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Indian Journal of Psychological Medicine 2020The sample size for a study needs to be estimated at the time the study is proposed; too large a sample is unnecessary and unethical, and too small a sample is...
The sample size for a study needs to be estimated at the time the study is proposed; too large a sample is unnecessary and unethical, and too small a sample is unscientific and also unethical. The necessary sample size can be calculated, using statistical software, based on certain assumptions. If no assumptions can be made, then an arbitrary sample size is set for a pilot study. This article discusses sample size and how it relates to matters such as ethics, statistical power, the primary and secondary hypotheses in a study, and findings from larger vs. smaller samples.
PubMed: 31997873
DOI: 10.4103/IJPSYM.IJPSYM_504_19 -
Trends in Cognitive Sciences Jul 2014People can rapidly form arbitrary associations between stimuli and the responses they make in the presence of those stimuli. Such stimulus-response (S-R) bindings, when... (Review)
Review
People can rapidly form arbitrary associations between stimuli and the responses they make in the presence of those stimuli. Such stimulus-response (S-R) bindings, when retrieved, affect the way that people respond to the same, or related, stimuli. Only recently, however, has the flexibility and ubiquity of these S-R bindings been appreciated, particularly in the context of priming paradigms. This is important for the many cognitive theories that appeal to evidence from priming. It is also important for the control of action generally. An S-R binding is more than a gradually learned association between a specific stimulus and a specific response; instead, it captures the full, context-dependent behavioral potential of a stimulus.
Topics: Animals; Association Learning; Attention; Awareness; Brain; Humans; Memory; Models, Psychological; Repetition Priming
PubMed: 24768034
DOI: 10.1016/j.tics.2014.03.004 -
Journal of Clinical Medicine Oct 2023Insulin resistance (IR) is a rather common condition that is often diagnosed on the basis of an arbitrary "increased insulin value" or the presence of symptoms...
Insulin resistance (IR) is a rather common condition that is often diagnosed on the basis of an arbitrary "increased insulin value" or the presence of symptoms indicative of the Metabolic Syndrome [...].
PubMed: 37835038
DOI: 10.3390/jcm12196394 -
ACS Photonics Oct 2022The polarization state of light is a key parameter in many imaging systems. For example, it can image mechanical stress and other physical properties that are not seen...
The polarization state of light is a key parameter in many imaging systems. For example, it can image mechanical stress and other physical properties that are not seen with conventional imaging and can also play a central role in quantum sensing. However, polarization is more difficult to image, and polarimetry typically involves several independent measurements with moving parts in the measurement device. Metasurfaces with interleaved designs have demonstrated sensitivity to either linear or circular/elliptical polarization states. Here, we present an all-dielectric meta-polarimeter for direct measurement of any arbitrary polarization state from a single-unit-cell design. By engineering a completely asymmetric design, we obtained a metasurface that can excite eigenmodes of the nanoresonators, thus displaying a unique diffraction pattern for not only any linear polarization state but all elliptical polarization states (and handedness) as well. The unique diffraction patterns are quantified into Stokes parameters with a resolution of 5° and with a polarization state fidelity of up to 99 ± 1%. This holds promise for applications in polarization imaging and quantum state tomography.
PubMed: 36281330
DOI: 10.1021/acsphotonics.2c00395 -
Optics Express Sep 2022The polarizations of electromagnetic (EM) waves are very important for transceivers. We propose a broadband polarization-insensitive polarization rotator (PIPR), which...
The polarizations of electromagnetic (EM) waves are very important for transceivers. We propose a broadband polarization-insensitive polarization rotator (PIPR), which can realize 90° polarization rotation for incident waves with an arbitrary azimuth angle. A unit of the PIPR is composed of two types of substrate integrated waveguide (SIW) units in a checkerboard pattern, which provides more than -0.2 dB transmission from 9.5 to 10.9 GHz. The electric field inside the cavity is analyzed to explain the working mechanism of the proposed rotator. A prototype is fabricated and measured to verify the proposed design, and satisfactory agreement between simulated and measured results is achieved, indicating that the converter has potential applications in imaging and communication systems.
PubMed: 36242472
DOI: 10.1364/OE.471970 -
Clinical Kidney Journal Dec 2021In haemodialysis (HD), unwanted substances (uraemic retention solutes or 'uraemic toxins') that accumulate in uraemia are removed from blood by transport across the... (Review)
Review
In haemodialysis (HD), unwanted substances (uraemic retention solutes or 'uraemic toxins') that accumulate in uraemia are removed from blood by transport across the semipermeable membrane. Like all membrane separation processes, the transport requires driving forces to facilitate the transfer of molecules across the membrane. The magnitude of the transport is quantified by the phenomenon of 'flux', a finite parameter defined as the volume of fluid (or permeate) transferred per unit area of membrane surface per unit time. In HD, as transmembrane pressure is applied to facilitate fluid flow or flux across the membrane to enhance solute removal, flux is defined by the ultrafiltration coefficient (KUF; mL/h/mmHg) reflecting the hydraulic permeability of the membrane. However, in HD, the designation of flux has come to be used in a much broader sense and the term is commonly used interchangeably and erroneously with other measures of membrane separation processes, resulting in considerable confusion. Increased flux is perceived to reflect more 'porous' membranes having 'larger' pores, even though other membrane and therapy attributes determine the magnitude of flux achieved during HD. Adjectival designations of flux (low-, mid-, high-, super-, ultra-) have found indiscriminate usage in the scientific literature to qualify a parameter that influences clinical decision making and prescription of therapy modalities (low-flux or high-flux HD). Over the years the concept and definition of flux has undergone arbitrary and periodic adjustment and redefinition by authors in publications, regulatory bodies (US Food and Drug Administration) and professional association guidelines (European Renal Association, Kidney Disease Outcomes Quality Initiative), with little consensus. Industry has stretched the boundaries of flux to derive marketing advantages, justify increased reimbursement or contrive new classes of therapy modalities when in fact flux is just one of several specifications that determine membrane or dialyser performance. Membranes considered as high-flux previously are today at the lower end of the flux spectrum. Further, additional parameters unrelated to the rate of diffusive or convective transport (flux) are used in conjunction with or in place of KUF to allude to flux: clearance (mL/min, e.g. of β-microglobulin) or sieving coefficients (dimensionless). Considering that clinical trials in nephrology, designed to make therapy recommendations and guide policy with economic repercussions, are based on the parameter flux they merit clarification-by regulatory authorities and scientists alike-to avoid further misappropriation.
PubMed: 34987784
DOI: 10.1093/ckj/sfab182 -
European Journal of Pediatrics Nov 2018Ensuring optimal nutrition is vital in critically ill children and enteral feeding is the main route of delivery in intensive care. Feeding intolerance is the most... (Review)
Review
Ensuring optimal nutrition is vital in critically ill children and enteral feeding is the main route of delivery in intensive care. Feeding intolerance is the most commonly cited reason amongst pediatric intensive care unit healthcare professionals for stopping or withholding enteral nutrition, yet the definition for this remains inconsistent, nebulous, and entirely arbitrary. Not only does this pose problems clinically, but research in this field frequently uses feeding intolerance as an endpoint and the heterogeneity in this definition makes the comparison of studies difficult and meta-analysis impossible. We reviewed the use of, and definitions of, the term feed intolerance in pediatric intensive care research papers in the last 20 years. Gastric residual volume remains the most common factor used to define feed intolerance, despite the lack of evidence for this. Healthcare professionals would benefit from further education to improve their awareness of the limitations of the markers to define feeding intolerance, and the international PICU community needs to agree a consistent definition of this phenomenon to improve consistency in both practice and research.Conclusion: This paper will provide a narrative review of the definitions of, evidence for, and markers of feeding intolerance in critically ill children. What is Known?: • Feeding intolerance is a commonly cited reason amongst pediatric intensive care unit healthcare professionals for stopping or withholding enteral nutrition. • There is no agreed definition for feeding intolerance in critically ill children. What is New?: • This paper provides an up to date review of the definitions of, evidence for, and markers of feeding intolerance in critically ill children. • Despite no evidence, gastric residual volume continues to drive clinical bedside decisions about enteral feeding and feeding tolerance.
Topics: Child; Critical Illness; Enteral Nutrition; Food Intolerance; Humans; Infant; Infant, Newborn; Intensive Care Units, Pediatric
PubMed: 30116972
DOI: 10.1007/s00431-018-3229-4 -
Journal of Medical Ethics Sep 1989The ethical problem of how to apportion limited resources amongst the needy has been forced on us by arbitrary limitation of health expenditure. Its solution would not...
The ethical problem of how to apportion limited resources amongst the needy has been forced on us by arbitrary limitation of health expenditure. Its solution would not be required if health expenditure were higher. Distribution of resources according to best value for money, assessed as Quality Adjusted Life Years (QALYs) per unit cost, has been suggested as a possible solution, but leads to absurd anomalies. In the calculation of QALYs the implied value of life is no more than the absence of suffering. The use of QALYs for the comparison of treatments that are symptomatic or life-saving therefore leads to serious undervaluation of life and treatments that prolong it. Moreover, distribution of resources by best value for money, however assessed, is inequitable since for a given degree of suffering those whose illnesses happen to be cheaper to treat will be treated in preference to those whose treatments are more expensive.
Topics: Economics; Health Care Rationing; Health Resources; Models, Statistical; Pain; Patient Selection; Quality of Life; Resource Allocation; Social Values; Stress, Psychological; United Kingdom; Value of Life
PubMed: 2795628
DOI: 10.1136/jme.15.3.143 -
Scientific Reports Feb 2020In this paper, a broadband metamaterial microwave absorber is designed, simulated and measured. Differently from the traditional method which is only based on unit cell...
In this paper, a broadband metamaterial microwave absorber is designed, simulated and measured. Differently from the traditional method which is only based on unit cell boundary conditions, we carried out full-wave finite integration simulations using full-sized configurations. Starting from an elementary unit cell structure, four kinds of coding metamaterial blocks, 2 × 2, 3 × 3, 4 × 4 and 6 × 6 blocks were optimized and then used as building blocks (meta-block) for the construction of numerous 12 × 12 topologies with a realistic size scale. We found the broadband absorption response in the frequency range 16 GHz to 33 GHz, in good agreement with the equivalent medium theory prediction and experimental observation. Considering various applications of metamaterials or metamaterial absorbers in the electromagnetic wave processing, including the radars or satellite communications, requires the frequency in the range up to 40 GHz. Our study could be useful to guide experimental work. Furthermore, compared to the straightforward approach that represents the metamaterials configurations as 12 × 12 matrices of random binary bits (0 and 1), our new approach achieves significant gains in the broadband absorption. Our method also may be applied to the full-sized structures with arbitrary dimensions, and thus provide a useful tool in the design of metamaterials with specific desired frequency ranges.
PubMed: 32020003
DOI: 10.1038/s41598-020-58774-1 -
Optics Express Sep 2023A group-delay-unit-based integrated silicon photonic integrated circuit (PIC) is employed as a reconfigurable analog radio frequency decoder, which provides a real-time...
A group-delay-unit-based integrated silicon photonic integrated circuit (PIC) is employed as a reconfigurable analog radio frequency decoder, which provides a real-time temporal and spectral analysis of any arbitrary multi-tone signal in the micro- and mm-wave range. The circuit is based on cascaded Mach-Zehnder interferometer embedded silicon microring resonators as variable delay units. The temporal decoding of the multi-tone input signal is demonstrated by tuning the signal with respect to the ring resonator delay and resonance. A one-to-one conformal time-to-frequency mapping provides real-time spectral decoding of the signal under test without additional digital signal processing. The idea is validated by several experimental results with single-tone and two-tone input signals in a compact, low-power, silicon PIC. The proposed real-time temporal analog frequency decoder may be very intriguing for high-speed, low-latency wireless applications, such as autonomous driving and 6G.
PubMed: 37710564
DOI: 10.1364/OE.494674