Frequency Standards Research Articles

Complication Patterns of Loop Ileostomy

Background: Loop ileostomy is a temporary diversion of small intestinal contents towards exterior through anterior abdominal wall. Though it is a good procedure for a better outcome of primary surgery it has itself many complications. Objective: To determine the clinical spectrum of loop ileostomy complications. Materials and method: This prospective study was conducted from January, 2017 to December, 2017. Consecutive 30 patients requiring loop ileostomy were enrolled in the study by purposive sampling and were categorized into Group A requiring emergency surgery and Group B planned for elective surgery. Data regarding sociodemographic, clinical, surgical and outcome profile were recorded in a pre-structured, interview and observation based, peer reviewed data collection sheet. Data were compiled, edited and analyzed with SPSS version 23. Data were presented as mean and standard deviation, frequency percentage and median with range. Results: The mean age of the patients were 32.79±5.19 years (age range: 20-43 years) and 49.16±6.17 years (age range: 28-76 years) in Group A and Group B respectively with sex ratio of male to female of 4:1 and 3:1. Out of 10 patients in Group A, 4(40%) patients underwent resection anastomosis with ileostomy and primary repair with loop ileostomy whereas 2(20%) patients underwent exteriorization of multiple perforation site. In Group B among 20 patients, 9(45%) underwent low anterior resection with loop ileostomy and 5(25%) patients underwent left hemicolectomy with loop ileostomy. Out of 10 patients in Group A, 5(50%) patients each suffered from skin excoriation and major wound infection. On the contrary, among 20 patients in Group B, 11(55%) and 4(20%) patients suffered from skin excoriation and stomal obstruction. Only skin excoriation was evident as statistically significantly higher in Group B than in Group A (p 0.03). Among the general complications, electrolyte imbalance (60% vs 40% in Group A and B respectively) and respiratory tract infection (10% each in Group A and B) were evident. Conclusion: Skin discoloration, skin edema, major and minor wound infection, prolapse, skin excoriation and stomal obstruction are the different spectrum of loop ileostomy complications in our perspective. Among them skin excoriation is much higher in routine cases than emergency surgery. Delta Med Col J. Jan 2021;9(1):17-22

Frequency Instability Impact of Low-Cost SDRs on Doppler-Based Localization Accuracy.

In this paper, we explore several widely available software-defined radio (SDR) platforms that could be used for locating with the signal Doppler frequency (SDF) method. In the SDF, location error is closely related to the accuracy of determining the Doppler frequency shift. Therefore, ensuring high frequency stability of the SDR, which is utilized in the location sensor, plays a crucial role. So, we define three device classes based on the measured frequency stability of selected SDRs without and with an external rubidium clock. We estimate the localization accuracy for these classes for two scenarios, i.e., short- and long-range. Using an external frequency standard reduces the location error from 20 km to 30 m or 15 km to 2 m for long- and short-range scenarios, respectively. The obtained simulation results allowed us to choose an SDR with appropriate stability. The studies showed that using an external frequency standard is necessary for minimizing SDR frequency instability in the Doppler effect-based location sensor. Additionally, we review small-size frequency oscillators. For further research, we propose two location sensor systems with small size and weight, low power consumption, and appropriate frequency stability. In our opinion, the SDF location sensor should be based on the bladeRF 2.0 micro xA4 or USRP B200mini-i SDR platform, both with the chip-scale atomic clock CSAC SA.45s, which will allow for minor positioning errors in the radio emitters.

Macroscopic effects in generation of attosecond XUV pulses via high-order frequency mixing in gases and plasma

We theoretically study the generation of attosecond XUV pulses via high-order frequency mixing (HFM) of two intense generating fields, and compare this process with the more common high-order harmonic generation (HHG) process. We calculate the macroscopic XUV signal by numerically integrating the 1D propagation equation coupled with the 3D time-dependent Schrödinger equation. We analytically find the length scales which limit the quadratic growth of the HFM macroscopic signal with propagation length. Compared to HHG these length scales are much longer for a group of HFM components, with orders defined by the frequencies of the generating fields. This results in a higher HFM macroscopic signal despite the microscopic response being lower than for HHG. In our numerical simulations in a gas target, the intensity of the HFM signal is several times higher than that for HHG, while for a plasma target the HFM generation efficiency is up to three orders of magnitude higher than for HHG. The HFM with relatively long generating pulses provides very narrow XUV lines ( δω/ω=4.6×10−4 ) with well-defined frequencies, thus allowing for a simple extension of optical frequency standards to the XUV range. Finally, we show that the group of HFM components effectively generated due to macroscopic effects provides a train of attosecond pulses such that the carrier-envelope phase of an individual attosecond pulse can be easily controlled by tuning the phase of one of the generating fields.

Utility of Repetitive Transcranial Magnetic Stimulation for Chronic Daily Headache Prophylaxis: A Systematic Review and Meta-Analysis.

Management of chronic daily headaches (CDH) remains challenging due to the limited efficacy of standard prophylactic pharmacological measures. Several studies have reported that repetitive transcranial magnetic stimulation (rTMS) can effectively treat chronic headaches. The objective was to determine the utility of rTMS for immediate post-treatment and sustained CDH prophylaxis. All procedures were conducted per PRISMA guidelines. PubMed, Scopus, Web of Science, and ProQuest databases were searched for controlled clinical trials that have tested the efficacy of rTMS on populations with CDH. DerSimonian-Laird random-effects meta-analyses were performed using the 'meta' package in R to examine the post- vs. pre-rTMS changes in standardized headache intensity and frequency compared to sham-control conditions. Thirteen trials were included with a combined study population of N = 538 patients with CDH (rTMS, N = 284; Sham, N = 254). Patients exposed to rTMS had significantly reduced standardized CDH intensity and frequency in the immediate post-treatment period (Hedges' g = -1.16 [-1.89, -0.43], p = 0.002 and Δ = -5.07 [-10.05, -0.11], p = 0.045 respectively). However, these effects were sustained marginally in the follow-up period (Hedges' g = -0.43 [-0.76, -0.09], p = 0.012 and Δ = -3.33 [-5.52, -1.14], p = 0.003). Significant between-study heterogeneity was observed, at least partially driven by variations in rTMS protocols. Despite the observed clinically meaningful and statistically significant benefits in the immediate post-treatment period, the prophylactic effects of rTMS on CDH do not seem to sustain with discontinuation. Thus, the cost-effectiveness of the routine use of rTMS for CDH prophylaxis remains questionable. Protocol preregistered in PROSPERO International Prospective Register of Systematic Reviews (CRD42021250100).

P1082 A comparative analysis of persistence of advanced therapies among patients with Inflammatory Bowel Disease in Taiwan

Abstract Background The prevalence of inflammatory bowel disease (IBD) has been rapidly increasing in Asia. Advanced therapies have significantly improved outcomes for moderate to severe cases of IBD. With the expanding availability of advanced therapies, the selection of the most suitable treatment option has become crucial. Among various factors, treatment persistence holds paramount importance. We present the first study in Asia that compares real-world persistence rates among advanced therapies in IBD patients in Taiwan. Methods In this retrospective cohort study, we enrolled patients with IBD who were treated with five advanced therapies: infliximab (IFX), adalimumab (ADA), vedolizumab (VDZ), ustekinumab (UST), and tofacitinib (TOF) at Linkou Chang Gung Memorial Hospital between October 2017 and April 2023. UST followed a standard maintenance dosing frequency of every 12 weeks, while TOF was permitted for use only as a second-line treatment option for UC in Taiwan. We compared baseline data and drug persistence rates within the first 52 weeks for the overall group, biologic-naïve patients, and biologic-experienced patients. Results A total of 432 IBD patients were included, with 173 (40%) having ulcerative colitis (UC) and 259 (60%) having Crohn's disease (CD). The majority of patients were male, with a mean age of 43.6 years and a mean BMI of 22.6. UST showed the highest rate of dose escalation (22%). Across all five drugs, the primary reason of discontinuation was secondary loss of response, with IFX having the highest discontinuation rate due to side effects (20%). Other baseline characteristics were presented in Table 1. Kaplan-Meier analysis revealed that all biologics exhibited a persistence rate of over 50% within the initial 52 weeks. UST demonstrated the highest 52-week persistence rates in overall (87.88%, p < 0.001, Figure 1a), biologic-naïve (96.55%, p = 0.002, Figure 1b) and biologic-experienced CD patients (80.56%, p=0.043, Figure 1c). Although no statistically significant differences were observed between advanced therapies in overall UC patients and other subgroup analyses (Figure 1d-1f). VDZ showed highest 52-week persistence in overall (69.05%, p=0.078, Figure 1d) and biologic-experienced (60.87%, p=0.751, Figure 1f) UC patients. UST had highest 52-week persistence in biologic-naïve UC patients (100%, p=0.329, Figure 1e). Conclusion In this pioneering real-world comparison of advanced therapies across one year in Asia, UST exhibited superior 52-week persistence rates in CD patients. However, the rate of dose escalation in UST was also the highest among these therapies. The study's limitations include its single-center nature and relatively small sample size.

ELECTRIC VEHICLE BASED ON STANDARD INDUSTRIAL COMPONENTS

The aim of this paper is to presents the complete design of an electric vehicle by using standard industrial components as VRLA batteries, AC induction motors and standard frequency converters. In comparison with dedicated components, the use of standard components has the following advantages: higher reliability, low price, broad range of products and suppliers, and high availability and technological independence. Besides this, we show that these components allow to make an easy and efficient electric differential without speed or steering sensors and they can perform regenerative braking.

Evaluation of the relativistic redshift in frequency standards at KRISS

Relativistic redshift correction should be accurately considered in frequency comparisons between frequency standards. In this study, we evaluated the relativistic redshift at Korea Research Institute of Standards and Science (KRISS) using three different methods, depending on whether the approach was traditional or modern or whether the geopotential model was global or local. The results of the three methods agreed well with one another, and the height of an Yb optical lattice clock (KRISS-Yb1) was determined to be 75.15 m with an uncertainty of 0.04 m with respect to the conventionally adopted equipotential surface W0CGPM , the value of which is defined to be 62 636 856.0 m2s−2. Accordingly, the relativistic redshift of KRISS-Yb1 was evaluated to be 8.193(4) × 10−15. These data are applicable to the frequency standards at KRISS, one of which regularly participates in the calibration of the International Atomic Time.

Comparison of the efficacy Talc solution injection through Chest Tube and Talcum Powder through Pleuroscopy for the Treatment of Malignant Pleural Effusion: a randomized clinical trial

Background: The aim of the present study was to compare the different outcomes and response rates of talc powder injection via chest tube and talc spray through thoracoscopy in the treatment of malignant pleural effusion in patients.
 Methods: In this randomized controlled trial, patients with malignant pleural effusion, who were hospitalized in the surgery and hematology-oncology departments of Shariati and Imam Khomeini Hospitals, were enrolled. The patients were randomly divided into two groups: chest tube and pleuroscopy, using simple randomization. The mean and standard deviation, frequency and percentage, independent sample t-tests, chi-square, and Fisher’s exact tests were used for data analysis. A p-value of less than 0.05 was considered statistically significant.
 Results: No significant difference was observed between the two groups in the incidences of chest pain, fever, and both symptoms (p > 0.05). The treatment success rates among the chest tube and pleuroscopy cases were 83.3% and 100%, respectively, and there was no significant difference between the two groups (p = 0.05). Among the five patients who had a recurrence, four (80%) had lung cancer, and one (20%) had liver cancer, and this difference was significant (P = 0.003). Regarding the rate of response to the treatment according to the side with effusion, among the people who had a relapse, two people (40%) had right-sided effusion, and three others (60%) had left-sided effusion (P = 0.623).
 Conclusions: Both techniques were safe, had minor side effects, were transient, and easy to manage. However, the recurrence of the disease in the thoracoscopic pleurodesis method was significantly less than in the chest tube.

Traceable frequency measurements with counters

Received signals from Global Navigation Satellite Systems (GNSS) are nowadays widely used by industry laboratories for ensuring metrological traceability for their respective range of calibration services in the field of time and frequency. Usually, a local frequency standard is steered by continuous GNSS signal reception providing at its output stable and accurate reference signals for the laboratory measurement equipment, in general for synthesizers and counters. Reception of GNSS signals is surely an adequate and practical tool for the purpose, however further steps are needed to establish traceability in a strict metrological sense. Based on already available guidelines and publications, this paper is a contribution to the discussion how metrological traceability to internationally accepted standards can be established in a calibration laboratory. We restrict the discussion to equipment in common use which may not necessarily be of the highest sophistication. In this spirit, we develop a detailed scheme for an uncertainty budget comprising all links of the traceability chain from the device under test to the SI second, the scale-unit of Coordinated Universal Time. Then we go through and apply this scheme step by step to a demonstration setup for frequency measurements with a counter with varying operational parameters. In this framework, a novel approach to distinguish between components of statistical measurement uncertainty is introduced. Furthermore, the limiting uncertainty contributions are discussed and based on a suitable set of parameters an expression for the best measurement capability is given. With this scheme at hand a user may develop an uncertainty budget adapted to his own setup, especially if acceptance from a national accreditation body is sought.

Assessment of CT-KUB as A Diagnostic Tool for Renal Stone Assessment in the Pediatric Population

Introduction Pakistan possesses a larger stone burden in paediatric patients. In the paediatric population, proper and timely diagnosis of renal stones to get the best stone-free rates is essential. This study aims to assess CT-KUB as a diagnostic tool for renal stones in the paediatric population before PCNL. Methodology This is a retrospective, cross-sectional study. Patients between 1 – 15 years with a diagnosis of renal stones were included in the study. Radiological investigations including Ultrasound KUB, X-ray KUB, and before the procedure, CT-KUB were documented. Pre-operative, per-operative, and postoperative complications are used to assess the success of the procedure. The statistical package of Social Sciences 22 was used to enter, sort, and analyze the data. Variables were analyzed in mean ± standard deviation and frequency and percentages. The chi-square test was used to assess the significance of mean differences keeping the p-value as ≤ 0.05. Results The mean age was 4.7 ± 3.8 years with a range of 1 -14 years. After the procedure, 104 (86.6%) were rendered stone-free after the first setting. Only 1 (0.8%) was converted to an open case (Pyelolithotomy). The mean stone size encountered was 1.3 ± 0.7 cm in greatest dimension as measured on the CT scan. Postoperatively, there was a hemoglobin drop of 2.3 ± 0.5 g/dl noted, mean operative time was 94.8 ± 17.4 minutes. Conclusion CT KUB proves to be an important and accurate preoperative diagnostic tool in assessing patients with renal stones in the paediatric population.

Risk ranking of rig up operation activities using multi-criteria decision-making methods based on fuzzy environment

The main aim of this research study is to determine the risk ranking of 29 failure modes of rig-up operations using a well-known and highly effective MCDM method i.e. Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (FTOPSIS). This method takes into account the four criteria which comprise human impact, property damage, environmental effect and company reputation as risk criteria. Three Experts in the field were invited to present the risk ranking of the relative importance of criteria and criteria performance of each risk (as failure mode) by utilizing linguistic variables which are then integrated in triangular fuzzy numbers for further analysis using the Fuzzy TOPSIS method. The evaluation concluded that FM20 (Collision between the offshore platform and boats) is the most dangerous risk with a coefficient of closeness (CCi) equal to 0.992 while the risk level of FM26 (foggy weather) was found least having a coefficient of closeness (CCi) of 0. Subsequently, sensitivity analysis of ranks concluded that FM1 (H2S inaccurate monitoring) is the most sensitive alternative with standard deviation and frequency of rank change was 5.16 and 15 respectively whereas FM20 (Collision between offshore platform and boats) is observed to be the least sensitive alternative. Fuzzy TOPSIS results were found in excellent correlations with the other reliable MCDM methods which include Fuzzy VIKOR (VIseKriterijumska Optimizacija I Kompromisno Resenje) and Fuzzy COPRAS (COmplex PRoportional ASsessment) yielding correlation of around 1. This study proves to be a landmark in the petroleum industry and significantly contributes to verifying safe practices, by taking appropriate actions in minimizing the risk level associated with different activities during rig-up operations.

Design of a novel wide-angle Rotman lens beamformer for 5G mmWave applications

The attachment of 5G with millimeter wave (mmWave) frequencies offers massive capacity and low latency to reveal the full 5G experiences. High directive gain and beamforming are considered essential for mmWave 5G systems. The main requirements of the beamforming network for 5G mmWave applications are the scanning coverage of ± 60° and SLL > 10 dB in a wide operational bandwidth over the standard 5G frequency bands. In this paper, a novel PCB-based wide-angle Rotman lens beamformer is designed, simulated, and successfully measured to meet the mentioned requirements for 5G mmWave applications. A comprehensive improved design methodology is provided for all components of the Rotman lens to reach a wide scanning angle, enhanced sidelobe level, and low scan loss. The end-fire Vivaldi antenna is selected as an array element for easy integration to the beamforming network as well as its capability to use in dual-polarization configuration. The proposed Rotman lens is operational in the 24–30 GHz frequency band covering 5G n257, n258, and n261 frequency bands. The results show a nearly constant 8 beams across the whole bandwidth steering from − 53° to 53° in 15° increments to provide ± 60° coverage with the SLL > 10 dB and scan loss < 1.9 dB. The retrieved novelties from this work contain an effective design methodology for an optimized Rotman lens with wide-scan angle and low phase and amplitude error, non-uniform distribution based array ports, and integration with end-fire antenna for possible dual polarization and 2-D beamforming capabilities. The comparison of the proposed beamformer with the most recent works shows several advantages in terms of integrated structure and performances including bandwidth, wide scanning angle, SLL, and scan loss. With such performances, this beamformer can be used for various mmWave and 5G applications such as advanced antenna systems, massive MIMO systems, and hybrid beamforming systems.

Quantitative EEG in the Differential Diagnosis of Dementia Subtypes.

Most neurodegenerative dementias present with substantial overlap in clinical features. Therefore, differential diagnosis is often a challenging task necessitating costly and sometimes invasive diagnostic procedures. A promising, non-invasive and cost-effective method is the widely available electroencephalography (EEG). Twenty-three subjects with Alzheimer's disease (AD), 28 subjects with dementia with Lewy bodies (DLB), 15 subjects with frontotemporal dementias (FTDs), and 22 healthy controls (HC) were enrolled. Nineteen channel computerized EEG recordings were acquired. Mean relative powers were calculated using the standard frequency bands. Theta/alpha ratio (TAR), theta/beta ratio (TBR), a spectral index of (alpha + beta)/(theta + delta) and an alpha reactivity index (alpha in eyes-open condition/alpha in eyes-closed condition) were also calculated. Receiver operating characteristic (ROC) analyses were performed to assess diagnostic accuracy. For the comparison of EEG measures across groups, we performed a multivariate ANOVA followed by univariate ANOVAs controlling for the effects of age, with post hoc tests. Theta power and TBR were increased in DLB compared to other groups. Alpha power was decreased in DLB compared to HC and FTD; and in AD compared to FTD. Beta power was decreased in DLB compared to AD and HC. Furthermore, regional analyses demonstrated a unique pattern of theta power increase in DLB; affecting frontal, central, parietal, occipital, and temporal regions. In AD, theta power increased compared to HC in parietal, occipital, and right temporal regions. TAR was increased in DLB compared to other groups; and in AD compared to HC. Finally, alpha reactivity index was higher in DLB compared to HC and FTD. In AD, EEG slowing was associated with cognitive impairment, while in DLB, this was associated with higher DLB characteristics. In the ROC analyses to distinguish DLB from FTD and AD, measures of EEG slowing yielded high area under curve values, with good specificities. Also, decreased alpha reactivity could distinguish DLB from FTD with good specificity. EEG slowing in DLB showed a diffuse pattern compared to AD, where a posterior and temporal slowing predominated. We showed that EEG slowing was satisfactory in distinguishing DLB patients from AD and FTD patients. Notably, this slowing was a characteristic finding in DLB patients, even at early stages, while it paralleled disease progression in AD. Furthermore, EEG slowing in DLB showed a diffuse pattern compared to AD, where a posterior and temporal slowing predominated. These findings align with the previous evidence of the diencephalic dysfunction in DLB.

Dual-interrogation method for suppressing light shift in Rb 778 nm two-photon transition optical frequency standard.

In this study, a dual-interrogation (DI) method was used to suppress the light shift in the Rb 778 nm 5S1/2→5D5/2 two-photon transition optical frequency standard (2hν-OFS). The approach used an auxiliary system to calibrate the light shift of the primary system in real time to mitigate the absolute light shift and suppress the sensitivity of the system to the light power. Results show that after using the DI method, the absolute light shift and light-power sensitivity of the system were reduced by a factor of 10. The proposed method will improve the accuracy of the Rb 778 nm 2hν-OFS and increase the mid- and long-term stability. The method can also be applied to other vapor-cell atomic frequency standards that experience light shifts.

Determination of Concentration of Active Pharmaceutical Ingredients in Different Brands of Artemether/Lumefantrine Tablets Sold in the Pharmacies in Uganda

Substandard, counterfeit and falsified antimalarial agents are a big challenge to effective malaria elimination interventions mainly in developing countries. In low-and middle-income countries (LMICs), the quality of antimalarial agents inclusive of AL is affected by several factors including insufficient regulation porous borders and limited funds. This study therefore focused evaluation of quality of different brands of fixed dose artemether/ lumefantrine tablets sold in Ugandan Pharmacies. This was an experimental study conducted using AL tablets obtained from different pharmacies in the different cities of Uganda purchased using mystery shopper method. The samples were screened for quality using visual inspection, assessed different physical quality parameters like weight variation, friability, disintegration and dissolution and content assay tests were also done both for the brands from the pharmacies and their correspondent LTR. The assay test was done using HPLC technique USP method. The samples were considered substandard if the API content was outside 90-110% range of the label claim. Data was analysed using descriptive statistics and presented as means with standard deviations and frequencies. Out of the 16 brands in the study, 14 brands (88%) passed the artemether assay and two brands failed at 89.8% and 110.2% of declared artemether content. For Lumefantrine assay, out of the 16 brands in the study, 14 brands (88%) passed the Lumefantrine assay except two brands (12%). The presence of A/L brands that are unregistered and the total assay failure of the brands of 18% for the AL tablets purchased causes alarm and the total assay failure of the brands of 18% for the AL tablets purchased calls for NDA to intensify on its operations to find out the conformity of the pharmacies to selling only registered medicines. Keywords: Artemether Lumefantrine, Quality, Tablets

Reliability of some tinnitus psychoacoustic measures

IntroductionPsychoacoustic measures are used to quantify tinnitus perception in clinical and research settings. Residual inhibition (RI), for instance, is defined as a temporary reduction in tinnitus loudness after the presentation of an acoustic stimulus. A novel approach was developed recently to assess the minimum sound level producing RI, the minimum residual inhibition level (MRIL), after the repeated presentation of short sounds separated by short periods of silence. Two studies were performed: the objective of the study 1 was to assess the reliability and the reproducibility of this measures as well as others, including the minimum masking level (MML). The objective of study 2 was to assess whether a smoother envelope of the sound would produce similar levels of MML and MRIL and improve listening comfort.MethodsThirty participants with chronic tinnitus completed each study. For study 1, MML and MRIL were obtained at the seven standard audiometric frequencies at around 1-month interval. For study 2, MML and MRIL were obtained using triangular and trapezoidal-shaped NBN signals centered at three different frequencies.ResultsThe mean absolute test-retest difference was 3 dB for both MML and MRIL [Intraclass correlation, ICC (2,1) of 0.70 and 0.84, respectively] for the measures obtained in test and retest (86% of cases for MML and 21% of cases for complete MRIL). While the two types of envelopes provided comparable MRIL, the “triangular” envelope provided more listening comfort.DiscussionIn sum, the novel approach provides quick and reliable MML and MRIL measurement, with the potential benefit of subtyping participants.

A cold-atom Ramsey clock with a low volume physics package

We demonstrate a Ramsey-type microwave clock interrogating the 6.835 GHz ground-state transition in cold 87\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{87}$$\\end{document}Rb atoms loaded from a grating magneto-optical trap (GMOT) enclosed in an additively manufactured loop-gap resonator microwave cavity. A short-term stability of 1.5×10-11τ-1/2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.5 \ imes 10^{-11} \ au ^{-1/2}$$\\end{document} is demonstrated, in reasonable agreement with predictions from the signal-to-noise ratio of the measured Ramsey fringes. The cavity-grating package has a volume of ≈\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\approx $$\\end{document}67 cm3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}$$\\end{document}, ensuring an inherently compact system while the use of a GMOT drastically simplifies the optical requirements for laser cooled atoms. This work is another step towards the realisation of highly compact portable cold-atom frequency standards.

Terahertz microcomb oscillator stabilized by molecular rotation

Controlling the coherence between light and matter has enabled the radiation of electromagnetic waves with a spectral purity and stability that defines the Système International (SI) second. Transitions between hyperfine levels in atoms are accessible in the microwave and optical domains, but faithfully transferring such stability to other frequency ranges of interest requires additional components such as optical frequency combs. Such spectral purity and stability are specifically sought out for the terahertz domain for both scientific and commercial applications, including precision studies of molecular physics, next-generation wireless communications, quantum sensors, and terahertz frequency standards. Currently, there is a lack of native frequency references in this spectral range, which is essential for the consistency of measurements and traceability. Small-scale terahertz oscillators, which leverage dissipative Kerr soliton microcombs, present a promising avenue for the generation of terahertz waves that rival the spectral purity of electronic alternatives. Here, we experimentally demonstrate the rotational spectroscopy of nitrous oxide (N2O) with a microcomb-based oscillator. To mitigate the frequency drift encompassed in such waves, we lock the frequency of the microcomb terahertz oscillator to that of a rotational transition of N2O, reducing the fractional frequency stability to a level of 5 × 10−12 at 10 s of averaging time. These results constitute a high performance terahertz oscillator that can be scaled down to a compact size while circumventing the need for frequency multiplication or division of frequency standards. This demonstrates a foundational component needed for future terahertz applications.

Compound reconfigurable symmetric slotted mimo antenna with abs enclosure for indoor wireless applications

This research work reports the Compound Reconfigurable MIMO Antenna (CRMA) utilizing RF PIN diodes for indoor wireless communication applications. The proposed CRMA comprises a quad-symmetric Slotted Radiator (SSR) with a common ground structure. It can perform frequency, polarization and pattern switching at frequency standards such as IEEE 802.11a/b/g/n (2.4/5.5 GHz), IEEE 802.11ax (6 GHz) and 5G/n78 (3.5 GHz). A parasitic element of a modified U-shaped stub is utilized to achieve polarization reconfiguration. Further, to achieve pattern reconfiguration two crossed-shaped slots are implemented. The proposed antenna achieves a bandwidth of 320 MHz at 2.4 GHz, 950 MHz at 3.5 GHz and 1870 MHz at 5.5 GHz. At these resonant frequencies, the antenna is capable of producing both circular and linear polarization with a pattern tilt towards different angular directions such as 30°, 120°, 210°, 300°, 330°, 240°, 150°, 60°. The designed CRMA follows orthogonal orientation and exhibits better diversity performance with ECC < 0.1, DG > 9 dB, TARC < -13 dB and CCL < 0.27 bps/Hz. Also, an Acrylonitrile Butadiene Styrene (ABS) enclosure is designed and fabricated to validate the performance of the antenna with casing, further to analyze the suitability of the antenna for indoor wireless applications

Temporal changes in the frequency of flood types and their impact on flood statistics

Standard flood frequency analysis assumes stationarity of flood conditions, i.e., no change of the distribution over time. However, long-term variability in climate and anthropogenic impacts question this assumption. Consequently, more and more non-stationary models are considered in flood frequency analyses. Yet, most of them only consider a change-point or trend in the magnitude of flood peaks while ignoring changes in the underlying flood geneses. Recent climate reports suggest such a change in frequency of certain flood-generating factors, e.g., the increase of frequency of heavy-rainfall events. In this study, flood types are applied to detect changes in the meteorological drivers of flood regimes. By application of a robust change-point test for the variance based on Gini’s Mean Difference, significant changes in the frequency of occurrence of certain flood types are detected. A clear tendency to more frequent heavy-rainfall floods and less snowmelt-induced floods is observed for many catchments in Central Europe. A special focus is laid on the shifts in winter floods, which occur less often and are replaced by rainfall-driven floods. The impacts of such changes on flood statistics are demonstrated by several approaches. Though the magnitude of flood peaks does not (necessarily) change, the changing frequency of floods leads to changing flood quantiles. Quantile estimations from traditional statistical analyses of annual series are compared to results of type-based flood statistics. It is shown how standard models are more affected by these changes because they are not able to compensate for changes in the frequency of individual flood types.