Enhanced Raman scattering based on a ZnO/Ag nanostructured substrate: an in-depth study of the SERS mechanism.

Combining semiconductor and noble metal nanostructures into a hybrid system has shown many complementary advantages in the optical properties, making them more attractive in practical applications. Herein, we prepared a semiconductor/noble metal hybrid system composed of Ag nanoparticles decorated on ZnO nanoplates acting as a surface-enhanced Raman scattering (SERS) substrate for probing methyl red. The tuning of the optical characteristics of the hybrid system was demonstrated through the changes in the absorption, fluorescence, and Raman spectra. The formation of the local electromagnetic field at the heterostructure interface plays a pivotal role in its SERS activity. Thanks to density functional theory calculations, methyl red's vibrational modes and symmetry properties were assigned to be consistent with the contribution of the neutral trans conformer and protonated state. Then, using Herzberg-Teller-surface selection rules, these assignments strongly support the realization that the SERS mechanism based on the ZnO/Ag substrate has a significant electromagnetic contribution versus the Ag substrate in which charge transfer plays a pivotal role. To the best of our knowledge, this is the first investigation that has clarified the mechanism and advantage of semiconductor/metal (ZnO/Ag nanostructures) even over noble metals (Ag nanoparticles) in SERS applications. Moreover, the SERS behavior based on the ZnO/Ag substrate was also examined and the results indicated high sensitivity and good repeatability.

Multiple primary squamous cell carcinomas of the oral cavity: A cross-sectional study in vietnam.

Background: Multiple primary squamous cell carcinomas (MPSCs) of the oral cavity are very uncommon in clinical practice. This study describes the clinical features, imaging, and treatment characteristics of the oral cavity with MPSCs at the same time of diagnosis in our center. Besides, we review the literature and prior studies on MPSCs. Study design: A retrospective, descriptive study from January 2019 to December 2021 was conducted on seven patients with MPSCs of the oral cavity at the time of their first diagnosis. Evaluation of the patient's characteristics, the treatment plan, the response to treatment, and the overall survival (OS). Results: Seven male patients ranging in age from 43 to 70 years (Mean: 53.5). Positron Emission Tomography/Computed Tomography (PET/CT) revealed a significantly increased standardized uptake value (SUV) in the index tumor (SUVi = 15.76 ± 1.96). The index tumor is often staged T3, T4; whereas the synchronous tumor is typically staged T1, T2. All patients had concurrent chemoradiotherapy (CCRT) and achieved a partial response in all cases. Mean OS was 14.71 ± 11.85 months. Conclusions: MPSCs of the oral cavity at the time of diagnosis are uncommon and associated with a poor prognosis for patients. Comprehensive clinical examination, combined imaging diagnostics, with PET/CT being critical for detecting the second lesion, particularly in patients with an advanced index tumor.

The impact of trans-arterial embolization on the result of chemoradiotherapy in oral cavity cancer.

Objectives: Evaluation of the hemostatic effect of trans-arterial embolization on patients with advanced oral cavity cancer who had bleeding complications while undergoing definitive concurrent chemoradiotherapy (CCRT). Additionally, assess the effect of trans-arterial embolization on treatment response following concurrent chemoradiotherapy, as well as overall survival (OS) and progression-free survival (PFS) in the group of patients following the intervention.Method: From September 2018-June 2021, a retrospective descriptive study was conducted on 16 patients with inoperable, locally advanced oral cavity cancer who received definitive concurrent chemoradiotherapy, experienced acute bleeding complications, and received selective intravascular intervention with various embolization materials at Vietnam National Cancer Hospital.Results: After selective embolization, 16/16 patients ceased bleeding; 1 patient re-bled for the second time after 3 weeks. The average duration of chemoradiotherapy interruption due to intervention was 6.7 days. After CCRT, 15/16 (93.75%) patients achieved a response, with 9/16 (56.25%) patients achieving a complete response. The median OS was 14 months (range, 3-26 months), and the median PFS was 10 months (range, 3-20 months). There were no significant complications, particularly neurological side effects.ConclusionsTumor bleeding is a common and serious complication of CCRT treatment in patients with locally advanced oral cavity cancer. Embolization is a safe and effective method of controlling acute bleeding that has no adverse effect on the outcome of definitive concurrent chemoradiotherapy.

External-Beam Radiotherapy Alone Management of Primary CNS Lymphoplasmacytic Lymphoma: A Vietnamese Case Report and Literature Review.

BACKGROUND: Primary central nervous system (CNS) lymphoma is an uncommon non-Hodgkin disease limited to the CNS, and most cases are diffuse large B-cell lymphomas. Other pathologies, including lymphoplasmacytic lymphoma (LPL), are exceedingly rare and poorly understood. The clinical presentation of primary CNS LPL is diverse. It depends on the original site and the tumor's extension. There is currently no consensus on a treatment strategy for this uncommon manifestation. To our knowledge, no previously published case was successfully treated with radiation therapy alone. CASE PRESENTATION: We present here a case of primary CNS LPL. A 46-year-old, previously healthy woman was presented with a worsening headache and lower extremity numbness. Multifocal enhanced masses were detected in an MRI with biopsy results consistent with LPL. A complete staging workup was performed with no evidence of systemic disease. The patient received external-beam radiotherapy alone and had a complete remission. After 2 years of follow-up, she remains disease-free. CONCLUSION: Radiation alone is a promising treatment option for primary CNS lymphoplasmacytic lymphoma.

Report on Unusual Sites of Lymph Node Metastases in Nasopharyngeal Carcinoma.

Nasopharyngeal carcinoma (NPC) is amongst the most common malignancies of head and neck cancers. Most patients are admitted to the hospital with advanced disease. NPC has a tendency toward early metastatic spread to cervical lymph nodes, and levels II and III are most commonly involved. A few reports have indicated specific metastatic sites of nasopharyngeal cancer, including lymph node metastasis and distant metastasis. Evidence of histopathology and immunohistochemistry is required to prove NPC origin. In many cases, surgery can be performed to obtain accurate evidence of the pathology. However, surgery can also affect the overall treatment plan and strategy for NPC and should be considered in the specific circumstances of the disease. Multidisciplinary consultation is required for these uncommonly specific metastases. Paying attention to the specific lymph node metastasis sites of NPC plays an important role in accurately diagnosing the stage, thereby giving an appropriate treatment strategy. It is also important in determining radiotherapy volumes because radiotherapy is the standard therapy for this disease. Herein, we are reporting 2 cases of NPC with clinical metastasis to unusual lymph node sites such as the parotid salivary gland and the cheek. Histological analyses from the resected specimens confirmed its nasopharyngeal origin. Lymph node metastases in the parotid gland and the cheek are unusual. In diagnosis and follow-up, it is necessary to evaluate carefully to make an accurate diagnosis and appropriate treatment plans for patients as well as early detect recurrent metastases at uncommon sites of lymph nodes.

Rational design of magnetically separable core/shell Fe3O4/ZnO heterostructures for enhanced visible-light photodegradation performance.

Magnetically separable core/shell Fe3O4/ZnO heteronanostructures (MSCSFZ) were synthesized by a facile approach, and their application for enhanced solar photodegradation of RhB was studied. The formation mechanism of MSCSFZ was proposed, in which Fe3O4 nanoparticles served as a template for supporting and anchoring the ZnO crystal layer as the shells. The morphology of MSCSFZ can be varied from spherical to rice seed-like structures, and the bandgap was able to be narrowed down to 2.78 eV by controlling the core-shell ratios. As a result, the MSCSFZ exhibited excellent visible-light photocatalytic activity for degradation of rhodamine B (RhB) in aqueous solution as compared to the controlled ZnO nanoparticles. Moreover, MSCSFZ could be easily detached from RhB solution and maintained its performance after 4 cycles of usage. This work provides new insights for the design of high-efficient core/shell recyclable photocatalysts with visible light photocatalytic performance.

Practical computation of the diffusion MRI signal of realistic neurons based on Laplace eigenfunctions.

The complex transverse water proton magnetization subject to diffusion-encoding magnetic field gradient pulses in a heterogeneous medium such as brain tissue can be modeled by the Bloch-Torrey partial differential equation. The spatial integral of the solution of this equation in realistic geometry provides a gold-standard reference model for the diffusion MRI signal arising from different tissue micro-structures of interest. A closed form representation of this reference diffusion MRI signal called matrix formalism, which makes explicit the link between the Laplace eigenvalues and eigenfunctions of the biological cell and its diffusion MRI signal, was derived 20 years ago. In addition, once the Laplace eigendecomposition has been computed and saved, the diffusion MRI signal can be calculated for arbitrary diffusion-encoding sequences and b-values at negligible additional cost. Up to now, this representation, though mathematically elegant, has not been often used as a practical model of the diffusion MRI signal, due to the difficulties of calculating the Laplace eigendecomposition in complicated geometries. In this paper, we present a simulation framework that we have implemented inside the MATLAB-based diffusion MRI simulator SpinDoctor that efficiently computes the matrix formalism representation for realistic neurons using the finite element method. We show that the matrix formalism representation requires a few hundred eigenmodes to match the reference signal computed by solving the Bloch-Torrey equation when the cell geometry originates from realistic neurons. As expected, the number of eigenmodes required to match the reference signal increases with smaller diffusion time and higher b-values. We also convert the eigenvalues to a length scale and illustrate the link between the length scale and the oscillation frequency of the eigenmode in the cell geometry. We give the transformation that links the Laplace eigenfunctions to the eigenfunctions of the Bloch-Torrey operator and compute the Bloch-Torrey eigenfunctions and eigenvalues. This work is another step in bringing advanced mathematical tools and numerical method development to the simulation and modeling of diffusion MRI.

Diffusion MRI simulation of realistic neurons with SpinDoctor and the Neuron Module.

The diffusion MRI signal arising from neurons can be numerically simulated by solving the Bloch-Torrey partial differential equation. In this paper we present the Neuron Module that we implemented within the Matlab-based diffusion MRI simulation toolbox SpinDoctor. SpinDoctor uses finite element discretization and adaptive time integration to solve the Bloch-Torrey partial differential equation for general diffusion-encoding sequences, at multiple b-values and in multiple diffusion directions. In order to facilitate the diffusion MRI simulation of realistic neurons by the research community, we constructed finite element meshes for a group of 36 pyramidal neurons and a group of 29 spindle neurons whose morphological descriptions were found in the publicly available neuron repository NeuroMorpho.Org. These finite elements meshes range from having 15,163 nodes to 622,553 nodes. We also broke the neurons into the soma and dendrite branches and created finite elements meshes for these cell components. Through the Neuron Module, these neuron and cell components finite element meshes can be seamlessly coupled with the functionalities of SpinDoctor to provide the diffusion MRI signal attributable to spins inside neurons. We make these meshes and the source code of the Neuron Module available to the public as an open-source package. To illustrate some potential uses of the Neuron Module, we show numerical examples of the simulated diffusion MRI signals in multiple diffusion directions from whole neurons as well as from the soma and dendrite branches, and include a comparison of the high b-value behavior between dendrite branches and whole neurons. In addition, we demonstrate that the neuron meshes can be used to perform Monte-Carlo diffusion MRI simulations as well. We show that at equivalent accuracy, if only one gradient direction needs to be simulated, SpinDoctor is faster than a GPU implementation of Monte-Carlo, but if many gradient directions need to be simulated, there is a break-even point when the GPU implementation of Monte-Carlo becomes faster than SpinDoctor. Furthermore, we numerically compute the eigenfunctions and the eigenvalues of the Bloch-Torrey and the Laplace operators on the neuron geometries using a finite elements discretization, in order to give guidance in the choice of the space and time discretization parameters for both finite elements and Monte-Carlo approaches. Finally, we perform a statistical study on the set of 65 neurons to test some candidate biomakers that can potentially indicate the soma size. This preliminary study exemplifies the possible research that can be conducted using the Neuron Module.

Microstructural organization of human insula is linked to its macrofunctional circuitry and predicts cognitive control.

The human insular cortex is a heterogeneous brain structure which plays an integrative role in guiding behavior. The cytoarchitectonic organization of the human insula has been investigated over the last century using postmortem brains but there has been little progress in noninvasive in vivo mapping of its microstructure and large-scale functional circuitry. Quantitative modeling of multi-shell diffusion MRI data from 413 participants revealed that human insula microstructure differs significantly across subdivisions that serve distinct cognitive and affective functions. Insular microstructural organization was mirrored in its functionally interconnected circuits with the anterior cingulate cortex that anchors the salience network, a system important for adaptive switching of cognitive control systems. Furthermore, insular microstructural features, confirmed in Macaca mulatta, were linked to behavior and predicted individual differences in cognitive control ability. Our findings open new possibilities for probing psychiatric and neurological disorders impacted by insular cortex dysfunction, including autism, schizophrenia, and fronto-temporal dementia.

Portable simulation framework for diffusion MRI.

The numerical simulation of the diffusion MRI signal arising from complex tissue micro-structures is helpful for understanding and interpreting imaging data as well as for designing and optimizing MRI sequences. The discretization of the Bloch-Torrey equation by finite elements is a more recently developed approach for this purpose, in contrast to random walk simulations, which has a longer history. While finite element discretization is more difficult to implement than random walk simulations, the approach benefits from a long history of theoretical and numerical developments by the mathematical and engineering communities. In particular, software packages for the automated solutions of partial differential equations using finite element discretization, such as FEniCS, are undergoing active support and development. However, because diffusion MRI simulation is a relatively new application area, there is still a gap between the simulation needs of the MRI community and the available tools provided by finite element software packages. In this paper, we address two potential difficulties in using FEniCS for diffusion MRI simulation. First, we simplified software installation by the use of FEniCS containers that are completely portable across multiple platforms. Second, we provide a portable simulation framework based on Python and whose code is open source. This simulation framework can be seamlessly integrated with cloud computing resources such as Google Colaboratory notebooks working on a web browser or with Google Cloud Platform with MPI parallelization. We show examples illustrating the accuracy, the computational times, and parallel computing capabilities. The framework contributes to reproducible science and open-source software in computational diffusion MRI with the hope that it will help to speed up method developments and stimulate research collaborations.

SpinDoctor: A MATLAB toolbox for diffusion MRI simulation.

The complex transverse water proton magnetization subject to diffusion-encoding magnetic field gradient pulses in a heterogeneous medium can be modeled by the multiple compartment Bloch-Torrey partial differential equation. Under the assumption of negligible water exchange between compartments, the time-dependent apparent diffusion coefficient can be directly computed from the solution of a diffusion equation subject to a time-dependent Neumann boundary condition. This paper describes a publicly available MATLAB toolbox called SpinDoctor that can be used 1) to solve the Bloch-Torrey partial differential equation in order to simulate the diffusion magnetic resonance imaging signal; 2) to solve a diffusion partial differential equation to obtain directly the apparent diffusion coefficient; 3) to compare the simulated apparent diffusion coefficient with a short-time approximation formula. The partial differential equations are solved by P1 finite elements combined with built-in MATLAB routines for solving ordinary differential equations. The finite element mesh generation is performed using an external package called Tetgen. SpinDoctor provides built-in options of including 1) spherical cells with a nucleus; 2) cylindrical cells with a myelin layer; 3) an extra-cellular space enclosed either a) in a box or b) in a tight wrapping around the cells; 4) deformation of canonical cells by bending and twisting; 5) permeable membranes; Built-in diffusion-encoding pulse sequences include the Pulsed Gradient Spin Echo and the Oscillating Gradient Spin Echo. We describe in detail how to use the SpinDoctor toolbox. We validate SpinDoctor simulations using reference signals computed by the Matrix Formalism method. We compare the accuracy and computational time of SpinDoctor simulations with Monte-Carlo simulations and show significant speed-up of SpinDoctor over Monte-Carlo simulations in complex geometries. We also illustrate several extensions of SpinDoctor functionalities, including the incorporation of T2 relaxation, the simulation of non-standard diffusion-encoding sequences, as well as the use of externally generated geometrical meshes.

Diffusion MRI simulation in thin-layer and thin-tube media using a discretization on manifolds.

The Bloch-Torrey partial differential equation can be used to describe the evolution of the transverse magnetization of the imaged sample under the influence of diffusion-encoding magnetic field gradients inside the MRI scanner. The integral of the magnetization inside a voxel gives the simulated diffusion MRI signal. This paper proposes a finite element discretization on manifolds in order to efficiently simulate the diffusion MRI signal in domains that have a thin layer or a thin tube geometrical structure. The variable thickness of the three-dimensional domains is included in the weak formulation established on the manifolds. We conducted a numerical study of the proposed approach by simulating the diffusion MRI signals from the extracellular space (a thin layer medium) and from neurons (a thin tube medium), comparing the results with the reference signals obtained using a standard three-dimensional finite element discretization. We show good agreements between the simulated signals using our proposed method and the reference signals for a wide range of diffusion MRI parameters. The approximation becomes better as the diffusion time increases. The method helps to significantly reduce the required simulation time, computational memory, and difficulties associated with mesh generation, thus opening the possibilities to simulating complicated structures at low cost for a better understanding of diffusion MRI in the brain.

Characteristics and mechanisms of cadmium adsorption onto biogenic aragonite shells-derived biosorbent: Batch and column studies.

Calcium carbonate (CaCO3)-enriched biomaterial derived from freshwater mussel shells (FMS) was used as a non-porous biosorbent to explore the characteristics and mechanisms of cadmium adsorption in aqueous solution. The adsorption mechanism was proposed by comparing the FMS properties before and after adsorption alongside various adsorption studies. The FMS biosorbent was characterized using nitrogen adsorption/desorption isotherm, X-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, Fourier-transform infrared spectroscopy, and point of zero charge. The results of batch experiments indicated that FMS possessed an excellent affinity to Cd(II) ions within solutions pH higher than 4.0. An increase in ionic strength resulted in a significant decrease in the amount of Cd(II) adsorbed onto FMS. Kinetic study demonstrated that the adsorption process quickly reached equilibrium at approximately 60 min. The FMS biosorbent exhibited the Langmuir maximum adsorption capacity as follows: 18.2 mg/g at 10 °C < 26.0 mg/g at 30 °C < 28.6 mg/g at 50 °C. The Cd(II) adsorption process was irreversible, spontaneous (-ΔG°), endothermic (+ΔH°), and more random (+ΔS°). Selective order (mmol/g) of metal cations followed as Pb2+ > Cd2+ > Cu2+ > Cr3+ > Zn2+. For column experiments, the highest Thomas adsorption capacity (7.86 mg/g) was achieved at a flow rate (9 mL/min), initial Cd(II) concentration (10 mg/L), and bed height (5 cm). The Cd(II) removal by FMS was regarded as non-activated chemisorption that occurred very rapidly (even at a low temperature) with a low magnitude of activation energy. Primary adsorption mechanism was surface precipitation. Cadmium precipitated in the primary (Cd,Ca)CO3 form with a calcite-type structure on the FMS surface. A crust of rhombohedral crystals on the substrate was observed by SEM. Freshwater mussel shells have the potential as a renewable adsorbent to remove cadmium from water.