Dose-response relationship between daily screen time and the risk of low back pain among children and adolescents: a meta-analysis of 57831 participants.

BACKGROUND: The risk of low back pain (LBP) increases steeply during adolescence, and adolescents with LBP are more likely to have low back pain in their adult years. This study aimed to investigate the dose-response relationship between daily screen time and the risk of low back pain among children and adolescents. METHODS: PubMed, the Cochrane Library, Embase, and Web of Science were searched to collect relevant studies on daily screen time and the risk of low back pain from the establishment of the database up to December 2022. Two investigators independently screened the literature, extracted data, and evaluated the risk of bias in the included studies. Stata16.0 was used to perform a dose-response meta-analysis and the methodological quality evaluation of the included studies. RESULTS: The results of the meta-analysis showed that there is a positive correlation between daily computer time (OR = 1.32, 1.05-1.60), daily mobile phone time (OR = 1.32, 1.00-1.64), daily TV watching (OR = 1.07, 1.04-1.09) and the risk of low back pain, separately. The dose-response meta-analysis showed that there is a linear relationship between daily computer use and low back pain. The risk of low back pain increased by 8.2% for each 1-hour of daily computer use. CONCLUSIONS: Screen time is related to the risk of low back pain, and there is a linear relationship between daily computer use and the risk of low back pain. A number of strategic measures should be taken to prevent adolescents from developing severe low back pain.

Ultrasonic thermometric measurement system for solid rocket combustion chambers.

Solid rocket motor (SRM) temperature is an important physical parameter for which there is no reliable in situ measurement device, apart from a thermocouple, for such a high temperature environment apart. In this study, an ultrasonic temperature measurement system was designed with an iridium-rhodium-40% alloy waveguide. Laboratory experiments showed that the device obtained ultrasonic signals up to 1800 °C with a temperature fitting curve from room temperature to 1800 °C. The thermometer also operated stably under high temperature and produced a repeatable calibration curve, at 97% repeatability. An error band was obtained with 95% confidence. At temperatures above 1000 °C, sensitivity gradually increased to a maximum of 0.0035 µs/°C. A corresponding application structure was established for an SRM before subjecting the sensor to a temperature test experiment. The temperature-time curve obtained detected a peak temperature at 1744 °C.

Formulation, production, in vitro release and in vivo pharmacokinetics of cinnamaldehyde sub-micron emulsions.

Objective: The purpose of this study was to study the effects of formulation of cinnamaldehyde submicron emulsion (CA-SME) and optimize the preparation process parameters of CA-SME, characterize CA-SME and study on in vitro release kinetics and in vivo pharmacokinetics.Methods: Single factor methodology was used to screen the formulation of CA-SME. Response surface methodology combined with Box-Behnken design (BBD) was used to optimize the process variables of CA-SME. The dynamic dialysis method was used to investigate the in vitro release of CA from CA-SME. The blood concentrations of CA in rats were measured after oral administration of CA-SME, with CA solution as reference.Results: The optimal formulation of CA-SME was as follows: 2.5% CA + 1.5% Tween-80 and Span-80 (1:1)+1.5% medium chain triglyceride (MCT)+1.5% Poloxamer-188 + 1.5% lecithin + 91.5% ultrapure water. With the entrapment efficiency (EE/%) of CA-SME as index, BBD experiments indicated that the optimum emulsification temperature, homogenization pressure and cycles were 56 °C, 52 MPa, and two cycles, respectively. The mean particle size and EE of optimum CA-SME were 257.23 ± 3.74 nm and 80.31 ± 0.68%, respectively. The in vitro release study exhibited that the release kinetics of CA-SME was first-order model. Pharmacokinetic parameters of CA-SME in rats were Tmax 60 min, Cmax 1063.41 mg/L, AUC0-∞ 113102.61 mg/L*min, respectively. Tmax, Cmax, and AUC0-∞ of CA-SME were 3, 3.5, and 2.3 times higher than that of CA solution, respectively. The pharmacokinetic parameters of CA-SME in rats were significantly higher than those of CA solution. Submicron emulsion shows great potential as delivery strategy for this volatile herbal oil in oral administration.

Cubic and hexagonal liquid crystal gels for ocular delivery with enhanced effect of pilocarpine nitrate on anti-glaucoma treatment.

The objective of this work was to investigate phytantriol-based liquid crystal (LC) gels including cubic (Q2) and hexagonal (H2) phase for ocular delivery of pilocarpine nitrate (PN) to treat glaucoma. The gels were produced by a vortex method and confirmed by crossed polarized light microscopy, small-angle X-ray scattering, and rheological measurements. Moreover, the release behaviors and permeation results of PN from the gels were estimated using in vitro studies. Finally, the anti-glaucoma effect of LC gels was evaluated by in vivo animal experiments. The inner structure of the gels was Pn3m-type Q2 and H2 phase, and both of them showed pseudoplastic fluid properties based on characterization techniques. In vitro release profiles suggested that PN could be sustainably released from LC gels within 48 h. Compared with eye drops, Q2 and H2 gel produces a 5.25-fold and 6.23-fold increase in the Papp value (p < .05), respectively, leading to a significant enhancement of corneal penetration. Furthermore, a good biocompatibility and longer residence time on precorneal for LC gels confirmed by in vivo animal experiment. Pharmacokinetic studies showed that LC gels could maintain PN concentration in aqueous humor for at least 12 h after administration and remarkably improve the bioavailability of drug. Additionally, in vivo pharmacodynamics studies indicated that LC gels had a more significant intraocular pressure-lowering and miotic effect compared to eye drops. These research findings hinted that LC gels would be a promising pharmaceutical strategy for ocular application to enhance the efficacy of anti-glaucoma.

A Novel Phytantriol-Based In Situ Liquid Crystal Gel for Vaginal Delivery.

The purpose of this paper was to evaluate the potential of in situ liquid crystal (LC) gels based on phytantriol (PYT) for vaginal delivery. The PYT-based in situ liquid crystal gels (PILGs) were prepared by a vortex method using PYT, ethanol (ET), and water (in the ratio of 64:16:20, w/w). The internal structures of PILGs and cubic LC gels (formed by PILG phase conversion) were confirmed by crossed polarized light microscopy (PLM) and small-angle X-ray scattering (SAXS). And the rheological tests showed that PILGs had small viscosity and excellent fluidity. The viscosities of cubic LC gels were 4~5 orders of magnitude higher than PILGs. In vitro phase conversion experiment showed that PILGs required little vaginal fluid (64.56 µL/100 mg) and time (3.92 s) to transform to LC gels. Furthermore, cubic LC gels could reside in the vaginas for more than 12 h in vivo. The in vitro release revealed that sinomenine hydrochloride (SMH) could be sustained released from the cubic gels over a period of 144 h, which was prior to SMH solution and carbomer gels. An in vivo vaginal mucosa irritation study indicated that PILGs were nonirritant and might be suitable for various vaginal applications. In conclusion, PILGs might represent a potential vaginal delivery strategy to overcome the limitations of traditional treatments.

Study on the transdermal penetration mechanism of ibuprofen nanoemulsions.

OBJECTIVE: The purpose of this study was to research the mechanism of percutaneous penetration of Ibuprofen (IBU) nanoemulsion. METHOD: Transdermal penetration mechanism of IBU nanoemulsion was investigated by using Fourier transform infra-red spectral analysis (FTIR), differential scanning calorimeter thermogram (DSC), and activation energy (Ea) measurement. The in vivo skin penetration test of rats was carried out using Rhodamine B nanoemulsion to simulate the process of drug penetration into the skin, and the frozen section of the skin was observed by confocal laser scanning microscopy (CLSM). RESULT: FTIR spectra and DSC thermogram of rat skin treated with IBU nanoemulsion showed that infiltration occurred due to disruption of the stratum corneum (SC) protein-lipid structure and increasing of fluidity, hydration, and disruption of the lipid bilayer structure of the SC. The significant reduce in Ea (1.255 kcal/mol) for IBU permeating rat skin suggested crucial disruption of the SC lipid bilayers (P < 0.05), which is speculated that nanoemulsion may create new pathways to promote drug penetration. CLSM revealed that Rhodamine B penetrated into the SC in a shorter period of time and it accumulated around the sebaceous glands. CONCLUSION: The study of skin penetration mechanism indicated that nanoemulsion can be perfectly well used as the transdermal penetration of poorly soluble drugs.