Linear Segmented Arc-Shaped Piezoelectric Branch Beam Energy Harvester for Ultra-Low Frequency Vibrations.

Piezoelectric energy harvesting systems have been drawing the attention of the research community over recent years due to their potential for recharging/replacing batteries embedded in low-power-consuming smart electronic devices and wireless sensor networks. However, conventional linear piezoelectric energy harvesters (PEH) are often not a viable solution in such advanced practices, as they suffer from a narrow operating bandwidth, having a single resonance peak present in the frequency spectrum and very low voltage generation, which limits their ability to function as a standalone energy harvester. Generally, the most common PEH is the conventional cantilever beam harvester (CBH) attached with a piezoelectric patch and a proof mass. This study investigated a novel multimode harvester design named the arc-shaped branch beam harvester (ASBBH), which combined the concepts of the curved beam and branch beam to improve the energy-harvesting capability of PEH in ultra-low-frequency applications, in particular, human motion. The key objectives of the study were to broaden the operating bandwidth and enhance the harvester's effectiveness in terms of voltage and power generation. The ASBBH was first studied using the finite element method (FEM) to understand the operating bandwidth of the harvester. Then, the ASBBH was experimentally assessed using a mechanical shaker and real-life human motion as excitation sources. It was found that ASBBH achieved six natural frequencies within the ultra-low frequency range (<10 Hz), in comparison with only one natural frequency achieved by CBH within the same frequency range. The proposed design significantly broadened the operating bandwidth, favouring ultra-low-frequency-based human motion applications. In addition, the proposed harvester achieved an average output power of 427 µW at its first resonance frequency under 0.5 g acceleration. The overall results of the study demonstrated that the ASBBH design can achieve a broader operating bandwidth and significantly higher effectiveness, in comparison with CBH.

[Complementation and function of methyl-metabolic pathway in Streptococcus mutans luxS null strain].

PURPOSE: To complement the activated methyl cycle (AMC) pathway at an AI-2 defect background in Streptococcus mutans (S. mutans) luxS null strain. METHODS: A sahH gene was amplified from Pseudomonas aeruginosa and introduced into the S. mutans luxS null strain to complement the methyl-metabolic disruption at an AI-2 defect background. Western blot, reverse-transcription PCR and AI-2 bioassay were performed to confirm the heterogenous expression of SahH in S. mutans luxS null strain. The data was statistically analyzed by SAS8.0 software package. RESULTS: LuxS and SahH were detected to express in Escherichia coli BL21 as well as their mRNA were confirmed to be successfully transcribed in S. mutans luxS null strain. AI-2 production was found in wide type S. mutans and its luxS-introduced luxS null strain but not found in the luxS null strain and its sahH and empty plasmid-introduced strains. CONCLUSIONS: A new S. mutans derivative with the AMC pathway complements while the AI-2 defect is constructed.

Characterization of oral bacterial diversity of irradiated patients by high-throughput sequencing.

The objective of this study was to investigate the compositional profiles and microbial shifts of oral microbiota during head-and-neck radiotherapy. Bioinformatic analysis based on 16S rRNA gene pyrosequencing was performed to assess the diversity and variation of oral microbiota of irradiated patients. Eight patients with head and neck cancers were involved in this study. For each patient, supragingival plaque samples were collected at seven time points before and during radiotherapy. A total of 147,232 qualified sequences were obtained through pyrosequencing and bioinformatic analysis, representing 3,460 species level operational taxonomic units (OTUs) and 140 genus level taxa. Temporal variations were observed across different time points and supported by cluster analysis based on weighted UniFrac metrics. Moreover, the low evenness of oral microbial communities in relative abundance was revealed by Lorenz curves. This study contributed to a better understanding of the detailed characterization of oral bacterial diversity of irradiated patients.

Exploring the dynamic core microbiome of plaque microbiota during head-and-neck radiotherapy using pyrosequencing.

Radiotherapy is the primary treatment modality used for patients with head-and-neck cancers, but inevitably causes microorganism-related oral complications. This study aims to explore the dynamic core microbiome of oral microbiota in supragingival plaque during the course of head-and-neck radiotherapy. Eight subjects aged 26 to 70 were recruited. Dental plaque samples were collected (over seven sampling time points for each patient) before and during radiotherapy. The V1-V3 hypervariable regions of bacterial 16S rRNA genes were amplified, and the high-throughput pyrosequencing was performed. A total of 140 genera belonging to 13 phyla were found. Four phyla (Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria) and 11 genera (Streptococcus, Actinomyces, Veillonella, Capnocytophaga, Derxia, Neisseria, Rothia, Prevotella, Granulicatella, Luteococcus, and Gemella) were found in all subjects, supporting the concept of a core microbiome. Temporal variation of these major cores in relative abundance were observed, as well as a negative correlation between the number of OTUs and radiation dose. Moreover, an optimized conceptual framework was proposed for defining a dynamic core microbiome in extreme conditions such as radiotherapy. This study presents a theoretical foundation for exploring a core microbiome of communities from time series data, and may help predict community responses to perturbation as caused by exposure to ionizing radiation.

Effects of intensity-modulated radiotherapy on human oral microflora.

This study aimed to evaluate changes in the biodiversity of the oral microflora of patients with head and neck cancer treated with postoperative intensity-modulated radiotherapy (IMRT) or conventional radiotherapy (CRT). Pooled dental plaque samples were collected during the radiation treatment from patients receiving IMRT (n = 13) and CRT (n = 12). Denaturing gradient gel electrophoresis (DGGE) was used to analyze the temporal variation of these plaque samples. The stimulated and unstimulated salivary flow rates were also compared between IMRT and CRT patients. Reductions in the severity of hyposalivation were observed in IMRT patients compared with CRT patients. We also observed that the temporal stability of the oral ecosystem was significantly higher in the IMRT group (69.96 ± 7.82%) than in the CRT group (51.98 ± 10.45%) (P < 0.05). The findings of the present study suggest that IMRT is more conducive to maintaining the relative stability of the oral ecosystem than CRT.

[Influence of Streptococcus mutans luxS gene on polysaccharide matrix metabolism].

PURPOSE: To investigate the effect of Streptococcus mutans luxS gene on polysaccharide matrix metabolism. METHODS: Based on the immobilization of magnetic beads by adherent cells,an assay of biofilm quantitative analysis was developed for the kinetic quantification of biofilm formation. S.mutans luxS gene mutant strain and wild-type strain were compared for their ability of utilizing exogenous carbohydrate to form extracellular polysaccharide matrix. SPSS 10.0 software package was used for statistical analysis. Dunnet t two-side test of one factor analysis of variance was performed. RESULTS: Both luxS mutant strain and wild-type strain could use exogenous carbohydrate to form polysaccharide matrix.With 1% sucrose added ,both strains completed their biofilm formation within one hour.When adding 1% glucose,these strains also accelerated the formation of biofilm,and this was more significant in the mutant strain. CONCLUSIONS: The luxS gene of S. mutans can regulate its extracellular polysaccharide matrix metabolism. Moreover, the regulation of this gene on biofilm formation is more probably via polysaccharide matrix pathway. Supported by National Natural Science Foundation of China(30872886), Research Fund of Science and Technology Commission of Shanghai Municipality(08DZ2271100),Shanghai Leading Academic Discipline Project(S30206) and Youth Phosphor Program of Science and Technology Commission of Shanghai Municipality (09QA1403700).

Modeling of diffusion transport through oral biofilms with the inverse problem method.

AIM: The purpose of this study was to develop a mathematical model to quantitatively describe the passive transport of macromolecules within dental biofilms. METHODOLOGY: Fluorescently labeled dextrans with different molecular mass (3 kD, 10 kD, 40 kD, 70 kD, 2000 kD) were used as a series of diffusion probes. Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum were used as inocula for biofilm formation. The diffusion processes of different probes through the in vitro biofilm were recorded with a confocal laser microscope. RESULTS: Mathematical function of biofilm penetration was constructed on the basis of the inverse problem method. Based on this function, not only the relationship between average concentration of steady-state and molecule weights can be analyzed, but also that between penetrative time and molecule weights. CONCLUSION: This can be used to predict the effective concentration and the penetrative time of anti-biofilm medicines that can diffuse through oral biofilm. Furthermore, an improved model for large molecule is proposed by considering the exchange time at the upper boundary of the dental biofilm.

[Study on the biofilm early formation of Streptococcus mutans luxS gene mutation].

OBJECTIVE: To investigate the effect of Streptococcus mutans luxS mutarotation on the early biofilm formation. METHODS: Based on the immobilization of magnetic beads by adherent cells, an assay of biofilm quantitative analysis was developed for the kinetic quantification of biofilm formation in this study. Streptococcus mutans luxS mutant strain was constructed and subject to this biofilm luxS mutant strain were compared. RESULTS: The delta luxS mutant started to form a biofilm from the 6th hour (delta BFI = 2.015), and the delta BFI of luxS mutant increased more quickly than that of the wild type strain, until reaching a complete immobilization of the beads after 10 hours (delta BFI = 7.025). The wild-type strain start to form a biofilm from the 10 th hour (delta BFI = 1.875) and the beads were completely immobilized between 12 and 14 hours. CONCLUSIONS: The luxS mutation can accelerate biofilm on a polystyrene surface during the mid-exponential growth phase. And a luxS-dependent signal may play an important role in the early biofilm formation of Streptococcus mutans.

[Identification of P. gingivalis P. intermedia P. nigrescens by 16S rDNA and membrane microarray chip].

PURPOSE: The aim of this study is to identify three kinds of black-pigmented periodontal pathogens P. gingivalis Pg, P. intermedia Pi, P. nigrescens Pn by 16S rDNA and microarray. METHODS: A pair of universal primers which can amplify a section of conservative domain of bacterial 16S rDNA based on the sequences of 16S rDNA in Genebank were designed. Then the specific oligonucleotide probes for Pg Pi Pn based on the sequences of the conservative domain were constructed. Standard bacterial genomic DNAs were amplified using the designed universal primers by PCR, and labeled by digoxigenin at the same time, the products of PCR were hybridized with the microarray in which the specific probes were added. The results of hybridization were analysed. RESULTS: The results of hybridization showed that the specific probes of Pg Pi Pn on microarray reacted only with corresponding PCR products of Pg Pi Pn, not reacted with others. CONCLUSION: The method of 16S rDNA and membrane microarray could be useful to identify Pg Pi Pn, and had high specificity. It will be developed into a kind of clinical bacterial detective system.

[Susceptibility of Streptococcus mutans biofilm to antimicrobial agents].

OBJECTIVE: To investigate the susceptibility of Streptococcus mutans (S. mutans) biofilms to antimicrobial agent by confocal laser scanning microscopy (CLSM). METHODS: S. mutans biofilms formed in vitro on glass slice were acted on with penicillin of different concentrations for 3 h. Then these biofilms were stained by fluorescence and were observed by CLSM. The bacterial density and viability of biofilms were recorded. RESULTS: When S. mutans biofilms were exposed to penicillin of 2 500 mg/L for 3 h, it was not completely killed. The higher the concentration of penicillin was, the weaker the biofilms against penicillin. CONCLUSIONS: Compared with planktonic S. mutans, S. mutans biofilms produced stronger resistance to penicillin. It suggests that we should find new strategies to control the infection caused by biofilm in clinic.