Role of temperature in de-mixing absorbance spectra composed of compound electrolyte solutions.

This work is focused on the role of temperature in the de-mixing of absorbance spectra measured in mixed aqueous Na2SO4 and NaNO3 solutions. First, the influence of temperature on the absorbance spectrum of demineralized water was determined. Second, the absorbance spectra of five separate electrolytes (NaNO2, NaNO3, CaCl2, K2CO3, and NaOH) at three temperatures (4°C, 25°C, and 50°C) for concentrations ranging from 0.0625 M to 0.5 M were examined. These five electrolytes show similar temperature dependencies. Finally, absorbance spectra of mixed solutions were investigated at temperatures of 5°C, 15°C, 25°C, 35°C, and 45°C for concentrations ranging from 0.0625 M to 0.5 M per electrolyte in the mixture. The spectral window from 650 to 1100 nm was utilized to observe the ionic and temperature influences on the vibrational modes of the OH bond in the solvent molecules. The effects of dissolving Na2SO4 and NaNO3 are nonlinearly cumulative at lower temperatures indicating extended alteration of the water structure beyond the first hydration shell. A similar trend was observed for a mixture of Na2CO3 and NaCl. Furthermore, it was found that higher temperatures are better for recovering the separate component absorption signatures of an electrolyte mixture. The near-infrared spectral regime is well suited for integrated sensing, and therefore these results can help in designing an integrated sensor to identify inorganic species in water.

Prokaryotic transport in electrohydrodynamic structures.

When a high-voltage direct-current is applied to two beakers filled with water, a horizontal electrohydrodynamic (EHD) bridge forms between the two beakers. In this work we study the transport and behavior of bacterial cells added to an EHD bridge set-up. Organisms were added to one or to both beakers, and the transport of the cells through the bridge was monitored using optical and microbiological techniques. It is shown that Escherichia coli top10 (Invitrogen, Carlsbad, CA, USA) and bioluminescent E. coli YMC10 with a plasmid (pJE202) containing Vibrio fischeri genes can survive the exposure to an EHD liquid bridge set-up and the cells are drawn toward the anode due to their negative surface charge. Dielectrophoresis and hydrostatic forces are likely to be the cause for their transport in the opposite direction which was observed as well, but to a much lesser extent. Most E. coli YMC10 bacteria which passed the EHD bridge exhibited increased luminescent activity after 24 h. This can be explained by two likely mechanisms: nutrient limitation in the heavier inoculated vials and a 'survival of the strongest' mechanism.

Gut Commensal Bacteroidetes Encode a Novel Class of Vitamin B12-Binding Proteins.

Human gut commensal Bacteroidetes rely on multiple transport systems to acquire vitamin B12 and related cobamides for fitness in the gut. In addition to a set of conserved transport proteins, these systems also include a diverse repertoire of additional proteins with unknown function. Here, we report the function and structural characterization of one of these proteins, BtuH, which binds vitamin B12 directly via a C-terminal globular domain that has no known structural homologs. This protein is required for efficient B12 transport and competitive fitness in the gut, demonstrating that members of the heterogeneous suite of accessory proteins encoded in Bacteroides cobamide transport system loci can play key roles in vitamin acquisition. IMPORTANCE The gut microbiome is a complex microbial community with important impacts on human health. One of the major groups within the gut microbiome, the Bacteroidetes, rely on their ability to capture vitamin B12 and related molecules for fitness in the gut. Unlike well-studied model organisms, gut Bacteroidetes genomes often include multiple vitamin B12 transport systems with a heterogeneous set of components. The role, if any, of these components was unknown. Here, we identify new proteins that play key roles in vitamin B12 capture in these organisms. Notably, these proteins are associated with some B12 transport systems and not others (even in the same bacterial strain), suggesting that these systems may assemble into functionally distinct machines to capture vitamin B12 and related molecules.

Densities and apparent molar volumes of atmospherically important electrolyte solutions. 2. The systems H(+)-HSO4(-)-SO4(2-)-H2O from 0 to 3 mol kg(-1) as a function of temperature and H(+)-NH4(+)-HSO4(-)-SO4)2-)-H2O from 0 to 6 mol kg(-1) at 25 °C using a Pitzer ion interaction model, and NH4HSO4-H2O and (NH4)3H(SO4)2-H2O over the entire concentration range.

A Pitzer ion interaction model has been applied to the systems H(2)SO(4)-H(2)O (0-3 mol kg(-1), 0-55 °C) and H(2)SO(4)-(NH(4))(2)SO(4)-H(2)O (0-6 mol kg(-1), 25 °C) for the calculation of apparent molar volume and density. The dissociation reaction HSO(4)(-)((aq)) ↔ H(+)((aq)) + SO(4)(2-)((aq)) is treated explicitly. Apparent molar volumes of the SO(4)(2-) ion at infinite dilution were obtained from part 1 of this work, (1) and the value for the bisulfate ion was determined in this study from 0 to 55 °C. In dilute solutions of both systems, the change in the degree of dissociation of the HSO(4)(-) ion with concentration results in much larger variations of the apparent molar volumes of the solutes than for conventional strong (fully dissociated) electrolytes. Densities and apparent molar volumes are tabulated. Apparent molar volumes calculated using the model are combined with other data for the solutes NH(4)HSO(4) and (NH(4))(3)H(SO(4))(2) at 25 °C to obtain apparent molar volumes and densities over the entire concentration range (including solutions supersaturated with respect to the salts).

Densities and apparent molar volumes of atmospherically important electrolyte solutions. 1. The solutes H2SO4, HNO3, HCl, Na2SO4, NaNO3, NaCl, (NH4)2SO4, NH4NO3, and NH4Cl from 0 to 50 °C, including extrapolations to very low temperature and to the pure liquid state, and NaHSO4, NaOH, and NH3 at 25 °C.

Calculations of the size and density of atmospheric aerosols are complicated by the fact that they can exist at concentrations highly supersaturated with respect to dissolved salts and supercooled with respect to ice. Densities and apparent molar volumes of solutes in aqueous solutions containing the solutes H(2)SO(4), HNO(3), HCl, Na(2)SO(4), NaNO(3), NaCl, (NH(4))(2)SO(4), NH(4)NO(3), and NH(4)Cl have been critically evaluated and represented using fitted equations from 0 to 50 °C or greater and from infinite dilution to concentrations saturated or supersaturated with respect to the dissolved salts. Using extrapolated densities of high-temperature solutions and melts, the relationship between density and concentration is extended to the hypothetical pure liquid solutes. Above a given reference concentration of a few mol kg(-1), it is observed that density increases almost linearly with decreasing temperature, and comparisons with available data below 0 °C suggest that the fitted equations for density can be extrapolated to very low temperatures. As concentration is decreased below the reference concentration, the variation of density with temperature tends to that of water (which decreases as temperature is reduced below 3.98 °C). In this region below the reference concentration, and below 0 °C, densities are calculated using extrapolated apparent molar volumes which are constrained to agree at the reference concentrations with an equation for the directly fitted density. Calculated volume properties agree well with available data at low temperatures, for both concentrated and dilute solutions. Comparisons are made with literature data for temperatures of maximum density. Apparent molar volumes at infinite dilution are consistent, on a single ion basis, to better than ±0.1 cm(3) mol(-1) from 0 to 50 °C. Volume properties of aqueous NaHSO(4), NaOH, and NH(3) have also been evaluated, at 25 °C only. In part 2 of this work (ref 1 ) an ion interaction (Pitzer) model has been used to calculate apparent molar volumes of H(2)SO(4) in 0-3 mol kg(-1) aqueous solutions of the pure acid and to represent directly the effect of the HSO(4)(-) ↔ H(+) + SO(4)(2-) reaction. The results are incorporated into the treatment of aqueous H(2)SO(4) density described here. Densities and apparent molar volumes from -20 to 50 °C, and from 0 to 100 wt % of solute, are tabulated for the electrolytes listed in the title and have also been incorporated into the extended aerosol inorganics model (E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) together with densities of the solid salts and hydrates.

Deliberating performance targets workshop: Potential paths for emerging PM2.5 and O3 air sensor progress.

The United States Environmental Protection Agency held an international two-day workshop in June 2018 to deliberate possible performance targets for non-regulatory fine particulate matter (PM2.5) and ozone (O3) air sensors. The need for a workshop arose from the lack of any market-wide manufacturer requirement for Ozone documented sensor performance evaluations, the lack of any independent third party or government-based sensor performance certification program, and uncertainty among all users as to the general usability of air sensor data. A multi-sector subject matter expert panel was assembled to facilitate an open discussion on these issues with multiple stakeholders. This summary provides an overview of the workshop purpose, key findings from the deliberations, and considerations for future actions specific to sensors. Important findings concerning PM2.5 and O3 sensors included the lack of consistent performance indicators and statistical metrics as well as highly variable data quality requirements depending on the intended use. While the workshop did not attempt to yield consensus on any topic, a key message was that a number of possible future actions would be beneficial to all stakeholders regarding sensor technologies. These included documentation of best practices, sharing quality assurance results along with sensor data, and the development of a common performance target lexicon, performance targets, and test protocols.

Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines.

Low intensity transcranial electrical stimulation (TES) in humans, encompassing transcranial direct current (tDCS), transcutaneous spinal Direct Current Stimulation (tsDCS), transcranial alternating current (tACS), and transcranial random noise (tRNS) stimulation or their combinations, appears to be safe. No serious adverse events (SAEs) have been reported so far in over 18,000 sessions administered to healthy subjects, neurological and psychiatric patients, as summarized here. Moderate adverse events (AEs), as defined by the necessity to intervene, are rare, and include skin burns with tDCS due to suboptimal electrode-skin contact. Very rarely mania or hypomania was induced in patients with depression (11 documented cases), yet a causal relationship is difficult to prove because of the low incidence rate and limited numbers of subjects in controlled trials. Mild AEs (MAEs) include headache and fatigue following stimulation as well as prickling and burning sensations occurring during tDCS at peak-to-baseline intensities of 1-2mA and during tACS at higher peak-to-peak intensities above 2mA. The prevalence of published AEs is different in studies specifically assessing AEs vs. those not assessing them, being higher in the former. AEs are frequently reported by individuals receiving placebo stimulation. The profile of AEs in terms of frequency, magnitude and type is comparable in healthy and clinical populations, and this is also the case for more vulnerable populations, such as children, elderly persons, or pregnant women. Combined interventions (e.g., co-application of drugs, electrophysiological measurements, neuroimaging) were not associated with further safety issues. Safety is established for low-intensity 'conventional' TES defined as <4mA, up to 60min duration per day. Animal studies and modeling evidence indicate that brain injury could occur at predicted current densities in the brain of 6.3-13A/m2 that are over an order of magnitude above those produced by tDCS in humans. Using AC stimulation fewer AEs were reported compared to DC. In specific paradigms with amplitudes of up to 10mA, frequencies in the kHz range appear to be safe. In this paper we provide structured interviews and recommend their use in future controlled studies, in particular when trying to extend the parameters applied. We also discuss recent regulatory issues, reporting practices and ethical issues. These recommendations achieved consensus in a meeting, which took place in Göttingen, Germany, on September 6-7, 2016 and were refined thereafter by email correspondence.

Computer-assisted navigational surgery enhances safety in dental implantology.

INTRODUCTION: Dental implants are increasingly used to restore missing dentition. These titanium implants are surgically installed in the edentulous alveolar ridge and allowed to osteointegrate with the bone during the healing phase. After osseo-integration, the implant is loaded with a prosthesis to replace the missing tooth. Conventional implant treatment planning uses study models, wax-ups and panoramic x-rays to prefabricate surgical stent to guide the preparation of the implant site. The drilling into the alveolar ridge is invariably a "blind" procedure as the part of the drill in bone is not visible. Stereotactic systems were first introduced into neurosurgery in 1986. Since then, computer-assisted navigational technology has brought major advances to neuro-, midface and orthopaedic surgeries, and more recently, to implant placement. CLINICAL FEATURE: This paper illustrates the use of real-time computer-guided navigational technology in enhancing safety in implant surgical procedures. OUTCOME AND CONCLUSION: Real-time computer-guided navigational technology enhances accuracy and precision of the surgical procedure, minimises complications and facilitates surgery in challenging anatomical locations.

Neuropsychological impairment from acute low-level exposure to carbon monoxide.

OBJECTIVE: To investigate the effects of acute low-level exposure to carbon monoxide on higher cognitive functions in healthy humans. DESIGN: An empirical study of the effects of low-level exposure to carbon monoxide on higher cognitive functions in young healthy volunteers and a matched nonexposed control group. SETTING: A dormitory at the Hebrew University campus in Jerusalem, Israel. PARTICIPANTS: Forty-five student volunteers who were exposed to carbon monoxide from residential kerosene stoves for 1.5 to 2.5 hours (air carbon monoxide concentrations of 17-100 ppm; mean +/- SD, 61 +/- 24 ppm) served as the experimental group and 47 nonexposed students served as the control group. MAIN OUTCOME MEASURES: A battery of neuropsychological tests was administered to each participant including digit span, the revised Wechsler Memory Scale for verbal and figural memory, Trail-Making Test parts A and B, digit symbol, block design, and the Rey Auditory Verbal Learning Test. RESULTS: Venous blood carboxyhemoglobin (Hbco) levels in participants of the study group ranged from 0.01 to 0.11 (mean +/- SD, 0.04 +/- 0.03) and correlated with air carbon monoxide concentrations (r = 0.39; P = .01). The experimental group scored significantly lower than controls on the following tests: digit span forward (P = .02), short-term (P = .008) and long-term semantic memory (P = .008), digit symbol (P = .004), block design (P = .009), recall of figural memory (P = .02), and Trail-Making part A (P = .04). No significant differences were found between the experimental and control groups in other tests. CONCLUSIONS: The lower scores on neuropsychological tests indicate dysfunctions in memory, new learning ability, attention and concentration, tracking skills, visuomotor skills, abstract thinking, and visuospatial planing and processing. These dysfunctions correspond with previous reports of carbon monoxide neurotoxic effects in patients with moderate carbon monoxide poisoning. Low-level exposure to carbon monoxide results in impairment of higher cognitive functions. Neuropsychological testing appears to be sensitive in the detection of subtle neurologic dysfunctions resulting from carbon monoxide poisoning.

Growth and neutralization of sulfate aerosols in human airways.

Evidence derived from in vivo and in vitro laboratory experiments, controlled human exposure studies, and epidemiological studies on mortality and morbidity point to a positive correlation between acid aerosol inhalation and lung impairment. The lung has two important lines of defense against acid aerosols: 1) neutralization by oral or nasal airway ammonia and 2) buffering by mucus lining of the airway. A mathematical model is developed to study the growth and endogenous ammonia neutralization of sulfate-containing aerosol particles in the human respiratory tract. It is shown that an accurate prediction of the luminal ammonia concentration and relative humidity in each generation is essential for quantifying the degree of neutralization of the acidic particles. The model predicts substantial growth and neutralization for small particles (< 0.1 micron), whereas larger particles (> 1.0 micron) experience negligible neutralization. The predicted neutralization of intermediate-sized particles depends on the parameter values used in the model. Water supersaturations that occur in the respiratory tract when ambient conditions are cool and humid cause rapid particle growth and consequently enhance neutralization. Thus the neutralization depends on the particle size as well as on ambient conditions.

Detailed flow patterns in the nasal cavity.

The human nasal cavity filters and conditions inspired air while providing olfactory function. Detailed experimental study of nasal airflow patterns has been limited because of the complex geometry of the nasal cavity. In this work, particle image velocimetry was used to determine two-dimensional instantaneous velocity vector fields in parallel planes throughout a model of the nasal cavity that was subjected to a nonoscillatory flow rate of 125 ml/s. The model, which was fabricated from 26 computed tomography scans by using rapid prototyping techniques, is a scaled replica of a human right nasal cavity. The resulting vector plots show that the flow is laminar and regions of highest velocity are in the nasal valve and in the inferior airway. The relatively low flow in the olfactory region appears to protect the olfactory bulb from particulate pollutants. Low flows were also observed in the nasal meatuses, whose primary function has been the subject of debate. Comparison of sequentially recorded data suggests a steady flow.

Development of a mathematical model that predicts optimal muscle activation patterns by using brief trains.

Because muscles must be repetitively activated during functional electrical stimulation, it is desirable to identify the stimulation pattern that produces the most force. Previous experimental work has shown that the optimal pattern contains an initial high-frequency burst of pulses (i.e., an initial doublet or triplet) followed by a low, constant-frequency portion. Pattern optimization is particularly challenging, because a muscle's contractile characteristics and, therefore, the optimal pattern change under different physiological conditions and are different for each person. This work describes the continued development and testing of a mathematical model that predicts isometric forces from fresh and fatigued muscles in response to brief trains of electrical pulses. By use of this model and an optimization algorithm, stimulation patterns that produced maximum forces from each subject were identified.

A predictive model of fatigue in human skeletal muscles.

Fatigue is a major limitation to the clinical application of functional electrical stimulation. The activation pattern used during electrical stimulation affects force and fatigue. Identifying the activation pattern that produces the greatest force and least fatigue for each patient is, therefore, of great importance. Mathematical models that predict muscle forces and fatigue produced by a wide range of stimulation patterns would facilitate the search for optimal patterns. Previously, we developed a mathematical isometric force model that successfully identified the stimulation patterns that produced the greatest forces from healthy subjects under nonfatigue and fatigue conditions. The present study introduces a four-parameter fatigue model, coupled with the force model that predicts the fatigue induced by different stimulation patterns on different days during isometric contractions. This fatigue model accounted for 90% of the variability in forces produced by different fatigue tests. The predicted forces at the end of fatigue testing differed from those observed by only 9%. This model demonstrates the potential for predicting muscle fatigue in response to a wide range of stimulation patterns.

Two-step, predictive, isometric force model tested on data from human and rat muscles.

Functional electrical stimulation can assist paralyzed individuals to perform functional movements, but muscle fatigue is a major limitation to its practical use. An accurate and predictive mathematical model can facilitate the design of stimulation patterns that optimize aspects of the force transient while minimizing fatigue. Solution nonuniqueness, a major shortcoming in previous work, was overcome with a simpler model. The model was tested on data collected during isometric contractions of rat gastrocnemius muscles and human quadriceps femoris muscles under various physiological conditions. For each condition tested, parameter values were identified using the force response to one or two stimulation trains. The parameterized model was then used to predict forces in response to other stimulation patterns. The predicted forces closely matched the measured forces. The model was not sensitive to initial parameter estimates, demonstrating solution uniqueness. By predicting the force that develops in response to an arbitrary pattern of stimulation, we envision the present model helping identify optimal stimulation patterns for activation of skeletal muscle during functional electrical stimulation.

The role of dispersion in particle deposition in human airways.

Aerosol dispersion and deposition are processes that occur concurrently in human airways. However, dispersion has not been properly accounted for in most deposition models. In this paper we have incorporated the latest understanding of dispersion into a dosimetry model and study the influence of dispersion on particle deposition in the lung. We show that dispersion influences the total deposition of inhaled particles and in particular increases the pulmonary deposition of fine mode particles. We also discuss how dispersion can help elucidate a number of clinical and epidemiologic results associated with particle deposition in the lung.

A mathematical model that predicts skeletal muscle force.

This study demonstrates the validity of a mathematical model that predicts the force generated by rat skeletal muscles during brief subtetanic and tetanic isometric contractions. The model consists of three coupled differential equations (ODE's). The first two equations represent the calcium dynamics and the third equation represents force dynamics. The model parameters were identified from brief trains of regularly spaces pulses [constant-frequency trains (CFT's)] that produce subtetanic muscle responses. Using these parameters, the model was able to predict isometric forces from other stimulation patterns. For the gastrocnemius muscles predictions were made for responses to CFT's with interpulse intervals (IPI's) ranging from 10 to 50 ms and variable-frequency trains (VFT's), where the initial IPI = 10 ms and the remaining IPI's were identical to those used for the CFT's. For the soleus muscles predictions were made for 10-100-ms CFT's. The shape of the predicted responses closely match the experimental data. Comparisons between experimental and modeled force-time integrals, peak forces, and time-to-peak also suggest excellent agreement between the model and the experiment data. Many physiological parameters predicted by the model agree with values obtained independently by others. In conclusion, the model accurately predicts isometric forces generated by rat gastrocnemius and soleus muscles produced by brief stimulation trains.

Conservative treatment of cutis aplasia.

Three cases of cutis aplasia are presented. The defects involved include full-thickness defects of scalp and cranium as well as full-thickness skin defects of the abdomen and thigh. All patients were treated conservatively with the use of Silvadene cream dressings. Healing was obtained in all patients.

Comparison of balloon dacryocystoplasty to probing as the primary treatment of congenital nasolacrimal duct obstruction.

PURPOSE: In children older than 18 months, primary probing procedures for congenital nasolacrimal duct obstruction (CNLDO) are thought to have lower rates of success. This study compares the results of primary probing to balloon dacryocystoplasty (DCP) in children stratified by age category. METHODS: In a retrospective chart review, 29 eyes with CNLDO that underwent balloon DCP in children older than 18 months were identified and age-matched to 29 eyes that underwent probing. The eyes were divided into 3 age categories: category 1 (18-24 months), category 2 (24-36 months), and category 3 (>36 months). RESULTS: Of the 29 eyes treated with balloon DCP (mean age, 37.1 months), 26 were successfully treated. Twenty-five of the 29 matched probed eyes (mean age, 31.1 months) were successfully treated, resulting in an overall success rate of 90% for balloon DCP and 86% for primary probing. Within each age category, the success rate varied but did not show an advantage to balloon DCP. The presence of crusting and expressible discharge from the puncta during preoperative evaluation predicted a successful probing (OR, 16; 95% CI, 1.3-192). CONCLUSION: Overall, balloon DCP did not appear to present an advantage as compared with primary probing as the initial treatment in these children. Primary probing has an impressive overall success rate that did not diminish in the children older than 36 months.

In-situ biofilm characterization in membrane systems using Optical Coherence Tomography: formation, structure, detachment and impact of flux change.

Biofouling causes performance loss in spiral wound nanofiltration (NF) and reverse osmosis (RO) membrane operation for process and drinking water production. The development of biofilm formation, structure and detachment was studied in-situ, non-destructively with Optical Coherence Tomography (OCT) in direct relation with the hydraulic biofilm resistance and membrane performance parameters: transmembrane pressure drop (TMP) and feed-channel pressure drop (FCP). The objective was to evaluate the suitability of OCT for biofouling studies, applying a membrane biofouling test cell operated at constant crossflow velocity (0.1 m s(-1)) and permeate flux (20 L m(-2)h(-1)). In time, the biofilm thickness on the membrane increased continuously causing a decline in membrane performance. Local biofilm detachment was observed at the biofilm-membrane interface. A mature biofilm was subjected to permeate flux variation (20 to 60 to 20 L m(-2)h(-1)). An increase in permeate flux caused a decrease in biofilm thickness and an increase in biofilm resistance, indicating biofilm compaction. Restoring the original permeate flux did not completely restore the original biofilm parameters: After elevated flux operation the biofilm thickness was reduced to 75% and the hydraulic resistance increased to 116% of the original values. Therefore, after a temporarily permeate flux increase the impact of the biofilm on membrane performance was stronger. OCT imaging of the biofilm with increased permeate flux revealed that the biofilm became compacted, lost internal voids, and became more dense. Therefore, membrane performance losses were not only related to biofilm thickness but also to the internal biofilm structure, e.g. caused by changes in pressure. Optical Coherence Tomography proved to be a suitable tool for quantitative in-situ biofilm thickness and morphology studies which can be carried out non-destructively and in real-time in transparent membrane biofouling monitors.