Reduced Exposure Time Research Articles

Phase retrieval through a one-dimensional ptychographic engine.

Ptychographic techniques are currently the subject of increasing scientific interest due to their capability to retrieve the complex transmission function of an object at very high resolution. However, they impose a substantial burden in terms of acquisition time and dimension of the scanned area, which limits the range of samples that can be studied. We have developed a new method that combines the ptychographic approach in one direction with Fresnel propagation in the other by employing a strongly asymmetric probe. This enables scanning the sample in one direction only, substantially reducing exposure times while covering a large field of view. This approach sacrifices ptychographic-related resolution in one direction, but removes any limitation on the probe dimension in the direction orthogonal to the scanning, enabling the scan of relatively large objects without compromising exposure times.

Virtual edge illumination and one dimensional beam tracking for absorption, refraction, and scattering retrieval

We propose two different approaches to retrieve x-ray absorption, refraction, and scattering signals using a one dimensional scan and a high resolution detector. The first method can be easily implemented in existing procedures developed for edge illumination to retrieve absorption and refraction signals, giving comparable image quality while reducing exposure time and delivered dose. The second method tracks the variations of the beam intensity profile on the detector through a multi-Gaussian interpolation, allowing the additional retrieval of the scattering signal.

Effects of spatial coherence in diffraction phase microscopy

Quantitative phase imaging systems using white light illumination can exhibit lower noise figures than laser-based systems. However, they can also suffer from object-dependent artifacts, such as halos, which prevent accurate reconstruction of the surface topography. In this work, we show that white light diffraction phase microscopy using a standard halogen lamp can produce accurate height maps of even the most challenging structures provided that there is proper spatial filtering at: 1) the condenser to ensure adequate spatial coherence and 2) the output Fourier plane to produce a uniform reference beam. We explain that these object-dependent artifacts are a high-pass filtering phenomenon, establish design guidelines to reduce the artifacts, and then apply these guidelines to eliminate the halo effect. Since a spatially incoherent source requires significant spatial filtering, the irradiance is lower and proportionally longer exposure times are needed. To circumvent this tradeoff, we demonstrate that a supercontinuum laser, due to its high radiance, can provide accurate measurements with reduced exposure times, allowing for fast dynamic measurements.

Improving the Gas Barrier Property of Clay–Polymer Multilayer Thin Films Using Shorter Deposition Times

Relatively fast exposure times (5 s) to aqueous solutions were found to improve the gas barrier of clay-polymer thin films prepared using layer-by-layer (LbL) assembly. Contrary to the common belief about deposition time (i.e., the longer the better), oxygen transmission rates (OTRs) of these nano-brick-wall assemblies are improved by reducing exposure time (from 1 min to 5 s). Regardless of composition, LbL films fabricated using shorter deposition time are always thicker in the first few layers, which correspond to greater clay spacing and lower OTR. A quadlayer (QL) assembly consisting of three repeat units of branched polyethylenimine (PEI), poly(acrylic acid) (PAA), PEI and montmorillonite (MMT) clay is only 24 nm thick when deposited with 1 min exposure to each ingredient. Reducing the exposure time of polyelectrolytes to 5 s not only increases this film thickness to 55 nm but also reduces the oxygen transmission rate (OTR) to 0.05 cm3/(m2 day atm), which is 2 orders of magnitude lower than the same film made using 1 min exposures. A conceptual model is proposed to explain the differences in growth and barrier, which are linked to polyelectrolyte relaxation, desorption, and interdiffusion. The universality of these findings is further exemplified by depositing clays with varying aspect ratios. This ability to quickly deposit high-barrier nanocomposite thin films opens up a tremendous opportunity in terms of commercial-scale processing of LbL assemblies.

Non‐pathogenic aquatic bacteria activate the immune system and increase predation risk in damselfly larvae

SummaryPathogens can increase vulnerability to predation through their harmful effects on hosts. Recently, it was shown that the mere activation of the immune system by pathogens may increase the host's risk of predation. Here, we test whether exposure to non‐pathogenic bacteria also activates the immune system and thereby increases vulnerability to predation.We exposedEnallagma cyathigerumdamselfly larvae to a non‐pathogenic strain of the bacteriumEscherichia coliand measured immune defence, anti‐predator behaviour and survival times in the presence of larval dragonfly predators. To evaluate whether non‐pathogenic bacteria also generated energy‐based trade‐offs leading to other fitness costs, we also quantified growth rate and survival in the absence of predators.Exposure to the non‐pathogenic bacterium did not affect survival in the absence of the predator but increased growth rate, possibly a response to reduce exposure time to the bacterium. Larvae exposed to the bacterium activated their immune response as shown by an increase in the activity of phenoloxidase and the number of haemocytes. The bacterium affected anti‐predator traits involved in avoiding detection by predators as well as traits involved in escape after detection. Pre‐exposed larvae showed higher activity levels and further increased the number of feeding strikes in the presence of predation risk, possibly driven by energetic constraints. Pre‐exposed larvae swam less often when attacked, but faster. This impaired anti‐predator response came at the ecological cost of increased vulnerability to predation.Our study demonstrated that exposure to non‐pathogenic bacteria increases vulnerability to predation, which is a novel type of antagonistic interaction. This highlights the unexplored possibility that non‐pathogens may play a role in maintaining variation in immune defence through insidious effects on predator–prey interactions. Since non‐pathogenic bacteria can be very abundant, this unexplored ecological cost of immune system activation in terms of increased predation may have major consequences in natural systems and may provide an unexplored new force underlying variation in immune defence.

Prior exposure influences the behavioural avoidance by an intertidal gastropod, Bembicium auratum, of acidified waters

Phenotypic plasticity may be critical to the maintenance of viable populations under future environmental change. Here we examined the role of behavioural avoidance of sub-optimal conditions in enabling the intertidal gastropod, Bembicium auratum, to persist in mangrove forests affected by the low pH runoff from acid sulphate soils (ASS). Behaviourally, the gastropod may be able to avoid periods of particularly high acidity by using pneumatophores and/or mangrove trunks to vertically migrate above the water line or by retreating into its shell. We hypothesised that (1) B. auratum would display greater and more rapid vertical migration out of acidified than reference estuarine waters, and (2) responses would be more pronounced in gastropods collected from acidified than reference sites. Gastropods from acidified sites showed significantly higher activity in and more rapid migration out of acidified waters of pH 6.2–7.0, than reference waters or waters of pH < 5.0. Gastropods from reference locations showed a significantly weaker response to acidified water than those from acidified waters, and which did not significantly differ from their response to reference water. At extremely low pHs, <5.0, a higher proportion of both acidified and reference gastropods retreated into their shell than at higher pHs. Both the migration of gastropods out of acidified waters and retraction into their shells serves to reduce exposure time to acidified waters and may reduce the impact of this stressor on their populations. The stronger response to acidification of gastropods from populations previously exposed to this stressor suggests that the response may be learned, inherited or induced over multiple exposures. Our study adds to growing evidence that estuarine organisms may exhibit considerable physiological and behaviour adaptive capacity to acidification. The potential for such adaptive capacity should be incorporated into studies seeking to forecast impacts to marine organisms of environmental change.

Effect of short LED lamp exposure on wear resistance, residual monomer and degree of conversion for Filtek Z250 and Tetric EvoCeram composites

ObjectivesThe latest LED dental curing devices claim sufficient curing of restorative materials with short curing times. This study evaluates mechanical and chemical properties as a function of curing time of two commercial composite filling materials cured with three different LED lamps. MethodsThe composites were Filtek Z250 (3M ESPE) and Tetric EvoCeram (Ivoclar Vivadent) and the LED curing devices were bluephase 16i (Ivoclar Vivadent), L.E.Demetron II (Kerr) and Mini L.E.D. (Satelec). Control samples were cured with a QTH-lamp (VCL 400, Kerr). The wear resistance after simulated tooth brushing, degree of conversion, curing depth, and amounts of residual monomers were measured after different curing times. ResultsThe results of this study show that short curing time with high-intensity LEDs may influence the bulk properties of the materials, resulting in lower curing depth and increased residual monomer content. The measured surface properties of the materials, degree of conversion and wear resistance, were not affected by short curing times to the same extent. SignificanceThis study demonstrates that reduced exposure time with high intensity LEDs can result in composite restorations with inferior curing depth and increased leaching of monomers. Dentists are recommended to use sufficient curing times even with high intensity LEDs to ensure adequate curing and minimize the risk of monomer leaching.

Pulsed electron holography

A technique of pulsed low-energy electron holography is introduced, which allows for recording highly resolved holograms within reduced exposure times. Therefore, stacks of holograms are accumulated in a pulsed mode with individual acquisition times as short as 50 μs. Subsequently, these holograms are aligned and finally superimposed. The resulting holographic record reveals previously latent high-order interference fringes and thereby pushing interference resolution into the sub-nanometer regime. In view of the non-damaging character of low-energy electrons, the method is of particular interest for structural analysis of fragile biomolecules.

Disinfection and sterilization: An overview

All invasive procedures involve contact by a medical device or surgical instrument with a patient's sterile tissue or mucous membranes. The level of disinfection or sterilization is dependent on the intended use of the object: critical (items that contact sterile tissue such as surgical instruments), semicritical (items that contact mucous membrane such as endoscopes), and noncritical (devices that contact only intact skin such as stethoscopes) items require sterilization, high-level disinfection, and low-level disinfection, respectively. Cleaning must always precede high-level disinfection and sterilization.

Time-resolved X-ray PIV technique for diagnosing opaque biofluid flow with insufficient X-ray fluxes

X-ray imaging is used to visualize the biofluid flow phenomena in a nondestructive manner. A technique currently used for quantitative visualization is X-ray particle image velocimetry (PIV). Although this technique provides a high spatial resolution (less than 10 µm), significant hemodynamic parameters are difficult to obtain under actual physiological conditions because of the limited temporal resolution of the technique, which in turn is due to the relatively long exposure time (~10 ms) involved in X-ray imaging. This study combines an image intensifier with a high-speed camera to reduce exposure time, thereby improving temporal resolution. The image intensifier amplifies light flux by emitting secondary electrons in the micro-channel plate. The increased incident light flux greatly reduces the exposure time (below 200 µs). The proposed X-ray PIV system was applied to high-speed blood flows in a tube, and the velocity field information was successfully obtained. The time-resolved X-ray PIV system can be employed to investigate blood flows at beamlines with insufficient X-ray fluxes under specific physiological conditions. This method facilitates understanding of the basic hemodynamic characteristics and pathological mechanism of cardiovascular diseases.

Sleeping Bubbles: Effects of Volatile Anesthetics in the Lateral Structure of Giant Unilamellar Vesicles

Volatile anesthetics have been widely used for more than 170 years. However, the mechanisms underlying the effects of anesthetics on membrane dynamics and structure are still under debate. Herein we study this problem for first time using fluorescence confocal microscopy experiments of giant Unilamellar Vesicles (GUVs). This approach allows obtaining spatially resolved information on membrane structure at a microscopic level.GUVs were prepared using DLPC/DPPC 3:7 mol. This mixture showed a characteristic gel (Lbeta)/liquid disordered (Lalfa) phase coexistence at room temperature, with line-shape domains (Lbeta) of variable width depending on the temperature[1]. The volatile anesthetic used was Sevoflurane. The administration strategies were two: high concentration with reduced exposure time; or low concentration (clinically relevant) with long term exposition.A dramatic alteration of the phase coexistence was observed, with a marked effect on the morphology of the gel phase domains. For the experiments with high anesthetic concentration, the boundaries of the domains became diffuse with an increment of the domain's perimeter/area ratio. When low anesthetic concentrations were used, a complete loss of the domains structure was observed with appearance of small circular shaped domains.Sevoflurane dramatically affected the lateral structure of the studied membranes, suggesting that similar mechanisms may occur in biological relevant membranes. Particularly, at low concentration of the anesthetic our results show some structural characteristic to that observed for cholesterol in canonical raft ternary lipid mixtures (formation of round domains). More research is underway to better understand the mechanisms underlying the sevoflurane effects on membranes.[1] L.A. Bagatolli and E. Gratton. 2000, Biophys J. 78:290-305.

Metformin Based Dual-Combination Therapies in Drug Naïve Type 2 Diabetic Patients

Metformin Based Dual-Combination Therapies in Drug Naïve Type 2 Diabetic Patients

A SiPM-based TOF-PET detector with high speed digital DRS4 readout

We have developed γ-ray detectors with good time resolution, to supplement positron emission tomography (PET) with time of flight (TOF) for better localization of the positron annihilation. This will improve the quality of medical images and reduce exposure times. We report results of LYSO scintillating crystals (3×3×15mm3) irradiated with a 22Na source and coupled to silicon photomultipliers (SiPMs) readout with a waveform digitizer. Improved time resolution, 188ps FWHM, was obtained with the signal trimmed by a clipping capacitance.

The Study of X-ray Lithography Using the DNQ-Novolak Type Photoresist

As a result of the rapid development of lithography, it enables semiconductor technology to design more devices in the same area, which therefore makes electronic products faster, more functional, and hold more components. The photoresist, playing an important role in lithography, constantly develops with a light wavelength used for exposure from early entire wavelengths to present optical and non-optical lithography. The light sources of optical lithography have moved from the early 436nm and 365nm wavelength to short-wavelength light gradually. It is a big issue to find a suitable photoresist under the exposure of 0.578nm X-Ray light source. In this paper we first proposed to use DNQ / Novolak photoresist sold in the market for the 0.578nm X-Ray lithography. In the experiment, it is discovered that the exposure amount of X-Ray can determine if the photoresist is positive or negative; in low doses, when the photoresist film thickness is increased with the reduced exposure time, and a critical level is reached, the Novolak liquid will become positive photoresist after it is exposed in certain time. The high-dose X-Ray beam will make Novolak resin bond break and result in free radicals, which, through resin crosslinking, can improve the internal strength, and reduce developer solubility so the Novolak liquid can become a negative photoresist. By using synthesized DNQ / Novolak photoresist under X-Ray exposure, we can reduce the process line width, and explore principles of photoresist imaging analysis under the different exposure doses.

Outrunning free radicals in room-temperature macromolecular crystallography.

A significant increase in the lifetime of room-temperature macromolecular crystals is reported through the use of a high-brilliance X-ray beam, reduced exposure times and a fast-readout detector. This is attributed to the ability to collect diffraction data before hydroxyl radicals can propagate through the crystal, fatally disrupting the lattice. Hydroxyl radicals are shown to be trapped in amorphous solutions at 100 K. The trend in crystal lifetime was observed in crystals of a soluble protein (immunoglobulin γ Fc receptor IIIa), a virus (bovine enterovirus serotype 2) and a membrane protein (human A(2A) adenosine G-protein coupled receptor). The observation of a similar effect in all three systems provides clear evidence for a common optimal strategy for room-temperature data collection and will inform the design of future synchrotron beamlines and detectors for macromolecular crystallography.

Greater costs of inducible behavioural defences at cooler temperatures in larvae of the mosquito, Aedes notoscriptus

The evolutionary maintenance of inducible defences is governed by the costs and benefits of the defensive traits. The defensive traits should increase the chances of survival in the presence of predators, but be costly in their absence. The costs and benefits of inducible defensive traits can be influenced by environmental conditions, which subsequently affect the ability of prey to induce those defensive traits. We examine how temperature affects the costs of behavioural defences in larval mosquitoes, Aedes notoscriptus, which reduce activity in the presence of predator cues to limit detectability. The costs of reducing activity could either be exacerbated at warmer temperatures via increased metabolic demand, or ameliorated at warmer temperatures via accelerated development reducing exposure time. We compared life history traits of A. notoscriptus reared in control conditions to those exposed to predation cues as larvae at 18, 23 and 28 °C. Larvae reared in predation cues reduced activity, grew and developed slower and emerged later and smaller. While the reduction in activity increased with temperature, the negative effects on life history of A. notoscriptus were greatest at the coolest temperature. Our results show that the costs of inducible defences in A. notoscriptus are temperature dependent. This work suggests that variation in the thermal environment may have a strong influence on the dynamics of predator–prey interactions and the evolutionary maintenance of plasticity of defensive traits in natural populations.

X-ray phase contrast for CO2 microangiography

We demonstrate a laboratory method for imaging small blood vessels using x-ray propagation-based phase-contrast imaging and carbon dioxide (CO2) gas as a contrast agent. The limited radiation dose in combination with CO2 being clinically acceptable makes the method promising for small-diameter vascular visualization. We investigate the possibilities and limitations of the method for small-animal angiography and compare it with conventional absorption-based x-ray angiography. Photon noise in absorption-contrast imaging prevents visualization of blood vessels narrower than 50 µm at the highest radiation doses compatible with living animals, whereas our simulations and experiments indicate the possibility of visualizing 20 µm vessels at radiation doses as low as 100 mGy. Experimental computed tomography of excised rat kidney shows blood vessels of diameters down to 60 µm with improved image quality compared to absorption-based methods. With our present prototype x-ray source, the acquisition time for a tomographic dataset is approximately 1 h, which is long compared to the 1–20 min common for absorption-contrast micro-CT systems. Further development of the liquid-metal-jet microfocus x-ray sources used here and high-resolution x-ray detectors shows promise to reduce exposure times and make this high-resolution method practical for imaging of living animals.

Depth of cure and hardness of indirect composite materials polymerized with two metal halide laboratory curing units

The purpose of this study was to evaluate the depth of cure and Knoop hardness of indirect composite materials polymerized with different laboratory curing units. Five composite materials designed for fixed restoration veneer (Artglass, Ceramage, Epricord, Prossimo, and Solidex) were filled into a cylindrical mold and then light-exposed by using the respective proprietary laboratory curing unit or two metal halide curing units (Hyper LII and Twinkle X). Depth of cure was determined by a scraping technique, as described in ISO 4049. Composites also underwent Knoop hardness testing after immersion in water. The results (n = 5) were analyzed with the Kruskal-Wallis test and Dunn's multiple comparison test. For three materials (Prossimo, Artglass, and Epricord), depth of cure after polymerization with the Twinkle X unit was greater than that after polymerization with the respective proprietary units. For the Ceramage and Artglass materials, the Twinkle X unit resulted in the highest Knoop hardness number (KHN), whereas, for the Prossimo material, the Hyper LII unit resulted in the highest KHN. The metal halide units were effective in enhancing the post-polymerization properties of specific composite materials while reducing exposure time.

Modified cytotoxicity evaluation of elastomeric impression materials while polymerizing with reduced exposure time

Objective. Cytotoxicity evaluation is an important step in biocompatibility assessment of dental impression materials. Previously, cytotoxicity evaluations were carried out on already set (‘set’) impression materials for contact time or extraction time of 24 h or longer in duration. However, clinically, dental impression materials are in contact with oral tissue while they are being set (‘polymerizing’), for no longer than 10 min. Hence, the aim of this study was to investigate the difference in results between ‘polymerizing’ and ‘set’ forms of impression materials as well as the difference in results between longer duration of contact or extraction time (12 or 24 h) and shorter duration of time (15 or 30 min). Materials and methods. Seven dental impression materials of different chemical compositions were tested. Two commonly used in vitro tests were used—test on extraction and test by direct contact. Both ‘polymerizing’ and ‘set’ forms of impression materials were used with different durations of extraction and contact (15 min, 30 min, 12 h and 24 h). Results. There were significant (p < 0.05) differences of cell viability and cell proliferation between the ‘polymerizing’ and ‘set’ impression materials. Also, significant (p < 0.05) differences were noted with variance in duration of time. Conclusion. In light of the results, it is recommended to use a ‘polymerizing’ state of dental impression material for cytotoxicity evaluation, with 15 or 30 min of contact between cell and dental impression materials and an extraction time of 15 or 30 min that is more reflective of clinical situations.

The clinical safety of dual axis rotational angiography in the diagnosis of coronary artery disease

Objective To observe the clinical safety of dual axis rotational coronary angiography (DARCA) in the diagnosis of coronary artery disease in Chinese population.Methods From March to December in 2010,74 patients undergoing diagnostic DARCA were enrolled.The improved isocentering technique was adopted in 34 of the patients at the end of the study during DARCA.Blood pressure,heart rate and symptoms were recorded immediately before-and-after contrast injections.Contrast dose,radiation exposure and procedure time for DARCA were recorded.Continuous variable data were analyzed using Student＇s t test,if normality assumption was violated,rank sum test would be used.Categorical variables were analyzed using x2 test.Results ( 1 ) Clinical safety:There was no chest pain documented during or immediately post-injection for all patients.Only 1 patient ( 1 ％ ) had an attack of ventricular tachycardia immediately after the contrast injection and then relieved automatically.Pre and post-injection systolic blood pressure values of left coronary artery were statistically different [ ( 116 ± 20 ) mm Hg vs.( 111 + 18) mm Hg( 1 mm Hg =0.133 kPa),t =3.303,P =0.001 ],and heart rates differed,too [ 73 ( 65- 84)bpm vs.71(64-78) bpm,Z =-4.789,P =0.001 ],but that imposed no clinical significance.(2)Contrast dose,radiation dose and procedure time:The mean contrast utilization,radiation dose and procedure time for DARCA were 28 (25-34) ml,8979 ( 6733-12 363 ) mGycm2 and 200 (164-270) s.Compared with conventional DARCA,improved isocentering technique during DARCA had less radiation exposure and procedure time in left coronary artery angiography and the whole coronary artery angiography [ left coronary artery angiographic radiation exposure:4004 (2932-5772) mGycm2 vs.5808 (4798- 8838) mGycm2,Z =-3.471,P =0.001 ;total radiation exposure:(8116 +2493) mGycm2 vs.( 11 371 ±4122) mGycm2,t =-4.176,P =0.001 ; left coronary artery angiographic procedure time:120 ( 80-180)s vs.150(126-214) s,Z =- 2.836,P =0.005; total procedure time:180 (139-240) s vs.220( 186-308 )s,Z =-3.004,P =0.003 ],but there was no statistically difference in contrast utilization [30(25-35) ml vs.27(25-34)ml,Z=-0.906,P=0.365].Conclusion This study demonstrates clinical safety of DARCA in the diagnosis of coronary artery disease in Chinese population.Compared with conventional isocentering technique of DARCA,improved isocentering technique can significantly reduce radiation exposure and procedure time on the basis of simplified operation,and replace the conventional isocentering technique,but randomized double-blind controlled studies should be conducted. Key words: Coronary angiography; Rotation