Centre for Advanced Laser Applications

The antifungal efficiency of Zinc oxide nanoparticles (ZnO NPs) was investigated against two pathogenic fungal species, F. oxysporum and P. expansum. The two fungi were identified at molecular level by nuclear ribosomal DNA internal transcribed spacer (ITS) identities. They have been submitted to the GenBank with accession numbers of AB753032 and AB753033 for F. oxysporum and P. expansum, respectively. The antifungal activity of ZnO NPs was found to be concentration dependent. Hence, maximal inhibition of mycelial growth corresponded to the highest experimental concentration (12 mg L−1), where 77 and 100% growth inhibition was observed for F. oxysporum and P. expansum, respectively. The effect of ZnO NPs on the mycotoxins fusaric acid and patulin production by F. oxysporum and P. expansum, respectively, was investigated using HPLC quantification. It was observed that ZnO NPs prevented both mycotoxins synthesis in a concentration dependent manner. Fusaric acid was reduced from 39.0 to 0.20 mg g-1while patulin production was reduced from 14.2 to 1.10 mg g-1 in control and 12 mg L−1ZnO NPs treated samples, respectively. The scanning electron microscopy (SEM) revealed obvious deformation in the growing mycelia treated with ZnO NPs in F. oxysporum which may be the cause of growth inhibition.   Key words: Zinc Oxide Nanoparticles (ZnO NPs), antifungal efficiency, Fusarium oxysporum, Penicillium expansum.

Psoriasis is a commonly encountered chronic dermatological disease, presenting with inflammatory symptoms in patients. Systemic treatment of psoriasis is associated with several adverse effects, therefore the development of a customized topical treatment modality for psoriasis would be an interesting alternative to systemic delivery. The therapeutic modality explored in this article was the comparative treatment of psoriatic patients using nanoparticulated methotrexate in the form of jojoba oil-based microemulsion with or without fractional erbium YAG laser. Assessment parameters included follow-up photography for up to 8 weeks of treatment, estimation of the psoriasis severity [TES (thickness, erythema, scales)] score, and histopathological skin evaluation. The prepared methotrexate microemulsion was clinically beneficial and safe in treatment of psoriasis vulgaris. The concomitant use of the fractional laser provided improvement in the psoriatic plaques within shorter time duration (3 weeks compared to 8 weeks of treatment), presenting an alternative topical treatment modality for psoriasis vulgaris.

Fluorescent proteins offer exceptional labeling specificity in living cells and organisms. Unfortunately, their photophysical properties remain far from ideal for long-term imaging of low-abundance cellular constituents, in large part because of their poor photostability. Despite widespread engineering efforts, improving the photostability of fluorescent proteins remains challenging due to lack of appropriate high-throughput selection methods. Here, we use molecular dynamics guided mutagenesis in conjunction with a recently developed microfluidic-based platform, which sorts cells based on their fluorescence photostability, to identify red fluorescent proteins with decreased photobleaching from a HeLa cell-based library. The identified mutant, named Kriek, has 2.5- and 4-fold higher photostability than its progenitor, mCherry, under widefield and confocal illumination, respectively. Furthermore, the results provide insight into mechanisms for enhancing photostability and their connections with other photophysical processes, thereby providing direction for ongoing development of fluorescent proteins with improved single-molecule and low-copy imaging capabilities.

A laser-assisted method for the fabrication of a flexible fiber supercapacitor (SC) and serially connected SCs within a seamless monofilament unit.

The interaction of light with the quantum-vacuum is predicted to give rise to some of the most fundamental and exotic processes in modern physics, which remain untested in the laboratory to date. Electron–positron pair production from a pure vacuum target, which has yet to be observed experimentally, is possibly the most iconic. The advent of ultra-intense lasers and laser accelerated GeV electron beams provide an ideal platform for the experimental realisation. Collisions of high energy γ -ray photons derived from the GeV electrons and intense laser fields result in detectable pair production rates at field strengths that approach and exceed the Schwinger limit in the centre-of-momentum frame. A detailed experiment has been designed to be implemented at the ATLAS laser at the centre of advanced laser applications. We show full calculations of the expected backgrounds and beam parameters which suggest that single pair events can be reliably generated and detected.

A BaCO₃/BaSnO₃/SnO₂ nanocomposite has been prepared using a co-precipitation method without adding any additives.

Monitoring of the spectrochemical and optical properties of biomaterials has been widely utilized in many biomedical applications for both diagnosis and therapy.

AIM: The aim of this study was to evaluate the association between vitamin B12 and its biomarkers and the risk of neural tube defects. METHODS: A total of 120 pregnant Egyptian women were included in the study. They were classified into two groups. Group A consisted of 50 women with neural tube defects in current pregnancy or with a history in previous pregnancies, and Group B consisted of 70 women with no history of neural tube defects in previous pregnancies or in the current pregnancy. All women were subjected to ultrasound anomaly scan and serum analysis of vitamin B12, homocysteine (Hcy), methyl malonic acid (MMA) and active vitamin B12 concentrations. Receiver operating characteristic curve analysis was used to determine the best cut-off values of vitamin B12. RESULTS: Serum levels of vitamin B12 were decreased in Neural tube defects (NTDs) cases compared to controls (2.736 vs 3.091 ng/mL; P = 0.0015), while Hcy and MMA concentrations were elevated (18.39 vs 13.95 μmol/L; P = 0.0008 and 263 vs 229.7 μmol/L; P = 0.003, respectively). Active vitamin B12 reduction was not statistically significant (96.8 vs 99.36 pmol/L; P = 0.8013). The optimal cut-off value of vitamin B12, 2.9 ng/mL, is the best threshold to expect neural tube defects, with a sensitivity of 60% and specificity of 74.29%. CONCLUSION: Low vitamin B12 is a risk factor for having a fetus with neural tube defects. The monitoring of MMA and Hcy levels might be important in understanding and following cases with neural tube defects. Adding vitamin B12 to folic acid may help to decrease the incidence of neural tube defects in the Egyptian population.

OBJECTIVE: The purpose of this work was to study the effect of poly-L-lysine-conjugated chlorin P6 (pl-cp6)-mediated antimicrobial photodynamic treatment (APDT) on collagen remodeling of murine excisional wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO). BACKGROUND DATA: Bacterial infection of wounds leads to compromised collagen remodelling. APDT-induced inactivation of bacteria and bacterial proteases are expected to restore collagen remodeling in wounds. However, published reports on the effect of PDT on wound healing are somewhat contradictory. One of the reasons for these observations could be the random sampling of wound repair outcomes by invasive technques such as histology. METHODS: Post-wounding time-dependent changes in collagen restoration were monitored noninvasively using polarization sensitive optical coherence tomography (PSOCT) and compared with histology and hydroxyproline level. Immunoblotting was performed to study matrix metalloproteinase (MMP) level. RESULTS: As indicated by retardance measurements from PSOCT images and immunoblotting, bacteria-infected wounds showed slower collagen restoration and higher MMP-8, 9 expression, than did uninfected wounds. In contrast, in infected wounds treated with pl-cp6 and light, retardance was higher (approximately twofold) compared with wounds treated with pl-cp6 alone. These results were consistent with lower MMP-8, 9 level on day 5, more ordered collagen matrix, and higher hydroxyproline content (approximately threefold) on day 18, observed in photodynamically treated wounds, compared with that of untreated infected wounds. CONCLUSIONS: APDT expedites healing in bacteria-infected wounds in mice by attenuating collagen degradation and by enhancing epithelialization, hydroxyproline content, and collagen remodelling.

The objective of this study was to investigate how a low-intensity laser affects the stability and reverse torque resistance of dental implants installed in the tibia of rabbits. Thirty rabbits received 60 dental implants with the same design and surface treatment, one in each proximal metaphysis of the tibia. Three groups were prepared (n = 10 animals each): conventional osseointegration without treatment (control group), surgical sites irradiated with a laser beam emitted in the visible range of 680 nm (Lg1 group), surgical sites irradiated with a laser beam with a wavelength in the infrared range of 830 nm (Lg2 group). Ten irradiation sessions were performed 48 hours apart; the first session was during the immediate postoperative period. Irradiation energy density was 4 J/cm(2) per point in 2 points on each side of the tibias. The resonance frequency and removal torque values were measured at 2 time points after the implantations (3 and 6 weeks). Both laser groups (Lg1 and Lg2) presented a significant difference between resonance frequency analysis values at the baseline and the values obtained after 3 and 6 weeks (P > .05). Although the removal torque values of all groups increased after 6 weeks (P < .05), both laser groups presented greater mean values than those of the control group (P < .01). Photobiomodulation using laser irradiation with wavelengths of 680 and 830 nm had a better degree of bone integration than the control group after 6 weeks of observation time.

Our detailed Raman, non-linear optical, and photoemission spectroscopic studies evince that the N-dopant configuration in graphene (blue-pyridinic, orange-graphitic, and red-pyrrolic) can be effectively tuned to mitigate electron-defect scattering.

BACKGROUND: Low-level laser therapy (LLLT) in the early stage of bone healing was demonstrated as a positive local biostimulative effect. It was also shown that platelet-rich fibrin (PRF) and nanohydroxyapatite alloplast (NanoHA) are effective in treating periodontal intrabony defects. AIM: The study aimed to evaluate the combined effects of LLLT (810 nm), PRF and NanoHA on induced intrabony periodontal defects healing. MATERIAL AND METHODS The study was conducted on 16 defects in 8 adult male rabbits (n = 16) divided into 4 groups; Control non-treated group (C), laser irradiated control group (CL), PRF+NanoHA graft (NanoHA-Graft+PRF) treated group and laser irradiated and treated group (NanoHA-Graft+PRF+L). CT radiography was made at baseline, 15 and 30 days later. The defects were induced in the form of one osseous wall defects of 10 mm height, 4 mm depth between the 1st and the 2nd molars using a tapered fissure drill coupled to a high-speed motor. Statistical analysis was done using ANOVA. RESULTS: (NanoHA-Graft+PRF+L) group significantly produced bone density higher than C, CL and NanoHA-G+PRF alone. CONCLUSION: The combination of LLLT+PRF+NanoHA as a treatment modality induced the best results in bone formation in the bone defect more than LLLT alone or PRF+NanoHA alone.

We report the results of our investigations on the use of Raman optical tweezers for label free analysis of cells in different phases of their cell cycle. The studies performed on human colon adenocarcinoma (Colo-205) cells synchronized in G0/G1 and G2/M phases showed that the DNA Raman band at 783 cm(-1) in the Raman spectra of optically trapped cells can provide information about the DNA content in the nucleus of the cell without the need for the isolation of the nucleus. The histograms of intensity of this band among the cell populations were found to corroborate the results obtained from fluorescence image cytometry performed on DAPI stained cells.

The spectroscopic detection of the excited-state resonances of a strongly coupled atom and optical cavity mode is complicated by inhomogeneous broadening, due to the variation of the dipole coupling constant with location in the cavity. Photon correlation spectroscopy circumvents the difficulty for slowly moving atoms using frequency-selective two-photon absorption and photon coincidence detection of the two-photon decay.

Continuous wave (cw) hydrogen fluoride (HF) chemical laser interactions with human corneal tissue have been studied in order to understand tissue heating phenomenology, effects, and mechanisms under well- characterized laser irradiation conditions. Time-resolved tissue front surface temperature measurements have been obtained during laser irradiation using an optical pyrometer system. Both front surface and in-depth temperature distributions have been calculated by 1D and 2D heat transfer models using realistic tissue optical and thermal properties data for comparison with experiment. The combined experimental/modeling results are useful for developing safe and effective laser microsurgical heating procedures.

BACKGROUND: Invasiveness is a major factor contributing to metastasis of tumour cells. Given the broad variety and plasticity of invasion mechanisms, assessing potential metastasis-promoting effects of irradiation for specific mechanisms is important for further understanding of potential adverse effects of radiotherapy. In fibroblast-led invasion mechanisms, fibroblasts produce tracks in the extracellular matrix in which cancer cells with epithelial traits can follow. So far, the influence of irradiation on this type of invasion mechanisms has not been assessed. METHODS: By matrix-embedding coculture spheroids consisting of breast cancer cells (MCF-7, BT474) and normal fibroblasts, we established a model for fibroblast-led invasion. To demonstrate applicability of this model, spheroid growth and invasion behaviour after irradiation with 5 Gy were investigated by microscopy and image analysis. RESULTS: When not embedded, irradiation caused a significant growth delay in the spheroids. When irradiating the spheroids with 5 Gy before embedding, we find comparable maximum migration distance in fibroblast monoculture and in coculture samples as seen in unirradiated samples. Depending on the fibroblast strain, the number of invading cells remained constant or was reduced. CONCLUSION: In this spheroid model and with the cell lines and fibroblast strains used, irradiation does not have a major invasion-promoting effect. 3D analysis of invasiveness allows to uncouple effects on invading cell number and maximum invasion distance when assessing radiation effects.

Combined with computed tomography (CT), the laser absorption spectroscopy technique is used to measure the two-dimensional distribution information of the flow field. The CT method needs an "integral parameter" as a known quantity. The integrated absorbance satisfies the criterion in the laser absorption spectral measurement. The direct absorption spectroscopy method directly measures the integrated absorbance. However, fitting the absorbance curve is difficult due to the distorted baseline in harsh environments. By contrast, the wavelength modulation spectroscopy (WMS) method has satisfactory noise rejection capability. The difficulty that introduces WMS method to measure the non-uniform flow distribution is the integrated absorbance cannot be written in a mathematical expression. Previous efforts focused on solving the average temperature, concentration, and pressure and recalculating the integrated absorbance. This paper aims to develop an integrated absorbance measurement based on the calibration-free WMS method for non-uniform flow, which is called the calibration-free WMS-A method. First, the relationship between the transmissivity and integrated absorbance was established. Then, integrated absorbance was written into the WMS harmonic signals and solved by comparing the measured and simulated signals. The systematic comparison between the WMS-A and the previous WMS method showed the effectivity of the WMS-A method for non-uniform flow measurement. The reliable integrated absorbance can considerably improve the two-dimensional reconstruction quality.

GaAs wafers are fragile and brittle and, therefore, the well-developed dicing saw technique, which is widely used in the silicon industry, faces serious problems when used for dicing GaAs wafers. GaAs wafers are very sensitive to changes in the dicing tools and to drifts in the dicing machinery, which makes the dicing difficult and causes some throughput issues. At the moment, the most commonly used dicing saw process is dicing with a 30 µm thick resinoid blade. Although, these blades provide high-quality kerf, they are also very fragile and, thus, have a very short life. Dicing of GaAs wafers with the Synova Laser MicroJet®, which implements a YAG- Nd laser beam confined in a water jet, gives exciting and promising results for a general solution of the problem. By means of the Laser MicroJet®, wafers as thin as 25 µm can be diced in streets of 30 – 50 µm width, providing kerf quality comparable to the dicing saw cut and in some cases even better than the dicing saw. The Synova MicroJet® increases the wafer throughput and under certain conditions yields 100% throughput. As far as we are aware, the presented results are the first for laser dicing of GaAs wafers, and, therefore, provoke a detailed discussion about the safety of the new technique. In this paper, we address the advantages and optimization, as well as safety issues of the laser water-jet dicing process for GaAs wafers.

Abstract Powder metallurgy processing has been used to produce copper compacts with fine grain sizes (1-10 μm) that are pinned by submicron-size to micron-size gas-filled voids in the volume fraction range 0.05-0.2. The effect of subsequent heat treatment on the grain size and void size and shape was quantified. These changes strongly depended on whether the powder was consolidated using a coldpressing-and-sintering route, or hot pressing; thus the pressed and sintered compacts densified further whereas the hot-pressed compacts exhibited swelling during subsequent thermal exposure. Such materials were mechanically tested in compression and tension at room temperature, and high yield strength, attributed to grain-size strengthening, was recognized. Tensile ductility in excess of 20% was simultaneously obtained although some unusual features, atypical of fcc metals, including upper and lower yield points and a low work-hardening rate were noted. Approximate calculations examining the interaction of dislocations with a void pair, an assembly of voids and the particular case of all voids being located at grain boundaries indicate that direct strengthening due to the voids is not the principal contributor to the high strength; rather it is the refinement in grain size that is responsible for the observed yield strength level.

A new quasi-two-dimensional oxyfluoride, Sr1-δFeO2-xFx, has been successfully synthesized by combining topotactic fluoridation and CaH2 reduction. The introduction of F through this synthesis provides a new route to introducing charge carriers into the square layered lattice through the formation of Fe(1+) ions. While the average crystal symmetry and magnetic structure remain the same as in the parent compound, the addition of F results in an enhanced buckling of the Fe(O/F)2 square plaquettes that is most likely topologically driven.