Gaussian-Distributed Spread-Spectrum for Covert Communications.

Covert communication techniques play a crucial role in military and commercial applications to maintain the privacy and security of wireless transmissions from prying eyes. These techniques ensure that adversaries cannot detect or exploit the existence of such transmissions. Covert communications, also known as low probability of detection (LPD) communication, are instrumental in preventing attacks such as eavesdropping, jamming, or interference that could compromise the confidentiality, integrity, and availability of wireless communication. Direct-sequence spread-spectrum (DSSS) is a widely used covert communication scheme that expands the bandwidth to mitigate interference and hostile detection effects, reducing the signal power spectral density (PSD) to a low level. However, DSSS signals possess cyclostationary random properties that an adversary can exploit using cyclic spectral analysis to extract useful features from the transmitted signal. These features can then be used to detect and analyse the signal, making it more susceptible to electronic attacks such as jamming. To overcome this problem, a method to randomise the transmitted signal and reduce its cyclic features is proposed in this paper. This method produces a signal with a probability density function (PDF) similar to thermal noise, which masks the signal constellation to appear as thermal white noise to unintended receivers. This proposed scheme, called Gaussian distributed spread-spectrum (GDSS), is designed such that the receiver does not need to know any information about the thermal white noise used to mask the transmit signal to recover the message. The paper presents the details of the proposed scheme and investigates its performance in comparison to the standard DSSS system. This study used three detectors, namely, a high-order moments based detector, a modulation stripping detector, and a spectral correlation detector, to evaluate the detectability of the proposed scheme. The detectors were applied to noisy signals, and the results revealed that the moment-based detector failed to detect the GDSS signal with a spreading factor, N = 256 at all signal-to-noise ratios (SNRs), whereas it could detect the DSSS signals up to an SNR of -12 dB. The results obtained using the modulation stripping detector showed no significant phase distribution convergence for the GDSS signals, similar to the noise-only case, whereas the DSSS signals generated a phase distribution with a distinct shape, indicating the presence of a valid signal. Additionally, the spectral correlation detector applied to the GDSS signal at an SNR of -12 dB showed no identifiable peaks on the spectrum, providing further evidence of the effectiveness of the GDSS scheme and making it a favourable choice for covert communication applications. A semi-analytical calculation of the bit error rate is also presented for the uncoded system. The investigation results show that the GDSS scheme can generate a noise-like signal with reduced identifiable features, making it a superior solution for covert communication. However, achieving this comes at a cost of approximately 2 dB on the signal-to-noise ratio.

Extracting knowledge networks from plant scientific literature: potato tuber flesh color as an exemplary trait.

BACKGROUND: Scientific literature carries a wealth of information crucial for research, but only a fraction of it is present as structured information in databases and therefore can be analyzed using traditional data analysis tools. Natural language processing (NLP) is often and successfully employed to support humans by distilling relevant information from large corpora of free text and structuring it in a way that lends itself to further computational analyses. For this pilot, we developed a pipeline that uses NLP on biological literature to produce knowledge networks. We focused on the flesh color of potato, a well-studied trait with known associations, and we investigated whether these knowledge networks can assist us in formulating new hypotheses on the underlying biological processes. RESULTS: We trained an NLP model based on a manually annotated corpus of 34 full-text potato articles, to recognize relevant biological entities and relationships between them in text (genes, proteins, metabolites and traits). This model detected the number of biological entities with a precision of 97.65% and a recall of 88.91% on the training set. We conducted a time series analysis on 4023 PubMed abstract of plant genetics-based articles which focus on 4 major Solanaceous crops (tomato, potato, eggplant and capsicum), to determine that the networks contained both previously known and contemporaneously unknown leads to subsequently discovered biological phenomena relating to flesh color. A novel time-based analysis of these networks indicates a connection between our trait and a candidate gene (zeaxanthin epoxidase) already two years prior to explicit statements of that connection in the literature. CONCLUSIONS: Our time-based analysis indicates that network-assisted hypothesis generation shows promise for knowledge discovery, data integration and hypothesis generation in scientific research.

The Clinical Use of Cricoid Pressure: First, Do No Harm.

Application of cricoid pressure (CP) during rapid sequence induction and intubation sequence has been a "standard" of care for many decades, despite limited scientific proof of its efficacy in preventing pulmonary aspiration of gastric contents. While some of the current rapid sequence induction and intubation guidelines recommend its use, other international guidelines do not, and many clinicians argue that there is insufficient evidence to either continue or abandon its use. Recently published articles and accompanying editorials have reignited the debate on the efficacy and safety of CP application and have generated multiple responses that pointed out the various (and significant) limitations of the available evidence. Thus, a critical discussion of available data must be undertaken before making a final clinical decision on such an important patient safety issue. In this review, the authors will take an objective look at the available scientific evidence about the effectiveness and safety of CP in patients at risk of pulmonary aspiration of gastric contents. We suggest that current data are inadequate to impose clinical guidelines on the use of CP because we acknowledge that currently there is not, and there may never be, a method to prevent aspiration in all patients. In addition, we reiterate that a universally accepted medical-legal standard for approaching the high-risk aspiration patient does not exist, discuss the differences in practice between the US and international practitioners regarding use of CP, and propose 5 recommendations on how future studies might be designed to obtain optimal scientific evidence about the effectiveness and safety of CP in patients at risk for pulmonary aspiration.

Point-of-Care Blood Testing: The Technology Behind the Numbers.

Minutes count in the operating room when it comes to treatment guidance and therapies. On a daily basis, anesthesiologists make hundreds of decisions, some based on laboratory results, when guiding patient therapies. When time is crucial, point-of-care testing is often utilized for expediency. However, point-of-care testing has its limitations. Providers should be aware of the limitations, including the potential for error in results-errors that could lead to improper treatment and possible patient harm. This article outlines the technical aspects and summarizes pitfalls in accuracy for 2 of the most commonly utilized point-of-care testing devices: glucose meters and hemoglobin meters.

Perioperative Considerations for Evolving Artificial Pancreas Devices.

Type 1 diabetes mellitus is a lifelong condition. It requires intensive patient involvement including frequent glucose measurements and subcutaneous insulin dosing to provide optimal glycemic control to decrease short- and long-term complications of diabetes mellitus without causing hypoglycemia. Variations in insulin pharmacokinetics and responsiveness over time in addition to illness, stress, and a myriad of other factors make ideal glucose control a challenge. Control-to-range and control-to-target artificial pancreas devices (closed-loop artificial pancreas devices [C-APDs]) consist of a continuous glucose monitor, response algorithm, and insulin delivery device that work together to automate much of the glycemic management for an individual while continually adjusting insulin dosing toward a glycemic target. In this way, a C-APD can improve glycemic control and decrease the rate of hypoglycemia. The MiniMed 670G (Medtronic, Fridley, MN) system is currently the only Food and Drug Administration-cleared C-APD in the United States. In this system, insulin delivery is continually adjusted to a glucose concentration, and the patient inputs meal-time information to modify insulin delivery as needed. Data thus far suggest improved glycemic control and decreased hypoglycemic events using the system, with decreased need for patient self-management. Thus, the anticipated use of these devices is likely to increase dramatically over time. There are limited case reports of safe intraoperative use of C-APDs, but the Food and Drug Administration has not cleared any device for such use. Nonetheless, C-APDs may offer an opportunity to improve patient safety and outcomes through enhanced intraoperative glycemic control. Anesthesiologists should become familiar with C-APD technology to help develop safe and effective protocols for their intraoperative use. We provide an overview of C-APDs and propose an introductory strategy for intraoperative study of these devices.

Multisite, multivendor validation of the accuracy and reproducibility of proton-density fat-fraction quantification at 1.5T and 3T using a fat-water phantom.

PURPOSE: To evaluate the accuracy and reproducibility of quantitative chemical shift-encoded (CSE) MRI to quantify proton-density fat-fraction (PDFF) in a fat-water phantom across sites, vendors, field strengths, and protocols. METHODS: Six sites (Philips, Siemens, and GE Healthcare) participated in this study. A phantom containing multiple vials with various oil/water suspensions (PDFF:0%-100%) was built, shipped to each site, and scanned at 1.5T and 3T using two CSE protocols per field strength. Confounder-corrected PDFF maps were reconstructed using a common algorithm. To assess accuracy, PDFF bias and linear regression with the known PDFF were calculated. To assess reproducibility, measurements were compared across sites, vendors, field strengths, and protocols using analysis of covariance (ANCOVA), Bland-Altman analysis, and the intraclass correlation coefficient (ICC). RESULTS: PDFF measurements revealed an overall absolute bias (across sites, field strengths, and protocols) of 0.22% (95% confidence interval, 0.07%-0.38%) and R2 > 0.995 relative to the known PDFF at each site, field strength, and protocol, with a slope between 0.96 and 1.02 and an intercept between -0.56% and 1.13%. ANCOVA did not reveal effects of field strength (P = 0.36) or protocol (P = 0.19). There was a significant effect of vendor (F = 25.13, P = 1.07 × 10-10 ) with a bias of -0.37% (Philips) and -1.22% (Siemens) relative to GE Healthcare. The overall ICC was 0.999. CONCLUSION: CSE-based fat quantification is accurate and reproducible across sites, vendors, field strengths, and protocols. Magn Reson Med 77:1516-1524, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

A novel approach to improving efficiency and cost saving in preoperative blood preparation.

BACKGROUND: Preoperative ordering of blood products has been an area of optimization due to considerable variability among physicians; overpreparation can lead to extra costs and underpreparation of blood can potentially compromise patient safety. STUDY DESIGN AND METHODS: We examined the potential cost savings of extending the storage interval of a presurgical type-and-screen sample from 7 to 14 days, thereby reducing the need for a new specimen on the day of surgery. RESULTS: Sensitivity analysis showed annual cost savings for our institution to be an estimated $38,770 ($22,420-$73,120). CONCLUSION: These results are even more robust when incorporating the additional potential savings from improved operating room efficiency.

Recent advances in perioperative glucose monitoring.

PURPOSE OF REVIEW: There is ongoing controversy surrounding the use of glucose monitoring in the perioperative setting. It is an important aspect of patient care, but the best way to go about monitoring this parameter is still up for debate. This article will review previously established data and new developments in this field. RECENT FINDINGS: Several different methods exist to measure blood glucose levels in the perioperative setting, including central laboratory devices, blood gas analyzers, and point-of-care devices. However, it has been recommended that point-of-care devices not be used on 'critically ill' patients, which throws into question the common use of these devices perioperatively. Recently, the Centers for Medicare and Medicaid placed a moratorium on this recommendation, and these devices continue to be a staple in the perioperative setting, but there are other methods of glucose monitoring that can be employed. SUMMARY: The monitoring of blood glucose levels in the perioperative patient remains an important part of patient care; however, debate still exist on how best to reliably measure blood glucose levels in the most effective manner.

Glucose Meters: Here Today, Gone Tomorrow?

OBJECTIVE: This special article will review the history of blood glucose meter hospital use and current issues surrounding their use in this patient population. STUDY SELECTION: Secondary to accuracy concerns that have been known, but likely underappreciated for many years, the U.S. Food and Drug Administration and Centers for Medicare and Medicaid Services are moving toward eliminating current blood glucose meters for use with critically ill patients. DATA SOURCES: Recent guidance from the U.S. Food and Drug Administration and Centers for Medicare and Medicaid Services along with several recent publications will be used as the primary data sources. DATA EXTRACTION: U.S. Food and Drug Administration, Centers for Medicare and Medicaid Services communications combined with recent interpretation of this guidance were used to provide this overview. DATA SYNTHESIS: Centers for Medicare and Medicaid Services have issued a temporary moratorium on the prohibition of the use of blood glucose meters in the critically ill. They have not given a deadline for the moratorium or solicited comments. CONCLUSIONS: Physicians who care for critically ill patients need to be cognizant of the accuracy and interference limitations of blood glucose meters and aware of the current regulatory situation.

Limitations of Significance Testing in Clinical Research: A Review of Multiple Comparison Corrections and Effect Size Calculations with Correlated Measures.

Modern clinical research commonly uses complex designs with multiple related outcomes, including repeated-measures designs. While multiple comparison corrections and effect size calculations are needed to more accurately assess an intervention's significance and impact, understanding the limitations of these methods in the case of dependency and correlation is important. In this review, we outline methods for multiple comparison corrections and effect size calculations and considerations in cases of correlation and summarize relevant simulation studies to illustrate these concepts.

Imaging Artifacts in Echocardiography.

Artifacts are frequently encountered during echocardiographic examinations. An understanding of the physics and underlying assumptions of ultrasound processing involved with image generation is important for accurate interpretation of 2D grayscale, spectral Doppler, color flow Doppler, and 3D artifacts and their clinical implications.

Universal intravenous access cleaning device fails to sterilize stopcocks.

BACKGROUND: Contamination of a central venous catheter may occur through use of conventional open-lumen stopcock devices (COLDs), or disinfectable, needleless, closed connectors (DNCCs). We investigated the effectiveness of a new universal IV access cleaning device (Site-Scrub) compared with 70% isopropyl alcohol prep pads for sanitizing COLDs or DNCCs inoculated with common catheter-associated pathogens. METHODS: Site-Scrub was compared with 70% alcohol prep pads for sanitizing contaminated female Luer lock COLD or DNCC filled with sterile saline or propofol and 2 common bacterial central venous catheter contaminants (Staphylococcus epidermidis or Pseudomonas aeruginosa). Devices were contaminated using a glove touch (COLD and DNCC) or syringe tip (COLD). The primary end point of the study was colony-forming units (CFU) after 24 hours. RESULTS: The use of glove touch contamination, the contaminants, S epidermidis and P aeruginosa, produced CFU in saline-filled COLDs treated with the Site-Scrub, but not in those treated with alcohol pads (P < 0.001). Similar results were observed with propofol-filled COLDs (P < 0.001). For DNCCs filled with saline or propofol, both alcohol and Site-Scrub effectively reduced CFU growth compared with contaminated controls (P < 0.001). When COLDs were contaminated by treated syringe tips, there was no significant evidence of reduction in CFU growth by using either alcohol pads or Site-Scrub compared with contaminated controls. CONCLUSIONS: These data suggest that when the inner surface of the COLD is contaminated, both alcohol pads and Site-Scrub were not significantly effective in decontaminating the COLD. When the COLD rim is contaminated, however, alcohol pads outperform Site-Scrub. DNCCs were uniformly decontaminated with either treatment. Future work should focus on better access systems because current COLDs are difficult to decontaminate.

The impact of a medically directed student registered nurse anesthesia staffing model on Postprocedural patient outcomes.

STUDY OBJECTIVE: In 2018, the American Society of Anesthesiologists stated that student registered nurse anesthetists (SRNAs) "are not yet fully qualified anesthesia personnel." It remains unclear, however, whether postprocedural outcomes are affected by SRNAs providing anesthesia care under the medical direction of anesthesiologists, as compared with medically directed anesthesiology fellows or residents, or certified registered nurse anesthetists (CRNAs). We therefore aimed to examine whether medically directed SRNAs serving as in-room anesthesia providers impact surgical outcomes. DESIGN: Retrospective, matched-cohort analysis. SETTING: Adult patients (≥18 years old) undergoing inpatient surgery between 2000 and 2017 at a tertiary academic medical center. PATIENTS: 15,365 patients exclusively cared for by medically directed SRNAs were matched to 15,365 cared for by medically directed CRNAs, anesthesiology residents, and/or fellows. INTERVENTIONS: None. MEASUREMENTS: The primary composite outcome was postoperative occurrence of in-hospital mortality and six categories of major morbidities (infectious, bleeding, serious cardiac, gastrointestinal, respiratory, and urinary complications). In-hospital mortality was analyzed as the secondary outcome. MAIN RESULTS: In all, 30,730 cases were matched using propensity score matching to control for potential confounding. The primary outcome was identified in 2295 (7.5%) cases (7.5% with exclusive medically directed SRNAs vs 7.4% with medically directed CRNAs, residents and/or fellows; relative risk, 1.02; 95% CI, 0.94-1.11). Thus, our effort to determine noninferiority (10% difference in relative risk) with other providers was inconclusive (P = .07). However, the medically directed SRNA group (0.8% [118]) was found to be noninferior (P < .001) to the matched group (1.0% [156]) on in-hospital mortality (relative risk, 0.75; 95% CI, 0.59-0.96). CONCLUSIONS: Among 30,730 patients undergoing inpatient surgery at a single hospital, findings were inconclusive regarding whether exclusive medically directed SRNAs as in-room providers were noninferior to other providers. The use of medically directed SRNAs under this staffing model should be subject to further review. Clinical Trial and Registry URL: Not applicable.