middle shafts of the three-axis turntable rotated with sinusoidal movements to simulate the roll and pitch fluctuations of helicopter-borne platform. The x-axis and y-axis frameworks of the prototype were controlled to rotate inversely halves of the measured rotation angles of the simulated attitude fluctuations by the POS. Hence, the emitting orientations of the pulsed laser beams reflected by the scanning mirror embedded in the prototype would not be affected by the dynamic changing of the roll and pitch fluctuations. Total 11 groups of experiments were carried out to verify the control performance and dynamic compensation effectiveness of the compensation prototype under 11 sets of sinusoidal attitude fluctuations with different frequencies and amplitudes. Experimental results show that, under the impact of different frequencies and amplitudes sinusoidal attitude fluctuations, the attitude compensation prototype can always significantly decrease the unfavorable influence of the attitude fluctuations and have good dynamic compensation effectiveness.

Calculation of Noise Barrier Insertion Loss Based on Varied Vehicle Frequencies

A single frequency of 500 Hz is used as the equivalent frequency for traffic noise to calculate the approximate diffraction in current road barrier designs. However, the noise frequency changes according to the different types of vehicles moving at various speeds. The primary objective of this study is the development of a method of calculating the insertion loss based on frequencies. First, the noise emissions of a large number of vehicles classified by speed and type were measured to obtain data the noise spectrum. The corresponding relation between vehicle type, speed, and noise frequency was obtained. Next, the impact of different frequencies on the insertion loss was analyzed and was verified to be reasonable in experiments with different propagation distances compared to the analysis of a pure 500 Hz sound. In addition, calculations were applied in a case with different traffic flows, and the effect of a road noise barrier with different types of constituents and flow speeds were analyzed. The results show that sound pressure levels behind a barrier of a heavy vehicle flow or with a high speed are notably elevated.

Impact of different frequencies in the entrapment of bacterial pathogens from drinking water using dielectrophoretic phenomena

The article has investigated the removal of water borne pathogens using dielectrophoresis (DEP) filter which is energized by varying the frequency of the applied potential from 10 kHz to 2 MHz with different voltage levels of 5; 10; 15 and 20 V. Separate experiments are conducted in artificially contaminated water samples with Escherichia coli, Staphylococcus aureus and Vibrio cholerae up to 2 h. The impact of signal frequency and voltages on DEP based water treatment system has been analyzed statistically. Results have demonstrated that an AC signal of 20 V with frequency range of 500 kHz to 2 MHz is suitable to remove the tested bacterial population and the rate of removal of E. coli is the highest with a dielectrophoretic filtration efficiency of 77.1%.

Repetitive transcranial magnetic stimulation in the treatment of obsessive-compulsive disorders: Double blind randomized clinical trial

Repetitive transcranial magnetic stimulation (rTMS) has become widely used as a therapeutic tool in psychiatric research. The aim of this study was to evaluate the impact of different frequencies of rTMS over right dorsolateral prefrontal cortex (DLPFC) in OCD. Forty five patients with OCD participated in the study. Patients were evaluated using: Yale-Brown obsessive compulsive scale (Y-BOCS), Hamilton Anxiety Rating Scale (HAM-A), and Clinical Global Impression-Severity scale (CGI-S). They were randomly classified into three groups: 1st group received 1Hz rTMS; 2nd group received 10Hz rTMS; and 3rd group received sham stimulation all at 100% of the resting motor threshold for 10 sessions. They were followed up after the last treatment session and 3 months later. There was a significant “time”דgroup” interaction for 1Hz versus Sham but not for 10Hz versus Sham. 1Hz versus 10Hz groups showed a significant interaction for Y-BOCS and HAM-A (P=0.001 and 0.0001 respectively). 1Hz rTMS has a greater clinical benefit than 10Hz or Sham. There was also a significantly larger percentage change in GCI-S in the 1Hz group versus either 10Hz or sham. We conclude that 1Hz-rTMS, targeting right DLPFC is a promising tool for treatment of OCD.

The long-term effects of fire regime on primary production of montane grasslands in South Africa

Natural grasslands deliver essential ecosystem services through plant production, which enhances water supply, nutrient cycling, soil retention and greenhouse gas mitigation. Although the condition of montane grasslands for provision of ecosystem services is maintained by regular annual or biennial burning, controversy exists over the impact of different frequencies and seasons of burning on grassland productivity. The objective of this study was to determine the long-term effects of different burning regimes on primary production and quality of the montane grasslands of the KwaZulu-Natal Drakensberg. There were no significant differences in the mean standing live mass between 30 years of annual winter and biennial spring burning. However, in unburnt areas productivity was 20% lower (118.2 g m−2) than in regularly burnt grassland (144.7–154.5 g m−2). Crude protein did not vary between the annual winter and biennial spring treatments (95–113 kg ha−1), but was significantly lower in unburned areas (45 kg ha−1). However, an infrequent fire in a protected area caused a temporary spike in crude protein (16%) compared with regular burning (5–10%), which can benefit wildlife. We conclude that montane grasslands can be burnt annually or biennially in the dormant season to promote long-term productivity.

Occasional tillage has no effect on soil microbial biomass, activity and composition in Vertisols under long-term no-till

Heavy rains in recent years have triggered an increase in herbicide-resistant weeds and crop diseases in long-term no-till (NT) farming systems in Queensland, Australia. As a possible solution, occasional or strategic tillage (ST) has been applied during summer fallow in two farms located near Jimbour and Biloela, Queensland, Australia. We investigated the impact of different frequencies (one to three passes) and timings (December, January and March) of tillage imposition on microbial indicators of soil health. Tillage implements included chisel plow sweeps at the Biloela site and narrow chisel point and offset disc at the Jimbour site. Seven soil samples were collected from each plot in April 2013 at 17, 10 and 2 weeks post-ST from 0 to 0.1 and 0.1 to 0.2 m depths and composited separately for each soil depth. Samples were analysed for microbial biomass C, enzyme activity, community-level physiological profiling (CLPP) via microrespirometry method and bacterial genetic fingerprinting. Overall, there were no significant differences for any of these parameters between NT and ST at both sites. However, irrespective of tillage treatments, significant differences between soil depths were found for enzyme activity (Biloela), substrate utilisation (Jimbour and Biloela) and bacterial genetic fingerprinting (Jimbour). There were no major effects of ST on the microbial indicators used either under different timings, frequencies or type of tillage implement. Therefore, ST with chisel plow sweeps, narrow chisel point and offset disc may be undertaken with minimal impact on soil microbial communities to combat problems associated with long-term NT Vertisols, such as weed and soil-borne disease outbreak in Queensland, Australia.

Evaluating the Utility of Drug Testing in an Outpatient Addiction Program

Objectives This study evaluated the impact of different frequencies of urine drug screening in an outpatient treatment program in terms of reducing the use of drugs or alcohol, supporting the patient's treatment goals, deterring the use of drugs or alcohol, and gathering more reliable information than self-reports. Methods This study involved 229 patients who were in treatment at the Calgary Health Region's Addiction Centre. Patients' weekly self-reports of drug/alcohol use were compared with their urine screens. Half the participants had all their urines tested, whereas the other half only had half their urine samples tested on a random biweekly schedule. All participants provided their opinions on the importance of drug testing compared with other possible motivating factors in assisting them in their recovery process. Results Adults were more likely to believe that urine testing is an important factor in their treatment than adolescents. Adolescents reported a lower likelihood to honestly report use during their treatment and were less likely to have any intrinsic motivation to stop using drugs or alcohol. Reducing the number of drug screens tested from weekly to a random biweekly schedule did not impact the deterrence value of the screens and had no impact on the amount of use during treatment. More frequent testing modestly increased the detection of unreported drug use in the patients. Conclusions Urine drug screens may play an especially important role in the treatment of adolescents. Clinical programs can balance cost effectiveness with clinical benefits to treatment by collecting frequent (eg, weekly) urine drug screens, but only testing a randomly selected half.

Bi‐level Programming Formulation and Heuristic Solution Approach for Dynamic Traffic Signal Optimization

Abstract: Although dynamic traffic control and traffic assignment are intimately connected in the framework of Intelligent Transportation Systems (ITS), they have been developed independent of one another by most existing research. Conventional methods of signal timing optimization assume given traffic flow pattern, whereas traffic assignment is performed with the assumption of fixed signal timing. This study develops a bi‐level programming formulation and heuristic solution approach (HSA) for dynamic traffic signal optimization in networks with time‐dependent demand and stochastic route choice. In the bi‐level programming model, the upper level problem represents the decision‐making behavior (signal control) of the system manager, while the user travel behavior is represented at the lower level. The HSA consists of a Genetic Algorithm (GA) and a Cell Transmission Simulation (CTS) based Incremental Logit Assignment (ILA) procedure. GA is used to seek the upper level signal control variables. ILA is developed to find user optimal flow pattern at the lower level, and CTS is implemented to propagate traffic and collect real‐time traffic information. The performance of the HSA is investigated in numerical applications in a sample network. These applications compare the efficiency and quality of the global optima achieved by Elitist GA and Micro GA. Furthermore, the impact of different frequencies of updating information and different population sizes of GA on system performance is analyzed.

Defect accumulation in fcc and bcc metals and alloys under cascade damage conditions – Towards a generalisation of the production bias model

In recent years, it has been shown that the problem of defect accumulation under cascade damage conditions can be properly addressed within the framework of production bias model (PBM) based on intracascade clustering of point defects, differences in the thermal stability of the resulting clusters and one-dimensional (1-D) diffusion of interstitial clusters. Within this framework, different aspects of defect accumulation such as the high swelling rate at low dislocation densities, enhanced swelling near grain boundaries, effects of grain size, irradiation dose and recoil energy on void swelling have been treated quantitatively. In the present work we have attempted to address the problem of differences in the defect accumulation behaviour between fcc and bcc metals under cascade damage conditions. In this analysis we have chosen copper and molybdenum to represent fcc and bcc metals, respectively. This choice was suggested by the fact (a) that a large amount of experimental information exists on these metals and (b) that the damage accumulation behaviour in copper can be fully accounted for in terms of the PBM. An analysis of the existing experimental observations in terms of the PBM raises the question about differences between the reaction kinetics of the one-dimensionally diffusing interstitial clusters with sinks in fcc and bcc metals. In the present paper, the impact of different frequencies of changes in the 1-D diffusion direction of such clusters on their reaction kinetics is discussed. The present considerations provide an appropriate framework for generalising the PBM in order to describe damage accumulation behaviour in metals and alloys in general, including the formation of void superlattices.