Effects of low level laser treatment on the survival of axotomized retinal ganglion cells in adult Hamsters

Injury to axons close to the neuronal bodies in the mammalian central nervous system causes a large proportion of parenting neurons to degenerate. It is known that optic nerve transection close to the eye in rodents leads to a loss of about half of retinal ganglion cells in 1 week and about 90% in 2 weeks. Using low level laser treatment in the present study, we demonstrated that treatment with helium-neon （660 nm） laser with 15 mW power could delay retinal ganglion cell death after optic nerve axotomy in adult hamsters. The effect was most apparent in the ifrst week with a short period of treatment time （5 minutes） in which 65–66% of retinal ganglion cells survived the optic nerve axotomy whereas 45–47% of retinal ganglion cells did so in optic nerve axotomy controls. We also found that single dose and early commencement of laser irradiation were important in protecting retinal ganglion cells following optic nerve axotomy. These ifndings thus convincingly show that appropriate laser treatment may be neuroprotective to retinal gan-glion cells.

Effect of low level laser therapy on dental pulp during orthodontic movement

AIM: To validate the protocol described here to be used in future clinical trials related to the effect of laser therapy on dental pulp. METHODS: Histologically treated samples from eight human healthy premolar teeth obtained from the middle root level were distributed in four groups: group 1(G1) absolute control; group 2(G2) only laser irradiation; group 3(G3) exposed only to orthodontics; and group 4(G4) treated with orthodontics and laser. Laser treatment was performed at 830 nm wavelength, 100 mW(energy 80 J/cm2, 2.2 J), for 22 s in the vestibular surface and 22 s in the palatal surface, 1 mm away from the dental root mucosa. Three staining methods were performed: hematoxylin-eosin(HE), Masson's Trichrome method and Gomori's method.RESULTS: The pulp histology parameters were evaluated and the results classified in to 3 parts: an inflammatory response, soft tissue response(dental pulp) and hard tissue response(dentin and predentin). There was no inflammation(chronic or acute) in any of the evaluated groups. The zones of pulp necrosis were found in one premolar of G3 and in one of G4; in groups G2 and G4 there was higher angiogenesis than in the other two groups. G4 group presented the highest level of vascularization. A reduced nerve density was observed in G3. A G2 specimen showed increased nerve density. A higher rate of calcification was observed in G1 compared to G2. Denticles, either real or false, were observed in G1, G2 and G3. Sclerosis of dentin and focal dentin loss was observed among all the groups. Secondary dentin was present in one sample in G1 and G2. A necrosis zone was found in one sample of G3 and G4. No differences between groups were observed in the odontoblast irregularity layer but the layer was wider in the group treated with laser only. A notable difference was detected in reduction of the cell-free layer between the groups G1 and G4. The findings in pulp tissue favor its adaptative response against dental movement induced by orthodontics. No definitive conclusions may be derived as this is a pilot study. CONCLUSION: The protocol described here was shown to be an effective method to evaluate changes in dental pulp submitted to low level laser in teeth under orthodontic movement.

Laser triangulation measurement of the level in a coal silo

Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines, such as the presence of dense dust, high humidity, and low illumination. A laser source and a camera were mounted at the top of the silo. The laser spot projected into the silo was imaged by the camera. The pinhole imaging principle allows the level to be found from the lateral shift of the spot image on the sensor. A pre-calibrated look-up table of the coal depth versus spot position was used to obtain the depth. The measurement accuracy depends on the step size used during pre-calibration. The actual application of a device designed according to these principles shows that it is easy to implement. The detection of the coal level in a silo at the low illumination level found in coal mines is demonstrated.

Low-level laser therapy enhances the number of osteocytes in calvaria bone defects of ovariectomized rats

Background : Osteoporosis can make bone repair difficult. Low-level laser therapy( LLLT) has been shown to be a promising tool for bone neoformation. This study aimed to analyze the effect of LLLT on calvaria bone defects of ovariectomized rats using stereology. Methods : Fifty-four Wistar rats were subjected to bilateral ovariectomy, and bone defects were created in calvaria after 150 days. The animals were divided into nine groups(n = ?6 per group), and 24 hours after the bone defects were created they received three, six or 12 sessions of LLLT at 0, 20 or 30 J/cm 2, using a 780-nm low-intensity GaAlAs laser. One-way ANOVA followed by Tukey ' s post hoc test was used for data processing. A difference of P < 0.05 was considered statistically significant. The parameters evaluated were osteocyte density( Nv_(ost)), total osteocyte number( Nto ost), trabecular surface density( Sv_t), and trabecular surface area( Sa_t). Results : Data obtained showed that Nto ost, Sv t, and Sa t in group G2 rats were significantly different from G1(0 J/cm^2)( P < 0.05). Compared to group G4, G5 presented higher values for the parameters Sv t and Sa t, and G6 presented significantly higher values for almost all the analyzed parameters( Nv _(ost), Nto_(ost), Sv_t, and Sa t)( P < 0.05). Compared to group G7, G8 showed a higher value only for the parameter Sa t, and G9 showed significantly higher values for parameters Nv ost, Nto ost, Sv_t, and Sa_t. Conclusion : We conclude that LLLT stimulated bone neoformation and contributed to an increase in the total number of osteocytes, especially with a laser energy density of 30 J/cm^2 given for six and 12 sessions.

Efficacy of super-pulsed 905 nm Low Level Laser Therapy (LLLT) in the management of Traumatic Brain Injury (TBI): A case study

Traumatic brain injury is a major health concern worldwide with massive financial and social impact. Conventional treatments primarily focus on the prevention of further damage to the brain parenchyma, while failing to address the already existent symptoms. Previous clinical studies have shown that Low Level Laser Therapy (LLLT) can significantly reduce pain and induce temporary vasodilation in capillaries, which the authors hypothesize can be used to improve the quality of life in TBI patients by treating their current symptoms, which are predominately migraine-like headaches. This case report illustrates the use of LLLT in the treatment of a patient with a TBI and the great clinical success achieved in the reduction of pain, as measured by VAS—achievable within five treatments of 10 minutes in duration.

Advance in Functional Restoration of Injured Nerve with Low Level Laser and its Utilization in the Dental and Maxillofacial Region

The inferior alveolar nerve and facial nerve are the two most important nerves in the dental and maxillofacial region.The injury to them is one of the major postoperative complications after alveolar surgery and orthognathic surgery.However,recovering the nerve function after injury takes a long time and the recovery effect tends to be unsatisfactory.In recent years,an intensively investigated technique,low level laser which has been applying in assisting the recovery of nerve function,has been gradually proved to be effective in clinically treating postoperative nerve injury.In this article we review in terms of the mechanisms involved in low level laser-assisted functional restoration of nerve injury and its clinical application in the recovery of nerve function in the dental and maxillofacial area as well.

Effects of wavelength,beam type and size on cerebral low-level laser therapy by a Monte Carlo study on visible Chinese human

Low-level laser therapy(LLLT)has been clinically utilized for many indications in medicine requiring protection from el/issue death,stimulation of healing and repair of injuries,pain reduction,swelling and inflammation.Presently,the use of LLLT to treat stroke,traumnatic brain injury and cognitive dysfunction are attracting growing interest.Near infrared light is capable of penetrating into the cerebral cortex,allowing noninvasive treatments to be caried out with few treatment-related adverse events.Optimization of LLLT treatment flfect is a crucial isse of this field;however,only a few experimental tests on mice for wavelength selection have been reported.We addressed this ssue by low-ost,straightforward and quantitative comparisons on light dosage distribution within visible Chinese human head by Monte Carlo modeling of near infrared light propagation.Optimized selection in wavelength,beam type and size were given based on comparisons among frequently used setups(ie,wavelengths:660,810 and 980 nm;beam type:Gaussian and flat beamn;beam diameter:2,4 and 6 cm).This study provided an fficient way for guiding the optimization of LLLT setup and selection on wavelength,beam type and size for clinical brain LLLT.

Induction of Autologous Bone-Marrow Stem Cells by Low-Level Laser Therapy Has Beneficial Effects on the Kidneys Post-Ischemia-Reperfusion Injury in the Rat

Acute renal failure has a 50% - 80% mortality rate. Currently, treatment options for this life-threatening disease are limited. Low-level laser therapy (LLLT) has been found to modulate biological activity. The aim of the present study was to investigate the possible beneficial effects of laser application to stem cells in the bone marrow, on the kidneys of rats that had undergone ischemia-reperfusion injury (IRI). IRI was induced by occlusion of the renal artery to 3- and 7-month-old rats for 15 or 30 minutes. In an additional experiment IRI was applied to both kidneys for 20 min each in 2-3-month-old rats. Rats were then divided randomly into two groups of control and laser-treated. Laser therapy (Ga-Al-As 810 nm, 200 mW output for 2 min) was applied to the bone marrow 1 and 7 days post-IRI to the kidneys, and rats were sacrificed 2 weeks later. Histomorphometry and immunohistochemistry were performed on kidney sections and blood markers for kidney function. Quantitative histomorphometric analysis revealed a reduction in dilatation of the renal tubules, restored structural integrity of the renal tubules, and reduced necrosis in the laser-treated rats as compared to the control, non-laser-irradiated group. C-kit positive cell density in kidneys post-IRI and laser-treatment was significantly (p = 0.015) 3.2-fold higher compared to the control group. Creatinine and blood urea nitrogen content were significantly lower in the laser-treated rats as compared to control. It is concluded that LLLT application to the bone marrow (BM) causes a significant increase in the density of mesenchymal stem cells in the kidneys post-IRI, probably by induction of stem cells in the BM, which subsequently migrate to the IRI kidney, significantly reducing the pathological features of the kidney and increasing kidney function post IRI.

Radiative lifetime measurements of odd-parity highly-excited levels of Sn I by time-resolved laser spectroscopy

Natural radiative lifetimes of five higher-lying odd-parity levels 5pTs ^3P1^0, 5p5d 1P1^0, 5p6d 3F2^0, 3D1^0 and 3F3^0 in neutral tin are measured by the time-resolved laser-induced fluorescence （TR-LIF） technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of evenparity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn, which may be useful for theoretically calculating excited heavy atoms.

Low-Level Laser Therapy versus Four Layers Compression Technique in the Treatment of Venous Ulcers

Objective: The aim of the study is to evaluate the effect of low-level laser therapy in comparison to compression bandage therapy in the treatment of venous ulcers. Subjects & Methods: This study was carried out in the period from March 2013 to March 2014. The study included 40 adult patients with a diagnosis of venous ulcer classified as C6 according to the clinical classification of CEAP classification. The patients were divided into 2 groups: the first one included 20 patients treated by low-level laser therapy at the Rheumatology and Rehabilitation department, and the second group included 20 patients in whom we use four layers compression bandaging at the vascular surgery department. Results: 32 ulcers were treated in group I and 35 ulcers were treated in group II. The patients of group I were 7 (35%) females and 13 (65%) males, their age range were (24 - 56) years. The patients of group II were 11 (55%) males and 9 (45%) females;their age ranges were (32 - 50) years. Measurements of the ulcers size by (cm2) were taken at the beginning of therapy, at 1 month, at 2 months and at 3 months later on. The calculation of the area of the ulcer was done by using the graph papers to document the ulcer’s perpendicular linear dimensions. According to the size of the ulcer, some ulcers heal within 1 month (15.6%) ulcers in group I, and (28.5%) in group II. Some ulcers heal within 2 months (28%) in group I, and (37%) in group II. The remaining ulcers heal within 3 months or more which are (56%) ulcers in group I, and (34.2%) ulcers in group II. The recurrence rate of chronic venous leg ulcer in compression bandage technique used in group II was the least one as the total number of recurrent cases were 5 (25%), followed by laser therapy used in group I. Conclusion: There was no significant efficacy of the low-level laser therapy over the four layers compression technique in the management of chronic venous ulcers.

Multi-level effects in the high-order harmonic generation driven by intense frequency-comb laser fields

High harmonic generation（HHG） driven by intense frequency-comb laser fields can be dramatically enhanced via multiphoton resonance by tuning the carrier-envelope phase（CEP） shift, without increasing the driving intensity. However,the multiphoton-resonant enhancement（MRE） factor in the realistic atomic hydrogen is much smaller than that in a twolevel system. To study the deviation, we present a theoretical investigation of the multiphoton resonance dynamics of three-level systems driven by intense frequency-comb laser fields. The many-mode Floquet theorem（MMFT） is employed to provide a nonperturbative and exact treatment of the interaction between the quantum system and the laser fields. The investigations show that the dipole interaction of a two-level system with the third level affects the multiphoton resonance dynamics and enhances the HHG spectra. It is the dipole interaction of the excited level of the two-level system with other levels that results in the smaller MRE factor in the realistic atomic system.

Coherent Features of Resonance-Mediated Two-Photon Absorption Enhancement by Varying the Energy Level Structure,Laser Spectrum Bandwidth and Central Frequency

The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited （TL）-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.

Effect of autologous mesenchymal stem cells induced by low level laser therapy on cardiogenesis in the infarcted area following myocardial infarction in rats

In this study, we investigated the hypothesis that photobiostimulation by low-energy laser therapy (LLLT) applied to the bone marrow (BM) of myocardial infarcted rats may attenuate the scarring processes that follow myocardial infarction (MI). Wistar rats underwent experimental MI. LLLT (Ga-Al-As diode laser) was applied to the BM of the exposed tibia at different time intervals post-MI (4 hrs, 48 hrs and 5 days). Sham-operated infarcted rats served as control. Infarct size was significantly reduced (55%) in the laser-treated rats as compared to the control non-treated rats, at 2 weeks post-MI. A significant 3-fold increase was observed in the density of desmin immunopositive stained cells 14 days post-MI in the infarcted area of the laser-treated rats as compared to the non-laser-treated controls. The electron microscopy from the control infarcted rat hearts revealed a typical interphase area between the intact myocardium and the infarcted area, with conspicuous fibroblasts with collagen deposition dispersed among them. In rats that were laser treated (to BM), the interphase zone demonstrated cells with different intracellular structures. There was also a significant increase in the percentage of c-kit positive cells and macrophages in the circulating blood of the laser treated rats as compared to control non treated ones. In the majority of the cells clusters of myofibrils anchored to well-developed Z-lines and structures resembling the morphological characteristics of mature intact cardiomyocytes were evident. In conclusion, LLLT to the BM of rats post-MI induces cardiogenesis mainly at the borders of the infarcted area in the heart.

Effect of Intrauterine Laser Therapy at the IVF Success Rate on Infertile Patients with a History of IVF Failure: A Pilot Non-Blinded Study

Backgrounds: While there’s developing proof aimed toward improving embryo implantation thru a focal point on great development, restrained studies have been performed on enhancing endometrial receptivity. Intrauterine Laser Therapy (LT) can be powerful in selling endometrial cell proliferation, therefore enhancing the achievement of assisted reproductive techniques (ART). The contemporary look at aimed to research the effectiveness of effective intrauterine lasers in growing endometrial thickness and the achievement of being pregnant rate. Materials and Methods: In the current clinical randomized trial (RTC) study, the infertile women (20 - 42 years old) referred to the infertility clinic in 2023-2024 who were candidates for IVF treatment with recurrent implantation failure (RIF) history were included. The patients were divided into two main groups: the intervention group;low level laser therapy (LLLT) after hormone administration) (n = 52) and the control group (hormone administration without LT) (n = 52). The IVF success rate and change in endometrial thickness before and after the LT were compared in groups. Results: There was a significant difference between groups (p Conclusion: It appears that the incorporation of Intrauterine LT in the realm of infertility could significantly impact as a novel supplementary treatment in improving endometrial receptivity and pregnancy rate.

Four-level model of ion-ion laser-induced collisional energy transfer and numerical calculations for Ca^+-Sr^+ system

The four-level model of laser-induced collisional energy transfer （LICET） for the ion-ion collision system is established based on the time-dependent SchrSdinger equation for the electron dynamics, through which the equations of motion of the probability amplitudes and cross section of the collision system are obtained. Numerical calculations are performed for the Ca＋ Sr＋ system, with the results showing that the peak of the LICET spectrum appears at a resonant frequency of the transfer laser. The magnitude of the obtained collision cross section is in the order of 10-16 cm2, and is comparable to that obtained in atomic systems, which indicates the validity of the established four-level model.

Application of Well-Known Antiviral Drugs in the Field Formed by the Unexplained Properties of Low-Level Laser Radiation in Therapy of Covid-19 and Chronic Viral Hepatitis

Low-level laser therapy (LLLT) or cold laser has been used in medicine for several decades. However, the method utilizes a direct contact of the light beam with a patient. Further research resulted in development of another method that enables remote transmission of the pharmacological properties of a medicament into a human body with the application of low-level laser radiation as the light source. 18 patients with different viral diseases were treated with the antiviral drugs placed into the field formed by the unexplained properties of low-level laser radiation of the “device for transfer of the pharmacological properties of a drug into the patient’s body”. This resulted in improvement of the patient’s condition, the absence of side effects and adverse reactions when using drugs in the proposed device and shortened therapy period for patients with chronic hepatitis C infection and Covid-19 patients. The long-term follow-up of the patients with chronic hepatitis B infection showed that hepatitis B virus remained at low replication levels under the influence of the therapy, which made it possible to avoid such formidable complications of the disease as cirrhosis of the liver and liver cancer.

基于Level-Set方法的小孔及熔池动态形成数值模拟

构建了激光深熔焊接三维混合态连续模型,模拟了固液界面过渡层的固、液态共存和熔池高于焊接表面的特征,并采用Level-Set方法追踪了气液界面的移动,计算得到了小孔和熔池的动态形成过程.结果表明,熔池在小孔前沿薄后沿厚,温度梯度在小孔前沿大后沿小,小孔及熔池前沿和后沿存在明显的非对称性;孔壁上蒸发的金属蒸气由孔壁流向小孔中轴线,且向孔外喷射;孔底吸收的激光功率密度最大,最高温度3 700 K位于孔底,高于汽化温度567 K;小孔形成的初期阶段孔深的变化较快,但随着小孔深度的增加,孔深变化速率逐渐下降.

一次典型高原低空风切变的成因和发展演变特征研究

低空风切变是航空飞行的重大威胁。为研究高原低空风切变的成因和发展演变特征,利用激光测风雷达资料、机场自动气象站资料和欧洲中期天气预报中心ERA5再分析资料,对2022年2月14日发生在西宁机场的低空风切变过程进行分析和研究。结果表明,高空动量下传与冷空气活动是当天低空风切变的主要成因。在高空动量下传主导期间,上升和下沉气流交替出现,超过16 m/s的偏西风迅速从500 m高度下降到地面,强偏西风触地后与原偏南风形成了风向切变,切变随偏西大风逐步向东偏南,进而影响机场。冷空气主导期间,上升气流明显,东偏南的冷气流与先前的偏西风形成“弧形”风向切变,切变随东偏南风的逐渐增厚和动量加强,逐步向西偏北推进,进而影响机场。

激光选区熔化成形多层级Gyroid点阵结构的力学性能研究

三周期极小曲面(TPMS)结构因其优异的力学性能,在航空航天领域关键零件轻量化方面展现出广阔的应用前景.为有效增强TPMS结构力学性能及其轻量化程度,提出一种基于应力场引导的多层级TPMS点阵结构设计优化方法,设计出多层级Gyroid点阵结构,采用激光选区熔化技术制备了相应的点阵结构,并与体积分数相同的初级Ti6Al4V Gyroid点阵结构进行了对比研究.在此基础上,通过有限元模拟和压缩试验,系统研究了多层级Gyroid点阵结构的压缩性能、变形行为和能量吸收性能.结果显示,与相同体积分数的初级Gyroid点阵结构相比,多层级Gyroid点阵结构压缩性能显著提升,其弹性模量、屈服强度和极限强度分别提高了约36.52%,58.55%和57.62%,能量吸收能力提升了约42.85%.此外,与初级Gyroid点阵结构在斜压杆中心区域的45°剪切断裂模式不同,多层级Gyroid点阵结构初期在填充区域发生层状断裂,随后在未填充区域的斜压杆中心区域发生45°剪切断裂.基于Johnson-Cook塑性模型和损伤模型所建立的有限元模型能够准确预测多层级Gyroid点阵结构的变形行为和力学性能,其预测误差在20%以内.文章所设计的多层级Gyroid点阵结构具有优异的力学性能和能量吸收能力,为航空航天领域高性能轻量化零件优化设计与制造提供了新的思路与技术支持.

High efficiency sub-nanosecond electro-optical Q-switched laser operating at kilohertz repetition frequency

Based on a theoretical model of Q-switched laser with the influences of the driving signal sent to the Pockels cell and the doping concentration of the gain medium taken into account,a method of achieving high energy sub-nanosecond Q-switched lasers is proposed and verified in experiment.When a Nd:YVO4 crystal with a doping concentration of 0.7 at.%is used as a gain medium and a driving signal with the optimal high-level voltage is applied to the Pockels cell,a stable single-transverse-mode electro-optical Q-switched laser with a pulse width of 0.77 ns and a pulse energy of 1.04 mJ operating at the pulse repetition frequency of 1 kHz is achieved.The precise tuning of the pulse width is also demonstrated.