High Penetration Depth Research Articles

Near-infrared light triggered drug release from mesoporous silica nanoparticles.

Stimuli triggered drug delivery systems enable controlled release of drugs at the optimal space and time, thus achieving optimal therapeutic effects. As one of the most important stimuli used in bioapplications, near-infrared (NIR) light possesses unique advantages such as deep tissue penetration with minimum auto-fluorescence & tissue scattering and high biosafety. Mesoporous silica nanoparticles (MSNs) are one of the most studied nanocarriers; apart from having a high surface area and large pore volume for loading of drugs, they can be easily functionalized with inorganic nanomaterials and stimuli responsive polymers or organic switch molecules, creating possibilities for designing complex stimuli triggered drug delivery systems. Considering the high tissue penetration depth of NIR light and the unique mesoporous structure of MSNs, NIR responsive inorganic nanoparticle functionalized MSNs can be further combined with stimuli responsive materials to form smart "nano-devices" for controlled drug delivery toward tumors, and to date much progress has been made. In this article, recent advances in the design of NIR triggered mesoporous silica drug delivery systems are systematically summarized and some outstanding studies are highlighted. We will also discuss the shortcomings, challenges and opportunities in the field.

Study of neuronal spike-frequency adaptation with transcranial magneto-acoustical stimulation

Transcranial magneto-acoustical stimulation (TMAS), utilizing focused ultrasound and a magnetostatic field to generate an electric current in tissue fluid to regulate the activities of neurons, has high spatial resolution and penetration depth. The neuronal spike-frequency adaptation plays an important role in the treatment of neural information. In this paper, we study the effects of ultrasonic intensity, magnetostatic field intensity and ultrasonic frequency on the neuronal spike-frequency adaptation based on the Ermentrout neuron model. The simulation results show that, the peak time interval becomes smaller, the interspike interval becomes shorter and the time of the firing of the neuron is shortened with the increasing of the magnetostatic field intensity. With the increase of the adaptive variables, the initial spike-frequency is shifted to the right with the magnetostatic field intensity, and the spike-frequency is linearly related to the increase of the magnetostatic field intensity in steady state. The simulation effect with change of the ultrasonic intensity is consistent with the change of magnetostatic field intensity. The change of the ultrasonic frequency has no effect on the neuronal spike-frequency adaptation. Under the different adaptive variables, with the increase of the adaptive variables, the initial spike-frequency amplitude decreased with the increasing of the ultrasonic frequency, and the spike-frequency is linearly related to the increase of the ultrasonic frequency in steady state. These results of the study can help us to reveal the mechanism of transcranial magneto-acoustical stimulation on the neuronal spike-frequency adaptation, and provide a theoretical basis for its application in the treatment of neurological disorders.

Au Nanoclusters Sensitized Black TiO2-x Nanotubes for Enhanced Photodynamic Therapy Driven by Near-Infrared Light.

The low reactive oxygen species production capability and the shallow tissue penetration of excited light (UV) are still two barriers in photodynamic therapy (PDT). Here, Au cluster anchored black anatase TiO2-x nanotubes (abbreviated as Au25 /B-TiO2-x NTs) are synthesized by gaseous reduction of anatase TiO2 NTs and subsequent deposition of noble metal. The Au25 /B-TiO2-x NTs with thickness of about 2 nm exhibit excellent PDT performance. The reduction process increased the density of Ti3+ on the surface of TiO2 , which effectively depresses the recombination of electron and hole. Furthermore, after modification of Au25 nanoclusters, the PDT efficiency is further enhanced owing to the changed electrical distribution in the composite, which forms a shallow potential well on the metal-TiO2 interface to further hamper the recombination of electron and hole. Especially, the reduction of anatase TiO2 can expend the light response range (UV) of TiO2 to the visible and even near infrared (NIR) light region with high tissue penetration depth. When excited by NIR light, the nanoplatform shows markedly improved therapeutic efficacy attributed to the photocatalytic synergistic effect, and promotes separation or restrained recombination of electron and hole, which is verified by experimental results in vitro and in vivo.

Reduced Apparent Diffusion Coefficient in Various Brain Areas following Low-Intensity Transcranial Ultrasound Stimulation.

Diffusion of water molecules closely related to physiological and pathological information of brain tissue. Low-intensity transcranial ultrasound stimulation (TUS) has advantages of noninvasive, high spatial resolution and penetration depth. Previous studies have demonstrate that TUS can modulate neuronal activity and alter cortical hemodynamic. However, how TUS affect diffusion of water molecules remain unclear. In this paper, in order to evaluate the effect of low-intensity TUS on the diffusion of water molecules in brain tissue, diffusion-weighted magnetic resonance (MR) imaging was performed in 19 healthy Sprague-Dawley rats in sham surgery group (six rats) and TUS group (thirteen rats) Subsequently, rats were stimulated by low-intensity transcranial ultrasound for 5 min in TUS group. Finally, rats of sham surgery group and TUS group were imaged again by diffusion-weighted MR imaging. The apparent diffusion coefficient (ADC) was measured in caudate putamen region and middle brain motor-related region of each rat in sham surgery group and TUS group. Surgery-related and TUS-related changes were calculated using a statistical analysis. The mean ADC values of marked regions of six rats in sham surgery group were 0.743 ± 0.031 (pre-surgery) and 0.745 ± 0.029 (post-surgery). The mean ADC values of marked regions of 13 rats in TUS group were 0.749 ± 0.032 (pre-TUS) and 0.712 ± 0.033 (post-TUS) Compared to the pre-TUS values, the mean ADC values of the rats decreased 4.9% (*P < 0.05) post-TUS. These results of this study demonstrate that low-intensity TUS can restrict the diffusion of water molecules in brain tissue.

Evanescent Field Study on a U-Shaped Silica Fiber Absorption Sensor Using Non-Sequential Ray Tracing

The ray tracing of unclad U-shape multimode fiber optic is examined by using Zemax simulation have been proposed. The influence of the geometry of sensing region such as absorbing medium refractive index, n2, shape of fiber and the bending radius is analyzed. Number of analysis ray is determined and the value of n2 is varied at 1, 1.3314, 1.359, 1.36, 1.37 and 1.4. The intensity of light propagate inside the fiber is reducing at high n2 and this graph pattern is supported by experimental result. A U-shaped sensor is used for the analysis because of the sensitivity is higher than straight fiber design due to their higher penetration depth. Zemax simulation shows that the fiber with bending radius 1.5 mm has higher response compared to fiber with radius 2.5 mm.

Effect of Activating Flux on Penetration in ATIG Welding of 316 Stainless Steel

Tungsten inert gas welding is popular in some industries due to the possibility of obtaining good weld bead surface and high-quality joint without any weld defect. However, compared to many welding processes, shallow penetration of TIG welding hinders its applicability to weld thick components in one pass, thus the productivity is relatively low. An increased depth of penetration can be achieved by Activated TIG (ATIG) welding leading to overall reduction in number of welding passes, and thus increasing productivity. In the present work, attempts were made to find out the optimum flux mixture of SiO and TiO from various ratio of mixtures by carrying out 2 2 bead-on-plate welding on AISI 316 Stainless Steel specimens. From the obtained experimental data, suitable flux ratio was tried to find out giving the highest depth of penetration.

Theoretical analysis of the effects of transcranial magneto-acoustical stimulation on neuronal firing rhythm and Ca2+ concentration with Chay neuron model

Transcranial magneto-acoustical stimulation (TMAS) utilizes low-intensity focused ultrasound and a magnetostatic field to generate an electric current in nerve tissue with high spatial resolution and penetration depth. The analysis of the neuronal firing rhythm that carries different stimulation signals is of great significance for the study of neural information coding. Moreover, the change in intracellular Ca2+ concentration is a response of neurons to external stimuli. However, how the TMAS affect the neuronal firing rhythm and Ca2+ concentration are unclear. In our study, we investigate the neuronal firing rhythm and Ca2+ concentration with TMAS under three types of ultrasound based on the Chay neuron model with simulation. The simulation results show that the modulation of the neuronal firing rhythm and Ca2+ concentration by TMAS is strongly dependent on types and parameters of ultrasound. This study indicates that TMAS can modulate the neuronal firing rhythm and Ca2+ concentration.

Review of GaN-based devices for terahertz operation

GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ∼90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaN-based devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.

Rare‐earth‐doped SiO2‐CaF2 glass ceramic nano‐particle with upconversion properties

AbstractRare‐earth‐doped upconversion nano‐phosphor shows new possibilities in the field of bioimaging because of its unique properties like higher penetration depth, low signal to noise ratio (SNR), good photo stability, and zero auto fluorescence. The oxyfluoride glass system is the combination of both fluoride and oxide where fluoride host offers high optical transparency due to low phonon energy and oxide network offers high physical stability. Thus, in the present work, an attempt has been made to synthesize 1 mol% Er3+ doped SiO2‐CaF2 glass ceramic nano‐particles through sol‐gel route. The synthesized glass ceramic particles were heat treated at 4 different temperatures starting from 600°C to 900°C.The X‐ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) analysis confirmed the formation of CaF2 nano‐crystals in the matrix which is 20‐30 nm in size. The vibrational spectroscopic analysis of the glass ceramics sample has been investigated by Fourier transform infrared (FTIR) spectroscopy. The UV‐Visible‐NIR spectroscopy analysis was carried out to analyze the absorption intensity in the near infrared region. Upon 980 nm excitation, the sample shows red emission corresponds to 4F9/2→4I15/2 energy level transition. The prepared nano‐particles showed excellent biocompatibility when tasted on MG‐63 osteoblast cells.

Performance study of metallic clad planar waveguide sensors in presence of graphene layer

In this paper, the performance of two metal clad planer waveguide based sensor in presence of a graphene layer just before or after the guiding layer is studied and compared. The analyses of waveguides are performed by analytical approach based on transfer matrix theory. In TM mode analysis, the dispersion characteristics of proposed waveguides show both the SPR mode and the waveguide modes. The penetration depth of SPR mode is increased with the graphene layer thicknesses in one considered configuration of waveguide and decreased in other considered configuration of waveguide. However, comparisons in considered waveguides are made on the basis of their sensitivity, detection accuracy and quality factor through the waveguide modes. It is observed that all these parameters are highly depends on the graphene layer thickness near the cutoff film thickness of waveguide modes due to the high penetration depth of light in cover media. Away from cutoff region, the presence of graphene layers before or after the guiding layer provides almost similar results. Based on obtained results, it is easy to choose an appropriate position and thickness of graphene layer for the guided-wave and radiated-wave applications.

Neuromodulation with nanoparticles.

Ultrasonic drug uncaging shows potential for noninvasive manipulation of the brain

Pilot-scale radiofrequency blanching of potato cuboids: heating uniformity.

Traditional hot water blanching has a slow heat transfer rate, whereas radiofrequency (RF) heating has the advantages of a much faster heating rate and a higher penetration depth. In the present study, RF heating was applied to improve heating uniformity for subsequent blanching experiments involving potato cuboids. Potato cuboids were treated in a pilot-scale, RF heating system (27.12 MHz, 6 kW) under different operating conditions. The dielectric constant increased first and then decreased with temperature, whereas the loss factor increased as the temperature increased. The results of the present study reveal that the electrode gap, sample height and NaCl solution had significant effects (P < 0.05) on the temperature distribution and heating uniformity of the sample after RF heating. The optimum RF heating uniformity was obtained at an electrode gap of 120 mm, a sample height of 60 mm and when immersed in NaCl solution of 0.5 s m-1 . The central heating pattern was presented in a sample. Cold spots were located at the edge of the top surface of the sample. The present study shows the great potential of RF heating for the blanching of vegetables. Future studies should aim to determine changes in the texture and nutrient contents of vegetables during RF heating. © 2017 Society of Chemical Industry.

The effect of surface morphology in copper oxide nanostructure to photo detector characteristics

We study the effect of structural properties of copper oxide nanostructure and its sensitivity for photo detector application. Copper oxide (CuO) nanostructures were prepared by combining the thermal evaporation with dry oxidation. We select CuO system at different thickness (around 90, 170, and 270 nm) and X-ray diffraction spectra confirms their polycrystalline structure. Scanning electron microscope images show the distinct CuO morphology surface for each sample on which the grain shape is changed and the size is grown with the increasing of the CuO thickness. Fourier-transform infra-red spectra reveals the high penetration depth of oxygen at ∼90 nm thick sample indicated by large Si-O-Si bond intensity. Photo current characterization for each sample is carried out to compare its light sensing properties. We found that the thickness of CuO nanostructure system is related to the sensitivity of device during the light exposure in which thinner samples have better performance. Furthermore different band gap for each CuO sample is predicted from its sensitivity at continuous light exposure. We suggest that the grain boundary and the distinct morphology might promote a unique confined nanostructure effect, resulting in band gap widening. These studies demonstrate a new approach for tunable photonic device efficiency that could be beneficial in reducing energy loss during energy conversion.

Numerical simulation study of factors affecting relative permeability modification for water-shutoff treatments

Polymer solutions and gels are frequently used to control excessive water production in oil and gas wells by reducing the permeability to water flow to a greater extent than to oil or gas flow (Relative Permeability Modifiers, RPM, or disproportionate permeability reduction, DPR). RPM and DPR can be used as synonymous in this study; however, specialists use RPM term for the cases in which permeability reduction is less compare to DPR. The significance of RPM agents, chemicals using in water-shutoff treatments, is that their placement does not require mechanical isolation. However, the performance of RPM treatment is still poor in field applications. This study applied numerical simulation methods to investigate the factors impacting RPM treatments on reservoir (Macroscopic) level. Furthermore, Design of Experiments (DOE) was used to rank these factors based on their influence on RPM performance (water cut reduction and oil recovery improvement).The results indicated that there are nine parameters which can enhance or downgrade the success of DPR treatments, treatments at oil/gas wells when use of DPR polymer or gel results in Disproportionate Permeability Reduction of treated formation. The performance of DPR treatment was more pronounced at low oil density, low oil viscosity, high gel penetration depth, and at high permeability heterogeneity among layers (linear flow is more dominated). However, the performance of DPR treatments was downgraded if the treatments were applied at high production flowrate, low ratio of residual resistance factor for water (Frrw) to residual resistance factor for oil (Frro), and high G-shape (crossflow indicator) values. Moreover, when the capillary forces dominate the flow (capillary-viscous number>10), RPM results were not largely encouraging due to water blocking effect. On the other side, in the viscous dominated flow, RPM performance was more pronounced. These factors which were studied in this work can promote a short-term successful remedy, a long-term successful treatment, or even a failed treatment. Some of these factors can be controlled; the operator can choose the optimum level of the parameter, like production flowrate. However, other factors cannot be controlled, but the value of this study is still increase probability of success the treatment prior to field application.

Imaging of Extracellular pH Using Hyperpolarized Molecules

AbstractMany diseases can overrule natural pH regulatory mechanisms and alter the extracellular pH (pHe). A non‐invasive method that resolves pHe in vivo with high spatial and temporal resolution could therefore improve diagnosis and monitoring of diseases, contributing to the concept of precision medicine. During the last decades, several techniques have been proposed to image pHe non‐invasively. The majority of these methods rely on magnetic resonance because of its good spatial resolution, high penetration depth, non‐ionizing radiation and excellent complimentary soft tissue contrast. Dissolution dynamic nuclear polarization (DNP) is an emerging concept to enhance nuclear magnetic resonance (NMR) signals by more than four orders of magnitude, making it possible to observe in vivo metabolic processes in real‐time. Here, we summarize and review recent developments in pHe imaging techniques based on hyperpolarization methods and give an overview of recently discovered hyperpolarized pH sensor molecules that have been applied in vitro and in vivo.

Curve fitting in Fourier transform near infrared spectroscopy used for the analysis of bacterial cells

Infrared spectroscopy is a prominent molecular technique for bacterial analysis. Within its context, near infrared spectroscopy in particular brings benefits over other vibrational approaches; these advantages include, for example, lower sensitivity to water, high penetration depth and low cost. However, near infrared spectroscopy is not popular within microbiology, because the spectra of organic samples are difficult to interpret. We propose a comparison of spectral curve-fitting methods, namely, techniques that facilitate the interpretation of most peaks, simplify the spectra and improve the prediction of bacterial species from the relevant near infrared spectra. The performances of three common curve-fitting algorithms and the technique based on the differential evolution were compared via a synthesized experimental spectrum. Utilizing the obtained results, the spectra of three different bacterial species were curve fit by optimized algorithm. The proposed algorithm decomposed the spectra to specific absorption peaks, whose parameters were estimated via the differential evolution approach initialized through Levenberg-Marquardt optimization; subsequently, the spectra were classified with conventional procedures and using the parameters of the revealed peaks. On a limited data set, the correct classification rate computed by partial least squares discriminant analysis was 95%. When we employed the peak parameters for the classification, the rate corresponded to 91.7%. According to the Gaussian formula, the parameters comprise the spectral peak position, amplitude and width. The most important peaks for bacterial discrimination were identified by analysis of variance and interpreted as N–H stretching bonds in proteins, cis bonds and CH2 absorption in fatty acids. We examined some aspects of the behaviour of standard curve-fitting algorithms and proposed differential evolution to optimize the fitting process. Based on the correct use of these algorithms, the near infrared spectra of bacteria can be interpreted and the full potential of near infrared spectroscopy in microbiology exploited.

Welding of thick plate copper with laser beam welding under vacuum

Today, copper is one of the most important materials and will become even more important in the future. It is used in a wide range of products, industry sectors, and plate thicknesses. The beam welding technologies laser beam welding and electron beam welding achieve high intensities and are thereby suitable to overcome the difficulties in the welding of copper, which are caused by properties such as high thermal conductivity. There is a high demand for the application of the laser beam in the welding of copper, but in industrial applications, a sufficient process capability is currently only achieved with a high welding speed and a high laser power level. At low welding speeds, process instabilities such as weld metal ejections occur. These ejections can cause critical welding defects which have to be prevented. At high welding speeds, the penetration depth decreases dramatically even if a high laser power is applied. In addition, the process control is hampered and the investment costs increase. By laser beam welding in vacuum, the process capability can be increased significantly. Weld metal ejections at low welding speeds are prevented. This increase in process stability can be transferred in a high penetration depth at a comparatively low laser power level. Sound welding of copper at a power level between 4 and 8 kW (intensity level 50–80 kW/mm2) of a multimode solid state laser becomes possible without weld metal ejections. A penetration depth of 3–8 mm is achieved.

High-speed pump-probe imaging of ultrashort pulsed laser cutting of polymers

Ultrashort pulsed laser processing is an effective technology for high-precision cutting, ablation, and drilling of almost all types of material, with low thermal input to the substrate. Polymers which are usually transparent for the laser pulses can be efficiently processed. The material is heated very fast resulting in direct evaporation of the irradiated material volume. On one hand, incubation effects occur due to changed surface roughness, voids, and chemical changes of the material, leading to a variation of energy absorption. On the other hand, if a high repetition rate and high pulse energy are applied to achieve high productivity at polymer cutting, heat accumulation occurs leading to melting and heat affected zones. An estimation of the pulse number dependent material modification and heat input which leads to these effects is not easily accessible for quantitative measurements. Furthermore, numerous process parameters influence the interaction making process analysis and optimization extensive. A versatile tool towards improved knowledge on ultrashort pulsed processes is pump-probe imaging. By using this, effects on a very short timescale such as nonlinear laser absorption, propagation of material waves and plasma generation can be visualized. The recording device in the setup which is applied for the analysis of polymer cutting and drilling in this paper is a high-speed camera with frame rates of up to 50 kHz. This enables recording video sequences contrary to taking a single picture. The authors utilized this to enable the observation of effects of heat accumulation which evolves after a large amount of pulses. Simultaneously, the authors were able to maintain the stated advantages of the pump-probe configuration. Therefore, under variation of several process parameters such as pulse repetition rate, pulse energy, and lateral pulse to pulse separation video sequences were recorded. By a variation of the pump-probe delays of 0 up to 5 ns, material wave propagation can be identified and optimized for evaluation. The points of origin of the observed waves are considered as the regions of highest nonlinear energy deposition; thus, the deposited energy distribution can be estimated. As every single pulse up to a pulse number of 1000 pulses is imaged, the transition from high penetration depth of the first incident pulses to strong surface absorption for an increasing pulse number due to incubation can be shown. Furthermore, strongly absorbing spots in the bulk volume caused by impurities and material modification lead to vapor generation under high pressure. Finally, the confined pressure is assumed to be a main reason for crack formation.

Innovative hybrid welding process for structural steelwork engineering—Laser submerged arc hybrid welding

The welding of thick metal sheets has become increasingly important for structural steelwork engineering applications (e.g., pipe- or crane building). Nowadays, welding tasks are performed using a time-consuming conventional submerged arc welding process. Here, a large number of welding passes are necessary, which leads to a thermally induced distortion. Therefore, there is a high demand for a welding process which allows a cost-effective welding of thick metal sheets. By the development of a laser beam submerged-arc hybrid welding process (LUPuS), a technique is created which combines the high penetration depth of the laser with the high thermal efficiency of the submerged arc process. This leads to synergy effects which predestine LUPuS for the given welding task. Earlier projects have shown a general feasibility of LUPuS. Steel plates with thicknesses of up to 50 mm have been joined without any welding issues using the double-sided single pass technique. However, different results of the notch impact test in the laser beam-dominated and submerged arc-dominated welding areas are noticeable. This contribution will demonstrate the effect on the mechanical-technological properties in the different welding seam areas by changing the flux and the wire of the submerged arc welding process. In order to investigate these properties, impact strength tests have been performed. Moreover, the dynamic behavior of the molten pool was studied. Furthermore, the results of the investigation of the weld metal structure are presented.

Upconversion nanoparticles for bioimaging

AbstractFluorescent labeling is a widely used indispensable tool in biology. Conventional downconversion fluorescence labels with ultraviolet or short-wavelength excitation suffer from autofluorescence, low signal-to-noise ratio, and incident photo damage to living organisms. However, upconverting fluorescent nanoparticles emit detectable photons of higher energy in the near-infrared (NIR) or visible range upon irradiation with a NIR light in a process termed upconversion. They overcome some of the disadvantages faced by conventional downconversion labels with the advantages including very low autofluorescence, absence of photo damage to living organisms, high detection sensitivity, and high depth of light penetration, thus making them an ideal fluorescent label for bioimaging. The present review focuses on the features of upconversion nanoparticles, the applications of upconversion nanoparticles in bioimaging, and the bioimaging equipments and methods and discusses the obstacles and development trend of upconversion nanoparticles in bioimaging; we hope this work will provide insights into the study of relevant fields. Upconversion nanoparticles have special photoluminescent properties. Substantial advancements have been made in the field of upconversion nanoparticles for bioimaging. A large number of modifications of upconversion nanoparticles are studied to make them more hydrophilic and biocompatible. At the same time, the safety and toxicity of nanoparticles have caused wide public concern.