Probe Distance Research Articles

Controlling radiolysis chemistry on the nanoscale in liquid cell scanning transmission electron microscopy.

When high-energy electrons from a scanning transmission electron microscope (STEM) are incident on a liquid, the vast majority of the chemical reactions that are observed are induced by the radiolysis breakdown of the liquid molecules. In the study of liquids, the radiolysis products of pure water are well known, and their rate of formation for a given flux of high-energy electrons has been studied intensively over the last few years for uniform TEM illumination. In this paper, we demonstrate that the temporal and spatial distribution of the electron illumination can significantly affect the final density of radiolysis products in water and even change the type of reaction taking place. We simulate the complex array of possible spatial/temporal distributions of electrons that are accessible experimentally by controlling the size, the scan rate and the hopping distance of the electron probe in STEM mode and then compare the results to the uniformly illuminated TEM mode of imaging. By distributing the electron dose both spatially and temporally in the STEM through a randomised "spot-scan" mode of imaging, the diffusion overlap of the radiolysis products can be reduced, and the resulting reactions can be more readily controlled. This control allows the resolution of the images to be separated from the speed of the induced reaction (which is based on beam current alone) and this facet of the experiment will allow a wide range of chemical reactions to be uniquely tailored and observed in all liquid cell STEM experiments.

Modeling and control of probe distance, substrate and probe of AFM using AFSMC in the presence of disturbances

Controlling the motion and its associated parameters is among the most important topics in the field of manipulation and displacement of nanoparticles. Accordingly, this article considers the control of nanomanipulation process in three general areas: 1) the distance between probe and surface, 2) the substrate, and 3) the probe of atomic force microscope (AFM). This study benefits from the adaptive fuzzy sliding-mode (AFSMC) control technique. Moreover, elliptical and cubic geometries are utilized. The results for the control of probe distance from substrate show that the system attains the acceptable value of 50 nm after 0.8 s. The desired output for the derivative of distance is fulfilled after 0.07 s. The results for the control of substrate in the horizontal direction show that for different values of λ, the desired value is obtained in different manners. The comparison between the results of this study and previous researches using the sliding mode control and proportional-integral-derivative method indicates the accuracy of the proposed method. The simulation results of the control of atomic force microscope probe for elliptical and cubic geometries demonstrate that the deviation of probe for these two geometries reaches its desired value in less than 0.04 s. However, the main difference is observed when investigating the position of atomic force microscope probe; the elliptical nanoparticle with an average radius of 75 nm has a delay of around 0.02 s for reaching the desired value compared with the cubic nanoparticle with a side length of 75 nm. In addition, the overshoot of elliptical geometry is more than that of cubic case. Finally, motion tracking along a specific path is simulated. In addition, trajectory assessment is realized on an actual experimental surface.

The extent of center-surround inhibition for colored items in working memory.

Remembering a color suppresses the representations of similar colors, but not of distinct colors, producing a center-surround inhibition (CSI) to resolve the competition between similar colors. In this study, three probe experiments were conducted to investigate the extent of CSI for colored items in working memory (WM). In Experiments 1 and 2, two WM items (distance 0°, 20°, 40°, or 60° in color space) were presented sequentially, one of which was cued to compare with the probe (matched or non-matched). The probe distance between the non-matched probe (NP) and cued WM item was 30° in Experiment 1 and 30°, 60°, or 90° in Experiment 2. Results for matched probe (MP) revealed that two WM items might produce a maximal CSI at distance 20°, and fall outside each other's inhibitory surround at distance 40°. However, the CSI was not found in the NP conditions (i.e., distance 30°, 60°, or 90°) in both Experiments 1 and 2, suggesting that the NP might be unsuitable for investigating the CSI in WM. In Experiment 3, participants were asked to discriminate which WM item was matched with the probe (no NP conditions). RTs were slowest at distance 20°, but were almost equal across distance 30°, 40°, 50°, or 60°. These results demonstrated that two WM items might produce a maximal CSI at distance 20°, and begin to fall outside each other's inhibitory surround at distance 30°.

Cerebrovascular Responses to Graded Exercise Between Young Healthy Men and Women

BackgroundDysfunctional cerebrovascular control is closely linked to the increased incidence of cerebrovascular and neurodegenerative diseases (e.g. small vessel occlusion, dementia and Alzheimer’s). Epidemiological evidence identifies sex‐specific differences in the course of prevention (risk factor) and treatment (prognosis) of cerebrovascular and brain diseases. Therefore, examining sex differences in cerebral blood flow (CBF) regulation is essential. Exercise provides a unique metabolic environment which influences systemic and CBF responses. Despite previous studies identifying muscle blood flow sex discrepancies to both handgrip and knee extensor exercise, CBF responses during exercise in women are underrepresented in the literature. Therefore, it remains unclear if sex differences in cerebrovascular control to exercise exists.PurposeTo compare CBF and cerebrovascular conductance index (CVCi) over a range of exercise intensities between men (MN) and women (WN).Methods24 young healthy adults (12 WN, 24.0±3.6 yrs) completed a graded‐exercise‐test (GXT, stage length 3‐min, 50W, 75W, 100W; after which MN increases by 40W, WN increased by 30W maintaining 60–80 RPM) on a recumbent cycle ergometer to volitional exhaustion. The highest completed stage was determined as Maximal Wattage (Wmax). Middle cerebral artery velocity (MCAv; transcranial Doppler ultrasound) and mean arterial pressure (MAP; finger photoplethysmography, CPP was calculated MAP – [0.7355* vertical distance of TCD probe from heart‐level]), were measured on a beat‐by‐beat basis to calculate CVCi = MCAv/CPP*100mmHg.ResultsMean ± SD, effect size using Ω2. MN and WN exhibited similar MCAv responses to changes in exercise intensity where peak MCAv was obtained ~ 60% Wmax (ΔMCAv, WN = 17.9 ± 3.6, MN = 16.0 ±7.01 cm/s, p = 0.4) and declined as intensity increased. There was a trend for WN to have a greater ΔMCAv with increasing relative exercise intensity (p = 0.05, Ω2 = 0.02) with the greatest difference between WN and MN observed at 100%Wmax (ΔMCAv, WN= 10.7±2.2, MN= 5.5± 1.3cm/s, p<0.01). Interestingly, MN had a greater exercise cerebral prefusion pressor response with increasing exercise intensity (p < 0.01, Ω2 = 0.05) with the largest difference being observed at 100% Wmax (ΔCPP, WN 37.7 ± 3.0, MN 47.3 ± 5.6 mmHg, p < 0.01). However, these differences did not compute into differences in ΔCVCi between the sexes over any exercise intensity (p = 0.8, Ω2 = 0.0).ConclusionsOur data suggest cerebrovascular responses to exercise are similar between sexes. However, the small effect sizes in MCAv and differences in ΔCPP indicate the study may be underpowered to detect differences in cerebrovascular control during high intensity exercise. Therefore, we conclude men and women have similar cerebrovascular responses during low to moderate exercise. However, further research into cerebrovascular and exercise pressor responses during high intensity exercise are warranted as our data remain inconclusive and literature has identified exercise sex differences in systemic and non‐cerebral peripheral circulations.

Subfemtometer scale color charge correlations in the proton

Color charge correlations in the proton at moderately small $x\sim 0.1$ are extracted from its light-cone wave function. The charge fluctuations are far from Gaussian and they exhibit interesting dependence on impact parameter and on the relative transverse momentum (or distance) of the gluon probes. We provide initial conditions for small-$x$ Balitsky-Kovchegov evolution of the dipole scattering amplitude with impact parameter and $\hat r \cdot \hat b$ dependence, and with non-zero $C$-odd component due to three-gluon exchange. Lastly, we compute the (forward) Weizsaecker-Williams gluon distributions, including the distribution of linearly polarized gluons, up to fourth order in $A^+$. The correction due to the quartic correlator provides a transverse momentum scale, $q > 0.5$ GeV, for nearly maximal polarization.

Efficacy of regenerative therapy in aggressive periodontitis: a systematic review and meta-analysis of randomised controlled clinical trials.

To analyse evidence regarding the efficacy of periodontal regenerative procedures in intrabony defects in patients treated for aggressive periodontitis (AgP). A systematic search of the literature for randomised controlled clinical trials including patients treated for aggressive periodontitis that compared a group treated with regenerative therapy with another group treated with surgical debridement alone was conducted by two independent reviewers. Six studies were included in the meta-analysis of clinical and/or radiographic parameters at 6 and 12months. Probing pocket depth was smaller at 6months in patients treated with regenerative therapies compared with those treated with regular debridement (1.00mm, p < 0.001, 95% CI (0.67, 1.34)). At 12months this difference was more marked (0.41mm, p = 0.12, 95% CI (- 0.10, 0.91)). The distance between the cemento-enamel junction and the alveolar crest at both 6 (1.36mm, p < 0.001, 95% CI (1.03, 1.68)) and 12months (0.90mm, p = 0.01, 95% CI (0.24, 1.56)) was smaller in the group treated with regeneration. The use of biomaterials for regenerative therapy in AgP may be more effective than surgical debridement. Better outcomes were observed in terms of probing pocket depth and distance between the cemento-enamel junction and the alveolar crest at 6months. Regeneration should be considered as a therapy to prevent tooth loss, although more studies with larger sample size and longer follow-up are needed. Periodontal regeneration is effective in the treatment of intrabony defects in patients with AgP, as it leads to better outcomes in clinical and radiographic parameters.

Determination of the spatial impulse response of compensating electrostatic voltmeters

The accumulation of surface charges is a crucial challenge, especially for HVDC components. Accumulated surface charges can change the electric field distribution and generate weak points, especially in case of superimposed transient voltages and, therefore lower the performance e.g. of insulators. Hence, an accurate measurement of the surface potential and so the surface charges is necessary to optimize these components. Commonly, the surface potential is measured with an electrostatic voltmeter. In this study a procedure for determining the spatial impulse response of a compensating electrostatic voltmeter depending on only the surface to probe distance is presented. Based on the performed measurements a mathematical model is developed to describe the capacitive influence and significance of the local surface potential on the measurement result. The actual measurement value is a weighted and averaged value given by the actual position and its surrounding, which is also confirmed by numerical simulations. The performed procedure enables high accuracy of the measurement of surface potentials and so of surface charges using different types of electrostatic voltmeters and shows the limitation of the measurement procedure. This knowledge increases the possibility to design optimized components for HVDC systems.

Prevention of Procedural Hypertension in the Irreversible Electroporation Ablation of Liver and Pancreatic Tumors Based on Distance from the Adrenal Gland.

Background and objectiveWhen irreversible electroporation (IRE) ablation of abdominal tumors, procedural hypertension often occurs, which often affects the progress of the ablation. Until now, there is no reasonable explanation for this phenomenon. The objective of this research was to explore the cause and solution of procedural hypertension in percutaneous IRE.MethodsIn this study, the treatment data of 4 consecutive groups of patients were used to confirm the cause of intraoperative hypertension and then verify the solution. A total of 155 patients with procedural hypertension were screened based on their medical records of pancreatic or hepatic IRE treatment. Procedural hypertension was monitored in 21 new patients, the correlation between serum catecholamines and hypertension was recorded and evaluated using regression analysis. Forty new patients were divided into two groups (distance from needle tip to adrenal gland, < 2 cm vs ≥ 2 cm), and the blood pressure was recorded and compared with two-way ANOVA. Eleven patients with ablative distance <2 cm were treated in advance with phentolamine to observe for the occurrence of procedural hypertension.ResultsOf the 21 re-enrolled patients with ablation of the pancreas and liver tumors, 9 developed intraoperative hypertension with significantly elevated serum catecholamines levels, epinephrine, norepinephrine and dopamine are all positively associated with hypertension, with P values were 0.0003, 0.0253, and 0.0015, respectively. For the two groups with different needle-insertion distances, hypertension in the < 2 cm group was more significant than that in the other group (for procedural hypertension, P< 0.01; for heart rate, P< 0.05), which was considered as a high-risk group. The occurrence of intraoperative hypertension could be completely prevented by using phentolamine prior to treatment.ConclusionHypertension occurs frequently during hepatic and pancreatic IRE because of the damage of adrenal gland. The safe distance of ablation probe for the adrenal gland was 2 cm. For high-risk patients, early drug prevention works well.

Penetration depth study of 830 nm low-intensity laser therapy on living dog tissue.

Background and Aim:Recent studies have shown that low-intensity laser therapy (LILT) enhances chronic wound healing, reduces pain, reduces inflammation, and improves post-operative rehabilitation. However, clinical outcomes in the veterinary use of LILT vary between different experimental studies. This is explained by improper laser parameter settings and limits of its penetration depth. This study aimed to investigate the penetration depth of 830 nm LILT on living dog tissue in different operating modes. This entailed continuous wave (CW) versus pulse wave (PW) and with contact versus non-contact techniques of the laser probe at different tissue-laser probe distances. The results can be applied for use in clinical practice.Materials and Methods:Twenty-four dogs that had undergone abdominal surgery were included in this study. The laser parameters were set at 200 mW, fluence of 4 J/cm2 and the laser power output denoted as mean output power (MOP) was measured by a power meter.Results:The MOP of the 830 nm CW laser was significantly higher than the PW laser (p<0.05). The MOP of the contact technique was significantly greater than that of the non-contact technique in both CW and PW modes (p<0.05). The MOP through the skin tissue was between 16.09 and 18.60 mW (8.05-9.30%) for the contact technique and 8.73 and 19.36 mW (4.37-9.68%) for the non-contact technique. In the muscle-skin layer, the MOP was between 0.50 and 1.56 mW (0.25-0.78%) and the MOP was not detected using the non-contact technique with a 5 cm tissue-laser probe distance.Conclusion:Our study indicates that 830 nm LILT (with laser parameter setting at 200 mW, fluence of 4 J/cm2 for both contact and non-contact techniques, and tissue-laser probe distance up to 5 cm) was appropriate for treatments within 14 mm of depth. However, the use of 830 nm LILT for an application in which the target tissue is deeper than 14 mm may limit its positive effect.

The Effect of Calcium on the Cohesive Strength and Flexural Properties of Low-Methoxyl Pectin Biopolymers.

Pectin binds the mesothelial glycocalyx of visceral organs, suggesting its potential role as a mesothelial sealant. To assess the mechanical properties of pectin films, we compared pectin films with a less than 50% degree of methyl esterification (low-methoxyl pectin, LMP) to films with greater than 50% methyl esterification (high-methoxyl pectin, HMP). LMP and HMP polymers were prepared by step-wise dissolution and high-shear mixing. Both LMP and HMP films demonstrated a comparable clear appearance. Fracture mechanics demonstrated that the LMP films had a lower burst strength than HMP films at a variety of calcium concentrations and hydration states. The water content also influenced the extensibility of the LMP films with increased extensibility (probe distance) with an increasing water content. Similar to the burst strength, the extensibility of the LMP films was less than that of HMP films. Flexural properties, demonstrated with the 3-point bend test, showed that the force required to displace the LMP films increased with an increased calcium concentration (p < 0.01). Toughness, here reflecting deformability (ductility), was variable, but increased with an increased calcium concentration. Similarly, titrations of calcium concentrations demonstrated LMP films with a decreased cohesive strength and increased stiffness. We conclude that LMP films, particularly with the addition of calcium up to 10 mM concentrations, demonstrate lower strength and toughness than comparable HMP films. These physical properties suggest that HMP has superior physical properties to LMP for selected biomedical applications.

Production of triterpenoid compounds from Ganoderma lucidum spore powder using ultrasound-assisted extraction

When ingested as a dietary supplement, Ganoderma lucidum spore powders (GLSP) provide various health benefits such as enhanced immunity, liver protection and anti-cancer effects. In this study, triterpenoid extraction from GLSP was achieved using an ultrasound-assisted process which was optimized using response surface methodology (RSM). Ultrasound-assisted extraction (UAE) was also compared to the most conventional chemical extraction method. For UAE, optimum extraction conditions were found to be ethanol concentration = 95% v/v; solvent to solid ratio = 50:1 mL/g; ultrasound time = 5.4 min; ultrasound power = 564.7 w, and ultrasound probe distance = 8.2 cm. At optimal UAE conditions, no significant differences were found between experimental (0.97 ± 0.04 %) and predicted values (99%); which indicates appreciable correlation at the 97% confidence interval. The findings show the application of Box–Behnken design (BBD) to predict and optimize triterpenoid yield for UAE of triterpenoid from GLSP. Furthermore, glucose consumption was 2.68 times that of control samples when tested with insulin-resistant HepG2 cell, showing potential use in type 2 diabetes. In addition, triterpenoid extracts show good biocompatibility and inhibition of antioxidant activity.

Identifying the Sources of Error When Using 3-Dimensional Printed Head Models with Surgical Navigation

The evaluation of sources of error when preparing, printing, and using 3-dimensional (3D) printed head models for training purposes. Two 3D printed models were designed and fabricated using actual patient imaging data with reference marker points embedded artificially within these models that were then registered to a surgical navigation system using 3 different methods. The first method uses a conventional manual registration, using the actual patient's imaging data. The second method is done by directly scanning the created model using intraoperative computed tomography followed by registering the model to a new imaging dataset manually. The third is similar to the second method of scanning the model but eventually uses an automatic registration technique. The errors for each experiment were then calculated based on the distance of the surgical navigation probe from the respective positions of the embedded marker points. Errors were found in the preparation and printing techniques, largely depending on the orientation of the printed segment and postprocessing, but these were relatively small. Larger errors were noted based on a couple of variables: if the models were registered using the original patient imaging data as opposed to using the imaging data from directly scanning the model (1.28 mm vs. 1.082 mm), and the accuracy was best using the automated registration techniques (0.74 mm). Spatial accuracy errors occur consistently in every 3D fabricated model. These errors are derived from the fabrication process, the image registration process, and the surgical process of registration.

Ultrasound assisted formation of essential oil nanoemulsions: Emerging alternative for Culex pipiens pipiens Say (Diptera: Culicidae) and Plodia interpunctella Hübner (Lepidoptera: Pyralidae) management.

Over the last years, nanotechnology has contributed to the development of new botanical insecticides formulations based on essential oils (EO), which are safe for the human health and the environment. Nanoemulsions (NEs) can enhance the bioactivity of the EO to prevent the premature volatility and degradation of the active ingredients. In our work, geranium EO (Geranium maculatum L.) was used to develop micro and nanoemulsions adding Tween 80 as surfactant. For NEs formulation, ultrasound was applied and the physicochemical and ultrasound parameters were optimized: oil: surfactant ratio = 1:2, ultrasound power = 65 W, sonication time = 2 min, cycles = 30 on/20 off and ultrasonic probe distance = 3.7 cm. The NEs obtained had 13.58 nm and polydisperse index (PDI) values of 0.069. They were stored at 25 °C and were stable for 60 days. The present study also demonstrated the potential of NEs to enhance the toxicity of geranium EO against larvae of Culex pipiens pipiens (EO LC50 = 80.97 ppm, NEs LC50 = 48.27 ppm) and Plodia interpunctella (EO + β-cypermethrin LD50 = 0.16 μg larvae-1, NEs + β-cypermethrin LD50 = 0.07 μg larvae-1). Overall, our findings pointed out that NEs can increase twofold the insecticidal efficacy of EO, and thus, they can be considered further for the development of botanical insecticides.

Effect of Ultrasonication on Membrane Structure and Flux Recovery for Whey Ultrafiltration

In this study, the effect of ultrasound irradiation on the flux recovery and fouling mitigation for the membranes made of the polysulfone by the phase inversion method were investigated. Two ultrasound irradiation regimes, including inside and outside the module, were chosen for this study. The experiments were conducted to investigate the effect of ultrasound irradiation on the membrane structure and cleaning. The ultrasound was irradiated in the frequency of 20 kHz and at the intensity of 25.5-127.4 W/cm2. When the membranes were irradiated directly out of the module, they may be damaged and the large holes were formed due to remaining in direct acoustic cavitation area. The flux recovery for the whey ultrafiltration process was increased with the increase of the irradiation time and the ultrasound intensity. The released energy which is the result of the cavitation threshold of bubbles indirectly may clean the foulant. During 60 min ultrasound irradiation, the flux recoveries were between 83-91% for membranes. At the probe distance of 1 cm from the module and after 20 min, the destruction or cracks in the membrane may be happened. The FE-SEM showed that the adjacent holes were connected and the crack was formed. The results for using the ultrasound for cleaning the fouled membranes showed that in the long distances, a large number of cavitation bubbles collapses before they reach to the membrane and in short distance, due to higher energy density, the produced acoustic and turbulence stream are increased and the membrane may be damaged.

The nascent wind of AGB star R doradus: evidence for a recent episode of enhanced mass loss

ABSTRACT We analyse ALMA observations of the SO(JK = 65 − 54) emission of the circumstellar envelope of oxygen-rich AGB star R Dor, probing distances between 20 and 100 au from the star where the nascent wind is building up. We give evidence for a radial outflow covering very large solid angles and displaying strong inhomogeneity both in direction and radially: it contains multiple cores and has a radial dependence suggesting an episode of enhanced mass loss that occurred a century or so ago. Our analysis also confirms the presence of a previously observed rotating disc.

Spin‐thermoelectric voltage in longitudinal SSE elements incorporating LPE YIG films and polycrystalline YIG slabs with an ultrathin Pt layer

AbstractA spin‐thermoelectric (STE) voltage is generated when a temperature gradient ∇T is applied to an element having a thin Pt layer coated on a magnetic substance. In this study, yttrium iron garnet (YIG) ferrimagnetic films prepared by liquid phase epitaxy (LPE) were tested as magnetic insulators. In addition, polycrystalline YIG slabs were tested to compare the STE voltages of film and slab samples. In a Pt coating and YIG film bilayer structure made by an ultrathin Pt layer of 1‐4 nm thickness and an LPE film of approximately 10 µm thickness, a large STE voltage of 600 µV was observed at a probe distance of 5 mm with a temperature difference ∆T of 30 K. On the other hand, the STE voltage of a Pt layer and YIG slab bilayer structure was 340 µV, which is roughly half of that of the Pt/YIG‐film element. The cause of the large voltage observed experimentally for the longitudinal spin Seebeck effect element incorporating an LPE YIG film was discussed mainly from the viewpoint of the Pt layer resistivity and the effects of YIG specimen surface conditions on crystallinity and the magnetization process.

Single Chromosome Aneuploidy Induces Genome-Wide Perturbation of Nuclear Organization and Gene Expression

Chromosomal aneuploidy is a defining feature of carcinomas and results in tumor-entity specific genomic imbalances. For instance, most sporadic colorectal carcinomas carry extra copies of chromosome 7, an aneuploidy that emerges already in premalignant adenomas, and is maintained throughout tumor progression and in derived cell lines. A comprehensive understanding on how chromosomal aneuploidy affects nuclear organization and gene expression, i.e., the nucleome, remains elusive. We now analyzed a cell line established from healthy colon mucosa with a normal karyotype (46,XY) and its isogenic derived cell line that acquired an extra copy of chromosome 7 as its sole anomaly (47,XY,+7). We studied structure/function relationships consequent to aneuploidization using genome-wide chromosome conformation capture (Hi-C), RNA sequencing and protein profiling. The gain of chromosome 7 resulted in an increase of transcript levels of resident genes as well as genome-wide gene and protein expression changes. The Hi-C analysis showed that the extra copy of chromosome 7 is reflected in more interchromosomal contacts between the triploid chromosomes. Chromatin organization changes are observed genome-wide, as determined by changes in A/B compartmentalization and topologically associating domain (TAD) boundaries. Most notably, chromosome 4 shows a profound loss of chromatin organization, and chromosome 14 contains a large A/B compartment switch region, concurrent with resident gene expression changes. No changes to the nuclear position of the additional chromosome 7 territory were observed when measuring distances of chromosome painting probes by interphase FISH. Genome and protein data showed enrichment in signaling pathways crucial for malignant transformation, such as the HGF/MET-axis. We conclude that a specific chromosomal aneuploidy has profound impact on nuclear structure and function, both locally and genome-wide. Our study provides a benchmark for the analysis of cancer nucleomes with complex karyotypes.

Further study of coupling efficiency of ultra-small gradient-index fiber probe

In this paper, the relationship between the coupling efficiency and transmission distance of different fiber optic probes is compared for further studying the focusing performance of ultra-small GRIN fiber probes. Taking an example of five typical ultra-small GRIN fiber probes such as single mode fiber (SMF), "SMF + 0.31mm 50/125 GRIN", "SMF + 0.36mm NCF + 0.12mm 50/125 GRIN", "SMF + 0.48mm 100/140 GRIN", "SMF + 0.48mm NCF + 0.14mm 50/125 GRIN", the relationships between the theoretical coupling efficiency and transmission distance are compared with experimental data. The obtained results show that an increase in the working distance of a probe causes increase of the transmission distance to maintain a higher coupling efficiency, and leads to gain of the waist diameter. Therefore, the comprehensive effects of the working distance, waist diameter and coupling efficiency must be taken into consideration in the process of optimizing the design parameters of ultra-small GRIN fiber probes.

Multipolar RFA of the liver: Influence of intrahepatic vessels on ablation zones and appropriateness of CECT in detecting ablation dimensions - Results of an in-vivo porcine liver model.

Radiofrequency ablation (RFA) is an important treatment option for hepatic tumors and metastases. Post-ablation recurrence rates are reported up to 36.5 percent and seem to depend on tumor size, intrahepatic localization of tumors and adjacent hepatic vessels. Multipolar RFA has the potential to overcome/reduce these limitations. Experimental and standardized data on achievable lesion sizes, influence of hepatic vessels and non-invasive evaluation of complete ablation is still insufficient. The aim of this study was to evaluate the influence of intrahepatic vessels on shape and size of multipolar RF-ablation zones in healthy porcine liver and to evaluate the appropriateness of immediate post-ablation contrast-enhanced computed tomography (CECT) in detecting RF-ablation dimensions. We conducted multipolar RFAs in each of the livers of 10 healthy, narcotized and laparotomized domestic pigs by inserting three parallel probes with a constant probe distance and a constant energy supply. In 4 ablations we interrupted hepatic blood flow using Pringle's maneuver. Immediate post-ablation CECT scans were acquired. After euthanasia the livers were sliced perpendicularly to the probes at the probes' active centers. CECT scans were reconstructed equivalently in order to compare RF-lesion size and shape to the macroscopic sections. In total, 19 RF-lesions were analyzed. Every RF-lesion that was ablated during physiological liver perfusion showed an irregular and cloverleaf-like shape (n = 15). Interrupting the hepatic blood flow during RFA led to well-defined, round and homogeneous ablation zones which were 3.8 times larger compared to RF-lesions ablated during continuous hepatic perfusion (n = 4). We found an excellent correlation between immediate post-ablation CECT slices and macroscopic sections when comparing RF-lesion diameters and area, although CECT tended to overestimate ablation dimensions. The interruption of hepatic blood flow using Pringle's maneuver during multipolar RFA with three applicators significantly reduces heat sink effects of hepatic vessels and generates large and coherent ablation zones. This approach should be considered in each case of ablation planning adjacent to larger hepatic vessels or when ablating larger tumor volumes. Immediate post-ablation CECT has limited value in detecting incomplete RFA periprocedurally.

Macromolecular crowding effects on energy transfer efficiency and donor-acceptor distance of hetero-FRET sensors using time-resolved fluorescence

Living cells are crowded with macromolecules and organelles, which affect a myriad of biochemical processes. As a result, there is a need for sensitive molecular sensors for quantitative, site-specific assessment of macromolecular crowding. Here, we investigated the excited-state dynamics of recently developed hetero-FRET sensors (mCerulean3–linker–mCitrine) in homogeneous and heterogeneous environments using time-resolved fluorescence measurements, which are compatible with fluorescence lifetime imaging microscopy (FLIM). The linker in these FRET constructs, which tether the mCerulean3 (the donor) and mCitrine (the acceptor), vary in both length and flexibility. Glycerol and Ficoll-70 solutions were used for homogeneous and heterogeneous environments, respectively, at variable concentrations. The wavelength-dependent studies suggest that the 425-nm excitation and the 475-nm emission of the donor are best suited for quantitative assessment of the energy transfer efficiency and the donor-acceptor distance of these FRET probes. Under the same experimental conditions, the enzymatically cleaved counterpart of these probes was used as a control as well as a means to account for the changes in the environmental refractive indices. Our results indicate that the energy transfer efficiency of these FRET probes increases as the linker becomes shorter and more flexible in pure buffer at room temperature. In addition, the FRET probes favor a compact structure with enhanced energy transfer efficiency and a shorter donor-acceptor distance in the heterogeneous, polymer-crowded environment due to steric hindrance. In contrast, the stretched conformation of these FRET probes is more favorable in the viscous, homogeneous environment with a reduced energy transfer efficiency and relatively larger donor-acceptor distance as compared with those in pure buffer, which was attributed to a reduced structural fluctuation of the mCerulean3–mCitrine FRET pair in the viscous, more restrictive glycerol-enriched buffer. Our findings will help to advance the potential of these hetero-FRET probes using FLIM for spatio-temporal assessment of the compartmentalized crowding in living cells.