Prediction of the drag coefficient of a 20-degree conical ribbon parachute

An empirical formula for the steady state drag coefficient of a 20 degree conical ribbon parachute is developed. The derived expression takes into account the effect of suspension line length and geometric porosity within the limits of practical design. Also included are factors which provide drag reduction due to skirt reefing and the wake behind a primary body. The calculated values are in agreement with the available experimental results

Maxillary expansion in an animal model with light, continuous force

Objectives: Maxillary constriction is routinely addressed with rapid maxillary expansion (RME). However, the heavy forces delivered by most RME appliances to expand the palate may lead to deleterious effects on the teeth and supporting tissues. The objective of this study was to explore a more physiologic maxillary expansion with light continuous force. Materials and Methods: Twenty 6-week-old Sprague-Dawley rats were equally divided into experimental (EXPT) and control (CTRL) groups. A custom-fabricated archwire expansion appliance made from 0.014-inch copper-nickel-titanium wire was activated 5 mm and bonded to the maxillary molar segments of animals in the EXPT group for 21 days. The force applied to each maxillary segment was 5 cN. Microfocus x-ray computed tomography and histological analyses were used to compare the tooth movement and bone morphology in the midpalatal suture and buccal aspect of the alveolar process between the EXPT and CTRL groups. Descriptive statistics (mean ± standard error of the mean) and nonparametric statistical tests were used to compare the outcomes across groups. Results: Compared to the CTRL group, there was a statistically significant increase in buccal tooth movement and expansion of the midpalatal suture in the EXPT group. There was no difference in the bone morphologic parameters between groups. The mineral apposition rate was increased on the buccal surface of the alveolar process in the EXPT group. Conclusions: Application of light, continuous force resulted in maxillary osseous expansion due to bilateral sutural apposition and buccal drift of the alveolar processes. This animal experiment provides a more physiologic basis for maxillary expansion

Wnt Signaling Related to Subchondral Bone Density and Cartilage Degradation in OA

The role of subchondral bone in the progression of osteoarthritis has been controversial for nearly 50 years.(1,2) The observation that subchondral sclerosis was nearly always present in end-stage disease led to the conclusion that the increased stiffness caused by a thicker subchondral bone plate detracted from the bone's ability to attenuate the loads imposed on the joint cartilage, increasing cartilage stresses and initiating the process of joint deterioration. Because cartilage damage does not always progress to full thickness cartilage loss and OA, Radin and Rose(3) proposed that the initiation and the progression of cartilage deterioration were separate processes

Calcineurin regulates APP metabolism: In vitro & In vivo studies

Alzheimer's disease (AD) is a complex neurodegenerative disease determined by the combination of environmental and genetic factors. AD is pathologically characterized by the accumulation of amyloid-[beta] peptide (A[beta]) and intraneuronal neurofibrillary tangles. Production of the A[beta] peptide by the regulated intra-membrane proteolysis of the [beta]-amyloid precursor protein (APP) by the [alpha], [beta] and [gamma] secretase enzymes is the central biological pathway in AD. Cognitive decline observed in AD models is dependent on A[beta] generation. Of particular interest to the work presented here is the observation that APP proteolysis and levels of A[beta] can be regulated by phosphorylation and phosphorylation-dependent events. Downstream effects mediated by soluble A[beta] aggregates include hyperactivation of a calcium (Ca2+) and calmodulin (CaM)-dependent, serine-threonine protein phosphatase calcineurin (CaN). In our study we investigate the role of CaN in AD, and specifically its ability to regulate APP metabolism. CaN acts as heterodimer of CaNA (catalytic subunit) and CaNB (regulatory subunit) and its phosphatase activity can be inhibited using pharmacological drug FK506. Using genetic and pharmacological manipulation of CaN in SH-SY5Y cells and cortical neurons as in vitro models and [gamma]-secretase reporter fly and transgenic fly expressing human APP and BACE as our in vivo AD model (Chakroborty et al), we demonstrate that CaN regulates the proteolytic processing of APP. We also observe a decrease in A[beta] and AICD levels on inhibition of CaN phosphatase activity. Furthermore, CaN inhibition rescues the A[beta] dependent, AD-like behavioral and cognitive deficits observed in our transgenic fly AD model. Overall, our results demonstrate CaN inhibition may rescue cognitive and neurodegenerative effects of A[beta] by regulating APP proteolytic processing. Our work also lays the ground for designing better and more specific drugs that inhibit CaN activity and can act as a potential AD therapeutic.Ph.D., Biological Sciences -- Drexel University, 201

The effect of corticision on root resorption with heavy and light forces

Objective:  To investigate the association between corticision and different force magnitudes with the amount of root resorption. Methods:  Forty-four male Wistar rats (7 week old) were evaluated after an orthodontic spring delivering either 10 or 100 g was placed on the left maxillary first molars to move molars mesially. Experimental rats were divided into four groups, with 11 animals in each group: (1) LF, no corticision and 10 g of orthodontic force; (2) LFC, corticision and 10 g of force; (3) HF, no corticision and 100 g of force; and (4) HFC, corticision and 100 g of force. Contralateral sides were used as unloaded controls. The total duration of the experimental period was 14 days. Two-dimensional (histomorphometric) and three-dimensional (volumetric, micro-focus X-ray computed tomography [microCT]) analysis of root craters were performed on maxillary first molars. Results:  Histomorphometric and microCT analysis revealed a significant amount of resorptive areas in the experimental groups when compared to unloaded controls. However, no significant difference was detected in the amount of resorption among the four experimental groups. Conclusions:  At day 14, neither the amount of force nor the cortical incision caused significant effect on root resorption that was registered by histomorphometric or microCT analysis

Cell and matrix response of temporomandibular cartilage to mechanical loading

OBJECTIVES: The generation of transgenic mice expressing green fluorescent proteins (GFPs) has greatly aided our understanding of the development of connective tissues such as bone and cartilage. Perturbation of a biological system such as the temporomandibular joint (TMJ) within its adaptive remodeling capacity is particularly useful in analyzing cellular lineage progression. The objectives of this study were to determine: (i) if GFP reporters expressed in the TMJ indicate the different stages of cell maturation in fibrocartilage and (ii) how mechanical loading affects cellular response in different regions of the cartilage. DESIGN/METHODS: Four-week-old transgenic mice harboring combinations of fluorescent reporters (Dkk3-eGFP, Col1a1(3.6 kb)-GFPcyan, Col1a1(3.6 kb)-GFPtpz, Col2a1-GFPcyan, and Col10a1-RFPcherry) were used to analyze the expression pattern of transgenes in the mandibular condylar cartilage (MCC). To study the effect of TMJ loading, animals were subjected to forced mouth opening with custom springs exerting 50 g force for 1 h/day for 5 days. Dynamic mineralization and cellular proliferation (EdU-labeling) were assessed in loaded vs control mice. RESULTS: Dkk3 expression was seen in the superficial zone of the MCC, followed by Col1 in the cartilage zone, Col2 in the prehypertrophic zone, and Col10 in the hypertrophic zone at and below the tidemark. TMJ loading increased expression of the GFP reporters and EdU-labeling of cells in the cartilage, resulting in a thickness increase of all layers of the cartilage. In addition, mineral apposition increased resulting in Col10 expression by unmineralized cells above the tidemark. CONCLUSION: The TMJ responded to static loading by forming thicker cartilage through adaptive remodeling

Dried fruit and public health – what does the evidence tell us?

A scientific workshop held in the UK explored the potential contribution of traditional dried fruits to public health, identified gaps in the evidence and addressed priorities for research. Presentations considered the categorisation and composition of dried fruits; dried fruit and gastrointestinal health; the polyphenol content of dried fruits and their potential contribution to health; dried fruit and appetite in relation to the psychology of snacking and obesity; dried fruit and dental health including its role as a snack; and conflicts in public health advice for dried fruits. A round table discussion explored the contribution of dried fruit to “five a day” fruit and vegetable intake and fibre intake, whether dried fruits have equivalence with fresh in terms of dietary advice, advice on snacking in relation to dental health and appetite control, informing the public about different types of dried fruits and avoiding consumer confusion, and future research requirements

Accuracy of Orthodontic Soft Tissue Prediction Software between Different Ethnicities

Objective: The objective of this study was to assess the accuracy of the soft tissue prediction module of Dolphin Imaging Software (DIS) in patients requiring extractions as part of the orthodontic treatment plan and compare its accuracy between different ethnicities. Materials and Methods: Initial and final records of 57 patients from three ethnic groups (African Americans, Caucasians, and Hispanics) who completed orthodontic treatment were included for assessment. The identified cases were managed non-surgically with dental extractions. A predictive profile was generated using DIS and compared to post-treatment lateral photographs. Actual and predictive profile photographs were compared using five designated parameters. The assessment parameters were evaluated using a manual protractor. ANOVA was used to compare differences between actual and predicted parameters between the specified groups and ICC was used to assess correlations between the data. Results: Neither ethnicity nor gender had a significant effect on the difference between predicted and final values. No significant difference was noted between the predicted and final images for the nasolabial angle. Significant differences were observed for the mentolabial fold, upper lip to E-line, and lower lip to E-line between predicted and actual images. Additionally, soft tissue convexity was significantly different (p=0.019). Additionally, a clinically significant difference was found for the mentolabial fold. Conclusion: Ethnicity and gender had no impact on the accuracy of predicted and actual image parameters. Overall, DIS demonstrated acceptable accuracy when simulating soft tissue changes after extraction therapy. Additional research on the accuracy of the software is warranted

Pyk2 deficiency enhances bone mass during midpalatal suture expansion

OBJECTIVE: To determine if Pyk2 deficiency increases midpalatal suture bone mass and preserves sutural integrity after maxillary expansion. SETTING AND SAMPLE: Thirty-six male Pyk2 knockout (KO) and control (WT) mice at 6 weeks of age. MATERIALS AND METHODS: Mice received nickel-titanium spring expanders delivering 0 g (no intervention control), 10 or 20 g force for 14 days. High-resolution micro-CT was used to determine bone volume/tissue volume (BV/TV), sutural width and intermolar width. Effects on osteoclasts, chondrocytes and suture morphology were determined by histomorphometry. RESULTS: Pyk2-KO controls (0 g) had 7% higher BV/TV compared with WT controls. Expanded Pyk2-KO maxillae also exhibited 12% (10 g) and 18% (20 g) higher BV/TV than WT mice. Although bone loss following expansion occurred in both genotypes, BV/TV was decreased to a greater extent in WT maxillae (-10% at 10g; -22% at 20 g) compared with Pyk2-KO maxillae (-11% only at 20 g). Expanded WT maxillae also showed a greater increase in sutural width, intermolar width and fibrous connective tissue width compared with expanded Pyk2-KO maxillae. Moreover, osteoclast number was increased 77% (10 g) and 132% (20 g) in expanded WT maxillae, but remained unchanged in expanded Pyk2-KO, compared to their respective controls. Cartilage area and chondrocyte number were increased to the same extent in expanded WT and Pyk2-KO sutures. CONCLUSIONS: These findings suggest that midpalatal suture expansion increases osteoclast formation in WT but not Pyk2-KO mice, leading to higher BV/TV in expanded Pyk2-KO maxillae. These studies suggest Pyk2-targeted strategies may be beneficial to increase bone density and preserve sutural integrity during maxillary expansion