Concept: The Chamber
We evaluated the influence of impurities in the vacuum chamber used for the fabrication of organic light-emitting diodes on the lifetime of the fabricated devices and found a correlation between lifetime and the device fabrication time. The contact angle of the ITO substrates stored the chamber under vacuum were used to evaluate chamber cleanliness. Liquid chromatography-mass spectrometry was performed on Si wafers stored in the vacuum chamber before device fabrication to examine the impurities in the chamber. Surprisingly, despite the chamber and evaporation sources being at room temperature, a variety of materials were detected, including previously deposited materials and plasticizers from the vacuum chamber components. We show that the impurities, and not differences in water content, in the chamber were the source of lifetime variations even when the duration of exposure to impurities only varied before and after deposition of the emitter layer. These results suggest that the impurities floating in the vacuum chamber significantly impact lifetime values and reproducibility.
Focal atrial tachycardias arise preferentially from specific locations within the atria. Careful analysis of the P wave can provide useful information about the chamber and likely site of origin within that chamber. Macro-reentrant atrial flutter also tends to occur over a limited number of potential circuits. In this case, the ECG usually gives a guide to the chamber of origin, but unless it shows a specific morphology it is less useful in delineating the circuit involved. Nonetheless, prior knowledge of the likely chamber of origin helps to plan the ablation strategy.
In order to determine the effects on foraminifera due to spilled crude oil in the “Herbei Spirit” incident, a study of benthic foraminiferal assemblages was carried out on sediment samples collected from the Sogeunri tidal flat, Taean Peninsula, Korea. Breakages of the chambers in the Ammonia beccarii and Elphidium subincertum species of the Sogeunri tidal flat with a low pH (6.98 on average) were marked. These chamber breakages occurred in 71.6% of A. beccarii and are thought to be caused by decalcification due to the fall in pH resulting from the “Hebei Spirit” oil spill. The factors that affect breakage of the chamber in benthic foraminifera under low pH condition may be not only deto decalcification but also to exposure duration of substrata in the tidal flat spilled crude oil.
Flow-through respirometry systems provide accurate measurement of gas exchange over long periods of time. However, these systems have limitations in tracking rapid changes. When an animal infuses a metabolic gas into the respirometry chamber in a short burst, diffusion and airflow in the chamber gradually alter the original signal before it arrives at the gas analyzer. For single or multiple bursts, the recorded signal is smeared or mixed, which may result in dramatically altered recordings compared to the emitted signal. Recovering the original metabolic signal is a difficult task because of the inherent ill conditioning problem. Here, we present two new methods to recover the fast dynamics of metabolic patterns from recorded data. We first re-derive the equations of the well-known Z-transform method (ZT method) to show the source of imprecision in this method. Then, we develop a new model of analysis for respirometry systems based on the experimentally determined impulse response, which is the response of the system to a very short unit input. As a result, we present a major modification of the ZT method (dubbed the ‘EZT method’) by using a new model for the impulse response, enhancing its precision to recover the true metabolic signals. The second method, the generalized Z-transform (GZT) method, was then developed by generalizing the EZT method; it can be applied to any flow-through respirometry system with any arbitrary impulse response. Experiments verified that the accuracy of recovering the true metabolic signals is significantly improved by the new methods. These new methods can be used more broadly for input estimation in variety of physiological systems.
The current study aims to elucidate in greater detail the dermal uptake of nicotine from air or from nicotine-exposed clothes, which was demonstrated recently in a preliminary study. Six non-smoking participants were exposed to gaseous nicotine (between 236 and 304 μg/m(3) ) over 5 h while breathing clean air through a hood. Four of the participants wore only shorts and two wore a set of clean clothes. One week later, two of the bare-skinned participants were again exposed in the chamber, but they showered immediately after exposure instead of the following morning. The two participants who wore clean clothes on week one, were now exposed wearing a set of clothes that had been exposed to nicotine. All urine was collected for 84 h after exposure and analysed for nicotine and its metabolites cotinine and 3OH-cotinine. All participants except those wearing fresh clothes excreted substantial amounts of biomarkers, comparable to levels expected from inhalation intake. Uptake for one participant wearing exposed clothes exceeded estimated intake via inhalation by >50%. Excretion continued during the entire urine collection period, indicating that nicotine accumulates in the skin and is released over several days. Absorbed nicotine was significantly lower after showering in one subject, but not the other. Differences in the normalized uptakes and in the excretion patterns were observed among the participants. The observed cotinine half-lives suggest that non-smokers exposed to airborne nicotine may receive a substantial fraction through the dermal pathway. Washing skin and clothes exposed to nicotine may meaningfully decrease exposure. This article is protected by copyright. All rights reserved.
- Proceedings of the National Academy of Sciences of the United States of America
- Published almost 5 years ago
A lost navigator must identify its current location and recover its facing direction to restore its bearings. We tested the idea that these two tasks-place recognition and heading retrieval-might be mediated by distinct cognitive systems in mice. Previous work has shown that numerous species, including young children and rodents, use the geometric shape of local space to regain their sense of direction after disorientation, often ignoring nongeometric cues even when they are informative. Notably, these experiments have almost always been performed in single-chamber environments in which there is no ambiguity about place identity. We examined the navigational behavior of mice in a two-chamber paradigm in which animals had to both recognize the chamber in which they were located (place recognition) and recover their facing direction within that chamber (heading retrieval). In two experiments, we found that mice used nongeometric features for place recognition, but simultaneously failed to use these same features for heading retrieval, instead relying exclusively on spatial geometry. These results suggest the existence of separate systems for place recognition and heading retrieval in mice that are differentially sensitive to geometric and nongeometric cues. We speculate that a similar cognitive architecture may underlie human navigational behavior.
The midsession reversal task has been used to investigate behavioral flexibility and cue use in non-human animals, with results indicating differences in the degree of control by environmental cues across species. For example, time-based control has been found in rats only when tested in a T-maze apparatus and under specific conditions in which position and orientation (i.e., egocentric) cues during the intertrial interval could not be used to aid performance. Other research in an operant setting has shown that rats often produce minimal errors around the reversal location, demonstrating response patterns similar to patterns exhibited by humans and primates in this task. The current study aimed to reduce, but not eliminate, the ability for rats to utilize egocentric cues by placing the response levers on the opposite wall of the chamber in relation to the pellet dispenser. Results showed that rats made minimal errors prior to the reversal, suggesting time-based cues were not controlling responses, and that they switched to the second correct stimulus within a few trials after the reversal event. Video recordings also revealed highly structured patterns of behavior by the majority of rats, which often differed depending on which response was reinforced. We interpret these findings as evidence that rats are adept at utilizing their own egocentric cues and that these cues, along with memory for the recent response-reinforcement contingencies, aid in maximizing reinforcement over the session.
Evaluation of nanoparticle emissions from a laser printer in an experimental chamber and estimation of the human particle dose
- Environmental science and pollution research international
- Published almost 2 years ago
The aim of this study was to evaluate the nanoparticle emissions from a laser printer in a chamber in conjunction with emissions from printers in a print room (PR) and to characterize the processes that lead to increased nanoparticle concentrations, as well as to estimate the human particle dose of the printers' users. Measurements were conducted in a small stainless steel environmental chamber under controlled conditions, where the evolution of particle size distributions (PSDs) with time and printed pages was studied in detail. Printer was generating nanoparticles (vast majority ˂ 50 nm with mode on ~ 15 nm) primarily during cold startup. Previously, 1-week sampling was also done in a PR at the Technical University of Crete, where the tested laser printer is installed along with three other printers. Similarly, as it was observed in the chamber study, printers' startup on any given day was characterized by a sharp increase in particle number (PN) concentrations. Average measured PN concentrations during printing hours in PR (5.4 × 103#/cm3) is similar to the one observed in chamber measurements (6.7 × 103#/cm3). The ExDoM2 dosimetry model was further applied to calculate the deposition of particles in the human respiratory tract. More precisely, the increase in particle dose for an adult Caucasian male was 14.6- and 24.1-fold at printers' startup, and 1.2- and 5.2-fold during printing in the PR and experimental chamber, respectively, compared to the exposure dose at background concentrations (BCs).
Technologies that efficiently integrate the sampling and sample preparation steps with direct introduction to mass spectrometry (MS), providing simple and sensitive analytical workflows as well as capabilities for automation, can generate a great impact in a vast variety of fields, such as in clinical, environmental, and food-science applications. In this study, a novel approach that facilitates direct coupling of Bio-SPME devices to MS using a microfluidic design is presented. This technology, named microfluidic open interface (MOI), which operates under the concept of flow-isolated desorption volume, consists of an open-to-ambient desorption chamber (V ≤ 7 μL) connected to an ionization source. Subsequently, compounds of interest are transported to the ionization source by means of the self-aspiration process intrinsic of these interfaces. Thus, any ionization technology that provides a reliable and constant suction, such as electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), or inductively coupled plasma ionization (ICP), can be hyphenated to MOI. Using this setup, the desorption chamber is used to release target compounds from the coating, while the isolation of the flow enables the ionization source to be continuously fed with solvent, all without the necessity of employment of additional valves. As a proof of concept, the design was applied to an ESI-MS/MS system for experimental validation. Furthermore, numerical simulations were undertaken to provide a detailed understanding of the fluid flow pattern inside the interface, then used to optimize the system for better efficiency. The analytical workflow of the developed Bio-SPME-MOI-MS setup consists of the direct immersion of SPME fibers into the matrix to extract/enrich analytes of interest within a short period of time, followed by a rinsing step with water to remove potentially adhering proteins, salts, and/or other interfering compounds. Next, the fiber is inserted into the MOI for desorption of compounds of interest. Finally, the volume contained in the chamber is drained and moved toward the electrospray needle for ionization and direct introduction to MS. Aiming to validate the technology, the fast determination of selected immunosuppressive drugs (e.g., tacrolimus, cyclosporine, sirolimus, and everolimus) from 100 μL of whole blood was assessed. Limits of quantitation in the subppb range were obtained for all studied compounds. Good linearity (r2 ≥ 0.99) and excellent precision, with (8%) and without (14%) internal standard correction, were attained.
The U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) guidance encourages jerky processors to use a single lethality step that will achieve a 5-log reduction of Salmonella. Many processors rely on internal temperature-time combinations recommended in this guidance. However, the efficacy of convective heating is highly dependent on relative humidity (RH). RH recommendations are vague because of variability in processing conditions and limited available data. This study was conducted to establish processing conditions for an entry-level commercial dehydrator (Harvest Saver R5A) to achieve a 5-log reduction of Salmonella. Unseasoned, unmarinated top round beef strips (65 mm thick) were inoculated with Salmonella (>7 log CFU/g) and processed with the chamber temperature set to 82.2°C for a total cook time of 60 min with the intake closed (closed oven). Modifications (product load and fan speed) were made in subsequent trials to improve lethality. After incubation at 37°C for 24 to 48 h, surviving Salmonella populations were enumerated on tryptic soy agar. In trial A, the maximum fan speed (2.5 m/s) with 30 kg of product resulted in 45 to 48.5% RH at 60 min, and a 5-log reduction of Salmonella was achieved in only 35.5% of the meat samples (54 of 152 samples). Increasing the product load by 40% (42 kg; trial B) increased RH in the chamber (57 to 85%) and resulted in improved lethality; a 5-log reduction was achieved in 95.0% of samples (131 of 138 samples). Because samples with reduced lethality were located on the windward side of the chamber, the fan speed was reduced (0.9 m/s; trial C1) to increase the RH, resulting in a 5-log reduction in 100% of the samples (138 of 138 samples). A replicate trial (trial C2) was conducted, and a 5-log reduction again was achieved in 100% of the samples. All trials exceeded recommendations by the FSIS; however, adequate Salmonella reduction was achieved only when the RH was >65% throughout. Product load and fan speed are practical parameters for processors to manipulate to increase the RH in closed systems and thus improve Salmonella lethality.