Shallow Penetration Depth Research Articles

Response of Various Yb3+-Doped Oxide Glasses to Different Radiation Treatments.

The radiation effects of electrons and protons on the spectroscopic and optical properties of oxide glasses doped with Yb3+ in various glass systems were investigated to understand the impact of the glass composition on the glass photo-response. Changes in the optical and emission properties were seen after the radiation treatment, and the magnitude of the changes depended on the irradiation source and dose. For all the investigated materials, the absorption coefficients in the 200–550 nm range increase post-irradiation, revealing the formation of defects in the glasses during the irradiation. While the spectroscopic properties of the tellurite glass remain unchanged, a small reduction in the Yb3+ emission intensity was seen after irradiating the phosphate, borosilicate, and germanate glasses, indicating that a reduction of Yb3+ to Yb2+ might occur in these glasses during the radiation treatment. The changes in the optical and spectroscopic properties after proton irradiation are small as they are localized at the surface of the glasses due to the shallow penetration depth of the proton in the glass. Even though the doses are small, the electron irradiation produces larger changes in the optical and spectroscopic properties since the electrons penetrate the entire volume of the glasses. All the changes in the optical and spectroscopic properties of the glasses were successfully reversed after a short heat treatment revealing the reversible nature of the photo-response of the investigated glasses.

NIR-II-Responsive CeO2-x@HA Nanotheranostics for Photoacoustic Imaging-Guided Sonodynamic-Enhanced Synergistic Phototherapy.

The therapeutic effect of photothermal therapy (PTT) and photodynamic therapy (PDT) is severely limited because of the shallow tissue penetration depth of the first near-infrared (NIR-I) light. Multifunctional nanotheranostics irradiated by the second near-infrared (NIR-II) light have received wide interest with respect to deeper tissue penetration, and sonodynamic therapy (SDT) synergistic phototherapy can achieve the complete elimination of tumors. Herein, we successfully constructed a single NIR-II light-induced nanotheranostic using cerium oxide (CeO2-x) with abundant oxygen vacancies for photoacoustic imaging-guided SDT-enhanced phototherapy for the first time. CeO2-x with surface crystalline disorder showed extensive NIR-II region absorption and an outstanding photothermal conversion ability. In addition, the CeO2-x layer with numerous oxygen defects can promote the separation of holes and electrons by ultrasound irradiation, which can remarkably enhance the efficacy of phototherapy to achieve high-efficiency tumor ablation. CeO2-x was surface modified with hyaluronic acid (HA) to prepare CeO2-x@HA to allow active tumor targeting efficiency. Both cell and animal experiments confirmed that all-in-one CeO2-x@HA exhibited a high therapeutic efficacy of SDT-enhanced PDT/PTT under 1064 nm laser irradiation, which achieved complete tumor eradication without systemic toxicity. This study significantly broadened the application of NIR-II-responsive CeO2-x for photoacoustic imaging-mediated SDT-enhanced phototherapy to the highly efficient and precise elimination of tumors.

Brain-based measures of nociception during general anesthesia with remifentanil: A randomized controlled trial.

BackgroundCatheter radiofrequency (RF) ablation for cardiac arrhythmias is a painful procedure. Prior work using functional near-infrared spectroscopy (fNIRS) in patients under general anesthesia has indicated that ablation results in activity in pain-related cortical regions, presumably due to inadequate blockade of afferent nociceptors originating within the cardiac system. Having an objective brain-based measure for nociception and analgesia may in the future allow for enhanced analgesic control during surgical procedures. Hence, the primary aim of this study is to demonstrate that the administration of remifentanil, an opioid widely used during surgery, can attenuate the fNIRS cortical responses to cardiac ablation.Methods and findingsWe investigated the effects of continuous remifentanil on cortical hemodynamics during cardiac ablation under anesthesia. In a randomized, double-blinded, placebo (PL)-controlled trial, we examined 32 pediatric patients (mean age of 15.8 years,16 females) undergoing catheter ablation for cardiac arrhythmias at the Cardiology Department of Boston Children’s Hospital from October 2016 to March 2020; 9 received 0.9% NaCl, 12 received low-dose (LD) remifentanil (0.25 mcg/kg/min), and 11 received high-dose (HD) remifentanil (0.5 mcg/kg/min). The hemodynamic changes of primary somatosensory and prefrontal cortices were recorded during surgery using a continuous wave fNIRS system. The primary outcome measures were the changes in oxyhemoglobin concentration (NadirHbO, i.e., lowest oxyhemoglobin concentration and PeakHbO, i.e., peak change and area under the curve) of medial frontopolar cortex (mFPC), lateral prefrontal cortex (lPFC) and primary somatosensory cortex (S1) to ablation in PL versus remifentanil groups. Secondary measures included the fNIRS response to an auditory control condition. The data analysis was performed on an intention-to-treat (ITT) basis. Remifentanil group (dosage subgroups combined) was compared with PL, and a post hoc analysis was performed to identify dose effects. There were no adverse events. The groups were comparable in age, sex, and number of ablations. Results comparing remifentanil versus PL show that PL group exhibit greater NadirHbO in inferior mFPC (mean difference (MD) = 1.229, 95% confidence interval [CI] = 0.334, 2.124, p < 0.001) and superior mFPC (MD = 1.206, 95% CI = 0.303, 2.109, p = 0.001) and greater PeakHbO in inferior mFPC (MD = −1.138, 95% CI = −2.062, −0.214, p = 0.002) and superior mFPC (MD = −0.999, 95% CI = −1.961, −0.036, p = 0.008) in response to ablation. S1 activation from ablation was greatest in PL, then LD, and HD groups, but failed to reach significance, whereas lPFC activation to ablation was similar in all groups. Ablation versus auditory stimuli resulted in higher PeakHbO in inferior mFPC (MD = 0.053, 95% CI = 0.004, 0.101, p = 0.004) and superior mFPC (MD = 0.052, 95% CI = 0.013, 0.091, p < 0.001) and higher NadirHbO in posterior superior S1 (Pos. SS1; MD = −0.342, 95% CI = −0.680, −0.004, p = 0.007) during ablation of all patients. Remifentanil group had smaller NadirHbO in inferior mFPC (MD = 0.098, 95% CI = 0.009, 0.130, p = 0.003) and superior mFPC (MD = 0.096, 95% CI = 0.008, 0.116, p = 0.003) and smaller PeakHbO in superior mFPC (MD = −0.092, 95% CI = −0.680, −0.004, p = 0.007) during both the stimuli. Study limitations were small sample size, motion from surgery, indirect measure of nociception, and shallow penetration depth of fNIRS only allowing access to superficial cortical layers.ConclusionsWe observed cortical activity related to nociception during cardiac ablation under general anesthesia with remifentanil. It highlights the potential of fNIRS to provide an objective pain measure in unconscious patients, where cortical-based measures may be more accurate than current evaluation methods. Future research may expand on this application to produce a real-time indication of pain that will aid clinicians in providing immediate and adequate pain treatment.Trial registrationClinicalTrials.gov NCT02703090

A hybrid analytical-numerical technique for solving soil temperature during the freezing process

The freeze-thaw cycle associated with climatic seasonality is a common phenomenon in cold regions affecting a wide range of subsurface processes. Due to the complex and highly nonlinear nature of the associated hydrologic processes, transient freeze-thaw dynamics are conventionally quantified in a numerical way. Here we present a hybrid analytical-numerical scheme for solving one-dimensional soil (or porous media) temperature profiles when the soil profile is subjected to unidirectional freezing (or thawing) conditions. This scheme divides the partially-frozen soil into multi-layers, each with constant thermal parameters and fixed-temperature boundaries. Temperature profiles within each layer were obtained by solving multiple moving-boundary problems. The proposed hybrid analytical-numerical scheme was tested into a freezing test of silty clay in a permafrost region on the Qinghai-Tibetan Plateau, and its solution was in good agreement with the finite element numerical solution. Results show that the proposed multi-layer method adapted well to the changes in unfrozen water content and thermal properties of soil over a wide range of subzero temperatures. By contrast, the freezing front's migration rate and penetration depth calculated by Neumann's classical solution, which only considers two zones (frozen and unfrozen), was found to be underestimated. As for our proposed multi-layer solution, by dividing the subsurface domain into many layers with smaller proportion ratios (thinner layers close to the freezing front), there was a slower penetration rate of the freezing front resulting in shallower penetration depth. The predicted profiles of temperature, thermal conductivity and diffusivity, heat flux, and dynamics of the freezing front were significantly impacted by the shape of the soil freezing curves and the magnitude of soil grain thermal conductivity, especially for the accuracy of long-term predictions.

Land-Streamer vs. Conventional Seismic Data for High-Resolution Near-Surface Surveys

Near-surface high-resolution seismic mapping is very important in many applications such as engineering and environmental. However, the conventional setup of the seismic technique requires planting geophones, connecting cables, and then collecting all equipment after completing the survey, which is time-consuming. In this study, we suggest using a land-streamer setup rather than the conventional setup for fast, accurate, and high-resolution near-surface seismic surveys. Only one field data set is recorded using both the conventional and the land-streamer setups. The recorded data is then compared in terms of time, frequency, wavenumber domains, and acquisition time. Following this, we compared the accuracy of the subsurface mapping of both setups using a synthetic example. The results show that the conventional setup can reach deeper depths but with lower accuracy, where the errors in imaging the local anomalies’ widths and thicknesses are 77% to 145% and 35% to 50%, respectively. The land-streamer setup provides accurate near-surface results but shallower penetration depth, here the errors in the anomalies’ widths and thicknesses are 5% to 12% and 10% to 20%, respectively.

Absorbed/Epithelial Power Density Assessment Using Plane-Wave Spectrum Method From Inside the Skin Tissue Above 6 GHz

In this paper, the idea of measurement inside the human skin liquid-filled phantom for 5G technologies is examined. Measurement inside the skin tissue phantom is almost off the table due to the shallow penetration depth of fields at millimeter and quasi-millimeter waves. Antenna-body interactions should be considered for absorbed power density (APD) assessment when the device is close to the human body. These effects can be considered to a large extent by measuring within the liquid phantom. The reconstruction technique is used to determine APD at the human skin surface using the backward plane-wave spectrum method through sampling the E-field at the specific distance within the phantom. The reconstruction errors were obtained using a planar array antenna at 10 to 60 GHz frequencies. These errors were no larger than 9.4%, 7.35%, 7.8% at 10, 24, and 60 GHz for assessing the maximum spatially-averaged power density for a separation distance between the device and tissue phantom larger than 1 mm. At last, the measuring requirement for the electric field was also investigated. The results suggest that the coupling/multiple-reflection effects are negligible when the separation distance between antenna and body is larger than λ.

Semiconductor Quantum Dots (CdX, X = S, Te, Se) Modify Titanium Dioxide Nanoparticles for Photodynamic Inactivation of Leukemia HL60 Cancer Cells

Titanium dioxide nanoparticles (TiO2-NPs) are highly efficient photosensitizers in traditional photodynamic therapy (PDT). The particle size of TiO2-NPs is small, only about 20 nm. However, the demands of ultraviolet light (UV) excitation feature shallow tissue penetration depth and may lead to severe tissue photon damage. Thus, in this research, TiO2-NPs are modified with semiconductor quantum dots (QDs) CdX (X = S, Te, Se) in various methods, such as ultrasonic, hydrothermal, sol-gel, aqueous phase, and hydrolysis precipitation. The transmission electron microscopy (TEM) images show that the size of CdSe-TiO2 is ranging from 6 to 14 nm. The ultraviolet-visible (UV-Vis) spectrum demonstrates that the CdX (X = S, Te, Se) modification can successfully extend the absorption range of TiO2-NPs into a different visible light region. CdSe QDs have the narrowest band gap compared with CdX (X = S, Te, Se) QDs. Visible light-activated CdSe-TiO2 nanocomposite shows the highest PDT inactivation efficiency toward HL60 cells compared with CdX-TiO2. The photogenerated carrier separation efficiency of CdSe-TiO2 nanocomposite is the highest shown in a fluorescence spectrum (FS). Furthermore, when conjugated with folic acid (FA), the prepared FA-CdX-TiO2 (X = S, Se) exhibits excellent cancer-targeting ability during PDT treatment. Optimum PDT efficiency of FA-CdSe-TiO2 indicates that photocatalytic and targeting ability is much higher than pure TiO2 and CdSe-TiO2. Our results provided a detailed investigation on the PDT performance of CdX (X = S, Te, Se) modified TiO2 and may act as a guide for further design of highly targeted performance visible-light response TiO2-NPs.

Image Processing and Luminescent Probes for Bioimaging Techniques with High Spatial Resolution and High Sensitivity

The balance of microenvironmental factors (including temperature, pH, ROS species, etc.) plays a crucial role in maintaining normal living organisms’ normal physiological activities and physiological functions. Therefore, armed with the unique superiorities of high spatial resolution, non-invasion, high sensitivity, real-time monitoring, and simple operation, luminescent imaging technology has been widely used in real-time and accurate monitoring of microenvironmental factors in these organisms to prevent, diagnose and treat related diseases in time. However, due to its optical imaging characteristics, it is also faced with such interference factors as relatively shallow imaging penetration depth, background fluorescence (biological autofluorescence) interference in a complex environment, uncertain probe concentration, and unstable laser power in the imaging process, which are not related to the analyte. As for the problems in imaging, such as the uncertainty of probe concentration and the fluctuation of instrument laser power, the ratio detection, and imaging technology with self-calibration function can effectively avoid these problems. As for background fluorescence interference in imaging, probes with long-life emission can be used in imaging. The long-life luminescence of probes from background fluorescence can be recognized by time-resolved luminescence imaging technology to reduce its impact. This paper briefly introduces and summarizes the relative research of ratio detection and imaging technology and time-resolved luminescence imaging technology.

Soft X-Ray Stimulated Lanthanide@MOF Nanoprobe for Amplifying Deep Tissue Synergistic Photodynamic and Antitumor Immunotherapy.

Combining photodynamic therapy (PDT) and immunotherapy has shown profound impact for synergistic treatment of malignant tumors. However, the shallow penetration depth of the traditional visible light activated PDT, immunosuppressive tumor microenvironment (TME), and poor immunogenicity of deep-seated solid tumors have significantly impeded the therapeutic efficiency. Herein, a soft X-ray activated nanoprobe is rationally engineered via integrating porphyrin Zr-based metal-organic framework with lanthanide NaYF4 :Gd,Tb@NaYF4 scintillator nanoparticles (SNPs) by a new in situ growth strategy for synergistic PDT and immunotherapy of tumor. The nanoprobe possesses remarkably enhanced reactive oxygen species (ROS) generation triggered by soft X-ray via further covalently grafting rose bengal on the nanoprobe, even at tissue depths of 3cm. Moreover, the soft X-ray induced ROS can act as potential immunogenic cell death (ICD) trigger, subsequently leading to the activation of the adaptive antitumor immune-response. Significantly, the boosted ROS generation can further modulate the immunosuppressive TME. This work provides new strategy of designing antitumor nanoprobes for soft X-ray triggered deep-tissue PDT and immune response, breaking the depth barriers suffered by the traditional photoactivated PDT or ICD using visible and near infrared light.

Investigations on transient support pressure transfer at the tunnel face during slurry shield drive part 1: Case A – Tool cutting depth exceeds shallow slurry penetration depth

Stability of the tunnel face is a key design aspect for slurry shield tunnelling. Two requirements have to be fulfilled during excavation in order to achieve a stable tunnel face. The first requirement is a sufficient slurry pressure in the excavation chamber of the shield to balance the pore water pressure and the earth pressure. Moreover, the fraction of the slurry pressure, which exceeds the pore pressure, has to be transferred efficiently on the soil grains to avoid possible collapse of the tunnel face. The pressure transfer theory currently being employed in the practice expects a filter cake formation on the tunnel face or a penetration zone through which the pressure transfer is assured. However, this practical assessment approach was originally developed for diaphragm walls and therefore the excavation process is neglected. Hereby, it is assumed, that the transfer mechanism on the tunnel face is built-up immediately and steadily. This assumption is not valid for the tunnel face of the slurry shield since the transfer mechanism is periodically destroyed by cutting tools. This paper introduces a new approach for the implementation of the formation process in the analysis of the pressure transfer in case of a shallow slurry penetration depth smaller than the cutting depth of the tools. First, existing theories dealing with the pressure transfer are reviewed. Consequently, a new approach describing the support pressure transfer for slurry shields is derived and implemented in a numerical seepage model. Calculations are carried out in order to determine the efficient amount of the pressure transfer during excavation.

Organic Semiconducting Luminophores for Near‐Infrared Afterglow, Chemiluminescence, and Bioluminescence Imaging

AbstractOptical imaging has played a pivotal role in deciphering in vivo bioinformatics but is limited by shallow penetration depth and poor imaging performance owing to interfering tissue autofluorescence induced by concurrent photoexcitation. The emergence of near‐infrared (NIR) self‐luminescence imaging independent of real‐time irradiation has timely addressed these problems. There are two main kinds of self‐luminescent agents, namely inorganic and organic luminophores. Inorganic luminophores usually suffer from long‐term biotoxicity concerns resulting from potential heavy‐metal ions leakage and nonbiodegradability, which hinders their further translational application. In contrast, organic luminophores, especially organic semiconducting luminophores (OSLs) with good biodegradable potential, tunable design, and outstanding optical properties, are preferred in biological applications. This review summarizes the recent progress of OSLs used in NIR afterglow, chemiluminescence, and bioluminescence imaging. Molecular manipulation and nanoengineering approaches of OSLs are discussed, with emphasis on strategies that can extend the emission wavelength from visible to NIR range and amplify luminescence signals. This review concludes with a discussion of current challenges and possible solutions of OSLs in the self‐luminescence field.

Interpreting strength parameters of strain-softening clay from shallow to deep embedment using ball and T-bar penetrometers

Full-flow penetrometers (ball and T-bar) are widely used for measurements of strength characteristics of clayey soils in offshore field investigations and laboratory tests. However, the accuracy of the estimated undrained shear strength is hampered by: (1) the drastic variation of the bearing factor for the penetrometer at shallow and transitional penetration depths where full-flow mechanisms are not achieved; and (2) the strain-softening of the soil, which results in a degradation of the estimated strength. This study conducted LDFE analyses to simulate the entire penetration process of full-flow penetrometers in strain-softening soils from shallow to deep embedment depths. Parametric studies were performed to investigate the effects of varied factors on the bearing factor and failure mechanism during the penetrometer penetration. Based on the LDFE analyses, empirical formulas are established to represent the critical penetration depths in the strain-softening soil, which are used to correct the bearing factor at shallow penetration depths. The discrepancies of the transitional failure mechanism and the trapped cavity bearing factor between ball and T-bar are emphasized. Finally, a back-analyses framework is proposed to estimate the strength parameters (including the original undrained shear strength prior to any strain-softening, and the strain-softening parameters) based on the measurements of the penetrometer during the first penetration from shallow to deep embedment depths. Through a series of model tests, the reliability of the back-analyses framework is validated.

A 16-Channel 13C Array Coil for Magnetic Resonance Spectroscopy of the Breast at 7T.

Considering the reported elevation of ω-6/ω-3 fatty acid ratios in breast neoplasms, one particularly important application of 13C MRS could be in more fully understanding the breast lipidome's relationship to breast cancer incidence. However, the low natural abundance and gyromagnetic ratio of the 13C isotope lead to detection sensitivity challenges. Previous 13C MRS studies have relied on the use of small surface coils with limited field-of-view and shallow penetration depths to achieve adequate signal-to-noise ratio (SNR), and the use of receive array coils is still mostly unexplored. This work presents a unilateral breast 16-channel 13C array coil and interfacing hardware designed to retain the surface sensitivity of a single small loop coil while improving penetration depth and extending the field-of-view over the entire breast at 7T. The coil was characterized through bench measurements and phantom 13C spectroscopy experiments. Bench measurements showed receive coil matching better than -17 dB and average preamplifier decoupling of 16.2 dB with no evident peak splitting. Phantom MRS studies show better than a three-fold increase in average SNR over the entirety of the breast region compared to volume coil reception alone as well as an ability for individual array elements to be used for coarse metabolite localization without the use of single-voxel or spectroscopic imaging methods. Our current study has shown the benefits of the array. Future in vivo lipidomics studies can be pursued. Development of the 16-channel breast array coil opens possibilities of in vivo lipidomics studies to elucidate the link between breast cancer incidence and lipid metabolics.

Assessing axial load transfer mechanism of open-ended tubular piles penetrating in weak rocks using three-dimensional discrete element method

In order to obtain a better understanding of the load transfer mechanism of open-ended tubular piles driven into weak rocks, numerical analysis is conducted to study the internal and external shaft frictions, base resistance and the stress distribution pattern in the surrounding rock mass. Meanwhile, since pile shoes are often applied when driving to the rock layer, a common inner pile shoe attached to the open-ended tubular pile was analysis and compared with the pile without a shoe. In this study, the discrete element method (DEM), which can mimic rock grains and the interaction between grains, is adopted due to its ability to simulate large deformation problems such as pile penetration process. The flat-joint model that allows partial damage at the contact interface was employed to replicate the discrete nature of the rock mass. The rock behaviour was calibrated against triaxial test results for a pyroclastic weak rock, and then the calibrated rock was employed for the simulation of pile penetration. A 30° segment of the true-scale model was simulated using the DEM with a height of 3 m and a radius of 1.5 m, which was composed of about 557,000 particles. Initial stresses were applied at the boundary of the testing chamber, while the side of the chamber was discretised into several sections with increasing horizontal stresses with depth to establish the at rest condition. Numerical results for penetration of an open-ended tubular pile show that the external shaft resistance of the pile with inner pile shoe increased approximately linearly as the pile penetrated deeper. In addition, the internal shaft friction was notably less than the external shaft friction for both piles with and without a shoe. Plugging was observed for both piles with and without a driving shoe. The inner pile shoe allowed the pile partial plugging to occur at shallower penetration depth. This study sheds a light on the load transfer mechanism of the open-ended tubular piles and the effect of the shoe on the axial capacity of the piles in weak rocks.

Black SnO2−x based nanotheranostic for imaging-guided photodynamic/photothermal synergistic therapy in the second near-infrared window

The shallow penetration depth of photothermal agents in the first near-infrared (NIR-I) window significantly limits their therapeutic efficiency. Multifunctional nanotheranostic agents in the second near-infrared (NIR-II) window have drawn extensive attention for their combined treatment of tumors. Here, for the first time, we created oxygen-deficient black SnO2−x with strong NIR (700–1200 nm) light absorption with NaBH4 reduction from white SnO2. Hyaluronic acid (HA) could selectively target cancer cells overexpressed CD44 protein. After modification with HA, the obtained nanotheranostic SnO2-x@SiO2-HA showed high dispersity in aqueous solution and good biocompatibility. SnO2−x@SiO2-HA was confirmed to simultaneously generate enough hyperthermia and reactive oxygen species with single NIR-II (1064 nm) light irradiation. Because HA is highly affined to CD44 protein, SnO2-x@SiO2-HA has specific uptake by overexpressed CD44 cells and can be accurately transferred to the tumor site. Furthermore, tumor growth was significantly inhibited following synergistic photodynamic therapy (PDT) and photothermal therapy (PTT) with targeted specificity under the guidance of photoacoustic (PA) imaging using 1064 nm laser irradiation in vivo. Moreover, SnO2−x@SiO2-HA accelerated wound healing. This work prominently extends the therapeutic utilization of semiconductor nanomaterials by changing their nanostructures and demonstrates for the first time that SnO2-x based therapeutic agents can accelerate wound healing. Statement of significanceThe phototherapeutic efficacy of nanotheranostics by NIR-I lightirradiation was restricted owing to the limitation of tissue penetration and maximum permissible exposure. To overcome these limitations, we hereby fabricated a NIR-IIlight-mediated multifunctional nanotheranostic based on SnO2−x. The introduction of oxygen vacancy strategy was employed to construct full spectrum responsive oxygen-deficient SnO2−x, endowing outstanding photothermal conversion, and remarkable production activity of reactive oxygen species under NIR-II light activation. Tumor growth was significantly inhibited following synergistic PDT/PTT with targeted specificity under the guidance of photoacoustic imaging using 1064 nm laser irradiation in vivo. Our strategy not only expands the biomedical application of SnO2, but also providea method to develop other inorganic metal oxide-based nanosystems for NIR-II light-activated phototheranostic of cancers.

The Strength Assessment for T-bar Penetrometer Tests at Shallow Embedment in Clay considering Strain Softening

The undrained shear strength of clay is important for deep-sea foundation design. T-bar penetrometer as a key tool has been widely used in laboratory and offshore site investigation. To obtain a continuous soil strength profile, it is necessary to apply shallow corrections before the penetrometer reaching the full-flow state. Meanwhile, the actual soil strength may be underestimated if the strain softening behavior is not considered. In this study, the process of T-bar penetration is analyzed for the soil with strain softening. The buoyancy effect on the bearing capacity factor is studied, which shown that the buoyancy mainly has an effect on the test soils with extremely low strength, but have little effect in the field tests. The characteristics of soil heave in the T-bar tests are analyzed to estimate soil sensitivities. To estimate the soil strength at shallow penetration depth, a relation to correct the T-bar bearing factors is built both on the soil with strain softening and no strain softening.

Effects of 9,300 nm Carbon Dioxide Laser on Dental Hard Tissue: A Concise Review.

A carbon dioxide laser at 9,300 nm has a high absorption affinity for water and a shallow depth of penetration. It can be used for soft tissue surgery and hemostasis. Besides, it matches well with the absorption characteristic of hydroxyapatite in enamel and dentine. Therefore, the laser possesses a great ability for energy transfer to dental hard tissues. It has a low risk of thermo-damage to the dentine–pulp complex because it has a shallow depth of heat absorption. Hence, the laser is safe for dental hard tissue preparation. A carbon dioxide laser at 9,300 nm can effectively alter the chemical structure of teeth. It increases the ratio of calcium to phosphorus and converts the carbonated hydroxyapatite to the purer hydroxyapatite of enamel and dentine. It can alter the surface morphology of a tooth through surface melting, fusion, and ablation of dentine and enamel. At higher power, it removes caries lesions. It can enhance the success of restoration by increasing the bond strength of dental adhesives to the dentine and enamel. A carbon dioxide laser at 9,300 nm can also be used with fluoride for caries prevention. The advancement of technology allows the laser to be delivered in very short pulse durations and high repetition rates (frequency). Consequently, the laser can now be used with high peak power. The objective of this review is to discuss the effects and potential use of a 9,300 nm carbon dioxide laser on dental hard tissue.

Uniform, Universal, Shadowless TIRF Microscopy Via Annular Fiber Bundle

Total internal reflection fluorescence (TIRF) illumination is a popular excitation method in fluorescence microscopy. TIRF illumination is generated when the excitation beam strikes the glass/water interface of the sample at an angle greater than the critical angle, creating an evanescent excitation field with a shallow penetration depth that is well-suited to studying single-molecules and surface features of a biological sample with a high signal-to-background ratio. TIRF is typically achieved by focusing the excitation laser beam to the outermost edge of the back focal plane (BFP) of the imaging objective; however, this approach suffers from imaging artifacts such as interference fringes from the coherent excitation source and shadowing artifacts caused by the unidirectional light and scattering objects in cells.

The synergistic effect of focused ultrasound and biophotonics to overcome the barrier of light transmittance in biological tissue.

Optical technology is a tool to diagnose and treat human diseases. Shallow penetration depth caused by the high optical scattering nature of biological tissues is a significant obstacle to utilizing light in the biomedical field. In this paper, light transmission enhancement in the rat brain induced by focused ultrasound (FUS) was observed and the cause of observed enhancement was analyzed. Both air bubbles and mechanical deformation generated by FUS were cited as the cause. The Monte Carlo simulation was performed to investigate effects on transmission by air bubbles and finite element method was also used to describe mechanical deformation induced by motions of acoustic particles. As a result, it was found that the mechanical deformation was more suitable to describe the transmission change according to the FUS pulse observed in the experiment.

Effect of Strain Rate on the Deformation Characteristic of AlN Ceramics under Scratching.

To clarify the influence mechanism of strain rate effect on deformation characteristics of aluminum nitride (AlN) ceramics, some varied-velocity nanoscratching tests were carried out using a Berkovich indenter in this paper. The deformation characteristics of the scratched grooves were observed using the scanning electron microscope. The experimental results showed higher scratch speed would lead to shallower penetration depth, fewer cracks, and indenter fewer slipping, which was more conducive to the plastic deformation of AlN ceramics. Considering the strain rate effect and the elastic recovery of material, a model for predicting the Berkovich indenter penetration depth under edge-forward mode was established. The prediction results were consistent with the experimental data, and the error was less than 5%, indicating that the model is effective. Based on the Boussinesq field, the Cerruti field, and the Sliding bubble field, a strain rate dependent scratch stress field model was established. The stress field revealed higher scratch speed may significantly reduce the maximum principal stress in the stress field under the indenter, which is the fundamental reason for reducing the crack damage and promoting the plastic deformation. The above study can provide theoretical guidance for reducing the processing damage of AlN ceramics.