Estimating of radiation output of X-RAY tube using mathematical model: Case of high-frequency machines

PURPOSE

During any radiological procedure, it is important to know the dose to be-administered to the patient and this can be done by estimating the output of the X-ray tube either with a dosimeter or with a mathematical equation or Monte Carlo simulations. The aim of this work is to develop a new mathematical model equation (NMME) for estimating the output of high-frequency X-ray tubes.

METHODS

To achieve this, data collected from ten machines in many regions of Cameroon were used (for nine machines) to build an initial model that does not take into account the anode angle and the tenth machine was used to test the model. Using the SpekCalc software, some simulations were carried out to evaluate the influence of the anode angle. This allowed the NMME to be proposed.

RESULTS

The deviations frequencies between 0.65% and 19.61% were obtained by comparing the output values obtained using initial model with the measured values. The statistical hypothesis test showed that the estimated values using initial model and NMME are in agreement with those measured unlike the Kothan and Tungjai model. For the tenth machine, the percentage difference between estimated and measured values is less than 8 %.

CONCLUSION

These results show that the proposed model performed better than the previous models. In the absence of a dosimeter, the NMME could be used to estimate the output of high frequency X-ray machines and therefore the radiation doses received by patients during diagnostic X-ray examinations.

Reduced Reward Processing in Schizophrenia: A Comprehensive EEG Event-Related Oscillation Study

It is well known that abnormal reward processing is a characteristic feature of various psychopathologies including schizophrenia (SZ). Reduced reward anticipation has been suggested as a core symptom of SZ. The present study aims to evaluate the event-related oscillations (EROs) delta, theta, alpha, beta, and gamma in patients with SZ during the Monetary Incentive Delay (MID) task, which elicits the neural activity of reward processing. Twenty-one patients with SZ and twenty-two demographically matched healthy controls were included in the study. EROs were compared between groups and correlation analyses were conducted to determine a possible relationship between clinical scores and ERO values. Compared with healthy controls, the SZ group had reduced (1) delta and theta amplitudes in the reward condition (2) total beta and non-incentive cue-related beta amplitudes, and (3) incentive cue-related frontal gamma amplitudes. These reductions can be interpreted as impaired dopaminergic neurotransmission and disrupted cognitive functioning in the reward processing of SZ. In contrast, SZ patients showed higher incentive cue-related theta and occipital gamma amplitudes compared to controls. These increments may reflect negative symptoms in SZ. Moreover, theta amplitudes showed a negative correlation with Calgary Depression Scale for Schizophrenia scores and a positive correlation with attentional impulsivity. This is the first study showing the impairments of SZ patients in EROs from delta to gamma frequency bands compared with healthy controls during reward anticipation. Being the first comprehensive study, our results can be interpreted as providing evidence for disrupted brain dynamics in the reward processing of SZ studied by EROs. It may become possible to help patients' wellness by improving our understanding of reward processing in schizophrenia and developing innovative rehabilitation treatments based on these findings.

[Recognition of high-frequency steady-state visual evoked potential for brain-computer interface]

Coding with high-frequency stimuli could alleviate the visual fatigue of users generated by the brain-computer interface (BCI) based on steady-state visual evoked potential (SSVEP). It would improve the comfort and safety of the system and has promising applications. However, most of the current advanced SSVEP decoding algorithms were compared and verified on low-frequency SSVEP datasets, and their recognition performance on high-frequency SSVEPs was still unknown. To address the aforementioned issue, electroencephalogram (EEG) data from 20 subjects were collected utilizing a high-frequency SSVEP paradigm. Then, the state-of-the-art SSVEP algorithms were compared, including 2 canonical correlation analysis algorithms, 3 task-related component analysis algorithms, and 1 task discriminant component analysis algorithm. The results indicated that they all could effectively decode high-frequency SSVEPs. Besides, there were differences in the classification performance and algorithms' speed under different conditions. This paper provides a basis for the selection of algorithms for high-frequency SSVEP-BCI, demonstrating its potential utility in developing user-friendly BCI.

Fine-scale dynamics of calcite precipitation in a large hardwater lake

In hardwater lakes, calcite precipitation is an important yet poorly understood process in the lacustrine carbon cycle, in which catchment-derived alkalinity (Alk) is both transformed and translocated. While the physico-chemical conditions supporting the supersaturation of water with respect to calcite are theoretically well described, the magnitude and conditions underlying calcite precipitation at fine temporal and spatial scales are poorly constrained. In this study, we used high frequency, depth-resolved (0-30 m) data collected over 18 months (June 2019 - November 2020) in the deeper basin of Lake Geneva to describe the dynamics of calcite precipitation fluxes at a fine temporal resolution (day to season) and to scale them to carbon fixation by primary production. Calcite precipitation occurred during the warm stratified periods when surface water CO₂ concentrations were below atmospheric equilibrium. Seasonally, the extent of Alk loss due to calcite precipitation (i.e., [30-42] g C m^-2) depended upon the level of Alk in surface waters. Moreover, interannual variability in seasonal calcite precipitation depended on the duration of stratification, which determined the volume of the water layer susceptible to calcite precipitation. At finer timescales, calcite precipitation was characterized by marked daily variability with dynamics strongly related to that of planktonic autotrophic metabolism. Increasing daily calcite precipitation rates (i.e., maximum values 9 mmol C m^-3 d^-1) coincided with increasing net ecosystem production (NEP) during periods of enhanced water column stability. In these conditions, calcite precipitation could remove as much inorganic carbon from the productive layers as NEP. This study provides mechanistic insights into the conditions driving pelagic calcite precipitation, and quantifies its essential contribution to the coupling of organic and inorganic carbon cycling in lakes.

"Sponge pattern" of the spleen: a rarely described high-frequency ultrasound pattern in HIV-positive patients

BACKGROUND

The spleen is frequently scanned in workup of infections. Hypoechoic splenic micro-abscesses are known signs of disseminated tuberculosis in HIV co-infected patients. The spleen of HIV patients is thus often scanned using high-frequency transducers.

METHODS AND FINDINGS

We describe a reticulo-nodular "sponge pattern" in the spleen of an HIV-positive patient with Hodgkin's lymphoma. Disseminated throughout the spleen, very small (1.5-2.0 mm) hypoechoic lesions having a branching reticulo-nodular distribution were seen. The lesions partly, but not entirely, follow splenic vasculature. Review of stored images of other patients identified 15 more cases showing a similar pattern. All patients were HIV positive, almost all with CD4 counts below 200 cells/mm³. Seven (44%) were additionally diagnosed with HHV-8-associated diseases, but the pattern was seen with various underlying opportunistic infections.

DISCUSSION AND CONCLUSION

After comparison with spleen microscopic anatomy, we hypothesize that the white pulp of spleens in our patients is hyperplastic or otherwise changed in consistency to be better visible by high-frequency ultrasound. Concomitant human herpesvirus-8 infection may be another cause of this visible white pulp. While we can only speculate about the etiology of the splenic "sponge pattern," it needs to be recognized as it may be misinterpreted as splenic micro-abscesses of disseminated infections, like tuberculosis in severely immune-compromised patients.

High-frequency rTMS improves quality of life and depressive symptoms in Parkinson's disease: A case report

Introduction

Parkinson's disease (PD) is a common neurodegenerative disorder, characterised by both motor and nonmotor symptoms. There is currently no cure for PD, although there are several treatment options for relieving PD symptoms. Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation therapy that shows promising results for the treatment of PD.

Methods

Here, we present a patient with PD. We investigated whether an accelerate form of high-frequency (HF) rTMS on the contralateral side to the patient's main difficulties is clinically effective in treating health-related quality of life (QoL) symptomatology and depressive symptoms in PD as well as the long-term effects of rTMS in PD during the maintenance phase.

Results

Results showed that HF-rTMS administered over the right primary motor cortex (M1) is a safe and well-tolerated treatment that improved the patient's health related QoL and depressive symptoms. These positive effects lasted at least five months post treatment.

Conclusion

Therefore, HF-rTMS over the right M1 can be a possible treatment option for patients with PD, although further investigations are necessary to validate the findings of the present case report.

High-frequency devices effect in vitro: promissing approach in the treatment of acne vulgaris?

BACKGROUND

Acne vulgaris is an inflammatory skin disorder leading to an impairment of quality of life and is therefore not only a cosmetic issue. Its pathogenesis is multifactorial - of particular importance is the colonization with the bacterium Propionibacterium acnes. A wide range of different treatment options exists including topical and systemic treatments depending on severity. High Frequency (HF) therapy, historically developed in the 19^th century, claims antimicrobial effects on acne skin, but solid data on its efficacy and mechanism of action is lacking.

OBJECTIVES

The main objective of this study was to determine the efficacy of HF therapy on skin flora and P. acnes in vitro using a commercial device as well as to review studies on the mechanism of action.

METHODS

The plasma source was investigated regarding electrical settings, heat, and ozone development. Bacterial skin flora, fungal isolates, and P. acnes were exposed to HF in vitro and compared to unexposed controls by evaluating the number of colonies on agar plates. To further analyze bacterial species from normal skin flora, 16S-sequencing was performed. Statistical analyses were carried out using row analysis and unpaired t-test.

RESULTS

HF treatment led to a significant reduction of almost every bacterial and fungal species investigated in this study. Moreover, the number of colonies forming units was significantly decreased in P. acnes after HF treatment compared to controls in vitro.

STUDY LIMITATIONS

The experiments were performed in vitro only. To assess clinical effects further in vivo experiments are necessary.

CONCLUSIONS

The results collected in this study, although in vitro, provide a mechanistic basis for HF as a complementary treatment option for patients with acne. It might also have a beneficial effect on patients with superficial infectious skin of the skin.

Dataset for Bitcoin arbitrage in different cryptocurrency exchanges

Bitcoin market's efficiency and liquidity questions are being comprehensively analyzed in scientific literature. This dataset serves academics for deeper analysis of these topics as well as it gives relevant information for spotting and evaluating risks in the market. Moreover, practitioners can benefit from the dataset and use it to identify patterns in the market, discover potential earning capabilities, and create effective arbitrage trading strategies. This is the first publicly available dataset that provides unique arbitrage data about pairs of cryptocurrency exchanges. The raw dataset was received by the Bitlocus LT, UAB. Using dplyr, reshape2, plyr packages in R we transformed dataset to show the amount of arbitrage which could be earned in 13 different cryptocurrency exchanges from 2019-01-01 to 2020-04-01. We used this dataset to create matrices for each day from 2019-01-01 to 2020-04-01 in order to perform network analysis on Bitcoin arbitrage opportunities (Bruzgė and Šapkauskienė [1]). However, this dataset is beneficial for other purposes such as the evaluation of market's seasonality and day of week effects. The dataset provides values in high-frequency intervals but it is possible to convert data to a suitable data format depending on the research question.

High-frequency monitoring of neonicotinoids dynamics in soil-water systems during hydrological processes

Neonicotinoids pollution poses a serious threat to aquatic ecosystems. However, there is currently little knowledge about how neonicotinoids are transferred from the agricultural environment to the aquatic environment. Here, we conducted in situ high-frequency monitoring of neonicotinoids in soil-water systems along the hydrological flow path during rainfall to explore the horizontal and vertical transport mechanisms of neonicotinoids. The collected samples included 240 surface runoff, 128 subsurface runoff, 60 eroded sediment, 120 soil and 144 soil solution, which were used to analyse neonicotinoids concentrations. Surface runoff, subsurface runoff and eroded sediment were the three main paths for the horizontal migration of neonicotinoids. In the CK (citrus orchards without grass cover) and grass-covered citrus orchards, there are 15.89% and 2.29% of the applied neonicotinoids were transported with surface runoff, respectively. While in the CK and grass-covered citrus orchards, there are only 1.23% and 0.19% of the applied neonicotinoids were transported with eroded sediment and subsurface runoff. Although the amount of neonicotinoids lost along with eroded sediment was small, the concentration of neonicotinoids in eroded sediment was two orders of magnitude higher than the concentration of neonicotinoids in sediments of the surface water. Meanwhile, neonicotinoids migrated vertically in soil due to water infiltration. In the CK and grass-covered citrus orchards, there are 57.64% and 24.36% of the applied neonicotinoids were retained in soil and soil solution, respectively, and their concentration decreased as soil depth increased. Another noteworthy phenomenon is that more neonicotinoids migrated to deeper soil layers under grass cover compared with no grass cover because grass roots promoted the formation of cracks and vertical preferential flow. Our results are expected to improve the accuracy of neonicotinoids pollution prediction by considering migration paths, including surface and subsurface runoff and eroded sediment.

Low-energy high-frequency Ho-YAG lithotripsy: is RIRS going forward? A case-control study

Retrograde Intra-Renal Surgery (RIRS) plays a primary role in renal stone treatment context. Energy, frequency and width of laser impulse can be modulated by surgeons to achieve better outcomes. In our study, patients with single renal stone sized 10-20 mm were retrospectively divided into two groups. Patients of Group 1 underwent RIRS with Low-Energy (LE) High-Frequency (HF) settings using Lumenis® 120-W high-power Ho:YAG laser. Patients of Group 2 (control) underwent RIRS using "standard" settings by means of Sphinx® Jr 30 W Ho:YAG system. Follow-up was conducted with a CT scan at 3 months after RIRS in both groups. Procedure success was defined as stone-free or presence of ≤ 4 mm fragments (Clinical Insignificant Residual Fragments-CIRF). A total number of 199 patients were included: 86 LE/HF RIRS (Group 1) vs 113 "conventional" RIRS (Group 2). Mean operative time was 56.6 (± 19.4) min in Group 1 vs 65.2 (± 25.2) min in Group 2 (p = 0.01). Mean hospitalization time was 2.5 ± 1.7 days for Group 1 vs 2.9 ± 3.2 days for Group 2 (p = 0.2). Peri-operative complications were counted: eight in Group 1 and 11 in Group 2 (p > 0.05). At 3-month control, stone-free rate was 69% (59/86 patients) in Group 1 vs 65% (73/113 patients) in Group 2 (p = 0.6). Success rate was 93% (80/86) in Group 1 in comparison to 82% (93/113) in Group 2 (p = 0.03). In conclusion, LE/HF RIRS seems to be a feasible and effective technique with a reduction of operative time and optimal results in terms of "stone-free" and "success" rates. Further studies are needed to ensure the validity of our results and to give evidence-based statements.

High-frequency rTMS over the dorsolateral prefrontal cortex on chronic and provoked pain: A systematic review and meta-analysis

BACKGROUND

High-frequency rTMS over the dorsolateral prefrontal cortex (DLPFC) has demonstrated mixed effects on chronic and provoked pain.

OBJECTIVES/METHODS

In this study, a meta-analysis was conducted to characterise the potential analgesic effects of high-frequency rTMS over the DLPFC on both chronic and provoked pain.

RESULTS

A total of 626 studies were identified in a systematic search. Twenty-six eligible studies were included for the quantitative review, among which 17 modulated chronic pain and the remaining investigated the influence on provoked pain. The left side DLPFC was uniformly targeted in the chronic pain studies. While our data identified no overall effect of TMS across chronic pain conditions, there was a significant short-term analgesia in neuropathic pain conditions only (SMD = -0.87). In terms of long-lasting analgesia, there was an overall pain reduction in the midterm (SMD = -0.53, 24.6 days average) and long term (SMD = -0.63, 3 months average) post DLPFC stimulation, although these effects were not observed within specific chronic pain conditions. Surprisingly, the number of sessions was demonstrated to have no impact on rTMS analgesia. In the analysis of provoked pain, our data also indicated a significant analgesic effect following HF-rTMS over the DLPFC (SMD = -0.73). Importantly, we identified a publication bias in the studies of provoked pain but not for chronic pain conditions.

CONCLUSIONS

Overall, our findings support that HF-DLPFC stimulation is able to induce an analgesic effect in chronic pain and in response to provoked pain. These results highlight the potential of DLPFC-rTMS in the management of certain chronic pain conditions and future directions are discussed to enhance the potential long-term analgesic effects.

The Daily Economic Indicator: tracking economic activity daily during the lockdown

The SARS-CoV-2 outbreak made clear the urgent need to depart from traditional statistics, typically released with a lag and available at a relatively low frequency. This led to unparalleled efforts to put forward high-frequency indicators to track economic developments timely. By resorting to non-traditional data sources, we propose a novel daily economic indicator to track economic activity in Portugal. It corresponds to the latent variable of a set of daily series within a factor model framework. We find a sudden and sharp drop in economic activity in mid-March 2020, when the lockdown of several activities was declared due to the COVID-19 pandemic. Since in this approach we address the complexities of high-frequency data without further smoothing, we are able to identify sudden changes of economic activity in a timely and daily manner in contrast with other approaches.

Flexible ureteroscopy using a 120-w holmium laser: The low-energy/high-frequency approach

With the spread of more powerful lasers and the advent of new technologies, endoscopic interventions for urolithiasis are continuously evolving. The aim of this study is to present our experience and technique regarding Low Energy (LE)/High Frequency (HF) lithotripsy by using a 120-W Holmium laser (Lumenis®). METHODS: We retrospectively analysed our prospectively maintained Retrograde Intra Renal Surgery (RIRS) database. Lithotripsy was performed using LE/HF settings with a Long Pulse Width (LPW) and consisted of the following steps: 1) contact Laser lithotripsy (LE/HF/LPW dusting - 0,5 J/50 Hz or 02 J/70 Hz); 2) extraction ofmain fragments; 3) non-contact Laser lithotripsy (LE/HF/Short Pulse Width Pop Dusting - 0,5 J /80Hz). Pre-operativeand peri-operative outcomes were collected. Post-operative complications were recorded according to Clavien-Dindo Grading System. Finally, all patients under went a CT scan at three months after RIRS to assess the success of procedure, defined as stone-free or presence of ≤4 mm fragments (Clinical Insignificant Residual Fragments - CIRF). RESULTS: Overall, 104 LE/HF/LPW RIRS from December 2017 to January 2019 were performed. Mean operative time was 59 (SD ±23) minutes, median post-operative stay was two days (IQR 2-3). The post-operative complication rate was 4,8%: one patient had nausea and vomiting (Clavien-Dindo I) and four patients developed urosepsis (Clavien-Dindo II). The success rate was 88,5% (71,2% stone-free and 17,3% CIRF). CONCLUSIONS: LE/HF/LPW RIRS seems to be safe and effective in terms of positive success rate, safety and standard operative time. However, randomized clinical trials are needed to compare this technique to standard RIRS.

Stanford Pragmatiec Effectiveness Comparison (SPEC) protocol: Comparing long-term effectiveness of high-frequency and burst spinal cord stimulation in real-world application

OBJECTIVES

High-frequency and burst stimulation are newer waveforms that have demonstrated promise compared to traditional tonic spinal cord stimulation (SCS), but more studies are needed to compare their effectiveness. We report the study methods for an ongoing, single center, pragmatic randomized clinical trial to compare the effectiveness of high-frequency and burst SCS in patients with chronic back and/or leg pain.

MATERIALS AND METHODS

Participants who are candidates for spinal cord stimulation are enrolled and screened. Participants will be randomly assigned using point-of-care randomization to receive either high-frequency or burst SCS. Data collection will be through Stanford Pain Management Center's learning healthcare system: CHOIR. CHOIR surveys include National Institutes of Health Patient Reported Outcomes Measurement Information System item banks, a body map, questions about pain intensity, pain catastrophizing scale, and questions about patients' pain experience and healthcare utilization. Participants will complete online surveys at baseline and then 1, 3, 6, 12, 18, 24 and 36 months after their device implant. All participants will use our routine process of trial and implant. Reported adverse events are monitored throughout the study. Our primary outcome is change from baseline in pain intensity at 12 months.

RESULTS

We hypothesize that high-frequency SCS is more effective than burst SCS in improving pain, physical function and pain interference in participants with chronic low back and/or leg pain.

CONCLUSIONS

The pragmatic nature of our proposed trial enables us to recruit a larger participant cohort faster and to follow up these participants longer than currently published clinical trials.

100 MHz bandwidth planar laser-generated ultrasound source for hydrophone calibration

High-frequency calibration of hydrophones is becoming increasingly important, both for clinical and scientific applications of ultrasound, and user safety. At present, the calibrations available routinely to the user community extend to 60 MHz. However, hydrophones that can measure beyond this are available, and ultrasonic fields often contain energy at higher frequencies, e.g., generated through nonlinear propagation of high-amplitude ultrasound used for therapeutic applications, and the increasing use of higher frequencies in imaging. Therefore, there is a need for calibrations up to at least 100 MHz, to allow ultrasonic fields to be accurately characterized, and the risk of harmful bioeffects to be properly assessed. Currently, sets of focused piezoelectric transducers are used to meet the pressure amplitude and bandwidth requirements of Primary Standard calibration facilities. However, when the frequency is high enough such that the size of the ultrasound focus becomes less than the hydrophone element's diameter, the uncertainty due to spatial averaging becomes significant, and can be as high as 20% at 100 MHz. As an alternate to piezoelectric transducers, a laser-generated ultrasound calibration source was designed, fabricated, and characterized. The source consists of an optically absorbing carbon-polymer nanocomposite excited by a large-diameter 1064 nm laser pulse of 2.6 ns duration. Peak pressure amplitudes of several Mega-Pascal were readily achievable, and the signal contained measurable frequency components up to 100 MHz. The variation in the pressure amplitudes was less than 2% from its mean over a three-hour test period. The ultrasound beam was sufficiently broad that the uncertainties due to spatial averaging were negligible.

Modulation of neuromuscular transmission using transcutaneous direct currents: An exploratory study

OBJECTIVE

To assess the in vivo long-lasting effects on neuromuscular transmission using transcutaneous stimulation with anodal and cathodal direct currents applied over the end-plate region (epDCS).

METHODS

An active DCS electrode was placed over the end-plate region of both abductor pollicis brevis and first dorsal interosseous muscles, with a reference electrode located on the forearm. Cathodal or anodal currents were applied (2.5mA during 15min). Repetitive nerve stimulation of the median and ulnar nerves at the wrist was performed before and after DCS: protocol A - 500 stimuli at 3Hz; protocol B - 30 stimuli at 30Hz. For both muscles, we measured changes in amplitude and area between the first and 4th compound muscle action potential (CMAP) and between the first and 500th CMAP (protocol A); and the change in amplitude and area between the first and 30th CMAP (protocol B).

RESULTS

Anodal current did not change any measurement. Using cathodal epDCS and median nerve testing, there was a larger increase in CMAP amplitude (p=0.046) and a smaller decrease in area (p=0.008) between the first and 30th response (protocol B). Using cathodal epDCS and ulnar nerve testing, there was a possible significant smaller amplitude decrease of the CMAP measured, between the first and fourth response (protocol A).

CONCLUSIONS

Cathodal transcutaneous direct currents over the end-plate may modulate end-plate function by increasing the release of quanta of acetylcholine (Ach) and/or the number of Ach receptors available. Future studies should address this topic.

Rainfall and conduit drainage combine to accelerate nitrate loss from a karst agroecosystem: Insights from stable isotope tracing and high-frequency nitrate sensing

Understanding where nitrate is mobilized from and under what conditions is required to reduce nitrate loss and protect water quality. Low frequency sampling may inadequately capture hydrological and biogeochemical processes that will influence nitrate behavior. We used high-frequency isotope sampling and in-situ nitrate sensing to explore nitrate export and transformation in a karst critical zone. Nitrate was mobilised during light rainfall, and transferred from soil layers to the karst matrix, where some nitrate was retained and denitrified. Nitrate isotopic composition changed rapidly during the rising limb of events and slowly during the falling limb. The main nitrate source was synthetic fertiliser (up to 80% during event flow), transported by conduit flow following high rainfall events, and this contribution increased significantly as discharge increased. Soil organic nitrogen contribution remained constant indicating at baseflow this is the primary source. Isotope source appointment of nitrate export revealed that synthetic fertilizer accounted for more than half of the total nitrate export, which is double that of the secondary source (soil organic nitrogen), providing valuable information to inform catchment management to reduce nitrate losses and fluvial loading. Careful land management and fertilizer use are necessary to avoid nitrate pollution in the karst agroecosystem, for example by timing fertilizer applications to allow for plant uptake of nitrate before rainfall can flush it from the soils into the karst and ultimately into catchment drainage.

Cascade Programming for 10 kHz Spinal Cord Stimulation: A Single Center Case Series of 114 Patients With Neuropathic Back and Leg Pain

OBJECTIVE

Ten kilohertz spinal cord stimulation (SCS) is usually initiated in a single-bipolar configuration over the radiological reference point T9/T10 intervertebral disc space for neuropathic back and leg pain. Cascade is a duty-cycled, multi-bipolar contact configuration across an entire eight-contact lead. Potential advantages by using a broader area of SCS coverage include mitigation against minor lead migration and a reduction in the need for reprogramming. We report here the results of a retrospective case series of 114 patients using Cascade.

MATERIALS AND METHODS

Retrospective data were collected over two years. We selected patients with neuropathic back with or without/leg pain who had a trial of SCS. Pain assessments using Numerical Rating Scales (NRS) and Patient Global Impression of Change (PGIC) scores were collected at baseline, six months, and last follow-up beyond 12 months (mean 15.1 months). Patients were programmed with 10 kHz SCS using Cascade during the trial, which was continued unless reporting inadequate pain relief. Morbidity and deviations from Cascade programming were also obtained.

RESULTS

At six months, 87 of 97 (90.6%) patients with active devices were using Cascade and 58 of 72 (81%) patients at the last follow-up >12 months. There was a significant reduction in back NRS (8.3 vs. 3.9 [p < 0.0001], N = 97) and leg pain (7.53 vs. 3.83 [p < 0.0001], N = 77) at 6 months and last follow-up >12 months back (8.3 vs. 3.95 [p < 0.0001] N = 72), leg (7.53 vs. 3.534 [p < 0.0001], N = 58). The PGIC score was 6 of 7 or all of 7 in 72% of patients (70/97) at six months and in 68% (49/72) of patients at the last follow-up beyond 12 months.

CONCLUSION

Cascade is an effective programming methodology that may have benefits over a single-bipole configuration for 10 kHz SCS, particularly during a trial of stimulation. Results from this study suggest it is a durable program for patients with neuropathic back and leg pain.

Temporal hydrochemical dynamics of the River Wensum, UK: Observations from long-term high-resolution monitoring (2011-2018)

In 2010, the UK government established the Demonstration Test Catchment (DTC) initiative to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology whilst maintaining food production capacity. A central component of the DTC platform was the establishment of a comprehensive network of automated, web-based sensor technologies to generate high-temporal resolution (30 min) empirical datasets of surface water, groundwater and meteorological parameters over a long period (2011-2018). Utilising 8.9 million water quality measurements generated for the River Wensum, this paper demonstrates how long-term, high-resolution monitoring of hydrochemistry can improve our understanding of the complex temporal dynamics of riverine processes from 30 min to annual timescales. This paper explores the impact of groundwater-surface water interactions on instream pollutant concentrations (principally nitrogen, phosphorus and turbidity) and reveals how varying hydrochemical associations under contrasting flow regimes can elicit important information on the dominant pollution pathways. Furthermore, this paper examines the relationships between agricultural pollutants and precipitation events of varying magnitude, whilst demonstrating how high-resolution data can be utilised to develop conceptual models of hydrochemical processes for contrasting winter and summer seasons. Finally, this paper considers how high-resolution hydrochemical data can be used to increase land manager awareness of environmentally damaging farming operations and encourage the adoption of more water sensitive land management practices.

20-kHz alternating current stimulation: effects on motor and somatosensory thresholds

BACKGROUND

High frequency alternating current (HFAC) stimulation have been shown to produce a peripheral nerve conduction block. Currently, all the studies applying HFAC stimulation in clinical studies, have employed frequencies below 10 kHz. The main aim of this work was to investigate the neuromodulatory effect of transcutaneous 20 kHz stimulation on somatosensory and pain thresholds, and maximal handgrip strength.

METHODS

A randomized, crossover, single-blinded, placebo-controlled trial was conducted following recruitment of fourteen healthy volunteers. Transcutaneous stimulation at 20 kHz and sham stimulation were applied over the ulnar and median nerves of fourteen healthy volunteers for 20 min. Maximal handgrip strength (MHS), mechanical detection threshold (MDT) and pressure pain threshold (PPT) were registered prior to, during (15 min), immediately after the end (20 min), and 10 min following stimulation.

RESULTS

The 20 kHz stimulation showed a lower MHS during the stimulation at the 15 min (30.1 kgs SE 2.8) and at 20 min (31.8 kgs, SE 2.8) when compared to sham stimulation (35.1 kgs, SE 3.4; p < 0.001 and 34.2 kgs, SE 3.4; p = 0.03, respectively). The 20 kHz stimulation resulted in a slight increase in MDT at 15 min (0.25 mN; 0.25-2.00) when compared to the sham stimulation (0.25 mN; 0.25-0.25; p = 0.02), and no effects were showed for PPT.

CONCLUSIONS

High-frequency stimulation at 20 kHz suggests a partial block of nerve activity. Studies in subjects with neurological disorders characterized by nerve hyperactivity are needed to confirm the clinical impact of this non-invasive electrical stimulation technique.

TRIAL REGISTRATION

NCT, NCT02837458. Registered on 12 April 2017.

Low-frequency rTMS is better tolerated than high-frequency rTMS in healthy people: Empirical evidence from a single session study

Low-frequency and high-frequency repetitive transcranial magnetic stimulation (rTMS) are similarly efficacious for treatment-resistant depression. Low-frequency is posited to be better tolerated than high-frequency rTMS, however, this is not supported by empirical evidence to date. This study aimed to quantify and compare the tolerability of low-versus high-frequency rTMS. Twenty healthy participants (mean age 38.6 ± 13.9 years) underwent low- and high-frequency rTMS administered on left frontal, fronto-central and central sites at 100% resting motor threshold. For the low-frequency protocol, 60 s of 1 Hz stimulation was applied at each site and for the high-frequency protocol, 3 × 5 s trains of 10 Hz stimulation with a 30 s inter-train interval were applied at each site. Tolerance for each stimulation type was assessed immediately after stimulation through participant ratings of overall intensity of scalp sensations, pain, muscle twitching, discomfort and any other sensation. Low-frequency rTMS was significantly less intense than high-frequency rTMS in overall intensity, pain, muscle twitching (all p < .01) and discomfort (p < .001). Limitations of this study include the healthy participant sample and administration of a single session of rTMS. While further work is needed in clinical samples using typical rTMS treatment protocols, these data provide the first evidence that low-frequency is better tolerated than high-frequency. These findings may inform clinical practice of rTMS treatment for depression (and other illnesses) by supporting the application of low-frequency protocols.

Simulation-based low-dose, high-frequency plus mobile mentoring versus traditional group-based training approaches on day of birth care among maternal and newborn healthcare providers in Ebonyi and Kogi States, Nigeria; a randomized controlled trial

Background

There is limited information from low and middle-income countries on learning outcomes, provider satisfaction and cost-effectiveness on the day of birth care among maternal and newborn health workers trained using onsite simulation-based low-dose high frequency (LDHF) plus mentoring approach compared to the commonly employed offsite traditional group-based training (TRAD). The LDHF approach uses in-service learning updates to deliver information based on local needs during short, structured, onsite, interactive learning activities that involve the entire team and are spaced over time to optimize learning. The aim of this study will be to compare the effectiveness and cost of LDHF versus TRAD approaches in improving knowledge and skill in maternal and newborn care and to determine trainees’ satisfaction with the approaches in Ebonyi and Kogi states, Nigeria.

Methods

This will be a prospective cluster randomized control trial. Sixty health facilities will be randomly assigned for day of birth care health providers training through either LDHF plus mobile mentoring (intervention arm) or TRAD (control arm). There will be 150 trainees in each arm. Multiple choices questionnaires (MCQs), objective structured clinical examinations (OSCEs), cost and satisfaction surveys will be administered before and after the trainings. Quantitative data collection will be done at months 0 (baseline), 3 and 12. Qualitative data will also be collected at 12-month from the LDHF arm only. Descriptive and inferential statistics will be used as appropriate. Composite scores will be computed for selected variables to determine areas where service providers have good skills as against areas where their skills are poor and to compare skills and knowledge outcomes between the two groups at 0.05 level of statistical significance.

Discussion

There is some evidence that LDHF, simulation and practice-based training approach plus mobile mentoring results in improved skills and health outcomes and is cost-effective. By comparing intervention and control arms the authors hope to replicate similar results, evaluate the approach in Nigeria and provide evidence to Ministry of Health on how and which training approach, frequency and setting will result in the greatest return on investment.

Trial registration

The trial was retrospectively registered on 24th August, 2017 at ClinicalTrials.Gov: NCT03269240.

Electronic supplementary material

The online version of this article (10.1186/s12913-018-3405-2) contains supplementary material, which is available to authorized users.

The effects and mechanism of phycocyanin removal from water by high-frequency ultrasound treatment

The effects and mechanism of phycocyanin removal from water by high-frequency ultrasound treatment were studied. The efficiency of sonication treatment in removing proteins derived from algal cells was investigated, and the factors influencing the process, including the effects of coagulation, were also studied. In addition, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), the three-dimensional fluorescence spectrum, and mass spectrum were used to illustrate the removal mechanism. The results indicated that phycocyanin can be degraded to the point where it is barely detectable in water samples after 180min of high-frequency sonication. While the total nitrogen (TN) concentration remained consistent during the entire sonication process (240min), about 78.9% of the dissolved organic nitrogen (DON) was oxidized into inorganic nitrogen. The sonication effect was greatly influenced by the ultrasound frequency, with 200kHz having the highest removal performance due to the large production of hydroxyl (HO) radicals. Coagulation was adversely influenced by sonication in the first 60min due to the cross-linking reaction between protein molecules caused by the sonication. The influence of sonication weakened with sonication time due to the further degradation of the proteins by ultrasound. The variation of the TN, DON, and inorganic nitrogen indicated that the main mechanism occurring during the high-frequency sonication of the phycocyanin was the direct oxidation of the radicals, which was totally different from of the mechanism occurring during ultrasound with low frequency.

A randomized, sham-controlled study of maintenance rTMS for treatment-resistant depression (TRD)

A few open-labeled studies have investigated the use of maintenance rTMS to prevent relapse for treatment-resistant depression (TRD) after rTMS treatment. We aim to assess the benefits of maintenance rTMS treatment for TRD patients who respond to rTMS treatment using a randomized, double-blind controlled design. Fifty eight TRD patients received rTMS over one month in an open-labeled design study (phase I). Responder patients were then randomized into active and sham high-frequency rTMS groups for the subsequent eleven months (phase II). The regularity of sessions was gradually reduced. The antidepressant effect of rTMS was evaluated using the Hamilton Depression Rating Scale (HDRS). Intention-to-treat analysis was performed to assess the effectiveness of maintenance sessions. Of the 58 patients included, 35 patients were responders after one month of active rTMS (phase I), and 17 patients were randomized for the maintenance sessions (phase II). The delta HDRS scores demonstrated a significant improvement between the first month and the fourth month in active group in comparison with sham group (phase II). There was no significant difference between these two groups for other periods of time. Repetitive TMS could represent a novel strategy for preventing relapse in TRD patients who respond to rTMS treatment. These results should be confirmed in a larger sample.

Disentangling the influence of hydroclimatic patterns and agricultural management on river nitrate dynamics from sub-hourly to decadal time scales

Despite extensive efforts to reduce nitrate transfer in agricultural areas, limited response is often observed in the nitrate concentration in rivers. To investigate the reasons for this limited response, nitrate dynamics in a 100km(2) agricultural catchment in eastern Germany was analysed from sub-hourly to decadal time-scales. Sub-hourly analysis of storm event dynamics during a typical hydrological year (2005-2006) was performed to identify periods of the year with high leaching risk and to link the latter to agricultural management practices in the catchment. Dynamic Harmonic Regression analysis of a 32-year (1982-2014) record of nitrate and discharge revealed that i) the long-term trend in nitrate concentration was closely related to that in discharge, suggesting that large-scale weather and climate patterns were masking the effect of improved nitrogen management on nitrate trends; ii) a persistent seasonal pattern with winter concentration maxima and summer minima could be observed, which was interpreted in terms of a dynamic nitrate concentration profile in the soil and subsoil; and iii) the catchment progressively changed from chemodynamic to more chemostatic behaviour over the three decades of study, which is a sign of long-term homogenisation of nitrate concentrations distribution over depth. This study shows that detailed physical understanding of nitrate dynamics across time scales can be obtained only through combined analysis of long-term records and high-resolution sensor data. Hence, a joint effort is advocated between environmental authorities, who usually perform long-term monitoring, and scientific programmes, which usually perform high-resolution monitoring.

Real-time monitoring of nutrients and dissolved organic matter in rivers: Capturing event dynamics, technological opportunities and future directions

Excessive riverine nutrient concentrations threaten aquatic ecosystem structure and functioning and can pose substantial risks to human health. Robust monitoring strategies are therefore required to generate reliable estimates of river nutrient loads and to improve understanding of the catchment processes that drive nutrient fluxes. Furthermore, these data are vital for prediction of future trends under changing environmental conditions and thus the development of appropriate mitigation measures. In recent years, technological developments have led to an increase in the use of in-situ nutrient analysers, which enable measurements at far higher temporal resolutions than can be achieved with discrete sampling and subsequent laboratory analysis. In this paper, we review the principles underlying the key techniques used for in-situ nutrient monitoring and highlight both the advantages, opportunities and challenges associated with high-resolution sampling programs. We then suggest how adaptive monitoring strategies, comprising several different temporal sample frequencies, controlled by one or more 'trigger variables' (e.g. river stage, turbidity, or nutrient concentration), can advance our understanding of catchment nutrient dynamics while simultaneously overcoming many of the practical and economic challenges encountered in typical in-situ river nutrient monitoring applications. We present examples of short-term variability in river nutrient dynamics, driven by complex catchment behaviour, which support our case for the development of monitoring systems that can adapt in real-time to rapid changes in environmental conditions. Finally, we suggest future research directions based on emerging technologies in this field.

Post-stimulation block of frog sciatic nerve by high-frequency (kHz) biphasic stimulation

This study determined if high-frequency biphasic stimulation can induce nerve conduction block that persists after the stimulation is terminated, i.e., post-stimulation block. The frog sciatic nerve-muscle preparation was used in the study. Muscle contraction force induced by low-frequency (0.5 Hz) nerve stimulation was recorded to indicate the occurrence and recovery of nerve block induced by the high-frequency (5 or 10 kHz) biphasic stimulation. Nerve block was observed during high-frequency stimulation and after termination of the stimulation. The recovery from post-stimulation block occurred in two distinct phases. During the first phase, the complete block induced during high-frequency stimulation was maintained. The average maximal duration for the first phase was 107 ± 50 s. During the second phase, the block gradually or abruptly reversed. The duration of both first and second phases was dependent on stimulation intensity and duration but not frequency. Stimulation of higher intensity (1.4-2 times block threshold) and longer duration (5 min) produced the longest period (249 ± 58 s) for a complete recovery. Post-stimulation block can be induced by high-frequency biphasic stimulation, which is important for future investigations of the blocking mechanisms and for optimizing the stimulation parameters or protocols in clinical applications.

Pressure attenuation during high-frequency airway clearance therapy across different size endotracheal tubes: An in vitro study

PURPOSE

High-frequency airway clearance therapy is a positive pressure secretion clearance modality used in pediatric and adult applications. However, pressure attenuation across different size endotracheal tubes (ETT) has not been adequately described. This study quantifies attenuation in an in vitro model.

MATERIALS AND METHODS

The MetaNeb® System was used to deliver high-frequency pressure pulses to 3.0, 4.0, 6.0 and 8.0mm ID ETTs connected to a test lung during mechanical ventilation. The experimental setup included a 3D-printed trachea model and imbedded pressure sensors. The pressure attenuation (Patt%) was calculated: Patt%=[(Pproximal-Pdistal)/Pproximal]x100. The effect of pulse frequency on Pdistal and Pproximal was quantified.

RESULTS

Patt% was inversely and linearly related to ETT ID and (y=-7.924x+74.36; R(2)=0.9917, P=.0042 for 4.0Hz pulse frequency and y=-7.382+9.445, R(2)=0.9964, P=.0018 for 3.0Hz pulse frequency). Patt% across the 3.0, 4.0, 6.0 and 8.0mm I.D. ETTs was 48.88±10.25%, 40.87±5.22%, 27.97±5.29%, and 9.90±1.9% respectively. Selecting the 4.0Hz frequency mode demonstrated higher Pproximal and Pdistal compared to the 3.0Hz frequency mode (P=.0049 and P=.0065). Observed Pdistal was <30cmH2O for all experiments.

CONCLUSIONS

In an in vitro model, pressure attenuation was linearly related to the inner diameter of the endotracheal tube; with decreasing attenuation as the ETT size increased.

Comprehensive identification of high-frequency and combination MHC-DMA and -DMB alleles in a cohort of Chinese rhesus macaques and cynomolgus macaques of Vietnamese origin

Rhesus and cynomolgus macaques are currently used as ideal animal models of immune response. Major histocompatibility complex (MHC) molecules play important roles in the susceptibility and/or resistance to many diseases. In this study, MHC-DMA and -DMB were first characterized by sequencing and cloning in 28 unrelated cynomolgus macaques from Vietnam and 34 unrelated Chinese rhesus macaques. A total of 23 novel alleles, including six high frequency alleles, were identified in this study. Our results showed that the alleles with the highest phenotypic frequencies were Mafa-DMA(∗)02:04:03 (57.1%), Mafa-DMB(∗)03:01:02 (76.9%), Mamu-DMA(∗)02:01:04 (88.2%), and Mamu-DMB(∗)03:02:02 (85%), respectively, indicating that distribution and frequencies of alleles had a few differences between Chinese rhesus macaques and cynomolgus macaques from Vietnam. Interestingly, compared to the cynomolgus macaques, we found that the combination of Mamu-DMA(∗)02:01:04-DMB(∗)03:02:02 was detected in 27 (79.4%) of 34 monkeys, suggesting that the combination of the MHC-DMA and -DMB alleles was probably a characteristic feature of the Chinese rhesus macaques. Our results will greatly increase the value of the two species as models for biomedical research.

Inactivation of Enterobacter aerogenes in reconstituted skim milk by high- and low-frequency ultrasound

The inactivation of Enterobacter aerogenes in skim milk using low-frequency (20kHz) and high-frequency (850kHz) ultrasonication was investigated. It was found that low-frequency acoustic cavitation resulted in lethal damage to E. aerogenes. The bacteria were more sensitive to ultrasound in water than in reconstituted skim milk having different protein concentrations. However, high-frequency ultrasound was not able to inactivate E. aerogenes in milk even when powers as high as 50W for 60min were used. This study also showed that high-frequency ultrasonication had no influence on the viscosity and particle size of skim milk, whereas low-frequency ultrasonication resulted in the decrease in viscosity and particle size of milk. The decrease in particle size is believed to be due to the breakup of the fat globules, and possibly to the cleavage of the κ-casein present at the surface of the casein micelles. Whey proteins were also found to be slightly affected by low-frequency ultrasound, with the amounts of α-lactalbumin and β-lactoglobulin slightly decreasing.

Modelling of a novel high-impedance matching layer for high frequency (>30 MHz) ultrasonic transducers

This work describes a new approach to impedance matching for ultrasonic transducers. A single matching layer with high acoustic impedance of 16 MRayls is demonstrated to show a bandwidth of around 70%, compared with conventional single matching layer designs of around 50%. Although as a consequence of this improvement in bandwidth, there is a loss in sensitivity, this is found to be similar to an equivalent double matching layer design. Designs are calculated by using the KLM model and are then verified by FEA simulation, with very good agreement Considering the fabrication difficulties encountered in creating a high-frequency double matched design due to the requirement for materials with specific acoustic impedances, the need to accurately control the thickness of layers, and the relatively narrow bandwidths available for conventional single matched designs, the new approach shows advantages in that alternative (and perhaps more practical) materials become available, and offers a bandwidth close to that of a double layer design with the simplicity of a single layer design. The disadvantage is a trade-off in sensitivity. A typical example of a piezoceramic transducer matched to water can give a 70% fractional bandwidth (comparable to an ideal double matched design of 72%) with a 3dB penalty in insertion loss.

Control of the higher eigenmodes of a microcantilever: applications in atomic force microscopy

While conventional techniques in dynamic mode atomic force microscopy typically involve the excitation of the first flexural mode of a microcantilever, situations arise where the excitation of higher modes may result in image artefacts. Strong nonlinear coupling between the cantilever modes in liquid environments may result in image artefacts, limiting the accuracy of the image. Similar observations have been made in high-speed contact mode AFM. To address this issue, we propose the application of the modulated-demodulated control technique to attenuate problematic modes to eliminate the image artefacts. The modulated-demodulated control technique is a high-bandwidth technique, which is well suited to the control of next generation of high-speed cantilevers. In addition to potential improvements in image quality, a high-bandwidth controller may also find application in multifrequency AFM experiments. To demonstrate the high-bandwidth nature of the control technique, we construct an amplitude modulation AFM experiment in air utilizing low amplitude setpoints, which ensures that harmonic generation and nonlinear coupling of the modes result in image artefacts. We then utilize feedback control to highlight the improvement in image quality. Such a control technique appears extremely promising in high-speed atomic force microscopy and is likely to have direct application in AFM in liquids.

A detailed analysis of the effect of repetitive transcranial magnetic stimulation on negative symptoms of schizophrenia: a double-blind trial

OBJECTIVE

The aim of the study was to assess the effect of rTMS not only on the general severity of negative schizophrenia symptoms, but also particularly on their individual domains, such as affective flattening or blunting, alogia, avolition or apathy, anhedonia, and impaired attention.

METHODS

Forty schizophrenic male patients on stable antipsychotic medication with prominent negative symptoms were included in the study. They were divided into two groups: 23 were treated with active and 17 with placebo rTMS. Both treatments were similar, but placebo rTMS was administered using a purpose-built sham coil. Stimulation was applied to the left dorsolateral prefrontal cortex (DLPFC). The stimulation frequency was 10 Hz; stimulation intensity was 110% of the individual motor threshold intensity. Each patient received 15 rTMS sessions on 15 consecutive working days (five working days "on" and two weekend days "off" design). Each daily session consisted of 20 applications of 10-second duration with 30-second intervals between sequences. The patients and raters were blind to condition of stimulation treatment.

RESULTS

The active rTMS led to a statistically significantly higher reduction of the Scale for the Assessment of Negative Symptoms (SANS) total score and of all domains of negative symptoms of schizophrenia. After Bonferroni adjustments for multiple testing, the statistical significance disappeared in alogia only.

CONCLUSION

High-frequency rTMS stimulation over the left DLPFC at a high stimulation intensity with a sufficient number of applied stimulating pulses may represent an efficient augmentation of antipsychotics in alleviating the negative symptoms of schizophrenia.

Salivary alpha-amylase and cortisol responsiveness following electrical stimulation stress in obsessive-compulsive disorder patients

Salivary α-amylase (sAA) serves as a marker of sympathoadrenal medullary system (SAM) activity. Salivary AA has not been extensively studied in obsessive-compulsive disorder (OCD) patients. In the current study, 45 OCD patients and 75 healthy volunteers were assessed with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), the Profile of Mood State (POMS), and the State-Trait Anxiety Inventory (STAI). Measures of heart rate variability (HRV), sAA, and salivary cortisol were also obtained following the application of electrical stimulation stress. The Y-BOCS and POMS Tension-Anxiety, Depression-Dejection, Anger-Hostility, Fatigue, and Confusion scores were significantly increased in patients with OCD compared with healthy controls. In contrast, Vigor scores were significantly decreased in patients with OCD relative to scores in healthy controls. There was no difference in HRV between the patients and the controls. Salivary AA levels in female and male OCD patients were significantly elevated relative to controls both before and after electrical stimulation. In contrast, there were no differences in salivary cortisol levels between OCD patients and controls. The elevated secretion of sAA before and after stimulation may suggest an increased responsiveness to novel and uncontrollable situations in patients with OCD. An increase in sAA might be a characteristic change of OCD.