Search

The current work aims to explore the structural and optical properties of Cu1−xNixO/ZnO nanostructured heterojunctions for optoelectronic applications. ZnO nanostructures and different Cu1−xNixO/ZnO (x; 0, 0.05, 0.10, 0.15 and 0.20) nanostructured heterojunctions were prepared by spray pyrolysis procedure on glass substrates. The surfaces morphology of the samples was examined by a scanning electron microscope (SEM). The energy dispersive X-ray (EDX) microscope was utilized to examine the elemental analysis. The XRD measurements show that ZnO nanostructures possess a hexagonal wurtzite structure, while Cu1−xNixO nanostructures possess monoclinic structures. The FT-IR spectroscopy was performed to explore the chemical bondings and functional groups. The UV–visible-NIR spectrophotometer was used to investigate the optical properties. The optical constants (refractive index, extinction coefficient, dielectric constants, optical conductivity) of the prepared samples have been investigated. The first-order linear optical susceptibility, third-order optical susceptibility and nonlinear refractive index are also studied. The obtained results show that the optical parameters of Cu1−xNixO/ZnO heterojunction could be tuned through controlling the Ni content. These novel findings nominate Cu1−xNixO/ZnO nanostructured heterojunctions for a plenty of optical, photocatalytic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

The structural, linear/nonlinear optical and dielectric properties of Cu0.9Co0.1−xSnxO (CCTO) nanostructured films have been studied for optoelectronic applications. CCTO films with different compositions were equipped by spray pyrolysis procedure. The structure, crystallographic and morphological properties were examined by FT-IR, XRD and SEM procedures. The FT-IR measurements expose clear alterations in the structures of CCTO films due to composition variation. XRD results reveal that all CCTO nanostructured films have the monoclinic structure with crystallite size changes from 24.2 to 18.7 nm. SEM micrographs show that CCTO films possess high porous surfaces. UV–Vis. NIR measurements are used to investigate the linear/nonlinear optical parameters of prepared films. The UV–Vis–NIR analysis reveals that all films have absorption coefficient values with orders range from 104 to 105 cm−1. The energy band gap Eg of CCTO films ranges from 1.24 to 1.14 eV upon varying x value. These findings are discussed on the basis of Moss Burstein effect and created defects. Clear impact of the composition (x) on the linear optical properties of CCTO is noticed. For example, the real dielectric constant εr varies from 23.97 to 9.74 via controlling the content composition. Moreover, the linear and nonlinear susceptibility and refractive index of CCTO films have been examined. This study proposes CCTO nanostructured films of environmentally friendly applications as photocatalysts, solar cells, optoelectronics and ultra-fast optical switching devices. [ABSTRACT FROM AUTHOR]

In the current work, the structural and optical characteristics of hematite (α-Fe2O3) have been tailored by individual and dual doping of Ba and Al for photocatalytic and eco-friendly applications. The doped and undoped hematite nanostructures were synthesized onto quartz substrates via the spray pyrolysis route. The surfaces' morphology, vibrational bands and structural properties were investigated based on FE-SEM, FT–IR and XRD measurements, respectively. The XRD analysis reveals that all samples have a rhombohedral hematite structure. The crystallite size varies from 20.8 nm (undoped hematite) to 27.6 nm (Ba-doped hematite), 24.3 nm (Al-doped hematite) and 22.8 nm (Ba/Al dual doped hematite). The optical transmittance, absorbance and reflectance spectra were recorded by a UV–Vis–NIR spectrophotometer. The UV–Vis–NIR analysis shows that Ba/Al dual doped hematite film possesses an optimal absorption amount in the region where the wavelength λ > 561 nm. The direct energy band gap (Eg) changes from 2.30 eV (undoped hematite) to 2.42 eV nm (Ba-doped hematite), 2.18 eV nm (Al-doped hematite) and 2.22 eV nm (Ba/Al dual doped hematite). Clear enhancement in the refractive index (n), dielectric constants and optical conductivity of the hematite NPs is attained via individual or dual doping of Ba and Al elements. For example, at λ = 550 nm, n of the undoped hematite increases from 1.88 to 1.91 (Ba-doped hematite), 2.07 (Al-doped hematite) and 1.97 (Ba/Al dual doped hematite). These novel results nominate the individual Ba, Al and Ba/Al dual doped hematite NPs for applications in photocatalysts and eco-friendly devices. [ABSTRACT FROM AUTHOR]

Lanthanum doped titanium dioxide (La/TiO2) was synthesized by a lengthy wet impregnation method with cobalt (Co/TiO2). The prepared composites were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). The XRD spectrum of TiO2 shows that the transition dopants are well dispersed within the TiO2 matrix. The SEM images show no noticeable morphological differences between the TiO2, La/TiO2, and Co/TiO2 composites. The dielectric properties and electrical of TiO2, La/TiO2, and Co/TiO2 were investigated within temperature and frequency of 25–120 °C and 100 Hz to 0.3 MHz, respectively. It was noted that the dielectric constant decreases with increasing temperature. TiO2 dielectric permittivity and electrical conductivity increased as a result of doping. In addition, the activation energy values for all samples were evaluated. By increasing frequency, activation energy values decreased and this decrease intensified when the Co ions are the substituents in the TiO2 matrix. Otherwise, the values of activation energy are constant for La-dopedTiO2. [ABSTRACT FROM AUTHOR]

A comprehensive study of atomic-layer deposited thulium oxide (Tm2O3) on germanium has been conducted using x-ray photoelectron spectroscopy (XPS), vacuum ultra-violet variable angle spectroscopic ellipsometry, high-resolution transmission electron microscopy (HRTEM), and electron energy-loss spectroscopy. The valence band offset is found to be 3.0±60.2 eV for Tm2O3/p-Ge from the Tm 4d centroid and Ge 3p3/2 charge-corrected XPS core-level spectra taken at different sputtering times of a single bulk thulium oxide sample. A negligible downward band bending of ~0.12 eV is observed during progressive differential charging of Tm 4d peaks. The optical band gap is estimated from the absorption edge and found to be 5.77 eV with an apparent Urbach tail signifying band gap tailing at ~5.3 eV. The latter has been correlated to HRTEM and electron diffraction results corroborating the polycrystalline nature of the Tm2O3 films. The Tm2O3/Ge interface is found to be rather atomically abrupt with sub-nanometer thickness. In addition, the band line-up of reference GeO2/n-Ge stacks obtained by thermal oxidation has been discussed and derived. The observed low reactivity of thulium oxide on germanium as well as the high effective barriers for holes (~3 eV) and electrons (~2 eV) identify Tm2O3 as a strong contender for interfacial layer engineering in future generations of scaled high-κ gate stacks on Ge. [ABSTRACT FROM AUTHOR]

In this paper, a new organic salt bis(2-ethyl-6-methylanilinium)tetrachloromercurate (II)) has been synthesized, characterized, and studied theoretically using DFT. The synthesized compound was found to crystallize in the monoclinic system with space group P21/c with the following unit cell parameters a = 23.1696(2), b = 25.7951 (6), c = 7.5980 (4) Å, β = 96.5790 (11)°, and Z = 8. Its atomic arrangement can be described asmutually alternating organic and inorganic entities in the (ab) plane. The cohesion is achieved through N-H...Cl hydrogen bonds and π...π stacking interacting neighboring aromatic cations. The PXRD was carried out. The intermolecular interactions in the crystal packing were investigated using Hirshfeld surface analysis. Its associated 2D fingerprint plots revealed their contribution quantitatively. High-resolution images of the surface were obtained by the SEM technique, and the EDX spectrum assured the existence of all nonhydrogen atoms. The infrared spectrum was used to gain more information about vibrational modes. Analysis of thermal differential and gravimetric (TGA/DTA) shows two-phase transitions observed at 362 and 394 K. AC conductivity measurements were performed to confirm these two-phase transitions. [ABSTRACT FROM AUTHOR]

In this paper, a new organic salt bis(2-ethyl-6-methylanilinium)tetrachloromercurate (II)) has been synthesized, characterized, and studied theoretically using DFT. The synthesized compound was found to crystallize in the monoclinic system with space group P21/c with the following unit cell parameters a = 23.1696(2), b = 25.7951 (6), c = 7.5980 (4) Å, β = 96.5790 (11)°, and Z = 8. Its atomic arrangement can be described asmutually alternating organic and inorganic entities in the (ab) plane. The cohesion is achieved through N-H...Cl hydrogen bonds and π...π stacking interacting neighboring aromatic cations. The PXRD was carried out. The intermolecular interactions in the crystal packing were investigated using Hirshfeld surface analysis. Its associated 2D fingerprint plots revealed their contribution quantitatively. High-resolution images of the surface were obtained by the SEM technique, and the EDX spectrum assured the existence of all nonhydrogen atoms. The infrared spectrum was used to gain more information about vibrational modes. Analysis of thermal differential and gravimetric (TGA/DTA) shows two-phase transitions observed at 362 and 394 K. AC conductivity measurements were performed to confirm these two-phase transitions. [ABSTRACT FROM AUTHOR]

A study into the optimal deposition temperature for ultra-thin La2O3 and Y2O3/Ge gate stacks has been conducted in this paper with the aim to tailor the interfacial layer for effective passivation of the Ge interface. A detailed comparison between the two lanthanide oxides ( La2O3 and Y2O3) in terms of band line-up, interfacial features, and reactivity to Ge using medium energy ion scattering, vacuum ultra-violet variable angle spectroscopic ellipsometry (VUV-VASE), X-ray photoelectron spectroscopy, and X-ray diffraction is shown. La2O3 has been found to be more reactive to Ge than Y2O3, forming LaGeOx and a Ge sub-oxide at the interface for all deposition temperature studied, in the range from 44 °C to 400°C. In contrast, Y2O3/Ge deposited at 400 °C allows for an ultra-thin GeO2 layer at the interface, which can be eliminated during annealing at temperatures higher than 525 °C leaving a pristine YGeOx/Ge interface. The Y2O3/Ge gate stack deposited at lower temperature shows a sub-band gap absorption feature fitted to an Urbach tail of energy 1.1 eV. The latter correlates to a sub-stoichiometric germanium oxide layer at the interface. The optical band gap for the Y2O3/Ge stacks has been estimated to be 5.7±0.1 eV from Tauc-Lorentz modelling of VUV-VASE experimental data. For the optimal deposition temperature (400 °C), the Y2O3/Ge stack exhibits a higher conduction band offset (∼2.3 eV) than the La2O3/Ge °2 eV), has a larger band gap (by about 0.3 eV), a germanium sub-oxide free interface, and leakage current (°10°7 A/cm2 at 1V) five orders of magnitude lower than the respective La2O3/Ge stack. Our study strongly points to the superiority of the Y2O3/Ge system for germanium interface engineering to achieve high performance Ge Complementary Metal Oxide Semiconductor technology. [ABSTRACT FROM AUTHOR]

Amorphous Ga2O3 thin films were deposited on p-type (111) and (100) surfaces of silicon and (100) germanium by atomic layer deposition (ALD). X-ray photoelectron spectroscopy (XPS) was used to investigate the band alignments at the interfaces using the Kraut Method. The valence band offsets were determined to be 3.49± 0.08 eV and 3.47± 0.08 eV with Si(111) and Si(100) respectively and 3.51eV± 0.08 eV with Ge(100). Inverse photoemission spectroscopy (IPES) was used to investigate the conduction band of a thick Ga2O3 film and the band gap of the film was determined to be 4.63±0.14 eV. The conduction band offsets were found to be 0.03 eV and 0.05eV with Si(111) and Si(100) respectively, and 0.45eV with Ge(100). The results indicate that the heterojunctions of Ga2O3 with Si(100), Si(111) and Ge(100) are all type I heterojunctions. [ABSTRACT FROM AUTHOR]

Two novel complexes, [(C7H10NO2)CdCl3]n(I) and [(C7H9NO2)CuCl2],havebeen synthesized and characterized. Single crystal X-ray diffraction revealed that in compound (I), 2,6-dimethanol pyridinium acts as a monodentate ligand through the O atom of the hydroxyl group. Contrarily, the 2,6-dimethanol pyridine ligand interacts tridentately with the Cu(II) ion via the nitrogen atoms and the two oxygen (O, O') atoms of the two hydroxyl groups. The structure's intermolecular interactions were studied using contact enrichment ratios and Hirshfeld surfaces. Following metal coordination, numerous hydrogen connections between entities and parallel displacement stacking interactions between pyridine rings dictate the crystal packing of both compounds. The aromatic cycles generate layers in the crystal for both substances. Powder XRD measurements confirmed the crystalline sample phase purity. SEM confirmed the surface homogeneity, whereas EDX semi-quantitative analysis corroborated the composition. IR spectroscopy identified vibrational absorption bands, while optical UV-visible absorption spectroscopy investigated optical properties. The thermal stability of the two materials was tested using TG-DTA. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ge gate MOS devices were investigated due to its applicability to sub 16nm node pMOST technology. [•] GeO2/Al2O3/HfO2 gate stacks were grown by a combined MBE and ALD technique. [•] Devices were characterised by various physical and electrical methods. [•] Devices were found to have low EOT and leakage currents and have small hysteresis. [Copyright &y& Elsevier]

The global rise in lower limb amputation cases necessitates advancements in prosthetic limb technology to enhance the quality of life for affected patients. This review paper explores recent advancements in the integration of EEG and fNIRS modalities for smart lower prosthetic limbs for rehabilitation applications. The paper synthesizes current research progress, focusing on the synergy between brain-computer interfaces and neuroimaging technologies to enhance the functionality and user experience of lower limb prosthetics. The review discusses the potential of EEG and fNIRS in decoding neural signals, enabling more intuitive and responsive control of prosthetic devices. Additionally, the paper highlights the challenges, innovations, and prospects associated with the incorporation of these neurotechnologies in the field of rehabilitation. The insights provided in this review contribute to a deeper understanding of the evolving landscape of smart lower prosthetic limbs and pave the way for more effective and user-friendly solutions in the realm of neurorehabilitation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 AlQahtani, Al-Naib and Althobaiti.)

Background: The risk of infection including tuberculosis (TB) infection or reactivation during biological therapy with the current various clinical application is a major concern. This risk may be higher in countries endemic to TB. Our aim of this study is to determine the risk of TB infection in patients receiving 3 biological treatments, Adalimumab, Etanercept and Tocilizumab., Methods: A retrospective cohort study extending over 2 years follow-up for all patients receiving Adalimumab, Etanercept and Tocilizumab for various clinical indications in a tertiary care center in Saudi Arabia., Result: Over the period of 2015-2019, A total of 410 patients received Adalimumab, 271 received Etanercept and 58 patients received Tocilizumab. Rheumatoid arthritis was the most common indication for therapy in all groups and for Adalimumab the most common indication was inflammatory bowel disease, for Etanercept was psoriatic arthritis and for Tocilizumab was juvenile idiopathic arthritis. After a mean follow up period of 36 ± 8.9 months for patients receiving Adalimumab, 21.5 ± 8.4 months for patients receiving Etanercept and 21 ± 2.5 months for patients receiving Tocilizumab there were no reported cases of TB infection in all groups. Only one patient was diagnosed with latent TB 7 months later after starting Adalimumab and tow patients after starting Etanercept. The overall Interferon Gamma Release Assays (IGRA) positivity rate was 9.7%. There was significant association between IGRA positivity rate and patient age. The cutoff age in which IGRA positivity has significantly increased was 53.20 years., Conclusion: In our study, patients receiving Etanercept, Adalimumab and Tocilizumab had no increased risk of TB infection. Only 0.3% of patients treated with Adalimumab and 0.9% of patients treated with Etanercept converted to a positive IGRA during therapy., Competing Interests: Declaration of Competing Interest We have no conflict of interest to declare., (Copyright © 2024. Published by Elsevier Ltd.)

Background: Sexually transmitted diseases (STDs) are a global issue facing the world. In a conservative community like Saudi Arabia, discussing such matters is considered taboo, and this might impact the awareness of STDs. Therefore, this study aims to determine if gender, level of education, and university affiliation influence the level of awareness of STDs., Methods: This research is a cross-sectional study that involves 389 students who are studying at King Saud University (KSU) and Imam Mohammad Ibn Saud Islamic University (IMAMU). Twenty-six questions were gathered from a previous study and implemented into the questionnaire and were validated after., Results: Overall, awareness about STDs was poor. Females scored higher than male participants (7.9 ± 3.3 vs. 7.1 ± 3.2, p < 0.017) respectively. Interestingly, undergraduates scored higher than postgraduates (4.7 ± 3.7 vs. 3.7 ± 3.3, p < 0.029). For the university, KSU students scored higher than their counterparts did at IMAMU (10.4 ± 5.7 vs. 8.9 ± 5.5, p < 0.01)., Conclusion: Female participants have shown a higher level of STD awareness than males, but the overall awareness is still extremely low. However, KSU scored higher than IMAMU As a result, appropriate education and promotion efforts about STDs must be implemented based on gender and education level., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, ALDosari et al.)

Myocardial infarction (MI) is the principal cause of premature death. Protecting myocardium from ischemia is the main focus of intense research. 7-hydroxy frullanolide (7-HF) is a potent anti-inflammatory agent, showing its efficacy in different acute and chronic inflammatory disorders such as atherosclerosis, suggesting it can be a potential cardioprotective agent. For the induction of MI, Sprague-Dawley rats (n = 5) were administered isoproterenol (ISO) 85 mg/kg s.c at 24 h intervals for two days. The potential cardioprotective effect of 7-HF and its mechanisms were explored by in vivo and in vitro methods. 7-HF significantly prevented the extent of myocardial injury by decreasing the infarct size, preserving the histology of myocardial tissue, and reducing the release of cardiac biomarkers. Further, 7-HF increased the mRNA expression of cardioprotective gene Nrf2 and reduced the mRNA expression of iNOS. 7-HF also improved cardiac function by decreasing the cardiac workload through its negative chronotropic and negative ionotropic effect, as well as by reducing peripheral vascular resistance due to the inhibition of voltage-dependent calcium channels and the release of calcium from intracellular calcium stores. In conclusion, 7-HF showed cardioprotective effects in the MI model, which might be due to modulating the expression of iNOS and Nrf2 genes as well as improving cardiac functions.

Lumbar puncture is a minimally invasive procedure that utilizes a spinal needle to puncture the lumbar epidural space to take a sample from the cerebrospinal fluid or inject drugs for diagnostic and therapeutic purposes. Physicians rely on their expertise to localize epidural space. Due to its critical procedure, the failure rate can reach up to 28%. Hence, a high level of experience and caution is required to correctly insert the needle without puncturing the dura mater, which is a fibrous layer protecting the spinal cord. Failure of spinal anesthesia is, in some cases, related to faulty needle placement techniques since it is blindly inserted. Therefore, advanced techniques for localization of the epidural space are essential to avoid any possible side effects. As for epidural space localization, various ideas were carried out over recent years to provide accurate identification of the epidural space. Subsequently, several methodologies based on mechanical and optical schemes have been proposed. Several research groups worked from different aspects of the problem, namely, the clinical and engineering sides. Hence, the main goal of this paper is to review this research with the aim of remedying the gap between the clinical side of the problem and the engineering side by examining the main techniques in building sensors for such purposes. This manuscript provides an understanding of the clinical needs of spinal needles from an anatomical point of view. Most importantly, it discusses the mechanical and optical approaches in designing and building sensors to guide spinal needles. Finally, the standards that must be followed in building smart spinal needles for approval procedures are also presented, along with some insight into future directions.

Introduction: The clot in transit is a rare manifestation of thromboembolic disease occurring usually in the setting of PE and frequently associated with poor outcomes. The best therapeutic option is not well established. We describe a series of 35 patients diagnosed with clots in transit including their therapeutic interventions and outcome between the period January 2016 to December 2020., Methods: a retrospective chart review of all patients with an Echocardiogram showing thrombi in the right heart chambers including patients with thrombus in the presence of central lines or other devices. We exclude patients where masses were described as tumors or vegetation and masses in the presence of bacteremia., Results: There were 35 patients with echocardiographic evidence of a thrombus in the right heart chambers. In 12 of those patients, the thrombus was related to an intracardiac catheter. 37.1% of CT chest was done along with Echocardiogram and showed a concomitant PE in 77%. On echocardiogram, 66% of the thrombi were mobile. RV strain was present in 17% while abnormal RVSP (>30 mmHg) was present in 74%. Respiratory support was required in 37.1% and only 17% required inotropic support. There was a total or partial resolution in 80% those who had repeated echocardiogram after four weeks of therapy. Heparin was started in the majority of patients (74%). Warfarin was the most frequently used follow-up anti-coagulant in 51.4%. The mortality rate was significantly higher in those patients with RVSP >50, UFH group, O2 or inotropic support. 26% of patients died within the first 28 days after the diagnosis, while first 7 days mortality was 6% only., Conclusion: a clot in transit in our study was not directly associated with poor outcomes in the first week of therapy, UFH is still the most frequently used initial method to treat clots in transit. However, only 26% had a total resolution of clot within 4 weeks of treatment., Competing Interests: Con fl ict of interest None., (© 2023 Saudi Heart Association.)

Objectives: To investigate the influence of viability assessment in the management of patients with ischemic cardiomyopathy (ICM)., Methods: This retrospective cohort study included all patients with ICM with moderate to severely reduced left ventricular ejection fraction (LVEF) who underwent viability assessment using cardiac magnetic resonance imaging (MRI) and echocardiogram as modalities of imaging. In addition, LVEF, modality of choice, and treatment plans were all extracted as main variables from the electronic database. One hundred 6 patients who met the inclusion criteria from December 2014 to December 2019 were included., Results: Posttreatment LVEF improved by 5% in the viable group compared to the nonviable group ( p =0.016). Regardless of the treatment received, 6 (8.8%) patients in the viable group died due to cardiac causes after an 18-month follow-up period; in contrast, 7 (18.4%) patients died due to cardiac causes in the nonviable group. However, despite that difference, this was not statistically significant ( p =0.153). Medical therapy alone was observed in 32 (84.2%) patients in the nonviable group compared to 32 (47.1%) in the viable group ( p <0.001). Although the reduction in hospitalization for cardiac reasons was not statistically significant, the viable arm had 50% fewer hospitalizations than the nonviable arm ( p =0.051)., Conclusion: Patients with viable myocardium had better outcomes in which LVEF significantly improved posttreatment. Additionally, there was a reduction in the number of hospitalizations for cardiac reasons in the viable group compared to the nonviable group, even though the difference was not statistically significant. However, further studies with a larger number of patients are needed to determine a definite conclusion., (Copyright: © Saudi Medical Journal.)

BACKGROUND Breakpoint cluster region (BCR)-Abelson murine leukemia (ABL1) and Janus Kinase-2 (JAK2) mutations have been thought to be mutually exclusive in myeloproliferative neoplasms (MNPs), but recent data suggest that they can occur together. CASE REPORT A 68-year-old man was referred to the hematology clinic because of an elevated white blood cell count. His medical history included type II diabetes mellitus, hypertension, and retinal hemorrhage. Fluorescence in situ hybridization analysis of the bone marrow was positive for BCR-ABL1 in 66/100 cells. Conventional cytogenetics was positive for the Philadelphia chromosome in 16/20 counted cells. The percentage of BCR-ABL1 was 12%. Considering the patient's age and medical comorbidities, he was started on imatinib 400 mg once daily. Further tests showed JAK2 V617F mutation positivity and absence of acquired von Willebrand disease. He was then started on aspirin 81 mg and hydroxyurea 500 mg once daily, which was later increased to 1000 mg daily. The patient achieved a major molecular response after 6 months of treatment, with undetectable BCR-ABL1 levels. CONCLUSIONS BCR-ABL1 and JAK2 mutations can co-existence in MNPs. Physicians must suspect the presence of one of the MPNs in chronic myeloid leukemia (CML) patients with persistent or increased thrombocytosis, an atypical course of the disease, or hematological abnormalities despite evidence of response or remission of CML. Therefore, testing for JAK2 should be performed accordingly. Combining cytoreductive therapy with tyrosine kinase inhibitors (TKIs) is a therapeutic option when both mutations are present, and TKI alone is not sufficient to control peripheral blood cell counts.

Near-infrared technology is an emerging non-invasive technique utilized for various medical applications. Recently, there have been many attempts to utilize NIR technology for the continues monitoring of blood glucose levels through the skin. Different approaches and designs have been proposed for non-invasive blood glucose measurements. Light photons penetrating the skin can undergo multiple scattering events, and the actual optical pathlength becomes larger than the source-to-detector separation (optode spacing) in the reflection-mode configuration. Thus, the differential pathlength factor (DPF) must be incorporated into the modified Beer-Lambert law. The accurate estimation of the DPF values will lead to an accurate quantification of the physiological variations within the tissue. In this work, the aim was to systematically estimate the DPF for human skin for a range of source-to-detector separations and wavelengths. The Monte Carlo (MC) method was utilized to mimic the different layers of human skin with different optical properties and blood and water volume fractions. This work could help improve the accuracy of the near-infrared technique in the measurement of physiological variations within skin tissue.

Diabetes is a serious health condition that requires patients to regularly monitor their blood glucose level, making the development of practical, compact, and non-invasive techniques essential. Optical glucose sensors-and, specifically, NIR sensors-have the advantages of being non-invasive, compact, inexpensive, and user-friendly devices. However, these sensors have low accuracy and are yet to be adopted by healthcare providers. In our previous work, we introduced a non-invasive dual-channel technique for NIR sensors, in which a long channel is utilized to measure the glucose level in the inner skin (dermis) layer, while a short channel is used to measure the noise signal of the superficial skin (epidermis) layer. In this work, we investigated the use of dual-NIR channels for patients with different skin colors (i.e., having different melanin concentrations). We also adopted a Monte Carlo simulation model that takes into consideration the differences between different skin layers, in terms of blood content, water content, melanin concentration in the epidermis layer, and skin optical proprieties. On the basis of the signal-to-noise ratio, as well as the sensitivities of both the epidermis and dermis layers, we suggest the selection of wavelengths and source-to-detector separation for optimal NIR channels under different skin melanin concentrations. This work facilitates the improved design of a compact and non-invasive NIR glucose sensor that can be utilized by patients with different skin colors.